Film forming apparatus

Abstract

To provide a film forming apparatus capable of suppressing separation of a solvent from ceramic particles on the surface of a ceramic support to increase a packing density of the ceramic particles, thereby forming a microscopic uniform ceramic separation film.SOLUTION: In a film forming apparatus 1 for forming a ceramic separation film containing ceramic particles on the outer peripheral surface of a cylindrical ceramic support 10, a rotation device 5 rotates the ceramic support 10 about its axis. A spray device 4 sprays a sol composition containing the ceramic particles to the outer peripheral surface of the ceramic support 10 rotated by the rotation device 5. A control unit 6 controls the rotation device 5 on the basis of a relative centrifugal force of the rotating ceramic support 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ceramic separation membrane forming apparatus. [Background technology]

[0002] A known technique for forming ceramic separation membranes is a dip coating method in which a ceramic support 10 is immersed in a slurry 13 of a sol composition in which ceramic particles are dispersed in a solvent, as shown in FIG. 4, to form a ceramic separation membrane on the surface of the ceramic support 10 (Patent Document 1).

[0003] Patent Document 2 discloses a spray coating method in which a slurry 13 is sprayed onto an end of a ceramic support 10 using a spray nozzle 43 shown in Fig. 2(a) to form a sealing layer made of the ceramic particles on the end. Although Patent Document 2 does not describe rotating the ceramic support 10, when spraying the slurry 13 onto the surface of a cylindrical ceramic support 10, operations such as rotating or moving the spray nozzle 43 or the ceramic support 10 are usually performed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7118871 [Patent Document 2] Japanese Patent Publication No. 2023-021136 Summary of the Invention [Problem to be solved by the invention]

[0005] To achieve both physical strength and permeability, ceramic separation membranes are generally formed in an asymmetric two-layer structure consisting of a support with physical strength and a separation layer with separation properties. Furthermore, when the ceramic support and the separation layer have different properties, such as pore size, an intermediate layer with intermediate properties is formed between the ceramic support and the separation layer. Both the separation layer and the intermediate layer are obtained by a membrane formation process in which a thin film is formed by spraying a sol composition in a slurry state, in which ceramic particles are dispersed in a solvent such as water, onto a porous support.

[0006] The dip coating method shown in Figure 4, which is one of the film formation processes, is a film formation method that makes use of surface tension by immersing the ceramic support 10, which is the object to be coated, in a slurry 13 and slowly pulling it up, making it possible to coat uniformly.

[0007] However, when an asymmetric structure is required for the ceramic separation membrane, it is necessary to cure or remove the unnecessary film layer from the surface that does not need to be coated in order to coat only the inner or outer periphery of the ceramic support 10. In addition, the pulling speed is closely correlated with the thickness of the film, and the film formation process takes a long time.

[0008] The spray coating method is a useful technique for solving the above problems when forming a film on the outer periphery of the ceramic support 10. A uniform, thin ceramic separation membrane can be obtained in a short time by rotating or traversing the spray nozzle 43 or the ceramic support 10. In addition, the thickness of the formed film can be easily controlled by changing the amount of liquid delivered and the weight.

[0009] However, when the slurry 13 is sprayed onto the ceramic support 10 using the spray nozzle 43, the solvent 12 such as water penetrates between the ceramic particles 10a of the ceramic support 10, and the film-forming surface of the ceramic support 10 appears dry, as shown in Figure 3(b). As a result, the ceramic particles 11 and the solvent 12 separate on the film-forming surface, causing them to lose fluidity, and rearrangement that fills the gaps between the ceramic particles 11 near the surface of the ceramic support 10 does not occur.

[0010] Furthermore, compared to dip coating, spray coating results in a lower packing density of ceramic particles 11 on the film formation surface, making it difficult to obtain a microscopically uniform film formation surface. If the packing density of ceramic particles 11 is low and microscopic gaps are present, the maximum diameter in the distribution of the formed pores will be large, so the thickness of the ceramic separation membrane formed on ceramic support 10 must be set large, which also causes a decrease in permeability.

[0011] Furthermore, when a large amount of slurry 13 is sprayed onto ceramic support 10 to achieve a wet membrane surface by spray coating, dripping of slurry 13 results in an uneven coating surface on the outer peripheral surface of ceramic support 10, as shown in Figure 2(a). Therefore, it is difficult to form a uniform ceramic separation membrane with a high packing density by the conventional spray coating method.

[0012] In view of the above, an object of the present invention is to provide a film forming apparatus that can suppress separation of the solvent and the ceramic particles on the surface of the ceramic support, increase the packing density of the ceramic particles, and form a microscopically uniform ceramic separation membrane. [Means for solving the problem]

[0013] Therefore, one aspect of the present invention is a film-forming apparatus for forming a ceramic separation membrane made of ceramic particles on the outer peripheral surface of a cylindrical ceramic support, comprising: a rotating device for rotating the ceramic support around its axis; a spraying device for spraying a sol composition containing the ceramic particles onto the outer peripheral surface of the ceramic support rotated by the rotating device; and a control unit for controlling the rotating device based on the relative centrifugal force of the ceramic support rotated by the rotating device.

