JP2003261698A - Method for modifying surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for modifying surface in which a fluororesin molded article can be firmly bonded to another member instead of metallic sodium treatment. <P>SOLUTION: The method for modifying the surface is characterized in that the plasma irradiation treatment is executed to a molded article whose main component is a fluororesin under the pressure of 1.5 Pa-25 Pa. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for modifying the surface of a molded article containing a fluororesin as a main component.

[0002]

2. Description of the Related Art Fluorine resin is water- and oil-repellent, wear-resistant,
It is used in various applications due to its excellent properties such as antifouling property, heat resistance, and chemical resistance, but it is generally costly because of its insufficient mechanical strength, dimensional stability, and cost. Various attempts have been made to bond or laminate a molded product containing a fluororesin as a main component with other members such as an appropriate inorganic material or organic material in order to make up for the disadvantage while making the best use of the advantage.

However, the fluororesin has a small surface free energy as compared with other resins, so that the surface is inactive, and although the above-mentioned excellent characteristics can be obtained due to the small surface free energy, Difficult to bond and wet with other substances. Therefore, in order to use a molded article containing a fluororesin as a main component as an adherend, for example, in the case of polytetrafluoroethylene (PTFE), a metal sodium treatment (after dipping in a sodium solution, exposed to the air to give a hydroxyl group, etc.) It is usually performed after performing a surface modification treatment such as (introducing) and then using an appropriate adhesive.

[0004]

However, the above-mentioned treatment with sodium metal does not give a molded article containing a fluororesin as a main component an adhesive strength sufficient to withstand practical adhesion to other mating members. Although it is possible, there are problems that a large amount of solvent has to be used, and that a dangerous and unstable treatment liquid is used and waste liquid treatment has an adverse effect on the environment. In addition, the above-mentioned sodium metal treatment has poor workability and has a risk of ignition. Therefore, instead of the treatment with metallic sodium, there is a demand for a method of modifying the surface of a molded product containing a fluororesin as a main component so that the molded product can have a sufficient adhesive strength to other mating members. The present invention has been made in order to solve the above problems, and its object is to replace the metal sodium treatment with a surface that enables strong adhesion to other members of the fluororesin molding. It is to provide a method for modifying the above.

[0005]

The present inventors have completed the present invention as a result of intensive research to solve the above problems. That is, the present invention is as follows. (1) 1.5 Pa for a molded product containing a fluororesin as a main component
A surface modification method comprising performing plasma irradiation treatment under a pressure of -25 Pa. (2) The method according to (1) above, wherein the plasma irradiation treatment is performed in an atmosphere gas selected from at least one of argon, water vapor, and ammonia. (3) The method according to (1) or (2) above, wherein the plasma irradiation treatment is performed at a temperature of 100 ° C to 250 ° C. (4) JIS K 68 of molded product after plasma irradiation treatment
The method according to any one of (1) to (3) above, wherein the adhesive strength at 25 ° C. according to the test of No. 54 is 30 N / cm or more. (5) A surface modification method, which comprises subjecting a molded article containing a fluororesin as a main component to plasma irradiation treatment under the conditions of a pressure of 5 Pa to 10 Pa, an argon atmosphere, and a temperature of 150 ° C to 220 ° C.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the plasma irradiation treatment in the surface modification method of the present invention, a discharge is generated by a direct current or an alternating current electric field in a predetermined atmosphere gas, and highly ionized plasma in a gas state is jetted. This is a process of irradiating the target object with light. In the present invention, a molded product containing a fluororesin as a main component (hereinafter, may be referred to as a “fluororesin molded product”) is treated, and 1.5 Pa to 25 Pa.
The major feature is that the surface of the fluororesin molded product is modified by performing plasma irradiation treatment under the pressure. The surface modification of fluororesin moldings by plasma irradiation has been performed in the past, but even when it is adhered to other members with an appropriate adhesive, it has enough adhesive strength to withstand practical use. There was no material that could modify the surface (generally, the adhesive strength that can withstand practical use is
Adhesion strength at room temperature (25 ° C) is 20 based on JIS K 6854 (Test method for 180 degree peel strength of adhesive)
N / cm or more). This time, the present inventors performed plasma irradiation under conditions that are lower than those of the prior art (pressure condition of the conventional plasma irradiation process: about 50 Pa to 200 Pa), so that the conventional metallic sodium treatment was performed. Without using, the adhesive strength (JIS K 6854 (test method for 180 degree peel strength of adhesive) at room temperature (25
The inventors have found a method for modifying the surface of a fluororesin molded article, which can obtain an adhesive strength equal to or higher than the adhesive strength at (° C.) of about 30 N / cm). According to such a surface modification method of the present invention, a large amount of solvent conventionally used in the metallic sodium treatment is used, a harmful and unstable treatment liquid is used to adversely affect the environment of waste liquid treatment, and workability is poor. To provide a fluororesin molded product whose surface has been modified to such an extent that it can be bonded to other members with a bonding strength that can withstand practical use without causing many problems such as the risk of ignition. You can

