US20130303635A1

US20130303635A1 - Oil-in-water emulsions

Info

Publication number: US20130303635A1
Application number: US13/976,305
Authority: US
Inventors: Wolfgang Gaschler
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2011-01-10
Filing date: 2012-01-09
Publication date: 2013-11-14
Also published as: JP2014503663A; CA2821380A1; CN103298999B; WO2012095393A1; EP2663689A1; BR112013016680A2; CN103298999A; EP2663689B1; ES2525942T3

Abstract

The invention relates to oil-in-water emulsions based on fatty alcohols and the use thereof as antifoams or deaerators for aqueous compositions. Such oil-in-water emulsions consist to at least 95% by weight of the following constituents:

a) 50 to 80% by weight, in particular 55 to 75% by weight and specifically 60 to 70% by weight, based on the total weight of the oil phase, of at least one alkanol having at least 16 carbon atoms, in particular having 16 to 20 carbon atoms, where the fraction of alcohols having 16 to 18 carbon atoms constitutes at least 80% by weight, in particular 90% by weight, specifically 95% by weight or at least 99%, based on the total amount of component A,
b) 1 to 10% by weight, in particular to 2 to 8% by weight, specifically 3 to 6% by weight, based on the total weight of the oil phase, of at least one further component B, which is selected from esters of C₁₂-C₃₆-alkanecarboxylic acids with polyglycerol and esters of C₁₂-C₃₆-alkanecarboxylic acids with C₁₂-C₃₆-alkanols, and mixtures thereof,
c) 10 to 49% by weight, in particular 20 to 40% by weight, specifically 25 to 35% by weight, based on the total weight of the oil phase, of at least one further component C, which is selected from organic substances which are liquid at 50° C. and 1013 mbar, at atmospheric pressure have a boiling point above 200° C., and at 25° C. and 1013 mbar have a solubility in water of less than 0.1 g/l.

Description

The invention relates to oil-in-water emulsions based on fatty alcohols and to the use thereof as antifoams or deaerators for aqueous compositions.
In numerous industrial processes, it is necessary to handle aqueous solutions and suspensions which have a tendency toward foam formation on account of their ingredients. This foam formation makes the process difficult to carry out and therefore has to be kept as low as possible or avoided altogether. Examples of foam-forming aqueous compositions are detergent-comprising compositions, saponin-comprising compositions, wastewater in water treatment plants, protein-comprising compositions such as soybean extracts and in particular paper stock suspensions, e.g. groundwood-and/or cellulose-comprising suspensions, as are used in particular in the paper industry for producing paper, board or cardboard.
Besides the formation of foam, which is permanently after-formed from coalescing air bubbles, the air incorporated in these systems, which is in a finely dispersed, stable form, also proves to be problematical. The reduction in the air content of these systems is therefore likewise of particular importance.
For these reasons, so-called antifoams and/or deaerators are added to the film-forming aqueous compositions during their processing and sometimes even during their production; these antifoams and/or deaerators, even at low use concentrations, suppress the undesired formation of foam, reduce the content of incorporated air or destroy foam which has already been produced.
The antifoams known from the prior art are often aqueous compositions based on oil-in-water dispersions or emulsions, the oil phase of which comprises at least one hydrophobic substance, for example mineral oils, silicone oils, polyalkylene oxides, esters thereof with fatty acids and ethers thereof with long-chain alcohols, native fats and/or oils, waxes, ester waxes or long-chain alcohols. Occasionally, the use of distillation residues which are formed during the production of long-chain alcohols in accordance with the Ziegler process or during oxo synthesis has also been reported (see e.g. EP-A 149812).
U.S. Pat. No. 4,950,420 discloses antifoams for the paper industry which comprise 10 to 90% by weight of a surface-active polyether, such as polyalkoxylated glycerol or polyalkoxylated sorbitol, and 10 to 90% by weight of a fatty acid ester of polyhydric alcohols, such as mono- and diesters of polyethylene glycol or polypropylene glycol.
EP-A 531713 and WO 94/08091 describe antifoams for the paper industry based on oil-in-water emulsions, the oil phases of which comprise alcohols, fatty acid esters, distillation residues, hydrocarbons in combination with polyglycerol esters.
DE 2157033 describes antifoams based on aqueous emulsions which comprise C₁₂-C₂₂-alkanols and/or C₁₂-C₂₂-fatty acid esters of di- to trihydric alcohols and paraffin oil or C₁₂-C₂₂-fatty acids.
Joshi et al. established in Colloids and Surfaces A: Physicochem. Eng. Aspects 263 (2005) 239-249 that the effectiveness of an antifoam based on fatty alcohol depends on its aggregate state. The effectiveness is highest if it is partly molten. This gives rise in the specialist field to the requirement to use mixtures of fatty acid alcohols which, being mixtures, have a broader melting range than pure substances.
In the prior art, the effectiveness of an antifoam is often measured by its ability to suppress foam formation at a liquid surface. Particularly in papermaking, however, it is also of importance to reduce the air content in the aqueous liquids produced during papermaking, particularly in the paper stock suspensions. Antifoams which are likewise able to act as deaerators are not often described in the prior art. The known antifoams often leave something to be desired with regard to the deaerating effect, particularly at temperatures below 50° C., e.g. in the range from 20 to <50° C.
The object of the present invention is to provide compositions which have high effectiveness both as antifoam and also as deaerator for aqueous compositions, in particular for aqueous paper stock suspensions.
These and other objects are achieved by oil-in-water emulsions, the oil phase of which consists to at least 95% by weight of the following constituents:

