Process for forming closed cell expanded low density polyethylene foam and products formed thereby

Abstract

The process for forming closed cell expanded low density polyethylene foam includes the steps of: providing a mixture including low density polyethylene pellets and an effective amount of hydrocarbon scavenger additives or degassing agents, such as glycerides; adding a primary blowing agent comprising one of liquid propane, liquid butane, and combinations thereof, to the mixture and gasifying the blowing agent to expand the low density polyethylene; forming the expanded low density polyethylene into sheets, curing the expanded low density polyethylene until 80%, generally at least 99%, of the primary blowing agent is dissipated from cells within the expanded low density polyethylene forming evacuated closed cell low density polyethylene sheets.

What is claimed is: 
     
         1 . A process of forming low density expanded polyethylene foam comprising the steps of:
 providing a mixture including low density polyethylene pellets and an effective amount of glycerides as a degassing agent;   adding a primary blowing agent comprising one of liquid propane, liquid butane, and combinations thereof, to the mixture and gasifying the blowing agent to expand the low density polyethylene;   forming the expanded low density polyethylene into sheets,   curing the expanded low density polyethylene until 80% of the primary blowing agent is dissipated from cells within the expanded low density polyethylene forming closed cell low density polyethylene sheets.   
     
     
         2 . The process of forming low density expanded polyethylene foam according to  claim 1  wherein at least 95% of the primary blowing agent is dissipated from cells within the expanded low density polyethylene before closed cell low density polyethylene sheets are subsequently processed. 
     
     
         3 . The process of forming low density expanded polyethylene foam according to  claim 1  wherein at least 99% of the primary blowing agent is dissipated from cells within the expanded low density polyethylene before closed cell low density polyethylene sheets are subsequently processed. 
     
     
         4 . The process of forming low density expanded polyethylene foam according to  claim 1  wherein the effective amount of glyceride is about 0.3-5% of the low density polyethylene by weight. 
     
     
         5 . The process of forming low density expanded polyethylene foam according to  claim 1  wherein the effective amount of glyceride is about 1-4% of the low density polyethylene by weight. 
     
     
         6 . The process of forming low density expanded polyethylene foam according to  claim 1  wherein the effective amount of glyceride is about 2.5% of the low density polyethylene by weight. 
     
     
         7 . The process of forming low density expanded polyethylene foam according to  claim 1  wherein the curing step is at least two days before closed cell low density polyethylene sheets are subsequently processed. 
     
     
         8 . The process of forming low density expanded polyethylene foam according to  claim 1  wherein the curing step is at least fifteen days before closed cell low density polyethylene sheets are subsequently processed. 
     
     
         9 . The process of forming low density expanded polyethylene foam according to  claim 1  wherein the curing step is about thirty days before closed cell low density polyethylene sheets are subsequently processed. 
     
     
         10 . A process of forming low density expanded polyethylene foam comprising the steps of:
 providing a mixture including low density polyethylene pellets and hydrocarbon scavenger additive in an amount of about 0.3-5% of the low density polyethylene by weight;   adding a primary blowing agent comprising one of liquid propane, liquid butane, and combinations thereof, to the mixture and gasifying the blowing agent to expand the low density polyethylene;   forming the expanded low density polyethylene into sheets,   curing the expanded low density polyethylene until 80% of the primary blowing agent is dissipated from cells within the expanded low density polyethylene forming closed cell low density polyethylene sheets.   
     
     
         11 . The process of forming low density expanded polyethylene foam according to  claim 10  wherein at least 95% of the primary blowing agent is dissipated from cells within the expanded low density polyethylene before closed cell low density polyethylene sheets are subsequently processed. 
     
     
         12 . The process of forming low density expanded polyethylene foam according to  claim 10  wherein at least 99% of the primary blowing agent is dissipated from cells within the expanded low density polyethylene before closed cell low density polyethylene sheets are subsequently processed. 
     
     
         13 . The process of forming low density expanded polyethylene foam according to  claim 10  wherein the hydrocarbon scavenger additive include glycerides, activated carbon, sodium bicarbonate, graphite, silica gels, zeolites, diatomaceous earth, petrogels, and mixtures of the above. 
     
     
         14 . The process of forming low density expanded polyethylene foam according to  claim 10  wherein the hydrocarbon scavenger additive include glycerides and wherein the effective amount of hydrocarbon scavenger additive is about 1-4% of the low density polyethylene by weight. 
     
     
         15 . The process of forming low density expanded polyethylene foam according to  claim 10  wherein the hydrocarbon scavenger additive include glycerides and wherein the effective amount of hydrocarbon scavenger additive is about 2.5% of the low density polyethylene by weight. 
     
     
         16 . The process of forming low density expanded polyethylene foam according to  claim 10  wherein the curing step is at least two days before closed cell low density polyethylene sheets are subsequently processed. 
     
     
         17 . The process of forming low density expanded polyethylene foam according to  claim 10  wherein the curing step is at least fifteen days before closed cell low density polyethylene sheets are subsequently processed. 
     
     
         18 . The process of forming low density expanded polyethylene foam according to  claim 10  wherein the curing step is about thirty days before closed cell low density polyethylene sheets are subsequently processed. 
     
     
         19 . An expanded low density polyethylene sheets in which at least 80% of the blowing agents are dissipated from cells within the expanded low density polyethylene forming evacuated closed cell low density polyethylene sheet. 
     
     
         20 . The expanded low density polyethylene sheet according to  claim 19  wherein at least 99% of the blowing agents are dissipated from cells within the expanded low density polyethylene sheet.