BULK POLYMERIZATION OF DICYCLOPENTADIENE

Abstract: 1. A process for the bulk polymerization of dicyclopentadiene which comprises contacting dicyclopentadiene with a catalyst comprising a) a tungsten compound of the formula wherein R represents a bulky alkyl group, having at least 3 carbon atoms or a hydrogen atom, with the proviso that at least one R represents a bulky alkyl group; R¹ is a hydrogen atom or an alkyl group of 1 to 10 carbon atoms; (m + n) are 6 and n is 1 or 2, and b) a tin compound of the formula wherein R² is an alkyl group of 1 to 10 carbon atoms or a phenyl group

Description: The invention relates to a process for the bulk polymerization of dicyclopentadiene, to the dicyclopentadiene polymer prepared by this process and to a catalyst system therefor. It is known from US Patent Specification 3,627,739 to polymerize dicyclopentadiene (abbreviated DCPD) to polydicyclo­ pentadiene (poly DCPD) with the aid of a tungsten catalyst. The obtained poly DCPD is rather brittle and has a low Izod impact strength. Efforts have been made to improve this product. According to European Patent Application 84,888 poly DCPD with improved properties had been prepared. European Patent Application 84,888 discloses a process for the polymerization in bulk of DCPD with the aid of a metathesis catalyst system, comprising e.g. phenol substituted tungsten hexachloride together with an activator, e.g. ethylaluminium dichloride, and diethylaluminium chloride or tetrabutyl tin, and the application further discloses that the used DCPD should be purified in order to prevent impurities from inhibiting the polymerization. It further stresses that it is often desirable to purify the starting materials even further by treatment with silica. Applicant has now found a versatile metathesis catalyst system for the polymerization of DCPD in bulk, which is more stable, less sensitive to oxygen and moreover can polymerize impure DCPD. Accordingly, the invention provides a process for the bulk polymerization of dicyclopentadiene which comprises contacting dicyclopentadiene with a catalyst comprising a) a tungsten compound of the formula wherein R represents a bulky alkyl group, having at least 3 carbon atoms or a hydrogen atom, with the proviso that at least one R represents a bulky alkyl group; R¹ is a hydrogen atom or an alkyl group of 1 to 10 carbon atoms; (m + n) are 6 and n is 1 or 2, and b) a tin compound of the formula wherein R² is an alkyl group of 1 to 10 carbon atoms or a phenyl group. It has been found that the tin compound, in contrast with the aluminium compound, is much less sensitive to oxygen, and consequently nitrogen atmospheres do not need to be used in the process according to the invention. Applicant has further found that the use of tetrabutyl tin, together with the above-defined tungsten compound did not polymerize DCPD. Tetramethyl tin and tetraethyl tin did not work either. Furthermore the above-mentioned European Patent Application 84,888 discloses that unmodified tungsten compound will rapidly polymerize DCPD. To prevent premature polymerization of the tungsten compound/DCPD solution a Lewis base or a chelating agent can be added. Consequently the use of WCl₆, often mentioned in the general prior art as one of the components of the metathesis catalyst, is not desirable in the process according to the invention. The tungsten compounds used as catalyst component in the process according to the invention contain in the phenyl nucleus a bulky alkyl group, preferably an isopropyl group, a tertiary butyl group or a neo-pentyl group. Suitable tungsten compounds may be represented by the following chemical formulae These two chemical formulae represent the reaction product obtained by reacting tungsten hexachloride with an appropriate amount of 2,6-diisopropylphenol and 2,6-di-tert.butyl-4-­ methylphenol respectively. Of the trialkyl tin hydrides those in which the alkyl group contains 1 to 6 carbon atoms are preferred, the tributyl tin hydride being most preferred. Triphenyl tin hydride may also be used. As stated already hereinbefore the DCPD may be impure, such like commercially available endo-DCPD. A technical grade of DCPD contains about 5 to 6 per cent by weight of codimers. The amount of the tungsten compound catalyst component used in the process according to the invention may range from 0.01 to 1 mol %, preferably from 0.02 to 0.1 mol %, calculated on the amount of DCPD. The mol ratio of the tin compound versus the tungsten compound ranges from 15:1 to 1:1, preferably from 12:1 to 3:1. It is observed, that anti-oxidants (such as Ionol, "Ionol" is a trade name), moisture and oxygen do not disturb the polymerization. Generally the polymerization takes place in bulk, but the catalyst components, viz. the above-defined tungsten compound and the tin compound, may be dissolved in a small amount of solvent, such as toluene. It is preferred to use, however, DCPD as a solvent. In case of the tin compound no solvent at all may also suffice, since the tin compound is a liquid. A preferred method for the polymerization of DCPD is to allow to contact a tungsten compound catalyst component stream with a tin compound catalyst component stream with each other, whereby at least one of the