GB1566310A

GB1566310A - Mercaptocarboxylic acid esters

Info

Publication number: GB1566310A
Application number: GB54128/76A
Authority: GB
Original assignee: Hoechst AG
Current assignee: Hoechst AG
Priority date: 1975-12-24
Filing date: 1976-12-24
Publication date: 1980-04-30
Also published as: JPS5283328A; IT1065676B; FR2336389A1; DE2558729A1; CA1095073A; NL7614037A; FR2336389B1; DK581976A; CH623035A5; LU76454A1; BE849858A; ATA951776A; AT350039B

Abstract

Mercaptocarboxylic esters of the formula I are prepared by reacting epoxides with mercaptocarboxylic acids. The substituents of the formula I have the meaning given in Patent Claim 1. The resulting compounds are intermediates for the synthesis of crop protection agents, lubricant additives and polymer additives. <IMAGE>

Description

(54) IMPROVEMENTS IN OR RELATING TO MERCAPTOCARBOXYLIC ACID ESTERS (71) We, HOECHST AKTIENGESELLSCHAFT, a body corporate organised according to the laws of the Federal Republic of Germany, of 6230 Frankfurt/Main 80, Postfach 80 03 20, Federal Republic of German, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to Mercaptocarboxylic acid esters.

Mercaptocarboxylic acid esters are used in many fields, for example as flotation or silver protection agents, as corrosion inhibitors or, especially, as starting materials for plastics additives.

We have found that mercaptocarboxylic acid esters distinguished by having a hydroxyl group in the p-position of the alcoholic radical can be prepared which are suitable especially as starting materials for plastics additives.

The present invention provides a mercaptocarboxylic acid ester of the general formula

wherein R1, R2, R3 and R4, any two or more of which may be the same or different, each represents a) a hydrogen atom; b) an unsubstituted or substituted phenyl radical or a cyclo-aliphatic radical having from 5 to 12 carbon atoms and which is unsubstituted or substituted; or c) an aliphatic radical having from 1 to 100, preferably 1 to 60, carbon atoms which is unsubstituted or substituted; and R2 and R3 together may also represent a bivalent aliphatic radical having from 3 to 10 carbon atoms in the chain which completes the ring and which is unsubstituted or substituted, wherein preferably the sum of all the carbon atoms in R1, R2, R3 and R4 is no more than 100, R5 represents an unsubstituted or substituted bivalent aromatic radical or a bivalent aliphatic radical having from 1 to 12 carbon atoms in the chain between the CO and SH groups and being unsubstituted or substituted, provided R1, R2, R3 and R4 may not all represent hydrogen atoms nor may three of them represent hydrogen atoms and one a hydroxymethyl group if R5 represents- CH2-, HCH2)2, or

each of Ra, Rb and Rc representing an unsubstituted or substituted aliphatic, aromatic, alicyclic or heterocyclic radical.

Preferably the sum of all the carbon atoms in R1 to R4 is more than 2 when R5 has the meaning given in the proviso above.

A cycloaliphatic radical represented by one or more of R1, R2, R3 and R4 is saturated or unsaturated; for example it may be a cycloalkyl or cycloalkenyl radical.

An aliphatic radical represented by one or more of R1, R2, R3 and R4 is saturated or unsaturated and is linear or branched; for example it may be an alkyl or alkenyl radical.

A bivalent aliphatic radical represented by R2 and R3 together is straight or branched chain, saturated or unsaturated; for example it may be an alkylene or alkenylene radical.

A bivalent aromatic radical represented by R5 is preferably an arylene radical.

A bivalent aliphatic radical represented by R5 is straight or branched chain, saturated or unsaturated; for example, it may be an alkylene or alkenylene radical.

Preferably, the sum of the number of carbon atoms in such radicals R1,R2, R3 and R4 is more than 2 and no more than 100.

The radicals mentioned above are unsubstituted or substituted by one or more substituents, any two or more of which may be the same or different.

Suitable substituents of phenyl and cycloaliphatic radicals represented by R1, R2, R3 and R4 are, for example, alkyl groups having from 1 to 9 carbon atoms, chlorine atoms and hydroxy groups.

Suitable substituents of aliphatic radicals represented by R1, R2, R3 and R4are, for example, phenyl radicals and cycloalkyl radicals having from 5 to 12 carbon atoms, the phenyl and cycloalkyl groups being unsubstituted or substituted as described above.

