JP2000178369A - Surface modification method for molded fluororesin item - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface modification method by which the surface of a molded fluororesin item can be modified so that the surface after the modification exhibits an excellent abrasion resistance and a stable strong adhesion to various adhesives and rubbers and which is advantageous in terms of cost by heating the item to its m.p. or higher before or after subjecting the item to an electrical discharge treatment in an atmosphere containing an unsaturated hydrocabon. SOLUTION: In a surface modification method of a molded fluororesin item by subjecting it to an electrical discharge treatment in an atmosphere containing an unsaturated hydrocarbon, the item is heated to the m.p. or higher, preferably to a temperature between about the m.p. +15 deg.C and about the m.p. +100 deg.C for 5 sec to 1 hr at least before or after the discharge treatment. This method can impart a sufficient adhesiveness even to polytetrafluoroethylene, i.e., a fluororesin which can not be given a sufficient adhesiveness by an electrical discharge treatment alone. The heating temperature is preferably 342-427 deg.C in the case of polytetrafluoroethylene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface modification method for modifying the surface of a fluororesin molding such as a fluororesin film by heat treatment and discharge treatment.

[0002]

2. Description of the Related Art Fluororesins have excellent properties that are not found in other resins, such as antifouling properties, heat resistance, chemical resistance, transparency, ultraviolet light degradation resistance, weather resistance, and water and oil repellency. . On the other hand, fluororesins are difficult to combine with other materials due to their characteristic poor adhesion. In addition, in order to apply another material to the fluororesin, it is necessary to carry out through an adhesive, but the adhesion with the adhesive is poor, and therefore, the adhesive surface on the fluororesin side is modified, and Attempts have been made to increase the adhesiveness of the material.

[0003] As a method for modifying the surface of a fluororesin molding, a flame treatment described in JP-B-63-10176 can be used.
2. Description of the Related Art Chemical treatment typified by metal sodium treatment and discharge treatment by excimer laser, plasma, or the like are known.
However, the treatment with metallic sodium has a danger of ignition, a problem with the environment due to the use of a large amount of solvent, and a problem with characteristics that the modified portion is vulnerable to ultraviolet rays and heat. Also,
The method using the excimer laser has a disadvantage that the processing area is small and the running cost is high.

[0004] Regarding the atmospheric pressure plasma processing, for example,
JP-A-5-92530 discloses a method for discharging a fluorine film in an inert gas atmosphere containing an organic compound having a functional group having the same or an affinity as the functional group of an adhesive as a mating material. Have been. However, according to this method, the dispersibility is poor when the liquid organic compound is supplied to the discharge space in the form of gas and fine particles at normal temperature and normal pressure, and the organic compound is fragmented in the discharge space and maintains the state of the starting material. Therefore, there is a problem that it is difficult to form a desired functional group on the surface of the fluorine film.

Japanese Patent Application Laid-Open No. Hei 6-107828 discloses a method of modifying a surface by atmospheric pressure plasma in which noble gas is used in an amount of 70 mol% or more, CO ₂ and C _n H _{2n + 2} (n = 1 to 4). A method using a hydrocarbon is disclosed,
The gas system is complicated and difficult to control, and the hydrocarbon as an additive gas is a saturated hydrocarbon having low reactivity, so that there is a problem that the processing speed cannot be increased so much to maintain good adhesive strength.

[0006]

SUMMARY OF THE INVENTION Further, Japanese Patent Laid-Open No.
In JP-A-6569 and JP-A-2-15171, glow discharge is carried out at atmospheric pressure, and surface modification of various polymers is attempted using the glow discharge, but sufficient properties can be obtained by a single surface treatment. It was hard to say.

On the other hand, combinations of surface treatments have been attempted. For example, Japanese Patent Application Laid-Open No. 6-220228 discloses a method in which a fluororesin surface is subjected to low-temperature plasma treatment and then irradiated with an excimer laser. However, this also has a problem that the cost is high.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to stably obtain high adhesiveness to various adhesives and rubbers and to improve abrasion resistance. An object of the present invention is to provide a surface modification method which is excellent and is advantageous in cost.

