Reactive monomer composition modified by a small-amount of lactones, an acrylic polyol resin, a curable resin composition, and a coating composition

Abstract

The present invention Nos. I and II relate to a hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones in which a proportion of monomers having two or more continuous chains (n≧2) of lactone is less than 50% (area % by GPC) which is obtained by a ring-opening polymerization of a lactone with a hydroxyalkyl(meth)acrylate, a method for the preparation thereof, and an acrylic polyol resin using thereof, (in the formula, R, R 1 , R 2 , and R 3 are independently a hydrogen or a methyl group, “j” is an integer of 2-6, xn pieces of R 4 and R 5 are independently a hydrogen atom or an alkyl group having a carbon number of 1-12, “x” is 4-7, “n” is 0 or an integer of not less than 1, and an average value of “n” in the composition is not less than 0.3 to less than 1.0). By allowing to react the composition with other ethylenic unsaturated monomer and to formulate with a commonly-used crosslinking agent and other commonly-used components, there can be obtained a well-balanced high quality finishing agent for industries, an ultraviolet ray- or electron beam-curable coating agent, a composition which can be modified for a reactive improver, etc., and an acrylic polyol resin using thereof. The present invention No. III relates to a curable resin composition containing 0.5-80 parts by weight of an acrylic polyol resin (A) obtained using a hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones and 0.5-50 parts by weight of a melamine resin (B) [total of the (A) and (B) does not exceed, 100 parts by weight] as essential components. By the composition, even in a melamine-based curing system which is low in price, there can be obtained a curable-type coating composition in which an acid resistance is improved and highly well-balanced between an acid resistance and abrasion resistance, and which is also excellent in flexural resistance and adhesion in recoating. The present invention No. IV relates to a curable resin composition containing 0.5-80 parts by weight of an acrylic polyol resin (A) containing a hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones as a polymerizing component and 0.5-50 parts by weight of a melamine resin (B) [total of the (A) and (B) does not exceed 100 parts by weight] as essential components. By the composition, even in a melamine-based curing system which is low in price, there can be obtained a curable-type coating composition in which an acid resistance is improved and highly well-balanced between an acid resistance and abrasion resistance. The present invention No. V relates to a curable resin composition containing 0.5-80 parts by weight of an acrylic polyol resin (A) obtained using a hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones and 0.5-50 parts by weight of a polyisocyanate compound (B) [total of the (A) and (B) does not exceed 100 parts by weight] as essential components. By the composition, even in an isocyanate-based curing system, there can be obtained a curable-type coating composition in which a pot life is long and workability is improved, and which is highly well-balanced between an acid resistance and abrasion resistance, and which can provide a coating layer which is excellent also in flexural resistance and adhesion in recoating. The present invention No. VI relates to a curable resin composition containing 0.5-80 parts by weight of an acrylic polyol resin (A) obtained using a hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones and 0.5-50 parts by weight of a polyisocyanate compound (B) [total of the (A) and (B) does not exceed 100 parts by weight] as essential components. By the composition, even in an isocyanate-based curing system, there can be obtained a curable-type coating composition in which a pot life is long and workability is improved, and which is highly well-balanced between an acid resistance and abrasion resistance, and which can provide a coating layer which is excellent also in flexural resistance and adhesion in recoating. The present invention No. VII relates to a thermosetting resin composition containing 2-50 parts of an acrylic polyol resin obtained using a hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones and 30-80 parts of an acrylic copolymer having an alkoxysilyl group. By the composition, there can be obtained a thermosetting resin composition in which crosslinking density is elevated and hardness and abrasion resistance are improved as well as solving a problem of acid resistance and odor. The present invention No. VIII relates to a carboxylic group-contained acrylate composition (a′) modified by a small amount of lactones represented by a formula described below by allowing to react a hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones with a carboxylic anhydride, (in the formula, R, R 1 , R 2 , and R 3 are independently a hydrogen or a methyl group, “j” is an integer of 2-6, xn pieces of R 4 and R 5 are independently a hydrogen atom or an alkyl group having a carbon number of 1-12, “x” is 4-7 , “n” is 0 or an integer of not less than 1, an average value of “n” in the composition is not less than 0.3 to less than 1.0 , R 6 is a residual group of a carboxylic acid, and “m” is an integer of 1-3), and relates to a method for the preparation thereof. By the method, there can be readily, efficiently, and economically obtained the carboxylic group-contained acrylate monomer composition modified by a small amount of lactones. The present invention No. IX relates to a curable resin composition containing 10-70 parts of an acrylic polycarboxylic resin essentially containing the carboxylic group-contained hydroxy(meth)acrylate monomer composition (a′) modified by a small amount of lactones as a polymerizing component and 0.5-80 parts of a polyepoxide. By the composition, there can be obtained a curable-type resin composition which can form a coating layer which is excellent in acid resistance, abrasion resistance, yellowing resistance, and outer appearance, and which is curable at a low temperature. The present invention No. X relates to a polyester unsaturated monomer (a″) modified by a small amount of lactones in which less than 1 mol of ε-caprolactone is allowed to react with 1 mol of a radically polymerizable unsaturated monomers containing carboxylic group under the presence of an acidic catalyst, and relates to a method for the preparation thereof. By the method, there can be readily and industrially prepared the monomer in a short step.

