JP6782310B2 - Photocatalyst film bonding method - Google Patents

Description

The present invention relates to a technique for joining photocatalytic membranes to each other.

For example, a photocatalyst layer, which is a layer of a fluororesin in which a photocatalyst powder having a photooxidizing action such as titanium dioxide is mixed in a membrane material used as a building material for constructing a membrane structure, is formed on one surface or both. There is a photocatalytic film on the surface of. The photocatalyst powder in the photocatalyst layer exerts a photooxidation action by receiving light such as sunlight, and exerts excellent functions such as antifouling, deodorization, and antibacterial action based on the oxidation action.

By the way, when the membrane structure is large to some extent, it becomes necessary to connect the photocatalyst film with another photocatalyst film.
The photocatalyst film is generally bonded by stacking the edges of the photocatalyst film with a predetermined width and then heating and welding the overlapped portion. Such welding is carried out by heating the overlapping portions of the adjacent photocatalyst films at a temperature higher than the melting point of the fluororesin while pressurizing them at an appropriate pressure in many cases.

However, even with such a welding method, there are cases where the peel strength of the joint is not sufficient. In order to eliminate such insufficient peel strength of the bonded portion, a thin fluororesin film that is different from the photocatalyst film to be bonded, for example, made of a fluororesin having a relatively low melting point and is more easily melted, is used as the photocatalyst film. A technique is used in which the peel strength of the joint portion of the photocatalyst film is increased by sandwiching it between the parts to be overlapped and then heating it. In this technique, the molten surface portion of the fluororesin film functions like an adhesive, so that the peel strength of the joint portion of the photocatalyst film is improved.

By the way, even when the fluororesin film as described above is used for bonding the photocatalyst film, the peel strength of the bonded portion may deteriorate. This possibility is not limited to the case where the edges of the photocatalyst film are bonded to each other, but generally occurs when the photocatalyst film is bonded. More precisely, the above-mentioned deterioration of the peel strength is caused by the passage of time after the joining, and the inventor of the present application describes the cause of the possibility of such deterioration of the strength as follows. I'm guessing.
One of the general methods for producing a photocatalyst film is to apply a dispersion liquid containing a photocatalyst powder and a fluororesin to a film material made of fluororesin, then dry the dispersion liquid and bake it at a high temperature. , A photocatalyst layer is formed on the surface of the film material.
By the way, in general, an additive which is an organic substance such as a surfactant is added to the above-mentioned dispersion liquid mainly for the purpose of improving the dispersibility of the fluororesin and the photocatalytic powder in the dispersion liquid. These additives remain in the photocatalyst layer for a certain period of time even after firing. Then, after the photocatalyst film is constructed as a part of the membrane structure, the remaining additives are oxidized by ultraviolet rays or by the photooxidizing action of the photocatalyst and gradually decomposed by irradiation with sunlight or the like. Becomes a decomposition product. The detailed mechanism is unknown at this time, but it is considered that the peeling strength of the joint may be deteriorated due to the above-mentioned decomposition products appearing on the surface of the photocatalyst film. In such a case, if it is a place other than the joint portion, the decomposition product or the like is washed away due to rainfall or the like, so that no problem occurs. The inventor of the present application believes that the presence of decomposition products and the like that have moved to the joint surface between the photocatalyst layer and the fluororesin film causes the deterioration of the peel strength at the above-mentioned joint portion.

An object of the present invention is to reduce the deterioration of the peel strength of the joints between photocatalytic films using a fluororesin film.

In order to solve the above-mentioned problems, the inventor of the present application proposes the following three inventions. For convenience, they are referred to as the first invention, the second invention, and the third invention, respectively.

According to the first invention, when photocatalyst films having a photocatalyst layer containing a fluororesin and a photocatalyst powder on at least one surface thereof are superposed with a predetermined width, the photocatalyst film is formed between the superposed portions of the photocatalyst film. A fluororesin film formed of a first fluororesin having a melting point equal to or lower than that of the basic fluororesin, which is a fluororesin that accounts for the majority of the contained fluororesins, is sandwiched, and in that state, the photocatalyst film is formed. This is a method of joining a photocatalyst film that joins the overlapped portions of the photocatalyst film via the fluororesin film by heating the overlapped portions.
In the first invention, the fluororesin film is a fluororesin having a melting point equal to or lower than that of the basic fluororesin, which contains a carbonate having a melting point of 330 ° C. or higher and a water solubility of 2 g / 100 g or lower. When a fluororesin film formed of a second fluororesin is provided on at least one surface thereof and the fluororesin film is sandwiched between the overlapping portions of the photocatalyst film, the carbonate-containing layer is formed. It is brought into contact with the photocatalyst layer.
As a result of the research of the present inventor, the decomposition products produced by the ultraviolet rays or the photooxidative action of the photocatalyst from the additives remaining in the photocatalyst layer of the photocatalyst film have a melting point of 330 ° C. or higher and a water solubility of 2 g / 100 g or lower. In order to promote peeling at the interface between the photocatalyst film and the fluororesin film after the photocatalytic action occurs, such as disappearing by reaction with a certain carbonate or being adsorbed by the carbonate. It turns out that it loses some required functionality. In the first invention, in a state where the carbonic acid-containing layer containing a carbonate in the fluororesin film is in contact with the photocatalyst layer, the overlapped portions of the photocatalyst film are bonded to each other via the fluororesin film. After the photocatalyst film was later constructed as a part of the film structure, decomposition products generated from the additive by ultraviolet rays or by the photooxidation action by the photocatalyst are formed on the photocatalyst layer and the carbonate-containing layer of the fluororesin film. Even if it moves to the joint surface of the photocatalyst film, the decomposition product disappears by the reaction with the carbonate or is adsorbed by the carbonate to promote the peeling at the joint interface between the photocatalyst film and the fluororesin film. Since some function necessary for the photocatalyst film is lost as described above, the peeling strength of the joint portion between the photocatalytic films is less likely to decrease for a long period of time.
Examples of carbonates having a melting point of 330 ° C. or higher and a water solubility of 2 g / 100 g or lower include calcium carbonate (CaCO ₃ ), barium carbonate (BaCO ₃ ), magnesium carbonate (MgCO ₃ ), and lithium carbonate (Li ₂ CO _3). ), Strontium carbonate (SrCO ₃ ), or a combination thereof can be used, and the above description of carbonate also applies to the cases of the second invention and the third invention.

