WO1994005623A1 - Esters - Google Patents

Abstract

Plasticizer esters are made from an alcohol mixture comprising cyclic and primary C5 and C6 aliphatic alcohols.

Description

"Esters" This invention relates to esters, more especially to esters suitable for use as plasticizers, and to a process for their manufacture.

Esters of aliphatic or aromatic polycarboxylic acids and aliphatic alcohols are extensively used in industry as plasticizers for, inter alia, vinyl resins. They are manufactured in large quantities by reaction of the acids or their anhydrides with the alcohols.

There is a continuing search in the industry for improvements in plasticizer esters, in terms of reduced raw material costs, improved plasticizer effect or, if possible, both.

The manufacturers of plasticized polymers have various requirements of the plasticizer and the resulting plasticized resin both in the manufacturing process and in the end product. These requirements differ from manufacturer to manufacturer depending on the manufactur¬ ing process and the end use of the product; in many cases there is a conflict between a given manufacturer's processing requirement and end use requirement.

Increasingly, manufacturers are requiring a plasticizer to be "fast fluxing", i.e., the temperature at which a mixture of the resin and plasticizer fuses, as in plastisol transformation or conversion to form a film, should be as low as possible. This requirement may be

problems may arise while if closed processing is employed, in which case the volatiles are returned to the system, the reduced proportion of plasticizer in the resulting product may enable the latter to meet environ¬ mental standards limiting the volatile organic content of materials which otherwise would not be met.

The end users of various plasticized resin products are also requiring better resistance to staining than the existing materials have. This is especially so in the case of vinyl flooring materials. These usually comprise a base layer and an intermediate, usually foamed, vinyl layer which is printed with a decorative pattern and often embossed. On the printed surface of the intermediate layer there is normally provided a clear transparent wear layer, which protects the printed layer from loss of surface colour from traffic wear. This wear layer must be resistant to staining by commonly encountered household items, for example shoe polish, mustard, and ball-point pen ink. The wear layer is often a plasticized vinyl or similar resin, and it has been found that the resistance to staining is heavily depen¬ dent on the plasticizer chosen.

There remains a need for a fast-fluxing plasticizer ester which enables stain-resistant plasticized resins to be manufactured.

Other desirable characteristics of plasticizer esters include a low tendency to migrate in or out of the polymer, good colour stability, and compatibility with other components of the resin.

In a first embodiment, the present invention provides a mixed ester composition obtainable from a polybasic acid and a mixture of aliphatic and cyclo- aliphatic monohydroxy compounds, the mixture comprising at least 80% by weight of C₅ and C₆ alcohols, at least 50% by weight of the mixture being primary alcohols and cycloaliphatic alcohols having the hydroxy group on a ring carbon atom (hereinafter "cyclic alcohols") .

The mixed ester composition will contain the possible esters in proportions depending on the propor¬ tions of the alcohols present in the mixture and on their relative reactivities in the conditions of reaction. For example, if the mixture consisted of a single C₅ alcohol and a single C₆ alcohol, the ester composition would contain di-Cs ester, di-Cg ester and mixed CsCg ester.

C₅ and Cg alcohols advantageously constitute at least 90%, and preferably at least 93%, by weight of the mixture. Advantageously also, the mixture contains, by weight, at most 10% C alcohols, at least 15% C₆ alcohols, at least 45% primary alcohols and at least 15% and preferably from 15% to 18%, cyclic alcohols, and at most 40% secondary and tertiary alcohols. In a particularly preferred embodiment, the mixture consists essentially of C5 and Cg alcohols. Any remainder of the mixture preferably comprises also C and C₇ alcohols, and more preferably only C₄ and C₇ alcohols.

Cyclic and primary alcohols advantageously constitute at least 60%, preferably at least 70%, by weight of the alcohol mixture. The weight ratio of primary to cyclic alcohol is advantageously within the range of 1:1 to 10:1, preferably in the range of from 1:1 to 5:1, and most preferably about 3:1. Secondary and any possible tertiary alcohols should desirably be present in a proportion of at most 40%, and preferably at most 20%, by weight of the mixture.

In a second embodiment, the invention provides a composition comprising a mixed ester of a polybasic acid and aliphatic and cycloaliphatic alcohols, in which at least 80% by weight of the esterifying alcohols are C₅ and C₆ alcohols and at least 50% by weight of the esterifying alcohols are primary and cyclic alcohols. Preferred embodiments are as described for the first embodiment except that the preferred primary:cyclic ratio is from 5:1 to 10:1. The primary alcohols may be linear or branched. The alcohols are advantageously saturated. The alcohols may contain substituents or functional groups that do not interfere with manufacture of esters or their plasticizer function but are preferably unsubstituted. Preferably, the mixture comprises al anols and cyclo- alkanols.

