Method and apparatus for manufacturing object using composite material comprising natural materials

Abstract

A method of manufacturing an object using a composite material comprising at least one polymeric material in which a material of natural origin is dispersed, the method comprising the steps of:-extruding the polymeric material in an extrusion section (2); -adding a material of natural origin to the polymeric material, thereby obtaining a composite material; -pressing the composite material to obtain the object. After cooling the polymer material downstream of the extrusion section (2), a material of natural origin is added to the polymer material.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for manufacturing an object using a composite material comprising a polymeric material into which a material of natural origin has been added. In particular, the material of natural origin may be a material derived from natural fibers, such as a material derived from wood fibers such as cellulose, lignin, and the like. Background Art

[0002] Synthetic polymeric materials are widely used in the packaging field. However, for reasons related to environmental protection, there is a strong need to replace synthetic polymeric materials with materials of natural origin, such as cellulosic materials.

[0003] There are various applications in which it is still not possible to replace synthetic polymeric materials with natural materials, for example due to the required properties of the finished product, or due to reasons related to the production methods that must be used to obtain the finished product. In these cases, it is desirable to successfully replace at least a portion of the polymeric material with a material of natural origin.

[0004] Therefore, the idea of using a composite material having a matrix formed of a synthetic polymer in which fibers of natural origin are dispersed has been devised. However, this presents considerable production difficulties, especially due to the risk of damaging the fibers of natural origin during the production process. Summary of the Invention

[0005] An object of the present invention is to improve a method and apparatus for manufacturing an object using a composite material comprising at least one polymeric material and a material of natural origin.

[0006] Another object is to provide an apparatus and method for manufacturing an object using a composite material comprising at least one polymeric material and a material of natural origin, wherein the risk of damaging the material of natural origin during the manufacture of the object is reduced.

[0007] Another object is to provide a method and apparatus that enable the manufacture of an object of good quality, having a lower environmental impact compared to an object made entirely of a synthetic polymeric material.

[0008] Another object is to provide a method and apparatus for manufacturing an object using a composite material comprising at least one polymeric material and a material of natural origin, which has good productivity.

[0009] In a first aspect of the present invention, there is provided a method for manufacturing an object using a composite material comprising at least one polymeric material in which a material of natural origin is dispersed, the method comprising the steps of:

[0010] - Extruding the polymeric material in an extrusion section to obtain a stream of polymeric material;

[0011] - Adding a material of natural origin to a polymer material stream, thereby obtaining a composite material;

[0012] - Pressing the composite material to obtain an object,

[0013] wherein, after cooling the polymer material downstream of the extrusion section, a material of natural origin is added to the polymer material stream.

[0014] Due to this aspect of the present invention, an object that has traditionally been made only of synthetic polymer materials can be made of a composite material that also includes a material of natural origin, which reduces the environmental impact of the finished product.

[0015] The method according to the first aspect of the present invention enables the manufacture of an object without damaging the material of natural origin. In fact, before adding the material of natural origin, the polymer material plasticized in the extrusion section is cooled to a temperature lower than the extrusion temperature of the polymer material in the extrusion section, but at this temperature, the polymer material can be formed in any case by pressing to obtain an object. In this way, the temperature of the polymer material can reach a value that the material of natural origin can withstand without degradation. In this way, an object of good quality is obtained.

[0016] Pressing and forming also reduces the internal stress and friction generated in the composite material, which helps to maintain its limited temperature.

[0017] In addition, pressing and forming can be carried out together with the extrusion of the polymer material, which makes it possible to obtain an object at a high production speed.

[0018] The production speed is also increased because the object is formed after the polymer material has been partially cooled, which makes it possible to cool the object more quickly after forming and thus reduce the cycle time.

[0019] In one embodiment, the polymer material is an amorphous polymer having a glass transition temperature.

[0020] In this embodiment, after cooling the polymer material downstream of the extrusion section to a temperature higher than the glass transition temperature of the amorphous polymer, a material of natural origin can be added to the polymer material.

[0021] In particular, in the extrusion section, the amorphous polymer can be brought to an extrusion temperature that is at least 80 °C higher than the glass transition temperature.

[0022] After cooling the amorphous polymer downstream of the extrusion section to a working temperature that is at least 50 °C higher than the glass transition temperature, a material of natural origin can be added to the amorphous polymer.

[0023] Using these values of the working temperature, the viscosity of the amorphous polymer remains low enough for it to be shaped by pressing.

[0024] In an alternative embodiment, the polymeric material may comprise a semi-crystalline polymer.

[0025] The semi-crystalline polymer comprises a crystalline portion and an amorphous portion. The crystalline portion has a melting temperature and a crystallization temperature. The amorphous portion has a glass transition temperature.

[0026] In the extrusion section, the polymeric material can be heated to a temperature above the melting temperature of the crystalline portion.

