DE2265728C2 - Process for the polymerization or copolymerization of vinyl chloride - Google Patents

Description

20th

The invention relates to "a process for the polymerization or copolymerization of vinyl chloride in non-emulsified aqueous suspension in the presence of a protective colloid.

It is known that essentially water-insoluble monoethylenically unsaturated monomers, such as vinyl chloride, in aqueous suspension in the presence of a number of natural and synthetic water-soluble Polymers used as protective colloids in the polymerization process serve, can be polymerized, producing products with a desired uniformity Particle size distribution is given Examples of such protective colloids or dispersants are methyl celluloses, Polyvinyl alcohol, gelatin and the hydroxypropylmethyl cellulose ether described in US-PS 2538051, which has a degree of methoxy substitution of about 1.6 to 2.0.

If the polymerization recipes and those used Processes lead to excessive foaming in the reactor, the use of the Materials with drill surface tension contribute to solving the problem. However, when a product has a high surface tension, such as hydroxyethyl cellulose is used for this purpose, the Control of the reaction more difficult, making the resulting particles hard, non-porous, glass-like Represent beads exhibiting inadequate plasticizer absorption.

Furthermore, the particle size distribution turns like this towards larger fractions and the plasticizer absorption becomes worse, if, like him, also for Cellulose protective colloid is the case, inadequate hydroxypropoymethylcellulose as protective colloid suspension polymerization of vinyl chloride is used.

It has now surprisingly been found that hydroxypropylmethylcellulose, those having a methoxy substitution degree greater than 0.4 to 13, as opposed to one Hydroxypropylmethylceüulose with a Methoxysub- go stitutiongrad from about 1. fc to 2.0 (as described in US Pat. No. 2,538,051, in is able to provide polymer particles of uniform size, which have a much better plasticizer absorption exhibit (108% versus 86%).

The invention relates to a process for the polymerization and copolymerization of vinyl chloride in non-emulsified aqueous suspension in the presence of polymerization catalysts and of water-soluble ones Hydröxypropyhnethylcelluloseäthern with a molar hydroxy substitution of 0.2 to 1.4 as Protective colloids in an amount of 0.05 to 5%, based on the weight of the monomer, which thereby is characterized in that "one is a hydroxypropyl methylcellulose ether with a degree of methoxy substitution of 0.4 to "13 is used

The preparation of the polymers with the desired Particle size can be achieved by using the described cellulose ether in a concentration which preferably ranges from 0.1 to 5% based on the weight of the monomer is used

The choice of viscosity depends on the system used. A number of products with viscosities from about .5 to 5OcP at a 2% concentration and 20 ⁰ C; prefer *. An example of a comonomer for copolymerization with vinyl chloride is vinyl acetate.

The choice of methoxy substitution and molar hydroxypropyl substitution as well as the viscosity depends on the system used. A product with a degree of methoxy substitution of 1.0 to 13 and a molar hydroxypropyl substitution of 0.75 to 1.0 and a viscosity of about 73 cP at a 2% concentration at 20 ^° C. is preferred

Furthermore, the polymerization, as it is at aqueous suspension polymerization reactions of the type described is usually the case in In the presence of a polymerization catalyst, it was found that in this regard Isopropyl percarbonate is particularly effective as a catalyst

Unless otherwise indicated below, all parts and percentages are by weight.

example
and comparison test

In each of the individual experiments, a glass-lined reaction vessel with a capacity of 7 ^ 71, which was equipped with a glass paddle stirrer, a dip tube made of stainless steel and a pressure reducing valve was provided, initially with Suction rinsed Then 3540 g of demineralized water and 3.54 g of surface-active water were added Medium (which is a 0.2% solution of the following indicated cellulose material in water) and 2 ^ 5 g of a 20% solution of the catalyst used isopropyl percarbonate in xylene added A partial vacuum was then created and, over the course of 5 minutes, while stirring with a Speed of rotation of 225 rpm 1770 g of vinyl chloride in the reaction vessel. The reactor temperature was then brought to 54 ° C. After a pressure decrease of 4.45 bar from the maximum pressure, that was The reaction vessel was cooled to the maximum, was then evacuated to 0 bar, whereupon it was increased to a pressure of 675 mbar was evacuated.

The polyvinyl chloride was removed from the reaction vessel, washed with water and filtered and dried ^{at 50 ° C. overnight.}

The following table shows the cellulose materials used and the polymers obtained described.

Table I. Comparative experiment according to the invention Hydroxypropylmethylcellulose Hydroxypropylmethylcellulose

1.66 to 1.95 methoxy groups, 1.0 to 13 methoxy groups,

0.1 to 0.20 hydroxypropyl groups 0.75 to 1.0 hydroxypropyl groups

% based on the Monomeire 0.2 0.2

Viscosity (2% at 20 ^° C. (CP)) 50 7.3

Bulk density (g / cm ³ ) 0.49 0.50

Polymerization Propertieseu

% Plasticizer absorption 86

(% absorbed dioctyl phthalate, 108

based on the resin weight)

Powder mixing time (min) 5 5, 2

Surface speculation (dyn / cm) 50.9 -

The above values show the improved plasticizer absorption achieved through the use of hydroxypropylmethyl cellulose is achieved with the specified methoxy and hydroxypropyl substitution.

Claims (1)

Claim: Process for the polymerization or copolymerization of vinyl chloride in non-emulsified aqueous suspension in the presence of polymerization catalysts and water-soluble hydroxypropylmethylcellulose ethers with a molar hydroxy substitution of 0.2 to 1.4 as protective conoids in an amount of 0.05 to 5%, based on the Monomer weight, characterized in that that one has a Hydroxvpropylmethylceüuloseäther with a methoxy substitution degree of 0.4 to 13 is used IS