Hollow rotary molded article

Abstract

A hollow rotationally molded article having an inner wall and a structure integrally formed with the inner wall, the inner wall defining an interior of the article, where the integrally formed structure protrudes into the interior of the article, the article being formed from a first layer and a second layer, the first layer includes one or more thermoplastic polymers and the second layer includes one or more fibrous materials.

Description

Field of the Invention

[0001] The present invention generally relates to rotationally moulded articles. In particular, embodiments of the present invention relate to a hollow composite container having at least a thermoplastic layer and a fibrous layer. Aspects of the present invention also relate to manufacturing the container using a rotational moulding process. The container can be used for storing and transporting powders, liquids, gases, and cryogenic substances, especially hazardous substances. Background Art

[0002] Storage tanks are widely used to transport both hazardous and non-hazardous materials such as liquids, gases, and powders. For the transportation of hazardous materials, storage tanks must comply with some local and international regulations.

[0003] Storage tanks for transporting hazardous materials are typically constructed of metal, which provides structural strength and is usually lined with an elastomeric lining to protect the metal from the corrosive nature of the tank contents.

[0004] However, lined metal storage tanks have many disadvantages, including their excessive weight, which increases transportation costs, and the possibility that over time the lining material degrades due to contact with the tank contents or separates from the inner wall of the metal container, requiring repair or replacement of the lining.

[0005] In addition, a problem that occurs in the case of material transportation (especially when transporting liquids) is that the liquid has inertia and, in its fluid state, tends to continue moving in the same direction when the transportation vehicle is maneuvered. During startup, stop, and turning, the liquid will fluctuate and slosh in the storage tank, making the vehicle more difficult to control or more unstable and imposing significant stress on the walls of the storage tank. One of the conventional ways to address this problem is to install baffles or surge plates inside the storage tank. This typically involves installing the baffles in the storage tank before assembling the tank heads or installing the baffles in smaller sections through manholes or other openings after the tank heads and then fixing the plates in place inside the storage tank (e.g., by welding or other mechanical fastening means). These plates provide a barrier to the movement of the liquid, improve stability, and reduce the forces exerted on the walls.

[0006] It is desirable to provide an improved storage tank that overcomes or ameliorates one or more of the disadvantages or problems of the prior art described above, or at least provides an alternative useful option.

[0007] The mention of any prior art in this specification is not an admission or implication that such prior art constitutes a part of the common general knowledge in any jurisdiction, nor does it mean that such prior art can be reasonably understood, regarded as relevant to, and / or combined with other prior art by a person skilled in the art. SUMMARY OF THE INVENTION

[0008] In a first aspect, the present invention provides a hollow rotationally molded article having an inner wall and a structure integrally formed with the inner wall, the inner wall defining the interior of the article, wherein the integrally formed structure projects into the interior of the article, the article being formed of a first layer and a second layer, the first layer comprising one or more thermoplastic polymers and the second layer comprising one or more fibrous materials.

[0009] Preferably, the one or more fibrous materials are at least partially infiltrated with the one or more thermoplastic polymers. Thereby, a beneficial multi-layer structure is produced that includes a substantially thermoplastic inner layer / first layer and a substantially fibrous second layer. The fibrous second layer can act as a suitable coupling layer adapted to enable the formation of additional layers therethrough. The thermoplastic inner layer can act as a barrier layer that is substantially impermeable to materials contacting the interior of the article. Additionally, the integrally formed structure of the article is seamlessly integrated into an article having this same multi-layer structure. Thus, there are no welds or connection lines between the article and the integrally formed structure.

[0010] The rotationally molded article can be referred to herein as a thermoplastic polymer / fibrous material composite (or similar name) when it has only the first and second layers.

[0011] In one embodiment, the article includes at least one cavity that extends into the interior of the article. For example, the at least one cavity can extend through the outer wall of the thermoplastic polymer / fibrous material composite. The cavity can be formed in the rotationally molded article by a protruding portion of the mold used to form the integrally formed structure of the rotationally molded article. Thus, in this embodiment, the integrally formed structure has a shape and configuration that substantially corresponds to the shape and configuration of the protrusion of the mold. Additionally, the cavity can have an inner surface profile that substantially corresponds to the outer surface profile of the integrally formed structure.

[0012] In one embodiment, a reinforcement is disposed within the cavity. The reinforcement can be configured to resist internal and / or external loads that the article, particularly the integrally formed structure, experiences under operating conditions. Examples of internal and external loads that may be experienced include one or more of the following: a pressure differential across a wall located between the integrally formed structure and the exterior of the article; a pressure differential across a wall located between the integrally formed structure and the interior of the article; loads generated by the movement of contents (e.g., fluids) within the article due to manipulation of the article - applicable to axial, radial, lateral, vertical, and / or tangential directions of the article; and loads applied to the article and the integrally formed structure by external structure supports and other external loading due to manipulation of the article. In one example, the reinforcement is configured to strengthen and / or stiffen the article. Preferably, the reinforcement is configured to strengthen and / or stiffen at least a portion of the integrally formed structure. For example, the reinforcement can be configured to strengthen and / or stiffen the base of the integrally formed structure.

[0013] The reinforcement can take any form suitable for strengthening and / or stiffening the integrally formed structure. In one embodiment, the reinforcement can be a curable material, such as a foam or other curable polymer. The curable material can be injected into the cavity and allowed to cure. In an alternative embodiment, the article can include a lid that is connected to the outer wall of the thermoplastic polymer / fiber material composite, the lid being configured to fluid - seal the cavity, wherein the reinforcement is a pressurized gas that is injected into the cavity after the cavity has been fluid - sealed through the lid. In a further alternative embodiment, the reinforcement can be a structural skin. The structural skin can be secured within the cavity by any suitable means (e.g., an adhesive). The stress skin is preferably formed from one or more fiber materials wet - laid into the cavity. For example, the stress skin can be a carbon - fiber - reinforced polymer and core sandwich that has been wet - laid into the cavity.

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

[0015] In a preferred embodiment, the reinforcement includes a structural skin and a support structure, the structural skin being fixed in the cavity and the support structure being fixed to the structural skin. Advantageously, fixing the support structure to the structural skin will facilitate better connection of the support structure to the cavity. A suitable adhesive may be used to fix the support structure to the structural skin.

[0016] In one embodiment, the reinforcement may be formed of any combination of the above-mentioned reinforcements.

[0017] The rotationally molded article may include a lid connected to the outer wall of the thermoplastic polymer / fiber material composite, the lid being configured to shield the reinforcement.

[0018] In one embodiment, the integrally formed structure protruding into the interior of the article is one or more baffles. Each of the one or more baffles may be in the form of a plate protruding into the interior of the article. For example, the one or more baffles may be in the form of an orifice plate protruding into the interior of the article. In an alternative embodiment, each of the one or more baffles may be substantially leaf-shaped and may protrude into the interior of the article.

