CURABLE COMPOSITION

Abstract: A curable composition comprising Component (A) a blocked polyisocyanate compound, Component (B) an active hydrogen compound having at least 2 active hydrogen atom-containing groups in the molecule, and Component (C) a catalyst expressed by the following formula (1), (R 1 , R 2 , R 3 , R 4 ) N + Y - wherein R 1 , R 2 , R 3 and R 4 denote hydrocarbon groups of 1 to 18 carbon atoms which are non-reactive to isocyanates and may be the same or different groups each other, and said groups may form heterocyclic rings via oxygen or nitrogen atoms, and Y - denotes an anion of a hydroxide, an alkoxide, an aryloxy or a carbonate, or an anion of a carboxylate, a sulfonate, a phosphate or a borate which may contain hydrocarbon groups. The composition is suitable for chipping-resistant coating material for automobiles.

Description: This invention relates to a curable composition comprising a blocked polyisocyanate compound, and more specifically to a (curable) resin composition which is suitable for chipping-resistant coating materials for vehicles such as automobiles. It is known that, in compositions composed mainly of blocked polyisocyanate compounds which are curable to provide urethane coating materials frequently used for chipping-resistant coating materials, organic heavy metal compounds such as zinc octylate, lead octylate and tin octylate and tertiary amine compounds such as triethylenediamine and triethylamine are used as catalysts, in order to lower the dissociation temperature of the blocked polyisocyanate compounds to impart thereto a low-temperature curing property. However, the use of a tertiary amine catalyst in the above-mentioned curable composition causes difficulties in attaining a sufficiently low dissociation temperature of the blocked polyisocyanate compound, and the use of an organic heavy metal catalyst, while being effective in lowering the dissociation temperature thereof to impart a low-temperature curing property, causes yellowing of the cured coating and also a heavy metal pollution problem. In order to solve these problems, JP-A-06-192364 disclosed the use of hydroxyl-containing quaternary ammonium salt compounds as catalysts capable of lowering the dissociation temperature of the blocked isocyanate compounds. However, hydroxyl-containing quaternary ammonium salt compounds, while being capable of lowering the dissociation temperature, did not provide satisfactory curing properties. US-A-4480071 discloses a moulding composition comprising an oxymethylene polymer, a blocked or unblocked isocyanate compound (in an amount of 0.2 to 2% by weight of polymer), a non-reinforcing particulate filler and a catalyst capable of reaction with the isocyanate. The catalyst may be an alkyl dimethyl benzyl ammonium saccharinate. EP-A-0533071 describes amine-boron adducts as reduced odour catalyst compositions for the production of polyurethanes. The adducts are the reaction products of tertiary amines and boron compounds. EP-A-0139895 discloses the use of an ammonium salt of an amine and alkylating ester of an acid of phosphorus as a latent, heat-activatable catalyst for the production of polyurethanes. The invention seeks to provide a catalyst which is capable of lowering the dissociation temperature of a blocked polyisocyanate compound and imparting thereto excellent low-temperature curing properties, and to provide a curable composition having no environmental problems. In order to achieve the above objective, the invention provides a curable composition comprising the components (A), (B) and (C), as follows; (A) a blocked polyisocyanate compound derived from a polyisocyanate compound and a blocking agent, (B) an active hydrogen compound containing at least two active hydrogen atom-containing groups in the molecule, and (C) a catalyst expressed by the following general formula (R 1 , R 2 , R 3 , R 4 ) N + Y - wherein R 1 , R 2 , R 3 , and R 4 denote the same or different hydrocarbon groups having 1 to 18 carbon atoms which are non-reactive to isocyanate and which groups may form heterocyclic ring(s) via oxygen or nitrogen atom(s), and Y - denotes an anion of a hydroxide, an