3,225,122 United States Patent 0 " 1C6 Patented Dec. 21, 1965

1 2 temperatures varying from room temperature to up to 3,225,122 350° F. temperature being suitable. It is to be under PREVENTION OF COLD FLOW IN CIS-POLY stood that the temperature employed should not be so BUTADIENE BY ADDING HYDROGENATED high as to cause degradation of the polymers. The blend DIENE POLYMER Nelson A. Stumpe, Jr., Bartlesville, Okla, assignor ing operation is continued for a period su?‘icient to obtain to Phillips Petroleum Company, a corporation of a homogeneous composition, e.g., for a period in the Delaware range of about 30 seconds to 10 minutes or longer. In No Drawing. Filed Oct. 12, 1962, Ser. No. 230,272 another method for blending the materials, solutions of 5 Claims. (Cl. 260-394) the polymers in a hydrocarbon solvent are thoroughly 10 mixed, after which the composition is recovered by con This invention relates to a method for preventing or ventional methods, such as by steam stripping or coagula substantially reducing the tendency of cis-polybutadiene tion in an alcohol. to cold ?ow. In one aspect, it relates to a novel com After being treated by the method of this invention, position containing cis-polybutadiene and a hydrogenated the cis-polybutadiene can then be packaged and stored polymer, in which the tendency of cis-polybutadiene to 15 or transferred for utilization elsewhere. The polymer cold ?ow is substantially reduced. composition can be blended, compounded, fabricated and In/recent years, a great deal of research work has cured according to procedures which are well known in been conducted in the ?eld of ole?n polymerization. the rubber art. While the present invention is not de Great advantages have been recently made in this ?eld pendent upon any particular reaction mechanism, it is as the result of the discovery of new catalyst systems. important that the hydrogenated polymer be intimately These catalyst systems are often described as being blended with the cis-polybutadiene in order to obtain the “stereospeci?c” since they are capable of polymerizing desired reduction in cold ?ow. monomers, particularly conjugated dienes, to a certain The hydrogenated polymers employed in the practice geometric con?guration. One of the products which of this invention are hydrogenated homopolymers of has attracted Widespread attention because of its superior 25 butadiene and copolymers of butadiene and styrene. properties is a polybutadiene containing a high percent The copolymer of butadiene and styrene preferably con age, e.g., at least 85 percent, of cis 1,4»addi-tion. The tains not more than 30 parts by weight of‘ styrene per physical properties of this high cis-polybutadiene are of 100 parts by weight of the total monomers. Any suitable such a nature that the polymer is particularly suitable for method can be employed in preparing the hydrogenated the fabrication of heavy duty tires and other articles for polymers, but it is preferred to use the method disclosed which conventional synthetic rubbers have heretofore by R. V. Jones and C. W. Moberly in U.S. Patent No. been comparatively unsatisfactory, However, in the 2,864,809. In accordance with the Jones and Moberly processing of high cis-polybutadiene, particularly in pack process, the polymer to be hydrogenated, after being freed aging, shipping and storage, a certain amount of dif?culty of salts or other materials which might act as hydrogena has been encountered because of the tendency of the 35 tion catalyst poisons, is charged to a hydrogenation reac polymer to cold ?ow when in the unvulcanized state. For tor, generally as a solution or a dispersion of the polymer example, if cracks or punctures develop in the package in ‘a suitable solvent. A hydrogenation catalyst, such as used in storing the polymer, polymer will flow from the a nickel-kieselguhr catalyst, is then added, hydrogen is package with a resulting loss or contamination and stick introduced into the reactor, and the temperature is raised ing together of stacked packages. 