JP4539688B2 - Reactive diluent for modifying thermosetting coating composition and coating composition using the same - Google Patents

Description

The present invention relates to a novel reactive diluent for obtaining a coating film excellent in acid resistance and weather resistance, particularly in car wash machine scratch resistance in the field of automobile coating and the like, and a paint containing the reactive diluent Relates to the composition.

As a method for making it difficult to scratch the top coat film for automobiles, the weight average molecular weight obtained by reacting a diisocyanate compound and caprolactone polyol is 1500 to 4000, and the hydroxyl value is 50 to 180 mgKOH / g. It contains 10 to 50% by weight of a urethane polyol, 30 to 80% by weight of a fluororesin copolymer having a hydroxyl value of 50 to 150 mgKOH / g reacted with fluoroolefin as an essential raw material component, and 10 to 40% by weight of a crosslinking agent. The characteristic coating composition is known (for example, refer patent document 1). However, this coating composition has a drawback that the initial water repellency does not last due to scratches generated during car washing because it is not sufficiently resistant to car wash machine scratches and is expensive because it contains fluorine. .

  Further, as a coating composition having excellent gasoline resistance, scratch resistance, acid resistance and water resistance, and particularly excellent chipping resistance, the number of primary hydroxyl groups is 3 to 5 per molecule, and the number average molecular weight is 1501 to 3000. And a polyester oligomer having a lactone modification amount of 30 to 85% and having an aliphatic hydrocarbon group having 4 to 22 carbon atoms not derived from a lactone, and a hydroxyl group of the hydroxyl group-containing polyester oligomer, an amino resin-based curing A resin composition containing an agent is known (for example, see Patent Document 2). However, this coating composition has a drawback that the acid rain resistance is lowered because the amino resin is an essential component.

  In addition, (A) fluoroolefin polymer units and suspensions as a coating composition with excellent durability (scratch resistance) against scratches caused by wiping with an automatic car wash machine or flapping flutter, and flying flaws that rise while driving A hydroxyl group-containing solvent-soluble fluorine-containing copolymer having a vinyl polymer unit having a polyester chain, (B) a number average molecular weight of 200 to 3000, a hydroxyl group at the terminal, and a hydroxyl value of 40 to 800 mgKOH / g. There is known a composition comprising a polycaprolactone polyol which is: (C) a curing agent having a functional group which reacts with a hydroxyl group. (For example, refer to Patent Document 3) However, in this coating composition, since the car-wash machine scratch resistance is not sufficient, the initial water repellency does not persist due to scratches generated during car washing, and also contains fluorine. There was a drawback of being expensive.

  Further, as a coating composition for obtaining a coating film excellent in car wash machine scratch resistance, acid resistance, stain resistance, water resistance and weather resistance, the hydroxyl value is 200 to 400 mgKOH / g, and the lactone compound is contained in the resin solid content. Hydroxyl group-containing resin (A) containing less than 25% by mass of a structural unit based on the above, hydroxyl group value resin having a hydroxyl value of 50 to 200 mgKOH / g and containing 25 to 75% by mass of a structural unit based on a lactone compound in the resin solids (B) A coating composition containing, as an essential component, a crosslinking agent (C) containing at least one functional group that reacts with a hydroxyl group in one molecule, the hydroxyl group-containing resin (A) and the hydroxyl group-containing resin ( A coating composition is known in which the ratio to B) is (A) / (B) = 90/10 to 10/90 in terms of resin solids mass ratio (for example, Patent Document 4). reference). However, both of the hydroxyl group-containing resins (A) and (B) are acrylic resins having a weight average molecular weight of 1,000 to 30,000, and have insufficient flexibility. Had the disadvantage of not being enough

JP-A-5-05556 JP-A-8-217787 Japanese Patent No. 3029627 JP 2007-039574 A

In the automotive coating field, it is excellent in acid resistance, stain resistance, water resistance, and weather resistance, and particularly used to obtain a coating composition capable of forming a coating film excellent in car wash machine scratch resistance and its coating composition. To provide a reactive diluent.

