Polishing pad and method of making same

Abstract

An article or polishing pad for altering a surface of a work piece includes a polymer matrix created by reaction injection molding of size controlled gas bubbles within a polyurethane matrix. The proposed liquid urethane precursor is first injected into an actuated mold and cured. The molded product is then removed from the mold and double side faced or ground to form a single thin polishing pad comprising a single layer of homogeneous material.

1 . A nonporous polishing pad of uniform microcellular size produced by introducing a gas into a polymeric resin contained in a pressurized tank, pumping the polymeric resin and gas mixture through a fine porosity stone mixer, mixing the polymeric resin and gas mixture with an isocyanate to form a resulting mixture, and injecting the resulting mixture into a mold.  
     
     
         2 . The polishing pad of  claim 1  wherein the polymeric resin and gas mixture are pumped through an emulsifier after being pumped through the fine porosity stone mixer.  
     
     
         3 . The polishing pad of  claim 1  wherein the polymeric resin and gas mixture are passed through a homogenizing mixer after being pumped through the fine porosity stone mixer.  
     
     
         4 . The polishing pad of  claim 1  wherein the gas is introduced into the polymeric resin through a sparging tube contained within the pressurized tank.  
     
     
         5 . The polishing pad of  claim 4  wherein the polymeric resin and gas mixture are pumped through an emulsifier after being pumped through the fine porosity stone mixer.  
     
     
         6 . The polishing pad of  claim 4  wherein the polymeric resin and gas mixture are passed through a homogenizing mixer after being pumped through the fine porosity stone mixer.  
     
     
         7 . The polishing pad of  claim 1  wherein the polymeric resin and gas mixture are recirculated through the pressurized tank, containing a mixer, and the fine porosity stone mixer prior to mixing the polymeric resin and gas mixture with the isocyanate.  
     
     
         8 . The polishing pad of  claim 1  wherein the uniform microcellular structure comprises a closed cell membrane having an average cell diameter within a range of about 0.05 to 100 micrometers.  
     
     
         9 . The polishing pad of  claim 8  wherein the average cell diameter comprises a range of about 0.05 to 30 micrometers.  
     
     
         10 . The polishing pad of  claim 1  wherein a surface material of the pad has a low coefficient of friction.  
     
     
         11 . The polishing pad of  claim 1  wherein the polymeric matrix formed from the resulting mixture comprises at least one of a polyurethane, a polyester, a polysulfone, and a polyvinyl acetate.  
     
     
         12 . The polishing pad of  claim 1  wherein said polymeric resin includes glycol as a catalyst.  
     
     
         13 . The polishing pad of  claim 1  wherein said polymeric resin comprises at least one of a polyurethane, a polyglycol, a polyether polyol, a polymer polyol, an aliphatic polyester polyol, an aromatic polyester polyol, a PTMEG, a PTHF, a castor oil based polyol, a polycaprolactone polyol, a hydroxyl terminated polybutadiene, an acrylic polyol, and a polyamine.  
     
     
         14 . The polishing pad of  claim 1  further comprising a porous transparent portion or porous translucent portion that is added to the pad subsequent to molding the pad.  
     
     
         15 . The polishing pad of  claim 1  further comprising grooves formed in a surface of the pad.  
     
     
         16 . The polishing pad of  claim 1  wherein the gas comprises at least one of an inert gas, a reactive gas, and a reductive gas.  
     
     
         17 . The polishing pad of  claim 16  wherein the gas comprises at least one of a dry air, an argon gas, a dry nitrogen gas, and a dry oxygen gas.  
     
     
         18 . The polishing pad of  claim 1  further comprising at least one of a surfactant and an ultraviolet stabilizer.  
     
     
         19 . A nonporous polishing pad of uniform microcellular size produced by introducing a gas into a polymeric resin through a recirculating pump which pumps the polymeric resin and gas mixture through a fine porosity stone mixer, mixing the polymeric resin and gas mixture with an isocyanate to form a resulting mixture, and injecting the resulting mixture into a mold.  
     
     
         20 . The polishing pad of  claim 19  wherein the polymeric resin and gas mixture are pumped through an emulsifier after being pumped through the fine porosity stone mixer.  
     
     
         21 . The polishing pad of  claim 19  wherein the polymeric resin and gas mixture are passed through a homogenizing mixer after being pumped through the fine porosity stone mixer.  
     
     
         22 . The polishing pad of  claim 19  wherein the polymeric resin and gas mixture are recirculated through a pressurized tank having a mixer and the fine porosity stone mixer prior to mixing the polymeric resin and gas mixture with the isocyanate.  
     
     
         23 . The polishing pad of  claim 19  wherein the uniform microcellular structure comprises a closed cell membrane having an average cell diameter within a range of about 0.05 to 100 micrometers.  
     
     
         24 . The polishing pad of  claim 23  wherein the average cell diameter comprises a range of about 0.05 to 30 micrometers.  
     
     
         25 . The polishing pad of  claim 19  wherein a surface material of the pad has a low coefficient of friction.  
     
