JPS62197470A - Water-dispersed paint - Google Patents

Abstract

PURPOSE:To provide a water-dispersed paint which is suitable for use as a priming sealer for porous substrates and has excellent adhesion to topcoating paints, by emulsifying a soln. of an acrylic resin having a specified MW and a specified glass transition temp. in an org. solvent. CONSTITUTION:100pts.wt. acrylic resin having an MW of 3,000 to 30,000 and a glass transition temp. of not lower than 30 deg.C (e.g., a methyl methacrylate/ styrene copolymer) is dissolved in 25-150pts.wt. org. solvent. If desired, a surfactant, etc. are added thereto. While stirring in a homogenizer, etc., water is gradually added thereto to emulsify the mixture, thus obtaining the desired water-dispersed paint. The paint is suitable for use as a primer to flow PVC emulsion paints. When a porous substrate is coated with the paint as a priming sealer, the resin penetrates into the substrate to impart sufficient adhesion. Further, the paint is a water-dispersed one and hence it has no fear of causing environmental pollution or a fire by the evaporation of the org. solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a water-dispersible paint used as an undercoat sealer for porous substrates.

(Background technology) When painting the surfaces of mortar, concrete, etc., these surfaces are porous and highly absorbent, so if you apply the top coat directly, the vehicle in the paint will be absorbed, causing the paint to dry. The durability of the porous base material was inhibited, making it impossible to form a paint film with sufficient physical properties and requiring repeated coatings.Therefore, in the past, when applying paint to the surface of these porous substrates, In the past, a solvent-based paint was used as a sealer to prepare the base, and then a top coat was applied.

In these solvent-based sealers, the resin dissolved in the solvent penetrates deep into the porous base material, so that an undercoat film with sufficient adhesion to the porous base material can be obtained.

However, this solvent-based sealer contains a large amount of volatile organic solvent, which poses problems such as air pollution and fire hazards during painting operations.

Therefore, in recent years, attempts have been made to use water-soluble resins and emulsion polymerization emulsions as sealers for the surface of porous substrates. However, water-soluble resins have problems with water resistance, chemical resistance, etc., and there is a risk that they will be damaged by the top coat, making it impossible to obtain sufficient adhesion with the top coat. Due to poor permeability into porous substrates, it is not possible to obtain an undercoat film with sufficient adhesion to the substrate. It has sufficient resistance to apply low pigment volume concentration emulsion paints (hereinafter referred to as "low PVC emulsion paints") such as water-based gloss paints, single-layer elastic paints, and multi-layer elastic intermediate coatings, that is, has a high glass transition point. At present, resin coating films cannot be formed using emulsion polymerization emulsions, and such resins are not water-soluble.
C. Water-based primer sealers that can be applied with emulsion paints are not available.

[Purpose of the invention]

This invention can be used as an undercoat sealer for porous substrates, and can be used to attach low PVC emulsion paints such as water-based gloss paints, single-layer elastic paints, and multi-layer elastic intermediate coats, and can prevent air pollution and fire hazards. The aim is to provide water-dispersible paints that are free from the dangers of

[Disclosure of the invention]

In order to achieve the above object, the present invention provides a water-dispersible paint used as a sealer for porous substrates, and which has a molecular weight of 3,000 to 30,000. An organic solvent containing acrylic resin with a glass transition temperature of 30°C or higher? The gist is a water-dispersed paint characterized by emulsion of &.

The present invention will be explained in detail below.

Acrylic resin, which is the main component, is a polymer compound mainly composed of an acrylic compound (Nanatsuma) having 7 acryloyl groups or methacryloyl groups, and it includes not only acrylic compounds such as acrylic compounds but also styrene. Copolymers with monomers other than acrylic compounds, such as vinyl diacetate, are also included within the scope. In this invention, such acrylic resin has a molecular size of 3000 to 30
000, and the glass transition temperature needs to be 30°C or higher. If the molecular weight of the acrylic resin is less than 3,000, the film-forming properties will be poor and a coating film with sufficient physical properties will not be possible. If it exceeds 30,000, the solubility in organic solvents will be poor and a large amount of organic solvent will be required. Therefore, the same problems as solvent-based sealers occur, and the advantages of water-based sealers are lost. When the glass transition temperature (Tg) of the acrylic resin is less than 30° C., the cohesive force is poor, so a coating film with sufficient physical properties cannot be formed, and the coating film is frequently contaminated. In order to raise the glass transition temperature of acrylic resin to 30°C or higher, the type of acrylic compound used must be appropriately selected and blended, or styrene, vinyl acetate, etc. as mentioned above may be appropriately blended. Just do it. Further, when using a material having a glass transition temperature of 70° C. or higher, the glass transition temperature can also be adjusted by using a small amount of plasticizer in combination.

After the above acrylic resin is dissolved in an organic solvent, a surfactant and a plasticizer are added as necessary.

Stabilizers and the like are added to form an oil layer.

Although the amount of the organic solvent to be blended is not particularly limited in the present invention, it is preferable that 25 to 150 parts by weight of the organic solvent be blended to 100 parts by weight of the acrylic resin. If the amount of the organic solvent is less than 25 parts by weight, it will be difficult to emulsify it with water, and even if emulsification is possible, there is a risk that sufficient permeability to the porous substrate will not be obtained. If the amount of the organic solvent exceeds 150 parts by weight, the advantages of making it water-based tend to be diminished.

