JP2002003510A - Method for producing vinyl chloride polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for obtaining a vinyl chloride polymer with a significant high bulk specific gravity. SOLUTION: The vinyl chloride polymer having a bulk specific gravity of 0.58 g/cc or more is obtained by using a modified polyvinyl alcohol, wherein the content of ethylene unit is 1-10 mol%, the degree of saponification is 90 mol% or more and the degree of polymerization is 600 or more, as a dispersion stabilizer for the suspension polymerization in the suspension polymerization of a vinyl chloride monomer in an aqueous medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a vinyl chloride polymer having a remarkably high bulk specific gravity by suspension polymerization of a vinyl chloride monomer.

[0002]

2. Description of the Related Art Generally, polyvinyl chloride (hereinafter referred to as PVC) is used.
Is a useful resin having excellent physical and mechanical properties, and is widely used as a hard and soft material. As a molding method of PVC, calender molding, extrusion molding, injection molding and the like are generally used. Particularly, in the case of extrusion molding of rigid PVC, development of PVC having a high bulk specific gravity is required from the viewpoint of increasing the amount of extrusion. Is required.

Further, a vinyl chloride paste resin is mixed with a compounding agent such as a plasticizer, a diluent, a stabilizer and other fillers by stirring and kneading to form a sol, which is formed by a method such as dipping, slush, rotation or coating. There is known a processing method of heating and gelling after the above. In this processing method, in order to improve moldability during processing by lowering the viscosity of the sol and improving the flowability, a vinyl chloride paste blend resin is used. Are used together. As the paste blend resin, a resin composed of a single spherical particle having an average particle diameter of 20 to 80 μm, a low porosity particle having a glassy shape, and a smooth surface is considered to be good. Here, too, there is a demand for the development of a vinyl chloride resin having a high bulk specific gravity.

In the case of producing a vinyl chloride resin industrially, a monomer such as vinyl chloride is dispersed in an aqueous medium in the presence of a dispersion stabilizer, and polymerization is carried out using an oil-soluble initiator. Suspension polymerization is widely practiced. In general, factors controlling the quality of a vinyl chloride polymer include a polymerization rate and water-
The monomer ratio, the polymerization temperature, the type and amount of the initiator, the type of the polymerization tank, the stirring speed, the type of the dispersion stabilizer, and the like are mentioned, and the influence of the type of the dispersion stabilizer is extremely large.

Heretofore, as a dispersion stabilizer for suspension polymerization of a vinyl chloride monomer, cellulose derivatives such as methylcellulose and carboxymethylcellulose or partially saponified polyvinyl alcohol have been used alone or in combination. However, there is a problem that these conventional dispersion stabilizers do not always satisfy the required performance described above.

In order to solve this problem, Japanese Patent Laid-Open Publication No.
No. 95104, JP-A-03-140303,
JP-A-06-80709, JP-A-08-2596
Japanese Patent Application Laid-Open No. 09-0909 proposes a dispersion stabilizer for suspension polymerization of a vinyl compound comprising a modified polyvinyl alcohol containing an ethylene unit. Also, Japanese Patent Application Laid-Open No. 10-27
No. 9610 proposes to use two types of partially saponified polyvinyl alcohol specified by the viscosity of the aqueous solution and the degree of saponification as a method for producing a vinyl chloride resin for paste blending.

By using these dispersion stabilizers for suspension polymerization, vinyl chloride polymers having a high bulk specific gravity have been obtained to some extent, but at present, they do not always reach a satisfactory level.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for obtaining a vinyl chloride polymer having a high bulk specific gravity.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a mixture of a vinyl chloride monomer or a monomer copolymerizable therewith (hereinafter, referred to as a mixture).
When the vinyl chloride-based monomer is subjected to suspension polymerization in an aqueous medium, the content of an ethylene unit is 1 to 10 mol% and the degree of saponification is 90 mol% as a dispersion stabilizer for suspension polymerization.
As described above, by using a modified polyvinyl alcohol having a polymerization degree of 600 or more, the bulk specific gravity is 0.58 g / cc.
The inventors have found that the vinyl chloride polymer described above can be obtained, and have completed the present invention.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a vinyl chloride polymer is obtained by subjecting a vinyl chloride monomer to suspension polymerization in an aqueous medium, and a monomer copolymerizable with the vinyl chloride monomer. As, ethylene, propylene, vinyl acetate,
Examples thereof include alkyl vinyl ether, acrylic acid or methacrylic acid and esters thereof. These monomers are preferably used in an amount not exceeding 20 parts by weight based on 100 parts by weight of the vinyl chloride monomer.

