JPH08157774A - Aqueous undercoating dispersion for inorganic porous substrate - Google Patents

Abstract

PURPOSE: To prepare an aq. undercoating dispersion for an inorg. porous substrate which is free from problems of unsatisfactory impregnation into an inorg. substrate, unsatisfactory adhesion, hot water resistance, and freeze-thaw resistance by mixing an aq. resin dispersion having a highly reduced particle diameter with a particular PVA. CONSTITUTION: An aq. undercoating dispersion, for an inorg. porous substrate, comprising: an aq. resin dispersion (A) prepd. by emulsion-polymerizing 100 pts.wt. radical-polymerizable ethylenically unsatd. monomer in the presence of 2.5 to 8 pts.wt. reactive surfactant having in its molecule a radical- polymerizable unsatd. double bond; and a polyvinyl alcohol having a degree of polymerization of 200 to 2600 and a saponification value of not less than 85mol%, the aq. resin dispersion and the polyvinyl alcohol being in the form of a mixture with the amt. of the polyvinyl alcohol being 2 to 30wt.% in terms of solid content ratio based on 100 pts.wt aq. resin dispersion (A).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous basecoat dispersion for an inorganic porous substrate, more specifically, lightweight concrete,
Reactive surface active that forms a good coating such as adhesion, water resistance, freeze-thaw resistance when applied to various inorganic substrates such as mortar, asbestos cement board, calcium silicate board, slate or gypsum board. The present invention relates to an aqueous undercoat dispersion for an inorganic porous substrate, which comprises a mixture of an aqueous resin dispersion having an extremely small average particle size copolymerized with an agent and polyvinyl alcohol (hereinafter abbreviated as PVA).

[0002]

2. Description of the Related Art As inorganic porous base materials, lightweight concrete, mortar, asbestos cement board, calcium silicate board,
There is slate or gypsum board, etc., both of which are porous and thus have low surface strength and easily absorb moisture, so if the surface is just finished with makeup, bleeding, peeling, absorption of water or moisture will cause freeze-thawing. By repeating, problems such as peeling of the finishing agent are likely to occur. It is customary to apply a sealer to the surface of the inorganic substrate for the purpose of improving such peel resistance.

As the resin used for the sealer of the inorganic porous base material, a moisture-curable urethane resin or a solvent type resin is used. However, toxicity and the risk of fire due to the use of organic solvents and environmental pollution have become problems, and there is a strong demand for making them aqueous.

Various water-based sealers containing water-soluble resins or water-dispersible resins as main components have been investigated.
Water-soluble resin as the main component has water resistance, and water-dispersible resin as the main component has poor impregnability and adhesion to the substrate, and must maintain peel resistance for a long time. Is difficult. Further, a method of mixing and using a water-soluble resin and a water-dispersible resin has been studied, and for example, a method of blending PVA with a specific polymer aqueous emulsion (Japanese Patent Laid-Open No. 53-97).
No. 018) has been proposed, but each of them has drawbacks, and a satisfactory water-based sealer has not been obtained. Further, in the epoxy-based sealer improved with such drawbacks, since it is a two-liquid mixed type, it is not easy to handle and there is a problem in toxicity.

[0005]

DISCLOSURE OF THE INVENTION As a result of various studies, the present inventors have found that in the production of an aqueous resin dispersion prepared by mixing an extremely fine particle diameter aqueous resin dispersion and a specific PVA,
It is a solution to problems such as insufficient impregnation into inorganic substrates, insufficient adhesion, hot water resistance, and freeze-thaw resistance.

