Styrene Block Copolymer Latex Crosslinking for Dip-Molded Products
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Solution Overview
Problem
Conventional latex compositions, particularly those using natural rubber, pose allergic risks and exhibit inadequate moldability and uniformity in dip-molded products, while synthetic alternatives like styrene-isoprene-styrene block copolymers face issues with tear strength and film thickness uniformity.
Innovation Solution
A method involving a styrene-based block copolymer with controlled toluene insoluble content, specifically between 30 to 95 wt%, is used, incorporating a redox-type polymerization initiator and activator for cross-linking, to enhance processability and produce films with high tear strength and soft texture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If latex of natural rubber is used, then the molded film can be obtained, but allergic symptoms occur and moldability is insufficient
Solution Approach 1:
The patent extracts the harmful proteins from natural rubber latex by using synthetic rubber alternatives, specifically styrene-based block copolymers, which do not contain the allergenic proteins present in natural rubber. This substitution eliminates the harmful effect while maintaining the desired moldability and film formation properties.
Solution Approach 2:
The patent changes the chemical composition parameters of the rubber latex by transitioning from natural rubber to synthetic styrene-based block copolymers with controlled molecular structures (defined by specific formulas with parameters n and m). This parameter change eliminates allergens while optimizing moldability through controlled polymer architecture and composition ratios.
2Object-affected harmful factors
If latex of synthetic polyisoprene with carboxyl group is used, then allergic symptoms are avoided, but moldability is insufficient and film thickness uniformity is poor
Solution Approach 1:
The patent optimizes the molecular parameters of the styrene-based block copolymer by controlling the ratio of styrene blocks (A) to diene blocks (B), defined by the formula A-B-Y-(B-A)n. It also controls the toluene insoluble content within 5-50 wt% and adjusts the degree of crosslinking (30-80 wt%), thereby improving film thickness uniformity and moldability while maintaining safety from allergic reactions.
Solution Approach 2:
The patent creates a composite latex system combining styrene-based block copolymer with specific crosslinking agents and processing additives. The crosslinked network structure (achieved through controlled crosslinking at 30-80 wt%) enhances the mechanical properties and uniformity of the formed film, while the block copolymer architecture provides both safety and processability.
3Strength
If styrene-based block copolymer with high toluene insoluble content is used, then tear strength is improved, but processability deteriorates
Solution Approach 1:
The patent identifies and optimizes the critical parameter of toluene insoluble content, controlling it within the specific range of 5-50 wt%. This parameter control balances the crosslinked network structure (providing tear strength) with the solubility and processability characteristics. The block copolymer architecture and crosslinking degree are adjusted to achieve this optimal balance.
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 method produces dip-molded products with superior tear strength, stress retention, and uniform film thickness, addressing the limitations of natural rubber and synthetic alternatives, and is suitable for applications like gloves and medical supplies.
Implementation Method 1
a toluene insoluble component formed by cross-linking of the styrene-based block copolymer in the latex
Data Source
AI summary
A latex of a styrene-based block copolymer comprising a styrene-based block copolymer and water is provided. The styrene-based block copolymer comprises a toluene insoluble content of 30 to 95 wt%. According to the present invention, it is possible to provide the latex of the styrene-based block copolymer that is superior in the processability and can provide a molded film such as a dip-molded product having the high tear strength, the high stress retention and the soft texture.