Suitable substituents of bivalent aliphatic radicals represented by R2 and R3 together are, for example, alkyl and aromatic, e.g. aryl or arylene, groups.

Other suitable substituents on radicals represented by R1, R2, R3 and R4 are, for example, ether, thioether, carboxyl, carboxylic acid ester, e.g. alkoxycarbonyl or alkanoyloxy, or epoxide groups or mercaptocarboxylic acid ester groups of the general formula --CHOHH-CH,,O--COO-R,-SH or halogen substituents.

Carbon-carbon double bonds may be present.

Suitable substituents of bivalent aliphatic radicals represented by R5 are, for example, phenyl and alkyl groups which may themselves be unsubstituted or substituted by carboxyl groups and carboxylic acid ester groups derived from polybasic mercaptocarboxylic acids and partial esters thereof.

More especially, in the compound of the general formula I R1, R2,R3and R4, any two or more of which may be the same or different, each represents a) a hydrogen atom, or b) a phenyl radical or a cycloalkyl or cycloalkenyl radical having from 5 to 12 carbon atoms; or c) a linear or branched alkyl radical having from 1 to 100 carbon atoms; R2 and R3 optionally being common members of a saturated or unsaturated bivalent aliphatic, e.g. alkylene, chain having from 3 to 10 carbon atoms, and the sum of all carbon atoms contained in the. radicals R1, R2, R3 and R4 being more than 2 but less than 100, and R5 represents an arylene group or a saturated or unsaturated bivalent aliphatic. e.g. alkylene, group having from 1 to 12 carbon atoms in the aliphatic, e.g. alkylene, chain.

A mercaptocarboxylic acid ester of the present invention may be prepared by reaction of a higher epoxide with a mercaptocarboxylic acid (or a salt thereof) according to the following scheme:

It Is surprising that the reaction proceeds as indicated, since, as is known, reaction of SH groups with epoxides readily yields p-hydroxy-thioethers, as described in J. Am. Chem. Soc. 82 (1960), p. 2511, where also the reaction of mercaptoacetic acid and mercaptopropionic acid with ethylene oxide is discussed.

According to this paper, products having the structure

should be obtained. Analysis of the products of the invention, however, clearly proves the reaction to proceed according to the above scheme, that is, no A- hydroxy-thioethers are formed, but mercaptocarboxylic acid esters are obtained.

Each of the symbols R1, R2 R3 and R4 in the general formula I preferably represents a hydrogen atom (the compounds where all four radicals are hydrogen being excluded, however), or a phenyl radical, unsubstituted or substituted by 1 or 2 substituents selected from alkyl radicals each having from 1 to 9 carbon atoms, chlorine atoms and OH groups, especially by 1 or 2 alkyl radicals, 1 or 2 chlorine atoms or 1 or 2 OH groups or a cycloalkyl or cycloalkenyl radical having from 5 to 12 carbon atoms and being unsubstituted or substituted in the same manner as the phenyl radical. Examples are phenyl, tolyl, xylyl, t-butylphenyl, nonylphenyl, chlorophenyl, hydroxyphenyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl and cyclododecyl radicals. Each of the symbols may furthermore represent a linear or branched alkyl or alkenyl radical having from 1 to 100, preferably 6 to 60, carbon atoms, unsubstituted or substituted by a phenyl group, a (C1 to C9)-alkylphenyl group or a cycloalkyl or cycloalkenyl group having from 5 to 12 carbon atoms. The radicals R1, R2, R3 and R4 especially aliphatic radicals may furthermore contain ether, thioether, carboxyl, carboxylic acid ester or epoxide substituents or mercaptocarboxylic acid ester substituents of the general formula

or halogen substituents, preferably 1 such substituent. Examples of these radicals are: -CH2-O-C18H37; -CH2-S-C12H25;

R2 and R3 may also represent a bivalent saturated or unsatured, unsubstituted, alkyl- or aryl-substituted, aliphatic radical having from 3 to 10 carbon atoms in the chain that completes the ring. In this case, the compounds of the invention are esters in which the alcoholic moiety is, for example, a A-hydroxycyclopentyl, A- hydroxycyclohexyl or A-hydroxycyclooctyl radical.