a) 50 to 80% by weight, in particular 55 to 75% by weight and specifically 60 to 70% by weight, based on the total weight of the oil phase, of at least one alkanol having at least 16 carbon atoms, in particular having 16 to 20 carbon atoms, where the fraction of alkanols having 16 to 18 carbon atoms constitutes at least 80% by weight, in particular at least 90% by weight, specifically at least 95% by weight or at least 99%, based on the total amount of component A,
b) 1 to 10% by weight, in particular 2 to 8% by weight, specifically 3 to 6% by weight, based on the total weight of the oil phase, of at least one further component B, which is selected from esters of C₁₂-C₃₆-alkanecarboxylic acids with polyglycerol and esters of C₁₂-C₃₆-alkanecarboxylic acids with C₁₂-C₃₆-alkanols, and mixtures thereof,
c) 10 to 49% by weight, in particular 20 to 40% by weight, specifically 25 to 35% by weight, based on the total weight of the oil phase, of at least one further component C, which is selected from organic substances which are liquid at 50° C. and 1013 mbar, at atmospheric pressure have a boiling point above 200° C., and at 25° C. and 1013 mbar have a solubility in water of less than 0.1 g/l.

Component A consists in particular of essentially unbranched alkanols having at least 16, in particular 16 to 20, carbon atoms, i.e. saturated alcohols having at least 16, in particular 16 to 20, carbon atoms, in which the fraction of alcohols having 16 to 18 carbon atoms constitutes at least 80% by weight, in particular at least 90% by weight, specifically at least 95% by weight or at least 99%, based on the total amount of component A, and which are linear to at least 80%, in particular at least 90% and specifically at least 95%. Such linear alkanols can be described by the following formula:
H—(CH₂)_n—OH
in which n is an integer of at least 16 and in particular is in the range from 16 to 20. The fraction of alkanols, in particular linear alkanols having 16 to 18 carbon atoms, in particular having 16 or 18 carbon atoms, is according to the invention at least 80% by weight, in particular at least 90% by weight, specifically at least 95% by weight or at least 99% by weight, based on the total weight of component A. Examples of alcohols suitable as component A are palmityl alcohol (cetyl alcohol), 1-heptadecanol, stearyl alcohol, arachyl alcohol (n-eicosanol), behenyl alcohol and mixtures thereof. Preferably, component A consists to at least 80%, in particular at least 90% and specifically at least 95%, of palmityl alcohol, stearyl alcohol or mixtures thereof.
According to the invention, component A comprises less than 20% by weight, based on component A, of alcohols having more than 18 carbon atoms. Preferably, component A comprises less than 10% by weight, in particular less than 5% by weight, specifically less than 1% by weight or less than 0.5% by weight, based on component A, of alcohols having more than 18 carbon atoms.
In a likewise preferred embodiment, palmityl alcohol or stearyl alcohol or a mixture of these alcohols is used as component A whereas component A is free (less than 0.5% by weight, based on component A) from alcohols having more than 18 carbon atoms.
According to the invention, the fraction of component A in the oil phase is 50 to 80% by weight, preferably 55 to 75% by weight, in particular 60 to 70% by weight, based on the total weight of the oil phase.
Component B is selected from esters of alkanecarboxylic acids with polyglycerol, esters of alkanecarboxylic acids with alkanols and mixtures thereof.
Esters of alkanecarboxylic acids with polyglycerol are understood as meaning a polyglycerol esterified with at least one fatty acid which has 12 to 36, in particular 16 to 30, specifically 18 to 24, carbon atoms. The fatty acids contemplated for the esterification of the polyglycerol may either be saturated fatty acids or unsaturated fatty acids and mixtures thereof. Fatty acids suitable for the esterification of the polyglycerol mixtures are preferably selected from saturated fatty acids having 12 to 36, in particular 16 to 30, specifically 18 to 24, carbon atoms. Examples of suitable saturated fatty acids are lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, behenic acid and montan wax acid. Examples of suitable unsaturated fatty acids are oleic acid, hexadecanoic acids, elaidic acid, eicosenoic acids and docosenoic acids such as erucic acid or brassidic acid, and also polyunsaturated acids, such as octadecenedienoic acids and octatrienoic acids, such as linoleic acid and linolenic acid, and mixtures of the specified saturated and unsaturated carboxylic acids. Preferably, the polyglycerol is esterified with saturated carboxylic acids having 18 to 24 carbon atoms, which are selected in particular from palmitic acid, stearic acid and behenic acid and mixtures thereof. In a specific embodiment, the polyglycerol ester is a polyglycerol esterified with behenic acid.
