WO2006110961A2

WO2006110961A2 - Novel corrosion inhibiting materials

Info

Publication number: WO2006110961A2
Application number: PCT/AU2006/000540
Authority: WO
Inventors: Andrew Joseph Koplick
Original assignee: A J Scientific Pty Ltd
Priority date: 2005-04-22
Filing date: 2006-04-24
Publication date: 2006-10-26
Also published as: WO2006110961A3

Abstract

In broad terms, the invention provides for novel corrosion inhibiting materials obtained by a chemical reaction between a Mannich base and other suitable reactants. The Mannich bases of this invention are derived from hydroxyaromatic compounds, secondary amines or cyclic secondary amines and aldehydes. The other reactants include: organo-metallic compounds, metal oxides, carboxylic acids, inorganic acids, inorganic acid derivatives, alkyl halides, organosilanes and quarternary ammonium derivatives and metal derivatives The corrosion inhibitors of the invention are liberated upon hydrolysis in the presence of humidity and are particularly suitable for incorporation in polymers, cements, paints, papers, cardboard, textiles.

Description

Novel corrosion inhibiting materials

TECHNICAL FIELD

This invention relates to methods and materials for the protection of metals from corrosion, more particularly - to corrosion inhibiting materials, including those materials that are suitable for water- and vapour- phase corrosion inhibition, to the incorporation of the corrosion inhibiting materials in polymers, and attachment to various substrates.

Further, the invention relates to polymers incorporating vapour-phase corrosion inhibitors and vapour-phase corrosion-inhibiting materials that are capable of releasing corrosion inhibitors as vapour and to methods of producing such polymers incorporating these vapour phase corrosion inhibitors.

BACKGROUND TO THE INVENTION

The metal-corrosion inhibitors are used in protecting metals from flash rusting, protecting metals exposed to corrosive environments in composite materials (e. g. cement); protecting electrical and electronic components as vapour-phase corrosion inhibitors; in fluids contained in various receptacles both aqueous (e. g. boilers, pipes) and non-aqueous (e. g. oil wells) and in humid atmospheres particularly during the transport of ferruginous metals; in coolant fluids for car radiators and industrial water coolers; in aqueous fluids for metal polishing and buffing; in aqueous fluids as metal chelates.

In this patent specification, unless otherwise made clear by the context: 'Metal' refers to any conventional metal and also alloys of metals such as carbon steel and metal alloys containing iron (mild steel) as well as zinc, aluminium, copper, brass, bronze. The metals can be in such diverse forms as rolls, sheets, tubes, coils, piano wire or guitar strings and various electrical and electronic devices, their electrical terminals and internal electrical connections.

Following is a brief review of the prior art regarding corrosion inhibiting materials. The corrosion inhibiting properties of Mannich bases were first noted in 1940 and in the early 1950's vapour phase corrosion inhibition first came in to prominence. Prior art examples include Mannich bases derived from either mono- or polyhydroxy aromatic compounds.

Mannich bases from monohvdroxyaromatic compounds Mannich bases derived from phenols with three dialkylaminomethyl groups in the 2, 4, 6-positions of the aromatic ring were synthesised by Bruson and Macmullen (U.S. Pat. No. 2,220,834; 1940) and were claimed as being soluble in water and noted as being useful as corrosion inhibitors. Also, phenols such as 2,4,6 tris(dimethylaminomethyl)phenol and 2,4-bis(dimethylaminomethyl)phenol that are soluble in mineral oil were disclosed as corrosion inhibitors for lubricating oils after tests in oil/water mixtures ( East German Pat. No.146754).

Bis(disubstituted-aminomethyl) phenols such as 2-(dialkylaminomethyl)-4- alkyiaminophenol and 2-(dialkylaminomethyl)-4-dialkylaminophenol have been disclosed as stablisers in cracked gasoline (U.S. Pat. No. 2,401 ,957) and several bis (disubstituted-aminomethyl)alkyl phenols (U.S. Pat. No. 4,322,304) have been reported as important additives for hydrocarbon fuel and lubricating compositions.

The following Mannich bases were disclosed in U.S. Pat. No. 3,779,855 as suitable emulsion stabilisers for polyester resins: 2,4,6- tris(dimethylaminomethyl)phenol, 2,4,6-tris(diethylaminomethyl)phenol, 2,4,6- tris(dimethylaminoethyl)phenol.

Mannich bases from polvhvdroxy aromatic compound

Mannich reaction products of diaminopropane with formaldehyde and salicylic acids were disclosed by Kaufman (U.S. Patent No.4,490,155) as novel motor fuel additives with detergent and corrosive inhibitive properties. The diamines were derivatives of N-alkyl-alkylene diamine such as N-oleyl-1 ,3-diamine or N-oleyl-N'- oleyl-1 ,3-diamine. Similarly, the use of high-molecular-weight alkyl-substituted phenols as well as high-molecular-weight alkyl-substituted derivatives of resorcinol, hydroquinone, cresol and catechol among others, to form Mannich condensation products was disclosed by Udelhofen (U.S. Pat. No. 4,231 ,759) and Chibnik (U.S. Pat. No. 4,083,699).

Mono-molecular Mannich bases derived from polyhydroxybenzenes such as hydroquinone were disclosed by Chenicek (U. S. Patent No. 2,553,441) as materials that prevent edible fats and oils of animal or vegetable origin from becoming rancid. Compounds such as 2, 5-bis(dialkylaminomethyl)-1 ,4- dihydroxybenzene (where the alkyl group can designate methyl, ethyl or morpholino) as well as 2-dimethylaminomethyl-4-methoxyphenol were claimed to inhibit oxidative deterioration of fats and oils. Mannich bases such as bis- ((dihydroxyalkyl)aminomethyl) hydroquinone were disclosed by Donovan and Bean (U.S. Patent No. 2,604,399) as highly water-soluble photographic developers that could also be used as oxidation inhibitors for gasoline, fatty oils and rubber. Dialkylaminomethyl resorcinol derivatives are disclosed in U.S. Patent No's: 3,798,051 ; 4,089,902 to Morita and in U.S. Patent No's 3,462,382; 3,504,040; 3,609.108 to Kolka, Tai and Moult. The tris-substituted resorcinol compounds referred to in the above-mentioned patent were claimed to impart increased adhesive properties to rubber.

Summarising the review of Mannich bases, it is concluded that although their corrosion inhibitive properties have been recognised for a long time, chemical compounds that allow the commercial use of Mannich bases for the purpose of vapour-phase corrosion inhibition were not developed and therefore the prior art applications did not include Mannich bases in vapour-phase applications

Vapour-phase corrosion inhibitors.

Vapour-phase corrosion inhibitors (VPCIs) have been used for many years and many attempts to incorporate them into polymer melts used for extrusion or moulding have been made. The basic problem is that known VPCIs have high volatility and reactivity at processing temperatures resulting in large losses of the VPCI material, chemical breakdown of the VPCIs and blistering or disfiguring of the extruded or moulded plastic. Since many VPCIs and their breakdown products are very toxic to humans their copious release during processing presents serious problems. There is also a need to address the issue of storage and usefulness of the polymeric film incorporating corrosion inhibitors for a given period after manufacture. It would be desirable to be able to store the polymeric film for very long periods before use. It would also be desirable to be able to conveniently incorporate corrosion inhibitors into polymers during processing of polymeric films. The introduction to US patent No. 5,958,115 to Bόttcher et al. provides a good overview of the problems involved in attempting to include VPCIs in plastic packaging materials and this overview is incorporated herein by reference. Bottcher et al. teach and address the problem of excessive volatility of known VPCIs by embedding VPCI in gels made from hydrolysed metal alkoxides, often modified with an organic polymer (e.g. cellulose derivatives, starch derivatives, polyalkane glycols, acrylate, methacrylate and styrene polymers) applied with solvents to produce fine powders. Examples provided by Bottcher et al. describe the use of these powders for dusting metal surfaces, for impregnating papers from liquid suspensions and for inclusion in varnishes applied to metals. This review, however, suggests no means for controlling the vapour pressure and the release conditions of the VPCI from materials in which the VPCIs are embedded.

There remains a need for new VPCIs that are less toxic, more stable and/or less prone to uncontrolled or excessive vapour loss.

There remain a need for novel stable and efficient corrosion inhibitors that are suitable for incorporation into paper, cements, paints, plastics and many other materials.

In applications, these materials are either in direct contact with metal parts or closely envelope these metal parts; and there remains a need to protect the metal parts from corrosion by using corrosion inhibitors incorporated in these materials and subsequently releasable form these materials when the metal parts are exposed to moisture.

When the above mentioned materials are in direct contact with metal parts the corrosion inhibitors are required to be releasable either in the liquid or vapour phase.

When the above-mentioned materials closely envelop the metal parts the corrosion inhibitors are required to be releasable as vapour with the required vapour pressure so that the volatile corrosion inhibitors adsorbed onto the metal surface from the gas phase, protect the metal surface from corrosion. OUTLINE OF INVENTION

In broad terms, the invention provides for novel corrosion inhibiting materials obtained by a chemical reaction between a Mannich base and other suitable reactants. The Mannich bases of this invention are derived from hydroxyaromatic compounds, secondary amines or cyclic secondary amines and aldehydes. The other reactants include:

• organo-metallic compounds • metal oxides

• carboxylic acids

• inorganic acids, inorganic acid derivatives, alkyl halides

• organosilanes

• quarternary ammonium derivatives and metal derivatives

The formation of the chemical compounds of this invention is diagrammatically presented in Fig.1.

The invention also provides for modified corrosion inhibiting materials obtained from an admixture of the corrosion inhibiting materials mentioned above and other complementary substances, wherein the complementary substances include:

• unsaturated conjugated acids and their derivatives

• unsaturated conjugated aldehydes and their derivatives

The invention teaches that the predetermined chemical and physical properties of the corrosion inhibiting materials and of the modified corrosion inhibiting materials are achieved by variations in the structure of the hydroxyaromatic compounds, secondary amines and aldehydes. The preparation of Mannich bases from the hydroxyaromatic compounds, aldehydes and amines is well documented in the chemical literature, however, this invention provides Mannich base compounds that have a range of suitable vapour pressures and solubility in aqueous fluids. This invention provides Mannich bases as corrosion inhibiting materials for the purposes of protecting metal surfaces from corrosive attack either in the vapour phase or in aqueous fluids. The gamut of chemical and physical properties required of such corrosion inhibiting materials is fulfilled by varying the chemical composition of the three main components that make up the Mannich bases, namely, hydroxyaromatic compounds, secondary amines and aldehydes.

This invention provides Mannich bases derived from the following: mono- and polyhydroxyaromatic compounds, secondary amines with saturated and unsaturated substituents, cyclic secondary amines in 5- or 6-membered ring compounds, cyclic secondary amines in azamacrocyclic rings having at least three nitrogen atoms; aldehydes both saturated and unsaturated.

Monohvdroxyaromatic compounds

Mannich bases, prepared from monohydroxyaromatic comounds such as phenol, dimethylamine and formaldehyde to afford 2,4,6-tris(dimethylaminomethyl)phenol, 2,4-bis(dimethylaminomethyl)phenol and 2,6-bis(dimethylaminomethyI)phenol were found to be good corrosion inhibitors in both the water- and vapour-phase. The properties of the above-mentioned Mannich bases, namely, high water solubility and high volatility, are ideally suited for applications in humid atmospheres and in confined spaces where there is considerable condensation occurring on the surface of the metal articles to be protected. It is surmised that, the polar dialkylaminomethyl and phenolic OH groups confer water solubility whereas the dialkylaminomethyl groups adjacent to the phenolic OH group in the ortho position confer volatility because of intramolecular H-bonding of the phenolic hydrogen to the nitrogen atom of the dialkylaminomethyl moiety. These properties allow for their use in both aqueous- and vapour- phases. For instance,

R is methyl.

The highly volatile Mannich bases mentioned above, however, required modification before they could be incorporated successfully into sachets, cardboard or polyolefinic films as water- and/or vapour-phase corrosion inhibitors. Thus, the present invention provides Mannich bases as well as other homologue derivatives in which the alkyl substituents on the nitrogen atom can be varied to adjust their physical and chemical properties for specific applications. This aspect is important when the designated inhibitors are intended for use in polymeric films as vapour- phase corrosion inhibitors, since the rate of exudation and release of inhibitor from the surface of the film can be more easily controlled.

