JPH08109207A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE: To obtain a nonskinned vinyl chloride polymer having excellent plasticizer absorption and gelling properties and a good particle diameter distribution and scarcely forming any scales on the inside wall of the polymerizer. CONSTITUTION: A vinyl chloride polymer is produced by subjecting a vinyl chloride monomer or a vinyl monomer mixture based thereon to a suspension polymerization reaction in the presence of a suspending agent in an aqueous medium, wherein the suspending agent comprises a partially saponified polyvinyl alcohol (1) having an average degree of polymerization of 150-600 and a degree of saponification of 20-55mol% and a cross-linked carboxylated copolymer (2) having a viscosity of 400cP or above as measured in the 1wt.% aqueous solution at 25 deg.C in a (1)/(2) weight ratio of 2-5, and the amount of the suspending agent used is 0.01-1.0wt.% based on the monomer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vinyl chloride polymer by a suspension polymerization method, and more specifically, it has no skin layer on the surface of a resin, and has a good monomer removal property and a good plasticizer absorbability. The present invention relates to a method for producing a vinyl chloride-based polymer.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a vinyl chloride polymer, a vinyl chloride monomer (a mixture of vinyl chloride or other copolymerizable monomer mainly containing vinyl chloride) in an aqueous medium is used. A method of performing suspension polymerization in the presence of a suspending agent such as polyvinyl alcohol and a cellulose derivative is known. And, as this suspending agent, polyvinyl alcohol having an excellent dispersibility is relatively often used.

However, the vinyl chloride polymer obtained by the conventional suspension polymerization method has a drawback that the particle size is nonuniform and the porosity is poor. In particular, if the porosity is poor, the plastic absorbability deteriorates, the workability during processing decreases, and the gelation rate becomes slow, so the processed product tends to be non-uniform,
It also has the drawback of increasing fish eyes. The disadvantage of the conventional suspension polymerization method is that there is a shell called a skin layer on the surface of the polymer, and this skin layer is an obstacle to improving the plasticizer absorbability and gelation property of the polymer. This is because Recently, attempts have been made to solve the above-mentioned drawbacks by using a partially saponified polyvinyl alcohol having a low saponification degree or a low polymerization degree as a suspending agent, but the result is insufficient.

As a method for producing a vinyl chloride polymer having no skin layer by suspension polymerization, a lipophilic sorbitan higher fatty acid ester and a hydrophilic polyoxyethylene higher fatty acid ester are combined in the presence of an alkali compound. The polymerization conversion rate is 5 to 4 after the polymerization is started.
A method in which a water-soluble cellulose derivative is added at the time of 0% (Japanese Patent Laid-Open No. 135192/1975); as a dispersant, a partially saponified polyvinyl having an average polymerization degree of 500 or less and a saponification degree of 60 mol% or less A method in which an alcohol is used and a water-soluble cellulose derivative is added at the time when the conversion of polymerization reaches 5 to 40% after initiation of polymerization (JP-A-57-14607); sorbitan higher fatty acid ester as a dispersant And a method of adding a water-soluble cellulose derivative when the conversion of polymerization reaches 5 to 40% after initiation of polymerization (JP-A-60-2
29907); a partially saponified polyvinyl alcohol having an average degree of polymerization of 500 or less and a degree of saponification of 60 mol% or less is used as a dispersant, and the polymerization conversion rate becomes 5 to 40% after the initiation of the polymerization. When the average polymerization degree is 700 or more,
A method of adding a partially saponified polyvinyl alcohol having a saponification degree of 75 mol% or more (JP-A-60-231705) has been proposed. However, in these methods, the obtained vinyl chloride-based polymer becomes a resin having a large particle size and the polymerization system is unstable, so that the generation of coarse particles and the adhesion of scale are severe, and the vinyl chloride-based polymer without a skin layer is used. A polymer cannot be obtained stably.

[0005]

The object of the present invention is to obtain a vinyl chloride polymer having no skin layer in a stable manner. Therefore, the obtained polymer has excellent plasticizer absorbability and gelation property. Another object of the present invention is to provide a method for producing a vinyl chloride-based polymer that can obtain a vinyl chloride-based polymer having a good particle size distribution and that has almost no scale attached to the inside of a polymerization vessel.

