CS272579B1 - Method of abs copolymer's latex stripping - Google Patents

Abstract

Latex stripping of the ABS copolymer by steam is carried out by continuous or non-continuous dosing of a methyl silicone preparation of the general formula(R)3 - Si -O - [Si (CH3)2 O]n Si - (R)3,where R is hydroxyl or methyl and n is a polymerization degree. The introduced methyl silicone preparation, which is dosed in polypropylene oil above the latex level of the ABS solution, has a molecular weight M of 400 to 500 units, while the concentration of the methyl silicone preparation amounts to 1 to 20 percent by weight. The solution of the methyl silicone preparation in polypropylene oil also contains 0.5 to 5 percent by weight of silicon oxide. The higher efficiency of this stripping method is characterized by a decrease of foaminess of ABS latex and slight decrease of consumption of stripping steam.

Description

The method of stripping ABS copolymers latex (57) The steam stripping of ABS copolymers by steam is carried out by continuous or discontinuous administration of the methylsilicone preparation of the general formula (r) ₃ - s - o - [si (ch ₃ ) ₂ - o] _n Si - (r) ₃ wherein R is hydroxyl or methyl and n is a polymerization step. Said methyl silicone composition, which is administered in polypropylene oil above the latex level of the ABS solution, has a molecular weight M of 400 to 500 units, wherein the concentration of the methyl silicone composition is 1 to 20% by weight.

The solution of the methyl silicone composition in the polypropylene oil also contains 0.5 to 5% by weight of silica. A higher effect of the solved stripping method results in a decrease in the foaming properties of the ABS latex and a slight decrease in the stripping steam consumption.

CS 272579 Bl

EN 272 579 81

The present invention relates to a process for stripping acrylonitrile-butadiene-styrene copolymers latex with water vapor while suppressing the formation of foam.

ABS copolymers are still largely produced by emulsion polymerization. After the polymerization, the ABS latex generally contains 1 to 5 wt. unreacted monomers (acrylonitrile, styrene, aminoethylstyrene) or non-polymerizable impurities (ethylbenzene, cumene, etc.). The hydrocarbons must be removed from the latex. Demonomerization is carried out either by heating and reducing the pressure or by introducing direct steam, i.e. by stripping. Due to the presence of emulsifiers in the latex, a thick layer of foam is formed above the surface during steam stripping.

If the process were carried out without suppressing the formation of foam, the foam would penetrate into another device (vapor condensers) and the hydrocarbons distilled off by the latex would eventually become clogged. The stripping process can be conducted by reducing the rate of steam introduction at which the formation of foam is less, but in this case the process is prolonged, the performance of the apparatus is reduced and the losses are lost because of self-coagulation. Another possibility is to suppress the formation of foam by various chemicals. For such demanding environments as stripping ABS latex, ie pH higher than 9.5, temperature 95-100 ° C, defoamers composed of alcohols, esters and ethers or mixtures thereof have not proven themselves.

However, effective antifoam agents are also known for this environment, e.g., silicone antifoams in the form of emulsions with a non-ionic or anionic emulsifier. However, in order to achieve a better suppression of foam formation, it is necessary to dispense the emulsions diluted. This increases the volume of mass to be heated to the stripping temperature and deteriorates the energy balance of the stripping process. One of the silicone defoamers is methyl silicone fluid. This preparation is used in the form of diluted emulsions.

The aforementioned disadvantages of the process of stripping ABS latex copolymers can be eliminated by the process of the invention, which consists in stripping with simultaneous or discontinuous administration above the latex level of the ABS latex solution of the methylsilicone composition in a polypropylene oil of molecular weight M = 400 to 500 units, wherein the concentration of methyl silicone preparation is 1 to 20% by weight, wherein the solution of the methyl silicone preparation in the polypropylene oil contains 0.5 to 5.0% by weight. silica.

A further advantage of said process is that the solvent of the silicone composition polypropylene oil is homogeneously dispersed into the ABS polymer and acts as a plasticizer.

The higher effect of the process according to the invention results in both a decrease in the foaming properties of the ABS latexes and a slight reduction in the amount of stripping steam or a lower total volume.

Polypropylene oil is a synthetic, liquid oily product of propylene polymerization. It consists of a mixture of strongly branched hydrocarbons from C8 to C18. Its other parameters:

specific gravity at 20 ° C in g / cm ¹ above 0.840 molecular weight 400 to 500 refractive index rig 1,4695 acid number in mg KOH / g 0 viscosity at 20 ° C in mPas over 600

Said solution may further comprise silica to better anchor the silicone component. The efficacy of the method of the invention was evaluated according to the published method of L. Voral, J. Trněný, printed in Synthetic Rubber 35, 1984, No. 7, pp. 72-88. The principle of the method is to determine the antifoam consumption as a function of time for a given moment from the beginning of stripping. The efficiency of the ABS latex stripping method is evaluated by comparing the total consumption of the texted antifoam at a given time to the total consumption of the standard antifoam at the same time.

CS 272 579 B1 where K is the ratio of the aggregate consumption M M of the antifoam at a given moment to the aggregate consumption of the antifoam of standard M _s at the same time since the beginning of the stripping. The lower the coefficient value, the more effective the defoamer is in the process.

Example 1

Injection-type ABS latex of 33.1% by weight containing 2.1% by weight of styrene and 0.8% by weight of acrylonitrile based on dry matter was used for testing. 10 liters of this latex are charged into a 30 liter model stripping reactor. A measured amount of steam is fed through the droplet separator and heater. The conductivity probe placed in the steam space of the stripping reactor regulates the dosing of the antifoam by a micro pump and simultaneously registers the amount. The control of the micro pump is provided by a relay, while the antifoam is only dosed until the foam level drops below the lower edge of the electrode. The consumption thus determined can be considered as minimal.

As a standard comparative defoamer, a silicone emulsion with a non-ionic emulsifier of the conventional commercial type was used.

The comparison time was chosen 20, 40 and 60 minutes from the beginning of the stripping.

Table

K in 20 minutes K in 40 minutes K in 60 minutes Ex. 1. 0.73 0.60 0.70 2. 0.70 0.65 0.65 3. 0.43 0.48 0.46 4. 0.55 0.60 0.57

SUBJECT OF THE INVENTION

1. A method of stripping latex copolymers of ABS with water vapor with the suppression of the

Claims (2)

SUBJECT OF THE INVENTION A method of stripping ABS copolymers with water vapor suppressing foaming with a methylsliconone preparation of the general formula (R) ₃ - (Si - O - Si (CH ₃ ) ₂ - o] _n - Si - (R) ₃ wherein R is hydroxyl or methyl an is a polymerization step, characterized in that the stripping is carried out simultaneously or continuously or above the latex level of an ABS solution of said methyl silicone composition in a polypropylene oil having a molecular weight M of 400 to 500 units, wherein the methyl silicone concentration is 1 to 20% by weight. 2. A process according to claim 1, wherein the solution of the methyl silicone composition in the polypropylene oil comprises 0.5 to 5% by weight of silica.