[0019] In one embodiment, the integrally formed structure protruding into the interior of the article is arranged to extend in a direction substantially parallel to the longitudinal axis of the article. In one example, the integrally formed structure protruding into the interior of the article is one or more baffles, and each of the one or more baffles is arranged to extend in a direction substantially parallel to the longitudinal axis of the article. In another embodiment, the integrally formed structure protruding into the interior of the article is arranged to extend in a direction substantially perpendicular to the longitudinal axis of the article (e.g., in a direction substantially parallel to the transverse direction of the article). In one example, the integrally formed structure protruding into the interior of the article is one or more baffles, and each of the one or more baffles is arranged to extend in a direction substantially perpendicular to the longitudinal axis of the article. In one embodiment, the integrally formed structure protruding into the interior of the article is arranged to extend in the radial direction of the article. In one example, the integrally formed structure protruding into the interior of the article is one or more baffles, and each of the one or more baffles is arranged to extend in the radial direction of the article.

[0020] In one embodiment, a plurality of baffles extend into the interior of the article from circumferentially spaced positions of the inner wall. In one embodiment, a plurality of baffles extend into the interior of the article from substantially opposite positions of the inner wall. For example, a pair of baffles may extend into the interior of the article from substantially opposite positions of the inner wall. The baffles (or pair of baffles) may be diametrically opposed. Preferably, when the article is viewed in a transverse cross-section, the plurality of circumferentially spaced baffles extend into the interior of the article and toward each other, thereby forming a gap between the baffles. In other words, the gap is defined as the area not covered by the baffles when the article is viewed in a transverse cross-section. In one example, when the article is viewed in a transverse cross-section, the gap is substantially V-shaped. In embodiments where the article extends generally in a horizontal direction (e.g., parallel to the ground), preferably the narrower end of the V-shaped gap is disposed at the lower end of the article and the wider end of the V-shaped gap is disposed at the upper end of the article. Preferably, the pair of baffles extend toward each other and form a substantially V-shaped gap therebetween. In an alternative embodiment, when the article is viewed in a transverse cross-section, the gap is substantially rectangular in shape. In another embodiment, when the article is viewed in a transverse cross-section, a single baffle may extend into the interior and form a gap. For example, when the baffle is in the form of an orifice plate, the gap may be defined by the orifices of the orifice plate. Alternatively, the gap may be defined by the space between the baffle and the inner wall.

[0021] In one embodiment, the gap may define from about 5% to about 95% of the total transverse cross-section of the interior. For example, the gap may define between about 5% and about 50% of the total transverse cross-section of the interior or between about 5% and about 30% of the total transverse cross-section of the interior.

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

[0023] In one embodiment, a plurality of spaced-apart baffles are disposed along the length of the article, e.g., spaced in a direction parallel to the longitudinal axis of the article. Preferably, a plurality of spaced-apart baffle pairs are disposed along the length of the article. In another embodiment, a plurality of baffles spaced apart about the perimeter or circumference of the article are provided.

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

[0025] The baffle or each baffle may include a first baffle wall and a second baffle wall, each of the first baffle wall and the second baffle wall extending from the inner wall of the article into the interior of the article and merging into a baffle tip. The first baffle wall and the second baffle wall may define a substantially planar surface disposed in a substantially transverse plane of the article (e.g., the first baffle wall and the second baffle wall may be substantially parallel). In an alternative embodiment, when the baffle is viewed in a transverse cross-section, the first baffle wall and the second baffle wall may be angled towards each other, thereby defining a baffle of a substantially U-shaped configuration. In another embodiment, the first baffle wall and the second baffle wall each extend from the inner wall of the article into the interior of the article and merge into a substantially curved baffle tip. In an alternative embodiment, the first baffle wall and the second baffle wall each extend from the inner wall of the article into the interior of the article and merge into a substantially flat baffle tip.

[0026] In another embodiment, the baffle or each baffle includes a tip transition portion located between the first baffle wall and the baffle tip and between the second baffle wall and the baffle tip. The tip transition portion is preferably substantially curved, thereby defining a smooth transition profile located 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 portion may be in the range of about 2 mm to about 500 mm or between about 5 mm and about 100 mm. The radius of curvature of the baffle tip (if substantially curved) may be in the range of about 2 mm to about 500 mm or between about 5 mm and about 100 mm.

[0027] In another embodiment, the baffle or each baffle includes a base transition portion that is located 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 is preferably in the range of about 2 mm to 500 mm or between about 5 mm and about 100 mm.

[0028] In one embodiment, the outer surface profile of the baffle or each baffle is substantially continuous with the inner wall, i.e., there is a seamless transition between the inner wall of the article, the first wall, the second wall, and the baffle tip. In a preferred embodiment, both the base transition portion and the tip transition are substantially curved. Advantageously, in this embodiment, the rotationally molded article can be more easily formed during rotational molding due to the provision of a suitably curved surface profile that enables an increase in the contact time between the mold used to form the article and the one or more thermoplastic polymers and the one or more fibrous materials. Thus, a more consistent bonding is achieved between the one or more fibrous materials and the one or more thermoplastic polymers.

[0029] The baffle or each baffle can partially define a boundary between adjacent compartments of the article. In this embodiment, the gap is adapted to maintain fluid communication between adjacent compartments of the article.

[0030] In one embodiment, the article includes a recess that is disposed around the perimeter of the cavity or each cavity. The recess can extend through the outer wall of the thermoplastic polymer / fiber material composite. The recess is configured to facilitate the bonding of one or more subsequent layers to the first layer and the second layer. For example, the recess can be configured to facilitate the bonding between the hollow thermoplastic polymer / fiber material composite and one or more subsequent layers. The recess and the cavity can be coaxial. The recess preferably includes a base that is adapted to facilitate the bonding of the thermoplastic polymer / fiber material composite to one or more subsequent layers. The base can include a bonding surface on which at least a portion of the one or more subsequent layers can be carried. The bonding surface can be substantially planar. The depth of the recess can be between about 1 mm and about 200 mm, or be about 1 mm to about 100 mm, or be about 5 mm to about 50 mm. The recess can further include sidewalls. The sidewalls preferably taper inwardly from the outer wall of the thermoplastic polymer / fiber material composite to the base of the recess. Advantageously, the inwardly tapering sidewalls facilitate the introduction of the one or more subsequent layers and their bonding to the thermoplastic polymer / fiber material composite.

[0031] The one or more thermoplastic polymers in the first layer include one or more of the following: ethylene homopolymers, ethylene copolymers, propylene homopolymers, propylene copolymers, fluoropolymers, polyvinyl chloride, polyvinylidene chloride, polyaryletherketones (e.g., polyetheretherketone), and polyamides.

[0032] In one 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 the following: glass fibers, carbon fibers, and basalt fibers or precursors thereof.

[0034] The one or more polymeric fibers may comprise one or two synthetic polymers and natural polymers.

[0035] The one or more polymeric fibers may include one or more of polyamides and polyolefins. Suitable polyolefins include polyethylene and polypropylene.

[0036] In one embodiment, the one or more fibrous materials include one or more woven fabric materials.

[0037] The one or more woven fabric materials may include one or more of the following: woven materials, knitted materials, and braided materials.

[0038] The one or more woven fabric materials comprise plied yarns. In one embodiment, the spacing between at least some of the yarns of the fibrous material of the second layer is from about 0.01 microns to about 5000 microns, or from about 0.1 microns to about 5000 microns, or between about 1 micron and about 5000 microns or between about 10 microns and about 5000 microns.

