Method for cleaning hollow articles with plasma

• US 5,700,327 A
• Filed: 03/10/1995
• Issued: 12/23/1997
• Est. Priority Date: 03/10/1995
• Status: Expired due to Fees

• Current Assignee: Polar Materials Incorporated
• Original Assignee: Polar Materials Incorporated
• Inventors: Frake, Kevin, Narendrnath, Kadthala R., Babacz, Robert J., Baylog, Melissa A.
• Primary Examiner(s): Soderquist, Arlen
• Assistant Examiner(s): CHAUDHRY, SAEED T
• Application Number:
  US08/402,091
• Time in Patent Office: 1,019 Days
• Field of Search: 134/1.1, 422/22, 422/23, 219/121.36, 219/121.4, 219/121.41, 219/121.43
• US Class Current: 134/1.1
• CPC Class Codes: B08B 7/0035 by radiant energy, e.g. UV, laser, light beam or the like

Abstract

A method of cleaning a hollow article comprises a step of introducing an oxidizing working gas into at least an interior portion of the hollow article, while a sub-atmospheric pressure is being maintained therein. Then, an electric field is applied, so as to convert the oxidizing working gas within at least the interior portion of the article into a low temperature plasma. This leads to oxidizing substances situated at least within the interior portion of the hollow article.

Claims

1. A method of removing organic compounds from an interior portion of a hollow container having interior and exterior portions and having organic compounds in said interior portion, said method comprising the steps of:

(a) introducing an oxidizing, working gas within an interior portion of said container having organic compounds therein, while maintaining sub-atmosphere pressure therein; and

(b) applying an electric field for converting said working gas within at least said interior portion into a low temperature plasma, and maintaining said plasma so that said plasma oxidizes substantially all of the organic compounds situated within said interior portion of the container.

2. The method of cleaning as claimed in claim 1, wherein in said step "b" said electric field is applied to said interior portion of said container from the exterior thereof.

3. The method of cleaning as claimed in claim 1, wherein said working gas includes one or more components selected from the group consisting of O₂, Ar and N₂.

4. The method of cleaning as claimed in claim 1, wherein said oxidizing, working gas is an oxygen-containing gas.

5. The method of cleaning as claimed in claim 1, wherein said working gas includes O₂ and Ar.

6. The method of cleaning as claimed in claim 1, wherein said electric field is a radio-frequency electric field.

7. The method of cleaning as claimed in claim 6, wherein said radio frequency electric field has frequency of 13.56 MHz.

8. The method of cleaning as claimed in claim 1, wherein said electric field is a microwave frequency electric field.

9. The method of cleaning as claimed in claim 1, wherein in said steps "a" and "b" a pressure of said working gas within said interior portion is between 0.1 and 0.5 Torr.

10. The method of cleaning as claimed in claim 1, wherein in at least said step "b" an operating pressure of said low temperature plasma is between 0.1 and 0.5 Torr.

11. The method of cleaning as claimed in claim 1, wherein said step "b" said electric field is applied by a pair of electrodes disposed adjacent to the container.

12. The method of cleaning as claimed in claim 11, wherein in said step "b" said electric field is generated by a power supply connected to said pair of electrodes, said power supply is capable of producing a high frequency discharge across said electrodes, so as to excite said oxidizing, working gas.

13. The method of cleaning as claimed in claim 1, wherein in said step "b" said oxidizing, working gas is introduced within interior portions of a plurality of containers and said electric field pulses causing pressure fluctuation within said interior potions of said plurality of containers facilitating removal products of oxidation from said interior portions.

14. The method of cleaning as claimed in claim 13, wherein said plurality of containers are made of a dielectric material and said pair of electrodes is applied from said exterior portions of said containers.

15. The method of cleaning as claimed in claim 14, wherein said containers are formed of a material selected from the group consisting of glass, plastic and ceramic.

16. The method of cleaning as claimed in claim 1, wherein the temperature of said low temperature plasma is below 40°

C.

17. The method of cleaning as claimed in claim 1 further comprising the steps of cleaning a closure for the container by exposing the closure to a plasma and uniting the closure with the container after said step of cleaning the closure and after said steps (a) and (b).

18. A method as claimed in claim 17 wherein said step of uniting the closure with the container is performed while said container is empty, to thereby provide a closed empty container for collection of an analytical sample.

19. A method as claimed in claim 18 wherein said organic compounds in said interior portion of said container are selected from the group consisting of volatiles, semivolatiles, greases, oils, and pesticides.

20. A method as claimed in claim 18 wherein said container, after said steps (a) and (b) and after said step of uniting the closure with the container, meets the specifications of US EPA OSWER directive #9240.0-05A.

21. A method of removing organic compounds from an interior portion of a hollow container having interior and exterior portions and having organic contaminants in said interior portion, said method comprising the steps of:

(a) introducing an oxidizing, working gas within said interior portion of said container having organic compounds therein while maintaining sub-atmospheric pressure therein; and

(b) applying an electric field for converting said working gas within at least said interior portion into a low temperature plasma, and maintaining said plasma so that said plasma oxidizes substantially all of the organic compounds situated within said interior portion of the container

the method further comprising the steps of cleaning a closure for the container by exposing the closure to a plasma and uniting the closure with the container after said step of cleaning the closure and after said steps (a) and (b)

wherein said step of uniting the closure with the container is performed within an enclosed clean room, said steps (a) and (b) being performed within a plasma treatment chamber, the method further comprising the steps of introducing the container from outside of said clean room into the plasma treatment chamber and transferring the container directly from the treatment chamber into the clean room after performing said steps (a) and (b).

22. A method as claimed in claim 21 wherein said step of uniting the closure with the container is performed while said container is empty, to thereby provide a closed empty container for collection of an analytical sample.

23. A method as claimed in claim 22 wherein said organic compounds in said interior portion of said container are selected from the group consisting of volatiles, semivolatiles, greases, oils, and pesticides.

24. A method as claimed in claim 22 wherein said container, after said steps (a) and (b) and after said step of uniting the closure with the container, meets the specifications of US EPA OSWER directive #9240.0-05A.