CS195301B2 - Method for the suspension polymerisation of vinyl chloride - Google Patents

Abstract

The technical problem of the suspension polymerisation of vinyl chloride, alone or in a mixture with other monomers, without it being adversely affected by the formation of encrustations in the polymerisation reactor, is solved by carrying out the polymerisation in the presence of a mixture of polyvinyl alcohols having a mean saponification number between 300 and 500, accompanied by substances of hydroxylic character, such as clays, bentonites and natural or artificial inorganic colloids.

Description

The present invention provides a process for the suspension polymerization of vinyl chloride, either alone or in admixture with other monomers.

It is known that the suspension polymerization of wooll chloride alone or vinyl chloride in admixture with other monomers leads to the accumulation of a considerable amount of polymer on the walls of the autoclave. The extent of this deposit is significantly influenced usually by the mixing method used, the formulation of the composition (type and amount of suspending agents and catalysts), the impurities present in the monomers and the number of polymerization cycles performed.

This deposit reduces the heat passage through the walls of the autoclave and makes it difficult to control the progress of the reaction; moreover, the product is heavily contaminated with hard and glassy crystals. The deposits are usually removed either manually or by high pressure water after each polymerization, which in any case requires one hour or more; moreover, in the case of manual cleaning, external hygiene problems arise for the operator in charge of the removal operation. Italian Patent No. 874,456 of Applicant B. F. Goodrich Co. This invention relates to suspension polymerization of vinyl chloride and alleviates the above mentioned disadvantages due to the addition of sodium hydroxide during the reaction in an amount of not more than 1000 ppm based on the monomers.

Thus, not only is the incrustation reduced, but also the deterioration, cutting and thermal stability of the polymer is achieved ... The addition of gentian hydroxide in an amount greater than 1000 ppm causes a tremendous deterioration of the product.

The present invention of the present invention is that the suspension polymerization of polyvinyl chloride alone or vinyl chloride poles in admixture with other monomers proceeds without the formation of deposits on the walls of the autoclave and without deterioration of the polymer properties due to the addition of vinyl polyols. 300 to 500 and diatomaceous earth or colloids of elements of the groups P, IIB, ΠΙΑ, IVA or VIII Mendeleev's periodic system containing hydroxyl groups during polymerization; only in the case of hydroxy-colloids, a strong inorganic acid or a hydrolyzable salt thereof is added at the end of the polymerization.

The vinyl chloride polymers produced according to the invention are granular vinyl chloride homopolymers or vinyl chloride copolymers containing about 80% or more vinyl chloride, or a knee of 20% or less vinylidene compounds containing a CH2 = C = terminal group. These vinylidene compounds include, for example, any. a compound of those known to those skilled in the art as being capable of copolymerizing with vinyl chloride includes, but is not limited to, various vinyl halides, vinylidene chloride, vinyl esters such as vinyl acetate or vinyl butyrate, acrylic or methacrylic esters such as methyl acrylate, butyl acrylates, isooctylacrylate, methyl methacrylate or hexyl methacrylate, maleic or fumaric acid esters, for example, diethyl maleate or dipropyl fumarate, aromatic vinyl monomers, for example styrene, monoolefins, for example ethylene, propylene or butylene, vinyl ethers, for example wool ethyl ether, allyl ester, allyl ester, allyl ester, , or similarly.

The polymerization reaction is conveniently performed under pressure in the presence of a monomer (oil) soluble catalyst at temperatures below about 100 ° C.

Suitable oil-soluble catalysts include, for example, lauryl peroxide, peroxydicarbonates, such as diisopropyl peroxydicarboinate, caprylyl peroxide, azodiisobutyronitrile, or the like, usually at temperatures in the range. . about 40 ° C to about 60 ° C. The amount used is as low as possible in accordance with a good polymerization rate of less than 1 part, for example 0.2 parts of lauryl peroxide or 0.02 parts of diisopropyl peroxydicarbonate. The catalyst can be used as such or directly prepared in a polymerization autoclave. Suspending agents that are used include all of the well known materials suitable for this purpose, for example gelatin, polyvinyl alcohol with low saponification number, water-soluble cellulose ethers such as methylcellulose and the like. The amount of polyvinyl alcohol having a saponification number of between 300 and 500 ranges from 0.01 to 0.5% by weight of the monomer, while the amount of natural substance or hydroxylated compound varies between 0.1 and 0, % By weight, based on the monomer dose (s).