[0027] After cooling the polymeric material downstream of the extrusion section to a temperature above the crystallization temperature of the crystalline portion, a material of natural origin can be added.

[0028] In one embodiment, the method includes the step of mixing the composite material in order to uniformly disperse the material of natural origin in the polymeric material.

[0029] The step of mixing the composite material can be carried out within a twin-screw extruder.

[0030] Due to the combined action of the two screws included in the twin-screw extruder, a particularly uniform dispersion of the material of natural origin in the polymeric material can be obtained, mixing the material of natural origin with the polymeric material without a significant increase in temperature.

[0031] Furthermore, the screws of the twin-screw extruder enable the feeding of the material of natural origin (even when the material of natural origin is in the form of natural fibers) without causing these fibers to become stuck in a fixed position during the mixing process.

[0032] In one embodiment, the step of pressing the composite material to obtain an object comprises cutting a continuous stream of the composite material to obtain a continuous dose of the composite material and compression molding each dose in a mold to form an object.

[0033] By compression molding, the composite material can be formed with high productivity without imposing excessive stress on its components.

[0034] In a second aspect of the present invention, there is provided an apparatus for manufacturing an object using a composite material comprising at least one polymeric material in which at least one material of natural origin is dispersed, wherein the apparatus comprises:

[0035] - an extrusion section for extruding the polymeric material;

[0036] - a cooler located downstream of the extrusion section for cooling the polymeric material;

[0037] - A metering unit, located downstream of the cooler, for adding a material of natural origin to the polymer material that has been cooled, thereby obtaining a composite material;

[0038] - A mixer for mixing the composite material;

[0039] - A pressing device for pressing the composite material to obtain an object.

[0040] Due to the cooler that cools the polymer material from the extrusion section, a material of natural origin can be added to the polymer material that has been partially cooled but still has sufficient fluidity to be pressed. In this way, the risk of damaging the material of natural origin due to high temperature is reduced, if not eliminated.

[0041] Therefore, objects containing a significant amount of a material of natural origin can be manufactured, which makes it possible to reduce the environmental impact of the finished product. Description of the Drawings

[0042] The present invention can be better understood and implemented with reference to the accompanying drawings, which show exemplary, non-limiting embodiments of the present invention, in which:

[0043] Figure 1 is a schematic top view showing a device for manufacturing an object using a composite material containing a material of natural origin;

[0044] Figure 2 is Figure 1 a schematic side view of the device;

[0045] Figure 3 is a schematic diagram showing the temperature distribution in the Figure 1 device in the case of using an amorphous polymer;

[0046] Figure 4 is a diagram similar to Figure 3 for a semi-crystalline polymer;

[0047] Figure 5 is a diagram showing the results of DSC analysis of an amorphous polymer using different scanning speed values;

[0048] Figure 6 is a diagram showing how the viscosity of an amorphous polymer varies with temperature using relatively low heating / cooling speed values;

[0049] Figure 7 is a diagram similar to Figure 6 for relatively high heating / cooling speed values. Detailed Description

[0050] Figure 1 and Figure 2Shown is a device 1 for manufacturing an object (e.g., an object intended for the packaging field). The object manufactured in the device 1 can be an object having a concave shape, such as a container, a lid for a container, a capsule, a preform for a container, etc.

[0051] The device 1 enables the manufacturing of an object from a composite material in which a material of natural origin is dispersed in a polymer matrix.

[0052] The polymer matrix is a matrix formed from at least one polymer material, which can be a synthetic polymer of the type conventionally used in the packaging field or can be a biodegradable polymer. Examples of synthetic polymers conventionally used in the packaging field include, for example, polyethylene (PE), polypropylene (PP), polymers of the polyester family, such as polyethylene terephthalate (PET). Biodegradable polymers that can be used to form the polymer matrix include polylactic acid (PLA) and its compounds, or polysaccharides, such as polymers derived from corn.

[0053] The material of natural origin dispersed in the polymer matrix can be a material derived from wood, such as cellulose or lignin, in the form of fibers or in the form of powder.

[0054] The term "polymer matrix" is used to indicate a material that is first transformed into a fluid state and then into which a material of natural origin is added. The term "polymer matrix" is not intended to introduce a limitation on the amount of the material of natural origin, which can even be present in a significant amount.

[0055] The composite material processed by the device 1 can also contain other additives, such as dyes, lubricants, and others.

[0056] The polymer material can be an amorphous polymer or a semi-crystalline polymer.

[0057] The amorphous polymer has a characteristic temperature, called the glass transition temperature T g . This temperature is the temperature at which the glass transition of the amorphous material occurs, that is, during heating, the amorphous material undergoes a solid-solid transition from a glassy, rigid, and brittle solid state to a fluid solid state. In the glassy solid state, the polymer chains of the amorphous material are substantially stationary, while in the fluid solid state, there is short-range movement of the polymer chains.

