DE1176869B - Process for the production of polyethylene - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: C 08 f

German KL: 39 c- 25/01

Number: 1176 869

File number: G 29409 IV d / 39 c

Filing date: April 7, 1960

Opening day: August 27, 1964

It is known to polymerize ethylene in the presence of catalysts which consist of mixtures of a heavy metal chloride and a metal hydride; however, chlorides and hydrides made from different metals have always been used in such processes. For example, according to the documents laid out in Belgian patent 551 056, mixtures of titanium tetrahalide and hydrides of metals of groups I and II of the Periodic Table or of thorium can serve as catalysts. A similar process is known from French patent specification 1,151,634, according to which halides of metals of the second and third main groups are additionally used as the third component, higher temperatures having to be used without this third component. Finally, from French patent specification 1,158,724 the use of lithium aluminum hydride together with the halides of titanium, zirconium or vanadium and from the laid-out documents of Belgian patent 567 208 the use of zirconium hydride alone as a catalyst is known. Thus, while in general ethylene polymerization catalysts of titanium tetrachloride are used with an alkali metal hydride and hydrides of metals of the II. Main Group of the Periodic Table or of aluminum, according to the invention now the use of titanium hydride of the composition TiH _{1, 75} proposed, together with titanium tetrachloride, ie That is, a chloride and a hydride of the same metal are used, which greatly facilitates the recovery or isolation of the catalyst residues and does not reduce the efficiency of the polymerization. It is to be regarded as surprising that the catalytic effectiveness of the new catalyst is not reduced if only a single metal is used for these two compounds. The aforementioned titanium hydride can be obtained by reducing titanium dioxide with calcium hydride.

The invention therefore relates to a process for the production of normally solid polyethylene by polymerizing ethylene at a temperature of 150 to 250 ⁰ C and an ethylene partial pressure of at least 3.5 kg / cm ² in a liquid inert solvent, in particular in a hydrocarbon, in presence of a group consisting of a metal hydride and titanium tetrachloride catalyst, wherein the weight ratio of metal hydride to titanium tetrachloride from 0.3: 1 and 3: 1, which is characterized in that one uses a catalyst as a metal hydride, titanium hydride of the composition TiH _{1, 75} contains.

Process for the production of polyethylene

Applicant:

W. R. Grace & Co., New York, N.Y. (V. St. A.)

Representative:

Dipl.-Cb.em. Dr. rer. nat. J. D. Frhr. v. Uexkull,

Patent attorney,

Hamburg-Hochkamp, Königgrätzstr. 8th

Named as inventor:
Frederick Benington, Columbus, Ohio,
Wendell Clarence Overhults, Silver Spring. Md.
(V. St. A.)

Claimed priority:

V. St. v. America April 20, 1959 (807 320)

In contrast to the previously held view that once zirconium hydride is unique and not through a hydride of another metal is replaceable and that on the other hand in one of a hydride and a chloride-based catalyst, two different metals should be used, titanium hydride of the composition mentioned is now used according to the invention with titanium tetrachloride. The advantage achieved in this way is - apart from the fact that zirconium hydride is a far less uniform Substance is - in that it is more advantageous from the technical point of view, only a metal in place of it of two metals in a composite catalyst to use. These advantages arise especially in the recovery of the catalyst residues, because there are no different metals must separate from each other and also in the purification of the polymer from the catalyst residues; Titanium dissolves in dilute, warm HCl, whereas zirconium is only slightly attacked.

Ethylene partial pressures of at least 7.03 kg / cm ² are desirable in order to start the reaction in the lower temperature ranges of the stated ranges. (All pressures given here relate to overpressure values.) The initial ethylene partial pressure is preferably 14.1 kg / cm ² or more. At higher temperatures, for example at least 200 ^° C., it is possible to carry out the polymerization at somewhat lower temperatures

■■■ · ■ · 409 658/505

Ethylene partial press to begin. For example, the ethylene partial pressure can be reduced by up to 3.5 kg / cm ^{2 at 225 ° C.} Although there is a minimum value in the relationship between the temperature and pressure values necessary at the start of the polymerization (ie, there is a lowest partial pressure of ethylene at which the polymerization can be initiated, which changes with temperature and vice versa), has been found as a general rule that once the polymerization has started. this can be continued within the ranges mentioned at lower temperatures and / or ethylene partial pressures.
Although the reaction occurs at relatively high levels, the weight ratio of titanium hydride to titanium tetrachloride is between 0.3: 1 and 3: 1, preferably between 2: 5 and 3: 5.

