JPH111504A - Method for producing vinyl chloride polymer - Google Patents

Abstract

(57) [Abstract] [Problem] It is excellent in polymerization stability, has few fish eyes,
Provided is a method for producing a vinyl chloride polymer having excellent productivity. (A) A water-soluble or water-dispersible polymer suspension dispersion stabilizer and an oil-soluble initiator are charged into a polymerization reactor together with water within 20% of the total charge, and (b) degassing is then performed. The charged warm water and the vinyl chloride monomer are simultaneously charged or the warm water is started to be charged slightly earlier.

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, and more particularly, to a method for producing a vinyl chloride polymer having excellent polymerization stability, low fish eyes and excellent productivity. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Vinyl chloride resins are inexpensive and have an excellent quality balance, and are therefore used in various fields such as soft fields and hard fields. For example, wire covering, wrap film, sheet, etc. in the soft field, pipe,
Window frames, films and the like. On the other hand, vinyl chloride-based resin as a material is a general-purpose resin in which inexpensiveness is an essential requirement, and various means for improving polymerization productivity have been conventionally attempted in order to reduce production costs. For example, a method of increasing the production volume per production by increasing the capacity of a polymerization vessel, charging the vinyl chloride monomer first, and then adding degassed hot water to shorten the heating time and produce A method has been proposed in which the productivity is further improved by simultaneously charging the vinyl chloride monomer and degassed hot water to shorten the charging and heating time.

For example, Japanese Patent Publication No. Sho 62-39601 discloses that a preheated aqueous medium (a mixture in which a dispersant is dissolved in water) and a homogeneous mixture of a vinyl chloride monomer and an initiator are simultaneously charged. Japanese Patent Publication No. 26488/1985 discloses a method of shortening the heating time and increasing the productivity by adding water in which the entire amount of the dispersant is dissolved and vinyl chloride monomer in which the entire amount of the initiator is dissolved. Japanese Patent Application Laid-Open No. 60-158207 discloses a method of increasing the productivity by setting the temperature to a predetermined temperature at the end of the preparation of the two, and includes a vinyl chloride monomer containing an initiator and a dispersant. Water is preliminarily mixed at a temperature of 50 ° C. or less, and the mixture is charged to a polymerization reactor while raising the temperature to a reaction temperature in a heat exchanger. JP-A-1-172407 discloses a method of charging a vinyl chloride monomer. At least 20 of the dispersant in With charged the weight ratio of water to vinyl chloride monomer in the polymerization vessel is 1.5
A method of charging the entire amount of the initiator and the like are disclosed below.

However, the method disclosed in JP-B-62-39601 requires a separate tank and a special mixer from the storage tank of the vinyl chloride monomer for the uniform mixing of the vinyl chloride monomer and the initiator. Not only does the charging operation become complicated, but also the initiation reaction proceeds rapidly at the same time as charging into the polymerization vessel, and the dispersant is evenly dispersed on the surface of the monomer oil droplets dispersed in water to form a stable protective layer. However, there is a disadvantage that polymerization stability is poor due to lack of time to perform, and that coarse particles are large and fish eyes are increased.

[0005] The method of Japanese Patent Publication No.
Although there is a slight time difference in the timing of charging the vinyl chloride monomer in which the entire amount of the initiator is dissolved and the water, there are the same drawbacks as in the method of Japanese Patent Publication No. 62-39601. The method disclosed in Japanese Patent Application Laid-Open No. 1-172407 is an improved method described above, but the polymerization stability tends to be impaired due to the fact that the charging time of the dispersant is delayed from the charging time of the monomer.

Further, in the method disclosed in Japanese Patent Application Laid-Open No. 60-158207, after pre-mixing water and a vinyl chloride monomer, the mixture is heated to a reaction temperature in a heat exchanger. The improvement effect cannot be expected as expected. As described above, the method of charging the hot water containing the dispersant and the vinyl chloride-based monomer containing the initiator at the same time or with a slight time difference is effective in improving productivity, but poor in polymerization stability. In addition, there are problems such as a large amount of coarse particles, an increase in fish eyes, and a problem that a large amount of a dispersant is required to enhance polymerization stability, resulting in an increase in cost.

