Cross-Reference to Related Application

This application claims the benefit of and priority to United States

Provisional Patent Application No. 61/727,209 filed November 16, 2012 under the title FIBER REINFORCED TAPE OR SHEET FOR REINFORCING PIPE.

The content of the above patent application is hereby expressly incorporated by reference into the detailed description hereof.

Background of the Invention

The present invention relates generally to the manufacture of fiber reinforced polymer pipe, and more particularly, to a tape or sheet comprising fiber, useful for reinforcing polymer pipe. The pipe is preferably spoolable polymer pipe.

Fiber reinforced polymer pipes provide high strength and stiffness, and are used for transporting various fluids such as oil, carbon dioxide, hydrocarbons, or water, typically at high pressures. Fiber reinforced polymer pipes exist in two general configurations: bonded, and unbonded. An unbonded, fiber reinforced, polymer pipe typically has three layers, an inner layer of polymer, an intermediate layer of reinforcing material, and an outer polymer layer. The intermediate layer is often applied to the inner layer of polymer in the form of a tape or sheet, typically, a tape comprising a reinforcing material such as glass fibers is wound or braided around the inner layer of polymer. An outer polymer layer is then applied to the intermediate layer. A bonded, fiber reinforced polymer pipe is similar, but the intermediate layer comprises both reinforcing material and a polymer that is compatible with the polymer of the inner and outer layers, and can be bonded thereto. There are a wide variety of manufacturing methods for the making of a bonded fiber reinforced pipe. One method includes applying a tape comprising a reinforcing material such as glass fiber and a polymer, to an inner pipe layer. The tape is either applied under heat and tension, or is heated after its application onto the inner pipe layer. This creates a thermal bonding of the polymer contained within the tape, to the inner layer. An outer layer is then typically heat extruded onto the tape, and bonds thereto upon application .

A further method of manufacturing a bonded fiber reinforced pipe includes wrapping an inner polymer pipe layer with a sheet or sleeve comprising a reinforcing material such as glass fiber and a polymer bondable to the inner polymer pipe layer. The sheet or sleeve is then heated to allow the polymer within the sheet or sleeve to bond to the polymer in the inner polymer pipe layer. Optionally but preferably, an outer polymer pipe layer is then added, typically also bondable and bonded to the sheet or sleeve.

One challenge in the manufacture of bonded fiber reinforced pipe is that the reinforcing material is typically not very compatible with the polymer. As such, for several decades, the composites industry has been researching methods for impregnating and bonding reinforcing material, such as fiberglass or carbon fibre filaments, to polymeric materials in order to create structural polymer composites. Both thermosetting and thermoplastic polymers have been used, and each of these material types has different process and material compatibility challenges. There are considerable challenges in manufacturing a tape, sleeve or sheet that contains a significant percentage of structural fiber filaments and that bonds well to the inner and outer polymer pipe layers. A further challenge exists in bonding two pipe lengths together at a pipe joint, where often, paradoxically, the weakest point of the joint will be the area around the reinforcing layer, due to imperfections in the bonding of the reinforcing layer to the inner and/or outer polymer layers of the pipe. Thus it is desirable to have a reinforcing tape, sheet or sleeve with improved bonding of (a) the reinforcing material to the polymer within the tape, sheet or sleeve, as well as (b) the tape, sheet or sleeve with the inner and/or outer layers of pipe. Summary of the Invention

According to one aspect of the present invention is provided a composite tape, comprising : a plurality of fibers selected from the group consisting of glass fibers, carbon fibers, and aramid fibers; and a vinyl acetate ethylene coating. In certain embodiments, the composite tape comprises a filler, for example, fumed silica and/or microcrystalline silica.

In certain embodiments, the plurality of fibers within the composite tape are unidirectional glass fibers. In other embodiments, the plurality of fibers within the composite tape are a multi dimensional glass fiber weave or braided.

