JP5626620B2 - Method for producing aqueous polyurethane dispersion - Google Patents

Description

  The present invention relates to an aqueous polyurethane dispersion using diphenylmethane diisocyanate (hereinafter abbreviated as “MDI”) and an aliphatic diisocyanate as an organic diisocyanate, and a method for producing the dispersion.

  Paints, adhesives and coating agents containing organic solvents have adverse effects on human bodies, safety and health problems such as explosion and fire, and pollution problems such as air pollution and water pollution. In order to improve these problems, the development of water system has been actively conducted in recent years.

  Various resins such as an acrylic resin, a polyurethane resin, a polyester resin, and a latex are used as the resin for the aqueous system. Among them, polyurethane resin is excellent in durability, abrasion resistance, and the like, and therefore, attempts to apply it to an aqueous system in various usages are widely made. For example, Patent Document 1 discloses a water-dispersible polyurethane-based paint, and Patent Document 2 discloses a water-dispersible polyurethane-based adhesive. These are water-based polyurethane resins alone, but in order to combine the characteristics of each resin, a combination of various resins such as an acrylic emulsion and a polyurethane emulsion has been studied.

  However, the water-based polyurethane resins described in Patent Document 1 and Patent Document 2 basically do not satisfy all required performances such as adhesiveness, adhesion, and alkali resistance, and the appearance of such resins has been desired. .

  As an improvement, Patent Document 3 discloses a water-dispersed urethane-urea using a specific aromatic diisocyanate and an aliphatic diisocyanate that is price competitive and has excellent heat resistance, chemical resistance, mechanical strength, and the like. It is shown. However, the aromatic diisocyanate in Patent Document 3 has a reactivity that is too high, so that the amount of introduction in the production method and the polyurethane resin is limited.

  In addition, for the purpose of obtaining higher mechanical strength of the resulting resin, a method of introducing only MDI as an aromatic diisocyanate has been studied (see, for example, Patent Document 4 and Patent Document 5). However, when MDI is used as the aromatic diisocyanate, the reactivity is too high as described above, and therefore an extremely excellent production (stirring) facility needs to be sophisticated. Moreover, even if the production (stirring) equipment is sophisticated, it is extremely difficult to produce a dispersion because of the high reactivity.

  Furthermore, in recent years, fields (uses) in which the obtained resin is required to have both properties such as toughness and flexibility have begun to appear.

Japanese Patent Laid-Open No. 4-198361 JP-A-5-117358 JP 2005-29793 A JP 62-109813 A JP-A-1-168756

  In view of the background as described above, the present invention can stably disperse even when MDI is used as an organic diisocyanate, even if the production (stirring) equipment is not extremely sophisticated, and even when using ordinary synthesis equipment. It is an object of the present invention to obtain an aqueous polyurethane dispersion excellent in water resistance.

  Another object of the present invention is to obtain an aqueous polyurethane dispersion capable of providing a resin having both the above-mentioned properties such as toughness and flexibility.

  The present invention further provides an aqueous polyurethane dispersion having excellent productivity (specifically, reaction control is easy, and the resulting polyurethane dispersion can be supplied to the market with stable quality). It aims to provide a method.

  MDI is 4,4′-diphenylmethane diisocyanate (hereinafter abbreviated as “4,4′-MDI”), 2,4′-diphenylmethane diisocyanate (hereinafter abbreviated as “2,2′-MDI”), It consists of three isomers of 2'-diphenylmethane diisocyanate (hereinafter abbreviated as "2,2'-MDI"). As a result of intensive studies to solve the above-described series of problems, the inventors of the present invention specified an MDI containing 2,4′-MDI at a specific ratio or higher and an aliphatic diisocyanate as the organic diisocyanate. It has been found that the above-described series of problems can be solved by using the ratio (mass ratio) together, and the present invention has been completed.

That is, the present invention is shown in the following (1) and (2) .