[0006]

DISCLOSURE OF THE INVENTION According to the present invention, vinyl chloride is prepared by suspension-polymerizing a vinyl chloride monomer or a mixture of vinyl-based monomers mainly containing this in an aqueous medium in the presence of a suspending agent. In the method for producing a polymer, the suspending agent is (1) a partially saponified polyvinyl alcohol having an average degree of polymerization of 150 to 600 and a degree of saponification of 20 to 55 mol%, and (2) a 1% by weight aqueous solution. of
A suspending agent comprising a carboxy group-containing crosslinked copolymer having a viscosity of 400 cP or more at 25 ° C., and having a weight ratio of the component (1) to the component (2) of 2 to 5; Is 0.01 to 1.0% by weight with respect to the monomer, and a method for producing a vinyl chloride polymer.

Hereinafter, the present invention will be described in detail. The suspending agent used in the present invention comprises the following component (1) which is a partially saponified polyvinyl alcohol, and the crosslinked carboxy group-containing copolymer of the following component (2).

The average degree of polymerization of the component (1) partially saponified polyvinyl alcohol is 150
~ 600, preferably 200-500, more preferably
200 to 400. If the average degree of polymerization is less than 150, the bulk specific gravity of the vinyl chloride polymer obtained will be low, and if it exceeds 600, the porosity of the polymer will be poor, such being undesirable. The degree of saponification of the partially saponified polyvinyl alcohol is 20 to 55 mol%, preferably 30 to 50 mol%, and more preferably 30 to 50 mol%. If the saponification degree is less than 20 mol%, the bulk specific gravity of the polymer will be low, and if it exceeds 55 mol%, the porosity of the polymer will be poor, such being undesirable. As the partially saponified polyvinyl alcohol used in the present invention, those obtained by a known method can be preferably used.

Component (2) The carboxyl group-containing crosslinked copolymer used in the present invention is a copolymerization with a polymerizable unsaturated carboxylic acid compound with a crosslinking agent.
ross linking). Examples of the polymerizable unsaturated carboxylic acid compound include acrylic acid, methacrylic acid, itaconic acid, chloroacrylic acid, cyanoacrylic acid, α-phenylacrylic acid, α-benzylacrylic acid, crotonic acid, maleic acid, and fumaric acid. , Sorbic acid and the like. These may be used alone or in combination of two or more. Among them, acrylic acid is preferable. As the cross-linking agent, two or more polymerizable

[0010]

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Examples of the compound having an end group include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; polybutadiene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, allyl acrylate, methylenebisacrylamide, divinyl ether, diallyl. Examples thereof include soluble polymerizable dienes such as ether. The following average formula (1)

[0012]

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(In the formula, R represents a hydrogen atom or a methyl group, and p, m and n are each a number of 0 or more and satisfy 0 <p + m + n ≦ 500. Only if hydrogen atom and n = 0, p + m =
The compounds represented by 1) are excluded. Specific examples of the compound represented by the general formula (1) include, for example, diethylene glycol bisallyl ether, diethylene glycol bismethallyl ether, or the formula:

[0014]

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The following can be mentioned. These may be used alone or in combination of two or more. Among them, the preferred crosslinking agent is the compound represented by the general formula (1), and more preferred is
These are diethylene glycol bisallyl ether and diethylene glycol bismethallyl ether.

As the polymerization initiator used in the above-mentioned cross-linking copolymerization, azo type, peroxide type and redox type polymerization initiators can be used, for example, azobisisobutyronitrile and 2,2'-azobis. (2,4-dimethyl-4-methoxyvaleronitrile), benzoyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, persulfate, or a combination of persulfate and percarbonate, persulfate Examples thereof include a combination of salt and sulfite.

Examples of the solvent used for the polymerization include benzene, toluene, n-hexane and ethyl acetate. The content ratio of the cross-linking agent and the polymerizable unsaturated carboxylic acid compound in the carboxyl group-containing cross-linked copolymer is usually, relative to the polymerizable unsaturated carboxylic acid compound, the cross-linking agent 0.
The amount is preferably 05 to 10% by weight, more preferably 0.1 to 5% by weight. If the content of the cross-linking agent is too small, the cross-linking may be insufficient, and if the cross-linking is too large, the resulting carboxyl group-containing cross-linked copolymer may not exhibit the dispersing effect.

