JP2007039497A - Water-based primer composition for inorganic porous substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based primer composition for inorganic porous substrates, which has both excellent water resistance and permeability to the inorganic porous substrates. <P>SOLUTION: This water-based primer composition for the inorganic porous substrates comprises an aqueous dispersion prepared by dispersing in an aqueous medium a polymer D (a part of A units are hydrolyzed) obtained by hydrolyzing a polymer C comprising 5 to 70 mass% of (meth)acrylic ester units (A units) having a solubility of 3 to 20 g in 100 g of water at 20°C and not having a hydrogen-bondable active hydrogen and 30 to 95 mass% of vinyl monomer units (B units) having a solubility of <3 g in 100 g of water at 20°C and having a weight-average mol.wt. of 1,000 to 100,000. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an aqueous composition suitable for undercoating of an inorganic porous substrate. More specifically, the present invention relates to an aqueous primer composition that is effective in preventing the precipitation of efflorescence powder on the surface of an inorganic porous substrate and improving the adhesion between the inorganic porous substrate and the topcoat.

An inorganic porous base material used for applications such as roof tiles and outer wall materials may be impregnated and coated with a primer for the purpose of reinforcing the base material or improving the adhesion with the top coating material.
Also, autoclave curing treatment may be performed to increase the strength of the inorganic porous substrate, and efflorescence powder is likely to precipitate during the autoclave curing. Is applied as a component.
As such a primer, an aqueous composition containing an ethylenically unsaturated carboxylic acid copolymer is known (see Patent Document 1). However, the use of the primer is limited because it does not have sufficient water resistance and does not have sufficient water resistance adhesion to the top coating.
In addition to the water-soluble type described in Patent Document 1, emulsion-type primer is also known, but emulsion-type primer is poor in permeability to inorganic porous substrates. In some cases, the above functions cannot be fully exhibited.

Japanese Patent Laid-Open No. 10-310739

An object of the present invention is to provide an aqueous primer for an inorganic porous substrate that is excellent in both water resistance and permeability to an inorganic porous substrate.

In order to solve the above problems, the aqueous primer composition for an inorganic porous substrate according to the invention described in claim 1 has a solubility in 100 g of water at 20 ° C. of 3 to 20 g and has hydrogen-bonding active hydrogen. No (meth) acrylic acid ester unit (A unit) 5 to 70% by mass and vinyl monomer unit (B unit) 30 to 95% by mass having a solubility in 100 g of water at 20 ° C. of less than 3 g as constituent units It contains an aqueous dispersion obtained by hydrolyzing a polymer C having a weight average molecular weight of 1,000 to 100,000, wherein a polymer D in which a part of the A unit is hydrolyzed is dispersed in an aqueous medium. And
The aqueous primer composition for an inorganic porous substrate according to claim 2 is the invention according to claim 1, wherein the polymer C is a vinyl monomer unit other than the A unit and the B unit ( E unit) 0.01 to 20% by mass is also included as a structural unit.
The aqueous primer composition for an inorganic porous substrate according to claim 3 is the invention according to claim 1 or 2, wherein the polymer C has an acid value of 50 mgKOH / g or less. And
The aqueous primer composition for an inorganic porous substrate according to claim 4 is the invention according to claim 1, wherein the polymer C has a glass transition temperature of 0 ° C. or higher. .
The aqueous primer composition for an inorganic porous substrate according to claim 5 is the invention according to claim 1, wherein the polymer D has an average particle diameter of 80 nm or less.
The aqueous primer composition for an inorganic porous substrate according to the invention described in claim 6 is the invention according to claim 1, wherein the solubility in 100 g of water at 20 ° C. is 3 to 20 g and hydrogen-bonding active hydrogen The (meth) acrylic acid ester having no carboxylic acid is methyl acrylate or methoxyethyl acrylate.
The aqueous undercoat composition for an inorganic porous substrate according to claim 7 is the invention according to claim 1, wherein the hydrolysis is ammonia corresponding to 10 to 90% of the number of moles of the A unit. It is characterized by being added ammonia water containing.
An inorganic porous substrate having the coating film of the invention according to claim 8 is obtained by coating the aqueous undercoat composition according to any one of claims 1 to 7.

