Method for manufacturing tubular member for fluid processing apparatus

Abstract

To provide a method for manufacturing a tubular member for a fluid processing apparatus capable of suppressing occurrence of pinholes in an insulating layer.SOLUTION: A method for manufacturing a tubular member for a fluid processing apparatus according to the present invention is a method for manufacturing a tubular member for a fluid processing apparatus that comprises a metallic tubular body and an insulating layer containing glass provided on at least an inner circumferential surface of the tubular body. The method includes: a step (S1) of forming a coating film by immersing the tubular body in a coating solution for forming the insulating layer stored in a processing bath, thereby coating the coating solution for forming the insulating layer onto at least the inner circumferential surface of the tubular body; and a step (S2) of obtaining the insulating layer by firing the coating film after the coating film is formed. In the step of forming the coating film, a coating film having a target thickness is formed without drying the coating film.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a tubular member for a fluid processing device, for manufacturing a tubular member for a fluid processing device used in a fluid processing device for processing a fluid. [Background technology]

[0002] For example, in automobiles and the like, the use of electrically heatable fluid treatment devices is being considered to purify exhaust gases with high efficiency from the time the engine is started. Such fluid treatment devices include a metallic cylindrical member (a can or a container body) and an electrically heated carrier disposed inside the cylindrical member, and are configured so that the electrically heated carrier can be heated by passing electricity through it, thereby raising the temperature of the catalyst supported on the electrically heated carrier to an activation temperature suitable for purifying exhaust gases.

[0003] If an electrically heated carrier is in electrical contact with a metal tubular member, applying a voltage to the electrically heated carrier also causes a current to flow through the tubular member, resulting in energy loss. Therefore, a technique for electrically protecting the tubular member by protecting the interior of the tubular member with an insulating material is known, as described in Patent Document 1 below. Patent Document 1 describes a "manufacturing method for a tubular member for a fluid treatment device having a metal tubular main body and an insulating layer containing glass provided on at least the inner circumferential surface of the tubular main body, the manufacturing method including the steps of spraying an insulating layer-forming coating liquid onto the inner circumferential surface of the tubular main body to form a coating film, and baking the coating film to obtain the insulating layer, wherein the spraying is performed while the tubular main body is rotated around its longitudinal axis." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-141162 Summary of the Invention [Problem to be solved by the invention]

[0005] When a coating film was formed by repeatedly applying and drying the insulating layer-forming coating liquid using the method described in Patent Document 1, pinholes (through holes) were sometimes generated after the coating film was baked, resulting in a decrease in insulation properties.

[0006] In the case of multiple coatings with drying in between, the surface of the previously formed coating film loses moisture from the subsequent insulating layer-forming coating liquid, reducing the fluidity of the subsequent insulating layer-forming coating liquid. This reduced fluidity makes it easier for large gaps to form between particles inside the coating film, and it is presumed that these gaps are the origin of pinholes that form during firing.

[0007] The present invention has been made to solve the above-mentioned problems, and one of its objects is to provide a method for manufacturing a tubular member for a fluid treatment device that can suppress the occurrence of pinholes in the insulating layer. [Means for solving the problem]

[0008] Item 1. In one embodiment, the present invention relates to a method for manufacturing a tubular member for a fluid treatment device, which has a metallic tubular body and an insulating layer containing glass provided on at least the inner circumferential surface of the tubular body, the method including the steps of: immersing the tubular body in an insulating layer-forming coating liquid stored in a treatment tank to apply the insulating layer-forming coating liquid to at least the inner circumferential surface of the tubular body to form a coating film; and forming the coating film and then baking the coating film to obtain an insulating layer, wherein in the coating film-forming step, a coating film having a target thickness is formed without drying the coating film.

[0009] Item 2. The present invention may relate to the method for producing a cylindrical member for a fluid treatment device according to Item 1, further comprising, before forming a coating film, a step of preparing a slurry as a coating liquid for forming an insulating layer, the slurry including a glass source and a solvent, and the step of preparing the slurry includes sieving the slurry to reduce the size of lumps of the glass source.

[0010] Item 3. The present invention may relate to the method for producing a cylindrical member for a fluid processing device according to Item 1 or 2, wherein the viscosity of the coating liquid for forming an insulating layer in the processing tank is 1 dPa·s or more and 50 dPa·s or less.

[0011] Item 4. The present invention may relate to the method for producing a cylindrical member for a fluid processing device according to any one of Items 1 to 3, wherein the speed at which the cylindrical body is introduced into the insulating layer-forming coating liquid is 30 mm / s or less.

[0012] Item 5. The present invention may relate to the method for manufacturing a cylindrical member for a fluid processing device according to any one of Items 1 to 4, wherein the lifting speed of the cylindrical body relative to the insulating layer-forming coating liquid is 0.1 mm / s or more. [Effects of the Invention]

[0013] According to one embodiment of the cylindrical member for a fluid treatment device of the present invention, in the step of forming the coating film, the coating film is formed to a target thickness without being dried, so that the occurrence of pinholes in the insulating layer can be suppressed. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view of a fluid treatment device including a tubular member for a fluid treatment device according to an embodiment of the invention. [Figure 2] FIG. 2 is a perspective view showing the honeycomb structure of FIG. 1. [Figure 3] 2 is an enlarged cross-sectional view of the cylindrical member in region III of FIG. 1. [Figure 4] 1 is a flowchart showing a method for manufacturing a cylindrical member for a fluid treatment device according to an embodiment of the present invention. [Figure 5] 5 is an explanatory view showing in more detail the process of forming the coating film in FIG. 4. [Figure 6] FIG. 5 is an explanatory view for explaining the effect of the step of forming the coating film in FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and the components can be modified and embodied without departing from the spirit of the present invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in each embodiment. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components of different embodiments may be appropriately combined.