The above carboxyl group-containing crosslinked copolymer is
The viscosity of a 1% by weight aqueous solution at 25 ° C. is 400 cP or more, preferably 1000 cP or more. If the viscosity is less than 400 cP, suspension polymerization becomes unstable, scale adhesion easily occurs, and coarse particles are easily generated in the obtained polymer particles,
Not preferred.

Suspending agent In the suspending agent used in the present invention, the weight ratio of the partially saponified polyvinyl alcohol of the above component (1) and the carboxyl group-containing crosslinked copolymer of the component (2) [component (1) / Ingredient (2))
Is 2 to 5, preferably 2 to 4. When this ratio is less than 2 (that is, when the ratio of the carboxyl group-containing crosslinked copolymer is high), a polymer without a skin layer cannot be obtained, and when it exceeds 5 (that is, partially saponified polyvinyl alcohol). Is higher), the polymerization system becomes unstable, coarse particles are generated in the polymer particles, and scale easily adheres to the inside of the polymerization vessel, which is not preferable.

The amount of the suspending agent charged is 0.01 to 1.0% by weight, preferably 0.05, based on the amount of the vinyl chloride monomer charged.
~ 1.0% by weight. If the charging amount is less than 0.01% by weight, the polymerization system becomes unstable, and if it exceeds 1% by weight, the particle size becomes small and it becomes difficult to recover the obtained resin powder, which is not preferable.

Suspension Polymerization of Vinyl Chloride Monomer The vinyl chloride-based monomer polymerized by the method of the present invention includes vinyl chloride alone, and other vinyl chloride-based monomers which can be copolymerized with vinyl chloride. A mixture with a monomer (usually 50% by weight or more of vinyl chloride) can be used. Examples of the monomer copolymerizable with vinyl chloride include vinyl acetate, vinyl propionate and other vinyl esters, and methyl acrylate. Examples thereof include acrylic acid esters or methacrylic acid esters such as ethyl acrylate, olefins such as ethylene and propylene, maleic anhydride, acrylonitrile, styrene, vinylidene chloride and the like.

As the polymerization initiator used in the suspension polymerization, known ones which are usually used in the polymerization of vinyl chloride-based monomers can be used. Specifically, for example, t-butylperoxy is used. Neodecanoate, t-butylperoxypivalate, t-hexylperoxyneodecanoate, t-hexylneohexanoate, t-hexylperoxypivalate, α-cumylperoxyneodecanate, 2,4 , 4-trimethylbenzyl-2-peroxy-2-neodecanate and other perester compounds; diisopropyl peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, dimethoxyisopropyl percarbonate Oxydicarbonate, diethoxyethyl peroxydicarbonate Percarbonate compounds such as; decanoyl peroxide, benzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide,

2,4-dichlorobenzoyl peroxide, p-methane hydroperoxide, isobutyryl peroxide, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, 3,5,5. Peroxides such as 5-trimethylhexanoyl peroxide and lauroyl peroxide; α, α′-azobisisobutyronitrile,
Examples thereof include oil-soluble polymerization initiators such as azo compounds such as α, α′-azobis (2,4-dimethylvaleronitrile) and α, α′-azobis (4-methoxy-2,4-dimethylvaleronitrile). it can. These may be used alone or in combination of two or more. If necessary, they can be used in combination with a water-soluble polymerization initiator such as potassium persulfate, ammonium persulfate, hydrogen peroxide and the like.

The amount of the polymerization initiator charged may be within a known range that is usually used in aqueous suspension polymerization of vinyl chloride and the like, but preferably, the amount of the monomer charged is 100 parts by weight.
The amount is 0.001 to 3 parts by weight, more preferably 0.01 to 0.1 parts by weight. The polymerization initiator, during the charging of water or monomers,
Alternatively, it may be added after the completion of the preparation, and it may be prepared by uniformly mixing it with the monomer in advance and preparing it together with the monomer, or further preparing it as an aqueous emulsion together with the aqueous medium.

