JP7742777B2 - Fluororesin coated materials - Google Patents

Description

The present invention relates to a fluororesin-coated component, and more specifically to a component having a coating layer made of a fluororesin that exhibits water-repellent properties.

It is known that the surface of fluororesin has a water-repellent function.
For example, Patent Document 1 discloses a polytetrafluoroethylene water-based cleaning jig that has been treated with fluorine gas, and discloses that the surface of the polytetrafluoroethylene water-based cleaning jig is treated with fluorine gas, resulting in a reduced surface energy and excellent water-draining properties (see Patent Document 1 [Abstract], [0013], etc.).

Japanese Patent Application Publication No. 7-142433

Patent Document 1 discloses that the water-shedding properties of a jig are improved by fluorine gas treatment compared to a jig made of untreated polytetrafluoroethylene, and it is therefore recognized that the water-repellent function of the jig is improved to some extent by fluorine gas treatment. However, it is necessary to separately treat the molded product with fluorine gas, which is relatively difficult to handle, and this may complicate the manufacturing process.
On the other hand, in recent years, there has been a demand for surfaces with even more water-repellent properties.
The strength of the water-repellent function is usually evaluated by the size of the contact angle between the surface of a fluororesin and water. The larger the contact angle, the greater the hydrophobicity, so a surface that shows a large contact angle with water indicates a higher water-repellent function. The contact angle with water on the surface of a fluororesin is generally 80 to 115°, so it is necessary to further increase this contact angle.

The object of the present invention is to provide a fluororesin-coated member with excellent water-repellent properties that can be easily manufactured without the need for a special treatment process to improve water-repellent properties. Because the fluororesin-coated member has excellent water-repellent properties, it can have improved corrosion resistance when in contact with corrosive chemicals, and improved thermal insulation when in contact with high-temperature chemicals.

After extensive research, the inventors discovered that by baking a component coated with a mixture of two fluororesins with different melting points at a temperature between the melting points of the two fluororesins, a fluororesin-coated component with an even larger contact angle with water can be obtained, and that this component has excellent water-repellent properties, which led to the completion of this invention.

The present specification includes the following embodiments.
1. A fluororesin coated member comprising a substrate and a coating layer coating at least a portion of the substrate, the coating layer being formed from a fluororesin mixture containing at least a first fluororesin and a second fluororesin, the first fluororesin having a higher melting point than the second fluororesin, the surface of the coating layer having a sea-island structure, and the island phases of the sea-island structure being composed primarily of the first fluororesin.
2. A fluororesin-coated member having a substrate and a coating layer that coats at least a portion of the substrate, wherein the coating layer is formed from a fluororesin mixture containing at least a first fluororesin and a second fluororesin, and wherein the contact angle of a water droplet on the surface of the coating layer is 120° or greater.
3. A method for producing a fluororesin-coated member, comprising: a mixing step of mixing at least a first fluororesin and a second fluororesin to obtain a fluororesin mixture; a coating step of applying the fluororesin mixture to at least a portion of a substrate to obtain a fluororesin-coated member; and a baking step of baking the fluororesin-coated member to obtain a fluororesin-coated member, wherein the baking step involves baking at a temperature between the melting points of the first fluororesin and the second fluororesin.

The fluororesin-coated member of an embodiment of the present invention has excellent water-repellent properties simply by undergoing a fluororesin coating process. Because the fluororesin-coated member has excellent water-repellent properties, for example, when it comes into contact with corrosive chemicals, it can have improved corrosion resistance, and when it comes into contact with high-temperature chemicals, it can have improved thermal insulation.

FIG. 1A shows an SEM image (surface shape) of the coating layer of Example 4. FIG. 1B shows an SEM image (elemental mapping of chlorine) of the coating layer of Example 4. FIG. 2A shows an SEM image (surface shape) of the coating layer of Example 6. FIG. 2B shows an SEM image (elemental mapping of chlorine) of the coating layer of Example 6. FIG. 3 shows the temperature changes when the fluororesin-coated member of Example 11, the fluororesin-coated member of Comparative Example 4, and the member of Comparative Example 5 (substrate (A2) itself) were subjected to a thermal history (heat cycle) of hot water (80°C) and water (20°C). 4 shows a photograph of the fluororesin-coated member of Example 11 immersed in hot water (80° C.), showing the formation of an air layer on the surface of the coating layer.

