JPH0987303A - Method for polymerizing vinyl chloride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polymerization method which is effective in considerably reducing the time required for feeding and heating per batch and in preventing foaming when a reflux condenser is operated to thereby prevent scale deposition on the inner walls of the polymerizer and condenser, and by which a vinyl chloride resin having excellent processability can be obtained. SOLUTION: A monomer feedstock to be polymerized which is either vinyl chloride alone or a mixture thereof with one or more monomers copolymerizable therewith and which has been heated to a temp. within ±5 deg.C based on a given polymerization temp. is fed into a polymerizer from the top of a reflux condenser simultaneously with an aqueous medium heated likewise.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, the polymerization of vinyl chloride-based monomers is usually carried out by a batch type water suspension polymerization method. That is, a method in which an aqueous medium and a dispersant are charged into a polymerization vessel, then a polymerization initiator is charged, and then a vinyl chloride monomer is charged after vacuum degassing the inside of the polymerization vessel and the temperature is raised to carry out a polymerization reaction. is there.

By the way, in recent years, in the production of vinyl chloride-based monomers, the size of a polymerization vessel has been increased and the polymerization time has been shortened in order to improve productivity. As one of the methods,
In order to remove reaction heat efficiently, a reflux condenser is attached to the polymerization vessel.

However, when attempting to remove the heat of reaction by the reflux condenser, foaming becomes remarkable especially at the initial stage of the polymerization, so that the foam of the polymerization suspension containing the polymerization initiator becomes the gas phase portion of the polymerization tank. It adheres to the wall surface, the inner wall of the reflux condenser, etc., and this becomes a scale and significantly hinders the efficiency of heat removal.
Since it adversely affects the particle formation in the initial stage of the polymerization, there are problems that particles having no internal voids called glass beads are generated, or the polymerization progresses in the form of bubbles to form coarse polymer particles.

Various polymerization methods have been proposed in order to prevent foaming when the reflux condenser is activated at the beginning of polymerization. For example, in JP-A-2-55707, a method of introducing nitrogen gas into a reflux condenser to start polymerization and then gradually purging nitrogen gas as the polymerization progresses to operate the reflux condenser to prevent foaming. Is disclosed. However, this method has a problem that it requires a very complicated operation.

Further, for example, JP-A-2-47481, JP-A-61-207410, and JP-A-60-2.
In JP-A-38305 and JP-A-61-115908, methods for preventing foaming by using a specific emulsifier and / or dispersant are disclosed in JP-A-3-212409 and JP-A-2-180908. Methods of using antifoam agents are disclosed. However, these methods have a problem that the obtained polyvinyl chloride is colored by using an emulsifier, a dispersant or a defoaming agent.

Further, in order to shorten the time required for one batch of polymerization, shortening of the charging time and heating time have been studied. For example, in JP-A-4-149204, a vinyl chloride monomer and an aqueous medium which has been heated in advance are mixed and then heated through a heat exchanger to a temperature of -10 ° C to + 5 ° C in the polymerization temperature and charged. Method: JP-A-60
JP-A-163906 discloses a method in which a part of an aqueous medium and a vinyl chloride-based monomer are charged, and then the remaining heated aqueous medium is heated to a temperature equal to or higher than a polymerization temperature and charged to a reaction temperature at the end of the charging; 60-26488, Japanese Patent Publication No. 6
2-39601 and JP-A-5-186506 disclose methods of charging a vinyl chloride monomer and a heated aqueous medium at the same time.

However, by mixing the heated aqueous medium and the vinyl chloride-based monomer at room temperature in this way, the internal pressure rapidly rises and foaming easily occurs, and glass beads and coarse particles are produced. There was a problem.

Further, in Japanese Patent Publication No. 4-12721,
A method is disclosed in which an aqueous medium at 50 ° C. or lower, a dispersant, a polymerization initiator, and a vinyl chloride-based monomer are mixed in advance, and then rapidly heated by a heat exchanger and charged into a polymerization tank. However, since the polymerization initiator is desired to be added, there is a risk that the polymerization may start during the premixing.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and an object thereof is to prepare a batch of polymerization by heating both a vinyl chloride monomer and an aqueous medium at the same time. It is possible to significantly reduce the charging time and the heating time per hit, and to prevent foaming during the operation of the reflux condenser when performing suspension polymerization of vinyl chloride resin in a large-scale polymerization vessel equipped with a reflux condenser. In addition, it prevents the scale from adhering to the inner wall of the polymerization vessel or the reflux condenser wall,
It is an object of the present invention to provide a method for polymerizing vinyl chloride from which a vinyl chloride resin having no glass beads or coarse particles and excellent workability is obtained.

[0011]

The method for polymerizing vinyl chloride according to the present invention comprises a vinyl chloride monomer or a vinyl chloride monomer heated to a predetermined polymerization temperature of ± 5 ° C. and a monomer which can be copolymerized therewith. It is characterized in that the mixture of the body and the aqueous medium heated to a polymerization temperature of ± 5 ° C. are simultaneously charged into the polymerization vessel from the top of the reflux condenser column.

