Field of the Invention

The present invention relates to recycled plastics material. More specifically, the present invention relates to cleaning of plastics materials, particularly ocean plastics materials, to obtain a higher purity recycled material. In some embodiments, the invention relates to recycled plastics material suitable as a precursor for foamed plastics products.

Background

Polymer plastics used in the marine and fishing industries, particularly fishing nets and materials commonly labelled “ocean plastics”, are of heterogeneous makeup that poses a particular challenge for recycling processes due to the presence of different plastics materials and the presence of non-plastics materials including carcasses, shells, oils, sea water salt, and due to an inherently high water content.

Materials collected for recycling may be offered to recycling facilities with various degrees of contamination. Materials may be traded as “washed” or “cleaned” when they are suitable for conventional processing steps, e.g. of a sand content low enough to allow shredding. However, such “washed”, or ’’cleaned”, products may still contain a relatively high content of non-plastics materials that would be considered contaminants, particularly sand, sea salt, and particularly water content, that is relatively high compared to other recyclable materials and that may interfere with other processing steps such as filtration, making such materials more difficult to process.

United Kingdom patent application GB1908603.2 by the present applicant, published as GB2575918, discloses procedures to reduce the moisture content of wet plastics materials such as fishing nets to improve recycling processes.

The present invention seeks to provide additional methods for cleaning materials for recycling purposes. Summary of the Invention

In accordance with a first aspect of the present invention, there is provided a recycling process for processing wet plastic nets materials, as defined in claim 1.

The recycling process comprises a step of comminuting the plastic nets material to provide a shredded plastics material, and a step of drying the shredded plastics material, wherein comminuting comprises a step of adding moisture to the plastic nets material.

The plastic nets material may comprise different material compositions and will be understood to comprise marine plastics material, particularly fishing nets. The plastic nets material may comprise nylon, such as polyamides (PA or PA6). The plastic nets material may comprise polypropylene (PP). The plastic nets material may comprise polyethylene (PE), particularly high density polyethylene (HDPE).

The step of comminution comprises reducing the net material to shorter filaments or flakes, usually by shredding it in shredders capable of processing plastic nets material. Such shredders can generate a significant amount of heat, such a friction heat. The heat is, hitherto, believed to be useful to aid the evaporation of water inherently contained in the marine plastics material.

The addition of moisture to the plastic nets material suggested herein is believed to reduce the heat developing during the comminution step/process, even though increasing the water content might appear counterintuitive when effort is subsequently put into reducing water content.

An observation underlying the present invention was that the less strong heat development allows the shredding process to be operated more effectively to generate smaller shreds, without the risk of overheating or blocking the shredder, which might otherwise be the case. It is also believed that the cutting/shearing elements such as shredder blades experience less wear and abrasion.

Another observation was that inherent water content of wet waste materials may be relatively high, but unevenly distributed in pockets such as knots, while other portions of the waste material might be relatively dry. The addition of moisture appears to achieve a more even distribution of water or other moisturising fluid.

In some embodiments, the recycling process comprises exposing the plastics material to a moisturising liquid prior to and/or during its comminution.

In some embodiments, the recycling process comprises atomising the moisturising liquid.

The moisturising liquid may be provided in the form of a spray or mist, for instance a water-based mist or water mist. Providing a mist in this form can be understood as providing a different, higher, ambient humidity level evenly exposing the different complex surfaces of the plastic material, particularly plastic nets material, to the moisture.

The mist may be provided via nozzles or a spray arrangement, such as spray arrangements that are suitable for providing a finely dispersed mist. It will be appreciated that mist may set on the plastics material in the form of water droplets and/or in the form of a film.

The process may comprise a step of controlling the temperature in an area in which the plastics material is exposed to the moisture. The air in that area may thereby be temperature controlled to allow it to hold a predetermined humidity level.

In some embodiments, the recycling process comprises adding a surfactant to the moisturising liquid.

By providing the surfactant in the moisturising agent, the moisturising agent can serve as a carrier, or matrix, to aid a more homogenous distribution of surfactant in low concentrations.

The surfactant may be added to the plastic nets material prior to, and/or during, the comminution process. In some embodiments, the recycling process comprises adding a deodorising agent prior to comminuting.

The deodorising agent may be a composition capturing volatile components that may otherwise contribute to unwanted odour. The deodorising agent may be a composition preventing the breakdown of components. The deodorising agent may comprise a masking component masking volatile components.

In some embodiments, the recycling process comprises adding a blending agent to aid blending of different plastics materials.

The blending agent may be a modifier or other suitable composition. For instance, blending agents may assist the blending of polypropylene (PP) with high density polyethylene (HDPE) during subsequent melting (blending) of the plastics materials.

Two or more of the surfactant, the deodorising agent, and/or the blending agent may be provided by the same component or composition.

In some embodiments, the recycling process comprises cleaning the shredded plastics material by conveying the shredded plastics material through a bath in a sedimentation tank.

