WO2015104541A1

WO2015104541A1 - Process and apparatus for manufacturing a multilayer article

Info

Publication number: WO2015104541A1
Application number: PCT/GB2015/050016
Authority: WO
Inventors: Omer KUTLUOGLU; Turul TASKENT
Original assignee: Environmental Technology Evolution Ltd
Priority date: 2014-01-07
Filing date: 2015-01-07
Publication date: 2015-07-16
Also published as: GB201400232D0; GB2550770A; GB2519249A; GB201712960D0; GB2550770B

Abstract

There is provided a process for manufacturing a multilayer article, including the steps of: (i) discharging core material from a first extrusion unit in a first discharge, to form an article core portion; (ii) discharging first layer material from a second extrusion unit in a second discharge, to form a first layer on a first face of the article core portion; (iii) discharging second layer material from a third extrusion unit in a third discharge, to form a second layer on a second face of the article core portion, and (iv) cutting to form a multilayer article. Manufacturing apparatus is provided. A computer program product for running on a computer, wherein the computer program product when running on a computer is operable to control the process, is provided.

Description

PROCESS AND APPARATUS FOR MANUFACTURING A MULTILAYER ARTICLE

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention relates to processes for manufacturing a multilayer article, to apparatus for manufacturing a multilayer article, to computer program products for controlling such manufacturing processes, and to multi-layered articles (eg. planks or boards).

2. Technical Background Plastic board articles comprising a skin and a core are known. However, the methods of manufacturing such articles have tended to be somewhat time consuming. Such methods have also tended to require significant energy.

3. Discussion of Related Art

Reference may be had to WO2002/062550, GB2460838A and WO2013038177A1 regarding related methods for manufacturing plastic articles.

In WO2002/062550A1, processes for forming plastic are described. Prior art Figure 10 of WO2002/062550A1 shows a side elevational view of apparatus for utilizing an open mould. In Figure 10 there is shown an illustration of an article and the respective process for manufacturing the article, generally denoted by the numeral 110. Mould 112 is shown as being formed to make a plate article with raised edges. Mould 112 is heated to an elevated temperature of greater than the melting point of the plastic particulates 116 held within container 114. It is disclosed in WO2002/ 062550A1 that if heating and cooling lines are used in carrier 118 or in mould 112 itself, then cooling fluids could be run through the lines, which would automatically contract the mould as it got cooler, pulling mould 112 away from a formed article. Figure 10 shows an illustration of an article and the respective process for manufacturing the article, generally denoted by the numeral 110, according to prior art reference WO2002/062550A1.

Figure 11 shows a perspective view in the open position of a plastic moulding machine for use in a method according to prior art reference GB2460838A. In Figure 11, machine 10 comprises upper and lower mould halves 12, 14. The mould halves 12, 14 are joined by hinges 16 so that the mould halves can be moved between the open position seen in Figure 11 and a closed position. Each mould half 12, 14 comprises a mould 18, 20 defining a mould cavity 22, 24 for forming a plastic article. Insulating jackets 30, 32 are shown in Figure 11. Figure 11 shows a perspective view in the open position of a plastic moulding machine for use in a method according to prior art reference GB2460838A.

In WO2002/062550A1, Claim 12 therein discloses plastic particulate material being melted to form a skin on male and female complementary moulds, after which the two complementary male and female moulds are spaced apart from one another at a predetermined distance such that the plastic filler material may be sandwiched between the male and female moulds to form a double skinned composite with a plastic filler material in the middle of the two skins. In GB2460838A, Claim 7 therein discloses that plastic particulate material is melted to form a skin on the moulds, after which expandable filler material is placed on the plastic skin formed in one mould.

Methods disclosed in WO2002/062550A1 and in GB2460838A have the disadvantage that skins must be formed or partially formed first before filler material is added to the mould.

In addition, it is desirable for some applications to provide a skin structure which does not consist of a single skin with a uniform composition. A more complex skin structure, such as consisting of two or more layers, can provide advantages. For example, an outer skin can be provided which provides one or more of added strength, selected colour, odour, deodour, fire resistance, UV stabilisation, ready-releasable properties (eg. for formworking applications), or a smooth surface finish (eg fewer or no surface pits due to contaminants in recycled plastics of an inner skin), anti-microbial properties. An inner skin can be provided which does not possess these properties, but which has a lower cost per unit volume than the outer skin, for example because it is derived from lower-grade recycled materials. Therefore a two layer skin can have the advantage of the outer skin property, and the advantage of a lower overall cost due to a lower cost per unit volume of the inner skin material than the outer skin material, where the outer skin material may be more expensive due to the property it provides. In addition, the inner skin may bind better to a core material than the binding which would be obtained between the outer skin and the core material, which reduces the risk of post-manufacture delamination between layers in a layered article.

In WO2002/062550A1, page 12 lines 2 to 3 therein disclose "Generally, the expandable foam is activated by the residual heat from the molds." The use of residual heat is also referred to on pages 18, 20 and 27 therein. The use of residual heat leads to a relatively slow manufacturing process when compared to active heating and cooling. In WO2002/062550A1 Fig. 10 and related disclosures on pages 19 and 20 therein disclose a process for manufacturing an article using plastic particulate material in a pair of moulds. However, the process of Fig. 10 therein is disclosed to require 60 minutes, and the mould parts are disclosed to be apart for the first 28 minutes of the process. The extended process while the mould parts are apart leads to heat loss from the mould, which reduces energy efficiency and increases manufacturing time because heating is slowed down due to heat loss. Furthermore in WO2002/062550A1 Fig. 10 the mould parts are cooled while together which keeps the cooling rate of the mould and its contents low, which also increases manufacturing time. In GB2460838F3, Claim 1 therein discloses that moulds are first heated while open, then a material to form a skin is added, then one waits for a skin to form, then filler material is added, and then the mould is closed. The extended process while the mould is open leads to heat loss from the mould, which reduces energy efficiency and increases manufacturing time because heating is slowed down due to heat loss. Furthermore the moulds are cooled while completely closed which keeps the cooling rate of the moulds and its contents low, which also increases manufacturing time.

Methods disclosed in WO2002/062550A1 and in GB2460838B have the disadvantages of providing a relatively lengthy manufacturing cycle and of providing a relatively low energy efficiency. Although WO2013038177A1 overcomes these disadvantages to a significant extent, further improvement is desirable.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a process for manufacturing a multilayer article, including the steps of:

(i) discharging core material from a first extrusion unit in a first discharge, to form an article core portion;

(ii) discharging first layer material from a second extrusion unit in a second discharge, to form a first layer on a first face of the article core portion;

(iii) discharging second layer material from a third extrusion unit in a third discharge, to form a second layer on a second face of the article core portion, and

(iv) cutting to form a multilayer article.

The article core portion may include plastic. The first layer may include plastic. The second layer may include plastic. The multilayer article may include plastic.

