WO2011098080A2

WO2011098080A2 - Method and arrangement for changing a plastic film

Info

Publication number: WO2011098080A2
Application number: PCT/DE2011/050003
Authority: WO
Inventors: Mario Schubert
Original assignee: Beuth Hochschule Für Technik Berlin
Priority date: 2010-02-09
Filing date: 2011-02-07
Publication date: 2011-08-18
Also published as: WO2011098080A3; DE102010007692A1

Abstract

The invention relates, inter alia, to a method for changing a plastic film (20). According to the invention, the plastic film is irradiated with electromagnetic radiation (M1, M2) and thereby the polymer structure of the plastic film - at least at the film surface - and at least one film property of the plastic film are changed by the electromagnetic radiation.

Description

description

The invention relates to a method for changing a plastic film. Such a method is known from European Patent Application EP 1 396 316 A2. In this prior art method perforation holes are baked in a plastic film by means of infrared radiation.

The invention has for its object to provide a method by which a plastic film can be changed very easily in terms of their properties. This object is achieved by a method having the features according to claim 1. Advantageous embodiments of the method are specified in subclaims. According to the invention, it is provided according to the invention that the plastic film is irradiated with electromagnetic radiation, thereby changing the polymer structure of the plastic film, at least on the film surface, and at least one film property of the plastic film, by the electromagnetic radiation.

The invention makes use, inter alia, on the recognition zunut ^¬ ze that the presence in a plastic film of poly ^¬ merstruktur or the molecular chains contained therein can be excited by electromagnetic radiation to oscillate and thereby the polymer structure or the arrangement of the polymer chains or molecular structure non-destructively permanently can change. For example, the perma- fabric film, in particular the sorption, the diffusion ^¬ and / or the desorption property of the plastic film dau ^¬ erhaft be modified, depending on the polymer structure and the excitation, which has triggered the swing. A change in the sorption and desorption can be caused for example by a radiation-induced change in the pore size at the surface of the plastic film.

The degree of crystallization of the plastic film can also be changed in a targeted manner: With semicrystalline plastics, the degree of crystallization will generally increase due to spherulites (folding crystals) and, as a rule, in the case of highly crystalline plastics due to recrystallization. In amorphous plastics, the morphology changes due to disorientation of the molecules. A change in the degree of crystallization and / or the orientation of the Mole ^¬ molecules usually changes diffusion property of art ^¬ material film. A significant advantage of the method according to the invention is that it can be carried out without much effort and with commercially available devices. The process therefore can be readily used, for example in the Verpa ^¬ ckungsindustrie to permeability, the permeability or Unalloyed, in particular, the gas permeability or

Gas impermeability of films or their GTR value (GTR: Gas Transmission Rate), to modify.

The method can be carried out with electromagnetic radiation of different wavelengths, for example with infrared radiation, visible radiation, X-radiation or gamma radiation; However, the use of microwaves, preferably in the frequency range, is particularly advantageous at 2.4 GHz. Because of their molecular structure, plastic films very simply absorb water and incorporate it into their molecular structure, so that the use of microwaves results in a particularly high degree of efficiency in the modification of the property or properties of the plastic film.

According to a particularly preferred embodiment of the method is provided that the irradiation of the plastic film takes place in an atmosphere in which at least one chemically active substance is contained, which is suitable in the

Plastic film penetrate and chemically alter the polymer structure of the plastic film at least on the film surface - ie only on the film surface or along the entire film thickness. In this advantageous embodiment of the method, a synergistic effect is exploited: So ^¬ probably electromagnetic radiation and chemically active substances are each in a position to change the natural sheep ^¬ th a plastic film permanently, but in combination this is achieved more quickly and efficiently , This is because - as already explained above - there is a swinging of the polymer molecules of the plastic film by the use of electromagnetic radiation. The oscillation causes local density fluctuations or local fluctuations of the volume between adjacent molecular chains, so that the penetration of chemically active substances into the polymer structure is simplified or assisted. In other words, the efficacy and the chemical activity of the chemically active substances is increased by the parallel or simultaneous exposure to electromagnetic radiation by a multiple and the efficiency of the process ent ^¬ speaking. The chemical activity of the chemically active substances can for example be based solely on incorporation of the substances within the polymer structure, without the polymer chains of the polymer structure having to be chemically altered as such.

