JPH07108944B2 - Surface modification method of fluororesin by laser light - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for surface modification of a chemically inactive fluororesin, and more specifically, the surface of a fluororesin containing a light absorbing substance is irradiated with laser light. The present invention relates to a surface modification method for improving adhesiveness and wettability, and is widely used for precision machinery / electronic device parts by laminating with various metals or polymer materials, building materials, damping materials, and the like.

[0002]

2. Description of the Related Art Fluororesin has excellent properties such as heat resistance, chemical resistance, and electrical characteristics, which are not found in other resins. However, since its surface is inactive, it is difficult to apply adhesives, paints, inks, etc., and it is difficult to form a composite with other materials. For this reason, several methods have been proposed as surface treatment techniques for fluororesins. For example, (1) E. R. Nelson et al .; Ind. Eng. C
hem. , 50 , 329, (1958) Chemical surface treatment method with complex compound solution made of tetrahydrofuran solution of sodium metal and naphthalene (2) Kakuda, Koishi; Industrial material, 29 , (2) 105 (1)
981) Surface treatment method by glow discharge (3) JP-B-53-22108 Surface treatment method by high frequency sputter etching in low pressure atmosphere (4) Ohgoshi et al .; Laser Science Research, No. 12,141
(1990) Surface modification method using ArF excimer laser and B (CH ₃ ) ₃ gas Although the method of (1) is widely used at present, a fire is generated during the treatment due to the use of metallic sodium. There are various problems in working such as induction, danger of odor, short life of treatment solution, and great care in handling the complex solution after treatment. Also,
When the treated surface is exposed to high temperature, there is a drawback that the adhesive strength is significantly reduced.

The method (2) has a remarkably low surface treatment effect as compared with a polymer containing no fluorine such as polyethylene.

The method (3) forms irregularities on the surface, but does not produce functional groups and is not sufficiently effective for improving adhesives having poor fluidity. It has the drawback that it needs to be handled with care because it easily disappears. Further, since the processing apparatus requires a vacuum system, there are drawbacks such as an increase in size, a slow processing speed, poor productivity, and adhesion of an etched resin component inside the apparatus.

In the method (4), since B (CH ₃ ) ₃ gas is used, it is necessary to perform irradiation in a closed system or a reduced pressure system, the apparatus becomes large, the processing speed is slow, and the productivity is poor. In addition, the gas is highly toxic and its working environment standards are severely limited, so that there are various operational problems such as requiring great care in handling.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel surface modification method which can solve the above-mentioned various problems and can greatly improve the adhesiveness and wettability of a fluororesin. To aim.

[0007]

[Means for Solving the Problems] Generally, fluororesins have a very small light absorption coefficient in the ultraviolet / visible region.
It is very difficult to induce a surface chemical reaction even when irradiated with high-intensity ultraviolet light such as KrF excimer laser light.
The present inventors have previously clarified that even in polyethylene which is inactive to excimer laser light, a surface chemical reaction can be effectively induced by adding a small amount of a photosensitizer such as benzophenone (Autumn 51st session). Proceedings of the Japan Society of Applied Physics, Lecture Proceedings III, p. 839 (1990)). With respect to the fluororesin, the photosensitizer and the fluororesin were mixed and molded with the expectation of the same effect. However, the photosensitizer was almost evaporated or decomposed because the molding temperature was high.
Therefore, as a result of intensive investigations based on these findings, the inventors of the present invention have solved the problems of the above-mentioned conventional techniques, and as a result, have a large light absorption coefficient in the ultraviolet / visible region, and further, molding of a fluororesin. Focusing on a light-absorbing heat-resistant polymer that withstands temperatures sufficiently, the surface of the fluororesin can be effectively modified by irradiating the fluororesin containing an appropriate amount of this with excimer laser light in the air at room temperature. The inventors have found that the adhesiveness and wettability can be greatly improved, and have reached the present invention.

(1) Fluororesin in the present invention Polytetrafluoroethylene (PTFE) Tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA) Tetrafluoroethylene-hexafluoropropylene copolymer (FEP) Tetrafluoroethylene-hexa Fluoropropylene-
Perfluoroalkoxyethylene copolymer (EPF) Tetrafluoroethylene-ethylene copolymer (ETF
E) Polychlorotrifluoroethylene (PCTFE) Trifluorochloroethylene-ethylene copolymer (EC
TFE) Polyvinylidene fluoride (PVDF) Molded product made of a polymer such as polyvinyl fluoride (PVF) or a mixture thereof.

(2) Light absorbing material used in the present invention wholly aromatic polyester polyetheretherketone (PEEK) polyimide (PI) polyetherketone (PEK) polyphenylene sulfide (PPS) aromatic polyamide polyarylate (PAR) polyether Imide (PEI) Polyamide imide (PAI) Polysulfone (PSU) Polyethersulfone (PES) and other heat resistant polymers or mixtures or similar thereof.