1 . A hydroxyalkyl(meth)acrylate composition modified by a small amount of lactones in which a proportion of monomers having two or more continuous chains (n≧2) of lactones is less than 50% (area % by GPC), the composition being represented by formula (1) described below,  
       
         
           
           
               
               
           
         
       
       (in the formula, R, R 1 , R 2 , and R 3  are independently a hydrogen or a methyl group, “j” is an integer of 2-6, xn pieces of R 4  and R 5  are independently a hydrogen or an alkyl group having a carbon number of 1-12, “x” is 4-7, “n” is 0 or an integer of not less than 1, an average value of “n” in a composition is not less than 0.3 to less than 1.0).  
     
     
         2 . A hydroxyalkyl(meth)acrylate composition modified by a small amount of lactones as claimed in  claim 1 , wherein a hydroxyalkyl(meth)acrylate which is employed as a raw material is a hydroxyethyl(meth)acrylate.  
     
     
         3 . A hydroxyalkyl(meth)acrylate composition modified by a small amount of lactones as claimed in  claim 1 , wherein a lactone monomer which is employed as a raw material is ε-caprolactone and/or valerolactone.  
     
     
         4 . A hydroxyalkyl(meth)acrylate composition modified by a small amount of lactones as claimed in  claim 1 , wherein the content of a lactone monomer remained in the composition is 0-10% by weight.  
     
     
         5 . A hydroxyalkyl(meth)acrylate composition modified by a small amount of lactones as claimed in  claim 1 , wherein the content of a hydroxyalkyl(meth)acrylate remained in the composition is not less than 20% by weight and not more than 50% by weight.  
     
     
         6 . A hydroxyalkyl(meth)acrylate composition modified by a small amount of lactones as claimed in  claim 1 , wherein the content of a di(meth)acrylate which is a by-product in said composition is not more than 2% by weight.  
     
     
         7 . A hydroxyalkyl(meth)acrylate composition modified by a small amount of lactones as claimed in  claim 1 , wherein the content of by-products produced by side reactions such as a Michael addition, an acrylic polymerization, a transesterification, and other side reactions is not more than 10% by weight in said composition.  
     
     
         8 . A hydroxyalkyl(meth)acrylate composition modified by a small amount of lactones as claimed in any one of claims  1 - 7 , wherein catalyst to be employed for a ring-opening polymerization in the preparation of said composition is less than 1000 ppm (weight) based on total amount of materials to be fed.  
     
     
         9 . A hydroxyalkyl(meth)acrylate composition modified by a small amount of lactones as claimed in any one of claims  1 - 8 , wherein the amount of a polymerization inhibitor for the hydroxyalkyl(meth)acrylate to be employed for a ring-opening polymerization in the preparation of said composition is not more than 1% by weight based on total amount of materials to be supplied.  
     
     
         10 . An acrylic polyol resin obtained using a hydroxyalkyl (meth)acrylate composition modified by a small amount of lactones as claimed in any one of claims  1 - 9  as a component for polymerization.  
     
