GB2034723A - A Preparation of Ethylene-alpha Olefine Copolymers - Google Patents

Abstract

Ethylene-???-olefine copolymers having a density of 0.850 to 0.945 which are suitable for molding or extrusion are obtained without many of the problems associated with high pressure or solution polymerization by copolymerizing ethylene, 1 to 40 mol% thereof of an ???-olefin having 5 to 18 carbon atoms and optionally a diene in a substantially solvent-free vapor phase condition and in the presence of a catalyst comprising a solid substance and an organoaluminium compound, said solid substance containing magnesium and titanium and/or vanadium.

Description

SPECIFICATION Process for Preparing a Copolymer This invention relates to a new process for preparing a medium or low density ethylene copolymer according to the vapor phase polymerisation method using a Ziegler-type catalyst of high activity.

More particularly, this invention is concerned with a process for preparing an ethylene-a-olefin copolymer having a density of 0.850 to 0.945, characterized in that ethylene and 1 to 40 mol% thereof of an a-olefin having 5 to 18 carbon atoms are copolymerized in a substantially solvent-free vapor phase condition and in the presence of a catalyst comprising a solid substance and an organoaluminium compound, said solid substance containing magnesium and titanium and/or vanadium.

Polyethylenes obtained by polymerization using a catalyst consisting of a transition metal compound and an organometallic compound are generally prepared according to the slurry polymerization process, and only those having a density not lower than 0.945 are produced which value is considered to be the limit of preventing polymer deposition and fouling on the inner wall or stirrer in the reactor interior at the time of polymerization.

Medium or low density polyethylenes having a density below 0.945 g/cm3 are prepared mainly by the so-called high pressure process using a radical catalyst. Quite recently, however, there has also been tried a high-temperature solution polymerization using a Ziegler-type catalyst.

Copolymerizing ethylene and other a-olefin using a catalyst containing a vanadium compound as one component has also been tried to prepare an elastomeric copolymer.

These polyolefin series plastics prepared according to the high pressure process or hightemperature solution polymerization using a Ziegler-type catalyst, and elastomers prepared using a vanadium compound-containing catalyst, exhibit superior performances and are used in various applications. For example, low density polyethylenes prepared according to the high pressure process are superior in transparency and flexibility, so are used in the field of films.

Elastomers resulting from polymerization of ethylene and propylene, or as the case may be, dienes such as dicyclopentadiene and ethylidenenorbornene, using a vanadiumcontaining catalyst, namely EPM and EPDM, have no unsaturated bond in the main chain, for which reason, as elastomers superior in heat- and weathering- resistance, they are often used for tires and tubes.

However, high pressure process polyethylenes are disadvantageous in that they are low in melting point, in stiffness, that is, inferior in heat resistance, and also in strength. And medium density polyethylenes prepared according to the high-temperature solution polymerization process are inferior in transparency and give a sticky impression.

As other uses of polyolefins adopted recently, we often experience that an improvement in the resistance to environmental stress cracking is requested by somewhat imparting an elastomeric character to plastics, or conversely their thermoelastic way of use is requested by imparting strength based on crystallinity to elastomers. It is a well-known fact, however, that if both components are mixed together for such purpose, it will cause deterioration of physical properties such as tensile strength and rigidity.

However, if it is possible to prepare a soft or semi-hard resin which resin itself is neither a crystalline plastic nor elastomer, but has an intermediate structure and exhibits a high-grade of elongation, then such resin itself will become suited for the above-mentioned purpose, or by blending it with other plastics it is made possible to impart an elastomeric character thereto and to improve the properties of the plastics.

Recently there have been made some reports on the production method for a resin which exhibits such an intermediate physical property. But those reports involve various drawbacks and many problems to be solved before application on an industrial scale.

For example, Japanese Patent Publication No.

11028/71 discloses a solution polymerization using an aromatic hydrocarbon solvent for the preparation of an ethylene-a-olefin copolymer.

This method, however, is disadvantageous in that the catalyst efficiency is poor and, because of a solution polymerization, it is troublesome to separate and recover the solvent.

