JP2010195982A - Polyurethane resin emulsion for water-based paint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyurethane resin emulsion for water-based paint, giving a dried coated film having an impact resistance which is the same with or better than that of a conventional water-based emulsion and having good time stability unattainable by conventional polyurethane resin emulsions. <P>SOLUTION: The polyurethane resin emulsion satisfies the conditions that the glass transition temperature of the polyurethane resin (U) is -110°C to -20°C and the linear expansion ratio representing the difference in the length of a dried film before and after being immersed in dimethylformamide at 25°C for 48 hr is 100-180%, provided that the dry film is obtained by drying the polyurethane resin emulsion at 105°C for 3 hr. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polyurethane resin emulsion for water-based paints. Specifically, the present invention relates to a polyurethane resin emulsion used for water-based paints.

  One of the uses of the polyurethane resin emulsion is an aqueous paint. As polyurethane resin emulsions that can be used for water-based paints, for example, polyurethane resin emulsions using a specific surfactant (Patent Document 1), polyurethane resin emulsions that define particle size distribution (Patent Document 2), and the like have been reported. . When these polyurethane resin emulsions are used in water-based paints, the impact resistance of the dried coating film is improved as compared with the case where emulsions other than polyurethane resins are used.

JP 2005-179484 A JP 2003-321648 A

  However, when the above polyurethane resin emulsion is used in an aqueous paint, there is a problem that the stability of the aqueous paint over time is not sufficient. The present invention is a polyurethane resin emulsion for water-based paint, and the impact resistance of the dry paint film of the water-based paint using the polyurethane resin emulsion of the present invention is comparable to that using a conventional polyurethane resin emulsion. Another object of the present invention is to provide a polyurethane resin emulsion that improves the day-to-day stability of water-based paints that cannot be achieved with conventional polyurethane resin emulsions.

The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems. That is, this invention is a polyurethane resin emulsion for water-based paints satisfying the following (1) to (2) containing a polyurethane resin (U) and an aqueous dispersion medium.
(1) The glass transition temperature of the polyurethane resin (U) is -110 ° C to -20 ° C.
(2) The linear expansion coefficient before and after the dried film obtained by drying the polyurethane resin emulsion at 105 ° C. for 3 hours is immersed in dimethylformamide at 25 ° C. for 48 hours is 100 to 180%.

The aqueous paint obtained by using the polyurethane resin emulsion for aqueous paints of the present invention has the following effects.
-The impact resistance of the dried coating film is comparable to that obtained using a conventional polyurethane resin emulsion.
・ The water paint has good stability over time.

  The polyurethane resin emulsion of the present invention contains a polyurethane resin (U) [hereinafter sometimes simply referred to as (U)], and an aqueous dispersion medium.

  The polyurethane resin (U) in the present invention is composed of a polyisocyanate component (a1), a polyol component (a2), a hydrophilic group-containing active hydrogen-containing component (a3), and, if necessary, other components (a4).

  As the polyisocyanate component (a1) constituting the (U) [hereinafter sometimes simply referred to as (a1)], those conventionally used for polyurethane production can be used. As (a1), an aromatic polyisocyanate (a11) having 2 or more isocyanate groups and having 6 to 20 carbon atoms (hereinafter abbreviated as C) (excluding carbon in the isocyanate groups, the same shall apply hereinafter), C2-18 aliphatic polyisocyanate (a12), C4-15 alicyclic polyisocyanate (a13), C8-15 araliphatic polyisocyanate (a14), and a modified product (a15) of these polyisocyanates. Can be mentioned. (A1) may be used alone or in combination of two or more.

  Examples of the C6-20 aromatic polyisocyanate (a11) include 1,3- and / or 1,4-phenylene diisocyanate, 2,4- and / or 2,6-tolylene diisocyanate (TDI), crude TDI, 4,4′- and / or 2,4′-diphenylmethane diisocyanate (MDI), crude MDI [crude diaminophenylmethane [condensation product of formaldehyde with an aromatic amine (aniline) or mixture thereof; diaminodiphenylmethane and a small amount (for example, 5-20% by weight) mixture with trifunctional or higher functional polyamines]: phosgenates: polyaryl polyisocyanates (PAPI)], 4,4′-diisocyanatobiphenyl, 3,3′-dimethyl-4,4 ′ -Diisocyanatobiphenyl, 3,3'-dimethyl-4,4 ' Diisocyanatodiphenylmethane, 1,5-naphthylene diisocyanate, 4,4 ', 4 "- triphenylmethane triisocyanate, etc. m- and p- isocyanatophenyl sulfonyl isocyanate.

  Examples of the C2-18 aliphatic polyisocyanate (a12) include ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), dodecamethylene diisocyanate, 1,6,11-undecane triisocyanate, and 2,2,4-trimethyl. Hexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethyl caproate, bis (2-isocyanatoethyl) fumarate, bis (2-isocyanatoethyl) carbonate, 2-isocyanatoethyl-2,6-diisocyanate And natohexanoate.

  Examples of the C4-15 alicyclic polyisocyanate (a13) include isophorone diisocyanate (IPDI), 4,4-dicyclohexylmethane diisocyanate (hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate (hydrogenated TDI), and bis. (2-isocyanatoethyl) -4-cyclohexene-1,2-dicarboxylate, 2,5- and / or 2,6-norbornane diisocyanate.

  Examples of the C8-15 araliphatic polyisocyanate (a14) include m- and / or p-xylylene diisocyanate (XDI), α, α, α ′, α′-tetramethylxylylene diisocyanate (TMXDI), and the like. Can be mentioned.

  As the modified polyisocyanate (a15), the modified polyisocyanate (urethane group, carbodiimide group, allophanate group, urea group, burette group, uretdione group, uretoimine group, isocyanurate group and / or oxazolidone group-containing modified product) A free isocyanate group content is usually 8 to 33%, preferably 10 to 30%, particularly 12 to 29%), such as modified MDI (urethane modified MDI, carbodiimide modified MDI, trihydrocarbyl phosphate modified MDI, etc.), urethane Examples include modified polyisocyanates such as modified TDI, biuret-modified HDI, isocyanurate-modified HDI, isocyanurate-modified IPDI, and urethane-modified polyisocyanates [excess polyisocyanates (such as TDI and MDI). ) As the polyol used for the production of reacting a polyol with the free isocyanate-containing prepolymer obtained, include low molecular weight polyols described below. Examples of the combination of two or more types include a combination of modified MDI and urethane-modified TDI (isocyanate-containing prepolymer).

  Among these polyisocyanate components (a1), preferred are C2-18 aliphatic polyisocyanate (a12) and C4-15 alicyclic polyisocyanate (a13), and more preferred are C4-15 fat. Cyclic polyisocyanates (a13), particularly preferred are IPDI and hydrogenated MDI.