To allow for their use in sachets, cardboard or polyolefinic films as vapour-phase corrosion inhibitors the following modifications to the initial chemical structures of the Mannich bases were made to enhance their sustained release properties: alkyl substituents are included on the hydroxyaromatic compound in the para position. Alkyl substituents (C1 to C20) replaced the dimethylaminomethyl moiety on the aromatic ring of the hydroxyaromatic compound in para position so that it would be less volatile and more compatible with the polyolefinic film, polyisobutene (low-, medium- and high-molecular weight) or hydrocarbon solvent.

Alkyl substitution in the para position of the Mannich bases, 2,6 bis(dimethylaminomethyl)phenol and 2-mono(dimethylaminomethyl)phenol affords inhibitors of less volatility and compatibility with polyolefinic substrates allowing for a sustained and controlled migration from the bulk of the substrates to the surface. The alkyl substituents can vary in length from C1 -C20 but preferably from C1 -C9 and they may be straight-chained, branched and/or unsaturated. For instance, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert.-butyl, octyl, nonyl, allyl, vinyl. The unsaturated substituents in the para position will allow the modified bases to be co-polymerised with acrylic or methacrylic acids to form water-dispersible polymers for use as corrosion inhibiting coatings.

Secondary amines with saturated and unsaturated substituents.

The secondary amines, as a group is the second component that can be varied to achieve desirable properties of the Mannich bases. Firstly considered, are the secondary amines with saturated and unsaturated substituents, in which the alkyl substituents on the N atom of the dialkylaminoalkyl moiety were lengthened to decrease the volatility of the Mannich base.

The alkyl substituents on the nitrogen atom can vary in length from C1-C20 but preferably from C1 -C12 and they may be straight-chained, branched and/or unsaturated, for instance, methyl, ethyl, propyl, butyl, isopropyl, isobutyl, tert.-butyl, octyl, nonyl, decyl, neodecyl, hexadecyl and allyl. In some instances, the unsaturated substituents will allow the modified Mannich bases to be co- polymerised with acrylic or methacrylic acid to form water-dispersible polymers for use in coatings. The long-chained alkyl substituents, for instance decyl and hexadecyl confer compatibility and increase the residence time in the polymeric substrates. Hence, the preferred amines utilised in the invention are secondary amines of the formula HN(RR') wherein R,R' are equivalent or different alkyl groups and may be linear, branched, saturated or unsaturated with C1-C12 carbon atoms, for example, R, R' may be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert.- butyl, decyl, allyl, sorbyl.

Cyclic secondary amines in 5- or 6-membered ring compounds The cyclic secondary amines in 5- and 6- membered-ring compounds, either saturated or unsaturated may also be used to prepare the Mannich bases, for example, pyrrole, pyrrolidine, piperidine, piperazine, methylpiperazine, N- hydroxyethylpiperazine, imidazole, benzimidazole, morpholine. Similarly, the polymeric Mannich base compounds are obtained by reaction between either a 4-alkylsubstituted phenol or resorcinol with the following cyclic secondary amines: hexahydropyrimidine, tetrahydroimidazole, imidazolidenone, imidazolidenethione in the presence of an aldehyde such as formaldehyde.

From one aspect of the invention, a novel corrosion-inhibiting and metal-chelating Mannich-base polymeric/cyclic compound is described. In one embodiment the compound is prepared by allowing either a para-substituted phenol or resorcinol to react with formaldehyde and hexahydropyrimidine. In another embodiment the compound is prepared by allowing para-alkylated dimethylolphenol to react with the hexahydropyrimidine. In yet another embodiment the compound is prepared by allowing N, N'-bis(hydroxymethyl) pyrimidine to react with a para-alkylated phenol. Cyclic secondary amines in azamacrocvclic rings having at least three nitrogen atoms

From another aspect, the Mannich bases are derived from cyclic secondary amines in azamacrocyclic rings having at least three nitrogen atoms. The reaction of the cyclic secondary amines (for example, tri- and tetra-azamacrocycles) with 2,4- dialkylsubstituted phenol in the presence of formaldehyde affords Mannich base chelating agents. The macrocyclic chelates that act as corrosion inhibitors also have other uses such as in X-ray imaging, magnetic resonance imaging (MRI) and heavy metal detoxification. The macrocyclic chelates may be prepared from the following cyclic secondary amines in azamacrocyclic rings: 1 ,4,8,11 - tetraazacyclotetradecane, 1 ,5,9,13-tetraazacyclohexadecane, 1 ,4,8,12- tetraazacyclopentadecane, 1 , 4,7,10-tetraazacyclododecane. 1 , 4, 7- triazacyclononane and cross-bridged 1 , 4, 7, 10- tetraazacyclododecane

Polvhvdroxyaromatic compounds

It has been found that Mannich bases derived from polyhydroxyaromatic compounds (polyhydroxybenzene and its derivatives) have out-standing corrosion- inhibiting properties both in the vapour- and aqueous-phase. The Mannich bases derived from polyhydroxyaromatic compounds display the requisite range of vapour pressures under ambient conditions enabling them to be suitable VPCIs when incorporated as mixtures of VPCIs in various substrates. Implementing a mixture of the Mannich bases, each with differing vapour pressure, enables a continual supply of corrosion inhibiting vapours to be maintained over prolonged periods.

The invention provides novel low-molecular-weight Mannich bases derived from polyhydroxybenzenes, hydroxybenzoic and polyhydroxybenzoic acids or their derivatives as well as novel metal-corrosion inhibitors.

The Mannich bases of the invention are preferably prepared under the usual Mannich reaction conditions by heating under reflux in an inert solvent, adding stoichiometric amounts of amines, formaldehyde and the corresponding polyhydroxybenzenes, hydroxybenzoic and polyhydroxybenzoic acids or their derivatives, while continually removing the water of reaction as it forms. The final product is obtained by distilling the solvent and residual reactants. In some cases, the reactants are heated under reflux at low temperatures as an aqueous mixture without solvent and the Mannich bases are extracted with ether, the ether dried, distilled and the product recrystallised from an alcohol such as methanol.

The corresponding Mannich bases of polyhydroxyaromatic compounds that were found to be suitable for use as corrosion inhibitors in the present invention include:

• mono-cyclic six-membered-ring aromatic compounds having at least one hydroxy group in the ring with at least one other group in the ring being a carboxylic acid group or its derivatives. The carboxylic acid groups are usually converted to an ester functional group with C1 to C8 that may be linear, branched, saturated or unsaturated. For example: 2-hydroxybenzoic acid (salicylic acid), 3-hydroxybenzoic acid and 4-hydroxybenzoic acid, 4- hydroxyallylbenzoate.

• mono-cyclic six-membered-ring aromatic compounds having two hydroxy groups in the ring such as 1 ,2-dihydroxybenzene (catechol), 1 ,3- dihydroxybenzene (resorcinol) and 1 ,4-dihydroxybenzene (hydroquinone).

• mono-cyclic six-membered-ring aromatic compound having two hydroxy groups in the ring with at least one other group substituted in the ring being either an alkyl or carboxylic acid group. The alkyl groups may be linear, branched, saturated or unsaturated and containing from C1 to C20, whereas the carboxylic acid group is usually converted to an ester functional group with C1 to C8 that may be linear, branched, saturated or unsaturated. For example, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5- dihydroxybenzoic acid, 2,6 -dihydroxybenzoic acid(gentisic acid), 3,4- dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid and 3,5-dihydroxytoIuene (orcinol),

• mono-cyclic six-membered-ring aromatic compound with three hydroxy groups substituted in the ring such as 1 ,2,3-trihydroxybenzene

(pyrogallol), 1 ,2,4- trihydroxybenzene (hydroxyhydroquinone), 1 ,3,5- trihydroxybenzene (phloroglucinol).

• mono-cyclic six-membered-ring aromatic compound with at least three hydroxy groups substituted in the ring as well as at least one other group substituted in the ring such as an alkyl or carboxylic acid group. Examples include 3,4,5- trihydroxybenzoic acid (gallic acid), 2,3,4- trihydroxybenzoic acid and 2,4,6- trihydroxybenzoic acid. The carboxylic acid group is usually converted to an ester functional group with C1 to C20 that may be linear, branched, saturated or unsaturated (e.g. propylgallate, laurylgallate). Esters of the acids are preferred during the formation of Mannich bases to avoid the formation of side-reactions.

• mono-cyclic six-membered-ring aromatic compound with at least one hydroxy group substituted in the ring together with at least one alkoxy and an alkyl group substituted in the ring. The alkyl and alkoxy groups may be saturated or unsaturated, linear or branched and contain from C1 -C20 carbon atoms (e.g. eugenol).

• mono-cyclic six-membered-ring aromatic compound with at least one hydroxy group substituted in the ring together with at least one alkoxy group. The alkoxy groups may be saturated or unsaturated, linear or branched and contain from C1-C20 carbon atoms (e.g. guaicol (2-methoxyphenol), 2- methoxyhydroquinone, 4-methoxyphenol.

Aldehydes used in the preparation of Mannich bases

From another aspect, formaldehyde, metaldehyde and paraldehyde are the aldehydes used in the synthesis of the Mannich bases in this invention. Unsaturated aldehydes such as alpha-methylacrylaldehyde, trans,trans-2,4- hexadienal, fra/7s,frans-2,4-hepadienaUrans,fra/7s- octadienal, trans,trans- nonadienal and frans-cinnamaldehyde may be incorporated into the molecular structure so that volatility as well as the chemical nature can be modified with the presence of conjugated double bonds. Also, the possibility of co-polymerising the molecule with acrylic or methacrylic acid for use as corrosion inhibiting coatings in aqueous media can be provided.The preferred aldehydes are those of the formula RCHO wherein R is H or C1 -C!2 hydrocarbyl both saturated and unsaturated. The main formaldehyde producing precursors include paraformaldehyde, trioxane or aqueous formaldehyde solutions. Other aldehydes include acetaldehyde, propionaldehyde, butyraldehyde, crotonaldehyde and benzaldehyde. Precursors with metal alkoxides and other metal derivatives

In one embodiment, the reactant is an organo-metallic compound. The invention provides for the reaction products resulting from the interaction of metal alkoxides and other metal derivatives with the following:

• Mannich bases

• amino alcohols

• carboxylic acids

A scheme depicting the formation of corrosion inhibiting materials from Mannich base, amino alcohols and carboxylic acid is presented in Fig.2. The scheme also demonstrates steps of attaching the organo-metallic compound to a metal oxide carrier or polymeric substrate and final liberation of the corrosion inhibitors upon hydrolysis.

The Mannich base is bonded to the metal centre of the organometallic compound as a nucleating ligand with or without other ligands such as amino alcohols and carboxylic acids. The invention provides for a wide range of the organo-metallic compounds, including, but not limited to the following substances: metal alkoxides and other metal derivatives such as, alkoxometal carboxylates, oxometal carboxylates or metal carboxylates, for example, Ti(OPr)₄ , Zr(OR)₄ , Sn(OR)₄ ,WO(OR)₄ , MoO(OR)₄ , H₂WO₄ , H₂ MoO₄ , B(OR)₃ , B(OH)₃ , RB(OH)₂, P(OR)₃ , PO(OR)₃ , RPO(OH)₂, AI(OI Pr)₃ , OAIOOCR, Si(OR)₄ ,RSi(OR)₄ where R is an alkyl substituent f rom C1 -C20, straight, branched, saturated or unsaturated.

