JPH02105807A - Preparation of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To prevent occurrence of polymer scales and to improve productivity by introducing a washing liquid with a specified linear velocity into a feed piping communicating with a polymn. vessel and a feed port of the polymn. vessel after a polymn. initiator is introduced into the polymn. vessel in the preparation of a polyvinyl chloride polymer. CONSTITUTION:Water, vinyl chloride and, if necessary, a copolymerizable vinyl monomer (e.g., ethylene), etc., are fed in a polymn. vessel and, in addition, a polymn. initiator (e.g., t-butyl peroxycarbonate) is introduced thereinto. Then, a feed pipe and a feed port where the polymn. initiator has passed through are washed with a washing liquid by making it flow at a linear velocity of 20cm/sec or higher by means of a pump. As the washing liquid, n-hexane, toluene, methanol, chloroform, acetone, etc., are used. A vinyl chloride polymer with high quality is obtd. by elevating the temp. and polymerizing the mixture.

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, there is a method of cleaning the piping and the charging port with a solvent, and a method of cleaning the piping and the charging port with a solvent. Methods have been proposed to prevent the intrusion of molecules.

[Problem to be solved by the invention]

However, in the former method of cleaning with a solvent, a large amount of solvent is required to completely remove the polymerization initiator that adheres to and remains on the piping and charging port, so the solvent remains in the polymer product. This can lead to quality deterioration and the generation of bad odors during molding. Therefore, there are restrictions on the amount of solvent to be used, and there is a problem 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 charging port, there is a problem in that the monomer enters into 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 increase productivity by preventing the formation of polymer scale, and to obtain high-quality product polymers by reducing the amount of solvent remaining in the polymer. An object of the present invention is to provide a method for producing a vinyl chloride polymer.

[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, add 20 cm of cleaning solution to the charging pipe leading into the polymerization vessel and the charging port of the polymerization vessel.
The purpose of the present invention is to provide a method for producing a vinyl chloride polymer, which is characterized in that washing is carried out by flowing at a linear velocity of /sec or more.

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 attached to and remaining on the piping and the charging port is controlled at a rate of 20 cm/sec or more, preferably 30 cm/s.
Clean by flowing a cleaning solution at a linear velocity of ec.

When the linear velocity of the cleaning liquid is less than 20 cm/sec,
The polymerization initiator remaining in the piping and charging port cannot be sufficiently washed away, and the polymerization initiator remains in the charging port, etc. This causes unreacted monomers to grow and become polymer scale, clogging the charging port, etc. There is a risk.

The linear velocity of the cleaning liquid can be increased to 20 cm/sec or more by reducing the cross-sectional area of the pipes and the outlet in the polymerization vessel at the charging port, or by increasing the pressure of the cleaning liquid supply pump. good.

The cleaning liquid used for the above cleaning is not particularly limited, and -a
Any suitable organic solvent may be used. For example, aliphatic hydrocarbons such as n-hexane, n-hebutane, and isooctane; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; alcohols such as methanol, ethanol, and 2-propanol; methyl chloride, chloride Halogenated hydrocarbons such as methylene and chloroform; Ethers such as ethyl ether and dichloroethyl ether; Ketones such as acetone, methylacetone, and methyl ethyl ketone; Esters such as methyl formate, methyl acetate, n-butyl acetate, and ethyl formate and derivatives thereof. These may be used alone or in combination of two or more.

The amount of cleaning liquid used is sufficient to clean the entire inner surface of the piping and charging port, and is not particularly limited, but it may be smaller than the amount of solvent used in conventional methods, and even a very small amount can remove the polymerization initiator. can.

In the present invention, the polymerization initiator to be removed by cleaning the piping and the charging port is not particularly limited, and may be any initiator used in conventional production of vinyl chloride polymers. For example, percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, jetoxyethyl peroxydicarbonate; t-butyl peroxyneodecanate, t-butyl peroxybivalate, t- Perester compounds such as hexyl peroxy bivalate, α-cumyl peroxy neodecanate; acetyl cyclohexyl sulfonyl peroxide, 2,4.4-1-
Peroxides such as trimethylpentyl-2-peroxyphenoxyacetate and 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 not limited either, and examples thereof include suspension polymerization and emulsion polymerization.

Examples of vinyl monomers other than vinyl chloride include ethylene, propylene, ■-butene, 1-pentene, ■-hexene, 1-heptene, 1-octene, ■-nonene, and
α-olefins such as -decene, l-undecene, 1-dodecene, 1-1-lysocene, ■-tetradecene, acrylic acid and methyl acrylate, acrylic acid esters such as 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 used is not particularly limited, and any conventionally commonly 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 bromine Oil-soluble emulsifiers such as bilene oxide block copolymer; 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 4, Comparative Examples 1 to 5 On each side, 980 kg of deionized water, 382 g of partially saponified polyvinyl alcohol, and 143 g of water-soluble methyl cellulose were charged into a stainless steel polymerization vessel with an internal volume of 200,042 mm, and the inside of the polymerization vessel was After degassing, 700 kg of vinyl chloride was charged. Next, 280 g of the polymerization initiator shown in Table 1 was introduced into the polymerization vessel using a metering pump, and then a cleaning solution adjusted to the linear velocity shown in Table 1 was flowed through the piping and charging port through which the polymerization initiator had flowed. Washed. However, in Comparative Example 5, no washing was performed.

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/c4, the polymerization was stopped. Unreacted monomers were collected and dehydrated. ,
A vinyl chloride polymer was obtained by drying.

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...--A little scale was attached.

C.--------A large amount of scale adhered and blocked the charging 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. Moreover, since only a small amount of cleaning liquid is needed,
The amount of solvent remaining in the product polymer is small, and a high quality vinyl chloride polymer can be obtained.

Agent Patent Attorney Iwamiya Comrade Procedural Amendment (Voluntary) 1. Indication of the case Patent Application No. 259036 of 1988 2. Name of the invention Address 4. Agent Address 2-6-1 Otemachi, Chiyoda-ku, Tokyo ( 206) Shin-Etsu Chemical Co., Ltd. 1-2-3 Kanda Jimbocho, Chiyoda-ku, Tokyo 101 Date of amendment order Number of claims increased by voluntary amendment None Subject of amendment
Contents of amendment in the Detailed Description of the Invention column of the specification Table 1 on page 11 of the specification is amended as shown in the attached sheet.

Claims (1)

[Claims] 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, after a polymerization initiator is introduced into the polymerization vessel, the preparation piping leading to the polymerization vessel and the polymerization 1. A method for producing a vinyl chloride polymer, which comprises washing by flowing a washing liquid through a charging port of a vessel at a linear velocity of 20 cm/sec or more.