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
  • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/08—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 halogenated hydrocarbons
  • D01F6/12—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 halogenated hydrocarbons from polymers of fluorinated hydrocarbons
• • 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
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H5/00—Special paper or cardboard not otherwise provided for
  • D21H5/12—Special paper or cardboard not otherwise provided for characterised by the use of special fibrous materials
  • D21H5/20—Special paper or cardboard not otherwise provided for characterised by the use of special fibrous materials of organic non-cellulosic fibres too short for spinning, with or without cellulose fibres

Definitions

• the present invention relates to fibrids and fibrils based on polymers of vinylidene fluoride. These fibrids and fibrils are a special form of fibers that have special physical properties
• Fibrids and fibrils made from polyolefins or polyamides are known. Their manufacture is e.g. described in the journal “Angewandte Chemie", 90 (1978), pp. 833-926 or in GB-PSs 14 91 050, 15 30 522 and 15 52 313. These known fibrids are mainly used as substitute products of pulp, e.g. in papermaking.
• Polyvinylidene fluoride has excellent dielectric properties, while the polymer from which the fibrids are obtained has reduced dielectric properties.
• the new fibrids can therefore be used in special areas in the electronics industry; for example, they can be embedded in media with a higher modulus of elasticity, so that the piezoelectric effect is enhanced.
• the new fibrids made of polyvinylidene fluoride can also be excellently used in filters for aggressive substances, even at higher temperatures of e.g. Use 120 0, e.g. in the filtration of nitric acid, where the known polyolefin fibrids cannot be used.
• PVDF polyvinylidene fluoride
• the new fibrids have a very large surface area, which can be up to 130 m / g.
• the high absorption capacity for water is surprising.
• PVDF - both in powder form and as a shaped body - has practically an adhesive property for water, the new fibrids contain more than 90% by weight of water after their production. Other liquids also adhere equally well to the new fibrids. This property is also retained when the new fibrids are dried and then treated with water with the addition of small amounts of surface-active substances.
• the new fibrids of the PVDF can be produced on the one hand analogously to the production of fibrids from polyamides: the polymer is dissolved in a suitable water-miscible solvent and the polymer precipitates in water under shear-inducing conditions. Suitable shear-inducing conditions are mentioned in the references mentioned above.
• PVDF powder can nevertheless be dissolved in acetone if the dissolving process is carried out just below the boiling point of acetone or if the PVDF powder is treated with acetone under pressure at temperatures above 52 ° C.
• up to 10% solutions of PVDF in acetone can be produced, which are stable at 20 ° C and, depending on the concentration, have a service life of between 10 and 24 hours at this temperature. Fibrids made of PVDF can be produced from these solutions in a manner known per se.
• solvents are the higher homologues of acetone, provided they are liquid * at room temperature. If necessary, the PVDF powder must be dissolved in these solvents in the same way as when using acetone. Ethylene and propylene carbonate, ⁇ -butyrolactone, dimethylacetamide, tetramethylurea and dimethyl sulfoxide are also suitable as solvents. Depending on the choice of solvent, fibrids with different contents of crystal form I are obtained under the same precipitation conditions.
• the polymer may also contain small amounts (up to 10 wt .-%) copolymerized further monomers * and miscible with water contains or grafted on.
• the melt flow index (MFJ according to DIN 53 735) should be between 0.1 and 200.
• PVDF with small amounts of copolymerized comonomers and or compounded additional polymers has further advantages: PVDF with copolymerized tetrafluoroethylene or other monomers from fluorinated olefins, with the same shear forces and the same solvents, give fibrids with a larger surface area and a higher PVDF content of the crystal form I. It has been shown that if the same solvents are used, the content of fibrids of crystal form I is directly dependent on the surface of the fibrids: the larger the surface, the greater the content of crystal form I.
• Crystal form I is understood to mean the crystal form which has the excellent dielectric properties (cf. J.Polym.Sc.:Part A, Vol. 3, pp. 4263-4278 (1965)). It is therefore possible to produce fibrids with defined dielectric properties by varying the shear forces and the polymerized second monomer.
• the fibrid content of crystallization form I can also be determined by varying the PVDF content in the solutions to be precipitated; the higher this is, the higher the content of crystallization form I.
• PVDF is compounded with other olefinic polymers in amounts of up to about 15% by weight, it is still possible to convert the new fibrids to one second way of producing:
• the compounds are processed into oriented films and these oriented films are mechanically crushed.
• fibrids of crystallization form I are also obtained.
• a highly crystalline PVDF (which likewise predominantly consists of crystallization form II) which is compounded with 0.5 to 10% by weight of an isotactic polypropylene is preferably used for the type of production.
• the production and orientation of the films from such a compound is carried out in a manner known per se, e.g. by extruding, then quenching and stretching in two directions perpendicular to each other.
• the mechanical stretching of the stretched film takes place at temperatures between -20 and -60 ° C.
• the shear-induced precipitation of PVDF fibrids from acetone solution is carried out as follows: Varying amounts of water are pumped through a nozzle with an inside diameter of 2 mm and an outside diameter of 3 mm.
• the o free-falling water jet has a constant length of 50 cm. After 50 cm the water jet hits a water surface of constant height; the height is maintained by means of an appropriate overflow. The is via an annular nozzle
• Example 2 acetone solution according to Example 1 applied to the water jet at constant pressure.
• the ring nozzle ends about 1 mm above the water outlet.
• Table 1 shows the results for a ring nozzle with a gap width of 0.8 mm, the water pressure being varied by changing the throughput speed. The higher the water pressure, the greater the shear-inducing forces.
• Example 5 is repeated with an annular nozzle which has a gap width of 0.4 mm. This measure increases the shear-inducing effect. Fibrids are obtained, the specific surface area of which has risen to 105 and the content of crystal form I was 75%.
• Tetrafluoroethylene used. Fibrids with a specific surface area of 85 and a crystal form 1 content of 85% are obtained.
• Example 3 The procedure of Example 3 is repeated with the difference that a 7.5% solution of a polyvinylidene fluoride with an MFJ of 20 in dimethyl sulfoxide (dissolving temperature 75 ° C.) is used. Fibrids with a specific surface area of 50 are obtained. These differ from those of Example 3 in that they have practically the pure crystal form I in the crystalline phase, which has been proven by IR absorption and X-ray diffraction.
• the biaxially stretched film thus obtained contains 75% crystal form I in the crystalline system of polyvinylidene fluoride.
• This film is cooled to -50 ° C. and then split with rapidly rotating knives. Fine-fiber polyvinylidene fluoride fibrils with a specific surface area of 95 are obtained.
• the crystal form I remains fully preserved after this process.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Textile Engineering (AREA)
• Dispersion Chemistry (AREA)
• Mechanical Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Artificial Filaments (AREA)
• Laminated Bodies (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=6118067

Family Applications (1)

Country Status (3)

Cited By (3)

Families Citing this family (2)

Citations (4)

• 1980
  • 1980-12-02 DE DE19803045333 patent/DE3045333A1/de not_active Withdrawn
• 1981
  • 1981-10-07 DE DE8181108023T patent/DE3166192D1/de not_active Expired
  • 1981-10-07 EP EP81108023A patent/EP0053242B1/fr not_active Expired
  • 1981-12-01 JP JP56191901A patent/JPS57121609A/ja active Pending

Patent Citations (5)

Also Published As

Similar Documents

Legal Events