JP3301151B2 - 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. More specifically, the present invention relates to a method for producing a vinyl chloride polymer for a paste, which gives a plastisol having a low viscosity and a good gelling property.

[0002]

2. Description of the Related Art A vinyl chloride polymer for a paste is generally produced by using a water-soluble polymerization initiator, or a vinyl chloride monomer comprising a mixture of vinyl chloride alone or a compound copolymerizable with vinyl chloride. (Hereinafter abbreviated as "vinyl chloride-based monomer") or emulsion polymerization of vinyl chloride-based monomer (hereinafter abbreviated as "oil-soluble polymerization initiator"). It is manufactured by a fine suspension polymerization method in which a monomer is previously made uniform and finer mechanically, dispersed in water, and then subjected to suspension polymerization. In the above polymerization method, the so-called seed polymerization method using a seed polymer is easy to control the particle size of the produced polymer, and the unit volume of the polymerization vessel
It is awarded because of its large production per unit time.

[0003] Among the seeding polymerization methods, the operation of the seeding emulsion polymerization method is usually such that water, seed polymer particles, an emulsifier, a water-soluble reducing agent, and a vinyl chloride monomer are charged and the temperature is raised to a predetermined reaction temperature. Thereafter, the polymerization is started by gradually adding a water-soluble polymerization initiator (sequential addition), and while removing the polymerization heat generated at this time by cooling, the reaction is performed while controlling the particle size of the generated polymer. To do so. It is a common practice to control the reaction rate by adjusting the rate of addition of the polymerization initiator.

[0004] The present inventors previously obtained a vinyl chloride-based monomer by seeding it by using a vinyl chloride-based polymer produced by a fine suspension polymerization method in the seed emulsion polymerization. The present inventors have found and proposed that a vinyl chloride polymer for pastes having a low viscosity of a plastisol to be obtained and having good gelling properties can be obtained (Japanese Patent Application No. 4-119515). In the present invention, fine suspension polymerization for obtaining a seed polymer is carried out by adding a large amount of a polymerization initiator such as 0.2% by weight or more to a vinyl chloride-based monomer, for 8 to 10 hours. When performed in a relatively short time, the amount of the oil-soluble polymerization initiator remaining in the polymer particles is large, and conversely, the amount of the oil-soluble polymerization initiator remaining is reduced. Then, there was a relationship that the reaction took an extremely long time. When the former polymer containing a large amount of the polymerization initiator is used as a seed and the temperature is increased by adding the vinyl chloride monomer and the water-soluble reducing agent at once according to the above-described seeding emulsification operation, the remaining polymerization is initiated. The reaction between the agent and the reducing agent rapidly occurs, and thereby the polymerization is rapidly accelerated, so that the reaction cannot be controlled. Therefore, in the present invention, a method of utilizing an oil-soluble polymerization initiator remaining in the polymer particles, further adding a water-soluble polymerization initiator, and sequentially adding a water-soluble reducing agent little by little is used. Was.

However, even in this method, the reaction is carried out in a state where a large amount of the polymerization initiator is present in the system.
In some cases, the polymerization initiator may be rapidly decomposed and a runaway reaction may occur. Therefore, there has been a problem that an excessive heat removal facility must be provided in preparation for danger. On the other hand, if the polymer particles having a small amount of the residual oil-soluble polymerization initiator are used as seeds, there is no problem in the reaction controllability,
Since it takes a long time to produce a seed polymer, it is not suitable for industrial practice. That is, sufficient productivity of the seed polymer,
No method has yet been obtained that satisfies both the ease of reaction control of seeded emulsion polymerization.

[0006]

An object of the present invention is to produce a vinyl chloride polymer for pastes capable of giving a plastisol having a low viscosity and a good gelling property by a seeding emulsion polymerization method. In addition, it is an object of the present invention to provide a method that simultaneously satisfies both sufficient productivity of a seed polymer and ease of reaction control of seeding emulsion polymerization in the production of a vinyl chloride polymer for a paste. .

[0007]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a vinyl chloride monomer composed of vinyl chloride alone or a mixture of vinyl chloride and a compound copolymerizable with vinyl chloride in an amount of 0.2 to 2 parts. The first step in which fine suspension polymerization is carried out using a polymerization initiator soluble in a vinyl chloride monomer in an amount of 1% by weight, and the polymerization initiator obtained in the polymerization in the first step contains the polymerization initiator remaining in the polymer particles. Second step of adding a water-soluble reducing agent to the latex to be subjected to heat treatment to substantially decompose and remove the residual polymerization initiator, and using the latex obtained in the second step as a seed polymer as a vinyl chloride-based polymer. A method of producing a vinyl chloride-based polymer including a third step of mixing with a monomer and performing seed emulsion polymerization.

