DE19536563A1 - Prodn. of expanded sheet from high-melt strength polypropylene@ - Google Patents

Abstract

A process is claimed for the prodn. of expanded sheet from a propylene-contg. polymer, which is melted with nucleating agent (NA) and opt. other additives in an extruder, treated with a physical blowing agent (BA) under pressure, cooled to the expansion temp., extruded as expanded (foamed) tube, cooled, cut to form a sheet, drawn off and wound on a spool. The melting of the polymer, mixing with BA and cooling of the gas-loaded melt are carried out in a twin screw extruder with a length of 30-42D (D = screw dia.) contg. equal synchronous parallel screws, the BA is injected at a pressure of less than 20 bar at the end of the inlet/plastification zone (IPZ) which is about 10-15D long, and the BA/polymer mixt. is homogenised to an expandable melt in a mixing zone (MZ) with a length of 3-6D which is connected to the IPZ. Also claimed is an appts. for carrying out this process. Pref. the extruder is supplied with propylene-contg. polymer at such a rate that it is operated in an underfed condition. Pref. propylene-contg. polymer is HMS polypropylene (HMS-PP) with a MFI 230/2.16 of 3-7 g/10 mins. and a tensile strength of 30-40 N/mm<2>, opt. combined with other polyolefin(s). Pref. BA is (iso)pentane, (iso)butane, CO2, N2 or a mixt. thereof (in which case the different components are fed in separately and directly one after the other); pref. BA is (iso)butane or CO2. Pref. NA comprise talcum, citric acid, NaHCO3, SiO2 and/or TiO2. The expanded sheet obtd. has a density of 0.2-0.5 (pref. 0.25-0.4) g/cm<3> and a thickness of 0.1-10 mm, and contains mainly closed, fine and uniform cells with an average dia. of 0.05-0.35 mm.

Description

The invention relates to a method and a device for Production of Foamed Films from a Polymer, containing propylene, which with a physical Propellant and a nucleating agent to a foamable polymer is mixed and the polymer together with the nucleating agent and optionally further additives in an extruder with a feeding and plasticizing zone, Mixed zone and cooling zone and heated with outlet nozzle and is melted, and the polymer melt the blowing agent added under pressure and then the fumigated Polymer melt to a temperature suitable for foaming is cooled and then foaming from the nozzle if necessary emerges as a hose, and the hose Subsequently inside and outside is cooled and then the hose in the longitudinal direction to form a sliced flat film and peeled off and possibly is wound up.

Such methods and devices are known.

For example, EP 0 570 221 A2 describes such Process for producing a foam sheet of polypropylene by means of a tandem extruder, which with a physical blowing agent and a nucleating agent a foamable polymer is mixed and the polymer together with the nucleating agent and optionally further Additives in the first extruder with a feeder and  Plasticizing zone and a mixing zone mixed and is melted, and the polymer melt the blowing agent under high pressure by means of a - 5000 pounds = 2250 kg - High-pressure pump is added and subsequently the fumigated Polymer melt to a temperature suitable for foaming is cooled in the second extruder and then under Foaming from an annular nozzle emerges as a hose, and the tube subsequently inside and outside is cooled and then the hose in the longitudinal direction sliced open and peeled off to form a flat film and possibly wound up.

A disadvantage of this method is the use of two Extruders in the so-called tandem arrangement, in which the first extruder for melting the polymer and the Mixing with the blowing agent and the second extruder for Cooling the foamable melt to one for foaming used at the exit from the ring nozzle suitable temperature becomes. On the one hand, such tandem extruders are special consuming and expensive, on the other hand is their efficiency measured in terms of equipment costs too low to be economical Foamed films, for example for packaging manufacture to be able to. Also appears the quality of the obtained foamed film to be improved, since the obtained Cell diameter is relatively large and the surface of the film too is uneven, for example, to print on the surface allow. Furthermore, the propellant must be sufficiently small To obtain cells, under high pressure of 100 bar and more by means of high-pressure pumps, which have a capacity of more than 300 bar (5000 pounds of pressure) are introduced.