Japanese Patent Publication No. 26185/72 proposes the copolymerization of ethylene and an -olefin using an aliphatic hydrocarbon halide as solvent. But this method is also disadvantageous in that a large amount of a low molecular weight copolymer is produced probably because the hydrocarbon halide solvent acts as a molecular weight adjuster, so that a formed article thereof is sticky on the surface. The said patent publication also discloses the use of lower hydrocarbons of C3 to C5 as solvent. In the polymerization using these solvents, however, it is necessary to raise the reaction pressure due to the vapor pressure from the solvents. In the solvent recovery step, moreover, it is necessary to compress and cool the solvent for its liquefaction.

Furthermore, in Japanese Patent Laying Open Print No. 41784/76 there is disclosed a slurry copolymerization of ethylene and butene-1. Also in this case there are found drawbacks such that the polymerization temperature and the composition of starting materials are specified minutely and at values outside the specified range the slurry becomes milky or mushy, which makes reactor operation and slurry transport difficult.

The above-mentioned drawbacks are, in summary, used on the low catalyst activity, troublesomeness of solvent separation and recovery because of a solution polymerization, a large quantity production of a low molecular weight copolymer due to chain transfer with solvent, and the necessity of specifying the polymerization temperature and the composition of starting materials in slurry polymerization to maintain the slurried state of polymer. The need to provide an extremely large amount of comonomer is a further drawback encountered in the above-proposed methods.

Recently, through many studes on the improvement of catalyst activity it has been learned that a catalyst system prepared by first attaching a transition metal to a magnesiumcontaining solid carrier such as MgO, Mg(OH)2, MgCI2, MgCO3, or Mg(OH)CI and then combining it with an organometallic compound, can serve as a catalyst of a remarkably high activity in olefin polymerization. It is also known that the reaction product of an organomagnesium compound such as RMgX, R2Mg or RMg(OR) and a transition metal compound can act as a high polymerization catalyst for olefins (see, for example, Japanese Patent Publication No 12105/64, Belgian Patent No 742,112, Japanese Patent Publication Nos 13050/68 and 9548/70).

However, even if a slurry polymerization or solution polymerization is carried out using such a high activity catalyst with carrier with a view to attaining reduction in density of polymer, the foregoing drawbacks heretofore have not been solved at all.

This invention provides a new method which reduces or eliminates some or all of the foregoing technical problems and drawbacks associated with the solution or slurry polymerization, such as low polymerization activity, polymer adhesion, low bulk density and the production of coarse polymer particles. According to the process of this invention, a vapor phase polymerization reaction can be conducted extremely stably, and besides, the catalyst removing step can be omitted, so a vapor phase polymerization process which as a whole is very simple could be attained for the copolymerization of ethylene and an a:-olefin having 5 to 18 carbon atoms.Furthermore, it has become clear that the copolymer of ethylene and an a-olefin of C5 to C,8 prepared according to the process of the invention is very superior in strength, impact resistance, transparency and resistance to environmental stress cracking, though a detailed description on this respect will be given hereinafter.

In more particular terms, this invention relates to a process for preparing an ethylene-a-olefin copolymer having a density of 0.850 to 0.945, characterized in that a mixture of ethylene and 1 to 40 mol% thereof of an a-olefin having 5 to 18 carbon atoms is contacted in vapor phase condition with a catalyst comprising a solid substance and an organoaluminium compound, said solid substance containing magnesium and titanium and/or vanadium.It has been found that according to the process of this invention, that is, if a vapor phase polymerization is carried out using ethylene and an -olefin of C5 to C18 in a quantitative ratio within the range specified herein and in the presence of a catalyst comprising a solid substance and an organoaluminium compound, said solid substance containing magnesium and titanium and/or vanadium, it is made possible to effect a vapor phase polymerization reaction in extremely high activity and very stably and , despite of the resulting polymer having stickiness, with reduced production ratio of coarse or ultra-fine particles, improved particle properties, high bulk density and minimized adhesion to reactor and conglomeration of polymer particles.It is quite unexpected and surprising that according to the process of this invention, not only a vapor phase polymerization reaction can be carried out extremely smoothly, but also medium and low density ethylene copolymers can be obtained easily.

