JPH0255707A - Manufacture of vinyl chloride resin - Google Patents

Abstract

PURPOSE:To suppress foaming of a polymerization suspension thereby preventing it from overflowing, and further to make is possible to produce a product which has no fish eyes by using a polymerizer equipped with a reflux condenser to introduce previously a non-condensable gas into the polymerization system when a vinyl chloride resin is subjected to suspension polymerization. CONSTITUTION:When vinyl chloride monomer or a mixture of vinyl chloride monomer with other monomer polymerizable therewith is subjected to suspension polymerization using a polymerizer equipped with a reflux condenser in the gas phase part of the polymerizer or outside the polymerizer, a non-condensable gas is previously introduced into the polymerization system (N2 gas is preferred from the point of view of the cost, the influence on the quality of the product, and the like), then the polymerization is started, and the non-condensable gas is purged from the polymerization system. According to the process, the feed of polymerization can be increased without causing overflow of the polymerization suspension into a conduit connecting the polymerizer with the reflux condenser and into the reflux condenser, formation of scale in the conduit and the reflux condenser is prevented, and a product which is excellent in quality and does not have fish eyes or the like can be produced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing vinyl chloride resin, and more specifically, to a method for producing vinyl chloride resin by suspension polymerization using a polymerization reactor equipped with a reflux condenser. Concerning improvements in methods.

[Conventional technology and problems]

In the production of vinyl chloride resins, reflux condensers are often used to improve productivity and save energy. However, in suspension polymerization accompanied by cooling using a reflux condenser, a remarkable foaming phenomenon occurs in the polymerization system, especially in the early stage of polymerization, and foams of the polymerization suspension containing the polymerization initiator are generated in the polymerization reactor. Scale adheres to the inner wall of the gas phase, the conduit connecting the polymerization reactor and the reflux condenser, and the inner wall of the reflux condenser and forms scale, which reduces the thermal efficiency of the reflux condenser and causes unfavorable quality results such as fish eyes. In addition, it is accompanied by many difficulties such as requiring a great deal of labor to remove the scale.Also, even after the middle stage of polymerization, the stirring effect decreases as the viscosity of the polymerization suspension increases. As the hold amp of the suspension decreases, the hold amplifier of the suspension increases, and in extreme cases, the suspension overflows into the above-mentioned conduit or the reflux condenser, where it polymerizes and becomes a mass of scale. This not only makes it difficult to operate the reflux condenser normally, but also causes unfavorable quality results such as fish eyes.

In other words, in order to use the reflux condenser industrially and stably,
It is necessary to prevent overflow of the suspension into the reflux condenser due to foaming during the entire period of polymerization.

Under these circumstances, various studies have been conducted to prevent foaming of suspensions, and methods for suppressing foaming after the middle stage of polymerization have been proposed by adjusting the supply of cooling water to the reflux condenser. (Unexamined Japanese Patent Publication No. 57-212212)
, a method of using a combination of specific polymerization catalysts (Japanese Patent Publication No. 62-1605) has been proposed.

However, foaming at the initial stage of polymerization is caused by the dispersant used to stabilize suspension polymerization existing in the aqueous phase without being adsorbed to the vinyl chloride resin particles, and it is difficult to prevent this foaming. In terms of practical use, prevention of foaming at the initial stage of polymerization has been an important issue in the industrial use of reflux condensers, as they have significant negative effects such as coarsening of particle size and deterioration of fish eyes.

[Means for solving problems]

In view of these circumstances, the inventors of the present invention have conducted intensive research to suppress foaming at the initial stage of polymerization, and have found that by introducing a non-condensable gas into the polymerization system in advance, foaming of the polymerization suspension can be suppressed. The present invention was completed based on the discovery that it can be completely suppressed.

That is, the present invention uses a polymerization reactor equipped with a reflux condenser in the gas phase part of the polymerization reactor or outside the polymerization reactor to copolymerize vinyl chloride monomer alone or with vinyl chloride monomer. When carrying out suspension polymerization of a mixture with a monomer, a non-condensable gas is introduced into the polymerization system in advance to initiate polymerization, and then the non-condensable gas is purged out of the polymerization system. The content is a method for producing vinyl chloride resin.

By introducing a non-[41 gas] into the polymerization system in advance, condensation of the monomer in the reflux condenser at the initial stage of polymerization is prevented,
As a result, it is possible to suppress the polymerization suspension and foaming of the turbid liquid, thereby preventing the 'pAi% liquid from overflowing into the reflux condenser.

The timing of introducing the non-condensable gas into the polymerization system is not particularly limited, and may be before or after the introduction of water, monomers, etc. It is necessary to introduce it.

In addition, the amount of non-condensable gas introduced is preferably an amount equivalent to the gas phase space volume of the polymerization reactor and reflux 2IiL condenser at the polymerization reaction temperature, but it depends on the type of dispersant and additives used during polymerization. Since the degree of ease of foaming of the polymerization suspension differs, this introduction amount is not necessarily required.

After the initiation of polymerization, the introduced non-condensable gas is purged out of the polymerization system,
The reflux condenser can be operated by passing cooling water through the jacket side of the reflux condenser, but the timing is determined depending on the balance between the polymerization calorific value and the heat removal capacity of the polymerization reactor, and the foaming of the polymerization suspension. It may be selected appropriately taking into consideration ease of use.

