CA2068374A1

CA2068374A1 - Mixtures suitable for stabilizing polymers

Info

Publication number: CA2068374A1
Application number: CA002068374A
Authority: CA
Inventors: Chiraranjan Podder; Harro Schlesmann; Herbert Eichenauer
Original assignee: Individual
Current assignee: Bayer AG
Priority date: 1991-05-14
Filing date: 1992-05-11
Publication date: 1992-11-15
Also published as: JPH05156077A; EP0513619A2; EP0513619A3; DE4115621A1

Abstract

MIXTURES SUITABLE FOR STABILIZING POLYMERS

A b s t r a c t Mixtures of thioenol ethers and phenolic antioxidants have a stabilizing effect on oxygen-sensitive polymers, more particularly rubber-modified polymers.

Le A 28 371- Foreign Countries

Description

- 2~8~7~

MIXTURES SUITABLE FOR STABILIZING POLYMERS

This invention relates to synergistic mixtures of phenolic antioxidants and thioenol ethers which have a stabilizing effect on oxygen-sensitive polymers, more particularly rubber-modified polymers.
Synthetic polymers, particularly those containing unsaturated bonds in the molecule chain, undergo degrada-tion reactions under the effect of oxygen, heat or light, resulting in a deterioration in the properties of the polymers and in problems in the practical application of the parts produced industrially from the polymers.
Numerous stabilizing mixtures for polym~rs, including combinations of sterically hindered phenols and sulfur-containing synergists, have already been described for preventing such degradation effectsO The prior art in this regard is represented inter alia by US-PS 4,321,191 and the literature cited therein.
It has now been found that mixtures of phenolic anti-oxidants and specially synthesi~ed thioenol ethers have a synergistic effect in regard to the stabilization of polymers against the above-mentioned degradation reactions.
In addition, the phenolic ~ntioxidants may readily be incorporated in admixture with the thioenol ethers in the polymers to be stabilized.
Accordingly, the present invention relates to mixtures of A) 1 to 99 parts by weight, preferably 10 to 90 parts by weight and, more preferably, 20 to 80 parts by weight of a thioenol ether corresponding to the following formula - Rl=CH_S_R2 in which Le A 28 371- 1 Fore i gn Countri es 2~3~

R1 is a linear or branched C318 alkenyl radical or a substitued or unsubstituted C5 ~ cycloalkenyl radical and RZ is a linear or branched C3-18 alkyl radical, a C6-10 aryl radical or a C7 l2 aralkyl radical; the alkyl radical may be additionally interrupted in the chain by a heteroatom or by several hetero-atoms, and B) 99 to 1 parts by weight, preferably 90 to 10 parts by weight and, more preferably, 80 to 20 parts by weight of a phenolic antioxidant.

Suitable linear or branched alkenyl radicals ~:Rl) are 15 those containing 3 to 18 carbon atoms and pre~erably 4 to 8 carbon atoms, such as n-butenyl, isobutenyl, n-pententyl, isopentenyl, n-hexenyl, n-heptenyl and n-octenyl raclicals, preferably isobutenyl and n-hexenyl radicals; suitable substituted or unsubstituted cycloalkenyl radicals are those containing 5 to 8 carbon atoms and preferably 5 to 6 carbon atoms, such as cyclopentenyl, methyl-substituted cyclopentenyl, cyclohexenyl and methyl-substituted cyclo-hexenyl radicals, preferably cyclohexenyl and methyl-substituted cyclohexenyl radicals.
Suitable linear or branched alkyl radicals (RZ~
containing 3 to 18 carbon atoms and preferably ~ to 18 carbon atoms, which may be interrupted by a hetero atom or by several hetero atoms, such as 0, S, N, are, for example, the n-octyl, n-decyl, n-dodecyl, tert. dodecyl cmd n-octadecyl radical, preferably the n-dodecyl, tert. dodecyl and n-octadecyl radical; suitable substituted and unsub-stituted aryl radicals containing 6 to 10 carbon a~oms and preferably 6 carbon atoms are the phenyl, o-, m- or p-methylphenyl, naphthyl and methyl-substituted naphthyl radical, preferably the phenyl and methyl-substituted Le A 28 371 2 ~, .

