Process for the preparation of dispersions of cross-linking agents in water

A method for preparing a stable aqueous polycarbodiimide dispersions, comprising the steps of:

• (1) reacting a polyisocyanate at 120-180° C. in the presence of 0.5-5% of a carbodiimide catalyst, to form an isocyanate functionalized polycarbodiimide with a mean value of 1-10 carbodiimide functions, wherein
• the isocyanate functionalized polycarbodiimide contains 5-30% by weight of a mono- or polyisocyanate comprising a hydrophobic group, wherein
• the mono- or polyisocyanate contributes to the formation of the isocyanate functionalized polycarbodiimide, and wherein
• the hydrophobic group is selected from the group consisting of a hydrocarbon containing 4-25 carbon atoms, a fluorinated hydrocarbon, a silicone functionalized hydrocarbon and a polysilicone,
• (2) terminating chain extending the isocyanate functionalized polycarbodiimide chain or terminating and extending said chain by adding 0.1 to 1.0 equivalent, with respect to the number of isocyanate functions in the isocyanate functionalized polycarbodiimide, of a first compound having a first isocyanate reactive group, the first compound comprising
• a hydrophilic group and one or more groups selected from amine and hydroxy functions, together with or followed by
• capping any remaining isocyanate functions with a second compound having a second isocyanate reactive group, the second compound comprising
• one or more groups selected from amine and hydroxy functions and optionally, a hydrophobic group, wherein
• the hydrophobic group is selected from the group consisting of a hydrocarbon containing 4-25 carbon atoms, a fluorinated hydrocarbon, a silicone functionalized hydrocarbon and a polysilicone, and
• dispersing the resulting compound in water to form an aqueous polycarbodiimide dispersion;
• and
• (3) adjusting the pH of the aqueous polycarbodiimide dispersion to 9-14 by adding a base or a buffer to the water during or after dispersing step (2).