In this invention, moreover, the copolymerization reaction can be conducted even at a relatively low temperature to easily afford medium or low density ethylene polymers, and this is very advantageous when viewed from the standpoint of adhesion to reactor and conglomeration of product. This point is also an advantage of the invention. Furthermore, the process of this invention easily affords medium or low density ethylene copolymers having a high melt index, and this point is another advantage of the invention. Thanks to these advantages, as has previously been described, the copolymer as referred to herein can be obtained efficiently by vapor phase polymerization.

ct-olefins of C5 to C,8 to be copolymerized with ethylene in the process of this invention function to adjust the density and molecular weight of copolymer, and the resulting copolymer is superior in transparency, appearance and gloss, and its flexibility and elasticity are excellent at low temperatures, not to mention at room temperatures. And, despite of such an excellent flexibility, the resulting polymer exhibits equal or even superior strength to that of ordinary polyolefins. Besides, the copolymer obtained according to the process of this invention scarcely contains unsaturated bond, residual catalyst or other impurities, for which reason it is very superior in weathering and chemicals-resistance, as well as electrical characteristics such as dielectric loss, break-down voltage and resistivity.

Also with respect to resistance to impact and to environmental stress cracking, the said copolymer exhibits very superior characteristics. Having these characteristics, the copolymer prepared according to the process of this invention can be formed into films, sheets, hollow containers, electric wires and various other products by known forming methods such as extrusion molding, blow molding, injection molding, press forming and vacuum forming. Specially in the field of films, it exhibits its characteristic features because of excellent strength, elongation, transparency, anti-blocking property, heat-sealing property and flexibility. What is worthy of special mention, moreover, is that according to the process of this invention, the hexane extract is very small in quantity and so it is possible to easily obtain a copolymer which satisfies the "U.S.Food Medicines Administration Standard on Extracts to be Contacted with Food" (n-hexane extract at 500C should be below 5.5% by weight), and the said copolymer can be safely used as a food packing film. Since the copolymer is superior in transparency, stiffness and resistance to environmental stress cracking, it is also suited to blow molding. Furthermore, the copolymer is a very superior resin also for use an an electric wire because of excellent electrical characteristics and easy appiication to extrusion molding.

In addition, the copolymer prepared according to the process of this invention contains olefins as components, so is very similar in structure and composition to known polyolefin resins; besides, it can be adjusted low in crystallinity, for which reason it is compatible with other polyolefin resins, specially compatible with high and low density polyethylene, polypropylene, and ethylenevinyl acetate copolymer. By blending the copolymer in question with these resins it is made possible to improve resistance to impact, to cold and to environmental stress cracking.

The catalyst system used in this invention comprises the combination of solid substance and an organoaluminium compound, said solid substance containing magnesium and titanium and/or vanadium. The said solid substance is obtained by attaching a titanium compound and/or vanadium compound by a known method to an inorganic solid carrier typical of which are metallic magnesium, magnesium hydroxide, magnesium carbonate, magnesium oxide and magnesium chloride; or double salt, double oxide, carbonate, chloride and hydroxide containing a metal selected from silicon, aluminium and calcium, and magnesium atom; further, these inorganic solid carriers treated or reacted with an oxygen-containing compound, a sulfur-containing compound, a hydrocarbon or a halogen containing substance.

As the titanium compound and/or vanadium compound referred to herein, mention may be made of halides, alkoxyhalides, oxides and halogenated oxides of titanium and/or vanadium.

Examples are tetravalent titanium compounds such as titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, monoethoxytrichlorotitanium, diethoxydichlorotitanium, triethoxymonochlorotitanium, tetraethoxytitanium, monoisopropoxytrichlorotitanium, diisopropoxydichiorotitanium and tetraisopropoxytitanium; various titanium trihalides obtained by reducing titanium tetrahalides with hydrogen, aluminum, titanium or an organometallic compound; trivaient titanium compounds obtained by reducing various tetravalent alkoxytitanium halides with an organometallic compound; tetravalent vanadium compounds, e.g. vanadium tetrachloride; pentavalent vanadium compounds such as vanadium oxytrichloride and orthoalkylvanadate; and trivalent vanadium compounds such as vanadium trichloride and vanadium triethoxide.

Among these titanium compounds and vanadium compounds, tetravalent titanium compounds are specially preferred.

The catalyst which may be used in the invention comprises the combination of a solid substance, which is obtained by attaching a titanium compound and/or a vanadium compound to the solid carrier exemplified previously, and an organoaluminium compound.

By way of illustrating preferred catalyst systems, mention may be made of the combination of an organoaluminium compound with the following solid substances (the R in the following formulae represents an organic radical and X represents halogen): Mg0-RX-TiCl4 system (see Japanese Patent Publication No.