As a result of intensive studies to solve the above problems, the present inventor has (a) a compound containing two or more hydroxyl groups in one molecule, (b) two non-yellowing isocyanates in a specific molecule. (C) a reactive diluent comprising a hydroxyl group-containing resin obtained by reacting a lactone compound, wherein the hydroxyl group-containing resin has a specific hydroxyl value and a specific weight average molecular weight. In addition, the above-mentioned problem can be solved by blending a reactive diluent containing a specific amount of a structural unit based on the lactone compound of component (c) into the coating composition, and in particular, a car wash resistant machine. The present inventors have found that a coating film having excellent scratch resistance can be formed, and have completed the present invention.

That is, the present invention is, (a) a compound containing two or more hydroxyl groups in one molecule, in (b) aliphatic bifunctional isocyanates and one or more of one molecule selected cycloaliphatic bifunctional isocyanates or al A reactive diluent comprising a hydroxyl group-containing resin obtained by simultaneously reacting a compound containing two non-yellowing isocyanate groups and (c) a lactone compound, wherein the hydroxyl group-containing resin has a hydroxyl value of 100 to 200 mg KOH / g, a weight average molecular weight of 1,000 to 2,000, and (c) 20 to 40% by mass of a structural unit based on a lactone compound as a component, Is to provide.

Further, the present invention is, (a) a compound containing two or more hydroxyl groups in one molecule, in (b) aliphatic bifunctional isocyanates and one or more of one molecule selected cycloaliphatic bifunctional isocyanates or al A reactive diluent comprising a hydroxyl group-containing resin obtained by reacting a compound containing two non-yellowing isocyanate groups and then adding a lactone compound (c), wherein the hydroxyl group-containing resin is a hydroxyl group The reactivity is 100 to 200 mg KOH / g, the weight average molecular weight is 1,000 to 2,000, and contains 20 to 40% by mass of a structural unit based on the lactone compound as the component (c). A diluent is provided.

The present invention also includes the reactive diluent, a hydroxyl group-containing acrylic resin having a hydroxyl value of 80 to 150 mgKOH / g and a weight average molecular weight of 3,000 to 100,000, and a polyfunctional isocyanate compound. The present invention provides a thermosetting coating composition characterized in that the content ratio of the reactive diluent and the hydroxyl group-containing acrylic resin is in the range of 5/95 to 15/85 in terms of resin mass ratio.
Moreover, this invention provides the thermosetting coating composition whose polyfunctional isocyanate compound is an isocyanurate compound in said thermosetting coating composition.

The reactive diluent of the present invention functions as a diluent when used in a thermosetting coating composition, reacts with the curing agent to become a cured resin component, and has excellent acid resistance and weather resistance. In particular, it is possible to form a coating film excellent in car wash machine scratch resistance, and also excellent in coating workability. Moreover, it is excellent in compatibility with the hydroxyl group-containing acrylic resin used as the resin component of the thermosetting coating composition.

The reactive diluent of the present invention is obtained by reacting (a) a compound containing two or more hydroxyl groups, (b) a compound containing two non-yellowing isocyanate groups, and (c) a lactone compound. However, the component (a), the component (b) and the component (c) may be reacted at the same time, or the component (a) and the component (b) are reacted in advance and then the component (c). May be subjected to an addition reaction.
The component (a) used in the present invention is a compound containing two or more hydroxyl groups in one molecule, and preferred specific examples include polyhydric alcohols usually used as raw materials for polyesters. However, for the component (a) of the present invention, an acrylic resin oligomer obtained by polymerizing a radical polymerizable monomer and a radical polymerizable monomer is not preferable in that it is difficult to obtain flexibility.

  Specific examples of the polyhydric alcohol (a) include the following divalent and trivalent or higher alcohols. Examples of the dihydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 1,5 -Pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,5-pentanediol, 2,2,4-trimethyl- Glycols such as 1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,4-cyclohexanedimethanol, neopentyl glycol , Bisphenol A alkylene oxide Additives, polyether diols such as polyethylene glycol and polypropylene glycol, α-olefin epoxides such as propylene oxide and butylene oxide, Cardura E-10 (trade name, manufactured by Shell Chemical Co., Ltd., glycidyl ester of synthetic highly branched saturated fatty acid), etc. Monoepoxy compounds, divalent polyols containing acid groups such as dimethylolpropionic acid and dimethylolbutanoic acid, alicyclic polyols such as 1,4-cyclohexanediol, hydrogenated bisphenol A, cyclohexyldimethylol, etc. Is mentioned.

