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
  • D01D5/098—Melt spinning methods with simultaneous stretching
  • D01D5/0985—Melt spinning methods with simultaneous stretching by means of a flowing gas (e.g. melt-blowing)
• • 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
  • D01D5/28—Formation of filaments, threads, or the like while mixing different spinning solutions or melts during the spinning operation; Spinnerette packs therefor
  • D01D5/30—Conjugate filaments; Spinnerette packs therefor
  • D01D5/36—Matrix structure; Spinnerette packs therefor

Definitions

• This invention relates to extrusion of polymer fibers, and in particular fibers that have a diameter of less than one micron.
• Fibers and filaments have been produced for many years using methods well known as melt blowing and spun laid fiber spinning. Melt blowing is typically associated with fibers of finite length whereas the spun laid process is typically associated with continuous filaments. In both of these technologies there has been an extended effort from many individuals to reduce the diameter of the fibers produced. Typical minimum fiber and filament diameters for these technologies is now on the order of 3 to 5 microns.
• One method for producing finer fibers is known as bicomponent spinning. In this method, disclosed for example in U.S. 5,162,074 to Hills and incorporated herein by reference, two or more polymers are extruded through specially designed spin packs which configure the filaments into arrangements known as side by side, sheath/core, islands in the sea or segmented pies.
• those of the islands in the sea and segmented pies are such that although the filaments of the combined components exceed 1 micron in diameter, the individual components can be separated from each other by post processing to result in filaments with a diameter of less than 1 micron.
• This post processing typically includes mechanical action to fracture the components apart at the segmented pie interfaces or chemically dissolving the sea polymer to leave only the islands polymer.
• These post processing steps can be both costly an inefficient.
• An article "Spunbonded nonwovens made from splittable bicomponent filaments" by Schilde, Erth, Heye and Blechschmidt, Chemical Fibers International VoI 57 No 1 , March 2007 describes multiple methods and the difficulties encountered in mechanical splitting of these fibers.
• Islands in the sea filaments provide the smallest known fiber diameters from melt polymers, ref “Spinning of Submicron diameter Fibers” and “Production of Sub-Micron Fibers in Nonwoven Fabrics” by Hagewood on Hills lnc website hillsinc.net where as many as multiple thousand of island fibers can exist within a single bicomponent filament.
• Complete removal of the sea polymer is a known issue with this technology as evidenced by art disclosed to facilitate this process. See for example U.S. 6,861,142 "Controlling the dissolution of dissolvable polymer components in plural component fibers".
• a plurality of polymers is spun through a spin pack designed to produce islands in the sea or segmented pie bicomponent filaments and then through a converging diverging gas nozzle.
• the spin pack is designed such that the bicomponent filaments are extruded through a single row of holes.
• the tip of the spin pack is tapered to direct the gas flow toward the extruded filaments.
• the gas nozzle is designed with a converging diverging cross section so that the gas velocity may reach sonic or even supersonic velocity.
• FIG.1 shows an example of an "island in the sea” configuration
• FIG. 2 shows an example of a segmented pie configuration.
• FIG. 3 shows an example of a side by side configuration.
• Fig.4 shows an example of a spinning apparatus of the invention.
• Fig. 5 shows an example of a configuration of gas nozzles.
• Fig. 6 shows a second example of a configuration of gas nozzles.
• pluricity is meant more than one.
• pluricity in the context of polymer coextrusion is meant that a plurality of polymers form distinct extrudate phases that are present along the cross section of the entire length of the fiber. Each phase shares a boundary with at least one other phase and the number of phases does not necessarily equal the number of polymers in the plurality. In other words, some of the phases may be multicomponent.
• the process of the invention is directed to a method for producing submicron fibers by melt spinning a plurality of polymers through a spinneret die in a plural component configuration and splitting the plural components into their individual parts by a high velocity gas nozzle.
• Fiber from any melt processible polymers can be produced by this method, such as polyesters, polyamides, polyolefins and many other polymers, but it is preferable to choose polymers that will facilitate the bursting of the filaments along the defined interfaces of the components.
