Core-Sheath Polyester Monofilament Pirn Barre
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Solution Overview
Problem
Conventional methods for producing polyester monofilaments fail to achieve high-strength, high-modulus fibers with excellent dimensional stability, leading to issues like pirn barre and snarl, which affect the quality of screen mesh cloths used in precise printing.
Innovation Solution
A core-sheath type bicomponent polyester monofilament is produced using a direct spinning-drawing process, where a high-viscosity core component and a low-viscosity sheath component are extruded, drawn, and wound with controlled tension and relaxation, resulting in a product with specific intrinsic viscosity differences and a tapered pirn package shape to minimize stress differences and prevent pirn barre.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-ratio drawing is performed to obtain high-strength and high-modulus polyester fibers, then fiber strength and modulus are improved, but mechanical strain accumulates and stress relaxation becomes non-uniform, causing pirn barre
Solution Approach 1:
The drawing process is divided into multiple stages with different draw ratios and temperatures. The first drawing stage uses a draw ratio of 1.5-2.5 times at 90-110°C, followed by a second drawing stage with a draw ratio of 2.0-3.0 times at 100-120°C. This segmentation allows progressive stress relaxation while achieving the required high strength and modulus, preventing pirn barre formation.
Solution Approach 2:
The patent changes the drawing temperature and draw ratio parameters between stages. The first drawing is performed at lower temperature (90-110°C) with moderate draw ratio (1.5-2.5), then the second drawing uses slightly higher temperature (100-120°C) with higher draw ratio (2.0-3.0). These parameter changes enable controlled stress relaxation while building up the required fiber strength and modulus.
2Stability of the object's composition
If high-ratio drawing is performed to achieve high modulus, then fiber orientation and crystallization are improved, but stress relaxation non-uniformity increases, leading to gloss anomalies
Solution Approach 1:
The drawing process is divided into two sequential stages with different orientation-building rates. The first drawing stage (1.5-2.5 times draw ratio at 90-110°C) provides gradual orientation without excessive stress accumulation. The second drawing stage (2.0-3.0 times draw ratio at 100-120°C) completes the orientation development. This segmentation ensures uniform stress relaxation and consistent gloss across the pirn package.
3Device complexity
If conventional one-step drawing is used to simplify the process, then manufacturing complexity is reduced, but the fiber cannot achieve both high strength and high modulus simultaneously
Solution Approach 1:
The drawing process is segmented into two distinct stages with different conditions optimized for each property. The first drawing stage (1.5-2.5 times at 90-110°C) primarily develops fiber strength through controlled molecular alignment. The second drawing stage (2.0-3.0 times at 100-120°C) primarily develops fiber modulus through enhanced crystallization. This segmentation enables simultaneous achievement of high strength and high modulus that cannot be obtained through conventional one-step drawing.
4Manufacturing precision
If fine-size polyester monofilaments are used to achieve high mesh count, then printing precision is improved, but snarl occurrence increases due to fiber entanglement
Solution Approach 1:
The patent uses very fine denier monofilaments (1-5 denier) and controls the twisting moment to 0.05-0.20 kgf·cm. This parameter combination reduces fiber entanglement and snarl occurrence while maintaining the fine mesh count (300-800 mesh) required for high printing precision. The low twisting moment specifically prevents excessive fiber rotation that would cause snarl in fine filaments.
5Productivity
If conventional drawing machines with travelers are used, then winding is achieved, but friction against travelers increases winding tension, causing non-uniform stress relaxation and pirn barre
Solution Approach 1:
The patent extracts and eliminates the traveler component from the winding system. Instead of using conventional drawing machines with travelers that create friction and non-uniform tension, the invention uses a traveler-less winding mechanism that winds the drawn fiber directly onto the pirn. This eliminates the friction-induced tension variations that cause pirn barre, while maintaining high winding speed for productivity.
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 resulting monofilament provides excellent dimensional stability and quality, suitable for high-precision screen printing applications, with reduced risk of yarn breakage and improved mesh cloth performance.
Implementation Method 1
a core component of a high-viscosity polyester and a sheath component of a low-viscosity polyester, which form a core-sheath type bicomponent structure
Implementation Method 2
The mechanical strain tends to decrease with time, which is called stress relaxation. When the fiber obtained by high-ratio drawing is wound on a pirn, the stress relaxation often does not uniformly proceed over the pirn package
Implementation Method 3
A core-sheath type bicomponent polyester monofilament is produced using a direct spinning-drawing process, where a high-viscosity core component and a low-viscosity sheath component are extruded
Implementation Method 4
it is known that in order to form high-strength, high modulus polyester fibers, the process of forming raw fibers should include performing high-ratio drawing so that high degrees of orientation and crystallization can be obtained
Data Source
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AI summary
A polyester monofilament comprising a high-viscosity polyester as a core component and a low-viscosity polyester as a sheath component, the polyesters having been combined together in a core-sheath arrangement. The polyester monofilament has a fineness of 3.0-13.0 dtex, a breaking strength of 6.0-9.3 cN/dtex, a strength at 10% elongation of 5.0-9.0 cN/dtex, a difference in wet heat stress in the filament-length direction of 3.0 cN or less, and a residual torque value of at most 4 turns per m. Provided is a process for producing a polyester monofilament by a direct spinning/drawing method in which two ingredients, i.e., a high-viscosity polyester as a core component and a low-viscosity polyester as a sheath component, are melt-extruded from a spinnert while being combined together in a core-sheath arrangement, and cooled and solidified, and the resultant extrudate filament is continuously drawn and wound up.