JP2006122755A - Manufacturing method of polyurethane resin-hardened coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a polyurethane resin-hardened coating film having high hardness, good transparency and smoothness and excellent film-forming properties. <P>SOLUTION: The method is employed to form a hardened coating film of an aqueous polyurethane resin composition containing an aqueous polyurethane resin and a compound having a polymerizable group on a substrate and comprises coating the polyurethane composition to a substrate and polymerizing the compound having a polymerizable group. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a polyurethane resin cured coating film, and more specifically, a method for producing a polyurethane resin cured coating film having high hardness, good transparency and smoothness, and excellent film forming properties. About.

Examples of polyurethane resin compositions that are easy to apply, do not require special coating equipment, and have a good finish are organic solvent-based polyurethane resin compositions and aqueous polyurethane resin compositions. From the viewpoint of contamination of the work environment due to volatilization of the organic solvent, the use of an aqueous polyurethane resin composition has attracted attention. And as a method of applying a water-based polyurethane resin composition to produce a polyurethane-based resin cured coating film, after adding a vinyl monomer containing a polyethylene-based unsaturated monomer to a carboxyl group-containing urethane prepolymer and dispersing in water, There has been proposed a method for producing a cured polyurethane resin coating film in which a free radical radical initiator is added and heated to apply an aqueous polyurethane-vinyl polymer dispersion obtained by polymerizing the vinyl monomer.
JP-A-5-132535

  However, in this method for producing a polyurethane resin-cured coating film, since the aqueous polyurethane-vinyl polymer dispersion liquid in which the polymerization of the vinyl monomer has already been completed by heating is applied before coating, the obtained coating film is There is a drawback that the hardness is not sufficient. In addition, if it is intended to obtain a coating film with high hardness, it is possible by appropriately selecting the raw materials constituting the resin, but in this case, without using an organic solvent as a film forming aid, There is a disadvantage that an excellent coating film cannot be obtained.

  The present invention has been made in view of such circumstances, and has an object of curing a polyurethane-based resin cured coating having high hardness, good transparency and smoothness, and excellent film forming properties. It is to provide a method for manufacturing a film.

  As a result of intensive investigations to solve these problems, the present inventors have applied a water-based polyurethane resin composition containing a water-based polyurethane resin and a compound having a polymerizable group on the adherend and then applied the polymerizable group. Surprisingly, it has been found that a cured coating film having high hardness, good transparency and smoothness, and excellent film forming property can be obtained by polymerizing a compound having As a result, the present invention has been completed.

  The present invention has been completed based on the above findings, and the gist of the present invention is a cured coating film of an aqueous polyurethane resin composition containing an aqueous polyurethane resin and a compound having a polymerizable group on an adherend. A method for producing a polyurethane resin cured coating film characterized by polymerizing a compound having a polymerizable group after coating an aqueous polyurethane resin composition on an adherend.

  According to the production method of the present invention, a cured polyurethane resin coating film having high hardness and good transparency and smoothness can be obtained. Furthermore, it is possible to produce a polyurethane-based resin cured coating film that exhibits excellent adhesion and film-forming properties to an adherend and also exhibits excellent weather resistance, solvent resistance, water resistance, pigment dispersibility, and the like. The production method of the present invention is a method that does not contaminate the working environment due to volatilization of the organic solvent, and can exhibit excellent environmental compatibility.

  Hereinafter, the present invention will be described in detail. The constituent elements described below are examples (representative examples) of the embodiments of the present invention, and the present invention is not limited to these contents. In the present specification, an aqueous polyurethane resin not containing a compound having a polymerizable group is referred to as “aqueous polyurethane resin”, and an aqueous dispersion containing a compound having a polymerizable group and an aqueous polyurethane resin is referred to as “aqueous polyurethane resin”. “Composition” and an aqueous polyurethane resin composition applied to an adherend and cured are expressed as “polyurethane resin cured coating film”.

  First, in the production of the polyurethane-based resin cured coating film of the present invention, the aqueous polyurethane resin and the compound having a polymerizable group constituting the aqueous polyurethane-based resin composition applied on the adherend will be described.

  The aqueous polyurethane resin used in the present invention has an average dispersed particle size of usually 500 μm or less, preferably 300 μm or less, more preferably 200 μm or less. When the average dispersed particle diameter exceeds 500 μm, problems such as deterioration of dispersion stability and deterioration of resin physical properties may occur. The weight average molecular weight of the aqueous polyurethane resin is usually 5,000 to 1,000,000, preferably 10,000 to 500,000. The nonvolatile content of the aqueous polyurethane resin is usually 20 to 70% by weight, preferably 25 to 60% by weight.

  The aqueous polyurethane resin can be produced by a known method. For example, a compound having an ionic salt-forming group and two or more hydroxyl groups or amino groups in the molecule, a polyisocyanate compound having two or more isocyanate groups in the molecule, and two or more hydroxyl groups in the molecule An aqueous polyurethane resin is produced using a polyol compound and a chain extender having two or more active hydrogen atoms capable of reacting with an isocyanate group in the molecule as main raw materials.

  Examples of the compound having an ionic salt-forming group and two or more hydroxyl groups or amino groups in the molecule are compounds having a carboxylic acid group or a sulfonic acid group. Specifically, glycolic acid, malic acid, glycine, Hydroxy acids such as alanine and 2,2′-bis (hydroxymethyl) alkanoic acid, aminocarboxylic acids, polyvalent hydroxy acids, taurine, sulfamic acid, aminosulfonic acid such as 2-hydroxyethanesulfonic acid, hydroxysulfonic acid, etc. Can be mentioned. In particular, 2,2'-bis (hydroxymethyl) alkanoic acid, which is versatile and provides good resin performance, is preferred. Hereinafter, description will be made using 2,2'-bis (hydroxymethyl) alkanoic acid.

