Porous polymeric films

• US 4,386,129 A
• Filed: 03/31/1981
• Issued: 05/31/1983
• Est. Priority Date: 03/31/1981
• Status: Expired due to Term

• Current Assignee: Standard Oil Company (BP PLC)
• Original Assignee: Standard Oil Company (BP PLC)
• Inventors: Jacoby, Philip
• Primary Examiner(s): HERBERT JR, THOMAS
• Application Number:
  US06/249,673
• Time in Patent Office: 791 Days
• Field of Search: 526/348, 526/351, 526/348.1, 428/220, 428/523, 428/215, 521/56, 521/63, 521/61, 521/64, 521/90, 521/94, 521/143, 264/176 R
• US Class Current: 428/215
• CPC Class Codes: B29C 67/202 comprising elimination of a solid or a liquid ingredient
• CPC Class Codes: C08J 2201/0424 containing halogen, nitrogen, sulphur or phosphorus atoms
• CPC Class Codes: C08J 2323/10 Homopolymers or copolymers of propene
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: C08J 9/26 by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out
• CPC Class Codes: Y10T 428/24967 Absolute thicknesses specified
• CPC Class Codes: Y10T 428/31938 Polymer of monoethylenically unsaturated hydrocarbon

Abstract

This invention relates to porous films having pores with polygonal cross sections and average pore diameters of about 3 to about 100 microns and the method for preparing these films. More particularly this invention relates to a porous film having pores with polygonal cross sections and average pore diameters of about 3 to about 100 microns formed from a resinous polymer of propylene and the process for forming the film which comprises the steps of (a) forming a film containing beta-spherulites and (b) selectively extracting the beta-spherulites.

Claims

1. A porous film with a thickness of about 0.010 to about 0.25 millimeters comprising a resinous polymer of propylene having alpha-form spherulites and polygonal pores with average diameters of about 3 to about 100 microns said pores corresponding to the location of beta-form spherulites.

5. The process of claim 1 wherein said extracting solvent is selected from the group consisting of toluene, carbon tetrachloride, or xylene.

2. A porous film having polygonal pores with average pore diameters from about 3 to about 100 microns said film prepared from resinous polymers of propylene capable of having at least 40% crystallinity by a process comprising the steps of

(a) dispersing in said resinous polymer a nucleating agent capable of producing beta-spherulites;

(b) forming by extrusion a film with a thickness of about 0.010 to about 0.25 millimeters from the molten product of step (a);

(c) cooling said film below the crystallization temperature of said polymer to form beta-spherulites; and

(d) selectively extracting said beta-spherulites from the cooled film product of step (c) with an extracting solvent to form the porous film product.

3. A process for preparing a porous film having polygonal pores with average pore diameters from about 3 to about 100 microns from resinous polymers of propylene capable of having at least 40% crystallinity said process comprising the steps of

(a) dispersing in said resinous polymer a nucleating agent capable of producing beta-spherulites;

(b) forming by extrusion a film with a thickness of about 0.010 to about 0.25 millimeters from the molten product of step (a);

(c) cooling said film below the crystallization temperature of said polymer to form beta-spherulites; and

(d) selectively extracting said beta-spherulites from the cooled film product of step (c) with an extracting solvent to form the porous film product.

4. The process of claim 3 wherein said nucleating agent has the structural formula ##STR2##

6. The process of claim 3 wherein at least 50 percent of the pores of said porous film have an average diameter greater than 5 microns.

7. A process for preparing a porous film from resinous polymers of propylene capable of having at least 40% crystallinity said process comprising the steps of

(a) dispersing in said resinous polymer a nucleating agent capable of producing beta-spherulites;

(b) forming by extrusion a film with a thickness of about 0.010 to about 0.25 millimeters from the molten product of step (a);

(c) cooling said film below the crystallization temperature of said polymer to form beta-spherulites; and

(d) contacting the film of step (c) with an extracting solvent at a temperature of about 95°

C. to about 100°

C. to selectively extract at least a portion of said beta-spherulites to form the porous film having polygonal pores with average pore diameters from about 3 to about 100 microns.