United States Patent Office Patented Sept
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3,467,637 United States Patent Office Patented Sept. 16, 1969 1. 2 diene (hereinafter called “bicycloheptadiene'). The reac 3,467,637 tion is carried out using a transition metal catalyst of the LOW MOLECULAR WEIGHT OLEFIN INTER Ziegler type. POLYMERS PREPARED IN THE PRESENCE OF The process described and the copolymers produced in BICYCLO2.2.1]HEPTA-2,5-DIENE Paul J. Prucna, Cheswick, Pa., assignor to PPG Indus the above manner have several distinguishing and ad tries, Inc., a corporation of Pennsylvania Vantageous characteristics. These include: No Drawing. Filled June 1, 1965, Ser. No. 460,551 (a) The process produces low molecular weight co int. C. C08f 15/40, 1/42 s polymer in good yields using easily practised reaction U.S. C. 260-80,78 8 Claims conditions; (b) Varying ratios of ethylene to the other monoolefin O can be employed, permitting variation in product struc ture and properties; ABSTRACT OF THE DISCLOSURE (c) The products are essentially linear and homogene This invention relates to low molecular weight poly ous in structure; mers of ethylene and other alpha monoolefins produced 5 (d) The copolymers are readily dissolved in common by reacting said monomers in the presence of a Ziegler organic Solvents, this being true even with copolymers catalyst and small amounts of bicyclo[2.2.1]hepta-2,5- containing low proportions (e.g., below 20 percent) of diene. The copolymers are useful inter alia in coatings, propylene or other comonomer, whereas ordinarily such adhesives and as tackifying resins. copolymers are quite crystalline and insoluble; and 20 (e) The copolymers are stable and have good aging Stacteristics, attributable to their saturated linear back Oe, This invention relates to low molecular weight co The preferred comonomer with ethylene is propylene, polymers of ethylene and other monoolefins, and, more but other terminal monoolefins such as butylene or iso particularly, to such copolymers produced in the presence 25 butylene can also be utilized. The proportion of the of bicyclo[2.2.1]hepta-2,5-diene. comonomer is not critical and can be varied widely; for Copolymers of ethylene and other alpha-olefins are example, the copolymers can contain from about 5 per known and are employed in various applications. How cent or less to about 99 percent of ethylene and from ever, these copolymers as ordinarily produced are of about 1 percent to 95 percent or more of the other relatively high molecular weight, usually having an in 30 monoolefin or olefins, with the preferred products con trinsic viscosity of 1.0 or more and a molecular Weight taining from about 40 to about 95 percent of ethylene. of at least 50,000. Heretofore, lower molecular weight The above percentages are by weight, and are based copolymers of ethylene and other monoolefins could only upon the total monoolefin content of the copolymer. be produced using difficult techniques and reaction con The concentration of bicycloheptadiene in the reac ditions, and, even using such methods, are obtained in 35 tion mixture is quite important to obtain copolymers of extremely low yield. the desired properties. If below about 0.01 mole per liter The present invention provides an easily practised is employed, the copolymer obtained does not attain the method of producing copolymers of ethylene and other desired low molecular weight and intrinsic viscosity; the monoolefins having relatively low molecular weight. presence of about 0.04 mole per liter of bicycloheptadiene These copolymers are useful as adhesives (pressure sen 40 provides an interpolymer of modified properties and a sitive and hot bonding), sealing and caulking compounds, relatively high degree of residual unsaturation. tape backings, plasticizers, and coatings, and in similar The copolymers obtained are essentially made up of applications in which the properties associated with their the monoolefins, but a small amount of bicycloheptadiene low molecular weight and linear structure make them becomes part of the polymer chains, probably terminating highly desirable. 45 these chains. The exact nature of the copolymer and the The copolymers of the invention have an intrinsic details of its structure are not known with certainty, al viscosity below those of the known copolymers of this though it is known that the properties of the copolymer type. For instance, copolymers of ethylene and propylene, are significantly different than those produced in the ab as produced herein, usually have an intrinsic viscosity sence of the bicycloheptadiene. In any event, the amount not higher than about 0.8. (Intrinsic viscosity is defined, 50 of diene incorporated in the polymer is not sufficient to for example, in the book by Allen entiled "Techniques provide appreciable amounts of residual unsaturation, as of Polymer Characterization,” Butterworth Publications, would be found in products which cure at ordinary tem Ltd., London, 1959; values as mentioned herein are peratures in air by an oxidative mechanism. measured in benzene at 25° C., using an Ubbelohde Dilu Various solvents can be employed