JPH04202503A - Production of vinyl chloride-based polymer powder - Google Patents

Abstract

PURPOSE:To obtain the title powder having excellent fluidity, hardly charging with electricity, suppressing reduction in bulk density by polymerizing a vinyl chloride-based monomer in an aqueous medium and after reaching a specific polymerization ratio, adding a small amount of a tetrafluoroethylene resin having specific particle diameter to the polymerization system. CONSTITUTION:A vinyl-based monomer containing a vinyl chloride monomer is polymerized in an aqueous medium and after polymerization ratio reaches 70%, 0.001-1.0 pt.wt. based on 100 pts.wt. of the vinyl-based monomer of a tetrafluoroethylene resin having 0.5-50mum average particle diameter is added to the polymerization system to give the objective powder.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for producing vinyl chloride polymer powder having good fluidity.

[Conventional technology]

Vinyl chloride polymers are vinyl chloride monomers or mixtures of vinyl monomers whose main component is vinyl chloride monomers.
Polymerize in an aqueous medium containing a suspending agent, a polymerization initiator, etc.
It is manufactured by dehydrating and drying the obtained polymer. However, this polymer powder tends to be charged with static electricity during drying or transportation, resulting in decreased fluidity and formation of blocks, which can clog the inside of the dryer or the transportation vibrator. Furthermore, since the bulk specific gravity of the charged polymer powder is significantly reduced, there is a problem in that when measuring by volumetric method, for example, a measurement error occurs between the powder and the actual weight. These phenomena occur significantly in winter when temperature and humidity are low. Various methods have been proposed to prevent static electricity, but by adding nonionic surfactants, anionic surfactants, or cationic surfactants to vinyl chloride polymer powder, it is possible to improve water retention on the surface of the polymer powder. A common method is to have However, the above method cannot sufficiently prevent a decrease in the bulk specific gravity or fluidity of the polymer powder, and may also impair the thermal stability of the product. In addition, in the conventional manufacturing method, scale adhesion on the inner wall of the polymerization vessel is also a problem.

[Problem to be solved by the invention]

The present invention has been made to solve the above-mentioned problems. An object of the present invention is to provide a method for producing a polymer powder.