alkoxide, an aryloxy or a carbonate; an anion of a sulfonate containing a hydrocarbon group; or a carboxylate, phosphate or borate which may contain a hydrocarbon group. The curable composition of the invention, as compared with those using conventional tertiary amine catalysts, can lower the temperature to start curing (dissociation temperature) by a least 10°C, thus effecting low-temperature curing to give excellent coating properties. When compared with those using organic heavy metal catalysts, it gives a superior anti-yellowing property of the cured coat and a superior storage stability as a coating material, and meets a high-level of safety standards, being free from environmental problems such as water pollution. Exhibiting the excellent properties thus far explained, the curable composition of the invention can be used with advantage for chipping-resistant coating materials for vehicles such as automobiles. The best method of carrying out the invention will now be described. Firstly, each of the components (A), (B) and (C) constituting the curable composition of the invention will be explained. Organic polyisocyanate compounds from which the blocked polyisocyanate compounds (A) are derivable include, for example, monomeric polyisocyanates, polymeric polyisocyanates, NCO group-terminated polyurethane prepolymer, and mixtures thereof. Among these organic polyisocyanates, monomeric polyisocyanates include, for example, aliphatic polyisocyanates such as hexamethylenediisocyanate (HDI) and lysine diisocyanate; alicyclic polyisocyanates such as dicyclohexylmethane diisocyanate (hydrogenated MDI), isophorone diisocyanate (IPDI), cyclohexane diisocyanate (CHDI), hydrogenated tolylene diisocyanate and hydrogenated xylylene diisocyanate; aromatic polyisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthylene diisocyanate (NDI), xylylene diisocyanate (XDI) and α, α, α', α',-tetramethylxylylene diisocyanate (TMXDI); and mixtures thereof. Examples of polymeric polyisocyanates are trimers of the above-mentioned monomeric polyisocyanates, modified polyisocyanates having biuret, urethodione and/or carbodiimide groups, and mixtures thereof. Examples of NCO group-terminated polyurethane prepolymer are reaction products of an excess monomeric or polymeric polyisocyanate with a polyether polyol, a polyester polyol, a polymer polyol, a polycarbonate polyol, or mixtures thereof. Prepolymers used are those reacted at an equivalent weight ratio of NCO to OH of usually 1.2 to 3.0, preferably 1.5 to 2.2. The number-average molecular weight of the prepolymers used is usually 500 to 10,000, preferably 700 to 8,000. In general cases, when the number-average molecular weight is smaller that 500, coatings become hard and brittle, thus lowering the chipping-resistant property thereof. When the number-average molecular weight is larger than 10,000, good adhesion to the substrates cannot be obtained. The amount of the NCO group in the prepolymer is usually 1 to 20% by weight, preferably 2 to 15% by weight. Blocking agents from which the blocked polyisocyanate compounds (A) are derivable include, for example, oxime compounds including ketoximes such as acetoxime, methyl ethyl ketoxime (MEK oxime) and methyl isobutyl ketoxime (MIBK oxime); lactam compounds such as ε-caprolactam, δ- valerolactam and γ-butyrolactam; phenol compounds such as phenol, m-cresol and xylenol; active methylene compounds including malonic diesters such as diethyl malonate, acetylacetone and acetoacetic esters such as ethyl acetoacetate; alcohol compounds such as methanol, ethanol and n-butanol; hydroxyl-containing ether compounds such as methyl cellosolve, butyl cellosolve and ethyl carbitol; hydroxyl-containing ester compounds such as ethyl lactate and amyl lactate; mercaptan compounds such as butyl mercaptan and hexyl mercaptan; acid amide compounds such as acetanilide, acrylamide and dimeric acid amide; imidazole compounds such as imidazole and 2-ethylimidazole; acid imide compounds such as succinic imide and phthalimide; and mixtures of more than one kind thereof. Preferable among these compounds are oxime compounds, lactam compounds and phenol compounds