IL21867A - Polymerisation of alpha-olefins - Google Patents

Description

The present invention relates to a process for the polymerization of alpha-ole ins, more particularly to a process for polymerizing alpha-ole ins in the presence of solvents, by means of catalytic systems containing chromium compounds and fluorine compounds (in addition to silicon compounds).

The process according to this invention is applicable to all olefins and diolefins having a double bond in the alpha-position. Examples of such substances are: ethylene, propylene, bu ene-1, isobutene, pentene-1, butadiene, isoprene and the like.

It is known to polymerize alpha-olefins in the presence of catalytic systems consisting of a carrier of silica, alumina or silica-alumina, and chromic anhydride or chromium sesquioxide or a mixture thereof* The chromium oxides are deposited by impregnating the carrier with a solution of chromic anhydride, or with a solution of chromium salts which can be easily converted into the anhydride or other chromium oxides by calcination, followed by drying and calcination of the resulting mass.

She invention consists in a process for polymerising an alpha-olefin comprising the steps of, contacting a solid carrier with chromyl halide; activating the catalytic system obtained by heating it in the presence of an inert gas or oxygen, or an oxygen-containing gas, and contacting the activated catalytic system with an alpha-olefin in the presence of an organic solvent or The carrier is usually a solid silicon containing compound. It may be silica, alumina, or silica/alumina. chromyl chloride^ and by subjecting the mass thus obtained to activation by heating in the presence of a gas.

In the above Patent Specification there were also described catalytic systems obtained by treating carriers containing silico compounds with a mixture of chromyl chloride and chromyl fluoride and subjecting the mass thus obtained to activation by heating. e use of such a catalytic system is envisaged in the present process.

The catalytic system used in the process of this invention may be activated by heating it at a temperature between 150° and 800°C in the presence of oxygen or of an oxygen-containing gas? or of a& inert gas (such as nitrogen) Best results in the subsequent polymerization are obtained when the catalytic system is activated at a temperature between 300° and 600°C.

The duration of the activation varies depending on the olefins to be subsequently polymerized and the characteristics of the polymer to be obtained? satisfactory results are obtained with activation periods below 24 hours; however, the best results are obtained with activation times between 1 and 8 hours.

The temperature at which the process of this invention is carried out varies depending on the alpha-olefin to be polymerized. Good results (especially in the polymerization of ethylene) are achieved by operating at temperatures below 210°C| however, the best results are obtained at temperatures between 80° and 160°C* The process according to this invention is carried polymerizations, and to ensure that the alpha-olefins are dissolved in the solvent or diluent in a sufficient quantity to ensure a smooth polymerisation. Pressures below 200 atm., e.g. between 20 and 80 atm may be used.

The process according to this invention is carried out in the presence of an organic solvent or a diluent which must be chemically inert with respect to the monomer and to the polymer formed, but may to a certain degree have a dissolving action on the polymer formed.

Suitable solvents are the sliphatic and cycloaliphatic hydrocarbonsj such as for example propane, butane, isobutane, n-pentane, iso-pentane, n-heptane, iso-octane or cyclohexane.

At the end of the polymerization the catalytic system is separated from the polymer and may be reactivated by heating as described above, -e¾—e¾ygen-¾ont«,3¾i«s. The polymer may be freed of the solvent by any conventional method.

The process of this invention gives a good yield of polymer of good c^ystallinity.

The invention will be particularly described with reference to the following examples.

Example 1 0.9 g of chromyl chloride were introduced into a reacto fitted with a bubbler and an upper outlet pipe.

The bubbler ¾ras connected to a nitrogen source while the upper outlet pipe was connected to a second reactor designed to work according to the fluid bed technique, and which contained 10 gr. of silica-alumina with 87$ silica and 13 the vapours of this latter we e passed over the silica-^ alumina, which was maintained at a temperature of 150°C.

After all the chromyl chloride had been deposited on the silica-alumina, a stream of dry air was fed in, and the temperature of the silica-alumina was raised to 520°C and maintained at this level for two hours.

After cooling, the catalytic system obtained was used for polymerizing ethylene in the following manner: 2.8 gr. of the catalytic system, prepared as described above, were suspended in 250 ml. of cyclohexane and the suspension was introduced into a 500 ml. autoclave and heated to 140°C, under a pressure of 36 a. of ethylene.

After wo hours the feeding of ethylene was stopped, the autoclave was cooled and discharged. After removal of the catalytic system and of the solvent 59 gr. of polyethylene were obtained.