Japanese Patent Application Laid-Open No. 58-21408 discloses a method in which water heated and deaerated in advance at 50 to 80 ° C. is charged, and Japanese Patent Publication No. 58-50603 discloses a method in which a dispersant and cold water are charged, followed by vinyl chloride. A method of charging a system monomer and finally charging heated water is disclosed. However, Japanese Patent Laid-Open No. 58
No. 21408 discloses that a vinyl chloride monomer containing an initiator is in direct contact with the inner wall of a polymerization vessel during charging, so that a film-like scale is easily generated, thereby significantly reducing the ability of a jacket to remove heat of polymerization. There is a problem that the polymerization time cannot be shortened.

[0008] Japanese Patent Publication No. 58-50603 has a problem that although it has an effect of improving fisheye, it takes a long time to prepare the fisheye, which is disadvantageous in terms of operation rate.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above prior art, and has a problem in a method of simultaneously charging hot water and a vinyl chloride monomer, namely, adhesion of scale to the inner surface of a polymerization vessel. Reduction of polymerization stability, generation of coarse particles, increase of fish eyes, etc.
An object of the present invention is to provide a method for producing a vinyl chloride-based polymer having high productivity, in other words, to improve in a well-balanced manner a variety of quality problems and a conflicting factor in productivity.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to improve various problems in quality and conflicting factors of productivity in a well-balanced manner. Found that it was possible to significantly increase productivity without the problems of
The present invention has been made.

That is, the present invention provides a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a monomer copolymerizable with the vinyl chloride monomer (hereinafter, both are referred to as vinyl chloride monomers). ) Is subjected to suspension polymerization in an aqueous medium, (a) water having a temperature of 0 to 40 ° C. is charged into a polymerization reactor in a range not exceeding 20% by weight of the total amount used, and water-soluble or water-dispersible An aqueous solution or aqueous dispersion of a polymer suspension / dispersion stabilizer (hereinafter, referred to as a dispersant) and an oil-soluble initiator are both charged into a polymerization reactor, and the polymerization reactor is degassed. A method for producing a vinyl chloride-based polymer, characterized in that the charged warm water and the vinyl chloride-based monomer are simultaneously or slightly warmed to be charged to complete the charging.

In the present invention, partially saponified polyvinyl acetate, methylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylic acid, vinyl acetate-maleic acid copolymer, styrene For example, a maleic acid copolymer, gelatin, starch, or the like is used. More preferably, at least one of the above dispersants is used in combination with polyethylene oxide.

In the above step (b), when the time from the start of the supply of degassed warm water to the start of the supply of the vinyl chloride monomer is within 2 minutes, the oil-soluble initiator may further contain an aqueous medium. When the emulsion type is emulsified or dispersed in water, a remarkable effect is exerted on the improvement of quality and productivity.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In carrying out the present invention, first, as the step (a), water having a temperature of 0 to 40 ° C. is used in an amount of 2% of the total amount used.
At the same time, the aqueous solution or the aqueous dispersion of the dispersant and the oil-soluble initiator are charged into the polymerization reactor at the same time that the polymerization reactor is charged in an amount not exceeding 0% by weight, and then the polymerization reactor is degassed. At this time, for example, in the method of simultaneously charging the vinyl chloride monomer and the whole amount of warm water from the beginning without carrying out the step (a), although the productivity is improved, many scales adhere to the inner tube wall of the polymerization vessel, The effect of improving fisheye is not always sufficient. In the method of charging an aqueous solution or aqueous dispersion of the dispersant during or after the step (b), the dispersant is uniformly dispersed on the surface of the monomer oil droplets dispersed in water, and the stable protective layer is formed. There is not enough time to form the polymer, so that the polymerization stability is poor, and the amount of coarse particles is large, and fish eyes are undesirably increased. Therefore, it is preferable that the aqueous solution or the aqueous dispersion of the dispersant is previously charged into the polymerization vessel together with water within 20% by weight of the total amount used. As described above, the polymerization is stabilized by previously charging the aqueous solution or the aqueous dispersion of the dispersant together with water within 20% by weight of the total amount to be used, thereby stabilizing the polymerization, reducing coarse particles and narrowing the particle size distribution. It becomes possible. If the amount of water to be charged in advance exceeds 20% by weight of the total amount used, the temperature of the reaction mixture at the end of the entire charging is too low, and it takes time to raise the temperature to a predetermined reaction temperature, The effect is diminished in terms of improving productivity.

