Method and apparatus for processing incoherent plastics

Abstract

An apparatus and a method for processing incoherent plastics are disclosed, in which the plastics are introduced inside a container in which a depression below 7.5 x 104 Pascal absolute is created so as to extract humidity from the plastics, in which a humidity value is detected in the plastics that have been extracted from said container and in which at least one operating parameter is feedback controlled in said container on the basis of said detected humidity value.

Description

Method and apparatus for processing incoherent plasticsBackground of the invention

[0001] The invention relates to an apparatus for processing incoherent plastics, i.e. in the form of granules and / or microgranules and / or pellets and / or powder and / or flakes or the like, in particular for dehumidifying plastics.

[0002] Specifically, but not exclusively, the invention can be usefully applied to dehumidifying incoherent plastics obtained from recycling (PCR), in particular plastics containing recycled polyethylene terephthalate.

[0003] Patent publication US 2021 / 276224 Al shows a process for drying granular polymer plastics that are dehumidified by a first flow of gas at a first temperature comprised between 100°C and 150°C, heated to a second temperature greater than the first temperature and dried at the second temperature by applying a set vacuum level.

[0004] One of the improvable aspects of the prior art is ensuring that the processed incoherent plastics reach the user machine (extruder, moulding machine, etc) with a desired degree of humidity.Summary of the invention

[0005] One object of the invention is to provide a solution that is able to overcome the aforesaid drawback of the prior art.

[0006] One object of the invention is to make available a solution that is alternative to those of the prior art to dehumidify incoherent plastics by using a vacuum process.

[0007] One object of the invention is to propose a suitable solution for controlling extracting humidity from incoherent plastics.

[0008] One advantage is to reduce the risk of production downtime due to the fact that a user machine used to transform the plastics is fed with incoherent plastics of inappropriate quality.

[0009] One advantage is to make a constructionally simple and cheap apparatus for processing incoherent plastics.

[0010] Such objects and advantages and still others are achieved by an apparatus and / or a method according to one or more of the claims set out below.Brief description of the drawings

[0011] The invention can be better understood and implemented with reference to theattached drawings that illustrate one embodiment thereof by way of non-limiting example in which:Figure 1 is a diagram in a vertical elevation of an example of an apparatus for dehumidifying incoherent plastics that is made according to this invention.Detailed description

[0012] With reference to the aforementioned figure, 1 has been used to indicate overall an apparatus for dehumidifying incoherent plastics.

[0013] The apparatus 1 comprises a container 2 configured to contain incoherent plastics. The incoherent plastics may comprise, in particular, plastics in the form of granules obtained from pelletization. The incoherent plastics may comprise, in particular, at least a percentage of post-consumer recycled plastics (PCR). The incoherent plastics may comprise, in particular, at least a percentage of post-consumer recycled plastics (PCR) in the form of granules obtained from pelletization. The incoherent plastics may comprise, in particular, one or more polymers included in the following set: polyethylene terephthalate (PET), polyamide (PA), acrylonitrile-butadiene- styrene (ABS), polyphenylene sulphide (PPS), polystyrene (PS), polyvinyl chloride (PVC), polysulfone (PSU), polymethylmethacrylate (PMMA), polyolefins in general.

[0014] The apparatus 1 comprises means for generating a depression inside the container. The means for generating a depression may comprise, in particular, an expelling conduit 3 connected to an outlet of the container 2 and a vacuum pump 4 arranged in the expelling conduit 3 to suck fluid (air) from the container 2.

[0015] The apparatus 1 comprises a path 5 configured to convey incoherent plastics from an outlet of the container 2 to a user 6.

[0016] The user 6 may comprise, in particular, a plastics extruding machine and / or a plastics moulding machine.

[0017] The apparatus 1 may comprise, in particular, means for making a flow of the incoherent plastics continuous along the path 5. The means for making the flow continuous may comprise, in particular, at least one accumulation volume 7 for accumulating the incoherent plastics arranged along the path 5.

[0018] The path 5 may comprise, in particular, a valve 8 arranged upstream of the accumulation volume 7 and a valve 9 arranged downstream of the accumulation volume 7.These valves 8 and 9 may be configured, in particular, to ensure a pressure seal (in particular, a seal at a lower pressure than an ambient pressure) of the accumulation volume 7.