  Examples of 2,2′-bis (hydroxymethyl) alkanoic acid include 2,2′-bis (hydroxymethyl) propionic acid and 2,2′-bis (hydroxymethyl) butanoic acid. 2'-bis (hydroxymethyl) butanoic acid is preferred. Hereinafter, 2,2'-bis (hydroxymethyl) propionic acid is abbreviated as DMPA (dimethylolpropionic acid), and 2,2'-bis (hydroxymethyl) butanoic acid is abbreviated as DMBA (dimethylolbutanoic acid). DMBA is very superior in solubility in water, organic solvents, polyol compounds and the like as compared with DMPA, and some have a solubility about 20 times that of DMPA. For example, the solubility in N-methylpyrrolidone (NMP) is such that DMPA only dissolves at 34 g / 20 ° C., 51 g / 50 ° C., and 75 g / 80 ° C. with respect to 100 g of NMP, whereas the solubility of DMBA is 92 g / 20 ° C. It dramatically increases to 164 g / 50 ° C. and 291 g / 80 ° C. As a result, the use of DMBA is very effective in reducing the amount of organic solvents used and eliminating solvents.

  The amount of carboxyl groups incorporated into the urethane prepolymer by 2,2'-bis (hydroxymethyl) alkanoic acid is usually 500 to 4000 when expressed in terms of the average molecular weight of the urethane prepolymer per one carboxyl group. When the average molecular weight of the urethane prepolymer is less than 500, the coating film properties and water resistance of the resulting resin are deteriorated, which is not preferable. Moreover, when the average molecular weight of the urethane prepolymer exceeds 4000, not only the self-emulsification property of the urethane prepolymer is insufficient, the average particle diameter of the dispersed particles is increased and the dispersion stability is deteriorated, but also a dense coating film is formed. It tends to be difficult to form.

  Examples of the polyisocyanate compound having two or more isocyanate groups in the molecule include 4,4'-diphenylmethane diisocyanate, 2,4- or 2,6-tolylene diisocyanate, 1,5-naphthalene diisocyanate, p- or Aliphatic diisocyanates such as aromatic diisocyanates such as m-phenylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,4-cyclohexylene diisocyanate, hydrogenated products of tolylene diisocyanate, fats such as hexamethylene diisocyanate Group diisocyanate, xylylene diisocyanate, m-tetramethylxylylene diisocyanate and the like. These polyisocyanate compounds may be used alone or in combination of two or more. Moreover, you may use together the polyfunctional isocyanate compound etc. which are the reaction products with polyfunctional polyols, such as a multimer of the said polyisocyanate compound, or a trimethylol propane, as needed.

  Among the above polyisocyanate compounds, aliphatic or alicyclic isocyanates are preferred from the viewpoint of the reactivity between isocyanate groups and water when dispersing the urethane prepolymer in water and the weather resistance of the resulting resin, The alicyclic isocyanate is more preferable because of compatibility with the compound having a polymerizable group.

  The polyol compound having two or more hydroxyl groups in the molecule is not particularly limited as long as it has two or more hydroxyl groups in one molecule. For example, polyether polyol, polyester polyol, polycarbonate polyol, polybutadiene polyol And hydrogenated polybutadiene polyol. Specifically, examples of the polyether polyol include polyethylene glycol, polypropylene glycol, poly (ethylene / propylene) glycol, and polytetramethylene ether glycol.

  Examples of the polyester polyol include a compound obtained by polycondensation of a low molecular weight diol and a dibasic acid, and a compound obtained by a ring opening reaction of a dibasic acid using a low molecular weight diol as an initiator. Examples of the low molecular weight diol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, and the like. . Examples of the dibasic acid used for the former polycondensation include adipic acid, azelaic acid, sebacic acid, isophthalic acid, terephthalic acid and the like. Examples of the dibasic acid used in the latter ring-opening reaction include polyε-caprolactone and polyβ-methyl-δ-valerolactone.

  Examples of the polycarbonate polyol include 1,6-hexanediol polycarbonate polyol, 3-methyl-1,5-pentanediol polycarbonate polyol, and mixed diol polycarbonate polyol having 4 to 6 carbon atoms. Examples of the polybutadiene polyol include a polyol composed of 1,4-polybutadiene and 1,2-polybutadiene. Examples of the hydrogenated polybutadiene polyol include those having a paraffin skeleton obtained by hydrogenating polybutadiene polyol.

  Among the above-mentioned polyols, amorphous or liquid is more preferable from the viewpoint of ease of handling. Moreover, the above-mentioned polyol compound can be used individually or in combination of 2 or more types. If necessary, ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, short chain diol such as 3-methyl-1,5-pentanediol, or In addition, a short-chain triol such as trimethylolpropane or glycerin or a trifunctional polyol obtained by adding propylene oxide, ethylene oxide, ε-caprolactone, or the like to these may be used in combination with the above-described polyol compound.

  The average molecular weight of the polyol is usually 500 to 10,000, preferably 500 to 4,000. When the average molecular weight is less than 500, the function as a polyol may not be exhibited. When the average molecular weight exceeds 10,000, the viscosity of the obtained urethane prepolymer becomes high, and the generation of aggregates during water dispersion, May cause poor dispersion.

  Examples of the chain extender having 2 or more active hydrogen atoms include ethylenediamine, 1,2-propanediamine, tetramethylenediamine, hexamethylenediamine, 1,4-cyclohexylenediamine, isophoronediamine, and 4,4'-dicyclohexylmethanediamine. Diamines such as m-xylylenediamine and phenylenediamine; polyethylene polyamines such as diethylenetriamine, triethylenetetramine and tetraethylenepentamine; and hydrazine, piperazine and hydrazine and dihydrazide compounds of adipic acid and phthalic acid. In addition, the aforementioned short-chain diol, short-chain triol, trifunctional polyol and the like may be used, and monoethanolamine, diethanolamine, aminoethylaminoethanol and the like may be used in combination with the aforementioned polyamine compound. You may use these individually or in combination of 2 or more types.

  The production of an aqueous polyurethane resin consists of a prepolymer synthesis process, a neutralization process, a water dispersion process, and a chain extension process, but the other processes are performed in any order except that the prepolymer synthesis process is performed first. Also good. The most common method is a method of sequentially performing a prepolymer synthesis step, a neutralization step, a water dispersion step, and a chain extension step.

