WO1999046062A2

WO1999046062A2 - A polyvinyl alcohol-containing pipeliner and method for use thereof

Info

Publication number: WO1999046062A2
Application number: PCT/US1999/005196
Authority: WO
Inventors: Travis W. Honeycutt; Baosheng Lee
Original assignee: Isolyser Company, Inc.
Priority date: 1998-03-10
Filing date: 1999-03-10
Publication date: 1999-09-16
Also published as: WO1999046062A3; AU2995899A

Abstract

A pipeliner for lining at least a segment of the interior surface of a pipe and a method for the use thereof. The pipeliner includes a polyvinyl alcohol-containing felt first layer which is adapted to face the interior surface of the pipe and a second layer which is adapted to face the interior opening defined by the interior surface of the pipe. The second layer is at least substantially impermeable and flexible. The method including at least the steps of applying a resin to the first layer of the pipeliner, forming a sealed pipeliner tube having an outer surface defined by the second layer of the pipeliner, placing the pipeliner tube into the pipe, everting it such that the first layer of the pipeliner contacts the interior surface of the pipe, and curing the resin in the first layer of the pipeliner by sufficiently altering its temperature.

Description

A POLYVINYL ALCOHOL-CONTAINING PIPELINER AND METHOD FOR USE THEREOF

Field of Invention

The present invention relates to a pipeliner for lining underground pipes in- situ and to methods for integrating the pipeliner into the underground pipe. More particularly, the present invention relates to a polyvinyl alcohol-containing pipeliner and a method for using polyvinyl alcohol-containing pipeliners to repair or restore underground pipes used to convey liquid or gaseous materials, such as water, water wastes and natural gas.

Background

Other pipeliners and methods for repairing underground pipes in-situ are known in the art. Conventional pipeliners are tubular indimension, and are typically formed by the combination of a needled felt and a curable resin and catalyst. Ninety- eight percent of the pipeliner tubes are needled from polyester fiber that is 6 denier or greater and have a staple length of four inches or greater. The remaining two percent are needled from comparably dimensioned glass or acrylic fiber. The curable resins in the art include vinyl modified polyester, vinylester and epoxy.

Pipeliners in the art today are generally of limited utility because they have low flexural strength, a low flexural modulus and a greater cross-sectional thickness. The lower flexural strength is due to the failure of bonding between the tube resin and felt.

Manufacturers attempt to overcome the structural inadequacy of the pipeliners in the art by using fabric that has a staple length of up to 6 inches. While increasing the staple length of the fabric fibers does compensate for the inherent weakness of the structure, it is not without consequence. The increase in staple length makes the resulting fabric more rigid and harder to card, and the resulting pipeliner less flexible and more difficult to use. Pipeliners in the art that are formed using modified polyester or vinylester resins are also unsafe for use in potable water pipes because they have residual crosslinking agent remaining in the resin.

Methods for repairing underground pipe in-situ known in the art typically include the steps of impregnating a pipeliner felt with a curable synthetic resin, inserting the liner into a deteriorated or damaged pipe, and applying pressure against the pipeliner to conform it to the shape of the area being treated as the resin hardens. The impregnation step is accomplished either prior to or following the insertion of the lining tube within the pipe. The insertion step is typically accomplished through use of a flexible carrier vehicle, by pulling the lining into place or by using an inflatable bladder removably disposed within the tube.

The efficacy of repair methods in the art have constrained the utility of the pipeliners used in those repairs. The thickness of the pipeliners in the art makes them rigid and awkward to use such that the successful performance of these methods is typically hampered, if not defeated. Repair work involving the pipeliners in the art typically requires the excavation of a broader installation site to insure sufficient access to install the pipeliners in the damaged pipes. It also typically requires the removal of greater lengths of undamaged pipe around the damaged pipe area to effectuate those repairs. The cost of the raw materials required to manufacture such pipeliners, as well as that of the additional labor required to effectuate repairs using them, are ultimately reflected in higher overall costs for pipeline repair. U.S. Letters Patent No. 5,706,861, issued to E. Wood, et al.; U.S. Letters Patent 5,680,885, issued to G. Catallo; and, U.S. Letters Patent 4,456,401, issued to A. Williams, disclose and claim examples of pipeliners and/or pipeliner repair methods known in the art.

