Method for preparing a porous fluoropolymer and preparing an article of same

• US 9,452,372 B2
• Filed: 10/18/2012
• Issued: 09/27/2016
• Est. Priority Date: 10/18/2012
• Status: Active Grant

• Current Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Original Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Inventors: Sadana, Anil K.
• Primary Examiner(s): HAUTH, GALEN H
• Application Number:
  US13/654,726
• Publication Number:
  US 20150202827A1
• Time in Patent Office: 1,440 Days
• US Class Current: 1/1
• CPC Class Codes: B01D 29/0093 Making filtering elements not provided for elsewhere
• CPC Class Codes: B01D 29/0095 Flat filtering elements B01D25/12, B01D25/26 take precedence
• CPC Class Codes: B01D 39/1661 sintered or bonded
• CPC Class Codes: B01D 39/1692 Other shaped material, e.g. perforated or porous sheets
• CPC Class Codes: B01D 67/003 by selective elimination of components, e.g. by leaching
• CPC Class Codes: B01D 71/36 Polytetrafluoroethene
• CPC Class Codes: B29B 11/12 Compression moulding
• CPC Class Codes: B29B 13/02 by heating B29B13/06, B29B13/08 take precedence
• CPC Class Codes: B29B 7/88 Adding charges , i.e. additives
• CPC Class Codes: B29C 67/202 comprising elimination of a solid or a liquid ingredient
• CPC Class Codes: B29K 2027/12 containing fluorine
• CPC Class Codes: B29K 2105/0005 containing compounding ingredients releasing, lubricating or separating agents B29C33/56, fibers B29K2105/08, B29K2105/12; fillers B29K2105/16, recycled material B29K2105/26
• CPC Class Codes: B29K 2105/04 cellular or porous
• CPC Class Codes: B29K 2105/251 Particles, powder or granules expandable particles B29K2105/046
• CPC Class Codes: C08J 2201/044 Elimination of an inorganic solid phase
• CPC Class Codes: C08J 2201/0444 Salts
• CPC Class Codes: C08J 2327/12 containing fluorine atoms
• CPC Class Codes: C08J 2327/18 Homopolymers or copolymers of tetrafluoroethylene
• 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: E21B 43/02 Subsoil filtering
• CPC Class Codes: E21B 43/12 : Methods or apparatus for controlling the flow of the obtained fluid to or in wells E21B43/25 takes precedence; valve arrangements E21B34/00
• CPC Class Codes: E21B 43/38 : in the well

Abstract

A method for preparing a porous fluoropolymer precursor includes combining a fluoropolymer and a removable additive to form a composition, the removable additive having a thermal decomposition temperature greater than a sintering temperature of the fluoropolymer, compressing the composition to form a preform, and sintering the preform to form the porous fluoropolymer precursor. A method for preparing a porous fluoropolymer includes disposing the porous fluoropolymer precursor in a removing agent, contacting the removable additive with the removing agent, and removing, by the removing agent, the removable additive from the porous fluoropolymer precursor to form the porous fluoropolymer, wherein the porous fluoropolymer comprises a plurality of pores formed by removing the removable additive.

Claims

1. A method for preparing a porous article, the method comprising:

combining a fluoropolymer and a removable additive to form a powder composition, the removable additive having a thermal decomposition temperature greater than a sintering temperature of the fluoropolymer;

the removable additive comprising an inorganic salt, glass, or a combination comprising at least one of the foregoing removable additives;

the inorganic salt comprising an alkali metal halide, alkali metal nitrates, alkali metal carbonate, alkali metal hydrogencarbonate, alkali metal phosphate, or a combination comprising at least one of the foregoing inorganic salts;

compressing the powder composition at room temperature to form a compressed composition;

sintering the compressed composition at atmospheric pressure to form a preform;

disposing the preform in a removing agent;

the preform consisting essentially of the fluoropolymer and the removable additive;

contacting the removable additive with the removing agent; and

removing, by the removing agent, the removable additive from the preform to form the porous article,

the porous article comprising a plurality of pores formed by removing the removable additive, a portion of the pores being connected and establishing fluid flow paths through the article;

wherein the fluoropolymer is selected such that the article has a surface energy less than about 30 milliNewtons per meter; and

the article is configured such that a fluid having a surface energy less than 40 milliNewtons per meter at 25°

C. has a higher flow rate through the pores of the article than a fluid having a surface energy greater than 40 mN/m at 25°

C.

2. The method of claim 1, further comprising:

disposing the powder composition in a mold prior to compressing the powder composition; and

removing the compressed composition from the mold before sintering the compressed composition.

3. The method of claim 1, wherein combining the fluoropolymer and the removable additive distributes the removable additive in the fluoropolymer, and the compressed composition has the removable additive distributed among the fluoropolymer.

4. The method of claim 1, wherein sintering the compressed composition is performed at a temperature from 79°

C. (175°

F.) to 371°

C. (700°

F.).

5. The method of claim 1, wherein the fluoropolymer is partially fluorinated.

6. The method of claim 1, wherein the fluoropolymer is completely fluorinated.

7. The method of claim 1, wherein the fluoropolymer comprises polytetrafluoroethylene, polyethylenetetrafluoroethylene, fluorinated ethylene propylene copolymer, perfluoroalkoxy polymer, polyvinylidene fluoride, polyvinylfluoride, polychlorotrifluoroethylene, polyethylenechlorotrifluoroethylene, chlorotrifluoroethylenevinylidene fluoride, perfluoroelastomer, tetrafluoroethylene-propylene elastomeric copolymer, perfluoropolyether, perfluorosulfonic acid, or a combination comprising at least one of the foregoing fluoropolymers.

8. The method of claim 1, wherein the removable additive is the glass which comprises silicon dioxide, aluminum oxide, barium oxide, bismuth trioxide, boron oxide, calcium oxide, cesium oxide, lead oxide, strontium oxide, a rare earth oxide, lanthanum oxide, neodymium oxide, samarium oxide, cerium oxide, or a combination comprising at least one of the foregoing glasses.

9. The method of claim 1, wherein the removable additive is present in the porous fluoropolymer precursor in an amount from 1 wt. % to 80 wt. %, based on the weight of the porous fluoropolymer precursor.

10. The method of claim 1, wherein a size of the removable additive is from 50 μ

m to 500 μ

m.

11. The method of claim 1, wherein the melting temperature of the removable additive is greater than the sintering temperature.

12. The method of claim 1, further comprising flowing the removing agent through the plurality of pores.

13. The method of claim 1, wherein removing the removable additive is performed at a temperature from 60°

C. to 90°

C.

14. The method of claim 1, wherein the removing agent comprises water, hydrogen fluoride, ammonium fluoride, alkali metal fluoride, antimony fluoride, ammonium bifluoride, alkali metal bifluoride, calcium bifluoride, alkylated ammonium tetrafluoroborate, potassium tetrafluoroborate, fluoroboric acid, tin bifluoride, tetrabutylammonium tetrafluoroborate, aluminum hexafluoride, or a combination comprising at least one of the foregoing removing agents.

15. The method of claim 1, wherein a size of the plurality of pores is from 50 μ

m to 500 μ

m.

16. The method of claim 1, wherein the article comprises a flow control device, filter, membrane, tubular, sand screen, motor cover, mesh, cover, sheet, or a combination comprising at least one of the foregoing.