JPH0573137B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a sealer for inorganic porous substrates, and more particularly to a sealer for inorganic porous substrates that has excellent properties such as adhesion, water resistance, durability, and suitability for overcoating. (Prior art and problems to be solved by the invention) Conventionally, relatively low molecular weight moisture-curing urethane resins, solvent-based resins, etc. have been used as resins for sealing inorganic porous substrates. . However, the former poses problems due to its toxicity, and the latter poses problems such as fire danger and environmental pollution due to the use of organic solvents, and there is a strong demand for water-based compositions. Various types of water-based sealers that have water-soluble resins or water-dispersible resins as their main ingredients have been studied. Those that have such properties have poor impregnating properties and adhesion to substrates, and do not have long-term durability. Furthermore, methods using a mixture of a water-soluble resin and an aqueous resin dispersion are being considered, such as a method of blending 5 to 80% of a water-soluble resin into an acrylic emulsion (Japanese Patent Application Laid-Open No. 141769/1989), Methods such as blending polyvinyl alcohol into a combined aqueous emulsion (Japanese Patent Application Laid-Open No. 53-97018) have been proposed, but each method has its own drawbacks, and a water-based sealer with sufficient performance has not been obtained. This is the current situation. (Technical means for solving the problems) The present invention solves the above-mentioned problems, namely, the toxicity, fire danger, and environmental pollution of sealers whose main components are moisture-curing urethane and solvent-based resins. This solution solves all the problems of water-based sealers such as water resistance, insufficient impregnation, insufficient adhesion, and durability. As a result of extensive research, the present inventors have found that an aqueous resin dispersion obtained by heat-treating an acrylic aqueous resin dispersion and a specific polyvinyl alcohol under specific conditions in the presence of a polymerization initiator can be used as a conventional aqueous sealer. The present inventors have discovered that they do not have any of the above-mentioned drawbacks, and that there is no fear of toxicity or environmental pollution, leading to the completion of the present invention. That is, the present invention provides an acrylic aqueous resin dispersion,
This relates to a sealer for inorganic porous substrates containing an aqueous resin dispersion obtained by heat-treating a mixture of polyvinyl alcohol with a saponification degree of 80 ol% or higher and a polymerization initiator at a temperature of 40°C or higher. . Examples of the acrylic aqueous resin dispersion in the present invention include acrylic resin emulsions as well as acrylic copolymer emulsions such as acrylic-styrene resin emulsions, acrylic-vinyl acetate emulsions, and acrylic-styrene-vinyl acetate emulsions. can. Such an acrylic aqueous resin dispersion is obtained by emulsion polymerization of an acrylic polymerizable monomer or this and other copolymerizable monomers by a well-known method. For example, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)
(Meth)acrylates such as acrylate and cyclohexyl (meth)acrylate; Acrylic cyanide compounds such as (meth)acrylonitrile; Hydroxy group-containing acrylic monomers such as hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate Acrylic amides or derivatives thereof such as (meth)acrylamide and N-methylol (meth)acrylamide; Amino group-containing acrylic monomers such as dimethylaminoethyl (meth)acrylate; Ethylene glycol di(meth)acrylate Polyfunctional acrylic monomers such as; glycidyl group-containing acrylic monomers such as glycidyl (meth)acrylate and allyl glycidyl ether; (meth)acrylic acid, crotonic acid, itaconic acid, fumaric acid,
Examples include acrylic unsaturated carboxylic acids such as maleic acid, monomethyl fumarate, and monoethyl maleate, or derivatives thereof, and one or more of these may be used. In addition to these acrylic monomers, styrene, α-methylstyrene, α-chlorostyrene,
Aromatic unsaturated monomers such as vinyl toluene; copolymerizable monomers such as vinyl halides such as vinyl fluoride and vinyl chloride; and vinyl esters such as vinyl acetate and vinyl propionate can also be used in combination. The aqueous acrylic resin dispersion of the present invention may be prepared by emulsion polymerizing the polymerizable monomers using a polymerization initiator in the presence or absence of an emulsifier. Examples of the polymerization initiator include ammonium persulfate, persulfate Known water-soluble or oil-soluble initiators such as potassium, hydrogen peroxide, and benzoyl peroxide can be used. Further, at this time, sodium bisulfite, L-ascorbic acid, etc. may be used as a reducing agent to form a redox-based initiator. Examples of emulsifiers used as necessary include anionic activators such as sodium lauryl sulfate and nonionic activators such as polyoxyethylene alkyl ether. Furthermore, a chain transfer agent such as lauryl mercaptan may be used for the purpose of controlling the molecular weight during polymerization. Furthermore, multi-stage emulsion polymerization may be performed by changing the composition of polymerizable monomers and the like at each stage during emulsion polymerization. The polyvinyl alcohol used in the present invention has a saponification degree of
