JP2012233038A - Surface-modified fluororesin film, method for manufacturing the same, apparatus for manufacturing the same, composite body including surface-modified fluororesin film, method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-modified fluororesin film having a high adhesive strength between a fluororesin film and an adherent and keeping a modification effect of the fluororesin film for a long period of time, a method for manufacturing the same, an apparatus for manufacturing the same, a composite body including the surface-modified fluororesin film, and a method for manufacturing the same.SOLUTION: In the surface-modified fluororesin film having a plasma-monomer polymerization layer (16) on at least one surface of the fluororesin film layer (15), the plasma-monomer polymerization layer (16) is a uniform thin film layer wherein a monomer including a reactive unsaturated group is graft-polymerized under a condition that the electric charge electrified on the fluororesin film layer is removed while plasma is irradiated. When an adherent (17) is stuck on the plasma-monomer polymerization layer (16), and the fluororesin film layer (15) and the adherent (17) are released, the upper part than the plasma-monomer polymerization layer (16) is broken.

Description

  The present invention relates to a surface-modified fluororesin film, a production method thereof, a production apparatus thereof, a composite including the surface-modified fluororesin film, and a production method thereof.

  In addition to being excellent in chemical stability and thermal stability, the fluororesin has characteristics such as a low friction coefficient because of its self-lubricating property. However, because of the chemical stability of fluororesins, it is difficult to laminate a sheet or film-like material to other materials with an adhesive. For example, to a stopper of a pharmaceutical container that can make use of chemical stability. The use of was not widespread.

  On the other hand, various methods for modifying the surface of a fluororesin molding have been proposed in order to allow the fluororesin to adhere to other materials with an adhesive. The most widely used surface modification method includes sodium-ammonia solution treatment. According to this method, it is known that the surface is chemically almost completely modified to allow adhesion to other materials. However, this modification makes the surface of the fluororesin brownish, which is not preferable in appearance. In addition, there is a possibility that metallic sodium may remain on the film, and in the case of medical rubber products that require strict quality control in particular, it may be an obstacle for foreign matter inspection, etc. Is required.

  The sodium-ammonia solution treatment is a chemical modification method, but a technique for modifying the surface of a fluororesin film using a physicochemical method has been studied. For example, Patent Document 1 discloses that when plasma treatment is performed, a negative voltage is applied to the surface of the molded product to inject physical ions into the surface of the molded product to roughen the surface. A modification method is described in which a chemical modification is performed by substituting the fluorine atom with another atom, and a silane coupling agent is applied after the plasma treatment. Patent Document 2 describes a modification method by changing the atomic composition of the surface of the fluororesin by ion implantation and forming fine protrusions on the surface. In addition, some of the present inventors have proposed vapor phase polymerization of monomers while irradiating plasma on the fluororesin surface in Patent Document 3 and Patent Document 4.

JP 2009-263529 A JP 2000-017091 A JP 2008-019393 A JP 2009-167323 A

  In the method of hydrophilizing by substituting the atoms on the inert surface with other atoms by plasma treatment as disclosed in Patent Document 1, the treated surface (modified surface) sinks inside the resin due to the thermal fluctuation of the polymer. It is known that there is a problem in the durability of the surface modification effect (hydrophilicity) due to factors such as liberation of the generated hydrophilic low molecular weight substance. Although a step of applying an adhesive layer of a silane coupling agent after plasma treatment is also described, it is necessary to apply the coating before the modification effect disappears, which is not preferable as a step. In addition, compared with general plasma processing, an apparatus for applying a negative voltage is required, and thus the equipment cost is high, which is not preferable. The modification by the ion implantation method disclosed in Patent Document 2 complicates a device for obtaining high-energy ions, and a high vacuum for injecting high-energy ions into a workpiece. Due to the necessity of performing the treatment in a moderate atmosphere, the equipment cost becomes high, and improvement has been desired. In addition, the conventional method has a problem that the adhesive strength between the fluororesin film and the rubber is low. Moreover, although the proposal of patent document 3 and patent document 4 improves peeling strength, there exists a problem in the charge charge of the film surface, and uniform thin film formation and higher adhesive strength were requested | required.

  In order to solve the above-described conventional problems, the present invention provides a surface-modified fluorine that can form a uniform thin film, has high adhesive strength between the fluororesin film and the adherend, and has a long-lasting modification effect of the fluororesin film. Provided are a resin film, a production method thereof, a production apparatus thereof, a composite including a surface-modified fluororesin film, and a production method thereof.

  The surface-modified fluororesin film of the present invention is a surface-modified fluororesin film having a plasma-monomer polymerization layer on at least one surface of the fluororesin film layer, wherein the plasma-monomer polymerization layer is irradiated with plasma. It is a uniform thin film layer obtained by graft polymerization of a monomer containing a reactive unsaturated group in a state in which a charge charged on the fluororesin film layer is removed.

  The method for producing the surface-modified fluororesin film of the present invention is a method for producing the surface-modified fluororesin film by forming a monomer polymerization layer on at least one surface of the fluororesin film layer in a chamber, A fluororesin film is placed on the electrical conductor sheet, and the fluororesin is in a state in which a voltage is applied between the plasma irradiation means and the electrical conductor sheet in a state where electric charges charged on the fluororesin film layer are removed. A monomer containing a reactive unsaturated bond group is supplied while irradiating the surface of the film with plasma, and the monomer is graft-polymerized on the surface of the fluororesin film to form a uniform thin film layer.

  The apparatus for producing a surface-modified fluororesin film of the present invention is an apparatus for producing the surface-modified fluororesin film by forming a monomer polymerization layer on at least one surface of the fluororesin film layer in a chamber, An electric conductor sheet for placing a fluororesin film and removing the charge charged on the fluororesin film layer; means for supplying a monomer containing a reactive unsaturated bond group in the chamber; and a surface of the fluororesin film And a plasma irradiation means for polymerizing the monomer, and means for applying a voltage between the plasma irradiation means and the electric conductor sheet.

  The composite including the surface-modified fluororesin film of the present invention is a composite in which an adherend is adhered directly or via an adhesive layer on the surface-modified fluororesin film, When the film and the adherend are peeled off, the film is broken at a portion above the surface-modified fluororesin film.