A fluororesin-coated member according to an embodiment of the present invention has a substrate and a coating layer that coats at least a portion of the substrate, and the coating layer is formed from a fluororesin mixture containing at least a first fluororesin (hereinafter referred to as the "first fluororesin") and a second fluororesin (hereinafter referred to as the "second fluororesin").

In the embodiment of the present invention, the "substrate" is not particularly limited as long as it is a substrate that can support a coating layer, preferably has excellent heat resistance and chemical resistance, and can provide the fluororesin-coated member of the embodiment of the present invention.
Examples of such substrates include metals such as aluminum, stainless steel, iron, and other metals, or alloys of several of these metals; inorganic compounds such as quartz glass and ceramics; and plastics such as aromatic polyetherketones such as polyetheretherketone (PEEK) and polyetherketone (PEK), polyethersulfone (PES), polyimide resins, and polyamideimide resins. Metals and inorganic compounds are preferred. Metals and inorganic compounds have high heat resistance and durability, and are easily kept clean, making them suitable for use as components in precision equipment manufacturing equipment such as semiconductor manufacturing equipment. The shape and size of the substrate are not particularly limited as long as the fluororesin-coated member of an embodiment of the present invention can be obtained. Examples include plate-like, rod-like, cylindrical, conical, and comb-like shapes. The shape and size can be selected appropriately depending on the application of the fluororesin-coated member.

In an embodiment of the present invention, a coating layer covers at least a portion of the substrate. The coating layer is formed from a fluororesin mixture containing at least a first fluororesin and a second fluororesin.

In the embodiments of the present invention, the "first fluororesin" and "second fluororesin" are resins that are normally understood to be fluororesins, and the melting point of the "first fluororesin" is higher than the melting point of the "second fluororesin." There are no particular limitations on these terms, as long as a fluororesin-coated member according to the embodiments of the present invention can be obtained. Note that "first" and "second" are used for convenience of explanation and are not limited to these terms, and mean that one of the fluororesins has a higher melting point than the other (that the melting points of the two types of fluororesins are different, or that the melting point of the first fluororesin and the melting point of the second fluororesin are different).

Examples of fluororesins that make up the first and second fluororesins include polytetrafluoroethylene (PTFE) (melting point: approximately 327°C), modified polytetrafluoroethylene (modified PTFE) (melting point: approximately 327°C), tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer (PFA) (melting point: approximately 310°C), tetrafluoroethylene/hexafluoropropylene copolymer (FEP) (melting point: approximately 260-275°C), ethylene/tetrafluoroethylene copolymer (ETFE) (melting point: approximately 270°C), ethylene/chlorotrifluoroethylene copolymer (ECTFE) (melting point: approximately 245°C), polychlorotrifluoroethylene (PCTFE) (melting point: approximately 210-220°C), polyvinylidene fluoride (PVDF) (melting point: approximately 156-178°C), and polyvinyl fluoride (PVF) (melting point: approximately 203°C).

In an embodiment of the present invention, the fluororesin has a particulate form and preferably has an average particle diameter of 500 μm or less, more preferably an average particle diameter of 1 to 250 μm, even more preferably an average particle diameter of 3 to 50 μm, and particularly preferably an average particle diameter of 5 to 25 μm.

In this specification, the average particle size of particles refers to the average particle size _D50 (median size meaning the particle size at 50% of the integrated value in the particle size distribution determined by the laser diffraction scattering method) obtained by measuring the particle size distribution using a laser diffraction scattering particle size distribution analyzer ("MT3300II" manufactured by Nikkiso Co., Ltd.).

Normal commercially available fluororesin products that can be used as fluororesin coating paints can be used.

The difference between the melting point of the first fluororesin and the melting point of the second fluororesin is preferably 10°C or more, more preferably 12 to 150°C, and even more preferably 15 to 120°C.
When the difference between the melting points of the first fluororesin and the second fluororesin is 10° C. or more, temperature control in the baking step becomes easy, which has the advantageous effect of improving productivity.

