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3,0?8247 Patented Feb. 19, l$$3 2 once of radical-forming catalysts, such as for example 3,078,247 per compounds (peroxides, hydroperoxides, per acids) at STABLE AQUEGUS EMULSlONS 0F ELASTGMERI€ CHLGROPRENE COPOLYMERS CON'i‘AlNlNG pH values from about 3 to 6. ZENC OXHDE with molecular oxygen or with persulphates are also suit Gustav Sinn, Bergisch-Neulrirchen, and Rosahl Dietrich and Heinz Esser, Koln-Starnmheim, Germany, assignors to Farbenfahrihen Bayer Alrtiengesellschatt, Lever lrusen, Germany, a corporation of Germany No Drawing. Filed Dec. 15, 1959, Ser. No. 859,555 Claims priarity, application Germany Dec. 19, 1953 4 Claims. (Cl. 260-2?!” Redox systems such as for example combinations of formamidinesulphinic acid able as catalysts. In this way, copolymers of chloro prene are obtained which can be satisfactorily cross linked with the said oxides. It is especially to be empha sised in this connection that the ?lms are already cross 10 linked in the manner of vulcanisation after being dried at room temperature. This discovery is surprising, since The present invention relates to aqueous emulsions of elastomeric chloroprene copolymers which are suitable for the production of shaped elements. It is known that vulcanising agents, such as sulphur or zinc oxide and vulcanisation accelerators must be added to the aqueous emulsions of synthetic elastomers, for ex ample aqueous emulsions of polymers of butadiene or its copolymers with styrene or acrylonitrile for the purpose of producing elastic ?lms. The ?lms produced from the latices are usually subjected to a vulcanisation process polymers which are composed only of chloroprene and methacrylic acid as polymerisation components do not produce a reproducible cross-linking with metal oxides. Furthermore, polymerisation mixtures containing a third copolymerisation component of the type described have the advantage that the polymerisation proceeds sur~ prisingly uniformly and in a readily controllable manner, whereas mixtures containing only chloroprene and meth acrylic acid polymerise in an extremely violent manner with strong heat of reaction, so that they are di?cult to control. In addition, when chloroprene and methacrylic acid are used alone, the major part of the methacrylic acid is not incorporated into the copolymer, but polym that the ?lms are given their optimum properties, such as for example high tearing strength, good elasticity, low .25 erises independently with formation of polymethacrylic which requires a relatively long time and relatively high temperatures. It is only by this vulcanisation process acid. abrasion and good resistance to oils and other chemicals. The zinc oxide or other oxides of polyvalent metals are It is also known to cross-link synthetic elastorners contain preferably introduced into the said copolymer emulsion ing carboxyl groups with Zinc oxide or other oxides of by the said emulsion being adjusted by means of ammonia polyvalent metals by these components being mixed and heated to temperatures higher than 50° C. According to 30 or other compounds with an alkali action to a pH value of about 6 to 6.5 and by adding to the emulsion a non the known processes, however, vulcanisates are obtained ionic stabiliser, such as for example a polyalkylene oxide which do not satisfy all requirements as regards their re derivative, in quantities of 1 to 5% by weight, calcu sistance to weather influences and ozone or their resist lated on the copolymer. For facilitating the incorpora ance to heat and chemicals. tion of the metal oxides into the said emulsions, they are The present invention is now concerned with an aque preferably dispersed beforehand by means of an aqueous ous emulsion of synthetic elastomer which is suitable for solution of a dispersing agent, such as for example sodium the production of cross-linking agents, the synthetic elasto methylene-bis-naphthalene sulphonate. mers consisting of a copolymer of 2-chlorobutadi-1,3-ene The emulsions according to the invention are excel (chloroprene), an nap-ethylene carboxylic acid and an ad 40 lently suitable for the production of ?lms and impregna ditional monomer which is capable of being copolym tions on very different materials, such as for example erised with the said components. textiles, paper and leather. As already mentioned above, Examples of ethylene carboxylic acids for the produc they have the surprising property that after they have tion of the said elastomers, are ou?-ethylenically unsatu been applied to the support and after the water has rated monocarboxylic acids, such as for example acrylic 'acid, methacrylic acid, as well as semiestcrs of fumaric 45 evaporated, they cross-link at room temperature. How ever, it is of course also possible to accelerate the cross ormaleic acid with saturated monohydric alcohols con linking by using elevated temperatures. The ?lms ob taiuing l to 18 carbon atoms, such as methanol, propanol, tained from these emulsions are further characterised by hexanol, cyclohexanol, dodecanol, octadecanol, further exceptionally good resistance to Weather in?uences, and more cap-ethylene dicarboxylic acids or their anhydrides, such as for example fumaric acid and maleic anhydride. 