JP5908345B2 - Die for forming honeycomb structure and method for manufacturing honeycomb structure using the same - Google Patents

Description

  The present invention relates to a technique for manufacturing a molded body, and more particularly to a honeycomb structure molding die and a method for manufacturing a honeycomb structure using the same.

  Conventionally, honeycomb filter structures are widely known for use in diesel particulate filters. This honeycomb filter structure has a structure in which one end side of some through holes of a honeycomb structure having a large number of through holes is sealed with a sealing material, and the other end side of the remaining through holes is sealed with a sealing material. Patent Document 1 discloses a mold used for manufacturing a honeycomb structure.

JP 2009-166386 A

  However, when the honeycomb structure 70 shown in FIG. 1 is extruded using a conventional mold, the outer peripheral skin 70a covering the side surface is not uniformly formed, and a defective product in which the internal through hole 70b is exposed may occur. There were many. In order to form the outer peripheral skin 70a having no defect, there is a problem that the outer peripheral skin 70a has to be thicker than necessary. The honeycomb structure 70 shown in FIG. 1 is a cylindrical body in which a large number of through-holes 70b are arranged substantially in parallel, and when viewed from the end face side of the honeycomb structure 70, the plurality of through-holes 70b are arranged in a square shape, that is, The through holes 70b are arranged so that the central axes thereof are located at the apexes of the squares.

  The present invention has been made in view of the above problems, and at the time of forming the honeycomb structure of the embodiment shown in FIG. 1, the thickness of the outer peripheral skin can be sufficiently reduced, and the occurrence of defects in the outer peripheral skin can be sufficiently suppressed. The purpose is to provide molds. Another object of the present invention is to provide a method for manufacturing a honeycomb structure using the mold.

  The mold for forming a honeycomb structure of the present invention has a cell structure in which a large number of through holes are arranged substantially in parallel and the plurality of through holes are arranged in a square when viewed from the end face side, and the side surface is covered with an outer peripheral skin. For extruding a honeycomb structure, and having a supply hole to which a paste-like raw material composition is supplied and a grid-shaped slit groove communicating with the supply hole to form a cell structure A mold body, a cover ring that is disposed so as to cover a peripheral portion of the surface of the mold body on which the slit groove is formed, and has an opening having an inner diameter corresponding to the outer diameter of the honeycomb structure; A spacer disposed between the cover ring and having an opening larger than the opening of the cover ring; and a holder for fixing the cover ring and the spacer to the mold body. When a circular coordinate system is set in which the arc having a radius r1 longer than the inner diameter of the ring and the center of the arc as the origin and the extending direction of the lattice-shaped slit groove as the X-axis direction and the Y-axis direction are set, the center angle is 0 It is defined by opening extensions provided at positions of °, 90 °, 180 ° and 270 °, respectively.

  When a cylindrical honeycomb structure is extruded, a spacer having a circular opening is conventionally used to form an outer peripheral skin (see FIG. 5). The spacer is made of a sheet-like material having a thickness of about 0.3 to 1.0 mm, and has an opening that is slightly larger than the opening of the cover ring. By disposing the spacer having such a configuration between the mold body and the cover ring, the raw material composition that has passed between the mold body and the cover ring becomes the outer peripheral skin.

  When the present inventors manufactured the honeycomb structure 70 of FIG. 1 using a conventional mold, as shown in FIG. 5, the center of the opening of the spacer is the origin O, and the lattice slit grooves of the mold body When a circular coordinate system is set in which the direction in which (broken line) extends is the X-axis direction and the Y-axis direction, defects are likely to occur in the outer peripheral skin at the center angles θ of 0 °, 90 °, 180 ° and 270 ° As a result, the inventors have made the above invention. In the cell structure having a square arrangement, the amount of the raw material composition used varies depending on the direction from the origin O to the outer periphery. This asymmetry is presumed to be the main cause of defects at the above positions. That is, in the honeycomb structure 70, for example, when the direction of the central angle is compared with the direction of 0 ° and the direction of 45 °, there are more partition walls constituting the cell structure in the direction of 0 °. It is considered that the raw material composition for forming the film is insufficient, and defects are likely to occur in the outer peripheral skin.