2~83~

phenyl radical; suitable aralkyl radicals containing 7 to 12 carbon atoms an~ preferably 7 to 8 carbon atoms are the benzyl and phenethyl radical, preferably the benzyl radi-cal.
The thioenol ethers according to the invention may be prepared in known manner, ~or example by reaction of suitable aldehydes with mercaptans in the presence of acids as catalysts to form the corresponding thioacetals. In ~
second reaction step, the compounds obtained are converted into the corresponding thioenol ethers by heat treatment with elimination of mercaptans. Thioenol ethers are also directly formed from mercaptan and aldehyde providing the mercaptan and aldehyde are used in a molar ratio of 1:1.
The following are examples of suitable thioenol ethers: 2-methyl-1-propenyl tert. dodecyl thioether, 1-hexenyl-n-dodecyl thioether, cyclohexylidene methyl-n-dodecyl thioether, 3-cyclohexen (l)-ylidene methyl-n-dodecyl thioether, 3-cyclohexen~ ylidene methyl-n-octadecyl thioether, 3-cyclohexen-(l)~ylidene methyl tert.
dodecyl thioether, 3-cyclohexen-(1)-ylidene methyl-n-octyl thioether, 3-cyclohexen-(1)-ylidene methyl cyclohexyl thioether, 3-methyl-(3)-cyclohexen~ ylidene methyl-n-dodecyl thioether, 3-cyclohexen-(1)-ylidene methyl-p-tolyl thioether and 3-cyclohexen-~1)-ylidene methyl benzyl thio-ether. 3-Cyclohexen-(l)-ylidene methyl-n-dodecyl thioether and l-hexenyl-n-dodecyl thioether are preferred.
The thioenol ethers may be used individually or in admixture with one another. The most favorable mixing ratio may readily be determined by preliminary tests and depends inter alia upon the polymer to be stabilized.
Phenolic antioxidants in the context of the invention are compounds which contain at least one sterically hinder-ed phenolic group. Examples of such compounds are 2,6-di-t-butyl-4-methylphenol, 2,4,6-tri-t-butylphenol, 2,2' methylene-bis-(4-methyl-6 t-butylphenol),2,2'-thio-bis-(4-Le A 28 371 3 2~8374 methyl-6-t-butylphenol),4,4'-thio bis-(3-methyl-6-t-butyl-phenol), 4,4'-butylidene-bis-(6-t-butyl-3-methylphenol), 4,4'-methylidena bis-~2,~-di-t-butylphenol), 2,2'-methyl-ene-bis-[4-methyl-6-(1-methylcyclohexyl)-phenol],tetrakis-[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate~-methane, 1,3,5-trimethyl-2,4,6-tris-(3,5-di-t butyl-4-hydroxybanzyl)-benzene, N,N'-hexamethylene-bis-(3,5-di-t-butyl-4-hydroxyhydrocinnamic acid amide), ~cta-decyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate, 1,3,5-tris-~3,5-di-t-butyl.-4-hydroxybenzyl)-isocyanurate, 1,1,3-tris-(5-t-butyl-4-hydroxy-2-methylphenyl3-butane, 1,3,5-tris-(3,5-di-t-butyl-4-hydroxybenzyl)-mesitylene, ethylene glycol bis--C3,3-bis-(3'-t-butyl-4'-hydroxyphenyl)-buty-rate], 2,2'-thiodiethyl-bis-3-(3,5-di-t-butyl-4-hydroxy-phenyl)-propionate, di-(3-t-butyl-4'-hydroxy-5-methyl-phenyl)-dicyclopentadiene, 2,2'-methylene-bis-(4-methyl-6-cyclohexylphenol), hexane-1,6-diol bis-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate, 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5~triazine, 3,5-di-t-butyl-4-hydroxybenzyl phosphonic acid diethyl ester and triethylene glycol bis-3-(t-butyl-4-hydroxy-5-methyl-phenyl)-propionate.
Preferred phenolic antioxidants are 2,6-di-t-butyl-4-methylphenol,octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate, 2,2'-methylene-bis-(4-methyl-6-cyclohexyl-phenol), 2,2'-methylene-bis-~4-methyl-6-t-butylphenol), triethylene glycol bis-3-(t-butyl-4-hydroxy-5-methyl-phenyl)-propionate and tetrakis-[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate]-methane.
In additio~, the mixtures according to the invention may contain phosphorus-containing stabilizers, such as distearyl pentaerykhritol diphosphite, tris-(nonylphenyl)-phosphite, tetrakis-(2,4-di-t-butylphenyl-4,4'-biphenyl--ene)~diphosphonite, tris-~2,4-di-t-butylphenyl)-phosphite, neopentyl glycol triethylene glycol diphosphite, diisodecyl Le A 28 371 4 2~37~