In the method for producing a vinyl chloride polymer according to the present invention, as the polymerization initiator, those conventionally used for the polymerization of vinyl compounds such as vinyl chloride can be used. As the polymerization initiator, for example, a percarbonate compound such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, t-butyl peroxyneodecanate, α-cumylperoxyneo Perester compounds such as decanate, acetylcyclohexylsulfonyl peroxide, peroxides such as 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, 2,2'-azobisisobutyronitrile, azobis-2 Azo compounds such as 2,4-dimethylvaleronitrile and azobis (4-methoxy-2,4-dimethylvaleronitrile). Further, potassium persulfate, ammonium persulfate, hydrogen peroxide and the like are used in combination. thing It can be.

In the method for producing a vinyl chloride polymer of the present invention, various additives can be added as required. Examples of the various additives include polymerization degree regulators such as acetaldehyde, butyraldehyde, trichloroethylene, perchloroethylene, and mercaptans, and polymerization inhibitors such as phenol compounds, sulfur compounds, and N-oxide compounds. It is also optional to add a pH adjuster, a scale inhibitor, a crosslinking agent, and the like, and a plurality of the above additives may be used in combination.

In the method for producing a vinyl chloride polymer of the present invention, the temperature of the aqueous medium used is not particularly limited,
Cold water of about 0 ° C. as well as warm water of 90 ° C. or more are suitably used. As constituents of this aqueous medium, in addition to pure water, an aqueous medium containing the above-mentioned various additional components or an aqueous medium containing another organic solvent can be exemplified. Further, in order to enhance the heat removal efficiency, a polymerization vessel equipped with a reflux condenser is also preferably used.

Further, in the method for producing a vinyl chloride polymer according to the present invention, the charge ratio of each component such as a vinyl chloride monomer, a polymerization initiator, a dispersion stabilizer, an aqueous medium and other additives, a polymerization temperature, etc. May be determined in accordance with the conditions employed in conventional suspension polymerization of vinyl chloride monomers. The order of charging the above components is not limited at all.
Also, a hot charge method in which warm water is used as the aqueous medium and the vinyl chloride monomer is heated before being charged into the polymerization vessel is preferably used.

The dispersion stabilizer for suspension polymerization used in the present invention is a modified polyvinyl alcohol having an ethylene unit content of 1 to 10 mol%, a degree of saponification of 90 mol% or more, and a degree of polymerization of 600 or more. . Preferably, the content of the ethylene unit is 1 to 9 mol%, and the degree of saponification is 95 mol%.
As described above, the modified polyvinyl alcohol has a degree of polymerization of 650 to 8000. 1 mol% ethylene unit content
When the amount is less than 10%, a vinyl chloride polymer having a high bulk specific gravity cannot be obtained. When the amount exceeds 10% by mole, the water solubility of the dispersion stabilizer is lowered and the handling property is deteriorated. If the degree of saponification is less than 90 mol%, a vinyl chloride polymer having a high bulk specific gravity cannot be obtained. If the degree of polymerization is less than 600, the polymerization stability will decrease.

In the present invention, the use amount of the dispersion stabilizer for suspension polymerization is not particularly limited.
0.01 to 2 parts by weight per part by weight, preferably 0.02 to 2 parts by weight.
-1.5 weight part is more preferable, and 0.02-1 weight part is further more preferable. When the amount is less than 0.01 part by weight, the polymerization stability decreases, and when the amount exceeds 2 parts by weight, the chemical oxygen demand (COD) of the polymerization waste liquid increases.