[0016] FIG. 1 is a cross-sectional view of a fluid processing device 1 including a tubular member 3 for a fluid processing device according to an embodiment of the present invention, and FIG. 2 is a perspective view showing a honeycomb structure 20 of FIG. 1. The tubular member 3 for a fluid processing device according to the embodiment of the present invention can be used in the fluid processing device 1 shown in FIG. 1. The fluid processing device 1 is a device for processing a fluid. The fluid processing device 1 is provided, for example, in an exhaust path of an automobile or the like, and can be used to process or purify exhaust gas emitted from the engine. However, the use of the fluid processing device 1 is not limited to purifying exhaust gas, and it may also be used to process other fluids, for example, by heating the fluid. Hereinafter, the "tubular member for a fluid processing device" may be simply referred to as the "tubular member."

[0017] As shown in FIG. 1, the fluid treatment device 1 may include an electrically heated carrier 2 , a cylindrical member 3 , and a buffer member 4 .

[0018] The electrically heated carrier 2 may have a honeycomb structure 20 and a metal electrode 21 connected to the honeycomb structure 20. Although not shown, an external power source such as a battery can be connected to the metal electrode 21 via a power cable. By applying a voltage to the honeycomb structure 20 through the metal electrode 21, the honeycomb structure 20 can be made to generate heat. This allows the temperature of the catalyst supported on the honeycomb structure 20 to be raised to an activation temperature before the engine starts.

[0019] As particularly shown in FIG. 2, the honeycomb structure 20 has a honeycomb structure part 200 and at least one electrode layer 201.

[0020] The honeycomb structure section 200 is a columnar member made of ceramics, and has an outer peripheral wall 202 and partition walls 203 disposed inside the outer peripheral wall 202 to define a plurality of cells 203a that form flow paths extending from one end face to the other end face. The columnar shape can be understood as a three-dimensional shape having a thickness in the extension direction of the cells 203a (axial direction of the honeycomb structure section 200). The ratio (aspect ratio) of the axial length of the honeycomb structure section 200 to the diameter or width of the end face of the honeycomb structure section 200 is arbitrary. The columnar shape may include a shape (flat shape) in which the axial length of the honeycomb structure section 200 is shorter than the diameter or width of the end face.

[0021] The outer shape of the honeycomb structure section 200 is not particularly limited as long as it is columnar, and can be other shapes such as a columnar shape with circular end faces (cylindrical shape), a columnar shape with oval end faces, a columnar shape with polygonal end faces (quadragonal, pentagonal, hexagonal, heptagonal, octagonal, etc.), etc. The size of the honeycomb structure section 200 is set such that the area of the end faces is 2000 to 65000 mm2 in order to increase heat resistance (suppress cracks that extend in the circumferential direction of the outer peripheral wall 202). 2 It is preferable that the thickness is 5000 to 25000 mm 2 It is more preferable that the end faces of the pillar-shaped honeycomb structures are polygonal. A plurality of pillar-shaped honeycomb structures each having a polygonal end face can be joined together and used.

[0022] Although there are no limitations on the shape of the cells 203a in a cross section perpendicular to the extending direction of the cells 203a, a square, a hexagon, an octagon, or a combination thereof is preferred. Among these, a square and a hexagon are preferred. By using such a cell shape, the pressure loss when exhaust gas flows through the honeycomb structure section 200 is reduced, and the purification performance of the catalyst is improved.

[0023] The thickness of the partition walls 203 that define the cells 203a is preferably 0.1 to 0.8 mm, and more preferably 0.1 to 0.6 mm. When the thickness of the partition walls 203 is 0.1 mm or more, it is possible to prevent a decrease in the strength of the honeycomb structure section 200. When the thickness of the partition walls 203 is 0.8 mm or less, it is possible to prevent an increase in pressure loss when exhaust gas flows through the honeycomb structure section 200 when the honeycomb structure section 200 is used as a catalyst carrier and a catalyst is carried thereon. In the present invention, the thickness of the partition walls 203 is defined as the length of a portion of a line segment that connects the centers of gravity of adjacent cells 203a and that passes through the partition walls 203 in a cross section perpendicular to the extension direction of the cells 203a.

[0024] The honeycomb structure section 200 has a cell density of 4 to 150 cells / cm in a cross section perpendicular to the extending direction of the cells 203a. 2 Preferably, the number of cells is 7 to 100. 2 By setting the cell density in this range, it is possible to increase the purification performance of the catalyst while minimizing the pressure loss when exhaust gas flows through it. 2 If the cell density is 150 cells / cm or more, a sufficient catalyst carrying area is ensured. 2 When the honeycomb structure section 200 is used as a catalyst carrier and a catalyst is carried thereon, excessive pressure loss during the flow of exhaust gas is suppressed if the honeycomb structure section 200 is used as a catalyst carrier and the cell density is a value obtained by dividing the number of cells by the area of one end face portion of the honeycomb structure section 200 excluding the outer peripheral wall 202 portion.