[0039] In one embodiment, the article includes a third layer that includes a plurality of filaments and one or more thermosetting polymers, the plurality of filaments selected from one or more of the following: carbon filaments, glass filaments, aramid filaments, and basalt filaments, wherein the second layer is disposed between the first layer and the third layer, and wherein the one or more fibrous materials are 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 outer side of the outer wall of the thermoplastic polymer / fibrous material composite. In this embodiment, the plurality of filaments engage the mating surface of the recess. In an alternative example, the third layer may be disposed over a lid that is connected to the cavity.

[0040] In another embodiment, the article includes a third layer that includes a plurality of filaments and one or more thermosetting polymers, the plurality of filaments being selected from one or more of the following: carbon filaments, glass filaments, aramid filaments, and basalt filaments, wherein the third layer is manually hand-laid onto the second layer, and wherein the one or more fiber materials are 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 outer side of the outer wall of the thermoplastic polymer / fiber material composite.

[0041] In one embodiment, the article includes a third layer that includes a plurality of filaments and one or more thermosetting polymers, the plurality of filaments being selected from one or more of the following: carbon filaments, glass filaments, aramid filaments, and basalt filaments, wherein the third layer is vacuum infused onto the second layer, and wherein the one or more fiber materials are 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 outer side of the outer wall of the thermoplastic polymer / fiber material composite.

[0042] In one embodiment, the one or more thermosetting polymers of the third layer include one or more of the following: vinyl ester, bismaleimide, polyester, polyacrylate, epoxy resin, and polyurethane.

[0043] In one embodiment, the filament diameter of the plurality of filaments of the third layer is 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 one embodiment, the plurality of filaments of the third layer are in one or more of the following forms: wound filaments, textile segments comprising a plurality of yarns, braided yarns, and chopped fibers.

[0045] In one embodiment, the thickness of the first layer is from about 0.1 mm to about 50 mm, the thickness of the second layer is from about 0.1 mm to about 5 mm, and the thickness of the third layer is from about 0.1 mm to about 1000 mm.

[0046] In one embodiment, the thermoplastic polymer is embedded in the gaps between the yarns of the fiber material of the second layer.

[0047] In one embodiment, the thermoplastic polymer is embedded within the structure of the individual yarns of the fiber material of the second layer.

[0048] In one embodiment, the tendrils of the fiber material of the second layer extend from the surface of the yarns into the first layer.

[0049] In one embodiment, the thermoplastic polymer does not fully penetrate through the thickness of the fiber layer. That is, at least a portion of the surface of the fiber layer is not fully penetrated by the thermoplastic polymer. Preferably, substantially all of the surface of the fiber layer is not fully penetrated by the thermoplastic polymer.

[0050] In a preferred form, the article is a hollow composite container (or a thermoplastic polymer / fiber material composite container), and the integral structure is configured to reduce the surge forces experienced by the hollow composite container during use. The integral structure may further be configured to reduce the 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 have an overall spherical, cylindrical, spherocylindrical, rectangular shape or any other shape commonly known in the art.

[0052] In a second aspect, the present invention provides a method of producing a hollow composite container, the method comprising:

[0053] applying one or more fiber materials to the inner surface of a hollow mold, the hollow mold including a structure protruding into the interior of the mold;

[0054] heating and rotating the hollow mold in the presence of one or more thermoplastic polymers within the hollow mold such that the polymers melt and at least partially penetrate the fiber materials;

[0055] cooling the mold such that the thermoplastic polymer solidifies; and

[0056] demolding a hollow thermoplastic polymer / fiber material composite container from the mold, the hollow thermoplastic polymer / fiber material composite container having an integrally formed structure protruding into the interior of the container.

[0057] Advantageously, the present invention enables the production of a hollow composite container having a substantially thermoplastic inner layer / first layer and a substantially fibrous second layer. The fibrous second layer may act as a suitable coupling layer adapted to enable the formation of additional layers therethrough. The thermoplastic inner layer may act as a barrier layer that is substantially impermeable to materials contacting the interior of the container. Additionally, the integrally formed structure of the container is seamlessly integrated into a container having this same multi-layer structure. Thus, there is no weld or connecting line between the container and the integrally formed structure.

[0058] It should be understood that the reference to the thermoplastic polymer / fiber material composite container refers to a hollow composite container having only the fiber material layer and the thermoplastic polymer layer.

[0059] In one embodiment, the method further comprises one or more of the following:

[0060] Applying a plurality of filaments to the exterior of the hollow thermoplastic polymer / fiber material composite container, the plurality of filaments being selected from one or more of the following: carbon filaments, glass filaments, aramid filaments, and basalt filaments, wherein prior to application, the plurality of filaments are at least partially wetted with one or more thermosetting polymers;

[0061] Applying a plurality of filaments to the exterior of the hollow thermoplastic polymer / fiber material composite container, followed by applying one or more thermosetting polymers, the plurality of filaments being selected from one or more of the following: carbon filaments, glass filaments, aramid filaments, and basalt filaments;

[0062] 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, the plurality of filaments being selected from one or more of the following: carbon filaments, glass filaments, aramid filaments, and basalt filaments.

[0063] Advantageously, providing this additional layer to the exterior of the hollow thermoplastic polymer / fiber material composite container increases the strength of the hollow composite container. The fiber layer of the hollow thermoplastic polymer / fiber material composite container facilitates the coupling of this additional layer thereto. Preferably, applying this additional layer causes the one or more fiber materials to be at least partially infiltrated with both the one or more thermoplastic polymers and the one or more thermosetting polymers.

[0064] In one embodiment, applying one or more fiber materials to the inner surface of a hollow mold includes fastening the one or more fiber materials to the inner surface of the hollow mold. The hollow mold may include fastening means (e.g., a fastening arrangement) for securing the one or more fiber materials to the inner surface of the hollow mold. In one embodiment, the method further includes holding the one or more fiber materials against 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 against the inner surface of the hollow mold. This can be achieved by supplying an air stream to the interior of the rotational molding device (where heating and rotation of the hollow mold occur), thereby applying a pressure differential across the one or more fiber materials to force the one or more fiber materials against the inner surface of the hollow mold. In one embodiment, a combination of gas pressure and a fastening arrangement may be employed to secure the one or more fiber materials to the inner surface of the hollow mold.

[0065] Applying one or more fiber materials to the inner surface of a hollow mold may include applying one or more of ceramic fibers and polymer fibers. Applying one or more ceramic fibers may include applying one or more of: glass fibers, carbon fibers, and basalt fibers or precursors thereof. Applying one or more polymer fibers may include applying one or two synthetic polymers and natural polymers. One or more polymer fibers may include one or more of polyamides and polyolefins. Suitable polyolefins include polyethylene and polypropylene.

[0066] In one embodiment, applying one or more fiber materials to the inner surface of a hollow mold includes applying a first fiber material to the inner surface of the hollow mold and applying a second fiber material to the first fiber material.

[0067] The one or more thermoplastic polymers may include one or more of: ethylene homopolymers, ethylene copolymers, propylene homopolymers, propylene copolymers, fluoropolymers, polyvinyl chloride, polyvinylidene chloride, polyaryletherketones (e.g., polyetheretherketone), and polyamides. The one or more thermoplastic polymers are preferably provided in powder form.

[0068] In one embodiment, the one or more fiber materials include one or more woven fabric materials. The one or more woven fabric materials may include one or more of the following: woven materials, knitted materials, and braided materials. The one or more woven fabric materials comprise plied yarns. In one embodiment, the spacing between at least some of the yarns of the fiber material is from about 0.01 microns to about 5000 microns, or from about 0.1 microns to about 5000 microns, or between about 1 micron and about 5000 microns or between about 10 microns and about 5000 microns.