     
         26 . The polishing pad of  claim 19  wherein the polymeric matrix formed from the resulting mixture comprises at least one of a polyurethane, a polyester, a polysulfone, and a polyvinyl acetate.  
     
     
         27 . The polishing pad of  claim 19  wherein said polymeric resin includes glycol as a catalyst.  
     
     
         28 . The polishing pad of  claim 19  wherein said polymeric resin comprises at least one of a polyurethane, a polyglycol, a polyether polyol, a polymer polyol, an aliphatic polyester polyol, an aromatic polyester polyol, a PTMEG, a PTHF, a castor oil based polyol, a polycaprolactone polyol, a hydroxyl terminated polybutadiene, an acrylic polyol, and a polyamine.  
     
     
         29 . The polishing pad of  claim 19  further comprising a porous transparent portion or a porous translucent portion that is added to the pad subsequent to molding the pad.  
     
     
         30 . The polishing pad of  claim 1   9  further comprising grooves formed in a surface of the pad.  
     
     
         31 . The polishing pad of  claim 19  wherein the gas comprises at least one of an inert gas, a reactive gas, and a reductive gas.  
     
     
         32 . The polishing pad of  claim 31  wherein the gas comprises at least one of a dry air, an argon gas, a dry nitrogen gas, and a dry oxygen gas.  
     
     
         33 . The polishing pad of  claim 19  further comprising at least one of a surfactant and an ultraviolet stabilizer.  
     
     
         34 . A method for making a nonporous polishing pad of uniform microcellular size comprising the steps of: 
 providing a polymeric resin contained in a pressurized tank having a mixer;    introducing a gas into the polymeric resin;    pumping the polymeric resin and gas mixture through a fine porosity stone mixer;    mixing an isocyanate into the polymeric resin and gas mixture to form a resulting mixture; and    injecting the resulting mixture into a mold.    
     
     
         35 . The method of  claim 34  further comprising the steps of: 
 removing a formed pad from the mold; and    grinding or facing at least one side of the pad to a desired thickness.    
     
     
         36 . The method of  claim 34  further comprising the step of forming a window in the pad.  
     
     
         37 . The method of  claim 36  wherein said window is formed by removing a portion of the pad and filling an opening created by the removed portion with a liquid polyurethane material that solidifies as a transparent portion or translucent portion of the pad.  
     
     
         38 . The method of  claim 36  wherein said window is formed by removing a portion of the pad and filling an opening created by the removed portion with a solid transparent portion or translucent portion that is bonded to the pad.  
     
     
         39 . The method of  claim 34  wherein the mold is an actuated mold which undergoes a reaction injection molding process.  
     
     
         40 . The method of  claim 34  wherein an average cell size of the pad is controlled by applying a plurality of shearing forces to the polymeric resin and gas mixture prior to adding the isocyanate.  
     
     
         41 . A method for making a nonporous polishing pad of uniform microcellular size comprising the steps of: 
 providing a polymeric resin contained in a pressurized tank having a mixer;    introducing a gas into the polymeric resin through a recirculating pump contained outside of the pressurized tank;    pumping the polymeric resin and gas mixture through a fine porosity stone mixer with the recirculating pump;    mixing an isocyanate into the polymeric resin and gas mixture to form a resulting mixture; and    injecting the resulting mixture into a mold.    
     
     
         42 . The method of  claim 41  further comprising the steps of: 
 removing a formed pad from the mold; and    grinding or facing at least one side of the pad to a desired thickness.    
     
     
         43 . The method of  claim 41  further comprising the step of forming a window in the pad.  
     
     
         44 . The method of  claim 43  wherein said window is formed by removing a portion of the pad and filling an opening created by the removed portion with a liquid polyurethane material that solidifies as a transparent or translucent portion of the pad.  
     
     
         45 . The method of  claim 43  wherein said window is formed by removing a portion of the pad and filling an opening created by the removed portion with a solid transparent portion or translucent portion that is bonded to the pad.  
     
     
         46 . The method of  claim 41  wherein the mold is an actuated mold which undergoes a reaction injection molding process.  
     
     
         47 . The method of  claim 41  wherein an average cell size of the pad is controlled by applying a plurality of shearing forces to the polymeric resin and gas mixture prior to adding the catalyst.  
     
     
         48 . The polishing pad of  claim 1  wherein the polymeric resin and gas mixture are directed through a high shear cavitation device prior to adding the isocyanate.  
     
     
         49 . The polishing pad of  claim 19  wherein the polymeric resin and gas mixture are directed through a high shear cavitation device prior to adding the isocyanate.  
     
     
         50 . The polishing pad of  claim 1  further comprising hardware incorporated into the polishing pad during the molding process, or after the molding process by machining away a portion of the pad.  
     
     
         51 . The polishing pad of  claim 19  further comprising hardware incorporated into the polishing pad during the molding process, or after the molding process by machining away a portion of the pad.  
     
     
         52 . The method of  claim 34  further comprising the step of incorporating hardware into the polishing pad during the molding process, or after the molding process by machining away a portion of the pad.  
     
     
         53 . The method of  claim 40  further comprising the step of incorporating hardware into the polishing pad during the molding process, or after the molding process by machining away a portion of the pad.