JPS6124407B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for producing a thermosetting solid resin composition,
More specifically, the present invention relates to a method for producing a thermosetting solid resin composition that can be advantageously used to prepare slurry or powder coatings.

[Prior Art] In recent years, as environmental pollution has increased, various efforts have been made to eliminate it from the viewpoint that substances such as solvents escaping from paints are also a contributing factor. Under such circumstances, so-called slurry paints, in which water-based paints such as water-soluble paints and emulsion paints, powder paints, and solid film-forming resins are dispersed in water to form a slurry, have been developed. Among them, powder paints and slurry paints are particularly advantageous over other paints in that they emit extremely few harmful emissions during the painting process, are easy to dispose of afterwards, and can be recycled. From a certain point of view, it is thought that it will occupy an important field of paints in the future.

Conventionally known methods for producing these powder paints and slurry paints include mixing a solid resin with pigments, crosslinking agents, etc. by hot melting, pulverizing the mixture to form a powder paint, and then producing the powder paint. A method of suspending it as it is in water to make a slurry paint
45529)). In addition to this, (1) a method of mixing a coagulating liquid with a liquid paint having a liquid portion that is miscible with the coagulating liquid, and thereby suspending the precipitated paint particles in water to form a slurry-like paint; A method of drying the precipitated paint particles to obtain a powder paint (see JP-A-48-52851), and (2) emulsion polymerization of a liquid composition containing a pigment, a polymerizable monomer, and a resin to form a polymer. Method of spray-drying materials to make powder coatings (Japanese Patent Application Laid-Open No. 50-33821
) is known.

However, all of these conventional methods have major technical or economical drawbacks, and have therefore been prevented from being widely put into practical use. For example, (1) above
This method uses a coagulating liquid that does not dissolve the non-solvent part of the liquid paint and causes precipitation to occur due to the difference in dissolving power, so a large amount of coagulating liquid that is miscible with the solvent part of the liquid paint is required. It is.
For example, when water is used as a coagulating liquid, a large amount of water, 6 to 73 times the amount of effective paint components, mixes with the solvent in the paint and forms a by-product, so if this water is simply discharged or evaporated, It causes water or air pollution, and is also extremely disadvantageous economically. Furthermore, even if the solvent is collected and reused in a closed cycle, the capital investment and operating energy costs for this would be enormous, and if the solvent in the paint is highly flammable such as acetone, There is also a great risk of fire and explosion, and the safety and protection equipment must be very strict.

In method (2) above, the pigment is subjected to a conventional dispersion treatment in the presence of a polymerizable monomer and a resin to obtain a liquid pigment dispersion composition, and then an initiator, crosslinking agent, emulsifier, additives, etc. are added to emulsify the pigment. After polymerization, the polymerization product is spray-dried to form a powder coating.
Unlike ordinary solution resins, all of the polymerizable monomers that functioned as solvents in the starting liquid pigment dispersion composition are substantially converted to resins in the final coating. The pigment/resin ratio inevitably becomes small, making it difficult to obtain a paint with a high pigment concentration, and the emulsifier used during emulsion polymerization remains in the paint as it is.
Deterioration in the appearance or performance of the coating film due to this is unavoidable.

[Objective of the Invention] The object of the present invention is to improve the above-mentioned conventional method for producing slurry paints and powder paints by using a substantially water-based resin composition liquid, in particular, by using a solvent as in the conventional method (1). It is not necessary, and even if the composition contains a solvent, it is extremely small, and the amount of solvent distributed in water during water solubilization or water dispersion is even smaller, so treatments such as its removal may be omitted or It is possible to prevent or reduce environmental pollution during paint manufacturing and painting, and to reduce the cost of processing, etc., and it is easy to adjust the pigment concentration if necessary, and it is easy to disperse or adjust the pigment. A method for producing a thermosetting solid resin composition for preparing slurry-like or powder-like paints, which has the same color as conventional liquid paints, and which can be carried out safely with relatively simple operations and equipment. Our goal is to provide the following.

