JPH0532706A - Production of vinyl chloride-based resin - Google Patents

Abstract

PURPOSE:To produce a vinyl chloride-based resin not causing a large amount of scale during polymerization without reducing gelatinizing performances, adsorption characteristics of plasticizer, solubility in organic solvent, etc. CONSTITUTION:A vinyl chloride monomer alone or together with another monomer copolymerizable therewith is subjected to suspension polymerization in an aqueous medium in the presence of an oil-soluble free radical initiator such as di-2-ethylhexylperoxy carbonate by using both a surfactant such as polypropylene oxide oleyl ether and a water-soluble thickening agent such as polyaluminum chloride.

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 resin by a suspension polymerization method.

[0002]

2. Description of the Related Art Vinyl chloride resins are excellent in mechanical strength, water resistance, chemical resistance, etc., and are used as molding materials for pipes, plates, etc., or are dissolved in a solvent to form an ink vehicle, It is used as a paint, adhesive, and binder for magnetic recording media.

By the way, there are emulsion polymerization method and solution polymerization method as the polymerization method of vinyl chloride resin, but the former emulsion polymerization method requires complicated treatments such as salting out and filtration, and the obtained resin. Is a fine powder and is difficult to handle. In the latter solution polymerization method, methanol, ethyl acetate,
Since a large amount of a solvent such as toluene is used, the cost becomes high and there is a problem in terms of safety. Therefore, it is often produced by a suspension polymerization method using water as a dispersion medium from the viewpoint of productivity and the reason that it is relatively free of impurities.

By the way, in the case of the water suspension polymerization method,
As a dispersant, a so-called polymer dispersant such as partially saponified polyvinyl alcohol or a cellulose derivative has been generally used.

However, when these polymer dispersants are used, it has been observed by a scanning electron microscope that the surface of the polymer particles is covered with a strong film mainly composed of the polymer dispersant. And the presence of this film causes insufficient gelation of the resin during molding and deterioration of plasticizer absorbability, and
There is a problem that it becomes a factor of an insoluble component when dissolved in an organic solvent.

As a method for solving the above-mentioned problem, Japanese Patent Laid-Open No.
0-228508, Japanese Patent Publication No. 52-27678, Japanese Patent Publication No. 60-50204, etc. propose to use a surfactant instead of the polymer dispersant in the water suspension polymerization method. Has been done.

[0007]

However, when a surfactant is used, a large amount of scale is generated during polymerization, which adheres to the wall surface of the polymerization tank and requires scale removal work. was there.

In view of the above points, the present invention is a vinyl chloride prepared by a water suspension polymerization method in which a large amount of scale does not occur during polymerization without lowering gelling performance, plasticizer absorbability, solubility in organic solvents and the like. An object of the present invention is to provide a method for producing a base resin.

[0009]

As a result of various studies in consideration of the above points, the present inventor has found that a vinyl chloride monomer or a vinyl chloride monomer and another monomer copolymerizable therewith in an aqueous medium. In carrying out suspension polymerization in the presence of an oil-soluble radical initiator, if a surfactant and a water-soluble thickener are used together, gelation performance, plasticizer absorbability, solubility in organic solvents, etc. are not reduced. The inventors have completed the present invention by discovering that the occurrence of scale can be suppressed.

In the present invention, other monomers copolymerizable with the vinyl chloride monomer include, for example, olefins such as ethylene, propylene and butylene, vinyl acetates such as vinyl acetate and vinyl propionate, isobutyl vinyl ether and cetyl vinyl ether. , Vinyl ethers such as phenyl ether, methyl (meth)
Acrylate, (meth) acrylates such as ethyl (meth) acrylate, vinylidene chloride, vinyl halides such as vinyl fluoride, dimethyl maleate,
Unsaturated dicarboxylic acid esters such as dimethyl fumarate, unsaturated dicarboxylic acid anhydrides such as maleic anhydride,
N-substituted maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide, acrylic acid, methacrylic acid, succinic acid mono (meth) acryloyloxyethyl ester, phthalic acid mono (meth) acryloyloxyethyl ester, maleic acid n-butyl ester Carboxyl-containing monomers such as monoester, maleic acid and fumaric acid, sulfonic acid group- or sulfonic acid group-containing monomers such as 2-acrylamido-2-methylpropane sulphonic acid and sodium methacryl sulphonate,
Phosphoric acid group-containing monomers such as acid phosphoxyethyl (meth) acrylate, acid phosphoxypropyl (meth) acrylate and 3-chloro-2-acid phosphoxypropyl (meth) acrylate, 2-hydroxy-3
-Quaternary ammonium chloride-containing monomers such as methacryloyloxypropyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, trimethyl-3-methacrylamido-propylammonium chloride, dimethylamino (meth) acrylate, diethylamino (meth) acrylate, N, N -Amino group-containing monomers such as dimethylaminopropyl acrylamide and t-butylaminoethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, polyethylene Glycol mono (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth)
Reaction products of (meth) acrylic acid such as acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl-2-acryloyloxyphthalate and polyhydric alcohol, N-methylol (meth) acrylamide and the like ( It is vinyl containing a hydroxyl group such as (meth) acrylic acid amide. Two or more kinds of these monomers can be used in combination depending on the intended use.

