JPH09302003A - Polymerization method of vinyl chloride monomer - Google Patents

Abstract

(57) Abstract: In batch suspension polymerization of vinyl chloride-based monomer, when the vinyl chloride monomer is additionally charged, stirring failure is prevented and the fish eye has a high bulk specific gravity. It is intended to provide a method for polymerizing a vinyl chloride-based monomer, which gives a vinyl chloride-based resin excellent in processability and having a low content. SOLUTION: When a vinyl chloride monomer is charged in a polymerization vessel together with an aqueous medium, a dispersant, and a polymerization initiator to carry out suspension polymerization, polymerization of the vinyl chloride monomer during the polymerization reaction into a polymer is carried out. With a conversion of 20 to 80%, vinyl chloride monomer and polyethylene oxide having an average molecular weight of 100,000 to 12 million are additionally added, and the addition amount of polyethylene oxide is added to the vinyl chloride monomer. To 0.002
~ 0.2% by weight.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for polymerizing vinyl chloride monomers.

[0002]

2. Description of the Related Art Conventionally, the polymerization of vinyl chloride-based monomers is usually carried out by a batch suspension polymerization method. That is, after an aqueous medium, a vinyl chloride monomer, a dispersant and a polymerization initiator were charged all at once in a polymerization vessel, the temperature was raised to carry out a polymerization reaction at a constant temperature to reach a predetermined polymerization conversion rate. At this point, the unreacted monomer is recovered, and a vinyl chloride polymer is produced through dehydration and drying steps.

By the way, in recent years, in the production of vinyl chloride-based monomers, in order to improve the productivity per batch, the vinyl chloride-based monomer is added when a predetermined polymerization conversion rate is reached after the initiation of the polymerization. The method of putting in is proposed. For example,
In Japanese Patent Application Laid-Open No. 50-97679, the polymerization conversion rate is 70.
A method of additionally adding 50% by weight or less of the monomer to the initially charged monomer in the range of up to 80% is disclosed. However, this method has a problem in that particles having a small number of voids, called fish eyes, increase in the obtained polymer, resulting in poor moldability.

Therefore, for example, Japanese Patent Laid-Open No. 61-19510.
In JP-A No. 1, a vinyl chloride-based monomer and a partially saponified polyvinyl alcohol having a degree of polymerization of 200 to 1,500 and a degree of saponification of 30 to 75 mol% are added at a polymerization conversion rate of 30 to 75%. Has proposed a method for obtaining a polymer having a high bulk specific gravity and excellent molding processability. However, in the suspension polymerization of vinyl chloride-based monomers, a phenomenon called a gelling effect occurs at the time when the polymerization conversion rate at the final stage of polymerization reaches 60 to 80%, the viscosity of the polymerization suspension increases, and stirring occurs. It is known that, since the effect is reduced, the overall heat transfer coefficient of the polymerization vessel is significantly reduced, and the heat of the polymerization reaction cannot be sufficiently removed.

Usually, the initial charging is carried out at an aqueous medium / monomer ratio of 1.0 to 1.5. However, if additional monomers are charged after the start of polymerization, the aqueous medium / monomer will be charged. However, since the ratio of the above is further reduced and the viscosity of the polymerization suspension is increased, the stirring at the final stage of the polymerization becomes extremely poor, and it is very difficult to remove the heat of the polymerization reaction. At this time, there is also a method in which water is additionally charged so that the initial charging ratio is not changed, but the initial charging amount is reduced and the productivity cannot be improved. Further, it is known that the addition of a surfactant temporarily improves stirring, but soon returns to a state of poor stirring.

By the way, recently, with the increase in the size of the polymerization vessel, a reflux condenser has been often attached to improve the heat removal amount. However, the stirring condition is extremely deteriorated and heat removal failure occurs. At this time, if heat is removed by the attached reflux condenser, the polymerization reaction suspension overflows into the reflux condenser or the polymerization reaction suspension scatters. There was a problem in that the reflux condenser could not be used due to the blockage, and the heat of the polymerization reaction could not be removed, resulting in a very dangerous state.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and its object is to polymerize vinyl chloride-based monomers in batch suspension polymerization of vinyl chloride-based monomers. At the time when the conversion rate reached 20 to 80%, when the vinyl chloride monomer was additionally charged, polyethylene oxide was added at the same time to prevent stirring failure and to obtain fish eyes with a high bulk specific gravity. Less
Moreover, it is intended to provide a method for polymerizing a vinyl chloride-based monomer, which gives a vinyl chloride-based resin excellent in moldability.

