JP2012021111A - Urethane coating composition and resin member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a urethane coating composition which can secure a characteristic such as the friction damage resistance and wear resistance of a curable coating even if used outdoors for a long period of time as a vehicle external trim.SOLUTION: The urethane coating composition contains low-molecular polyol (a), acrylic polyol (b), a silica particle (c) and polyisocyanate (d). The low-molecular polyol (a) has at least two or more hydroxy groups per molecule, its molar weight is 60-500, and its hydroxy group value is 500-2,000 mg.KOH/g. The urethane coating composition contains 0.5-30 wt.% of the low-molecular polyol (a), 0.5-20 wt.% of the acrylic polyol (b), and 20-70 wt.% of the silica particle (c) based on the total weight of (a) to (d) components, and is compounded with the polyisocyanate (d) at a rate at which an equivalence ratio of NCO/(the sum OH of (acrylic polyol (b))+(low-molecular polyol (a))) is 0.5-2.0.

Description

  The present invention relates to a urethane coating composition and a resin member coated with the same. More specifically, the present invention relates to a urethane coating composition capable of forming a cured coating film excellent in scratch resistance, abrasion resistance, chemical resistance, weather resistance, and the like on the surface of a resin molded body.

  Synthetic resins such as acrylic resin, polycarbonate resin, polystyrene resin, and ABS resin are easy to mold, lightweight, and excellent in impact resistance, and are used in various fields. However, moldings made of these resins are inferior in scratch resistance and abrasion resistance to the surface of glass, etc., so scratches or dents are caused by scratching with nails, contact with or contact with dust and pebbles. As a result, aesthetics and functions are easily impaired. In order to solve this, a method of covering and protecting the surface of a resin molded body with a coating film having excellent scratch resistance is generally performed, and various paints having such functions have been proposed. Among them, a cured coating using a urethanization reaction between a polyol and a polyisocyanate is suitable for low-temperature thermal curing and short-time curing in which a resin molded body does not undergo thermal deformation, and various coatings have been proposed. .

  For example, Patent Document 1 and Patent Document 2 describe a resin molded body using a urethane resin paint having rubber elasticity. These urethane resin coatings contain a polyol having a hydroxyl value of 10 to 200 mg · KOH / g. Moreover, in patent document 3 and patent document 4, the resin molding which utilized the silica fine particle as a reinforcing material of urethane resin coating is described in acrylic polyol and polyisocyanate. The hydroxyl value of the acrylic polyol used in Patent Document 3 is about 10 to 200 mg · KOH / g, and the hydroxyl value of the acrylic polyol used in Patent Document 4 is about 50 to 100 mg · KOH / g. On the other hand, Patent Document 5 describes the applicability of urethane paints using low-molecular multibranched polyether polyols. The polyether polyol has a molecular weight (Mn) of 1,000 to 4,000 and a hydroxyl value of 150 to 350 mg · KOH / g.

JP-A-7-258601 JP 11-228719 A JP 2002-327146 A JP 2008-296539 A JP 2008-94907 A

  Since the coating film having rubber elasticity of Patent Document 1 and Patent Document 2 has an effect of restoring scratches and dents by its elastic recovery force, the scratch resistance of the coating film is improved. However, the hydroxyl value of the polyol used is about 10 to 200 mg · KOH / g, and the crosslinking density in the coating film is low. Therefore, it has sufficient characteristics against relatively weak rubbing, but it is used for a long time outdoors, such as when it is worn by a hard substance such as pebbles or sand (for example, when applied to a vehicle interior / exterior product). It does not have coating film hardness or wear resistance that can withstand Also, since the polyol used has a relatively high polarity, for example, the obtained coating film is resistant to gasoline and kerosene with low polarity, but is contaminated with oil with relatively high polarity such as brake oil. There was a problem that it was easy.

  Moreover, in Patent Document 3, although the coating film hardness and various chemical resistances are improved, the hydroxyl value of the acrylic polyol used is low, and high scratch resistance and wear resistance such as interior and exterior products of vehicles are also required. It does not have sufficient characteristics that it can be used with any member. Even in Patent Document 4, the acrylic polyol has a low hydroxyl value, and thus has the same problem as described above. In Patent Document 5, it is expected that the crosslinking density in the coating film is improved as compared with the case of using acrylic polyol, but there is no description about the coating film characteristics.

  Therefore, the present invention solves the above-mentioned problems, and the object of the present invention is to provide the coating film with scratch resistance, abrasion resistance, and resistance even under conditions of long-term outdoor use such as vehicle exterior products. An object of the present invention is to provide a urethane coating composition capable of ensuring properties such as chemical resistance and weather resistance, and a resin member coated with the urethane coating composition.

