Hollow Rotomolded Products

Abstract

The hollow rotomolded product has an interior wall defining the interior of the hollow rotomolded product and an integrally formed structure with the interior wall, the integrally formed structure protruding into the interior of the hollow rotomolded product, and the hollow rotomolded product is formed from a first layer comprising one or more thermoplastic polymers and a second layer comprising one or more fibrous materials.

Description

[Technical Field]

[0001] The present invention relates generally to rotomolded (rotationally molded) products. Specifically, embodiments of the present invention relate to hollow composite containers having at least a thermoplastic layer and a fibrous layer. Aspects of the present invention also relate to the manufacture of containers utilizing a rotational molding process. The containers may find use in the storage and transport of powders, liquids, gases, and cryogenic materials, particularly hazardous materials. [Background technology]

[0002] Tanks are widely used for the transportation of materials such as liquids, gases, powders, etc., both hazardous and non-hazardous. For the transportation of hazardous materials, tanks must meet many local and international regulations.

[0003] Tanks for the transport of hazardous materials are generally constructed from metal to provide structural strength and are lined with a resilient liner to protect the metal from the corrosive properties of the tank contents.

[0004] However, lined metal tanks have many drawbacks, including the excessive weight of the tank, which increases transportation costs, and the possibility that the liner material may deteriorate or become detached from the interior wall of the metal tank over time due to contact with the tank contents, requiring repair or replacement of the liner.

[0005] Additionally, a problem that arises with material transportation, especially when transporting liquids, is that liquids have inertia and, in their fluid state, tend to continue moving in the same direction as the transport vehicle is moving. During starting, stopping, and turning, surges and sloshes of liquid within the tank make the vehicle more difficult or unstable to control and place significant stresses on the tank walls. Traditionally, one way to address this problem is by installing baffles or surge plates within the tank. This generally involves attaching baffles to the tank before assembling the tank head, or attaching baffles in smaller segments after the tank head through manholes or other openings, and then fastening the plates in place within the tank (e.g., by welding or other mechanical fastening means). These plates provide a barrier to liquid movement, improving stability and reducing forces exerted on the walls.

[0006] It would be desirable to provide an improved tank that overcomes or ameliorates one or more of the above-mentioned shortcomings or problems of the prior art, or at least provides a useful alternative option.

[0007] The reference to any prior art herein is not an admission or suggestion that this prior art forms part of the common general knowledge in any jurisdiction, or that this prior art would be understood by, considered relevant, and / or could reasonably be expected to be combined with other pieces of prior art by a person skilled in the art. Summary of the Invention

[0008] In a first aspect, the present invention provides a hollow rotomolded product having an interior wall defining an interior of the hollow rotomolded product and a structure integrally formed with the interior wall, the integrally formed structure protruding into the interior of the hollow rotomolded product, the hollow rotomolded product being formed from a first layer comprising one or more thermoplastic polymers and a second layer comprising one or more fibrous materials.

[0009] Preferably, one or more fibrous materials are at least partially infiltrated with one or more thermoplastic polymers. Thus, an advantageous multilayer structure is produced, including a substantially thermoplastic inner / first layer and a substantially fibrous second layer. The fibrous second layer can function as a suitable tie layer adapted to allow additional layers to be formed therewith. The thermoplastic inner layer can function as a barrier layer that is substantially impermeable to materials that contact the interior of the hollow rotomolded product. Furthermore, the integrally formed structure of the hollow rotomolded product is seamlessly integrated into the hollow rotomolded product having this same multilayer structure. Thus, there are no welds or bond lines between the hollow rotomolded product and the integrally formed structure.

[0010] The rotomolded product when having only the first and second layers may be referred to herein as a thermoplastic polymer / fiber material composite (or the like).

[0011] In embodiments, the hollow rotomolded product includes at least one cavity extending into the interior of the hollow rotomolded product. For example, the at least one cavity may extend through the outer wall of the thermoplastic polymer / fiber material composite. The cavity may be formed in the rotomolded product by a protruding portion of a mold used to form the integrally formed structure of the rotomolded product. Thus, in such embodiments, the integrally formed structure is of a shape and configuration substantially corresponding to the protruding portion of the mold. Furthermore, the cavity may have an interior surface profile substantially corresponding to the exterior surface profile of the integrally formed structure.

[0012] In embodiments, a stiffener is disposed within the cavity. The stiffener can be configured to resist internal and / or external loads experienced by the hollow rotomolded product, particularly the integrally formed structure, under operating conditions. Examples of internal and external loads that may be experienced include one or more of: a pressure differential across the wall between the integrally formed structure and the exterior of the hollow rotomolded product; a pressure differential across the wall between the integrally formed structure and the interior of the hollow rotomolded product; loads due to movement of contents (e.g., fluids) within the hollow rotomolded product resulting from moving the hollow rotomolded product, which may be applied axially, radially, laterally, vertically, and / or tangentially to the hollow rotomolded product; and loads imparted to the hollow rotomolded product, as well as the integrally formed structure, from external structural supports and other external loads as a result of moving the hollow rotomolded product. In one example, the stiffener is configured to stiffen and / or strengthen the hollow rotomolded product. Preferably, the stiffener is configured to stiffen and / or strengthen at least a portion of the integrally formed structure, for example, the stiffener may be configured to stiffen and / or strengthen the base of the integrally formed structure.

[0013] The reinforcement may take any form suitable for stiffening and / or strengthening the integrally formed structure. In one embodiment, the reinforcement may be a curable material, such as a foam or other curable polymer. The curable material may be injected into the cavity and allowed to harden. In an alternative embodiment, the hollow rotomolded product may include a cover connected to the outer wall of the thermoplastic polymer / fiber material composite configured to fluidly seal the cavity, and the reinforcement is pressurized gas injected into the cavity after the cavity is fluidly sealed by the cover. In a further alternative embodiment, the reinforcement may be a structural skin. The structural skin may be secured to the cavity by any suitable means, for example, an adhesive. The stressed skin is preferably formed from one or more fiber materials wet-laid into the cavity. For example, the stressed skin may be a carbon fiber reinforced polymer and core sandwich wet-laid into the cavity.

[0014] In a further alternative embodiment, the reinforcement may include a brace structure adapted to be connected within the cavity. Preferably, the brace structure includes a plurality of brace elements fixed within the cavity and arranged to stiffen and / or strengthen the integrally formed structure. In one embodiment, the plurality of brace elements are fixedly arranged in a spaced apart relationship relative to one another, and one or more of the brace elements extend in a different direction than the other brace elements. In an embodiment, one or more of the brace elements may extend in a direction at an angle relative to the other brace elements. The angle may be from about 1° to about 90° (e.g., one or more brace elements may extend substantially perpendicular to the other brace elements). Preferably, the plurality of brace elements are arranged in a substantially lattice frame structure adapted to allow connection of the brace structure to a cavity. The brace elements may be of a substantially beam-like configuration. One or more of the brace elements may include an attachment portion formed or secured along a portion of the one or more brace elements, e.g., one or each longitudinal side, the attachment portion being shaped to allow connection of the brace element to a cavity. In a preferred form, the brace elements may be formed from a wet-laid fiber-reinforced polymer (using a suitable thermosetting resin). The brace elements may be secured using an adhesive (e.g., a thermosetting adhesive). The brace structure may be formed from one or more reinforcing materials, including wood, metal, polymer, and composite materials.

[0015] In a preferred embodiment, the reinforcement includes a structural skin secured within the cavity and a brace structure secured to the structural skin. Advantageously, securing the brace structure to the structural skin will facilitate better connection of the brace structure to the cavity. The brace structure may be secured to the structural skin using a suitable adhesive.

[0016] In embodiments, the reinforcement material may be formed from any combination of the reinforcements mentioned above.

[0017] The rotomolded product may include a cover connected to an outer wall of the thermoplastic polymer / fiber material composite, the cover configured to shield the reinforcement material.