Mannich bases derived from mono- and polyhydroxyaromatic compounds bond to metal centres of organo-metallic compounds either as mono- or bidentate- ligands forming complexes that are designated in this invention as corrosion inhibiting precursors. The organo-metallic compounds may simultaneously form reaction products with the above-mentioned Mannich bases, long-chained aliphatic acids both saturated and unsaturated (e.g. isostearic, myristic, octanic, nonanoic, sorbic ) as well as bi-, tri-, or tetradentate aminoalcohols such as isopropanolamine , N- methylethanolamine, N-ethylethanolamine, N,N-dimethylethanolamine, diethanolamine, diisopropanolamine, N-methylpropylamine and triethanolamine to give mixed species. This introduction of long-chained aliphatic carboxylic acids into the organo-metallic precursors allows for an increased solubility in the polymeric olefinic material and a delayed diffusion/migration from the bulk of the material. Consequently, a sustained release of useful corrosion inhibitors from the substrate over a longer period is achieved. Importantly, the bonding of the long-chained aliphatic carboxylic acid to the organo-metallic precursor affects only the solubility and diffusion of the precursor in the polymeric olefinic material but not the volatility of the actual corrosion inhibitive materials such as the Mannich bases, carboxylic acids (e.g. sorbic acid) and amino alcohols that are also bonded to the same organo-metallic compound. These precursors are involatile at ambient temperatures (20-30° C) and stable if kept in moisture-free atmospheres. The latent corrosion inhibitors bound as precursors remain dormant until moisture hydrolyses the organo-metallic bond and releases the corrosion inhibitor as vapour. Unexpectedly, it was found that the precursors are stable at melt temperatures in excess of 200 ⁰C on hot metallic surfaces during extrusion of polymeric material, enabling them to be easily incorporated into polymeric films without rupture. It has been found that following the preparation of polymeric films, these precursors migrate or diffuse through the polymeric material to its surface, where, upon hydrolysis, the volatile corrosion- inhibiting Mannich base and other volatile corrosion inhibiting substances such as amino alcohols or carboxylic acids are released.

Additional inclusion of the extremely volatile materials such as dimethylaminoethanol and dimethylaminopropanol ensures that the confined space, for which these vapours are intended, is rapidly saturated with corrosion inhibiting vapours. Conversely, the Mannich bases derived from polyhydroxybenzenes of this invention enable the use of corrosion inhibitors with a wide range of vapour pressures effecting an extended service period of the substrate by the continual supply of vapours. In some instances, the reaction product with alkoxides, such as, B(OR) ₃ , is not easily hydrolysed but is an excellent corrosion inhibitor in the aqueous phase. The introduction of polyhydroxy acids and their derivatives such as gallic acid and its ester derivatives (propyl and lauryl gallate) is useful because of their oxygen scavenging capabilities. Both propyl and lauryl gallate would bond through the multiple hydroxy groups. To provide sufficient corrosion protection of metal surfaces it is preferable to have the vapour pressure in the range from 0.002 Pa to 2 Pa. The invention therefore provides for the corrosion inhibiting materials that are derived as stated above to release two or more vapour phase corrosion inhibitors of different molecular weight and volatility. The corrosion inhibitors with low volatility have low vapour pressure, whereas high volatility results in high vapour pressure. The low volatility inhibitors are included to effect a rapid inhibition of corrosion. The rapidity with which the volatile inhibitors are liberated is proportional to the concentration of water in the environment and their high volatility results in minimising the time lag between changes in corrosive conditions and the coverage of metal surface by the inhibitor that protects the metal from corrosion. The low vapour pressure components are essential to maintain this protection over a longer period.

It is to be emphasised that the invention provides for materials wherein the volatility can be varied within a family of chemically similar substances. Members of one family react with and are liberated from, for example, organo-metallic compounds in a similar fashion.

Unexpectedly, the highly volatile amino alcohol, N₁N dimethylethanolamine when allowed to react with titanium tetraisopropoxide formed a stable compound that was successfully incorporated into low-density polyethylene from which a film was blown. Upon hydrolysis, N, N dimethylethanolamine was released from a sample of the film as a vapour-phase corrosion inhibitor and prevented the corrosion of a metal surface.

In another embodiment, the corrosion inhibiting materials were formed in which both the Mannich base and the amino alcohol are covalently bonded to the metal centre of the organometallic compound. Thus, this invention provides mixed organo-metallic species as corrosion inhibiting materials (precursors) that can be easily incorporated into polyolefinic substrates and release simutaneously corrosion inhibitors of varying volatility. The amino alcohols include: 2- methylaminoethanol, 2-dimethylaminoethanol, 1-amino-2-propanol, 1 , 1¹-2-propanol,diethanolamine and triethanolamine. In still another embodiment the corrosion inhibiting material resulting from sequential chemical reactions of an organometallic compound with the Mannich base and the carboxylic acid such that both the Mannich base and carboxylic acid are covalently bonded to the metal centre of the organometallic compound. In this manner, corrosion-inhibiting volatile and unsaturated carboxylic acids such as frans-cinnamic acid, trans, frans-2,4-hexadienoic acid and trans,trans-λ ,3- butadiene-1 ,4-dicarboxylic acids can be efficiently incorporated into polyolefinic substrates. To prevent, the carboxylic acid from attaching to the tertiary N atom of the Mannich base, the reaction with the given organo-metallic conpound is carried out sequentially. The molar ratio of the Mannich base and carboxylic acid to the organo-metallic compound has to be such that allows both to bond to the metal centre.

Metal oxides From another aspect, the other reactant is a metal oxide, including: calcium oxide or zinc oxide. Corrosion inhibiting materials derived from the Mannich bases and the metal oxides are used as corrosion inhibiting additives in admixture with polyisobutene because of their tacky and adhesive properties. Application of such blends on tapes made from textiles or polymers as pipe-wraps provides good corrosion protection for metal surfaces.

Quaternerised Mannich bases

From another aspect the present invention discloses that the tertiary-N atoms of the Mannich bases may be easily converted to quaternary ammonium centres by reaction with inorganic acids, inorganic acid derivatives, or alkyl halides (e.g. HCI, HNO₂ , H₃ PO_4,, H₂ MoO₄ , H₂WO₄ , phosphonic acids, alkylphosphonic acids, RCI, where R may be alkyl ) giving rise to salts with the corresponding anions and through subsequent reactions the anions may be substituted by corrosion-inhibiting anions such as , for example, MoO₄ ^2' , Mo_xOy^2", NO₂ ^' . To confer polymer compatibility a longer-chain organic acid, alkyl halide or acid halide is attached to the remaining tertiary-N centre. The alkyl moiety may be straight-chained branched and/or unsaturated from C1-C20. For instance, the acids may be myristric, octanoic, propionic, isostearic, frans-cinnamic acid, frans, fra/7s-2,4-hexadienoic acid and trans,transA ,3-butadiene-1 ,4-dicarboxylic acid. Polyhydroxy acids such as gallic acid are useful as oxygen scavengers and were able to be incorporated into polyethylene through the use of these quatemerised Mannich bases. The reaction products such as those mentioned above provide a means of introducing corrosion imhibiting anions into polyolefinic substrates which in turn diffuse and migrate to the surface of the polymer together with the Mannich base.

Phenolic hvdroxyl group

From still another aspect, the present invention discloses reaction products, useful as corrosion inhibitors, obtained from the reaction between the phenolic hydroxyl group of the Mannich base and quaternary ammonium derivatives, metal cations and silanes containing reactive groups such as isocyanate or epoxy, for example, isocyanatopropyltrimethoxysilane or glycidoxypropyltrimethoxysilane. The quaternary ammonium group is selected from the following: alkyltrimethylammonium wherein the alkyl group is a C8 to C18-substituent; dialkyldimethylammonium wherein the alkyl groups are C8 to C18-substituent or a mixture of the above; alkyltrihydroxyethylammonium wherein the alkyl group is a C8 to C18-substituent. The quaternary ammonium phenolates of this invention are oil soluble and can be incorporated into hydrocarbon polymeric films such as polyethylene, polypropylene, polyisobutene or into hydrocarbon oils over a wide range of concentrations. Metal salts (e.g. Ca, Zn) of these Mannich bases that are involatile and stable to heat were incorporated into polyolefinic films or polyisobutenes (low- to high-molecular weight) whereupon with moisture the corrosion inhibiting Mannich bases are slowly released. Products from the reaction with silanes are useful for the protection of metals with additional bonding to the metal surface by establishment of metal-oxygen -silicon bonds. Alkaline earth metal cations as well as cations such as cerium (III) can be introduced into the aqueous phase through the phenolic hydroxyl group.

Admixtures

Protecting metal surfaces from corrosion in enclosures with polymeric materials requires that the corrosion inhibitors are both volatile and water soluble so that moisture condensing on the surface does not displace the inhibitors or hinder their bonding ability to the metal surface. In this regard, certain complementary substances with lesser volatility than the Mannich bases but good water solubility and inhibitive properties fulfil the need of protecting metals under extremely humid conditions.

From a further aspect it has been found that certain unsaturated conjugated acids or their salts and unsaturated conjugated aldehydes can be incorporated into polyolefinic films and used as aqueous- and/or vapour-phase corrosion inhibitors in the confined environment enclosing metallic articles. It has been found unexpectedly, that the calcium and potassium salts of fr-ans,frans-2,4-hexadienoic acid (sorbic acid salts) and frans,frans-2,4-hexadienoic acid (sorbic acid) were able to be incorporated into low-density polyethylene and utilised as aqueous- and/or vapour-phase corrosion inhibitors respectively. Potassium or calcium sorbate after incorporation into polyolefinic films was found to migrate or exude from the film and confer corrosion resistant properties to moisture surrounding the film.

Sorbic acid {trans, trans-2, 4-hexadienoic acid) was found to have sufficient vapour pressure at ca. 18-20° C to inhibit corrosion of a nail suspended in moist vapour. Contrary to the disclosures of the prior art, potassium sorbate at the same concentrations as for sorbic acid of this invention, displayed poor vapour-corrosion inhibition. A significant advantage of having sorbic acid or its salts as a complementary substance in admixture with Mannich bases or corrosion inhibitive materials is that it is non-toxic and is readily incorporated into polyolefinic substrates.

Admixtures of Mannich bases with unsaturated conjugated acids or their salts wherein the unsaturated conjugated acids are trans,trans -2, 4-hexadienoic acid (sorbic acd), trans,trans - 1 ,3-butadiene-1 ,4-dicarboxylic acid (muconic acid), cinnamic acid and their salts are either Ca, K or derivatives from aminoalcohols such as 2- methylaminoethanol, 2-dimethylaminoethanol, 1-amino-2-propanoi, 1 ,1¹- 2-propanol,diethanolamine and triethanolamine were also found to be complementary to the corrosion inhibitive properties of the Mannich bases and provide for a thorough corrosion inhibitive mixture.

Similarly, reaction products of Mannich bases with organo-metallic compounds can be formulated in admixtures with the acids described above. Other related conjugated systems such as the aldehydes trans, trans-2, 4-hexadienal transjrans -2,4-hepadienal, trans, fraπs-2,4-octanal and trans,trans- 2,4-nonadienal as well as fra/is-cinnamaldehyde, may also be incorporated into polyethylene for use as vapour-phase corrosion inhibitors as admixtures or be further modified by reaction with aminosilanes or epoxy silanes respectively, to afford materials that are exemplary aqueous corrosion inhibitors for metal surfaces. When aminopropyltriethoxysilane or 3-(2-aminoethylamino)propyltrimethoxysilane are allowed to react with the above-mentioned aldehydes Schiff bases were formed and found to be useful as inhibitors in aqueous fluids.

The previous discussion has dealt with corrosion inhibiting material derived from the Mannich bases and the other reactants. The following section discusses methods and techniques to incorporate previously described vapour phase corrosion inhibiting materials and admixtures into organic polymeric substrates and inorganic carriers

VPCI precursors bonded to inorganic carriers and grafted to organic polymeric substrates

For the purposes of better controlling the distribution, migration and release of VPCIs from the substrates into which they are incorporated, this invention provides:

1. the modification of inorganic substances by covalent bonding of VPCI precursors to inorganic metal oxide carriers such as silica, alumina, talc, mica, hydrotalcite or clay minerals such as montmorillonite or metakaolin from which VPCI can either be released by hydrolysis under neutral or alkaline conditions (pH 8-9); the modified substrates (or carriers) are useful as fillers for cement, epoxide, polyesters and acrylic coatings as well as for polyolefinic substrates and the like.