The step of cleaning the shredded plastics material may be carried out before the step of drying the shredded plastics material.

In accordance with a second aspect of the present invention, there is provided a recycling process for processing wet plastic nets materials as defined in claim 8.

The recycling process comprises comminuting the plastic nets material to provide a shredded plastics material, cleaning the shredded plastics material, and drying the shredded plastics material, wherein cleaning the shredded plastics material comprises conveying the shredded plastics material through a bath in a sedimentation tank.

The bath is preferably a water bath, although another suitable medium may be used. The present process provides the removal of contaminant particles such as salt, broken shell pieces and particularly sand by allowing these to detach and sink during a bathing process.

In some embodiments, the recycling process comprises agitating the bath.

The agitation may be carried out in a manner minimising turbulent flow in the sedimentation tank.

The bathing process is accelerated by agitation of the bath. However, too strong agitation may result in turbulences causing sediment to be whirled up and randomly reattach to the plastics material. Agitation by way of paddles or jet generation, e.g. water injection or air injection at relatively slow speeds, is sufficient to generate a relatively gentle water movement while avoiding turbulent remixing.

The agitation speed should be such that the sedimentation of heavier, but relatively small particles such as sand particles is not prevented. It will be understood that the agitation may still cause a somewhat slower sedimentation.

The shreds in such a bath are present as a relatively dense bulk of intermingling shreds, in practically permanent contact with other shreds. The agitation is believed to increase the likelihood of individual shreds brushing along each other, increasing a sand-removing effect by shred-to-shred contact.

In some embodiments, the recycling process comprises submerging the shredded plastics material by agitating the bath in the sedimentation tank.

By submerging, it is understood that the otherwise floatable plastics material is moved to submerge against its inherent buoyancy and allowed to eventually resurface. It is believed that, during the buoyant phase, attached particles such as sand grains are more likely to detach and sink in the sedimentation tank.

The shredded plastic material may be submerged by using a paddle arrangement to agitate the bath. In some embodiments, the recycling process comprises using a jet arrangement to agitate the bath in the sedimentation tank.

The jets may be gas jets. The jets may be liquid jets. The liquid may be the same as used in the bath, e.g. water or density-adjusted water (e.g. salt water).

The shredded plastics material provides a surface area against which paddles or jet thrust can act to provide the agitation, without requiring large amounts of energy.

The agitation may involve a shreds-submerging arrangement, which may be achieved by agitation means moving the shreds material with a vertical vector component relative to the bath surface. The agitation may be vertical (down to submerge and up to resurface) while moving in a conveying direction, such that the shredded material is urged to follow a generally re-entrant path. The agitation may be vertical against the conveying direction, such that the shredded material is urged to follow a vertical loop, submerging, to move backwards while submerged, against the conveying direction (against a flow direction of shreds material floating at the bath surface), and returning into the conveying direction when resurfacing. The agitation may be in cross flow, comprising a vertical component, such that the shredded material follows a generally helical path during which it is submerged and resurfaces once, or at least once, or several times. The make-up of the shredded material is relatively complex and may still comprise different materials and shred sizes, and so it will be appreciated that not every shred piece will necessarily follow the same path in the bath.

Preferably, the agitation is carried out a low thrust levels to maintain laminar flow properties to reduce, and as much as possible avoid, whirling up particles.

In some embodiments, the recycling process comprises draining sediment from the sedimentation tank while shredded plastics material is being washed in the sedimentation tank.

Sediment may be drained continually or intermittently, for instance via an outlet at an appropriate location such as the bottom of the tank that can be opened or shut from time to time. Sediment may be drained during the agitation process. This reduces the availability of sediment to be whirled up to re-enter circulation and thereby re-attach to shredded plastics material.

In some embodiments, the recycling process comprises a step of filtering liquid drained from the sedimentation tank, to a degree allowing it to be reused as replenishing fluid for the sedimentation tank.

In some embodiments, the recycling process comprises replenishing the sedimentation tank while the shredded plastics material is conveyed through the sedimentation tank.

The replenishing may be controlled to occur at a rate corresponding to the draining rate, providing a steady-state amount of washing fluid. It will be appreciated that the replenishing step may be carried out while shredded plastics material is being washed in the sedimentation tank, to provide a supply of clean washing fluid.

In some embodiments, the recycling process comprises removing the shredded plastics material from the sedimentation tank, drying the shredded plastics material, melting the shredded plastics material and forming it into a recycled plastics material.

In some embodiments, the recycling process comprises forming an intermediate recycled plastics material such as a pellet. In some embodiments, the melting may be carried out via an extrusion process. Likewise, the forming operation may be carried out using an extrusion process, cutting process, or combinations of an extrusion and cutting process. The plastics material so formed will be understood to be generally solid, comprising however impurities commensurate with the presence of water and contaminants that may be present in the form of holes or surface dimples.