• polyethylene terephthalate (PET) and polyethylene (PE) may be spun with polyester as the island polymer and polyethylene as the sea polymer.
• PET polyethylene terephthalate
• PE polyethylene
• PE polyethylene
• the choice of a high melt flow polyethylene with a standard viscosity polyester will enhance the bursting of the filaments along the weak boundaries without loss of polyester fiber properties due to excessive heating or polymer degradation.
• the island fibers comprise more than 50%, or more preferably, more than 75% of the bicomponent filament, then the amount of sea polymer in the final product is reduced.
• the filaments Once the filaments have been burst into their individual components by the high velocity gas flow, there is no difficulty in separating the sea polymer from the island polymer.
• the bursting causes the island polymer to retain their shape as well defined filaments while the sea polymer fragments into particles and fibers.
• a sea polymer is chosen such that it is an easily dissolvable polymer, such as polyvinyl alcohol, the removal issues in conventional bicomponent fibers are no longer present.
• the sea polymer can be chosen to add functionality to the final product.
• the PE can be used as a bonding agent. A post heat treatment or calendering operation will cause the PE fragments and fibers to bond the PET filaments to create a strong nonwoven sheet.
• the final fiber size distribution in the nonwoven product will be more precise than conventional melt blowing.
• the fibers produced by the process of the invention do not have to be circular in cross section. It should be noted that as the percentage of island polymer is increased above about 50%, the island filaments tend toward hexagonal type packing creating flat sided filaments as opposed to circular cross sections.
• segmented pie or hollow segmented pie filaments the individual components are wedge shaped. In any of these cases, the diameter or minor dimensions of the individual components are controlled such that they are less than 1 micron.
• Another preferred embodiment comprises the above method plus electrostatic charging of the filaments.
• FIGS 1 - 3 are shown examples of fiber configurations for a two polymer system.
• Figure 1 shows an "island in the sea” configuration.
• Figure 2 shows a "segmented pie” configuration, and figure 3 shows a side by side configuration. All three of these configurations can be used in the process of the invention, but the invention is not limited to them, and any configuration in which a plurality of phases coexist in the cross section of the fiber and along the length of the fiber can be used.
• FIG. 4 a schematic diagram shows the various major components of the apparatus.
• two polymers are fed to the apparatus via inlets 41 and 42.
• the invention is not limited to two polymers and multiple inlets can be used.
• the polymers then flow through a set of distribution plates (43) that feed the polymers to a tapered die tip (44).
• the polymers entering the tip are essentially in the desired configuration required before melt splitting, for example in the configurations of figures 1 - 3.
• Gas is fed to the apparatus through an inlet (48) and into a nozzle (45).
• the nozzle has the effect of accelerating the gas to a velocity in the range of 0.7 to 1.4 times the speed of sound.
• Fiber and gas then exit the apparatus together, and optionally past needles (46) to which an electrostatic charge is applied.
• the needles (46) are mounted in an electrostatic insulator plate (47) to prevent arcing to the bottom of the spin pack.
• the gas nozzles may be arranged in the bottom plate as a row of individual circular nozzles corresponding to the polymer die holes on a one to one basis as shown in Figure 5.
• the gas nozzle may be configured as a slot jet as shown in Figure 6.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Textile Engineering (AREA)
• Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)
• Multicomponent Fibers (AREA)
• Chemical Or Physical Treatment Of Fibers (AREA)
• Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)
• Nonwoven Fabrics (AREA)

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• 2008
  • 2008-07-10 KR KR1020107002876A patent/KR20100045469A/ko not_active Withdrawn
  • 2008-07-10 JP JP2010516235A patent/JP2010533247A/ja active Pending
  • 2008-07-10 WO PCT/US2008/069587 patent/WO2009009632A2/en not_active Ceased
  • 2008-07-10 BR BRPI0812614A patent/BRPI0812614A2/pt not_active IP Right Cessation
  • 2008-07-10 CN CN200880023834A patent/CN101688330A/zh active Pending
  • 2008-07-10 EP EP08772500A patent/EP2165011A2/en not_active Withdrawn

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