3514/76); Mg-SiCl4-R0H-TiCl4 system (see Japanese Patent Publication No. 23864/75), MgCl4-Al(OR)3-TiCl4 system (see Japanese Patent Publications Nos 152/76 and 151 11/77, MgCl2-SiCl4-R0H-TiCl4 system (see Japanese Patent Laying Open Print No.

106581/74), Mg(00CR)2-Al(OR)3-TiCl4 system (see Japanese Patent Publication No. 11 710/77, Mg-P0Cl3-TiCl4 system (see Japanese Patent Publication No.153/76) and MgCl2-Al0Cl- TiCI4 system (see Japanese Patent Laying Open Print No. 133386/76).

To illustrate another example of catalyst system which may be suitably used in the invention, mention may be made of the combination of the reaction product of an organomagnesium compound such as a Grignard compound and a titanium compound and/or a vanadium compound, and an organoaluminium compound. As the organomagnesium compound there may be used those represented by the general formulae RmgX, R2Mg and RMg(OR) wherein R is an organic radical and X is halogen, and ether complexes thereof, or these organomagnesium compounds after modification with other organometallic compounds such as organosodium, organolithium, organopotassium, organoboron, organocalcium and organozinc.

Such catalyst systems, for example, comprise the combination of the following solid substances and an organoaluminium compound: RMgX- TiCI4 system (see Japanese Patent Publication No.39470/75)

system (see Japanese Patent Laying Open Print No. 119977/74),

system (see Japanese Patent Laying Open Print No. 119982/74).

In these catalyst systems, a titanium compound and/or a vanadium compound may be used as the addition product with an organocarboxylic acid ester; further, the magnesium-containing solid carriers previously exemplified may be contacted, before use, with an organocarboxylic acid ester; and also an organoaluminium compound may be used as the addition product with an organocarboxylic acid ester. Furthermore, in every case in the invention, the catalyst system used therein may be prepared in the presence of an organocarboxylic acid ester and this causes no trouble.

As the organocarboxylic acid ester referred to herein there may be employed various aliphatic, alicyclic and aromatic carboxyiic acid esters, preferably aromatic carboxylic acids of C7to C,2, e.g. alkylesters such as methyl and ethyl of benzoic acid, anisic acid and toluic acid.

Examples of organoaluminium compounds which may be used in the invention are those represented by the general formulae R3AI, R2AIX, Rail2, R2AIOR, RAI(OR)X and R3AI2X3 wherein R is C; to C20 alkyl or aryl, X is halogen and R may be same or different, such as triethylaluminium, triisobutylaluminium, trihexylaluminium, trioctyaluminium, diethylaluminiumchloride, ethylaluminium sesquichloride, and mixtures thereof.

The amount of an organoaluminium compound to be used in the invention is not specially limited, but usually it may range from 0.1 to 1000 mols per mol of a transition metal compound.

In the polymerization reaction, a mixture of ethylene and an a-olefin of C5 to C,8 is allowed to polymerize in vapor phase using a known reactor such as a fluidized bed or agitation vessel.

The polymerization conditions involve temperatures ranging usually from 20 to 1 1 OOC, preferably from 500 to 1000C, and pressures from atmospheric pressure to 70 kg/cm2. G, preferably from 2 to 60 kg/cm2. G. Adjustment of the molecular weight can be made by changing the polymerization temperature, the molar ratio of catalyst or the amount of comonomer, but the addition of the hydrogen into the polymerization system is more effective for this purpose. Of course, the process of this invention can be applied, without any trouble, to two or more stage polymerization reactions involving different polymerization conditions such as different hydrogen and comonomer concentrations and different polymerization temperatures.

In this invention, moreover, the foregoing catalyst system may be contacted with an a- olefin before its use in the vapor phase polymerization reaction whereby it is made possible to largely improve the polymerization activity and assure a more stable operation than in untreated condition. Various a-olefins are employable in the above treatment, preferably those having 3 to 12 carbon atoms and more preferably those having 3 to 8 carbon atoms, typical of which are propylene, butene-1, pentene-1, 4-methylpentene-1, heptene-1, hexene-1, octene-1, and mixtures thereof.The temperature and time for such contact treatment for the catalyst used in the invention with an aolefin can be selected in wide range, for example, 0 to 2000C, preferably 0 to 1 1 OOC, and 1 minutes to 24 hours.