Further, the temperature of the water to be charged in advance is 0 to 40 ° C.
The use of water in this temperature range ensures sufficient polymerization stability and makes it possible to significantly improve coarse particles and fish eyes.
If this temperature exceeds 40 ° C., the oil-soluble initiator charged together with the aqueous solution or the aqueous dispersion of the dispersant in this step is decomposed at once, and the polymerization starts too soon after charging the monomers, so that the polymerization vessel can wall is started. This is not preferable because the scale of the particles increases and coarse particles that cause fish eyes are generated.

Next, in the step (a), an oil-soluble initiator is charged into a polymerization reactor together with an aqueous solution or aqueous dispersion of a dispersant, and the polymerization reactor is degassed. At this time, the oil-soluble initiator may be charged in the form of a solution dissolved in an organic solvent such as isoparaffin, but is preferably charged in the form of an emulsion type emulsified or dispersed in water. This (a)
In the method in which the oil-soluble initiator is not charged in advance in the process but is charged during or after the step (b), the time required for the oil-soluble initiator to be uniformly dispersed in the monomer oil droplets dispersed in water. The target margin is small, and in terms of quality, variation among particles is likely to occur. Such variation among particles often leads to generation of abnormal particles called fish eyes, in particular, permanent fish eyes. Therefore, the oil-soluble initiator is preferably charged in advance with water or an aqueous solution or dispersion of a dispersant at 0 to 40 ° C.

Conventionally, a method has been proposed in which an oil-soluble initiator is uniformly mixed with a vinyl chloride-based monomer and charged into a polymerization vessel. However, in this method, a separate tank or a special measuring equipment for uniform mixing has been proposed. Is not practical.
In addition, there is also a disadvantage that the monomer containing the initiator must be kept at a temperature as low as possible in order to avoid an initiation reaction due to decomposition of the initiator.

Next, in step (b), warm water degassed in advance and a vinyl chloride monomer are simultaneously or simultaneously charged with warm water. Needless to say, the amount of warm water charged here is the amount obtained by subtracting the amount of water previously charged in the step (a) from the total amount of water used for polymerization. Although the degassed warm water and the vinyl chloride-based monomer may be started at the same time, it is preferable to start warm water slightly earlier. If this time difference is long, the time required for preparation becomes long, and the effect is diminished in terms of improving productivity. Therefore, the time difference should be within 2 minutes.

There is no particular limitation on the time required for charging the hot water and the vinyl chloride monomer. Particularly, a monomer, such as a vinyl chloride monomer, which is pressurized at once by contact with hot water in a polymerization vessel is used. When used, charging may be difficult depending on the lifting capacity of the pump used. Therefore, it is necessary to use a pump having a head capacity and a charging capacity suitable for a desired charging time.

Here, the total amount of water used for the polymerization in the present invention is not particularly limited, and may be determined so as to achieve both productivity and quality as long as the polymerization stability is not impaired. For example, the total amount of water at the start of the polymerization may be 0.8 to 1.5 in terms of the weight ratio of water to the vinyl chloride-based monomer. Further, as the polymerization proceeds, the vinyl chloride-based monomer and the polymer may be used. Although the slurry volume is reduced due to the difference in specific gravity, water may be added continuously, intermittently, or collectively as long as the amount does not exceed the reduced amount.

The water-soluble or water-dispersible polymer suspension stabilizer used in the present invention includes partially saponified polyvinyl acetate, methylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylic acid, vinyl acetate Maleic acid copolymer, styrene-maleic acid copolymer, gelatin, starch and the like can be mentioned. More preferably, at least one of the above dispersants is used in combination with polyethylene oxide. When the dispersing agent is used alone, unless the amount of the dispersing agent is considerably increased, the protective power of the monomer oil droplets at the time of initial dispersion is weak, and a sufficient protective power is secured by combining at least one of these with polyethylene oxide. Is done.

The amount of the dispersant used is a vinyl chloride monomer 1
The amount is 0.005 to 0.1 part by weight, preferably 0.01 to 0.08 part by weight, per 100 parts by weight. This amount is 0.00
If the amount is less than 5 parts by weight, the initial dispersing power of the monomer is insufficient, and the amount of coarse particles of the produced resin increases. On the other hand, if it exceeds 0.1 parts by weight, the dispersing power becomes too strong, resulting in so-called overdispersion, and the particle size distribution of the produced resin becomes wide and the number of fine particles increases.