streams contains the DCPD, and to polymerize the DCPD. For example it is possible to dissolve the tungsten catalyst in DCPD and either to dissolve the tin catalyst in DCPD or in another solvent or to use the tin catalyst without any solvent. After both streams have contacted with each other, the resulting mixture may be injected or poured into a mould, where the polymerization takes place. The polymerization is exothermic, but heating up the mould to about 50 to 100 °C is preferred. The tin catalyst as well as the tungsten catalyst may be stored in DCPD for some time, provided that the DCPD contains only a few parts per million (ppm) of water or less. The tin catalyst is storable in DCPD during one to two months without loosing its activity. Even the tungsten catalyst and the catalyst prepared in Example 2 described hereinafter admixed with each other in dry DCPD under nitrogen may be stored for one day, without loosing activity. The properties of the poly DCPD, obtained by the process according to the invention are: During the polymerization of DCPD, fillers, anti-oxidants, stabilizers, pigments, plasticizers may be present in the reaction mixture. The catalyst system used is specifically of interest for reaction injection moulding or casting. Because of the low viscosity of the DCPD/catalyst system, the polymerization is very suitable for large castings with intricate moulds. Polymerization temperatures of up to 200 °C are reached in exothermic reactions. The poly DCPD obtained by the process according to the invention may be subjected to a heat-treatment of 200 °C to 300 °C for about 1 hour or longer. After this heat-treatment the glass transition temperature of the polymer has been increased to about 160 °C. This post-curing treatment may be beneficial to certain uses of the poly DCPD. The invention further relates to a two component catalyst system, comprising a) a tungsten compound of the formula wherein R represents a bulky alkyl group, having at least 3 carbon atoms or a hydrogen atom, with the proviso that at least one R represents a bulky alkyl group; R¹ is a hydrogen atom or an alkyl group of 1 to 10 carbon atoms, (m + n) are 6 and n is 1 or 2, b) a tin compound of the formula wherein R² is an alkyl group of 1 to 10 carbon atoms or a phenyl group The two component catalyst system may form part of a package wherein at least one of the components is dissolved in dicyclopentadiene. It is possible to manufacture drums containing DCPD together with a pre-determined amount of one of the components, e.g. the tungsten catalyst and drums containing DCPD with the tin catalyst in an amount adapted to the desired mol ratio of components to be used in the polymerization of DCPD. Example 1 (Preparation of catalyst 1) 2 g of WC1₆ was weighed in a 100 ml dried serum cap bottle and dissolved in 40 ml of dried toluene under a dry nitrogen blanket. 1,73 ml of dried 2,6-diisopropylphenol was added slowly at 100 °C. The evolved HC1 was collected in an excess of aqueous sodium hydroxide solution. The reaction mixture was kept for 4 h at 100 °C. The product was isolated by evaporation of the solvent and is referred to herein as catalyst 1. Example 2 (Preparation of catalyst 2) 4 g of WC1₆ was weighed in a 100 ml dried serum cap bottle and dissolved in 20 ml of dried toluene under a dry nitrogen blanket. A solution of 6.6 g dried 2,6-ditert.butyl-4-methylphenol (Ionol) in 20 ml of dried toluene was added slowly at 95 °C. The evolved HC1 was collected in an excess of aqueous sodium hydroxide solution. The reaction mixture was kept for 4 h at 95 °C. The product was isolated by evaporation of the solvent, and is referred to herein as "catalyst 2". In the polymerization experiments a technical grade of DCPD was used, which contained: 3,5 % isopropenyl-2-norbornene 1,1 % 5-cis and trans-1-propenyl-2-norbornene 0,7 % 5-methyl tetrahydroindene 70 ppm water If dry DCPD was used, it contained less than 1 ppm of water. Example 3 0.08 g of catalyst 1 was dissolved in 40 g of DCPD in a 100 ml serum cap bottle. 3 ml of a 0.2 mol/l solution of tributyl tin hydride in toluene was added at ambient temperature by means of a hypodermic syringe. The bottle was shaken thoroughly and placed in an oil-bath of 90 °C. The reactive mix gelled very rapidly and an exothermic polymerization was observed. A maximum temperature of 200 °C after 4.5 minutes from initiation was observed. Example 4 0.09 g of catalyst 1 was dissolved in 40 g of DCPD in a 100 ml serum cap bottle. 2.5 ml of a 0.3 mol/l solution of triphenyl tin hydride in toluene was added at ambient temperature by means of a hypodermic syringe. The bottle was shaken thoroughly and placed in an oil-bath of 90 °C. An exothermic polymerization was observed for which a maximum temperature of 160 °C after 4.5 minutes from initiation was recorded. Example 5 0.07 g of catalyst 2 was dissolved in 40 g of DCPD in a 100 ml serum cap bottle. 2.5 ml of a 0.25 mol/l tributyl tin hydride solution in toluene was added at ambient temperature by means of a hypodermic syringe. The bottle was shaken thoroughly and placed in an oil-bath of 90 °C. An exothermic polymerization was observed for which a maximum temperature of 150 °C after 11 minutes from initiation was recorded. Example 6 (Comparative experiment) 0.08 g of catalyst 1 was dissolved in 40 g of DCPD in a 100 ml serum cap bottle. 