  Examples of the polyol component (a2) [hereinafter sometimes simply referred to as (a2)] include a polymer polyol (a21) having a number average molecular weight of 400 to 5,000, and a low molecular polyol having a number average molecular weight of less than 400 ( a22).

Examples of the polymer polyol (a21) include polyether polyol (a211), polyester polyol (a212), and polycarbonate polyol (a213).
The number average molecular weight of (a21) is usually 400 to 5,000, preferably 500 to 5,000, and more preferably 1,000 to 3,000. [In the following, the number average molecular weight may be abbreviated as Mn. ]

  Mn can be measured by gel permeation chromatography (hereinafter GPC) using tetrahydrofuran as a solvent and polystyrene as a standard.

  Examples of the polyether polyol (a211) include aliphatic polyether polyols and aromatic ring-containing polyether polyols.

  Aliphatic polyether polyols include aliphatic low molecular weight active hydrogen atom-containing compounds (divalent to octavalent or higher aliphatic polyhydric alcohols having a hydroxyl group equivalent of 30 to less than 150, and primary as active hydrogen atom-containing groups. Alternatively, an alkylene oxide (hereinafter abbreviated as AO) adduct of a compound containing a secondary amino group can be used.

  The aliphatic polyhydric alcohol to which AO is added includes a linear or branched aliphatic dihydric alcohol [(di) ethylene glycol, (di) propylene glycol, 1,2-, 1,3-, 2,3- And 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol and 1,12 -Dodecanediol, etc.] and alicyclic dihydric alcohols [low molecular diols having a cyclic group, such as those described in JP-B No. 45-1474], aliphatic trihydric alcohols [glycerin, trimethylolpropane, trialkanolamine, etc. And aliphatic tetravalent or higher alcohol [pentaerythritol, diglycerin, triglycerin, dipenta Risuritoru, sorbitol, sorbitan, and the like is sorbide, etc.].

  Examples of the compound containing a primary or secondary amino group to which AO is added include alkyl (1 to 12 carbon atoms) amine, and (poly) alkylene polyamine (2 to 6 carbon atoms of an alkylene group, 1 number of alkylene groups). -4, and the number of polyamines 2-5).

  As the aromatic ring-containing polyether polyol, an AO adduct of an aromatic low-molecular-weight active hydrogen atom-containing compound (dihydric to octavalent or higher, phenols and aromatic amines having a hydroxyl group equivalent of 30 to less than 150) is used. it can.

  Examples of phenols to which AO is added include hydroquinone, catechol, resorcin, bisphenol A, bisphenol S, and bisphenol F, and examples of aromatic amines include aniline and phenylenediamine.

  As AO used for manufacture of an AO adduct, C2-C12 or more AO, for example, ethylene oxide (hereinafter abbreviated as EO), propylene oxide (hereinafter abbreviated as PO), 1,2-, 2, Examples include 3- and 1,3-butylene oxide, tetrahydrofuran (THF), α-olefin oxide, styrene oxide, epihalohydrin (such as epichlorohydrin), and combinations of two or more thereof.

  Examples of the aliphatic polyether polyol include polyoxyethylene polyol [polyethylene glycol (hereinafter abbreviated as PEG)], polyoxypropylene polyol [polypropylene glycol (hereinafter abbreviated as PPG)], polyoxyethylene / propylene polyol, and polytetraethylene. And methylene ether glycol (hereinafter abbreviated as PTMG).

  Examples of the aromatic ring-containing polyether polyol include polyols having a bisphenol skeleton, such as EO addition product of bisphenol A [EO2 mol addition product of bisphenol A, EO4 mol addition product of bisphenol A, EO6 mol addition product of bisphenol A, bisphenol A. EO 8 mol adduct, bisphenol A EO 10 mol adduct, bisphenol A EO 20 mol adduct, etc.] and bisphenol A PO adduct [bisphenol A PO 2 mol adduct, bisphenol A PO 3 mol adduct, bisphenol A PO5 mole adducts, etc.], and resorcin EO or PO adducts.

As the polyester polyol (a212), a conventional method, that is, a diol component (the same as described above) and a dicarboxylic acid component {aliphatic dicarboxylic acid (succinic acid, adipic acid, azelaic acid, sebacic acid, etc.), aromatic dicarboxylic acid ( Terephthalic acid, isophthalic acid, phthalic acid, etc.) alone or a mixture of two or more thereof, etc.}, a condensed polyester polyol obtained by reacting (condensing), or a lactone (ε-caprolactone, γ-butyrolactone, γ -A polylactone polyol obtained by ring-opening polymerization of valerolactone alone or a mixture of two or more thereof.

  The condensed polyester polyol is a polyester of a low molecular weight (usually less than Mn300) polyhydric alcohol and a polyvalent carboxylic acid or an ester-forming derivative thereof.

  Examples of the low molecular weight polyhydric alcohol include divalent to octavalent or higher aliphatic polyhydric alcohol having a hydroxyl group equivalent of 30 or more and less than 150 and divalent to octavalent or more of hydroxyl group equivalent of 30 to less than 150. AO low molar adducts of phenol can be used.

  Examples of polycarboxylic acids or ester-forming derivatives thereof include aliphatic dicarboxylic acids (succinic acid, adipic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, etc.), alicyclic dicarboxylic acids (dimer acid, etc.), aromatic Dicarboxylic acids (terephthalic acid, isophthalic acid, phthalic acid, etc.) and trivalent or higher polycarboxylic acids (trimellitic acid, pyromellitic acid, etc.), and their anhydrides (succinic anhydride, maleic anhydride, phthalic anhydride) Acid, trimellitic anhydride, etc.), their acid halides (such as adipic acid dichloride), their low molecular weight alkyl esters (such as dimethyl succinate and dimethyl phthalate), and combinations thereof.

  Examples of the condensed polyester polyol include polyethylene adipate diol, polybutylene adipate diol, polyhexamethylene adipate diol, polyhexamethylene isophthalate diol, polyneopentyl adipate diol, polyethylene propylene adipate diol, polyethylene butylene adipate diol, polybutylene hexamethylene Adipate diol, polydiethylene adipate diol, poly (polytetramethylene ether) adipate diol, poly (3-methylpentylene adipate) diol, polyethylene azelate diol, polyethylene sebacate diol, polybutylene azelate diol, polybutylene sebacate diol And polyneopentyl terephthalate diol That.

  A polylactone polyol is a polyaddition product of a lactone to a low molecular weight polyhydric alcohol. As the lactone, a lactone having 4 to 12 carbon atoms can be used, and examples thereof include 4-butanolide, 5-pentanolide, and 6-hexanolide. It is done. Examples of the polylactone polyol include polycaprolactone diol, polyvalerolactone diol, and polycaprolactone triol.