The recycled plastics material, which may be a pellet, may be characterised by the presence of sand particles, at a level not exceeding 5%, 4%, 3%, 2% or 1% (w/w). In embodiments, the sand content in the recycled plastics material is no more than 1% (w/w). The sand content may be difficult to measure in the final product/pellet, but can be estimated from sand collected by filters during the plastic melting stage. As a rule of thumb, however, commercial filters known to the applicant are expected to expire relatively quickly if they are used to melt nets material that is conventionally labelled ‘clean’. To the best of the applicant’s knowledge, attempts to establish more wide-spread recycling of marine netting material have hitherto failed, due to the processing difficulties arising from its sand content. Indeed, marine recycled plastics today may be labelled as “ocean -bound’ plastics, by which is meant that such plastics materials have been prevented from being disposed into a marine environment. Such ocean bound plastics have, however, not been recovered from a marine environment, which is believed to be the case due to difficulties in handling the associated contaminants. As such, the presence of sand quantities in a recycled product or in a recycled pellet can be taken as an indication that marine netting material was used, and that prior to melting, a washing/bathing step was carried out in the afore-described manner, to reduce the sand content to about 10% or less, preferably to about 5% or less, before passing shredded materials through the filters of the melting stage.

The recycled plastics material formed by the present invention may be of an extrusion grade suitable for foam-forming extrusions. The extrusion grade may be defined by forming an extrusion (a test extrusion) from recycled plastics material, such as pellets, of relatively thin sheet form or film form. The test extrusion may be used to establish whether or not it exceeds a threshold level of imperfections. For instance, the extrusion may be graded as to whether it shows no more than 100, 90, 80, 70, 60, 50, 40, 30, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2 surface imperfections, or no more than 1 surface imperfection, per pre-defined area, e.g. per 25 cm ² . The sheet or film may, for testing purposes, be made of a thickness revealing on a sheet surface the presence of an imperfection within its body. To this end, the sheet or film may be no thicker than 0.25 mm, 0.5 mm, 0.75 mm, 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm. The number of imperfections may be counted by visual inspection or other suitable method. Imperfections may be defined as discontinuities such as dimples in an otherwise smooth surface. In test runs, the cleaning steps of the aforementioned aspects were carried out, and repeated e.g. by supply of clean water, to achieve a degree of purity corresponding to no more than 20 imperfections per 25 cm ² , for a test extrusion sheet measuring 5 cm ^c 5 cm with 0.5 mm thickness. An imperfection was defined as a surface dimple indicative of a sand particle within the extrusion volume (sheet thickness). The pellet may be used as a component for the manufacture of a recycled material. Pellets are particularly suited for handling, including storing, dispensing, metering, mixing with other pellets, and melting in an even and controllable manner, and are therefore a preferred intermediary for the manufacture of recycled plastics articles requiring an even, homogenous composition.

It will be understood that the melting process can be controlled in temperature phases to filter different plastics materials, e.g. the higher melting temperature ranges of PET/PVC can be utilised to separate these from PP/HDPE materials of relatively lower melting temperature ranges. The melting and curing process may be controlled to maintain a certain level of mixing, e.g. of PP with HDPE that might otherwise show a tendency to separate. It was an appreciation by the applicant that the temperature- based separation of different plastics materials is further improved by reducing the sand load on filter arrangements used in such processes, which increases the longevity of the filter components. The sand removal is believed, therefore, to contribute at least in part to a higher degree of purity of the resulting plastics material, or, as may be applicable, a better control over blending properties of different plastics material fractions (such as a blend of PP and HDPE).

In accordance with a third aspect of the present invention, there is provided a method of forming a foam product as defined in claim 17. The method comprises forming recycled plastics material (particularly material according to the first aspect or second aspect) by melting the recycled plastics material to form a intermediary plastics material, dissolving an inert gas into the intermediary plastics material, allowing the intermediary plastics material to expand into a foamed plastic material, and subjecting the foamed plastic material to irradiation.

In some embodiments, melting the recycled plastics material into an intermediary plastics material comprises, or is constituted by, forming the recycled plastics material into an extruded profile. In that case, allowing the intermediary plastics material to expand will be understood as meaning that the extruded profile to expand is allowed to expand into a foamed plastic material.

The extruded profile may be an extruded sheet, such as a generally planar profile. In some embodiments, the method comprises introducing the recycled plastics material into a mould.

The recycled plastics material may be injection-moulded. For instance, the method may be used for the manufacture of a moulded shoe component such as an outer sole component, insole, cushioning component or other shoe component.

It will be understood that the recycled plastics material may have been obtained using any one of the embodiments described in relation to the first aspect and/or the second aspect, as well as combinations of two or more of such embodiments.

In some embodiments, the method comprises tolerating the presence of sand grains and/or marine particles in the recycled plastics material.