The inorganic porous substrate having a film treated with the aqueous undercoat composition of the present invention has excellent blocking resistance and efflorescence resistance, and excellent adhesion to the top coating (dry adhesion, water adhesion). The frost damage resistance was excellent.

In this specification, acrylic and methacryl are collectively referred to as (meth) acryl.
The polymer C, which is an intermediate raw material of the main component of the primer composition of the present invention, has a (meth) acrylic acid ester unit having a solubility in 100 g of water at 20 ° C. of 3 to 20 g and no hydrogen-bonding active hydrogen. (A unit) 5 to 70% by mass and 30 to 95% by mass of vinyl monomer unit (B unit) whose solubility in 100 g of water at 20 ° C. is less than 3 g is included as a constituent unit, and the weight average molecular weight is 1000 to 100,000. The polymer.

The unit (A unit) is a (meth) acrylic acid ester (hereinafter also referred to as a hydrophilic (meth) acrylic acid ester) having a solubility in 100 g of water at 20 ° C. of 3 to 20 g and having no hydrogen-bonding active hydrogen. It is an important component for imparting water dispersibility to the polymer. The solubility in 100 g of water is preferably 3 to 10 g, more preferably 3 to 7 g. If it is less than 3 g, the inorganic porous substrate treated with the undercoat composition has insufficient water adhesion, and if it exceeds 20 g, the water adhesion and frost damage resistance are insufficient.
The mechanism for improving the water-resistant adhesion is inferred as follows. That is, when the ester portion of the hydrophilic (meth) acrylic acid ester unit is hydrolyzed, a carboxyl group is generated. As a result of crosslinking of the polymer by the action of the generated carboxyl group and calcium ions in the inorganic porous substrate, it is presumed that the water-resistant adhesion is excellent.
It is considered that the (meth) acrylic acid ester having a solubility of less than 3 g is insufficient in water-resistant adhesion because the hydrolysis is not sufficiently performed.

  The hydrophilic (meth) acrylic acid ester unit (A unit) does not have hydrogen-bonding active hydrogen. The group having hydrogen-bonding active hydrogen is a group typified by a hydroxyl group, amino group, thiol group, carboxyl group, sulfonic acid group, amide group, phosphoric acid group, etc., and does not have hydrogen-bonding active hydrogen. The (meth) acrylic acid ester is a (meth) acrylic acid ester that does not have these groups.

  Specific examples of the hydrophilic (meth) acrylic acid ester include methyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, methoxyethyl methacrylate, ethoxyethyl methacrylate and the like. Methyl acrylate and methoxyethyl acrylate are preferable in order to make the obtained coating particularly excellent in water resistance, and methyl acrylate is most preferable.

  The ratio of the hydrophilic (meth) acrylic acid ester unit is 5 to 70% by mass, preferably 5 to 50% by mass based on 100% by mass of all monomer units constituting the polymer C, and 20 to 50% by mass. % Is more preferable. If it exceeds 70 mass%, the water resistance of the resulting coating will be poor, and if it is less than 5 mass%, the impregnation property to the resulting inorganic porous substrate will be poor.

A vinyl monomer (hereinafter also referred to as hydrophobic vinyl monomer) unit (B unit) having a solubility in 100 g of water at 20 ° C. of less than 3 g is intended to impart water resistance and detergent resistance to the polymer. It is an important ingredient.
Specific examples of hydrophobic vinyl monomers include methyl methacrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, decyl (meth) acrylate, and (meth) acrylic acid n. -Hexyl, (meth) acrylic acid esters such as 2-ethylhexyl (meth) acrylate, and aromatic vinyl monomers such as styrene, α-methylstyrene, monochlorostyrene, vinyltoluene and the like. Two or more of these monomers may be used in combination.