[0019] The apparatus 1 comprises sensor means 10 configured to detect a humidity value in the incoherent plastics along the path 5. The sensor means 10 may be arranged so as to detect in line a humidity value directly in the continuous flow of incoherent plastics (in real time and without collecting samples). The sensor means 10 may comprise, in particular, at least one humidity sensor, in particular of capacitive type. The sensor means 10 may be arranged, in particular, along the path 5 downstream of the accumulation volume 7.

[0020] The apparatus 1 comprises control means CPU configured to adjust through feedback at least one process operating parameter of the plastics, in particular an operating parameter in the container 2, on the basis of signals sent by the sensor means 10.

[0021] The control means CPU may be configured, in particular, to so control the means for generating the depression that the operating parameter adjusted through feedback comprises an intensity of the depression generated in the container 2. It is possible to arrange a vacuum sensor VC operating in the container 2. In particular, it is possible to control the vacuum pump 5 (for example, by a vacuum switch or other device suitable for making a pressure constant) such that the depression in the container 2 is lower than 7.5 x 104Pascal absolute, or lower than 5 x 104Pascal absolute, or lower than 2.5 x 104Pascal absolute, or lower than 1.4 x 104Pascal absolute. In particular, the setpoint value for controlling the vacuum pump 5 will decrease (more intense depression) if the humidity detected in the plastics by the sensor means 10 is higher than a set threshold value. The setpoint value for controlling the vacuum pump 5 will increase (less intense depression) if the humidity detected in the plastics by the sensor means 10 is lower than a set threshold value.

[0022] It is possible to correlate the residual humidity value in the incoherent plastics (value detectably by the sensor means 10) with the degree of vacuum in the container 2 (degree of vacuum detectable by the vacuum sensor VC). The correlation between residual humidity and degree of vacuum (for example, determined empirically) enables the degree of vacuum present in the container 2 to be modulated on the basis of the required residualhumidity value. This enables the user 6 to be supplied with plastics with the desired residual humidity value, a value that is correlated with the degree of vacuum generated in the container 2.

[0023] The apparatus 1 may comprise, in particular, means for heating the incoherent plastics in the container 2. The means for heating may comprise, in particular, means for sending radio frequency waves.

[0024] The means for heating may comprise, in particular, at least one electrode 11 connected to a radio frequency source 12. The electrode 11 may be arranged, in particular, inside the container 2 and be immersed in the plastics. The means for heating may comprise, in particular, two or more electrodes 11.

[0025] The radio frequency waves may have, in particular, a frequency comprised between 300 KHz and 300 GHz, more in particular a frequency comprised between 1 MHz and 1 GHz, or comprised between 1 MHz and 100 MHz, or comprised between 10 MHz and 100 MHz, or comprised between 1 MHz and 50 MHz, or comprised between 10 MHz and 50 MHz. In one practical non-limiting embodiment, a generator has been used that is selectively configurable at 13.56 MHz or 27.12 MHz, even if it is anyway possible to use other frequencies.

[0026] The radio frequency waves may be generated, in particular, by making use of at least one electrode 11 in contact with the container 2. The power and / or the frequency of the radio frequency generator 12 may be adjusted (in particular by the electronic and programmable control means CPU).

[0027] Each electrode 11 may be bar-shaped. Each bar may extend in length with a longitudinal axis arranged vertically. The electrodes 11 may be, in particular, parallel to one another.

[0028] Each electrode 11 may be cylindrical in shape. In particular, it is possible to arrange two or more cylinders arranged inside one another, in particular in a coaxial manner (for example, coaxially with respect to an axis of the container 2).

[0029] The arrangement of the cylinders inside one another (in particular, at a mutual distance so as to form a gap between two adjacent cylinders, where each gap is occupied by incoherent plastics) enables a radio frequency field to be generated. The number of cylinders (one, two, three, four, five or more than five) may be chosen, in particular, infunction of the geometry and / or the dimensions of the container.

[0030] The plastic building material of the electrodes 11 may comprise, in particular, at least one metal plastic material like, for example, copper, aluminum, brass, special alloys, or also a combination of the aforesaid materials.

[0031] The control means CPU may be configured, in particular, to control the means for heating the plastics so that the operating parameter adjusted through feedback comprises a heating intensity of the incoherent plastics in the container 2.