2. grafting of VPCI precursors, that contain unsaturated bonds, to polymers such as polyethylene vinyl alcohols (EVOH), low-, medium- and high- molecular-weight polyisobutene by radical polymerisation and their incorporation as composites into polyolefinic substrates such as polyethylene or polypropylene. 3. The modified substances or carriers are grafted to the organic polymers such as polyethylene vinyl alcohols (EVOH) through the use of unsaturated bonds present in the precursors and radical graft initiators; these composites are then incorporated into polyolefinic substrates. 4. the covalent bonding of VPCI precursors through the formation of metal- oxygen bonds to organic polymeric materials with abundant carboxylic acid and /or hydroxyl groups such as polyacrylic, polymethacrylic acids, polyvinyl alcohol (PVOH) and polyethylene vinyl alcohol (EVOH); these composites may then be incorporated into other organic polymers e.g. polyolefinic substrates or used as such to release VPCI on hydrolysis.

The present invention discloses the reaction of vapour-phase corrosion-inhibiting precursors (VPCI precursors) with active hydroxyl groups on various substrates such as zeolites, silica, alumina, talc, hydrotalcite and clays such as montmorillanite or metakaolin.

In the preferred embodiment the inorganic substrates are particulate carriers. In one example these particulate carriers comprise nano-particles. In another example, the nano-particles are attached to a microparticle. In the further example, the nano- particles and micro-particles of the particulate carrier are of differing chemical composition.

The corrosion inhibiting materials were made from the Mannich bases, amino alcohols, both saturated and unsaturated carboxylic acids and organometallic compounds (for example metal alkoxides, oxometal carboxylates) in varying ratios so that some reactive alkoxy groups of the organometallic compounds were free to interact with hydroxyl groups on the inorganic substrates forming covalent metal- oxygen bonds. These modified carriers were useful in enabling corrosion inhibitors to be incorporated into various composites such as cement, polyester, epoxide and acrylic coatings as well as polyolefinic substrates. Unsaturated acid groups allow the VPCI attached to the inorganic substrates as well as the VPCI themselves to be grafted to various polymeric substances, e. g. polyethylene vinyl alcohols (EVOH) and polyolefinic materials (polyethylene, polypropylene, polyisobutene), by radical polymerisation; these composites may be incorporated into other polymeric substrates. In this manner, the surface area for absorbing the VPCI is greatly increased and allows for a more controlled distribution, diffusion/migration and release of the vapour-phase corrosion inhibitors.

In the preferred embodiment the organo-metallic compounds comprise trialkyl borates with saturated and unsaturated substituents, tetraethylorthosilicate, aluminium triisopropoxide, oxoaluminium carboxylates and titanium tetraisopropoxide.

Graft polymers can be produced by activating the dissolved, suspended or melted polyolefinic polymer (e.g. polyethylene, polypropylene, polyisobutene or polyethylene vinyl alcohol (EVOH) with a radical initiator, adding either the corrosion inhibitor with ethylenically unsaturated carboxylic acid groups themselves or the corrosion inhibiting material that includes the corrosion inhibitors attached to the inorganic substrate. Examples of suitable ethylenically unsaturated carboxylic acids include acrylic, methacrylic, crotonic and frans-cinnamic acids. In some cases, the graft polymer from EVOH and VPCI, is added to a molten polyolefinic substrate in which was previously intermixed a natural or synthetic hydrotalcite.

The covalent bonding of VPCI through the formation of metal-oxygen bonds to carboxylic acid groups and /or hydroxyl groups of the polymers such as polyacrylic, polymethacrylic acids, polyvinyl alcohol (PVOH) and polyethylene vinyl alcohol (EVOH) affords composites; these composites are incorporated into other organic polymeric substances e.g. polyolefinic substrates or used as such to release VPCI on hydrolysis.

Dendrimers

The present invention provides novel dendrimers resulting from the reaction of Mannich bases derived from certain poly-hydroxyaromatic compounds ( such as hydroquinone, resorcinol or phloroglucinol (1 ,3,5-trihydroxybenzene)) with metallo- organic compounds (such as metal alkoxides, alkoxometal carboxylates, alkylmetal oxides, oxometal carboxylates or metal carboxylates, For example, Ti(OPr)₄ , Zr(OR)₄ , Sn(OR)₄ , Sn(OR)₂, R₂SnO, WO(OR)₄ , MoO(OR)₄ , H₂WO₄₁ H₂ MoO₄ , B(OR)₃ , B(OH)₃ , RB(OH)₂, P(OR)₃ , PO(OR)₃ , RPO(OH)₂, AI(O ¹Pr)₃, OALOOCR, Si(OR)₄, RSi(OR)₄,, where R is an alkyl substituent from C1-C20, straight, branched, saturated or unsaturated.

The dendrimers produced form the above materials are generally unstable under corrosion causing conditions. The dendrimers formed from some organo-metallic compounds (e.g. B(OR) ₃ , ) however, are not easily hydrolysed under neutral conditions and are good corrosion inhibitors in the aqueous phase. Thus, the present invention allows for various types of multi-functional Mannich base corrosion inhibitors to be incorporated into protective coatings as dendrimers, preferably at concentrations sufficient to inhibit corrosion without affecting the physical properties of the coating. Hydrolysis by hydroxide ion formed under corrosion causing conditions would allow the slow release of corrosion inhibiting Mannich bases and nano-sized metal hydroxides/oxides. The protective coatings may be any of the known types of protective coatings based on film forming polymers of resins, in particular, epoxy resins, vinyl resins or alkyd resins.

The physical and chemical properties of the highly branched macromolecules formed by successive reactions of these polyfunctional monomeric Mannich bases with metallo-organic derivatives depend on the initial core molecules and the subsequent number of iterative steps. For instance the 3^rd generation of dendritic Mannich base corrosion inhibitors with an initial core of phloroglucinol may have up to 12 peripheral boric acid moieties, whereas, the 3^rd generation of dendrimers with an initial core of boric acid may have up to 12 peripheral phioroglucinol Mannich bases groups. It is not necessary to bond with all the pendant hydroxyl groups on the periphery to form an effective corrosion inhibitive dendrimer. The peripheral hydroxyl groups may be allowed to react with such reactants as epoxy-or isocyanate-functionalised silanes, to give enhanced adhesion to metal surfaces. Interaction of the pendant hydroxyl groups with metallo-organic derivatives such as oxoalumimium carboxylates would provide compatibility with hydrocarbon polymers. Depending on the type of alkyl group in the dialkylaminomethyl groups of the Mannich base the secondary structure of the dendritic molecule could display either hydrophobic or hydrophilic behaviour.

The above-mentioned modifying reactions, described earlier involving the phenolic hydroxyl group and the tertiary N atoms of the dialkylaminoalkyl moiety of the Mannich bases apply to 1^st to n^th generation dendrimers produced from these bases and selected metallo-organic derivatives described above.

Application of Mannich bases in pipe wraps The present invention provides new cost-effective corrosion inhibiting material used to protect buried conduits made of iron, steel or concrete reinforced with steel by incorporating the corrosion inhibiting materials into a textile or polymer wrap that provides a conduit contacting layer with the corrosion-inhibiting material impregnated therein. The corrosion-inhibiting material may be selected from Mannich bases or their reaction products with organo-metallic compounds. The slow release of the corrosion-inhibiting Mannich bases is achieved by modifying the structure of the Mannich bases through the use of various amines, aldehydes or hydroxy aromatic compounds. For increased impact and tensile strength, high-density cross-laminated polyethylene (HDCLPE) provides an outer layer of the wrap whilst a low-density polyethylene allows the slow migration of the corrosion-inhibiting material towards the surface of the conduit. Usually, a layer of medium density polyethylene is interposed between the outer and inner later to prevent migration of the corrosion inhibiting materials away from the metal surface. The present invention also provides Mannich bases as well as other materials such as amino alcohols and carboxylic acids that are bound to organo-metallic compounds from which corrosion-inhibiting materials are released by hydrolysis after emerging from the bulk to the surface of the polymeric carrier. Diffusion or migration of the corrosion inhibiting materials including both Mannich bases and precursors made from

Mannich bases and organo-metallic compounds or other reactants depends heavily on the structure of the Mannich bases. The structure is related to the type of hydroxy aromatic hydrocarbons, amines and aldehydes that are utilised to prepare these Mannich bases.

Another significant advantage for such an application is that the VPCI is only produced in the presence of moisture so that its concentration is directly related to the danger of corrosion and useless losses can be readily prevented by hermetic storage prior to use as a corrosion inhibitor. Corrosion inhibiting materials derived from Mannich bases and metal oxides such as zinc oxide and calcium oxides have shown promise as corrosion inhibiting additives in admixture with polyisobutene because of their tacky and adhesive properties. Application of such blends on tapes made from textiles or polymers as pipe-wraps provides excellent corrosion protection for metal surfaces. Reaction products derived from the reaction of Mannich bases with carboxylic acid containing organo-metallic compounds such as oxoalumiuiumstearate can be conveniently dissolved in low-and medium-weight molecular polyisobutene, thus allowing an easy dosing of polymer melts with polyisobutene containing corrosion-inhibiting material during extrusion to produce films of polyethylene or polypropylene. Alternatively, the polymeric or plastic material can be extrusion or moulding feedstock, such as pellets or beads, as well as extruded or moulded plastic materials and products. Preferably, commonly available plastics are used, such as polyethylene, polypropylene, polyacrylate, polyester, nylon, ABS, etc. Generally, polyolefinic films will be most suitable.

Reaction products derived from the reaction of the Mannich bases with carboxylic acid containing organo-metallic compounds such as oxoalumiuiumstearate can be conveniently intermixed in low-and medium-weight molecular polyisobutene and applied as pipe wraps. Any moisture present at the metal surface will release the Mannich base corrosion inhibitor that is attached to the organometallic compound upon hydrolysis.

DESCRIPTION OF FIGURES

Figure 1 is a scheme depicting formation of chemical compounds of this invention.

Figure 2 shows a scheme depicting the formation, attachment to substrates and liberation of corrosion inhibitors of this invention. Figure 3 shows pathways for formation of Mannich base salts in accordance with the examples from 1 to 4 of the invention.

Figure 4 depicts a chemical structure of a dendrimer in accordance with the 39^th example of the invention

Figure 5 depicts a proposed chemical structure of a polymeric Mannich base prepared in accordance with the 40^th example of the invention.

Figure 6 depicts chemical structures and interactions in accordance with the 42^nd example of the invention.

Figure 7 depicts chemical structures and interactions in accordance with the 43^rd example of the invention. DESCRIPTION OF EXAMPLES

Having broadly portrayed the nature of the present invention, forty three particular examples will now be described by way of illustration to highlight the novelty and utility of the present invention but not with the intention of unduly limiting the scope of the invention.

Unless otherwise mentioned, the examples were prepared from a commercial source of Mannich base derivatives known as DMP-30 (Rohm & Haas) or Ancamine K54 (Air products & Chemicals). DMP-30 and Ancamine K54 have 2,4,6- tris(dimethylaminomethyl)phenol as the main component with lesser amounts of 2,6-bis(dimethylaminomethyl) phenol. A technical grade of DMP-30 containing 2,4,6-tris(dimethylaminomethyl)phenol with up to 30% of 2,6- bis(dimethylaminomethyl) phenol was used throughout in the present specification. Consequently, the average molecular weight was calculated as ca. 245. Examples 1 to 4 illustrate the preparation of ionic salts from 2, 4, 6- tris(dimethylaminomethyl)phenol and 2,6-bis(dimethylaminomethyl) phenol (DMP- 30), sodium molybdate and carboxylic acids. Examples 5 to 13 illustrate the preparation of metal complexes from metal alkoxides or oxymetal carboxylates with 2, 4, 6-tris(dimethylaminomethyl)phenol and 2,6-bis(dimethylaminomethyl) phenol (DMP-30). Examples 14 to 15 illustrate the reaction of various metal oxide/hydroxide substrates with 2, 4, 6-tris(dimethylaminomethyl) phenol and 2,6- bis(dimethylaminomethyl) phenol (DMP-30). Examples 16 to 17 illustrate the preparation of potassium sorbate, sorbic acid and DMP-30 reaction mixtures. Examples 18 to 20 illustrate the preparation of graft corrosion-inhibiting precursors. Example 21 illustrates the attachment of corrosion-inhibiting precursors to metal oxide particles. Example 22 illustrates an admixture of VPCI precursor and polyisobutene. Example 23 illustrates the preparation of corrosion-inhibitive adhesive with polyisobutene for a pipe-wrap. Examples 24 to 35 illustrate the preparation of Mannich bases from various polyhydroxy aromatic compounds and other miscellaneous reactions. Examples 36 to 38 illustrate the preparation of precursors from polyhydroxybenzene Mannich bases. Example 39 illustrates the preparation of a 3^rd generation dendrimer from boric acid and 2, 4, 6- tris(diethylaminomethyl)-1 ,3,5-trihydroxybenzene. Examples 40 to 41 illustrate the preparation of macro-cyclic Mannich bases. Examples 42 to 43 illustrate chemical techniques for attaching of the corrosion inhibitors to inorganic and organic substrates.

