3,838,140 United States Patent Office Patented Sept. 24, 1974 1. 2 is salts, in particular sodium or potassium salts of the fol 3,838,140 lowing types of compounds: long chain fatty acids, colo MOLECULARWEIGHT REGULATON EN phony or colophonyl derivatives, e.g. colophony obtained CELOROPRENE POLYMERS Rudolf Mayer-Mader, Cologne, and Jurgen Boldt, from wood, tall oil colophony, disproportionated colo Opladen, Germany, assignors to Bayer Aktiengesell phony or partly polymerised colophony, higher alcohol schaft, Leverkusen, Germany sulphates and aryl sulphnic acids, e.g. alkylbenzene sul No Drawing. Filed Nov. 9, 1972, Ser. No. 305,134 phonic acids, and the condensation product of formalde Claims priority, application Germany, Nov. 13, 1971, hyde with a naphthalene sulphonic acid. P 21 S6 452.3 The concentration of the organic monomer in the emul Int, C. C08d 3/14: CO8f 1/80, 3/32 O sion used as starting material is not of decisive importance. U.S. C. 260- 92.3 4 Claims It is generally 30 to 60%, based on the total weight of the emulsion when preparing the polymer. ABSTRACT OF THE DISCLOSURE The pH is preferably in the alkaline region. Polymerisa tion may be carried out at temperatures of between 0° C. A process for polymerising a monomer composition of 5 and 80° C. and is preferably carried out between 30° C. chloroprene and 0 to 50% by weight of one or more other and 50° C. copolymerisable monomers in aqueous emulsion on radi Polymerisation is stopped when monomer conversion cal forming catalysts in the presence of a selected dialkoxy has reached a stage at which a polymer which is soluble xanthate disulphide and a mixture of the polymer thus in benzene is obtained. The appropriate point at which obtained with a benzene insoluble cross-linked chloroprene 20 polymerisation is stopped depends to a certain extent on polymer. the amount of dialkoxyxanthogendisulphide used but is generally at a monomer conversion of about 50 to 70%. It is known to polymerise chloroprene in the presence The usual "stopping agents' such as those indicated in of dialkylxanthogendisulphides as molecular weight regu U.S. Patent 2,576,009 are used for stopping polymerisa lators (see British Patent No. 512,458). It is also known 25 tion. Unreacted monomer is removed in known manner, to use mercaptans for regulating the molecular weight (see e.g. by steam distillation as described in U.S. Patent No. U.S. Patent No. 2,567,117). 2,467,769. If polymerisation is stopped when not more than 70% Up to 50% of the chloroprene may be replaced by some of the monomers have reacted, the polychloroprenes ob other copolymerisable monomer. Suitable comonomers tained by these methods are soluble in benzene, i.e. they 30 for this purpose are, for example, vinyl aromatic com are not crosslinked. Polychloroprene polymers which are pounds Such as styrene, vinyl toluenes and vinyl naphtha particularly easy to process are obtained by mixing such lenes, aliphatic conjugated diolefine compounds such as benzene soluble polychloroprenes which are not cross 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene and linked with cross-linked benzene insoluble chloroprene 2,3-dichloro-1,3-butadiene, vinyl ethers, esters and ketones polymers (see British Patent No. 1,158,970 and German 35 Such as methylvinylether, vinyl acetate and methylvinyl Offenlegungsschrift No. 2,008,673). ketone, and esters, amides, and nitriles of acrylic acid and These mixtures, however, have insufficient thermal sta methacrylic acid such as ethyl acrylate, methyl methacry bility if dialkylxanthate disulphides are used as molecular late, methacrylamide and acrylonitrile. weight regulators (their Mooney viscosity increases on This invention also relates to a mixture of a benzene exposure to heat) and insufficient mechanical strength 40 Soluble uncross-linked chloroprene polymer (a) and a when mercaptains are used as molecular weight regulators. benzene-insoluble cross-linked chloroprene polymer (b), This invention relates to a process for polymerising a wherein the benzene-soluble chloroprene polymer is a monomer composition comprising chloroprene and 0 to polymer of chloroprene and if desired of up to 50% by 50% by weight based on total monomer composition of 45 Weight (based on the monomer mixture) of another co one or more copolymerisable monomers in an aqueous polymerisable monomer which has been obtained in the emulsion on radical forming initiators, in the presence of presence of 0.1 to 20 parts by weight per 100 parts by 0.1 to 20 parts by weight per 100 parts by weight of Weight of monomer of a dialkoxyxanthate disulphide of monomer composition of a dialkoxyXanthogendisulphide the formula of the formula 50 V/, s s V/, (CIA-o-c-s-s-C-O-(CH.) not to -- to-tely 55 in which R and R' represent methyl or ethyl. The benzene soluble chloroprene polymer