[0009]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies on the treatment used in combination with the discharge treatment. Later, by performing the treatment of heating the fluororesin above the melting point, it is excellent in abrasion resistance, found that high adhesiveness can be obtained stably to various adhesives and rubber, etc., to complete the present invention Reached.

That is, the surface modification method of the present invention is a surface modification method in which a discharge treatment is performed on a fluororesin molded article in an atmosphere containing an unsaturated hydrocarbon. The method includes a step of performing a heat treatment at a temperature equal to or higher than the melting point of the resin molded product. here,
`` Perform the heat treatment at least before or after the discharge treatment '' is a concept that includes the case where the heat treatment is performed both before and after the discharge treatment.If the heat treatment is further performed before the discharge treatment, Those that have been subjected to a heat treatment during the production of the fluororesin molded article are included.

As the material and the shape of the fluororesin molding, various ones can be mentioned as described later, and the fluororesin molding is made of polytetrafluoroethylene (PT).
It is preferably a film or sheet of FE).

At this time, the heat treatment is performed at 342 to 427 ° C.
The temperature is preferably in the range of

According to the surface modification method of the present invention, as shown in the results of the examples described below, excellent wear resistance and high adhesion to various adhesives, rubbers, etc. can be obtained. Can be done. The reason is not clear, but is considered as follows. In other words, by performing the heat treatment above the melting point,
The small protrusions generated on the surface of the fluororesin made the bonding of functional groups more dense and stronger in the subsequent discharge treatment, and in addition, the elastic modulus and tensile strength of the fluororesin itself improved. From this, it is considered that the strength at the time of bonding and peeling the discharge treatment surface of the heat treatment base material with an adhesive or the like was improved. At that time, since the surface of the hydrophilic functional group containing oxygen, such as a carboxyl group, is formed thick by the discharge treatment, it is considered that the adhesiveness is stably obtained with various adhesives and the abrasion resistance is excellent.

When the fluororesin molding is a polytetrafluoroethylene (PTFE) film or sheet, the effect of the combined use of heat treatment and discharge treatment is remarkable as compared with other fluororesins. And the present invention is particularly effective. In other words, in the case of other fluororesins, an effect of improving the adhesiveness to some extent can be expected only by the discharge treatment, whereas in the case of polytetrafluoroethylene (PTFE), as shown in the comparative example, only the discharge treatment has a sufficient adhesiveness. However, by performing the combined treatment as in the present invention, sufficient adhesiveness can be realized. Also,
Since the fluororesin molding is a film or sheet, the heat treatment can be performed continuously in a short time.

At this time, the heat treatment is performed at 342 to 427 ° C.
When performed at a temperature within the range described above, as shown in the results of Examples described later, the adhesive force increases critically at a temperature of 342 ° C., and the effect of improving the adhesive force is particularly remarkable. Also, 42
When the temperature exceeds 7 ° C., although there is no difference in the adhesive properties, the substrate tends to be broken due to a decrease in tensile strength at the time of molding, a remarkable dimensional change after molding, and wrinkles and appearance problems are likely to occur. Tend to occur.

Further, prior to the heat treatment, it is preferable to carry out an electron beam irradiation treatment in an inert gas atmosphere. In this case, as shown in the results of Examples described later, the adhesion is further improved. . Note that by setting the inert gas atmosphere, the decomposition and degradation of the fluororesin can be suppressed.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in the order of a fluororesin molded article, heat treatment, and discharge treatment.

(Fluororesin Molded Article) The form of the fluororesin molded article to be treated includes various forms such as a film, a sheet, a plate, a tube, and a bulk. A film or a sheet-like material is preferable because it can be disposed between the electrodes for efficient processing. The film or sheet may be a porous body or a laminate.

The fluororesin is not particularly limited as long as it contains a fluorine atom in the molecule. Specifically, polytetrafluoroethylene (PTF
E) and its modified products, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), tetrafluoroethylene-ethylene copolymer (ETFE),
Tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-vinylidene fluoride copolymer (TFE / VdF), tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinyl ether copolymer (EPA), poly Chlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), chlorotrifluoroethylene-vinylidene fluoride copolymer (CTFE / VdF), polyvinylidene fluoride (PVd)
F), polyvinyl fluoride (PVF) and the like.
Among them, as described above, polytetrafluoroethylene (P
TFE) is preferred.