The step of extruding or moulding the recycled plastics material may be understood as a separate step to the foregoing step of forming a recycled plastics material. For instance, the material may be processed by one of several extrusion steps. In one extrusion process, recycled plastic material may be formed to an intermediate component, for instance to form a pellet. In another extrusion process, the intermediate component may be formed into a final article. In another extrusion process, part of the intermediate component material may be sacrificed for a test extrusion to provide a purity grading.

The recycled plastics material according to embodiments of the first aspect and/or second aspect may comprise a residual amount of sand and marine particles such as small shell pieces. Conventionally, such recycled plastics material with sand contamination was considered unsuitable for subsequent processing into foamed articles. The applicants found that the presence of residual sand, while still to some extent interfering with a foaming process, results in only an occasional larger-than- average foam bubble that for practical purposes can be tolerated in some products. In trials, it was possible to achieve an estimated sand content of no more than between 5% and 1% (w/w), estimated by the amount of sand removed during the washing stage (by weighting shredded material before and after bathing, and weighing the mass of the removed sediment), and by the amount of sand captured by the filtering systems of the melting equipment. The residual amount of sand may be no more than 5%, 4%, 3%, 2%, or 1% (w/w).

The recycled plastics material may be an extrusion-grade plastics material, by which is meant that the material shows no more than a pre-defined number of surface imperfections per surface area of a test extruded sheet. For instance, the material may, when used for forming a test extruded sheet, show no more than 100, 90, 80, 70, 60, 50, 40, 30, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2 or no more than 1 surface imperfection per 25 cm ² . For higher purity requirements, the test extruded sheet may show no more than 100, 90, 80, 70, 60, 50, 40, 30, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2 or no more than 1 surface imperfection per 100 cm ² .

The processing steps of the first and second aspects may be carried out to achieve a defined purity value, as required by the subsequent application. Using a test extrusion, it is possible to provide a grade of purity of a batch, such as, e.g. 100/25cm2 or 20/25cm2. For foamed articles, it is believed that a purity of no more than 40, 30 or 20 imperfections per 25cm2 is required. One reason for the required degree of purity is the subsequent processing in highly specialised equipment such as extrusion filters that would otherwise require maintenance. A lower degree of purity such as 100 imperfections per 25 cm ² , may be tolerated for more robust equipment. The benefit of the method disclosed herein is that the sand content and therefore the suitability for use with sensitive equipment such as extrusions for foamed articles can be defined more accurately.

In some embodiments, the method comprises applying predetermined high pressure and high temperature conditions during the time of dissolving the inert gas into the intermediary plastics material.

In some embodiments, the method comprises, after a predetermined holding time, reducing the pressure and/or temperature to thereby cause the intermediary plastics material to expand.

In some embodiments, the inert gas comprises nitrogen. In some embodiments, the method is used in the manufacture of a foam material of lesser density than water.

In some embodiments, the method is used in the manufacture of a surfboard, bodyboard, or other type of floatation device.

In some embodiments, the method is used in the manufacture of a foamed shoe component, such as a sole component.

In accordance with another aspect of the present invention, there is provided a surfboard, bodyboard, or flotation device as defined by claim 25, the surfboard, bodyboard, or flotation device, respectively having been manufactured according to the third aspect.

Foam products such as surfboards or flotation devices may be covered with a liner or material sheet to provide an even surface, particularly at outer surfaces thereof.

Recycled plastics material processed in accordance with the invention may be characterised by the presence of impurities such as sand grains, and/or by the presence of heterogeneous foam areas among otherwise relatively homogenous regions of average bubble size in a foamed article, such as a few larger-than-average bubbles that would otherwise not be expected in a virgin plastics foamed article.

Recycled plastics material processed in accordance with embodiments of the first and second aspects may be used in the manufacture of non-foamed articles, such as components used in the manufacture of shoes. Likewise, the same material and pellets may be used for the manufacture of foamed components.

Recycled plastics material processed in accordance with embodiments of the first, second or third aspects may be used for the manufacture of foamed articles, such as cushioning components, packaging components, medical and healthcare devices, protective garments and components thereof, furniture, sound damping components, and others. Description of the Figures

Exemplary embodiments of the invention will now be described with reference to the Figures, in which:

Figure 1 is a diagram showing an exemplary sequence of processing steps of parts of a recycling process; and

Figure 2 is a diagram showing an exemplary sequence of processing steps of parts of another recycling process.

Description

The present disclosure is concerned with a phase of the recycling cycle after marine plastics, particularly fishing nets, have been collected.