The amount of an a-olefin to be brought into contact with the catalyst can also be selected in wide range, but usually it ranges from 1 g. to 50,000 g., preferably 5 g. to 30,000 g., per gram of the solid substance and it is desired that 1 g. to 500 g. of the a-olefin per gram of the solid substance be reacted. The pressure in such contact treatment can be optionally selected, but desirably it ranges from -1 to 100 kg/cm2. G.

In the above treatment of the catalyst with an a-olefin, the total amount of an organoaluminium compound may be first combined with the solid substance and then contacted with the a-olefin, or alternatively part of the organo aluminium compound may be combined with the solid substance, then contacted with the a-olefin and the remaining portion of the organoaluminium compound may be separately added in the vapor phase polymerization of ethylene. Furthermore, the catalyst may be contacted with an a-olefin in the presence of hydrogen gas, or other inert gas such as nitrogen, argon or helium.

a-olefins to be copolymerized with ethylene in the process of this invention are those having 5 to 1 8 carbon atoms and they may be of a straight chain or branched. Examples are pentene-1, hexene-1, 4-methylpentene-1, heptene-1, octene-1, nonene-1, decene-1, undecene-1, dodecene-1, tridecene-1, tetradecene-1, pentadecene-1, hexadacene-1, heptadecene-1, octadecene-1, and mixtures thereof.

The amount of an a-olefin to be copolymerized with ethylene in the process of this invention should be in the range of from 1 to 40 mol% based on the amount of ethylene. Outside this range, it is impossible to obtain the object product of the invention, namely an ethylene-aolefin copolymer having a density of 0.850 to 0.945. The amount of such a-olefin can be adjusted easily according to the composition ratio of the vapor phase in the polymerization vessel.

In the process of this invention, moreover, various dienes may be added as termonomers in the copolymerization reaction such as butadiene, 1,4-hexadiene, 1,5-hexadiene, vinylnorbornene, ethylidenenorbornene and dicyclopentadiene.

Working examples of this invention are described below, but it is to be understood that these examples are for purpose of illustration to work the invention and are not intended to place limitation thereon.

Example 1 1 kg. of anhydrous magnesium chloride, 50 g.

of 1 ,2-dichloroethane and 1 70 g. of titanium tetrachloride were subjected to ball milling for 1 6 hours at room temperature in a nitrogen atmosphere to allow the titanium compound to be attached to the carrier. The resulting solid substance contained 35 mg. of titanium per gram thereof.

A stainless steel autoclave was used as the apparatus for the vapor phase polymerization and there were used a blower, a flow rate adjuster and a dry cyclone to form a loop, and the temperature of the autoclave was adjusted by passing a warm water through jacket.

To the autoclave adjusted to 850C were fed the solid substance prepared above and triethyaluminium at the rates of 250 mg/hr and 50 mmol/hr, respectively, and also introduced were ethylene, 4-methylpentene- 1 and hydrogen while making adjustment so that the 4methylpentene-1/ethylene ratio (in molar ratio) in the vapor phase in the autoclave was 0.035 and the hydrogen gas pressure was 22% of the total pressure, and a polymerization was made while the gases in the system were circulated by the blower. The resulting ethylene copolymer had a bulk density of 0.395, a melt index (MI) of 1.4 and a density of 0.930, the greater part of which was composed of powders with particles sizes in the range of from 250 to 500 ju. The polymerization activity was high, 173,500 g. copolymer/g.Ti.

After continuous operation for 10 hours, the autoclave was opened and its interior was checked to find it being clean with no polymer adhesion to the innner wall and stirrer. That is, it is apparent that a very stable operation is assured according to the process of this invention though it was unattainable in the slurry polymerization shown in Comparative Example 1 as will be referred to hereinafter.

The resulting copolymer was formed into a film 400 mm in fold diameter by 30 4 thick through a 75 mmF inflation film forming die in a 50 mm) extruder, which film was superior in strength and in transparency.

The film was subjected to the extraction with hexane at 500for4 hours to give 2.10% extract.

Comparative Example 1 Using the same catalyst as that used in Example 1 and hexane as solvent, a continuous slurry polymerization was conducted at 850C.

