JPH05214028A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To diminish fisheyes and improve heat stability. CONSTITUTION:Vinyl chloride monomer or a mixture of vinyl chloride monomer and a monomer copolymerizable therewith is polymerized by vapor-phase polymerization in the presence of a seed polymer containing, uniformly dispersed therein, a solution of a polymerization initiator in an inert solvent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing a vinyl chloride homopolymer or copolymer, that is, a vinyl chloride polymer, by gas phase polymerization.

[0002]

2. Description of the Related Art Polyvinyl chloride resin (hereinafter abbreviated as PVC) is inexpensive and has excellent chemical and physical properties, so that it is mass-produced and used in a wide range of fields. ..

Among the PVC production methods, the suspension polymerization method is the most excellent polymerization method in terms of polymerization control and quality. However, since an aqueous medium is used, a great amount of energy is required to dry the product, and the waste water is discharged. Since it is a dispersant and unreacted monomer contained in, there is an environmental problem. Further, since the batch method is used in terms of productivity, there is a limit even in the case of a large-sized polymerization can considering the quality.

The emulsion polymerization method is not versatile in view of its limited use and inclusion of impurities such as emulsifiers in products.

The gas phase polymerization method is described in JP-A-47-29474, in which an inert solid substance is introduced as a seed polymer into a fluidized bed reactor or a horizontal reactor to form a gaseous monomer in the presence of an initiator. A method of reacting the body is described. Also, JP-A-6
No. 0-49011 describes a vertical gas phase reactor equipped with a spray nozzle for seed polymer slurry.

The gas phase polymerization method is considered to be a promising process in the future because it can be continuous, but its application is limited in soft applications such as films because fish eyes are generated.

[0007] A method known as a method for increasing the bulk specific gravity of a gas phase polymer product is a fine powder PV obtained by emulsion polymerization.
Method of using C as a seed polymer (Japanese Patent Laid-Open No. 54-5009)
No. 0), the known method does not always satisfy the fish eye characteristics even if the bulk specific gravity increases.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vapor phase polymerization method of vinyl chloride which has improved fish eye characteristics of the product.

[0009]

[Means for Solving the Problems] When carrying out gas phase polymerization, it is considered essential to allow the seed polymer to exist in the polymerization system in order to adjust the particle shape of the produced polymer and to provide a place for the polymerization. ..

Further, the method of supporting a polymerization initiator on this kind of polymer is considered to be an important factor affecting the physical properties and particle morphology of the product. As a method of adding the polymerization initiator, it is possible to add a liquid vinyl chloride monomer in which the polymerization initiator is dissolved to the seed polymer and then evaporate only the vinyl chloride monomer. This method is the simplest and excellent method for uniformly supporting the polymerization initiator on the seed polymer. However, the obtained gas phase polymerized product had remarkably poor fish eye characteristics and could not be used.

The present inventors have made earnest studies on the improvement of fish-eye characteristics of a vapor-phase polymerized product of vinyl chloride.
The inventors have found that these technical problems can be solved by uniformly dispersing a polymerization initiator in a seed polymer in advance and then performing gas phase polymerization, and have reached the present invention described below.

That is, according to the present invention, in the vapor phase polymerization of a vinyl chloride monomer or a vinyl chloride monomer and a monomer copolymerizable therewith, the seed polymer and the polymerization initiator are added in the presence of an inert solvent. A method for producing a vinyl chloride-based polymer, which comprises uniformly mixing and then performing gas phase polymerization.

The inert solvent used in the present invention is not particularly limited as long as it dissolves the polymerization initiator and does not inhibit radical polymerization even if a trace amount remains in the seed polymer. For example, a solvent that does not dissolve PVC such as primary, secondary, and tertiary alcohols having 1 to 10 carbon atoms, straight-chain or cyclic hydrocarbons having 5 to 10 carbon atoms, ketones such as cyclohexanone and acetone, during polymerization Solvents that do not cause chain transfer are preferred.

The gas phase polymerized product obtained by the present invention is not only excellent in fish-eye characteristics, but also effective in thermal stability. That is, when PVC powder was placed in a test tube and the hydrochloric acid gas generated by heating to 180 ° C. was discolored to blue with Congo red test paper, the time required for discoloration was longer when an inert solvent was used. I understood it.

