Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/08—Melt spinning methods
  • D01D5/088—Cooling filaments, threads or the like, leaving the spinnerettes
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D4/00—Spinnerette packs; Cleaning thereof
  • D01D4/02—Spinnerettes
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/18—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polymers of unsaturated nitriles, e.g. polyacrylonitrile, polyvinylidene cyanide

Definitions

• This invention relates to a process for melt-spinning fiber-forming polymers at an increased production rate per spinnerette. More particularly, this invention relates to such a process wherein a spinnerette with more orifices per given area than previously possible is employed.
• the greater density of orifices may arise from closer crowding of conventional sized orifices and associated counterbores, from close crowding of smaller orifices and associated counterbores, or by employing multiple orifices per counterbore.
• a fiber-forming polymer is heated to a temperature at which it melts, is extruded through a spinnerette plate to form filaments which rapidly cool to become solid, and the resulting filaments are then further processed to provide the desired fiber.
• the spinnerette plate that is employed in such processing must contain capillaries to provide the desired filaments while satisfying two additional requirements.
• the capillaries must be of such dimensions as to satisfy back-pressure requirements and must be sufficiently spaced from one another as to prevent premature contact between the emerging fibers that would result in sticking together or fusion of filaments with one another. To satisfy the back-pressure requirements, the capillaries are provided with counterbores of sufficient diameter and depth.
• fusion melts which can be extruded through a spinnerette plate to provide filaments.
• These fusion melts comprise a homogeneous composition of a fiber-forming polymer and a melt assistant therefor.
• the melt assistant is a material which enables the polymer to form a melt at a temperature below which the polymer would normally melt or decompose and becomes intimately associated with the molten polymer so that a single phase melt results.
• the melt assistant must be used in proper proportions with the polymer to provide the single-phase fusion melt. If a low boiling melt assistant is used the melt assistant in proper amounts and the polymer often must be heated at pressures above atmospheric pressure to provide the fusion melt.
• a process for melt-spinning an acrylonitrile polymer fiber which comprises providing a homogeneous fusion melt of a fiber-forming acrylonitrile polymer and water at a temperature above the boiling point of water at atmospheric pressure and at a temperature and pressure which maintains water in single phase with said polymer and extruding said fusion melt through a spinnerette assembly containing a spinnerette plate having an orifice density of at least 18 per square centimeter directly into a steam-pressurized solidification zone maintained under conditions such that the rate of release of water from the nascent extrudate avoids deformation thereof.
• the spinnerette plate has orifices of 60 to 160 microns and the acrylonitrile polymer has a kinematic molecular weight in the range of 30,000 to 60,000.
• the spinnerette plate has a plurality of counterbores within each of which are contained at least 3 capillaries.
• Another preferred embodiment includes the step of stretching the nascent extrudate while it remains within said solidification zone to provide desirable textile properties.
• the present invention by employing a fusion melt of an acrylonitrile fiber-forming polymer and water at a temperature above the boiling point of water at atmospheric pressure and at a temperature and pressure that maintains water and the polymer in a single phase and by extruding the fusion melt directly into a steam-pressurized solidification zone maintained under conditions such that the rate of release of water from the nascent extrudate avoids deformation thereof, provides filamentary extrudates which do not stick together as they emerge from the spinnerette orifices. Since the filaments have no tendency to stick together as they emerge from the spinnerette, the orifices of the spinnerette plate can be located closer together and more orifices can be provided in the spinnerette plate. As a result, the productivity of a spinnerette can be greatly increased without negatively affecting the quality of the resulting fiber.
• the present invention also enables the use of orifices of reduced cross-section relative to those conventionally employed in melt-spinning. As a result an even greater number of orifices can be present in the spinnerette plate.
• the process of the present invention in this embodiment employs fiber-forming polymers of lower molecular weight than conventionally employed. Unexpectedly, the fiber obtained possessses good fiber properties in spite of the low molecular weight of the fiber-forming fiber. It is believed these good fiber properties are the result of processing steps employed.
• the spinnerette plate used in the process of the present invention contains a much greater density of orifices per unit area than do conventional spinnerette plates used in melt spinning by conventional procedures.
• prior art melt-spinning spinnerette plates have a density of 5-10 orifices per square centimeter at most.
