JPH10231304A - Continuous suspension polymerization of vinyl chloride-based monomer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for polymerizing a vinyl chloride-based monomer by which the generation of coarser particles and void-free particles called glass beads of a vinyl chloride-based resin can be suppressed in a continuous suspen sion polymerization of the resin. SOLUTION: The amount of a dispersing agent used is 0.2-2wt.% based on a vinyl chloride-based monomer when continuously feeding a raw material mixture liquid comprising a vinyl chloride monomer alone or a mixture comprising the vinyl chloride monomer and monomers copolymerizable therewith, the dispersing agent and an aqueous medium to a polymerizer and carrying out a continuous suspension polymerization of the vinyl chloride-based monomer in the aqueous medium containing the dispersing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a continuous suspension polymerization method for vinyl chloride monomers.

[0002]

2. Description of the Related Art Conventionally, in the polymerization of vinyl chloride monomers, usually, a vinyl chloride monomer, an aqueous medium, a dispersant, a polymerization initiator, and the like are charged into a stainless steel polymerization vessel, and the reaction temperature is kept constant. It is performed by a batch-type water suspension polymerization method in which polymerization is performed while performing controlled heat removal. On the other hand, a continuous suspension polymerization method has been proposed to further increase the productivity. However, when this continuous suspension polymerization method is applied to the polymerization of vinyl chloride, there is a problem of coarsening, in which the particle size of the produced polymer increases, and what is called glass beads having no voids in the polymer particles is produced. There is a problem such as lowering of the temperature, and it has not been put to practical use.

In the above continuous suspension polymerization method, it is also important to control the particle size of the product resin to be obtained. Regarding the control of the particle structure of the polymer, for example, Japanese Patent Application Laid-Open No. 57-19 / 1982
2402, JP-A-57-205402, JP-A-58-91701, JP-B-6-102682.
Japanese Patent Publication No. 6-102683, Japanese Patent Publication No. 6-1
Various proposals have been made in, for example, Japanese Patent Publication No. 02685. However, although effective in controlling the particle size of styrene or the like, no effect was observed in preventing the generation of coarse particles and glass beads due to polymerization of a vinyl chloride monomer.

Some proposals have been made to prevent agglomeration of polymers during the initial stage of polymerization, which is called sticky state, in which the resin has high adhesiveness. For example, JP-A-56-118407 discloses a method in which the polymerization temperature of the first polymerization vessel among a plurality of polymerization vessels is set higher to lower the viscosity of the polymer;
Japanese Patent Application Publication No. 9-9751 discloses a method of providing a plurality of superposing units in a sticky state in parallel;
No. 8081 proposes a method for increasing the agitation of a polymerization vessel having a sticky state among a plurality of polymerization vessels. However, both methods
There are problems such as the necessity of complicated operations and the reduction of the volumetric efficiency of the polymerization vessel.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to reduce the resin coarse particles and the generation of glass beads in continuous suspension polymerization of a vinyl chloride resin. An object of the present invention is to provide a continuous suspension polymerization method of a vinyl chloride monomer which can be suppressed.

[0006]

The continuous suspension polymerization method of the vinyl chloride monomer according to the present invention comprises a vinyl chloride monomer alone or a mixture of a vinyl chloride monomer and a monomer copolymerizable therewith. A raw material mixture consisting of a vinyl chloride monomer comprising a dispersant and an aqueous medium is continuously supplied to a polymerization vessel, and the vinyl chloride monomer is subjected to continuous suspension polymerization in an aqueous medium containing a dispersant. In this case, the amount of the dispersant used is 0.2 to 2% by weight based on the vinyl chloride monomer.

The vinyl chloride monomer used in the present invention includes a vinyl chloride monomer alone; and a mixture of a vinyl chloride monomer and a monomer copolymerizable therewith.

The monomers copolymerizable with the vinyl chloride monomer include, for example, vinyl esters such as vinyl acetate and vinyl propionate; and (meth) methyl such as methyl (meth) acrylate and ethyl (meth) acrylate. ) Acrylic acid esters: 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.

The continuous polymerization method referred to in the present invention refers to a method in which raw materials are continuously supplied to a single polymerization vessel or a plurality of polymerization vessels connected to one another, and products are simultaneously discharged.

In order to carry out the continuous suspension polymerization method of the present invention, a vinyl chloride monomer, an aqueous medium, a dispersant, a polymerization initiator and the like are quantitatively supplied to a polymerization vessel. However, vinyl chloride monomer, aqueous medium, dispersant, polymerization initiator, etc.
In the method of directly supplying the liquid to the polymerization reactor, the production of the droplets of the vinyl chloride-based monomer becomes insufficient, and the particle size of the obtained resin may become large.

