Abstract:
A liner material suitable for a pipe comprising a substrate having inner and outer surfaces including a coating of impermeable resin on the outer surface of the substrate, characterized in that the substrate with the coating resists substantial delamination at temperatures of greater than 150° F., has a kinetic coefficient of friction of ≦0.8, and a flex modulus of less than 200,000 psi.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims the benefit of the filing date of U.S. Provisional Application Ser. Nos. 60/622,149 filed Oct. 26, 2004 and 60/580,032 filed Jun. 16, 2004, the teachings of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to providing a composite material for lining pipes or conduits. More particularly, the present invention relates to providing a composite material having increased flexibility, a relatively low coefficient of friction and resistance to heat induced delamination, for use in, e.g., lateral and main sewer line reinforcement as well as potable water, gas, and industrial applications in both horizontal or vertical configurations.  
       BACKGROUND  
       [0003]     Conduits or pipelines, particularly underground pipes, such as sanitary sewer pipes, storm sewer pipes, water lines and gas lines that are employed for conducting fluids frequently require repair due to deterioration or damage that leads to leakage or pot holes. The leakage may be inward from the environment into the interior or conducting portion of the pipe or may be outward from the conducting portion of the pipe into the surrounding environment. In either case, it is desirable to avoid this leakage.  
         [0004]     The leakage may be due to improper installation of the original pipe, deterioration of the pipe as a result of normal aging, or the effects of conveying corrosive or abrasive material. Cracks at or near pipe joints may be due to environmental conditions such as earthquakes or the movement of large vehicles or similar natural or man made vibrations, root infiltration, as well as other causes. Regardless, these leakages are undesirable and may result in the loss of conveyed fluids or result in the damage of the surrounding environment or may even pose a dangerous public health hazard. In the case of sewer lines, ground water leakage into the pipe causes significant increase in the volume of effluent to be treated at sewage treatment plants. If leakage continues, structural failure of the existing conduit may result due to loss of soil and side support of the conduit.  
         [0005]     Repair of the lines by digging and pipe replacement is increasingly difficult and less economical. As a result, various methods have been devised for in-place repair or rehabilitation of existing pipelines. One method for pipeline no-dig or trenchless rehabilitation is forming a new pipe within the damaged pipe using a method called Cured-In-Place and is referenced in patents such as the Insituform.RTM process as described in U.S. Pat. Nos. 4,009,063, 4,064,211, and 4,135,958; the contents of which are incorporated herein by reference.  
         [0006]     This process may be accomplished by extrusion coating an “impermeable layer” of a thermoplastic polymer, typically urethane, vinyl or LLDPE film onto a felt or non-woven absorbing layer, forming a tube from this laminate with the film side out by sewing the edges together or heat bonding a supporting backing strip of the substrate, bonding a film over the seam to render it impermeable, impregnating the absorbent material with a thermally curable liquid resin and installing the pipelining material through everting; a process whereby the resin impregnated tube is inverted into the pipe using water, steam, air or a combination thereof; or it can be pulled into place via a winch. The thermoset resin is then in contact with the interior surface of the pipe unless it is pulled-in-place or used in conjunction with a calibration tube or a bladder. Steam, air or hot water is then applied to provide radial pressure to the tube and to initiate the exothermic curing of the thermosetting resin. These liners are generally referred to as cured-in-place-pipes or “CIPP liners” and the installation of the CIPP liners is referred to a CIPP installation.  
         [0007]     In order to withstand the rigors of production, wet-out, transportation and installation of the tube as well as withstanding the high exotherm of thermosetting resins, the extruded film “impermeable layers” of the main line tubes are generally between 0.010 inches to 0.020 inches thick. The thickness of the film also facilitates attaining an adequate bond between the impermeable layer and absorbent layer, because attaining high bond strength requires that the thermoplastic film partially penetrate and mechanically bond with the fibers of the absorbent layer. The degree of penetration is a function of lamination pressure and extrudate temperature at the time of lamination. Proper bonding requires conditions that are difficult to achieve with thinner thermoplastic films. If the bonds fail, delamination occurs that can result in the tube failing.  
