Abstract: Disclosed is a process for production of a polytetrafluoroethylene (PTFE) sheet, which is superior in productivity compared to conventional processes and can reduce the cost of production. Also disclosed is a process for production of a PTFE seal tape. The processes comprise the following steps (i) to (iii): (i) applying a force to a PTFE particle suspension comprising PTFE particles, a surfactant and water (a dispersion medium) so that the particles can come close to each other or contact with each other, thereby forming a PTFE-containing solid material having the water and the surfactant included therein; (ii) shaping the solid material into a sheet-like form; and (iii) reducing the water content in the sheet-like solid material.

Abstract: The present invention provides a method of manufacturing a polytetrafluoroethylene (PTFE) product offering better productivity and a higher degree of flexibility in form of the product to be obtained than the conventional methods of manufacturing a PTFE product, and a method of manufacturing PTFE particle aggregate obtained as an intermediate while manufacturing a PTFE product. According to the manufacturing methods, aggregate of PTFE particles including water and a surfactant is obtained by applying force to a dispersion of PTFE particles containing PTFE particles, a surfactant and water as a dispersion medium, where the force makes the PTFE particles approach or contact with each other. Such a manufacturing method may be carried out, for example, with a chamber (1) shown in FIG. 1.

Abstract: The present invention provides a method of manufacturing a polytetrafluoroethylene (PTFE) product offering better productivity and a higher degree of flexibility in form of the product to be obtained than the conventional methods of manufacturing a PTFE product, and a method of manufacturing PTFE particle aggregate obtained as an intermediate while manufacturing a PTFE product. According to the manufacturing methods, aggregate of PTFE particles including water and a surfactant is obtained by applying force to a dispersion of PTFE particles containing PTFE particles, a surfactant and water as a dispersion medium, where the force makes the PTFE particles approach or contact with each other. Such a manufacturing method may be carried out, for example, with a chamber (1) shown in FIG. 1.

Abstract: A sound-permeable film (11) includes: a porous membrane (13) that contains polytetrafluoroethylene as its main component, allows sound to pass therethrough, and prevents an foreign object such as a water drop from passing therethrough; and a heat-resistant double-sided adhesive sheet (15) that is disposed on a part of at least one of main surfaces of the porous membrane (13).

Abstract: The present invention provides a water-proof sound-transmitting membrane including a polytetrafluoroethylene (PTFE) porous membrane, in which the waterproofness is enhanced further with little lowering of the sound transmittance. The water-proof sound-transmitting membrane includes the PTFE porous membrane. The PTFE porous membrane includes a first porous layer, and a second porous layer stacked on and integrated with the first porous layer by a binding force acting between PTFE matrices. The first porous layer and the second porous layer each are composed of PTFE with a number-average molecular weight of 5.0×107 or more determined by a standard specific gravity method. At least one layer selected from the first porous layer and the second porous layer has an average pore diameter of 1 ?m or less. The water-proof sound-transmitting membrane has a surface density of 1 g/m2 to 10 g/m2.

Abstract: A water-proof sound-transmitting membrane 10 includes a polytetrafluoroethylene porous membrane 1 and has a surface density of 1 to 20 g/m2. The polytetrafluoroethylene porous membrane 1 includes a first porous layer 1a, and a second porous layer 1b stacked on and integrated with the first porous layer 1a by a binding force acting between polytetrafluoroethylene matrices.

Abstract: A sound-permeable film (11) includes: a porous membrane (13) that contains polytetrafluoroethylene as its main component, allows sound to pass therethrough, and prevents an foreign object such as a water drop from passing therethrough; and a heat-resistant double-sided adhesive sheet (16) that is disposed on a part of at least one of main surfaces of the porous membrane (13).

Abstract: Disclosed is a process for production of a polytetrafluoroethylene (PTFE) sheet, which is superior in productivity compared to conventional processes and can reduce the cost of production. Also disclosed is a process for production of a PTFE seal tape. The processes comprise the following steps (i) to (iii): (i) applying a force to a PTFE particle suspension comprising PTFE particles, a surfactant and water (a dispersion medium) so that the particles can come close to each other or contact with each other, thereby forming a PTFE-containing solid material having the water and the surfactant included therein; (ii) shaping the solid material into a sheet-like form; and (iii) reducing the water content in the sheet-like solid material.

Abstract: The present invention provides a method of manufacturing a polytetrafluoroethylene (PTFE) product offering better productivity and a higher degree of flexibility in form of the product to be obtained than the conventional methods of manufacturing a PTFE product, and a method of manufacturing PTFE particle aggregate obtained as an intermediate while manufacturing a PTFE product. According to the manufacturing methods, aggregate of PTFE particles including water and a surfactant is obtained by applying force to a dispersion of PTFE particles containing PTFE particles, a surfactant and water as a dispersion medium, where the force makes the PTFE particles approach or contact with each other. Such a manufacturing method may be carried out, for example, with a chamber (1) shown in FIG. 1.

Abstract: The present invention provides a filter medium reducing an increase in pressure drop while in use even in an environment where ultrafine particles form a large proportion of the particles to be collected. The filter medium includes a porous polytetrafluoroethylene (PTFE) membrane, an air-permeable supporting member and a web layer made of polymeric fibers formed by electrospinning (charge induction spinning, electrostatic spinning). The filter medium of the present invention may include an air-permeable adhesive layer adjacent to the web layer.