Classifications

• • 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
  • D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
  • D01F6/70—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyurethanes
• • 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
  • D01D5/40—Formation of filaments, threads, or the like by applying a shearing force to a dispersion or solution of filament formable polymers, e.g. by stirring

Definitions

• the invention relates to plastic fibrids according to the preamble of claim 1.
• Plastic fibrids are non-spinnable, highly surface-rich fibers with irregular fiber morphology. They are made up of crystalline and amorphous fiber parts and represent very small fiber units. The possible uses of these fibers have increased significantly in recent years. In addition to the conventional areas of application, such as in paper production, the increasing importance of the recyclability of products enables further sales markets to be opened up.
• Plastic fibrids made of polyethylene (HDPE, LLDPE) and polypropylene (PP) are known to date.
• the plastic fibrids are manufactured using the flash spinning process.
• the plastics are emulsified in a water-solvent mixture under pressure and temperature and the emulsion is sprayed into a vacuum.
• the solvent evaporates, the temperature drops sharply and the plastic is transformed into fibrids under crystallization.
• plastics which are economically and technically suitable in normally available solvents, such as e.g. aliphatic hydrocarbons, are soluble. The result is products that have to be subjected to post-treatment.
• Plastic fibrids made of polyacrylonitrile (PAN) or polyaromatics are made from prefabricated splicable fibers.
• the way to produce the fibrids is via foils or staple fibers.
• the film is extruded, cut, hidden and mechanically fibrillated.
• the film is stretched many times its length under the influence of heat.
• the molecules must be oriented at a temperature below the crystallite melting point. There is a significant increase in tear strength and a decrease in elongation at break in the stretching direction.
• Spun fibers are specially stretched (high modulus) to increase the tendency to splice.
• the use of the fibrids is essentially based on the raw material properties of the starting plastics.
• the invention has for its object to create new plastic fibrids.
• polyurethane-based fibrids preferably from a hydroxyl polyurethane
• the fibrids are characterized by the desired fibril fineness and shortness of 0.1 to 5 mm during manufacture.
• the fibrids according to the invention are characterized in that they consist of a polyurethane (PUR) which is injected as a low-viscosity jet into a shear field formed by liquid jets, torn apart by the liquid jets and by cooling, crystallization and orientation to fibrids is formed.
• PUR polyurethane
• the polyurethane-based fibrids have a specific surface area of 1 to 10 m 2 / g and can be dispersed in water without pretreatment and additives.
• the Schopper-Riegler value is approx. 10 o .
• the softening temperature is between 45 - 70 o C with good temperature stability up to over 200 o C.
• the inventive method for producing fibrids based on thermoplastic polyurethane is based on the idea that at temperatures below its decomposition temperatures between 50 o C and 350 o C, in particular 200 o C and 300 o C, to heat and to a viscous mass to tear up.
• the polyurethane jet After heating, the polyurethane jet has a viscosity of less than 200 pscal.seconds, preferably less than 100 (Pa.s).
• the low-viscosity polyurethane is freely sprayed into a high-energy shear field at a pressure between 100 and 1000 bar at high speed.
• the shear field forms liquid or gaseous atomizing jets that are aligned with a center and hit the polyurethane jet with high kinetic energy at pressures between 100 and 1000 bar.
• the atomizing jets preferably consist of cryogenic liquefied gases, such as the inert gases nitrogen and argon. Water can also be used at pressures above 100 bar.
• cryogenic liquefied gases such as the inert gases nitrogen and argon. Water can also be used at pressures above 100 bar.
• the polyurethane torn in the shear field with liquid nitrogen jets forms fibrids on cooling, crystallization and orientation.
• the polyurethane melted in an extruder is freely sprayed into the atomization chamber at a temperature of 50 ° C. to 350 ° C. through a nozzle which determines the polyurethane jet geometry.
• the spray pressure is at least 100 bar and is only limited by technical and economic limits with regard to its maximum pressure, for example 1000 bar.
• the polyurethane jet immediately reaches the center of the shear field generated by a nozzle system.
• the nozzle system consists of flat jet or full jet nozzles, which are arranged at an angle of 30 to 150 ° to the polyurethane jet.
• the polyurethane jet is torn apart by the energy of the shear field and at the same time extremely cooled.
• the kinetic energy of the atomizing medium preferably a liquefied inert gas, in particular nitrogen
• the large temperature difference of up to 650 K cause the polyurethane to be so heavily loaded that it is broken up into fibrids.
• the fibrids accumulate at the bottom of the reaction space. They can be removed through an opening in the reaction chamber.
• the resulting nitrogen gas is conveyed through a filter and a cyclone via a recovery circuit.
• the nitrogen required by the nozzle system of the shear field enters the nozzle system from an insulated tank via a high-pressure pump in a liquid state and under high pressure.
• the fibrids produced show clear variations in the density and length of the individual fibrids and are in their free surface below the products produced by emulsion or dissolving of the surfaces, these have more hidden surfaces.
• the controllability of the fibril sizes has been significantly expanded via the method according to the invention, so that a very fine pulp can be achieved.
• Desmocoll KA 8634 investigated is a polyurethane from Bayer AG.
• Desmocoll KA 8634 is an extremely strongly crystallizing, elastic hydroxyl polyurethane with very low thermoplasticity.
• the extremely easy-flowing PUR type from Bayer AG was broken up into fibrids in the shear field with cryogenic liquefied nitrogen.
• Desmocoll The physical properties of Desmocoll are listed below: Trade name: Desmocoll Type: KA 8634 Manufacturer: Bayer AG Softening temperature: 45 - 70 o C Density: approx. 1.2 g / cm at 20 o C
• Desmocoll was cut up under the test conditions given in the table.
• thermoplastic polyurethane The fibrids made of thermoplastic polyurethane are characterized by high fineness, few melt particles and good adhesion.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Textile Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Mechanical Engineering (AREA)
• Nonwoven Fabrics (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Artificial Filaments (AREA)

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• 1995
  • 1995-07-04 DE DE1995124356 patent/DE19524356C1/de not_active Expired - Fee Related
• 1996
  • 1996-05-30 EP EP96108678A patent/EP0753607A3/fr not_active Withdrawn

Patent Citations (2)

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