Process for forming microporous sheet

• US 3,929,949 A
• Filed: 06/21/1974
• Issued: 12/30/1975
• Est. Priority Date: 06/21/1974
• Status: Expired due to Term

• Current Assignee: DVSG Holding GmbH
• Original Assignee: John G. Hollick, John T. Day
• Inventors: Day, John T., Hollick, John G.
• Primary Examiner(s): Anderson, Philip
• Application Number:
  US05/481,780
• Time in Patent Office: 557 Days
• Field of Search: 264/41,53,45.8,321,331 260/2.5AY 428/264,265,305,425,904
• US Class Current: 264/46.4
• CPC Class Codes: B29C 44/30 Expanding the moulding material between endless belts or rollers B29C44/203 takes precedence
• CPC Class Codes: B29C 53/36 Bending and joining, e.g. for making hollow articles B29C53/56 takes precedence
• CPC Class Codes: B29C 67/202 comprising elimination of a solid or a liquid ingredient
• CPC Class Codes: B29L 2007/00 Flat articles, e.g. films or sheets B29L2024/00 takes precedence
• CPC Class Codes: B29L 2023/20 Flexible squeeze tubes, e.g. for cosmetics
• CPC Class Codes: B32B 2305/026 Porous
• CPC Class Codes: B32B 2375/00 Polyureas; Polyurethanes
• CPC Class Codes: B32B 27/12 next to a fibrous or filamentary layer
• CPC Class Codes: B32B 27/40 comprising polyurethanes
• CPC Class Codes: C08J 2375/04 Polyurethanes
• CPC Class Codes: C08J 9/283 a discontinuous liquid phase emulsified in a continuous macromolecular phase
• CPC Class Codes: D06N 3/14 with polyurethanes
• CPC Class Codes: Y10S 428/904 Artificial leather
• CPC Class Codes: Y10T 428/249978 Voids specified as micro
• CPC Class Codes: Y10T 442/3854 Woven fabric with a preformed polymeric film or sheet

Abstract

Process for forming a microporous polyurethane body in which process a body of an emulsion is prepared of which the discontinuous phase is a non-solvent liquid and the continuous phase is a liquid polymeric material which sets through reaction to solid condition, the liquid emulsion is formed as a layer and reacted under conditions preserving the uniformity of the emulsion to form a resilient gel structure and the layer is subjected to physical pressure to express a substantial portion of the non-solvent liquid from the layer leaving a fine microporous structure after release of the pressure. The reaction is continued to advance the state of cure and any remaining nonsolvent liquid is removed from the solidified layer.

Claims

1. IN THE PROCESS OF FORMING A MICROPOROUS SHEET OF SOLID POLYURETHANE COMPRISING THE STEPS OF CASTING AN EMULSION OF FINE DROPLETS OF A VOLATILE ORGANIC LIQUID AS THE INTERNAL PHASE IN A CONTINOUS PHASE COMPRISING REACTIVE MATERIAL CONVERTIBLE THROUGH REACTION TO SOLIDIFIED, RESILIENT POLYURETHANE, SAID ORGANIC LIQUID BEING SUBSTANTIALLY NON-SOLVENT FOR AND NONREACTIVE WITH SAID REACTIVE MATERIAL, BEING IMMISCIBLE IN SAID CONTINUOUS PHASE AND BEING PRESENT IN AMOUNT FORM ABOUT 60% TO ABOUT 300% BY WEIGHT BASED ON THE WEIGHT OF THE REACTIVE MATERIAL, SAID ORGANIC LIQUID CONTAINING CATALYTIC OR OTHER NON-VOLATILE MATERIALS WHICH ARE UNDESIRABLE IN THE FINAL SHEET, REACTING SAID MATERIAL AT A TEMPERATURE BELOW THE BOILING POINT OF SAID LIQUID SO THAT THE LIQUID NEVER BOILS TO CAUSE THE EMULSION TO GEL AND SOLIDIFY WITH SAID DROPLETS HELD IN THE SOLIDIFIED MATERIAL AND REMOVING SAID LIQUID WITHOUT EXPANDING THE SOLIDIFIED MATERIAL LEAVING PORES AND DISCONTINUITIES IN THE SOLIDIFIED MATERIAL TO CONSTITUTE PASSAGEWAYS FOR AIR AND VAPOR, THE IMPROVEMENT WHICH COMPRISES FORMING A LAYER OF THE LIQUID EMULSION, REACTING THE MATERIALS OF THE CONTINUOUS PHASE OF THE EMULSION TO A RESILIENT STATE CAPABLE OF RETURN TO SUBSTANTIALLY ITS INITIAL THICKNESS WHEN PRESSED TO 50% OF ITS INITIAL THICKNESS UNDER CONDITIONS PRESERVING THE UNIFORMITY OF THE EMULSION, SUBJECTING THE RESILIENT MATERIAL TO PHYSICAL PRESSURE OF SHORT DURATION PROMPTLY AFTER REACHING SAID RESILIENT CONDITION AND BEFORE COMPLETION OF SAID REACTION TO EXPRESS FROM SAID SHEET A SUBSTANTIAL PORTION OF SAID NON-SOLVENT LIQUID TOGETHER WITH MATERIALS DISSOLVED OR CARRIED IN SAID NON-SOLVENT LIQUID AND TO CLEAR PORES AND PASSAGEWAYS, COMPLETING SAID REACTION TO FORM A STABLE SOLID BODY AND REMOVING FURTHER ORGANIC LIQUID FROM THE SOLIDIFIED MATERIAL.

2. The process of forming a microporous sheet of solid polyurethane as defined in claim 1 in which said layer of emulsion is subjected to physical pressure to express at least about 40% of the non-solvent liquid promptly after reaction to a stage in which said physical pressure will cause less than 10% permanent loss in thickness in the sheet.

3. The process of forming a microporous sheet of solid polyurethane as defined in claim 2 in which said physical pressure is applied by passing said layer between rolls.

4. The process of forming a microporous sheet of solid polyurethane as defined in claim 3 in which said emulsion is introduced between spaced release surfaces to form a layer while said emulsion is liquid and in which one of said release surfaces is stripped from said layer of emulsion when said emulsion has thickened to a stage where the emulsion is no longer freely liquid and maintains undeformed the surface from which the release surface is stripped and thereafter the layer is subjected to said physical pressure to express said non-solvent liquid.

5. The process of forming a microporous sheet of solid polyurethane as defined in claim 4 in which a fibrous backer sheet is laid on the surface of said layer of emulsion after stripping said release surface wHen said emulsion has reached a pre-gelled stage in which it is sufficiently fluid to wet and adhere to said backer sheet but sufficiently thick to prevent said backer sheet from sinking, said layer of emulsion is further reacted to said resilient state suitable for expression of said non-solvent liquid and the combined backer sheet and layer of emulsion is subjected to pressure to remove non-solvent liquid.