Examples of trihydric or higher alcohols include glycerin, trimethylolethane, trimethylolpropane, diglycerin, pentaerythritol, dipentaerythritol, sorbitol, and the like, and 2 in the molecule such as bisphenol A diglycidyl ether. A compound having at least one epoxy group can also be used as a trivalent or higher alcohol.
Among the above polyhydric alcohols, trimethylolpropane, dimethylolpropionic acid, dimethylolbutanoic acid, hydrogenated bisphenol A, from the viewpoint of the balance between the hardness and flexibility of the coating composition using a reactive diluent, 1,4-cyclohexanedimethanol is preferred, a combination of trimethylolpropane (TMP) and 1,4-cyclohexanedimethanol (CHDM), wherein the molar ratio of TMP to CHDM is 15/85 to 45/55 When it exists in a range, the case where it exists in the range of 20 / 80-40 / 60 more preferably is especially preferable at the point of the balance of hardness and flexibility.

Among polyhydric alcohols, dimethylol alkanoic acids such as dimethylolpropionic acid and dimethylolbutanoic acid having a carboxyl group are advantageous because they also serve as acid catalysts for esterification and urethanization reactions. When dimethylolalkanoic acid is not used, an acid catalyst may be used.
A polyhydric alcohol may be used individually by 1 type, and may be used in combination of 2 or more type.
Further, as the component (a) used in the present invention, a low molecular weight polyester obtained by reacting in advance a polyol containing two or more hydroxyl groups and a carboxylic acid containing two or more carboxyl groups may be used. However, from the viewpoint of flexibility, a polyester having a linear structure obtained from a polyol containing two hydroxyl groups and a carboxylic acid containing two carboxyl groups is preferable.

Used in the present invention component (b) is a compound containing two non-yellowing isocyanate groups in one or more of one molecule selected et or aliphatic bifunctional isocyanates and cycloaliphatic bifunctional isocyanates.
Specific examples of the component (b) include aliphatic bifunctional isocyanates such as hexamethylene diisocyanate (HDI), fats such as isophorone diisocyanate (IPDI) and 4,4'-methylenebis (cyclohexyl isocyanate) (hydrogenated MDI). Although cyclic bifunctional isocyanate etc. can also be used, isophorone diisocyanate is particularly preferable from the viewpoint of the balance between the hardness and flexibility of the coating composition using a reactive diluent.
(B) A component may be used individually by 1 type and may be used in combination of 2 or more type.

Specific examples of the lactone compound used as the component (c) of the present invention include ε-caprolactone, γ-butyrolactone, δ-valerolactone, γ-valerolactone, γ-caprolactone, γ-nonanoic lactone, δ- Although dodecanolactone etc. are mentioned, (epsilon) -caprolactone is especially preferable. (C) The lactone of component may be used individually by 1 type, and may be used in combination of 2 or more type.
The hydroxyl value of the hydroxyl group-containing resin that is the reactive diluent of the present invention is preferably 100 to 200 mgKOH / g, more preferably 130 to 190 mgKOH / g, and particularly preferably 150 to 190 mgKOH / g. When the hydroxyl value of the hydroxyl group-containing resin, which is a reactive diluent, is less than 100 mgKOH / g, the coating strength cannot be obtained and the stain resistance is reduced. When the hydroxyl value exceeds 200 mgKOH / g, the SP (solubility parameter) of the resin The value increases, the SP value with the curing agent is different, and the compatibility is lowered, resulting in poor appearance of the coating film.

The weight average molecular weight of the hydroxyl group-containing resin that is the reactive diluent of the present invention is preferably 1,000 to 2,000, more preferably 1,400 to 2,000, and particularly preferably 1,600 to 1,800. When the weight average molecular weight of the hydroxyl group-containing resin that is a reactive diluent is less than 1,000, sufficient coating film hardness is difficult to obtain, and when it exceeds 2,000, due to a decrease in compatibility with the hydroxyl group-containing acrylic resin, The appearance of the coating film becomes poor.
The content ratio of the component (c) of the hydroxyl group-containing resin that is the reactive diluent of the present invention is preferably 20 to 40% by mass as a structural unit based on the lactone compound in the hydroxyl group-containing resin that is the reactive diluent. 40 mass% is more preferable, and 30-40 mass% is especially preferable. When the proportion of the component (c) of the hydroxyl group-containing resin that is a reactive diluent is less than 20% by mass, the car wash resistance of the coating film decreases, and when it exceeds 40% by mass, the compatibility of the paint decreases and the coating The hardness and stain resistance of the film are reduced.