Next, when polyethylene oxide is used in combination, the amount thereof is 0.001 to 0.02 parts by weight, preferably 0.002 to 0.02 parts by weight per 100 parts by weight of the vinyl chloride monomer.
0.01 parts by weight. If the amount is less than 0.001 part by weight, the protective power of the initially dispersed monomer is insufficient, so that the amount of coarse particles of the formed resin increases, or in extreme cases, the polymerization is not normally performed and the whole is hardened. May form clumps. Also 0.
If the amount exceeds 02 parts by weight, the protective power is too strong, and the particle size distribution of the produced resin is widened and the number of fine particles increases.

Of these, particularly preferred dispersants include a combination of partially saponified polyvinyl acetate having a degree of saponification of 60 to 95% and a degree of polymerization of 400 to 4000, and polyethylene oxide having an average molecular weight of 600,000 or more. In the present invention, it is important that the stirring operation is performed at the same time as the start of the step (b), and that the vinyl chloride monomer oil droplets in the polymerization vessel are dispersed in warm water by stirring shearing force and homogenized as soon as possible. The stirring speed varies depending on the shape of the stirring blade, but when the stirring speed is 5 m / sec or more, the effect of the present invention can be easily exhibited. At a stirring blade peripheral speed of less than 5 m / sec, homogenization of the dispersion system becomes incomplete, resulting in an increase in fish eyes, an increase in particle size distribution, an increase in coarse particles and fine particles, and the like. A stirring blade suitable for maintaining a stirring blade peripheral speed of 5 m / sec or more is an inclined paddle or a blue margin blade.

In the present invention, hot water which has been degassed in advance is used. The temperature of the hot water is preferably 50 to 80 ° C., and it is preferable to control the polymerization as high as possible from the viewpoint of improving productivity. When the temperature reaches a predetermined polymerization temperature in the course of the charging process and the polymerization has been started, a conventional heat removal method, for example, heat removal by a jacket, heat removal by a reflux condenser, heat removal by an internal jacket, is used. The polymerization reaction may be controlled by utilizing such factors.

As the polymerization initiator in the present invention, conventionally known ones may be used. Among these initiators, one or more initiators having a 10-hour half-life temperature of 30 to 65 ° C. are preferably used. preferable. The amount of the initiator used depends on the type and polymerization temperature, but is preferably 0.005 to 0.5 parts by weight per 100 parts by weight of the vinyl chloride monomer. By using this amount of initiator, the polymerization time can be reduced to 6 hours or less. Examples of such a polymerization initiator include acetylcyclohexylsulfonyl peroxide, 2,4,4 trimethylpentyl-2-peroxyneodecanoate, di-2-ethylhexylperoxydicarbonate, and di (2-ethoxyethyl) peroxide. Oxydicarbonate, t-butyl peroxypivalate, 3,
Organic peroxide initiators such as 5,5-trimethylhexanoyl peroxide; azo initiators such as azobisisobutyronitrile and azobis-2,4, -dimethylvaleronitrile; Two or more kinds can be used in combination.

These oil-soluble initiators may be used by dissolving them in a solvent. However, as described above, it is preferable to use emulsifiers or dispersants to emulsify or disperse in water. The emulsion or dispersion of the initiator is prepared by emulsifying or dispersing the initiator solution in water. Specifically, a solution prepared by dissolving an initiator in a solvent such as isoparaffin so as to have an initiator concentration of 30 to 80% by weight is used in an amount of 20 to 100 parts per 100 parts of water, and an emulsifier or dispersant is added in an amount of 5 to 100 parts by weight. 200 parts, and 0-20 if necessary
It can be prepared by adding 0 parts of antifreeze and stirring. The limits of these amounts have no critical significance, as long as they can be emulsified or dispersed stably. The temperature at the time of emulsification or dispersion is preferably from about −20 ° C. to about 30 ° C.

Examples of the solvent for dissolving the oil-soluble initiator include aromatic hydrocarbons such as toluene, xylene and benzene; aliphatic hydrocarbons such as hexane and isoparaffin; ketones such as acetone and methyl ethyl ketone; Esters such as ethyl acetate, butyl acetate, dioctyl phthalate and the like can be mentioned, and these can be used alone or in combination of two or more.

Examples of emulsifiers include sorbitan esters such as sorbitan monolaurate, sorbitan monostearate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan tristearate, sodium stearate, sodium lauryl sulfate, dodecyl Metal soaps such as sodium benzenesulfonate, ethers such as polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene nonylphenyl ether, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyoxyethylene stearate Such as esters, lauryl trimethyl ammonium chloride,
Examples include quaternary ammonium salts such as distearyl dimethyl ammonium chloride and alkylbenzyl dimethyl ammonium chloride, and these can be used alone or in combination of two or more.