The method for producing a composite including the surface-modified fluororesin film of the present invention is a method for producing a composite in which rubber is directly vulcanized and molded on the surface-modified fluororesin film. The rubber material is vulcanized and molded on the film under the conditions of a heating temperature of 130 to 180 ° C. and a processing time of 5 to 20 minutes.

  According to the present invention, a surface-modified fluororesin film having a uniform thin film formation and high adhesive strength can be provided by removing the charge on the surface of the fluororesin film when forming a thin film. More specifically, when the adherend is adhered to the surface-modified fluororesin film directly or via an adhesive layer, and the fluororesin film layer and the adherend are peeled off, the plasma-monomer polymerization layer is above the surface. It is possible to provide a surface-modified fluororesin film that has high adhesive strength to such an extent that it can be partially broken, can be uniformly adhered, and can maintain the modification effect of the fluororesin film for a long period of time. That is, the resin layer formed by the plasma polymerization method can provide a uniformly and firmly bonded composite, and the modified layer is stable, so that a long-term inventory is possible.

1A and 1B are cross-sectional views showing a fracture portion after a peeling test of a composite in one embodiment of the present invention. 2A to D show a basic pattern of destruction in the destructive inspection, FIG. 2A is an adhesive cohesive failure, FIG. 2B is an adhesive failure (interface failure), and FIG. 2C is a material failure (base material destruction, adherend) Destruction), FIG. 2D is an example of mixed destruction. FIG. 3A is a schematic cross-sectional view of a composite including a modified film and rubber in one example of the present invention, and FIG. 3B is a cross-sectional view showing a fracture portion after the peeling test. 4A and 4B are cross-sectional views showing a peeling test method in one embodiment of the present invention. FIG. 5 is a schematic explanatory view of a plasma polymerization apparatus in one embodiment of the present invention. FIG. 6 is a schematic cross-sectional view showing the main part of the apparatus in one embodiment of the present invention. FIG. 7A is a photograph of the composite obtained in the comparative example of the present invention, and FIG. 7B is a photograph of the composite obtained in one example of the present invention. FIG. 8 is a graph showing the results of a peel test for the composite in one example of the present invention. 9A-C are the results of analysis by the ATR method using a Fourier transform infrared spectroscopy (FTIR) measuring apparatus showing the destruction phenomenon between the rubber and the fluororesin film in Example 1 of the present invention, and FIG. 9A is the transmission of the fluororesin surface. 9B shows the reflection spectrum of the release surface of the fluororesin, and FIG. 9C shows the transmission spectrum of the rubber surface. FIG. 10 shows the results of the evaluation of the adhesion between the modified film and the rubber when the vulcanization temperature and the treatment time are changed in Example 3 and Comparative Example 2 (conditions of Patent Document 4) of the present invention. FIG. 11 is a view showing a medical rubber product used for a prefilled syringe in one embodiment of the present invention. FIG. 12 is a perspective view of a medical rubber product in one embodiment of the present invention. FIG. 13 is a sectional view of a medical rubber product in one embodiment of the present invention.

  In the composite of the present invention, the fluororesin film layer, the plasma-monomer polymerization layer formed on at least one surface of the film layer, and the adherend are bonded directly or via an adhesive layer on the monomer polymerization layer. When the fluororesin film layer and the adherend are peeled off, the portion above the plasma-monomer polymerization layer is broken. This will be described with reference to the drawings. FIG. 1A shows a broken state of the composite of one embodiment of the present invention. The composite 10 has a fluororesin film layer 1, a plasma-monomer polymerization layer 2 formed on the surface thereof, and an adherend (3a, 3b) directly adhered thereto. When peeled off, material destruction occurs at the parts (3a, 3b) of the adherend. 4 is a destruction part. FIG. 1B shows another broken state, in which the composite 10 is deposited through the fluororesin film layer 1, the plasma-monomer polymerization layer 2 formed on the surface thereof, and the adhesive layer (5a, 5b) thereon. The material 6 is bonded. When the fluororesin film layer and the adherend are peeled off, adhesive breakage occurs at the adhesive layer (5a, 5b). 4 is a destruction part. As shown in FIGS. 1A and 1B, the composite of the present invention does not break between the fluororesin film layer 1 and the plasma-monomer polymerization layer 2, but breaks at a portion above the plasma-monomer polymerization layer 2. In the present specification, a layer obtained by polymerizing a monomer by plasma irradiation is referred to as a plasma-monomer polymerization layer.

In the adhesion using an adhesive, when a destructive inspection is performed, it can be generally classified into the following four types of destructive phenomena.
(1) Cohesive failure: The cured adhesive layer is destroyed. Occurs when the strength of the adhesive is lower than the strength of the adherend. For example, as shown in FIG. 2A, the adhesive layers 8a and 8b between the adherend 7 and the adherend 9 are broken. 11 is a destruction part.
(2) Adhesive failure: The interface between the adhesive layer and the adherend is destroyed. Occurs when the adhesion is insufficient. For example, as shown in FIG. 2B, the interface between the adherend 7 and the adhesive layer 8 is broken. Reference numeral 12 denotes a broken portion.
(3) Adhering material destruction: The base material layer (adhering material) itself is destroyed. In this case, the adhesive and the adhesive force have sufficient strength, and this occurs when the strength of the base material layer (the adherend) is weak. For example, as shown in FIG. 2C, the adherends 7a and 7b are broken. 13 is a destruction part.
(4) Mixed breakdown: At least two of the above (1) to (3) are mixed. For example, as shown in FIG. 2D, destruction is caused at the broken portions 14 a to 14 c of the adherend 7 and the adhesive layer 8.

  Since the composite of the present invention does not break between the fluororesin film layer 1 and the plasma-monomer polymerization layer 2, but breaks at the portion above the plasma-monomer polymerization layer 2, the fluororesin film layer 1 and the plasma- It turns out that the adhesive force between the monomer polymerization layers 2 is considerably higher than that of the other layers. The state of destruction at the portion above the plasma-monomer polymerization layer 2 may be any of the states (1) to (4). For example, as shown in FIG. 3A, a plasma-monomer polymerization layer 16 is formed on the surface of the fluororesin film layer 15, and a rubber material 17 is vulcanized thereon to form a rubber layer 17 to obtain a composite 20. When the fluororesin film layer 15 and the rubber layer 17 of the composite 20 are peeled off, the rubber layer 17 breaks the material at the broken portion 18.

