JPH07110881B2 - Suspension polymerization method of vinyl chloride monomer - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an improved method for suspension polymerization of vinyl chloride-based monomers, and more particularly to a high quality chloride having excellent porosity, fish eye, plasticizer absorption and particle size characteristics. The present invention relates to a suspension polymerization method for producing a vinyl-based resin by high-speed polymerization with high productivity.

[0002]

2. Description of the Related Art Generally, in suspension polymerization of vinyl chloride-based monomers, the vinyl chloride-based monomers are dispersed as oil droplets in an aqueous medium by stirring and suspending agent, and the polymerization reaction occurs inside the oil droplets. proceed. At the same time, the processes of coalescence, dispersion and aggregation / dispersion of oil droplets occur, and the obtained polymer particles become an aggregate of fine particles having voids inside, which are composed of a plurality of oil droplets. Therefore, in the suspension polymerization of vinyl chloride, the formulation of the suspending agent such as the type and amount of the suspending agent is very important, which is the stability of the polymerization, the quality of the resin such as the residual monomer amount, the plasticizer absorbability and the fish. It is known to be the controlling factor of the eye.

As the suspending agent, various water-soluble polymers such as gelatin, methyl cellulose and partially saponified polyvinyl acetate are mainly used industrially. Many proposals have been made to use two kinds of partially saponified polyvinyl acetate in combination as a suspending agent formulation for obtaining high-quality polymer particles, for example, JP-A Nos. 52-115890 and 52-115890. 53-43792, JP-A-53-136089,
JP-A-55-112210, JP-A-62-10160
9 and JP-A-62-260803.

As a suspension formulation in which three kinds of partially saponified polyvinyl acetate are combined, Japanese Patent Publication No. 60-50807 discloses the purpose of suppressing the formation of fish eyes in a molded article.
(A) Average saponification degree 70 to 90 mol%, average degree of polymerization 100
0 or more partially saponified polyvinyl alcohol component, (B) average saponification degree 65 to 85 mol%, average degree of polymerization 400 or more 1
Less than 000 partially saponified polyvinyl alcohol component, and (C) average saponification degree 55 to 90 mol%, average degree of polymerization 40
Dispersion stabilizers for suspension polymerization of vinyl chloride comprising less than 0 partially saponified polyvinyl alcohol component are disclosed.

Further, in JP-A-62-263206,
A water-soluble partially saponified polyvinyl acetate having a saponification degree of 85 to 90 mol% and a viscosity of a 4% aqueous solution at 20 ° C. of 25 to 65 cp, and a saponification degree of 65 to 75 mol%, and The water-soluble partially saponified polyvinyl acetate having a viscosity of 5.0 to 6.0 cp at 20 ° C. and a saponification degree of 35 to 50 mol% and a polymerization degree of 200 to 800 An oil-soluble partially saponified polyvinyl acetate is used in combination, and the combined amount ratio is /
In the weight ratio of 9/1 to 1/1, and (+
) / Weight ratio of 8/1 to 2/1 is disclosed to produce a polymer having a high specific gravity by improving polymer productivity and molding processability. .

However, in any of these methods, if the so-called high-speed polymerization is completed to complete the polymerization within 6 hours, the quality of the obtained vinyl chloride resin such as fish eyes, plasticizer absorbability and particle size is deteriorated. I had a flaw.

On the other hand, in order to improve the productivity in producing a vinyl chloride resin, the polymerization rate is increased to the limit of the heat removal capacity to complete the polymerization in a short time, and the polymerization vessel is enlarged to make one batch. It is important to increase the production amount per unit and enhance the heat removal capacity of the polymerization reaction heat of the polymerization reactor.

Regarding the high-speed polymerization method for shortening the polymerization time, for example, a method of using a highly active initiator as a polymerization initiator (Japanese Patent Laid-Open No. 53-73280), a uniform polymerization rate can be obtained by combining initiators having different activities. Method for achieving this (JP-A-56
Various polymerization methods have been proposed, such as JP-A-149407 and JP-A-1-31810). However, in any of these methods, not only the thermal stability and hue of the resulting resin are lowered, but also particle formation during polymerization becomes unstable,
As a result, coarsening of particles or increase of fish eyes are caused, and there is a problem that a product having commercial value cannot be obtained.

