Gas storage vessel including continuous fiber thermoplastic composite material

Abstract

A gas storage vessel particularly suited for storing hydrogen gas. Methods for producing the gas storage vessel are disclosed. Advantageously, robust, pressure-resistant high strength gas storage vessels are provided owing to the inclusion of a structural layer including high continuous fiber loadings in a thermoplastic polymer system derived from cyclic monomers and / or oligomers, which is 100% recyclable.

Description

GAS STORAGE VESSEL INCLUDING CONTINUOUS FIBER THERMOPLASTIC COMPOSITE MATERIALFIELD OF THE INVENTION

[0001] The present invention relates to a gas storage vessel particularly suited for storing hydrogen gas. Methods for producing the gas storage vessel are disclosed. Advantageously, robust, pressure-resistant high strength gas storage vessels are provided owing to the inclusion of a structural layer including high continuous fiber loadings in a polymer system derived from cyclic monomers and / or oligomers.BACKGROUND OF THE INVENTION

[0002] Alternative fuel sources are sought throughout the world to replace fossil fuels as primary energy sources, especially for the transportation field.

[0003] While electric batteries provide one means to replace fossil fuels, drawbacks exist. For example, most electric batteries alone are not powerful enough to move heavy trucks, trains and airplanes. In addition, long charging times inhibit adoption of electric battery technology. For commercial vehicles, long charging times mean reduced productivity since the vehicles are idle during charging.

[0004] Hydrogen is another alternative fuel that can be produced using solar power and wind power which can be stored and transported. Hydrogen generated through the use of green energy such as solar power, wind power, wave energy or hydroelectricity is considered green hydrogen.

[0005] Green hydrogen is the ultimate renewable and clean energy for the hydrogen economy. For storage of hydrogen, there are multiple solutions for stationary storage that can be installed and used by power plants, utility microgrids, manufacturing facilities, and even households. However, for cars, trucks, trailers, airplanes, etc., storing and transporting hydrogen is still the most challenging task.

[0006] Traditional gas storage vessels are typically made of metal, which are heavy and difficult to transport. Metal storage vessels are also prone to corrosion and damage.

[0007] Storage vessels for hydrogen, natural gas or other gases in which safety is of utmost importance should be light in weight, durable and able to withstand high pressures, such as at least 700 bar (70 mPa) for hydrogen.

[0008] In order to meet these requirements, storage tanks fabricated with continuous fiber reinforced thermosetting composite materials have been developed in the art. However, recycling and reuse of thermoset composite materials is a drawback, even though relatively high fiber loadings can be achieved and high strength vessels can be produced.

[0009] In an effort to overcome the drawbacks of gas storage vessels prepared utilizing thermoset composite materials, thermoplastic composite material gas storage vessels have also been developed.

[0010] U.S. 2018 / 0363849 relates to a pressure vessel comprising a hollow body comprising endless fibers embedded in a thermoplastic polymer, in which the thermoplastic polymer comprises one or more polyamides containing one or more aliphatic monomeric units, wherein the one or more polyamides have a CH2-ratio of at least 5.5 and less than 10, calculated by identifying the number of different aliphatic monomeric units in the one or more polyamides; determining the number of CH2 groups per aliphatic monomeric unit for each of these different aliphatic monomeric units; calculating the sum of the so determined numbers of CH2 groups; dividing said sum by the number of different aliphatic monomeric units in the one or more polyamides; taking into account only the aliphatic monomeric units present in the one or more polyamides in an amount of at least 10 wt.% with respect to the total weight of the one or more polyamides.

[0011] CN115625913 relates to the technical field of pressure containers and hydrogen energy sources, and discloses a thermoplastic polyimide composite material winding layer type IV gas cylinder preparation method, which comprises the following steps: preparing a monomer resin solution from a dianhydride monomer and a diamine monomer, placing the monomer resin solution in a gum dipping tank, and transversely penetrating through a continuous fiber bundle; heating to enable in-situ amidization polymerization to form polyamide acid prepreg, and winding the polyamide acid prepregon the surface of the liner of the type IV plastic gas cylinder; and heating to produce thermoplastic polyimide and carrying out air tightness detection. The gas cylinder inner container and the winding layer resin base body are both made of thermoplastic resin and can be recycled. The inner container of the gas cylinder is a plastic inner container, and the working pressure can reach 35 MPa. The drawback of this chemistry and process is that it requires the use of a solvent to dissolve dianhydride and diamine monomers and an additional step of heat treatment to remove the residual solvent. In addition, it requires high polymerization temperature in a range that is higher than the melting point or softening point of some of the inner liner plastics such as polyethylene, polypropylene, polystyrene, polycarbonate, polyvinyl chloride, ethylene vinyl alcohol, and some polyesters and polyamides.