[0032] Each electrode 11 may be controlled by a set point value of the power supplied to the electrode 11. Each electrode 11 may be controlled by a maximum threshold value, which must not be exceeded, of a temperature of a surface of the electrode 11. Each electrode 11 may be controlled by a set point value of the temperature of the surface of the electrode 11. The power may be supplied to the electrode 11 continuously, or as pulse trains to avoid localized overheating and / or plasticization of the plastics.

[0033] The apparatus 1 may comprise, in particular, means for governing a dwell time of the incoherent plastics in the container 2. The means for controlling a dwell time may comprise, in particular, at least one plugging member 13 (for example, a movable shutter) arranged at the outlet of the container 2. The plugging member 13 is controllable by the control means CPU.

[0034] The control means CPU may be configured, in particular, to control the means for so controlling the dwell time that the operating parameter adjusted through feedback comprises a dwell time of the incoherent plastics in the container 2.

[0035] The apparatus 1 may comprise, in particular, at least one plugging member 14 (for example, a movable shutter) arranged at the outlet of the accumulation volume 7. The plugging memberl4 is controllable by the control means CPU.

[0036] The apparatus 1 may comprise, in particular, an accumulation volume 15 arranged upstream of the container 2. The apparatus 1 may comprise, in particular, a valve 16 arranged upstream of the accumulation volume 15 and a valve 17 arranged downstream of the accumulation volume 15. The apparatus 1 may comprise, in particular, a valve 18 arranged for connecting the accumulation volume 15 with the external environment. The valves 16, 17 and 18 may be configured, in particular, to ensure a pressure seal (in particular, a seal at a lower pressure than an ambient pressure) of the accumulation volume

[0037] A method for processing incoherent plastics comprises the step of introducing the incoherent plastics into the container 2. The method comprises the step of generating a depression in the container 2 so as to extract humidity from the incoherent plastics.

[0038] The method comprises the step of extracting the dehumidified incoherent plastics from the container 2. The method comprises the step of detecting a humidity value in the dehumidified incoherent plastics extracted from the container 2. The humidity value may be detected, in particular, in the continuous flow of the incoherent plastics, in particular by a humidity sensor, for example of capacitive type or of another type (also of known type).

[0039] The method comprises the step of adjusting through feedback at least one process operating parameter on the basis of the aforesaid detected humidity value. The process operating parameter that is adjusted through feedback may comprise, in particular, an operating parameter in the container 2.

[0040] The depression in the container 2 may be controlled so as to be lower than 7.5 x 104Pascal absolute, or lower than 5 x 104Pascal absolute, or lower than 2.5 x 104Pascal absolute, or lower than 1.4 x 104Pascal absolute. The depression may be controlled so as to be greater than 2 x 103Pascal absolute.

[0041] It is possible for the aforesaid operating parameter to comprise an intensity of the depression generated in the container 2.

[0042] The method may comprise the heating step of heating the incoherent plastics in the container 2. The operating parameter adjusted through feedback may comprise, in particular, an intensity of the aforesaid heating. The heating step may comprise, in particular, hitting the incoherent plastics with radio frequency waves.

[0043] The radio frequency waves may have a frequency comprised between 300 KHz and 300 GHz. The radio frequency waves may have a frequency comprised between 1 MHz and 1 GHz, or comprised between 10 MHz and 100 MHz, or comprised between 1 MHz and 50 MHz, or comprised between 10 MHz and 50 MHz.

[0044] It is possible for the operating parameter adjusted through feedback to comprise a dwell time of the incoherent plastics in the container 2.

[0045] The dwell time may be controlled so as to be comprised between 15 and 150minutes, or comprised between 30 and 150 minutes, or comprised between 15 and 120 minutes, or comprised between 30 and 120 minutes.

[0046] The step of extracting the plastics from the container 2 may comprise making a flow of the incoherent plastics extracted from the container continuous by the accumulation volume 7 arranged downstream of the container 2.

[0047] In one embodiment that is not illustrated, it is possible to provide a process stage upstream of the container 2, in which the incoherent plastics are preheated in a container upstream (up to a set temperature) by a flow of process gas. The plastics are taken from the container upstream and then introduced into the container 2 in depression (at a pressure lower than ambient pressure). The plastics in the container 2 may be, in particular, heated (for example by radio frequency waves).

