MATERIAL

The present invention relates to an extrusion apparatus for the processing of polymeric material, in particular and preferably for the manufacture of synthetic filaments for the textile industry.

The present invention thus finds particular application in the textile industry and in the manufacture of yarns for synthetic fibres such as polyester and polyamide.

Different extrusion techniques of polymers exploiting extrusion systems, typically single or double cochlea, are known in the prior art, where the polymer is extruded in several stages, generally three, one of feeding/melting/softening of the polymers,“loaded” in incoherent form, one of compression and one of volumetric dosage, wherein the melt or softened polymer is pushed towards a further device, typically a tube or matrix.

In order to improve the quality of the yarn, in the most cutting-edge solutions the extruders are equipped with sections, usually interposed between the first and the third stage, which facilitate the extraction of possible impurities, with low molecular weight or volatile, from the polymer structure.

In one of such solutions, a double co-rotative parallel cochlea extruder is used, wherein the joint action of the elements of each screw/cochlea performs an intense mechanical action on the molten polymer, helping the release of impurities; the arrangement of one or more suction mouths along the peripheral mantle of the extruder allows the interception and removal of volatile components released by agitation, increasing the quality of the polymer to be spun.

Disadvantageously, this solution is all the more effective in the removal of impurities the greater the mechanical action of hammering and fragmentation performed by the two cochleas, which impacts negatively on the mechanical and structural properties of the polymer.

In this light, the prior art proposes a further solution, shown in document US2005047267, which shows a single-screw extruder equipped with a special station for the extraction of volatiles is interposed between the melting and extrusion stages.

In the solution shown in that document, the extraction station has a very particular conformation, provided with a plurality of high-speed rotating screws, angularly spaced apart and individually arranged within a respective longitudinal conduct.

The presence of single high-speed rotatable“little screws” close to small conducts facilitates the constant renewal of the outer surface of the molten mass, promoting the separation between high and low molecular weight components.

In addition, at a predetermined section of the conducts, there are also radial suction mouths from which the volatile components removed by the action of the screws are extracted.

Disadvantageously, also the solution just described has drawbacks related to both suction location and shaking/extraction action.

In fact, the presence of a plurality of rotating screws at different speeds from the one of the extruder entails the necessity to provide a complex system of transmissions or independent actuations and greatly increases the complexity and cost of the system.

Moreover, the positioning of one or more radial suction mouths at certain points in the apparatus greatly limits the ability to extract impurities, since the vacuum action is only maximum by the mouth, but increasingly loses effectiveness with the distance from it.

The object of the present invention is therefore to provide an extrusion apparatus for processing polymeric material that overcomes the drawbacks of the prior art cited above. In particular, object of the present invention is to provide an extrusion apparatus for the processing of polymeric material capable of efficiently removing impurities without compromising the quality of the yarn.

Still, object of the present invention is to provide an extrusion apparatus for the processing of polymeric material with a simple structure and easy maintenance.

Said objects are achieved by an extrusion apparatus for the processing of polymeric material having the features of one or more of the following claims.

In particular, the extrusion apparatus comprises at least one melting station and one pumping (or extrusion) station. Such stations preferably define the first and second stages described above.

The melting station comprises a receiving section of a polymeric material in incoherent form, an advancement member of said polymeric material along a moving direction and at least one heating assembly configured to raise the temperature of the melting station above a predetermined melting or softening temperature of the polymeric material.

The pumping station is placed operatively downstream of said melting station and is designed to (or configured to) push the molten or softened polymeric material inside a tube or matrix.

According to one aspect of the present invention, the apparatus further comprises a centrifugation station operatively interposed between said melting station and said pumping station and configured to extract possible volatile components from said polymeric material.

Advantageously, the presence of a station that shakes the polymeric material by exploiting the centrifugal force generated by a central element reduces the mechanical action of “fragmenting” the melt mass and, at the same time, is of simple implementation.

Preferably, the centrifugation station comprises a tubular casing extending along its own central axis and provided with an inner tubular wall and heating means of said inner tubular wall. More preferably, the centrifugation station further comprises a rotatable rotor about said central axis and provided with a plurality of blades to distribute the molten polymeric material on said inner tubular wall easing the evacuation of said volatile components from a radially inner zone of said tubular casing.