Further, there is proposed a method (Japanese Patent Laid-Open No. 58-120613) using, as a polymerization initiator, tertiary octyl peroxy neodecanoate which is a highly active initiator having a good hue of the resin to be obtained. Was done. According to this method, the hue of the resin is certainly good, but there is a drawback that the particles become coarse and fish eyes increase, and even if it is applied to the high-speed polymerization method, the quality of the vinyl chloride resin is not always high. It was not something that I could do, but something that was unsatisfactory.

On the other hand, in order to increase the size of the polymerization vessel, the jacket area per unit volume of the polymerization vessel is made relatively small to reduce the heat removal ability. JP-B-58-8405), a method of improving the flow velocity of the cooling water flow of the jacket, or a method of improving the flow path of the baffle (JP-A-58-160241) have been proposed. By these means, the heat removal capacity can be improved to some extent, but the effect is slight.

Therefore, a reflux condenser is added to a large-scale polymerization vessel of 40 m ³ or more to carry out high-speed polymerization within 5 hours (Japanese Patent Publication No. 1-1808).
No. 2) is also proposed. According to this method, it is necessary to increase the heat removal load of the condenser, and therefore clogging of the condenser due to foaming during polymerization, an increase in fish eyes in the product, and a decrease in bulk specific gravity during operation,
There are many quality problems. It is also possible to improve the heat removal capability of the polymerization vessel by passing low-temperature cooling water that has been cooled in advance through the jacket, but this is not economical because it requires running costs in addition to investment in cooling equipment.

Further, a so-called inner jacket type polymerization vessel in which a heating / cooling jacket is enclosed in the polymerization vessel main body has a large heat transfer coefficient as compared with a conventional outer jacket type polymerization vessel, and can be suitably used for polymerization of vinyl chloride. Is known (JP-A-57-147502). However, using this internal jacket type polymerization vessel, even if the polymerization rate is increased simply by selecting an initiator and increasing the amount, there are problems of particle coarsening and fisheye increase as described above, and a resin that is satisfactory in terms of quality can be obtained. I couldn't get it. That is, a production method of polymerizing high-quality vinyl chloride by a high-speed polymerization within 6 hours using an inner jacket type large-sized polymerization vessel of 40 m ³ or more has not been technically established.

[0013]

The object of the present invention is to produce a vinyl chloride resin having high porosity and excellent fish eye, plasticizer absorbability and particle size characteristics by high-speed polymerization with high productivity. An object is to provide an improved suspension polymerization method.

[0014]

The object of the present invention is to:
When a monomer mainly composed of vinyl chloride is suspension polymerized in an aqueous medium and the polymerization is completed within 6 hours, (a) a saponification degree of 75 to 85 mol% and an average polymerization degree of 100 are used as a suspending agent.
0 or more partially saponified polyvinyl acetate, (b) saponification degree 65
.About.75 mol%, partially saponified polyvinyl acetate having an average degree of polymerization of 500 to 900, (c) partially saponified polyvinyl acetate having a degree of saponification of 15 to 54 mol%, and an average degree of polymerization of 100 to 1200,
50% by weight of the total amount of the initiator used in the polymerization, in combination with one or more perester initiators having a 10-hour half-life temperature of 34 to 50 ° C. as an oil-soluble polymerization initiator.
Use above, and conversion rate is at least 5% from the start of polymerization
It is achieved by controlling the net stirring power per 1 m ³ of the content liquid of the polymerization vessel to reach 1.0 to 3.0 kW / m ³ until the temperature reaches 0.

In order to more effectively achieve the object of the present invention, the total amount of the suspending agents (a) and (b) charged per 100 parts by weight of the monomer is 0.03 to 0.15 parts by weight. Part, suspension agent
The charging amount of (c) is 0.01 to 0.2 parts by weight, and
Charge ratio (a) / (b) of (a) and (b) is 0.2 to 5.0
It is good to say Further, the present invention can be advantageously carried out by using a large-sized inner jacket type polymerization vessel having an inner volume of 40 m ³ or more, which is equipped with a stirrer and a jacket for heating / cooling is included in the inner surface of the polymerization vessel body.

The present invention will be described in detail below. In the present invention, among the monomers mainly composed of vinyl chloride monomer, examples of the monomers other than vinyl chloride include alkyl vinyl esters represented by vinyl acetate and alkyl vinyl ethers represented by cetyl vinyl ether. , Α-monoolefins such as ethylene or propylene, (meth) acrylic acid alkyl esters such as methyl acrylate and methyl methacrylate, and vinylidene chloride, styrene and the like are exemplified, provided that they are copolymerizable. It is not limited to these.