[0012] Even in view of these attempts to provide storage vessels that are ultimately recyclable and reusable, there is still a need for high strength, pressure-resistant gas storage vessels including a continuous fiber thermoplastic composite material having high fiber loadings, for example at least 60% by weight or at least 70% by weight or more. There is also still a need for methods to produce gas storage tanks that are economical and relatively easy to utilize.SUMMARY OF THE INVENTION

[0013] The problems of the prior art and others are solved by the present invention which provides gas storage vessels including a structural layer including a continuous fiber thermoplastic composite material in which the continuous fiber is present at a relatively high loading based on total weight of continuous fiber and polymer in the layer. Continuous fiber thermoplastic composite materials are also disclosed herein. Methods for producing gas storage tanks comprising continuous fiber thermoplastic composite materials are additionally described.

[0014] In one aspect or embodiment, a gas storage vessel is disclosed, comprising a liner having a hollow body with an internal volume that is adapted to store a gas such as hydrogen, and a pressure-resistant structural layer disposed on at least one portion of an outer surface of the liner. The liner is optional in some embodiments. The structural layerincludes a continuous fiber thermoplastic composite material in which the continuous fiber is present at a high loading based on the total weight of the thermoplastic polymer and continuous fiber in the structural layer. The thermoplastic polymer is derived from at least one or more of cyclic monomers and one or more oligomers including a cyclic group, that can undergo ring opening polymerization.

[0015] In an additional aspect or embodiment, the structural layer includes the continuous fiber wound around at least one portion of the liner in a spiral pattern, in a longitudinal direction, circumferential direction, or in a lateral direction, or a combination thereof.

[0016] Still another aspect or embodiment of the present invention relates to providing a gas storage vessel having an operating pressure between 1 bar (0.1 mPa) and 1 ,500 bars (150 mPa), preferably between 1 bar (0.1 mPa) and 1000 bars (100 mPa), more preferably between 1 bar (0.1 mPa) and 700 bars (70 mPa), meeting type IV pressure vessel requirements.

[0017] Another aspect or embodiment of the present invention relates to a method for producing a gas storage tank including the steps of obtaining a continuous fiber having a length, contacting the continuous fiber with a composition comprising one or more of cyclic monomers and oligomers with a cyclic group that are thermoplastic polymer precursors to form a continuous fiber thermoplastic composite material; and forming at least a portion of a structural layer of the gas storage tank with the continuous fiber thermoplastic composite material through polymerization of the one or more monomers and oligomers. The polymerization can take place one or more of i) before winding, ii) during winding and iii) after winding onto an inner liner or a core that can be removed after forming the tank. Heating may optionally be utilized to speed up the polymerization process.

[0018] In a further aspect or embodiment, a gas storage vessel is disclosed, comprising a liner having a hollow body with an internal volume and at least one aperture; and a pressure-resistant structural layer disposed on at least one portion of an outer surface of the liner, wherein the structural layer includes a continuous fiber thermoplastic composite material comprising a continuous fiber and a thermoplastic polymer in which thecontinuous fiber is present at a loading of at least 60% by weight, based on the total weight of thermoplastic polymer and continuous fiber in the structural layer, wherein the thermoplastic polymer is derived from a resin composition including one or more of a cyclic monomer or oligomer including a cyclic group, the resin composition having a viscosity less than 50 cP (mPa-s) or between 1 cP (mPa-s) and 50 cP (mPa-s), at the wetting and / or polymerization temperature of the cyclic monomer or oligomer as measured according to ISO 2555, and wherein the continuous fiber has a length of at least 100 meters.

[0019] In still a further aspect or embodiment, the continuous fiber has a length of at least 1000 meters.

[0020] Still another aspect or embodiment, the continuous fiber loading is at least 70 by weight based on the total weight of continuous fiber and polymer in the structural layer.

[0021] In a further aspect or embodiment, the continuous fiber is wound and / or braided around at least one portion of the liner.

[0022] In an additional aspect or embodiment, the continuous fiber is one or more of a glass fiber, an aramid fiber, a carbon fiber, a basalt fiber, an ultra-high molecular weight polyethylene fiber, a boron fiber, and a natural fiber.

[0023] In a further aspect or embodiment, the thermoplastic polymer has a molecular weight (Mw) that ranges from about 500 to about 2,000,000 g / mol measured according to ASTM by gel permeation chromatography.

[0024] In yet a further aspect or embodiment, the tank has a pressure rating of at least 1500 bars (150 mPa), 700 bars (70 mPa) or 350 bars (25 mPa).

[0025] In a further aspect or embodiment, the cyclic monomer or oligomer includes an amide group.