[0025] Providing the outer peripheral wall 202 of the honeycomb structure section 200 is useful from the viewpoint of ensuring the structural strength of the honeycomb structure section 200 and suppressing leakage of the fluid flowing through the cells 203a from the outer peripheral wall 202. Specifically, the thickness of the outer peripheral wall 202 is preferably 0.05 mm or more, more preferably 0.10 mm or more, and even more preferably 0.15 mm or more. However, if the outer peripheral wall 202 is too thick, the strength becomes too high, which disrupts the strength balance with the partition walls 203 and reduces thermal shock resistance. Therefore, the thickness of the outer peripheral wall 202 is preferably 1.0 mm or less, more preferably 0.7 mm or less, and even more preferably 0.5 mm or less. Here, the thickness of the outer peripheral wall 202 is defined as the thickness in the direction normal to the tangent of the outer peripheral wall 202 at the measurement point when the portion of the outer peripheral wall 202 whose thickness is to be measured is observed in a cross section perpendicular to the extension direction of the cells 203a.

[0026] The honeycomb structure section 200 is preferably made of ceramics and has electrical conductivity. There are no particular restrictions on the volume resistivity of the honeycomb structure section 200 as long as it can generate heat by Joule heat when current is applied, but it is preferably 0.1 to 200 Ωcm, and more preferably 1 to 200 Ωcm. In the present invention, the volume resistivity of the honeycomb structure section 200 is a value measured at 25°C by a four-terminal method.

[0027] The material of the honeycomb structure member 200 is not limited to, but can be selected from the group consisting of oxide ceramics such as alumina, mullite, zirconia, and cordierite, and non-oxide ceramics such as silicon carbide, silicon nitride, and aluminum nitride. Silicon-silicon carbide composites and silicon carbide / graphite composites can also be used. Among these, from the viewpoint of achieving both heat resistance and electrical conductivity, it is preferable that the material of the honeycomb structure member 200 contains a silicon-silicon carbide composite or a ceramic containing silicon carbide as the main component. When the material of the honeycomb structure member 200 is said to contain a silicon-silicon carbide composite as the main component, it means that the honeycomb structure member 200 contains 90 mass% or more of the silicon-silicon carbide composite (total mass) of the entire honeycomb structure member 200. Here, the silicon-silicon carbide composite material contains silicon carbide particles as aggregate and silicon as a binder that bonds the silicon carbide particles, and it is preferable that a plurality of silicon carbide particles are bonded by the silicon so as to form pores between the silicon carbide particles. When the material of the honeycomb structure part 200 is said to be mainly composed of silicon carbide, it means that the honeycomb structure part 200 contains silicon carbide (total mass) in an amount of 90 mass% or more of the entire material.

[0028] When the honeycomb structure 200 contains a silicon-silicon carbide composite material, the ratio of the "mass of silicon as a binder" contained in the honeycomb structure 200 to the sum of the "mass of silicon carbide particles as aggregate" contained in the honeycomb structure 200 and the "mass of silicon as a binder" contained in the honeycomb structure 200 is preferably 10 to 40 mass%, and more preferably 15 to 35 mass%.

[0029] The outer peripheral wall 202 and the partition walls 203 may be porous. If they are porous, the porosity of the outer peripheral wall 202 and the partition walls 203 is preferably 35 to 60%, and more preferably 35 to 45%. The porosity is a value measured with a mercury porosimeter. Furthermore, the outer peripheral wall 202 and the partition walls 203 may be dense, and if they are dense, the porosity of the outer peripheral wall 202 and the partition walls 203 may be 10% or less, or 5% or less.

[0030] The average pore diameter of the outer peripheral wall 202 and the partition walls 203 of the honeycomb structure section 200 is preferably 2 to 15 μm, and more preferably 4 to 8 μm. The average pore diameter is a value measured by a mercury porosimeter.

[0031] At least one electrode layer 201 is provided on the outer surface of the outer peripheral wall 202. The electrode layer 201 may extend from one end to the other end of the honeycomb structure part 200 in the extending direction of the cells 203a. The electrode layer 201, together with the outer peripheral wall 202, constitutes the outer peripheral surface of the honeycomb structure 20.

[0032] Although one electrode layer 201 may be provided on the entire outer peripheral surface of the honeycomb structure 20, in this embodiment, a pair of electrode layers 201 are provided, which are spaced apart from each other in the circumferential direction of the honeycomb structure section 200 and extend in strip shapes in the extension direction of the cells 203a. In a cross section of the honeycomb structure section 200 perpendicular to the extension direction of the cells 203a, one of the pair of electrode layers 201 is disposed on the opposite side of the center of the honeycomb structure section 200 from the other electrode layer 201. In FIG. 2, only one of the pair of electrode layers 201 is shown. In a cross section perpendicular to the extension direction of the cells 203a, 0.5 times the central angle of each electrode layer 201 may be 15 to 89°. The central angle of the electrode layer 201 may be the angle formed by two line segments connecting both ends of the electrode layer 201 and the center of the honeycomb structure section 200 in a cross section of the honeycomb structure section 200 perpendicular to the extension direction of the cells 203a. When the honeycomb structure section 200 is cylindrical, this angle may be the interior angle of a sector formed by the two line segments and the electrode layer 201.

[0033] The thickness of the electrode layer 201 is preferably 0.01 to 5 mm, more preferably 0.01 to 3 mm. By setting the thickness within this range, uniform heat generation is possible. If the thickness of the electrode layer 201 is thinner than 0.01 mm, the electrical resistance may be high, which may result in inconsistent heat generation. If the thickness is thicker than 5 mm, the honeycomb structure 20 may be damaged during canning. Furthermore, if the electrode layer 201 is too thin, the effect of adjusting the outer diameter when varying the outer diameter of the honeycomb structure 20 in the extension direction of the cells 203a due to variations in the thickness of the electrode layer 201 is reduced, as described below. If the electrode layer 201 is too thick, the holding force of the portions without the electrode layer 201 is reduced, making them more likely to fall off during a vibration test. Furthermore, if the electrode layer 201 is too thin, the resistance value of the electrode layer 201 is insufficient, which makes it easier for current to flow through the substrate (honeycomb structure portion 200), resulting in unstable heat generation distribution, reduced purification performance, and damage to the substrate. On the other hand, if the electrode layer 201 is too thick, current will easily flow through the electrode layer 201, and the electrode layer 201 will easily generate heat, which will result in unstable heat distribution, a decrease in purification performance, and damage to the substrate.