Any two or more of the radicals R1, R2, R3 and R4 may be the same or different.

Preferred mercaptocarboxylic acid esters are those where R1 is derived from linear, aliphatic hydrocarbons having from 6 to 58, preferably 8 to 40, and especially 12 to 36, carbon atoms, preferably alkyl, and each of R2, R3 and R4 represents a hydrogen atom, or R4 represents a methyl or ethyl group.

Rs preferably represents an alylene group, for example a phenylene or naphthylene group, or a saturated or unsaturated bivalent aliphatic group having from 1 to 12, preferably 1 to 5, and especially 1 or 2, carbon atoms in the aliphatic chain between CO and SH. This chain is preferably saturated. It may be substituted by one or more phenyl groups or alkyl radicals having from 1 to 16 carbon atoms; furthermore, the alkyl or phenyl substituents of the alkylene chain may be substituted by one or more carboxyl or carboxylic acid ester groups derived from polybasic mercaptocarboxylic acids and the partial esters thereof Suitable mercaptocarboxylic acids for the manufacture of the mercaptocarboxylic esters of the invention are, for example, mercaptoacetic acid, 2- and 3-mercaptopropionic acid, 2-, 3- and 4-mercaptobutyric acid, 2mercaptovaleric acid, cs-mercaptohexanoic acid, 3-mercapto-4-ethylenehexanoic acid, 4-mercaptocaproic acid, 3-mercapto-2,3-dimethylbutyric acid, 3-mercapto-4hydroxybutyric acid, 2-mercapto-3-methylbutyric acid, 3-mercapto-4,5dimethylhexanoic acid, 2-mercaptolauric acid, 2-mercapto-oleic acid, 2mercaptostearic acid, thiomalic acid and the semiesters thereof, 2- and 3mercaptoglutaric acid and the semiesters thereof, thiocitric acid and the partial esters thereof, dithiolactic acid, 2-mercaptopimelic acid and the semiesters thereof, 2-mercaptosuberic acid and the semiesters thereof, thiosalicylic acid and 3mercapto-2-naphthoic acid; mercaptoacetic and 3-mercaptopropionic acid being preferred.

Suitable epoxides are for example epoxidized olefins e.g. 2,3-epoxypentane, but especially epoxidized a-olefins e.g. 1,2-epoxyhexane, -octane, -dodecane, octadecane; or long-chain epoxides or epoxide mixtures, for example epoxidised C20 to C24, C20 to C28, C26 to C52, or C30+ a-olefin fractions obtainable e.g.

according to the Ziegler synthesis; furthermore aryl-substituted epoxides, e.g.

styrene oxide, tri- and tetraphenylethylene oxide; glycidyl ethers of alcohols and phenols, e.g. octanol, octadecanol, phenol or nonylphenol; glycidylthioethers of mercaptans, e.g. octanethiol, dodecane-thiol, octadecane-thiol or thiophenol; glycidyl esters of carboxylic acids, e.g. octanoic, lauric, stearic, benzoic, phydroxybenzoic or p-t-butylbenzoic acid; epoxidized fatty acids and fatty acid esters, e.g. 9,10-epoxystearic acid and the esters thereof; epoxidized natural oils, e.g. epoxidized castor oil or soybean oil, the epoxide groups per molecule contained in these oils optionally being reacted with mercaptocarboxylic acids either completely or partially; 9,10-epoxyoctadecanol, 2,3 - epoxy - 2,6 dimethyloctene - (7) - ol - (6); epoxy-2,6-dimethyloctadiene, 4,5-epoxyhex-2-enic acid methyl ester; cyclic epoxides, e.g. epoxycyclopentane, -hexane, -octane; epoxycyclooctatriene, 1,2- and 2,3-epoxytetraline, 3,4-epoxytricyclo-(0,3,4, 1)decene (obtainable from dicyclopentadiene), or hexachloro-2,3-epoxynorbornene.

Especially suitable epoxides are cheap industrial grade products such as glycidyl ethers, -esters and -thioethers, especially epoxidized fatty acids and fatty acid esters and epoxidized cr-olefins. Of course, the starting epoxides and mercaptocarboxylic acids should be chosen above all having regard to the intended application of the products of the invention.