EP 0 520 028 B1 describes the preparation of a foamed sheet of selected HMS polypropylenes below Use of two extruders in tandem. to Achieving certain functions of the obtained film, such as Gas-tightness or the like, the foamed film with one or several functional layers are coated, this both through a corresponding nozzle during manufacture  the foamed sheet as well as by laminating the Foamed film after its production with a separate supplied functional layer can be done. The disadvantage is Here too, the operation of the tandem extruder with high Pressures over 120 bar and the relatively low throughput of 50 Up to 50 kg / h, foamed Polyolefinfolien selected To obtain HMS polypropylene grades with high rigidity.

GB 1,400,494 describes a process for the preparation of foamed webs of a polymer, such as polypropylene Extrusion of the polymer along with a physical Propellants, such as hydrocarbons, from an annular Nozzle in which the web leaving this in an outside and internally cooled annular gap foams. The obtained Foamed web has a nonuniform cell structure leathery outer skins and is so strong inside foamed, that they can easily be divided into two parts with one each smooth outer skin can be torn apart, taking forms a velvet-like structure on the crack surface. such Lanes are therefore only for very specific applications, at suitable for this velvet-like surface.

The object of the invention is to provide a method and a Apparatus for producing foamed films from a Polymer, containing propylene, to create, which is a special have uniform and fine-celled foam structure and themselves therefore especially for further processing by thermoforming, such as deep drawing, vacuum forming are suitable. The known methods should also be simplified in their construction and increased Achievement as previously possible should be achieved to the Production of such foamed films more economical do.

This object is achieved by the method according to the invention the characterizing features of claim 1 solved. A Apparatus for carrying out the method according to the invention is characterized by the features of claim 18.  

Advantageous embodiments of the invention are the Subclaims removable.

According to the invention, a process for the preparation of Foamed films of a polymer containing propylene, proposed in which the melting of the polymer, mixing the polymer melt with the physical blowing agent and Cooling the gassed foamable thus obtained Polymer melt in a twin-screw extruder of a length from 30 to 42 D (D = screw diameter) with same and carried out in the same direction rotating parallel screws and the physical blowing agent becomes smaller with one pressure 20 bar at the end of about 10 to 15 D long intake and Plasticizing zone of the twin-screw extruder into the melted (plasticized) polymer is passed and in which, adjoining the feeder and plasticizing zone Mixing zone with a 3 to 6 D corresponding length of Twin-screw extruder with the molten polymer too a foamable polymer melt is homogenized.

The invention teaches that when such a Twin-screw extruders with the same and in the same direction rotating parallel screws and gassing with propellant at very low pressures, a foamed sheet is obtained, which is particularly uniform and fine-celled foamed and which already has a relatively good smooth and even surface has, which gives the film a pleasant grip and optionally a printing of this surface after the allows known methods.

The inventively proposed twin-screw extruder represents a much simpler structure than the two Tandem extruder, as is the state of the art, and thus reduces the plant costs.

Furthermore, in the interior of the mixing zone of the invention prevails used and designed twin-screw extruder, in the the physical blowing agent is introduced, in contrast  for the tandem extruder a particularly low pressure below 20 bar, preferably below 15 bar, so that the blowing agent with low Pressure below 20 bar, preferably below 15 bar to below 10 bar, such as 3 to 8 bar is initiated and the Conveyor for supplying the physical blowing agent in the method according to the invention only this low pressure must muster. On expensive and wear-prone High pressure pumping systems for the otherwise usual pressures far above 100 bar can thus in the method according to the invention be waived.

Surprisingly, it turns out that despite the interference of the Propellant in the mixing zone at a relatively low pressure a good homogenization takes place and slides with a excellent foaming and fine cell and smooth Surface to be obtained. This is achieved by the invention the particularly intensive mixture of polymer, Nucleating agent and physical blowing agent due to Homogenization and mixing of the blowing agent with achieved in the same direction rotating twin screws.

According to a preferred embodiment of the method of the Twin-screw extruder with such an amount of polymer fed that this is operated underfed. This can the mixing of the polymer with the nucleating agent and intensified the physical blowing agent and thus still a better film result can be achieved.