That is, the object of the present invention can be solved by the following means.
[1] A urethane coating composition containing an acrylic polyol (b), silica particles (c), a polyisocyanate (d), and a low molecular polyol (a) having a molecular weight lower than that of the acrylic polyol, The low molecular polyol (a) has at least two or more hydroxyl groups per molecule, has a molecular weight of 60 to 500, and a hydroxyl value of 500 to 2,000 mg · KOH / g, (a) To 0.5 to 30% by weight of the low molecular weight polyol (a), 0.5 to 20% by weight of the acrylic polyol (b), and 20 to 20% of the silica particles (c) based on the total weight of the component (d). The polyisocyanate (d) is contained in an amount of ˜70% by weight, and the equivalent ratio of NCO / (total polyol OH of acrylic polyol (b) + low molecular polyol (a)) is 0.5 to 2.0. Characterized by compounding in case, urethane coating composition.
[2] The urethane coating composition according to [1], which contains 1 to 10 parts by weight of an ultraviolet absorber with respect to 100 parts by weight of the components (a) to (d).
[3] A resin member comprising a cured coating film formed by coating the surface of a resin molding with the coating composition according to [1] or [2] and curing the coating composition.
[4] The resin member according to [3], wherein the resin member is a vehicle interior / exterior product.

  According to the urethane coating composition of the present invention, properties such as scratch resistance, abrasion resistance, chemical resistance and weather resistance of the coating film can be ensured even under conditions of outdoor use for a long time. Moreover, it is hard to be polluted with oils having a relatively high polarity such as brake oil. Therefore, for example, by applying the urethane coating composition of the present invention as a curing film to a resin molded article such as a vehicle exterior product, the above effects can be exhibited to the maximum, and scratch resistance, abrasion resistance, Chemical resistance and weather resistance can be improved.

  The urethane coating composition of the present invention contains an acrylic polyol (b), silica particles (c), a polyisocyanate (d), and a low molecular polyol (a) having a molecular weight relatively lower than that of the acrylic polyol. .

(A) Low molecular polyol The low molecular polyol used in the present invention is a component that improves the crosslink density of the coating film to be formed, and has the effect of improving the scratch resistance and abrasion resistance of the coating film surface. The low molecular polyol used in the present invention has at least two hydroxyl groups per molecule. When the number of hydroxyl groups per molecule is one, the cross-linking density of the formed coating film is not sufficient, and there is a risk that the scratch resistance and wear resistance of the coating film will be lowered. Moreover, the molecular weight shall be 60-500 and low molecular weight. However, if the molecular weight is less than 60, there is a possibility that the solubility in the coating composition is lowered and the flexibility imparted to the coating film is lowered. On the other hand, if the molecular weight exceeds 500, the distance between crosslinks becomes long, so that the necessary crosslink density as a coating film cannot be obtained, and there is a risk of lowering scratch resistance and wear resistance. Preferably it is 70-400, More preferably, it is 80-300, More preferably, it is 90-200. The hydroxyl value is 500 to 2,000 mg · KOH / g. When the hydroxyl value is less than 500 mg · KOH / g, the necessary cross-linking density as a coating film cannot be obtained, and there is a risk of lowering scratch resistance, wear resistance, and solvent resistance. On the other hand, when the hydroxyl value exceeds 2,000 mg · KOH / g, there is a risk that the solubility in the coating composition is lowered and the flexibility imparted to the coating film is lowered. Preferably it is 600-1900, More preferably, it is 700-1800, More preferably, it is 800-1700.

  The blending amount of the low molecular polyol in the present invention needs to be in the range of at least 0.5 to 30% by weight with respect to the total weight of the coating film forming components (a) to (d) of the coating composition, 1 to 20 weight% is especially preferable. If the blending amount of the low molecular weight polyol is less than 0.5% by weight, the effect of improving the scratch resistance is small, and if it exceeds 30% by weight, the internal stress of the coating film becomes large, and defects such as a decrease in adhesion and cracks in the coating film occur. Since it becomes easy to occur, it is not preferable.