Among the other monomers copolymerizable with the vinyl chloride monomer described above, a reaction product of (meth) acrylic acid and a polyhydric alcohol, a (meth) acrylic acid amide such as N-methylol (meth) acrylamide, etc. Hydroxyl group-containing vinyl monomers such as have a reactive double bond and a hydroxyl group, and vinyl chloride resins, which are copolymers of this monomer and vinyl chloride monomers, include acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Excellent solubility in ketones such as ketones, cyclic ethers such as tetrahydrofuran and dioxane, acetic acid esters such as methyl acetate and ethyl acetate, and organic solvents such as mixed solvents of these organic solvents and toluene. It is particularly preferably used for applications such as agents and binders for magnetic recording materials.

The amount of the other monomer that can be copolymerized with the vinyl chloride monomer depends on the intended use. Especially when used for the purpose of dissolving in an organic solvent, the solubility of the obtained resin in an organic solvent decreases when the amount of this monomer decreases, the viscosity becomes too high, and a vinyl chloride-based resin obtained when the amount is too high The mechanical strength originally possessed by the resin is lost, and the film strength of the coating film is lost. Therefore,
It is preferable that the vinyl chloride monomer is 60 to 99% by weight, and the monomer copolymerized therewith is 40 to 1% by weight, and more preferably 70 to 9% vinyl chloride monomer.
It is 5% by weight, and the amount of the monomer copolymerized therewith is 30 to 30%.
It is 5% by weight.

The oil-soluble radical initiator is not particularly limited, and those conventionally used for polymerization of vinyl chloride can be used. For example, azobis-based compounds such as azobisisobutyronitrile and dimethylazobisvaleronitrile, or lauroyl peroxide, benzoyl peroxide, di-t-butyl peroxide, t-butylperoxy-2-ethylhexanate. ,
Examples thereof include organic peroxides such as t-butyl peroxyisobutyrate, di-2-ethylhexyl peroxydicarbonate, di-3-methoxybutyl peroxycarbonate and diisopropyl peroxydicarbonate.

These oil-soluble radical initiators may be used alone or in combination of two or more. Further, the addition amount is appropriately determined depending on the polymerization conditions,
Generally, 0.01 to 3 parts by weight is preferably added to 100 parts by weight of the total amount of vinyl chloride monomer and other monomers, and more preferably 0.1 to 1 part by weight. If it is less than 0.01 parts by weight, the yield will be poor, and if it exceeds 3 parts by weight, the polymerization temperature will easily rise and the pressure in the polymerization vessel will rise more than necessary.

In the present invention, as the surfactant,
Both nonionic surfactants and anionic surfactants commonly used in emulsion polymerization are preferably used. Examples of the former nonionic surfactant include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkylene alkyl ether, polyoxyethylene- Polyoxypropylene block polymer, polyoxyethylene fatty acid ester,
Sorbitan monolaurate, polyethylene lanolin alcohol ether, polyoxyethylene lanolin fatty acid ester, polyoxyethylene alkylamine ether,
Examples thereof include fatty acid diethanolamide.

Examples of the latter anionic surfactants include higher alcohol sulfate ester soda, sodium alkylbenzene sulfonate, sodium β-naphthalene sulfonate, dialkyl sulfosuccinate sodium salt, polyoxyethylene alkyl ether phosphate and polyoxy. Examples thereof include ethylene alkyl ether sulfate ester.

Among these surfactants, nonionic surfactants having an HBL of 9 or less and a molecular weight of 1000 or more are more preferably used. For example, it is a surfactant mainly composed of polypropylene oxide, and specific examples thereof include polypropylene oxide alkyl ether, polypropylene oxide alkyl ester, polypropylene oxide alkyl allyl ether and the like.