[0014] In one aspect of the present invention, in the film forming apparatus, the spraying device includes a guide section that follows the axial direction of the ceramic support, a running section that can reciprocate along the guide section, and a spray nozzle that is provided on the running section and sprays the sol composition onto the outer peripheral surface of the ceramic support.

[0015] In one aspect of the present invention, the film forming apparatus further includes a storage tank for storing the sol composition, and a liquid feed pump for supplying the sol composition from the storage tank to the spray device in a manner that allows the flow rate to be adjusted.

[0016] In one aspect of the present invention, the film forming apparatus further includes a recovery device that recovers the sol composition sprayed onto the ceramic support, and an adjustment tank that adjusts the concentration of ceramic particles in the recovered sol composition and supplies the sol composition to the storage tank. [Effects of the Invention]

[0017] According to the present invention, separation of the solvent and the ceramic particles on the surface of the ceramic support can be suppressed, and the packing density of the ceramic particles can be increased, thereby forming a microscopically uniform ceramic separation membrane. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a block diagram of a film formation apparatus according to one embodiment of the present invention. [Figure 2] (a) Cross-section of a ceramic support showing dripping of slurry, (b) Cross-section of a ceramic support rotating with slurry being sprayed. [Figure 3] (a) Schematic illustration of the rearrangement of ceramic particles on a wet coating surface, (b) Schematic illustration of the arrangement of ceramic particles on a dry coating surface. [Figure 4] FIG. 1 is an explanatory diagram of a dip coating method. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] The film forming apparatus 1 of the embodiment of the present invention shown in Figure 1 sprays a sol composition containing ceramic particles 11 in the form of a slurry 13 onto the outer surface of a cylindrical ceramic support 10 rotating at a predetermined relative centrifugal force, thereby realizing a wet film forming surface on the outer surface of the ceramic support 10.

[0021] The film forming apparatus 1 includes a storage tank 2, a liquid pump 3, a spray device 4, a rotation device 5, a control unit 6, a recovery device 7, and an adjustment tank 8.

[0022] The storage tank 2 stores a sol composition in the form of a slurry 13, in which ceramic particles 11 are dispersed in a solvent 12. The storage tank 2 is appropriately equipped with a stirring device as shown in the figure in order to maintain a homogeneous slurry 13. As the material for the ceramic particles 11, for example, α-alumina having an average particle size of 0.3 to 5.0 μm or well-known ceramics as exemplified in Patent Documents 1 and 2 can be used. As the solvent 12, well-known solvents such as water and organic solvents as exemplified in Patent Documents 1 and 2 can be used.

[0023] The liquid feed pump 3 supplies the slurry 13 to the spray nozzle 43 in a manner that allows the flow rate to be adjusted. As the liquid feed pump 3, for example, a tube pump, a syringe pump, a diaphragm pump, or the like can be used.

[0024] The spraying device 4 sprays the slurry 13 onto the outer peripheral surface of the ceramic support 10 rotated by the rotation device 5. The spraying device 4 includes a guide section 41, a traveling section 42, and a spray nozzle 43. The guide section 41 is provided above the ceramic support 10 along the axial direction of the ceramic support 10. The traveling section 42 is capable of reciprocating within the guide section 41. The traveling section 42 is driven by a power source such as a motor, and the traveling speed can be varied as desired by changing the output of the power source. The spray nozzle 43 is provided on the traveling section 42 and sprays the slurry 13 onto the outer peripheral surface of the ceramic support 10. An example of the spray nozzle 43 is a split nozzle. The nozzle diameter of the spray nozzle 43 is, for example, in the range of 0.5 mm to 2.5 mm.

[0025] The rotation device 5 includes a motor 50 that continuously rotates a gripping unit 51 that horizontally grips the ceramic support 10 around the axis O of the ceramic support 10 shown in Fig. 2(b). The rotation speed of the gripping unit 51 is output to the control unit 6 as the rotation speed of the ceramic support 10 and is used to calculate the relative centrifugal force RCF of the ceramic support 10.

[0026] The gripping unit 51 is connected to the output shaft of the motor 50. The gripping unit 51 includes a collet chuck 52 of a known internal diameter gripping type as a gripping tool for the ceramic support 10. The collet chuck 52 is inserted into the hollow portion 101 of the ceramic support 10 as shown in FIG. 1 and grips the inner peripheral surface of one end of the ceramic support 10. The gripping tool is not limited to the internal diameter gripping type, and a well-known external diameter gripping type collet chuck that grips the outer peripheral surface of one end of the ceramic support 10 may also be used. Furthermore, the gripping unit 51 may grip only one end of the ceramic support 10 as shown in the same figure, or may grip both ends depending on the size of the ceramic support 10.