40 to the desired level. When the desired degree of hydro It is an object of this invention, therefore, to provide genation has been obtained, the catalyst is removed. a method for eliminating or substantially reducing the Additional solvent is frequently added to decrease the tendency of cis-polybutadiene to cold ?ow when in the viscosity of the mixture and to facilitate catalyst removal, unvulcanized state. ‘ which can be accomplished by ?ltration, magnetic separa Another object of the invention is to provide a novel 45 tion, or other suitable means. The solvent is ?nally composition which contains cis-polybutadiene and a removed, preferably in vacuo, and the product is re small amount of a material which prevents or substantial covered. The hydrogenated polymers employed in pre ly reduces cold ?ow. paring the compositions of this invention are those which Other and further objects and advantages of the in the normal unsaturation of the polymeric starting ma vention will become apparent to those skilled in the art 50 terial is reduced by at least 50 percent by hydrogena upon consideration of the accompanying disclosure. tion. In other words, the hydrogenated polymers have The present invention is concerned with a method for a residual unsaturation of less than 50 percent, based treating cis~polybutadiene so as to reduce substantially upon the theoretical value of 100 percent for the un~ its tendency to cold flow. The invention resides in the hydrogenated polymer. It is preferred that the hydro— discovery that the tendency of cis-polybutadiene to cold 55 genated polymers have a degree of unsaturation in the flow can be reduced if the polymer is blended with a range of 5 to 30 percent of that originally present in the minor amount of a hydrogenated polymer. Broadly unhydrogenated polymer. speaking, the method of this invention comprises the step The present invention is generally applicable to poly of blending’cis-polybutadiene with a minor amount of butadienes containing a high percentage of cis 1,4-addi a material selected from the group consisting of hydro tion. It is usually preferred that the cis-polybutadiene genated homopolymers of 1,3-butadiene and hydrogenated contain at least 85 percent, cis l,4-addition,. e.g., 85 to 98 copolymers of 1,3-butadiene and styrene. The amount percent and higher. The cis-polybutadiene can be pre of the hydrogenated polymer employed in the blend is pared by polymerizing l,3-butadiene with any one of a usually in the range of 1 to 20 parts by weight per 100 large number of diiierent stereospeci?c catalyst systems. parts by weight of the cis-polybutadiene. Any suitable 65 It is usually preferred to employ a catalyst which is se method which will give an intimate blend can be used lected from the group consisting of (1) a catalyst com in blending the cis-polybutadiene with the hydrogenated prising an organomet-al compound having the formula polymer. A convenient method for preparing the com RmM, wherein R is an alkyl, cycloalkyl, aryl, alkaryl, position is to blend the materials on a roll mill, in a Ban 70 aralkyl, alkylcycloalkyl, cycloalkylalkyl, arylcycloalkyl or bury mixer, or similar kneading device. Any suitable 'cycloalkylaryl radical, M is aluminum, mercury, zinc, be temperature can be employed in the mixing operation, ryllium, cadmium, magnesium, sodium or potassium, and 3,225,122 3 4 m is equal to the valence of the metal M, and titanium tetrachloride, and silicon tetraiodide; triphenylaluminum, tetraiodide, (‘2) a catalyst comprising an organometal ’ titanium tetrachloride, and gallium'triiodide; triisobutyl compound having the formula RnM’, wherein R is an aluminum, titanium tetraiodide and tin tetrachloride; tri organo radical as de?ned above, M’ is aluminum, mag isobutylaluminum, titanium tetraiodide and antimony nesium, lead, sodium or potassium, and n is equal to trichloride; triisobutylaluminum, titanium tetraiodide and the valence of the metal M’, titanium tetrachloride and aluminum trichloride; triisobutylaluminum, titanium titanium tetraiodide, (3) a catalyst comprising an organo tetraiodide, and tin tetrabromide; triethylgallium, titanium metal compound having the