JP2002225204A - Modified fluororesin coated material and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a practical method for producing a fluororesin coated material having high adhesion properties between the fluororesin and a base material and showing no deformation. SOLUTION: The method for producing the modified fluororesin coated material comprises coating the surface of the base material, having thermal stability at a temperature of the melting point of the fluororesin or higher, with the fluororesin and irradiating the surface of the fluororesin film with an ionizing radiation to cause a crosslinking reaction of the fluororesin and a chemical reaction between the fluororesin and the surface of the base material to be carried out at the same time, thereby achieving a strong adhesion between the both.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a modified fluororesin coating material and a method for producing the same. More specifically, the present invention relates to a composite material in which the surface of a substrate is covered with a fluororesin film modified by crosslinking.

[0002]

2. Description of the Related Art Fluororesins are excellent plastics having properties such as heat resistance, chemical resistance, non-adhesion, water repellency, stain resistance, lubricity, and friction resistance. It is a resin material that is increasingly used in industrial and consumer applications such as packing, gaskets, tubes, insulating tapes, bearings, and roof films for air domes. In addition, it is a promising material as a heat control material for artificial satellites because of its excellent atomic oxygen resistance. However, fluororesins are highly sensitive to radiation, and especially for polytetrafluoroethylene (hereinafter referred to as PTFE), the irradiation dose is 1 kGy.
If it exceeds, its mechanical properties deteriorate, so it cannot be used in a radiation environment such as space or nuclear facilities.

In the use as a coating material of a fluororesin, PTFE is applied to a metal surface such as an iron or a frying pan.
There is already a technique for applying and coating a coating.
However, the bonding between the chemically extremely stable PTFE and the base material is not performed by a chemical bond such as a covalent bond, but is based on a physical bond. When added, the resin is easily separated from the substrate. Therefore, no unique material has been developed yet, in which a building material such as a tin roof or a tiled roof is coated with a fluororesin to take advantage of features such as water repellency, antifouling property, and lubricity. The disadvantages of PTFE itself, such as being weak to radiation, easily abraded, and insufficiently transparent, remain the same even with the coating material.

In order to improve the radiation resistance of PTFE, the present inventors have already applied for a patent application (JP-A-6-116).
No. 423), a method for producing modified PTFE, characterized by irradiating ionizing radiation at a temperature equal to or higher than the crystal melting point of PTFE in the absence of oxygen. However, even in this modified PTFE made of a powder or a molded body, the chemical properties are extremely stable and insoluble in almost all solvents. Even if these are coated on a base material such as a metal by a method such as coating, the adhesion between the PTFE and the base material is not a chemical bond but a physical bond. Not. In addition, tetrafluoroethylene-based copolymers other than PTFE are also chemically very stable materials, and when coated with a coating, adhesion to a substrate is not performed by chemical bonding. The resin was easily separated from the material, and the adhesive properties as a coating material were insufficient.

[0005]

As described above, the fluororesin has poor adhesion to other kinds of base materials, and the sheet or tube-like fluororesin molded film, particularly, the film thickness of 300 or less.
Radiation cross-linking of thin films of less than μm is accompanied by significant deformation such as wrinkles and distortions. Therefore, there is a need for a practical method for producing a fluororesin coating material that has high adhesion between the fluororesin and the substrate and does not cause deformation.

[0006]

According to the present invention, to solve the above-mentioned problems, a surface of a substrate having thermal stability at a temperature not lower than the melting point of the fluororesin is coated with the fluororesin, By irradiating the surface of the resin film with ionizing radiation, a cross-linking reaction of the fluororesin and a chemical reaction between the fluororesin and the substrate surface are simultaneously caused, thereby achieving strong adhesion between the two. A method for producing a modified fluororesin coating material.

Therefore, in the modified fluororesin-coated material thus obtained, the surface of a substrate having thermal stability at a temperature equal to or higher than the melting point of the fluororesin is coated with the crosslinked fluororesin film. In addition, the substrate and the fluororesin film are firmly adhered to each other by chemical bonding. Further, in this modified fluororesin coating material, the thickness of the fluororesin can be 300 μm or less, and the thickness uniformity can be within ± 10% of the average value of the film thickness.

