JPH0611877B2 - Powder coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a powder coating composition using a vinyl chloride polymer obtained by a suspension polymerization method.

[Background of the Invention]

The powder coating composition has been obtained by adding a liquid plasticizer to a vinyl chloride polymer having a proper particle size range, and completely absorbing the liquid plasticizer into the vinyl chloride polymer under stirring and heating. Dry powder is used.

Plane smoothness is an important coating performance in powder coating, and for that purpose, it is desired that the powder coating has high melt fluidity at the time of heating and baking.

[Conventional technology]

Conventionally, vinyl chloride-based polymers used as powder coating compositions of this kind are mainly produced by suspension polymerization, but vinyl chloride-based polymers produced by such suspension polymerization are Insufficient melt fluidity during heating, a method of lowering the softening point of the vinyl chloride polymer (conventional method 1) and a method of increasing the amount of liquid plasticizer added (conventional method 2) ) And are provided.

[Problems to be solved by the invention]

Conventional method 1 is vinyl chloride, vinyl ether, vinyl acetate,
Although means for copolymerizing propylene or the like is used, the melt fluidity at the time of heating is improved by the copolymerization of the above monomers,
There is a problem that the rigidity of the formed coating film is lowered and the weather resistance is also poor. In the conventional method 2, the hardness of the formed coating film is lowered and the plasticizer is volatilized when used outdoors. However, when used indoors or in a room such as a vehicle, there is a problem that fogging occurs due to volatilization of the plasticizer.

[Means for solving problems]

The present invention solves the problems in the conventional method 2 among the above-mentioned conventional problems, and as a means thereof, a vinyl chloride monomer or a vinyl chloride monomer as a main component can be copolymerized with the monomer. When carrying out polymerization by suspending a monomer mixture containing a monomer as a subcomponent in water, in the water, the saponification degree is 65 to 80 per 100 parts by weight of the monomer or the monomer mixture.
Viscosity of a 4% by weight aqueous solution at 20 ° C is 2 to 9 cp
s of polyvinyl alcohol A of 0.01 to 0.2 parts by weight, and a saponification degree of 30 to 55 mol% and an aqueous solution of 4% by weight of polyvinyl alcohol B having a viscosity of 6 to 15 cps at 20 ° C. of 0.001 to
The vinyl chloride polymer obtained by adding 0.1 part by weight as a suspending agent is used as the resin component of the powder coating material.

The present invention is described in detail below.

The feature of the present invention is to use two kinds of polyvinyl alcohols A and B as the suspending agent as described above. That is, as the polyvinyl alcohol A, an aqueous solution having a saponification degree of 65 to 80 mol% and a 4% by weight (hereinafter simply referred to as "%") viscosity at 20 ° C. of 2 to 9 cps is used, and as the polyvinyl alcohol B, a saponification degree of 30 is used. ~ 55 mol% of a 4% aqueous solution of 20
A viscosity of 6 to 15 cps at 0 ° C is used. Polyvinyl alcohol A is added to 100 parts by weight of vinyl chloride monomer or 100 parts by weight of other copolymerizable monomer mixture.
More preferably 0.01 to 0.2 parts by weight (hereinafter simply referred to as "parts")
0.05 to 0.15 part, and polyvinyl alcohol B is preferably 0.001 to 0.1 part, more preferably 0.005 to 0.05 part. The viscosities of polyvinyl alcohols A and B in the present invention are measured by a Heppler viscometer.

In the present invention, if desired, other suspension agents such as polyvinyl alcohol, methyl cellulose, gelatin and the like may be added as the suspending agent in addition to the above polyvinyl alcohol, and further anionic and nonionic surfactants may be added.
The addition amount of each composition described above should be so small as not to affect the physical properties of the obtained vinyl chloride polymer.

Other monomers copolymerizable with the vinyl chloride monomer in the present invention include vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, isopropyl vinyl ether and n-butyl vinyl ether, olefins such as ethylene and propylene, and methyl. Acrylic esters such as acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, methacrylic esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, vinyl acetate, styrene, acrylonitrile, vinylidene chloride Other monomers copolymerizable with vinyl chloride, such as vinyl chloride, vinyl fluoride and vinylidene fluoride, may be copolymerized, but the copolymerization amount of the above monomers is the total amount with the vinyl chloride monomer. Amount that becomes a secondary component based on the standard It should be the amount which is employed as the resin in the vinyl chloride resin powder coating composition, i.e. it is desirable to small enough not to influence the physical properties of the vinyl chloride polymer.

