JPH0438773B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for surface modification of polymer resins such as plastic films, and more particularly to a method for surface modification of fluororesins. [Prior Art] Today, polymer resins are widely used;
In various applications, poor adhesion of polymer resin surfaces has always been a problem. For this reason, surface modification is being investigated using various techniques such as corona discharge treatment, plasma treatment, chemical etching treatment, and sandblasting treatment. Among these, fluororesins are known to have a lower modification effect than other resins and are extremely difficult to modify. This means that, conversely, techniques that are effective for modifying heat-resistant polymer resins are also considered to be effective techniques for surface modification of other resins. Now, several modification techniques have been proposed for such fluororesins, which are difficult to surface modify. U.S. Pat. No. 3,296,011 includes glycidyl methacrylate, methyl methacrylate, acrylonitrile, styrene, p-chlorostyrene, vinyl butyl ether, methyl vinyl ketone, vinyl acetate, 1-hexane, xylene, hexane, cyclohexane, carbon tetrachloride, chloroform, tetrahydrofuran, A method of corona discharge treatment in a gas containing diethyl sulfone, N-vinyl-2-pyrrolidone, tetrapropyl titanate, etc. has been proposed, and a method of corona discharge treatment in acetone is disclosed in JP-A No. 12900/1983. . These methods modify the surface and improve adhesion, but they have the following drawbacks. Surface modification of the resin material allows the resins to adhere to each other through heat sealing. Although it is better to lower this heat sealing temperature, these methods still do not have a sufficient temperature lowering effect. For example, using these methods, a tetrafluoroethylene-hexafluoropropylene copolymer will bond at about 240°C, but in actual use it will bond at about 200°C.
Below, it is preferably used at about 180°C. If the fluororesin modified by these methods is placed under high temperature and high humidity after heat sealing, the adhesive strength will rapidly decrease. It also exhibits similar deterioration characteristics when exposed to ultraviolet rays. In various applications, the surface to be modified is
It is desirable to limit the modification to only the surface to be modified. This requirement is particularly strong for fluororesins. However, these methods have the serious drawback that the back side of the treated side is sparsely treated. For this reason, if the film is left in a rolled state after processing, so-called blocking occurs, in which the films stick together.
This phenomenon is called Ura Utsuri, and is a phenomenon that often occurs during corona discharge treatment. In JP-A-60-9734, the present inventors proposed a method of processing under specific low-temperature plasma conditions using air, CO ₂ , H ₂ , N ₂ , NH ₃ , and Ar. This method, especially the low-temperature plasma treatment using NH ₃ gas, is extremely effective, and the treated tetrafluoroethylene-hexafluoride ethylene copolymer film can be produced at temperatures of 180°C to 200°C if the processing conditions are selected. It can be bonded under certain conditions, and its adhesive strength with epoxy resins is also significantly improved. However, as a result of further study by the present inventors, in order to carry out effective reforming treatment, it is necessary to perform low-temperature plasma treatment using a gas containing NH ₃ at a gas concentration of 2% or more, and therefore treatment with ammonia is necessary. It became clear that it would be difficult to actually use it industrially due to corrosion of the equipment, deterioration of the vacuum pump oil, and residual ammonia odor within the equipment. [Problems to be Solved by the Invention] The present invention was devised in view of the various drawbacks of the prior art, and its purpose is to improve workability,
Another object of the present invention is to provide a processing method that can impart good and stable heat-sealing properties and adhesive properties to a fluororesin molded article without causing any change over time or backing. [Means for Solving the Problems] The object of the present invention is to use a gas of a compound represented by C _o H _2o+2 (n is an integer from 1 to 8) when modifying the surface of a polymer resin. This is achieved by a method for surface modification of a polymer resin, characterized in that the surface of the polymer resin is exposed to an electric discharge that is initiated and maintained by the application of a high voltage in a gas atmosphere containing plasma and that does not form a plasma polymer. . As the polymer resin used in the present invention, all known polymer resins can be used, but fluorocarbon resins are preferable because they have a large modifying effect. Examples of fluororesins include polymers and copolymers of fluorine-based monomers such as tetrafluoroethylene, trifluorochloroethylene, hexafluoropropylene, perfluoroalkoxyethylene, vinyl fluoride, and vinylidene fluoride, or polymers and copolymers of these monomers. copolymers of these monomers with monomers other than fluorine-based monomers, and mixtures of these polymers with other polymers. Among them, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer (hereinafter referred to as FPE), and tetrafluoroethylene-perfluoroalkoxyethylene copolymer (hereinafter referred to as FPE)
PFA), tetrafluoroethylene-hexafluoropropylene-perfluoroalkoxyethylene copolymer (hereinafter referred to as EPE), etc. are preferred, and particularly
FEP, PFA, EPE are preferred. The form of these polymeric resins is not particularly limited, and may take various forms such as block, plate, sheet, film, rod, and tube, but film is particularly preferred. The discharge in the present invention is started and maintained by applying a high voltage in a gas atmosphere containing C _o H _{2o +2} gas,
In addition, the discharge does not form plasma polymers. Normally, when discharge treatment is performed in an organic compound gas, a layer made of a plasma polymer is formed on the surface, but when this polymer is formed, the fluorine film cannot obtain heat sealing properties. The pressure of the gas atmosphere containing C _o H _2o+2 gas used in the present invention is not particularly limited;
More preferable conditions for not forming plasma polymerization and for effective modification treatment are 1 to 1.