Examples of suitable alcohol mixtures are, by weight,

(A) C₄ and below <2%, C₅ and C₆ 94%, C₇ and above <5%; primary C₅ and Cg 52.2%, cyclic C₅ and Cg 18.6%, total primary and cyclic 70.8%;

(B) C₄ and below <2%; C₅ and Cg 94.5%, C₇ and above <4%; primary C5 and Cg 58.3%, cyclic C5 and Cg 16.6%; total primary and cyclic 74.9%;

(C) C₄ and below <2%, C₅ and Cg 94.7%, C₇ and above <4%, primary C₅ and Cg 63.6%, cyclic C₅ and Cg 14.4%, total primary and cyclic 78%.

In these examples, all the identified primary and. cyclic alcohols were C5 and Cg alcohols but it is to be understood that the requirement for a minimum of 50% for primary and cyclic alcohols applies to the fraction as a whole.

The alcohol mixture is conveniently one obtained by the Fischer-Tropsch process, by passing steam over hot coal or peat, passing the resulting carbon monoxide and hydrogen over a metallic catalyst, advantageously iron- based, at high temperature and pressure, and recovering the low molecular weight alcohols (which are inter alia C to C₇) produced. The product may be hydrofinished if desired or required to remove aldehyde or olefin impurities.

Accordingly, the invention also provides the use of an alcohol mixture, obtained by the Fischer-Tropsch process from coal or peat and separation from the products of a fraction comprising at least 80% by weight of C₅ and Cg alcohols in which fraction primary alcohols and cyclic alcohols constitute at least 70% by weight, in the manufacture of a plasticizer ester composition.

The invention further provides a process for the manufacture of an ester of a polybasic acid and a mixture of alcohols, which comprises subjecting coal or peat to the Fischer-Tropsch process, separating from the products a fraction comprising at least 80% by weight of C₅ to Cg alcohols in which fraction primary alcohols and cyclic alcohols constitute at least 50% by weight, and esterify¬ ing the alcohol-containing fraction with a polybasic acid or acidic derivative thereof.

The invention still further provides a process for the manufacture of a plasticized polymer which comprises carrying out the above-specified ester-manufacturing process and incorporating the ester in a polymer.

The polybasic acid is advantageously tribasic or, preferably, dibasic. The acid may be inorganic or organic; if the latter, carboxylic acids are preferred. Among organic acids, aromatic acids are preferred. As acids suitable for making fast fluxing esters with the alcohol mixture, there may be mentioned phthalic, isophthalic, terephthalic, adipic, fumaric, azeleic, sebacic, trimellitic, pyromellitic, and phosphoric acids.

The esters may be produced by methods known per se or described in the literature from the alcohols and the relevant acid or, preferably, where appropriate, the anhydride, optionally in the presence of a solvent. Elevated, temperatures are employed to drive the reaction toward completion by removal of the water produced. Catalysts may be employed. Suitable catalysts include, for example, a titanium catalyst e.g. a tetraalkyl titanate, especially tetra-propyl ortho titanate, or a sulphonic acid, e.g., p-toluene sulphonic acid. Any catalyst present in the reaction product may be removed by alkali treatment and water washing. Advantageously, the alcohol is used in slight molar excess relative to- the number of acid groups in the acid.

For ease of integration into the resin to be plasticized, the ester composition of the invention advantageously has a viscosity of at most 50 mPas, and preferably between 35 and 45 mPas, at 20°C.

The ester composition of the invention may be used as a plasticizer for numerous polymers, for example, cellulose acetate; homo- and copolymers of aromatic vinyl compounds e.g. styrene or of vinyl esters with carboxylic acids e.g., ethylene/vinyl acetate copolymers; halogen-containing polymers, especially vinyl chloride homo- and copolymers, more especially those copolymers with vinyl esters of carboxylic acid, esters of unsaturated carboxylic acids and/or olefins; nitrile rubbers; and post-chlorinated vinyl chloride polymers. Poly(vinyl chloride) is of especial interest.

The proportion of plasticizer may vary within wide limits, but is generally 10 to 200 parts by weight per 100 parts of polymer, more especially 20 to 60 parts per 100.

The ester composition of the invention may be used alone as plasticizer, or in admixture with other plas¬ ticizers, for example, dibutyl, dipentyl, dihexyl, diheptyl, dioctyl, dinonyl or didecyl (iso- or n- in each case) phthalates or adipates, or butyl benzyl phthalate. If used in admixture, it is the total proportion of plasticizer that is advantageously within the ranges given above.