(1) An isocyanate group-terminated prepolymer obtained by reacting an organic diisocyanate (A), a polyol (B), and a carboxyl group-containing glycol (C) is used as a neutralizing agent (D). The aqueous polyurethane dispersion obtained by neutralizing and dispersing in water and then performing a chain extension reaction with a chain extender (E), wherein the organic diisocyanate (A) is 2,4′- It consists of diphenylmethane diisocyanate (A1) containing 75% by mass or more of diphenylmethane diisocyanate and aliphatic diisocyanate (excluding alicyclic diisocyanate) (A2), and the mass ratio of (A1) and (A2) is (A1) / (A2) = 60/40 to 90/10, and the polyol (B) is a polyol having a number average molecular weight of 800 to 6,000. And the carboxyl group-containing glycol (C) is dimethylolpropionic acid or dimethylolbutanoic acid.
(2) Moreover, the manufacturing method of an aqueous | water-based polyurethane dispersion makes neutralizing agent (D) the isocyanate group terminal prepolymer obtained by making organic diisocyanate (A), polyol (B), and carboxyl group-containing glycol (C) react. ), And then dispersed in water and then subjected to a chain extension reaction with a chain extender (E), wherein the organic diisocyanate (A) is 2,4. It consists of diphenylmethane diisocyanate (A1) containing at least 75% by weight of '-diphenylmethane diisocyanate and hexamethylene diisocyanate (A2), and the mass ratio of (A1) to (A2) is (A1) / (A2) = 60 / 40 to 90/10, polyol (B) is a polyol having a number average molecular weight of 800 to 6,000, and carboxyl Containing glycol (C), characterized in that dimethylolpropionic acid or dimethylol butanoic acid.

  According to the present invention, when MDI is used as an organic diisocyanate, an aqueous polyurethane dispersion excellent in dispersibility can be obtained even if the production (stirring) equipment is not extremely sophisticated.

  Further, according to the present invention, it is also possible to provide an aqueous polyurethane dispersion capable of obtaining a resin having both performances such as toughness and flexibility.

  Furthermore, according to the present invention, even when MDI is used as an organic diisocyanate, productivity (specifically, reaction control is easy, and the resulting polyurethane dispersion can be supplied to the market with stable quality. It is also possible to provide a method for producing an aqueous polyurethane dispersion excellent in

  The present invention will be described in further detail.

In the method for producing an aqueous polyurethane dispersion of the present invention, an isocyanate group-terminated prepolymer obtained by reacting an organic diisocyanate (A), a polyol (B), and a carboxyl group-containing glycol (C) is used as a neutralizing agent (D). The aqueous polyurethane dispersion obtained by neutralizing and dispersing in water and then performing a chain extension reaction with a chain extender (E), wherein the organic diisocyanate (A) is 2,4′- It consists of diphenylmethane diisocyanate (A1) containing 75% by mass or more of diphenylmethane diisocyanate and aliphatic diisocyanate (excluding alicyclic diisocyanate) (A2), and the mass ratio of (A1) and (A2) is (A1) / (A2) = 60/40 to 90/10, and polyol (B) is a polyol having a number average molecular weight of 800 to 6,000 And the carboxyl group-containing glycol (C) is dimethylolpropionic acid or dimethylolbutanoic acid.

<Organic diisocyanate (A)>
As mentioned above, as the organic diisocyanate (A) used in the aqueous polyurethane dispersion of the present invention, MDI (A1) containing 75% by mass or more of 2,4′-MDI, and aliphatic diisocyanate (alicyclic diisocyanate). ( Excluding) (A2) is (A1) / (A2) = 60/40 to 90/10 in mass ratio (preferably (A1) / (A2) = 65/35 to 85/15 in mass ratio, From the viewpoint of obtaining a resin having both excellent toughness and flexibility in the obtained resin, it is particularly preferable that (A1) / (A2) = 70/30 to 80/20) by mass ratio. The ratio is used together. When this ratio is deviated, specifically, in the case of (A1) / (A2) = 0/100 to 59/41, there is a problem that the viscosity is increased and solidified during water dispersion in the production of the aqueous polyurethane dispersion. . Also, in the case of (A1) / (A2) = 91/9 to 100/0, a resin having either or both of excellent toughness and flexibility can be obtained (in other words, desired of the present invention Inability to obtain a resin having the performance to achieve this) occurs.

