JP7625803B2 - Aqueous polyurethane resin dispersion and composition thereof - Google Patents

Description

The present invention relates to an aqueous polyurethane resin dispersion and an aqueous polyurethane resin dispersion composition in which a polyurethane resin is dispersed in a mixed medium of an organic solvent and water. The present invention also relates to a method for producing the aqueous polyurethane resin dispersion and a film produced from the dispersion.

Water-based polyurethane resin dispersions can produce coatings that have adhesive properties, abrasion resistance, and rubber-like properties, and because they reduce volatile organic compounds compared to conventional solvent-based polyurethanes, they are increasingly being used as an environmentally friendly material to replace solvent-based polyurethanes.

It is known that this aqueous polyurethane resin dispersion and its manufacturing method can maintain drying and thickening properties by using an organic solvent such as dipropylene glycol dimethyl ether. It is also known to use ammonia or triethylamine as a low-boiling neutralizing agent (see Patent Documents 1 and 2).

In addition, an aqueous polyurethane resin dispersion that uses a specific dialkylaminomethylolalkane compound as a neutralizing agent is known as an aqueous polyurethane dispersion that has excellent dispersibility in water or a mixed medium of organic solvents and water, and can keep the viscosity low when the solid content is high. (See Patent Document 3)

JP 2010-143946 A International Publication No. 2016/163394 JP 2018-62572 A

In aqueous polyurethane resin dispersions used in coating agents, textile printing inks, and printing inks such as flexographic and gravure printing, it is desirable for them to exhibit excellent coating film properties (adhesion, water resistance, oil resistance, heat resistance, etc.) even at low temperatures and in short drying times, from the viewpoints of energy saving, low cost, and reduced environmental impact.
In addition, as described in Patent Documents 1 and 2, when ammonia or triethylamine is used as a neutralizing agent, it gives off an odor, and therefore further improvement is required in the working environment during the production and use of the aqueous polyurethane resin dispersion.
Furthermore, the use of the high-boiling point neutralizing agent used in Patent Document 3 may deteriorate the coating film properties such as adhesion, water resistance, and abrasion resistance.
Therefore, an object of the present invention is to further improve the working environment during the production and use of an aqueous urethane resin dispersion, and to provide an aqueous urethane resin dispersion having excellent water resistance and dispersibility.

The inventors discovered that by using a neutralizing agent or organic solvent having a boiling point in a specific range and controlling the constituent units of the aqueous polyurethane resin dispersion, it is possible to reduce the odor of the aqueous polyurethane resin dispersion and improve both the water resistance and dispersibility of the aqueous polyurethane resin dispersion, which led to the present invention.

Specifically, the present invention is as follows:

1. An aqueous polyurethane resin dispersion having structural units derived from a polyol compound (Aa), a polyisocyanate compound (Ab), an acidic group-containing polyol compound (Ac), a neutralizing agent (Ad) and a chain extender (Ae), comprising an organic solvent (Af) and water (Ag),
The boiling point of the neutralizing agent (Ad) is 100° C. or higher and 150° C. or lower,
the average boiling point of the organic solvent (Af) is 150° C. or higher and 180° C. or lower, which is calculated by the formula [Σ(Tn×Rn/100)] as the sum of the products of the boiling points Tn (° C.) of the organic solvents in the organic solvent (Af) and the mass ratios Rn (mass%) of the organic solvents to the total amount of the organic solvent (Af);
Aqueous polyurethane resin dispersion.

2. The aqueous polyurethane resin dispersion according to 1 above, wherein the melting point of the chain extender (Ae) is 50°C or higher.

3. The aqueous polyurethane resin dispersion according to 1 or 2 above, wherein the chain extender (Ae) is a piperazine compound represented by the following formula (1) or a dihydrazide compound represented by the following formula (2).

（式中、Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４はそれぞれ水素原子又は炭素原子数１～４の直鎖状若しくは分岐状アルキル基である。）

(In the formula, R ¹ , R ² , R ³ and R ⁴ are each a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms.)

（式中、Ｚ^１は炭素原子数１～６の直鎖状又は分岐状アルキレン基である。）

(In the formula, ^Z1 is a linear or branched alkylene group having 1 to 6 carbon atoms.)

4. The aqueous polyurethane resin dispersion according to any one of 1 to 3 above, wherein the polyurethane resin has an acid value of 18 to 35 mgKOH/g.
5. The aqueous polyurethane resin dispersion according to any one of 1 to 4 above, wherein the polyol compound (Aa) comprises a polycarbonate polyol compound (Aa1).

6. The aqueous polyurethane resin dispersion according to 5 above, in which the polyol component of the polycarbonate polyol compound (Aa1) is a linear and/or branched aliphatic polyol.

7. The aqueous polyurethane resin dispersion according to 5 or 6, wherein the polyol compound (Aa) includes a polyol compound (Aa2) other than the polycarbonate polyol compound (Aa1) and the acidic group-containing polyol (Ac).

8. The aqueous polyurethane resin dispersion according to any one of 1 to 7 above, wherein the organic solvent is a dialkylene glycol dialkyl ether.

9. The aqueous polyurethane resin dispersion according to any one of 1 to 8 above, wherein the neutralizing agent (Ad) is an aminoalcohol compound represented by the following formula (3):

（式中、Ｒ^５及びＲ^６はそれぞれ炭素原子数１～４の直鎖状又は分岐状アルキル基を示し、Ｚ^２は炭素数１～６の直鎖状又は分岐状のアルキレン基を示す。）

(In the formula, ^R5 and ^R6 each represent a linear or branched alkyl group having 1 to 4 carbon atoms, and ^Z2 represents a linear or branched alkylene group having 1 to 6 carbon atoms.)

10. The aqueous polyurethane resin dispersion according to any one of 1 to 9 above, wherein the polyisocyanate compound (Ab) is an aliphatic polyisocyanate compound and/or an alicyclic polyisocyanate compound.

11. The aqueous polyurethane resin dispersion according to any one of 1 to 10 above, wherein the weight average molecular weight of the polyurethane resin is 50,000 or more.

12. An aqueous polyurethane resin dispersion composition comprising the aqueous polyurethane resin dispersion described in any one of 1 to 11 above.

13. The aqueous polyurethane resin dispersion composition according to claim 12, further comprising at least one selected from an acrylic resin emulsion, an olefin resin emulsion, and a polyester resin emulsion.

14. An aqueous polyurethane resin dispersion composition according to 12 or 13 above for use in paints, coating agents or inks.

15. (I) A step of reacting a polyol compound (Aa), a polyisocyanate compound (Ab) and an acidic group-containing polyol (Ac) in the presence of an organic solvent to obtain a polyurethane prepolymer;
(II) mixing the polyurethane prepolymer with water;
(III) neutralizing the acidic groups of the polyurethane prepolymer with a neutralizing agent (Ad); and (IV) polymerizing the polyurethane prepolymer with a chain extender (Ae),
The boiling point of the neutralizing agent (Ad) used in the step (III) is 100° C. or higher and 150° C. or lower,
the average boiling point of the organic solvent (Af) is 150° C. or more and 180° C. or less, which is calculated by the formula [Σ(Tn×Rn/100)] as the sum of the products of the boiling points Tn (° C.) of each organic solvent in the organic solvent (Af) contained in the aqueous polyurethane resin dispersion and the proportions Rn (mass%) of each organic solvent in the total amount of the organic solvent (Af);
12. A method for producing the aqueous polyurethane resin dispersion according to any one of 1 to 11 above.

16. The method for producing the aqueous polyurethane resin dispersion according to 15 above, further comprising the following step (V):
(V) A step of mixing the polyurethane prepolymer or the aqueous polyurethane resin dispersion with an organic solvent.

17. A polyurethane resin film produced from the aqueous polyurethane resin dispersion described in any one of 1 to 11 above.

The present invention can further improve the working environment during the production and use of aqueous urethane resin dispersions, and provide aqueous urethane resin dispersions that have water resistance and dispersibility.

The aqueous urethane resin dispersion of the present invention is an aqueous polyurethane resin dispersion having structural units derived from a polyol compound (Aa), a polyisocyanate compound (Ab), an acidic group-containing polyol (Ac), a neutralizing agent (Ad) and a chain extender (Ae), and containing an organic solvent (Af) and water (Ag), in which the boiling point of the neutralizing agent (Ad) is 100°C or higher and 150°C or lower, and the average boiling point of the organic solvent (Af), calculated as the sum of the products of the boiling points Tn (°C) of each organic solvent in the organic solvent (Af) and the mass ratio Rn (mass%) of each organic solvent in the total amount of the organic solvent (Af) by the formula: [Σ(Tn×Rn/100)], is 150°C or higher and 180°C or lower. Unless otherwise noted, the boiling point means the boiling point under atmospheric pressure.

When used in printing ink applications, in addition to the issues mentioned above, the drying process must be completed in a short time because the substrate is passed through a drying oven while being printed. In particular, when printing on plastic film, drying at high temperatures must be avoided in consideration of the heat resistance of the film. This often results in insufficient drying, and moisture and solvent may remain in the film, making it easy for the physical properties of the coating to deteriorate.
Furthermore, when a high-boiling neutralizing agent is used, it may remain in the coating film when dried at a low temperature for a short time, and may deteriorate the physical properties of the coating film, such as adhesion, water resistance, and abrasion resistance.
In the aqueous polyurethane resin dispersion of the present invention, these problems can be solved by using a neutralizing agent or an organic solvent having a boiling point in a specific range and controlling the constituent units.