[Means for Solving the Problems] The method for producing a vinyl chloride polymer powder of the present invention, which has been made to achieve the object 1iii, comprises adding a vinyl monomer containing a vinyl chloride monomer to an aqueous medium. After the polymerization rate reaches 70%, 0.001 to 1.0 weight of tetrafluoroethylene resin having an average particle size of 0.5 to 50 μm is added to 100 parts by weight of the vinyl monomer. part is added to the polymerization system. The vinyl monomer that is the raw material for the vinyl chloride polymer powder is vinyl chloride monomer alone, or 50% by weight or more of vinyl chloride monomer and other vinyl monomers that can be copolymerized with vinyl chloride monomer. It is a mixture with monomers. Examples of vinyl monomers copolymerizable with vinyl chloride monomers include vinyl esters such as vinyl acetate and vinyl propionate, methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate. Mention may be made of acrylic or methacrylic acid esters, olefins such as ethylene and propylene, vinyl ethers such as lauryl vinyl ether and inbutyl vinyl ether. Also, maleic anhydride,
Acrylonitrile, styrene, and vinylidene chloride can also be polymerized. These may be used singly or in combination. The additive tetrafluoroethylene resin has an average particle size of 0.
Use one with a diameter of 5 to 50 μm. Average particle size is 0.5μ■
If the molecular weight is less than 50 μm or more than 50 μm, dispersion into the polymerization system is poor and the fluidity improving effect is low. Tetrafluoroethylene resin is made from vinyl monomer 1, which is a raw material.
0.001-1.00 parts by weight. It is desirable to add +1 part by weight. If the amount is less than 0.001 parts by weight, the fluidity of the obtained polymer powder will not be improved. Even if 10 parts by weight or more is added, no further effect can be expected and it is uneconomical. The tetrafluoroethylene resin is added after the polymerization rate of the reaction system reaches 70%. If it is added at a polymerization rate of less than 70%, it is not preferable because it will adversely affect the formation of polymer particles. When adding tetrafluoroethylene resin to the polymerization system, it may be added in powder form or dispersed in water, but it is preferable to disperse it in water and charge it with a pump. For dispersion, a dispersion aid used in the production of vinyl chloride polymers may be used in combination. Furthermore, during polymerization, dispersion aids and polymerization initiators that have been conventionally used in the production of vinyl chloride polymers can be used. Dispersing aids include, for example, water-soluble cellulose ethers such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose, water-soluble or oil-soluble partially saponified polyvinyl alcohol, acrylic acid polymers, gelatin, etc. Water-soluble polymers, sorbitan monolaurate, sorbitan triolate, sorbitan monostearate, glycerin tristearate and oil-soluble emulsifiers such as ethylene oxide-propylene oxide block copolymers, polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate and These include water-soluble emulsifiers such as lauric acid, calcium carbonate, calcium phosphate, and sodium dodecylbenzenesulfonate. These may be used singly or in combination. Examples of polymerization initiators include percarbonate compounds such as di-2-ethylhexyl peroxydicarbonate, diisopropyl peroxydicarbonate and jetoxyethyl peroxydicarbonate, t-butyl peroxybivalate, t- xylperoxy and valate, a-cumylperoxyneodecanate and 2
,4.4-trimethylpentyl-2-peroxy-2-
perester compounds such as neodecanate, acetylcyclohexylsulfonyl peroxide, 2,4.4-
peroxides such as trimethylpentyl-2-peroxyphenoxyacetate, 3.5.5-1-limethylhexanoyl peroxide and lauroyl peroxide;
Azo compounds such as azobis-2,4-dimethylvaleronitrile and azobis(4-methoxy-2,4-dimethylvaleronitrile), as well as potassium persulfate, ammonium persulfate, hydrogen peroxide, cumene hydroperoxide, etc. One type or a combination of multiple types can be used. During polymerization, various polymerization conditions such as the method of charging the aqueous medium, vinyl monomer, dispersion aid, polymerization initiator, etc. to the polymerization vessel, charging ratio, and polymerization temperature may be set in the same manner as in the past. In the production method of the present invention, if necessary, polymerization regulators and chain transfer agents used in the production of vinyl chloride polymers, pl
(It is also optional to add regulators, gelling improvers, antistatic agents, crosslinking agents, stabilizers, fillers, buffering agents, scale inhibitors, etc.) Furthermore, antioxidants can be added to inhibit polymerization reactions, It can also be added to the polymerization system before the start of polymerization, during polymerization, or after the end of polymerization for the purpose of preventing deterioration of the polymer. [Example] The present invention will be explained in detail below. Examples 1 to 3 are Examples to which the invention is applied and Comparative Examples 1 to 4 are examples to which the present invention is not applied.Example 1 In a stainless steel polymerization vessel with an internal volume of 2000°C, 980 kg of deionized water and 382 g of partially saponified polyvinyl alcohol were placed. After charging 143g of water-bathable methylcellulose and deaerating the inside of the container, 700kg of vinyl chloride monomer was added.
