Source: http://www.google.com/patents/US6531085?dq=6,799,467
Timestamp: 2016-05-24 12:57:04
Document Index: 678919369

Matched Legal Cases: ['Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'application No. 60', 'Application No. 60']

Patent US6531085 - Method for improving strength of elastic strand - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsWe have determined that strength characteristics of elastic strand improve when the strand is heated. Thus, the present invention is directed to improving strength characteristics of an elastic strand by heating the strand. The strand may be heated by thermal conduction and/or convection, by irradiative...http://www.google.com/patents/US6531085?utm_source=gb-gplus-sharePatent US6531085 - Method for improving strength of elastic strandAdvanced Patent SearchPublication numberUS6531085 B1Publication typeGrantApplication numberUS 09/715,807Publication dateMar 11, 2003Filing dateNov 16, 2000Priority dateNov 19, 1999Fee statusLapsedAlso published asCN1425085A, EP1235954A1, US6962749, US20030094737, WO2001036727A1Publication number09715807, 715807, US 6531085 B1, US 6531085B1, US-B1-6531085, US6531085 B1, US6531085B1InventorsPeiguang Zhou, Wing-Chak NgOriginal AssigneeKimberly-Clark Worldwide, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (12), Non-Patent Citations (5), Referenced by (8), Classifications (25), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetMethod for improving strength of elastic strand
16. The method of claim 2 further comprising the step of regulating the elastic strand's exposure to water vapor before or after heating, the method comprising the additional steps of:
placing the strand in a container comprising a barrier material; and closing the container. 17. The method of claim 16 wherein the container comprising a barrier material is closed at a time t1, time t1 being after the time when the strand is first produced and before the time when the strand is shipped from the geographical site at which the strand is first produced to the geographical site at which the strand is used.
18. The method of claim 17 wherein the specific humidity around the strand does not exceed 0.017 pounds-mass of water vapor per pound-mass of dry air between time t1 and time t2, time t2 being the time when the closed container comprising a barrier material is first opened.
19. The method of claim 17 wherein the specific humidity around the strand does not exceed 0.01 pounds-mass of water vapor per pound-mass of dry air between time t1 and time t2, time t2 being the time when the closed container comprising a barrier material is first opened.
20. The method of claim 17 wherein the specific humidity around the strand does not exceed 0.005 pounds-mass of water vapor per pound-mass of dry air between time t1 and time t2, time t2 being the time when the closed container comprising a barrier material is first opened.
22. The method of claim 21 wherein closing the container comprising a barrier material comprises heat sealing the container, the barrier material, or both.
24. The method of claim 23 wherein the desiccant material comprises calcium chloride, calcium sulfate, silica gel, a molecular sieve, Al2O3, or some combination of thereof.
This application claims priority from U.S. Provisional Application Nos. 60/166,348 filed on Nov. 19, 1999 and 60/171,467 filed on Dec. 22, 1999.
In some representative embodiments, the elastic strand comprises polyester, polyurethane, polyether, polyamide, polyacrylate, polyester-b-polyurethane block co-polymer, polyether-b-polyurethane block co-polymer, or polyether-b-polyamide block co-polymer.
In other embodiments of the present invention, the elastic strand is processed by steps comprising: providing an elastic strand, the elastic strand having been made by steps comprising extruding, spinning, or otherwise making the strand; heating the strand so that the peak-load value of the heated elastic strand is about 10% greater, specifically about 20% greater, particularly about 30% greater, and more particularly about 40% greater than the peak-load value of the elastic strand before heating; and regulating exposure of the strand to water or water vapor, as disclosed in co-pending U.S. Patent Application No. 60/166348, entitled “Method for Regulating Strength Degradation in an Elastic Strand,” which was filed on Nov. 19, 1999 and from which the present non-provisional application both claims priority and incorporates by reference in a manner consistent herewith. The co-pending application is generally directed to a method for regulating exposure of an elastic strand to water or water vapor, thereby regulating degradation of strength characteristics of the strand due to the action of water vapor or water on the strand. Accordingly, the present invention is directed to methods encompassing both heat treating the elastic strand to increase its strength characteristics, and regulating exposure of the strand to water or water vapor to minimize or eliminate strength degradation.
FIGS. 4 and 4.A. show perspective views of a tensile tester.
The present invention may be used in conjunction with the subject matter disclosed in co-pending U.S. Patent Application No. 60/166348. When the elastic strand is susceptible to attack by water (e.g., by hydrolysis), then degradation of the strand's strength due to the action of water may be regulated by regulating the strand's exposure to water or water vapor. If the elastic strand is made, stored, shipped, or otherwise processed so that the strength of the strand degrades significantly due to the action of water or water vapor, then heat treatment of the strand in accordance with the present invention will likely be less effective in improving strength. As discussed below, the strand's exposure to water or water vapor may be regulated before the strand is heated, when the strand is heated, after the strand is heated, or some combination thereof.
Alternatively, the elastic strand can be irradiated with microwave radiation to heat the strand. A suitable microwave generator and cavity is described in U.S. Pat. No. 5,536,921, issued Jul. 16, 1996 to Hedrick et al., which is hereby incorporated by reference in a manner consistent herewith. This device, useful for on-line treatment of sheet-like materials, may also be used for in-line treatment of elastic strand. The device comprises a cylindrical single-mode model TM010 resonating-cavity microwave applicator, and is available from International Business Machines Corporation, a business having offices at Armonk, N.Y. The diameter of the applicator of this model is 4 inches, and the output power can be adjusted continuously up to 6.0 kW at a frequency of 2450 MHz. The elastic strand can be directed through the cavity so that the strand is exposed to a plurality of microwave standing waves within the cavity. As the elastic material passes through the standing waves the incident microwave energy is converted into heat within the strand. An example of using a microwave generator to continuously treat a web, rather than a strand, is given in U.S. Pat. No. 5,916,203 issued Jun. 29, 1999 to Brandon et al. and entitled “Composite Material with Elasticized Portions and a Method of Making the Same,” which is hereby incorporated by reference in a manner consistent herewith. This same approach can be used to heat an elastic strand, or a plurality of elastic strands.
