Abstract: Provided is a material that can be easily biaxially oriented, homogeneously stretched even with a high draw ratio, and formed into a PTFE porous membrane with low pressure loss. The present invention relates to a polytetrafluoroethylene mixture comprising: a fibrillable modified polytetrafluoroethylene; and a fibrillable polytetrafluoroethylene homopolymer, the polytetrafluoroethylene homopolymer having strength at break of 25 N or higher.

Abstract: This invention relates to a multi-stage stretching operation for production of expanded stretched porous polytetrafluoroethylene (ePTFE) fibrous materials with minimal node size and minimized filament sizes. A plurality of stretching or expansions may be implemented on the film including combinations of MDO and TDO stretches including at least two longitudinal stretches and at least one transverse stretch. Subsequent stretches occur at rates generally less than a prior similar longitudinal or transverse type of expansion.

Abstract: Provided is a material that can be easily biaxially oriented, homogeneously stretched even with a high draw ratio, and formed into a polytetrafluoroethylene porous membrane with low pressure loss. The present invention relates to a polytetrafluoroethylene mixture comprising: a modified polytetrafluoroethylene; and a fibrillable polytetrafluoroethylene homopolymer, the modified polytetrafluoroethylene having an extrusion pressure to a cylinder, at a reduction ratio of 1600, of 70 MPa or higher.

Abstract: A filter medium for an air filter unit for collecting dust from an airflow includes a pre-collection layer, a principal collection layer and an air-permeable cover layer. The pre-collection layer collects a part of the dust in the air flow. The principal collection layer includes a porous polytetrafluoroethylene film. The principal collection layer is positioned on a downstream side of the air flow relative to the pre-collection layer to collect dust that passes through the pre-collection layer. The air-permeable cover layer is positioned as an outermost surface layer of the filter medium on an upstream side of the air flow to allow dust in the air flow to pass through. The air-permeable cover layer is configured to suppress deformation of a surface of the filter medium caused by pressing force from an outside. Preferably, an air filter unit includes the filter medium in a zigzag shape.

Abstract: Provided is a material that can be easily biaxially oriented, homogeneously stretched even with a high draw ratio, and formed into a polytetrafluoroethylene porous membrane with low pressure loss. The present invention relates to a polytetrafluoroethylene mixture comprising: a modified polytetrafluoroethylene; and a fibrillable polytetrafluoroethylene homopolymer, the modified polytetrafluoroethylene having an extrusion pressure to a cylinder, at a reduction ratio of 1600, of 70 MPa or higher.

Abstract: Provided is a material that can be easily biaxially oriented, homogeneously stretched even with a high draw ratio, and formed into a PTFE porous membrane with low pressure loss. The present invention relates to a polytetrafluoroethylene mixture comprising: a fibrillable modified polytetrafluoroethylene; and a fibrillable polytetrafluoroethylene homopolymer, the polytetrafluoroethylene homopolymer having strength at break of 25 N or higher.

Abstract: A filter medium includes a porous film and a support material supporting the porous film. The porous film includes polytetrafluoroethylene, has an average pore diameter of at least 2.5 ?m, and has a porosity of at least 95%. A pressure loss is less than 100 Pa when air is passed through the filter medium at a velocity of 5.3 cm/sec. A collection efficiency of NaCl particles is at least 95% when air including NaCl particles with a particle diameter of 0.3 ?m is passed through the filter medium at a velocity of 5.3 cm/sec. A PF value is at least 30, where PF={?log [(100?collection efficiency (%))/100]/pressure loss (Pa)}×1000. A dust holding capacity of polyalphaolefin particles held in the filter medium is at least 15 g/m2 when air including polyalphaolefin particles with a count median diameter of 0.25 ?m is continuously passed through the filter medium at a velocity of 5.3 cm/sec and pressure loss reaches 300 Pa.

Abstract: A method of manufacturing a filter medium that has a PF value that exceeds 32, the PF value calculated from the pressure loss and the collection efficiency of the filter medium according to the following formula: PF=[?log(permeability (%)/100)/(pressure loss (Pa)]×1000[Formula 1] in which permeability (%)=100?collection efficiency (%). In this method, 380 ml or more of a liquid lubricant at 20° C. is added per 1 kg of a PTFE fine powder, this compound is processed into a tape shape and elongated to obtain a PTFE porous film, and an air permeable support member is heat laminated to at least one surface of the PTFE porous film.

Abstract: The present invention provides a culture container and a cap for a container having a ventilation filter medium or a medium similar thereto that can exchange carbon dioxide gas in the culture container with atmospheric air, and prevent the contamination of sterilized culture medium inside the culture container with fungi, mites, and the like. A culture bottle includes a bottle unit, and a cap that is mounted on an opening. The cap includes a cap unit, and a ventilation filter medium. A hole is provided in the cap unit. The ventilation filter medium includes a plurality of micropores having a pore diameter between 0.1 and 50 micrometers, and is mounted on the hole.