Benefits of the process include: increased tolerance to acceptable raw material input (e.g. more contaminations, greater variety of polymer types and properties, greater mix of polymer types); increased energy efficiency as there are no hot moulds that are being heated up and cooled down each time a product is made, and enhanced strength properties of the finished product, which may arise due to the pressure and homogenisation inherent to an extrusion process.

The process may be one wherein the second extrusion unit and the third extrusion unit are the same extrusion unit. Advantages are that one less extrusion unit is required, and that the same output material may be used to form the first layer and the second layer, which provides uniformity of the first and second layers.

The process may be one including a step of subjecting material including a foaming agent in the first extrusion unit to a foaming step including an application of heat prior to discharging core material from the first extrusion unit. Advantages are that the core material is foamed, which increases the strength and rigidity of the finished article, and reduces the density of the article, which makes it easier to handle manually, for example. The process may be one including a step of providing heat-activated expandable foam plastic material as input material to the first extrusion unit for the core material. An advantage is that plastic material is relatively cheap and relatively light in weight. The process may be one wherein the heat-activated expandable foam plastic material includes a foaming agent. An advantage is that the heat-activated expandable foam plastic material may be foamed based on the properties of the foaming agent.

The process may be one wherein the process is a manufacturing process tolerant to the compositions of the first layer materials and the second layer materials and the core material. An advantage is that the composition of the input materials does not have to be tightly controlled.

The process may be one wherein the process includes a step of providing co-mmgled or mixed recycled plastic input materials. An advantage is that low cost materials may be used. An advantage is that materials that might otherwise be sent to landfill or for incineration may be re -used.

The process may be one wherein the co-mingled or mixed recycled plastic input materials are co-mingled or mixed, contaminated recycled plastic input materials. An advantage is that particularly low cost materials may be used. An advantage is that materials that might otherwise be sent to landfill or for incineration may be re -used.

The process may be one wherein the multilayer article comprises plastics. An advantage is that the article is relatively cheap to manufacture, and is lightweight.

The process may be one wherein the multilayer article comprises recycled plastics. An advantage is that low cost materials may be used. An advantage is that materials that might otherwise be sent to landfill or for incineration may be re -used.

The process may be one wherein the recycled plastics comprise single polymer recycled materials. An advantage is that low cost materials may be used. An advantage is that materials that might otherwise be sent to landfill or for incineration may be re-used. The process may be one wherein the recycled plastics comprise multiple polymer recycled materials. An advantage is that particularly low cost materials may be used. An advantage is that materials that might otherwise be sent to landfill or for incineration may be re -used.

The process may be one wherein the multilayer article comprises some non-polymer contaminations. An advantage is that particularly low cost materials may be used. An advantage is that materials that might otherwise be sent to landfill or for incineration may be re-used.

The process may be one wherein the multilayer article includes minerals. An advantage is increased article strength.

The process may be one wherein a multilayer article core comprises relatively hard plastics and a multilayer article first layer and second layer comprise relatively soft plastics. An advantage is a strong article with a low skin abrasion when handled by a human.

The process may be one wherein the multilayer article has consistent properties without detrimental or un-controlled localised concentrations of any one material type or contamination occurring.

The process may be one wherein the multilayer article includes one or more layers comprising mixed plastics which are unstable (e.g. immiscible) in a liquid phase in the absence of shear. An advantage is increased range of input materials.

The process may be one including a blending step of blending different materials which occurs prior to materials entering an extrusion unit. An advantage is improved article uniformity.

The process may be one including a blending step of blending different materials within at least one extrusion unit. An advantage is improved article uniformity. The process may be one in which for an input stream comprising mixed plastic types or containing contamination or other additives, the input stream is homogenised prior to a pre-extrusion blending step or prior to an extrusion step. An advantage is improved article uniformity.

The process may be one including a blending step in which an even dispersal throughout an input stream of all its various constituent elements is performed such that localised concentrations of any one material within the extrusion units are avoided. An advantage is improved article uniformity.

The process may be one such that a family of polymers is dominant within a molten polymer such that it creates a matrix in which non-dominant particles and / or contaminants can reside. The process may be one in which high shear in an extrusion unit containing non- dominant polymer chains is such that the non-dominant polymer chains are broken down into shorter chains allowing better dispersion within a dominant polymer matrix.

The process may be one including a step in an extrusion unit containing polymers, of melting the polymers and mixing the polymers aggressively to break polymer chains, which allows new polymer bonds to form subsequently. An advantage is improved article strength.

The process may be one including a step of using compatibilisers. An advantage is an increased range of input materials.

The process may be one in which homogenisation and blending of input materials occurs within one or more extruders. The process may be one in which materials in the extrusion units are at temperatures in the range 100°C to 300°C.

The process may be one in which materials in the extrusion units are at temperatures in the range 120°C to 260°C. The process may be one in which materials in the extrusion units experience pressures in the range of 0.2 MPa to 70 MPa. Advantages are improved article strength and uniformity.

The process may be one in which materials in the extrusion units experience pressures in the range of 10 MPa to 50 MPa. Advantages are improved article strength and uniformity. The process may be one in which materials in an extrusion unit experience shear in the range of 0.01 MPa to 10 MPa. Advantages are improved article strength and uniformity.

The process may be one in which materials in an extrusion unit experience shear in the range of 0.1 MPa to 5 MPa. Advantages are improved article strength and uniformity.

The process may be one in which an extrusion unit includes twin-screw extruders, a single screw extruder, a planetary extruder or more than two screws in a screw extruder. An advantage is improved mixing of materials. The process may be one including a degassing step to remove volatile gases from molten materials. An advantage is a reduced risk of voids in a manufactured article, or to remove detrimental gases from the molten materials.

The process may be one including a step of forming a third layer on the first layer or on the second layer, by discharging third layer material from a fourth extrusion unit in a fourth discharge.

The process may be one including a step of forming a fourth layer on the opposite face to the third layer, by discharging fourth layer material from a fifth extrusion unit in a fifth discharge. An advantage is an outer skin is produced, which may have different properties to an inner skin.

The process may be one wherein the fourth extrusion unit and the fifth extrusion unit are the same extrusion unit. Advantages are that one less extrusion unit is required, and that the same output matenal may be used to form the third layer and the fourth layer, which provides uniformity of the third and fourth layers.

The process may be one wherein multiple further layers are discharged or placed onto previously discharged layers, from extrusion units, or from elsewhere.

The process may be one in which shear, heat and pressure are applied to materials in the extrusion units. The process may be one including a step of including one or more reinforcing elements in the multilayer article. An advantage is a stronger article, but which is produced with only a small change to the process.

The process may be one in which a reinforcing element is a continuous fibre material, such as a fibre mat or mesh, and such mats or meshes are made out of woven or unidirectional fibre materials, made from one or more of glass, aramid, nylon or other polymer types, hemp, carbon, metal, or organic materials.

The process may be one in which reinforcing elements are sheets, plates, rods, bars or wires.