[0069] The one or more thermosetting polymers may include one or more of the following: vinyl esters, bismaleimides, polyesters, polyacrylates, epoxy resins, and polyurethanes.

[0070] In one embodiment, the filament diameter of the plurality of filaments is from about 0.1 microns to about 500 microns, or from about 0.1 microns to about 100 microns, or from about 0.1 microns to about 50 microns, or from about 1 micron to about 20 microns.

[0071] In one embodiment, the plurality of filaments are in one or more of the following forms: wound filaments, textile segments comprising multiple yarns, braided yarns, and staple fibers.

[0072] In one embodiment, the thickness of the first layer is from about 0.1 mm to about 50 mm, the thickness of the second layer is from about 0.1 mm to about 5 mm, and the thickness of the additional layer is from about 0.1 mm to about 1000 mm.

[0073] In one embodiment, the thermoplastic polymer is embedded in the gaps between the yarns of the fiber material located in the second layer.

[0074] In one embodiment, the thermoplastic polymer is embedded within the structure of the individual yarns of the fiber material in the second layer.

[0075] In one embodiment, the tendrils of the fiber material in the second layer extend from the surface of the yarns into the first layer.

[0076] In one embodiment, the thermoplastic polymer does not completely penetrate through the thickness of the fiber layer. That is, at least a portion of the surface of the fiber layer is not completely penetrated by the thermoplastic polymer. Preferably, substantially all of the surface of the fiber layer is not completely penetrated by the thermoplastic polymer.

[0077] In one embodiment, the structure that projects into the interior of the mold of the hollow mold is one or more baffle mold parts, each of the one or more baffle mold parts being adapted to create cavities of substantially the same form in the hollow composite container (specifically, the hollow thermoplastic polymer / fiber material composite container), and thereby create the integrally formed structure that projects into the interior of the container, which in this embodiment is one or more baffles.

[0078] In one embodiment, the method includes reinforcing the integrally formed structure that projects into the interior of the container, e.g., reinforcing the baffle or each baffle. Preferably, reinforcing the baffle or each baffle occurs when an additional layer is applied to the hollow thermoplastic polymer / fiber material composite container. Preferably, reinforcing the baffle or each baffle includes inserting a reinforcement into each cavity. The reinforcement can take any form suitable for strengthening and / or stiffening the baffle. In one embodiment, the reinforcement can be a curable material, such as a foam or other curable polymer. The curable material can be injected into the cavity and allowed to cure. In an alternative embodiment, the method includes covering the cavity to fluidically isolate the cavity from the external environment of the container and injecting a pressurized gas into the sealed cavity. In a further embodiment, reinforcing the baffle or each baffle includes inserting a structural skin into each cavity.

[0079] In another embodiment, reinforcing the baffle or each baffle includes inserting a support structure into each cavity. The support structure can include a plurality of support elements that are fixed within the cavity and are arranged to strengthen and / or stiffen the baffle. The method can include forming the support structure by fixedly arranging the plurality of support elements relative to one another, followed by inserting the support structure into each cavity and fixing the support structure.

[0080] In one embodiment, reinforcing the baffle or each baffle includes inserting any combination of the above-mentioned reinforcements into each cavity.

[0081] In one embodiment, the method further includes forming a recess around the periphery of the cavity in the outer wall of the hollow thermoplastic polymer / fiber material composite container. The hollow mold can include a protrusion that is disposed around the periphery of the structure that projects into the interior of the mold, thereby forming the recess that extends through the outer wall of the hollow thermoplastic polymer / fiber material composite container. Alternatively, the recess can be formed after the hollow thermoplastic polymer / fiber material composite container is demolded from the mold.

[0082] It should be understood that the second aspect of the present invention may include any features defined relative to the first aspect of the present invention.

[0083] In a third aspect, the present invention provides a hollow composite container having an inner wall and a structure integrally formed with the inner wall, the inner wall defining the interior of the container, wherein the integrally formed structure projects into the interior of the container, the container being formed by a first layer and a second layer, the first layer comprising one or more thermoplastic polymers and the second layer comprising one or more fibrous materials.

[0084] It should be understood that the third aspect of the present invention may include any features defined relative to the first and second aspects of the present invention.

[0085] As used herein, unless the context otherwise requires, the term "comprise" and variations of the term such as "comprising", "comprises" and "comprised" are not intended to exclude additional additives, components, integers or steps.

[0086] Further aspects of the present invention and further embodiments of the aspects described in the foregoing paragraphs will become apparent from the following description, which is given by way of example and with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Figure 1 A perspective view of a hollow composite container according to an embodiment of the present invention is shown;

[0088] Figure 2 Shows Figure 1 A perspective partial view of the hollow composite container, wherein a portion of the container wall is hidden to show some underlying structure;

[0089] Figure 3 Is Figure 1 A transverse cross-sectional view of the hollow composite container, which shows a pair of baffles therein;

[0090] Figure 4 Shows Figure 1 A perspective partial view (and enlarged view) of the hollow composite container, wherein a portion of the container wall is hidden to show some underlying structure, the underlying structure including a baffle reinforcement structure;

[0091] Figure 5 A perspective view of a support structure according to an embodiment of the present invention is shown;

[0092] Figure 6 Shows Figure 1Cross-sectional view of the baffle of the container, which specifically shows the multi-layer structure of the container;

[0093] Figure 7 Cross-sectional view of the alternating baffle, which specifically shows the multi-layer structure of the container;

[0094] Figure 8 Cross-sectional view of another alternating baffle, which specifically shows the multi-layer structure of the container;

[0095] Figure 9 Cross-sectional view of another hollow composite container, which shows the baffle pairs therein;

[0096] Figure 10 Cross-sectional view of another hollow composite container, which shows four baffle groups therein;

[0097] Figure 11 Cross-sectional view of another hollow composite container, which shows the orifice plate therein;

[0098] Figure 12 Cross-sectional view of another hollow composite container, which shows the baffle pairs extending along the longitudinal direction of the container; and

[0099] Figure 13 Shows Figure 12 Perspective partial view of the hollow composite container, where a part of the container wall is hidden to show some underlying structures. Detailed Description

[0100] Refer to Figure 1 , the figure depicts a rotationally molded article in the form of a hollow composite container 10. As will be understood from the following discussion, the container 10 is adapted to contain and transport hazardous materials including chemicals, etc. However, it will be readily understood that the container 10 can be used to contain and transport non-hazardous goods as well as in similar sectors such as fuel and cargo storage tanks for constructing transport vehicles and in aerospace applications.

[0101] As will be described in further 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 structure container. As used herein, a 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 a rotational molding process, while a reference to a hollow composite container (or the like) may additionally include a reference to a modified form of a hollow thermoplastic polymer / fiber material composite container. For example, in certain applications, additional layers are added to a hollow thermoplastic polymer / fiber material composite container after the rotational molding process to render the container suitable for such applications. Thus, to avoid doubt, hollow composite container 10 includes additional layers which have been added to a hollow thermoplastic polymer / fiber material composite container after the rotational molding process. The multi-layered structure will be described in further detail below.

