pH-Responsive Nonwoven Binder for Dispersibility and Wet Strength
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Solution Overview
Problem
Existing methods for treating nonwoven substrates with water-borne formaldehyde-free compositions struggle to achieve a balance between dispersibility and maintaining desirable wet strength, as disclosed in U.S. Patent No. 5,451,432, which is not adequately addressed in terms of achieving improved dispersibility while preserving strength.
Innovation Solution
A method involving the formation of an aqueous nonwoven binder with an emulsion polymer containing 10% to 30% monoethylenically-unsaturated monoacid monomer, modified with a tri-substituted N-atom compound having a pKb of 4 to 7, applied to a nonwoven substrate, heated to 120 °C to 220 °C, and then immersed in an aqueous medium with a final pH <5 to create a dispersible nonwoven substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a nonwoven substrate is treated with a water-borne formaldehyde-free composition to improve dispersibility, then the dispersibility is enhanced, but the wet strength is compromised
Solution Approach 1:
The invention modifies the emulsion polymer by incorporating specific monomer ratios (10-30% monoethylenically-unsaturated monoacid monomer) and adjusting the glass transition temperature to -20°C to 30°C. The polymer is also modified with tri-substituted N-atom compounds having specific pKb values (4-7), creating a chemically tailored binder that provides both dispersibility and wet strength through controlled chemical parameters
Solution Approach 2:
The invention creates a composite binder system combining emulsion polymer with specific copolymerized units and tri-substituted N-atom modifications. This composite material integrates multiple functional components: the emulsion polymer provides base structure, the monoacid monomer units contribute to pH responsiveness for dispersibility, and the tri-substituted N-atom modifications enhance wet strength, achieving both contradictory requirements simultaneously
2Stability of the object's composition
If the emulsion polymer is modified with tri-substituted N-atom compound to enhance dispersibility, then the dispersibility improves, but the complexity of the binder formulation increases
Solution Approach 1:
The invention specifies precise parameter ranges to control complexity: monoacid monomer content (10-30% by weight), glass transition temperature (-20°C to 30°C), and modifier pKb values (4-7). These defined parameters create a systematic approach to formulation that, while chemically sophisticated, provides reproducible results and manageable complexity through standardized specifications
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
This method enhances the dispersibility of nonwoven substrates while maintaining a beneficial level of wet strength, as demonstrated by increased tensile strength at specific pH levels, indicating improved performance compared to unmodified emulsion polymers.
Implementation Method 1
an aqueous nonwoven binder comprising an emulsion polymer
Implementation Method 2
heating the contacted nonwoven to a temperature of from 120 °C to 220 °C
Implementation Method 3
the nonwoven substrate can, under appropriate conditions, be caused to disintegrate into at least one of: smaller pieces, aggregates of fibers, individual fibers
Data Source
AI summary
A method for forming a dispersible nonwoven substrate in an aqueous medium including: a) forming an aqueous nonwoven binder including a selected emulsion polymer wherein the polymer has been modified with a compound comprising a tri-substituted N-atom, the compound having a pKb of from 4 to 7; b) contacting a nonwoven substrate with the aqueous nonwoven binder; c) heating the contacted nonwoven to a temperature of from 120 °C to 220 °C; and d) immersing the contacted heated nonwoven in an aqueous medium having a final pH<5 is provided. A dispersible nonwoven substrate in an aqueous medium formed by the preceding method and a method for providing a dispersed nonwoven in an aqueous medium are also provided.