As described above, the carbonate-containing layer in the first invention has a second fluororesin having a melting point equal to or lower than that of the basic fluororesin, and a second fluororesin having a melting point of 330 ° C. or higher and a water solubility of 2 g / 100 g or lower. It is formed by a certain carbonate. The reason why the second fluororesin constituting the carbonate-containing layer is a fluororesin having a melting point equal to or lower than that of the basic fluororesin is to increase the meltability of the fluororesin in the carbonate-containing layer, so that the photocatalyst films can be used together. This is because the peel strength of the joint can be increased.
The method for producing a fluororesin film in which a carbonate-containing layer is formed on at least one surface of the first fluororesin is basically free. For example, the fluororesin film has a melting point of 330 on the dispersion of FEP (tetrafluoroethylene / hexafluoropropylene copolymer) on at least one surface of the fluororesin film base material formed of the second fluororesin. It can be produced by applying a dispersion liquid to which carbonate powder, which is a carbonate powder having a temperature of ° C. or higher and a water solubility of 2 g / 100 g or less, is applied and drying the dispersion liquid. After the dispersion is dried, the FEP and carbonate contained in the FEP dispersion are further heated and fired to further strengthen the adhesion between the first fluororesin and the carbonate-containing layer. Since the fluororesin in the carbonate-containing layer on the surface of the fluororesin film melts at the time of joining the photocatalyst films, the above-mentioned firing process is not always necessary.
The carbonate-containing layer is provided on one surface of the fluororesin film base material formed of the second fluororesin, or on both surfaces. The photocatalyst film to be bonded may have a photocatalyst layer on only one surface thereof, or may have a photocatalyst layer on both surfaces. When joining photocatalyst films having a photocatalyst layer only on one surface thereof, the photocatalyst films are usually joined so that the surfaces having the photocatalyst layer are oriented in the same direction. In this case, the fluororesin film sandwiched between the photocatalyst films overlapped with each other has only one surface in contact with the photocatalyst layer. In this case, it is sufficient that the carbonate-containing layer is provided only on the surface of the fluororesin film that comes into contact with the photocatalyst layer. On the other hand, when the photocatalyst films having the photocatalyst layers on both surfaces are bonded to each other, both surfaces of the fluororesin film sandwiched between the overlapped portions of the photocatalyst films come into contact with the photocatalyst layers. In this case, the carbonate-containing layer is provided on both surfaces of the fluororesin film that comes into contact with the photocatalyst layer of the photocatalyst film.

The above-mentioned first fluororesin used in the fluororesin film of the first invention is also a fluororesin having a melting point equal to or lower than that of the basic fluororesin, like the second fluororesin. The reason why the melting point of the first fluororesin is such is the reason already described that the melting point of the second fluororesin is such, including the cases of the second invention and the third invention described below. Is the same as.
The "basic fluororesin" in the photocatalyst film of the first invention is as follows. As described above, the photocatalyst film has a photocatalyst layer, and the photocatalyst layer contains a fluororesin. By the way, the photocatalyst film usually contains a fluororesin in a portion other than the photocatalyst layer. The fluororesin contained in the photocatalyst layer and the fluororesin contained in the portion of the photocatalyst film other than the photocatalyst layer may or may not be the same. Further, the fluororesin contained in the portion of the photocatalyst film other than the photocatalyst layer may be one type or two or more types. Since a plurality of types of fluororesin in the photocatalyst film may be mixed or laminated in this way, in the first invention, the fluororesin that occupies the majority of the fluororesin contained in the photocatalyst film is defined as the basic fluororesin. (The standard for determining "majority" shall be weight). For example, when the basic fluororesin is PTFE, a photocatalyst film in which a FEP layer is provided on a relatively thick layer of PTFE and a photocatalyst layer is provided on the upper layer is an example of a basic fluororesin in a photocatalyst film. It becomes. The photocatalyst film may include a base material woven from an inorganic fiber such as glass fiber or a material other than fluororesin such as glass beads for increasing the bulk of the fluororesin, but these are photocatalysts. It shall not affect the determination of which of the fluororesins that occupy the film is the basic fluororesin. The above description of the "basic fluororesin" also applies to the cases of the second invention and the third invention.

In the first invention, it is also possible to make the second fluororesin the same as the first fluororesin. As a result, when the photocatalyst films are bonded to each other, it becomes easier to strengthen the adhesion between the carbonate-containing layer of the fluororesin film and the first fluororesin.

Also in the second invention, when the photocatalyst films having the photocatalyst layer containing the fluororesin and the photocatalyst powder on at least one surface thereof are superposed with a predetermined width, the photocatalyst film is formed between the overlapped portions of the photocatalyst film. A fluororesin film formed of a first fluororesin having a melting point equal to or lower than that of the basic fluororesin, which is a fluororesin that accounts for the majority of the contained fluororesins, is sandwiched, and in that state, the photocatalyst film is formed. This is a method for joining a photocatalyst film that joins the overlapped portions of the photocatalyst film via the fluororesin film by heating the overlapped portions.
Then, in the second invention, the fluororesin film having a carbonate powder, which is a carbonate powder having a melting point of 330 ° C. or higher and a water solubility of 2 g / 100 g or lower, attached to at least one surface thereof. When the fluororesin film is sandwiched between the overlapping portions of the photocatalyst film, the surface of the fluororesin film to which the carbonate powder is attached is brought into contact with the photocatalyst layer.
The second invention differs from the first invention in that the fluororesin film of the first invention has a carbonate-containing layer containing a second fluororesin and a carbonate on a film base material formed of the first fluororesin. On the other hand, in the fluororesin film of the second invention, the carbonate powder is simply adhered to at least one surface of the fluororesin film formed of the first fluororesin which is substantially the same as the film base material. The point is that it is.
Even if such a fluororesin film to which the carbonate powder is attached is used, the peel strength of the bonded portion when the edges of the photocatalyst film are bonded to each other is less likely to decrease for a long period of time, as in the case of the first invention.
The carbonate powder may be attached to at least one surface of the fluororesin film, but may be attached to both surfaces. In the case of the first invention, the carbonate-containing layer may be provided on only one surface of the fluororesin film or on both surfaces for the same reason.

The method of adhering the carbonate powder to the fluororesin film may be any method.
For example, the carbonate powder can be attached to at least one surface of the fluororesin film by electrostatic adhesion by causing the fluororesin film to be charged with static electricity. Alternatively, the carbonate powder is adhered to at least one surface of the fluororesin film, and the carbonate powder sprinkled on the at least one surface of the fluororesin film is applied to the at least one surface of the fluororesin film. It can be done by pressing. These two methods can be easily used because the work of adhering the carbonate powder to the fluororesin film can be performed at the site where the photocatalyst films are bonded to each other.
Even if the carbonate powder and the fluororesin film are not firmly fixed, when the photocatalyst film is bonded to each other by sandwiching the fluororesin film between the overlapping portions of the photocatalyst film, the photocatalyst film is formed. Since the carbonate powder can be arranged on the interface between the photocatalyst layer and the fluororesin film, it does not affect the action and effect of the second invention.