  In the composite of the present invention, the plasma-monomer polymerization layer may be formed on one surface of the fluororesin film or on both surfaces. When forming on both surfaces, another substance can be adhered to both surfaces. Alternatively, another substance can be adhered to one surface, and printing can be formed on the other surface.

  As the adherend of the present invention, any material may be used. Examples thereof include rubber, resin, fiber, wood, paper, stone, metal, metal plating, conductive paste, metal paste, printing ink, and coating film.

  In the present invention, the adherend directly adhered on the plasma-monomer polymerization layer may be self-adhered by curing a thermosetting resin or rubber on the plasma-monomer polymerization layer. In this case, the fluororesin film layer and the thermosetting resin or rubber are self-adhered by the curing of the thermosetting resin or rubber through the plasma-monomer polymerization layer. Curing of the thermosetting resin or rubber occurs by vulcanization. More specifically, a crosslinking reaction occurs by vulcanization, and the composition is cured by crosslinking. In the above, the self-adhesion by curing means that the substrate is bonded to the fluororesin film layer through the plasma-monomer polymerization layer without using an adhesive. Then, when the fluororesin film layer and the thermosetting resin or rubber are peeled off, destruction of the adherend of the thermosetting resin or rubber occurs.

  The thickness of the monomer polymerization layer using plasma is preferably 500 nm or less. With this film thickness, a monomer polymerization layer having a uniform thickness can be formed, and the bonding strength between the fluororesin film layer and the adherend is high. More preferably, the thickness of the plasma-monomer polymerization layer is in the range of 1 to 100 nm, and more preferably in the range of 5 to 50 nm.

  The film thickness of the “uniform thin film” as used in the present invention is as described above, and the term “uniform” means that there are no bubbles observed visually at the interface between the fluororesin film layer and the adherend when it is made into a composite. That is. When bubbles that are visually observed are present, the bonding strength of the portion becomes weak. More specifically, rubber vulcanization molding is performed on the surface of the modified fluororesin film, and in a composite having a size of 100 mm in length and 100 mm in width, the interface between the fluororesin film layer and the rubber is visually observed. Those with no air bubbles are called “uniform”.

  In the plasma-monomer polymerization layer, a fluororesin film is placed on a holder having an electric conductor sheet disposed on the surface, and plasma is applied to the surface of the fluororesin film in a state where a voltage is applied between the plasma irradiation means and the electric conductor sheet. A monomer containing a reactive unsaturated bond group is supplied while irradiating the above, and the monomer is graft-polymerized by plasma on the surface of the fluororesin. Thereby, a thin film can be formed in a state in which the electric charge charged to the fluororesin film layer is removed. The plasma-monomer polymerization layer can be uniformly formed on the surface of the fluororesin film by devising the manufacturing apparatus. The voltage between the plasma irradiation means and the electric conductor sheet is preferably in the range of 1 to 50 kV. When plasma-monomer polymerization is performed with a voltage applied between the plasma irradiation means and the electrical conductor sheet, surface modification by plasma is promoted, and a strong plasma-monomer polymerization layer is formed despite its thin film thickness. can do. This thin film is also considered to have molecules oriented.

  The fluororesin is polytetrafluoroethylene (PTFE), a copolymer of tetrafluoroethylene and a small amount of perfluoroalkoxide (modified PTFE), a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene- Examples include ethylene copolymer (PETFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), or tetrafluoroethylene-hexafluoropropylene copolymer (PEP). it can. These fluororesins are chemically stable, but have poor surface activity and are difficult to adhere to rubber. Here, the film refers to a molded product formed into a substantially flat plate shape. The method for forming the film is not particularly limited, and examples thereof include compression molding, skived molding, cast molding, cutting molding, and melt extrusion molding. The thickness of the film is not particularly limited, but the film thickness is preferably 10 μm to 150 μm.

  The surface-modified fluororesin film of the present invention is a uniform thin film comprising a plasma-monomer polymerization layer formed on at least one surface. Accordingly, it is possible to provide a surface-modified fluororesin film that has a high adhesive strength to such an extent that it breaks at a portion above the plasma-monomer polymerization layer, and the modification effect of the fluororesin film lasts for a long period of time.

  The manufacturing apparatus of the present invention will be described with reference to FIG. FIG. 5 is a schematic explanatory view of the plasma polymerization apparatus 31. The plasma polymerization apparatus 31 includes a draft chamber 32 and a process gas supply apparatus 33, and a processing chamber 34 for modifying the surface of the fluororesin film 35 and a temperature controller 40 are installed in the draft chamber 32. The processing chamber 34 is provided with a transport device 36 for the fluororesin film 35 and a holder 37 for holding the fluororesin film 35. A monomer gas supply device 38 and a plasma generator (plasma head) 39 are installed in the processing chamber 34. The entrance / exit (conveying port) of the fluororesin film 35 is partitioned by gas curtains 41a and 41b. A plasma generating power source 42 is connected to the plasma generating device (plasma head) 39. The draft chamber 32 is provided with a blower 43 and exhausts the gas in the draft chamber 32 as indicated by an arrow 44. The process gas supply device 33 is provided with a process gas cylinder 45 for purge and gas curtain and a process gas pump 46 for generating plasma. The gas from the process gas cylinder 45 is sent to the draft chamber 32 while the flow rate is controlled by the flow meter 47. The gas from the process gas pump 46 is supplied to the processing chamber 34 while the flow rate is controlled by the mass flow controller 48. A monomer vapor is generated from the monomer gas supply device 38 in the draft chamber 32, and the monomer is graft-polymerized on the surface of the fluororesin film 35 while moving the plasma generator (plasma head) 39 in the XY direction. It is preferred to form a layer. At this time, an electric conductor sheet is disposed on the surface of the holder 37 to form a thin film while removing the electric charge charged on the fluororesin film layer.