Advantageously, in this way it is possible to remove/suck all the volatiles extracted from the centrifugation action, which distributes the polymer on the radially outer wall, from a single radially inner area of the casing, thus releasing the extraction efficiency from the positioning of the suction mouth.

Note that the centrifugation station is preferably shaped to promote a feed along said central axis of the polymeric material distributed on the inner tubular wall.

In the preferred embodiment, the casing, heating means and rotor define at least partially a thin film evaporator.

The blades then “spread” the molten polymeric material on the inner tubular wall at high speed, promoting a release of volatiles contained in the polymer that find their way out into a radially inner area of the casing.

In this regard, preferably each rotor blade extends between a radially inner portion, proximal to the central axis, and a radially outer portion, proximal to the inner tubular surface of the casing.

More preferably, the rotor is configured so that the volume contained between two adjacent blades and the inner tubular wall section interposed between them is substantially free, except for the layer of molten polymeric material coated on said inner tubular wall.

Advantageously, in this way the centrifugation station has a large free volume in the radially internal area, such to facilitate the extraction and suction of impurities.

In regards, preferably, with reference to a section of the casing in a plane transverse to said central axis, the surface occupied by the rotor is lower than 50% of the casing’s entire area of the casing delimited by a projection, on said transverse plane, of the tubular inner wall.

Preferably, moreover, in order to facilitate the extraction of volatiles, the centrifugation station comprises at least one suction assembly configured for sucking said volatile components from the radially inner portion of the casing.

Advantageously, the large space available to volatiles in the radially inner area of the casing, together with the presence of an suction unit acting in that radially inner (i.e. central) area maximizes the extraction efficiency of impurities.

In a preferred embodiment, the central axis of the casing has a predominantly vertical orientation, favouring the advancement of polymeric material by falling along the inner tubular wall and the release of volatile impurities upwards.

Advantageously, in this way, the action of the suction unit may even be unnecessary and, in any case, is facilitated.

These and other features with the related technical advantages, will become more apparent from the following exemplary, therefore non limiting, description of a preferred, therefore not exclusive, embodiment of an apparatus for the processing of polymeric material, in particular and preferably for the processing of synthetic filaments for the textile industry, as illustrated in the attached figures, wherein:

- Figure 1 shows a schematic side view of an apparatus for the processing of polymeric material according to the present invention;

- Figure 2 shows an enlarged detail of Figure 1 ;

- Figure 3 shows a schematic view and an enlargement of a cross- section according to line Ill-Ill of Figure 2;

With reference to the appended figures, number 1 generically indicates an apparatus for the processing of polymeric material according to the present invention.

Preferably, the apparatus 1 is of the type used in spinning of synthetic fibres, such as for example polyester and polyamide fibres. In particular, the extrusion apparatus 1 according to the invention finds application in the realization of the synthetic wire from a predetermined amount of polymeric material originally in inconsistent or granular form.

The polymeric material, which can also be recycled, is preferably polyester or polyamide, but could also be of another type if necessary.

The extrusion apparatus 1 comprises a melting station 2, a pumping station 3 (or extrusion) and, according to the invention, a centrifugation station 4 interposed between said melting station 2 and pumping station 3. Melting station 2 is configured to receive the polymeric material in incoherent form, overheat it and mix it such to make it malleable and fluid. Preferably, the melting station 2 has a receiving section 5 of the polymeric material in incoherent form, an advancement member 6 of said polymeric material along a direction of movement “M” and a heating group 7 configured to raise the temperature of the melting station 2, in particular in correspondence with a material containment zone, above a predetermined melting or softening temperature of the polymeric material.

The receiving section 5 thus has an opening, preferably provided with funnel or hopper, from which the polymeric material can be loaded.

In the embodiment illustrated in figure 1 , automatic or automated loading means 8 are provided, represented by a conveyor belt. Alternatively, however, the loading of the polymeric material could also be performed manually.

In the preferred embodiment, the melting station 2 comprises a mantle 9 extending along its own main axis“A” and within which a reception volume of the polymeric material is defined and the advancement member 6 is arranged.

