Manufacturing method of molded body and structure using shellac

Abstract

The present invention provides a method for producing a molded article using shellac, which can easily and appropriately produce a molded article by using shellac as a mold for a molded article. [Solution] The method includes the steps of: applying a shellac solution, in which shellac is dissolved in alcohol, to the periphery of a model of a molded product made of expanded polystyrene or a model of a molded product produced with a 3D printer; applying sand or metal powder as aggregate to the shellac solution applied to the model of the molded product in the previous step; and evaporating the alcohol content of the shellac solution and hardening it so that it is reinforced by the sand or metal powder, thereby obtaining a molded body as a mold for the molded product.

Description

[Technical Field]

[0001] The present invention relates to a method for producing molded bodies and structures using shellac, which is simpler and has a higher degree of freedom than metal materials and allows for the production of molded bodies or structures such as porous molded bodies. [Background technology]

[0002] Shellac, a natural resin, is soluble in alcohol but insoluble in other organic solvents such as toluene, and has traditionally been used as an ink binder and a moisture-proofing agent for pharmaceuticals and food products.

[0003] Another conventional method for producing porous metal bodies is a method for producing porous metal materials based on aluminum or aluminum alloys or other metals or alloys, in which at least one type of base metal is coated around at least one type of spacer resin, and these are connected so that the resin or voids are disposed at the connecting portions, and then compression-molded, after which the spacer is removed by thermal decomposition or dissolution, and the metals are joined together by sintering, diffusion bonding, adhesive bonding, or a similar joining method (Patent Document 1).This method allows for the production of porous metal materials that control the size and distribution of voids and the thickness of the matrix walls, as well as the porosity, and minimizes holes in the walls of the base material to eliminate open pores on the surface, or that have controlled sizes and shapes of interconnecting pores. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-292888 A (page 1) Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved in the method for manufacturing molded bodies and structures using shellac is that although shellac has traditionally been used as an ink binder and a moisture-proofing agent for pharmaceuticals and foods, there has been no proposal to use shellac to easily and appropriately manufacture molded bodies such as porous molded bodies.

[0006] Therefore, an object of the present invention is to provide a method for producing molded bodies and structures using shellac, which can easily and appropriately produce molded bodies such as porous molded bodies by using shellac. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention has the following configuration. According to one embodiment of the method for manufacturing a molded body using shellac of the present invention, the method includes the steps of: mixing a metal powder with a shellac solution in which shellac is dissolved in alcohol to obtain a shellac-mixed fluid; placing the shellac-mixed fluid into a manufacturing mold; and evaporating the alcohol content of the shellac-mixed fluid to obtain a molded body.

[0008] In addition, according to one embodiment of the method for producing a molded body using shellac of the present invention, pores can be generated by heating the alcohol at a temperature above the boiling point of the alcohol to boil it, or by heating the shellac at a temperature above the heat-hardening temperature to harden it in a suspended state.

[0009] Furthermore, one embodiment of the method for producing a molded body using shellac according to the present invention is characterized in that it includes the steps of: applying a shellac solution, in which shellac is dissolved in alcohol, to the periphery of a molded product model made of expanded polystyrene or a molded product model produced by a 3D printer; applying sand or metal powder as aggregate to the shellac solution that has been applied to the molded product model in the previous step; and evaporating the alcohol content of the shellac solution and hardening it so that it is reinforced by the sand or metal powder, thereby obtaining a molded body as a mold for the molded product.

[0010] According to one embodiment of the method for producing a molded body using shellac of the present invention, a step of obtaining a molded body as a mold for a molded article using the shellac is Previous The process can be characterized by including a step of applying a lost foam coating agent used when producing castings by the lost foam method to the periphery of a molded product model made of expanded polystyrene or a molded product model produced by a 3D printer, and a step of applying sand or metal powder as aggregate to the lost foam coating agent applied to the molded product model in the previous step.

[0011] Furthermore, according to one embodiment of the method for producing a molded body using shellac according to the present invention, at least some of the steps for obtaining the molded body as the molded product die can be performed multiple times.

[0012] Furthermore, according to one embodiment of the method for producing a molded body using shellac of the present invention, after obtaining a molded body as a mold for the molded article, dry sand or CO2 sand is used to obtain a structure as a casting mold to reinforce the molded body.

[0013] Furthermore, according to one embodiment of the method for producing a molded article using shellac according to the present invention, the model of the molded article is formed from a polystyrene material, and is removed by dissolving it in a limonene solution or by heating it to melt it, thereby obtaining a molded article serving as a mold for the molded article having a hollow space for forming the molded article.

[0014] Furthermore, one embodiment of the method for manufacturing a structure using shellac according to the present invention is characterized by including a step of using a shellac solution in which shellac is dissolved in alcohol, utilizing the adhesive properties of the shellac to bond at least two adherends, which are adherends, from among a punched metal, a plate-shaped honeycomb, a metal member other than the punched metal or the plate-shaped honeycomb, glass wool, carbon fiber, and a molded body prepared by mixing the shellac and metal powder, thereby bonding them into multiple layers.

[0015] Furthermore, according to one embodiment of the method for manufacturing a structure using shellac according to the present invention, the method can be characterized by including the steps of: obtaining a shellac-mixed fluid by mixing a metal powder with a shellac solution in which the shellac is dissolved in alcohol; stacking the adherends together using the shellac-mixed fluid as an interlayer adhesive; and adhering multiple metal plates in a stacked state by evaporating the alcohol content of the shellac-mixed fluid. [Effects of the Invention]

[0016] The method for producing molded bodies and structures using shellac of the present invention has the particularly advantageous effect of enabling molded bodies such as porous molded bodies and lightweight structures that are excellent in heat insulation and sound absorption properties to be produced simply and appropriately by using shellac. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, examples of the method for producing a molded body and a structure using shellac according to the present invention will be described.

[0018] The method for producing a molded body using shellac according to the present invention includes the steps of: mixing a metal powder with a shellac solution in which shellac is dissolved in alcohol to obtain a shellac-mixed fluid; placing the shellac-mixed fluid in a mold; and evaporating the alcohol content of the shellac-mixed fluid to obtain a molded body. While aluminum powder is used as the metal powder, it is not limited thereto, and powders of other metals can also be used. Furthermore, a shellac solution diluted with, for example, 75% alcohol can be used.

[0019] According to the method for producing a molded body using shellac of the present invention, the metal powder serves as an aggregate and the shellac functions as a binder, which has the particularly advantageous effect of enabling a molded body to be produced more easily and appropriately than when molding is performed using only metal materials.

[0020] Shellac is a natural resin, and its properties are as follows: specific gravity: 1.02-1.12, specific heat: 0.53 (0°C), softening point: 70-80°C, acid value: 60-80, saponification value: 200-260, iodine value: 15-30 (Wissin method), heat curing time: 2-6 minutes (JIS K5909 170°C), volume resistivity: 1015-1016 Ω·cm, dielectric constant: 3.5-4.0, electrical insulation strength: 40-80 kV / mm, SP value: 12.5±2.0.

[0021] In addition, as an example of a method for producing a molded body using shellac according to the present invention, the step of vaporizing the alcohol content of the shellac mixed fluid can include a step of boiling the alcohol by heating at a temperature above the boiling point of the alcohol, or of generating pores by heating at a temperature above the thermosetting temperature of the shellac to thermoset it in a suspended state.

[0022] According to this, the method for manufacturing a molded body using shellac according to the present invention is a method of bonding metal material (powder) with a resin binder, which has the special advantage of not requiring large-scale equipment.In contrast, porous metals are generally obtained by methods using molten metal (metal melting) or fused metal (sintering) by heat, which require large-scale equipment and result in high manufacturing costs.

[0023] Furthermore, shellac is a natural resin with a wide molecular weight distribution, from low to high molecular weight, and its thermosetting properties do not reach the final hardening point all at once, but can be adjusted to any hardening state. In other words, because the polymerization caused by thermosetting occurs gradually, it is very different from synthetic resins, which harden all at once, and the degree of hardening can be adjusted as desired by specifying the heating temperature and time. Another major feature of shellac resin is that it melts once before hardening.

[0024] Next, specific examples of methods for manufacturing molded bodies using shellac are described below, divided into dense and porous molded bodies. Basically, the natural resin shellac is used as a binder for metal powder, and a shellac solution diluted with, for example, 75% alcohol can be used. The aluminum powder and shellac are suspended in the alcohol to form a slurry. When more alcohol evaporates than necessary, the shellac begins to harden.

[0025] The manufacturing method for a dense mold (dense molding) involves placing the shellac mixed fluid into the mold as described above, then placing the mold into an oven where the alcohol is evaporated. For example, the oven temperature is set to 70°C. This low temperature, below the boiling point of alcohol, causes the alcohol to evaporate, resulting in a dense material. In other words, by gently evaporating the alcohol, the weight of the aluminum creates a dense material without porosity.

[0026] Furthermore, by evaporating the alcohol below its boiling point, the shellac solidifies and bonds to the aluminum powder, as mentioned above. Shellac in this state can be turned back into a slurry-like material by utilizing its thermoplastic properties at temperatures between 70 and 80°C. In other words, due to its properties of both thermoplasticity and thermosetting, the material can be recycled before it hardens.

[0027] The porous mold (porous molded body) manufacturing method involves pouring the shellac-mixed fluid into a mold as described above. The mold containing the shellac-mixed fluid is then placed in an oven and heated for, for example, 30 minutes at a preset oven temperature of, for example, 170°C. This produces a porous molded body (in this example, a molded body with a 10 cm square and a thickness of approximately 2 cm). Since the thermosetting temperature of shellac is 170°C, heating at temperatures above this temperature causes the suspended shellac to thermoset. The solidified metal becomes porous (see Figure 2). It is believed that the porous molded body is formed by suddenly raising the temperature, causing the alcohol to boil and vaporize, creating porosity. In other words, the shellac-containing alcohol is boiled, creating porosity through vaporized gas. During heating, the shellac was visually observed boiling. The heating time varies depending on the size and shape of the molded body, the size of the oven, and the preheating conditions. For example, a porous molded body was obtained in approximately 5 minutes for a small object.

[0028] Next, the affinity of the molded body using the above-described shellac with metals will be described.

[0029] Experiments were conducted on the bonding ability of the shellac to gray cast iron, stainless steel, and steel as examples of metal materials. When the shellac-mixed fluid, which forms a molded body using shellac, was brought into contact with these metals and thermally cured at 170°C, in all cases, the shellac-mixed body bonded to the metal material in such a way that it could not be released from the mold. This confirmed that shellac, being a natural resin, easily bonds with natural substances and has good affinity. Fluorine and silicone are suitable as mold release agents.

[0030] The above manufacturing method does not require metal melting equipment, and a molded body using shellac can be easily produced with an oven at about 200°C. In other words, according to the present invention, large-scale equipment is not required. Furthermore, by controlling the temperature and time, it is possible to produce either porous or dense materials. Shellac is a natural resin that is not produced from fossil fuels, making it environmentally friendly as biomass. Furthermore, because shellac is a natural resin, it does not produce harmful gases even when heated.

[0031] Furthermore, because it is a natural resin, it has a high affinity with natural mineral substances (iron, stainless steel, glass, etc.). By utilizing this property, when a molded body (such as an aluminum porous metal molded body) of a required thickness using shellac is sandwiched between metal plates such as steel plates, the bodies are bonded using shellac as an adhesive, making it possible to produce lightweight soundproofing materials, vibration-damping materials, and heat insulating materials that combine sound insulation and attenuation properties. Furthermore, these metal plates can also be made into perforated plates (punched metal).

[0032] Next, a method for applying the method for producing a molded body using shellac according to the present invention to the production of a molded product (casting mold or resin molding mold) will be described below.

[0033] The method for manufacturing a molded body (such as a mold) using shellac according to the present invention is characterized by comprising the steps of: applying a shellac solution, in which shellac is dissolved in alcohol, to the periphery of a molded product model made of expanded polystyrene or a molded product model manufactured using a 3D printer; applying sand or metal powder as aggregate to the shellac solution that was applied to the molded product model in the previous step; and evaporating the alcohol content of the shellac solution and hardening it so that it is reinforced by the sand or metal powder, thereby obtaining a molded body (such as a mold) as a mold for the molded product.

[0034] In this case, the process includes, before or after the step of obtaining a molded body as a mold for a molded product using the shellac, a step of applying a lost foam coating used in producing castings by the lost foam method to the periphery of a molded product model made of expanded polystyrene or a molded product model produced by a 3D printer, and a step of applying sand or metal powder as aggregate to the lost foam coating applied to the molded product model in the previous step, thereby producing a molded body (mold) that is more resistant to crumbling, stronger, and more stable as a mold for a molded product. As the lost foam coating, for example, Styromol 144 from Foseco Japan Limited (6-1-10 Miyuki-dori, Chuo-ku, Kobe) can be used.

[0035] Furthermore, for example, in the case of a molded product model made of expanded polystyrene, dissolving and fluidizing the molded product model using a solvent such as a limonene solution, as described below, and then discharging the model, the inner surface of the mold formed by the lost foam wash may become rough, making the sand or metal powder aggregate more likely to peel off. Therefore, to reinforce the inner surface of the mold, the inner surface of the mold may be coated with shellac by dipping it in, for example, the aforementioned shellac solution or a mixed solution of the shellac solution with sand or other ingredients. This allows the inner surface of the mold to be suitably coated with a thin layer of shellac, improving the finish of the casting surface.

[0036] In addition, while the expanded polystyrene (Styrofoam) used in ordinary lost foam is expanded 30 to 50 times, the expanded polystyrene molded product model of the present invention can be made denser by lowering the expansion rate, allowing for the production of molded products (castings) with a fine-grained surface.

[0037] Furthermore, by performing at least some of the above-mentioned steps for obtaining a molded body as a molded product mold multiple times, a molded body (casting mold) as a molded product mold that is more resistant to collapse, stronger, and more stable can be obtained.

[0038] That is, one example of a method for reinforcing the molded body described above involves a series of steps: applying a shellac solution, in which shellac is dissolved in alcohol, to the periphery (surface) of a molded product model made of expanded polystyrene or a molded product model produced by a 3D printer; applying sand or metal powder to the shellac solution previously applied to the molded product model; and evaporating the alcohol content of the shellac solution to harden the shellac solution into a state reinforced by the sand or metal powder. By performing this series of steps multiple times, a molded body can be obtained as a mold for a molded product. Note that while the final step of the process of evaporating the alcohol content of the shellac solution to harden the shellac solution into a state reinforced by the sand or metal powder requires complete hardening, the previous steps only require hardening to the extent that the portion of the film layer formed by the shellac solution that contacts the master mold does not deform; complete hardening is not necessary. Similarly, the series of steps may also be performed multiple times with the lost foam mold wash described above.

[0039] Furthermore, after obtaining a molded body as a mold for the molded product, a structure as a mold can be obtained using dry sand or CO2 sand to form a mold that reinforces the molded body, thereby obtaining a reinforced and stable structure (mold) as a mold for the molded product.

[0040] That is, one method of reinforcing the molded body (mold) is to apply a shellac solution, in which shellac is dissolved in alcohol, to the periphery of the model, and to attach sand, etc., to form a film-like molded body made of the shellac solution and sand, and then bury the molded body in CO2 sand so that it is backed by self-hardening CO2 sand, and harden the CO2 sand, thereby obtaining a molded body (mold) that serves as a molded product backed up by CO2 sand.

[0041] According to the above-described method for producing a molded body using shellac, a molded body can be easily formed as a mold for a molded product such as a casting mold. That is, this molded body can be suitably used as a mold for metal casting or a mold for resin molding. This makes it suitable for high-mix, low-volume production. Furthermore, models for molded products such as castings produced by 3D printers can also be formed using, for example, 3D printer wax resins used in lost-wax casting, in addition to polystyrene, which will be described later.

[0042] As an example of a method for manufacturing a molded body (mold) using shellac, a prototype (model) of the casting is formed from polystyrene material, and is removed by dissolving it in a limonene solution or by melting it by heating, thereby obtaining a mold with a hollow space in which the casting will be formed.

[0043] This method allows for the easy and efficient formation of a mold with a hollow space for forming a casting. For example, it can include the following steps: First, a solvent such as limonene solution is poured into a polystyrene pattern (master) to swell and dissolve it. The dissolved, paste-like polystyrene pattern is then removed from the mold. Subsequently, or without the step using a solvent such as limonene solution, the polystyrene pattern is heated to melt, fluidize, and flow out. Molten metal can then be poured into the space created in the shellac mold to produce (cast) the casting. In the case of a molded product made of expanded polystyrene, the molded product pattern can be appropriately dissolved, fluidized, and discharged using a heated limonene solution.

[0044] Specific process examples of the above-mentioned embodiment are described below. Note that, although the following describes an example using a molded product model manufactured by a 3D printer, the present invention is not limited to this, and it goes without saying that a molded product model made of expanded polystyrene (manufactured in the same process as a lost foam model) may also be used. 1) Create a model (prototype) using polystyrene (PS) material using a 3D printer. 2) A molded body (e.g., a casting mold) using shellac is produced by thickly coating a model created using a 3D printer with the aforementioned shellac solution and sand or metal powder. The coating method involves showering sand or other materials onto a model to which the shellac solution has been applied by dipping, thereby efficiently adhering the sand or other materials. Before or after this step, as described above, it is also recommended to perform a step of applying a lost foam coating to the periphery of the model and a step of adhering sand or metal powder as aggregate to the lost foam coating. In this case, too, showering sand or other materials onto a model to which the lost foam coating has been applied by dipping can efficiently adhering the sand or other materials. While the above-described steps using the shellac solution or lost foam coating can be performed once or twice to obtain an appropriate molded body, they may be repeated as needed to obtain a more reliable molded body. 3) The 3D printer model (PS material) can be removed by dissolving it in a solvent such as limonene solution. Alternatively, the 3D printer model (PS material) can be removed by heating and melting it. For example, by heating it to about 250°C, the 3D printer model (PS material) can be melted and flowed out. 4) The 3D printer model (PS material) becomes hollow, and the hollow mold (thick coating) is buried in dry sand or backed up with CO2 sand as needed. If the molded item formed using this mold is small, dry sand can be adequately backed up, while CO2 sand can be used for large items. Note that if the molded item is made using the other CO2 sand methods mentioned above, where the shellac coating is backed up with CO2 sand, there is no need to bury it in dry sand. 5) Molten metal is poured into the hollow area to create a casting.

[0045] In the above examples, the polystyrene model is removed by injecting a solvent such as limonene solution into it to melt it, or by heating and melting the polystyrene model. However, since it takes time to melt the polystyrene model, as a solution to this problem, the polystyrene model is made hollow and has the minimum wall thickness necessary to maintain its shape. This shortens the dissolution time required to remove the polystyrene model.

[0046] When manufacturing a mold, it is advisable to pre-fabricate the runner with a standard shape made of polystyrene foam and connect it to a model created using a 3D printer, as described above. The polystyrene foam portion dissolves extremely easily in organic solvents such as limonene solution, allowing for the appropriate and easy manufacture of a mold with a hollow cavity for forming a casting. Furthermore, the molded body described above, which is made using a shellac-mixed fluid obtained by mixing metal powder with the shellac solution described above, can be used as a core when manufacturing molded products.

[0047] Next, a method for manufacturing a structure using shellac, in which a structure in which a plurality of metal plates are bonded together in a stacked state, will be described.

[0048] This method for manufacturing a structure using shellac is characterized by including the steps of: mixing a metal powder with a shellac solution in which shellac is dissolved in alcohol to obtain a shellac-mixed fluid; laminating metal plates together using the shellac-mixed fluid as an interlayer adhesive; and bonding multiple metal plates together in a stacked state by evaporating the alcohol content of the shellac-mixed fluid.

[0049] This makes it possible to easily provide a structure in which multiple metal plates are stacked together using adhesion with shellac. In this structure in which multiple metal plates are stacked together, the shellac-mixed fluid hardens between the layers of the metal plates and functions as an adhesive layer, and the thickness of the shellac-mixed fluid between the layers of the metal plates can be made sufficiently thinner than the thickness of the molded body using shellac as described above.

[0050] Furthermore, when the metal plate is a perforated plate or a low-height honeycomb plate, for example, perforated plates or plate-like honeycombs can be stacked with their perforations offset, and the aforementioned shellac-mixed fluid can be interposed between each layer. Then, the shellac-mixed fluid can be hardened to obtain a metal plate laminate (structure) in which multiple perforated plates are stacked more firmly. That is, the shellac-mixed fluid can penetrate the perforations of the perforated plates or honeycombs and harden, thereby increasing the bonding strength between the perforated plates. In this case, by heating the shellac-mixed fluid to generate pores as described above, the perforated plates can be bonded together, and a lightweight structure can be obtained in which vibrations and sound can be absorbed and suppressed by the porous structure. Note that the shellac solution mainly penetrates and bonds the metal plate surfaces where they come into contact.

[0051] In addition, methods for manufacturing structures utilizing the adhesive properties of shellac are not limited to the above methods and include a step of using a shellac solution in which shellac is dissolved in alcohol to bond at least two adherends, including a punched metal, a honeycomb plate, a metal member other than the punched metal or the honeycomb plate, glass wool, carbon fiber, or a molded body containing a mixture of shellac and metal powder, to form multiple layers. The two adherends may be combinations of various materials, or may be materials of the same type, such as two punched metals. This method allows for the rational manufacture of lightweight structures and structures with improved thermal insulation and sound absorption properties.

[0052] Furthermore, the above-mentioned structures using shellac are not limited to those formed by laminating planar members (bonded members) together in layers, but also include structures formed by bonding curved or bent planar members together in layers, and structures formed into a sandwich-like layered structure by sandwiching and bonding a bonded member between a pair of planar members.

[0053] The present invention has been described above in various ways using preferred embodiments, but the present invention is not limited to these embodiments, and it goes without saying that many modifications can be made within the scope of the invention without departing from the spirit of the invention.

Claims

1. A method for producing a molded body using shellac, comprising the steps of: applying a shellac solution in which shellac is dissolved in alcohol to the periphery of a model of a molded product made of expanded polystyrene or a model of a molded product produced by a 3D printer; applying sand or metal powder as aggregate to the shellac solution applied to the model of the molded product in the previous step; and evaporating the alcohol content of the shellac solution and hardening it so that it is reinforced by the sand or metal powder, thereby obtaining a molded body as a mold for a molded product.

2. The method for producing a molded body using shellac according to claim 1, characterized in that it includes, as a step prior to the step of obtaining a molded body as a mold for a molded product using the shellac, a step of attaching a lost foam mold wash used when producing castings by the lost foam method to the periphery of a model of a molded product made of expanded polystyrene or a model of a molded product produced by a 3D printer, and a step of attaching sand or metal powder as aggregate to the lost foam mold wash attached to the model of the molded product in the previous step.

3. 3. The method for producing a molded body using shellac according to claim 2, wherein at least some of the steps for obtaining the molded body as the molded product are carried out a plurality of times.

4. After obtaining a molded body as a mold for the molded product, dry sand or CO is used to reinforce the molded body. ２ 4. The method for producing a molded body using shellac according to claim 3, wherein the structure as a mold is obtained using sand.

5. The method for producing a molded product using shellac according to any one of claims 1 to 4, characterized in that the model of the molded product is made of a polystyrene material, and is taken out by dissolving it in a limonene solution or by melting it by heating, thereby obtaining a molded product as a mold for a molded product having a hollow space for forming the molded product.