Also in the third invention, when the photocatalyst films having the photocatalyst layer containing the fluororesin and the photocatalyst powder on at least one surface thereof are superposed with a predetermined width, the photocatalyst film is formed between the overlapped portions of the photocatalyst film. A fluororesin film formed of a first fluororesin having a melting point equal to or lower than that of the basic fluororesin, which is a fluororesin that accounts for the majority of the contained fluororesins, is sandwiched, and in that state, the photocatalyst film is formed. This is a method for joining a photocatalyst film that joins the overlapped portions of the photocatalyst film via the fluororesin film by heating the overlapped portions.
Then, in the third invention, the fluororesin film to which a carbonate having a melting point of 330 ° C. or higher and a water solubility of 2 g / 100 g or lower is added is used.
The third invention differs from the first invention in that the fluororesin film of the first invention has a carbonate-containing layer containing a second fluororesin and a carbonate on a film base material formed of the first fluororesin. On the other hand, the fluororesin film of the third invention uses a fluororesin film itself to which the carbonate is added.
Even if such a fluororesin film to which carbonate powder is added is used, the peel strength of the bonded portion when the photocatalyst films are bonded to each other is less likely to decrease for a long period of time, as in the case of the first invention.
Since the fluororesin film of the third invention originally contains a carbonate, when the photocatalyst film has a photocatalyst layer on only one surface or a photocatalyst layer on both surfaces. Can also be handled.

As the basic fluororesin, the first fluororesin, and the second fluororesin in the first to third inventions, various ones can be used. However, the basic fluororesin, the first fluororesin, and the second fluororesin must satisfy the relationship as already described for their melting points.
Examples of the fluororesin used for the basic fluororesin, the first fluororesin, and the second fluororesin include polytetrafluoroethylene (hereinafter referred to as PTFE, which has a melting point of 327 ° C.) and a tetrafluoroethylene / ethylene copolymer (hereinafter referred to as PTFE). Hereinafter, it is referred to as ETFE, which has a melting point of 260 to 270 ° C.), a tetrafluoroethylene / perfluoroalkyl vinyl ether-based copolymer (hereinafter, referred to as PFA, which has a melting point of 310 ° C.), and tetrafluoroethylene / hexafluoropropylene. System copolymer (hereinafter referred to as FEP; melting point is 260 ° C.), polychlorotrifluoroethylene (hereinafter referred to as PCTFE; melting point is 220 ° C.), polyfluorovinylidene (hereinafter referred to as PVDF; melting point is 151 to 178 ° C.), polyvinyl fluoride (hereinafter referred to as PVF; the melting point is 203 ° C.) and the like.
For example, PTFE, ETFE, or FEP can be used as the basic fluororesin, and FEP can be used as the first fluororesin.

FIG. 5 is a cross-sectional view conceptually showing the contents of a method for joining fluororesin films to each other according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view showing the structure of the photocatalyst film shown in FIG. FIG. 5 is a side view showing the relationship between the photocatalyst film and the fluororesin film when joining is performed by using the method of joining the photocatalyst films described with reference to FIG.

Hereinafter, preferred first, second, and third embodiments of the present invention will be described.
Common objects in each embodiment shall be designated by a common reference numeral, and common description shall be omitted in some cases.

<< First Embodiment >>
In the first embodiment, as shown in the perspective view of FIG. 1, two photocatalyst films 1 are laminated and joined to a portion to be overlapped with a predetermined width via a sandwiched fluororesin film 2. As a result, the two photocatalyst films 1 are joined.
In FIG. 1, the edges of the photocatalyst film 1 are overlapped with each other by a predetermined width to join the edges of the photocatalyst film 1, but the bonded portion is not necessarily the edge of the photocatalyst film 1. Not limited to departments.

The photocatalyst film 1 is, for example, an existing one, and is not limited to this, and is configured as shown in the cross-sectional view of FIG. The photocatalyst film 1 includes a base material which is a cloth formed by weaving or knitting glass fibers 11 in the center thereof. The base material in this embodiment is made by weaving glass fiber 11. Both sides of the base material are coated with a fluororesin layer 12 made of fluororesin. The fluororesin forming the fluororesin layer 12 can be appropriately selected from known fluororesins, and can be, for example, any one of PTFE, ETFE, PFA, FEP, PCTFE, PVDF, and PVF. In this embodiment, the fluororesin layer 12 is formed of PTFE (melting point is 327 ° C.). Although not shown, the fluororesin layer 12 may have multiple layers such as a PTFE layer and a FEP layer.
A photocatalyst layer 13 is provided on at least one outermost layer of the fluororesin layer 12. In the photocatalyst film 1 shown in FIG. 2, the photocatalyst layer 13 is provided on only one side of the photocatalyst film 1. The thickness of the photocatalyst layer 13 is relatively thin compared to the thickness of the fluororesin layer 12. The photocatalyst layer 13 contains a fluororesin and a photocatalyst powder. Further, in the photocatalyst layer 13, additives such as a surfactant used in the production process are applied at least during the production of the photocatalyst film 1 itself or the processing such as bonding (before the photocatalytic action by the photocatalyst occurs). It remains, albeit slightly. The fluororesin contained in the photocatalyst layer 13 may or may not be the same as the fluororesin forming the fluororesin layer 12, but in this embodiment, the two are different. In this embodiment, the fluororesin contained in the photocatalyst layer 13 is FEP.
As described above, the photocatalyst layer 13 is relatively thinner than the fluororesin layer 12. Therefore, the fluororesin that occupies the majority of the weight ratio of the fluororesin contained in the photocatalyst film 1 is PTFE that forms the fluororesin layer 12. That is, the basic fluororesin referred to in the present application is PTFE in this embodiment.
The photocatalyst film 1 may not have the above-mentioned base material, and may be composed of the fluororesin layer 12 and the photocatalyst layer 13.

Next, the fluororesin film 2 will be described with reference to FIG.
The fluororesin film 2 includes a film base material 21 and a carbonate-containing layer 22 that covers at least one surface of the film base material 21.
The film base material 21 is basically made of only fluororesin except for a small amount of residues such as additives. The fluororesin forming the film base material 21 is a fluororesin having a melting point equal to or lower than that of the basic fluororesin, and corresponds to the first fluororesin in the present application. Since the basic fluororesin is PTFE as described above and its melting point is 327 ° C., the fluororesin forming the film base material 21 is selected from those having a melting point of 327 ° C. or lower. Although not limited to this, in this embodiment, the fluororesin forming the film base material 21 has a melting point of FEP of 260 ° C. The carbonate-containing layer 22 is composed of a fluororesin and a carbonate powder. The fluororesin contained in the carbonate-containing layer 22 is a fluororesin having a melting point equal to or lower than that of the basic fluororesin, and corresponds to the second fluororesin in the present application. Although not limited to this, in this embodiment, the fluororesin contained in the carbonate-containing layer 22 is FEP. If the fluororesin contained in the carbonate-containing layer 22 is FEP, the fluororesin contained in the carbonate-containing layer 22 and the fluororesin constituting the film base material 21 are the same, but these are always the same. It does not have to be.
As the fluororesin forming the film base material 21, it is preferable to use a fluororesin having a melting point equal to or lower than that of the basic fluororesin, and more preferably, the fluororesin forming the film base material 21 and the carbonate-containing layer 22 are used. For both of the fluororesins contained, it is preferable to use a fluororesin having a melting point equal to or lower than that of the basic fluororesin. This makes it possible to join more firmly.