The degree of saponification is 80 mol% or more, preferably 87 mol% or more. Use of polyvinyl alcohol with a saponification degree of less than 80 mol % is not preferred because the degree of crystallinity decreases or the hydrophilicity becomes strong, resulting in a decrease in water resistance when used as a sealer for inorganic porous substrates. The amount of polyvinyl alcohol used in the present invention is not particularly limited, but when used as a sealer for inorganic porous substrates, the solid content is determined based on 100 parts by weight of the aqueous resin dispersion in terms of adhesion to the substrate and water resistance. The ratio is preferably in the range of 1 to 30 parts by weight, more preferably 5 to 25 parts by weight. Further, the degree of polymerization of the polyvinyl alcohol in the present invention is preferably in the range of 200 to 2,600, more preferably in the range of 500 to 2,400 in terms of water resistance and viscosity of the aqueous resin dispersion finally obtained. . The polyvinyl alcohol used in the present invention is a polymer in which a portion of the vinyl alcohol units are substituted with other vinyl monomer units, or a polymer in which a portion of the hydrogen atoms of the hydroxyl groups present in the polyvinyl alcohol are substituted with other compounds. For example, a partially butyralized polymer may be used. As the polymerization initiator used in producing the aqueous resin dispersion of the present invention, those used in the emulsion polymerization of the aqueous resin dispersion described above can be used as they are. Also,
The above-mentioned reducing agent may be used if necessary. The amount of the polymerization initiator used at this time is 0.02 to 0.2% by weight based on the total solid content of the aqueous acrylic resin dispersion and polyvinyl alcohol (0.01 to 0.1% by weight in terms of solid content of polyvinyl alcohol). If it is less than 0.02% by weight, the effect of its addition will not be effectively expressed, while if it exceeds 0.2% by weight, the viscosity will increase excessively during the heat treatment process, and the suitability as a sealer for inorganic porous substrates will be lost. . The sealer for inorganic porous substrates of the present invention contains a mixture consisting of the acrylic resin dispersion, polyvinyl alcohol with a saponification degree of 80 mol% or more, and a polymerization initiator.
It is obtained by heat treatment at a temperature of 40 degrees Celsius or higher, preferably at a temperature of 50 to 95 degrees Celsius. In the present invention, the significance of heat-treating the above mixture is that, compared to a simple mixture of an acrylic aqueous resin dispersion and polyvinyl alcohol, when applied to an inorganic porous substrate, the impregnation into the substrate is reduced. In addition to improving adhesion and water resistance, the amount of polyvinyl alcohol used can also be reduced. If the heat treatment temperature is less than 40°C, the decomposition of the polymerization initiator will be extremely slow, and the solubility of polyvinyl alcohol in water will decrease, and the heat treatment effect will not be effectively exerted, resulting in an inorganic porous group having the above characteristics. I can't get a sealer for wood. The sealer for inorganic porous substrates of the present invention contains the aqueous acrylic resin dispersion obtained by the above procedure. This aqueous resin dispersion can be used as it is as the sealer for inorganic porous substrates of the present invention, but if necessary, it may be used by adding film-forming aids, pigments, fillers, toners, wetting agents, etc.
However, the amount of pigment, filler, and toner used is 100 parts by weight of the aqueous resin dispersion (in terms of non-volatile content) in order not to impair the characteristics of the above-mentioned acrylic aqueous resin dispersion.
The amount is preferably 300 parts by weight or less. (Effects of the Invention) The sealer for inorganic porous substrates of the present invention is an aqueous resin dispersion obtained by heat-treating a mixture consisting of an acrylic aqueous resin dispersion, polyvinyl alcohol, and a polymerization initiator, as described above. It contains as an active ingredient, and is excellent in terms of durability such as frost damage resistance, lifting resistance during the application of the top coat, and interlayer adhesion with the top coat. , concrete, lightweight aerated concrete, slate board,
It can be suitably used as a sealer for base materials such as calcium silicate plates. (Examples) The present invention will be described in detail below with reference to Examples, but the present invention is not limited to the following Examples. In addition, parts in the examples are by weight unless otherwise specified. Production example 1 500ml of deionized water was added to a separable flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer.
