JPH01158008A - Production of vinyl chloride based polymer - Google Patents

Abstract

PURPOSE:To obtain a polymer having excellent quality with high productivity, by introducing an oil-soluble polymerization initiator into a polymerizer and washing a pipe and charging inlet with water and steam in suspension polymerizing vinyl chloride monomer in an aqueous medium. CONSTITUTION:Vinyl chloride monomer or a mixture of a vinyl based monomer consisting essentially of the vinyl chloride (e.g., containing >=50wt.% vinyl chloride and further vinyl acetate, ethyl acrylate) is suspension polymerized in an aqueous medium. In the process, an oil-soluble polymerization initiator (e.g., diisopropyl peroxydicarbonate or potassium persulfate) is introduced into a polymerizer and a pipe and charging inlet leading thereto are then washed with water or steam (preferably water at >=90 deg.C) to produce the aimed polymer. Thereby scales are prevented from sticking to the charging inlet for the polymerization initiator and improvement in quality is contrived without any residual solvent in the product.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for producing a vinyl chloride polymer, particularly a method for producing a vinyl chloride polymer that has excellent product quality and high productivity. be.

(Prior art and its problems) When a vinyl chloride polymer is subjected to suspension polymerization in an aqueous medium, the oil-soluble polymerization initiator used for this process remains attached to the pipes leading into the polymerization vessel and the charging port. However, there is a problem in that monomers that adhere there during polymerization grow as polymer scale, eventually clogging the charging port. As a countermeasure against this problem, methods have been proposed in which the piping and the charging port are cleaned with a polymerization initiator solvent, and the charging port is further closed after cleaning with the solvent.

However, if a sufficient amount of solvent is used to completely remove the polymerization initiator in the former method, the solvent will remain in the vinyl chloride polymer of the product and may cause odor problems during molding. As there are restrictions on the amount of solvent used, sufficient cleaning cannot be carried out, and some amount of polymerization initiator remains in the charging port. Polymer scale grows due to the monomer, which also clogs the charging port. On the other hand, even with the latter method, in which the charging port is closed after a certain amount of cleaning, a small amount of monomer may enter the charging port through the gap, which also creates polymer scale and clogs the charging port. Something happened.

As mentioned above, during suspension polymerization of vinyl chloride polymer using an oil-soluble polymerization initiator, if the polymerization operation is continued for a long period of time, if a solvent is used to the extent that the charging port is not clogged with adhesion scale, the solvent will be mixed into the vinyl chloride polymer. If the type and amount of solvent is adjusted to avoid this problem, the inlet will become clogged with scale, making it necessary to remove the scale, so it is hoped that a good solution will emerge. Ta.

(Means for solving the problem) The present invention was achieved as a result of intensive research to solve this problem, and it uses a vinyl chloride monomer or a mixture of vinyl monomers mainly composed of vinyl chloride. When carrying out suspension polymerization in an aqueous medium, after introducing an oil-soluble polymerization initiator into the polymerization vessel, the piping and charging port leading thereto are washed with water or steam. To explain this, the present invention provides a method for producing an oil-soluble polymerization initiator after charging it into a polymerization system, in order to prevent polymer scale from adhering to the charging piping and charging port. Immediately after charging the oil-soluble polymerization initiator into the polymerization tank, water or water at a temperature such that the half-life of the polymerization initiator used is within 1 hour is passed through the tank to recover unreacted monomers and the polymerization operation is started. By continuing until the end of the polymerization to remove residual polymerization initiator and preventing unreacted monomers from entering the charging port, or by washing the above-mentioned areas with hot water or steam at 90°C or higher, This is achieved by completely removing the residual polymerization initiator.

Therefore, the quality of the water used in these methods may be the same as the water normally used in polymerization systems, and the amount of water depends on the state in which it is constantly flowing throughout the charging port, that is, the opening diameter of the charging port. , as long as it is always filled with water.

Further, the water used here is preferably kept at a temperature such that the half-life of the polymerization initiator used is within 1 hour. According to this, the polymerization initiator remaining in the polymerization initiator charging pipe and the charging port is decomposed and washed away, so it is thought that scale adhesion can be prevented. It should be noted that the temperature of the water may be maintained at a temperature at which the half-life of the polymerization initiator is within 1 hour for a certain period of time for one polymerization system, and does not need to be maintained throughout the period of washing with water.

On the other hand, cleaning using hot water or steam at 90°C or higher,
It is possible to use the steam available in the factory as a heat source, which has the advantage of not requiring any special equipment, and because it completely decomposes residual polymerization initiators in a short period of time, cleaning time can be reduced. The time can be shortened to less than one hour, and depending on the type of polymerization initiator used, similar effects may be obtained in several seconds.

In addition to vinyl chloride monomers, the starting materials used for this polymerization include vinyl chloride monomers and a mixture of vinyl monomers that are copolymerizable with vinyl chloride (50% by weight or more of vinyl chloride). The comonomer copolymerized with vinyl chloride is vinyl acetate.

Vinyl esters such as vinyl propionate; acrylic esters or methacrylic esters such as methyl acrylate and ethyl acrylate; olefins such as ethylene and propylene; maleic anhydride; acrylonitrile; styrene; vinylidene chloride; and other copolymers with vinyl chloride Examples include possible monomers.

The suspending agent used in this suspension polymerization may be those commonly used in the past, such as water-soluble cellulose ethers such as methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose; acrylic acid polymers, gelatin, etc. Water-soluble polymers: oil-soluble emulsifiers such as sorbitan monolaurate, sorbitan triolate, glycerin tristearate, and ethylene oxide propylene oxide block copolymers; water-soluble such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, and sodium laurate There are emulsifiers, etc., and these are used singly or in combination of two or more.