The pipeliner of the present invention preferably includes a polyvinyl alcohol- containing felt which solves the problems manifested by pipeliners in the art and does so while reducing the costs for its production and installation. As more particularly shown in Table I, a polyvinyl alcohol-containing felt pipeliner provides up to a twofold increase in flexural strength and flexural modulus over those pipeliners. It also permits the use of shorter staple length fibers which makes the resulting material easier to card, easier to handle and more adaptable to installations including up to two or three layers of material. The polyvinyl alcohol-containing felt pipeliner can be used as a structural member or a pressure pipe, as well. Because shorter fibers are used in the pipeliner, the pipeliner is more flexible when installed and less excavation is required to create an access area sufficient to install the polyvinyl alcohol- containing pipeliner. Moreover, the increased flexural modulus of polyvinyl alcohol- containing felt pipeliner its adaptable to a number of variably dimensioned pipes.

SUMMARY OF THE INVENTION

The pipeliner for lining at least a segment of an underground pipe of the present invention includes a first layer formed of a polyvinyl alcohol-containing felt material and a second layer formed of a substantially impermeable material which coats one side of the first layer of the pipeliner. The first layer comprises a totally or partially woven or non-woven polyvinyl alcohol or a mixture thereof. The second layer is flexible and acts as a liquid barrier in the pipeliner.

The method for lining at least a segment of the interior of an underground pipe using a polyvinyl alcohol-containing pipeliner includes at least the steps of applying a resin to the first layer of the pipeliner, forming a pipeliner tube wherein the first layer defines an outer surface and the second layer defines an inner surface, placing the sealed tube into the pipe, everting the pipeliner such that the first layer of the pipeliner faces the interior surface of the pipe and the second layer of the pipeliner faces the internal volume defined by the interior surface of the pipe, and curing the resin in the first layer of the pipeliner by sufficiently altering the temperature of the resin.

DETAILED DESCRIPTION

The pipeliner for lining at least a segment of an underground pipe includes a first layer comprising polyvinyl alcohol and a second layer formed of a substantially impermeable material which coats one side of the first layer of the pipeliner. The polyvinyl alcohol material may comprise totally or partially woven or non-woven polyvinyl alcohol fibers or a mixture thereof, is preferably in the form of a felt, and can be formed by using any well-known technique for making woven, non-woven, knitted or otherwise formed fabric. The polyvinyl alcohol material is preferably a needled felt material. Most preferably, the first layer is a polyvinyl alcohol containing felt comprising a non-woven, needled fiber. The substantially impermeable material forming the second layer is flexible and acts as a liquid barrier in the pipeliner.

Once the pipeliner has been cured, polyvinyl alcohol containing pipeliners are often 20% to 100% stronger than similar polyester fiber/resin combinations. It is believed that this increased strength is due to the hydroxyl groups present on the exterior of the polyvinyl alcohol fiber which are reactive with many systems but which produce the best synergy with epoxy resins to form a true matrix. It is chemically resistant and can be used in chemical applications with minimal pipe degradation. Polyvinyl alcohol also is safe for use in potable water pipes as no residual monomers result from its production.

The first layer is preferably 1/2-100 mm thick, more preferably 1-50 mm thick, even more preferably 2-15 mm thick, and most preferably 3-6 mm thick. When a polyvinyl alcohol felt is used in the first material, the density of the felt, based on a 3 mm of thickness, is preferably 22-30 oz/yd², and most preferably 26-27 oz/yd². The thickness and density of the first layer will, of course, increase when the first layer is impregnated with resin.

