JPH05140501A - Vinylidene chloride-based copolymer emulsion coating composition - Google Patents

Abstract

PURPOSE:To obtain an aqueous coating composition, composed of a vinylidene chloride-based copolymer emulsion resin, aluminum tripolyphosphate and a polyhydric alcoholic compound and excellent in rust preventing properties and heat resistance without causing cracks even in thick-film coating. CONSTITUTION:An aqueous coating composition is obtained by blending (A) 14-80 pts.wt. vinylidene chloride-based copolymer emulsion resin, e.g. an emulsion of a copolymer of vinylidene chloride, vinyl chloride, an alkyl acrylate and an alpha, beta-unsaturated carboxylic acid with (B) 1-10 pts.wt. aluminum tripolyphosphate and (C) 1-10 pts.wt., preferably 2-6 pts.wt. polyhydric alcohol (preferably sorbitol or polyglycerol) having 837 KOHmg/g hydroxyl value as essential components and, as necessary, other fillers such as nonpollution type rust preventing pigments, talc or calcium carbonate, colorants such as carbon black or titanium white, solvents, stabilizers, defoaming agents, etc. This aqueous coating composition is excellent in rust preventing properties and heat resistance without causing cracks even in thick-film coating.

Description

Detailed Description of the Invention

The present invention relates to a water-based rust preventive coating composition which is excellent in rust resistance and heat resistance, and further relates to a water-based paint composition which does not cause cracking even when applied to a high film thickness. Specifically, heat resistance is improved by adding a specific additive to a vinylidene chloride-based coating composition having excellent rust prevention, and further cracking occurs even when coated with a high film thickness. The present invention relates to a new technology of a composition without a metal.

[0002] In recent years, with the replacement of solvent-based paints with water-based paints as a method for solving air pollution pollution and petroleum resource consumption by organic solvents, water-based paints having the same performance as solvent-based paints and excellent antirust properties. Is desired. Among various resins for water-based paints, vinylidene chloride-based copolymer emulsion resins have a low water vapor transmission rate and excellent barrier properties, and are very suitable as resins for anticorrosion paints.

Particularly, by adding aluminum tripolyphosphate as a rust preventive pigment, the rust preventive performance is remarkably improved. 40μ for general water-based acrylic emulsion paint
When the dry coating film of No. 1 is formed on a dull steel plate, the salt spray resistance of the coating film is about 96 hours at most, but the dry coating film of the paint in which aluminum tripolyphosphate is mixed with vinylidene chloride copolymer emulsion resin. The salt spray resistance is about 480 hours, and it shows outstanding performance in terms of rust prevention. However, this paint
Hydrogen chloride is desorbed from the resin by heating at 20 ° C. for 20 minutes, and the resin is decomposed, resulting in blackening of the coating film and coating film defects such as blister.

When the present inventors examined this phenomenon, it was found that aluminum tripolyphosphate blended as a rust preventive pigment accelerates the decomposition of the resin when heated. However, aluminum tripolyphosphate is an essential component for obtaining excellent anticorrosion properties. Therefore, at present, vinylidene chloride-based copolymer emulsion resin paints are relatively limited to use in applications where heat is not applied, and cannot be used in applications where heat is applied, such as around the engine of an automobile. .. Furthermore, this paint is applied in a high film thickness,
There is also a drawback that a portion that causes a high film thickness, for example, a accumulated portion at the time of dipping coating, causes cracking during drying, and since it has excellent rust-preventing property, improvement of those defects has been strongly desired.

The present inventors have conducted earnest research on a coating composition which is excellent in rust resistance and heat resistance and does not cause cracking even in a high film thickness. As a result, a vinylidene chloride copolymer containing aluminum tripolyphosphate is found. It has been found that the above problems can be overcome by adding a specific polyhydric alcohol compound to the emulsion resin paint.

Thus, according to the present invention, a vinylidene chloride copolymer emulsion resin, aluminum tripolyphosphate and a polyhydric alcohol compound having a hydroxyl value of 837 KOH mg / g or more, preferably sorbit or polyglycerin are essential. As a component, the weight parts (solid content) of these three components are respectively 14 to 80 parts by weight, 1 to 10 parts by weight and 1 to 10 parts by weight, preferably 20 to 50 parts by weight, 4
The coating composition is characterized by being 8 to 8 parts by weight and 2 to 6 parts by weight, and further containing a filler, a colorant and the like as required.

