CATALYTIC COPOLYMERISATION OF 4-METHYLPENTENE

Abstract: A copolymer is produced by copolymerizing 4-methyl-­ pentene-1 with another C2-20 α-olefin in a hydrocarbon solvent which can be the monomer, in the presence of a Ziegler-Natta catalyst (e.g. TiCl₃ and an alkyl aluminium halide). In a first stage a homopolymer or random copolymer of 4-methylpentene-1 having an α-olefin content of not more than 3 mol% and an intrinsic viscosity of at least 2.5 dl/g is formed, and in a second stage a random copolymer having an α-olefin content higher than that of the first polymer and no higher than 9 mol% and an intrinsic viscosity of at least 2.5 dl/g is formed, and the produced copolymer insoluble in the solvent is separated to recover a 4-methylpentene-­ 1 copolymer containing from 5 to 80% by weight of the first polymer. Polymerization is at 0-90°C, at atmospheric to 5 kg/cm² pressure. The process produces a solvent-insoluble copolymer in an increased yield without impairing transparency of the copolymer. If the copolymer is not moldable, its molecular weight is reduced by decomposition at 250-330°C or with a peroxide catalyst.

Description: This invention relates to a process for producing a copolymer comprising 4-methylpentene-1 and a minor proportion of other α-olefin and to the resultant copolymer, and to the moldable decomposition product thereof. A homopolymer of 4-methylpentene-1 is a light-weight resin having excellent transparency. It is known that the transparency of the 4-methylpentene-1 homopolymer can further be improved by modifying it with a small amount of a straight chain α-olefin having from 5 to 18 carbon atoms, as disclosed in Japanese Patent Publication No. 22077/75. In the usual processes for producing 4-methyl-pentene-1 polymers by slurry polymerization, a powdery polymer which is insoluble in a polymerization solvent is separated and recovered as the sole product. Recovery of both a solvent-insoluble polymer and a solvent-soluble polymer requires complicated procedures and entails high cost. Conventional processes for producing random co-polymers comprising 4-methylpentene-1 and a minor proportion of other α-olefin produce a solvent-insoluble polymer in a low yield as compared with the case of producing a 4-methylpentene-1 homopolymer, resulting in higher production costs. One object of this invention is to provide a process for producing a random copolymer comprising 4-methylpentene-1 and a minor proportion of another α-olefin by which an increased yield of a solvent-insoluble polymer can be attained. Another object of this invention is to provide a process for producing a random copolymer comprising 4-methylpentene-1 and a minor proportion of another α-olefin, which has excellent transparency and impact resistance. A further object of this invention is to provide a 4-methylpentene-1 resin composition suitable for molding. In general, the aforesaid 4-methylpentene-1 copolymer preferably has a high α-olefin content for improving transparency and impact resistance, while a low α-olefin content is preferred for improving yield of the polymer insoluble in the polymerization solvent. The inventors have conducted extensive studies for the purpose of satisfying these conflicting requirements and, as a result, found that the above objects of the present invention can be accomplished by a two-stage process comprising a first stage in which a copolymer having a low α-olefin content and a high intrinsic viscosity is prepared and a second stage in which a copolymer having a higher α-olefin content than that of the copolymer obtained in the first stage and a high intrinsic viscosity is prepared. The present invention provides a process for producing a copolymer comprising 4-methylpentene-1 and other α-olefin by copolymerizing 4-methylpentene-1 and other α-olefin in a hydrocarbon solvent in the presence of a Ziegler-Natta catalyst, wherein the copolymerization comprises a first stage in which (A) a homopolymer or random copolymer of 4-methylpentene-1 having an α-olefin content of not more than 3 mol% and an intrinsic viscosity of at least 3.5 dℓ/g is prepared having an α-olefin content higher than that of the polymer (A) and no higher than 9 mol% and an intrinsic viscosity of at least 3.5 dℓ/g is prepared, and the produced copolymer insoluble in the solvent is separated to recover a 4-methylpentene-1 copolymer containing from 5 to 80% by weight of the polymer (A). The present invention further provides a 4-methylpentene-1 resin composition which is obtained by thermal decomposition or peroxide decomposition of the above-prepared 4-methylpentene-1 copolymer The polymer (A) preferably contains not more than 2 mol%, and more preferably not more than 1.5 mol%, of α₋olefin. The copolymer (B) preferably contains not more than 8 mol% of α-olefin. The terminology "intrinsic viscosity" as used herein means the intrinsic viscosity as measured in tetralin at 135°C. The polymers (A) and (B) have an intrinsic viscosity of at least 3.5 dℓ/g, and preferably at least 5 