[0027] The control unit 6 controls the motor 50 of the rotation device 5 based on the relative centrifugal force RCF of the ceramic support 10 calculated from the rotation speed rpm of the ceramic support 10 output from the rotation device 5.

[0028] The relative centrifugal force RCF is calculated by the following equation (1) based on the number of rotations per minute (rpm) of the ceramic support 10 and the outer radius r shown in FIG. 2(b).

[0029]

number

[0030] The optimal relative centrifugal force RCF of the ceramic support 10, which ensures a wet membrane formation surface on the outer peripheral surface of the ceramic support 10 and promotes rearrangement of the ceramic particles 11, varies depending on the materials and properties of the ceramic support 10 and the slurry 13, and the desired thickness of the ceramic separation membrane.

[0031] The optimum relative centrifugal force RCF corresponds to the relative centrifugal force RCF of the ceramic support 10 at which the outer peripheral surface of the ceramic support 10 is uniformly wetted with the slurry 13, and is obtained by a rotation test of the ceramic support 10 sprayed with the slurry 13. This optimum relative centrifugal force RCF, together with the outer radius r of the ceramic support 10, is set in advance in the control unit 6 as a control factor of the rotation device 5. Then, the control unit 6 controls the rotation of the gripper 51 of the rotation device 5 so that the relative centrifugal force RCF calculated by Equation (1) based on the rotation speed rpm of the ceramic support 10 input from the rotation device 5 becomes the optimum relative centrifugal force RCF.

[0032] The recovery device 7 recovers the slurry 13 sprayed onto the ceramic support 10. The recovery device 7 includes a slurry receiver 71 that receives the slurry 13 that has dropped from the ceramic support 10, and a recovery pump 72 that transfers the slurry 13 provided from the slurry receiver 71 to the adjustment tank 8.

[0033] The adjusting tank 8 adjusts the slurry 13 recovered by the recovery pump 72 to a desired ceramic particle concentration, and then transfers it to the storage tank 2 by pumping.

[0034] An example of the operation of the film forming apparatus 1 will be described below with reference to FIGS.

[0035] First, in the control unit 6, the formation of a gas flow near the surface of the ceramic support 10 due to the rotation of the ceramic support 10, the behavior of the slurry 13 as a non-Newtonian fluid, and the scattering of excess slurry 13 due to the relative centrifugal force RCF are taken into consideration, and the relative centrifugal acceleration of the ceramic support 10 is set, for example, in the range of 0.2 to 2 G. Furthermore, the rotation speed rpm of the ceramic support 10 is set in the control unit 6 based on equation (1) corresponding to the optimal relative centrifugal force RCF.

[0036] The rotation of the ceramic support 10 is accelerated by the relative centrifugal acceleration under the control of the motor 50 of the rotation device 5 by the control unit 6, and then the ceramic support 10 rotates continuously at the set rotation speed rpm. Then, the slurry 13 is sprayed onto the outer peripheral surface of the rotating ceramic support 10 from the spray nozzle 43 of the spray device 4 that reciprocates above the ceramic support 10 in the axial direction of the ceramic support 10.

[0037] The solvent 12 of the slurry 13 applied to the outer peripheral surface of the ceramic support 10 attempts to penetrate between the ceramic particles 10a of the ceramic support 10, but is prevented from penetrating between the ceramic particles 10a by the relative centrifugal force RCF generated by the rotation of the ceramic support 10. As a result, the outer peripheral surface is kept wet with the slurry 13, preventing separation of the ceramic particles 11 and the solvent 12.

[0038] The relative centrifugal force RCF is appropriately adjusted during the spraying process by controlling the operation of the traveling part 42 and the rotation speed of the ceramic support 10. For example, while the ceramic support 10 is rotating, the spray nozzle 43 sprays the slurry 13 while moving in one direction along the axial direction of the ceramic support 10 by the traveling part 42. Then, the rotation speed of the ceramic support 10 is reduced by the rotation device 5 to reduce the relative centrifugal force RCF, and the spray nozzle 43 sprays the slurry 13 while moving in the other direction along the axial direction by the traveling part 42.

[0039] The amount of slurry 13 supplied from the storage tank 2 to the spray device 4 is changed as appropriate by controlling the rotation speed of the liquid feed pump 3. In particular, by adjusting the amount of slurry 13 supplied in conjunction with the nozzle diameter of the spray device 4, the traveling speed of the traveling part 42, and the rotation speed of the ceramic support 10, the thickness of the ceramic separation membrane made of ceramic particles 11 formed on the outer peripheral surface of the ceramic support 10 can be adjusted as appropriate.