  For example, first, 2,2′-bis (hydroxymethyl) alkanoic acid, a polyisocyanate compound, a polyol compound having two or more hydroxyl groups in the molecule, and if necessary, a short-chain diol is reacted to form an NCO group at the terminal. A urethane prepolymer having the following is produced.

  The reaction temperature for producing the urethane prepolymer is usually 20 to 120 ° C, preferably 40 to 100 ° C, more preferably 50 to 95 ° C. When the temperature is lower than 40 ° C., the raw material has poor solubility and the reaction rate tends to be slow. Moreover, when temperature exceeds 100 degreeC, reaction with a carboxyl group and an isocyanate group will occur easily, and there exists a danger that a gel-like thing will be produced in a urethane prepolymer, or the whole will gelatinize.

  The reaction time depends on the reaction temperature in each stage of reaction, the solid content, etc. and is not generally determined, but is usually about 1 to 40 hours. In addition, when DMPA is used as the 2,2'-bis (hydroxymethyl) alkanoic acid, the reaction time of the urethane prepolymer reaction may be longer than that of DMBA.

  In the synthesis of the urethane prepolymer, the equivalent ratio of the NCO group of the polyisocyanate compound to the hydroxyl group of the polyol component is usually NCO / OH = 1.1 / 1 to 30/1, preferably NCO / OH = 1.1 / 1 to 1. The range is 15/1. Since the urethane prepolymer contains a compound having a polymerizable group, the viscosity of the urethane prepolymer can be lowered and the operation of emulsification / dispersion can be facilitated, so that it is not necessary to use an organic solvent. .

  As described above, an organic solvent may not be usually used, but when it is used, an organic solvent having a boiling point of 50 to 120 ° C. is preferable so that it can be easily removed after the resin is made aqueous. For example, acetone (boiling point 56.3 ° C), methyl ethyl ketone (boiling point 79.6 ° C), methyl isobutyl ketone (boiling point 117 ° C), tetrahydrafuran (boiling point 66 ° C) 1,4-dioxane (boiling point 101.4 ° C), Examples include ethyl acetate (boiling point 76.8 ° C.) and toluene (boiling point 110.6 ° C.). Among these, in view of good solubility of the polyurethane resin and easy removal, acetone and methyl ethyl ketone are preferable, and acetone is more preferable. In addition, when DMPA is used in the production of the urethane prepolymer, it is preferable to use the above organic solvent because of its low solubility. However, when DMBA is used, it is necessary to use an organic solvent because of its high solubility. There is no.

  In addition, when an organic solvent is used from the early stage of urethane prepolymer synthesis, the aqueous polyurethane resin finally produced tends to be soft (modulus change). In other words, if an organic solvent is used during the synthesis of the urethane prepolymer, the arrangement of the urethane prepolymer molecular chain component, the urethane prepolymer molecular weight, etc. change. There may be a drawback that it becomes large and a coating film hardness decreases.

  The prepolymer reaction may be non-catalyzed, but in order to accelerate the reaction, for example, organometallic catalysts such as dibutyltin dilaurate, dibutyltin dioctoate, stannous octoate, triethylenediamine, toluethylamine, tributylamine, etc. A tertiary amine catalyst may be used.

  In the urethane prepolymer reaction, it is preferable to use a polymerization inhibitor in the presence of air in order to prevent polymerization of a compound having a polymerizable group described later due to heat. The amount of the polymerization inhibitor used is usually in the range of about 10 to 2000 ppm, preferably in the range of 10 to 1000 ppm, relative to the compound having a polymerizable group. As a polymerization inhibitor, hydroquinone, hydroquinone monomethyl ether, tert-butylcatechol, p-benzoquinone, 2-mercaptobenzimidazole, 2,2,4-trimethyl-1,2-dihydroquinoline, N, N-di-β- Naphthyl-p-phenylenediamine, 4,4-butylidene-bis (3-methyl-6-tert-butylphenol, phenyl-β-naphthylamine, 2,2-methylenebis (4-methyl-6-tert-butyl) phenol, 2 -Radical polymerization inhibitors such as mercaptobenzimidazole, diphenylpicrylhydrazyl, galvinoxyl, ferdazil, N-nitrosophenylhydroxylamine aluminum salt, sulfur and nitro compounds.

  After producing the urethane prepolymer, a basic substance is added to neutralize the carboxyl groups in the urethane prepolymer chain, and after dissolving or dispersing in water, the urethane prepolymer is chain extended with a chain extender. Further, after the urethane prepolymer is produced, the chain may be subsequently extended with a chain extender or a polyisocyanate compound, and then a basic substance may be added and dissolved or dispersed in water.

  Basic substances include tertiary amines such as trimethylamine, triethylamine, methyldiethylamine and tripropylamine, alkanolamines such as dimethylethanolamine, methyldiethanolamine and triethanolamine, and hydroxides of alkali metals such as ammonia, sodium and potassium And carbonates. Of these, tertiary amines and alkanolamines are preferred. The usage-amount of a basic substance is 0.5-1.2 equivalent normally with respect to 1 equivalent of carboxyl groups of a urethane prepolymer.

  Next, the obtained urethane prepolymer is dispersed in water. As a method for dispersing the urethane prepolymer in water, an ordinary stirrer is used. As the stirrer, an agitator having a stirring blade such as an anchor type, a paddle type, or a turbine type can be used. In order to obtain a uniform aqueous dispersion having a smaller particle size, a homomixer, homodisper, homogenizer, line mixer or the like can be used.

  The water used is preferably demineralized water. As the metal content in the desalted water, the total content of alkali metal and alkaline earth metal is usually 5 ppm or less, preferably 2 ppm or less. Further, the total metal content in the 3rd to 14th group in the periodic table is usually 5 ppm or less, preferably 2 ppm or less.

  Examples of the compound having a polymerizable group constituting the aqueous polyurethane resin composition include compounds capable of addition polymerization such as radical polymerization, anion polymerization, and cationic polymerization, and coordination polymerization, such as polymerizable double bonds and triple bonds. Examples include compounds having a bond. And as a compound which has a polymeric group, the compound which does not contain the group which reacts with isocyanate, such as a hydroxyl group, a carboxyl group, a silanol group, an amino group, and a glycidyl group, is suitable.