50 also good resistance to heat and chemicals, while at the same time they approach the vulcanisates of natural rub These carboxylic acids are advantageously incorporated by polymerisation in quantities of 1/2 to 10% by weight into the said elastomers. > Suitable as other copolymerisation components for the production of the elastomers are conjugated diole?nes, 55 such as for example butadiene, isoprene, dichlorobutadi one, as well as monovinyl compounds which are free ber as regards elasticity properties and physical values. In the following examples, the parts indicated are parts by weight. EXAMPLE 1 (a) 100 parts of water, 3 to 5 parts of surface-active paraf?n sulphonate (emulsi?er) and 0.5 part of sodium from carboxyl groups, such as styrene and acrylonitrile. pyrop-hosphate are stirred in a pressure-tight vessel with These copolymerisation components are advantageously 96 parts of chloroprene, which has been freed by Way of used in quantities from about 2 to 10%, calculated on 60 an acid-activated bleaching earth column from the sta the total monomers. Particularly suitable as cross-link biliser, for example phenthiazine, and is heated, together ing agent is zinc oxide. Further suitable agents are cal with 4 parts of methacrylic acid and 0.5 part of n-dode cium oxide, barium oxide, strontium oxide, magnesium cylmercaptan, to a temperature of 40° C. Polymerisa oxide, cadmium oxide, tin oxide, dibutyl-tin oxide or hy tion starts after adding 0.0005 part of potassium per drates thereof. ‘It is advisable to add these cross-linking 65 sulphate. agents to the aqueous emulsions in quantities of about 2 With a conversion of 80%, the reaction is stopped by toy10% by weight, calculated on the aforesaid copoly adding 1 to 2 parts of Ibis-(Z-hydroxy-3-cyclohexyl~5 mers. methylphenyl)-methane, which are dissolved in 1 to 2 ‘ For the production of the copolymers, the said com ponents are emulsi?ed in an aqueous medium with the aid of the usual emulsi?ers and polymerised in the pres parts of chloroprene and emulsi?ed with 2 to 4 parts of va 2% emulsi?er solution. The latex has gas removed therefrom in a stirrer-type 3,078,247 4 3 tioned in Example a are replaced by 91 parts of mono Example 1 are replacedby 93.5 parts of chloroprene and 2.5 parts of vbutacliene and if the procedure adopted is in other respects as previously described, there is, ob tained a latex which cross-links satisfactorily with zinc meric chloroprene and 5 parts of butadiene and if the oxide and which provides the following strength values: vessel‘ and it is concentrated to a solid content of about 48%. (b) If the 96 parts of monomeric chloroprene men~ procedure is in other respects the same as that described under a, a latex is obtained which has been prepared with the, polymerisation speeds indicated in Table I. For Table III comparison purposes, the table includes the polymerisa tion speeds of the latex according to Example a. It will 10 clearly be seen that the addition of *butadiene has con siderably lowered the polymerisation speed, and experi Latex without zinc oxide F ence shows that this produces a more uniform polymer structure with‘ the‘ monomers having very different polymerisation speeds such as chloroprene and meth acrylic acid. Table l [Latex according to Ex. 1a] Metha- Buta- crylic acid diene content, ing time, Yield g. of solid rubber in 100 g. content, percent, hours of latex 0 1 2 3 0 32 g. 40 g. 48 g. percent 4 Latex with‘ zinc oxide Vulcan. in hot air at 100° C. D F D 100 l, 370 115 900 100 , l, 105 128 920 100 106 1, 320 1, 800 135 147 800 830 95 1, 390 146 850 110 1,310 ' 139 820 108 1, 320 120 7 Operat 0 3% EXAMPLE 3 If the 96 parts of monomeric chloroprene indicated in 25 Example 1 are replaced by'86 parts of chloroprene and 10 parts ofbutadiene and if the procedurefollowed is in other respects as previously described, there is obtained 44 g.=80% yield a latex which can be satisfactorily cross-linked with zinc oxide andwhich, gives the-followingstrength values: [Latex according to Ex. 1b] 4 5 0 1 2 3 4 5 30 0 21.5 g. Table I V' 29 'g. 32 g. 34 g. 40 g. 42 g. 6 7 Latex without zinc oxide 35 Latex with zinc oxide Vulcan. in hot air at 100° C. 44 g.=80% yield F D 51 63 51 63 05 02 75 After zinc oxide has been added to the latex obtained according to Example 1a and after it has been cast to F 1. 