In the present invention, the dispersion stabilizer for suspension polymerization is:
It can be obtained by copolymerizing a vinyl ester monomer and ethylene according to a conventionally known method, for example, a method described in JP-A-08-259609, and saponifying the obtained copolymer by an ordinary method. As the polymerization method of the copolymer, conventionally known methods such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, and an emulsion polymerization method can be applied. As the polymerization catalyst, depending on the polymerization method, an azo catalyst, a peroxide catalyst,
A redox catalyst or the like is appropriately selected. The saponification reaction is
Alcohol decomposition and hydrolysis using a conventionally known alkali catalyst or acid catalyst can be applied. Among them, a saponification reaction using methanol as a solvent and using a NaOH catalyst is simple and most preferable.

Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurate, Examples thereof include vinyl palmitate, vinyl stearate, vinyl oleate, and vinyl benzoate, with vinyl acetate being particularly preferred.

The dispersion stabilizer for suspension polymerization used in the present invention may contain other monomer units as long as the gist of the present invention is not impaired. As such a monomer, for example, propylene, n-butene, α-olefins such as isobutylene, acrylic acid and salts thereof,
Methyl acrylate, ethyl acrylate, acrylic acid n-
Propyl, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate,
2-ethylhexyl acrylate, dodecyl acrylate,
Acrylates such as octadecyl acrylate,
Methacrylic acid and its salts, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, Methacrylic esters such as dodecyl methacrylate and octadecyl methacrylate, acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and salts thereof, acrylamidopropyldimethylamine and A salt thereof or a quaternary salt thereof, acrylamide derivatives such as N-methylolacrylamide and derivatives thereof, methacrylamide, N-methylmethacrylamide, N-ethylmethyl Acrylamide, methacrylamide propanesulfonic acid and salts thereof, methacrylamide propyl dimethylamine and a salt thereof or a quaternary salt, N
-Methacrylamide derivatives such as methylol methacrylamide and derivatives thereof, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-
Propyl vinyl ether, n-butyl vinyl ether,
vinyl ethers such as i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene chloride; vinylidene fluoride; Halogenated vinylidenes, allyl compounds such as allyl acetate and allyl chloride, maleic acid and salts or esters thereof, vinylsilyl compounds such as vinyltrimethoxysilane, and isopropenyl acetate.

In the present invention, the dispersion stabilizer for suspension polymerization may be improved in water solubility by introducing an ionic group such as an ammonium group, a carboxyl group, a sulfonic acid group or an amino group. 2-16 carbon atoms
May be introduced. In this case, the degree of saponification of the dispersion stabilizer is determined from the vinyl ester group and the vinyl alcohol group, and does not include the degree of saponification of the introduced ionic group, nonionic group or alkyl group. Also,
According to a conventionally known method, thiolacetic acid, a terminal obtained by polymerizing a vinyl ester-based monomer such as vinyl acetate in the presence of a thiol compound such as mercaptopropionic acid, and saponifying the obtained vinyl ester-based polymer. Modified products can also be used. The dispersion stabilizer for suspension polymerization in the present invention is water at 5 to 100 ° C, preferably 10 to 100 ° C.
It is preferably water-soluble in 90 ° C. water.

In the present invention, the dispersion stabilizer may be used alone. However, when a vinyl monomer such as vinyl chloride is subjected to suspension polymerization in an aqueous medium, the polymerization degree is usually from 100 to 100.
4000 and a polyvinyl alcohol polymer having a saponification degree of 30 to 99 mol%, water-soluble cellulose ethers such as methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose, water-soluble polymers such as gelatin, sorbitan monolaurate and sorbitan triolate And oil-soluble emulsifiers such as glycerin tristearate and ethylene oxide-propylene oxide block copolymer, and water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate and sodium laurate. The amount of the vinyl monomer is not particularly limited.
It is preferably 0.01 to 2.0 parts by weight per 00 parts by weight.