The degree of esterification of the polyglycerol esters is generally 20 to 100%, preferably 60 to 100%, based on the number of hydroxyl functions in the polyglycerol.
Preferred polyglycerol esters are in particular those which are obtainable by esterifying polyglycerol mixtures which comprise 15 to 40% by weight of diglycerol, 30 to 55% by weight of triglycerol and 10 to 25% by weight of tetraglycerol, in each case based on the total amount of the polyglycerol, where the total amount of di-, tri- and tetraglycerol constitutes at least 60% by weight, in particular at least 80% by weight. In particular, mixtures with the following composition are used for the esterification:
0 to 10% by weight of glycerol,
15 to 40% by weight of diglycerol,
30 to 55% by weight of triglycerol,
10 to 25% by weight of tetraglycerol,
0 to 15% by weight of pentaglycerol,
0 to 10% by weight of hexaglycerol and
0 to 5% by weight of more highly condensed polyglycerols.
In particular, the polyglycerol esters are those which are obtainable by esterifying one of the polyglycerol mixtures described above with at least one saturated carboxylic acid having 18 to 24 carbon atoms, the carboxylic acid being selected in particular from palmitic acid, stearic acid and behenic acid and mixtures thereof.
In the compositions according to the invention, particular preference is given to those polyglycerol esters which are obtainable by esterifying behenic acid with a polyglycerol mixture which consists of 0 to 10% by weight of glycerol, 15 to 40% by weight of diglycerol, 30 to 55% by weight of triglycerol, 10 to 25% by weight of tetraglycerol, 0 to 15% by weight of pentaglycerol, 0 to 10% by weight of hexaglycerol and 0 to 5% by weight of more highly condensed polyglycerols.
The polyglycerol mixtures used for the esterification are accessible for example by alkaline catalyzed condensation of glycerol at elevated temperatures (cf. e.g. Fette, Seifen, Anstrichmittel, 88th volume, No. 3, pages 101 to 106 (1986)) or as in DE-A 3842692 by reaction of glycerol with epichlorohydrin in the presence of acidic catalysts at elevated temperatures. However, the mixtures are also obtainable by mixing together the pure polyglycerol components, e.g. diglycerol, triglycerol and tetraglycerol.
The polyglycerols esterified with alkanecarboxylic acids are known, e.g. from EP 531713 and WO 94/08091. They are typically prepared by esterification of polyglycerol, in particular by esterification of the polyglycerol mixtures described above, with the desired fatty acid or mixture of fatty acids or ester-forming derivatives thereof, e.g. C₁-C₄-alkyl esters thereof, by methods known per se. As a rule, the procedure is carried out in the presence of an acidic esterification catalyst such as sulfuric acid, p-toluenesulfonic acid, citric acid, phosphorous acid, phosphoric acid, hypophosphorous acid or basic catalysts, such as sodium methylate or potassium tert-butylate.
Further suitable as component B are esters of C₁₂-C₃₆-alkanecarboxylic acids with C₁₂-C₃₆-alkanols. They are understood to include substances which are obtainable by esterification of at least one, preferably saturated, mono- to dibasic, preferably monobasic, alkanecarboxylic acid having 12 to 36, in particular 16 to 30, specifically 18 to 24, carbon atoms with a C₁₂-C₃₆-alkanol. The alkanols suitable for the esterification are preferably saturated, linear and mono- to dihydric, in particular monohydric. They have 12 to 36, in particular 16 to 30, specifically 18 to 24, carbon atoms. It is also possible to use mixtures of alkyl esters of alkanoic acids. Suitable examples of alkyl esters of alkanoic acids are palmityl palmitate, stearyl stearate, arachyl arachate, behenyl behenate and lignoceryl lignocerate. Preferred esters of C₁₂-C₃₆-alkanecarboxylic acids with C₁₂-C₃₆-alkanols are behenyl behenate and stearyl stearate and mixtures thereof.
