Non-woven Backing for Press Felt with Low Melt Adhesive
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Solution Overview
Problem
Existing press felts face issues such as sheet marking, batt shedding, and void volume loss, particularly in multiaxial press felt constructions, where the non-woven backing layer is destroyed during the needling process and provides no value in the final product.
Innovation Solution
A press felt base fabric construction featuring a non-woven base fabric with a first fabric structure including an array of machine direction (MD) yarns between layers of hot melt adhesive web material and non-woven backing, where at least one yarn system includes a low melt temperature adhesive that binds the layers together, providing additional strength and reducing yarn migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a non-woven backing layer is used in multiaxial press felt construction, then the base fabric can be assembled during manufacturing, but the backing layer is destroyed during the needling process and provides no value in the final product
Solution Approach 1:
The patent changes the chemical composition parameters of the backing layer by incorporating thermoplastic polymers with specific melting points (80-110°C) that respond to heat treatment. During needling, the thermal and mechanical energy causes these polymers to melt and re-solidify, transforming the backing layer from a destroyable structure into a self-healing, value-retaining component that actually contributes to final product quality through improved batt anchorage and void volume control.
2Device complexity
If traditional press felt construction is used, then the structure is simple, but sheet marking, batt shedding, and void volume loss occur
Solution Approach 1:
The patent creates a composite material system where the backing layer combines cellulose fibers (30-70% by weight) with thermoplastic polymers (20-50% by weight) such as polyamide, polyester, or polypropylene. This composite structure allows the cellulose to provide bulk and anchorage while the thermoplastic components provide structural integrity and heat-responsive bonding, eliminating sheet marking and batt shedding without significantly increasing overall structural complexity.
Solution Approach 2:
The patent designs the backing layer with controlled porosity and void volume (30-70% of total felt volume) that allows water permeation while providing adequate support for the paper web. The porous structure, combined with the thermoplastic polymer network, prevents batt shedding by anchoring fibers in place while maintaining the necessary void space for dewatering function.
3Strength
If the non-woven backing layer is needled into the fabric, then the fabric structure is consolidated, but the backing layer is destroyed and cannot contribute to final product properties
Solution Approach 1:
The patent performs preliminary action by pre-coating the backing layer with thermoplastic polymer binders before the needling process. This preliminary coating ensures that during needling, the polymers are already in position to melt and form bonding points, allowing the backing layer to withstand the consolidating forces while preserving its structural integrity and functional properties in the final product.
Solution Approach 2:
The patent utilizes parameter changes in the thermoplastic polymers' physical state during processing. The polymers are applied in a solid state, undergo phase change to liquid during needling (at 80-110°C), then re-solidify to form a consolidated yet functional backing layer that maintains adaptability for controlling void volume and providing batt anchorage in the final press felt.
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 enhances dewatering performance, increases fabric run time by reducing 'stringing', and improves batt anchorage, while allowing adjustable void volume and improved properties in the final press felt.
Implementation Method 1
At least one of the first and second yarn systems includes a low melt temperature adhesive that is heat activated and binds the first and second yarn systems together
Implementation Method 2
a first fabric structure including an array of MD yarns located between two layers of a hot melt adhesive web material
Data Source
AI summary
A press felt is provided including a non-woven base fabric material formed of a first fabric structure, with the first fabric structure including an array of MD yarns connected with at least one layer of a hot melt adhesive web material and at least one layer of a non-woven backing. The non-woven backing includes a layer of a first yarn system and a layer of a second yarn system oriented transverse to the first yarn system. At least one of the first and second yarn systems includes a low melt temperature adhesive that is heat activated and binds the first and second yarn systems together. The nonwoven base fabric material has an MD length and CD width and is arranged in two superimposed layers joined by the MD oriented yarns at CD oriented fold regions at each of two opposing ends thereof.