JP3307784B2 - Method for producing vinyl chloride polymer - Google Patents

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 particularly, to a method for producing a porous material having no skin layer on the surface of a resin, and having good demonomerization and plasticizer absorption. The present invention relates to a method for producing a water-soluble vinyl chloride 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 another copolymerizable monomer mainly composed of 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. As the suspending agent, polyvinyl alcohol having excellent dispersing ability is used relatively frequently.

[0003] However, the vinyl chloride polymer obtained by the conventional suspension polymerization method has the disadvantage that the particle size is uneven and the porosity is poor. In particular, when the porosity is poor, the plastic absorbability deteriorates, the workability at the time of processing decreases, and the gelation rate decreases, so that the processed product tends to be uneven,
There is a drawback that fish eyes also increase. One of the drawbacks of the conventional suspension polymerization method is that a shell called a skin layer exists on the polymer surface, and this skin layer hinders the improvement of the plasticizer absorption and gelation properties of the polymer. Because it is. Recently, attempts have been made to solve the above-mentioned disadvantages by using a partially saponified polyvinyl alcohol having a low degree of saponification or a low degree of polymerization as a suspending agent, but the results have been insufficient.

A method for producing a vinyl chloride polymer having no skin layer by suspension polymerization is to combine a lipophilic sorbitan higher fatty acid ester and a hydrophilic polyoxyethylene higher fatty acid ester in the presence of an alkali compound. Used, and the polymerization conversion rate is 5 to 4 after the initiation of polymerization.
A method in which a water-soluble cellulose derivative is added at 0% (JP-A-50-135192); partially saponified polyvinyl having an average degree of polymerization of 500 or less and a saponification degree of 60 mol% or less as a dispersant. A method in which a water-soluble cellulose derivative is added at the point when the polymerization conversion rate becomes 5 to 40% after the initiation of polymerization using alcohol (Japanese Patent Application Laid-Open No. 57-14607); And adding a water-soluble cellulose derivative when the polymerization conversion rate becomes 5 to 40% after the initiation of the polymerization (Japanese Patent Application Laid-Open No. Sho 60-2).
No. 29907); As a dispersant, 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. When the average degree of polymerization is 700 or more,
A method of adding a partially saponified polyvinyl alcohol having a saponification degree of 75 mol% or more (Japanese Patent Laid-Open No. 60-231705) has been proposed. However, in these methods, the resulting vinyl chloride polymer becomes a resin having a large particle size, and the polymerization system is also unstable. The polymer cannot be obtained stably.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a vinyl chloride polymer having no skin layer stably, so that the resulting polymer is excellent in a plasticizer absorbing property and a gelling property. Another object of the present invention is to provide a method for producing a vinyl chloride-based polymer which can obtain a vinyl chloride-based polymer having a good particle size distribution and scarcely adhere to scale in a polymerization vessel.

[0006]

SUMMARY OF THE INVENTION The present invention provides a vinyl chloride monomer or a mixture of vinyl monomers based on vinyl chloride, which is subjected to suspension polymerization in an aqueous medium in the presence of a suspending agent. In the method for producing a polymer, the suspending agent comprises (1) a partially saponified polyvinyl alcohol having an average degree of polymerization of 150 to 600 and a saponification degree 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 at 25 ° C. of 400 cP or more 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.

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 a 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. When the average polymerization degree is less than 150, the bulk specific gravity of the obtained vinyl chloride polymer becomes low, and when it exceeds 600, the porosity of the polymer becomes poor, which is not preferable. The degree of saponification of the partially saponified polyvinyl alcohol is 20 to 55 mol%, preferably 30 to 50 mol%, more preferably 30 to 50 mol%. When the saponification degree is less than 20 mol%, the bulk specific gravity of the polymer becomes low, and when it exceeds 55 mol%, the porosity of the polymer becomes poor, which is not preferable. As the partially saponified polyvinyl alcohol used in the present invention, those obtained by a known method can be suitably used.