In particular, the receiving volume extends between the receiving section 5 and a feeding mouth 10 from which the melting station 2 releases the molten or softened polymeric material.

In this regard, the heating unit 7 includes one or more heating bodies arranged in correspondence with the mantle 9 and configured to increase its temperature.

Such heating bodies may be of electrical nature, such as for example resistive bodies (metallic, ceramic or mixed), or of fluid nature, such as for example conducts for liquids or gases.

In the preferred embodiment, the heating bodies develop along the main axis“A” around the reception volume such to heat the polymeric material evenly.

Preferably, the heating group 7 is configured to bring the temperature of the coat and/or polymeric material between 200 and 350 °C, more preferably between 230 and 310 °C.

Note that, preferably, the melting station 2 extends predominantly along the horizontal; in other words, as illustrated by example in figure 1 , preferably the main axis“A” has a predominantly horizontal orientation.

The advancement member 6 is preferably defined by a screw or cochlea 11 , which preferably has a variable thread along the main axis in order to vary its action according to the density of the polymeric material, inconsistent and rigid in the proximity of the receiving section 5 and fluid and homogeneous in the vicinity of the release mouth 10.

Preferably, the cochlea or screw 1 1 is rotatably moved about the main axis by a rotary actuation; in the preferred embodiment, the rotary actuation is configured to move the cochlea or screw 1 1 at a rotational speed comprised between 5 to 100 rpm, more preferably between 10 to 70 rpm. Note that, preferably, the feeding mouth 10 is configured such to release the polymeric material at atmospheric pressure.

In other words, the melting station 2 is configured to release the molten (or softened) polymeric material into the centrifugation station 4, situated immediately downstream of the feeding mouth 10, with a pressure drop. Preferably, in correspondence with the feeding mouth 10 there is a metering device, such as a gear pump, configured to deliver precisely molten (or softened) polymeric material to the centrifugation station 4.

The centrifugation station 4, as said operatively interposed between the melting station 2 and the pumping station 3 (which will be better described below), is configured to extract from the polymeric material (molten or softened) any volatile components.

Advantageously, the presence of a station configured to extract volatile components (or impurities) by centrifugation of the product, that is by exploiting the centrifugal force for its agitation, favours an optimization of the extraction while maintaining, at the same time, the quality of the product.

Such centrifugation station 4 extends between a supply section 4a, associated with the melting station 2, and a release section 4b, associated with the pumping station 3.

Preferably, the centrifugation station 4 comprises a tubular casing 12 extending along its own central axis“B” and provided with a tubular inner wall 12a. Such a casing 12 thus develops between the feed section 4a and the release section 4b.

In the preferred embodiment, the tubular casing 12 has, at least in part, a substantially cylindrical conformation delimited

internally from said inner tubular wall 12a.

Note that the inner tubular wall 12a internally delimits a centrifugation chamber having a radially inner zone and a radially outer zone.

In order to maintain the consistency of the polymeric material malleable, the centrifugation station 4 further comprises heating means 13 of said inner tubular wall 12a configured to raise its temperature or maintain the temperature within a certain range (or around a predetermined value).

This value or temperature range is function of the type of polymeric material treated, as its entity is linked to the melting or softening temperature of the material to be maintained during the centrifugation phase.

Preferably, as previously reported, the operating temperature of the heating means 13 is between 200 and 350 °C, more preferably between 230 and 310 °C. The type of heating means 13 is in itself known and will not be discussed in detail below.

In order to generate the centrifugal action necessary to promote the extraction of impurities (or volatile components), the centrifugation station 4 comprises a rotor 14 rotatable about said central axis“B” and provided with a plurality of blades 14a to distribute the molten polymeric material on the inner tubular wall 12a favouring the evacuation of said volatile components from the radially inner zone of said tubular casing 12.

The centrifugation station 4 comprises an actuator assembly 14b configured to move the rotor 14 with a predetermined rotational speed. Preferably, the rotor 14 is moved at a higher rotating speeds than the screw or cochlea 11 of the melting station 2.