  As the polycarbonate polyol (a213), one or more alkylene diols having an alkylene group having 4 to 12 carbon atoms, preferably 6 to 10 carbon atoms, more preferably 6 to 9 carbon atoms, and a low molecular carbonate compound. (For example, dialkyl carbonate having 1 to 6 carbon atoms of alkyl group, alkylene carbonate having 2 to 6 carbon atoms, diaryl carbonate having 6 to 9 carbon atoms, or the like) condensation while causing a dealcoholization reaction The polycarbonate polyol manufactured by making it be mentioned is mentioned.

  Examples of the alkylene diol having an alkylene group having 4 to 12 carbon atoms include linear alkylene diols (eg, tetramethylene diol, pentamethylene diol, hexamethylene diol, heptamethylene diol, octamethylene diol, and nonamethylene diol) and branched alkylene diols. (For example, 2-methylpentanediol, 3-methylpentanediol, 2-methylhexanediol, 3-methylhexanediol, 2-methylheptanediol, 3-methylheptanediol, 4-methylheptanediol, 2-methyloctanediol, 3-methyloctanediol, 4-methyloctanediol, etc.), and particularly preferred are tetramethylenediol, pentamethylenediol, hexamethylene Ol and nonamethylene diol, intended for the branch which is 3-methyl-1,5-pentanediol and 2-methyl-1,8-octanediol.

  Examples of the polycarbonate polyol (a213) include crystalline polycarbonate diol and amorphous polycarbonate diol. Examples of crystalline polycarbonate diols include “Nipporan 980R” (manufactured by Nippon Polyurethane Co., Ltd.), “Placcel CD220” (manufactured by Daicel Corporation), etc., and amorphous polycarbonate diols such as “PCDL T4672” (Asahi Kasei) Co., Ltd.), “PCDL T5652” (Asahi Kasei Co., Ltd.), “Kuraray Polyol C-2090” (Kuraray Co., Ltd.), and the like. Of the polycarbonate polyols (a213), crystalline polycarbonate diols, particularly “Niporan 980R” are preferred.

  As the low molecular polyol (a22) having a Mn of less than 400, polyhydric alcohols having 2 to 15 carbon atoms [dihydric alcohols (for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, neo Pentyl glycol, 1,6-hexanediol, 1,8-octanediol, 1,4-cyclohexanedimethanol, diethylene glycol, etc.); trihydric alcohols (eg glycerin, trimethylolpropane, etc.); ethylene oxides of these polyhydric alcohols And / or propylene oxide low molar adducts (Mn less than 400) and the like].

  Among the high-molecular polyols (a21), aliphatic polyether diols and aliphatic polyester diols are preferable from the viewpoint of impact resistance, and particularly preferable are PTMG, polybutylene adipate diol, polyhexamethylene adipate diol, and two of them. It is a combination of more than species.

  As the hydrophilic group-containing active hydrogen-containing component (a3) [hereinafter sometimes simply referred to as (a3)], a dialkyl alkanoic acid having 6 to 24 carbon atoms can be used, for example, 2,2-dimethylol. Examples include propionic acid (abbreviated as DMPA), 2,2-dimethylolbutanoic acid, 2,2-dimethylolheptanoic acid, 2,2-dimethyloloctanoic acid, and the like. These salts such as salts of amines (triethylamine, alkanolamine, morpholine, etc.) and / or alkali metal salts (sodium salt, etc.) can also be used.

  Examples of the other component (a4) include a chain extender (a41) and a terminator (a42).

  (A41) includes diamines having 2 to 10 carbon atoms (for example, ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, toluenediamine, piperazine, etc.), polyalkylene polyamines (for example, diethylenetriamine, triethylenetetramine, etc.), hydrazine Alternatively, derivatives thereof (dibasic acid dihydrazide such as adipic acid dihydrazide), amino alcohols having 2 to 10 carbon atoms (such as ethanolamine, diethanolamine, 2-amino-2-methylpropanol, triethanolamine, etc.) and the like can be mentioned.

Examples of (a42) include monoalcohols having 1 to 8 carbon atoms (methanol, ethanol, isopropanol, cellosolves, carbitols, etc.), monoamines having 1 to 10 carbon atoms (monomethylamine, monoethylamine, monobutylamine, dioxygen) Mono- or dialkylamines such as butylamine and monooctylamine; mono- or dialkanolamines such as monoethanolamine, diethanolamine and diisopropanolamine).
The total amount of (a41) and (a42) used is usually 0.8 equivalents or less, preferably 0.7 equivalents or less, based on the equivalent of the NCO group in (a1). Based on the equivalent of the NCO group of (a1), it is usually 0.3 equivalent or less, preferably 0.2 equivalent or less.

  The polyurethane resin (U) in the present invention is a urethane resin obtained from a urethane prepolymer (u) in which at least one of the end groups is an isocyanate group [hereinafter sometimes simply referred to as (u)]. preferable.

  The glass transition temperature (hereinafter abbreviated as Tg) of the polyurethane resin (U) is a factor affecting the impact resistance of the dry paint film of the water-based paint using (U), and is usually −110 to −20 ° C. The temperature is preferably −105 to −25 ° C., more preferably −100 to −30 ° C. A dry paint film of an aqueous paint using an emulsion containing a polyurethane resin having a Tg of less than −110 ° C. or more than −20 ° C. is inferior in impact resistance.

  The dry film of the polyurethane resin emulsion used when measuring Tg was cast in a film shape so that the film thickness was 0.2 ± 0.1 mm based on the solid content concentration, and the film was 3 at 105 ° C. It is obtained by drying with a time-smooth dryer (hereinafter, the dry film of the polyurethane resin emulsion shall be obtained by this method).

  The Tg of the polyurethane resin (U) is a dynamic viscosity obtained by cutting a dry film of a polyurethane resin emulsion into a size of 3.0 ± 0.5 cm × 0.5 ± 0.2 cm × 0.2 ± 0.1 mm. The loss elastic modulus E ″ is measured in the range of a fundamental frequency of 11 Hz and a temperature range of −110 to 180 ° C. with an elasticity measuring device Rheogel-E4000 (manufactured by UBM), and is obtained by a temperature giving the maximum value.

  The method of bringing the Tg of (U) within the scope of the present invention mainly includes the selection of the type of the polymer polyol (a21), the optimization of the crosslinking point density, and the optimization of the weight ratio of the urethane group and the urea group. Can be mentioned.

  Of the polymer polyol (a21), the Tg is lowered by using the polyether diol (a211) or the polyester diol (a212), and particularly when the aliphatic polyether diol or the aliphatic polyester diol is used, the Tg tends to be lowered.

