JPH0726165A - Coating composition resistant to heat-blocking - Google Patents

Abstract

PURPOSE:To obtain a coating composition composed of an emulsion obtained by the emulsion polymerization of an alpha,beta-ethylenic monomer in the presence of a specific polymerizable emulsifier, a pigment and a specific amount of colloidal silica, having excellent thermal blocking resistance and exhibiting excellent stability. CONSTITUTION:This composition is composed of (A) an emulsion produced by the emulsion polymerization of an alpha,beta-ethylenic monomer (e.g. methyl acrylate and styrene) in the presence of a polymerizable emulsifier of the formula I (A is 2-4C alkylene; R1 is H or methyl; R2 is 8-24C hydrocarbon group or acyl; m is 0-50; Z is H or nonionic or anionic hydrophilic group), (B) a pigment mixture and (C) colloidal silica (preferably having particle diameter of 5-50nm) of an amount satisfying the formula II and 5<=X<=9O (Y is defined by the formula III; X is defined by the formula IV). The pH of the composition is preferably >=8.5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant blocking resistant coating composition which prevents blocking due to heat.

[0002]

2. Description of the Related Art When the surface coated with a coating composition has a blocking property due to heat, it has a drawback that it adheres to each other. Therefore, for example, a coating composition for a packaging material, a floor surface, a wall surface, etc. is strongly required to have good heat blocking resistance. In particular, the paint for factory line painting of construction boards is important in heat blocking resistance because boards dried by heating after coating are stacked. Conventionally, as a heat-resistant paint, there is an inorganic paint, and as one of them, colloidal silica paint is known.
Colloidal silica-based paints have a smaller amount of alkali components than other inorganic-based paints, and are superior in water resistance and chemical resistance, but they have the drawback of weak adhesion, so to supplement the adhesion Attempts have been made to use colloidal silica in combination with a synthetic resin bander. For example, JP-A-56-578
No. 60 "Coating composition for building materials" describes an aqueous coating composition comprising a mixture of a water-soluble or water-dispersible acrylic copolymer and colloidal silica. However, since the water-soluble or water-dispersible acrylic copolymer is used, there are problems in water resistance and alkali resistance.

JP-A-59-71316 "Water-dispersible coating composition" is based on an aqueous resin dispersion obtained by emulsion polymerization of a monomer and colloidal silica in the presence of a surfactant. Water dispersible coating compositions are described. However, there is a problem in water resistance and alkali resistance probably because the surfactant remains in the coating film. JP-A-5
9-152972 "water resistant coating composition" includes:
A water-resistant coating composition is described in which an aqueous emulsion obtained by emulsion-polymerizing vinylsilane and an acrylic monomer using a polymerizable emulsifier is mixed with colloidal silica. It is said that the polymerizable emulsifier disclosed in JP-A-59-152972 has insufficient stability after the polymerization, probably because colloidal silica is blended and a pigment is further added to form a coating. There was a flaw.

[0004]

None of these coating compositions can satisfy both the stability and the heat blocking resistance of the paint. There is a drawback that stability tends to deteriorate when heat-resistant blocking is improved. The present invention provides an excellent heat-resistant blocking-resistant coating composition that solves such problems by incorporating a specific amount of colloidal silica into a special emulsion.

[0005]

MEANS FOR SOLVING THE PROBLEMS The present invention provides "1. an α, β-ethylenic monomer represented by the following structural formula (1) structural formula (1)

[0006]

[Chemical 2]

(In the formula, A is an alkylene group having 2 to 4 carbon atoms, R ₁ is a hydrogen atom or a methyl group, R ₂ is a hydrocarbon group having 8 to 24 carbon atoms or an acyl group, m
Is a number from 0 to 50, and Z is a hydrogen atom or a nonionic or anionic hydrophilic group. ), A mixture of an emulsion and a pigment emulsion-polymerized using a polymerizable emulsifier, and the following formulas (1) and (2)

[0008]

[Equation 4]

Formula (2)

[0010]

[Equation 5]

A heat-blocking coating composition comprising an amount of colloidal silica satisfying the above conditions. 2. The heat-resistant blocking-resistant coating composition according to item 1, wherein X is 20 ≦ X ≦ 70. 3. The heat-resistant blocking-resistant coating composition according to item 1 or 2, wherein the colloidal silica has a particle size of 5 to 500 nm. 4. The ratio of the synthetic resin particle diameter of the synthetic resin aqueous emulsion and the particle diameter of the colloidal silica is expressed by the following mathematical expression (3) mathematical expression (3)

[0012]

[Equation 6]