2 ml of a 0.3 mol/l tetramethyl tin solution in toluene was added at ambient temperature by means of a hypodermic syringe. The bottle was shaken thoroughly and placed in an oil-bath of 90 °C. No polymerization at all was observed. Example 7 0.08 g of catalyst 1 together with 0.08 g of Ionol were dissolved in 40 g dried DCPD and stored at room temperature. After six days 2 ml of a 0.3 mol/l solution of tributyl tin hydride in toluene was added. The bottle was shaken thoroughly and placed in an oil-bath of 90 °C. An exothermic polymerization was observed for which a maximum temperature of 195 °C after 3 minutes from initia­ tion was recorded. Example 8 0.07 g of catalyst 2 was dissolved in 40 g of dried DCPD and stored at room temperature. After 7 days 2 ml of a 0.3 mol/l solution of tributyl tin hydride in toluene was added. The bottle was shaken thoroughly and placed in an oil-bath of 90 °C. An exothermic polymerization was observed with a T max of 200 °C after 14 minutes from initiation. Example 9 0.022 g of tributyl tin hydride was dissolved in 10 g of dried DCPD and stored at room temperature. After 31 days this solution was added to a freshly prepared solution of 0.02 g of catalyst 1 in 10 ml of dried DCPD. The reactive mix was homogenized and heated in an oil-bath of 90 °C. An exothermic polymerization was observed with a T max of 170 °C. Example 10 0.25 g of catalyst 2 was dissolved in 105 g of dried DCPD. 5.8 ml of a 0.3 mol/l solution of tributyl tin hydride in toluene was added. The mixture was homogenized and stored in contact with the atmosphere. After 1 day 40 ml of the mixture, which was still a thin liquid, was heated till 90 °C in an oil-bath. An exothermic polymerization was still observed with a T max of 170 °C. Example 11 0.5 g of catalyst 2 was dissolved in 350 g of technical DCPD in contact with the atmosphere. 1.4 ml of tributyl tin hydride was added whereafter the solution was thoroughly homogenized in contact with the atmosphere. The reactive mix was poured in a preheated (110 °C) aluminium mould of 35 × 10 × 1 cm. The mould was kept at 110 °C for 45 minutes whereafter the temperature was raised till 200 °C at which temperature the mould was kept for another 45 minutes. After cooling a polymer sheet was extracted from the mould which was free from any DCPD odour. Example 12 (Comparative experiment) 0.086 g of catalyst 2 was dissolved in 20 g dry DCPD in a 100 ml serum cap bottle. 0.257 g tetrabutyl tin in 20 g dry DCPD was added at room temperature by means of a hypodermic syringe. The bottle was shaken thoroughly and placed in an oil-bath of 90 °C. No polymerization at all was observed.

Claims: 1. A process for the bulk polymerization of dicyclopentadiene which comprises contacting dicyclopentadiene with a catalyst comprising a) a tungsten compound of the formula wherein R represents a bulky alkyl group, having at least 3 carbon atoms or a hydrogen atom, with the proviso that at least one R represents a bulky alkyl group; R¹ is a hydrogen atom or an alkyl group of 1 to 10 carbon atoms; (m + n) are 6 and n is 1 or 2, and b) a tin compound of the formula wherein R² is an alkyl group of 1 to 10 carbon atoms or a phenyl group. 2. A process according to claim 1, wherein the tungsten compound has the formula wherein both R's are isopropyl groups 3. A process according to claim 1, wherein the tungsten compound has the formula wherein both R's are tertiary butyl groups 4. A process according to any one of the preceding claims, wherein the tin compound is tributyl tin hydride. 5. A process according to any one of the claims 1 to 3, wherein the tin compound is triphenyl tin hydride. 6. A process according to any one of the preceding claims, wherein the polymerization takes place in bulk, without any other solvent than dicyclopentadiene. 7. A process according to claim 6, wherein at least the tungsten compound is stored in dicyclopentadiene. 8. A process according to claim 6 or 7, wherein the tin compound is stored in dicyclopentadiene. 9. A process according to any one of the claims 6 to 8, wherein a tungsten compound catalyst component stream and a tin compound catalyst component stream, one of which streams at least contains the dicyclopentadiene, are allowed to contact with each other, and to polymerize the dicyclopentadiene. 10. A process according to claim 9, wherein after both streams have been contacted with each other, the resulting mixture is injected or poured into a mould, where polymerization of the dicyclopentadiene takes place. 11. A two component catalyst system, comprising a) a tungsten compound of the formula wherein R represents a bulky alkyl group, having at least 3 carbon atoms or a hydrogen atom, with the proviso that at least one R represents a bulky alkyl group; R¹ is a hydrogen atom or an alkyl group of 1 to 10 carbon atoms; (m + n) are 6 and n is 1 or 2, and b) a tin compound of the formula wherein R² is an alkyl group of 1 to 10 carbon atoms or a phenyl group

Inventors: KRAMER, ARRIS HERMAN, SJARDIJN, WILLEM
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1986
Main classification: C08G61
IPC codes: C08F2, C08G61, C08F4, C08F32