In the suspension polymerization method of the present invention, an oil-soluble initiator such as benzoyl peroxide, lauryl peroxide, cumene hydroperoxide or azobisisobutyronitrile is usually dissolved in the vinyl chloride monomer in an amount of about 0.1 to 1%. Then, the suspension is suspended in water in which the above-mentioned suspending agent or, if desired, an electrolyte is dissolved, and the mixture is usually heated and stirred at 50 to 70 ° C to carry out polymerization. In this case, the concentration of the vinyl chloride-based monomer is usually 10 to 60%, preferably about 20 to 40%.

The vinyl chloride polymer obtained by such a suspension polymerization method is powdery and separated from water, washed with water and dried.

To prepare a powder coating composition, the obtained vinyl chloride polymer is mixed with a liquid plasticizer such as dibutyl phthalate, dioctyl phthalate, tricresyl phosphate, and the like.
The mixture is heated to 90 to 130 ° C. and stirred to completely absorb the plasticizer into the vinyl chloride polymer to prepare a dry powder. The amount of the plasticizer added may be 10 to 100 parts by weight based on 100 parts of the vinyl chloride polymer.

[Action]

 The operation of the present invention is as follows.

Polyvinyl alcohol B forms a film that does not hinder the absorption of the plasticizer by the vinyl chloride polymer particles, but polyvinyl alcohol B alone has low dispersion stability and it is difficult to smoothly carry out suspension polymerization. It was never used as a dispersant for polymerization. Therefore, in the present invention, the polyvinyl alcohol A is used together to carry out suspension polymerization. However, polyvinyl alcohol A has a saponification degree of 65.
It is in the range of ~ 80 mol%, but at 4 ° C aqueous solution at 20 ° C.
If the viscosity at 9 is more than 9 cps, even if polyvinyl alcohol B is mixed, the absorption of the plasticizer by the vinyl chloride polymer particles is hindered. Thus, the vinyl chloride polymer obtained by the suspension polymerization method of the present invention has extremely good absorbability with respect to the liquid plasticizer, and the liquid plasticizer has already been chlorinated at the stage of the powder coating composition as a dry powder. The vinyl polymer is internally absorbed sufficiently uniformly.

〔The invention's effect〕

The vinyl chloride polymer used in the present invention is a powder coating composition excellent in melt flow characteristics during heating and baking by blending a small amount of a plasticizer as compared with a vinyl chloride polymer produced by a conventional method. According to the composition of the present invention, the surface smoothness is improved without inconveniences such as a decrease in coating film hardness, volatilization of the plasticizer and generation of fogging caused by the plasticizer, according to the composition of the present invention. The coating film can be easily formed.

Example 1 Pure water 1200 and saponification degree in an autoclave with an internal capacity of 2400
Polyvinyl alcohol A having a viscosity of 6 cps at 20 ° C. in an aqueous solution of 70 mol% and 4%, 400 g, and a saponification degree of 33 mol% and 4%
Add 150 g of polyvinyl alcohol B having a viscosity of 10 cps at 20 ° C. and stir for 3 hours.

Next, after adding 3 kg of cumene hydroperoxide, the inside of the autoclave was replaced with nitrogen, and the inside of the autoclave was evacuated to -600 mmHg. In the autoclave in such a state, 650 kg of vinyl chloride monomer is added and polymerization is carried out at 65 ° C. The internal pressure of the autoclave to stop the beginning polymerizing cooling when dropped from 10.8 kg / cm ₂ G to 8.8kg / cm ₂ G. The obtained slurry is dehydrated with a decanter and dried with a fluid dryer. A vinyl chloride polymer is obtained with a yield of 86%. The physical properties of the obtained vinyl chloride polymer are shown in Table 1.

Next, 1 kg of the above vinyl chloride polymer, 300 g of DOP (dioctyl phthalate) and 50 g of a heat stabilizer were blended with stirring with a 10 Henschel mixer, the internal temperature was heated to 110 ° C., and then cooled. The powder coating composition obtained was evaluated and the results are listed in Table 1.

Comparative Example 1 The same procedure as in Example 1 was carried out except that 550 g of polyvinyl alcohol A having a saponification degree of 70 mol% and a 4% aqueous solution having a viscosity of 6 cps at 20 ° C. was added as a suspending agent.