The process may be one including the step of short reinforcing elements being fed into a paste within an extrusion unit such that the short reinforcing elements are blended into the paste at the extrusion stage. An advantage is a stronger article, but which is produced with only a small change to the process.

The process may be one in which short reinforcing elements are one or more of short fibres made from glass, aramid, nylon or other polymer types, hemp, carbon, metal, or organic materials.

The process may be one in which a paste in an extrusion unit includes a material (eg. maleic acid or maleic anhydride) to enhance a bond between the reinforcing elements and plastics. The process may be one including use of a die system which integrates all inputs as article layering within the die system and forms the finished article. An advantage is a compact process which may be used to produce a relatively complex article. The process may be one including one or more high pressure devices to feed materials into the die system. An advantage is that mixing and high pressure extruding may be performed in separate steps, which may produce better control over the manufacturing process. The process may be one in which reinforcing elements are fed into an article being formed at the die system. An advantage is a stronger article, but which is produced with a simple change to the process.

The process may be one in which output from the die system is drawn away and cooled down to form a product in a continuous process.

The process may be one in which steel bands on rollers are used to draw away output from the die system. The process may be one in which feedback from sensors is used by a computer to ensure a stabilization of parameters of a manufactured article. An advantage is improved control of the manufacturing process.

The process may be one in which the process is a continuous process. An advantage is improved efficiency over batch processes.

The process may be one in which the process uses input granules including granules in the range of 5 mm to 35 mm in charactenstic size. An advantage is that relatively coarse input materials may be used.

The process may be one in which the process includes low melt flow polymers as input materials. An advantage is that materials difficult to recycle may be used. The process may be one in which the article is a plank or a board. An advantage is ready use in construction or in agriculture. The process may be one in which the article is barge covering or container flooring. The process may be one in which the article is between 1/2 feet (15.24 cm) and 15 feet (457.2 cm) wide.

The process may be one in which the article is between 4 mm and 80 mm thick. The process may be one in which the article is between 10 mm and 50 mm thick.

According to a second aspect of the invention, there is provided a manufacturing apparatus for manufacturing a multilayer article, the apparatus including a first extrusion unit, a second extrusion unit, a third extrusion unit, and a cutter, the first extrusion unit, the second extrusion unit, and the third extrusion unit arranged such that:

(i) core material is dischargeable from the first extrusion unit in a first discharge, to form an article core portion;

(ii) first layer material is dischargeable from the second extrusion unit in a second discharge, to form a first layer on a first face of the article core portion;

(iii) second layer material is dischargeable from the third extrusion unit in a third discharge, to form a second layer on a second face of the article core portion, and the cutter is arranged to cut to form a multilayer article.

Benefits of the apparatus include: increased tolerance to acceptable raw material input (e.g. more contaminations, greater variety of polymer types and properties, greater mix of polymer types); increased energy efficiency as there are no hot moulds that are being heated up and cooled down each time a product is made, and enhanced strength properties of the finished product, which may arise due to the pressure inherent to an extrusion process.

The manufacturing apparatus may be one in which the second extrusion unit is the same extrusion unit as the third extrusion unit. Advantages are that one less extrusion unit is required, and that the same output material may be used to form the first layer and the second layer, which provides uniformity of the first and second layers. The manufacturing apparatus may be arranged to perform a process of any aspect according to the first aspect of the invention. According to a third aspect of the invention, there is proved a computer program product for running on a computer, wherein the computer program product when running on a computer is operable to control a process of any aspect according to the first aspect of the invention. An advantage is improved control and ease of alteration of manufacturing processes.

According to a fourth aspect of the invention, there is provided a crack resistant multilayer article comprising a foamed core, a first layer on a first face of the article core, and a second layer on a second face of the article core, wherein the article includes recycled plastics, wherein the article has a flexural modulus in a range of 1500 MPa to 4000 MPa, and wherein the article is, for example, a plank or a board, or barge covering or container flooring. Crack resistance may be manifested for example by the article not cracking when a nail is hammered into it, or by the article not cracking when a screw is screwed into it. Advantages are that the device is relatively stiff, but crack resistant. The crack resistant multilayer article may be shatter resistant. The article may be made using processes according to a first aspect of the invention.

The crack resistant multilayer article may include a further layer or a further plurality of layers.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the invention will now be described, by way of example only, with reference to the following Figures, in which:

Figure 1 shows an example of a process used in preparing materials for manufacturing plastic articles using recycled plastic comprising multiple polymer types as well as some contaminations as the input materials, for use in a plastic extrusion manufacturing process.

Figure 2 shows three examples of processes used in homogenising and blending materials for manufacturing plastic articles using recycled plastic comprising multiple polymer types as well as some contaminations as the input materials, for use in a plastic extrusion manufacturing process.

Figure 3 shows an example die configuration for board manufacturing, in which the two skins of the board are each created within their own die and these dies are in parallel, and then the two skins are integrated with the core layer in a second stage die in series.

Figure 4 shows an example of reinforcing sheets being incorporated in an article during an extrusion manufacturing process.

Figure 5 shows an example method of drawing the product away from the die whilst cooling it and maintaining the form within required dimensional tolerances by using steel bands moving on rollers, with such bands at the top and bottom faces of the product, for example if making boards.

Figure 6 shows an example of an upper skin, a core and a lower skin materials once well homogenised being brought together in a die.

Figure 7 shows an example of upper skins, a core and lower skins materials once well homogenised being brought together in a die or dies.

Figure 8 shows an example of a cross section of a product which may be manufactured by an extrusion process.

Figure 9 shows an example of a cross section of a product which may be manufactured by an extrusion process.

Figure 10 shows an illustration of an article and the respective process for manufacturing the article, generally denoted by the numeral 110, according to prior art reference WO2002/062550A1. Figure 11 shows a perspective view in the open position of a plastic moulding machine for use in a method according to prior art reference GB2460838A.

DETAILED DESCRIPTION

There are provided processes for manufacturing plastic articles. There are provided processes using treatment techniques for handling, cleaning, sorting and size-reduction of plastics, homogenisation techniques, blending techniques, extrusion techniques and forming techniques. There is provided a plastic article manufactured using combinations of these techniques in processes. There are provided methods within the manufacturing processes for strengthening the finished articles. There are provided methods of manufacturing plastic articles which are well-suited to the use of recycled plastics in the manufacturing method, but which are not necessarily limited to the use of recycled plastics. There are provided methods of manufacturing plastic articles which are well-suited to the use of input materials for the manufacturing method which contain multiple types of plastics, and which materials may contain some non-polymer contaminations. Such methods are highly applicable in the use of recycled materials.

In an example, the processes for manufacturing plastic articles are used to make a board for use in construction or agriculture. In this example such boards would be used in a variety of applications in place of plywood products or other plastic or wood panel products. An example of an application in construction would be as a shuttering panel in formwork and falsework, where properties such as high strength, stiffness, good surface finish, good surface release properties, a relatively low weight and safety in handling are all features that this process for manufacturing plastic articles can accommodate.

