United States Patent Office Patented June 8, 1965

3,188,304 United States Patent Office Patented June 8, 1965

2 3,188,304 Now, however, it has been found that mercaptain modi CBL RUBBER POLYMERZAION PRO CESSES fiers are not equivalent in “hot” and “cold' rubber emul USNG AMCXTURE OF DECYL AND UNECYL sion polymerization systems. Surprisingly, in accord with MERCAPANSAS MODEFERS this invention, significant improvements are obtained in Roland H. Goshon, Fort Washington, Harry E. Alert, "cold' polymerization recipes for a styrene-butadiene sys Lafayette Hil, Bernard Bachholz, Fiorigwin, and tem when a modifier is employed which is a mercaptain Alfred C. Whiton, Norristown, Pa., assignors to containing 9, 10 or 11 carbon atoms in its molecule (i.e., Penasalt Chemicals Corporation, Philadelphia, Pa., a nonyl, decyl, and undecyl mercaptans) and these improve corporation of Penasylvania ments result also when the modifier used is a mixture of No Drawing. Fied July 17, 1961, Ser. No. 24,318 O these mercaptains. 6 Clains. (C. 260-84.3) One particular advantage found in using nonyl, decyl This invention deals with the preparation of synthetic or undecyl mercaptain as a modifier in “cold' rubber. rubber as obtained from styrene and butadiene and is par polymerization recipes is that improved modifier efficiency ticularly concerned with the use of certain mercaptans as is obtained. Modifier efficiency can be empirically meas modifiers in those polymerization processes carried out 5 ured in a synthetic rubber polymerization system by meas below about 50 F. (e.g. cold rubber processes). uring the Mooney viscosity of the dry polymer produced It is old in the art to use mercaptans as modifiers in the from such a system. At a given concentration level in emulsion polymerization of olefinic monomers such as the System, a modifier which produces a soft (low Mooney styrene and butadiene to obtain elastomeric products. viscosity) polymer is classified as more efficient than a Such polymerization modifiers are substances which are 20 modifier which produces a stiff (high Mooney viscosity) included in a polymerization recipe to make possible the polymer. The processability of a polymer is dependent production of a plastic, workable polymer. With no mod upon its viscosity and an efficient modifier is desired in ifier present in the recipe a tough, unworkable polymer is Synthetic rubber recipes, since less of it will be required produced. The exact role which the modifier plays in a to produce a polymer of specified Mooney viscosity. An free-radical initiated polymerization has been the subject 25 of much study, especially in butadiene-styrene emulsion other specific advantage obtained from this invention is copolymerization systems and it has been established that that the use of the decyl and undecyl mercaptans or their the modifier functions primarily as a chain transfer agent mixture is not adversely affected by the presence of resid in a free radical mechanism, and in this manner it controls ual olefin which is often present in the mercaptain from the molecular weight (and hence the processability) of the 30 its process of manufacture. This is particularly important polymer. where unreacted styrene used in the “cold" rubber manu Wolthan, in his U.S. Patent 2,281,613, disclosed that facture is recycled for further polymerization with the control of the polymerization is provided and plasticity butadiene component. As this recycle occurs, the olefin of the polymers obtained by incorporating in the aqueous contaminant from the mercaptain builds up in the styrene emulsion an aliphatic mercaptain having at least six carbon 35 monomer. With dodecyl mercaptain, for example, the atoms in an aliphatic linkage. In U.S. 2,378,030 Olin dis presence of Small amounts of the olefin from which the closed his improvement in the use of aliphatic mercaptains mercaptain is derived can build up to an amount on the having between 8 and 16 carbon atoms and pointed out order of 0.1 to 0.2 part per hundred parts of monomer the particular advantage of achieving high efficiency in and this significantly reduces modifier