  According to the present invention, by providing the opening expansion portion at a specific location of the spacer, the extrusion amount of the raw material composition for the outer peripheral skin can be increased at the location. For this reason, the defect generation | occurrence | production of an outer periphery skin can fully be suppressed compared with the case where the conventional metal mold | die with which the spacer which has a circular opening was simply mounted | worn is used. Also, since it is not necessary to make the entire outer skin thicker than necessary according to the location where defects are likely to occur, adjustment of the mold (adjustment of spacer opening size, thickness, etc.) to form a sufficiently thin outer skin )It can be performed.

  From the viewpoint of obtaining the effects of the present invention more highly and stably, the mold of the present invention preferably satisfies one or both of the following conditions. (1) The opening expansion portion is defined by an arc having a radius r2, and the ratio r1 / r2 is 1 to 10. (2) The expansion width of the opening expansion portion is 1 to 5 mm.

  The present invention provides a method for manufacturing a honeycomb structure using the above mold. That is, the method for manufacturing a honeycomb structure according to the present invention includes a step of mounting the mold on an extrusion molding apparatus, a paste-like raw material composition supplied to the extrusion molding apparatus, and a honeycomb structure extruded from the mold. Obtaining. According to this method, a honeycomb structure having a thin outer peripheral skin can be manufactured with a sufficiently high yield by the action of the mold.

  According to the present invention, at the time of forming the honeycomb structure of the aspect shown in FIG. 1, the thickness of the outer peripheral skin can be sufficiently reduced, and the occurrence of defects in the outer peripheral skin can be sufficiently suppressed.

(A) is a perspective view which shows an example of a honeycomb structure, (b) is the elements on larger scale of a honeycomb structure. It is a fragmentary end view which shows the structure of the peripheral part of a metal mold | die. It is a top view which shows an example of the spacer with which the metal mold | die which concerns on this invention is provided. It is a top view which shows the other example of the spacer with which the metal mold | die which concerns on this invention is provided. It is a top view which shows the spacer with which a metal mold | die main body and the conventional metal mold | die are mounted | worn. It is a schematic sectional drawing which shows an example of the extrusion molding apparatus with which the metal mold | die which concerns on this invention was mounted | worn. It is a figure which shows the structure of the baffle plate with which an extrusion molding apparatus is provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. First, prior to description of the mold according to the present invention, a honeycomb structure (green molded body) before firing will be described.

<Honeycomb structure>
A honeycomb structure 70 shown in FIG. 1 is obtained by extruding a raw material composition. As shown in FIG. 1 (a), the honeycomb structure 70 is a cylindrical body having an outer peripheral skin 70a forming side surfaces and a large number of through-holes 70b arranged in parallel. The cross-sectional shape of the through hole 70b is a square as shown in FIG. The plurality of through holes 70b are arranged in a square arrangement in the honeycomb structure 70 as viewed from the end face side, that is, the central axes of the through holes 70b are respectively located at the apexes of the square. The square size of the cross section of the through hole 70b can be set to 0.8 to 2.5 mm on a side, for example.

  The length in the direction in which the through hole 70b of the honeycomb structure 70 extends is not particularly limited, but may be 40 to 350 mm, for example. Moreover, the outer diameter of the honeycomb structure 70 is not particularly limited, but may be, for example, 100 to 320 mm.

  The raw material composition forming the honeycomb structure 70 is not particularly limited, but in the case of manufacturing a DPF honeycomb structure, an inorganic compound source powder that is a ceramic raw material, an organic binder such as methylcellulose, and the necessary Additives added depending on From the viewpoint of high temperature resistance of the honeycomb structure, suitable ceramic materials include alumina, silica, mullite, cordierite, glass, oxides such as aluminum titanate, silicon carbide, silicon nitride, and the like. The aluminum titanate can further contain magnesium and / or silicon.

  For example, when manufacturing an aluminum titanate honeycomb structure, the inorganic compound source powder includes an aluminum source powder such as α-alumina powder and a titanium source powder such as anatase-type or rutile-type titania powder. Furthermore, magnesium source powders such as magnesia powder and magnesia spinel powder and / or silicon source powders such as silicon oxide powder and glass frit can be included.

  Examples of the organic binder include celluloses such as methylcellulose, carboxymethylcellulose, hydroxyalkylmethylcellulose, and sodium carboxymethylcellulose; alcohols such as polyvinyl alcohol; and lignin sulfonate.

  Examples of the additive include a pore former, a lubricant and a plasticizer, a dispersant, and a solvent.

