Rheology modifier

A process comprising contacting a solvent-free melt of a polyisocyanate branching agent;

• a water-soluble polyalkylene glycol having an Mw of from 2000 to 11,000 Daltons;
• and a diisocyanate with a polymerization promoting catalyst under conditions sufficient to form a hydrophobically modified alkylene oxide urethane polymer;
• with the proviso that either:
• 1) the solvent-free melt further includes a hydrophobic capping agent prior to contact of the melt with the catalyst;
• or 2) a hydrophobic capping agent is added to the melt after contact of the melt with the catalyst;
• wherein the molar equivalent ratio of glycol to polyisocyanate branching agent is from 4 to 20;
• and the molar equivalent ratio of total isocyanate groups to glycol hydroxyl groups is 1.1 to 1.6.