The gas phase polymerization of the present invention can be applied to both homopolymerization and copolymerization of vinyl chloride. Copolymerizable monomers include vinyl halides such as vinyl fluoride and vinyl bromide; ethylene, propylene, n
-Olefins such as butene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl laurate, vinyl stearate; unsaturated acids and their esters such as acrylic acid, methacrylic acid, itaconic acid; methyl vinyl ether, ethyl vinyl ether Vinyl ethers such as; maleic acid, fumaric acid, maleic anhydride or their derivatives; styrene and its derivatives; vinylidene chloride,
Examples thereof include vinylidene fluoride.

The polymerization initiator used in the gas phase polymerization of the present invention is preferably an organic peroxide usually used in the polymerization of vinyl chloride. For example, acyl peroxides such as uroyl peroxide and benzoyl peroxide; peroxy esters of organic acids such as tertiary butyl peroxypivalate; dioxy carbonates such as diisopropyl peroxydicarbonate; azobisdimethylvaleronitrile. Examples of such azo compounds, acetylcyclohexylsulfonyl peroxide, and the like. These polymerization initiators are added in an amount of 0.005 to monomer.
3% by weight is used.

The polymerization pressure is 0.45 to 0.99 with respect to the saturated vapor pressure Ps at the total temperature. Polymerization pressure is 0.
When it is lower than 45, the polymerization rate is remarkably lowered, and when the polymerization pressure is higher than 0.99, fish eyes increase, which is not preferable.

The polymerization temperature may be a commonly used temperature, 3
0 to 70 ° C is adopted.

[0019]

EXAMPLES The present invention will now be described in more detail by way of examples, which should not be construed as limiting the invention thereto.
The evaluation methods used in the examples are shown below.

(1) Fish-eye test Formulation: PVC / DOP / Ca-Zn stabilizer / organic phosphorus-based stabilizing aid / ultra-blue = 100/50 / 1.5 / 0.5 / 3
(Parts by weight) Conditions: 150 ° C. (2) Bulk specific gravity It was measured by the method of JIS K6721.

(3) Average particle size Measured with Microtrac (manufactured by Nikkiso Co., Ltd.).

(4) Thermal stability test 2 g of PVC powder was put in a test tube and placed in an oil bath for 180
The sample was heated to 0 ° C., and the time at which the Congo red test paper turned blue with the generated gas was measured.

Reference Example 1 (Method of supporting polymerization initiator on seed polymer) 500 g of methanol in which 0.5 g of lauroyl peroxide was dissolved was added to 50 g of PVC having an average particle size of 11 μm, and the mixture was sufficiently stirred. After removing the methanol with an evaporator, the PVC powder was dried under vacuum at 30 ° C.

Example 1 A 1-liter autoclave was charged with 30 g of a seed polymer (Reference Example 1) carrying a polymerization initiator in advance, and vacuum deaeration and nitrogen substitution were repeated 5 times. While stirring with the anchor type stirring blade, 60
The temperature was raised to ° C. After another depressurizing reactor was sufficiently degassed and replaced with nitrogen, vinyl chloride monomer was charged in a liquid phase and the temperature was raised to 50 ° C. A 1 l autoclave and a vinyl chloride monomer tank were connected to introduce a vinyl chloride monomer. The polymerization pressure at that time was 7.1 kg / cm ² G. 200g after 6 hours
Of vinyl chloride monomer was consumed. The 1 l autoclave was cooled to remove unreacted vinyl chloride monomer, and then the polymer was taken out. The yield was 122 g. The physical properties of the obtained polymer were measured by the methods described above.

Example 2 The procedure of Example 1 was repeated, except that hexane was used as an inert solvent for supporting the polymerization initiator on the seed polymer. The results are shown in Table 1.

Comparative Example 1 A polymer was obtained in the same manner as in Example 1 except that 30 g of PVC having an average particle size of 11 μm and 0.3 g of lauroyl peroxide were separately charged.

Comparative Example 2 Example 1 was repeated except that vinyl chloride monomer was used instead of methanol when the polymerization initiator was supported on the seed polymer.
According to. The results are shown in Table 1.

[0028]

[Table 1]

[0029]

As described above, by using the seed polymer in which the polymerization initiator is uniformly supported in advance, not only the fish eye characteristics of the vinyl chloride resin but also the thermal stability can be improved, which is industrially useful. Is clear.

Claims (1)

[Claims] 1. In a gas phase polymerization of a vinyl chloride monomer or a vinyl chloride monomer and a monomer copolymerizable therewith, after an inert solvent in which a polymerization initiator is dissolved is uniformly dispersed in a seed polymer. A method for producing a vinyl chloride-based polymer, which comprises polymerizing.