The plasticized polymeric compositions of the invention may be made up in numerous forms and have various end-uses. For example, they may be in the form of a dryblend, a paste, or a plastisol, depending on the grade of the resin employed. They may be used, for example, as coatings, in dipping, spraying, rotational moulding, or self-supporting films and sheets, and may readily be foamed. End uses include flooring materials, wall coverings, moulded products, upholstery materials, leather substitutes, and coated fabrics.

The following examples, in which percentages are by weight unless otherwise stated, illustrate the invention: Example 1 - Preparation of ester

A mixture of alcohols. Sample A above, which contained as its major components, by gas chromatographic analysis, 1-pentanol 35.4%, 2-hexanol 12.7%, cyclo- pentanol 12.0%, l-hexanol 8.0%, methyl-cyclopentanol 5.0%, 3-methyl-l-butanol 4.8%, 2-methyl-l-butanol 4.0%, 2-heptanol 2.7% and 2-methyl-2-pentanol 1.2%, was used in this preparation. 2.4 moles of alcohol were treated with 1 mole of phthalic anhydride in the presence of 0.009 mole tetra-isopropy1 orthotitanate catalyst at tempera¬ tures ranging from 175°C to 195°C under vacuum ranging from 500 mm to 200 mm Hg (about 67 to 27 kPa) , monitoring the progress of esterification by measuring the weight of water removed. The resulting ester was washed with a 5% NaOH solution and filtered over Decalite. The product had a residual alcohol content less than 0.1%, a water content less than 0.1%, an acidity less than 0.1 mg KOH/g and, at 20°C, a density of 1.03 ± 0.005 and a viscosity of 42 ± 2mPas.

The resulting ester was saponified to determine the proportion of the major components. These were found to be 1-pentanol 28.6%, 2-hexanol 15.6%, l-hexanol 12.8%, 2-heptanol 5.6%, cyclopentanol 3.9%, methyl-cyclopentanol 3.9%, 3-methyl-l-butanol 3.7%, 2-methyl-l-butanol 3.7%, 2-methyl-2-pentanol 1.4%, and cyclohexanol 1.1%, giving a proportion of primary and cyclic alcohol-derived groups in the mixed ester of at least 57.7%.

Example 2 - Preparation of ester In a similar manner, sample B above was esterified with phthalic anhydride. Analysis of the major starting alcohol and alcohols resulting from saponification of the mixed ester gave the following results:

Starting alcohol, % Ester, %

1-pentanol 33.6 25.5

2-methyl-l-butanol 13.1 9.3 cyclopentanol 11.4 2.1

2-hexanol 10.7 15.9

3-methyl-l-butanol 7.8 4.7 methyl cyclopentanol 4.3 2.4 l-hexanol 3.8 7.3

2-heptanol 1.8 4.4

2-methyl-2-pentanol 1.4 1.7 cyclohexanol 0.9 0.7

Example 3 - Tests on plasticized resins In this example, the mixed ester prepared in Example 1 was used as a plasticizer for poly(vinyl chloride) and the properties of the plasticized resin in plastisol and finished forms compared with those of the same resin plasticized with commercially available plasticizer esters. In each case the resin was Solvic (trade mark) 367 NC, an emulsion polymer. As stabilizer 0.5 part dibutyl tin mercaptide was used per 100 parts of resin. The esters used were as follows:

Table 1

Ester Identification

1 product of Example 1

A di-n-heptyl phthalate

B mixed branched C₇-linear

C₄ phthalate

C mixed linear C₇-linear

C₄ phthalate

D di-isopentyl phthalate

E di-isoheptyl phthalate

F butyl benzyl phthalate

G di-2-ethylhexyl phthalate

H di-isohexyl phthalate.

J 1:1 mixture of F and G

50 parts of each plasticizer identified in Table 1 above were blended with 100 parts of poly(vinyl chloride) and 0.5 part stabilizer to form a plastisol. After 1 day, the Haake viscosity of the plastisols ranged between 12 Pas for the plastisol containing ester A, E, or H to 26 Pas for C and D, at low shear rates (about 10 sec^-1) , falling to values within the range of 7.0 to 11 Pas at higher shear rates (200 to 450 sec^-1) with the exception, at the higher shear rates, of the mixture J which actually increased its viscosity to 18 Pas as shear rate was increased to between 100 and 200 sec^-1. The material plasticized by the ester of the invention had a viscosity of about 24 Pas at low shear rate falling to 8 Pas at 300 sec^-1.

The gelation temperature of each formulation was determined using a Geigy temperature gradient gelation block. Plastisols generally show a transition from the liquid to the solid phase extending over a distinct temperature range, the lower end being the gelation temperature, (G in Table 2 below) and the higher the tack-free temperature (TF in Table 2 below) , the range for a given resin varying with the plasticizer. The results for the plasticizer esters tested are shown in Table 2 below.

