JPS634874B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aqueous coating composition particularly suitable for building materials. As the lifespan of buildings increases, these building materials are required to have finishes that are not only fire-resistant but also highly durable.Furthermore, with the mass production of building materials, speeding up of painting and finishing is required. Hitherto, no coating composition has been developed that satisfies these requirements. In other words, coating compositions containing cement as a main component or coating compositions containing semi-hydrated plaster as a main component, so-called "Setsukou Plaster", are conventionally known as representative examples, but the former has a short pot life; Furthermore, since a cured coating is formed by a hydration reaction, the resulting coating is prone to cracks due to volumetric shrinkage, and also has the disadvantage of being susceptible to defects such as efflorescence. Also, the latter is
Generally, the adhesion strength to the substrate is weak, and therefore there are drawbacks such as the need to stretch a wire mesh over the substrate for a foothold. In view of the prior art as described above, the present invention aims to provide a coating composition with excellent performance. These purposes are (a)(i) Acrylic acid or methacrylic acid ester copolymer emulsion resin (ester has 1 to 1 carbon atoms)
8 alkyl group) or a copolymerized emulsion resin of the above acrylic acid or methacrylic acid ester and styrene (styrene content is 30% by weight or less) Solid content...2 to 15% by weight (ii) Bisphenol type epoxy emulsion resin solid Minutes: 1 to 5% by weight (iii) Filler: 25 to 70% by weight (iv) α-type or β-type hemihydrate: 20 to 60% by weight (v) Color pigment: 1 to 5% by weight (vi) 0.8 to 1.2 of the epoxy emulsion resin;
It consists of an equivalent amount of polyamide resin or aliphatic polyvalent amine curing agent, and if necessary, a small amount of various additives, and the weight ratio of [(i) + (ii)] / (iv) is
This is achieved with an aqueous coating composition having a viscosity of 50 to 1000 poise, consisting of 100 parts by weight of a mixture with a pH of 7.5 to 9.5, ranging from 0.15 to 0.28, and (b) 15 to 70 parts by weight of water. The coating composition of the present invention can be coated in a thick film without causing coating defects such as cracks at room temperature or forced drying, so it can be applied not only on-site but also on a factory line. Since the specific composite material is blended in a specific ratio, a coating film with excellent long-term durability, adhesion, alkali resistance, fire resistance, sound absorption, moisture absorption, etc. can be obtained. An alkyl ester monomer having 1 to 8 carbon atoms of acrylic acid, which is a component constituting the acrylic acid or methacrylic ester copolymer emulsion resin used in the present invention, and a carbon number 1 of methacrylic acid.
The alkyl esters of the alkyl ester monomers of ~8 include methyl, ethyl, n-butyl, isobutyl, tert-butyl, 2-ethylhexyl, benzyl, propyl, isopropyl, sec-
Butyl etc. are typically used. Esters having 9 or more carbon atoms are unsuitable because gels may be generated during emulsion polymerization or the emulsion particles may become highly hydrophobic. Copolymer emulsion resins of these acrylic acid (or methacrylic acid) esters and styrene are also used, but if styrene is used in an amount of 30% by weight or more, the weather resistance of the resulting emulsion coating film will be significantly reduced, resulting in poor durability. It is not preferred as a required outdoor emulsion resin. Particularly preferred acrylic acid or methacrylic esters are methyl methacrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, and when styrene is used,
Particularly preferred is 20% by weight or less. If necessary, it is also possible to copolymerize several weight percent of functional group monomers such as acrylic acid, methacrylic acid, and 2-hydroxyethyl methacrylate. Since the acrylic acid (or methacrylic acid) ester copolymer emulsion resin or the copolymerized emulsion resin of acrylic acid (or methacrylic acid) ester and styrene used in the present invention is mixed with semi-hydrated slag, it has a high stability when mixed with semi-hydrated slag. For this purpose, ethers such as alkylphenol polyethylene ether, polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyethylene glycol oleyl ether; sorbitan alkyl ester, polyoxy Nonionic surfactants such as esters such as ethylene sorbitan fatty acid ester and polyglycol fatty acid ester; nonionic surfactants such as polypropylene glycol polyethylene glycol polymer, polyoxyethylene alkylamide, and polyoxyethylene alkylamine can be used alone or in combination with anionic surfactants to form a nonionic surface. It is necessary to use a large amount of active agent and a small amount of anionic surfactant. Advantageously, the molecular weight of these acrylic emulsion resins is from 50,000 to 300,000, preferably from 100,000 to 200,000. Further, the minimum film forming temperature is preferably 5° C. or lower; if it is higher than that, cracks and cracks are likely to occur during film forming. Further, the acrylic emulsion resin preferably has a viscosity of 100 cps or less when the solid content is 40% by weight. 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 or crack due to fading during drying. These resins are blended in the mixture (a) at a solid content of 2 to 15% by weight. If the resin content is less than 2% by weight, the initial hardness, weather resistance, and water resistance of the coating film will decrease. On the other hand, if the resin content exceeds 15% by weight, thick film coating (approximately 1 to 10 mm) cannot be achieved and cracks and cracks are likely to occur. Furthermore, the bisphenol type epoxy emulsion resin used in the present invention is an aromatic diglycidyl ether obtained from bisphenol A and epichlorohydrin, and has an average molecular weight of 350 to 350.