<MDI (A1) containing 75% by mass or more of 2,4′-MDI>
As described above, MDI is composed of three isomers: 4,4'-MDI, 2,4'-MDI, and 2,2'-MDI. The isomer composition ratios of these MDIs in the present invention can ensure excellent dispersibility in the obtained aqueous polyurethane dispersion, and also can improve productivity (specifically, reaction control is easy and the resulting polyurethane dispersion can be obtained). From the viewpoint of being excellent in stable quality and being able to be supplied to the market), when the MDI is 100% by mass, the content of 2,4′-MDI is 75% by mass or more (preferably 80%). It is necessary to be 95.0% by mass or more, particularly preferably from the viewpoint that the more stable dispersibility of the aqueous polyurethane dispersion and productivity can be reliably obtained. The isomer composition ratio of MDI can be obtained from a calibration curve based on the area percentage of each peak obtained by GPC or gas chromatography (hereinafter abbreviated as “GC”).

<Aliphatic diisocyanate (excluding alicyclic diisocyanate) (A2)>
Aliphatic diisocyanates (excluding alicyclic diisocyanates) used in the present invention (A2) include tetramethylene diisocyanate, hexamethylene diisocyanate, 3-methyl-1,5-pentane diisocyanate, 2-methyl-1,5-pentane. Examples thereof include diisocyanate and lysine diisocyanate. Further, urethanized products, urea compounds, allophanates, biuret compounds, carbodiimide compounds, ureton iminates, uretdione compounds, isocyanurate compounds, etc. obtained by reacting with these polymeric substances and active hydrogen group-containing compounds are also included.

In the present invention, from the viewpoint of easily obtained the desired aqueous polyurethane dispersions in the present invention, to use by selecting hexamethylene diisocyanate as aliphatic di- isocyanate (A2) (hereinafter abbreviated as "HDI".) preferable.

<Port polyol (B)>
The Lupo triol used in the present invention, the number average molecular weight and polyester polyols or polyether polyols or polycarbonate polyols 800～6,000 is used.

  More specifically, polyester polyols include phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, succinic acid, malonic acid, adipic acid, 1,4-cyclohexyl dicarboxylic acid, maleic acid, fumaric acid, and other two types. Basic acid and the like, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, cyclohexane-1,4-diol, glycerin, trimethylolpropane, pentaerythritol, etc. From the polyols Polyester polyols obtained by the polycondensation reaction are employed. Further, cyclic esters such as ε-caprolactone, polyester amide polyols in which a part of the diol is changed to amines such as hexamethylene diamine and isophorone diamine can be used.

  Polyether polyols include the above diols, polyols, or these and amines such as ethylenediamine, propylenediamine, toluenediamine, metaphenylenediamine, diphenylmethanediamine, alkylene oxides such as ethylene oxide and propylene oxide, and methylglycidyl. A polyether polyol obtained by addition polymerization of an ether, an alkyl such as phenyl glycidyl ether or an aryl glycidyl ether, a cyclic ether such as tetrahydrofuran is used.

  As the polycarbonate polyol, a polycarbonate polyol obtained by a reaction of the diols or polyols with ethylene carbonate, diethyl carbonate, diphenyl carbonate or the like is used.

<Carboxyl group-containing glycol (C)>
As the carboxyl group-containing glycol (C) used in the present invention, dimethylolpropionic acid or dimethylolbutanoic acid having two terminal hydroxyl groups is used.
By using this carboxyl group-containing glycol, it is possible to increase the water dispersibility of the prepolymer by a free carboxyl group.

<Neutralizing agent (D)>
The neutralizing agent (D) used in the present invention neutralizes the carboxyl group of the carboxyl group-containing low molecular glycol incorporated in the urethane prepolymer main chain, and gives the effect of further improving the water dispersibility of the polyurethane resin. . Examples of the neutralizing agent (D) include tertiary amines (such as triethylamine).

<Chain extender (E)>
As the chain extender ( E ) used in the present invention, a compound having two or more active hydrogens is used. Examples of the compound having two or more active hydrogens include ethylenediamine (EDA), ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, diethanolamine, diethylenetriamine (DETA), and triethylene. Examples include tetramine, tetraethylenepentamine, and pentaethylenehexamine.