A range of 1,000 Torr is preferred, and a range of 3 to 800 Torr is more preferred. When processing fluororesin, plasma polymerization tends to occur at less than 1 Torr, so the range of optimal conditions such as discharge power and processing time is narrow, resulting in poor processing reproducibility, and adhesion by heat sealing. There are problems such as the optimum conditions for improving adhesion to epoxy resins and the like are different. Moreover, if it exceeds 1000Torr, it is difficult to maintain the discharge stably.
Treatment becomes less effective. When the gas atmosphere exceeds 1 Torr, the discharge tends to become arc discharge and it becomes difficult to maintain the discharge. Therefore, it is preferable to cover the electrode to which high voltage is applied with a dielectric material such as glass. It is preferable to maintain an appropriate temperature of the electrodes by cooling the inside with water or the like. The high voltage application electrode preferably has a hollow rod-like structure, and the refrigerant flowing inside is air,
Examples include freon and water, with water being preferred. Examples of the dielectric material covering the surface of the conductor include rubber, glass, and ceramic, but glass is preferred, and its thickness is preferably 0.1 to 5 mm. It is preferable to select a dielectric material that has sufficient withstand voltage for the applied voltage. The shape of the electrode that supports the object to be processed is selected depending on the form of the object to be processed, but in the case of a long object such as a film, a drum-shaped electrode that can support the object to be processed is preferable. The size thereof is preferably formed to have a diameter twice or more, for example, the diameter of the rod-shaped high voltage applying electrode. It is also important to cover at least the surface of the drum-shaped electrode with a dielectric material, and the thickness and material of the dielectric material are the same as in the case of the rod-shaped electrode. The number of high voltage applying electrodes and the electrodes supporting the object to be processed does not need to be the same, and it is preferable to provide two or more high voltage applying electrodes for one electrode supporting the object to be processed. The distance between the electrodes is preferably set appropriately depending on the discharge conditions, and is usually appropriately selected in the range of 0.05 to 10 cm depending on the pressure conditions. The frequency of the high voltage applied to the high voltage application electrode is not particularly limited, but it is preferably selected in the range of 20kHz to 55MHz, more preferably 50kHz to 500kHz.
It is Hz. The electrode supporting the object to be processed may be grounded, or it may be floated above the ground and connected to an output terminal that is a pair of an imaging terminal with a high voltage application electrode of a high voltage power source. Naturally, it is also preferable that the high voltage power supply has a matching circuit. In the present invention, the gas composition of the atmosphere is extremely important, and at least C _o H _{2o +2} (n is 1 to 8)
It is necessary to contain a compound gas, more preferably CH ₄ where n is 1 to 4, most preferably n=1. It is preferable that the atmospheric gas contains at least 1 mol% or more, preferably 3 mol% or more, and more preferably 5 mol% or more of C _o H _2o+2 gas. Gases for diluting C _o H _2o+2 gas include He, Ne, Ar, Kr, excluding O ₂ and gases containing O ₂ .
Inert gases such as Xe, CO ₂ and N ₂ or mixed gases thereof are preferred, and Ar or an inert gas containing 40 mol % or more of Ar is more preferred. Further, a preferred diluent gas combination is Ar and CO ₂ or Ar and N ₂ . In a gas atmosphere containing C _o H _2o+2 gas, as the pressure increases, discharge starts in a stable state,
Although it becomes difficult to maintain, it becomes possible to stably start the discharge by diluting the C _o H _2o+2 gas with Ar. 50 mol% or more at pressures of 1 Torr or more
It is preferable to use a gas composition containing Ar. Furthermore, in order to improve the surface tension, it is more preferable to add CO ₂ gas. The amount of CO ₂ added is 10
~60 mol% is preferred. The discharge power when processing polymer resin is as follows:
A discharge power density of 30 to 3000 W·min/m ² is preferable, more preferably 100 to 20000 W·min/m ² or more, and still more preferably 350 to 1500 W·min/m ² . The discharge power density here is the product of the power input into the discharge space and the time divided by the discharge area.When processing long sheets such as films continuously, the discharge power density is the product of the power input into the discharge space and time divided by the discharge area. It is the amount obtained by dividing the electric power generated by the length of the discharge space in the direction perpendicular to the longitudinal direction of the film (width direction of the film) and the traveling speed of the film passing through the discharge space. Next, the method of the present invention will be explained using an example of an implementation apparatus. In FIG. 1, a polymer resin film 1 is sent out to a discharge treatment section by a delivery roll 2, and in a gas having a predetermined composition supplied from a gas introduction system 8.
