Claims
- 1. A fluid retentive container comprising a supporting mass lined with an impervious cover structure which comprises a nonwoven polyolefin fabric, mat or web, fused externally on one side and placed with that side against said mass and having unfused fiber on the other external side, the unfused fibrous side being coated with a mixture containing asphalt and asbestos fibers.
- 2. A structure according to claim 1 wherein the polyolefin is polypropylene.
- 3. A storage pit, pond or reservoir comprising as a liner extending over its inner walls an impervious cover structure according to claim 1.
- 4. A storage container or tank adapted to contain a liquid having therein on its walls to protect its walls against loss of fluid an impervious cover structure according to claim 1.
- 5. A structure according to claim 1 wherein the polyolefin is polypropylene and the fabric has a weight in the approximate range of about 3-8 ounces per square yard and the asbestos fiber has an average length of from about 0.01 to about 0.1 inches.
- 6. A cover structure according to claim 1 wherein said fabric is a needle punched fabric having a weight in the approximate range of about 3-8 oz/yd2 and containing crimped staple of about 2-20 denier and about 1/2 to about 3 inches long, a tensile strength of about 10-75 lbs./inch of width, and a thickness of about 1-5 mm with the fused side being less than about 10 percent of the thickness of the fabric.
- 7. A cover structure according to claim 1 wherein said asphalt has a penetration of about 20-50, a minimum ductility at 77.degree.F of about 5, and a Ring and Ball softening temperature of about 160-175.degree.F, and wherein said asbestos fibers have a fiber length of about 0.01-0.1 inch and are present in said mixture in an amount of about 4-10 parts/100 parts by weight of asphalt.
- 8. A cover structure according to claim 1 wherein the fabric was made by fusing both major faces of a nonwoven polyolefin fabric, mat or web, thereafter capping one of the fused faces with a layer of unfused fibers, and then coating the layer of unfused fibers with a mixture of asphalt and asbestos fibers.
- 9. A cover structure according to claim 8 wherein the capping is nylon or polypropylene fibers added by a needle punch operation.
Parent Case Info
This is a division of our copending application Ser. No. 207,800, filed Dec. 14, 1971, entitled "Impervious Barrier Comprising Polyolefin Fabric, Asphalt and Asbestos" and now Pat. No. 3,864,157.
This invention relates to an impervious cover structure. In one of its aspects, it relates to a cover structure comprising a polyolefin fabric, asphalt and asbestos fibers. In another of its aspects, the invention comprises a surface or object to which has been applied an impervious cover structure comprising a polyolefin, for example, a nonwoven polyolefin fabric, mat, or web, the polyolefin being impregnated with a mixture containing asphalt and asbestos fibers. It also relates to a method for producing covers or coatings as described herein. Further, in a specific aspect, the invention relates to a reservoir of pond or other container which is rendered fluid retentive by applying thereto an impervious cover structure according to the invention.
In one of its concepts, the invention provides a cover structure which is produced by fusing externally on one side, or at least on one side, a polyolefin fabric, mat, or web, laying said fabric, mat, or web with its fused side against an object surface or ground to be rendered impervious and then coating said fabric, mat, or web on a provided unfused external side with a mixture containing asphalt and asbestos fibers.
In another of its concepts, the invention provides a reservoir, container or pond having a liner or structure applied to the surface thereof as herein described.
Various liners have been provided for covering objects or surfaces or the ground to render these impervious to fluids, for example, to water, or other liquids. In places at which the fluid or liquid exerts considerable pressure against the covering structure or liner, leakage is often observed. This leakage occurs at so-called pin hole openings in the coating or covering structure. These leaks have been observed, particularly with nonwoven fabrics which have been coated with various sealants. Thus, in fairly deep pond liner applications, it has been observed that asphalt sealed nonwoven polypropylene fabric can develop pin hole leaks which may be due to cold flow.
We have now conceived of an improved cover structure. Thus, we have conceived that if the nonwoven fabric is provided with a fused external side and a nonfused external side, and is laid fused side against the object to be covered or fused side down on the ground as in the lining of a pond and is then covered or coated with asphalt-containing asbestos fibers, as further described herein, the resulting structure will not develop leaks.