540 1, 500 1, 460 1, 460 l, 450 1, 435 1, 410 D S8 100 115 119 118 118 120 080 040 920 020 895 865 810 form a ?lm with a thickness of approximately 0.8 mm., it is not possible for this latex to be cross-linked in a satisfactorily reproducible manner at room temperature or even at higher temperatures (up to 110° C.). The reason for this is to be found in the non-uniform poly EXAMPLE 4 mer structure (see Table II). In contrast hereto, when operating in the same manner with the latex of Example If the 96 parts of monomeric chloroprene indicated in 1b, there are obtained the strength values which are in Example 1 are replaced by.91 parts of chloroprene and 5 dicated in Table II and which can be satisfactorily re 50 parts of acrylonitrile and if the procedure in other rc produced, and these strength values are to be attributed spects is as previously described, a latex is obtained which to a uniform cross-linking. For latices containing ZnO, can be cross-linked satisfactorily with zinc oxide‘ and which 5 g. of ZnO were used to 100 'g. of copolymer. The has the following strength values: values for the tearing strength (kg/cm?) are given un der F and the values for elongation (percent) are given under D. Table V Table II Latex according to Table 1, Ex. In Vulcan. in hot air at 100° 0. Latex with- Latex with out zine ZnO oxide Latex without zinc oxide Latex according to Table I, Ex. 1 Latex without zinc oxide F Latex with zinc oxide F D F D F D F 87 93 100 100 104 108 110 950 940 930 930 890 830 800 92 04 97 100 107 108 110 880 870 860 845 840 790 750 05 08 100 100 108 118 128 1, 470 1, 340 1,320 1, 310 1, 250 1,210 1,200 187 192 197 200 210 210 212 Latex with zinc oxide 00 Vulcan. in hot air at 100° C. 42 83 87 93 07 98 114. D 870 970 880 870 860 850 S20 D 70 1, 54.0 1, 140 1,100 1, 050 1, 010 l 010 1, 000 F D 13-1 140 141 146 148 150 126 880 860 8-10 830 820 820 315 EXAMPLE 5 If the 96 parts of monomeric chloroprene indicated in Example 1 are replaced by 91 parts of chloroprene and 5 parts of dichlorobutadiene and if the procedure in other If the 96 parts of monomeric chloroprene indicated in 75 respects is as previously described, a latex is obtained EXAMPLE 2 3,078,247 6 5 with, said chloroprene being incorporated in said copoly which can be satisfactorily cross-linked with zinc oxide and which has the following strength values: Table VI Latex Without zinc oxide mer in a higher amount by weight than the sum of the other two said monomers, the addition of zinc oxide being made after adjusting said aqueous emulsion to a pH value Latex with zinc oxide of about 6 to 6.5, the amount of zinc oxide being 2 to 10% based on the amount of the emulsion, and the amount of F on the copolymer. non-ionic stabilizer added being 1 to 5% by weight based Vulcan. in hot air at 100° C. F D D 2. The process of claim 1 wherein said synthetic elas 57 67 1, 385 1, 375 120 128 910 925 74 80 85 92 1, 335 1, 320 1, 260 1, 240 134 140 140 135 905 865 845 805 75 1, 210 120 760 10 tomer is a copolymer of 80 to 97.5 percent by weight of chloroprene, 0.5 to 10 percent by weight of an alpha, bcta-ethylenically unsaturated monocarboxylic acid, and 2 to 10 percent by weight of a monomer selected from the group consisting of an additional conjugated diole?n 15 having 4 to 6 carbon atoms, styrene and acrylonitrile. 3. A stable aqueous emulsion of a synthetic elastomer EXAMPLE 6 which is suitable for the production of cross-linked shaped elements which contains 2 to 10 percent by weight, based If the 96 parts of monomeric chloroprene indicated in Example 1 are replaced by 91 parts of chloroprene and 5 on the total amount of emulsion, of zinc oxide as a cross parts of dichlorobutadiene and if the procedure in other 20 linking agent, 1 to 5 percent, based on the copolymer, of respects is as previously described, a latex is obtained which can be satisfactorily cross-linked with zinc oxide and which has the following strength values: Table VII Latex without zinc oxide D 109 114 113 113 120 124 120 1, 200 1, 160 1, 120 1, 100 1,100 1,080 1,020 F D 149 157 160 174 184 180 160 a copolymer of chloroprene, an alpha,beta-ethylene carboxylic acid, and an additional ole?nically unsaturated monomer which is copolymerizable therewith, the chloro 25 prene content of said copolymer being higher, in amount by weight, than the sum of the other two said monomers, said emulsion having a pH value of about 6 to 6.5. 4. The aqueous emulsion of claim 3 wherein said syn thetic elastomer is a copolymer of 80 to 97.5 percent by 30 weight of chloroprene, 0.5 to 10 percent by weight of an Latex with zinc oxide Vulcan. in hot air at 100° C. F a non-ionic emulsi?er, and a synthetic elastomer which is 890 910 830 820 810 790 750 What is claimed is: 1. Process for the production of a stable aqueous emul sion of a synthetic elastomer which is suitable for the alpha,beta-ethylenically unsaturated monocarboxylic acid, and 2 to 10 percent by weight of a monomer selected from the group consisting of an additional conjugated diole?n having 4 to 6 carbon atoms, styrene and acrylonitrile. 35 production of cross-linked shaped elements which com pp 0 prises adding zinc oxide and a non-ionic stabilizer to an aqueous emulsion of a copolymer of chloroprene, an alpha,beta-ethylene-carboxylic acid, and an ole?nically unsaturated monomer which is copolymerizable there References Cited in the ?le of this patent UNITED STATES PATENTS 2,710,292 2,859,193 2,959,821 Brown ______________ __ June 7, 1955 Kowalewski __________ _._ Nov. 4, 1958 Kolb ________________ __ Nov. 15, 1960 OTHER REFERENCES Brown et al.: “Rubber World,” volume 130, No. 6, September 1954, pages 784-788.