DE1495649B2 - PROCESS FOR SULFOCHLORINATION OF CHLORINATED LOW PRESSURE POLYAETHYLENE - Google Patents

Description

It is known to carry out the chlorination or sulfochlorination of polymers of ethylene which are produced by the high pressure process. These produced by the high pressure process Äthylenpolymerisaten there are products which dissolve at about 6O ⁰ C in many solvents. The chlorination or sulfochlorination of these substances has been carried out in solution or suspension with or without the aid of catalysts or ultraviolet light.

The known process has also been carried out in stages, using different temperatures. If one tries to apply these known processes to polyethylene which has been produced by the low pressure process, for example in accordance with German patent specification 973 636, it is found that, due to the insolubility of the low pressure polyethylene in the solvents claimed, initially only a superficial chlorination occurs ^{below 100 ° C.} the polymer receives. These products only dissolve when the chlorine content is very high, but no uniform reaction products are formed.

By using pre-chlorinated polyethylenes, it is then possible to use the sulfochlorination in homogeneous solution at the respective reaction temperature the desired chlorosulphochlorinated Manufacture of polyethylene.

This is only possible with the method according to the invention. Would you z. B. polyethylenes insoluble in boiling carbon tetrachloride, e.g. B. obtained by the Ziegler process polyethylenes, in contrast to the process according to the invention in a heterogeneous phase, for. B. suspended in carbon tetrachloride, chlorosulphochlorinated, one also obtained chlorosulphochlorinated polyethylenes with the same chlorine and sulfur content as the products according to the invention, but these products chlorosulphochlorinated in the heterogeneous phase are only chlorosulphochlorinated on their surface, but not inside the particles . As a result, these particles are inhomogeneous and thermally very unstable, since the concentration of chlorine atoms and sulfochloride groups on the surface of the particles is very high, which is known to promote thermal elimination of hydrochloric acid. Da (up to 15O ⁰ C 100) are needed for the technical processing of the chlorsulfochlorierten products, however, often higher temperatures, it appears that only those products are technically usable, as are obtained by the inventive process.

The preceding the claimed method Druckanchlorierung can be carried out either so that the low pressure polyethylene is heated with a saturated solution of chlorine, carbon tetrachloride solution in an autoclave at 105 to 110 ⁰ C and a time is kept at this temperature, a pressure depending on the amount of chlorine applied from 2 to 30 atm, or you can inject chlorine into a suspension of low-pressure polyethylene in carbon tetrachloride in a closed autoclave, whereby initially no pressure is created because the chlorine is immediately dissolved in the carbon tetrachloride. Only when it is subsequently heated to 105 to 150 ° C are pressures of 20 to 150 atm. Furthermore, some of the chlorine can be injected during the reaction, even at elevated temperatures, whereby care must be taken that the hydrochloric acid formed can escape through a regulating valve. If at least enough chlorine is introduced into the polymer in this way that a reaction product soluble in carbon tetrachloride has formed, which is the case with a chlorine content of at least 5 to 10%, the reaction mixture is allowed to cool, relaxed and the solution of the partially chlorinated is carried out Polymer over into a stirred tank. In this, the sulfochlorination is carried out at atmospheric pressure up to the desired chlorine and sulfur content at room or elevated temperatures. In this way, better utilization of the autoclave is achieved and, in addition, the sulfochlorination prevents liquefaction of the gaseous reactants. The sulfochlorination reaction can be accelerated both thermally and catalytically (e.g. by ultraviolet light, azo contacts, peroxides). Of course, starting products of different high molecular weights can be treated according to the present invention. The polyethylenes formed after the treatment according to the invention and containing both chlorine and sulfur are raw materials for lacquers and synthetic rubbers.

Compared to sulfochlorinated high-pressure polyethylene, sulfochlorinated polyethylene prepared according to the invention are distinguished Products through a more favorable flow ratio, as can be seen from the following table:

ReI. viscosity
of the sulfochlorinated
Product at 25 ° C
1% in xylene

Exit in grams at

150 ° C from a nozzle of

2.08 mm in 10 minutes

at a load of

3 kg / cm ^a

Sulphochlorinated high pressure polyethylene
(25% Cl and 1.5% S)

Sulphochlorinated low pressure polyethylene
(25% Cl and 1.5% S)

1.1

1.1

1.95
1.98

0.28
0.51

The table shows that at 25 ° C. the two products I and II are approximately equally viscous (column 3). At 150 ° C, however, the sulfochlorinated low-pressure polyethylene has a lower viscosity and is characterized by a better flow behavior from (column 4).

