JPH01275610A - Manufacture of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To improve the quality and productivity, by polymerizing vinyl chloride in an aqueous medium in the presence of a polymerization initiator while specific parts of a polymerizer are washed with water. CONSTITUTION:Vinyl chloride and if desired, other vinyl monomer are polymerized in an aqueous medium in the presence of a polymerization initiator (e.g., di-2-ethylhexyl peroxydicarbonate), and a feed pipe which leads to the polymerizer and the inlet of the polymerizer are washed with a washing liquid comprising a non-aromatic solvent, preferably, of the given formula (wherein R<1-2> are each H or alkyl) and having a solubility parameter of 7.5-10.5[cal.cm<-3>]<1/2> after the initiator is introduced into a polymerizer.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing a vinyl chloride polymer, and in particular a method for producing a vinyl chloride polymer that can produce a high quality vinyl chloride polymer with high productivity. The present invention relates to a method for producing a polymer.

[Conventional technology]

During the production of vinyl chloride polymers, after the polymerization initiator is supplied into the polymerization vessel through the charging piping and the charging port of the polymerization vessel, the polymerization initiator adheres to and remains on the piping and the charging port, and the monomer content is lost during polymerization. May react with bodies to form polymer scale. When this polymer scale grows, it clogs the piping or the feed port, so the grown polymer scale must be removed.

Therefore, as a method to remove the polymerization initiator that adheres to and remains on the piping and the charging port and to prevent the formation of polymer scale, the piping and the charging port can be cleaned with an aromatic solvent such as toluene or a saturated hydrocarbon solvent such as isoparaffin. A method has been proposed in which the inlet is closed after washing to prevent the monomer from entering.

[Problem to be solved by the invention]

By the way, in the former method of cleaning with a saturated hydrocarbon solvent such as isoparaffin, the cleaning ability is low and it is difficult to perform sufficient cleaning. Solvents are mainly used. However, if this aromatic solvent remains in the product,
It volatilizes during molding, causing toxicity and odor problems. Therefore, there are restrictions on the amount of aromatic solvent used, and there is a problem in that sufficient washing cannot be performed and some amount of the polymerization initiator remains, resulting in the formation of polymer scale if polymerization is carried out over a long period of time. In addition, in the latter method of closing the loading port,
There was a problem in that monomers entered the piping through the gap in the closed charging port, resulting in the formation of polymer scale.

Therefore, the purpose of the present invention is to provide a high quality product that can prevent the formation of polymer scale, thereby achieving high productivity, and without the risk of causing toxicity problems even if the solvent remaining in the polymer evaporates during molding. An object of the present invention is to provide a method for producing a vinyl chloride polymer, which can yield a product polymer of .

[Means to solve the problem]

The present invention solves the above problems in a method for producing a vinyl chloride polymer in which vinyl chloride or a vinyl monomer containing vinyl chloride is polymerized in an aqueous medium, in which a polymerization initiator is added to a polymerization vessel. After introduction, the charging piping leading into the polymerization reactor and the charging port of the polymerization reactor are cleaned with a cleaning solution consisting of a non-aromatic solvent with a solubility parameter of 7.5 to 10.5 (cal-cm-'). The present invention provides a method for producing a vinyl chloride polymer.

In the present invention, the charging piping leading into the polymerization vessel and the charging port of the polymerization vessel mainly refer to the piping for supplying the polymerization initiator into the polymerization vessel and the initiator supply port in the polymerization vessel to which the piping is connected. However, other pipes and feed ports may be used, such as pipes and ports for supplying monomers or other additives.

In the present invention, the polymerization initiator that adheres to and remains in the piping and charging port has a solubility parameter of 7.5 to 10.5.
(cal cm-3) ””, preferably 8.0
The solubility parameter is less than 7.5 (cal-cm-') or 10.5. (cal・cm−3) If a non-aromatic solvent exceeding 1/t is used, the ability to wash the polymerization initiator will be poor, and the polymerization initiator will remain in the charging port, resulting in unreacted monomers. may grow into polymer scale, which may clog the charging port.

The above-mentioned cleaning liquid is a non-aromatic solvent having a solubility parameter having the above-mentioned value, and preferably has the following formula: [In the above formula, R
1 and R2 may be the same or different and are a hydrogen atom or an alkyl group, such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, tert-
Butyl group, n-pentyl group, n-hexyl group, etc.]
It is expressed as

Specific examples of non-aromatic solvents represented by the above formula include methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, isobutyl acetate, 5ec-butyl acetate, ethyl propionate, n-butyl propionate, and butyric acid. methyl,
Examples include ethyl butyrate and n-butyl butyrate.

These can be used alone or in combination of two or more.

The amount of cleaning liquid to be used is sufficient to clean the entire inner surface of the piping and charging port, and is not particularly limited, but it is not limited to the amount of solvent used in conventional methods that use aromatic solvents or the amount of solvent used in methods that use isoparaffin. The polymerization initiator can be removed even in a very small amount.

In the present invention, the polymerization initiator that is removed by cleaning the piping and charging port is not particularly limited, and any of those used in the conventional production of vinyl chloride polymers is effective. For example, percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, jetoxyethyl peroxydicarbonate;
- Perester compounds such as hexyl peroxy pivalate and α-cumyl peroxy neodecanate; acetyl cyclohexyl sulfonyl peroxide, 2,4.4-
) peroxides such as dimethylpentyl-2-peroxyphenoxyacetate, 3,5゜5-trimethylhexanoyl peroxide; azobis-2,4-dimethylvaleronitrile, azobis(4-methoxy-2,4-dimethylvaleronitrile) Examples include azo compounds such as nitrile). These can be used alone or in combination of two or more.

