Rheology modifier

Abstract

The present invention relates to a composition comprising a hydrophobically modified alkylene oxide polyurethane characterized by having a M, of from 50,000 to about 150,000 Daltons and a polydispersity of 2.5 to about 5.0. The present invention further relates to a multi-step process for the preparation of the hydrophobically modified polymer.

1 . A process comprising the steps of:
 a) contacting a polyisocyanate branching agent with a stoichiometric excess of a water-soluble polyalkylene glycol under such conditions to form a mixture of the polyalkylene glycol and a branched poly-hydroxyalkylene oxide urethane;   b) contacting the mixture of the polyalkylene glycol and the branched poly-hydroxyalkylene oxide urethane with a difunctional linking agent selected from the group consisting of diisocyanates, epihalohydrins, and gem-dihalides, under such conditions to form a branched urethane polymer containing hydroxyl-reactive end groups; and   c) contacting the branched urethane polymer containing hydroxyl-reactive end groups with a capping agent under such conditions to form a hydrophobically modified alkylene oxide urethane, wherein the capping agent is characterized by either of the following formulas:   
       
         
           
           
               
               
           
         
       
       where R 2  is a C 4 -C 30 -alkyl, -aryl, or -aralkyl group; R 3  is H or a C 4 -C 30 -alkyl, -aryl, or -aralkyl group; R 4  is a C 4 -C 30 -alkyl, -aryl, or -aralkyl group; Y a C 2 -C 8 -alkylene group; W is N or P; x is an integer from 0 to 200; and Z is O or NH. 
     
     
         2 . The process of  claim 1  wherein the polyalkylene glycol is a polyethylene glycol having a weight average molecular weight in the range of 4000 to 20,000 Daltons. 
     
     
         3 . The process of  claim 1  wherein the polyisocyanate branching agent includes a cyanurate trimer or a biuret trimer, or a combination thereof, which trimers are characterized by the following formulas: 
       
         
           
           
               
               
           
         
       
       where R is a C 4 -C 30 -alkylene group. 
     
     
         4 . The process of  claim 1  wherein the polyisocyanate branching agent includes HDI isocyanurate (trimer) or IPDI isocyanurate (trimer) or a combination thereof and the polyethylene glycol has a weight average molecular weight in the range of 7000 to 9000 Daltons. 
     
     
         5 . The process of  claim 4  wherein the difunctional linking agent is a C 4 -C 20 -diisocyanate. 
     
     
         6 . The process of  claim 5  wherein the capping agent is a C 8 -C 20 -alcohol. 
     
     
         7 . The process of  claim 5  wherein the capping agent is a C 8 -C 20 -alcohol-C 2 -C 4 — alkoxylate. 
     
     
         8 . A process comprising the steps of:
 a) contacting HDI isocyanurate trimer with a stoichiometric excess of polyethylene glycol having a weight average molecular weight in the range of 7000 to 9000 Daltons under such conditions to form a mixture of the polyethylene glycol and a branched poly-hydroxyethylene oxide urethane;   b) contacting mixture of the polyethylene glycol and the branched poly-hydroxyethylene oxide urethane with hexamethylene diisocyanate under such conditions to form a branched urethane polymer containing isocyanate end groups; and   c) contacting the branched urethane polymer containing isocyanate end groups with a C 8 -C 20  alcohol under such conditions to form a hydrophobically modified ethylene oxide urethane.   
     
     
         9 . The process of  claim 8  wherein the capping agent is n-decanol or 2-butyl-1-octanol. 
     
     
         10 . A composition comprising a hydrophobically modified alkylene oxide polyurethane characterized by having a M w  of from 50,000 to about 150,000 Daltons and a polydispersity of 2.5 to about 5.0. 
     
     
         11 . The composition of  claim 10  wherein the hydrophobically modified alkylene oxide polyurethane is a hydrophobically modified ethylene oxide polyurethane having a M w  of from 70,000 to about 90,000 Daltons and a polydispersity of 2.9 to about 3.3. 
     
     
         12 . The composition of  claim 10  wherein the hydrophobically modified alkylene oxide polyurethane is a hydrophobically modified ethylene oxide polyurethane having a M w  of from 110,000 to about 140,000 Daltons and a polydispersity of 4.2 to about 4.6. 
     
     
         13 . The composition of  claim 10  which further includes polymer-encapsulated or partially encapsulated opacifying pigment particles.