  The optimization of the crosslinking point density of (U) is to bring the total molar concentration (mmol / g) in the polyurethane resin (U) of the active hydrogen-containing compound having 3 or more functional groups and the polyisocyanate having 3 or more functional groups into the optimal range. It is possible by setting.

  The “crosslinking point density” in the present invention means the above total molar concentration, and the value is preferably 0.10 to 1.00 mmol / g, more preferably 0.15 to 0.95 mmol / g. g, particularly preferably 0.20 to 0.80 mmol / g. If the cross-linking point density is 0.10 mmol / g or more, the stability over time tends to be further improved, and if it is 1.00 mmol / g or less, the Tg is relatively low, so the impact resistance of the dried coating film is high. There is a tendency to further improve.

In order to set the crosslinking point density in (U) as a target value, it is preferable to set the charged weights of (a1), (a2), (a3), and (a4) according to the following formula.
In the following, the unit of weight is g.
Target crosslinking point density (mmol / g) = [{(number of average functional groups of (a1) −2) × charge weight of (a1) / average molecular weight of (a1)} + {(average number of functional groups of (a2) −2) × (a2) preparation weight / (average molecular weight of (a2)} + {(average number of functional groups of (a3) −2) × (a3) preparation weight / (a3) average molecular weight} + {(( a4) average number of functional groups-2) × (a4) charged weight / (a4) average molecular weight}] × 1000 / predicted total weight of resin components after emulsion production

Here, the predicted total weight of the resin component after the emulsion production = (charge weight other than the solvent at the time of prepolymer production) + (charge weight of extender other than water at the time of emulsion production in the post-process + charge of stop agent) + (extension) Weight of water acting as an agent), and the weight of water acting as an extender is calculated by the following equation:
Weight of water acting as extender = {predicted equivalent number of residual NCO of prepolymer− (equivalent number of amine extender + equivalent number of terminator)} × 18 ÷ 2
The number of equivalents is the number of moles of the molecule × the average number of functional groups per molecule.

  Optimization of the weight ratio of urethane group [—NH—COO—] and urea group [—NH—CO—NH—] is the preparation of (a1), (a2) and (a3) during production of prepolymer (u). This is possible by setting the total number of equivalents.

As described above, in order to set the Tg of (U) to −110 ° C. to −20 ° C., the ratio of the total weight of urethane groups and urea groups based on the weight of (U) is preferably 7.0 to 30. 0%, more preferably 7.5 to 29.5%, particularly preferably 8.0 to 29.0%.
Each ratio of a urethane group and a urea group is not specifically limited, Only a urethane group may be sufficient and only a urea group may be sufficient.

Aqueous paint using a polyurethane resin emulsion having a total weight ratio of urethane groups and urea groups of 7.0% or more has better aging stability, and if it is 30.0% or less, the dry paint film of the aqueous paint is resistant to water. Greater impact properties.
In order to make the Tg of (U) within the scope of the present invention using a polymer polyol other than aliphatic polyether diol and aliphatic polyester diol, the total weight of urethane groups and urea groups is 8.0 to 8.0. It is desirable to be within the range of 15.0% by weight.

In order to set the urethane group content in (U) as a target value, it is preferable to set the total number of charged equivalents of (a2) and (a3) during the production of (u) according to the following formula.
Target urethane group content (%) = [total number of equivalents of (a2) and (a3) × 59 ÷ predicted total weight of resin components after emulsion production] × 100

In order to set the urea group content in (U) as a target value, it is preferable to set according to the following formula from the number of charged equivalents of (a1) used in (u).
Target urea group content (%) = 100 × [{number of charged equivalents of (a1) −total number of charged equivalents of (a2) and (a3)} × 57 × amine extender ratio] + {(a1) Number of charged equivalents—total number of charged equivalents of (a2) and (a3)} ÷ 2 × 57 × (1-extender ratio)] ÷ predicted total weight of resin components after emulsion production

The amine extender ratio in the above formula is the ratio of the equivalent of the amine extender to the equivalent of the isocyanate group present at the end of (u) and is calculated by the following formula.
Amine extender ratio = (equivalent number of amine extender + equivalent number of stopper) / (equivalent number of amine extender + equivalent number of stopper + equivalent number of water acting as extender)

  The linear expansion coefficient before and after immersing the dry film of the polyurethane resin emulsion of the present invention in dimethylformamide is a factor affecting the daily stability of the aqueous paint using (U), and is usually 100 to 180%. , Preferably it is 100 to 175%, More preferably, it is 100 to 170%. The linear expansion coefficient before and after the dry film of the polyurethane resin emulsion is immersed in dimethylformamide does not fall below 100%, and the aqueous paint using the polyurethane resin emulsion exceeding 180% is inferior in stability over time.

The linear expansion coefficient was obtained by cutting a dry film of polyurethane resin emulsion into a size of 1.0 ± 0.2 cm × 4.0 ± 0.3 cm × 0.2 ± 0.1 mm as a test piece, The test piece is immersed in dimethylformamide at 25 ° C. for 48 hours, the length of the diagonal line of the test piece before and after immersion is measured, and the linear expansion coefficient can be obtained by the following equation.
Linear expansion coefficient (%) = [Diagonal length of test piece after immersion / Diagonal length of test piece before immersion] × 100

  In order to set the linear expansion coefficient before and after the dried film was immersed in dimethylformamide within the scope of the present invention, the crosslinking point density of (U) was set to be 0.10 to 1.00 mmol / g. And, it is desirable to set the ratio of the total weight of the urethane group and the urea group based on the weight of (U) to 7.0 to 30.0% by weight.

  The storage elastic modulus E ′ of the polyurethane resin (U) at −30 to −10 ° C. is preferably 10 to 1,500 MPa, more preferably 20 to 1,400 MPa, from the viewpoint of the impact resistance of the dry coating film of the water-based paint. Particularly preferred is 30 to 1,300 MPa.

  The storage elastic modulus E ′ at −30 to −10 ° C. was obtained by cutting a dry film of a polyurethane resin emulsion into a size of 3.0 ± 0.5 cm × 0.5 ± 0.2 cm × 0.2 ± 0.1 mm. The storage elastic modulus E ′ was measured at a fundamental frequency of 11 Hz and a temperature range of −50 to 100 ° C. with a dynamic viscoelasticity measuring device Rheogel-E4000 (manufactured by UBM), and at −30 to −10 ° C. It can be measured as the storage elastic modulus E ′.

  In order to make the storage elastic modulus E ′ of (U) within the scope of the present invention, it is preferable to use the polyether diol (a211) or the polyester diol (a212) in the polymer polyol (a21). Using an aliphatic polyether diol and an aliphatic polyester diol, the crosslinking point density of (U) is set to 0.10 to 1.00 mmol / g, and urethane groups and urea groups based on the weight of (U) It is desirable to set the ratio of the total weight to 7.0 to 30.0% by weight.