Examples of the dispersant used for dispersing the initiator include partially saponified polyvinyl acetate, methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, polyvinylpyrrolidone, maleic anhydride-vinyl ether copolymer, ethylene oxide-propylene oxide. Block copolymers and the like can be mentioned, and these can be used alone or in combination of two or more.

Examples of the antifreeze include methanol, ethanol, ethylene glycol, propylene glycol and the like, and these can be used alone or in combination of two or more. The monomer used in the present invention is a monomer containing vinyl chloride as a main component, specifically, a vinyl chloride monomer alone or containing 70% by weight or more of vinyl chloride and copolymerized with vinyl chloride. A mixture with possible monomers.

Examples of monomers copolymerizable with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate, α-olefins such as ethylene, propylene and isobutyl vinyl ether, 1-chloropropylene and 2-chloropropylene. Chlorinated olefins such as butylene,
Examples include (meth) acrylates such as methyl (meth) acrylate, maleic anhydride, acrylonitrile, styrene, vinylidene chloride, and the like, and these can be used alone or in combination of two or more. .

Further, polymerization degree regulators, chain transfer agents, pH regulators, gelling improvers, antistatic agents, emulsifiers, stabilizers, which are conventionally used for the polymerization or copolymerization of vinyl chloride monomers,
A known technique can also be used arbitrarily without any difficulty for the scale inhibitor and the like and the preparation method thereof, and the amount of use can be in accordance with a conventionally known method.

[0034]

EXAMPLES The present invention will be described more specifically with reference to the following Examples and Comparative Examples, which are not intended to limit the present invention. In the following examples, “parts” means “parts by weight” and “%” means “% by weight” unless otherwise specified. Further, ion-exchanged water was used for all the water in this example.

The characteristic values of the obtained vinyl chloride polymer were measured by the following methods. (1) Fish eye Dioctyl phthalate 5 in 100 parts of vinyl chloride polymer
0 parts, 2 parts of calcium stearate, 1 part of barium stearate, and 0.02 part of carbon black were added and sufficiently stirred and mixed, and then the surface temperature was adjusted to 150 ° C.
The mixture was put into an inch roll and kneaded, and a roll sheet having a thickness of 0.3 mm was cut out in 4 minutes. The number of transparent particles observed in the area of 100 mm ^{2 of the} surface of the collected roll sheet was counted and shown. (2) Scale inside the polymerization vessel The inside of the polymerization vessel after the polymerization was observed, and the amount of scale attached to the tube wall and around the stirring blade was visually examined. ◎: hardly adhered, ：: little adhered amount,
Δ: large amount of adhesion, ×: extremely large amount of adhesion (3) Average particle size, particle size distribution According to JIS K-6721, 42, 60, 80, 1
Using a sieve of 00, 120, 145, 200 mesh,
The mixture was sieved with a sieve shaker, and the average particle diameter was defined as the 50% by weight passage diameter. The particle size distribution was expressed by percentage by measuring the weight of the vinyl chloride polymer remaining on each mesh. Of these, the amount of polymer remaining on 42 mesh was defined as coarse particles, and the amount passing through 200 mesh was defined as passes. (4) Charging time and polymerization time The time from the start of charging of the hot water fork or vinyl chloride monomer to the end of charging all of them is the total charging time, and after all the charging is completed, the internal temperature is raised to a predetermined polymerization temperature. The time required for heating was defined as the heating time. Example 1 In a 2,000-L stainless steel polymerization vessel equipped with a stirrer and a reflux condenser, 80 L of water (hereinafter referred to as pre-charged water) at a temperature of 25 ° C, which corresponds to 10% of the total amount used, was saponified 79%. 8.0 L of a 3% aqueous solution of partially saponified polyvinyl acetate having a polymerization degree of 2000 (hereinafter referred to as PVA1) and 12.1 L of a 0.5% aqueous solution of polyethylene oxide having an average molecular weight of 4.5 million (hereinafter referred to as PEO1)
And 50 parts of an isoparaffin solution of di-2-ethylhexyl peroxydicarbonate having a concentration of 70%, and 100 parts of water.
, 20 parts of methanol, 10 parts of partially saponified polyvinyl acetate (80% saponification, 300 degree of polymerization), and 10 parts of polyoxyethylene sorbitan monolaurate, and an initiator prepared by stirring at -10 ° C. 1.6 L of emulsion (PVA based on 100 parts of vinyl chloride monomer)
The charged amounts of 1 and PEO1 were 0.036 parts and 0.009 parts, respectively, and the charged amount of di-2-ethylhexyl peroxydicarbonate was 0.045 parts), and the inside of the polymerization vessel was degassed by a vacuum pump. Then, 716 L of warm water whose temperature had been adjusted to 70 ° C. after degassing was started to be charged into the polymerization vessel at a rate of 42 L / min, and one minute later, 740 L of vinyl chloride monomer was started to be charged at a rate of about 41 L / min. The warm water was charged in about 17 minutes, and the vinyl chloride monomer was charged in about 18 minutes.