     
         11 . A method for the preparation of a hydroxyalkyl (meth)acrylate composition modified by a small amount of lactones wherein a proportion of monomers having not less than 2 continuous chains (n≧2) of lactones is less than 50% by mol (GPC area %), characterized in that a hydroxyalkyl(meth)acrylate is allowed to react with a lactone in a reaction molar ratio of more than 1 in the case of preparing the polylactone-modified hydroxyalkyl(meth)acrylate through allowing to react the hydroxyalkyl(meth)acrylate with a lactone monomer by ring-opening polymerization according to a reaction represented by a general formula (2) described below,  
       
         
           
           
               
               
           
         
       
       (in the formula, R, R 1 , R 2 , and R 3  are independently a hydrogen or a methyl group, “j” is an integer of 2-6, xn pieces of R 4  and R 5  are independently a hydrogen or an alkyl group having a carbon number of 1-12, “x” is 4-7, “n” is 0 or an integer of not less than 1, and an average value of “n” in a composition is not less than 0.3 to less than 1.0).  
     
     
         12 . A method for the preparation of a hydroxyalkyl (meth)acrylate composition modified by a small amount of lactones as claimed in  claim 11 , wherein said hydroxyalkyl(meth)acrylate is hydroxymethylacrylate or hydroxyethylmethacrylate.  
     
     
         13 . A method for the preparation of a hydroxyalkyl (meth)acrylate composition modified by a small amount of lactones as claimed in  claim 1  or  12  wherein said lactone monomer is ε-caprolactone and/or valerolactone.  
     
     
         14 . A method for the preparation of a hydroxyalkyl (meth)acrylate composition modified by a small amount of lactones as claimed in any one of claims  11 - 13 , wherein an average value of n in said composition is not less than 0.35 and not more than 1.0.  
     
     
         15 . A method for the preparation of a hydroxyalkyl (meth)acrylate composition modified by a small amount of lactones as claimed in any one of claims  11 - 13 , wherein the content of said lactone remained in said composition is 0-10% by weight.  
     
     
         16 . A method for the preparation of a hydroxyalkyl (meth)acrylate composition modified by a small amount of lactones as claimed in any one of claims  11 - 13 , wherein the content of the hydroxyalkyl(meth)acrylate remained in said composition is not less than 20% by weight and not more than 50% by weight.  
     
     
         17 . A method for the preparation of a hydroxyalkyl (meth)acrylate composition modified by a small amount of lactones as claimed in any one of claims  11 - 13 , wherein the content of a di(meth)acrylate which is a by-product in the composition is not more than 2% by weight.  
     
     
         18 . A method for the preparation of a hydroxyalkyl (meth)acrylate composition modified by a small amount of lactones as claimed in any one of claims  11 - 13 , wherein the content of by-products produced by side reactions such as a Michael addition, an acrylic polymerization, a transesterification, and other side reactions is not more than 10% by weight in said composition.  
     
     
         19 . A method for the preparation of a hydroxyalkyl (meth)acrylate composition modified by a small amount of lactones as claimed in any one of claims  11 - 18 , wherein the amount of a catalyst to be employed in the reaction of the lactone with the hydroxyalkyl(meth)acrylate is less than 1000 ppm (by weight) based on total amount of materials to be fed.  
     
     
         20 . A method for the preparation of a hydroxyalkyl(meth)acrylate composition modified by a small amount of lactones as claimed in any one of claims  11 - 18 , wherein the content of a polymerization inhibitor for the lactone and the hydroxyalkyl(meth)acrylate is not more than 1% by weight based on total amount of materials to be fed.  
     
     
         21 . A curable resin composition comprising 0.5-80 parts by weight of an acrylic polyol resin (A) obtained using a hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones represented by the above-described formula (1) as claimed in  claim 1 , in which a proportion of monomers having not less than 2 continuous chains (n≧2) of lactones is less than 50% (GPC area %), as polymerizing components, and 0.5-50 parts by weight of a melamine resin (B), total of the (A) and (B) not exceeding 100 parts by weight.  
     
     
         22 . A curable resin composition as claimed in  claim 21 , wherein said hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones is obtained using a hydroxyethyl(meth)acrylate.  
     
     
         23 . A curable resin composition as claimed in  claim 21  or  22  wherein the hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones is obtained using ε-caprolactone, δ-valerolactone, γ-butyrolactone, or a mixture thereof.  
     