In one preferred embodiment of the process of the invention, an epoxide of the general formula

wherein R1 represents an alkyl group having from 6 to 58 carbon atoms and R4 represents a hydrogen atom or a methyl or ethyl group; the sum of the carbon atoms in R1 and R4 being from 6 to 60, is reacted with mercaptoacetic acid or 3mercaptopropionic acid.

The mercaptocarboxylic acid esters of the invention are prepared, for example, as follows: The components are allowed to react, with agitation, at temperatures of from 20 to 2000 C. In order to obtain a quantitative conversion, it is generally advantageous to use an excess of mercaptocarboxylic acid; however, an epoxide excess may also be employed.

The reaction may be carried out in the presence or absence of a solvent; examples of suitable solvents are liquid, chlorinated hydrocarbons, e.g.

chloroform, carbon tetrachloride or chlorobenzene, aromatic hydrocarbons, e.g.

toluene or xylene, or aliphatic hydrocarbons, e.g. hexane, heptane or petrol fractions.

The reaction may also be carried out in the presence of catalysts; examples of suitable catalysts are iron(III) chloride, alkali metal salts of carboxylic acids, e.g.

sodium acetate, potassium benzoate or potassium stearate, or ammonium salts of carboxylic acids, e.g. ammonium laurate, triethylammonium octoate or tetraethylammonium stearate. Of course, also the corresponding salts of the mercaptocarboxylic acids used may be employed. The amount of catalyst is preferably from 0.1 to 5, more preferably from 0.5 to 2, parts by weight per 100 parts by weight of mercaptocarboxylic acid ester. The use of catalysts is recommended in the case of epoxides having a poor reactivity; in general, however, the reaction may be carried out without a catalyst. The reaction time is normally from I to 10 hours, and the proceeding reaction is controlled by determining the epoxide number.

The mercaptocarboxylic acid esters of the invention are interesting intermediate products, for example for the synthesis of plant protecting products and additives for lubricants or plastic materials.

Some typical representatives of the mercaptocarboxylic acid esters of the invention are cited below; the invention, however, is not limited to these substances: 2-hydroxydodecyl-mercaptoacetic acid ester

2-hydroxyoctadecyl-mercaptopropionic acid ester

2-hydroxy-C2e,,24-alkyl-mercapto-acetic acid ester

2-hydroxy-C2428-alkyl-mercaptopropionic acid ester

2-hydroxy-C30±alkyl-mercaptoacetic acid ester

2-hydroxycyclohexyl-mercaptopropionic acid ester

bis-(2-hydroxy-C20~24-alkyl)-mercaptosuccinic acid ester

Hydroxy esters obtainable by reaction of the epoxy groups contained in epoxidized soybean oil with 1, 2 or 3 mols of mercaptoacetic acid or mercaptopropionic acid, the epoxide groups being reacted either completely or partially, for example

or isomers thereof.

The following Examples illustrate the invention. In order to characterise the products, the acid number AN (mg KOH/g, according to DGF M IV 2 (57)), the saponification number SN (mg KOH/g, according to DGF M IV 2 (57)), the flow point/drop point (according to DGF M III 3 (57)) and the epoxide number EPN are indicated (DGF=Deutsche Gesellschaft fir Fettforschung).

EXAMPLE 1: After flushing with nitrogen, a four-necked flask of 1 litre capacity and provided with agitator, inner thermometer, condenser and dropping funnel is charged with 552 g (3 mols) of 1,2-epoxydodecane. The contents of the flask are heated to 1 100C in-a slight nitrogen current. At this temperature 322 g (3.5 mols) of mercaptoacetic acid are added dropwise within 2 hours (exothermic reaction), and the reaction is then allowed to proceed for a further 3 hours at 110"C. Subsequently the contents of the flask are washed several times in a heatable 2 litre washing tube at 50"C, until the washing water attains a pH of 6-7. The upper organic phase is then dried at 100"C in a rotary evaporator under reduced pressure of 120 mm.

A product liquid at 300C is obtained.

Yield: 790 g 2-hydroxydodecyl-mercaptoacetic acid ester=96 of the theoretical yield.

Analysis results: AN=5.0; calc.: 0 SN=195; calc.: 204,5 S=11.2%; calc.: 11.7% EPN=0.030/,; calc.: 0% molecular weight: 310 IR spectrum: SH, ester, OH- and hydrocarbon absorptions.

