Cellular structures and viscoelastic polyurethane foams

Abstract

The present invention discloses a structure comprising a plurality of three dimensional cells, wherein each cell comprises exterior walls defining an interior void wherein the walls comprise a plurality of struts and windows, the struts forming borders for the plurality of windows, wherein the struts have a plurality of pores. The present invention further discloses a viscoelastic foam having a ratio of elastic modulus (E′) at 20° C. to 25% compression force deflection (CFD) of 25 to 125.

1 . A viscoelastic foam having a ratio of elastic modulus (E′) at 20° C. to 25% compression force deflection (CFD) of 25 to 125. 
     
     
         2 . The foam of  claim 1  wherein the air flow as measured by ASTM D-3574 Test G is greater than 2 scfm. 
     
     
         3 . The foam of  claim 1  or  2  wherein the foam has a tan delta greater than 0.3 over the temperature range of 0 to 40 C.°. 
     
     
         4 . The foam of  claim 3  wherein the foam exhibits a resiliency of no greater than 20% as measured according to the ATSM D-3574-H ball rebound test. 
     
     
         5 . A polyol composition comprising:
 a1) from 30 to 80 weight percent of at least one polyoxypropylene or a polyoxyethylene-polyoxypropylene polyol,   having an average equivalent weight between 100 and 2000   and an average nominal hydroxy functionality of 2-4,   with the proviso if the polyol is a polyoxyethylene-polyoxypropylene polyol, the polyoxypropylene content is at least 70% by weight of the polyol;   a2) from 5 to 50 weight percent of a polyoxyethylene or a a polyoxyethylene-polyoxypropylene polyol,   having an average equivalent weight between 100 and 1000;   and an average nominal hydroxy functionality of 2-4,   with the proviso if the polyol is a polyoxyethylene-polyoxypropylene polyol, the polyoxyethylene content is at least 70% by weight of the polyol; and   a3) from 1 to 20 wt % of a monol or blend of monols having an average equivalent weight of 500 or greater wherein the monol or blend of monol comprises >60% by weight of a polyoxyalkylene wherein the alkylene oxide contains 4 or more carbon atoms;   a polyoxyalkylene polyol having a functionality of 2 to 4, an equivalent weight of 500 to 3000 wherein the alkylene oxide contains greater than 60% by weight of alkylene oxides having 4 or more carbon atoms;   is a polybutadiene having an equivalent weight of 2250 to 6000.   or a combination thereof.   
     
     
         6 . The composition of  claim 5  wherein the polyol a1) comprises two separate polyols a1a) having an equivalent weight of 200 to 700, and a1b) having an equivalent weight of greater than 700. 
     
     
         7 . The polyol composition of  claim 5  or  claim 6  wherein the polyoxypropylene content based on a1a) and a1b) is at least 75 wt percent. 
     
     
         8 . The polyol composition of  claim 7  wherein the polyoxypropylene content based on a1a) and a1b) is at least 85 wt percent. 
     
     
         9 . The polyol composition of any one of  claims 5  to  8  wherein component a30 is a monol derived from a alkylene oxide having 4 to 20 carbon atoms and the monol has a molecular weight of 1,000 to 7,000 daltons. 
     
     
         10 . The polyol composition of any one of  claims 5  to  8  wherein the component a3) is polybutadiene having an equivalent weight of 2200 to 5500. 
     
     
         11 . A reaction system for the preparation of a viscoelastic polyurethane foam, comprising:
 a) a polyol composition of any one of  claims 5  to  10 ;   b) a polyisocyanate composition;   c) from 0.5 to 3.5 wt % of water based on the total weight of a) and optionally d) additives and auxiliaries known per se   wherein the isocyanate index is from 70 to 115.   
     
     
         12 . The reaction system of  claim 11  wherein the polyisocyanate is a blend of TDI 2,4- and 2,6-isomers. 
     
     
         13 . The reaction system of  claim 11  wherein the polyisocyanate has a number average functionality of isocyanate groups of greater than 2.1 and consists predominantly, on a weight bases, of one or more polyisocyanates of the MDI series. 
     
     
         14 . The reaction system of any one of  claims 11  to  13  wherein the composition further comprises e) an amount of an additive sufficient to reduce the blow-off time of the reaction mixture, wherein the additive is selected from
 1) alkali metal or transition metal salts of carboxylic acids; 
 2) 1,3,5-tris alkyl- or 1,3,5-tris (N,N-dialkyl amino alkyl)-hexahydro-s-triazine compounds; and 
 3) carboxylate salts of quaternary ammonium compounds, 
 
       wherein said additive is dissolved in at least one other component of the reaction mixture. 
     
     
         15 . A viscoelastic polyurethane material produced from the reaction system of any one of  claims 11  to  14 . 
     
     
         16 . The viscoelastic polyurethane foam of  claim 15  wherein the foam exhibits a resiliency of no greater than 15% as measured according to ASTM D-3574-H ball rebound test. 
     
     
         17 . A process for preparing a viscoelastic polyurethane foam, comprising
 A) forming a reaction mixture including at least   a) an isocyanate reactive component comprising the polyol composition of any one of  claims 6  to  14 ;   b) at least one polyisocyanate,   c) water in an amount of 0.5 to 3.5 weight percent of a), and   d) optional additives and auxiliaries known per se; and   B) subjecting the reaction mixture to conditions sufficient to cause the reaction mixture to expand and cure to form a viscoelastic polyurethane foam.   
     
     
         18 . A structure comprising a plurality of three dimensional cells, wherein each cell comprises exterior walls defining an interior void wherein the walls comprise a plurality of struts and windows, the struts forming borders for the plurality of windows, wherein the struts have a plurality of pores. 
     
     
         19 . The structure of  claim 18  wherein greater than 50% of the windows are open. 
     
     
         20 . The structure of  claim 18  or  19  wherein the pores have a width of less than 90 μm.