Water is gradually added to the oil layer thus formed while stirring it with a homomixer or the like to form an emulsion, thereby producing the water-dispersed paint of the present invention.

In the water-dispersed paint of this invention, the resin dispersed in water is a resin solution in which acrylic resin is dissolved in an organic solvent, so it can penetrate deep into the porous substrate and form an undercoat film. can do.

As described above, the water-dispersed paint of the present invention has an acrylic resin with a high glass transition temperature as its main component, so it can be used as a low-resistance paint, such as water-based glossy paints, single-layer elastic paints, and multi-layer elastic intermediate coatings. It can be used as an undercoat for PVC emulsion paints, etc. Moreover, since it is water-based and contains only a small amount of organic solvent, there is no risk of pollution or fire due to the volatilization of organic solvents, and it does not contain a large amount of solvent, which is a flying component. Because there is no
It is also possible to reduce costs.

The water-dispersed paint of this invention can be used as it is as an undercoat sealer for a topcoat, but if a pigment is added to the oil layer before dispersion, it can also be used as a colored undercoat for a transparent topcoat. can.

Examples of porous substrates to which the water-dispersible paint of this invention can be applied include lightweight concrete precast concrete, lightweight cellular concrete, and mortar.

Concrete, asbestos cement board, calcium silicate board,
Examples include pulp cement board, wood wool cement board, 1 gypsum board, hardboard, plaster 2 gypsum plaster, dolomite plaster, slate board, wood, etc.

Next, examples of the present invention will be described together with comparative examples and conventional examples.

(Example 1) *Synthesis of acrylic resin (solution) The inside of a 2-liter reaction vessel equipped with a stirrer, a cooling pipe, and a temperature control device was previously purged and saturated with nitrogen gas. Thereafter, 62 parts by weight of xylene was charged into this container, and the temperature was raised and maintained at 110° C. while stirring.

While stirring was continued, a monomer solution having the composition shown in Table 1 was added dropwise into the reaction vessel over a period of 3 hours. After dropping the entire amount, stirring was continued for 30 minutes while maintaining the temperature at 110°C, and then a mixture of 5 parts by weight of xylene and 0.5 parts by weight of an initiator (Kaya Ester O manufactured by Kayaku Nuri Co., Ltd.) was added for 30 minutes. The monomers were added dropwise and stirring was continued for an additional 30 minutes to completely react the monomers, and the reaction was completed. When the acrylic resin in the obtained reaction solution was measured, the glass transition temperature was 70°C.

The molecular weight was 15,000.

Table 1 * Creation of water-dispersed paint Using the acrylic resin obtained as above as a reaction solution, add a plasticizer, stabilizer and surfactant to form an oil layer, and mix with a homomixer. A water-dispersible paint was obtained. Table 2 shows the amount of each component.

The water-dispersible paint prepared as shown in Table 2 above was applied to a slate board with a brush and dried for 2 to 3 hours to form an undercoat film.
As a top coat, a low PvC emulsion paint (N-DAN Uni, manufactured by Nippon Paint Co., Ltd.) was applied to a thickness of about 1 inch and dried to obtain a top coat film.

After the top coat was dried, a cross-cut hatching test and a beering test were conducted to observe initial adhesion, and a water resistance test and alkali resistance test were also conducted. The results are shown in Table 4.

(Example 2) The components of Example 1 were further mixed with an antifoaming agent, water, and a titanium dispersion paste as a pigment to obtain a white enamel undercoat paint. Table 3 shows the amount of each component. The composition of the titanium dispersion paste is 68.1% by weight of water (hereinafter referred to as "%"), 29.0% titanium oxide, 1.45% thickener, 0.58% dispersant, and 0.58% antifoaming agent. It contains 0.58% of an agent and 0.29% of a preservative.

This undercoat paint was applied in the same manner as in Example 1, dried,
A similar test was conducted using N-DAN Uni as a top coat. The results are also shown in Table 4.

(Comparative Example) A test was conducted in the same manner as in the example except that an acrylic emulsion (ice-making sealer manufactured by Nippon Paint Co., Ltd.) was used as the emulsion polymerization emulsion in the undercoat paint.

(Conventional example) A test was conducted in the same manner as in the example except that DAN Sealer White manufactured by Nippon Paint Co., Ltd. was used as a solvent-based sealer for the undercoat paint. The test results of the comparative example and the conventional example are also shown in Table 4.

〔Effect of the invention〕

The water-dispersed paint of the present invention is constructed as described above, and has a molecular weight of 3,000 to 30,000. Glass transition temperature 30
Low PVC as it is made of acrylic resin with a temperature above ℃
Suitable for undercoating such as emulsion paints, the resin is in solution form and penetrates into the porous base material, so it has sufficient adhesion, and since it is water-based, it is free from pollution caused by the volatilization of organic solvents.
There is no risk of fire, and there are no volatile components.
Cost can be reduced.

Claims (2)

[Claims] (1) A water-dispersed paint used as a sealer for porous substrates, etc., characterized by being made into an emulsion of an organic solvent solution containing an acrylic resin with a molecular weight of 3,000 to 30,000 and a glass transition temperature of 30°C or higher. A water-dispersible paint. (2) Claim 1, in which the amount of organic solvent blended is 25 to 150 parts by weight based on 100 parts by weight of the acrylic resin.
Water-dispersible paint as described in Section 1.