Electroblowing Multiple Layered Sheet with Dual Solvent Concentrations

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Solution Overview

Problem

The electroblowing process for producing fiber webs often results in webs with either excessive solvent, causing sticking to the collection screen, or insufficient solvent, leading to poor surface stability and handling issues during web removal.

Innovation Solution

A multiple layered sheet is created by electroblowing a polymer solution through two spinning beams with different solvent concentrations, one with 0-30% solvent and the other with 30-70% solvent, ensuring the web does not stick to the screen while maintaining sufficient tackiness for stability, achieved by controlling liquid stream throughput and forwarding gas temperature.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the solvent concentration in the fiber at laydown is increased to improve web tackiness and surface stability, then the web sticking to the screen problem is worsened

Engineering Contradiction:

Improvesurface stabilityVSAvoidweb sticking to screen

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The invention divides the web into multiple layers with different solvent concentrations. The bottom layer (first web) has low solvent concentration (0-30 wt%) to prevent sticking to the screen, while the top layer (second web) has high solvent concentration (30-70 wt%) to provide sufficient tackiness and surface stability for handling. This segmentation allows each layer to fulfill its specific function without compromise.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the web structure are assigned different solvent concentrations based on their functional requirements. The layer in contact with the screen has low solvent content for easy removal, while the outer layers have high solvent content for handling stability. This local differentiation of properties resolves the contradiction between non-sticking and tackiness requirements.

Inventive Principle:

Principle #3Local quality

2Object-generated harmful factors

If the solvent concentration in the fiber at laydown is decreased to prevent web sticking to the screen, then the web surface stability and handling capability are worsened

Engineering Contradiction:

Improveweb sticking to screenVSAvoidweb handling

Core Design Contradiction:

Object-generated harmful factorsVSEase of operation

Solution Approach 1:

The web is segmented into functional layers: a bottom layer with low solvent concentration (0-30 wt%) that prevents screen sticking, and top layers with high solvent concentration (30-70 wt%) that provide the necessary tackiness for handling operations. This layered structure allows simultaneous optimization of both screen release and handling properties.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The solvent concentration is locally optimized for each web layer's function. The screen-contacting layer has low solvent content for easy removal, while the handling-exposed layers have high solvent content for sufficient tackiness. This spatial variation in composition resolves the contradiction between non-sticking and ease of handling.

Inventive Principle:

Principle #3Local quality

3Device complexity

If a single solvent concentration is used in the fiber at laydown, then the process is simplified, but the web cannot simultaneously achieve easy screen removal and sufficient handling stability

Engineering Contradiction:

Improveprocess complexityVSAvoidweb handling and screen removal

Core Design Contradiction:

Device complexityVSEase of operation

Solution Approach 1:

Rather than using a single uniform solvent concentration, the process segments the web into multiple layers with different solvent concentrations. This segmentation enables the web to exhibit both easy screen removal (from the low-solvent bottom layer) and sufficient handling stability (from the high-solvent top layers), overcoming the limitations of a simplified single-concentration approach.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The web is constructed as a composite structure with layers of different solvent concentrations, analogous to composite materials. This composite approach allows the web to combine properties that would be mutually exclusive in a homogeneous structure, achieving both easy screen removal and adequate handling stability simultaneously.

Inventive Principle:

Principle #40Composite materials

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 process allows for successful removal of the web from the collection screen without damage and enhances surface stability for handling, enabling effective solvent removal and suitable tackiness through the combination of low and high solvent concentration webs.

Implementation Method 1

spinning an electrically conductive liquid stream comprising a polymer dissolved in a solvent through at least two spinning beams comprising a linear array of spinning nozzles in the presence of a forwarding gas and an electric field to form fibers

Methodology Applied

Scientific EffectElectric field: Electric Field

Implementation Method 2

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentUS8361365B2Process for electroblowing a multiple layered sheet

Publication Date: 2013.01.29 DUPONT SAFETY & CONSTRUCTION INC

AI summary

A process for electroblowing a multiple layered sheet using multiple spinning beams to produce different component webs wherein the sheet doesn't stick to the forming screen and has improved web stability.