Binder composition for casting molding

Abstract

The mold-making binder composition of the present invention contains furan resin, water, and hydrolyzed starch, wherein the mass ratio of furan resin to hydrolyzed starch (mass of furan resin / mass of hydrolyzed starch) is 20 to 95, and the glucose equivalent of the hydrolyzed starch is 60 or more. According to the mold-making binder composition of the present invention, a mold-making binder composition that uses sugars without modification processes and can suppress economic and energy costs can be provided.

Description

Technical Field

[0001] This invention relates to a binder composition for casting molds. Background Technology

[0002] Generally, acid-curing molds are manufactured as follows: A mold-making binder composition containing an acid-curing resin and a curing agent composition containing sulfonic acid, sulfuric acid, phosphoric acid, etc., are added to refractory particles such as silica sand. These are then mixed, and the resulting mixed sand is filled into prototypes such as wooden molds, allowing the acid-curing resin to cure. For acid-curing resins, furan resins and phenolic resins are used; for furan resins, furfuryl alcohol, furfuryl alcohol-urea-formaldehyde resin, furfuryl alcohol-formaldehyde resin, furfuryl alcohol-phenol-formaldehyde resin, and other known modified furan resins are used. This mold-making method allows for highly flexible molding operations, and the molds have excellent thermal properties, thus enabling the production of high-quality castings. Therefore, it is widely used in casting mechanical parts, construction machinery parts, and automotive parts.

[0003] As mentioned above, furfuryl alcohol is widely used as a component of acid-curing resins such as furan resins. However, the manufacturing process of furfuryl alcohol involves hydrolyzing and dehydrating raw materials composed of agricultural byproducts such as corn cobs to obtain furfural, followed by hydrogenation of furfural, resulting in high manufacturing costs. Furthermore, the furfural manufacturing process generates a large amount of residue as waste (Chinese Patent Application Publication No. 103113548). In addition, in recent years, furfuryl alcohol and furfural manufacturing plants have sometimes experienced unstable supply due to shutdowns or reduced production caused by environmental regulations. Against this backdrop, there is a demand for inexpensive alternatives to furfuryl alcohol that have low environmental impact and high supply stability.

[0004] Sugars are an example of inexpensive reagents that have low environmental impact and high supply stability. There are also reports on methods for manufacturing furan resins that use sugars to replace part of furfuryl alcohol (Chinese Patent Application Publication No. 102861867). Summary of the Invention

[0005] The mold-making binder composition of the present invention contains furan resin, water, and hydrolyzed starch, wherein the mass ratio of furan resin to hydrolyzed starch (mass of furan resin / mass of hydrolyzed starch) is 20 to 95, and the glucose equivalent of the hydrolyzed starch is 60 or more. Detailed Implementation

[0006] Because sugars have poor solubility in furan resins, modifications such as reactions with furan resins have been necessary to improve their solubility. However, these modifications require complex processes and incur significant economic and energy costs.

[0007] This invention provides a mold-forming binder composition that uses sugars without modification processes and can suppress economic and energy costs.

[0008] The mold-making binder composition of the present invention contains furan resin, water, and hydrolyzed starch, wherein the mass ratio of furan resin to hydrolyzed starch (mass of furan resin / mass of hydrolyzed starch) is 20 to 95, and the glucose equivalent of the hydrolyzed starch is 60 or more.

[0009] According to the present invention, a mold-forming binder composition can be provided that uses sugars without modification processes and can suppress economic and energy costs.

[0010] Hereinafter, one embodiment of the present invention will be described.

[0011] <Binder Composition for Casting Molding>

[0012] The mold-making binder composition of this embodiment (hereinafter, also referred to as binder composition) contains furan resin, water, and hydrolyzed starch, wherein the mass ratio of furan resin to hydrolyzed starch (mass of furan resin / mass of hydrolyzed starch) is 20 to 95, and the glucose equivalent of the hydrolyzed starch is 60 or more.

[0013] The binder composition according to this embodiment uses sugars without requiring a modification process and can suppress economic and energy costs. The reason why the binder composition of this embodiment achieves such an effect is not yet certain, but the following is considered.

