JPS60110702A - Branched acrylic resin, its production and coating resin composition - Google Patents

Abstract

PURPOSE:To obtain a branched low-viscosity acrylic resin suitable for use in coatings, etc., and excellent in coating properties, by reacting a specified polyfunctional epoxy compound with a carboxyl group-terminated acrylic prepolymer. CONSTITUTION:A carboxyl group-terminated acrylic prepolymer of formula I (wherein X is an acrylic prepolymer chain having a weight-average MW of 1,000-100,000 and a glass transition point of -20-100 deg.C) is prepared by polymerizing a monomer other than a carboxyl group-containing monomer (e.g., styrene) in the presence of a carboxyl group-containing chain transfer agent (e.g., mercaptoacetic acid) and a polymerization initiator. This prepolymer is reacted with a polyfunctional epoxy compound of formula II (wherein R is an aliphatic or aromatic hydrocarbon or the like, and n is 2-6), e.g., neopentyl glycol diglycidyl ether, to obtain a branched acrylic resin of formula III.

Description

[Detailed description of the invention]

The present invention relates to a novel branched acrylic resin, a method for producing the same, and a resin composition for coatings. Conventionally, acrylic resin, alkyd resin J3, and polyester resin have been mainly used as paint resins. -C showed particularly excellent performance. However, acrylic resins that satisfy such performance have a higher molecular weight than alkyd resins and polynisder resins that are normally used for paints, resulting in higher viscosity and lower nonvolatile content in paints at the same dilution rate. It had the disadvantage that it was difficult to achieve high non-blurization. On the other hand, in accordance with the recent social needs for low pollution and energy saving, it is preferable that the amount of solvent contained in the paint be as small as possible, and therefore it has been necessary to develop a resin with a low viscosity for the same non-volatile content. The conventional methods for reducing the viscosity of acrylic resins have been to reduce the molecular weight of the acrylic resin itself, or to copolymerize a highly soluble 7-mer, but the former method However, there was a drawback that durability such as weather resistance and chemical resistance, which is characteristic C of acrylic resin, deteriorated. On the other hand, the latter method has good solubility.
Because of the use of fluorine, there were drawbacks such as a decrease in solvent resistance and a decrease in mechanical strength. The present invention is based on the fact that such conventional techniques do not take into account the three-dimensional structural factors of resins, and it is necessary to use a resin composition that is normally used for paints and without drastically reducing the molecular weight. The present invention was developed by researching methods for reducing resin viscosity. The novel acrylic 1Thl resin of the present invention uses a polyfunctional epoxy compound having 2 or more glycidyl groups as a core material, and combines the glycidyl group of the epoxy compound as the core material with the carboxyl group-terminated acrylic resin. By carrying out an addition reaction with a polymer, a radial structure with an epoxy compound as the core can be provided. Therefore, it is thought that low viscosity can be achieved in such a new 1U acrylic resin due to the solubility of the polyfunctional 1-boxylated metal material serving as the core material and the radial structure of the resin molecule. Furthermore, the novel acrylic resin of the present invention has the advantage that the skeleton of the carboxyl-terminated acrylic prepolymer is a monomer other than carboxyl group-containing monomers, which are used as raw materials for acrylic resins for ordinary paints. Since it can be obtained by copolymerizing ZUMA in any combination, it can have a chemical composition similar to that of ordinary acrylic resins for paints, and therefore there is no appreciable difference in the performance of the coating film. Such carboxyl group is a 110 initiator that is usually used in the polymerization of acrylic resins, except for carboxyl group-containing monomers.