[0034] The pair of electrode layers 201 in this embodiment each includes a separator 2010 and a first partial electrode layer 2011 and a second partial electrode layer 2012 separated by the separator 2010. The separator 2010 may be a slit provided between the first partial electrode layer 2011 and the second partial electrode layer 2012. The slit may be filled with a material having a higher volume resistivity than the first partial electrode layer 2011 and the second partial electrode layer 2012. The first partial electrode layer 2011 and the second partial electrode layer 2012 are strip-shaped with a predetermined width in the circumferential direction of the honeycomb structure section 200, and the separator 2010 is linear and narrower than the first partial electrode layer 2011 and the second partial electrode layer 2012. However, the arrangement of the separator 2010 and the first partial electrode layer 2011 and the second partial electrode layer 2012 is not limited to this form as long as they can be connected to the metal electrode 21 described below.

[0035] 1, a metal electrode 21 is fixed on an electrode layer 201. By applying a voltage to the honeycomb structure section 200 through the metal electrode 21 and the electrode layer 201, the honeycomb structure section 200 can be made to generate heat.

[0036] From the viewpoint of making it easier for electricity to flow through the electrode layer 201 , the volume resistivity of the electrode layer 201 is preferably 1 / 200 or more and 1 / 10 or less of the volume resistivity of the honeycomb structure section 200 .

[0037] The material of the electrode layer 201 can be a conductive ceramic, a metal, or a composite material (cermet) of a metal and a conductive ceramic. Examples of the metal include a single metal such as Cr, Fe, Co, Ni, Si, or Ti, or an alloy containing at least one metal selected from the group consisting of these metals. Examples of the conductive ceramic include, but are not limited to, silicon carbide (SiC), and metal compounds such as metal silicides such as tantalum silicide (TaSi2) and chromium silicide (CrSi2).

[0038] In a manufacturing method of the honeycomb structure 20 having the electrode layers 201, first, an electrode layer forming raw material containing ceramic raw materials is applied to the side surface of a dried honeycomb body, and then dried to form a pair of unfired electrode layers extending in a strip shape in the extension direction of the cells 203a on the outer surface of the outer wall 202, sandwiching the central axis of the dried honeycomb body, thereby producing a dried honeycomb body with unfired electrode layers. Next, the dried honeycomb body with the unfired electrode layers is fired to produce a fired honeycomb body having the pair of electrode layers 201. In this way, a honeycomb structure 20 having the electrode layers 201 is obtained.

[0039] By supporting a catalyst on the honeycomb structure 200, the electrically heated support 2 can be used as a catalyst body. Examples of the catalyst include precious metal catalysts and other catalysts. Examples of precious metal catalysts include three-way catalysts and oxidation catalysts in which precious metals such as platinum (Pt), palladium (Pd), and rhodium (Rh) are supported on the pore surfaces of alumina and contain promoters such as ceria and zirconia, and NOx storage reduction catalysts (LNT catalysts) containing alkaline earth metals and platinum as nitrogen oxide (NOx) storage components. Examples of catalysts that do not use precious metals include NOx selective reduction catalysts (SCR catalysts) containing copper-substituted or iron-substituted zeolites. Two or more catalysts selected from these catalysts may also be used. There are no particular limitations on the catalyst support method, and it can be performed in accordance with the conventional method for supporting a catalyst on the honeycomb structure 20.

[0040] The metal electrode 21 may have a connection portion 210 disposed on the electrode layer 201 and a lead portion 211 led out from the connection portion 210. Although not shown in detail, the connection portion 210 may be configured in a comb shape having a plurality of teeth, some of which may be connected to the first partial electrode layer 2011 (see FIG. 2) and the other teeth may be connected to the second partial electrode layer 2012 (see FIG. 2). The connection portion 210 may be formed in an arc shape along the outer peripheral surface of the honeycomb structure 20. The lead portion 211 may be erected from one end of the connection portion 210 and led out to the outside of the tubular member 3, and a power cable may be connected to this lead portion 211.

[0041] The cylindrical member 3 is a metal member that holds the honeycomb structure 20. The cylindrical member 3 is also called a can or a can body. Various metals can be used to form the cylindrical member 3, and examples of such metals include stainless steel, titanium alloys, copper alloys, aluminum alloys, and brass. Among these, stainless steel is preferred because of its high durability, reliability, and low cost.

[0042] The tubular member 3 can surround the honeycomb structure 20 in the circumferential direction of the honeycomb structure 20. The inner diameter of the tubular member 3 at the outer periphery of the honeycomb structure 20 may be constant in the extension direction of the cells 203a. The part of the tubular member 3 with a constant inner diameter may be called a body portion. The outer periphery of the honeycomb structure 20 may be understood as the outside of the honeycomb structure 20 in the radial direction of the honeycomb structure 20, and as the position between the end faces of the honeycomb structure 20 in the extension direction of the cells 203a.

[0043] From the viewpoint of durability and reliability, the plate thickness of the tubular member 3 may be, for example, 0.1 mm to 10 mm, 0.3 mm to 5 mm, or 0.5 mm to 3 mm. The length of the portion of the tubular member 3 where the inner diameter is constant at the outer periphery of the honeycomb structure 20 may be longer than the axial length of the honeycomb structure 20, and may be, for example, 30 mm to 600 mm, 40 mm to 500 mm, or 50 mm to 400 mm.