The heat-resistant blocking-resistant coating composition as described in any one of items 1 to 3, which satisfies the following condition. 5. 5. The heat-resistant blocking-resistant coating composition according to any one of items 1 to 4, wherein the colloidal silica is a colloidal silica surface-treated with an aluminate ion. 6. The heat-resistant blocking-resistant coating composition according to any one of items 1 to 5, wherein the pH of the paint is 8.5 or more. Regarding

[0014]

The first feature of the present invention is to use an emulsion obtained by polymerizing an α, β-ethylenic monomer with a polymerizable emulsifier represented by the following formula (1). Formula (1)

[0015]

[Chemical 3]

As the polymerizable emulsifying agent, an alkali salt of alkylallyl sulfosuccinate, sodium (glycerin n-alkenyl succinoyl glycerin) borate, an alkali salt of sulfopropyl maleic acid monoalkyl ester, polyoxyethylene of acrylic acid or methacrylic acid. Alkyl esters and the like are known. The polymerizable emulsifier is copolymerized with the α, β-ethylenic monomer, and by being incorporated into the resin, unlike a general emulsifier remaining in the aqueous phase, it has various advantages, but on the other hand, From the viewpoint of stability, it is considered that the stability is remarkably deteriorated by adding colloidal silica and further adding a pigment or the like. The polymerizable emulsifier represented by the formula (1) has a structure different from that of other polymerizable emulsifiers, and it is considered that the polymerizable emulsifier has an unsaturated group, a hydrophilic group, and a hydrophobic group. -Even when copolymerized with an ethylenic monomer,
Effectively arranged on the surface of resin particles that became emulsion,
The stability is significantly improved compared to other polymerizable emulsifiers.

A second feature of the present invention is the incorporation of a specifically limited amount of colloidal silica. According to the study of the present inventor, the thermal blocking property of the coating composition is the composite ratio of PWC (pigment weight ratio) and colloidal silica of the composition (a value obtained by dividing the amount of colloidal silica by the total amount of polymer and colloidal silica). It has been revealed that is greatly affected by. From the viewpoint of heat blocking resistance, the larger the amount of colloidal silica compounded, the greater the effect. However, when the amount of colloidal silica increases,
Not only does the coating become brittle, the elongation and bending strength of the coating decrease, the weather resistance of the coating deteriorates, cracks easily form in the coating, and the gloss also decreases. Further, when the content of colloidal silka is large, the water permeability of the coating film is large and efflorescence is likely to occur. In addition, the function as a protective layer is reduced.

According to the study of the present inventor, in order to develop the heat blocking resistance, the composite ratio (Y) of colloidal silica is
Between the composition and PWC (X) of the composition, Y ≧ 25-1 / 4X
It turns out that there is a relationship. When the composite rate (Y) of colloidal silica was Y <25-1 / 4X, the effect of colloidal silica was not obtained and heat blocking resistance was not exhibited.

PWC (X) is in the range of 5 ≦ X ≦ 90, and when X> 90, the adhesion is not obtained, and when 5 <X, the hiding property is not provided and the function as a coating cannot be obtained. Particularly preferably 20
≦ X ≦ 70. The colloidal silica used in the present invention is not particularly limited, but those having a particle size of 5 to 500 nanometers are preferable.

The relationship between the particle size of colloidal silica and the particle size of synthetic resin of the synthetic resin aqueous emulsion is expressed by the following mathematical formula (3).

[0021]

[Equation 7]

It is preferable that If the particle size ratio is smaller than 5, the amount of colloidal silica used for developing heat-resistant blocking property tends to increase, and in order to develop the desired heat-resistant blocking property with a smaller amount of colloidal silica used. It is preferable that the ratio of particle diameters is larger than 5.

The pH of the paint is preferably 8.5 or higher. Since colloidal silica is stabilized by forming an electric double layer by alkali ions, if the charge balance is lost, the stability is impaired.

When the pH of the paint is 8.5 or less, it is preferable to use colloidal silica whose surface is treated with aluminate ions. This silica has aluminosilicate ions formed on a part of the surface of silica particles, and is produced by adding aluminum hydroxide to colloidal silica in the form of aluminate ions and reacting with silanol groups on the surface of silica particles. To be done.

The α, β-ethylenic monomer used in the present invention includes methyl acrylate, ethyl acrylate,
Acrylic esters such as butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate; methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid Methacrylic acid esters such as lauryl; acrylonitrile, methacrylonitrile; styrene, methylstyrene, chlorostyrene; methyl crotonate, ethyl crotonate, dibutyl maleate, diethyl fumarate, and other acrylic acid esters, methacrylic acid esters Other than unsaturated carboxylic acid esters or unsaturated polyvalent carboxylic acid esters; vinyl acetate, vinyl dipropionate, vinyl laurate, vinyl stearate, vinyl pivalate and veova (shell Vinyl esters such as vinyl esters of saturated carboxylic acids branched at TM) alpha-position, such as the Gakusha; vinyl chloride, vinylidene chloride; ethylene is one or more of such. Of these, it is particularly preferable to combine a monomer having a high glass transition temperature and a monomer having a low glass transition temperature.