In the present invention, suspension is carried out under known conditions except that a predetermined amount of a suspension agent in which the above-mentioned component (1) polyvinyl alcohol and the component (2) carboxyl group-containing crosslinked copolymer are combined is used. Polymerization can be carried out. For example, the amount of the aqueous medium used to suspend and disperse the monomer is
The amount of the aqueous medium charged relative to the amount of the monomer charged is 1.0
The amount may be up to 1.5 times by weight, and water may be added during the polymerization, if necessary. In the present invention, it is optional to add, to the polymerization system, a polymerization regulator, a pH regulator and the like, which are appropriately used for the polymerization of vinyl chloride monomer and the like, if necessary.

[0026]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following. [Example 1] As the component (1), an average degree of polymerization of 230 and a degree of saponification
60 g of partially saponified polyvinyl alcohol of 48 mol% and a cross-linked acrylic acid copolymer (trade name: Hibiswako 104, having a viscosity of 2500 cP (1 wt% aqueous solution: 25 ° C.) as the component (2).
15 g of Wako Pure Chemical Industries, Ltd.) was dissolved in 60 kg of warm water, and the mixture was placed in a stirrer with an internal volume of 100 liters and a jacketed stainless steel polymerization vessel. After evacuating the inside of the vessel, 30 kg of vinyl chloride monomer was charged and stirred for 3 minutes, and then t-butyl peroxyneodecanate 21 was added as a polymerization initiator.
After charging g, the temperature was raised to 57 ° C. to start polymerization. Polymerization was performed while maintaining the temperature at 57 ° C, and the internal pressure of the polymerization vessel was 6 kg / cm.
Polymerization was terminated at the time when the pressure dropped to ² G, and then unreacted monomers were collected, and then the resulting slurry composition was dehydrated and dried to obtain a vinyl chloride polymer.

The vinyl chloride polymer thus obtained was evaluated for bulk specific gravity, particle size distribution, plasticizer absorption amount, plasticizer absorption time, scale adhesion, and the presence or absence of a skin layer as follows. The results are shown in Table 1.

<Bulk Specific Gravity> Measured in accordance with JIS K-6721. <Particle size distribution> Measured according to JIS Z-8801. <Amount of absorbed plasticizer> Glass fiber was packed in the bottom of an aluminum alloy container having an inner diameter of 25 mm and a depth of 85 mm, and 10 g of the obtained vinyl chloride polymer was added as a sample. Add 15 cc of dioctyl phthalate (DOP) to this and let it stand for 30 minutes.
The P was well permeated into the polymer. Then, the excess DOP was centrifuged under an acceleration of 1500 G, and the DO absorbed in 10 g of the polymer was removed.
The amount of P was measured, and the converted amount per 100 g of the polymer was defined as the plasticizer absorption amount.

<Plasticizer absorption time> 400 g of the obtained vinyl chloride polymer powder was placed in a Brabender plastograph (planetary mixer), and preheated (4 minutes) while stirring at 60 rpm to 80 ° C. , Add DOP 200g to it,
The time from the time of the addition to the time when the reduction of the torque was completed was measured and taken as the plasticizer absorption time. <Scale Adhesion> After the completion of polymerization, the state of polymer scale adhesion in the polymerization vessel was visually observed. <Presence or absence of skin layer> The obtained vinyl chloride polymer was observed with an electron microscope to confirm the presence or absence of a skin layer.

Example 2 Instead of the crosslinked acrylic acid copolymer used in Example 1, a viscosity of 400 cP (1 wt% aqueous solution: 25
(° C) cross-linked acrylic acid copolymer (trade name: Hibiswako
103, manufactured by Wako Pure Chemical Industries, Ltd.) was used to obtain a vinyl chloride polymer in the same manner as in Example 1, and the bulk specific gravity, particle size distribution, plasticizer absorption amount, plasticizer absorption time, scale adhesion, and presence / absence of skin layer. Was evaluated. The results are shown in Table 1.