In the preferred embodiment, the actuator assembly 14b is configured to move the rotor with a rotating speed between 100 and 500 rpm, more preferably between 1 10 and 250 rpm, still more preferably between 130 and 200 rpm.

Note that, preferably, the casing 12, the heating means 13 and the rotor 14 define at least in part a thin-film evaporator.

Preferably, the rotor 14 extends along the central axis“B” with a plurality of blades 14a angularly spaced apart; the blades may be monolithic each extending along the useful length of the rotor 14 or, as in the illustrated embodiment, discrete and defined by a sequence of individual elements arranged in sequence along the central axis“B”.

Each blade 14a (or each individual member) of the rotor 14 preferably extends between a radially inner portion 15a, proximal to the central axis “B”, and a radially outer portion 15b, proximal to the inner tubular wall 12a of the casing 12.

More specifically, the radially outer portion 15b of the blade has an end spaced from the inner tubular wall 12a of the casing by a gap defining the thickness of the layer of polymeric material“spread” on the same inner tubular wall 12a. Preferably, said distance between the end of the radially outer portion 15b of the blade and the inner tubular wall 12a of the casing 12 is less than 10 mm, more preferably comprised between 1 and 3 mm.

Advantageously, in this way the rotational speed of the rotor 14 together with the space insisting between the end of the blade 14a and the casing 12 causes the molten (or softened) polymeric material to be directed and distributed on the inner tubular wall 12a.

Preferably, furthermore, the rotor 14 is configured so that the volume contained between two adjacent blades 14a and the interposed inner tubular wall section 12a is substantially free, except for the layer of molten polymeric material spread on said inner tubular wall 12a.

In other words, the rotor is shaped so that between two adjacent blades there is a free volume in correspondence with said radially inner zone of the casing, defining an escape route for the volatile components released from the polymeric material during centrifugation.

Thus, the centrifugation station 4 is configured to extract the volatile components of the polymeric material from a central, i.e. radially inner, zone of the casing.

Advantageously, in this way it is possible to eliminate suction or opening mouths from the inner tubular wall 12a of the casing 12, at least in correspondence with a working area of the rotor 14.

In regards, with the objective of maximising that aspect, with reference to a section of the casing 12 in a transverse plane of the central axis“B”, the surface occupied by the rotor is less than 50% of the whole area of the casing 12 delimited by a projection, on said transverse plane, of the inner tubular wall 12a.

Advantageously, the free volume inside the casing, preferably located in the radially inner zone of the centrifugation chamber, is large enough to allow the evacuation of the volatile components.

It should be noted that, in addition to generating a radial centrifugal action, the centrifugation station must transfer the polymeric material from the feeding section 4a to the release section 4b.

Therefore, the centrifugation station 4 is shaped to promote a feed along said central axis“B” of the polymeric material distributed on the inner tubular wall 12a.

In the illustrated embodiment, also for reasons of construction simplicity, the centrifugation station 4 is shaped so that the central axis“B” has a predominantly vertical orientation.

In this way, the polymeric material distributed on the inner tubular wall 12a of the casing 12 from the rotor 14 tends to proceed along the central axis “B” by falling.

Advantageously, moreover, the vertical development of the casing favours the evacuation of volatile components that tend to rise upwards even in absence of ventilation.

Alternatively, however, further embodiments may be envisioned in which the rotor 14 and/or the casing are shaped to generate, in addition to a centrifugal action, also an axial pushing action along the central axis“B”.

In the preferred embodiment, the centrifugation station 4 comprises at least one suction assembly 16 configured for sucking volatile components from the radially inner zone of the casing 12.

Preferably, the suction unit 16 includes a vacuum generating device placed in fluid connection with an suction mouth 17 arranged coaxially with the casing 12.

The vacuum generating device is preferably configured to generate a depression that brings the pressure value below 20 mbar, preferably below 10 mbar, more preferably between 1 and 8 mbar.

In the preferred embodiment, the suction assembly 16 is located near the feeding section 4a of the centrifugation station.