EXAMPLE 2: 131.5 g (1.43 mols) of mercaptoacetic acid are introduced into the apparatus described in Example 1 and heated to 1200C. At this temperature 434 g (1.3 equivalents) of an epoxide prepared from a C224-a-olefin mixture and having an EPN of 12.9% are added dropwise within 90 minutes (exothermic reaction), and the reaction is allowed to proceed for a further 5 hours at 1200C.

The contents of the flask are then diluted with 0.5 1 of toluene and washed to neutral at 650C in the washing tube described in Example 1. Under the conditions indicated in Example 1, the toluene is distilled off in a rotary evaporator at a temperature of up to 1000C and under reduced pressure of up to 1020 mm, thus leaving a slightly turbid melt.

Yield:530 g 2-hydroxy-C2O,24-alkylmercaptoacetic acid ester (=96%) in the form of a wax-like white product having a flow/drop point of 59/60 C.

Analysis results: EPN=0.05%; calc.: 0% AN= 6; calc.: 0 SN=129; calc.: 132 S=7.3%; calc.: 7.5% MW: 473 IR spectrum: similar to that of Example 1.

A sample of the ester was saponified for 3 hours with 2N sodium hydroxide solution. After acidification, the water-insoluble product obtained was analysed, the results being as follows: An=9 SN=9 S=0.8%; calc.: 0%.

This test shows that the reaction of the epoxide with mercaptoacetic acid yielded substantially the ester and not the thioether.

EXAMPLE 3: 117.8 g (1.12 mols) 3-mercaptopropionic acid and 470 g (1.02 equivalents) of an l,2-epoxy-C24128-alkane having an EPN of 9.55 MO are heated to 120"C in the apparatus described in Example 1. After 5 hours at this temperature the contents of the flask are worked up as indicated in Example 2.

Yield: 555 g of 2-hydroxy-C24,28-alkyl-3-mercaptopropionic acid ester (=96%) in the form of a wax-like, nearly white product having a flow point/drop point of 79/79.5"C.

Analysis results: AN=9; calc.: 0 SN=95; calc.: 99 S=5.3%; calc.: 5.6% EPN=0.1%; calc.: 0% MW: 569 IR spectrum: similar to that of Example 1.

A product prepared in the same manner, but in the presence of 600 ml of xylene as solvent and worked up according to Example 1 had practically identical properties.

EXAMPLE 4: In the apparatus described in Example 1, 75.5 g (0.502 mol) of thiomalic acid are reacted with 480 g (1.04 equivalents) of the epoxide used in Example 3 within 6 hours at 1400C, and worked up as indicated in Example 2.

Yield: 540 g of bis-(2-hydroxy-C24,28-alkyl)-thiomalic acid ester (=97%) in the form of a wax-like, nearly white product having a flow point/drop point of 71/72"C.

Analysis results: AN=10; calc.: 0 SN=103; calc.: 105 S=3.2%; calc.: 2.9% EPN=0.02%; calc.: 0% MW: 1075.

EXAMPLE 5: 78 g (0.85 mol) of mercaptoacetic acid are heated for 5 hours at 100"C with 488 g (0.75 equivalents) of a l,2-epoxy-C20-alkane having an EPN of 6.6% in the presence of 3 g of iron(III)chloride, and subsequently, the batch is worked up as indicated in Example 2.

Yield: 545 g of 2-hydroxy-C30-alkyl-mercaptoacetic acid ester (=96.5%) in the form of a wax-like, nearly white product having a flow point/drop point of 87/88"C.

Analysis results: AN=3; calc.: 0 SN=72; calc.: 76 S=4.2%; calc.: 4.3% EPN=0.3%; calc.: 0% MW: 683 IR spectrum: similar to that of Example 1.

EXAMPLE 6: 55.2 g (0.6 mol) of mercaptoacetic acid are reacted for 5 hours at 120"C with 540 g.(l.96 equivalents) of epoxidized soybean oil having an EPN of 15.6% and a molecular weight of 950, and worked up.

Yield: 580 g of a yellowish, viscous liquid (=97.5%).

Analysis results: AN=2; calc.: 0 SN=227; calc.: 220 S=3.2%; calc.: 3.2% EPN=9.1%; calc.: 9.8% MW: 1150.

In this Example, only part of the epoxide radicals are converted to the A- hydroxy ester group.