The polymerization initiator may also be one conventionally used in vinyl chloride polymerization, such as percarbonates such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and jetoxyethyl peroxydicarbonate. Compound; perester compound such as t-butyl peroxyneodecanate, t-butylperoxypivalate, -hexylperoxypivalate, α-cumylperoxyneodecanate; acetylcyclohexylsulfonyl peroxide, 2.4
．． Peroxides such as 4-trimethylpentyl-2-peroxyphenoxyacetate and 3,5.5-trimethylhexanoyl peroxide; azobis-2,4-dimethylvaleronitrile, azobis(4-methoxy-2,4-dimethyl (valeronitrile); furthermore, potassium persulfate, ammonium persulfate, hydrogen peroxide, etc., and these can be used alone or in combination of two or more.

The other conditions for this polymerization, the method of charging the aqueous medium, vinyl chloride monomer, other comonomers, suspending agent, etc. The polymerization conditions such as the degree of polymerization may also be the same.

Further, if necessary, polymerization regulators, chain transfer agents, pH regulators, gelling improvers, antistatic agents, scale inhibitors, etc., which are appropriately used in vinyl chloride polymerization, may be added.

(Examples) Hereinafter, specific aspects of the present invention will be explained using Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 In a stainless steel polymerization vessel with an internal volume of 2000 Q, 980 kg of deionized water and 3 ml of partially saponified polyvinyl alcohol were placed.
After charging 82 g of water-soluble methyl, 143 g of water-soluble cellulose and deaerating the inside of the polymerization vessel, 700 kg of vinyl chloride monomer was charged, and then 280 g of di-2-ethylhexyl peroxydicarbonate was added using a metering pump. Pour 2Q of deionized water into the preparation, the preparation piping, and the preparation port.
Washed with. Within that 2Q.

The temperature for 500cc was 80°C. After the start of the polymerization until the unreacted monomer was collected at the end of the polymerization, deionized water was continued to flow at a flow rate of 10 ml/min. As for the polymerization operation, the temperature inside the vessel was raised to 66°C while stirring to start polymerization, and when the internal pressure of the polymerization vessel decreased to 6.0 kg/aIG, the polymerization was stopped and unreacted monomers were collected and dehydrated. After drying, a vinyl chloride polymer according to the present invention was obtained.

After this polymerization, the polymerization initiator charging piping and charging port were disassembled, and the state of polymer scale adhesion at these locations was evaluated using the following criteria, and the amount of residual solvent in the polymer was measured using the following criteria. The results measured by this method are shown in Table 1.

(Method for evaluating scale adhesion) O: No scale adhesion.

0... Some scale was attached.

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

(Method for Measuring the Amount of Remaining Solvent) 5 g of the polymer was placed in a vial, heat treated at 130° C. for 30 minutes, and the gas phase of the vial was analyzed by gas chromatography, which was expressed in ppm.

Example 2゜After repeating the same polymerization as in the previous example 100 times, the same 111
The results of the observations and measurements are also listed in Table 1.

Example 3 After repeating the same polymerization as in Example 1 1000 times, the same wt observation and measurement were performed and the results are also listed in Table 1.

Example 4゜ Polymerization was carried out in the same manner as in Example 1, except that instead of washing with 2Q of deionized water, washing was performed with steam at a pressure of 15 kg/cdG for 3 minutes, and the same a observation and measurements were performed. 1
Also listed in the table.

Example 5゜ After repeating the same polymerization as in the previous example 100 times, the same 11!
The results of the observations and measurements are also listed in Table 1.

Example 6 After repeating the same polymerization as in Example 4 1000 times, the same observations and measurements were performed, and the results are also listed in Table 1.

Comparative Example 1 In Example 1, the polymerization initiator charging pipe and charging port were cleaned with 300 cc of toluene instead of continuous cleaning with deionized water, and then with 50 cc of deionized water.
Polymerization was carried out in exactly the same manner except that 0 cc was used, and after the polymerization, the same observations and measurements were performed. The results are also listed in Table 2.

Comparative Example 2゜ Polymerization was carried out in exactly the same manner as in the previous example except that n-hexane was used instead of toluene for washing, and the results of similar observations and measurements are also shown in Table 2.

Comparative Example 3゜Polymerization was carried out in exactly the same manner as in Comparative Example 1, except that the charging piping and charging port were not washed with toluene and deionized water after charging the polymerization initiator, and the same observations and measurements were carried out. The results are also listed in Table 2.

(Effects of the Invention) According to the present invention, (1) Scale adheres to the polymerization initiator charging port, clogging it, requiring unnecessary labor to remove it, and reducing productivity.

■No solvent remains in the polymerized product, improving quality.

Procedural amendment

Claims (1)

[Claims] 1. When a vinyl chloride monomer or a mixture of vinyl monomers mainly composed of vinyl chloride is subjected to suspension polymerization in an aqueous medium, an oil-soluble polymerization initiator is added to the polymerization vessel. 1. A method for producing a vinyl chloride polymer, which comprises washing the pipes and charging port leading to the vinyl chloride polymer with water or steam after introducing the vinyl chloride polymer. 2. The method for producing a vinyl chloride polymer according to claim 1, wherein the water used for washing is at a temperature such that the half-life of the polymerization initiator used is within 1 hour. 3. The method for producing a vinyl chloride polymer according to claim 1, wherein the water used for washing has a temperature of 90° C. or higher.