  The ratio of the hydrophobic vinyl monomer unit is 30 to 95% by mass, preferably 50 to 95% by mass, and 50 to 80% by mass based on 100% by mass of all monomer units constituting the polymer C. More preferred. When the amount is less than 30% by mass, the resulting film has poor water resistance, and when it exceeds 95% by mass, the efflorescence resistance and normal adhesion are inferior.

  The polymer C is a vinyl monomer (hereinafter also referred to as other vinyl monomer) unit other than the hydrophilic (meth) acrylate unit (A unit) and the hydrophobic vinyl monomer unit (B unit). (E unit) may be included. The monomer unit is used as necessary to adjust the physical properties of the polymer C.

  Examples of other vinyl monomers include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, itaconic acid monomethyl ester, fumaric acid monomethyl ester, fumaric acid monobutyl ester, maleic anhydride, monomethyl Α, β-ethylenically unsaturated carboxylic acids such as itaconic acid, butyl ester or maleic acid monobutyl ester and salts thereof, sulfonyl groups such as acrylamide propanesulfonic acid, sulfoethyl sodium acrylate, sulfopropyl sodium methacrylate Vinyl monomers containing hydroxy groups such as 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, glycerol (meth) acrylate, etc. Mass, Contains acid amide groups or N-alkyl group-substituted amide groups such as (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide and N-methylolacrylamide Phosphoric monomers such as vinyl monomers, acid phosphooxyethyl methacrylate, acid phosphooxyethyl acrylate, and acid phosphooxypropyl acrylate, polyethylene glycol mono (meth) acrylate having a polyoxyalkylene chain with an average addition mole number of 4 to 100 mol Or monomers containing a polyoxyethylene glycol group such as polypropylene glycol mono (meth) acrylates.

  The proportion of other vinyl monomer units is preferably 20% by mass or less, more preferably 10% by mass or less, and still more preferably 5% by mass or less, based on 100% by mass of all monomer units constituting the polymer C. . If it exceeds 20% by mass, the water resistance of the resulting coating is unfavorable. Although there is no particular lower limit, it is substantially meaningless to use less than 0.01% by mass.

The polymer C has a weight average molecular weight of 1,000 to 100,000, preferably 1500 to 50,000. When the weight average molecular weight exceeds 100,000, the composition is inferior in the impregnation property to the base material, and the obtained coating film has low adhesion to the base material in a normal state. When the weight average molecular weight is less than 1000, the resulting coating has a low strength.
The polymer C is produced by a known method (for example, solution polymerization method, bulk polymerization method, etc.). A chain transfer agent may be used in the polymerization. Moreover, you may superpose | polymerize at 100 degreeC or more high temperature.

  The polymer C preferably has an acid value of 50 mgKOH / g or less, and more preferably 30 mgKOH / g or less. If the acid value exceeds 50 mgKOH / g, the resulting film may have poor water resistance.

  The polymer C preferably has a glass transition temperature of 0 ° C or higher, more preferably 0 to 70 ° C. If the glass transition temperature is too low, the water resistance and freeze-thaw resistance of the resulting film may be deteriorated. If the glass transition temperature is too high, the composition may be difficult to form a film. The glass transition temperature can be measured by a differential scanning calorimeter (DSC).

  The polymer D is a main component of the composition for treating the inorganic porous substrate, and exhibits a good balance of blocking resistance, efflorescence resistance, adhesion to the top coating, and frost damage resistance. The polymer D is obtained by subjecting the polymer C to a hydrolysis treatment.