In the present invention, the three types of partially saponified polyvinyl acetate constituting the suspending agent are (a) a saponification degree of 75-8.
5 mol%, partially saponified polyvinyl acetate having an average degree of polymerization of 1000 or more, (b) saponification degree of 65 to 75 mol%, partially saponified polyvinyl acetate having an average degree of polymerization of 500 to 900, (c) saponification degree of 15 ˜54 mol%, partially saponified polyvinyl acetate having an average degree of polymerization of 100 to 1200, all of which are known and commercially available.

Both the partially saponified polyvinyl acetate (a) and (b) components are the main components of the suspending agent. If the saponification degree of the component (a) is less than 75 mol%, the dispersion becomes unstable and the effect is small, and if it exceeds 85 mol%, the fish eyes in the resin increase. If the average degree of polymerization is less than 1000, the effect of stabilizing the dispersion is small, and the range of 1200 to 270
It is preferably in the range of 0. If the degree of saponification of the component (b) is less than 65 mol%, it is difficult to dissolve in water and the protective power is low, the dispersion of the monomer is unstable, and coarse particles eventually increase, and if it exceeds 75 mol%. Those having a low surface activity and a low porosity of the polymer particles are generated, and the fish eyes in the resin increase. Further, if the average degree of polymerization is less than 500, the protective power is low and the number of coarse particles increases, and if it exceeds 900, the number of fish eyes in the resin increases.

Further, the component (c) is poorly soluble in cold water, increases the porosity of the polymer particles, and suppresses the formation of fish eyes. If the degree of saponification is too low or too high, fish eyes will increase. Further, if the average degree of polymerization is less than 100 or exceeds 1200, the dispersion stability decreases.

The amount of each component of these suspending agents used is such that the total amount of the monomers (a) and (b) charged per 100 parts by weight of the monomer is 0.03 to 0.15 parts by weight, preferably 0.04 ~
0.1 parts by weight, and the weight ratio (a) of (a) and (b)
/ (B) is 0.2 to 5.0, preferably 0.25 to 4.0
Is. If the total amount of (a) and (b) charged is less than 0.03 part by weight, the suspension stability of the monomer oil droplets and polymer particles during polymerization will be impaired, and coarse particles will increase. Or the porosity decreases, and if it exceeds 0.15 parts by weight, the particle size becomes fine,
There is a disadvantage that the bulk specific gravity is reduced. (a) and (b)
When the weight ratio (a) / (b) with is less than 0.2, the particle size becomes finer and the bulk specific gravity decreases, and when it exceeds 5.0, the porosity is impaired and fisheye and plasticizer absorption There is a disadvantage that the quality such as sex is deteriorated.

When the amount of the suspension agent (c), which is the remaining component of the suspension agent system of the present invention, is less than 0.01 part by weight, the effect of suppressing fish eyes cannot be exhibited. Further, if the charged amount exceeds 0.2 parts by weight, the particle size becomes fine and the bulk specific gravity decreases, which is a disadvantage.

The polymerization initiator used in the present invention is 10
Time half-life temperature is 34 to 50 ° C, preferably 36 to 48
It is necessary to use an initiator having a perester structure in the range of ℃, and one or more of them is 50% by weight or more, preferably 6
It is preferable to use 5% by weight or more. Here, the 10-hour half-life temperature means that the initiator is decomposed in a benzene solvent at a concentration of 0.1 mol and the concentration is reduced to half the initial concentration.
It is the temperature when it takes time, and is an index showing the rate of decomposition of the initiator, that is, the activity.

If the 10-hour half-life temperature exceeds the above range, the resulting vinyl chloride resin will become coarse particles or the particle shape will become irregular even within a specific stirring power range, resulting in fish eye It causes an increase or a decrease in bulk specific gravity. Further, when the amount of the perester initiator used in the above range is less than 50% by weight of the total amount of the initiator used for the polymerization, the thermal stability and the hue of the obtained vinyl chloride resin are deteriorated. Can not achieve the purpose of.

