JPH0218690B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a fluororesin adhesive structure that can be bonded with an adhesive and has extremely high adhesive strength. Fluoroplastics have excellent heat resistance, chemical resistance, and weather resistance, as well as unique properties such as friction resistance and non-adhesion, and are used in industrial fields such as chemicals, electricity, and machinery. . However, on the other hand, the excellent properties of fluororesins make them extremely difficult to process. In particular, the non-adhesive property of fluororesins poses a major obstacle in laminating them with other materials such as rubber, metals, and plastics, forcing restrictions on the development of their applications. In the past, several methods have been proposed for imparting adhesive properties to fluororesin, including chemical treatment in which the surface of the fluororesin base material is etched with a sodium-ammonia complex salt or a sodium-naphthalene complex compound. Laws can be mentioned. However, this method not only requires the use of dangerous chemicals, but also has the problem that the adhesive activity imparted by coloring or etching the treated surface is lost in a relatively short period of time. In addition, by applying a dispersion containing fluororesin powder and filler powder such as metal oxide powder to the surface of a fluororesin base material and then heating it, a layer of a mixture of fluororesin powder and filler can be formed. A method is also known in which the fluororesin base material is bonded to another material by forming a filler on the surface of the base material and using the anchoring function of the filler contained in the mixture layer. According to this method, there is no danger of using chemicals as in chemical treatment methods, but the surface of the filler powder in the mixture layer is likely to be covered with a fluororesin film, and the fluororesin base material can be mixed with other materials. When gluing, the anchoring force may not be sufficiently exerted. As a result of intensive studies to improve the latter method, the inventors of the present invention found that a mixed thin layer of fluororesin powder and filler powder formed on the surface of a fluororesin base material was subjected to atmospheric pressure within a predetermined range. It has been discovered that the anchoring function of the thin layer is increased by sputter etching treatment under these conditions, and that when the base material is bonded to other materials through this thin layer, the adhesive strength is improved, and the present invention has been made. This is what we have come to complete. That is, the method for manufacturing the fluororesin adhesive structure according to the present invention is such that the volume ratio of the fluororesin powder with an average particle size of 0.05 to 50μ and the filler powder with an average particle size of 10μ or less is
A dispersion of 95/5 to 50/50 is applied to the surface of a fluororesin base material, and then heated to a temperature higher than the melting point of the fluororesin to form fluororesin powder and filler powder on the surface of the base material. The method is characterized in that a mixed thin layer is fused and formed, and then the mixed thin layer is subjected to a sputter etching treatment under an atmospheric pressure of 0.0005 to 0.5 Torr. In the present invention, the fluororesin as a component of the fluororesin base material or the mixed thin layer formed on the surface of the base material is not particularly limited, and various fluororesins can be used, but polytetrafluorocarbon Ethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE) Application of the present invention to ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), etc.
These resins are of high value because they are used industrially and there is a desire to improve adhesive strength. Also,
In the present invention, it is preferable that the constituent components of the fluororesin base material and the constituent components of the mixed thin layer be of the same type of fluororesin, from the viewpoint of thermal fusion strength between the base material and the mixed thin layer. The dispersion used in the present invention has an average particle size of 0.05 to
A fluororesin powder with a diameter of 50μ and a filler powder with an average particle diameter of 10μ or less are contained as dispersoids, and the volume ratio of the two is 95/5 to 50/50, preferably 90/10 to 60/40. As the filler, metal oxides or silicon compounds that do not dissolve in the dispersion medium and have heat resistance can be used. Specific examples of metal oxides include aluminum oxide, zinc oxide, titanium oxide, chromium oxide, iron oxide, and cobalt oxide. Specific examples of silicon compounds include fine particulate silicon oxide, aluminum silicate, etc.
Examples include calcium silicate, diatomaceous earth, and kaolin. This filler is used in powder form with an average particle size of 10μ or less. The average particle size of the filler is
If it is 10μ or more, when the filler powder is mixed with the fluororesin powder into a dispersion medium and made into a dispersion liquid, the filler powder settles quickly and tends to separate, making it difficult to apply a dispersion liquid with a uniform composition to the surface of the fluororesin base material. This is not desirable because it becomes Further, the fluororesin powder used has an average particle size of 0.05 to 50 .mu.m in order to improve dispersibility and prevent the thickness of the mixed thin layer formed on the surface of the fluororesin base material from becoming unnecessarily thick. The volume ratio of the above fluororesin powder and filler powder is 95/
It is blended in a range of 5 to 50/50. Filler powder is 5
If the volume is less than %, even if the thin mixed layer formed on the base material is subjected to the sputter etching process described below,
When this material is bonded to other materials, there is almost no effect of improving the adhesive strength, and if it exceeds 50% by volume, the amount of fluororesin powder used as a binder for forming a mixed thin layer becomes too small and the base material becomes too small. Both are undesirable because the adhesive strength between the material and the filler powder decreases and the filler powder falls off from the mixed thin layer formed on the surface of the substrate. As the dispersion medium, non-toxic, unnatural water, trichlorotrifluoroethane, etc. are suitable, but tetrachloroethane, trichloroethylene, methylchloroform, etc. can also be used. Furthermore, a surfactant can be added to improve the stability of the dispersion. The ratio of the dispersoid to the dispersion medium in the dispersion liquid is 3/97 to 50/3 in terms of volume ratio from the viewpoint of stability of the dispersion liquid and workability when coating on the surface of the fluororesin base material.