Note that it is desirable to gradually purge the non-a-condensed gas from the top of the reflux condenser in consideration of ease of foaming of the polymerization suspension and control stability of the polymerization reaction temperature.

Further, the type of non-condensable gas is not particularly limited, but nitrogen gas is suitable from the viewpoint of cost and influence on the quality of the vinyl chloride resin used as a product.

In the present invention, other monomers that can be copolymerized with the vinyl chloride monomer include, for example, olefins such as ethylene and propylene, vinyl esters such as vinyl acetate and vinyl stearate, methyl acrylate, and methacrylic acid. Examples include acrylic esters such as methyl, acid esters and anhydrides such as maleic acid or fumaric acid, nitrile compounds such as acrylonitrile, or vinylidene compounds such as vinylidene chloride, which may be used alone or in combination of two or more. used.

The dispersant used in the present invention may be any known dispersant, such as partially saponified polyvinyl alcohol, vinyl acetate, etc.
Examples include maleic anhydride copolymer, styrene maleic anhydride copolymer, polyvinylpyrrolidone, gelatin, starch, methyl cellulose, hydroxypropyl cellulose, and the like, and these may be used alone or in combination of two or more.

Examples of the polymerization initiator used in the present invention include azo compounds such as azobisisobutyronitrile and azobis2,4-dimethylvaleronitrile, lauroyl peroxide, [-butylpivalate, di-2-ethylhexylperoxy] Known initiators include organic peroxides such as dicarbonate and isopropyl peroxydicarbonate, and these may be used alone or in combination of two or more.

Furthermore, in the present invention, mercapkune disulfide, trichloroethylene, etc. are used as polymerization degree regulators, and alcohols, saturated hydrocarbons such as hexane and heptane, aromatics such as benzene and toluene, DOP, etc. are used as additives.
There is no problem in using a stabilizer such as epoxy soybean oil in combination.

The polymerization reaction temperature range in the present invention is usually 40 to 75°C, but is not particularly limited.

[Action/Effect]

According to the present invention, when a vinyl chloride resin is subjected to suspension polymerization using a polymerization reactor equipped with a reflux condenser, a polymerization suspension is introduced into the conduit connecting the polymerization reactor to the reflux condenser and the reflux condenser. It is possible to increase the amount of polymerization charged without overflowing, prevent scale formation inside the conduit and reflux condenser, and eliminate product quality problems such as fish eyes. It becomes possible to use it continuously, and its industrial significance is extremely large.

〔Example〕

Examples and comparative examples of the present invention are shown below, but these do not limit the present invention in any way.

In addition, regarding the obtained vinyl chloride resin, fish eye was measured by the following method. That is, vinyl chloride resin 1
00 parts by weight, DOP 50 parts by weight, Tribase 3 parts by weight,
Thoroughly mix 0.5 parts by weight of stearic acid, 0.4 parts by weight of titanium dioxide, and 0.2 parts by weight of carbon blank.
A sheet was prepared by kneading it for 8 minutes with an 8-inch roll at 40°C to a thickness of 0.2 mm, and the sheet was 10 cm x 10 cm.
I counted the number of fish eyes inside.

Example space capacity is 0.05 ff? 1,7n with a reflux condenser with a heat transfer area of 5d? In a polymerization reactor, 12 parts of water in which 0.07 parts by weight of partially saponified polyvinyl alcohol was dissolved was added.
0 parts by weight of polymerization initiator di-2-ethylhexylhexyloxydicarbonate-1 and 0,024 parts by weight of t-
0.024 parts by weight of butyl peroxyneodecanoate was added, and after degassing, 0.39 Nn (nitrogen gas) was introduced, followed by 100 parts by weight of vinyl chloride monomer (+r to 600). After starting polymerization by raising the temperature of the polymerization reactor to 57°C, nitrogen gas was gradually purged out of the polymerization system from the top of the reflux condenser, and cooling water was gradually passed through the jacket of the reflux condenser. , from 1 hour after the start of polymerization until the internal pressure of the polymerization reactor drops by 1kir/- from the steady pressure and recovery of unreacted monomers begins, the amount of heat removed in the reflux condenser is 30.00kcal/Hr. Polymerization was carried out under conditions such that:

Using this method, a total of 10 batches of polymerization were performed without cleaning the inside of the reflux condenser, and then the reflux condenser was disassembled and the inside inspected. No polymer particles or scale were observed on the conduit connecting the two.

In addition, the number of fish eyes of the 10th batch product was good with 3 pieces.

Comparative Example Polymerization was carried out in the same manner as in Example, except that nitrogen gas was not introduced.

After performing the second batch of polymerization without cleaning the reflux condenser using this method, we inspected the inside of the reflux condenser and the conduit connecting the polymerization reactor and the reflux condenser, and found that overflowing polymer particles were present. , a film-like scale was formed.

The second batch of products had a very large number of fish eyes, 75 pieces.

Claims (1)

[Claims] 1. Vinyl chloride monomer alone or copolymerized with vinyl chloride monomer using a polymerization reactor equipped with a reflux condenser in the gas phase of the polymerization reactor or outside the polymerization reactor. When carrying out suspension polymerization of a mixture with other monomers that can be used, a non-condensable gas is introduced into the polymerization system in advance to initiate polymerization, and then the non-condensable gas is purged out of the polymerization system. A method for producing a vinyl chloride resin, characterized by: 2. The manufacturing method according to claim 1, wherein the non-condensable gas is nitrogen.