An object of the invention is to provide a cover structure. A further object of the invention is to provide a fluid or liquid impervious cover structure suitable for application to objects to be protected against fluid or liquid. A further object of the invention is to provide a liner for liquid storage ponds. A still further object of the invention is to provide a cover structure of improved character in that it will withstand liquid pressure of considerable magnitude, yet not develop leaks. A further object of the invention is to provide a cover structure comprising a nonwoven fabric covered with asphalt which will not flow, once cured, due to cold flow through "windows" in the nonwoven fabric.
Other aspects, concepts, objects, and the several advantages of this invention are apparent from this disclosure, drawing, and the appended claims.
According to the invention, there if provided an impervious cover structure which comprises a nonwoven polyolefin fabric, mat, or web, fused externally on one side and having unfused fiber on the other external side thereof, the fused side being laid against the material to be covered, the unfused fibrous side being coated with a mixture containing asphalt and asbestos fibers.
The asphalt-asbestos mixture which is applied is usually applied as a cut-back asphalt. The cut-back asphalt is prepared from an air-blown asphaltic material having a penetration of about 20-50, preferably 25-35, a minimum ductility at 77.degree.F of 5, and a Ring and Ball softening temperature of 160.degree.-175.degree.F.
The cut-back solvent used to prepare the cut-back asphalt is selected from kerosene, cycle oil, Stoddard solvent, or, in general, a hydrocarbon based material having an initial boiling point in the range of 160.degree.-450.degree.F, preferably 200.degree.-300.degree.F.
Sufficient cut-back oil is used to make the resultant blend applicable to the surface by hot application not exceeding about 250.degree.F (melting point of polypropylene) at a temperature which will not adversely melt the fabric or by spray or brush technique at ambient temperatures. Usually about 20-100 parts by weight of solvent, preferably about 40-70 parts by weight per 100 parts by weight of asphaltic material, are used.
The asbestos fiber is added to the cut-back asphalt in amounts from about 4-10 parts/100 parts by weight of cut-back asphalt. It can have a fiber length of about 0.01-0.1 inch, preferably about 0.03-0.06 inch. While the presence of longer fibers can be tolerated, the preferred range is more readily handled by the usual equipment and best improves the desirable properties of the asphalt, such as the penetration values.
It has been found that using an approximately 4 oz/yd.sup.2 fabric, an asbestos fiber content of about 6-8, or more, parts/100 parts of cut-back asphalt is preferred, while for a 5-oz. web a fiber content of about 5-6 in the cut-back asphalt is sufficient.
The fabric is made from about 2-20 denier, preferably about 3-8 denier crimped staple about 1/2 to about 3 inches long; a batt of these fibers is needle punched by conventional means and the needle-punched fabric is then passed through a pair of nip rolls, one of which is heated above the melting point of the fibers to heat-fuse the fibers on one side. The amount of fusion is adjusted to give the final product a tensile strength of from about 10 lbs. to about 75 lbs./inch of width, the strength depending both on the amount of fusion, weight of fabric, and denier of the fiber. The fabric is about 1-5 mm thick under no compression and ordinarily less than about 10 percent of the thickness of the fabric is fused.
The polypropylene fabric should have a weight of at least about 3.5-4 oz/yd.sup.2 and is fused on one side only. A heavier fabric weighing about 5-6 oz/yd.sup.2 is now preferred. Much heavier fabrics become uneconomical and heavy to handle.
A capped product, i.e., a light fabric fused on both sides, having a "cap" of 1-2 oz/yd.sup.2 of additional fiber, e.g., nylon, attached to one side thereof by an added needle punch operation and having a total weight between about 4.0 and about 5.5 oz/sq yard is also suitable. The added fiber now acts as does the unfused side of the fabric which is fused on one side only. Thus, the capped side is the one to which the cut-back asphalt/asbestos mixture is applied.
It is obvious that there are a number of variables which coact to provide an effective leak-proof liner. Under mild conditions, for example, a shallow, sweet water pit or ditch, an asphalt with higher penetration can be used and a more fluid cut-back formulation containing less asphalt can be used. For more severe conditions, deep water, higher temperature and brine, for example, a lower penetration asphalt is used with a heavier mat and more asbestos; this more viscous material may have to be applied hot (v.s.). These and other variables can be determined by mere routine testing by one skilled in the art in possession of this disclosure.
It is essential, however, that the asbestos fibers in the mixture be forced by the flow of the liquid through the mat into immediate contact with the surface of the mat where they become imbedded in the unconsolidated top surface of the fabric and lodge in the interstitial voids present therein.
US Referenced Citations (5)
Divisions (1)
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207800 |
Dec 1971 |
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Patent Grant
3953974
