Background of the invention

The invention relates to multilayer composite product structures.

These days, recycling materials and products is subject to more and more stringent requirements. The recycling of thermosetting plastic materials and products made of them, especially those containing fibres (glass, carbon, plas tics, natural etc.), know commonly as fibre reinforced plastics or FRPs, is very challenging. Those technologies under study like pyrolysis and solvolysis are at yet at relatively low technical readiness level, consume huge amounts of energy and chemicals and leave contaminated fibre and chemical substances residues that are highly complex for any disposal options. Cement kiln is one of the options experienced today what to do with FRP-waste but the type of special grade of ce ment produced has limited demand in the market and it is not a circular recycling option but an end of life method. Therefore, the ever-increasing need exists to de velop soonest possible new environmentally friendly sustainable technologies for the recycling of such materials and circular products made thereof for boosting material efficiency in all plastics.

Brief description of the invention

It is an object of the invention to develop a new multilayer product and a new method for forming a multilayer product. The invention is characterised by what is stated in the independent claims. Embodiments of the invention are dis closed in the dependent claims.

The invention is based on the multilayer product having at least two layers or more. At least one layer or two layers consist(s) of End of Life (EoL) waste of fibre reinforced thermosetting plastic (FRP) or discarded production waste of fibre reinforced thermosetting plastic combined into a thermoplastic matrix. The thermoplastic matrix and thermosetting plastic and fibres are par tially chemically connected to each other by one or more binders or coupling agents. Such a solution creates a product whose production is able to make use of waste material whose recycling is very challenging.

In accordance with an embodiment, the product has a surface layer and a core layer so that the core layer comprises End of Life waste of fibre rein forced thermosetting plastic (FRP) combined into a thermoplastic matrix. This means that waste that is of lower quality, not adequate for the surface layer, con tains typically contamination, is made of old materials maybe containing non- wanted substances, and difficult to utilize may also be recycled and carries resid ual value.

According to another embodiment, the product has a surface layer and a core layer so that the core layer comprises End of Life waste of fibre reinforced thermosetting plastic (FRP) combined into a thermoplastic matrix, and the sur face layer comprises fibre reinforced thermosetting plastic from discarded pro duction waste combined into a thermoplastic matrix, but the surface layer is free from the End of Life waste of fibre reinforced thermosetting plastic. This way, product is achieved whose surface characteristic may be made adequate to fulfil the requirements set by the application, but nevertheless lower quality material with a challenging recyclability may be utilized. This helps increase the recyclabil ity degree of waste materials and raise material efficiency in general of all plastics waste.

The idea behind a third embodiment is that the maximum particle size of the thermosetting plastic of the surface layer is smaller than 1 mm. In such a case, it may be ensured that the properties of the surface layer are kept at an adequately high level.

The presented solution develops and establishes in the global markets (primarily in construction) several new multilayer product designs containing both thermoplastic and cured thermosetting materials in alternative mixed mate rial composite formulations.

The presented solution is able to offer cost effective, affordable bulky solutions into global volume markets and applications "fit for purpose" where most lucrative solutions are found among mechanical recycling and thereafter uti lization of the FRP-waste as reinforcement (and not a filler) in multilayer thermo plastic product structures.

Brief description of the drawings

The invention will now be described in greater detail by means of pre ferred embodiments and with reference to the attached drawings, in which

Figure 1 is an end view of a multilayer product in cross-section;

Figure 2 is an end view of a second multilayer product in cross- section;

Figure 3 is an end view of a third multilayer product in cross-section; Figure 4 is an end view of a fourth multilayer product in cross-section; Figure 5 is an end view of a fifth multilayer product in cross-section; Figure 6 is an end view of a sixth multilayer product in cross-section; Figure 7 is an end view of a seventh multilayer product in cross- section;

Figure 8 is an end view of an eighth multilayer product in cross- section; and

Figure 9 is an end view of a ninth multilayer product in cross-section.

Detailed description of the invention

Figure 1 shows a multilayer product 1 which has two layers, that is, a surface layer 2 and core layer 3. The surface layer 2 refers to a layer which in a usage situation of the product may be more visible or more subject to environ mental conditions, for example, or for whose properties are for some other rea son set higher requirements than the properties of the core layer.

Figure 2 shows a multilayer product 1 in which the surface layer 2 is totally encasing the core layer 3. The embodiment of Figure 2 may be carried out by the use of co-extrusion, for example. In the embodiments of Figures 1 and 2, the multilayer product 1 may be a plank, board, plate, or slab, for example.