As a result of intensive research to achieve this objective, the present inventors have discovered that an acidic substance acts on an aqueous composition containing a resin that is stably retained in water due to the anionic activity of the neutralized carboxyl group. Even if all or part of the resin composition is agglomerated, mechanical granulation treatment such as stirring or spraying at the same time as or before or after the application of the acidic substance will cause the anion activity to be lost and the particle size to be uniform. It has been found that fine resin composition particles are precipitated.

[Structure of the Invention] The present invention has been completed based on the above-mentioned findings, and the gist thereof is to dissolve monomers and resins by a reaction in a system containing a water-miscible solvent. An acidic substance is added to an aqueous resin composition liquid containing a neutralized resin selected from alkyd resins, acrylic resins, and acrylic modified alkyd resins, and a crosslinking agent selected from epoxy resins, aminoplast resins, and blocked polyisocyanate compounds. The method of producing a thermosetting solid resin composition is characterized in that the particles of the resin composition are precipitated by performing granulation treatment at the same time or before or after the reaction.

The alkyd resin, acrylic resin, or acrylic-modified alkyd resin in the present invention may be obtained by a conventional method of resin synthesis in the presence of a solvent. The acrylic-modified alkyd resin can be obtained by copolymerizing an acrylic polymerizable monomer with an alkyd resin having an active site that can be grafted, such as a polymerizable unsaturated group or a mercapto group. As the solvent, an alcohol-based solvent (eg, isopropanol) or an ether-based solvent (eg, ethyl cellosolve, butyl cellosolve) that dissolves both the monomer and the resin and is miscible with water may be used. By neutralizing the carboxyl groups of these resins according to conventional methods,
The resin can be dissolved or decomposed in water. Agents used for the above neutralization (hereinafter referred to as neutralizing agents) include inorganic basic compounds (potassium hydroxide, sodium hydroxide, potassium carbonate, etc.) ammonia or organic amines (monomethylamine,
triethylamine, monoethanolamine, dimethylethanolamine, triethanolamine,
(ethylenediamine, diethylenetriamine, etc.)
can be mentioned.

As the above-mentioned crosslinking agent, ordinary crosslinking resins or compounds can be used as long as they can react with the functional groups (carboxyl group, hydroxyl group, etc.) present in the molecules of alkyd resin, acrylic resin, or acrylic modified alkyd resin. In particular, it is desirable to use a resin that is itself compatible with the above-mentioned resin, or at least is compatible with the resin during baking to provide a uniform coating film. Specifically, examples of compounds that can react with carboxyl groups include epoxy resins having two or more epoxy groups; examples of compounds that can react with hydroxyl groups include urea resins, melamine resins (such as hexamethoxymethylolmelamine), and amino acids such as benzoguanamine. Examples include plasto resins and polyisocyanate compounds having blocked isocyanate groups.

The above-mentioned crosslinking agent may be mixed into either the resin solvent solution itself obtained by synthesis, its neutralized product, or a system in which the neutralized product is dissolved or dispersed in water, depending on its property against solvents or water. good.
In addition, if mixing is difficult, various mixing methods may be adopted as necessary, such as mixing in a molten state, emulsification mixing, or dissolving in a solvent and mixing.

In the case of the aqueous resin composition liquid containing the above resin neutralized product and crosslinking agent, pigments, colorants, modifiers (e.g., natural resins, cellulose derivatives such as cellulose acetate butyrate, alkyds, etc.) may be added as necessary. resin, acrylic resin, vinyl resin) may be blended. The nonvolatile content of such aqueous resin composition liquid is usually set at 5 to 80% by weight, preferably 10 to 60% by weight.

