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.