Claims
- 1. In the process for flash-spinning plexifilamentary film-fibril strands of a fiber-forming crystalline polyolefin at a temperature of 130.degree. C. to 300.degree. C. and at a mixing pressure greater than autogenous pressure from a solution consisting essentially of 8 to 35 weight percent of the polyolefin and 92 to 65 weight percent of a spin liquid comprising at least one saturated C.sub.4 -C.sub.7 hydrocarbon, electrostatically charging the strands, and laying the strands as a sheet on a continuously moving surface;
- wherein the improvement comprises conducting the electrostatic charging step in an atmosphere comprising at least one charge-improving compound, such that said charge-improving compound belongs to one of groups A and B,
- wherein group A comprises compounds that have an atmospheric boiling temperature of less than 100.degree. C. and consists of one of carbon dioxide, hydrofluorocarbons, hydrochlorofluorocarbons, perfluorocarbons, alcohols, aliphatic ketones, and polar solvents; and
- wherein group B consists of compounds not listed in group A that are within the following categories of compounds: compounds of the types listed in group A except having atmospheric boiling temperatures of at least 100.degree. C.; halogen gases; acid halides; halocarbons, except fully halogenated chlorofluorocarbons, that are not listed in group A; hydroxylic compounds, ethers, carboxylic acids; esters; sulfur compounds; non-aliphatic ketones; aldehydes; nitro compounds; nitrogen oxides; nitriles; ammonia; amines; amides; and halogenated derivatives of the above compounds which do not already contain a halogen atom;
- such that the atmosphere comprises at least 0.1 ppm of charge-improving compounds, up to ten weight percent of group A charge-improving compounds, and less than seventy-five weight percent of group B charge improving compounds.
- 2. The process according to claim 1 wherein said atmosphere comprises at least one group A charge-improving compound.
- 3. The process according to claim 1 wherein said atmosphere comprises at least one group B charge-improving compound.
- 4. The process according to claim 1 wherein said at least one charge-improving compound is a component of the spin liquid.
- 5. In the process for flash-spinning plexifilamentary film-fibril strands of a fiber-forming crystalline polyolefin at a temperature of 130.degree. C. to 300.degree. C. and at a mixing pressure greater than autogenous pressure from a solution consisting essentially of 8 to 35 weight percent of the polyolefin and 92 to 65 weight percent of a spin liquid comprising at least one saturated C.sub.4 -C.sub.7 hydrocarbon, electrostatically charging the strands, and laying the strands as a sheet on a continuously moving surface;
- wherein the improvement comprises conducting the electrostatic charging step in an atmosphere comprising at least one charge-improving compound, predominantly in gas of vapor form, such that said charge-improving compound belongs to one of groups A and B,
- wherein group A comprises compounds that have an atmospheric boiling temperature of less than 100.degree. C. and consists of one of carbon dioxide, hydrofluorocarbons, hydrochlorofluorocarbons, perfluorocarbons, alcohols, aliphatic ketones, and polar solvents; and
- wherein group B consists of compounds not listed in group A that are within the following categories of compounds; compounds of the types listed in group A except having atmospheric boiling temperatures of at least 100.degree. C.; halogen gases; acid halides; halocarbons that are not listed in group A; hydroxylic compounds, ethers, carboxylic acids; esters; sulfur compounds; non-aliphatic ketones; aldehydes; nitro compounds; nitrogen oxides; nitriles; ammonia; amines; amides; and halogenated derivatives of the above compounds which do not already contain a halogen atom;
- wherein said at least one charge-improving compound is introduced directly, as a gas, vapor, or mist, into the electrostatic charging atmosphere.
- 6. The process according to claim 1 where said at least one charge-improving compound has an atmospheric boiling temperature in the range of 0.degree. C. to 150.degree. C.
- 7. The process according to claim 6 where said at least one charge-improving compound has an atmospheric boiling temperature in the range of 20.degree. C. to 90.degree. C.
- 8. The process according to claim 1 wherein said at least one charge-improving compound is a halogenated compound.
- 9. The process according to claim 8 wherein said at least one charge-improving compound is a halogenated organic compound.
- 10. The process according to claim 9 wherein said at least one charge-improving compound is a hydrochlorofluorocarbon.
- 11. The process according to claim 9 wherein said at least one charge-improving compound is a hydrofluorocarbon.
- 12. The process according to claim 8 wherein said halogenated charge-improving compound includes at least one chlorine atom.
- 13. The process according to claim 8 wherein said halogenated charge-improving compound includes at least one fluorine atom.
- 14. The process according to claim 8 wherein said halogenated charge-improving compound includes at least one bromine atom.
- 15. The process according to claim 8 wherein said halogenated charge-improving compound includes at least one iodine atom.
- 16. The process according to claim 1 wherein the atmosphere comprises from 10 ppm to 10 weight percent of charge-improving compounds.