It is preferable to set it in the range of 50. A dispersion containing a fluororesin powder and a filler powder as a dispersoid can be prepared by dispersing the fluororesin powder and filler powder separately in a dispersion medium and then mixing them together, or by dispersing the fluororesin powder and filler powder in a dispersion solution containing one of the powders. It can be obtained by adding and mixing the other powder. Furthermore, filler powder can also be used by dispersing it in a polymerization solution obtained by emulsion polymerization of a fluorine-based monomer. In the present invention, first, the above-described dispersion containing fluororesin powder and filler powder as dispersoids is applied to a predetermined surface of a fluororesin base material. The dispersion can be applied to the surface of the substrate by pouring, dipping, roll coating, gravure coating, spraying, or the like. After applying the dispersion liquid to the surface of the fluororesin base material in this manner, the base material is heated to a temperature higher than the melting point of the fluororesin, and a mixed thin layer of the fluororesin powder and filler powder is applied to the base material. Form a fusion bond on the surface. The preferred heating temperature varies depending on the type of fluororesin, and is, for example, 350 to 390°C in the case of PTFE, 310 to 380°C in the case of FEP or PFA, and 290 to 340°C in the case of ETFE. In addition, when the fluororesin constituting the base material and the fluororesin powder in the dispersion are different in type, at least one of them is preferably heated to a temperature higher than the melting point of both fluororesins. The thickness of this mixed thin layer is set depending on the particle size and content of the filler powder in the thin layer, but is usually about 0.5 to 70 microns, preferably about 1 to 10 microns. In addition, in the present invention, in order to prevent the formation of voids in the mixed thin layer due to evaporation of the dispersion medium during the heating, preheating is performed in advance at the evaporation temperature of the dispersion medium prior to the heating, and a portion of the dispersion medium is can also be removed. In the present invention, the mixed thin layer thus formed on the surface of the fluororesin base material is subjected to a sputter etching treatment. The sputter etching process for mixed thin layers is performed at an atmospheric pressure of 0.0005 to 0.5 Torr.
Conducted under the following conditions. This is because if the atmospheric pressure is less than 0.0005 Torr, the discharge for sputter etching will not be sustained, and if it is more than 0.5 Torr, the etching rate will drop significantly and the discharge itself will become unstable. Furthermore, other sputter etching processing conditions include the normal frequency of several hundred KHz to several tens of MHz, the practically allocated frequency for industrial use of 13.56MHz, and the discharge power of 0.1 to several tens of MHz.
