IL43990A - Method of spining fiber using a fusion-melt polymer composition - Google Patents

Abstract

1452400 Melt spinning refractory polymers AMERICAN CYANAMID CO 22 Jan 1974 [5 Feb 1973 2 March 1973 23 March 1973 10 April 1973 5 July 1973] 02985/74 Heading B5B Shaped articles including filaments and films, are prepared by extruding a single phase fusion melt of a refractory polymer esp. acrylonitrile, but also other high melting point polymers, and a melt assistant i.e. a substance which is capable, when used under pressure sufficient to prevent boiling at temperatures above its atmospheric boiling point, of reducing the melting point of the refractory polymer to a temperature below the degradation range of the polymer, other than normal solvents for the polymer, at a temperature Tf which is above the single phase melt melting point temperature M and also above the boiling point at atmospheric pressure of said melt assistant through a spinnerette directly into a pressurized solidification zone wherein the following conditions obtain (1) there is a partial pressure of melt assistant such that the composition profile across the crosssection of the nascent extrudate so produced remains relatively flat: (2) the concentration of melt assistant retained in said nascent extrudate remains at a value at least 70% of the concentration of melt assistant in said single phase fusion melt, and (3) the temperature of the nascent extrudate is below said temperature Tf but not lower than 20‹ C. below said temperature M. Preferred melt assistants are 1-4C-alkanols, acetonitrile, formic or acetic acids, water or a dilute solution of an inorganic salt in water, the solution being too dilute to act as a solvent for acrylonitrile. Thus a blended mixture of polymer and melt assistant is extruded through a spinnerette 12 into a pressurized chamber 13 and the filaments 21 are drawn under tension by a rotary godet or thread advancing rolls 22 and then wound up on yarn package 30 or relaxed in a steam chamber 33 prior to wind up. [GB1452400A]

Claims (3)

A process for melt-spinning shaped articles of refractory polymer comprising: extruding a single phase fusion melt consisting essentially of refractory both as hereinbefore defined polymer and melt assistant/at a temperature which is above the single phase fusion melt melting point temperature M and also above the boiling point at atmospheric pressure of said melt assistant through a spinnerette directly into a pressurized solidification zone wherein the following conditions obtain: (1) the composition profile across the cross-section of the nascent extrudate so produced remains relatively flat; (2) the concentration of melt assistant retained in said nascent extrudate remains at a value at least 70% of the concentration of melt assistant in said single phase fusion melt; and (3) the temperature of the nascent extrudate is below said temperature Tf but not lower than about 20°C. below said temperature M. 2. A process as defined in Claim 1 wherein said refractory polymer is acrylonitrile polymer. 3. A process as defined in Claim 2 wherein said melt assistant comprises acetonitrile. 4. A process as defined in Claim 2 wherein said melt assistant comprises an aliphatic alcohol of 1 to 4 carbon atoms. 5. A process as defined in Claim 2 wherein said melt assistant comprises formic acid or acetic acid. 6. A process as defined in Claim 2 wherein said melt assistant consists essentially of water and said solidification zone contains steam under pressure. 7. A process as defined in Claim 2 wherein the melt assistant in said single phase fusion melt is a dilute aqueous salt solution and the solidification zone contains steam under pressure. 8. A process as defined in Claim 2 further characterized in that the shaped article is drawn while in said solidification zone at a linear speed of about 25 to 250 times the linear speed of said single phase fusion melt through said spinnerette. 9. A shaped article prepared by the process of Claim 8. 10. An acrylonitrile polymer fiber having a denier between 0.5 and 80 prepared by the process of Claim 8. 11. A process as defined in Claim 8 additionally comprising the step of relaxing the thus-drawn shaped article in a free-to-shrink condition. 12. A process as defined in Claim 8 further characterized in that the shaped article is drawn while in said solidification zone at a linear speed of about 5 to 150 times the linear speed of said single phase fusion melt through said spinnerette in a first stage followed by a second state of about 1.1 to 30 times. 13. A process as defined in Claim 12 additionally comprising the step of relaxing the thus-drawn shaped article in a free-to-shrink condition. 14. A process for melt-spinning shaped articles of refractory polymer comprising: extruding a single phase fusion melt consisting essentially of re- both as hereinbefore defined fractory polymer and melt assistant/ at a temperature T_ which is above the single phase fusion melt melting point temperature M and also above the boiling point at atmospheric pressure of said melt assistant through a spinnerette directly into a pressurized solidification zone wherein the following conditions obtain: (1) the partial pressure of melt assistant is between 56% and 110% of the vapor pressure of the melt assistant at temperature Tf; (2) the temperature T is at least equal to the saturation temperature of the melt assistant at a vapor pressure equal to said partial pressure p; and (3) the total pressure P is at least equal to said partial pressure p; said conditions ensuring boundary control of any evaporation of melt assistant from the nascent extrudate produced. 15. A process as defined in Claim 13 wherein said solidification zone contains steam under pressure. 16. A process as defined in Claim 13 wherein the melt assistant in said single phase fusion melt is an organic melt assistant and wherein said solidification zone contains steam under pressure. 17. A process as defined in Claim 13 wherein said refractory polymer is acrylonitrile polymer. 18. A process as defined in Claim 17 wherein said melt assistant is water and said solidification zone contains steam under pressure. 19. A process as defined in Claim 18 wherein the partial pressure p is between 80% and 100% of the vapor pressure of water at temperature and the total pressure P is equal to or does not substantially exceed such partial pressure p. 20. A process as defined in Claim 17 wherein the melt assistant in said single phase fusion melt is a solution of a higher boiling solute in a lower boiling solvent for such solute and the melt assistant in said solidification zine comprises said solvent. 21. A process as defined in Claim 20 wherein said solute is an inorganic salt and said solvent is water, said solution being of a concentration too dilute to serve as a solvent for said acrylonitrile polymer. 22. An acrylonitrile polymer fiber prepared by melt-spinning a single phase fusion melt of acrylonitrile polymer and melt assistant and drawing the nascent filament 25 to 250 times the linear speed of the single phase fusion melt through the spinnerette from which it is spun to produce a fiber having a denier of between 0.5 and 80. 23. The process of Claim 1 further characterized by drying said fibers at a temperature above 90°C. while substantially preventing loss of water from the freshly melt-spun fibres at any temperature below about 90°C. 3 until said drying step, thereby minimizing the tendency of such fibers to form voids and micro-voids therein. S. HOROWIT & CO. AGENTS FOR APPLICANTS CLAIMS:

1. A process for preparing an acrylonitrile polymer fiber which comprises spinning a homogeneous single phase fusion melt of acrylonitrile polymer and water at a temperature ranging from minimum melt temperature to below the temperature of significant polymer degradation to produce an extrudate, cooling the extrudate in a steam pressure zone from the molten state to a stretchable plastic state, maintaining superatmospheric steam pressure in the pressure zone such that water in the plastic extrudate is vaporized at a rate substantially equivalent to the rate of diffusion of water through the extrudate and the surface zone of the extrudate is kept moist to minimize skin formation, and stretching the extrudate while in -such plastic stretchable state to at least 25X.

2. A process as defined in Claim 1 additionally comprising the step of relaxing the thus-drawn fiber in a free-to-shrink condition.

3. A process as defined in Claim 1 further characterized by drying said fiber at a temperature above 90°C. while substantially preventing loss of water from the freshly spun fiber at any temperature below about 90°C, until said drying step, thereby minimizing the tendency of such fiber to form voids and micro-voids therein. AGENTS FOR APPLICANTS