In the present invention, the plasma irradiation pressure is 1.
If it is less than 5 Pa, plasma is not stably generated, so that the surface modification of the fluororesin molded product by plasma irradiation is not sufficiently performed, and the above-mentioned adhesive strength at room temperature is achieved when bonded to another member. Not possible (Comparative Example 1)
reference). Further, when the plasma irradiation pressure exceeds 25 Pa, the energy during plasma irradiation is too low to sufficiently modify the surface of the fluororesin molded product, and as a result, when it is bonded to another member, Such an adhesive strength at room temperature cannot be achieved (see Comparative Example 2). Also,
From the viewpoint of improving the etching efficiency of the surface of the fluororesin molded product by the plasma irradiation treatment, the pressure condition of plasma irradiation is 2 Pa to 20 Pa, and from the viewpoint of improving the etching efficiency and the adhesive strength, 5 Pa to 10 Pa. More preferable.

The plasma irradiation in the present invention is not particularly limited as long as it is carried out within the above pressure range, and the atmosphere gas to be used is not particularly limited. Usually, argon, water vapor, nitrogen, oxygen, hydrogen, air, ammonia, used for plasma irradiation helium,
CF ₄ and a mixed gas of two or more of these can be used. From the viewpoint of improving the etching efficiency of the surface of the fluororesin molded product by the plasma irradiation treatment, argon, water vapor, ammonia, and a mixed gas of two or more of these are preferable.

Regarding the temperature condition during plasma irradiation,
There is no particular limitation as long as plasma irradiation is performed within the above pressure range, but from the viewpoint of improving the etching efficiency of the surface of the fluororesin molded product by the plasma irradiation treatment, 100 ° C to
It is preferably in the temperature range of 250 ° C,
More preferably, it is within the temperature range of 220 ° C. If the temperature condition is less than 100 ° C., sufficient adhesive force cannot be obtained (surface modification by plasma irradiation treatment tends to be insufficient), which is not preferable. Further, if the temperature condition exceeds 250 ° C., the fluororesin molding may be deformed, which is not preferable.

Among the above-mentioned methods, the surface modification method of the present invention provides a fluororesin-molded product having a surface modified so as to achieve particularly excellent adhesive strength when bonded to a mating member. Plasma treatment is performed on the fluororesin molded product under a pressure of 1.5 Pa to 25 Pa and a temperature of 100 ° C to 250 ° C in an atmosphere gas selected from argon, water vapor, nitrogen, ammonia, helium, and air. It is preferable to carry out, in particular, to obtain a fluororesin molded product whose surface has been modified so as to realize an adhesive strength superior to the adhesive strength between the fluororesin molded product obtained by the conventional sodium metal treatment and the mating member. From the viewpoint that the pressure is 5 Pa to 10 Pa and the temperature is 150 ° C. to 220 ° C. in an argon atmosphere, the fluororesin molding is subjected to plasma irradiation treatment. It is particularly preferred to carry out.

The power output frequency during plasma irradiation in the present invention is not particularly limited as long as plasma irradiation is performed within the above pressure range, but the plasma irradiation treatment improves the etching efficiency of the surface of the fluororesin molding. From the viewpoint, it is preferably 50 W to 1000 W. If the power output frequency is less than 50 W, sufficient adhesive force cannot be obtained (surface modification by plasma irradiation treatment tends to be insufficient), which is not preferable. Further, if the power supply output frequency exceeds 1000 W, it is necessary to use a special and expensive plasma irradiation device, which tends to increase the cost, which is not preferable.

Further, the time of the plasma irradiation treatment in the present invention varies depending on the pressure, the atmospheric gas, the temperature, and the power output frequency, and is not particularly limited, but good adhesiveness is obtained within the above-mentioned pressure range of the present invention. It is preferable to perform irradiation for 5 minutes to 60 minutes from the viewpoint of efficiently obtaining a fluororesin molded product having This is because if the irradiation time is less than 5 minutes, it tends to be impossible to obtain a sufficient adhesive force, and if it exceeds 60 minutes, the production efficiency tends to decrease.

