Styrenic Copolymer Blend Reducing Mold Shrinkage
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Solution Overview
Problem
Current polymer blends used in injection molding, particularly styrene copolymers, face challenges with high mold shrinkage, which limits their ability to produce complex geometries, such as automotive parts, where low mold shrinkage is essential.
Innovation Solution
A polymer blend comprising 89.0 to 99.5 wt-% of styrene copolymers A (like SAN, SMA, ABS, ABS/PA, and ASA) combined with 0.5 to 4.5 wt-% of styrene-butadiene or styrene-isoprene block copolymers B, and optionally 0 to 5.0 wt-% of additives C, significantly reduces mold shrinkage by at least 5% compared to pure styrene copolymers A.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If styrene copolymers are used in injection molding, then processing is simplified and cost is reduced, but mold shrinkage remains too high for complex geometries
Solution Approach 1:
The patent applies composite materials by creating a polymer blend consisting of styrene copolymer A (89.0-99.5 wt.%) and block copolymer B (0.5-4.5 wt.%). This composite approach combines the processing advantages of styrene copolymers with the low shrinkage characteristics of block copolymers, achieving both ease of manufacture and low mold shrinkage simultaneously.
Solution Approach 2:
The patent applies parameter changes by modifying the compositional parameters of the polymer system. By adjusting the weight percentages of components A and B, and by selecting specific types of styrene copolymers and block copolymers with appropriate molecular weights and compositions, the patent optimizes the balance between processing ease and mold shrinkage reduction.
2Manufacturing precision
If block copolymer B is added to reduce mold shrinkage, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The patent applies local quality by specifying that only small amounts (0.5-4.5 wt.%) of block copolymer B are needed to achieve the low shrinkage effect. This localized addition of the secondary component minimizes the complexity increase while maintaining the precision improvement, as the block copolymer serves a specific functional role rather than requiring complete system redesign.
Data Source
AI summary
The invention relates to polymer blends of a styrene copolymer A selected from the group consisting of styrene acrylonitrile copolymers (SAN), styrene acrylonitrile maleic anhydride terpolymers (SMA), styrene acrylic copolymers, acrylonitrile butadiene styrene terpolymers (ABS), acrylonitrile butadiene styrene terpolymers with polyamide (ABS/PA), and acrylonitrile styrene acrylate terpolymers (ASA); and at least one copolymer B selected from the group consisting of styrene-butadiene block copolymers (SBC) and styrene-isoprene block copolymers (SIS); wherein the mold shrinkage of the polymer blend is reduced by at least 5% compared to the mold shrinkage of the pure styrene copolymer A.A process for the preparation of the polymer blends and the uses of the polymer blends in an injection molding process are described.