Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Nonwoven fabric
Reexamination Certificate
2000-04-05
2004-07-27
Morris, Terrel (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Nonwoven fabric
C442S340000, C442S344000, C162S100000, C162S141000, C162S149000, C162S156000, C162S157100, C162S157500
Reexamination Certificate
active
06767851
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
In the manufacture of a wide variety of products, especially molded products, chopped fiber (e.g. glass fiber) mats are used in the molding operation and typically saturated with resin. These mats have conventionally been produced by air laid techniques, at a production rate that is normally between about 20-30 m/min., and must be relatively thick/dense otherwise they have too many holes and discontinuities to be fully effective in molding on other subsequent processing operations. These mats are typically made of fiber bundles having five or more fibers per bundle, typically about 10-450 fibers/bundle.
Glass tissue produced by the wet laid method or by the foam method comprises individual fibers or fiber bundles with very few (typically less than five) fibers in a bundle. Sometimes, some fiber bundles have not dispersed fully into the slurry. These poorly dispersed fiber bundles are elongated bundles, because the individual fibers of the bundle have slid with respect to each other. The length of an elongated fiber bundle is much longer than the length of the individual fibers. The fiber bundles that enter the slurry formation process comprise fibers that have the same length as the fiber bundle, since the yarn (typically about 10-450 fibers) is cut into bundles having a predetermined length in cutters. Elongated fiber bundles are defects in the fiber tissue, causing an uneven surface configuration of the tissue. In a poor quality glass tissue, there may be as much as about 5-10% elongated fiber bundles.
Exemplary prior art techniques for making glass fiber mats by the air laid method and making glass fiber tissue by the wet laid method are described in K. L. Loewenstein: The Manufacturing Technology of Continuous Glass Fibres, 1993 (incorporated by reference herein).
According to the present invention the limitations of the prior art mats described above are substantially overcome or minimized by employing one or more simple yet effective techniques. According to the present invention preferably the fibers are held in the bundles with a non-water soluble sizing, such as epoxy resin or PVOH, and/or 5-450 (e.g. about 10-450) fibers are provided in each bundle, each fiber having a diameter of about 7-500 microns, preferably about 7-35 microns, and at least about 85% of the fibers have a length of 5-100 mm, preferably about 7-50 mm (and all narrower ranges within these broad ranges).
According to the invention it is possible to produce mats having a substantially uniform density yet can be of much lower density than can be produced using air laid techniques. For example, mats can be produced having a density as low as 50 gm/in
2
, or even less. The mats may be produced much more rapidly than by air laid techniques, and a wider variety is possible. For example, mats having multiple layers of different physical properties and/or compositions may readily be produced. These advantageous results are accomplished by using a water or foam laid process, so that production speeds of well over 60 m/min. (typically over 80 m/min, e.g. about 120 m/min.) are readily achieved, along with highly uniform mats of a wide variety of constructions. Utilization of the foam process is preferred, however, for many reasons, including process efficiency. Using the foam process the slurry can have 0.5-5% (or any smaller range within that broad range) fibers by weight, whereas in the wet laid process the maximum fiber content is about 0.05% by weight. If a larger percentage of fibers is used in the wet laid process then the viscosity of the liquid must be increased (by introducing additives), and that causes several problems, including the formation of air bubbles. This would require still further additives, making the wet laid process much more difficult and expensive compared to the foam process.
According to one aspect of the present invention there is provided a non-woven mat of chopped strands, comprising: A plurality of fibers disposed in a non-woven configuration to define a mat. At least 20% of the fibers in fiber bundles having between 5-450 fibers per bundle and the length of the bundles being substantially the same as the lengths of the fibers forming the bundles, and wherein at least 85% of the fibers of the fiber bundles have a diameter of between about 7-500 microns.
Preferably at least 85%, up to substantially 100%, of the fibers in the bundles have a length of between 5-100 mm, preferably 7-50 mm, most preferably between about 20-30 mm, and at least 50%, preferably at least 85% of substantially 100%, of the fibers in the bundles have a diameter of between 7-35 microns. Typically the fibers in the fiber bundle are held together with a substantially water insoluble sizing, such as epoxy resin or PVOH. Preferably substantially all of the fibers in a bundle are substantially straight.
The invention is particularly useful where at least 10% (preferably at least about 50%, up to substantially 100%) of the fibers in fiber bundles comprise reinforcement fibers selected from the group consisting essentially of glass, aramid, carbon, polypropylene, acrylic, and PET fibers, and combinations thereof. The invention is particularly suitable for use with glass fibers.
By practicing the invention it is possible to make mats with an extremely wide density range, e.g. between about 50-900 g/m
2
, yet with substantially uniform density. For example, the mat may have a substantially uniform density of less than 75 g/m
2
(even below 50 g/m
2
depending the fibers utilized). When the mat has a density between about 50-150 g/m
2
, 90% of the fibers in the fiber bundles have between 10-200 fibers per bundle. Typically at least 85% of the fibers in the fiber bundles have between 10-450 fibers per bundle and a length substantially the same as the length of the fiber bundle.
According to another aspect of the present invention a method of producing a non-woven chopped strand mat is provided comprising: (a) Forming a slurry of fibers in a liquid or foam (preferably foam) wherein at least 20% of the fibers in the slurry are in fiber bundles in which the fibers are held in the bundles by a substantially non-water soluble sizing. (b) Forming a non-woven web from the slurry on a foraminous element. And (c) withdrawing at least one of liquid and foam from the slurry on the foraminous element so as to form a non-woven mat. Preferably the slurry in (a) has between about 0.5-5% by weight fibers. The liquid process practice may be entirely conventional, and the foam process practice may be such as shown in U.S. Pat. No. 5,904,809, issued May 18, 1999 (the disclosure of which is hereby incorporated by reference herein). The invention also relates to products made from this method.
Because the invention uses a liquid or foam process as opposed to air laid process, the speeds of production are much greater. That is, (b) and (c) may be practiced at a speed of at least 60 m/min, typically at least 80 m/min, and may easily achieve speeds of 120 m/min. The foraminous may have any suitable conventional construction such as a conventional wire, or dual or multiple wires, etc. For example (a)-(c) may even be practiced using a moving web of fabric which becomes part of the mat produced as the foraminous element (or one of a plurality of such elements). Also by utilizing the invention (particularly such as by utilizing a segmented head box, such as shown in copending application Ser. No. 09/255,755, filed Feb. 23, 1999, the disclosure of which is incorporated by reference herein, or U.S. Pat. No. 4,445,974.
In the method typically (a) forming a slurry of fibers in a liquid or foam (preferably foam) wherein at least 20% of the fibers in the slurry are in fiber bundles in which the fibers are held in the bundles by a substantially non-water soluble sizing; (b) forming a non-woven web from the slurry on a foraminous element; and (c) withdrawing at least one of liquid and foam from the slurry on the foraminous element so as to form a non-woven mat. For example (a) is practiced using at least 10% (for
Bohm Juha
Jansson Juhani
Kostamo Harri
Rökman Kay
Ahlstrom Glassfibre Oy
Morris Terrel
Nixon & Vanderhye P.C.
Salvatore Lynda
LandOfFree
Chopped strand non-woven mat production does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Chopped strand non-woven mat production, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Chopped strand non-woven mat production will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3207845