The irradiation of the plastic film is preferably carried out in an atmosphere containing an aerosol in which at least one chemically active substance is contained in droplet form. A droplet treatment of the plastic film shows a ^¬ be Sonders great efficiency. Alternatively or additionally, during the irradiation of the plastic film, the atmosphere may contain vapor in which one or more chemically active substances are contained in droplet form or in particulate form.

Irradiation of the plastic film can, for example in an atmosphere in which one or more surface-active substances are mixed ^¬ hold corresponds in gaseous state.

A further increase in the process efficiency can be achieved in an advantageous manner if the irradiation of the plastic film is carried out in an overpressure atmosphere. In the event of excess pressure atmosphere, the chemically active substances can more easily and more quickly penetrate located within the polymer structure cavities whose size by irradiating the plastic film with electromagnetic ^¬ shear radiation and caused thereby swinging of the molecular chains is increased.

With a view to increasing efficiency, it is also considered advantageous if the plastic film is is charged electrostatically. An electrostatic charge interacts with the chemically active substances or substances and can further accelerate their penetration into the polymer structure.

The method described can be used, for example, to modify the surface properties of a plastic film so that a subsequent coating of the film (for example as part of a printing process) adheres better than before. This can be achieved particularly easily if during the irradiation chemically active substances are used which are surface-active or surface-active. The invention also relates to a device for changing a plastic film. According to the invention, it is provided with respect to such a device that it has an electromagnetically shielded housing with an irradiation area therein and at least one radiation source for generating electromagnetic radiation, wherein the housing has an entry slot for introducing the synthetic material film and an exit slot for carrying out the plastic film. With regard to the advantages of the device according to the invention, reference is made to the advantages of the method according to the invention, since the advantages of the device according to the invention essentially correspond to those of the method according to the invention. According to a particularly preferred embodiment of the device it is provided that the inlet slot and / or the outlet slot is sealed by a sealing roller pair with two rotatably mounted sealing rollers. This allows it in a particularly simple way to generate an overpressure in the housing and to accelerate the penetration of the chemically active substances in the plastic film. The distance between the two sealing rollers is preferably adjustable in order to allow optimal sealing even with different thicknesses of film. The sealing rollers can be, for example, han ^¬ spindles are soft and conductive foam rollers.

The sealing rollers are preferably electrically insulated from the housing; this allows namely, electrostatically charge the Art ^¬ material film outside the housing and charged introduce into the housing. As already mentioned, chemically active substances act particularly quickly and efficiently on electrostatically charged plastic film.

A seal between the housing and the sealing rollers can be achieved in a particularly simple and advantageous manner with electrically insulating sealing brushes, which bear against the sealing rollers and bring about electrical insulation of the sealing rollers relative to the housing. The electrically insulating sealing brushes are preferably held at one end of the brush by the housing and preferably abut with their other brush end to the respectively associated sealing roller. Site at ^¬ or can brush seal in addition, an electrically insulating tape, in particular an electrically isolie ^¬ rendes rubber band may be employed.

According to a further particularly preferred embodiment of the device is provided that it has at least two feed points, where electromagnetic radiation is discharged, wherein one of the at least two Einspeisestel ^¬ len is arranged below the processing slot formed by the entry slot and the exit slot and emits electromagnetic radiation towards the processing plane upwards and wherein the other of the at least two feed points is arranged above the processing plane and electromagnetic radiation in the direction ^¬ machining processing level radiates down. In this embodiment, a two-sided processing of the plastic film in a particularly simple manner possible.

The two feed-in points can be fed by the same generator. Alternatively, the two feed points are each fed by an individual generator.

An electrostatic charging is preferably arranged in front of the entrance slit which is suitable to electrically charge the art ^¬ material film prior to entry into the electromagnetically shielded housing. Charging in particular increases the effectiveness of chemically active substances in the atmosphere in the housing.

It is also considered advantageous if at least two transport devices are arranged in the housing which are suitable for transporting a film along the predetermined transport direction extending from the entry slot to the exit slot. One of the transport devices is preferably arranged in front of the irradiation area, viewed along the transport direction, and the other transport device, viewed along the transport direction, is preferably arranged behind the irradiation area. Preferably, the transport speeds of the two transport devices are set differently and the two transport devices are adapted to effect an extension of the plastic film along the conveying direction. Such stretching can take place in the longitudinal direction as well as in the transverse direction, for example by the use of

Drill rollers at or in the two transport devices.

