JPH0588751B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coating composition for polyurethane resin molded articles having good primer function and topcoat function. Polyurethane resin has excellent flexibility, lightness,
Due to its moldability, its molded products are widely used in automobiles, ships, airplanes, furniture, etc. However, the weather resistance of polyurethane resins used for molded products is extremely poor due to their chemical structure, and they are usually coated for purposes such as protection and to increase the added value of molded products. Conventionally, the coating system has generally been to apply a primer specifically designed for polyurethane resin, and then apply an ordinary flexible topcoat. As a special primer, one using MDI (4,4'-diphenylmethane diisocyanate)-based polyurethane resin is known, and its functions are strong adhesion to polyurethane resin molded products and flexibility that follows the material. It provides flexibility and covers pinholes scattered on the surface of the material. As flexible topcoats, there are known one-component curing paints such as acrylic melamine resin, polyester melamine resin, and alkyd melamine resin, and two-component curing paints such as acrylic isocyanate resin and polyester isocyanate resin. has been
Its functions include finish quality such as gloss and sharpness, as well as heat and
These include durability against light, rain, chemicals, etc., and flexibility that follows the material. However, with this conventional painting method,
A minimum of two steps are required to apply and dry the primer, then apply and bake the topcoat. In addition, due to the design of the molded product, when a two-tone finish is used and some unpainted parts are left unpainted, there is a problem in that the weather resistance of the unpainted parts deteriorates significantly and yoking occurs after approximately one year, which is not aesthetically pleasing. The present inventors have conducted intensive studies to solve the above-mentioned problems, and have found that an epoxy group-containing compound and pyrrolidone or its derivatives are added to a flexible top coat consisting of a polyester resin and a crosslinking agent (melamine resin or polyisocyanate). It was discovered that the coating composition obtained by adding the above-mentioned compound has both good primer function and topcoat function, leading to the completion of the present invention. Therefore, according to the present invention, for a thermosetting coating composition containing (A) a polyester polyol resin and (B) a crosslinking agent as main components,
A coating composition for a polyurethane resin molded article is provided, which contains (C) pyrrolidone or a derivative thereof and (D) an epoxy group-containing compound having a number average molecular weight of 100 to 10,000. By applying the coating composition of the present invention to a polyurethane resin molded article, it can provide both primer and topcoat functions in one step, providing a coated article with functions equivalent to or superior to conventional two-step coated articles. It is something to do. The coating composition of the present invention will be explained in detail below. The polyester polyol resin used as component (A) is phthalic acid and its acid anhydride, isophthalic acid, terephthalic acid, trimellitic acid and its acid anhydride, hexahydrophthalic acid and its acid anhydride, succinic acid, adipic acid, pimeline. acid,
Polybasic acid components such as sebacic acid and brassylic acid, and polyol components such as ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, 1,6-hexanediol, trimethylolpropane, glycerin, pentaerythritol, and tricyclidecanedimethanol. and can be produced by condensation polymerization according to a conventional method. At this time, the molecular weight may be adjusted by using, for example, benzoic acid, pt-butylbenzoic acid, etc. as an end-capping agent. In addition, as part of the above acid components, coconut oil fatty acids, tall oil fatty acids,
Oil-denatured fatty acids such as castor oil fatty acids may also be used. Further, it may be modified by chain extension with 1,6-hexamethylene diisocyanate or the like. These polyester polyol resins must have a hydroxyl value necessary for crosslinking and preferably have appropriate flexibility. The crosslinking agent of component (B) is for crosslinking and curing the polyester polyol resin of component (A), and usually an aminoaldehyde resin or a polyisocyanate compound is used. An aminoaldehyde resin is produced by reacting an aldehyde with an amino component such as melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, or dicyandiamide. Examples of the aldehyde to be reacted with the amino component include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. The aminoaldehyde resin is modified with a suitable alcohol, and examples of alcohols used for modification include methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-
