JPS63162770A - Water-base covering composition for cement base plate - Google Patents

Abstract

PURPOSE:To obtain the title composition which gives a uniform covering film free from sagging, cracking, etc., by mixing two kinds of specified emulsion resins, a hollow inorganic powder, cement, a pigment, a curing agent comprising a polyamide resin or aliphatic polyamine, and water. CONSTITUTION:2-15wt%, on a solid basis, 1-8C alkyl (meth)acrylate copolymer emulsion resin (a) having a minimum film-forming temperature of 5 deg.C or lower is mixed with 1-5wt%, on a solid basis, bisphenol epoxy emulsion resin (b) obtained by dispersing in water in the presence of an emulsifier a resin which comprises an aromatic diglycidyl ether, has an average molecular weight of 350-1,000, and is made from bisphenol A and epichlorohydrin, 10-40wt% hollow inorganic powder (c) having an average particle diameter of 30-300mum, 20-60wt% cement (d), 1-5wt% color pigment (e), a curing agent (f) comprising a polyamide resin or an aliphatic polyamine, the weight ratio of (a+b) to (f) being 0.15-0.28:1 and the equivalent ratio of (b) to (f) being 1:0.8-1.2, and if required, a filler and an additive. 100pts.wt. this mixture is then mixed with 15-70pts.wt. water to give the title composition having a viscosity of 50-500P.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an aqueous coating composition for cement substrates having uneven surfaces that is less likely to cause sagging or cracking.

<Prior art and problems> Mortar, concrete, cement such as slate: Building materials using M-grade substrates are often used for exterior materials, block walls, etc.

As the lifespan of buildings increases, these building materials are required to have highly durable finishes, and with the mass production of building materials, speedy painting finishing is also required. A coating composition that satisfies this requirement has not yet been developed. In other words, conventionally, for example, when painting an uncured cement product, after leaving it for 1 to 2 weeks, the surface of the cement product was coated.
Unless the coating composition is applied after adjusting the hydrogen content and water content, coating film defects such as peeling and discoloration may occur. Furthermore, if a conventional coating composition, such as a coating composition containing acrylic emulsion resin and cement as the main components, is applied and then a topcoat is applied with a solvent-based paint with excellent weather resistance, the undercoat film lacks solvent resistance. Therefore, there were drawbacks such as reduced gloss and wrinkles in the coating film. Also recently,
In order to impart fashionability to cement product substrates, substrates with wavy or random uneven patterns formed on the surface of the substrate have become widely used.

If a thick film of paint is applied to a cement substrate with such an uneven surface, the paint will sag, and the paint will accumulate in the recesses, resulting in a thicker film than necessary.Conversely, the convex parts will become a thin film, making it difficult to form a uniform paint film. Furthermore, there were other drawbacks such as cracking in the coating film.

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, it is an object of the present invention to provide a coating composition with excellent performance that does not have the above-mentioned drawbacks.

<Means for solving the problem> These objectives are as follows: (a) (i) Copolymer emulsion resin of acrylic acid or methacrylic acid alkyl ester (alkyl group has 1 to 8 carbon atoms) solid content... 2 to 15% by weight (ii) Bisphenol type epoxy emulsion resin solid content...1 to 5% by weight (iii)
Hollow inorganic powder with average particle size of 30-300μ
...10-40% by weight (iv) cement
...20-60% by weight (v) Coloring pigment
... 1 to 5% by weight (Vl) of a polyamide resin or aliphatic polyvalent amine curing agent in an amount of 0.8 to 1.2 equivalents of the epoxy emulsion l fat, and further a small amount of various additives as necessary, and ( (i) + (ii)) / (iv) 100 parts by weight of a mixture having a gravimetric ratio of (0.15 to 0.28) and 100 parts by weight of a mixture and 15 to 70 parts by weight of water. This is achieved with a 50-500 poise aqueous coating composition.

The coating composition of the present invention can be applied immediately not only to hardened cement substrates with uneven surfaces but also to uncured cement substrates, so the construction period can be shortened, and the coating composition can form a thick film without causing sagging or cracking when dried at room temperature or by forced drying. Since it can be painted, it can be applied not only on-site but also on a factory line.Furthermore, because it contains a specific proportion of organic and inorganic composite materials, it has excellent long-term durability, adhesion, and alkali resistance. A coating film is obtained, and even if a water-based or solvent-based paint is repeatedly applied as a top coat, it is possible to obtain a coating film without the above-mentioned coating film defects.