The reaction for obtaining a hydroxyl group-containing resin which is a reactive diluent is composed of a compound containing two or more hydroxyl groups as component (a) and a compound containing two non-yellowing isocyanate groups as component (b). And (c) the addition reaction II of the lactone compound as the component (c) to the hydroxyl group of the compound obtained in the addition reaction I. It consists of two reactions.
The addition reaction I is allowed to react for 1 to 3 hours at a temperature of 110 to 130 ° C, and the addition reaction II is allowed to react for 2 to 4 hours at a temperature of 140 to 160 ° C.
In the case where all of the components (a), (b), and (c) are charged into a reaction kettle and reacted simultaneously, the components (a) and (b) are reacted in advance, Also in the case of the reaction, as a reaction step, it is preferable from the viewpoint of reaction efficiency and safety that the reaction is first performed under the conditions of the addition reaction I and then the reaction is performed under the conditions of the addition reaction II.

For the reaction between the hydroxyl group-containing compound and the isocyanate compound in addition reaction I, a reaction catalyst usually used for urethane paints can be used.
Specific reaction catalysts include tin catalysts such as dibutyltin dilaurate, acid catalysts such as organic carboxylic acids, and basic catalysts such as tertiary amines.
The reactive diluent is synthesized in a solvent, but it is preferable not to use an alcohol-based solvent so as not to react with an isocyanate group. Preferable solvents include aromatic solvents, ester solvents, ketone solvents and the like.
The reactive diluent may contain a solvent, and it is preferable that the content of the solvent is small. The content of a preferable solvent is preferably 50% by mass or less, and more preferably 45% by mass or less with respect to the total amount of the reactive diluent.

The reactive diluent of the present invention is a thermosetting coating composition by using a hydroxyl group of a hydroxyl group-containing resin that is a reactive diluent and a polyfunctional isocyanate compound that is a crosslinking agent that reacts with a hydroxyl group of a hydroxyl group-containing acrylic resin. As can be used.
The reactive diluent of the present invention has a role as a modifier of a hydroxyl group-containing acrylic resin, and the mixing ratio of the reactive diluent and the hydroxyl group-containing acrylic resin is 5/95 to 15/85 in terms of resin mass ratio. A range is preferable, More preferably, it is the range of 7/93-13/87.
When the mixing ratio of the reactive diluent is less than 5% by mass, the coating film hardness becomes insufficient, and when it exceeds 15% by mass, the weather resistance decreases due to the influence of the reactive diluent containing a large amount of low molecular weight. .

The hydroxyl group-containing acrylic resin is obtained by copolymerization of a hydroxyl group-containing acrylic monomer and another radical polymerizable monomer under the usual synthesis conditions of an acrylic resin.
The weight average molecular weight of the hydroxyl group-containing acrylic resin is preferably 3,000 to 100,000, more preferably 3,000 to 50,000, and particularly preferably 4,000 to 30,000. When the weight average molecular weight of the hydroxyl group-containing acrylic resin is less than 3,000, the curability is inferior, and when it exceeds 100,000, the viscosity at the time of forming the coating film is increased, so that the appearance of the coating film is lowered.
Moreover, 80-150 mgKOH / g is preferable and, as for the hydroxyl value of a hydroxyl-containing acrylic resin, 90-145 mgKOH / g is especially preferable.

  Hydroxyl group-containing acrylic resin As hydroxyl group-containing acrylic monomers, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, allyl alcohol, (meth) acrylic acid 2-hydroxypropyl, 3-hydroxypropyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate and / or ethylene oxide Examples thereof include propylene oxide adducts, and 4-hydroxybutyl (meth) acrylate is particularly preferable from the viewpoint of balance between hardness and flexibility.