<Polyol compound (Aa)>
The polyol compound (Aa) used in the present invention has two or more hydroxyl groups in one molecule. This polyol compound (Aa) preferably contains a polycarbonate polyol compound (Aa1), and may contain other polyol compounds (Aa2) as optional components.
When the polyol compound (Aa) contains the polycarbonate polyol compound (Aa1) or, as an optional component, another polyol compound (Aa2), the dispersibility of the aqueous urethane resin can be improved.

The polyol compound (Aa) preferably contains 30% by mass or more of the polycarbonate polyol compound (Aa1) relative to the total amount of the polyol compound (Aa), more preferably 40% by mass or more, even more preferably 50% by mass or more, and even more preferably 60% by mass or more. There is no particular upper limit to the content of the polyol compound (Aa1), and it may account for the total amount of the polyol compound (Aa), i.e., 100% by mass.

The polycarbonate polyol compound (Aa1) is obtained by reacting one or more polyol components with a carbonate ester or phosgene. From the viewpoints of safety and handling of reagents, etc., it is easy to produce, and there is no by-production of terminal chlorinated products. Therefore, polycarbonate polyols obtained by reacting one or more polyol monomers with a carbonate ester are preferred.

As the polyol component of the polycarbonate polyol compound (Aa1), known compounds can be used. For example, aliphatic polyols such as linear aliphatic diols such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, and 1,9-nonanediol, branched aliphatic diols such as 2-methyl-1,3-propanediol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, and 2-methyl-1,8-octanediol, trifunctional or higher polyhydric alcohols such as trimethylolpropane and pentaerythritol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanediol, 1,3-cyclopentanediol, 1,4-cycloheptanediol, 2,5-bis(hydroxymethyl)-1,4-dioxane, and 2,7-norbornanediol aromatic diols such as 1,4-benzenedimethanol, 1,3-benzenedimethanol, 1,2-benzenedimethanol, 4,4'-naphthalenedimethanol, and 3,4'-naphthalenedimethanol; polyester polyols of hydroxycarboxylic acids and diols such as polyester polyols of 6-hydroxycaproic acid and hexanediol; polyester polyols of dicarboxylic acids and diols such as polyester polyols of adipic acid and hexanediol; and polyether polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Among these, alicyclic polyols and/or aliphatic polyols are preferred, and aliphatic polyols are more preferred.
As the polyol containing an alicyclic structure (for example, an alicyclic polyol or a combination of an alicyclic polyol and an aliphatic polyol), a combination of 1,6-hexanediol and 1,4-cyclohexanedimethanol, or a combination of 1,5-pentanediol and 1,4-cyclohexanedimethanol is preferred.
As the aliphatic polyol, a linear and/or branched aliphatic polyol is preferable, and a linear or branched aliphatic polyol is more preferable. As the linear and/or branched aliphatic polyol, 1,6-hexanediol, 1,5-pentanediol, or 2-methyl-1,3-pentanediol is preferable, and 2-methyl-1,3-pentanediol is more preferable from the viewpoint of the water resistance of the coating film obtained from the aqueous polyurethane resin dispersion.

The polyol component of the polycarbonate polyol compound (Aa1) may be used alone or in combination with multiple types.

The carbonate ester is not particularly limited, but examples thereof include aliphatic carbonate esters such as dimethyl carbonate and diethyl carbonate; aromatic carbonate esters such as diphenyl carbonate; and cyclic carbonate esters such as ethylene carbonate. In addition, phosgene capable of producing polycarbonate polyol can also be used. Among these, aliphatic carbonate esters are preferred, and dimethyl carbonate is more preferred, in view of the ease of producing the polycarbonate polyol compound (Aa1).

The polyol compound (Aa1) may contain ether bonds or ester bonds in its molecule in a number less than the average number of carbonate bonds in one molecule, as long as the properties of the polycarbonate polyol are not impaired.

The polycarbonate polyol compound (Aa1) preferably has a number average molecular weight (Mn) of 400 to 5,000. When Mn is 400 or more, the performance as a soft segment is good, and cracks are unlikely to occur when a coating film is formed. When Mn is 5,000 or less, the reactivity of the polycarbonate polyol compound (Aa) with the isocyanate compound (Ab) is not reduced, and problems such as the production process of the urethane prepolymer taking a long time, the reaction not proceeding sufficiently, and the viscosity of the polycarbonate polyol becoming high and difficult to handle do not occur. The Mn of the polycarbonate polyol compound (Aa1) is preferably 500 to 3,500, more preferably 600 to 2,500. In the present invention, Mn is a value calculated from the hydroxyl value and the quantitative value of the composition by ¹ H-NMR or gas chromatography after alkali hydrolysis.

From the viewpoint of dispersibility of the aqueous urethane resin, the hydroxyl value of the polycarbonate polyol compound (Aa1) is preferably 20 to 300 mgKOH/g, more preferably 30 to 230 mgKOH/g, and even more preferably 45 to 200 mgKOH/g.

A method for producing a polycarbonate polyol compound (Aa1) from a polyol component and a carbonate ester includes, for example, adding a carbonate ester and an excess number of moles of polyol relative to the number of moles of the carbonate ester to a reactor, reacting for 5 to 6 hours at a temperature of 160 to 200°C and a pressure of about 50 mmHg, and then reacting for several hours at 200 to 220°C and a pressure of a few mmHg or less. In the above reaction, it is preferable to carry out the reaction while removing the by-product alcohol from the system. In that case, if the carbonate ester escapes from the system by forming an azeotrope with the by-product alcohol, an excess amount of carbonate ester may be added. In the above reaction, a catalyst such as titanium tetrabutoxide may be used.

<Other polyol compounds (Aa2)>
The polyol compound (Aa) may contain other polyol compounds (Aa2) other than the polyol compound (Aa1) and the acidic group-containing polyol (Ac) described later. Such other polyol compounds (Aa2) are preferably contained in an amount of less than 70 mass% relative to the total amount of the polyol compound (Aa), more preferably contained in an amount of less than 60 mass%, even more preferably contained in an amount of less than 50 mass%, and even more preferably contained in an amount of less than 40 mass%. Depending on the physical properties required for the aqueous polyurethane resin, the type and amount of the other polyol compounds (Aa2) can be appropriately adjusted by a person skilled in the art within a range that does not impair the effects of the present invention, but the other polyol compounds (Aa2) do not have to be contained in the polyol compound (Aa).

Other polyol compounds (Aa2) that can be used include known compounds, such as polyester polyols, polyether polyols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, random copolymers or block copolymers of ethylene oxide and propylene oxide or ethylene oxide and butylene oxide, short chain aliphatic diols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 3-methyl-1,5-pentanediol, and 2-butyl-2-ethyl-1,3-propanediol, alicyclic diols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and hydrogenated bisphenol A, and diols such as bisphenol A, hydroquinone, bishydroxyethoxybenzene, and alkylene oxide adducts thereof. From the viewpoints of dispersibility of the aqueous urethane resin and hydrolysis resistance of a coating film obtained from the aqueous polyurethane resin dispersion, it is preferable to use a polyether polyol as the other polyol compound (Aa2), and it is more preferable to use polytetramethylene glycol.
The other polyol compound (Aa2) as described above may be a commercially available product or may be prepared separately.

<Polyisocyanate Compound (Ab)>
As the polyisocyanate compound (Ab), known compounds can be used. For example, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate (TDI), 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 2,4-diphenylmethane diisocyanate, 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatodi ... Aromatic polyisocyanate compounds such as phenylmethane, 1,5-naphthylene diisocyanate, 4,4',4''-triphenylmethane triisocyanate, m-isocyanatophenylsulfonyl isocyanate, and p-isocyanatophenylsulfonyl isocyanate; ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), dodecamethylene Aliphatic polyisocyanate compounds such as diisocyanate, 1,6,11-undecane triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethyl caproate, bis(2-isocyanatoethyl) fumarate, bis(2-isocyanatoethyl) carbonate, and 2-isocyanatoethyl-2,6-diisocyanatohexanoate; isophorone diisocyanate Examples of the polyisocyanate compound include alicyclic polyisocyanate compounds such as 4,4'-dicyclohexylmethane diisocyanate (H12MDI or hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate (hydrogenated TDI), bis(2-isocyanatoethyl)-4-dicyclohexene-1,2-dicarboxylate, 2,5-norbornane diisocyanate, and 2,6-norbornane diisocyanate. The polyisocyanate compound (Ab) may have a structure that is partially or entirely derivatized by isocyanuration, carbodiimidization, biuretization, or the like.

Among the above polyisocyanate compounds (Ab), from the viewpoint of improving the adhesion of the coating film obtained from the aqueous polyurethane resin dispersion to the substrate, an alicyclic polyisocyanate compound is preferred, from the viewpoints of hardness and breaking energy, isophorone diisocyanate (IPDI) or 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI) is more preferred, and from the viewpoint of blocking resistance of the coating film, 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI) is even more preferred.
The polyisocyanate compound (Ab) may be used alone or in combination of two or more kinds.