For the inventive method and the device can Twin screw extruder with screw diameters from 40 to 130 mm, preferably 65 to 125 mm are used. The Feeding and plasticizing zone is in about 10 to 15 D (D = screw diameter of the extruder) corresponding length executed to complete melting of the with the Nucleating agent provided polymer. The inventive method allows by the particular intensive mixing processes in twin-screw extruder, the special mixing zone in which the physical blowing agent in  the polymer melt is introduced, very short, namely about 3 to 6 D perform and still the most fine-celled Structure and good surface quality of the foamed film too receive. At this mixing zone closes at a Total length of about 30 to 42 D of twin screw extruder a sufficiently long section, designed as a cooling zone to the foamable polymer melt when homogenized on a for foaming at the exit from the extruder or the Tempering suitable temperature nozzle.

In a particularly advantageous embodiment of the invention is the polymer in the feeding and plasticizing zone Temperatures heated from 190 to 220 ° C, where it is plasticized and subsequently the physical Blowing agent at the end of this intake and plasticizing zone in the mixing zone into the polymer melt to form a foamable polymer is introduced. The so fumigated Polymer melt is subsequently in the mixing zone and cooling zone well mixed, homogenized, while passing through the cooling zone until its exit from the nozzle on one Temperature level is maintained - cooled - that is one Exit temperature of the gassed polymer melt from the nozzle from about 175 to 195 ° C.

Particularly good results in the production of foamed Films are obtained by the process according to the invention, when used as a high-performance polypropylene Melt strength, usually as HMS polypropylene which uses an MFI (230 ° C, 2.16). from 3 to 7 g / 10 min and a tensile strength of 30 to 40 N / mm² having. Such HMS polypropylene is for example, by the company Himont under the name Himont PF 814 commercially available and for example in the U.S. Patent 4,916,198, U.S. Patents 5,047,446 and 5,047,485. Such HMS polypropylene can be used alone or in admixture with other polyolefins foamed for the production Films are used according to the invention. such HMS polypropylenes are due to their increased melt strength  difficult to process. The inventive method allows an economical processing of such HMS polypropylenes, especially for the production of stiff, Self-supporting foam films, the following also one Thermoforming can be subjected.

Be advantageous to the polymer already in the supply to twin-screw extruder according to the invention nucleating agent added to facilitate the subsequent foaming. Such nucleating agents may be inorganic Nucleating agents such as talc, silicic acid, kaolin and / or Carbonates and sulfates, preferably of alkaline earth metals, such as Sodium bicarbonate, metal oxides, such as titanium dioxide, Antimony trioxide and / or organic compounds, such as Be citric acid. Here are commercial mixtures Of sodium bicarbonate and citric acid gladly used.

As physical blowing agents, in particular (iso) pentane, (Iso) butane, carbon dioxide or nitrogen are used, while it is also possible to use mixtures thereof. The foamed obtained by the process according to the invention In its properties, such as fineness, density, Thickness etc. through the use of several, in particular two different blowing agents are affected. Advantageous these are separated from the polymer melt and immediately one after the other at the end of the infeed and plasticizing zone of the supplied twin-screw extruder according to the invention. It is preferred, the blowing agent at the lowest possible pressure zuzumischen, preferred are pressures below 12 bar.

It was found that when using (iso) butane as the only Propellant a very fine-celled uniform foam low density below 0.4 g / cm³, preferably below 0.32 g / cm³ also obtained with a high inflation ratio up to 1: 3 can be.

When using (iso) pentane is in particular a very fine cellular foam of higher densities above 0.3 g / cm³ at  low inflation ratio or preferably without inflating the obtained extruded films.

When using 100% carbon dioxide as a blowing agent is a uniform fine-celled foam obtained, the fine However, cells are larger in average than those used with Pentane or butane.

The use of carbon dioxide as a propellant in particular manufacturing advantages in terms of plant engineering, because of the incombustibility of carbon dioxide the Safety measures in the operation, for the easily combustible Propellant pentane and butane are required, omitted can. This is a very significant economic Advantage for the manufacturing plants.

According to one proposal of the invention, it is preferable to have a Blending of butane and carbon dioxide as blowing agent use. Preference is given here at least 50 wt .-% Butane used, with the proportions of carbon dioxide between 50 to 10 wt .-% vary. With such mixtures become very fine-cell foams at low density with a large Obtained blow-up ratio that does not collapse.

