Epoxy-Crosslinked XNBR Dip Molding Composition for Stress Retention
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Solution Overview
Problem
Existing crosslinking methods for carboxyl group-containing nitrile rubber elastomers, such as XNBR, fail to achieve satisfactory stress retention rate and flexibility, and there is a need for improved wearability, fit, and ease of fine operations in gloves while maintaining tensile strength and fatigue durability.
Innovation Solution
A dip molding composition containing a carboxyl group-containing nitrile rubber elastomer with specific structural units and an epoxy crosslinking agent, along with a pH modifier, is used to create crosslinked structures, enhancing stress retention rate and flexibility in molded articles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional crosslinking methods (sulfur vulcanization or metal crosslinking) are used for XNBR, then tensile strength can be maintained, but stress retention rate and flexibility are insufficient
Solution Approach 1:
The patent changes the chemical parameters of the crosslinking system by using epoxy crosslinking agents instead of traditional sulfur or metal-based crosslinking. This chemical parameter change enables both high tensile strength and high stress retention rate (>80%) to be achieved simultaneously, resolving the contradiction between strength and reliability.
Solution Approach 2:
The patent creates a composite crosslinked structure by combining epoxy crosslinking agents with specific carboxyl group-containing XNBR elastomers. This composite approach allows the material to exhibit both high tensile strength and excellent stress retention properties that cannot be achieved with single crosslinking methods.
2Object-affected harmful factors
If accelerator-free crosslinking is used to avoid type IV allergy, then health safety is improved, but stress retention rate and flexibility remain insufficient
Solution Approach 1:
The patent extracts and eliminates the harmful vulcanization accelerators from the crosslinking system while maintaining effective crosslinking through epoxy chemistry. This removal of harmful substances prevents type IV allergy while the epoxy crosslinking mechanism ensures high stress retention rate and flexibility are achieved.
Solution Approach 2:
The patent introduces epoxy crosslinking agents as intermediary substances that enable crosslinking without requiring harmful accelerators. These epoxy intermediaries react with carboxyl groups on the XNBR chains to form crosslinked structures, providing both safety (no type IV allergy) and performance (high stress retention).
3Strength
If low-temperature polymerization is used to improve tensile strength, then tensile strength is improved, but rubber elasticity and stress retention rate are reduced
Solution Approach 1:
The patent changes the post-polymerization parameters by applying epoxy crosslinking treatment to low-temperature polymerization XNBR. This secondary parameter change compensates for the loss of rubber elasticity caused by low-temperature polymerization, achieving both high tensile strength and high stress retention rate simultaneously.
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 composition produces molded articles with improved stress retention rate, flexibility, and tensile strength, while avoiding type I and type IV allergies, and is applicable to gloves and other products.
Implementation Method 1
an epoxy crosslinking agent containing an epoxy compound that contains three or more glycidyl ether groups in one molecule and has a basic skeleton containing an alicyclic, aliphatic or aromatic hydrocarbon
Data Source
Figure 1(a)~1(c)
AI summary
Provided is a dip molding composition which contains at least: a carboxyl group-containing nitrile rubber elastomer; an epoxy crosslinking agent containing an epoxy compound that contains three or more glycidyl ether groups in one molecule and has a basic skeleton containing an alicyclic, aliphatic or aromatic hydrocarbon; and a pH modifier. In this dip molding composition, the elastomer contains 50% by weight or more, 78% by weight or less of a conjugated diene monomer-derived structural unit, 20% by weight or more, 30% by weight or less of an ethylenically unsaturated nitrile monomer-derived structural unit, and 3.5% by weight or more, 6% by weight or less of an ethylenically unsaturated carboxylic acid monomer-derived structural unit; the elastomer has an MEK-insoluble content of 60% by weight or more, 80% by weight or less; and the epoxy crosslinking agent has an MIBK/water distribution ratio of 50% or higher.