[0026] In yet a further aspect or embodiment, a gas storage vessel, comprises a pressureresistant structural layer including a continuous fiber thermoplastic composite material comprising a continuous fiber and a thermoplastic polymer in which the continuous fiber is present at a loading of at least 60% by weight, based on the total weight ofthermoplastic polymer and continuous fiber in the structural layer, wherein the thermoplastic polymer is derived from a resin composition including one or more of a cyclic monomer or oligomer including a cyclic group, the resin composition having a viscosity less and 50 cP (mPa-s) or between 1 cP (mPa-s) and 50 cP (mPa-s), at the wetting and / or polymerization temperature of the cyclic monomer or oligomer as measured according to ISO 2555, wherein the continuous fiber has a length of at least 100 meters.

[0027] In still another aspect or embodiment, a method for producing a gas storage vessel comprises the steps of: obtaining a continuous fiber having a length of at least 100 meters; contacting the continuous fiber with a resin composition comprising one or more cyclic monomers and oligomers including a cyclic group that are thermoplastic polymer precursors thereby forming a continuous fiber thermoplastic composite material, wherein the resin composition has a viscosity less than and 50 cP (mPa-s) or between 1 cP (mPa-s) and 50 cP (mPa-s), at the wetting and / or polymerization temperature of the cyclic monomer or oligomer as measured according to ISO 2555; and forming at least a portion of a structural layer of the gas storage vessel with the continuous fiber and cyclic monomer through polymerization of the one or more cyclic monomers and oligomers including a cyclic group, wherein the continuous fiber thermoplastic composite material includes continuous fiber present at a loading of at least 60% by weight, based on the total weight of the thermoplastic polymer and continuous fiber in the structural layer.

[0028] In a further aspect or embodiment, the method further includes the step of winding and / or braiding the continuous fiber thermoplastic composite material around a liner in order to form the structural layer.

[0029] In an additional aspect or embodiment, the method further includes the step of polymerizing the one or more cyclic monomers and oligomers including the cyclic group after the winding step.

[0030] In still another aspect or embodiment, further including the step of removing the liner from the gas storage vessel.

[0031] In an additional aspect or embodiment, further including providing multiple liquid baths in series, wherein one of the baths includes the resin composition and an activator and a second bath includes the resin composition and a catalyst.

[0032] In still another aspect or embodiment, the continuous fibers are routed first through the bath containing the liquid resin-activator composition followed by routing the continuous fibers through the bath including the liquid resin-catalyst composition.

[0033] In yet another aspect or embodiment, the method further includes the step of performing a post treatment step on the gas storage vessel to enhance polymerization and reduce residual stress.

[0034] For the avoidance of doubt, it is understood that while various embodiments or aspects of the invention are described individually, it should be clear that two or more embodiments or aspects can be, and often times are, present in a single device or practiced in a method according to the present invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention will be better understood and other features and advantages will become apparent by reading the detailed description of the invention, taken together with the drawings, wherein:

[0036] FIG. 1 illustrates a gas storage vessel according to one embodiment of the invention;

[0037] FIG. 2 is a schematic view of one embodiment of a manufacturing process for producing a gas storage vessel including structural layer with a continuous fiber thermoplastic composite material according to the invention; and

[0038] FIG. 3 is a process flow diagram describing the primary steps for producing a gas storage vessel of the invention.DETAILED DESCRIPTION OF THE INVENTION

[0039] The present invention includes a gas storage vessel comprising a pressureresistant structural layer including a continuous fiber thermoplastic composite materialwherein the continuous fiber is present at a relatively high loading by weight based on the weight of the thermoplastic polymer and continuous fiber in the structural layer. Methods for preparing gas storage vessels are described herein. Continuous fiber thermoplastic composite materials and methods of their preparation are also detailed herein.

[0040] With reference to FIG. 1 , a gas storage vessel 10 is illustrated. Vessel 10 in some embodiments includes a liner 20 having a hollow body 22 with an internal volume 24 and at least one aperture 26. Vessel 10 includes a gas inlet 40 and a gas outlet 42, each preferably including a valve 44. Optionally, vessel 10 can have only one in let / outlet valve.

[0041] A structural layer 50 including a continuous fiber thermoplastic composite material is disposed on at least a portion of an outer surface of the liner 20 when present. When liner 20 is not present, the internal volume 24 is within structural layer 50. Preferably, the structural layer 50 covers a substantial portion of the liner, for example greater than 80%, greater than 90% or higher. Preferably the structural layer covers substantially all of the liner 20.

[0042] FIG. 2 is a schematic illustration of one embodiment of a manufacturing process for producing a gas storage vessel including a continuous fiber thermoplastic composite material according to the invention.