[0102] In the depicted embodiment, container 10 has a substantially spherocylindrical shape. However, alternative container shapes may also be provided, such as cylindrical, rectangular or any other shape commonly known in the art.

[0103] Now referring Figure 2 to a partial cross-sectional view of, in which one half of the outer wall 16 of the container has been removed, but the internal structure associated with that half of the wall is retained for explanatory purposes. Container 10 includes an inner wall 12 which defines an interior 14 of container 10. Container 10 further includes a structure integrally formed with inner wall 12 in the form of a plurality of baffles 20 projecting into interior 14 of container 10 and having a substantially lobed shape. Baffles 20 are provided to reduce the effects of surge forces which may be caused by movement of the contents contained within container 10 during transport. Such surge forces can make it more difficult to control a vehicle carrying container 10 and can also impose significant stresses on the walls of container 10. Thus, baffles 20 provide an impediment to movement of the contents contained within container 10 (in this case, movement generally parallel to the longitudinal axis of the container) and significantly reduce the forces imposed on the container walls during vehicle turning, stopping and starting.

[0104] As Figure 2 shown, three spaced-apart opposing pairs of baffles 20 extend into interior 14 of container 10. However, it should be understood that different baffle arrangements, different baffle shapes and different numbers of baffles may also be employed. Baffles 20 are formed by a structure of corresponding shape in a baffle mold (not shown) used to form container 10. As a result of forming baffles 20 by a structure of corresponding shape in the baffle mold, cavities 18 are formed in the outer wall of the hollow thermoplastic polymer / fiber material composite container formed during the rotational molding process.

[0105] Each baffle 20 includes a first baffle wall 22 and a second baffle wall 24, the first baffle wall extending from the inner wall 12 towards the interior 14, and the second baffle wall extending from the inner wall 12 towards the interior 14. The first baffle wall 22 and the second baffle wall 24 define substantially planar surfaces that are angled towards each other relative to the longitudinal axis of the baffle. Thus, when viewed in a transverse cross-section, the baffle has a substantially U-shaped configuration. The first baffle wall 22 and the second baffle wall 24 extending into the interior 14 of the container 10 smoothly merge into a substantially curved baffle tip 26 through a substantially curved tip transition portion 25 disposed between the first baffle wall 22 and the baffle tip 26 and between the second baffle wall 24 and the baffle tip 26 (best shown in Figure 6 ). The radius of curvature of the tip transition portion 25 can range from about 2 mm to about 500 mm. This curvature of the tip transition portion 25 is an important feature for enhancing the manufacturability of the container 10 having the integrally formed baffle 20. One of the challenges in manufacturing the container 10 is to ensure sufficient contact time between the thermoplastic polymer and the fibrous material throughout the hollow mold during the rotational molding process. Since there are many challenges in rotational molding a multi-layer structure of complex shape, providing a hollow mold with a portion having a corresponding shape for the substantially curved tip transition portion 25 increases the contact time between the thermoplastic polymer and the fibrous material around this complex portion of the mold.

[0106] A smooth substantially curved base transition portion 27 is provided between the inner wall 12 and the first baffle wall 22 and between the inner wall 12 and the second baffle wall 24 at the base 23 of each baffle 20 (as Figure 6 shown). Similar to the tip transition portion 25, providing a substantially curved base transition portion 27 between the inner wall 12 and the first baffle wall 22 and between the inner wall 12 and the second baffle wall 24 is important in facilitating the proper formation of the baffle 20 during the rotational molding process. Significant discontinuities in the surface shape (such as sharp corners and bends) increase the complexity of producing the container 10 having an integrally formed structure (such as the baffle 20 having the necessary structural integrity). Thus, it is most preferred that the outer surface profile 21 of the baffle 20 is substantially continuous with the inner wall, i.e., a seamless transition is provided between the inner wall 12, the first baffle wall 22, the second baffle wall 24, and the baffle tip 26.

[0107] Now referring to Figure 3, The figure provides a transverse cross-sectional view of the container 10, with particular attention to the baffle pair 20, which extends from substantially opposite positions on the inner wall 12 into the interior 14 of the container 10. Each baffle 20 extends slightly less than half the diameter of the interior 14. Thus, a gap 29 is provided between the respective tips 26 of the baffles 20. In the present embodiment, due to the particular arrangement of the baffles 20, when viewed in cross-section, the gap 29 has a substantially V-shaped configuration, where the narrower end of the V-shaped gap 29 is located at the lower end of the container 10 and the wider end of the V-shaped gap 29 is located at the upper end of the container 10. Providing the wider end of the V-shaped gap 29 at the upper end of the container 10 in applications where the container 10 is substantially horizontally oriented (i.e., approximately parallel to the ground) is advantageous as it improves access to the interior 14 of the container 10 (access is typically provided through a manhole at 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 a greater sloshing load at the lower points of the container 10 (i.e., a lower center of gravity of the contents within the container).

[0108] As will be appreciated by Figure 2 Understood, each baffle 20 partially defines a boundary between adjacent compartments within the container 10. In the present embodiment, the container 10 has three pairs of baffles 20, each pair of baffles partially defining a boundary between adjacent compartments within the container 10 - there are four compartments 30a, 30b, 30c, 30d within the container 10. Each gap 29 between each pair of baffles 20 is adapted to maintain fluid communication between adjacent compartments of the container 10.

[0109] Referring to Figure 4 , the baffles 20 are reinforced using a suitable reinforcement structure 40, which is mounted within the cavity 18 of the container 10. The reinforcement is configured to resist the internal and external loads experienced by the container 10, particularly the baffles 20, under operating loads. Specifically, the reinforcement is configured to strengthen and / or stiffen the baffles 20.

[0110] As in the case of the baffles 20, the cavity 18 has a substantially U-shaped configuration in cross-section and is defined by a first outer baffle wall 17 (the exterior of the first baffle wall 22), a second outer baffle wall 19 (the exterior of the second baffle wall 24), and a substantially curved outer wall 15 (the exterior of the baffle tip 26). In the present embodiment, the reinforcement structure 40 includes a structural skin 42, which is formed from a medium-strength carbon fiber-reinforced polymer and a core sandwich wet-laid into each cavity 18. Specifically, the structural skin 42 is applied along most of the interior of the cavity, i.e., along the first outer baffle wall 17, the second outer baffle wall 19, and the outer wall 15.

[0111] While for some applications, the separate structural cortex 42 may be sufficient to provide the necessary reinforcement for the baffle 20 to withstand operating loads, in the present embodiment, the structural cortex 42 additionally facilitates the connection of the support structure 44 to the cavity 18. As Figure 4 Best shown in the close-up view of the cavity 18 in Figure 5 , the support structure 44 includes a plurality of support elements that are fixed in the cavity 18 to strengthen and / or reinforce the baffle 20. The support elements include: a plurality of first support beams 45 that are oriented substantially perpendicular to the baffle tip 26 and extend between the first outer baffle wall 17 and the second outer baffle wall 19; a plurality of second support beams 46 that are oriented substantially parallel to the baffle tip 26 and extend in a direction substantially perpendicular to the beams 45; and splints 47 that are fixed along each longitudinal side of the beams 45 and 46, and the splints 47 are shaped such that the beams 45, 46 can be connected to the cavity 18. The beams 45, 46 and the splints 47 are formed of wet-laid carbon fiber (using a suitable thermosetting resin) and are fixed to the structural cortex 42 using an adhesive. While each of the beams 45, 46 can be individually connected to the structural cortex 42 (thereby forming the support structure 44), it is preferred that the support structure 44 be preformed (or partially preformed) by fixedly arranging a plurality of beams 45 in a spaced-apart relationship relative to one or more of the beams 46 (each of the beams 45, 46 already having the splints 47 formed or fixed therewith), and the one or more support structures 44 can then be installed in the cavity 18. Figure 5 An example of a suitable preformed support structure is shown. After the support structure 44 is installed in the cavity 18, the cavity can be closed by a lid (not shown) that is connected to the outer wall of the hollow thermoplastic polymer / fiber material composite container and is configured to shield the reinforcement and provide a consistent outer profile for the hollow thermoplastic polymer / fiber material composite container. However, in other embodiments, a lid may not be used.