Component (2) The carboxyl group-containing crosslinked copolymer used in the present invention is obtained by crosslinking a polymerizable unsaturated carboxylic acid compound with a crosslinking agent.
rosslinking). 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 And sorbic acid. These can be used alone or in combination of two or more. Among them, acrylic acid is preferred. As the crosslinking agent, two or more polymerizable molecules in one molecule

[0010]

Embedded image

And aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; polybutadiene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, allyl acrylate, methylene bisacrylamide, divinyl ether and diallyl. Examples thereof include soluble polymerizable dienes such as ether. The following average formula (1)

[0012]

Embedded image

(Wherein, R represents a hydrogen atom or a methyl group, p, m, and n are each a number greater than or equal to 0 and satisfying 0 <p + m + n ≦ 500. P + m = only when hydrogen atom and n = 0
Excluding the number satisfying 1). Specific examples of the compound represented by the general formula (1) include, for example, diethylene glycol bisallyl ether, diethylene glycol bismethallyl ether, or a compound represented by the formula:

[0014]

Embedded image

The following can be mentioned. These can be used alone or in combination of two or more. Among them, preferred crosslinking agents are compounds represented by the above general formula (1), and more preferred are:
Diethylene glycol bisallyl ether and diethylene glycol bismethallyl ether.

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

Examples of the solvent used for the polymerization include benzene, toluene, n-hexane, ethyl acetate and the like. The content ratio of the crosslinking agent and the polymerizable unsaturated carboxylic acid compound in the carboxyl group-containing crosslinked copolymer is usually 0.1% relative to the polymerizable unsaturated carboxylic acid compound.
It is preferably from 05 to 10% by weight, more preferably from 0.1 to 5% by weight. If the content of the crosslinking agent is too small, crosslinking may be insufficient, and too much crosslinking may be excessive, and the dispersing effect of the obtained carboxyl group-containing crosslinked copolymer may not be exhibited.

The carboxyl group-containing crosslinked copolymer is
The viscosity of the 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.

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

The amount of the suspending agent is 0.01 to 1.0% by weight, preferably 0.05% by weight, based on the amount of the vinyl chloride monomer.
~ 1.0% by weight. If the charged 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 collect the obtained resin powder, which is not preferable.

Suspension Polymerization of Vinyl Chloride Monomer The vinyl chloride monomer to be polymerized by the method of the present invention is not only vinyl chloride alone, but also other vinyl chloride-based monomers copolymerizable therewith. A mixture with the monomer (usually, 50% by weight or more of vinyl chloride) can be used. Examples of monomers copolymerizable with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate, and methyl acrylate. And acrylates such as ethyl acrylate or methacrylate, olefins such as ethylene and propylene, maleic anhydride, acrylonitrile, styrene, and vinylidene chloride.

As the polymerization initiator used for the suspension polymerization, known ones usually used for polymerization of vinyl chloride monomers can be used. Specifically, for example, t-butylperoxy is used. Neodecanoate, t-butylperoxypivalate, t-hexylperoxyneodecanate, t-hexylneohexanoate, t-hexylperoxypivalate, α-cumylperoxyneodecanate, 2,4 Perester compounds such as 2,4-trimethylbentyl-2-peroxy-2-neodecanate; diisopropylperoxydicarbonate, di-2-ethoxyethylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, dimethoxyisopropylperoxide Oxydicarbonate, diethoxyethyl peroxydicarbonate Percarbonate compounds such as; decanoyl peroxide, benzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide,

2,4-dichlorobenzoyl peroxide, p-methanehydroperoxide, isobutyryl peroxide, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxy acetate, 3,5 Peroxides such as 5-trimethylhexanoyl peroxide and lauroyl peroxide; α, α'-azobisisobutyronitrile;
Examples 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 can be used alone or in combination of two or more. If necessary, these can be used in combination with a water-soluble polymerization initiator such as potassium persulfate, ammonium persulfate, and hydrogen peroxide.

The amount of the polymerization initiator to be charged may be in a known range commonly used in aqueous suspension polymerization of vinyl chloride or the like.
It is 0.001 to 3 parts by weight, more preferably 0.01 to 0.1 part by weight. The polymerization initiator, during the preparation of water or monomer,
Alternatively, it can be added after the completion of the charging, and may be uniformly mixed with the monomer in advance and charged together with the monomer, or may be charged together with the aqueous medium as an aqueous emulsion.