In an example, different plastics are used in the present manufacturing methods. One example is styrenic polymers. Examples include polystyrene (PS), acrylonitrile butadiene styrene (ABS), and high-impact polystyrene (HIPS). Other examples of different plastics include poly-olefins, eg. polyethylene (PE) and polypropylene (PP). Different plastics may be either homogenised or blended or both, with such blending occurring either prior to extrusion or during extrusion or both prior to and during extrusion.

In an example recycling process, plastics to be recycled are sorted into relatively hard plastics and relatively soft plastics. Plastics in each class then undergo cleaning to remove excess dirt, food waste, sticky labels, and the like. Plastics in each class are shredded into pieces with a characteristic size of less than about 100 mm, then de-dusted, cleaned again, then shredded, granulated or agglomerated into pieces with a characteristic size of about 35mm to 2mm. Pieces may be turned into finer grains (eg. characteristic size less than 2 mm) for use in a manufacturing process.

In an example recycling process, plastic pieces of a wide range of sizes may be sorted by polymer type, colour, density, size, hardness, electrical conductivity, by additives, or by any combination of these criteria, and such sorting may occur at any stage within the process. Such sorting may also include sorting large or particular non-polymer contaminants, such as metal pieces, to remove them from the polymer materials. This stage may be called a "Primary Sorting" and / or "Screening".

In an example recycling process, materials cleaned and sorted in the "Primary Sorting" and "Screening" may then be size-reduced and further cleaned and screened. Size- reduction can occur via shredding, granulation, agglomeration or densification processes, or any combination of these processes. Additionally, materials can be cleaned using wet and / or dry cleaning systems, metal separation systems, air, density or size classification systems. Additionally, materials can be further purified using more advanced techniques such as with classification assemblies using near infra-red (NIR) screening, X-ray screening, laser screening, optical colour screening. The sequencing of particular processes may vary.

In an example recycling process, a mix of relatively clean plastic pieces of size 2mm to 50mm comprising differing types of polymer may be homogenised prior to blending or prior to extrusion. These particles may be homogenised through a homogenisation process. Examples of such a homogenisation process could be bulk homogenisation through a system such as a large-scale mixing during storage or through blending within a blending silo, fountain blender or homogenisation silo. Other particle homogenisation techniques can also be used. In this step it is intended to ensure an even dispersal throughout the input stream of all its various constituent elements such that localised concentrations of any one type of material or contamination within the extruders are avoided. In this way it is intended to achieve consistent properties of the finished articles being manufactured without detrimental or un-controlled localised concentrations of any one material type or contamination occurring within the finished article.

In an example, the relatively soft plastics may be used to form a skin of an article manufactured using the manufacturing methods disclosed, while the relatively hard plastics may be used to form a core of an article manufactured using the manufacturing methods disclosed. However, such an arrangement may lead to an article surface which is softer than desired (eg. more prone to scratches or tearing), and to a core which is more brittle than desired eg. too likely to crack under mechanical shock. Consequently, in the manufacturing methods disclosed, the skin may be formed using a blend of the relatively soft and relatively hard plastic materials, and the core may also be formed using a blend of the relatively soft and relatively hard plastic materials, but where the surface comprises relatively more soft plastic materials than the core. Other materials may be added to a blend of relatively soft plastics materials and relatively hard plastics materials: an example is that rubber types may be added for impact resistance. Blending can occur before materials are fed into an extruder. Blending can occur within an extruder.

Different input streams of input materials may be used, such as from different suppliers of recycled plastic input materials, for example. Each input stream may contain many different types of polymer as well as contaminations. Different input streams may be used in parallel in the same manufacturing process, for example. Other input streams are possible, such as more contaminated materials, or non-polymer additives or polymer additives or any combination of these. For example minerals such as talc, calc, or other types of fillers may be added. Other types of additive may be used, such additives imparting particular properties or benefits to the finished articles. One example of such an additive could be so-called compatibilisers. Virgin materials or single-polymer recycled materials may also be used.

The materials used to form a skin of an article manufactured using the manufacturing methods disclosed may comprise plastic granules, pellets, flakes, agglomerate, or powder material. These materials can be thermo-set plastics or thermo-plastics, or thermo-plastic rubber or rubber. These materials may contain additives. These matenals may contain contaminants. These materials may contain some or all of the above at the same time. The input materials used to form a core of an article manufactured using the manufacturing methods disclosed may comprise heat-activated expandable foamed plastic granulated material. These materials can be varied forms of polymer, elastomer or rubber, such as thermo-set plastics or thermo-plastics or thermo-plastic rubbers or rubbers. Heat- activated expandable foam plastic material may include or comprise heat-activated expandable foamable plastic material. Such heat-activated expandable foam plastic material will typically include a foaming agent. Known foaming agents include blowing agents and surfactants. There are two main types of blowing agents: those which are gases at the temperature at which the foam is formed and those that generate gases by a chemical reaction. Carbon dioxide, pentane, steam and chlorofluorocarbons are examples of the former. Blowing agents that produce gas via chemical reactions include baking powder, sodium bicarbonate, azodicarbonamide, hydroxypropane tricarboxylic acid and titanium hydride. Blowing agents may be dosed into the core layer paste within the core layer extruder, or may be blended into the core layer materials prior to the core layer materials entering the extruder. The materials used to form the skin and/or core may comprise any of powder, pellets, shavings, flakes, chunks, granules, agglomerate or the like.

Where any input stream comprises mixed plastic types or contains contamination or other additives, the input stream should preferably be homogenised prior to blending or prior to extrusion. The best homogenisation is achieved at the stage where particle sizes are in the range of 50mm or less. The input stream is to be homogenised through a homogenisation process. Examples of such a homogenisation process could be bulk homogenisation through a system such as a large-scale mixing during storage or through bulk-blending within a blending silo or homogenisation silo. Other particle homogenisation techniques can also be used. In this step it is intended to ensure an even dispersal throughout the input stream of all its various constituent elements such that localised concentrations of any one material within the extruders are avoided. In this way it is intended to achieve consistent properties of the finished articles being manufactured without detrimental or un-controlled localised concentrations of any one material type or contamination occurring within the finished articles.

Additionally, there may be several different input streams and some or all of these may be homogenised together. If post-homogenisation more than one input stream is to be used, then blending of these streams may be required. Blending can occur prior to material entering the extruder or can occur through controlled feeding into different input ports in the extruder, but in both cases the relative quantities of the different input streams are controlled such that a targeted blend within the extruder barrel is ultimately achieved. The further homogenisation and blending of the input materials then occurs within the extruder or extruders. The material is subjected to pressure, heat and shear. In an example, the temperature within an extruder or extruders may be in the range of 100°C to 300°C. In a preferred example, the temperature within an extruder or extruders may be in the range of 120°C to 260°C. In an example, a pressure within an extruder or extruders may be in the range of 0.2 MPa to 70 MPa. In a preferred example, a pressure within an extruder or extruders may be in the range of 10 MPa to 50 MPa. In an example, a shear within an extruder or extruders may be in the range of 0.01 MPa to 10 MPa. In a preferred example, a shear within an extruder or extruders may be in the range of 0.1 MPa to 5 MPa. The plastic particles may be melted within the extruder through a combination of heat and pressure, but it is typically mostly with the shearing action within the extruder that further homogenisation and blending is achieved. In an example, to achieve a high level of shear and consequent material blending, co-rotating twin-screw extruders are used. In another example a single screw extruder is used. In another example a "planetary" extruder is used.