[0008]

Means for Solving the Problems A method for polymerizing a vinyl chloride-based monomer according to the present invention is a method in which a vinyl chloride-based monomer is mixed with an aqueous medium,
When the polymerization conversion of the vinyl chloride-based monomer into the polymer during the polymerization is carried out by suspending polymerization in a polymerization vessel together with the dispersant and the polymerization initiator, the vinyl chloride monomer content is 20% to 80%. Body and polyethylene oxide having an average molecular weight of 100,000 to 12,000,000 are additionally added, and the addition amount of polyethylene oxide is 0.0 with respect to the vinyl chloride monomer additionally added.
It is characterized in that it is from 02 to 0.2% by weight.

The vinyl chloride monomer used in the present invention refers to a vinyl chloride monomer alone or a monomer composition mainly composed of the vinyl chloride monomer. Examples of the monomer composition include a mixture of a vinyl chloride monomer and a monomer other than vinyl chloride.
As the monomer other than the vinyl chloride, those that can be copolymerized with the vinyl chloride monomer, for example, vinyl acetate,
Vinyl esters such as vinyl propionate; (meth) methyl (meth) acrylate, ethyl (meth) acrylate, etc.
Acrylic acid ester: In addition to olefins such as ethylene and propylene, maleic anhydride, acrylonitrile, styrene, vinylidene chloride and the like can be mentioned, but not limited thereto.

In the present invention, polyethylene oxide is used as a dispersant, and its average molecular weight is 100,000 or more, preferably 2 million or more. The average molecular weight is
When the amount is less than 100,000, the dispersant has no effect of preventing defective stirring. The upper limit of the molecular weight is 1,20
It is 0,000.

The amount of the polyethylene oxide used is 0.002 to 0.2% by weight based on the vinyl chloride-based monomer additionally added as described later. 0.002
If it is less than 10% by weight, the effect of preventing poor stirring as a dispersant is not exhibited, and if it exceeds 0.2% by weight, the effect is saturated, which is economically undesirable.

Examples of the dispersant used in the present invention other than the above-mentioned polyethylene oxide include those usually used in suspension polymerization of vinyl chloride. Examples thereof include methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and hydroxy. Water-soluble cellulose such as propylmethyl cellulose; water-soluble polymers such as partially saponified polyvinyl alcohol, acrylic acid and gelatin; water-soluble emulsifiers such as sorbitan monolaurate and polyoxyethylene sorbitan monolaurate; May be used in
Two or more kinds may be used in combination.

The amount of the dispersant used is preferably 0.005 to 2% by weight based on the vinyl chloride monomer.

The polymerization initiator used in the present invention includes
For example, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, α
-Cumylperoxy neodecanoate, t-butylperoxy neodecaneate, t-butylperoxypivalate, t-butylperoxy-3,5,5-trimethylhexanoate, acetylcyclohexylsulfonyl peroxide, 2, 4,4-trimethylpentyl-2-peroxyphenoxyacetate, lauroyl peroxide and the like can be mentioned, and these may be used alone or in combination of two or more kinds.

In the production method of the present invention, the polymerization reaction is carried out as follows. Ion-exchanged water, a vinyl chloride-based monomer, a dispersant, and a polymerization initiator are charged into the polymerization vessel, and then the temperature is raised to a predetermined temperature to carry out a suspension polymerization reaction. In the above polymerization reaction, the polymerization conversion rate of the vinyl chloride-based monomer is 2
When it reaches 0 to 80%, a vinyl chloride-based monomer is additionally charged and polyethylene oxide is added. The polyethylene oxide may be added before or during the additional charging of the vinyl chloride-based monomer.

By adding the above-mentioned polyethylene oxide, the polymerization conversion ratio of the vinyl chloride-based monomer is 60 to 60.
It is effective for preventing poor stirring at the time of 80%, and particularly for maintaining good stirring even when a vinyl chloride monomer is additionally charged.

Examples of the method for additionally charging the vinyl chloride-based monomer include a method of charging the vinyl chloride monomer into the polymerization vessel with a metering pump; a method of charging the polymerization vessel with nitrogen gas or the like at a pressure higher than the internal pressure of the polymerization vessel and charging the polymerization vessel at once. . Further, polyethylene oxide is dissolved in water and then added in the same manner as the vinyl chloride-based monomer.

