Sealing material for solar cell modules, and manufacturing method thereof

Abstract

Disclosed are a sealing material for solar cell modules and a manufacturing method thereof capable of endowing good transparency and heat resistance to the sealing material for solar cell modules while using a polyethylene-based resin. The disclosed sealing material for solar cell modules uses a polyethylene-based resin with a density of 0.900 g/cm3 or less, and an MFR between 0.1 g/10 min and 1.0 g/10 min. The sealing material is obtained by melt molding a resin composition containing a polyethylene-based resin with density 0.890 g/cm3 or less, and a polymerization initiator contained at 0.02 mass % or more but less than 0.5 mass % of the composition, wherein the density difference of the resin composition before and after the melt molding is within 0.05 g/cm3, and the MFR difference of the resin composition before and after the melt molding is 1.0 g/10 min or greater.

1 . A sealing material for use in a solar cell module, comprising: a monolayer or multilayer film comprising a resin composition containing at least 90 mass % of a polyethylene-based resin with a density of at most 0.900 g/cm 3  and containing substantially no crosslinking coagent,
 the monolayer or multilayer film having a MFR of from 0.1 g/10 min to 1.0 g/10 min as measured at 190° C. under a load of 2.16 kg according to JIS K 7210.   
     
     
         2 . The sealing material according to  claim 1 , wherein the polyethylene-based resin is metallocene-type linear low density polyethylene. 
     
     
         3 . The sealing material according to  claim 1 , wherein the polyethylene-based resin contains a copolymer obtained by copolymerization using an α-olefin and an ethylenic unsaturated silane compound as comonomers. 
     
     
         4 . The sealing material according to  claim 1 , which has a gel fraction of at most 25%. 
     
     
         5 . The sealing material according to  claim 1 , which has a polystyrene-equivalent weight average molecular weight of from 120,000 to 300,000. 
     
     
         6 . The sealing material according to  claim 1 , which has at least two layers different in the MFR. 
     
     
         7 . The sealing material according to  claim 6 , wherein the layers include a layer with a relatively high MFR arranged as an outermost layer and another layer with a relatively low MFR arranged as an intermediate layer. 
     
     
         8 . A solar cell module having the sealing material according to  claim 1 . 
     
     
         9 . A method for producing a sealing material for use in a solar cell module, comprising: melt molding a resin composition containing a polyethylene-based resin with a density of at most 0.900 g/cm 3  and 0.02 mass % to less than 0.5 mass % of a polymerization initiator. 
     
     
         10 . The method for producing a sealing material for use in a solar cell module according to  claim 9 , wherein the composition contains 0.02 mass % to 0.2 mass % of the polymerization initiator. 
     
     
         11 . The method for producing a sealing material for use in a solar cell module according to  claim 9 , wherein the polymerization initiator is an organic peroxide. 
     
     
         12 . The method for producing a sealing material for use in a solar cell module according to  claim 9 , wherein the melt molding is performed at a temperature at least 50° C. higher than the melting point of the polyethylene-based resin. 
     
     
         13 . The method for producing a sealing material for use in a solar cell module according to  claim 9 , wherein a difference in the density of the resin composition between before and after the melt molding is at most 0.05 g/cm 3 , and
 a difference in the MFR of the resin composition between before and after the melt molding is at least 1.0 g/10 min as measured at 190° C. under a load of 2.16 kg according to JIS K 7210.   
     
     
         14 . The method for producing a sealing material for use in a solar cell module according to  claim 9 , wherein the sealing material has at least two layers different in polymerization initiator content. 
     
     
         15 . The method for producing a sealing material for use in a solar cell module according to  claim 14 , wherein the layers include a layer with a relatively low polymerization initiator content arranged as an outermost layer and another layer with a relatively high polymerization initiator content arranged as an intermediate layer. 
     
     
         16 . The sealing material according to  claim 2 , wherein the polyethylene-based resin contains a copolymer obtained by copolymerization using an α-olefin and an ethylenic unsaturated silane compound as comonomers. 
     
     
         17 . The sealing material according to  claim 3 , which has a gel fraction of at most 25%. 
     
     
         18 . The sealing material according to  claim 4 , which has a polystyrene-equivalent weight average molecular weight of from 120,000 to 300,000. 
     
     
         19 . The sealing material according to  claim 5 , which has at least two layers different in the MFR. 
     
     
         20 . The sealing material according to  claim 3 , which has at least two layers different in the MFR.