  In the hydrolysis, a part of the hydrophilic (meth) acrylic acid ester unit (A unit) contained in the polymer C is hydrolyzed. The hydrolyzed hydrophilic (meth) acrylic acid ester unit is converted into a (meth) acrylic acid unit or a (meth) acrylate unit (hereinafter, both are also referred to as a (meth) acrylic acid (salt) unit). Converted. The produced (meth) acrylic acid (salt) unit makes the dispersibility of the polymer better by the action of carboxylic acid or carboxylate.

  Hydrolysis is performed by adding an alkali or an acid and heating as necessary. It is preferable to use an alkali for the hydrolysis, and it is more preferable to use a volatile alkali such as ammonia.

The proportion of hydrolysis is preferably 5 to 99 mol%, more preferably 10 to 90 mol%, still more preferably 20 to 80 mol% of the hydrophilic (meth) acrylic acid ester unit (A unit), and 30 to 30 mol%. Most preferred is 75 mol%.
The rate of hydrolysis is controlled, for example, by the amount of alkali used. The proportion of alkali used is preferably 10 to 90%, more preferably 20 to 80%, and most preferably 30 to 75% based on the number of moles of hydrophilic (meth) acrylic acid ester units (A units).

  One of the features of the present invention is that at least part of the (meth) acrylic acid (salt) unit of the polymer D hydrolyzes the hydrophilic (meth) acrylic acid ester unit (A unit) of the starting polymer C. It is to be obtained. This is presumed that the aqueous primer composition for inorganic porous substrates of the present invention contributes to both excellent water resistance and permeability to inorganic porous substrates. Yes. The mechanism is discussed below.

  When the polymer D becomes emulsion particles dispersed in an aqueous medium, (meth) acrylic acid produced by hydrolyzing the hydrophilic (meth) acrylate unit (A unit) of the starting polymer C ( A large amount of (salt) units are distributed in the vicinity of the surface of the emulsion particles made of the polymer D. Conversely, many hydrophilic (meth) acrylic acid ester units (A units) that are not hydrolyzed are distributed in the vicinity of the center of the emulsion particles made of the polymer D. When the (meth) acrylic acid (salt) unit is localized in the vicinity of the surface of the emulsion particles, it is considered that the dispersion stability of the emulsion particles is excellent and the permeability to the inorganic porous substrate is improved. Since the emulsion particles as a whole contain a relatively small amount of (meth) acrylic acid (salt) units, it is considered that the water resistance is excellent.

  However, unlike the polymer D of the present invention, a polymer obtained by emulsion polymerization of a monomer mixture containing a predetermined proportion of (meth) acrylic acid (salt) from the beginning is homogeneously (meth) acrylic acid ( Salt) units, and there is no difference in the content ratio of (meth) acrylic acid (salt) units in the vicinity of the surface and the center of the emulsion particles. Therefore, it is considered that the balance between water resistance and permeability to the inorganic porous substrate is inferior.

  Now, after the emulsion particles in the composition of the present invention are deeply impregnated inside the inorganic porous substrate, the hydrophilic (meth) acrylate unit (A unit) remaining in the emulsion particles is an inorganic porous group. It is rapidly hydrolyzed at the part of the surface that contacts the material. It is considered that the produced carboxy group is cross-linked by polyvalent metal ions such as calcium ions in the inorganic porous substrate to reinforce the strength of the inorganic porous substrate.

  The polymer D dispersed in the aqueous medium preferably has an average particle size of 80 nm or less. When the average particle diameter exceeds 80 nm, the impregnation property to the substrate is lowered, and the adhesion in a normal state may be small.

The following aspects are illustrated as an aqueous dispersion manufacturing process in which the polymer D is dispersed in an aqueous medium.
(1) 10 to 90% (preferably 20 to 80%, more preferably 30 to 30%) of the number of moles of hydrophilic (meth) acrylic acid ester units (A units) in the solution of polymer C dissolved in an organic solvent. Aqueous ammonia containing a molar amount of ammonia corresponding to 75%) is added, and the organic solvent is distilled off while adding water under heating and stirring.
(2) 10 to 90% (preferably 20 to 80%) of the number of moles of hydrophilic (meth) acrylic acid ester units (A units) in the aqueous dispersion in which particles of polymer C are dispersed in an aqueous medium. , More preferably 30 to 75%), aqueous ammonia containing a molar number of ammonia is added, and the mixture is heated and stirred.