efficiency and causes the use of tertiary-dodecyl mercaptain as obtained by con 40 the rubber obtained to be stiff and undesirable. On the densation of triisobutylene with hydrogen sulfide. Addi other hand, use of decyl and undecyl mercaptains contam tional study in the use of mercaptan modifiers resulted in inated with starting, unreacted olefin (e.g. decenes and additional advances. For example, Crouch and Mashofer described in U.S. Patents 2,549,961 and 2,549,962 the ad undecenes) causes no adverse effects and actually results vantage of using blends of tertiary alkyl mercaptains hav 45 in a slight improvement in efficiency. ing 8 to 16 carbon atoms per molecule. In all of the above Still another unexpected advantage in the use of nonyl, disclosures the research was directed to and the disclosures decyl and undecyl mercaptains or their mixtures is that they are specific to the use of such mercaptain modifiers in enable a high conversion rate to be achieved. It has been styrene-butadiene polymerization recipes carried out at observed that the conversion rate is adversely affected about 50° C. or higher. 50 When certain mercaptans (particularly those containing Immediately after World War II, however, it was less than nine carbon atoms) are used in “cold" rubber learned that rubber having improved properties for tire polymerization recipes. treads was obtained when polymerization was carried out In order to facilitate discussion of the mercaptains they at temperatures of about 50 F. or lower and in the pres Will be referred to as C. mercaptains where C refers to a ence of an organic peroxide or hydroperoxide initiator. 55 hydrocarbon radical and x is the number of carbon atoms This development lead to the well-known “cold' rubber per molecule. Thus, Co is nonyl mercaptan, Co is decyl of commerce. In using modifiers for the cold polymeriza mercaptan, C11 is undecyl mercaptan, etc. The C, Co, tion recipes the industry logically used the same mercaptain and C11 mercaptains used in accord with the invention modifiers employed for the previously known “hot” rubber 60 have highly branched alkyl chains and are predominantly recipes and these were found to work quite well. Of Secondary and tertiary mercaptains. These compounds are particular value and predominantly used were tertiary readily prepared in accord with the known methods for dodecyl mercaptain and a mixture of tertiary mercaptains the addition of H2S to olefins. Because mixtures of olefins containing 12, 14 and 16 carbon atoms. are normally used for the HS addition, rectification of 3,188,804 s 3 A. the mercaptain mixture is carried out to isolate the C9, In the actual polymerization procedure, normal polym Co, and C1 mercaptains. Reference is made to U.S. erization ingredients and the usual operating techniques 2,392,554 for details of the mercaptain preparation process. will be employed except that the mercaptain modifier will In that patent it is pointed out that these mercaptain mix be a C9, Co, or C11, or a mixture of these mercaptains. tures are made by the method which comprises the re As indicated, peroxides or hydroperoxides will be used action of hydrogen sulfide with an olefinic polymer selected as catalysts (e.g. p-menthane hydroperoxide, cumene hy from the group consisting of polymers of propylene, butyl droperoxide, phenylcyclohexyl hydroperoxide, etc.) and ene, amylene and their mixtures. such recipes for “cold' rubber recipes are discussed by it will be understood that the C3, Co, and C1 mer G. S. Whitby in his book "Synthetic Rubber, John Wiley captains are not discrete compounds, but comprise isomer 0 & Sons, 1954. The amount of modifier used will be in mixtures. As indicated above, however, the compounds accord with usual practice and will vary from about are predominantly secondary and tertiary mercaptains and 0.05-0.50 part per hundred parts of monomer. Less than the purity of the rectified fractions will be on the order this annount of modifier results in too stiff a polymer of 90-100% mercaptain by weight. It will also be under product whereas more than about 0.50 phm. causes too stood, for example, that