[0112] While the depicted embodiment of the support structure 44 is substantially in the form of a lattice-like frame with the beams 45, 46 arranged substantially perpendicular to each other, it should be understood that the support structure 44 can take many other different arrangements. Additionally, while the reinforcement structure 40 in the present embodiment is provided in the form of a combination of the structural cortex 42 and the support structure 44, this need not be the case. In other embodiments, the reinforcement structure can be a curable material, such as a foam or other curable polymer, that has been injected into the cavity 18 and allowed to cure. In an alternative embodiment, instead of using the reinforcement structure itself, the cavity 18 can be reinforced by injecting a pressurized gas therein (after fluid-sealing the cavity with a suitable lid).

[0113] ReferenceFigure 6 , the container 10 is formed of a multi-layer structure, the multi-layer structure including a first inner layer 52 and a second layer 54, the first inner layer including one or more thermoplastic polymers, and the second layer including one or more fibrous materials. As a result of the rotational molding process explained in more detail below, one or more fibrous materials are at least partially infiltrated with one or more thermoplastic polymers. The thermoplastic polymer inner layer 52 acts as a barrier layer that is substantially impermeable to materials contacting the inner layer 52, while the fibrous second layer 54 acts as a suitable coupling layer adapted to achieve a proper coupling with other layers formed therewith. In addition, the baffle 20 of the container 10 is seamlessly integrated into the container 10 having the same multi-layer structure, the multi-layer structure having a first layer and a second layer. Thus, there is no weld line between the container 10 and the baffle 20.

[0114] The thermoplastic polymer used to construct the first layer 52 is preferably resistant to various substances and conditions. For example, it is resistant to one or more of high pH, low pH, oxidizing agents, reducing agents, solvents, high-pressure gases, low-temperature substances, permeation, and abrasion.

[0115] One or more thermoplastic polymers in the first layer 52 include one or more of the following: ethylene homopolymers, ethylene copolymers, propylene homopolymers, propylene copolymers, fluoropolymers, polyvinyl chloride, polyvinylidene chloride, polyaryletherketones (e.g., polyetheretherketone), and polyamides.

[0116] Suitable fluoropolymers include one or more of the following: polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, perfluoroalkoxyalkanes, fluorinated ethylene-propylene, ethylene tetrafluoroethylene, ethylene chlorotrifluoroethylene, polyethylene tetrafluoroethylene, and polyethylene chlorotrifluoroethylene.

[0117] One or more fibrous materials of the second layer 54 may include one or more of ceramic fibers and polymer fibers.

[0118] Container 10 includes reinforcing layers 56, 58 that are configured to increase the strength and stiffness of the container 10. The reinforcing layers 56, 58 are applied to the thermoplastic polymer / fiber material composite container in a variety of 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 layer can be vacuum-infused. In a further example, the reinforcing layer can involve: (1) filament winding one or more of carbon filaments, glass filaments, aramid filaments, and basalt filaments around the exterior 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 of carbon filaments, glass filaments, aramid filaments, and basalt filaments around the exterior of the container 10, followed by the application of one or more thermosetting polymers; or (3) applying one or more thermosetting polymers to the exterior of the container 10, followed by filament winding one or more of carbon filaments, glass filaments, aramid filaments, and basalt filaments. As a result of applying the reinforcing layers 56, 58, one or more fiber materials of the second layer 54 are at least partially infiltrated with one or more thermoplastic polymers of the first layer 52 and one or more thermosetting polymers of the reinforcing layers 56, 58.

[0119] The one or more thermosetting polymers can include one or more of the following: vinyl ester, bismaleimide, polyester, polyacrylate, epoxy resin, and polyurethane.

[0120] As previously mentioned, there can be many variations of the baffles and integral baffle arrangements mentioned above.

[0121] Figure 7 An alternative embodiment is provided in which the hollow thermoplastic polymer / fiber material composite container includes an insert 62 that is provided around the periphery of the cavity 18. The insert 62 is configured to facilitate the engagement between the hollow thermoplastic polymer / fiber material composite container and one or more reinforcing layers. The insert 62 includes a base 64 that is adapted to facilitate improved engagement of the reinforcing layer 56 with the container 10, particularly around the cavity 18. The base 64 includes a substantially planar engagement surface 66 on which the reinforcing layer 56 can be seated. The insert 62 further includes a sidewall 65 that tapers inwardly 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 improved introduction of the reinforcing layer 65 and its engagement with the thermoplastic polymer / fiber material composite container. The outermost reinforcing layer 58 of the fiber-reinforced polymer is applied over the entirety of the hollow thermoplastic polymer / fiber material composite container to increase the strength and stiffness of the container 10. In an alternative embodiment, a single reinforcing layer is provided for the entire container 10.

[0122] Figure 8 An additional alternative embodiment is provided, specifically, an alternative embodiment regarding the baffle 20. In this embodiment, relative to Figure 7 the embodiment of, the baffle 20' includes a flat baffle tip 26'. However, it should be understood that the outer surface profile of the baffle 20' remains substantially continuous with the inner wall 12', i.e., a seamless transition is provided between the inner wall 12', the first baffle wall 22', the second baffle wall 24', and the baffle tip 26' due to the substantially curved tip transition portion 25' and the substantially curved base transition portion 27'.

[0123] Figure 9 An additional alternative embodiment of the container 10 is provided. In this embodiment, a transverse cross-sectional view of the container 10 shows a pair of diametrically opposed baffles 20” that extend into the interior 14 of the container 10. The shape of the gap 29” located between the corresponding tips 26” of the baffles 20” is substantially rectangular.

[0124] Figure 10 An additional alternative embodiment of the container 10 is provided. In this embodiment, a transverse cross-sectional view of the container 10 shows four circumferentially equally spaced baffles 20”' that extend into the interior 14 of the container 10. The gap 29”' located between the corresponding tips 26”' of the baffles 20”' is substantially cross-shaped.

[0125] Figure 11 An additional alternative embodiment of the container 10 is provided. In this embodiment, a transverse cross-sectional view of the container 10 shows a single baffle in the form of an orifice plate 20”” that extends into the interior 14 of the container 10. The shape of the gap 29”” located between the tips 26”” of the orifice plate 20”” (i.e., the shape of the orifice) is substantially circular.

[0126] Figure 12 and 13 An additional alternative embodiment of the container 10 is provided. In this embodiment, a transverse cross-sectional view of the container 10 shows a pair of diametrically opposed baffles 20””' that extend into the interior 14 of the container 10. In this embodiment, the baffles 20””' extend in a direction substantially parallel to the longitudinal axis of the container 10. This arrangement can be specifically used in applications where the container 10 is vertically oriented during use (such as in aerospace applications).

