Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Scrim – Woven scrim
Reexamination Certificate
2000-01-12
2002-04-02
Juska, Cheryl A. (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Scrim
Woven scrim
C442S020000, C442S026000, C442S038000, C442S040000, C442S049000, C442S320000, C442S352000, C442S353000, C442S355000, C428S357000, C428S362000
Reexamination Certificate
active
06365532
ABSTRACT:
BACKGROUND OF THE INVENTION
Synthetic fiber felts are useful as filters and are well-known in the art. U.S. Pat. No. 4,361,619 to Forsten, et al. discloses a filter of poly(tetrafluoroethylene) and glass fibers made by blending 1-35 weight percent glass fibers and 65-99 weight percent poly(tetrafluoroethylene) fibers to make a carded web which was crosslapped to form a batt and then needled to form a felt. This crosslapped batt could also be needled to a supporting scrim of woven poly(tetrafluoroethylene) to form a felt or felted scrim.
U.S. Pat. No. 4,361,619 further disclosed in Example 2 the carding of blends containing straight glass fiber and crimped PTFE fiber. The patent states that even with the addition of a crimped fiber blends of more than 50 weight percent glass fiber were extremely difficult to card. Experience of those skilled in this art has shown that the term “extremely difficult” in this context means that the blend may not process through the card, that the quality of the carded web may not be sufficient to make a useful product, or that the speed of the card must be significantly reduced in order that any arrangement of fibers resembling a web be produced. The maximum speed of the card that can be achieved when the concentration of glass fibers is greater than 50 by weight of the blend is in the range of 1 meter/minute. The overall result has been that carding blends that contain more than 50% by weight glass fiber has not been practical.
The difficulty in making felts containing more than 50% by weight glass fiber has been attributed to the lack of crimp in glass fiber. Accordingly, those skilled in the art related to making glass fibers have suggested that curly glass fibers would be more processible in forming felts than straight fibers. This has not proven to be the case.
Curly or irregularly shaped fibers were made by spinning a combination of two glasses into a fiber. U.S. Pat. No. 2,998,620 to Stalego discloses curly glass fibers of dual glass compositions. Stagelo teaches producing curly fibers by passing two glass compositions, each having different coefficients of thermal expansion, through the orifices of a spinner. The glasses are extruded in aligned integral relationship such that these fibers curl naturally upon cooling.
U.S. Pat. No. 3,073,005 to Tiede discloses an improved, faster process for making bicomponent (dual) curly glass fiber compositions of Stalego
Both Stalego and Tiede disclose an improvement in the carding of these bicomponent glass fibers when crimped soluble fibers are blended with the glass fibers.
Additional work has been performed by others, and most recently International Patent Applications WO95/12554, which discloses glass compositions which make useful dual glass fibers, and WO95/29880, which discloses dual glass fibers having special bonding properties have been published.
The primary producer of curly glass fibers, Owenings-Corning Fiberglas Corporation of Toledo, Ohio, has disclosed in published articles (such as Mechanical Engineering, volume 117, number 2, page 38, February 1995) that their dual glass fiber, sold under the trademark MIRAFLEX, has high resilience and is recommended for use in insulation. In addition it has been stated that this dual glass fiber can be carded and needled in traditional textile processes. However, attempts, by the present inventor and others, to actually card such dual glass fibers as MIPAFLEX at commercially accepted carding speeds have not heretofore been successful. The high resilience of the curly glass fiber acts to preclude normal carding. Art applicable to low modulus fibers such as British Patent No.1,030,570, which teaches an improved carding process for nylon, is not applicable to the very high modulus, fragile glass fiber.
SUMMARY OF THE INVENTION
The present invention provides an intimate cardable blend of fibers comprising a dual glass fiber and an uncrimped fiber wherein the uncrimped fiber are present in an amount equal to or greater than the amount of the dual glass fiber. The blend may further comprise a third fiber, which is a crimped fiber.
The fiber blends of the present invention are easily carded at commercially acceptable carding speeds to form uniform, coherent webs from which batts and felts may be formed.
The preferred fiber blend of the present invention comprises an intimate blend of from about 1-30 weight percent dual glass fiber, from about 1-60 weight percent uncrimped fiber, and from about 10-98 weight percent of a crimped fiber, wherein the uncrimped fiber is present in an amount equal to or greater than the amount of the dual glass fibers.
A preferred uncrimped fiber is “DE” type glass, and the preferred crimped fiber is a fluoropolymer fiber. Of particular value for the crimped fiber is PTFE fiber. Most preferred are blends containing about 20 weight percent dual glass fiber, 30 to 50 weight percent “DE” type uncrimped glass fiber and 50 to 30 weight percent crimped fluoropolymer fibers.
The present invention also provides filter felts comprised of a layered batt formed from these fiber blends and a scrim wherein the layered batt of fibers is comprised of an intimate blend of from about 1-30 weight percent dual glass fiber, from about 1-60 weight percent uncrimped fiber, and from about 10-98 weight percent of a crimped fiber, wherein the uncrimped fiber is present in an amount equal to or greater than the dual glass fibers. Filter felts (felts or felted scrims) of the present invention may be laminated to a membrane or other suitable substrate.
The present invention also provides a method by which batts and felts can be made.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to an intimate cardable blend of fibers wherein one of the fibers is a dual glass fiber and the other is an uncrimped fiber. This combination of the two types of fibers allows practical textile processing of the dual glass fiber.
The term dual glass fiber as used herein means a glass fiber made from two or more glass compositions having different coefficients of expansion. Dual glass fibers may also be known as irregularly-shaped glass fibers or bi-glass fibers. These glass fibers are not straight, but instead curl after spinning producing a natural, random twist. Ideally, a cross sectional view of the fiber would show one half of the fiber to be formed of a first glass composition, and the other half of the fiber to be formed of a second glass composition.
A preferred form of dual glass fiber is sold by Owens-Corning Fiberglas, Inc. under the trademark MIRAFLEX. MIRAFLEX has been reported to be produced from two different forms of sodium borosilicate glass fused together into a single filament. Unlike conventional straight glass fibers, MIRAFLEX fibers have random twist, and are advertised as being soft, flexible, silky to the touch, and virtually itch-free. The high resilience of the fiber makes it especially suitable for use in rolled insulation, where the fiber, and thus the insulation, may be tightly rolled to form a compact package which recovers much of the initial bulk and loft when unrolled.
The uncrimped fiber of the present invention is an essentially straight fiber without significant bends, twist, curl or irregularities of shape. The preferred uncrimped fiber is “DE” type glass fiber or other straight suitable glass fibers. While it is not fully understood, the addition of the uncrimped fiber appears to reduce the resiliency of the dual glass fibers, thereby reducing the loft or fluffiness of the blend and allowing practical textile operating speeds. Other uncrimped fibers which may be useful in this invention are uncrimped aramid fibers, such as paraaramids, uncrimped fluoropolymer fibers, such as PTFE and PFA fibers, uncrimped polyethylene or polypropylene fibers, uncrimped polyamide fibers, uncrimped polyester, polyimide or polyphenylene sulfide fibers.
The term fluoropolymer as used herein means poly(tetrafluoroethylene) (PTFE) and polymers generally known as fluorinated olefinic polymers, for example, co-polymers of tetrafluoroethylene and hexafluor
E. I. du Pont de Nemours and Company
Juska Cheryl A.
Ruddock Ula C.
LandOfFree
Cardable blends of dual glass fibers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cardable blends of dual glass fibers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cardable blends of dual glass fibers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2905543