Hereinafter, the present invention will be described in more detail. Examples of the vinyl chloride monomer used as a raw material in the present invention include vinyl chloride alone or a mixture of vinyl chloride and a compound copolymerizable therewith. Examples of the compound copolymerizable with vinyl chloride include olefins such as ethylene, propylene and n-butene; vinyl esters such as vinyl acetate, vinyl propionate and vinyl stearate; acrylic acid, methacrylic acid and itacone Unsaturated carboxylic acids such as acids or alkyl esters thereof; methyl vinyl ether, octyl vinyl ether,
Vinyl ethers such as lauryl vinyl ether; maleic acid, fumaric acid or esters thereof; unsaturated nitriles and the like. One or a mixture of two or more of these compounds is used. The amount of the compound copolymerizable with vinyl chloride is 30% by weight or less based on the total amount of the monomers,
In particular, the content is preferably 20% by weight or less.

In the polymerization of the first step of the present invention, for example, a vinyl chloride monomer is mixed with water, an oil-soluble polymerization initiator and an emulsifier, and homogenized using an emulsifier to form fine droplets. Then, a method is employed in which the mixture is dispersed and heated to carry out suspension polymerization. As the emulsifier (homogenizer), for example, a colloid mill, a high-speed pump, a pipeline mixer, an ultrasonic disperser, a vibration stirrer and the like can be used.

After the fine suspension polymerization, the polymer is subjected to a decomposition treatment of the residual oil-soluble polymerization initiator in the second step in a latex state without drying. As the oil-soluble polymerization initiator used in the first step, heat generation during homogenization treatment
It is preferable to use a material having high stability against these physical forces so that decomposition by an impact (for example, due to a stirring blade of a homogenizer) does not occur. For example, lauroyl peroxide,
Organic peroxides such as t-butyl peroxypivalate, azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, and azo compounds can be used.

[0011] These oil-soluble polymerization initiators are used in an amount of 0.2 to 2% by weight based on the vinyl chloride monomer. When the amount of the initiator is less than 0.2% by weight, the polymerization reaction takes 16 to 24 hours,
Alternatively, a longer time is required, and when the amount exceeds 2% by weight, the reaction of fine suspension polymerization becomes too fast,
Reaction controllability deteriorates. A more preferred amount of the initiator is 0.3 to 1% by weight based on the vinyl chloride monomer.

When the fine suspension polymerization is carried out under the above-mentioned conditions, the polymerization reaction can be completed in a short time such as about 6 to 10 hours. 0.2 to 2% by weight of the polymerization initiator remains. When the reaction is carried out by adding 0.2 to 2% by weight of the polymerization initiator with respect to the monomer, the polymerization initiator is consumed by the reaction, but the conversion of the monomer is not 100% but 75 to 2%.
Since it is 85%, the residual amount of the polymerization initiator in the produced polymer particles is also about 0.2 to 2% by weight.

In order to obtain a seed polymer for the seeding polymerization in the third step, the average particle size of the polymer obtained in the first step is 0.3 to 0.8 μm, preferably 0.4 to 0 μm. 0.7μ
m. The emulsifier used for the polymerization in the first step is not particularly limited.For example, alkali metal salts and ammonium salts of higher alcohol sulfates such as sodium lauryl sulfate, and alkylbenzenesulfonic acid such as sodium salt of dodecylbenzenesulfonic acid are used. Alkali metal salts and ammonium salts, alkali metal salts and ammonium salts of higher fatty acids, anionic surfactants such as alkali metal salts of dialkyl sulfosuccinates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, sorbitan fatty acid esters, One or a mixture of two or more nonionic surfactants such as polyoxyethylene higher fatty acid esters are used. The emulsifier is 0.1 to 3 based on the vinyl chloride monomer.
% By weight, especially 0.3 to 1.0% by weight.

Further, as an emulsifying aid, a compound having 10 to 1 carbon atoms is used.
The higher alcohol of No. 8 can be used in combination of 0.3 to 2% by weight. In the present invention, as the second step, the oil-soluble polymerization initiator remaining in the polymer particles of the latex obtained in the first step is decomposed and removed by heat treatment in the presence of a water-soluble reducing agent.