In many cases, all or most of the aqueous resin composition liquid prepared in this way causes agglomeration when exposed to an acidic substance. granulation treatment (hereinafter referred to as acid treatment). The acidic substances used here are:
Any material that can dissolve in water and supply hydrogen ions may be used, such as inorganic acid aqueous solutions such as sulfuric acid, hydrochloric acid, phosphoric acid, and carbonic acid, formic acid, acetic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, lactic acid, butyric acid, and glycol. Examples include aqueous organic acids such as acetic acid, and acid gases such as carbon dioxide gas and sulfur dioxide gas. The concentration of the inorganic acid aqueous solution or organic acid aqueous solution may be selected depending on the particle state (particle size, particle shape, etc.) of the granular resin composition precipitated by the acid treatment, and is usually 1N or less, preferably 0.2N or less. desirable. In addition, in the case of acidic gas, there is no problem even if it is used alone, but it can be used by appropriately mixing it with a non-reactive gas such as air or nitrogen if necessary. The amount of such an acidic substance to be used may be generally set to be about equivalent or more to the neutralized carboxyl group of the above-mentioned resin neutralized product.

The acid treatment may be carried out as appropriate based on the shape, size, etc. of the particles of the resulting resin composition, and for example, the method described below may be employed.

(a) A method of stirring at high speed while gradually blowing the acidic gas into the aqueous resin composition liquid.

(b) A method in which the aqueous resin composition liquid is gradually added to the acid aqueous solution while stirring at high speed, or vice versa. At this time, water-soluble polymer compounds with dispersibility such as polyethylene oxide and poval, cellulose derivatives such as hydroxycellulose, or low-molecular dispersants represented by so-called cationic or nonionic surfactants are added to the acid aqueous solution. By allowing it to exist, more rounded spherical resin composition particles are precipitated. According to the paint obtained using such particles, when coated, the surface of the object to be coated can be more densely filled, so that a smoother and glossier coating film can be obtained.

(c) A method of spraying the aqueous resin composition liquid on the surface of the acid aqueous solution or into the acid aqueous solution, with stirring if necessary.
In this case as well, it is advantageous to have a dispersant present in the acid aqueous solution as in the method (b) above.

(d) A method of spraying an aqueous resin composition liquid into the acid gas stream.

(e) A method in which the acid aqueous solution and the aqueous resin composition liquid are brought into contact with each other in a sprayed state.

Through this acid treatment, the neutralized carboxyl groups of the resin neutralized product in the aqueous resin composition liquid are affected by the acidic substance, become free carboxyl groups, and undergo a granulation action, resulting in a change in the resin composition. Particles of matter precipitate. In general, regarding the shape of particles, methods (c), (d), and (e) yield shapes that are much closer to true spheres than methods (a) and (b) above. The particle size of this particle is
Conditions for the above acid treatment (e.g. viscosity of the aqueous resin composition liquid, stirring speed, aperture of the spray nozzle, spray viscosity, etc.)
It can be adjusted as appropriate.

Next, the system after the acid treatment is subjected to normal separation treatment (separation, sieving, centrifugation, etc.) after neutralizing excess acidic substances in the system with the above-mentioned neutralizing agent, if necessary. Particles of the resin composition are separated. In addition, when the above acid treatment is performed by method (d) or method (e), the particles can be directly separated.

A slurry-like paint can be obtained by subjecting the thus obtained thermosetting solid resin composition of the present invention to an appropriate post-treatment.

That is, the particles of the resin composition are washed with water to remove low-molecular salts produced by acid treatment, as well as unreacted neutralizers and acidic substances, and then subjected to pulverization treatment if necessary. It is redispersed in water to a predetermined non-brightening content to obtain a slurry-like paint with uniform particle size and no coarse particles. When using the slurry paint for painting, especially if the non-volatile content exceeds a certain level, the paint may be left stationary or separated by a method such as centrifugation and the supernatant water removed as appropriate. .

The above coating methods include, for example, air spray coating, electrostatic coating, dipping coating, roll coater coating,
A method such as brush painting can be employed, and by baking and drying under appropriate conditions after application, a smooth and glossy coating can be obtained.

When this slurry paint is applied using the normal spray coating method, water evaporates faster during application than with conventional water-based baking paints such as water-soluble or emulsion paints, so a thicker paint film can be obtained. As a result, painting work efficiency is greatly improved. Furthermore, the coating film formed after baking and drying has a higher
It is recognized that it has excellent smoothness and gloss.