Therefore, a raw material mixture comprising a vinyl chloride monomer, an aqueous medium and a dispersant is prepared in advance and supplied to a polymerization vessel. Also, when preparing the raw material mixture, it is necessary to mix well the raw materials of the vinyl chloride monomer, the aqueous medium and the dispersant with a static mixer or the like to produce good droplets of the vinyl chloride monomer. There is. It has been found that the amount of the dispersant has a great effect on producing good droplets in this raw material mixture, and greatly contributes to controlling the particle size of the product resin.

In the continuous suspension polymerization method of the present invention, when mixing the above-mentioned raw material mixture, the amount of the dispersant is added to the vinyl chloride monomer in an amount of 0.2 to 2% by weight. Even when the amount of the dispersant is less than 0.2% by weight, the particle size can be controlled by controlling the supply temperature of the raw material mixture, but by adding 0.2% by weight or more, more excellent particles can be obtained. A resin having a shape can be obtained. On the other hand, when the amount of the dispersant exceeds 2% by weight, the particle diameter becomes too fine, and the resin is easily scattered at the time of discharge.

Examples of the dispersant used in the present invention include those usually used for suspension polymerization of vinyl chloride. Examples thereof include water-soluble cellulose such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and hydroxypropyl methyl cellulose; 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, which may be used alone, Two or more kinds may be used in combination.

The above-mentioned polymerization initiator is supplied to the polymerization vessel through a pipe different from the raw material mixture.

Preferably, the raw material mixture is heated to a temperature range of (t-10) ° C. to (t + 5) ° C. with respect to a predetermined polymerization temperature (t ° C.) and supplied to the polymerization vessel. When the temperature of the raw material mixture is lower than (t-10) ° C., when this raw material mixture is supplied to the polymerization reactor, an abnormal foaming phenomenon occurs due to rapid heating, and the particle size of the obtained resin is coarse. Become something. Further, the temperature of the raw material mixture is (t +
5) When the temperature exceeds ℃, since the polymerization reaction of the vinyl chloride monomer is an exothermic reaction, not only does the burden of removing the reaction heat increase, but also the polymerization reaction may run away.

When the above-mentioned raw material mixture reaches a predetermined polymerization rate, the raw material is continuously supplied to the polymerization reactor at a constant speed. In this case, each raw material is supplied from a separate piping line to a static mixer and mixed. Then, the raw material mixture may be supplied to the polymerization vessel, or the raw material mixture may be prepared in a separate pressure vessel with a stirrer and supplied to the polymerization vessel.

As the above-mentioned static mixer, for example, those commercially available from Toray Engineering Co., Ltd. and Noritake Company can be used.

It is preferable that the charging section of the raw material mixture is supplied to a liquid phase section of a polymerization vessel. By the introduction into the liquid phase portion, the scattering of the raw material mixture can be prevented, and the scale can be prevented from adhering to the upper mirror portion.

In the polymerization method of the present invention, an oil-soluble initiator usually used for suspension polymerization of vinyl chloride is used as the polymerization initiator. As the oil-soluble initiator, for example,
Di-2-ethylhexylperoxydicarbonate, diethoxyethylperoxydicarbonate, α-cumylperoxyneodecanate, t-butylperoxyneodecanate, t-butylperoxypivalate, t-butylperoxy- 3,5,5-trimethylhexanoate, acetylcyclohexylsulfonyl peroxide,
Examples thereof include 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate and lauroyl peroxide. These may be used alone or two or more of them may be used in combination.

The amount of the polymerization initiator used is preferably 0.001 to 2% by weight based on the vinyl chloride monomer.

In the polymerization method of the present invention, a polymerization regulator, a chain transfer agent, a polymerization inhibitor, a pH regulator, a stabilizer, a scale inhibitor and the like, which are used for the polymerization of the vinyl chloride monomer, are added. Is also good.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

(Example 1) In a stainless steel reaction tank equipped with a jacket having an inner volume of 200 L and a stirring blade, 90 kg of ion-exchanged water at 40 ° C and a partially saponified polyvinyl alcohol having a saponification degree of 72 mol% (Nippon Synthetic Chemical Company, Ltd.) 525 g of “Gohsenol KZ-06” manufactured by the company
Vacuum to 00mmHg, 75kg vinyl chloride monomer
Was charged. Then, a polymerization initiator α-cumylperoxy neodecaneate (“Parkmill ND” manufactured by NOF Corporation) 6
After pressurizing 0 g, the inside of the polymerization vessel was heated to 57 ° C. 57
As soon as the temperature reached ° C, the supply of the raw material mixture was started, and at the same time, the extraction of the slurry was started so as to keep the internal volume constant, thereby performing a continuous polymerization reaction.