  Specific examples of the low molecular polyol in the present invention include ethanediol, propanediol, 1,4-butanediol, 1,6-hexanediol, cyclohexyldimethanol, methylpropanediol, neopentylglycol, butylethylpropanediol, Examples include glycerin, trimethylol ethane, trimethylol propane, polycaprolactone triol, ditrimellirol propane, pentaerythritol, polycaprolactone tetraol, dipentaerythritol, sorbitol, mannitol, and the like. These may be used alone or in combination of two or more. Examples of commercially available products of polycaprolactone triol include Polyol 3940 and R3600 manufactured by Perstorp, and Plaxel 303 manufactured by Daicel Chemical. Moreover, as a commercial item of polycaprolactone tetraol, there are Polyol 4525 and Polyol 4800 manufactured by Perstorp.

(B) Acrylic polyol The acrylic polyol used in the present invention is a component mainly imparting flexibility to a coating film and adhesion to a resin molded body as a substrate, and is a radical polymerizable unsaturated monomer. Is a hydroxyl group-containing (meth) acrylic polymer obtained by radical polymerization of the polymer, and known ones can be used.

The following can be mentioned as a representative example of a radically polymerizable unsaturated monomer.
<Hydroxyl group-containing (meth) acrylic monomer>
2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 6-hexanolide addition polymer of 2-hydroxyethyl methacrylate (degree of polymerization 1-6), glyceryl (meth) acrylate, glyceryl-1-methacryloyloxy Ethyl urethane etc.
<Radically polymerizable unsaturated monomer>
Esters of acrylic acid or methacrylic acid: for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylic acid C1-18 alkyl or cycloalkyl ester of acrylic acid or methacrylic acid such as hexyl, octyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, octyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate ; Alkoxyalkyl esters of acrylic acid or methacrylic acid such as methoxybutyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxybutyl (meth) acrylate; glycidyl acrylate or glycidyl methacrylate Rate and C3~18 monocarboxylic acid compound (e.g., acetic acid, propionic acid, oleic acid, stearic acid, lauric acid) adduct of, or adducts of Cardura E-10 with unsaturated acids such as acrylic acid.
α, 1-ethylenically unsaturated carboxylic acid: for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid and the like.
Glydisyl group-containing vinyl monomer: For example, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, and the like.
Amides of acrylic acid or methacrylic acid: for example, acrylamide, N-methylolacrylamide, N-butoxymethylacrylamide and the like.
An ethylenically unsaturated monomer having an alkoxysilane group: for example, 1-methacryloxytrimethoxysilane.
Others: Examples include acrylonitrile and methacrylonitrile.

  These radically polymerizable unsaturated monomers are appropriately selected according to desired resin physical properties, and may be used alone or in combination of two or more. The copolymerization of the hydroxyl group-containing acrylic monomer and the radical polymerizable unsaturated monomer can be carried out according to a method known per se, for example, by solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization and the like. In general, the polymerization can be carried out by reacting the above two or more monomer components in a suitable solvent in the presence of a polymerization catalyst, usually at a temperature of 40 to 170 ° C. for 4 to 10 hours.

  As the polymerization initiator, for example, an initiator for radical polymerization such as an azo compound, a peroxide compound, a diazo compound, or a redox compound can be used. The acrylic polyol thus obtained is preferably a polymer acrylic polyol having a weight average molecular weight (Mw) of 5,000 to 200,000. If the Mw is less than 5,000, the imparting of flexibility to the coating film is reduced, and if it exceeds 200,000, the compatibility with the coating composition is reduced, resulting in whitening of the coating film during film formation. There is a fear. More preferably, it is 10,000-100,000, More preferably, it is 20,000-80,000.

  The blending amount of the acrylic polyol in the present invention is at least 0.5 to 20% by weight with respect to the total weight of the coating film forming components (a) to (d) of the coating composition. When the blending amount of the acrylic polyol is less than 0.5%, the effect of addition is small, and when the blending amount exceeds 20% by weight, the scratch resistance and wear resistance are lowered, which is not preferable. Preferably it is 1-15, More preferably, it is 2-15, More preferably, it is 5-10.

  The acrylic polyol used in the present invention preferably has a hydroxyl value of 1 to 200 mgKOH / g based on the resin. An acrylic polyol having a hydroxyl value lower than 1 on the resin basis has a low crosslink density in the coating film, which has an undesirable effect on solvent resistance and the like. In addition, when an acrylic polyol having a hydroxyl value larger than 200 is used, it adversely affects the stretchability of the coating film. The hydroxyl value based on the resin is a theoretical value or a value measured according to 6.4 of JISK-1557.