On the other hand, a powdered coating material can be obtained by drying the washed resin composition particles as they are or by redispersing them in water according to a conventional method (hot air drying, spray drying, vacuum drying, etc.). Such coatings can be used in the same manner as conventional powder coatings in similar application methods. The advantage of such a powder coating is that, compared to the conventional method of pulverizing a solid resin composition that does not contain substantially water, there is no risk of dust scattering or dust explosion during the pulverization process, and there is no risk of dust explosion. Not only does it generate less noise, as mentioned above, it is easy to select the shape and adjust the particle size, and the type of resin used can be freely selected from a wide range of options.

[Effects of the Invention] According to the method of the present invention having the above-described structure, a large amount of a solvent mixture can be produced as a by-product, unlike the conventional method (1) in which the resin component is precipitated by utilizing the difference in the dissolving power of the solvent. There is no need to worry about contaminating the air, etc., and therefore, the process of recycling, collecting, removing, etc. can be omitted, making it highly economical, and when using acetone, etc. There is little risk of explosion, etc. In the method of the present invention, an inorganic basic compound of a monovalent metal is preferably used as a neutralizing agent, for example, sodium hydroxide is used, and an aqueous hydrochloric acid solution is combined with this as an acidic substance. The salt produced as a by-product is harmless common salt. Therefore, it is more advantageous and economically superior to the conventional method (1) in terms of waste treatment. Note that when an inorganic basic compound of a divalent metal is used as a neutralizing agent, a water-insoluble salt is generally produced as a by-product, but in this case as well, it can be allowed to remain as long as it does not adversely affect the formed coating film. There is no problem.

In addition, in the method of the present invention, since the aqueous resin composition liquid before acid treatment has the same form as a normal liquid paint,
When pigment dispersion is required, conventional liquid paint technology can be used as is, so if the method of the present invention is applied to paint production, it can be used to create conventional powder paints or slurry paints in which powder paints are dispersed in water. In comparison, the adsorption of the resin to the pigment is good, which results in excellent gloss and smoothness.Furthermore, since conventional color toning methods can be used, color toning can be done very easily and with high precision.

Furthermore, in the method of the present invention, starting from a solvent solution of alkyd resin, acrylic resin and/or acrylic modified alkyd resin, using this to obtain an aqueous resin composition liquid, and subjecting the liquid to acid treatment,
From the beginning, without using water-based resin compositions,
Since a thermosetting solid resin composition can be produced, it can greatly contribute to the expansion of the technology for obtaining the solid resin composition.

[Examples] Next, the present invention will be specifically described with reference to Examples and Reference Examples. In the Examples and Reference Examples, "parts" means "parts by weight."

Example 1 Nonvolatile content of an acrylic resin whose constituent monomers are 14.5 parts of acrylic acid, 8.9 parts of hydroxypropyl acrylate, 14.9 parts of methyl methacrylate, 16.1 parts of n-butyl methacrylate, 26 parts of styrene, and 16.6 parts of n-butyl acrylate. A dimethylethanolamine aqueous solution is allowed to act on an 80% by weight ethyl cellosolve solution to obtain an aqueous acrylic resin liquid (non-volatile content: 38% by weight) with a neutralization rate of 100%. 35 parts of this resin liquid, 2.9 parts of hexamethoxymethylolmelamine, and 0.71 part of aluminum powder whose surface is coated with a hydrophilic substance are dispersed and mixed, and then 30 parts of water is added and mixed to prepare an aqueous resin composition liquid.

Next, add 63.61 parts of the aqueous resin composition liquid to 500ml.
Add dropwise to a 1/20N aqueous hydrochloric acid solution while stirring using a high-speed lab mixer (time: approximately 15 minutes). After dropping, the excess acid in the system is neutralized with a 1N potassium hydroxide aqueous solution, and then sieved through a 250-mesh sieve to obtain a thermosetting solid resin composition with a particle size of 10 to 30 μm.

