Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1997-11-28
2002-04-30
Dixon, Merrick (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S392000
Reexamination Certificate
active
06379794
ABSTRACT:
The present invention is directed to chemically treated bundles of fibers such as strands and yarn, which have been coated, encapsulated or otherwise treated with a coating and/or impregnant composition in addition to the sizing or binder conventionally applied to the fibers as they are produced, as well as to the impregnant composition itself. Fibers so treated may be processed into numerous products such as polymeric products, braided reinforcing or woven fabrics, and reinforcement for cables of optical fibers.
Glass fibers are conventionally produced by flowing molten glass through the orifices in a glass fiber bushing. As the molten glass passes through the holes in the bushing, it is cooled and solidifies into very small diameter (on the order of microns) fibers which are treated with a sizing composition which protects and conditions them for further processing. This protective sizing coating may contain lubricants, silanes, emulsifiers, antioxidants, antistatic agents, biocides, starches, oils, film forming polymers and a number of other ingredients known in the art. The exact composition of the sizing is dependent on the ultimate use of the fibers.
One deficiency of glass fibers is their flex fatigue. An attempt to solve the problem of providing a glass fiber with sufficient flexibility to be used in woven and nonwoven fabrics is described in U.S. Pat. No. 4,762,751 to Girgis et al., dated Aug. 9, 1988. This patent teaches a secondary coating having elastomeric curable polyurethanes, crosslinking agents, softeners and water. The fibers treated with this composition do not possess the desired amount of stiffness for certain applications, however. In addition, since polyurethane is a relatively expensive ingredient, the use of these fibers is somewhat limited.
Another impregnant known in the industry is a resorcinol formaldehyde latex or RFL coating which is used in making fibers which are compatible with rubber goods. The use of RFL coatings gives rise to a number of environmental and health concerns which limits their use..
It is an object of the present invention to provide less expensive flexible glass fibers which have been coated with an impregnant composition which is compatible with a range of polymers and can be used in a number of applications in which relative stiffness is needed. Such applications can include brushes, belts, hoses, filter felt for the paper industry, carpet backing, and reinforcement for optical fibers.
SUMMARY OF THE INVENTION
The objects of the invention are accomplished by sized fibers having a coating of a moisture reduced residue of a chemical coating and/or impregnating composition, hereafter referred to as the impregnant composition. The components of the impregnant composition are water soluble, emulsifiable or dispersible and comprise, in addition to water, a curable acrylic latex, and either a second acrylic latex, a wax, or a mixture of both and optionally, a thermoplastic polyurethane latex. The amount of the first acrylic latex, dispersion or emulsion can range from about 2.5 up to about 55 weight percent, while the amount of the second acrylic latex that can be curable and/or wax can range from about 0.5 to about 10 weight percent. When present, the amount of the polyurethane can range from about 2 up to about 50 weight percent. The aforementioned amounts are based on the weight percent of the aqueous impregnant composition. With the presence of the polyurethane, the second acrylic latex, which can be different from the first latex, and/or the wax is present as a third component. The amount of water in the aqueous impregnant composition is an amount to provide the composition with between 1 and 60 percent solids before drying. When the aforementioned components are the only ones present, the balance of the impregnant composition can be water. Although the impregnant composition may also include a water soluble dye in an amount sufficient to impart a color to the residue on the fibers. Also plasticizers with appropriate emulsifiers, where necessary, and curing and/or crosslinking agents like those known in the art can be present.
The glass fibers are treated with a fiber protectant to reduce interfilament abrasion. This aqueous first chemical composition or sizing may include film forming polymer liquids, emulsions, dispersions, and latices; silane coupling agents; lubricants; antifoams; antistatic agents; emulsifiers; bactericides or any other ingredient(s) known in the art to be useful in sizing fibers, though preferably not starch, in addition to water. The sizing is present on the fibers in an amount between about 0.5 percent and 5 percent by weight after drying. The sized fibers may be gathered together into bundles and further treated with the impregnant composition of this invention.
The process of impregnation includes passing the bundles of fibers or strands through a bath or dip of the impregnant composition and may include exposing the fibers to elevated temperatures for a time sufficient to at least partially dry the composition. The fiber bundles having the moisture reduced residue of the aqueous impregnant composition typically have a dip pick-up (DPU) of between about 5 to about 30 weight percent.
A plurality of fibers with the impregnant composition thereon can have excellent hydrolytic stability, good adhesion to several polymers such as styrene-butadiene-rubber (SBR), polyvinyl chloride (PVC), polyurethanes and others and are flexible yet stiff enough to be used in the manufacture of various and sundry materials. These can include: brushes, filters, reinforcement for rubber and/or elastomeric articles like belts and hoses, reinforcement for fiber optic cables, and geotextile applications. Additionally the coated and impregnated plurality or bundle of fibers having the dried residue of the impregnating composition has good corrosion resistant properties.
DETAILED DESCRIPTION OF THE INVENTION
The invention is particularly applicable to high modulus, low elongation (a modulus of elongation of at least 7×10
6
psi and an elongation at break of at most 5 percent) fibers or filaments. Glass fibers are most often used in practicing the invention and such fibers tend to be sensitive to interfilament abrasion. Examples of such glass fibers are described at page 29 of
The Manufacturing Technology of Continuous Glass Fibers
by K. L. Loewenstein, published in 1973 and 1983 by Elsevier Scientific Publishing Company, Library of Congress Card Number: 72-97429.
The glass fibers are treated with a fiber protectant to reduce interfilament abrasion. This aqueous first chemical composition or sizing may include silane coupling agents, lubricants, antifoams, antistatic agents, emulsifiers, bactericides or any other ingredient(s) known in the art to be useful in sizing fibers, though preferably not starch, in addition to water. The sizing is present on the fibers in an amount between about 0.5 percent and 5 percent by weight after drying. A plurality of the sized fibers or filaments may, be gathered together into bundles and further treated with the impregnant composition of this invention.
When the fibers used to practice this invention are glass fibers, they may be of any type, such as E-glass, D-glass, S-glass and low boron and/or fluorine glass to which a sizing is applied as the fibers are formed. The sizing may be applied in many ways; such as with-a roller, by spraying, by a belt or other means. The glass fibers usually have between 0.5 and 5 weight percent of the sizing composition on their surface after drying. Drying may be done at room temperature or at elevated temperatures. The sized glass fibers are typically gathered together into bundles or strands comprised of many individual fibers and wound onto a spool for further processing.
The ingredients of the aqueous sizing may be any known to those skilled in the art and usually comprise silanes, lubricants, antifoams, antistatic agents, emulsifiers, bactericides or any other ingredient(s) known in the art to be useful in sizing fibers, in addition to water. Althou
Dixon Merrick
PPG Industries Ohio Inc.
Siminerio Andrew C.
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