  Examples of the pore-forming agent include carbon materials such as graphite; resins such as polyethylene, polypropylene and polymethyl methacrylate; plant materials such as starch, nut shells, walnut shells and corn; ice; and dry ice.

  Lubricants and plasticizers include alcohols such as glycerine; higher fatty acids such as caprylic acid, lauric acid, palmitic acid, arachidic acid, oleic acid and stearic acid; metal stearates such as aluminum stearate, polyoxyalkylene alkyl And ether (POAAE).

  Examples of the dispersant include inorganic acids such as nitric acid, hydrochloric acid and sulfuric acid; organic acids such as oxalic acid, citric acid, acetic acid, malic acid and lactic acid; alcohols such as methanol, ethanol and propanol; ammonium polycarboxylate Surfactant etc. are mentioned.

  As the solvent, alcohols and water can be used. Examples of alcohols include monohydric alcohols such as methanol, ethanol, butanol, and propanol; dihydric alcohols such as propylene glycol, polypropylene glycol, and ethylene glycol;

<Mold>
The mold 20 shown in FIG. 2 is for forming the honeycomb structure of the embodiment shown in FIG. The mold 20 includes a mold body 21 having a material supply hole 21 a and a slit groove 21 b, a cover ring 22, a spacer 24, and a holder 28.

  The mold body 21 has a surface S1 disposed on the upstream side and a surface S2 disposed on the downstream side when mounted on the extrusion molding apparatus. A plurality of raw material supply holes 21a are formed on the surface S1, and a lattice-shaped slit groove 21b communicating with the raw material supply holes 21a is formed on the surface S2. The raw material composition supplied from the surface S1 side of the mold body 21 reaches the surface S2 side through the raw material supply holes 21a and the slit grooves 21b, and is extruded as a cell structure arranged in a square shape. Examples of the material of the mold body 21 include carbon steel; special steel containing nickel, chromium, tungsten and the like.

  The cover ring 22 is arrange | positioned so that the peripheral part of surface S2 of the metal mold body 21 may be covered. The cover ring 22 has an opening having an inner diameter corresponding to the outer diameter of the honeycomb structure to be formed. In other words, regardless of the outer shape of the mold body 21, a honeycomb structure having a desired outer diameter can be obtained by using the cover ring 22 having a predetermined inner diameter. Examples of the material of the cover ring 22 include carbon steel; special steel containing nickel, chromium, tungsten and the like.

  The spacer 24 is disposed between the mold body 21 and the cover ring 22. The spacer 24 is made of a sheet-like material having a thickness of about 0.3 to 1.0 mm. Specific examples of the material of the spacer 24 include metals such as copper, paper, and resins. The spacer 24 has an opening 24 a that is slightly larger than the opening of the cover ring 22. By arranging the spacer 24 having an opening that is slightly larger than the opening of the cover ring 22 between the mold body 21 and the cover ring 22, a gap is provided between them. The raw material composition that has passed through this gap becomes the outer peripheral skin.

  As shown in FIG. 3, the opening 24 a of the spacer 24 is defined by an arc 24 b having a radius r <b> 1 longer than the opening radius of the cover ring 22 and four opening expansion portions 24 c. When the four opening expansion portions 24c set a circular coordinate system in which the center of the arc 24b is the origin and the extending direction of the slit groove 21b of the mold body 21 is the X axis direction and the Y axis direction, respectively (see FIG. 5), Center angles are provided at positions of 0 °, 90 °, 180 ° and 270 °, respectively. The spacer 24 is important in that the opening 24a has a predetermined size and shape, and as long as the spacer 24 can be appropriately disposed between the mold body 21 and the cover ring 22, the overall size and The shape is not limited.

  The spacer 24 shown in FIG. 3 is used when a cover ring having an inner diameter of 145 mm is used. The opening 24a is formed by four opening expansion portions 24c each having an arc 24b having a radius r1 of 75 mm and an arc having a radius r2 of 13 mm. It is defined. The distance between the center of r2 and the center of r1 is 64 mm.

  The spacer 25 shown in FIG. 4A is used when a cover ring having an inner diameter of 145 mm is used, and the opening 25a is an expansion of four openings including an arc 25b having a radius r1 of 75 mm and an arc having a radius r2 of 31 mm. It is defined by the part 25c. The distance between the center of r2 and the center of r1 is 46 mm.