(3) Other additives In addition to the above light-absorbing substances, additives such as glass fiber, carbon fiber, graphite and bronze for imparting abrasion resistance may be used in combination. (4) Laser Light Used in the Present Invention As laser light, ultraviolet and visible laser light can be used, but ultraviolet laser light having a wavelength of 400 nm or less is suitable, and KrF or ArF excimer laser light is preferable.

(5) In the present invention, the laser beam irradiation is usually carried out in the atmosphere, but it may be carried out under reduced pressure or in an oxygen atmosphere.

(6) In the present invention, the laser light irradiation is usually carried out at room temperature, but it may be carried out under heating or cooling.

(7) Method of Mixing / Molding PTFE Resin and Light Absorbing Material The conventional method may be used for mixing and molding the PTFE resin and light absorbing material. PTFE resin powder (particle size 1
0-30 μm) and a light-absorbing substance, a tumbler mixer,
Using a mixer such as a Henschel mixer, dry mix in powder form, and put the mixed powder in a mold to obtain 160 to 500
Preform at a pressure of kg / cm ² to make a preform. The molding method is as follows:
Any method such as a free baking method of sintering at a sintering temperature of 80 ° C., a hot molding method of placing in a mold and sintering, or a continuous molding method using a ram extruder may be used.

(8) Mixing / molding method of heat-melting type fluororesin such as PFA and light absorbing substance A general method is used for mixing and molding the fluororesin such as PFA and the light absorbing substance. Good. Fluorine resin such as PFA and light absorbing material can be mixed with a tumbler mixer,
The mixture is preliminarily dry-mixed by using a mixer such as a hexshell mixer, and then pelletized through an extruder. It is also possible to knead using a roll kneader or a Banbury mixer kneader and pelletize with a sheet pelletizer. The blended pellets are molded into rods, tubes, films and the like using an injection molding machine and an extrusion molding machine.

[0015]

The action mechanism of the present invention is considered as follows.
That is, a high-intensity laser beam is absorbed by the light-absorbing substance added to the fluororesin in a very short time, and the energy absorbed by the light-absorbing substance causes energy transfer to the fluororesin or induces ablation. As a result, the fluorine atom on the surface of the fluororesin is effectively desorbed, and a carbonyl group or the like is generated due to the reaction with a carbon-carbon double bond (C = C) or oxygen, or surface carbonization occurs. The C = C bond and the carbonyl group thus generated are chemically active, and the surface carbonization forms an uneven surface morphology. Therefore, chemical bonding force, intermolecular force, mechanical anchoring effect, etc. It is considered that the adhesiveness and wettability were significantly improved by the above. The formation of C═C bond and carbonyl group and surface carbonization were observed by measurement by X-ray photoelectron spectroscopy.

[0016]

EXAMPLES The present invention will be described in detail based on examples.

Example 1 PTFE resin powder ("Fluon G-1" manufactured by Asahi Fluoro Co., Ltd.)
63 ") and 5 parts of wholly aromatic polyester (" Econol E-101 "manufactured by Sumitomo Chemical Co., Ltd.) are dry-mixed using a Henschel mixer, and put into a mold of 135 (75) φ, 320 kg / A preform having an outer diameter of 135 mm, an inner diameter of 75 mm, and a height of 100 mm was preformed at a pressure of cm ² , put in a hot air heating furnace, sintered at 360 ° C. for 3 hours, and then slowly cooled to room temperature to be a sintered molded product. Got Using this peeling machine, a skiving sheet having a thickness of 300 μm was prepared using a peeling machine to prepare a sample piece for excimer laser light irradiation.

Irradiation with excimer laser light was performed as follows. That is, thoroughly wash with ethanol before irradiation,
A sample piece having a width of 30 mm and a length of 150 mm dried in the air is set in a sample holder, and the irradiation position is aligned with the optical axis. Then, an excimer laser HyperEX-460 manufactured by Lumonix Co., Ltd.
KrF excimer laser light (wavelength: 248 nm, fluence: 101 mJ / cm ² · pulse) was irradiated with 622 shots at room temperature in the atmosphere. After irradiation, a mask was used to make the width 30 mm and the length 15 mm. The fluence of the excimer laser light was adjusted by placing a concave lens made of quartz between the excimer laser and the mask, changing the distance between the lens and the sample piece, and measured with a power meter manufactured by Scientech.