The amount of polyisocyanate compound (Ab) used is preferably such that the ratio (isocyanate group/hydroxyl group (molar ratio)) of the isocyanate group of polyisocyanate compound (Ab) to the hydroxyl group of the total polyol (total of polyol compound (Aa) and acidic group-containing polyol (Ac)) is 1.2 to 2.0, more preferably 1.3 to 1.7.

<Acidic Group-Containing Polyol (Ac)>
The acidic group-containing polyol (Ac) is a polyol containing two or more hydroxyl groups and one or more acidic groups in one molecule. The acidic group-containing polyol (Ac) may be used alone or in combination of two or more kinds.

As the acidic group-containing polyol (Ac), known polyols can be used. Examples include dimethylolalkanoic acids such as 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid; N,N-bishydroxyethylglycine, N,N-bishydroxyethylalanine, 3,4-dihydroxybutanesulfonic acid, and 3,6-dihydroxy-2-toluenesulfonic acid. Among these, from the viewpoint of ease of availability, dimethylolalkanoic acids having 4 to 12 carbon atoms and containing two methylol groups are preferred, and among dimethylolalkanoic acids, 2,2-dimethylolpropionic acid is more preferred.

In the aqueous polyurethane resin dispersion, the total hydroxyl equivalent number of the polyol compound (Aa) and the acidic group-containing polyol (Ac) is preferably 40 to 3000. If the hydroxyl equivalent number is within this range, it is easy to manufacture an aqueous polyurethane resin dispersion containing the obtained polyurethane resin. From the viewpoint of the rupture energy of the coating film obtained from the aqueous polyurethane resin dispersion obtained, the hydroxyl equivalent number is preferably 50 to 1000, more preferably 100 to 500, and even more preferably 200 to 400.

The hydroxyl group equivalent number can be calculated by the following formulas (1) and (2).
Hydroxyl equivalent number of each polyol component=molecular weight of each polyol component/number of hydroxyl groups of each polyol component (1)
Total hydroxyl equivalent number of polyol components=M/total mole number of polyol components (2)
In formula (2), M represents [[hydroxyl equivalent number of polycarbonate polyol component × number of moles of polycarbonate polyol component] + [hydroxyl equivalent number of acidic group-containing polyol × number of moles of acidic group-containing polyol] + [hydroxyl equivalent number of other polyol × number of moles of other polyol]].

<Neutralizing agent (Ad)>
The aqueous polyurethane resin dispersion of the present invention is obtained by neutralizing the acidic groups in the polyurethane resin with a neutralizing agent (Ad) and dispersing the polyurethane resin in an aqueous medium. The neutralizing agent (Ad) may be used alone or in combination of two or more kinds.

The boiling point of the neutralizing agent (Ad) is 100°C or higher and 150°C or lower, because it volatilizes and disappears from the polyurethane film at the temperature (usually 25 to 180°C) when the mixed medium of the organic solvent and water in the coating material composition is dried, resulting in even better adhesive strength.

Furthermore, from the viewpoint of the odor of the aqueous polyurethane resin dispersion and the water resistance of the coating film obtained from the aqueous polyurethane resin dispersion, the boiling point of the neutralizing agent is preferably 110°C or higher and 145°C or lower, and more preferably 120°C or higher and 140°C or lower.

Specific examples of the neutralizing agent (Ad) include amino alcohol compounds represented by the following formula (3):

In the formula, ^R5 and ^R6 each represent a linear or branched alkyl group having 1 to 4 carbon atoms, and from the viewpoints of the dispersibility of the aqueous polyurethane resin and the stability of the obtained aqueous polyurethane dispersion, each is preferably an alkyl group having 1 to 2 carbon atoms.
^Z2 represents a linear or branched alkylene group having 1 to 6 carbon atoms, and from the viewpoint of the water resistance of the aqueous polyurethane resin, is preferably a linear alkylene group having 1 to 4 carbon atoms.

As the neutralizing agent (Ad), a known neutralizing agent can be used. For example, 2-(dimethylamino)ethanol (boiling point: 135°C), 1-(dimethylamino)ethanol (boiling point: 101°C), 1-(ethylmethylamino)methanol (boiling point: 109°C), 1-(diethylamino)methanol (boiling point: 130°C), 3-(dimethylamino)-1-propanol (boiling point: 164°C), 2-(ethylmethylamino)ethanol (boiling point: 145°C), 2-(dimethylamino)-1-propanol (boiling point: 150°C), 3-(dimethylamino)-2-butanol (boiling point: 145°C) can be mentioned. Furthermore, from the viewpoint of odor and water resistance of the aqueous polyurethane resin dispersion, 1-(dimethylamino)ethanol, 2-(dimethylamino)ethanol, 1-(ethylmethylamino)methanol, and 1-(diethylamino)methanol are preferred, and 2-(dimethylamino)ethanol is more preferred.

When the neutralizing agent (Ad) is used, the amount used is preferably in the range of 0.8 to 2.0 times the number of moles of the acidic groups contained in the aqueous polyurethane resin dispersion. When the amount of the neutralizing agent (Ad) used is 0.8 times or more the number of moles of the acidic groups contained in the aqueous polyurethane resin dispersion, the stability of the resulting dispersion is high, and when it is 2.0 times or less, a coating film with high water resistance and abrasion resistance can be obtained under low temperature conditions of 80°C or less and short drying times of several seconds to several minutes.

<Chain extender (Ae)>
The chain extender (Ae) is a compound having reactivity with the isocyanato group of the polyurethane prepolymer. The chain extender (Ae) may be used alone or in combination of two or more kinds.

Furthermore, the melting point of the chain extender (Ae) is 50°C or higher, and from the viewpoint of the dispersibility of the aqueous polyurethane resin and the blocking resistance of the coating film obtained from the composition containing the aqueous polyurethane resin dispersion, it is preferably 80°C or higher and 200°C or lower, and more preferably 100°C or higher.

Any known chain extender (Ae) can be used. For example, amine compounds such as ethylenediamine (melting point: 8°C), 1,4-tetramethylenediamine (melting point: 27°C), 2-methyl-1,5-pentanediamine (melting point: -7°C), 1,6-hexamethylenediamine (melting point: 42°C), 3-aminomethyl-3,5,5-trimethylcyclohexylamine (melting point: 10°C), 1,3-bis(aminomethyl)cyclohexane (melting point: -70°C or less), and xylylenediamine (melting point: 14°C); piperazine compounds such as piperazine (melting point: 110°C) and 2,5-dimethylpiperazine (melting point: 116°C); dihydrazide compounds such as adipic acid dihydrazide (melting point: 181°C); water, etc. are mentioned, and a piperazine compound represented by the following formula (1) or a dihydrazide compound represented by the following formula (2) is preferable, and a piperazine compound represented by the following formula (1) is more preferable.

In the formula, R ¹ , R ² , R ³ and R ⁴ are each a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, and from the viewpoints of reactivity with an isocyanate group and ease of availability, a hydrogen atom or a methyl group is preferred, and a hydrogen atom is more preferred. In addition, one type of piperazine compound may be used alone, or multiple types may be used in combination.

In the formula, ^Z1 is a linear or branched alkylene group having 1 to 6 carbon atoms, and preferably a linear alkylene group having 4 to 6 carbon atoms. In addition, one type of dihydrazide compound may be used alone, or multiple types may be used in combination.

The number average molecular weight (Mn) of the chain extender (Ae) is preferably 300 or less. Having an Mn of 300 or less is necessary to increase the cohesive strength of the polyurethane resin, and the use of a piperazine compound or a dihydrazide compound increases the Mn of the polyurethane resin and is also preferable from the viewpoint of the durability of the coating film obtained from the aqueous polyurethane resin dispersion, and a piperazine compound is even more preferable from the viewpoint of the water resistance of the coating film obtained from the aqueous polyurethane resin dispersion.

The amount of the chain extender (Ae) added is preferably equal to or less than the equivalent of the isocyanato group that is the starting point of chain extension in the resulting urethane polymer. If the chain extender (Ae) is added in an amount exceeding the equivalent of the isocyanato group, the molecular weight of the chain-extended urethane polymer may decrease, causing a decrease in cohesive force, which may result in a decrease in the durability of the coating film obtained from the aqueous polyurethane resin dispersion.

<Organic solvent (Af)>
The aqueous polyurethane resin dispersion contains a polyurethane resin, an organic solvent (Af) and water (Ag), and the polyurethane resin is dispersed in a mixed medium of the organic solvent (Af) and the water (Ag).

The average boiling point of the organic solvent (Af) is 150°C or higher and 180°C or lower. The average boiling point is preferably 165°C or higher and 175°C or lower. By setting the average boiling point within this range, a coating film with high water resistance and abrasion resistance can be obtained under low temperature conditions of 80°C or lower and short drying times of several seconds to several minutes.

The average boiling point of the organic solvent (Af) is calculated as the sum of the products of the boiling points Tn (°C) of each organic solvent in the organic solvent (Af) and the mass ratio Rn (mass%) of each organic solvent in the organic solvent (Af) using the formula: [Σ(Tn × Rn/100)].