Hexane as polymerization solvent containing 5 mg/l of the solid catalyst and 1 mmol/l of triethylaluminium was fed at the rate of 401/her, and also fed were ethylene, 4-methylpentene-1 (20 mol% of ethylene) and hydrogen at the rates of 10 kg/hr, 6 kg/hr and 2Nm3/hr, respectively, and a continuous polymerization was made on condition that the residence time was 1 hour. The resulting copolymer was continuously withdrawn as slurry. In 3 hours, the polymer slurry withdrawing pipe was obturated and the polymerization was compelled to be discontinued.

The interior of the reactor was checked to find that the hexane layer was emulsified and a large amount of a rubbery polymer adhered to the gasliquid interface and also to the polymer withdrawing pipe.

The copolymer prepared above had a bulk density of 0.248, Ml of 0.74 and a density of 0.932.

Example 2 Polymerization was carried out in the same manner as in Example 1 except that the 4methylpentene-1/ethylene ratio was 0.14 and the hydrogen gas pressure was 1 5% of the total pressure.

The resulting ethylene copolymer had a MI of 2.3, a bulk density of 0.384 and a density of 0.896, and the polymerization activity was 147,000 g. copolymer/g.Ti.

After continuous operation for 10 hours, the interior of the reactor was checked to find no polymer adhesion to the inner wall and stirrer.

The copolymer after subjected to press forming was transparent, having a breaking point strength of 193 kg/cm2 and an elongation of 630%.

Example 3 Polymerization was carried out in the same manner as in Example 1 except that hexene-1 was used in place of 4-methyl-pentene-1.

The resulting ethylene copolymer had a bulk density of 0.399, Ml of 1.3 and a density of 0.933, and the polymerization activity was 186,500 g . copolymer/g Ti.

After continuous operation for 10 hours, the polymerization was discontinued and the reactor inside was checked to find no polymer adhesion.

The resulting polymer was formed into an inflation film 30 y thick, which film was superior in strength and in transparency. The hexane extract of the film was 0.17%.

Example 4 830 g. of anhydrous magnesium chloride, 50 g. of aluminium oxychloride and 170 g. of titanium tetrachloride were subjected to ball milling for 16 hours at room temperature in a nitrogen atmosphere. The resulting solid substance contained 41 mg. of titanium per gram thereof.

The solid substance prepared above and triethylaluminium were fed at the rates of 200 mg/hr and 50 mmol/hr, respectively, and a polymerization was made at 850C in the same way as in Example 1, with the proviso that the comonomer to be copolymerized was hexene-1, the hexene-1/ethylene ratio in the vapor phase was 0.07 and the hydrogen gas pressure was 1 6% of the total pressure.

After continuous operation for 10 hours, the interior of the autoclave was checked to find no polymer adhesion.

The resulting copolymer had a bulk density of 0.408, Ml of 1.1 and a density of 0.915, and the polymerization activity was very high, 194,500 g. ethylene-copolymer/g . Ti.

The copolymer was formed into a film 400 mm in fold diameter by 30 > thick in the same manner as in Example 1, which film was superior in both strength and transparency. The hexane extract of the film was 0.36%.

Comparative Example 2 Using the same catalyst as that used in Example 2 and n-paraffin as solvent, a solution polymerization was carried out. That is, n-paraffin containing 25 mg/l of the solid substance prepared in Example 2 and 5 mmol/l of triethylaluminium was fed at the rate of 401/her, and also fed were ethylene, hexene-1 and hydrogen at the rates of 10 kg/hr, 6 kg/hr and 550N l/hr, respectively, and a continuous polymerization was made at 1 600C on condition that the residence time was 1 hour. The resulting ethylene copolymer had a Ml of 0.34 and a density of 0.947, and the polymerization activity was 7,800 g . copolymer/g . Ti.

Thus in the case of a solution polymerization, despite of a large amount of hexene-1 used, the polymer density is not lowered so much and the polymerization activity is low, it being apparent that this is an example of inefficient polymerization.

Example 5 Copolymerization was carried out in the same manner as in Example 4 except that the hexene 1/ethylene ratio was 0.28 and the hydrogen gas pressure was 10% of the total pressure.

The resulting ethylene copolymer had a Ml of 1.9, a bulk density of 0.379 and a density of 0.870, and the polymerization activity was 171,000 g. copolymer/g . Ti.

