摘要:
A method of laminating at least two gas permeable sheet materials includes: (1) providing at least a first gas permeable sheet material, wherein at least a portion of at least a surface region of the first sheet material is thermoplastic material; (2) providing at least a second gas permeable sheet material of polytetrafluoroethylene; (3) superposing the sheet materials; and (4) contacting the sheet materials with a heating means to heat the thermoplastic material to a temperature from 140° to 230° C., so as to melt the thermoplastic material and laminate the sheet materials to one another, without the application of direct pressure in the thickness direction of the sheet materials during the contacting step so as to form a gas permeable laminate.
摘要:
A porous polytetrafluoroethylene film which is excellent as an air filter used in clean rooms in a semiconductor industry, which is suitable for the collection of microparticles floating in a gas such as air and exhibits a low pressure drop is provided. The film has an average pore size of from 0.2 to 0.4 .mu.m and exhibits a pressure drop of from 20 to 50 mmH.sub.2 O when air is passed through it at a flow rate of 5.3 cm/sec. The film is prepared by stretching biaxially unsintered polytetrafluoroethylene at specific temperatures.
摘要:
An object is to provide a polytetrafluoroethylene (PTFE) porous composite film which has substantially no defect portion. There is provided the PTFE porous composite film by stretching a composite along its width direction which composite is composed of at least two overlapped films longitudinally stretched at a temperature not higher than a melting point of a sintered PTFE material, each film being obtained by paste-extruding and semi-sintering thereafter a PTFE produced by emulsion polymerization.
摘要:
Cotton-like polytetrafluoroethylene materials are obtained by opening a uniaxially stretched article of molded polytetrafluoroethylene by a mechanical force. Those cotton-like materials comprise the 5 to 150 mm long fibers having branches and crimps and non-uniform section. The cotton-like materials are excellent in intermingling property and can be easily made into non-woven fabrics.
摘要:
A filter apparatus that is compact and that provides a large filtration area includes filter elements each constructed in cylindrical form by spirally winding a filter medium. Such medium includes a porous membrane of a polytetrafluoroethylene having a pore diameter of 0.1 to 5 .mu.m and low pressure loss and one or a pair of sheets composed of fibers made of a thermally melting synthetic resin. One end of the cylindrical filter element is connected to a respective through hole in a rigid support plate, and the opposite end is blocked.
摘要:
A polytetrafluoroethylene porous film, which is prepared by stretching a semisintered polytetrafluoroethylene material and heating the stretched material at a temperature higher than the melting point of sintered polytetrafluoroethylene, has an area ratio of fibrils to nodes of from 99:1 to 75:25, an average fibril diameter of from 0.05 to 0.2 .mu.m, a largest node area of not larger than 2 .mu.m.sup.2 and an average pore size of from 0.2 to 0.5 .mu.m and achieves low pressure loss.
摘要:
A process for producing a multilayer polytetrafluoroethylene porous membrane is disclosed, which process comprises at least two layers having different average pore diameters, the process comprising the steps of: filling the inside of a cylinder of an extruding mold distinctively with at least two kinds of polytetrafluoroethylene fine powders with each of which a liquid lubricant has been mixed; paste-extruding the powders to obtain a multilayer extrudate, which is then optionally rolled; removing the liquid lubricant from the multilayer extrudate or the rolled multilayer extrudate to obtain an unsintered multilayer structure; subsequently heating the unsintered multilayer structure at a temperature not lower than the melting point of sintered polytetrafluoroethylene to obtain a semisintered multilayer structure; and then stretching the semisintered multilayer structure at least monoaxially. A semisintered polytetrafluoroethylene multilayer structure capable of being used as an intermediate material for the above process is also disclosed.
摘要:
A porous PTFE film having a thin thickness and good permeability is produced by coating an emulsion of polytetrafluoroethylene on a substrate surface, in particular, a porous polytetrafluoroethylene substrate which has not been heated at a melting point of unsintered polytetrafluoroethylene or higher, heating the coated substrate at a temperature not lower than a melting point of sintered polytetrafluoroethylene to semi-sinter polytetrafluoroethylene, optionally removing the semi-sintered polytetrafluoroethylene film from the substrate, and then stretching the semi-sintered film at least in one direction.
摘要:
A process for producing a multilayer polytetrafluoroethylene porous membrane comprising at least two layers having different average pore diameters is disclosed, the process comprising the steps of: filling the inside of a cylinder of an extruding mold distinctively with at least two kinds of polytetrafluoroethylene fine powders with each of which a liquid lubricant has been mixed; subsequently paste-extruding the powders to obtain a multilayer extrudate, which is then optionally rolled; and then stretching the extrudate or the rolled extrudate at least monoaxially after the liquid lubricant is removed therefrom or without removing the liquid lubricant.