Consolidated Fibrous Structure with Low-Temperature Fusion

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Solution Overview

Problem

The high temperature and pressure requirements for consolidating thermoplastic fibers into fibrous structures hinder the co-processing of polypropylene fibers with other materials and increase manufacturing costs due to the need for large metal molds.

Innovation Solution

A method involving fibers with a core and multiple polymer layers, where a first layer with a high melting temperature and a second layer with lower viscosity are used, allowing for consolidation at lower temperatures and pressures by applying heat and pressure to fuse the layers and fill interstices with a polymer blend, reducing manufacturing costs and improving performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high temperature and pressure are applied to consolidate thermoplastic fibers, then the fibrous structure achieves desired performance attributes, but the processing temperature becomes too high for co-processing with other materials and manufacturing costs increase

Engineering Contradiction:

Improveperformance attributes of fibrous structureVSAvoidprocessing temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent changes the chemical composition parameters of the polymer layers, specifically using a first polymer with at least 70% α-olefin units and a second polymer with at least 50% α-olefin units and specific molecular weight (7,000-50,000 g/mol). This compositional parameter change enables consolidation at lower temperatures (below 250°F) while maintaining structural integrity and performance attributes.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite fibrous structure with multiple polymer layers having different properties. The first layer contains a polymer with higher melting temperature while the second layer contains a polymer with lower melting temperature and lower viscosity. This composite approach allows the structure to be consolidated at lower temperatures than conventional single-material systems.

Inventive Principle:

Principle #40Composite materials

2Strength

If high pressure is applied to consolidate thermoplastic fibers, then the fibrous structure achieves desired density and strength, but autoclavable processes become cost-effective only at pressures above 45-100 psi

Engineering Contradiction:

Improvestrength of fibrous structureVSAvoidprocessing pressure

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The patent changes the viscosity parameter of the second polymer to be at least one-tenth the viscosity of the first polymer at 170°C. This viscosity parameter change enables the material to be consolidated at lower pressures (including autoclavable pressures of 45-100 psi) while still achieving the desired density and strength through the blend filling interstices.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If large metal molds are used for consolidation, then large parts can be manufactured, but machinery cost and finished part cost increase significantly

Engineering Contradiction:

Improvemanufacturability of large partsVSAvoidmanufacturing cost

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The patent changes the consolidation parameters to lower temperature and pressure conditions, which enables the use of cost-effective autoclavable processes instead of expensive large metal molds. The specific polymer composition and viscosity parameters allow consolidation at autoclavable pressures, significantly reducing machinery cost and finished part cost while maintaining the ability to manufacture large parts.

Inventive Principle:

Principle #35Parameter changes

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 enables the production of consolidated fibrous structures with improved stiffness and peel strength at lower temperatures and pressures, reducing manufacturing costs and enabling the use of cost-effective processes.

Implementation Method 1

heat and optionally pressure are applied to the fibrous layer causing at least a portion of the second layers of the fibers in each fibrous layer fuse to other first or second layers of the fibers within the same fibrous layer, at least a portion of the second layers of the fibers of each fibrous layer fuse with at least a portion of the first or second layers of the fibers in an adjacent fibrous layer

Methodology Applied

Scientific EffectFusion:

Implementation Method 2

at least a portion of the interstices to be filled with a blend of the first and second polymers, where the blend filling the interstices comprises at least 80% wt the second polymer

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Data Source

PatentUS8029633B2Method of forming a consolidated fibrous structure

Publication Date: 2011.10.04 MILLIKEN & CO

AI summary

A method of consolidating thermoplastic fibrous layers by providing a plurality of fibers having a core with an exterior surface portion comprising polypropylene and a first layer disposed on at least a portion of the core containing at least 70% alpha-olefin units which is formed into a first fibrous layer. A second fibrous layer is applied to the first fibrous layer which second layer contains a second polymer being a co-polymer having at least 50% alpha-olefin units which is characterized by a number-average molecular weight of about 7,000 to 50,000 g/mol, a viscosity of between about 2,500 and 150,000 cP measured at 170° C. and a melting temperature lower than the melting temperature of the exterior surface of the core. Heat and optionally pressure are applied to the assembly to consolidate the layers.