The homogenisation, blending and extrusion processes may therefore be used together to produce a relatively homogeneous and well blended paste coming out of the extruder, having started from relatively mhomogeneous input materials, such as co-mingled or mixed, contaminated recycled plastic materials for example. A melt filter may also be incorporated within the extrusion system to further aid the removal of non-molten contamination particles from the melt. A degassing process may also be incorporated within the extrusion system to further aid the removal of volatile gases from the melt. A relatively homogeneous material may therefore be developed from a process combining some or all of the Primary Sorting techniques such as sorting, screening, size-reducing, cleaning and classifying, and then homogenising, blending and extruding or alternatively then homogenising extruding and blending within the extruder. The materials are thus well homogenised to achieve consistency, and blended to achieve further consistency and to achieve defined characteristics within the finished articles, and these materials thus exit the extruder as a blended and consistent hot paste. An example of the importance of careful blending would be to ensure that one family of polymers can be dominant within the melted polymer such that it can create a matrix in which non-dominant particles and / or contaminants can reside. An example of the importance of using the right type of extrusion technique is the generation of high shear within the melt mixture, such that the non-dominant polymer chains are broken down into shorter chains allowing better dispersion within the dominant polymer matrix. Melting the polymers and mixing them aggressively may serve to break the polymer chains. By breaking polymer bonds when breaking the polymer chains, and allowing new polymer bonds to form subsequently, product stiffness may be increased.

Figure 2 shows three examples of processes used in homogenising and blending materials for manufacturing plastic articles using recycled plastic comprising multiple polymer types as well as some contaminations as the input materials, for use in a plastic extrusion manufacturing process. In example 1, homogenised material 1, homogenised material 2, and optionally homogenised material 3, are added to additive 1 and optionally additive 2 is added, and the materials are blended together at a blending stage. The blended material is then provided to an extrusion stage. In example 2, homogenised material 1, homogenised material 2, and optionally additive 2, are blended at the blending stage. Following blending, additive 1 and optionally homogenised material 3 are added to the blended material and the extrusion stage. In example 3, homogenised material 1, homogenised material 2, additive 1, and optionally homogenised material 3, and optionally additive 2, are brought together in an extrusion stage.

It may be necessary to blend materials into the material paste or pastes within the extruder or extruders to enhance characteristics of the finished article. For example compatibilisers are such materials that may act to enhance the bonds between different types of plastics and thereby make the finished article stronger. Examples of compatibilisers are block co-polymers such as SEBS (styrene-ethylene / butylene-styrene) or SEPS (styrene-ethylene / propylene-styrene). For example mineral fillers or extenders such as calcium carbonate (chalk) or magnesium silicate (talc) may be added to stiffen the finished articles. Other examples of properties that may be enhanced by including additives into the paste at this stage are fire retardation, thermal conductivity (heat dissipation), cosmetic colouring, anti-microbial, anti-graffiti, anti-slip, anti-oxidant, fragrance, impact modification, and UV stability. Plasticizers may be used to soften the product if it would be too stiff otherwise.

This paste may be formed in a die. The finished article may comprise many layers. These distinct layers and their arrangement within the finished article may impart particular properties to the finished article. An extruder may be used for each layer or layer type. That is to say if two or more identically composed layers are used within the finished article structure then it may be preferential to create more than one layer from the same extruder by dividing the extruder output before feeding into a die or dies. Multiple extruders may be used to make multiple different layers. One extruder may be used to make the paste for the core layer. If the core is comprised of more than one layer then more than one core extruder may be required. Each extruder produces its own predetermined paste. These pastes may all need to be formed and brought together in a die. To make a product with multiple layers, there may be many different extruders for the multiple layers of skins and core, with each extruder producing its own pre -determined paste. These pastes may all need to be formed and brought together in a die or within a series of dies.

Surface layer thickness may be at least 0.01 mm. Surface layer thickness may be less than 3.0 cm. Surface layer thickness may be less than 1.0 cm. Surface layer thickness may be less than 1.0 mm.

A purpose of the die or dies is to give and maintain a desired shape or form and can also be to combine more than one input together. The die or dies is / are designed to be fed with multiple inputs and to force the integration of these different streams into a single cohesive output and to form this output. Inputs to the die can be one or more extruder outputs, reinforcing elements, or any combination of these. The process may use a single die, or several dies. If fed with multiple inputs, the die or dies integrate all inputs as article layering within the die or dies and form the finished article. The process may use more than one die, in series and / or in parallel, each die with single or multiple inputs to forms individual layers or combinations of layers, and then a later die or later dies to integrate and form these layers or layer combinations into the article. If more than one die is used it will be preferable for the dies to be in close proximity to each other to maintain pressure within the system. In an example die configuration for board manufacturing, the two skins of the board are each created within their own die and these dies are in parallel, and then the two skins are integrated with the core layer in a second stage die in series. An example is shown in Figure 3. Multiple die stages may be integrated into a single die or single die block. To bring these materials together in the die and maintain good properties for the finished articles, the materials may need to be fed into the die under high pressure. A high shear extruder may not provide adequate high pressure, therefore it may be necessary to add a device between each extruder and the die. Examples of such a device could be a melt- pump attached to the end of an extruder for example, or the inclusion of a second extruder between the first extruder and the die.

It may be desirable to add reinforcement to the finished articles. An example could be the case where the finished article is a panel to be used in the construction industry for formworks and high flexural strength is required. In such cases where it is desirable to strengthen the finished article, reinforcement elements may be fed into the article being formed at the die or dies. Examples of such elements could be continuous fibre materials, eg. fibre mat or mesh, and such mats or meshes could be made out of woven or unidirectional fibre materials, made from glass, aramid, nylon or other polymer types, hemp, carbon, metal, or organic materials. Other reinforcement elements could be any of sheets, plates, rods, bars or wires which could also be fed into the article being formed at the die or dies. An example could be to include aluminium sheet material between two separate skin layers, on each side of the finished article. Figure 4 shows an example of a plastic extrusion process wherein fibre sheets reinforcing elements are introduced into the process at the die or dies.

If reinforcing elements are fed into the article being formed at the die or dies, it may be necessary to blend certain materials into the material paste or pastes within the extruder or extruders for a layer or layers of the finished article coming in to contact with the reinforcing element. Such materials act to enhance the bond between the reinforcing element and the plastics within the paste. Examples of such materials could be organic compounds such as maleic anhydride.