Such a fluororesin film 2 can be manufactured, for example, as follows.
In this embodiment, the fluororesin film 2 is formed on at least one surface of the film base material 21 formed of FEP as a carbonate having a melting point of 330 ° C. or higher and a water solubility of 2 g / 100 g on a dispersion of FEP. , Calcium carbonate was added to the dispersion, and the dispersion was dried to produce the product. The carbonate that satisfies the above conditions is any one of calcium carbonate (CaCO ₃ ), barium carbonate (BaCO ₃ ), magnesium carbonate (MgCO ₃ ), lithium carbonate (Li ₂ CO ₃ ), and strontium carbonate (SrCO ₃ ). Alternatively, combinations can be used.
The film base material 21 may be formed into a film by melt extrusion using FEP pellets as a fluororesin as a raw material, or a dispersion of FEP may be thinly applied to the surface of a metal plate such as stainless steel and dried. It can be produced by firing and peeling from a metal plate, but an existing fluororesin film may be used. Examples of the existing fluororesin film include neofluorinated FEP film manufactured and sold by Daikin Industries, Ltd.
The dispersion in which calcium carbonate powder is added to the FEP dispersion for forming the carbonate-containing layer 22 is a FEP aqueous dispersion (solid content 54% by weight, manufactured by Mitsui-Dupont Fluorochemical Co., Ltd., product number: FEP 120- 1000 g of JR), 0.54 g to 54 g of calcium carbonate powder (manufactured by Kishida Chemical Co., Ltd., product number: 000-13435) with a particle size of 10 to 20 μm, 1000 g of purified water, silicone-based surfactant (momentive performance) 40 g of Material's Japan GK, product number: SILWET L-77) was mixed in a container and adjusted by stirring. The particle size of the carbonate is not limited to the above range, but it is preferable to use a carbonate having a particle size of 0.03 to 100 μm, and more preferably one having a particle size of 1 to 30 μm. Is good.
The dispersion was applied to the film substrate 21 on both sides by a dipping coating method, air-dried, and then dried at 60 ° C. for 5 minutes to form a carbonate-containing layer 22. After this, firing may be performed at a temperature equal to or higher than the melting point of FEP, but this is omitted in this embodiment.
The weight ratio of the calcium carbonate powder to the FEP in the carbonate-containing layer 22 after drying can be 0.1% to 10%, more preferably 0.1% to 5%. By using the fluororesin film 2 on which the carbonate-containing layer 22 having a weight ratio within the above range is laminated is used for bonding the photocatalytic film, sufficient peel strength of the bonded portion can be maintained even after a certain period of time has passed after the occurrence of the photocatalytic action. Is possible.

The fluororesin film 2 as described above is formed by cutting or the like so as to correspond to the shape and size of the bonded portion of the photocatalyst film 1, and as shown in FIG. 1, the two photocatalyst films 1 are formed. It is sandwiched between the parts to be overlapped with the predetermined width of. Then, in that state, the hot plate is pressed against the overlapped portion of the two photocatalyst films 1 and heated to be heat-welded. A well-known hot plate welding machine can be used for such heat welding. The heating temperature at this time was at least a temperature equal to or higher than the melting point of the FEP, and in this embodiment, the heating was performed at 370 ° C. for 70 seconds. As described above, the overlapped portions of the photocatalyst film 1 are joined to each other via the fluororesin film.
When the fluororesin film 2 is sandwiched between the overlapped portions of the two photocatalyst films 1, the carbonate-containing layer 22 of the fluororesin film 2 is brought into contact with the photocatalyst layer 13 of the photocatalyst film 1. Arrange as follows.
The photocatalyst film 1 includes one having the photocatalyst layer 13 on only one side as shown in FIG. 3 (A) and one having the photocatalyst layer 13 on both sides as shown in FIG. 3 (B).
When the photocatalyst film 1 has the photocatalyst layer 13 on only one side, when the photocatalyst film 1 is joined, the directions of the surfaces of the two photocatalyst films 1 on the side where the photocatalyst layer 13 is located are usually aligned. In this case, only one surface of the fluororesin film 2 sandwiched between the overlapping portions of the photocatalyst film 1 comes into contact with the photocatalyst layer 13 of the photocatalyst film 1. Therefore, it is sufficient that the fluororesin film 2 used in this case is provided with the carbonate-containing layer 22 only on one surface thereof. The fluororesin film 2 may be sandwiched between the overlapped portions of the two photocatalyst films 1 so that the carbonate-containing layer 22 on one of the surfaces is in contact with the photocatalyst layer 13. However, even in this case, the fluororesin film 2 having the carbonate-containing layers 22 on both sides can be used. Then, even if the fluororesin film 2 is sandwiched between the overlapping portions of the photocatalyst film 1 without considering the front and back sides of the fluororesin film 2, the carbonate-containing layer 22 of the fluororesin film 2 is the photocatalyst film 1. It comes into contact with the photocatalyst layer 13.
On the other hand, when the photocatalyst film 1 has photocatalyst layers 13 on both sides, the fluororesin film 2 sandwiched between the overlapped portions of the photocatalyst film 1 is formed on both sides of the photocatalyst film 1 on both sides. It will come into contact. Therefore, the fluororesin film 2 used in this case needs to be provided with the carbonate-containing layer 22 on both surfaces thereof.

<< Second Embodiment >>
Also in the second embodiment, the photocatalyst films 1 are bonded to each other.
The method is substantially the same as in the case of the first embodiment. What is different is the configuration of the fluororesin film 2.
Unlike the case of the first embodiment, the fluororesin film 2 of the second embodiment does not have the carbonate-containing layer 22 described in the case of the first embodiment on any surface thereof. That is, the fluororesin film 2 of the second embodiment may be the same as the film base material 21 of the first embodiment.