For example, if there are two types of organic solvents, and the boiling points and masses of the first organic solvent are Ta (° C.) and Ma (g), and the second organic solvent is Tb (° C.) and Mb (g), respectively,
Average boiling point of organic solvent (°C) = Ta x Ma / (Ma + Mb) + Tb x Mb / (Ma + Mb)
It can be calculated as follows.

As the organic solvent (Af), from the viewpoint of dispersing the polyurethane resin in water, a hydrophilic organic solvent is preferable. Specifically, ketones such as acetone (boiling point: 56 ° C.) and ethyl methyl ketone (boiling point: 80 ° C.); pyrrolidones such as N-methylpyrrolidone (boiling point: 202 ° C.) and N-ethylpyrrolidone (boiling point: 218 ° C.); ethers such as diethyl ether (boiling point: 35 ° C.), dipropylene glycol dimethyl ether (DMM) (boiling point: 175 ° C.), and dibutyl diglycol (boiling point: 255 ° C.); alcohols such as methanol (boiling point: 65 ° C.), ethanol (boiling point: 78 ° C.), n-propanol (boiling point: 97 ° C.), isopropanol (boiling point: 83 ° C.), ethylene glycol (boiling point: 197 ° C.), and diethylene glycol (boiling point: 244 ° C.); and amides such as 3-methoxy-N,N-dimethylamide (boiling point: 216 ° C.). It is preferable to use alcohols or ethers, and it is more preferable to use ethers.
As the alcohols, dialkylene glycols such as ethylene glycol and diethylene glycol are preferred. As the ethers, for example, dialkylene glycol dialkyl ethers such as diethylene glycol butyl methyl ether (boiling point: 212° C.) and dipropylene glycol methyl-n-propyl ether (boiling point: 210° C.) are preferred, and from the viewpoints of availability and viscosity of the solvent, dipropylene glycol dimethyl ether (boiling point: 175° C.) is more preferred.

From the viewpoint of improving the dispersibility and film-forming properties of the polyurethane resin, the amount of organic solvent (Af) in the aqueous polyurethane resin dispersion is preferably 1 to 20 mass%, more preferably 1 to 15 mass%, and even more preferably 1 to 10 mass%.

The amount of organic solvent (Af) relative to the total mass of the polyurethane prepolymer obtained from the polyol compound (Aa), the polyisocyanate compound (Ab) and the acidic group-containing polyol (Ac) and the chain extender (Ae) is preferably 1 to 30% by mass, more preferably 3 to 30% by weight, and even more preferably 5 to 25% by mass, from the viewpoints of improving dispersion stability, storage stability, ease of production and use, fire resistance, and the thickening and drying properties of the aqueous polyurethane resin dispersion.

<Water (Ag)>
The aqueous polyurethane resin dispersion contains a polyurethane resin, an organic solvent (Af) and water (Ag), and the polyurethane resin is dispersed in a mixed medium of the organic solvent (Af) and the water (Ag).
The amount of water (Ag) in the aqueous polyurethane resin dispersion is preferably 40 to 90 mass%, more preferably 50 to 80 mass%, and even more preferably 55 to 70 mass%. From the viewpoint of improving the dispersibility of the polyurethane resin and the film-forming property, the mass ratio of the organic solvent (Af) to the water (Ag) (organic solvent (Af)/water (Ag)) is preferably 0.01 to 0.5, more preferably 0.03 to 0.4, and even more preferably 0.05 to 0.25.

<Polyurethane resin>
The polyurethane resin of the present invention has structural units derived from a polyol compound (Aa), a polyisocyanate compound (Ab), an acidic group-containing polyol (Ac), a neutralizing agent (Ad) and a chain extender (Ae). The polyurethane resin of the present invention preferably has the following characteristics.

(NCO/OH)
In the present invention, the molar ratio NCO/OH of the hydroxyl groups (OH) of the polyol compound (Aa) and the acidic group-containing polyol (Ac) to the isocyanato groups (NCO) of the polyisocyanate compound (Ab) in the aqueous polyurethane resin dispersion is preferably 1.1 to 5, more preferably 1.15 to 3, even more preferably 1.2 to 2, and even more preferably 1.3 to 1.7. When the value of NCO/OH is within such a range, the water resistance of the coating film tends to be improved.

(alicyclic structure)
The polyurethane resin contained in the aqueous polyurethane resin dispersion preferably contains an alicyclic structure from the viewpoint of adhesion to the substrate. The alicyclic structure is not limited in the number of ring members as long as it is an aliphatic ring structure. It is preferable to design it so that it contains a 6-membered ring (cyclohexylene group) because it is easy to obtain as a raw material. The alicyclic structure may be derived from any of the raw materials of the polyurethane, but is preferably derived from the polyisocyanate compound (Ab). Examples of the structural unit having an alicyclic structure include, as the polyol compound (Aa), a diol having an alicyclic structure in the main chain such as 1,4-cyclohexanedimethanol or a polycarbonate polyol (Aa1) obtained therefrom, and as the polyisocyanate compound (Ab), hydrogenated MDI, etc. are mentioned. The content ratio of the alicyclic structure is calculated based on the entire alicyclic structure contained in each of these structural units.

The content of the alicyclic structure in the polyurethane resin is preferably 20 to 40 mass% based on the solid content, and more preferably 25 to 38 mass%. If the content of the alicyclic structure is less than 20 mass%, the coating film obtained from the aqueous polyurethane resin dispersion becomes significantly sticky, and if the content of the alicyclic structure exceeds 40 mass%, dispersibility tends to deteriorate. The content of the alicyclic structure is calculated from the charging ratio of each raw material of the aqueous polyurethane resin dispersion.

(pH)
The pH of the aqueous polyurethane resin dispersion is preferably from 5.0 to 10.0, more preferably from 6.0 to 9.5, and even more preferably from 6.5 to 9.0.

(Weight average molecular weight)
From the viewpoint of durability of the low-temperature dried coating film, the weight-average molecular weight (Mw) of the polyurethane resin is preferably 50,000 or more, and more preferably 100,000 or more. By making the weight-average molecular weight 50,000 or more, the coating film can exhibit superior durability.

(Resin ratio)
The proportion of the polyurethane resin in the aqueous polyurethane resin dispersion is preferably from 5 to 60% by mass, and more preferably from 20 to 50% by mass.

(Acid value)
The acid value of the polyurethane resin is 18 to 35 mgKOH/g, preferably 19 to 32 mgKOH/g, and more preferably 20 to 29 mgKOH/g, based on the solid content, from the viewpoint of dispersibility of the polyurethane resin and water resistance of the coating film obtained from the aqueous polyurethane resin dispersion. If the acid value of the polyurethane resin is greater than 35 mgKOH/g based on the solid content, the water resistance of the coating film obtained from the aqueous polyurethane resin dispersion tends to deteriorate. If the acid value is less than 18 mgKOH/g based on the solid content, the dispersibility of the polyurethane resin tends to decrease.
The acid value can be measured in accordance with the indicator titration method of JIS K 1557. In the measurement, the neutralizing agent used to neutralize the acidic groups is removed before measurement. For example, when an organic amine is used as the neutralizing agent, the aqueous polyurethane resin dispersion is applied onto a glass plate, and the coating film obtained by drying at a temperature of 60° C. and a reduced pressure of 20 mmHg for 24 hours is dissolved in N-methylpyrrolidone (NMP), and the acid value can be measured in accordance with the indicator titration method of JIS K 1557.

<Method for producing aqueous polyurethane resin dispersion>
The aqueous polyurethane resin dispersion can be produced by a known method described in WO 2016/039396, WO 2016/163394, etc. For example, the following production method can be mentioned.
The first production method is a method in which all of the raw materials are mixed, reacted, and dispersed in water or a mixed medium of an organic solvent and water to obtain an aqueous polyurethane resin dispersion.
The second production method is a method in which all of the polyol components are reacted with a polyisocyanate to produce a prepolymer, the acidic groups of the prepolymer are neutralized, and then the prepolymer is dispersed in water or a mixed medium of an organic solvent and water, and a chain extender is reacted therewith to obtain an aqueous polyurethane resin dispersion.
As a method for producing the aqueous polyurethane resin dispersion, the above-mentioned second production method is preferred because it is easy to control the molecular weight.

In particular, in the present invention, the aqueous polyurethane resin dispersion can be produced by a method including the following steps (I) to (IV).
(I) a step of reacting a polyol compound (Aa), a polyisocyanate compound (Ab) and an acidic group-containing polyol (Ac) in the presence of an organic solvent to obtain a polyurethane prepolymer;
(II) mixing the polyurethane prepolymer with water;
(III) a step of neutralizing the acidic groups of the polyurethane prepolymer with a neutralizing agent (Ad), and (IV) a step of increasing the molecular weight of the polyurethane prepolymer with a chain extender (Ae).

Furthermore, the production method of the present invention may include a step (V) in addition to the steps (I) to (IV).
(V) A step of mixing the polyurethane prepolymer or the aqueous polyurethane resin dispersion with an organic solvent.
This step (V) is carried out in the case where the average boiling point of the organic solvent used in step (I) is not 150° C. or higher and 180° C. or lower, in order to further mix an organic solvent with the polyurethane prepolymer or the aqueous polyurethane resin dispersion, and adjust the average boiling point of the organic solvent after mixing to 150° C. or higher and 180° C. or lower.
In addition, even when the average boiling point of the organic solvent used in the step (I) is 150° C. or higher and 180° C. or lower, the step (V) may be carried out from the viewpoint of improving the dispersion stability, storage stability, ease of production and use, fire resistance, and thickening and drying properties of the aqueous polyurethane resin dispersion.