It is 10Watt/ ^cm2 . The lower the discharge power, the longer the treatment time needs to be, so in practice it is better to increase the discharge power and reduce the treatment time (the degree of surface treatment is approximately expressed as the product of the discharge power and the treatment time). ). In the present invention, in order to perform sufficient sputter etching treatment on the mixed thin layer in a short time, the product of discharge power (Watt/cm ² ) and treatment time (sec) is approximately 0.1
~200Watt・sc/cm ² Preferably about 1~100watt・
It is best to set the discharge power and processing time so that the discharge rate is sec/cm ² . Various gases can be used as the atmospheric gas, but in practice, inert gases such as argon, air, water vapor, carbon dioxide gas, etc. are used. Next, an example of a sputter etching processing apparatus will be explained with reference to the drawings. Reference numeral 1 denotes an exhaust pipe connected to a vacuum pump (not shown) for exhausting gas in the reduced pressure container 2, 3 indicates a valve for introducing atmospheric gas into the reduced pressure container 2, and 4 indicates a fluororesin base material 5. It is an electrode for sputter etching the mixed thin layer 6 formed on the surface of the external matching box 7 (impedance matching device), which is electrically insulated from the reduced pressure vessel 2 and connected to an external matching box 7 (impedance matching device) using a lead wire hermetically sealed. ), and is further led to a high frequency power source 8. 9 is a shielding electrode for electrode 4, and a high frequency power source 8
It is electrically connected to the ground side of the 10 is a counter electrode which is also connected to the ground side of the high frequency power source 8. The reduced pressure container 2 serves to maintain the atmospheric pressure constant, and if a metal reduced pressure container is used, it is connected to the ground side of the high frequency power source 8. The matching box 7 is a circuit consisting of capacitance and inductance, and performs impedance matching. Next, to explain the outline of the sputter etching process principle, when the potential on the electrode 4 side is negative with respect to the counter electrode 10, positive ions generated as a result of discharge are accelerated and collide with the surface of the mixed thin layer 6. Then, sputter etching is performed. At this time, the positive charges of the collided positive ions accumulate on the surface of the mixed thin layer 6, increasing the surface potential, so the potential difference between this surface and the counter electrode 10 becomes small, and the discharge is maintained. It becomes difficult to do. However, in the next half cycle of the high-frequency voltage, the potential on the electrode 4 side becomes positive with respect to the counter electrode 10, so electrons enter the surface of the mixed thin layer 6 from the discharge space, and the negative charge that the electrons have Neutralizes the positive ions that have accumulated on the surface. As a result, when the potential on the electrode 4 side becomes negative with respect to the counter electrode 10 in the next half cycle of the high frequency voltage, the potential difference between the two becomes large and discharge occurs, and the generated positive ions are accelerated. It impinges on the surface of the mixed thin layer 6, making it possible to carry out sputter etching.
The above steps are repeated for each cycle of the high frequency voltage, and the surface of the mixed thin layer 6 is sputter etched. By subjecting the surface of the mixed thin layer to sputter etching using the apparatus described above, the adhesive strength with other materials is improved. This is because the fluororesin film covering the filler powder is removed by sputter etching, exposing the filler powder on the surface of the mixed thin layer, and this exposed filler powder has excellent adhesion to other materials. It is inferred that the main reason for this is that it performs an anchoring function. The present invention is configured as described above, and since the mixed thin layer formed on the surface of the fluororesin base material is subjected to sputter etching treatment, it is possible to provide a structure that can firmly adhere to other materials. . Further, unlike conventional chemical treatment methods, this method not only does not cause discoloration of the treated surface, but also has the characteristics that the treatment effect hardly deteriorates over time. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 Finely particulate titanium oxide (manufactured by Kanto Kagaku Co., Ltd., trade name: Titanium Oxide GR) having an average particle size of 0.03 μm was uniformly dispersed in an 8% by weight aqueous solution of a nonionic surfactant. Separately, an aqueous dispersion of PTFE powder having an average particle size of 0.2 μm (manufactured by Mitsui Fluorochemical Co., Ltd., trade name: Teflon 30-J) is prepared. These two are mixed to form a dispersion liquid in which the volume ratio of PTFE powder to titanium oxide powder is 60/40, and the volume ratio of these dispersoids to water as a dispersion medium is 10/90. Next, one side of a PTFE sheet with a thickness of 0.2 mm was masked, immersed in the above dispersion, pulled up, preheated at a temperature of 80 °C for 10 minutes, part of the water was removed, and the mask was removed. , and further heated at a temperature of 380° C. for 5 minutes to form a thin layer of the mixture with a thickness of 3 μm on one side of the PTFE sheet. After that, the PTFE sheet was set in the sputter etching processing equipment shown in the drawing, and the atmospheric pressure was maintained at 5 × 10 ^-3 Torr while introducing argon gas.
Apply a high frequency voltage of 13.56MHz to generate a discharge force.