Into an apparatus similar to that described in Example 1, were introduced 1.8 gr. of chromyl chloride and 20 gr. of silica-alumina. The chromyl chloride was deposited on the silica-alumina using the technique described in Example 1, except that oxygen was used instead of nitrogen. After all the chromyl-chloride had been deposited on the silica-alumina, the feeding of oxygen was continued for another 20 hours, then the catalytic system w s activated for 2 hours at 510°C in a stream of dry air. 1.8 gr. of the catalytic system thus obtained were introduced into a 500 al autoclave containing 250 ml of cyclohexane. Then, for two hours and at 140°C under a The catalytic system was prepared in the following manne ί 5 gr. of chromyl chloride were introduced into a glass container fitted with a bubbler tube for gases and a gas discharging pipe. A stream of an inert gas was fed through the bubbler and the inert gas-chrorayl chloride vapour mixture was conveyed through the outlet pipe to a reactor containing silica-alumina with 87$ of silica. After abou 1 hour the feeding of the gaseous mixture was stopped and the catalytic system activated by heating for 2 hours at 500°C in a stream of dry air. 2.7 gr. of the catalytic system thus obtained were introduced into an autoclave together with 250 cc of cyclohexane. The autoclave was closed and heated to 140°Cj ethylene was then introduced at an average pressure of 40 atia. for 2 hours.

At the end of this operation, the autoclave was opened and the solvent and the catalytic system were separated from the reaction product. 60 gr. of solid, white polyethylene were obtained.

Example 4 The catalyst was prepared as described in Example 1 and contained 3. 7$ of chromium. 8.4 gr. of this catalyst v/ere. activated at 520°C for two hours in a stream of dry air and cooled in a nitrogen stream; thereupon they were introduced together with 200 cc of n-heptane into a 500 ml autoclave provided with a central stirrer and previously purged with nitrogen and put under vacuum.

The autoclave was then closed, heated to 95°C and autoclave. The polymers thus obtained were extracted with n-penta e by boiling under reflux for 20 hours.

In this way, 18 gr. of a viscous, liquid fraction, soluble in pentane, was obtained.

The residue from the extraction with pentane was boiled under reflux with n-heptane for 20 hours; 2.50 gr. of a solid, waxy fraction, soluble in n-heptane was obtained.

The part insoluble in boiling n-heptane was separated from the exhausted catalyst by extraction with boiling xylene, and 1.9 gr. of solid, crystalline polypropylene were obtained.

Exaaple 5 The catalyst was prepared as described in Example 1 and contained 1.615¾ of chromium. 9 gr. of this catalyst were activated at 500°C for 2 hours in a stream of dry air and then cooled in a stream of nitrogen. Into a 500 ml„ autoclave provided with a central stirrer and a heating oil circuit were introduced 150 cc of n-heptene into which had been suspended the catalyst activated beforehand, and 150 cc of 1-hexene. The autoclave was then closed, purged with nitrogen and heated at 120°C.

After 2 hours the heating was stopped, the autoclave was cooled and then opened. Prom it (besides the exhausted catalyst, the solvent, and the exhausted 1-hexene) 14 gr. of oily 1-hexene polymers were extracted.

Example 6 1.4 gr. of chromyl chloride were introduced into a glass container provided with a bubbler. The container was at 400 C for 2 hours, The chromyl chloride was then conveyed on to the silica-alumina in the form of vapours by means of a stream of dry air.

When all the chromyl chloride had been introduced into the reactor containing the silica-alumina, the reactor was heated in a stream of dry air to 300°C for half an hour and the temperature was raised to 500°C and maintained at that level for 2 hours. The catalyst thus prepared Has cooled in a stream of dry nitrogen. 8.5 gr. of this catalyst (whic contained 2.02 of chromium) were put into a 2000 ml autoclave fitted with a central stirrer, together with 150 cc of n-heptane.

The autoclave was then heated to 160°C, and ethylene at about 40 atm Example 7 The catalyst was prepared in an apparatus similar to that described in Example 6. 1.4 gr. of chromyl chloride were conveyed at room temperature, by means of a stream of dry air on to 23 gr. of ketjen γ-alumina dried beforehand at 500°C for 2 hours. The alumina-containing reactor was heated in a stream of dr air to 300°C for half an hour and then at 500°C for 2 hours.

The cooling was carried out in a stream of dry nitrogen. The catalyst thus prepared contained 2.14$ of chromium. a pressure of 40 atm. was fed into it.

At the end of the reaction, the autoclave contained 32 gr; of solid, crystalline polyethylene.

Example 8 The catalyst was prepared by passing 0.9 gr. of Cr02 ClgOve 15 gr. of Ketjen silica, dried beforehand at 350°C for 1 hour,; the equipment and the preparation technique of the catalyst were the same as those illustrated in Example 6. The catalyst contained 1.58$ of chromium.