As a heat treatment method, for example, a method of adding a water-soluble reducing agent to a predetermined amount of water and this latex as it is or after degassing, and heating in the absence of a vinyl chloride monomer is employed. it can. The temperature of the heat treatment is 4
It is desirable to select from the range of 0 to 80 ° C, preferably the range of 60 to 75 ° C. The processing temperature is preferably lower for the dispersion stability of the latex, but the processing time tends to be longer. Although the treatment time depends on the temperature of the heat treatment, about 10 to 200 minutes is used.

The kind of the water-soluble reducing agent used in the heat treatment is not particularly limited, and a water-soluble inorganic reducing agent such as sodium sulfite, sodium hydrogen sulfite, ammonium sulfite, sodium pyrosulfite, etc., and ascorbic acid or its metal Water-soluble organic reducing agents such as salts and sodium formaldehyde sulfoxylate can be used. The amount of the reducing agent used must be stoichiometric or more with respect to the oil-soluble polymerization initiator contained in the polymer particles in the latex. This treatment may be carried out by providing a treatment facility separate from the polymerization system, but is carried out in a polymerization reactor for performing the emulsion polymerization of the third step, and the same treatment is performed using the treated latex as a seed polymer. It is efficient to carry out the third step of polymerization in a reactor. In this case, the reducing agent used in the emulsion polymerization may be added together.

In this heat treatment, the pH of the system is adjusted using sodium carbonate, sodium hydrogen carbonate, or the like.
Adjustment to the alkaline side of 8 to 13 or presence of heavy metal ions such as copper ions and iron ions is effective in promoting decomposition. The term “substantially decompose and remove the residual polymerization initiator” as used in the present invention means that the polymerization reaction by the oil-soluble polymerization initiator remaining in the polymer particles obtained by the fine suspension polymerization in the first step is performed. It does not substantially occur at the time of seeding emulsion polymerization, meaning that the reaction control is not adversely affected.
The presence or absence of the influence of this reaction depends on whether the monomer is charged in the emulsion polymerization operation of the third step, and when the temperature is raised to a predetermined temperature, heat generation due to polymerization is observed before the addition of the water-soluble polymerization initiator is started. Can be determined by (If there is heat generation, polymerization by the remaining oil-soluble polymerization initiator has occurred.)

The relationship between the residual amount of the oil-soluble polymerization initiator in the latex after the heat treatment and the influence on the seeding emulsion polymerization in the third step is determined by the reaction temperature of the emulsion polymerization, the latex (seed polymer)
Varies depending on the amount of used and the type of the oil-soluble polymerization initiator used, and cannot be uniformly specified. As an example, a latex prepared using lauroyl peroxide is used as a seed polymer, and the reaction temperature is 55 ° C., and the amount of the latex used is 4 to 4.
When polymerization was carried out at 6% by weight (based on monomer), if the content of lauroyl peroxide in the polymer particles was less than 0.05%, almost no influence on the seed emulsion polymerization was observed.

When the oil-soluble polymerization initiator remains in the polymer particles so as to affect the seeded emulsion polymerization, the polymerization reaction is started when the reducing agent and the vinyl chloride monomer are charged and the temperature is raised as described above. When the process starts, the particle size of the produced polymer cannot be controlled, and the quality of the product deteriorates. In addition, in some cases, the reaction cannot be controlled, and a runaway reaction may occur. Next, as a third step, using the latex obtained in the second step as a seed polymer, introducing a vinyl chloride monomer into the system, raising the temperature, and adding a water-soluble polymerization initiator. Thus, seeding emulsion polymerization can be started. Before introducing the monomer, if necessary, water, an emulsifier, a reducing agent or other auxiliaries can be added or added.

As the polymerization initiator for the emulsion polymerization in the third step, various water-soluble polymerization initiators are used. Examples thereof include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; water-soluble peroxides such as hydrogen peroxide; and redox initiators comprising these and the above-described water-soluble reducing agents. In order to adjust the pH of the reaction system so that the decomposition of the redox initiator proceeds more smoothly, a pH adjuster (buffer) such as sodium hydrogen carbonate or sodium dihydrogen phosphate can also be used.

Examples of the emulsifier used in the emulsion polymerization include alkali metal salts and ammonium salts of higher alcohol sulfates exemplified in the description of the fine suspension polymerization in the first step.
One or a mixture of two or more anionic or nonionic surfactants such as alkyl metal salts and ammonium salts of alkyl benzene sulfonic acids can be used. The emulsifier used in the third step may be the same as or different from the emulsifier used in the first step.