The vinylidene chloride copolymer emulsion resin in the present invention means an emulsion of a copolymer of vinylidene chloride and another comonomer, examples of which include vinylidene chloride, vinyl chloride, alkyl acrylate and aliphatic Examples thereof include copolymer emulsion resins derived from α, β-unsaturated carboxylic acids (see JP-B-62-41534 or 62-59131).

Aluminum tripolyphosphate (for example, K-White manufactured by Teika Co., Ltd.) is a pollution-free rust preventive pigment,
When blended with vinylidene chloride copolymer emulsion resin, it shows excellent rust-preventing effect.
A film having a thickness of 0 μ and having durability of 480 hours or more is formed.

With other pollution-free rust preventive pigments such as zinc phosphate and calcium molybdate, blister occurs at a film thickness of 40 μ in 24 hours in a salt spray resistance test, and sufficient performance cannot be obtained.

Therefore, in the present invention, it is essential to use aluminum tripolyphosphate in order to obtain excellent anti-rust property, especially salt spray resistance.

Aluminum tripolyphosphate must be added in an amount of 1 to 10 parts by weight. When the amount is 1 part by weight or less, the rust preventive property is not sufficient, and when it is 10 parts by weight or more, further improvement in the rust preventive property cannot be expected. Further, aluminum tripolyphosphate can be used in combination with other pigments as long as it is contained in the paint in an amount of 1 to 10 parts by weight.

[0012] Conventionally, as a heat resistance improver for chlorine-containing resins, compounds of metal soap type, lead type, organic tin type, epoxy type, phosphoric acid ester type and the like have been known. Among them, aluminum tripolyphosphate is used. There was no compound that improved the heat resistance of the vinylidene chloride copolymer emulsion resin coating material contained and had good salt spray resistance. For example, metal soap-based and lead-based resins improve heat resistance, but cannot be used because they significantly lower the salt spray resistance as compared with paints containing no such additives. On the contrary, the organic tin-based compound accelerates the decomposition of the resin by heat, which further lowers the heat resistance. Phosphoric acid ester improves the heat resistance of this coating, but has the drawback of reducing the initial adhesion of the coating. Although the epoxy system improves the heat resistance, blistering occurs in 24 to 48 hours in the salt spray resistance test.

Unlike the conventional additives as described above, the polyhydric alcohol compound having a hydroxyl value of 837 KOH mg / g or more used in the present invention significantly improves heat resistance,
It has the function of not deteriorating the salt spray resistance at all, and also has the function of preventing the occurrence of cracks in the high film thickness portion. By blending this polyhydric alcohol compound,
The heat resistance is remarkably improved to have a durability of 120 ° C./3 hours or more, and the salt spray property is not deteriorated at all, and cracks do not occur even in the paint reservoir.

Suitable polyhydric alcohol compounds include:
Diglycerin, tetraglycerin, octaglycerin,
There are polyglycerin such as decaglycerin, glucose, sorbit, trimethylol, ethane, trimethylolpropane and erythritol.

Of these polyhydric alcohol compounds, those having a larger hydroxyl value have a better heat resistance improving effect,
The hydroxyl value must be at least 837 KOH mg / g or more. A polyhydric alcohol compound having a hydroxyl value higher than this can be expected to have a heat resistance improving effect unless the compound itself is decomposed or evaporated by heating. Especially sorbit or polyglycerin
Among the polyhydric alcohol compounds, not only does it have an excellent effect of improving heat resistance, but it also has an advantage of being able to completely prevent the occurrence of cracks occurring in the high film thickness portion of the dry coating film. The polyhydric alcohol compound is 1 to 10 parts by weight, preferably 2 to
It is necessary to mix 6 parts by weight. When the amount is 1 part by weight or less, the heat resistance is not sufficient, and when it is 10 parts by weight or more, the salt spraying property is deteriorated.

These polyhydric alcohol compounds can be used singly or as a mixture of two or more kinds, and there is no limitation on the addition method and the addition timing. For example, in the case of direct or particularly solid, water is added to facilitate addition. It can be added in the form of a solution of a solvent or a solvent at the time of polishing the pigment, or can be added later to the finished paint.

In the composition of the present invention, if necessary, other pollution-free rust preventive pigments, fillers such as talc and calcium carbonate,
In addition to coloring agents such as carbon black and titanium white, compounding agents such as a solvent, a stabilizer and an antifoaming agent can be added as required.

Examples of the present invention will be shown below. In the examples
All parts and percentages are by weight unless otherwise noted.