Figure 1 shows a sequence of steps of a recycling process 10. In step 12, nets are received often in bulk comprising entangled net material, and may include nylon (typically polyamide, PA6 and derivatives thereof), polypropylene (PP), polyethylene, particularly high-density polyethylene (HDPE). The material may also comprise PVC and/or PET articles such as bags, bottles or bottle caps. The material may therefore be of a considerably heterogeneous composition. Furthermore, the different plastics material types may also have been exposed to different levels of sea water, UV (sun) light and chemical treatment. The plastics material, including fishing net strings, rope and the like, may include portions that are relatively brittle as well as portions that are relatively firm and robust. Further, the material may have varying degrees of elasticity and ‘sponginess’ of the net fibres. Some materials, particularly nylon, can be expected to have a relatively solid cross-section, meaning that contaminant material is to be found on the outer surfaces. Other materials may comprise cavities in which contaminant material may be embedded or intertwined.

Step 14 is a sorting step, which may be carried out by hand, to separate prima facie non-plastics materials such as nautical metal and biological material from the plastics material, as well as removing if desired PVC/PET materials such as bottles. Alternatively to or in combination with manual sorting, machine sorting may be used, for instance using machine vision systems, sensors and machine object handling systems. Machine sorting may comprise machine learning and artificial intelligence- based systems. Machine sorting may be used for some or all parts of the sorting procedure, for instance for detection and identification and/or for object handling and removal processes, and may be used under supervision of a human operator or autonomously.

After the first sorting step 14, the plastics material is subjected to a comminution step 16. The comminution step may involve a shredder, for instance a single-shaft shredder that is relatively robust against entanglement by nets. The shredder should be of a shredding speed and force able to deal with relatively strong plastics materials that may be included in the bulk of plastics material. Shredding may include a combination of tearing, crushing and/or cutting processes.

The plastics material is reduced to a size of around 10 mm to about 30 mm, typically about 5/8 inch or about 15 mm (1 in = 25.4 mm). The size leaving the shredder can be controlled to some extent by a filtering step, or sieving step, although it will be understood that flexible filamentous shreds, as those expected from shredded nets, may be able to pass through a filter in different configurations, leading to some degree of variation in the size and length of the shredded plastics material fibres. Different sieving/filtering sizes may be used to obtain other shred sizes.

The shredded plastic obtained in the comminution step 16 is less likely to entangle, and therefore believed to be better suited for some bath agitation methods carried out subsequently.

Before, during and/or after the comminution step 16, the process includes a step 18 of adding moisture to the plastics material. The moisture may be provided in the form of a spray or mist. The step 18 of adding moisture may include a nebulising step, or atomising step. In step 18, the plastics material is exposed to a fine spray in the form of a mist. The mist provides for practical purposes a more humid environment and helps to ensure the moisture reaches more surfaces of the plastics material than would otherwise be the case.

The liquid added in step 18 may comprise a detergent additive. The detergent additive may assist in the separation of contaminant material from the plastics material. The liquid added in step 18 may comprise a deodorising additive. The deodorising additive assists in reducing, and practically eliminating, unwanted odour from a final product. The liquid added in step 18 may comprise a fragrant additive. The fragrant additive may allow providing a degree of control over the odour a final product may exhibit. By providing additives in the form of a finely distributed spray or mist, relatively small proportions of additives can be distributed relatively homogeneously throughout the different surfaces of the plastics material.

If the step 18 of adding moisture is carried out before or during the comminution step 16, the added moisture may reduce the heat generation during the shredding step.

Hitherto, the water content of fishing nets, which is understandably often higher than in other recyclable plastics materials, was often considered as a problem, because the water needs to be removed prior to subsequent melting as part of the recycling process. For instance, in United Kingdom patent application GB1908603.2 by the present applicant, it is suggested to utilise heat developing during the shredding process to promote water evaporation, to reduce subsequent drying requirements.

The suggestion made in the present disclosure is to add moisture, which is believed to result in less heat generation than would otherwise be the case in the absence of such added moisture. Without wishing to be bound by theory, it is believed that, counterintuitively, adding a relatively small amount of moisture creates a form of lubrication, helping to preserve shredder equipment, such as shredder blades, and thereby reduces the demands and mechanical wear placed on the shredder equipment. The resultant reduced heat generation allows, in turn, the shredding process to run more effectively, to be controlled to produce smaller shreds that may subsequently be easier to dry.

In step 20, the shredded plastics material is passed through a metal detector. In step 20, metal pieces that may have been missed in step 14 are removed.

In step 22, the shredded plastics material is fed into a separation tank. The separation tank is provided with a suitable washing medium such as water. The washing medium is selected for an appropriate density to allow the shredded plastics material to float. In trials, shredded HDPE and PP material tended to exhibit floating behaviour with normal water. The washing medium may be density adjusted, for instance with salts, to promote a floating behaviour of plastics shreds, particularly when a relatively large fraction of nylon is expected. In step 24, the shredded plastics material is conveyed along in the separation tank. The shredded plastics material may be moved along a linear path, or along a circular path (stirred). The shredded plastics material is moved slowly, to encourage detachment of contaminant particles while minimising turbulent flow characteristics. Preferably, the plastics material is conveyed by relatively gentle agitation, using paddles, gas jets or water jets, or along an incline or slide.