Alkyl ester monomers of acrylic acid having 1 to 8 carbon atoms, methacrylic acid (7) alkyl ester monomers having 11 to 8 carbon atoms, which are components of the copolymerized emulsion resin of acrylic acid or methacrylic acid alkyl ester used in the present invention. Alkyl groups include methyl, ethyl, n-butyl, isobutyl, tert-butyl, 2
-Ethylhexyl, benzyl, propyl, isopropyl, 5eC-butyl, etc. are typically used.

Alkyl groups having 9 or more carbon atoms may generate a gel during emulsion polymerization or make emulsion particles highly hydrophobic, making them unsuitable for the synthesis of emulsion resins for cement admixture. or,
A copolymer emulsion resin containing up to 30% by weight of styrene in these acrylic acid (or methacrylic acid) alkyl esters may also be used. However, 30% by weight of styrene
If this is used, the weather resistance of the resulting emulsion coating film will be significantly reduced, making it undesirable for use as an outdoor emulsion resin that requires durability.

Particularly preferred acrylic acid or methacrylic acid alkyl esters include methyl methacrylate, ethyl acrylate,
Butyl acrylate, 2-ethylhexyl acrylate, and when styrene is used, 20% by weight or less is particularly preferred. Furthermore, if necessary, it is also possible to copolymerize several 1% functional group monomers such as acrylic acid, methacrylic acid, and 2-hydroxyethyl methacrylate. Since the copolymerized emulsion resin of acrylic acid (or methacrylic acid) alkyl ester used in the present invention is mixed with cement, it is preferable to have alkali resistance and excellent cement mixing stability. Nonionic surfactants are suitable as emulsifiers. Advantageously, these acrylic emulsion resins have a molecular weight of 50,000 to 300,000, preferably 100,000 to 200,000. Further, the minimum film forming temperature is preferably 5° C. or lower. This is because if it exceeds this range, cracks are likely to occur during film formation. Also, acrylic emulsion resin has a viscosity of 10 Qc when the solid content is 40% by weight.
ps or less is preferable. If it exceeds that range, it is necessary to increase the amount of water to lower the viscosity, which lowers the solids content and makes the coating film more likely to crack due to fading during drying.

These resins have a solid content of 2 to 2 in the mixture (a).
It is blended at a ratio of 15% by weight. If the resin content is less than 2%, the initial hardness and weather resistance of the coating film will decrease, and efflorescence will likely occur. On the other hand, if the resin content exceeds 15% by weight, thick film coating (approximately 0.5 to 10% by weight) cannot be achieved and cracks are likely to occur.

The bisphenol-type epoxy emulsion resin used in the present invention is made into a water-dispersible type by using an aromatic diglycidyl ether obtained from bisphenol A and epichlorohydrin and having an average molecular weight of 350 to 1000 as an emulsifier. The solid content used in the mixture (a) is 1 to 5% by weight. 1 resin
If it is less than 5% by weight, the adhesion to the substrate will be reduced, and if it exceeds 5% by weight, the weather resistance of the formed coating will be significantly reduced.

The hollow inorganic powder used in the present invention is a powder that is completely hollow inside and the hollow part is completely closed by a shell, or a powder that is in the form of independent or open cells with partition walls inside, such as pumice, Its average particle size is 30-30
A value of approximately 0μ is appropriate. If the average particle size is less than 30μ, cracking tends to occur, and the strength of the coating film decreases.
If it exceeds 00μ, it tends to sag, and the coating film lacks smoothness, resulting in poor appearance.

Representative examples of the hollow inorganic powder include glass balloons, glass balloons, aluminosilicate balloons, silica balloons, alumina balloons, zirconia balloons, and carbon balloons. In particular, from the viewpoint of coating film strength, it is desirable to have a 50% breaking hydrostatic pressure of 10 kg/ci or more, and specific examples include glass balloons, aluminosilicate balloons, alumina balloons, and zirconia balloons. This hollow inorganic powder is blended to obtain coatings without sagging or cracking even in thick coatings, to improve brittleness, and to increase the coating composition.Furthermore, it reduces the specific gravity of the coating composition and improves coating workability. It also has the effect of improving. In addition, when applying a thick film to a cement substrate with an uneven surface using only ordinary fillers such as extender pigments and aggregates,
Sauces and cracks cannot be prevented. The hollow inorganic powder is blended in the mixture (a) at a ratio of 10 to 40,
The above effects can be obtained within this range.

