Patent Description:
In particular, the present invention is particularly suitable for processing substantially liquid viscous material.

In machines for processing viscous liquids in continuous mode, such as for example a screw extruder, it is particularly useful to "thin" the volume of the treated liquid, in order to transform it into an equivalent volume with a lower thickness and a greater surface extension.

In other words, in a volume having x, y, z coordinates, the thinning entails increasing the surface extension of the x-y or x-z or z-y planes respectively with respect to the z or y or x dimension.

The thinning described above is particularly useful in some applications such as, for example:.

In all the four examples cited above, it is very useful for the material to be transformed into a thin film, with a defined and constant thickness, for example ranging between <NUM> micron and <NUM> microns. The lower the film thickness, the faster the above processes take place.

Documents <CIT> and <CIT> describe machines for degassing viscous liquids. However, the solutions described in these documents have limitations in terms of efficiency and speed of the process.

Documents <CIT>, <CIT> and <CIT> are also known, which describe machines for processing viscous material that are equipped with a material inlet from above and with an outlet spaced from the inlet by about <NUM>/<NUM> of circumference. Said machines do not achieve the desired incorporation effect and can be hardly combined with existing processors.

It is therefore an object of the present invention to provide an assembly for processing viscous material which is free from the drawbacks of the prior art.

In particular, it is an object of the present invention to provide an assembly for processing viscous material which is efficient and, at the same time, easy and economical to realise.

In accordance with these purposes, the present invention relates to an assembly for processing viscous material according to claim <NUM>.

Thanks to the connection between the process duct and the pumping duct, at least a part of the viscous material is subjected to at least one passage in the pumping channel. This determines an increase in the interface surface and therefore an optimisation of the process to which the material is subjected.

It is also an object of the present invention to provide a method for processing viscous material as claimed in claim <NUM>.

Further characteristics and advantages of the present invention will become clear from the following description of an embodiment thereof, with reference to the figures of the attached drawings, in which:.

In <FIG>, the reference number <NUM> denotes an assembly for processing viscous material according to the present invention.

The assembly <NUM> comprises a process duct <NUM> and a pumping device <NUM>, which, in use, are coupled together (see <FIG>).

The process duct <NUM> (better visible in <FIG>) extends along a longitudinal axis A between an inlet <NUM> and an outlet <NUM>.

In use, the process duct <NUM> is fed with viscous material, as we will see in detail below, for example from a screw extruder <NUM>. In the process duct <NUM>, the viscous material advances in one advancing direction D.

In the example described and shown herein, the process duct <NUM> has a substantially rectangular flow section.

Preferably, the section of the process duct <NUM> is constant.

It is understood that the process duct <NUM> may have a different section, for example circular or for example with a double lobe.

The process duct <NUM> has an opening <NUM> and an opening <NUM>, through which the process duct <NUM> is in communication with the pumping device <NUM>.

Preferably, the opening <NUM> and the opening <NUM> are arranged side by side. In the example described and shown herein, the opening <NUM> and the opening <NUM> are arranged the one next to the other along a direction orthogonal to the longitudinal axis A.

Preferably, the openings <NUM> and <NUM> are arranged so that the passage of material through them occurs along respective directions F7 and F8 substantially orthogonal to the flow direction D.

The opening <NUM> and the opening <NUM> have a width W, intended as the axial dimension, and a height H, intended as the dimension orthogonal to the width W.

Preferably, the opening <NUM> has a width W greater than the width W of the opening <NUM>.

In the example described and shown herein, the assembly <NUM> comprises a screw extruder <NUM> (schematically represented in <FIG>) coupled to the process duct <NUM> to feed viscous material to the process duct <NUM>.

The screw extruder <NUM> can be either single screw or twin screw (co-rotating or counter-rotating). The process duct <NUM> can be directly coupled to the extrusion cylinder of the screw extruder <NUM> or connected to the outlet from the screw extruder <NUM>.

The material advancing in the process duct <NUM> is under pressure. Preferably, the material has a pressure higher than <NUM> and less than <NUM> bar in the process line <NUM>. More preferably, the material pressure is higher than <NUM> and less than <NUM> bar and even more preferably higher than <NUM> and less than <NUM> bar.

In this way the passage of the material from the process duct <NUM> to the pumping device <NUM> is facilitated, as we will see in detail below.

If the material in the process duct <NUM> is under pressure, albeit light, the entry of the liquid into the pumping device <NUM> is in fact easier and more timely.

According to a variant not shown, the assembly <NUM> comprises an overpressure element arranged downstream of the process duct <NUM>. The overpressure element can be a pump, typically a "melt" pump, or a flow restrictor.

