JPS6042259B2 - Method for producing thermosetting solid resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a thermosetting solid resin composition, and more particularly, a method for producing a thermosetting solid resin composition that can be advantageously used for preparing slurry or powder coatings. Regarding the method.

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 these, powder paints and slurry paints are particularly advantageous compared to other paints in that they emit extremely few harmful substances during the painting process, are easy to dispose of afterwards, and can be recycled. Because of its advantages, it is expected that it will occupy an important field in 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. There is a method of suspending it as it is in water to form a slurry paint (see Japanese Patent Application Laid-Open No. 481-4554).

In addition, there is also a method in which a coagulating liquid is mixed with a liquid paint having a liquid portion that is miscible with the coagulating liquid, and the precipitated paint particles are suspended in water as it is to form a slurry-like paint, and the above-mentioned precipitated Method of drying paint particles to make powder paint (see Japanese Patent Application Laid-open No. 52851/1985)
and (2) a method is known in which a liquid composition containing a pigment, a polymerizable monomer, and a resin is subjected to emulsion polymerization, and then the polymerized product is spray-dried to obtain a powder coating (see Japanese Patent Publication No. 33821/1983). ing. 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, method (1) above uses a liquid that does not dissolve the non-solvent part of the liquid paint as a coagulating liquid and causes precipitation to occur due to the difference in solubility. A large amount of liquid is required. For example, when water is used as a coagulating liquid, a large amount of water, 6 to 73 times the effective paint component, mixes with the solvent in the paint and forms a by-product, so if this water is simply discharged or evaporated, , causing water or air pollution, and being economically disadvantageous as well. 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, so safety and protection equipment must be rigorous. In the above method (2), 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 further an initiator,
After adding cross-linking agents, emulsifiers, additives, etc. and carrying out emulsion polymerization,
Because the polymerized product is spray-dried to form a powder coating, unlike ordinary solution resins, all of the polymerizable monomers that functioned as a solvent in the starting liquid pigment dispersion composition are removed. is essentially converted into a resin in the final paint, which inevitably results in a small pigment/resin ratio, making it difficult to obtain a paint with a high pigment concentration.Furthermore, the emulsifier used during emulsion polymerization remains unchanged. It may remain in the paint, and it is difficult to avoid deterioration in the appearance or performance of the paint film due to it. The purpose of the present invention is to use a substantially water-based resin composition liquid in contrast to the above-mentioned conventional methods for producing slurry paints and powder paints, so that a solvent is not essential as in the conventional method (1), and Even if the composition liquid 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 processes such as its removal are omitted or greatly simplified. It is possible to prevent or reduce environmental pollution during paint production and painting, reduce the cost of treatment, etc., and adjust the pigment concentration if necessary. A method for producing a thermosetting solid resin composition for preparing slurry or powder coatings, in which pigment dispersion or color adjustment is as easy as in conventional liquid coatings, and the method involves relatively simple operations and The objective is to provide a method that can be carried out safely with sufficient equipment.

As a result of intensive research to achieve this objective, the present inventors have developed an aqueous resin composition liquid containing a resin that is safely retained in water due to the cationic activity of the amine group neutralized by acid. Even if all or part of the resin composition is agglomerated when a basic substance is applied, the cation activity can be reduced by mechanical granulation such as stirring or spraying at the same time or before or after applying the basic substance. It has been found that fine resin composition particles of uniform particle size are precipitated. The present invention was completed based on the above-mentioned findings, and the gist of the present invention is to dissolve or disperse epoxy resins, acrylic resins, and A salt is added to an aqueous resin composition liquid containing at least one alkyd resin and at least one crosslinking agent among epoxy resins, aminoblast resins, and polyisocyanate resins that are reactive with crosslinkable functional groups in the resin. - A method for producing a thermosetting solid resin composition, which comprises performing granulation treatment at the same time or before or after applying a basic substance to precipitate particles of the resin composition with a particle size of 50 μm or less. Exists.

