JPH0532938A - Aqueous chipping-resistant coating composition - Google Patents

Abstract

PURPOSE:To provide an aqueous chipping-resistant coating composition excellent in chipping resistance, adhesion and blister resistance in high temperature baking and suitable for surface coating of the back of the floor of an automobile, a side sill, etc. CONSTITUTION:Based on 100 pts.wt. solid matter of (A) a water dispersion type resin (e.g. styrene-butadiene copolymer latex or acrylatebutadiene copolymer latex), (B) 50-250 pts.wt., preferably 80-200 pts. wt. filler (e.g. talc or potassium carbonate) and (C) 0.07-15 pts.wt., preferably 0.3-5 pts.wt. organic polymer heat- sensitive gelling agent (e.g. starch, its derivative or organopolysiloxane- polyoxyalkylene copolymer) are blended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based chipping-resistant coating composition, and more particularly to a water-based chipping-resistant coating composition having excellent blister resistance during high temperature baking. The coating composition of the present invention is suitable, for example, for surface coating of floors, side seals, fuel tanks, front aprons, tire houses, etc. of automobiles.

[0002]

2. Description of the Related Art An underfloor of a car, a tire house, and the like are coated with a chipping-resistant paint in order to protect them from damage caused by flying stones during traveling. As a chipping-resistant paint, vinyl chloride plastisol-based paints have been mainly used in recent years in place of conventional bitumen-based paints.

However, the vinyl chloride plastisol-based coating composition has problems such as deterioration of the coating film during baking at high temperature, deterioration of durability due to migration and volatilization of plasticizer, and waste treatment.
Recently, studies have been conducted on water-based chipping resistant paints. For example, a coating material using a styrene-acrylic acid 2-ethylhexyl-acrylic acid copolymer emulsion (JP-A-58-187468), a styrene-butadiene-acrylic acid-acrylamide copolymer latex and a specific powdery filler. Coating material (Japanese Patent Laid-Open No. 59-7
No. 5954) has been proposed.

These water-based chipping-resistant paints can exhibit good chipping resistance in a coating film having a relatively thin film thickness, but blister of the coating film due to evaporation of water during baking at high temperature. It has problems such as cracks and cracks, or peeling. In particular, in the case of seams of sheet metal constituting the underside of automobiles, etc., the dry film thickness of the coating film is 1500-500.
Since it is a relatively thick film of about 2000 μm, it is important to prevent blistering during baking. However, the dry coating thickness of the conventionally proposed water-based chipping resistant coating is, for example,
200-800 μm (JP-A-58-187468) or 100-1000 μm (JP-A-59-75954)
No.), and a thick film exceeding 1000 μm is likely to cause blisters during baking.

[0005]

An object of the present invention is to provide a water-based system which has good chipping resistance, adhesion to metal and cationic electrodeposition coating for automobiles, etc., and excellent blister resistance during high temperature baking. An object is to provide a chipping-resistant coating composition.

As a result of intensive studies to overcome the problems of the prior art, the present inventor has found that an aqueous composition obtained by mixing a water-dispersible resin with a filler and an organic polymer heat-sensitive gelling agent is a thin film. However, it has been found that chipping resistance and adhesion are good, and that blisters and cracks do not occur during high temperature baking even when a thick film is formed, and the present invention has been completed based on the findings.

[0007]

Thus, according to the present invention, 50 to 250 parts by weight of the filler and 0.1 to 100 parts by weight of the organic polymer heat-sensitive gelling agent are added to 100 parts by weight of the solid content of the water-dispersible resin.
There is provided a water-based chipping-resistant coating composition characterized by containing 07 to 15 parts by weight.