[0014] Starch tends to have poor solubility relative to furan resins, but it has been found that by using hydrolyzed starch with a specific glucose equivalent (DE equivalent) and setting the mass ratio of furan resin to hydrolyzed starch (mass of furan resin / mass of hydrolyzed starch) within a specific range, a certain or higher solubility relative to both water and furan resin can be obtained. Therefore, by setting the mass ratio of furan resin to hydrolyzed starch within a specific range, the solubility to furan resin can be improved, thus eliminating the need for special modification of the sugars. After preparing the binder composition, even after prolonged storage, the sugars do not separate from the furan resin components and can maintain a uniform state. Therefore, it is believed that the binder composition according to this embodiment uses sugars without requiring a modification process and can suppress economic and energy costs. Furthermore, it is believed that the binder composition does not separate during the mixing process with the curing agent composition and refractory particles, forming a uniform adhesive layer, thereby maintaining mold strength.

[0015] [Furan resin]

[0016] Examples of the aforementioned furan resins include substances formed from one of the following: furfuryl alcohol, furfuryl alcohol condensates, furfuryl alcohol and aldehyde condensates, furfuryl alcohol and urea and aldehyde condensates (urea-modified furan resin), urea and ethylurea and aldehyde condensates (urea-ethylurea cocondensation resin), melamine and aldehyde condensates, and urea and aldehyde condensates; and substances formed from mixtures of two or more of these. Additionally, substances formed from two or more cocondensates selected from these can also be used. From the viewpoint of improving the curing speed and mold strength of the mold, substances selected from one or more of furfuryl alcohol, furfuryl alcohol condensates, and furfuryl alcohol and urea and aldehyde condensates, as well as their cocondensates, are preferred.

[0017] The monomer composition used in the synthesis of the above-mentioned furan resin contains furfuryl alcohol. Depending on the target condensate, one or more monomers selected from, for example, aldehydes, urea, phenols, and melamine can be used.

[0018] Examples of aldehydes mentioned above include formaldehyde, acetaldehyde, glyoxal, furfural, terephthalaldehyde, and hydroxymethylfurfural, and one or more of these can be used appropriately. From the viewpoint of improving mold strength, formaldehyde is preferred; from the viewpoint of reducing formaldehyde generation during molding, furfural, terephthalaldehyde, and hydroxymethylfurfural are preferred.

[0019] Examples of the aforementioned phenols include phenol, cresol, resorcinol, bisphenol A, bisphenol C, bisphenol E, and bisphenol F, and one or more of these may be used.

[0020] In the case of manufacturing a condensate of furfuryl alcohol and an aldehyde, it is preferable to use 0.01 to 1 mole of aldehyde relative to 1 mole of furfuryl alcohol. Furthermore, in the case of manufacturing a condensate of furfuryl alcohol, an aldehyde, and urea, it is preferable to use 0.05 to 3 moles of aldehyde and 0.03 to 1.5 moles of urea relative to 1 mole of furfuryl alcohol.

[0021] The reaction temperature for synthesizing furan resin varies depending on the raw materials used. From the viewpoints of reducing the viscosity of the resulting binder composition, minimizing aldehyde residue, shortening manufacturing time, preventing runaway reactions of the furan resin, and preventing evaporation of the raw materials, a temperature of 50–150°C is preferred, more preferably 70–130°C, and even more preferably 80–130°C. Similarly, from the same viewpoint, the reaction time for synthesizing furan resin is preferably 0.5–12 hours, more preferably 1–10 hours, and even more preferably 3–8 hours.

[0022] When manufacturing furan resins, the furan resin, furfuryl alcohol (a raw material), water contained in the raw material, and water generated during the reaction, etc., can be retained from an economic point of view. The furan resin composition contains furan resin, furfuryl alcohol, and components other than furan resin, such as water.

[0023] From the viewpoint of improving mold strength, the content of furan resin in the above-mentioned binder composition is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 65% ​​by mass or more. From the viewpoint of reducing viscosity, the content of furan resin in the above-mentioned binder composition is more preferably 98% by mass or less, and even more preferably 95% by mass or less. Furthermore, from the viewpoints of improving mold strength and reducing viscosity, the content of furan resin in the binder composition of this embodiment is preferably 50 to 98% by mass, more preferably 60 to 95% by mass, and even more preferably 65 to 95% by mass.