The coating step can be carried out by applying a fluororesin paste or a solution containing the fluororesin to the surface of the substrate, or by attaching a fluororesin film to the surface of the substrate. Irradiation with ionizing radiation following this coating step is performed in an oxygen-free atmosphere at 100
Performed at a temperature in the range of ~ 400 ° C and an irradiation dose of 1 kG
It is preferably in the range of y to 10 MGy.

The substrate is preferably selected from a polyimide resin, a metal material, ceramics, and glass, and is preferably a material having excellent heat resistance. The substrate may be in any form, but is preferably in the form of a plate, foil, tube, or fiber.

The present invention meets the demand for improving the low adhesiveness between a substrate and a fluororesin, which is a disadvantage of the conventional fluororesin coating material. In other words, it not only has radiation resistance when used in a radiation environment such as space or a nuclear facility, but also solves all problems in mechanical properties, etc., and has a smooth surface and uniform film thickness and Provided is a composite material in which a base material is covered with a radiation-resistant fluororesin film, and the base material and the fluororesin film are firmly adhered to each other by a chemical bond.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the manufacturing method of the present invention, first, the surface of a base material made of metal, ceramics, glass, or a polymer material and having a plate-like, foil-like, tubular, or fibrous shape is used. A material coated with a desired thickness of the fluororesin is prepared by applying a fluororesin paste or a liquid mixed with the fluororesin, or by adhering a fluororesin film to the surface of the substrate. The term "apply to the surface of the substrate" as used herein includes not only the outer surface of the substrate but also the inner surface of a tubular member or the like, and the former case is generally referred to as coating, and the latter case is referred to as lining. In some cases. The method for applying or sticking may be any method routinely performed by those skilled in the art. For example, when applying a solution in which a fluororesin is mixed, a liquid (a so-called dispersion) in which a powder of a fluororesin is uniformly dispersed is applied to a substrate. As a liquid for dispersing the powder efficiently, ie, a dispersion medium, water and an emulsifier, water and alcohol, water and acetone, or a mixed solvent of water, alcohol, and acetone can be used. Can be readily selected and prepared by those skilled in the art. At this time, the particle size of the fluororesin powder is preferably 50 μm or less, and more preferably, the size is equal to or less than the desired film thickness of the finally obtained coating material. If the particle size exceeds 50 μm, it is difficult to achieve the desired uniformity of the film thickness, which is not preferable.

After applying the dispersion to the substrate, the dispersion medium is removed by air drying or hot air drying.
Then, it is immediately fired at a temperature in the range of 100 to 400 ° C, preferably 260 to 380 ° C, which is higher than the crystal melting point of the fluororesin.

Next, this material is placed in an oxygen-free atmosphere, and ionizing radiation is applied to the surface of the fluororesin film in a dose range of 1 kGy to 10 MGy while maintaining the temperature range of 250 to 400 ° C., preferably 250 to 350 ° C. Irradiate. At this time, the above-described firing and radiation irradiation may be performed simultaneously. If the temperature of the atmosphere is lower than 250 ° C., the radiation crosslinking reaction of the fluororesin does not occur, and if the temperature of the atmosphere exceeds 400 ° C., the thermal decomposition of the fluororesin is promoted and the material properties are deteriorated. In addition, if the irradiation dose is less than 1 kGy, the reaction by radiation is insufficient, and no improvement in characteristics can be expected.
Past studies have shown that irradiation with radiation exceeding 0 MGy does not significantly improve the properties of the fluororesin itself due to crosslinking, and further irradiation is not preferred.

[0014] Irradiation of the radiation causes crosslinking of the fluororesin, and the base material and the fluororesin chemically adhere to each other due to a chemical reaction. Further, according to this method, the surface of the fluororesin film can be made smooth, and the uniformity of the thickness can be made within ± 10% of the average value of the film thickness. If the thickness uniformity is greater than ± 10%, not only the dimensional accuracy and appearance of the material will be problematic, but also if the friction surface is used particularly in applications requiring wear resistance. Point contact is likely to occur locally, which is not preferable. The reason that the fluororesin film can be prepared uniformly in this way is that the resin is irradiated with ionizing radiation while maintaining the resin in a temperature range not lower than its crystal melting point, so that the resin is in a state where it is easy to move, and when the resin is crosslinked, It is considered that the surface tension is generated by the slight contraction.