These surfactants may be used alone or in combination of two or more kinds. The amount of addition is 0.1 parts by weight with respect to 100 parts by weight of vinyl chloride monomer (and the total amount of other monomers) used in the polymerization.
˜5 parts by weight is preferably added, and more preferably 0.3 to 2 parts by weight. When it is less than 0.1 part by weight,
If the resin particles easily block, and the amount exceeds 5 parts by weight, the resin particles become too fine and the residual surfactant deteriorates the water resistance of the coating film such as paint, which is not preferable.

A known polymer dispersant such as partially saponified polyvinyl alcohol or cellulose may be used in combination with the above surfactant. However, the total amount of surfactant used is 3
It is preferable to set it in the range of 0% by weight or less. This is because if the amount exceeds 30% by weight, the scale generation amount increases, which is not preferable.

In the present invention, the water-soluble thickener is one having a Brookfields viscosity of 5 cps or more at 20 ° C. when dissolved in 0.1 part by weight of water in 100 parts by weight. For example, sodium alginate, propylene glycol alginate, sodium carboxymethyl cellulose, calcium carboxymethyl cellulose,
Sodium starch glycolate, sodium starch phosphate, methyl cellulose calcium, sodium polyacrylate, polyallylamide, cross-linked (meth) acrylic acid-based polymer, polyvinylpyrrolidone, polyaluminum chloride, etc., in the above range In this case, various kinds of organic and inorganic substances can be used.

These water-soluble thickeners may be used alone or in combination of two or more. The addition amount is 0.0 with respect to 100 parts by weight of vinyl chloride monomer (and the total amount of other monomers) used during the polymerization.
It is preferably added in an amount of 01 to 0.5 part by weight, more preferably 0.005 to 0.3 part by weight. If the amount is less than 0.005 parts by weight, the resin particles easily block,
If it exceeds 0.3 parts by weight, the resin particles become too fine and the residual water-soluble thickener reduces the water resistance of the coating film such as a paint, which is not preferable.

By the way, it is preferable that such a vinyl chloride resin has a reduced viscosity when dissolved in a solvent. Therefore, it is preferable to suppress the degree of polymerization to a low level. To lower the degree of polymerization, there is a method of increasing the polymerization temperature to perform the polymerization.
Since the vapor pressure of the vinyl chloride monomer becomes high and the pressure resistance of the polymerization vessel must be increased, it is preferable to use a chain transfer agent during the polymerization.

As such a chain transfer agent, those conventionally used as a chain transfer agent can be used. Examples thereof include thioethers such as n-dodecyl mercaptan and mercaptoethanol, and halogenated hydrocarbons such as dichloroethylene, trichloroethylene, chloroform, carbon tetrachloride and carbon tetrabromide. Also, two or more kinds can be used in combination. Particularly, thioethers are preferably used.

The amount of these chain transfer agents added is such that vinyl chloride or vinyl chloride and monomer 100 copolymerized therewith are added.
It is usually about 0.05 to 1 part by weight with respect to parts by weight.
If it is less than 0.05 parts by weight, the effect of suppressing the degree of polymerization is small,
This is because if it exceeds 1 part by weight, even if it is added more than that, it is not so effective in suppressing the degree of polymerization.

The method of adding the chain transfer agent is as follows.
A method in which the addition is performed twice or more over a period of 1/3 or more of the polymerization time from the initial stage of polymerization is adopted.
That is, for example, in the case of adding the chain transfer agent in two divided portions, the first addition is performed at the initial stage of polymerization, and the remaining second addition is performed after 1/3 of the polymerization time. is there.

More preferably, the number of additions is increased by finely dividing and the addition is preferably performed over the entire polymerization time. The amount of one addition is not particularly limited, but it is preferable to make it proportional to the polymerization rate of the monomer in the divided addition intervals.

As the water suspension polymerization method in the invention, any method which has been carried out in the conventional water suspension polymerization of vinyl chloride may be adopted. For example, after supplying water, a surfactant and an oil-soluble radical initiator into the polymerization vessel and reducing the pressure,
A method may be mentioned in which a vinyl chloride monomer (and other monomer) is press-fitted with stirring and heated.