[0058] The glass transition occurs when the rotational motion of the kinetic units of the amorphous polymer material is not hindered due to an increase in temperature. Since, in the same material, the kinetic units can be of different types, the rotational motion is not hindered within a certain temperature range, and thus the glass transition occurs within a certain temperature range rather than at a specific predetermined temperature.

[0059] Once the temperature range within which the rotational motion of the kinetic units of the amorphous polymer material is not hindered is known by differential scanning calorimetry (DSC), the glass transition temperature T can be determined by conventional calculations. g 。

[0060] The glass transition is affected by the heating or cooling rate of the material under consideration.

[0061] This is visible in Figure 5 which shows the results of differential scanning calorimetry (DSC) on a sample of the amorphous polymer material. Figure 5 During differential scanning calorimetry, the sample is heated, held at a constant temperature, and then cooled, and this is done multiple times.

[0062] To study the effect of the heating or cooling rate of the sample on the glass transition temperature T, multiple scanning rates (i.e., heating or cooling rates) are considered during the heating and cooling processes described below:

[0063] For the tests relative to heating, the behavior of the sample was studied when heating the sample from 0 °C to 200 °C for each of the speeds indicated above. In contrast, for the tests relative to cooling, the behavior of the sample was studied during the cooling process from 200 °C to 0 °C for each of the aforementioned speeds. g v

[0064] v 1 = 5 °C / min

[0065] v 2 = 20 °C / min

[0066] v3 = 50 °C / min

[0067] v4 = 80 °C / min

[0068] The test results shown in

[0069] Figure 5 are summarized in Table 1 below, which shows that the glass transition temperature T varies with the heating or cooling rate (scanning rate) used. In particular, when heating the sample, the glass transition temperature T

[0070] Figure 5 The test results shown in g varies as the heating or cooling rate (scanning rate) used changes. In particular, when heating the sample, the glass transition temperature Tg It increases with the increase of the heating rate, changing from a value of 89.2 °C for a heating rate of 5 °C / min to a value of 99 °C for a heating rate of 80 °C / min.

[0071] In contrast, when cooling the sample, the glass transition temperature T g usually decreases with the increase of the cooling rate, changing from a value of 85.7 °C for a cooling rate of 5 °C / min to a value of 82.1 °C for a cooling rate of 80 °C / min.

[0072]

[0073] Table 1

[0074] Furthermore, as can be seen from Table 2 below, the difference between the glass transition temperature measured during the heating of the sample at a predetermined scanning rate and the glass transition temperature measured during the cooling of the sample at the same scanning rate increases with the increase of the scanning rate.

[0075] Scanning speed [°C / min] <![CDATA[ΔT g = T g (heating) - T g (cooling)]]> 5 89.2-85.7＝3.5℃ 20 91.5-86.3＝5.2℃ 50 95.3-83.7＝11.6℃ 80 99-82.1＝16.9℃

[0076] Table 2

[0077] Several studies have also been carried out, which have demonstrated how the even viscosity of amorphous polymers is affected by the heating or cooling rate.

[0078] Figure 6 and Figure 7 show how the viscosity of the amorphous polymer material changes with temperature for different heating or cooling rate values.

[0079] In particular, Figure 6 the curve C1 of [[]] refers to the change in viscosity in a sample heated from 160 °C to 210 °C at a heating rate of 1 °C / min. In contrast, Figure 6 the curve C2 of [[]] refers to the change in viscosity in a sample cooled from 210 °C to 160 °C at a cooling rate of 1 °C / min.

[0080] Figure 7 the curve C3 of [[]] refers to the change in viscosity in a sample heated from 150 °C to 220 °C at a heating rate of 10 °C / min. In contrast, Figure 7 the curve C4 of [[]] refers to the change in viscosity in a sample cooled from 220 °C to 150 °C at a cooling rate of 10 °C / min.

[0081] In all cases analyzed, the viscosity decreases with the increase of temperature. However, if the heating / cooling rate is relatively low, as in the case of [[]], the viscosity change depending on the temperature during the heating process can almost be superimposed on the viscosity change depending on the temperature during the cooling process. Figure 6 the case of [[]], the viscosity change depending on the temperature during the heating process can almost be superimposed on the viscosity change depending on the temperature during the cooling process.

[0082] In contrast, if the heating / cooling rate is relatively high, such as in the case of Figure 7 , a significant difference was noted between the curve showing how the viscosity changes during cooling and the curve showing how the viscosity changes during heating.

[0083] Typically, if the heating / cooling rate is high enough, for a given temperature, the viscosity measured during cooling is lower than the viscosity measured during heating.