  The production of the prepolymer (u) in the present invention is usually carried out by a reaction at 20 ° C to 150 ° C, preferably 60 ° C to 110 ° C, and the reaction time is usually 2 to 15 hours. The production of (u) can be carried out in the presence or absence of an organic solvent substantially nonreactive with NCO groups. The prepolymer usually has a free NCO group content of 2-9%.

  The average hydroxyl equivalent of the hydroxyl group-containing component during the production of (u) is preferably 50 to 450, more preferably 80 to 420, and particularly preferably 100 to 400.

  [Number of charged equivalents of (a1)] / [total number of charged equivalents of (a2) and (a3)] during the production of (u) is preferably 1.10 to 1.90, more preferably 1. 15 to 1.85, particularly preferably 1.20 to 1.80.

The upper limit of the content of the carboxyl group [—COOH] in (U) is usually 4.0% by weight (in the following, “%” represents “% by weight unless otherwise specified”), the stability of the emulsion, and the viscosity when used as an aqueous paint. From this viewpoint, it is preferably 0.3 to 3.5%, more preferably 0.4 to 3.4%, and particularly preferably 0.5 to 3.3%. In addition, the carboxyl group content in this invention makes content converted into the carboxyl group from this carboxylate group the carboxyl group content even if it is the carboxylate group (-COO-) by which the carboxyl group was neutralized.
In order for the carboxyl group content in (U) to be within the above range, it is preferable to set the amount of (a3) charged during the production of (u) according to the following formula.

  Target carboxyl group content (%) = [weight corresponding to COOH based on the charged amount of (a3) / total weight of resin components after emulsion production] × 100

  In the urethanization reaction, in order to promote the reaction, a catalyst used in a normal urethane reaction may be used if necessary. Examples of the catalyst include amine catalysts such as triethylamine, N-ethylmorpholine, triethylenediamine, and cycloamidines [1,8-diaza-bicyclo [5,4,0] -7-undecene described in US Pat. No. 4,524,104. (San Apro Co., Ltd., DBU) and the like]; tin-based catalysts such as dibutyltin dilaurate, dioctyltin dilaurate and tin octylate; titanium-based catalysts such as tetrabutyl titanate.

  The polyurethane resin emulsion of the present invention comprises an aqueous medium containing a chain extender (a41) and / or a terminator (a42) as necessary after hydrophilizing (neutralizing) (u) as necessary or while making it hydrophilic. A polyurethane resin emulsion is mixed to produce a polyurethane resin emulsion, and the reaction [chain extension by water or (a41) and / or termination of reaction by (a42)] is carried out until NCO groups are substantially eliminated. The temperature in mixing and reaction with the aqueous medium is usually 10 ° C to 60 ° C, preferably 20 ° C to 50 ° C.

  The amount of the aqueous medium used is such that the content of the polyurethane resin (U) is 20 to 60%, preferably 30 to 50% based on the weight of the emulsion.

  Hydrophilization (neutralization) may be performed after the production of the polyurethane resin emulsion. When chain extension according to (a41) and / or reaction termination according to (a42) is performed, (u) is dispersed in an aqueous medium, and then (a41) and / or (a42) is added and (u) and It is preferable to react.

  In addition, a solution of (u) is produced by reacting (a1) with the above active hydrogen-containing component in the presence of an organic solvent (S) (hereinafter sometimes simply referred to as (S)) (a41) And / or (a42), or by reacting (a1) with the above active hydrogen-containing component and optionally (a41) and / or (a42) in the presence of an organic solvent in one step. A polyurethane resin emulsion (U) can also be produced by producing an organic solvent solution and dispersing it in an aqueous medium. Also in this case, the hydrophilization (neutralization) may be performed before or after the production of the polyurethane resin emulsion.

  The hydrophilic solvent (S) used in the above reaction and contained in the aqueous medium can be used without any problem as long as it is substantially non-reactive with NCO groups and hydrophilic (water miscible). Examples thereof include ketones such as acetone and ethyl methyl ketone, esters, ethers, amides, and alcohols. Of these, acetone is preferred.

  The weight ratio of water to the hydrophilic solvent in the aqueous medium is usually 100/0 to 50/50, preferably 100/0 to 80/20, and particularly preferably 100/0.

  When a hydrophilic solvent is used in (S) and / or the aqueous medium, these may be distilled off as necessary after production of the polyurethane resin emulsion.

  An apparatus for emulsifying and dispersing the polyurethane resin (U), the solvent solution of (U), the urethane prepolymer (u) or the solvent solution of (u) in an aqueous medium is not particularly limited, and examples thereof include an emulsifier of the following method. . 1) Vertical stirring system, 2) Rotor-stator system [for example, “Ebara Milder” (manufactured by Ebara Manufacturing Co., Ltd.)], 3) Line mill system [for example, line flow mixer], 4) Stationary tube mixing Formula [for example, static mixer], 5) Vibration type [for example, “VIBRO MIXER” (manufactured by Chilling Industries Co., Ltd.)], 6) Ultrasonic impact type [for example, ultrasonic homogenizer], 7) High pressure impact type [for example, Gaurin homogenizer (Gaurin)], 8) Emulsification [e.g. membrane emulsification module] and 9) Centrifugal membrane contact [e.g. fillmix]. Of these, 1), 2), 5), 8) and 9) are preferred.

  When chain extension according to (a41) and / or reaction termination according to (a42) is performed, the prepolymer is dispersed in an aqueous medium using a continuous emulsifier [preferably 2) such as Ebara Milder, Next, it is preferable to add (a41) and / or (a42) using a batch type emulsifier [preferably the above 1) vertical stirring method] and mix and react with the prepolymer.

  The concentration of the solid content of the polyurethane resin emulsion of the present invention is preferably 20 to 60% by weight, more preferably 30 to 50% (in the following, unless otherwise specified,% represents% by weight). In the present invention, “solid content” refers to components other than the aqueous dispersion medium.

Hereinafter, a method for preparing an aqueous paint using the polyurethane resin emulsion of the present invention will be described.
In addition to the polyurethane resin emulsion of the present invention, other resin emulsions or water-soluble resins may be used in combination with the water-based paint, if necessary, for the purpose of assisting in forming a coating film or improving the binder function.

  Examples of other resin emulsions or water-soluble resins used in combination with water-based paints include polyurethane resin emulsions other than the polyurethane resin emulsion of the present invention, polyacrylic resin emulsions, polyester resin emulsions, water-soluble polyurethane resins, water-soluble polyacrylic resins, and Examples include water-soluble polyester resins. These other resin emulsions or water-soluble resins can be appropriately selected from those commonly used in each application for each application of the water-based paint.

