DE1024715B - Continuous process for the polymerization of ethylene alone or in a mixture with other olefins - Google Patents

Description

GERMAN

The invention relates to the controlled, continuous polymerization of ethylene to linear polymers of certain melt flow using a coordination catalyst system. To the invention gives novel and valuable polymers which have the particular desired melt flow, Contain titanium and for the most part or almost exclusively from long, unbranched polyethylene chains exist.

It is known that ethylene under very high pressures in the presence of catalysts which free radicals able to form, can be converted into solid polymers. These are solid ethylene polymers but no linear hydrocarbons, as one might expect from the chemistry of vinyl polymerization, but are subject to side reactions during their formation, through which branched-chain and unsaturated components be built into the chain structure. Recently it has been used as a new catalyst system for polymerization proposed an activated titanium complex of ethylene. This catalyst is called a coordination catalyst because it is believed that the reactive catalyst component coordinates with ethylene-unsaturated molecules and thereby the polymerization caused. The active catalyst system is obtained when titanium is of a valence state is reduced from 3 and higher to a value below 3. This is done by adding strong reducing agents, such as organometallic compounds or metal hydrides, to titanium tetrachloride or titanium trichloride and the like Ti (IV) or Ti (III) compounds. The density of the solid ethylene polymers obtained with these catalyst systems exceeds, at least to a certain extent, that of the known solid polyethylenes produced by radical chain polymerization with the exception of those polymers that are produced at pressures of more than 5000 atm. The ones with coordination catalysts Ethylene polymers produced are straight-chain hydrocarbons in which one or at both ends of at least some of the molecules have vinyl groups. There is very little methyl substitution in the ultrared recognizable with little or no content of transunsaturated fractions or carbonyl groups. The polymers generally have an extremely high molecular weight and often only one little or no melt flow. Such polymers are hereinafter referred to as linear ethylene polymers designated. The polymers produced by the process according to the invention are homogeneous polymers, that contain small amounts of titanium.

The technical usefulness of ethylene polymers, e.g. B. for injection molding and melt extrusion, depends in large part on its melt flow. It is believed that the melt flow of the polymer of

Continuous process
for the polymerization of ethylene alone
or in a mixture with other olefins

Applicant:

EI du Pont de Nemours and Company,
Wilmington, Del. (V. St. A.)

Representative: Dr.-Ing. W. Abitz, patent attorney,
Munich 27, Gaußstr. 6th

Claimed priority:

V. St. v. America November 23, 1954 to January 27
and January 28, 1955

Arthur William Anderson, Wilmington, Del.,

John MacMillan Bruce Jr., Clavmont, DeL,

Ernest Lynwood Fallwell, Warren John Brehm,

Donald Lee Brebner, Wilmington, DeL,

and GeIu Stoeff Stamatoff, Newark, Del. (V. St. A.),

have been named as inventors

its molecular weight is determined that, for. B. less a polymer with a higher molecular weight easily flows as one with a lower molecular weight. A standardized measuring method for the Melt flow of polymers is the melt index test, which is detailed in the ASTM manual as Test ASTM-D-1238-52-T is described. This test is generally used to characterize the melt flow properties of ethylene polymers and is used accordingly here. Technical solid Polyethylenes generally have a melt index in the range of 0.2 to 3. It was therefore high Importance of finding methods with which to use highly reactive coordination catalysts the degree of polymerization can be regulated so that the melt flow of the resulting polymer in is the desired melt index range.

The purpose of the invention is to provide a continuous process for the polymerization of ethylene with a high rate of polymerization with the formation of solid, linear polymers of a predeterminable one Melt flow in the melt index range from 0.005 to 3, which after separation from the polymerization medium Titanium included.