the term "Co mercaptan' re 5 great a softening of the polymer. Preferably, from about fers to a fraction consisting essentially of decyl mer 0.10 to 0.3 phin. will be used. captan, but there will also be present small amounts of C11 mercaptain and probably traces of other mercaptains. EXAMPLE 1. Likewise the term 'C mercaptain” refers to a fraction Butadiene-styrene copolymers were prepared by polym consisting essentially of undecyl mercaptain with decyl 20 erization at 43 F. according to the following SBR-1500 and other mercaptains present in small amounts. "Ca recipe. mercaptain' is likewise predominantly nonyl mercaptain ingredients: Parts by weight with trace amounts of other mercaptains. The C9, C10 and Butadiene ------72 C1 mercaptain mixtures will also be of a comparable purity Styrene ------28 and will contain the C9, C10, and C11 mercaptain com 25 Water ------200 ponents in weight ratios ranging from about 10:90 to Mercaptain ------Variable 90:10 for two component systems and for three com Rosin soap ("iDresinate” 214) ------4.50 ponent systems the lowest concentration of a single con Sodium sulfonate dispersant ("Daxad' ponent will be about 5% by weight. Because of avail 11) ------0.10 ability, the preferred modifier will be a Co and C11 mix 30 Sequestrant (Versene Fea Specific) ------0.04 ture which will consist essentially of approximately equal FeSO47H2O ------0.12 amounts by weight of Co and C11 mercaptan. When K4P2O7 ------0.15 using the C component, it will be used preferably in a Na3PO4'12H2O ------0.30 mixture with the Co and/or C11 mercaptain because of p-Menthane hydroperoxide ------0.04 its tendency to lower conversion rates. As indicated, the 35 mercaptains are prepared by reaction of H2S with the The mercaptains used were C9, C10, C1, a mixture of es appropriate olefins and since different sources of olefins sentially 50:50 parts by weight of C1 and C11 mercaptains will contain somewhat different proportions of compo and, as a control, a polymer made with commercial C ments, the mercaptain products will vary accordingly. mercaptain obtained by reaction of propylene tetramer Complete purification is neither practical nor necessary. 40 with HS. A separate control polymer was used for com The following Table A indicates the physical properties parison in each case in order to overcome any differences of the C9, Co, and C11 mercaptains and their mixtures due to polymerization technique in the batch polymer as obtained from several commercial olefin Sources: ization enployed. Results are determined by comparing

Table A PROPERTIES OF MERCAPTAIN

Olefin CSH and CSF CSH CuSH CoSH, CioSH, CSI mixture fraction fraction and C11SH mixture

Source A: Distillation range: Distillation range: Distillation range: - ul Cs-0.8% 76°-90° C. at 5 mm. 90°-1045° C. at 15 78-82° C. at 4 milm. Co-1.5% Refr. index: nD25=1.4578 C10-43.9% nD23=1.4575 nD25=1.4562 percent S=17.3 Cti-44.7% percent S=17.7 percent S=18.1 (Theory=17.0) C1-9.1% (Theory=18.4) Source B: - Distillation range: - Distillation range: -- "S", 969-105° C. at 5mm, 86325 Cat36 Co-5% n25a1.4570 nm. v C10-53% percent S=8.2 n25=4569 C11-25% percent S=17.7 C12-3% Source C: ------B.P. 198° C. at 760 Commercial C9. percent S=19.3

As indicated, the C9, Co, and C11 mercaptains will be Mooney viscosity values and the fairest comparison of used in accord with this invention in "cold' rubber polym 70 these various mercaptains is achieved by comparing the erization recipes (i.e. in aqueous emulsion systems at difference in Mooney viscosity between the experimental temperatures between about 15 F. and 50 F.). The and the control polymer. Mooney viscosity values were monomers employed for the elastomer preparation will determined in the usual manner at 212 F. on the raw, be a diene such as butadiene or isoprene, and a comono uncompounded polymer after a one-minute preheat plus mer such as styrene or alpha-methyl styrene. 