Silane-Crosslinked Polymer Latex for Formaldehyde-Free Fiber Bonding
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Solution Overview
Problem
Existing polymer latex binders used in fiber structures, such as those for construction and paper applications, often emit formaldehyde during curing, which is hazardous, and require high temperatures and long curing times, increasing energy consumption and production costs.
Innovation Solution
A polymer latex obtained through emulsion polymerization of a mixture comprising 60-75 wt.% aliphatic conjugated diene, 10-30 wt.% vinyl aromatic compound, 0.5-5 wt.% ethylenically unsaturated silane with silicon-bonded hydrolysable groups, 0.1-8 wt.% ethylenically unsaturated acid, and optional additional monomers, which self-crosslinks without emitting formaldehyde and allows for lower curing temperatures and shorter times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional polymer latex binders containing self-crosslinking monomers (e.g., N-methylolamide functional ethylenically unsaturated monomers) are used to fortify fiber structures, then the desired mechanical strength and alkali resistance are achieved, but formaldehyde is released during curing which is hazardous and may be classified as carcinogenic
Solution Approach 1:
The patent removes the harmful formaldehyde-generating components (N-methylolamide functional monomers and crosslinking agents) from the binder composition, replacing them with alternative polymers that achieve crosslinking through silane chemistry or other formaldehyde-free mechanisms, thereby extracting the harmful element while preserving the binding function
Solution Approach 2:
The invention employs composite binder systems combining multiple polymer types (acrylic, vinyl acetate, styrene-butadiene, epoxy-functional polymers) with silane crosslinkers to achieve the required mechanical strength and alkali resistance without relying on formaldehyde-based crosslinking chemistry
2Strength
If conventional binders are used to achieve adequate bonding strength in fiber structures, then the desired mechanical properties are obtained, but high curing temperatures and long curing times are required which increase energy consumption and production costs
Solution Approach 1:
The patent modifies the chemical composition parameters of the binder to enable crosslinking reactions that proceed at lower temperatures and faster rates, specifically using silane-based crosslinking systems that can cure at reduced temperatures compared to traditional formaldehyde-based systems
Solution Approach 2:
The invention replaces thermal-mechanical curing processes (high temperature and long duration) with chemical crosslinking mechanisms that occur more rapidly at lower temperatures, substituting the need for intensive energy input with more efficient chemical reaction pathways
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 solution provides fiber structures with enhanced alkali resistance, abrasion resistance, solvent resistance, and tensile strength while eliminating formaldehyde emission and reducing energy consumption by enabling lower curing temperatures and shorter processing times.
Implementation Method 1
A polymer latex obtainable by emulsion polymerization of a mixture of ethylenically unsaturated monomers
Implementation Method 2
0.5 to 5 wt.-% of at least one ethylenically unsaturated silane bearing at least one silicon bonded hydrolysable group
Data Source
AI summary
The present invention relates to a polymer latex obtained from the emulsion polymerization in aqueous medium of a mixture of ethylenically unsaturated monomers comprising: (a) more than 60 wt.-% to 75 wt.-% of at least one aliphatic conjugated diene (b) 10 wt.-% to 30 wt.-% of at least one vinyl aromatic compound; and (c) 0.5 to 5 wt.-% of at least one ethylenically unsaturated silane bearing at least one silicon bonded hydrolysable group; (d) 0.1 to 8 wt.-% of at least one ethylenically unsaturated acid; and (e) 0 to 20 wt.-% of at least one further ethylenically unsaturated compound different from any of compounds (a) to (d), the weight percentages being based on the total amount of monomers and add up to 100 wt.-%, to a binder comprising said polymer latex and to a fiber structure fortified by said binder.