JP2024013612A - Manufacturing method of molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of manufacturing a molded product having high dimensional accuracy without applying a mold-release agent nor cleaning a mold.

SOLUTION: A manufacturing method of a molded product includes a mold packing step of vacuum-packing a mold having a recess with a resin film packing material and a casting solidification step of injecting slurry including ceramic powders and/or metal powders into the recess of the vacuum-packed mold and solidifying the slurry.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a method for manufacturing a molded article.

A mold casting method, which is a type of cast molding method, is known as a method for manufacturing a molded body (for example, Patent Document 1). In the mold casting method, a molded body is manufactured by casting a slurry containing a specified powder such as ceramic powder or metal powder, a reactant, a gelling agent, etc. into a mold, and solidifying (hardening) it within the mold. It's a method.

In the mold casting method, a mold release agent has conventionally been applied to the inner wall surface of the mold in order to make it easier to release the molded article from the mold. In addition, the mold after the molded product has been released has slurry residue, mold release agent, etc. attached to it, so it is necessary to clean it by immersing the mold in a cleaning liquid and brushing it (for example, Patent Document 2).

Here, FIG. 8 shows a conventional molding process for manufacturing a molded body that requires dimensional accuracy in the outer diameter.
As shown in FIG. 8, first, a lower mold 110 and an upper mold 120 are prepared as components of the mold 100, and a mold release agent 130 is applied to each of the lower mold 110 and the upper mold 120 (P1). Next, the lower mold 110 and the upper mold 120 are assembled to produce the mold 100 (P2). Next, the slurry 140 is poured into the mold 100 and solidified (hardened) (P3). Thereafter, the molded body 150 can be obtained by releasing each mold (P4). After the mold release, the lower mold 110 and the upper mold 120 are cleaned in order to manufacture the next molded product.

JP2021-37658A Japanese Patent Application Publication No. 2020-131708

In the conventional method for producing a molded article by mold casting, it is necessary to apply a mold release agent to the mold before molding and to clean the mold after molding.
However, when applying a mold release agent, uneven coating may occur, making it difficult to release the mold. Further, when cleaning the mold, foreign matter may be mixed into the molded product due to insufficient cleaning of the mold. Therefore, it is difficult to use the same mold to mold products with different compositions. Furthermore, the area of equipment for applying the mold release agent and cleaning the mold also increases. In particular, when molding products with different compositions, it is necessary to provide equipment for cleaning molds for each product. Furthermore, the process time required for applying the mold release agent and cleaning the mold is long, which causes a decrease in the productivity of the molded body. Furthermore, application of a mold release agent and cleaning of the mold require the use of chemicals, which has a large impact on manufacturing costs and environmental impact.

It is an object of the present invention to solve the above-mentioned problems, and in particular, to provide a method that can produce a molded article with good dimensional accuracy without applying a mold release agent or cleaning a mold. .

As a result of intensive research to solve the above problems, the inventor of the present invention vacuum-packaged a mold having a concave portion with a resin film packaging material, and by performing molding using this vacuum-packed mold, The inventors have discovered that it is possible to omit the application of a molding agent and the cleaning of the mold, and have completed the present invention.
That is, the above-mentioned problem is solved by the following present invention, and the present invention is as follows.

[1] A mold packaging step of vacuum packaging a mold having a concave portion with a resin film packaging material;
A method for manufacturing a molded body, comprising a casting and solidifying step of injecting a slurry containing ceramic powder and/or metal powder into the recessed portion of the vacuum-packaged mold and solidifying the slurry.

[2] The production of the molded body according to [1], further comprising, after the casting solidification step, a mold release step of repressurizing the resin film packaging material in which the mold is vacuum-packaged and releasing the molded body. Method.

[3] The method for manufacturing a molded body according to [1] or [2], wherein in the casting and solidifying step, after injecting the slurry, a lid material is placed above the recess of the mold.

[4] The method for producing a molded article according to any one of [1] to [3], wherein the resin film packaging material has thermoplasticity, mold releasability, shape followability, and chemical resistance.

[5] The resin constituting the resin film packaging material is one or more selected from polyethylene resin, polypropylene resin, polystyrene resin, acrylonitrile styrene resin, ABS resin, vinyl chloride resin, polymethyl methacrylate resin, and polyethylene terephthalate resin. A method for producing a molded article according to any one of [1] to [4].

[6] The method for producing a molded article according to any one of [1] to [5], wherein the recessed portion of the mold is maintained horizontally in the casting solidification step.