More precisely, the suction mouth 17 is located in such an area of the centrifugation station 4 so that the feeding section 4a is interposed between said suction mouth 4a and the release section 4b. In this way, the suction mouth 17 is arranged outside of a polymeric material feeding path. In the illustrated embodiment, the suction mouth 17 is positioned at a higher height than the feeding section 4a.

Advantageously, in this way, the suction of the volatiles acts in counter- current with respect to the advancement, by fall, of the polymeric material. Preferably, said suction mouth 17 is provided with a filter 17a dimensioned to prevent solid/liquid particles of the polymeric material from clogging the suction unit.

In other words, between the casing centrifugation chamber 12 and the vacuum generating device, the filter 17a, preferably defined by a predefined mesh or a layer of filter material, is interposed.

Preferably, moreover, the centrifugation station 4 is provided with at least a dragging member or a screw 18 placed near the release section 4b in order to guide the centrifuged polymeric material to said pumping station 3.

Preferably, the driving member or screw 18 is keyed on the same central shaft of the rotor 14.

In the preferred embodiment, therefore, the rotor 14 has a central shaft 19 extending between a first end, constrained to the actuation group, and a second end, provided with the drive member or screw 18.

In the preferred embodiment, the driving member or screw 18 has a substantially conical conformation in order to reduce the area of the release section 4b and generate a pushing on the polymeric material such as to allow its access to the pumping station (or extrusion).

Such pumping station 3 then develops between a receiving mouth 3a of the polymeric material, arranged immediately downstream of the release section 4b of the centrifugation station 4, and an extrusion head 20.

In particular, the pumping station comprises therein a pushing member 21 , preferably defined by a screw or cochlea of suitable size, and heating means 22 meant to keep the polymeric material sufficiently malleable.

The pushing member 21 is moved by an actuator 23 (e.g. motor), preferably dedicated and independent from that of the melting station 2. The differences between the pushing member 21 and the heating means 22 of the pumping station 3 and, respectively, the advancement member 6 and the heating group 7 of the melting station 2 are generally known by themselves, such as for example the presence of the dosage device described above.

In the illustrated embodiment, the pumping station 3 develops along its own predominant axis“C”, which preferably has a horizontal orientation. Thus, in the preferred embodiment the extrusion apparatus 1 has a“step” configuration, with the melting station developing horizontally, the centrifugation station developing vertically and the pumping station developing horizontally.

In this way, the action of the cochleas in the two horizontal melting and pumping stations and that of the thin film evaporator of the centrifugation station are maximized and optimized.

Alternatively, however, the pumping station may comprise, instead of a cochlea, a gear pump or similar device, which may have orientation aligned with that of the centrifugation station (preferably vertical).

Alternatively, however, the melting, centrifugation and pumping stations may be coaxial and aligned with each other.

The extrusion apparatus 1 described above therefore allows to perform a particularly innovative method of extrusion of a polymeric material.

The method involves softening the material, initially provided in an incoherent/granular form, and advancing the softened material by releasing it in a centrifugation station at atmospheric pressure.

The centrifugation station may be, preferably but not necessarily, the one described above provided with a casing 12 provided with a radially inner wall 12a and a rotor 14.

In the centrifugation station 4, the softened material is centrifuged by a radial pushing action generated by the rotation of the rotor 14 and simultaneously spread on the radially inner wall 12a of the casing 12 by the blades 14a. Moreover, the polymeric material (spread and softened) is advanced along the centrifugation station and pushed into a pumping station where extrusion is completed through an extrusion head, from which spinning starts.

The invention achieves the intended objects and offers important advantages.

In fact, the operation of a centrifugation station interposed between the melting and pumping stages allows to maximize the purification of the material without compromising its structural quality.

In particular, the use of a thin-film evaporator that can be driven at a speed which is independent from that of the extrusion screws/cochleas and capable of spreading the material on the heated walls of the casing, favours the migration of volatile components from the polymeric material and, above all, allows their extraction from a radially internal area of the centrifugation chamber.

Moreover, the suction of the volatile components carried out coaxially to the centrifugation station allows to maximize the suction action in all the areas of the casing.

Moreover, the development of the centrifugation station orthogonal to that of the melting and pumping stations makes the system simple and compact in its longitudinal development.