and particularly preferable are methyl ethyl ketoxime, ε - caprolactam and xylenol. The component (A) can be prepared according to known methods, for example, by reacting a blocking agent with an organic polyisocyanate at 50 to 150°C, at an equivalent weight ratio of the NCO group of the organic polyisocyanate to the active hydrogen group of the blocking agent of usually 1 to 2, preferably 1.05 to 1.5. As the component (B) are included, for example, polyhydric alcohols, a polyether polyol obtained by adding ethylene oxide and/or propylene oxide to a polyhydric alcohol, an epoxy resin modified polyol obtained by reacting a bisphenol type epoxy resin with an amine such as diethanolamine, a polyester polyol obtained by condensation polymerization of a polybasic acid with a polyhydric alcohol, polylactone polyols,polycarbonate polyols, an acrylic polyol such as a copolymer of a vinyl monomer containing a hydroxyl group such as β - hydroxyethyl (meth)acrylate with other vinyl monomers, polybutadiene polyols, a partially saponified compound of an ethylene-propylene copolymer, a polyoxyalkylene polyamine described in JP-B-05-073793, an alkylene oxide adduct of a (poly)alkylene polyamine, a ketiminized compound of a polyoxyalkylene polyamine, a ketiminized compound of a polyamide compound, a ketiminized compound of a (poly)alkylene polyamine, and mixtures thereof. Furthermore, in the compounds expressed by formula (1) that are used as the component (C), R 1 , R 2 , R 3 and R 4 , representing hydrocarbon groups having 1 to 18 carbon atoms which are non-reactive to isocyanates and which may form heterocyclic rings by containing oxygen or nitrogen atoms, include, for example, aliphatic alkyl groups such as methyl, ethyl, propyl, hexyl, decyl, lauryl and stearyl groups; alicyclic alkylene groups such as cyclotetramethylene, cyclopentamethylene and cyclohexamethylene groups; aralkyl groups such as a benzyl group; aryl groups such as phenyl and naphthyl groups; and heterocyclic groups formed by including oxygen or nitrogen atoms such as oxacyclohexylene, azacyclohexylene, 1,5-diazabicyclo-(4,3,0)-5-nonenylene, 1,8-diazabicyclo-(5,4,0)-7-undecelene, cyclohexa-1,3-dienylene, 4-dimethylamino-cyclohexa-1,3-dienylene, methylcyclohexa-1,3-dienylene, cyclopenta-1,3-dienylene azamethylcyclopenta-1,3-dienylene, azaethylcycloazapenta-1,3-dienylene, azapentamonoenylene, azamethylpentamonoenylene and azadimethylpentamonoenylene groups. Particularly preferable are aliphatic alkyl groups and heterocyclic groups formed by including oxygen or nitrogen atoms. Alkoxide anion in Y - include, for example, methoxy and ethoxy anions. As aryloxy anion are included anions of phenolate, resorcinate and naphtholate. Examples of carboxylate anion which may contain hydrocarbon groups are aliphatic monocarboxylate anions such as anions of formate, acetate, propionate, octylate, 2-ethylhexoate and laurate; aliphatic polycarboxylate anion such as anions of oxalate, malonate, succinate, glutarate and adipate; aromatic monocarboxylate anion such as anions of benzoate, toluylate, naphthoate and ethyl benzoate; and anions of phthalate, isophthalate, terephthalate, nitrophthalate and trimellitate. As sulfonate anion which may contain hydrocarbon groups are, for example, anions of benzenesulfonate, toluenesulfonate and alkylbenzenesulfonate, and as phosphate anion which may contain hydrocarbon groups are, for example, dialkylphosphate ester anion. Furthermore, the borate anions which may contain hydrocarbon groups include anions obtained by removing protonic hydrogen atoms from the complexes of a monovalent or divalent alcohol with boric acid, which are expressed, for example, by the following formulae, wherein R denotes a methyl, an ethyl, a propyl or a benzyl group and R' an ethylene or a propylene group. Preferable as Y - are aliphatic or aromatic monocarboxylate anions and particularly are anions of octylate and formate. One of the preferable compounds expressed by the general formula (1) is a quaternary ammonium carboxylate salt, typical examples of which are methyltriethylammonium octylate salt, N-8-methyl-1,8-diazabicyclo[5,4,0]-7-undecene octylate