[0048] It is possible to provide an embodiment (not shown) that comprises a process stage upstream, in which the plastics are subjected to a pelletization process (by extrusion) to obtain plastics in granules, and a main stage, wherein plastics in granules supplied by the stage upstream (at a temperature greater than ambient temperature) are removed and introduced into the container 2 in depression (at a pressure lower than ambient pressure), where they may be heated (for example by radio frequency waves). In practice, the plastics in granules leaving a pelletization stage are supplied, with transfer in line, to the entry to a dehumidification stage with vacuum (and possible heating) in the container 2, which enables a thermal residue to be exploited that is present in the plastics in granules leaving the pelletization stage to improve the efficiency of the dehumidification stage with vacuum in the container 2. This two-stage method (dehumidification stage by vacuum in the container 2 that is preceded in line by a pelletization stage) may be used, in particular, for recycled polymer plastics (PCR plastics) or for other plastics that could suffer high temperature treatment over a long period.

[0049] It is possible to provide at least two embodiments of processes with two stages: a first embodiment in which a stage with depression precedes a stage with a flow of process gas; and a second embodiment in which a stage with depression follows a stage with a flow of process gas. It is also possible to provide at least one embodiment of a process with three stages, in which a stage with depression follows a stage upstream with a flow of process gas and precedes a stage downstream with a flow of process gas.

[0050] In one embodiment (which is not illustrated), it is possible to provide for a process stage to be arranged downstream in the path 5 of the plastics between the container 2 and the user 6, in which the plastics that are already processed at least partially and that are removed from the container 2 and introduced into a container downstream (not illustrated), are processed further (to extract at least one undesired substance, for example humidity) by a flow of process gas inside the container downstream.

[0051] The process container downstream of the container 2 may be arranged along the path 5, in particular, between the container 2 and the accumulation volume 7, or between the accumulation volume 7 and the user 6. In one embodiment (which is not illustrated), it is possible to provide two process containers (with flow of process gas) downstream of the container 2 arranged along the path 5, one arranged between the container 2 and the accumulation volume 7 and another arranged between the accumulation volume 7 and the user 6.

Claims

CLAIMS1. Method for processing incoherent plastics, said method comprising the following steps: introducing incoherent plastics into a container (2); generating a depression in said container (2) so as to dehumidify said incoherent plastics; extracting incoherent plastics from said container (2); detecting a humidity value in said incoherent plastics extracted from said container (2); feedback controlling at least one process operating parameter based on said detected humidity value; wherein said step of extracting plastics comprises making continuous a flow of said incoherent plastics extracted from said container (2) by means of an accumulation volume (7) arranged downstream of said container (2), said detecting step comprises detecting said humidity value in line in said continuous flow of said incoherent plastics downstream of said accumulation volume (7).

2. Method according to claim 1, comprising the step of heating said incoherent plastics, said at least one operating parameter comprising a heating intensity.

3. Method according to claim 2, wherein said heating step comprises investing said incoherent plastics with radiofrequency waves; said radiofrequency waves having, in particular, a frequency between 300 KHz and 300 GHz, or between 1 MHz and 1 GHz, or between 10 MHz and 100 MHz, or between 1 MHz and 50 MHz, or between 10 MHz and 50 MHz.

4. Method for processing incoherent plastics, in particular according to any one of the preceding claims, said method comprising the following steps: introducing incoherent plastics into a container (2); generating a depression in said container (2) so as to dehumidify said incoherent plastics; extracting incoherent plastics from said container (2); detecting a humidity value in said incoherent plastics extracted from said container (2); feedback controlling at least one process operating parameter based on said detected humidity value; heating said incoherent plastics, said at least one operating parameter comprising a heating intensity; wherein said heating step comprises investing said incoherent plastics with radiofrequency waves by means of at least one electrode (11) that is arranged inside said container (2) and that is immersed in said incoherent plastics.

5. Method for processing incoherent plastics, in particular according to any one of thepreceding claims, said method comprising the following steps: introducing incoherent plastics into a container (2); generating a depression in said container (2) so as to dehumidify said incoherent plastics; extracting incoherent plastics from said container (2); detecting a humidity value in said incoherent plastics extracted from said container (2); feedback controlling at least one process operating parameter based on said detected humidity value; heating said incoherent plastics, said at least one operating parameter comprising a heating intensity; wherein said heating step comprises investing said incoherent plastics with radiofrequency waves with a frequency between 1 MHz and 1 GHz.