(C) Silica particle The silica particle used for this invention has the effect | action which improves the abrasion resistance of a cured coating film. The average particle diameter of the silica particles is preferably as small as possible from the viewpoint of the light transmittance of the curable resin. Specifically, the average particle diameter of the silica particles is preferably 300 nm or less. More preferred are fine particles of 100 nm or less, and even more preferred are fine particles of 50 nm or less. The silica particles are added to the coating composition in the form of silica sol dispersed in an organic solvent. In the state dispersed in the organic solvent, the surface of the silica particles is usually surface-treated in advance with various silane compounds (silane coupling agents). By performing the surface treatment, the long-term storage stability of the curable resin is further improved, and the chemical resistance and weather resistance of the obtained molded product are also improved.

  The compounding quantity of a silica particle shall be at least 20 to 70 weight% with respect to the total weight of coating-film formation component (a)-(d). A range of 30 to 60% by weight is particularly preferred. If it is such a compounding quantity, while the abrasion resistance of the coating film by an addition effect will fully express, the crack by the cure shrinkage of a coating film can be suppressed.

  Examples of silica particles dispersed in an organic solvent (silica sol) and commercial products thereof (manufactured by Nissan Chemical Co., Ltd.) include methanol-dispersed silica sol (trade name: MA-ST), isopropyl alcohol-dispersed silica sol (trade name: IPA- ST), n-butanol-dispersed silica sol (trade name: NBA-ST), ethylene glycol-dispersed silica sol (trade name: EG-ST), xylene / butanol-dispersed silica sol (trade name: XBA-ST), ethyl cellosolve-dispersed silica sol (product) Name: ETC-ST), butyl cellosolve dispersed silica sol (trade name: BTC-ST), dimethylformamide dispersed silica sol (trade name: DBF-ST), dimethylacetamide dispersed silica sol (trade name: DMAC-ST), methyl ethyl ketone dispersed silica sol (product) Name: MEK-ST , Methyl isobutyl ketone-dispersed silica sol (trade name: MIBK-ST), ethyl acetate-dispersed silica sol (trade name: EAC-ST), and the like. These may be used alone or in combination of two or more.

(D) Polyisocyanate As the polyisocyanate used in the present invention, a known one can be used, which is a bifunctional or higher functional isocyanate compound. Examples of the bifunctional isocyanate include hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, 1-3 bis (isocyanatomethyl) cyclohexane, 4,4-dicyclohexyl diisocyanate, and the like. In particular, from the viewpoint of increasing the crosslinking density of the coating film and improving the weather resistance and stain resistance of the coating film, a trifunctional or higher functional isocyanate compound is preferable. The trifunctional or higher functional isocyanate compound is synthesized using the above diisocyanate as a starting material, and includes a burette body, a trimethylolpropane adduct body, an isocyanurate body, and an allophanate body. Moreover, these block type isocyanates can also be used. Examples of commercially available products include a hexamethylene diisocyanate burette (trade name: Duranate 24A-100), a hexamethylene diisocyanate adduct (trade name: Duranate P-301-75E), and hexamethylene diisocyanate manufactured by Asahi Kasei Chemicals Corporation. Isocyanurate form (trade name: Duranate TPA-100), block type isocyanate (trade name: Duranate MF-K60X), and trimethylolpropane adduct of 1-3 bis (isocyanatomethyl) cyclohexane manufactured by Mitsui Chemicals, Inc. ( Trade name: Takenate D-120N), isocyanurate form of 1-3 bis (isocyanatomethyl) cyclohexane (trade name: Takenate D-127N), trimethylolpropane adduct of isophorone diisocyanate Door body (trade name: Takenate D-140N) and, Sumika Bayer Urethane Co., Ltd. of the allophanate of hexamethylene diisocyanate (trade name: Desmodur XP2679) and the like. These may be used alone or in combination of two or more.

In the present invention, the polyisocyanate is mixed so that the equivalent ratio of NCO / (acrylic polyol (b) + low molecular acrylic polyol (a) total OH) is 0.5 to 2.0. Used. When the equivalent ratio is less than 0.5, the cross-linking density of the coating film is lowered, resulting in poor solvent resistance, water resistance, and weather resistance. On the other hand, if the polyisocyanate is excessively exceeding 2.0, the coating film becomes brittle and weather resistance is lowered, and a satisfactory result in drying properties may not be obtained. In addition, since the NCO group content (%) of the polyisocyanate compound is defined by a theoretical value or an actual measurement value (JISK1603-1), a necessary amount is calculated by the following formula (1) using these values. be able to.