[0084] At the same temperature, the difference between the viscosity measured during heating and the viscosity measured during cooling increases with increasing heating / cooling rate. Further, at the same temperature, during heating, the viscosity increases with increasing heating rate (i.e., the curve showing how the viscosity changes during heating in a graph of the type shown in Figure 6 and Figure 7 moves upward), while during cooling, the viscosity decreases with increasing cooling rate (i.e., the curve showing how the viscosity changes during cooling in a graph of the type shown in Figure 6 and Figure 7 moves downward).

[0085] Thus, if one compares the behavior of a material during heating and during cooling, amorphous polymer materials exhibit hysteresis in the viscosity trend as a function of temperature. The more pronounced this hysteresis, the higher the heating / cooling rate.

[0086] Thus, for a given temperature, the faster an amorphous polymer material is cooled, the more its viscosity decreases.

[0087] As described above, semi-crystalline polymers have an amorphous portion and a crystalline portion. The amorphous portion has a glass transition temperature T g . In contrast, the crystalline portion has a melting temperature T f and a crystallization temperature T C . The melting temperature T f is the temperature at which the crystalline portion of a semi-crystalline material converts from the solid state to the molten state during cooling. The crystallization temperature T C is the temperature at which the crystalline portion of a semi-crystalline material crystallizes during cooling. The crystallization temperature T C is lower than the melting temperature T F .

[0088] As described previously for the glass transition, crystallization and melting also do not occur at a specific temperature, but rather over a temperature range. However, the common practice is to define a single value for the melting temperature, and a single value for the crystallization temperature, which are calculated from the relative range in a standardized manner.

[0089] For semi-crystalline materials, the crystallization temperature of the crystalline part is typically significantly higher than the glass transition temperature of the amorphous part.

[0090] Device 1 includes an extruder 2, which is suitable for feeding at least one polymeric material of a polymer matrix intended to form a composite material. The polymeric material can be inserted into the extruder 2 through a hopper 3. The polymeric material can be in the form of pellets. If the composition of the composite material requires more than one polymeric material, more than one polymeric material can also be inserted into the extruder 2.

[0091] The extruder 2 can be a single-screw extruder, that is, having a single extrusion screw. However, this condition is not necessary, and other types of extruders can be used instead of the single-screw extruder.

[0092] The polymeric material is fed along a path P initially within the extruder 2. At the same time, the polymeric material is heated to obtain a polymeric material in a fluid state. The screw of the extruder 2 homogenizes the polymeric material from a thermal perspective.

[0093] The extruder 2 defines an extrusion section, where the temperature of the polymeric material is heated until it reaches the extrusion temperature T 1 .

[0094] Device 1 further includes a cooler 4, which is positioned downstream of the extruder 2 and is used to cool the continuous flow of the extruded polymeric material in such a way that the temperature of the polymeric material drops below the extrusion temperature T reached in the extruder 2 1 value.

[0095] The cooler 4 can include a heat exchanger, such as a heat exchanger with an external jacket in which a cooling fluid circulates. The heat exchanger can operate as a countercurrent heat exchanger.

[0096] In an alternative embodiment, the cooler 4 can be included in the extruder 2, in the sense that the cooler 4 can include a cooling section positioned downstream of the extrusion section within the extruder 2.

[0097] Generally, in the cooler 4, the temperature of the polymeric material is reduced to a value at which the polymeric material retains sufficient fluidity to enable subsequent shaping.

[0098] More specifically, the temperature to which the polymeric material is cooled in the cooler 4 can vary according to various factors, one of which is the type of polymeric material being processed.

[0099] Figure 3Refers to the case where the polymeric material processed in device 1 is an amorphous polymer and shows how the temperature of the amorphous polymer (as shown on the y-axis) varies according to the position of the amorphous polymer along path P inside device 1. This position is shown on the x-axis.

[0100] At an initial temperature that can be equal to the ambient temperature T A the amorphous polymer enters the extruder 2.

[0101] Figure 3 The stretch P1 in g refers to the step of heating the amorphous polymer inside the extruder 2. During this step, the temperature of the amorphous polymer increases from its initial value when it enters the extruder 2 to an extrusion temperature T 1 that is higher than the glass transition temperature T

[0102] In an exemplary embodiment, it can be the case that T 1 ≥Tg + 70 °C, for example T 1 ≥Tg + 80 °C.

[0103] At the extrusion temperature T 1 the polymer chains of the amorphous polymer have reached sufficient mobility such that the amorphous polymer can be extruded.

[0104] When feeding the polymeric material inside the extruder 2, the temperature of the polymeric material is kept constant, equal to the value T 1 , as shown by the horizontal stretch P2 in Figure 3 .

[0105] In the cooler 4, the temperature of the polymeric material is reduced to an operating temperature T g that is higher than the glass transition temperature T 2 of the amorphous polymer.