     
         24 . A curable resin composition as claimed in any one of claims  21 - 23 , wherein said acrylic polyol resin (A) is composed of 5-70 parts by weight of the hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones, 0-90 parts by weight of an alkyl(meth)acrylate having a carbon number of 1-20, 0-30 parts by weight of a (meth)acrylic acid, and 0-40 parts by weight of other polymerizable unsaturated monomer.  
     
     
         25 . A curable resin composition as claimed in any one of claims  21 - 24  wherein said acrylic polyol resin (A) has a hydroxyl group value of 5-250 and a number average molecular weight of 3,000-300,000.  
     
     
         26 . A melamine-curable type water-based coating composition comprising 5-30 parts by weight of an acrylic polyol resin (A) obtained using a hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones represented by the above-described general formula (1) as claimed in claim, wherein a proportion of monomers having not less than 2 continuous chains (n≧2) of lactones is less than 50% (GPC area %), as polymerizing components, and 10-60 parts by weight of an amino-plasto resin (IV-B).  
     
     
         27 . A melamine-curable type water-based coating composition as claimed in  claim 26 , characterized by composing of (i) 3-40% by weight of the hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones, (ii) 1-20% by weight of α, β-unsaturated carboxylic acid, (iii) 1-25% by weight of an N-alkoxymethyl (meth)acrylate having a carbon number of 1-6 in an alkyl group, and (iv) an aromatic vinyl monomer and an alkyl(meth)acrylate which are contained in an amount that 100% by weight minus total weight % of the above components (i), (ii), and (iii).  
     
     
         28 . A melamine-curable type water-based coating composition as claimed in  claim 26  or  27 , wherein said acrylic polyol resin (A) has a number average molecular weight of 2,000-50,000, a hydroxyl group value of 10-150 mg-KOH/g, and a Tg point of 0-60 C.  
     
     
         29 . A melamine-curable type water-based coating composition as claimed in any one of claims  26 - 28 , wherein said amino-plasto resin (IV-B) is at least one of a guanamine resin (k) selected from a melamine resin (j), benzoguanamine, spyroguanamine, acetoguanamine, and phthaloguanamine, and/or a melamine-guanamine cocondensed resin (1).  
     
     
         30 . A melamine-curable type water-based coating composition as claimed in any one of claims  26 - 29 , which is employed for cars, home electric appliances, and cans for beverages and foods.  
     
     
         31 . A curable resin composition comprising 50-90parts by weight of an acrylic polyol resin (V-A) obtained using a hydroxyalkyl(meth)acrylate composition (a) modified by small amount of lactones, represented by the above-described general formula (1) as claimed in  claim 1 , in which a proportion of monomers having not less than 2 continuous chains (n≧2) of lactones is less than 50% (GPC area %), and 50-10 parts by weight of a polyisocyanate compound (V-B), total of the (V-A) and (V-B) not exceeding 100 parts by weight.  
     
     
         32 . A curable resin composition as claimed in  claim 31 , wherein said acrylic polyol resin (V-A) is composed of 5-65% by weight of the hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones, 0-30% by weight of a vinyl monomer having hydroxyl group, and other vinyl-based monomers (residual weight).  
     
     
         33 . A curable resin composition comprising 0.5-80 parts by weight of an acrylic polyol resin (VI-A) having carboxylic group and a functional group obtained by allowing to react a hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones, represented by the general formula (1) claimed in  claim 1 , wherein a proportion of monomers having not less than 2 continuous chains (n≧2) of lactones is less than 50% (GPC area %), with a vinyl monomer having carboxylic group and other vinyl monomers, and 0.5-50 parts by weight of a polyisocyanate compound (VI-B), total of the (VI-A) and (VI-B) not exceeding 100 parts by weight.  
     
     
         34 . A curable resin composition as claimed in  claim 33 , wherein said acrylic polyol resin (VI-A) is a vinyl-based copolymer having carboxylic group and a functional group, said copolymer being obtained by allowing to react a reaction product of a hydroxyl group-contained resin and a (meth)acrylic anhydride with a vinyl-based monomer having carboxylic group and other vinyl-based monomers, said hydroxyl group-contained resin being obtained by polymerizing a hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones.  
     
     
         35 . A curable resin composition as claimed in  claim 33 , wherein said acrylic polyol resin (VI-A) is a resin obtained using said hydroxyl group-contained resin as claimed in  claim 34  and at least one selected from a urethane resin having hydroxyl groups, an epoxy resin having hydroxyl groups, a cellulose derivative having hydroxyl groups, and a polyester resin having hydroxyl groups.  
     