Also in the method of joining the photocatalyst films 1 of the second embodiment, the fluororesin film 2 is formed by cutting so as to correspond to the shape and size of the joined portion of the photocatalyst film 1, and is shown in FIG. As described above, it is sandwiched between the portions of the two photocatalyst films 1 to be overlapped with a predetermined width, but in the second embodiment, before that, at least one surface of the fluororesin film 2 has a melting point of 330 ° C. or higher. A carbonate powder having a water solubility of 2 g / 100 g or less is attached.
As a method of adhering the carbonate powder to the fluororesin film 2, for example, the fluororesin film 2 is charged with static electricity and the fluororesin film 2 is sprinkled with the carbonated powder, or the fluororesin powder is sprinkled on the charged fluororesin film 2. The carbonate powder is attached to the fluororesin film 2 by inserting an electrostatically charged fluororesin film 2 or the like. As is well known, fluororesin has a property of being extremely easily charged with static electricity. Therefore, to charge the fluororesin film 2 with static electricity is, for example, rubbing the fluororesin film 2 with a cloth made of an appropriate chemical fiber. You can do it easily.
The amount of carbonate powder to adhere to the fluorine resin film 2 may be a 0.01mg~0.8mg / cm ^2, preferably, it is preferable to 0.01mg~0.3mg / cm ^2. The particle size of the carbonate powder can be selected from the same range as in the first embodiment.
Alternatively, the carbonate powder can be attached to the fluororesin film 2 by sprinkling the carbonate powder on the fluororesin film 2 and pressing the carbonate powder against the fluororesin film 2 with, for example, a cloth or a paper towel. Is.
As described above, the carbonate powder can be attached to the fluororesin film 2 to form the carbonate-adhering layer 22 instead of the carbonate-containing layer 22.
Whether the carbonate powder is attached to only one surface of the fluororesin film 2 or the carbonate powder is attached to both surfaces of the fluororesin film 2 depends on only one surface of the fluororesin film 2 of the first embodiment. It depends on whether the containing layer 22 is provided or the carbonate-containing layer 22 is provided on both surfaces.

The fluororesin film 2 to which the calcium carbonate powder is adhered as described above is sandwiched between the portions of the two photocatalyst films 1 to be overlapped with a predetermined width, and in that state, the two photocatalyst films 1 are laminated. The combined portion is heated under the same conditions as in the first embodiment while being pressed by a hot plate welding machine to be heat-welded.
As described above, the overlapped portions of the photocatalyst film 1 are joined to each other via the fluororesin film.

<< Third Embodiment >>
Also in the third embodiment, the photocatalyst films 1 are bonded to each other.
The method is substantially the same as in the case of the first embodiment. What is different is the configuration of the fluororesin film 2.
The fluororesin film 2 of the third embodiment is obtained by adding a carbonate powder having a melting point of 330 ° C. or higher and a water solubility of 2 g / 100 g or lower to FEP, which is the first fluororesin described in the first embodiment. It has become.
The method for producing such a fluororesin film 2 is as follows.

The fluororesin film 2 has, for example, 10 kg of FEP pellets as a fluororesin (manufactured by Mitsui-Dupont Fluorochemical Co., Ltd., product number: FEP 100-J), having a melting point of 330 ° C. or higher and a water solubility of 2 g / 100 g or lower. As a carbonate powder, 1 g to 500 g of calcium carbonate powder (manufactured by Shiraishi Calcium Co., Ltd., product number: Softon 1200) having an average particle size of 1.8 μm is added and melted at 320 ° C. using a well-known melt extruder. By extrusion molding, it can be processed into a film shape.
It is also possible to knead the pellets and calcium carbonate powder at 320 ° C. with a well-known twin-screw kneading extruder, and then process them into a film by a well-known compression molding machine.
In these cases, the weight ratio of the carbonate powder to the fluororesin can be in the range of 0.01% to 5%, preferably 0.1% to 3%.

The fluororesin film 2 containing the carbonate powder obtained as described above is sandwiched between the portions of the two photocatalyst films 1 to be overlapped with a predetermined width, and in that state, the two photocatalyst films 1 are laminated. The overlapped portion of 1 is heated while being pressed by a hot plate welding machine to be heat-welded.
As described above, the overlapped portions of the photocatalyst film 1 are joined to each other via the fluororesin film.
In the fluororesin film 2 of the third embodiment, since the carbonate powder is dispersed on the entire surface including both surfaces thereof, even when the photocatalyst film 1 to be bonded has the photocatalyst layer 13 on only one side thereof. It can also be applied when it is held on both sides.

An experimental example will be described below. First, the preparation method of the sample used in the experimental example will be described together.

<Sample 1>
[Sample 1-1]
As an example of the fluororesin film 2 of the first embodiment, the following was produced.
The dispersion liquid obtained by adding carbonate powder to the FEP dispersion for forming the carbonate-containing layer 22 of the fluororesin film 2 of Sample 1-1 is a FEP aqueous dispersion (solid content 54% by weight, Mitsui. Dupont Fluorochemical Co., Ltd., product number: FEP 120-JR) 1000 g, calcium carbonate powder with a particle size of 10 to 20 μm (Kishida Chemical Co., Ltd., product number: 000-13435) 4 g, purified water 1000 g, silicone type 40 g of a surfactant (manufactured by Momentive Performance Materials Japan GK, product number: SILWET L-77) was mixed in a container and adjusted by stirring.
The above dispersion is applied to both sides of a FEP film base material (FEP film having a thickness of 0.125 mm) 21 by a dipping coating method, air-dried, and then dried at 60 ° C. for 5 minutes to form a carbonate-containing layer 22. The formed fluororesin film 2 was produced.
The weight ratio of the calcium carbonate powder to the FEP in the carbonate-containing layer 22 after drying is 0.7%.

[Sample 1-2]
As another example of the fluororesin film 2 of the first embodiment, the following was produced.
The dispersion liquid in which the carbonate powder was added to the FEP dispersion for forming the carbonate-containing layer 22 of the fluororesin film 2 of Sample 1-2 was a FEP aqueous dispersion (solid content 54% by weight, Mitsui. Dupont Fluorochemical Co., Ltd., product number: FEP 120-JR) 1000 g, calcium carbonate powder with a particle size of 10 to 20 μm (Kishida Chemical Co., Ltd., product number: 000-13435) 7 g, purified water 1000 g, silicone type 40 g of a surfactant (manufactured by Momentive Performance Materials Japan GK, product number: SILWET L-77) was mixed in a container and adjusted by stirring.
The above dispersion is applied to both sides of a FEP film base material (FEP film having a thickness of 0.125 mm) 21 by a dipping coating method, air-dried, and then dried at 60 ° C. for 5 minutes to form a carbonate-containing layer 22. Fluororesin film 2 was produced.
The weight ratio of the calcium carbonate powder to the FEP in the carbonate-containing layer 22 after drying is 1.2%.

