Gel compositions with depot action based on a polyurethane matrix and relatively high molecular weight polyols and containing active ingredients, and a process for their preparation

A gel containing an active ingredient comprising:

• (a) 15-62 wt. % (based on (a)+(b)) of a high molecular weight covalently cross-linked polyurethane matrix which polyurethane matrix is produced from an isocyanate and a polyol having functionalities such that the product of those functionalities is at least 5.2;
• (b) 85-38 wt. % (based on (a)+(b)) of a liquid dispersing agent which is bonded to the matrix by secondary valence forces, said dispersing agent being a polyhydroxyl compound having a molecular weight of from 1,000 to 12,000 and an OH number from 20 to 112 which dispersing agent is substantially free from hydroxyl compounds having a molecular weight below 800;
• and
• (c) 0.1-50 wt. % (based on (a)+(b)) of active ingredient.

A process for the preparation of an anhydrous polyurethane matrix gel composition containing an active ingredient comprising reacting

• (a) a diisocyanate and/or polyisocyanate with
• (b) a polyhydroxyl compound having a molecular weight of from 1,000 to 12,000 and an OH number of from 20 to 112 and being substantially free of hydroxyl compounds having a molecular weight below 800, and
• (c) 0.1 to 50 wt. % (based on (a)+(b)) of an active ingredient
• said gel composition having an isocyanate index in the range of 15 to 50 with the product of the isocyanate and hydroxyl functionalities being at least 5.2.