[0018] In an embodiment, the integrally formed structure that protrudes into the interior of the hollow rotomolded product is one or more baffles. The one or more baffles can each be in the form of a plate that protrudes into the interior of the hollow rotomolded product. For example, the one or more baffle plates can be in the form of an orifice plate that protrudes into the interior of the hollow rotomolded product. In an alternative embodiment, the one or more baffles can each be substantially leaf-shaped and protrude into the interior of the hollow rotomolded product.

[0019] In an embodiment, the integrally formed structures projecting into the interior of the hollow rotomolded product are arranged to extend in a direction substantially parallel to the longitudinal axis of the hollow rotomolded product. In one example, the integrally formed structures projecting into the interior of the hollow rotomolded product are one or more baffles, each of which is arranged to extend in a direction substantially parallel to the longitudinal axis of the hollow rotomolded product. In another embodiment, the integrally formed structures projecting into the interior of the hollow rotomolded product are arranged to extend in a direction substantially perpendicular to the longitudinal axis of the hollow rotomolded product (e.g., extend in a direction substantially parallel to the transverse direction of the hollow rotomolded product). In one example, the integrally formed structures projecting into the interior of the hollow rotomolded product are one or more baffles, each of which is arranged to extend in a direction substantially perpendicular to the longitudinal axis of the hollow rotomolded product. In embodiments, the integrally formed structures projecting into the interior of the hollow rotomolded product are positioned to extend radially about the hollow rotomolded product. In one example, the integrally formed structures projecting into the interior of the hollow rotomolded product are one or more baffles, each of the one or more baffles being positioned to extend radially about the hollow rotomolded product.

[0020] In embodiments, the baffles extend from circumferentially spaced locations on the inner wall into the hollow rotomolded product. In embodiments, the baffles extend from substantially opposing locations on the inner wall into the hollow rotomolded product. For example, a pair of baffles can extend from substantially opposing locations on the inner wall into the hollow rotomolded product. The baffle (or pair of baffles) can be diametrically opposed. Preferably, the circumferentially spaced baffles extend into the hollow rotomolded product and toward each other, thereby forming a gap between them when the hollow rotomolded product is viewed in cross section. In other words, the gap is defined as the area not covered by the baffles when the hollow rotomolded product is viewed in cross section. In one example, the gap is substantially V-shaped when the hollow rotomolded product is viewed in cross section. In embodiments in which the hollow rotomolded product extends generally horizontally (e.g., parallel to the ground), the narrow end of the V-shaped gap is preferably disposed at the bottom end of the hollow rotomolded product and the wide end of the V-shaped gap is disposed at the top end of the hollow rotomolded product. Preferably, a pair of baffles extend toward each other and form a substantially V-shaped gap therebetween. In an alternative embodiment, the gap is substantially rectangular when the hollow rotomolded product is viewed in cross section. In another embodiment, a single baffle may extend inward and form the gap when the hollow rotomolded product is viewed in cross section. For example, if the baffle is in the form of an orifice plate, the gap may be defined by the orifice of the orifice plate. Alternatively, the gap may be defined by the space between the baffle and the interior wall.

[0021] In embodiments, the gaps may define from about 5% to about 95% of the total cross-section of the interior. For example, the gaps may define from about 5% to about 50% of the total cross-section of the interior, or from about 5% to about 30% of the total cross-section of the interior.

[0022] In one embodiment, the baffles may be arranged substantially symmetrically about an axis perpendicular to the longitudinal axis of the hollow rotomolded product. For example, a pair of baffles may be arranged substantially symmetrically about an axis perpendicular to the longitudinal axis of the hollow rotomolded product. In another embodiment, the baffles may be arranged substantially symmetrically about an axis parallel to the longitudinal axis of the hollow rotomolded product. For example, a pair of baffles may be arranged substantially symmetrically about an axis parallel to the longitudinal axis of the hollow rotomolded product. In a further embodiment, the baffles may be arranged substantially asymmetrically about an axis parallel to the longitudinal axis of the hollow rotomolded product. For example, a pair of baffles may be arranged substantially asymmetrically about an axis parallel to the longitudinal axis of the hollow rotomolded product. In yet a further embodiment, the baffles may be arranged substantially asymmetrically about an axis perpendicular to the longitudinal axis of the hollow rotomolded product. For example, a pair of baffles may be disposed substantially asymmetrically about an axis perpendicular to the longitudinal axis of the hollow rotomolded article.

[0023] In an embodiment, a plurality of spaced-apart baffles are disposed along the length of the hollow rotomolded product, e.g., along a direction parallel to the longitudinal axis of the hollow rotomolded product. Preferably, a plurality of spaced-apart pairs of baffles are disposed along the length of the hollow rotomolded product. In another embodiment, a plurality of baffles are provided spaced around the periphery or circumference of the hollow rotomolded product.

[0024] While various baffle arrangements are described above, it will be understood that different baffle arrangements and different baffle shapes may also be employed. Furthermore, any combination of the above baffle arrangements and / or shapes may be utilized in any given embodiment.

[0025] The or each baffle may include a first baffle wall and a second baffle wall, each extending from an inner wall of the hollow rotomolded product into the hollow rotomolded product and meeting at a baffle tip. The first and second baffle walls may define substantially planar surfaces disposed in a substantially transverse cross-section of the hollow rotomolded product (e.g., the first and second baffle walls may be substantially parallel). In an alternative embodiment, the first and second baffle walls may be angled relative to one another, thereby defining a substantially U-shaped baffle when the baffle is viewed in cross-section. In another embodiment, the first and second baffle walls each extend from an inner wall of the hollow rotomolded product into the hollow rotomolded product and meeting at a substantially curved baffle tip. In an alternative embodiment, the first baffle wall and the second baffle wall each extend from an inner wall of the hollow rotomolded product into the interior of the hollow rotomolded product and meet at a substantially flat baffle tip.

[0026] In another embodiment, the or each baffle includes tip transition portions between the first baffle wall and the baffle tip, and between the second baffle wall and the baffle tip. The tip transition portions are preferably substantially curved, thereby defining smooth transition profiles between the first baffle wall and the baffle tip, and between the second baffle wall and the baffle tip. The radius of curvature of the tip transition portions may range from about 2 mm to about 500 mm, or from about 5 mm to about 100 mm. The radius of curvature of the baffle tips, if substantially curved, may range from about 2 mm to about 500 mm, or from about 5 mm to about 100 mm.

[0027] In another embodiment, the or each baffle includes a base transition portion between the inner wall and the base of the baffle (e.g., between the inner wall and the first baffle wall, and between the inner wall and the second baffle wall). Preferably, the base transition portion is substantially curved. The radius of curvature of the base transition portion preferably ranges from about 2 mm to 500 mm, or from about 5 mm to about 100 mm.

[0028] In embodiments, the exterior surface profile of the or each baffle is substantially continuous with the interior wall, i.e., there is a seamless transition between the interior wall, first wall, second wall, and baffle tip of the hollow rotomolded product. In preferred embodiments, the base transition portion and tip transition are all substantially curved. Advantageously, in such embodiments, the rotomolded product can be more easily formed during rotational molding due to the provision of a suitable curved surface profile that allows for improved contact time between the mold used to form the hollow rotomolded product and the one or more thermoplastic polymers and one or more fibrous materials. As a result, a more consistent bond between the one or more fibrous materials and the one or more thermoplastic polymers is achieved.

[0029] The or each baffle may partially define a boundary between adjacent sections of the hollow rotomolded product, in such an embodiment, the gap is adapted to maintain fluid communication between adjacent sections of the hollow rotomolded product.