[Sample 1-3]
As still another example of the fluororesin film 2 of the first embodiment, the following was produced.
The dispersion liquid in which calcium carbonate powder was added to the FEP dispersion for forming the carbonate-containing layer 22 of the fluororesin film 2 of Sample 1-3 was a FEP aqueous dispersion (solid content 54% by weight, Mitsui. Dupont Fluorochemical Co., Ltd., product number: FEP 120-JR) 1000 g, calcium carbonate powder with a particle size of 10 to 20 μm (Kishida Chemical Co., Ltd., product number: 000-13435) 18 g, purified water 1000 g, silicone type 40 g of a surfactant (manufactured by Momentive Performance Materials Japan GK, product number: SILWET L-77) was mixed in a container and adjusted by stirring.
The above dispersion is applied to both sides of a FEP film base material (FEP film having a thickness of 0.125 mm) 21 by a dipping coating method, air-dried, and then dried at 60 ° C. for 5 minutes to form a carbonate-containing layer 22. Fluororesin film 2 was produced.
The weight ratio of the calcium carbonate powder to the FEP in the carbonate-containing layer 22 after drying is 3.2%.

<Sample 2>
[Sample 2-1]
As an example of the fluororesin film 2 of the second embodiment, the following was produced.
Sample 2-1 was prepared on a paper towel on a FEP film substrate 21 having a thickness of 0.125 mm, a length of 600 mm, and a width of 75 mm as calcium carbonate powder (made of Shiraishi calcium, product number: Softon 1200, average particle size 1. It is a fluororesin film 2 in which a carbonate-adhering layer 22 is formed instead of a carbonate-containing layer by adhering calcium carbonate powder to both sides of the FEP film by adhering 8 μm) and rubbing against the FEP film.
The amount of calcium carbonate attached to this calcium carbonate-attached FEP film was 0.012 mg / cm ² .

[Sample 2-2]
As another example of the fluororesin film 2 of the second embodiment, the following was produced.
Sample 2-2 was prepared on a paper towel on a FEP film substrate 21 having a thickness of 0.125 mm, a length of 600 mm, and a width of 75 mm as calcium carbonate powder (made of Shiraishi calcium, product number: Softon 1200, average particle size 1. 8 μm) was attached and rubbed against the FEP film to prepare a fluororesin film 2 in which calcium carbonate powder was adhered to both sides of the FEP film to form a carbonate adhering layer 22 instead of the carbonate-containing layer.
The amount of calcium carbonate attached to this calcium carbonate-attached FEP film was 0.22 mg / cm ² .

<Sample 3>
[Sample 3-1]
As an example of the fluororesin film 2 of the third embodiment, the following was produced.
Sample 3-1 is a calcium carbonate powder (manufactured by Shiraishi Calcium Co., Ltd.) having an average particle size of 1.8 μm as a carbonate in 10 kg of FEP pellets (manufactured by Mitsui DuPont Fluorochemical Co., Ltd., product number: FEP 100-J). A 0.125 mm thick calcium carbonate-containing FEP film produced by adding 10 g of Softon 1200) and extrusion molding while melting in the range of 320 to 380 ° C. using a well-known melt extruder. is there.
In this case, the weight ratio of the calcium carbonate powder to the fluororesin was 0.1%.

[Sample 3-2]
As another example of the fluororesin film 2 of the third embodiment, the following was produced.
Sample 3-2 is a calcium carbonate powder (manufactured by Shiraishi Calcium Co., Ltd.) having an average particle size of 1.8 μm as a carbonate in 10 kg of FEP pellets (manufactured by Mitsui DuPont Fluorochemical Co., Ltd., product number: FEP 100-J). It was manufactured by adding 100 g of Softon 1200) and using a well-known melt extruder to extrude while melting in the range of 320 to 380 ° C., and contains calcium carbonate with a thickness of 0.125 mm. It is a FEP film.
In this case, the weight ratio of the calcium carbonate powder to the fluororesin was 1.0%.

[Sample 3-3]
As still another example of the fluororesin film 2 of the third embodiment, the following was produced.
Sample 3-3 is a calcium carbonate powder (manufactured by Shiraishi Calcium Co., Ltd.) having an average particle size of 1.8 μm as a carbonate in 10 kg of FEP pellets (manufactured by Mitsui DuPont Fluorochemical Co., Ltd., product number: FEP 100-J). It was manufactured by adding 300 g of softon 1200) and using a well-known melt extruder to extrude while melting in the range of 320 to 380 ° C., and contains calcium carbonate with a thickness of 0.125 mm. It is a FEP film.
In this case, the weight ratio of the calcium carbonate powder to the fluororesin was 3.0%.

[Sample 3-4]
As still another example of the fluororesin film 2 of the third embodiment, the following was tried to be produced, but the fluororesin film 2 could not be obtained.
In sample 3-4, 10 kg of FEP pellets (manufactured by Mitsui DuPont Fluorochemical Co., Ltd., product number: FEP 100-J) and calcium carbonate powder having an average particle size of 1.8 μm as a carbonate (manufactured by Shiraishi Calcium Co., Ltd., I tried extrusion molding while adding 500 g of product number: Softon 1200) and melting it in the range of 320 to 380 ° C using a well-known melt extruder, but foaming and holes are severe, and it is not possible to mold a uniform film. It was difficult.
In this case, the weight ratio of the calcium carbonate powder to the fluororesin was 5.0%.

<Sample for comparison>
As an alternative to the fluororesin film 2, calcium carbonate was not contained or adhered to the commercially available 0.125 mm-thick FEP film used for Samples 1-1 to 1-3, Samples 2-1 and 2-2. The case where it was used as it was was prepared as a sample for comparative example.

<Photocatalytic membrane>
The photocatalyst film contains a photocatalyst on the outermost layer of an existing membrane material in which PTFE is coated on both sides of a glass fiber woven fabric having an average thickness of 0.4 mm by about 0.2 mm, and FEP is coated on both sides of the PTFE by about 10 μm. A photocatalyst layer is provided by applying the above-mentioned FEP dispersion.
The composition of the FEP dispersion liquid containing the photocatalyst was as follows.
The dispersant was 2000 g of an aqueous dispersion (solid content 28% by weight, custom-made product) using anatase-type TiO ₂ having a particle size of 1 nm to 100 nm, 3000 g of purified water, and an aqueous dispersion of FEP (solid content 54% by weight). , Mitsui DuPont Fluorochemical Co., Ltd., product number: FEP 120-JR) 4148 g, silicon-based surfactant (Momentive Performance Materials Japan GK, product number: SIRWET L-77) 137.2 g, respectively Then, they were mixed and stirred to prepare. The weight ratio of FEP to titanium oxide powder is 20:80.
The FEP layer containing the photocatalyst was coated by the following manufacturing process.
First, on the film material whose outermost layer is FEP, the dispersant is applied to both sides of the outermost layer by a dipping coating method, dried at 60 ° C. for 3 minutes, and then the drying temperature is gradually raised. Finally, the film was fired at 300 ° C. for 3 minutes and naturally cooled to experimentally produce a film material containing titanium oxide-containing FEP layers on both sides as a photocatalytic film.

