JPS5814446B2 - Polymerization method of vinyl chloride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved process for the homo- or copolymerization of vinyl chloride.

When vinyl chloride is polymerized alone or together with a monomer that can be copolymerized with vinyl chloride (hereinafter simply referred to as polymerization), the inner walls of the polymerization tank, backflow condenser, stirring blades, baffle plates, and various attached piping connections, etc., are damaged during the polymerization operation. The cooling capacity of the polymerization tank may be reduced because the polymer adheres to the loading area where the monomer comes into contact with the polymer, or the polymer that has once adhered and peeled off may be inside a vinyl chloride homopolymer or copolymer (hereinafter referred to as the product). This causes problems such as contamination with other substances and deterioration of product quality.

Therefore, it is customary to clean the inside of the polymerization tank after each polymerization and then perform the polymerization again, but this requires the labor and time of many people, resulting in a decrease in the operating rate of the polymerization tank and an increase in product costs. There is.

Many methods have been proposed to prevent polymer adhesion to the inner wall of the polymerization tank, but although these methods are effective in preventing polymer adhesion, they may slow down the polymerization rate or affect the physical properties of the product. There are various drawbacks such as deterioration, and none of these methods are satisfactory for industrial use.

An object of the present invention is to provide a practical polymerization method that does not cause the above-mentioned adverse effects and sufficiently prevents polymer adhesion during the polymerization of vinyl chloride.

As a result of repeated research, the present inventors have found that when polymerizing vinyl chloride, if hemicellulose is applied in advance to the inner walls of the polymerization tank and other parts of the polymerization equipment and equipment attached to the polymerization tank that come into contact with the monomer during the polymerization operation, it is possible to polymerize the polymer. The present invention was achieved based on the discovery that the adhesion of polymer was greatly reduced, and even a small amount of adhering polymer could be easily removed by washing with water, etc., and there were no adverse effects such as slowing down the polymerization reaction or deteriorating the physical properties of the product. did.

Hemicellulose as used in the present invention is a general term for polysaccharides that are widely present along with cellulose in plants, and the sugar groups serving as constituent units include D-glucose, D-mannose, and D-
Galactose, D-xylose, L-arabinose, and D-glucuronic acid are known, and can be collectively referred to as natural polymer compounds having a degree of polymerization of about 100 to 300 and a molecular weight of about 15,000 to 45,000.

Industrially, cellulose and hemicellulose are separated using caustic alkali, but the portion that is soluble in a 17.5% caustic soda solution is collectively called hemicellulose, which also contains small amounts of impurities such as low-molecular cellulose. It will be done.

In carrying out the present invention, hemicellulose is applied to the inner wall of a polymerization tank in the form of a solution dissolved in a solvent.

In this case, the medium for the coating liquid is not particularly limited, but alkaline aqueous solutions such as caustic soda and caustic potash are practical.

There are no particular limitations on the preparation of the coating solution, and it may be carried out under conditions such that hemicellulose is dissolved in the solvent.

It is not clear why polymer adhesion can be prevented if the hemicellulose of the present invention is applied to the inner wall of a vinyl chloride polymerization tank, etc., but it is probably because the polar groups represented by the 10H group of hemicellulose are hydrophilic. It is thought that this is because it acts as a base and makes the wall surface of the part of the polymerization tank that comes into contact with the monomer hydrophilic.

In fact, it has been observed that untreated wall surfaces of polymerization tanks and the like exhibit considerable water repellency, whereas wall surfaces treated with the present invention have extremely good wettability with water and exhibit hydrophilic properties.

Therefore, it is considered that the monomer is prevented from approaching the wall surface during the polymerization reaction, which is effective in preventing polymer adhesion.

In carrying out the present invention, a solution in which hemicellulose is dissolved is applied to the inner wall of the polymerization tank, etc., and the concentration of cellulose in the solution can be in the range of 0.01 to 20% by weight. Preferably, it is used in a range of 0.05 to 10% by weight, which is convenient for coating operations.

In the present invention, application refers to the presence of cellulose on the wall of the vessel as a result, not the mode of operation, and the method of application is not particularly limited, but it is usually carried out by brush application, spraying, etc. The coating amount is not particularly limited, but it is usually preferably 0.005 to 10 g/m8.

Coating may be carried out before the start of polymerization for each batch, or polymerization may be continued for several batches or more by simply washing with water after coating.

The polymerization to which the present invention can be applied is not only the homopolymerization of vinyl chloride, but also monomers copolymerizable with vinyl chloride, such as olefins such as ethylene and propylene, vinyl monomers such as vinyl acetate and styrene, maleic acid, and maleic acid. It can be effectively applied to copolymerization with dicarboxylic acid monomers such as acid esters, fumaric acid, and fumaric esters.

Furthermore, the polymerization format to which the present invention can be applied can be effectively applied to aqueous suspension polymerization of the above monomers, aqueous emulsion polymerization, and so-called bulk polymerization containing only the above monomers without a polymerization medium under each usual polymerization condition.

According to the method of the present invention, the effect of preventing polymer adhesion is much greater than that of conventional methods, and there are no adverse effects such as slowing down the polymerization rate or deteriorating various physical properties of the product.

The present invention will be explained below with reference to Examples.

Example 1 1.0 kg of fine pieces of coniferous wood from which dust etc. were removed was mixed into 4. Ol
After extraction with acetone, oil and fat were removed by extraction with a mixed solution of 3 liters of ethyl alcohol and 1 liter of benzene.

The defatted wood fine pieces were washed with an acetic acid aqueous solution containing 3% sodium chlorite to remove the lignin contained in the wood into the filtrate.

The obtained holocellulose was dissolved in 10% caustic soda solution for 8 hours.
After immersion treatment at 0° C. for 2 hours, acetic acid was added to the extract after filtration to adjust the pH to 8.5, and the resulting hemicellulose precipitate was separated and dried.

The amount of hemicellulose collected after drying was 112 g.

The hemicellulose thus obtained was dissolved in an aqueous solution of caustic soda, containing 2.0% by weight of hemicellulose and 2.0% by weight of caustic soda.
A coating solution containing 0% by weight and 96.0% by weight of water was prepared.

The coating solution prepared as described above was sprayed onto the inner wall of a stainless steel polymerization tank having an internal volume of 7 m8.

After such treatment, deionized water 3000k
g, 2000 kg of vinyl chloride, 0.6 kg of t-butyl peroxypivalate, and 2 to 2 partially saponified polyvinyl alcohols with a degree of saponification of 80 mol%, and the pressure was 5 kg at 57°C.
The reaction was continued until it reached /cm'.

After the reaction was completed, the unreacted vinyl chloride monomer was collected, and after the polymer slurry was discharged, the weight of the polymer attached to the inner wall of the polymerization tank was determined.

The polymer slurry was dehydrated and dried to obtain a product, and as shown in Table 1, the amount of polymer adhesion was significantly small according to the method of the present invention, and the adhering polymer could be easily washed away with simple water washing. Ta.

The physical properties of the obtained product were also excellent. Comparative example 1

Claims (1)

[Claims] 1. When vinyl chloride is polymerized alone or with monomers that can be copolymerized with vinyl chloride in an aqueous medium or in bulk, hemicellulose is applied in advance to the inner wall of the polymerization tank and to the parts of the equipment that come into contact with the monomer during the polymerization operation. A method for monopolymerizing or copolymerizing vinyl chloride, which method comprises coating the vinyl chloride.