IT202100026603A1 - SYSTEM AND METHOD OF COOLING A PLASTIC FILM IN BLOW FORMING - Google Patents

Description

Description of the industrial invention entitled:

?SYSTEM AND METHOD OF COOLING A PLASTIC FILM IN BLOW FORMING?

Description

Field of invention

This invention? relating to a cooling system for a plastic film in blow molding. In a further aspect, the present invention is relating to a calibration cage and a blow molding film system equipped with a plastic film cooling system.

Finally, the present invention is relating to a method of cooling a plastic film in blow molding.

Known art

In polymer technology, blow molding is ? a process used to obtain polymer films of reduced thickness, typically between 15-500 ?m, using blow-filming systems. Such films can be used for example to produce packaging films, plastic bags, or greenhouse films.

The plastic material, i.e. the polymer, in a solid state (for example granules or powder) is initially fed into an extruder. A typical extruder used in the industrial sector? essentially made up of a cylinder inside which one or two worm screws rotate. In correspondence with the supply to the cylinder ? a loading hopper for the plastic material in solid state is provided, while at the cylinder exit there is post a ?supply chain? or ?matrix? from which the molten plastic material comes out.

The product extruded from the die is then blown using a suitable blow molding head, creating a bubble shape. The blown air allows the diameter of the bubble to be increased and, at the same time, reduces its wall thickness, forming the tubular plastic film of the desired thickness. The tubular film then passes through a cooling ring and subsequently through a calibration cage, being pulled upwards by appropriate rollers, defining the stretching phase which has the aim of stabilizing the geometry and morphology of the material.

Due to stretching in the longitudinal direction and blowing, the polymer melt is subjected to a biaxial elongation flow. The deformation in the two directions therefore orients the macromolecules in both the longitudinal and circumferential directions. These two actions take place within the so-called "frost line", while the deformation above the aforementioned section in which the solidification of the polymer occurs, i.e. the crystallization, are determined solely by the mechanical action on the tubular plastic film during handling. In known types of blow molding systems, the cooling of the extruded and filmed tubular plastic film is achieved through contact with air at room temperature along the entire path down to the calibration cage. For this reason, the extension of known types of systems is often notable despite the devices responsible for producing the tubular plastic film occupying only a small portion of the entire extension.

Furthermore, the cooling temperature of the tubular plastic film negatively influences the speed. of production, constituting a bottleneck in relation to the need? to adapt production to capacity? for cooling and stabilizing the extruded and filmed tubular plastic film.

It would therefore be desirable to have a cooling system for tubular plastic films in blow molding capable of minimizing the above-mentioned drawbacks. In particular, it would be desirable to have a cooling system for the tubular plastic film in blow molding capable of maximizing production and, at the same time, minimizing the extension of the systems in which it is used.

Furthermore, it would be desirable to have a calibration cage for blow molding and a blow mold film system capable of minimizing the above-mentioned drawbacks. In particular, it would be desirable to have a calibration cage for blow molding filming and a blow molding film plant with reduced construction and assembly costs, capable of improving the speed of production. production of tubular plastic film.

Summary of the invention

Purpose of the present invention? provide a cooling system for a tubular plastic film in blow molding capable of minimizing the aforementioned problems.

In particular, the purpose of the present invention? provide a cooling system for a tubular plastic film in blow molding capable of considerably reducing the temperature of the tubular plastic film in a small space.

Finally, an aim of the present invention? provide a calibration cage and a blow molding film system with reduced production and assembly costs, capable of guaranteeing effective cooling of the extruded tubular plastic film.

The above-mentioned purposes are achieved by a cooling system of a tubular plastic film in blow molding, in accordance with the attached claims.

The cooling system? characterized by the fact of understanding:

- a cooling body for the tubular plastic film, defined by a containment structure for the tubular plastic film and provided with an inlet portion and an outlet portion of the tubular plastic film and cooling means suitable for introducing a flow of air at a predetermined temperature within the cooling body;

- first means for regulating the size of the inlet portion, operatively coupled to the inlet portion;

- second means for regulating the size of the outlet portion, operatively coupled to the outlet portion;

- control means operationally connected to the first and second size adjustment means;

wherein the control means are adapted to operate the cooling means as a function of the temperature of the tubular plastic film, and

in which the control means are capable of operating the first size adjustment means and the second size adjustment means as a function of the diameter of the tubular plastic film to be cooled and as a function of the predetermined conveyance direction of the introduced air flow.