In one preferred embodiment, component B comprises at least one of the above-described esters of alkanecarboxylic acids with polyglycerol (also referred to below as polyglycerol esters), in particular at least one of the polyglycerol esters stated as being preferred or particularly preferred. In one preferred embodiment, component B comprises at least one of the above-described polyglycerol esters which is obtainable by esterification of the above-described polyglycerol with at least one saturated carboxylic acid having 18 to 24 carbon atoms, where the carboxylic acid is selected in particular from palmitic acid, stearic acid and behenic acid and mixtures thereof. In one particularly preferred embodiment, component B comprises at least one of the above-described polyglycerol esters which is obtainable by esterification of behenic acid with a polyglycerol mixture consisting of 0 to 10% by weight of glycerol, 15 to 40% by weight of diglycerol, 30 to 55% by weight of triglycerol, 10 to 25% by weight of tetraglycerol, 0 to 15% by weight of pentaglycerol, 0 to 10% by weight of hexaglycerol and 0 to 5% by weight of more highly condensed polyglycerols.
In one preferred embodiment, component B consists to at least 80% by weight, in particular to at least 90% by weight, specifically to at least 95% by weight, based on the total weight of component B, or exclusively of at least one of the above-described polyglycerol esters, in particular at least one of the polyglycerol esters stated as being preferred or particularly preferred. In one particularly preferred embodiment, component B consists to at least 80% by weight, in particular to at least 90% by weight, specifically to at least 95% by weight, based on the total weight of component B, or exclusively of at least one of the above-described polyglycerol esters which is obtainable by esterification of the above-described polyglycerol with at least one saturated carboxylic acid having 18 to 24 carbon atoms, where the carboxylic acid is selected in particular from palmitic acid, stearic acid and behenic acid and mixtures thereof. In one particularly preferred embodiment, component B consists to at least 80% by weight, in particular to at least 90% by weight, specifically to at least 95% by weight, based on the total weight of component B, or exclusively of at least one of the above-described polyglycerol esters which is obtainable by esterification of behenic acid with a polyglycerol mixture consisting of 0 to 10% by weight of glycerol, 15 to 40% by weight of diglycerol, 30 to 55% by weight of triglycerol, 10 to 25% by weight of tetraglycerol, 0 to 15% by weight of pentaglycerol, 0 to 10% by weight of hexaglycerol and 0 to 5% by weight of more highly condensed polyglycerols.
According to the invention, the fraction of component B in the oil phase is 1 to 10% by weight, preferably 2 to 8% by weight, in particular 3 to 6% by weight, based on the total weight of the oil phase.
Component C present in the oil-in-water emulsions according to the invention is one or more organic substances which are liquid at 50° C. and 1013 mbar, at atmospheric pressure have a boiling point above 200° C., e.g. in the range from 200 to 400° C., in particular of at least 250° C., and which at 25° C. and 1013 mbar are essentially insoluble in water, i.e. have a solubility in water of less than 0.1 g/l. Suitable substances are hydrocarbons and triglycerides of fatty acids, in particular those having 12 to 22 carbon atoms. Component C preferably consists to at least 80% by weight, in particular 90% by weight, specifically 95% by weight, based on the total weight of component C, of one or more hydrocarbons, which are in particular nonaromatic, i.e. aliphatic or cycloaliphatic, and have a boiling point of at least 200° C., preferably at least 250° C., e.g. in the range from 200 to 400° C. or 250 to 400° C. at 1.013 bar, such as, for example, liquid paraffins, white oils, soft paraffins or other standard commercial mineral oils.
According to the invention, the fraction of component C in the oil phase is 10 to 49% by weight, preferably 20 to 40, in particular 25 to 35% by weight, based on the total weight of the oil phase.
To stabilize the oil phase in the aqueous emulsion, the emulsions according to the invention advantageously comprise at least one surface-active substance. The emulsions according to the invention comprise the at least one surface-active substance generally in an amount from 0.1 to 10% by weight, in particular in an amount from 0.5 to 5% by weight, based on the oil phase.
Suitable surface-active substances are, in principle, all substances known for the stabilization of hydrophobic particles or droplets in aqueous systems, e.g. anionic, cationic, amphoteric and/or nonionic emulsifiers, and also water-soluble ionic and nonionic polymers, preferably ionically amphiphilic copolymers which have cationic or anionic groups and whose molecular weight, in contrast to the emulsifiers, is usually above 1000 daltons. Surface-active substances are sufficiently known to the person skilled in the art, e.g. from Ullmann's Encyclopedia of Industrial Chemistry, 5th ed. vol. A9, pp. 297-339.