formula RaM”, wherein R tetraiodide, and aluminum tribromide; triethylaluminum, is an organo radical as de?ned above, M" is aluminum titanium tetraiodide, and arsenic trichloride; and tribenzyl or magnesium and in is equal to the valence of the metal 10 aluminum, titanium tetraiodide, and germanium tetra M”, a compound having the formula TiXb, wherein X chloride. is chlorine or bromine and b is an integer from 2 to 4, The polymerization process for preparing cis-poly inclusive, and elemental iodine, (4) a catalyst compris butadiene is carried out of the presence of a hydrocarbon ing an organometal compound having the formula diluent which is not deleterious to the catalyst system. RXM’”, wherein R is an organo radical as de?ned above, 15 Examples of suitable diluents include aromatic, paraf M’” is aluminum, gallium, indium or thallium, and ?nic, and cycloparaf?nic hydrocarbons, it being under x is equal to the valence of the metal M’”, a titanium stood that mixtures of these materials can also be used. halide having the formula TiX4, wherein X is chlorine Speci?c examples of hydrocarbon diluents, include benz or bromine, and an inorganic halide having the for~ ene, toluene, n-butane, isobutane, n-pentane, isooctane, mula MivIc, wherein M1" is beryllium, zinc, cadmium, 20 n-dodecane, cyclopentane, cyclohexane, methylcyclo aluminum, gallium, indium, thallium, silicon, germa hexane, and the like. It is often preferred to employ nium, tin, lead, phosphorus, antimony, arsenic and his aromatic hydrocarbons as the diluent. muth, and c is an integer from 2 to 5 inclusive, and The amount of the catalyst used in preparing the cis

‘(5 a catal st com risin"a an or ano com ound hav polybutadiene product can vary over a rather wide range. ing the formula RXM’”, wherein R, M’”, and x are The amount of the organometal used in the catalyst com de?ned above, titanium tetraiodide, and an inorganic position is usually in the range of 0.75 to 20 mols per halide having the formula MvXd, wherein Mv is alumi mol of the halogen-containing component, i.e., a metal num, gallium, indium thallium, germanium, tin, lead, halide with or without a second metal halide or elemental phosphorus, antimony, arsenic or bismuth, X is chlo iodine. The mol ratio actually used in a polymerization rine or bromine, and d is an integer from 2 to 5, in~ 30 will depend upon the particular components employed in elusive. The R radicals of the aforementioned formulas the catalyst system. However, a preferred mol ratio is preferably contain up to and including 20 carbon atoms. generally from 1:1 to 12:1 of the organometal com The following are examples of preferred catalyst sys pound to the halogen-containing component. When us tems which can be used to polymerize 1,3-butadiene to ing a catalyst comprising an organometal compound and a cis 1,4-polybutadiene; triisobutylaluminum and tita more than one metal halide, e.g., titanium tetrachloride nium tetraiodide; triethylaluminum and titanium tetra and titanium tetraiodide, titanium tetrachloride or tetra iodide; triisobutylaluminum, titanium tetrachloride and bromide and aluminum iodide, the mol ratio of the tetra titanium tetraiodide; triethylaluminum, titanium tetra chloride or tetrabromide to the iodide is usually in the chloride and titanium tetraiodide; diethylzinc and tita range of 0.05:1 to 5:1. With a catalyst system com nium tetraiodide; dibutylmercury and titanium tetraiodide; 40 prising an organometal compound, a titanium chloride triisobutylaluminum, titanium tetrachloride and iodine; or bromide and elemental iodine, the mol ratio of tita— triethylaluminum, titanium tetrabromide and iodine; n nium halide to iodine is generally in the range of 10:1 amylsodium and titanium tetraiodide; phenylsodium and to 0.25:1, preferably 3:1 to 0.25:1. The concentration titanium tetraiodide; n-butylpotassium and titanium tetra of the total catalyst composition, i.e., organometal and iodide; phenylpotassium and titanium tetraiodide; n 45 halogen-containing component, is usually in the range of amylsodium, titanium tetrachloride and titanium tetra 0.01 to 10 