The first layer preferably comprises a plurality of polyvinyl alcohol fibers. The polyvinyl alcohol fibers preferably are 1/4 - 12 denier thick, more preferably Vι-6, and most preferably 1-3 denier thick. The polyvinyl alcohol fibers are preferably 1/4 - 10 inches long, more preferably Vι-5 inches long, and most preferably 1-3 inches long. In the most preferred embodiment that fibers are about 1.5 deniers thick, and 1.5 inches long. The smaller fiber size provides the felt of the preferred embodiment with greater surface tension properties and a greater surface area to hold the resin to the fabric better and thereby reduce the resin's tendency to drain or pool and produce a weak pipe. It also provides for a felt which is easier to card and a pipeliner product that is more flexible overall and easier to install. The degree of polymerization of the polyvinyl alcohol preferably is 900-3000, more preferably 1200-2000, and most preferably 1700. The polyvinyl alcohol is preferably greater than 90% saponified, more preferably greater than 95% saponified, most preferably greater than 98%.

The composition and thickness of the substantially impermeable coating material of the second layer of the pipeliner of the present invention may be selected for optimum properties based upon the type of underground pipe being repaired. Where the underground pipe is used for conveying water or sewage, for example, polyurethane is a preferred coating material. In other applications, other materials such as polyethylene and polyvinyl chloride may be preferred coating material selections. A prefeπed thickness for coating the polyvinyl alcohol containing felt of the present invention is 1-100 mils. The thickness of the substantially impermeable coating material on the polyvinyl alcohol containing felt is preferably 2-50 mils, more preferably 3-25 mils, even more preferably 4-15 mils, and still even more preferably 10-12 mils.

The second layer of the pipeliner of the present invention is joined to the first layer according to coating techniques known in the art including laminating, extrusion coating, spraying, dipping and roll coating. In the prefeπed embodiment, the pipeliner is fabricated by extrusion coating the substantially impermeable second layer onto the first layer.

The first layer of the pipeliner preferably comprises a curable resin material. Such materials preferably include epoxy resins, polyester resins, vinyl ester resins, phenolic resins, alkyds, allylics, amino plastics and polyurethanes, most preferably epoxy resins. When the curable resin is present, the first layer preferably comprises 5- 75 wt.% of polyvinyl alcohol, more preferably 10-50 wt.%, and even more preferably 12-30 wt.% polyvinyl alcohol material. The first layer preferably comprises 25-95 wt.%) resin, more preferably 50-90 wt.% resin, and still even more preferably 70-88 wt.%) resin. Prefeπed resins are heat curable, preferably at from room temperature to about 200 °F, more preferably 120°-180°F, and most preferably 140°F-160°F. The curable resin may comprise a wetting agent for the resin. Wetting agents are used where an increase in the speed of initial resin wet-out and/or an increase in the resin retention capacity of the felt is desired. Flouro-based or silicon-containing wetting agents are preferably used to improve the spread of resin throughout the felt, and the capacity of the felt to retain resin. The wetting agent of the preferred embodiment is Fluorad 171, manufactured by 3M. Other useful types of wetting agents will be apparent to one of skill in the art, as well. As those skilled in the art are aware, the measure of wetting agent used is a function of the weight of the resin employed in the process. The weight of the wetting agent used in the prefeπed embodiment of the present invention is .0001%-.r% by weight of resin, more preferably .001 %-.0 %.

In another embodiment the pipeliner comprises only the first layer discussed above. In this manner multiple layers can be applied to the interior surface of a pipe, to form a rigid sleeve within the pipe, before another impermeable layer is inserted into the pipe (either by itself or as a two layer pipeliner discussed above) to form a substantially impermeable barrier.