  The following compounds can be used as the compound having a polymerizable group. For example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, (meth) acrylate Libutyl, (meth) acrylic acid pentyl, (meth) acrylic acid hexyl, (meth) acrylic acid 2-ethylhexyl, (meth) acrylic acid octyl, (meth) acrylic acid isooctyl, (meth) acrylic acid nonyl, (meth) Isononyl acrylate, isodecyl (meth) acrylate, isooctyl (meth) acrylate, 2- (2-ethoxyethoxy) ethyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, (meth) acrylic Methoxyethyl acid, isobornyl (meth) acrylate Tetrahydrofurfuryl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, (meth) acrylic acid Examples include (meth) acrylic acid alkyl esters such as methoxybutyl, ethoxybutyl (meth) acrylate, polyethylene glycol methyl ether (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, and 2-ethylhexyl carbitol (meth) acrylate.

  Furthermore, amide groups such as acrylamide, N-butoxymethyl (meth) acrylamide, N-methylacrylamide, N, N-dimethylacrylamide, N-isopropylacrylamide, diacetone acrylamide, N-vinylformamide, acetoacetoxyethyl (meth) acrylate, etc. The compound which has is mentioned.

  Further, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl methacrylate, N, N-dimethylaminopropylacrylamide methyl chloride quaternary salt, N, N-dimethylaminopropyl methacrylate, pentamethylpiperidyl (meta ) Monomers having a tertiary amino group such as acrylate, (meth) acryloylmorpholine, monomers containing nitrogen such as N-vinylpyrrolidone, N-vinylimidazole, N-vinylcarbazole; cyclopentyl (meth) acrylate, cyclohexyl (meta) ) Acrylate, isobornyl (meth) acrylate, 4-tertiary butylcyclohexyl (meth) acrylate, dihydroxycyclopentadienyl (meth) acrylate, dicyclopentenyl (meth) acrylate , Cycloaliphatic monomers such as dicyclopentenyloxyethyl (meth) acrylate; aromatic monomers such as styrene, α-methylstyrene, phenyl methacrylate, 2-phenoxyethyl (meth) acrylate, and benzyl (meth) acrylate; vinyl Examples thereof include silicon-containing monomers such as triethoxysilane and γ-methacryloyloxypropyltrimethoxysilane; fluorine-containing monomers such as octafluoropentyl (meth) acrylate and perfluorocyclohexyl (meth) acrylate.

  Furthermore, divinylbenzene, zinc acrylate, tri (meth) allyl isocyanurate, tris (2-acryloyloxyethyl) isocyanurate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa ( (Meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, hexanediol di (meth) acrylate, nonanediol di (meth) acrylate, dipropylene glycol di (meth) ) Acrylate, tripropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) Acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, EO-modified bisphenol A di (meth) acrylate, ethoxylated bisphenol A di (meth) acrylate, ethoxylated 1,6-hexanediol di (meth) ) Acrylate, trimethylol propane ethylene oxide adduct, (meth) acrylated urethane resin (eg, Ebecryl 220, SARTOMER-CN964, CN965 etc.), (meth) acrylated epoxy resin (eg, SARTOMER-CN104), ( Compounds having polyfunctional unsaturated double bonds such as (meth) acrylated polyester and polyether; methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, Vinyl ethers such as sobutyl vinyl ether, octadecyl vinyl ether, vinyl cyclohexyl ether, vinyl-4-hydroxybutyl ether, butanediol-1,4-divinyl ether; triple bond-containing compounds such as propiolic acid ester, propargyl alcohol; NBR (acrylonitrile-butadiene Copolymers), SBR (styrene-butadiene copolymers), elastomers such as chlorosulfonated polyethylene; vinylidene chloride; (meth) allyl chloride; vinyl propionate; vinyl pyrrolidone; nibyl caprolactam; vinyl carbazole; Divinylethyleneurea; tetramethylpiperidyl (meth) acrylate and the like.

  The amount of the compound having a polymerizable group is usually in the range of 90/10 to 1/99, preferably 70/30 to 5/95, by weight ratio to the solid content of the aqueous polyurethane resin.

  In the aqueous polyurethane resin composition, a known polymerization initiator may be used for the purpose of accelerating the polymerization of the compound having a polymerizable group. As the polymerization initiator, water-soluble polymerization initiators and oil-soluble polymerization initiators can be used. Specifically, azo compounds such as azobisisobutyronitrile and azobisisobutylvaleronitrile, benzoyl peroxide, isobutyryl Oxide, Octanoyl peroxide, Cumylperoxyoctate, t-Butylperoxy-2-ethylhexanoate, t-Butyl hydroperoxide, t-Butylperoxyacetate, Lauryl peroxide, Di-t-butylperoxide Examples thereof include organic peroxides such as oxide, di-2-ethylhexyl peroxydine carbonate and cumene hydroperoxide, and inorganic peroxides such as potassium persulfate, ammonium persulfate and hydrogen peroxide.

  The organic or inorganic peroxide may be used as a redox polymerization initiator in combination with a reducing agent. Reducing agents for use as redox initiators include thioureas, amines, sucrose, copper, iron, cobalt, vanadium and other fatty acid salts and metal complexes, L-ascorbic acid, L-sorbic acid, meta Examples thereof include sodium bisulfite, ferric sulfate, ferric chloride, Rongalite and the like.

  The usage-amount of a polymerization initiator is 0.05-5 weight% normally with respect to the compound which has a polymeric group, Preferably it is the range of 0.05-3 weight%.

  Furthermore, a curing accelerator may be added to the aqueous polyurethane-based resin composition in addition to the above-described polymerization initiator (mainly organic peroxide). Examples of the curing accelerator include organic sulfonimides such as o-benzoixsulfimides, amines such as diethylamine, triethylamine, N, N-dimethylparatoluidine, 1,2,3,4-tetrahydroquinone, copper chloride, Examples include organic metal salts such as copper octylate, and a promoter such as a secondary or tertiary amine may be used in combination as necessary.