as the liquid re tion Viscometer.) They are produced by copolymerizing 55 action medium for the copolymerization. It is only neces sary that the solvent be substantially inert to the reactants ethylene and at least one monoolefin, preferably of the and catalysts employed, and to this end moisture and sim structure ilar reactive contaminants should be excluded. Suitably RCH=CH purified xylene, benzene or similar aromatic hydrocar where R is lower alkyl, in a reaction mixture containing 60 bon solvent is generally utilized, although aliphatic hy inert organic solvent in the presence of from about 0.01 drocarbons, halogenated solvents, and others can also be to about 0.04 mole per liter of bicycloL2.2.1]hepta-2,5- used. 3,467,637 3 4 The reaction is carried out using a transition metal of equal volumes of ethylene and propylene at a rate catalyst of the Ziegler type. Ziegler catalysts (sometimes Sufficient to maintain saturation of the solution, and 6.34 called Ziegler-Natta catalysts) are well known and are milliliters of bicycloheptadiene and 3.6 milliliters of a of various compositions, but usually involve reaction 1.4 molar solution of ethyl aluminum sesquichloride in products of an alkyl aluminum compound and a transi benzene were added. Cooling with ice water was main tion metal compound. A number of such catalysts are de tained throughout the polymerization, which was initiated scribed in U.S. Patents 3,131,171; 3,153,023; 3,159,615; by the addition of 12.5 milliliters of 0.02 molar solution 3,168,504; and others. Among the most efficient catalysts of vanadium oxybis(acetylacetonate) in benzene. The for the present polymerizations have been found to be concentration of the vanadium compound was about 0.1 vanadium compounds, and especially vanadium tris(acet millimole per liter and the concentration of the ethyl ylacetonate) or vanadium oxybis(acetylacetonate). Other O aluminum sesquichloride was 2.0 millimoles per liter. vanadium compounds that can be used include vanadium Polymerization began immediately, as evidenced by a rise tetrachloride and vanadium oxytrichloride. in temperature to 15° C.; reaction conditions were main The concentration of such vanadium compounds in the tained for 7 minutes after the addition of the vanadium reaction mixture is important; for example, in the case 15 compound. of the preferred vanadium oxybis(acetylacetonate) and The reaction was terminated by the addition of 25 vanadium tris(acetylacetonate) the concentration should milliliters of methanol; the reaction mixture was washed be not higher than about 0.002 mole per liter in order with 5 milliliters per liter of concentrated HCl and then to produce the desired products in efficient amounts. The washed with 500 milliliter increments of distilled water minimum concentration is not critical, since any amount 20 until acid-free. Benzene was removed by evaporation at produces some copolymer, but it is generally preferred to reduced pressure, and when most of the benzene had been have at least about 0.001 millimole of vanadium com removed, about 1 liter of aromatic naphtha (Solves.so pound per liter. An alkyl aluminum halide is utilized as 100; boiling range 150 C. to 170° C.) was added and the cocatalyst with these vanadium compounds, typical stripping was continued until about three-quarters of the compounds being ethyl aluminum chloride, ethyl alumi 25 Solves.so 100 had been removed, thus also removing re num sesquichloride, diethyl aluminum chloride, butyl alu sidual bicycloheptadiene. The solution remaining had a minum sesquichloride and ethyl aluminum sesquiiodide. solids content of 13.9 percent and a Gardner-Holdt vis The amount of alkyl aluminum halide is usually between cosity of Z6. The copolymer obtained had an intrinsic about 3 moles and about 30 moles per mole of vanadium viscosity in benzene at 25 C. of 0.62 deciliter/gram. compound. 30 A corresponding copolymer to that of Example 1, made With the foregoing exceptions, the reaction conditions using the same conditions but without bicycloheptadiene, are those generally employed in polymerizations of this precipitated during the polymerization and had an in type. The temperature is ordinarily maintained at room trinsic viscosity of 1.45 dil./g. temperature or somewhat below, temperatures as low as Example 2 -80 C. being suitable. The monoolefins are generally fed 35 to the reaction vessel as the polymerization progresses, Example 1 was repeated using 0.01 mole of bicyclo and either atmospheric pressure or elevated pressure can heptadiene per liter of reaction mixture. After termination be employed. of the reaction with methanol, the solution was poured In a typical procedure for producing these copolymers, into a large excess of methanol, thereby precipitating the the solvent is saturated with ethylene and the other mono 40 copoylmer. There were obtained 39 grams of white co olefin or monoolefins in the proportions to achieve the polymer, corresponding to a catalyst efficiency of 736 desired copolymer composition, and the bicycloheptadi grams of polymer per gram of vanadium oxybis(acetyl ene is added, followed by the alkyl aluminum compound.