Further, a stirrer equipped with a blue margin blade was operated at the same time as the vinyl chloride monomer was charged, and the rotation speed was adjusted so that the peripheral speed of the stirring blade became 8.6 m / sec. The internal temperature started to rise gradually at the same time as the start of the charging, and the internal temperature at the end of the entire charging was 46 ° C. Next, as a result of performing temperature control using a jacket and a reflux condenser, the time required for the internal temperature to reach 57 ° C. was 10 minutes. Therefore, the heating time is 10 minutes.

The internal temperature was maintained at 57 ° C., and the polymerization was stopped when the internal pressure of the polymerization reactor dropped by 1 kg / cm ² from the steady pressure, and the unreacted monomer was recovered to terminate the polymerization. The obtained slurry was dehydrated and dried to obtain a vinyl chloride polymer, and each characteristic value was measured (see Table 1). Example 2 Example 1 was repeated except that 0.46 L of a solution of di-2-ethylhexylperoxydicarbonate dissolved in isoparaffin at a concentration of 70% was used instead of the emulsion of di-2-ethylhexylperoxydicarbonate. Under the same charging and polymerization conditions, a vinyl chloride polymer was obtained and used for measuring various characteristic values. Example 3 A vinyl chloride polymer was obtained under the same charging and polymerization conditions as in Example 1, except that the time difference between the start of charging the degassed warm water and the vinyl chloride monomer was not 1 minute, and the charging was started at the same time. And various characteristic values. Example 4 A partially saponified polyvinyl acetate having a saponification degree of 88% and a polymerization degree of 2300 instead of PVA1 (hereinafter referred to as P
VA2) and a polymer having a saponification degree of 78% and a polymerization degree of 600 (hereinafter referred to as PVA3) were combined, and the same preparation and polymerization conditions as in Example 1 were used except that 0.04 part and 0.02 part were used, respectively. To obtain a vinyl chloride polymer,
It was used for measurement of various characteristic values. Example 5 A vinyl chloride polymer was obtained under the same preparation and polymerization conditions as in Example 1 except that PVA1 and PVA3 were combined, 0.08 parts and 0.02 parts were used, and PEO1 was not used. It was used for measurement. Comparative Example 1 The same amount of PVA1 as in Example 1 was used without using pre-charged water.
And an aqueous solution of PEO1 and an emulsion of di-2-ethylhexylperoxydicarbonate were charged, and the inside of the polymerization vessel was degassed by a vacuum pump. Then, after degassing, 70
Warm water whose temperature was adjusted to ° C was started to be charged at a rate of about 42 L / min, and one minute later, a vinyl chloride monomer was started to be charged at a rate of about 41 L / min. 800 L of warm water was added in about 19 minutes, and 740 L of vinyl chloride monomer was charged in about 18 minutes. The internal temperature at the end of the entire preparation was 52 ° C., and the time required for the internal temperature to reach 57 ° C. was 5 minutes as a result of performing temperature control using a jacket and a reflux condenser. Therefore, the heating time is 5 minutes. Thus, a vinyl chloride polymer was obtained and subjected to measurement of various characteristic values. Comparative Example 2 A vinyl chloride polymer was obtained under the same charging and polymerization conditions as in Example 1 except that the temperature of the pre-charged water was changed to 50 ° C., and used for measurement of various characteristic values. Comparative Example 3 240 L corresponding to 30% of the total amount of water used in advance charge
A vinyl chloride polymer was obtained under the same charging and polymerization conditions as in Example 1 except that about 550 L of degassed 70 ° C. warm water was charged at 44 L / min for about 13 minutes, and used for measurement of various characteristic values. Provided. Comparative Example 4 A vinyl chloride polymer was obtained under the same preparation and polymerization conditions as in Example 1 except that the time difference between the start of the warm water supply and the preparation of the vinyl chloride monomer was changed to 10 minutes. Was used for the measurement. Comparative Example 5 The same aqueous solution of the dispersant as used in Example 1 was used in parallel with the preparation of warm water, instead of the preparation and the pre-charged water and the initiator. That is, at the same time as starting to charge the vinyl chloride monomer in Example 1, 3% of PVA1
The aqueous solution was introduced into the warm water line through the measuring line at a rate of about 2 L / min, mixed and started charging in the line, and the charging was completed in about 4 minutes. Simultaneously with the completion of the charging of the PVA1 aqueous solution, a 0.5% aqueous solution of PEO1 was introduced into the warm water line through the measuring line at a rate of about 4 L / min, mixed in the line, and charged, and the charging was completed in about 3 minutes. .
The amounts of PVA1 and PEO1 charged were the same as in Example 1. Except for this, a vinyl chloride polymer was obtained under the same conditions as in Example 1 and used for measuring various characteristic values. Comparative Example 6 The emulsion of the same initiator used in Example 1 was used in parallel with the charging of the vinyl chloride monomer, instead of charging it together with the pre-charged water and the aqueous dispersant solution in advance. That is, in Example 1, at the same time as the start of the vinyl chloride monomer charging, 1.6 L of the initiator emulsion was passed through the charging line for the initiator cut into the vinyl chloride monomer charging line.
Charged at a rate of 4 L / min for 4 minutes. Except for this, a vinyl chloride polymer was obtained under the same preparation and polymerization conditions as in Example 1, and used for measurement of various characteristic values.