In certain embodiments, the composite tape comprises more than 60%by weight of glass fiber.

In certain embodiments, the composite tape has less than 3% void content, for example, 2% or less void content.

According to a further aspect of the present invention is provided a method for making a composite tape, comprising :

contacting a plurality of fibers selected from the group consisting of glass fibers, carbon fibers, and aramid fibers with a water based vinyl acetate ethylene solution or emulsion comprising vinyl acetate ethylene copolymer; and drying the vinyl acetate ethylene copolymer to form the composite tape.

In certain embodiments, the water based vinyl acetate ethylene solution or emulsion further comprises a filler, for example, fumed silica and microcrystalline silica. In certain embodiments, the method further comprises removing excess vinyl acetate ethylene solution before drying.

In certain embodiments, the drying comprises a heating of the vinyl acetate ethylene to > 180°C, for example, between 180 and 190°C.

In certain embodiments, the plurality of fibers are a plurality of unidirectional glass fibers. In certain other embodiments,

the plurality of fibers are a two dimensional glass fiber weave. A further aspect of the present invention is a method of manufacturing a fiber reinforced pipe, comprising wrapping, under heat and tension, the tape as hereindescribed, or a tape manufactured by the method as hereindescribed, around the outside diameter of a polyolefin pipe, such that the tape is bonded to the polyolefin pipe.

In certain embodiments, the heat applied is sufficient to heat the tape to between 180-190°C. In certain embodiments, the method further comprises enveloping the tape bonded to the polyolefin pipe with an outer polyolefin layer.

In certain embodiments, the polyolefin pipe is a polyethylene pipe. In certain embodiments, the outer polyolefin layer is an outer polyethylene layer.

In another aspect of the present invention is provided a fiber reinforced pipe comprising : an inner polyolefin layer; an intermediate layer comprising the tape as hereindescribed or a tape manufactured by the method as hereindescribed; and an outer polyolefin layer.

In certain embodiments, the inner polyolefin layer is an inner polyethylene layer. In certain embodiments, the outer polyolefin layer is an outer polyethylene layer.

Brief Description of the Drawings

Figure 1 illustrates a plurality of substantially parallel, continuous length fibers utilized to make the tape, sheet or sleeve according to certain aspects of the invention. Figure 2 illustrates a two dimensional woven sheet of fibers utilized to make the tape, sheet or sleeve according to certain aspects of the invention.

Figure 3 is a schematic representation of a method of manufacturing a composite tape of the present invention.

Figure 4 is a photograph of a composite tape of the present invention .

Figure 5 is a schematic representation of a method of manufacturing a composite tape of the present invention.

Detailed Description of the Invention

We have manufactured a new fiber composite, which can be made into tape, sheets, or sleeves, and which is excellent for use in making a bonded fiber reinforced pipe. The composite comprises reinforcing fibers coated with a water based vinyl-acetate-ethylene (VAE) polymer. The water based VAE polymer (emulsion) provides excellent fiber wetting ability, and allows for the production of a composite with desirable fiber: polymer ratios.

Without being limited to theory, we believe that the use of a water based polymer provides better wetting, resulting in less voids between the polymer and the fiber within the composite. A variety of reinforcing fibers can be used, for example, glass, carbon, or aramid fiber. Glass fibers may be various forms of glass, including Si0 ₂ , Al ₂ 0 ₃ , B ₂ 0 ₃ , CaO and MgO in various ratios, and may be of varying length and thickness. Carbon fibers are carbonized polyacrylonitrile fibers, pitch resins, or rayon . Aramid fiber are most commonly known as Kevlar, Nomex and Technora. Typically, fibers have a substantially continuous length, and a diameter ranging from 9 to 17 μιη, and are spun or wound into larger threads, which may also be woven into two and three dimensional configurations. In certain embodiments, the fiber materials are a unidirectional glass, carbon or aramid fiber, as illustrated in Figure 1. In other embodiments, the fiber is woven into a two dimensional sheet, as illustrated in Figure 2. Three dimensional fiber configurations, such as a rope, are also possible. In one preferred embodiment, a plurality of unidirectional glass fibers are used. In a second preferred embodiment, a two dimensional sheet of woven glass fiber having the configuration illustrated in Figure 2 is used.