weight percent, preferably in the range of iodide; triphenylaluminum and titanium tetraiodide; tri— 0.01 to 5 weight percent, based on the total amount of phenylaluminum, titanium tetraiodide and titanium tetra 1,3-butadiene charged to the reactor system. chloride; triphenylaluminum, titanium tetrachloride and The process for preparing cis-polybutadiene can be iodine; tri-alpha-naphthylaluminum, titanium tetrachlo- ' carried out at temperatures varying over a rather wide ride and iodine; tribenzylaluminum, titanium tetrabromide range, e.g., from —100 to 250° F. It is usually pre and iodine; diphenylzinc and titanium tetraiodide; di-2 ferred to operate at a temperature in the range of ~30 tolylmercury and titanium tetraiodide; tricyclohexylalumi to 160° F. The polymerization reaction can be carried num, titanium tetrachloride and titanium tetraiodide; out under autogenous pressure or at any suitable pressure ethylcyclopentylzinc and titanium tetraiodide; tri(3-iso suf?cient to maintain the reaction mixture substantially butylcyclohexyl)aluminum and titanium tetraiodide; in the liquid phase. The pressure will thus depend upon tetraethyllead, titanium tetrachloride and titanium tetra the particular diluent employed and the temperature at iodide; trimethylphenyllead, titanium tetrachloride and which the polymerization is conducted. However, higher titanium tetraiodide; diphenylmagnesium and titanium pressures can be employed if desired, these pressures tetraiodide; di-n-propylmagnesium, titanium tetrachloride 60 being obtained by some such suitable method as the and titanium tetraiodide; dimethylmagnesium, titanium pressurization of the reactor with a gas which is inert tetrachloride and iodine; diphenylmagnesium, titanium with respect to the polymerization reaction. tetrabromide and iodine; methylethylmagnesium, and Various materials are known to be detrimental to the titanium tetraiodide; dibutylberyllium and titanium tetra catalyst employed in preparing the cis-polybutadiene. iodide; diethylcadmium and titanium tetraiodide; diiso These materials include carbon dioxide, oxygen and water. propylcadmium and titanium tetraiodide; triisobutylalu It is usually desirable, therefore, that the butadiene and minum, titanium tetrachloride, and antimony triiodide; the diluent be freed of these materials as well as other triisobutylaluminum, titanium tetrachloride and alumi materials which may tend to inactivate the catalyst. num triiodide; triisobutylaluminum, titanium tetrabro Furthermore, it is desirable to remove air and moisture mide, and aluminum triiodide; triethylaluminum, tita from the reaction vessel in which the polymerization is nium tetrachloride and phosphorus triiodide; tri-n-dodec to be conducted. ylaluminum, titanium tetrachloride and tin tetraiodide; Upon completion of the polymerization reaction, the triethylgallium, titanium tetrabromide and aluminum tri reaction mixture is then treated to inactivate the catalyst iodide; tri-n-butylaluminum, titanium tetrachloride, and and recover the rubbery polymer. A suitable method for antimony triiodide; tricyclopentylaluminum, titanium accomplishing this result involves steam stripping the 3,225,122 5 6 diluent from the polymer. In another suitable method, Table‘ II a catalyst inactivating material, such as an alcohol, is EVALUATION OF CIS~POLYBUTADIENE RUBBER CON added to the mixture so as to inactivate the catalyst and TAINING HYDRO GENATED POLYBUTADIENE cause precipitation of ‘the polymer. The polymer is then separated from the alcohol and diluent by any suitable A B C means, such as decantation or ?ltration. It has been found to be advantageous to add an antioxidant, such as cis-Polybutadiene ______100 100 100 4,4’-methylene-bis-(2,6-di-ter't-butylphenol), to the poly Hydrogenated polybutadiene, 17% un saturation ______10 mer solution prior to recovery of the polymer. The Hydrogenated polybutadiene, 8% un saturation- _ _ _ 10 polymer which has been recovered by these methods is Carbon black 50 50 50 then treated in accordance with the present invention Zinc oxide_ _ 3 3 3 Stearic acid 2 2 2 so as to reduce the tendency of the polymer to cold flow. Philrmin 5 a- 10 10 10 A more comprehensive understanding of the invention Flexamine b__ l 1 1 Sulfur ______1. 