salt and 1,2,3,4-tetramethylimidazolinium octylate salt. A quaternary ammonium salt of an organic acid, which may be a carboxylate salt, can be obtained, for example, 1 ○ by reacting a quaternary ammonium hydroxide with an organic acid or 2 ○ by reacting a tertiary amine with a carbonic acid diester to obtain a quaternary ammonium carbonate which is then reacted with an organic acid. The method 2 ○ is preferable, because thereby a product of a high purity can easily be obtained. In the preparation method 2 ○, preferably used as tertiary amines are trimethylamine, triethylamine, 1,5-diazabicyclo[4,3,0]-5-nonene, 1,8-diazabicyclo-[5,4,0]-7-undecene or 1,2,4-trimethylimidazoline. Preferable as organic acids are organic carboxylic acids, among which aliphatic monocarboxylic acids, particularly formic acid or octylic acid, are more preferable. A quaternary ammonium sulfonate or phosphate salt can be obtained by reacting a tertiary amine with a carbonic acid diaster to obtain a quaternary ammonium carbonate which is then reacted either with a sulfonic acid or dialkylphosphoric acid ester. A quaternary ammonium borate salt can be obtained, for example, as described in US-A-4192759, by reacting a complex of boric acid and a monovalent or divalent alcohol with a quaternary ammonium hydroxide. The content of each component of the curable composition of the invention will next be explained. In 100% by weight of the curable composition are present 60 to 95% by weight of the blocked polyisocyanate (Component A) and 35% by weight or less of the active hydrogen compounds having at least 2 active hydrogen-containing groups in the molecule (Component B), the ratio of Component A to Component B being such that the equivalent ratio of the NCO group to the active hydrogen group is preferably 1 to (0.1 to 2.5), particularly preferably 1 to (0.5 to 1.5). When the equivalent ratio of the active hydrogen group is smaller than 0.1 or larger than 2.5, curing tends usually to become unsatisfactory. The amount to be used of the catalyst expressed by the general formula (1) (Component C) is usually 0.01 to 5% by weight, preferably 0.05 to 2% by weight based on the sum total of the weights of Components (A), (B), and (C). The curable composition of the invention is cured by heating usually at 90 to 180°C, preferably at 100 to 170°C, more preferably at 110 to 150°C, for 10 to 80 minutes, preferably for 10 to 60 minutes. To the curable composition of the invention can be added, according to need, pigments, fillers, solvents, and the like. As pigments are included, for example, inorganic pigments such as titanium oxide, carbon black, red oxide and oxide yellow, and organic pigments such as phthalocyanine blue and phthalocyanine green. Examples of fillers are clay, calcium carbonate, barium sulfate, talc, alumina, silica, barytes, vermiculite and china clay. As solvents are included, for example, aromatic hydrocarbon solvents such as toluene, xylene and trimethylbenzene; ester solvents such as ethyl acetate, butyl acetate and "DBE" (a mixture of dimethyl succinate, dimethyl glutarate and dimethyl adipate); ether solvents such as Cellosolve acetate and Carbitol acetate; ketone solvents such as methyl ethyl ketone and cyclohexanone; and mixed solvents of more than one kind thereof. The curable composition of the invention can also be combined, according to need, with various kinds of additive, for example, natural resins or synthetic resins such as vinyl chloride resin, vinyl chloride sol, phenol resin, ketone resin, synthetic rubber, unsaturated polyester resin, epoxy resin, melamine resin, urea resin and rosin resin; levelling agents; anti-sagging agents; anti-foaming agents; surfactants; curing accelerators; anti-cissing agents; pigment dispersing agents and antistatic agents. The method of preparing chipping-resistant coating materials for vehicles using the curable composition of the invention will be explained in detail. Typical coating material can be obtained by mixing the components described below with a mixing apparatus, for example, a disperser, a three-roll mill, a ball mill, a steel mill, a pebble mill, and attritor, a sand