[Compound]

[0020]

[Table 1] (1) Thickener QP 52000H (Union Carbide Co., main component hydroxyethyl cellulose) 1.5 parts dissolved in 120 parts water and 0.2 parts 2% ammonia water (2) Defoamer (Bevaloid, (Mixture of mineral oil and hydrophobic silica) (3) Stabilizer (ICI, polyoxyethylene-polyoxypropylene block copolymer) (4) Wetting agent (Nisshin Chemical Industry Co., Ltd., acetylene glycol) (5) Dispersion Agent (6) Aluminum tripolyphosphate (Taika Co., Ltd.) (7) Talc (Takehara Chemical Industry Co., Ltd.) (8) ICI's vinylidene chloride emulsion resin (vinylidene chloride, vinyl chloride, alkyl acrylate and aliphatic α, β- (60% emulsion of copolymer of unsaturated carboxylic acid) (9) Flashlash anti-lasting agent Mix and disperse the above ingredients in order from the top with a tabletop disper while stirring. And paint.

[Test and evaluation method] width 5 cm, length 15 cm,
The coating composition was applied to a 0.8 mm thick iron plate with a bar coater and dried at room temperature for 1 day to form a film having a thickness of 50 μm. The heat resistance of the coating was examined by leaving the coating in a constant temperature bath at 120 ° C. Further, the paint was applied to an iron plate, dried at room temperature for 7 days, and then subjected to a salt spray test according to the method defined in JIS K5400 for evaluation.

Width 5 cm, length 15 cm, thickness 0.3 mm
The zinc steel sheet was bent at an angle of 90 °, 0.5 g of the coating composition was placed on the bent portion, set at room temperature for 10 minutes, dried at 80 ° C for 10 minutes, and allowed to stand at room temperature to examine the occurrence of cracks.

The evaluation of the crack prevention property is ○ (no crack), △ (somewhat cracked) and × (cracked)
Displayed in.

[0024]

【Example】

[Examples 1 to 8] 5.94 parts of aluminum tripolyphosphate (K-White) as a rust preventive pigment and 6 parts of a 50% aqueous solution of the polyhydric alcohol compound shown in Table 2 (3 parts as a solid content). Was used to make a paint according to the paint formulation above.

[Comparative Example 1] 5.94 parts of aluminum tripolyphosphate (K-White) was used as a rust preventive pigment, and a paint was prepared according to the above-mentioned paint formulation without using a polyhydric alcohol compound.

Comparative Example 2 Calcium molybdate as a rust preventive pigment (MC-400WR manufactured by Kikuchi Dye Co., Ltd.)
The same procedure as in Comparative Example 1 was carried out except that 5.94 parts were used.

[Comparative Example 3] The same procedure as in Comparative Example 1 was carried out except that 5.94 parts of zinc phosphate (Kikuchi dye Co., Ltd. ZP-NF) was used as a rust preventive pigment.

Comparative Example 4 Comparative Example 1 except that 5.94 parts of aluminum tripolyphosphate (K-White) was used as a rust preventive pigment and 1 part of an epoxy resin (Epicoat 828 manufactured by Yuka Shell Epoxy Co., Ltd.) was used. I went the same way.

Example 9 1 part of aluminum tripolyphosphate (K-White) as a rust preventive pigment and 6 parts of a 50% aqueous solution of sorbit as a polyhydric alcohol compound (3 parts as a solid content) were used in the above coating composition. Therefore, the paint was created.

[Example 10] The same procedure as in Example 9 was carried out except that 10 parts of aluminum tripolyphosphate (K-White) was used as a rust preventive pigment.

Example 11 5.94 parts of aluminum tripolyphosphate (K-White) was used as a rust preventive pigment, and 2 parts of a 50% aqueous solution of sorbit as a polyhydric alcohol compound (1 part as a solid component). The same procedure as in Example 9 was carried out except that it was used.

[Example 12] 5.94 parts of aluminum tripolyphosphate (K-White) was used as a rust preventive pigment, and 20 parts of a 50% aqueous solution of sorbit as a polyhydric alcohol compound (10 parts as a solid component). The same procedure as in Example 9 was carried out except that it was used.

[0033]

[Table 2]

Claims (2)

[Claims] 1. A vinylidene chloride copolymer emulsion resin, aluminum tripolyphosphate and a hydroxyl value of 83.
It comprises a polyhydric alcohol compound of 7 KOH mg / g or more as an essential component, and the weight parts (solid content) of these three components are respectively 14 to 80 parts by weight, 1 to 10 parts by weight and 1 to 10 parts by weight. A coating composition characterized by the above. 2. The coating composition according to claim 1, wherein the polyhydric alcohol compound is sorbit or polyglycerin.