dℓ/g. In the case where the 4-methylpentene-1 copolymers obtained by the process of the present invention are unsuitable for molding as produced due to their high molecular weights, they can be decomposed by heat or with peroxides so as to have reduced molecular weights suitable for molding. The thermal decomposition is preferably carried out at a temperature of from 250 to 330°C. The peroxides which can be used preferably include compounds having a half-life period of 10 hours at a temperature of at least 100°C, such as dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butyl peroxyhexane or di-t-butyl peroxide. To ensure obtaining the desired effects of the present invention, the proportion of the polymer (A) in the whole solvent-insoluble polymer ranges from 5 to 80%, preferably from 20 to 80%, and more preferably from 40 to 80%, by weight. The polymerization is carried out in the substantial absence of water or oxygen as is usual in the conventional polymerization of α-olefins. Hydrogen is a preferred molecular weight regulator. As the polymerization temperature becomes low, the yield of the solvent insoluble polymer increases but the polymerization activity decreases. Accordingly, the polymerization temperature is selected from the range of from 0 to 90°C, preferably from 20 to 70°C, and more preferably from 30 to 60°C. The polymerization pressure is preferably from atmospheric pressure to 5 bar (5 kg/cm²). The Ziegler-Natta catalyst which can be used in the present invention preferably is a stereospecific polymerization catalyst for α-olefins as described in Japanese Patent Applications (OPI) Nos. 59916/82, 126401/84 and 228504/85 (the term "OPI" as used herein means an unexamined published application ). More specifically, transition metal compounds to be used include titanium trichloride obtained by reducing titanium tetrachloride with aluminium, an organoaluminum compound, or an organomagnesium compound; and titanium compounds, carried on magnesium halides or silicon dioxide. Organometallic compounds to be used preferably include organoaluminum compounds, e.g., a trialkyl-aluminum, a dialkylaluminum halide or an alkylaluminum sesquihalide. The hydrocarbon solvent to be used for polymerization preferably includes those which scarcely dissolve the produced 4-methylpentene-1 copolymers, such as aliphatic hydrocarbons, e.g., heptane, hexane, pentane or butane, The 4-methylpentene-1 monomer itself may also serve as a polymerization solvent. The α-olefins which can be copolymerized with 4-methylpentene-1 preferably include those havng from 2 to 20 carbon atoms, e.g., ethylene, propylene, butene, pentene, n-hexene-1, 3-methylbutene-1, 4-methylhexene-1, n-octene-1, n-decene-1 or n-octadecene-1. Of these, straight chain α-olefins having from 5 to 18 carbon atoms are more preferred. The present invention will now be illustrated in detail with reference to the following non-limitative examples, wherein the parts are by weight. EXAMPLES 1 TO 7 A 1 litre volume autoclave was thoroughly dried and purged with nitrogen gas. From 0.1 to 0.3 g of titanium trichloride (produced by Marubeni-Solvay Co., Ltd.), 1 g of diethylaluminum chloride, from 0.05 to 15 Nℓ of hydrogen, 325 g or 4-methylpenene-1, and decene-1 in an amount shown in Table 1 were charged into the autoclave, and two-stage polymerization was carried out using 4-methylpentene-1 as a polymerization solvent under conditions shown in Table 1. After completion of the polymerization, n-butanol was added to the polymerization system to stop the reaction. The resulting slurry was filtered at the polymerization temperature. The solvent-insoluble polymer recovered as filter cake was washed with a hydrochloric acid aqueous solution and then washed with methanol until the washings had become neutral, to recover the polymer as a white powder. On the other hand, the solvent-soluble polymer was recovered from the filtrate, and the yield of the solvent-insoluble polymer was calculated from the formula: Upon completion of the first stage polymerization, a part of the resulting slurry was sampled, and its slurry concentration was measured to obtain the amount of the polymer (A). Further, the polymer (A) was isolated from the slurry and purified to determine the decene-1 content and intrinsic viscosity of the polymer (A). The decene-1 content and intrinsic viscosity of the polymer (B) were calculated from those values of the polymer (A) and the solvent-insoluble polymer [(A) + (B)]. The intrinsic viscosity [η] was measured in tetralin at 135°C by use of a Ubbellohde viscometer. The decene-1 content was determined by infrared spectrophotometry. The haze of the resulting copolymer was determined as follows. A resin compound comprising 100 parts of the copolymer and, as stabilizers, 0.5 part of 2,6-di-t-butylhydroxytoluene and 0.1 part of tetrakis[methylene-3-(3′,5′-di-t-butyl-4-hydroxyphenyl)propionate]methane was kneaded at 280°C and compression-molded into a 1.0 mm-thick sheet according to JIS K6758 except for changing