The polymerization initiator having a perester structure used in the present invention includes 2,4,4-trimethylpentylperoxy-2-neodecanoate, tert-butylperoxyneodecanoate, (α, α-
Bis-neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, tert-hexylperoxyneodecanoate and the like are generally mentioned, but are not limited thereto. Further, other initiators that can be used as a mixture with the perester initiator of the present invention as long as it is less than 50% by polymerization of all the initiators used for polymerization include di-2-ethylhexyl peroxydicarbonate and di- ( 2-ethoxyethyl) peroxycarbonate-based initiators such as peroxydicarbonate 3, 5,
Diacyl peroxide initiators such as 5-trimethylhexanoyl peroxide, α, α-azobis-2,
An azo compound-based initiator such as 4-dimethylvaleronitrile is generally mentioned, but the initiator is not particularly limited.

In carrying out the present invention, further, from the initiation of polymerization until the conversion rate at which the skeleton of the polymer particle structure is formed reaches at least 5%, preferably 15 to 30.
% To 1.0% to 3.0 kW / m ³ , preferably 1.2 to 3.0
2.5 kW / m ³ , more preferably 1.5 to 2.0 kW / m ³
Polymerization is performed as.

When the net stirring power is less than 1.0 kW / m ³ , the frequency of dispersion and coalescence of the suspension oil droplets of the vinyl chloride monomer is low, and the porosity of the produced polymer particles is small and This causes problems such as a wide distribution, coarse particles, and poor plasticizer absorbability, resulting in increased fish eyes. On the other hand, if it exceeds 3.0 kW / m ³ , the coalescence frequency of oil droplets becomes too high, and the oil droplets or polymer particles tend to agglomerate due to collisions, resulting in coarse particles, or dispersion depending on other polymerization conditions. If it progresses too much, the particle size becomes finer and the bulk specific gravity decreases, so that the object of the present invention cannot be achieved. When the polymerization conversion rate exceeds 5%, oil droplets are less likely to be dispersed and aggregated. Therefore, the stirring power after the polymerization conversion rate of 5% is not particularly limited, as long as the inside of the polymerization vessel is uniformly stirred.

A method for controlling the stirring power of the polymerization vessel is described in detail, for example, in "Chemical Engineering Association, edited by: Chemical Engineering Handbook, Revised Third Edition, pages 1065 to 1115, 1968, Maruzen Co., Ltd." As described above, by using an empirical formula and a diagram showing the relationship between the Reynolds number Re and the power number Np of the stirring system for the stirring devices of various shapes, or by measuring the power under a certain stirring condition The power can be arbitrarily adjusted by experimentally obtaining Np as a constant and changing the rotation speed of the stirring blade.

That is, the density of the contents of the polymerization vessel is ρ (kg
/ M ³ ), viscosity coefficient μ (kg / m · sec), stirring blade rotation speed n (1 / sec), blade length d (m), gravity conversion coefficient g _C (kg · m / Kg)・ Sec ² ), Re and Np are Re = ρnd ² / μ Np = P ・, respectively, where P (Kg / m · sec) is the net stirring power that does not include loss in the speed reduction mechanism and shaft seal. It is defined by g _C / ρn ³ d ⁵ , and Np is determined from known literature or experiments.
Can be asked.

The Np value of the agitator of a large-scale polymerization vessel which is generally adopted in the suspension polymerization method for vinyl chloride type monomers is in the range of about 0.2 to 2. The amount of liquid in the polymerization vessel is V
If it is (m ³ ), the net stirring power Pv (kW / m ³ ) per unit volume of the polymerization vessel can be calculated according to the following equation. Pv = Npρn ³ d ⁵ / 102Vg _C Therefore, when the net stirring power is adjusted using a specific stirring device, the power is proportional to the cube of the rotation speed of the stirring blade, The power can be controlled by changing the number.

The shape of a stirring device such as a stirring blade used in the present invention and a baffle used if desired is not particularly limited, and conventionally, in the suspension weight method of a vinyl chloride monomer, it has been generally used. A known stirring device that has been adopted can be used, examples of stirring blades include turbine blades, fan turbine blades, Faudler blades, and blue margin blades, and examples of baffles include plate-type, cylindrical-type, D-type, A loop type, a finger type, etc. are illustrated, but a pipe (rod type) baffle, a D type baffle, and an E type (finger type) baffle are preferable. These stirring blades and baffles may be those commonly used in the polymerization of vinyl chloride. For example, "Handbook of Chemical Engineering" or "Koji Saeki: Polymer Manufacturing Process, 157-159".
Page, 1971, Industrial Research Board ".