The first aspect of the present invention is the presence of 100 parts by weight of a radically polymerizable ethylenically unsaturated monomer in the presence of 8 parts by weight or less of a reactive surfactant having a radically polymerizable unsaturated double bond in the molecule. And an aqueous resin dispersion (A) which is emulsion-polymerized with polyvinyl alcohol having a degree of polymerization of 200 to 2600 and a saponification degree of 85 mol% or more in a solid content ratio of 2 to 100 parts by weight of the aqueous resin dispersion (A). It is an aqueous undercoat dispersion for an inorganic porous substrate, which is composed of a mixture of ˜30% by weight. The second invention is a reaction in which water, 0 to 70% by weight of an ethylenically unsaturated monomer, and 10 to 80% by weight of the above reactive surfactant are added in the method for producing an aqueous resin dispersion (A). Add 30 to 100% by weight of the above monomer and 20 of the above reactive surfactant in a kettle.
The aqueous undercoat dispersion for an inorganic porous substrate according to the first aspect of the present invention, wherein a mixture containing ˜90% and water is dropped and radically polymerized by an organic initiator to have an average particle size of 10 to 100 nm.

The third invention is such that a reactive surfactant having an unsaturated double bond capable of radical polymerization in the molecule is added to 2 parts per 100 parts by weight of an ethylenically unsaturated monomer capable of radical polymerization.
It is an aqueous undercoat dispersion for inorganic porous substrates of the first invention, which is -5 parts by weight.

The ethylenically unsaturated monomers used in the present invention include (meth) acrylic acid alkyl ester monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate. Acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, para-vinyl benzoic acid, para-vinyl, acid-based monomers such as, ethyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, etc. Benzenesulfonic acid, etc., styrene, alphamethylstyrene, vinyltoluene, vinyl acetate, vinyl propionate, etc. can be used.

It is preferable to use an acid-based monomer in combination in order to improve stability during production or during storage of the aqueous resin dispersion. For this purpose, the acid-based monomer may be used in an amount of 0.05 to 5 parts by weight based on the total amount of the monomers.

Further, acrylamide and N- are mainly used for the purpose of adjusting fluidity and drying property and improving stability during resin storage.
Methylol acrylamide, hydroxyethyl acrylate, hydroxylpropyl acrylate, hydroxyethyl methacrylate and the like can be used. Further, ethylene glycol dimethacrylate, diallyl phthalate, divinylbenzene and the like can be used for the purpose of imparting a crosslinked structure to the film.

The reactive surfactant used in the present invention is an anionic or nonionic surfactant having at least one unsaturated double bond capable of radical polymerization in the molecule, for example, the following general formula (1) , (2) sulfosuccinate-based compounds (commercially available products include, for example, Kae Co., Ltd. Latemur S-120P, S-180A, Sanyo Kasei Co., Ltd.).
Eleminol JS-2, etc.), an alkylphenol ether type represented by the general formula (3) (commercially available products are Aqualon HS-10 and RN-20 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.).
Etc.)

General formula (1)

[0013]

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R ₁ : alkyl group having 12 to 30 carbon atoms M ₁ : Na, NH ₄ , K

General formula (2)

[0016]

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R ₁ : alkyl group having 12 to 30 carbon atoms M ₁ : Na, NH ₄ , K

General formula (3)

[0019]

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R ₂ : alkyl group having 8 to 12 carbon atoms X: H or SO ₃ M ₂ M ₂ : Na, NH ₄ , K n: 1 to 200

In emulsion polymerization, these may be used alone or in combination of two or more.

The reactive surfactant is used in an amount of 8 parts by weight or less based on 100 parts by weight of the ethylenically unsaturated monomer. 2.5
If the amount is less than or equal to parts by weight, the particle size of the resin dispersion becomes large, and if it is greater than or equal to 8 parts by weight, the particle size becomes smaller.

One of the features of the present invention is that 10 to 80% by weight of the reactive surfactant is charged into the reaction vessel at the start of the polymerization in the dropwise polymerization. That is, a predetermined amount of water and a part of the reactive surfactant are put in advance in the reaction vessel, and the monomer is dropped and polymerized. Here, up to 70% by weight of the monomers can be added together. If the amount of the reactive surfactant put in advance in the reaction kettle is less than the above value, the resin particle size becomes large, which is not preferable, and conversely, if the amount is more than the above value, less active agent is used in the subsequent polymerization process. Therefore, the stability of the polymerization system deteriorates. In addition, it is also possible to use a non-reactive emulsifier if necessary.