6. Method according to claim 5, wherein said radiofrequency waves have a frequency between 10 MHz and 100 MHz, or between 1 MHz and 50 MHz, or between 10 MHz and 50 MHz.

7. Method according to any one of the preceding claims, wherein said depression is controlled to be less than 7.5 x 104absolute Pascals, or less than 5 x 104absolute Pascals, or less than 2.5 x 104absolute Pascals, or less than 1.4 x 104absolute Pascals.

8. Method according to any one of the preceding claims, wherein said depression is controlled to be greater than 2 x 103Pascal absolute.

9. Method according to any one of the preceding claims, wherein said at least one operating parameter comprises an intensity of said depression.

10. Method according to any one of the preceding claims, wherein said at least one operating parameter comprises a residence time of said incoherent plastics in said container (2).

11. Method according to claim 10, wherein said residence time is controlled to be between 15 and 150 minutes, or between 30 and 150 minutes, or between 15 and 120 minutes, or between 30 and 120 minutes.

12. Method according to any one of the preceding claims, wherein said incoherent plastics comprises post-consumer recycled plastics in the form of pelletized granules.

13. Apparatus for processing incoherent plastics, said apparatus comprising: a container (2) configured to contain incoherent plastics; means for generating a depression in said container (2); a path (5) configured for the transport of incoherent plastics froman outlet of said container (2) towards a user (6); sensor means (10) configured to detect a humidity value in the incoherent plastics along said path (5); control means (CPU) configured to feedback control at least one process operating parameter based on signals emitted by said sensor means (10); means for making continuous a flow of the incoherent plastics along said path (5), said means for making continuous including an accumulation volume (7) of the incoherent plastics arranged along said path (5), said sensor means (10) being arranged so as to detect said humidity value in said continuous flow of incoherent plastics, said sensor means (10) being arranged downstream of said accumulation volume (7).

14. Apparatus according to claim 13, wherein said sensor means (10) comprises at least one capacitive humidity sensor.

15. Apparatus for processing incoherent plastics, in particular according to claim 13 or 14, said apparatus comprising: a container (2) configured to contain incoherent plastics; means for generating a depression in said container (2); a path (5) configured for the transport of incoherent plastics from an outlet of said container (2) towards a user (6); sensor means (10) configured to detect a humidity value in the incoherent plastics along said path (5); control means (CPU) configured to feedback control at least one process operating parameter based on signals emitted by said sensor means (10); means for heating the incoherent plastics in said container (2), said control means (CPU) being configured to control said means for heating so that said at least one feedback-controlled operating parameter includes a heating intensity of the incoherent plastics in said container (2); said means for heating includes means for emitting radiofrequency waves with at least one electrode (11) that is connected to a radio frequency source (12) and that is arranged inside said container (2) to be immersed in the incoherent plastics.

16. Apparatus for processing incoherent plastics, in particular according to any one of claims 13 to 15, said apparatus comprising: a container (2) configured to contain incoherent plastics; means for generating a depression in said container (2); a path (5) configured for the transport of incoherent plastics from an outlet of said container (2) towards a user (6); sensor means (10) configured to detect a humidity value in the incoherent plastics along said path (5); control means (CPU) configured to feedbackcontrol at least one process operating parameter based on signals emitted by said sensor means (10); means for heating the incoherent plastics in said container (2), said control means (CPU) being configured to control said means for heating so that said at least one feedback-controlled operating parameter includes a heating intensity of the incoherent plastics in said container (2); said means for heating comprising means for emitting radiofrequency waves, said control means (CPU) being configured to control said means for emitting radiofrequency waves with a frequency between 1 MHz and 1 GHz.

17. Apparatus according to claim 16, wherein said control means (CPU) is configured to control said means for emitting radiofrequency waves with a frequency between 10 MHz and 100 MHz, or between 1 MHz and 50 MHz, or between 10 MHz and 50 MHz.

18. Apparatus according to any one of claims 13 to 17, wherein said control means (CPU) is configured to control said means for generating depression such that said at least one feedback-controlled operating parameter comprises an intensity of said depression generated in said container (2).

19. Apparatus according to any one of claims 13 to 18, comprising means for governing a residence time of the incoherent plastics in said container (2), said control means (CPU) being configured to control said means for governing so that said at least one feedback-controlled operating parameter includes a residence time of the incoherent plastics in said container (2); said means for governing including, in particular, a plugging member (13) of an outlet of said container (2).

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