[0015] The thickness of the modified fluororesin coating material obtained by irradiation with radiation is preferably 300 µm or less. If the film thickness exceeds 300 μm, the gas generated during the cross-linking treatment tends to cause deformation, and foaming easily occurs inside the cross-linked resin, which is not preferable. This film thickness can be arbitrarily adjusted by controlling the powder concentration of the dispersion in the coating step or by selecting the number of times of application. When the fluororesin film is attached to the surface of the base material, the final thickness of the fluororesin film can be adjusted by adjusting the thickness of the film.

The chemical bonding state between the fluororesin and the substrate is as follows:
An X-ray photoelectron spectroscopy (ESC) capable of qualitatively and quantitatively analyzing elements on a material surface and elucidating the bonding state of each atom from a chemical shift of a signal obtained.
A) can be confirmed.

As the fluororesin in the present invention, a tetrafluoroethylene polymer, a polytetrafluoroethylene (PTFE) which is a copolymer thereof, and a tetrafluoroethylene / hexafluoropropylene copolymer (FE) are used.
P), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene copolymer (ETFE and PVd
F) and the like, and also includes those made of a mixed resin material composed of two or more kinds of resins, and those composed of a resin composition obtained by adding a different component other than a fluororesin to these. Examples of such different components include fibrous or powdery materials such as glass, carbon, metals, metal oxides, ceramics, heat-resistant organic materials, and minerals.

The ionizing radiation in the present invention means an electron beam, an X-ray, a neutron beam, a high energy ion, or a mixed radiation thereof. The temperature of the atmosphere during irradiation with ionizing radiation is controlled by heating the atmosphere using an indirect or direct heat source such as a normal gas circulation type thermostat, infrared heater or panel heater, or electronic control. The heat generated by controlling the energy of the electron beam obtained from the accelerator can be directly used as a heat source. Further, the irradiation in an oxygen-free atmosphere of the present invention refers to an atmosphere in which the atmosphere is replaced with an inert gas such as helium or nitrogen, in addition to a vacuum.
By using an oxygen-free atmosphere, the chemical reaction between the fluororesin and the base material and the crosslinking reaction of the fluororesin during irradiation are promoted, and conversely, oxidative decomposition can be prevented.

The shape of the material used as the base material in the present invention can be arbitrarily selected.
Alternatively, fibrous or the like is preferable. The material is copper,
In addition to metal materials such as aluminum and their alloys, ceramics, glass, and polymer materials (for example, polyimide resin) are listed. All materials that wake up apply.

[0020]

EXAMPLES The present invention will be specifically described below with reference to examples. However, the scope of the present invention is not limited by these examples, and modifications and structural elements which can be easily made by those skilled in the art. The scope of the invention is defined by the appended claims, including substitutions.

[0021]

Example 1 A liquid was prepared by dispersing 60 parts of PTFE fine powder having an average particle size of 0.25 μm in 100 parts of a dispersion medium composed of water and acetone. This liquid is applied to a polyimide resin film (KAPTON, manufactured by DuPont, hereinafter referred to as “Kapton”) having a thickness of 75 μm and a size of 5 cm × 5 cm, and drying is repeated. By firing the material at 340 ° C., a preformed body having a thickness of 110 μm was produced. The preform was transferred to an irradiation container at 340 ° C. in an argon gas atmosphere, and irradiated with electrons accelerated to 300 kV by an electron accelerator at 100 kGy. Due to the crosslinking reaction, the powder particles completely disappear,
The applied PTFE layer became transparent. In the obtained coating material, the Kapton and the PTFE layer did not peel even by bending or rubbing, and a strong adhesion state was obtained.