[0044] An outlet opening 30 corresponding to the outlet portion 211 may be provided on the circumferential surface of the cylindrical member 3, and a power cable can be connected to the outlet portion 211 from outside the cylindrical member 3 through the outlet opening 30.

[0045] The tubular member 3 may be provided with a first end opening 31 and a second end opening 32 spaced apart in the extension direction of the cells 203a. The inner diameters of the first end opening 31 and the second end opening 32 may be smaller than the inner diameter of the tubular member 3 at the outer periphery of the honeycomb structure 20. Exhaust gas is introduced into the interior of the tubular member 3 from one of the first end opening 31 and the second end opening 32, and the exhaust gas that has passed through the cells 203a of the honeycomb structure 20 inside the tubular member 3 can be discharged to the outside of the tubular member 3 from the other of the first end opening 31 and the second end opening 32. One of the first end opening 31 and the second end opening 32 into which the exhaust gas is introduced may be referred to as an inlet opening, and the other of the first end opening 31 and the second end opening 32 from which the exhaust gas is discharged may also be referred to as an outlet opening. Moreover, one end face of the honeycomb structure 20 into which the exhaust gas is introduced may be called an inlet end face, and the other end face of the honeycomb structure 20 from which the exhaust gas exits may be called an outlet end face.

[0046] The buffer member 4 is disposed between the honeycomb structure 20 and the tubular member 3. The buffer member 4 may be wrapped around the outer periphery of the honeycomb structure 20. The buffer member 4 is provided with a through hole 40 corresponding to the lead-out portion 211, and a power cable can be connected to the lead-out portion 211 from the outside of the tubular member 3 through the through hole 40. The buffer member 4 may be made of a material that can be compressed in the radial direction of the honeycomb structure 20. There are no particular restrictions on the material of the buffer member 4, but a non-expanding ceramic fiber mat, a thermally expandable mineral material mat, or the like can be used.

[0047] Next, FIG. 3 is an enlarged cross-sectional view of the cylindrical member 3 in region III of FIG.

[0048] As particularly shown in FIG. 3, the cylindrical member 3 of this embodiment has a metallic cylindrical main body 33 and an insulating layer .

[0049] The cylindrical body 33 may be understood to refer to a base material of the cylindrical member 3 on which the insulating layer 34 is provided. As described above, the cylindrical body 33 can surround the honeycomb structure 20 in the circumferential direction of the honeycomb structure 20, and may have an extraction opening 30, a first end opening 31, and a second end opening 32. The metal constituting the cylindrical body 33 is the same as the metal constituting the cylindrical member 3.

[0050] The insulating layer 34 is provided on the inner peripheral surface 33a of the cylindrical main body 33. By providing such an insulating layer 34, it is possible to increase the electrical resistance between the cylindrical main body 33 and the honeycomb structure 20 or to electrically insulate them from each other. This makes it possible to reduce the current flowing through the cylindrical member 3 when a voltage is applied to the electrically heated carrier 2, thereby reducing energy loss.

[0051] The insulating layer 34 may be provided on the inner peripheral surface 33a of the cylindrical main body 33 at least at the outer peripheral position of the honeycomb structure 20. In the illustrated embodiment, the insulating layer 34 is provided over the entire inner peripheral surface 33a of the cylindrical main body 33. A region where the insulating layer 34 is not formed may be provided on the outer side of the end face of the honeycomb structure 20 in the extending direction of the cells 203a. As in the illustrated embodiment, the insulating layer 34 may further be provided on the outer peripheral surface 33b of the cylindrical main body 33.

[0052] The electrical insulation of the insulating layer 34 preferably satisfies JIS standard D5305-3 in order to prevent leakage of electricity to surrounding drain pipes, and the insulation resistance per unit voltage may be, for example, 100 Ω / V or more. The insulating layer 34 is preferably moisture-impermeable and moisture-non-absorbent. Specifically, the insulating layer 34 is preferably dense and configured to be impermeable to and non-absorbent of water. "Dense" means that the porosity of the insulating layer 34 is small, and the porosity of the insulating layer 34 may be, for example, 10% or less, or, for example, 8% or less.

[0053] The insulating layer 34 contains glass. The composition of the glass is not particularly limited, and glasses having various compositions can be used. Specific examples of glass include silicate glass, borosilicate glass, barium glass, boron glass, strontium glass, aluminosilicate glass, soda zinc glass, and soda barium glass. These may be used alone or in combination of two or more.

[0054] The glass is preferably glass containing crystalline matter. When the glass contains crystalline matter, an insulating layer 34 that is resistant to softening and deformation even at high temperatures (for example, 750°C or higher) can be obtained. Furthermore, an insulating layer 34 that has excellent adhesion to the cylindrical main body 33 can be obtained. Specifically, the difference in thermal expansion coefficient with the cylindrical main body 33 (metal) can be reduced, and thermal stress generated during heating can be reduced. The presence or absence of crystalline matter (crystals) can be confirmed by X-ray diffraction.

[0055] In one embodiment, the glass contains silicon and boron. Silicon may be contained in the glass in the form of SiO2; boron may be contained in the glass in the form of B2O3. Specifically, the glass is a SiO2-B2O3-based glass (borosilicate glass). The silicon content in the glass is preferably 5 mol% to 50 mol%, more preferably 7 mol% to 45 mol%, and even more preferably 10 mol% to 40 mol%. The boron content in the glass is preferably 5 mol% to 60 mol%, more preferably 7 mol% to 57 mol%, and even more preferably 8 mol% to 55 mol%.

