JPS6123658A - Gloss coating of aqueous emulsion type - Google Patents

Abstract

PURPOSE:A gloss coating of aqueous emulsion type which has excellent gloss, pattern forming properties, and elasticity, comprising an aqueous suspension of calcium carbonate obtained by grinding titanium oxide and a synthetic resin emulsion in specified proportions in an aqueous medium. CONSTITUTION:An aqueous emulsion coating comprising 5-70pts.wt., on a solid basis, aqueous dispersion of calcium carbonate obtained by grinding limestone in an aqueous medium, 95-30pts.wt. titanium oxide, and a pigment component and a synthetic resin emulsion in a volume proportion of 30-5%:70-95% on a solid basis. If necessary, a color pigment other than titanium oxide can be added to give a gloss coating other than that of white color. An aforementioned coating in which the PVC content is reduced to 5-10% will have a higher resin content, have excellent elasticity of the coating film, can give a coating of a thickness of several mm. in one coat, and can form a desirable protruded spray pattern and roller pattern.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an aqueous emulsion gloss coating.

[Prior art] Emulsion paints use aqueous emuls of synthetic resins such as vinyl acetate resins and acrylic resins as a vehicle, and color pigments, extender pigments, thickeners, pigment dispersants, freeze stabilizers, It is made by combining anti-inflammatory and h3.

Water-based emulsion type gloss paint is one of the fields of most interest among emulsion paints, but in order to make a paint with a gloss level, for example, t:QQ° specular reflectance of 70% or more, , the pigment volume concentration (PVC) must be at least 30% or less.

In addition, PVC (Pigient Volume Co.
centration) is expressed by the following equation.

Pigment volume PVC (%) = X 10
0Resin volume + Pigment volume As is well known, titanium oxide is mainly used as a pigment in emulsion paints for white paints, but it has the ability to coat thickly,
Extender pigments such as calcium carbonate, clay, talc, and mica are generally used in combination as control agents for toning properties, fluidity, storage stability, and paint cost.

However, since the addition of these extender pigments has the property of significantly reducing the gloss of the coating film, it has conventionally been impossible to add these extender pigments to paints that require high gloss.

The reason for the loss of gloss is that the particle size of these extender pigments used in emulsion paints is coarser than that of titanium oxide, and the particle shapes of clay, talc, mica, etc. are rod-like or flake-like, making it difficult to paint. It is thought that it may roughen the membrane surface.

In order to solve this problem, attempts have been made to use extremely finely ground extender pigments and light calcium carbonate, but the water absorption becomes extremely large, causing shrinkage cracks in the dried paint film, and the use of light calcium carbonate. Since the density of the film was lost, a high-gloss coating could not be obtained.

By the way, heavy calcium carbonate is produced by air-classifying limestone using an impact crusher such as a hammer crusher, but unlike light calcium carbonate, it has a low water absorption rate and does not cause shrinkage cracks in dried paint films. There are advantages, which occur less often. However, when this is used in combination with titanium oxide, the gloss level is extremely reduced.

The inventor of the present invention has conducted various studies to take advantage of the advantages and overcome the disadvantages of heavy calcium carbonate, and has found that the extreme decrease in gloss that occurs when used in combination with titanium oxide is due to the particle size of the heavy calcium carbonate used. I discovered that it is not something that can only be brought about by

In other words, we prepare a dry-pulverized powder in which naturally occurring limestone is dry-pulverized and air-classified, and a wet-pulverized powder in which naturally occurring limestone is wet-pulverized using water as a medium, classified in water, dried in the sun, and then crushed in a crusher in various particle sizes. The degree of reduction in gloss was investigated by using it together with titanium oxide in an aqueous emulsion type gloss paint.

As a result, PVC i made entirely of titanium oxide.

% and 25% gloss paints (60' specular reflectance) both showed high values of 90% and 87%, and Pv
It was hardly affected by the increase in C, but when a part of titanium oxide was replaced with the above-mentioned dry powder, pulverized powder, powder, or wet pulverized powder, the larger the PvC and the larger the degree of substitution, the higher the degree of substitution. In both cases, the gloss level decreased significantly.

