摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
Fluorocarbon wax dispersions are produced by telomerization of tetrafluoro-ethylene or mixtures of tetrafluoro-ethylene with other olefinic monomers. The stable wax dispersions and the pulverulent fluorocarbon waxes obtained are, inter alia, valuable additives for lubricants and polishes.
摘要:
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. The resins obtained are particularly suitable for the paste extrusion process for producing cable insulation and highly stretchable, unsintered tapes, and, after appropriate working up, also for the ram extrusion and the press-sinter technique.
摘要:
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.