The present invention will be described in detail below. (Water Dispersible Resin) The water dispersible resin used in the present invention is not particularly limited, and examples thereof include aromatic vinyl-conjugated diene copolymer latex such as styrene-butadiene copolymer latex, ethyl acrylate-butadiene. (Meth) acrylic acid ester such as copolymer latex-
Unsaturated nitrile-conjugated diene copolymer latex such as conjugated diene copolymer latex, acrylonitrile-butadiene copolymer latex, vinyl acetate- (meth) acrylic acid ester copolymer latex, (meth) acrylic acid ester copolymer Examples include latexes or emulsions such as emulsions, natural rubber latex, and aqueous polyurethane dispersions. These water-dispersible resins include carboxyl group, hydroxyl group, N-methylol group, glycidyl group,
It may contain one or more functional groups such as sulfonic acid groups.

Examples of main monomers for obtaining the water-dispersible resin include conjugated dienes such as 1,3-butadiene and isoprene; aromatic vinyl monomers such as styrene and methylstyrene; acrylonitrile and methacrylonitrile. Unsaturated nitrile monomers such as; methacrylic acid esters such as methyl methacrylate; acrylic acid esters such as ethyl acrylate and butyl acrylate; and the like.
Examples of the functional monomer include ethylenically unsaturated carboxylic acids such as acrylic acid and methacrylic acid; amide group-containing monomers such as acrylamide and N-methylol acrylamide; epoxy group-containing units such as glycidyl methacrylate. Body; hydroxyl group-containing monomer such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate;
Etc. can be mentioned.

These monomers can be used in an appropriate combination. For example, in the case of a conjugated diene-based copolymer, 20 to 75% by weight of conjugated diene, aromatic vinyl or unsaturated nitrile, ( (Meth) acrylic acid ester 20-
The water-dispersible resin copolymerized at a ratio of 75% by weight and a functional monomer of 0.1 to 5% by weight has an excellent balance of physical properties such as adhesion, film-forming property, strength and flexibility. preferable.

The water-dispersible resin can be usually obtained by an emulsion polymerization method by combining the above various monomers.
The emulsion polymerization is carried out in an aqueous medium in the presence of a catalyst under the coexistence of a surfactant and / or a protective colloid, and if necessary, a pH adjusting agent, a polymerization degree adjusting agent, a defoaming agent, etc. may be further appropriately added. It can be added.

Among these water-dispersible resins, styrene-butadiene copolymer latex, acrylate-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex and (meth) acrylic acid ester copolymer emulsion are coating physical properties. It is particularly preferable from the standpoint of price balance. Further, these water-dispersible resins can be used alone or in admixture of two or more.

(Filler) As the filler used in the present invention, talc, calcium carbonate, diatomaceous earth, mica, kaolin, barium sulfate, magnesium carbonate, silica, silica aerogel, hirulite, graphite, alumina, Examples of the powder include titanium oxide and carbon black. Titanium oxide and carbon black can also be used as a coloring agent. The particle size of these fillers can be appropriately selected, but those having an average particle size of 0.05 to 100 μm are preferable, and one kind or two or more kinds are used.

These fillers are used in a proportion of 50 to 250 parts by weight, preferably 80 to 200 parts by weight, based on 100 parts by weight of the solid content of the water-dispersible resin. If the blending ratio of the filler is less than 50 parts by weight, blistering occurs during baking (drying / curing) of the coating film, and if it exceeds 250 parts by weight, the adhesiveness decreases and the chipping resistance sharply decreases. To do.

(Organic polymer heat-sensitive gelling agent) Examples of the heat-sensitive gelling agent used in the present invention include starch and its derivatives, organopolysiloxane-polyoxyalkylene copolymer, polyoxyalkylene of phenol or alkylphenol. An organic polymer heat-sensitive gelling agent such as an adduct, a polyoxyalkylene adduct of bisphenol, a polyoxyalkylene adduct of a condensate of phenol or an alkylphenol and formalin can be used.

It is preferable to use tapioca starch as the starch and ester group-containing tapioca starch as the esterified starch. Organopolysiloxane-
As the polyoxyalkylene copolymer, TPA438
0 (manufactured by Toshiba Silicone Co.) and TPA4390 (manufactured by Toshiba Silicone Co.) are preferably used.