The frequency of plasma excitation electric field of the power source for plasma irradiation in the present invention is not particularly limited, and DC, 5
Constant frequency alternating current such as 0 Hz, alternating current between 1 kHz and 100 kHz, radio wave such as 13.56 MHz, 2.45G
Although microwaves such as Hz can be used, radio waves such as 13.56 MHz are preferable.

The plasma irradiation in the present invention is specifically realized by ICP high-density plasma irradiation, RIE general-purpose plasma irradiation, atmospheric pressure plasma irradiation, or the like.

The fluororesin, which is the main component of the molded article in the present invention, is not particularly limited as long as it is a monomer containing fluorine polymerized or copolymerized with another suitable monomer. Specifically, polytetrafluoroethylene (PT
FE), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride system (THV), polyvinylidene fluoride system (PVDF), polychlorotrifluoroethylene system (PCTFE), chlorotrifluoroethylene-ethylene system (ECTFE), tetra Examples of various conventionally known fluororesins such as fluoroethylene-ethylene type (ETFE), tetrafluoroethylene-hexafluoropropylene type (FEP), and tetrafluoroethylene-perfluoroalkyl vinyl ether type (PFA). Among them, in the fluororesin molding obtained by using PTFE, PFA, FEP or the like, the surface energy is low and the adhesiveness is poor, so the surface modification method of the present invention is particularly useful.

The above-mentioned fluororesin molded product is prepared by mixing a composition containing a fluororesin and, if necessary, other additives, by using an apparatus such as a Henschel mixer which is commonly used in this field. It is prepared by Further, it can be appropriately molded into a desired shape by a method such as compression molding, sintering, ram extrusion or the like which is usually used for molding a fluororesin.

There is no particular limitation on the mating member to be bonded to the fluororesin molded product surface-modified by the method of the present invention by using an adhesive, and conventionally known metal materials (iron, aluminum, SUS, copper, etc.). Members made of various materials such as wood, glass, rubber, plastic (polyethylene, polyvinyl chloride, etc.) can be used. The surface modification method of the present invention is very useful, among others, in the adhesion to a member formed of a metal material, which is often used for adhesion to a fluororesin molding such as an oil seal. .

The adhesive used for adhering the fluororesin molded product surface-modified by the method of the present invention and the mating member is not particularly limited, and examples thereof include epoxy resin adhesives and fluororubber adhesives. Various conventionally known adhesives such as adhesives, polyimide resin adhesives and modified epoxy polyimide resin adhesives can be preferably used.

Examples of the epoxy resin adhesive include bisphenol epoxy resin adhesive, novolac epoxy resin adhesive, biphenyl epoxy resin adhesive, dicyclopentadiene epoxy resin adhesive and the like. .

Examples of the fluorine-based adhesive include vinylidene fluoride, perfluoroalkyl vinyl ether,
Tetrafluoroethylene, hexafluoropropylene,
Examples of the adhesive include a polymer obtained by polymerizing a fluorine-based monomer such as vinyl fluoride or a fluororesin such as a copolymer obtained by combining a plurality of monomers, or a fluororubber as a main component. The copolymer may be a copolymer with a polyolefin such as polyethylene or polypropylene.

Examples of the above-mentioned polyimide resin adhesive include bisallylnadiimide adhesive, maleimide adhesive, nadic acid polyimide adhesive and the like.

The above-mentioned modified epoxy polyimide resin type adhesive means an adhesive containing a polyimide resin and an epoxy resin as main components. As the polyimide resin serving as the base polymer, various conventionally known ones such as aliphatic polyimide, alicyclic polyimide, and aromatic polyimide are used, and are not particularly limited, but among them, heat resistance and compatibility with epoxy resin From the viewpoint of, it is preferable to use aromatic polyimide. Further, among them, thermosetting polyimides such as bisallylnadiimide-based polyimide, nadic acid-based polyimide, bismaleimide-based polyimide, and acetylene-terminated polyimide are preferable. Examples of the epoxy resin include aromatic epoxy resins such as bisphenol type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, naphthalene type epoxy resin, neopentyl glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and tetrahydrophthalate. Examples thereof include aliphatic epoxy resins such as acid diglycidyl ester and heterocyclic epoxy compounds such as triglycidyl isocyanate. As these epoxy resins, those dissolved in a conventionally known solvent such as methyl ethyl ketone are used. The epoxy resin may be a one-pack type or a two-pack type, but it is preferable to use a two-pack type thermosetting epoxy resin from the viewpoint of heat resistance.