[0030] In embodiments, the hollow rotomolded product includes a recess disposed around the periphery of the cavity or cavities. The recess may extend through the outer wall of the thermoplastic polymer / fiber material composite. The recess is configured to facilitate engagement of one or more subsequent layers with the first and second layers. For example, the recess may be configured to facilitate engagement between the hollow thermoplastic polymer / fiber material composite and one or more subsequent layers. The recess and the cavity may be coaxial. The recess preferably includes a base adapted to facilitate engagement of the thermoplastic polymer / fiber material composite with one or more subsequent layers. The base may include an engagement surface upon which at least a portion of the one or more subsequent layers may be supported. The engagement surface may be substantially planar. The recess may have a depth of between about 1 mm and about 200 mm, or between about 1 mm and about 100 mm, or between about 5 mm and about 50 mm. The recess may further include a sidewall. The sidewall preferably tapers inward from the outer wall of the thermoplastic polymer / fiber material composite to the base of the recess. Advantageously, the inwardly tapered sidewalls facilitate improved introduction and engagement of one or more subsequent layers with the thermoplastic polymer / fiber material composite.

[0031] The one or more thermoplastic polymers in the inner layer may include one or more of ethylene homopolymer, ethylene copolymer, propylene homopolymer, propylene copolymer, fluoropolymer, polyvinyl chloride, polyvinylidene chloride, polyaryletherketone (e.g., polyetheretherketone), and polyamide.

[0032] In an embodiment, the one or more fibrous materials of the second layer include one or more of ceramic fibers and polymeric fibers.

[0033] The one or more ceramic fibers may include one or more of glass fibers, carbon fibers, and basalt fibers, or precursors thereof.

[0034] The one or more polymeric fibers may include one or both of a synthetic polymer and a natural polymer.

[0035] The one or more polymeric fibers may comprise one or more of a polyamide and a polyolefin. Suitable polyolefins include polyethylene and polypropylene.

[0036] In an embodiment, the one or more fibrous materials comprise one or more textured woven materials.

[0037] In embodiments, the one or more engineered textile materials may include one or more of a woven material, a knit material, and a braided material.

[0038] The one or more textured woven materials comprise plied yarns. In embodiments, the spacing between at least some of the yarns of the fibrous material of the second layer is from about 0.01 micrometers to about 5000 micrometers, or from about 0.1 micrometers to about 5000 micrometers, or from about 1 micrometer to about 5000 micrometers, or from about 10 micrometers to about 5000 micrometers.

[0039] In an embodiment, the hollow rotomolded product includes a third layer including one or more carbon, glass, aramid, and basalt filaments and a plurality of filaments selected from one or more thermosetting polymers, the second layer being disposed between the first and third layers, and the one or more fibrous materials being at least partially infiltrated with both one or more thermoplastic polymers and one or more thermosetting polymers. Preferably, the third layer is provided on the exterior of the outer wall of the thermoplastic polymer / fibrous material composite. In such an embodiment, the plurality of filaments engage with the engagement surface of the recess. In an alternative example, the third layer may be disposed on a cover connected to the cavity.

[0040] In another embodiment, the hollow rotomolded product includes a third layer including a plurality of filaments selected from one or more of carbon, glass, aramid, and basalt filaments and one or more thermosetting polymers, the third layer being manually hand-laid onto the second layer, and the one or more fibrous materials being at least partially infiltrated with both the one or more thermoplastic polymers and the one or more thermosetting polymers. Preferably, the third layer is provided on the exterior of the outer wall of the thermoplastic polymer / fibrous material composite.

[0041] In another embodiment, the hollow rotomolded product includes a third layer including a plurality of filaments selected from one or more of carbon, glass, aramid, and basalt filaments and one or more thermosetting polymers, the third layer being vacuum infused into the second layer, and the one or more fibrous materials being at least partially infiltrated with both the one or more thermoplastic polymers and the one or more thermosetting polymers. Preferably, the third layer is provided outside an outer wall of the thermoplastic polymer / fibrous material composite.

[0042] In embodiments, the one or more thermosetting polymers of the third layer include one or more of vinyl esters, bismaleimides, polyesters, polyacrylates, epoxies, and polyurethanes.

[0043] In embodiments, the plurality of filaments of the third layer have a filament diameter of from about 0.1 micrometers to about 500 micrometers, or from about 0.1 micrometers to about 100 micrometers, or from about 0.1 micrometers to about 50 micrometers, or from about 1 micrometer to about 20 micrometers.

[0044] In embodiments, the plurality of filaments of the third layer are in the form of one or more of wound filaments, a fabric section comprising a plurality of threads, braided yarns, and chopped fibers.

[0045] In an embodiment, the first layer has a thickness of about 0.1 mm to about 50 mm, the second layer has a thickness of about 0.1 mm to about 5 mm, and the third layer has a thickness of about 0.1 mm to about 1000 mm.

[0046] In an embodiment, the thermoplastic polymer is embedded in the interstices between the threads of the fibrous material of the second layer.

[0047] In an embodiment, the thermoplastic polymer is embedded within the structure of the individual threads of the fibrous material of the second layer.

[0048] In an embodiment, tendrils of fibrous material of the second layer extend from the surface of the yarn into the first layer.

[0049] In embodiments, the thermoplastic polymer does not completely infiltrate the thickness of the fibrous layer, i.e., at least a portion of the surface of the fibrous layer is not completely penetrated by the thermoplastic polymer. Preferably, substantially all of the surface of the fibrous layer is not completely penetrated by the thermoplastic polymer.

[0050] In a preferred form, the hollow rotomolded product is a hollow composite container (or thermoplastic polymer / fiber material composite container), and the integral structure is configured to reduce surge forces experienced by the hollow composite container during use. The integral structure may be further configured to reduce surge forces experienced by any structure to which the hollow composite container is attached.

[0051] The hollow composite container (or thermoplastic polymer / fiber material composite container) may be generally spherical, cylindrical, spherocylindrical, rectangular, or of any other shape commonly known in the art.

[0052] In a second aspect, the present disclosure provides a method of producing a hollow composite container, the method comprising: applying one or more fibrous materials to an interior surface of a hollow mold, the hollow mold including structures protruding into the interior of the mold; heating and rotating a hollow mold in the presence of one or more thermoplastic polymers within the hollow mold such that the thermoplastic polymers melt and at least partially infiltrate the fibrous material; cooling the mold so that the thermoplastic polymer solidifies; and removing the hollow thermoplastic polymer / fiber material composite container from the mold, the hollow thermoplastic polymer / fiber material composite container having an integrally formed structure projecting into the interior of the container.

[0053] Advantageously, the present invention allows for the production of a hollow composite container having a substantially thermoplastic inner / first layer with a substantially fibrous second layer. The fibrous second layer can function as a suitable tie layer adapted to allow additional layers to be formed therewith. The thermoplastic inner layer can function as a barrier layer that is substantially impermeable to materials that contact the interior of the container. Furthermore, the integrally formed structure of the container is seamlessly integrated into this same multi-layered container. Therefore, there are no welds or bond lines between the container and the integrally formed structure.

[0054] It should be understood that references to a thermoplastic polymer / fibrous material composite container are references to a hollow composite container when it has only the fibrous material and thermoplastic polymer layers in question.

[0055] In an embodiment, the method comprises one or more of the following steps: applying a plurality of filaments selected from one or more of carbon, glass, aramid, and basalt filaments to the exterior of the hollow thermoplastic polymer / fiber material composite container, wherein prior to application, the plurality of filaments are at least partially wetted with one or more thermosetting polymers; applying a plurality of filaments selected from one or more of carbon, glass, aramid, and basalt filaments to the exterior of a hollow thermoplastic polymer / fiber material composite container, followed by applying one or more thermosetting polymers; The method further includes applying one or more thermosetting polymers to the exterior of the hollow thermoplastic polymer / fiber material composite container, followed by applying a plurality of filaments selected from one or more of carbon, glass, aramid, and basalt filaments.

[0056] Advantageously, providing this additional layer on the exterior of the hollow thermoplastic polymer / fiber material composite container results in increased strength of the hollow composite container. The fibrous layer of the hollow thermoplastic polymer / fiber material composite container facilitates bonding of this additional layer thereto. Preferably, application of this additional layer results in the one or more fibrous materials being at least partially infiltrated with both one or more thermoplastic polymers and one or more thermosetting polymers.