EXAMPLE 7: 147 g (1.6 mols) of mercaptoacetic acid are heated for 5 hours at 1200C with 435 g (1.57 equivalents) of the epoxidized soybean oil cited in Example 6, and worked up as usual.

Yield: 550 g of a yellowish, highly viscous liquid (=95%).

Analysis results: AN=6; calc.: 0 SN=269; calc.: 286 S=7.9%; calc.: 8.7% EPN=0.l%; calc.: 0% MW: 1370.

In this Example, all epoxide radicals of the epoxidized soybean oil were converted to the hydroxy ester group.

EXAMPLE 8: A four-necked flask having a capacity of 250 ml and provided with the devices specified in Example 1 is charged with 92 g (1 mol) of mercaptoacetic acid, and the contents of the flask as heated to 115 C; at this temperature 98 g (1 mol) of cyclohexene oxide are added dropwise within one hour (exothermic reaction). The contents of the flask are maintained at 1 150C for a further 5 hours and subsequently washed with water and worked up as indicated in the previous Examples.

Yield: 145 g of p-hydroxycyclohexyl-mercaptoacetic acid ester (=76.3%) in the form of a colorless liquid.

Analysis results: AN=9; calc.: 0 SN=280; calc.: 295 S=16.4 / calc.: 16.8% EPN=0.05%; calc.: 0% MW: 205.

EXAMPLE 9: 101 g (1.1 mols) of mercaptoacetic acid are introduced into the apparatus described in Example 1. At 1200C, 150 g (I mol) of 1,2-epoxy-3-phenoxypropane are allowed to drop in within 30 minutes, and agitation is continued for a further hour at the same temperature.

190 g (78.5%) of mercaptoacetic acid ester of 2-hydroxy-3-phenoxypropanol are obtained in the form of a viscous liquid.

Analysis results: AN=I5; calc.: 0 SN=217; calc.: 231 S=12.7; calc.: 13.2% EPN=0.09%; calc.: 0% EXAMPLE 10: This Example shows the further treatment of a mercaptocarboxylic acid ester of the invention to give a plastics additive, and the stabilising effect thereof in PVC.

36.1 g (0.1 mol) of dioctyl-tin oxide and 124.5 g (0.2 equivalents) of 2-hydroxy C2,28-alkyl-3-mercaptopropionic acid ester of Example 3 are melted in a 250 ml glass flask. Subsequently, a reduced pressure of 10 mm Hg is established and maintained at 1000C for 3 hours, the water of reaction formed being taken off via a cooling trap having a temperature of -80 C. 158.0 g (99.5%) of a light coloured, wax-like organo-tin mercaptide of the formula

having a flow point/drop point of 73/74"C are obtained.

100 parts by weight of a mass-polymerised polyvinyl chloride having a K value of 67 were homogeneously mixed with 20 parts of dioctylphthalate, 0.5 parts of a lubricant based on montan wax (montanic acid ester of ethylene glycol) and 1.0 parts of the organo-tin compound.

For determining the dynamic thermostability, the mixture was applied to a laboratory two-roll mill heated to 1750C and laminated at 20 rpm until the rough sheet had become black, that is, for 80 minutes.

For comparison, the same amount of the commercial dioctyl-tin-bisthioglycolic acid iso-octyl ester stabiliser was incorporated in a parallel test.

However, despite the tin content being twice as high, the dynamic thermostability attained was also 80 minutes only.

WHAT WE CLAIM IS: 1. A mercaptocarboxylic acid ester of the general formula

wherein R1, R2, R3 and R4, any two of which may be the same or different, each represents a hydrogen atom; or an unsubstituted or substituted phenyl radical or a cycloaliphatic radical having from 5 to 12 carbon atoms and which is unsubstituted or substituted; or an aliphatic radical having from I to 100 carbon atoms which is unsubstituted or substituted; and R2 and R3 together may also represent a bivalent aliphatic radical ha"ing from 3 to 10 carbon atoms in the chain which completes the ring and which is unsubstituted or substituted, R5 represents an unsubstituted or substituted bivalent aromatic radical or a bivalent aliphatic radical having from 1 to 12 carbon atoms in the chain between the CO and SH groups and being unsubstituted or substituted, provided R, R2, R2 and R4 may not all represent hydrogen atoms nor may three of them represent hydrogen atoms and one a hydroxymethyl group if R5 represents -CH2-, CH2)2-, or

2. A mercaptocarboxylic acid ester of the general formula

wherein R1, R2, R3 and R4, any two or more of which may be the same or different, each represents a hydrogen atom; or an unsubstituted or substituted phenyl radical or a cycloaliphatic radical having from 5 to 12 carbon atoms and which is unsubstituted or substituted; or

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

having a flow point/drop point of 73/74"C are obtained.