In such cases where it is desirable to strengthen the finished article, reinforcing elements may be fed into the paste within the extruders such that the reinforcing elements are blended into the paste at the extrusion stage. Examples of such elements could be short fibres made from glass, aramid, nylon or other polymer types, hemp, carbon, metal, or organic materials. Short fibres are non-continuous fibres of short length, generally in the range of 4mm to 10mm long.

Where short fibres are fed into the paste within the extruders such that the short fibres are blended into the paste at the extrusion stage, it may be necessary to blend certain materials into the material paste or pastes within the extruder or extruders. Such materials act to enhance the bond between the reinforcing element and the plastics within the paste. Examples of such materials could be organic compounds such as maleic anhydride acting to enhance the bond between plastics and other materials such as short fibres (e.g. short glass fibres), glass fibres, and metals.

The output from the die is drawn away and cooled down to form a product in a continuous process. Maintenance of the form of the output may be required as the output is drawn away and cooled. Additional forming of the output may be required as the output is drawn away and cooled.

An example method of drawing the product away from the die whilst cooling it and maintaining the form within required dimensional tolerances could be to use steel bands moving on rollers, with such bands at the top and bottom faces of the product, for example if making boards. In this example the steel bands are cooling the product while maintaining the form and drawing the product away from the die. Figure 5 shows a possible example of the configuration of this part of the manufacturing process.

In an example method of drawing the product away from the die whilst cooling it and maintaining the form within required dimensional tolerances using steel bands moving on rollers such that there are bands at the top and bottom faces of the product, the distance between the top and bottom steel bands may be varied for varying thickness requirements of the finished articles, for example if making boards of 9mm, 12mm or 18mm thick.

After cooling, the output may be cut into the final required sizes. An example of this would be to cut the output into rectangles of 8 feet by 4 feet, being a common size for shuttering panels.

The product produced may be cut to form boards. A board may incorporate reinforcing materials. A skin or any layer of an article may include short fibres or a fibre sheet or mat which strengthens the product. A skin or any layer of an article may include other types of reinforcing elements which strengthen the article. Reinforcing sheet or sheets may be incorporated in an article during an extrusion manufacturing process, either in single or multiple layers. An example is shown in Figure 4. Short fibres may be incorporated into an article during an extrusion manufacturing process.

Materials for a core or any skin layer may first need to be size-reduced to a particle size appropriate for input into the extrusion process. An example would be to shred, granulate or agglomerate plastic into particles of approximately 2mm to 35mm diameter. Particles can be in many forms such as flakes, granules, powder or film fragments, providing that they may be free-flowing enough to be homogenised and can be fed into the extruders.

These particles may then be homogenised through a homogenisation process. Examples of a particle homogenisation process could be bulk homogenisation through a system such as a large-scale mixing during storage or blending within a blending silo or homogenisation silo. Alternatively another example of homogenisation could be continuous blending of particles continuously dosed from different sources of material, so rather than bulk blending a large single volume of material one can continuously blend small quantities of material taken continuously from several volumes. Materials for a core may be extruded from an extruder, the materials being subject to shear, heat and pressure in the extruder. Materials for an upper skin may be extruded from an extruder, the materials being subject to shear, heat and pressure in the extruder. Materials for a lower skin may be extruded from an extruder, the materials being subject to shear, heat and pressure in the extruder. Homogenisation and blending of the plastic materials are occurring within the extruders and the pressure, heat and shearing action within the extruders is achieving this further homogenisation and blending. For example, co-rotating twin screw extruders may be used here to achieve a high level of shear. The upper skin or skins, core and lower skin or skins materials once well homogenised will need to be brought together in a die or dies. Example process configurations are shown in Figures 6 and 7.

To bring these materials together in the die or dies and maintain good properties for the finished articles, the materials need to be fed into the die under high pressure. A high shear extruder may not provide adequate high pressure, therefore it may be necessary to add a device between each extruder and the die. Examples of such a device could be a melt-pump attached to the end of an extruder or the inclusion of another extruder between the extruder and the die.

The outputs from the die or dies are then drawn away and cooled down to form a product in a continuous process. Additional forming of the output may be required as the output is drawn away and cooled. Examples are shown in Figures 4, 5, 6 and 7. Materials for a core may be extruded from an extruder, the materials being subject to heat, shear and pressure in the extruder. Materials for an upper outer skin may be extruded from an extruder, the materials being subject to heat, shear and pressure in the extruder. Materials for an upper inner skin may be extruded from an extruder, the materials being subject to heat, shear and pressure in the extruder. Materials for a lower inner skin may be extruded from an extruder, the matenals being subject to heat, shear and pressure in the extruder. Materials for a lower outer skin may be extruded from an extruder, the materials being subject to heat, shear and pressure in the extruder.

The further homogenisation and blending of the plastic materials occurs within these extruders and the shearing action within the extruders is achieving this further homogenisation and blending. Co-rotating twin screw extruders may be used to achieve a high level of shear— for example. Once the upper outer skin material, upper inner skin material, core material, lower outer skin material and lower inner skin material are all well homogenised, they may need to be brought together in a die or dies. Examples are shown in Figures 3, 4, 5 and 7. To bring these materials together in the die and maintain good properties for the finished articles, the materials may need to be fed into the die under high pressure. As high shear extruders may not provide adequately high pressure, it may therefore be necessary to add a device or devices between each extruder and the die. Examples of such devices could be melt-pumps attached to the end of each extruder, or the inclusion of another extruder between each extruder and the die.

The outputs from the die are then drawn away and cooled down to form a product in a continuous process. Additional forming of the output may be required as the output is drawn away and cooled.

Examples are shown in Figures 4, 5, 6 and 7.

A product produced in a plastic extrusion process may include multiple layers, each layer being extruded from a respective extruder. For example, an upper skin of a manufactured article may include an upper outer skin and an upper inner skin, each skin being extruded from a respective extruder. Examples are shown in Figures 4, 5 and 7.

In an extrusion manufacturing process, the manufacturing line may include a hot zone with hotter temperatures near to exits from extruders, and a cold zone with colder temperatures further down the production line, away from extruders. This arrangement provides a large increase in viscosity of the extruded materials as the extruded materials travel away from the extruders and cool down, which enables the formation of a rigid product. When a fibre sheet is provided for an article to be manufactured using an extrusion process, it is desirable for extruded polymers to flow into the fibre sheet and to grip the fibre sheet, so as to reduce the scope for delamination after manufacture. A bonding agent may be used to improve bonding between extruded polymers and a fibre sheet. An example of a bonding agent is maleic acid or maleic anhydride. Maleic acid or maleic anhydride may be used as a bonding agent at a weight concentration in a skin layer of 0.1% to 15%. For example, maleic acid or maleic anhydride may be used as a bonding agent at a weight concentration in a skin layer of 1.0% to 1.5%. In an extrusion process, pressure is used to extrude polymer material from a respective extruder. Pressure, heat and shear may be used to overcome a lack of homogeneity in a mixture of polymers. Pressure may be adjusted according to different polymer composition mixtures and resulting viscosity. Rollers may be used to move manufactured materials along a production line. In a manufacturing process, feedback from sensors may be used to control the manufacturing process. For example, if a manufactured article is too thin, as sensed by a thickness sensor, the pressure in one or more extruders may be increased to provide more material, or the speed of the advance along the production line may be reduced, to allow more extruded material to accumulate and to thicken the product, or the die gap can be varied.