<Test content>
The photocatalyst film was bonded by heat welding with the fluororesin film 2 according to the above sample and the comparative example sandwiched between them, and the peel strength was tested.

[Heat welding]
The photocatalyst film was bonded by sandwiching the fluororesin film 2 by heat welding in the following manner.
Two sheets of the above photocatalyst film cut into a width of 150 mm and a length of 600 mm are laminated, and a calcium carbonate-containing FEP dispersion prepared in Samples 1-1 to 1-3, which acts as an adhesive, is applied between them. FEP film (width 75 mm, length 600 mm), FEP film with calcium carbonate attached (width 75 mm, length 600 mm) prepared in Samples 2-1 and 2-2, and Samples 3-1 to 3-3. A calcium carbonate-containing FEP film (width 75 mm, length 600 mm) or a comparative example FEP film (width 75 mm, length 600 mm) to which calcium carbonate is not attached is sandwiched, and a hot plate set temperature of 370 ° C. and welding time are obtained. Each bonded sample having a width of 75 mm and a length of 600 mm was prepared under the conditions of 70 seconds and a pressure of 0.5 kg / cm ² .

[Peeling test sample collection]
As a peeling test sample from each of the above-mentioned joint samples, two pieces of width 50 mm and length 150 mm are cut out from the central portion in the longitudinal direction of width 75 mm and length 600 mm, and one piece is not subjected to accelerated exposure test for initial peeling test evaluation described later. The remaining one was used as a sample, and the remaining one was used as a sample for evaluation of the post-exposure peeling test described later 1000 hours after the accelerated exposure test.

[Promoted exposure test]
For the accelerated exposure test, a xenon weather meter (SX75-2 manufactured by Suga Test Instruments, irradiance 180 W / m ² (300 to 400 nm), 18 minutes in 120 minutes: irradiation + water spray, 102 minutes in 120 minutes: irradiation only) was used. Then, exposure for 1000 hours was performed on the sample for evaluation of the peeling test after exposure.

[Peeling test]
A peeling test was performed on the above-mentioned sample for initial peeling test evaluation and the sample for post-exposure peeling test evaluation.
The peeling test was performed according to (JIS K6404-5, method B). However, the size of the test piece to be subjected to one peeling test is 20 mm in width × 150 mm in length, and 2 from both the initial peeling test evaluation sample having a width of 50 mm × 150 mm and the post-exposure peeling test evaluation sample. The books were collected one by one.
Of these test pieces, a portion 50 mm from one end side in the longitudinal direction was manually peeled off, and then a peeling test was performed with a tensile tester. The peeling test result was evaluated by visually determining the ratio of the peeled portion between the fluororesin and the glass fiber woven fabric on the peeled surface after the peeling test and using the average value of the two fibers.
Generally, in such a material, the peel strength when the fluororesin and the glass base cloth are peeled off is generally high, whereas the peel strength when the fluororesin and the fluororesin are peeled off is relatively low. This is because it is known.

※「初期剥離試験評価用サンプル」と、「暴露後剥離試験評価用サンプル」の各数値は、剥離した面のうちガラス繊維織物とフッ素樹脂の間で剥離した部分の割合（％）
※「剥離強度の向上度の評価」の上欄の各数値は、比較用試料と比較した場合に向上した分の数値
※「剥離強度の向上度の評価」の下欄の○、△、×は、比較用試料と比較した場合に向上した分の数値に基づき、剥離強度の向上の程度を、以下の評価凡例により３段階で評価した評価結果
×：１０％未満
△：１０〜２５％
○：２５％以上 [Peeling test result]
A peeling test was conducted on the sample for initial peeling test evaluation and the sample for post-exposure peeling test evaluation. Based on the results, Table 1 below shows the ratio of the area where the peeling occurred between the glass fiber woven fabric and the fluororesin (PTFE) in the photocatalyst film to the total area of the joint and the evaluation result of the degree of improvement in the peeling strength. ..

* Each value of "Sample for initial peeling test evaluation" and "Sample for evaluation of peeling test after exposure" is the ratio (%) of the peeled part between the glass fiber fabric and the fluororesin on the peeled surface.
* Each numerical value in the upper column of "Evaluation of peel strength improvement" is the numerical value of the improvement when compared with the comparison sample. * ○, △, × in the lower column of "Evaluation of peel strength improvement" Is an evaluation result in which the degree of improvement in peel strength is evaluated in three stages according to the following evaluation legend based on the numerical value of the improvement when compared with the comparative sample. ×: Less than 10% Δ: 10 to 25%
◯: 25% or more

As described above, for initial peeling test evaluation regardless of whether the samples 1-1 to 3-3 are sandwiched between the photocatalyst films and bonded, or the comparative sample is sandwiched between the photocatalyst films and bonded. In the case of the sample peeling test, each numerical value of the "sample for initial peeling test evaluation" is 100%. This means that even when the same comparative sample as in the prior art is used for bonding or when Samples 1-1 to 3-3 are used for bonding, the peeling is performed between the photocatalyst membrane and the comparative sample. It means that everything occurs inside the photocatalyst film, not between the photocatalyst film or between the photocatalyst film and Samples 1-1 to 3-3, that is, the bonding surface between the bonded photocatalyst films. That is, in the state where the accelerated exposure test was not performed, even when the samples 1-1 to 3-3 were sandwiched between the photocatalyst films and bonded, the comparative sample was sandwiched between the photocatalyst films and bonded. In this case as well, it can be seen that the strength of the bond between the photocatalyst films is so high that the photocatalyst films are destroyed before the bonded photocatalyst films are peeled off at the bonding surface.
On the other hand, when the comparative sample is sandwiched between the photocatalyst films and bonded, the value of "sample for post-exposure peeling test evaluation" is 55%. This means that when the peeling test was performed, peeling occurred at the bonding surface between the bonded photocatalyst layers for 45% of the bonded portion prior to the destruction of the photocatalyst film. That is, it can be seen that the strength of the bonded portion formed by sandwiching the comparative sample between the photocatalyst films may deteriorate when the accelerated exposure test is performed.
On the other hand, when the samples 1-1 to 3-3 are sandwiched between the photocatalyst films and bonded, the respective numerical values of the "sample for evaluation of peeling test after exposure" are 65% to 100%. The junction where Samples 1-1 to 3-3 are sandwiched between the photocatalyst films is the same as when the comparative sample is sandwiched between the photocatalyst films even after the exposure test. In comparison, the deterioration of peel strength is small. In particular, it can be said that the deterioration of the peel strength is not abbreviated for the sample 2-2 having the above value of 100% because it has the same joint strength as the joint portion that has not undergone the exposure test. For other products, the lowest value is 65%, so the peel strength of the joint is higher than when a comparative sample with a value of 55% is sandwiched between photocatalyst films. Improvements are being seen. Except when sample 2-2 is used, sample 1-2, sample 1-3, sample 2-1 and sample with "○" in the lower column of "evaluation of improvement in peel strength". In 3-2, even after the exposure test, the decrease in the peel strength of the joint portion from before the exposure test is small.
Even when other carbonates, that is, barium carbonate, magnesium carbonate, lithium carbonate, and strontium carbonate were used, almost the same results as this test result were obtained.