- 17. The process according to claim 16 where the atmosphere comprises from 25 ppm to 1.0 weight percent of charge-improving compounds.
- 18. The process according to claim 8 wherein said halogenated charge-improving compound is a halogenated non-organic compound.
- 19. The process according to claim 8 wherein said halogenated charge-improving compound is a halogenated hydroxylic compound.
- 20. The process according to claim 8 wherein said halogenated charge-improving compound is a halogenated ether.
- 21. The process according to claim 8 wherein said halogenated charge-improving compound is a halogenated carboxylic acid.
- 22. The process according to claim 8 wherein said halogenated charge-improving compound is a halogenated ester.
- 23. The process according to claim 8 wherein said halogenated charge-improving compound is a halogenated ketone.
- 24. The process according to claim 8 wherein said halogenated charge-improving compound is a halogenated amine.
- 25. The process according to claim 8 wherein said halogenated charge-improving compound is a halogenated aldehyde.
- 26. The process according to claim 8 wherein said halogenated charge-improving compound is a halogenated sulfur compound.
- 27. The process according to claim 1 wherein said at least one charge-improving compound is carbon dioxide.
- 28. The process according to claim 1 wherein said at least one charge improving compound is perfluoro(n-methylmorpholine).
- 29. The process according to claim 1 wherein said at least one charge-improving compound is a non-halogenated compound.
- 30. The process according to claim 29 wherein said at least one charge-improving compound has an atmospheric boiling temperature of less than 100.degree. C. and is selected from the group consisting of alcohols, ketones, esters, ethers, and carboxylic acids.
- 31. The process according to claim 29 wherein said at least one charge-improving compound is a sulfur compound.
- 32. The process according to claim 8 wherein said halogenated charge-improving compound is a fully halogenated compound.
- 33. The process according to claim 32 wherein said fully halogenated charge-improving compound includes at least one fluorine atom.
- 34. The process according to claim 33 wherein said charge-improving compound is a fully fluorinated organic compound.
- 35. The process according to claim 34 wherein said charge-improving compound is a fully fluorinated hydrocarbon.
- 36. The process according to claim 1 wherein said at least one charge-improving compound is water.
- 37. In the process for flash-spinning plexifilamentary film-fibril strands of a fiber-forming crystalline polyolefin at a temperature of 130.degree. C. to 300.degree. C. and at a mixing pressure greater than autogenous pressure from a solution consisting essentially of 8 to 35 weight percent of the polyolefin and 92 to 65 weight percent of a spin liquid comprising at least one saturated C.sub.4 -C.sub.7 hydrocarbon, electrostatically charging the strands, and laying the strands as a sheet on a continuously moving surface;
- wherein the improvement comprises providing an effective amount of at least one charge-improving compound into the atmosphere in which the strands are electrostatically charged to obtain a ten percent improvement of the charging efficiency for a constant web charge, the charging efficiency is calculated by the following formula, ##EQU3## such that: E=charging efficiency;
- I.sub.g =ion gun current; and
- I.sub.tp =target plate current;
- and wherein the charge-improving compound belongs to one of groups A and B, wherein:
- group A comprises compounds that have an atmospheric boiling temperature of less than 100.degree. C. and consists of one of carbon dioxide, hydrofluorocarbons, hydrochlorofluorocarbons, perfluorocarbons, alcohols, aliphatic ketones, and polar solvents; and
- group B consists of compounds not listed in group A that are within the following categories of compounds: compounds of the types listed in group A except having atmospheric boiling temperatures of at least 100.degree. C.; halogen gases; acid halides; halocarbons, except fully halogenated chlorofluorocarbons, that are not listed in group A; hydroxylic compounds, ethers, carboxylic acids; esters; sulfur compounds; non-aliphatic ketones; aldehydes; nitro compounds; nitrogen oxides; nitriles; ammonia; amines; amides; and halogenated derivatives of the above compounds which do not already contain a halogen atom;
- such that the atmosphere comprises up to ten weight percent of group A charge-improving compounds, and less than seventy-five weight percent of group B charge improving compounds.
- 38. The process according to claim 37 wherein an effective amount of charge-improving compounds provides at least a 25 percent improvement of charging efficiency.
- 39. The process according to claim 38 wherein an effective amount of charge-improving compounds provides at least a 60 percent improvement of charging efficiency.
- 40. The process according to claim 39 wherein an effective amount of charge-improving compounds provides at least a 100 percent improvement of charging efficiency.
RELATED PATENT APPLICATIONS
This patent application is a continuation-in-part patent application of commonly owned U.S. patent application Ser. No. 08/037,562 which was filed Mar. 26, 1993, now abandoned.
US Referenced Citations (7)
Continuation in Parts (1)
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Number |
Date |
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Parent |
37562 |
Mar 1993 |
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