[0057] In an embodiment, the step of applying one or more fiber materials to the inner surface of the hollow mold includes fixing the one or more fiber materials to the inner surface of the hollow mold. The hollow mold may include fixing means (e.g., a fixing device) for fixing the one or more fiber materials to the inner surface of the hollow mold. In an embodiment, the method further includes holding the one or more fiber materials to the inner surface of the hollow mold while heating and rotating the hollow mold. For example, gas pressure may be used to hold the one or more fiber materials to the inner surface of the hollow mold. This may be achieved by supplying a gas flow to the interior of a rotational molding apparatus (in which the hollow mold is heated and rotated), thereby applying a pressure differential across the one or more fiber materials to press the one or more fiber materials against the inner surface of the hollow mold. In an embodiment, a combination of gas pressure and a fixing device may be employed to fix the one or more fiber materials to the inner surface of the hollow mold.

[0058] Applying one or more fibrous materials to the interior surface of the hollow mold may include applying one or more of ceramic fibers and polymer fibers. The applying one or more ceramic fibers may include one or more of glass fibers, carbon fibers, and basalt fibers, or precursors thereof. The applying one or more polymer fibers may include one or both of synthetic polymers and natural polymers. The one or more polymer fibers may include one or more of polyamides and polyolefins. Suitable polyolefins include polyethylene and polypropylene.

[0059] In an embodiment, applying one or more fibrous materials to the interior surface of the hollow mold includes applying a first fibrous material to the interior surface of the hollow mold and applying a second fibrous material to the first fibrous material.

[0060] The one or more thermoplastic polymers may include one or more of an ethylene homopolymer, an ethylene copolymer, a propylene homopolymer, a propylene copolymer, a fluoropolymer, a polyvinyl chloride, a polyvinylidene chloride, a polyaryletherketone (e.g., a polyetheretherketone), and a polyamide. The one or more thermoplastic polymers are preferably provided in powder form.

[0061] In embodiments, the one or more fibrous materials comprise one or more textured woven materials. In embodiments, the one or more textured woven materials may comprise one or more of a woven material, a knit material, and a braided material. The one or more textured woven materials comprise plied yarns. In embodiments, the spacing between at least some of the yarns of the fibrous material is between about 0.01 micrometers and about 5000 micrometers, or between about 0.1 micrometers and about 5000 micrometers, or between about 1 micrometer and about 5000 micrometers, or between about 10 micrometers and about 5000 micrometers.

[0062] The one or more thermosetting polymers may include one or more of vinyl esters, bismaleimides, polyesters, polyacrylates, epoxies, and polyurethanes.

[0063] In embodiments, the plurality of filaments have a filament diameter of from about 0.1 micrometers to about 500 micrometers, or from about 0.1 micrometers to about 100 micrometers, or from about 0.1 micrometers to about 50 micrometers, or from about 1 micrometer to about 20 micrometers.

[0064] In embodiments, the plurality of filaments is in the form of one or more of wound filaments, a fabric section comprising multiple threads, braided yarn, and chopped fibers.

[0065] In an embodiment, the first layer has a thickness of about 0.1 mm to about 50 mm, the second layer has a thickness of about 0.1 mm to about 5 mm, and the additional layer has a thickness of about 0.1 mm to about 1000 mm.

[0066] In an embodiment, the thermoplastic polymer is embedded in the interstices between the threads of the fibrous material of the second layer.

[0067] In an embodiment, the thermoplastic polymer is embedded within the structure of the individual threads of the fibrous material of the second layer.

[0068] In an embodiment, tendrils of fibrous material of the second layer extend from the surface of the yarn into the first layer.

[0069] In embodiments, the thermoplastic polymer does not completely infiltrate the thickness of the fibrous layer, i.e., at least a portion of the surface of the fibrous layer is not completely penetrated by the thermoplastic polymer. Preferably, substantially all of the surface of the fibrous layer is not completely penetrated by the thermoplastic polymer.

[0070] In an embodiment, the hollow mold structures that protrude into the interior of the mold are one or more baffle mold sections each adapted to generate cavities of substantially the same shape within a hollow composite container (particularly a hollow thermoplastic polymer / fiber material composite container), whereby the integrally formed structures protrude into the interior of the container, in this embodiment, are one or more baffles.

[0071] In an embodiment, the method includes reinforcing an integrally formed structure that protrudes into the interior of the container, e.g., reinforcing the or each baffle. Preferably, reinforcing the or each baffle occurs before applying an additional layer to the hollow thermoplastic polymer / fiber material composite container. Preferably, reinforcing the or each baffle includes inserting a reinforcing material into each cavity. The reinforcing material may take any form suitable for stiffening and / or strengthening the baffle. In one embodiment, the reinforcing material may be a hardenable material, e.g., foam or other hardenable polymer. The hardenable material may be injected into the cavity and allowed to harden. In an alternative embodiment, the method includes covering the cavity to fluidly seal the cavity from an environment external to the container, and injecting pressurized gas into the sealed cavity. In a further embodiment, reinforcing the or each baffle includes inserting a structural skin into each cavity.

[0072] In another embodiment, reinforcing the or each baffle includes inserting a brace structure into each cavity. The brace structure may include a plurality of brace elements secured within the cavity and arranged to stiffen and / or strengthen the baffle. The method may include forming the brace structure by securing and arranging a plurality of brace elements to one another, followed by inserting and securing the brace structure into each cavity.

[0073] In an embodiment, reinforcing the or each baffle includes inserting any combination of the reinforcing elements mentioned above into each cavity.

[0074] In an embodiment, the method further includes forming a recess in the outer wall of the hollow thermoplastic polymer / fiber material composite container around the periphery of the cavity. The hollow mold may include protrusions disposed around the periphery of the structure that protrude into the interior of the mold, thereby forming the recess extending through the outer wall of the hollow thermoplastic polymer / fiber material composite container. Alternatively, the recess may be formed after the hollow thermoplastic polymer / fiber material composite container is removed from the mold.

[0075] It will be appreciated that the second aspect of the invention may include any of the features defined in relation to the first aspect of the invention.

[0076] In a third aspect, the present invention provides a hollow composite container having an interior wall defining an interior of the container and a structure integrally formed with the interior wall, the integrally formed structure projecting into the interior of the container, the container being formed from a first layer comprising one or more thermoplastic polymers and a second layer comprising one or more fibrous materials.

[0077] It will be appreciated that the third aspect of the invention may include any of the features defined in relation to the first and second aspects of the invention.

[0078] As used herein, unless the context requires otherwise, the term "comprise" and variations of the term such as "comprising," "comprises," and "comprised" are not intended to exclude further additives, ingredients, integers, or steps.

[0079] Further aspects of the invention, and further embodiments of the aspects described in the previous paragraphs, will become apparent from the following description, given by way of example and with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0080] [Figure 1] 1 shows a perspective view of a hollow composite container according to an embodiment of the present invention. [Figure 2] 2 is a perspective partial view of the hollow composite vessel of FIG. 1, with a portion of the vessel wall obscured to reveal part of the underlying structure; [Figure 3] 2 is a cross-sectional view of the hollow composite vessel of FIG. 1 showing a pair of baffles therein. [Figure 4] 2 shows a perspective partial view (with a close-up) of the hollow composite vessel of FIG. 1, with a portion of the vessel wall obscured to reveal a portion of the underlying structure, including the baffle reinforcement structure; [Figure 5]1 shows a perspective view of a brace structure according to an embodiment of the present invention; [Figure 6] Specifically, a cross-sectional view of the baffle of the vessel of FIG. 1 is shown, illustrating the multi-layer structure of the vessel. [Figure 7] 10A-10C show cross-sectional views of alternative baffles, specifically showing the multi-layer construction of the vessel. [Figure 8] 10 shows a cross-sectional view of another alternative baffle, specifically showing the multi-layer construction of the vessel. [Figure 9] FIG. 10 is a cross-sectional view of another hollow composite vessel showing a pair of baffles therein. [Figure 10] FIG. 10 is a cross-sectional view of another hollow composite vessel showing a group of four baffles therein. [Figure 11] FIG. 10 is a cross-sectional view of another hollow composite vessel showing an orifice plate therein. [Figure 12] FIG. 10 is a cross-sectional view of another hollow composite vessel showing a pair of baffles therein extending longitudinally of the vessel. [Figure 13] 13 shows a perspective partial view of the hollow composite vessel of FIG. 12, with a portion of the vessel wall obscured to reveal part of the underlying structure. DETAILED DESCRIPTION OF THE INVENTION

[0081] 1, which shows a rotomolded product in the form of a hollow composite container 10. As will be appreciated from the discussion that follows, container 10 is suitable for use in containing and transporting hazardous materials, including chemicals and the like. However, it will be readily appreciated that container 10 can be used to contain and transport non-hazardous hollow rotomolded products as well as find employment in similar sectors such as the construction of fuel and cargo tanks for transportation vehicles, and in aerospace applications.