Specific examples of other radical polymerizable monomers used for the hydroxyl group-containing acrylic resin include, for example, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, and isobutyl acrylate. , Sec-butyl acrylate, hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate , N-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, methacrylic acid Lil, stearyl methacrylate, styrene, acrylonitrile, methacrylonitrile, acrylamide, and methacrylic amide and the like, can be used as one or more mixtures.

When performing radical polymerization of the radical polymerizable monomer, a radical polymerization initiator may be added. Examples of the radical polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 4,4′-azobis-4-cyanovaleric acid, 1- Azo compounds such as azobis-1-cyclohexanecarbonitrile, dimethyl-2, 2′-azobisisobutyrate, methyl ethyl ketone peroxide, cyclohexanone peroxide, 3,5,5-trimethylhexanone peroxide, 1,1-bis ( t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) -cyclohexane, 2,2-bis (t-butylveroxy) octane, t-butylhydroper Okindo, diisopropylbenzene hydroperoxide, dicumyl peroxide, t-butylcumylperoxy , Isobutyl peroxide, lauroyl peroxide, benzoyl peroxide, diisopropyl peroxydicarbonate, t-butyl peroxy 2-ethylhexanoate, t-butyl baroxyneodecanate, t-butyl peroxylaurate, t- Examples thereof include organic peroxides such as butyl peroxybenzoate and t-butyl baroxysopropyl carbonate. A radical polymerization initiator may be used individually by 1 type, or may be used in combination of 2 or more type.

Although the compounding quantity of a radical polymerization initiator does not have a restriction | limiting in particular, It is preferable to set it as 0.01-20 mass% with respect to the whole quantity of a radically polymerizable monomer. In these radical polymerization initiator systems, reduction of dimethylaniline, ferrous sulfate, ferrous chloride, ferrous acetate and other ferrous salts, acidic sodium sulfite, sodium thiosulfate, Rongalite, etc. The agents may be combined, but it should be selected with care so that the polymerization temperature does not become too low.
As the curing agent used in the thermosetting coating composition, a polyfunctional isocyanate compound is preferable. Specific examples of the polyfunctional isocyanate compound include p-phenylene diisocyanate, biphenyl diisocyanate, tolylene diisocyanate, 3, 3 '-Dimethyl-4,4'-biphenylene diisocyanate, 1,4-tetramethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexane-1,6-diisocyanate, methylene bis (phenyl isocyanate), lysine methyl ester diisocyanate, Bis (isocyanate ethyl) fumarate, isophorone diisocyanate, methyl cyclohexyl diisocyanate, 2-isocyanate ethyl-2, 6-diisocyanate hexanoate and These biuret (three per molecule isocyanate groups), isocyanurate (1 3 molecules per isocyanate group) and the like can be mentioned, isocyanurate compounds, weather resistance, from the viewpoint of heat resistance.

The isocyanate compound may or may not be blocked, but as the isocyanate compound having a blocked isocyanate group, a polyisocyanate compound having two or more isocyanate groups in one molecule, such as hexamethylene diisocyanate, phenylene diisocyanate. An isocyanate compound obtained by blocking a polyisocyanate such as xylylene diisocyanate or isophorone diisocyanate with an active methylene-based or oxime-based blocking agent such as methyl acetoacetate or dimethyl malonate.
The preferred content ratio of the hydroxyl group-containing resin, which is a reactive diluent used in the present invention, and the hydroxyl group-containing acrylic resin and the polyfunctional isocyanate compound is such that the compounding amount of the isocyanate group with respect to the hydroxyl group in the reactive diluent and the hydroxyl group-containing acrylic resin is as follows. The functional group ratio is preferably 1 / 0.5 to 1.5, more preferably 1 / 0.8 to 1.2.

The thermosetting coating composition of the present invention is used as it is, or as necessary, as an organic solvent, various additives, for example, an ultraviolet absorber, a light stabilizer, an antioxidant, a surfactant, a surface conditioner, a curing agent. A reaction catalyst, an antistatic agent, a fragrance, a dehydrating agent, and a rheology adjusting agent such as polyethylene wax, polyamide wax, and internally crosslinked resin fine particles can be added and used.
The thermosetting coating composition of the present invention may be used as a clear coating, or may be used as a colored coating by blending colorants such as dyes and pigments.