According to a variant shown in <FIG>, the process duct <NUM> houses at least one rotating extrusion screw <NUM> and provided with a core 17a.

In this case, the extrusion screw <NUM> has, in correspondence with the openings <NUM> and <NUM>, a portion without thread in which only the smooth core 17a suitable for circumferential dragging (see in particular <FIG>) is present. Preferably, in the variant of <FIG>, the process duct <NUM> is equipped with a deviating element <NUM>, which extends from the internal surface of the process duct <NUM> and is substantially arranged between the openings <NUM> and <NUM>. The deviating element <NUM> has a face 18a arranged substantially facing the core 17a of the screw <NUM> and almost in contact with the core 17a so as to have sufficient clearance to allow the free rotation of the core 17a. In use, the deviating element <NUM> contributes to forcing the material circulating in the duct <NUM> to travel an obligatory path around the core 17a between the openings <NUM> and <NUM>.

With reference to <FIG>, <FIG> and <FIG>, the pumping device <NUM> is equipped with a stator <NUM>, comprising a cylindrical seat <NUM> (visible only in <FIG> and <FIG>), and with a cylindrical rotor <NUM> (visible only in <FIG> and <FIG>), which is housed in the cylindrical seat <NUM> and is coupled to the stator <NUM> with a sliding seal.

The rotor <NUM> is rotatable around an axis of rotation B substantially parallel to the longitudinal axis A and has an outer face <NUM> with at least one groove <NUM>, which forms with the inner surface <NUM> of the cylindrical seat <NUM> of the stator <NUM> a respective pumping channel <NUM>.

The outer face <NUM> of the rotor <NUM> and the inner cylindrical surface <NUM> of the stator <NUM> are concentric and facing each other and have respective radii of curvature so that the clearance between the rotor <NUM> and the stator <NUM> is reduced to a minimum within the tolerances that allow an easy rotation of the rotor <NUM> with respect to the stator <NUM>.

Each pumping channel <NUM> extends between at least one input <NUM> and at least one output <NUM> (better visible in <FIG> and <FIG>).

The input <NUM> and the output <NUM> are in fluid connection with the process duct <NUM>. In other words, in use, the material advancing in the process duct <NUM> is fed to the pumping channel through the input <NUM> and is discharged in the process duct <NUM> through the output <NUM>.

In the example described and shown herein, the input <NUM> is in connection with the opening <NUM>, while the output <NUM> is connection with the opening <NUM>.

Preferably, each groove <NUM> extends in a circumferential direction orthogonal to the axis of rotation B, so as to define respective substantially annular pumping channels <NUM>.

In the example described and shown herein, the outer face has six grooves, <NUM>, four of which contribute to forming respective pumping channels <NUM>, while the remaining two are dedicated to forming respective purge channels <NUM>.

In particular, the pumping channels <NUM> are arranged between the purge channels <NUM>.

The purge channels <NUM> are dedicated to the eventual venting of the material which circulates in the pumping channels <NUM> adjacent thereto and which reaches the purge channels <NUM> through the clearance space between rotor <NUM> and stator <NUM>.

The purge channels <NUM> are connected to the opening <NUM> but are not connected to the opening <NUM>. In other words, each purge channel <NUM> is equipped with an outlet <NUM> (<FIG>) but is not equipped with an inlet in connection with the process duct <NUM>. As already mentioned, in fact, the material enters the purge channels <NUM> through the clearance space between rotor <NUM> and stator <NUM>.

Preferably, each pumping channel <NUM> is equipped with a scraper element <NUM> (<FIG>) arranged in the groove <NUM> substantially at the output <NUM>.

The scraper element <NUM> preferably has a profile configured to creep into the groove <NUM> so as to detach the material from the external face <NUM> of the rotor <NUM> and facilitate the passage of the material present in the pumping channel <NUM> through the output <NUM>.

The scraper elements <NUM> of the pumping channels <NUM> are supported by a frame <NUM> connected to the stator <NUM> (<FIG>).

Also each purge channel <NUM> is equipped with a scraper element <NUM> configured to creep into the groove <NUM> so as to detach the material from the external face <NUM> of the rotor <NUM> and facilitate the passage of the material present in the purge channel <NUM> through the outlet <NUM> of the purge channel <NUM>.

In this way, all the material that accidentally ends up in the purge channels <NUM> is introduced back into circulation in the process duct <NUM>.