         [0008]     Styrene and non-styrene based thermosetting resins such as polyester, epoxies or vinyl esters are commonly used as thermosetting resins in CIPP applications. To determine if adequate bonding between the film and the absorbent layer has been achieved the industry uses, among other tests, the “Hot Styrene Test.” The “Hot Styrene Test” determines the solvating effect of a styrene monomer and heat on the composite to ascertain if the combination adversely affects the coating due to excessive swelling or softening of the coating. In this manner, the bonding of the coating with the substrate can be evaluated. If the thermoset resin is not styrene based, the “Hot Styrene Test” is still a good overall test to detect possible delamination issues.  
         [0009]     Reportedly, the industry has had problems utilizing the CIPP process for lateral lines, which are lines extending from the main line sewer pipe to individual homes or businesses. These lines are typically smaller in diameter than the main sewer lines and may have a number of bends. The thick coating layer and thick absorbing layers used in main lines are undesirable in lateral lines because the total composite is either too thick or lacks sufficient stretch and creates wrinkles or tucks in the bends, which create hang-ups and plugging in the pipe.  
         [0010]     Regardless of the substrate, a thicker film is more difficult to invert in smaller diameter pipes because the thicker substrate/coating composite lacks flexibility. When soft thermoplastic urethanes are used, a purported higher coefficient of friction makes inversion more difficult. LLDPE films are purportedly undesirable as they are considerably stiffer than the thermoplastic urethane. LLDPE constructions also cannot be solvent welded, which is commonly used for seaming or patching the tube during manufacturing, resin impregnation or installation.  
         [0011]     A seamless loop knit fabric tube has reportedly been employed for lateral repair but there is no way to maintain good polymer to substrate adhesion due to the nature of the bonding surface of the loop knit. Reportedly, good adhesion is not obtained because the extruded polymer skin cannot be easily applied to the tube with sufficient heat and pressure while in a seamless construction.  
         [0012]     It is therefore an object of the current invention to provide a coating for a substrate that is suitable for pipe rehabilitation, including lateral lines and other conduits, which exhibits excellent adhesion (to the substrate), flexibility and heat resistance. More specifically, with said heat resistance, higher installation exotherm temperatures are permitted and therefore installation times are faster.  
         [0013]     It is more specifically an object of the present invention to provide a coating that exhibits such suitable adhesion and flexibility and heat resistance, and which also specifically has a targeted heat resistance, measured by, e.g., a “Hot Styrene Test”.  
         [0014]     It is also a specific object of this invention to provide a polymer coating that is chemically reacted and formed on an absorbent substrate, with a selected thickness, which provides relatively good elasticity and elongation properties, and which is suitable for use in lateral sewer line rehabilitation.  
         [0015]     It is also a further object of this invention to provide a polymer coating for a substrate that has a relatively low coefficient of friction, which allows the surface to readily slide over itself during installation when using an inversion method to repair lateral sewer liner and/or other conduits.  
         [0016]     It is also a further object of this invention to provide a thinner coating with the above attributes mentioned for applications including, but not limited to, the rehabilitation for sanitary sewers, manhole reconstruction, spot repairs, potable water, industrial and vertical rehabilitation applications.  
       SUMMARY  
       [0017]     A liner material suitable for a pipe comprising a substrate having inner and outer surfaces including a coating of impermeable resin on the outer surface of the substrate, characterized in that the substrate with the coating resists substantial delamination at temperatures of greater than 150° F., has a kinetic coefficient of friction of ≦0.8, and a flex modulus of less than 200,000 psi.  
         [0018]     A conduit lined with a lining material comprising a conduit having an interior surface, a substrate having inner and outer surfaces, including a coating of impermeable resin on the outer surface of the substrate characterized in that the substrate with the coating resists substantial delamination at temperatures of greater than 150° F., wherein the coating has a kinetic coefficient of friction of ≦0.8 and flex modulus of less than 200,000 psi. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     The present invention relates to providing a composite material for lining pipes or conduits. Particularly, the present invention relates to providing a composite material having a chemically reacted coating adhered to a substrate. More particularly, the present invention relates to providing a composite material having a relatively low coefficient of friction, increased flexibility and resists heat induced delamination.  
         [0020]     In an embodiment of the present invention, a chemically reactive material is disposed onto a substrate including, but not limited to, fabrics, non-woven, woven, knitted, foam or a combination thereof. More preferably, the substrate is absorbent. The chemically reactive material is then cured and bonds to the substrate to form a coating. It should also be appreciated that the chemically reactive material can be disposed on one or both sides of the substrate.  
