JPH06239906A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To obtain vinyl chloride polymer having fine porous particles which can be suitably used in powder molding, particularly suitable for thin-wall molded products. CONSTITUTION:Vinyl chloride only or a mixture thereof with a minor amount of copolymerizable monomers is subjected to suspension polymerization in an aqueous medium using an oil-soluble polymerization initiator wherein 0.5 to 5 pts.wt., per 100 pts.wt. of the monomers, of polyvinyl alcohol having 65 to 75 mole % saponification degree and 500 to 900 average polymerization degree is used as a suspension stabilizer.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a vinyl chloride polymer by a suspension polymerization method. In particular, the present invention relates to a method for producing a vinyl chloride polymer suitable for powder molding, which is porous and has a small average particle diameter by using a specific suspension formulation.

[0002]

2. Description of the Related Art Powder blends of vinyl chloride polymer are dry-blended with plasticizers, stabilizers, pigments, and other fillers and auxiliaries that are added as needed. Produce interior materials. This powder molding method is
It is recognized to be superior to the vacuum forming method and paste sol forming method in terms of shapeability, designability, weight reduction, workability, and the like.
As described above, the vinyl chloride resin composition for powder molding used in the powder molding method, as exemplified in JP-A-60-161451, uses vinyl chloride-based polymers obtained by various polymerization methods. Specifically, it is a suspension polymerization method. Above all, a porous material having a high plasticizer absorption rate is desired.

As a suspension polymerization method for obtaining the particle size of a porous vinyl chloride-based polymer, there are disclosed in JP-A-52-115890 and JP-A-52-115890.
54-46284, JP-B-63-39606, JP-B-60-508
In JP 07, JP 55-112210 A, JP 56-39768 A, etc., a method using one or more partially saponified polyvinyl alcohols having various degrees of saponification and polymerization is disclosed. Has been done. The particle size of the polymer obtained by these methods is
It is as large as 100 to 200 μ. As a method for producing a small particle size vinyl chloride polymer by the suspension polymerization method,
As described in 1-50242, there is a method of adding an emulsifier during suspension polymerization. The polymer obtained by this method is a so-called blending resin for polyvinyl chloride paste resin. This blending resin is intended for the effect of fluidizing and reducing the viscosity of the paste sol. Although it has a small particle size, the particle is not porous and has a dense and smooth surface.

[0004]

In the prior art, vinyl chloride resin having high porosity has a large particle size,
On the contrary, if the particle size is small, the porosity is low.
Therefore, a vinyl chloride resin powder having a small particle size, which has a porosity having a plasticizer absorption capacity similar to that of a general-purpose vinyl chloride resin powder and is suitable for forming a thin-walled molded product by powder molding A method of manufacturing is provided.

[0005]

The present invention is a suspension polymerization of vinyl chloride alone or a mixture of vinyl chloride and a monomer copolymerizable therewith in an aqueous medium using an oil-soluble polymerization initiator. The saponification degree is 65 to 7 as a suspension stabilizer.
5 mol% of partially saponified polyvinyl alcohol having an average degree of polymerization of 500 to 900 is added in an amount of 0.5 to 5 per 100 parts by weight of the monomer.
The present invention provides a method for producing a vinyl chloride polymer characterized by being present in an amount of 1 part by weight.

Among the monomers mainly composed of vinyl chloride in the present invention, the monomer copolymerizable with vinyl chloride is
Examples thereof include alkyl vinyl esters such as vinyl acetate, alkyl vinyl ethers such as cetyl vinyl ether, α-monoolefins such as ethylene and propylene, and (meth) acrylic acid alkyl esters such as methyl acrylate and methyl methacrylate. But is not limited to these.

The oil-soluble polymerization initiator used in the present invention is
Peroxydicarbonate-based initiators such as di-2-ethylhexyl peroxydicarbonate and di- (2-ethoxyethyl) peroxydicarbonate, 3, 5, 5,
-Diacyl peroxide initiators such as trimethylhexanoyl peroxide, α, α-azobis-2,4
An azo-based initiator such as dimethylvaleronitrile,
And 2,4,4-trimethylpentyl peroxy neodecanoate, tert-lipyl peroxy neodecanoate, tert-hexyl peroxypivalate, and other perester-based initiators are exemplified. It is not limited to the initiator.

The type and amount of these initiators are selected so that the polymerization is completed at a predetermined polymerization temperature and polymerization time, and one kind or a combination of two or more kinds is used. Usually, the amount is 0.01 to 2 parts by weight per 100 parts by weight of the monomer.

The suspension polymerization in the aqueous medium of the present invention may be carried out under well-known conditions using well-known equipment except for the suspension stabilizer described below.