• the spinnerette plate contains at least about 18 orifices per square centimeter, preferably at least 25, 50 or more per square centimeter. This enables the process of the present invention to provide a substantial increase in productivity from a given spinnerette. Since processing of the melt is under conditions which lead to nascent extrudates which do not stick together or deform, the higher density of spinnerette orifices is possible.
• melt-spinning spinnerette plates have orifices of about 200--400 microns or larger diameter at their exits ends.
• the process of the present invention may employ orifice of such conventional diameters but preferably uses orifices in the range of about 60 - 160 microns diameter at their exit ends. This provision not only allows a greater number of orifices to be positioned in the spinnerette plate to increase productivity but also enables finer denier fiber to be provided at a given stretch ratio.
• the spinnerette plate of the present invention contains a number of capillaries located within each counterbore.
• the counterbores are necessary to enable the spinnerette plate to operate at a suitable level of back-pressure.
• the spinnerette plate as a whole will contain a substantially greater number of capillaries than the prior art spinnerette plates associated with melt spinning because the problem of sticking together of nascent extrudates is eliminated.
• Increased productivity is provided by increasing the density of capillaries in the spinnerette plate and the number of capillaries in each counterbore beyond the operative limits of conventional melt-spinning spinnerette plates which have restrictions as to hole density imposed by fusing of individual filaments.
• a homogeneous fusion melt of a fiber-forming acrylonitrile polymer that can form a fusion melt with water at a temperature above the boiling point of water at atmospheric pressure and at a pressure and temperature sufficient to maintain water and the polymer in a single fluid phase.
• Polymers falling into this category are known in the art.
• Preferred acrylonitrile fiber-forming polymers are those having kinematic molecular weights ranging from about 30,000 to 60,000, as defined below.
• the fusion melt is prepared at a temperature above the boiling point at atmospheric pressure of water and eventually reaches a temperature and pressure sufficient to maintain water and the polymer in a single, fluid phase.
• the homogeneous fusion melt thus provided is extruded through the spinnerette plate of the present invention directly into a steam-pressurized solidification zone that controls the rate of release of water from the nascent filaments so that deformation thereof is avoided and the process is able to provide filaments which solidify without sticking together one with another in spite of the close proximity of adjacent capillaries.
• the extruded filaments may be processed according to conventional procedures to provide desirable filamentary materials which may have application in textile and other applications.
• the pressurized solidification zone used in the process of the present invention is a critical feature of the process. If this pressurized solidification zone is omitted, water is so rapidly released from the nascent filaments which would emerge into atmospheric conditions that the filaments would become inflated or deformed and interfere with neighboring filaments and necessitate reduction in the number of operative spinnerette capillaries which would defeat the object of the invention.
• the pressurized solidification zone operating at suitable steam pressure, the rate of release of water can be controlled as the nascent filaments solidify so that foaming and deformation thereof is avoided and optimum stretching is possible.
• the particular pressure of steam will vary widely depending upon the polymer employed, the spinning temperature employed and the like.
• the useful values for given systems are those values which minimize or avoid foaming or other forms of deformation of the filaments and provide optimum stretching. These values can readily be determined for any given system of polymer and water taking into account the teachings herein given.
• a particularly preferred embodiment of the process of the present invention is drawing the nascent extrudate while it remains in the steam-pressurized solidification zone. Such drawing can be accomplished in one or more stretches and can eliminate any subsequent drawing normally required for fiber orientation. It is particularly preferred to conduct drawing in two stages with the stretch ratio of the second stage being larger than that of the first stage. It is also preferred to relax the drawn fiber in steam generally under conditions which provide from about 20% to 35% filament shrinkage.
• Kinematic average molecular weight (M k ) is obtained from the following relationship: wherein ⁇ is the average effluent time (t) in seconds for a solution of 1 gram of the polymer in 100 milliliters of 53 weight percent aqueous sodium thiocyanate solvent at 40°C multiplied by the viscometer factor and A is the solution factor derived from a polymer of known molecular weight and in the present case is equal to 3,500.
• a single phase fusion melt was prepared using a copolymer containing 89.3% acrylonitrile and 10.7% methyl methacrylate and having an intrinsic viscosity of 1.52.