A discharge is started and maintained between the high voltage application electrode 3 and the drum-shaped electrode 4 by the high voltage supplied and applied from the high voltage power source 5, and the surface is modified, and then the drum-shaped electrode 4 is wound up. It is wound up on roll 7. In this device, the drum-shaped electrode 4 is insulated from the ground, but the wiring to the drum-shaped electrode of the output transformer 6 and the drum-shaped electrode may be grounded. In addition, this apparatus is provided with a vacuum exhaust system 9 etc. because it is an example of processing in a pressure atmosphere lower than atmospheric pressure, but when processing is carried out in a pressure atmosphere higher than atmospheric pressure, as shown in Fig. 2. The structure of the gas atmosphere space forming equipment 10 is simplified, and the entire processing apparatus is simplified. [Example] The present invention will be specifically described below with reference to Examples, and the physical properties in the Examples were measured by the following methods. [Measurement method and evaluation criteria for physical properties] Bonding of films together using an adhesive Araldite Rapid (Ciba Geigy Limited, manufactured in Switzerland, Showa Kobunshi Co., Ltd.) was used as the adhesive.
After applying this to one side of the film, pasting the films together, and crimping by rolling a glass rod with a diameter of 10 mm by hand, it was heated at 100℃ for 30
I was curious for a minute. Attaching the films together by thermal adhesion Using a heat sealer, the films were adhered under the conditions of a hot plate temperature of 180 to 240°C, a pressure of 1.5 Kg/cm ² , and a heat sealing time of 10 seconds. Measurement of Adhesive Strength The obtained sample was subjected to a 180 degree peel test using a universal tensile tester (manufactured by Toyo Baldwin, Tensilon). The tensile speed was 200 mm/min. Examples 1 to 11 FEP films (Toyoflon, manufactured by Toray Industries, Inc.) having a thickness of 25 μm were treated using a mixed gas containing CH ₄ in the apparatus shown in FIG. 1 under the conditions shown in Table 1. The high voltage application electrode was covered with 1 mm thick glass.
An iron tube whose interior was cooled with water at 25°C was used, and the gap between the electrodes was set to 10 mm. The evaluation results are shown in Table 1. As is clear from Table 1, all of the samples obtained according to the present invention had a yield of 380g/380g in heat sealing at 180°C and adhesion with epoxy resin.
It showed an adhesive strength of over 1 cm. The 25μ thick FEP film begins to stretch with a tension of 380g/cm.
The film stretched. Therefore, if the adhesive strength is 380 g/cm or more, it can be judged that the adhesive strength is practically sufficient for applications using FEP. Examples 12 and 13, Comparative Example 1 Using the apparatus shown in FIG. 2, the same FEP films as used in Examples 1 to 11 were processed. The gas composition is
Examples 12 and 13 are _CH4 - _CO2 -Ar (15:10:75),
In Comparative Example 1, acetone-N ₂ (10:90) was used, and the discharge power density (W·min/m ² ) was 520 in Example 12, and 767 in Example 13 and Comparative Example 1. In each example and comparative example, the pressure was approximately atmospheric pressure (760 Torr), and the high voltage application electrode was covered with glass.
The interior was water cooled. The drum-shaped electrode was covered with rubber, and the inside was also water-cooled. The gap between the electrodes is 1
mm. The adhesive strength of these samples was examined using the heat sealing method described above. In addition, to check whether there was any back-printing, we tested whether it was possible to write on the untreated surface using Magizu ink (penterpene N50, oil-based). As a result, in Examples 12 and 13, a sufficient adhesive strength of 380 (g/cm) or more was obtained by heat sealing at 180° C., and no back side peeling was observed. On the other hand, in Comparative Example 1, heat sealing at 180°C was 30 (g/cm), and heat sealing at 210°C was 120 (g/cm).
(g/cm) and 380% at 240°C.
(g/cm) or more, sufficient adhesive strength was obtained. Furthermore, in Comparative Example 1, there were some areas on the untreated surface that could be written with magic ink, and back-printing was observed. Example 14 The same FEP film used in Example 1 and
A polyimide film (“Kapton” manufactured by Toray Industries, Inc.) with a thickness of 25 μm was prepared using the same equipment as in Example 12.
It was treated under the same conditions. Next, the treated surfaces of the treated films were aligned and laminated at a lamination speed of 0.5 m/min using a roll laminator whose roll temperature was adjusted to 260°C.
min, and bonded at a linear pressure of 10 kg/cm. When we measured the adhesive strength between the films, we found that it was 0.4
It showed a high adhesive strength of more than Kg/cm, and the FEP film caused netting. [Effects of the Invention] Since the present invention is configured as described above, it is possible to achieve a remarkable modification effect even on resins that are difficult to surface modify, such as fluorine films, and
This makes modification by electrical discharge industrially possible without causing corrosion of equipment or environmental pollution unlike conventional methods. 【table】

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing one example of an apparatus for implementing the present invention, and FIG. 2 is a schematic sectional view showing another example. 1...Polymer resin to be treated, 3...High voltage application electrode,
4...Counter electrode, 5...High voltage power supply, 6...Output transformer.

Claims (1)

[Claims] 1 When modifying the surface of polymer resin, C _o
In a gas atmosphere containing a gas of a compound represented by H _{2o +2} (n is an integer from 1 to 8), the above-mentioned polymer A method for surface modification of polymer resin, characterized by exposing the resin surface.