The peel strength of the test piece irradiated with the laser beam was measured as follows. That is, width 25 mm, length 1
50mm, 300μm thick stainless steel plate and width 30m
Epoxy adhesive (“Bond E Set Cleaner” manufactured by Konishi Co., Ltd.) was applied to each of the test pieces measuring m, 150 mm in length, and 300 μm in thickness, the coated surfaces were overlaid, and the weight (bottom surface 6 cm × 6 cm, 3 kg) was applied. ) Was placed and left for 12 hours or more for adhesion. Then, as shown in FIG. 1, the test piece was pulled in a direction of an arrow at a speed of 10 mm / min with a tensile tester (Autograph P-100 manufactured by Shimadzu Corporation), and 180 °.
As a result of measuring the peel strength, a value of 7.5 kg / 25 mm was obtained. This value is the value of unirradiated test piece (0.1kg / 25m
It was significantly larger than that of m) and the adhesion was greatly improved.

The wetting index of the sample piece was measured according to Japanese Industrial Standard K6768. That is, a series of mixed liquids having different surface tensions are applied to the test piece,
The numerical value of the surface tension of the mixed solution which was determined to be wet with the test piece was determined. As a result, a value of 44 dyn / cm was obtained as the wetting index, which was significantly larger than the value of the unirradiated test piece (<31 dyn / cm), and the wettability was also significantly improved.

Examples 2 to 14 Table 1 shows the results (Examples 2 to 14) when the kind of the light absorbing substance, the composition of the PTFE resin powder and the light absorbing substance and the laser light irradiation conditions were changed. . The method of preparing the test piece, the method of irradiating the laser beam, and the method of measuring the peel strength and the wetting index are all the same as in Example 1.

Example 15 80 parts of PFA resin pellets ("Polyflon AP-210" manufactured by Daikin Industries, Ltd.) and polyether ether ketone ("Victort PEEK" manufactured by Mitsui Toatsu Chemicals, Inc.)
150 P ") 20 parts are mixed using a Henschel mixer, and then a twin screw extruder is used to obtain a cylinder temperature of 370 ° C.
Were mixed and pelletized. The pellets thus obtained were extruded from a T-die at a cylinder temperature of 360 ° C. using a uniaxial extruder to prepare a test piece having a thickness of 300 μm, which was used as a sample for excimer laser light irradiation. Table 1 shows the excimer laser light irradiation conditions and the results. PT
Similar to the FE resin, the PFA resin also had improved adhesion. The method of irradiating the excimer laser light and the method of measuring the peeling strength are the same as in Example 1.

Comparative Example 1 Table 1 shows the results of the PTFE test pieces containing no light absorbing substance. In this case, the adhesion and wettability were hardly improved. The laser light irradiation conditions are as shown in Table 1, and the method for preparing the test piece and the method for measuring the peel strength and the wetting index are the same as in Example 1.

Comparative Example 2 Table 1 shows the results of PFA test pieces containing no light-absorbing substance. In this case, the adhesion and wettability were hardly improved. The PFA test piece preparation method and excimer laser light irradiation conditions are the same as in Example 15, and the peel strength and wetting index measurement methods are the same as in Example 1.

[0025]

[0026]

EFFECTS OF THE INVENTION According to the present invention, by irradiating the surface of a fluororesin molded article with a high-intensity ultraviolet laser beam, it is possible to process efficiently in a short time and at room temperature in the atmosphere
The surface can be treated with a very simple operation, and the adhesiveness and wettability can be greatly improved. In particular, the improved adhesiveness enables a wide range of composites of fluororesin moldings and other materials, and is a novel surface modification technique that can be expected to be used in a wide range of fields.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a method for measuring a 180 ° peel strength of a test piece according to the present invention.

[Explanation of symbols]

 1: Test piece, 2: Adhesive, 3: Stainless plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunichi Sugimoto 25-1 Mitsui Minamimachi, Neyagawa City, Osaka Pref., Japan Atomic Energy Research Institute Osaka Branch (72) Inventor Yoshiro Hirashima 14-5 Shimokitada, Neyagawa City, Osaka Spinning Kurashiki (72) Inventor Masao Endo 14-5 Shimokita-machi, Neyagawa-shi, Osaka Kurashiki Spinning Co., Ltd. (72) Inventor Tomohiro Nagase 14-5 Shimokita-machi, Neyagawa-shi, Osaka Kurashiki Spinning Co., Ltd. Inside Technical Research Laboratory (56) Reference JP-A-2-196834 (JP, A)

Claims (3)

[Claims] 1. A method for modifying the surface of a fluororesin, which comprises irradiating a surface of the fluororesin containing a light-absorbing substance with laser light. 2. The method according to claim 1, wherein the light-absorbing substance is a heat-resistant substance which can withstand the molding temperature of the fluororesin, is mixed with the fluororesin and is then molded, and the surface of the molded product is irradiated with laser light. 3. The light-absorbing substance is wholly aromatic polyester, polyetheretherketone, polyimide, polyetherketone, polyphenylene sulfide, aromatic polyamide, polyarylate, polyetherimide, polyamideimide, polysulfone, polyethersulfone, etc. 3. The method of claim 2 which is a polymer of the above or a mixture or analog thereof.