Butyl alcohol, 2-ethylbutanol, 2-
Ethylhexanol, benzyl alcohol, lauryl alcohol, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol ethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monomethyl ether (methyl carbitol), diethylene glycol monoethyl ether (ethyl carbitol),
Examples include diethylene glycol monobutyl ether (butyl carbitol). When using hexamethoxymethylmelamine or a melamine resin in which a portion of its methoxy groups are substituted with an alcohol of C4 _or more as the aminoaldehyde resin, it is preferable to add a commonly used curing catalyst such as para-toluenesulfonic acid. The polyisocyanate compound may be one that is normally commercially available, and includes Biuretz type, isocyanurate type, polyhydric alcohol addition type, and the like. The isocyanate monomers used as these raw materials are selected from those having good weather resistance, such as hexamethylene diisocyanate and isophorone diisocyanate. When using these curing agents, it is a two-part type in which the base paint (polyester polyol resin) and curing agent (polyisocyanate compound) are mixed immediately before use. It can also be used as a one-component paint as a block type isocyanate compound. Pyrrolidone or its derivative as component (C) is used for the purpose of swelling the surface of the polyurethane resin molded product, and is used in an amount of 5 to 200 PHR (parts by weight/
(100 parts by weight of resin of components (A), (B) and (D))
Preferably, 10 to 100 PHR is added. Pyrrolidone or its derivatives are liquid at room temperature and have a strong ability to dissolve many organic compounds, so they are generally widely used as industrial solvents. Specifically, 2-pyrrolidone, N-methyl-2
-pyrrolidone, N-vinyl-2-pyrrolidone, and the like. These pyrrolidones or their derivatives are so-called "strong solvents" and have a strong cohesive force, such as polyurethane resin moldings, and can even swell thermosetting resins. However, because of its high boiling point, water absorption, and high price, it is not normally used as a paint solvent. If the amount of component (C) added exceeds 200PHR,
Due to its high boiling point, it remains in the coating film even after baking, causing problems such as moisture absorption and adhesiveness of the coating film, resulting in a decrease in moisture resistance. It is unsuitable because it has little swelling effect and reduces adhesion. The epoxy group-containing compound of component (D) has a polarity based on its glycidyl group or hydroxyl group, so the polar groups have a strong affinity with the polyurethane resin, and exhibit strong adhesion to the polyurethane resin molded product. The epoxy group-containing compound of component (D) used for the above purpose is an epoxy group-containing compound.

A compound having one or more formulas in one molecule. As such epoxy group-containing compounds, compounds known per se can be used, and include, for example, polyglycidyl ethers of polyphenols that can be produced by reacting polyphenols with epichlorohydrin in the presence of an alkali. Ru. Examples of polyphenols that can be used here include bis(4-hydroxyphenyl)-2,2-propane, 4,4'-dihydroxybenzophenone, and bis(4-hydroxyphenyl)-1,1- Ethane, bis-(4-hydroxyphenyl)-1,1-isobutane, bis(4-hydroxy-tert-butyl-phenyl)-2,2-propane, bis(2-hydroxynaphthyl)methane, 1,5- Examples include dihydroxynaphthalene. It is also possible to use an epoxy group-containing compound obtained by reacting diglycidyl ether with a polyphenol as described above and further reacting this with epichlorohydrin. For these polyphenols, hydrogenated compounds in which hydrogen is added to some or all double bonds of the aromatic ring can also be used, and hydrogenated compounds are preferable from the viewpoint of weather resistance. Other epoxy group-containing compounds that can be used include polyglycidyl ethers of phenolic novolac resins and polyglycidyl ethers of polyhydric alcohols. Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,4-propylene glycol, 1,5-pentanediol, 1,2,6-
Hexanetriol, glycerol, bis(4-
hydroxycyclohexyl)-2,2-propane,
Examples include sorbitol. In addition to the above, monohydric alcohols such as phenol and 2-ethylhexyl alcohol can also be used. Furthermore, polyglycidyl esters of polycarboxylic acids such as succinic acid, glutaric acid, terephthalic acid, 2,6-naphthalene dicarboxylic acid, dimerized linolenic acid and the like can also be used. An epoxy group-containing monomer, such as glycidyl acrylate or glycidyl methacrylate, by itself or in combination with one or more other polymerizable ethylenically unsaturated monomers, such as methyl acrylate, ethyl acrylate, methyl methacrylate, acrylamide. Epoxy group-containing acrylic polymers obtained by polymerizing with , methacrylamide, acrylonitrile, methacrylonitrile, styrene, etc. can also be used.