It is obvious that such a behavior with a plastic, its further processing by Mixing in pigments, fillers and vulcanization accelerators on the roller takes place, the processing much easier.

Further properties of sulfochlorinated low-pressure polyethylenes which are valuable for some purposes become evident in its vulcanizates. These show compared to those treated accordingly known sulfochlorinated polyethylenes greater hardness and greater notch toughness.

For example, 1 1

20th

In a suspension of 25 g of low-pressure polyethylene (»? Spec., O. = 1.12) and 0.01 g of azoisobutyronitrile in 500 ml of a carbon tetrachloride solution containing 15 g of chlorine, the mixture is heated to 105 to 115 ° C. in an autoclave. After 30 minutes, the mixture is allowed to cool and the solution of the partially chlorinated polyethylene is transferred to a second vessel which is provided with inlet pipes for SO ₂ and Cl ₂ .

Now 10 g of chlorine are added to the solution with continuous addition of a further 0.02 g of azoisobutyronitrile at a rate of 0.16 g / min. initiated, then the viscous solution was gassed at a temperature of 30 ° C with gaseous sulfur dioxide (0.14 g / min.) and chlorine (0.15 g / min.) for 1 hour. The reaction product is freed from the dissolved gases by passing in nitrogen, precipitated with methanol and finally dried in vacuo at 1 mm. There are formed 43 g of a white, rubber-elastic product with a content of 28 ° / ₀ chloro, of which 1.9% portable chlorine and 2.1% sulfur.

Example 2

a) 200 g of polyethylene (?? _S pec./c. = 1.2, measured as a 0.5% solution in tetrahydronaphthalene at 130 ° C) produced with a Ziegler contact, consisting of TiCl ₄ + A1 (C ₂ H ₅ ) ₃ are dissolved in a nickel autoclave with 21 carbon tetrachloride at 110 ° C. At this temperature, 40 g of liquid chlorine are then injected in 45 minutes. After stirring for a further 15 minutes, the mixture is cooled to 60 ° C. and the pressure is released.

At 6O ⁰ C then 40 g of sulfur dioxide and 110 g of chlorine are passed in 2 hours. At the same time, the reaction mixture is irradiated with a UV lamp through a window. After a further 10 minutes, the reaction mixture is blown out with nitrogen. The sulfochlorinated polyethylene is isolated by precipitation with methanol. The analysis found: sulfur 1.2%; Chlorine 25.4%.

b) For comparison, a polyethylene of the same type as that used in Example 2 a) was not used now homogeneous, but heterogeneously chlorosulfochlorinated.

200 g of polyethylene (as in Example 2) are suspended in 21 carbon tetrachloride with stirring. In 90 g of chlorine are passed into this suspension at 50 to 60 ° C. under UV irradiation over the course of 3 hours. In 70 g of sulfur dioxide and 100 g of chlorine are passed in for a further 2 hours. After stirring and Blowing out with nitrogen, the powdery colorless substance is suctioned off and washed with methanol. at the analysis found: 4.1% sulfur and 22.6% chlorine.

Samples of the two chlorosulfochlorinated polyethylenes were then placed in a heating cabinet for 8 hours at 90.degree kept. Then a determination of the chlorine and Sulfur content carried out, which resulted, as the table shows, that the heterogeneous chlorosulf ochlorinated Polyethylene has split off hydrochloric acid. In addition, there was a brown discoloration.

SuIf chlorinated polyethylene Example 2

after
Manufacturing

after
Heat treatment comparison test

after
Manufacturing

after
Heat treatment

S 1.2%
Cl 25.4%

1.2%
25.2%

4.1%
22.6%

4.0%
20.5%

Claims (1)

Claim: A process for the chlorosulphonation of chlorinated Niederdruckpolyäthylenen, which have been obtained by chlorinating Niederdruckpolyäthylenen in boiling below 100 ⁰ C hydrochlorofluorocarbons under pressure at temperatures of 100 to 160 ° C, characterized in that subsequent to the chlorination, the incipiently chlorinated Niederdruckpolyäthylene at normal pressure and at can react further to temperatures between 20 and 8O ⁰ C to the desired chlorine and sulfur dioxide and Sulfochloridgehalt with chlorine.