  FIG. 6 is a schematic sectional view of the draft chamber 32 of the apparatus. An electric conductor sheet 50 is disposed on the holder 37, and the fluororesin film 35 is placed thereon. The processing chamber 34 has a monomer gas atmosphere, and a plasma 52 is irradiated from a plasma generator (plasma head) 39 above the fluororesin film 35. The purge gas 51 is supplied from the upper part in the processing chamber 34, and the gas curtains 41a and 41b are formed by the ejection of the purge gas from the pipe above the entrance / exit (conveying port). Thus, an apparatus for modifying the surface of the fluororesin film 35 is configured. The processing chamber 34 may be hermetically sealed and the atmospheric pressure may be controlled by a vacuum pump or the like, or the processing chamber is an open system, and the processing gas supplied to the processing chamber is set to a pressure higher than the atmospheric pressure by the process gas. Inflow may be prevented. The latter is preferred industrially. In addition, for the purpose of suppressing the turbulence of the gas in the processing chamber due to the driving of the transfer device, which will be described later, it is preferable to provide a mechanism for suppressing the gas turbulence by supplying a certain amount of the same gas as the process gas in the vicinity of the transfer device.

  The plasma generator is an apparatus that generates plasma for performing plasma polymerization. An apparatus for generating plasma is not particularly specified, and a known apparatus can be used. Preferably, the plasma generator is an atmospheric pressure corona discharge device. In this case, the normal pressure does not strictly mean 1 atmospheric pressure (1013 hPa), but may be pressurized within a range of 1014 to 2000 hPa as necessary.

  The conditions for generating plasma are not particularly limited as long as a plasma atmosphere of a process gas described later can be formed. In the case of the atmospheric pressure corona discharge device described above, the frequency varies depending on the device, but the applied voltage frequency of 1 kHz to 100 kHz, the discharge voltage of 1 kV to 24 kV, the pulse modulation frequency of 10 Hz to 200 Hz, and the pulse duty of 50% to 99%. preferable. More preferably, a high frequency of 20 kHz and a high voltage of 24 kV are applied, the pulse modulation frequency is 60 Hz, and the pulse duty is 99%. One plasma generator may be installed in the processing chamber, and the apparent processing speed can be improved by installing a plurality of plasma generating apparatuses.

  The process gas supply apparatus is a flow path for introducing a gas serving as a plasma source from the outside of the plasma polymerization apparatus into the plasma generation apparatus. The process gas is preferably an inert gas or nitrogen. Examples of the inert gas include argon and helium. An inert gas is preferable because it is easy to maintain plasma. Nitrogen gas is preferable from the viewpoint of cost. The purity of the gas is not so necessary, and general industrial purity (99.99 vol.%) May be used. In this case, for the purpose of preventing the influence of oxygen contained in the atmosphere, the process chamber is closed and replaced with process gas, or the process chamber is opened and the process chamber is supplied to supply a process gas to atmospheric pressure or higher. Alternatively, it is preferable to prevent the inflow of air by installing gas curtains at the entrance and exit of the processing chamber. The supply amount of the plasma gas can be appropriately set according to the size of the plasma generator. In the case of the atmospheric pressure corona discharge device of the size described in the examples, 30 SLM to 50 SLM is preferable.

  The holder is a device for holding the fluororesin film. The surface of the holder is an electric conductor sheet. The part where the holder is in contact with the film is the surface opposite to the part where the plasma generated by the plasma generator hits the film. The area where the holder and the film are in contact with each other is not particularly specified, but it is preferable that they are in contact with each other over an area where the plasma is irradiated.

  The electric conductor sheet on the surface of the holder is preferably grounded with respect to the potential of plasma discharge. Although there is no designation | designated in particular in the material of a holder, the holder which has copper, aluminum, stainless steel etc. on the surface is mentioned, for example. The shape of the holder is not particularly specified, but a plate-like shape is preferable in order to contact the film uniformly and in a large area. There is no specific designation for the method of bringing the film and the holder into uniform contact, but for example, the holder may be pressed against the fixed film with a constant pressure, or the film may be fixed on the holder. .

  The details of the reason why the desired surface modification can be obtained when the holder is an electric conductor sheet are unknown, but it is known that a so-called charge-up phenomenon occurs in which the film surface is charged when the film is plasma treated. The inventors speculate that this electric charge is released from the film surface by using the holder as an electric conductor sheet, and more uniform plasma polymerization is performed.

  There is no particular designation for the transport device, and it is only necessary to have a mechanism capable of transporting a desired part of the film to the part of the plasma generator. For example, a stage that can be operated in the XY axis direction may be provided to convey a desired part of the film to the part of the plasma generator, or the apparatus and film that can convey the plasma generator in the X axis direction may be transferred to the Y axis. The object may be achieved by a combination of apparatuses capable of conveying in the direction. The transport device may transport the holder. For example, the holder may be fixed to the site of the plasma generator and only the film may be transferred by the transfer device, or the film and the holder may be transferred simultaneously with the film fixed to the holder.

The processing speed of the film is not particularly specified, and may be appropriately adjusted within a range in which a desired modification is obtained. In the case of using the apparatus of Examples described later and other conditions, it is preferable to perform the treatment in a range of 1 to 10 seconds per 1 cm ² .

  The monomer gas supply device is a device for supplying monomer gas. When the monomer itself is gaseous at room temperature, it can be used as it is. In the case of liquid and solid, it can be used as a gas by heating. When acrylic acid, which will be described later, is used as a monomer, heating is necessary because acrylic acid is in a liquid state, and the monomer gas supply device has components that appropriately heat the monomer and components that keep the gas supply section warm and prevent liquefaction. It is preferable to provide. The monomer gas may be supplied to the processing chamber by applying an appropriate pressure, or the monomer gas may be directly supplied by performing the above gasification with a monomer gas supply device provided in the processing chamber. .

  It is desirable to supply the monomer gas uniformly in the processing chamber. That is, it is desirable to supply the monomer gas both to the vicinity of the plasma generator where plasma polymerization is performed and to the vicinity of the film where plasma polymerization is not performed. For this reason, a method of supplying a monomer gas by mixing it with a process gas to the plasma generator is not preferred, and a method of supplying the monomer gas into the processing chamber is suitable. That is, a method of supplying the monomer gas directly to the processing chamber by performing the above-described gasification with a monomer gas supply device provided in the processing chamber is preferable. Uniformly supplying the monomer gas into the processing chamber enables surface modification by plasma polymerization, and surface modification by remaining radicals continues even at the film part after the plasma treatment. It can be performed.