709 880/442

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According to the invention, this is achieved by not simply adding controlled amounts to this case Ethylene in a liquid hydrocarbon in which limit end-grouping agents. However, at the ethylene and a catalyst are dissolved, resulting in the polymerization of ethylene in the presence of a dissolved linear polymer of ethylene polymerized, coordination catalyst the speed of the Abdas a predetermined melt flow in a melt fracture reaction, which is the molecular weight of the polymer index range from 0.005 to 3.0. The catalyst is determined to be much more dependent on temperature contains titanium of a valence state below 3. as the rate of the polymerization reaction. Here one works at a reaction temperature in the range of the speed from 150 to 230 ° under a sufficient ethylene speed of the termination reaction over that of the polymer pressure, increased by considerable amounts of ethylene in solution to io sationsreaktion addition, so that hereby the keep. By regulating the reaction temperature, the average chain length of the polymer is shortened, Half of this range is kept at high polymerization. So you can determine the molecular weight with the help of the temperature rate regulate the melt flow of the resulting poly- perature.

merisates in a melt index range from 0.005 to 3. The active titanium of the coordination catalyst is

It has been found that continuous polymers are most easily formed from a trivalent or tetravalent titanium ion in the presence of a coordination catalyst, such as titanium tetrachloride or tetrapropyl Adjustment of the reaction temperature so directed titanate, obtained by treating the same with a metal can that under certain process organic reducing agents, such as Grignard reagent, or conditions while maintaining a high poly- a metal alkyl converts, suitable compounds are merization rate titanium-containing polymers of 20 z. B. phenyl magnesium bromide, lithium butyl, lithium aleinem given degree of polymerization. To this ammonium tetradecyl, tin tetrabutyl and the like Purpose one works at temperatures above the active titanium can in an earlier process stage or The crystalline melting point of the polymer is formed under pressure in the presence of the ethylene to be polymerized at which there are considerable amounts of ethylene in the poly. It was found that the reduction was in solution Dissolve merisate catalyst phase. In addition, the 25 runs fast enough that the regulation of the polymer is necessary Ethylene solubility is not impaired by a suitable choice of the degree of sation. The highest catalytic Solvent and pressure reached. To the extent that the activity of the coordination catalyst is achieved, Ethylene in the solvent is consumed dissolves when equivalent amounts of the reducing agent and the used in the polymerization phase due to the ethylene over titanium compound; such a printing further ethylene; this dissolving process is therefore preferred. However, it is also possible Stirring made easier. As a liquid medium to solve the with not exactly equivalent amounts of catalyst to Monomers and the polymer are used in inert coal works and the polymerization process by means of the Hydrogen, which direct the activity of the catalyst temperature. Of course, changes with change Do not disturb the system. the catalyst activity also the degree of polymerization

It has already been proposed to use high molecular weight linear 35 and thus the molecular weight range of the polymer with the help of coordination catalyst, which you get when working in a temperature system Reached in a wide range of working conditions ranging from 150 to 230 °. The procedure for to manufacture. So you can polymers that have a low control of the molecular weight of linear Ethylenpolyoder have no melt flow, with the most diverse merizates, which the melt flow of the polymer Conditions received, e.g. B. determined at room temperature and 40, is therefore only suitable in a specific Atmospheric pressure and also at higher temperatures range of catalyst ratios. Under »Cataly- and high pressures. Here, the coordination ratio «becomes the equicatalyst in this description can be used in dissolved form or as a finely divided solid valent ratio of titanium compound to reducing substance. However, it has hitherto been understood as medium, i.e. H. the ratio of the product no method has been developed with which one can obtain continuity of titanium and number of moles of titanium compound ierlich polymers of constant melt flow with the product of the number of metal-carbon bin reproducible Establish polymerization rates and the number of moles of reducing agent. It was could ask. The process according to the invention found that high polymerization rates creates this possibility by regulating the polymer can be obtained when this catalyst ratio im degree of sation. The radical 50 was known to range from 0.4 to 1.4. Outside of this range chain polymerization a temperature decrease because the rate of polymerization of ethylene falls Reduces melt flow in a very irregular manner. rapidly from and under the conditions of this procedure At the same time, however, the lowering of the temperature allows only limited regulation of the polymerization the rate of polymerization falls sharply or leads to polymers with undesired set. A method of controlling the polymerisation 55 melt flow properties. So can with a Katalygrad without influencing the polymerization rate ratio of 0.4, the melt flow of the polymer speed was not previously known. When working with it can be increased from 0.005 to 1.5 when using the reaction coordination catalysts The catalyst temperature needs to be increased from 150 to 230 °, and with a self not necessarily a mutual dependency catalyst ratio of 1.4 the melt flow of the poly of polymerization rate and Polymeri- 60 merisates can be increased from 0.008 to 3, if the to effect the degree of sation. The invention works in a reaction temperature increased from 150 to 230 °. The before area, where there is no such dependency. added catalyst ratio is 0.96; at this value In the case of polymerization with coordination catalysts, the melt flow of the polymer produced increases by In striking contrast to the radical chain poly- 0.006 to 2.5, if the reaction temperature is 150 merization does not increase the growth of the polymer molecules 65 to 230 °. The melt index is a logarithmic through a relatively fast overmixing function of the reciprocal of the absolute enamel transfer reaction with the monomer or with the final temperature and can be grouped on the basis of the following forming organic compounds, such as cyclobenes, experimentally determined values for each hexane and the aliphatic hydrocarbons, ratio determined in the range given above completed. Therefore, the degree of polymerization can become 70.