mill, a sand grinder, a roll mill, a pot mill and a bladed high-speed agitator. Here, the sum total of the weights of Components A, B and C is expressed as 100% by weight. Component (A) 10 to 70% by weight, preferably 20 to 60% by weight Component (B) 1 to 30% by weight, preferably 2 to 20% by weight Component (C) 0.01 to 5% by weight, preferably 0.05 to 2% by weight Pigments 5 to 70% by weight, preferably 10 to 60% by weight Fillers 5 to 70% by weight, preferably 10 to 60% by weight Solvents 10 to 70% by weight, preferable 20 to 50% by weight Various Additives 0.5 to 10% by weight, preferably 1 to 7% by weight The coating materials described above are used for coating chemically treated or non-treated iron plates, galvanized iron plates, and anionic electrodeposited or cationic electrodeposited iron plates. They are also used to form intercoat or topcoat layers on iron plates coated with other coating material. Coating can be carried out by brushing, by roller coating, by spatula coating, with the use of an air-spray coater, an airless spray coater and a hot airless spray coater. The use of an airless spray coater is preferable, because by the use of an air-spray coater it takes a longer time to obtain necessary coating thicknesses. When an airless spray coater is used, necessary coating thicknesses can be obtained, usually by 1 stroke or 2 strokes depending on the stroke speed. The curable composition of the invention can be used for chipping-resistant coating materials for automobiles, coating materials for electric wires, coating materials for precoated metals, and the like, being particularly suitable for chipping-resistant coating materials for automobiles. When used for chipping-resistant coating materials for automobiles, the baking temperature (curing temperature) is usually higher than 90°C, preferably 100 to 170°C, particularly preferably 110 to 150°C. Baking time (curing time) is usually less than 120 minutes, preferably 10 to 60 minutes. The dry coating thickness for chipping-resistant coating material is usually 20 to 500 µm, preferably 50 to 300 µm. When the coating thickness is less than 20 µm, the desired chipping-resistant property cannot be obtained. On the other hand, when the coating thickness exceeds 500 µm, difficulties such as the formation of voids and sagging tend to arise. Examples Embodiments of the invention will now be explained in more detail with reference to the following Examples, in which "parts" means "parts by weight" and"%" means "% by weight". Testing methods used in these Examples will also be explained. (1) Temperature at which curing started (Examples 1 to 4 and Comparative Examples 1 to 2) Each curable composition was coated onto a test piece at a dry coating thickness of 100 µm, which was mounted on a rigid pendulum type viscoelastometer (Rheovibron DDV-OPA3, manufactured by Orientech, Inc.), and measurements were made under the following temperature rise condition. The temperature at which logarithmic decrement starts decreasing (the pendulum is damped by an increase in viscosity due to the start of curing) defined the temperature at which curing started. The lower the start temperature of curing, the lower the temperature of dissociation and, accordingly, the better the low-temperature curing property. Condition of temperature rise 1; Temperature was raised from room temperature to 80°C in 3 minutes and then from 80°C to 200°C in 24 minutes. (2) Time lapse to start of curing (Examples 9 to 10 and Comparative Examples 5 to 6). Each curable composition was coated onto a test piece at a dry coating thickness of 100 µm, which was mounted on a rigid pendulum type viscoelastometer mentioned above, and measurements were made under the following temperature rise conditions. For each temperature rise condition, the time required from the moment when the temperature reached 120°C to the moment when logarithmic decrement starts decreasing (when the pendulum is damped by an increase in viscosity due to the start of curing) defined the time lapse to the start of curing. The shorter the time lapse to the start of curing, the better the curing property. Condition of temperature