[0043] Process line 100 is equipped with spools 112 of single fibers, tows or yarns of continuous fibers 110. At least one and preferably multiple strands of the composite fibers 110 are utilized. Process line 100 includes a resin bath 120 including a tank 124 having a resin composition 122 therein, the latter containing polymerizable cyclic monomers and / or oligomers including a cyclic group as well as any additional components that aid in forming the gas storage vessel of the invention.

[0044] The continuous fibers 110 are routed through the liquid resin composition 122 within resin bath 120 whereby continuous fibers are wetted or otherwise impregnated with the resin composition to a desired extent. In preferred embodiments, multiple strands of continuous fibers are individually wetted in the liquid resin composition before being combined. The resin composition 122 in resin bath 120 is maintained at a temperature at or above a melting point of the polymerizable cyclic monomers and / or oligomersincluding a cyclic group. Optionally, multiple liquid baths can be used in a series, one for cyclic monomer and / or oligomer containing an activator if an activator is used and another for cyclic monomer and / or oligomer containing a catalyst The continuous fibers 110 are routed first through the resin-activator bath followed by the resin-catalyst bath. The sequence or order can also be reversed depending on the polymerization kinetics.

[0045] The one or more continuous fibers 110 contacted with the resin composition 122 are removed from the bath and transferred to a guide 130 including a heating device. A heating device can include for example heating elements or wires operatively connected to guide 130 and / or a space heater located within sufficient proximity to the guides which contact the continuous fiber. The guide can traverse a travel path 132 in order to aid in winding the continuous fibers into a gas storage vessel or part of a gas storage vessel. The continuous fibers are wound onto a form 142 such as a liner that becomes part of the gas storage vessel or core such as a mandrel that can be removed from the continuous fiber thermoplastic composite after it is wound into the form of a gas storage vessel 140. The travel path 132 as illustrated is generally lateral to the process flow direction shown in order to aid winding the continuous fiber thermoplastic composite material onto a form 142.

[0046] In some embodiments, the process line 100 includes a vessel manipulating device 144 that is able to move the form 142 in one or more of an X, Y and Z direction to aid in forming the gas storage vessel 140. The tank manipulating device 144 is also able to rotate the form 142 in preferred embodiments. In one embodiment the tank manipulating device includes a winder, or robotic arm or arms that manipulate the form 142.

[0047] The heating device provided with guide 130 aids in polymerizing the one or more cyclic monomers and / or oligomers including a cyclic group of the resin composition contacted with the continuous fibers 110. Suitable temperatures depend on factors such as monomers and oligomers utilized, as well as desired degree of polymerization prior to winding on form 142. Multiple heaters can be used in different locations to enhance polymerization before, during and after the fiber winding process. Optionally the formed pressure vessel can be further heated after winding in an autoclave oven for a period of time to strengthen the mechanical integrity of the pressure vessel. It is preferred to keepthe vessel rotating during the autoclave heating process to prevent unevenness of resin distribution and temperature distribution. The residence time in the autoclave oven depends on the resin chemistry and the desired level of polymerization. It is preferred to have the residence time in the autoclave oven for less than 3 hrs, more preferred less than 2 hours, even more preferred less than 1 hr, and most preferred less than 30 minutes.

[0048] In some embodiments, the process line includes multiple winding devices. The use of multiple winding devices allows for braiding of the continuous fiber thermoplastic material, which enhances strength of the structural layer.

[0049] Methods for producing gas storage vessels utilizing the processing line 100 according to the invention are further described herein below.

[0050] Gas Storage Vessel

[0051] The gas storage vessel 10 of the invention exhibits desirable structural integrity which allows it to be employed as a hydrogen storage vessel or natural gas storage vessel, or a vessel for other gases as desired by the end user. The gas storage vessel has an internal volume generally disposed within a liner 20 having a hollow body, when present, or within the structural layer 50 when a liner 20 is not present. The liner and structural layer 50 have at least one aperture. Two apertures are shown in FIG. 1 in the form of inlet 40 and outlet 42.

[0052] In a preferred embodiment, the gas storage vessel has a cylindrical shape, such as illustrated, with the one or more outlets being placed or located at the ends of the cylinder. The shape of the vessel and thus the shape of the liner, when present, and structural layer disposed on the liner are generally determined by end use. When cylindrical, the gas storage vessel can have a diameter that ranges between 20 cm and 2 m, preferably between 30 cm and 1 m, and more preferably between 35 and 65 cm. The length of the gas storage vessel also depends upon ends uses thereof. Example lengths ranges between 50 cm and 10 m. Generally longer lengths are usually employed for bulk gas transport.

[0053] Operating temperatures of the gas storage vessel vary depending upon end use as well. When utilized for hydrogen storage, the vessel generally has an operating temperature between -60°C to 300°C, more preferably below 200°C, even more preferably below 100°C, and most preferably below 75°C.