The aqueous resin composition liquid in the present invention includes a water-soluble or water-dispersible resin, a crosslinking agent, and, if necessary, a common coloring agent.
It consists of a system in which modifiers and the like are dissolved or dispersed in water using conventional methods without using ordinary surfactants.

The above water-soluble or water-dispersible resin has an amine group (
In other words, any resin may be used as long as it contains a primary, secondary or tertiary amine or a quaternary ammonium base and can be dissolved or dispersed in water by neutralizing some or all of these with an organic or inorganic acid. .

Of course, it may have other functional groups (eg, hydroxyl group, epoxy group, etc.) in addition to the above-mentioned amine group. Specific examples of these resins include epoxy resins, acrylic resins, and alkyd resins. The above-mentioned epoxy resins include copolymers of epoxy group-containing unsaturated compounds such as glycidyl ether of phenol, glycidyl ether of phenol aldehyde condensates, glycidyl acrylate, glycidyl methacrylate, and other polymerizable monomers. For typical epoxy resins or epoxy modified resins, various organic amino compounds (for example, j
An example is one to which diethanolamine is added. Acrylic resins include nitrogen-containing vinyl compounds such as acrylic esters or methacrylic esters having amino groups (for example, dimethylaminoethyl methacrylate) and/or vinylpyridines and vinylimidazole, and vinyl compounds without free acid groups. An example is a copolymer of As an alkyd resin, an acrylic ester or methacrylic ester having an amino group (for example, dimethylaminoethyl methacrylate) and a vinyl compound having no free acid group are grafted onto an alkyd resin having a grafting active site (for example, a mercapto group). Examples are given below. One or a mixture of two or more of the exemplified resins may be used. Note that these resins only need to be substantially water-soluble or water-dispersible, and the system may contain a solvent to an extent that does not interfere with granulation. The acid used for the neutralization may be either an organic acid or an inorganic acid, such as formic acid, acetic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, lactic acid, butyric acid, glycolic acetic acid, and sulfuric acid; Examples include inorganic acids such as hydrochloric acid, phosphoric acid, and carbonic acid. The above-mentioned crosslinking agent may be a general crosslinking resin or compound that can react with the functional groups (amine group, hydroxyl group, epoxy group, etc.) present in the molecule of the water-soluble or water-dispersible resin. Particularly desirable are those which are themselves compatible with water-soluble or water-dispersible resins, or at least are compatible upon baking to give a uniform coating film.

Specifically, for example, as a substance that can react with an amine group, 2
Epoxy resins having more than one epoxy group, those that can react with hydroxyl groups include urea resins, melamine resins (such as hexamethoxymethylol melamine), aminoblast resins such as benzoguanamine, and polyisocyanates having blocked isocyanate groups. Examples include resin. The above-mentioned modifier is one that is compatible with the water-soluble or water-dispersible resin and has the effect of modifying coating film performance, such as natural resins, cellulose derivatives such as cellulose acetate butyrate, alkyd resins, Examples include acrylic resin and vinyl resin.

When using the above-mentioned crosslinking agent or modifier, if the agent is liquid, it may be mixed as is with the water-soluble or water-dispersible resin, or if it is solid and difficult to mix, it may be mixed in a molten state, or Various mixing methods may be employed as required, such as emulsifying mixing or dissolving and mixing in a solvent.

The aqueous resin composition liquid may be prepared according to a conventional method. For example, a resin liquid dissolved or dispersed in water is added with a crosslinking agent, and if necessary, pigments, colorants, and modifying agents. Add the agent, etc. and mix to form the desired aqueous liquid. The non-volatile content of such aqueous resin composition liquid is usually 5 to 8 weight%,
Preferably, the saliva amount is set to 10 to 6%. In many cases, all or most of the aqueous resin composition liquid prepared in this way causes agglomeration when treated with a basic substance. It is subjected to mechanical granulation treatment (hereinafter referred to as base treatment) before and after.