rise 2; Temperature was raised from room temperature to 120°C in 2 minutes and then kept at 120°C. Condition of temperature rise 3; Temperature was raised from room temperature to 130°C in 2 minutes and then kept at 130°C. Condition of temperature rise 4; Temperature was raised from room temperature to 140°C in 2 minutes and then kept at 140°C. (3) Gel fraction Each curable composition was poured into a tray at a dry coating thickness of 200 to 400 µm and the composition was then cured under predetermined conditions, temperatures and times thereof being described in Tables 1 and 3, to obtain a film. The film of the curable composition thus obtained was cooled down to room temperature followed by cutting into rectangular pieces of ca. 1 cm sides, wherefrom an amount of ca. 1 g was weighed (S g) and put into an Erlenmeyer flask which had previously been dried and weighed (T 1 g). Into the flask was poured 50 ml of an equal volume mixture of methanol and acetone, which was then heated under reflux at ca. 60°C for 3 hours followed by filtering the sample with a filter paper which had previously been dried and weighed (T 2 g). The insoluble material and the filter paper were put into the Erlenmeyer flask, which was then dried at 105°C for 45 minutes. After having been cooled down to room temperature, the whole Erlenmeyer flask was weighed (Gg). Using the results of the weight measurements, gel fraction (%) was determined from the following equation. The larger the gel fraction, the more complete the degree of curing. Gel fraction (%) = [{G-(T 1 + T 2 )} / S] x 100 (4) Mechanical Properties Each curable composition was poured into a tray at a dried coating thickness of 150 to 200 µm and the composition was then cured by heating 140°C for 40 minutes to obtain a film. The thus obtained film was cooled down to room temperature followed by punching into a No. 3 dumbbell in accordance with JIS K-6251, and measurements were made at a temperature of 20°C for the tensile break strength and elongation thereof. (5) Anti-yellowing Property Each curable composition was poured into a tray at a dry coating thickness of 150 to 200 µm and the composition was then cured under the curing conditions described in Table 1 to obtain a film. The thus obtained film was cooled down to room temperature, and measurements were made for the Yellow Index thereof by means of a multi-light source spectrocolorimeter (MSC-2, manufactured by Suga Testing Machines, Inc.). The smaller the value, the better the anti-yellowing property. Samples that are denoted "Non-measurable" in Tables 1 and 3 are those which could not be measured because the resin was in a half-cured state exhibiting a high tackiness. (6) Appearance of Coating Film (Coating Film Properties) Onto a steel plate, which had been electrodeposited with an epoxy-type cationic electrodeposition coating material followed by curing by baking (hereinafter referred to as electrodeposited plate), was sprayed with an airless spray gun the coating material of Examples or Comparative Examples (hereinafter referred to as chipping-resistant coating material) at a coating thickness after drying of 150 µm. The plate was then heated at 140°C for 20 minutes, and the coating film thus obtained was submitted to inspection for visual appearance such as blister, skim, pinhole, and so on. Criteria of appearance are as follows. o ○; No blister, void, pinhole, wrinkle and sag are observed. ○; Some voids are observed; however they are very small and present practically no problem. X; Any one of blister, void, pinhole, wrinkle and sag are observed in large numbers. (7) Chipping-resistant Property An electrodeposited plate of 100 x 100 x 0.8 mm mentioned above was coated with chipping-resistant coating material at a coating thickness after drying of 150 µm followed by heating at 140°C for 20 minutes. The thus obtained coated plate was then coated with a melamine alkyd resin type intercoating material at a coating thickness after drying of 30 µm followed by heating at 140°C for 20 minutes. Then, according to JIS B-1181, onto the thus obtained intercoat coated plate was dropped, from a height of 2 m through a tube of 