During step 24, the shreds are allowed to float at the top while small particles such as sand are allowed to sink to the bottom of the separation tank. In the separation tank, different degrees of inertia between plastic shreds and sand are utilised to allow sand to detach from shredded plastics material and to sink. Agitation is believed to reduce the separation time that would otherwise be required without agitation to achieve a comparable level of purity. It will be appreciated that the optimal degree of agitation is influenced by the size of the shreds, their buoyancy, and to some extent by the type of the shredded material that can be of different density and floating properties. It was an appreciation underlying the present invention that too much agitation may lead to particles such as sand being re-mixed in the sedimentation tank, leading to a practical equilibrium in which further agitation does not reduce the sand content despite otherwise aiding in separating sand from the shreds.

In step 26, sediment and contaminants are removed from the separation tank. The sand may be discharged from the bottom of the separation tank, for instance by partially draining the separation tank. The separation tank may, to this effect, contain one or more outlets that allow contents to be removed from an appropriate collection area, e.g. via a drain at its lower end. Step 26 may be carried out concurrently with and/or after step 24, to remove particles from the separation tank while the shredded material is being conveyed. It will be understood that the sediment may be removed while the bulk, or practically all, of the shredded plastics material remains floating in the separation tank. A concurrent removal of particles such as sand makes them unavailable for recirculation and thereby reduces the likelihood of sand re-attaching to shredded plastics material. In step 28, the separation tank is supplied with fresh separation fluid, e.g. re-filled or ‘topped up’. The replenishing fluid is usually water but other fluids (e.g., density- adjusted water) may be used. Step 28 may be carried out concurrently with step 26. The level of replenishing may correspond to the level of draining sediment in step 26, to create a steady-state amount of fresh separation fluid. Step 28 may be carried out concurrently with step 24, such that the water is replenished by jets also aiding the conveying process of the shredded material.

In embodiments, only one of step 24 and step 26 may be carried out, as each helps to reduce the amount of contaminants, particularly sand, in the shredded material.

When both steps 24 and 26 are carried out, this was found to result in an even lower sand content in a relatively short separation time. In batch trials, the sand content was reduced from about 15-20 %, which was previously considered a low sand content of a “clean” material, to less than 5 %. To provide an illustration of the amounts of material that may be involved in a washing process, trial batches consisted of up to 600 kg nets material (gross weight of nets material after manual removal of contaminants) entering the washing step, from which about 70 kg sand were removed, leaving about 530 kg shredded plastics material. The process is believed to be able to handle sand contents of about 7% to 20% (wherein “sand” is understood as referring also to broken shell parts and other contaminants).

A relatively low sand content is of interest herein particularly for recycled plastics material that is to be used for the manufacture of foamed plastics articles. When the recycled material is used as substrate for foamed articles, individual particles such as sand grains disturb an otherwise more even formation of foam bubbles, leading to foam products with heterogeneous bubble sizes. To provide an illustrative example, a foamed body intended as a floatation device such as a surfboard, bodyboard and the like, requires foams formed with an average bubble size in the region of a few millimetres or less. The presence of sand may lead to isolated foam bubbles of several centimetres diameter, rendering a foamed material less suitable as a surfboard product.

Furthermore, the steps 22 to 28 may also achieve a better level of removal of higher density “random plastics” materials, such as PET strings or wrappers. In an optional step 30, the discharged fluid is filtered to a degree of purity that allows it to be re-introduced as fresh separation fluid during step 28. The optional step 30 may be carried out in another separation tank and/or filter arrangement that is optimised for the removal of liquid from sediment, particularly sand. It will be understood that in step 30, no or practically no buoyant shredded plastics material is present and so the separation step 30 can be optimised for the removal of particles without limitations imposed by the presence of shredded material. For instance, step 30 may involve a finer filtering mesh, or a different degree of agitation than would be appropriate in step 24.

In optional step 32, the cleaned fluid is returned for use in step 24.

In step 34, the shredded material is subjected to a de-watering process. The de watering process may involve mechanical and thermal de-watering. Mechanical de watering may involve a step 36 of passing the shredded material over a vibrating sieve arrangement. Vibration and agitation assist the ‘shaking’ of the shredded material and is believed to assist in loosening, and breaking down, of clumps or ‘balls’ of shredded material. Thermal de-watering may involve a step 38 of passing the shredded material through a stream of heated air. It will be understood that the heated air may pass relative to the shredded material in counter flow, cross flow and/or concurrent flow. Preferably, the stream of heated air is blown at a strength sufficiently to perfuse the shredded material, as this may to some degree be entangled or sticking together while wet.

In embodiments, only one of step 36 and step 38 may be carried out. During the development of the present process, it was found that a combination of both steps 36 and 38 achieves a lower water content quicker than would otherwise by the case. After step 34, the water content may be no more than 20 % or lower. It will be understood that a lower water content, for instance 25%, 20%, 15%, 12.5%, 10%, or less, may be achieved by increasing the exposure time of the shredded material during step 36 and/or step 38.