  Moreover, you may add a well-known chain transfer agent, for example, an octyl mercaptan, a lauryl mercaptan, 2-mercaptoethanol, a dodecyl mercaptan, a thioglycerin etc., in order to adjust the molecular weight in superposition | polymerization of the compound which has a polymeric group.

  The aqueous polyurethane resin composition may contain a stabilizer. Examples of the stabilizer include polymerization inhibitors such as benzoquinone, hydroquinone, hydroquinone monomethyl ether, and phenols, and chelating agents such as organic chelating agents and polymer chelating agents.

  Examples of organic chelating agents include NTA (nitrilotriacetic acid), EDTA (ethylene diamine tetraacetic acid), DTPA (diethylene triamine pentaacetic acid), glycine, alanine and other aminocarboxylic acids or salts thereof; citric acid, malic acid, tartaric acid, glutamic acid, Hydroxycarboxylic acids such as lactic acid, DMPA (dimethylolpropionic acid), DMBA (dimethylolbutanoic acid) and gluconic acid or salts thereof; ether carboxylic acids such as CMT (carboxymethyl tartronate) and CMOS (carboxymetyl oxysuccinate) or salts thereof; CETSA and thioether carboxylic acids such as (carboxyethyl thiosuccinate) or salts thereof. Examples of the salt include sodium salt, potassium salt, monoethanolamine salt, diethanolamine salt, and triethanolamine salt. Among these, glycine, alanine, citric acid, malic acid, tartaric acid, gluconic acid, CETSA or a salt thereof is preferable.

  Polymeric chelating agents include acrylic acid, methacrylic acid, maleic anhydride, α-hydroxyacrylic acid, polymers of itaconic acid or their copolymers and their salts, starch, cellulose or other molecules with oxygen atoms. The compound which oxidized the natural polymer containing, the compound which carried out carboxymethylation, the compound which introduce | transduced the carboxyl group, or its salt is mentioned. Examples of the salt include sodium salt, potassium salt, monoethanolamine salt, diethanolamine salt, and triethanolamine salt. Among these, acrylic acid and maleic anhydride polymers, copolymers or salts thereof are preferred.

  In addition, the aqueous polyurethane resin composition of the present invention includes pigments, dyes, leveling agents, thickeners, antifoaming agents, crosslinking agents, light-resistant stabilizers, flame retardants, anti-yellowing agents, You may mix | blend well-known additives, such as a film | membrane auxiliary agent and an organic solvent. The blending ratio is such that the non-volatile content of the aqueous polyurethane resin composition is usually in the range of about 1.0 to 99.0% by weight. In addition, plasticizers such as phthalate ester, adipate ester, phosphate ester, polyester, and epoxy are used to improve the film-forming properties when drying a cured coating and the flexibility and elongation of the coating. May be added.

  The method of the present invention is a method for producing a cured coating film of an aqueous polyurethane resin composition containing an aqueous polyurethane resin and a compound having a polymerizable group on an adherend, the aqueous polyurethane resin on the adherend It is characterized by polymerizing a compound having a polymerizable group after applying the resin composition.

  First, addition and mixing of an aqueous polyurethane resin and a compound having a polymerizable group will be described. The method of adding and mixing the aqueous polyurethane resin and the compound having a polymerizable group is not particularly limited. For example, (1) a method of adding and mixing a compound having a polymerizable group when producing an aqueous polyurethane resin. (2) Any method of adding and mixing a compound having a polymerizable group after producing an aqueous polyurethane resin may be used. Among them, the method (1) of adding and mixing a compound having a polymerizable group when producing an aqueous polyurethane resin is preferable. Further, after adding and mixing the aqueous polyurethane resin and the compound having a polymerizable group by the methods (1) and (2), (3) polymerizing a part of the compound having a polymerizable group to form a polymerizable group. A method in which a part of the compound is left can also be employed.

  First, (1) a method of adding and mixing a compound having a polymerizable group when producing an aqueous polyurethane resin will be described. For example, the compound having a polymerizable group may be added at any step from the neutralization step, the water dispersion step, and the chain extension step before, during or after the synthesis of the urethane prepolymer.

  Moreover, you may perform the addition of the compound which has a polymeric group at once or in multiple times. When adding over several times, for example, when adding a compound having a polymerizable group to a mixed solution of a urethane prepolymer and a compound having a polymerizable group, the addition time is not particularly limited. Add a compound with a polymerizable group before, during or after neutralization of the polymer, at any time after neutralization, or during or after water dispersion of the neutralized urethane prepolymer until the chain extension is completed I can do it. The compound having a polymerizable group to be added may be the same kind, a different kind or a mixture of two or more kinds of the compound having a polymerizable group added previously.

  The ratio (weight ratio) of the urethane prepolymer and the compound having a polymerizable group is usually urethane prepolymer: compound having a polymerizable group = 10: 90 to 99: 1, preferably urethane prepolymer: a compound having a polymerizable group. = 30:70 to 95: 5. If the weight ratio is less than 10, it is difficult to obtain the mechanical properties, adhesion to the substrate, abrasion resistance, flexibility, etc., which are the characteristics of urethane. Film hardness, film-forming property, weather resistance, etc. may deteriorate.

  Since the above urethane prepolymer is self-emulsifying due to having an ionic group, when the compound having a polymerizable group is hydrophobic, the compound having a polymerizable group is dispersed in water by acting as an emulsifier. (Microencapsulation). That is, the resulting aqueous polyurethane resin composition has a core-shell structure in which a compound having a polymerizable group is a core part and a self-emulsifiable aqueous polyurethane resin is a shell part. Therefore, the use of an external emulsifier such as sodium dodecylbenzenesulfonate used in emulsification of a compound having a general polymerizable group is basically from the viewpoint of water resistance of the resin cured coating film and adhesion to the substrate. Although not required, a small amount of an emulsifier may be added in order to improve the dispersion stability of the aqueous polyurethane resin composition or the stability when polymerizing it.

  When an aqueous dispersion of a urethane prepolymer and a compound having a polymerizable group is formed, chain extension of the urethane prepolymer may be performed. In this case, the urethane prepolymer having a terminal NCO group encapsulating a compound having a polymerizable group can be used for chain extension.