The VAE polymer, when used to coat the fiber materials, is in a water based solution, as an emulsion, and may contain other compounds. For example, a fumed silica, such as Cab-O-Sil® M-5 (Cabot Corporation, Montana) may be added to the solution, and has been found to be an excellent filler which has good thermal conductivity in the solution and efficiently fills the voids in the composite. Microcrystalline silica may also be used as a filler, to reduce costs. Adhesion promoters, such as silane-based adhesion promoters, may be added to the solution to promote the adhesion of the polymer within the composite tape to a polymer it is being bonded to.

The vinyl acetate ethylene copolymer preferably has >40% vinyl acetate, with the remainder being ethylene. The VAE copolymer is used as an emulsion in water. It has been found that a relatively soft VAE with a low Tg (about - 15°C) provided improved impact resistance properties.

To make the composite tape, the fibers are passed through a bath of a water based solution comprising the VAE polymer. The VAE polymer wets the fibers, and the resultant VAE-coated fibers are passed through a light pressure roller to remove excess solution . The fibers are then dried, for example, using infra red heating elements. Alternatively or in addition, plasma treatment may be used to functionalize the VAE polymer to the glass fiber to enhance adhesive properties of the polymer. It has been found that, when using glass fiber, the VAE polymer bonds well to the glass fibers without the need for coupling agents. Optionally, once the composite tape has been prepared as described above, it can be coated or laminated with a thin film of polymer, such as polyethylene. Such a coating provides a better, more durable surface for rolling or storing the tape before it is bonded to the pipe, and enhances bonding of the tape to the pipe. Alternatively, the composite tape may be laminated with a thin adhesive based film. The composite tape, wrap or sleeve can be used to manufacture a fiber- reinforced polymer pipe, as follows. The tape is wrapped around a polymer pipe using a tension winding process under heat (approx. 180- 190°C) and tension . Due to the heat and tension, the tape fusion bonds to the pipe, and to itself, as it is being wound arou nd the pipe. The tape may be wrapped around the pipe in a variety of configurations, for example, helically wrapped at an angle of less than 15 degrees relative to the longitudinal axis. Alternatively, a more aggressive ang le, for example, 45 degrees, may be used . Several different wrapping angles may also be used : for example, a first tape may be helica lly wrapped in a first helical direction, then the first tape, or a second tape, may be helically wrapped in a second helica l d irection opposite the first helical direction . Thus, the resultant pipe would have two layers of fiber reinforcement, in opposing directions, all bonded to the pipe and providing reinforcement in more than one direction . An outer coating of polymer, bonded to the outer layer of tape, is then provided .

Due to the incredible fiber wetting capability of the VAE solution, it a llows for an alternate man ufacturing method for fiber- reinforced polymer pipe. Instead of using the composite tape as described above, the VAE solution can be used to manufacture a pipe in situ. In th is alternate approach, reinforcing fibers are wound about a polymer pipe. The reinforcing fibers are then im pregnated with a VAE copolymer, used as an emu lsion in water as described above. The impregnating can be done by passing the polymer pipe through a bath or spray using conventional bath or spray apparatus. Optionally, the reinforcing fibers can be passed through a light pressure roller to remove excess VAE copolymer emulsion solution . The fibers are then dried as described above, using infra red heating elements and/or plasma treatment. It has been found that the VAE polymer bonds well to the fibers and to the polymer pipe without the need for coupling agents.

