Abstract: The present invention provides a microporous polyolefin membrane of high permeability and novel structure, and also provides a method of producing the same, wherein its average pore size is gradually decreases from at least one membrane surface towards its center. The method of producing the microporous polyolefin membrane comprises the steps of extruding the solution, composed of 10 to 50 weight % of (A) a polyolefin having a weight-average molecular weight of 5×105 or more or (B) a composition containing this polyolefin and 50 to 90 weight % of a solvent, into a gel-like formed article and removing the solvent therefrom, wherein a treatment step with a hot solvent is incorporated.

Abstract: A method for producing a microporous polyolefin membrane formed by fine fibrils, the membrane comprising (A) a polyolefin having a weight-average molecular weight of 5×105 or more or (B) a composition containing Component (A), connected to each other, and having micropores of 0.05 to 5 ?m in average pore size and crystal lamellas of Component (A) or (B) being in a specific alignment state. The method includes extruding a solution of Component (A) or (B) in a solvent into a gel-like formed article; thermally setting the article, with or without stretching, at least at the crystal dispersion temperature of Component (A) or (B), but at melting point of Component (A) or (B) plus 30° C. or lower; and removing the solvent.

Abstract: A microporous polyolefin membrane is formed by fine fibrils, comprising (A) a polyolefin having a weight-average molecular weight of 5×105 or more or (B) a composition containing component (A), connected to each other, and has micropores of 0.05 to 5 &mgr;m in average pore size and crystal lamellas of component (A) or (B) being in a specific orientation state. The membrane is produced by extruding a solution of component (A) or (B) in a solvent, into a gel-like formed article; thermally setting the article, with or without stretching, at least at the crystal dispersion temperature of component (A) or (B), but at melting point of component (A) or (B) plus 30° C. or lower; and removing the solvent.

Abstract: The present invention provides a microporous polyolefin membrane of high permeability and novel structure, and also provides a method of producing the same, wherein its average pore size is gradually decreases from at least one membrane surface towards its center. The method of producing the microporous polyolefin membrane comprises the steps of extruding the solution, composed of 10 to 50 weight % of (A) a polyolefin having a weight-average molecular weight of 5×105 or more or (B) a composition containing this polyolefin and 50 to 90 weight % of a solvent, into a gel-like formed article and removing the solvent therefrom, wherein a treatment step with a hot solvent is incorporated.

Abstract: It is an object of the present invention to provide a microporous polyolefin membrane, high in pin puncture strength, adequate in pore diameter and high in porosity, comprising (A) an ultra-high-molecular-weight polyolefin having a weight-average molecular weight of 5×105 or more, or (B) a composition containing an ultra-high-molecular-weight polyolefin having a weight-average molecular weight of 5×105 or more, and having a porosity of 30 to 95%, bubble point exceeding 980 KPa and pin puncture strength of 4,900 mN/25 &mgr;m or more. The membrane can be used as a filter or as a separator for a battery.

Abstract: It is an object of the present invention to provide a microporous polyolefin membrane, high in elongation and porosity, low in shrinkage, and capable of improving battery characteristics, safety and productivity, when used for battery separators. The microporous polyolefin membrane of the present invention comprises (A) an ultra-high-molecular-weight polyolefin having a weight-average molecular weight of 5×105 or more, or (B) a composition containing an ultra-high-molecular-weight polyolefin having a weight-average molecular weight of 5×105 or more, and having a porosity of 45 to 95%, elongation at break of 300% or more, bubble point exceeding 980 KPa and thermal shrinkage in the TD direction of 3% or less. The present invention also provides a method for producing the above microporous polyolefin membrane.

Abstract: The thin film of non-protonic electrolyte comprises the microporous polyolefin film impregnated with an immobilized non-protonic electrolytic solution, where the film is treated to have improved affinity for the non-protonic solution by graft polymerization of the film with a monomer which can dissolve the non-protonic electrolytic solution, coating of the film with terminal-modified polypropylene which can dissolve the non-protonic electrolytic solution or coating of the film with wax which can dissolve the non-protonic electrolytic solution. The electrolyte-immobilized liquid-film conductor comprises the microporous polyolefin film impregnated with an immobilized non-protonic electrolytic solution, where the film contains an electron-conductive substance and is treated to have improved affinity for the non-protonic solution. The thin film of non-protonic electrolyte comprising the microporous polyolefin film gives a polymer battery, such as lithium battery, when combined with an anode and cathode.