In 10 hours, the supply of the starting gases was stopped to terminate the polymerization reaction and the reactor inside was checked to find no polymer adhesion therein.

The resulting ethylene-hexene-1 copolymer was subjected to press forming and the formed article was high in transparency, having a breaking point strength of 180 kg/cm2 and an elongation of 650%.

Example 6 A continuous polymerization was carried out in the same manner as in Example 4 except that an equimixture of hexene-1, octene-1 and decene-1 (trade name "dialen 610") was used as comonomer in place of hexene-1.

The resulting ethylene copolymer had a bulk density of 0.395, Ml of 1.2 and a density of 0.918, and the polymerization activity was 190,300 9. copolymer/g . Ti.

The copolymer was formed into an inflation film 30 y thick in the same way as in Example 1, which film was superior in both strength and stiffness and was high in transparency. The hexane extract of the film was 0.73%.

Example 7 830 g. of anhydrous magnesium chloride, 120 g. of anthracene and 170 g. of titanium tetrachloride were subjected to ball milling in the same manner as in Example 1 to give a solid substance, which contained 40 mg. of titanium per gram thereof.

Using the same apparatus as that used in Example 1 and at 800C there were fed the solid substance obtained above and triisobutylaluminium at the rates of 500 mg/hr and 150 mmol/hr, respectively, and also fed were Dialen 610 (trade name, an equimixture of hexene-1, octene-1 and decene-1) as comonomer, ethylene and hydrogen while making adjustment so that the comonomer/ethylene ratio in the vapor phase was 0.14 and the hydrogen gass pressure was 1 5% of the total pressure.

The polymerization was continued stably for 10 hours, then the autoclave was opened and the reactor inside was checked to find no polymer adhesion therein.

The polymerization activity was 143,000 g . copolymer/g . Ti, and the resulting polymer had a bulk density of 0.394, Ml of 2.6 and a density 0.909.

The polymer was formed into an inflation film, which film was superior in both stiffness and transparency. The hexane extract of the film was 2.6%.

Example 8 Polymerization was carried out in the same manner as in Example 7 with the proviso that the polymerization temperature, the Dialen 610/ethylene ratio and the hydrogen gas pressure were adjusted to 850C, 0.07 and 30% of the total pressure, respectively.

After continuous operation for 10 hours, the polymerization was discontinued and the interior of the autoclave was checked to find it being clean with no polymer adhesion therein.

The resulting copolymer had a bulk density of 0.395, Ml of 6.4 and a density of 0.917, and the polymerization activity was 128,000 g.

copolymer/g. Ti.

Example 9 Using the same catalyst as that used in Example 7 there was conducted polymerization in the same manner as in Example 7 with the proviso that dodecene was used in place of Dialen 610 and the dodecene/ethylene ratio and the hydrogen gas pressure were adjusted to 0.25 and 10% of the total pressure, respectively.

The polymerization was continued for 10 hours without any trouble. After termination of the reaction, the interior of the autoclave was checked to find no polymer adhesion therein.

The resulting copolymer had a bulk density of 0.389, MI of 1.9 and a density of 0.881, and the polymerization activity was 110,300 g. copolymer/g . Ti.

The copolymer after subjected to press forming was transparent and had a breaking point strength of 185 kg/cm2, an elongation of 700%.

Example 10 400 g. of magnesium oxide and 1,300 g. of anhydrous aluminium chloride were reacted together at 3000C for 4 hours, and 950 g. of the reaction product and 1 70 g. of titanium tetrachloride were treated in the same way as in Example 1 to give a solid substance, which contained 39 mg. of titanium per gram thereof.

Using the same apparatus as that used in Example 1 there were fed as catalyst the solid substance prepared above and triisobutylaluminium at the rates of 500 mg/hr and 250 mmol/hr, respectively, and a polymerization was made at 850C while there were circulated a mixed gas consisting of ethylene and 12% thereof in the vapor phase of 4methylpentene-1 and hydrogen gas adjusted to 9% of the total pressure.

After continuous operation for 1 8 hours, the reactor inside was checked to find no polymer adhesion therein.

The resulting copolymer had a bulk density of 0.443, Ml of 0.68 and a density of 0.918, it was composed of oval particles of a narrow particle size distribution with an average particle diameter of 500 u. The polymerization activity was 179,000 g . copolymer/g . Ti.