As can be appreciated, the entirety of the desired thickness of reinforcing fibers can be wound around the polymer pipe and impregnated in the matter described above, or, in an a lternative embodiment, th is can be done in stages, with a portion of the desired th ickness wound around the polymer pipe, then impregnated and optionally dried, then the remainder of the desired thickness wound then impregnated and optionally dried. Multiple 'layers' of reinforcing fibers can be created in this manner. Each of the layers can be identical to the one below, or different, for example, with a different directionality.

Optionally, once the reinforced pipe has been prepared as described above, it can be coated or laminated with a thin film of polymer, such as polyethylene.

As can also be appreciated, instead of winding reinforcing fibers around the polymer pipe, a sleeve of reinforcing fibers may be fitted to the pipe, then treated with the VAE copolymer emulsion solution as described above.

Example 1 : Manufacturing of a Composite Tape A water-based vinyl acetate ethylene (VAE) solution was prepared with the following composition, by weight percent: water: 65-68%; Fumed silica (M-5, Cabot Corporation, Montana) : 1.3%; ; Vinyl acetate ethylene (Dairen Chemical Corporation, Taiwan) : 32.9%. The VAE solution 20 was added to a bath 22 as shown in Figure 3. Glass fibers 24 comprising a plurality of continuous glass strands of between 9 and 17 μιη, to a thickness of about 0.5 mm and a width of about 2.5 cm, were pulled through the VAE solution 20, from a roll of glass fiber 26. Rollers 28, 30, 32, 34 were used to aid in keeping constant tension on the glass fibers 24 as they were being pulled through . Press rollers 36, 38 were used to remove excess VAE solution from the glass fibers 24 as they exited the bath 22. Optionally, an additional set of press rollers 40, 42 were used to further remove excess VAE solution and to hence accelerate the drying of the VAE on the glass fibers. The glass fiber 24 was pulled through a drying chamber 44 containing infrared heaters to dry the VAE solution, resulting in the desired composite tape. Optionally, and as shown, heated, dried composite glass fiber/VAE tape can be immediately wrapped onto a polyolefin liner pipe 46. One advantage of wrapping and reinforcing a pipe 46 immediately after manufacturing of the composite tape is that the heating provided in the drying chamber 44 is sufficient to allow the composite tape to fusion bond to the pipe 46. Ideally, the fusion bonding of the composite tape to the pipe 46 is done at between 180- 190°C. A second advantage is that the tension required to apply the composite tape to the pipe 46 is provided, at least in part, by tension provided by rollers 28, 30, 32, 34 and press rollers 26, 38, 40, 42.

Speed of glass fiber travel through the VAE solution 20 can be modified to optimize coating of the glass fibers 24 with VAE solution 20. Speed of glass fiber travel through the system will also affect drying time, however, drying time can also be optimized by the length of the drying chamber 44 and the frequency and intensity of the infra-red heaters within the drying chamber 44. We have found that a drying time of 2 to 2.5 minutes, (with power at 400 Watts) for 1 minute, followed by 1 to 1.5 minutes at 1500 Watts) at a wavelength of 2 μιη, worked well for a 0.5 mm thickness of tape.

The composite tape was found to have a composite density of 1.69, as compared to a theoretical composite density of 1.657, meaning that the process provided tape with a void content of about 2%. The composite tape was found to have a tensile strength of 111 lb/mm ² . The composite tape was found to be approximately 35% glass fiber by volume, the remainder being the VAE and fillers. Visually, the composite tape was found to have very few to no loose fibers, as shown in Fig. 4.

Example 2 : Manufacturing of a Laminated Composite Tape

A laminated composite tape was prepared, as follows and as described in Figure 5. Generally, the method was similar to the method of preparing the composite tape as described in Example 1, with an added step of laminating the tape with a thin adhesive based film after the drying step.