  In addition, the plasma by argon gas is blue, and the plasma containing monomer gas often shows other colors. For example, when acrylic acid is used as the monomer gas, the plasma color is green. In Example 1 to be described later, the plasma is colored green, and from this, it can be confirmed that the monomer gas of acrylic acid supplied into the processing chamber is supplied at a sufficient concentration in the vicinity of the plasma generator. .

  The monomer gas is not particularly specified, but a monomer containing a reactive unsaturated bond group is preferable. The monomer containing the reactive unsaturated bond group is preferably gasified and supplied to the plasma irradiation region. Examples of the monomer containing a reactive unsaturated bond group include (meth) acrylic monomers, acetylene monomers, and alcohol monomers. The monomer gas used may be a single substance or a mixture of plural substances. Specifically, acrylic acid or its derivatives include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, tridecyl acrylate , Stearyl acrylate, cyclohexyl acrylate, propyl acrylate, benzyl acrylate, isopropyl acrylate, sec-butyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, dimethylaminoethyl acrylate, diethylamino acrylate Ethyl, glycidyl acrylate, tetrahydrofurfuryl acrylate, allyl acrylate, ethyl glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate Acrylic acid or its derivatives, such as alcohol, 2-ethoxyethyl acrylate, ethoxyethoxyethyl acrylate, 2-methoxyethyl acrylate, phenoxyethyl acrylate, phenoxypolyethylene glycol acrylate, and dimethylaminoethylmethyl chloride acrylate. Can be mentioned.

  Methacrylic acid or its derivatives include methacrylic acid, methyl methacrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate. , Propyl methacrylate, benzyl methacrylate, isopropyl methacrylate, sec-butyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, methacrylic acid Tetrahydrofurfuryl, allyl methacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, dimethac Tetraethylene glycol diacid, 1,3-butylene glycol dimethacrylate, trimethylolpropane trimethacrylate, 2-ethoxyethyl methacrylate, ethoxyethoxyethyl methacrylate, 2-methoxyethyl methacrylate, phenoxyethyl methacrylate, methacrylic acid Examples thereof include methacrylic acid such as phenoxypolyethylene glycol, dimethylaminoethyl methyl chloride salt, and glycidyl methacrylate, or derivatives thereof.

  Examples of the acetylene monomer include acetylene, diacetylene, and propargyl alcohol. Examples of the alcohol-based monomer include alkyl alcohols containing an unsaturated bond having 2 to 10 carbon atoms in addition to the alcohol.

  Among these, acrylic monomers are preferable, and acrylic acid or a derivative thereof, and methacrylic acid or a derivative thereof are more preferable. Acrylic acid is particularly preferable because it is easily available and easily gasified as described later. Methacrylic acid is also particularly preferred for the same reason.

  The supply amount of the monomer gas can be appropriately changed according to the type of the monomer gas and the capacity of the processing chamber. When the above-mentioned acrylic acid is used as the monomer gas, the concentration in the processing chamber is preferably 100 to 10,000 ppm. The management of the supply amount can be achieved simply by, for example, maintaining the vapor pressure constant by keeping the liquid substance to be used as the monomer gas at a constant temperature and diffusing it in the processing chamber. In the case of the above-mentioned acrylic acid, although depending on the capacity of the processing chamber, preferable results are obtained in the range of 50 ° C to 70 ° C.

  The power source for plasma generation is not particularly specified, and a known device may be used as long as it can supply voltage, frequency, and the like required by the plasma generation device.

  The fluororesin film to be modified may be a composite with another substance as long as the surface to be modified is a fluororesin. For example, a fluororesin film in which a metal film or the like is coated on one side of the fluororesin film may be prepared, and the fluororesin on the uncoated side may be modified. Alternatively, a fluororesin film in which another resin or the like is laminated on one surface may be prepared, and the fluororesin on the non-laminated surface may be modified.

  When rubber is used as the adherend, the raw rubber is butyl rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, natural rubber, chloroprene rubber, acrylonitrile butadiene rubber and other nitrile rubber, hydrogenated nitrile rubber, norbornene rubber , Ethylene propylene rubber, ethylene-propylene-diene rubber, acrylic rubber, ethylene acrylate rubber, fluorine rubber, chlorosulfonated polyethylene rubber, epichlorohydrin rubber, silicone rubber, urethane rubber, polysulfide rubber, phosphansen rubber or 1, 2-polybutadiene or the like is used.

  One of these may be used alone, or two or more of these may be used in combination. The rubber used in the rubber composite is not limited to the above, but butyl rubber and / or ethylene-propylene-diene rubber (hereinafter referred to as EPDM rubber) is preferable. Butyl rubber is preferred because of its excellent gas permeation resistance and water vapor permeation resistance. A known compound may be used as the butyl rubber, and examples thereof include isobutylene-isoprene copolymer rubber, halogenated isobutylene-isoprene copolymer rubber (hereinafter referred to as “halogenated butyl rubber”), and modified products thereof. Examples of the modified product include a brominated product of a copolymer of isobutylene and p-methylstyrene. Of these, halogenated butyl rubber is more preferable from the viewpoint of easy crosslinking, and chlorinated butyl rubber or brominated butyl rubber is more preferable.

  Also, EPDM rubber is preferable because of its excellent processability. EPDM rubber includes a non-oil-extended EPDM rubber composed only of a rubber component and an oil-extended EPDM rubber containing an extension oil together with the rubber component. Any type of EPDM rubber can be used in the present invention. Examples of the diene monomer in the EPDM rubber include dicyclopentadiene, methylene norbornene, ethylidene norbornene, 1,4-hexadiene, and cyclooctadiene.

  Furthermore, the combination of halogenated butyl rubber and EPDM rubber is more preferable because of good compatibility, excellent gas resistance and water vapor resistance, and excellent workability. When the rubber composite is a medical rubber product such as a gasket for a syringe, for example, butyl rubber having a low gas permeability is preferred as the main component of the rubber. As the crosslinking agent, it is preferable to use triazine derivative crosslinking from the viewpoint of cleanliness.