[7] The method for producing a molded article according to any one of [1] to [6], wherein the slurry further contains a reactant, a gelling agent, and a dispersion medium.

According to the present invention, it is possible to provide a method that can produce a molded article with good dimensional accuracy without applying a mold release agent or cleaning a mold.

It is a cross-sectional schematic diagram for explaining a mold packaging process. It is a cross-sectional schematic diagram for explaining a casting solidification process. It is a cross-sectional schematic diagram for explaining the state in which the lid material is arranged in the casting solidification process. FIG. 3 is a schematic cross-sectional view for explaining a state in which a lid material is placed via a spacer in a casting solidification process. FIG. 2 is a schematic cross-sectional view for explaining a state in which a vacuum-packaged mold is placed on a horizontal stand in a casting solidification process. It is a cross-sectional schematic diagram for explaining a mold release process. It is a result of DSC in an example. FIG. 2 is a schematic cross-sectional view for explaining a conventional manufacturing process.

Embodiments of the present invention will be specifically described below. The present invention is not limited to the following embodiments, and modifications and improvements may be made to the following embodiments as appropriate based on the common knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that such materials also fall within the scope of the present invention.

A method for producing a molded article according to an embodiment of the present invention includes a mold packaging step and a casting solidification step. Moreover, the method for producing a molded article according to the embodiment of the present invention can further include a mold release step after the casting solidification step. Each of these steps will be explained.

<Mold packaging process>
A schematic cross-sectional view for explaining the mold packaging process is shown in FIG.
As shown in FIG. 1, the mold packaging process is a process of vacuum packaging a mold 10 having a recess 11 with a resin film packaging material 20. Specifically, in the mold packaging process, a mold 10 having a recess 11 and a resin film packaging material 20 are prepared, and after the mold 10 is placed in the resin film packaging material 20, the resin film packaging material 20 is By removing the air inside, the mold 10 is vacuum packaged with a resin film packaging material 20.

The resin film packaging material 20 is not particularly limited as long as it can vacuum-package the mold 10, but preferably has thermoplasticity, mold releasability, shape followability, and chemical resistance. By using the resin film packaging material 20 having such characteristics, a molded article with good dimensional accuracy can be stably obtained.

When the resin film packaging material 20 has thermoplasticity, it means that the resin film packaging material 20 is formed from a thermoplastic resin. Since the resin film packaging material 20 has thermoplasticity, the mold 10 can be reliably packaged by vacuum packaging. The melting point of the thermoplastic resin is not particularly limited, but is preferably 300°C or lower.

The resin film packaging material 20 having mold releasability means that the resin film packaging material 20 is difficult to adhere to the molded body. Since the resin film packaging material 20 has mold releasability, the molded body can be easily separated from the mold 10 vacuum-packed with the resin film packaging material 20 during the mold release process described below.

The resin film packaging material 20 having shape followability means that the resin film packaging material 20 can be brought into close contact so as to follow the shape of the mold 10 during vacuum packaging. In order for the resin film packaging material 20 to have shape followability, it is preferable that the elongation rate of the resin film packaging material 20 at 23±2° C. is 50% or more. Here, the elongation rate of the resin film packaging material 20 refers to the maximum amount of deformation immediately before the resin film packaging material 20 breaks (for example, after deformation) with respect to the initial dimension (for example, length) of the resin film packaging material 20. means the ratio of the length of Since the resin film packaging material 20 has shape followability, a molded article with good dimensional accuracy can be stably obtained.

When the resin film packaging material 20 has chemical resistance, it means that it has resistance to the chemicals used in manufacturing the molded body (for example, the chemicals used in the slurry 30) and does not dissolve. Since the resin film packaging material 20 has chemical resistance, it is possible to suppress foreign matter from entering the molded article.

Examples of resins used for the resin film packaging material 20 include thermoplastic resins such as polyethylene resin, polypropylene resin, polystyrene resin, acrylonitrile styrene resin, ABS resin, vinyl chloride resin, polymethyl methacrylate resin, and polyethylene terephthalate resin. . These resins can be used alone or in combination of two or more. Further, the resin film packaging material 20 may have a single layer structure, or may have a multilayer structure of two or more layers. If the resin film packaging material 20 is made of such a resin, the above characteristics can be obtained.

The thickness of the resin film packaging material 20 is not particularly limited as long as the above characteristics can be obtained, but it is 0.01 to 1.0 mm, more preferably 0.02 to 0.5 mm. If the thickness of the resin film packaging material 20 is less than 0.01 mm, the resin film packaging material 20 may be torn during vacuum packaging. Moreover, if the thickness of the resin film packaging material 20 exceeds 1.0 mm, the shape followability of the resin film packaging material 20 with respect to the mold 10 may not be sufficient.