For example, 2 as an azo-nitrile compound. 2'-Azo-bis-isobutyronitrile, 1.1'-azo-bis-1-cyclobutani(·lyl, 2'-azo-bis-2methylbutyronitrile, etc., j'
zo compounds such as -(2,3-diazo-bicyclo[2.2,1]hebden-2,2,2'-azo-bis-propane, 1,1'-azo-bis-1-phenylatanate, etc. Also, as a peroxide compound,

[-butyl peroxide, benzoyl peroxide, [-butyl hydroperoxide, cumenehyde 1 bar Aquizide, etc. are used to initiate polymerization, and (1) a compound containing carboxyl J4 as a chain transfer agent. For example, a carboxyl group can be introduced at the end of the acrylic prepolymer by using mercaptocholic acid, 2-mercaptopropanoic acid, 3-mercaptopropanoic acid, O-mercaptobenkyzoic acid, or the like. On the other hand, monomers other than carboxyl group-containing monomers,
C, (2) a carboxyl group-containing initiator, for example, 4. /I' -7 Zobis (4-
A carboxyl group can also be introduced into one end of the acrylic prepolymer by initiating polymerization using cyanopentanoic acid), diglutaric peroxide, or the like. Monomers other than carboxyl group monomers used in the polymerization of such acrylic prepolymers can be divided into neutral monomers and functional group-containing monomers. Neutral monomers include tyrene, propylene, butadiene, isoprene, chlorobrene, vinyl chloride, vinyl bromide,
vinyl fluoride, nylidene chloride, methyl vinyl ether,) nocrylate esters (e.g. methyl, ethyl, butyl esters, etc.) methacrylate esters (e.g.
methyl, ethyl, butyl ester, etc.) 21-lyl derivatives (e.g. acrylonitrile, methacryloni]-lyl, etc.)
, styrene, styrene derivatives such as α-methylstyrene), and the like. On the other hand, examples of the functional group-containing polymer include acrylamide, methacrylamide, etc. as the alkoxy group-containing monomer, N-methylol acrylamide, N-
The human U xyl group stone-containing monomers include 2-hydroxyethyl acrylate-l-, 2-hydroxypropyl acrylate,
Examples include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and N-methylol acrylamide. In the polymerization of such an acrylic prepolymer, polymerization methods such as bulk polymerization, solution polymerization, and if necessary suspension polymerization are used, and initiation is carried out by a total amount charging method, an initiator dropping method, or a seven-drop method. Decomposition of agent hot stone or higher, usually 70℃~1
A prepolymer can be synthesized by stirring the reaction at 70° C. for 1 to 8 hours. When synthesizing such a prepolymer, the amount of the carboxylic chain transfer agent used in method (1) used to avoid introducing carboxyl groups at the terminals is 0.2 in terms of solid content weight ratio of the prepolymer. Weight % to 8fi hanging %, preferably 0. It is in the chemical range of 3% to 5% by weight. On the other hand, hand payment (2)
When using a carboxyl-based initiator of C, the amount used depends on the solid fraction ratio of the prepolymer. triple i
fi%~1 21fil-%, good jl L < 4yo 0
, in the range of 4% by weight to 8% by weight. The above method (1
) If the amount of the carboxyl group-containing chain transfer agent used in method (2) exceeds the above 8% by weight, and if the amount of the carboxyl group-containing initiator used in method (2) exceeds the above 12Φm%, the molecular weight of the prepolymer In terms of durability performance such as C1 weather resistance and chemical resistance, the molecular weight of NoI Kryl 481 11ii is reduced, which is the objective of the present invention.
cannot exert sufficient effects. - h1 carboxyl group-containing (1 chain transfer Eh agent use is less than 042% by weight, carboxyl cloud-containing initiator usage interval is 0
．． If J is less than 3% by weight, the molecule fr5 of the prepolymer will increase dramatically, and the reactivity of the glycidyl group of the polyfunctional epoxy compound will be low. It takes a long time to synthesize the resin, and the molecular weight of the acrylic resin, which is the object of the wood invention, becomes too large, resulting in increased viscosity and problems such as being unsuitable for use as paint resin. 1 with a carboxyl group at the end synthesized under the above polymerization conditions