75 1. 75 1. 75 may be obtained by referring to the following illustrative NOBS Special 0 ______. 1. 05 ‘1.05 1. 05 examples, which are not intended, however, to be unduly limitative of the invention. PROCESSING DATA EXAMPLE I A series of runs was carried out in which varying Mooney (MS 1% at 212° F.) 1 ______41 41 44 Extrusion at 250° F. 2: ‘ amount of hydrogenated polybutadiene was blended with 20 inJmin ______42. 5 34 45. 3 cis-polybutadiene on a cold roll mill. The blending op gJmin ______114 95 122. 5 erations took from about 2 to 3 minutes, and homogeneous Rating (Garvey die) ______-- 6- 7 _ 7 mixtures were obtained in all cases. The resulting blends PHYSICAL PROPERTIES (30 MIN. CURE AT 307° F.) were tested in order to determine their tendency to cold ?ow. The results of these tests are shown below in 25 vXlO“, moles/cc.3 ______1. 59 1.59 1. 81 Table I. 300% modulus, p.s 4. 840 855 905 The cis-polybutadiene used in preparing the blends con Tensile, p.s.i. 4-.." ___ 2550 2575 2540 Elongation, percent 4. ______590 610 580 tained 94.9 percent cis 1,4-addition, 2.0 percent trans 1,4 Resilience, percent 5 ______74. 5 73. 9 73. 3 Heat build up, AT, ° F.0 ______49. 7 50. 7 45. 9 addition, and 3.1 percent 1,2-addition. The polymer was Shore A hardness 7 ______60 60. 5 58 prepared by polymerizing 1,3~butadiene with a catalyst ob 30 tained by mixing triisobutylaluminum, titanium tetrachlo ride and free iodine. The hydrogenated polybutadienes *1 Aromatic oil. _ were prepared by hydrogenating an emulsion polybuta 11 Physical mixture of complex diarylamine~ketone reaction diene .in methylcyclohexane, using a nickel-kieselguhr cata ():t (65 %) and N,N’ ~ dipheuyl ~ p - phenylenediamine lyst. “ hl-oixydiethylene~2-benzothiazyl sul?namide. 1 ASTM D297-55T. Table l 2Extrusion is carried out at 250° F. by essentially the same procedure as described by Garvey et al., Ind. & Eng. Chem. 34, 1309 (1942). As regards the rating ?gure, 12 designates an extruded product considered to be perfectly formed whereas lower numerals indicate less perfect Blend No ______1 2 3 4 ‘ 5 i 6 products. 40 3 Determined by the Swelling Method of Kraus, as described cis‘Polybutadiene ______100 100 100 100 100 100 in Rubber World 135, 67*73, 254-260 (1956). Hydrogenated polybutadiene ‘1.. ______5 1O 15 ______.. 4ASTM D412-51T. Scott Tensile Machine L-6. Tests Hydrogenated polyloutadiene b.______5 10 made at 80° F. d [10w 0 ______4. 45 2. 2O 1. 85 l. 35 2. l1 1. ‘i0 5ASTM D945-55 (modi?ed). Yerzley oscillograph. Test ». .1 specimen ‘is a right circular cylinder 0.7 inch in dlameter and 1 inch high. “ASTM D623-52T. Method A, Goodrich Flexometer, .143 u 17% unsaturation. lhsT/sq. inch load, 0.175 inch stroke. Test speclmen is a right 1’ 8% unsaturation. circular cylinder 0.7 inch ‘in diameter and 1 inch high. ° Cold-FlowmGlass Plate Method. Method is based on the 7ASTM D676-55T. Shore Durometer, Type A. change in contact area of four right circular cylinders of rubber compressed between two glass plates. The cold {low The data in Table II demonstrate that the physical prop rating is the ratio of the ?nal contact area to the original erties of the parent cis-polybutadiene are unimpaired by contact area. Four pellets, approximately 0.450 inch in di~ 50 ameter and the same ‘in height, are measured with a hand incorporation of the hydrogenated polybutadienes. micrometer and recorded as thousandths of an inch. The The composition of this invention is suitable for all average diameter is obtained and squared. Glass plates 3” x 11” weighing an average of 26-27 grams, which have uses for which cis-polybutadiene per so can be employed. been cleaned and polished with silicone lens tissue, are used It is particularly useful in the manufacture of tire treads, for the test. Four rubber pellets are positioned at the cor tire carcass stocks, and other rubbery articles. It can be ners of a 1.5” x 2” rectangle Within the glass plate. An 55 other glass plate