[0054] Liner

[0055] A liner 20 is present in one embodiment of the present invention as a form or foundation for the structural layer 50. The liner may also possess properties which contribute to the gas tightness of the storage vessel.

[0056] The liner is preferably formed from a thermoplastic material that can be recycled once storage vessel has reached its end life. Non limiting examples of suitable liner materials include metal; polyolefins such as polypropylene and polyethylene; polystyrene; polyvinyl chloride; ethylene vinyl alcohol; polyamide; polycarbonate; and polyesters such as polyethylene terephthalate and other suitable thermoplastic polymers. The polymeric liner can be produced through injection molding, blow molding and rotational molding and other suitable processes.

[0057] Liner thickness varies depending upon the gas diffusion barrier required by the particular gas being stored within the gas storage vessel and its mechanical integrity needed during winding and polymerization.

[0058] In other embodiments of the invention, the structural layer 50 including the continuous fiber thermoplastic composite material is formed on a removable core that is taken out of the gas storage vessel prior to being put into service, and preferably after the continuous fiber reinforced composite materials have been formed into the structural layer. In a preferred embodiment, the continuous fibers contacted with the composition comprising one or more of cyclic monomers and oligomers with a cyclic group which are thermoplastic polymer precursors are wound onto a supporting removable core, such as a mandrel. After polymerization of the monomers or oligomers, the core is taken out.

[0059] Structural Layer

[0060] The structural layer 50 includes a continuous fiber thermoplastic composite material comprising at least a continuous fiber and a thermoplastic polymer.

[0061] Continuous Fiber

[0062] The structural layer 50 according to the invention includes at least one continuous fiber. Continuous fibers are also known in the art as endless fibers, elongated fibers or the like. For purposes of the invention, the term “continuous fiber” as utilized herein defines a fiber having a length of at least 10 meters, preferably at least 100 meters, more preferably at least 1 ,000 meters, and most preferably at least 10,000 meters. In preferred embodiments the continuous fibers of the invention have a length that ranges between 10 meters and 10,000 meters, and preferably between 100 meters and 1 ,000 meters. The L / D ratio of the fiber is preferably higher than 500.

[0063] The continuous fiber of the present invention may comprise a single fiber, filament and individual strand, or a bundle of multiple strands of continuous fibers and filaments. Bundles of fibers are often considered yarns. Carbon fibers are typically made with 1 to 400,000 thousand (1 k to 400k) individual fibers oriented in the same direction and tightly packed into one tow and wound onto a spool. Both small and large tows of carbon fiber can be used to make pressure vessels of the invention with small tows being preferred for their better mechanical performance. Multiple individual single strands from multiple spools of single fibers, filaments or tows can be individually contacted or wetted with the resin composition comprising one or more of cyclic monomers and oligomers with a cyclic group that are thermoplastic polymer precursors before being wound onto the liner or core together as a bundle or prepreg. It is preferred to have substantially all surface areas of individual fibers wetted in order to increase the strength and physical integrity of the fiber composite.

[0064] The continuous fiber can be cylindrical in shape or non-cylindrical. The cross section of the fiber can be circular or non-circular such as ellipsoidal, triangular, square, rectangular, pentagonal, hexagonal, trapezoidal, parallelogram and other irregular and non-symmetrical shapes.

[0065] The continuous fiber of the present invention may be formed of materials that include, but are not limited to, glass fibers, aramid fibers, carbon fibers, natural fibers, a basalt fiber, ultra-high molecular weight polyethylene, and a boron fiber and combinations thereof.

[0066] In some embodiments, the continuous fiber may be provided with a coating on at least a portion thereof in order to improve compatibility and / or adhesion between the continuous fiber and the cyclic monomers and oligomers with a cyclic group that are thermoplastic polymer precursors before being wound onto the liner or core together as a bundle or prepreg. Suitable coatings are known to those of ordinary skill in the art.

[0067] In an important aspect of the present invention, the continuous fiber is present in the structural layer in a sufficient amount to provide pressure integrity to the gas storage vessel.

[0068] Due to the composition of the structural layer, the continuous fibers are present in an amount of at least 60% by weight, 70% by weight, at least 80% by weight or at least 85% by weight based on the total weight of the continuous fiber and thermoplastic polymer in the structural layer.