[0038]

[Table 1]

As is clear from Table 1, when the vinyl chloride monomer and the entire amount of warm water are simultaneously charged without using any pre-charged water, the internal scale of the polymerization vessel increases (Comparative Example 1). Further, when the temperature of the pre-charged water is set to 50 ° C., the coarse particles increase, the particle size distribution is wide, and both the scale inside the polymerization vessel and the fish eyes increase significantly (Comparative Example 2). Further, when the amount of the pre-charged water is 30% of the total used amount, the fisheye is good, but the internal temperature at the end of all the charges is too low, so that the temperature rise time is long (Comparative Example 3).

Next, if the time difference between the start of the warm water supply and the start of the vinyl chloride monomer start is set to 10 minutes, the total preparation time becomes longer (Comparative Example 4). Furthermore, in the method in which the dispersant is charged in parallel during the charging of warm water, the particle size distribution is widened and the number of fish eyes is extremely large (Comparative Example 5). In addition, in the method in which the initiator is charged in parallel during the charging of the vinyl chloride monomer, the effect of improving fisheye is not sufficient (Comparative Example 6).

On the other hand, it can be seen that in all of the examples of the present invention, the particle size distribution is narrow and the fish eyes are small.

[0042]

According to the method of the present invention, a vinyl chloride polymer having less fish eyes can be obtained and the productivity is greatly improved. Thus, the industrial value of the present invention is extremely large. It is.

Claims (4)

[Claims] When a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a monomer copolymerizable with a vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium, the temperature of (a) is preferably 0
At the same time, water at -40 ° C is charged into the polymerization reactor in an amount not exceeding 20% by weight of the total amount used, and an aqueous solution or aqueous dispersion of a water-soluble or water-dispersible polymer suspension / dispersion stabilizer; The polymerization reactor is degassed after charging the agents together, and the polymerization reactor is degassed. (B) The preliminarily degassed warm water and the vinyl chloride monomer are simultaneously or slightly warmed to start charging, and the charging is completed. A method for producing a vinyl chloride polymer. 2. The water-soluble or water-dispersible polymer suspension dispersion stabilizer is partially saponified polyvinyl acetate, methylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylic acid, vinyl acetate-maleic acid copolymer. 2. The method according to claim 1, comprising a combination of at least one selected from the group consisting of coalesced coal, styrene-maleic acid copolymer, gelatin and starch. 3. The method according to claim 1, wherein the time from the start of the supply of the degassed hot water to the start of the supply of the vinyl chloride monomer is within 2 minutes. 4. The production method according to claim 1, wherein the oil-soluble initiator is an emulsion type emulsified or dispersed in an aqueous medium.