By using the heat-resistant adhesive as described above, it is possible to maintain a strong adhesiveness with the mating member not only at room temperature but also at a high temperature of about 160 ° C. (JIS K The adhesive strength at high temperature (160 ° C.) of the 6854 adhesive measured according to the 180-degree peel strength test method is, for example, 20 N / cm or more.

[0024]

[Irradiation conditions]

・ Pressure: 2 Pa ・ Atmosphere gas: Argon ・ Temperature: 200 ° C. ・ Power output frequency: 200 W ・ Irradiation time: 15 minutes ・ Plasma excitation electric field frequency: 13.56 MHz As a fluororesin sheet, glass fiber is used for 100 parts by weight of PTFE. 5 parts by weight and 5 parts by weight of molybdenum disulfide (solid lubricant) were mixed and used to mold a fluororesin composition. A cold rolled steel plate (SPC material) was used as a mating member to be bonded. The adhesion between the fluororesin sheet and the iron plate was performed at 250 ° C. for 10 minutes. When the adhesive with the obtained fluororesin sheet was subjected to a 180 ° peel strength test of an adhesive based on JIS K 6854 at 25 ° C., the adhesive strength was 35.
It was 6 N / cm.

Example 2 An adhesive was obtained in the same manner as in Example 1 except that the plasma irradiation treatment was performed under the pressure condition of 5 Pa. When a 180-degree peel strength test was conducted in the same manner as in Example 1, the adhesive strength was 63.2 N / cm.

Example 3 An adhesive was obtained in the same manner as in Example 1 except that the pressure condition was 10 Pa and the irradiation time was 30 minutes. When a 180-degree peel strength test was conducted in the same manner as in Example 1, the adhesive strength was 54.5 N / cm.

Example 4 An adhesive was obtained in the same manner as in Example 1 except that the pressure condition was 20 Pa and the irradiation time was 60 minutes. When a 180-degree peel strength test was conducted in the same manner as in Example 1, the adhesive strength was 34.5 N / cm.

Example 5 Example 1 was repeated except that the plasma irradiation was performed under the following conditions. [Irradiation conditions] -Pressure: 2 Pa-Atmosphere gas: mixed gas of water vapor and air-Temperature: 200 ° C-Power output frequency: 500 W-Irradiation time: 30 minutes-Plasma excitation electric field frequency: 13.56 MHz Same as Example 1. When subjected to a 180 degree peel strength test, the adhesive strength was 32.3 N / cm.

Example 6 The same procedure as in Example 1 was carried out except that the plasma irradiation was carried out under the following conditions. [Irradiation conditions] -Pressure: 5 Pa-Atmosphere gas: Ammonia-Temperature: 200 ° C-Power output frequency: 400 W-Irradiation time: 20 minutes-Plasma excitation electric field frequency: 13.56 MHz Similar to Example 1, 180 degree peeling strength When a hardness test was conducted, the adhesive strength was 38.8 N / cm.

Example 7 Example 1 was repeated except that the plasma irradiation was performed under the following conditions. [Irradiation conditions] -Pressure: 5 Pa-Atmosphere gas: mixed gas of helium and nitrogen-Temperature: 200 ° C-Power output frequency: 500 W-Irradiation time: 30 minutes-Plasma excitation electric field frequency: 13.56 MHz Same as in Example 1 When subjected to a 180 degree peel strength test, the adhesive strength was 41.5 N / cm.

Example 8 As a fluororesin sheet, a fluororesin composition obtained by mixing 15 parts by weight of carbon graphite and 5 parts by weight of carbon fiber with 100 parts by weight of PTFE was used, and plasma was produced under the following conditions. The same procedure as in Example 1 was performed except that the irradiation was performed. [Irradiation conditions] -Pressure: 5 Pa-Atmosphere gas: Argon-Temperature: 200 ° C-Power output frequency: 200 W-Irradiation time: 15 minutes-Plasma excitation electric field frequency: 13.56 MHz Similar to Example 1, 180 degree peeling strength When a hardness test was conducted, the adhesive strength was 48.0 N / cm.

Example 9 Example 9 was repeated except that a modified epoxy polyimide resin adhesive was used as the adhesive. When a 180-degree peel strength test was conducted in the same manner as in Example 1, the adhesive strength was 35.0 N / cm.

Example 10 Example 10 was repeated except that an aluminum plate was used as a mating member. 1 as in the first embodiment
When the 80-degree peel strength test was conducted, the adhesive strength was 44.
It was 5 N / cm.