[0127] Example method

[0128] An example of a method suitable for producing a hollow composite container will now be described. However, it should be understood that alternative methods may also be employed.

[0129] The method involves preparing a hollow mold for producing a hollow composite container. In this embodiment, this involves suitably preparing a plurality of hollow mold elements which, when assembled together, form the mold for the entire hollow composite container. In this example, the hollow mold elements include a generally cylindrical section and two generally hemispherical end sections. The generally cylindrical section includes structures projecting into the interior of the mold in the form of pairs of baffle mold parts. The baffle mold parts may be integrally formed parts of the cylindrical section or the baffle mold parts may be formed by one or more separate components which may be suitably fixed to the cylindrical section. The hollow mold elements may be formed from a substantially steel framework.

[0130] A first fibrous material is held to the inner surface of each hollow mold element by suitable fastening means (e.g., a suitable fastening arrangement). In this example, ceramic fibers are used. A suitable adhesive is then applied to the outer surface of the first fibrous material. This is followed by fixing the position of a second fibrous material on top of the first fibrous material 160. In this example, polymer fibers are used. Although two fibrous materials have been applied to the inner surface of each hollow mold element, those skilled in the art will understand that one or more fibrous materials may be used during this process stage. Further, the two fibrous materials mentioned are only considered exemplary as alternative fibrous materials may be employed during this process. Although it is not necessary to apply the same arrangement and type of fibrous materials to each hollow mold element, this is preferred in terms of forming a homogeneous and consistent hollow composite container.

[0131] After each hollow mold element has been prepared, the hollow mold elements are suitably assembled and fixed together to form the mold for the entire hollow composite container. The assembled mold is then inserted into a rotational molding apparatus.

[0132] An example is shown by placing approximately 350 kg of polyethylene powder into the rotational molding apparatus before it is closed. While the assembled mold is undergoing rotation and conventional rotational mold heating, gas pressure is used to hold the fibrous material layers against the inner surface of the hollow mold. This is achieved by supplying an air stream into the interior of the rotational molding apparatus, thereby applying a pressure differential across the fibrous material to force the fibrous material against the inner surface of the assembled mold.

[0133] During the duration of the entire rotational molding process, various rotational molding parameters are considered and varied throughout the process to produce a suitable hollow composite container. These parameters include:

[0134] ● Mould temperature and heating method;

[0135] ● Rotation speed of the rotational moulding equipment (about the longitudinal axis);

[0136] ● Tilt speed of the rotational moulding equipment (about the transverse axis);

[0137] ● Tilt angle - the maximum angle relative to the longitudinal axis achieved by rotating the moulding equipment about the transverse axis;

[0138] ● Pressure - the pressure inside the mould used to help hold the fibrous layer against the inner surface of the mould and maintain contact between the molten polyethylene and the fibrous layer; and

[0139] ● Time - how long certain parameters are maintained.

[0140] Throughout the process, attention should be paid to adjusting the set temperature, mould temperature and pressure of the rotational moulder equipment to ensure that a suitable polyethylene "build-up" is established on the inner surface of the assembled mould (especially at the baffle structure). As previously mentioned, the formation of the baffle structure has been carefully designed to ensure that the contact time between the polyethylene and the baffle structure is sufficient to produce a moulded baffle with appropriate structural integrity in the resulting hollow composite container.

[0141] After the polyethylene has been properly melted and dispersed, the set temperature and mould temperature of the rotational moulder equipment are reduced, and then finally the heating is switched off to allow the mould to cool, causing the polyethylene to solidify. When the temperature measured inside the mould is suitably low (and well below the melting point of the polyethylene powder), the pressure is released through the outlet valve. Near the end of the process, the rotation of the rotational moulding equipment about both the longitudinal and transverse axes is stopped. The hollow thermoplastic polymer / fibre material composite container, which has structures (e.g., baffles) protruding into the interior of the container, can then be demoulded from the mould.

[0142] A thickness gauge is used to check the thickness of the resulting thermoplastic polymer / fibre material composite container, and external inspection shows that the fibrous layer is firmly attached to the polyethylene by partial rather than complete wetting through the polyethylene into the fibrous layer. Visual internal inspection shows that the thickness of the internal polyethylene layer is always sufficient and there are no obvious thin spots.

[0143] A second example is shown by placing approximately 225 kg of polyethylene powder into the rotational molding apparatus prior to closing the rotational molding apparatus. The previous steps for preparing the hollow mold were carried out according to the first trial run. Similar to the first trial run, various rotational molding parameters varied throughout the duration of the rotational molding process to produce a suitable hollow composite container. As will be understood 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 will be reduced. The temperature and pressure employed were additionally similar to those employed in the first trial run.

[0144] A thickness gauge was again used to check the thickness of the resulting thermoplastic polymer / fiber material composite container, and an external inspection showed that the fiber layer was firmly attached to the polyethylene by partial rather than complete wetting through the polyethylene into the fiber layer. A visual internal inspection showed that the thickness of the internal polyethylene layer was always sufficient, but there was a certain appearance of thin spots.

[0145] The next stage of the process involves strengthening the baffle structure. In the present embodiment, this is achieved by inserting a reinforcement into a cavity formed in the outer wall of the hollow thermoplastic polymer / fiber material composite container. However, it should be understood that in other embodiments, although not desirable, the baffle structure can be strengthened from the inside of the container. There are many possible ways in which the cavity can be suitably strengthened to meet the load requirements of the hollow composite container, for example, in particular the surge forces experienced by the container 10 or any structure to which the container 10 is attached during use.

[0146] In the present embodiment, a structural skin formed of a polymer and core sandwich reinforced with medium-strength carbon fibers is wet-laid into the cavity. In addition to the structural skin, further reinforcement is provided by inserting a support structure into the cavity. The support structure includes a plurality of support elements, each support element being made of a polymer reinforced with wet-laid standard-strength carbon fibers, and the plurality of support elements are fixed to the structural skin using a suitable adhesive (e.g., a synthetic resin such as a thermosetting adhesive).

[0147] The hollow thermoplastic polymer / fiber material composite container is then enhanced as follows: multiple filaments are applied to the exterior of the hollow thermoplastic polymer / fiber material composite container, the multiple filaments being selected from one or more of the following: carbon filaments, glass filaments, aramid filaments, and basalt filaments, wherein prior to application, the multiple filaments are at least partially wetted with one or more thermosetting polymers. Thus, a hollow composite container with increased strength and stiffness is formed. The fiber layer of the hollow thermoplastic polymer / fiber material composite container facilitates its coupling with the reinforcing layer, whereby the fiber material is at least partially infiltrated with both one or more thermoplastic polymers and one or more thermosetting polymers.

[0148] It should be understood that the invention, as disclosed and defined in this specification, extends to all alternative combinations of two or more of the individual features mentioned or evident in the text or drawings. All such different combinations constitute various alternative aspects of the invention.

Claims

1. A hollow rotationally molded article having an inner wall and a structure integrally formed with the inner wall, the inner wall defining the interior of the article, wherein the integrally formed structure projects into the interior of the article, the article being formed from a first layer and a second layer, the first layer comprising one or more thermoplastic polymers and the second layer comprising one or more fiber materials.