Thereby, ? It is possible to obtain cooling of the tubular plastic film by cooling the portions sliding in the cooling body.

Preferably, the first size adjustment means comprises an iris diaphragm device provided with a plurality of of slats operationally connected to restrict the size of the inlet portion to the desired size.

Preferably, the second size adjustment means comprises an iris diaphragm device provided with a plurality of of slats operationally connected to restrict the size of the outlet portion to the desired size.

Thereby, ? Is it possible to precisely adjust the dimensions of the entry and exit portions according to needs? operational, in accordance with the present invention.

Even more? preferably, the first size adjustment means and/or the second size adjustment means comprise a rotating ring coupled to the slats, and

the control means are capable of rotating the rotating ring nut according to the desired size of the inlet portion and/or the outlet portion.

In this way, the movement of the slats constituting the size adjustment means can be carried out uniformly and quickly.

Preferably, the control means are suitable for operating the first size adjustment means and the second size adjustment means to define the direction of conveyance of the introduced air flow in such a way as to allow contact of the air flow with the tubular plastic film at the inlet portion and the outlet of the air flow at the outlet portion.

Thereby, ? It is possible to optimize flow management and reduce the energy expenditure used.

Preferably, the cooling body has a cylindrical containment structure.

Preferably, the cooling means have an air flow inlet device arranged on the containment structure at the inlet portion.

The above-mentioned purposes are further achieved by a calibration cage of a tubular plastic film in blow molding, in accordance with the attached claims.

The calibration cage? characterized by the fact of comprising a cooling system of a tubular plastic film in the blow molding according to one or more of the attached claims.

Finally, the above-mentioned purposes are further achieved by a blow molding filming system, in accordance with the attached claims. The blow molding film system includes:

- a blow molding film head, for the production of a tubular plastic film;

- one or more? extruders arranged upstream of the blow molding film head for feeding the extruded plastic material;

- a calibration cage arranged downstream of the blow molding head;

the blow molding film plant? characterized by the fact of comprising a cooling system of a tubular plastic film in the blow molding according to one or more of the attached claims positioned downstream of the blow molding head.

Preferably, the cooling system of a tubular plastic film in blow molding is ? placed in correspondence with the calibration cage.

Description of the figures

These and further characteristics and advantages of the present invention will be evident from the description of the preferred embodiment, illustrated by way of example and not by way of limitation in the attached figures, in which: - Figure 1? a perspective view of a preferred embodiment of the cooling system of a plastic film, in accordance with the present invention;

- Figure 2? a side plan view of the cooling system of a plastic film of Figure 1;

- Figure 3? a sectional view A-A of the cooling system of a plastic film of Figure 2;

- Figure 4? a schematic sectional view of the cooling system of a plastic film in Figure 1, illustrating the direction of conveyance of the air flow.

Detailed description of the invention

The blow molding film production process, known as blown film, consists, as is known, in the extrusion of a polymer melt through an annular hole. The extruded product is blown using an appropriate blowing film head, defining a bubble shape which is then inflated by means of air blown inside, defining a tube which is subsequently stretched. The blown air allows the diameter of the bubble to be increased and, at the same time, reduces its wall thickness, forming the tubular plastic film of the desired thickness.

With reference to Figures 1-4, ? illustrated is the preferred embodiment of the system 10 for cooling a tubular plastic film 1 in blow molding, in accordance with the present invention.

Figure 1 ? a perspective view of a preferred embodiment of the cooling system 10 of a tubular plastic film 1, in accordance with the present invention, comprising a body 110 for cooling the tubular plastic film 1, defined by a containment structure of the aforementioned film 1 tubular plastic. In particular, the containment structure allows the tubular plastic film 1 to be kept in the desired path during its movement, ensuring that cooling can be achieved without inadvertently modifying its geometry, as described in greater detail below.

As illustrated in the attached Figures, the containment structure defined by the cooling body 110 has a cylindrical shape. In the preferred embodiment, this conformation occurs both in the external portion and in the internal portion.