Reference Example 1 After washing with water, the solid resin composition obtained in Example 1 is redispersed in water so that the nonvolatile content is 50% by weight to produce a slurry paint. After applying this slurry paint to a polished steel plate by air spraying,
After baking and drying at 160° C. for 30 minutes, the resulting coating film was smooth and had good gloss and a good metallic feel. Furthermore, when the coating film was subjected to a DuPont impact test, it showed an impact strength of 20 cm or more (500 g), indicating that it was sufficiently crosslinked.

Reference Example 2 After washing the solid resin composition obtained in Example 1 with water,
A powder coating is produced by drying in a fluidized bed dryer at 50°C for 3 hours. When this powdered paint was applied electrostatically to a matte steel plate and then baked and dried at 160°C for 30 minutes, a well-crosslinked coating film was obtained that was smooth, had good gloss, had a good metallic feel, and was fully crosslinked.

Example 2 Nonvolatile content of alkyd resin (number average molecular weight 1500, acid value 56, hydroxyl value 30, monomer composition: soybean oil 35% by weight, neopentyl glycol 25% by weight, isophthalic acid 15% by weight, trimellitic acid 25% by weight) 100 parts of a neutralized resin solution obtained by reacting triethylamine with a 70% by weight isopropanol solution, 30 parts of benzoguanamine as a crosslinking agent, 60 parts of titanium oxide (product name: "Tipaque R-820 Titanium" manufactured by Ishihara Sangyo Co., Ltd.)
1 part and 640 parts of water are dispersed and mixed to prepare an aqueous resin composition liquid.

Next, the aqueous resin composition liquid is air-sprayed onto the water surface of a container filled with a 1/20 N hydrochloric acid aqueous solution (at this time, the hydrochloric acid aqueous solution is stirred). Separate the precipitated particles using a centrifuge,
A thermosetting solid resin composition having a true spherical shape of 50μ or less is obtained.

Reference Example 3 After washing with water, the solid resin composition obtained in Example 2 is redispersed in water so that the nonvolatile content becomes 50% by weight to produce a slurry paint. After applying this slurry paint to a polished steel plate by air spraying,
After baking and drying at 160°C for 30 minutes, the resulting coating film was smooth and had good gloss. Furthermore, when the coating film was subjected to an Erichsen test, it was found to be 3 mm or more, indicating sufficient crosslinking.

Reference Example 4 After washing the solid resin composition obtained in Example 2 with water,
A powder coating is produced by drying in a fluidized bed dryer at 50°C for 3 hours. When this powdered paint was electrostatically applied to a matte steel plate and then baked and dried at 160°C for 30 minutes, a smooth and well-crosslinked coating film was obtained that exhibited good gloss.

Example 3 100 parts of the alkyd resin solvent solution of Example 2 and a 50% by weight methyl ethyl ketone solution of 14 parts of tolylene diisocyanate resin blocked with ethanol were mixed, and the mixture was treated with dimethylethanolamine to achieve a neutralization rate of 70. % resin mixture is obtained.
114 parts of this mixed solution, 30 parts of the titanium oxide of Example 2, and 350 parts of water are dispersed and mixed to prepare an aqueous resin composition liquid.

Next, the aqueous resin composition liquid is air-sprayed into a carbon dioxide gas stream to obtain true spherical particles, which are collected to obtain a thermosetting solid resin composition.

Reference Example 5 The solid resin composition obtained in Example 3 was washed with water and redispersed in water to a non-volatile content of 50% by weight to obtain a slurry paint, and the solid resin composition was washed with water and dried to obtain a powder. Paint.

Example 4 10 parts of alkyd resin having a mercapto group with the following composition and special values, 15 parts of acrylic acid, 15 parts of 2-hydroxyethyl methacrylate, 38 parts of methyl methacrylate, 19 parts of styrene, 8 parts of n-butyl acrylate.
and 30 parts of butyl cellosolve to obtain a liquid composition.