The surface condition of the coating material was analyzed by ESCA. In the polyimide, the signal indicating the bond between the carbon atom of 285.6 eV and the aromatic ring and the signal indicating the bond between the carbon atom and the oxygen atom of 289.2 eV were greatly reduced, and the signal indicating the bond between PTFE and the carbon atom was detected. It was confirmed that PTFE was chemically bonded to Kapton. The measurement signal of Kapton by ESCA is shown in FIG. This indicates that the site to which the carbon atom is bonded is a benzene ring and an oxygen atom. FIG. 2 shows measurement signals of the Kapton / PTFE coating material. This indicates that the site to which the carbon atom is bonded is mainly a fluorine atom. Kapton and Kapton / PTFE
The element ratio in the coating material is shown in Table 1 below. This shows a state where fluorine atoms are bonded to the surface of the film due to the composite of PTFE.

[0023]

[Table 1]

Next, when the thickness of the coating material was measured with a micrometer at any five points of the sample, the thickness was 105 μm ± 2 μm, and a coating material having a smooth surface and a uniform thickness was obtained. The coating material was cut out into a ASTM-1822L type dumbbell test piece and subjected to a tensile test by Instron. As a result, a good value equivalent to that of untreated Kapton (thickness: 75 μm) was shown. Table 2 below shows the values of elongation at break and tensile strength as tensile properties.

[0025]

[Table 2]

[0026]

Example 2 PTFE fine powder 5 having an average particle size of 0.3 μm with respect to 100 parts of a dispersion medium composed of water and acetone.
A liquid in which 0 parts were dispersed was prepared. This liquid has a thickness of 5
A 0 μm, 5 cm × 5 cm size titanium foil was applied and dried, and then the composite film was fired at 340 ° C. to produce a 66 μm thick preform. The preform was transferred to an irradiation container at 340 ° C. in an argon gas atmosphere, and electrons accelerated to 800 kV by an electron accelerator were supplied to 500 kG.
Irradiated y. As in Example 1, the cross-linking reaction completely eliminated the powder particles, and the applied PTFE layer became transparent. In the obtained coating material, peeling of the titanium foil and the PTFE layer did not occur even by bending or rubbing, resulting in a strong adhesion state.

Observation of the cross section of this coating material with an electron microscope confirmed that the adhesion between the titanium foil and PTFE was good. In addition, the surface of the PTFE was polished cleanly with sandpaper, and the surface condition was evaluated by ESCA.
As a result, a signal due to the bonding of the modified PTFE and the titanium atom was detected at 466.4 eV together with the signal of the titanium atom at 460.8 eV, and it was confirmed that the bonding was achieved chemically.

[0028]

Example 3 A liquid was prepared by dispersing 40 parts of PTFE fine powder having an average particle size of 0.45 μm in 100 parts of a dispersion medium composed of water and acetone. This liquid is repeatedly applied to an aluminum plate having a thickness of 75 μm and a size of 5 cm × 5 cm and dried, and then the composite plate material is fired at 340 ° C. to obtain a 1.2 mm-thick preform. Was prepared. The preform was transferred to an irradiation container at 340 ° C. in an argon gas atmosphere, and irradiated with electrons accelerated to 2 MV by an electron accelerator at 150 kGy. As in Example 1, the cross-linking reaction completely eliminated the powder particles, and the applied PTFE layer became transparent. In the obtained coating material, the aluminum plate and PTFE can be bent or rubbed.
No delamination occurred, resulting in a strong bond.

When the cross section of this coating material was observed with an electron microscope, it was confirmed that the adhesion between the aluminum plate and PTFE was good. When the surface condition of this coating material was analyzed by ESCA in the same manner as in Example 2, a signal due to the bonding of the modified PTFE and the aluminum atom was detected at 122.9 eV together with a signal of 117.5 eV of the aluminum atom. It was confirmed that they were bound together.

The coating material and P as a control were
The dynamic friction coefficient and the specific wear amount of a 100% TFE film (thickness: 1 mm) were measured by a thrust-type friction and wear tester. The test results are shown in Table 3 below. This indicates that the PTFE film causes abnormal abrasion and the film is shaved, whereas the abrasion is significantly suppressed in the modified coating material.