100 parts by weight of a mass-polymerised polyvinyl chloride having a K value of 67 were homogeneously mixed with 20 parts of dioctylphthalate, 0.5 parts of a lubricant based on montan wax (montanic acid ester of ethylene glycol) and 1.0 parts of the organo-tin compound.

For determining the dynamic thermostability, the mixture was applied to a laboratory two-roll mill heated to 1750C and laminated at 20 rpm until the rough sheet had become black, that is, for 80 minutes.

For comparison, the same amount of the commercial dioctyl-tin-bisthioglycolic acid iso-octyl ester stabiliser was incorporated in a parallel test.

However, despite the tin content being twice as high, the dynamic thermostability attained was also 80 minutes only.

WHAT WE CLAIM IS: 1. A mercaptocarboxylic acid ester of the general formula

wherein R1, R2, R3 and R4, any two of which may be the same or different, each represents a hydrogen atom; or an unsubstituted or substituted phenyl radical or a cycloaliphatic radical having from 5 to 12 carbon atoms and which is unsubstituted or substituted; or an aliphatic radical having from I to 100 carbon atoms which is unsubstituted or substituted; and R2 and R3 together may also represent a bivalent aliphatic radical ha"ing from 3 to 10 carbon atoms in the chain which completes the ring and which is unsubstituted or substituted, R5 represents an unsubstituted or substituted bivalent aromatic radical or a bivalent aliphatic radical having from 1 to 12 carbon atoms in the chain between the CO and SH groups and being unsubstituted or substituted, provided R, R2, R2 and R4 may not all represent hydrogen atoms nor may three of them represent hydrogen atoms and one a hydroxymethyl group if R5 represents -CH2-, CH2)2-, or

each of Ra, Rb and Rc representing an unsubstituted or substituted aliphatic, aromatic, alicyclic or heterocyclic radical.
2. A mercaptocarboxylic acid ester of the general formula

wherein R1, R2, R3 and R4, any two or more of which may be the same or different, each represents a hydrogen atom; or an unsubstituted or substituted phenyl radical or a cycloaliphatic radical having from 5 to 12 carbon atoms and which is unsubstituted or substituted; or

an aliphatic radical having from 1 to 100 carbon atoms which is unsubstituted or substituted; and R2 and R3 together may also represent a bivalent aliphatic radical having from 3 to 10 carbon atoms in the chain which completes the ring and which is unsubstituted or substituted, R5 represents an unsubstituted or substituted bivalent aromatic radical or a bivalent aliphatic radical having from 1 to 12 carbon atoms in the chain between the CO and SH groups and being unsubstituted or substituted, provided R1, R2, R2 and R4 have a total of more than 2 carbon atoms when R5 represents -CH-, CH2)2- or

each of Ra, Rb and Rc representing an unsubstituted or substituted aliphatic, aromatic, alicyclic or heterocyclic radical.
3. A compound as claimed in Claim 1, wherein R1, R2, R3 and R4 have a total of more than 2 carbon atoms.
4. A compound as claimed in any one of Claims 1 to 3, wherein R1,R2, R3and R4 have a total of no more than 100 carbon atoms.
5. A compound as claimed in any one of Claims 1 to 4, wherein R1,R2, R3and R4, any two or more of which may be the same or different, each represents a) a hydrogen atom; b) a phenyl group or a cycloalkyl or cycloalkenyl group having from 5 to 12 carbon atoms, the phenyl and cycloaliphatic groups being unsubstituted or substituted by one or two (C1-C9) alkyl or hydroxy groups or chlorine atoms, or c) an alkyl or alkenyl radical having from 1 to 100 carbon atoms, which is unsubstituted or substituted by a phenyl or a (C1-C9-) alkylphenyl group or by a cycloalkyl or cycloalkenyl group having from 5 to 12 carbon atoms, or by an ether, thioether, carboxyl, carboxylic acid ester or epoxide group or a group of the general formula -CHOH-CH2-O-CO-R -SH or is halogen-substituted, and R2 and R3 together may also represent a bivalent aliphatic radical having from 3 to 10 carbon atoms in the chain which completes the ring and being unsubstituted or substituted by an alkyl or aryl group.
6. A compound as claimed in Claim 5, wherein at least one of the radicals represented by R1, R2, R2 and R4 is -CH2-O-C18H27; -CH2-S-C12H25;
7. A mercaptocarboxylic acid ester of the general formula

