Styrenic Block Copolymer Latex for High Strength and Comfort
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Solution Overview
Problem
Existing synthetic rubber latexes struggle to achieve a balance between high tensile strength and comfort properties, particularly in thin articles like surgical gloves and condoms, where increasing tensile strength often compromises flexibility and user comfort.
Innovation Solution
A latex comprising a styrenic block copolymer with 2 or more poly(vinyl aromatic) blocks and at least one block of polymerized conjugated diene, combined with a vulcanizing agent, specifically sulfur and accelerators, to create cross-linking and enhance tensile strength while maintaining comfort-related properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional synthetic rubber latexes are used to increase tensile strength, then tensile strength is improved, but comfort properties and flexibility deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molecular weight of the styrenic block copolymer (150,000 to 250,000), the molecular weight of poly(vinyl aromatic) blocks (9,000 to 15,000), and the content of poly(vinyl aromatic) blocks (8 to 15 wt%). These parameter optimizations enable the latex to achieve high tensile strength while maintaining flexibility and comfort properties, resolving the contradiction between strength and ease of operation
Solution Approach 2:
The patent uses composite materials by combining styrenic block copolymer with specific vulcanizing agents to create a cross-linked network structure. This composite approach allows the material to exhibit both high tensile strength and retained flexibility, overcoming the trade-off between strength and comfort
2Ease of manufacture
If conventional block copolymers are used without vulcanization, then ease of manufacture is improved, but tensile strength deteriorates
Solution Approach 1:
The patent applies self-service by incorporating vulcanizing agents directly into the latex formulation, enabling the material to undergo self-vulcanization during the dipping and drying process. This eliminates the need for separate vulcanization equipment or complex multi-step manufacturing processes, maintaining ease of manufacture while achieving high tensile strength
Solution Approach 2:
The patent applies preliminary action by pre-mixing the vulcanizing agents with the styrenic block copolymer latex before the dipping process. This preliminary incorporation ensures that vulcanization occurs automatically during article formation, achieving high strength without adding complex post-processing steps
3Productivity
If thin films are produced from conventional latices, then productivity is improved, but tensile strength deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the molecular weight and composition of the styrenic block copolymer to achieve exceptional strength-to-thickness ratio. The specific parameter ranges (molecular weight 150,000 to 250,000, poly(vinyl aromatic) block content 8 to 15 wt%) enable production of ultra-thin films with tensile strength exceeding 100 N/mm, maintaining high productivity while achieving superior strength
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 results in articles with significantly improved tensile strength and reduced stress at low elongation, indicating enhanced comfort and flexibility, while also producing thinner films without significant process modifications.
Implementation Method 1
combined with a vulcanizing agent, specifically sulfur and accelerators, to create cross-linking and enhance tensile strength
Data Source
AI summary
Articles with enhanced tensile strength and comfort are prepared from a latex comprising water and a styrenic block copolymer, wherein the styrenic block copolymer has 2 or more poly(vinyl aromatic) blocks and at least one block of polymerized conjugated diene, wherein the styrenic block copolymer has a weight average molecular weight of 150,000 to 250,000, the poly(vinyl aromatic) blocks have a weight average molecular weight ranging from 9,000 to 15,000, and the content of poly(vinylaromatic) blocks in the styrenic block copolymer ranges from 8 to 15 %wt, based on the total styrenic block copolymer, by a process which comprises coating a surface with the latex to obtain a film, wherein the latex comprises a vulcanising agent. The invention also provides a latex comprising such a styrenic block copolymer and a vulcanising agent, as well as a styrenic block copolymer that is particularly suitable for use in such a latex.