After adding 8 parts of sodium lauryl sulfate,
The temperature was raised to 70° C. while stirring and blowing nitrogen gas. After that, 160 parts of methyl methacrylate,
A polymerizable monomer mixture consisting of 80 parts of styrene, 152 parts of butyl acrylate, and 8 parts of methacrylic acid was uniformly dropped over 2 hours. 10% at the same time during this period
10 parts of an aqueous ammonium persulfate solution was uniformly added dropwise over 2 hours. Thereafter, the mixture was aged for 1 hour and then cooled. The thus obtained aqueous resin dispersion (1) exhibited the following special values: non-volatile content of 43.5%, pH of 9.0, viscosity of 150 cps (B-type viscometer), and minimum film forming temperature of 35°C. 200 parts of the obtained aqueous resin dispersion (1) and Kuraray Poval
PVA-117 (Polyvinyl alcohol manufactured by Kuraray Co., Ltd.:
10% aqueous solution with polymerization degree of 1700 and saponification degree of 98-99 mol%)
After charging 150 parts into a separable flask, the temperature was raised to 70° C. while stirring while blowing nitrogen gas. Thereafter, 2 parts of a 1% aqueous solution of ammonium persulfate was added, and heat treatment was performed at 70°C for 60 minutes.
Immediately after the heat treatment was completed, it was cooled and 6.3 parts of 25% ammonia water was added to obtain an aqueous resin dispersion (1). The obtained aqueous resin dispersion (1) has a nonvolatile content of 29.0
%, PH8.9, viscosity 3000 cps (B-type viscometer), and the minimum film forming temperature was 0°C or less. The resulting aqueous resin dispersion (1) was coated on a Teflon plate and dried, then peeled off and the resulting coating film was heated at boiling point for 4 hours using a Soxhlet extractor with water as a solvent to obtain polyvinyl When alcohol was extracted from the paint film, it was confirmed that 0.2 parts of polyvinyl alcohol was extracted per 100 parts of the paint film. Production Example 2 After 350 parts of deionized water was charged into the same separable flask as used in Production Example 1, the temperature was raised to 60° C. while stirring while blowing nitrogen gas. After that, 200 parts of methyl methacrylate, 100 parts of cyclohexyl methacrylate, 90 parts of 2-ethylhexyl acrylate, 4 parts of glycidyl methacrylate
10 parts of Emulgen 950 (manufactured by Kao Corporation: polyoxyethylene nonyl phenyl ether) and Lebenol WZ to a polymerizable monomer mixture consisting of 6 parts of acrylic acid and 6 parts of acrylic acid.
A pre-emulsion mixture prepared by adding 16 parts of a 25% aqueous solution of sodium polyoxyethylene nonyl phenyl ether sulfate (manufactured by Kao Corporation) and 120 parts of deionized water was uniformly dropped over a period of 3 hours. During this time, 60 parts of a 2% aqueous potassium persulfate solution and 12 parts of a 5% aqueous sodium bisulfite solution were added to the flask in portions every 10 minutes until the dropwise addition of the pre-emulsion mixture was completed. After the dropwise addition was completed, the mixture was aged for 1 hour and cooled. The thus obtained aqueous resin dispersion (2) exhibited the following special values: nonvolatile content of 42.5%, pH of 9.1, viscosity of 84 cps (B-type viscometer), and minimum film-forming temperature of 65°C. 200 parts of the obtained aqueous resin dispersion (2) and Kuraray Poval PVA-205 (manufactured by Kuraray Co., Ltd. Polyvinyl alcohol: degree of polymerization 500,
After charging 290 parts of a 10% aqueous solution with a degree of saponification of 87 to 89 mol%) into a separable flask, the temperature was raised to 50° C. with stirring while blowing nitrogen gas. Thereafter, 14.5 parts of a 2% aqueous solution of hydrogen peroxide and 3 parts of a 5% aqueous L-ascorbic acid solution were added, heat treated for 2 hours, cooled, and 25% aqueous ammonia was added.
5.7 parts were added to perform neutralization. The thus obtained aqueous resin dispersion (2) exhibited the following special values: non-volatile content of 24.5%, pH of 8.9, viscosity of 45 cps (B-type viscometer), and minimum film-forming temperature of 23°C. After coating the obtained aqueous resin dispersion (2) on a Teflon plate and peeling it off, polyvinyl alcohol was extracted from the resulting coating film in the same manner as in Production Example 1. It was confirmed that 0.5 part of polyvinyl alcohol was extracted. Production Example 3 After heating the aqueous resin dispersion (1) obtained in Production Example 1 to 85°C immediately after the completion of polymerization, the aqueous resin dispersion (1)
5% per 200 parts of Kuraray Poval PVA-124 (manufactured by Kuraray Co., Ltd. Polyvinyl alcohol: degree of polymerization 2400,
Saponification degree 98-99 mol%) was added to 100 parts, and then 2%
After adding 1 part of potassium persulfate aqueous solution and heating for 30 minutes, it was cooled and neutralized by adding 6.3 parts of 25% aqueous ammonia to obtain an aqueous resin dispersion (3). Ta. The obtained aqueous resin dispersion (3) exhibited special values of non-volatile content of 30.0%, pH of 9.0, viscosity of 220 cps (B type viscometer), and minimum film forming temperature of 13°C. The obtained aqueous resin dispersion (3) was applied on a Teflon plate, and polyvinyl alcohol was extracted from the resulting coating film in the same manner as in Production Example 1. As a result, polyvinyl alcohol was extracted at 0.1 per 100 parts of the coating film.