The mold 10 has a recess 11 . Since the recess 11 of the mold 10 is a region into which the slurry 30 is injected, it has a shape corresponding to the outer shape (side surface and one surface) of the molded body. Therefore, the recess 11 of the mold 10 is not particularly limited, and may be appropriately determined depending on the shape of the molded product to be produced.

A conventional mold 100 configured by combining a plurality of molds 100 (a lower mold 110 and an upper mold 120) as shown in FIG. It was difficult to control the amount of the mold release agent 130 applied, and it was also necessary to prepare the mold 100 according to the thickness of the molded article. On the other hand, the mold 10 used in the embodiment of the present invention is one mold 10, and the thickness can be easily controlled by adjusting the amount (for example, mass) of the slurry 30. Moreover, since the mold release property of the molded body is ensured by the resin film packaging material 20, there is no need to control the amount of the mold release agent 130 applied.

The material constituting the mold 10 is not particularly limited, but metals (aluminum, aluminum alloy, SUS steel, nickel alloy, etc.), ceramics, and the like can be used.
Vacuum packaging of the mold 10 using the resin film packaging material 20 can be performed using a commercially available vacuum packaging machine. The conditions for vacuum packaging are not particularly limited as long as the resin film packaging material 20 can sufficiently follow the shape of the mold 10, and may be appropriately set according to the vacuum packaging machine used.

<Casting solidification process>
A schematic cross-sectional view for explaining the casting and solidifying process is shown in FIG.
As shown in FIG. 2, the casting solidification process is a process in which slurry 30 is injected into the recess 11 of the vacuum-packed mold 10 and solidified.
Slurry 30 includes ceramic powder and/or metal powder. Moreover, the slurry 30 can further contain a reactant, a gelling agent, and a dispersion medium, if necessary.

Examples of the ceramic powder include, but are not limited to, alumina powder, zirconia powder, aluminum nitride powder, silicon carbide powder, and the like. A single type of these ceramic powders may be used, or two or more types may be used in combination. Furthermore, examples of the metal powder include, but are not particularly limited to, platinum powder, tungsten powder, molybdenum powder, and the like. A single type of these metal powders may be used, or two or more types may be used in combination. The content of ceramic powder and/or metal powder in slurry 30 is not particularly limited, but can be, for example, 40 to 80% by mass.

The reactant contains a reactive functional group that reacts with the gelling agent to cause a curing reaction (gelling reaction). Examples of the reactant include water, polyhydric alcohols (diols such as ethylene glycol, triols such as glycerin, etc.), polybasic acids (dicarboxylic acids, etc.), and the like. The content of the reactant in the slurry 30 is not particularly limited, but can be, for example, 0.05 to 5% by mass.

A gelling agent is an additive that reacts with a reactive functional group contained in a reactant to cause a curing reaction. Examples of the gelling agent include MDI (4,4'-diphenylmethane diisocyanate), HDI (hexamethylene diisocyanate), and TDI (tolylene diisocyanate). The gelling agent preferably has at least one of an isocyanate group (-N=C=O) and an isothiocyanate group (-N=C=S). Thereby, the reaction between the gelling agent and the reactant can be promoted. The content of the gelling agent in the slurry 30 is not particularly limited, but can be, for example, 1 to 10% by mass.

A dispersion medium is an additive for dispersing a predetermined powder. Examples of the dispersion medium include esters having two or more ester groups, such as polybasic acid esters (such as dimethyl glutarate), acid esters of polyhydric alcohols (such as triacetin), and aliphatic polyvalent esters. The content of the dispersion medium in the slurry 30 is not particularly limited, but can be, for example, 10 to 40% by mass.

Further, the slurry 30 may further contain additives (eg, dispersion aids, catalysts, etc.) known in the technical field, as necessary.
The dispersion aid is an additive for reducing the viscosity of the slurry 30. Examples of the dispersion aid include sorbitan fatty acid esters, polycarboxylic acid copolymers, and polymer phosphate ester salt compounds. The content of the dispersion aid in the slurry 30 is not particularly limited, but can be, for example, 0.5 to 5% by mass.

The catalyst is an additive for further promoting the reaction between the gelling agent and the reactant. Examples of the catalyst include triethylenediamine, hexanediamine, 6-dimethylamino-1-hexanol, and DBN (diazabicyclononene). The content of the catalyst in the slurry 30 is not particularly limited, but can be, for example, 0.01 to 3% by mass.