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The amount of catalyst to be added depends on the influence. Oxygen in amounts of 2 to 200 parts depending on the concentration of ethylene in the carbon - per million changes the activity of the catalyst system hydrogen in the reaction zone, the desired poly - in the course of the reaction and thereby causes the degree of polymerization and the residence time of the reaction Formation of a polymer of different polymer mixtures in the reaction zone. When determining the degree of addition 5, z. B. a polymer with a settling amount of catalyst is believed to have a wide spread of the molecular weight. With a 1 mole of catalyst, 1 mole of polymer is produced. For the specific oxygen concentration, the melt index is the reasons given below, the conversion of dissolved of the reaction product in the initial stages of the poly-ethylene to dissolved polymer should be about 50% of the total merization and falls as the reaction proceeds, the amount of dissolved ethylene. As the polymer gradually decreases. When the amount of oxygen is increased to over 200 parts per million, which is only partially soluble in hydrocarbon solvents, the overall rate drops, and polymerisation is preferably carried out to a proportionate polymerisation. Small amounts of water-diluted solution of the polymer in the substance do not affect the polymerization, but in the case of hydrocarbons. A separation of the polymerizate in a content of about 1 ° / ₀ of the weight of the monomers rich phase decreases during Polymerisationskreislaufes 15 the degree of polymerization of the resulting polymer, must be avoided at all costs. So you can in the method according to the invention against

To determine the molecular weight and therefore the melt flow, if necessary, use hydrogen as an additional means of regulating the molecular weight of the polymer by choosing the reaction temperature. Since one can regulate, both the monomer and, however, according to the invention, the polymerization anyway, have to be dissolved in the polymer. Since ethylene polymers perform in a regulated manner and so the most varied of hydrocarbon solvents can only produce polymers in solid form, it is advisable to carry out little, but in molten form not sufficiently soluble and no additional ones that affect the molecular weight, the reaction temperature must be above the poly variable, such as hydrogen and oxygen, a.
merisate melting point. The temperature must be used as reaction media for the continuous

be at least 150 °, in order to ensure complete melting of ethylene, of course, of the resulting polymer and hydrocarbons, such as benzene, cyclohexane, n-hexane, to avoid its precipitation from the reaction phase. Butane, pentane, heptanes and the like are used.
At such a temperature the lower limit is. The method according to the invention is not suitable

of the melt flow, which is obtained with the lowest catalyst only for the production of linear ethylene homopolymers, ratio of 0.4, 0.005, determined by means of 30 but also for the production of copolymers, the melt index test. If the temperature of the as of ethylene with propylene, butene-1, butadiene or reaction zone and the catalyst ratio increases other olefins. For this purpose it is only necessary that the melt flow of the resulting poly also increase, that the monomer and the resulting ethylene. At 230 ° at a catalyst ratio, polymer in which the hydrocarbon is soluble will be.
of 1.4, a melt index of 3 is obtained, which is to be seen precisely as a low-viscosity melt for production of linear ethylene polymers. A lowering of the temperature to below 150 ° certain melt flow and the continuous flow can cause partial precipitation of the polymer in the process, which must be avoided if the polymerization method of the catalyst can be effectively kept under control target. 40 sets, which reduces costs and