The suspension stabilizer used in the present invention has a saponification degree of 65 to 75 mol% and an average degree of polymerization of 500 to 90.
It is a partially saponified polyvinyl alcohol of 0. When the saponification degree is less than 65 mol% or the average degree of polymerization is less than 500, the suspension stability becomes insufficient, and it is difficult to reduce the particle size of the obtained polymer and to make it porous. is there. If the degree of saponification exceeds 75 mol% or the average degree of polymerization exceeds 900, the porosity is insufficient.

The amount of the suspension stabilizer is 0.5 to 5 parts by weight per 100 parts by weight of the monomer. It is preferably 1 to 3 parts by weight. If the amount is less than 0.5 part by weight, the intended average particle size cannot be obtained. Even if it exceeds 5 parts by weight, the effect of reducing the particle size is relatively small, and the quality is rather deteriorated.

The polymerization temperature is set depending on the kind of the oil-soluble polymerization initiator, but is usually 30 to 80 ° C.

The amount of water in the aqueous medium is usually in the range of 0.3 to 1 in terms of the weight ratio of monomer / water, but it may be injected during the polymerization to compensate for the decrease in the liquid surface due to the volume contraction accompanying the polymerization. it can.

In the present invention, as a procedure for charging water, a vinyl chloride monomer, a suspending agent and an initiator, any method used in ordinary suspension polymerization of a vinyl chloride monomer can be adopted. . If desired, other additives such as mercaptoalkanols, chain transfer agents such as alkyl thioglycolates, glycerin esters of higher fatty acids or nonionic surfactants such as sorbitan esters, pH regulators and polymerization inhibitors You may use agents.

[0015]

Thus, according to the present invention, the average particle size is 2
It is possible to produce a porous vinyl chloride polymer having a porosity of 0.2 cc / g or more, although it is as small as about 0 to 50 μm. This vinyl chloride-based polymer has excellent plasticizer absorbability (dry blending property) and is particularly suitable for thin-wall molding when used for powder molding.

[0016]

EXAMPLES The present invention will be described in more detail below with reference to examples, but% in the examples and comparative examples is based on weight unless otherwise specified. The physical properties of the vinyl chloride polymer shown in each example were measured by the following methods.・ Average particle size: Measure the particle size distribution with a laser light diffraction particle sizer (Malvern, Mastersizer),
The volume average particle size was determined. -Coarse grain content: Passed through a JIS Z 8801 standard sieve (opening 0.35 mm) and expressed as the proportion remaining on the sieve.・ Porosity: 10 kg / cm ² G to 120 kg / c using a porosimeter (1250-2 type) manufactured by Carlo Erba Co.
The volume of mercury injected per 1 g of vinyl chloride-based polymer particles during pressurization up to m ² G is shown.・ Plasticizer absorbency: Using Labo Plastomill manufactured by Toyo Seiki Seisakusho, put 500 g of vinyl chloride polymer and 200 g of dioctyl phthalate in a container whose jacket temperature is kept at 88 ° C, and rotate at 100 rpm. The torque was recorded while stirring, and the time (minutes) until the mixing torque decreased and became stable was shown.

Example 1 A 100-liter autoclave was charged with 45 kg of deionized water, 300 g of partially saponified polyvinyl alcohol having a saponification degree of 73 mol% and an average degree of polymerization of 800, and 7.5 g of dioctyl peroxy digabonate. Thirty
After degassing to mmHg and removing oxygen, 30 kg of vinyl chloride monomer was charged and heated to 60 ° C. under stirring conditions,
Polymerization started. When the pressure in the autoclave at the start of the polymerization dropped by 1.5 kg / cm ³ , 3 g of 2,6-di-t-butyl 4-methylphenol was added to stop the polymerization,
Unreacted vinyl chloride monomer was purged, the contents were taken out, and dehydrated and dried. Table 1 shows the physical properties of the obtained polymer particles.
Shown in.

Examples 2 and 3 and Comparative Examples 1 to 4 Polymerization was carried out under the same conditions as in Example 1 except that the kind and amount of partially saponified polyvinyl alcohol were changed to those shown in Table 1 to obtain polymers. The particles were obtained. The physical properties of the obtained polymer particles are shown in Table 1.

Comparative Example 5 The physical properties of a commercially available paste vinyl chloride resin blending resin 103Z _X A (manufactured by Nippon Zeon Co., Ltd.), which is a vinyl chloride resin having a small particle size, were evaluated. The results are shown in Table 1.

[0020]

[Table 1]

Claims (1)

[Claims] 1. A suspension stabilizer for suspension polymerization of vinyl chloride alone or a mixture of vinyl chloride and a monomer copolymerizable therewith in an aqueous medium using an oil-soluble polymerization initiator. , Saponification degree 65-75 mol%, average degree of polymerization 50
A method for producing a vinyl chloride polymer, characterized in that 0.5 to 5 parts by weight of 0 to 900 partially saponified polyvinyl alcohol is present per 100 parts by weight of the monomer.