Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-10-05
2001-10-16
Hoke, Veronica P. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S096000, C524S366000, C524S463000
Reexamination Certificate
active
06303682
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to flash-spinning of polymeric, plexifilamentary, film-fibril strands. More particularly, this invention relates to a spin fluid that may be used in existing commercial equipment with minimum changes in the equipment, and to a spinning process using existing commercial equipment in which the spinning process utilizes compounds having very low ozone depletion potential, and in which the spinning process is carried out utilizing compounds that are either non-flammable or of very low flammability.
BACKGROUND OF THE INVENTION
Commercial spunbonded products made from polyethylene plexifilamentary film-fibril strands have been produced by flash-spinning from trichlorofluoromethane; however, trichlorofluoromethane is an atmospheric ozone depletion chemical, and therefore, alternatives have been under investigation. Shin U.S. Pat. No. 5,032,326 discloses one alternative spin fluid, namely, methylene chloride and a co-spin agent halocarbon having a boiling point between −50° C. and 0° C. As pointed out in Kato et al. U.S. Pat. No. 5,286,422, the Shin methylene chloride-based process is not entirely satisfactory, and the '422 patent discloses an alternative, specifically, a spin fluid of bromochloromethane or 1,2-dichloroethylene and a co-spin agent of, e.g., carbon dioxide, dodecafluoropentane, etc.
Published Japanese Application JO5263310-A (published Oct. 12, 1993) discloses that three-dimensional fiber favorable for manufacturing flash-spun non-woven sheet may be made from polymer dissolved in mixtures of spin agents where the major component of the spin agent mixture is selected from the group consisting of methylene chloride, dichloroethylene, and bromochloromethane, and the minor component of the spin agent mixture is selected from the group consisting of dodecafluoropentane, decafluoropentane, and tetradecafluorohexane. However, it is known, for example, that methylene chloride is an animal carcinogen and dichloroethylene is somewhat flammable.
U.S. Pat. No. 5,023,025 to Shin discloses a process for flash-spinning plexifilamentary film-fibril strands of fiber-forming polyolefin from a group of halocarbon liquids that present a greatly reduced ozone depletion hazard. The patent discloses 1,1-dichloro-2,2,2-triflouroethane (HCFC-123) as a preferred halocarbon (halogenated hydrocarbon). HCFC-123 is a very good spin agent for polypropylene but not for polyethylene, and in the latter case a very high spinning pressure would be required. As such, for use with polyethylene, a co-spin agent has to be employed that is capable of dissolving polyethylene at relatively low pressures (i.e., a strong solvent). The '025 patent also discloses dichlorodifluoroethane (HCFC-132b and its isomers) and dichlorofluoroethane (HCFC-141b and its isomers), all of which have significant disadvantages. For example, HCFC-132b is a good spin agent, but toxic. HCFC-141b is also a good spin agent, but somewhat flammable, and moreover exhibits a relatively high ozone depletion potential.
SUMMARY OF THE INVENTION
The present invention is a process for the preparation of plexifilamentary film-fibril strands of synthetic fiber-forming polyolefin which comprises flash-spinning at a pressure that is greater than the autogenous pressure of the spin fluid into a region of lower pressure, a spin fluid comprising (a) 5 to 30 wgt. % synthetic fiber-forming polyolefin, and (b) a primary spin agent selected from the group consisting of 1,1,2-trichloro-2,2-difluoroethane (HCFC-122) and isomers thereof; 1,1,3-trichloro-2,2,3,3-tetrafluoropropane (HCFC-224ca) and isomers thereof; 1,2-dichloro-3,3,3-trifluoropropane (HCEC-243db) and isomers thereof; and 1,2-dichloro-1-fluoroethylene (HCFC-1121). A co-spin agent can be present in the spin fluid in an amount sufficient to raise the cloud point pressure of the spin fluid by at least 50 pounds per square inch (psi) (345 kPa).
This invention is also a spin fluid comprising (a) 5 to 30 wgt. % synthetic fiber-forming polyolefin, and (b) a primary spin agent selected from the group consisting of HCFC-122 and isomers thereof, HCFC-224ca and isomers thereof, HCFC-243db and isomers thereof, and HCFC-1121. A co-spin agent can be present in the spin fluid in an amount sufficient to raise the cloud point pressure of the spin fluid by at least 50 psi (345 kPa).
This invention is also directed to a process for the preparation of microcellular foam fibers from synthetic fiber-forming polyolefin which comprises flash-spinning at a pressure that is greater than the autogenous pressure of the spin fluid into a region of lower pressure, a spin fluid comprising (a) at least 40 wgt. % synthetic fiber-forming polyolefin, and (b) a primary spin agent selected from the group consisting of HCFC-122 and isomers thereof.
REFERENCES:
patent: 3564088 (1971-02-01), Woodell
patent: 3851023 (1974-11-01), Brethauer et al.
patent: 5023025 (1991-06-01), Shin
patent: 5032326 (1991-07-01), Shin
patent: 5039460 (1991-08-01), Shin
patent: 5081177 (1992-01-01), Shin
patent: 5147586 (1992-09-01), Shin et al.
patent: 5286422 (1994-02-01), Kato et al.
patent: 5369165 (1994-11-01), Kato et al.
patent: 5672307 (1997-09-01), Shin et al.
patent: 5985196 (1999-11-01), Shin et al.
patent: 6162379 (2000-12-01), Shin et al.
patent: Hei 5-263310 (1992-03-01), None
patent: 06041810 (1994-02-01), None
patent: WO97/25460 (1997-07-01), None
Shin Hyunkook
Siemionko Roger Keith
E. I. Du Pont de Nemours and Company
Hoke Veronica P.
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