Figure 3 shows a multilayer product 1 that is a round pipe whose out er layer is the surface layer 2, and the inner layer is the core layer 3. The product according to Figure 3 may also be a square and/or rectangular pipe or channel and/or another kind of rotationally symmetrical pipe or channel. Such a pipe or channel may be, for example, a pipe or channel that in use stays visible or subject to environmental conditions, which is why the outer surface has certain property requirements set for it, such as aesthetics or fire protection. The requirements for the properties of the inner surface, instead, are less demanding.

Figure 4 shows a multilayer product 1 whose inner layer is the surface layer 2 and the outer layer is the core layer 3. Such a pipe may be, for example, a pipe to be buried in the ground and whose property requirements for the outer layer differ from the property requirements of the inner layer. For example, the outer layer may be required to be stiffer and/or harder than the inner layer. The inner layer, for its part, needs to be smoother and/or more durable, such as better toughness and/or chemical resistance than the outer layer. The product accord ing to Figure 4 may also be a square and/or rectangular pipe or channel and/or another kind of rotationally symmetrical pipe or channel.

Figure 5 shows a multilayer product 1 in which both the innermost layer and the outermost layer are the surface layer 2. There may be one or more intermediate layer between the surface layers. In the embodiment of Figure 5, the multilayer product 1 has one core layer 3 between the surface layers. In the em- bodiment of Figure 5, stricter requirements may be set for the innermost and outermost layer than for the layer in between them.

Figure 6 shows a multilayer product 1 which has a surface layer 2 at the top and bottom, as seen in the Figures, and between them a core layer 3. Fig ure 7 shows a multilayer product 1 in which the surface layer 2 is adapted from its top side and partly or entirely from both sides on the core layer 3.

The multilayer product 1 may also comprise hollows. Hollows of prod ucts made by extrusion, for example, of which hollows there may be one or more, may be internal cavities 4 in the longitudinal direction of the product, as Figure 8 shows. Furthermore, the hollows may be grooves 5 in the sides of the product as shown in Figure 9. Hollows may be used in deck planks, for example. The hollows may be rectangular, round, oval, or of another shape in cross section. The manu facture of multilayer products of Figures 6 to 9 is also achievable by means of conventional multilayer extrusion.

In addition to the embodiments of Figures 1 to 9, the multilayer prod uct 1 may be, for example, a ribbed or corrugated 2-layer pipe which has a smooth inner surface, a 3-layer pipe with smooth inner and outer layers and a ribbing or corrugation between them, a pipe on top of which there is fastened a reinforcement profile continuing spirally around it, a square or rectangular pro file, 1 or U or L beam, a container, vessel, tank, sewerage or separating well, bottle, canister, another profile or container.

According to an embodiment, the multilayer product 1 is a structure according to Figure 1, in which the core layer 3 comprises fibre reinforced ther mosetting plastic FRP, obtained from anywhere, and combined into thermo plastic, and the surface layer 2 comprises thermoplastic but excludes thermoset ting plastic waste. If the thermoplastic of the core layer 3 and the surface layer 2 adhere sufficiently to each other, no additive layer is needed between the layers. If, however, the thermoplastics of the different layers do not naturally adhere to each other, then a layer of adhesion polymer is formed between the surface layer 2 and core layer 3. The thermoplastic used may be virgin material or recycled ma terial, and may include, for example, fibres, minerals, colouring agents, colourants and/or accessory agents etc.

The manufacturing method of the multilayer product 1 may be, for ex ample, extrusion, press moulding, moulding, blow moulding, rotational moulding, or intrusion. The multilayer product 1 may also be manufactured by first manu facturing a 1-layer semi-finished product from a material mixture and finishing it in its final form by coating or by casting, glueing or heat welding it in another ma terial as a so-called hybrid material. Coating may take place by a number of ways and alternative surface materials. Coating may be performed by laminating, spraying or painting, for example.

The core layer 3 may consist of a material mixture which consists of hardened, fibre reinforced thermosetting plastic waste, originating from products that are at the end of their life cycle or discarded production waste of such a product combined into a thermoplastic matrix. The thermoplastic matrix and thermosetting plastic are chemically connected to each other by one or more binders or coupling agents. In addition, the material mixture may contain other materials as well, such as natural fibre, cellulose, aluminium film, minerals, glass or carbon fibre etc. The discarded production waste of a thermosetting plastic product may consist of surplus pieces, cuttings, or grinding waste left over in connection with production.

Thermosetting plastic waste consisting of products at the end of their life cycle may originate from, for example, products formed of fibre reinforced thermosetting plastic, such, as boats, vessels, aeroplanes, containers, tanks, sports and recreational gear, windmill blades, pipes, construction profiles, various parts of transport means, cars, and airframes, laminates and other consumables, com prising hybrid products in which fibre reinforced thermosetting plastic is coupled with other material such as wood.