  In the vulcanization adhesion between the fluororesin film and the rubber, heat and pressure are applied for a predetermined time in a state where they are in contact with each other, and the fluororesin film is adhered to the fluororesin film while crosslinking the rubber. The time and temperature for performing the vulcanization adhesion are set according to the necessity for crosslinking of the uncrosslinked rubber blend. As an example, the rubber material is preferably vulcanized and molded on the surface-modified fluororesin film under the conditions of a heating temperature of 130 to 180 ° C. and a processing time of 5 to 20 minutes. Regarding the pressure at the time of vulcanization adhesion, the pressure in a known rubber crosslinking method is employed. In general, a pressure sufficient to fill the rubber without gaps may be applied to a mold that is a female mold of the molded product, and the pressure is about 20 MPa for a small product such as a medical rubber plug.

  When a resin is used as the adherend, in the case of a thermosetting resin, it can be self-adhered by curing of the thermosetting resin in the same manner as the rubber. This reaction occurs mainly by addition reaction. When thermoplastic resin, fiber, wood, paper, stone, or metal is used as the adherend, an adhesive is used. As the adhesive, a thermosetting resin or a thermoplastic resin-based adhesive, an elastomer adhesive, a mixed adhesive, a hot melt adhesive, or the like can be used. In the case of a coating film such as a conductive paste, metal paste, metal plating, printing ink, or paint, a solvent system, a curing system, a melting system, or the like can be used.

  FIG. 11 is a view showing a medical rubber product used for a prefilled syringe applicable as a composite of the present invention. A prefilled syringe is a syringe prefilled with a medicine. A syringe gasket 61 is mounted on the prefilled syringe 60, and the core 63 is made of a rubber elastic material. Since the tip 62 of the core is in contact with the drug, it is integrally formed with a fluororesin film. FIG. 12 is a perspective view of the syringe gasket 61, and FIG. 13 is a cross-sectional view of the syringe gasket 61. The outer surface 64 as well as the tip is integrally formed of a fluororesin film. A thread groove is formed in the inner side surface 65, and a mandrel is attached thereto.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

(Example 1, Comparative Example 1)
(1) Manufacturing apparatus for plasma-monomer polymerization layer formation A surface-modified fluororesin film was manufactured using the apparatus shown in FIGS. As the plasma generator, an atmospheric pressure corona discharge device was used, and PLASMASTREAM PSC1002 manufactured by Pearl Industrial Co., Ltd. was used. The pair of electrodes of the normal pressure corona discharge part is a 2 mmφ tungsten rod and has the same external shape (length 5 cm, mounting interval 3 cm, tip discharge part bent in a letter shape). The interval was 0.5 to 3 cm. The distance between the tip of the corona discharge electrode head and the fluororesin film treated surface was 9 mm.

A fluororesin film was fixed on the holder. The following was used as a holder.
(1) Glass epoxy copper clad laminate having a thickness of 1.6 mm, a width of 211 mm, and a length of 338 mm (Example 1)
(2) Glass epoxy plate having a thickness of 1.6 mm, a width of 210 mm, and a length of 297 mm (Comparative Example 1)
When a glass epoxy copper clad laminate (Example 1) was used, the holder was grounded with respect to the potential of atmospheric pressure corona discharge. The glass epoxy plate (Comparative Example 1) was used for charge charging that charges the surface of the fluororesin film.

  As the fluororesin film, PTFE (manufactured by Nippon Valqua Industries, VALFLON (registered trademark), thickness 0.08 mm), the size of the film was 21 cm in length and 30 cm in width.

  The monomer gas was gasified by introducing 270 g of liquid acrylic acid into a monomer gas supply device having an opening length of 296 mm and a width of 38 mm and a depth of 59 mm and heating to 60 ° C. As acrylic acid, acrylic acid (purity 98 mass%, 500 ml) manufactured by Wako Pure Chemical Industries, Ltd. was used.

  Argon was used as the process gas and supplied to the plasma generator at a flow rate of 30 SLM. Argon gas is an argon cylinder (47 L) for instrument made by Air Liquide Industrial Gas Co., Ltd., purity 99.9995 vol. %It was used.

  A plasma flow was obtained from the plasma generator by applying a high voltage (about 24 kV) at a high frequency (20 kHz) from a plasma generating power source. As discharge conditions other than the above, the pulse modulation frequency was 60 Hz and the pulse duty was 99%. This plasma flow was applied to the fluororesin film to modify the entire film surface. The plasma irradiation apparatus was reciprocated once while moving in the X-axis direction at 4 mm / sec. After one reciprocation, the holder and the film on the holder were moved by moving 10 mm in the Y-axis direction to process the entire film surface.

  The film after the plasma polymerization treatment was subjected to ultrasonic cleaning to remove excess monomer and polymer on the film surface. For ultrasonic cleaning, an ultrasonic cleaner USK-4R manufactured by ASONE Co., Ltd. was used, and the conditions were set to 1000 ml of ethanol usage and oscillation power: High, and the treatment was performed for 10 minutes. Then, it was dried at room temperature in the tabletop hood until the surface ethanol was vaporized to obtain a final modified film. The thickness of the plasma-monomer polymerization layer of the obtained modified fluororesin film was 10 nm (measured with a thin film surface scan profiler (KLA Tencor, P-15)).

  Molding of the composite of the obtained modified film and rubber was performed by vulcanization molding. Unvulcanized rubber sheet (halogenated butyl rubber, thickness 2 mm) containing 2-di-n-butylamino-4,6-dimercapto-s-triazine (manufactured by Sankyo Kasei Co., Ltd., Disnet DB (registered trademark)) as a crosslinking agent ) Was prepared, and the modified surface of the modified film and the unvulcanized rubber sheet were placed in a press mold in a state of being stacked. Vulcanization molding was performed at a temperature of 150 ° C., a treatment time of 40 minutes, and a treatment pressure of 1.6 MPa to obtain a composite of a fluororesin film and rubber. The rubber thickness after vulcanization was 1.95 mm. FIG. 7A shows a photograph of the composite when a glass epoxy plate (Comparative Example 1) is used as a holder, and FIG. 7B shows a photograph of the composite when a glass epoxy copper clad laminate (Example 1) is used. Show. 7A-B shows an example in which rubber having a size of 100 mm in length and 100 mm in width is vulcanized on a film having a size of 90 mm in length and 70 mm in width.