Examples of the cement used in the present invention include Portland cement, blast furnace cement, silica cement, and alumina cement, but the type thereof is not particularly limited. In the present invention, cement is blended in the above-mentioned mixture (a) at a ratio of 20 to 60% by weight. If the weight of the cement is less than 20% by weight, cracking is likely to occur when the film is thick, and adhesion is reduced. On the other hand, if it exceeds 60% by weight, the coating film becomes brittle and efflorescence is likely to occur.

The colored pigment used in the present invention is typically a general inorganic pigment, but depending on the color, an organic pigment having alkali resistance and weather resistance may also be used. For example, to color black, use carbon blank, iron oxide, etc., for red, use Bengara, etc., for green, use chromium oxide, for blue, use cyanine blue, etc. For white, use titanium dioxide, etc. can be exemplified.

The coloring pigment is blended in the above mixture (a) in a ratio of 1 to 5 by weight, and by blending within this range, sufficient coloring can be achieved.

As the curing agent for epoxy resins used in the present invention, polyamide resins obtained by polycondensation of diamines or diamine transparent conductors with dibasic acids or dibasic acid derivatives, or aliphatic polyamide resins such as ethylenediamine, diethylenetriamine, triethylenetetramine, etc. Polyvalent amines or aliphatic polyamines modified with phenolic resins, epoxy resins, etc. are suitable. It is necessary to use the curing agent in an amount of 0.8 to 1.2 equivalents based on the epoxy group of the epoxy resin. If the amount is less than 0.8 equivalents or more than 1.2 equivalents, the original properties of the epoxy resin, such as adhesion and flexibility, will be significantly reduced, and other performances such as durability will also be deteriorated, which is not preferable.

Examples of additives used in the present invention include dispersants, antifoaming agents, thickeners, preservatives, antifungal agents, and coating agents to improve pigment dispersibility, coating workability, and storage stability. Examples include film-forming aids for improving the film-forming properties of the film.

In addition, in the present invention, in order to improve the brittleness of the coating film and increase its weight, extender pigments such as calcium carbonate, barium sulfate, talc, and clay; and fillers such as aggregates with a particle size of 300 μm or less such as silica sand are added to the above mixture (a). It is also possible to incorporate it within the range of 40% by weight or less.

The weight ratio of (i) the solid content of copolymerized emulsion resin of alkyl ester of acrylic acid or methacrylic acid, (ii) the solid content of epoxy emulsion resin, and (iv) cement in the above mixture (a) is [(i)+(ii)
3/<iv) -0.15 to 0.28. If this ratio is smaller than 0.15, the initial hardness of the coating film will not be achieved and efflorescence will occur, making it impossible to form a thick film with good coating performance. 0.2
When it is larger than 8, cracks tend to occur when the film is thick.

The above ((ii) + (vi)) / [(i) + (ii)
The weight ratio of ) + (vi)) is particularly preferably 0.2 to 0.45; if this ratio is smaller than 0.2, the adhesion will be reduced, while if this ratio is larger than 0.45, the weather resistance will be reduced. Sexuality decreases.

The aqueous coating composition of the present invention comprises the above mixture (a) 100
15 to 70 parts by weight of water is added to the heavy base portion to give the composition a viscosity of 50 to 500 poise. This is because, within this range, cement hardenability and painting workability are good. If the amount of water is less than 15 parts by weight, the acrylic emulsion will tend to aggregate when mixed with cement, while if it exceeds 70 parts by weight, the solid content will decrease and it will become loose and crack when drying.

The present inventors have used vinyl acetate-based emulsion resins such as vinyl acetate resin, vinyl acetate-acrylic resin, and ethylene-vinyl acetate resin, or styrene-butadiene-based emulsion resins, which are typically used in the paint industry, as emulsion resins. We have also investigated emulsion resins that have been used in the past, but for example, the former has poor weather resistance, alkali resistance, and lacks long-term durability, and the latter has poor weather resistance and is not suitable for the present invention. found.

