Abstract: An optical waveguide having a core-sheath structure whose core comprises a terpolymer based on vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, is suitable for transmission paths of ca. 10 to ca. 100 m and can also be used at a temperature of above 100.degree. C. without significant reduction of the transmission path.

Abstract: An optical waveguide having a core/sheath structure whose sheath comprises a polymer which is based on vinylidene fluoride and at least one other vinyl monomer containing fluorine and has been modified and crosslinked with a trisalkoxyvinylsilane, is suitable for transmission paths of ca. 10 to 100 m and can also be used at a temperature above 100.degree. C. without any significant reduction in the transmission path.

Abstract: An optical waveguide having a core/sheath structure whose sheath comprises a terpolymer based on vinylidene fluoride, tetrafluoroethylene and hexafluorpropylene, is suitable for transmission paths of ca. 10 to 100 m and can also be used at a temperature of above 100.degree. C. without significant reduction of the transmission path.

Abstract: A process for the continuous agglomeration of granular tetrafluoroethylene polymer powders which cannot be processed from the melt to give molding powders having a high bulk density, an improved powder flow and particle stability and a narrow particle size distribution is described. In this process, the powder to be agglomerated is first introduced uniformly into a pretreatment stage and is dispersed and pre-agglomerated in this stage in the liquid agglomeration medium, composed of water and an organic liquid capable of wetting polytetrafluoroethylene, is then agglomerated to the desired average particle diameter in an agglomeration stage and is finally treated further in an after-treatment stage in order to develop the final shape of the particles. Finally, the powder is separated from the liquid medium and is dried.

Abstract: A semiconductor laser device comprises a plurality of layers of semicondung materials, first contact means providing electrical contact to a basal layer of the device and second contact means providing electrical contact to an upper layer of the device, with at least one layer disposed between the basal layer and the upper layer being selected to be sufficiently thin that size quantization occurs, i.e. that a semiconductor device with a quantum well structure is created. The second contact means comprises a first strip-like contact overlying a first lasing region of the device and a second strip-like contact overlying a second lasing region of the device. The light losses associated with photons generated by laser action in the first region are intentionally made different from the light losses associated with photons generated by laser action in the second region which permits laser action at two distinct wavelengths in a monolithic device.

Abstract: A method and an apparatus are described by producing optical radiation pulses with a duration of the order of picoseconds (10.sup.-12 s) and less using external mode locking of the longitudinal laser modes of a semiconductor laser element operating in an external resonator. In the method of the invention the gain modulation, needed for synchronous mode locking, of the active semiconductor laser element is effected by modulation of the electrical pumping current by way of a high-speed optoelectronic switch, that for its part is controlled by a mode locked master laser. The present method combines the advantages of synchronous optical pumping, as used in commercial mode locked dye laser systems, with the simple type of electrical pumping of commercially available semiconductor laser diodes, more especially double heterostructure laser diodes.

Abstract: The invention relates to films and tubular structures which are selectively permeable to liquids and gases which are based on a copolymer composed of a copolymerized fluorinated olefin, copolymerized vinyl acetate and, optionally, a copolymerized olefin. It is possible for the acetate groups of the copolymer to have been saponified to form OH groups. The films or tubular structures have in each case an inherent, latent capacity for modifying their structure and are at the same time oleophobic and oleophilic. The invention also embraces processes for the preparation of the shaped articles described and processes for modifying their structure. The invention also relates to the use of shaped articles according to the invention.

Abstract: The present invention relates to molded articles of an open-cell structure, containing a copolymer which is comprised of copolymerized, fluorinated olefin, copolymerized vinyl acetate and optionally copolymerized olefin, the acetate groups of the copolymer being optionally saponified into OH groups. The molded articles possess an inherent latent structural convertibility and have effective pores of a diameter in the range from 0.002 to 10 .mu.m. The invention further includes processes for the preparation of the specified molded articles and processes for converting their structure. The invention also relates to several uses of molded articles according to the invention.

Abstract: The present invention relates to molded articles of an open-cell structure, containing a copolymer which is comprised of copolymerized, fluorinated olefin, copolymerized vinyl acetate and optionally copolymerized olefin, the acetate groups of the copolymer being optionally saponified into OH groups. The molded articles possess an inherent latent structural convertibility and have effective pores of a diameter in the range from 0.002 to 10 .mu.m. The invention further includes processes for the preparation of the specified molded articles and processes for converting their structure. The invention also relates to several uses of molded articles according to the invention.

Abstract: A process for the continuous agglomeration of granular tetrafluoroethylene polymer powders which cannot be processed from the melt to give molding powders having a high bulk density, an improved powder flow and particle stability and a narrow particle size distribution is described. In this process, the powder to be agglomerated is first introduced uniformly into a pretreatment stage and is dispersed and pre-agglomerated in this stage in the liquid agglomeration medium, composed of water and an organic liquid capable of wetting polytetrafluoroethylene, is then agglomerated to the desired average particle diameter in an agglomeration stage and is finally treated further in an after-treatment stage in order to develop the final shape of the particles. Finally, the powder is separated from the liquid medium and is dried.

Abstract: Free-flowing sintering powders based on polymers containing at least 98.5% by weight of tetrafluoroethylene units can be prepared from colloidal polymer dispersions obtained in a customary manner by emulsion polymerization, stirring being carried out initially, optionally with the addition of an inorganic salt, until thickening, indicated by optical inhomogeneities, is achieved, an organic liquid which wets the polymer particles and is soluble in water to the extent of not more than 15% by weight then being added and stirring then being continued until granules are produced. The polymers preferably contain up to 1.5% by weight of polymerized units of at least one modifying, perfluorinated monomer. The free-flowing sintering powders have a high bulk density, an excellent flow time and further advantageous properties. They can be provided with customary fillers and are suitable for ram extrusion and for press-sinter processing to give sintered blocks and subsequently veneer-cut films.