The vinyl chloride-copolymerizable monomer may be initially supplied together with water, or may be dissolved in the vinyl chloride monomer and then injected together with the vinyl chloride monomer. When the polymerization rate of the vinyl chloride-copolymerizable monomer is faster than that of vinyl chloride, it is preferable to add them in divided portions from the beginning to the end of the polymerization, or to add them in small amounts continuously. This is preferable because a uniform copolymer can be obtained.

The polymerization temperature is usually 40 to 85 ° C., and the polymerization time is usually 2 to 20 hours. In addition, in order to adjust the degree of polymerization of the obtained vinyl chloride resin, it is preferable to add a chain transfer agent such as mercaptoethanol or n-dodecylmercaptan during the polymerization as described above.

After completion of the polymerization, unreacted vinyl chloride monomer and the like are removed from the polymerization vessel, and then the polymer slurry is taken out and subjected to treatments such as washing, dehydration and drying to obtain a particulate vinyl chloride resin.

[0031]

Embodiments of the present invention will be described below. In addition,
Parts means parts by weight. In the following examples, the measuring method of each component, insoluble component and scale amount was as follows. (1) Scale Adhesion Rate After the polymerization, the polymerization slurry is taken out, the polymerization vessel is opened, and the polymerization scale adhering to the inside is taken out,
It was dried and weighed. The ratio of this weight to the weight of the resin taken out as a slurry after drying is defined as the scale adhesion rate (%) [= (scale weight / (dry weight of slurry + scale weight) × 100]. (2) Vinyl chloride Component Chlorine content is measured by oxygen flask combustion method to determine vinyl chloride content (3) Hydroxyl group-containing vinyl component Acetic anhydride and pyridine are used to determine hydroxyl group-containing vinyl component content (4) Nitrogen-containing vinyl component Elemental analysis The amount of nitrogen component is measured by a device (CHN Coder MT-5, manufactured by Yanagimoto Seisakusho Co., Ltd.) (4) Number of vinyl components containing insoluble matter 1 g of the resin obtained is 1: 1 by weight of methyl ethyl ketone and toluene. Ratio) Dissolved in 99 g of mixed solvent and adjusted to a 1% by weight solution, fine particle analyzer in solution (Partical Counter KL-01, manufactured by Lion Corporation) Lysis solution 10m using
The number of particles of insoluble foreign matter of 20 μm or more in 1 is measured and taken as the number of insoluble foreign matters. (Example 1) In a jacketed 25 l pressure resistant polymerization machine equipped with a stirrer, 133 parts of ion-exchanged water, 0.05 part of di-2-ethylhexyl peroxydicarbonate as an oil-soluble radical initiator, and polypropylene oxide as a surfactant. After supplying 1 part of oleyl ether and 0.1 part of polyaluminum chloride as a water-soluble thickening agent and sealing the polymerization vessel to eliminate air, 100 parts of vinyl chloride monomer was press-fitted, then, while stirring, 58 The temperature was raised to 0 ° C, and suspension polymerization was carried out while the temperature inside the polymerization vessel was maintained at 58 ° C.

Thirty minutes after the internal pressure of the polymerization vessel started to drop, cooling water was passed through the jacket to cool the polymerization vessel,
After cooling, unreacted vinyl chloride monomer, etc. are removed, and the polymerized slurry is taken out and washed with ion-exchanged water.
It was dried to obtain polyvinyl chloride (PVC).

The PVC obtained was in the form of a white powder, and when observed under a scanning electron microscope at a magnification of 2000, it was in a so-called skinless state without a coating layer on the particle surface. In addition, the viscosity average degree of polymerization (JIS K6
721) and the scale attachment rate are as shown in Table 1. (Examples 2 to 6) PVC was polymerized in the same manner as in Example 1 except that the types and amounts of the surfactant and the water-soluble thickener and the amount of 2-hydroxypropyl acrylate were as shown in Table 1. Obtained.

Each of these PVCs was in a skinless state as in Example 1, and had a viscosity average polymerization degree (JI).
(According to SK6721) and scale adhesion rate are as shown in Table 1. (Comparative Example 1) Example 1 except that no water-soluble thickener was added.
Polymerization was carried out in the same manner as above to obtain PVC.

For this PVC, the same measurement as in Example 1 was performed. The results are shown in Table 1. (Comparative Example 2) Example 3 except that no water-soluble thickener was added.
Polymerization was carried out in the same manner as above to obtain PVC.

For this PVC, the same measurement as in Example 1 was performed. The results are shown in Table 1. (Comparative Example 3) Example 6 except that no water-soluble thickener was added.
Polymerization was carried out in the same manner as above to obtain PVC.