In carrying out high-speed polymerization within 6 hours in the present invention, for example, an inner jacket type polymerization vessel described in JP-A-57-147502, that is, a jacket for heating / cooling is included on the inner surface of the polymerization vessel main body. By carrying out the above-mentioned high-speed polymerization using a polymerization vessel having an improved heat transfer performance, particularly a polymerization vessel having an internal volume of 40 m ³ or more with improved heat removal ability, the object of the present invention can be further improved. Can be achieved. Of course, it is also possible to adopt a method in which a reflux condenser is attached to the polymerization vessel to additionally remove the heat of polymerization reaction.

In the present invention, the time required to complete the polymerization, that is, the polymerization time, means the content of the polymerization vessel at a predetermined temperature after the monomer, the initiator, the suspending agent and water are charged. After reaching the polymerization temperature, the pressure in the polymerization vessel was changed to the natural pressure at the polymerization temperature for a while, and then the pressure drop started as the unreacted monomer decreased, and the width of the drop became 2 kg / cm ² . Until time. From the safety aspects such as temperature control and pressure control of the polymerization vessel, the polymerization time is 3 ~
It is preferably 6 hours. Examples of the method of completing the polymerization in the present invention include a method of adding a polymerization inhibitor and a method of collecting unreacted monomers from the polymerization vessel.

[0033]

As described above, according to the present invention, a vinyl chloride resin which is porous and has excellent fish eye, plasticizer absorbability and particle size characteristics can be produced with high productivity, and is thus extremely useful.

[0034]

EXAMPLES The present invention will be specifically described below with reference to examples, but% and parts in the examples and comparative examples are based on weight unless otherwise specified. The physical properties of the vinyl chloride resin were measured by the following methods.

(1) Fisheye Dioctyl phthalate 45 was added to 100 g of vinyl chloride resin.
g, cadmium stearate 2 g, barium stearate 1 g and green toner 1 g are added and mixed,
Kneaded with a 6 inch roll at 145 ° C for 6 minutes to give a thickness of 0.4
The number of transparent particles observed on a 100 cm ² surface of the sheet was indicated. (2) Average particle size It was shown as a 50% passage size by a sieve analysis using a JIS-standard wire mesh. (3) Coarse Grain Fractions indicated by the percentage remaining on a 60-mesh wire net were determined by a sieve analysis using a JIS-standard wire net. (4) Bulk Specific Gravity The value measured according to the method specified in JIS K6721 is shown. (5) Porous using a mercury press-in type porosimeter manufactured by Aminco USA
The volume of mercury injected per gram of vinyl chloride resin during pressurization from atmospheric pressure to 14000 psi is shown. (6) Absorption of plasticizer Using a lab blast mill manufactured by Toyo Seiki Co., Ltd., 400 g of vinyl chloride resin and polyester polymer plasticizer PN250 (Adeka Argus Chemical Co., Ltd.) were placed in a container whose jacket temperature was maintained at 85 ° C. Made) 240g, and rotation speed 6
The torque was recorded while stirring at 0 rpm, and the time until the mixing torque decreased and became stable was shown. (7) Thermal stability A mixture of 100 parts of polyvinyl chloride, 60 parts of di-2-ethylhexyl phthalate, 2 parts of a Ba-Zn stabilizer and 2 parts of an epoxy stabilizer is roll-kneaded at 160 ° C for 5 minutes,
The formed sheet was heated in a gear open at 190 ° C., and the change in hue with time was observed. In order to judge whether the thermal stability was good or bad, the time at which the sheet started to turn black was ranked as follows.

Rank A: Blackening time 120 minutes or more Rank B: 〃 120 minutes to 105 minutes Rank C: 〃 105 minutes to 90 minutes

Experiment No. 1 A Faudler-type four receding blade having a blade length of 1.7 m and four pipe baffles having an outer diameter of 0.22 m were mounted on a diameter of 3.2.
After degassing the inner jacket type stainless steel polymerization vessel having an internal volume of 45 m ^{3 and} a vinyl chloride monomer of 100 parts (16.5
Ton), 130 parts of water, 0.050 part of partially saponified polyvinyl acetate having a saponification degree of 80 mol% and an average polymerization degree of 2200 as a suspending agent, a saponification degree of 73 mol% and an average polymerization degree of 8
00 partly saponified polyvinyl acetate 0.020 part, saponification degree 33 mol% and average polymerization degree 300 partially saponified polyvinyl acetate 0.035 part, and as a polymerization initiator 2,
Charge 0.050 part of 4,4 trimethylpentyl peroxy-2-neodecanoate, and rotate the stirring blade at 112 rpm.
The contents of the polymerization vessel were heated to 57 ° C under stirring while controlling the rpm.
The temperature was raised to start polymerization.