Abstract: The present invention provides a culture container and a cap for a container having a ventilation filter medium or a medium similar thereto that can exchange carbon dioxide gas in the culture container with atmospheric air, and prevent the contamination of sterilized culture medium inside the culture container with fungi, mites, and the like. A culture bottle includes a bottle unit, and a cap that is mounted on an opening. The cap includes a cap unit, and a ventilation filter medium. A hole is provided in the cap unit. The ventilation filter medium includes a plurality of micropores having a pore diameter between 0.1 and 50 micrometers, and is mounted on the hole.

Abstract: A method of manufacturing a filter medium that has a PF value that exceeds 32, the PF value calculated from the pressure loss and the collection efficiency of the filter medium according to the following formula:

Abstract: An air filter medium is provided with a porous film made from a polytetafluoroethylene, and a non-woven fabric laminated on at least one side of the porous film. The non-woven fabric has an apparent density satisfying the following equation: apparent density (g/cm3)<1.5×(basis weight (g/m2)/1000)+0.11. The filter medium is produced by a process that includes a first step of producing a porous film formed from a polytetrafluoroethylene, and a second step of laminating a non-woven fabric on at least one side of the porous film on heating roll that has undergone a non-adhesive treatment. The filter medium is used to manufacture an air filter pack, while the air filter pack is used to manufacture an air filter unit.

Abstract: An air filter medium comprising a porous polytetrafluoroethylene film and an air-permeable support member laminated on at least one surface of said porous film and having a PF1 value exceeding 22, which is calculated according to the following formula: PF1=[−log(Penetration (%)/100)/Pressure loss (mmH2O)]×100 in which the penetration (%)=100−Collection efficiency from a pressure loss (unit: mmH2O) measured when an air is flowed through the air filter medium at a flow velocity of 5.3 cm/sec. and a collection efficiency (unit: %) measured using dioctyl phthalate having a particle size of 0.10 to 0.12 &mgr;m. This air filter medium has a low pressure loss and a high collection efficiency.

Abstract: A filter medium which has an average pore diameter of more than 0.5 &mgr;m, a pressure loss of 2-50 mmH2O determined when air is permeated therethrough at a velocity of flow of 5.3 cm/sec, and a PF value of 18-12, which is calculated in accordance with the following equation on the basis of this pressure loss and a collection efficiency using DOP of a grain size of 0.10-0.12 &mgr;m.

Abstract: The present invention provides acicular fine particles made up of iron and carbon, and these acicular metal iron fine particles can be prepared by contacting acicular iron carbide fine particles with a reducing agent containing no carbon atom. Further, the present invention provides a magnetic coating composition and magnetic recording medium containing the above acicular metal iron fine particles.

Abstract: An acicular fine particulate material which is coated with a compound containing at least one element selected from among elements of Groups III and IV of the Periodic Table in Periods 5 and 6, the acicular fine particulate material being one of (i) an acicular fine particulate material containing iron carbide, (ii) an acicular fine particulate material containing iron carbide, metallic iron and carbon, and (iii) an acicular fine particulate metallic iron containing carbon, is prepared by a promoted reduction reaction while being effectively prevented from sintering and consequently affords magnetic recording media having a high recording density.

Abstract: The present invention provides acicular particles (A) containing an iron carbide, which have (a) a free carbon content of at most 20 wt. %, and (b) and Fe.sub.5 C.sub.2 ratio(x) of at least 70% and a coercive force of 3.times.+300 to 7.times.+270 Oe, the ratio(x) being expressed by ##EQU1## where S1 is the X-ray diffraction strength of Fe.sub.5 C.sub.2, and S2 is the X-ray diffraction strength of Fe.sub.3 O.sub.4.The invention further provides particles (B) containing nickel and an iron carbide.The invention further provides acicular particles containing an iron carbide which are obtained by heating an aqueous dispersion of ferric hydroxide in an alkaline system in the presence of a water-soluble compound capable of coordinating to iron to obtain acicular .alpha.-ferric oxide and contacting the product with a carbon-containing reducing-and-carburizing agent or with a mixture of the agent and a carbon-free reducing agent, with or without contacting the product with the carbon-free reducing agent.

Abstract: A magnetic coating composition comprising acicular particles containing iron carbide and a main magnetic material.

Abstract: The present invention provides a process for preparing iron carbide fine particles having an average particle size (long axis) of 0.1 to 2 .mu.m and an average axial ratio of 3 to 20, which comprises,(a) optionally contacting an iron compound selected from the group consisting of iron oxyhydroxide fine particles and iron oxide fine particles with a reducing agent which does not contain carbon atom, the iron compound being, prior to the above contact, coated with iron compound or iron compound and cobalt compound, and with aluminum compound or silicon compound, and(b) contacting the iron compound of the above (a) with a reducing-and-carburizing agent containing carbon atom or a mixture thereof with a reducing agent which does not contain carbon atom.

Abstract: The present invention relates to novel acicular particles, processes for using the same, and magnetic materials prepared from such particles. In particular, the invention relates to an acicular particulate material containing iron carbide and having a high coercive force (Hc) an orientation property in a magnetic field.