2. The hollow rotationally molded article according to claim 1, wherein the one or more fiber materials are at least partially infiltrated with the one or more thermoplastic polymers.

3. The hollow rotationally molded article according to claim 1 or 2, wherein the article comprises at least one cavity extending towards the interior of the article, the cavity comprising an inner surface profile that substantially corresponds to the outer surface profile of the integrally formed structure.

4. The hollow rotationally molded article according to claim 3, wherein the article comprises a recess disposed around the periphery of the at least one cavity, the recess being configured to facilitate the bonding of one or more subsequent layers to the first and second layers.

5. The hollow rotationally molded article according to claim 3 or 4, further comprising a reinforcement disposed in the at least one cavity, the reinforcement being configured to strengthen and / or reinforce at least a portion of the integrally formed structure.

6. The hollow rotationally molded article according to claim 5, wherein the reinforcement comprises a structural skin fixed in the at least one cavity.

7. The hollow rotationally molded article according to claim 5 or 6, wherein the reinforcement comprises a support structure adapted to be connected in the at least one cavity, the support structure comprising a plurality of support elements fixed in the cavity and arranged to strengthen and / or reinforce the integrally formed structure.

8. The hollow rotationally molded article according to claim 7, wherein the support elements have a substantially beam-like form and are arranged in a substantially lattice-like framework.

9. The hollow rotationally molded article according to claim 7 or 8, dependent on claim 6, wherein the support structure is fixed to the structural skin.

10. The hollow rotationally molded article according to any one of the preceding claims, wherein the integrally formed structure projecting into the interior of the article is one or more baffles.

11. The hollow rotationally molded article according to claim 10, wherein the one or more baffles are arranged to extend in a direction substantially parallel to the longitudinal axis of the article.

12. The hollow rotationally molded article according to claim 10, wherein the one or more baffles are arranged to extend in a direction substantially perpendicular to the longitudinal axis of the article.

13. The hollow rotationally molded article according to claim 12, wherein the baffle pair extends into the interior of the article from substantially opposite positions of the inner wall, and a gap is formed between the baffle pair.

14. The hollow rotationally molded article according to claim 13, wherein when the article is viewed in a transverse cross-section, the gap is substantially V-shaped, with the narrower end of the V-shaped gap disposed at the lower end of the article and the wider end of the V-shaped gap disposed at the upper end of the article.

15. The hollow rotationally molded article according to any one of claims 10 to 14, wherein the baffle or each baffle comprises a first baffle wall and a second baffle wall, each of the first baffle wall and the second baffle wall extending from the inner wall of the article into the interior of the article and merging into a baffle tip.

16. The hollow rotationally molded article according to claim 15, wherein when the baffle is viewed in a transverse cross-section, the first baffle wall and the second baffle wall are angled towards each other, thereby defining a substantially U-shaped baffle.

17. The hollow rotationally molded article according to claim 15 or 16, wherein the baffle or each baffle comprises a tip transition portion located between the first baffle wall and the baffle tip and between the second baffle wall and the baffle tip, wherein the tip transition portion is substantially curved, thereby defining a smooth transition profile located between the first baffle wall and the baffle tip and between the second baffle wall and the baffle tip.

18. The hollow rotationally molded article according to claim 17, wherein the radius of curvature of the tip transition portion is in the range of about 2 mm to about 500 mm.

19. The hollow rotationally molded article according to any one of claims 15 to 18, wherein the article comprises a substantially curved base transition portion located between the inner wall and the first baffle wall and between the inner wall and the second baffle wall.

20. The hollow rotationally molded article according to any one of claims 15 to 19, wherein the outer surface profile of the baffle or each baffle is substantially continuous with the inner wall, thereby providing a seamless transition between the inner wall, the first wall, the second wall and the baffle tip of the article.

21. The hollow rotationally molded article according to any one of the preceding claims, wherein the one or more thermoplastic polymers in the first layer comprise one or more of the following: ethylene homopolymer, ethylene copolymer, propylene homopolymer, propylene copolymer, fluoropolymer, polyvinyl chloride, polyvinylidene chloride, polyaryletherketone and polyamide.

22. The hollow rotationally molded article according to any one of the preceding claims, wherein the one or more fiber materials in the second layer comprise one or more of the following: glass fiber, carbon fiber and basalt fiber or precursors thereof.

23. A hollow rotationally molded article according to any one of the preceding claims, wherein the article comprises a third layer comprising a plurality of filaments and one or more thermosetting polymers, the plurality of filaments being selected from one or more of the following: carbon filaments, glass filaments, aramid filaments, and basalt filaments, wherein the second layer is disposed between the first layer and the third layer, and wherein the one or more fiber materials are at least partially infiltrated with both the one or more thermoplastic polymers and the one or more thermosetting polymers.

24. A hollow rotationally molded article according to claim 23, wherein the one or more thermosetting polymers of the third layer comprise one or more of the following: vinyl ester, bismaleimide, polyester, polyacrylate, epoxy resin, and polyurethane.

25. A hollow rotationally molded article according to any one of the preceding claims, wherein the article is a hollow composite container, and the integral structure is configured to reduce the surge forces experienced by the hollow composite container during use.

26. A method of producing a hollow composite container, the method comprising: applying one or more fiber materials to an inner surface of a hollow mold, the hollow mold comprising a structure protruding into the interior of the mold; heating and rotating the hollow mold in the presence of one or more thermoplastic polymers such that the polymer melts and at least partially infiltrates the fiber materials; cooling the mold such that the thermoplastic polymer solidifies; and demolding a hollow thermoplastic polymer / fiber material composite container from the mold, the hollow thermoplastic polymer / fiber material composite container having an integrally formed structure protruding into the interior of the container.

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

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

29. The method according to claim 27, wherein the one or more thermosetting polymers include one or more of the following: vinyl ester, bismaleimide, polyester, polyacrylate, epoxy resin, and polyurethane.

30. The method according to any one of claims 26 to 28, wherein applying one or more fibrous materials to the inner surface of the hollow mold includes applying one or more of the following: glass fiber, carbon fiber, and basalt fiber or precursors thereof.

31. The method according to any one of claims 26 to 29, wherein the one or more thermoplastic polymers include one or more of the following: ethylene homopolymer, ethylene copolymer, propylene homopolymer, propylene copolymer, fluoropolymer, polyvinyl chloride, polyvinylidene chloride, polyaryletherketone, and polyamide.

32. The method according to any one of claims 26 to 30, wherein the structure protruding into the interior of the mold of the hollow mold is one or more baffle mold parts, and each of the one or more baffle mold parts is adapted to create cavities of substantially the same form in the hollow thermoplastic polymer / fiber material composite container.

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

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

35. The method according to claim 33 or 34, wherein reinforcing the integrally formed structure includes inserting a support structure into each cavity, wherein the support structure includes a plurality of support elements fixed in the cavity and arranged to strengthen and / or reinforce the integrally formed structure.

36. The method according to any one of claims 26 or 35, wherein the hollow mold further includes a protrusion disposed around the periphery of the structure protruding into the interior of the mold, wherein the hollow thermoplastic polymer / fiber material composite container thus includes a recess extending through the outer wall of the thermoplastic polymer / fiber material composite and disposed around the periphery of the cavity.

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