2,886,560 United States Patent Office Patented May 12, 1959 2 example up to 200 atmospheres, preferably 1-100 at 2,886,560 mospheres. By this it is possible to influence the mo lecular weight and the space time yield. In general POLYMERIZATION OF ETHYLENE the process is carried out at temperatures of from about Heinz Weber, Ludwigshafen (Rhine), Hans Boehm, 0° to 150° C., preferably from 10° to 100° C., but it Speyer, Georg Schiller, Mannheim, and Karl Stange, 3) is also possible to work at lower or higher temperatures; Wesseling, Germany, assigEgors to Badische Anilin- & for example up to 200C. Soda-Fabrik Aktiengeselischaft, Ludwigshafen (Rhine), The ethylene which preferably is highly concentrated, Germany for example of 99.2 to 99.8 percent strength, can be No Drawing. Application November 28, 1955 purified with potassium vapor by freezing, by Washing Serial No. 549,504 O with organo-aluminum compounds or with zinc alkyls or also by passing the ethylene over the heated copper Claims priority, application Germany November 27, 1954 catalyst. It is of special advantage to dissolve or sus 3 Claims. C. 260-94.9) pend the catalyst in an anhydrous organic liquid and This invention relates to the production of high molec 5 then to feed in ethylene in a state of fine dispersion. ular weight polyethylene in the presence of catalysts. A suspension of polyethylene is obtained. When work It has already been proposed to polymerize ethylene ing at moderately increased pressure, the polymeriza with the aid of a mixed catalyst of aluminum chloride, tion can be conducted batchwise in autoclaves or con titanium tetrachloride and aluminum. By this process tinuously by pressing the ethylene into the lower part solid polymerization products are obtained. In the ab 20 of a reaction tube and withdrawing the resultant poly sence of titanium tetrachloride only oily products are mer suspension in a direction counter-current or co-cur formed. During the polymerization reaction of ethylene rent therewith. It is also possible to spray the catalyst in the presence of aluminum and aluminum chloride into the reaction vessel and to allow the reaction to halogen-containing aluminum alkyls are formed (Hall proceed throughout the whole volume of the reaction and Nash, J. Inst. Petrol. Techn. 24, 471/95 (1938)). 25 vessel. The polyethylene can be purified by washing We have now found, that the properties of high molec for example with water, organic liquids, as for exam ular weight and film forming polyethylene can easily be ple methanol, or solutions of acids in water or organic modified by polymerizing ethylene in the presence of a solvents, as for example hydrochloric acid in methanol, titanium halide in combination with a previously formed and thus stripped of catalyst components. Its strength halogen-containing aluminum alkyl. 30 properties are improved if it is carefully heated in Especially suitable titanium halides are titanium tri Waco, chloride, titanium tetrachloride, titanium oxychloride Ethyl aluminum chlorides have already been proposed and the corresponding bromides. Titanium trichloride is for polymerizing ethylene. These catalysts, however, advantageously prepared by reduction of titanium tetra only yield liquid polymers. It has also been proposed chloride with hydrogen. Among suitable aluminum com 35 to polymerize ethylene with halogen-free metal alkyls, pounds there may be mentioned in particular mixtures as for example aluminum triethyl. Depending on the of diethyl aluminum monochloride and monoethyl alu experimental conditions, there are thereby formed low minum dichloride, particularly their mixtures in equi molecular weight unitary olefines together with soft or molecular proportions, for example ethyl aluminum hard paraffin wax or film-forming polyethylene. In sesquichloride and the components of the same. Ethyl 40 the latter case it is necessary to use very high pressures, aluminum sesquichloride can be prepared according to up to about 2,000 atmospheres, but the polymerization Grosse and Mavity, J. Organ. Chem. 5, 106 (1940). in this case proceeds at a relatively slow rate. The catalysts can be prepared for example by the The following examples will further illustrate this slow addition of a solution of a titanium tetrahalide to a invention and how the same is to be carried out in prac solution of a halogen-containing aluminum alkyl, if 45 tice but the invention is not restricted to these exam necessary while cooling with ice and stirring. A sus ples. The parts are parts by weight. pension is obtained which can be introduced into the Example I reaction vessel with the exclusion of air. It is also possible to prepare the suspension in the reaction vessel. To 140 parts of octane 0.26 