The thermosetting coating composition of the present invention is preferably used as a top coating composition. The finish coating method of the top coating composition of the present invention is, for example, a two-coat one-bake coating finishing method in which a colored base coat is applied on a substrate and the thermosetting coating composition of the present invention is applied as a top coating composition without cross-linking. An overcoat paint finishing method in which a colored base coat is applied on a substrate, an uncoated coating is applied as it is, an overcoat paint is applied, and simultaneously baked, and then the thermosetting paint composition of the present invention is applied as an overcoat paint. In the overcoat paint finishing method, in order to ensure adhesion with the undercoat, a primer paint is applied, and the thermosetting paint composition of the present invention is applied as an overcoat paint in an uncrosslinked state. Is mentioned.

The colored base coat paint, top coat paint, overcoat paint, and primer paint are heated as necessary, adjusted to a desired viscosity by adding an organic solvent or a reactive diluent, and then air sprayed, statically coated. Coating is performed using a commonly used coating machine such as an electric air spray, roll coater, flow coater, dipping type coating machine, or a brush, bar coater, applicator, or the like. Of these, spray coating is preferred.
Moreover, as a base material on which the thermosetting coating composition of the present invention is applied, organic materials such as wood, glass, metal, cloth, plastic, foam, elastic body, paper, ceramic, concrete, gypsum board, and inorganic materials are used. Etc. These base materials may have been surface-treated in advance, or may have a coating film formed on the surface in advance.
Although the specific example was shown so far, the coating finish method of the thermosetting coating composition of this invention is not restrict | limited at all by these.

Although there is no restriction | limiting in particular in the thickness of the coating film obtained by apply | coating the thermosetting coating composition of this invention, The film thickness after drying is usually 10-150 micrometers, and 10-100 micrometers is more preferable.
Examples of the coated article obtained by the thermosetting coating composition of the present invention include structures, wooden products, metal products, plastic products, rubber products, processed paper, ceramic products, and glass products. More specifically, automobiles, automotive parts (for example, parts such as bodies, bumpers, spoilers, mirrors, wheels, interior materials, etc., of various materials), metal plates such as steel plates, motorcycle parts, motorcycle parts , Road materials (eg, guardrails, traffic signs, noise barriers, etc.), tunnel materials (eg, side walls, etc.), ships, railway vehicles, aircraft, furniture, musical instruments, household appliances, building materials, containers, office supplies, Examples include sports equipment and toys.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. Unless otherwise specified, “parts” and “%” mean “parts by mass” and “% by mass”, respectively. In addition, resin solid content says the heating residue measured by the method described in JISK5601-1-2.

<Production of reactive diluent D-1>
A 4-necked flask equipped with a thermometer, Dean Stark (a fractionator for removing water and the like in the condensation reaction during polyester synthesis), a reflux condenser, a nitrogen inlet tube, and a stirrer, 14.6 parts of methanol, 5.8 parts of trimethylolpropane, 1.6 parts of dimethylolbutanoic acid, 17.9 parts of isophorone diisocyanate, 22.1 parts of ε-caprolactone, 22.7 parts of methyl amyl ketone, and 150 ° C. The reaction was terminated when it was confirmed by the infrared absorption spectrum that the isocyanate peak had disappeared. Thereafter, the mixture was stirred while adding 15.3 parts of methyl amyl ketone, the resin solid content was 62.0% by mass, the hydroxyl value was 175 mgKOH / g, the lactone content (content of the structural unit based on the lactone compound) was 35.6% by mass, A solution of reactive diluent D-1 having a weight average molecular weight of 1,800 was obtained.

<Production of reactive diluent D-2>
In a four-necked flask equipped with a thermometer, Dean Stark, reflux condenser, nitrogen inlet tube, stirrer, 12.2 parts 1,4-cyclohexanedimethanol, 7.6 parts trimethylolpropane, dimethylolbutanoic acid 1 .6 parts, 17.4 parts of isophorone diisocyanate, and 20.8 parts of methyl amyl ketone were reacted at a temperature of 120 ° C. for 2 hours. After confirming that the isocyanate peak had disappeared in the infrared absorption spectrum, ε -23.2 parts of caprolactone was charged, the temperature was raised to 150 ° C and reacted for 3 hours to complete the reaction. Thereafter, the mixture was stirred while adding 17.2 parts of methyl amyl ketone, resin solid content 62.0% by mass, hydroxyl value 184 mgKOH / g, lactone content (content of structural unit based on lactone compound) 37.5% by mass, A solution of reactive diluent D-2 having a weight average molecular weight of 1,800 was obtained.