Each of the working conditions will be better visible; by analyzing other examples which are intended merely to illustrate the invention without limiting the scope thereof.

Example · 1

The following mixture, in an amount based on 100 parts of vinyl chloride (CVM), was charged to a 25 cubic meter reactor equipped with a stirrer and a Pfaudler breakwater:

CVM H2O methylcellulose NaHCO3 tert-butylcyclohexylperoxodicarbonate

100 ALIGN!

150

0,035

0.02

0.03

·. The stirrer was rotated at 120 rpm and the reaction temperature was 55 ° C. After nine hours the reaction was no longer traceable and therefore the remaining monmer was distilled off; the conversion was approximately 70%. The manually removed incrustations weighed about 8 kg. The product density was 490 g / l.

Example 1 a d 2

Reaction mixture according to. of Example 1, 0.06 parts of Mg (OH) 2 were added. 5 batches were carried out before the purification operation; 10 kilograms of increments were removed. The conversion, which was higher in the initial batches · and · which gradually decreased, was on average about 78 percent.

Example 3

The batch was operated as in Example 2, only the amount of Mg (OH) 2 was increased to 0.2 part. After 15 batches, 11 · kg of deposit was removed. .. · J.

The average conversion was around 87%. Also in this. the number of cycles decreased the degree of conversion with increasing sediment on the walls. Also. The resulting density (53% g / l) was higher than in Example 1. Also the thermal stability was becoming worse and unacceptable.

A sample from this series of cycles was treated with 0.02 parts (NH *) 2SO4, and after washing, a product with normal thermal stability was obtained. This was also done in other examples where Mg (OH) 2 was used.

Example 4

The procedure of the example was repeated except that 0.07 parts of polyvinyl alcohol with a saponification number of 420 was added. After 50 sticks, the walls appeared completely free of incrustations. The conversion was 93% at all batches and the density was 480 g / l.

This formulation at. test in smaller size reactors and at different mixing speeds · gave the same results.

Of course, in this case, it was necessary to appropriately adjust the ratio of primary suspending agents to obtain the desired morphological characteristics.

Example 5.

Worked as ·. In the example · 4, only Mg (OH) 2 was replaced with 0.05 parts of commercial bentonite (Ultragel 300). After 30 batches, 5 kg of incrustations were removed.

The average reagent conversion of 92 '· ° / σ and density · 450 g / L without further treatment with (NH4') 2SO 6 · was optimal in thermal stability.

Claims (4)

SUBJECT A process for the suspension polymerization of vinyl chloride or vinyl chloride alone in admixture with other monomers in suspending agents, preferably water catalyzed by lauroyl, capry peroxide, azodiisobutyronitrile, peroxodicarbonates, preferably tert-butylcyclohexyl peroxydicarbonate, in the presence of suspending agents, e.g. polyvinyl alcohol with low esterification number or cellulose ethers, preferably methylcellulose, buffers, preferably acidic carbonate, characterized in that the polymerization is carried out in the presence of a mixture of polyvinyl alcohols with an average saponification number lying between 300 and 500, the amount of these polyvinyl alcohols with low saponification number ranges from 0.01 to 0.5 weight percent based on mono- And / or further in the presence of a compound selected from the group of diatomaceous earth and magnesium hydroxide in an amount varying from 0.1 to 0.5 weight percent based on the monomer (s). 2. A method according to claim 1, wherein the polyvinyl alcohol has a saponification number between 300 and 500. 3. A method according to claims 1 and 2, characterized in that:. that amount of added! the polyol of the alcohol is 0.01 to 0.5% by weight, based on the weight of the monomers. 4. The process according to claim 1, wherein the amount of added bentonite magnesium hydroxide or diatomaceous earth in the case of polyvinyl alcohol is 0.1 to 0.5% by weight, based on the weight of the monomers.