(2) Uniformity evaluation From FIG. 7A-B, when a glass epoxy board (comparative example 1) is used, although a bubble is seen between a fluororesin film and rubber | gum, a glass epoxy copper clad laminated board (Example) Such a bubble is not seen in the composite using 1). From this, it was confirmed that the modified fluororesin film obtained in Example 1 was formed with a uniform thin film. On the other hand, in Comparative Example 1, air bubbles entered between the fluororesin film and the rubber and were non-uniform.

(3) Peeling test To perform a peeling test of the composite obtained in Example 1, as shown in FIG. 4A, a modified film having a plasma-monomer polymerization layer 22 formed on the surface of a fluororesin film 21 was obtained. Further, by sandwiching an untreated fluororesin film 25 of about half the size between the modified film and the rubber 23, the scissors 25 required to fix the modified film to the chuck of the peeling tester was secured. Unvulcanized rubber sheet (halogenated butyl rubber, thickness 2 mm) containing 2-di-n-butylamino-4,6-dimercapto-s-triazine (manufactured by Sankyo Kasei Co., Ltd., Disnet DB (registered trademark)) as a crosslinking agent ) Was prepared, and the modified surface of the modified film and the unvulcanized rubber sheet were placed in a press mold in a state of being stacked. Vulcanization molding was performed at a temperature of 150 ° C., a treatment time of 40 minutes, and a treatment pressure of 1.6 MPa to obtain a composite of a fluororesin film and rubber.

The peeling test was performed according to JIS K 6854 (also ASTM D 1876). The composite obtained above was cut into a width of about 25 mm, the rubber part 23 and the film part 21a were fixed in a 180 ° peel test, and then peeled at a speed of 100 mm / min, and the tensile strength was measured. The result is shown in FIG. The horizontal axis of the graph is the distance moved by the crosshead, and the vertical axis is the load. From here, the maximum load and the elongation of PTFE can be read. From FIG. 8, the maximum point load was 3.69 N / mm, and the elongation at that time was 83.0825 mm. Further, the rubber began to peel off at a point exceeding 2 N / mm, and finally the rubber was broken. In order to investigate what kind of fracture phenomenon occurs between the rubber and fluororesin film, the surface of the fluororesin film at the separated part is analyzed using a Fourier transform infrared spectroscopy (FTIR) measuring device (Thermo Nicolet, Avatar 360). did. FIGS. 9A to 9C are analysis results by an ATR method using a Fourier transform infrared spectroscopy (FTIR) measuring apparatus showing a breaking phenomenon between a rubber and a fluororesin film in Example 1 of the present invention. 9A shows the transmission spectrum of the fluororesin surface, FIG. 9B shows the reflection spectrum of the release surface of the fluororesin, and FIG. 9C shows the transmission spectrum of the rubber surface. The reflection spectrum of the graft polymer film was not detected because the polymer film was very thin. In FIG. 9A, peaks of —CF ₂ — and —CF ₃ are observed near 1100 to 1200 cm ⁻¹ , but these peaks are not seen in FIG. 9B. In addition, in FIG. 9B, the same peak as the peak due to the talc added to the rubber and rubber in FIG. Conceivable. From this result, it was confirmed that the adhesion between the modified film and the rubber had a very strong tensile strength exceeding the breaking stress of the rubber. From this, it was found that the adhesion between the fluororesin film and the rubber was improved when the glass epoxy copper clad laminate (Example 1) was used as a holder. The sample before the peeling test was as shown in FIG. 3A, and the sample after the test was as shown in FIG. 3B.

  The thickness of the plasma-monomer polymerization layer of Comparative Example 1 was 62.5 nm (measured with a thin film surface scan profiler (KLA Tencor, P-15)).

(Example 2)
A modified film was produced under the same conditions and in the same manner as in Example 1 using PFA (manufactured by Daikin Industries, Ltd., NEOFLON PFA film (NEOFLON: registered trademark), thickness: 25 μm)). A composite of a modified film and rubber obtained by the same method as in Example 1 was molded. As a result, the modified film and the rubber were uniformly and firmly adhered, and the same result as that obtained when PTFE was used was obtained. In the peeling test, the adherend was destroyed. Further, even in the evaluation of uniformity described in Example 1, no bubbles were observed between the fluororesin film and the rubber, and it was confirmed that the film was a uniform thin film.

(Example 3, Comparative Example 2)
A modified film was prepared by the method described in Example 1 using acrylic acid (acrylic acid manufactured by Wako Pure Chemical Industries, Ltd. (purity 98% by mass, 500 ml)) as the monomer gas (Example 3). Acrylic acid was gasified by heating to 60 ° C. to prepare a modified film. Further, as Comparative Example 2, a modified film was prepared by the apparatus and method described in Patent Document 4. Further, vulcanization molding of the resulting modified film / rubber composite was performed in the same manner as in Example 1. FIG. 10 shows the evaluation results of the adhesion state when vulcanization molding is performed under the conditions of a heating temperature of 130 to 180 ° C., a processing time of 5 to 90 minutes, and a processing pressure of 1.6 MPa. The evaluation of the adhesion state is confirmed by visual confirmation after adhesion, and the film on the surface of the composite is cut with a cutter, and the peeled state when the film having a width of 2 to 3 mm is artificially pulled with tweezers Judged. Evaluation criteria are as follows: △ is visually free of bubbles but has a low adhesion rate of about 10%, ◯ is visually and free of bubbles and has an adhesion rate of about 50%, and ◎ is visually and mixed of bubbles The adhesion rate was almost 100%, and peeling with tweezers was almost difficult. The results of vulcanization molding at a heating temperature of 180 ° C. and a processing time of 5 minutes, 10 minutes, 20 minutes, 40 minutes or a heating temperature of 150 ° C. and a processing time of 40 minutes among the points in FIG. 10 are described in Example 1. The results are for the modified film prepared by the method (Example 3), and the other results are for the modified film prepared by the apparatus and method described in Patent Document 4 (Comparative Example 2). As can be seen from FIG. 10, in Example 3, a strong composite having an adhesion rate of almost 100% was obtained, and better results were obtained compared to the conventional method (Comparative Example 2). In the uniformity evaluation described in Example 1, it was confirmed that Example 3 formed a uniform thin film with no bubbles observed between the fluororesin film and the rubber. On the other hand, in Comparative Example 2, air bubbles entered between the fluororesin film and the rubber and were non-uniform.