Examples of Suitable Anionic Emulsifiers are

salts, in particular sodium and ammonium salts, of higher fatty acids,
salts, in particular the sodium and ammonium salts, of sulfated ethoxylation products of C₆-C₂₂-alkylphenols, such as nonylphenol or octylphenol,
salts, in particular the sodium and ammonium salts, of C₄-C₂₂-alkylarylsulfonates,
salts, in particular the sodium and ammonium salts, of sulfonates of naphthalene,
salts, in particular the sodium and ammonium salts, of sulfonated C₈-C₂₂-alkyldiphenyl oxides, in particular of bis-sulfonated C₈-C₂₂-alkyldiphenyl oxides, such as bis-sulfonated dodecyldiphenyl oxide,
salts, in particular the sodium and ammonium salts, of naphthalenesulfonic acid-formaldehyde condensates or naphthalenesulfonic acid-formaldehyde-urea condensates,
and also salts, in particular the sodium and ammonium salts, of di-C₄-C₂₀-alkyl sulfosuccinates.

Examples of Suitable Nonionic Emulsifiers are:

alkoxylated C₆-C₂₂-alkylphenols with a degree of ethoxylation of preferably in the range from 5 to 50,
ethoxylated unsaturated oils such as reaction products of castor oil with 30 to 40 mol equivalents of ethylene oxide, and
adduct formation products of ethylene oxide and/or propylene oxide with aliphatic alcohols having as a rule 12 to 20 carbon atoms, e.g. with fatty alcohols, with polyhydric alcohols, with amines, and also with carboxylic acids.
The emulsions according to the invention preferably comprise at least one emulsifier, in particular at least one anionic emulsifier in an amount of from 0.1 to 10% by weight, in particular in an amount of from 0.5 to 5% by weight, based on the oil phase. In one specific embodiment, the emulsions according to the invention comprise at least one anionic emulsifier selected from the salts, in particular the sodium and ammonium salts, of sulfated ethoxylation products of C₆-C₂₂-alkylphenols.
Examples of surface-active anionic polymers are homopolymers of acrylic acid, homopolymers of methacrylic acid, copolymers of acrylic acid and methacrylic acid in any desired molar ratio, copolymers of acrylic acid and maleic acid in any desired molar ratio, copolymers of methacrylic acid and maleic acid, polyvinylsulfonic acid, polyacrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, copolymers of acrylic acid and acrylamide or methacrylamide, copolymers of methacrylic acid and acrylamide or methacrylamide, or the alkali metal and ammonium salts of the specified polymers with molar masses of, for example, 1500 to 300 000.
Preferred anionic surface-active polymers are amphiphilic copolymers comprising acid groups and comprising, in copolymerized form,

(a) hydrophobic monoethylenically unsaturated monomers and
(b) monoethylenically unsaturated carboxylic acids, monoethylenically unsaturated sulfonic acids, monoethylenically unsaturated phosphonic acids or mixtures thereof,
and optionally monomers (c) different therefrom, and also the salts, in particular the sodium and the ammonium salts, of such copolymers.

Examples of hydrophobic monoethylenically unsaturated monomers are: styrene, methylstyrene, ethylstyrene, acrylonitrile, methacrylonitrile, C₂- to C₁₈-olefins, esters of monoethylenically unsaturated C₃- to C₅-carboxylic acids and monohydric alcohols, vinyl alkyl ethers, vinyl esters or mixtures thereof. From this group of monomers, preference is given to using isobutene, diisobutene, styrene and acrylic acid esters such as ethyl acrylate, isopropyl acrylate, n-butyl acrylate and sec-butyl acrylate.
Examples of monomers (b) are: acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, vinylsulfonic acid, 2-acrylamidomethylpropane-sulfonic acid, acrylamidopropane-3-sulfonic acid, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate, styrenesulfonic acid, vinylphosphonic acid or mixtures thereof, with preference being given to acrylic acid, methacrylic acid and maleic acid and also their anhydride.
The molar mass of the amphiphilic copolymers is generally 1000 to 100 000 and is preferably in the range from 1500 to 10 000. The acid numbers of the anionic amphiphilic copolymers are generally 50 to 500, preferably 150 to 350 mg of KOH/g of polymer.
Suitable surface-active polymers for stabilizing the compositions according to the invention are also:

- graft polymers of 5 to 40 parts by weight of N-vinylformamide per 100 parts by weight of a polyalkylene glycol with a molar mass of from 500 to 10 000,
- zwitterionic polyalkylenepolyamines,
- zwitterionic polyethyleneimines,
- zwitterionic polyetherpolyamines or
- zwitterionic crosslinked polyalkylenepolyamines.