Another feature of the present invention is that an organic initiator is used as a radical polymerization initiator. It is not preferable to use an inorganic peroxide such as ammonium peroxide or sodium peroxide instead of the organic peroxide, because the particle size becomes large during the polymerization process. As the organic initiator, organic peroxides such as tert-butyl perbenzoate, dilauryl peroxide, benzoyl peroxide and tert-butyl hydroperoxide are preferable. These organic peroxides can be used alone, or may be used in a redox type by being used in combination with a reducing agent such as sodium erythorbate.

The organic initiator is used in an amount of 0.5 to 10 parts by weight based on 100 parts by weight of the monomer. Of these, 10 to 50% by weight of the organic polymerization initiator is added to the reaction vessel in advance, and the rest is added to the monomer and the reactive surfactant and added dropwise.

In the present invention, the amount of the ethylenic monomer to be dropped is 50 to 20 with respect to 100 parts by weight of the ethylenic monomer.
It is preferable to add 0 parts by weight of water together with the remaining amount of the reactive surfactant as a pre-emulsion. The reaction time is 1 to 5 hours, and during this period, the monomer can be continuously added dropwise or intermittently. Reaction temperature is 50-9
0 ° C.

In the present invention, copper ions such as cupric sulfate and cupric chloride and transition metal ions such as ferric sulfate and ferric chloride are added to the water system of the reaction vessel at 10 ^-7 to 10 ^-5 mol / mol. It can be added in the range of 1 liter.

In the emulsion polymerization of the present invention, sodium acetate, sodium citrates, sodium bicarbonate and the like can be used as a buffer, and mercaptans such as stearyl mercaptan and t-dodecyl mercaptan can be used as a chain transfer agent.

The PVA used in the present invention has a saponification degree of 8
It is 5 mol% or more. The use of PVA having a saponification degree of 80 mol% or less is not preferable because the hydrophilicity becomes strong and the water resistance is lowered. The addition amount is preferably in the range of 2 to 30 parts by weight in terms of solid content relative to 100 parts by weight of the aqueous resin dispersion. Further, the degree of polymerization of PVA is preferably in the range of 200 to 2400 from the viewpoint of water resistance.

The aqueous resin dispersion obtained by the present invention is
Although it can be used as a sealer for an inorganic porous substrate, a film forming aid, a pigment, a filler, a toner, a wetting agent, a defoaming agent and the like may be blended as necessary.

[0031]

The present invention will be described below with reference to examples. In the examples, “part” means “part by weight” and “%” means “% by weight”.

Example 1 A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser was charged with the reaction can amount shown in Table 1 and saturated with nitrogen gas. The drops in Table 1 are mixed in advance. After raising the internal temperature to 65 ° C., a reaction kettle amount of a polymerization initiator was added, and after 5 minutes, dropping was started. The dropping amount was dropped in 3 hours, the mixture was aged at 80 ° C. for another 2 hours and then cooled, and the pH was adjusted to 8 to 9 with ammonia.
Adjusted to. An aqueous PVA solution was added to the obtained resin dispersion and uniformly stirred and mixed to give a solid content of 29.0% and a viscosity of 5800.
A resin dispersion having a cps and a particle size of 68 nm was obtained.

[0033]

[Table 1]

* 1 Eleminol JS-2 Sanyo Kasei Co., Ltd. reactive surfactant (38% active ingredient) * 2 PVA2 Saponification degree 98.5 Polymerization degree 1700 1
2% aqueous solution

Examples 2 to 5 In the same manner as in Example 1, resin dispersions were obtained by changing the types and amounts of ethylenic monomer, reactive activator and PVA.

[0036]

[Table 2]

* 2 PVA2 Saponification degree 98.5 Polymerization degree 1700 12% aqueous solution * 5 PVA1 Saponification degree 88 Polymerization degree 1000 2
0% aqueous solution * 6 PVA3 Saponification degree 98.5 Polymerization degree 2000 1
2% aqueous solution * 7 PVA4 Saponification degree 98.5 Polymerization degree 24001
0% aqueous solution Latemur S-180A Kao Co., Ltd. active ingredient 30% Aqualon HS-10 Daiichi Kogyo Seiyaku Co., Ltd. active ingredient 98%

Comparative Examples 1 to 6 Example using non-reactive activator (Comparative Example 1), Example using small amount of reactive activator (Comparative Example 2), Example using large amount of reactive activator ( Comparative Example 3), an example in which the degree of saponification of PVA is 85 mol% or less (Comparative Example 4), an example in which the amount of PVA added is less than that of the aqueous resin dispersion (A) (Comparative Example 5), P
A resin dispersion was produced according to Example 1 for an example (Comparative Example 6) in which VA was added more than the above-mentioned aqueous resin dispersion (A).