The vinyl chloride polymer obtained according to the present invention is subjected to a commercialization process such as drying by a well-known method. During the commercialization process, various commonly used emulsifiers for adjustment, antioxidants, and other auxiliaries / modifiers can be added. In addition, the obtained vinyl chloride polymer is mixed with a plasticizer, a stabilizer, a filler, an antioxidant, an ultraviolet absorber, an antistatic agent, a coloring agent, a release agent, etc. as a resin for the paste, and mixed with a plastisol. Or used as an organosol.

[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 scope of the present invention. “Parts” and “%” in the examples indicate “parts by weight” and “% by weight”, respectively. In the following Examples and Comparative Examples, the primary particle diameter and the solid content are values measured by the following method for the vinyl chloride polymer latex obtained by fine suspension polymerization or emulsion polymerization.

Spray drying of polymer latex: After filtering a vinyl chloride-based polymer latex through a 20-mesh wire netting, polyoxyethylene nonylphenyl ether (average degree of polymerization of polyoxyethylene portion) is used as a nonionic surfactant for adjustment. Was added to the polymer (solid content) in an amount of 0.3% by weight, and a small spray dryer (SAN) was added.
Production by iro Atomizer
-Minor type), and then pulverized by a hammer mill (manufactured by Hosokawa Micron, MA-5 type).

Primary particle diameter: The average particle diameter of the vinyl chloride polymer in a latex state is measured using a laser diffraction particle size distribution analyzer LA-700 manufactured by Horiba Seisakusho. Solid content: about 1 g of vinyl chloride polymer latex
Is collected and precisely weighed (referred to as W ₀ ). This is heated for 1 hour in an oven maintained at 105 ° C. to evaporate water.
After cooling 30 minutes in a desiccator, and weighed again (and W _1), it calculates the solid concentration as W ₁ / W ₀ × 100. (Referring to the volatile matter measurement method of JIS-K6721)

Amount of residual oil-soluble polymerization initiator: The latex is freeze-dried, and a fixed amount of the dried polymer is dissolved in THF (tetrahydrofuran, special grade of reagent) so as to have a fixed volume, and this is subjected to GPC manufactured by Tosoh Corporation. (Gel Permeation Chromatograph) Using a device, the peak area corresponding to the polymerization initiator is measured by a calibration curve separately prepared from a standard sample.

Viscosity: 100 parts of a vinyl chloride polymer, 70 parts of DOP, 10 parts of calcium carbonate, 2 parts of a stabilizer (Sn type) and 3 parts of epoxidized soybean oil, and a planetary mixer (HOBART MIXER
N-50 type, THE HOBART MFG. CO.
) To obtain a plastisol.
After aging this plastisol in a constant temperature and humidity room at 23 ° C. and a humidity of 50% for 2 hours, the viscosity was measured with a B8H type viscometer (Brookfield Viscometer, manufactured by Tokimec Co., Ltd.).
r), the number of rotations is 5 using a # 6 (or # 7) rotor.
Measure at 0 rpm.

Viscosity stability: The sol prepared and measured for viscosity is stored in a constant temperature and humidity room at 23 ° C. and 50% humidity, and the viscosity is measured again after 7 days. The ratio of the viscosity after 7 days to the initial viscosity is defined as AI (Aging Index) as an index of viscosity stability. Gelling property: 100 parts of a vinyl chloride polymer and 60 parts of DOP are blended, and a sol obtained by stirring and mixing using a chemical stirrer is subjected to vacuum defoaming, 23 ° C. and 50% humidity.
Aging for 2 hours in a constant temperature and humidity room. This sol has a diameter of 20
A predetermined amount is sampled in a glass tube having a diameter of 100 mm, and while being heated in an oil bath at 100 ° C., the viscosity is measured using a B8R type viscometer (using a # 7 rotor) manufactured by Tokimec Co., Ltd. The viscosity and the heating time are graphed, and the value of the viscosity is 160 Pa · s.
The time at which (1600 poise) is reached is defined as the gelation time and is used as a measure of gelling property.