Graft polymers of N-vinylformamide on polyalkylene glycols are described, for example, in WO-A-96/34903. The grafted-on vinylformamide units may optionally be up to 10% hydrolyzed. The fraction of grafted-on vinylformamide units is preferably 20 to 40% by weight, based on polyalkylene glycol. Preference is given to using polyethylene glycols with molar masses of from 2000 to 10 000.
Zwitterionic polyalkylenepolyamines and zwitterionic polyethyleneimines are known, for example, from EP-B 112592. Such compounds are obtainable, for example, by firstly alkoxylating a polyalkylenepolyamine or polyethyleneimine, e.g. with ethylene oxide, propylene oxide, and/or butylene oxide, and then quaternizing the alkoxylation products, e.g. with methyl bromide or dimethyl sulfate, and then sulfating the quaternized alkoxylated products with chlorosulfonic acid or sulfur trioxide. The molar mass of the zwitterionic polyalkylenepolyamines is, for example, 1000 to 9000, preferably 1500 to 7500. The zwitterionic polyethyleneimines preferably have molar masses in the range from 2000 to 1700 daltons.
The compositions according to the invention preferably comprise at least one anionic surface-active substance. This is preferably selected from the aforementioned anionic emulsifiers, the aforementioned acid-carrying, water-soluble polymers and mixtures thereof.
For the stability of the emulsions according to the invention, it has proven advantageous if they comprise 0.05 to 8% by weight, in particular 0.1 to 5% by weight, based on the oil phase, of at least one acid-having water-soluble homo- or copolymer, preferably of a salt thereof and optionally at least one anionic emulsifier. The emulsifiers are preferably likewise used in an amount of from 0.05 to 5% by weight, based on the total weight of the oil phase. In particular, those emulsions which comprise at least one anionic emulsifier and at least one of the aforementioned acid-carrying water-soluble polymers are advantageous.
Besides the oil phase, the emulsions according to the invention can comprise, as further disperse constituent, finely divided, virtually water-insoluble, inert solids with particle sizes (weight-average particle diameter) below 20 μm, preferably in the range from 0.1 to 10 μm. If desired, the emulsion according to the invention comprises these further inert solids in an amount of, for example, 0.1 to 50% by weight, preferably 1 to 35% by weight, based on the weight of the oil phase of the oil-in-water emulsions. Suitable inert solids are in particular inorganic solids such as e.g. kaolin, chalk, bentonite, talc, barium sulfate, silicon dioxide, zeolites, but also organic solids such as urea-formaldehyde pigments, melamine-formaldehyde pigments and microcrystalline cellulose, where the inert inorganic solids may also be hydrophobized, e.g. by treatment with trialkylsilyl halides. In contrast to the oil phase, these inert solids are solid at a temperature of 100° C. In one preferred embodiment of the invention, the emulsions comprise no finely divided, virtually water-insoluble, inert solids different from components A, B and C.
As a rule, the solids content of the oil-in-water emulsion according to the invention is in a range from 10 to 50% by weight, in particular 15 to 45% by weight, specifically 20 to 40% by weight, based on the total weight of the oil-in-water emulsion.
The emulsions according to the invention frequently comprise one or more thickeners for setting the viscosity required for the respective application. In principle, it is possible to use all thickeners known for thickening oil-in-water systems. These include natural thickeners such as polysaccharides, carrageenates, Tragacanth, alginates, starch, caseinates, modified organic polymers such as carboxymethylcellulose, synthetic thickeners such as polyacrylic acids, polyvinyl alcohol, polyethylene glycols, polyacrylamides, and, in particular, copolymers of acrylamide with ethylenically unsaturated carboxylic acids, in particular with acrylic acid, and optionally with comonomers. These thickeners are described in EP-A 149 812, the disclosure of which is hereby referred to. Further suitable thickeners are mentioned in the overview article by Warren. B. Shapiro, Oil-in Water-Emulsions, Cosmetics & Toiletries, vol. 97, 1982, 27-33. Particular preference is also given to so-called associative thickeners, e.g. hydrophobically modified polyurethanes, hydrophobically modified cellulose ethers, which build up high molecular weight network structures in accordance with the principle of hydrophobic interaction in aqueous phase. Associative thickeners are known to the person skilled in the art, e.g. J. Bielemann, Additives for Coatings, Wiley-VCH Weinheim 2000 and are commercially available, e.g. under the names RHOPLEX® and PRIMAL® TT 935 from Rohm & Haas, USA. In one preferred embodiment of the invention, the emulsions comprise no thickener.
In addition, the emulsions according to the invention also frequently comprise commercially available biocides for preservation, e.g. formaldehyde, isothiazolinone compounds such as the products sold by Arch Chemicals under the name PROXEL® and the products sold by Thor Chemie GmbH under the name ACTICIDE®.
To prepare the emulsion according to the invention, as a rule the oil phase is emulsified in the aqueous phase. For this, a melt of components A, B and C of the oil phase will usually be incorporated, i.e. emulsified, into an aqueous phase which optionally comprises one or more surface-active substances. The incorporation and/or emulsification generally takes place at temperatures above the melting point of the oil phase, e.g. at temperatures in the range from 55 to 100° C. The incorporation takes place in a manner known per se for producing emulsions by using apparatuses such as e.g. dispersing devices, in which the components of the emulsion are subjected to a considerable shear gradient. In order to obtain particularly stable oil-in-water emulsions, the emulsification of the oil phase in the aqueous phase is preferably carried out in the presence of surface-active substances.
Emulsifying the oil phase in the aqueous phase gives oil-in-water emulsions. Immediately after preparation, these generally have a viscosity in the range from 300 to 3000 mPa·s (determined in accordance with Brookfield at 25° C., e.g. with spindle 4 at 20 revolutions per minute).
The average particle size (weight average of the droplet diameter) of the oil-in-water emulsion is generally below 25 μm, preferably in the range from 0.1 to 15 μm, in particular 0.5 to 10 μm, determined by means of light scattering at 20° C.
The oil-in-water emulsions according to the invention can be used as antifoams and/or deaerators for controlling foam and/or deaeration of aqueous media, for example in the food industry, the starch industry, in waste treatment plants or in the paper industry. Preference is given to their use as borehole solution and in the paper industry, in particular during pulp cooking, pulp washing, the grinding of paper stock, papermaking and the dispersion of pigments for papermaking. Specifically, the oil-in-water emulsions according to the invention are used in the paper industry as deaerators of paper stock suspensions. Particular preference is given here to the use as deaerators of the headbox in papermaking.
As antifoams or deaerators, the oil-in-water emulsions are generally used in amounts of from 0.01 to 2 parts by weight per 100 parts by weight of the foam-forming aqueous liquid, preferably in amounts of from 0.02 to 1 part by weight per 100 parts by weight of the foam-forming liquid, in particular in amounts of from 0.05 to 0.5 parts by weight per 100 parts by weight of the foam-forming liquid.
The advantages of the emulsions according to the invention are evident particularly at temperatures in the range from 20 to 50° C.
The examples below are intended to illustrate the invention in more detail and are not to be understood as being limiting.