A molded article such as a fluororesin film can be produced by a known method corresponding to various materials, and a film or a sheet-like substance is formed by, for example, compressing and firing a fluororesin powder and then cutting it by a cutting method. Or a method in which an auxiliary agent is mixed with a fluororesin powder, extruded, and then roll-molded. For films and the like obtained by such a production method, it is necessary to separately perform a heat treatment, but when a fluororesin molded article is produced by heating at a temperature equal to or higher than the melting point, and the surface during production is maintained as it is. Does not require a separate heat treatment. For example, PTF
In the case of a film or the like obtained by applying an aqueous solution in which E powder is dispersed to a support such as an aluminum foil and fusing it at a humidity higher than the melting point, since a heat treatment has already been performed, if a direct discharge treatment is performed, Good. This is the same for bulk molded products.

(Heat treatment) The heat treatment is performed at least before or after the discharge treatment. The heating temperature in the heat treatment is equal to or higher than the melting points of various fluororesins, and is preferably in the range of about + 15 ° C to + 100 ° C. For example, in the case of PTFE, heat treatment is performed at a melting point of 327 ° C. or higher, preferably 342 to 427 ° C., and more preferably 3 to 427 ° C.
The heat treatment is performed at 50C to 380C.

If the heating temperature is lower than the melting point + 15 ° C., the effect of the heat treatment is slow. If the heating temperature is higher than the melting point + 100 ° C., no remarkable difference is observed in the adhesive properties. There is a tendency for the substrate to be easily broken, a dimensional change after molding, wrinkles and appearance problems.

The heating time is preferably from 5 seconds to 1 hour. If it is less than 5 sec, although depending on the temperature and the thickness of the base material, the heat transfer is insufficient in the bulk direction and the plane direction, and the adhesive property tends to be hardly exhibited. If it exceeds 1 hour, the decomposition of the fluororesin proceeds, harmful substances such as hydrogen fluoride are generated, and the productivity tends to decrease.

The heating device used may be a vertical type or a horizontal type. In the case of horizontal type, if tension is applied to the substrate by increasing the speed on the winding side from the speed on the unwinding side,
The appearance is also good. In the case of the vertical type, when the base material is transported from the bottom to the heating unit, excessive tension occurs,
Since it is difficult to control the elongation of the base material, it is preferable to convey the base material from top to bottom. The heating device may be a continuous type or a batch type.

The heat source used for heating the heating device may be any heat source as long as it can be heated to the above-mentioned temperature range. However, it is preferably infrared light, and the wavelength is particularly preferably 0.8 to 5 μm because it is easy to obtain a high temperature. Are preferred. At this time, it is preferable to arrange infrared heaters without gaps or to arrange them in a staggered manner so that heat is uniformly transmitted to the base material. If wrinkles still occur, remove the wrinkles by flowing the heat-treated substrate again along a curved roll heated at a temperature near the melting point, or by sandwiching it between two heated rolls under pressure. Preferred. However, in the case of following the curved roll, it is preferable to perform the discharge treatment on the opposite side because the adhesive force is hard to appear on the side along the curved roll.

The cooling after the heating is not particularly limited to an air cooling method in which air or nitrogen is blown, or a water cooling method in which the substrate is immersed or sprayed in water. This is because a portion having a high cooling rate tends to be transparent and has a variation in appearance as compared with a portion having a low cooling rate. In the present invention, since the discharge treatment is usually performed at room temperature, the discharge treatment is preferably performed after the fluororesin is cooled to 50 ° C. or lower, particularly 30 ° C. or lower.

(Discharge treatment) The discharge treatment is performed in an atmosphere containing unsaturated hydrocarbon. Examples of the form of the discharge treatment include various discharges that can generate plasma such as glow discharge and corona discharge (so-called plasma discharge), and various discharges that can activate molecules in a gas phase or fluororesin. Can also be adopted. These are disclosed in JP-B-37-17485, JP-B-49-12900, and U.S. Pat. No. 3,296,011. Further, the pressure of the discharge atmosphere may be set to a pressure corresponding to the above-described various discharges. As the surface reforming device for performing the discharge treatment, a device according to the form and pressure of various kinds of discharge treatment may be appropriately selected. In the present invention, in particular, from the viewpoint of equipment costs and processing costs, the discharge processing is performed at 500 to 1%.
It is preferable to generate plasma under a pressure of 000 torr (hereinafter referred to as "atmospheric pressure plasma processing").