[0082] As explained in more detail below, container 10 is formed in part by a rotational molding process, which, in the case of container 10, results in the formation of a multi-layered structured container. As used herein, reference to a hollow thermoplastic polymer / fiber material composite container (or the like) is a reference to a container produced as a direct result of the rotational molding process, while reference to a hollow composite container (or the like) may also include reference to modified forms of the hollow thermoplastic polymer / fiber material composite container. For example, in certain applications, additional layers are added to the hollow thermoplastic polymer / fiber material composite container after the rotational molding process to create a container suitable for such applications. Thus, for the avoidance of doubt, hollow composite container 10 includes additional layers added to the hollow thermoplastic polymer / fiber material composite container after the rotational molding process. Multi-layer structures will be explained in more detail below.

[0083] In the depicted embodiment, the container 10 is of a substantially spherocylindrical shape, however, alternative container shapes such as cylindrical, rectangular, or any other shape commonly known in the art may also be provided.

[0084] Referring now to the partial cross-sectional view of FIG. 2 , one half of the container outer wall 16 has been removed, while the internal structure associated with that wall half remains for illustrative purposes. The container 10 includes an interior wall 12 that defines an interior 14 of the container 10. The container 10 further includes structure integrally formed with the interior wall 12 in the form of a plurality of substantially lobe-shaped baffles 20 that protrude into the interior 14 of the container 10. The baffles 20 are provided to reduce the effects of surge forces that may be caused by the movement of contents contained within the container 10 during transport. Such surge forces can make a vehicle carrying the container 10 more difficult to control and can place significant stress on the walls of the container 10. Thus, the baffles 20 provide a barrier to the movement of contents contained within the container 10 (in this example, movement in a direction generally parallel to the longitudinal axis of the container) and significantly reduce forces exerted on the container walls during vehicle turns, stopping, and starting.

[0085] As shown in Figure 2, three pairs of spaced-apart, opposing baffles 20 extend into the interior 14 of the container 10. However, it will be understood that different baffle arrangements, different baffle shapes, and different numbers of baffles may also be employed. The baffles 20 are formed by correspondingly shaped configurations of a baffle mold (not shown) used to form the container 10. As a result of the formation of the baffles 20 by correspondingly shaped configurations of the baffle mold, cavities 18 are formed in the outer wall of the hollow thermoplastic polymer / fiber material composite container formed in the rotational molding process.

[0086] Each baffle 20 includes a first baffle wall 22 extending from the inner wall 12 toward the interior 14 and a second baffle wall 24 extending from the inner wall 12 toward the interior 14. The first baffle wall 22 and the second baffle wall 24 are angled slightly relative to each other with respect to the baffle longitudinal axis and define substantially planar surfaces. Thus, the baffle is substantially U-shaped when viewed in cross section. The first baffle wall 22 and the second baffle wall 24 extending into the interior 14 of the vessel 10 merge smoothly into substantially curved baffle tips 26 via substantially curved tip transition portions 25 (best shown in FIG. 6 ) disposed between the first baffle wall 22 and the baffle tips 26 and between the second baffle wall 24 and the baffle tips 26. The radius of curvature of the tip transition portions 25 can range from about 2 mm to about 500 mm. This curvature of the tip transition portion 25 is an important feature in enhancing the manufacturability of the container 10 having the integrally formed baffle 20. One of the challenges in manufacturing the container 10 is ensuring there is sufficient contact time between the thermoplastic polymer and the fibrous material throughout the hollow mold during the rotomolding process. Because rotomolding complex shaped multi-layer structures presents many challenges, providing a hollow mold having a shaped portion that corresponds to the substantially curved tip transition portion 25 enhances the contact time between the thermoplastic polymer and the fibrous material around this complex portion of the mold.

[0087] The base 23 of each baffle 20 is provided with smooth, substantially curved base transition portions 27 (best shown in FIG. 6 ) between the interior wall 12 and the first baffle wall 22, and between the interior wall 12 and the second baffle wall 24. Similar to the tip transition portions 25, providing substantially curved base transition portions 27 between the interior wall 12 and the first baffle wall 22, and between the interior wall 12 and the second baffle wall 24 is important in facilitating the proper formation of the baffle 20 in the rotational molding process. Significant discontinuities in surface geometry, such as sharp angles and bends, increase the complexity of producing a container 10 having an integrally formed structure, such as the baffle 20, with the necessary structural integrity. Therefore, it is most preferred that the exterior surface profile 21 of the baffle 20 be substantially continuous with the interior wall, i.e., a seamless transition is provided between the interior wall 12, the first baffle wall 22, and the second baffle wall 24 and the baffle tip 26.

[0088] 3, which provides a cross-sectional view of the vessel 10 with particular focus on a pair of baffles 20 extending from substantially opposite locations on the interior wall 12 into the interior 14 of the vessel 10. Each baffle 20 extends slightly less than half the diameter of the interior 14. As a result, a gap 29 is provided between the respective tips 26 of the baffles 20. In this embodiment, due to the particular arrangement of the baffles 20, the gap 29 is substantially V-shaped when viewed in cross section, with a narrow end of the V-shaped gap 29 disposed at the bottom end of the vessel 10 and a wider end of the V-shaped gap 29 disposed at the top end of the vessel 10. Providing the wider end of the V-shaped gap 29 at the top of the container 10 is advantageous in applications where the container 10 is oriented substantially horizontally (i.e., approximately parallel to the ground) because it improves access to the interior 14 of the container 10 (access is generally provided by a manhole in the top of the container 10), provides an air gap at the top of the container 10 to assist in emptying the contents of the container 10, and ensures that there is a greater sloshing load at a lower point within the container 10 (i.e., having the center of gravity of the contents further down in the container).

[0089] As can be seen in Figure 2, each baffle 20 partially defines a boundary between adjacent compartments of the vessel 10. In this embodiment, the vessel 10 has three pairs of baffles 20, with each pair of baffles partially defining a boundary between adjacent compartments of the vessel 10. That is, the vessel 10 has four compartments 30a, 30b, 30c, and 30d. Each gap 29 between each pair of baffles 20 is adapted to maintain fluid communication between adjacent compartments of the vessel 10.

[0090] 4, the baffle 20 is reinforced with a suitable reinforcing structure 40 located within the cavity 18 of the vessel 10. The reinforcement is configured to resist the internal and external loads experienced by the vessel 10, and particularly the baffle 20, under operating loads. Specifically, the reinforcement is configured to stiffen and / or strengthen the baffle 20.

[0091] As with baffles 20, cavities 18 are substantially U-shaped in cross section and defined by first outer baffle wall 17 (outside first baffle wall 22), second outer baffle wall 19 (outside second baffle wall 24), and substantially curved outer wall 15 (outside baffle tip 26). In this embodiment, reinforcing structure 40 includes a structural skin 42 formed from a medium strength carbon fiber reinforced polymer and core sandwich that is wet-laid into each cavity 18. Specifically, structural skin 42 is applied along a substantial portion of the cavity interior, i.e., along first outer baffle wall 17, second outer baffle wall 19, and outer wall 15.