Polymerization was continued while maintaining this rotation speed and temperature, and when the pressure of the polymerization vessel, which was 8.7 kg / cm ² at the beginning of the polymerization, dropped to 6.7 kg / cm ² , the polymerization vessel was not yet discharged. The reaction monomer was recovered and the polymerization was completed. Then, the contents of the polymerization vessel were taken out and dehydrated and dried to obtain a vinyl chloride polymer. The net stirring power Pv was 1.5 kW / m ³ at the start of the polymerization, but thereafter gradually increased with the progress of the polymerization, and was 1. when the polymerization conversion rate reached 5%.
6 kW / m ³ , which is almost 1.8 kW / after conversion of 30%
It showed a constant value of m ³ . The polymerization time was 4.3 hours, and the conversion rate at the completion of polymerization was 85%.

Experiment Nos. 2 to 11 Polymerization was carried out under the same conditions as Experiment No. 1 except that the partially saponified polyvinyl acetate shown in Table 1 was used as the suspending agent. The polymerization time, the net stirring power Pv, and the conversion rate upon completion of the polymerization were all the same as in Experiment No. 1.

Experiment Nos. 12 to 20 Polymerization was carried out under the same conditions as Experiment No. 1 except that the polymerization initiators shown in Table 2 were used. The net stirring power Pv and the conversion rate upon completion of the polymerization were all the same as in Experiment No. 1.

Experiment Nos. 21 to 28 Polymerization was carried out under the same conditions as in Experiment No. 1 except that the stirring blade rotation speed shown in Table 3 was used. The polymerization time and the conversion upon completion of the polymerization were all the same as in Experiment No. 1. The physical properties of the vinyl chloride resin thus obtained are shown in Tables 1 to 3.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasumichi Ishii One day, 2767 Niihama Shiojima, Kurashiki-shi, Okayama Zeon Corporation (72) Inventor Masahisa Okawa 5-1 Sokai-cho, Niihama-shi, Ehime Sumitomo Chemical Industrial Co., Ltd. (72) Inventor Isao Ouchi 16 Kuchiha Chemical Industry Co., Ltd. 16 Nishikicho, Iwaki, Fukushima Prefecture (72) Inventor Hideki Wakamori 16 Ochiai Nishikicho, Iwaki, Fukushima Prefecture (72) Inventor Yamato Tamio 1-2 Harumi-cho, Tokuyama City, Yamaguchi Prefecture Sun Arrow Chemical Co., Ltd.

Claims (3)

[Claims] 1. When suspension-polymerizing a vinyl chloride-based monomer in an aqueous medium and completing the polymerization within 6 hours, (a) a saponification degree of 75 to 85 mol% is used as a suspending agent. Partially saponified polyvinyl acetate having an average degree of polymerization of 1000 or more,
(b) Saponification degree 65-75 mol%, average degree of polymerization 500-9
00 partially saponified polyvinyl acetate, (c) saponification degree 15-
54 mol% and partially saponified polyvinyl acetate having an average degree of polymerization of 100 to 1200 are used in combination, and one or two having a 10-hour half-life temperature of 34 to 50 ° C. as an oil-soluble polymerization initiator are used.
50% by weight or more of the total amount of the initiators used in the polymerization, and the net stirring per 1 m ³ of the content liquid in the polymerization vessel from the start of the polymerization until the conversion rate reaches at least 5%. A suspension polymerization method of a vinyl chloride-based monomer, characterized in that power is controlled to 1.0 to 3.0 kW / m ³ . 2. A suspending agent (a) per 100 parts by weight of a monomer.
And the total amount of (b) charged is 0.03 to 0.15 part by weight, and the amount of suspension agent (c) charged is 0.01 to 0.2 part by weight,
In addition, the charge weight ratio (a) / (b) of (a) and (b) is 0.2 to
It is 5.0, The suspension polymerization method of the vinyl chloride type monomer of Claim 1 characterized by the above-mentioned. 3. A large-scale inner jacket type polymerization vessel having an internal volume of 40 m ³ or more, equipped with a stirrer and having a heating / cooling jacket installed inside the polymerization vessel main body, is used. Suspension polymerization method for vinyl monomers.