DE2127412A1 - Process for the production of thermally stable polyvinyl chloride - Google Patents

Description

Process for the production of thermally "stable polyvinyl chloride"

The invention relates to a process for the production of thermally stable polyvinyl chloride, in which tert _e -butyllithium of high purity is used as the catalyst.

In the Czechoslovak patent no .:. ···· (PV 440-70) the polymerization and production of thermally stable polyvinyl chloride was described in which a lithium complex is used as a catalyst, which is produced by the reaction of alkyllithium with an organic compound of metals of group IV or with an alcohol

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holat of a metal of the I. - III. Group of periodic System of elements, by themselves or with substances of the electron donor type, arises, with the polymerization is carried out at temperatures of - 20 to + 30 ° C.

It has been found that even the sole tert _{o-butyllithium,} which has not yet been used as such for the polymerization of vinyl chloride, at polymerisation w organizations in the solvent or without a solvent advantageously leads to such polymers having a high molecular weight and a narrow distribution of molecular weights. Although the proportions of isotactic and syndiotactic structures represented in these products differ only insignificantly from polymers produced by radical polymerization, these products have increased thermal stability. This stability of the polymers, together with the linearity of their chains and the high degree of polymerisation, make the polymers according to the invention particularly suitable for the production of thermally stressed objects, for example for the insulation of electrical conductors or for the production of threads which, because of their thermal stability, in the technical practice can be used.

The proposed method for producing thermally stable polyvinyl chloride is to that the polymerization in the temperature range from -20 to

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+ 3O ⁰ C, is carried out advantageously in the range from 0 to + 2O ⁰ C and at pressures in the range from 1 to 4 at, with tert-butyllithium as a catalyst

—1 maximum content of impurities of 1. 10 wt, #,

with advantage of 1. 10 wt. $, Is used. The regulation of the molecular weight of the obtained polyvinyl chloride can advantageously by varying the concentration of catalyst in relation to the vinyl chloride (in a ratio of 1. 10, ^"4 to 1. 10 ~ ^2, advantageously of ^

1 β 10 ^J to 3 · 10, or by the concentration of the monomer in the solvent or by changing the temperature. In order to keep the concentration of the catalyst constant and low, the catalyst is added successively in partial doses, the concentration of the catalyst advantageously being based on the ratio of tert-butyllithium: vinyl chloride 2. 10 " ⁴

to.i.410 is set.

The advantage of catalytic polymerization using " Use of high-purity tert-butyllithium as a catalyst in that the polymerization proceeds much faster than when using free radical initiators emulsion, suspension, block or solution polymerization, or in the case of photopolymerization · Above In addition, the rate of polymerization can be very effectively controlled by changing the catalyst concentration.

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ORIGINAL INSPECTED

tration, possibly the monomer concentration and to a certain extent also be regulated by changes in temperature was, which is particularly evident in the case of polymers with a high molecular weight.At temperatures around + 20 ° C, this process only requires minimal requirements with regard to the dissipation of the heat of polymerization _{or the like}

In addition, considerably more advantageous, i. h «narrower distributions of the molecular weights than can be achieved with the usual radical polymerizations The polymer is practically completely linear, with only minimal branching and therefore has excellent physical-mechanical properties. Of the The fact that it contains practically no defective areas causes its increased stability to heat and Exposure to light, as well as against other harmful influences · It can thus be used with advantage for all purposes can be used for which polymers produced by radical polymerisation were previously used

The polymerization according to the invention can be carried out in common

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Apparatus types carried out with only minimal adjustments because it does not require expensive cooling.

The invention is further illustrated by some exemplary embodiments explained, which only illustrate the invention, but in no way limit it to this.

example 1

A polymerization reactor, with or without a stirrer, from which the air has been removed and replaced with inert gas, is charged with 28.7 g of rectified vinyl chloride; after tempering, a hydrocarbon solution of the catalyst (tert _c -butyllithium) in the ratio

-5

nis tert-butyllithium ι vinyl chloride of 3.3 · 10 was added. After 2 hours of polymerization, the reaction is terminated by adding water. The precipitated polymer is washed through with water and methanol and dried. 4.965 g are obtained, i.e. h x 17.3 #, polyvinyl chloride. The molecular weight calculated from the empirical formula according to Danus amounts to Mn = 62,400. In comparison with a suspension polyvinyl chloride with a K value of 85, the thermal stability of the product produced is 30 minutes at 180 ° C. without the addition of a stabilizer; a commercial product starts to break down after just 20 minutes.

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Example 2

Procedure as in Example 1, insert: 28.2 g of rectified vinyl chloride; t = 12 ° C, L = 2 hours, tert-butyllithium: vinyl chloride = 1.67. 10 ^'5. Polymer yield 3.19 g, ie 10.3 wt. $ £ g] = 1.114, d. H _e Mn = 58 00Oo

Example 3

A method as in Example 1 using _0: 31, 6g vinyl chloride, t = 5 ° C, L = 2 hours, tert-butyllithium _e: Vinyl chloride = 1.67 x 10 ~. ⁵ Yield = 4.124 g of polyvinyl chloride, ie 13.05 °. L ^ = ¹ » ⁵¹⁶ ♦ ^d · ^h · ^lkl = ⁷¹

Example 4

Procedure as in example 1. Use: 8 g vinyl chloride, 30 ml heptane, t = 20 ° 0.77 = 4 hours, tert-butyl li

-2
thium: vinyl chloride = 1 «10. Yield of polymer 2.522 g, ie 31.2 ^ CgI = 0.4, ie Mn = 15,270.

Example 5

Procedure as in example 1. Use: 4.6 g vinyl chloride, 27.9 g heptane, t = 20 ° C, TT = 2.25 hours, tert, -

2 butyllithium: vinyl chloride = 3.33. 10. Yield to

Polymer 0.833 g of polyvinyl chloride, ie 17 #  \ jr £} = 0.1275, ie Mn = 3500.

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Example 6

Procedure as in example 1 "insert: 32.2 g vinyl chloride. At 20 ° C, the catalyst was dosed in three successive portions (interval between two Additions 8 hours). T = 24 hours, tert-butyl li-

thium: vinyl chloride = 1.1 x 10 " ^5. Yield 8.74 # ie

2.64 grams of polyvinyl chloride. fyl = 2.128, ie Mn = 134 000

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Claims (3)

PATENT CLAIMS: . 1.; Process for the production of thermally stable polyvinyl chloride, characterized in that the polymerization is carried out at temperatures between -20 and +30 C, advantageously in the range from 0 to + 20 ° C and at pressures between 1 and 4 at tert _c -butyllithium with a maximum content of impurities -1 -4 approvals from 1. 10 wt. $, With an advantage of 1.10 1 °. is used. 2. The method according to claim 1, characterized in that for the purpose of regulating the molecular weight of the resulting polyvinyl chloride is the concentration of the catalyst in relation to the Vinyl chloride in the ratio of 1. 10 " ⁴ to 1 _β 10 ~ ² , —3 —3 with advantage of 1. 10 to 3 «10, is changed, 3. The method according to claim 1 and 2, characterized in that the catalyst is gradually added in divided doses, wherein the concentration of the catalyst with advantage in the ratio of tert-butyllithium: Vinyl chloride of 2 _β 10 ~ ⁴ to 4. 10 ~ ^{4 is} maintained. 1 09851/1650