[0056] In addition to silicon and boron, the glass may contain other components (metal elements) such as magnesium, barium, lanthanum, zinc, and calcium. For example, the glass may further contain magnesium. Magnesium may be contained in the glass in the form of MgO. In this case, the magnesium content in the glass is preferably 10 mol % or more, and more preferably 15 mol % to 55 mol %. Furthermore, the glass may further contain barium, for example. Barium may be contained in the glass in the form of BaO. In this case, the barium content in the glass is preferably 3 mol % to 30 mol %, more preferably 5 mol % to 25 mol %, and even more preferably 6 mol % to 20 mol %.

[0057] In this specification, the element content in glass is the molar ratio of the element when the amount of all atoms in the glass excluding oxygen atoms is taken as 100 mol %. The amount of atoms of each element in glass is measured, for example, by inductively coupled plasma (ICP) atomic emission spectrometry.

[0058] The thickness of the insulating layer 34 may be 30 μm or more and 800 μm or less. When the thickness of the insulating layer 34 is 30 μm or more, sufficient insulation can be obtained. From the viewpoint of more reliably obtaining sufficient insulation, the thickness of the insulating layer 34 is preferably 50 μm or more, more preferably 100 μm or more, and even more preferably 150 μm or more. When the thickness of the insulating layer 34 is 800 μm or less, pressure on the honeycomb structure 20 can be reduced and damage to the honeycomb structure 20 can be prevented, so the thickness is preferably 600 μm or less.

[0059] As will be explained in detail later, the insulating layer 34 can be obtained by forming a coating film on at least the inner surface 33a of the cylindrical main body 33 using a slurry as a coating liquid for forming an insulating layer containing a glass source, and then firing the coating film.

[0060] Next, Figure 4 is a flowchart showing a method for manufacturing a cylindrical member 3 for a fluid processing device according to an embodiment of the present invention, Figure 5 is an explanatory diagram showing in more detail the process of forming the coating film in Figure 4, and Figure 6 is an explanatory diagram explaining the effect of the process of forming the coating film in Figure 4.

[0061] A method for manufacturing a tubular member 3 for a fluid processing device according to an embodiment of the present invention is a method for manufacturing a tubular member 3 having a metallic tubular body 33 and an insulating layer 34 containing glass provided on at least the inner circumferential surface 33a of the tubular body 33. As shown in Fig. 4, this manufacturing method includes a step of forming a coating film (step S1) and a step of obtaining the insulating layer 34 (step S2).

[0062] The process of forming the coating film (step S1) is a process of forming a coating film on at least the inner surface 33a of the cylindrical main body 33 by immersing the cylindrical main body 33 in a coating liquid for forming an insulating layer stored in a treatment tank 50 as shown in Figure 5.

[0063] In the step of forming a coating film in this embodiment, a coating film having a target thickness is formed without drying the coating film.

[0064] In the case of multiple coatings with drying in between, in other words, when a coating film is formed by multiple immersion steps with drying in between, the solvent or water of the subsequent insulating layer-forming coating liquid is taken away by the surface of the previously formed coating film after drying, reducing the fluidity of the subsequent insulating layer-forming coating liquid, as shown in Figure 6(a). This reduction in fluidity makes it easier for large gaps to form between particles inside the coating film, and these gaps are more likely to cause pinholes in the insulating layer 34 during firing.

[0065] On the other hand, when a coating film of the target thickness is formed without drying, as in the present embodiment, there is room for the particles to move within the coating film or solvent before the coating film is baked, and the moved particles tend to fill gaps, as shown in Fig. 6(b), which makes it possible to prevent pinholes from forming in the insulating layer 34 due to gaps between particles.

[0066] Forming a coating film of the target thickness without a drying interval includes forming a coating film by immersing the cylindrical main body 33 in the coating liquid for forming an insulating layer once. Forming a coating film of the target thickness without a drying interval also includes forming a coating film by immersing the cylindrical main body 33 in the coating liquid for forming an insulating layer multiple times without placing the cylindrical main body 33 in a dryer during the coating film formation and without leaving the cylindrical main body 33 for 10 minutes or more.

[0067] The viscosity of the insulating layer-forming coating liquid in the treatment tank 50 is preferably 1 dPa·s or more and 50 dPa·s or less. A viscosity of 1 dPa·s or more prevents dripping during application, ensuring the required film thickness. A viscosity of 50 dPa·s or less makes it easier to remove bubbles. The viscosity of the insulating layer-forming coating liquid is more preferably 2 dPa·s or more and 40 dPa·s or less, and even more preferably 5 dPa·s or more and 20 dPa·s or less. The viscosity of the insulating layer-forming coating liquid may be measured at 20°C using a coaxial double-cylinder rotational viscometer with an inner cylinder constant speed method in accordance with JIS Z8803:2011.

[0068] The speed at which the cylindrical body 33 is introduced into the insulating layer-forming coating liquid is preferably 30 mm / s or less. An introduction speed of 30 mm / s or less can prevent air bubbles from being entrained. The introduction speed of the cylindrical body 33 is more preferably 20 mm / s or less, and even more preferably 10 mm / s or less. By setting the introduction speed within the above range, the generation of air bubbles can be prevented. From the viewpoint of work efficiency, an introduction speed of 0.1 mm / s or more is preferable.

[0069] The pulling speed of the cylindrical main body 33 relative to the insulating layer-forming coating liquid is preferably 0.1 mm / s or more. A pulling speed of 0.1 mm / s or more allows adjustment of the film thickness. The pulling speed of the cylindrical main body 33 is more preferably 1 mm / s or more, and even more preferably 10 mm / s or more. By setting the pulling speed within the above range, it is possible to achieve any film thickness with a small number of dippings. From the viewpoint of film thickness adjustment, a pulling speed of 50 mm / s or less is preferable.

