Cholate Emulsifier Stabilizes Nitrile Latex for Dip Molding
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Solution Overview
Problem
The latex composition for dip molding, particularly nitrile-based latex, faces issues with syneresis and reduced stability during the double dip molding process, leading to defects such as coagulation and reduced tensile strength and wearability in gloves.
Innovation Solution
Incorporating a cholate-based emulsifier into a carboxylic acid-modified nitrile-based copolymer latex composition to enhance particle dispersibility and stability, thereby increasing syneresis time and improving the physical properties of the molded articles, including tensile strength and wearability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a nitrile-based latex is used instead of natural rubber latex to avoid protein allergies, then allergen safety is improved, but wearability deteriorates due to relatively high modulus
Solution Approach 1:
The patent modifies the chemical composition parameters of the nitrile-based latex by incorporating specific additives (polyethylene glycol, silane crosslinking agents, and metal salts) to change the physical properties of the polymer network, thereby reducing the modulus while maintaining the allergen-free characteristic of nitrile-based material
Solution Approach 2:
The patent creates a composite latex system by combining nitrile-based polymer with multiple functional additives including polyethylene glycol as a plasticizer, silane crosslinking agents for network formation, and metal salts as catalysts, achieving a balance between low modulus for wearability and high stability for manufacturing
2Manufacturing precision
If a double dip molding method is used to reduce defective rate, then manufacturing precision is improved, but syneresis occurs reducing latex stability
Solution Approach 1:
The patent performs preliminary stabilization of the latex composition by adding polyethylene glycol and silane crosslinking agents before the dip molding process, creating a pre-crosslinked network that prevents syneresis during the subsequent molding operations
Solution Approach 2:
The patent introduces silane crosslinking agents as intermediary substances that mediate between the latex polymer chains and crosslinking agents, forming a stable gel network structure that prevents syneresis while allowing the double dip molding process to proceed
3Manufacturing precision
If syneresis time is increased to improve latex stability, then manufacturing precision is improved, but the process time increases
Solution Approach 1:
The patent makes the syneresis process continuous and controlled by maintaining a stable latex composition through pre-crosslinking, allowing the useful action of water removal to continue smoothly without interruption or excessive delay, achieving both stability and time efficiency
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 use of a cholate-based emulsifier in the latex composition significantly increases syneresis time, improves stability, and enhances the tensile strength and wearability of dip-molded articles like gloves, reducing defects and maintaining physical properties at an equivalent or higher level.
Implementation Method 1
including a cholate-based emulsifier when preparing a carboxylic acid-modified nitrile-based copolymer latex composition, an aggregation of latex particles in a latex composition is suppressed to improve dispersibility
Implementation Method 2
a syneresis phenomenon occurs in a molded article produced by primary dip molding
Data Source
AI summary
A latex composition for dip molding includes a carboxylic acid-modified nitrile-based copolymer latex and a cholate-based emulsifier, wherein the cholate-based emulsifier is included in an amount of 0.02 to 3 parts by weight based on a solid content with respect to a solid content of 100 parts by weight of the carboxylic acid-modified nitrile-based copolymer latex. A method of preparing the latex composition for dip molding and a molded article produced using the same are also provided.