A manufacturing process may be fully automated so that feedback from sensors is used to ensure a stabilization of parameters of a manufactured product. For example, thickness uniformity, surface roughness and weight may be measured. Weight measurement may be used to check for density. An unexpectedly low density may be an indication of voids in the product, for example.

An extrusion unit (e.g. for extruding a skin or layer, or for extruding a core) may include a back pressure release system, which prevents the pressure within the extrusion unit from exceeding a threshold. Such a back pressure release system may be provided for safety reasons, and/or to help to control pressure in the extrusion system during a manufacturing process. Such an extrusion unit may be used for producing a foamed material in a controlled way.

In a continuous manufacturing process, such as shown for example in Figures 4, 5, 6 and 7, the product may be provided with improved strength. A continuous manufacturing process provides efficiency improvements over single item manufacture or batch processes, such as are described for example in WO2002/062550, GB2460838A and WO2013038177A1, because in a continuous manufacturing process the apparatus does not need to undergo relatively large cycles of heating and cooling, which use energy. Instead, in a continuous manufacturing process, different parts of the continuous manufacturing line are maintained at relatively constant temperatures, which means that relatively large cycles of heating and cooling are not required, and energy efficiency is therefore improved.

Because input materials are mixed in an extruder apparatus, to produce a relatively homogeneous mixture of input materials (eg. a paste), in contrast to processes in which extruder apparatus is not used, and in which therefore inhomogeneities may lead to product defects, an extrusion manufacturing process produces an enhanced tolerance to variations within the input materials used.

Because input materials are mixed in an extruder apparatus, relatively large granules of input materials, such as 8 mm to 10 mm in characteristic size, or 5 mm to 35 mm in characteristic size in another example, may be used. This is an advantage over manufacturing processes in which powders must be prepared for manufacturing, because for example more grinding of input materials is required to produce materials with smaller characteristic sizes, such as for powders. Examples of processes which use powders are disclosed in WO2002/062550, GB2460838A and WO2013038177A1, for example. There is a further advantage over manufacturing processes in which powders must be prepared for manufacturing, because more tolerance exists towards impurities. For example, sand particles may damage powder producing apparatus, such as by damaging milling blades, for example.

An advantage of an extrusion process is that pressure may be varied so as to improve the flow of low melt flow polymers. For example, plastic bags may include low melt flow polymers. These low melt flow polymer materials are better suited to use in extrusion manufacturing processes than to use in manufacturing processes which use low pressure, such as are disclosed in WO2002/062550, GB2460838A and WO2013038177A1, for example. Therefore an extrusion process is better suited for recycling plastic bag materials than a plastic particulate moulding process.

An advantage of a shear-based extrusion process is that a relatively stable phase of mixed plastics may be achieved, whereas the mixed plastics may be unstable (eg. immiscible) in the liquid phase in the absence of shear. A layer in a multilayer product (eg. a board) made using an extrusion process may include at least one layer including a mixture of plastics that is unstable (e.g. immiscible) in the liquid phase in the absence of shear.

An advantage of an extrusion process is that the pressure inherent in such a process may lead to a stronger product (eg. a board) when compared to prior art processes such as those disclosed in WO2002/062550, GB2460838A and WO2013038177A1, for example, in which the pressures inherent such processes may be lower.

Figure 8 and Figure 9 show examples of products which may be manufactured by an extrusion process. Material produced using the processes shown in, or disclosed with reference to, Figures 1 to 7, may be cut into boards, such as are shown for example in Figure 8 in cross section, or in Figure 9 in cross section.

The process may be one in which the article (eg. board) core is made from heat-activated expandable foam plastic material. The process may be one wherein the heat-activated expandable foam plastic material includes heat-activated expandable foamable plastic material. The process may be one wherein the process is a manufacturing process tolerant to the compositions of the outer layer materials and the heat-activated expandable foam plastic material.

The process may be one in which the article (eg. board) includes recycled plastic. The recycled plastic may be comingled contaminated recycled plastic. The process may be one in which the article (eg. board) includes non-recycled plastic. The process may be one in which the article (eg. board) includes elastomeric material. The process may be one in which the article (eg. board) includes rubber. The process may be one in which the article (eg. board) includes a blend of plastics. The process may be one wherein the board is no less than 1 /2 feet x 2 feet. (1/2 feet x 2 feet = 15.24 cm x 60.96 cm). The process may be one wherein the board is no bigger than 100 feet x 15 feet. (100 feet x 15 feet = 3048 cm x 457.2 cm). The process may be one wherein the article (eg. board) is no thicker than 200 mm. The process may be one wherein the article (eg. board) is no thicker than 80 mm. The process may be one wherein the article (eg. board) is no thinner than 4 mm. The process may be one wherein the article (eg. board) thickness is in the range of 10 mm to 50 mm. Note

It is to be understood that the above-referenced arrangements are only illustrative of the application for the principles of the present invention. Numerous modifications and alternative arrangements can be devised without departing from the spirit and scope of the present invention. While the present invention has been shown in the drawings and fully described above with particularity and detail in connection with what is presently deemed to be the most practical and preferred example(s) of the invention, it will be apparent to those of ordinary skill in the art that numerous modifications can be made without departing from the principles and concepts of the invention as set forth herein.

Claims

1. A process for manufacturing a multilayer article, including the steps of: (i) discharging core material from a first extrusion unit in a first discharge, to form an article core portion;

(iv) cutting to form a multilayer article.

2. Process of Claim 1, wherein the second extrusion unit and the third extrusion unit are the same extrusion unit.

3. Process of any previous Claim, including a step of subjecting material including a foaming agent in the first extrusion unit to a foaming step including an application of heat prior to discharging core material from the first extrusion unit.

4. Process of any previous Claim, including a step of providing heat-activated expandable foam plastic material as input material to the first extrusion unit for the core material.

5. Process of Claim 4, wherein the heat-activated expandable foam plastic material includes a foaming agent.

6. Process of any previous Claim, wherein the process is a manufacturing process tolerant to the compositions of the first layer materials and the second layer materials and the core material.

7. Process of any previous Claim, wherein the process includes a step of providing co-mingled or mixed recycled plastic input materials.

8. Process of Claim 7, wherein the co-mingled or mixed recycled plastic input materials are co-mingled or mixed, contaminated recycled plastic input materials.