• This fusion melt was extruded through a spinnerette having 1266 capillaries each of diameter 200 microns. Each of the capillaries was centered in a counter bore of 2.0 millimeters in diameter and dispersed at a spacing of 4.0 millimeters center-to-center in the spinnerette plate, the density of orifices being 5 per square centimeter of spinnerette plate extrusion surface. Extrusion was conducted at 176°C and the extrudate issued directly into a solidification zone maintained at 25 psig i.e.
• Example 1 The procedure of Example 1 was repeated in every material detail except that a polypropylene melt free of melt assistant and designated as fiber grade having a melt index of 3 (Trademark Rexene PP-3153) was employed and extrusion was conducted at 260-280°C directly into air. The extrudates stuck together as they emerged from the spinnerette and the desired individual filaments could not be obtained.
• a polypropylene melt free of melt assistant and designated as fiber grade having a melt index of 3 (Trademark Rexene PP-3153) was employed and extrusion was conducted at 260-280°C directly into air. The extrudates stuck together as they emerged from the spinnerette and the desired individual filaments could not be obtained.
• Example 1 compared to Comparative Example A shows that the process of the present invention provides desirable fiber using closely spaced orifices.
• Comparative Example B compared to Example 1 shows that other melt-spinning compositions are not effectively processed using closely spaced orifices.
• Example numbers and spinnerette plate details are given below:
• a fusion melt of 14% water and 86% of an acrylonitrile polymer of the following composition was prepared:
• This polymer had a kinematic molecular weight value of 40,000.
• the extrusion temperature was 170°C and extrusion was directly into a steam-pressurized solidification zone maintained at 13 pounds per square inch gauge i.e. a gauge pressure of 89047 N/m 2.
• the extrudates were stretched at a stretch ratio of 4.2 in a first stage and 9.8 in a second stage, dried at 138°C and steam relaxed at 116°C. No filament breakage or sticking occurred.
• the fiber obtained had the following properties:
• Example 6 Following the procedure of Example 6 in every material detail, an additional run was made using a polypropylene melt free of melt assistant and designated as fiber grade having a melt index of 3 (Trademark Rexene PP-3153) in place of the fusion melt of example. Extrusion was conducted at 260-280°C directly into air. The extrudates stuck together as they emerged from the spinnerette and the desired individual filaments could not be obtained.
• Example 6 The process of Example 6 was again repeated in every material detail except that the polymer employed was a copolymer of 94% acrylonitrile and 6 methyl acrylate having a kinematic molecular weight of 48,000. No filament breakage or sticking occurred during extrusion and the filter obtained had substantially the same properties as those of Example 6.
• a fusion melt of 1 5% water and 85% of the acrylonitrile polymer of the following composition was prepared at autogeneous pressure and 170°C:
• the fusion melt was spun at 170°C through a spinnerette assembly having orifice characteristics as follows:
• the extrusion was directly into a solidification zone pressurized with saturated steam at 15 pounds per square inch i.e. 102746 N/m 2 .
• the extruded filaments were stretched in a first stage at a stretch ratio of 3.8 and in a second stage at 6.7 for a total stretch of 25.5x.
• the filaments were dried at 138°C and relaxed in steam at 116°C. Fiber of about 12 denier per filament was obtained having the following properties:
• melt polypropylene (Rexene Grade PP 3153) of fiber grade having a melt index of 3 dg/min was prepared at 260°C and extruded into static air at 25°C. The melt emerging from the union of the individual filaments issuing from single capillaries. Thus, filaments of the desired denier were not obtained using this spinnerette plate design.
• Example 13 The procedure of Example 13 was again followed with the following exceptions:
• the polymer had a kinematic molecular weight value of 40,000 and the spinnerette assembly had the following characteristics:
• Example 13 Following the procedure of Example 13, a number of runs were made using spinnerette assemblies of different design in each run as shown in Table III which also gives the example number. In each instance, continuous spinning was effected wtih no sticking together of the individual filaments.

Landscapes

• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Mechanical Engineering (AREA)
• Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)
• Artificial Filaments (AREA)

Priority Applications (1)

Applications Claiming Priority (6)

Publications (2)

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Family Applications (1)

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• 1979
  • 1979-07-06 DE DE7979301311T patent/DE2963480D1/de not_active Expired
  • 1979-07-06 GR GR59530A patent/GR72246B/el unknown
  • 1979-07-06 EP EP19790301311 patent/EP0008853B1/en not_active Expired
  • 1979-07-17 AR AR27733879A patent/AR222340A1/es active
  • 1979-07-26 PT PT6998979A patent/PT69989A/pt unknown
  • 1979-08-08 BR BR7905093A patent/BR7905093A/pt unknown
  • 1979-08-21 TR TR2132079A patent/TR21320A/xx unknown
  • 1979-08-23 ES ES483587A patent/ES483587A1/es not_active Expired

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