The surface of the mixed thin layer was sputter etched for 15 seconds at a rate of 1Watt/ ^cm2 (the amount of discharge treatment was
15 Watt·sec/cm ² ), the power was turned off and the pressure returned to normal pressure to obtain a sheet-shaped PTFE adhesive structure (Sample 1). The above PTFE adhesive structure and a 2 mm thick aluminum plate were bonded using an epoxy adhesive (manufactured by Konishi Co., Ltd., product name: Bond E Set Clear) by heating at a temperature of 80°C for 60 minutes, and the adhesive strength was The results are shown in Table 1 below. Adhesion strength is at temperature 25
It was measured by the 180° peeling method at a temperature of 300 mm/min at a tensile speed of 300 mm/min. For comparison, a PTFE adhesive structure (sample 2) obtained in the same manner as sample 1 except that the volume ratio of fluororesin powder and titanium oxide powder was 98/2 and one side of the PTFE sheet were prepared. At the same time, data are shown for a sheet (Sample 3) which was subjected to only sputter etching treatment without forming a mixed thin layer. The adhesive structure obtained by performing the same procedure as in Sample 1 except that the volume ratio of the fluororesin powder and the titanium oxide powder was 40/60 was the same as that of the fluororesin powder compared to the titanium oxide powder. was insufficient, the binder effect of the resin powder was small, and when the mixed thin layer was touched by hand, the titanium oxide powder fell off. Example 2 Ultrafine colloidal silica powder (manufactured by Dupont, trade name: Ryuudox AS) having an average particle size of 0.015 μm was uniformly dispersed in an 8% by weight aqueous solution of a nonionic surfactant. Separately, an aqueous dispersion of PTFE powder having an average particle size of 0.2 μm (manufactured by Daikin Corporation, trade name Polyflon D-1) is prepared. These two are mixed to form a dispersion liquid in which the volume ratio of PTFE powder to colloidal silica powder is 80/20, and the volume ratio of these dispersoids to water as a dispersion medium is 20/80. Next, the dispersion was applied to one side of a PTFE sheet with a thickness of 0.05 mm using a gravure coater, and
Preheat for a minute. Thereafter, heating above the melting point of PTFE and sputter etching treatment of the mixed thin layer formed on one side of the PTFE sheet by the heating were sequentially performed under the conditions shown in Table 1 to obtain a sheet-like PTFE adhesive structure (Sample 4). ) was obtained. The adhesive strength of this structure was measured under the same conditions as in Example 1. The results obtained are shown in Table 1. For comparison, data for the case where the mixed thin layer was bonded to the iron plate without undergoing sputter etching treatment (sample 5) is also shown. Example 3 Ultrafine anhydrous silica powder with an average particle size of 0.007μ (manufactured by Nippon Aerosil Co., Ltd., trade name Aerosil #800)
was uniformly dispersed in an 8% by weight aqueous solution of nonionic surfactant. On the other hand, apart from this, an aqueous dispersion of FEP powder with an average particle size of 0.3μ (manufactured by Daikin, trade name: NEOFLON)
Prepare ND-1). These two are mixed to form a dispersion liquid in which the volume ratio of FEP powder to anhydrous silica powder is 90/10, and the volume ratio of these dispersoids to water as a dispersion medium is 30/70. Next, the above dispersion liquid is poured onto one side of a 0.25 mm thick FEP sheet and preheated at a temperature of 80° C. for 10 minutes. Thereafter, heating above the melting point of FEP and sputter etching treatment of the mixed thin layer formed on one side of the FEP sheet by the heating were sequentially performed under the conditions shown in Table 1 to obtain a sheet-like FEP adhesive structure (Sample 6). ) was obtained. The adhesive strength of this structure was measured under the same conditions as in Example 1. The results obtained are shown in Table 1. For comparison, data for the case where the mixed thin layer was bonded to the iron plate without undergoing sputter etching treatment (sample 7) is also shown. Example 4 Everything was the same as Example 1 except that PTFE powder with an average particle size of 35μ was used, the preheating was at 80°C for 30 minutes, and the heating and sputter etching conditions were set as shown in Table 1. A sheet-like PTFE adhesive structure (Sample 8) was obtained by the same operation. The adhesive strength of the structure is shown in Table 1. Example 5 A sheet-like adhesive structure (Sample 9) was obtained by carrying out the same procedure as in Example 1 except for using diatomaceous earth powder with an average particle size of 7 μm. The adhesive strength of the structure is shown in Table 1.

[Table] As is clear from the above examples and comparative examples,
It can be seen that the adhesive structure made of fluororesin obtained by the method of the present invention has a high adhesive strength with other materials.

[Brief explanation of drawings]

The drawing is a schematic diagram showing an example of a sputter etching processing apparatus used in the present invention. 2...Reduced pressure container, 4...Electrode, 5...Fluororesin base material, 6...Mixed thin layer, 8...High frequency power source, 9
...Shield electrode, 10...Counter electrode.

Claims (1)

[Claims] 1 The volume ratio of fluororesin powder with an average particle size of 0.05 to 50μ and filler powder with an average particle size of 10μ or less is 95/5 to 95/5.
By applying a 50/50 dispersion onto the surface of a fluororesin base material and then heating it above the melting point of the fluororesin, a thin layer of a mixture of fluororesin powder and filler powder is formed on the surface of the base material. 1. A method for producing an adhesive structure made of fluororesin, characterized in that the thin mixed layer is sputter etched under conditions of an atmospheric pressure of 0.0005 to 0.5 Torr.