  The aqueous medium may be water itself or a mixture of water and an organic solvent miscible with water. When the aqueous medium is a mixture of an organic solvent miscible with water and water, the proportion of water is preferably 50% by mass or more, and more preferably 70% by mass or more.

  The aqueous undercoat composition for an inorganic porous substrate may be an aqueous dispersion itself in which the polymer D is dispersed in an aqueous medium, but various additives are added as necessary. May be.

The aqueous undercoat composition for an inorganic porous substrate may contain a color pigment, an extender pigment, a filler, an antifoaming agent, a film forming aid and the like.
As a specific example of the film forming aid, dialkyl esters of aromatic dibasic acids such as dibutyl phthalate and dioctyl phthalate can be used. In addition, aliphatic dialkyl esters such as dibutyl succinate and dioctyl succinate can be used. Cellosolve compounds such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether can be used. Propylene glycol ether compounds such as propylene glycol monoethyl ether can be used, carbitol compounds such as diethylene glycol monoethyl ether and diethylene glycol monobutyl ether can be used, and triethylene glycol monoethyl ether, tripropylene glycol monomethyl ether, etc. Triglycol ether compounds can be used. The amount of the film forming aid used is preferably about 1 to 20 parts by mass based on 100 parts by mass of the polymer in the undercoat composition.

  As for the aqueous | water-based undercoat composition for inorganic porous base materials, that whose ratio of solid content (nonvolatile component) is 1-50 mass% is preferable, and what is 3-20 mass% is more preferable. When the ratio of the solid content is less than 1% by mass, the number of times of coating is increased in order to ensure the coating film thickness. On the other hand, if it exceeds 50% by mass, the permeability to the substrate is inferior, so that the substrate reinforcing property is lowered, and the adhesion and blocking resistance of the top coat may be deteriorated.

  As an inorganic porous base material to which the primer composition of the present invention is applied, various aggregates such as various cements, calcium silicate, gypsum, lime and the like that harden by a hydration reaction are used. A material in which fibers or the like are blended is formed, and examples thereof include those conventionally used for ordinary building materials. Cement concrete, cement mortar, ALC (autoclave lightweight concrete), PC (precast concrete), slate board, calcium silicate board, asbestos cement board, wood chip cement board, pulp cement board, calcium carbonate board, inorganic board, lightweight cellular concrete board, etc. Building materials, ceramic siding boards, structural materials, civil engineering materials, or industrial materials can be used.

  The application time of the aqueous undercoat composition for inorganic porous substrates is applied before curing for autoclave curing, and is applied before applying the top coating for sealers for top coating. It is important to impregnate the substrate, and it is desirable to apply directly to the substrate.

  The coating method is not particularly limited, and can be performed by a conventionally known coating method such as a roller, brush, air spray, airless spray, shower coat, flow coat, roll coat, or dipping.

The inorganic porous substrate having a film obtained by coating the aqueous undercoat composition has excellent blocking resistance and efflorescence resistance, and excellent adhesion to the top coating (dry adhesion, water adhesion). Excellent resistance to frost damage.

The mechanism by which the water-based undercoat composition for inorganic porous substrates of the present invention is excellent in both water resistance and permeability to inorganic porous substrates is not clear, but it can be dispersed in an aqueous medium. It has only the minimum necessary carboxy group, and the easily hydrolyzable ester group in the hydrophilic (meth) acrylic acid ester unit is changed to a carboxy group in an alkaline atmosphere of an inorganic porous base material. It is presumed that the water resistance is improved by crosslinking with calcium ions on the surface of the porous substrate.

  The present invention will be described more specifically with reference to examples. “Part” in each example means “part by mass”.

