Polyurethane aqueous dispersion, adhesive, synthetic leather and paint
There is provided an aqueous polyurethane dispersion that makes it possible to prepare an adhesive, a paint, and the like capable of forming an adhesion layer as a cured film whose physical properties such as strength are unlikely to be changed even by a change in temperature, the aqueous polyurethane dispersion having excellent storage stability. The aqueous polyurethane dispersion is an aqueous polyurethane dispersion containing: resin particles formed with a polyurethane having a hydroxy group at a terminal thereof; and water as a dispersion medium, wherein the polyurethane has a structure derived from a urethane prepolymer, the urethane prepolymer has a constituent unit derived from a polyol containing a polyether polyol; a constituent unit derived from a polyisocyanate containing an aliphatic polyisocyanate and an alicyclic polyisocyanate; and a constituent unit derived from an acidic group-containing polyol, the polyurethane has an acid value of 30 mgKOH/g or lower, the polyol further contains a polycarbonate polyol, and the mass ratio of the polyether polyol (C) to the polycarbonate polyol (D), (C):(D), is 20:80 to 95:5.
1 . An aqueous polyurethane dispersion comprising:
resin particles formed with a polyurethane having a hydroxy group at a terminal thereof; and
water as a dispersion medium,
wherein the polyurethane has a structure derived from a urethane prepolymer,
the urethane prepolymer comprises:
a constituent unit derived from a polyol, the polyol comprising:
a polyether polyol,
a polycarbonate polyol, and
an acidic group-containing polyol; and
a constituent unit derived from a polyisocyanate comprising an aliphatic polyisocyanate and an alicyclic polyisocyanate,
the polyurethane has an acid value of 30 mgKOH/g or lower,
the polyurethane has a hydroxyl value in a range from 0.5 mg/KOH/g to 35.9 mgKOH/g, and
the mass ratio of the polyether polyol (C) to the polycarbonate polyol (D), (C): (D), is in a range from 20:80 to 95:5.
2 . The aqueous polyurethane dispersion according to claim 1 , wherein
the urethane prepolymer is a reaction product having an isocyanate group at a terminal thereof, the reaction product obtained by reacting the polyisocyanate and the polyol in a ratio of an isocyanate group (NCO group) in the polyisocyanate to a hydroxy group (OH group) in the polyol, [NCO group/OH group (molar ratio)], of larger than 1, and
the polyurethane is a reaction product obtained by reacting the urethane prepolymer and an alkanolamine.
3 . The aqueous polyurethane dispersion according to claim 2 , wherein the polyurethane is a reaction product obtained by reacting 10 mol % or more of the alkanolamine based on the amount of isocyanate group in the urethane prepolymer.
4 . The aqueous polyurethane dispersion according to claim 2 , wherein the alkanolamine is an alkanolmonoamine.
5 . The aqueous polyurethane dispersion according to claim 2 , wherein the urethane prepolymer is a reaction product obtained by reacting the polyisocyanate and the polyol in a ratio of the isocyanate group (NCO group) in the polyisocyanate to the hydroxy group (OH group) in the polyol, [NCO group/OH group (molar ratio)], of larger than 1 but not exceeding 1.7.
6 . The aqueous polyurethane dispersion according to claim 1 , wherein the molar ratio of the aliphatic polyisocyanate (A) to the alicyclic polyisocyanate (B), (A): (B), is in a range from 10:90 to 90:10.
7 . The aqueous polyurethane dispersion according to claim 1 , wherein the mass ratio of the polyether polyol (C) to the polycarbonate polyol (D), (C): (D), is in a range from 25:75 to 90:10.
8 . The aqueous polyurethane dispersion according to claim 1 , wherein the resin particles have a cumulative 50% particle size (D 50 ) in a range from 5 to 500 nm in the particle size distribution on a volume basis.
9 . An adhesive comprising:
the aqueous polyurethane dispersion according to claim 1 ; and
an isocyanate-based curing agent.
10 . Synthetic leather comprising an adhesion layer formed with the adhesive according to claim 9 .
11 . A paint comprising the aqueous polyurethane dispersion according to claim 1 .