[0106] More specifically, it can be the case that T 2 ≥Tg + 50 °C.

[0107] In Figure 3 the temperature reduction in the cooler 4 is indicated by the stretch P3. During the subsequent operation the amorphous polymer remains at a substantially constant temperature, equal to the operating temperature T 2 , especially when shaping the amorphous polymer to obtain an object, as shown by the stretch P4 in Figure 3 .

[0108] Figure 4 Refers to the case where the polymeric material processed in device 1 is a semi-crystalline polymer, for the glass transition temperature T gand the crystallization temperature T of the crystalline portion C and the melting temperature T f have predetermined values.

[0109] In this case, in the extruder 2, the semi-crystalline polymer is heated to an extrusion temperature T f higher than the melting temperature T 1 of the crystalline portion, as indicated by the line segment P1. The semi-crystalline polymer is maintained at the temperature T 1 , as indicated by the line segment P2, until it enters the cooler 4.

[0110] In the first exemplary embodiment, in the cooler 4, the semi-crystalline polymer is cooled until it reaches an operating temperature T 2(A) which is higher than the crystallization temperature T C of the crystalline portion, but lower than its melting temperature T f . This is indicated by the line segment P3(A) in Figure 4 , and the next line segment P4(A) indicates that the temperature of the amorphous polymer remains substantially constant after cooling in the cooler 4 until an object is formed.

[0111] In the second exemplary embodiment, it may be the case that in the cooler 4, the semi-crystalline polymer is cooled until it reaches an operating temperature T 2(B) , although this operating temperature is lower than the temperature T 1 of the material at the outlet of the extruder 2, but this operating temperature is still higher than the melting temperature T f of the crystalline portion. This is indicated by the line segment P3(B) in Figure 4 , and the next line segment P4(B) indicates that the temperature of the semi-crystalline polymer remains substantially constant after cooling in the cooler 4 until an object is formed.

[0112] In Figure 4 the two embodiments shown, the operating temperature reached by the semi-crystalline polymer at the outlet of the extruder 2 is significantly higher than the glass transition temperature of the amorphous portion because this temperature is much lower than the crystallization temperature.

[0113] Similar to the slopes of the line segments P3(A) and P3(B) in Figure 4 , the slope of the line segment P3 in Figure 3 indicates the cooling rate of the polymer material in the cooler 4 and, in the case of an amorphous polymer, is related to the apparent viscosity.

[0114] Downstream of the cooler 4, the apparatus 1 has an addition zone 5 for adding materials of natural origin, such as cellulose fibres or powders, to the continuous flow of polymer material. The addition zone 5 may include a metering unit 6 of a known type for inserting the materials of natural origin in dosed amounts into the polymer material stream.

[0115] In the metering unit 6, or in another metering unit placed close to the metering unit 6, other additives may also be added to the polymer material stream. Alternatively, the additives may be added to the polymer material upstream of the metering unit 6 (e.g. in the extruder 2) or even downstream of the extruder 2.

[0116] The apparatus 1 also includes a mixer 7 for mixing the continuous flow of polymer material, to which materials of natural origin and any additives have been added, so as to obtain a chemically and thermally homogeneous composite material.

[0117] The mixer 7 may include a twin-screw extruder 8, i.e. an extruder equipped with two screws rotatable about respective parallel axes (e.g. horizontal axes) and capable of homogeneously mixing the composite material.

[0118] In addition to ensuring a particularly effective mixing action due to the combined action of the two screws, the twin-screw extruder 8 also enables the composite material to be processed without undue stress being exerted thereon, so that the temperature of the composite material remains substantially constant, i.e. a significant heat increase is avoided.

[0119] In an alternative embodiment, the mixer 7 may be of a type different from the twin-screw extruder. For example, the mixer 7 may include a single-screw extruder or another type of dynamic mixer.

[0120] Firstly, if the materials of natural origin include fibres, it is suitable to use a dynamic mixer, i.e. a dynamic mixer having rotating mixing members capable of actively pushing the fibres forward and preventing the fibres from stopping and blocking the mixer.

[0121] The addition zone 5 may be positioned in the initial part of the mixer 7 relative to the feed direction of the compound in the apparatus 1.

[0122] The mixer 7 defines a mixing section for mixing a composite material comprising at least polymer material, materials of natural origin and additives (if necessary).

[0123] The mixer 7 may be thermally regulated, for example with oil or another fluid, to keep the temperature of the compound substantially constant.

[0124] In one embodiment, the cooling section and the mixing section can be integrated in the extruder 2, that is to say, the cooling section and the mixing section can be in the form of corresponding cooling zones and mixing zones located downstream of the extrusion section of the extruder 2.