<Optional component>
The aqueous polyurethane dispersion in the present invention comprises the specific organic diisocyanate (A), the polymer polyol (B), the carboxyl group-containing low molecular glycol (C), the neutralizer (D), and the chain extender (E). If necessary, a viscosity reducing agent having an effect of promoting dispersion in water (solubility in water of 0.1 to 40% by mass and flash point of 50 ° C. or more) can be added. . Specific examples of the viscosity reducing agent include dipropylene glycol dimethyl ether (trade name: dimethylpropylene diglycol (abbreviation: DMM, solubility in water: 37.0 mass%, flash point: 65 ° C.), diethylene glycol dibutyl ether (commercial product). Name: Dibutyldiglycol, Abbreviation: DBDG, Solubility in water: 0.3 mass%, Flash point: 122 ° C., N-methylpyrrolidone (abbreviation: NMP, Solubility in water: (optional) mass%, flash point) : 91 ° C).

  Further, in the aqueous polyurethane dispersion in the present invention, a metal catalyst such as dibutyltin dilaurate or zinc naphthenate, or triethylenediamine, if necessary, for the purpose of accelerating the reaction in forming a polyurethane resin. A resin catalyst (urethanization catalyst) as a curing catalyst (polymerization catalyst) for urethane reaction, such as an amine catalyst such as N-methylmorpholine, can be used in combination.

  Furthermore, for the purpose of enhancing the desired physical properties of the aqueous polyurethane dispersion of the present invention and adding various physical properties, various additives include flame retardants, plasticizers, antioxidants, ultraviolet absorbers, fillers, Internal release agents, reinforcing materials, matting agents, conductivity imparting agents, charge control agents, antistatic agents, lubricants, and other processing aids can be used.

<Method for producing aqueous polyurethane dispersion>
Next, a method for producing the aqueous polyurethane dispersion of the present invention will be described. The series of specific organic diisocyanate (A), polymer polyol (B), and carboxyl group-containing low molecular glycol (C) are reacted. Under the present circumstances, you may interpose the viscosity reducing agent which has the effect which promotes the dispersion | distribution to the water mentioned as said arbitrary component, and a urethanization catalyst in a reaction system. Next, the carboxyl group is neutralized with the tertiary amine (D) to obtain an isocyanate group-terminated prepolymer having a carboxylic acid amine salt and having improved water dispersibility. After this isocyanate group-terminated prepolymer is dispersed in water and emulsified, the aqueous polyurethane dispersion of the present invention is obtained by performing a chain extension reaction with the chain extender (E).

  In this case, the step of emulsifying by dispersing the isocyanate group-terminated prepolymer in water is a system in which water is pre-charged rather than adding and dispersing water in the system in which the isocyanate group-terminated prepolymer is preliminarily charged. It is preferable to add and disperse an isocyanate group-terminated prepolymer therein to emulsify.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is limited to these and is not interpreted. In the examples and comparative examples, “parts” and “%” indicate “parts by mass” and “mass%”, respectively, unless otherwise specified.

<Example 1>
To reduce the viscosity of 228.9 g of polyol A, 24.2 g of dimethylolpropionic acid (DMPA), and 2,000 ml of reactor equipped with a stirrer, thermometer, nitrogen seal tube, and condenser As an optional component, 70.0 g of dimethylpropylene diglycol (DMM) was charged and stirred at 90 ° C. and mixed uniformly. Subsequently, after cooling to 60 ° C., 140.0 g of 2,4′-MDI and 15.2 g of HDI were charged and reacted at 80 ° C. for 2 hours with stirring. Next, 70.0 g of N-methylpyrrolidone (NMP) was charged as an optional component for lowering the viscosity, and further stirred for 1 hour. After stirring, after confirming that the isocyanate group content before neutralization is 3.7% by mass, 18.3 g of triethylamine (TEA) was added to neutralize the carboxyl group, and the polyurethane having an isocyanate group at the terminal A prepolymer was obtained.
Next, using a stirrer (Homomixer manufactured by Tokushu Kika Kogyo Co., Ltd.), 755.4 g of water was charged and phase-inverted while stirring. Immediately after the phase inversion, amine water (15% aqueous solution) consisting of 66.3 g of water and 11.7 g of ethylenediamine (EDA) was charged in advance to carry out emulsification and chain extension reaction between water and amine.
The reaction was terminated when the presence of isocyanate groups was no longer confirmed by FT-IR, to obtain “PH-A1” which was an aqueous polyurethane dispersion (resin emulsion). Dispersion “PH-A1” has a solid content of 30%, a pH of 9.5, a viscosity at 25 ° C. of 140 mPa · s, an average particle size (measurement apparatus: manufactured by Otsuka Electronics Co., Ltd .: electrophoretic light scattering system “ELS”) -800 "measured) was 180 nm.
Table 1 shows a series of results. In Table 1, “isocyanate group content before neutralization (* 1)” indicates the content of isocyanate group before introducing neutralizer (D), chain extender (E), and water. (The same applies below).