The coating layer of the fluororesin-coated member of an embodiment of the present invention may comprise a mixture of the first fluororesin and the second fluororesin, and the mixing ratio is not particularly limited; however, the first fluororesin:second fluororesin ratio is preferably 1:9 to 9:1 by mass, and more preferably 2:8 to 9:1 by mass.
If the coating layer of the fluororesin-coated member is a mixture of the first fluororesin and the second fluororesin, the water-repellent function (magnitude of contact angle) is advantageously improved compared to the water-repellent function (magnitude of contact angle) of each resin alone.

The surface of the coating layer of the fluororesin-coated member according to the embodiment of the present invention preferably has a phase-separated structure.
In the present disclosure, a phase-separated structure refers to a structure in which a first phase mainly composed of the first fluororesin and a second phase mainly composed of the second fluororesin are present without being completely melted and mixed together. Either the first phase or the second phase may be melted to form a smooth phase, but it is preferable that at least one of them has a granular resin shape. The first phase preferably contains 50% by mass or more of the first fluororesin, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more. The second phase preferably contains 50% by mass or more of the second fluororesin, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more.

The surface of the coating layer of the fluororesin-coated member according to an embodiment of the present invention preferably has a sea-island structure.
In the present disclosure, the term "sea-island structure" refers to a structure consisting of two types of parts: a smooth, approximately flat part (referred to as "sea") and a part with clearly uneven undulations (referred to as "islands"). The unevenness of the island part may be the overlapping of particles. The abundance ratio of the sea part to the island part does not necessarily need to be such that the sea part is more abundant, and the island part does not necessarily need to be surrounded by the sea part, and the island part may surround the sea part. The smooth, flat sea part may, for example, be able to melt and adhere the island part to the substrate, thereby fixing the coating layer to the substrate.

The island phases (island portions) of the sea-island structure are preferably composed mainly of the first fluororesin.
The island phase preferably contains the first fluororesin in an amount of 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more.

The sea phase (sea portion) of the sea-island structure is preferably composed mainly of the second fluororesin.
The sea phase preferably contains the second fluororesin in an amount of 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more.

The combination of the first fluororesin and the second fluororesin is not particularly limited as long as it is a combination of the above-mentioned fluororesins that have a difference in melting point, and for example, the combination of polytetrafluoroethylene (PTFE) and tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer (PFA), the combination of PTFE and polychlorotrifluoroethylene (PCTFE), the combination of PTFE and tetrafluoroethylene/hexafluoropropylene copolymer (FEP), the combination of PTFE and ethylene/tetrafluoroethylene copolymer (ETFE), the combination of modified polytetrafluoroethylene (modified PTFE) and PFA, the combination of modified PTFE and PCTFE, the combination of modified PTFE and FEP, the combination of modified PTFE and ETFE, the combination of PFA and PCTFE, the combination of PFA and FEP, the combination of PFA and ETFE.
The combination of the first fluororesin and the second fluororesin is preferably a combination of PTFE and PFA, a combination of PTFE and PTCFE, a combination of modified PTFE and PFA, a combination of modified PTFE and PTCFE, or a combination of PFA and PCTFE.

The contact angle of a water droplet on the surface of the coating layer of the fluororesin-coated member according to an embodiment of the present invention is preferably 120° or more, more preferably 120° to 170°, even more preferably 135° to 170°, and even more preferably 150° to 170°.
When the contact angle of a water droplet on the surface of the coating layer is 120° or more, the improvement in the water repellency has the advantageous effect of reducing the duration of contact of the liquid with the coating surface.

Therefore, the fluororesin-coated member according to an embodiment of the present invention has excellent heat insulation and solvent resistance in applications where the surface of the coating layer comes into contact with a solvent (e.g., an aqueous solvent). This is thought to be because the coating layer has low wettability to solvents (or media) such as water, which reduces contact with the solvent, resulting in excellent heat insulation and solvent resistance.