To produce a foamed film is the foamable Polymer preferably extruded from an annular die and the thus formed tubular tube is after his Escaping from the nozzle inside and / or outside with Cooling air applied. This admission can for example, by blowing. It is also possible the tubular tube by means of appropriate, at the nozzle mounted cooling rings in particular on the inside by means of Cooling contact cooling.

Furthermore, the emerging from the annular nozzle Foamed foil for longitudinal and transverse concealment on the inside be acted upon with compressed air, so that the foamed film is inflated from the inside and the diameter of the  tubular tube is enlarged and the tubular Tube is stretched. The thus inflated tube is subsequently guided over a cooling ring, by means of Contact cooling further cools the tubular tube and calibrated this in its diameter.

The cooling ring is preferably from a temperature control unit by means of the cooling ring flowing water on one kept appropriate temperature. The with the invention Method achievable blow-up ratio, d. H. The relationship from the diameter of the outlet opening of the hose from the annular nozzle to the cooling ring diameter is about 1: 1 to 1: 3, preferably up to 1: 2.2.

After the foamed hose has passed over the cooling ring it has cooled down to temperatures from 140 to 160 ° C that he was to form a shallow Film web continuously along its longitudinal extent can be cut open. Also it is with the method according to the invention, the hose at two, preferably opposite areas cut up so that 2 film webs are formed. The Slicing is still done in a heated state so far the film web, the subsequent flattening to a level track without waves allows.

The film webs thus formed are continuously from deducted a trigger device and can either wound up or inline of a finishing, like one Laminating or thermoforming station to be supplied. In particular, it is with the method according to the invention possible, the film webs after removal in the longitudinal direction the cutting of the film web again up to four times to stretch, for example, by a suitably increased Off speed. Through this stretching, the surface can the foamed sheet can be further improved and Wrinkles are avoided. In particular, the stands out Foamed polypropylene film produced according to the invention  through a pleasant body-friendly grip, d. H. a high degree of comfort due to smoothness and softness.

Such foamed films according to the invention Methods advantageously have densities of about 0.2 to 0.5 g / cm³, preferably about 0.25 to 0.4 g / cc, consist of predominantly closed, fine and even cells with an average cell diameter of 0.05 to 0.35 mm and can be produced in thicknesses of about 0.1 to 10 mm. On The reason for the HMS polypropylenes used is stiff, self-supporting foamed films that are compact compared to Slides of the same material have the advantage of lower Basis weight, the higher comfort as well Have insulating properties with respect to cold / heat.

The produced by the process according to the invention Foamed film is ideal for Further processing by thermoforming, it is z. B. for Deep-drawing of food packaging, such as meat dishes, Ice cream cups, etc. suitable. The according to the invention Method produced foamed sheet, such as HMS-poly propylene, can directly with a suitable functional layer, such as a single or multi-layered compact, d. H. unfoamed film, one or both sides be laminated. Such a compact film can then For example, a layer that is gas and liquid tight is about an EVOH layer for food packaging respectively. Furthermore, the invention is foamed Polypropylene film for use in laminates Insulating properties, trim parts in automotive construction and Construction excellent.

In a particularly advantageous embodiment of the invention is It also suggested that the fumigated foamable Polymer melt inside the annular nozzle before Outlet from the nozzle with at least one compact material is coated. In this way it is possible to completely up laminating the foamed sheet after its formation  to dispense, thereby saving a procedural step and the procedure is simplified. Moreover, it is at an im Inside the annular nozzle coating possible, to change different coating variants quickly because no specially constructed laminating film can be provided got to.

Furthermore, the twin-screw extruder according to the invention offers in the extrusion of foamed sheets of a polymer, containing propylene, a particularly high performance, the ab a screw diameter of 65 mm already at 130 kg / h Screw diameters over 120 mm even over 800 kg / h. A preferred power range is about 250 to 350 kg / h, if twin-screw extruder with a Screw diameter D in the range of 80 to 90 mm used become.

The inventive method is described below with reference to a Embodiment explained in more detail in the drawing. It demonstrate:

Fig. 1 is a side view of an apparatus for performing the method in a schematic representation.

Fig. 2 is a side view of the twin-screw extruder in an enlarged view of FIG. 1.

As shown in Fig. 1, the apparatus for producing foamed polypropylene films comprises a twin-screw extruder 1 with a cylinder with internal same and co-rotating parallel screws, at the outlet end of a preferably annular nozzle 12 is attached. The twin-screw extruder 1 is driven by the drive 2 .