Furthermore, epoxidized polybutadiene, epoxidized polycycloalkene, etc. can also be used. The above-mentioned epoxy group-containing compounds suitably have a number average molecular weight of 100 to 10,000, preferably 200 to 5,000, particularly polyglycidyl ethers of polyphenols and their epoxy equivalents having an epoxy equivalent of 2,000 or less, preferably 87 to 1,000. Hydrogenates and polyglycidyl ethers of polyhydric alcohols are preferred. Examples of commercially available products include polyphenol polyglycidyl ether type Epikote 828 (manufactured by Schiel Kagaku Co., Ltd.) with an average molecular weight of 380 and epoxy equivalent of approximately 190; hydrogenated polyphenol polyglycidyl ether type Santo ST-5080 (manufactured by Toto Kasei Co., Ltd.) with an average molecular weight of approx. 1200, epoxy equivalent: about 600 Polyglycidyl ether type polyhydric alcohol Denacol EX314 (manufactured by Nagase Sangyo Co., Ltd.) Average molecular weight: 260, epoxy equivalent: about 145. The number average molecular weight of the epoxy group-containing compound is 10,000
If it is larger, the compatibility of the base resin with the polyester polyol will deteriorate, and the diffusion rate to the material surface will decrease, resulting in a decrease in adhesion. If the number average molecular weight is less than 100, it generally evaporates easily and is difficult to remain in the coating film components, and even if it remains, problems such as stickiness may occur. Furthermore, if the epoxy equivalent is 2000 or more, the concentration of epoxy groups in the molecule is low, resulting in a decrease in adhesion to the material. The blending amount of the epoxy group-containing compound (D) is (A)
The proportion is 5 to 50 parts by weight, preferably 10 to 30 parts by weight, based on a total of 50 to 95 parts by weight of component and component (B), so that the total amount is 100 parts by weight.
If the amount is less than 5 parts by weight, the adhesion will be poor, and if it exceeds 50 parts by weight, the strength of the coating will decrease, and durability, weather resistance, physical properties, etc. will decrease. The solvent used in the coating composition of the present invention is a solvent commonly used in coatings. However, as a crosslinking agent,
When using a polyisocyanate compound, among the following alcohol solvents cannot be used. Examples of solvents include aromatic solvents such as toluene and xylene, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, and acetic acid.
