DE1155600B - Process for the production of ethylene polymers or copolymers - Google Patents

Description

GERMAN

PATENT OFFICE

116415 IVd / 39c

REGISTRATION DATE: MAY 12, 1959

NOTICE THE REGISTRATION AND ISSUE OF EDITORIAL: OCTOBER 10, 1963

It is already known that peroxy compounds are an important class of free radical generating Represent catalysts for the polymerization of ethylene under high pressures and at elevated pressures Temperatures with the production of solid polymers are useful. To these known peroxide compounds include certain tertiary alkyl percarboxylates, such as B. tert-butyl perbenzoate and the tert-butyl esters of pertoluic, perphthalic and peracetic acid.

In the application of these peroxy compounds require temperatures which are at the upper end of the normal range for the polymerization, for example, above 160 ⁰ C in a continuous process, and above about 110 ⁰ C at ansatzweisem work so fast enough free radicals are released to appropriate polymerization to obtain.

The high-pressure polymerization of ethylene at temperatures of 200 ⁰ C and above results in polyethylenes, so to speak, have a normal density. If one causes polymerisation at significantly lower temperatures, for example below 160 or below 100 ⁰ C at ansatzweisem work, polyethylenes can be obtained with higher densities and higher mechanical strength, which are particularly valuable for certain applications. According to the invention, peroxide catalysts are used which enable the high pressure polymerization including the copolymerization of ethylene at such low temperatures with reasonable polymerization rates.

The invention relates to a process for the preparation of Äthylenpolymerisaten or -mischpolymerisaten by polymerization of ethylene alone or together with other copolymerizable monomers at a pressure of at about 500 and a temperature from 40 to 160 ⁰ C in a continuous process, or between 40 and 100 ° C in the case of batchwise conversion in the presence of a peroxide catalyst and optionally in the presence of an inert reaction medium, a chain transfer agent or an antioxidant, characterized in that the peroxide catalyst used is an ester of mono- or diperoxyoxalic acid of the general formula

XCOCOOOR

uses, in which R is a hydrocarbon radical which, apart from aromatic systems, is saturated and connected to the oxygen atom through a tertiary carbon atom, and X — OOR or -OY Process for the production of

Ethylene polymers
or copolymers

Applicant:

Imperial Chemical Industries Limited,
London

Representative: Dr.-Ing. H. Fincke, Dipl.-Ing. H. Bohr and Dipl.-Ing. S. Staeger,

Patent attorneys,
Munich 5, Müllerstr. 31

Claimed priority:
Great Britain May 14, 1958 (No. 15 443)

Andrzej Pajaczkowski, Northwich, Cheshire

(Great Britain),
has been named as the inventor

denotes, where Y is, apart from aromatic systems, a saturated hydrocarbon radical.

The radical R can, for example, be a tertiary alkyl or a 1-alkylcycloalkyl radical or a through Be aryl or cycloalkyl-substituted alkyl or polycyclic hydrocarbon radical, where each of these radicals is attached to the oxygen atom through a tertiary carbon atom. The rest of Y can e.g. B. an alkyl radical with preferably no more than 12 carbon atoms or an aryl-aralkyl or cycloalkyl radical which may have hydrocarbon substituents.

According to one embodiment of the invention, di-tert-alkyl peroxyoxalates, e.g. B. Di-tert-butyl peroxyoxalate

(CHg) ₃ C • OO • CO • CO • OO • C (CH ₃ > 3

applied, which initiate the polymerization at 40 to 8O ⁰ C with a batch reaction on a small scale. Alkyl tertiary alkyl peroxyoxalates, e.g. B. ethyl tert-butyl peroxyoxalate

C2H5O · CO · CO · OO · C (CHs) ₃

are also very suitable catalysts. The tert-butyl peroxy compounds generally have

309 727/325

believe that they are the most readily available catalysts because tert-butyl hydroperoxide, from which they can be made, is readily available commercially. Other catalysts which can be obtained smoothly and used according to the invention are e.g. B. n-butyl tert-butyl peroxyoxalate, cyclohexyl tert-butyl peroxyoxalate, 2-ethylhexyl tert-butyl peroxyoxalate, 3,5,5-trimethylhexyl - tert. - butyl peroxyoxalate, ethyl - a, a - dimethylbenzyl peroxyoxalate, di - tert. - amyl peroxyoxalate