Slurry 30 can be prepared by mixing each of the above components. Since solidification (hardening) of the slurry 30 starts from the time when each component is mixed, it is preferable that the slurry 30 is injected into the recess 11 of the vacuum-packed mold 10 as quickly as possible after the slurry 30 is prepared.

The conditions for solidifying the slurry 30 injected into the recesses 11 of the vacuum-packed mold 10 are not particularly limited, and may be adjusted as appropriate depending on the components of the slurry 30 used. For example, the slurry 30 can be solidified by standing at room temperature (25° C.) for 2 to 6 hours.

In the casting solidification process, after the slurry 30 is injected into the recess 11 of the vacuum-packed mold 10, a lid material 40 is placed above the recess 11 of the vacuum-packed mold 10, as shown in FIG. You may. By arranging the lid material 40, excessive drying of the surface of the molded product solidified in the recess 11 of the vacuum-packed mold 10 (the surface not in contact with the recess 11) is suppressed, and the characteristics of the front and back surfaces of the molded product are improved. It is possible to suppress the occurrence of a difference. Moreover, it is also possible to suppress the occurrence of warpage in the molded article.

The lid material 40 is not particularly limited, and materials made of materials such as metals and ceramics can be used. Further, the lid member 40 may be placed in direct contact with the mold 10, or may be placed in indirect contact with the mold 10 via a spacer (for example, an O-ring). In particular, as shown in FIG. 4, when injecting the slurry 30 to the upper end of the recess 11 of the mold 10, from the viewpoint of avoiding contact between the lid material 40 and the slurry 30, the slurry 30 is injected indirectly through a spacer 50 or the like. It is preferable to arrange it so that it is in contact with.

In the casting solidification process, it is preferable to maintain the recess 11 of the vacuum-packed mold 10 horizontally. By maintaining the concave portion 11 of the vacuum-packed mold 10 horizontally, a molded product having a uniform thickness can be obtained. A method for maintaining the recess 11 of the mold 10 horizontally is not particularly limited, but for example, the vacuum-packed mold 10 may be placed on a horizontal table 60 as shown in FIG.

<Mold release process>
A schematic cross-sectional view for explaining the mold release process is shown in FIG.
As shown in FIG. 6, the mold release process is a process of releasing the molded body 70 (solidified slurry 30) from the vacuum-packed mold 10. For example, by turning the mold 10 upside down, the molded body 70 can be released from the mold 10 by weight.
Since the resin film packaging material 20 is interposed between the molded body 70 and the mold 10, the molded body 70 can be easily released from the mold 10 due to the releasability of the resin film packaging material 20. can.

In the mold release step, the mold 70 may be released from the mold by restoring the pressure inside the resin film packaging material 20 in which the mold 10 is vacuum-packaged. By restoring the pressure inside the resin film packaging material 20 in this manner, the releasability of the molded body 70 is further improved.
The method for restoring the pressure inside the resin film packaging material 20 is not particularly limited, and for example, the method may be to simply release the vacuum by tearing the resin film packaging material 20, or by using air introducing means after tearing the resin film packaging material 20. Air may be introduced into the resin film packaging material 20 by.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

<Manufacture of molded object>
A molded body was manufactured by sequentially performing a mold packaging process, a casting solidification process, and a mold release process. In this production, seven molded bodies were produced under the same conditions.
In the mold packaging process, a mold with a recess (300 mm long x 300 mm wide x 5 mm deep) is wrapped in a resin film packaging material (As One Corporation, made of high-density polyethylene (PE), 0.1 mm thick x 550 mm wide x 5 mm deep). 900 mm), and vacuum packaging was carried out so that the mold and resin film packaging material were in close contact with each other.

In the casting and solidifying process, a mold vacuum-packed with a resin film packaging material was placed on a horizontal stand, and then slurry was injected into the recesses of the vacuum-packed mold. The slurry contains 71% by mass of alumina powder, 1% by mass of dispersion aid, 25% by mass of dispersion medium, 0.1% by mass of catalyst, 0.2% by mass of ion exchange water, and 0.2% by mass of reactant. %, by mixing 2.5% by mass of a gelling agent. Thereafter, a lid material was placed above the recess into which the slurry was injected via an O-ring, and the material was cured for 4 hours.
In the mold release step, the lid material was removed, the mold was turned upside down, and the pressure inside the resin film packaging material was restored to release the molded body.