[0070] The target thickness of the coating film can be determined depending on the desired thickness (after firing) of the insulating layer 34. Specifically, the target thickness of the coating film may be about 2 to 5 times the thickness of the insulating layer 34 after firing.

[0071] The step of obtaining the insulating layer 34 (step S2) is a step of forming a coating film and then baking the coating film to obtain the insulating layer 34. The baking temperature is preferably 1100°C or lower, more preferably 600°C to 1100°C, and even more preferably 700°C to 1050°C. The baking time is, for example, 5 to 60 minutes, and may be 8 to 15 minutes.

[0072] The coating liquid for forming an insulating layer may be obtained and used from a third party, but as shown in Figure 4, the manufacturing method according to this embodiment may further include a step (step S3) of preparing a slurry as the coating liquid for forming an insulating layer containing a glass source and a solvent before forming the coating film.

[0073] The insulating layer-forming coating solution may contain raw materials as glass sources, and may also contain glass frit. Specific examples of raw materials include silica sand (silicon source), dolomite (magnesium and calcium source), alumina (aluminum source), boric acid, barium oxide, lanthanum oxide, zinc oxide (zinc oxide), and strontium oxide. The raw materials are not limited to oxides, and may be, for example, carbonates or hydroxides. Glass frit is typically obtained by pulverizing glass synthesized from the raw materials (e.g., pulverizing in two stages: coarse pulverization and fine pulverization). The synthesis is typically performed by melting the glass at high temperatures (e.g., 1200°C or higher) for a long period of time.

[0074] The solvent refers to a liquid medium contained in the insulating layer-forming coating liquid, and is a concept that encompasses solvents and dispersion media. The solvent may be water or an organic solvent. The solvent is preferably water or a water-soluble organic solvent such as alcohol, and more preferably water. The amount of the solvent to be added is, for example, preferably 50 to 300 parts by mass, and more preferably 80 to 200 parts by mass, per 100 parts by mass of the glass source.

[0075] The insulating layer-forming coating liquid (slurry) may contain a slurry aid. Examples of the slurry aid include resins, plasticizers, dispersants, thickeners, and various additives. The type, number, combination, and amount of the slurry aid may be appropriately determined depending on the purpose.

[0076] The step of preparing the slurry of this embodiment may include sieving the slurry to reduce the size of lumps of the glass source material. In other words, the step may include breaking down the agglomerates of the glass source material contained in the slurry by sieving. Reducing the size of the lumps of the glass source material allows the particles to move more smoothly in the coating film or solvent, and can suppress the occurrence of pinholes in the insulating layer 34 due to gaps between the particles.

[0077] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Example]

[0078] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0079] In the examples, the inventors fabricated prototype tubular members 3 each having an insulating layer 34 formed on the inner circumferential surface 33a of the tubular body 33 by immersing the tubular body 33 in a coating solution for forming an insulating layer stored in a treatment tank 50 (hereinafter, the method of forming a coating solution by immersion may be referred to as the "dip method"). In the examples, a coating film of a target thickness was formed by immersion once or twice without drying during the coating film formation process. Furthermore, in the examples, the inventors varied the presence or absence of sieving of the slurry (a mixture of silicate glass and water) when preparing the coating solution for forming the insulating layer, the viscosity of the coating solution for forming the insulating layer, the speed at which the tubular body 33 was introduced into the coating solution for forming the insulating layer, and the speed at which the tubular body 33 was raised up from the coating solution for forming the insulating layer. The number of pinholes of 100 μm or larger was then counted for the prototype tubular members 3. The results are shown in Table 1 below.

[0080] Additionally, as a comparative example, the inventors also formed a coating film of a target thickness while drying the coating film in the coating film forming process. In comparative example 1, a method of forming a coating film by spraying slurry onto the inner circumferential surface 33a of the cylindrical main body 33 (hereinafter, a method of forming a coating film by spraying may be referred to as a "spray method") was employed. In comparative example 2, a dipping method was employed, as in examples 1 to 13. The number of pinholes of 100 μm or larger was also investigated in the comparative example. The results are shown in Table 1 below.

[0081] [Table 1]

[0082] (Common conditions) The following points are common to the Examples and Comparative Examples. Water was used as the solvent, and silicate glass was used as the glass source. 100 parts by mass of silicate glass was used in combination with 100 parts by mass of water. The viscosity was controlled by adjusting the amount of the solvent. The cylindrical body 33 was made of SUS430, had a diameter of 90 mm, and was 200 mm long. The coating was baked at 850°C for 60 minutes in an air baking furnace to obtain the insulating layer 34.

[0083] (Method for checking the number of pinholes) The number of pinholes was investigated by the following method. The number of pinholes in the insulating layer 34 provided on the inner circumferential surface 33a of the cylindrical main body 33 prototyped in the examples and comparative examples was investigated. A portion (body portion) of the cylindrical member 3 with a constant inner diameter of φ90 mm was cut into a semicircular shape along the diameter direction, and an area of 100 mm × 100 mm was observed under a microscope to count the number of pinholes of 100 μm or larger.

[0084] In Table 1, "◎" in the "Pinhole" row indicates that the number of pinholes within the above-mentioned range was 0 to 1. Similarly, "◯" indicates that the number of pinholes was 2 to 10, "△" indicates that the number of pinholes was 11 to 20, and "×" indicates that the number of pinholes was 21 or more. The ratings of "◎" to "△" indicate that the material is suitable for practical use because sufficient insulation is ensured, and "×" indicates that the material is difficult to practically use because insulation is impaired.