  You may add to the obtained water-based polyurethane resin the hardening | curing agent which has 2 or more of functional groups which can react with a carboxyl group in 1 molecule. This curing agent may be water-soluble, water-dispersible or hydrophobic. Examples of the functional group that reacts with the carboxyl group include, for example, an epoxy group, a carbodiimide group, an oxazoline group, and an aziridine group. You may use a hardening | curing agent individually or in combination of 2 or more types. By using the curing agent, the carboxyl group reacts and the crosslinking density is improved, so that a resin having higher durability can be obtained. That is, a highly water-resistant resin is obtained by the disappearance of the hydrophilic carboxyl group.

  Next, (2) a method of adding a compound having a polymerizable group after producing an aqueous polyurethane resin will be described. The method for producing an aqueous polyurethane resin in this method is the same as the method for adding a compound having a polymerizable group when producing an aqueous polyurethane resin, except for adding a compound having a polymerizable group (1). It is.

  That is, the aqueous polyurethane resin is composed of a compound having an ionic salt-forming group and two or more hydroxyl groups or amino groups in the molecule, a polyisocyanate compound having two or more isocyanate groups in the molecule, and two or more in the molecule. And a chain extender having two or more active hydrogen atoms capable of reacting with an isocyanate group in the molecule. In addition, the production process of the aqueous polyurethane resin includes a prepolymer synthesis process, a neutralization process, a water dispersion process, and a chain extension process. This is the same method as that for adding a compound having a polymerizable group to.

  And after manufacturing aqueous polyurethane resin, the compound which has a polymeric group is added. The method of adding a compound having a polymerizable group to an aqueous polyurethane resin is a method of adding and mixing a compound having a polymerizable group to an aqueous polyurethane resin, or conversely, an aqueous solution to a compound having a polymerizable group. In this method, a polyurethane resin is added and mixed. The compound having a polymerizable group to be used may be the same, different or a mixture of two or more. For mixing and stirring, a normal stirrer can be used, for example, a stirrer having a stirring blade such as an anchor type, a paddle type, or a turbine type can be used. In order to obtain a uniform aqueous dispersion having a smaller particle size, a homomixer, homodisper, homogenizer, line mixer or the like can be used.

  Next, (3) a method of polymerizing a part of the compound having a polymerizable group to leave a part of the compound having a polymerizable group will be described. In this method, (1) a method of adding a compound having a polymerizable group when producing an aqueous polyurethane resin, or (2) a method of adding a compound having a polymerizable group after producing an aqueous polyurethane resin, During or after the production of the aqueous polyurethane resin composition, a polymerization initiator is added to polymerize the compound having a polymerizable group. Next, after the polymerization of the compound having a polymerizable group is completed, a compound having a polymerizable group is further added, and the mixture is stirred and dispersed. In addition, you may add a polymerization inhibitor before adding the compound which has a polymeric group as needed. As the polymerization initiator and polymerization inhibitor to be used, the above-mentioned polymerization initiators and polymerization inhibitors can be used.

  The compound having a polymerizable group is added by a method of adding a compound having a polymerizable group to an aqueous polyurethane resin composition in which the polymerization of the compound having a polymerizable group is completed, or conversely, by polymerization. Any method of adding a compound having a polymerizable group to an aqueous polyurethane resin composition in which polymerization of a compound having a polymerizable group has been completed may be used. The compound having a polymerizable group to be added may be the same, different or a mixture of two or more. For mixing and stirring, a normal stirrer can be used. For example, a stirrer having a stirring blade such as an anchor type, a paddle type, or a turbine type can be used. In order to obtain a uniform aqueous dispersion having a smaller particle size, a homomixer, homodisper, homogenizer, line mixer or the like can be used.

  In the method of the present invention, it is important to polymerize a compound having a polymerizable group after coating the aqueous polyurethane resin composition prepared as described above on an adherend.

  That is, an aqueous polyurethane resin composition is applied onto an adherend and cured while polymerizing (oligomerizing) a compound having a polymerizable group to form a polyurethane resin cured coating film. The polyurethane-based resin cured coating obtained by curing while polymerizing (oligomerizing) the compound having a polymerizable group in the aqueous polyurethane-based resin composition on the adherend has a conventional polymerizable group. The hardness is higher than that of a polyurethane resin-cured coating film obtained by polymerizing the compound having the water-based polyurethane resin composition on the adherend and then curing it.

The application method of the aqueous polyurethane resin composition is not particularly limited, and examples thereof include a brush coating method, a roll coating method, a spray coating method, a flow coating method, and a dipping method. The coating amount to the adherend is not particularly limited, 0.0001-0.1 / cm ² at normal solids, preferably 0.0001~0.05g / cm ^2.

  Redox polymerization, anaerobic polymerization, oxidation polymerization, coordination polymerization and the like can be applied as a polymerization method of the compound having a polymerizable group in the present invention. Of these, the redox polymerization method is preferred.

  In the anaerobic polymerization, when the aqueous polyurethane resin composition is applied and water is volatilized, the compound having a polymerizable group in the aqueous polyurethane resin composition is polymerized by blocking in water or from the outside air. Is the method. In addition, as the oxidative polymerization, when water is volatilized by applying an aqueous polyurethane resin composition, the compound having a polymerizable group in the aqueous polyurethane resin composition is oxidized by oxygen in the air. This is a polymerization method.

  For the purpose of increasing the polymerization rate, degree of polymerization, etc., the aqueous polyurethane resin composition may contain a polymerization initiator, or after applying the polymerization initiator to the adherend, the aqueous polyurethane resin Polymerization on the adherend, such as a method of applying the composition, a method of adhering an adherend coated with an aqueous polyurethane resin containing a polymerization initiator and an adherend coated with an aqueous polyurethane resin composition, etc. A polymerization initiator may be present so as to act on the compound having a functional group. As the polymerization initiator to be used, the aforementioned polymerization initiators can be used. The amount of the polymerization initiator present at the time of polymerization of the compound having a polymerizable group is usually 0.05 to 5% by weight, preferably 0.05 to 3% by weight, based on the compound having a polymerizable group.