For this PVC, the same measurement as in Example 1 was performed. The results are shown in Table 1.

[0038]

[Table 1]

As is clear from these results, Examples 1 to 1
The polyvinyl chloride of 6 had no film on the surface of the particles, and the scale was hardly generated during the polymerization, and the scale did not adhere to the inner wall of the polymerization vessel. On the other hand, a large amount of scale adhered to the inner wall of the polymerization vessel in the case where the water-soluble thickener of Comparative Example was not used in combination. (Example 7) In a 25 l pressure resistant polymerization vessel with a jacket equipped with a stirrer, 133 parts of ion-exchanged water, 0.18 part of t-butylperoxy-2-ethylhexanate as an oil-soluble radical initiator, and a surfactant. After supplying 1 part of polypropylene oxide oleyl ether and 0.1 part of polyaluminum chloride as a water-soluble thickener, sealing the polymerization vessel to eliminate air, 65 parts of vinyl chloride monomer was press-fitted, and then vinyl chloride 35 10 parts of a post-additive composition consisting of 11.5 parts of 2-hydroxypropyl acrylate
Weight% was pressed in. While stirring, raise the temperature to 80 ° C,
Immediately after the temperature in the polymerization vessel reached 80 ° C., the rest of the post-addition composition was divided into 120 and added every 2 minutes to carry out suspension polymerization.

After 5 minutes from the completion of the addition, cooling water was passed through the jacket to cool the polymerization vessel. After cooling, unreacted vinyl chloride monomer and the like were removed, and the polymerization slurry was taken out and washed with ion-exchanged water. Then, it was dried to obtain a vinyl chloride resin.

The resin thus obtained was in the form of white powder, and
The monomer component (wt%), the number of insoluble foreign matters (20 μm or more) and the scale adhesion rate (%) are as shown in Table 2. (Examples 8 to 13) Polymerization was performed in the same manner as in Example 7 except that the types and amounts of the surfactant and the water-soluble thickener were as shown in Table 2, to obtain vinyl chloride resin.

The same measurement as in Example 7 was carried out for each of the vinyl chloride resins. The results are shown in Table 2. (Comparative Examples 4 to 6) The types and amounts of the surfactants are as shown in Table 2, except that the water-soluble thickener is not used.
A vinyl chloride resin was obtained in the same manner as in Example 7.

The same measurement as in Example 7 was performed for each of the vinyl chloride resins. The results are shown in Table 2. (Comparative Example 7) Water-soluble polymer dispersant (hydroxypropyl cellulose) without using a surfactant and a water-soluble thickener.
A vinyl chloride resin was obtained in the same manner as in Example 7 except that 0.4 part was used.

About this vinyl chloride resin, Example 7
The same measurement as in the above was performed. The results are shown in Table 2.

[0045]

[Table 2]

As is clear from this result, the results of Examples 7 to
In No. 13, there was little generation of scale, adhesion to the inner wall of the polymerization vessel was extremely small, and the obtained resin did not contain insoluble foreign matter. On the other hand, in Comparative Examples 4 to 6 in which the water-soluble thickener was not used in combination, a large amount of scale adhered to the inner wall of the polymerization vessel even though there was no insoluble foreign matter, and the surfactant and the water-soluble thickener were used. In Comparative Example 7 in which the water-soluble polymer dispersant was used without using the scale, the scale adhesion was relatively small, but the number of insoluble foreign matters was extremely large. (Example 14) 25 l with a jacket equipped with a stirrer
In a pressure-resistant polymerization vessel, 133 parts of ion-exchanged water, 0.18 parts of t-butylperoxy-2-ethylhexanate as an oil-soluble radical initiator, the total amount of vinyl chloride monomer and 2-hydroxypropyl acrylate to be used for polymerization. In contrast, 1 part of polypropylene oxide oleyl ether as a surfactant and 0.1 part of polyallylamide as a water-soluble thickener were supplied, the polymerization vessel was closed to eliminate air, and then 65 parts of vinyl chloride monomer was press-fitted. Then, 10% by weight of a post-addition composition comprising 35 parts of vinyl chloride monomer, 11.5 parts of 2-hydroxylpropyl acrylate and 0.22 part of mercaptoethanol as a chain transfer agent was press-fitted. While stirring, the temperature was raised to 74 ° C., and immediately after the temperature in the polymerization vessel reached 74 ° C., the rest of the post-addition composition was divided into 120 and added sequentially every 2 minutes to carry out suspension polymerization. .