[0125] The temperature of the composite material in the mixer 7 can be kept constant, for example, substantially equal to the temperature value of the polymer material at the outlet of the cooler 4, as Figure 3 shown by the line segment P4 in Figure 4 or the line segments P4(A) or P4(B) in

[0126] The temperature of the composite material in the mixer 7 is lower than the degradation temperature at which the materials of natural origin and / or any additives start to degrade. In this way, when adding the materials of natural origin and / or any additives to the polymer material stream from the cooler 4, they will not be damaged by the high temperature.

[0127] In the cooler 4, the polymer material from the extruder 2 can be subjected to a relatively high cooling rate, for example, higher than or equal to 5 °C / min. In one embodiment, the cooling rate of the polymer material in the cooler 4 can be higher than or equal to 10 °C / min.

[0128] Adopting a relatively high cooling rate has important consequences, especially in the case where the polymer material is an amorphous polymer.

[0129] In fact, using a high cooling rate, the glass transition temperature T g of the amorphous polymer is reduced relative to the glass transition temperature achieved with a lower cooling rate, as previously referred to Figure 5 and as described in Tables 1 and 2. This means that, in Figure 3 the curve of, by increasing the cooling rate in the line segment P3 (i.e., the slope of the line segment P3), a lower temperature can be obtained in the line segment P4. In other words, by rapidly cooling the material in the cooler 4, the glass transition temperature can be reduced and thus the working temperature T 2 of the polymer material in the mixer 7 can be reduced and at the same time it can be shaped. In fact, the working temperature T 2 is a predetermined amount, which is higher than T g , for example 50 °C, such that the reduction of T g can also reduce T 2 .

[0130] Furthermore, by adopting a relatively high cooling rate in the cooler 4, the viscosity of the polymer material is lower than the viscosity that the polymer material would reach if it were slowly cooled, as previously seen in Figure 6 and Figure 7As described. This enables the composite material to maintain sufficient fluidity even when a relatively low temperature is reached in the cooler 4 and thus even when the composite material operates at a relatively low working temperature T 2 and thus enables it to be shaped.

[0131] At the outlet of the mixer 7, a discharge pipe 9 is provided, which discharge pipe terminates at an outlet, and a continuous flow of the composite material comprising the polymeric material, the material of natural origin and any additives leaves the outlet at a temperature substantially equal to temperature T 2 (or T 2(A) or T 2(B) ).

[0132] The outlet may be defined by the discharge section of a nozzle placed at the end of the discharge pipe 9.

[0133] In the illustrated example, the outlet is directed upwards such that the flow of the composite leaves the outlet in a substantially vertically upwards direction. However, this condition is not necessary and the outlet may be oriented differently from that shown in Figure 1 and Figure 2 . For example, the outlet may be oriented in such a way that the flow of the composite material leaves the discharge pipe 9 in a substantially vertically downwards direction, or in a substantially horizontal direction or an inclined direction.

[0134] The apparatus 1 also includes at least one separating element 11 or separator for separating a dose or a dose 12 of the composite material from the continuous flow of the composite material leaving the outlet. The dose 12 corresponds to the amount of the composite material required to form an object.

[0135] The apparatus 1 also includes at least one conveying element 13 or conveyor for moving the dose 12 away from the outlet.

[0136] In the illustrated example, the separating element 11 is the edge of the conveying element, in particular the lower edge of the conveying element 13, which edge passes by the outlet in order to scrape off the amount of the composite material emerging during the interval between two successive passes of the conveying element 13. However, this condition is not necessary since separating elements 11 different from those shown in Figure 1 may also be used, such as a single blade moving independently of the conveying element 13.

[0137] The apparatus 1 also includes pressing means which include at least one mould 14 for forming an object from the dose 12. The mould 14 is configured to form an object from the dose 12 by compression moulding.

[0138] The mold 14 may include a first half - mold 15 and a second half - mold 16 that are movable relative to each other between an open position Q1 and a closed position Q2 along a molding line D, which is vertical in the illustrated example.

[0139] In the open position Q1, the first half - mold 15 and the second half - mold 16 are spaced apart from each other such that a dose 12 of composite material can be released between the first half - mold 15 and the second half - mold 16. Additionally, in the open position Q1, an already - formed object can be removed from the mold 14.

[0140] In the closed position Q2, the first half - mold 15 and the second half - mold 16 are close to each other in such a way that an enclosed forming chamber is defined between the first half - mold 15 and the second half - mold 16, and this forming chamber has a shape corresponding to the shape of the object.

[0141] In the illustrated example, the first half - mold 15 is a concave half - mold with a cavity, and the second half - mold 16 is a convex half - mold including a punch. The concave half - mold is positioned below the convex half - mold in such a way that the dose 12 is released into the cavity of the concave half - mold. However, this is not necessary, and in an alternative embodiment not shown, the convex half - mold can be positioned below the concave half - mold in such a way that the dose 12 is released onto the upper surface defined by the punch.