Abstract: The present invention provides a thin film of non-protonic electrolyte and electrolyte-immobilized liquid-film conductor, easily produced into a thin film and to have a large area, securely holding the non-protonic electrolytic solution over a wide temperature range, and showing stability for extended periods and improved mechanical strength. They comprise a polyolefin film with a solvent-resistant polyolefin as the basic component, which is impregnated with the non-protonic electrolytic solution to immobilize it. The polyolefin composition for the film contains a terminal-modified polypropylene having, in the terminal chain, a functional group showing an affinity for the solvent for the electrolytic solution for the thin film of non-protonic electrolyte, and further contains an electron-conductive substance in addition to the terminal-modified polypropylene for the electrolyte-immobilized liquid-film conductor. As a result, the polyolefin film stably holds the solvent for the electrolytic solution.

Abstract: A method for producing a highly permeable microporous polyolefin membrane including the steps of preparing a polyolefin solution containing 5-40 weight % of a polyolefin or a polyolefin composition and 95-60 weight % of a solvent, the polyolefin having a weight-average molecular weight of not less than 3.times.10.sup.5 and less than 1.times.10.sup.6 and a weight-average molecular weight/number-average molecular weight of 5-300, and the polyolefin composition having a weight-average molecular weight of not less than 3.times.10.sup.5 and less than 1.times.10.sup.6 and a weight-average molecular weight/number-average molecular weight of 5-300 as a whole, extruding the polyolefin solution, stretching the extrudate uniaxially at a draft ratio of 3-50 in a molten state, cooling the stretched extrudate to solidify to a gel-like sheet, removing residual solvent, drying the resultant sheet, and heat-setting at a temperature of 80.degree. C. or higher and its melting point or lower.

Abstract: A microporous polyolefin composite membrane, preferably for use as a battery separator, comprising a microporous polyolefin membrane and a polyolefin nonwoven fabric laminated on at least one surface of the microporous polyolefin membrane. The composite membrane has a thickness of 25 to 200 .mu.m, a porosity of 30 to 70%, an air permeability of 100 to 2000 sec/100 cc and a surface opening area ratio of 50 to 90% on at least one outer surface thereof. The microporous polyolefin membrane comprises a matrix polyolefin component which is a polyolefin having a weight average molecular weight of 5.times.10.sup.5 or more or a polyolefin mixture containing the polyolefin having a weight average molecular weight of 5.times.10.sup.5 or more, and has a porosity of 30 to 95%, an air permeability of 100 to 2000 sec/100 cc, an average open pore diameter of 0.001 to 1 .mu.m and a tensile strength at break of 500 kg/cm.sup.2 or more.

Abstract: An efficient method of producing a microporous polyolefin membrane having improved tensile strength and pierce strength is provided, in which a solution having dissolved therein 5% by weight to 50% by weight of a polyolefin whose weight-average molecular weight is in the range of 5.times.10.sup.5 to 2.5.times.10.sup.6 and whose weight-average molecular weight to number-average molecular weight ratio is less than 10, is extruded and rapidly cooled to obtain a gel-like product which is then stretched and has remaining solvent removed therefrom.

Abstract: A method of producing a microporous polyolefin membrane having a relatively large pore size and a high permeability, the membrane being suitable for use in water treatment, microfiltration, etc. The method comprises dissolving a polyolefin composition in a solvent to prepare a solution, extruding the solution through a die lip into a form of gel-like sheet, rapidly cooling the gel-like sheet, removing a residual solvent in the cooled sheet by a washing solvent, and drying the resultant sheet to remove the washing solvent. The polyolefin composition is a mixture of (A) an ultra high molecular weight polyolefin having a weight average molecular weight of 5.times.10.sup.5 or more and (B) a polyolefin having a weight average molecular weight less than 5.times.10.sup.5, and a weight ratio of (B)/(A) is 0.2 to 20.