Methods for making a light transmissive foamed polymer sheet

Abstract

In some embodiments, a foamed polymer sheet comprises: a polymeric material and cells located in the polymeric material. The cells have a size distribution, D 90 of greater than or equal to 300 μm and the sheet has a light transmission of greater than or equal to about 5%. In another embodiment, the cells have an average diameter, as measured along a major axis, of about 1 mm to about 4 mm, and the sheet has a light transmission of greater than or equal to about 5%. In another embodiment, a method of making a foamed polymeric sheet comprises: combining a blowing agent with a polymeric material to form a mixture, nucleating bubbles in the mixture, and cooling the mixture. The mixture is at a sufficient temperature and the cells have a sufficient cell size such that the sheet has a light transmission of greater than or equal to 10%.

1 . A method of making a foamed polymeric sheet, comprising:
 melting a polymeric material;   combining a blowing agent with the polymeric material to form a mixture in an extruder;   inhibiting foaming prior to exiting the extruder;   nucleating bubbles in the mixture, wherein the mixture is at a sufficient temperature to enable production of cells having a cell size distribution, D 90  of about 0.3 mm to about 2.5 mm; and   forming the mixture into a sheet having a first side and a second side;   wherein the sheet has a light transmission of greater than or equal to 5%.   
     
     
         2 . The method of  claim 1 , wherein the sheet has a density of less than or equal to about 600 kg/m 3 . 
     
     
         3 . The method of  claim 1 , wherein the sufficient temperature of the cooling part of the extruder is about 180° C. to about 260° C. 
     
     
         4 . The method of  claim 3 , wherein the sufficient temperature is about 180° C. 
     
     
         5 . The method of  claim 1 , wherein an amount of blowing agent combined with the polymeric material is about 0.5 wt % to about 5 wt %, based upon a total weight of the mixture. 
     
     
         6 . The method of  claim 5 , further comprising forming a first cap layer on the first side and a second cap layer on the second side, and wherein the first cap layer and/or the second cap layer is co-extruded with the sheet. 
     
     
         7 . The method of  claim 6 , wherein the polymeric material is polycarbonate. 
     
     
         8 . The method of  claim 1 , wherein an amount of blowing agent combined with the polymeric material is about 0.5 wt % to about 4 wt % CO 2 , and about 0.25 wt % to about 2 wt % of a different blowing agents, wherein weight percent is based upon a total weight of the mixture. 
     
     
         9 . The method of  claim 1 , further comprising combining a nucleating agent with the polymeric material, wherein the nucleating agent is selected from the group consisting of talc, glass-fibers, fumed silica, titanium dioxide, a citric acid and sodium bicarbonate mixture, zinc oxide, and combinations comprising at least one of the foregoing. 
     
     
         10 . The method of  claim 9 , wherein the nucleating agent comprises talc. 
     
     
         11 . The method of  claim 1 , wherein the blowing agent is selected from the group consisting of pentane, butane, ethanol, IPA, acetone, CO 2 , N 2 , ammonia gas, and combinations comprising at least one of the foregoing. 
     
     
         12 . The method of  claim 1 , wherein the light transmission is greater than or equal to 10%. 
     
     
         13 . The method of  claim 1 , wherein forming the mixture into a sheet comprises forming the mixture into a multiwall sheet. 
     
     
         14 . A method of making a foamed polymeric sheet, comprising:
 combining a blowing agent with a polymeric material to form a mixture;   nucleating bubbles in the mixture to form cells; and   cooling the mixture between calibration plates to produce the foamed polymeric sheet;   wherein the mixture is at a sufficient temperature and the cells have a sufficient cell size such that the foamed polymeric sheet has a light transmission of greater than or equal to 10%.   
     
     
         15 . A method of making a foamed polymeric sheet, comprising:
 melting a polymeric material;   combining a blowing agent with the polymeric material to form a mixture in an extruder;   inhibiting foaming prior to exiting the extruder;   nucleating bubbles in the mixture, wherein the mixture is at a sufficient temperature to enable production of cells having a cell size, as measured along a major axis, of 1 mm to 1.5 mm; and   forming the mixture into a sheet having a first side and a second side;   forming a first cap layer on the first side and a second cap layer on the second side;   wherein the sheet has a light transmission of greater than or equal to 5%.   
     
     
         16 . The method of  claim 15 , wherein the first cap layer and/or the second cap layer is co-extruded with the sheet. 
     
     
         17 . The method of  claim 16 , wherein the light transmission is greater than or equal to 10%. 
     
     
         18 . The method of  claim 16 , wherein the first cap layer and/or the second cap layer comprises a UV absorber 
     
     
         19 . The method of  claim 15 , wherein the polymeric material is polycarbonate.