The amount of the vinyl chloride-based monomer additionally charged is preferably 5% by weight or more of the vinyl chloride-based monomer initially charged in order to obtain a vinyl chloride-based resin having a high bulk specific gravity, and the upper limit is particularly preferable. Although not limited, it is preferably up to 30% by weight of the vinyl chloride monomer. If it exceeds 30% by weight, the polymerization time becomes long and the efficiency is lowered.

The polymerization reaction is stopped when the internal pressure of the polymerization vessel is lowered from the pressure during operation by a predetermined pressure, or when a predetermined time has elapsed after the start of polymerization or after the vinyl chloride-based monomer was additionally charged. Next, the jacket and the reflux condenser are cooled, the remaining unreacted monomer is discharged as an exhaust gas, and the obtained slurry is dehydrated and dried to obtain a vinyl chloride resin.

The structure of the polymerization vessel (pressure autoclave) used in the present invention is not particularly limited, and a known structure having a reflux condenser, which has been conventionally used for polymerization of vinyl chloride, can be used. . Further, the stirring blade may be a general-purpose one such as a faudler blade, a paddle blade, a turbine blade, a fan turbine blade, or a bull margin blade, and the combination with a baffle plate is not particularly limited.

(Function) In the present invention, when the polymerization conversion rate of the vinyl chloride monomer during the polymerization reaction reaches 20 to 80%, polyethylene oxide is added together with the vinyl chloride monomer to be additionally charged. As a result, good agitation can be maintained even at the time of so-called gel effect in the final stage of polymerization, and high productivity can be obtained. Further, the obtained vinyl chloride-based resin has large voids despite having a high bulk specific gravity, has few fish eyes, and is excellent in molding processability. Furthermore, even if additional vinyl chloride monomer is charged using a polymerization vessel equipped with a reflux condenser, it is possible to prevent the suspension polymerization solution from scattering to the top of the polymerization vessel and to prevent the suspension polymerization solution from overflowing. sell.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

(Example 1) An internal volume of 660 liters and a pressure-resistant transparent glass for observing the inside during the polymerization reaction were placed in the upper part of a polymerization vessel, 300 kg of ion-exchanged water, and a saponification degree of 70.
After charging 150 g of mol% partially saponified polyvinyl alcohol ("Gohsenol KZ-06" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), the inside of the polymerization vessel was vacuum degassed to 13 kPa. Then, after charging 250 kg of vinyl chloride monomer, 200 g of a polymerization initiator di-2-ethylhexyl peroxydicarbonate (“Perloyl OPP” manufactured by NOF Corporation) and t
-75 g of butyl peroxyneodecanate ("Perbutyl ND" manufactured by NOF CORPORATION) was press-fitted with nitrogen, and then the temperature was raised to 57 ° C to start the polymerization reaction.

From 2 hours after the start of polymerization (40% conversion of polymerization) to the end of the additional charging of vinyl chloride monomer, polyethylene oxide having an average molecular weight of 4.3 million (P.
EO-18 ") aqueous solution with a polyethylene oxide amount of 7.
It was added continuously so as to be 5 g. After 3 hours from the start of polymerization (polymerization conversion rate 60%), 50 kg of vinyl chloride monomer was added to 3 times.
It was additionally charged into the polymerization vessel over 0 minutes. 57 ° C after that
Then, the polymerization reaction was continued, and when the pressure in the polymerization vessel dropped to 0.6 MPa, cooling was started, unreacted monomers were recovered, and the polymerization reaction was stopped. The resulting polymer slurry was dehydrated and dried to obtain a vinyl chloride resin.

(Examples 2, 3 and Comparative Examples 1 to 4) A vinyl chloride resin was prepared in the same manner as in Example 1 except that the average molecular weight and addition amount of polyethylene oxide were changed as shown in Table 1. Obtained.

(Embodiment 5) An inner volume of 660 liters, a pressure-resistant transparent glass for observing the inside during the polymerization reaction, installed in a polymerization vessel, 300 kg of ion-exchanged water, and a saponification degree of 70
After charging 75 g of mol% partially saponified polyvinyl alcohol (“Gohsenol KZ-06” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 75 g of hydroxypropylmethyl cellulose (“Metrose 65SH50” manufactured by Shin-Etsu Chemical Co., Ltd.), the inside of the polymerization vessel was vacuum-decompressed to 13 kPa. I noticed. Then, after charging 250 kg of vinyl chloride monomer, 200 g of a polymerization initiator di-2-ethylhexyl peroxydicarbonate (“Perloyl OPP” manufactured by NOF Corporation) and t-butyl peroxyneodecanate (manufactured by NOF Corporation) "Perbutyl ND") 7
After pressurizing 5 g with nitrogen, the temperature was raised to 57 ° C. to start the polymerization reaction.