  In the curing reaction of the polyisocyanate and the polyol in the present invention, triethylamine, tetra (2-ethylhexyl) titanate, di-n-butyltin dilaurate, 1,4-diazabicyclo [2.2.2] octane, or the like is necessary. A cure accelerating catalyst can be added. The amount used in the case of using these catalysts is usually 0.001 to 10 parts by mass, preferably 0.01 to 5 parts by mass, and most preferably 0.1 to 1 part by mass with respect to 100 parts by mass of the polyisocyanate. . These curing accelerating catalysts may be used alone or in combination of two or more.

  In the present invention, the coating composition can be diluted with an organic solvent in order to adjust the solid content of the coating composition. As the organic solvent, alcohol-based, carboxylic acid ester-based, ketone-based, amide-based, ether-based, aliphatic and aromatic hydrocarbon-based solvents are used. Examples of alcohol solvents include methanol, isopropyl alcohol, n-butanol, diacetone alcohol, 2-methoxyethanol (methyl cellosolve), 2-ethoxyethanol (ethyl cellosolve), 2-butoxyethanol (butyl cellosolve), and tertiary amyl. Alcohol, etc .; carboxylate solvents such as ethyl acetate, n-propyl acetate, butyl acetate, butyl formate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, acetone, cyclohexanone; amide solvents such as dimethyl Formamide, dimethylacetamide, etc .; ether solvents include diethyl ether, methoxytoluene, 1,2-dimethoxyethane, 1,2-dibutoxyethane, 1,1-dimethoxymethane Emissions, 1,1-dimethoxyethane, 1,4-dioxane, tetrahydrofuran and the like; aliphatic and aromatic hydrocarbon solvents, hexane, pentane, xylene, toluene, and benzene. These organic solvents may be used alone or in combination of two or more. Among these components, carboxylic acid esters such as ethyl acetate, butyl acetate, methyl ethyl ketone, and methyl isobutyl ketone, and ketone-based solvents, which are mixed with a polar solvent such as alcohol, are soluble, volatile and It is preferable from the viewpoint of adhesion.

(E) Ultraviolet absorber Moreover, it is preferable to add an ultraviolet absorber to the coating composition of this invention. The UV absorber improves the weather resistance of the coating film to be formed and absorbs the transmitted UV light in order to prevent deterioration of the surface of the resin molded body as a base material due to the UV light transmitted through the coating film. Has an effect. The blending amount is 1 to 10% by weight, preferably 2 to 5% by weight, based on the total weight of the coating film forming components (a) to (d). When the amount of the UV absorber used is less than 1% by weight, the effect of improving the weather resistance of the coating film is small. However, it is not preferable because the adhesion and scratch resistance of the coating film are lowered.

  Suitable ultraviolet absorbers in the present invention are salicylate compounds, benzophenone compounds, benzotriazole compounds, hydroxyphenyltriazine compounds, and the like. Examples of benzophenone compounds include 2-hydroxybenzophenone, 5-chloro-2-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 4-dodecyloxy- 2-hydroxybenzophenone, 2-hydroxy-4-octadecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone; salicylate compounds include phenyl Salicylate, p-tert. -Butylphenyl salicylate, p- (1,1,3,3, -tetramethylbutyl) phenyl salicylate, 3-hydroxyphenylbenzoate, phenylene-1,3-dibenzoate; benzotriazole compounds include 2- (2 -Hydroxy-5-methylphenyl) benzotriazole, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- (2-hydroxy-5-tert.-butylphenyl) -5-chlorobenzotriazole, 2- (2-hydroxy-3,5-di-tert.-butylphenyl) benzotriazole, 2- (2-hydroxy-5-tert.-butylphenyl) benzotriazole, 2- (2-hydroxy-4-octyloxyphenyl) ) Benzotriazole; hydroxyphenyltriazine Examples of the compound include 2,4-bis (2-hydroxy-4-butyroxyphenyl) -6- (2,4-bis-butyroxyphenyl) -1,3,5-triazine, 2- [4 [(2 -Hydroxy-3- (2'-ethyl) hexyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethoxyphenyl) -1,3,5-triazine, 2- (2-hydroxy And -4- [1-octyloxycarbonylethoxy] phenyl) -4,6-bis (4-phenylphenyl) -1,3,5-triazine. These ultraviolet absorbers can be used alone or in admixture of two or more. In particular, those having good compatibility with the coating film forming components (a) to (d) and having a large extinction coefficient in the ultraviolet region are preferable for preventing deterioration in weather resistance of the coating film and the resin molded product. Examples of such an ultraviolet absorber include 2- (2-hydroxy-4- [1-octyloxycarbonylethoxy] phenyl) -4,6-bis (4-phenylphenyl) -1,3,5-triazine. Can be mentioned.