The solid content of the polyurethane resin emulsion of the present invention in the aqueous coating is usually 0.1 to 60% by weight, preferably 1 to 50% by weight, based on the weight of the aqueous coating.
Further, the solid content of the other resin emulsion and the water-soluble resin in the water-based paint is usually 60% by weight or less, preferably 50% by weight or less based on the weight of the water-based paint.

  The water-based paint can further contain one or more kinds of a crosslinking agent, a pigment, a pigment dispersant, a viscosity modifier, an antifoaming agent, a preservative, a deterioration preventing agent, a stabilizer, an antifreezing agent and the like.

Examples of the crosslinking agent include water-soluble or water-dispersible amino resins, water-soluble or water-dispersible polyepoxides, water-soluble or water-dispersible polyisocyanate compounds, and polyethylene urea.
The addition amount of the crosslinking agent is usually 0 to 30%, preferably 0.1 to 20%, based on the solid content weight of the aqueous dispersion.

  Examples of the pigment include inorganic pigments having a solubility in water of 1 or less, such as white pigments, black pigments, gray pigments, red pigments, brown pigments, yellow pigments, green pigments, blue pigments, purple pigments and metallic pigments; and organic pigments, For example, natural organic pigment synthetic organic pigments, nitroso pigments, nitro pigments, pigment dye-type azo pigments, azo lakes made from water-soluble dyes, azo lakes made from poorly soluble dyes, lakes made from basic dyes, lakes made from acid dyes, xanthan lakes , Anthraquinone lake, pigments from vat dyes, phthalocyanine pigments, and the like. The pigment content is usually 50% or less, preferably 30% or less, based on the weight of the water-based paint.

  Examples of the pigment dispersant include various surfactants [anionic, cationic, nonionic, amphoteric] and a polymeric emulsifying dispersant (Mn 1,000 to 20,000). Preferred are the polymeric emulsifying dispersant. It is. The content of the pigment dispersant is usually 20% or less, preferably 15% or less, based on the weight of the pigment.

As a viscosity modifier, a thickener, for example, an inorganic viscosity modifier (such as sodium silicate or bentonite), a cellulose-based viscosity modifier (such as methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, Mn is usually 20,000 or more), Protein (casein, casein soda, casein ammonium, etc.), acrylic (sodium polyacrylate, ammonium polyacrylate, etc., Mn is usually 20,000 or more), and vinyl (polyvinyl alcohol, etc., Mn is usually 20,000) Above).
The content of the viscosity modifier is usually 5% or less, preferably 3% or less, based on the weight of the aqueous paint.

  Examples of antifoaming agents include long-chain alcohols (such as octyl alcohol), sorbitan derivatives (such as sorbitan monooleate), silicone oils (such as polymethylsiloxane and polyether-modified silicone), and the like. The content of the antifoaming agent is usually 5% or less, preferably 3% or less, based on the weight of the aqueous paint.

  Examples of the preservative include organic nitrogen sulfur compound-based preservatives, organic sulfur halide-based preservatives, and the like. The content of the preservative is usually 5% or less, preferably 3% or less, based on the weight of the aqueous paint.

  Examples of deterioration inhibitors and stabilizers (such as ultraviolet absorbers and antioxidants) include hindered phenols, hindered amines, hydrazines, phosphoruss, benzophenones, and benzotriazoles. The content of deterioration inhibitors and stabilizers (such as UV absorbers and antioxidants) is usually 5% or less, preferably 3% or less, based on the weight of the aqueous paint.

Examples of the antifreezing agent include ethylene glycol and propylene glycol.
The content of the antifreezing agent is usually 5% or less, preferably 3% or less, based on the weight of the aqueous paint.

  A solvent may be further added to the water-based paint. Examples of the solvent to be added include monohydric alcohols (such as methanol, ethanol, and propanol), glycols (such as ethylene glycol, propylene glycol, and diethylene glycol), trivalent or higher alcohols (such as GL), and cellosolves (such as methyl and ethyl cellosolve). Etc. can be used. The content ratio of the solvent to be added is preferably 20% or less, more preferably 15% or less, based on the weight of the aqueous paint.

  In order to make an aqueous paint using the polyurethane resin emulsion of the present invention, the polyurethane resin emulsion of the present invention and the above-mentioned one are mixed and stirred. When mixing, all components may be mixed simultaneously or each component may be added stepwise.

  The solid content concentration of the water-based paint is preferably 10 to 70%, more preferably 15 to 60%.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these. Hereinafter, the part means part by weight.
Example 1
In a simple pressure reactor equipped with a stirrer and a heater, 410 parts of polytetramethylene glycol [PTMG 2,000, manufactured by Mitsubishi Chemical Corporation] of Mn 2,000, 42 parts of 1,4 butanediol, DMPA 36 parts, 312 parts of IPDI and 200 parts of acetone (1) were charged while introducing nitrogen. Thereafter, the mixture was heated to 95 ° C. and subjected to urethanization reaction for 5 hours to produce a prepolymer. After cooling the reaction mixture to 40 ° C., 306 parts of acetone (2) and 27 parts of triethylamine are added and mixed, and 1,905 parts of water are further added and emulsified with a rotor-stator type mechanical emulsifier. A dispersion was obtained. While stirring, 87 parts of a 10% diethylenetriamine aqueous solution was added to the obtained aqueous dispersion, followed by stirring at 50 ° C. for 5 hours to carry out a chain extension reaction. Thereafter, acetone was removed at 65 ° C. under reduced pressure to obtain a polyurethane resin emulsion (No. 1).

  In the same manner as in Example 1, using the raw materials shown in Tables 1 and 2, the polyurethane resin emulsions Nos. 2 to 7 and Comparative Examples 1 to 5 in Comparative Examples 1 to 5 were used. 2-No. 12 was produced. “PTMG1000” and “PTMG3000” (manufactured by Mitsubishi Chemical Co., Ltd.) are polytetramethylene glycols of Mn 1,000 and 3,000, respectively, and “Nipporan 4073” (manufactured by Nippon Polyurethane Co., Ltd.) is a polymethylene of Mn 2,000. Hexamethylene adipate diol, “Nipporan 981” (manufactured by Nippon Polyurethane Co., Ltd.) is a polycarbonate diol having an alkylene group of 6 carbon atoms with Mn of 1,000. Tables 1 and 2 show the crosslinking point density of the obtained polyurethane resin emulsion and the ratio of the total weight of urethane groups and urea groups to the polyurethane resin.