[0092] While in some applications, the structural skin 42 alone may be sufficient to provide the necessary reinforcement for the baffle 20 to withstand operational loads, in this embodiment, the structural skin 42 also facilitates connection of a brace structure 44 to the cavity 18. As best shown in the close-up view of the cavity 18 in FIG. 4 , the brace structure 44 includes a plurality of brace elements secured to the cavity 18 to stiffen and / or strengthen the baffle 20. The brace elements include a plurality of first brace beams 45 oriented substantially perpendicular to the baffle tip 26 and extending between the first outer baffle wall 17 and the second outer baffle wall 19, a plurality of second brace beams 46 oriented substantially parallel to the baffle tip 26 and extending in a direction substantially perpendicular to the beams 45, and wedges 47 secured along each longitudinal side of the beams 45 and 46, the wedges 47 being shaped to enable connection of the beams 45, 46 to the cavity 18. The beams 45, 46 and wedges 47 are formed from wet-laid carbon fiber (using a suitable thermosetting resin) and secured to the structural skin 42 using an adhesive. Each of the beams 45, 46 may be individually connected to the structural skin 42 (thereby forming the brace structure 44), or the brace structure 44 is preferably pre-formed (or partially pre-formed) by securely arranging a plurality of beams 45 in a spaced-apart relationship with one or more beams 46 (each of which has a pre-formed or secured wedge 47) to form one or more brace structures 44 that can be installed in the cavity 18. An example of a suitable pre-formed brace structure is shown in FIG. 5. After the brace structure 44 is installed in the cavity 18, the cavity can then be closed with a cover (not shown) that is connected to the outer wall of the hollow thermoplastic polymer / fiber material composite container and configured to shield the reinforcement and provide a consistent exterior profile for the hollow thermoplastic polymer / fiber material composite container. However, in other embodiments, a cover may not be used.

[0093] While the depicted embodiment of the bracing structure 44 is in the form of a lattice frame structure having beams 45, 46 arranged substantially perpendicular to one another, it will be understood that the bracing structure 44 can assume many other different configurations. Furthermore, while the reinforcing structure 40 in this embodiment is provided as a combination of the structural skin 42 and the bracing structure 44, this need not be the case. In other embodiments, the reinforcing structure may be a hardenable material, such as a foam or other hardenable polymer, that is injected into the cavity 18 and allowed to harden. In an alternative embodiment, rather than using a reinforcing structure itself, the cavity 18 may be reinforced by injecting pressurized gas therein (after fluidly sealing the cavity with a suitable cover).

[0094] Referring to FIG. 6, the container 10 is formed with a multi-layer structure including a first inner layer 52 including one or more thermoplastic polymers and a second layer 54 including one or more fibrous materials. As a result of a rotational molding process, described in more detail below, the one or more fibrous materials are at least partially infiltrated with one or more thermoplastic polymers. The thermoplastic polymer inner layer 52 functions as a barrier layer that is substantially impermeable to materials that contact the inner layer 52, while the fibrous second layer 54 functions as a suitable tie layer adapted to allow additional layers to be formed therewith. Furthermore, the baffle 20 of the container 10 is seamlessly integrated into the container 10, which has the same multi-layer structure with the first and second layers. Therefore, there are no weld lines between the container 10 and the baffle 20.

[0095] Thermoplastic polymers for use in the construction of first layer 52 preferably have resistance to a variety of substances and conditions, such as resistance to one or more of high pH, low pH, oxidizing agents, reducing agents, solvents, propellants, cryogenic substances, permeation, and abrasion.

[0096] The one or more thermoplastic polymers of the first layer 52 may include one or more of an ethylene homopolymer, an ethylene copolymer, a propylene homopolymer, a propylene copolymer, a fluoropolymer, a polyvinyl chloride, a polyvinylidene chloride, a polyaryletherketone (e.g., a polyetheretherketone), and a polyamide.

[0097] Suitable fluoropolymers include one or more of polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, perfluoroalkoxyalkanes, fluorinated ethylene-propylene, ethylene tetrafluoroethylene, ethylene chlorotrifluoroethylene, polyethylene tetrafluoroethylene, and polyethylene chlorotrifluoroethylene.

[0098] The one or more fibrous materials of the second layer 54 may include one or more of ceramic fibers and polymeric fibers.

[0099] The container 10 includes reinforcing layers 56, 58 configured to increase the strength and rigidity of the container 10. The reinforcing layers 56, 58 are applied to the thermoplastic polymer / fiber material composite container in several ways. In one example, the reinforcing layers 56, 58 (e.g., fiber-reinforced polymer laminates) can be manually hand-laid onto the container 10. In another example, the reinforcing layers can be vacuum-infused. In further examples, the reinforcing layers can include (1) filament winding one or more carbon, glass, aramid, and basalt filaments onto the outside of the container 10, where the filaments are at least partially wetted with one or more thermosetting polymers prior to application; (2) filament winding one or more carbon, glass, aramid, and basalt filaments onto the outside of the container 10 followed by application of one or more thermosetting polymers; or (3) applying one or more thermosetting polymers to the outside of the container 10 followed by filament winding one or more carbon, glass, aramid, and basalt filaments. As a result of applying the reinforcing layers 56, 58, the one or more fibrous materials of the second layer 54 are at least partially infiltrated with both the one or more thermoplastic polymers of the first layer 52 and the one or more thermosetting polymers of the reinforcing layers 56, 58.

[0100] The one or more thermosetting polymers may include one or more of vinyl esters, bismaleimides, polyesters, polyacrylates, epoxies, and polyurethanes.

[0101] As previously mentioned, there can be many variations on the baffles and overall baffle arrangements mentioned above.

[0102] FIG. 7 provides an alternative embodiment in which a hollow thermoplastic polymer / fiber material composite container includes an insert 62 provided around the periphery of the cavity 18. The insert 62 is configured to facilitate engagement between the hollow thermoplastic polymer / fiber material composite container and one or more reinforcing layers. The insert 62 includes a base 64 adapted to facilitate improved engagement of the reinforcing layer 56 to the container 10, particularly around the cavity 18. The base 64 includes a substantially planar engagement surface 66 on which the reinforcing layer 56 may be supported. The insert 62 further includes a sidewall 65 that tapers inward from the outer wall of the thermoplastic polymer / fiber material composite container to the base 64 of the insert 62. The tapered sidewall 65 facilitates introduction and improved engagement of the reinforcing layer 65 with the thermoplastic polymer / fiber material composite container. An outermost reinforcing layer 58 of fiber-reinforced polymer is applied to the entire hollow thermoplastic polymer / fiber material composite container to increase the strength and rigidity of the container 10. In an alternative embodiment, a single reinforcing layer is provided throughout the container 10.

[0103] Figure 8 provides a further alternative embodiment, specifically with respect to baffle 20. In this embodiment, compared to the embodiment of Figure 7, baffle 20' includes a flat baffle tip 26'. However, it will be appreciated that the exterior surface profile of baffle 20' is still substantially continuous with inner wall 12', i.e., with a seamless transition provided between inner wall 12', first baffle wall 22', second baffle wall 24', and baffle tip 26' due to substantially curved tip transition portion 25' and substantially curved base transition portion 27'.

[0104] 9 provides a further alternative embodiment of the vessel 10. In this embodiment, a cross-sectional view of the vessel 10 reveals a pair of diametrically opposed baffles 20'' extending into the interior 14 of the vessel 10. The gap 29'' between the tips 26'' of each of the baffles 20'' is substantially rectangular.

[0105] 10 provides a further alternative embodiment of the vessel 10. In this embodiment, a cross-sectional view of the vessel 10 reveals four circumferentially equally spaced baffles 20''' extending into the interior 14 of the vessel 10. The gaps 29''' between the tips 26''' of each of the baffles 20 are substantially cross-shaped.

[0106] 11 provides a further alternative embodiment of the vessel 10. In this embodiment, a cross-sectional view of the vessel 10 reveals a single baffle in the form of an orifice plate 20'''' extending into the interior 14 of the vessel 10. The gap 29'''' between the tips 26'''' of the orifice plate 20'''' is substantially circular (i.e., the shape of the orifice).