75 four minutes operation of the large rotor. The values 8,188,804 5 6 obtained were then added to give the values in the table The mercaptans used were an essentially 50:50 mixture which follows: of C10 and C11 mercaptain and a commercially available Table I C12 mercaptain derived from propylene tetramer. As in EFFECT OF WARIOUS MERCAPTAN MODIFIERS ON BUTA previous examples, Mooney viscosity data were used to DIENE-STYRENE COPOLYMERS PREPARED BY SBR-1500 5 evaluate the modifier efficiencies. Table III lists the time RECIPE of polymerization, the percent conversion, and Mooney Mooney viscosity viscosity data. (MIL 1-4 at 22°F) Change in Table III Experimental ploymer Mooney EFFICIENCY OF WARIOUS MERCAPTAINS IN SBR-1000 modifier (0.20 phm.) Control viscosity vs. 0. (“HOT) RUBBER RECIPIES EEEstalpolymer d:55,.2Upnia. control CSH) Polymeri- Percent Mooney viscosity data Mercaptain modifier zation cover CoSH------55.5 58.0 -2, 5 (0.30 phm.) time (hrs.) sion CoSH------33.5 47.5 -15.0 ML 1-4 MI, 1'--10' C11SH------33.5 55.5 -22.0 5 C1GSH--CISH 31.0 56.5 -25.5 CoSH--C11SH------2.0 10.3 9.5 16.0 4.0 26.7 phim. =parts per hundred parts of total monomers. 6.0 44.2 It is clearly evident from the data in the above table 7.75 56.8 Cu2SH------2.0 10.7 21.0 7.5 that the modifier efficiency of the C mercaptain is greater 20 4.0 26.7 than that of the commercially used C12 mercaptain, and 6.0 43.6 the C10, C11 and mixture of Clo and C11 mercaptains are 7.75 55.8 very much superior in modifier efficiency. CoSH-HC11SH------2.5 19.2 39.0 32,0 5.0 89.5 On the other hand, when a C and C mercaptain was 8.0 64.6 used in a similar test procedure, no improvement over 9.25 72.2 the C1 mercaptain was obtained and it was found that Ci2SH------2.5 19.3 40.0 32.5 reaction rate was also very much lowered. 5.0 39.6 8.0 64.7 EXAMPLE 2.-EFFECT OF OLEFIN 9.25 7.3 CONTAMINATION Using the same SBR-1500 recipe and procedure of 30 It is quite evident from Table III that with SBR-1000 Example 1, polymers were prepared with 0.20 phm. of rubber recipes, the Co and C11 mercaptans are not signifi a C12 and a mixture (essentially 50:50) of C10 and C11 cantly better than the commercially available C12 mercap mercaptain modifiers and also with these modifiers which tan. Thus, it is clear that the present invention is limited were contaminated with the starting olefins from which to the use of Co and C11 mercaptans in low temperature the mercaptains were prepared by HS addition. Again, polymerization systems such as SBR-1500 recipes where Mooney viscosity values were used to compare modifier polymerization is carried out attemperatures below about efficiencies with uncontaminated controls. Table II 50 F. shows the experimental details and the results obtained. EXAMPLE 4-COMPARISON OF CISH AND CuSH Table II 40 MIXTURE WITH OTHER MERCAPTAN MIX SBR-1500 POLYMERS MODIFIED WITH ALKYL MERCAP TURES TANS CONTAMINATED WITH OLEFINS Using the procedure of Example 1 with the same SBR Modifier (0.20 phm.) Contaminant Mooney viscosity (ML1'--ML 4. 1500 recipe, polymerizations were made using a commer at 212 F.) cially available mercaptain mixture known as Mixed Ter 45 tiary Mercaptans (MTM available from Phillips Petro C10SEI-CSE.------0.1 phm. C10 and C1 35.0 leum Co.) and consisting essentially on a weight basis of olefins, 38 CoS-C11SE.------None------.5 60% C1 mercaptan, 20% C14 mercaptan and 20%. C16 mercaptan. Table IV indicates the conditions of the po C12SH- -- 0.1 phm.C. olefin 6.5 CISH -- None------50.5 lymerization and compares the product with the Co and 50 C11 mercaptain mixture of this invention. It is clear from Table II that a stiff rubber is obtained when as little as 0.1 phm. of C12 olefin is present in the Table IV polymerization system along with the C.12 mercaptain COMPARISON OF CoS AND CSE MIXTURE WITH OTHER modifier. However, the same amount of olefin con MIXED TERTARY MERCAPTAINS IN SBR-500 RECIPE taminant in the mercaptain modifiers of this invention causes no adverse effect, but possibly a favorable slight Rate data Mooney viscosity data Mercaptain modifier softening effect in the rubber polymer. A slightly softer (0.17phin.) Time, Percent polymer was also obtained with a Co mercaptain contain hrs. conver- ML 1'--4 ML 1'-10 ing 0.10 phm. of Co olefin as compared to a Co mer SO captain without olefin contamination. Likewise, a C11 60 60% C12, 20% C14, 20% C16- 1.5 9.7 >136 29 mercaptain containing 0.1 phm. of C11 olefin showed no 4.0 42.8 stiffening effects on an SBR-1500 recipe. 