Abstract:
A process for producing a nanoporous polymer film of no greater than 10 micron thickness having low dielectric constant value, comprising the steps of: (a) providing a polymer in a solution with at least two solvents for the polymer in which a lowest boiling solvent and a highest boiling solvent have a difference in their respective boiling points of approximately 50°C or greater; (b) forming a film of the polymer in solution with at least the two solvents on a substrate; (c) removing a predominant amount of the lowest boiling solvent; (d) contacting the film with a fluid which is a non-solvent for the polymer, but which is miscible with the at least two solvents to induce phase inversion in the film; (e) forming an average pore size in the film in the range of less than 30 nanometers. The present invention is also nanoporous films made by the above process.
Abstract:
A para-oriented aromatic polyamide porous film, which comprises fibrils having a diameter of not more than 1 µm and which has such a structure that the fibrils are planary arranged in the form of a network or nonwoven fabric and laminated in the form of a layer, wherein the thermal linear expansion coefficient at 200 to 300°C of the film is within ±50 x 10 -6 /°C and a percentage of vacant spaces is from 30 to 95% and a battery separator using the porous film are described. Furthermore, a process for producing the porous film is described, which comprises the following steps (a) to (c): (a) forming a film-like material from a solution containing 1 to 10% by weight of a para-oriented aromatic polyamide having an inherent viscosity of 1.0 to 2.8 dl/g and 1 to 10% by weight of a chloride of an alkali metal or an alkali earth metal in a polar amide solvent or a polar urea solvent; (b) maintaining the film-like material at a temperature of not less than 20°C or not more than -5°C to deposit the para-oriented aromatic polyamide; and (c) immersing the film-like material obtained in step (b) in an aqueous solution or an alcoholic solution to elute the solvent and chloride of the alkali metal or alkali earth metal, followed by drying to obtain the para-oriented aromatic polyamide porous film. It is to provide a para-aramid porous film having uniformity and fine vacant spaces, which can not be accomplished by a nonwoven fabric, a process for producing the same and a battery separator produced by using the para-aramid porous film, by making use of characteristics of a para-aramid (e.g. high heat resistance, high rigidity, high strength, etc.).
Abstract:
A porous polybenzimidazole (PBI) particulate resin is disclosed. This resin is easily dissolved at ambient temperatures and pressures. The resin is made by: dissolving a virgin PBI resin in a highly polar solvent; precipitating the dissolved PBI in a bath; and drying the precipitated PBI, the dried precipitated PBI being porous. The porous PBI resin may be dissolved by: mixing a porous PBI resin with a highly polar solvent at ambient temperatures and pressures to form a solution.
Abstract:
A polymetaphenylene isophthalamide-based polymer porous film having a satisfactory porous structure that exhibits excellent gas permeability and heat resistance. It is produced by a process which comprises casting a dope of the polymetaphenylene isophthalamide-based polymer and coagulating it in a coagulating bath. The porous film may also contain inorganic whiskers, and a composite porous film may be formed in combination with a separate thermoplastic polymer film.
Abstract:
A polymetaphenylene isophtha lamide-based polymer porous film having a satisfactory porous structure that exhibits excellent gas permeability and heat resistance. It is produced by a process which comprises casting a dope of the polymetaphenylene isophthalamide-based polymer and coagulating it in a coagulating bath. The porous film may also contain inorganic whiskers, and a composite porous film may be formed in combination with a separate thermoplastic polymer film.
Abstract:
The invention relates to a process for the preparation of porous polyolefin particles, which process comprises the following steps:1) dissolution of at least one crystallizable polyolefin in a solvent, which results in a solution being formed which comprises 0.1-50 wt. % polyolefin, and the initial polyolefin solution formed containing between 5 ppm and 20 wt. % of nucleating agent,2) dispersion of the resulting polyolefin solution in a non-solvent, at a temperature that is higher than the crystallization temperature of the polyolefin in the polyolefin solution, upon which a multiphase system is formed,3) cooling of the multiphase system, with simultaneous stirring, the cooling rate being between 0.05 and 10.degree. C./min, down to a temperature which is below the crystallization temperature of the polyolefin in the polyolefin solution, so that strong, polyolefin-containing particles are formed,4) separation of the polyolefin-containing particles from the liquid(s),5) drying of the polyolefin-containing particles at a temperature that is below the crystallization temperature of the polyolefin in the initial polyolefin solution.
Abstract:
Porous, distensible, gel-like membranes which in tubular form are suitable as implants, e.g., vascular prostheses and a process for the preparation thereof. The membranes are formed by a spraying, phase-inversion technique which employs thermodynamically unstable polymer solutions and is accomplished by separately spraying the unstable solution and a nonsolvent onto a rotating surface. Prostheses from the highly porous tubular membranes have shown a high degree of patency and completeness of the healing process and are useful for direct implantation in the body or for extracorporeal vascular accesses.
Abstract:
Porous cellulose beads are prepared by distributing droplets of a solvent mixture containing a cellulose derivative into a precipitating solution to form porous beads which are then washed and hydrolyzed to form porous cellulose beads. The porous cellulose beads, which may be cross-linked, if desired, by suitable treatment, are useful carriers to which enzymes can be immobilized. The beads may also be used for the separation of enzymes, proteins, nucleic acids and the like, or to remove metal ions from dilute mining solutions.