[0024] 〔water〕

[0025] The water content of the above-mentioned adhesive composition is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 3% by mass or more. However, from the viewpoint of maintaining the curing reaction rate, the water content of the adhesive composition is preferably 30% by mass or less, more preferably 25% by mass or less. In addition, from the viewpoint of adjusting the adhesive composition to a workable viscosity and maintaining the curing reaction rate, the water content of the adhesive composition is preferably 0.5 to 30% by mass, more preferably 1 to 25% by mass, and even more preferably 3 to 25% by mass.

[0026] In the synthesis of various condensates such as furfuryl alcohol and aldehyde condensates, aqueous solutions of raw materials are used or condensation water is generated, so the condensate is usually obtained as a mixture with water. When such condensates are used in adhesive compositions, water can be removed as needed using a distillation apparatus, but as long as the curing reaction rate can be maintained, it is not necessary to specifically remove it during manufacturing.

[0027] [Hydrolyzed starch]

[0028] The aforementioned hydrolyzed starch is a substance obtained by hydrolyzing starch using acids, enzymes, etc. From the viewpoint of the compatibility of the hydrolyzed starch with the furan resin, the glucose equivalent of this hydrolyzed starch is 60 or more, preferably 70 or more. From an economic point of view, the glucose equivalent of this hydrolyzed starch is preferably 99 or less, more preferably 80 or less. Here, glucose equivalent is also called dextrorose equivalent value, which is a measure of reducing sugar in the form of glucose, representing the proportion of reducing sugar relative to the total solid content of the reducing sugar, and is used as an indicator of the degree of decomposition of starch. In this specification, the glucose equivalent is determined by the method described in the examples.

[0029] As the aforementioned hydrolyzed starch, products such as Fuji Syrup (trade name) (Kato Chemical) are available as commercially available products.

[0030] From the viewpoint of the compatibility between the hydrolyzed starch and the furan resin, the mass ratio of the furan resin to the hydrolyzed starch (mass of the furan resin / mass of the hydrolyzed starch) is 20 to 95, preferably 70 to 90.

[0031] From the viewpoint of the compatibility of the hydrolyzed starch with water, the mass ratio of water to the hydrolyzed starch (mass of water / mass of the hydrolyzed starch) is 1 to 30, preferably 2 to 20.

[0032] From an economic point of view, the content of the hydrolyzed starch is preferably 1% by mass or more, more preferably 2% by mass or more. From the viewpoint of the compatibility of the hydrolyzed starch with the furan resin and the viewpoint of casting strength, the content of the hydrolyzed starch is preferably 20% by mass or less, more preferably 10% by mass or less. From the viewpoint of economic efficiency, the compatibility of the hydrolyzed starch with the furan resin, and the viewpoint of casting strength, the content of the hydrolyzed starch is preferably 1 to 20% by mass, more preferably 2 to 10% by mass.

[0033] [Curing Accelerator]

[0034] The binder composition of this embodiment may include a curing accelerator from the viewpoint of preventing mold cracking and improving the final mold strength. As a curing accelerator, from the viewpoint of improving the final mold strength, it is preferably selected from one or more compounds represented by the following general formula (1) (hereinafter referred to as curing accelerator (1)), phenol derivatives, aromatic dialdehydes, and tannins.

[0035] [Chemical Formula 1]

[0036]

[0037] [In the formula, X1 and X2 represent any one of the following: hydrogen atom, CH3, or C2H5.]

[0038] From the viewpoint of improving the final strength of the mold, the content of the curing accelerator in the above-mentioned binder composition is preferably 0.5% by mass or more, more preferably 1.8% by mass or more, even more preferably 2.5% by mass or more, and even more preferably 3.0% by mass or more. From the viewpoint of the solubility of the curing accelerator in furan resin and the viewpoint of improving the final strength of the mold, the content of the curing accelerator in the binder composition is preferably 63% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0039] Examples of curing accelerators (1) include 2,5-dihydroxymethylfuran, 2,5-dimethoxymethylfuran, 2,5-diethoxymethylfuran, 2-hydroxymethyl-5-methoxymethylfuran, 2-hydroxymethyl-5-ethoxymethylfuran, and 2-methoxymethyl-5-ethoxymethylfuran. Among these, 2,5-dihydroxymethylfuran is preferred from the viewpoint of improving the final mold strength.