Comparative Example 2 The procedure of Example 1 was repeated, except that 550 g of polyvinyl alcohol A ′ having a viscosity of 35 cps at 20 ° C., which was an aqueous solution having a saponification degree of 80 mol% and a concentration of 4%, was added as a suspending agent.

Example 2 As a suspending agent, polyvinyl alcohol A having a saponification degree of 70 mol% and a 4% aqueous solution having a viscosity of 6 cps at 20 ° C., 400 g and a saponification degree of 33 mol% and a 4% aqueous solution having a viscosity of 10 cps at 20 ° C. Alcohol B (150 g) is added, the polymerization is carried out at a polymerization temperature of 58 ° C., and the polymerization is stopped when the internal pressure drops from 9 kg / cm ₂ G to 7 kg / cm ₂ G. A vinyl chloride polymer was obtained with a yield of 87%. Other polymerization conditions are the same as in Example 1. Next, 1 kg of the above vinyl chloride polymer, 800 g of DOP, and 50 g of heat stabilizer.
Is blended under stirring with a 10 Henschel mixer, the internal temperature is heated to 110 ° C., and then cooled.

The powder coating composition obtained was evaluated and the results are listed in Table 1.

Comparative Example 3 The same procedure as in Example 2 was carried out except that 550 g of polyvinyl alcohol A ′ having a viscosity of 35 cps at 20 ° C. of a 4% aqueous solution having a saponification degree of 80 mol% was added as a suspending agent to carry out polymerization.

(Stability at the time of heating) The measuring method will be described.

(1) Preparation of pellets 0.5 g of the coating composition was compressed in a mold with 2 kg / cm ₂ G to obtain a diameter of 10
Make a cylindrical pellet of mm.

(2) Heating Heat the resulting pellets in a gear oven heat aging tester.
Gel at 10 minutes at 200 ℃.

(3) Calculation Melt fluidity is calculated before and after heating. The pellet before heating is shown in FIG. 1, and the pellet after heating is shown in FIG.

1 and 2, melt fluidity (1) = (d-10) / h {h: height of pellet before heating (mm), d: diameter of pellet after heating (mm)} The larger the value calculated by the formula, the better the melt fluidity during heating.

(Plasticizer absorbency) 10 g of powdered vinyl chloride polymer and 10 g of plasticizer (DOP) are thoroughly mixed with a spatula in a glass container. A part (5 g) of the obtained mixture is placed in a centrifuge tube equipped with a 325 mesh strainer and centrifuged at 2000 rpm for 2 minutes. By centrifugation, the plasticizer not absorbed by the vinyl chloride polymer is removed. The sample weight after centrifugation was weighed to determine the amount of absorbed plasticizer.

(Bulk specific gravity) According to JIS-k-6741.

(Average degree of polymerization) According to JIS-k-6721.

As shown in Table 1, the vinyl chloride-based polymers of the present invention (Examples 1 and 2) were superior in plasticizer absorbability as compared with Comparative Examples 1, 2 and 3 in which polyvinyl alcohol B was not added, and The coating compositions of the present invention (Examples 1 and 2) have markedly better melt flowability than Comparative Examples 1, 2 and 3 even with the same amount of DOP added.

Comparative Example 2 using polyvinyl alcohol A ′ having a viscosity of 35 cps at 20 ° C. in a 4% aqueous solution has a plasticizer absorbability and melting property of a vinyl chloride polymer, as compared with Comparative Example 1 using polyvinyl alcohol A alone. Flowability deteriorates.

[Brief description of drawings]

1 and 2 are explanatory views showing the melting property of the coating composition pellets. FIG. 1 is a pellet before heating, and FIG. 2 is a pellet after heating.

Claims (1)

[Claims] 1. A suspension of a vinyl chloride monomer or a monomer mixture containing a vinyl chloride monomer as a main component and another monomer copolymerizable with the monomer as a subordinate component in water. Polyvinyl alcohol having a saponification degree of 65 to 80 mol% and a 4 wt% aqueous solution having a viscosity of 2 to 9 cps at 20 ° C. in 100 parts by weight of the monomer or monomer mixture in the polymerization. A 0.01-0.2 parts by weight, saponification degree 30-55 mol%
And a vinyl chloride polymer obtained by adding 0.001 to 0.1 part by weight of polyvinyl alcohol B having a viscosity of 6 to 15 cps of a 4% by weight aqueous solution at 20 ° C. with a plasticizer. Powder coating composition