  Examples of commercially available products include TINUVIN-PS, TINUVIN99-2, TINUVIN109, TINUVIN328, TINUVIN384-2, TINUVIN900, TINUVIN928, TINUVIN1130 (above, benzotriazole series), TINUVIN400, TINUVIN405, TINUVIN477, TINUVIN4, TINUVIN4 TINUVIN479 (above, hydroxyphenyltriazine type) and the like. Particularly, those having good compatibility with the coating film forming components (a) to (d) include TINUVIN 99-2, TINUVIN 384-2, TINUVIN 900, TINUVIN 928, TINUVIN 1130, TINUVIN 400, TINUVIN 477, TINUVIN 479, and the like.

  The coating composition of the present invention comprises a predetermined amount of the low molecular polyol (a), the acrylic polyol (b), the silica particles (c), the polyisocyanate (d) and, if necessary, the ultraviolet absorber (e) in an organic solvent. It can be produced by mixing in a uniform manner. In addition, various other additives commonly used in the paint industry as necessary, for example, antioxidants, antifoaming agents, leveling agents, rheology control agents, viscosity modifiers (for example, cellulose acetate and cellulose acetate butyrate) Matting agents, light stabilizers (for example, hindered amine compounds, etc.), dyes, pigments and the like can be appropriately used in conventional amounts within a range that does not impair the effects of the present invention.

  As the resin molded product used in the present invention, any known resin can be used regardless of the type. For example, various resins can be used regardless of a thermoplastic resin or a thermosetting resin. Specific examples include polymethyl methacrylate resin, polycarbonate resin, polystyrene resin, acrylonitrile / styrene copolymer resin, polyvinyl chloride resin, acetate resin, ABS resin, polyester resin, polyamide resin, and the like. Among these, the effects of the present invention can be maximized as long as it is a resin molded product that is not weather resistant itself, such as polycarbonate resin, and is likely to cause discoloration, deterioration, deterioration, etc. when used outdoors. .

  The method for coating the coating composition of the present invention on the surface of the resin molded body is not particularly limited, and known methods such as brush coating, flow coating, dip coating, spray coating, and spin coating can be employed.

  As for the film thickness of the cured coating film formed by hardening | curing the coating composition of this invention, 1-30 micrometers is preferable. When the thickness of the cured coating film is less than 1 μm, the effect of preventing the surface deterioration of the resin molded body as the base material is particularly small, and when it exceeds 30 μm, the adhesiveness with the base material is reduced and the occurrence of cracks is observed. Therefore, it is not preferable.

  As a curing means of the coating composition of the present invention, it is carried out by heat treatment. The heat treatment temperature is room temperature or higher and 200 ° C. or lower, preferably 40 ° C. or higher and 150 ° C. or lower. The heating time varies depending on the heating temperature, but is about several minutes to several hours.

  When the coating composition of the present invention is employed, a urethane coating film having a better balance in various properties such as scratch resistance, abrasion resistance, chemical resistance and weather resistance than conventional urethane coating films is provided. Can do. Moreover, even when exposed to the outdoors for a long time, these resistances are ensured well. Accordingly, it is possible to prevent deterioration of the resin molded body to be applied even in a long-term outdoor use environment.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these. In addition, in each table | surface, the mixture ratio of each component was shown by the weight part.

