Ethylene Vinyl Acetal Interlayer Film Autoclave Process
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Solution Overview
Problem
The production of laminated safety glass using ethylene vinyl acetal interlayer films results in high crystallinity, leading to decreased optical quality due to partial melting and crystallization during the autoclave process, which affects the yellowness index, turbidity, and light transmission.
Innovation Solution
A process involving an autoclave step at a temperature below the melting point of ethylene vinyl acetals and rapid cooling of the laminate to minimize crystallization, along with specific production methods for ethylene vinyl acetal interlayers, such as melt extrusion and cooling rates, to maintain optical quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the autoclave step is conducted at conventional temperatures (equal to or above the melting temperature of ethylene vinyl acetal), then complete lamination and bonding are achieved, but the interlayer film undergoes partial melting and subsequent crystallization, leading to high crystallinity and decreased optical quality
Solution Approach 1:
The patent changes the temperature parameter of the autoclave step from conventional temperatures (equal to or above melting point) to a lower temperature range (below melting point, specifically 80-120°C). This parameter change prevents the interlayer film from undergoing melting and crystallization, thereby maintaining optical quality while still achieving adequate lamination and bonding through extended processing time or optimized pressure conditions.
2Ease of manufacture
If rapid cooling is applied to prevent crystallization, then optical quality is improved, but the lamination process becomes more complex and energy-intensive
Solution Approach 1:
The patent applies preliminary action by conducting the autoclave lamination at a temperature below the melting point of the ethylene vinyl acetal interlayer film from the beginning. This prevents crystallization before it can occur, eliminating the need for subsequent rapid cooling steps. The lamination is achieved under controlled low-temperature conditions, and the optical quality is maintained without requiring complex post-processing cooling systems.
3Ease of manufacture
If the autoclave temperature is lowered below the melting temperature of ethylene vinyl acetal, then crystallization is prevented and optical quality is improved, but the lamination bonding efficiency decreases
Solution Approach 1:
The patent maintains continuous useful action by optimizing the combination of temperature, pressure, and time parameters in the autoclave process. Although the temperature is lowered below the melting point to prevent crystallization, the lamination process continues effectively through sustained pressure and extended processing time. This ensures continuous bonding action without interruption or need for reheating, maintaining productivity while improving optical quality.
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
The process significantly improves the optical quality of laminated glass by reducing turbidity and yellowness index, achieving stable lamination and energy efficiency while maintaining the integrity of the interlayer film.
Implementation Method 1
producing a laminate by heating the sandwich structure of step a or the pre-laminate of step b in an autoclave
Implementation Method 2
the final step in the production of glass laminates is usually an autoclave step in which the glass/interlayer/glass sandwich is subjected to elevated temperatures and pressures
Implementation Method 3
cooling the laminate of step c, wherein the temperature Tc in the autoclave step of step c is below the melting temperature of the ethylene vinyl acetal or wherein temperature Tc is equal to or above the melting temperature of the ethylene vinyl acetal and the cooling rate Qd of the cooling of step d is equal to or more than 10 K/min
Data Source
AI summary
The present invention is directed to a process for the production of interlayer films comprising ethylene vinyl acetals with improved crystallinity and optical properties.