Example 1 To DMP-30 (2.45g, 0.01 mol) dissolved in distilled water (20 g) in a beaker was added cone. HCI (0.73g, ca. 2.0cm³ , 0.02mol, 31.5%HCI w/w). After stirring at room temperature, Na₂Moθ₄.2H₂O (2.41 g, 0.01 mol) was added to the solution and stirred at room temperature for 15 minutes. On the addition of myristic acid (2.3g, 0.01 mol) in ethanol to the above solution, a white precipitate formed, that was removed from the reaction mixture by filtration through a Buchner funnel and washed several times with distilled water to remove the NaCI by-product. After drying in air the product was yellow in colour.

Example 2

To DMP-30 (2.45g, 0.01 mol) dissolved in distilled water (20 g) in a beaker was added cone. HCI (0.73g, ca. 2.0 cm³ , 0.02mol, 31.5%HCI w/w). After stirring at room temperature, myristic acid (2.3g, 0.01 mol) in ethanol was added to the above solution. No precipitate formed at this stage. On the further addition of Na2MoO₄.2H₂O (2.41 g, 0.01 mol) a milky solution developed to give a white precipitate which on filtering and air-drying became yellow in colour.

Example 3

To DMP-30 (2.45g, 0.01 mol) dissolved in distilled water (20 g) in a beaker was added cone. H₃PO₄ (2.30 g, 1.4cm, 85%). After stirring at room temperature, myristic acid (2.3g, 0.01 mol) in ethanol was added to the above solution. No precipitate formed at this stage. On the further addition of Na₂MoO₄^H₂O (2.41 g, 0.01 mol) a milky solution developed to give a white precipitate which on filtering, washing and air-drying became yellow in colour.

Example 4

To DMP-30 (7.35g, 0.03mol) dissolved in distilled water (2Og) in a beaker was added cerium (III) nitrate hexahydrate (4.34g, 0.01 mol) and then sodium molybdate dihydrate (3.63g, 0.015mol). After stirring with myristic acid (6.Og, 0.03mol) a white precipitate formed that was filtered and washed with distilled water to remove the dissolved salts. Chemical reactions of the above four example are demonstrated in Fig. 3, which depicts schematically the pathways for the formation of Mannich base salts. The scheme shows the interaction of phosphoric acid with a Mannich Base to give a quaternary salt which is then further reacted with sodium molybdate and finally with a carboxylic acid to give a complex salt. The complex with the molybdate anion is incorporated into polymers and transported to the surface where it inhibits corrosion in presence of water.

Example 5 n-Octyltriethoxysilane (27.65g 0.01 mol) and DMP-30 (49.Og, 0.2mol) were heated at (150- 18O⁰C) for ca. 2 hours in a conical flask (500 cm³) under reflux in the presence of dibutyl tin dilaurate with the exclusion of moisture. The colour of the mixture changed from yellow to a dark red-brown during this time. In one test, the reaction product (1.Og) was added to water (10Og) in a glass jar. The product initially floated as an oily layer then slowly dispersed on hydrolysis to give a yellow solution. A nail suspended in the humid atmosphere above the solution as well as a nail immersed in the aqueous layer with the hydrolysed product remained visibly rust free after standing for 7 days at room temperature (20-30⁰C). The product was suitable for incorporation in polymeric and other substrates.

Example 6

Oxoaluminium octoate (18.6g, 0.1 mol) and DMP-30 (24.5g 0.1 mol) were allowed to react by heating briefly for 1 -2 minutes at 100⁰C and then cooled. In one test, the reaction product (1.Og) was added to water (10Og) in a glass jar. The product initially floated as an oily layer then slowly dispersed on hydrolysis to give a yellow solution and a white precipitate. A nail suspended in the humid atmosphere above the solution as well as a nail immersed in the aqueous layer with the hydrolysed product remained visibly rust free after standing for two months at room temperature (20-30⁰C). The product was suitable for incorporation in polymeric and other substrates.

Example 7

Titanium tetraisopropoxide (28.43g, 0.1 mol) and DMP-30 (49.Og, 0.2mol) were mixed together and an exothermic reaction occurred whilst the reaction mixture became dark red. The reaction product (1.Og) was dispersed in water (100g) in a glass jar with a lid. The product hydrolysed readily in water as evidenced by the fine white precipitate and yellow-coloured aqueous solution. A nail suspended in the humid atmosphere above the solution as well as a nail immersed in the aqueous layer with the hydrolysed product remained visibly rust free after standing for two months at room temperature (20-3O⁰C). The product was suitable for incorporation in polymeric and other substrates.

Example 8

Tetraethylorthosilicate (20.8g, 0.1 mol) and DMP-30 (49.Og, 0.2mol) were mixed in a conical flask (250cm³ ) and heated on a hot plate under reflux in the presence of dibutyl tin dilaurate (0.5g) with the exclusion of moisture for about 30-40 minutes. The reaction product (1.Og) was dispersed in water (10Og) in a glass jar with a lid. The product hydrolysed readily in water as evidenced by the fine white precipitate and yellow coloured aqueous solution. . A nail suspended in the humid atmosphere above the solution as well as a nail immersed in the aqueous layer with the hydrolysed product remained visibly rust free after standing for two months at room temperature (20-30⁰C). The product was suitable for incorporation in polymeric and other substrates. Example 9

Titanium tetraisopropoxide (28.43g, 0.1 mol) and N₁N dimethylethanolamine

(26.73g, 0.3moi) were heated up to 14O⁰C under reflux for 20 minutes. After this time the volatile material was allowed to escape by removing the condenser whilst the temperature remained at ca. 14O⁰C for about 1-5 minutes. This indicated that a heat-stable compound was formed between the ethanolamine and titanium alkoxide. The product was suitable for incorporation in polymeric and other substrates.

Example 10 Tetraethylorthosilicate (20.8g, 0.1 mol) and N,N-dimethylethanolamine (26.7g,

0.3mol) were heated under reflux in the presence of dibutyl tin dilaurate (0.5g) with the exclusion of moisture for about 30-40 minutes. The displaced ethanol was distilled at atmospheric pressure as the temperature of the reaction mixture reached 130° C and kept at this temperature for about 1-2 hours. To test the heat stability of the product the reaction mixture was heated briefly to 170° C and it was noted that the colour changed from straw yellow to a slightly darker yellow-orange. The product was suitable for incorporation in polymeric and other substrates.

Example 11

To boric acid (8g, 0.13mol) dissolved in ethanol (10cm³ ) was added DMP-30 (98.Og, 0.4mol) and the mixture was heated to 120° C and kept at this temperature for 15-20 minutes. On heating to 140° C the syrupy mixture became translucent with the complete dissolution of boric acid.

In one test, the reaction product (0.6g) was added to water (100g) in a glass jar at room temperature. The product initially floated then slowly dissolved to give a yellow solution. A nail suspended in the humid atmosphere above the solution became rusty after ca. 12h, whereas a nail immersed in the aqueous layer with the dissolved product remained visibly rust free after standing for two months at room temperature (20-30⁰C). The results show that the reaction product is not hydrolysed under the present conditions as evidenced by the rusting of the suspended nail. The product was suitable for incorporation in polymeric and other substrates.

Example 12

Oxoaluminium stearate (6Og, 184mmol in 100g hydrocarbon solution of white spirits) was allowed to react with DMP-30 (9Og, 368mmol) at room temperature {ca. 25° C) and then gradually heated to 110-120° C and kept at this temperature for about 10-20 minutes. The reaction product remained fluid and stable after heating without any thickening. . The product was suitable for incorporation in polymeric and other substrates.

Example 13

To titanium tetraisopropoxide (56.8g, 0.2mol) was added sequentially isostearic acid (56.8g, 0.2mol) and DMP-30 (98g, 0.4mol). The mixture was stirred and heated to 100 C in a beaker to allow the displaced isopropanol to volatise in the fume-hood. The reaction mixture remained stable after heating. The product was suitable for incorporation in polymeric and other substrates.

Example 14 To an excess of zinc oxide (8.1g, o.i mol) was added DMP-30 (24.5g, 0.1 mol) and acetic acid (0.14g) as catalyst. The mixture was heated and stirred in a beaker to about 170-180° C after which the colour changed from white to a pale yellow. If heated beyond 200° C a brown toffee-like substance results. A nail immersed in the aqueous layer with the hydrolysed product remained visibly rust free after standing for 7 days at room temperature (20-30°C).

Example 15

To an excess of calcium oxide (16.8g, 0.03mol) in a beaker was added DMP-30

(24.5g, 0.01 mol) and acetic acid (0.1 g). The mixture was heated to about 180- 19O⁰C and the colour of the reaction product changed from yellow to dark green. On cooling, the product remained malleable.

Example 16

Potassium sorbate (44.8g, 0.29mol), sorbic acid (44.8g, 0.40mol) and DMP-30

(49.Og, 0.2mol) were heated to caΛ 00-11O⁰C in an open beaker. A white soft material formed that was water soluble. A small sample of the reaction product (0.5g) was added to water (10Og) in a glass jar at room temperature. The product dissolved to give a colourless solution into which an abraded nail was immersed. The nail remained visibly rust free after standing for two months at room temperature 20-3O⁰C.

Example 17 Sorbic acid (44.8g, 0.40mol) dissolved in ethanol (ca. 25ml) and DMP-30 (49.Og,

0.20mol) were gradually heated in a beaker to about 100-110⁰ C. The ethanol evaporated to give an oil-like product. The reaction product (0.1 g) was added to water (100g) in a glass jar at room temperature. The product dissolved to give a colourless solution into which an abraded nail was immersed. The nail remained visibly rust free after standing for two months at room temperature 20-30⁰C. Preparation of graft corrosion-inhibitive precursors

Example 18

Freshly distilled aluminium isopropoxide (20.43g, 0.1 mol) was dissolved in dry hexane (5Og). Methacrylic acid (8.61 g, 0.1 mol) was dissolved in dry hexane (5Og) and added to the alkoxide solution over a period of about 15 minutes. After the addition, the mixture was stirred for an additional 10 minutes at room temperature (ca. 25OC). DMP-30 (49.0Og, 0.2 mol) was added to the above mixture and heated under reflux for about 30 minutes. The volatile substances were removed^' by vacuum distillation to afford the VPCI precursor that can be grafted to other polymeric substrates.

Example 19

Aluminium isopropoxide (20.43g, 0.1 mol) was dissolved in dry hexane (5Og).

Methacrylic acid (8.61 g, 0.1 mol) was dissolved in dry hexane (5Og) and added to the alkoxide solution over a period of about 15 minutes. After the addition, the mixture was stirred for an additional 10 minutes at room temperature {ca. 25⁰C). DMP-30 (24.5Og, 0.1 mol) was added to the above mixture and heated under reflux for about 30 minutes. The resultant VPCI precursor was added tolOOOg of dry hexane in a 2-1 beaker to which was added 50Og of hydrotalcite previously dried at 50-60⁰C and vigorously stirred. The dispersion was dried by rotary evaporation under vacuum to remove all volatile substances affording a modified hydrotalcite that was further dried in an oven at 50-60° C. The treated hydrotalcite can be added directly to melted polyolefinic substrates or grafted to such polymers as polyethylene vinyl alcohol (EVOH) in the presence of radical initiators.

Example 20 Triisopropyl borate (18.81 , 0.1 mol) was dissolved in dry hexane (5Og). Methacrylic acid (8.61 g, 0.1 mol) was dissolved in dry hexane (5Og) and added to the alkoxide solution over a period of about 15 minutes. After the addition, the mixture was stirred for an additional 10 minutes at room temperature (ca. 25°C). DMP-30 (49.0Og, 0.2 mol) was added to the above mixture and heated under reflux for about 30 minutes. The volatile substances were removed^' by vacuum distillation to afford the VPCI precursor that can be grafted to other polymeric substrates.