[0040] Examples of phenol derivatives include resorcinol, cresol, hydroquinone, phloroglucinol, and methylene bisphenol. Resorcinol is preferred from the viewpoints of deep curing of the mold and improving the final mold strength. From the viewpoints of the solubility of the phenol derivative in furan resin and improving the final mold strength, the content of the aforementioned phenol derivative in the binder composition is preferably 1 to 25% by mass, more preferably 2 to 15% by mass, and even more preferably 3 to 10% by mass. When using resorcinol, from the viewpoints of the solubility of resorcinol in furan resin and improving the final mold strength, the content of resorcinol in the binder composition is preferably 1 to 10% by mass, more preferably 2 to 7% by mass, and even more preferably 3 to 6% by mass.

[0041] Examples of aromatic dialdehydes include terephthalaldehyde, o-phthalaldehyde, and iso-phthalaldehyde, as well as their derivatives. Their derivatives refer to compounds having alkyl or other substituents on the aromatic ring of an aromatic compound having two formyl groups as its basic skeleton. From the viewpoint of preventing mold cracking, terephthalaldehyde and its derivatives are preferred, and terephthalaldehyde is more preferred. From the viewpoint of ensuring sufficient dissolution of the aromatic dialdehyde in the furan resin and suppressing the odor of the aromatic dialdehyde itself, the content of the aromatic dialdehyde in the binder composition is preferably 0.1 to 15% by mass, more preferably 0.5 to 10% by mass, and even more preferably 1 to 5% by mass.

[0042] Examples of tannins include condensed tannins and hydrolyzed tannins. Examples of these condensed and hydrolyzed tannins include tannins with pyrogallol or resorcinol skeletons. Additionally, extracts containing these tannins can be added, such as bark extracts, extracts from natural sources like plant leaves, fruits, seeds, and plant galls.

[0043] [Other additives]

[0044] The binder composition described above may further include additives such as silane coupling agents. For example, if a silane coupling agent is included in the binder composition, the final strength of the resulting mold can be further improved, which is therefore preferable. As silane coupling agents, aminosilanes such as N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, and 3-aminopropyltrimethoxysilane can be used; epoxysilanes such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane, ureosilane, mercaptosilane, sulfide silane, methacryloxysilane, and acryloyloxysilane can be used. Aminosilanes, epoxysilanes, and ureosilanes are preferred. More preferably, it is an aminosilane or an epoxysilane, and even more preferably an aminosilane. Among aminosilanes, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane is preferred. From the viewpoint of improving the final strength of the mold, the content of the silane coupling agent in the binder composition is preferably 0.01% by mass or more, more preferably 0.05% by mass or more. From the same viewpoint, the content of the silane coupling agent in the binder composition is preferably 1.0% by mass or less, more preferably 0.5% by mass or less.

[0045] From the viewpoint of suppressing economic costs, the above-described binder composition may contain one or more alcohols selected from methanol, ethanol, ethylene glycol, propylene glycol, and glycerol. The content of this alcohol is preferably 1% by mass or more, more preferably 2% by mass or more. From the viewpoint of suppressing the reduction in mold strength, the content of the alcohol is preferably 10% by mass or less. Furthermore, from the viewpoint of preventing freezing at low temperatures and suppressing the reduction in mold strength, the content of the alcohol is preferably 1 to 10% by mass, more preferably 2 to 10% by mass.

[0046] From the viewpoint of improving mold strength, the above-mentioned adhesive composition may include urea. The urea referred to here is urea that has not undergone a condensation reaction with formaldehyde, furfuryl alcohol, etc., and may be a substance remaining as an unreacted component or a separately added substance. From the viewpoints of improving mold strength and reducing formaldehyde concentration, the content of the urea in the above-mentioned adhesive composition is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, and even more preferably 1.0% by mass or more. From the viewpoints of improving curing speed and the storage stability of the adhesive composition, the content of the urea in the above-mentioned adhesive composition is preferably 10% by mass or less, more preferably 6.0% by mass or less, and even more preferably 4.5% by mass or less.