(C ₂ H ₅ C (CH3> 20OCOCOOO (CH3) 2CC2H5), bis (a, a-dimethylbenzylperoxy) oxylate
(C ₆ H ₅ C (CHa) ₂ OOCOCOOO (CHa) ₂ CC ₆ H ₅ )

Di-p-menthyl peroxyoxalate (Z ■ CO · CO · Z), where Z is a mixture of

OO—

00 - and

-00-

Me Me Me Me Me Me

is (the rings are saturated), di-l-phenylcyclohexyl peroxyoxalate

CH ₂ -CH ₂ C ₆ H ₅ H ₅ C ₆ CH ₂ -CH ₂

CH ₂ CC CH ₂

CH ₂ - CH ₂ OO • CO • CO • OO CH ₂ - CH ₂

Bis (p-isopropyl-a, a-dimethylbenzyl peroxy) oxalate

(H (CHa) ₂ C • C ₆ H ₄ • C (CHa) ₂ • OO • CO • CO • OO • C (CHa) ₂ • QH ₄ • C (CHa) ₂ ) and the peroxalates obtained by reacting Decahydronaphthalene hydroperoxide

0OH

the rings are saturated

can be obtained with the dichloride of oxalic acid or the chloride of the monoester of oxalic acid.

The temperature at which the ethylene polymerization is carried out is in continuous operation, between 40 and 16O ⁰ C, with the preferred pressure is up to 2000 at 1000 in order to achieve as economic reaction rates. In batch polymerization, the temperature is between 40 and 10O ⁰ C. For the particular catalyst selected, the temperature at which the greatest effectiveness is obtained depends on the other reaction conditions and also on whether the process is carried out batchwise or continuously, with the most favorable temperature for a continuous process within the stated ranges is higher than for a batch process when the other conditions are similar. The polymerization can be carried out in the presence of a chain transfer agent, e.g. B. of hydrogen, a saturated hydrocarbon, e.g. B. ethane, propane or cyclohexane, or a chlorinated hydrocarbon, e.g. B. carbon tetrachloride. An inert reaction medium, such as benzene or petroleum ether, can also be present, or the polymerization can be carried out with the exclusion of any liquid which does not take part in the reaction. Antioxidants can also be introduced into the reaction space. The choice of temperature, pressure, reactants and reaction medium in the

♦ The scope of the protection request is determined by the melt index and the density of the product should have.

British patent 677,641 describes the polymerization of ethylene at low temperatures with peroxydicarboxylic acid esters as catalysts. Opposite these, they point to the procedure The catalysts used in the invention have a number of advantages. So they are less toxic, are generally more effective catalysts for polymerization and can in many cases are more easily introduced into a continuous reaction system because of their better solubility in hydrocarbons. In addition, deliver the simplest and preferred compounds which are used according to the invention, namely the tert-butyl compounds (di-tert-butyl peroxyoxalate and alkyl tert-butyl peroxyoxalates), lighter free Radicals as di-tert-butyl peroxydicarbonate, and the latter has the further disadvantage that it consists of a thermally very unstable precursor, the tert-butyl chloroformate is produced.

Copolymers of ethylene and other copolymerizable monomers, such as vinyl

esters, methyl methacrylate and propylene, can also be made using the catalysts mentioned getting produced.

The invention is explained in more detail in the following examples.

Example 1 describes the preparation of di-tert-butyl peroxyoxalate; yet will for this Manufacturing method of the catalyst does not require protection.

example 1

0.9 g of pure dry tert-butyl hydroperoxide were added dropwise with 5.08 g of oxalyl chloride. The reaction mixture was kept at -15 ° C by stirring and external cooling. After two thirds of the chloride had been added, a solid began to form, whereupon 50 ecm of dry ether was added. After all of the chloride had been added, stirring was continued for 15 minutes. The ethereal solution was washed with aqueous sodium bicarbonate and water and dried over sodium sulfate. The solid was recrystallized at -75 ⁰ C, filtered and redissolved in fresh, dry ether. After evaporation of the solvent, 51 remained as crystalline residue di-tert-butyl peroxyoxalate, mp. 51.5 to ⁰ C under the direct decomposition, which explodes in contact with a flame, or by subjecting it to one beat.