The copolymer, without pelletizing, was formed into a hollow 600 cc bottle by means of a high-speed blow molding machine, which bottle had a clean surface with no drawn-down observed.

Example 11 Polymerization was carried out in the same manner as in Example 10 with the limitation that the proportion of 4-methylpentene-1 to ethylene was 5.5% and the hydrogen gas pressure was 30% of the total pressure.

In 10 hours, the polymerization was discontinued and the interior of the polymerization vessel was checked to find no polymer adhesion therein.

The resulting copolymer had a bulk density of 0.375, Mi of 4.3 and a density of 0.930, and the polymerization activity was 181,000 9. copolymer/g . Ti.

Claims (20)

Claims

1. A process for preparing an ethylene-a-olefin copolymer having a density of 0.850 to 0.945, characterized in that ethylene and 1 to 40 mol% thereof of a-olefin having 5 to 1 8 carbon atoms are copolymerized in a substantially solvent-free vapor phase condition and the the presence of a catalyst comprising a solid substance and an organoaluminium compound, said solid substance containing magnesium and titanium and/or vanadium.

2. A process according to claim 1, in which said solid substance is obtained by attaching a titanium compound and/or a vanadium compound to a magnesium-containing inorganic solid carrier.

3. A process according to claim 2, in which said magnesium-containing inorganic solid carrier is selected from metallic magnesium, magnesium hydroxide, magnesium carbonate, magnesium oxide and magnesium chloride.

4. A process according to claim 2, in which said magnesium-containing inorganic solid carrier is selected from double salt, double oxide, carbonate, chloride and hydroxide containing magnesium atom and a metal selected from silicon, aluminium and calcium.

5. A process according to claim 2, 3 or 4 in which said magnesium-containing inorganic solid carrier is further treated or reacted with an oxygen-containing compound, a sulfur-containing compound, a hydrocarbon or halogen-containing substance.

6. A process according to any one of claims 2 to 5 in which said magnesium-containing inorganic solid carrier is contacted with an organocarboxylic acid ester before its use in the preparation of said solid substance.

7. A process according to claim 1, in which said solid substance is a reaction product of an organomagnesium compound and a titanium compound and/or a vanadium compound.

8. A process according to claim 7, in which said organo-magnesium compound is a compound represented by the general formula RMgX, R2Mg or RMg(OR) wherein R is an organic radical and X is halogen.

9. A process according to any one of claims 2 to 8 in which said titanium compound and/or vanadium compound is a halide, alkoxyhalide, oxide or halogenated oxide of titanium and/or vanadium.

10. A process according to any one of claims 2 to 9 in which said titanium compound and/or vanadium compound is used as the addition product with an organocarboxylic acid ester in the preparation of said solid substance.

11. A process according to any one of claims 1 to 10 in which said organoaluminium compound is used as the addition product with an organocarboxylic acid ester.

12. A process according to any one of claims 1 to 11 in which the catalyst system is prepared in the presence of an organo-carboxylic acid ester.

13. A process according to any one of claims 1 to 12 in which said copolymerization is carried out at a temperature in the range of from 200 to 11 O0C and at a pressure in the range from atmospheric to 70 kg/cm2 G.

14. A process according to any one of claims 1 to 13 in which said copolymerization is carried out in the presence of hydrogen.

1 5. A process according to any one of claims 1 to 14 in which the catalyst system is contacted beforehand with an a-olefin for 1 minute to 24 hours at a temperature in the range of from 0 to 2000C and at a pressure in the range of from -1 to 100 kg/cm2 G, and thereafter the copolymerization is carried out.

1 6. A process according to any one of claims 1 to 1 5 in which said a-olefin to be copolymerized with ethylene is selected from pentene-1, hexene 1, 4-methylpentene-1, heptene-1, octene-1, nonene-1, decene-1, undecene-1, dodecene-1, tridecene-1 , tetradecene-1, pentadecene-1, hexadecene-1, heptacene-1, octadecene-1, and mixtures thereof.

17. A process a claimed in claim 1, substantially as hereinbefore described with particular reference to the Examples.

18. A process as claimed in claim 1, substantially as illustrated in any one of the Examples.

19 A copolymer of ethylene and an a-olefin, when prepared by the process claimed in any one of the preceding claims.

20. An article fabricated from the copolymer claimed in claim-19.