These polyurethane resins are obtained by casting a polyurethane resin emulsion in the form of a film with a film thickness of 0.2 ± 0.1 mm based on the solid content and drying it at 105 ° C. for 3 hours in a wind-air dryer. The linear expansion coefficient after dipping the dried film of the polyurethane resin emulsion in dimethylformaldehyde at 25 ° C. for 48 hours and the storage elastic modulus E ′ of the dried film at −30 to −10 ° C. were evaluated by the following evaluation methods. . The results are shown in Table 3 and Table 4.
<Tg of polyurethane resin>
A polyurethane resin emulsion dried film obtained by casting a polyurethane resin emulsion in a film form in an amount of 0.2 ± 0.1 mm based on the solid content and drying it at 105 ° C. for 3 hours with a wind dryer. Is cut into a size of 3.0 ± 0.5 cm × 0.5 ± 0.2 cm × 0.2 ± 0.1 mm using a dynamic viscoelasticity measuring device Rheogel-E4000 (manufactured by UBM). The loss elastic modulus E ″ was measured in a frequency range of 11 Hz and a temperature range of −100 to 180 ° C., and the temperature at which the loss elastic modulus E ″ reached the maximum value was defined as Tg.

<Linear expansion coefficient after being immersed in the organic solvent of the dry film of a polyurethane resin emulsion>
A polyurethane resin emulsion dried film obtained by casting a polyurethane resin emulsion into a film shape in an amount of 0.2 ± 0.1 mm based on the solid content and drying it at 105 ° C. for 3 hours with a wind dryer. Was immediately cut into a size of 1.0 ± 0.2 cm × 4.0 ± 0.3 cm × 0.2 ± 0.1 mm after drying, and the length of the diagonal line of the test piece was measured. Subsequently, the test piece was immersed in dimethylformamide at 25 ° C. for 48 hours, and after immersion, the solvent on the surface of the test piece was wiped off, the length of the diagonal line of the test piece was measured immediately, and the linear expansion coefficient was obtained by the following formula. It was.
Linear expansion coefficient (%) = [Diagonal length of test piece after immersion / Diagonal length of test piece before immersion] × 100

<Storage elastic modulus E ′ of polyurethane resin at −30 to −10 ° C.>
Polyurethane resin emulsion obtained by casting a polyurethane resin emulsion in a film shape in an amount of 0.2 ± 0.1 mm based on the solid content and drying it at 105 ° C. for 3 hours with a wind dryer. A dry viscoelasticity measuring device Rheogel-E4000 (manufactured by UBM Co., Ltd.) is obtained by cutting a dry film of the size of 3.0 ± 0.5 cm × 0.5 ± 0.2 cm × 0.2 ± 0.1 mm. The storage elastic modulus E ′ was measured at a fundamental frequency of 11 Hz and a temperature range of −50 to 100 ° C.

（注１）−２０℃での貯蔵弾性率Ｅ’

(Note 1) Storage elastic modulus E ′ at −20 ° C.

Evaluation Example 1 [Evaluation 1 as water-based paint for automobiles]
27 parts of ion exchange water, aqueous polyester resin emulsion [solid content 25%, “Vylonal MD-1480”, manufactured by Toyobo Co., Ltd.] 38 parts, titanium oxide [“CR-93”, manufactured by Ishihara Sangyo Co., Ltd.] 35 parts , Carbon black [“FW200P”, manufactured by Degussa Co., Ltd.] 1 part, barium sulfate [“W-1”, manufactured by Takehara Chemical Co., Ltd.] 35 parts, talc [“Hytron”, manufactured by Takehara Chemical Co., Ltd.] 9 Parts, wetting agent [solid content 70%, “SN Wet 366”, San Nopco Co., Ltd.] 5 parts, settling agent [solid content 20%, “Dispalon AQ-600”, Enomoto Kasei Co., Ltd.] 7 parts Then, 2 parts of a 10% aqueous solution of dimethylaminoethanol was mixed and dispersed with a paint conditioner for 30 minutes. Here, aqueous melamine resin [solid content 85%, “Cymel 1141”, manufactured by Mitsui Cytec Co., Ltd.] 10 parts, 17 parts of 1-nonanol, and polyurethane resin emulsion No. 1 obtained above. 1 was mixed with 200 parts of stirring. Furthermore, it prepared so that it might become a viscosity of 300 mPa * s [25 degreeC, TOKIMEC Co., Ltd. rotational viscometer (60 rpm)] using ion-exchange water, and the aqueous coating material (A-1) was obtained.

  In the same manner as in Evaluation Example 1, polyurethane resin emulsion No. 1 instead of polyurethane resin emulsion No. 1 2-No. 12 was used to produce water-based paints (A-2) to (A-12).

<Storage stability test of water-based paint>
About each of water-based paints (A-1) to (A-12), 130 g is put in a glass bottle having an inner diameter of 4.0 cm and a volume of 140 ml and stored at 25 ° C. for 24 hours or 20 days (presence of aggregates) and viscosity. Changes were evaluated. The viscosity was measured at 25 ° C. with a rotary viscometer (60 rpm) manufactured by TOKIMEC. The results are shown in Tables 5 and 6.

<Impact resistance test of coating film>
Water-based paints (A-1) to (A-12) were spray-coated on a 10 cm × 20 cm steel plate and heated at 150 ° C. for 20 minutes to form a 25 μm coating film. Using this coated steel plate, an impact resistance test was conducted with a load of 500 g using a DuPont system in accordance with JIS K-5600-5-3. The results are shown in Tables 5 and 6.

（注１）
○：試験後、塗膜表面のキズが少ない。
△：試験後、塗膜表面のキズは大きいが、鋼板は露出していない状態。
×：試験後、塗膜表面のキズが大きく、鋼板が露出している状態。

(Note 1)
○: There are few scratches on the coating film surface after the test.
Δ: After the test, the surface of the coating film is greatly scratched, but the steel sheet is not exposed.
X: The state where the scratches on the coating film surface are large and the steel sheet is exposed after the test.

Evaluation Example 2 [Evaluation 2 as water-based paint for automobiles]
613 parts of ion exchange water, aqueous polyacrylic resin emulsion [solid content 50%, “AE981A”, manufactured by JSR Corporation] 166 parts, aluminum pigment [solid content 60%, “010WD”, manufactured by Showa Aluminum Powder Co., Ltd.] 71 parts, layered silicate [“KMP-590”, manufactured by Shin-Etsu Chemical Co., Ltd.] 7 parts, antifoaming agent [“SN deformer 393”, manufactured by San Nopco Co., Ltd.] 4 parts, thickener [solid content 30%, “Viserizer AP-2”, Sanyo Chemical Industries, Ltd.] 33 parts, dimethylethanolamine 6 parts, Polypropylene glycol [“Sanix PP-950”, Sanyo Chemical Industries, Ltd.] 7 parts, Ethylene glycol mono 94 parts of butyl ether and 27 parts of N-methyl-2-pyrrolidone were mixed and dispersed for 30 minutes by a paint conditioner. Here, aqueous melamine resin [solid content 85%, “Cymel 1141”, manufactured by Mitsui Cytec Co., Ltd.] 66 parts, 117 parts of 1-nonanol, and polyurethane resin emulsion No. 1 obtained above. 1 was mixed with 200 parts of stirring. Furthermore, it prepared so that it might become a viscosity of 300 mPa * s [25 degreeC, TOKIMEC Co., Ltd. rotational viscometer (60 rpm)] using ion-exchange water, and the aqueous coating material (B-1) was obtained.