pentaerythritol diphosphite, tristearyl phosphite, tri-lauryl phosphite, triphenyl phosphite, and/or nitrogen-containing stabilizers, preferably aromatic amines, such as 4,4l-di-t-octyl diphenylamine, 4,4'-di~ -dimethyl-benzyl)-diphenylamine,phenyl-~naphthylamine,N-isopropyl-N'-phenyl-p-phenylenediamine, N-phenyl~2-naphthylamine and/or phenyl-2-aminonaphthalene.
The mixtures according to the invention may contain the above-mentioned phosphorus-containing and/or nitrogen-con~aining stabilizers in cruantities of up to 50 paxts byweight, preferably in cruantities of up to 45 parts by weight and, more preferab~y, in quantities of up to 40 parts by weight, based on 100 parts by weight of the mixture of A+B.
The synergistic mixtures according to the invention are suitable as stabilizers for stabili~ing polymers against oxidative degradation or other changes produced by the effect of oxygen.
Polymers which may be stabilized by addition of the mixtures according to the invention are, for example, acrylonitrile/butadiene/styrene terpolymers (ABS), methyl methacrylate~butadiene/styrene terpolymers (MBS), acrylo-nitrilejstyrene/acrylate rubber terpolymers (ASA), acrylo-nitrile/EPDM rubber/styrene terpolymers ~AES), high-impact polystyrene (HIPS), polycarbonate/ABS blends, polycar-bonate/ASA blends, polycarbonate/MBS blends, polyphenylene oxide/HIPS blends, rubber-modified polyamides (polyamide-6, polyamid 66, polyamide-12), rubber-modified polyesters (polyethylene terephthalate, polybutylene terephthalate), rubber-modified polyolefins (polyethylene, polypropylene).
The mixtures according to the invention are suitable as stabilizers ~or stabilizing rubbers, for exar,lple polybutadiene, pulyisoprene, bu~adiene/
styrene-copolymers, butadiene/acrylonitrile-copolymers, EPDM-rubbers, polychloroprene, too; further they are suitable for polyoleFins, for example polyethylene and polypropylene.
The mixtures according to the invention are particularly efFective in the stabilization of ABS polymers~ MBS polymers, styrene/acrylonitrile copolymcrs, d -methyl styrene/acrylonitrile copolymers, high-impact polystyrene, polyolefins and rubber polymers and also polymer blends Le A 28 371 5 2~6~3~

containing these polymers. Apart from being very effec-tive, the mixtures according to the invention are extremely easy to incorporate by virtue o~ their liquid or readily fusible form.
The quantities in which the mixtures according to the invention are used for stabilization amount to between Ool and 5 parts by weight, pre~erably to between 0.2 and 4 parts by weight and, more preferably, to between 0~5 and 3 parts by weight per 100 parts by weight polymer to be stabilized.
The stabilizer composition may be added to the polymer material in solid form, in the fo~m of a solution or in the form of a dispersion or an emulsion. The constituents of the mixture may also be added to the polymer in various forms. The stabilizer composition may be incorporated in emulsion or solution on kneaders or rollers, depending on the state of the polymer to be stabilized.
The present invention also relates to stabilized polymeric molding compounds which are characterized in that they contain 0.1 to 5 parts by weight, preferably 0.2 to 4 parts by weight and, more preerably, 0.5 to 3 parts by weight per 100 parts by weight polymer of the mixture according to the invention of phenolic antioxidant and a thioenol ether.
Examples Example 1 (Preparation of thioenol ethers) 3-Cyclohexen-(1)-ylidene methyl-n-dodecyl thioether:
A mixture of 110.1 g (1 mol) tetrahydrobenzaldehyde, 202.4 g (1 mol) n-dodecyl mercaptan and 500 ml toluene containing 2.6 g p-toluene sulfonic acid is heated for 3 hours to boiling temperature on a water separator. After the elimination of water has stopped, the reaction mixture Le A 28 371 6 - 2~337~

is washed free from acid and is then fractionated in a high vacuum. 3-Cyclohexan~ ylidene methyl-n-dodecyl thio-ether is obtained in a yield of 240 g. The thioenol compounds listed in Table 1 wera prepared in the manner described above.