Example 1 First Step: Preparation of Polymer Particles Containing Oil-soluble Polymerization Initiator by Fine Suspension Polymerization A 300-liter premixing tank equipped with a stirrer and an emulsifier was charged with ions. Exchanged water 100 kg, lauroyl peroxide 300 g (0.5% by weight based on monomer), sodium lauryl sulfate 400 g, lauryl alcohol 20
After 0 g was added and the premixing tank was degassed, 60 kg of a vinyl chloride monomer was added, and the mixture was maintained at 35 ° C. with uniform stirring. Next, while dispersing into fine droplets using an emulsifier, the dispersion liquid was transferred to a 300-liter polymerization tank equipped with a stirrer that had been degassed in advance. After the transfer of the dispersion was completed, the temperature of the polymerization tank was raised to 55 ° C., and polymerization was started with stirring. The internal pressure of the polymerization tank is 1.0 kg from the reaction pressure
/ Cm ² (100 kPa), the reaction was stopped, and the unreacted monomer was recovered. The reaction time was 8 hours, and the average particle size of the polymer particles in the obtained latex was 0.5 μm.
m, the solid content concentration was 32%, and the amount of the remaining polymerization initiator was 0.1%.
3%.

<Comparative Example 1> (Preparation of polymer particles having small residual amount of oil-soluble polymerization initiator by fine suspension polymerization method) In Example 1, 300 g of lauroyl peroxide was used.
Reference Example 1 except that 45 g of t-butyl peroxypivalate (0.075% by weight based on the monomer) was used instead of the above, the homogenization treatment temperature was 30 ° C., and the polymerization temperature was 50 ° C.
Polymerization was carried out in the same manner as described above. The reaction time is 18 hours,
The average particle size of the polymer particles in the obtained latex was 0.7
μm, solids concentration 35%, residual polymerization initiator amount 0.0
It was less than 5%.

<Reference Example> (Decomposition conditions of residual oil-soluble polymerization initiator in polymer particles) In the above polymerization tank, 100 kg of ion-exchanged water, 60 g of sodium pyrosulfite, 6 kg of the latex prepared in Example 1 were used.
(In terms of solid content), 20 g of sodium hydrogen carbonate, and 0.1 g of sodium bicarbonate.
After charging 100 g of a 03% aqueous cupric chloride solution,
And kept at this temperature. 10 minutes after reaching 60 ° C,
After 20 minutes, 30 minutes and 60 minutes, a sample was taken from the bottom of the tank,
The amount of oil-soluble polymerization initiator was analyzed.

Example 2 (Second Step, Third Step: Heat Treatment and Seeding Emulsion Polymerization) The latex prepared in Example 1 was subjected to heat treatment and seeding emulsion polymerization as follows. After charging 65 kg of ion-exchanged water, 6 kg of latex (in terms of solid content), 60 g of sodium pyrosulfite, 20 g of sodium hydrogen carbonate, and 100 g of a 0.03% cupric chloride aqueous solution in a 300-liter polymerization tank equipped with a stirrer. Degas, 60 ° C
For 30 minutes. Then 19 kg of vinyl chloride monomer
The temperature in the polymerization vessel was adjusted to 53 ° C., and a 0.2% aqueous potassium persulfate solution previously dissolved was added little by little to initiate polymerization. Thereafter, the reaction was performed while controlling the addition rate of the aqueous solution of potassium persulfate and the flow rate of the cooling water so as to maintain a constant polymerization rate and reaction temperature. When the polymerization conversion was about 8%, the addition of a total of 40 kg of vinyl chloride monomer was started at a rate of about 8 kg / h. When the polymerization conversion reached about 10%, about 8% aqueous solution of sodium lauryl sulfate (total amount: 6 liters, 500 g as sodium lauryl sulfate) was continuously added at a rate of 1 liter / h. The pressure in the tank is 1.0 kg / cm ² (100 kPa) from the saturation pressure of vinyl chloride at 53 ° C.
When the temperature decreased, the polymerization was stopped, and the unreacted monomer was recovered. The reaction time was 6.5 hours, the average particle size of the polymer particles in the obtained vinyl chloride polymer latex was 0.7 μm,
The solid concentration was 40%.

Example 3 (Second Step, Third Step: Heat Treatment and Seeding Emulsion Polymerization) In place of the reducing agent (sodium pyrosulfite) used in Example 2, 60 g of sodium formaldehyde sulfoxylate was used. The polymerization reaction was carried out in the same manner as in Example 1 except that a 0.4% aqueous solution of hydrogen peroxide was used instead of the 0.2% aqueous potassium persulfate solution as the polymerization initiator.
The reaction time was 7.0 hours, the average particle size of the polymer particles in the obtained latex was 0.8 μm, and the solid content concentration was 39%.