Therefore, when the average boiling point of the organic solvent (Af) in the aqueous polyurethane resin dispersion of the present invention is 150° C. or higher and 180° C. or lower, it may not be necessary to carry out the step (V).
The average boiling point of the organic solvent is calculated including not only the organic solvent used in step (I) but also the organic solvent used in step (V).

In this manufacturing method, the boiling point of the neutralizing agent (Ad) and the average boiling point of the organic solvent (Af) used are the same as described above.

<Composition>
The aqueous polyurethane resin dispersion composition of the present invention contains the aqueous polyurethane resin dispersion and can be used for paints, coating agents, or inks. When the composition is used for paints, coating agents, or inks, it is called a paint composition, a coating agent composition, or an ink composition, respectively.

In addition to the aqueous polyurethane resin dispersion, other resins may be added to the composition of the present invention. Examples of other resins include polyester resin, acrylic resin, polyether resin, polycarbonate resin, polyurethane resin, epoxy resin, alkyd resin, polyolefin resin, vinyl chloride resin, etc., and among them, it is preferable to add polyester resin, acrylic resin, or polyolefin resin, more preferably to add at least one selected from acrylic resin emulsion, olefin resin emulsion, and polyester resin emulsion, and further preferably to add acrylic resin emulsion.
These may be used alone or in combination. The other resin preferably has one or more hydrophilic groups. Examples of the hydrophilic group include a hydroxyl group, a carboxyl group, a sulfonic acid group, and a polyethylene glycol group.
The emulsion refers to a state in which a resin is dispersed in water or in a mixed medium of an organic solvent and water.

Polyester resins can usually be produced by an esterification reaction or transesterification reaction between an acid component and an alcohol component. As the acid component, compounds that are usually used as acid components in the production of polyester resins can be used. As the acid component, for example, aliphatic polybasic acids, alicyclic polybasic acids, aromatic polybasic acids, etc. can be used.

The hydroxyl value of the polyester resin is preferably from 1 to 80 mgKOH/g, more preferably from 5 to 60 mgKOH/g, and even more preferably from 10 to 30 mgKOH/g. The acid value of the polyester resin is preferably from 1 to 100 mgKOH/g, more preferably from 5 to 50 mgKOH/g, and even more preferably from 10 to 40 mgKOH/g.
The weight average molecular weight of the polyester resin is preferably from 3,000 to 50,000, and more preferably from 5,000 to 20,000.

The acrylic resin includes a polymer consisting of repeating units containing (meth)acrylic acid ester and/or (meth)acrylic acid. Here, (meth)acrylic acid means at least one of acrylic acid and methacrylic acid.

Commercially available acrylic resin emulsions include, for example, Pegal (registered trademark) 862 (Tg: -10°C), 865 (Tg: -12°C), 751 (Tg: 25°C), and LC6154 (Tg: 64°C) manufactured by Koatsu Gas Kogyo Co., Ltd., Polysol (registered trademark) AP-3900 (Tg: 10°C), AP-1020 (Tg: 23°C), AP-4735, TI-3052, and SE-4210E (Tg: -50°C) manufactured by Showa Denko K.K., and Nikasol (registered trademark) manufactured by Nippon Carbide Industries Co., Ltd. ) FX5697H (Tg: -60°C), FX3750 (Tg: -30°C), FX2138 (Tg: -17°C), FX2555 (Tg: -17°C), FX2033 (Tg: 8°C), FX2018 (Tg: 27°C), FX672K (Tg: 53°C), Parabond LX-5 (Tg: -40°C), G-60 (Tg: -30°C), LX-2 (Tg: -30°C) manufactured by Daiso Chemical Co., Ltd., and Aron (registered trademark) NW-400 (Tg: -41°C) manufactured by Toagosei Co., Ltd.

The Tg (glass transition temperature) of the acrylic resin is preferably -80°C to 60°C, more preferably -55°C to 0°C, and even more preferably -40°C to -20°C. When the Tg of the acrylic resin is 60°C or lower, the adhesion is better. When the Tg of the acrylic resin is -80°C or higher, the chemical resistance is better.

The acrylic resin emulsions may be used alone or in combination.

Examples of the polyolefin resin include a polyolefin resin obtained by polymerizing or copolymerizing an olefin monomer with other monomers according to a conventional polymerization method, and dispersing the polyolefin resin in water using an emulsifier, or a resin obtained by emulsion polymerization of an olefin monomer with other monomers. In some cases, the polyolefin resin may be chlorinated to use a so-called chlorinated polyolefin modified resin.
Examples of olefin monomers include α-olefins such as ethylene, propylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-hexene, 1-decene, and 1-dodecene; and conjugated or non-conjugated dienes such as butadiene, ethylidenenorbornene, dicyclopentadiene, 1,5-hexadiene, and styrenes. These monomers may be used alone or in combination.
Examples of other monomers copolymerizable with the olefin monomer include vinyl acetate, vinyl alcohol, maleic acid, citraconic acid, itaconic acid, maleic anhydride, citraconic anhydride, and itaconic anhydride. These monomers may be used alone or in combination of two or more kinds.

The paint composition, coating composition, and ink composition of the present invention may contain a curing agent, which can improve the water resistance, etc., of the coating film or multi-layer coating film, coating film, or printed matter obtained using the paint composition or coating composition.

Coloring pigments, extender pigments, and luster pigments can be added to the paint composition, coating composition, and ink composition of the present invention.
Examples of color pigments include titanium oxide, zinc oxide, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, threne pigments, and perylene pigments. These may be used alone or in combination. In particular, it is preferable to use titanium oxide and/or carbon black as the color pigment.
Examples of the extender pigment include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, and alumina white. These may be used alone or in combination. In particular, it is preferable to use barium sulfate and/or talc as the extender pigment, and it is more preferable to use barium sulfate.
Examples of the luster pigment that can be used include aluminum, copper, zinc, brass, nickel, aluminum oxide, mica, aluminum oxide coated with titanium oxide or iron oxide, and mica coated with titanium oxide or iron oxide.

The paint composition, coating composition and ink composition of the present invention may contain, as necessary, conventional additives such as thickeners, curing catalysts, ultraviolet absorbers, light stabilizers, defoamers, plasticizers, surface conditioners and anti-settling agents. These may be used alone or in combination.

The method for producing the paint composition, coating composition, and ink composition of the present invention is not particularly limited, and known production methods can be used. In general, the paint composition and coating composition are produced by mixing the aqueous polyurethane resin dispersion with the various additives, adding an organic solvent and water, and adjusting the viscosity according to the application method.

The paint composition, coating composition, and ink composition of the present invention may contain an organic solvent, but the organic solvent content can be reduced and the composition can be used by dispersing the composition in a mixed medium of organic solvent and water. This is advantageous from the standpoint of environmental conservation, safety, resource conservation, etc.

Materials to be coated with a paint composition, coated with a coating composition, or applied with an ink composition include metals, plastics, inorganic materials, wood, etc.

Examples of methods for applying a paint composition or a coating composition include bell coating, spray coating, roll coating, shower coating, and dip coating. Examples of methods for applying an ink composition include inkjet printing, flexographic printing, gravure printing, reverse offset printing, sheet-fed screen printing, and rotary screen printing. The drying process for a water-based ink composition involves passing the substrate through a drying oven while printing, and must be completed in a short period of time. However, particularly when printing on a plastic film, drying at high temperatures must be avoided in consideration of the heat resistance of the film. In water-based flexographic printing, low-temperature drying at 40 to 80°C is generally performed for 1 to 300 seconds.

There are no particular limitations on the thickness of the coating film after curing, but it is preferable for it to be 1 to 100 μm, and more preferably 1 to 50 μm.

<Polyurethane resin film>
The polyurethane resin film of the present invention is obtained from the aqueous polyurethane resin dispersion.

The aqueous polyurethane resin dispersion is applied to a releasable substrate, dried and cured by heating or other means, and then the cured polyurethane resin is peeled off from the releasable substrate to obtain a polyurethane resin film.

The heating method may be a method using the heat of the reaction itself, or a method using the heat of the reaction in combination with active heating of the mold. An example of active heating of the mold is a method in which the mold is placed in a hot air oven, electric furnace, or infrared induction heating furnace.

The heating temperature is preferably 40 to 200°C, and more preferably 60 to 160°C. By heating at such a temperature, drying can be performed more efficiently. The heating time is preferably 0.0001 to 20 hours, and more preferably 1 to 10 hours. By using such a heating time, a polyurethane resin film with higher hardness can be obtained. Drying conditions for obtaining a polyurethane resin film include, for example, heating at 120°C for 3 to 10 seconds.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these.