Example 21

Triisopropyl borate (18.81 , 0.1 mol) was dissolved in dry hexane (5Og). Methacrylic acid (8.61 g, 0.1 mol) was dissolved in dry hexane (5Og) and added to the alkoxide solution over a period of about 15 minutes. Methacrylic acid (8.61 g, 0.1 mol) was dissolved in dry hexane (5Og) and added to the alkoxide solution over a period of about 15 minutes. After the addition, the mixture was stirred for an additional 10 minutes at room temperature (ca. 25°C). DMP-30 (24.5Og, 0.1 mol) was added to the above mixture and heated under reflux for about 30 minutes. The resultant VPCI precursor was added to100Og of dry hexane in a 2-I beaker to which was added 50Og of hydrotalcite previously dried at 50-60⁰ C and vigorously stirred. The dispersion was dried by rotary evaporation under vacuum to remove all volatile substances affording a modified hydrotalcite that was further dried in an oven at 50- 60° C. The treated hydrotalcite can be added directly to melted polyolefinic substrates or grafted to such polymers as polyethylene vinyl alcohol (EVOH) in the presence of radical initiators

Polvisobutenes as carrier of VPCI precursors

Example 22 To titanium tetraisopropoxide (56.8g, 0.2mol) was added sequentially isostearic acid (56.8g, 0.2moi) and DMP-30 (98g, 0.4mol). The mixture was stirred and heated to 100 C in a beaker to allow the displaced isopropanol to volatilise in the fume-hood. The reaction mixture remained stable after heating. The product was incorporated into low-molecular weight polyisobutene whilst hot for ease of mixing. The mixture was easily incorporated into polyethylene during extrusion and the precursor was tested as a vapour-phase corrosion inhibitor and found to be highly effective.

Example 23

To an excess of zinc oxide (40.7g, O.δmol) was added DMP-30 (24.5g, 0.1 mol) and acetic acid (0.14g) as catalyst. The mixture was heated and stirred in a beaker to about 170-180° C after which time the colour changed from white to a pale yellow. If heated beyond 200° C a brown toffee-like substance results. The resultant viscous and tacky product was added to low-molecular-weight polyisobutene (20Og) that had been previously heated. The reaction product was miscible in polyisobutene affording a convenient vehicle by which corrosion inhibiting material can be introduced into a low-density polyethylene during extrusion to form thin films. The reaction product can also be applied to the surface of a textile material or other polymeric carrier to form a wrap for steel conduits.

Polyhydroxybenzene Mannich bases Example 24

To paraformaldehyde (6.Og, 0.2mol) dissolved in isopropanol (20cm³) was added diethylamine (14.6g, 20.7cm³, 0.2mol) and the mixture was heated under reflux for about 20 minutes until homogeneous. 4-Hydroxybenzoic acid (13.8g, 0.1 mol) in 30cm³ isopropanol was added to the mixture and the resultant solution heated under reflux for caΛ .0 hour. The volatile material was removed by distillation under vacuum to leave a liquid residue. The reaction product (1.Og) was dispersed in water (100g) in a glass jar with a lid. A nail suspended in the humid atmosphere above the solution corroded after standing overnight. A nail immersed in the aqueous layer with the reaction product remained visibly rust free after standing for one month at room temperature (20-30⁰C).

Example 25

To paraformaldehyde (6.Og, 0.2mol) dissolved in isopropanol (20cm³ ) was added diethylamine (14.6g, 20.7cm³, 0.2mol) and the mixture was heated under reflux for about 20 minutes until homogeneous. 2-Hydroxybenzoic acid (13.8g, 0.1 mol) or salicylic acid in 30 cm³ isopropanol was added to the mixture and the resultant solution heated under reflux for caΛ .0 hour. The volatile material was removed by distillation under vacuum to leave a liquid residue. The reaction product (1.0g) was dispersed in water (100g) in a glass jar with a lid. A nail immersed in the aqueous layer with the reaction product remained visibly rust free after standing for one month at room temperature (20-30⁰C).

Example 26

Aqueous formaldehyde (16.22g of 37%solution, 6.Og CH₂O, 0.2 mol) was added drop-wise to a mixture of hydroquinone (11.Og, 0.1 mol) and diethylamine (14.6g, 20.7cm³, 0.2mol). The mixture was stirred and maintained at about 30-4O⁰C for about 30 minutes. The reaction mixture was extracted with ether, dried, the ether evaporated to give the reaction product. The resultant reaction product (1.Og) was dispersed in water (100g) in a glass jar with a lid. A nail immersed in the aqueous layer with the reaction product remained visibly rust free after standing for two months at room temperature (20-30⁰C).

Example 27

Aqueous formaldehyde (32.4g of 37%solution, 12.Og CH₂O, 0.4 mol) was added drop-wise to a mixture of hydroquinone (11.Og, 0.1 mol) and diethylamine (29.2g, 41.4cm³, 0.4 mol). The mixture was stirred and maintained at about 30-40⁰C for about 30 minutes. The reaction mixture was extracted with ether, dried, the ether evaporated to give the reaction product. The resultant reaction product (1.Og) was dispersed in water (100g) in a glass jar with a lid. A nail immersed in the aqueous layer with the reaction product remained visibly rust free after standing for two months at room temperature (20-30⁰C). Example 28

Aqueous formaldehyde (16.22g of 37%solution, 6.Og CH₂O, 0.2mol) was added drop-wise to a mixture of hydroquinone (11.Og, O.i.mol) and dimethylamine (22.5g; 25.3cm³, 40%of aqueous solution, 0.2mol). The mixture was stirred and maintained at about 30-40⁰C for about 30 minutes. The reaction mixture was extracted with ether, dried, the ether evaporated to give the reaction product. The resultant reaction product (1.Og) was dispersed in water (100g) in a glass jar with a lid. A nail suspended in the humid atmosphere above the solution remained visibly rust free for 7days. A nail immersed in the aqueous layer with the reaction product remained visibly rust free after standing for two months at room temperature (20-30⁰C). Example 29

Aqueous formaldehyde (32.4g of 37%solution, 12.Og CH₂O, 0.4 mol) was added drop-wise to a mixture of hydroquinone (11.0g, 0.1 mol) and dimethylamine (45g; 50.7cm³, 40% aqueous solution, 0.4mol). The mixture was stirred and maintained at about 30-40⁰C for about 30 minutes. The reaction mixture was extracted with ether, dried, the ether evaporated to give the reaction product. The resultant reaction product (1.Og) was dispersed in water (100g) in a glass jar with a lid. A nail immersed in the aqueous layer with the reaction product remained visibly rust free after standing for two months at room temperature (20-30⁰C).

Example 30 To paraformaldehyde (9.Og, 0.3mol) dissolved in isopropanol (20cm³ ) was added diethylamine (21.9g, 31.0cm³, 0.3mol) and the mixture was heated under reflux for about 20 minutes until homogeneous. Resorcinol (11.Og, 0.1 mol) in 30 cm³ isopropanol was added to the mixture and the resultant solution heated under reflux for 1-2 hour. The volatile material was removed by distillation under vacuum to leave a liquid residue. The reaction product (1.Og) was dispersed in water (100g) in a glass jar with a lid. A nail suspended in the humid atmosphere above the solution remained visibly rust free for 7 days. A nail immersed in the aqueous layer with the reaction product remained visibly rust free after standing for two months at room temperature (20-30⁰C). Example 31

To paraformaldehyde (9.Og, 0.3mol) dissolved in isopropanol (20cm³) was added diethylamine (21.9g, 31.0cm³, 0.3mol) and the mixture was heated under reflux for about 20 minutes until homogeneous. 1 , 3, 5-trihydroxybenzene dihydrate (16.2g, 0.1 mol) in 30 cm³ isopropanol was added to the mixture and the resultant solution heated under reflux for 1-2 hour. The volatile material was removed by distillation under vacuum to leave a liquid residue. The reaction product (1.Og) was dispersed in water (100g) in a glass jar with a lid. A nail immersed in the aqueous layer with the reaction product remained visibly rust free after standing for two months at room temperature (20-30⁰C).

Example 32

To paraformaldehyde (6.Og, 0.2mol) dissolved in isopropanol (20cm³) was added diethylamine (14.6g, 20.7cm³, 0.2mol) and the mixture was heated under reflux for about 20 minutes until homogeneous. Gallic acid (17.Og, 0.1 mol) in 30cm³ isopropanol was added to the mixture and the resultant solution heated under reflux for 1 -2 hour. The volatile material was removed by distillation under vacuum to leave a liquid residue. The reaction product (1.0g) was dispersed in water (100g) in a glass jar with a lid. A nail immersed in the aqueous layer with the reaction product remained visibly rust free after standing for two months at room temperature (20- 3O⁰C).

Example 33

To paraformaldehyde (6.Og, 0.2mol) dissolved in isopropanol (20cm³) was added diethylamine (14.6g, 20.7cm³, 0.2mol) and the mixture was heated under reflux for about 20 minutes until homogeneous. Propyl gallate (21.2g, 0.1 mol) in isopropanol (50 cm³) was added to mixture and the resultant solution heated under reflux for 1 -2 hour. The volatile material was removed by distillation under vacuum to leave a liquid residue. The reaction product (1.0g) was dispersed in water (100g) in a glass jar with a lid. A nail immersed in the aqueous layer with the reaction product remained visibly rust free after standing for two months at room temperature (20- 3O⁰C).

Example 34

To paraformaldehyde (3.Og, 0.1 mol) dissolved in isopropanol (20cm³) was added diethylamine (7.3g, 10.4cm³, 0.1 mol) and the mixture was heated under reflux for about 20 minutes until homogeneous. Eugenol (16.4g, 0.1 mol) in 50 cm³ isopropanol was added to the mixture and the resultant solution heated under reflux for 1-2 hour. The volatile material was removed by distillation under vacuum to leave a liquid residue. The reaction product (1.Og) was dispersed in water (100g) in a glass jar with a lid. A nail suspended in the humid atmosphere remained visibly rust free for 3 days A nail immersed in with the reaction product remained visibly rust free after standing for two weeks at room temperature (20-30⁰C).

Example 35

Hydroquinone (5.5g, 0.25mol) was dissolved in about 20 cm ³ of an alcohol /water

(70%) mixture and diethanolamine (10.5g, O.δmol) was added with stirring during which time the solution was cooled to CaAS⁰C. A formaldehyde solution (40.6g, 37%; 15.Og, O.δmol, CH₂O) was added drop-wise with stirring over a period of 30 minutes and the solution was then stirred at room temperature for an additional hour. The volatile material was removed by distillation under vacuum to leave a syrupy residue. The reaction product was dispersed in water (100g) in a glass jar with a lid. A nail suspended in the humid atmosphere above the solution was covered in rust after standing over-night A nail immersed in the aqueous layer with the reaction product remained visibly rust free after standing for one month at room temperature (20-30⁰C).

Precursors from polvhvdroxybenzenes Example 36

Titanium tetraisopropoxide (2.84g, 0.01 mol) and the reaction product from Example

27 (4.48g, 0.02mol) were mixed together and an exothermic reaction occurred whilst the reaction mixture became dark red. An aliquot of the reaction product (2.Og) was dispersed in water (100g) in a glass jar with a lid. The product hydrolysed readily in water as evidenced by the fine white precipitate and yellow- coloured aqueous solution. A nail suspended in the humid atmosphere above the solution as well as a nail immersed in the aqueous layer with the hydrolysed product remained visibly rust free after standing for two weeks at room temperature (20-30⁰C). The product was suitable for incorporation in polymeric and other substrates.

Example 37

Oxoaluminium stearate (6.Og, 18.4mmol in 100g hydrocarbon solution of white spirits) was allowed to react with the reaction product from Example 27 (8.2g, 36.8mmol) at room temperature {ca. 25° C) and then gradually heated to 110-120° C and kept at this temperature for about 10-20 minutes. The reaction product remained fluid and stable after heating without any thickening. The product was suitable for incorporation in polymeric and other substrates.

