JPH11279143A - Preservation of 2-mercaptoethanol and production of vinyl chloride-based polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preserving 2-mercaptoethanol, capable of stably preserving the 2-mercaptoethanol used as a chain transfer agent on the polymerization of vinylic monomers, and to provide a method for producing a vinyl chloride-based polymer capable of giving molded products having excellent thermal stability on the molding processes and excellent initial colorability by using the 2-mercaptoethanol. SOLUTION: This 2-mercaptoethanol is preserved by a means capable of reducing the concentration of dithiodiethanol, an impurity produced from the preserved 2-mercaptoethanol, to <=10 wt.% based on the 2-mercaptoethanol, when the 2-mercaptoethanol is preserved in such a state as giving a dithiodiethanol concentration of >=10 wt.% based on the 2-mercaptoethanol, when simply preserved in a metal tank. A vinyl chloride-based monomer is polymerized using the 2-mercaptoethanol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for preserving 2-mercaptoethanol used as a chain transfer agent in the polymerization of vinyl monomers. The present invention also relates to a method for producing a vinyl chloride polymer, and more particularly, to a method for producing a vinyl chloride polymer which is excellent in thermal stability during molding and can provide a molded article having excellent initial coloring properties. It is.

[0002]

2. Description of the Related Art Conventionally, it has been known to add a chain transfer agent to a polymerization system when producing a vinyl polymer having a relatively low degree of polymerization, especially a vinyl chloride polymer. As the chain transfer agent, saturated hydrocarbons such as n-hexane, unsaturated chlorinated hydrocarbons such as trichloroethylene, aldehydes such as acetaldehyde, and mercaptans such as 2-mercaptoethanol are disclosed.

Among these chain transfer agents, 2-mercaptoethanol, in particular, has a relatively high chain transfer efficiency, can control the degree of polymerization with a small amount, and has little adverse effect on the quality of the polymer. Widely used. The storage and preparation equipment for 2-mercaptoethanol is usually installed in a high-pressure gas facility, and therefore requires a metal tank, particularly a stainless steel tank, and a supply piping system. Also, 2-mercaptoethanol is used by storing a certain amount in the tank in order to simplify the carrying-in work and to automate the preparation equipment, and the amount used is very small. It tends to be preserved for a period.

[0004] For further method of adding the 2-mercaptoethanol polymerization system, in terms such as to relax the refill when working mercaptan odor to the point and storage tanks increase the quantitative performance, water or an organic solvent such as methanol It is diluted and added to the polymerization system. With such preparation equipment and method, 2
-When mercaptoethanol is used, the deterioration of 2-mercaptoethanol in ancillary facilities such as tanks and charging pipes during storage progresses, and a significant increase in dithiodiethanol as an impurity is observed.

[0005] A polymer obtained by using 2-mercaptoethanol having an increased amount of dithiodiethanol has problems such as poor thermal stability at the time of molding and deterioration of the initial coloring property of a molded article.

[0006]

Accordingly, an object of the present invention is to reduce the generation of dithioethanol as an impurity when 2-mercaptoethanol used as a chain transfer agent is stored in a metal tank, particularly a stainless steel tank. In the method of preserving and preserving, and the suspension polymerization method of the vinyl chloride polymer using the same, it is possible to obtain a molded article having excellent heat stability at the time of molding and obtaining a molded article having good initial coloring property. An object of the present invention is to provide a method for producing a united product.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have reached the present invention. That is, the present application includes the following inventions and embodiments.

[0008] In the method of storing 2-mercaptoethanol in a metal tank, the concentration of dithiodiethanol, which is an impurity generated from the stored 2-mercaptoethanol, is reduced to 10% by weight or less based on 2-mercaptoethanol. how to.

When 2-mercaptoethanol is stored in a state where the concentration of dithiodiethanol, which is an impurity, is simply 10% by weight or more based on 2-mercaptoethanol when 2-mercaptoethanol is simply stored in a metal tank, 2-mercaptoethanol to be stored is used. The concentration of dithiodiethanol, which is an impurity produced from
A method of preserving by means such that it becomes less than weight%.

[0010] The method for storing 2-mercaptoethanol described in the above or [2], wherein the method for storing 2-mercaptoethanol is storing in a metal tank in a state of being diluted with a stock solution of 2-mercaptoethanol or deoxygenated water.

The method for storing 2-mercaptoethanol according to any one of the above items, wherein the method for storing 2-mercaptoethanol uses a metal tank and ancillary equipment obtained by treating the inside of the metal tank and ancillary equipment with a coating material. How to save.