The polymer used for the production of the foamed film, for example an HMS polypropylene, is conveyed from a silo 13 via a feed line E2 to a metering device 3 , in which it is mixed with the nucleating agent and optionally other additives. From the metering device 3 , this mixture passes through the intake opening 11 in the cylinder in the twin-screw extruder. 1

As can also be seen from FIG. 2, from the intake opening 11 of the twin-screw extruder extends a pull-in and plasticizing zone in the working direction A of the twin-screw extruder 1 , which has a length L1 of approximately 10 to 15 D. In this feed and plasticizing zone, the polymer is heated to temperatures of about 190 to 210 ° C and melted and is fully plasticized at the end of the draw-in and plasticizing.

At the end of the intake and plasticizing zone, the physical blowing agent, which is supplied from a conveyor 4 via a line El, is introduced into the polymer melt via an opening 10 in the cylinder of the twin-screw extruder 1 . The thus molten polymer melt is subsequently thoroughly mixed in the adjoining the opening 10 mixing zone M of the twin-screw extruder, which has a length of about 3 to 6 D from the co-rotating screws of twin screw extruder 1 , so that a foamable polymer melt with particularly uniform and fine distribution of the blowing agent is obtained.

In the subsequent to the mixing zone M cooling zone K of the twin screw extruder 1 , the foamable melt is further homogenized and mixed, but it is heated to a suitable temperature for the exit from the nozzle by appropriate cooling of the cylinder of the twin screw in the cooling zone, ie on a temperature of about 175 to 195 ° C at its exit from the annular nozzle 12th The total length L of the twin-screw extruder is preferably 30 to 42 D, with D being preferably selected in the range of 50 to 100 mm.

The foamable melt exits from the annular nozzle 12 as a tubular tube S and is cooled on the outside by a cooling ring 5 by blowing by means of cooling air of ambient temperature about 14-16 ° C.

At the same time, the hose S is inflated by the brought in accordance with arrow B and against the discharge direction of the hose S in the interior of which blown compressed air, ie its diameter increases. Subsequently, the hose S is pulled with its enlarged diameter over a cooling mandrel 6 . The cooling mandrel 6 is flowed through a temperature control unit with a cooling medium, so that the tube S undergoes further cooling on the inside by contact with the cooling mandrel 6 . The blow-up ratio, ie the diameter of the outlet opening of the hose S from the annular nozzle 12 to that of the cooling mandrel 6 , is about 1: 1 to 1: 3.

After the further cooling of the tube S on the outer surfaces of the cooling ring 6 , the tube S has a temperature of about 135 to 160 ° C and is solidified so that it is cut by a cutter 8 , for example knives, at two opposite regions in the longitudinal direction can. In this case, two film webs 9 a, b are formed from the hose S, which are subsequently flattened without problems due to their heat and are pulled off by a take-off device 7 containing a plurality of take-off rollers. From there, the flattened film webs in a manner not shown, either wound or inline a further processing device, such as a laminator for coating the foamed film with a compact film or a thermoforming station supplied.

By a suitable choice of the take-off speed of the take-off device 7 , it is also possible, not yet solidified still lying at a temperature of 135 to 160 ° C film webs 9 a, b in the longitudinal extent to four times, ie in the ratio 1: 1 to 1: 4 to stretch.

For the production of foamed films, which should be coated with a compact film, as may be required for food packaging, the annular nozzle 12 may also be designed as coextrusion to already the fumigated polymer melt before leaving the nozzle 12 with at least one to coat compact material, wherein for the supply of each compact material is advantageously used in each case a further, so-called co-extruder.

It is with the method and the device according to the invention possible, foamed films based on polypropylene, in particular containing HMS polypropylene, which over a particularly uniform and fine-celled structure and are very thermoformable, what follows can be seen in an example.

example

A twin-screw extruder with two equal and co-rotating parallel screws of 85 mm diameter (D) was mixed at a screw speed of 47 min ^-1 with a HMS polypropylene (Himont PF 814) in an amount of 98.6 wt .-% mixed with 0.8 wt .-% talc and 0.4 wt .-% Hydrocerol® Boehringer Ingelheim KG (sodium bicarbonate and citric acid) fed from a metering device with about 250 kg / h.