With reference to <FIG> and <FIG>, each groove <NUM> preferably has a diverging section towards the outside of the rotor <NUM>. In other words, each groove <NUM> is equipped with diverging lateral faces <NUM> towards the outside of the rotor <NUM>. It has been verified, in fact, that this geometry is more efficient than other geometries (for example rectangular) in favouring the pressurisation of the liquid material near the output <NUM>.

However, it is understood that the groove <NUM> can also have a section of a different shape, such as for example rectangular or triangular, etc..

Preferably, at least one groove <NUM> houses at least a portion of a laminator element <NUM>, which is fixed to the stator <NUM>. The portion of the laminator element <NUM> that engages the groove <NUM> of the rotor <NUM> has a shape substantially complementary to the groove <NUM> so as to define, between the laminator element <NUM> and the groove <NUM> at least one gap <NUM>.

In the example described herein, the shape of the laminator element <NUM> is such as to define two gaps <NUM>, each of which is defined between the laminator element <NUM> and the walls <NUM> of the groove <NUM>.

Preferably, the gaps <NUM> defined by the laminator element <NUM> are gradually converging towards along the direction of rotation (i.e. circumferentially) starting from the inlet up to the end of the laminator element <NUM>. In this way, at the laminator element <NUM>, the material flows are of the elongation type thanks to the convergence of the gaps <NUM> along the pumping duct <NUM>.

Preferably, the laminator element <NUM> is arranged in the groove <NUM> just downstream of the input <NUM> of the pumping channel <NUM>.

Preferably, the laminator element <NUM> extends inside the groove <NUM> for a circumferential stretch less than the total length of the pumping channel <NUM>. More preferably, the laminator element <NUM> extends inside the groove <NUM> for a circumferential stretch less than <NUM>% of the total length of the pumping channel <NUM>.

In this way, the material entering through the input <NUM> meets the laminator element <NUM>, which is dimensioned so as to create, thanks to the presence of the gaps <NUM>, two separate flows of material along the walls <NUM> of the groove <NUM>.

In other words, the laminator element <NUM> increases the interface surface of the material flowing in the pumping channel <NUM>.

Downstream of the laminator element <NUM>, the material flows are shear-free and, under particular process conditions, they can move at the same speed of rotation as the rotor <NUM> without being subjected to shear stress, until there is an accumulation and pressurisation of the material near the output <NUM> of the pumping duct <NUM>.

The circumferential length of the portion of the pumping duct <NUM> in which the flow is typically of the shear-free type is preferably ranging between <NUM>° and <NUM>°.

With reference to <FIG>, <FIG> and <FIG>, each laminator element <NUM> extends along a plane transversal to the axis of rotation B.

Preferably, the laminator element <NUM> moves in a direction of oscillation E substantially parallel to the axis of rotation B. This allows to keep the tolerances between laminator element <NUM> and walls <NUM> substantially unchanged. In this way, the thickness of the film of material that passes through the laminator element <NUM> also remains unchanged and consequently the cutting speed, the elongation, and the relative stresses.

When the rotor <NUM> is rotating, in fact, any axial displacements of the rotor <NUM>, mostly due to phenomena of non-homogeneous thermal expansion with the stator <NUM>, are automatically translated to the laminator elements <NUM>, for example by means of spacers not shown and suitably arranged, leaving the design distance between the laminator elements <NUM> and the walls <NUM> of the pumping channels <NUM> substantially unchanged.

Basically, thanks to the possibility of oscillation of the laminator element <NUM>, the thickness of the separated flows downstream of the laminator element <NUM> remains substantially unchanged throughout the entire duration of the process.

Preferably, each laminator element <NUM> can oscillate along the direction E independently of the other laminator elements <NUM>.

According to a variant not shown, a plurality of laminator elements, arranged so as to subject the material to successive laminations, are housed inside a same groove. This can lead to an increase in the dispersive effect inside the pumping channel <NUM>.

According to a further variant, not shown, the pumping channel <NUM> is without laminator elements. This solution is particularly suitable for applications where it is intended to discharge a reduced stress on the material to be treated, for example in the presence of fragile fibres in the material that circulates in the pumping channel <NUM>, such as for example glass, carbon fibres, basalt, or natural fibres, etc..

A further variant envisages that the rotor comprises pumping channels equipped with laminator elements and pumping channels without laminator elements.

Preferably, the rotor <NUM> is supported by two bearings <NUM> at the ends and is suitable for being made to rotate at very high speeds, over <NUM> RPM. This speed, in relation to the diameter of the rotor <NUM>, ranging for example between <NUM> and <NUM>, is equivalent to peripheral speeds ranging between approximately <NUM> and <NUM>/s.