Examples of the monomer copolymerizable with the vinyl chloride monomer used in the present invention include vinyl esters such as vinyl acetate and vinyl propionate; (meth) acrylates such as methyl acrylate and ethyl acrylate. 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, a reactor equipped with a reflux condenser and a jacket is used. The jacket of the reactor is heated to a polymerization temperature of ± 5 ° C, and the reflux condenser is heated to a polymerization temperature of ± 5 ° C.
It is preferable to heat in the range of 0 ° C to + 5 ° C. After degassing the inside of the polymerization vessel under vacuum, the vinyl chloride monomer and the aqueous medium, which have been heated to a polymerization temperature of ± 5 ° C in advance, are simultaneously charged into the polymerization vessel from the top of the reflux condenser. When the vinyl chloride-based monomer and the aqueous medium are added, the polymerization vessel is preferably heated to a polymerization temperature of ± 5 ° C. The polymerization temperature is usually
It is a temperature determined by setting the degree of polymerization.

Examples of the vinyl chloride-based monomer include vinyl chloride monomer alone, vinyl chloride monomer and a mixture of monomers copolymerizable with the vinyl chloride monomer.

As a method of charging the vinyl chloride monomer and the aqueous medium, the vinyl chloride monomer and the aqueous medium are introduced through separate pipes and charged into the polymerization vessel while mixing in the reflux condenser. Method; vinyl chloride monomer and aqueous medium in a separate container in advance, or in a line, static mixer,
A method in which a suspension obtained by mixing with a line mixer or the like is charged from the top of the reflux condenser column may be used.

The method of charging the vinyl chloride-based monomer and the aqueous medium through separate pipes is to start charging both at the same time and end at the same time; first start charging the aqueous medium and then the vinyl chloride-based monomer. How to put in and finish at the same time;
Begin to charge vinyl chloride monomer and aqueous medium at the same time,
A method of terminating the charging of the vinyl chloride monomer first, and then terminating the charging of the aqueous medium, and the like may be mentioned. If there is, it is not particularly limited.

When the charging of the vinyl chloride-based monomer and the aqueous medium is completed, the temperature of the reaction solution is set to the polymerization temperature ± 5 ° C. Furthermore, the polymerization temperature is preferably ± 2 ° C.
It is. When the temperature of the reaction liquid at the end of the charging becomes low, it takes time to raise the temperature to a predetermined polymerization temperature, and the time per polymerization batch cannot be shortened. Further, if the temperature becomes higher, the polymerization reaction will proceed rapidly when the polymerization initiator is subsequently added, making it difficult to remove the heat of reaction.

A dispersant is used in the polymerization method of the present invention. As a method for adding the dispersant, a vinyl chloride-based monomer,
A method of charging the aqueous medium in advance before charging it; a method of charging the vinyl chloride-based monomer and the aqueous medium at the same time; a method of charging after the vinyl chloride-based monomer is charged. Method may be used.

When the dispersant is charged, the stirrer of the reactor is preferably operated, and after the dispersant is charged, it is preferable to press-in the polymerization initiator to start the polymerization.

Examples of the dispersant include those usually used in suspension polymerization of vinyl chloride. For example, water-soluble cellulose such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose; partially saponified polyvinyl alcohol, Polyethylene oxide, acrylic acid, water-soluble polymers such as gelatin, sorbitan monolaurate, water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate and the like, these may be used alone,
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.

Furthermore, polymerization regulators, polymerization inhibitors, pH regulators, stabilizers, scale inhibitors and the like which are commonly used in the polymerization of vinyl chloride type monomers may be added.

The above polymerization reaction is stopped when the internal pressure of the polymerization reactor falls below a predetermined pressure from the pressure during operation, or when a certain time has elapsed from the start of polymerization. Cool the jacket and reflux condenser, exhaust the remaining unreacted monomer,
The obtained slurry is dehydrated and dried to obtain a vinyl chloride polymer.

[0025]

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) Internal volume 2 m^ThreeJacket and
57 with a stainless steel polymerization reactor jacket equipped with a stirring blade.
℃, reflux condenser after heating to 60 ℃, saponification degree 72 mol
% Of partially saponified polyvinyl alcohol (Nippon Gosei Kagaku Co., Ltd.)
"Gothenol KZ-05") 600 g, hydroxy
Propyl methylcellulose (Shin-Etsu Chemical Co., Ltd. “Metrose
65SH50 ") After charging 375 g, 1 in the polymerization vessel
Vacuum was applied to 00 mmHg. Then heat to 55 ° C
750 kg of vinyl chloride monomer and
900 kg of on-exchanged water is supplied to the top of the reflux condenser through a separate pipe.
Part was charged into the polymerization vessel. Vinyl chloride monomer at this time
And the introduction of ion-exchanged water started at the same time and ended at the same time.
The temperature of the suspension after charging was 57 ° C. Then heavy
Compound initiator di-2-ethylhexyl peroxydicarbone
600 g of Tote (“Perloyl OPP” manufactured by NOF CORPORATION)
After pressurizing with nitrogen, control the internal temperature to 57.5 ° C and carry out the polymerization reaction.
Started. After 4 hours, the pressure in the polymerization vessel was 7.0 kg /
cm ²Since the temperature has dropped to G, cooling starts and the unreacted unit
The body was recovered and the polymerization reaction was stopped. Obtained polymer slurry
Was dehydrated and dried to obtain a vinyl chloride resin.