<Examples 2-5, Comparative Examples 1-4 >
According to the composition (blending ratio) shown in Table 1, “PH-A2” to “PH-A5” and “PH-B1”, which are aqueous polyurethane dispersions (resin emulsions), based on the same method as in Example 1 above. It was obtained - the "PH-B 4".
Of these, “PH-B3” (Comparative Example 3) was increased in viscosity at the time of water dispersion and finally solidified, and thus various confirmations of the state as an aqueous polyurethane dispersion (resin emulsion) were stopped ( In the dispersion state column in Table 1, "X (* 2)" is indicated).
Also, For the "PH-B4" (Comparative Example 4), at the time of starting to charge the water, because the foam has occurred that might be caused by excessive high reactivity of the isocyanate groups with water, an aqueous polyurethane dispersion Was discontinued (indicated as “× (* 3)” in the column of dispersion state in Table 1).
Table 1 shows a series of results.

  The details of the composition (each component) in Table 1 are as follows.

<2,4′-MDI (corresponding to the organic diisocyanate (A1) of the present invention)>
(I) MDI peak area ratio by GPC = 100%
(Ii) Ratio of 4,4′-MDI in MDI = 1% (measured by GC)
(Iii) Ratio of 2,4′-MDI in MDI = 98% (measured by GC)
(Iv) Ratio of 2,2′-MDI in MDI = 1% (measured by GC)
(V) Isocyanate group content = 33.6%
<4,4'-MDI>
(I) MDI peak area ratio by GPC = 100%
(Ii) 4,4′-MDI ratio in MDI = 98% (measured by GC)
(Iii) Ratio of 2,4′-MDI in MDI = 1% (measured by GC)
(Iv) Ratio of 2,2′-MDI in MDI = 1% (measured by GC)
(V) Isocyanate group content = 33.6%
<HDI (corresponding to the organic diisocyanate (A2) of the present invention)>
Hexamethylene diisocyanate <Polyol A (corresponding to port polyol of the present invention (B))>
Polytetramethylene ether glycol Nominal number average molecular weight = 1,000
Nominal functional group = 2
Nominal hydroxyl value = 112 (mgKOH / g)
Product name “PTG-1000SN” (Hodogaya Chemical Co., Ltd.)
<DMPA (corresponding to the carboxyl group-containing Yugu recall (C) of the present invention)>
Dimethylolpropionic acid Trade name “DMPA” (manufactured by GEO Specialty Chemicals)
<DMM (optional component)>
Dimethylpropylene diglycol (abbreviation: DMM)
Solubility in water: 37.0% by mass
Flash point: 65 ° C
Product name "dimethylpropylene diglycol" (manufactured by Nippon Emulsifier Co., Ltd.)
<NMP (optional component)>
N-methyl-2-pyrrolidone Solubility in water: (optional) mass%
Flash point: 91 ° C
Product name "N-methyl-2-pyrrolidone" (Mitsubishi Chemical Corporation)
<TEA (corresponding to the neutralizing agent (D) of the present invention)>
Triethylamine Trade name "Triethylamine" (manufactured by Kishida Chemical Co., Ltd.)
<EDA (corresponding to the chain extender (E) of the present invention)>
Ethylenediamine Product name "Ethylenediamine" (manufactured by Tosoh Corporation)
<Water>
purified water

<Evaluation of dispersion state in aqueous polyurethane dispersion>
About each water-based polyurethane dispersion obtained in each Example and comparative example (except one part), 200g was prepared for each in the glass sample bottle, and it left still in 25 degreeC atmosphere for 24 hours. After standing, the dispersion state was visually confirmed and evaluated. The results are shown in Table 1 .
“◯”: A uniform dispersion state is maintained.
“Δ”: Some signs of liquid phase separation are observed.
“×”: high viscosity, solidified or cannot be evaluated (see above).