It is also considered advantageous if the device has a cooling device arranged behind the outlet slit, as seen along the conveying direction, and which is suitable for cooling foil emerging from the housing. As mentioned above, plastic films are what ^¬ serhaltig generally, making it the while irradiating the plastic film with electromagnetic radiation to a heating

Plastic films can come. A cooling of the plastic film immediately after the radiation treatment particularly well preserves the property change of the plastic film caused by the rays and / or the chemical substances.

The cooling device can take, for example, an air shower to ^¬ which is suitable for directing cooling air onto the film, thereby cooling the film is effected.

Alternatively or additionally, the device may have a discharging device arranged behind the outlet slit, as viewed along the conveying direction, which is suitable for electrostatically discharging the electrostatically charged film emerging from the housing.

Alternatively or additionally, the device may be located behind the outlet, viewed along the direction of conveyance. Slit disposed thickness measuring device, which is adapted to measure the thickness of the exiting the housing film. Measured values of such a thickness measuring device can be advantageously used for process control.

Alternatively or additionally, the device may have a thickness measuring device arranged in the housing, which is suitable for measuring the thickness of the film located in the irradiation area. Measured values of such thickness measuring device ^¬ can be used advantageously also for process control.

Alternatively or additionally, a temperature tower measuring device which is suitable for measuring the temperature of the film in the irradiation area can be arranged in the housing.

As mentioned above, the housing of the device preference ^¬ example is sealed such that gauge pressure can build up inside the housing a Ü.

It is regarded as advantageous, if the housing least has to ^¬ a feed point through which can be at ^¬ least one chemically active substance into the housing interior single feed, which is suitable einzu in plastic film ^¬ penetrate and the polymer structure of the plastic film at least to chemically change at the film surface.

The device preferably also has an evaporation device which is suitable for forming an aerosol or a vapor with at least one chemically active substance, which is suitable for penetrating into plastic film and the polymer. Merstruktur the plastic film to change chemically at least on the film surface.

The invention further relates to an arrangement with at least two devices, as described above, wherein the devices - as seen along the transport direction of the plastic film - are arranged one behind the other and emerging from the exit slot of an upstream device plastic film directly or indirectly in the Entry slot of a downstream device is fed. Such a cascaded arrangement makes it possible, for example, to use successively chemically active substances which are incompatible with one another, for example because they react with one another and therefore can not be used simultaneously in the same apparatus.

The invention will be explained in more detail with reference to a Ausführungsbei ^¬ game; show it

Figure 1 shows an embodiment of a device for

Modifying a plastic film, which is explained by way of example with reference to this embodiment, the inventive ^¬ inventive method, and

Figure 2 shows another embodiment of a pre ^¬ direction for changing a plastic film.

FIG. 1 shows a device 10 for changing at least one property of a plastic film 20, which is passed through the device 10 along a conveying direction B and wound on a downstream take-up roll 30. With the device 10 can be the Polymer structure and thus permanently change, for example, the permeability of the plastic film 20.

The device 10 comprises an electrostatic charging device 40, which is arranged at the input of the device 10. The electric charging device 40 - as seen along the conveying direction B of the plastic film 20 - downstream is an electromagnetically shielded housing 50 to which an evaporation device 60 is connected. Downstream of the housing 50 are a thickness measuring device 70, a cooling device 80 and a discharge device 90.

The electrostatic charging device 40 is equipped with electrically conductive brushes 100, which rest on the plastic film 20 and lead to an electrostatic charge of the plastic film 20 when appropriately charged with an electrical potential.

The electromagnetically shielded housing 50 is equipped with two radiation sources 110 and 120, each formed by a microwave generator. The upper radiation source 110 in FIG. 1 generates a microwave radiation, which is identified by an arrow with the reference symbol M1. The microwave radiation M 1 is radiated from the feed point 130 of the radiation source 110 downwards and thus onto the upper side of the plastic film 20.

The bottom in the figure 1 radiation source 120 generates micro-wave radiation ^¬ M2 to that of the feed point 140

Radiation source 120 is radiated upward and hits the bottom of the plastic film 20. In FIG. 1, moreover, two transport devices 200 and 210 can be recognized, which can transport the plastic film 20 along the conveying direction B. The transport speed of the two transport devices 200 and 210 can provide a ^¬ preferably individually thereby, so that is possible to achieve stretching or compression of the plastic film 20 during the transport through the irradiation area SB. The transport device 200 is preferably arranged in front of the irradiation area SB, viewed in the direction of conveyance B; The transport ^device 210 is preferably located behind the ^{irradiation area} SB.

