Claims
- 1. A process for producing a porous film or sheet, which process comprises the steps of melt-extruding a composition consisting essentially of an ultra-high molecular weight polyethylene having a viscosity-average molecular weight of 500,000 to 4,000,000 and a plasticizer thereby forming a film or sheet, giving a deforming stress to the film or sheet to effectuate melt-draft, and after cooling, removing the plasticizer from the obtained film or sheet.
- 2. A process for producing a porous film or sheet having a porosity of 30 to 50%, which process comprises the steps of melt-extruding a composition consisting essentially of an ultra-high molecular weight polyethylene having a viscosity-average molecular weight of 500,000 to 4,000,000 and a plasticizer thereby forming a film or sheet, giving a deforming stress thereto to effectuate melt-draft, and after cooling, removing the plasticizer from the obtained film or sheet.
- 3. A process for producing a porous film or sheet, which comprises the steps of:
- (a) melt-extruding a composition consisting essentially of an ultra-high molecular weight polyethylene having a viscosity-average molecular weight in a range of 500,000 to 4,000,000 and a plasticizer into a film or a sheet;
- (b) applying a deforming stress to the extruded film or sheet while in a molten state to effectuate melt-drafting;
- (c) cooling; and thereafter
- (d) removing the plasticizer for the resulting film or sheet.
- 4. The process according to claim 3, wherein the deforming stress applied to the extruded film or sheet in step (b) provides melt-draft ratio of 5 to 1,000 as represented by the following formula:
- Melt-draft ratio=(D.times..rho..sub.1)/(t.times..rho..sub.2)
- D: die gap (mm)
- .rho..sub.1 : melt density (g/cm.sup.3) of resin composition
- t: thickness (ram) of the molded film or sheet
- .rho..sub.2 : solid density (g/cm.sup.3) of the molded film or sheet.
- 5. The process according to claim 3, wherein the melt extrusion of step (a) is carried out at a temperature of 140.degree. to 240 .degree. C.
- 6. The process according to claim 3, wherein the melt-draft of step (b) is carried out at a temperature of 130.degree. to 240.degree. C.
- 7. The process according to claim 3, wherein step (c) the melt-drafted film or sheet is cooled so that the cooling solidification time represented by the following formula is not more than 50 seconds:
- T=L/(V.sub.1 -V.sub.0).times.ln(V.sub.1 /V.sub.0)
- T: cooling solidification time (sec)
- L: distance (cm) between the lip outlet and cooling and solidifying line
- V.sub.0 : resin transfer speed (cm/sec) composition at the lip outlet
- V.sub.1 : resin transfer speed (cm/sec) composition in the cooling and solidifying line.
- 8. The process according to claim 3, wherein the plasticizer is removed in step (d) by extraction with an organic solvent.
- 9. The process according to claim 3, wherein in step (a) the resin composition is melt-extruded into a film or sheet from a die having a die gap of 2 to 20 mm.
Priority Claims (2)
Number |
Date |
Country |
Kind |
4-340659 |
Dec 1992 |
JPX |
|
5-109619 |
May 1993 |
JPX |
|
Parent Case Info
This is a division of application Ser. No. 08/140,359, filed Oct. 25, 1993 (now abandoned).
US Referenced Citations (5)
Foreign Referenced Citations (4)
Number |
Date |
Country |
355 214 |
Feb 1990 |
EPX |
547 237 A1 |
Jun 1993 |
EPX |
2-94356 |
Apr 1990 |
JPX |
WO 9301623 |
Jan 1993 |
WOX |
Non-Patent Literature Citations (2)
Entry |
Database WPI Derwent Publications Ltd., London AN 93-191608�24! & JP-A-5 117 440 May 1993 (Mitsubishi Kasei Corp.) Abstract. |
Database WPI Derwent Publications Ltd., London AN 88-107426�16! & JP-A-62 254 806 (Mitsubishi Chem. Ind. KK.) Nov. 1987 Abstract. |
Divisions (1)
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Number |
Date |
Country |
Parent |
140359 |
Oct 1993 |
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