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Example 2 The parts mentioned are all parts by weight, based on ~olid constituents.
All DSC measurements were carried out using a Perkin Elmer DSC 2 (purging gas oxygen 3.6 l/h, heating rate in dynamic measurement 20 K/min., isothermal measurement at 180C~. Dry, stabili~ed graft rubber powder, particle size O.5 to 0.1 mm, was used for the measurements.
The following substances were used in the tests described hereinafter:

A. Graft rubber latex obtained by radical emulsion poly-merization of 50 parts by weight of a styrene:acrylo-nitrile (72:28) mixture in the presence of 50 parts by weight of a polybutadiene latex having an average particle diameter (d50) of 0.~ ~m.

B. Octadecyl-3-(3,5-di-tert.-butyl~4~hydroxyphenyl)-propionate (Irganox 1076, a product of Ciba Geigy) C. Dilauryl thiodipropionate (Irganox PS 800, Ciba Geigy) D. 3-Cyclohexen-~l)-ylidene methyl-n-dodecyl thioether 2S ~ H-S-(CH2)11CH3 E. 1-Hecenyl-n-dodecyl thioether CH3-(cH2)3-cH=cH-s-(cH2)llcH3 F. Cyclohexylidene methyl dodecyl thioether O--CH-S- (CH2) 11CH3 G. 3-Methyl-(3)-cyclohexen-(1)-ylidene methyl-n-dodecyl thioether Le A 28 371 9 2 ~ 7 ~

,- ~
$S~CH-S- (CH2) ~ ~C~3 H. 3-Cyclohexen ~ ylidene methyl octadecyl thioekher ~ H-S-~H2)17CH3 0 I. 3-Cyclohexen (13-ylidene methyl-tert.-dodecyl thio-ether ~ fH3 1 ~ H S ~ ~CH2~H

K. 2-Methyl-1-propenyl tert.-dodecyl thioether CH3 ~ IH3 C=CH-S ~ -~H2 ~H3 CH3 3 Preparation of a stabilizer dis~ersion using the phenolic antioxidant B and a sulfur-containinq com~nent (C to K) A hot solution of 6.5 parts of a nonionic emulsifier (ethoxylated nonylphenol) in 93.5 parts by weight water is added with vigorous stirring (Ultraturrax) to a mixture of 50 parts by weight phenolic antioxidant B and 50 parts by weight sulfur-containing component, followed by st:irring until a stable dispersion is formed. The stirring times required to obtain a stable dispersion are shown in Table 2.

Stabilization of the qraft rubber latex A and workinq up The above-described stabilizer dispersions were added to the graft rubber latex described under A in such quanti-~e A 28 371 lo 2~83~

ties that a content of 1 part by weight phenolic antioxi-dant B and 1 part by weight sulfur-containing component was obtained for 100 parts by weight graft rubber. The latex was then calculated with a solution of a magnesium sulfate/
S acetic acid mixture, the polymer was removed after filtra-tion of the precipitation mixture and was then dried in vacuo at 70C. The graft rubber powder was sieved using a Hav~r ~ Boecker test sieving machine comprising vibrating sieves, after which the sieve fraction having a particle size of 0.5 to 0.1 mm was used for the DSC measurements.

Testinq of the natural color of ABS polymers after thermo-plastic ~rocessinq 40 Parts by weight of the non-sieved gra~t polymer powder were homogeneously mixad in an internal mixe:r with 60 parts by weight of a styrene:acrylonitrile (72:28) copolymer and 2 parts by weight of a lubricant ~penta-erythritol tetrastearate), after which the mixture was granulated and injection molded at 240C to flat plates.
These plates were used to evaluate the natural color on the basis of the following scale:

1 = very light 2 = light 3 = slight yellowing Le A 28 371 11 2~37~

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Claims

1. Mixtures of A) 1 to 99 parts by weight of a thioenol ether corre-sponding to the following formula R1=CH-S-R2 in which R1 is a linear or branched C3-18 alkenyl radical or a substitued or unsubstituted C5-8 cycloalkenyl radical and R2 is a linear or branched C3-18 alkyl radical, a C6-10 aryl radical or a C7-12 aralkyl radical; the alkyl radical may be additionally interrupted in the chain by a heteroatom or by several hetero-atoms, and B) 99 to 1 parts by weight of a phenolic antioxidant.

2. The use of the mixtures claimed in claim 1 for stabil-izing polymers.

3. Polymeric molding compounds containing the mixture claimed in claim 1 in quantities of 0.1 to 5% by weight, based on the polymer.

4. Polymeric molding compounds as claimed in claim 3 containing ABS polymers, MBS polymers, high-impact poly-styrene, polyolefin or rubber polymers.

Le A 28 371 13