The atmosphere in which the discharge treatment is performed contains unsaturated hydrocarbons, and examples of unsaturated hydrocarbons include alkenes such as ethylene, propylene and butylene, and alkynes. In consideration of the reactivity in the discharge treatment, 1 is preferably selected from alkynes having 2 to 4 carbon atoms.
Although it is more than one kind, examples of such alkyne include acetylene, methylacetylene, 1-butyne, 2-butyne and the like, and acetylene is particularly preferable.

Further, other components contained in the discharge atmosphere include helium, argon, neon, krypton, and the like.
A rare gas such as xenon or an inert gas such as nitrogen may be used. Further, a reactive organic compound or an inorganic compound may be contained as long as the effect of the present invention by addition of the alkyne is not impaired.

Hereinafter, a preferred embodiment of the present invention will be described with reference to an example in which a fluororesin film is subjected to an atmospheric pressure plasma treatment. FIG. 1 is a schematic configuration diagram of an example of an apparatus used for atmospheric pressure plasma processing. The apparatus includes a high-voltage applying means for forming a plasma discharge, a processing chamber 11 for introducing and discharging a gas to maintain an oxygen concentration and a pressure, and introducing acetylene or a mixed gas containing acetylene into a discharge space. And a transport mechanism for feeding and winding the fluororesin film 1 while transporting it.

The high voltage application means is composed of a high voltage application side electrode 3 connected to a high frequency power supply 9 and covered with a dielectric 3a, and a ground side electrode 2a provided below the silicon rubber layer 2b of the main roll 2. You. An inert gas cylinder 10b is connected to the processing chamber 11 via a flow meter 10a, exhausted from an exhaust port 8, and an oxygen concentration and a pressure are monitored by a vacuum gauge 6 and an oxygen concentration meter 7. You. A supply means of acetylene or the like includes a gas cylinder 4c of acetylene or the like, a flow meter 4
b and the nozzle 4c. The transport mechanism includes a feeding unit and a winding unit (not shown) of the fluororesin film 1, a rotating roll 5 a provided at an entrance and an exit of the processing chamber 11, and a main roll 2 facing the high-voltage application side electrode 3.
It is composed of support rolls 5b provided before and after that.

The shape of the high-voltage application electrode 3 is not particularly limited, but when the object to be processed is a wide film, a rod-shaped object is preferable because a uniform processing can be performed. Ground electrode 2
The a (main roll 2) preferably has a cylindrical shape because it also has a function of transporting the fluororesin film 1, which is an object to be processed. The distance between the electrodes is set to 1 to 5 mm, and -10 to the set value.
% To + 10% is preferable for stabilizing discharge. If it is less than 1 mm, it is difficult to maintain the uniformity of the distance between the electrodes, and if it is more than 5 mm, the voltage load tends to increase. The variation of the distance between the electrodes is -10 against the set value.
If it exceeds% to + 10%, a short circuit tends to occur at the shortest part between the electrodes. The high frequency power supply 9 is used for voltage application, and the frequency can be arbitrarily selected from a low frequency (kHz), a high frequency (MHz), and a microwave (GHz). Since it becomes difficult, 200 kHz or less is preferable. In addition, the frequency is preferably 1 kHz or more in order to efficiently perform a polymerization reaction of a single gas or a composite gas containing an acetylene gas. More preferably, 20 to
80 kHz. Even in the case of low frequency, it is preferable to coat one or both of the electrodes with a dielectric such as glass, rubber, ceramics, etc. in order to prevent arc discharge.

The treatment chamber 11 is filled with an inert gas such as argon, helium, or nitrogen to adjust the oxygen concentration and the pressure so as to discharge an inert gas introduction system, an additive gas containing acetylene, and a decomposition gas thereof. It is preferable to use a hermetic type in which an exhaust system is installed for the purpose. For this reason, when the fluororesin film 1 to be treated is guided from the atmosphere outside the processing, the entrance and the exit of the conveyance are coated with a metal having a low frictional resistance such as chrome plating to prevent air from being mixed. It is preferable to sandwich the film between the rolls 5a. When the film is conveyed between rolls having a large frictional resistance such as rubber at both the entrance and the exit, the adhesive strength after treatment tends to decrease.