Example 38

To an excess of zinc oxide (4g, 0.05 mol) was added the reaction product from example 27 (2.2g, 0.01 mol) and acetic acid (0.1 g) as catalyst. The mixture was heated and stirred in a beaker to about 170-180⁰C until water stopped evolving. The colour of the reaction mixture was observed to change from white to a pale yellow colour. A nail immersed in an aqueous solution with the hydrolysed product remained visibly rust free after standing for 7 days at room temperature (20-30⁰C).

Dendrimer preparation

Example 39

2,4,6-Tris(diethylaminomethyl)-1 ,3,5-trihydroxybenzene (11.4g, 0.03mol) from example 8 was added to boric acid (0.62g, 0.01 mol) and the mixture was heated to 100-110⁰C allowing the boric acid to react completely with the evolution of water. The addition of further amounts of boric acid (3.72g, O.Oδmol) was carried out over a period of ca. 20 minutes whilst the reaction temperature was maintained at 100- 11O⁰C. On completion of the reaction the 2^nd generation dendrimer was formed. The successive addition of 1 ,3,5-trihydroxybenzene Mannich base (22.8g, 0.06mol) afforded the 3^rd generation dendrimer after reaction had taken place with the pendant hydroxyl groups of the boric acid on the periphery. Structure of the resulting dendrimer is shown in Fig. 4. The dendrimer of this example comprises a core 1 , and three generations or shells numbered from 2 to 4. The core of this example is derived from B(OH)₃, but may also be derived from B(OR)₃.

Macrocvclic Mannich bases

Example 40

To paraformaldehyde (6.Og, 0.2mol) dissolved in isopropanol (20cm³) was added 1 ,3-hexahydropyrimidine (17.2g, 0.2mol) and the mixture was heated under reflux for about 20 minutes until homogeneous.4-Methylphenol (21.6g, 0.2mol) in 30cm³ isopropanol was added to the mixture and the resultant solution heated under reflux for caΛ .0 hour. The volatile material was removed by distillation under vacuum to leave a residue. The reaction product (1.0g) was dispersed in water (100g) in a glass jar with a lid. A nail suspended in the humid atmosphere above the solution corroded after standing overnight. A nail immersed in the aqueous layer with the reaction product remained visibly rust free after standing for one month at room temperature (20-30⁰C). Proposed chemical structure of the resulted product in shown in Fig. 5. This figure depicts a general representation of a polymeric Mannich base, where n>=3.

Example 41

To N,N'-bis(hydroxymethyl)1 ,3-hexahydropyrimidine(3.84g, 0.03mol) dissolved in isopropanol (20cm³) was added 4-methylphenol (3.24g, 0.3mol) and the mixture was heated under reflux for about 20 minutes until homogeneous.. The volatile material was removed by distillation under vacuum to leave a residue. The reaction product (1.Og) was dispersed in water (100g) in a glass jar with a lid. A nail immersed in the aqueous layer with the reaction product remained visibly rust free after standing for one month at room temperature (20-30⁰C).

Example 42 Chemical reactions of this example are illustrated in Fig 6, OM is an organometallic compound with unreacted alkoxy groups OR₁ where R is alkyl an moiety such as isopropyl, CA is a carboxylic acid, MB is a Mannich base. A corrosion inhibiting material derived from the organometallic compound, the carboxylic acid and the Mannich base reacts with a polymeric substrate (polyvinyl alcohol) containing hydroxyl groups, to afford a composite in which the Mannich base and carboxylic acid are attached to the polymer through metal-oxygen-carbon bonds. Upon hydrolysis the Mannich base and the carboxylic acid are liberated from the composite (not shown in the Fig.6).

Example 43 In this example, as illustrated in Fig. 7 a corrosion inhibiting material is attached to a particulate carrier (shaded area). The corrosion inhibiting material has two corrosion inhibitors, one of which is a Mannich Base attached to the carrier through an organometallic compound OM1 whereas the other is an amino alcohol attached to the carrier through the same organometallic compound OM1. In addition, a carboxylic acid (CA) with unsaturated carbon bonds is attached to the carrier through another organometallic compound OM2. The unsaturated bonds are available for further bonding with a polymeric substrate EVOH by radical graft initiators. The resulting composite is, therefore, (i) attached to the polymer through covalent carbon-carbon bond and (ii) is ready to liberate corrosion inhibitors in presence of humidity upon hydrolysis.

Claims

CLAIMS:

1 Corrosion inhibiting material resulting from a chemical reaction of a Mannich base with at least one reactant wherein: the Mannich base is derived from hydroxyaromatic compounds, secondary amines or cyclic secondary amines, and aldehydes, and the reactant is one of the following:

• organo-metallic compounds

• metal oxides

• carboxylic acids • inorganic acids, inorganic acid derivatives, alkyl halides

• organosilanes

• quartemary ammonium derivatives and metal derivatives

2 Corrosion inhibiting material according to claim 1 wherein the reactant is either an organo-metallic compound or a metal oxide and the Mannich base is bonded to the metal centre of said organometallic compound or said metal oxide as a nucleating ligand with or without other ligands such as amino alcohols and carboxylic acids.

3 Corrosion inhibiting material according to claim 2 wherein the organo-metallic compound is as follows: metal alkoxides and other metal derivatives such as, alkoxometal carboxylates, oxometal carboxylates or metal carboxylates, for example, Ti(OPr)₄ , Zr(OR)₄ , Sn(OR)₄ ,WO(OR)₄ , MoO(OR)₄ , H₂WO₄ , H₂ MoO₄ , B(OR)₃ , B(OH)₃ , RB(OH)₂, P(OR)₃ , PO(OR)₃ , RPO(OH)₂, AI(OI Pr)₃ , OAIOOCR, Si(OR)₄ ,RSi(OR)₄ where R is an alkyl substituent from C1 -C20, straight, branched, saturated or unsaturated.

4 A corrosion inhibiting material of claim 2 , wherein the metal oxide compounds include: calcium oxide or zinc oxide

5 A corrosion inhibiting material of claim 2 and 3 resulting from sequential chemical reactions of an organometallic compound with a Mannich base and an amino alcohol such that both the Mannich base and amino alcohol are covalently bonded to the metal centre of the said organometallic compound.

6 A corrosion inhibiting material of claim 1 and 3 resulting from sequential chemical reactions of an organometallic compound with a Mannich base and a carboxylic acid such that both the Mannich base and carboxylic acid are covalently bonded to the metal centre of the said organometallic compound. 7 Corrosion inhibiting material resulting from a chemical reaction between organo- metalic compounds of claim 3 and amino alcohols. 8 Corrosion inhibiting material resulting from a chemical reaction between organo- metalic compounds of claim 3 and carboxylic acids.

9 Corrosion inhibiting material of claim 8 wherein the carboxylic acids include: fra/7s-cinnamic acid, frans, fra/7s-2,4-hexadienoic acid and trans,trans~ 1 ,3- butadiene-1 ,4-dicarboxylic acid. 10 A corrosion inhibiting material of claim 1 resulting from sequential chemical reactions of a Mannich base, with the reactant wherein the reactant is selected from at least one carboxylic acid or alkyl halide together with an inorganic acid or inorganic acid derivatives or a mixture thereof such that the tertiary nitrogen atoms of the said Mannich base are quatemerised affording Mannich base salts with the corresponding anions

1 1 A corrosion inhibiting material of claim 10 wherein the carboxylic acid include : myristric, octanoic, propionic, isostearic, trans-cinnamic acid, trans,trans-2,4- hexadienoic acid and trans,trans-1 ,3-butadiene-1 ,4-dicarboxylic acid.

12 A corrosion inhibiting material of claim 10 wherein the alkyl halides (RCI) includes those in which R designates alkyl chains of length from C4 to C20 .

13 A corrosion inhibiting material of claim 10 wherein the inorganic acids and their derivatives include: HCI, HNO₂. H₃ PO₄, H₂MoO₄ , H₂WO₄ , phosphonic acids, alkylphosphonic acids.

14 A corrosion inhibiting material of claim 10 wherein the anions derived from theinorganic acids such as HCL or H₃PO₄ are substituted with corrosion- inhibiting anions such as MoO₄ ^2",Mo_xO_y ², NO₂ ^" .

15 A corrosion inhibiting material according to claim 10 wherein the carboxylic acid and alkyl halides have long-chain alkyl moieties either straight-chained, branched and/or unsaturated from C1 -C20 to confer compatibility with polyolefinic hydrocarbons.The carboxylic acids and derivatives include myristric, octanoic, propionic, isostearic, frans-cinnamic acid, trans,trans-2,4- hexadienoic acid and frans, fra/7s-1 ,3-butadiene-1 ,4-dicarboxylic acid

16 A corrosion inhibiting material according to claim 10 wherein to scavenge oxygen from the environment the carboxylic acid is gallic acid. 17 A corrosion inhibiting material of claim 1 resulting from a chemical reaction between the phenolic hydroxyl group of a Mannich base wherein the reactants are either organosilanes, quartemary ammonium derivatives or metal derivatives. 18 A corrosion inhibiting material of claim 17 wherein the said phenolic hydroxyl group reacts with a glycidoxy- functional group of glycidoxypropyltrimethoxysilane or an isocyanato functional group of isocyanatopropyltrimethoxysilane.

19 A corrosion inhibiting material of claim 17 resulting from a chemical reaction between the phenolic hydroxyl group of a Mannich base and quaternary ammonium derivatives, wherein the quaternary ammonium group is selected from the following: alkyltrimethylammonium wherein the alkyl group is a C8-C18- substituent; dialkyldimethylammonium wherein the alkyl group is a C8-C18- sustituent or a mixture of the above; alkyltrihydroxyethylammonium wherein the alkyl group is a C8-C18-substituent.

20 A corrosion inhibiting material of claim 17 resulting from a chemical reaction between the phenolic hydroxyl group of a Mannich base and a metal derivative such as calcium hydride to afford a metal salt that is involatile and stable to heat. 21 A modified corrosion inhibiting material resulting from an admixture of a corrosion inhibiting material of claim 1 and unsaturated conjugated acids or their salts wherein the unsaturated conjugated acids are trans,trans -2,4-hexadienoic acid (sorbic acd), trans,trans- 1 ,3-butadiene-1 ,4-dicarboxylic acid (muconic acid), cinnamic acid and their salts are either Ca, K or derivatives from aminoalcohols such as 2- methylaminoethanol, 2-dimethylaminoethanol, 1- amino-2-propanol, 1 ,1¹-2-propanol,diethanolamine and triethanolamine. 22 A corrosion inhibiting material according to claim 1-8, wherein the corrosion inhibiting material obtained from a reaction involving an organo-metallic compound is a precursor that releases a corrosion inhibitor by hydrolysis. 23 A corrosion inhibiting material according to claim 22, wherein the hydroxy aromatic compounds, secondary or cyclic secondary amines and aldehydes used for the derivation of the Mannich bases are selected to allow release of the corrosion inhibitor as vapour. A corrosion inhibiting material of claim 23, wherein the composition of hydroxy aromatic compounds, secondary or cyclic secondary amines and aldehydes used for derivation of Mannich bases is adjusted to provide for the vapour pressure to be in the range from 0.002 Pa to 2 Pa. A corrosion inhibiting material according to claim 23 wherein, the hydroxy aromatic compound used for the derivation of the Mannich base is a monohydroxy aromatic compound so that the resulting corrosion inhibiting vapour has a relatively high vapour pressure. A corrosion inhibiting material according to claim 25 wherein the monohydroxy aromatic compound is phenol. A corrosion inhibiting material according to claim 25 wherein the monohydroxy aromatic compound is a mono-cyclic six-membered-ring aromatic compounds having at least one hydroxy group in the ring with at least one other group in the ring being a carboxylic acid group, for example : 2-hydroxybenzoic acid (salicylic acid), 3-hydroxybenzoic acid and 4-hydroxybenzoic acid, 4- hydroxyallylbenzoate. A corrosion inhibiting material according to claim 27 wherein the carboxylic acid groups are further converted to an ester functional group with C1 to C8 carbon atoms that may be linear, branched, saturated or unsaturated, for example:.4- hydroxy allylbenzoate, 2- hydroxy methylbenzoate (methyl salicylate). A corrosion inhibiting material according to claim 25 wherein the monohydroxy aromatic compound is having at least one alkoxy and at least one alkyl group substituted in the ring; the alkyl and alkoxy groups may be saturated or unsaturated, linear or branched and contain from C1 -C20 carbon atoms (e.g. eugenol). A corrosion inhibiting material according to claim 25 wherein the monohydroxy aromatic compound is having at least one alkoxy group substituted in the ring; the alkoxy groups may be saturated or unsaturated, linear or branched and contain from C1-C20 carbon atoms such as in guaicol (2-methoxyphenol), 2- methoxyhydroquinone or 4-methoxyphenol. A corrosion inhibiting material according to claim 23 wherein, the hydroxy aromatic compound used for the derivation of the Mannich base is a polyhydroxy aromatic compound and the number of hydroxy groups in the polyhydroxy aromatic compound is selected to achieve a desirable vapour pressure of the resulting corrosion inhibiting vapour; the larger number of the hydroxy groups selected the lower the vapour pressure of the corrosion inhibiting vapour.

