Method for manufacturing ethylene vinyl acetate copolymer sheet for solar cell encapsulant
Provided is a method for manufacturing a sheet for a solar cell encapsulant which has stability against yellowing after a crosslinking process and thus good appearance with improved productivity in the sheet manufacture process, specifically to a method for manufacturing a sheet for a solar cell encapsulant characterized by melt-mixing a resin composition with an organic peroxide, a co-crosslinking agent and a silane coupling agent at the degradation temperature of the organic peroxide or less, wherein the resin composition is obtained by melt-mixing EVA resin with an antioxidant, an UV absorber and a light stabilizer at 80-220° C., and forming a sheet from the obtained melt-mixed resin composition.
1. A method for manufacturing a sheet for a solar cell encapsulant, comprising:
(1) melt-mixing an EVA resin with an antioxidant, UV absorber and light stabilizer at 80-220° C. and producing EVA resin composition pellets;
(2) dry-blending the EVA resin composition pellets with organic peroxide(s) as a crosslinking agent, a co-crosslinking agent and a silane coupling agent at the degradation temperature of the organic peroxide or less, and melt-mixing the resulting blend, each of the crosslinking agent, the co-crosslinking agent and the silane coupling agent being used at an amount of 0.3-1.5 parts by weight based on 100 parts by weight of the EVA resin; and
(3) forming the sheet from the resultant of the step (2).
2. The method according to claim 1 , wherein in the step (1), 0.005-0.1 parts by weight of the antioxidant, 0.1-0.5 parts by weight of the UV absorber and 0.01-0.3 parts by weight of the light stabilizer, based on 100 parts by weight of the EVA resin, are melt-mixed.
3. The method according to claim 2 , wherein the EVA resin has 25-32 wt % of a vinyl acetate content and 6-30 g/10 minutes of melting index measured at 190° C. under 2.16 kg load.
4. The method for manufacturing a sheet for a solar cell encapsulant according to claim 2 , wherein the antioxidant is at least one selected from the group consisting of phenolic antioxidants, phosphite antioxidants and sulfur antioxidants.
5. The method according to claim 2 , wherein the UV absorber is at least one selected from the group consisting of benzophenone UV absorbers and benzotriazole UV absorbers.
6. The method according to claim 2 , wherein the light stabilizer is a hindered-amine light stabilizer.
7. The method according to claim 1 , wherein the EVA resin has 25-32 wt % of a vinyl acetate content and 6-30 g/10 minutes of melting index measured at 190° C. under 2.16 kg load.
8. The method for manufacturing a sheet for a solar cell encapsulant according to claim 1 , wherein the antioxidant is at least one selected from the group consisting of phenolic antioxidants, phosphite antioxidants and sulfur antioxidants.
9. The method according to claim 1 , wherein the UV absorber is at least one selected from the group consisting of benzophenone UV absorbers and benzotriazole UV absorbers.
10. The method according to claim 1 , wherein the light stabilizer is a hindered-amine light stabilizer.
11. The method according to claim 1 , wherein two or more organic peroxides having different degradation temperatures from each other are used as the crosslinking agent.
12. The method according to claim 1 , wherein the pellets are formed by an extruder.
13. The method according to claim 1 , wherein the pellets are formed by an extruder at a temperature of 190° C.