Example 3 Instead of the crosslinked acrylic acid copolymer used in Example 1, a viscosity of 5000 cP (1 wt% aqueous solution:
A vinyl chloride polymer was obtained in the same manner as in Example 1 except that a cross-linked acrylic acid copolymer (trade name: Hibiswako 105, manufactured by Wako Pure Chemical Industries, Ltd.) at 25 ° C.) was used. Bulk specific gravity, particle size distribution, plasticizer absorption The amount, the plasticizer absorption time, the scale adhesion, and the presence or absence of the skin layer were evaluated. The results are shown in Table 1.

Example 4 A vinyl chloride polymer was obtained in the same manner as in Example 1 except that the amounts of the partially saponified polyvinyl alcohol and the crosslinked acrylic acid copolymer were changed to 60 g and 30 g, respectively. The bulk specific gravity, particle size distribution, plasticizer absorption amount, plasticizer absorption time, scale adhesion, and the presence or absence of a skin layer were evaluated. The results are shown in Table 1.

[Example 5] A vinyl chloride polymer was obtained in the same manner as in Example 1 except that the amounts of the partially saponified polyvinyl alcohol and the crosslinked acrylic acid copolymer used were 30 g and 15 g, respectively. The bulk specific gravity, particle size distribution, plasticizer absorption amount, plasticizer absorption time, scale adhesion, and the presence or absence of a skin layer were evaluated. The results are shown in Table 1.

Comparative Example 1 A vinyl chloride polymer was obtained in the same manner as in Example 1 except that the amounts of the partially saponified polyvinyl alcohol and the crosslinked acrylic acid copolymer were changed to 15 g and 30 g, respectively. The bulk specific gravity, particle size distribution, plasticizer absorption amount, plasticizer absorption time, scale adhesion, and the presence or absence of a skin layer were evaluated. The results are shown in Table 1.

Comparative Example 2 Instead of the suspending agent used in Example 1, 60 g of partially saponified polyvinyl alcohol having an average degree of polymerization of 230 and a saponification degree of 48 mol%, and an average degree of polymerization of 780 and a saponification degree of 73.9 mol. % Vinyl acetate polymer was obtained in the same manner as in Example 1 except that a suspending agent consisting of 30 g of partially saponified polyvinyl alcohol was used. Bulk specific gravity, particle size distribution, plasticizer absorption,
The plasticizer absorption time, scale adhesion, and the presence or absence of a skin layer were evaluated. The results are shown in Table 1.

[0036]

[Table 1]

From the results shown in Table 1, the vinyl chloride polymer obtained according to the present invention has no skin layer on the resin surface,
It is confirmed that the particle size distribution is also sharp, the plasticizer absorbability is excellent, and the scale in the polymerization vessel hardly adheres. On the other hand, even if a partially saponified polyvinyl alcohol and a cross-linked copolymer having the same physical properties as the suspending agent of the present invention are used in combination, their ratio is different from the range of the present invention, When the ratio is high (Comparative Example 1) and when a suspending agent of a combination different from the suspending agent of the present invention is used (Comparative Example 2), the skin layer is present in the polymer and the plasticizer absorbability It is observed that the scale is bad and the scale is attached.

[0038]

EFFECTS OF THE INVENTION According to the present invention, a vinyl chloride polymer having no skin layer can be stably obtained, and vinyl chloride having excellent plasticizer absorbability and gelation property and a good particle size distribution. A system polymer can be obtained. Further, it is possible to obtain a vinyl chloride-based polymer in which scale hardly adheres to the inside of the polymerization vessel and coarse particles are not generated.

Claims (1)

[Claims] 1. A method for producing a vinyl chloride-based polymer, which comprises suspension-polymerizing a vinyl chloride monomer or a mixture of vinyl-based monomers mainly comprising the same in an aqueous medium in the presence of a suspending agent, The suspending agent is (1) an average degree of polymerization of 150 to 600, a degree of saponification of 20 to 55 mol% of partially saponified polyvinyl alcohol, and (2) a 1 wt% aqueous solution having a viscosity of 400 cP at 25 ° C.
Consisting of a carboxy group-containing crosslinked copolymer that is the above,
Moreover, the weight ratio of the component (1) to the component (2) is 2 to 5; the amount of the suspending agent is 0.01 to 1.
A method for producing a vinyl chloride-based polymer, characterized in that it is 0% by weight.