The basic substance used here may be one that can dissolve in water and accept hydrogen ions, such as inorganic base aqueous solutions such as sodium hydroxide, potassium hydroxide, potassium carbonate, ammonia water, triethylamine, dimethyl Examples include aqueous organic base solutions such as aminoethanol, and basic gases such as ammonia gas. The concentration of the inorganic base aqueous solution, ammonia water, and organic base aqueous solution may be selected depending on the particle state (particle size, particle shape, etc.) of the granular resin composition precipitated by the base treatment, and is usually 1N or less,
It is preferably 0.2N or less. Further, in the case of basic gas, there is no problem even if it is used alone, but it is preferable to mix it with a non-reactive gas such as air or nitrogen as necessary. The amount of the basic substance to be used may be generally set to be about equivalent or more to the neutralized amine group in the water-soluble or water-dispersible resin. The base treatment may be carried out as appropriate based on the shape, size, etc. of the particles of the resulting resin composition. For example, the method shown below may be adopted.

(a) A method in which the basic gas is gradually blown into the aqueous resin composition liquid while stirring at high speed.

(b) A method in which the aqueous resin composition solution is gradually added to the aqueous base solution or aqueous ammonia while stirring at high speed, or vice versa.

In this case, a water-soluble polymer compound with dispersibility such as polyethylene oxide or poval in an aqueous base solution or aqueous ammonia, a cellulose derivative such as hydroxycellulose, or a low-molecular dispersant represented by a so-called anionic or nonionic surfactant. By allowing the above particles 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 onto the surface of the aqueous base solution or aqueous ammonia or into the aqueous base solution or aqueous ammonia, with stirring if necessary.

In this case as well, it is advantageous to have a dispersant present in the aqueous base solution or aqueous ammonia, as in the method (b) above. (d) A method of spraying the aqueous resin composition liquid into the basic gas stream.

(e) A method of contacting the aqueous base solution or aqueous ammonia with the aqueous resin composition liquid in a sprayed state.

By such base treatment, the neutralized amine groups of the water-soluble or water-dispersible resin in the aqueous resin composition liquid are affected by the basic substance, becoming free amine groups and undergoing a granulation action. As a result, particles of the resin composition are precipitated.

In general, regarding the shape of particles, the above (a) and (b)
Compared to the method, the methods (c), (d), and (e) yield a shape that is closer to a true sphere in the lateral layer. The particle size of the particles can be adjusted as appropriate by the conditions of the base treatment (for example, the viscosity of the water-soluble or water-dispersible resin liquid, the stirring speed, the diameter of the spray nozzle, the spray viscosity, etc.). Next, the system after the base treatment is neutralized with the above-mentioned acid to neutralize excess basic substances in the system, if necessary, and then subjected to normal separation treatments (filtration, sieving, centrifugation, etc.). The particles of the resin composition are separated.

In addition, when the above-mentioned base treatment is performed by method (d) or method (e), the particles can also be directly fractionated. A slurry-like paint can be obtained by subjecting the thus obtained thermosetting solid resin composition of the present invention, which usually has a particle size of about 50 μm or less, to an appropriate post-treatment.

That is, the particles of the resin composition are washed with water to remove low-molecular salts produced as by-products by base treatment, as well as unreacted acids and basic substances, and then subjected to pulverization treatment if necessary, and then subjected to a predetermined pulverization treatment. It is redispersed in water to become a non-volatile content to obtain a slurry-like paint with a 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. good. As the above-mentioned painting method, for example, air spray painting, electrostatic painting, dip painting, roll coater painting, brush painting, etc. have been adopted, and by baking and drying under appropriate conditions after application, a smooth and glossy coating is achieved. membrane 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, resulting in a thicker paint film. This makes it easier to do this, and therefore, painting work efficiency is also significantly improved.

Furthermore, it has been recognized that the coating film formed after baking and drying is superior in terms of smoothness and gloss compared to coating films of conventional powder coatings that are compositionally similar. On the other hand, the resin composition particles after washing with water are dried as they are or after being redispersed in water according to a conventional method (hot air drying, spray drying,
(vacuum drying, etc.), a powdered coating material is obtained.