32 A corrosion inhibiting material according to claim 31 wherein, the polyhydroxy aromatic compound is having two hydroxy groups in the ring such as 1 ,2- dihydroxybenzene (catechol), 1 ,3-dihydroxybenzene (resorcinol) and 1 ,4- dihydroxybenzene (hydroquinone).

33 A corrosion inhibiting material according to claim 32 wherein the polyhydroxy aromatic compound is having two hydroxy groups (the dihydroxyaromatic compound) in the ring and at least one other group substituted in the ring being either an alkyl or carboxylic acid group.

34 A corrosion inhibiting material according to claim 33 wherein the alkyl groups may be linear, branched, saturated or unsaturated and containing from C1 to C20, such as 3,5-dihydroxytoluene (orcinol), 35 A corrosion inhibiting material according to claim 33 wherein the dihydroxyaromatic compound with one carboxylic acid group is, for example, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6 -dihydroxybenzoic acid(gentisic acid), 3,4-dihydroxybenzoic acid, 3,5- dihydroxybenzoic acid. 36 A corrosion inhibiting material according to claim 35 wherein the carboxylic acid group is further converted to an ester functional group with C1 to C8 carbon atoms that may be linear, brunched, saturated or unsaturated.

37 A corrosion inhibiting material according to claim 31 wherein, the polyhydroxy aromatic compound includes three hydroxy groups in the ring such as 1 ,2,3- trihydroxybenzene (pyrogallol),1 ,2,4- trihydroxybenzene (hydroxyhydroquinone),

1 ,3,5- trihydroxybenzene (phloroglucinol).

38 A corrosion inhibiting material according to claim 37 wherein the polyhydroxy aromatic compound is having three hydroxy groups in the ring and at least one other group substituted in the ring being carboxylic acid group, such as 3,4,5- trihydroxybenzoic acid (gallic acid), 2,3,4- trihydroxybenzoic acid and 2,4,6- trihydroxybenzoic acid.

39 A corrosion inhibiting material according to claim 22, wherein the secondary amines (e.g. dialkyl) used for the derivation of the Mannich bases include those with alkyl substituents on the nitrogen atom that can vary in length from C1 to C20 but preferably from C1 to C12 and are selected to be straight-chained, branched and/or unsaturated. A corrosion inhibiting material according to claim 22, wherein the cyclic secondary amines used for the derivation of the Mannich bases are either saturated or unsaturated in 5- or 6- membered rings, including , pyrrole, pyrrolidine, piperidine, piperazine, N-methylpiperazine, N- hydroxyethylpiperazine, N-isopropylhydroxylamine, N-methylhydroxylamine, imidazole, benzimidazole, morpholine, hexahydropyrimidine, tetrahydroimidazole, imidazolidenone, imidazolidenethione and also cyclic secondary amines in azamacrocyclic rings including 1 ,4,8, 1 1 - tetraazacyclotetradecane, 1 ,5,9,13-tetraazacyclohexadecane, 1 ,4,8,12-tetraazacyclopentadecane, 1 , 4,7,10-tetraazacyclododecane, 1 , 4, 7-triazacyclononane and cross-bridged 1 , 4, 7, 10- tetraazacyclododecane. A corrosion inhibiting material according to claim 39, wherein the length of the alkyl substituents attached to the nitrogen of the secondary amines (e.g dialkyl) is chosen to achieve a preselected vapour pressure of the resulting corrosion inhibiting vapour; the larger the size of the alkyl substituents group the lower the vapour pressure of the corrosion inhibiting vapour. A corrosion inhibiting material according to claim 39 wherein the alkyl substituents are selected from the following groups: methyl, ethyl, propyl, butyl, isopropyl, isobutyl, tert.-butyl, octyl, nonyl decyl, neodecyl, hexadecyl, allyl.;

A corrosion inhibiting material according to claim 23 wherein, the aldehydes used for the derivation of the Mannich base include: formaldehyde, metaldehyde, paraldehyde, glyoxal, acetaldehyde, acrylaldehyde, crotonaldehyde, isobutyraldehyde, alpha-methylacrylaldehyde, trans,trans-2,4- hexadienal, fra/?s,fraA7s-2,4-hepadienal,frans,ifra/?s- octadienal, trans,trans- nonadienal and frans-cinnamaldehyde A corrosion inhibiting material according to claim 43, wherein the length of the alkyl chain of the aldehyde is selected to achieve a desirable vapour pressure of the resulting corrosion inhibiting vapour; the longer the length of the alkyl chain the lower the vapour pressure of the corrosion -inhibiting vapour. 45 Corrosion inhibiting material of claim 1 wherein the reactant is the organometallic compound and the organometallic compound is also bonded to a particulate carrier.

46 Corrosion inhibiting material of claim 45 wherein the ratio of the Mannich base to the said organo-metallic compound is varied to allow undisplaced alkoxy groups of the said organo-metallic compound to interact with reactive hydroxyl groups of the particulate carriers forming covalent metal-oxygen bonds with the said carriers.

47 Corrosion inhibiting material according to claim 1 wherein the reactant is the organo-metallic compound and the Mannich base is bonded to the metal centre of the organometallic compound as a nucleating ligand with other ligands such as aminoalcohols and carboxylic acids.

48 Corrosion inhibiting material according to claim 47 wherein the organometallic compound is also bonded to a particulate carrier 49 Corrosion inhibiting material according to claim 45 or 48 , wherein the particulate carrier comprises particles of zeolites, silica, alumina, talc, hydrotalcite or clays such as montmorillanite or metakaolin. 50 Corrosion inhibiting material according to claim 49 wherein the said particles are nano-particles. 51 Corrosion inhibiting material according to claim 50 wherein the said nano- particle are attached to a micro-particle. 52 Corrosion inhibiting material according to claims 46 and 47 wherein the ratio of the Mannich base and ligands to the said organo-metallic compound is varied to allow the inclusion of both ethylenically unsaturated carboxylic acid moieties and undisplaced alkoxy groups of the said organo-metallic compound; interaction of the ethylenically unsaturated carboxylic acid moieties with a polyolefinic substrates affords covalent carbon-carbon bonds by radical grafting to polyolefinic substrates, whereas the undisplaced alkoxy groups allow bonding to a particulate carrier. 53 Corrosion inhibiting material according to claim 52 wherein the polyolefinic substrates include polyvinyl alcohol(PVOH) or polyethylene vinyl alcohol

(EVOH) 54 Corrosion inhibiting material according to claim 52 or wherein polyolefinic substrates include polyethylene or polypropylene Corrosion inhibiting material according to claim 47 wherein the ratio of the

Mannich base and ligands to the said organo-metallic compound is varied to allow the inclusion of ethylenically unsaturated carboxylic acid moieties of the said organo-metallic compound; interaction of the ethylenically unsaturated carboxylic acid moieties with a polyolefinic substrate affords covalent carbon- carbon bonds by radical grafting to polyolefinic substrates. Corrosion inhibiting material according to claim 47 wherein the ratio of the

Mannich base and ligands to the said organo-metallic compound is varied to allow undisplaced alkoxy groups of the said organo-metallic compound to interact with active hydroxyl groups on hydrophillic polymeric substrates forming covalent carbon-oxygen-metal bonds with the said substrates; the said substrate includes: polyacrylic and polymethacrylic acids, polyvinyl alcohol(PVOH) and polyethylene vinyl alcohol(EVOH). Corrosion inhibiting material comprising admixture of the corrosion inhibiting materials of claims 53, 55 and 56, and polyethylene or polypropylene. A corrosion inhibiting material of claim 1 , wherein the reactant is the organo- metallic compound; the corrosion inhibiting material is obtained as a dendrimer, comprising a core and shells oriented around the core; the shells include a number of interior shells and an exterior shell; the exterior shell comprises denditic branches having terminal groups available for addition or substitution reactions . A corrosion inhibiting material of claim 58 wherein the Mannich base is the core of the dendrimer. A corrosion inhibiting material of claim 58 wherein the organo-metallic compound is the core of the dendrimer. A corrosion inhibiting material of claim 58 wherein the terminal groups of the dendritic branches of the external shell are the phenolic hydroxyl functional groups of the Mannich base. A corrosion inhibiting material of claim 58 wherein the terminal groups of the dendritic branches of the external shell are the alkoxy groups of the organo- metallic compounds A corrosion inhibiting Mannich base dendrimer of claim 62 wherein the alkoxy groups are further attached to particles to form covalent metal-oxygen bonds 64 A corrosion inhibiting material of any of the preceding claims incorporated in corrosion protection substrates.

65 A corrosion protection substrate of claim 64, wherein the substrate is made of polyolefinic materials including polyethylene, polypropylene, polyisobutene and also from epoxy resin, or acrylic materials.

66 A corrosion inhibiting substrate of claim 64, wherein the substrate is paper, cardboard or textiles.

67 A corrosion inhibiting substrate of claim 64, wherein the substrate is made of cement. 68 A corrosion protecting substrate of claim 64, the substrate having bulk and surfaces and the corrosion inhibiting material is incorporated in the bulk and is allowed to migrate to the surfaces of the substrate, where the corrosion inhibiting material liberates corrosion inhibitors upon hydrolysis in the presence of humidity. 69 A corrosion protecting substrate of claims 64-68, wherein the substrate is dispensed as a flexible film.

70 The dendrimer of claim 58 with the core and the shells numbered from 1 to n, where 1- corresponds to the core, numbers from 2 to n-1 correspond to the inner shells and number n designates the outer shell, so that the dendrimer contains n elements wherein of any two consecutive elements one comprises the Mannich base and the other comprises the organo-metallic compound.

71 The dendrimer of claim 70 wherein the chemical composition of the Munnich base of the k-th element of the dendrimer varies from that of the (k+2) element of the dendrimer. 72 A modified corrosion inhibiting material resulting from an admixture of the corrosion inhibiting material of claim 1 and unsaturated conjugated aldehydes wherein the unsaturated conjugated aldehydes such as the aldehydes trans,trans-2,4-hexaό\ena\ trans,trans -2,4-hepadienal, trans, fra/7s-2,4-octanal and frans, fra/7S- 2,4-nonadienal as well as frans-cinnamaldehyde, are also incorporated into polyethylene for use as vapour-phase corrosion inhibitors as admixtures.

73 A modified corrosion inhibiting material resulting from an admixture of a corrosion inhibiting material of claim 1 and unsaturated conjugated aldehydes wherein the unsaturated conjugated aldehydes such as the aldehydes trans,trans-2,4-hexadienal trans,trans -2,4-hepadienal, trans,trans-2,4-octanal and trans.trans- 2,4-nonadienal as well as trans-cinnamaldehyde.

74 A modified corrosion inhibiting material of claim 73 wherein the material is further modified by reaction with aminosilanes or epoxy silanes respectively, to afford materials that are exemplary aqueous corrosion inhibitors for metal surfaces.

75 A modified corrosion inhibiting material of claim 74 wherein the further modification is conducted by allowing an aminopropyltriethoxysilane or 3-(2- aminoethylamino) propyltrimethoxysilane to react with the aldehydes Schiff bases.

76 Corrosion inhibiting material of claim 7 wherein the amino alcohols include:2- methylaminoethanol, 2-dimethylaminoethanol, 1-amino-2-propanol, 1 ,1¹-2- propanol.diethanolamine and triethanolamine.