[0039]

[Table 3]

* 2 PVA2 Saponification degree 98.5 Polymerization degree 1700 12% aqueous solution * 5 PVA1 Saponification degree 88 Polymerization degree 1000 2
0% aqueous solution * 8 PVA5 Saponification degree 80 Polymerization degree 300 2
0% aqueous solution Sannole NES Lion's anionic activator (38% active ingredient)

Polymerization stability and particle size of the aqueous resin dispersions obtained in Examples and Comparative Examples were measured and the results are shown in Table 4. In addition, a film forming aid is added to the aqueous resin dispersion to adjust it, and the calcium silicate plate and the flexible board plate are adjusted to 2%.
After coating with 0 g / m ² (dry) and drying with hot air at 130 ° C. for 10 minutes, the adhesion to the substrate, hot water resistance and freeze-thaw resistance were examined. The results are as shown in Table 5.

Test Method Primary Adhesion: The coating film was cut with a cutter-knife at 2 mm intervals and 5 ×.
After cross-cutting No. 5 and pressure bonding a cello tape, the peeled coating film was observed for the remaining state.

Warm water resistance: A test piece coated with a coating film was heated to 50 ° C.
The film was immersed in warm water for 7 days for observation of the state of the coating film, and dried for 2 days at room temperature to perform an adhesion test by the above method.

Freeze-thaw resistance: immersion in water at 10 ° C. for 2 hours,
One cycle was 2 hours of freezing in air at -20 ° C for 100 cycles, and the coating film was observed for 100 cycles and dried at room temperature for 2 days to perform an adhesion test by the above method.

As the judgment of the above test, ◯: the appearance of the coating film was not abnormal and the coating film was not peeled at all Δ: small blister was observed, and the coating film was partially peeled ×: large blister was observed, In addition, the coating film was completely peeled off

[0046]

[Table 4]

[0047]

[Table 5]

[0048]

INDUSTRIAL APPLICABILITY The aqueous resin dispersion of the present invention was able to obtain a coating film of an undercoat dispersion having good adhesion, water resistance and freeze-thaw resistance to an inorganic porous substrate.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area C09D 133/04 PGF

Claims (3)

[Claims] 1. Emulsion polymerization of 100 parts by weight of a radically polymerizable ethylenically unsaturated monomer in the presence of 8 parts by weight or less of a reactive surfactant having a radically polymerizable unsaturated double bond in the molecule. The degree of polymerization with the aqueous resin dispersion (A) is 200 to
2600, polyvinyl alcohol with a saponification degree of 85 mol% or more
Is a mixture of 100 parts by weight of the aqueous resin dispersion (A) in a solid content ratio of 2 to 30% by weight, and an aqueous undercoat dispersion for an inorganic porous substrate. 2. A reaction kettle containing water, 0 to 70% by weight of an ethylenically unsaturated monomer and 10 to 80% by weight of the above reactive surfactant in the method for producing an aqueous resin dispersion (A). A mixture containing 30 to 100% by weight of the above monomer, 20 to 90% of the above reactive surfactant, and water was added dropwise to the mixture to radically polymerize with an organic initiator to obtain an average particle diameter of 10 to 100.
The water-based undercoat dispersion for an inorganic porous substrate according to claim 1, having a thickness of nm. 3. A reactive surfactant having a radical-polymerizable unsaturated double bond in the molecule is 2 to 5 parts by weight with respect to 100 parts by weight of the radical-polymerizable ethylenically unsaturated monomer. 1. An aqueous undercoat dispersion for an inorganic porous substrate according to 1.