Within the 15 D long and 220-240 ° C heated feeder and plasticizing zone, the polymer became complete plasticized. At the end of this intake and plasticizing zone were 0.2 wt .-% butane as a physical blowing agent with introduced a pressure of 7 bar in the polymer melt and this fumigated polymer melt in the 4 D long mixing zone mixed.

Subsequently, the fumed polymer melt at the next Mixing to an outlet temperature of about 190 ° C in  the 14 D long cooling zone until it exits the nozzle tempered. The out of the nozzle through an annular Outlet opening of 220 mm diameter emerging foaming hose was inflated in the ratio 1: 2.2 with compressed air of 15 ° C and subsequently via one of a Controlled cooling mandrel controlled at 140 ° C pulled a diameter of 488 mm, the hose at Inflated on the outside by means of cooling air of 15 ° C acted upon has been. After cooling to a temperature of about 140 to 150 ° C, the hose was made of foamed HMS polypropylene cut into film webs, the continuously with a take-off speed of 5.4 m / min. flat and evenly laid, and the following characteristics showed:

Thickness of the film | 2100 μm Density of the film 0.39 g / cm³ average cell diameter 0.08 mm

Overall, the extruded foam sheet was in Longitudinal stretch stretched twice.

This film had a very smooth surface, the one easy printing enabled, and excellent Thermoforming properties.

Claims (22)