wherein R1, R2, R2 and R4, any two or more of which may be the same or different, each represents a) a hydrogen atom; b) a phenyl radical or a cycloalkyl or cycloalkenyl radical having from 5 to 12 carbon atoms; or c) an alkyl radical having from 1 to 100 carbon atoms; R2 and R3 optionally being common members of a saturated or unsaturated bivalent aliphatic chain having from 3 to 10 carbon atoms, and R1, R2, R3 and R4 have in total more than 2 but less than 100 carbon atoms, and R5 represents an arylene group or a saturated or unsaturated bivalent aliphatic group having from I to 12 carbon atoms in the chain.
8. A compound as claimed in any one of Claims I to 7, wherein an aliphatic radical represented by one or more of R1, R2, R3 and R4 has from 1 to 60 carbon atoms.
9. A compound as claimed in Claim 1, wherein R, represents an alkyl group having from 6 to 58 carbon atoms, R2 and R3 each represent hydrogen atoms and R4 represents a hydrogen atom or a methyl or ethyl group, the sum of the carbon atoms in R1, R2, R3 and R4 being from 6 to 60.
10. A compound as claimed in Claim 9, wherein the alkyl group represented by R1 has from 8 to 40 carbon atoms.
11. A compound as claimed in Claim 10, wherein the alkyl group represented by R, has from 12 to 36 carbon atoms.
12. A compound as claimed in any one of Claims 1 to 11, wherein R5 represents an arylene group or a bivalent aliphatic group having from 1 to 5 carbon atoms in the chain between CO and SH and which is unsubstituted or substituted by one or more phenyl groups or alkyl substituents having from 1 to 16 carbon atoms, the phenyl or alkyl groups being unsubstituted or substituted by one or more carboxyl groups or carboxylic acid ester groups derived from a polybasic mercaptocarboxylic acid or the partial ester thereof.
13. A compound as claimed in Claim 12, wherein R5 represents aphenylene or naphthylene group or a bivalent aliphatic group having 1 or 2 carbon atoms in the chain between CO and SH.
14. A compound as claimed in any one of Claims 9 to 11, wherein R5 represents an alkylene group having 1 or 2 carbon atoms.
15. A compound as claimed in Claim 1, which is specifically listed herein.
16. A process for the preparation of a mercaptocarboxylic acid ester as claimed in Claim 1, which comprises reacting an epoxide of the general formula

wherein R1, R2, R2 and R4 have the meanings given in Claim 1, with a mercaptocarboxylic acid of the general formula HOOC-R4-SH wherein R6 has the meaning given in Claim 1 or a salt thereof.
17. A process as claimed in Claim 16, wherein the reaction is carried out at a temperature in the range of from 20 to 2000 C.
18. A process as claimed in Claim 16 or Claim 17, which is carried out in the presence of a solvent.
19. A process as claimed in any one of Claims 16 to 18, which is carried out in the presence of a catalyst.
20. A process as claimed in any one of Claims 16 to 19, which comprises reacting an epoxide of the general formula

wherein R1 represents an alkyl group having from 6 to 58 carbon atoms and R4 represents a hydrogen atom or a methyl or ethyl group; the sum of the carbon atoms in R, and R4 being from 6 to 60, with mercaptoacetic acid or 3mercaptopropionic acid.
21. A process as claimed in any one of Claims 16 to 19, wherein the epoxide is epoxidized soybean oil which is reacted with 1, 2 or 3 mols of mercaptoacetic or 3mercaptopropionic acid.
22. A process as claimed in Claim 16, carried out substantially as described in any one of the Examples 1 to 9 herein.
23. A compound as claimed in Claim 1, whenever prepared by a process as claimed in any one of Claims 16 to 22.