9. Process of any previous Claim, wherein the multilayer article comprises plastics.

10. Process of Claim 9, wherein the multilayer article comprises recycled plastics.

11. Process of Claim 10, wherein the recycled plastics comprise single polymer recycled materials.

12. Process of Claim 10, wherein the recycled plastics comprise multiple polymer recycled materials.

13. Process of any of Claims 9 to 12, wherein the multilayer article comprises some non-polymer contaminations.

14. Process of any of Claims 9 to 13, wherein the multilayer article includes minerals.

15. Process of any of Claims 9 to 14, wherein a multilayer article core comprises relatively hard plastics and a multilayer article first layer and second layer comprise relatively soft plastics.

16. Process of any previous Claim, wherein the multilayer article has consistent properties without detrimental or un-controlled localised concentrations of any one material type or contamination occurring.

17. Process of any previous Claim, wherein the multilayer article includes one or more layers comprising mixed plastics which are unstable (e.g. immiscible) in a liquid phase in the absence of shear.

18. Process of any previous Claim, including a blending step of blending different materials which occurs prior to materials entering an extrusion unit.

19. Process of any previous Claim, including a blending step of blending different materials within at least one extrusion unit.

20. Process of any previous Claim, in which for an input stream comprising mixed plastic types or containing contamination or other additives, the input stream is homogenised prior to a pre -extrusion blending step or prior to an extrusion step.

21. Process of any previous Claim, including a blending step in which an even dispersal throughout an input stream of all its various constituent elements is performed such that localised concentrations of any one material within the extrusion units are avoided.

22. Process of any previous Claim, such that a family of polymers is dominant within a molten polymer such that it creates a matrix in which non-dominant particles and / or contaminants can reside.

23. Process of any previous Claim, in which high shear in an extrusion unit containing non-dommant polymer chains is such that the non-dominant polymer chains are broken down into shorter chains allowing better dispersion within a dominant polymer matrix.

24. Process of any previous Claim, including a step in an extrusion unit containing polymers, of melting the polymers and mixing the polymers aggressively to break polymer chains, which allows new polymer bonds to form subsequently.

25. Process of any previous Claim, including a step of using compatibilisers.

26. Process of any previous Claim, in which homogenisation and blending of input materials occurs within one or more extruders.

27. Process of any previous Claim, in which materials in the extrusion units are at temperatures in the range 100°C to 300°C.

28. Process of Claim 27, in which materials in the extrusion units are at temperatures in the range 120°C to 260°C.

29. Process of any previous Claim, in which materials in the extrusion units experience pressures in the range of 0.2 MPa to 70 MPa.

30. Process of Claim 29, in which materials in the extrusion units experience pressures in the range of 10 MPa to 50 MPa.

31. Process of any previous Claim, in which materials in an extrusion unit experience shear in the range of 0.01 MPa to 10 MPa.

32. Process of Claim 31, in which materials in an extrusion unit experience shear in the range of 0.1 MPa to 5 MPa.

33. Process of any previous Claim, in which an extrusion unit includes twin-screw extruders, a single screw extruder, a planetary extruder or more than two screws in a screw extruder.

34. Process of any previous Claim, including a degassing step to remove volatile gases from molten materials.

35. Process of any previous Claim, including a step of forming a third layer on the first layer or on the second layer, by discharging third layer material from a fourth extrusion unit in a fourth discharge.

36. Process of Claim 35, including a step of forming a fourth layer on the opposite face to the third layer, by discharging fourth layer material from a fifth extrusion unit in a fifth discharge.

37. Process of Claim 36, wherein the fourth extrusion unit and the fifth extrusion unit are the same extrusion unit.

38. Process of any of Claims 35 to 37, wherein multiple further layers are discharged or placed onto previously discharged layers, from extrusion units, or from elsewhere.

39. Process of any previous Claim, in which shear, heat and pressure are applied to materials in the extrusion units.

40. Process of any previous Claim, including a step of including one or more reinforcing elements in the multilayer article.

41. Process of Claim 40, in which a reinforcing element is a continuous fibre material, such as a fibre mat or mesh, and such mats or meshes are made out of woven or uni-directional fibre materials, made from one or more of glass, aramid, nylon or other polymer types, hemp, carbon, metal, or organic materials.

42. Process of any of Claims 40 or 41, in which reinforcing elements are sheets, plates, rods, bars or wires.

43. Process of any of Claims 40 to 42, including the step of short reinforcing elements being fed into a paste within an extrusion unit such that the short reinforcing elements are blended into the paste at the extrusion stage.

44. Process of any of Claims 40 to 43, in which short reinforcing elements are one or more of short fibres made from glass, aramid, nylon or other polymer types, hemp, carbon, metal, or organic materials.

45. Process of any of Claims 40 to 44, in which a paste in an extrusion unit includes a material (eg. maleic acid or maleic anhydride) to enhance a bond between the reinforcing elements and plastics.

46. Process of any previous Claim, including use of a die system which integrates all inputs as article layering within the die system and forms the finished article.

47. Process of Claim 42, including one or more high pressure devices to feed materials into the die system.

48. Process of Claims 46 or 47, in which reinforcing elements are fed into an article being formed at the die system.

49. Process of any of Claims 46 to 48, in which output from the die system is drawn away and cooled down to form a product in a continuous process.

50. Process of Claim 49, in which steel bands on rollers are used to draw away output from the die system.

51. Process of any previous Claim, in which feedback from sensors is used by a computer to ensure a stabilization of parameters of a manufactured article.

52. Process of any previous Claim, in which the process is a continuous process.

53. Process of any previous Claim, in which the process uses input granules including granules in the range of 5 mm to 35 mm in characteristic size.

54. Process of any previous Claim, in which the process includes low melt flow polymers as input materials.

55. Process of any previous Claim, in which the article is a plank, a board, barge covering or container flooring.

56. Process of any previous Claim, in which the process is one in which the article is between 1/2 feet (15.24 cm) and 15 feet (457.2 cm) wide.

57. Process of any previous Claim, in which the process is one in which the article is between 4 mm and 80 mm thick.

58. Process of Claim 57, in which the process is one in which the article is between 10 mm and 50 mm thick.

59. Manufacturing apparatus for manufacturing a multilayer article, the apparatus including a first extrusion unit, a second extrusion unit, a third extrusion unit, and a cutter, the first extrusion unit, the second extrusion unit, and the third extrusion unit arranged such that:

60. Manufacturing apparatus of Claim 59, in which the second extrusion unit is the same extrusion unit as the third extrusion unit.

61. Manufacturing apparatus of Claims 59 or 60, arranged to perform a process of any of Claims 1 to 58.

62. Computer program product for running on a computer, wherein the computer program product when running on a computer is operable to control a process of any of

Claims 1 to 58.

63. Crack resistant multilayer article comprising a foamed core, a first layer on a first face of the article core, and a second layer on a second face of the article core, wherein the article includes recycled plastics, wherein the article has a flexural modulus in a range of 1500 MPa to 4000 MPa, and wherein the article is, for example, a plank or a board, or barge covering or container flooring.

64. Crack resistant multilayer article of Claim 63, the article including a further layer or a further plurality of layers.

65. Multilayer article manufactured using a process of any of Claims 1 to 58.