Recycled Resin Composition Suppressing Die Build-Up
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Solution Overview
Problem
The compatibility between polyolefin resin and EVOH in recycled laminate materials leads to phase-separation issues, resulting in defects like die build-up, fish eyes, and poor appearance in formed products, with existing solutions either failing to prevent coloration or impairing the compatibilizing effect.
Innovation Solution
A resin composition comprising an ethylene-vinyl acetate copolymer and a saponified ethylene-vinyl acetate copolymer with an ethylene content of not less than 70 mol%, combined with hydrotalcite and higher fatty acid metal salts, to enhance compatibility and prevent coloration in recycled materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a higher ethylene content EVA saponification product (ethylene content ≥70 mol%) is used to improve compatibility with polyolefin resin, then the compatibilizing effect is enhanced and die build-up is suppressed, but the resulting regrind layers are colored yellow or red
Solution Approach 1:
The invention changes the ethylene content parameter of the EVA saponification product to ≥70 mol% (higher than conventional EVOH which has 10-60 mol% ethylene content). This parameter change improves compatibility with polyolefin resin while the invention accepts the resulting coloration as a trade-off, since the primary goal is to prevent die build-up and improve appearance quality
Solution Approach 2:
The invention applies the higher ethylene content EVA saponification product specifically as a compatibilizer in the interface region between polyolefin resin and EVOH layers, rather than throughout the entire laminate. This localized application targets the compatibility problem at the layer interface while minimizing overall material changes
2Object-affected harmful factors
If a smaller amount of higher ethylene content EVA saponification product is used to suppress coloration, then the yellow/red coloring is reduced, but the compatibilizing effect is impaired and die build-up problems persist
Solution Approach 1:
The invention establishes a specific ethylene content parameter threshold (≥70 mol%) that ensures sufficient compatibilizing effect. By setting this minimum threshold, the invention guarantees that the EVA saponification product has high enough ethylene content to effectively compatibilize the polyolefin resin and EVOH interface, preventing die build-up while accepting the associated coloration
3Reliability
If conventional EVOH (ethylene content 10-60 mol%) is used to maintain gas barrier property, then excellent gas barrier performance is achieved, but compatibility with polyolefin resin is poor causing phase separation and fish eyes in formed products
Solution Approach 1:
The invention segments the EVA saponification product into two functional components: conventional EVOH (10-60 mol% ethylene content) that provides gas barrier properties, and higher ethylene content EVA saponification product (≥70 mol% ethylene content) that provides compatibilizing function. This segmentation allows each component to fulfill its specific function without compromise
Solution Approach 2:
The invention creates a composite material system combining conventional EVOH with higher ethylene content EVA saponification product. The composite structure integrates the gas barrier properties of conventional EVOH with the compatibility enhancement of high-ethylene-content EVA, achieving both functions simultaneously in the laminate
Data Source
AI summary
A resin composition is provided, which comprises: an ethylene-vinyl acetate copolymer (A); and a saponified ethylene-vinyl acetate copolymer (B) having an ethylene content of not less than 70 mol %, wherein the component (B) is present in a proportion of 1 to 30 parts by weight based on 100 parts by weight of the component (A). Where the resin composition is used in combination with a scrap laminate including a polyolefin resin layer and an EVOH layer for recycling the scrap laminate, die build-up is suppressed, and a product formed from the resulting recycled material is excellent in appearance and substantially free from coloration.