Spunbond Mat Consolidation via Heated Rolls and Water Jets
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Solution Overview
Problem
Heavier and more voluminous nonwoven filament mats are difficult to consolidate effectively without damaging the mat or disrupting its uniformity, as existing methods like water jets or thermoconsolidation can cause irregularities and require complex slippage prevention.
Innovation Solution
A method involving extruding hot thermoplastic filaments, cooling and stretching them, depositing them on an air-permeable sieve belt, prewetting with low-pressure water jets, and then consolidating with high-pressure water jets, while using heated outfeed rolls for preconsolidation to maintain mat stability and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy and voluminous filament mats are consolidated by traditional water jet methods, then consolidation is achieved, but unwanted irregularities occur in the mat
Solution Approach 1:
The patent applies preliminary action by using heated outfeed rolls to pre-consolidate and stabilize the filament mat before it undergoes water jet consolidation. This preliminary thermal treatment prepares the mat structure to withstand the subsequent hydraulic consolidation without developing irregularities, thereby resolving the contradiction between achieving consolidation and maintaining mat uniformity.
Solution Approach 2:
The patent changes the physical parameters of the consolidation process by introducing thermal energy through heated outfeed rolls before hydraulic consolidation. This parameter change (adding temperature control) modifies the mat's mechanical properties, making it more resistant to deformation during water jet treatment, thus maintaining uniformity while achieving consolidation.
2Reliability
If heavy and voluminous nonwovens are consolidated by mechanical needling or hydraulic needling, then consolidation is achieved, but the mat must be separated from the belt causing damage and non-uniformity
Solution Approach 1:
The patent utilizes phase transitions by applying thermal energy through heated outfeed rolls to partially melt and re-solidify the filament structure in place on the belt. This thermal phase change enables consolidation without mechanical separation, eliminating the harmful effects of mat damage and non-uniformity while achieving effective consolidation.
Solution Approach 2:
The heated outfeed rolls act as an intermediary between the filament mat and the consolidation process. Instead of directly separating and mechanically needling the mat, the thermal intermediary gradually consolidates the structure in place, preventing damage and maintaining uniformity while achieving the desired consolidation effectiveness.
3Reliability
If heat is applied long enough to melt filaments in the core region for consolidation, then good consolidation is achieved, but the surface is overcooked and melted
Solution Approach 1:
The patent applies segmentation by dividing the consolidation process into two distinct stages: first, thermal pre-consolidation using heated outfeed rolls that applies gentle heat to stabilize the mat structure, and second, hydraulic consolidation using water jets that provides the intense localized heat needed for core region filament melting. This segmentation allows each stage to perform its specific function without causing surface overcooking.
Solution Approach 2:
The patent implements local quality by using heated outfeed rolls that apply thermal energy selectively to the mat structure without directly contacting the surface filaments. The thermal energy penetrates to the core region where consolidation is needed, while the surface remains protected from excessive heat, thus achieving core consolidation without surface degradation.
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 allows for reliable hydraulic consolidation and delivery of the mat to final treatment without impairing its quality, ensuring uniform filament distribution and minimizing energy consumption in producing high-mass per unit area spunbond webs.
Implementation Method 1
air is sucked through the belt from below in order to stabilize the mat
Implementation Method 2
The mat is wetted on the belt
Implementation Method 3
consolidated mat with a high-pressure water-jet treatment
Implementation Method 4
heated outfeed rolls for preconsolidation
Data Source
AI summary
A spunbond web is made by extruding a multiplicity of hot thermoplastic filaments, passing the filaments along an upstream stretch of a path, cooling and stretching the filaments as they move along the upstream stretch of the path, and depositing the cooled and stretched filaments at a downstream end of the upstream stretch on a foraminous belt such that the filaments form a mat thereon. The belt is continuously displaced the belt so as to move the mat downstream along a downstream leg of the path. The mat on the belt, then consolidated with a high-pressure water-jet treatment, and further processed.