Five minutes after the addition was completed, cooling water was passed through the jacket to cool the polymerization vessel. After cooling, unreacted vinyl chloride monomer and the like were removed, and a polymerization slurry was taken out and washed with ion-exchanged water. Then, it was dried to obtain a vinyl chloride resin.

The obtained resin was in the form of white powder, and its monomer composition and viscosity average degree of polymerization (according to JIS K6721) were as shown in Table 3. The scale adhesion rate (%) was as shown in Table 3. Example 15 A vinyl chloride resin was obtained by polymerizing in the same manner as in Example 14 except that the amount of mercaptoethanol was 0.44 part.

The same measurement as in Example 14 was performed on this resin. The results are shown in Table 3. (Example 16) 0.11 part at the time of preparation and 0.2% after 2 hours without mixing mercaptoethanol in the post-addition composition.
Polymerization was carried out in the same manner as in Example 14 except that 11 parts were added in two batches to obtain a vinyl chloride resin.

The same measurement as in Example 14 was performed on this resin. The results are shown in Table 3. (Example 17) A vinyl chloride resin was obtained by polymerizing in the same manner as in Example 14 except that n-dodecyl mercaptan was used instead of mercaptoethanol.

The same measurement as in Example 14 was performed on this resin. The results are shown in Table 3. Example 18 A vinyl chloride resin was obtained by polymerization in the same manner as in Example 14 except that 10 parts of N-cyclohexylmaleimide was further added to the post-addition composition.

For this resin, the same measurement as in Example 14 was performed. The results are shown in Table 3. (Example 19) Polymerization was performed in the same manner as in Example 14 except that polyethylene lauryl ether was used instead of polypropylene oxide ether as a surfactant and sodium polyacrylate was used instead of polyacrylamide as a water-soluble thickener. A vinyl chloride resin was obtained.

The same measurement as in Example 14 was performed on this resin. The results are shown in Table 3. (Comparative Example 8) Polymerization was carried out in the same manner as in Example 14 except that no chain transfer agent was used to obtain a vinyl chloride resin.

About this vinyl chloride resin, Example 1
The same measurement as in the case of 4 was performed. The results are shown in Table 3. (Comparative Example 9) A vinyl chloride resin was obtained by polymerizing in the same manner as in Example 14 except that mercaptoethanol was not added separately but was added all at once during the charging.

The same measurement as in Example 14 was performed on this resin. The results are shown in Table 3. (Comparative Example 10) A vinyl chloride resin was obtained by polymerizing in the same manner as in Comparative Example 14 except that a double amount of mercaptoethanol was added at the time of charging.

The same measurement as in Example 14 was performed on this resin. The results are shown in Table 3. Comparative Example 11 A vinyl chloride resin was obtained by polymerizing in the same manner as in Example 14 except that the water-soluble thickener was not used.

The same measurement as in Example 14 was performed on this resin. The results are shown in Table 3.

[0058]

[Table 3]

As is clear from these results, in Examples 14 to 19 in which the surfactant and the water-soluble thickener are used in combination and the chain transfer agent is dividedly added, the resin having a low scale attachment rate and a low polymerization degree is used. Is obtained, and the viscosity when dissolved in an organic solvent can be lowered. In contrast,
In the comparative example, the degree of polymerization was high and a resin having a desired low degree of polymerization could not be obtained.

[0060]

As described above, according to the method of the present invention,
It is possible to reduce the generation of scale during the polymerization, and to prevent the scale from adhering to the inner wall of the polymerization vessel, thereby eliminating obstacles to polymerization production.

A film is not formed on the surface of the particles of the obtained vinyl chloride resin, and the gelling performance, plasticizer absorbability,
It cannot reduce the solubility in organic solvents.
In the invention in which the chain transfer agent is dividedly added, the vinyl chloride resin can have a low degree of polymerization, and the viscosity when dissolved in an organic solvent is lowered.

Claims (2)

[Claims] 1. A suspension of a vinyl chloride monomer or a vinyl chloride monomer and another monomer copolymerizable therewith in the presence of an oil-soluble radical initiator in an aqueous medium in the suspension polymerization, and a surfactant and a water-soluble agent. A method for producing a vinyl chloride resin, which comprises using a thickener. 2. The vinyl chloride resin according to claim 1, wherein the chain transfer agent is added in two or more divided portions over a period of at least 1/3 of the polymerization time from the beginning of the polymerization. Production method.