[Synthesis of aqueous polyurethane resin dispersion]
(Example S1: Synthesis of aqueous polyurethane resin dispersion A)
In a reaction vessel, 320.1 g (0.358 mol) of ETERNACOLL UM90 (1/3) (registered trademark; polycarbonate polyol manufactured by Ube Industries, Ltd.; number average molecular weight 894; hydroxyl value 125.5 mg KOH/g; polycarbonate polyol obtained by reacting 1,4-cyclohexanedimethanol and 1,6-hexanediol (molar ratio 1:3) with dimethyl carbonate) (Aa1), 48.8 g (0.364 mol) of 2,2-dimethylolpropionic acid (Ac), 312.8 g (1.193 mol) of 4,4'-dicyclohexylmethane diisocyanate (Ab), and 233.0 g of dipropylene glycol dimethyl ether (DMM) (Af) were mixed and reacted at 78 to 84 ° C. for 4.5 hours while stirring in a nitrogen atmosphere.
Next, 301.6 g of the resulting reaction mixture was taken out and added to a mixture of 554 g of water and 12.5 g (0.140 mol) of 2-dimethylaminoethanol (DMAE) (Ad), and the mixture was stirred vigorously.
Thereafter, 43.3 g (0.130 mol) of a 35% aqueous solution of 2-methyl-1,5-pentanediamine (MPMD) (Ae) was added to the resulting reaction mixture and further reacted to obtain an aqueous polyurethane resin dispersion A. No aggregates were observed.

(Example S2: Synthesis of aqueous polyurethane resin dispersion B)
In a reaction vessel, 379.9 g (0.380 mol) of ETERNACOLL UH100 (registered trademark; polycarbonate polyol manufactured by Ube Industries, Ltd.; number average molecular weight 999; hydroxyl value 112.3 mg KOH/g; polycarbonate polyol obtained by reacting 1,6-hexanediol with dimethyl carbonate), 49.6 g (0.370 mol) of 2,2-dimethylolpropionic acid, 283.6 g (1.081 mol) of 4,4'-dicyclohexylmethane diisocyanate, and 232.3 g of dipropylene glycol dimethyl ether (DMM) were mixed and reacted at 77 to 87°C for 7 hours with stirring in a nitrogen atmosphere.
Next, 327.0 g of the resulting reaction mixture was taken out and added to a mixture of 640 g of water and 17.0 g (0.190 mol) of 2-dimethylaminoethanol (DMAE), and the mixture was stirred vigorously.
Thereafter, 16.2 g (0.093 mol) of adipic acid dihydrazide (ADH) was added to the resulting reaction mixture and further reacted to obtain an aqueous polyurethane resin dispersion B. No aggregates were observed.

(Example S3: Synthesis of aqueous polyurethane resin dispersion C)
In a reaction vessel, 350.7 g (0.351 mol) of ETERNACOLL UH100 (registered trademark; polycarbonate polyol manufactured by Ube Industries, Ltd.; number average molecular weight 999; hydroxyl value 112.3 mg KOH/g; polycarbonate polyol obtained by reacting 1,6-hexanediol with dimethyl carbonate), 61.8 g (0.461 mol) of 2,2-dimethylolpropionic acid, 348.6 g (1.329 mol) of 4,4'-dicyclohexylmethane diisocyanate, 236.6 g of dipropylene glycol dimethyl ether (DMM), and 0.5 g of tetrabutoxytitanium were mixed and reacted at 78 to 90°C for 5 hours with stirring in a nitrogen atmosphere.
Next, 326.4 g of the resulting reaction mixture was taken out and added to a mixture of 641 g of water and 20.3 g (0.228 mol) of 2-dimethylaminoethanol (DMAE), and the mixture was stirred vigorously.
Thereafter, 11.9 g (0.138 mol) of piperazine was added to the resulting reaction mixture and the mixture was further reacted to obtain an aqueous polyurethane resin dispersion C. No agglomerates were observed.

(Example S4: Synthesis of aqueous polyurethane resin dispersion D)
In a reaction vessel, 380.3 g (0.388 mol) of ETERNACOLL UH100 (registered trademark; polycarbonate polyol manufactured by Ube Industries, Ltd.; number average molecular weight 980; hydroxyl value 114.5 mg KOH/g; polycarbonate polyol obtained by reacting 1,6-hexanediol with dimethyl carbonate), 67.8 g (0.505 mol) of 2,2-dimethylolpropionic acid, 382.5 g (1.458 mol) of 4,4'-dicyclohexylmethane diisocyanate, 288.4 g of dipropylene glycol dimethyl ether (DMM), and 0.1 g of dibutyltin (IV) dilaurate were mixed and reacted at 80 to 90°C for 5 hours while stirring in a nitrogen atmosphere.
Next, 392.8 g of the resulting reaction mixture was taken out and added to a mixture of 726 g of water and 23.8 g (0.267 mol) of 22-dimethylaminoethanol (DMAE), and the mixture was stirred vigorously.
Thereafter, 57.7 g (0.174 mol) of a 35% aqueous solution of 2-methyl-1,5-pentanediamine (MPMD) was added to the resulting reaction mixture and further reacted to obtain a dispersed aqueous polyurethane resin dispersion D. Some aggregates were observed.

(Example S5: Synthesis of aqueous polyurethane resin dispersion E)
In a reaction vessel, 350.6 g (0.358 mol) of ETERNACOLL UH100 (registered trademark; polycarbonate polyol manufactured by Ube Industries, Ltd.; number average molecular weight 980; hydroxyl value 114.5 mg KOH/g; polycarbonate polyol obtained by reacting 1,6-hexanediol with dimethyl carbonate), 84.6 g (0.631 mol) of 2,2-dimethylolpropionic acid, 398.1 g (1.517 mol) of 4,4'-dicyclohexylmethane diisocyanate, 250.4 g of dipropylene glycol dimethyl ether (DMM), and 0.1 g of tetrabutoxytitanium were mixed and reacted at 80 to 90°C for 5 hours with stirring in a nitrogen atmosphere.
Next, 389.2 g of the resulting reaction mixture was taken out and added to a mixture of 737 g of water and 23.6 g (0.265 mol) of 2-dimethylaminoethanol (DMAE), and the mixture was stirred vigorously.
Thereafter, 52.0 g (0.157 mol) of a 35% aqueous solution of 2-methyl-1,5-pentanediamine (MPMD) was added to the resulting reaction mixture and further reacted to obtain a dispersed aqueous polyurethane resin dispersion E. Some aggregates were observed.

(Example S6: Synthesis of aqueous polyurethane resin dispersion F)
In a reaction vessel, 422.1 g (0.422 mol) of ETERNACOLL UH100 (registered trademark; polycarbonate polyol manufactured by Ube Industries, Ltd.; number average molecular weight 999; hydroxyl value 112.3 mg KOH/g; polycarbonate polyol obtained by reacting 1,6-hexanediol with dimethyl carbonate), 49.8 g (0.371 mol) of 2,2-dimethylolpropionic acid, 302.2 g (1.152 mol) of 4,4'-dicyclohexylmethane diisocyanate, 292.2 g of dipropylene glycol dimethyl ether (DMM), and 0.7 g of dibutyltin (IV) dilaurate were mixed and reacted at 80 to 90°C for 7.5 hours with stirring in a nitrogen atmosphere.
Next, 348.2 g of the resulting reaction mixture was taken out and added to a mixture of 629 g of water and 16.4 g (0.184 mol) of 2-dimethylaminoethanol (DMAE), and the mixture was stirred vigorously.
Thereafter, 7.76 g (0.090 mol) of piperazine was added and the mixture was further reacted to obtain an aqueous polyurethane resin dispersion F. No agglomerates were observed.

(Example S7: Synthesis of aqueous polyurethane resin dispersion G)
Into a reaction vessel equipped with a stirrer, a thermometer, and a heater, 60.2 g (0.926 mol) of polytetramethylene ether glycol (PTMG, manufactured by Mitsubishi Chemical Corporation; number average molecular weight 650; hydroxyl value 172.7 mgKOH/g) (Aa2), ETRNACOLL UM90 (1/3) (registered trademark; polycarbonate polyol manufactured by Ube Industries, Ltd.; number average molecular weight 894; hydroxyl value 125.5 mg KOH/g; polycarbonate polyol obtained by reacting 1,4-cyclohexanedimethanol and 1,6-hexanediol (molar ratio 1:3) with dimethyl carbonate) 180.5 g (0.202 mol), 24.0 g (0.179 mol) of 2,2-dimethylolpropionic acid, 175.8 g (0.670 mol) of 4,4'-dicyclohexylmethane diisocyanate, 143.9 g of dipropylene glycol dimethyl ether (DMM), and 0.4 g of dibutyltin (IV) dilaurate were mixed and reacted at 78 to 90°C for 6 hours while stirring in a nitrogen atmosphere.
Next, 332.4 g of the resulting reaction mixture was taken out and added to a mixture of 642 g of water and 13.8 g (0.155 mol) of 2-dimethylaminoethanol (DMAE) that was being vigorously stirred.
Thereafter, 8.35 g (0.097 mol) of piperazine was added and the mixture was further reacted to obtain an aqueous polyurethane resin dispersion G. Some aggregates were observed.