Therefore, the present inventor investigated drying of wet-pulverized powder by replacing sun drying with different drying methods, such as heat drying and spray drying. However, even if such different drying methods were employed, the decrease in glossiness could not be prevented.

Based on the results of such research, the present inventors believe that the surface activity of individual particles in the dry state of heavy calcium carbonate powder and the state of the powder affect the gloss when added to paint. I've come to a conclusion.

Therefore, the inventor of the present invention tried dispersing dry-pulverized powder and wet-pulverized powder in water and blending them in a wet state with titanium oxide in a paint, but in both cases, the decrease in gloss was significant.

The present inventor continued to study further, and when the slurry-like calcium carbonate aqueous dispersion obtained by pulverizing by wet pulverization and classification in water was blended into a glossy paint as it was in combination with titanium oxide without drying, it was found that the glossiness The results showed an unexpected effect in that the degree of decrease in

The present inventors believe that wet pulverization increases the surface activity of heavy calcium carbonate particles, and that if they are blended in that state into a water-based emulsion-type glossy paint, the surface activity of the heavy calcium carbonate particles increases. We believe that this is due to improved compatibility with titanium oxide, dispersibility in paints, and compatibility with resins, resulting in good results in terms of gloss. However, if it is dried and turned into powder, such surface activity is lost, which is thought to have an adverse effect on gloss.

Therefore, if dry pulverized materials as well as wet pulverized materials are dried, they exhibit properties that cannot be used in water-based emulsion type glossy paints.

This is true for the gloss of a water-based emulsion type gloss paint in which PVC2S% and 65% by weight of the total titanium oxide is replaced with calcium carbonate (when tested under extremely harsh conditions, the total titanium oxide The gloss level was 87% when using dry-milled powder, but it decreased to 17% when it was replaced with dry-milled powder, and 45% when it was replaced with wet-milled powder. Without drying the slurry-like calcium carbonate aqueous dispersion that has been classified in the
This can be understood from the fact that when used as is in combination with titanium oxide, it exhibited an extremely excellent gloss level of 78%. (See Figure 1) [Summary of the Invention] That is, the present invention provides an aqueous dispersion of calcium carbonate obtained by pulverizing limestone using water as a medium, with a solid content of 5 to 70%.
The solid content of the pigment component and the solid content of the synthetic resin emulsion are 30 parts by volume.
It is an aqueous emulsion type glossy paint in which ~5% = 70-95%.

Of course, colored pigments other than titanium oxide can be added to the aqueous emulsion type glossy paint of the present invention, if necessary, to make a glossy paint other than white.

As a precaution, since heavy calcium carbonate is a natural product, it is natural that the aqueous calcium carbonate dispersion used in the present invention contains trace amounts of impurities other than calcium carbonate.

Surprisingly, it has been found that when the slurry-like calcium carbonate aqueous dispersion is used in combination, the thick coating properties of the paint are improved, and when the suction is applied, a desirable beading pattern is formed. It has also been found that a preferable convex pattern can be formed by roller coating.

Therefore, in the aqueous emulsion type gloss paint of the present invention, the paint with PvC lowered to 5 to 10% has a high resin content,
It has extremely good film elasticity, can be coated several times thicker with one coat, and can form a desirable convex spray pattern or roller pattern. Such a paint is called a single-layer elastic finish coating material in the market, but according to the present invention, an emulsion-type single-layer elastic finish coating material with excellent gloss, pattern-forming properties, and elasticity can be produced.

[Example] The slurry-like calcium carbonate aqueous dispersion used in the present invention is prepared by pulverizing naturally occurring limestone with water using a ball mill, edge runner, colloid mill, etc. to form a slurry, and classifying the slurry in water. It is manufactured by dehydrating it to an appropriate amount of water, but at this time polyphosphate (sodium birophosphate, P
o1yron 135■ (Benkiser Kna
psack Gn+bH)), BoIJ 7 acrylate (Hydroparat 1706 (HenkelIn
ternatinal GIlbH)), polycarboxylate (Dispex @N-40, ^-40 (All
ied Co11 aids), Quinflow■54
0 (Nippon Zeon), styrene-maleic acid monoester copolymer (S14A 1440 H (ARCOChcv)
Facial dispersants such as ical), dispersion stabilizers such as hydroxyethyl cellulose, methyl cellulose, polyacrylates, etc. may also be added.