As discussed in co-pending U.S. Patent Application No. 60/166348, in some instances bobbins of elastic strand, after being first wound up, may be processed or treated in some fashion by unwinding the bobbin, treating the strand, and then winding the strand up once more. This co-pending application also discloses that an elastic strand's exposure to water vapor can be regulated in order to regulate strength degradation in the strand. Thus an elastic strand that is heat treated by the manufacturer of the strand can also be processed, stored, handled, or shipped in a manner that regulates exposure of the strand to water vapor.
Co-pending U.S. Patent Application No. 60/166348 gives a number of examples by which an elastic strand's exposure to water vapor can be regulated. These same methods may be used with elastic strand before it is heat treated, after it is heat treated, or both before and after the strand is heat treated. If the elastic strand has already been heat treated, then bobbins, spools, or reels of the heat-treated strand may be stored in a controlled-humidity or controlled-temperature room or facility. If these bobbins are shipped to another location, then these bobbins can be packaged in a container comprising a barrier material resistant to the penetration of water vapor. If the elastic strand is placed in a container comprising a barrier material while in a low-humidity environment, then the micro-environment immediately around the elastic strand inside the container will correspond to that low-humidity environment. After the container is closed (e.g. by thermally sealing a plastic bag), subsequent processing steps can be carried out so that the humidity or temperature outside the container is not regulated. In one aspect, the container would likely not be opened until the elastic strand was to be used as a raw material in a production process.
As disclosed in co-pending U.S. patent application No. 60/166348, a desiccant material may be placed near the elastic strand—including elastic strand that has been heat treated—before closing the container comprising a barrier material. To the extent that the container allows water vapor to penetrate into and around the elastic strand, the desiccant acts to preferentially adsorb or absorb the water vapor. Accordingly, the desiccant helps to keep the humidity inside the container at a level that minimizes strength degradation.
Rather than heat the strand at the site where the strand is made, bobbins of the elastic strand can be heated at the site where the strand is used as a raw material. If the elastic strand is not shipped in a sealed container comprising a barrier material, then the elastic strand could be heated when it is received, or after storage but prior to the strand being used as a raw material. If the elastic strand is stored prior to use, the strand could be stored in an environment in which humidity is regulated, either by controlling humidity directly or by controlling temperature, as disclosed in co-pending U.S. Patent Application No. 60/166348.
As stated above, one embodiment of the invention is directed to controlling the humidity of one or more of the processing and/or handling steps following extrusion or spinning. Alternatively, the temperature of the processing and/or handling step(s) may be controlled to limit the capacity of the air to hold water vapor. For example, the step in which the elastic strand is first wound up at a winder may be carried out in a controlled-humidity or controlled-temperature environment. Processing steps upstream or downstream of the first winder may also be carried out in a controlled-humidity or controlled-temperature environment. As used herein, “first winder” refers to the winder at which the strand is first wound up after it is extruded or spun; “upstream” refers to those processing steps that occur after the strand is extruded or spun, but before the first winder; and “downstream” refers to those processing steps that occur after the first winder. If one or more additional processing steps occur after the first winding step at a separate unwinding/winding station (i.e., a station where the elastic strand is unwound, processed in some way, and rewound), these one or more additional processing steps may be carried out in a controlled-humidity or controlled-temperature environment. To the extent that bobbins of elastic strand are stored prior to use or shipment, the bobbins may be stored in a controlled-humidity or controlled-temperature environment. If elastic strand is being shipped to another location, the step in which the elastic strand is prepared —perhaps involving another step in which the elastic strand is unwound and then wound back up again—and packaged for shipment may also be carried out in a controlled-humidity or controlled-temperature environment. And the step of shipping or transporting the elastic strand itself may be carried out in a controlled-humidity or controlled-temperature environment.
A bobbin of GLOSPAN 840 (Globe), an elastic strand comprising a polyester-b-polyurethane block copolymer, was obtained from Globe Manufacturing Company. The elastic strand had been coated with a silicone-based lubricant. Samples of the strand were placed in a forced-air oven, model number OV-490A-2, made by Blue M, a business having offices at Blum Island, Ill. The oven was preheated to a temperature of 100� C. prior to samples of the strand being placed in the oven. At selected times of exposure to these conditions, samples of the strand were withdrawn from the oven and taken to a testing room. Generally about 15 to 30 minutes elapsed between the time the sample was withdrawn from the controlled environment and the time the sample was tested.
A bobbin of LYCRA 1040, an elastic strand comprising a polyether-b-polyurethane block copolymer, was obtained from Dupont Corp., a business having offices in Wilmington, Del. Samples of the strand were placed in a forced-air oven, model number OV-490A-2, made by Blue M, a business having offices at Blum Island, Ill. The oven was preheated to a temperature of 100� C. prior to samples of the strand being placed in the oven. At selected times of exposure to these conditions, samples of the strand were withdrawn from the oven and taken to a testing room. Generally about 15 to 30 minutes elapsed between the time a sample was withdrawn from the controlled environment and the time the sample was tested.
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