[0085] As shown in Table 1, in Examples 1 to 13, in which a coating film of the target thickness was formed without a drying interval, the results of the investigation into the number of pinholes were "◎" to "△". In contrast, in Comparative Examples 1 and 2, in which a coating film of the target thickness was formed with a drying interval, the results of the investigation into the number of pinholes were "×". From these results, it was confirmed that the formation of a coating film of the target thickness without a drying interval can suppress the occurrence of pinholes in the insulating layer 34.

[0086] In Examples 2 and 3, cylindrical members 3 were produced under the same conditions except for whether or not they were sieved. In Example 3, where sieving was not performed, the result of the investigation into the number of pinholes was "△", while in Example 2, where sieving was performed, the result of the investigation into the number of pinholes was "◎". From these results, it was confirmed that sieving can more reliably suppress the occurrence of pinholes in the insulating layer 34.

[0087] In Examples 4 to 7, cylindrical members 3 were produced under the same conditions except for the viscosity of the insulating layer-forming coating liquid. In Examples 6 and 7, where the viscosity was less than 1 dPa·s or more than 50 dPa·s, the result of the investigation into the number of pinholes was "△", but in Examples 4 and 5, where the viscosity was 1 dPa·s or more and 50 dPa·s or less, the result of the investigation into the number of pinholes was "◯". These results confirmed that by setting the viscosity of the insulating layer-forming coating liquid to 1 dPa·s or more and 50 dPa·s or less, the occurrence of pinholes in the insulating layer 34 can be more reliably suppressed.

[0088] In Examples 8 to 10, cylindrical members 3 were fabricated under the same conditions except for the injection speed of the cylindrical body 33 into the insulating layer-forming coating liquid. In Example 9, where the injection speed exceeded 30 mm / s, the pinhole count was evaluated as "△." In Examples 8 and 10, where the injection speed was 30 mm / s or less, the pinhole count was evaluated as "◯" or "◎." These results confirm that setting the injection speed of the cylindrical body 33 into the insulating layer-forming coating liquid to 30 mm / s or less can suppress the entrapment of air bubbles and more reliably suppress the occurrence of pinholes in the insulating layer 34. In Example 8, where the injection speed was relatively fast at 30 mm / s, Example 10, where the injection speed was relatively slow at 0.1 mm / s, had fewer pinholes. Therefore, although a slower injection speed may be used, an injection speed of 0.1 mm / s or more is considered acceptable from the standpoint of work efficiency.

[0089] In Examples 11 to 13, cylindrical members 3 were fabricated under the same conditions except for the lifting speed of the cylindrical main body 33 relative to the insulating layer-forming coating solution. In Example 12, where the lifting speed was less than 0.1 mm / s, the pinhole count was evaluated as "△." In Examples 11 and 13, where the lifting speed was 0.1 mm / s or higher, the pinhole count was evaluated as "◯" or "◎." These results confirm that by raising the cylindrical main body 33 relative to the insulating layer-forming coating solution at a speed of 0.1 mm / s or higher, the occurrence of pinholes in the insulating layer 34 can be more reliably suppressed. A slow lifting speed, such as in Example 12, tends to result in a thinner coating film, whereas a fast lifting speed, such as in Examples 11 and 13, tends to result in a thicker coating film. By setting the lifting speed at 0.1 mm / s or higher, as in Examples 11 and 13, a sufficient film thickness can be ensured, and it is believed that even if air bubbles are entrained during coating, they are less likely to become pinholes. In addition, Example 13, which had a relatively fast pulling speed of 50 mm / s, had fewer pinholes than Example 11, which had a relatively slow throwing speed of 0.1 mm / s. Therefore, although it is conceivable to increase the throwing speed, it is conceivable to keep the pulling speed at 50 mm / s or less from the viewpoint of film thickness control. [Explanation of symbols]

[0090] 1: Fluid treatment equipment 3: Cylindrical member for fluid treatment device (cylindrical member) 33: Cylindrical body 33a: Inner peripheral surface 34: Insulating layer 50: Treatment tank

Claims

1. A method for manufacturing a cylindrical member for a fluid processing device, comprising: a metallic cylindrical body; and an insulating layer including glass provided on at least an inner circumferential surface of the cylindrical body, the method comprising: a step of immersing a cylindrical body in a coating liquid for forming an insulating layer stored in a treatment tank, thereby coating the coating liquid for forming an insulating layer on at least an inner circumferential surface of the cylindrical body to form a coating film; a step of forming the coating film and then baking the coating film to obtain the insulating layer; Including, In the step of forming the coating film, the coating film having a target thickness is formed without drying the coating film. A method for manufacturing a cylindrical member for a fluid treatment device.

2. The method further includes a step of preparing a slurry as the insulating layer-forming coating liquid, which contains a glass source and a solvent, before forming the coating film; The step of preparing the slurry includes sieving the slurry to reduce lumps of the glass source. The method for manufacturing the cylindrical member for a fluid treatment device according to claim 1 .

3. The viscosity of the insulating layer forming coating liquid in the treatment tank is 1 dPa·s or more and 50 dPa·s or less. The method for manufacturing the cylindrical member for a fluid treatment device according to claim 2 .

4. The speed at which the cylindrical body is introduced into the insulating layer-forming coating liquid is 30 mm / s or less. The method for manufacturing the cylindrical member for a fluid treatment device according to claim 3 .

5. The pulling speed of the cylindrical body relative to the insulating layer forming coating liquid is 0.1 mm / s or more. The method for manufacturing the cylindrical member for a fluid processing device according to claim 3 .

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