According to further embodiments, not illustrated, the conformation of the cooling body could be different, presenting any useful conformation for both the external portion and the internal portion. Figure 2 ? a side plan view of the cooling system 10 where ? illustrated is the cooling body 110 provided with an inlet portion 111 and an outlet portion 112 of the tubular plastic film 1. These inlet 111 and outlet 112 portions are arranged in succession, i.e. the inlet portion 111 ? arranged downstream of the outlet portion 112 with respect to the direction of advancement (not shown) of the tubular plastic film 1. The cooling body 110 therefore defines a duct for the tubular plastic film 1, this duct extending between the inlet portion 111 and the outlet portion 112. Figure 3 illustrates the section A-A of the system 10 for cooling the plastic film 1, where first size adjustment means 211 are arranged in correspondence with the inlet portion 111. These first size adjustment means 211 are operationally connected to the aforementioned inlet portion 111, thus allowing the opening of the relevant inlet or entry of the duct defined therein to be adjusted. Similarly, second size adjustment means 212 are arranged in correspondence with the outlet portion 112. These second size adjustment means 212 are operationally connected to the aforementioned outlet portion 112, thus allowing the opening of the relevant outlet to be adjusted or the extraction of the duct defined therein.

The function of the size adjustment means 211, 212 is, therefore, to precisely control the gap of the respective input 111 and output 112 portions in such a way that this can be determined according to the needs. expressed at every moment of operation.

Size adjustment by the aforementioned size adjustment means 211, 212 can be achieved. also affect the shape of the lights, modifying or reducing the shape already? provided for the respective input 111 and output 112 portions. In particular, the ports can have a circular or oval shape, as in the preferred embodiment, but also a polygonal shape, for example square or rectangular.

In the preferred embodiment described therein, the first size adjustment means 211 comprises an iris diaphragm device provided with a plurality of iris diaphragm devices. of lamellae operatively connected to restrict the size of the inlet portion 111 to the desired size. Likewise, the second size adjustment means 212 also comprises an iris diaphragm device provided with a plurality of of slats operatively connected to restrict the size of the outlet portion 112 to the desired size.

The aforementioned lamellas (not illustrated) are arranged in correspondence with the peripheral portion of the cooling body 110 in correspondence with the relative inlet 111 or outlet 112 portion. These can be moved from an open position in which they are substantially adjacent to the peripheral edge and maximize the clearance of the relevant entry portion 111 or exit portion 112, in partial overlap in succession, to a closed position in which they extend from the peripheral edge to the center of the relevant entry portion 111 or exit portion 112, in which the ?mutual overlap area? reduced.

Therefore, the use of an iris diaphragm device allows the definition of a substantially circular light, as the blades create a conformation of the light equidistant from the center of the respective portion on which they are arranged. By using differentiated movements for the slats, it is also possible to define lights of any geometry.

According to further embodiments, not illustrated, ? It is possible to define different size adjustment means between the input portion and the output portion.

The cooling of the tubular plastic film 1? entrusted to suitable cooling means capable of introducing a flow of air at a predetermined temperature into the cooling body 110.

The cooling means are preferably made by means of a device 210 for introducing an air flow, as illustrated in Figures 1 and 2, such as to allow the temperature of the tubular plastic film 1 to be rapidly lowered. In particular, this air flow inlet device 210 is arranged on the containment structure in correspondence with the inlet portion 111, but it could equally be arranged in a different position or be external to the containment structure although operationally connected with it.

The air flow is therefore introduced into the cooling body 110 so that it this can reach and contact the tubular plastic film 1, as illustrated in Figure 4 and described in greater detail below.

Finally, the cooling system 10 includes suitable control means (not shown) operationally connected to the first 211 and second 212 size adjustment means as well as? to the previously described cooling means.

These control means are suitable for activating the cooling means according to the temperature of the tubular plastic film 1. Furthermore, the control means are suitable for activating the first size adjustment means 211 and the second size adjustment means 212 as a function of the diameter of the tubular plastic film 1 to be cooled and as a function of the predetermined conveyance direction of the air flow entered.

Therefore, the control means allow the values of the lights of the input 111 and output 112 portions to be adjusted, including the phasing and area values. The phasing value corresponds to the opening or closing period of the iris diaphragm devices, or of the relative blades, at each instant or at predetermined instants. Furthermore, to allow the correct management of the air flow within the cooling body 110, it is Is it possible to define the relationship between the input port and the outlet port in such a way as to determine the path of the air flow according to the needs? cooling. The value of the area? the measurement of the opening, or closing, of the light, which is determined with the phasing and width of the light, from which ? It is possible to obtain the section of the flow entering or extracting from the duct.

The control means are, therefore, suitable for activating the first size adjustment means 211 and the second size adjustment means 212 to define the direction of conveyance of the introduced air flow in such a way as to allow contact with the air flow. air with the tubular plastic film 1 at the inlet portion 111 and the exit of the air flow at the outlet portion 112, as illustrated in Figure 4 where the arrows exemplify the movement of the air flow.