1000 resin is made into a water-dispersed type using an emulsifier, and the solid content of the resin is 1 to 5% by weight in the mixture (a). If the resin content is less than 1% by weight, the adhesion to the substrate will be reduced, and if it exceeds 5% by weight, the weather resistance of the formed coating film will be significantly reduced. The fillers used in the present invention include extender pigments such as calcium carbonate, barium sulfate, magnesium carbonate, talc, clay, and other inorganic particulate materials, and aggregates such as silica sand. The filler is blended in the mixture (a) in a proportion of 25 to 70% by weight. This is because within this range, a coating film free of cracks and cracks can be obtained even in thick coating films. Further, the hemihydrate crystal used in the present invention is α type or β type, and the method utilizes the fact that the hemihydrate crystal transforms into needle-like crystals of dihydrate crystal and hardens. The hardening mechanism is due to the entanglement of crystals, and the transition of dihydrate to needle-shaped crystals is accompanied by an apparent volumetric expansion, so cracks due to volumetric contraction are less likely to occur as with cement, and efflorescence is much less likely to occur. will decrease. Furthermore, the curing of the semi-hydrated slag can be slowed down by the use of an alkaline component such as a curing agent for epoxy resin, which will be described later, resulting in a longer pot life and improved workability. In the present invention, the hemihydrate is blended in the above mixture (a) in a proportion of 20 to 60% by weight. If the amount of semi-hydrated film is less than 20% by weight, cracks and cracks will easily occur when forming a thick film. On the other hand, if it exceeds 60% by weight, the coating film becomes brittle.
Furthermore, water resistance is significantly reduced. Further, the coloring 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 be used. For example, if you want to color it black, you can use carbon black, iron oxide, etc. If you want to color it red, you can use Bengara, etc.
For green, examples include chromium oxide, for blue, cyanine blue, etc., and for white, titanium dioxide, etc. The colored pigment is 1 in the above mixture (a)
It is blended in a proportion of ~5% by weight, and sufficient coloring can be achieved by blending within this range. Further, as the curing agent for epoxy resins used in the present invention, polyamide resins or ethylenediamine obtained by polycondensation of diamines or diamine derivatives and dibasic acids or dibasic acid derivatives, etc.
Aliphatic polyvalent amines such as diethylenetriamine and triethylenetetramine or phenolic resins,
Aliphatic polyamines modified with epoxy resins and the like are suitable. It is necessary to use the curing agent in an amount of 0.8 to 1.2 equivalents of 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. Additives used in the present invention include, for example, 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. Furthermore, the solid content of (i) acrylic acid (or methacrylic acid) ester copolymer emulsion resin or copolymerization emulsion resin of acrylic acid (or methacrylic acid) ester and styrene in the mixture (a); and (ii)
the sum of the solid content of the epoxy emulsion resin, and (iv)
The weight ratio with semi-hydrated water is [(i) + (ii)] / (iv) = 0.15
~0.28. If this ratio is less than 0.15, the initial hardness of the coating film will not be achieved, the water resistance will decrease, and a thick film with good coating performance cannot be formed.On the other hand, if this ratio is greater than 0.28 When the film is thick, cracks and cracks are more likely to occur. In addition, the weight ratio of [(ii)+(vi)]/[(i)+(ii)+(vi)] is particularly preferably 0.2 to 0.45; if this ratio is smaller than 0.2, the adhesion will decrease; On the other hand, this ratio
If it is larger than 0.45, the weather resistance decreases. Further, the pH of the mixture (a) is suitably 7.5 to 9.5. PH
If it is less than 7.5, the curing process will be rapid, the pot life will be shortened, and workability will be reduced. On the other hand, if the pH exceeds 9.5, the resin, additives, etc. will be saponified by alkali, which is not preferable. The aqueous coating composition of the present invention comprises 100% of the above mixture (a)