Physicochemical Test Methods

The average particle size (weight-average particle diameter d₅₀) of the particles of the oil phase emulsified in water was determined with the help of a Coulter counter from Beckmann.
The viscosity was determined using a Brookfield rotary viscometer model RVT, spindle 4 at 20 revolutions per minute at 25° C.
The solids content was determined by back-weighing the samples following storage in a drying cabinet at 110° C. to constant weight.
The average air content was determined by pumping in each case 101 of a foam-developing paper stock suspension 0.1% (groundwood) in a container made of a transparent plastic for 5 minutes. The amount of air formed in the stock suspension was then ascertained using an air measuring device (e.g. based on impedance methods as in the case of the Sonica device from Conrex or based on sonic speed measurements as in the case of Sonatrac from Cidra). To assess the effectiveness of a deaerator, the average air content was stated 5 minutes after adding the deaerator.
If the paper suspension is pumped round in the absence of an antifoam for 5 minutes, then an average air content of 4% by volume is obtained. By adding in each case 5 mg/l of an effective deaerator to the paper stock suspension, this value is significantly reduced, meaning that it is a measure of the effectiveness of a deaerator.
After testing, the temperature of the paper stock suspension in each case was 30 or 40° C., the temperature being kept constant to +/−1° C. during the 5 minute test. In this terminology, the more effective the antifoam, the lower the average air content in the paper stock suspension.
The parts stated in the examples are parts by weight.
The C_16/18-fatty alcohol used below as component A consists to 32% by weight of a linear C₁₆-alcohol, to 67% by weight of a linear C₁₈-alcohol and to 1% by weight of a linear C₂₀-alcohol. The melting range of this mixture is 51 to 52° C.
The C₂₀₊-alcohol used in the comparative examples as component A consisted of 3% by weight of a linear C₁₈-alcohol, 45% by weight of a linear C₂₀-alcohol, 25% by weight of a linear C₂₂-alcohol, 15% by weight of a linear C₂₄-alcohol and 12% by weight of higher alcohols. The melting range of this mixture was 45° C. to 54° C.
The polyglycerol ester used as component B was prepared by esterifying a polyglycerol mixture consisting of 27% diglycerol, 44% triglycerol, 19% tetraglycerol and 10% more highly condensed polyglycerols with behenic acid. The degree of esterification was 60%.
The hydrocarbon (paraffin) used as component C has a melting point of 38° C.
The surface-active substances used were:
sodium salt of the sulfuric acid half-ester of isooctylphenol ethoxylated with 25 mol/mol of ethylene oxide as anionic emulsifier;
anionic copolymer of 70% by weight of acrylamide and 30% by weight of acrylic acid with a K value of 270.

EXAMPLE 1

The components of the oil phase were firstly heated to a temperature of 110° C. and then incorporated into the aqueous phase heated to 80° C. by means of a dispersing device.
The oil phase had the following composition, based on the total weight of the emulsion:

- 20 parts of the C_16/18-fatty alcohol,
- 9 parts of paraffin and
- 1 part of polyglycerol ester.