Table 2

Formulation 1 A B C D E F G H J G, °C 59.7 64.3 61.9 60.4 55.8 67.7 58.9 70.6 62.5 60.9

TF, °C 64.0 67.7 65.7 64.4 61.0 72.1 61.8 74.4 67.0 65.2

The gelation and tack free temperatures are about 10°C below those noted for the formulation using G, di-2- ethylhexyl phthalate, the most commonly used commercial plasticizer, and compare favourably with those obtained using F, butyl benzyl phthalate, commonly used when a fast fluxing plastisol is required, and very favourably with those using J, the mixture of di-2-ethylhexyl and butyl benzyl phthalates.

The ester mixture according to the invention accordingly meets the requirements for a fast fluxing plasticizer.

Table 3 below illustrates the volatility of the plasticizers, measured by heating the plastisols for 5 minutes at 160°C and 180°C. The table gives the percentage weight loss in each case, and a relative weight loss, using the di-2-ethylhexyl phthalate- plastisol material G as standard.

Table 3

Formulation 1 A B C D E F G H J

Wt loss, 0.93 0.36 0.70 0.75 1.14 0.31 0.33 0.31 0.64 0.36

%, 160°C

Relative to 3.1 1.2 2.3 2.5 3.7 1.0 1.1 1.0 2.1 1.2 G,160°C

Wt loss, 4.84 2.19 4.35 4.24 5.97 2.48 2.54 2.02 3.77 2.28

%,180°C

.Relative to 2.5 1.1 2.1 2.1 3.0 1.2 1.3 1.0 2.0 1.2 G,180°C

Formulations containing the various plasticizers were made into films , and subjected to staining with yellow dye, black marker, blue ball point pen ink, ketchup , mustard, and shoe polish. The known superior performance of Formulation F over, for example. Formulations E and G, was equalled or surpassed by Formulation 1. None of the films showed any sign of plasticizer incompatibility and no differences were observed in the transparencies or greying effect between the formulations E, F, G and 1.

Claims

1. A mixed ester composition obtainable from a polybasic acid and a mixture of aliphatic and cycloaliphatic monohydroxy compounds, the mixture comprising at least 80% by weight of C5 and Cg alcohols, primary alcohols and cycolaliphatic alcohols having the hydroxy group on a ring carbon atom (hereinafter "cyclic alcohol") constituting at least 50% by weight of the mixture.

2. A composition comprising a mixed ester of a polybasic acid and aliphatic and cycloaliphatic alcohols, in which at lest 80% by weight of the esterifying alcohols are C5 and Cg alcohols and at least 50% by weight of the esterifying alcohols are primary and cyclic alcohols.

3. A composition as claimed in claim 1 or claim 2, wherein the weight ratios of primary alcohols to cyclic alcohols is within the range of from 10:1 to 1:1.

4. A composition as claimed in any one of claims 1 to 3, wherein C5 and Cg alcohols constitute at least 93% by weight of the mixture.

5. A composition as claimed in any one of claims 1 to 4, wherein the mixture also comprises C4 and C7 alcohols.

6. A composition as claimed in any one of claims 1 to 5, wherein the alcohols are saturated aliphatic and cycloaliphatic alcohols.

7. A composition as claimed in any one of claims 1 to 6, wherein the acid is a dibasic acid.

8. A composition as claimed in any one of claims 1 to 7, which has a viscosity of at most 50 mPas to 20°C.

9. A composition as claimed in any of claims 1 to 8, wherein the alcohol mixture is one obtained from coal or peat by the Fischer-Tropsch process and separation of the desired alcohol mixture, optionally with subsequent hydrofinishing.

10. The use of an alcohol mixture, obtained by the Fischer- Tropsch process from coal or peat and separation from the products of a fraction comprising at least 80% b weight of C5 and Cβ alcohols in which fraction primary alcohols and cyclic alcohols constitute at least 70% be weight, in the manufacture of a plasticizer ester composition.

11. A process for the manufacture of an ester of a polybasic acid and a mixture of acids, which comprises subjecting coal or peat to the Fischer-Tropsch process, separating from the products a fraction comprising at least 80% by weight of C5 and Cg alcohols in which fraction primary alcohols and cyclic alcohols constitute at least 50% by weight, and esterifying the alcohol-containing fraction with a polybasic acid or acidic derivative thereof.

12. A process for the manufacture of a plasticized polymer, which comprises incorporating an ester produced by the process of claim 11 into a polymer.

13. A polymeric composition comprising a vinyl polymer and mixed ester composition as claimed in any one of claims 1 to 9.