[0047] It should be noted that urea in the adhesive composition can be determined by LC / MS analysis as follows: The sample was prepared by diluting it 100-fold with a 50 / 50 acetone / water mixture, and then further diluted 100-fold with the mobile phase.

[0048] (LC / MS analysis conditions)

[0049] Column: Unison UK-Amino HT

[0050] Mobile phase: 0.1% TFA acetonitrile / water = 95 / 5

[0051] Flow rate: 0.2 mL / min

[0052] Column temperature: 40℃

[0053] MS: SIM m / z: 61.0 [M+H]+

[0054] [Phenolic resin]

[0055] From the viewpoint of improving the flexibility of the mold and increasing the final strength of the mold, the above-mentioned binder composition may contain phenolic resin. Examples of phenolic resins include those with a weight-average molecular weight of 1000 or more and 5000 or less.

[0056] From the viewpoint of improving the flexibility of the mold and increasing the final strength of the mold, the weight-average molecular weight of the phenolic resin is preferably 1000 or more, more preferably 1400 or more. From the same viewpoint, it is preferably 5000 or less, more preferably 2500 or less. Therefore, 1000 to 5000 is preferred, more preferably 1400 to 2500.

[0057] From the viewpoints of improving the flexibility of the mold and increasing the final strength of the mold, the dispersion (weight-average molecular weight / number-average molecular weight ratio) of the phenolic resin is preferably 1.2 or more, more preferably 1.8 or more. From the viewpoints of improving the storage stability of the binder composition, improving the flexibility of the mold, and increasing the final strength of the mold, the weight-average molecular weight of the phenolic resin is preferably 5.0 or less, more preferably 3.5 or less. Therefore, 1.2 to 5.0 is preferred, and 1.8 to 3.5 is more preferred.

[0058] As the aforementioned phenolic resin, conventionally known phenolic resins can be used, for example, a substance composed of one of the following: a primary phenolic resin, a phenolic varnish-type phenolic resin, and a phenolic resin having the structure described in Japanese Patent Application No. 2009-292862; or a substance composed of a mixture of two or more of these.

[0059] It should be noted that, generally speaking, phenols such as phenol, cresol, and xylenol can be used as phenols for obtaining methyl phenolic resins. From the viewpoints of improving the flexibility of the mold and increasing the final strength of the mold, phenol is preferred among these. Aldehydes such as formaldehyde, glyoxal, paraformaldehyde, furfural, and 5-hydroxymethylfurfural can be used as aldehydes for obtaining methyl phenolic resins. From the viewpoints of improving the flexibility of the mold and increasing the final strength of the mold, paraformaldehyde is preferred. Alkaline catalysts such as potassium hydroxide and sodium hydroxide can be used as alkaline catalysts for obtaining methyl phenolic resins.

[0060] In addition, generally speaking, the phenols and aldehydes used to obtain phenolic varnish-type phenolic resins can be the same substances as those used in methyl phenolic resins.

[0061] When manufacturing phenolic resin compositions, in addition to phenolic resin, the materials include raw materials, water contained in the raw materials, and water generated during the reaction, which can be removed from an economic point of view.

[0062] From the perspectives of solubility, improving the flexibility of the mold, and increasing the final strength of the mold, methyl phenolic resin is preferred among the aforementioned phenolic resins.

[0063] From the viewpoints of solubility, improving the flexibility of the mold, and increasing the final strength of the mold, the content of the phenolic resin in the above-mentioned binder composition is 2% by mass or more and 35% by mass or less.

[0064] From the viewpoints of improving the flexibility of the mold and increasing the final strength of the mold, the content of the phenolic resin in the above-mentioned binder composition is more preferably 8% by mass or more. From the viewpoints of solubility, improving the flexibility of the mold, and increasing the final strength of the mold, the content of the phenolic resin in the above-mentioned binder composition is more preferably 20% by mass or less. Therefore, 8 to 20% by mass is more preferred.

