DD200025A1 - METHOD FOR THE TREATMENT OF DISPERSIONS FROM VINYL CHLORIDE POLYMERISES - Google Patents

Abstract

The invention relates to a process for the treatment of dispersions of vinyl chloride polymers after completion of the polymerization. The method is designed so that in the pressure degassing a foaming and thus an over-distribution of dispersion is avoided in the expansion vessel, the speed of the pressure degassing and the space-time yield is not reduced. The treatment of the dispersions of vinyl chloride polymers which are prepared using known initiators and polymerization auxiliaries is carried out according to the invention such that, after the end of the polymerization, an aqueous solution of ethoxylated polypropylene glycols of the general formula ## STR1 ## with a = 2-40, b = 15-90 and c = 2-40 and / or alcohol or Alkylphenolalkylenoxidaddukten of the general formula with n = 5-40 and m = 2-40, wherein R is an aliphatic and or aliphatic-aromatic hydrocarbon radical having 10-20 carbon atoms, in concentrations from 0.005-5 wt .-% based on the solids content, is metered into the polymerization. formulas

Description

232103

Title of the invention

Process for the treatment of dispersions of vinyl chloride polymers

Field of application of the invention

The invention relates to a method-for the treatment of dispersions of Vinylcbloridpolymerisaten after termination; '~ \ account the polymerization.

Characteristic of the known technical solution

In the pressure degassing of dispersions of Vinylcbloridpolymerisaten it comes after completion of the polymerization, caused by the existing pressure of vinyl chloride nichtbtuingesetzten the formation of foam, which slowly collapses only in the downstream expansion vessel. At the same time a part of the dispersion is entrained in the expansion vessel.

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It is known that the speed of the pressure degassing can be adapted to the particular circumstances by technological measures (DT 2 832 972). The foam can also be destroyed mechanically or by the addition of defoaming agents in the expansion tank. The disadvantage is that, especially with rapid degassing, a flash tank of sufficient volume is required to completely absorb the foam. For strongly foaming dispersions, the degassing must be throttled, which leads to an extension of the cycle times. The entrained Vinylcbloridpolymerisat must be isolated by an additional process step from the expansion vessel.

Z e l _mm the invention

The aim of the invention is to carry out the pressure degassing of dispersions of vinyl chloride polymers after completion of the polymerization in an economically advantageous manner and without technological changes in the polymerization process.

-The technical problem, which is solved by the invention. , · ..

The invention has for its object to provide a method for the treatment of dispersions of vinyl chloride polymer. After the polymerization has ended, the seeds, which are prepared using known initiators and polymerization auxiliaries, are used to develop the

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Foam formation is reduced in the pressure degassing and an overshoot of dispersion is avoided in the expansion vessel, without the speed of the pressure degassing and the space-time yield is reduced.

- The features of the invention

The object is achieved according to the invention by treating the dispersion of vinyl chloride polymers in such a way that, after the end of the polymerization, an aqueous solution of etboxylated polypropylene glycols of the general formula

E - (OCH ₂ -CH ₂ ) _a - (OCH-CH ₂ ) _b - (OCH ₂ -CH ₂ ) _c - OH

CH ₃

with a = 2-40, b = 15-90 and c s 2-40 and / or of alcohol or alkylphenol alkylene oxide adducts of the general formula

\ R - (OCH ₂ -CH ₂ ) _n - (OCH-CH ₂ ) _m -OH

represents 40 .wobei R is an aliphatic or alipbatisch-aromatiscber hydrocarbon rust 10 -20 C-atoms, metered into the polymerization reactor, and thereafter the existing monomer pressure is depressurized to atmospheric pressure - with η = 5 - ² K), and m =. 2

In this case, concentrations of 0.005 to 5% by weight, based on the solids content of the polymer dispersion, are used.

For the process according to the invention, particularly ethoxylated polypropylene glycols are suitable in which the block consisting of propylene oxide units has a molecular weight of 1000-3000.

As Alkylenoxidaddukte z. For example, ethylene oxide-propylene oxide adducts of fatty alcohols, nonyl or dodecylphenol are preferred.

The process according to the invention is not bound to any particular degree of conversion of the polymerization, but is most effective after the pressure drop has occurred with regard to the concentrations to be used.

example 1

A mixture of 900 Tin. Water, 1.3% of a hydroxypropylmethylcellulose, 0.3 T in. Sodium bicarbonate, 0.3 Tin "dicetyl, 0.2 Tin" of lauroyl peroxide and 460 Tino vinyl chloride was introduced into a pressure autoclave and polymerized with stirring at a temperature of 62 ⁰ C, "The degree of filling of the autoclave was 82%, after 6 hours at a conversion of 85%, the unreacted vinyl chloride relaxed.

The relaxation time was 10 minutes and- _v ca _e .5.% De.s PVC obtained were driven with the foam in the flash vessel.

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Example 2

In a polymerization batch according to Example 1, an aqueous solution of ethoxylated polypropylene glycols of the following formula

H - (OCH ₂ -CH ₂ ) ₈ - (OCH-CH ₂ ) ₃₅ - (OCH ₂ -CH ₂ ) _Q - OH

pressed after the onset of pressure drop at 0.45 MPa in a concentration of 0.005 wt .-% based on the amount of PYC obtained in the polymerization reactor.

In 8 minutes, the dissociation of vinyl chloride without vinyl was complete, and only traces of PVC were overdriven into the flash tank.

Example 3

To a polymerization batch according to Example 1, 0.025% by weight, based on the solids content of the PVC suspension, of a nonylbenzene-ethylene oxide-propylene oxide adduct with 8 mol of ethylene oxide and 4 mol of propylene oxide in aqueous solution at 0.52 MPa was added.

The time to relax to normal pressure was 7 minutes, and no PVC was forced into the expansion vessel, "

Claims (1)

invention claim 1, "Process for the treatment of dispersions of vinyl chloride polymers, which are prepared using known initiators and polymerization aids, to prevent the foaming in the pressure degassing, characterized in that after completion of the polymerization, an aqueous solution of ethoxylated polypropylene glycols of the general formula H - (OCH ₂ -GH ₂ ) _a - (OCH-CH ₂ ) _b -. (OCH ₂ -CH ₂ ) ₀ - OH CH ₃ with a = 2 - 40, b = 15 - 90 and c = 2 - 40 and / or of alcohol or. Alkylphenolalkylenoxidaddukten the general formula R - (OCH ₂ -CH ₂ ) _n - (OCH-CH ₂ ) _m -OH with η = 5-40 and m = 2-40, wherein R is an aliphatic or alipbatiscb-aromatic hydrocarbon radical having 10-20 carbon atoms, in concentrations of 0.005-5 "by weight, based on the solids content, in the Polymerization reactor is metered •. 2e Process for the treatment of dispersions of vinyl cbloridpolymerisaten according to item 1 characterized by that ethoxylated polypropylene glycols, in which nen of consisting of propylene oxide units block has a molecular weight of 1000 - 3000, be used 232103 4 Process for the treatment of dispersions of cbloridpolyinerisaten according to item 1, characterized in that etbylene oxide-propylene oxide adducts of the fatty alcohols, nonyl or Dodecylpbenols be used.