In step 40, the shredded material, now washed and dried, undergoes a further inspection for the presence of contaminants and/or metal materials that will be removed. At step 40, only occasional contaminations are expected such as small broken shell pieces, and a relatively low sand content. Similar to step 14, the detection and removal may be carried out manually, or either or both may, partially or entirely, be carried out by suitably configured automated systems.

At this stage, it will be appreciated the shredded material may still contain residual amounts of sand, but at levels estimated to be typically no more than 5% or significantly less than 5%. The original weight bulk plastics material may have decreased by more than 10%, e.g. from about 600kg to about 530kg, during the washing step, and may have decreased by more than 15%, or by more than 20%. The amount of sand may be reduced further by appropriate control of the agent added in step 18 and/or by appropriate control of the separation parameters during steps 22 to 32.

In step 42, the shredded material is melted, whereby the shredded material is fed into a compactor which may hold in the region of 60 kg of the shredded material, although other amounts and/or other compactor sizes may be used. The melting process may be carried out, for instance, at temperatures in the region of 250°C to 260°C, or no less than 230°C, 240°C or 250°C, and no more than 260°C, 270°C, 280°C. The melting temperature should be sufficient to allow the material in question to melt fully, while avoiding temperatures that are so high, or pyrolytic, that they cause disintegration of the material to be recycled.

In step 44, the melted material undergoes a filtration step to remove contaminants, which at this level can be expected to be constituted by relatively small particles such as dust etc. The preceding washing steps 22-32 achieve that the levels of sand are so low, e.g. in the region of between 10% and 5% (w/w) or less than 5%, that the filters of subsequent re-processing systems are able to handle the amount of sand without expiring too quickly. Too high a sand content would result in too quick an expiry of the filtering systems, whereas the lower sand content allows the plastics processing filters to operate effectively and reduce sand content to less than 5%, potentially less than about 1%, even below 1% in a product or pellet. It will be understood that a higher sand content may be tolerated when either the load on the filters, and/or the regular maintenance or exchange of filters, is not considered overly burdensome. To provide illustrative exemplary values, the pressures on the filters during filtration are usually in a region of up to 350 bar. Pressure levels close to or higher may cause backflush behaviour that may even result in a reduction of the pressure level to about 250 bar. As can be imagined, operation at these pressure levels requires a high standard of purity, or, respectively, a low content of sand particles.

In step 46, the melted material is allowed to dry sufficiently to be separable into granular form such as pellets. In step 48, the granular material is cooled, typically first in a water bath followed by a hot air stream. A pellet in final form may have a water content of less than 0.1 %, usually less than 0.08 %. A pellet in final form may have a melt flow index (MFI) of less than 0.8 (190°C @ 2.16kk g/10min), rendering it suitable for the production of foamed articles. It will be understood that the properties are exemplary and that the processes can modulated to obtain other properties. For instance, PP recycled material may have a melt flow index (MFI) in the region of 1.

It will be appreciated that the recycled material may still contain a certain, albeit relatively low, amount of sand. Furthermore, the recycled material is expected to contain residual amounts of the additives supplied during step 18, which may be noticeable by the absence of strong odours or otherwise characteristic odours usually observed in recycled marine plastics material. Likewise, the recycled material may be characterised by the presence of embedded fragrant additives no usually expected in recycled plastics material. Such residual additives are usually undesirable for subsequent processing, particularly for foamed products, because they may lead to an unknown level of interference with subsequent processing steps, such as leading to undesirable levels of foam bubble heterogeneity.

By way of the present invention, the relatively lower content of sand is believed to more than offset disadvantages that may have to be tolerated due to the presence of additives, while providing a better performing recycled ingredient that may, optionally, also be considered to offer a more pleasant olfactory experience than was hitherto believed to be possible.

One practical method of defining a level of purity is to use an intermediate recycled plastics material, such as pellets obtained by step 46, to form a test extrusion. To provide one example, the pellets may be used to extruded a sheet of about 5 cm ^c 5 cm (25 cm ² ), or of about 10 cm ^c 10 cm (100 cm ² ). The sheet may have a thickness not exceeding 0.25, mm, 0.5 mm, 0.75 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, or 10 mm. Using pellets made from fishing net material, a plate extruded in this manner is often of dark colour, practically black or dark green in appearance, one or both surfaces of the surface appearing shiny.

A test extrusion of this type can be formed with a relatively smooth, visually “shiny” surface. Any imperfection from water content or particles such as dust or sand will prominently show as a dimple in the otherwise smooth surface. If the surface is otherwise smooth, variations in reflective behaviour will reveal a surface imperfection such as a dimple so that this it is readily detectable, e.g. by visual inspection.