The above α, β-ethylenic monomer contains 2
At 0% by weight or less, an α, β-ethylenic monomer having a functional group can be used in combination. Examples of the α, β-ethylenic monomer having a functional group include unsaturated carboxylic acids, unsaturated carboxylic acid amides, N-methylol compounds of unsaturated carboxylic acid amides, vinylsilanes, acetoacetyl group-containing monomers, and Examples thereof include monomers having two or more saturated groups.

[0027]

EXAMPLES The present invention will now be specifically described with reference to Examples. First, an example of producing a copolymer emulsion containing colloidal silica is shown, and then an example containing a pigment is shown.

Production Example A Methyl methacrylate 60 parts by weight Butyl acrylate 40 parts by weight Methacrylic acid 1.3 parts by weight in the presence of 3 parts by weight of the polymerizable emulsifier (A) represented by the following structural formula (1). The mixed monomer was emulsion polymerized to obtain a synthetic resin emulsion. The obtained synthetic resin emulsion had a solid content of 48% by weight and a particle size of 100 nm. The pH of 100 parts by weight of this synthetic resin emulsion was adjusted, and 50 parts by weight of colloidal silica having a solid content of 40% by weight and a particle size of 13 nm was added and mixed uniformly to obtain a colloidal silica composite emulsion having a pH of 9.5. It was Structural formula (1)

[0029]

[Chemical 4]

Production Examples B to I In Production Example A, synthetic resin emulsions were obtained by changing the polymerizable emulsifier and the mixed monomer composition as shown in Table 1. Colloidal silica shown in Table 1 was added to this synthetic resin emulsion to obtain a colloidal silica composite emulsion. Only in Production Example E, the colloidal silica composite emulsion had a pH of 7.5.
Is. The polymerizable emulsifier (B), colloidal silica (I), (II) and (III) in Table 1 are as follows. Structural formula of polymerizable emulsifier (B)

[0031]

[Chemical 5]

Colloidal silica (I) is a colloidal silica having a solid content of 40% by weight and a particle diameter of 13 nm. Colloidal silica (II) is a colloidal silica having a solid content of 30% by weight and a particle size of 8 nm. Colloidal silica (III) is a colloidal silica surface-treated with aluminate ions having a solid content of 40% by weight and a particle diameter of 21 nm.

[0033]

[Table 1]

Production Examples A to D (Production Example for Comparison) Production Example A except that a polymerizable emulsifier different from the structural formula of the present invention was used in Production Example A as shown in Table 2.
An emulsion was obtained in the same manner as in. In Table 2, polymerizable emulsifiers (a), (b), (c) and (d) are as follows. The polymerizable emulsifier (a) is sodium alkylallylsulfosuccinate. The polymerizable emulsifier (b) is an alkenyl sulfosuccinic acid ammonium salt. The polymerizable emulsifier (c) is polyoxyethylene alkylpropenyl phenyl ether sulfuric acid ester ammonium salt. The polymerizable emulsifier (d) is sodium dodecylbenzene sulfonate.

Production Example E and F (Production Example for Comparison) An emulsion was obtained in the same manner as in Production Example A except that the amount of colloidal silica used in Production Example A was reduced as shown in Table 2. .

[0036]

[Table 2]

Example 1 The colloidal silica composite emulsion obtained in Production Example 1 was used to uniformly mix pigments and the like, the pH was adjusted to 9.0 with 10% by weight aqueous ammonia, and the mixture was produced with a urethane thickener. Immediately after that, the viscosity (initial viscosity) was adjusted to 1,000 centipoise to obtain a heat-resistant blocking resistant coating composition having the following composition. Colloidal silica composite emulsion 100 parts by weight Titanium oxide 44 parts by weight Calcium carbonate 22 parts by weight Pigment dispersant 0.6 parts by weight Wetting agent 0.7 parts by weight Thickener (2% methylcellulose aqueous solution) 14 parts by weight Defoaming agent 0. 3 parts by weight 1: 1 diluted solution of film-forming aid and water 16 parts by weight The amount of resin-silica composite in the heat-resistant blocking-resistant coating composition obtained in Example 1 was calculated by the following mathematical formula (4) 29.4.
Met. Formula (4)

[0038]

[Equation 8]

The PWC (pigment weight ratio) was calculated by the following equation (2) and was 60.0. Formula (5)

[0040]

[Equation 9]

The heat-blocking coating composition obtained in Example 1 satisfied the following mathematical formula (1). Formula (1)

[0042]

[Equation 10]

Examples 2 to 6 Heat-resistant blocking-resistant coating compositions as shown in Table 3 were obtained in the same manner as in Example 1 except that the colloidal silica composite emulsion used in Example 1 was replaced by Production Examples BF. However, the pH of the heat-resistant blocking-resistant coating composition of Example 5 was 8.2.