The process according to the invention is reduced to a minimum with residues in the polymer moderate ethylene pressures. The pressure in the be. The polymer is obtained in dissolved form, Wes reaction zone must be high enough so that its removal from the reaction vessel is not so Evaporation of all of the ethylene from the polymeriza- difficult, expensive and time-consuming as with many others tion medium prevented and that is in the reaction medium 45 process for the polymerization of ethylene. The polymerized Ethylene is replaced. In addition, the dissolved polymer can be precipitated in pure form, Pressure high enough above the vapor pressure of the solution, eliminating the need for expensive washing processes. The means of production lie at the polymerization temperature to the nisse also have better properties, for. B. a ver reaction medium in the liquid phase, which improved stiffness.

Pressures above 150 at are suitable. If one works like this, 50 The concentration of ethylene in the medium before precipitated linear, titanium-containing ethylene polymers suitable for polymerization is twice as great as after passage for numerous purposes, especially in passage through the reaction zone, that is, from the solution obtained according to the invention 50 ° / ₀ igem forming of films, formed and extruded production set of the originally dissolved ethylene, so there are enough nits such as pipes, wire insulation, threads, impermeable ethylene available to increase the polymerisation rate permissible coatings of paper, etc.
of the amount of dissolved ethylene. The examples serve to further explain the

close. More ethylene is available due to the driving according to the invention, but without it being exhaustive ethylene pressure in the reaction phase. to be marked.
Higher degree of conversion of ethylene to polymer

are possible, provided that only the polymerization rate is 60 Example 1

as such, regardless of the amount of the dissolved

Ethylene is. The used in the method according to the invention

The polymerization of ethylene by the process of separate apparatus is known in the art of the most satisfactory natural polymerizations according to the invention and is therefore only for a better understanding of the experimental humidity and no other sources if the polymerization mixture is practically free of 65 briefly described for results. It can contain hydroxyl groups which are modified to inactivate the invention.
Catalyst can lead. Purified ethylene gas, from which water and

It has also been found that both hydrogen and carbon dioxide are removed, resulting in a heat exchange Oxygen passed the activity of the catalyst system 70 exchanger, which is charged with a coolant.

The ethylene is liquefied by a feed pump brought to the desired reaction pressure. The ethylene emerging from the pump is mixed with the Main stream of solvent mixed. The combined stream then goes to and from a preheater this into the heated reaction vessel equipped with a stirrer. The main stream of solvent is in front Addition of ethylene purified by pouring it through quiescent beds of silicon dioxide gel and lithium aluminum hydride passes and then combined with a solvent stream in which the titanium tetrachloride catalyst is resolved. The other reactant of the catalyst system is directly and separately as Solution is pumped into the reaction vessel.

The flow of reaction product is from the reaction vessel through a pressure reducing valve into a separator passed, in which the polymer precipitates from the solution and from the solvent and the not converted gaseous ethylene is separated. The ethylene is cleaned separately and in a cycle returned. Yield and melt index of the polymer in this continuously operated plant using cyclohexane as solvent, ίο titanium tetrachloride and lithium aluminum tetradecyl as Catalyst components is obtained are listed below. The table shows how the Melt index is influenced by the temperature within the catalyst ratio described above.

Attempt no.