[0012] The method for storing 2-mercaptoethanol according to any one of [1] to [3], wherein when 2-mercaptoethanol is stored in the tank, a gas phase portion in the tank is replaced with an inert gas.

When a vinyl chloride-based monomer or a mixture of a vinyl chloride-based monomer and a copolymerizable monomer is subjected to suspension polymerization in an aqueous medium in the presence of an oil-soluble initiator, a chain transfer agent is used. Using 2-mercaptoethanol stored in a metal tank at a concentration of dithiodiethanol, which is an impurity in 2-mercaptoethanol, of 10% by weight or less based on 2-mercaptoethanol. A method for producing a vinyl chloride-based polymer, characterized by comprising:

[0014] The method for producing a vinyl chloride-based polymer according to the above, wherein the method for storing 2-mercaptoethanol in a metal tank is the method for storing the 2-mercaptoethanol stored in the metal tank.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The concentration of dithiodiethanol contained in 2-mercaptoethanol used in the present invention is 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight or less based on 2-mercaptoethanol. The purity of commercially available 2-mercaptoethanol is very high, but it contains trace amounts of impurities such as dithiodiethanol.

For normal use, such impurities do not cause any problem. However, since this high-purity 2-mercaptoethanol is charged into a polymerization vessel, it is stored in a metal tank, particularly a stainless steel tank. When used in the storage tank, the influence of oxygen in the storage tank or the metal component in the stainless steel material serves as a catalyst, and 2-mercaptoethanol, which is pure, gradually changes to dithiodiethanol, which is an impurity. As a result, dithiodiethanol which is an impurity in 2-mercaptoethanol increases. Other trace amounts of impurities contained in 2-mercaptoethanol hardly change, and what changes after storage is the concentrations of 2-mercaptoethanol and dithiodiethanol.

In particular, when 2-mercaptoethanol is stored in a tank after being diluted with water that has not been deoxygenated and used, the concentration of dithiodiethanol relative to 2-mercaptoethanol in a short period of time (about 1 to 2 weeks) is reduced. 10% by weight
Tend to exceed. When 2-mercaptoethanol having a dithiodiethanol concentration of more than 10% by weight is used for polymerization as a chain transfer agent for a vinyl monomer, for example, a vinyl chloride-based polymer obtained by polymerizing a vinyl chloride-based monomer using the same is used. The thermal stability of the coalescence is poor, and the initial colorability of the molded product is also poor.

Hereinafter, a method for producing a vinyl chloride polymer using 2-mercaptoethanol as a chain transfer agent will be described, but the method of the present invention is not limited to polymerization of vinyl chloride.

If the concentration of dithiodiethanol contained in the 2-mercaptoethanol used in the present invention is within the above range, there is no particular limitation on the method of addition. For example, the compound may be added at once, dividedly added, continuously added. The method of adding is mentioned. There is no particular limitation on the timing of addition, and examples thereof include a method of adding during the preparation of the polymerization material and a method of adding during the polymerization.

The method of preserving 2-mercaptoethanol used in the present invention is not particularly limited as long as the concentration of dithiodiethanol can be maintained within the above range, but it is desired to maintain the concentration within the range for a long period of time. In this case, it is preferable to use 2-mercaptoethanol diluted in a stock solution or deoxygenated water in a tank and a charging pipe for use. Further, the inside of a metal storage tank and the charging pipe is treated with a coating material. By using what was done,
It is possible to prevent an increase in dithiodiethanol.

As the coating material treatment, Teflon lining,
Glass lining and the like can be mentioned. In addition, by replacing the gas phase inside the storage tank with an inert gas, it is possible to further prevent an increase in dithiodiethanol. Examples of the type of the inert gas include helium, nitrogen, and argon.

In the present invention, a commonly used suspension polymerization method can be applied as it is, for example, specifically, the following method is used.

Deionized water, a dispersion stabilizer and a polymerization initiator are charged into a jacketed pressure-resistant polymerization vessel equipped with a stirrer, and the pressure is reduced. Next, a vinyl chloride-based monomer is injected under pressure, and the inside of the polymerization vessel is heated while stirring to initiate polymerization. As the polymerization conditions at that time, the polymerization temperature was 20 to 90 ° C., and the polymerization time was 1
After completion of the polymerization, the unreacted vinyl chloride-based monomer is recovered, and the slurry is taken out and dehydrated and dried to obtain a vinyl chloride-based polymer.