In order for the acrylic prepolymer to maintain low viscosity without impairing the durability such as weather resistance and chemical resistance, solvent resistance, mechanical strength, etc. of the acrylic resin, which is the objective of the present invention, , the gravity average molecular weight of the acrylic prepolymer (measured by gel permeation chromatography, converted to polystyrene) 1°000 to 100,000. Moreover, it is preferable that the temperature of the crow transition hot stone is -20°C to 100°C. The acrylic prepolymer synthesized under these conditions and containing carboxyl groups at the terminals is subjected to an addition reaction with the glycidyl groups of the polyfunctional epoxy compound containing two or more glycidyl groups, thereby producing the novel object of the present invention. Used in the production of acrylic resin. The polyfunctional epoxy compound is a substance having two or more lysidyl groups, and these compounds may be saturated or unsaturated aliphatic, alicyclic, aromatic or heterocyclic compounds, and chlorine , hydroxyl group, 1-del group, etc., and these compounds may be monomeric or polymeric. The polyfunctional epoxy compound of the present invention includes epoxidized esters of unsaturated alcohols and polyvalent aliphatic acids,
For example, di(2,3-epoxyhexyl adipate),
Di(2,3-epoxybutyl) oxuate, amber extract (
2,3-epoxyhexyl), di(2,3-epoxybutyl) phthalate, and other glycidyl group-containing nitrogen compounds, such as diglycidylaniline and di- and triclycidylamine. Particularly preferred polyfunctional epoxy compounds for use in the production of the novel acrylic resins of the present invention are glycidyl ethers, particularly glycidyl ethers of polyhydric phenols d3 and polyhydric alcohols. Glycidyl ethers of polyhydric phenols and polyhydric alcohols can be obtained by reacting shrimprochlorohydrin with desired polyhydric phenols or polyhydric alcohols in the presence of an alkali. For example, diglycidyl ether of bisphenol A, diglycidyl ether of resorcinol,
1-liglycidyl ether of phlorogludinol, triglycidyl ether of trihydroxydibiphenyl, polyglycidyl ether of phenol/formaldehyde/noholak, polyglycidyl ether of O-cresol formaldehyde/noholak, diglycidyl ether of J3 and butanediol, polypropylene Diglycidyl ether of glycol, diglycidyl ether of neopentyl glycol, triglycidyl ether of glycerin, triglycidyl 1- of trimethylolpropane
Other polyfunctional epoxy compounds include diglycidyl isophthalate, a boxy compound derived from aromatic dicarboxylic acids, etc. , diglycidyl phthalate, diglycidyl ester of linol dimer acid and triglycidyl isocyanurate, detraphenylolethane epoxy, and the like. In the reaction between the polyfunctional epoxy compound having two or more glycidyl groups and the carboxyl group-terminated acrylic prepolymer, the number of moles of glycidyl groups in the polyfunctional epoxy compound and the carboxyl group in the carboxyl group-terminated acrylic prepolymer are 1 to 1. :0.6 to 1:1.4, preferably 10,8
~1:1.2, if necessary, add a solvent that does not react with the monoC glycidyl group or the carboxyl group, and at a reaction temperature of 80°C to 180°C, preferably 100°C to 160°C, carboxyl group-terminated acrylic The reaction rate as measured by the acid value of unreacted carboxyl groups of the prepolymer is 80% or more. For the reaction between the glycidyl group and the carboxyl group, for example, a mW catalyst can be used as a reaction catalyst, if necessary. Examples of the base catalyst include pyridine, isoquinoline, quinoline, and N. N-dimethylcyclohexylamine, α-picolinetri-butylamine, triethylamine, N-1 thylmorboline, N,N-dimethylaniline, N-(β-hydroxyethyl)amine, N-ethyl-3,.5-dimethyl Organic amines such as dimethylcoronatutuamine derived from morpholine and coconut oil, etc., or inorganic alkalis such as caustic soda and caustic potash are used.The acrylic resin obtained by such a reaction is a nuclear material. It has a polyfunctional epoxy compound as an epoxy compound, and the reaction between the glycidyl group and the carboxyl group in the epoxy compound creates
-〇〇〇+-(. Through the 1-1 bond of cl-1-, it is possible to give a radial structure covering the epoxy compound as a core. The purpose of the present invention is to achieve low viscosity of the new acrylic resin without impairing durability such as weather resistance and chemical resistance, solvent resistance, mechanical strength, etc. The weight average molecular weight of acrylic resin (gel permeation chromatography measurement, polystyrene equivalent) is 2,000 to 200.