[0069] Polymerizable Monomers and Oligomers

[0070] The finished structural layer 50 includes at least one polymer derived from plurality of a) monomers having a cyclic group and b) oligomers including a cyclic group. The monomers and / or oligomers are used to form a resin composition or polymer precursor composition that has a low viscosity at the processing and / or wetting temperature. Different resin compositions require different wetting and polymerization temperatures. A person skilled in the art can find the best or optimal wetting and polymerization temperatures for different cyclic monomers or oligomers with or without polymerization catalysts and / or activators. That said, the viscosity of the resin system has a viscosity less than 50 cP (mPa-s) or between 1 cP (mPa-s) and 50 cP (mPa-s), preferably between 3 cP (mPa-s) and 30 cP (mPa-s) and more preferably between 5 cP (mPa-s) and 25 cP (mPa-s) at the wetting and / or polymerization temperature of the cyclic monomer oroligomer as measured according to ISO 2555 (2024). Examples of the viscosity of some of the cyclic monomers or oligomers are listed in Table 1 .Table 1

[0071] Examples of cyclic monomer or oligomer systems are AP-Nylon and NYRIM systems from Bruggemann. AP-Nylon is a reactive system with cyclic monomer being caprolactam with very low viscosity above its melting point (79°C). Activator and catalyst come in two separate packages. The advantage of such a system is its low wetting and polymerization temperature (typically from 100 to 160°C). NYRIM system is also caprolactam based but with different amount of elastomer component built into its backbone to improve is impact resistance.

[0072] The resin composition including the specific monomers and / or oligomers is contacted with, imbibes, or wets the continuous fiber. Thereafter, polymerization is performed, with or without a suitable catalyst and activator. The low viscosity of the resin composition allows for the relatively high loading of fibers compared to the weight of the polymer produced resin composition. After polymerization, the resulting polymer has a relatively high number average molecular weight (Mn) that ranges generally from about 500 to about 2,000,000, preferably from 2000 to about 500,000, and more preferably from 10,000 to 100,000 g / mol as measured by gel permeation chromatography (GPC).

[0073] The number average molecular weight and distribution of any type of polymer described in this application are measured by gel permeation chromatography (GPC). The polymer is dissolved in a suitable solvent, such as THF, (typically 0.001-0.010 wt.%), and an appropriate quantity is injected into a GPC device. One suitable GPC device isavailable from Waters of Milford, MA as a Waters Breeze Dual Pump LC. The GPC analysis is performed at an appropriate elution rate (1 to 10 mL / min). The molecular weight distribution is characterized by the signals from UV and refractive index detectors, and number average molecular weights are calculated using a calibration curve generated from a series of narrow molecular weight distribution polystyrenes with peak molecular weights of 500 to 1 ,000,000 as standard.

[0074] Examples of suitable monomers and oligomers include, but are not limited to, caprolactam, lactone, caprolactone (i.e. cyclic poly(caprolactone) oligomer), a cyclic polyester oligomer, a cyclic polyolefin oligomer, a cyclic poly(phenylene oxide) oligomer, a cyclic poly(phenylene sulfide) oligomer, a cyclic polyphenylsulfone oligomer, a cyclic polyetherimide oligomer, and / or co-oligomers thereof. In some embodiments, the cyclic oligomer contains or is a macrocyclic polyester oligomer, for example, a macrocyclic poly(butylene terephthalate) oligomer, a macrocyclic poly(ethylene terephthalate) oligomer, and / or co-oligomers thereof. Combinations of the monomers and oligomers may be utilized in various embodiments.

[0075] As used herein, a "macrocyclic polyester oligomer" (MPO) is understood to mean a macrocyclic oligomer containing structural repeat units having an ester functionality. A macrocyclic polyester oligomer typically refers to multiple molecules of one specific repeat unit formula. However, a macrocyclic polyester oligomer also may include multiple molecules of different or mixed formulae having varying numbers of the same or different structural repeat units. In addition, a macrocyclic polyester oligomer may be a co-polyester or multi-component polyester oligomer, i.e., an oligomer having two or more different structural repeat units having ester functionality within one cyclic molecule.

[0076] The thermoplastic polymer derived from cyclic monomers and / or oligomers offers processing advantages of a thermoset, having low viscosity above the monomer or oligomer’s melting point which is good for fiber wetting, while retaining material properties of a thermoplastic once polymerized, enabling the production of a robust thermoplastic structural layer including the continuous fiber.

[0077] The resulting continuous fiber thermoplastic composite has very high strength, in addition to excellent toughness due to the high molecular weight of the thermoplastic resin. In addition, the structural layer, and preferably gas storage vessel, is fully recyclable as the thermoplastic resin can be melted down and re-used.

[0078] Other Components

[0079] The structural layer may optionally include other components that impart beneficial properties to the gas storage tank formed therewith. Example components include, but are not limited to, heat stabilizers, flame retardants, colorants, lubricants, UV stabilizers, impact modifiers, nucleating agents, antioxidants, activators, and catalysts.

[0080] Polymerization catalysts employed in certain embodiments of the invention are capable of catalyzing the polymerization of the one or more of cyclic monomers and oligomers with a cyclic group. Organotin and organotitanate compounds are preferred catalysts, although other catalysts and activators may be used as desired.