The polymerization initiator used in the present invention may be any one generally used as a polymerization initiator in a suspension polymerization method. Examples thereof include tert-butylperoxyneodecanoate and tert-hexylperoxyneo. Perester compounds such as decanoate, tert-hexylperoxypivalate, tert-butylperoxypivalate, α-cumylperoxyneodecanoate, tert-hexylperoxyneohexanoate; diisopropyl peroxydicarbonate , Di-2
-Ethylhexyl peroxydicarbonate, di-2-
Percarbonate compounds such as ethoxyethylperoxydicarbonate and dimethoxyisopropylperoxydicarbonate; peroxide compounds such as benzoyl peroxide, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, and acetylcyclohexyl peroxide; Examples include azo compounds such as' -azobisisobutyronitrile, 2,2'-azobis-2, and 4-dimethylvaleronitrile, which can be used alone or in combination of two or more.
As the dispersion stabilizer used in the present invention, for example,
Water-soluble or oil-soluble partially saponified polyvinyl alcohol; methylcellulose, hydroxyethylcellulose,
Water-soluble cellulose such as hydroxypropylcellulose and hydroxypropylmethylcellulose; water-soluble polymers such as acrylic acid polymer, methylvinylether-maleic anhydride copolymer, styrene-maleic anhydride copolymer, gelatin; sorbitan monolaurate, sorbitan Monostearate, glycerin monostearate,
Examples include oil-soluble emulsifiers such as ethylene oxide propylene oxide block copolymers, and water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, and sodium laurate. These may be used alone or in combination of two or more. can do.

In the present invention, when carrying out the present invention, a vinyl monomer copolymerizable with a vinyl chloride monomer or a polymer graft polymerizable with a vinyl chloride monomer is added as necessary. And may be polymerized.

In the present invention, the vinyl chloride monomer is
A vinyl chloride monomer or a mixture of a vinyl monomer and a vinyl monomer copolymerizable therewith.

Examples of the vinyl monomer copolymerizable with the vinyl chloride monomer include vinyl esters such as vinyl acetate, vinyl propionate, vinyl caproate, vinyl laurate and vinyl stearate; ethylene, propylene, Olefins such as isobutylene; alkyl or aryl vinyl ethers such as isobutyl vinyl ether, phenyl vinyl ether and octyl vinyl ether; halogenated olefins such as vinylidene chloride, vinyl fluoride, allyl chloride and vinyl bromide; ethyl acrylate;
-Butyl acrylate, n-butyl methacrylate, 2
-Ethylhexyl acrylate, 2-ethylhexyl methacrylate, acrylic acid or methacrylic acid esters such as stearyl methacrylate; acrylic acid, methacrylic acid, crotonic acid, acrylonitrile, maleic anhydride, and acrylic derivatives such as itaconic anhydride; These can be used alone or in combination of two or more. Examples of the polymer that can be graft-copolymerized with a vinyl chloride monomer include ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer, chlorinated polyethylene, polyurethane, polybutadiene-styrene-methyl methacrylate. Copolymer (MB
S), polybutadiene-acrylonitrile- (α-methyl) styrene copolymer (ABS), polybutyl acrylate, butyl rubber, polystyrene, styrene-butadiene copolymer, cross-linked acrylic rubber, and the like. It can be used in combination of the above.

In the production method of the present invention, before, during or after the polymerization, other polymerization additives such as a gelling improver, a pH adjuster, an antistatic agent, a crosslinking agent,
Stabilizers, fillers, antioxidants, scale inhibitors and the like may be used.

[0029]

EXAMPLES Hereinafter, the production method of the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In Examples and Comparative Examples, the thermal stability test and the initial coloring test were performed by the following methods.

(Thermal stability test) Vinyl chloride polymer 10
0 parts by weight, 3 parts by weight of a dibutyltin malate-based stabilizer, and 0.2 parts by weight of a fatty acid ester-based lubricant are blended, and 150 g of the blend is kneaded for 5 minutes with a 6-inch roll at a roll surface temperature of 150 ° C. to a thickness of 1 mm. Was obtained. The time required for the test piece cut from the sheet molded body to be blackened in an oven at 190 ° C. was measured. The longer the time until the blackening, the better the thermal stability.