The method of the present invention can be applied to any conventionally known polymerization of vinyl chloride or vinyl monomer mixtures containing vinyl chloride.

The polymerization type is also not limited, and examples thereof include suspension polymerization, emulsion polymerization, solution polymerization, and bulk polymerization.

Examples of vinyl monomers other than vinyl chloride include ethylene, propylene, 1-butene, 1-pentene, 1-
hexene, 1-heptene, 1-octyne, ■-nonene,
α-olefins such as 1-decene, 1-undecene, 1-dodecene, 1-)lysocene, and 1-tetradecene, acrylic acid esters such as acrylic acid and methyl acrylate, and ethyl acrylate, methacrylic acid and methyl methacrylate, Methacrylic acid esters such as ethyl methacrylate,
Maleic acid and its esters, vinyl compounds such as vinyl acetate, vinyl propionate, and alkyl vinyl ether; maleic anhydride; acrylonitrile; styrene; vinylidene chloride; other monomers copolymerizable with vinyl chloride and mixtures thereof. .

When a dispersant is used in the polymerization of the present invention, the dispersant to be used is not particularly limited, and any conventionally most used dispersant may be used. Water-soluble cellulose ethers such as methylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose; partially saponified polyvinyl alcohol; acrylic acid polymers; water-soluble polymers such as gelatin; sorbitan monolaurate, sorbitan triolate, glycerin tristearate, ethylene oxide propylene Examples include oil-soluble emulsifiers such as oxide block copolymers; water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, and sodium laurate. These can be used alone or in combination of two or more.

Other conditions during polymerization in the method of the present invention, methods for charging the aqueous medium, vinyl chloride and other vinyl monomers, dispersants, etc. to the polymerization vessel may be carried out in the same manner as conventional methods and are not particularly limited. Further, the polymerization conditions such as the charging ratio and polymerization temperature are also the same.

Furthermore, if necessary, polymerization modifiers, chain transfer agents, pH adjusters, gelling improvers, antistatic agents, scale inhibitors, etc. that are commonly used in the production of vinyl chloride polymers may be added. be.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

Examples 1 to 3, Comparative Examples 1 to 3 On each side, 980 kg of deionized water, 382 g of partially saponified polyvinyl alcohol, and 143 g of water-soluble methylcellulose were charged into a stainless steel polymerization vessel with an internal volume of 2000 ffi, and the interior of the polymerization vessel was After degassing, 700 kg of vinyl chloride was charged. Next, 280 g of di-2-ethylhexyl oxydicarbonate) was introduced into the polymerization vessel using a metering pump, and then the pipes and charging ports through which the polymerization initiator passed were introduced using the solvents shown in Table 1 (Examples 1 to 2). 3 and Comparative Examples 1 and 2) Washed with 200 cc or not washed (Comparative Example 3).

While stirring the inside of the polymerization vessel, the temperature was raised to 57°C to start polymerization, and when the internal pressure of the polymerization vessel decreased to 6.0 kg/cd, the polymerization was stopped, and unreacted monomers were collected. After dehydration and drying, a vinyl chloride polymer was obtained.

After polymerization, disassemble the polymerization initiator charging piping and charging port, observe the state of polymer scale adhesion at these locations, and evaluate based on the criteria below. It was measured by the method. The results are shown in Table 1.

(Method for evaluating scale adhesion) A-----No scale adhesion.

B--- Some scale was attached.

c-1111--A large amount of scale adhered and blocked the feed port.

(Method for measuring residual solvent amount) 5 g of the obtained polymer was placed in a vial and heated at 130°C for 30 minutes.
After heat treatment for 0 minutes, the gas phase of the vial was analyzed by gas chromatography, and the measured amount of residual solvent was
Shown in pm.

〔Effect of the invention〕

The method for producing a vinyl chloride polymer of the present invention can prevent the formation of polymer scale, so there is no need to remove the polymer scale, and high productivity can be achieved. Furthermore, there is no risk of toxicity even if the cleaning solvent remaining in the product polymer evaporates during molding.
A vinyl chloride polymer that can be safely handled can be obtained.

Agent Patent attorney Comrade Iwamiya 1, Indication of the case Patent Application No. 104893 of 1988 2) Name of the invention Process for producing vinyl chloride polymers 3, Person making the amendment Relationship with the case Patent applicant address Chiyoda, Tokyo Ward Otemachi 2-6-1 Name (2
06) Shin-Etsu Chemical Co., Ltd. 4, Agent address: 1-2-36 Kanda Jimbocho, Chiyoda-ku, Tokyo 101
, Number of claims increased by amendment None 7, Subject of amendment Detailed explanation of the invention in the specification Column 8, Contents of amendment

Claims (2)

[Claims] (1) In a method for producing a vinyl chloride polymer, in which vinyl chloride or a vinyl monomer containing vinyl chloride is polymerized in an aqueous medium, a charging device that is passed into the polymerization vessel after introducing a polymerization initiator into the polymerization vessel. The solubility parameter is 7.5 to 10.5 [cal cm^
-^3] A method for producing a vinyl chloride polymer, which comprises washing with a cleaning liquid consisting of a non-aromatic solvent having the following ratio: -^3]^1^/^2. (2) A method for producing a vinyl chloride polymer according to claim 1, wherein the non-aromatic solvent has a general formula: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [In the formula, R^ 1 and R^2 may be the same or different,
hydrogen atom or alkyl group].