     
         36 . A curable resin composition as claimed in  claim 33  wherein said acrylic polyol resin (VI-A) is a resin obtained using said hydroxyl group-contained resin claimed in  claim 34  and a urethane resin having hydroxyl groups.  
     
     
         37 . A curable resin composition as claimed in  claim 33  wherein said polyisocyanate compound (VI-B) is a polyisocyanate compound containing an epoxy resin.  
     
     
         38 . A curable resin composition as claimed in anyone of claims  31 - 37 , wherein said hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones is a product obtained using hydroxyethyl(meth)acrylate.  
     
     
         39 . A coating characterized by containing (i) crosslinked particles obtained by dispersing a mixture of an acrylic polyol resin (VI-A) with a polyisocyanate compound (VI-B) into a water-based medium and by crosslinking thereof, or (ii) composite-type-crosslinked particles composed of a urethane-urea/ethylene-based resin obtained through polymerizing polymerizable ethylenic unsaturated compounds containing a hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones in water in which crosslinked urethane-urea particles are dispersed, as resin components for forming a thin layer.  
     
     
         40 . A coating as claimed in  claim 39  characterized by containing not less than 50% by weight of crosslinked particles having particle diameter of not more than 1 m and, moreover, an average molecular weight between crosslinking points within a range of 300-2,000, as resin components for forming a thin layer.  
     
     
         41 . A coating as claimed in  claim 39  or  40 , wherein said crosslinked particles have a layer-formable temperature of not more than 100° C.  
     
     
         42 . A coating as claimed in any one of claims  39 - 41 , wherein said content of the crosslinked particles is not less than 70% in said resin components for forming a thin layer.  
     
     
         43 . A coating as claimed in any one of claims  39 - 42 , characterized by containing 1-25% by weight of a crosslinking agent together with the crosslinked particles as said resin components for forming a thin layer.  
     
     
         44 . A coating as claimed in any one of claims  39 - 43 , characterized by further containing a thin layer-formable resin having a reactive group other than the crosslinked particles as said resin components for forming a thin layer.  
     
     
         45 . A coating as claimed in any one of claims  39 - 44 , wherein said crosslinked particles contain pigments in an inside thereof.  
     
     
         46 . A thermosetting resin composition which comprises 2-50parts of an acrylic polyol resin (VII-A) containing a hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones represented by the general formula (1) as claimed in claim 1, wherein a proportion of monomers having not less than 2 continuous chains (n≧2) of lactones is less than 50% (GPC area %), and 30-80 parts of an acrylic copolymer (VII-B) having an alkoxysilyl group, total of the (VII-A) and (VII-B) being 100 parts by weight.  
     
     
         47 . A thermosetting resin composition as claimed in  claim 46 , wherein said acrylic polyol resin (VII-A) has at least one kind selected from an acid anhydride group, an epoxy group, amino group, and carboxylic group.  
     
     
         48 . A thermosetting resin composition as claimed in  claim 46  or  47 , wherein said acrylic copolymer (VII-B) having an alkoxysilyl group has a group represented by general formula (VII-3) described below,  
       
         
           
           
               
               
           
         
       
       (in the formula, R 6  represents an alkyl group having a carbon number of 1-10, R 7  and R 8  are a hydrogen atom or a monovalent hydrocarbon group selected from an alkyl group, an aryl group, and an aralkyl group which have a carbon number of 1-10, “a” is the number of a substituent group, and it represents an integer of 0, 1, or 2).  
     
     
         49 . A thermosetting resin composition as claimed in  claim 48 , wherein said acrylic copolymer (VII-B) having an alkoxysilyl group has at least one kind selected from an acid anhydride group, an epoxy group, amino group, and carboxylic group.  
     
     
         50 . A thermosetting resin composition as claimed in  claim 48  or  49 , wherein said acrylic copolymer (VII-B) having an alkoxysilyl group has a number average molecular weight of 1,000-30,000.  
     
     
         51 . A thermosetting resin composition as claimed in any one of claims  48 - 50 , wherein said acrylic copolymer (VII-B) having an alkoxysilyl group contains 5-90% by weight of an alkoxysilyl group-contained monomer (VII-b) having a polymerizable unsaturated double bond as a polymerizing component.  
     