In an embodiment of the present invention,
a mixing step of mixing at least a first fluororesin and a second fluororesin to obtain a fluororesin mixture (or dispersion);
a coating step of applying the fluororesin mixture to at least a part of a substrate to obtain a fluororesin-coated member;
a baking step of baking the fluororesin-coated member to obtain a fluororesin-coated member,
In the baking step, baking is performed at a temperature between the melting point of the first fluororesin and the melting point of the second fluororesin.

The method for producing a fluororesin-coated member according to an embodiment of the present invention includes a mixing step of mixing at least a first fluororesin and a second fluororesin to obtain a fluororesin mixture (or dispersion).
For the first fluororesin and the second fluororesin, reference can be made to the above descriptions of the first fluororesin and the second fluororesin.
In the mixing step, the mixing method and mixing conditions (mixing temperature, mixing speed, dispersion solvent, mixing concentration) can be appropriately selected as long as the fluororesin-coated member according to an embodiment of the present invention can be produced.

The fluororesin mixture may be a mixture of the first fluororesin and the second fluororesin, and the mixing ratio is not particularly limited; however, the first fluororesin:second fluororesin ratio is preferably 1:9 to 9:1 by mass, and more preferably 2:8 to 9:1 by mass.
If the coating layer of the fluororesin-coated member is a mixture of the first fluororesin and the second fluororesin, the water-repellent function (magnitude of contact angle) is advantageously improved compared to the water-repellent function (magnitude of contact angle) of each resin alone.

The difference in melting point between the first fluororesin and the second fluororesin in the fluororesin mixture is preferably 10°C or more, more preferably 12 to 150°C, and even more preferably 15 to 120°C.
When the difference between the melting points of the first fluororesin and the second fluororesin is 10° C. or more, temperature control in the baking step becomes easy, which has the advantageous effect of improving productivity.

A method for producing a fluororesin-coated member according to an embodiment of the present invention includes a coating step of applying the fluororesin mixture to at least a part of a substrate to obtain a fluororesin-coated member.
For the substrate, reference can be made to the above description of the substrate.
In the coating step, the coating method and conditions can be appropriately selected from commonly known conditions for powder coating, spray coating, and the like.

The fluororesin-coated member of an embodiment of the present invention includes a baking step of baking the fluororesin-coated member to obtain the fluororesin-coated member, and the baking step includes baking at a temperature between the melting point of the first fluororesin and the melting point of the second fluororesin.
In the firing step, the firing method and firing conditions can be appropriately selected from commonly known conditions.

The baking temperature is a temperature between the melting points of the first fluororesin and the second fluororesin. It is speculated that baking within this temperature range melts the second fluororesin but not the first fluororesin, and therefore unevenness can be preferably formed on the surface of the coating layer despite the formation of the coating layer.
Since appropriate irregularities are formed on the surface of the coating layer, the fluororesin-coated member of the embodiment of the present invention can be easily produced without the need for a special treatment step to improve water repellency, and yet it exhibits excellent water repellency and also excellent heat insulation, solvent resistance, etc. It is believed that the member of the embodiment of the present invention exhibits excellent effects for the reasons described above, but the present invention is not limited by these reasons.

The fluororesin-coated member of the embodiment of the present invention can be suitably used in applications where fluororesin-coated members have traditionally been used, and further, the fluororesin-coated member of the embodiment of the present invention can be suitably used in applications where heat resistance and solvent resistance are required.
The fluororesin-coated member according to the embodiment of the present invention can be suitably used in, for example, semiconductor manufacturing equipment, liquid crystal manufacturing equipment, solar cell manufacturing equipment, pharmaceutical manufacturing equipment, and chemical manufacturing equipment.

The present invention will be explained in more detail below using examples and comparative examples, but these examples are merely one aspect of the present invention and the present invention is not limited in any way by these examples.