The oxygen concentration in the processing chamber 11 is 1 to 1000 pp
m, preferably 5 to 200 ppm. If it is less than 1 ppm, it is difficult to adjust the oxygen concentration.
If it is more than 00 ppm, the adhesive strength with the adhesive tends to decrease. The pressure is preferably 500 to 1000 torr. If the pressure is less than 500 torr, it is difficult to adjust the pressure.
If it is larger than 00 torr, the discharge tends to be difficult to stabilize.

The blowing position of the nozzle 4a depends on the introduction amount of acetylene or the like, but the blowing port of the nozzle is directed to the plasma discharge region and 1 to 50 mm from the intersection of the plasma discharge region and the fluororesin film. It is preferable that the outlet is present at a distance of. If it is less than 1 mm, the distribution difference of acetylene in the plasma region becomes large, and this tends to lead to variations in processing and adhesive characteristics. If it is larger than 50 mm, the uniformity of the treatment increases, but the gas concentration tends to be low and the adhesive properties tend to be low. In order to eliminate such a decrease in concentration, a cover may be provided in the vicinity of the discharge region so that acetylene or the like is supplied into the cover and a part of the cover is exhausted.

Further, the amount of acetylene introduced varies depending on the plasma discharge region and the processing speed. However, a fluororesin film having a base material width of 250 mm is coated between an aluminum electrode having a thickness of 20 mm and width of 300 mm and a ground electrode having a diameter of 100 mm and width of 400 mm. When passing through the plasma region at a transport speed of 1 m / min for processing, the amount of acetylene introduced is 0.1 to 10 L / mi.
n is preferred. If it is less than 0.1 L / min, the amount of the functional group formed is small, and the adhesive strength with the adhesive tends to decrease. If it is more than 10 L / min, a powdery decomposition product is apt to be deposited, whereby the adhesive strength tends to be hardly developed. Such an introduction amount substantially corresponds to 0.01 to 10% by volume in the concentration of acetylene in the discharge region.

(Others) In the present invention, it is preferable to perform an electron beam irradiation treatment in an inert gas atmosphere prior to the heat treatment. As the inert gas used,
The same thing as the case of the above-mentioned discharge treatment can be used.

The irradiation with the electron beam is carried out in the range of room temperature to 100 ° C., and the dose is 1 to 20 Mrad and 50 to 300 Mrad.
It is preferably performed at kV. As an electron beam irradiation apparatus, those described in JP-A-10-288700 and the like can be used.

In the present invention, it is preferable to carry out a surface roughening treatment prior to the above-mentioned heat treatment, whereby the adhesive strength can be further improved. Examples of the method of the surface roughening treatment include various mechanical treatments using a sandpaper, a grinder, a sandblast, or the like.

The type of adhesive for bonding the surface-modified fluororesin film or the like according to the present invention may be appropriately selected according to the type of the rubber or pressure-sensitive adhesive as the mating material. For rubbers with NR or NBR as the mating material, a halogen polymer-based adhesive can be used as a silicone-based adhesive. For a fluorine-based rubber, a silane coupling agent can be used. For a urethane-based rubber, a phenol-based adhesive can be used.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and the like showing specific configurations and effects of the present invention will be described below. In addition, the evaluation data in each Example etc. is based on the following evaluation method.

(Epoxy Adhesive Strength) A steel plate and a film were adhered by a roller using a mixture of an epoxy adhesive (manufactured by Konishi, Bond E) in a ratio of 1: 1 and a curing agent, and then heated to 100 ° C. Heating was performed for 1 hour to bond them. Thereafter, the film was peeled at an angle of 180 °, and the peel strength at that time was measured.