,000°Glass transition temperature -20°C -1,00°C is preferable. To summarize the above (in the present invention, R is an aliphatic, alicyclic, aromatic or heterocyclic hydrocarbon residue, and 11 is an integer of 2 to 6). and the formula X-Cool-1 (wherein X is the weight average molecular weight 1,000 to 100°
A new branched acrylic resin C1 is manufactured by reacting an acrylic prepolymer having a terminal carboxyl group (acrylic prepolymer chain with a glass transition temperature of 20 to 100°C). ), and the weight average molecular fi32.00
It will be easily understood that the glass transition temperature has a special value of 0 to 200,000°C and a glass transition temperature of -20 to 100°C. When the acrylic resin of the present invention that satisfies the above conditions is used as an acrylic resin for paint, it may be used as it is or, if necessary, other resins such as acrylic resins other than the present invention, alkyd resins, polyester resins, and polyether resins may be used. , nitrate fiber cord, urethane resin, vinyl acetate resin, polyvinyl alcohol resin, vinyl chloride resin, etc., and when using C as a hardening resin, phenol resin, melamine resin, Guanamine resin, urea resin, isocyanate compound,
It can be used as an acrylic clear paint by adding epoxy resin or the like. When making the acrylic resin of the present invention into a paint, if necessary, solvents commonly used in the paint industry, such as hydrocarbon solvents such as toluene, xylene, Tsurpez 100 and Tsurpez 150, ethyl acetate, butyl acetate, etc. , ester solvents such as acetic acid L70 solve, acetic acid trichloride, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, n
- Alcohol solvents such as propatool, n-butanol, isobutanol, methylisobutylcarbinol, cyclohexanol, ether alcohol J3 such as methyl cellosolve, cellosolve, butyl cellosolve, butyl carbitol, dioxane, and one or two ether solvents. In addition to the above, a silicone-based, fluorinated-based, acrylic-based, polyether-based, or other surfactant may be added as necessary. On the other hand, when used as an acrylic enamel paint, the acrylic resin of the present invention, alone or other 41
? Various inorganic and organic pigments that are commonly used in the paint industry by mixing one or more types of 1 fat, such as zinc white, titanium oxide, antimony white, carbon black, iron black, red iron black, mapi] Yellow, for buttons, cadmium e [''-1 zinc sulfide, lithopone, barium sulfate, lead sulfate, barium carbonate, calcium carbonate, white lead,
Alumina white etc. are also used as organic pigments such as azo, polycondensed azo, metal complex azo,
Benzimidazolones, phthalocyanines (blue, green), thioindigos, anthraquinones, flavanthrones, indanthrenes, anthrapyridines,
One or more of bilanthrone series, isoindolinone series, perylene series, perinone series J3, and quinacridone series are mixed, and if necessary, the solvents and/or surfactants listed in the preparation of the acrylic clear paint are added. One or more agents are added to produce a dispersion base using a conventional dispersion machine such as a roll mill dispersion machine, a ball mill dispersion machine, a sand grind mill dispersion machine, a planetary mixer, a high speed dispersion machine, etc. . An acrylic enamel paint is prepared using the thus obtained dispersion base as it is, or by adding the acrylic resin of the present invention alone or one or more of the other resins mentioned above, and/or a solvent, a surfactant, etc. as necessary. I can help you. The acrylic clear paint and acrylic enamel paint containing the acrylic resin of the present invention obtained by such a method satisfy the characteristics of low viscosity and high non-porous paint as the object of the present invention, and when coated and removable, the acrylic clear paint and acrylic enamel paint contain the acrylic resin of the present invention. Durability J3 such as weather resistance and chemical resistance, solvent resistance, and mechanical strength, which are characteristics of resin, can be sufficiently maintained. Typical synthesis examples and examples of the novel acrylic resin of the present invention are shown below. In these production examples and examples, parts or percentages are by weight unless otherwise specified. Synthesis Example 1 (Synthesis of acrylic prepolymer) 224 parts of xylene is charged into a reaction vessel equipped with a dropping funnel, a cooling tube, a nitrogen introduction tube, a thermometer, and a stirring blade, and the temperature is raised to 130°C. 45 parts of 2-hydroxyethyl methacrylate, 336 parts of methyl methacrylate, 60 parts of n-butyl acrylate
parts, 127 parts of styrene monomer, thioglycol M26