Temperature, ⁰ C

Pressure, at

Weight ratio of cyclohexane to ethylene

Molar ratio of TiCl ₄ to 10 ^e moles of C ₂ H ₄

Catalyst ratio TiCl ₄ to LiAl (n C ₁₀ H ₂₁ ) ₄

Throughput (space velocity per minute)

Yield per unit of time and reaction space, melt index

182

200
7.6

430
0.966
0.111

184.19
0.04

191

200
7.66

430
0.977
0.110

206.61
0.08

198

200 5.90

262 1.11 0.119

60.54 0.16

222

200 7.92

511 0.920 0.122

70.47 1.05

Example 2

Following the procedure of Example 1, ethylene and butene-1 were copolymerized under the following working conditions and using aluminum triisobutyl _{as a reducing agent for the TiCl 4:}

Attempt No. 5! 6th

Temperature, ⁰ C

Pressure, at

Molar ratio

Cyclohexane to ethylene ..
Molar ratio

Butene-1 to ethylene

Molar ratio

( _{TiCl 4 to} ethylene) -10 ⁶ ...
Molar ratio of TiCl ₄ to AlR ₃ .
Yield per unit of time

and reaction space,

Melt index

density

° / ₀ butene in the copolymer

174 100

6.6 0.805

68 0.35

624

0.90 16.7

156 100

12.7 0.49

109 0.51

384

0.5 0.906 13.0

Example 3

Following the procedure of Example 1, ethylene and decene were copolymerized under the following working conditions and using aluminum triisobutyl _{as reducing agent for the TiCl 4:}

attempt 7th 170 No. 8th 201 135 Temperature, ° C 100 Pressure at 6.5 Molar ratio 11.7 Cyclohexane to ethylene .. 1.26 Molar ratio 0.65 Decene to ethylene 124 Molar ratio 96 0.71 (TiCl ₄ to ethylene) 10 ^e ... 0.32 Molar ratio of TiCl ₄ to AlR ₃ . 944 Yield per unit of time 432 4.8 0.7 0.926 h ■ m ¹ 0.926 4.8 Melt index 4.8 density ° / ₀ decene in the copolymer

Claims (6)

Patent claims: 1. Continuous process for the polymerization of ethylene alone or in a mixture with others Olefins to solid polymers with a melt index in the range from 0.005 to 3, characterized in that that a solution of ethylene in a non-polymerizable hydrocarbon is continuously Introduced into a reaction zone and the ethylene polymerized in the presence of a catalyst from such amounts of a titanium compound and an organometallic reducing agent is that the Equivalent ratio of titanium compound to reducing agent, d. H. the ratio of the product Valence of titanium and number of moles of titanium compound to the product of meta-carbon bonds and the number of moles of the reducing agent is 0.4 to 1.4, the reaction temperature being set to ISO to 230 ° and keeps the pressure at such a level that the reaction medium remains liquid and the ethylene remains dissolved, and polymerizes only to such a conversion that the polymer is removed from the reaction zone in dissolved form can be withdrawn continuously. 2. The method according spoke 1, characterized in that the solvent used is cyclohexane. 3. The method according to claim 1, characterized in that there is titanium tetrachloride as the titanium compound used. 4. The method according to claim 1, characterized in that one is used as the organometallic reducing agent Lithium aluminum tetraalkyl is used. 5. The method according to claim 1, characterized in that that the concentration of ethylene in the solvent measured at 10 to 20 percent by weight. 6. The method according to claim 1 and 2, characterized in that one is ethylene in the presence of Polymerized catalyst obtained by mixing titanium tetrachloride with a lithium aluminum tetraalkyl, particularly lithium aluminum tetradecyl, in a molar ratio in the range from 0.4: 1 to 1.4: 1 is formed in a non-polymerizable hydrocarbon, the temperature being at a Mole ratio of 0.4: 1 holds at 150 ° if a melt index of 0.005 is desired, and up to 230 ° increased if a melt index of 1.5 is desired, while changing the aforementioned Molar ratio to 1.4: 1 keeps the reaction temperature at 150 ° if a melt index of 0.008 is desirable, and to 230 ° if a melt index of 3 is desired, whereupon the polyethylene separated from the desired melt index from the reaction mixture. ■ © 709 880/442 2.58