  In the same manner as in Evaluation Example 2, polyurethane resin emulsion no. 1 instead of polyurethane resin emulsion No. 1 2-No. 12 was used to produce water-based paints (B-2) to (B-12).

<Storage stability test of water-based paint>
About each of the water-based paints (B-1) to (B-12), 130 g was put in a glass bottle having an inner diameter of 4.0 cm and a volume of 140 ml, and the appearance (presence of aggregates) and viscosity after storage at 25 ° C. for 24 hours or 20 days. Changes were evaluated. The viscosity was measured at 25 ° C. using a rotary viscometer (60 rpm) manufactured by TOKIMEC. The results are shown in Table 7 and Table 8.

<Impact resistance test of coating film>
The aqueous paints (B-1) to (B-12) obtained above were spray-coated on a 10 cm × 20 cm steel plate and heated at 150 ° C. for 20 minutes to form a 25 μm coating film. Using this coated steel plate, an impact resistance test was conducted with a load of 500 g using a DuPont system in accordance with JIS K-5600-5-3. The results are shown in Table 7 and Table 8.

（注１）
○：試験後、塗膜表面のキズが少ない。
△：試験後、塗膜表面のキズは大きいが、鋼板は露出していない状態。
×：試験後、塗膜表面のキズが大きく、鋼板が露出している状態。

(Note 1)
○: There are few scratches on the coating film surface after the test.
Δ: After the test, the surface of the coating film is greatly scratched, but the steel sheet is not exposed.
X: The state where the scratches on the coating film surface are large and the steel sheet is exposed after the test.

Evaluation Example 3 [Evaluation as a general water-based paint other than automotive applications]
90 parts of ion-exchanged water, 70 parts of thickener [“Biseriser AP-2”, manufactured by Sanyo Chemical Industries, Ltd.], 10 parts of pigment dispersant [“Calibon L-400”, manufactured by Sanyo Chemical Industries, Ltd.] In addition, 140 parts of titanium oxide [“CR-93”, manufactured by Ishihara Sangyo Co., Ltd.], carbon black [“FW200P”, manufactured by Degussa Co., Ltd.], and 160 parts of calcium carbonate were mixed and dispersed with a paint conditioner for 30 minutes. Here, 20 parts of 1-nonanol, 200 parts of an acrylic emulsion [“Polytron Z330”, manufactured by Asahi Kasei Co., Ltd.], and the polyurethane resin emulsion No. obtained above were used. 1 was mixed with 200 parts of stirring. Furthermore, it prepared so that it might become a viscosity of 150 mPa * s [25 degreeC, TOKIMEC Co., Ltd. rotational viscometer (60 rpm)] using ion-exchange water, and the water-based coating material (C-1) was obtained.

  In the same manner as in Evaluation Example 3, polyurethane resin emulsion No. 1 instead of polyurethane resin emulsion No. 1 2-No. 12 was used to produce water-based paints (C-2) to (C-12).

<Storage stability test of water-based paint>
About each of water-based paints (C-1) to (C-12), 130 g was put in a glass bottle having an inner diameter of 4.0 cm and a volume of 140 ml, and the appearance (presence of aggregates) and viscosity after storage for 24 hours or 20 days at 25 ° C. Changes were evaluated. The viscosity was measured at 25 ° C. using a rotary viscometer (60 rpm) manufactured by TOKIMEC. The results are shown in Table 9 and Table 10.

<Impact resistance test of coating film>
The aqueous paints (C-1) to (C-12) obtained above were spray-coated on a 10 cm × 20 cm steel plate and heated at 150 ° C. for 20 minutes to form a 25 μm coating film. Using this coated steel plate, an impact resistance test was conducted with a load of 500 g using a DuPont system in accordance with JIS K-5600-5-3. The results are shown in Table 9 and Table 10.

（注１）
○：試験後、塗膜表面のキズが少ない。
△：試験後、塗膜表面のキズは大きいが、鋼板は露出していない状態。
×：試験後、塗膜表面のキズが大きく、鋼板が露出している状態。

(Note 1)
○: There are few scratches on the coating film surface after the test.
Δ: After the test, the surface of the coating film is greatly scratched, but the steel sheet is not exposed.
X: The state where the scratches on the coating film surface are large and the steel sheet is exposed after the test.

  The polyurethane resin emulsion of the present invention can be suitably used as a polyurethane resin emulsion for water-based paints, and can be used for a wide range of applications requiring excellent storage stability or impact resistance. For example, polyurethane resin emulsions for automobile paints, building material paints, home appliance paints, plastic paints, adhesives and fiber processing (pigment printing, non-woven fabrics, sizing agents for reinforcing fibers, binders for antibacterial agents, etc.) Is available.

Claims (5)

A polyurethane resin emulsion for water-based paints containing a polyurethane resin (U) and an aqueous dispersion medium and satisfying the following (1) and (2).
(1) The glass transition temperature of the polyurethane resin (U) is -110 ° C to -20 ° C.
(2) The linear expansion coefficient before and after immersing a dry film having a film thickness of 0.2 ± 0.1 mm obtained by drying the polyurethane resin emulsion at 105 ° C. for 3 hours in dimethylformamide at 25 ° C. for 48 hours is 100- 180%.   The storage elastic modulus E ′ at −30 to −10 ° C. of a dry film having a film thickness of 0.2 ± 0.1 mm obtained by drying the polyurethane resin emulsion at 105 ° C. for 3 hours is 10 to 1,500 MPa. 1. The polyurethane resin emulsion according to 1.   The polyurethane resin emulsion according to claim 1 or 2, wherein the polymer polyol component constituting the polyurethane resin (U) is an aliphatic polyether diol or an aliphatic polyester diol having a number average molecular weight of 500 to 5,000.   The polyurethane resin emulsion according to any one of claims 1 to 3, wherein the polyurethane resin (U) has a crosslinking point density of 0.10 to 1.00 mmol / g.   The polyurethane resin according to any one of claims 1 to 4, wherein the total weight of urethane groups and urea groups contained in the polyurethane resin (U) is 7.0 to 30.0 wt% based on the weight of the polyurethane resin (U). Emulsion.