Example 1
A 3-liter glass 4-necked flask equipped with a stirrer, reflux condenser, thermometer, nitrogen inlet tube and dropping funnel was charged with 150 parts of ethylene glycol monobutyl ether and purged with nitrogen, and the internal temperature was raised to 80 ° C. did. On the other hand, a monomer mixture comprising 50 parts of methyl methacrylate, 30 parts of butyl acrylate, 20 parts of methyl acrylate, 3 parts of benzoyl peroxide and 130 parts of isopropyl alcohol was dropped into the polymerization vessel over 3 hours, and then further 82 ° C. The reaction was continued for 2.5 hours to complete the polymerization. Next, 12 parts of 25% aqueous ammonia (corresponding to 70% of the number of moles of methyl acrylate) was added and maintained at 82 ° C. for 5 hours, and then water was added while distilling off the organic solvent to obtain an aqueous dispersion having a solid content of 20%. Got the body.

(Example 2)
150 parts of ion-exchanged water and 3 parts of New Coal 707SF (manufactured by Nippon Emulsifier) were charged into a 3-liter glass four-necked flask equipped with a stirrer, reflux condenser, thermometer, nitrogen inlet tube and dropping funnel. On the other hand, a monomer mixed solution obtained by mixing and emulsifying 43 parts of ion-exchanged water, 40 parts of methyl methacrylate, 20 parts of butyl acrylate, 40 parts of methyl acrylate, 0.7 part of t-dodecyl mercaptan and 1 part of New Coal 707SF with a homogenizer. Prepared separately, 10% of the monomer mixture was charged into the flask. Furthermore, after adding 4 parts of 2.5% ammonium persulfate aqueous solution, the inside of the flask was purged with nitrogen, and the temperature was raised to 80 ° C. to conduct a polymerization reaction. After 30 minutes, the remaining monomer mixture and 4 parts of a 2.5% ammonium persulfate aqueous solution were separately added dropwise to the flask over 3 hours, and after completion of the addition, the mixture was reacted at 82 ° C. for 2.5 hours. The polymerization was terminated. Next, 11.4 parts of 25% aqueous ammonia (corresponding to 50% of the number of moles of methyl acrylate) was added and kept at 82 ° C. for 5 hours, followed by cooling to produce an aqueous dispersion.

(Comparative Examples 3, 4, 6)
A comparative aqueous dispersion was produced in the same manner as in Example 1 except that the monomer composition and the amount of ammonia were changed as shown in Table 1.
(Comparative Example 5)
A comparative aqueous dispersion was produced in the same manner as in Example 2 except that the monomer composition and the amount of ammonia were changed as shown in Table 1.
(Comparative Example 7)
A comparative aqueous dispersion was produced in the same manner as in Example 2 except that the hydrolysis treatment by addition of ammonia was not performed.
(Comparative Example 8)
A comparative aqueous dispersion was produced in the same manner as in Example 2 except that the amount of ammonia was 120% based on the number of moles of methyl acrylate.

(Evaluation)
The following evaluation was performed using the aqueous dispersion and the comparative aqueous dispersion as an undercoat composition. The evaluation results are shown in Table 1.

1) Blocking resistance After spray coating the primer composition to a thickness of 40 g / m ^{2 on two} slate plates and drying at 100 ° C. for 5 minutes, the slate plates are coated with each other. Was pressed at a load of 400 g / cm ² and heated at 180 ° C. for 10 hours in the presence of water vapor, then cooled to room temperature and manually peeled between the two slate plates. evaluated. The evaluation criteria are as follows.
A: Good with no adhesion. B: Slightly adhered, but can be peeled off with a light force, and there is no practical problem. Δ: It was not peeled off unless a strong force was applied.