Thermosetting plastic may be one or more of the following: epoxy, polyester, vinyl ester, phenolic resin, amino resin, polyurethane, cross-linked thermoplastic such as cross-linked polyethylene PEX or a combination of the above.

Thermoplastic may be one or more of the following, for example: thermoplastic elastomer TPE, polyvinyl chloride PVC, polyolefin, such as poly butene PB, polyethene PE and polypropene PP, polystyrene PS, acrylonitrile bu tadiene styrene ABS, polymethyl-methacrylate PMMA, polybutyl acrylate PBA, polylactic acid PLA, polyhydroxyalcanoethylene PHA, polyhydroxybutyrate PHB, acrylonitrile styrene acrylate ASA, polyethylene terephthalate PET, polyamide PA, polycarbonate PC, polyacetal POM, polyvinylidene fluoride PVDF, ethylene chloro- trifluoroethylene ECTFE, fluorinated ethylene propylene FEP, modified fluoro- alcoxy MFA, perfluoroalcoxy PFA or a combination of the above. The thermo plastic material may also include another material than those referred to in the above and, mixed to it, there may be components cross-linking it in connection with its processing such as peroxide and/or silane compounds. Thermoplastic polymer may be virgin oil-based or bio-based thermoplastic from their manufac turers, recycled plastic provided by recyclers, or plastic waste gathered from an ywhere.

The surface layer 2 in connection with the core layer 3 may be of the thermoplastic described in the above or other thermoplastic and/or thermo plastic mixture to which another material has been added, such as colourants, fire protection materials, minerals and other binder and coupling agents, fillers and additives, and/or the surface layer 2 may consist of a material mixture which comprises fibre reinforced thermosetting plastic from discarded production waste combined into a thermoplastic matrix, but is free from the End of Life waste of fibre reinforced thermosetting plastic.

When the material mixture referred to last in the above as the surface layer 2 on the outer surface of the product being manufactured, for example, and when it is installed subject to sunlight it is recommended that the maximum par ticle size of the thermosetting plastic waste is <100 gm and that the thermoset ting plastic waste originates from discarded production waste and not products at the end of their life due to aging and weakening by sunshine, rain etc.

When the material mixture is used as a core layer 3 on an inner surface of a manufactured product, for example, the inner surface being under a surface layer 2 made of another material, discarded production waste as well as product waste flows at the end of their life cycle may be used, in which case the thermo setting plastic particle size has no restrictions, but the thermosetting plastic par ticles may even be in the millimetre order of magnitude.

According to an embodiment, the material mixture has fibre reinforced thermosetting plastic at least 10% and no more than 80%. In such a case, the amount of thermoplastic (recycled and virgin) in the material mixture is at least 20% and no more than 85%.

Chemical binders and coupling agents include, for example, anhydric acid (g-MAH) maleated in a polymer, peroxide, silane, ethene copolymers, styrene acrylate nitric glyceride methacrylate SAG, styrene acryl nitride maleic anhydride terpolymer SAM, ethylene-propylene-diene-monomer grafted maleic anhydride EPDM-g-MAH, styrene ethene butene styrene SEBS and SEBS-g-MAH, polyolefin graft acryl functions, antioxidant mixtures, costabilizers and reactive additives, mixtures of alifatic resins and olefins to combine different materials and two pol ymers to reduce energy between phases to add adhesion and dispersing. Com- mercial brands include, for example, Entira, Recycloblend, Fine-Blend, Elvaloy, Amplify and Fusabond. According to an embodiment, the amount of chemical binders and coupling agents in the material mixture is at least 1% and no more than 6%.

According to an embodiment based on commonly available polyethene plastic (PE) matrix, the flexural strength (MOR) of the material mixture of the sur face layer 2 and core layer 3 is at least 20 MPa in minimum and typically >30 MPa. Further, the flexural modulus (MOE) of the material mixture is at least 3 GPa in minimum and typically >4GPa. Water absorption of the material mixture in room temperature/28days in water immersion is at most 5% by weight and typically <3% at maximum, and in a 24h test <1%. Also, in accordance with the same em bodiment the surface hardness Brinell of the material mixture surface layer 2 is at least 55 in minimum and typically >60. In an embodiment based on another bulk polymer polypropylene plastic (PP, harder) matrix the MOR and MOE values can be expected to exceed the values of those above given to polyethylene plastic (PE, softer) matrix.

A person skilled in the art will find it obvious that, as technology ad vances, the basic idea of the invention may be implemented in many different ways. The invention and its embodiments are thus not restricted to the examples described above but may vary within the scope of the claims.