<Production of reactive diluents D-3 to D-9>
Reactive diluents D-3 to D-9 were synthesized in the same manner as reactive diluent D-1, except that the raw materials shown in Table 1 and Table 2 were used.

<Production of hydroxyl group-containing acrylic resin A-1>
A 4-neck flask equipped with a thermometer, a reflux condenser, a stirrer, and a dropping funnel was charged with 32.4 parts of methyl amyl ketone, and heated to 140 ° C. while stirring under a nitrogen stream. Next, radical polymerization of 9 parts of styrene, 21.6 parts of 4-hydroxybutyl acrylate, 15.2 parts of n-butyl acrylate, 13.8 parts of n-butyl methacrylate and 0.4 part of acrylic acid at a temperature of 140 ° C. The dripping component which mixed uniformly the volatile monomer and 0.8 part of t-butylperoxy-2-ethylhexanoate as a polymerization initiator was dripped at constant speed from the dropping funnel over 2 hours. After completion of dropping, the temperature of 140 ° C. was maintained for 1 hour, and then the reaction temperature was lowered to 115 ° C. Thereafter, a polymerization initiator solution prepared by dissolving 0.2 part of t-butylperoxy-2-ethylhexanoate in 6.6 parts of xylene as a polymerization initiator was added as an additional catalyst. The reaction was terminated when the time was maintained to obtain a hydroxyl group-containing acrylic resin A-1.

<Production of hydroxyl group-containing acrylic resins A-2 to A-4>
The hydroxyl group-containing acrylic resins A-2 to A-4 were synthesized in the same manner as the hydroxyl group-containing acrylic resin A-1, except that the raw materials shown in Table 3 were used.

<Examples 1-5, Comparative Examples 1-8>
The raw materials described in Tables 4 and 5 were sequentially mixed and stirred uniformly to prepare clear paints CC-1 to CC-13.

Notes in Table 4 and Table 1) Crosslinking agent N3300: Desmodur N3300: trade name, manufactured by Sumika Bayer Urethane Co., Ltd., liquid HDI isocyanurate type resin (non-volatile content: 100% by mass, NCO content: 23% by mass )
2) Ultraviolet absorber solution: Tinuvin 900, trade name, 20% by weight xylene solution manufactured by Ciba Specialty Chemicals 3) Light stabilizer solution: Tinuvin 292, trade name, 20% by weight xylene solution manufactured by Ciba Specialty Chemicals 4) Surface conditioner solution: BYK-300, trade name, 10% by mass xylene solution manufactured by BYK-Chemie Corporation 5) Diluting solvent: mixed solvent of 1: 1 by mass ratio of xylene / butyl acetate

<Creation of test piece and examination of coating film performance>
Cation electrodeposition paint Aqua No. 4200 (trade name, manufactured by BASF Coatings Japan Co., Ltd.) was electrodeposited to a dry film thickness of 20 μm and baked at 175 ° C. for 25 minutes. 560 (trade name, manufactured by BASF Coatings Japan Co., Ltd.) was air-sprayed to a dry film thickness of 30 μm and baked at 140 ° C. for 30 minutes. Next, Bellcoat No., which is a solvent-based basecoat paint. Air spray coating 6000 black (trade name, manufactured by BASF Coatings Japan Co., Ltd., paint color: black) with a dry film thickness of 15 μm, setting at 20 ° C. for 3 minutes, and then applying the above clear paint to Solvesso 100 (trade name) , Esso Co., Aromatic Petroleum Naphtha) diluted with paint viscosity (Ford Cup No. 4, 25 seconds at 20 ° C.) by air-spraying to a dry film thickness of 40 μm by wet-on-wet method. It was painted and baked at 140 ° C. for 30 minutes to prepare a test piece.
In all of the examples, the base coat paint was applied to the bell coat no. 6000 white (trade name, manufactured by BASF Coatings Japan Co., Ltd., paint color: white) was used.