     
         52 . A thermosetting resin composition containing 0.1-20 parts by weight of a catalyst (VII-C) for curing based on 100 parts by weight of a thermosetting resin composition as claimed in any one of claims  48 - 51 .  
     
     
         53 . A thermosetting resin composition as claimed in  claim 52 , wherein said catalyst (VII-C) for curing is an organic tin compound, an acidic phosphate, a mixture-or reaction product of the acidic phosphate with an amine, a saturated or unsaturated polyvalent carboxylic acid, a saturated or unsaturated polyvalent carboxylic anhydride, a reactive silicone compound, an organic titanate compound, an organic aluminum compound, or a mixture thereof.  
     
     
         54 . A top coat clear coating comprising a thermosetting resin composition as claimed in any one of claims  46 - 53 .  
     
     
         55 . A method for the preparation of a carboxylic group-contained acrylate composition (a′) modified by a small amount of lactones represented by a general formula (VIII-3) described below characterized by allowing to react a hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones represented by the above-described general formula (1) claimed in  claim 1  in which a proportion of monomers having not less than 2 continuous chains (n≧2) of lactones is less than 50% (GPC area %) with a carboxylic acid or anhydride thereof (VIII-b) represented by a general formula (VIII-2) described below,  
       
         
           
           
               
               
           
         
       
       (in the formula, R, R 1 , R 2 , and R 3  are independently a hydrogen or a methyl group, “j” is an integer of 2-6, xn pieces of R 4  and R 5  are independently a hydrogen or an alkyl group having a carbon number of 1-12, “x” is 4-7, “n” is 0 or an integer of not less than 1, an average value of “n” in said composition is not less than 0.3 to less than 1.0, R 9  is a residual group of a carboxylic acid, and “m” is an integer of 1-3).  
     
     
         56 . A method for the preparation of a carboxylic group-contained acrylate composition (a′) modified by a small amount of lactones as claimed in  claim 55 , characterized in that a reaction of said hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones with said carboxylic acid or anhydride thereof (VIII-b) is conducted at a temperature range of 40-160° C.  
     
     
         57 . A method for the preparation of a carboxylic group-contained acrylate composition (a′) modified by a small amount of lactones as claimed in  claim 55  or  56 , characterized in that a reaction of the hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones with said carboxylic acid or anhydride thereof (VIII-b) is conducted under the presence of oxygen and a polymerization inhibitor.  
     
     
         58 . A method for the preparation of a carboxylic group-contained acrylate composition (a′) modified by a small amount of lactones as claimed in any one of claims  55 - 57 , characterized in that 0.9-1.1 mol of said carboxylic acid or anhydride thereof (VIII-b) is allowed to react with 1 mol of said hydroxyalkyl(meth)acrylate composition (a) modified by a small amount of lactones.  
     
     
         59 . A curable resin composition which comprises 10-70 parts of an acrylic polycarboxylic acid resin (A′) containing said carboxylic group-contained acrylate composition (a′) modified by a small amount of lactones, represented by the general formula (VIII-3) as claimed in  claim 55 , in which a proportion of monomers having not less than 2 continuous chains (n≧2) of lactones is less than 50% (GPC area %), as a polymerizing component, and 10-80 parts of a polyepoxide (IX-B).  
     
     
         60 . A curable resin composition as claimed in  claim 59 , characterized in that said carboxylic group-contained hydroxy(meth)acrylate composition (a′) modified by a small amount of lactones is obtained by allowing to react said hydroxyalkyl(meth)acrylate composition modified by a small amount of lactones, represented by the general formula (1) as claimed in claim 1, in which a proportion of monomers having not less than 2 continuous chains (n≧2) of lactones is less than 50% (GPC area %), with said carboxylic acid or anhydride thereof represented by general formula (VIII-2) as claimed in  claim 55 .  
     
     
         61 . A curable resin composition as claimed in  claim 60 , characterized in that said carboxylic group-contained hydroxy(meth)acrylate composition (a′) modified by a small amount of lactones is obtained by allowing to react 0.9-1.1 mol of said carboxylic acid or anhydride thereof with respect to 1 mol of said hydroxy(meth)acrylate composition (a) modified by a small amount of lactones.  
     