The polyoxyalkylene adduct of the condensate of alkylphenol and formalin has an average degree of condensation of butylphenol or nonylphenol and formalin condensate of 3 to 8 and an average number of moles of ethylene oxide and propylene oxide of 30 to 300. It is preferred to use some. These are used alone or in combination of two or more.

The heat-sensitive gelling agent is a water-dispersible resin having a solid content of 1%.
It is used in an amount of 0.7 to 15 parts by weight, preferably 0.1 to 10 parts by weight, and more preferably 0.3 to 5 parts by weight with respect to 00 parts by weight. If it is less than 0.07 parts by weight, blisters are likely to occur during high temperature baking, and if it is used in excess of 15 parts by weight, the storage stability of the chipping resistant coating becomes insufficient.

The cloud point or gelatinization temperature of these heat-sensitive gelling agents is preferably 30 to 140 ° C., more preferably 4
It is 0 to 100 ° C. If the cloud point or gelatinization temperature is less than 30 ° C, the storage stability of the chipping-resistant coating composition tends to be insufficient, and if it exceeds 140 ° C, the effect of preventing blistering may be insufficient.

(Water-based chipping-resistant coating composition) The water-based pitching-resistant coating composition of the present invention contains a water-dispersible resin, a filler, and an organic polymer heat-sensitive gelling agent. For example, additives such as usual dispersants, wetting agents, thickeners, defoaming agents, antifreezing agents and lightening agents can be added as appropriate.

As a method for producing the water-based chipping-resistant coating composition, a water dispersible resin, a dispersant and a heat-sensitive gelling agent are uniformly mixed using a disperser such as a general kneader or disper, and then talc or the like. The method of mixing and kneading the filler, other additives and the like is preferable.

As properties of the water-based chipping-resistant coating composition, the nonvolatile content (solid content) is 60% by weight or more, the specific gravity is 1.0 to 1.6, the pH is 6 to 9, and the BH type viscometer (20r
It is preferable that the measured value in pm) is 100 to 500 poise at 20 ° C.

These water-based anti-chipping paints are mainly used for protecting metal or existing coatings. For example, it is applied to the floor undersides of automobiles, side seals, fuel tanks, front aprons, electrodeposition coating surfaces such as tire houses, intermediate coating film surfaces or top coating film surfaces.

As a coating method, for example, a usual coating method such as a spray coating method, a brush coating method, a roll coating method and a spatula coating method is adopted, but an airless spray method is generally used.
The baking drying of the water-based anti-pitting paint is generally performed by predrying at about 80 ° C. and then heating in an oven under the temperature condition of 120 to 180 ° C.

The dry coating thickness is generally 500-100.
Although it is a thin film of 0 μm, it is 1500-500 at seams of sheet metal etc.
Since it is a thick film of 2000 μm, it is especially important to prevent blistering during baking. Even with such a thick film, the water-based chipping-resistant coating material of the present invention can provide a blister-free coating film during high temperature baking.

[0026]

EXAMPLES The present invention will be specifically described below with reference to reference examples, examples and comparative examples, but the present invention is not limited to these examples unless the gist thereof is exceeded. The parts and% in these examples are based on weight unless otherwise specified. The methods for measuring the physical properties of the water-based chipping resistant coating compositions obtained in the following examples are as follows.

<Blister resistance> A water-based chipping-resistant coating composition was airlessly coated on a coating plate obtained by cationic electrodeposition coating on a zinc phosphate treated plate so that the dry film thickness was about 1500 μm. After setting for 2 to 5 minutes, the product was baked and dried at 140 ° C. for 30 minutes, and blisters (blisters in the coating film) generated during the drying were visually observed and evaluated in the following 4 stages. A: No blister occurred. ○: There was a slight blister in some parts. △ = Blisters occurred in a considerable part. × = Blisters occurred on the entire surface.