In this regard, in the preferred embodiment the first size adjustment means 211 comprise a rotating ring coupled to the blades of the iris diaphragm device, in which the control means are adapted to rotate the rotating ring according to the desired size of the portion 111 entry. Preferably, moreover, the second size adjustment means 212 also comprise a rotating ring coupled to the blades of the iris diaphragm device, in which the control means are adapted to rotate the rotating ring according to the desired size of the output portion 112. Furthermore, it is possible to envisage the use of the rotating ring nut even for only one of the aforementioned first and second size adjustment means.

The ring? connected to the cooling system 10 preferably in correspondence with the peripheral portion of the cooling body 110 in correspondence with the relative inlet 111 or outlet 112 portion. The ring nut allows the simultaneous and uniform movement of all the slats connected to it, this movement being carried out by rotating the aforementioned ring nut. For example, clockwise rotation can? arrange the slats in correspondence with the aforementioned closed position in which they extend from the peripheral edge to the center of the relevant inlet portion 111 or outlet portion 112, while anti-clockwise rotation can? arrange the slats in correspondence with said opening position in which they are substantially adjacent to the peripheral edge and maximize the light of the relevant inlet portion 111 or outlet portion 112.

This invention? also relating to a calibration cage of a tubular plastic film 1 in blow molding, not shown, and comprising the cooling system 10 of a tubular plastic film 1 in blow molding as previously described. So, ? It is possible to use the cooling system 10 according to the present invention directly in the calibration cage during the production of the tubular plastic film 1, thus containing the reduction of the extension of the possible plant responsible for blow molding filming through the considerable cooling obtainable for the tubular plastic film 1 during passage through the aforementioned duct.

Finally, the present invention is relating to a blow molding film plant, not illustrated, comprising, in succession, an extruder for feeding the extruded plastic material, a blow mold film head for producing the tubular plastic film 1 and arranged downstream of the aforementioned extruder and a calibration cage arranged downstream of the blow molding head.

Unlike film-forming systems of the known type, the system according to the present invention also includes the system 10 for cooling the tubular plastic film 1 as previously described. This cooling system 10? arranged downstream of the blow molding head and therefore allows the cooling of the newly made tubular plastic film 1.

This cooling system 10 can? be, therefore, placed downstream of the calibration cage or placed between the calibration cage and the blow molding head. According to a further embodiment, not illustrated, the cooling system 10 of the tubular plastic film 1 could be arranged in correspondence with the calibration cage. There? allows you to minimize the costs of construction and assembly of the system, as well as to optimize the extension of the same system.

Further elements part of the blow molding film system can be, for example, the movement rollers and a pinching calender which respectively allow the movement of the tubular plastic film 1 as well as the closure of the bubble formed.

The use of the cooling system 10 of a tubular plastic film 1 according to the present invention is described below, in particular through use within a blow molding film plant in accordance with the present invention.

The production process of the tubular plastic film 1 includes at least the following phases.

Feeding phases of at least one solid plastic material into at least one extruder for producing the molten plastic material.

The plastic material in solid state, for example the polymer in granules or powder, is initially fed into an extruder, via a loading hopper for the plastic material in solid state. At the exit of the extruder cylinder? a "matrix" is placed, into which the flow of plastic melt is forced to enter with a speed constant, defining an annular die to form a ?tube? continuous flow of plastic fluid.

Phase of feeding the melted plastic material to a blow molding film head for the production of a tubular plastic film.

Leaving the annular matrix, a polymer tube is formed, while the plastic melt that flows? blown by an air flow along the tubular plastic film 1 itself. The product extruded from the die is then blown through the blow molding head, creating a "bubble conformation". Initially, the polymer tube created is inflated by an internal pressure, due to the blowing of air coming from an orifice of the annular matrix, slightly higher than atmospheric pressure. Is it created like this? the bubble conformation. The blown air allows the diameter of the bubble to be increased and, at the same time, reduces its wall thickness, forming the tubular plastic film 1 of the desired thickness.

Feeding phase of the tubular plastic film 1 to a calibration cage located downstream of the blow molding film head.

The tubular plastic film 1 passes through a calibration cage, being pulled upwards by the handling rollers, defining the stretching phase which has the aim of stabilizing the geometry and morphology of the material. The internal pressure and the axial draft contribute to the bi-axial extension of the tubular plastic film 1.