     
         62 . A curable resin composition as claimed in any one of claims  59 - 61 , characterized in that said acrylic polycarboxylic acid resin (A′) is a copolymer of 5-80% by weight of a carboxylic group-contained ethylenic unsaturated monomer with 20-95% by weight of an ethylenic unsaturated monomer not having carboxylic group, provided that the ratio of the carboxylic group-contained hydroxy(meth)acrylate composition (a′) modified by a small amount of lactones is 5-50% by weight in said the acrylic polycarboxylic acid resin (A′), and said copolymer has at least two carboxylic groups on average in the molecule and an acid value of 5-300 mgKOH/g-solid and a number average molecular weight of 500-8000.  
     
     
         63 . A curable resin composition as claimed in any one of claims  59 - 62 , characterized in that said acrylic polycarboxylic acid resin (A′) having terminal carboxylic group is an acrylic polycarboxylic acid resin (bA′) in which carboxylic groups are blocked by a blocking group which can produce carboxylic groups by heat and/or water.  
     
     
         64 . A curable resin composition as claimed in any one of claims  59 - 63 , characterized in that said polyepoxide (IX-B) is an acrylic polyepoxide having an epoxy equivalent of 50-700 and a number average molecular weight of 200-10000.  
     
     
         65 . A curable resin composition as claimed in any one of claims  59 - 64 , characterized in that said polyepoxide (IX-B) is a polyepoxide having hydroxyl group and an epoxy group which is obtained by copolymerization of 5-70% by weight of (i) a hydroxyl group-contained ethylenic unsaturated monomer having a structure represented by general formula (4) described below with 10-60% by weight of (ii) an epoxy group-contained ethylenic unsaturated monomer and 0-85% by weight of (iii) an ethylenic unsaturated monomer not having an epoxy group which is optionally added,  
       
         
           
           
               
               
           
         
       
       in the formula, R is a hydrogen atom or a methyl group, and X is an organic chain shown by formula (5) described below or an organic chain shown by formula (6) described below, 
       —O—Y—(OCO—(CH 2 ) m —) q —  (5) 
       (in the formula, Y is a linear or branched alkylene group having a carbon number of 2-8, “m” is an integer of 3-7, and “q” is an integer of 0-4),  
       
         
           
           
               
               
           
         
       
       (in the formula, R is a hydrogen atom or a methyl group, and “n” is an integer of 2-50).  
     
     
         66 . A curable resin composition as claimed in any one of claims  59 - 65 , and which further contains 0.1-10 parts by weight of an antioxidant (IX-C).  
     
     
         67 . A curable resin composition as claimed in any one of claims  59 - 66 , and which further contains 5-70 parts by weight of a polyester polycarboxylic acid (IX-D) having an acid value of 30-350 mg-KOH/g-solid.  
     
     
         68 . A curable resin composition as claimed in any one of claims  59 - 67 , and which further contains 0.1-10 parts by weight of crosslinked resin particles (IX-E).  
     
     
         69 . A clear coating composition containing a curable resin composition as claimed in any one of claims  59 - 68  as a binder.  
     
     
         70 . A method for coating which comprises a step in which a water-based or a solvent-based base coating is coated on a substrate coated by under-coating or internally-coating; a step in which a clear coating composition as claimed in  claim 69  is coated on the base coating without curing a layer of said base coating; and a step in which said layer of said base coating and a layer of said clear coating composition are cured by heating.  
     
     
         71 . A polyester unsaturated monomer composition modified by a small amount of lactones, in which a proportion of monomers having not less than 2 continuous chains (n≧2) of lactones is less than 50% (GPC area %), which is obtained by a ring-opening polymerization of a lactone monomer with respect to a polymerizable unsaturated monomer containing carboxylic group.  
     
     
         72 . A polyester unsaturated monomer composition modified by a small amount of lactones as claimed in  claim 71 , wherein said polymerizable unsaturated monomer containing carboxylic group is at least one kind selected from a group consisting of a (meth)acrylic acid, itaconic acid, β-(meth)acryloyloxyethyl succinic acid, β-(meth)acryloyloxyethyl maleic acid, β-(meth)acryloyloxyethyl phthalic acid, maleic acid, a monoalkyl maleate (a carbon number in an alkyl group is 1-12), tetrahydrophthalic acid, and an anhydride thereof.  
     