The rotor <NUM> is preferably fixed to a speed reducer, in turn connected to a preferably electric motor, driven by a frequency converter in order to be able to vary the speed in the range allowed by the reducer and by the frequency that can be set in the frequency converter.

With reference to <FIG>, the stator <NUM> preferably has a through opening <NUM>, which creates an aperture in at least one of the pumping channels <NUM>.

In the example described and shown herein, the opening <NUM> has the function of allowing, depending on the application, the exit of gas-air or the entry of solid additives, such as fibre powders, etc..

In other words, the opening <NUM> creates a discontinuity of the inner surface <NUM> of the stator <NUM>, creating an aperture in the pumping channel <NUM>, for the functions described above.

As anticipated, depending on the applications the opening <NUM> can be exploited in different ways.

If the assembly <NUM> is used for the incorporation of fillers in the material (example case shown in the attached figures), the opening <NUM> is connected to a loading hopper <NUM> through which solid particles such as powder fillers, fibres, granules, etc. are fed.

If the assembly <NUM> is used to degas the material or to obtain a molecular re-gradation of the material, the opening <NUM> is connected to a vacuum pump (not shown for simplicity's sake in the attached figures).

If the assembly <NUM> is used for the introduction of liquid additives or for the introduction of gas into the material, the opening <NUM> is connected to a source for feeding some liquid or some gas to be mixed with the material circulating in the pumping duct <NUM>.

If the assembly <NUM> is used to cool the material circulating in the pumping duct <NUM> (for example overheated by lamination), the opening <NUM> is engaged by a cooling element (not shown in the attached figures) in which pressurised water or other coolant such as ethylene glycol circulate.

The viscous materials that can be processed are all thermoplastic polymers, such as, for example Polypropylene, Polyethylene, Polyamide, Polystyrene, Acrylonitrile-Butadiene-Styrene, Polysulfone, Polyimide, Polyvinyl Chloride, Polyethylene Terephthalate, Polycarbonate etc..

Furthermore, food liquids such as chocolate, etc. can also be processed.

The solid additives that can be fed through the opening <NUM> into the material processed in the pumping channels <NUM>, can be, for example, mineral powders, wood flour, powders of organic substances, solid or hollow glass spheres, calcium carbonate, talc, clays, carbon black, graphite etc., nano particles such as carbon nano tubes (CNT), graphene etc., organic and inorganic pigments, titanium dioxide and in general, powders characterized by dimensions ranging between <NUM> and <NUM>,<NUM>, and again glass fibres, carbon, basalt, natural fibres etc..

The gases that can be fed through the opening <NUM> into the material processed in the pumping channels <NUM> can be, for example, CO<NUM>, Nitrogen, etc..

The gases that can be removed from the material processed in the pumping channels <NUM> are: monomeric or oligomeric residues, water vapor, reaction by-products such as oxygen, hydrogen, etc..

The products coming out of the process obtained with the apparatus of the invention can be compound in granules or finished products such as plates, tubes, profiles, films, yarns, etc..

According to a variant not shown in the attached figures, the assembly <NUM> can comprise at least one ON/OFF valve arranged so as to control the communication between the process duct <NUM> and the pumping device <NUM>.

The assembly <NUM> according to the present invention is preferably equipped with a sealing system <NUM>, which blocks the release of material at the sides of the rotor <NUM>.

The sealing system <NUM> comprises the purge channels <NUM> already described, which receive any material released from the pumping channels <NUM> adjacent thereto and discharge it directly into the process duct <NUM>.

Preferably, the sealing system <NUM> also comprises a viscous seal <NUM> defined by two grooves of the stator <NUM>, preferably coil shaped, which are axially arranged respectively between the respective purge channel <NUM> and the respective bearing <NUM> of the rotor <NUM>.

Preferably, the sealing system <NUM> also comprises two static seals <NUM>, preferably packings, which are respectively arranged between the respective viscous seal <NUM> and the respective bearing <NUM> of the rotor <NUM>.

According to a variant shown in <FIG>, various pumping devices <NUM> configured for different applications are coupled in series to the process duct <NUM>. In other words, the process duct <NUM> is equipped with a plurality of pairs of openings (not visible in <FIG>) to which a plurality of pumping devices <NUM> are respectively connected.

Each pumping device <NUM> is arranged to carry out a specific processing. For example, a first pumping device 3a comprises the hopper <NUM> to carry out the introduction of powders and a second pumping device 3b comprises a vacuum pump <NUM> to carry out a degassing. In this way, moreover, each pumping device <NUM> can have more convenient dimensions and a reduced distance between the bearings. This allows to avoid bending the rotor during the process. Moreover, in this way the areas of the pumping device which operate under vacuum conditions are separated from the areas which do not operate under vacuum conditions.