In the piping, a partially saponified polyvinyl alcohol having a saponification degree of 72 mol% ("Gohsenol KZ-06" manufactured by Nippon Synthetic Chemical Co., Ltd.) ) Was mixed, then ion-exchanged water at 40 ° C was further added, and the mixture was mixed with a static mixer. At this time, the temperature of the raw material mixture was 30 ° C., and the supply rate of the raw material mixture was 25 kg / hr for the vinyl chloride monomer and a saponification degree of 72 mol%.
3% by weight aqueous solution of partially saponified polyvinyl alcohol
831 g / hr and ion-exchanged water was 29.2 kg / hr.

As a polymerization initiator, α-cumylperoxyneodecanate (“Parkmill N” manufactured by NOF Corporation) is used.
D ") was continuously charged into the polymerization reactor at a rate of 20 g / hr through another pipe. After performing the continuous polymerization reaction for 30 hours, the supply of the raw material mixture was stopped, and the mixture was cooled and exhausted to stop the continuous polymerization reaction, and the content (polymer slurry) was taken out. The polymer slurry was dehydrated and dried to obtain a vinyl chloride resin.

Example 2 In preparing a raw material mixture,
Using ion-exchanged water at 86 ° C, adjust the temperature of the raw material mixture to 5
A vinyl chloride resin was obtained in the same manner as in Example 1 except that the temperature was changed to 5 ° C.

Comparative Example 1 A vinyl chloride resin was obtained in the same manner as in Example 1 except that the supply rate of a 3% by weight aqueous solution of a partially saponified polyvinyl alcohol having a saponification degree of 72 mol% was 666 g / hr. Was. At this time, the amount of the dispersant used was 0.08% by weight based on the vinyl chloride monomer.

Comparative Example 2 A polymer slurry was prepared in the same manner as in Example 1 except that the supply rate of a 3% by weight aqueous solution of partially saponified polyvinyl alcohol having a saponification degree of 72 mol% was 18,326 g / hr. I got At this time, the amount of the dispersant used was 2.2% by weight with respect to the vinyl chloride monomer.

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) Particle size distribution Measured according to JIS K8801. (2) Bulk specific gravity Measured according to JIS K6721. (3) Porosity Using a mercury intrusion porosimeter, 2,000 kg / c
The porosity was determined by measuring the volume of mercury injected under pressure per 100 g of vinyl chloride resin at m ² G. (4) Glass Ball Sieve with a standard sieve of 42 mesh, the particles remaining on the sieve were observed with a microscope, and the number of translucent particles was counted. (5) Gelation time A stabilizer was added to a vinyl chloride resin to prepare the following resin composition, and 65 g of this resin composition was charged into a plastograph “Rheocord 90” manufactured by Haake Corporation at 190 ° C. and 50 rpm.
The time until gelation was measured.・ 100 parts by weight of vinyl chloride resin ・ 2 parts by weight of dibutyltin mercapto (“JF-10B” manufactured by Sankyoki Gosei Co., Ltd.) ・ 0.5 parts by weight of ester wax (“WAX-0P” manufactured by Hoechst)

[0030]

[Table 1]

[0031]

The method for continuous suspension polymerization of a vinyl chloride monomer according to the present invention has the above-mentioned constitution, and the obtained vinyl chloride resin has a good particle size distribution because it does not have coarse particles. Since the formation of beads is suppressed, the gelling performance is excellent. Therefore, in the present invention, the same one as the vinyl chloride resin obtained by the batch suspension polymerization method can be obtained.

Claims (1)

[Claims] 1. A raw material mixture comprising a vinyl chloride monomer alone or a mixture of a vinyl chloride monomer and a monomer copolymerizable therewith, a dispersant, and an aqueous medium. When the continuous supply of the vinyl chloride monomer to an aqueous medium containing a dispersant is performed by continuously supplying the vinyl chloride monomer to the polymerization vessel, the dispersant is used in an amount of 0 to the vinyl chloride monomer. 2. A continuous suspension polymerization method for a vinyl chloride monomer, characterized in that the amount is from 2 to 2% by weight.