20 mm diameter, iron hexagon nuts of the 3rd kind-M-4 shape, while the coated plate was being held at an angle of 45° with the falling direction of the nut. Measurements were made for the total weight of the nuts (Kg) required to make a mark, by the impact of the falling nuts, on the coating film that reaches as deep as the metal surface. The larger the value, the better the chipping-resistant property. (8) Storage Stability Chipping-resistant coating material was stored at 40°C for 10 days and measurements were made for the rate of increase of viscosity thereof during the storage period. The smaller the rate of increase, the better the storage stability. Preparation Example 1 A urethane prepolymer of NCO content of 4.8% was obtained by reacting 273 parts of dicyclohexyl-methane diisocyanate, 208 parts of polytetramethylene glycol (number average molecular weight: 1,000), 28 parts of trimethylolpropane and 400 parts of an aromatic solvent (Pegasole R-100, manufactured by Mobile Oil, Inc.), under a stream of nitrogen at 80 to 100°C for 8 hours. To the prepolymer obtained was added 91 parts of methyl ethyl ketoxime and reaction was allowed to take place at 60 to 80°C for 2 hours. By inspection of the infrared spectrum of the reactant, absence of isocyanate group therein was confirmed; thus a blocked polyisocyanate (A-1; solid content 60%) was obtained. Preparation Example 2 A urethane prepolymer of NCO content of 5.7% was obtained by reacting 203 parts of tolylene diisocyanate, 234 parts of polytetramethylene glycol (number-average molecular weight; 1,000), 31 parts of trimethylolpropane and 400 parts of an ester solvent (DBE, manufactured by Du Pont, Inc.), under a stream of nitrogen at 60 to 80°C for 6 hours. To the prepolymer was added 135 parts of ε - caprolactam and reaction was allowed to take place at 80 to 100°C for 3 hours. By inspection of the infrared spectrum of the reactant, absence of isocyanate group therein was confirmed; thus, a blocked polyisocyanate (A-2; Solid content 60%) was obtained. Preparation Example 3 Into an autoclave equipped with a stirrer was charged triethylamine (1 mole), dimethyl carbonate (1.5 mole) and methanol (2.0 mole), which were reacted at a reaction temperature of 110°C for 12 hours to obtain a methanol solution of methyltriethylammoniummethyl carbonate. To the thus obtained solution was added octylic acid (1 mole) followed by removing carbon dioxide gas evolved and methanol to obtain methyltriethylammonium octylate (C-1). Preparation Example 4 In the same way as in Preparation Example 3, except that 1 mole of 1,8-diazabicyclo[5,4,0]-7-undecene was used instead of triethylamine, was obtained N-8-methyl-1,8-diazabicyclo [5,4,0]-7-undecene octylate (C-2). Preparation Example 5 In the same way as in Preparation Example 3, except that formic acid was used instead of octylic acid, was obtained methyltriethylammonium formate (C-3). Examples 1 to 4 and Comparative Examples 1 to 2 Components described in Table 1 were mixed together and measurements were made on these mixtures for the temperature at which curing started according to the testing method described above. Measurements were also made, according to the testing methods described above, for gel fraction, mechanical properties and anti-yellowing property thereof under the curing condition described in Table 1. The results are tabulated in Table 1. Examples 5 to 8 and Comparative Example 3 to 4 Components described in Table 2 were mixed together and measurements were made on coating films obtained for appearance and chipping-resistant property according to the testing methods described above. Testing for storage stability of coating material was also made. The results are tabulated in Table 2. Examples 9 to 10 Comparative Examples 5 to 6 Components described in Table 3 were mixed together and measurements were made on these mixtures for the time lapse to the start of curing according to the testing method described above. Measurements were also made, on cured specimens obtained, according to the testing methods described above, for mechanical properties and anti-yellowing property. The results are tabulated in Table 3.