[0031]

[Table 3]

[0032]

Example 4 FEP dispersion solution (brand 120
-J: Mitsui-Dupont Fluorochemical Co., Ltd.) (average particle size: 0.2 μm, FEP54 to 100 parts of dispersion medium)
(A part dispersed) was applied to a copper plate having a thickness of 500 μm and a size of 5 cm × 5 cm, dried and then fired at 270 ° C. to produce a preform having a thickness of 550 μm. The preformed body was transferred to an irradiation container in a nitrogen gas atmosphere at 280 ° C., and irradiated with electrons accelerated to 2 MV by an electron accelerator at 300 kGy. As in Example 1, the powdery particles completely disappeared due to the crosslinking reaction, and the applied FEP layer became transparent. In the obtained coating material, the copper plate and the FEP layer did not peel even by bending or rubbing, and a strong adhesion state was obtained.

When the cross section of this coating material was observed with an electron microscope, it was confirmed that the adhesion between the copper plate and PTFE was good. Example 2 Regarding the surface condition of this coating material
When analyzed by ESCA in the same manner as described above, 122.
Modified F to 127.7 eV with a signal of copper atom of 5 eV
A signal due to the binding of EP and a copper atom was detected, and it was confirmed that they were chemically bound.

[0034]

According to the method of the present invention, a fluororesin coated on a base material such as polyimide is irradiated with radiation while being supported by the base material, and undergoes a chemical reaction with the base material and the fluororesin itself. Cross-linking reaction proceeds. Therefore, it is possible to easily produce a fluororesin coating material having a smooth surface and a uniform film thickness by firmly bonding the substrate and the fluororesin film by chemical bonding.

[Brief description of the drawings]

FIG. 1 is a graph showing a measured signal of Kapton by ESCA.

FIG. 2 is a graph showing measured signals of a Kapton / PTFE coating material by ESCA.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08J 7/00 305 C08J 7/00 305 // C08L 79:08 C08L 79:08 (72) Inventor Yone Tabata Ho 5-2-2-1, Kasugacho, Nerima-ku, Tokyo Hills Nerima Kasugacho 601 F-term (reference) 4D075 BB29X BB42Z DA06 DA15 DB01 DB13 DB14 DB53 EA21 EB18 4F073 AA05 AA32 BA31 BB01 BB03 CA41 CA42 CA65 EA02 EA65 HA05 4F100 AB01 AB12 AB33 AD00A AG00A AK17B AK18B AK49A AL01B AL05B AT00A BA02 BA07 DA11 DA20 DE01 EH46 EJ05B EJ42 EJ52 EJ53 GB07 GB51 JB01 JJ03 JJ03A JK02 JK09 JL06 JL11 JL14 YY00B

Claims (8)

[Claims] The surface of a substrate having thermal stability at a temperature equal to or higher than the melting point of the fluororesin is covered with a crosslinked fluororesin film, and the substrate and the fluororesin film are chemically bonded to each other. A modified fluororesin coating material that is strongly bonded. 2. The film thickness of the fluororesin is 300 μm or less, and the uniformity of the thickness is ± 10% with respect to the average value of the film thickness.
The modified fluororesin coating material according to claim 1, which is within the range. 3. The modified fluororesin coating material according to claim 1, wherein the fluororesin is one or more selected from tetrafluoroethylene-based polymers and tetrafluoroethylene-based copolymers. . 4. The base material is selected from a polyimide resin, a metal material, ceramics, and glass,
The modified fluororesin coating material according to claim 1, which is a material having excellent heat resistance. 5. The modified fluororesin coating material according to claim 1, wherein the substrate is a material in any form selected from a plate, a foil, a tube, and a fiber. 6. A method of coating a surface of a substrate having thermal stability at a temperature equal to or higher than the melting point of the fluororesin with the fluororesin, and then irradiating the surface of the fluororesin film with ionizing radiation. A cross-linking reaction and a chemical reaction between the fluororesin and the substrate surface simultaneously, thereby achieving a strong adhesion between the two.
A method for producing a modified fluororesin coating material. 7. The coating step is performed by applying a fluororesin paste or a liquid containing the fluororesin to the surface of the substrate, or by attaching a fluororesin film to the surface of the substrate, The method according to claim 6, wherein the uniformity of the thickness of the fluororesin coating film after irradiation with ionizing radiation is within ± 10% of the average value of the film thickness. 8. The method according to claim 6, wherein the irradiation with the ionizing radiation is performed in an oxygen-free atmosphere at a temperature in the range of 250 to 400 ° C., and the irradiation dose is in the range of 1 kGy to 10 MGy.