Example 1 A PTFE film (No. 900, manufactured by Nitto Denko) having a thickness of 200 μm was heated at a temperature shown in Table 1 for 1 minute by a drier (heating method is a non-contact / batch method), and then a curved metal was heated. It was cooled to 25 ° C. while applying tension in the longitudinal direction with a drum. Next, using a device as shown in FIG. 1, nitrogen as an inert gas was introduced into the processing chamber at 100 L / min to create an atmosphere with an oxygen concentration of 50 ppm, and a rod-shaped aluminum anode coated with a dielectric was formed. The interval between the cathodes coated with silicon rubber was set to 3 mm, the frequency was 50 kHz, and the voltage was 13 k.
v AC voltage was applied to discharge. Acetylene gas was introduced into the discharge space at a flow rate of 1 L / min, the surface along the metal drum was directed to the anode side, the back surface was brought into contact with the cathode, and transported at a speed of 1 m / min.

Table 1 and FIG. 2 show the adhesive strength at 180 ° peel after the electric discharge treated surface of the obtained film and the steel plate were bonded with an epoxy adhesive. Table 1 shows the specific gravity of the base material after the heat treatment and the contact angle with water after the heat treatment. In addition, the contact angle of the discharge-treated surface when the heat treatment was not performed was 117 °.

[0045]

[Table 1] As shown in the results of Table 1 and FIG. 2, the adhesive force is critically increased at 342 ° C. corresponding to the melting point + 15 ° C., and the effect of improving the adhesive force is particularly remarkable. In addition,
A change in specific gravity was observed, and it is presumed that the heat treatment changed the solid structure. In addition, since the contact angle with water is increased by the heat treatment, it can be seen that unevenness (projections) is generated on the surface by the heat treatment.

Example 2 A PTFE film having a thickness of 100 μm (No. 900, manufactured by Nitto Denko) was transferred to a vertical furnace heater having a furnace length of 3 m (the heating method was a continuous type in which the material was transferred from top to bottom) at a temperature of 380 ° C. The speed was set to 3 m / min on the entrance side and 3.5 m / min on the exit side, and heat treatment was performed continuously. This continuous base material is
It was cut into a cm square, and the discharge treatment and adhesion evaluation were performed under the same conditions as in Example 1.

The 180 ° peel adhesive strength is 0.4 kg / c.
m. Further, after the discharge treatment, the treated surface was rubbed 10 times with a load of 18 g / cm ² using a bencot (manufactured by Asahi Kasei Corporation, 70% cotton cellulose + 30% polyester), and the epoxy adhesive strength was also maintained at 0.4 kg / cm. I was

Next, a polyolefin-based primer was applied to the treated surface and dried, and then the uncured NBR was heated and pressed to bond the treated film and the steel sheet. The treated film was peeled from the steel plate at 180 ° peel. The peeling at this time was a cohesive failure of the rubber, and no peeling at the interface was observed.

Base material before heating (No 900)
The surface properties and physical properties of the substrate and the heated substrate (heat-treated product) were measured, and the results are shown in Tables 2 and 3.

[0050]

[Table 2] (Measurement conditions) #ESCA: Using Kratos, AXIS-His (manufactured by Shimadzu), the take-out angle was measured at 90 ° with respect to the sample.

[0051]

[Table 3] #Tensile breaking strength: gap 50mm, sample width 10m
Set to m and measured with Tensilon (manufactured by Shimadzu). Measurement temperature: 25 ° C., measurement direction: longitudinal direction #Elastic modulus: set to a frequency of 1 Hz, sample 20 × 10 mm, and measured with DMS200 (Seiko Denshi Kogyo). Measurement temperature 0 to 200 ° C, temperature rise 2 ° C / min As shown in the results of Tables 2 and 3, the surface shape and surface chemical properties are changed by the heat treatment, and furthermore, physical properties such as strength and elastic modulus are shown. Is changed.

Example 3 A procedure in which a solution of PTFE powder dispersed in water (XAD953, manufactured by Asahi ICI Fluoropolymers Co., Ltd.) was applied to an aluminum foil, and heated and fused at 380 ° C. five times to obtain a thickness of 50 μm. Was prepared.