Polymerization of ethylene was carried out at 140°C and 40 atm. for one hour in an autoclave as described in Example 7» using 8.3 gr. of the catalyst previously described and suspended in 150 cc of n-heptane. 200 gr. of solid, white polyethylene were obtained.

Example 9 A catalyst containing 2. $ by weight of chromium was prepared as' described in Example 1. It was activated in a stream of dry nitrogen at 350°C for 2 hours and then cooled in the stream of nitrogen. 47 gr. of this catalyst suspended in 250 ml of n«-heptane were introduced into a 1000 ml autoclave, in which ethylene was polymerized at 140°C under a pressure of 40 atm. A^ter 1 hour, 472 gr. of solid white crystalline polyethylene were obtained.

Example 10 2 gr. of chromyl chloride were placed into a Monel bubbler through which a gaseous mixture containing 90$ of SL, and 10 of HP was passed at a throughput of 500/ml per fiie gaseous mixture leaving the bubbler (consisting of chromyl chloride, chromyl fluoride, chromyl chlorofluoride, hydrogen chloride, hydrogen fluoride and nitrogen) was passed at room temperature through a stainless steel reactor containing 100 gr. of Davison silica-alumina (of 87 of silica). When no more chromyl chloride remained in the bubbler, the flow of hydrogen fluoride was stopped, while the flow of nitrogen was continued in order to purify the catalyst from occasional acid vapors physically retained on it.

The catalyst obtained contained 1.37$ of chromium. 12.5 gr. of this catalyst, activated at 500°C for 4 hours in a stream of dry air and cooled in a stream of nitrogen, were suspended in 250 ml of n-heptane. This suspension was introduced into a 1000 ml autoclave, into which ethylene was then introduced at 140°G and under a pressure of 40 atm.

After 1 hour, 243 gr. of solid, white, crystalline polyethylene were obtained.

Example 11 A catalyst prepared as described in Example 1 and containing 3. of chromium was activated for 2 hours at 400°C in a stream of dry air and cooled in a stream of nitrogen. 9.4 gr. of the catalyst thus prepared, suspended in 200 ml of n-heptane were introduced into an autoclave equipped with a central stirrer and previously purged with dry nitrogen.

The autoclave was then heated to 140°C while ethylene was introduced into it at a pressure of 40 atm. The ethylene was kept at a temperature of about 140 C and at 40 atm. for 1 hour, Bxample 12 9.5 gr. of a catalyst, prepared according to Example 1, and containing 1.6$ by weight of chromium, wore activated for 2 hours in dry air at 50Q°C, and introduced in an autoclave containing 200 ml of iso-octane. The autoclave was then closed and heated to 140°C and at the same time ethylene was introduced into it at 35 atea. pressure After one hour the autoclave was vented and cooled. From it 410 gr. of polyethylene were extracted.

Claims (1)

1. HAVING particularly described and ascertained the nature of said invention ar d in what the same is to he declare that what claim A process for polymerising an comprising the steps contacting a solid carrier with chromyl activating the catalytic system obtained by heating it in the presence of an inert gas or or an and contacting the activated catalytic system with an in the presence of an organic solvent or A process as claimed in Claim 1 in which the solid carrier is a solid A process as claimed in Claim 1 or 2 in which the carrier or process as claimed in any one preceding claim in which a mixture of chromyl chloride and chromyl fluoride is used to prepare the catalytic A process as claimed in any one preceding claim in which the catalytic system is activated by it at a temperature between 150 and 800 A process as claimed in Claim 5 which the catalytic system is activated by heating it at a temperature between and A process as claimed in any one preceding claim in which the activation lasts up to 24 A process as claimed in Claim 7 in which the activation lasts from 1 to 8 process as claimed in any one preceding claim A process as claimed in Claim 9 in is carried at a temperature between and A process as claimed in any one preceding claim in which the is carried out at a pressure below 200 A process as claimed in Claim 11 in which the polymerisation is carried out at a pressure between 20 and 80 A process as claimed in any one preceding claim in which the polymerisation is carried out in the presence of an aliphatic or cycloalipha ic hydrocarbon as the organic solvent or A process as claimed in Claim 13 in which the organic solvent or diluent is isobutane isooctane or A process as claimed in any one preceding claim in which the undergoing polymerisation is A process as claimed in any one of the preceding claims in after the the catalyst is separated from the polymer and reactivated by heating in the presence of or of an taining A process for the polymerisation of an substantially as herein described with reference to the of when obtained by the process claimed in any one of the preceding insufficientOCRQuality