The coating film performance of the obtained test piece was evaluated by the following evaluation method. The results are shown in Tables 6 and 7.
(1) Coating film hardness Using a König pendulum hardness meter manufactured by Eriksen, the coating film hardness at 25 ° C was measured and evaluated. The Koenig pendulum hardness tester sets the fulcrum of the pendulum on the horizontally placed paint film and measures the paint film hardness by the number of vibrations of the pendulum. The higher the number of vibrations, the higher the hardness. .
◎: 90 times or more ○: 80 times or more △: 70 times or more ×: less than 70 times

(2) Car wash machine scratch resistance (scratch resistance)
After applying muddy water (JIS Z-8901-84, 8 types of dust / water / neutral detergent = 10/99/1 mass ratio) on the test plate by brush, the car wash brush was applied at 150 rpm in the car wash machine for automobiles. Rotate for 10 seconds and wash the test plate with running water. After the above operation was repeated twice, the L * value of the degree of scratches on the surface of the test plate was measured using a color difference meter (CR-331 Minolta Camera Co., Ltd.). The ΔL * value was calculated by the following formula, and the car wash machine scratch resistance was evaluated from the value.
ΔL * value = L * value after test−L * value before test ◎: ΔL * value is less than 1 ○: ΔL * value is 1 or more and less than 2 Δ: ΔL * value is 2 or more and less than 3 ×: ΔL * value Is 3 or more

(3) Accelerated weather resistance Using a xenon lamp method accelerated weather resistance tester (JIS K5600 7.7 (1999)), after exposure for 1,000 hours, the 60 ° specular glossiness of the coating film was measured using a digital variable gloss meter ( Measured by Suga Test Instruments Co., Ltd., and compared with the initial gloss value, the gloss retention was calculated.
○: Gloss retention 90% or more △: Gloss retention 80% or more, less than 90% ×: Gloss retention 80% or less

(4) Acid resistance After 0.2 mL of 40 mass% sulfuric acid aqueous solution was put on the test plate in a spot shape, it was heated at 60 ° C. for 15 minutes, then washed with water and visually evaluated for the degree of occurrence of stain marks.
○: Almost no change is observed in the coating film.
Δ: Slight traces are observed.
X: A remarkable water spot is seen.

(5) Compatibility In a beaker, 50 g of a hydroxyl group-containing acrylic resin and 50 g of a reactive diluent are weighed, and 20 g of xylene is added and stirred uniformly. Next, this mixed solution is hung on a transparent glass plate, left in a vertical state for 10 minutes, and then the transparency of the coating film on the glass plate is determined.
○: Transparent and free of white turbidity x: White turbidity is observed

Claims (4)

(A) compounds containing two or more hydroxyl groups in one molecule, (b) two non-yellowing aliphatic bifunctional isocyanates, and in one or more of one molecule selected cycloaliphatic bifunctional isocyanates or al A reactive diluent comprising a hydroxyl group-containing resin obtained by simultaneously reacting a compound containing an isocyanate group and (c) a lactone compound, the hydroxyl group-containing resin having a hydroxyl value of 100 to 200 mgKOH / g, weight average A reactive diluent having a molecular weight of 1,000 to 2,000 and containing 20 to 40% by mass of a structural unit based on the lactone compound as component (c). (A) compounds containing two or more hydroxyl groups in one molecule, (b) two non-yellowing aliphatic bifunctional isocyanates, and in one or more of one molecule selected cycloaliphatic bifunctional isocyanates or al A reactive diluent comprising a hydroxyl group-containing resin obtained by reacting a compound containing an isocyanate group and then (c) an addition reaction of a lactone compound, the hydroxyl group-containing resin having a hydroxyl value of 100 to 200 mgKOH / g, Reactive diluent characterized by having a weight average molecular weight of 1,000 to 2,000 and containing 20 to 40% by mass of a structural unit based on the lactone compound of component (c). The reactive diluent according to claim 1, comprising a hydroxyl group-containing acrylic resin having a hydroxyl value of 80 to 150 mg KOH / g and a weight average molecular weight of 3,000 to 100,000 and a polyfunctional isocyanate compound. And a content ratio of the reactive diluent to the hydroxyl group-containing acrylic resin is in the range of 5/95 to 15/85 in terms of resin mass ratio. The thermosetting coating composition according to claim 3, wherein the polyfunctional isocyanate compound is an isocyanurate compound.