(Example 2) Internal volume 2 m^ThreeJacket and
57 with a stainless steel polymerization reactor jacket equipped with a stirring blade.
℃, reflux condenser After heating to 60 ℃, 100 in the polymerization vessel
Vacuum was applied to mmHg. Then preheat to 55 ° C
Preheated to 55 ° C with 750 kg of vinyl chloride monomer
900 kg of deionized water with a static mixer
While mixing, the mixture was charged into the polymerization reactor from the top of the reflux condenser column.
At the same time, the partially saponified polyvinyl chloride with a saponification degree of 76 mol%
Alcohol (Kuraray's "Poval L-8") 750
g and polyethylene oxide with an average molecular weight of 4.3 million
110g of "PEO-18" manufactured by Yusei Chemical Co., Ltd.
Was. The temperature of the suspension after charging was 56 ° C. Next
Then, the polymerization initiator di-2-ethylhexyl peroxydica
Carbonate (Nippon Yushi Co., Ltd. "Perloyl OPP") 60
After pressurizing 0 g with nitrogen, control the internal temperature to 57.5 ° C and
The combined reaction started. After 4 hours, the pressure in the polymerization vessel was 7.0.
Kg / cm ²Since the temperature has dropped to G, cooling has started and no reaction has occurred.
The monomer was recovered and the polymerization reaction was stopped. Polymer obtained
The slurry was dehydrated and dried to obtain a vinyl chloride resin.

Comparative Example 1 Example 1 was repeated except that the vinyl chloride monomer was added at room temperature (25 ° C.) without heating.
Polymerization reaction was carried out in the same manner as above to obtain a vinyl chloride resin.

(Comparative Example 2) Ion-exchanged water was preheated to 75 ° C., and the vinyl chloride monomer was not heated to room temperature (25 ° C.).
A polymerization reaction was carried out in the same manner as in Example 2 except that the vinyl chloride resin was obtained as it was, to obtain a vinyl chloride resin.

(Comparative Example 3) Ion-exchanged water was preheated to 75 ° C, and the vinyl chloride monomer was not heated at room temperature (25 ° C).
750 g of partially saponified polyvinyl alcohol having an average degree of polymerization of 200, a degree of saponification of 45.3 mol% and a block character of 0.8 as a dispersant, and polyethylene oxide having an average molecular weight of 4.3 million (“PEO manufactured by Sumitomo Seika Co., Ltd.” -18 ") except that 110 g was used, a polymerization reaction was carried out in the same manner as in Example 2 to obtain a vinyl chloride resin. The block character was determined by peak analysis in the methylene region of the ¹³ C-NMR spectrum. That is, in the methylene region, (OH, OH), (O
H, OAc), (OAc, OAc) [representing the number of moles of 2 unit chains in Poval], three peaks corresponding to 2 unit chains appear, and the absorption intensity is proportional to the structure of 3 units. . Then, the block character η is calculated by the following formula (reference: “Poval”, Polymer Publishing Association, April 1981).
Revised new edition issued January 1, P246-249). η = (OH, OAc) / 2 · (OH) (OAc) Here, (OH) and (OAc) represent the number of moles of vinyl alcohol and vinyl acetate units in Poval, respectively.

The vinyl chloride resins obtained in the above Examples and Comparative Examples were evaluated as follows, and the results are shown in Table 1. (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 2,000 Kg / c using a mercury porosimeter
The porosity was determined by measuring the volume of mercury press-fitted per 100 g of vinyl chloride resin with m ² G. (5) Glass beads Sifted through a 42 mesh standard sieve, the particles remaining on the sieve were observed under a microscope, and the number of semitransparent particles was calculated. (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.

[0032]

[Table 1]

[0033]

Industrial Applicability The vinyl chloride polymerization method of the first invention is as described above, and in the batchwise polymerization, the time per batch can be greatly shortened, and at the same time, the slurry is formed by foaming the monomer. Since it is possible to prevent the scattering of particles, it is possible to prevent the scale from adhering. Further, the vinyl chloride polymer particles obtained do not have glass beads, have a high porosity for a high bulk specific gravity, and have a good particle size distribution,
Gel time is short.

Claims (1)

[Claims] 1. A vinyl chloride monomer which has been heated to a predetermined polymerization temperature of ± 5 ° C. when a vinyl chloride monomer alone or a vinyl chloride monomer and a monomer copolymerizable therewith are polymerized. A mixture of a vinyl chloride monomer and a monomer copolymerizable therewith, and an aqueous medium heated to a predetermined polymerization temperature of ± 5 ° C. are simultaneously charged into the polymerization vessel from the top of the reflux condenser column. And a method for polymerizing vinyl chloride.