# US 8,784,710 B2 · Expandable polymer membrane and tubes, and a method of manufacturing thereof

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- Number: US 8,784,710 B2
- Document ID: US8784710B2
- Status: Granted
- Kind: B2
- Application number: 12/726,707
- Filed: 2010-03-18
- Published: 2011-01-20
- Granted: 2014-07-22
- Earliest claimed: 2009-07-16
- Assignees: Phillips Scientific Inc.
- Applicants: Douglas R. Hansen; James V. Phillips
- Inventors: Douglas R. Hansen; James V. Phillips
- Web page: https://patentgrep.com/patent/US8784710B2

## CPC

- B29C 55/143: {firstly parallel to the direction of feed and then transversely thereto}
- B01D 53/228: {characterised by specific membranes}
- B01D 67/002: {from melts}
- B01D 67/0027: {by stretching}
- B01D 67/0083: {Thermal after-treatment}
- B01D 67/0086: {Mechanical after-treatment}
- B01D 67/0088: {Physical treatment with compounds, e.g. swelling, coating or impregnation}
- B01D 71/36: Polytetrafluoroethylene
- B29C 43/006: {Pressing and sintering powders, granules or fibres}
- B29C 48/08: flexible, e.g. films
- B29C 48/09: Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
- B29C 55/005: {characterised by the choice of materials}
- B29C 67/04: Sintering (combined with compression B29C43/00)
- B01D 2323/42: Details of membrane preparation apparatus
- B29C 43/22: of articles of indefinite length
- B29C 48/022: {characterised by the choice of material}
- B29C 48/07: Flat, e.g. panels
- B29C 48/885: External treatment, e.g. by using air rings for cooling tubular films
- B29C 48/906: {using roller calibration}
- B29C 48/908: {characterised by calibrator surface, e.g. structure or holes for lubrication, cooling or venting}
- B29C 48/91: Heating, e.g. for cross linking
- B29C 48/912: {of tubular films}
- B29C 53/56: Winding and joining, e.g. winding spirally {(winding in general B65H)}
- B29C 53/60: using internal forming surfaces, e.g. mandrels
- B29K 2027/18: PTFE, i.e. polytetrafluoroethylene {, e.g. ePTFE, i.e. expanded polytetrafluoroethylene}
- B29K 2105/04: cellular or porous
- B29L 2031/755: {Membranes, diaphragms}
- Y10T 428/269: including synthetic resin or polymer layer or component
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- B29K: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR {MOULDS, } REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29L: INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A method of making an expanded polytetrafluoroethylene (ePTFE) membrane including the steps of: providing an unsintered or partially sintered ePTFE membrane; matting the unsintered or partially sintered ePTFE membrane; and immediately thereafter, sintering the matted ePTFE membrane. A method for making ePTFE tubes includes the steps of: providing an unsintered or partially sintered ePTFE membrane; wrapping the ePTFE membrane around a mandrel or form tool to form an ePTFE tube; matting the ePTFE tube; immediately thereafter, sintering the matted ePTFE tube; and removing the sintered ePTFE tube from the mandrel or form tool.

## Claims

### Claim 1

A method of making an ePTFE membrane including the steps of:
providing an unsintered or partially sintered ePTFE membrane;
matting said unsintered or partially sintered ePTFE membrane consisting of:
wetting said unsintered or partially sintered ePTFE membrane with a wettable liquid; and
drying said wetted ePTFE membrane with heat, thereby removing said wettable liquid and forming a matted ePTFE membrane; and immediately thereafter
sintering said matted ePTFE membrane,
wherein matting said unsintered or partially sintered membrane reduces the thickness of the unsintered or partially sintered membrane between 25-90%.

### Claim 2 (depends on 1)

The method of making an ePTFE membrane according to claim 1 wherein matting said unsintered or partially sintered membrane reduces the thickness of said unsintered or partially sintered ePTFE membrane between 40-80%.

### Claim 3 (depends on 1)

The method of making an ePTFE membrane according to claim 1 wherein matting said unsintered or partially sintered membrane reduces the thickness of said unsintered or partially sintered ePTFE membrane between 60% and 75%.

### Claim 4 (depends on 1)

The method of making an ePTFE membrane of claim 1 where:
said wettable liquid being selected from the group consisting of: an alcohol and a mineral solvent;
said alcohol being a lower alkyl alcohol; and
said mineral solvent being naptha.

### Claim 5 (depends on 1)

The method of making an ePTFE membrane according to claim 1 where said step of wetting said unsintered or partially sintered ePTFE membrane with a wettable liquid includes the step of spraying said wettable liquid on top of said unsintered or partially sintered ePTFE membrane with a sprayer moving back and forth across said membrane.

### Claim 6 (depends on 1)

The method of making an ePTFE membrane according to claim 1 where said step of drying said wetted ePTFE membrane includes heating said ePTFE membrane under a preheat heater;
said preheat heater being set to a temperature of between 400° F. and 600° F.

### Claim 7 (depends on 6)

The method of making an ePTFE membrane according to claim 6 where said preheat heater is set to a temperature of 550° F.

### Claim 8 (depends on 1)

The method of making an ePTFE membrane according to claim 1 where said step of sintering said matted ePTFE membrane includes heating said membrane in a high temperature oven to a sintering temperature, said sintering temperature being between 600° F. and 1100° F.

### Claim 9 (depends on 8)

The method of making an ePTFE membrane according to claim 8 where said sintering temperature is between 750° F. and 935° F.

### Claim 10 (depends on 1)

The method of making an ePTFE membrane according to claim 1 where said step of sintering said matted ePTFE membrane includes the step of fine tuning sintering via visual detection;
said step of fine tuning sintering via visual detection including adjusting said sintering temperature based on the opaqueness of said membrane.

### Claim 11 (depends on 1)

The method of making an ePTFE membrane according to claim 1 where said step of providing an unsintered or partially sintered ePTFE membrane includes the steps of:
mixing a fine powder polytetrafluoroethylene resin with a lubricant creating a mix;
compressing said mix into a preform mold;
extruding said molded mix into a tape;
calendering said extruded tape;
evaporating said lubricant from said extruded tape;
stretching said calendered tape in the machine direction; and
stretching said calendered tape in the transverse direction;
thereby, forming an unsintered or partially sintered ePTFE membrane.