  The temperature and time for polymerizing and curing the compound having a polymerizable group are not particularly limited, and known conditions can be used. For example, the temperature for polymerization and curing is not generally determined depending on the polymerization method and conditions, but is usually 10 to 80 ° C. and the time is usually about 1 minute to 5 hours. Moreover, the well-known conditions depending on the above-mentioned polymerization method to implement can be applied to the atmosphere which superposes | polymerizes the compound which has a polymeric group.

  The polymerization of the compound having a polymerizable group in the present invention is performed without applying heat or light energy as described above. That is, according to the method of the present invention, it is possible to obtain a polyurethane resin cured film having a high hardness without using a device such as an ultraviolet ray generator or an oven. However, for the purpose of increasing the polymerization rate, polymerization degree, etc., energy such as heat or light may be applied.

  Examples of the adherend include polyolefins such as polyethylene and polypropylene or surface treated products thereof, polyester or surface treated products thereof, polystyrene, vinyl chloride, polyamide, ABS, PPO (polyphenylene oxide), polycarbonate, acrylic resin, melamine resin decorative board, Examples thereof include a bakelite plate, a plastic such as expanded polystyrene, and a blend or modified product thereof. In addition, metal-deposited plastic, steel or its surface-treated product, copper, aluminum, aluminum alloy, titanium alloy, magnesium alloy and other metals, glass, ceramics, slate plates, mineral materials such as cardboard, corrugated paper, paperboard, Examples include paper-based materials such as kraft paper, pre-coated metal, electrodeposition coated plates, mortar, concrete, and wood-based materials. Of these, wood materials are preferable, and for example, single plates and boards such as wood, medium fiber board, hard board, particle board, and plywood, or processed products thereof are preferable.

  The method of the present invention can be used for adhesion and surface treatment of flash panels, decorative plywood, prefabricated panels, laminated timber, etc., and wood for wire sticking, hozo, dowel, tome, hagi, square wood, other assembly and furniture assembly, etc. It can be applied to industry.

  The method of the present invention is also suitable for constructions that cannot be heated and dried, such as wood paints, outdoor paints, and on-site construction paints, and constructions that cannot be irradiated with ultraviolet rays.

  The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In the following examples, “%” means weight% and “ratio” means weight ratio unless otherwise specified.

  Pencil hardness is a pencil ("Uni" (trade name) manufactured by Mitsubishi Pencil Co., Ltd.) using a new pencil of 6B to 6H, exposing the core of one end of the pencil without sharpening the core, and others While holding the end and slowly moving the exposed core to the coating surface of the coating while maintaining a contact angle of about 30 degrees with the weight of the pencil only, the occurrence of scratches on the coating surface Observe the presence or absence visually. At this time, the hardness of the hardest pencil that does not cause scratches was defined as the pencil hardness.

Example 1:
(1) Method of adding a compound having a polymerizable group when producing an aqueous polyurethane resin:
In a four-necked 2 L separable flask equipped with a condenser, thermometer, charging port and stirring device, 158.4 g of trimethylolpropane EO addition triacrylate, 30.0 g of isobornyl methacrylate, 52.6 g of isophorone diisocyanate (IPDI) , 18.3 g of 1,6-hexanediol adipate having an average molecular weight of 2000, 17.5 g of dimethylolbutanoic acid (DMBA, manufactured by Nippon Kasei Chemical Co., Ltd.), and 9.0 mg of p-methoxyphenol were charged and heated to 80 ° C. Polymer reaction was performed. After about 30 minutes, the reaction solution became a homogeneous solution, and the reaction was completed in 5 hours. The average molecular weight of the urethane prepolymer was 3200.

  The obtained urethane prepolymer solution was cooled to 40 ° C., and 12.0 g of triethylamine was uniformly mixed. Subsequently, 639.3 g of demineralized water was added dropwise to invert the urethane prepolymer solution and dispersed in water. After the phase inversion was completed, 3.3 g of 80% hydrazine hydrate was diluted with 13.9 g of demineralized water and added to extend the urethane prepolymer. The produced aqueous polyurethane resin composition was a uniform milky white liquid and no aggregates were observed.

  Next, 1.9 g of cumene hydroperoxide was added, applied to a glass plate, and allowed to stand in a temperature-controlled room at a temperature of 25 ° C. and a humidity of 40% for 24 hours to cure while curing (redox polymerization). The obtained cured coating film had good film-forming properties, was transparent and had no turbidity, was highly glossy (excellent smoothness), and had a pencil hardness of 2H.

Example 2:
(2) Method of adding a compound having a polymerizable group after producing an aqueous polyurethane resin:
Into a four-necked 2 L separable flask equipped with a condenser, a thermometer, a charging port, and a stirrer, 133.6 g of IPDI, 190.4 g of polytetramethylene ether glycol (PTMG1000, manufactured by Mitsubishi Chemical) with an average molecular weight of 1000, DMBA 18. 0 g was weighed and stirred at a liquid temperature of 90 ° C. while blowing nitrogen gas to produce a urethane prepolymer. After stirring for 1 hour, the content of the isocyanate group was measured by titration. As a result, it reached the theoretical NCO%, so the liquid temperature was cooled to 50 ° C. After reaching 50 ° C., 12.3 g of triethylamine was added to neutralize, and the mixture was stirred for 30 minutes. Next, 571.4 g of demineralized water was added dropwise over 6 minutes to phase invert the urethane prepolymer. An aqueous solution in which 15.4 g of hydrazine monohydrate is diluted with 64.3 g of demineralized water is added dropwise over 7 minutes to perform chain extension, and stirred at 40 ° C. for 3 hours to form an aqueous polyurethane resin having a solid content of 34.9% by weight Got.

  Next, 38.0 g of polypropylene glycol dimethacrylate was added to the aqueous polyurethane resin obtained while stirring and stirred for 30 minutes. After stirring, an aqueous polyurethane resin composition having good dispersion stability without phase separation even when allowed to stand for 1 day was obtained.

  1.9 g of cumene hydroperoxide was added, applied to a glass plate, and allowed to stand in a temperature-controlled room at a temperature of 25 ° C. and a humidity of 40% for 24 hours to cure while curing (redox polymerization). The obtained cured coating film had good film-forming properties, was transparent and had no turbidity, had high gloss (excellent smoothness), and had a pencil hardness of H and high hardness.

