Electret webs with charge-enhancing additives

Patent metadata

Field	Value
Publication number	US-9815068-B2
Application number	US-201314654934-A
Country	US
Kind code	B2
Filing date	Mar 15, 2013
Priority date	Dec 28, 2012
Publication date	Nov 14, 2017
Grant date	Nov 14, 2017

Abstract

Electret webs include a thermoplastic resin and a charge-enhancing additive. The charge-enhancing additive is a divalent metal-containing substituted-mercaptobenzimidazolate salt. The electret webs may be a non-woven fibrous web or a film. The electret webs are suitable for use as filter media.

First claim

What is claimed is:

1. An electret web comprising:
a thermoplastic resin; and
a charge-enhancing additive comprising a divalent metal-containing substituted-mercaptobenzimidazolate salt.

2. The electret web of claim 1 , wherein the web comprises a non-woven fibrous web.

3. The electret web of claim 1 , wherein the web comprises a film.

4. The electret web of claim 1 , wherein the divalent metal-containing substituted-mercaptobenzimidazolate salt comprises a salt with the structure (a):

wherein M comprises a divalent metal;
the group R1 comprises a hydrogen atom, or an alkyl group;
the groups R2 , R3 , R4 , and R5 independently comprise a hydrogen atom, an alkyl, an aryl, a heteroalkyl, a substituted alkyl, substituted aryl, or alkoxy.

5. The electret web of claim 1 , wherein the divalent metal-containing substituted-mercaptobenzimidazolate salt comprises a salt with the structure (a):

wherein M comprises Zn, Ni, or Fe;
the group R1 comprises a hydrogen atom, or an alkyl group with 1-3 carbon atoms;
the group R2 , comprises an alkyl group with 1-3 carbon atoms; and
the groups R3 , R4 , and R5 independently comprise a hydrogen atom, an alkyl, an aryl, a heteroalkyl, a substituted alkyl, substituted aryl, or alkoxy.

6. The electret web of claim 1 , wherein the divalent metal-containing substituted-mercaptobenzimidazolate salt comprises a salt with the structure (a):

wherein M comprises Zn;
the groups R1 , R3 , R4 , and R5 each comprise a hydrogen atom; and
the group R2 comprises a methyl group.

7. The electret web of claim 1 , wherein the thermoplastic resin comprises:
polyolefin; polyvinyl chloride; polystyrene; polycarbonate; or polyester.

8. The electret web of claim 1 , wherein the divalent metal-containing substituted-mercaptobenzimidazolate salt comprises 0.02-5.0% by weight of the web.

9. The electret web of claim 1 , wherein the web contains an electrostatic charge, wherein the charge is imparted through corona treatment, hydrocharging, or a combination thereof.

10. The electret web of claim 1 , wherein the web contains an electrostatic charge, wherein the charge is imparted through corona treatment.

11. The electret web of claim 1 , wherein the web further comprises at least one additional additive selected from pigments, light stabilizers, primary and secondary antioxidants, metal deactivators, hindered amines, hindered phenols, fatty acid metal salts, triester phosphites, phosphoric acid salts, fluorine-containing compounds and combinations thereof.

12. An electret filter medium comprising:
a web comprising:
a thermoplastic resin; and
a charge-enhancing additive comprising a divalent metal-containing substituted-mercaptobenzimidazolate salt.

13. The electret filter medium of claim 12 , wherein the divalent metal-containing sub stituted-mercaptobenzimidazolate salt comprises a salt with the structure (a):

wherein M comprises a divalent metal;
the group R1 comprises a hydrogen atom, or an alkyl group;
the groups R2 , R3 , R4 , and R5 independently comprise a hydrogen atom, an alkyl, an aryl, a heteroalkyl, a substituted alkyl, substituted aryl, or alkoxy.

14. The electret filter medium of claim 12 , wherein the divalent metal-containing substituted-mercaptobenzimidazolate salt comprises a salt with the structure (a):

wherein M comprises Zn, Ni, or Fe;
the group R1 comprises a hydrogen atom, or an alkyl group with 1-3 carbon atoms;
the group R2 , comprise an alkyl group with 1-3 carbon atoms; and
the groups R3 , R4 , and R5 independently comprise a hydrogen atom, an alkyl, an aryl, a heteroalkyl, a substituted alkyl, substituted aryl, or alkoxy.

15. The electret filter medium of claim 12 , wherein the divalent metal-containing substituted-mercaptobenzimidazolate salt comprises a salt with the structure (a):

wherein M comprises Zn;
the groups R1 , R3 , R4 , and R5 each comprise a hydrogen atom; and
the group R2 comprises a methyl group.

16. The electret filter medium of claim 12 , wherein the thermoplastic resin comprises:
polyolefin; polyvinyl chloride; polystyrene; polycarbonate; or polyester.

17. The electret filter medium of claim 12 , wherein the divalent metal-containing substituted-mercaptobenzimidazolate salt comprises 0.02-5.0% by weight of the web.

18. The electret filter medium of claim 12 , wherein the web contains an electrostatic charge, wherein the charge is imparted through corona treatment, hydrocharging, or a combination thereof.

19. The electret filter medium of claim 12 , wherein the web contains an electrostatic charge, wherein the charge is imparted through corona treatment.

20. The electret filter medium of claim 12 , wherein the web further comprises at least one additional additive selected from pigments, light stabilizers, primary and secondary antioxidants, metal deactivators, hindered amines, hindered phenols, fatty acid metal salts, triester phosphites, phosphoric acid salts, fluorine-containing compounds and combinations thereof.

21. The electret filter medium of claim 12 , wherein the filter medium has a % Penetration Ratio of at least 300% at a face velocity of 6.9 centimeters per second when tested according to the X-ray Discharge Test.

22. The electret filter medium of claim 12 , wherein the filter medium has an Initial Quality Factor of at least 0.3 (mm of H 2 O) −1 at a face velocity of 6.9 centimeters per second, and after exposure to X-rays for 60 minutes, a Quality Factor of less than 50% of the Initial Quality Factor, when tested according to the X-ray Discharge Test.

23. The electret filter medium of claim 12 , wherein the filter medium retains at least 85% filtration performance as measured by Quality Factor after aging for 72 hours at 71° C.

Assignees

• 3M Innovative Properties Co

Inventors

• Schultz Nathan E
• Li Fuming B
• Sebastian John M

Classifications

• B01D39/1623

  of synthetic origin · CPC title

• D01F1/10

  Other agents for modifying properties · CPC title

• B01D39/083

  of organic material · CPC title

• D04H1/4382

  Stretched reticular film fibres; Composite fibres; Mixed fibres; Ultrafine fibres; Fibres for artificial leather · CPC title

• D01F6/06

  from polypropylene · CPC title