Example 11 Example 11 was repeated except that plasma irradiation was performed under the following conditions. [Irradiation conditions] -Pressure: 10 Pa-Atmosphere gas: mixed gas of water vapor and air-Temperature: 100 ° C-Power output frequency: 100 W-Irradiation time: 30 minutes-Plasma excitation electric field frequency: 40 kHz As in Example 1. When a 180-degree peel strength test was conducted, the adhesive strength was 41.5 N / cm.

Example 12 The procedure of Example 2 was repeated except that a modified epoxy polyimide resin adhesive was used as the adhesive. When a 180-degree peel strength test was conducted in the same manner as in Example 1, the adhesive strength was 37.5 N / cm.

Example 13 The procedure of Example 2 was repeated, except that a polyimide resin adhesive was used as the adhesive. 1 as in the first embodiment
When the 80-degree peel strength test was conducted, the adhesive strength was 34.
It was 0 N / cm.

Example 14 Example 14 was repeated except that a fluororubber adhesive was used as the adhesive. When a 180-degree peel strength test was conducted in the same manner as in Example 1, the adhesive strength was 47.5 N /
It was cm.

Example 15 The procedure of Example 2 was repeated, except that an aluminum plate was used as a mating member. 1 as in the first embodiment
The 80-degree peel strength test showed that the adhesive strength was 53.
It was 5 N / cm.

Example 16 A stainless steel plate (SUS304) as a mating member
The same procedure as in Example 2 was performed except that was used. When a 180-degree peel strength test was conducted in the same manner as in Example 1, the adhesive strength was 52.0 N / cm.

Example 17 The same procedure as in Example 1 was carried out except that the plasma irradiation treatment was carried out under the pressure condition of 10 Pa. When a 180-degree peel strength test was conducted in the same manner as in Example 1, the adhesive strength was 3
It was 1.5 N / cm.

Comparative Example 1 An adhesive was obtained in the same manner as in Example 1 except that the plasma irradiation treatment was performed under the pressure condition of 1 Pa. When a 180-degree peel strength test was conducted in the same manner as in Example 1, the adhesive strength was 7.0 N / cm.

Comparative Example 2 Example 1 was repeated except that the plasma irradiation was performed under the following conditions. [Irradiation conditions] -Pressure: 30 Pa-Atmosphere gas: Argon-Temperature: 200 ° C-Power output frequency: 200 W-Irradiation time: 60 minutes-Plasma excitation electric field frequency: 13.56 MHz Similar to Example 1, 180 degree peeling strength When the hardness test was conducted, the adhesive strength was 10.8 N / cm.

Comparative Example 3 An adhesive was obtained in the same manner as in Example 1 except that the plasma irradiation treatment was performed under the pressure condition of 30 Pa. When a 180-degree peel strength test was conducted in the same manner as in Example 1, the adhesive strength was 8.5 N / cm.

[Evaluation Criteria] Regarding Examples 1 to 17 and Comparative Examples 1 to 3, JIS K 6854 (18 of adhesive)
The above adhesive strength at room temperature (25 ° C) based on the 0 degree peel strength test) passes 30 N / cm or more, 30 N / c
Less than m was rejected.

[0045]

As is apparent from the above description, according to the present invention, a method of modifying the surface which enables strong adhesion of a fluororesin molded article to another member in place of the metallic sodium treatment is provided. Can be provided.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshiji Miyashita             Mitsubishi Electric, 8 Nishino-cho, Higashi-Mukojima, Amagasaki City, Hyogo Prefecture             Line Industry Co., Ltd. (72) Inventor Hitoshi Shimoura             663 Minoshima, Arita-shi, Wakayama Mitsubishi Electric Works             Minoshima Works Co., Ltd. F-term (reference) 4F073 AA01 BA16 CA01 CA65 CA68                       CA71 HA01 HA04

Claims (5)

[Claims] 1. A molded article containing a fluororesin as a main component,
A surface modification method comprising performing plasma irradiation treatment under a pressure of 1.5 Pa to 25 Pa. 2. The method according to claim 1, wherein the plasma irradiation treatment is performed in an atmosphere gas selected from at least one of argon, water vapor and ammonia. 3. The method according to claim 1, wherein the plasma irradiation treatment is performed at a temperature of 100 ° C. to 250 ° C. 4. The JIS of the molded product after plasma irradiation treatment.
Adhesion strength at 25 ° C of 30N according to K 6854 test
/ Cm or more, The method in any one of Claims 1-3. 5. A surface modification method, characterized in that a molded product containing a fluororesin as a main component is subjected to a plasma irradiation treatment under the conditions of a pressure of 5 Pa to 10 Pa, an argon atmosphere, and a temperature of 150 ° C. to 220 ° C. .