A method for lining the interior of at least a segment of underground pipe using a polyvinyl alcohol-pipeliner having a polyvinyl alcohol-containing first layer and a substantially impermeable second layer includes at least the steps of applying a resin to the first layer of the pipeliner, forming a sealed pipeliner tube wherein the second layer comprises the outer surface, placing the sealed pipeliner tube within the pipe being repaired, everting the sealed tube such that the first layer contacts the interior surface of the pipe, and curing the resin of the first layer by sufficiently altering the temperature of the resin.

In a preferred embodiment, the curable resin is applied to the pipeliner when the pipeliner is near the job site and the liner then is mechanically manipulated to insure the uniformity and completeness of the dispersion of the resin throughout the entire length of the polyvinyl alcohol-containing fiber being used. Thereafter, the pipeliner is formed as a sealed tube by any well-known method including heat- sealing, gluing, or sewing laminated poly-vinyl alcohol felt material such that the first layer is on the outside of the tube.

The method of the present invention further includes the step of placing the sealed pipeliner tube into the pipe and everting the sealed tube such that the first layer contacts the interior surface of the pipe. The pipeliner is placed into and positioned within the pipe using techniques known in the art. The step of everting the pipe is accomplished by techniques known in the art, as well. In the prefeπed embodiment, hydraulic pressure is used to evert the pipeliner into the pipe such that the barrier coating faces toward the interior of the pipe defined by the interior surface of the pipe and the resin-containing first layer faces the interior surface of the pipe.

The step of curing the resin in the first layer is preferably accomplished by the flow of fluid through the pipeliner pipe and the heating of that fluid to a temperature sufficient to cure the resin in the everted pipeliner tube. The fluid that is flowed through the pipeliner for this purpose is preferably the fluid which provided the hydraulic pressure to evert the pipeliner into place within the pipe being restored. A generally appropriate temperature range appropriate for curing the resin in the pipeliner ranges from room temperature to approximately 200 °F. In the prefeπed embodiment, the appropriate fluid temperature range for setting the pipeliner resin is between 120-160°F. Other methods of curing the resin in the first layer of the pipeliner tube are known to those skilled in the art.

Testing performed during the assembly of the data illustrated in Table I has shown that the pipeliner is a composite and that at least some of the polyvinyl alcohol in integrated within the felt during the creation of the composite. Moreover, when treated with the resin and cured, this integrated composite shows improved compatibility with the resin. Other improvements are set forth in the data. Moreover, it is noted that while the data shown illustrates results from testing using both polyester and epoxy resins, such results are not necessarily limited to these two classes of resin. While the invention has been disclosed in its preferred forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents as set forth in the following claims.

TABLE I

Alpha polyester: Alpha polyester resin used was a high molecular weight isophthalic/terephthalic unsaturated polyester resin sold as L471AA-20D resin by Alpha/Owens Corning, LLC, Collierville, TN.

Epoxy resin: Epon type supplied by Shell Chemical Company, Houston, TX.

Claims

What is claimed is:

1. A pipeliner for lining an interior surface of a pipe comprising: a. a first layer comprised of a polyvinyl alcohol containing material that is adapted to absorb a liquid curable material; and b. a second layer comprised of a material at least substantially impermeable to fluid flowing through the pipe.

2. The pipeliner of claim 1 wherein the polyvinyl alcohol containing material is 2-15 mm thick.

3. The pipeliner of claim 1 wherein the polyvinyl alcohol containing material is 3-6 mm thick.

4. The pipeliner of claim 1 wherein the density of the polyvinyl alcohol containing material, based on a 3 mm of thickness, is 26-27 oz/yd².

5. The pipeliner of claim 1 wherein the polyvinyl alcohol containing material comprises a plurality of polyvinyl alcohol fibers.

6. The pipeliner of claim 1 wherein the polyvinyl alcohol containing material comprises a plurality of polyvinyl alcohol fibers, and the polyvinyl alcohol fibers are V2-6 denier in diameter.

7. The pipeliner of claim 1 wherein the polyvinyl alcohol containing material comprises a plurality of polyvinyl alcohol fibers, and the polyvinyl alcohol fibers are 1-3 denier in diameter.