During the process the tubular plastic film 1 cools and solidifies, so that it can be folded between the handling rollers that pull it. Cooling is normally carried out by forced convection by blowing air through the cooling ring located at the outlet of the filming head. In steady state conditions the quantity? of air inside the bubble? constant and small losses are compensated by air that is blown inside so that the pressure remains constant. Due to stretching in the longitudinal direction and blowing, the polymer melt is subjected to a biaxial elongation flow in the two directions of ?Machine Direction? (MD) and ?Transverse Direction? (TD). As soon as the polymer melt leaves the supply chain? already? partially oriented in MD due to the forced passage through the die and undergoes further stretching in MD due to the movement of the towing with the handling rollers.

The MD orientation effect can be evaluated through the value of the ?Take Up Ratio? (TUR), that is? through the ratio between the speed? of towing (Vt) and the speed? coming out of the molten polymer supply chain (Vu). The TD orientation effect is, however, obtained through ?inflation? which causes the molten polymer to stretch in a direction almost perpendicular to the direction of extrusion. The inflation value? generally indicated by the ?Blow Up Ratio? (BUR), and ? expressed by the ratio between the diameter of the bubble (Db) and the diameter of the die (Df). The ?global stretch ratio? (RS) ? given, therefore, by the influence of the individual contributions of the BUR and the TUR and can be evaluated through the ratio between the thickness of the film in the die (i.e. the width of the air gap) and the thickness of the film after cooling (SF).

? it should be underlined that the air cannot get out of the bubble, since? this is clamped by the calender located downstream of the calibration cage. In this way the tubular plastic film 1 is thus stretched in the circumferential or transverse direction. At the end of the extrusion process, the winding of the tubular plastic film 1 causes elongation in the longitudinal direction and produces stretching. The deformation in the two directions therefore orients the macromolecules in both the longitudinal and circumferential directions. These two actions occur up to a defined height of the frost line, while the deformation of the bubble beyond the aforementioned frost line and beyond the crystallization? negligible and determined only by the mechanical action on the tubular plastic film 1 during handling as described in greater detail below. In this area the speed? of the tubular plastic film 1 varies going from the extrusion one to the stretching one, and the radius of the same tubular plastic film 1 goes from that of the die to the final one of the tubular plastic film 1.

The solidified tubular plastic film 1 is finally pulled upwards and flattened into a double-layer sheet by the handling rollers and the pinching calender which close the bubble and form an hermetic seal in the final part.

The aforementioned production process of the tubular plastic film 1 further includes the cooling of the tubular plastic film 1 by means of the cooling system 10 according to the present invention.

This cooling is, therefore, carried out downstream of the filming head, depending on the positioning of the cooling system 10 in the system, as previously described. In this regard, the tubular plastic film 1 is introduced into the cooling body 10, as illustrated in Figure 4, relating to a schematic section view of the cooling system 10 of the tubular plastic film 1 of Figure 1, illustrating the direction of conveyance of the air flow.

The activation of the cooling means of the cooling system 10 allows the introduction of an air flow at a predetermined temperature within the cooling body 110, for example the introduction of air at a temperature lower than that of the tubular plastic film 1 extruded and filmed by the device 210 for introducing an air flow.

The introduction of the air flow into the containment body 110 is not possible. sufficient to ensure the cooling of the tubular plastic film 1, i.e. a considerable quantity may be necessary. of energy to ensure effective cooling. To allow the temperature of the tubular plastic film 1 to be rapidly lowered, it is, in fact, necessary for the air flow to be introduced into the cooling body 110 in such a way as to reach and contact the tubular plastic film 1 uniformly along its external surface, as it is not possible to cool the tubular plastic film 1 from its inside.

In this regard, the containment structure of the cooling body 110 allows the tubular plastic film 1 to be kept in the desired path during its movement, ensuring that cooling can be carried out without inadvertently modifying its geometry. The size adjustment means 211, 212 therefore allow the light of the respective input 111 and output 112 portions to be precisely controlled in such a way that this can be determined according to the needs. expressed at every moment of operation.

In the case of immediate cooling, the control means operatively connected to the first 211 and second 212 size adjustment means and to the cooling means will actuate the aforementioned cooling means according to the temperature of the tubular plastic film 1. In particular, by first operating the cooling means, for the introduction of air at a temperature lower than that of the tubular plastic film 1, and subsequently the first size adjustment means 211 and the second size adjustment means 212, in such a way that the former are substantially adjacent to the sliding tubular plastic film 1 and the latter are further apart from the same sliding tubular plastic film 1. The operation of the first 211 and second 212 size adjustment means is preferably implemented by means of the rotation command of the ring nut, such as to arrange the relative slats in the desired position. In this way, the cooling system 10 defines a direction of conveyance of the air flow introduced in such a way as to allow the contact of the air flow with the tubular plastic film 1 in correspondence with the inlet portion 111 and the exit of the flow of air at the outlet portion 112, as illustrated in Figure 4.

