Froth and method of producing froth

Abstract

Foam for making pads and belts with controlled, reproducible microcellular structure and method of making such foam in a fast and efficient manner. Under constant pressure and temperature, a prepolymer is mixed with the nucleation surfactant in a tank in the presence of a frothing agent metered into the tank by way of a dip tube or sparge. The nitrogen gas is sheared into small bubbles and is drawn off from the headspace of the tank creating a continuous flow of nitrogen. The pressure of the tank may vary from any absolute pressure down to near complete vacuum, thereby all but eliminating the pressure requirement. The froth of the present invention has a more consistent cell structure and increased cell count.

1 - 24 . (canceled) 
     
     
         25 . A method of producing a high density, microcellular pad or belt composing the steps of placing a thermosetable liquid polymer or prepolymer resin and nucleation surfactant in at least one tank, agitating said thermosetable liquid polymer or prepolymer resin and nucleation surfactant through the use of at least one impeller, metering a frothing agent into said tank by way of a tube or sparge located below said impeller, drawing off said frothing agent from the headspace of said tank so as to reach a steady state of continuous flow of the frothing agent from below said impeller to said headspace of said tank, metering the resin froth under pressure to a mix head, combining the resin froth with a curative, and injecting or pouring the resin froth into a mold; said pad or belt being free of hollow microelements or microballoons. 
     
     
         26 . The method of  claim 25 , wherein a catalyst is added to said curative or said froth prior to entering said mold. 
     
     
         27 . The method of  claim 25 , wherein a blowing agent is added to said curative or said froth prior to entering said mold. 
     
     
         28 . The method of  claim 25 , wherein said froth is metered into a mixhead at a pressure ranging from atmospheric to 200 psi. 
     
     
         29 . A method of making high density foam with controlled, reproducible microcellular structure by mechanical frothing, comprising agitating a liquid polymer resin in the presence of a frothing agent and nucleation surfactant at a controlled temperature and any absolute pressure in order to produce a stable froth, metering the resin froth under pressure to a mixhead, optionally combining the resin froth with a curative for the resin, and injecting or pouring the resin froth into a mold. 
     
     
         30 . The method of  claim 29 , wherein the resin is a thermoset polymer. 
     
     
         31 . The method of  claim 29 , wherein the resin is a polyurethane. 
     
     
         32 . The method of  claim 29 , wherein the nucleation surfactant is a block copolymer containing at least one block comprising polydimethylsiloxane, and at least one other block comprising polyether, polyester, polyamide, or polycarbonate segment. 
     
     
         33 . The method of  claim 29 , wherein the nucleation surfactant is a block copolymer containing at least one block comprising siloxane polyalkyleneoxide, and at least one block comprising polyether, polyester, polyamide, or polycarbonate segment. 
     
     
         34 . A froth for producing microcellular pads and belts with consistent cell structures or properties, comprising a polymer or thermosetable polymer, a nucleation surfactant, and a frothing agent, wherein said froth is free of hollow polymeric microelements or microballoons. 
     
     
         35 . The froth of  claim 34  wherein said nucleation surfactant is a block copolymer containing at least one block comprising polydimethylsiloxane or siloxane polyalkyleneoxide, and at least one other block comprising polyether, polyester, polyamide, or polycarbonate. 
     
     
         36 . The froth of  claim 34 , wherein said polymer resin is a polyurethane. 
     
     
         37 . The froth of  claim 34 , wherein said froth has a specific gravity within the range of 0.7-1.0 g/cc. 
     
     
         38 . The froth of  claim 34 , wherein said froth has a specific gravity within the range of 0.8-0.95 g/cc. 
     
     
         39 . A high density microcellular pad or belt with consistent cell structures, comprising a polymer or thermosetable polymer, a nucleation surfactant, and a frothing agent, wherein said froth is free of hollow polymeric microelements or microballoons. 
     
     
         40 . The pad or belt of  claim 39 , wherein said nucleation surfactant is a block copolymer containing at least one block comprising polydimethylsiloxane or siloxane polyalkyleneoxide, and at least one other block comprising polyether, polyester, polyamide, or polycarbonate. 
     
     
         41 . The pad or belt of  claim 39 , wherein said polymer resin is a polyurethane. 
     
     
         42 . The pad or belt of  claim 39 , wherein said pad or belt has a specific gravity within the range of 0.5-1.2 g/cc. 
     
     
         43 . The pad or belt of claim  3 , wherein said pad or belt has a specific gravity within the range of 0.7-1.0 g/cc. 
     
     
         44 . The pad or belt of  claim 39 , wherein said pad or belt has a specific gravity within the range of 0.85-0.95 g/cc. 
     
     
         45 . The pad or belt of  claim 39 , wherein said pad or belt has open-called structures.