Composition and special values of alkyd resin Monomer composition Neopentyl alcohol 69.4 parts Trimethylolpropane 33.4 parts Isophthalic acid 119.7 parts Adipic acid 13.2 parts Thioglycolic acid 16.6 parts Acid number 10 or less Number average molecular weight 1800 Weight average molecular weight 4500 Viscosity (nonvolatile content 60 weight %, Gardner bubble viscometer) L~R 25 parts of the above liquid composition was placed in a Kolben and heated to 130°C.
Add the above liquid composition to this while stirring while maintaining the
A mixture of 110 parts of azobisisobutyronitrile and 1.5 parts of azobisisobutyronitrile is added dropwise over a period of 3 hours. After dropping, stir at the same temperature for 1 hour. Next, 36 parts of a 10% by weight aqueous solution of sodium hydroxide was added at 110°C, followed by stirring for 30 minutes, and further 150 parts of water was added at 100°C or lower to obtain a neutralized acrylic-modified alkyd resin aqueous solution. This resin liquid
To 130 parts, 10 parts of hexamethylol melamine and 30 parts of aluminum powder (trade name "Alpaste 5105WA" manufactured by Toyo Aluminum Co., Ltd.) are added and dispersed to prepare an aqueous resin composition liquid.

Next, 130 parts of the aqueous resin composition liquid is diluted with 200 parts of water, and then 700 parts of a 1/10N hydrochloric acid aqueous solution is added thereto and thoroughly stirred with a lab mixer to form granules. Next, after neutralizing the excess acid with a 1/10N aqueous sodium hydroxide solution, the aqueous medium was removed and the particle size was 10 to 20 μm.
A thermosetting solid resin composition is obtained.

Reference Example 6 The solid resin composition obtained in Example 4 was thoroughly washed with water (in this case, the by-formed salt is harmless sodium chloride and is completely removed by washing with water), and then the nonvolatile content was adjusted to 50% by weight. The slurry is then redispersed in water to produce a slurry paint. This slurry paint is air-sprayed onto a polished steel plate and then heated to 160°C.
After baking and drying for 30 minutes, a smooth coating film with good gloss was obtained.

Furthermore, when the solid resin composition was washed with water and then dried to form a powder coating in the same manner as in Reference Example 2, the baked coating film obtained was also found to have sufficient performance.

Example 5 Alkyd resin (number average molecular weight 1410, acid value 55, hydroxyl value 20, monomer composition: 30% by weight of soybean oil, 25% by weight of neopentyl glycol, 15% by weight of isophthalic acid, 5% by weight of adipic acid, 25% by weight of trimellitic acid) A composition containing 100 parts of isopropanol/butyl cellosolve (1:1) solution with a nonvolatile content of 80% by weight) and 18 parts of epichlorohydrin bisphenol A epoxy resin (trade name "Epicote #828" manufactured by Ciel Chemical Co., Ltd.) was added with dimethyl ethanol. A neutralized resin liquid is obtained by the action of an amine, and 640 parts of water and 60 parts of the titanium oxide of Example 2 are dispersed and mixed to prepare an aqueous resin composition liquid.

Next, this aqueous resin composition liquid is treated in the same manner as in Example 2 to obtain a thermosetting solid resin composition.

Reference Example 7 The solid resin composition obtained in Example 5 was prepared as Reference Example 3.
A slurry-like paint was obtained by processing in the same manner as above, and this was air-sprayed onto a polished steel plate, and then baked and dried at 130℃ for 30 minutes.The resulting coating showed good gloss, and the surface was coated with xylene for 20 minutes. After rubbing twice, there was no shine or sink and it was sufficiently cured.

Claims (1)

[Claims] 1 Contains a resin having a carboxyl group in the molecule selected from alkyd resins, acrylic resins, and acrylic-modified alkyd resins obtained by dissolving both monomers and resin and reacting the monomers in a water-miscible solvent. A base is added to the reaction mixture to neutralize the carboxyl groups, and the resulting neutralized mixture is mixed with a crosslinking agent selected from epoxy resins, aminoplast resins and blocked polyisocyanate compounds, and other substances as necessary. An aqueous solution obtained by mixing an optional component of with water is subjected to a granulation treatment at the same time or before or after the action of an acidic substance to precipitate particles containing the resin and a crosslinking agent. A method for producing a thermosetting solid resin composition.