Each component used in each example and comparative example is as follows.
<(A) Low molecular polyol>
a-1: trimethylolpropane (solid content 100%, hydroxyl number 3, molecular weight 135, hydroxyl value 1,254 mg · KOH / g)
a-2: cyclohexyldimethanol (solid content 100%, hydroxyl number 2, molecular weight 144, hydroxyl value 778 mg · KOH / g)
a-3; Glycerin (solid content 100%, hydroxyl number 3, molecular weight 92, hydroxyl value 1,800 mg · KOH / g)
a-4; polycaprolactone tetraol (solid content: 100%, hydroxyl number: 4, molecular weight: 426, hydroxyl value: 525 mg · KOH / g, Polyol 4525 manufactured by Perstorp)
<(B) Acrylic polyol>
b-1: A three-necked eggplant type flask was equipped with a condenser and a stirrer, charged with 158.1 g of methyl isobutyl ketone (MIBK), and heated to 65 ° C. while stirring in a nitrogen atmosphere. A mixture of 46.0 g of MIBK, 5.0 g (38 mmol) of hydroxyethyl methacrylate, 79.7 g (474 mmol) of cyclohexyl methacrylate and 4.8 g of a polymerization initiator (Perhexyl PV manufactured by NOF Corporation, 70% solid content) was mixed with 2 parts. After dropwise addition over time, the reaction was continued for 5 hours. Further, the temperature was raised to 85 ° C. and reacted for 1 hour and 30 minutes, and then cooled to room temperature. Acrylic polymer (solid content 30%, weight average molecular weight (Mw) 25,000, theoretical hydroxyl value 25 mg · KOH / g )
b-2: A three-necked eggplant-shaped flask was equipped with a condenser and a stirrer, charged with 158.5 g of tertiary amyl alcohol (TAA), and heated to 65 ° C. while stirring in a nitrogen atmosphere. To this, 24.3 g of TAA, 63.0-hexanolide addition polymer of 2-hydroxyethyl methacrylate (Placcel FM1 made by Daicel Chemical Industries), 42.9 g (430 mmol) of methyl methacrylate and a polymerization initiator (day) A mixture of 4.3 g of Perhexyl PV (Oil Co., Ltd., solid content 70%) was dropped over 2 hours, and the reaction was continued for 5 hours. Further, the temperature was raised to 85 ° C. and reacted for 1 hour and 30 minutes, and then cooled to room temperature. Acrylic polymer 2 (solid content 30%, weight average molecular weight (Mw) 80,000, theoretical hydroxyl value 100 mg · KOH / g) was obtained.
The weight average molecular weight (Mw) was calculated using GPC (Shodex KD column, DMF eluent manufactured by Showa Denko KK).
<(C) Silica particles>
c-1; methyl isobutyl ketone-dispersed silica sol (solid content 30%, average particle size 10-20 nm, MIBK-ST manufactured by Nissan Chemical Co., Ltd.)
c-2; ethyl acetate-dispersed silica sol (solid content 30%, average particle size 10 to 20 nm, EAC-ST manufactured by Nissan Chemical Co., Ltd.)
<(D) Polyisocyanate>
d-1: isocyanurate of hexamethylene diisocyanate (solid content 100%, NCO group content 23.0%, Duranate TPA-100 manufactured by Asahi Kasei Chemical Co., Ltd.)
d-2: hexamethylene diisocyanate allophanate (solid content 80%, effective NCO group content 15.5%, Desmodur XP2679 manufactured by Sumika Bayer Urethane Co., Ltd.)
<(E) UV absorber>
e-1: Hydroxyphenyltriazine-based ultraviolet absorber (TINUVIN479 manufactured by BASF)
e-2: Benzotriazole ultraviolet absorber (TINUVIN 384-2 manufactured by BASF)

(Examples 1-19, Comparative Examples 1-10)
The above components (a) to (e) are blended in the proportions shown in Tables 1 to 3, and 0.06 g of di-n-butyltin dilaurate as a curing catalyst as an additive (0.6% by weight of component (d)) ), 0.5 g of a light stabilizer (TINUVIN 152 manufactured by BASF) and 0.8 g of a leveling agent (BYK375 manufactured by Big Chemie) were added to prepare coating compositions of Examples 1 to 19 and Comparative Examples 1 to 10. Each coating composition was applied onto a polycarbonate resin plate (Mitsubishi Gas Chemical Co., Ltd. Iupilon) using a bar coater so that the film thickness after curing was 10 μm, and heated in an oven set at 115 ° C. for 20 minutes. Cured. The prepared test piece was allowed to stand at room temperature for several days and evaluated by the following test method. Each evaluation result is shown to Tables 4-6.

