The present invention provides a powdered polycarbodiimide compound which can improve the hydrolytic resistance of an ester resin, hardly causes an increase in viscosity when added to and mixed with the ester resin, and has high handling properties, and an ester resin composition comprising the same. The powdered polycarbodiimide compound according to the present invention is represented by the following formula (1), and has a melting point of 50° C. or more:

##STR00001##

wherein R.sup.1 and R.sup.2 each represent a residue of an organic compound (excluding ethanol) having one functional group reactive with an isocyanate group, wherein the functional group is removed from the organic compound; R.sup.3 represents a divalent residue of a diisocyanate compound from which two isocyanate groups are removed; the diisocyanate compound has a hydrocarbon group which directly bonds to the two isocyanate groups; R.sup.4 represents a divalent residue of a diol compound from which two hydroxyl groups are removed; X.sup.1 and X.sup.2 each represent a bond formed by a reaction of the functional group with the isocyanate group; m and n each represent a number of 1 to 20; and p represents a number of 2 to 20.

Provided is a carbodiimide-based, waterborne resin crosslinking agent that can improve the storage stability of a waterborne resin composition including a waterborne resin together with the crosslinking agent and further also improve the water resistance and the solvent resistance of a cured product of the waterborne resin. A waterborne resin crosslinking agent-containing liquid and a waterborne resin composition are prepared using a waterborne resin crosslinking agent comprising a hydrophobic polycarbodiimide compound and a water-soluble organic compound as blending components, wherein the water-soluble organic compound is one or more selected from the group consisting of an alkylene glycol-based compound, a water-soluble polymer other than the alkylene glycol-based compound, and a surfactant other than the alkylene glycol-based compound or the water-soluble polymer.

Provided are a carbodiimide-based, waterborne resin crosslinking agent that not only is excellent in the storage stability when the crosslinking agent and a waterborne resin are caused to coexist, but also can improve physical properties such as solvent resistance and water resistance of a cured product of the waterborne resin, and a waterborne resin crosslinking agent-containing liquid and a waterborne resin composition comprising the same. The waterborne resin crosslinking agent of the present invention comprises a predetermined polycarbodiimide compound (A) having an oxyalkylene group, a predetermined polycarbodiimide compound (B), and a surfactant (C), each polycarbodiimide compound has a structure in which an isocyanate group is capped with a predetermined end-capping compound at each of both terminals, a total content of the oxyalkylene group in (A) is 15% by mass or more, a total content of the oxyalkylene group in (A) and (B) based on a total amount of (A) and (B) is 10% by mass or less, and a content of (C) is 0.1 to 20 parts by mass based on a total content of (A) and (B) of 100 parts by mass.

Provided is a waterborne resin crosslinking agent and the like capable of inhibiting lowering of gloss (relative specular glossiness) of cured films (waterborne resin coating films) after heating. The waterborne resin crosslinking agent includes a polycarbodiimide compound (A) and a polycarbodiimide compound (B); the polycarbodiimide compound (A) has a structure in which isocyanate groups at both terminals are each capped with a hydrophilic organic compound, and at least one of the hydrophilic organic compounds has a molecular weight of 340 or more; the polycarbodiimide compound (B) has a structure in which isocyanate groups at both terminals are each capped with a monool compound having 3 to 18 carbon atoms; when the monool compound has 3 to 17 carbon atoms, the polycarbodiimide compound (A) is in an amount of 5 to 95 parts by mass per 100 parts by mass in total of the polycarbodiimide compound (A) and the polycarbodiimide compound (B); and when the monool compound has 18 carbon atoms, the polycarbodiimide compound (A) is in an amount of 30 to 70 parts by mass per 100 parts by mass in total of the polycarbodiimide compound (A) and the polycarbodiimide compound (B).

A waterborne resin crosslinking agent is provided, wherein the waterborne resin crosslinking agent of the present invention includes a polycarbodiimide compound (A) and a polycarbodiimide compound (B); the polycarbodiimide compound (A) has a structure in which the isocyanate groups at both terminals are each capped with a predetermined hydrophilic organic compound; the polycarbodiimide compound (B) has a chain diisocyanate compound as a structural unit, and has a structure in which the isocyanate groups at both terminals are each capped with a predetermined organic compound, and the polycarbodiimide compound (A) is in an amount of 5 to 90 parts by mass per 100 parts by mass in total of the polycarbodiimide compounds (A) and (B).

Provided is a waterborne resin crosslinking agent, as well as a waterborne resin crosslinking agent-containing liquid and a waterborne resin composition, including the waterborne resin crosslinking agent. The waterborne resin crosslinking agent of the present invention includes a polycarbodiimide compound (A) and a polycarbodiimide compound (B); the polycarbodiimide compound (A) has a structure in which the isocyanate groups at both terminals are each capped with a predetermined hydrophilic organic compound; the polycarbodiimide compound (B) has, as a structural unit, a diisocyanate compound having one cyclohexyl ring or one benzene ring, and has a structure in which the isocyanate groups at both terminals are each capped with a predetermined organic compound, and the polycarbodiimide compound (A) is in an amount of 5 to 90 parts by mass per 100 parts by mass in total of the polycarbodiimide compounds (A) and (B).

A fluorine-free composition includes at least one polycarbodiimide compound derived from a carbodiimidization reaction of a carbodiimidization reaction mixture comprising at least one oligomer, wherein the oligomer comprises at least one isocyanate end group and at least two repeating units, wherein each of the at least two repeating units comprises at least one hydrocarbon group having at least 16 carbon atoms. The composition may also include at least one paraffin wax. Such compositions are useful for treating fibrous substrates to enhance their water-repellency.

The polycarbodiimide composition is a reaction product of polyisocyanate having a primary isocyanate group with alcohol, wherein the alcohol contains at least one oxyethylene-containing alcohol containing an oxyethylene group, and at least one oxyethylene-noncontaining alcohol containing no oxyethylene group, the at least one oxyethylene-noncontaining alcohol has a solubility parameter of 11.20 (cal/cm.sup.3).sup.1/2 or less.

Phenyl isocyanates are removed from a solvent stream obtained from an MDI and/or PMDI manufacturing process by reaction in the presence of a carbodiimidization catalyst to form the corresponding N,N-diphenylcarbodiimides. The N,N-diphenylcarbodiimides can be recycled into the MDI and/or PMDI manufacturing process where they can react with MDI and/or PMDI to form uretonimines. The uretonimines have at most minimal effect on the properties and usefulness of the MDI and/or PMDI product and so can be left in the MDI and/or PMDI product.

A fluorine-free composition includes at least one polycarbodiimide compound derived from a carbodiimidization reaction of a carbodiimidization reaction mixture comprising at least one oligomer, wherein the oligomer comprises at least one isocyanate end group and at least two repeating units, wherein each of the at least two repeating units comprises at least one hydrocarbon group having at least 16 carbon atoms. The composition may also include at least one paraffin wax. Such compositions are useful for treating fibrous substrates to enhance their water-repellency.