EVA Sheet Manufacturing via Segmented Melt-Mixing
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Solution Overview
Problem
The existing methods for manufacturing EVA sheets for solar cell encapsulants face limitations in productivity due to low process temperatures, which can lead to pre-crosslinking and yellowing issues, and poor dispersion of additives, resulting in reduced transparency, flexibility, and adhesiveness.
Innovation Solution
A method involving melt-mixing EVA resin with antioxidants, UV absorbers, and light stabilizers at 80-220°C, followed by melt-mixing with organic peroxides, co-crosslinking agents, and silane coupling agents at or below the organic peroxide's degradation temperature to form a sheet, ensuring uniform dispersion and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the process temperature is raised to improve productivity and uniform dispersion of additives, then the dispersion of additives improves, but pre-crosslinking occurs due to degradation of organic peroxides
Solution Approach 1:
The patent divides the manufacturing process into two distinct stages: (1) preliminary mixing of EVA resin with additives at 80-220°C to achieve uniform dispersion, and (2) subsequent mixing with organic peroxides at or below their degradation temperature to prevent pre-crosslinking. This segmentation allows each stage to be optimized independently, resolving the contradiction between achieving good dispersion and preventing premature peroxide degradation.
Solution Approach 2:
The patent performs preliminary mixing of EVA resin with additives (antioxidants, UV absorbers, light stabilizers) at elevated temperatures (80-220°C) before introducing organic peroxides. This preliminary action ensures uniform dispersion of additives while the temperature is still controlled to be at or below the peroxide degradation temperature, preventing pre-crosslinking while achieving the desired dispersion quality.
2Reliability
If the process temperature is kept low to prevent pre-crosslinking, then stability against pre-crosslinking is maintained, but productivity remains limited
Solution Approach 1:
The patent optimizes the temperature parameter within a specific range (80-220°C) that is high enough to ensure good dispersion of additives but low enough to prevent degradation of organic peroxides. By carefully controlling this parameter, the patent achieves both reliability (preventing pre-crosslinking) and improved productivity (through better dispersion and reduced rework).
3Reliability
If all components are mixed and melt-mixed together at once under low shear force conditions, then pre-crosslinking is avoided, but uniform dispersion of additives is not achieved
Solution Approach 1:
The patent segments the mixing process into two distinct operations: first mixing EVA resin with additives at 80-220°C to achieve uniform dispersion, then separately mixing with organic peroxides at controlled temperatures. This segmentation ensures that the low shear force condition is maintained during peroxide incorporation (preventing pre-crosslinking) while the initial mixing stage achieves uniform dispersion of additives.
Solution Approach 2:
The patent performs preliminary mixing of EVA resin with additives before introducing organic peroxides. This preliminary action ensures that additives are uniformly dispersed in the EVA matrix while the temperature is controlled to prevent peroxide degradation, thereby achieving both uniform dispersion and preventing pre-crosslinking.
4Manufacturing precision
If the process temperature is raised to improve dispersion, then uniform dispersion of additives is achieved, but yellowing occurs after crosslinking
Solution Approach 1:
The patent carefully controls the process temperature parameter within the range of 80-220°C, which is high enough to ensure uniform dispersion of additives but low enough to prevent degradation of organic peroxides that would lead to yellowing. By optimizing this parameter, the patent achieves both good dispersion and prevents yellowing after crosslinking.
Solution Approach 2:
The patent performs preliminary mixing of additives with EVA resin at controlled temperatures (80-220°C) before introducing organic peroxides. This preliminary action ensures uniform dispersion of additives while maintaining temperatures that prevent peroxide degradation and subsequent yellowing, thereby resolving the contradiction between dispersion quality and yellowing prevention.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances productivity and stability against yellowing, maintaining good appearance and physical properties while minimizing the amount of residual crosslinking agents, thereby improving sheet formability and resistance to yellowing.
Implementation Method 1
organic peroxides used in a solar cell encapsulant are generally those having a low degradation temperature (1 hour half-life temperature) such as no more than 150° C.
Implementation Method 2
crosslinking and binding them together by heat at a certain temperature and pressure
Implementation Method 3
if the melt-mixing process is carried out under the conditions for raising shear force in order to increase productivity, heat is generated which may promote the degradation of the organic peroxides
Implementation Method 4
an antioxidant, a light stabilizer, a UV absorber and the like are used
Implementation Method 5
a UV absorber... at which the degradation starts is very low in practice
Data Source
AI summary
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.