A solution of 5.4 parts of azobisisobutyronitrile was charged into the dropping funnel. The contents of the dropping funnel were added dropwise at a constant rate over 3 hours at 130° C. under a nitrogen atmosphere. After the completion of dropping, the temperature was maintained at 130°C for 30 minutes. Next, a solution of C, 0.56 parts of azobisisobutyronitrile, and 176 parts of xylene was charged into the dropping load. This is added dropwise at a uniform rate over 30 minutes. After the dropwise addition was completed, the temperature was maintained at 130° C. for 1 hour to complete the polymerization. cold fAj
After taking out the contents, clear and colorless acrylic prepolymer A
I got it. The exemption for acrylic prepolymers is shown in Table 1.Synthesis Examples 2 to 4 Acrylic prepolymers e,,C,0@4':? Ta. The characteristics of the acrylic prepolymer are shown in Table 1. (Leaving space below) Table 1 1 -; Fufu 1 Rice ~ (Synthesis Example 5 (Synthesis of branched acrylic resin) The ingredients of Synthesis Example 1 were placed in a reaction vessel equipped with a cooling tube, nitrogen introduction tube, thermometer, and stirring blade. 451 parts of acrylic prepolymer A synthesized by the method (trade name Deinukol EX411, manufactured by Nagase Kasei Koraku ■),
Diglycerose triglycidyl ether 28 parts, xylene 21 parts, Firmin DMC (Kao Soaplin) O, '72
A portion of the solution was poured into a reubene and the temperature was raised to 140°C. After raising the temperature, it was maintained at 140° for 10 hours to complete the addition reaction,
Branched acrylic resin-F was obtained. Branched acrylic resin
The special numbers of E are shown in Table 2]. Synthesis Examples 6 to 10 Branched acrylic resins [~J] were obtained in the same manner as in Synthesis Example 5 using the J formulations shown in Table 2. The special properties of the branched acrylic resin are shown in Table-2. (Leaving space below) Table 2 (3) Product name Nismy Epoxy ELG-300 (manufactured by Sumitomo Chemical Co., Ltd.) (4) Product name: Bunacol EX-321 (
(manufactured by Nagase Kasei Kogyo) (5) Product name: Bunacol EX-4
11 (Made by Nagase Kasei Ko'IM Layer) Synthesis Examples-11 to 13 (
Comparative Resin) Comparative Resin I was prepared according to the method of Synthesis Example 5 with the formulation shown in Table 3.
〈~M was obtained. The characteristics of this resin are shown in Table 3. Table-3 U8 5 → 4 9 7 7 ] 1 ) 0 (1) Tokyo Keiki E-type viscometer (2) Gel permeation chromatography (polystyrene conversion) Example 1 Obtained in Synthesis Examples 1 to 3 Acrylic prepolymer = 1 to 3,
Branched acrylic resins 5 to 10 obtained in Synthesis Examples 5 to 10
and Comparative Resin 11.1 obtained in Synthesis Example 11.13.
Each of 3 was diluted with a solvent (xylene/acetic acid butylene - 1/1) to prepare a varnish with a resin solid content of 50%. The viscosity of the obtained varnish was measured using a cone-plate viscometer, and the results shown in Table 4 were obtained. When the viscosity of these varnishes is plotted against the heavy chain average molecular weight of the resin in Blots 1 to J, the results shown in Figure 1 are obtained, indicating that the branched acrylic resin exhibits a low viscosity at the same weight average molecular weight. Table 4 (Continued on next page) (Continued from Table 4) Example 2 Branched acrylic resin-G obtained in Synthesis Example 5.7 and having almost the same weight average molecular weight and Synthesis Example 13 Using comparative resin M, titanium oxide (R-820) was mixed with a paint shaker (Red Dehil Co., Ltd.) according to the dispersion mixture shown in Table 5.
20 units of specular gloss (Murakami gloss meter GM)
-26D type) was set at 40 or higher. Dispersion blending example Table-5 The viscosity of each of the obtained dispersion pastes was measured using a cone-plate viscometer (E-type viscosity 51, Tokyo 31 equipment ■).Table-5
I got a result of 6 and 1 [. The use of branched acrylic resins reduces the mucilage of the dispersed paste by about 35%. Table-6 (1) Shear rate 7 (3,85ec-5 viscosity (
2) Shear rate 384. Viscosity example at O5ec-'
3 Using the branched acrylic resin G used in Example 2 and the comparative resin M according to the formulation shown in Table 7, a carbon rack (MA-100 Mitsubishi Carbon ) to obtain a dispersion paste (disperse until the specular gloss becomes 80 or higher). The viscosity results of each of the obtained dispersion pastes are shown in Table 8. By using a branched acrylic resin, the viscosity becomes approximately 115, and the resin exhibits Newtonian flow. Dispersion blending example Table-7 Table-8 Example-4 Using comparative resin K, branched acrylic resin F, and acrylic prepolymer 〇, which have approximately the same weight average molecular weight, Table-
Mabikoero (LLXLO) was prepared using the same formulation as in Example 2 according to the formulation shown in Example 9.