The components used in this example are listed below.
(A) Substrate (A1) 2 mm thick aluminum plate (100 mm x 50 mm) (also referred to as "(A1) aluminum substrate")
(A2) Cylindrical SUS304 (Φ10 mm × 100 mm) with a hole (Φ2 mm × 50 mm) provided in the center of one end on the axial side (also referred to as "(A2) SUS base material")

(B) Fluorine Resin (B1) Tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer (NEOFLON (registered trademark) PFA ACX-34 (trade name) manufactured by Daikin Industries, Ltd.), melting point 310°C, particle size D ₅₀ 25 μm (also referred to as "(B1) PFA")
(B2) Polychlorotrifluoroethylene (NEOFLON (registered trademark) PCTFE M-300H (product name) manufactured by Daikin Industries, Ltd.), melting point 220°C, particle size D ₅₀ 9 μm (also referred to as "(B2) PCTFE")
(B3) Polytetrafluoroethylene (Polyflon (registered trademark) PTFE Lubron (registered trademark) L-5 (product name) manufactured by Daikin Industries, Ltd.), melting point 327°C, particle size D ₅₀ 6 μm (also referred to as "(B3) PTFE")

Measurement of average particle diameter ( _D50 ) of particles The average particle diameter ( _D50 ) of the fluororesin was determined by measuring the particle size distribution of the particles using a laser diffraction scattering particle size distribution analyzer ("MT3300II" manufactured by Nikkiso Co., Ltd.) to obtain the average particle diameter ( _D50 ) of the particles (median diameter meaning the particle diameter at 50% of the integrated value in the particle size distribution obtained by the laser diffraction scattering method). The average particle diameter ( _D50 ) of each particle was as described above.

Preparation of Fluororesin-Coated Member of Example 1 (B1) PFA and (B2) PCTFE were added to ethylene glycol monobutyl ether in a mass ratio of B1/B2 = 90/10 and mixed to prepare a dispersion. The dispersion was spray-coated onto an aluminum substrate (A1) to obtain a coating layer of fluororesin powder on the aluminum substrate (A1). This coating layer was baked in an oven at 280°C for 60 minutes to obtain the fluororesin-coated member of Example 1. Because the coating layer had a sea-island structure, its thickness was not uniform, but was in the range of approximately 25 to 50 μm.

Production of fluororesin-coated members of Examples 2 to 9 Fluororesin-coated members of Examples 2 to 9 were obtained using the same method as that described in Example 1, except that the fluororesins shown in Table 1 were used in the mass ratios shown in Table 1.

Production of fluororesin-coated member of Example 10 A fluororesin-coated member of Example 10 was produced using the same method as that described in Example 5, except that (B3) PTFE was used instead of (B1) PFA and the baking temperature was changed from 280°C to 320°C.

Production of fluororesin-coated member of Comparative Example 1 (B2) A fluororesin-coated member of Comparative Example 1 was produced using the same method as that described in Example 1, except that no PCTFE was used and the baking temperature was changed from 280°C to 320°C.

Production of Fluororesin-Coated Member of Comparative Example 2 A fluororesin-coated member of Comparative Example 2 was produced using the same method as that described in Example 1, except that (B1) PFA was not used.

Production of Fluororesin-Coated Member of Comparative Example 3 A fluororesin-coated member of Comparative Example 3 was produced in the same manner as in Example 5, except that the baking temperature was changed from 280°C to 320°C.

Measurement of contact angle was carried out in accordance with JIS R 3257 using a contact angle meter "FACE CA-DT" (trade name) manufactured by Kyowa Interface Science Co., Ltd. Specifically, a fixed amount of droplet (pure water) was dropped onto a horizontally placed sample surface using a dispenser, and the angle between the sample surface and a line connecting one of the end points of the sample surface where the droplet was in contact with the apex of the droplet was determined. This was doubled to calculate the contact angle θ (θ/2 method).

Observation of Surface Shape of Coating Layer and Elemental Analysis For the fluororesin-coated members of Examples 4 and 6 described above, observation of the surface shape of the coating layer and elemental analysis were carried out using a scanning electron microscope (SEM) "FrexSEM 1000" (product name) equipped with an energy dispersive X-ray (EDX) analyzer manufactured by Hitachi High-Technologies Corporation.
After observing the surface shape at an accelerating voltage of 15.0 kV and 500x magnification, elemental mapping of chlorine was performed. An image of the surface shape of the coating layer of Example 4 is shown in Figure 1A, and an image of the elemental mapping of chlorine is shown in Figure 1B. An image of the surface shape of the coating layer of Example 6 is shown in Figure 2A, and an image of the elemental mapping of chlorine is shown in Figure 2B.

