Crosslinkable stabilized composition for a nonwoven substrate and process for preparing the same
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Solution Overview
Problem
The manufacturing of nonwoven products using polymer dispersions often results in the production of formaldehyde as a by-product, which is undesirable for both manufacturers and consumers, and efforts to reduce formaldehyde levels have led to products with insufficient wet tensile strength and stability.
Innovation Solution
A crosslinkable stabilized composition for nonwoven substrates is developed, comprising an aqueous dispersion of vinyl acetate-ethylene copolymers, a polyvinyl alcohol dispersion stabilizer, and a copolymer with maleic anhydride or maleic acid units, which achieves a free formaldehyde content of 5 ppm or less and maintains viscosity stability over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If crosslinking agents are used to improve wet tensile strength, then wet tensile strength is improved, but formaldehyde production increases
Solution Approach 1:
The patent changes the chemical parameters of the crosslinking system by replacing traditional formaldehyde-based crosslinking agents with isocyanate crosslinking agents. This parameter change allows achieving crosslinking functionality without producing formaldehyde, thus resolving the contradiction between improving wet tensile strength and reducing formaldehyde production.
Solution Approach 2:
The patent converts the harmful effect of formaldehyde production into a benefit by using alternative crosslinking chemistry (isocyanate-based) that not only eliminates formaldehyde but also provides superior crosslinking performance. The isocyanate groups react with hydroxyl groups on the polyvinyl alcohol to form stable crosslinks, achieving both low formaldehyde and high strength.
2Object-generated harmful factors
If formaldehyde levels are reduced in polymer dispersion, then formaldehyde content is reduced, but wet tensile strength becomes insufficient
Solution Approach 1:
The patent introduces isocyanate crosslinking agents as intermediaries that mediate between the polymer chains. These agents form crosslinks without requiring formaldehyde, acting as a bridge that provides the necessary structural reinforcement for wet tensile strength while avoiding the harmful formaldehyde byproduct.
Solution Approach 2:
The patent creates a composite crosslinking system combining polyvinyl alcohol base polymer with isocyanate crosslinking agents. This composite approach allows achieving the desired mechanical properties through synergistic interaction between the polymer matrix and crosslinking network, eliminating the need for formaldehyde-based systems.
3Strength
If crosslinking agents are used to improve tensile strength, then tensile strength is improved, but dispersion stability deteriorates
Solution Approach 1:
The patent applies preliminary action by adding the isocyanate crosslinking agent before the crosslinking reaction is initiated. The agent is pre-distributed throughout the dispersion in a stable form, and crosslinking is triggered only when desired through moisture or heat activation. This preliminary distribution ensures uniform crosslinking without premature aggregation that would destabilize the dispersion.
Solution Approach 2:
The patent introduces dynamic control over the crosslinking process by using isocyanate groups that remain relatively stable under storage conditions but become highly reactive upon exposure to moisture or heat. This dynamic behavior allows the dispersion to remain stable during storage and processing, then crosslink rapidly when activated, achieving both stability and 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 composition provides nonwoven products with enhanced wet and dry tensile strength, while maintaining low formaldehyde levels and viscosity stability, making it suitable for applications such as wet and dry wipes.
Implementation Method 1
Vinyl acetate and ethylene are copolymerized in the presence of a polyvinyl alcohol dispersion stabilizer to form vinyl acetate-ethylene copolymers
Implementation Method 2
The copolymer and vinyl acetate-ethylene copolymers are crosslinked
Data Source
AI summary
A crosslinkable stabilized composition for a nonwoven substrate includes an aqueous dispersion of vinyl acetate-ethylene copolymers, a polyvinyl alcohol dispersion stabilizer, and a copolymer comprising maleic anhydride units or a copolymer comprising maleic acid units. The composition exhibits a free formaldehyde content of 5 ppm or less.