  The spacer 26 shown in FIG. 4B is used when a cover ring having an inner diameter of 145 mm is used, and the opening 26 a has four opening expansions consisting of an arc 26 b having a radius r 1 of 75 mm and an arc having a radius r 2 of 15 mm. It is defined by the part 26c. The distance between the center of r2 and the center of r1 is 64 mm.

  Depending on the viscosity of the raw material composition and the size of the honeycomb structure to be formed, the ratio r1 / r2 of the radius r1 of the arc that forms most of the opening of the spacer and the radius r2 of the opening extension is preferably 1 to 10, more preferably 5-8. If this ratio is less than 1, the outer peripheral skin of the honeycomb structure tends to be thicker than necessary, while if it exceeds 10, the effect of suppressing defects in the outer peripheral skin tends to be insufficient.

  When a honeycomb structure having an outer diameter of about 100 to 320 mm is formed, the expansion width of the opening expansion portion (width W shown in FIGS. 3 and 4) is preferably 1 to 5 mm, more preferably 2 ~ 3mm. If the expansion width is less than 1 mm, the effect of suppressing defects in the outer peripheral skin tends to be insufficient, while if it exceeds 5 mm, the outer peripheral skin of the honeycomb structure tends to be thicker than necessary.

  As shown in FIG. 2, the holder 28 is for fixing the cover ring 22 and the spacer to the mold body 21. Examples of the material of the holder 28 include carbon steel; special steel containing nickel, chromium, tungsten and the like.

  According to the mold 20 provided with the spacers as shown in FIGS. 3 and 4, the extrusion amount of the raw material composition for the outer peripheral skin can be increased at the location where the opening extension portion is provided. For this reason, compared with the case where the conventional spacer 27 shown in FIG. 5 is used, the defect generation | occurrence | production of an outer periphery skin can fully be suppressed. Also, since it is not necessary to make the entire outer skin thicker than necessary according to the location where defects are likely to occur, adjustment of the mold (adjustment of spacer opening size, thickness, etc.) to form a sufficiently thin outer skin )It can be performed.

<Extrusion molding equipment>
The extrusion molding apparatus 10 shown in FIG. 6 is equipped with the above-described mold 20 and is for manufacturing a honeycomb structure 70 from a powdery or paste-like raw material composition.

  The extrusion molding apparatus 10 includes a screw 2A provided at the upper stage in the housing 1 and a screw 2B provided at the lower stage. The screws 2A and 2B are for kneading the raw material composition supplied from the inlet 1a and transferring it downstream through the flow path 1b. A vacuum chamber 3 is provided between the screws 2A and 2B, and the raw material composition can be degassed by reducing the pressure in the vacuum chamber 3. The raw material composition in the vacuum chamber 3 is introduced into the lower screw 2B by a roller 3a.

  The extrusion molding apparatus 10 includes a rectifying plate 5 provided on the downstream side of the screw 2B, a mold 20 from which a molded body 70A made of a raw material composition is extruded, a resistance tube 9 that communicates the flow path 1b and the mold 20 with each other. Is further provided. The resistance tube 9 has a tapered inner flow path, and the flow path cross-sectional area gradually decreases from the upstream side toward the downstream side. In addition, when manufacturing 70A of diameters larger than the diameter of the screw 2B etc., the resistance tube 9 may have the enlarged part from which a flow-path cross section becomes large toward the downstream from upstream. A support base 15 for supporting the molded body 70A is installed next to the extrusion molding apparatus 10 so that the molded body 70A extruded from the mold 20 is not deformed. Prior to the introduction of the raw material composition into the mold 20, the rectifying plate 5 is intended to make the flow velocity distribution uniform.

  The rectifying plate 5 is provided so as to be detachable with respect to the housing 1 and is disposed between the screw 2 </ b> B and the mold 20. The rectifying plate 5 has a plurality of openings 5a penetrating in the thickness direction. The rectifying plate 5 may have a net-like resistor (not shown) in order to enhance the effect of adjusting the flow rate. FIG. 7A is a front view of the current plate 5, and FIG. 7B is a cross-sectional view of the current plate 5.