The control means are also suitable for activating the first size adjustment means 211 and the second size adjustment means 212 as a function of the diameter of the tubular plastic film 1 to be cooled. In the case of a change in the size of the tubular plastic film 1, the control means operatively connected to the first 211 and the second 212 size adjustment means will actuate the first size adjustment means 211 and the second size adjustment means 212 , so that the positioning of the slats adapts to the dimensions, reduced or increased, in the tubular plastic film 1 in production, while still maintaining the positioning specifications relating to cooling and the direction of the air flow to be conveyed. The movement of the slats is operated with the same operational characteristics described previously. The control means, according to the present invention, can be implemented by a manually operated system or by an electronic, automatic or manual operated system, while maintaining the inventive concept of the present invention.

Claims (10)

1. System (10) for cooling a tubular plastic film (1) in blow molding characterized by comprising: - a body (110) for cooling the said tubular plastic film (1), defined by a containment structure of the said tubular plastic film (1) and provided with an inlet portion (111) and an outlet portion (112) of said tubular plastic film (1) and of cooling means suitable for introducing a flow of air at a predetermined temperature into said cooling body; - first means (211) for adjusting the size of said inlet portion (111), operatively coupled to said inlet portion (111); - second means (212) for adjusting the size of said outlet portion (112), operatively coupled to said outlet portion (112); - control means operationally connected to said first (211) and second (212) size adjustment means; wherein the said control means are suitable for operating the said cooling means as a function of the temperature of the said tubular plastic film (1), and wherein the said control means are suitable for operating the said first size adjustment means (211) and the said second size adjustment means (212) as a function of the diameter of the said tubular plastic film (1) to be cooled and in operation of the predetermined conveyance direction of said introduced air flow. 2. System (10) for cooling a tubular plastic film (1) in blow molding according to claim 1, wherein said first size adjustment means (211) comprise an iris diaphragm device provided with a plurality of of lamellae operatively connected to restrict the size of said inlet portion (111) to the desired size. 3. System (10) for cooling a tubular plastic film (1) in blow molding according to claim 1 or 2, wherein said second size adjustment means (212) comprise an iris diaphragm device provided with a plurality ? of blades operatively connected to restrict the size of said output portion (112) to the desired size. 4. System (10) for cooling a tubular plastic film (1) in blow molding according to claim 2 or 3, in which said first means (211) for adjusting the size and/or said second means (212) for size adjustment include a rotating ring coupled to the said slats, and wherein the said control means are adapted to rotate the said rotating ring according to the said desired dimension of the said inlet portion (111) and/or of the said outlet portion (112). 5. System (10) for cooling a tubular plastic film (1) in blow molding according to one or more? of claims 1 to 4, wherein the said control means are adapted to operate the said first (211) size adjustment means and the said second (212) size adjustment means to define the said direction of conveyance of the said flow of air introduced in such a way as to allow the contact of the said air flow with the said tubular plastic film (1) in correspondence with the said inlet portion (111) and the exit of the said air flow in correspondence with the said portion (112) output. 6. Cooling system (10) of a tubular plastic film (1) in blow molding according to one or more? of claims 1 to 5, in which the said cooling body (110) has the said containment structure with a cylindrical shape. 7. System (10) for cooling a tubular plastic film (1) in blow molding according to one or more? of claims 1 to 6, wherein the said cooling means have a device (210) for introducing the said air flow arranged on the said containment structure in correspondence with the said inlet portion (111). 8. Calibration cage of a tubular plastic film (1) in blow molding characterized by the fact of comprising a system (10) for cooling a tubular plastic film (1) in blow molding according to one or more? of claims 1 to 7. 9. Blowing film system including: - a blow molding film head, for the creation of a tubular plastic film (1); - one or more? extruders arranged upstream of said blow molding film head for feeding the extruded plastic material; - a calibration cage arranged downstream of said blow molding head; the said blow molding film plant? characterized by the fact of comprising a system (10) for cooling a tubular plastic film (1) in the blow molding according to one or more? of claims 1 to 7 arranged downstream of said blow molding film head. 10. Blow film system according to claim 9, wherein the said system (10) for cooling a tubular plastic film (1) in the blow film is positioned in correspondence with said calibration cage.