[0142] Furthermore, the first half - mold 15 and the second half - mold 16 can be positioned in such a way that the molding line D is not vertical. The molding line D can be, for example, horizontal or inclined.

[0143] The conveying element 13 is movable along a path, which can be, for example but not exclusively, a circular closed path, in such a way as to pick up the dose 12 that the separating element 11 has separated from the continuous flow of composite material and convey the dose 12 towards the mold 14.

[0144] In the illustrated example, there are a plurality of conveying elements 13 that are movable along a closed path, which can be circular. The conveying elements 13 can be supported by a conveying turntable 17 that is rotatable about a rotational axis Y, which can be, for example, vertical.

[0145] When the conveying element 13 is placed between the first half - mold 15 and the second half - mold 16 of the mold 14 positioned in the open position Q1, the dose 12 is released onto the lower half - mold by the conveying element 13 and the conveying element 13 returns towards the outlet of the duct 9 to pick up a new dose 12.

[0146] In the illustrated example, there are a plurality of molds 14 that are movable along a closed path, which can be circular. The molds 14 can be mounted, for example, in the outer peripheral region of a molding turntable 18 that is rotatable about an axis Z, which can be, for example, vertical.

[0147] During operation, one or more polymer materials (e.g., in the form of pellets) are inserted into the extruder 2. Here, the polymer material is heated and melted until it reaches the maximum extrusion temperature T 1 , in the case of a semi-crystalline polymer, the maximum extrusion temperature T 1 is higher than the melting temperature T of the crystalline part f and the glass transition temperature T of the amorphous part g . If the polymer material is an amorphous polymer, the temperature T of the polymer material is reached in the extruder 2 1 , which temperature is at least 80 °C higher than the glass transition temperature and is designed to be subsequently reduced before adding the materials of natural origin.

[0148] Downstream of the extruder 2, the polymer material is cooled in the cooler 4. The temperature of the polymer material reached in the cooler 4 is lower than the maximum temperature reached by the polymer material in the extruder 2, but in any case higher than the glass transition temperature of the polymer material (if it is amorphous) or higher than the crystallization temperature of the crystalline part (if the polymer material is a semi-crystalline polymer).

[0149] After the polymer material has been cooled, materials of natural origin and / or one or more additives can be added. The materials of natural origin and / or additives are added to the polymer material after the temperature of the polymer material has been reduced in the cooler 4, in such a way as to reduce the risk of damaging the materials of natural origin and / or additives due to high temperature.

[0150] Then the composite obtained by adding materials of natural origin and / or one or more additives to the polymer material is mixed to make its composition uniform, e.g., in a twin-screw extruder 8.

[0151] In this way, a fluid stream of the composite material is obtained, from which the doses 12 can be separated by cutting or scraping. Then each dose 12 is conveyed towards the mold 14 and released into the mold 14. Here, the dose 12 can be compression molded when the material forming the dose 12 is at a temperature higher than the glass transition temperature (if the polymer matrix of the composite includes an amorphous polymer) or higher than the crystallization temperature of the crystalline part (if the polymer matrix of the composite includes a semi-crystalline polymer). More specifically, the composite forming the dose 12 can be molded between a first half-mold 15 and a second half-mold 16, which are held in the closed position Q2 until the object obtained reaches a consistency sufficient to be handled without damage. At this time, the mold 14 is brought into the open position Q1 for removing the object and receiving a new dose 12.

[0152] Device 1 and the related operating method ensure a wide degree of freedom in the selection of the composite material components. In fact, by cooling the polymeric material before adding materials or additives of natural origin, it is possible to use materials of natural origin that degrade at relatively low temperatures and that would not be usable if added to the polymeric material in extruder 2.

[0153] Similar reasons apply to the additives. By adding the additives after the polymeric material has been cooled, the range of available additives is extended, since even thermosensitive additives can be used, which would be damaged if added to the polymeric material heated to high temperatures (as is the case in extruder 2).

[0154] Device 1 and the related operating method also increase the flexibility of the composition of the object with respect to the amount of additives used. For example, one of the additives used in extrusion is a plasticizer, which can even be used to avoid reaching excessive temperatures during extrusion. By cooling the polymeric material in cooler 4 before adding materials and / or additives of natural origin, the amount of plasticizer can be reduced or even its use avoided. In fact, the cooling that the polymeric material undergoes in cooler 4 makes the temperature reached in extruder 2 substantially irrelevant in terms of the risk of damaging materials and / or additives of natural origin.

[0155] Device 1 and the related operating method enable an object to be manufactured with high productivity, which has a limited environmental impact compared to an object made entirely of synthetic polymeric materials.