For best results, the titanium hydride catalyst component should be used under an inert atmosphere, e.g. B. argon or another noble gas or nitrogen, produced, stored and used for synthesis container used by polyethylene.

example

5.1 g titanium hydride (TiH, where jc = 1.75) and 5.5 ml of titanium tetrachloride (0.05 mol) were under

Ethylene partial pressures, for example at 352 to 703 kg / cm ² 15 nitrogen placed in a shaking autoclave, which can be carried out and higher, predominantly equipped with a gas supply and a gas outlet

and contained 50 ml of dry hexane. The autoclave was sealed and pressurized with practically pure ethylene until the pressure was about 14.1 kg / cm ² . The autoclave was then heated ^{to about 200 ° C. while shaking.} After the beginning of the ethylene absorption (which was noticeable by a pressure drop on the measuring device), the autoclave was pressurized again with ethylene to one

from 190 to 210 ⁰ C when using an ethylene pressure in the range of 35.2 to 70.4 kg / cm ² upright partial pressure of 21.1 to 35.2 kg / cm ² good results. (which corresponds to an ethylene partial pressure of 17.6 to Under these conditions, polyethylene has a 52.7 kg / cm ² ). The heating, shaking and melting point of 131 to 132 ° C, and repeated pressurization with ethylene, a melt index of 0.1 was achieved. Continued at higher temperatures for 13 hours, after which the shaking is stopped, the melting point of the 3 ° formed decreases, the autoclave is cooled and the pressure of ethylene decreases somewhat, and the melt index increases. was burdened. After opening the autoclave, a means was found to obtain product by changing the blackish or dark purple solid polyethylene action temperature. This was prepared by boiling in a number of polyethylenes, which have an isopropanol-HCl solution, by filtering and various physical properties. 35 drying cleaned. The dry, purified poly-other measures for changing the molecular ethylene weighed 22 g and had a softening point

but the additional costs of such pressure-resistant devices in general compared to the advantages which result from higher yields and / or shorter reaction times.

In the practice of reaction temperatures in the range 150-225 ⁰ C and Äthylenteildrücke in the range from 14.1 to 91.4 kg / cm ² are preferred. For example, there is a temperature range

weight and the crystallinity of the polymer are familiar to the person skilled in the art.

As the reaction medium, any inert solvent can be used, which among those used Temperature and pressure conditions is liquid and which has a solvent capacity for ethylene. Such solvents are known to those skilled in the polyethylene production. It will be inert, liquid hydrocarbons are preferred as solvents, these preferably being essentially do not contain any substances that react with the catalyst, such as water, carbon dioxide, Oxygen, acetylene, ammonia; as well as ethers, ketones and similar reactive organic compounds. Suitable solvents include pentane, hexane, heptane, cyclohexane, octane, benzene, Xylene and toluene.

The amount of the catalyst is not critical. Relatively small quantities can be

Form moderately large amounts of polyethylene. In general

mine the practical range is 0.2 to 2 g

Total catalyst (TiH ₁ , ₇₅ and TiCl ₄ ) per mole (28 g) Publications considered:

of polymerized ethylene. Larger documents of Belgian patents can also be used

Amounts of catalyst are used, but 60 No. 551 056, 567 208;

cleaning is made more difficult. French patents No. 1 151 634,1 158 724.

from 126 to 127 ° C and a melting point of 131 to 132 ⁰ C, which is characteristic of polyethylene with high density.

Claims (1)

Claim: Process for the production of normally solid polyethylene by polymerizing ethylene at a temperature of 150 to 250 ° C and an ethylene partial pressure of at least 3.5 kg / cm ² in a liquid inert solvent, in particular in a hydrocarbon, in the presence of one of a metal hydride and titanium tetrachloride existing catalyst, wherein the weight ratio of metal hydride to titanium tetrachloride from 0.3: 1 and 3: 1, characterized in that a catalyst is used, the metal as titanium hydride TiH the composition ₁ containing _{75 miles.} 409 658/505 8.64 © Bundesdruckerei Berlin