(1) Transparency: The haze (%) measured with a haze meter (NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd.) was used as the evaluation standard for transparency.
(2) Adhesiveness: According to JIS K 5400 8.5.2, cuts that penetrate the coating film of the test piece and reach the ground surface in a grid pattern with a spacing of 1 mm according to the grid tape method. The number of squares that are left without peeling off the coating film is observed by visually observing the adhesion state of the coating film after the adhesive tape is applied on the grid and then the tape is peeled off. It was set as an evaluation standard for adhesion.
(3) Scratch resistance: The steel wool (# 000) loaded with a load of 13.7 KPa was placed on the coating surface of the test piece and tested under the test conditions of 11 reciprocations with a rubbing tester. While measuring haze (%) similarly to the property test, the appearance was evaluated according to the following evaluation criteria.
○: The value obtained by subtracting the haze after the test from the haze before the test is 3 or less; the value obtained by subtracting the haze after the test from the haze before the test is greater than 3 (4) Abrasion resistance; The wear wheel was subjected to a wear test under the conditions of CS10F, 500 rotations × 500 g load, and the haze (%) was measured in the same manner as the transparency test of (1) above.
(5) Pencil hardness: Based on JISK5400, using a pencil scratch hardness tester (No. 553 manufactured by Yasuda Seisakusho Co., Ltd.), a pencil is slid on the paint film surface with a load of 1 kg. The pencil hardness was examined. When the film was torn, it was judged as a scratch, and other dents and line marks were judged not to be scratches.
(6) Heat resistance: The test piece was left in an atmosphere at 120 ° C. for 240 hours, and the presence or absence of coating film cracks was visually observed and evaluated according to the following evaluation criteria. Moreover, about the coating film of the test piece after completion | finish of observation, it tested by the adhesiveness test method of said (2) coating film, and evaluated adhesiveness.
○: No cracks are observed ×: Cracks are observed (7) Chemical resistance: Acid resistance test reagent (0.1 mol / l HCl aqueous solution) and alkali resistance test reagent on the coating surface of the test piece Each of (0.1 mol / l NaOH aqueous solution) was dropped and allowed to stand in an atmosphere at 25 ° C. for 24 hours, and then the appearance change of the coating film was visually observed and evaluated according to the following evaluation criteria. High-octane gasoline was dropped on the coating film surface of the test piece and allowed to stand in an atmosphere of 50 ° C. for 1 hour, and then the appearance change of the coating film was visually observed and evaluated according to the following evaluation criteria. Brake oil (brake fluid 2500H, TOYOTA) is dropped on the coating film surface of the test piece, left to stand in an atmosphere of 25 ° C. for 24 hours, and then the appearance change of the coating film is visually observed and evaluated according to the following evaluation criteria. did.
○: No change is observed in the coating film ×: Changes in the coating film such as blistering and clouding are observed (8) Weather resistance; Accelerated weathering tester (manufactured by Suga Test Instruments Co., Ltd., Metalling Weather Meter M6T type) Tested under conditions including irradiation intensity of 1 kW / m2, black panel temperature of 63 ± 3 ° C, humidity of 50% RH, and 9 minutes of rain in 60 minutes. Appearance of coating film and plastic resin plate, and presence or absence of coating film cracks Was evaluated according to the following evaluation criteria.
Appearance: ○: Abnormalities such as yellowing are not observed in the paint film and polycarbonate resin plate
X: Abnormalities such as yellowing are observed in the coating film and the polycarbonate resin plate
Cracks: ○: No coating film cracks are observed ×: Coating film cracks are observed Further, for the test pieces after the evaluation was completed, the YI value (yellowness) of the test pieces was measured using a MINOLTA spectrophotometer CM3500d, The change in yellowness was evaluated.

From the results of Tables 4 to 6, the urethane paint composition comprising a specific amount of acrylic polyol, silica particles, polyisocyanate, and a specific low-molecular-weight polyol is used, so that scratch resistance, pencil hardness, and abrasion resistance are higher than those of conventional urethane paints. It can be said that a cured film having an excellent balance in various characteristics such as wear and chemical resistance can be provided. Furthermore, even when using a weather resistance tester that artificially accelerates material deterioration by blending a coating film forming component and a predetermined amount of UV absorber, good appearance and transparency are maintained, It was confirmed that the deterioration of the resin molded body can be prevented even in a long-term outdoor use environment.

Claims (4)

A urethane coating composition containing an acrylic polyol (b), silica particles (c), a polyisocyanate (d), and a low molecular polyol (a) having a lower molecular weight than the acrylic polyol,
The low molecular polyol (a) has at least two hydroxyl groups per molecule, has a molecular weight of 60 to 500, and a hydroxyl value of 500 to 2,000 mg · KOH / g,
The low molecular polyol (a) is 0.5 to 30% by weight, the acrylic polyol (b) is 0.5 to 20% by weight, and the silica particles (a) to (d) are combined with the total weight of the components (a) to (d). c) 20 to 70% by weight,
The urethane having the equivalent ratio of NCO / (acrylic polyol (b) + low molecular polyol (a) total OH) of 0.5 to 2.0. Paint composition.   2. The urethane coating composition according to claim 1, comprising 1 to 10 parts by weight of an ultraviolet absorber with respect to 100 parts by weight of the components (a) to (d).   A resin member comprising a cured coating film formed by coating the surface of a resin molded body with the coating composition according to claim 1 or 2 and curing the coating composition. The resin member according to claim 3, wherein the resin member is a vehicle exterior product.