the compressing temperature to 280°C. The pressed sheet was dipped in dimethyl phthalate, and its haze was measured according to ASTM D 1003. The results of these measurements are shown in Table 1. COMPARATIVE EXAMPLES 1 TO 6 4-Methylpentene-1 and decene-1 were random copolymerized in one stage according to the conventional process or in two stages as in the present invention, except that the produced polymers (A) and (B) had low intrinsic viscosities. The polymerization conditions and results obtained are shown in Table 1. It can be seen from Table 1 that the process according to the present invention produces solvent-insoluble 4-methylpentene-1 copolymers in improved yields while retaining high transparency of the copolymers. EXAMPLE 8 A hundred parts of the copolymer as prepared in Example 1 was mixed with 0.2 part of tetrakis[methylene-3-(3′,5′-di-t-butyl-4-hydroxyphenyl)propionate]methane (produced by Ciba-Geigy AG) and 0.1 part of bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite (produced by Borg-Warner Corp.) as stabilizers, and 100 ppm of 2,5 dimethyl-2,5-di-t-butyl peroxyhexane as a polymer decomposing agent. The blend was subjected to decomposing granulation in a single-screw granulator at a cylinder temperature of 270°C. The resulting pellets had an intrinsic viscosity of 2.3 dℓ/g and a melt flow rate (260°C, 5 kg of 4 g/10 min., indicative of a molecular weight suited for molding. When the pellets were molded into a compression-molded sheet of 1 mm thick in the same manner as in the foregoing examples, the haze of the compression-molded sheet was found to be 1.4%. As described above, 4-methylpentene-1 copolymers excellent in transparency and impact resistance can be produced by the two-stage process of the present invention comprising a first stage for obtaining a 4-methylpentene-1 polymer having a low α-olefin content and a high intrinsic viscosity and a second stage for obtaining a copolymer having an α-olefin content higher than that of the polymer obtained in the first stage and a high intrinsic viscosity. The thus obtained 4-methylpentene-1 copolymer can be decomposed thermally or with a peroxide to obtain a resin composition having satisfactory molding properties.

Claims: A process for producing a 4-methylpentene-1 copolymer comprising copolymerizing 4-methylpentene-1 and another α-olefin in a hydrocarbon solvent in the presence of a Ziegler-Natta catalyst, characterised in that the copolymerization comprises a first stage in which (A) a homopolymer or random copolymer of 4-methylpentene-1 having an α-olefin content of not more than 3 mol% and an intrinsic viscosity, as measured in tetralin at 135°C, of at least 3.5 dℓ/g is prepared and a second stage in which (B) a random copolymer having an α-olefin content higher than that of the polymer (A) and no higher than 9 mol% and an intrinsic viscosity, as measured in tetralin at 135°C, of at least 3.5 dℓ/g is prepared, and the produced copolymer insoluble in the solvent is separated to recover a 4-methylpentene-1 copolymer containing from 5 to 80% by weight of the polymer (A). A process as claimed in Claim 1, wherein said other α-olefin is straight chain α-olefin having from 5 to 18 carbon atoms. A process as claimed in Claim 1, wherein the polymer (A) has an α-olefin content of not more than 2 mol%. A process as claimed in Claim 3, wherein said α-olefin content of polymer (A) is not more than 1.5 mol%. A process as a claimed in any of Claims 1 to 4, wherein said polymer (B) has an α-olefin content of not more than 8 mol%. A process as claimed in any preceding claim, wherein the polymers (A) and (B) have an intrinsic viscosity of at least 5 dl/g. A process as claimed in any preceding claim, wherein the recovered 4-methylpentene-1 copolymer contains from 20 to 80% by weight of the polymer (A). A process as claimed in Claim 7, wherein said content of recovered 4-methylpentene-1 copolymer is from 40 to 80% by weight of the polymer (A). A process as claimed in any preceding claim, wherein said copolymerization is carried out at a temperature of from 0 to 90°C. A process as claimed in Claim 9, wherein said copolymerization temperature is from 20 to 70°C. A process as claimed in Claim 10, wherein said copolymerization temperature is from 30 to 60°C. A moldable polymeric composition which is obtained by subjecting a thermal decomposition or decomposition with a peroxide a 4-methylpentene-1 copolymer which was produced by a process as claimed in any preceding claim. A 4-methylpentene-1 resin composition as claimed in Claim 12, wherein thermal decomposition is carried out at a temperature of from 250 to 330°C. A 4-methylpentene-1 resin composition as claimed in Claim 12, wherein said peroxide is dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butyl peroxyhexane or di-t-butyl peroxide.

Inventors: WAKAMATSU, KAZUKI, WAKATSUKI, KIZUKU
Applicants: SUMITOMO CHEMICAL COMPANY, LIMITED
Application year: 1987
Main classification: C08F210
IPC codes: C08F255, C08F297, C08F8, C08F2, C08F10, C08F210