JPH01178508A - Preparation of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To obtain a vinyl chloride polymer of high quality with high productivity, by washing a feeding pipe and a feeding hole with a washing liq. at a specified temp. after a polymn. initiator is introduced into a polymn. tank when vinyl chloride monomer is polymerized in an aq. medium. CONSTITUTION:When vinyl chloride or a vinyl monomer contg. vinyl chloride is polymerized in an aq. medium. a polymn. initiator (e.g., diisopropyl peroxycarbonate) is introduced into a polymn. tank before a feeding pipe and a feeding hole of the polymn. tank communicating with the polymn. tank are washed with a washing liq. at such a temp. that the half-life of the polymn. initiator reaches 30min or less. As the formation of polymer scales can be prevented, it becomes unnecessary to remove the polymer scales and it is thereby possible to achieve a high productivity. Moreover, as it needs a smaller amt. of a washing agent to be used, the amt. of the solvent remaining in the produced polymer is small and it is thereby possible to obtain a polyvinyl chloride polymer of high quality.

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.

[Prior art] During the production of vinyl chloride polymers, after a polymerization initiator is supplied into a polymerization vessel through a charging pipe and a charging port of a polymerization vessel, the polymerization initiator adheres to and remains on the piping and charging port. It may react with monomers during polymerization 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. This scale removal work must be carried out while the manufacturing operation is stopped, which causes a decrease in productivity.

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 that the invention seeks to solve]

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 obtain high 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). It is an object of the present invention to provide a method for producing a vinyl chloride polymer that can produce the following.

[Means for solving problems]

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, a method for producing a vinyl chloride polymer, which comprises cleaning the charging pipe leading into the polymerization vessel and the charging port of the polymerization vessel with a cleaning solution at a temperature such that the half-life of the polymerization initiator is 30 minutes or less. It provides:

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 on the piping and charging port is cleaned with a heated cleaning solution, and the temperature of this cleaning solution is such that the half-life of the polymerization initiator used is 30 minutes or less. It is necessary. Here, the half-life of a polymerization initiator refers to the time it takes for the polymerization initiator to decompose and its concentration to become half of its initial concentration. Generally, this half-life shortens as the temperature increases, and furthermore, the polymerization starts. It also varies depending on the type of agent. When cleaning with a cleaning solution whose half-life exceeds 30 minutes, the decomposition of the polymerization initiator is slow;
Cannot be completely removed by washing. Therefore, the polymerization initiator remains in the piping and/or the charging port, reacts with unreacted monomers, generates polymer scale, and clogs the piping and/or the charging port.

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

In the present invention, the organic solvent is appropriately selected depending on the polymerization initiator used. In other words, if the temperature at which the half-life of the polymerization initiator used is 30 minutes or less is higher than the boiling point of the organic solvent, the organic solvent will evaporate inside the piping or polymerization tank during cleaning, and the piping will be damaged. If the internal pressure rises or the temperature exceeds the ignition point of the organic solvent, there is a risk of fire, which is dangerous. Therefore, the organic solvent for cleaning must be stable and have a boiling point, ignition point, and decomposition point higher than the temperature at which the half-life of the polymerization initiator used is 30 minutes or less.

The amount of cleaning liquid to be used for cleaning is not particularly limited, as long as it can clean the entire inner surface of the piping and charging port, but conventionally,
The effects of the present invention can be obtained with a very small amount without requiring the amount as proposed.

The method for heating the cleaning liquid to the above temperature may be any commonly used method and is not particularly limited.

In the present invention, the polymerization initiator that is removed by cleaning the piping and the feed port is not particularly limited, and may be one that is used in the conventional production of vinyl chloride polymers. For example, percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, jetoxyethyl peroxydicarbonate; t-butyl peroxyneodecanate,
t-7' chill peroxypivalate, t-to-t''z/
Perester compounds such as Lz peroxyvivalate and α-cumyl peroxyneodecanate; acetylcyclohexylsulfonyl peroxide, 2°4.4-trimethylpentyl-2-peroxyphenoxyacetate,
3.5. Peroxides such as 5-1-limethylhexanoyl peroxide; azo compounds such as azobis-2,4-dimethylvaleronitrile, azobis(4-methoxy-2,4-dimethylvaleronitrile), etc. Can be mentioned. 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, and 1-
Hexene, 1-heptene, 1-octene, ■-nonene,
α-olefins such as l-decene, 1-undecene, 1-dodecene, 1-tridecene, and 1-tetradecene, acrylic acid and its esters, methacrylic acid and its esters, maleic acid and its esters, vinyl acetate, propion Examples include vinyl compounds such as acid vinyl 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 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] The present invention will be described in detail below 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 methylcellulose were charged into a stainless steel polymerization vessel with an internal volume of 20,001 mm, and the inside of the polymerization vessel was desorbed. After that, 700 kg of vinyl chloride was charged. Next, polymerization initiator 2 shown in Table 1
After introducing 80 g into the polymerization vessel using a metering pump, the piping and charging port through which the polymerization initiator passed were heated to the temperature shown in Table 1 (example) or the solvent was heated to 20°C (comparative example).
Washed for 50 d.

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/cn, the polymerization was stopped and unreacted monomers were collected. , dehydrated and dried to obtain a vinyl chloride polymer.

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) ◎−−−−−−−No scale adhesion.

′　　O-・-scale was attached a little.

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

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

Examples 5-7, Comparative Examples 6-8 Same as Example 1 except that on each side, di-2-ethylhexyl peroxydicarbonate was used as a polymerization initiator and ethylbenzene at the temperature shown in Table 2 was used as a cleaning agent. Polymerization was carried out in the same manner, and the state of adhesion of the polymer scale was evaluated in the same manner.

The results are shown in Table 2.

〔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 agent is needed,
The amount of solvent remaining in the product polymer is small (high quality vinyl chloride polymer can be obtained).

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 A method for producing a vinyl chloride polymer, which comprises cleaning the charging port of a vessel with a cleaning solution at a temperature such that the half-life of the polymerization initiator is 30 minutes or less.