<(Reference Example) Evaluation of film properties using aqueous polyurethane dispersion>
For each aqueous polyurethane dispersion obtained in each example, the aqueous polyurethane dispersion was cast on a plate glass and dried at 25 ° C. for 5 days to prepare a dry film having a predetermined film thickness, which is described below. Physical properties were measured. A series of results are shown in Table 2.
<Tensile properties>
Tensile test (25 ° C .: 100% modulus, strength at break, elongation):
Tensile speed = 200 mm / min. A sample was prepared by punching with a No. 4 dumbbell of JIS K6301 (1995).
Tensile property measuring device: Tensilon UTA-500 manufactured by Orientec Co., Ltd.
<Tear properties>
Tear test (25 ° C .: tear strength):
It measured according to JIS K7312.

  As shown in Table 1, MDI (A1) in which the ratio of 2,4′-MDI is 75% by mass or more, hexamethylene diisocyanate as aliphatic diisocyanate (A2), and mass ratio of (A1) and (A2) When used together in the range of 60/40 to 90/10, a good aqueous polyurethane dispersion having a low viscosity and a small average particle size was obtained.

  In addition, as described in Table 1, as the tendency, as the ratio of MDI (A1) in which the ratio of 2,4′-MDI was 75% by mass or higher was higher, the average particle diameter was larger. When the mass ratio of (A1) to (A2) is in the range of 91/9 to 100/0, the average particle diameter is at a level exceeding 200 nm. As described in Table 1, this leads to a tendency for the viscosity of the aqueous polyurethane dispersion itself to increase, and it seems that there is a possibility of causing a problem depending on the intended use.

  In addition, as shown in Table 1, as a tendency, when the ratio of hexamethylene diisocyanate as the aliphatic diisocyanate (A2) becomes a certain level or more, there is a problem that the viscosity is increased during water dispersion and solidifies. I found it.

  In addition, when the physical property of the film | membrane obtained as a reference example was evaluated using the aqueous polyurethane dispersion "PH-A1"-"PH-A5" obtained as an Example in Table 1, as shown in Table 2. Thus, a resin (film) having the performance desired in the present invention, that is, both the performance of toughness and flexibility was obtained.

The aqueous polyurethane dispersion obtained by the present invention is suitably used in various water-based polyurethane resin applications such as aqueous paints and aqueous adhesives, particularly in fields where both excellent toughness and excellent flexibility are desired. be able to.

Claims (2)

After the isocyanate group-terminated prepolymer obtained by reacting the organic diisocyanate (A), polyol (B), and carboxyl group-containing glycol (C) is neutralized with the neutralizing agent (D) and then dispersed in water. An aqueous polyurethane dispersion obtained by performing a chain extension reaction with a chain extender (E),
The organic diisocyanate (A) is composed of diphenylmethane diisocyanate (A1) containing 75% by mass or more of 2,4′-diphenylmethane diisocyanate and aliphatic diisocyanate (excluding alicyclic diisocyanate) (A2), and (A1) And the mass ratio of (A2) is (A1) / (A2) = 60/40 to 90/10,
The polyol (B) is a polyol having a number average molecular weight of 800 to 6,000,
The method for producing an aqueous polyurethane dispersion, wherein the carboxyl group-containing glycol (C) is dimethylolpropionic acid or dimethylolbutanoic acid. After the isocyanate group-terminated prepolymer obtained by reacting the organic diisocyanate (A), polyol (B), and carboxyl group-containing glycol (C) is neutralized with the neutralizing agent (D) and then dispersed in water. An aqueous polyurethane dispersion obtained by performing a chain extension reaction with a chain extender (E),
The organic diisocyanate (A) is composed of diphenylmethane diisocyanate (A1) and hexamethylene diisocyanate (A2) containing 75% by mass or more of 2,4′-diphenylmethane diisocyanate, and the mass ratio of (A1) and (A2) is (A1) / (A2) = 60/40 to 90/10,
The polyol (B) is a polyol having a number average molecular weight of 800 to 6,000,
The method for producing an aqueous polyurethane dispersion, wherein the carboxyl group-containing glycol (C) is dimethylolpropionic acid or dimethylolbutanoic acid.