part of titanium tetra Suitable solvents for the titanium halides are for example 50 chloride and 0.45 part of ethyl aluminum sesquichloride aliphatic or saturated cyclic hydrocarbons, as for example (molar ratio Ti:Al=0.38) are added with the exclusion pentane, octane, cyclohexane or heavy gasoline. The of oxygen and moisture and the mixture is heated to halogen-containing aluminum alkyls can also be dis 50° C. for 30 minutes while nitrogen free of oxygen is solved in the said liquids which preferably are purified passed through. Then 12 parts of dry ethylene free of and dried. oxygen are fed in per hour with intense agitation, the A ratio of about 0.3 to 2.5 mols, preferably of 0.5 to reaction occurring immediately with a rapid rise in 0.8 mol of a titanium halide to 1 mol of the halogen temperature. By cooling a temperature of between 50° containing aluminum alkyl compound is most effective. and 55° C. is maintained. After some time the absorp To a great extent the molecular weight of the polyethyl tion which is quantitative at first falls off gradually. ene and the polymerization speed are dependent on the 60 The unreacted portion of the ethylene is recirculated molar ratio in which the components forming the cata with the feed of the fresh gas being cut down propor lyst have been brought together. By increasing the pro tionally. After about 6 hours the resultant polymer is portion of titanium halide in the mixed catalyst the separated, washed and dried, 42 parts of a white pulver molecular weight of the polyethylene is lowered, while ulent polyethylene having a melting point of 133.5° the polymerization speed is raised. The activity of the C. being obtained. At this temperature the crystalline catalyst can be increased by heating the mixture of a portions will vanish in the polarized light. The tensile titanium halide and the halogen-containing aluminum al Strength is 409 kilograms per square centimeter with kyl before adding the ethylene. reference to the initial cross section of the sample. The With such a catalyst ethylene can be polymerized 70 conventional viscosity in para-diisopropylbenzene at rapidly at normal pressure. It may be advantageous 150° C. is 0.340 according to G. V. Schulz (Makromole to polymerize at a moderately increased pressure, as for kulare Chemie 13 (1954), pages 71-74 (1./g)). 2,886,560 3 4. Example 2 Example 5 Using a catalyst of 0.28 part of titanium tetrachloride A catalyst consisting of 0.49 part of titanium tetra and 0.30 part of ethyl aluminum sesquichloride (molar chloride and 0.43 part of diethyl aluminum monochlo ratio of Ti:Al=0.6), ethylene is polymerized as de ride is prepared in the manner described in Example 3. scribed in Example 1. After 6 hours 42 parts of a white Then 12 parts of ethylene are fed in per hour, the un pulverulent polyethylene are obtained, the polyethylene converted gas being recirculated. After 6 hours 36 having a melting point of 130.5 C. and a tensile strength parts of polyethylene are obtained which has a melting of 401 kilograms per square centimeter. The conven point of 133° C. and a tensile strength of 350 kilo tional viscosity is 0.265 measured by the method of G. 0 grams per square centimeter. The conventional viscos V. Schulz. ity is 0.31 measured by the method of G. V. Schulz. Example 3 We claim: To 140 parts of octane 0.40 part of titanium tetra 1. A process for the polymerization of gaseous ethyl chloride and 0.37 part of ethyl aluminum sesquichlo ene in the presence of a polymerization catalyst which ride are added with the exclusion of oxygen and mois 5 comprises polymerizing the gaseous ethylene at a tem ture and the mixture is heated to 50° C. nitrogen free perature from 10-100° C. and a pressure of 1-100 at of oxygen being passed through. Then dry ethylene mospheres absolute in the presence of a catalytic amount which is free of oxygen is fed in with vigorous agitation of a mixed catalyst of ethyl aluminum sesquichloride at a rate of 12 parts per hour, the nitrogen current be and titanium tetrachloride having a ratio of about 0.5- ing cut down simultaneously. The reaction occurs im 20 0.8 mol of titanium tetrachloride per mol of ethyl alu mediately with a marked rise in the temperature of the minum sesquichloride. reaction mixture. By cooling a temperature of be 2. A process for the polymerization of gaseous ethyl tween 50° and 55° C. is maintained. After some time ene in the presence of a polymerization catalyst which the absorption of gas which was quantitative at the start comprises polymerizing the gaseous ethylene at a tem abates gradually. The escaping ethylene is recirculated, 25 perature from 10-100° C. and a pressure of 1-100 at the feed of the fresh gas being cut down proportionately.