In addition, it can be seen in FIG. 1 that the entry slot E50 of the housing 50 is sealed with a sealing roller pair which comprises two rotatably mounted sealing rollers 300 and 310. The two sealing rollers 300 and 310 drü ^¬ CKEN to the plastic film 20, and thus effect a seal of the housing interior of the housing 50 from the external environment.

Since, as already mentioned, the plastic film 20 is preferably electrostatically charged by the electrostatic charging device 40 or its brushes 100, the two sealing rollers 300 and 310 are preferably electrically insulated from the housing 50. For this purpose, can ^¬ example, electrically insulating sealing brush 320 may be provided, which are held by the housing 50 and to the

Sealing rollers 300 and 310 abut.

Also, the exit slot A50 of the housing 50 is isolated in corre ^¬ sponding manner. So he also has a sealing roller pair with two rotatably mounted sealing rollers 300 and 310, the Press on the plastic film 20 and thus the Ge ^¬ housing 50 seal. Also, the two sealing rollers 300 and 310 in the area of the outlet slot A50 are electrically insulated from Ge ^¬ housing 50 by corresponding sealing brushes 320th

In order to measure the temperature of the plastic film 20 during the treatmen ^¬ development within the housing 50, inner ^¬ half of the housing 50 is preferably provided a temperature sensor 400, the rarotstrahlung the Inf- generated by the plastic film 20 IR measures and with this to the temperature the plastic film 20 closes to form a corresponding measurement ^¬ value.

The device 10 according to FIG. 1 can be operated, for example, as follows:

First, the evaporator 60 forms an aerosol or vapor containing at least one chemically active substance capable of penetrating into the plastic film 20 and chemically altering the polymer structure of the plastic film. Such a change of the plastic film 20 can he ^¬ summarize the entire layer thickness of the plastic film or alternatively limited only to the film surface of the plastic film 20. Suitable chemically active substances which are suitable for changing the polymer structure of the plastic film 20 are, for example:

- antistatic agents,

anionogenic / anionic, cationogenic / cationic or iniogenic polymer sequences, and

- Antiseptic substances, such as ZnO particles.

The aerosol formed by the evaporation device 60 or the vapor formed by the evaporation device 60 reaches the feed point 150 of the housing 50 and thus also in the irradiation area SB, which is arranged between the two radiation sources 110 and 120. With the two radiation sources 110 and 120 is electromag netic radiation ^¬, in the form of microwave radiation Ml and M2, is generated and directed to the plastic film 20th The microwave radiation M1 and M2 causes the atoms or molecules in the polymer structure of the plastic film 20 to vibrate, thereby changing the space or the distance between the molecules within the polymer structure. This made it ^¬ light of the or the chemically active substances, which are fed from the evaporation device 60 in the housing 50, einzudrin- into the polymeric structure of the plastic film and to modify this gene completely or only in the surface region permanently. The effect or the Oberflächenakti ^¬ tivity of the chemically active substances, which are fed by the evaporation device 60 is, by the microwave radiation Ml and M2 - thus greatly enhanced - and by the hervorgeru- characterized fene molecule swing.

In order to further increase the influence of the microwave radiation M 1 and M 2 and the influence of the chemically active substances, the plastic film 20 can be mechanically acted upon by the two transport devices 200 and 210. In ^¬ example, it is possible to stretch the plastic film 20 along the conveying direction B or to compress. In addition, it is possible to stretch the plastic film 20 in width and thus cause a biaxial orientation of the polymer molecules in the plastic film 20. Stretching the plastic film 20 in the width ^¬ example, by drill rolls possible in the two transport means 200 and 210 are arranged or alternatively form the transport devices 200 and 210 alone.

After the plastic film in the housing 50 with the aid of microwave radiation Ml and M2 as well as the chemically active substances in the atmosphere within the housing 50 has been behan ^¬ delt 20, it enters to the thickness measuring device 70, with the resulting post-treatment thickness of the

Plastic film 20 is measured. Such a measurement makes it possible to optimally control the process run, in particular the mode of operation of the transport devices 200 and 210.

Since in plastic films usually - chemically conditioned - water is stored, which is heated by microwave radiation, the emerging from the housing 50 plastic film 20 is preferably cooled with the cooling device 80 before it is discharged electrostatically with the discharge device 90 and finally wound on the take-up roll 30 , The method described in connection with FIG. 1 assumes, for example, that radiation generators 110 and 120 use microwave generators which generate microwave beams M1 and M2 on the output side. Alternatively or additionally, radiation sources can be used, the output side other types of electromagnetic

Generate radiation, such as infrared radiation, X-rays or gamma rays.