The aqueous coating composition of the present invention as described above is applied to the surface of a cement substrate by a conventional coating method such as spray coating, roller coating, flow coating, etc. The aqueous coating composition of the present invention can provide a good coating even in a thick film of about 0.5 to 10 mm, and is force-dried at room temperature or at a temperature of 100° C. or lower. Moreover, a top coat can be further applied satisfactorily to the obtained coating film. The materials used as this top coat include, for example, acrylic ester copolymer resins, styrene-based resins such as styrene-acrylic ester copolymers, vinyl acetate-based resins such as vinyl acetate-acrylic ester copolymers, and vinyl chloride resins. Polymers obtained by solution polymerization of vinyl chloride, such as polyacrylic acid ester copolymer, acrylic urethane based on acrylic ester, acrylic urethane resin based on styrene-acrylic ester, fluoroolefin and vinyl ether as essential components, and crosslinked. solvent-based paints based on fluorine-containing copolymer resins, acrylic ester-based paints, styrene-based paints such as styrene-acrylic ester copolymers, vinyl acetate-based paints such as vinyl acetate-acrylic ester copolymers, etc. water-based paints based on emulsion resins, unsaturated polyesters, polyesters (
meth)acrylate, urethane(meth)acrylate,
- Examples include epoxy (meth)acrylate and acrylic (meth)acrylate resin type UV-curable paints.

<Effects of the Invention> The coating composition of the present invention does not sag even when applied to a cement substrate having an uneven surface, provides a coating film with a uniform thickness, and can be coated in a thick film without causing cracks or the like. It is.

Furthermore, since it can be applied to uncured cement substrates, the construction period can be shortened, and it also has long-term durability, excellent adhesion, alkali resistance, and excellent topcoat properties.

The present invention will be explained in more detail with reference to Examples below.

The blending ratios of the compositions in Examples and Comparative Examples are shown in parts by weight.

Examples 1 to 3 and Comparative Examples 1 to 5 The aqueous coating compositions having the formulations shown in Table 1 were coated with an average height difference of about 7.
The coating was applied by spraying onto the surface of a corrugated asbestos slate board with a wavy surface to give a total dry film thickness of 2.0 mm, and the coating was left at room temperature for 7 days to harden.

Adhesion of the obtained colored asbestos slate board, accelerated efflorescence test, freeze-thaw cycle test, accelerated weather resistance test,
The results of each test on the appearance of the coating film are shown in the lower part of Table 1. The test method and evaluation were performed as follows.

(1) Adhesion test method: 2 mm cellophane tape peeling test of coating film Evaluation: ◎...5 015 0, ○...49
150-26150, ×...25150 or less (2) Efflorescence acceleration test Test method: 20 cycles evaluation in saturated slaked lime atmosphere [5°C x 16 hours → 20°C x 8 hours] Evaluation: ◎...No abnormality at all , ○...There is a very small abnormality, X...There is a complete abnormality (3) Freeze-thaw cycle test Test method: (-20℃ x 16 hours freezing → room temperature x 8 hours)
35 cycle evaluation: ◎... No abnormality at all, ○... Very few abnormalities, ×... Fully abnormal (with cracks) (4) Accelerated weathering test test method: Sunshine carbon irradiation for 2000 hours Evaluation: ◎... No abnormalities at all, ○... Very few abnormalities, ×... Fully abnormalities (with chalking) (5) Paint film appearance test method, second sight judgment evaluation: 20... Uniform coating film formation ○...Very little sagging and cracking X...Many sagging and cracking As is clear from Table 1, the aqueous coating composition of the present invention had excellent coating performance. However, Comparative Example 1 in which excessive cement was added, Comparative Example 2 without hollow inorganic powder, Comparative Example 3 without epoxy resin, Comparative Example 4 without acrylic resin, and Comparative Example 5 using vinyl acetate resin. All had poor coating film performance.

Claims (2)

[Claims] (1) (a) (i) Copolymer emulsion resin of acrylic acid or methacrylic acid alkyl ester (the alkyl group has 1 to 8 carbon atoms) Solid content...2 to 15% by weight (ii) Bisphenol type epoxy emulsion Resin solid content...1 to 5% by weight (iii) Hollow inorganic powder with an average particle size of 30 to 300μ...10 to 40% by weight (iv) Cement...20 to 60% by weight (v) Coloring pigment... 1 to 5% by weight (vi) 0.8 to 1% of the epoxy emulsion resin.
2 equivalents of polyamide resin or aliphatic polyamine curing agent,
and further comprises fillers and additives as necessary, and the weight ratio of [(i)+(ii)]/(iv) is 0.1
An aqueous coating composition for a cement substrate having a textured surface and having a viscosity of 50 to 500 poise, comprising 100 parts by weight of a mixture in the range of 5 to 0.28 and (b) 15 to 70 parts by weight of water. (2) The aqueous coating composition according to claim (1), wherein the copolymer emulsion resin (a)(i) has a minimum film forming temperature of 5°C or less.