DD200024B1 - PROCESS FOR REMAINING REMOVAL FROM WAESSEN VINYL CHLORIDE POLYMERISATE DISPERSIONS - Google Patents

Description

with a = 2-40, b = 15-90 and c = 2-40 and / or alcohol or. Alkylphenolalkylenoxidaddukte of the general formula S - (OCH ₂ -CH ₂ ) _n - (0CH-CH ₂ ) _m - OH

with η = 5-40 and m = 2-40, wherein R represents an aliphatic or aliphatic-aromatic hydrocarbon radical having 10-20 carbon atoms, in concentrations of 0.005-5 wt .-%, based on the Festoffgehalt, before or during the Schleppmittelbehandlung be added in aqueous solution.

Field of application of the invention

The invention relates to a method for preventing foam formation in the removal of residual monomers from aqueous vinyl chloride polymer dispersions.

Characteristic of the known technical solution In the residual monomer removal from aqueous vinyl chloride polymer dispersions following the polymerization occurs

especially in vacuum and simultaneous Schleppmittelbehandlung foaming on, the significant disturbances in the

Operation caused. These foams can be minimized by various methods. It is known that ζ. Β. by mechanical Measures such as passing the water vapor through a ceramic or metal filter with 20μπτι pore size or by installation

Foaming is reduced by foam breakers or intensive stirring (GB 2013520, DE 2832972).

Also, the blowing of steam just below the liquid level in such a way that condense over 50% of the vapor,

prevents foaming, while the addition of polymethylsiloxane-based defoamers has no effect (DE 2744462).

Furthermore, various silicone-based anti-foaming agents, or mixtures of various surfactants, are known

are known for aqueous systems which are used in the textile, detergent and paper industry (eg.

DE 2625706, DE 2943754).

In the steam generation is also known that the foaming occurring during the boiling process by adding Polyoxyalkylene glycols or Polyoxyalkylenglykolmonoäthern can be prevented (DE-PS 819289, DE-PS 871289). A disadvantage of the known methods for reducing the formation of foam in the removal of residual monomers that the

technical measures a different efficiency in the various Vinylchloridpolymerisat-

Have dispersions. The requisite technological changes must meet the foaming properties of

appropriate dispersions are adjusted and complicate a continuous procedure of the entire system. Essind z.T. longer residence times or higher temperatures required to reduce the effectiveness of the

To avoid residual monomer removal. This inevitably leads to thermal damage to the polymer. Object of the invention

The aim of the invention is to prevent the occurrence of residual monomer removal from aqueous vinyl chloride polymer dispersions foaming in an economically advantageous manner and without technological changes.

Explanation of the essence of the invention

- The technical problem which is solved by the invention.

The invention has for its object to provide a method for preventing foam formation in the removal of residual monomers from aqueous vinyl chloride polymer dispersions containing known emulsifiers or dispersants to develop without a reduction in throughput or obstruction of the degassing occurs, a longer residence time and the associated thermal damage to the vinyl chloride is avoided.

- The features of the invention

The object is achieved in that the vinyl chloride polymer dispersion at temperatures S 60 "C ethoxylated polypropylene glycols of the general formula

-2- 321

H - (OCH ₂ -CE ₂ ) _a - (OCH-CH ₂ ) _b -

- OH

with a = 2-40, b = 15-90 and c = 2-40 and / or alcohol or Alkylphenolalkylenoxidaddukte of the general formula R - (0CH ₂ -CH ₂ ) _n -. (00H-GH ₂ ) _m - OH

with π = 5-40 and m = 2-40, wherein R is an aliphatic or aliphatic-aromatic hydrocarbon radical having 10-20 carbon atoms, are added.

The addition o.g. Compounds are in concentrations of 0.005-5 wt .-%, based on the solids content of the polymer dispersion, before or during the treatment of the entraining agent in aqueous solution.

For the inventive method, such compounds have proved to be favorable, which have a sufficient water solubility, whereby a fast and uniform distribution in the aqueous vinyl chloride polymer dispersion is guaranteed, combined with great foam-damping effect.

The process according to the invention relates in particular to vinyl chloride polymer dispersions having a solids content of 15-50% by weight and is not limited to any specific technological variant of the known processes of residual monomer removal. The type of entrainer is without influence on the effectiveness of the method according to the invention.

Exemplary embodiments 1-6

A 25% solids PVC suspension obtained by conventional polymerization processes was steamed at 100 ° C to remove unreacted vinyl chloride. After a few minutes, a stable foam formed. The foam height was about ^{2/3 of} the filling level of the demonomerization boiler. The following substances were added to this PVC suspension:

connection EO. PO EO = mol of ethylene oxide R Link concentration T foam height A 16 35 PO = mol of propylene oxide Type % ° c % B 8 4 R = remainder nonylphenyl without - - 100 C 8 5 Cio-Ci6 alkyl ~ A 0.1 25 10 A 0.05 45 6 B 0.03 55 4 C 0.05 30 <1 A + C 0.01 + 0.02 25 5 The following table summarizes the experimental conditions and the results obtained: example No. 1 2 3 4 5 6

The temperature given in the table represents the temperature of the addition of the aqueous solution to the PVC suspension.

Claims (1)

-1- 321 04 Invention claim: A method for preventing foam formation in the removal of residual monomers from aqueous vinyl chloride polymer dispersions containing known emulsifiers or dispersants, characterized in that the aqueous Vinytchloridpolymerisat dispersion at temperatures <60 ° C sthoxylierte polypropylene glycols of the general formula H - (OC _{0 0} CH.), - (OCH-CH ₀ X - (0CH ₀ CH ₀₎ -. OH ti. c. Ά d.Dd. c Q