in this mix ture is therefore the product whose preparation has been described above. in which R and R' represent methyl or ethyl. Benzene insoluble cross-linked chloroprene polymers The basic polymerisation process of chloroprene is 60 suitable for the mixture with the soluble chloroprene poly known in the art, see e.g. U.S. Patents Nos. 3,042,652; mer described above may be prepared by various proc 3,147,317 and 3,147,318. esses which yield a cross-linked polymer in latex form. For In the process of this invention, the dialkoxyxanthogen example, chloroprene may be polymerised to a high con disulphides of Formula I are generally used in quantities version (i.e. about 90 to 100%) in the absence of a chain of 0.1 to 20 parts by weight per 100 parts of monomers, 65 transfer agent or with only small quantities of such a sub preferably 0.15 to 1 part by weight. Dialkoxyxanthogen stance, e.g. an alkyl mercaptain or dialkoxyxanthogendi disulphides of Formula I are known. sulphide. A suitable process resulting in high conversion Polymerisation is carried out in aqueous emulsion using has been described in U.S. Patent No. 3,147,317. Another a polymerisation catalyst which forms free radicals, e.g. method of forming a cross-linked chloroprene polymer an alkali metal persulphate (such as potassium persul 70 consists in including in the polymerisation system a mono phate). Any of the usual emulsifiers may be used for pre mer which is copolymerised with chloroprene and which paring the monomer emulsion. These include water-soluble contains two or more polymerisable double bonds. Suit 3,838,140 3 4. able comonomers for this purpose are, for example, divin EXAMPLES ylbenzene and esters of acrylic acids and polyhydroxy compounds such as alkylene glycols, dihydroxybenzene or 1. Preparation of benzene soluble polychloroprenes with trimethylolpropane. di-(3-oxapentyl-1) Xanthogendisulphide These polymerisations are effected by the same meth 5 A monomer mixture of ods which yield benzene soluble chloroprene polymers 100 parts by weight of chloroprene and but monomer conversion can be higher, e.g. up to 90 to 100%. X parts by weight of di-(3-oxa-pentyl-1)-xanthogendisul Another method of producing cross-linked chloroprene phide polymers which are suitable for the purposes of this in 10 and a mixture of vention consists in subjecting the latex of an uncross 120 parts by weight of demineralised water, linked chloroprene polymer to an after-treatment by 5 parts by weight of the sodium salt of a dispropor which the polymer in the latex is cross-linked. Examples - tionated abietic acid, of suitable methods are irradiation with actinic light as 0.5 parts by weight of the sodium salt of a condensation in U.S. Patent No. 3,042,652 and treatment with an or 5 product of naphthalene sulphonic acid and formalde ganic peroxy compound as in U.S. Patent No. 3,147,318. hyde, In the preparation of the cross-linked chloroprene 0.5 parts by Weight of sodium hydroxide and polymer, up to about 20% of the chloroprene may be 0.5 parts by Weight of tetrasodium pyrophosphate were replaced by another monomer. Examples of such mono prepared Separately. mers have been mentioned above in the description of 20 the preparation of the benzene soluble chloroprene The monomer mixture is emulsified in the aqueous polymer. phase, the emulsion is heated to 43° C. and polymerisa The benzene insoluble chloroprene polymer preferably tion is initiated by dropwise addition of an activator solu used is a copolymer of chloroprene and 2 to 20% by tion of 2.5 parts by weight of formamidine sulphinic weight, based on the quantity of chloroprene, of a di 25 acid and 97.5 parts by weight of water. ester of dihydric aliphatic alcohol and an acrylic acid. Polymerisation is stopped when 65-70% of the mono These diesters correspond to the formula, mers have been converted, the remaining monomers are removed by Steam distillation and a sample of the poly mer is isolated from the resulting latex by electrolyte 30 precipitation followed by drying. The experiment was carried out with various quantities R1 O O R2 of di- (3-oxapentyl-1)-xanthogendisulphide. The results are shown in Table I. in which R1 and R2 represent hydrogen, alkyl radicals containing 1-4 carbon atoms or chlorine and X repre TABLE I sents an alkylene radical with 2-20 carbon atoms. Exam Mooney Farts by viscosity ples of such compounds are: ethylene dimethacrylate, weight of ML-4 propylene dimethacrylate, butylene dimethacrylate, iso Xanthiate (100° C.) of butylene dimethacrylate, ethylene diacrylate, propylene 40 disulphide the polymer Experiment: diacrylate, butylene diacrylate and isobutylene diacrylate. >200 The polymerisation process for the preparation of these 140 products is similar to the usual method of polymerisation 59 42 of chloroprene in aqueous emulsions.