(Example S8: Synthesis of aqueous polyurethane resin dispersion H)
Into a reaction vessel, 59.7 g (0.912 mol) of polytetramethylene ether glycol (PTMG, manufactured by Mitsubishi Chemical; number average molecular weight 650; hydroxyl value 172.7 mgKOH/g), ETRNACOLL 179.8 g (0.185 mol) of UP100 (registered trademark; polycarbonate polyol manufactured by Ube Industries, Ltd.; number average molecular weight 972; hydroxyl value 115.5 mg KOH/g; polycarbonate polyol obtained by reacting 2-methyl-1,3-propanediol with dimethyl carbonate), 23.6 g (0.176 mol) of 2,2-dimethylolpropionic acid, 167.6 g (0.639 mol) of 4,4'-dicyclohexylmethane diisocyanate, 143.1 g of dipropylene glycol dimethyl ether (DMM), and 0.3 g of dibutyltin (IV) dilaurate were mixed and reacted at 83 to 90°C for 6.5 hours with stirring in a nitrogen atmosphere.
Next, 335.9 g of the resulting reaction mixture was taken out and added to a mixture of 639 g of water and 13.8 g (0.155 mol) of 2-dimethylaminoethanol (DMAE), and the mixture was stirred vigorously.
Thereafter, 7.91 g (0.092 mol) of piperazine was added to the resulting reaction mixture and the mixture was further reacted to obtain an aqueous polyurethane resin dispersion H. No agglomerates were observed.

(Example S9: Synthesis of aqueous polyurethane resin dispersion I)
In a reaction vessel, 37.2 g (0.057 mol) of polytetramethylene ether glycol (PTMG, manufactured by Mitsubishi Chemical; number average molecular weight 650; hydroxyl value 172.7 mgKOH/g), ETERNACOLL 210.0 g (0.216 mol) of UP100 (registered trademark; polycarbonate polyol manufactured by Ube Industries, Ltd.; number average molecular weight 972; hydroxyl value 115.5 mg KOH/g; polycarbonate polyol obtained by reacting 2-methyl-1,3-propanediol with dimethyl carbonate), 22.1 g (0.165 mol) of 2,2-dimethylolpropionic acid, 137.3 g (0.618 mol) of isophorone diisocyanate, 133.0 g of dipropylene glycol dimethyl ether (DMM), and 0.3 g of dibutyltin (IV) dilaurate were mixed and reacted at 83 to 90° C. for 6.5 hours with stirring in a nitrogen atmosphere.
Next, 335.0 g of the resulting reaction mixture was taken out and added to a mixture of 640 g of water and 14.0 g (0.157 mol) of 2-dimethylaminoethanol (DMAE), and the mixture was stirred vigorously.
Thereafter, 8.22 g (0.095 mol) of piperazine was added to the resulting reaction mixture and further reacted to obtain an aqueous polyurethane resin dispersion I. No agglomerates were observed.

(Comparative Example S1: Synthesis of Aqueous Polyurethane Resin Dispersion J)
In a reaction vessel, 822.9 g (0.942 mol) of ETERNACOLL UM90 (1/3) (registered trademark; polycarbonate polyol manufactured by Ube Industries, Ltd.; number average molecular weight 873; hydroxyl value 128.5 mg KOH/g; polycarbonate polyol obtained by reacting 1,4-cyclohexanedimethanol and 1,6-hexanediol (molar ratio 1:3) with dimethyl carbonate), 122.6 g (0.914 mol) of 2,2-dimethylolpropionic acid, 800.0 g (3.049 mol) of 4,4'-dicyclohexylmethane diisocyanate, and 600.5 g of dipropylene glycol dimethyl ether (DMM) were mixed and reacted at 76 to 85 ° C. for 5 hours while stirring in a nitrogen atmosphere. The reaction mixture was cooled to 80° C., and 92.5 g (1.04 mol) of triethylamine was added thereto and mixed.
Next, 2040 g of the resulting reaction mixture was taken out and added to 2875 g of water, followed by vigorously stirring.
Thereafter, 288.5 g (0.869 mol) of a 35% aqueous solution of 2-methyl-1,5-pentanediamine (MPMD) was added to the resulting reaction mixture and further reacted to obtain an aqueous polyurethane resin dispersion J. No agglomerates were observed.

(Comparative Example S2: Synthesis of Aqueous Polyurethane Resin Dispersion K)
In a reaction vessel, 500.0 g (0.559 mol) of ETERNACOLL UM90 (1/3) (registered trademark; polycarbonate polyol manufactured by Ube Industries, Ltd.; number average molecular weight 894; hydroxyl value 125.5 mg KOH/g; polycarbonate polyol obtained by reacting 1,4-cyclohexanedimethanol and 1,6-hexanediol (molar ratio 1:3) with dimethyl carbonate), 74.9 g (0.558 mol) of 2,2-dimethylolpropionic acid, 492.4 g (1.877 mol) of 4,4'-dicyclohexylmethane diisocyanate, and 365.4 g of dipropylene glycol dimethyl ether (DMM) were mixed and reacted at 77 to 84 ° C. for 5.5 hours with stirring in a nitrogen atmosphere.
Next, 376.1 g of the resulting reaction mixture was taken out and added to a mixture of 550 g of water and 17.2 g (0.147 mol) of 2-(dimethylamino)-2-methyl-1-propanol (DMAMP), and the mixture was stirred vigorously.
Thereafter, 57.7 g (0.174 mol) of a 35% aqueous solution of 2-methyl-1,5-pentanediamine (MPMD) was added to the resulting reaction mixture and further reacted to obtain a dispersed aqueous polyurethane resin dispersion K. No agglomerates were observed.

The acid value of the polyurethane resin in the aqueous polyurethane resin dispersion obtained in the above examples and comparative examples was measured in accordance with the indicator titration method of JIS K 1557.

The main compounds and acid values used in Examples S1 to S9 and Comparative Examples S1 and S2 are shown in Table 1.

The abbreviations in the table are as follows:
H12MDI: 4,4'-dicyclohexylmethane diisocyanate IPDI: isophorone diisocyanate DMAE: 2-(dimethylamino)ethanol DMAMP: 2-(dimethylamino)-2-methyl-1-propanol MPMD: 2-methyl-1,5-pentanediamine ADH: adipic acid dihydrazide

[Production of aqueous polyurethane resin dispersion composition]
(Examples E1 and E2 and Comparative Examples E1 and E2)
An ink composition was obtained by mixing 87% by mass of the aqueous polyurethane resin dispersion obtained in Examples S1 and S2 or Comparative Examples S1 and S2, 5.2% by mass of a pigment dispersion (EMF Pink 2B-1, manufactured by Toyo Color Co., Ltd.), 0.6% by mass of a silicon-based surfactant (BYK-345, manufactured by BYK-Chemie Co., Ltd.) and 7.2% by mass of dipropylene glycol dimethyl ether (DMM, boiling point 175°C) as an additional organic solvent, relative to the total amount of the ink composition. Since dipropylene glycol dimethyl ether was the only organic solvent used, the average boiling point was 175°C.

(Comparative Example E3)
The same procedure was carried out as in Example E2, except that N-methylpyrrolidone (NMP, boiling point 202° C.) was used as the additional organic solvent. The aqueous polyurethane resin dispersion contained 7.2% by mass of dipropylene glycol dimethyl ether, and the added N-methylpyrrolidone was 7.2% by mass, so the average boiling point was 188.5° C.

(Comparative Example E4)
The same procedure was followed as in Example E2, except that 3-methoxy-N,N-dimethylamide (KJ Chemical Co., Ltd., KJCMPA (registered trademark)-100, boiling point 216°C) was used as the additional organic solvent. When calculated in the same manner as in Comparative Example 3, the average boiling point was 195.5°C.

(Examples E3 to E10)
The aqueous polyurethane resin dispersions obtained in Examples S2 to S9 were mixed at 45.5% by mass relative to the total mass of the ink composition, an acrylic resin emulsion (PEGAL 865 (registered trademark) manufactured by Koatsu Gas Kogyo Co., Ltd.) at 33.7% by mass, a pigment dispersion (EMF Pink 2B-1 manufactured by Toyo Color Co., Ltd.) at 5.5% by mass, a surfactant (BYK-345 manufactured by BYK-Chemie Co., Ltd.) at 0.6% by mass, and water at 14.7% by mass to obtain an ink composition.

[Evaluation of aqueous polyurethane dispersion and ink composition thereof]
The aqueous polyurethane dispersions and ink compositions thereof obtained in the respective Examples and Comparative Examples were measured and evaluated as follows.

(Dispersibility)
The aqueous polyurethane dispersions obtained in Examples S1 to S9 and Comparative Examples S1 and S2 were visually evaluated as follows.
◯: The urethane prepolymer was dispersed, and a good aqueous polyurethane resin dispersion was obtained.
Δ: The urethane prepolymer was dispersed and an aqueous polyurethane resin dispersion was obtained, but some aggregates were observed.
×: The urethane prepolymer was not dispersed, and an aqueous polyurethane resin dispersion was not obtained.

(Odor)
The aqueous polyurethane resin dispersions obtained in Examples S1 to S9 and Comparative Examples S1 and S2 were placed in sample bottles, which were then sealed and left to stand for at least one hour. The odor intensity felt when the lids of the filled sample bottles were opened was evaluated as follows.
Good: No amine odor is detected.
Δ: A slight amine odor is detected.
×: Amine odor is felt.

