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
1998-11-13
2002-04-30
Wu, David W. (Department: 1713)
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...
C524S507000, C524S513000, C524S522000, C524S555000, C524S556000, C525S123000, C525S185000
Reexamination Certificate
active
06380298
ABSTRACT:
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION
The present invention relates to a high strength superabsorbent coating capable of rapidly absorbing water, which is suitable for coating reinforcing fibers, or for coating articles comprising reinforcing fibers, such as reinforced rods and cables. More specifically, the coating is formed from a composition comprising a superabsorbent polymer precursor which, upon cure, forms a polymer with a high water swelling ability; and a film-forming polymer. As a modification to adapt the coating to pultruded articles, the coating composition may also include a viscosity-modifying agent.
The inventive concept also relates to articles coated with the superabsorbent coating composition, such as glass rods; and methods of applying such coatings. The novel coating of this invention demonstrates a high level of water absorption in fresh and salt-water environments, and excellent spreading and coating ability when applied to a substrate.
BACKGROUND OF THE INVENTION
Deterioration caused by the invasion of moisture beneath the exposed surfaces of articles used in outdoor environments is a well-known problem. This deterioration includes oxidative deterioration caused by reaction of water with the surfaces of reinforcing fibers used in these articles, as well as water-induced corrosion. In marine environments, the problems associated with waterlogging are particularly compounded by the salinity of the environment. The presence of salt in such aqueous environments hastens the oxidative decomposition.
Articles affected by the deterioration described above include reinforced fibers made of glass, carbon, polymer or mixtures thereof, or items containing such reinforcing fibers. The term “articles”, as used herein, is specifically intended to include reinforcing fiber materials known in the art, as well as products made using one or more of these fibers collectively or dispersed within a matrix of any type. The term also includes articles manufactured using reinforced fiber products, such as structural materials or in equipment. Examples of such articles include such as reinforced rods and cables, such as fiber optic or telecommunications cables. These telecommunications cables are often used in situations where they are buried underground or submerged in water over long periods. As such, protection from water damage is critical to the structural integrity of these cables and to the success of the functions they are intended to perform. A telecommunications cable, for example, may include a core comprising a glass rod that acts as a stiffening or reinforcing member. This rod contributes to the rigidity of the cable. When water penetrates to contact the core element of the cable, corrosion or chemical deterioration of the cable infrastructure may result.
In order to combat the problems associated with this waterlogging damage, several strategies have been devised in an attempt to provide water resistance to cables and other reinforced articles, and to protect their sensitive inner surfaces from contact with water or water vapor present in the surrounding environment. These techniques for making water-repellent articles have included wrapping the articles in a protective sheathing material; or sealing the surface to be protected. Sealing techniques may include chemically manipulating the surface layer of the article to render it resistant to water-absorption, or applying a repellent coating.
The technique of covering the surface with a protective sheathing material is conventional. It includes for example, using a wrap or tape made of an impervious polymer with water-blocking ability, or treating the wrapping material with an emulsion or solution of a water-blocking polymer. The sheathing process does not require application of a chemical compound or treatment to the surface of the article, rather the protection is derived only from the coverage by the sheathing material.
Coatings used to repel water traditionally have been composed of substances that are both insoluble and impenetrable to water, and therefore presented a physical barrier to encroaching moisture. Such barrier coatings have included materials such as greases or gels. In the case of cables, for example, these coatings are applied by extrusion under pressure. There are however, certain drawbacks associated with this type of coating. Greases or gels are difficult to handle because of their slipperiness, and they contribute an unpleasant feel to the coated article. This is an important factor to be considered in the manufacturing process, particularly because it affects the ease of handling of the cable during splicing operations. Greases and gels also undergo changes in viscosity at low or high temperatures. These viscosity changes may affect the freeze/thaw performance and therefore the stability of the coating. Poor performance in these respects therefore affects the stable performance of the cables.
More recently, greaseless, water-resistant dry coatings have been devised which, of themselves, have some degree of water-absorbing capacity. This ability to absorb water allows the coating to absorb the moisture contacting the article, while preventing direct contact with the sensitive surfaces. The absorbent component in these dry waterblocking coatings is a dry, granulated superabsorbent polymer that swells and absorbs upon contact with water. The superabsorbent polymers are usually characterized in terms of their swell rate, swell capacity and gel strength. Traditional uses for these dry superabsorbent polymers have primarily included personal hygiene product articles, food packaging articles and chemical spill cleanup compositions, however recent experimentation has included using these dry polymers to form coatings for other articles such as reinforced cables. For example, U.S. Pat. No. 5,689,601 to Hager, herein incorporated by reference, discloses a dry waterblocking coating for reinforcing fiber articles using a powdered or granulated water-soluble dry blocking ingredient encased in one or more thin layers of a sheathing polymer. This casing restricts the degree of water absorption that can be achieved by the granular polymer, and accordingly the swell capacity of this coating is limited.
The superabsorbent polymers traditionally used in dry waterblocking cable coating applications are dry, granular polymers that are incorporated into various substrates such as yarn, binders and tape. The substrates typically also contain glass fibers as a form of reinforcement. However, as discussed above, the coatings formed with dry granulated blocking agents suffer the limitations of limited water swelling ability and swell rate as a necessary consequence of optimizing the gel strength. In the context of surface coatings, gel strength is defined as the ability to prevent water from wicking down the cable axis, particularly when the cables are used in aqueous environments where they are exposed to elevated water pressures. The swelling ability is directly related to the degree of cross-linking of the superabsorbent polymer. As the degree of cross-linking increases, so does the gel strength, but there is a related decrease in the swell rate and swell capacity of the polymer. The swell rate defines the amount of water that the coating absorbs over a fixed period of time. The swell capacity denotes the maximum amount of water or fluid absorbed by the coating, based on a measure of its dry weight. Consequently, coatings made of dry, granular, water-insoluble polymer are limited in their water-absorbing performance, as measured in terms of the swell rate and swell capacity.
Generally, coatings for reinforced fibers, strands and articles such as cables that are made from these fibrous materials are applied to the surface of the fibrous material and then cured before further processing, if any, occurs. The means of applying coatings, in general, differs depending on whether a fluid coating is used or whether a solid particulate coating is being applied.
In the case of powdered coatings, the c
Flautt Martin Charles
Hager Thomas P.
Priest James Robert
Stotler David V.
Eckert Inger H.
Egwim Kelechi
Owens Corning Fiberglas Technology Inc.
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