[0065] From the viewpoint of improving the final strength of the mold, the total content of the furan resin and the phenolic resin in the above-mentioned binder composition is preferably 50% by mass or more. From the viewpoint of improving the final strength of the mold, the total content of the furan resin and the phenolic resin in the above-mentioned binder composition is preferably 95% by mass or less. Therefore, 50% to 95% by mass is preferred.

[0066] The above-described binder composition is suitable for molding self-curing molds. Here, a self-curing mold refers to a mold in which the polymerization reaction proceeds and the mold solidifies over time when the binder composition and curing agent composition are mixed in sand. The temperature of the sand used in this case is in the range of -20°C to 50°C, preferably 0°C to 40°C. For sand at such temperatures, by adding an appropriate amount of curing agent to the sand, the mold can be properly cured.

[0067] <Mold Composition>

[0068] The above-described binder composition can be mixed with a refractory particle and a curing agent composition to prepare a casting composition. The casting composition of this embodiment contains the above-described binder composition, refractory particles, and curing agent composition.

[0069] [Refractory particles]

[0070] As the aforementioned refractory particles, conventionally known refractory particles such as silica sand, chromite sand, zircon sand, olivine sand, bauxite sand, mullite sand, and synthetic mullite sand can be used. In addition, refractory particles that have been recycled from used refractory particles or refractory particles that have undergone regeneration treatment can also be used.

[0071] [Curing agent composition]

[0072] The curing agent composition described above can be used without particular limitation if it contains a curing agent that cures the adhesive composition described above. Examples of such curing agents include acid-based curing agents, such as sulfonic acid compounds like xylenesulfonic acid (especially m-xylenesulfonic acid), toluenesulfonic acid (especially p-toluenesulfonic acid), and methanesulfonic acid; phosphoric acid compounds like phosphoric acid and acidic phosphate esters; and acidic aqueous solutions containing sulfuric acid, etc. From a workability point of view, these compounds are preferably aqueous solutions. Furthermore, the curing agent may contain one or more solvents selected from alcohols, ether alcohols, and esters, or carboxylic acids.

[0073] From the viewpoint of improving the final mold strength, the content of the curing agent in the above-mentioned curing agent composition is preferably 5 to 50% by mass, more preferably 10 to 40% by mass.

[0074] In the above-mentioned casting composition, relative to 100 parts by weight of refractory particles, it preferably contains 0.5 to 3.0 parts by weight of the above-mentioned binder composition and 0.07 to 2.0 parts by weight of the above-mentioned curing agent composition.

[0075] Furthermore, from the viewpoint of improving mold strength, the content of the curing agent composition in the mold composition is preferably 0.1 parts by mass or more, more preferably 0.14 parts by mass or more, even more preferably 0.2 parts by mass or more, preferably 0.8 parts by mass or less, more preferably 0.6 parts by mass or less, and even more preferably 0.4 parts by mass or less, relative to 1.0 parts by mass of the binder composition. In summary, from the viewpoint of improving mold strength, the content of the curing agent composition in the mold composition is preferably 0.1 to 0.8 parts by mass, more preferably 0.14 to 0.6 parts by mass, and even more preferably 0.2 to 0.4 parts by mass, relative to 1.0 parts by mass of the binder composition.

[0076] <Methods for Manufacturing Casting Molds>

[0077] The mold can be manufactured by curing the above-mentioned mold composition. In the mold manufacturing method of this embodiment, the mold can be manufactured directly using conventional mold manufacturing processes. As a preferred mold manufacturing method, a mold manufacturing method having the following steps can be cited: a mixing step of mixing refractory particles, the above-mentioned mold molding binder composition, and a curing agent composition for curing the above-mentioned mold molding binder composition to obtain a mold composition; and a curing step of filling the above-mentioned mold composition into a mold box and curing the mold composition.

[0078] The above mixing process preferably includes: a first mixing step of mixing refractory particles and a mold-forming curing agent composition containing a curing agent composition; and a second mixing step of mixing a mold-forming binder composition into the resulting mixture after the first mixing step.