The ink compositions obtained in Examples E1 and E2 and Comparative Examples E1 to E4 were evaluated as follows.
(Water friction resistance evaluation method (1))
The ink composition was applied to a commercially available PET film using a bar coater #10 and dried at 45°C for 1 minute to produce a print. The resulting print was rubbed with an AATCC standard test cloth as a rubber, the rubber was immersed in water, and the coating surface was rubbed back and forth 10 times with a Gakushin tester (manufactured by Ohira Rika Kogyo Co., Ltd.) at a load of 400 g. The water rub resistance was evaluated based on the number of reciprocations at which the print was scratched. The evaluation criteria were as follows.
◯: The print was damaged after seven or more passes.
Δ: The print was scratched after 4 or more but less than 7 strokes.
×: The print was damaged after less than four strokes.

The results of the ink compositions, the average boiling points of the organic solvents, and the water-friction resistance evaluation (1) obtained in Examples E1 and E2 and Comparative Examples E1 to E4 are shown in Table 2. Table 2 also shows the results of the evaluation of the dispersibility and odor of the aqueous polyurethane resin dispersions used in Examples E1 to E2 and Comparative Examples E1 to E4.

The ink compositions obtained in Examples E3 to E10 were evaluated as follows.
(Water friction resistance evaluation method (2))
The ink composition was applied to a commercially available PET film using a bar coater #3 and dried at 45°C for 5 minutes to produce a print. The resulting print was rubbed with an AATCC standard test cloth as a rubber, the rubber was immersed in water, and the coating surface was rubbed back and forth 10 times with a Gakushin tester (manufactured by Ohira Rika Kogyo Co., Ltd.) at a load of 400 g. The water rub resistance was evaluated based on the number of reciprocations at which the print was scratched. The evaluation criteria were as follows.
.circle.: No scratches were observed even after 10 reciprocations.
◯: The print was damaged after six or more passes.
Δ: The print was scratched after 3 or more but less than 6 strokes.
×: The print was damaged after less than three strokes.

The ink compositions evaluated in Examples E3 to E10 and the results of the water-resistant friction evaluation (2) are shown in Table 3. The results of the evaluation of the dispersibility and odor of the aqueous polyurethane resin dispersions used in Examples E3 to E10 are also shown in Table 3.

Comparing Example E1 with Comparative Examples E1 and E2, it became clear that by using a neutralizing agent with a boiling point of 100°C or higher and 150°C or lower, odor was reduced and an aqueous polyurethane resin dispersion with excellent water abrasion resistance was obtained. In addition, comparing Example E2 with Comparative Examples E3 and E4, it became clear that by setting the average boiling point of the organic solvent to 180°C or lower, an aqueous polyurethane resin dispersion with excellent water abrasion resistance was obtained.

In addition, a comparison of Examples E3 to E6 revealed that the use of a piperazine compound or a dihydrazide compound as a chain extender resulted in an aqueous polyurethane dispersion with even better dispersibility.

In addition, when comparing Example E4 and Example E7, it became clear that by setting the acid value of the polyurethane resin to 20 to 29 mgKOH/g, an aqueous polyurethane resin dispersion with even better water-friction resistance could be obtained.

Furthermore, when Example E8 is compared with Examples E9 and E10, it becomes clear that the use of a linear and/or branched aliphatic polyol makes it possible to obtain an aqueous polyurethane resin dispersion with even better dispersibility.

According to the present invention, it is possible to further improve the working environment during the production and use of an aqueous urethane resin dispersion, and to provide an aqueous urethane resin dispersion having sufficient water resistance and dispersibility.
The aqueous urethane resin dispersion of the present invention can be used as a paint, a coating agent, or an ink.

Claims (12)

An aqueous polyurethane resin dispersion comprising a polyurethane resin having structural units derived from a polyol compound (Aa), a polyisocyanate compound (Ab), an acidic group-containing polyol compound (Ac), a neutralizing agent (Ad) and a chain extender (Ae), an organic solvent (Af) and water (Ag),
The polyol compound (Aa) contains a polycarbonate polyol compound (Aa1),
the polyisocyanate compound (Ab) is an aliphatic polyisocyanate compound and/or an alicyclic polyisocyanate compound,
The acidic group-containing polyol (Ac) is a dimethylol alkanoic acid having 4 to 12 carbon atoms,
The boiling point of the neutralizing agent (Ad) is 100° C. or higher and 150° C. or lower,
the average boiling point of the organic solvent (Af) is 150° C. or higher and 180° C. or lower, which is calculated by the formula [Σ(Tn×Rn/100)] as the sum of the products of the boiling points Tn (° C.) of each organic solvent in the organic solvent (Af) and the mass ratios Rn (mass%) of each organic solvent to the total amount of the organic solvent (Af);
The chain extender (Ae) is a piperazine compound represented by the following formula (1) or a dihydrazide compound represented by the following formula (2),
The neutralizing agent (Ad) is an amino alcohol compound represented by the following formula (3),
The organic solvent (Af) is a dialkylene glycol dialkyl ether;
An aqueous polyurethane resin dispersion (however, excluding an aqueous polyurethane resin dispersion further containing an acrylic polymer. Further, excluding an aqueous polyurethane resin dispersion containing a composite resin obtained from a urethane resin having a hydrophilic group and a vinyl polymer having a hydroxyl group).

(In the formula, R ¹ , R ² , R ³ and R ⁴ are each a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms.)

(In the formula, ^Z1 is a linear or branched alkylene group having 1 to 6 carbon atoms.)

(In the formula, ^R5 and ^R6 each represent a linear or branched alkyl group having 1 to 4 carbon atoms, and ^Z2 represents a linear or branched alkylene group having 1 to 6 carbon atoms.) The aqueous polyurethane resin dispersion according to claim 1, wherein the melting point of the chain extender (Ae) is 50°C or higher. The aqueous polyurethane resin dispersion according to claim 1 or 2, wherein the polyurethane resin has an acid value of 18 to 35 mg KOH/g. The aqueous polyurethane resin dispersion according to any one of claims 1 to 3 , wherein the polyol component of the polycarbonate polyol compound (Aa1) is a linear and/or branched aliphatic polyol. The aqueous polyurethane resin dispersion according to any one of claims 1 to 4 , wherein the polyol compound (Aa) includes a polyol compound (Aa2) other than the polycarbonate polyol compound (Aa1) and the acidic group-containing polyol (Ac). The aqueous polyurethane resin dispersion according to any one of claims 1 to 5 , wherein the polyurethane resin has a weight average molecular weight of 50,000 or more. An aqueous polyurethane resin dispersion composition comprising the aqueous polyurethane resin dispersion according to any one of claims 1 to 6 (however, excluding aqueous polyurethane resin dispersion compositions further comprising an acrylic polymer, and excluding aqueous polyurethane resin dispersion compositions further comprising a composite resin obtained from a urethane resin having a hydrophilic group and a vinyl polymer having a hydroxyl group). The aqueous polyurethane resin dispersion composition according to claim 7 , further comprising at least one selected from an olefin resin emulsion and a polyester resin emulsion. The aqueous polyurethane resin dispersion composition according to claim 7 or 8 for use in paints, coating agents or inks. (I) a step of reacting a polyol compound (Aa), a polyisocyanate compound (Ab) and an acidic group-containing polyol (Ac) in the presence of an organic solvent (Af) to obtain a polyurethane prepolymer;
(II) mixing the polyurethane prepolymer with water;
(III) neutralizing an acidic group of the polyurethane prepolymer with a neutralizing agent (Ad); and (IV) polymerizing the polyurethane prepolymer with a chain extender (Ae),
The boiling point of the neutralizing agent (Ad) used in the step (III) is 100° C. or higher and 150° C. or lower,
the average boiling point of the organic solvent (Af) is 150° C. or more and 180° C. or less, which is calculated by the formula [Σ(Tn×Rn/100)] as the sum of the products of the boiling points Tn (° C.) of each organic solvent in the organic solvent (Af) contained in the aqueous polyurethane resin dispersion and the proportions Rn (mass%) of each organic solvent in the total amount of the organic solvent (Af);
The polyol compound (Aa) contains a polycarbonate polyol compound (Aa1),
the polyisocyanate compound (Ab) is an aliphatic polyisocyanate compound and/or an alicyclic polyisocyanate compound,
The acidic group-containing polyol (Ac) is a dimethylol alkanoic acid having 4 to 12 carbon atoms,
The chain extender (Ae) is a piperazine compound represented by the following formula (1) or a dihydrazide compound represented by the following formula (2),
The neutralizing agent (Ad) is an amino alcohol compound represented by the following formula (3),
The organic solvent (Af) is a dialkylene glycol dialkyl ether;
A method for producing the aqueous polyurethane resin dispersion according to any one of claims 1 to 6 .

(In the formula, R ¹ , R ² , R ³ and R ⁴ are each a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms.)

(In the formula, ^Z1 is a linear or branched alkylene group having 1 to 6 carbon atoms.)

(In the formula, ^R5 and ^R6 each represent a linear or branched alkyl group having 1 to 4 carbon atoms, and ^Z2 represents a linear or branched alkylene group having 1 to 6 carbon atoms.) A method for producing the aqueous polyurethane resin dispersion according to claim 10 , further comprising the following step (V):
(V) A step of mixing the polyurethane prepolymer or the aqueous polyurethane resin dispersion with an organic solvent (Af). A polyurethane resin film produced from the aqueous polyurethane resin dispersion according to any one of claims 1 to 6 .