PHA Multifilament Spinning Layout for Breakage-Free Fine Filaments
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Solution Overview
Problem
Existing methods for producing multifilaments containing poly(3-hydroxybutyrate) resin face challenges in achieving high productivity due to filament breakage and fusion during the spinning process, particularly when increasing the haul-off roll speed.
Innovation Solution
A method involving a spinning nozzle with non-uniformly distributed discharge holes, where the peripheral region has a higher density of discharge holes, and gas cooling at specific temperature and speed ranges to control filament cooling and crystallization, allowing for increased haul-off speed without breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the roll speed at the time of hauling off the filamentous resin composition is increased, then productivity is improved, but filament breakage and fusion occur
Solution Approach 1:
The invention changes the temperature parameter of the gas flow from the conventional range (not lower than glass transition temperature and not higher than crystallization temperature) to a specifically lower range (not lower than -50°C and not higher than the glass transition temperature). This parameter change allows the filamentous resin composition to be cooled more effectively before hauling off, enabling higher roll speeds without filament breakage or fusion, thus resolving the contradiction between productivity and reliability.
Solution Approach 2:
The invention replaces the conventional mechanical cooling method (relying on ambient cooling or mild air flow) with a controlled cold gas flow system. This substitution enables precise temperature control of the filamentous resin composition, allowing it to maintain structural integrity at higher hauling speeds, thereby resolving the contradiction between productivity improvement and prevention of filament defects.
2Temperature
If the speed of the air flow is increased to improve cooling effect, then cooling efficiency is improved, but the patent indicates cooling effect is too small when speed is less than 0.1 m/s
Solution Approach 1:
The invention fundamentally changes the temperature parameter of the gas flow from ambient or mildly cooled conditions to a specifically low temperature range (not lower than -50°C and not higher than the glass transition temperature). This parameter change enables effective cooling even at very low gas flow speeds (0.01 m/s or greater and less than 0.10 m/s), resolving the contradiction between cooling efficiency and gas flow speed by making the gas itself much colder rather than relying on higher flow rates.
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 approach enhances the productivity of multifilaments by reducing filament breakage and fusion, achieving a small average fineness of single filaments while maintaining flexibility and strength.
Implementation Method 1
cooling the raw filaments by blowing gas onto the raw filaments in the molten state
Implementation Method 2
a temperature of the gas is from (Tc - 45) to (Tc - 20)°C [Tc is a crystallization temperature of the composition including the poly(3-hydroxyalkanoate) resin]
Data Source
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AI summary
The present invention provides a method for producing a multifilament, the method making it possible to increase the productivity of a multifilament containing a poly(3-hydroxybutyrate) resin and having a small average value of the fineness of single filaments. The present invention is a method for producing a multifilament including 50 or more single filaments by melt spinning, the method including the steps of: (A) obtaining 50 or more raw filaments in a molten state by discharging a composition including a poly(3-hydroxyalkanoate) resin from a spinning nozzle; and (B) cooling the raw filaments by blowing gas onto the raw filaments in the molten state. The spinning nozzle includes a nozzle surface including 50 or more discharge holes. The nozzle surface is segmented into a central region and a peripheral region surrounding the central region. An outer edge of the central region and an outer edge of the peripheral region are similar in shape to each other and share a same area centroid. A similarity ratio between the outer edge of the central region and the outer edge of the peripheral region is 1 : 2. The number of discharge holes present in the peripheral region exceeds 75% of the number of discharge holes present on the nozzle surface. A temperature of the gas is from (Tc - 45) to (Tc - 20)°C [Tc is a crystallization temperature of the composition including the poly(3-hydroxyalkanoate) resin]. A speed of the gas is 0.01 m/s or greater and less than 0.10 m/s. An average value of fineness of the single filaments is from 3.0 dtex to 15.0 dtex.