[0079] In the above mixing process, acid-curing resin, curing accelerator, water, silane coupling agent and other additives, acidic substances and solvents may be added to a degree that does not hinder the effect of this embodiment.

[0080] In the above mixing process, as a method for mixing the raw materials, a generally known method can be used. For example, a method of adding the raw materials using an intermittent mixer for mixing, or a method of supplying the raw materials to a continuous mixer for mixing can be cited.

[0081] Example

[0082] Hereinafter, specific embodiments of the present invention will be described.

[0083] <Examples 1-9, Comparative Examples 1-4>

[0084] [Preparation of furan resin composition]

[0085] In a three-necked flask, 100 parts by weight of furfuryl alcohol, 35 parts by weight of paraformaldehyde, and 13 parts by weight of urea were mixed and the pH was adjusted to 9 with a 25% by weight aqueous sodium hydroxide solution. The reaction mixture was heated to 100°C and reacted at the same temperature for 1 hour. The pH was adjusted to 4.5 with 37% by weight hydrochloric acid, and the reaction was further carried out at 100°C for 1 hour. Subsequently, the pH was adjusted to 7 with a 25% by weight aqueous sodium hydroxide solution, 5 parts by weight of urea were added, and the reaction was carried out at 100°C for 30 minutes to obtain a furan resin composition. The furan resin composition consisted of 71.7% by weight of urea-modified furan resin, 19.5% by weight of furfuryl alcohol, and 8.8% by weight of water.

[0086] [Glucose equivalent]

[0087] Accurately weigh 2.5 g of the sample and dissolve it in water to make 200 mL. Accurately weigh 10 mL of this liquid, add 10 mL of 0.04 mol / L iodine solution and 15 mL of 0.04 mol / L sodium hydroxide solution, and let it stand in the dark for 20 minutes. Next, add 5 mL of 2 mol / L hydrochloric acid and mix, then titrate with 0.04 mol / L sodium thiosulfate solution. If the liquid turns slightly yellow near the titration endpoint, add 2 drops of starch indicator and continue titrating. The endpoint is defined as the moment when the color disappears. Perform a blank test and calculate the glucose equivalent (DE) using the following formula.

[0088] DE=(ba)×f×3.602 / (1 / 1000) / (200 / 10) / [A×(100-B)×100]×100

[0089] [In the formula, a represents the titration value (mL), b represents the blank value (mL), f represents the factor value of the sodium thiosulfate solution, A represents the amount of sample weighed (mg), and B represents the moisture content of the sample (%).]

[0090] [Solubility of hydrolyzed starch]

[0091] The following operations 1 to 4 were performed sequentially on the glass solenoids containing the various adhesive compositions listed in Table 1 to dissolve the adhesive compositions. The adhesive composition dissolved with the operation numbered lower indicates higher solubility. Here, dissolution means that after each operation, the glass solenoid is visually observed to have become a homogeneous, transparent liquid. The results are shown in Table 1.

[0092] 1: Perform ultrasonic treatment (37kHz) in water at 25℃ for 1 hour.

[0093] 2: Perform ultrasonic treatment (37kHz) at 50℃ for 1 hour.

[0094] 3: Perform 2Hr ultrasonic treatment (37kHz) in water at 50℃.

[0095] 4: Perform 4Hr ultrasonic treatment (37kHz) in water at 50℃.

[0096] 5: Insoluble (phase separation occurs in the binder composition due to hydrolysis of starch)

[0097] [Storage stability of the adhesive composition]

[0098] Each binder composition in which hydrolyzed starch was dissolved through the above operation was placed at room temperature (25°C) for 1 week and visually evaluated according to the following criteria.

[0099] ○: Hydrolyzed starch is uniformly dissolved in the binder composition.