(Initial coloring test) Vinyl chloride polymer 1
00 parts by weight, 3 parts by weight of a dibutyltin malate-based stabilizer, and 0.2 parts by weight of a fatty acid ester-based lubricant are blended, and 150 g of the blend is kneaded for 5 minutes with a 6-inch roll at a roll surface temperature of 150 ° C., to a thickness of 1 mm. Was obtained.
Subsequently, the sheet compacts were laminated, and were heated at 175 ° C. and 50 k
A press molded body having a thickness of 5 mm was obtained under the conditions of g / cm 2 and pressurization for 15 minutes. The initial coloring property is determined by the yellow value (Y
I) was obtained by measuring with a color difference meter. The smaller the value of YI, the better the initial coloring property.

Examples 1 to 5 Table 1 shows the results of storage of 2-mercaptoethanol in Example 1. The results of polymerization of vinyl chloride by using it were also shown.

140 parts by weight of deionized water (14000 kg), 0.10 part by weight of partially saponified polyvinyl alcohol, tert-butyl peroxypivalate were placed in a stainless steel polymerization vessel equipped with a stirrer and a jacket having an inner volume of 30 m ^3. 0.05 parts by weight and 0.03 parts by weight of 2-mercaptoethanol containing dithiodiethanol shown in Table 1 were put therein, and the pressure was reduced. Then, vinyl chloride monomer 100
A part by weight was charged, the temperature was raised to 61 ° C. through hot water in a jacket while stirring the inside of the polymerization vessel, and polymerization was started while maintaining this temperature. When the pressure in the polymerization reactor dropped from the pressure in the steady state of the polymerization reaction by 3.0 kg / cm ² , the unreacted vinyl chloride monomer was recovered. The polymerization time was 6 hours.

The slurry was taken out of the polymerization vessel and dehydrated and dried to obtain a vinyl chloride polymer at a polymerization conversion of 85%. The evaluation results of the obtained vinyl chloride polymer are shown in Table 1. The obtained vinyl chloride polymer was excellent in heat stability and initial coloring property.

The dithiodiethanol in 2-mercaptoethanol before storage was 0.2% by weight.

Comparative Example 1 When stored in a stainless steel tank with a 15% by weight aqueous solution in Table 1 for 2 weeks, dithiodiethanol was increased to 16% by weight.

Example 1 except that 2-mercaptoethanol containing dithiodiethanol shown in Table 1 was used.
The same operation as described above was performed. The polymerization time was 6 hours.

When the slurry was taken out of the polymerization vessel and dehydrated and dried, a vinyl chloride polymer was obtained at a polymerization conversion of 85%. The evaluation results of the obtained vinyl chloride polymer are shown in Table 1. The obtained vinyl chloride polymer was inferior in heat stability and initial coloring property.

[0039]

[Table 1]

[0040]

According to the present invention, it is possible to obtain a vinyl chloride polymer which is excellent in thermal stability at the time of molding and can process a molded article having good initial coloring property. The value is extremely high.

Claims (7)

[Claims] 1. A method for storing 2-mercaptoethanol in a metal tank, wherein the concentration of dithiodiethanol, which is an impurity generated from the stored 2-mercaptoethanol, becomes 10% by weight or less based on 2-mercaptoethanol. How to save. 2. When 2-mercaptoethanol is simply stored in a metal tank, the concentration of dithiodiethanol as an impurity is 10% by weight based on 2-mercaptoethanol.
A method of preserving in such a state that the concentration of dithiodiethanol, which is an impurity generated from the preserved 2-mercaptoethanol, is 10% by weight or less based on 2-mercaptoethanol. 3. The method for preserving 2-mercaptoethanol according to claim 1 or 2, wherein the 2-mercaptoethanol is stored in a metal tank after being diluted with a stock solution of 2-mercaptoethanol or deoxygenated water. How to store mercaptoethanol. 4. The method for preserving 2-mercaptoethanol according to any one of claims 1 to 3, wherein a metal tank and ancillary equipment obtained by treating the inside of the metal tank and ancillary equipment with a coating material are used. A method for storing 2-mercaptoethanol according to the above. 5. The method according to claim 1, wherein when 2-mercaptoethanol is stored in the tank, the gas phase in the tank is replaced with an inert gas.
-How to store mercaptoethanol. 6. A suspension polymerization of a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a copolymerizable monomer in an aqueous medium in the presence of an oil-soluble initiator. In a method in which 2-mercaptoethanol used as a transfer agent is stored and used in a metal tank, the concentration of dithiodiethanol, which is an impurity in 2-mercaptoethanol, is 10% by weight or less based on 2-mercaptoethanol. A method for producing a vinyl chloride polymer. 7. The method for producing a vinyl chloride polymer according to claim 6, wherein the method for storing 2-mercaptoethanol in a metal tank uses the one stored by the method according to any one of claims 1 to 5.