<Evaluation>
(1) Mold releasability In the production of seven molded bodies, the mold releasability of the molded bodies was evaluated. As a result, it was confirmed that all seven molded products had good mold releasability.
For comparison, an attempt was made to produce a molded article using the conventional method of applying a mold release agent to the same mold as described above and casting slurry. In this production as well, seven molded bodies were produced under the same conditions. Further, the type of slurry and curing conditions were the same as above. As a result, among the seven molded bodies, six molded bodies had good mold releasability, but one molded body had insufficient mold releasability.

(2) Molded object quality evaluation 1 (DSC)
DSC (differential scanning calorimetry) was performed at 0 to 100 μm on the front and back surfaces of the molded product obtained above, which was subjected to only drying as a post-treatment. DSC was performed using a differential scanning calorimeter under the conditions of atmosphere: air and temperature increase rate: 10° C./min.
Further, for comparison, a molded body was manufactured in the same manner as the above manufacturing method except that the lid material was not placed above the recess into which the slurry was injected, and DSC was performed in the same manner as above.
The DSC results are shown in FIG.
As shown in FIG. 7, when no lid material was placed, the difference in DSC curves between the front surface and the back surface became large. This is presumed to be because drying progressed on the released surface and resin segregation occurred. On the other hand, when the lid material was placed, the difference in DSC curves between the front surface and the back surface became smaller, and it was confirmed that there was almost no difference in quality between the front surface and the back surface.

(3) Quality evaluation of molded body 2 (flatness and thickness difference)
When the shape (flatness and thickness difference) of the molded article obtained above was three-dimensionally measured, it was confirmed that the same shape as the conventional method was obtained.

As can be seen from the above results, according to the present invention, it was possible to provide a method for manufacturing a molded article with good dimensional accuracy without applying a mold release agent or cleaning a mold. In particular, Table 1 shows the difference in effectiveness between the method of the present invention and the conventional method of applying a mold release agent and cleaning the mold (FIG. 8).

As shown in Table 1, while the conventional method had a yield of 70% when releasing the molded body, the method of the present invention can improve the yield to 100%. Ta. In addition, the method of the present invention does not require the equipment area required for applying a mold release agent and cleaning the mold, and also reduces the equipment area required for vacuum packaging compared to the equipment required for applying a mold release agent and cleaning the mold. The area was significantly reduced to one-tenth. In addition, the method of the present invention does not require the application of a mold release agent and the cleaning of the mold, and the work time required for vacuum packaging is 30 minutes compared to the work time required for the conventional application of a mold release agent and cleaning of the mold. 1, the productivity of the molded body was significantly improved. Furthermore, while the conventional method required the use of a mold release agent and a cleaning solution and two precision molds (a lower mold and an upper mold), the method of the present invention requires the use of a mold release agent and a cleaning solution. is not necessary, and it was possible to produce a molded article with the same quality as conventional molds using one mold.

10 Mold 11 Recess 20 Resin film packaging material 30 Slurry 40 Lid 50 Spacer 60 Horizontal stand 70 Molded object 100 Mold 110 Lower mold 120 Upper mold 130 Mold release agent 140 Slurry 150 Molded object

Claims (7)

a mold packaging step of vacuum packaging a mold having a concave portion with a resin film packaging material;
A method for manufacturing a molded body, comprising a casting and solidifying step of injecting a slurry containing ceramic powder and/or metal powder into the recessed portion of the vacuum-packaged mold and solidifying the slurry. 2. The method for producing a molded body according to claim 1, further comprising, after the casting and solidifying step, a mold release step of repressurizing the resin film packaging material in which the mold is vacuum-packaged and releasing the molded body. The method for producing a molded body according to claim 1 or 2, wherein in the casting and solidifying step, after injecting the slurry, a lid material is placed above the recess of the mold. The method for producing a molded article according to claim 1 or 2, wherein the resin film packaging material has thermoplasticity, mold releasability, shape followability, and chemical resistance. The resin constituting the resin film packaging material is one or more selected from polyethylene resin, polypropylene resin, polystyrene resin, acrylonitrile styrene resin, ABS resin, vinyl chloride resin, polymethyl methacrylate resin, and polyethylene terephthalate resin. Item 2. A method for producing a molded article according to item 1 or 2. The method for manufacturing a molded body according to claim 1 or 2, wherein the recessed portion of the mold is maintained horizontally in the casting solidification step. The method for producing a molded body according to claim 1 or 2, wherein the slurry further contains a reactant, a gelling agent, and a dispersion medium.