1 Photocatalyst film 2 Fluororesin film 11 Glass fiber 12 Fluororesin layer 13 Photocatalyst layer 21 Fluororesin film base material 22 Carbonate-containing layer

Claims (12)

Photocatalyst films having a photocatalyst layer containing a fluororesin, a photocatalyst powder, and a surfactant as an organic additive on at least one surface thereof are superposed with a predetermined width.
A first fluororesin having a melting point equal to or lower than that of the basic fluororesin, which is a fluororesin that occupies the majority of the fluororesins contained in the photocatalyst film, between the overlapped portions of the photocatalyst film. A fluororesin film, which is a separate body from the photocatalyst film, formed by
It is a method of joining a photocatalyst film that joins the overlapped portions of the photocatalyst film via the fluororesin film by heating the overlapped portion of the photocatalyst film in that state.
The basic fluororesin containing a carbonate consisting of at least one of calcium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, and strontium carbonate having a melting point of 330 ° C. or higher and a water solubility of 2 g / 100 g or lower as the fluororesin film. A carbonate-containing layer formed of a second fluororesin, which has the same or lower melting point as the fluororesin, is used on at least one surface of the fluororesin film made of the first fluororesin .
When the fluororesin film is sandwiched between the overlapped portions of the photocatalyst film, the carbonate-containing layer is brought into contact with the photocatalyst layer.
Method of joining photocatalytic membrane. In the fluororesin film, a dispersion liquid obtained by adding the carbonate powder, which is the carbonate powder, to the dispersion of FEP is applied to at least one surface of the fluororesin film base material formed of the second fluororesin. Manufactured by drying the dispersion,
The method for joining a photocatalyst film according to claim 1. The second fluororesin is the same as the first fluororesin.
The method for joining a photocatalyst film according to claim 1 or 2. Photocatalyst films having a photocatalyst layer containing a fluororesin, a photocatalyst powder, and a surfactant as an organic additive on at least one surface thereof are superposed with a predetermined width.
A first fluororesin having a melting point equal to or lower than that of the basic fluororesin, which is a fluororesin that occupies the majority of the fluororesins contained in the photocatalyst film, between the overlapped portions of the photocatalyst film. A fluororesin film, which is a separate body from the photocatalyst film, formed by
It is a method of joining a photocatalyst film that joins the overlapped portions of the photocatalyst film via the fluororesin film by heating the overlapped portion of the photocatalyst film in that state.
As the fluororesin film, a carbonate consisting of at least one of calcium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, and strontium carbonate having a melting point of 330 ° C. or higher and a water solubility of 2 g / 100 g or lower on at least one surface thereof. Using the one to which the carbonate powder, which is the powder of
When the fluororesin film is sandwiched between the overlapped portions of the photocatalyst film, the surface of the fluororesin film to which the carbonate powder is attached is brought into contact with the photocatalyst layer.
Method of joining photocatalytic membrane. The carbonate powder is adhered to at least one surface of the fluororesin film by electrostatic adhesion by causing the fluororesin film to be charged with static electricity.
The method for joining a photocatalyst film according to claim 4. The carbonate powder is adhered to at least one surface of the fluororesin film, and the carbonate powder sprinkled on the at least one surface of the fluororesin film is pressed against the at least one surface of the fluororesin film. Do by
The method for joining a photocatalyst film according to claim 4. Photocatalyst films having a photocatalyst layer containing a fluororesin, a photocatalyst powder, and a surfactant as an organic additive on at least one surface thereof are superposed with a predetermined width.
A first fluororesin having a melting point equal to or lower than that of the basic fluororesin, which is a fluororesin that occupies the majority of the fluororesins contained in the photocatalyst film, between the overlapped portions of the photocatalyst film. A fluororesin film, which is a separate body from the photocatalyst film, formed by
It is a method of joining a photocatalyst film that joins the overlapped portions of the photocatalyst film via the fluororesin film by heating the overlapped portion of the photocatalyst film in that state.
As the fluororesin film, a carbonate consisting of at least one of calcium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, and strontium carbonate having a melting point of 330 ° C. or higher and a water solubility of 2 g / 100 g or lower is contained in the first fluororesin. Use what was added to
Method of joining photocatalytic membrane. The basic fluororesin is PTFE.
The method for joining a photocatalyst film according to any one of claims 1, 4, or 7. The first fluororesin is FEP.
The method for joining a photocatalytic membrane according to any one of claims 1, 4, 7, or 8. First fluorine, which is a fluororesin having a melting point equal to or lower than that of the basic fluororesin, which is a fluororesin that accounts for the majority of the fluororesins contained in the photocatalyst film, used in the method for joining the photocatalyst film according to claim 1. A fluororesin film formed of resin,
The basic fluororesin is PTFE.
The melting point is the same as or higher than that of the basic fluororesin, which contains a carbonate consisting of at least one of calcium carbonate, barium carbonate, magnesium carbonate, lithium carbonate and strontium carbonate having a melting point of 330 ° C. or higher and a water solubility of 2 g / 100 g or lower. A fluororesin film having a carbonate-containing fluororesin layer formed of the following fluororesin, which is a second fluororesin , on at least one surface of the fluororesin film made of the first fluororesin . First fluorine, which is a fluororesin having the same or lower melting point as the basic fluororesin, which is a fluororesin that accounts for the majority of the fluororesins contained in the photocatalyst film, used in the method for joining the photocatalyst film according to claim 7. A fluororesin film formed of resin,
The basic fluororesin is PTFE.
A carbonate consisting of at least one of calcium carbonate, barium carbonate, magnesium carbonate, lithium carbonate and strontium carbonate having a melting point of 330 ° C. or higher and a water solubility of 2 g / 100 g or lower is added to the first fluororesin .
Fluororesin film. The carbonate is calcium carbonate,
The method for joining a photocatalyst film according to any one of claims 1, 4, or 7-9.

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