According to the present invention, the bulk specific gravity is 0.58 g / c.
c or more vinyl chloride-based polymers can be produced.
Here, the bulk specific gravity of the vinyl chloride polymer refers to JIS K
The value measured by the method described in 6721. A vinyl chloride polymer having a bulk specific gravity of less than 0.58 g / cc has low productivity at the time of molding and, when used as a blend resin of a polyvinyl chloride paste resin, improves the fluidity of a sol and The physical properties of the molded article after heat molding are reduced.

[0023]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. In the following examples, “%” and “parts” are “% by weight” unless otherwise specified.
And "parts by weight".

(Analysis of Modified Polyvinyl Alcohol Polymer) (1) Measurement of Degree of Polymerization The degree of polymerization was measured according to JIS-K6726.

(2) Measurement of degree of saponification Measured according to JIS-K6726.

(Polymerization of Vinyl Chloride Monomer and Characteristic Evaluation of Vinyl Chloride Polymer Obtained)

(1) Measurement of bulk specific gravity Measured according to JIS-K6712.

(2) Measurement of Average Particle Diameter The obtained vinyl chloride polymer powder was subjected to a JIS standard sieve (opening: 355, 250, 180, 150, 125, 10).
6,75 μm), a rosin-Rammler plot was performed, and the particle size at which the cumulative weight distribution became 50% was defined as the average particle size.

(3) Scale Amount After the polymerization was completed, the amount of the vinyl chloride polymer adhered to the polymerization tank including the stirrer was measured, and the amount was calculated as a percentage by weight based on all the obtained vinyl chloride polymers.

Example 1 An autoclave made of glass lining was charged with 40 parts of deionized water in which a dispersion stabilizer shown in Table 1 was dissolved and 0.04 part of a 70% toluene solution of diisopropyl peroxydicarbonate, and the inside of the autoclave was 50 mmHg.
After degassing until oxygen was reached to remove oxygen, 30 parts of a vinyl chloride monomer were charged, and the temperature was raised to 57 ° C. with stirring to carry out polymerization. At the start of polymerization, the pressure in the autoclave is 8.5 k
g / cm ² G, but 4.5 k 7 hours after the start of polymerization.
The polymerization was stopped when g / cm ² G was reached, the unreacted vinyl chloride monomer was purged, and the contents were taken out and dehydrated and dried. The polymerization yield of PVC was 85%, the amount of scale was 5% by weight, and the average degree of polymerization was 1050. P obtained
Table 1 shows the results of evaluating the polymerizability and performance of VC.
PVC having a very high bulk specific gravity of 0.69 g / cc
Was obtained with good polymerization stability.

Examples 2 to 8 and Comparative Examples 1 to 5 The results obtained by operating in the same manner as in Example 1 except that the dispersion stabilizers shown in Table 1 were changed are shown in Table 1.

[0032]

[Table 1]

[0033]

According to the production method of the present invention, a vinyl chloride polymer having a high bulk specific gravity can be obtained with good polymerization stability. Further, the vinyl chloride-based polymer obtained by the production method of the present invention is suitable as a vinyl chloride-based resin for hard materials and for paste blends.

Claims (4)

[Claims] When a vinyl chloride monomer or a mixture thereof with a monomer copolymerizable therewith is subjected to suspension polymerization in an aqueous medium, the content of ethylene units as a dispersion stabilizer for suspension polymerization is from 1 to 1. 10 mol%, the degree of saponification is 90 mol% or more, and
A method for producing a vinyl chloride polymer having a bulk specific gravity of 0.58 g / cc or more, characterized by using a modified polyvinyl alcohol having a degree of polymerization of 600 or more. 2. The vinyl chloride according to claim 1, wherein the amount of the modified polyvinyl alcohol is 0.01 to 2 parts by weight based on a mixture of the vinyl chloride monomer and a monomer copolymerizable therewith. A method for producing a polymer. 3. The method for producing a vinyl chloride polymer according to claim 1, wherein the vinyl chloride polymer is a vinyl chloride polymer for paste blending. 4. The method for producing a vinyl chloride polymer according to claim 1, wherein the vinyl chloride polymer is a vinyl chloride polymer for hard materials.