8. The pipeliner of claim 1 wherein the polyvinyl alcohol containing material comprises a plurality of polyvinyl alcohol fibers, and the polyvinyl alcohol fibers are 14-5 inches long.

9. The pipeliner of claim 1 wherein the polyvinyl alcohol containing material comprises a plurality of polyvinyl alcohol fibers, and the polyvinyl alcohol fibers are 1-3 inches long.

10. The pipeliner of claim 1 wherein the polyvinyl alcohol containing material comprises a needled non-woven polyvinyl alcohol felt.

11. The pipeliner of Claim 1 , wherein the first layer further comprises an absorbed curable material.

12. The pipeliner of Claim 1 , wherein the first layer further comprises an absorbed curable material, wherein the curable material is selected from the group consisting of epoxy resins, polyester resins, vinyl ester resins, phenolic reins, alkyds, allylics, amino plastics and polyurethanes.

13. The pipeliner of claim 1 wherein the first layer comprises: a. 10-50 wt.%) polyvinyl alcohol; and b. 50-90 wt.% resin.

14. The pipeliner of claim 1 wherein the first layer comprises: a. 12-30 wt.% polyvinyl alcohol; and b. 70-88 wt.%) resin.

15. The pipeliner of claim 1 wherein the first layer further comprises an epoxy resin that is heat curable at 120┬░-180┬░F.

16. The pipeliner of claim 1 wherein the first layer further comprises a resin that comprises .001 -.01 wt. %. of a flouro-based or silicon-containing wetting agent.

17. The pipeliner of Claim 1 in the form of a tube.

18. The pipeliner of Claim 1 in the form of a tube comprising two edges formed by joining the two edges Using sealing methods selected from the group consisting of heat-sealing, heating and sewing.

19. The pipeliner of Claiml, wherein the second layer is selected from the group consisting of polyurethane, polyethylene and polyvinyl chloride.

20. The pipeliner of Claim 1 wherein the second layer is joined with the first layer of material according to a technique selected from the group consisting of laminating, extrusion coating, spraying, dipping, and roll coating.

21. The pipeliner fo claim 1 wherein the second layer is joined with the first layer by extrusion coating.

22. A method for lining at least a segment of the interior surface of a pipe with a pipeliner, wherein the pipeliner comprises: a.) a first layer comprised of a polyvinyl alcohol containing material adapted as a resin absorbing material; and b.) a second layer comprised of a material at least substantially impermeable to fluid flowing through the pipe.

23. A method for lining at least a segment of the interior surface of a pipe, the method comprising the steps of: a.) applying a resin to a first layer of pipeliner, the pipeliner comprising a first layer polyvinyl alcohol containing material adapted as a resin absorbing material and a second layer material which is at least substantially impermeable to fluid flowing through the pipe; b.) forming a sealed tube wherein the second layer comprises the outer surface of the tube; c.) placing the sealed tube within the pipe; d.) everting the sealed tube such that the first layer contacts the interior surface of the pipe; and e.) curing the resin in the first layer by sufficiently altering the temperature of the resin.

24. The method of Claim 25 wherein the step of everting the tube comprises pressurizing fluid and coursing the pressurized fluid through the pipe such that pressure exerted by the fluid everts the tube into contact with the interior surface of the pipe.

25. The method of Claim 38 wherein the step of curing the resin in the first layer comprises heating the fluid coursed through the pipe to a temperature sufficient to cure the resin.

26. A pipeliner for lining at least a segment of the interior surface of a pipe, the pipeliner comprised of first and second layers, the first layer adapted to face the interior surface of the pipe and being curable to adhere to the interior surface of the pipe, and the second layer adapted to face the interior opening of the pipe defined by the interior surface of the pipe, the second layer being at least substantially impermeable to the material flowing through the pipe, the first layer comprising polyvinyl alcohol.