[0107] 12 and 13 provide a further alternative embodiment of the vessel 10. In this embodiment, a cross-sectional view of the vessel 10 reveals a pair of diametrically opposed baffles 20'''''' extending into the interior 14 of the vessel 10. In this embodiment, the baffles 20'''''' extend in a direction substantially parallel to the longitudinal axis of the vessel 10. Such an arrangement may be particularly useful in applications where the vessel 10 is oriented vertically during use, such as aerospace applications. [Example]

[0108] An example of a suitable method for producing hollow composite containers will now be described, however, it will be understood that alternative methods may also be employed.

[0109] The method includes preparing a hollow mold for producing a hollow composite container. In this embodiment, this involves the suitable preparation of a plurality of hollow mold elements that, when assembled together, form the mold for the entire hollow composite container. In this example, the hollow mold element includes a generally cylindrical section and two generally hemispherical end sections. The generally cylindrical section includes a structure that protrudes into the interior of the mold, the structure being in the form of a pair of baffle mold segments. The baffle mold segments may be an integrally formed part of the cylindrical section, or the baffle mold segments may be formed from one or more separate components that can be suitably secured to the cylindrical section. The hollow mold elements may be formed substantially from a steel frame.

[0110] A first fibrous material is held to the interior surface of each hollow mold element by an appropriate fastening means, e.g., a suitable fastening device. In this example, ceramic fibers are used. A suitable adhesive is then applied to the exterior surface of the first fibrous material. Following this, a second fibrous material is secured in place on top of the first fibrous material 160. In this example, polymer fibers are used. While two fibrous materials are applied to the interior surface of each hollow mold element, those skilled in the art will understand that one or more fibrous materials may be used during this stage of the process. Furthermore, the two mentioned fibrous materials should be considered merely exemplary, as alternative fibrous materials may be employed in this process. While it is not necessary to have the same arrangement and type of fibrous material applied to each hollow mold element, it is preferred in forming a homogeneous and consistent hollow composite container.

[0111] Once each of the hollow mold elements has been prepared, they are suitably assembled and secured together to form the entire hollow composite container mold, and the assembled mold is then inserted into a rotational molding apparatus.

[0112] An example was demonstrated by placing approximately 350 kg of polyethylene powder into the rotational molding apparatus before closing. Gas pressure is used to hold the fiber material layer against the interior surface of the hollow mold while the assembled mold is rotated and subjected to conventional rotational mold heating. This is achieved by supplying a gas flow inside the rotational molding apparatus, thereby applying a pressure differential across the fiber material, forcing it against the interior surface of the assembled mold.

[0113] Throughout the rotomolding process, various rotomolding parameters are considered and varied throughout the process to produce a suitable hollow composite container. These parameters include: Mold temperature and heating method; · rotational speed of the rotational molding device (around the longitudinal axis); · Inclination speed of the rotational molding device (around the horizontal axis); · Tilt angle - the maximum angle reached by the rotation of the mold device around its horizontal axis relative to the longitudinal axis; Pressure - the pressure within the mold that holds the fiber layer against the inner surface of the mold and helps maintain contact between the molten polyethylene and the fiber layer; and Timing - the amount of time a particular parameter is held.

[0114] Throughout the process, care is taken to adjust the rotational molding equipment temperature set point, mold temperature, and pressure to ensure that a suitable "lay-up" of polyethylene is established on the interior surfaces of the assembled mold, particularly in the baffle structure. As mentioned earlier, the molding of the baffle structure is carefully designed to ensure that the contact time between the polyethylene and the baffle structure is sufficient to produce molded baffles with suitable structural integrity within the produced hollow composite container.

[0115] Once the polyethylene is suitably melted and dispersed, the set temperature of the rotational molding machine and the mold temperature are reduced, and finally the heat is turned off, allowing the mold to cool and solidify the polyethylene. When the temperature measured within the mold is suitably low (and well below the melting point of the polyethylene powder), the pressure is released through the outlet valve. Towards the end of the process, rotation of the rotational molding machine about both the longitudinal and transverse axes is stopped. The hollow thermoplastic polymer / fiber material composite container, with structures (e.g., baffles) protruding into the container's interior, can then be removed from the mold.

[0116] A thickness gauge was used to confirm the thickness of the produced thermoplastic polymer / fiber composite container, and external inspection showed that the fibrous layer was strongly secured to the polyethylene by partial, but not complete, wetting of the polyethylene into the fibrous layer. Endoscopic examination showed that the inner polyethylene layer was of sufficient thickness throughout, with no thin spots.

[0117] A second example was demonstrated by loading approximately 225 kg of polyethylene powder into the rotomolding apparatus prior to closure. The steps leading up to preparing the hollow mold were the same as in the first trial run. As with the first trial run, various rotomolding parameters were varied throughout the rotomolding process to produce a suitable hollow composite container. As will be appreciated by those skilled in the art, given the significantly lower amount of polyethylene powder used in the second trial run, most of the hold times for the temperature and pressure parameters would be reduced. The temperatures and pressures employed were otherwise similar to those employed in the first trial run.

[0118] A thickness gauge was again used to verify the thickness of the produced thermoplastic polymer / fiber composite container, and external inspection showed that the fibrous layer was strongly secured to the polyethylene with partial, but not complete, wet-through of the polyethylene into the fibrous layer. Endoscopic examination showed that the inner polyethylene layer was of sufficient thickness overall, although there were some thin spots present.

[0119] The next step in the process involves the baffle structure being reinforced. In this embodiment, this is accomplished by inserting reinforcement material into cavities formed in the outer wall of the hollow thermoplastic polymer / fiber material composite container. However, it will be appreciated that in other embodiments, although less desirable, the baffle structure can be reinforced from the inside of the container. There are many possible ways in which the cavities can be suitably reinforced to meet the loading requirements of the hollow composite container, for example, specifically, surge forces experienced by the container 10 or by any structure to which the container 10 is secured during use.

[0120] In this embodiment, a structural skin formed of a medium strength carbon fiber reinforced polymer and core sandwich is wet laid into the cavity. In addition to the structural skin, further reinforcement is provided by inserting a bracing structure into the cavity. The bracing structure includes a plurality of bracing elements, each made of wet laid standard strength carbon fiber reinforced polymer, which is secured to the structural skin using a suitable adhesive (e.g., a synthetic resin such as a thermosetting adhesive).

[0121] The hollow thermoplastic polymer / fiber material composite container is then reinforced by applying a plurality of filaments selected from one or more of carbon, glass, aramid, and basalt filaments to the exterior of the hollow thermoplastic polymer / fiber material composite container, the plurality of filaments being at least partially wetted with one or more thermosetting polymers prior to application, thus forming a hollow composite container with increased strength and rigidity. The fibrous layer of the hollow thermoplastic polymer / fiber material composite container facilitates bonding of the reinforcing layer thereto, thereby resulting in the fibrous material being at least partially wetted with both one or more thermoplastic polymers and one or more thermosetting polymers.

[0122] It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or apparent from the text or drawings, all of these different combinations constituting various alternative aspects of the present disclosure.

Claims

1. 1. A hollow rotomolded product having an interior wall defining an interior of the hollow rotomolded product and an integrally formed structure with the interior wall, the integrally formed structure projecting into the interior of the hollow rotomolded product, the hollow rotomolded product being formed from a first layer comprising one or more thermoplastic polymers and a second layer comprising one or more fibrous materials.

2. The hollow rotomolded product of claim 1 , wherein the one or more fibrous materials are at least partially infiltrated with the one or more thermoplastic polymers.

3. 3. The hollow rotomolded product of claim 1 or 2, wherein the hollow rotomolded product includes at least one cavity extending toward the interior of the hollow rotomolded product, the cavity including an interior surface profile that substantially corresponds to an exterior surface profile of the integrally formed structure.

4. 4. The hollow rotomolded product of claim 3, wherein the hollow rotomolded product includes a recess disposed around a periphery of the at least one cavity, the recess configured to facilitate engagement of one or more subsequent layers to the first and second layers.