The water phase consisted, based on the total weight of the emulsion, of:

- 68.3 parts of water,
- 1 part of the anionic emulsifier,
- 0.5 part of the anionic copolymer and
- 0.2 part of sodium hydroxide solution.

The physical properties and the deaerating effect of this emulsion are given in table 2.
The examples and comparative examples given in table 1 were prepared in an analogous manner. The quantitative data are % by weight, based on the total weight of the emulsion. The composition of the water phase corresponded in all examples to the water phase of example 1. The physical properties and the deaerating effect of this emulsion are given in table 2.

	TABLE 1

	Example

Component	1	2	3	4	5	C1	C2	C3	C4

C_16/18-fatty	20	20	20	20	17.5	20	20	10	10
alcohol
C₂₀₊-alcohol	—	—	—	—	2.5	—	—	10	5
Polyglycerol	1	—	1	—	1	—	—	1	1
ester
Behenyl	—	3	—	3	—	—	—	—	—
behenate
Paraffin	9	7	—	—	9	—	10	9	9
Palm oil	—	—	9	7	—	10	—	—	—

TABLE 2

Physical properties and deaerating effect of the antifoams

Average particle

Viscosity

Solids content

Air content [%]

	size [μm]	[mPa · s]	[%]	30° C.	40° C.

1	2.1	420	29.8	0.1	0.1
2	2.2	470	29.9	0.1	0.1
3	2.1	450	29.7	0.2	0.2
4	2.0	490	29.8	0.2	0.2
5	2.3	440	29.9	0.3	0.2
C1	2.2	390	29.7	0.8	1.0
C2	2.2	420	29.8	1.0	1.2
C3	2.6	360	29.8	0.5	0.4
C4	2.3	390	29.9	0.4	0.4

Claims

1: An oil-in-water emulsion, comprising:

an oil phase,

wherein the oil phase comprises at least 95% by weight of

from 50 to 80% by weight, based on a total weight of the oil phase, of an alkanol having at least 16 carbon atoms, wherein a fraction of the alkanol having 16 to 18 carbon atoms comprises at least 80% by weight, based on a total amount of the alkanol;

from 1 to 10% by weight, based on the total weight of the oil phase, of at least one ester selected from the group consisting of a C₁₂-C₃₆-alkanecarboxylic acid with polyglycerol and of a C₁₂-C₃₆-alkanecarboxylic acid with a C₁₂-C₃₆-alkanol; and

from 10 to 49% by weight, based on the total weight of the oil phase, of an organic substance, wherein the organic substance is liquid at 50° C. and 1013 mbar, at atmospheric pressure the organic substance has a boiling point above 200° C., and at 25° C. and 1013 mbar the organic substance has a solubility in water of less than 0.1 g/l.

2: The oil-in-water emulsion according to claim 1, wherein the alkanol consists essentially of unbranched alkanols.

3: The oil-in-water emulsion according to claim 1, wherein the alkanol comprises at least 80% by weight of at least one alkanol is selected from the group consisting of palmityl alcohol and stearyl alcohol.

4: The oil-in-water emulsion according to claim 1, wherein the at least one ester is at least 80% by weight from the ester comprising a C₁₈-C₂₄-alkanecarboxylic acid with polyglycerol.

5: The oil-in-water emulsion according to claim 4, wherein polyglycerol-comprising ester is obtained by esterification of polyglycerol with behenic acid.

6: The oil-in-water emulsion according to claim 1, wherein the organic substance comprises at least 80% by weight of an aliphatic hydrocarbon oil.

7: The oil-in-water emulsion according to claim 1, wherein a solid content of the oil-in-water emulsion is of from 10 to 50%.

8: The oil-in-water emulsion according to claim 1, wherein a weight-average particle size of the oil-in-water emulsion is of from 0.5 to 10 μm.

9: A method for producing an antifoam or deaerator in an aqueous composition, comprising:

producing the antifoam or deaerator with the oil-in-water emulsion according to claim 1.

10: A method for producing a deaerator for an aqueous paper stock suspension, comprising:

producing the deaerator for the aqueous paper stock suspension with the oil-in-water emulsion according to claim 1.

11: A method for producing a deaerator in a headbox of papermaking comprising:

producing the deaerator in the headbox of papermaking with the oil-in-water emulsion according to claim 1.

12: A method of employing the oil-in-water emulsion according to claim 8, comprising:

employing the oil-in-water emulsion at a temperature of from 20 to 50° C.

13: The method according to claim 9, wherein the producing is producing at a temperature of from 20 to 50° C.

14: The method according to claim 10, wherein the producing is producing at a temperature of from 20 to 50° C.

15: The method according to claim 11, wherein the producing is producing at a temperature of from 20 to 50° C.