Comparative Example 2 (Seeding Emulsion Polymerization without Decomposition of Residual Polymerization Initiator) The charging operation was carried out in the same manner as in Example 2, and after the completion of degassing, the operation was carried out in Example 2 at 60 ° C. for 30 minutes. The vinyl chloride monomer was immediately charged without performing the operation of holding for one minute. Then, in order to carry out the polymerization reaction, when the temperature was raised, the temperature in the vessel continued to rise even after reaching the expected reaction temperature of 53 ° C., and the temperature control became impossible, and there was a risk of reaction runaway. Therefore, the monomer in the tank was removed and collected outside the system, and the reaction was interrupted.

Comparative Example 3 (Seeding Fine Suspension Polymerization) Using the latex prepared in Example 1 as a seed polymer, polymerization was carried out as follows. In a 300 liter polymerization tank equipped with a stirrer, 65 kg of ion-exchanged water, 6 kg of latex (in terms of solid content), 2 parts of sodium hydrogen carbonate
After charging 0 g and 100 g of 0.03% cupric chloride aqueous solution, the mixture was degassed, and 19 kg of vinyl chloride monomer was charged. The temperature in the polymerization vessel was adjusted to 53 ° C., dissolved in advance, and a 0.6% aqueous sodium pyrosulfite solution was continuously added little by little to initiate polymerization. Thereafter, the reaction was carried out while controlling the addition rate of the aqueous sodium pyrosulfite solution and the flow rate of the cooling water so as to maintain a constant polymerization rate and reaction temperature. Since the polymerization conversion rate is about 8%, the total amount is 40k.
g of vinyl chloride monomer was started to be added at a rate of about 8 kg / h. When the polymerization conversion reached about 10%, about 8% aqueous solution of sodium lauryl sulfate (total amount: 6 liters, 500 g as sodium lauryl sulfate) was continuously added at a rate of 1 liter / h. The pressure in the tank is 53
1.0 kg / cm from the saturation pressure of vinyl chloride
^{When the} pressure dropped by ² (100 kPa), the polymerization was stopped, and the unreacted monomer was recovered. The reaction time was 7.5 hours, the average particle size of the polymer particles in the obtained vinyl chloride polymer latex was 0.9 μm, and the solid content concentration was 39%.

The result of measuring the amount of lauroyl peroxide, which is an oil-soluble polymerization initiator, remaining in the polymer particles subjected to the heat treatment in the above reference example by the above-described method was as follows.
The results are shown in Table 1. Examples 2 and 3 and Comparative Example 2
The powdery polymer obtained by drying and pulverizing the vinyl chloride-based polymer latex produced in the above-mentioned steps 3 to 3 above,
The viscosity, viscosity stability, and gelling property were measured by the method described in Table 2, and the results are shown in Table 2 together with the polymerization data.

[0037]

[Table 1] *: The analysis lower limit of the calibration curve method by GPC is 0.05%, which means that the lower limit is less than the lower limit.

[0038]

[Table 2]

[0039]

According to the method of the present invention, a reaction can be carried out with good controllability as in Examples 2 and 3, using a seed polymer which can be produced in a shorter reaction time as in Example 1. . In Comparative Example 2, which did not use the method of the present invention, the reaction could not be controlled, and the reaction had to be stopped. Also,
The plastisol prepared using the vinyl chloride-based polymer obtained by the method of the present invention is different from the plastisol prepared using the polymer prepared by the conventional seeded fine suspension polymerization method (Comparative Example 3) in both viscosity and gelling property. Are better. Therefore, it is particularly useful in the processing field such as the production of molded articles and the production of vinyl chloride leather by a coating method.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08F 2/18-2/30

Claims (1)

(57) [Claims] 1. A solvent which is soluble in 0.2 to 2% by weight of a vinyl chloride monomer based on vinyl chloride alone or a mixture of vinyl chloride and a compound copolymerizable therewith. The first step of performing fine suspension polymerization using a polymerization initiator,
A water-soluble reducing agent is added to the latex containing the polymerization initiator remaining in the polymer particles, obtained by the polymerization in the first step, and a heat treatment is performed to substantially decompose and remove the remaining polymerization initiator. A method for producing a vinyl chloride-based polymer, comprising the steps of: a step of mixing the latex obtained in the second step as a seed polymer with a vinyl chloride-based monomer and performing seed emulsion polymerization.