Using this, a discharge treatment was performed under the same conditions as in Example 1. 180 ° peel adhesion is 0.55
kg / cm. After the electric discharge treatment, the treated surface was treated with Bencot (manufactured by Asahi Kasei Corporation, cotton cellulose 70% + polyester 30%) at a load of 18 g / cm ² for 10 minutes.
The epoxy adhesive strength after rubbing was 0.5 kg / cm, and almost no decrease in adhesive strength was observed.

Comparative Example 1 The same discharge treatment and adhesion evaluation were performed in Examples 1 and 2 except that no heat treatment was performed. No epoxy adhesive strength
900 at 100 μm, both 0.05 kg / cm,
No. 900 was 200 μm, and was 0.1 kg / cm in both cases.

Example 4 No. 900 (100 μm) was heated at 370 ° C. for 1 minute, cooled and discharged in the same manner as in Example 1. The epoxy adhesive strength of the obtained film was 0.55 kg / cm.

Next, the order of the heat treatment and the discharge treatment is changed,
After the discharge treatment of No. 900 (100 μm), the epoxy adhesive strength of the substrate subjected to the heating and cooling treatment was 0.3 kg / cm.

Example 5 Modified PTFE sheet (M12 manufactured by Daikin Co., Ltd. at 360 ° C.)
After sintering 150 kg / cm ^{2 for} 2 days and cutting to a thickness of 75 μm) in the same manner as in Example 4, the film subjected to the discharge treatment had an epoxy adhesive strength of 0.9 kg / cm.

In the same manner as in Example 4, after the modified PTFE sheet was subjected to a discharge treatment, the epoxy adhesive force of the film subjected to the heating and cooling treatment was 0.2 kg / cm. According to this result, the effect of improving the adhesive strength is more remarkable when the discharge treatment is performed after the heat treatment, but the heat treatment at or above the melting point may be performed before or after the discharge treatment.

Comparative Example 2 A discharge treatment was performed in the same manner as in Example 5 except that the modified PTFE sheet was not subjected to heat treatment.
The epoxy adhesive strength of the obtained film is 0.1 kg / cm
It became.

Example 5 The surface of No. 900 (200 μm) was rubbed with sandpaper so as to be perpendicular to the peeling direction at the time of measurement. At that time, the product was reciprocated 10 times at a speed of 5 m / min with a load of 18 g / cm ² using a product number: A280 as sandpaper.

Thereafter, the substrate was heated at 370 ° C. for 1 minute, cooled in the same manner as in Example 1, and the epoxy adhesive strength of the substrate subjected to the discharge treatment was 2.45 kg / cm.

Example 6 No. 900 (200 μm) was irradiated with an electron beam of 5 Mrad and 100 kv in a nitrogen atmosphere. Then, at 370 ° C, 1
min, cooled in the same manner as in Example 1, and subjected to discharge treatment. The epoxy adhesion of the obtained film is 1.35.
kg / cm.

Example 7 FEP sheet (Neoflon, manufactured by Daikin Co., Ltd., 250 μm)
m) is rubbed with a Bencot and 0.05k with epoxy adhesive strength
After subjecting the base material to g / cm to a heat treatment, a discharge treatment was performed under the same conditions as in Example 1. The epoxy adhesive strength of the obtained film was 1.2 to 1.2 when the heating condition was 240 ° C. for 1 min.
2.2 at 1.9 kg / cm, 260 ° C (melting point) 1 min
2.45 kg / cm, 2.65 to 280 ° C for 1 min
It became 2.75 kg / cm.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an apparatus used for atmospheric pressure plasma processing.

FIG. 2 is a diagram showing a relationship between a heating temperature and an adhesive force in Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluororesin film 2a Grounding electrode 3 High voltage application side electrode 4c Gas cylinder of acetylene etc.

Claims (3)

[Claims] 1. A surface modification method for subjecting a fluororesin molded article to a discharge treatment in an atmosphere containing an unsaturated hydrocarbon, wherein the heating is performed at least before or after the discharge treatment at a temperature not lower than the melting point of the fluororesin molded article. A method for modifying the surface of a fluororesin molding, comprising a step of performing a treatment. 2. The surface modification method according to claim 1, wherein the fluororesin molded product is a polytetrafluoroethylene (PTFE) film or sheet. 3. The surface modification method according to claim 2, wherein said heat treatment is performed at a temperature within a range of 342 to 427 ° C.