The concentration of calcium carbonate in the slurry is not particularly specified, but a slurry of 80% or more is difficult to prepare, and a slurry of 20% or less is unstable and contains too much water, making it unsuitable for paint preparation. The particle size of the calcium carbonate particles in the slurry is mostly in the range of 0.1 micron to 1 micron.

The titanium oxide used in the present invention may be either anatase type or rutile type, but rutile type is usually preferred.

Other pigments that can be used in combination can be any pigment that can be used in emulsion paints.

Examples include iron oxide red, iron oxide black, iron oxide yellow, chrome yellow, cobalt blue, and phthalocyanine blue.

Next, the synthetic resin emulsion used in the present invention includes vinyl esters such as vinyl acetate, vinyl esters of saturated carboxylic acids branched at the α-position, unsaturated carboxylic esters such as acrylic esters, methacrylic esters, maleic diesters, It is obtained by emulsion polymerization of one or more vinyl monomers such as styrene, ethylene, vinyl chloride, and acrylonitrile.

Other monomers having copolymerizable functional groups, such as acrylic acid, methacrylic acid, crotonic acid, N-methylolacrylamide, and divinylbenzene, can also be added to the monomers.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

Production Example 1 Natural limestone was coarsely crushed using a hammer crusher, placed in a ball mill with water, and sodium birophosphate was added as a pigment dispersant and sodium polyacrylate was added as a dispersion stabilizer at 0.1% each to the limestone. After operating for 48 hours, it was discharged into a water tank and classified in water, with 90% of the particles having a particle size of 0.5 to 1. A slurry calcium carbonate dispersion with a concentration of 75% was obtained.

Production Example 2 The slurry calcium carbonate obtained in Production Example 1 was dried in the sun and crushed using a Nara-type pulverizer to obtain powdered calcium carbonate.

Examples 1 to 4 The components shown in Table 1 were uniformly stirred and mixed to obtain titanium oxide: L lucium carbonate = 35:65, PVC = 10%, 15%, 2
I got 0% and 25% gloss paint.

[Margin below L] Comparative Examples 1 to 4 The components shown in Table 2 were uniformly stirred and mixed to produce titanium oxide 100
%, pvc=io%, 15%, 20%, 25% gloss paints were obtained.

Margin below E] Comparative Examples 5 to 8 The ingredients in Table 3 were uniformly stirred and mixed to produce titanium oxide: FH.
WI force) Lt sim = 35:65, pvc-io%,
I got 15%, 20%, and 25% paint.

[Left below] Comparative Examples 9 to 12 Commercially available heavy calcium carbonate obtained by crushing and classifying natural limestone in the air was used as powdered heavy calcium carbonate.The ingredients in Table 4 were uniformly stirred and mixed, and then oxidized. Titanium: Calcium carbonate-35: 65, PVC = 10%, 15%,
20%, 25% paint.

[Margins below] The paints obtained in Comparative Test Examples 1 to 4 and Comparative Examples 1 to 4.5 to 8.9 to 12 were applied to a glass plate with a 0.3 inch thick applicator and dried for 4 days to form a coating film. A sample was prepared, and the gloss of the coating film was measured at 60°GLO8S using a gloss meter GM-3 manufactured by Murakami Color Research Institute.

The test results are shown in Table 5 and FIG.

[Margin below]

[Brief explanation of the drawing]

Figure 1 shows the gloss of the coating film obtained in the comparative test (60°GLO
8S) PVC (%) (7) Ifl relation t'/y
There are 7 te.

Claims (1)

[Claims] 1. A pigment component consisting of 5 to 70 parts by weight of an aqueous dispersion of calcium carbonate obtained by crushing limestone using water as a solid content, and 95 to 30 parts by weight of titanium oxide, and a synthetic resin emulsion, The solid content of the pigment component and the solid content of the synthetic resin emulsion are 30-5% by volume: 70-5%
95% water-based emulsion type gloss paint.