The present invention provides a suspension according to known conditions, except that a predetermined amount of a suspending agent obtained by combining the above-mentioned component (1) of polyvinyl alcohol and the component (2) of the carboxyl group-containing crosslinked copolymer is used. Polymerization can be performed. For example, the charged amount of the aqueous medium used to suspend and disperse the monomer is
The amount of aqueous medium charged relative to the amount of monomer charged is 1.0
It may be in the range of 1.5 to 1.5 times by weight, and water can be added during the polymerization as needed. In the present invention, if necessary, a polymerization regulator, a pH regulator and the like appropriately used for polymerization of a vinyl chloride monomer and the like may be optionally added to the polymerization system.

[0026]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following. [Example 1] As the component (1), the average degree of polymerization was 230 and the degree of saponification was
60 g of a 48 mol% partially saponified polyvinyl alcohol and a crosslinked acrylic acid copolymer having a viscosity of 2500 cP (1% by weight aqueous solution: 25 ° C.) as a component (2) (trade names: Hibiswako 104,
A suspension agent consisting of 15 g of Wako Pure Chemical Industries, Ltd.) was dissolved in 60 kg of warm water, and this was charged into a 100-liter inner volume agitator and jacketed stainless steel polymerization vessel. After evacuation of the vessel, 30 kg of a vinyl chloride monomer was charged and stirred for 3 minutes. Then, t-butyl peroxyneodecanate 21 was used as a polymerization initiator.
g, and the temperature was raised to 57 ° C. to initiate polymerization. Furthermore, polymerization was carried out while maintaining the temperature at 57 ° C., and the internal pressure of the polymerization vessel was 6 kg / cm.
^The polymerization was terminated at the time of dropping to ² G, and after the unreacted monomer was recovered, 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 described below. Table 1 shows the results.

<Bulk specific gravity> Measured according to JIS K-6721. <Particle size distribution> Measured according to JIS Z-8801. <Amount of plasticizer absorbed> 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 charged as a sample. Add 15cc of dioctyl phthalate (DOP) to this and leave it for 30 minutes to
P was fully penetrated into the polymer. After that, the excess DOP was centrifuged at 1500 G acceleration, and the DO absorbed by 10 g of polymer was absorbed.
The amount of P was measured, and the reduced amount per 100 g of the polymer was defined as the amount of plasticizer absorbed.

<Plasticizer Absorption Time> 400 g of the obtained vinyl chloride polymer powder was placed in a Brabender plastograph (planetary mixer), and heated to 80 ° C. by preheating (4 minutes) while stirring at 60 rpm. , Add 200g of DOP to this,
The time from the time of the addition to the time when the decrease of the torque was completed was measured and defined as the plasticizer absorption time. <Scale adhesion> After the polymerization was completed, the state of adhesion of the polymer scale 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 The crosslinked acrylic acid copolymer used in Example 1 was replaced with a viscosity of 400 cP (1% by weight aqueous solution: 25
° C) cross-linked acrylic acid copolymer (trade name: Hibiswako
103, manufactured by Wako Pure Chemical Industries, Ltd.), a vinyl chloride polymer was obtained 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 the presence or absence of a skin layer Was evaluated. Table 1 shows the results.

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

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. , 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. Table 1 shows the results.

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 were changed to 30 g and 15 g, respectively. , 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. Table 1 shows the results.

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. , 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. Table 1 shows the results.

Comparative Example 2 In place 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 chloride 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, and the bulk specific gravity, the particle size distribution, the plasticizer absorption amount,
The plasticizer absorption time, scale adhesion, and the presence or absence of a skin layer were evaluated. Table 1 shows the results.

[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 recognized that the particle size distribution is sharp, the plasticizer absorbability is excellent, and the scale in the polymerization vessel hardly adheres. On the other hand, even when a partially saponified polyvinyl alcohol having the same physical properties as the suspending agent of the present invention is used in combination with the cross-linked copolymer, the ratio thereof is different from the range of the present invention, and the cross-linked copolymer When the ratio was large (Comparative Example 1) and when a suspending agent different from the suspending agent of the present invention was used (Comparative Example 2), the skin layer was present in the polymer and the plasticizer absorption And the scale was found to adhere.

[0038]

According to the present invention, a vinyl chloride polymer having no skin layer can be stably obtained, and a vinyl chloride polymer having excellent plasticizer absorption and gelling properties and a good particle size distribution can be obtained. A polymer can be obtained. Further, it is possible to obtain a vinyl chloride-based polymer in which scale is hardly adhered to the polymerization vessel and coarse particles are not generated.

Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08F 2/16-2/20

Claims (1)

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