With reference to <FIG>, in use, the material fed to the process duct <NUM>, is subjected to one or more passages through the pumping channels <NUM> and, after each passage, is cyclically discharged in the process duct <NUM>.

The number of passages of a particle of material inside the pumping channel <NUM> is given with a good approximation by the ratio between the recirculation flow rate and the axial flow rate (Qrec/Qax).

Wherein axial flow means the flow rate fed to the process duct <NUM>, arriving from a material pumping apparatus (for example a screw extruder <NUM>) and recirculation flow rate means the flow rate of material that circulates in all pumping channels <NUM> (value depending on various variables such as geometric and operational ones such as the passage section of the pumping channel, the depth of the pumping channel, the axial distance between the walls of the pumping channel, the thickness of the material downstream of the laminator element <NUM> and the speed of the rotor <NUM>).

Since the place where the processes of dispersion and surface exposure of the material take place is the pumping channel <NUM>, it is clear that the number of passages of the material through the pumping channels <NUM> identifies the number of treatments to which all the material is subjected.

It is evident that a ratio Qrec/Qax < <NUM> implies that not all the liquid has passed once through the pumping channels <NUM>, whereas Qrec/Qax = <NUM> implies that there has been a single passage of all the material through the pumping channels <NUM> and finally Qrec/Qax > <NUM> implies that all the liquid has passed more than once through the pumping channels <NUM>.

In greater detail, the recirculation flow rate Qrec is substantially equivalent to the volume of the material stowed in the pumping channel <NUM> multiplied by the rotation speed of the rotor <NUM> and by the number N of the pumping channels <NUM>.

In the particular example described and shown herein, in which the pumping channel <NUM> is equipped with at least one laminator element <NUM>, the flow rate Qrec can be summarized by the following expression: <MAT> where:.

It is known that in the processes to which the invention typically applies it is often useful to design several passages of the same material through the pumping channel <NUM>.

In case of use of the assembly <NUM> according to the present invention for degassing purposes of the material, studies have shown that more than one degassing passage may be necessary for an optimal degassing. It is understood that the number of optimal passages can vary according to the applications of the assembly according to the present invention.

However, it is important to underline that, thanks to the flexibility of the present solution, it is possible to set the operation of the assembly <NUM> so as to obtain a desired number of passages inside the pumping device <NUM> in order to optimise the process for which the assembly <NUM> is employed.

Advantageously, the assembly and the method according to the present invention is particularly useful for producing compounds of thermoplastic material, in the form of granules or of films, sheets, plates, profiles, tubes, yarns, etc., with either compact or expanded structure.

Claim 1:
Assembly for processing viscous material comprising:
• a process duct (<NUM>) extending along a longitudinal axis (A) between an inlet (<NUM>) and an outlet (<NUM>); in use, the process duct (<NUM>) being fed with viscous material, for example coming from a screw extruder (<NUM>); wherein, in use, the viscous material advances in the process duct (<NUM>) in one advancing direction (D);
• at least one pumping device (<NUM>) provided with:
- a stator (<NUM>) comprising a cylindrical seat (<NUM>);
- at least one cylindrical rotor (<NUM>), which is housed in the stator (<NUM>) and is coupled to the stator (<NUM>) with a sliding seal; wherein the rotor (<NUM>) is configured to rotate around a rotating axis (B) substantially parallel to the longitudinal axis (A) and has an outer face (<NUM>) with at least one groove (<NUM>), which forms with the inner surface (<NUM>) of the stator (<NUM>) at least one pumping channel (<NUM>);
wherein the pumping device (<NUM>) is configured so that the pumping channel (<NUM>) extends between at least one input (<NUM>) and at least one output (<NUM>); the input (<NUM>) and the output (<NUM>) being in fluid connection with the process duct (<NUM>), so that, in use, the viscous material advancing in the process duct (<NUM>) is fed to the pumping channel (<NUM>) through the input (<NUM>) and is discharged in the process duct (<NUM>) through the output (<NUM>);
characterized in that
the process duct (<NUM>) has a first opening (<NUM>) in connection with the input (<NUM>) of the pumping channel (<NUM>) and a second opening (<NUM>) in connection with the output (<NUM>) of the pumping channel (<NUM>); and in that
the input (<NUM>) and the output (<NUM>) of the pumping channel (<NUM>) are substantially arranged side by side along a direction orthogonal to the axis of rotation (B) .