         [0021]     In another preferred embodiment, the substrate material is also impregnated with a thermosetting resin, typically an unsaturated polyester crosslinkable by addition polymerization, whereby the unsaturated polyester is reacted after installation of the liner material. More preferably, an unsaturated polyester/polystyrene, vinyl ester or epoxy is used to impregnate the substrate.  
         [0022]     In one preferred embodiment, the chemically reactive material is deposited onto a web of the substrate by transfer coating and the combined substrate/coating is constructed into a tube. In another preferred embodiment, the coating is impermeable. In another preferred embodiment, the coating thickness is less than 0.010 inches thick and more preferably less than 0.005 inches thick.  
         [0023]     The transfer coating process may generally consist of knife over roll coating a curable or fusible liquid coating onto a casting paper or other reusable carrier surface, curing the coating to a solid by heating or other means, optionally applying an adhesive coating and laminating to a substrate. Likewise, it is possible to produce a product under this invention by forming a skin by applying a non-crosslinked coating or coatings to the paper, followed by a crosslinked “adhesive” layer which bonds the skin to the absorbent substrate. Additionally, it is possible to produce products using a combination of crosslinked or non-crosslinked coatings which are coated directly onto the absorbent substrate.  
         [0024]     Likewise, it should also be appreciated that it is possible to prepare a crosslinked film coating for use in this invention by other means, such as extrusion and film lamination. Preferably, the extruded materials may be crosslinked on the substrate by thermal energy at temperatures higher than their processing temperature or by use of radiation crosslinking. More preferably, an adhesive layer may be used to achieve optimum bond to the substrate during lamination, either during extrusion or post lamination.  
         [0025]     It should be appreciated that a number of crosslinkable or thermoset coatings may be applied in the present invention including, but not limited to, two-part urethane formulations and epoxies. In addition, it is contemplated that other suitable polymers may include PVC copolymers, polyester, acrylic, natural rubber, nitrile, or butyl rubber, which may all be chemically reacted on the substrate surface. Accordingly, one may coat the substrate with a thermoplastic polymer, and through the use of thermal energy or even chemical initiators, invoke a crosslinking reaction such that the thermoplastic polymer becomes adhered to the substrate material. In addition, it should be noted that effective bonding of the aforementioned polymers may be facilitated by an appropriate adhesive. Preferably, this is a crosslinked adhesive which may consist of the general class of urethanes, acrylics, epoxies, polyesters, polyamides, blends or copolymers thereof, or others with resistance to the “Hot Styrene Test.” 
         [0026]     Preferably, a two part polyurethane or polyurea formulation may be applied in the present invention. More preferably, the coating should be thermally resistant to withstand the “Hot Styrene Test.” More specifically, the coating herein should be thermally resistant to those temperatures that may be achieved after the coating is applied to the substrate, and at that point where the substrate, installed in a lateral sewer line or other conduit, and impregnated with, e.g., thermosetting resins is cured to provide conduit rehabilitation.  
         [0027]     Most preferably, the coating should exhibit a relatively low coefficient of friction (0.8 or less) to facilitate the everting process where the coating will contact itself, and, low stiffness and modulus (flex modulus of 200,000 psi or less) to ease inversion and installation. Also most preferably, the coating should exhibit axial and radial stretch properties allowing for ease of navigation through a passageway.  
         [0028]     More preferably, the coating will have a coefficient of friction between 0.1-0.8, including all incremental values and ranges therebetween. In addition, the coating will preferably have a flex modulus between 1000-100,000 psi, including all incremental values therebetween.  
         [0029]     It should also be appreciated that a number of substrates may be used in the present invention including, but not limited to, various felts, non-wovens, loop knit fabrics, spun bonded, melt blown, foams, spacer fabrics, fiberglass (scrims, mats, chopped or composites), etc. More preferably, for use in laterals, the substrates have high stretch characteristics.  
         [0030]     The present invention pertains to various installation methods including, but not limited to, pulled in place and inversion methods.  
         [0031]     The foregoing description is provided to illustrate and explain the present invention. However, the description hereinabove should not be considered to limit the scope of the invention set forth in the claims appended here to.