The extraction of polyvinyl alcohol was confirmed. Comparative Production Example 1 200 parts of the aqueous resin dispersion (1) obtained in Production Example 1
After adding 6.3 parts of 25% aqueous ammonia, 150 parts of a 10% aqueous solution of Kuraray Poval PVA-117 was mixed to obtain a comparative aqueous resin dispersion (1). This comparative aqueous resin dispersion (1) has a nonvolatile content of 29.0%, a pH of 8.9, and a viscosity of
It showed a special value of 2200 cps (B-type viscometer) and a minimum film formation temperature of 0°C or less. Production Example 1
When polyvinyl alcohol was extracted using the same method as above, it was confirmed that 12.7 parts of polyvinyl alcohol were extracted per 100 parts of the coating film. Comparative Production Example 2 200 parts of the aqueous resin dispersion (2) obtained in Production Example 2
After adding 5.7 parts of 25% aqueous ammonia, 290 parts of a 10% aqueous solution of Kuraray Poval PVA-205 was added and mixed well to obtain a comparative aqueous resin dispersion (2).
This comparative aqueous resin dispersion (2) has a non-volatile content of 24.6%,
PH9.2, viscosity 36cps (B type viscometer), minimum film forming temperature 45
℃ was shown. When polyvinyl alcohol was extracted from the coating film obtained by applying this comparison aqueous resin dispersion (2) on a Teflon plate in the same manner as in Production Example 1, 23.4 parts of polyvinyl alcohol was extracted per 100 parts of the coating film. Extraction of polyvinyl alcohol was confirmed. Comparative Production Example 3 Kuraray Poval PVA-117 was placed in a separable flask equipped with a stirrer, reflux condenser, and thermometer.
After charging 600 parts of a 10% aqueous solution, the temperature was raised to 70° C. with stirring while blowing nitrogen gas. Thereafter, 8 parts of a 1% aqueous solution of ammonium persulfate was added, and heat treatment was performed at 70°C for 60 minutes. 152 parts of the obtained heat-treated PVA-117 aqueous solution was added to Production Example 1.
After adding to 200 parts of the aqueous resin dispersion (1) obtained in
After thorough mixing, 6.3 parts of 25% aqueous ammonia was added to obtain a comparative aqueous resin dispersion (3). This comparative aqueous resin dispersion (3) has a non-volatile content of 28.9%, a pH of 8.8,
The viscosity was 2080 cps (B-type viscometer), and the minimum film forming temperature was 0°C or less. This comparative aqueous resin dispersion
When polyvinyl alcohol was extracted from the coating film obtained by applying (3) on a Teflon plate in the same manner as in Production Example 1, it was confirmed that 10.9 parts of polyvinyl alcohol were extracted per 100 parts of the coating film. Production Example 1 Aqueous resin dispersions (1) to (3) obtained in Production Examples 1 to 3
Using the comparative aqueous resin dispersions (1) to (3) obtained in Comparative Production Examples 1 to 3, the aqueous resin dispersions (1), (3) and the comparative aqueous resin dispersions (1) to ( 3) as is, and the aqueous resin dispersion (2) as CS- for 100 parts of the dispersion (2).
12 (film-forming aid manufactured by Chitsuso Co., Ltd.) was added to create sealers for inorganic porous substrates (1) to (3) and comparative sealers for inorganic porous substrates (1) to (3), respectively. ), these were coated at 20 g/m ² on the inorganic porous substrate shown in Table 1, and after drying in a hot air dryer at 120°C for 10 minutes,
The adhesion of the coating film to the substrate, hot water resistance, and frost damage resistance were examined. The results were as shown in Table 1.

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Claims (1)

[Claims] 1. Acrylic aqueous resin dispersion, degree of saponification 80 mol%
A sealer for an inorganic porous substrate, characterized in that it contains an aqueous resin dispersion obtained by heat-treating a mixture consisting of the above polyvinyl alcohol and a polymerization initiator at a temperature of 40° C. or higher. 2. The sealer for inorganic porous substrates according to claim 1, which contains polyvinyl alcohol in a solid content ratio of 1 to 30 parts by weight based on 100 parts by weight of an acrylic aqueous resin dispersion. 3 The degree of polymerization of polyvinyl alcohol is 200 to 2600
The sealer for inorganic porous substrates according to claim 1 or 2.