5.5 59.3 5.75 63.2 EXAMPLE 3.- USE OF SBR-1000 ("HOT") 50% C10, 50% C11------... 5 19.3 52.0 45.0 RUBBER RECIPES 4.0 44.0 A rubber was prepared from styrene and butadiene 5.5 59.6 by polymerization at 122 F. of the following SBR-1000 5.75 60.4 recipe. It is clear that the Co-C11 mercaptain mixture is vastly Ingredients: Parts by weight superior to the MTM mixture in modifier efficiency. Butadiene ------72 70 Styrene ------28 EXAMPLE 5-COMPARATIVE EFFICIENCIES OF Water ------180 Co-C MERCAPTAN MIXTURES AND C MER Mercaptain ------0.30 CAPTAN IN SBR-1500 RECIPES Sodium fatty acid soap ------4.7 The data presented in following Table V were obtained K2S2O8 ------0.40 75 in accordance with the procedures detailed in Example 1. 3,188,304. 7 8 Table V It is clear from the above table that the Co, Co and C1 COMPARATIVE EFFICIENCIES OF Co-C MERCAPTAN mercaptain blends give improved efficiency over C1 mere WS. C. MERCAPTAN captan. Also of interest is that the polymerization rate is not significantly affected at even the higher concentra Rate data Mooney viscosity Modifier tions of C9 mercaptain although there is some slight de Mercaptain concentra crease in rate when the C content of the blend is about modifier tion, phin. Time, Percent 75% by weight or higher. hrs. Coller ML 1'--4 ML 1--0 Sion EXAMPLE 7-EFFECT OF C MERCAPTAN IN BLEND OF Co AND C MERCAPTAN CO-C1------0.7 9.8 46.0 40.5 O 42.7 Using the polymerization recipe of Example 1, the data 57.3 5 58.4 in Table VI were obtained: 0.20 20.8 53.5 5.5 Table 7II 44, 8 PERFORMANCE OF WARIOUS BLENDS OF TERTIARY-C 58.3 5 AND Co-C1. MERCAPTANS IN SBR-1500 RECIPE (Co-C 5 57.8 MERCAPTAN CONTROL) C1G-C1------0, 6 18.3 52.5 46.0 40.3 60.8 Rate data, Mooney viscosity 5 60.0 Mercaptain modifier T C12------9.2 60.5 52.5 (0.20 phm.) Tinae, Percent 41.5 hrs. conver- M. 1-4 ML 1--10' 60.8 sion i. 6, 5 C10-C11------0.5 22.3 60.5 53.0 50:50 biend of Co and Co- 5 21.9 45.5 39.5 45.0 Cit (: ) mercaptains. 4. ) 43.4 57.0 5.75 62.5 i 60.4 6.0 67. O CO-C11------0.14 22.3 6.0 54.0 C1-C1 inercaptain unix- 1.5 20.0 39.5 34, 5 47.1 ture (1:1). 4. 0 45.5 58.5 5.25 59.5 i 60 5.5 6.8 Cia------0.20 23.5 56.5 48.0 25.5 blend of C and Co- 1.519.0 45.0 38.) 47.6 C11 (1:1) mercaptains. 4.0 40. 6 59.3 6.0 65.3 i : 59.9 75:25 blend of C9 and 5 7.6 43.0 3.0 Cio-C11 (i:1) mercap- 4.0 40.7 Study of the above table indicates that at the same rate tans. 6.0 62, 4 and conversion the Co-C11 mercaptain gave lower Mooney Co-C1 mercaptain mix- 1.5 8.6 37.0 32.5 ture (1:1). 4.0 43.7 viscosities at 0.17 phm. than did C.12 mercaptain at 0.20 5.5 60.7 phm. From this and the remaining data in the table it 10:90 blend of Cg and ... 5 20. O 34.5 30, O is estimated that the Cio-C1 mercaptain is 20% to 25% C6-C11 (1:1) mercap- 4.0 50. more efficient as a polymerization modifier. tans, 5. 57.4 40 90:10 blend of Cs and Co- 1.5 13.5 41.0 35.0 EXAMPLE 6.-COMPARISON OF C, C AND C. C11 (1:1) mercaptains. 4.0 44.3 BLENDS WITH C MERCAPTAN Co-Citi mercaptain naix- 1.5 20.3 39.0 33.5 Following the polymerization recipe of Example 1 the ture (1:1). 4.0 50.2 data in Table VI were obtained: 5.0 59.6 Table VI PERFORMANCE OF WARIOUS BLENDS OF TERTLARY-C The above data indicate not only that mixtures of C9, AND Co-C MERCAPTAINS IN SEBR-500 RECIPE C1 and C11 mercaptains are useful modifiers, but also the surprising fact that at the 10% level of Ca mercaptain in a Rate data Mooney viscosity C-C mixture the modifiers' efficiency is increased over Mercaptain modifier the Co-C mixture. Furthermore, this latter improve (0.20 phm.) Time, Percent IS. Oye ME 1'--4 ML 1--07 ment achieved with no loss in rate of polymerization. sion It will be understood that in certain applications it may be desirable to obtain advantages by combining the C9, 50:50 blend of C9 and Cio- 16.6 4.5 36.0 C10, C11 or mixtures of Co, C10 and C11 mercaptains with C1 (1:1) mercaptains. 38.5 other modifiers. Thus, for example, this invention can : 59. be used to upgrade an inefficient modifier by adding C2SH------8. 