[0040] The slurry 13 sprayed from the spray nozzle 43 is applied to the ceramic support 10, but a portion of it cannot remain on the ceramic support 10 and falls into a slurry receiver 71 due to gravity and centrifugal force. The slurry 13 collected in the slurry receiver 71 is transferred to the adjustment tank 8 by a recovery pump 72. The slurry 13 introduced into the adjustment tank 8 is adjusted to a desired concentration of ceramic particles 11 and then supplied to the storage tank 2.

[0041] According to the membrane formation apparatus 1 described above, the relative centrifugal force (RCF) generated by the rotation of the ceramic support 10 acts on the slurry 13 on the outer peripheral surface of the ceramic support 10, thereby suppressing separation of the ceramic particles 11 and the solvent 12 on the outer peripheral surface, resulting in a wet membrane formation surface. Therefore, as shown in FIG. 3(a), rearrangement of the ceramic particles 11 is promoted on the outer peripheral surface of the ceramic support 10, causing other ceramic particles 11 to be interposed in the gaps between the ceramic particles 11, thereby increasing the packing density of the ceramic particles 11. As a result, a uniform membrane surface and narrow pore distribution are achieved on the outer peripheral surface of the ceramic support 10, enabling the ceramic separation membrane formed on the outer peripheral surface to be thinner, thereby improving permeation performance.

[0042] In addition, the ceramic support 10 is continuously rotated by the rotation device 5, and the slurry 13 is sprayed onto the outer peripheral surface of the ceramic support 10 from the spray nozzle 43 that moves back and forth in the axial direction of the ceramic support 10, thereby promoting uniform rearrangement of the ceramic particles on the outer peripheral surface.

[0043] Furthermore, the rotation of the rotating ceramic support 10 can be controlled so that the relative centrifugal force RCF of the ceramic support 10 becomes an optimum value, so that the ceramic particles of the ceramic support 10 can be rearranged efficiently and arbitrarily.

[0044] The amount of slurry 13 supplied from the storage tank 2 to the spray device 4 can be appropriately changed by controlling the rotation speed of the liquid feed pump 3, so that the ceramic separation membrane formed on the outer peripheral surface of the ceramic support 10 can be arbitrarily adjusted to a predetermined thickness. In particular, by controlling the traveling speed of the traveling part 42 and the rotation speed of the ceramic support 10 in combination, the membrane thickness can be arbitrarily and uniformly adjusted.

[0045] Furthermore, the slurry 13 sprayed onto the ceramic support 10 is recovered by the recovery device 7, and the concentration of the ceramic particles 11 in the slurry 13 is adjusted to a desired concentration in the adjustment tank 8 before being supplied to the storage tank 2, thereby enabling the effective use of the slurry 13.

[0046] As described above, the film forming apparatus 1 can shorten the process time compared to the dip coating method and can achieve the same packing density of ceramic particles 11 in the ceramic separation membrane formed on the ceramic support 10 as that achieved by the dip coating method. Therefore, the drawbacks of the conventional spray coating method are overcome, and the ceramic separation membrane can be made thinner, improving its permeation performance. [Explanation of symbols]

[0047] 1...Film deposition equipment 2...Storage tank 3...Liquid transfer pump 4...spray device, 41...guide section, 42...travel section, 43...spray nozzle 5...rotation device, 50...motor, 51...gripping portion, 52...collet chuck 6...Control section 7...recovery device, 71...slurry receiver, 72...recovery pump 8…Adjustment tank 10... ceramic support, 11... ceramic particles, 12... solvent, 13... slurry

Claims

1. A film forming apparatus for forming a ceramic separation membrane made of ceramic particles on an outer peripheral surface of a cylindrical ceramic support, a rotating device for rotating the ceramic support about its axis; a spraying device that sprays a sol composition containing the ceramic particles onto the outer peripheral surface of the ceramic support rotated by the rotating device; a control unit that controls the rotation device based on a relative centrifugal force of the ceramic support rotated by the rotation device; A film forming apparatus comprising:

2. The spray device is a guide portion along the axial direction of the ceramic support; a traveling section that can reciprocate along the guide section; a spray nozzle provided in the traveling section for spraying the sol composition onto the outer peripheral surface of the ceramic support; 2. The film forming apparatus according to claim 1, further comprising:

3. a storage tank for storing the sol composition; a liquid feed pump that supplies the sol composition from the storage tank to the spray device in a manner that allows the flow rate to be adjusted; 2. The film forming apparatus according to claim 1, further comprising:

4. a recovery device for recovering the sol composition sprayed onto the ceramic support; an adjusting tank for adjusting the concentration of ceramic particles in the collected sol composition and supplying the sol composition to the storage tank; The film forming apparatus according to claim 3 , further comprising:

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