[0100] ×: Separation of hydrolyzed starch phase in the binder composition

[0101] [Mold strength]

[0102] Under conditions of 25°C and 55% RH, 0.40 parts by weight of a curing agent composition (Kao Lightener C-17: manufactured by Kao-Quaker) were added to 100 parts by weight of furan-regenerated silica sand. Then, 0.8 parts by weight of a binder composition obtained by mixing the pre-prepared amounts of the components shown in Table 1 were added. These were mixed to obtain the mold compositions for each example and comparative example. The obtained mold compositions were filled into cylindrical specimen frames with a diameter of 50 mm and a height of 50 mm. Demolding was performed after 2 hours. Compressive strength (MPa) was measured 24 hours after filling using the method described in JIS Z 2604-1976. It should be noted that when comparing compressive strength, the binder composition used in preparing the mold compositions was stored at room temperature for 1 week and then shaken before use. The results are shown in Table 1. Examples 1-9 showed compressive strengths of 4.7 MPa or higher. On the other hand, Comparative Examples 1-4 showed compressive strengths of 4.4 MPa or lower. This is believed to be due to the separation of hydrolyzed starch phase in the binder composition in the comparative example and the aggregation of hydrolyzed starch in the casting composition.

[0103] [Table 1]

[0104]

Claims

1. A binder composition for casting mold making, It contains furan resin, water, and hydrolyzed starch. The furan resin is a urea-modified furan resin. The mass ratio of the furan resin to the hydrolyzed starch, i.e., the mass of the furan resin / the mass of the hydrolyzed starch, is 20 to 95, and the glucose equivalent of the hydrolyzed starch is 70 or higher. The mass ratio of water to the hydrolyzed starch, i.e., the mass of water / the mass of the hydrolyzed starch, is 1 to 30. The water content is 0.5% to 30% by mass.

2. The binder composition for casting mold making according to claim 1, wherein, The content of the hydrolyzed starch is 1% to 20% by mass.

3. The binder composition for casting mold making according to claim 1 or 2, wherein, The glucose equivalent of the hydrolyzed starch is below 99.

4. The binder composition for casting mold making according to claim 1 or 2, wherein, The mass ratio of the furan resin to the hydrolyzed starch is 70-90.

5. The binder composition for casting mold making according to claim 1 or 2, wherein, The content of the hydrolyzed starch is 2% to 10% by mass.

6. The binder composition for casting mold making according to claim 1 or 2, wherein, The mass ratio of water to the hydrolyzed starch, i.e., the mass of water / the mass of the hydrolyzed starch, is 2 to 20.

7. The binder composition for casting mold making according to claim 1 or 2, wherein, The water content is 1% to 25% by mass.

8. The binder composition for casting mold making according to claim 1 or 2, wherein, The water content is 3% to 25% by mass.

9. The binder composition for casting mold making according to claim 1 or 2, wherein, The content of the furan resin is 50% to 98% by mass.

10. The binder composition for casting molds according to claim 1 or 2, wherein, The content of the furan resin is 60% to 95% by mass.

11. The binder composition for casting mold making according to claim 1 or 2, wherein, The content of furan resin is 65% to 95% by mass.

12. The binder composition for casting mold making according to claim 1 or 2, wherein, The furan resin is selected from one or more of the following: furfuryl alcohol condensate with urea and aldehydes, and urea condensate with ethylurea and aldehydes.

13. A composition for casting molds, comprising: The refractory particles, the mold-making binder composition according to any one of claims 1 to 12, and the curing agent composition comprising a curing agent for curing the mold-making binder composition.

14. The casting composition according to claim 13, wherein, The content of the binder composition for casting is 0.5 to 3.0 parts by mass relative to 100 parts by mass of the refractory particles.

15. The casting composition according to claim 13 or 14, wherein, The content of the curing agent composition is 0.07 to 2.0 parts by weight relative to 100 parts by weight of the refractory particles.

16. The casting composition according to claim 13 or 14, wherein, The content of the curing agent composition is 0.1 to 0.8 parts by weight relative to 1.0 parts by weight of the adhesive composition for casting.

17. The casting composition according to claim 13 or 14, wherein, The curing agent composition contains one or more selected from xylenesulfonic acid, toluenesulfonic acid, methanesulfonic acid, phosphoric acid, acidic phosphate ester, and sulfuric acid.

18. A method for manufacturing a casting mold, comprising: A mixing step of mixing refractory particles, a mold-forming binder composition according to any one of claims 1 to 12, and a curing agent composition comprising a curing agent for curing the mold-forming binder composition to obtain a mold composition; and a curing step of filling the mold composition into a mold box and curing the mold composition.

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