Claims: A curable composition which comprises (A) a blocked polyisocyanate compound derived from a polyisocyanate compound and a blocking agent, (B) an active hydrogen compound having at least 2 active hydrogen atom-containing groups in the molecule, and (C) a catalyst expressed by the following general formula (1), (R 1 , R 2 , R 3 , R 4 ) N + Y - wherein R 1 , R 2 , R 3 and R 4 denote the same or different hydrocarbon groups having 1 to 18 carbon atoms which are non-reactive to isocyanate, which groups may form heterocyclic ring(s) via oxygen or nitrogen atom(s), and Y - denotes an anion of a hydroxide, an alkoxide, an aryloxy or a carbonate; an anion of a sulfonate containing a hydrocarbon group; or a carboxylate, phosphate or borate, which may contain a hydrocarbon group. The curable composition according to claim 1, which is constituted by each of components (A), (B) and (C). The curable composition according to claim 1 or claim 2, with which is combined an additive selected from pigments, fillers, solvents, natural resins, synthetic resins, levelling agents, anti-sagging agents, anti-foaming agents, surfactants, curing accelerators, anti-cissing agents, pigment dispersing agents and antistatic agents. The curable composition as claimed in any one of claims 1 to 3, which contains the component (A) in an amount of 60 to 95% by weight based on the curable composition, the component (B) in an amount not larger than 35% by weight based on the curable composition, and the component (C) in an amount of 0.01 to 5% by weight, based on the total weight of the components (A), (B) and (C) . The curable composition as claimed in any one of claims 1 to 4, which comprises 10 to 70% by weight of the component (A), 1 to 30% by weight of the component (B), 0.01 to 5% by weight of the component (C), 5 to 70% by weight of a pigment, 5 to 70% by weight of filler, 10 to 70% by weight of a solvent and 0.5 to 10% by weight of another additive, based on the total weight of components (A), (B) and (C). The curable composition as claimed in any one of claims 1 to 5, wherein the equivalent ratio of the active hydrogen atom-containing groups in (B) to the blocked isocyanate groups in (A) is 0.1 to 2.5, preferably 0.5 to 1.5. The curable composition as claimed in any one of claims 1 to 6, wherein said polyisocyanate compound is an isocyanate-terminated polyurethane prepolymer derived from an organic polyisocyanate and a polyol. The curable composition as claimed in claim 7, wherein said prepolymer has a number-average molecular weight of 500 to 10,000 and an isocyanate group content of 1 to 20% by weight. The curable composition as claimed in any one of claims 1 to 8, wherein the blocking agent is an oxime compound, a lactam compound or a phenol compound. The curable composition as claimed in any one of claims 1 to 9, wherein said anion Y - is a carboxylate anion which may contain a hydrocarbon group, preferably an octanoate anion or a formate anion. The curable composition as claimed in any one of claims 1 to 9, wherein (C) is a quaternary ammonium salt of an organic acid obtainable by reacting a tertiary amine with a carbonic acid diester to obtain a quaternary ammonium carbonate which is then reacted with an organic acid. The curable composition as claimed in claim 11, wherein said tertiary amine is selected from the group consisting of trimethylamine, triethylamine, 1,5-diazabicyclo[4,3,0]-5-nonene, 1,8-diazabicyclo[5,4,0]-7-undecene and 1,2,4-trimethylimidazoline. The curable composition as claimed in claim 11 or 12, wherein said organic acid is a carboxylic acid, preferably an aliphatic monocarboxylic acid. Use, for providing a coating material, of a curable composition as claimed in any one of claims 1 to 13. Use, as claimed in claim 14, of the curable composition as a chipping-resistant coating for an automobile, a coating for electric wire or a coating for precoated metal, particularly chipping-resistant coating for an automobile. A process for applying a coating material onto an object selected from a chemically treated iron plate, non-treated iron plate, galvanized iron plate, cationic electro-deposited iron plate and an anionic electro-deposited iron plate, or as intercoat or topcoat onto an iron plate coated with another coating material, in which a curable composition as claimed in any one of claims 1 to 13 is coated onto the object or as intercoat or topcoat onto an iron plate to be coated or coated with another material and then cured under heating, thereby to provide the coating material thereon. A process according to claim 16, wherein the curing is carried out at a temperature of 90 to 180°C for 10 to 80 minutes. A cured product obtainable by curing the curable composition as claimed in any one of claims 1 to 13 under heating, preferably to a temperature of 90 to 180°C.

Inventors: ITOH TETSUO, MATSUNAGA SHUNJI, ITOH, TETSUO, MATSUNAGA, SHUNJI, ITOH, Tetsuo Sanyo Chemical Industries Ltd., MATSUNAGA, Shunji Sanyo Chemical Industries Ltd.
Applicants: SANYO CHEMICAL IND LTD, SANYO CHEMICAL INDUSTRIES, LTD.
Application year: 1995
Main classification: C08G18
IPC codes: C08G18