  The rectifying plate 5 is preferably a structure that hardly causes distortion even when pressure is received from the upstream side. From this viewpoint, the material of the rectifying plate 5 is preferably carbon steel, for example. Examples of suitable materials other than carbon steel include special steels containing nickel, chromium, tungsten and the like. The thickness of the current plate 5 is preferably 10 to 100 mm from the viewpoint of ensuring sufficient strength.

  The rectifying plate 5 has a plurality of openings 5a having a diameter of 1 to 10 mm penetrating in the thickness direction. The opening ratio of the rectifying plate 5 is preferably 30 to 80%. When the current plate 5 having an opening ratio of less than 30% is used, a sufficient amount of the raw material composition cannot be passed per unit time unless the upstream pressure is excessively increased, and the pressure is the allowable pressure of the apparatus. It is easy to become more. On the other hand, the current plate 5 having an aperture ratio exceeding 80% tends to have insufficient strength. The opening ratio of the rectifying plate 5 is preferably 40 to 80%, and more preferably 50 to 80%.

  Here, the “aperture ratio” means a value calculated by dividing the total area of the openings on one surface of the current plate 5 by the area of the one surface (excluding the peripheral edge covered by the housing). . In the case of a rectifying plate in which the flow passage cross-sectional area of the opening is not constant, the aperture ratio is the minimum value in all the rectifying plate cross sections perpendicular to the flow direction of the raw material composition.

<Manufacturing method of honeycomb structure>
Next, a method for manufacturing the honeycomb structure 70 using the extrusion molding apparatus 10 will be described. First, the mold 20 is mounted on the extrusion molding apparatus 10. When the preparation of the extrusion apparatus 10 is completed, the raw material composition is introduced into the flow path 1b from the inlet 1a. By operating the screws 2A, 2B and the roller 3a, the raw material composition is kneaded and transferred downstream. The kneaded material is passed through the opening 5 a of the rectifying plate 5 to make the flow velocity distribution uniform, and then introduced into the mold 20 through the resistance tube 9. The linear velocity of the raw material composition on the downstream side of the mold 20 is preferably about 10 to 150 cm / min.

  The raw material composition having a uniform flow velocity distribution is extruded from the mold 20 and the compact 70 </ b> A is collected on the support base 15. A honeycomb structure 70 is obtained by cutting the formed body 70A into a predetermined length. According to this method, a honeycomb structure having a thin outer peripheral skin can be manufactured with a sufficiently high yield by the action of the mold 20.

20 ... mold, 21 ... mold body, 21a ... raw material supply hole, 21b ... slit groove, 22 ... cover ring, 24, 25, 26 ... spacer, 24a, 25a, 26a ... opening, 24b, 25b, 26b ... arc 24c, 25c, 26c ... opening expansion part, 27 ... conventional spacer, 28 ... holder, 70 ... honeycomb structure, 70a ... outer peripheral skin, 70b ... through hole, S1 ... upstream surface of the mold body, S2 ... The downstream side of the mold body.

Claims (4)

A mold for extruding a honeycomb structure having a cell structure in which a large number of through holes are arranged substantially in parallel and the plurality of through holes are arranged in a square when viewed from the end face side, and whose side surfaces are covered with an outer peripheral skin Because
A mold body having a supply hole to which a paste-like raw material composition is supplied and a lattice-shaped slit groove for communicating with the supply hole to form the cell structure;
A cover ring that is disposed so as to cover a peripheral portion of a surface of the mold body on the side where the slit groove is formed, and has an opening having an inner diameter corresponding to the outer diameter of the honeycomb structure;
A spacer disposed between the mold body and the cover ring and having an opening larger than the opening of the cover ring;
A holder for fixing the cover ring and the spacer to the mold body,
The opening of the spacer is a circular coordinate system in which the arc having a radius r1 longer than the radius of the cover ring and the center of the arc as the origin and the extending direction of the lattice slit groove as the X axis direction and the Y axis direction, respectively. , The mold defined by the opening expansion portions provided at the central angles of 0 °, 90 °, 180 ° and 270 °, respectively.   The mold according to claim 1, wherein the opening extension is defined by an arc having a radius r2, and the ratio r1 / r2 is 1 to 10.   The metal mold | die of Claim 1 or 2 whose expansion width of the said opening expansion part is 1-5 mm. A step of mounting the mold according to any one of claims 1 to 3 on an extrusion molding device;
And supplying a paste-like raw material composition to the extrusion molding apparatus to obtain a honeycomb structure extruded from the mold.

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