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. According to the method of the present invention having the above configuration, a large amount of a solvent mixture is not produced as a by-product unlike the conventional method (1) in which precipitation is performed by utilizing the difference in the dissolving power of the solvent with respect to the resin component. There is less concern about contamination such as
It is highly economical as removal and other treatments can be omitted.
Furthermore, there is less risk of explosion, which is a concern when acetone or the like is used.

In the method of the present invention, hydrochloric acid is used as the acid used to neutralize the water-soluble or water-dispersible resin, and when this is combined with an aqueous sodium hydroxide solution as the basic substance, the salt produced as a by-product is harmless common salt. This method is more advantageous than the conventional method (1) in terms of waste treatment and is also economically superior. In addition,
When an aqueous inorganic base solution of a divalent metal is used as a basic substance, water-insoluble salts are generally produced as by-products, but in this case as well, they can be allowed to remain as long as they do not adversely affect the formed coating film. No problem. In addition, the method of the present invention
Since the aqueous resin composition liquid before base treatment has the same form as a normal liquid paint, if pigment dispersion is required, conventional liquid paint technology can be used as is.
When the method of the present invention is applied to the production of paints, compared to conventional powder paints or slurry paints in which powder paints are dispersed in water, resin adsorption to pigments is better, resulting in superior gloss and smoothness. Since conventional color toning methods can be used, color toning can be done very easily and with high precision.

Next, the present invention will be specifically explained with reference to Examples, Reference Examples, and Comparative Examples.

In addition, "parts" in these examples means "parts by weight." Example 1 Epoxy resin (trade name “Epicote 10” manufactured by Shell Chemical Co., Ltd.
01'') and 105 parts of diethanolamine in the presence of 2(a) parts of isopropanol in a nitrogen gas stream.
The reaction was carried out at °C for 3 hours to obtain an aminoepoxy resin liquid.

To 143 parts of the resin liquid, 6% of glacial acetic acid was added. After adding and cationizing 500 parts of deionized water, 16 parts of blocked polyisocyanate resin and 3 parts of titanium oxide (trade name "Tiebake R-820 Titanium" manufactured by Ishihara Sangyo Co., Ltd.) were added.
An aqueous resin composition liquid is prepared by adding and dispersing the liquid. Next, the aqueous resin composition liquid is diluted with 2 parts of water, and then added dropwise to a 0.05N aqueous potassium monohydroxide solution with vigorous stirring.

After dropping, excess alkali in the system is neutralized with a 0.1N aqueous monoacetic acid solution, and then centrifuged to obtain a thermosetting solid resin composition with a particle size of 50 μm or less. Reference Example 1 After washing with water, the solid resin composition obtained in Example 1 was redispersed in water to a nonvolatile content of 5% to produce a slurry paint.

When this slurry paint was air-sprayed onto a polished steel plate and then baked and dried at 180°C for 20 minutes, the resulting paint film showed good gloss and good smoothness.

Furthermore, when the coating film was subjected to a DuPont impact test, 20c
It showed 7n or more (50 revision) and was recognized to be sufficiently crosslinked. Example 2 An aminoacrylic resin with a glass transition point of 65°C and a weight average molecular weight of 18,000 (non-volatile content: 80 wt. %, solvent: isopropyl alcohol/water = 1/1 (weight ratio)), add one part of hexamethoxymethylolmelamine (trade name "Cymel 303" manufactured by American Cyanamid) and thoroughly knead. Furthermore, 5 parts of aluminum powder (trade name "L-579" manufactured by Silver Line) and 5 parts of isopropyl alcohol.
A mixed dispersion of 100% was added and mixed, and then a 0.1N monohydrochloric acid aqueous solution was added to prepare an aqueous resin composition liquid.