Heat insulation property (A2) SUS substrate was used as the substrate.
The coating layer (film thickness 150 μm) of Example 5 was applied to the entire surface of the substrate to obtain a fluororesin-coated member of Example 11.
The coating layer (film thickness 150 μm) of Comparative Example 2 was applied to the entire surface of the substrate, to obtain a fluororesin-coated member of Comparative Example 4.
The substrate itself was used as the member of Comparative Example 5.

A thermocouple was inserted into a hole provided at one end of the SUS base material (A2) of each member in the axial direction, and the other end was immersed in hot water (80°C) for 15 seconds, with a length of 80 mm. The other end was then immersed in cold water (20°C) for 15 seconds, with a length of 80 mm. This heat cycle was repeated five times.
The results are shown in Figure 3. The fluororesin-coated member of Example 11 had a low temperature increase rate and a low temperature decrease rate, which indicates that it has a high heat insulating effect. Furthermore, the temperature change of the member was small, which indicates that the fluororesin-coated member was subjected to less thermal stress.
A photograph of the fluororesin-coated member of Example 11 immersed in hot water (80°C) is shown in Figure 4. It was observed that an air layer was formed on the surface of the coating layer. The formation of this air layer is also expected to contribute to the heat insulating effect.

The fluororesin-coated members of Examples 1 to 11 each comprise: (i) a substrate and a coating layer that coats at least a portion of the substrate, the coating layer being formed from a fluororesin mixture containing at least a first fluororesin and a second fluororesin, the melting point of the first fluororesin being higher than the melting point of the second fluororesin, the surface of the coating layer having a sea-island structure, the island phase of the sea-island structure being composed primarily of the first fluororesin; or (ii) a substrate and a coating layer that coats at least a portion of the substrate, the coating layer being formed from a fluororesin mixture containing at least a first fluororesin and a second fluororesin, the contact angle of a water droplet on the surface of the coating layer being 120° or greater. Therefore, the fluororesin-coated members of Examples 1 to 11 have excellent water repellency and also excellent heat insulation.

In contrast, the fluororesin-coated members of Comparative Examples 1 to 4 do not satisfy (i) or (ii) above, and therefore do not necessarily have sufficient water repellency or heat insulation.

The fluororesin-coated member of an embodiment of the present invention has excellent water-repellent properties simply by undergoing a fluororesin coating process. Because the fluororesin-coated member has excellent water-repellent properties, for example, when it comes into contact with corrosive chemicals, it can have improved corrosion resistance, and when it comes into contact with high-temperature chemicals, it can have improved thermal insulation.

This application claims priority under Article 4 of the Paris Convention based on application number 2019-221571 filed in Japan on December 6, 2019. The contents of this application are incorporated herein by reference.

Claims (4)

A substrate and a coating layer that covers at least a portion of the substrate,
the coating layer is formed of a fluororesin mixture containing at least a first fluororesin and a second fluororesin,
the first fluororesin is a tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer,
the second fluororesin is polychlorotrifluoroethylene,
the contact angle of a water droplet on the surface of the coating layer is 135° or more;
the surface of the coating layer has a sea-island structure,
The island phase of the sea-island structure is composed mainly of the first fluororesin.
Fluororesin coated parts. The fluororesin-coated member according to claim 1, wherein the mixing ratio of the first fluororesin to the second fluororesin in the fluororesin mixture is 1:9 to 9:1. A semiconductor manufacturing device, a liquid crystal manufacturing device, a solar cell manufacturing device, a pharmaceutical manufacturing device, or a chemical manufacturing device, comprising the fluororesin-coated member according to claim 1 or 2. a mixing step of mixing at least a first fluororesin and a second fluororesin to obtain a fluororesin mixture;
a coating step of applying the fluororesin mixture to at least a part of a substrate to obtain a fluororesin-coated member;
a baking step of baking the fluororesin-coated member to obtain a fluororesin-coated member,
In the baking step, baking is performed at a temperature between the melting point of the first fluororesin and the melting point of the second fluororesin,
the first fluororesin is a tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer,
The second fluororesin is polychlorotrifluoroethylene.
A method for producing the fluororesin-coated member according to claim 1.