     
         73 . A polyester unsaturated monomer composition modified by a small amount of lactones as claimed in  claim 72 , wherein said polymerizable unsaturated monomer containing carboxylic group is a (meth)acrylic acid, and which is obtained by a reaction represented by formula (X-1) described below,  
       
         
           
           
               
               
           
         
       
       (in the formula, R and R 1  are independently a hydrogen or a methyl group, xn pieces of R 4  and R 5  are independently a hydrogen or an alkyl group having a carbon number of 1-12, “x” is 4-7, “n” and “n” in said composition are 0 or an integer of not less than 1, and an average value of “n” in said composition is not less than 0.3 to less than 1.0).  
     
     
         74 . A polyester unsaturated monomer composition modified by a small amount of lactones as claimed in any one of claims  71 - 73 , wherein said lactone monomer is ε-caprolactone and/or valerolactone.  
     
     
         75 . A polyester unsaturated monomer composition modified by a small amount of lactones as claimed in any one of claims  71 - 74 , characterized in that the proportion of monomers having not less than 2 continuous chains (n≧2) of lactones is less than 40% (GPC area %)  
     
     
         76 . A polyester unsaturated monomer composition modified by a small amount of lactones as claimed in anyone of claims  71 - 75 , wherein the content of said lactone monomer remained in the composition is 0-10% by weight.  
     
     
         77 . A polyester unsaturated monomer composition modified by a small amount of lactones as claimed in anyone of claims  71 - 76 , wherein the content of said remained polymerizable unsaturated monomer containing carboxylic group is not less than 20% by weight and not more than 50% by weight.  
     
     
         78 . A polyester unsaturated monomer composition modified by a small amount of lactones as claimed in anyone of claims  71 - 77 , wherein the content of a di(meth)acrylate of said polymerizable unsaturated monomer containing carboxylic group which is a by-product in said composition is not more than 2% by weight.  
     
     
         79 . A polyester unsaturated monomer composition modified by a small amount of lactone as claimed in anyone of claims  71 - 78 , wherein the content of by-products produced by side reactions such as a Michaels addition, an acrylic polymerization, a transesterification, and other side reactions is not more than 10% by weight.  
     
     
         80 . A polyester unsaturated monomer composition modified by a small amount of lactone as claimed in anyone of claims  71 - 79 , wherein the amount of a catalyst to be employed in said ring-opening polymerization is less than 1000 ppm (by weight) based on total amount of materials to be fed.  
     
     
         81 . A polyester unsaturated monomer composition modified by a small amount of lactone as claimed in any one of claims  71 - 80 , wherein a polymerization inhibitor is not more than 1% by weight based on total amount, which is employed for a (meth)acrylic acid in said ring-opening polymerization.  
     
     
         82 . A method for the preparation of a polyester unsaturated monomer composition modified by a small amount of lactone, wherein 0.3-less than 1.0 mol of a lactone monomer is polymerized by ring-opening with respect to 1 mol of a radically polymerizable unsaturated monomers containing carboxylic group, whereby, a proportion of monomers having not less than 2 continuous chains (n≧2) of lactones is adjusted to less than 50% (GPC area %).  
     
     
         83 . A method for the preparation of a polyester unsaturated monomer composition modified by a small amount of lactone as claimed in  claim 82 , wherein an acidic catalyst is a Lewis acid or a Br nsted acid.  
     
     
         84 . An acrylic resin using a polyester unsaturated monomer composition modified by a small amount of lactone as claimed in any one of claims  71 - 81 .  
     
     
         85 . A method for the preparation of a polyester unsaturated monomer composition modified by a small amount of lactone, characterized in that 0.3-less than 1.0 mol of a lactone monomer is polymerized by ring-opening with respect to 1 mol of a radically polymerizable unsaturated monomer containing carboxylic group using a stannous halide, monobutyltin tris-2-ethylhexanate, stannous octoate, dibutyltin dilaurate, or a mixture thereof as a catalyst, followed by separating the unreacted radically polymerizable unsaturated monomer containing carboxylic group.  
     
     
         86 . A method for the preparation of a polyester unsaturated monomer composition modified by a small amount of lactone as claimed in  claim 85 , wherein the catalyst to be employed in said ring-opening polymerization is less than 1000 ppm by weight based on total amount to be fed.