From 2 hours after the start of polymerization (40% conversion of polymerization) to 4 hours after the start of polymerization (80% conversion of polymerization), an aqueous solution of polyethylene oxide having an average molecular weight of 8 million (“PEO-28” manufactured by Sumitomo Seika) Was continuously added so that the amount of polyethylene oxide was 5 g. At the same time, continuously add 50 kg of vinyl chloride monomer,
The introduction of polyethylene oxide and vinyl chloride monomer was completed at the same time. After that, the polymerization reaction was continued at 57 ° C., and when the pressure in the polymerization vessel dropped to 0.6 MPa, cooling was started to collect unreacted monomers and stop the polymerization reaction.
The resulting polymer slurry was dehydrated and dried to obtain a vinyl chloride resin.

(Examples 6, 7 and Comparative Examples 5-8) A vinyl chloride resin was prepared in the same manner as in Example 5 except that the average molecular weight and addition amount of polyethylene oxide were changed as shown in Table 2. Obtained.

Tables 3 and 5 show the state of stirring during polymerization and the state of scale adhesion.

The vinyl chloride resins obtained in the above Examples and Comparative Examples were evaluated as follows, and the results are shown in Tables 3 and 4.
It was shown to. (1) Degree of polymerization Measured in accordance with JIS K6721. (2) Particle size distribution Measured according to JIS K8801. (3) Bulk specific gravity Measured according to JIS K6721. (4) Porosity Using a mercury porosimeter, the porosity was determined by measuring the volume of mercury press-fitted per 100 g of vinyl chloride resin at 196 MPa. (5) Fisheye 100 g of the obtained vinyl chloride resin was mixed with 1 part of tribasic lead sulfate.
g, lead stearate 2 g, phthalate plasticizer 4
A resin composition was prepared by adding 0 g and a pigment 0.2 g, and the resin composition was kneaded with a two-roll roll at 145 ° C. for 5 minutes,
A resin sheet having a thickness of 0.2 mm was prepared, and the number of transparent particles in this sheet was measured. (6) Gelation time Into 100 g of the obtained vinyl chloride resin, 2 g of dibutyltin mercapto (“JF-10B” manufactured by Sankyo Machine Gosei Co., Ltd.) and an ester wax (“WAX-OP” manufactured by Hoechst) are added.
A resin composition was prepared by adding 0.5 g, and 65 g of this resin composition was added to Haake Plastograph “Reo Code 90”.
Then, the time until gelation was measured at 190 ° C. and 50 rpm.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

[0035]

[Table 5]

[0036]

The method for polymerizing a vinyl chloride-based monomer of the present invention is as described above, and even if an additional charge of the vinyl chloride monomer is added, it is possible to prevent the stirring failure at the final stage of the polymerization.
In addition, there is no scale adhesion in the polymerization vessel, and in particular, even in a polymerization vessel equipped with a reflux condenser, it is possible to prevent the suspension from scattering or overflowing into the upper portion of the polymerization vessel. Further, the obtained vinyl chloride resin has a high bulk specific gravity, a high porosity, a small number of fish eyes, and excellent molding processability.

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Claims (2)

[Claims] 1. Suspension polymerization by charging a vinyl chloride monomer consisting of a vinyl chloride monomer alone or a monomer composition mainly composed of the vinyl chloride monomer together with an aqueous medium, a dispersant and a polymerization initiator into a polymerization vessel. When the polymerization conversion rate of the vinyl chloride-based monomer into the polymer during the polymerization reaction is between 20 and 80%, the vinyl chloride monomer and polyethylene oxide having an average molecular weight of 100,000 to 12 million are added. The method for polymerizing a vinyl chloride monomer, wherein the amount of polyethylene oxide added is 0.002 to 0.2% by weight based on the vinyl chloride monomer additionally added. 2. The method for polymerizing a vinyl chloride monomer according to claim 1, wherein a polymerization vessel equipped with a reflux condenser is used.