Abstract: Fluoropolymer dispersions containing colloidal particles of a partially modified tetrafluoroethylene polymer, the fluoropolymer resin powder obtained therefrom by coagulation and a process for the preparation of the dispersions mentioned are described. The particles have a three-shell particle structure, the particle core and the other particle shell consisting of a tetrafluoroethylene polymer provided with a modifying fluoro-olefinic comonomer and the inner particle shell consisting of tetrafluoroethylene homopolymer. Fluoro-olefins, perfluoro-olefins, halogenofluoro-olefins and completely or partially fluorinated vinyl ethers are used as the modifying comonomers.The preparation is effected by the seed technique or intermediate letting down method, the modified core being formed in the first phase and the modifying comonomer being subsequently metered into the continuing tetrafluoroethylene polymerization in the second phase.

Abstract: Aqueous colloidal dispersions of fluorinated polymers can be concentrated, after adding a stabilizing emulsifier, to high solids contents by ultrafiltration over customary semi-permeable membranes if pumps which keep the dispersion free from contact with components which cause frictional forces are used for conveying the dispersion. A considerable proportion of the stabilizing emulsifier added and high proportions of the fluorine-containing emulsifier originally contained in the fluorinated polymer dispersion from the emulsion polymerization can be removed via the aqueous permeate. The fluorine-containing emulsifier can be recovered by a downwstream basic anion exchanger and the stabilizing emulsifier contained in the filtrate flowing out of the anion exchanger can be concentrated in this filtrate by reverse osmosis and optionally recycled into the ultrafiltration process.

Abstract: Free-flowing sintering powders based on polymers containing at least 98.5% by weight of tetrafluoroethylene units can be prepared from colloidal polymer dispersions obtained in a customary manner by emulsion polymerization, stirring being carried out initially, optionally with the addition of an inorganic salt, until thickening, indicated by optical inhomogeneities, is achieved, an organic liquid which wets the polymer particles and is soluble in water to the extent of not more than 15% by weight then being added and stirring then being continued until granules are produced. The polymers preferably contain up to 1.5% by weight of polymerized units of at least one modifying, perfluorinated monomer. The free-flowing sintering powders have a high bulk density, an excellent flow time and further advantageous properties. They can be provided with customary fillers and are suitable for ram extrusion and for press-sintering processing to give sintered blocks and subsequently veneer-cut films.

Abstract: To elute fluorinated emulsifying acids, especially perfluoro-carboxylic acids, from basic anion exchangers a mixture of dilute mineral acid and polar organic solvents is used. The solvent should be miscible with water preferably to an extent of at least 40%. By this process the required amount of eluent and the time of elution can be reduced while simultaneously the amount of recovered emulsifying acid can be improved. The process is especially suitable for the recovery of fluorinated emulsifiers in the coagulation or concentration of fluoropolymer latices.

Abstract: Mixtures of (a) copolymers of ethylene and tetrafluoroethylene, which in addition optionally contain up to 10 mole % of units of at least one ethylenically mono-unsaturated monomer copolymerizable with tetrafluoroethylene, with (b) phosphorus acids which in one of their tautomeric forms contain 2 or 3 oxygen atoms and 1 or 2 hydrogen atoms directly bonded to each phosphorus atom, or with salts of such acids, are described. These mixtures possess improved heat stability and can, where appropriate with interpolation of a melt granulation process, be used, in particular, for the coating of metals. Component (b) is added to the copolymer (a) in the dry form or preferably in the form of a solution during working up, and in particular is added either to the pulverulent copolymer or, more especially, to a moist product, isolated from dispersions, after the last washing process.

Abstract: The invention relates to a process for the copolymerization of tetrafluoroethylene with perfluorinated alkylvinyl ethers of the formulaCF.sub.3 --(CF.sub.2).sub.n --O--CF.dbd.CF.sub.2wherein n is 1 to 3, in the presence of hexafluoropropene, and the thermoplastic terpolymers so obtained. The copolymerization may be carried out according to the suspension process or the emulsion process in liquid phase in the presence of liquid chain transfer agents. In the presence of hexafluoropropene, the amount of perfluoro(alkyl vinyl) ethers incorporated in the copolymer is considerably increased. The terpolymers in accordance with this invention are distinguished by a number of interesting properties, and are useful for melt processing to shaped articles and as coating materials.

Abstract: Polymers on the basis of tetrafluoroethylene are produced in the presence of a redox system as catalyst consisting of a usual peroxidic compound as oxidizing component and a water-soluble nitrogen compound liberating in situ a diimine under the polymerization conditions. The polymers obtained can be processed, inter alia, into thick walled articles on a ram extruder or into large sintered block free from crack formation.

Abstract: Polymers of tetrafluoroethylene are produced by suspension polymerization in the presence of small amounts of definite perfluorinated ethers. The products obtained have improved processing properties.

Abstract: An optical waveguide having a core/sheath structure whose sheath comprises a terpolymer based on vinylidene fluoride, tetrafluoroethylene and hexafluorpropylene, is suitable for transmission paths of ca. 10 to 100 m an can also be used at a temperature of above 100.degree. C. without significant reduction of the transmission path.