-IL? -4fl 41. − / Q n +et
R surface AL'H; dispersion until l 4+<50 or more). The viscosity results for each dispersion amount obtained are shown in Table-10. What about branched acrylic resin? The viscosity of the acrylic prepolymer is reduced by about 60% compared to the 1M resin and by about 80% for the acrylic prepolymer. Examples of dispersion and blending Table-9 Table-10 Procedural amendments August 31, 1980, Commissioner of the Patent Office, Case 1 1981 Patent Application No. 21814 Gauze 2 Title of the invention Branched acrylic resin, its manufacturing method, and paint resin Relationship with the case of the person who amends the composition 3 Patent applicant address: 2-1-2 Oyodokita, Oyodo-ku, Osaka Name: Nippon Paint Co., Ltd. Representative: Masao Suzuki 4 Agent address: 3-57 Kyobashi, Higashi-ku, Osaka 540 Building River Center 6th Floor Name Patent Attorney (6871) Takeo Ito 5. Date of amendment order 6. Number of inventions increased by amendment 7. Subject of amendment 7. Detailed explanation of the invention in the specification Contents of amendment to class 8 As attached (1) ) Insert the following on page 8 of the specification, line 7, after "May be introduced."
- "Furthermore, by using (1) a compound containing a carboxyl group as a chain transfer agent and (2) the same compound as a carboxyl group-containing initiator together, a carboxyl group can be introduced at the end of the acrylic prepolymer. I can.”

Claims (1)

[Claims] (1) Formula % Formula % (wherein R is an aliphatic, ring group, aromatic or heterocyclic hydrogen residue, X is an acrylic prepolymer chain, 1) is 2-
Integer of 6> For expressed weight average molecule (gel permeation chromatography measurement, polystyrene conversion) 2.000
~200,000. Glass transition temperature -20℃~100℃
branched acrylic resin. (2> Acrylic prepolymer has a weight average molecular weight of 1゜00
Glass transition humidity at 0~100.000 -20~100℃
The resin according to claim 1, which is a resin according to claim 1. (3) A polyfunctional epoxy compound represented by the formula (wherein R is an aliphatic, ring ring, aromatic or heterocyclic hydrocarbon residue, and 0 is an integer of 2 to 6) and the formula X is for weight average molecule 1.0'OO~100°00
0, Crow transition temperature Fj, 20-100"C(f)/
A branched acrylic resin represented by the formula (in which R1, Method of manufacturing resin. (4)>Claim 3, wherein the crylic prepolymer is made using a carboxyl group-containing chain transfer agent corresponding to 0.2 to 8% solid content of the prepolymer. the method of. (5) The method according to claim 3, wherein the acrylic prepolymer is prepared using a carboxyl group-containing initiator corresponding to 0.3 to 12% by weight of the solid content of the prepolymer. (6) The method according to claim 4, wherein the carboxyl group-containing chain transfer agent is selected from the group consisting of mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, and O-mercaptobenzoic acid. . (7) The method according to claim 5, wherein the carboxyl group-containing initiator is 4,4'-azobiscyanopentanoic acid or peroxide diglutaric acid. (8) The polyfunctional epoxy compound is selected from neopentyl glycol diglycidyl ether, trimethylolpropane 1-heryglycidyl ether, pentaerythritol-i-traglycidyl l-thyl, and sorbyl polyglycidyl ether. A method according to claim 3. (9) Formula % Formula %) (In the formula, R is an aliphatic, cyclic, aromatic, or heterocyclic hydrocarbon residue X is an acrylic prepolymer chain, n is a 2-
(an integer of 6) (weight average molecular weight expressed by gel vermiaction test U71-graphic measurement, polystyrene conversion) 2.000
~200,000. Glass transition temperature = 20°~100°C
A resin composition for paint, comprising a branched acrylic resin as a film-forming resin.