[0081] Depending upon the properties desired, the amounts of each optional ingredient can vary.

[0082] Method for Producing the Gas Storage Vessel and Structural Layer Thereof

[0083] The method for producing a gas storage vessel includes the steps of obtaining a continuous fiber having a desired length and contacting the continuous fiber with a composition comprising one or more cyclic monomers and oligomers including a cyclic group which are thermoplastic polymer precursors thereby forming a continuous fiber thermoplastic composite material. In one embodiment, the contacting of the continuous fiber with the monomers and / or oligomers involves providing a dip tank or trough including the monomer or oligomer resin composition. The continuous fiber is preferably unwound from a spool or creel and passed through the resin composition bath in the dip tank. Thereby, the continuous fiber is contacted with the resin system which wets or otherwise coats, or the like, the continuous fiber to a desired extent.

[0084] The resin system or resin composition is maintained at a temperature at, or preferably above, the melting point of the one or more cyclic monomers and oligomerswith a cyclic group. Accordingly, temperature of the resin composition will vary depending on particular monomers and / or oligomers selected for use.

[0085] Thereafter, the continuous fiber thermoplastic composite material is applied to the liner. Preferably the composite material is wound around the liner so that a desired portion thereof is covered. As described herein, the winding can be, but is not limited to, a circumferential winding, a longitudinal winding, a spiral winding, a lateral winding or combinations thereof. During winding or once the desired configuration of composite material on the liner has been achieved, the monomers and / or oligomers are polymerized. Polymerization temperature depends upon the monomers utilized. That said, polymerization temperatures generally range from about 50°C to about 300°C, preferably from about 100°C to about 250°C, more preferably from 100°C to 200°C, and most preferably from 120°C to 160°C. Multiple heaters can be used in different locations to enhance polymerization before, during and after the fiber winding process. Optionally the formed pressure vessel can be further heated after winding in an autoclave oven for a period of time to strengthen the mechanical integrity of the pressure vessel. It is preferred to keep the vessel rotating during the autoclave heating process to prevent unevenness of resin distribution and temperature distribution. The residence time in the autoclave oven depends on the resin chemistry and the desired level of polymerization. It is preferred to have the residence time in the autoclave oven for less than 3 hrs, more preferred less than 2 hours, even more preferred less than 1 hr, and most preferred less than 30 minutes.

[0086] In view of the above, FIG. 3 presents a process flow diagram describing the primary steps for producing a gas storage vessel of the invention.

[0087] In step 200, multiple single fibers or yarns enter a molten resin tank or extruder die for contacting or wetting by the resin composition in the tank including one or more cyclic monomers and oligomers with a cyclic group, at or above the melting point thereof. Optionally, multiple liquid baths can be used in series, one for cyclic monomer and / or oligomer with an activator if the activator is used, another one for cyclic monomer and / or oligomer with a catalyst. The continuous fibers are routed first through the resin-activatorbath followed by the resin-catalyst bath. The sequence or order can also be reversed depending on the polymerization kinetics.

[0088] In step 210, fiber bundles are formed by combining multiple single fibers or yarns. Polymerization is also started.

[0089] In step 220, a position guide moves the resin-infused fiber bundles or tape under heating to speed up polymerization.

[0090] In step 230, the fiber bundles or tape(s) are wound and / or braided onto a core or liner under heating.

[0091] In step 240, post treatment of the pressure tank is optionally performed if needed to enhance polymerization and reduce residual stress.

[0092] Step 250 involves quality inspection and testing of the produced gas storage vessel.

[0093] For the avoidance of doubt, the compositions and methods of the present invention encompass all possible combinations of the components, including various ranges of said components, disclosed herein. It is further noted that the term ‘comprising’ does not exclude the presence of other elements. However, it is also to be understood that a description of a product comprising certain components also discloses a product consisting of these components. Similarly, it is also to be understood that a description on a process comprising certain steps also discloses a process consisting of these steps.

[0094] In accordance with the patent statutes, the best mode and preferred embodiment have been set forth; the scope of the invention is not limited thereto, but rather by the scope of the attached claims.

Claims

WHAT IS CLAIMED IS:1 . A gas storage vessel, comprising: a liner having a hollow body with an internal volume and at least one aperture; and a pressure-resistant structural layer disposed on at least one portion of an outer surface of the liner, wherein the structural layer includes a continuous fiber thermoplastic composite material comprising a continuous fiber and a thermoplastic polymer in which the continuous fiber is present at a loading of at least 60% by weight, based on the total weight of thermoplastic polymer and continuous fiber in the structural layer, wherein the thermoplastic polymer is derived from a resin composition including one or more of a cyclic monomer or oligomer including a cyclic group, the resin composition having a viscosity less than 50 cP (mPa-s) or between 1 cP (mPa-s) and 50 cP (mPa-s), at the wetting and / or polymerization temperature of the cyclic monomer or oligomer as measured according to ISO 2555, and wherein the continuous fiber has a length of at least 100 meters.