The viscosity of the composition is 50 to 1000 poise by blending 15 to 70 parts by weight of water. This is because within this range, the curability and coating workability of the coating film are good. In addition, if the amount of water is less than 15 parts by weight, the acrylic emulsion will tend to aggregate when mixed with a half-water mixture, while if it exceeds 70 parts by weight, the solid content will decrease and it will become dull during drying, causing cracks and cracks. . In addition, the present inventors used vinyl acetate emulsion resins such as vinyl acetate resin, vinyl acetate-acrylic resin, ethylene-vinyl acetate resin, or styrene-butadiene emulsion resin, which are typically used in the paint industry. We also considered emulsion resin, but
For example, the former has poor weather resistance and alkali resistance, and also lacks long-term durability, while the latter has poor weather resistance and is therefore not suitable for the present invention. The aqueous coating composition of the present invention as described above can be applied to building materials such as asbestos cement board, pulp cement board, wood wool cement board, wood chip cement board, perlite board, Keikal board, charcoal mug board, settsukou board, or plywood. I can do it. The coating method is, for example, spray coating, flow coating, etc. on the surface of the building material base material, but it is also possible to apply a thick coating film of about 1 to 10 mm, so it is also possible to finish with an uneven pattern using a pattern roller etc. , forced drying at room temperature or below 100℃. The present invention will be explained below with reference to Examples. In the examples, parts and percentages are based on weight. Examples 1 to 3 and Comparative Examples 1 to 4 The aqueous coating compositions shown in Table 1 were spray-coated onto the surface of an asbestos slate board to a dry film thickness of approximately 1.5 mm, and the coating was left at room temperature for 7 days to form a coating film. Hardened. The results of the adhesion test, water resistance test, freeze-thaw cycle test, and accelerated weather resistance test of the obtained asbestos slate board are shown in the lower part of Table 1. The test method and evaluation were performed as follows. (1) Adhesion Test method: 2mm cellophane tape peeling test of coating film Evaluation: ◎...50/50, 〇...49/50 to 26/50, ×...
25/50 or less (2) Water resistance test Test method: Immersed in tap water for 1 month Evaluation: ◎...No abnormality at all, 〇...Extremely some abnormalities, ×...All abnormalities (3) Freeze-thaw cycle test Test method : [-20℃ x 16 hours freezing → room temperature x 8 hours] 35 cycles Evaluation: ◎...no abnormality, ○...very few abnormalities, ×...complete abnormalities (cracks present) (4) Accelerated weathering resistance test Test method: Sunshine carbon irradiation for 2000 hours Evaluation: ◎...no abnormality, ○...very small abnormality, ×...complete abnormality (with yoking) As is clear from Table 1, the aqueous coating composition of the present invention had excellent coating performance, but compared to Comparative Example 1 in which an excessive amount of hemihydrate was added, Comparative Example 2 in which no epoxy resin was added, Comparative Example 3 in which an acrylic resin containing an excessive amount of styrene was used, and vinyl acetate. In Comparative Example 4 using resin, the coating film performance was poor.

【table】

[Table] Examples 4 to 6 The aqueous coating compositions of Examples 1, 2, and 3 were spray-coated onto the surface of an uncured plaster board to a dry film thickness of approximately 1.5 mm, dried to the touch, and then heated at 80°C. After heating for 20 minutes, it was left at room temperature for 4 days. The resulting coating film had excellent coating performance similar to Examples 1, 2, and 3.

Claims (1)

[Scope of Claims] 1 (a)() Acrylic acid or methacrylic acid ester copolymer emulsion resin (ester is an alkyl group having 1 to 8 carbon atoms) or copolymerization emulsion resin of the above-mentioned acrylic acid or methacrylic acid ester and styrene. (Styrene content is
(30% by weight or less) Solid content: 2 to 15% by weight () Bisphenol type epoxy emulsion resin solid content: 1 to 5% by weight () Filler: 25 to 70% by weight () α type or β-type hemihydrate
......20 to 60% by weight () Coloring pigment ......1 to 5% by weight () 0.8 to 5% of the above epoxy emulsion resin
consisting of 1.2 equivalents of polyamide resin or aliphatic polyvalent amine curing agent, and [()+()]/
The weight ratio of () is in the range of 0.15 to 0.28 Ω
an aqueous coating composition having a viscosity of 50 to 1000 poise, comprising 100 parts by weight of a mixture of 7.5 to 9.5 and (b) 15 to 70 parts by weight of water. 2 The above [()+()]/[()+()+(
)]
2. Aqueous coating composition according to claim 1, characterized in that the weight ratio of 0.2 to 0.45. 3. The aqueous coating composition according to claim 1, wherein the minimum film forming temperature of the acrylic copolymer emulsion resin is 5° C. or lower.