[0156] In particular, in device 1, the manufacture of the object takes place together with the production of the composite material, since the mixer 7 for the composite material, in which materials of natural origin and polymeric materials are mixed, is located on the same production line as the pressing device. In this way, the composite material is fed directly to the pressing device without being pre-cooled to ambient temperature.

[0157] The pressing device can include a molding turntable as in the case shown in Figure 1 and Figure 2 or a plurality of molds positioned in a linear or matrix arrangement, or even a single mold in a fixed position.

[0158] In any case, by compression molding, for example, it is possible to orient the macromolecules or chains of the polymeric material and the fibers of the materials of natural origin in order to obtain an object made of composite material with a relatively high level of mechanical properties.

[0159] In addition, if the polymeric material intended to form the polymeric matrix is a semi-crystalline polymer, the crystalline portions may be affected by the phenomenon of flow-induced crystallization, and based on this, the high speed reached by the polymeric material within the device 1 causes an increase in the crystallization of the crystalline portions. In this way, the mechanical properties of the formed object are further improved.

Claims

1. A method for manufacturing an object using a composite material, said composite material comprising at least one polymeric material with a material of natural origin dispersed in said at least one polymeric material, wherein, the method comprises the following steps: - extruding said polymeric material in an extrusion section (2); - adding said material of natural origin to said polymeric material, thereby obtaining said composite material; - pressing said composite material to obtain said object, wherein, downstream of said extrusion section (2), after cooling said polymeric material, said material of natural origin is added to said polymeric material.

2. The method according to claim 1, wherein, said object is a packaging assembly.

3. The method according to claim 1 or 2, wherein, said object is a concave object, optionally selected from the group comprising: closure elements for containers, containers, capsules, preforms for containers.

4. The method according to one of the preceding claims, wherein, The polymer material includes a semi-crystalline polymer, the semi-crystalline polymer includes an amorphous portion and a crystalline portion, and wherein, when the polymer material is at a temperature higher than or equal to the crystallization temperature (T C ) of the crystalline portion, the material of natural origin is added to the polymer material.

5. The method according to claim 4, wherein, In the extrusion section (2), the semi-crystalline polymer is heated to an extrusion temperature (T 1 ), and the extrusion temperature (T 1 ) is higher than the melting temperature (T f ) of the crystalline part.

6. The method according to any one of claims 1 to 3, wherein, The polymer material includes an amorphous polymer having a glass transition temperature (T g ), and wherein, when the polymer material is at an operating temperature (T g ) above the glass transition temperature (T 2 ) of the amorphous polymer, the material of natural origin is added to the polymer material, and the operating temperature (T 2 ) is optionally at least 50 °C higher than the glass transition temperature (T g ) of the amorphous polymer.

7. The method according to claim 6, wherein, In the extrusion section (2), the amorphous polymer is heated to an extrusion temperature (T 1 ), and the extrusion temperature (T 1 ) is at least 80 °C higher than the glass transition temperature (T g ) of the amorphous polymer.

8. The method according to any one of the preceding claims and further comprising a step of mixing said composite material obtained by adding said material of natural origin to said polymeric material, the mixing step being optionally carried out in a twin-screw extruder (8).

9. The method according to any one of the preceding claims, wherein, downstream of said extrusion section, the polymeric material is cooled at a cooling rate of higher than or equal to 5 °C / minute, preferably higher than or equal to 10 °C / minute.

10. The method according to any one of the preceding claims, wherein, the step of pressing said composite material to obtain said object comprises: cutting a continuous stream of the composite material to obtain a dose (12) of the composite material, and shaping said dose (12) by compression in a mold (14) to obtain said object.

11. The method according to any one of the preceding claims, wherein, said material of natural origin comprises cellulose in the form of fibers or powder.

12. An apparatus for manufacturing an object using a composite material, said composite material comprising at least one polymeric material with at least one material of natural origin dispersed in said at least one polymeric material, wherein, the apparatus comprises: - an extrusion section (2) for extruding said polymeric material; - a cooler (4) positioned downstream of said extrusion section (2) for cooling said polymeric material; - a metering unit (6) positioned downstream of said cooler (4) for adding said material of natural origin to the already cooled polymeric material, thereby obtaining said composite material; - a mixer (7) for mixing said composite material; - a pressing device (18) for pressing said composite material to obtain said object.

13. The apparatus according to claim 12, wherein, said mixer (7) comprises a twin-screw extruder (8).

14. The apparatus according to claim 12 or 13, wherein, The pressing device (18) includes a mold (14) for molding the object by compression molding.

15. The apparatus according to claim 14, further comprising a separating element (11) for separating a dose (12) of composite material from a continuous stream of composite material, the continuous stream of composite material coming from the cooler (4).

16. The apparatus according to claim 15, further comprising a conveying element (13) movable along a path for conveying the dose (12) towards the mold (14).

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