Next, a mixed solution of 5 (1) parts of a 0.1N aqueous sodium monohydroxide solution and 1 W of polyethylene oxide is added to the aqueous resin composition liquid, and the mixture is stirred using a high-speed laboratory mixer to form granules.

Next, excess alkali is neutralized with a 0.1N monohydrochloric acid aqueous solution, and then centrifuged to obtain a thermosetting solid resin composition with a particle size of 50 μm or less. Reference Example 2 After washing with water, the solid resin composition obtained in Example 2 was redispersed in water to a nonvolatile content of 5% to produce a slurry paint.

When a baked paint film was formed using this slurry paint under the same conditions as in Reference Example 1, the paint film showed good gloss and was smooth, with good metallic appearance, indicating that it was sufficiently crosslinked. Admitted. Reference Example 3 The solid resin composition obtained in Example 2 was washed with water and then dried in a fluidized bed dryer to produce a powder coating.

After applying this powdered paint electrostatically to a satin steel plate,
When baked and dried at ℃, it shows a smooth and good gloss.
A sufficiently cross-linked coating film with good medallion feel was obtained. Comparative Example 1 A thermosetting solid resin composition obtained by mixing 130 parts of the aqueous resin composition liquid of Example 2 with 400 parts of a 1% calcium chloride aqueous solution had an amorphous shape with a particle size of several sizes. Even after drying, particles with a particle size of 50 μm or less could not be obtained without pulverization.

Example 3 Glass transition by reacting methyl methacrylate, n-butyl acrylate, 2-hydroxyethyl methacrylate, styrel and dimethylaminoethyl meccrylate with an alkyd resin (4) having a mercapto group having the following composition and specific values. Acrylic graft amino alkyd resin with a weight average molecular weight of 21,000 (non-volatile content: 8% by weight) at a temperature of 60°C.
To 100 parts of solvent: isopropyl alcohol/water = 1/1 (weight ratio), polyisocyanate resin 4 having a blocked isocyanate group was added, thoroughly kneaded, and then titanium oxide 2 of Example 1 was added. , a mixed dispersion of part (a) water and 0.1 part of anionic surfactant is dispersed and mixed,
Next, a 0.1N monohydrochloric acid aqueous solution is mixed to prepare an aqueous resin composition liquid.

Composition and special values of alkyd resin (4) Monomer composition Neopentyl alcohol 69.4 parts Trimethylolpropane 33.4 parts, Isophthalic acid
119.7 parts adipic acid
131 parts thioglycolic acid
16.6 parts Acid value 10
Number average molecular weight: 1800 Weight average molecular weight: 4500 Viscosity (non-volatile content: 6% by weight, Gardner bubble viscometer)
L-R Next, after diluting the aqueous resin composition liquid with water to a non-volatile content of 1% by weight,
This is sprayed with an air spray gun, and at the same time, a 0.1N aqueous sodium monohydroxide solution is sprayed with another spray gun, and the two are brought into contact to obtain a thermosetting solid resin composition in the shape of a true sphere with a particle size of 50 μm or less. .

Reference Example 4 After washing with water, the solid resin composition obtained in Example 3 was redispersed in water so that the nonvolatile content was 5% by weight to produce a slurry paint.

When a baked paint film was formed using this slurry paint under the same conditions as in Reference Example 1, the paint film showed good gloss and was found to be sufficiently crosslinked. Reference Example 5 The solid resin composition obtained in Example 3 was washed with water and then dried under reduced pressure using a rotary evaporator to produce a powder coating.

Claims (1)

[Claims] 1. Reactive with at least one resin of epoxy resin, acrylic resin, and alkyd resin dissolved or dispersed in water by neutralizing the amine group in the molecule with acid, and with the crosslinkable functional group in the resin. At least one of epoxy resin, aminoplast resin and polyisocyanate resin
The aqueous resin composition liquid containing the seed crosslinking agent is subjected to a granulation treatment at the same time or before or after the action of a basic substance to precipitate particles of the resin composition with a particle size of 50μ or less. A method for producing a thermosetting solid resin composition.