A process for the production of foamed sheets of a polymer containing propylene, which is mixed with a physical blowing agent and a nucleating agent to a foamable polymer and the polymer together with the nucleating agent and optionally other additives in an extruder with a feed and plasticizing zone , Mixing zone and cooling zone and is heated and melted with outlet nozzle, and the blowing agent is added to the polymer melt under pressure and then the fumigated polymer melt is cooled to a suitable foaming temperature and then exiting as a hose with foaming from the nozzle, and subsequently inside and outside is cooled and then the tube is cut in the longitudinal direction to form a flat film and peeled off and possibly wound up, characterized in that the melting of the polymer, mixing the polymer melt with the physical Treibmit tel and cooling the gassed foamable polymer melt thus obtained in a twin-screw extruder of length 30 to 42 D (D = screw diameter) is carried out with the same and co-rotating parallel screws and the physical blowing agent with a pressure of less than 20 bar at the end of about 10 to 15 D long feed and plasticizing zone of the twin screw extruder is passed into the molten (plasticized) polymer and is homogenized in the adjoining the plasticizing and plasticizing mixing zone with a 3 to 6 D corresponding length of the twin screw extruder with the molten polymer to form a foamable polymer melt , 2. The method according to claim 1, characterized in that the Twin-screw extruder with such an amount of polymer is fed, that this is operated underfed. 3. The method according to any one of claims 1 or 2, characterized characterized in that as the polymer containing propylene HMS polypropylene with an MFI (230 ° C; 2.16) from 3 to 7 g / 10 min and a tensile strength of 30 to 40 N / mm² alone or in mixture with one or more Polyolefins is used. 4. The method according to any one of claims 1 to 3, characterized characterized in that as a physical blowing agent (Iso) pentane, (iso) butane, carbon dioxide or nitrogen or Mixtures thereof are used. 5. The method according to claim 4, characterized in that at Use of two or more different propellants these separated the polymer melt and immediately be supplied in succession. 6. The method according to claim 5, characterized in that as Propellant (iso) butane and carbon dioxide are fed. 7. The method according to any one of claims 1 to 6, characterized characterized in that as nucleating agent talc, Citric acid, sodium bicarbonate, silicon dioxide, Titanium dioxide or mixtures thereof are used. 8. The method according to any one of claims 1 to 7, characterized characterized in that foams of a density of 0.2 to 0.5 g / cm³, preferably 0.25 to 0.4 g / cm³ produced become. 9. The method according to any one of claims 1 to 8, characterized characterized in that foam foils with predominantly closed, fine and even cells with one  average cell diameter from 0.05 to 0.35 mm getting produced. 10. The method according to any one of claims 1 to 9, characterized characterized in that foamed sheets of a thickness of 0.1 to 10 mm are produced. 11. The method according to any one of claims 1 to 10, characterized characterized in that the melting of the polymer in the Feed and plasticizing zone of the twin-screw extruder at temperatures of the polymer from 190 to 220 ° C. and the polymer melt after the addition of the blowing agent in Passing through the cooling zone maximum on this Temperature level is maintained and the fumigated Foamable polymer melt with a temperature of 175 to 195 ° C emerges from the annular nozzle. 12. The method according to any one of claims 1 to 11, characterized characterized in that the from the annular nozzle exiting hose inside and / or outside with Cooling air and pressurized inside to a Blowing ratio of 1: 1 to 1: 3, preferably to 1: 2.2 to achieve and after inflating the hose calibrated on the inside by means of a cooling mandrel and is cooled by a contact. 13. The method according to any one of claims 1 to 12, characterized characterized in that emerging from the nozzle tubular hose immediately thereafter inside and / or outside via a cooling ring for Contact cooling is performed. 14. The method according to any one of claims 1 to 13, characterized characterized in that the tubular tube during removal from the nozzle in the longitudinal direction by a factor of 4 is stretched.   15. The method according to any one of claims 1 to 14, characterized characterized in that the fumigated foamable Polymer melt within the annular nozzle before Exit from the nozzle with at least one compact (not foamed) material is coated. 16. The method according to any one of claims 1 to 15, characterized characterized in that the hose to a temperature of Cooled to 135 to 155 ° C and cut in this state and laid flat. 17. The method according to any one of claims 1 to 16, characterized characterized in that after cutting the hose the flattened film web with a on or multilayer compact film on one or both sides is laminated. 18. Apparatus for producing foamed films a polymer containing propylene which is substituted with a physical blowing agent and a nucleating agent a foamable polymer is mixed, containing an extruder with a feeding and plasticizing zone, Mixing zone and cooling zone in which the polymer together with the nucleating agent and optionally other additives is melted and the polymer melt the Propellant added under pressure and subsequently the fumigated polymer melt on a suitable for foaming Temperature is cooled, a conveyor for Feeding the physical blowing agent into the extruder, an annular nozzle located at the exit end of the extruder is arranged to the foamable polymer melt to form a foamed tubular tube, at least one cooling mandrel over which the foamed tubular tube is pulled and by means of blowing with Cooling air is cooled, a cutting device for Cutting the hose lengthwise to form a foamed sheet and a trigger device for stripping and possibly winding the foamed film,  characterized in that as an extruder for melting of the polymer, mixing the polymer melt with the physical blowing agent and cooling the thus obtained foamable polymer melt a twin-screw extruder a length of 30 to 42 D with the same and in the same direction rotating parallel augers is provided and the physical blowing agent from the conveyor with a pressure less than 20 bar at the end of about 10 to 15 D long intake and plasticizing zone of the Twin screw extruder into the molten one (plasticized) polymer is introduced and in the, itself adjoining the intake and plasticizing zone Mixing zone with a 3 to 6 D corresponding length of Twin-screw extruder with the molten polymer is miscible to a foamable polymer melt. 19. The apparatus according to claim 18, characterized in that as annular nozzle, a coextrusion die for coating the fumigated polymer melt within the nozzle with at least one compact (non-foamed) material is provided, wherein for the supply of each compact Material in the coextrusion each one more Extruder is provided. 20. Device according to one of claims 18 or 19, characterized characterized in that an annular nozzle with a thereto on the outside and / or inside arranged cooling ring purpose Contact cooling of emerging from the annular nozzle tubular hose is provided. 21. Device according to one of claims 18 to 20, characterized characterized in that a twin-screw extruder with a Length (L) from 30 to 42 D with a feeder and Plasticizing zone of a length of 10 to 15 D and a Mixing zone with a length of 3 to 6 D and a cooling zone with a length of 24 to 10 D for the processing of Polypropylene with high melt strength with an MFI (230 ° C, 2.16) from 3 to 7 g / 10 min and one  Tensile strength of 30 to 40 N / mm² to foamed sheets with a density of 0.2 to 0.5 g / cm³ and a thickness of 0.1 is provided to 10 mm. 22. Device according to one of claims 18 to 21, characterized characterized in that in the transition region from the intake and plasticizing zone to the mixing zone two Feeders each with a delivery pressure below 20 bar are provided for propellant.