A reduction in the viscosity is achieved and improvements in the storage stability and the heat resistance of the coating film are achieved.

An aqueous dispersion of a polyurethane resin according to an embodiment is obtained by a reaction of a polyol (A), a polyisocyanate (B), and a chain extender (C). The polyol (A) includes an aromatic polyester polyol (A1), and an aliphatic diol (A2) having a hydrocarbon group in a side chain. The chain extender (C) includes a compound (C1) having three primary and/or secondary amino groups and not having hydroxy groups, and a compound (C2) having one or more hydroxy groups and two or more primary and/or secondary amino groups. The acid value is 11.0 to 23.0 mgKOH/g and the hydroxyl value is 8.0 to 23.0 mgKOH/g.

The present disclosure provides a method of preparing a bio-based waterborne polyurethane intermediate. The method comprises the following steps: (a) mixing bio-based isocyanate compound, sorbitol, fatty acid-substituted glycolipid, dihydroxyl-terminated polydialkylsiloxane, and a solvent; (b) adding a first initiator to a mixture of step (a) to carry out polymerization; and (c) adding water, an emulsifier, and acetic acid to the product of step (b) to form the bio-based waterborne polyurethane intermediate. The present disclosure also provides a method of preparing a bio-based polyurethane-acrylic hybrid fluorine-free water repellent. The bio-based polyurethane-acrylic hybrid fluorine-free water repellent is derived from aforesaid bio-based waterborne polyurethane intermediate and an acrylic-based fluorine-free water repellent.