Example 4
As a holder, an aluminum tape attached to the surface of the glass epoxy plate used in Example 1 was used, and a composite of a fluororesin film and rubber was obtained under the conditions and method described in Example 1. As a result, the adhesiveness improvement of the fluororesin film and rubber | gum comparable as the case where a glass epoxy copper clad laminated board was used as a holder was obtained. In the peeling test, the adherend was destroyed. Further, even in the evaluation of uniformity described in Example 1, no bubbles were observed between the fluororesin film and the rubber, and it was confirmed that the film was a uniform thin film.

  From the above, the modified fluororesin films of the examples of the present invention have high adhesive strength, confirming superiority over conventional products.

  The surface-modified fluororesin film of the present invention includes, in addition to those shown in the examples, a laminate film laminated with a polyester film or a polyolefin film, a printed material, a printed circuit board, an electronic circuit, a battery separator, a waterproof moisture-permeable cloth, a filter It can be applied to a wide range of insert molded bodies, rollers, solid electrolyte membranes for fuel cells, solar cell surface protection sheets, building material sheets and the like.

1,15 Fluororesin film layer 2,16,22 Plasma-monomer polymerization layer 3a, 3b, 6, 7, 7a, 7b, 9 Adhering material 4, 11, 12, 13, 14a, 14b, 14c, 18 Destruction portion 5a, 5b, 8, 8a, 8b Adhesive layers 10, 20 Composites 17, 17a, 17b Rubber layer 21 Fluorine resin film 21a Fluorine resin film gripping peeling part 23 Rubber layer 24 Destruction part 25 Untreated fluorine resin film 31 Plasma Polymerization device 32 Draft chamber 33 Process gas supply device 34 Processing chamber 35 Fluororesin film 36 Transport device 37 Holder 38 Monomer gas supply device 39 Plasma generator (plasma head)
40 Temperature controller 41a, 41b Gas curtain 42 Plasma generating power supply 43 Blower 44 Exhaust gas 45 Purge and gas curtain process gas cylinder 46 Plasma generating process gas pump 47 Flow meter 48 Mass flow controller 49 Ground 50 Electric conductor sheet 51 Purge gas 52 plasma

Claims (14)

A surface-modified fluororesin film having a plasma-monomer polymerization layer on at least one surface of the fluororesin film layer,
The plasma-monomer polymerization layer is a uniform thin film layer obtained by graft polymerization of a monomer containing a reactive unsaturated group in a state in which a charge charged on the fluororesin film layer is removed while irradiating plasma. A surface-modified fluororesin film. When adhering the adherend directly or through the adhesive layer on the surface-modified fluororesin film,
The surface-modified fluororesin film according to claim 1, wherein when the surface-modified fluororesin film and the adherend are separated, the surface-modified fluororesin film is broken at a portion above the surface-modified fluororesin film.   The adherend directly adhered on the surface-modified fluororesin film is self-adhered by curing a thermosetting resin or rubber on the surface-modified fluororesin film. Surface-modified fluororesin film.   The surface-modified fluororesin film according to any one of claims 1 to 3, wherein the thin film layer has a thickness of 500 nm or less. A method for producing a surface-modified fluororesin film according to any one of claims 1 to 4, wherein a monomer polymerization layer is formed on at least one surface of the fluororesin film layer in a chamber,
In a state where a fluororesin film is placed on the electrical conductor sheet and the electrical charge charged on the fluororesin film layer is removed,
Supplying a monomer containing a reactive unsaturated bond group while irradiating the surface of the fluororesin film with a voltage applied between the plasma irradiation means and the electrical conductor sheet, the surface of the fluororesin film A method for producing a surface-modified fluororesin film, wherein the monomer is graft-polymerized to form a uniform thin film layer.   The surface modification according to claim 5, wherein a monomer vapor is generated in the chamber and a thin film layer is formed by graft polymerization of the monomer on the surface of the fluororesin film while moving a plasma generator (plasma head). A method for producing a fluororesin film.   The method for producing a surface-modified fluororesin film according to claim 5 or 6, wherein the electrical conductor sheet is grounded.   The method for producing a surface-modified fluororesin film according to any one of claims 5 to 7, wherein a voltage between the plasma irradiation means and the electric conductor sheet is in a range of 1 to 50 kV.   The method for producing a surface-modified fluororesin film according to any one of claims 5 to 8, wherein an inert gas is supplied into the chamber. An apparatus for producing a surface-modified fluororesin film according to any one of claims 1 to 4, wherein a monomer polymerization layer is formed on at least one surface of the fluororesin film layer in a chamber,
An electrical conductor sheet for placing the fluororesin film and removing the charge charged on the fluororesin film layer;
Means for supplying a monomer containing a reactive unsaturated bond group into the chamber;
Plasma irradiation means for polymerizing the monomer on the surface of the fluororesin film;
An apparatus for producing a surface-modified fluororesin film, comprising means for applying a voltage between the plasma irradiation means and the electric conductor sheet. A composite in which an adherend is adhered directly or via an adhesive layer on the surface-modified fluororesin film according to any one of claims 1 to 4,
A composite comprising a surface-modified fluororesin film, wherein when the surface-modified fluororesin film and the adherend are peeled, the surface-modified fluororesin film is broken at a portion above the surface-modified fluororesin film.   The surface-modified fluororesin film according to claim 11, wherein the adherend is rubber, resin, fiber, wood, paper, stone, metal, metal plating, printing ink, conductive paste, metal paste, or coating film. Containing complex.   The adherend is self-adhering by curing a thermosetting resin or rubber on the surface-modified fluororesin film, and the surface-modified fluororesin film and the adherend are peeled off. A composite comprising the surface-modified fluororesin film according to claim 11 or 12, which destroys the adherend. A method for producing a composite in which rubber is directly vulcanized and molded on the surface-modified fluororesin film according to any one of claims 1 to 4,
A rubber material is vulcanized and molded on the surface-modified fluororesin film under conditions of a heating temperature of 130 to 180 ° C. and a treatment time of 5 to 20 minutes. Method.