Analysis: Ci ₀ Hi ₈ O ₆ : Calculated ... C 51.3, H 7.7%;
found ... C 51.2, H 7.7%.

Infrared absorption characteristic of the carbonyl group at 1812 (s) and 1779 (s) cm> (in ether).

0.25 ecm of a solution which contained 5.0 g of the di-tert-butyl peroxyoxalate in 100 ecm of ethyl ether each was placed in a high-pressure reaction vessel made of stainless steel, cooled to 30.degree. The vessel was closed, flushed several times with ethylene containing less than 2 parts per million oxygen, and finally ethylene was injected up to 1000 atm. The temperature of the vessel was increased to 65 ^° C. When the pressure in the vessel began to drop, fresh ethylene was injected to bring the pressure back up to 1000 atm. After 57 minutes the total pressure drop was 100 at; the ethylene was drained and the jar cooled and opened. It contained 5.6 g of white polymer.

For comparison purposes, 0.25 ecm of a solution containing 5.0 g of tert-butyl peracetate per 100 ecm Gasoline contained, applied in place of the di-tert-butyl peroxyoxalate solution. There was a temperature of HOC and a pressure of 1400 at required-Hch, to achieve a polymerization rate similar to that obtained with di-tert-butyl peroxyoxalate was comparable.

Example 2

0.25 ecm of a solution containing 5.0 g of ethyl tert-butyl peroxyoxalate contained in 100 ecm gasoline, were used for the polymerization of ethylene according to the im Example 1 described manner applied. The pressure was 1000 at and the temperature 7OC. The total pressure drop after 57 minutes was 100 atm. 6.4 g of white polymer were obtained generated.

Example 3

0.25 ecm of a solution which contained 5.0 g of 3,5,5-trimethylhexyl-tert-butylperoxyoxalate per 100 ecm of gasoline was used for the polymerization of ethylene in accordance with the method of Example 1. The temperature was 7O ⁰ C and the pressure at. The total pressure drop amounted to 100 minutes at. There were produced 6.0 g of white polymer.

Example 4

0.25 ecm of a solution which contained 4.4 g of n-butyl tert-butyl peroxyoxalate per 100 ecm of gasoline was used in accordance with the procedure of Example 1 for the polymerization of ethylene. The pressure was 1400 at the temperature 6O ⁰ C. The total pressure drop amounted to 100 at 36 minutes. There was obtained 5.7 g of a white polymer.

Claims (3)

PATENT CLAIMS: 1. A process for the preparation of Äthylenpolymerisaten or -mischpolymerisaten by polymerization of ethylene alone or together with other copolymerizable monomers at a pressure of about 500 at and at a temperature from 40 to 160 ⁰ C in a continuous process, or between 40 and 100 ⁰ C at a batchwise reaction in the presence of a peroxide catalyst and optionally in the presence of an inert reaction medium of a chain transfer agent or an antioxidant. characterized in that the peroxide catalyst used is an ester of mono- or diperoxyoxalic acid of the general formula X-CO-CO-OO-R uses, in which R is a hydrocarbon radical that. apart from aromatic systems, saturated and with the oxygen atom via a tertiary Carbon atom, and X is --OOR or -OY, where Y is apart from aromatic systems, is a saturated hydrocarbon radical. 2. The method according to claim 1, characterized in that at a pressure of 1000 polymerized until 2000 at. 3. The method according to claim 1 or 2, characterized in that one is used as the peroxide catalyst a di-tert-alkyl peroxyoxalate, especially di-tert-butyl peroxyoxalate, or a compound of the formula given in claim 1, in which Y is an alkyl radical having 1 to 12 carbon atoms, especially ethyl tert-butyl peroxyoxalate. 3,5,5-trimethylhexyl-tert-butyl peroxyoxalate or n-butyl-tert-butyl peroxyoxalate. References considered: British Patent No. 677,641. © 309 727/325 10.