Example 3:
(3) A method of polymerizing a part of the compound having a polymerizable group and leaving a part of the compound having a polymerizable group:
A polyester polyol (P-2010, manufactured by Kuraray Co., Ltd.) 148 having a methyl methacrylate of 148.0 g, IPDI of 57.6 g, and an average molecular weight of 2000 was added to a four-necked 2 L separable flask equipped with a condenser, a thermometer, a charging port, and a stirring device. 0.0 g, DMBA 16.4 g, and p-methoxyphenol 0.015 g were charged, and the temperature was raised to 80 ° C. After about 30 minutes, the reaction solution became a homogeneous solution, and the reaction was completed in 5 hours. The average molecular weight of the urethane prepolymer was 3000, and the weight ratio of the urethane prepolymer and the compound having a polymerizable group was 60:40.

  The urethane prepolymer solution was cooled to 40 ° C., and 11.2 g of triethylamine was added and mixed uniformly. Then, 631.6 g of demineralized water was added dropwise, and the urethane prepolymer solution was phase-shifted into water and dispersed. After the phase inversion was completed, 4.2 g of 80% hydrazine hydrate was diluted with 17.9 g of demineralized water and added to extend the urethane prepolymer. While introducing nitrogen gas into the flask, 1.5 g of potassium persulfate was dissolved and added to 28.5 g of demineralized water, the temperature was kept at 75 ° C., and the mixture was reacted for 3 hours to polymerize the compound having a polymerizable group. A uniform aqueous urethane / acrylic composite resin resin having a content of 35% was obtained. The produced aqueous urethane / acrylic composite resin was a uniform milky white liquid and no aggregate was observed.

  While stirring the obtained aqueous urethane / acrylic composite resin, 60.0 g of ethoxylated bisphenol A dimethacrylate 14.0 g of trimethylolpropane EO-added triacrylate was added and stirred for 30 minutes. Even if the mixture was allowed to stand for 1 day after stirring, it was an aqueous polyurethane resin composition having no phase separation or the like and good dispersion stability.

  Next, 0.8 g of cumene hydroperoxide was added and applied to a glass plate, and cured in a light-shielded temperature of 25 ° C. in a constant temperature room with a humidity of 40% for 24 hours while curing (redox polymerization). The obtained cured coating film had good film-forming properties, was transparent and had no turbidity, was highly glossy (excellent smoothness), and had a pencil hardness of 2H.

Comparative Example 1:
In Example 1, trimethylolpropane EO addition triacrylate, isobornyl methacrylate and p-methoxyphenol were not used, and polytetramethylene ether glycol was used instead of 1,6-hexanediol adipate. The same raw material as 1 was used, and an aqueous polyurethane resin composition was produced at the same charging ratio.

  That is, in a four-necked 2 L separable flask equipped with a cooling pipe, a thermometer, a charging port, and a stirring device, 106.3 g of IPDI and polytetramethylene ether glycol having an average molecular weight of 2000 (“PTMG2000” (trade name) manufactured by Mitsubishi Chemical Corporation) ) 239.2g and DMBA 35.4g were charged, and the temperature was raised to 80 ° C to react with the urethane prepolymer.

  When the obtained urethane prepolymer solution was cooled to 40 ° C., the viscosity was very high and stirring was difficult. Therefore, 95.2 g of N-methylpyrrolidone was added to lower the viscosity. Thereafter, 20.6 g of triethylamine was mixed uniformly. 665.0 g of demineralized water was added dropwise to invert and disperse the urethane prepolymer solution in water. After the phase inversion was completed, 7.5 g of 80% hydrazine hydrate was diluted with 30.8 g of demineralized water and added to extend the urethane prepolymer. The produced aqueous polyurethane resin was a uniform milky white liquid and no aggregates were observed.

  Next, without adding cumene hydroperoxide, the obtained aqueous polyurethane resin was applied to a glass plate and cured by being left in a temperature-controlled room at a temperature of 25 ° C. and a humidity of 40%. The obtained coating film was transparent, free of turbidity and the like, and had high gloss, but the pencil hardness was 6B or less, and a coating film with high hardness was not obtained. Moreover, since N-methylpyrrolidone was used, volatilization of the organic solvent was recognized at the time of coating film manufacture.

Comparative Example 2:
In Example 2, the same raw material as Example 2 was used except that polyethylene glycol dimethacrylate was not used, and an aqueous polyurethane resin was produced at the same charging ratio.

  Next, without adding cumene hydroperoxide, the obtained aqueous polyurethane resin was applied to a glass plate and cured by being left in a temperature-controlled room at a temperature of 25 ° C. and a humidity of 40%. The obtained coating film was slightly turbid, low in gloss, pencil hardness was 6B or less, and a high hardness coating film was not obtained.

Comparative Example 3:
In Example 3, the same raw material as in Example 3 was used except that ethoxylated bisphenol A dimethacrylate and trimethylolpropane EO addition triacrylate were not used, and an aqueous urethane / acrylic composite resin resin was produced at the same charging ratio.

  Next, without adding cumene hydroperoxide, the obtained aqueous urethane / acrylic composite resin resin was applied to a glass plate and cured by being left in a temperature-controlled room at a temperature of 25 ° C. and a humidity of 40%. The obtained coating film was slightly turbid, low in gloss, pencil hardness was 6B or less, and a high hardness coating film was not obtained.

Claims (3)

  A method for producing a cured coating film of an aqueous polyurethane resin composition comprising an aqueous polyurethane resin and a compound having a polymerizable group on an adherend, wherein the aqueous polyurethane resin composition is applied on the adherend. A method for producing a cured polyurethane resin film, comprising polymerizing a compound having a polymerizable group.   The production method according to claim 1, wherein the compound having a polymerizable group is an acrylic ester compound or a methacrylic ester compound.   The production method according to claim 1, wherein the polymerization of the compound having a polymerizable group is carried out by any one of redox polymerization, anaerobic polymerization, oxidation polymerization, and coordination polymerization.