5. 5. The hollow rotomolded product of claim 3 or 4, further comprising a reinforcement disposed within the at least one cavity, the reinforcement configured to stiffen and / or strengthen at least a portion of the integrally formed structure.

6. The hollow rotomolded product of claim 5 , wherein the reinforcement comprises a structural skin secured within the at least one cavity.

7. 7. The hollow rotomolded product of claim 5 or 6, wherein the reinforcement comprises a bracing structure adapted to be connected within the at least one cavity, the bracing structure comprising a plurality of bracing elements secured within the cavity and arranged to stiffen and / or strengthen the integrally formed structure.

8. 8. The hollow rotomolded product of claim 7, wherein the bracing elements are of a substantially beam-like configuration and arranged in a substantially lattice-like framework.

9. 9. The hollow rotomolded product of claim 7 or 8, when dependent on claim 6, wherein the bracing structure is fixed to the structural skin.

10. 10. The hollow rotomolded product of any one of claims 1 to 9, wherein the integrally formed structure projecting into the interior of the hollow rotomolded product is one or more baffles.

11. 11. The hollow rotomolded product of claim 10, wherein the one or more baffles are arranged to extend in a direction that is substantially parallel to a longitudinal axis of the hollow rotomolded product.

12. 11. The hollow rotomolded product of claim 10, wherein the one or more baffles are arranged to extend in a direction that is substantially perpendicular to a longitudinal axis of the hollow rotomolded product.

13. 13. The hollow rotomolded product of claim 12, wherein a pair of baffles extend from substantially opposite locations on the interior wall into the interior of the hollow rotomolded product, forming a gap between the pair of baffles.

14. 14. The hollow rotomolded product of claim 13, wherein the gap is substantially V-shaped when the hollow rotomolded product is viewed in cross-section, with a narrow end of the V-shaped gap disposed at a lower end of the hollow rotomolded product and a wide end of the V-shaped gap disposed at an upper end of the hollow rotomolded product.

15. 15. The hollow rotomolded product of any one of claims 10 to 14, wherein the or each baffle comprises a first baffle wall and a second baffle wall, each extending from the inner wall of the hollow rotomolded product into the interior of the hollow rotomolded product and meeting at a baffle apex.

16. 16. The hollow rotomolded product of claim 15, wherein the first baffle wall and the second baffle wall are angled relative to one another, thereby defining a substantially U-shaped baffle when the baffle is viewed in cross-section.

17. 17. The hollow rotomoulded product of claim 15 or 16, wherein the or each baffle includes tip transition portions between the first baffle wall and the baffle tip, and between the second baffle wall and the baffle tip, the tip transition portions being substantially curved thereby defining smooth transition profiles between the first baffle wall and the baffle tip, and between the second baffle wall and the baffle tip.

18. 18. The hollow rotomolded product of claim 17, wherein the radius of curvature of the tip transition portion ranges from about 2 mm to about 500 mm.

19. 19. The hollow rotomolded product of any one of claims 15 to 18, wherein the hollow rotomolded product includes substantially curved base transitions between the inner wall and the first baffle wall and between the inner wall and the second baffle wall.

20. 20. The hollow rotomoulded product of any one of claims 15 to 19, wherein the exterior surface profile of the or each baffle is substantially continuous with the interior wall, thereby providing a seamless transition between the interior wall, the first wall, the second wall and the baffle tip of the hollow rotomoulded product.

21. 10. The hollow rotomolded product of any one of the preceding claims, wherein the one or more thermoplastic polymers in the first layer comprise one or more of an ethylene homopolymer, an ethylene copolymer, a propylene homopolymer, a propylene copolymer, a fluoropolymer, a polyvinyl chloride, a polyvinylidene chloride, a polyaryletherketone, and a polyamide.

22. 22. The hollow rotomolded product of any one of claims 1 to 21, wherein the one or more fibrous materials in the second layer comprise one or more of glass fibers, carbon fibers, and basalt fibers, or precursors thereof.

23. 23. The hollow rotomolded product of any one of claims 1 to 22, wherein the hollow rotomolded product includes a third layer comprising a plurality of filaments selected from one or more of carbon, glass, aramid, and basalt filaments and one or more thermosetting polymers, the second layer being disposed between the first layer and the third layer, and the one or more fibrous materials being at least partially infiltrated with both the one or more thermoplastic polymers and the one or more thermosetting polymers.

24. 24. The hollow rotomolded product of claim 23, wherein the one or more thermosetting polymers of the third layer include one or more of vinyl esters, bismaleimides, polyesters, polyacrylates, epoxies, and polyurethanes.

25. 25. The hollow rotomolded product of any one of claims 1 to 24, wherein the hollow rotomolded product is a hollow composite container, and the unitary structure is configured to reduce surge forces experienced by the hollow composite container during use.

26. 1. A method for producing a hollow composite container, said method comprising: applying one or more fibrous materials to an interior surface of a hollow mold, the hollow mold including structures projecting inwardly of the hollow mold; heating and rotating the hollow mold in the presence of one or more thermoplastic polymers within the hollow mold, causing the thermoplastic polymers to melt and at least partially infiltrate the fibrous material; cooling the hollow mold to solidify the thermoplastic polymer; and removing a hollow thermoplastic polymer / fiber material composite container from the hollow mold, the hollow thermoplastic polymer / fiber material composite container having an integrally formed structure projecting into the interior of the container.

27. 27. The method of claim 26, further comprising the step of reinforcing the integrally formed structure before applying an additional layer to the hollow thermoplastic polymer / fiber material composite container.

28. Further comprising one or more of the following steps: applying a plurality of filaments selected from one or more of carbon, glass, aramid, and basalt filaments to the exterior of the hollow thermoplastic polymer / fiber material composite container, wherein prior to application, the plurality of filaments are at least partially wetted with one or more thermosetting polymers; applying a plurality of filaments selected from one or more of carbon, glass, aramid, and basalt filaments to the exterior of the hollow thermoplastic polymer / fiber material composite container, followed by applying one or more thermosetting polymers; applying one or more thermosetting polymers to the exterior of the hollow thermoplastic polymer / fiber material composite container, followed by applying a plurality of filaments selected from one or more of carbon, glass, aramid, and basalt filaments; 27. The method of claim 26, wherein:

29. 28. The method of claim 27, wherein the one or more thermosetting polymers comprise one or more of vinyl esters, bismaleimides, polyesters, polyacrylates, epoxies, and polyurethanes.

30. 29. The method of any one of claims 26 to 28, wherein applying one or more fiber materials to the interior surface of the hollow mold comprises applying one or more of glass fiber, carbon fiber, and basalt fiber, or precursors thereof.

31. 30. The method of any one of claims 26 to 29, wherein the one or more thermoplastic polymers comprise one or more of an ethylene homopolymer, an ethylene copolymer, a propylene homopolymer, a propylene copolymer, a fluoropolymer, polyvinyl chloride, polyvinylidene chloride, a polyaryletherketone, and a polyamide.

32. 31. The method according to any one of claims 26 to 30, wherein the structures of the hollow mold projecting into the interior of the hollow mold are one or more baffle mold sections each adapted to generate cavities of substantially the same shape within the hollow thermoplastic polymer / fiber material composite container.

33. 33. The method of claim 32, further comprising reinforcing the integrally formed structure by inserting a reinforcing material into each cavity.

34. 34. The method of claim 33, wherein reinforcing the integrally formed structure includes inserting a structural skin into each cavity.

35. 35. The method of claim 33 or 34, wherein reinforcing the integrally formed structure comprises inserting a bracing structure into each cavity, the bracing structure comprising a plurality of bracing elements secured within the cavity and arranged to stiffen and / or strengthen the integrally formed structure.

36. 36. The method of claim 26 or 35, wherein the hollow mold further includes protrusions arranged around the periphery of the structure that protrude into the interior of the mold, whereby the hollow thermoplastic polymer / fiber material composite container includes recesses extending through the outer wall of the thermoplastic polymer / fiber material composite, the recesses being arranged around the periphery of the cavity.

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