2) Eflorescence resistance Cement paste (Cement / felt fiber / water prepared at a mass ratio of 100/4/35 processed into a flat plate and left for 30 minutes) 40 g / m ² in solid content on the surface The undercoat composition was spray-coated so as to have a thickness of, and allowed to dry. Further, after autoclaving (180 ° C., about 10 hours, in the presence of water vapor), the surface of the coating film was observed. Evaluation was performed according to the following criteria.
◎: No whitening ○: Slightly whitened but no problem in practical use △: Whitened ×: Whitening was remarkable

3) Dry adhesion (normal adhesion)
The undercoat composition was applied on a calcium silicate plate so as to have a solid content of 40 g / m ² , and then dried at 100 ° C. for 20 minutes. Further, a commercially available water-based top coating material was applied so as to have a thickness of 75 g / m ² and dried at 100 ° C. for 20 minutes to prepare a test plate. Using a cutter knife, the coating film was cut into a grid at intervals of 4 mm to form 25 cells. After pressure-sensitive adhesive tape (Nichiban adhesive tape) was pressure-bonded to the coating film, it was peeled off at once. The adhesion was evaluated according to the following formula from the area (number of squares) of the sealer film pieces remaining in the form of calcium silicate plate without peeling off. The closer the value is to 100, the better the adhesion. Adhesion is an indicator of the permeability of the composition into the inorganic porous substrate.
Adhesiveness (%) = 100 × number of cells remaining / 25

4) Water-resistant adhesion The same test plate used for dry adhesion evaluation was prepared, immersed in warm water at 60 ° C. for 24 hours, and allowed to stand at room temperature for 24 hours. Sex was tested.

5) Frost resistance test The same test plate used for dry adhesion evaluation was frozen at −20 ° C. × 18 hours and thawed at 20 ° C. × 8 hours, and the coating film after repeating this cycle 40 times. The condition was evaluated. The evaluation criteria are as follows. Abnormality means peeling, cracking or blistering.
◎: No abnormality ○: Slight abnormality was observed △: Abnormality was observed ×: Remarkable abnormality was observed

  It is useful as a primer for the purpose of reinforcing an inorganic porous substrate used for applications such as roof tiles and outer wall materials, or improving adhesion with a top coating.

Claims (8)

The solubility in 100 g of water at 20 ° C. is 3 to 20 g and (meth) acrylic acid ester unit (A unit) having no hydrogen bonding active hydrogen is 5 to 70% by mass, and the solubility in 100 g of water at 20 ° C. is 3 g. A part of the A unit obtained by hydrolyzing the polymer C having a weight average molecular weight of 1,000 to 100,000 containing 30 to 95% by mass of a vinyl monomer unit (B unit) as a constituent unit An aqueous primer composition for an inorganic porous substrate, comprising an aqueous dispersion in which the prepared polymer D is dispersed in an aqueous medium. The said polymer C is an inorganic porous base material of Claim 1 which also contains 0.01-20 mass% of vinyl monomer units (E unit) other than the said A unit and B unit as a structural unit. Aqueous primer composition. The said polymer C is an aqueous primer composition for inorganic porous base materials of Claim 1 or 2 whose acid value is a 50 mgKOH / g or less thing. The said polymer C is an aqueous primer composition for inorganic porous base materials of Claim 1 whose glass transition temperature is a 0 degreeC or more thing. The said polymer D is an aqueous | water-based undercoat composition for inorganic porous base materials of Claim 1 whose average particle diameter is a thing of 80 nm or less. The inorganic porous substrate according to claim 1, wherein the (meth) acrylic acid ester having a solubility in 100 g of water at 20 ° C of 3 to 20 g and having no hydrogen-bonding active hydrogen is methyl acrylate or methoxyethyl acrylate. Aqueous undercoat composition. The aqueous primer for an inorganic porous substrate according to claim 1, wherein the hydrolysis is performed by adding ammonia water containing ammonia corresponding to 10 to 90% of the number of moles of the A unit. Composition. An inorganic porous substrate having a coating film coated with the aqueous primer composition according to claim 1.