Examples 7 to 9 The colloidal silica composite emulsions used in Example 1 were prepared in Production Examples G, H and I (silica composite amount of resin (=
Y) was replaced with 43.5, 25.9, 5.5), and the heat-resistant blocking-resistant coating composition was prepared in the same manner as in Example 1 except that the use ratios of titanium oxide and calcium carbonate were changed as shown in Table 3. Got

Comparative Examples 1 to 4 (Comparative Examples with Different Polymeric Emulsifiers Used) Compositions were prepared in the same manner as in Example 1 except that the colloidal silica composite emulsion used in Example 1 was replaced by Production Examples a to d. Obtained.

Comparative Examples 5 and 6 (Comparative Examples Not Satisfying Formula (1)) The colloidal silica composite emulsion used in Example 1 was replaced with Production Examples E and F, and the ratios of titanium oxide and calcium carbonate used were shown in Table 4. Example 1 except that instead of
A composition was obtained in the same manner as in.

Test Method The heat resistance and heat blocking resistance of the heat blocking resistant coating compositions obtained in Examples and the compositions obtained in Comparative Examples were evaluated by the following methods. The test results are shown in Tables 3 and 4.

[0048]

[Table 3]

[0049]

[Table 4]

(Paint stability) The sample was sealed in a glass container and left in a thermostat at 50 ° C. for 7 days to measure the viscosity of the sample. The sex was judged.

[0051]

[Equation 11]

B: The increase rate of viscosity is less than 5. B: Increase rate of viscosity is 5 to 10. X: The increase rate of viscosity exceeded 10, or the fluidity was lost.

(Heat-resistant blocking resistance) A sample was coated on high-quality paper in a wet weight of 30 g / m ² , and the temperature was 1 ° C. at 80 ° C.
Dry for 0 minutes. Next, two coated plates were overlapped with each other, and two metal plates kept at a predetermined temperature were used, and pressed with a load of ² kg / cm ² for 10 seconds. After cooling to room temperature, the laminated high-quality papers were peeled off, and the minimum temperature was measured until the coated surfaces could not be adhered and peeled off to determine the heat-resistant blocking resistance. ○: It was 210 ° C or higher. Δ: 110 to 200 ° C. ×: It was 100 ° C or lower.

[0054]

The coating composition of the present invention has good heat blocking resistance and excellent stability. The conventional coating composition has the excellent effect of improving both required performances as compared with the decrease in stability when the heat-resistant blocking property is improved.

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Claims (6)

[Claims] 1. An α, β-ethylenic monomer is represented by the following structural formula (1) structural formula (1): (In the formula, A is an alkylene group having 2 to 4 carbon atoms, and R ₁
Is a hydrogen atom or a methyl group, and R ₂ has 8 to ₂ carbon atoms.
4 is a hydrocarbon group or an acyl group, m is a number of 0 to 50, and Z is a hydrogen atom or a nonionic or anionic hydrophilic group. ), A mixture of an emulsion and a pigment emulsion-polymerized using a polymerizable emulsifier, and the following formulas (1) and (2) Formula (2) [Equation 2] A heat-resistant blocking-resistant coating composition comprising an amount of colloidal silica satisfying the above requirement. 2. The heat-resistant blocking resistant coating composition according to claim 1, wherein X is 20 ≦ X ≦ 70. 3. The particle size of colloidal silica is 5 to 500.
The heat-blocking coating composition according to claim 1, which is nanometer. 4. The ratio of the synthetic resin particle diameter of the synthetic resin aqueous emulsion to the colloidal silica particle diameter is expressed by the following mathematical formula (3), mathematical formula (3), and Any one of claims 1 to 3 having a relationship satisfying
A heat-resistant blocking-resistant coating composition as described in the above item. 5. The heat-resistant blocking-resistant coating composition according to claim 1, wherein the colloidal silica is a colloidal silica surface-treated with aluminate ions. 6. The heat-resistant blocking-resistant coating composition according to claim 1, wherein the coating has a pH of 8.5 or more.