<Adhesiveness> A water-based chipping-resistant coating composition was airlessly coated on a coating plate obtained by cationic electrodeposition coating on a zinc phosphate treated plate so that the dry film thickness was about 100 μm.
After setting for 2 to 5 minutes, bake and dry at 140 ° C for 30 minutes, leave at room temperature for about 2 hours, and then set according to JIS-K-5400.
In accordance with (6.15), the coating film is scribed with 1 mm wide burrs (total of 100 pieces), cellophane tape is brought into close contact, and then peeled off to measure the adhesion rate (number / 100 pieces) of the coating film, The following four grades were used for evaluation. A = 100/100 A = 80 to 99/100 B = 50 to 79/100 X = 49 or less / 100

<Chipping resistance> A water-based chipping-resistant coating composition was airlessly coated on a coating plate obtained by cationic electrodeposition coating on a zinc phosphate-treated plate so that the dry film thickness was about 800 μm. After setting for 2 to 5 minutes, it was baked and dried at 140 ° C. for 30 minutes and left at room temperature for one day. A M-4 nut defined in JIS was continuously dropped from a height of 2 m on a test piece set at an angle of 60 degrees, and the total weight of the dropped nut when the substrate was exposed was evaluated.

Reference Example 1 (Production of Polymer Latex A) In an autoclave equipped with a stirrer, 100 parts of water, 1.0 part of sodium dodecylbenzenesulfonate, 1.5 parts of potassium persulfate, 40 parts of butadiene, styrene. 58 parts and 2 parts of methacrylic acid were charged and reacted at 60 ° C. for 15 hours. Then, after cooling to room temperature, ammonia water was added to adjust the pH to 8 to obtain a copolymer latex (latex A).

[Examples 1 to 4 and Comparative Examples 1 to 3] According to the compounding recipe shown in Table 1, a water-dispersible resin (Latex A), a dispersant (Demol EP: manufactured by Kao Corporation) in a container, An organic polymer heat-sensitive gelling agent (manufactured by Kao, trade name Latemur NP-5150; polyoxyalkylene adduct of alkylphenol and formalin condensate, cloud point 45 ° C.) was uniformly mixed with a stirrer, and then talc (Asada Milling Company name, SWB; average particle size 11 μm), calcium carbonate (Maruo calcium, R heavy carbon; average particle size 12 μm), carbon black (Toyo Ink Mfg. Co., Ltd. product name WSBK)
-7; average particle size 0.07 μm) was gradually added and sufficiently stirred to obtain a water-based chipping-resistant coating composition. The physical properties of each of the obtained water-based chipping resistant coating compositions were measured, and the results are shown in Table 1.

[0032]

[Table 1]

As is clear from the results shown in Table 1, the water-based chipping-resistant coating composition of the present invention has good blister resistance even under a high temperature baking condition of 140 ° C. and even in the case of a thick film. Moreover, it can be seen that the adhesiveness and chipping resistance are also excellent.

Example 5 An organic polymer heat-sensitive gelling agent was used as an organopolysiloxane-polyoxyalkylene copolymer (manufactured by Toshiba Silicone Co., trade name TPA4390; cloud point 5).
(5 ° C.) Same as Example 1 except that the content was changed to 2.0 parts.

[Example 6] An organic polymer heat-sensitive gelling agent was esterified starch (manufactured by Nitto Kagaku Co., trade name Z-300;
Ester group-containing tapioca starch, gelatinization temperature 63 ° C)
The same procedure as in Example 1 was performed except that the content was changed to 8.0 parts. The results of Examples 5-6 are shown in Table 2.

[0036]

[Table 2]

From the results shown in Table 2, it can be seen that the water-based chipping-resistant coating composition of the present invention is excellent in each performance even if the kind of the heat-sensitive gelling agent is changed.

[0038]

EFFECTS OF THE INVENTION The water-based chipping-resistant coating composition of the present invention does not deteriorate chipping resistance and adhesion, and does not cause blister or crack in a thick film, as compared with the prior art. Back, side seal, fuel tank,
It is suitable for surface coating of front aprons, tire houses, etc.

Claims (1)

Claims: 1. A water-dispersible resin containing 100 parts by weight of a solid content of 50 to 250 parts by weight of a filler and 0.07 to 15 parts by weight of an organic polymer heat-sensitive gelling agent. A water-based anti-chipping coating composition comprising: