JPH11104785A - Mold forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold which is easily disintegrable, easy in regeneration into sand, excellent in mold strength and does not cause the deterioration of working environment due to hazardous odor occurrence. SOLUTION: In this mold forming method, the composition of mold is as follows: one or more aggregate of silicon sand, zircon sand, olivine sand, chromite sand, alumina sand, and mullite sand; and natural oligosaccharide group and/or starch of 2-10 monosaccharide unit or oligosaccharide of 2-10 monosaccharide unit being obtained from high polymer saccharide group; and one or more thermosetting resin of water soluble phenolic resin, urea resin, melamine resin, and epoxy resin against 100 weight portion aggregate. The weight ratio of solids content is as follows; oligosaccharide: thermosetting resin = 50:50=95:5. Furthermore, the mold forming composite being obtained by adding and mixing 0.5-10 weight portion of water soluble oligo caking additive, solids content concentration of which is 20-75 wt.%, is filled in a mold model. Then, after the mold is stored in a closed container, the water in the mold is compulsorily removed at the container inner pressure of 48 kPa or less, and is dry-hardened.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a mold by drying and curing a composition for molding using an oligoadhesive containing an oligosaccharide as a main component under reduced pressure.

2. Description of the Related Art There are various methods for molding a mold.
There are a wide variety of binders used for this purpose, but they are roughly divided into inorganic binders and organic binders. As a molding method using an inorganic binder, there is a method of hardening a silicate mainly with ferrosilicon (N process), dicalcium silicate (dical method), or CO ₂ gas. A mold using silicate has disadvantages such as poor disintegration after casting and generation of a large amount of waste. As a molding method using an organic binder, a thermosetting mold such as a shell mold method, a room temperature curable mold in which a furan resin or a phenol resin is cured using an acid or an ester, or an urethane resin or a phenol resin in an amine gas, Ester gas or CO ₂
There is a molding method such as a gas-curable mold that cures with a gas.
At the time of mold making using these organic binders, there are drawbacks such as generation of odors such as formaldehyde and deterioration of the working environment due to the use of organic solvents, toxic hardeners or catalysts. In addition, these are binders, organic solvents,
There is a disadvantage that the cured product of the curing agent, the catalyst and the binder is thermally decomposed to generate various harmful gases and odors, thereby deteriorating the working environment in the factory and the external environment around the factory. On the other hand, as binders of these inorganic binders and organic binders that do not have the above-mentioned drawbacks, there is a technique of using a water-soluble glue binder using a natural product or a dextrin derived from a natural product. 52-120
225, JP-A-59-76642, JP-B 3-
21254 publication). However, a large amount of a water-soluble glue binder is required to obtain the strength of a practically usable mold. In addition, molds using a water-soluble glue binding agent, because the strength of the mold is significantly deteriorated due to the absorption of moisture in the air after the molding,
There is a restriction in the work process that the pouring must be performed immediately after molding. Furthermore, when these water-soluble glue binders are stored in an aqueous solution, they are easily rotted by microorganisms and the like, and have drawbacks in storage stability and hygiene. Techniques relating to a method of drying and curing a mold using these water-soluble glue binders and a method of forming a mold are disclosed in JP-B-61-20384 and JP-A-57-978.
36 and JP-A-57-175053. However, at the time of molding these molds, a method of heating the kneading sand and forcibly drying by blowing hot air is used, but there is an economic disadvantage due to equipment and heat energy costs.

The problems of the disintegration of the inorganic binder and the waste sand as described above, the lack of mold strength, the storage stability, and the working environment of conventional water-soluble glue binders and organic binders. As a result of intensive research to obtain a mold that has solved the drawbacks such as adverse effects on the environment and the external environment, oligosaccharides and water-soluble thermosetting resins are essential components, and oligosaccharides containing auxiliary agents, silane coupling agents and surfactants By using a binder and drying and hardening under reduced pressure using a vacuum pump, it is easy to disintegrate and sand is easy to regenerate, excellent in mold strength and storage stability, and in the work environment due to harmful odor generation. The inventors succeeded in obtaining a template without deterioration, and reached the present invention.

According to the present invention, there is provided a molding method comprising one or more aggregates of silica sand, zircon sand, olivine sand, chromite sand, alumina sand, and mullite sand, and 100 parts by weight of the aggregate. On the other hand, a monosaccharide unit having 2 to 10 natural oligosaccharides and / or a monosaccharide unit obtained from starch or a high molecular saccharide has 2 to 10 oligosaccharides and a water-soluble phenol resin, urea resin, melamine resin, It is composed of one or more thermosetting resins of epoxy resin, and their solid content weight ratio is oligosaccharide: thermosetting resin = 50: 50-9.
5: 5, and 0.5 to 10 parts by weight of a water-soluble oligo-binding agent having a solids concentration of 20 to 75% by weight was added and mixed. And the mold is placed in a closed container.
The method is characterized in that the water in the mold is forcibly removed at a pressure of 8 kPa or less and dried and cured. The present invention will be described in more detail. The aggregate used in the present invention includes silica sand, zircon sand, olivine sand, chromite sand, alumina sand, mullite sand and the like. Oligo binder having a solid content of 20 to 75% by weight based on 100 parts by weight of aggregate
It is an object of the present invention to provide a method in which 0 parts by weight are added, kneaded sand obtained by kneading an aggregate and a binder is filled in a desired model, which is dried under reduced pressure and cured to form a mold. The present invention is an application of the VRH method, which is one of the mold making methods, and is a method for vacuum forming. The drying method will be described in more detail. A kneaded sand obtained by using an oligo binder is filled in a mold, the mold is placed in a closed container, and the pressure in the vacuum box is increased to 48.0 kPa by a vacuum pump. In the following, the water in the mold is forcibly removed. The pressure in the vacuum box is kept at 48.0 kPa or less until moisture in the mold is removed, and after drying and curing, the pressure is returned to the atmospheric pressure (101.3 kPa), and then the mold is taken out. As shown in FIG. 1, a method of placing a mold in a closed container and drying it in a vacuum is performed by a vertical method in which a closed container (vacuum box) 1 or a mold 2 moves up and down as indicated by an arrow in FIG. As shown in the figure, a slide type in which the mold 2 moves left and right as indicated by the arrow in the figure, and further, as shown in FIG. There is a stationary type in which the mold 2 is placed, the periphery of the mold 2 is covered with an airtight flexible film 4, and a vacuum is applied. The oligosaccharide used in the present invention refers to a natural oligosaccharide having a monosaccharide unit of 2 to 10 or a saccharide obtained by hydrolyzing a polysaccharide such as starch using an acid or an enzyme. In the present invention, saccharides other than oligosaccharides having one unit are called monosaccharides, and saccharides having 11 or more units are called polysaccharides. When a polysaccharide is used as a binder, the solubility in water is low, a large amount of water is required to prepare an aqueous solution, and a long time is required in the mold drying step. In addition, the viscosity when dissolved in water is high, and the kneadability with the aggregate is deteriorated, and the fluidity of the obtained kneaded sand is also deteriorated. When a monosaccharide is used as a binder, it is appropriate in terms of water solubility and viscosity of an aqueous solution, but does not provide high mold strength after drying and curing. Further, they have disadvantages such as poor moisture resistance and poor storage stability of the mold, and are not suitable as a binder. on the other hand,
When an oligosaccharide is used as a binder, it is easy to prepare an aqueous solution, and since the viscosity of the aqueous solution is low, the kneadability with sand is good, and the obtained kneaded sand (that is, a composition for mold molding) is obtained. Has good fluidity. In addition, a sufficiently high mold strength can be obtained for practical use. The oligo-binding agent in the present invention prevents the decay of the oligosaccharide by microorganisms while maintaining the advantages of the oligosaccharide as the above-mentioned binding agent, and until the molten aluminum or iron at the time of pouring solidifies. In order to maintain the hot strength involved in maintaining the shape of the mold during
Water-soluble phenolic resin, urea resin, melamine resin,
It contains at least one type of epoxy resin as an essential component. These resins are heat-cured by the heat of the molten metal and serve to impart heat resistance to the mold. Water-soluble polymers such as polysaccharides, proteins, polyvinyl alcohol, and sodium polyacrylate can be used together as auxiliary agents in the oligo binder. Further, the oligo-binding agent may also contain a silane coupling agent or a surfactant, so that higher normal strength of the template and better storage stability can be obtained. The solid content concentration of the oligo binder in the present invention is 20 to 75% by weight.
And preferably 30 to 65% by weight. If the solid content exceeds 75% by weight, the viscosity of the oligo binder increases, making it difficult to sufficiently knead the aggregate and the binder and deteriorating the fluidity of the kneaded sand. On the other hand, when the solid concentration is less than 20% by weight, the amount of water is large and not only takes much time to dry the mold, but also a practically usable mold strength cannot be obtained. The mixing ratio of the oligosaccharide as an essential component in the oligo binder and the water-soluble thermosetting resin is such that the oligosaccharide is 50 to 95% by weight of the solid content. If the content of the oligosaccharide in the solid content exceeds 95% by weight, the proportion of the water-soluble thermosetting resin is small, the effect of the thermosetting resin on the mold strength and moisture resistance is small, and rot is prevented. The antibacterial effect to prevent is also reduced. On the other hand, if the content is less than 50% by weight, the above-mentioned advantages of the oligosaccharide cannot be sufficiently exhibited, and conversely, the proportion of the water-soluble thermosetting resin becomes large. The working environment is deteriorated due to the generation of odor at the time of hot water. The oligosaccharide used in the oligo binder in the present invention is a naturally occurring one or a saccharide obtained by hydrolyzing a naturally occurring polysaccharide with an acid or an enzyme. About 50% as an aqueous suspension to which acid or α-
Amylase and further β-amylase are added for hydrolysis. When hydrolyzed with acid, about 70-150 ° C, α
-Amylases are hydrolyzed at 70-100 ° C, followed by β-amylase at 50-70 ° C to hydrolyze starch in a paste state to obtain a desired molecular weight distribution in the range of monosaccharide units 2-10. Stop the reaction with. After the completion of the reaction, it is necessary to neutralize with an alkali when using an acid and deactivate the enzyme when using an enzyme. The obtained oligosaccharide solution having the saccharide composition of the monosaccharide units 2 to 10 can be concentrated as required to obtain a solution having a desired concentration. Furthermore, it is possible to dry and store it as a powder for a long time. As one of the essential components of the binder of the present invention,
A thermosetting resin such as a water-soluble phenol resin, urea resin, melamine resin, and epoxy resin is used. As the water-soluble phenol resin, a resol-type water-soluble phenol resin, a novolak-type water-soluble phenol resin, and an emulsion-type water-dispersible phenol resin can be used. These phenolic resins are obtained by condensing phenols and aldehydes in the presence of an alkali or acid catalyst. Examples of phenols include phenol, cresol, resorcinol, bisphenol A, bisphenol F, bisphenol C, bisphenol H, cumylphenol, nonylphenol, isopropenylphenol purified residue, bisphenol A purified residue, bisphenol F purified residue, butylphenol, phenylphenol And phenols including ethyl phenol, octyl phenol, amyl phenol, naphthol, catechol, hydroquinone, pyrogallol, and substituted substances thereof. Aldehydes include formalin, paraformaldehyde, furfural,
α-Polyoxymethylene, acetaldehyde, etc., but not limited thereto. Examples of the catalyst for condensing these phenols and aldehydes include acidic substances such as oxalic acid, hydrochloric acid, and sulfuric acid, and organic acid metal salts, or alkali metal water such as potassium hydroxide, sodium hydroxide, and lithium hydroxide. There are oxides or hydroxides of alkaline earth metals. As other water-soluble thermosetting resins, urea, methylol urea, dimethylol urea, urea resin containing dihydroxyethylene urea as a main component, melamine and the above aldehydes are obtained by reacting with an alkali or an acid as a catalyst. A melamine resin or an epoxy resin containing a compound having a glycidyl group obtained by reacting a phenol or a phenol novolak resin with epichlorohydrin can be used. In addition, those based on the definition and manufacturing method described in “Adhesion Handbook” (edited by the Japan Adhesion Association), Vol. 2, Chapter 5, Chapter 5 can also be used. These water-soluble phenolic resins, urea resins, melamine resins, and epoxy resins improve the mold strength and increase the heat during pouring by heating after vacuum drying or polymerizing by the heat of pouring or crosslinking reaction with oligosaccharides. This has the effect of improving the inter-strength. Further, it is effective in improving the storage stability of the mold by improving the moisture resistance of the mold, and is also effective in preventing decay due to the influence of microorganisms on the binder itself. In addition, water-soluble polymers such as polysaccharides, proteins, polyvinyl alcohol, and sodium polyacrylate as adjuvants have a lower drying rate than oligosaccharides due to their lower solubility in water than oligosaccharides. Separates to form a strong film.
Since this film is superior to oligosaccharides in moisture resistance, when added to an oligosaccharide binder, the moisture resistance of the mold is improved. The polysaccharide refers to simple or complex polysaccharides of vegetable or animal origin. For example, starch, modified starch, dextrin, cellulose, modified cellulose, dextran, levan, alginic acids, pectin, hemicellulose, glucomannan, galactomannan, vegetable gum, hyaluronic acid and the like. A protein refers to a vegetable or animal protein containing a peptide. For example, it refers to proteins derived from animals and fungi such as soybean protein, wheat protein, other beans, cereal proteins, casein, albumin, collagen, and hemoglobin. These proteins also include enzymes derived from plants, animals and fungi. Polyvinyl alcohol includes completely saponified, intermediate saponified, partially saponified polyvinyl alcohol, and has a polymerization degree of 200 to
Those having about 3000 are preferred. Also includes modified polyvinyl alcohol. These adjuvants are added to the oligo binder at a solid content of 1 part by weight per 100 parts by weight of the solid content.
Up to 30 parts by weight can be used. These auxiliaries can be added at the time of kneading the oligo binder and the aggregate, and can be used after kneading. Further, by using a silane coupling agent or a surfactant in combination with the oligo binder in the present invention, the fluidity of the kneading sand and the strength of the mold can be further improved. As the silane coupling agent, γ-glycidoxypropyltrimethoxysilane, γ
-Aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, N-glycidyl-N, N-bis (3- (trimethoxysilyl)
Propyl) amine and the like can be used. The above silane coupling agent is added to the oligo binder in a solid content of 10%.
It is preferable to add 0.1 to 5 parts by weight to 0 part by weight. As the surfactant that can be used in the present invention, a nonionic surfactant, a cationic surfactant, an anionic surfactant, an amphoteric surfactant, a silicone-based surfactant, a fluorine-based surfactant, and the like can be used. The surfactant is not particularly limited. These surfactants have an effect of improving the wettability between the aggregate and the binder, and also improve the fluidity of the kneaded sand when filling the model. By improving the fluidity, the filling density of the mold is improved, high mold strength is obtained, and a mold having an excellent surface can be obtained. The blending amount of the surfactant is 10% of the solid content of the oligo binder.
0.01 to 5 parts by weight per 0 parts by weight is preferred.

EXAMPLES Hereinafter, the method of molding a mold according to the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist. [Example 1] Using corn starch as a starting material, an oligosaccharide solution was prepared as follows. Water was added to the corn starch to make a 30% suspension, the pH was adjusted to 6.0, and α-amylase (Kristase T10, manufactured by Daiwa Kasei Co., Ltd.) was added to 100 parts by weight of the suspension. After adding 0.03 parts by weight, a hydrolysis reaction was carried out at 90 to 100 ° C.
Oxalic acid was added when the average monosaccharide unit became about 5 in the analysis by high performance liquid chromatography using a column of Oligo PW (manufactured by Tosoh Corporation).
H4.3 or less, and the reaction was completed. Then, concentration and drying were performed to obtain a powdered oligosaccharide. The average monosaccharide unit was 5.7. 42.5 parts by weight of the oligosaccharide, an alkaline resole type phenol resin (manufactured by Gunei Boden Co.
PA-14, solid content 50% by weight) 15.0 parts by weight, water 4
2.5 parts by weight were mixed to obtain an oligosaccharide binder. Next, the oligo was added to 100 parts by weight of silica sand (Iidero F-6 No. 6 silica sand).
4.0 parts by weight of a binder was added and kneaded with a kneader for 60 seconds to obtain kneaded sand. 10mm × 10mm × 60
After having been molded into an aluminum mold for taking 5 mm test pieces, it was carried into a vertical closed container (vacuum box) 1 as shown in FIG. The pressure in the vacuum box was set to 0.8 kPa and maintained for 1 to 5 minutes. The bending strength of the obtained mold was measured immediately after molding and after being stored for 48 hours in a thermo-hygrostat (25 ° C., 60%). Table 1 shows the results. [Example 2] Oligosaccharide 4 obtained in the same manner as in Example 1
2.5 parts by weight, 11 parts by weight of an alkaline resole type phenol resin (TPA-14 manufactured by Gunei Boden Co., Ltd.)
3.5 parts by weight of casein (manufactured by Nissei Kyoei Co., Ltd.), silane coupling agent (A-1100 manufactured by Nippon Unicar Co., Ltd.)
0.5 parts by weight and 42.5 parts by weight of water were mixed to obtain an oligo binder. Thereafter, a mold was formed in the same manner as in Example 1, and the bending strength was measured. Table 1 shows the results. [Example 3] 4.0 parts by weight of an oligo-binding agent obtained in the same manner as in Example 2 was added to 100 parts by weight of silica sand (Iideyo F-6 No. 6 silica sand), and the mixture was kneaded for 60 seconds. The mixture was kneaded to obtain a kneaded sand. The kneaded sand was put into an aluminum mold for taking 5 test pieces of 10 mm × 10 mm × 60 mm and then was carried into a vertical closed container (vacuum box) 1 as shown in FIG. The pressure in the vacuum box was kept at 24.0 kPa for 1 to 10 minutes. Immediately after molding of the obtained mold and in a thermo-hygrostat (25
(° C., 60%) for 48 hours. Table 1 shows the results. [Example 4] 4.0 parts by weight of an oligo-binding agent obtained in the same manner as in Example 2 was added to 100 parts by weight of silica sand (Iideyo F-6 silica sand), and the mixture was kneaded for 60 seconds. The mixture was kneaded to obtain a kneaded sand. The kneaded sand was put into an aluminum mold for taking 5 test pieces of 10 mm × 10 mm × 60 mm and then was carried into a vertical closed container (vacuum box) 1 as shown in FIG. The pressure in the vacuum box was set to 48.0 kPa and maintained for 1 to 20 minutes. Immediately after molding of the obtained mold and in a thermo-hygrostat (25
(° C., 60%) for 48 hours. Table 1 shows the results. [Comparative Example 1] 4.0 parts by weight of an oligo-binding agent obtained in the same manner as in Example 2 was added to 100 parts by weight of silica sand (Iideyo F-6 No. 6 silica sand) and the mixture was kneaded for 60 seconds. The mixture was kneaded to obtain a kneaded sand. After embedding the kneaded sand in an aluminum mold for taking 5 test pieces of 10 mm x 10 mm x 60 mm, Fig. 1
The container was carried into a vertical closed container (vacuum box) 1 as shown in FIG.
The pressure in the vacuum box was set to 60.0 kPa and maintained for 5 to 30 minutes. Immediately after molding of the obtained mold and in a thermo-hygrostat (2
(5 ° C., 60%) for 48 hours. Table 1 shows the results. [Comparative Example 2] Oligosaccharide 4 obtained in the same manner as in Example 1
6.0 parts by weight, 3.5 parts by weight casein (manufactured by Nissei Kyoeki Co., Ltd.), silane coupling agent (manufactured by Nippon Unicar Co., Ltd.)
A-1100) 0.5 parts by weight of water and 50.0 parts by weight of water were mixed to obtain an oligo binder. Next, 4.0 parts by weight of the oligo binder was added to 100 parts by weight of silica sand (Iideyo F-6 No. 6 silica sand), and the mixture was kneaded with a kneader for 60 seconds to obtain kneaded sand. After kneading sand was put into an aluminum mold for taking 5 test pieces of 10 mm × 10 mm × 60 mm, hot air at 250 ° C. was sent into the mold at a pressure of 98 kPa for 2 minutes, and hot air drying was performed. Lastly, dry air at room temperature was passed through the mold at a pressure of 98 kPa for 20 seconds to mold. The bending strength of the obtained mold was measured immediately after molding and after being stored for 48 hours in a thermo-hygrostat (25 ° C., 60%). Table 1 shows the results.

[Table 1] Mold strength and change

According to the present invention described in detail above, kneaded sand is produced using an oligosaccharide and a water-soluble thermosetting resin, an auxiliary agent, an oligo-binding agent containing a silane coupling agent and a surfactant. Then, the kneaded sand is dried and cured under reduced pressure to provide a mold molding method capable of obtaining a mold having high strength, excellent moisture resistance, and extremely low odor in a short time.

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[Procedure amendment]

[Submission date] December 11, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Added

[Correction contents]

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a method of placing a mold in a closed container and vacuum-drying the same in the mold making method of the present invention.

FIG. 2 is an explanatory view showing another example of a method of vacuum-drying by placing a mold in a closed container in the mold making method of the present invention.

FIG. 3 is an explanatory view showing another example of a method of placing a mold in a closed vessel and drying in a vacuum in the mold making method of the present invention.

[Description of symbols] 1 Closed container (vacuum box) 2 Mold 3 Perforated plate 4 Airtight flexible membrane

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Akihiro Okubo 700 Shukudaizamachi, Takasaki City, Gunma Prefecture Gunei Chemical Industry Co., Ltd.

Claims (4)

[Claims] 1. One or more aggregates of silica sand, zircon sand, olivine sand, chromite sand, alumina sand, and mullite sand, and the monosaccharide unit is 2 to 10 with respect to 100 parts by weight of the aggregates. A monosaccharide unit obtained from natural oligosaccharides and / or starch or high molecular weight saccharides and 2 to 10 oligosaccharides and one or more heat-soluble phenolic resins, urea resins, melamine resins and epoxy resins Water-soluble oligo viscosities which consist of curable resins and whose solid content weight ratio is oligosaccharide: thermosetting resin = 50: 50-95: 5 and whose solid content concentration is 20-75% by weight The composition for mold molding obtained by adding and mixing 0.5 to 10 parts by weight of a binder is filled in a mold model, and the mold is placed in a closed container. Forcibly removed and dried A mold molding method characterized by curing. 2. The oligo binder according to claim 1, wherein at least one of polysaccharides, proteins, polyvinyl alcohol and sodium polyacrylate is used as an adjuvant with respect to 100 parts by weight of the solid content of the oligo binder. The method according to claim 1, wherein 1 to 30 parts are included. 3. The silane coupling agent is added to the oligo binder in an amount of 100 parts by weight of the solid content of the oligo binder.
The method according to claim 1, wherein the mold includes one to five parts. 4. The method according to claim 1, wherein the oligo binder contains 0.01 to 5 parts by weight of a surfactant with respect to 100 parts by weight of the solid content of the oligo binder. The mold molding method according to any one of the above.