2. The vessel according to claim 1 , wherein the continuous fiber has a length of at least 1000 meters.

3. The vessel according to claim 1 or claim 2, wherein the continuous fiber loading is at least 70% by weight.

4. The vessel according to any of claims 1 to 3, wherein the continuous fiber is wound and / or braided around at least one portion of the liner.

5. The vessel according to any of claims 1 to 4, wherein the continuous fiber is one or more of a glass fiber, an aramid fiber, a carbon fiber, a basalt fiber, an ultra-high molecular weight polyethylene fiber, a boron fiber, and a natural fiber.

6. The vessel according to any of claims 1 to 5, wherein the thermoplastic polymer has a molecular weight (Mw) that ranges from about 500 to about 2,000,000 g / mol measured according to ASTM by gel permeation chromatography.

7. The vessel according to any of claims 1 to 6, wherein the tank has a pressure rating of at least 350 bars (35 mPa).

8. The vessel according to any of claims 1 to 7, wherein the cyclic monomer or oligomer includes an amide group.

9. A gas storage vessel, comprising: a pressure-resistant structural layer including a continuous fiber thermoplastic composite material comprising a continuous fiber and a thermoplastic polymer in which the continuous fiber is present at a loading of at least 60% by weight, based on the total weight of thermoplastic polymer and continuous fiber in the structural layer, wherein the thermoplastic polymer is derived from a resin composition including one or more of a cyclic monomer or oligomer including a cyclic group, the resin composition having a viscosity less and 50 cP (mPa-s) or between 1 cP (mPa-s) and 50 cP (mPa-s), at the wetting and / or polymerization temperature of the cyclic monomer or oligomer as measured according to ISO 2555, wherein the continuous fiber has a length of at least 100 meters.

10. The vessel according to claim 9, where the continuous fiber has a length of at least 1000 meters.

11. The vessel according to claim 9 or claim 10, wherein the continuous fiber loading is at least 70% by weight.

12. The vessel according to any of claims 9 to 11 , wherein the continuous fiber is wound and / or braided around at least one portion of the liner.

13. The vessel according to any of claims 9 to 12, wherein the continuous fiber is one or more of a glass fiber, an aramid fiber, a carbon fiber, a basalt fiber, an ultra-high molecular weight polyethylene fiber, a boron fiber, and a natural fiber.

14. The vessel according to any of claims 9 to 13, wherein the thermoplastic polymer has a molecular weight (Mw) that ranges from about 500 to about 2,000,000 g / mol measured according to ASTM by gel permeation chromatography.

15. The vessel according to any of claims 9 to 14, wherein the tank has a pressure rating of at least 350 bars (35 mPa).

16. The vessel according to any of claims 9 to15, wherein the cyclic monomer or oligomer includes an amide group.

17. A method for producing a gas storage vessel, comprising the steps of: obtaining a continuous fiber having a length of at least 100 meters; contacting the continuous fiber with a resin composition comprising one or more cyclic monomers and oligomers including a cyclic group that are thermoplastic polymer precursors thereby forming a continuous fiber thermoplastic composite material, wherein the resin composition has a viscosity less than and 50 cP (mPa-s) or between 1 cP (mPa-s) and 50 cP (mPa-s), at the wetting and / or polymerization temperature of the cyclic monomer or oligomer as measured according to ISO 2555; and forming at least a portion of a structural layer of the gas storage vessel with the continuous fiber and cyclic monomer through polymerization of the one or more cyclic monomers and oligomers including a cyclic group, wherein the continuous fiber thermoplastic composite material includes continuous fiber present at a loading of at least 60% by weight, based on the total weight of the thermoplastic polymer and continuous fiber in the structural layer.

18. The method according to claim 10, wherein the method further includes the step of winding and / or braiding the continuous fiber thermoplastic composite material around a liner in order to form the structural layer.

19. The method according to claim 11 , further including the step of polymerizing the one or more cyclic monomers and oligomers including the cyclic group after the winding step.

20. The method according to claim 18, further including the step of removing the liner from the gas storage vessel.

21. The method according to claim 17, further including providing multiple liquid baths in series, wherein one of the baths includes the resin composition and an activator and a second bath includes the resin composition and a catalyst.

22. The method according to claim 21 , wherein the continuous fibers are routed first through the bath containing the liquid resin-activator composition followed by routing the continuous fibers through the bath including the liquid resin-catalyst composition.

23. The method according to claim 18, further including the step of performing a post treatment step on the gas storage vessel to enhance polymerization and reduce residual stress.

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