is positioned over the top of the pellets such extruded, reinforced with conventional reinforcing agents, that it is directly over the bottom plate and a 160 gram 3” x 4” lead plate is placed on top. The assembly is blended with other polymers, such as natural and synthetic allowed to stand 18 hours at 80° F‘. after which the lead rubbers, extended with conventional extender oils, and weight is removed and the contact area observed through the glass plate. Measurement is ?rst taken across the longest vulcanized using recipes that are well known in the rubber dimension of the contact area and a second measurement art. taken at right angles to the ?rst one. The eight measure 60 ments (two for each pellet) are recorded and averaged to As will be evident to those skilled in the art, many obtain a ?nal average diameter. :The value is squared and variations and modi?cations of the invention can be prac divided by the initial average diameter squared to obtain the cold flow. ticed in view of the foregoing disclosure. Such variations and modi?cations are believed to come within the spirit The data in Table I show that the tendency of the cis 65 and scope of the invention. polybutadiene to cold ?ow was substantially reduced by I claim: blending therewith small amounts of hydrogenated poly 1. A rubbery, unvulcanized composition of matter butadiene. comprising a blend of (1) a major amount of cis-poly EXAMPLE II butadiene containing at least 85 per-cent cis-1,4 addition, Runs were conducted in which blends No. 3 and 6 of 70 and (2) a minor amount of a material selected from the Example I were compounded and cured and certain phys group consisting of a hydrogenated homopolyrner of 1,3 ical properties determined. A control run was also car butadiene and a hydrogenated copolymer of 1,3-butadiene ried out in which the cis-polybutadiene was similarly and styrene, in which the residual unsaturation of said treated. The data obtained in these runs is shown below hydrogenated polymer is less than 50 percent of that in Table -II. 75 originally present in the unsaturated polymer. 3,225,122 7 8 2. A rubbery, unvulcanized composition of matter ual unsaturation of less than 50 percent of the saturation ,comprising a blend of (1) a cis-polybutadiene containing originally present in the unhydrogenated polymer, said at least 85 percent cis 1,4-addition, and (2) from 1 to 20 blending occurring at a temperature varying from room parts by weight per 100 parts by weight of said cis-poly temperature to 350° F. for a time su?icient to obtain a butadiene of a hydrogenated polymer selected from the homogeneous composition. group consisting of a hydrogenated homopolymer of 1,3— 57 The method of claim 4 in which said hydrogenated butadiene and a hydrogenated copolymer of 1,3-butadiene polymer has a degree of unsaturation in the range of 5 to and styrene, in which the residual unsaturation of said hy 30 percent of that originally present in the unhydrogenated drogenated polymer is less than 50 percent of that original polymer. I ly present in the unsaturated polymer. 3. The composition of claim 2 in which said hydro References Cited by the Examiner genated polymer has a degree of unsaturation in the range UNITED STATES PATENTS of 5 to 30 percent of that originally present in the unhy~ drogenated polymer. 2,730,515 .1/1956 McCracken et al. ____ 260——80.7 2,834,751 5/1958 Jones ______260-889 4. A method for reducing the tendency of a cis-poly 15 butadiene to cold ?ow when in the unvulcanized state 2,864,809 12/1958 Jones et a1 ______260-—94.7 which comprises blending a cis-polybutadiene containing 3,060,989 10/1962 Railsback et al. _____ 260-894 at least 85 percent cis 1,4-addition with from 1 to 20 parts FOREIGN PATENTS by Weight per 100 parts by weight of said cis-polybutadiene 144,858 1/1952 Australia. of a hydrogenated polymer selected from the group con- 20 sisting of a hydrogenated polymer of 1,3-butadiene and a MURRAY TILLMAN, Primary Examiner. hydrogenated copolymer of 1,3-butadiene and styrene, said hydrogenated polymers being solid and containing a resid WILLIAM H. SHORT, Examiner.