Insert. While stirring inside the polymerization vessel, add di-2-ethylhexyl peroxydicarbonate 28 as a polymerization initiator.
At the same time as 0 g was injected using a high-pressure pump, the temperature began to rise to initiate polymerization, and once the temperature inside the polymerization vessel rose to 58°C, stirring was continued while maintaining that temperature. When the polymerization rate reached 85%, 4 parts with an average particle size of 151111 was added to 100 parts by weight of the vinyl monomer mixture.
005 parts by weight of fluorinated ethylene resin is added and polymerization is continued. The reaction was stopped when the internal pressure of the polymerization vessel reached 5.5 kg/cm"G, and after recovering the unreacted monomer,
After dehydration and drying, a vinyl chloride polymer powder was obtained. Furthermore, after obtaining the powder, the inner wall of the polymerization vessel was observed to confirm the presence or absence of scale adhesion. Example 2 A vinyl chloride polymer powder was obtained in the same manner as in Example 1, except that a tetrafluoroethylene resin having an average particle size of 10 μm was added. Example 3 Powder of vinyl chloride polymer was prepared in the same manner as in Example 1, except that 0.15 parts by weight of tetrafluoroethylene resin with an average particle size of 10 um was added when the 1 polymerization rate reached 75%. Obtained. Comparative Example 1 A vinyl chloride polymer powder was obtained in the same manner as in Example 1 except that the tetrafluoroethylene resin was not added. Comparative Example 2 A vinyl chloride polymer powder was obtained in the same manner as in Example 1, except that the timing of adding the tetrafluoroethylene resin was changed to when the polymerization rate reached 60%. Comparative Example 3 A vinyl chloride polymer powder was obtained in the same manner as in Example 1, except that a tetrafluoroethylene resin having an average particle size of 70 μm was added. Comparative Example 4 0 amine surfactant instead of tetrafluoroethylene resin
．． A vinyl chloride polymer powder was obtained in the same manner as in Example 1, except that 3 parts by weight was added. The following tests were conducted on the vinyl chloride polymer powders obtained in Examples 1 to 3 and Comparative Examples 1 to 4 above.・Flowability test The obtained powder of each vinyl chloride polymer was heated to 140% O'C.
After being left in an RH (7) environment for a day and night, JIS K-6
100 cc of the sample was placed in a funnel for measuring bulk specific gravity according to 721 regulations, and the falling time from the funnel was measured. In addition, each polymer powder was left to stand overnight in the same manner and was mixed for 5 minutes at 60 rpm using a Brabender planetary mixer to be charged, and then the falling time from the funnel was measured in the same manner as above. - Bulk specific gravity measurement test After each polymer powder was left in an environment of 0° C. and 40% RH for a day and night, the bulk specific gravity was measured according to the method specified in JIS K-6721. In addition, each polymer powder that had been left to stand day and night was charged by mixing at 60 rpm for 5 minutes using a Brabender planetary mixer, and then the bulk specific gravity was measured in the same manner as above.・Thermal stability test 100 parts by weight of vinyl chloride polymer and the following compound: 2.5 parts by weight of zinc stearate 0.7 parts by weight of barium stearate 0.7 parts by weight of lead base
0.5 parts by weight dioctyl phthalate 30.0
After adding parts by weight and kneading with a roll at 165°C for 5 minutes,
Create a sheet with a thickness of 1 liter. Heat this sheet to 195℃
The thermal stability was determined by placing the sample in an oven and measuring the time until it turned black. Table 1 shows the test results of the fluidity test, bulk specific gravity measurement test, and thermal stability test. According to these test results, the vinyl chloride polymer powder obtained by the production method of the present invention has sufficient fluidity without a decrease in powder fluidity due to electrostatic charge, and the bulk specific gravity does not decrease due to environmental changes. It can be seen that there is no fluctuation and it is stable. Basic required properties such as thermal stability are also fully met. Moreover, the effect of suppressing scale adhesion on the inner wall of the polymerization vessel during polymerization was also obtained. Effects of the Invention As explained in detail above, according to the method for producing vinyl chloride polymer powder of the present invention, it is possible to produce vinyl chloride polymer powder that is less likely to be charged. The produced polymer powder has a reduced bulk specific gravity and fluidity.
Moreover, the quality required for a vinyl chloride polymer is ensured.

Claims (1)

[Claims] 1. Polymerize a vinyl monomer containing a vinyl chloride monomer in an aqueous medium, and after the polymerization rate reaches 70%, the average particle size is 0 with respect to 100 parts by weight of the vinyl monomer. .5~5
A method for producing a vinyl chloride polymer powder, which comprises adding 0.001 to 1.0 parts by weight of a 0 μm tetrafluoroethylene resin to a polymerization system.