- Ester solvents such as butyl and ethyl acetate, alcohol solvents such as methanol and n-butanol, cellosolve solvents such as ethyl cellosolve, butyl cellosolve, ethylene glycol monoethyl ether acetate (cellosolve acetate), ethyl carbitol, butyl carbitol, etc. Thor,
Carbitol solvents such as diethylene glycol monoethyl ether acetate (carbitol acetate), saturated hydrocarbon solvents such as heptane, octane, and cyclohexane, and one or two of the following: ether solvents, petroleum solvents, mineral spirits, etc. The above is used. The coating composition of the present invention can be made into a coating by blending pigments using a conventional pigment dispersion method. Examples of pigments that can be used include inorganic pigments such as metal oxides and hydroxides, chromates, silicates, sulfides, sulfates, and carbonates, various organic pigments, carbon black, and various metals. Pigments used in regular paints, such as flakes, are used. Of course, even transparent coating compositions containing no pigment can be used. The coating composition of the present invention may contain, as desired, a plasticizer or plastic resin, a coating-strengthening resin, a dispersant, a coating surface conditioner, a fluidity conditioner, an ultraviolet absorber, an ultraviolet stabilizer, an antioxidant, and a crosslinking agent. Various known additives such as reaction accelerators and crosslinking reaction inhibitors can be added and used. The method for producing the coating composition of the present invention using the above-mentioned components may be performed using the same equipment and steps as in conventional coating production methods. For example, use a suitable dispersion machine such as a ball mill, sand mill, or roll mill to create a pigment paste by dispersing the pigment in a mixture of binder and solvent, then add the necessary ingredients and mix uniformly with a disperser, etc. It can be made into a paint using a method. The coating composition of the present invention can be applied by conventional coating methods. In other words, paint diluted with a solvent to a suitable viscosity for painting can be applied at room temperature or at elevated temperatures using an air spray machine, airless spray machine, various electrostatic coating machines, dipping, roll coating machine, brushing, etc. . After coating, the coating composition of the present invention is crosslinked and cured by heating or at room temperature. The heating conditions are, for example, 70% when using aminoaldehyde resin as a crosslinking agent.
Appropriate temperature and time conditions may be selected within the range of 1 to 100 minutes at ~180°C. In addition, when polyisocyanate compound is used as a crosslinking agent, it can be used at room temperature to 180℃.
All you have to do is choose an appropriate temperature and time condition within the range of 1 minute to 24 hours. The coating composition of the present invention may be applied onto a polyurethane molded article and used as is, or it may be further coated with a top coat to achieve a two-tone color finish. The coating film made of the composition of the present invention thus obtained exhibits strong adhesion to polyurethane resin molded articles,
It maintains good adhesion not only in the initial adhesion through the cross-over adhesion test, but also in the moisture resistance test, gasoline immersion test, and weather resistance test. Furthermore, it fully satisfies the performances required as a top coat for polyurethane resin molded articles, such as gloss, sharpness, chemical resistance, physical properties, and weather resistance. The mechanism by which strong adhesion is obtained is that the pyrrolidone solvent in the coating material first penetrates into the skin of the polyurethane resin molded product and causes it to swell. The polyester polyol resin and aminoaldehyde resin (or polyisocyanate compound) diffuse and permeate into the swollen material skin. This process is accelerated by compounds containing epoxy groups. Epoxy groups are highly polar and have a high affinity with urethane structures, which also have high polarity, resulting in strong adhesion. In this way, the polyester polyol resin and aminoaldehyde resin that have penetrated into the skin of the polyurethane resin molded product react and crosslink and harden by being baked. That is, the coating composition of the present invention penetrates into the skin of the material, crosslinks and cures, and therefore integrates with the material and exhibits strong adhesion. Further, since there are no particular restrictions on the polyester polyol resin and aminoaldehyde resin, ordinary ones conventionally used as top coats for polyurethane resin molded products can be used. Hereinafter, the effects of the present invention will be explained using examples.
Note that parts and % indicate parts by weight and % by weight. [Preparation of coating material] A reaction-injection molding polyurethane resin (RIM-PU) molded product used for automobile exteriors, or its fiber reinforced product (R-RIM PU), was dissolved in trichloroethane vapor for 1 hour.
It was degreased and used as a test piece. Example 1 A polyester polyol resin, an aminoaldehyde resin, a black pigment, and a solvent were mixed in the following weight ratio and dispersed in a ball mill to obtain a black paste. Part 60% polyester polyol resin solution (Note 1) 108.3 60% aminoaldehyde resin solution (Note 2) 41.7 Furnace type carbon black (Note 3) 3 Xylene 20 Cellosolve acetate 20 193 (Note 1) Manufactured by Mitsui Toatsu Chemical Co., Ltd. Product name Orester
- Pyrrolidone and the like were blended as shown below to obtain black enamel. Part Black paste 193 Epicote 828 (Note 4) 10 2-pyrrolidone 20 Silicone oil KP-323 (Note 5) 0.01 223.01 (Note 4) Manufactured by Ciel Chemical Co., Ltd., polyphenol type epoxy compound (Note 5) Manufactured by Shin-Etsu Chemical Co., Ltd. The thus obtained paint was mixed with xylene/butyl acetate/methyl ethyl ketone = 50/30/20 (weight ratio).