Imperfections may not be visible if present within the body of the extrusion. As such, the thinner the extrusion, the more likely it is that all imperfections within a thickness of a sheet provide a visible imperfection at the surface of the sheet. E.g. a 1 mm or 2 mm thick extrusion is believed to be so thin so as to show imperfections on the surface for every imperfection. However, aspects such as transparency, ease of handling, ease of storage etc may require a different form of test extrusion. In this manner, it is possible to provide an imperfection measure of pellets used for subsequent extrusion requiring a supply of foam-quality extrusion grade material.

An extrusion, if made from virgin pellet material, is expected to show no sand or silt imperfection, although may show water inclusion imperfections depending on manufacturing conditions.

An extrusion made from recycled ocean plastics is expected to show some imperfections, because it is practically impossible to remove all contaminant material. To provide illustrative values, recycled material obtained by way of the present invention may show in the region of 20 surface dimples per 25 cm ² or, correspondingly, in the region of 80 surface dimples per 100 cm ² . As may be imagined, the method allows a sacrificial portion of intermediate recycled plastics material, .e.g 2 kg pellets from 600 kg batch (which may be about 2000 pellets of typical industry grade pellet size) to be extruded to form one or more test films or thin sheet, to assess the number of imperfections per 2kg. It can readily be seen how the method allows a surrogate indicator to be provided for the number of sand particles per kg. It will be understood that the precise limit required for a subsequent use of the extrusion grade pellets will be application dependent. However, the use of test extrusions in this manner provides a practical way of testing the degree of purity of sand-contaminated ocean plastics recycled material. The level of purity has, to the best of the applicant’s knowledge, not been tested in the industry and has, consequently, not been achieved previously.

The purity grade thus achieved, and thus definable, allows the pellets to be used as extrusion-grade pellets for subsequent extrusion in high-purity applications, such as foam forming.

Foam forming extrusion machinery is relatively expensive and requires careful filtering to avoid contamination, as this may result in significant maintenance costs and downtime, if not the destruction of filters and machinery. For this reason, foamed plastics materials were hitherto manufactured practically only from pure virgin materials that can be relied on to be of extrusion grade purity suitable for forming foamed products.

Figure 2 shows a sequence of steps of a method 50 of forming a foamed article 1. In step 52, granular recycled plastics material 3 obtained by method 10, optionally mixed with other ingredients 4 such as virgin plastics material, is formed into a sheet 5 constituting a profile. Step 52 may be carried out as an extrusion process. Alternatively, the step 52 may be constituted by introduced plastics material into a mould, e.g. by injection moulding. In step 54, a gas 6, which may be an inert gas such as nitrogen, is dissolved into the sheet 5. In step 54, the sheet 5 or plastics material is exposed to temperature and pressure levels to achieve a predetermined degree of perfusion of the sheet 5 with the gas. In step 56, the temperature and pressure levels are reduced to allow the gas to expand, causing thereby an expansion of the sheet or plastics material into a foamed precursor 7. In step 58, the foamed precursor is treated, e.g. irradiated, to stabilise the foamed precursor 7 into a stable foam material 9. In step 60, a foamed article 1 is made from the stable foam material 9. Optionally, the foamed article or parts thereof are provided with a cover such as a sheet surface.

It will be understood that the parameters for the amount of recycled material and other material in the composition, the type and composition of the gas, temperature, pressure, irradiation strength, type of irradiation, and exposure times of each one of the foregoing can be modulated to achieve a desired foam quality.

A foamed article 1 made in accordance with the method 50 may exhibit a certain level of elasticity and flexibility, or ‘bendiness’, commensurate with the type of plastics material. The foamed article may also have a certain level of strength, being of generally unitary form after extrusion or moulding. The properties make the foamed material less likely to break under pressure levels they may typically experience in normal use e.g. during water sport activities. This is a contrast to polystyrene bodies that, when they break, also tend to disintegrate into a large number of discrete polystyrene particles . The strength imparted by the unitary, cohesive character of the applicant’s foamed article has been found to render the foamed article 1 particularly suitable as flotation device such as a surfboard. A typical density of a flotation device may be in the region of 5 kg/m ³ , 10 kg/m ³ , 20 kg/m ³ , 30 kg/m ³ , 40 kg/m ³ or 50 kg/m ³ , and/or no higher than 100 kg/m ³ , 90 kg/m ³ , 80 kg/m ³ , 70 kg/m ³ or 60 kg/m ³ , although it will be appreciated that these values are illustrative examples and not necessarily intended to limit the invention. A typical foam composition for a body board may have between 20 kg/m ³ and 40 kg/m ³ , or between 25 kg/m ³ and 35 kg/m ³ .

While the present invention is described in the relation to surfboards as example, it will be understood that the recycled material having the presently achieved higher degree purity may be used for other foamed articles and non-foamed articles, such as shoe components. Foamed articles in accordance with the invention may be used as cushioning components, packaging components, medical and healthcare devices, protective garments and components thereof, furniture, sound damping components, and others.