A water-based vinyl acetate ethylene (VAE) solution was prepared with the following composition, by weight percent: water: 65-68%; Fumed silica (M-5, Cabot Corporation, Montana) : 1.3%; ; Vinyl acetate ethylene (Dairen Chemical Corporation, Taiwan) : 32.9%. The VAE solution 60 was added to a bath 62. Glass fibers 64 were pulled through the VAE solution 60, from a roll of glass fiber 66 and a glass fiber guide 68. A roller 70 was used as a wetting/drying guide, and to aid in keeping constant tension on the glass fibers 24 as they were being pulled through . Press rollers 72, 74 were used to remove excess VAE solution from the glass fibers 24 as they exited the bath 22. Optionally, an additional set of press rollers (not shown) were used to further remove excess VAE solution and to hence accelerate the drying of the VAE on the glass fibers. The glass fiber was pulled through a drying chamber 76 containing infrared heaters to dry the VAE solution, resulting in the desired composite tape. The composite tape was then pulled through a laminator 82, which applied tape from laminating tape rolls 78, 80 to the composite tape. The laminated, composite tape was then rolled onto laminated product roll 84. The rotation of laminated product roll 84 provided the pulling action to bring the tape through the system. Accordingly, speed of glass fiber travel through the VAE solution 60 can be modified to optimize coating of the glass fibers 24 with VAE solution 20, by varying the rotation speed of laminated product roll 84. Speed of glass fiber travel through the system will also affect drying time, however, drying time can also be optimized by the length of the drying chamber 76 and the frequency and intensity of the infra-red heaters within the drying chamber 76.

Example 3 : Manufacturing of a Composite Sheet A water-based vinyl acetate ethylene (VAE) solution was prepared as described in Example 1. The VAE solution was added to a bath . A sheet of woven glass fiber was dipped into the VAE solution. The sheet was then placed on a non- porous table and excess VAE solution was removed by applying a roller on the sheet, by hand. The sheet was then placed in a drying chamber containing infrared heaters to dry the VAE solution, resulting in the desired composite sheet.

We have found that a drying time of 2 to 2.5 minutes, (with power at 400 Watts for 1 minute, followed by 1 to 1.5 minutes at 1500 Watts at a wavelength of 2 μιη, worked well for a 0.5 mm thickness of sheet.

The composite sheet was found to have a void content of about 2%. Visually, the composite sheet was found to have very few to no loose fibers. Example 4: Manufacturing of a Reinforced Pipe

A composite tape made as described in Example 1 was heated to between 180 - 190 °C and wrapped, under tension, around a polyethylene pipe. The tape was wrapped at an angle of about 30 degrees relative to the longitudinal axis, and the pipe was slowly moved forward during the wrapping resulting in multiple layers (approximately 3-4) of tape wrapped around itself as the tape was wrapped around the pipe. A second tape was heated to between 180- 190°C and similarly wrapped, under tension, around the first wrapped tape, at an angle of about 60 degrees relative to the longitudinal axis, resulting in multiple layers (approximately 3-4). The composite tape bonded to itself and to the pipe during the process, resulting in a pipe, reinforced in two directions. An outer coating layer of polyethylene was extruded at a thickness of about 5 mm, completely bonding to and enveloping the composite tape.

Example 5 : Manufacturing of a Reinforced Pipe

A woven carbon fiber tape was wrapped, under tension, around a polyethylene pipe. The tape was wrapped at an angle of about 30 degrees relative to the longitudinal axis, and the pipe was slowly moved forward during the wrapping resulting in multiple layers (approximately 3-4) of tape wrapped around itself as the tape was wrapped around the pipe.

The tape-wrapped pipe was then passed through a sprayer apparatus, which sprayed sufficient VAE solution (prepared as described in Example 1) to saturate the tape. The pipe was then passed through rollers to remove excess VAE solution, which was recycled. Pipe was then passed through a drying chamber containing infrared heaters to dry the VAE solution, resulting in the desired composite coated pipe.

The process was repeated, with a second woven carbon fiber tape (alternatively, a fiber glass tape) wrapped, under tension, at an angle of about 60 degrees relative to the longitudinal axis, followed by VAE spray and drying.