48, 5 4.5 40.2 CSH, CoSH, C11SH or their mixture to the poor modi i. 58.8 fier. 25:75 blend of Cg and Cio- 19.7 41, 0 35.5 The advantages of the invention are clearly evident Cui (1:1) mercaptains. 4.5 60 from the above examples and the invention represents a 61.3 decided advance in the art of rubber technology. It will, 75:25 bend of C9 and Co- 7.4 43.0 36.5 of course, be evident to the skilled art worker that many C11 (iii) Intercaptains. 43.0 modifications and changes may be made from the above 60.3 description and examples without departing from the C2SH------18, 7 58.0 49.0 45.0 65 spirit and scope of the invention. 6.0 We claim: 10:90 blend of C9 and Cio- 8.5 35, 5 31.5 1. In the process of preparing a cold rubber polymer C11 (1:1) mercaptains. 43.4 by copolymerizing a butadiene and a styrene in an aque : 5 59.2 ous emulsion system, the improvement which comprises 90:0 blend of C9 and C10- 17.0 40,0 34. 0 70 modifying said polymerization with a mercaptain mixture C11 (1:1) mercaptains. 49 consisting of decyl and undecyl mercaptain, and wherein : 59.2 said mercaptains are secondary and tertiary isomers and C2SH------20.5 55.5 47.5 46. are present in an amount sufficient to limit the molecular 58.2 weight of said polymer to a plastic workable mass, Said 75 mercaptain mixture being prepared by the reaction of 3,188,304 O hydrogen sulfide with an olefinic polymer selected from sisting of polymers of propylene, butylene, amylene and the group consisting of polymers of propylene, butylene, mixtures of such olefinic polymers. amylene and mixtures of such olefinic polymers. 5. In the process of preparing a cold rubber polymer by copolymerizing styrene and butadiene in an aqueous emul 2. A process as in claim 1 wherein the mercaptain modi sion system, the improvement which comprises modifying fier mixture is used in an amount from about 0.05 to said polymerization with from about 0.10 to about 0.3 about 0.50 part per 100 parts of monomers. part per one hundred parts of monomers of a mercaptain 3. In the process of producing a rubber copolymer by modifier comprising a mixture of essentially equal parts copolymerizing styrene and butadiene in an aqueous by weight of decyl and undecyl mercaptains, said decyl emulsion system at a temperature between about 15 and and undecyl mercaptains consisting essentially of second 50 F., the improvement which comprises modifying such 0. ary and tertiary mercaptains, said mercaptain mixtures polymerization with from about 0.10 to about 0.3 part per being prepared by the reaction of hydrogen sulfide with 100 parts of monomers of a mercaptain mixture of decyl an olefinic polymer selected from the group consisting of and undecyl mercaptan, wherein said mercaptains are polymers of propylene, butylene, amylene and mixtures secondary and tertiary isomers and said mercaptain mix 15 of such olefinic polymers. ture is prepared by the reaction of hydrogen sulfide with 6. The process of claim 4 wherein the mercaptain modi an olefinic polymer selected from the group consisting of fiers are contaminated with olefin. polymers of propylene, butylene, amylene and mixtures of such olefinic polymers. References Cited by the Examiaer 4. In the process of preparing a cold rubber polymer 20 UNITED STATES PATENTS by copolymerizing a styrene and a butadiene in an aque ous emulsion system, the improvement which comprises 2,549,961 4/51 Crouch et al. ------260-84.3 modifying said polymerization with from about 0.05 to 2,625,537 1/53 Kolthoff et al. ------260-94.4 about 0.50 part per one hundred parts of monomers of a 2,739,138 3/56 Karasch et al. ------260-84.3 mercaptain modifier comprising a mixture of decyl and 25 OTHER REFERENCES undecyl mercaptain in a weight ratio of 10:90 to 90:10, said decyl and undecyl mercaptains consisting essentially Whitby: Synthetic Rubber, 1954, Wiley & Sons, Inc., of secondary and fertiary mercaptains, said mercaptain N. Y., pages 222 and 246. mixtures being prepared by the reaction of hydrogen sul 30 JOSEPH L. SCHOFER, Primary Examiner. fide with an olefinic polymer selected from the group con M. LEBMAN, Examiner.