In addition, it is possible to generate an overpressure with the evaporation device 60 in the housing 50 in order to accelerate the action of the chemically active substances on the plastic film 20. A positive pressure within the Gehäu ^¬ ses 50 is in the embodiment according to Figure 1 by allows the sealing rollers 300 and 310, which seal the entrance ^¬ slot E50 and the exit slot A50 of the housing 50 and thus allow within the housing 50, a higher pressure than the ambient pressure.

2 shows another embodiment of a device 10 for changing a plastic film 20. The device 10 according to FIG. 2 corresponds to the device 10 according to FIG. 1, only the sealing brushes 320 are replaced by electrically insulating sealing strips 320 '.

Reference sign list

10 device

20 plastic film

30 take-up roll

40 charging device

50 housings

60 evaporation device

70 thickness measuring device

80 cooling device

90 discharge device

100 brushes

110 radiation source

120 radiation source

130 feed-in point

140 feed-in point

200 transport device

210 transport device

300 sealing roller

310 sealing roll

320 sealing brushes

320 'sealing tape

400 temperature sensor

A50 exit slot

B Carriage

BE processing level

E50 entry slot

150 feed-in point

IR infrared radiation

Ml microwave radiation

M2 microwave beam

SB irradiation area

Claims

claims

A method of modifying a plastic film (20), characterized in that

- The plastic film with electromagnetic radiation (Ml, M2) irradiated and

characterized the polymeric structure of the plastic film - is changed by the electromagnetic radiation and at least one see films ^¬ property of the plastic film - at least at the film surface.

2. The method according to claim 1,

characterized in that

the plastic film (20) is stretched and irradiating the plastic film in a hyperbaric atmosphere Runaway ^¬ leads is in the at least one chemically active substance is contained which is capable of penetrating in the plastic film, and

the at least one chemically active substance is incorporated in the poly ^¬ merstruktur the plastic film (20) where ^¬ by the polymeric structure of the plastic film - is altered and at least one intrinsic film ^¬ shank of the plastic film - at least at the film surface.

3. The method according to claim 2,

characterized in that

the polymer chains of the polymer structure of the plastic film remain unchanged due to the incorporation of the chemical substance.

4. The method according to any one of the preceding claims, characterized in that he ^¬ follows irradiating the plastic film in an atmosphere in which at least one chemically active substance is contained ^¬ th, which is suitable einzudrin ^¬ gene in the plastic film and to change the polymer structure of the plastic film at least at the film surface chemically.

5. The method according to any one of the preceding claims,

characterized in that

the irradiation of the plastic film in a Überdruckatmo- sphere is performed.

6. The method according to any one of the preceding claims,

characterized in that

The plastic film is electrostatically charged before the irradiation.

7. The method according to any one of the preceding claims,

characterized in that

the plastic film is at least irradiated with microwave radiation.

8. Device (10) for changing a plastic film (20), characterized by

an electromagnetically shielded housing (50) having therein an irradiation area (SB) and

at least one radiation source (110, 120) for generating electromagnetic radiation (M1, M2),

wherein the housing has an entrance slot (E50) for inserting the plastic film and an exit slot (A50) for discharging the plastic film.

9. Apparatus according to claim 8,

characterized in that the entry slot and / or the exit slot is sealed by a sealing roller pair with two rotatably mounted sealing rollers (300, 310).

10. Apparatus according to claim 9,

characterized in that

the sealing rollers are electrically insulated from the housing.

11. Device according to one of the preceding claims 8-10, characterized in that

the device has at least two feed points (130, 140) at which electromagnetic radiation is emitted,

wherein one of the at least two feed points (140) un ^¬ terhalb of the working plane formed by the entrance slit and the exit slit (BE) and emits electromagnetic radiation in the direction of machining ^¬ planar upwardly and

wherein the other of the at least two feed points (130) is arranged above the working ^plane and emits electromagnetic radiation in the direction of the working plane downwards.

12. Device according to one of the preceding claims 8-11, characterized in that

in the housing at least two transport devices (200, 210) are arranged, which are suitable, a film along a predetermined, extending from the entrance slot to the exit slot conveying direction

(B) to carry

wherein one of the transport devices - seen in the direction of transport - before the Be radiation area and the other transport device - viewed along the direction of transport - is arranged behind the irradiation area.