viscosity 18 seconds (Food cup #4, 20
℃). The diluted paint was air-sprayed onto the above-mentioned coating material to a dry film thickness of approximately 30 microns, left to stand at room temperature for 10 minutes, and then baked in an electric hot air dryer at a temperature of 120°C for 30 minutes to form a coated board. I made it. Furthermore, half of the obtained painted plate was masked,
A test coated plate was prepared by applying and baking a commercially available top coat for plastics (manufactured by Kansai Paint Co., Ltd., trade name: Soflex No. 1200 White) in the same manner as above.
The test results of the obtained coated plates are shown in Table 2. Example 2 An epoxy compound, N-methyl-2-pyrrolidone, etc. were blended in the following manner to a black paste prepared in the same manner as in Example 1 to obtain a black enamel. Part Black paste 171.6 Santoto ST-5080 20 (Note 6) N-Methyl-2-pyrrolidone 90 Silicone oil KP-323 0.01 281.61 (Note 6) Hydrogenated polyphenol type epoxy compound manufactured by Toto Kasei Co., Ltd. Below, Example 1 and Test coated plates were made by painting and baking in the same manner. The test results of the obtained coated plates are shown below.
Shown in 2. Example 3 A polyester resin, a black pigment, and a solvent were mixed in the following weight ratio and dispersed in a ball mill to obtain a black paste. Part 100% polyester resin 60 (Note 7) Furnace type carbon black 3 (Note 3) Xylene 20 Cellosolve acetate 20 103 (Note 7) Manufactured by Sumitomo Bayer, trade name: Dismohen 670 In addition to the above black paste, epoxy compound, N
-Vinyl-2-pyrrolidone and the like were blended as shown below to obtain black enamel. Black paste 103 Denacol EX-314 (Note 8) 16 N-vinyl-2-pyrrolidone 10 Silicone oil KP-323 0.01 129.01 (Note 8) Manufactured by Nagase Sangyo Co., Ltd., polyhydric alcohol-based epoxy compound Obtained black enamel 129.01 24 parts of Diuranate 24A-100 (manufactured by Asahi Kasei Kogyo Co., Ltd.) as a polyisocyanate was added to the sample, and the coating was immediately baked in the same manner as in Example 1 to prepare a test coated plate. The test results of the obtained coated plates are shown in Table 2. Comparative Example 1 Among the black enamel formulations of Examples 1 to 3,
A test coated plate was prepared by coating and baking the sample (as shown in Table 1) without the epoxy compound and pyrrolidone compound in the same manner as in Example 1. The test results of the obtained coated plates are shown in Table 2.

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[Table] * Values are solid content ratio ** Values are PHR

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Claims (1)

[Claims] 1 (A) polyester polyol resin and (B)
For a thermosetting coating composition containing a crosslinking agent as a main component, (C) pyrrolidone or its derivative and (D)
A coating composition for a polyurethane resin molded article, characterized in that it contains an epoxy group-containing compound having a number average molecular weight of 100 to 10,000. 2. The polyurethane resin molding according to claim 1, wherein the blending amount of component (C) is 5 to 200 parts by weight based on a total of 100 parts by weight of components (A), (B), and (D). Paint composition for goods. 3 The blending amount of component (D) is 5 to 50 parts by weight (the total amount of components (A), (B), and (D)) to the total of 50 to 95 parts by weight of components (A) and (B). 100
The coating composition for a polyurethane resin molded article according to claim 1, which has a ratio of (parts by weight).