JPH0550177A - Resin composition for casting sand - Google Patents

Abstract

PURPOSE:To provide a resin composition for casting sand, improving by using process curing water-soluble phenol resin as binder with organic ester. CONSTITUTION:This resin composition for organic ester type casting sand has the water-soluble phenol resin and aromatic aldehyde as essential components. By using the above binder composition for casting sand, and curing with the organic ester, odor of formalin generated at the time of molding the casting sand mold and at the time of casting is drastically restrained, and working environment is remarkably improved.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a resin composition used for producing a sand mold for casting in a self-hardening mold and a gas-curing mold. More specifically, the present invention relates to an improved resin composition for foundry sand, which is used in a process of using a water-soluble phenol resin as a binder and curing it with an organic ester.

[0002]

2. Description of the Related Art As a molding method for producing a mold such as a main mold or a core using an organic binder, a self-hardening mold method, a cold box mold method, and a cloning method (shell method) are known. In particular, the organic self-hardening mold molding method has already become a general-purpose molding method in place of the inorganic type from the viewpoints of productivity, casting quality, safety and health mainly in the field of mechanical casting. On the other hand, conventionally,
To manufacture molds at medium and high speeds, a so-called Coated Sand is used in which phenolic resin is coated on granular refractories.
A cloning method in which a mold is produced by heating and curing is widely used. However, energy saving during mold manufacturing,
In order to improve the mold production speed and the quality of molds and castings, the cold box mold method, which cures at room temperature with a gaseous or aerosol substance, is seriously attempted to be introduced in the casting industry as a mold manufacturing method that replaces the cloning method. Is coming.

[0003]

As a binder composition used in the organic self-hardening mold molding method and the gas-curable mold molding method, a casting in which a water-soluble phenol resin is used as a binder and is cured with an organic ester. A binder composition for sand is disclosed in JP-A-50-130627, JP-A-58-154433, JP-A-58-154433.
It is known from, for example, JP-A-58-154434. Mold molding method using this binder, while having a feature that the influence of vulcanization is less than that of the casting molding method using an acid-curable resin because it does not contain a sulfur atom in the binder, There were problems such as insufficient mold strength, generation of formaldehyde during molding and casting, and improvement of working environment due to this formaldehyde odor.

[0004]

DISCLOSURE OF THE INVENTION As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a binder composition for foundry sand in which a water-soluble phenol resin is used as a binder and is hardened by an organic ester. By using an organic ester-curable resin composition for molding sand, which comprises one or more aromatic aldehydes in combination with a water-soluble phenolic resin, the mold strength and molding sand mold are generated and cast. The inventors have found that formaldehyde odor is significantly suppressed and the working environment is significantly improved, and have completed the present invention. That is, the present invention relates to a resin composition for organic ester-curable foundry sand, which comprises a water-soluble phenolic resin and an aromatic aldehyde as essential components.

Examples of the aromatic aldehyde used in the present invention include terephthalaldehyde, salicic acid aldehyde, cinnamaldehyde, benzaldehyde and the like. The above compound may be added directly to the water-soluble phenol resin, may be added at the stage of synthesizing the water-soluble phenol resin, or may be partially reacted with phenol in advance. By using the resin composition for foundry sand of the present invention, the mold strength and formaldehyde odor during molding and casting of the foundry sand can be significantly suppressed and the working environment can be significantly improved. Its action is estimated as follows. That is, by allowing one or more aromatic aldehydes to be present in the water-soluble phenolic resin, the curing reactivity is further enhanced, and formaldehyde generated during the curing reaction of the water-soluble phenolic resin is captured. It is thought that formaldehyde odor is suppressed. As a method of allowing the aromatic aldehyde to be present in the water-soluble phenolic resin, it may be simply dissolved, but it may be added at the reaction stage of the water-soluble phenolic resin and incorporated into the chemical structure of the resin composition. Alternatively, a part of formalin or the like may be replaced. Alternatively, when the resin is mixed with the molding sand or reclaimed sand to be used for molding, the above compounds are directly pretreated in an aqueous solution, a solvent solution (dissolved in an organic ester or other solvent), and a dispersion liquid. It does not matter even if it is kneaded in the form such as.
By using one or more of these aromatic aldehydes, mold strength and formaldehyde odor generated during molding and casting are significantly suppressed, and the working environment is improved.

To produce the sand resin composition for casting of the present invention, the aromatic aldehyde according to the present invention is usually added to the solid content of the water-soluble phenolic resin in relation to the water-soluble phenolic resin.
0.1 to 50% by weight, preferably 1.0 to 20% by weight is used.
When the amount of the aromatic aldehyde is 0.1% by weight or less, there is almost no effect of suppressing the formaldehyde odor generated during molding and casting of the mold, and conversely, when it is 50% by weight or more, the mold strength is reduced.
Therefore, when the proportion of the aromatic aldehyde contained in the water-soluble phenolic resin is in the range of 1.0 to 20% by weight, the effect of suppressing the mold strength and formaldehyde odor is extremely exhibited.

In order to produce a sand mold for casting using the resin composition for foundry sand of the present invention by a self-hardening mold making method, 100 parts by weight of a refractory granular material and 100% by weight of a resin for foundry sand as a binder are used. A conventional self-hardening mold manufacturing process is carried out by kneading 0.4 to 15 parts by weight of the composition, preferably 0.6 to 5 parts by weight, and 0.05 to 9 parts by weight, preferably 0.1 to 5 parts by weight of an organic ester which is a curing agent, by a known method. Can be used as it is to manufacture a mold. When the resin composition for molding sand of the present invention is used in combination with a silane coupling agent, the silane coupling agent is 0.001 to 1 part by weight, preferably 100 parts by weight of the resin composition for molding sand of the present invention. A mold can be molded by adding 0.002 to 0.5 part by weight and using the same process as above.

The above-mentioned compounds used in the present invention may be added in powder form to foundry sand or reclaimed sand. However, a solvent solution of an aromatic aldehyde or a slurry dispersion thereof may be prepared and added in advance. Good. Ethanol as solvent,
Examples include lower alcohols such as propanol, polyhydric alcohols such as glycerin and ethylene glycol, and commonly known solvents such as acetone and ester compounds. The organic ester which is a curing agent used in the present invention includes lactones or monohydric or polyhydric alcohols having 1 to 10 carbon atoms and 1 carbon atom.
The organic ester derived from an organic carboxylic acid of ~ 10 is used alone or in a mixture, in the self-hardening mold molding method, γ-butyrolactone, propion lactone, ε-caprolactone, ethyl formate, ethylene glycol diacetate, ethylene glycol monoacetate. , Triacetin, etc. are preferably used, and methyl formate is preferably used in the gas-curable molding method. The binder composition for foundry sand of the present invention is not particularly limited by either the self-hardening mold molding method or the gas-curable mold molding method.

The water-soluble phenolic resin used in the present invention is a resin curable with an organic ester, such as phenols, cresol, resorcinol, 3,5-xylenol, bisphenol A, and phenols including other substituted phenols. , A phenolic resin obtained by reaction with formaldehyde, acetaldehyde, furfural aldehyde, a mixture of aldehydes, etc. in a large amount of an aqueous solution of an alkaline substance. Suitable alkaline substances used in the preparation of these water-soluble phenolic resins are sodium hydroxide, potassium hydroxide, lithium hydroxide and mixtures thereof, with potassium hydroxide being most preferred. As the refractory granular material, reclaimed sand such as chromite sand, zircon sand, olivine sand, and alumina sand is used in addition to silica sand containing quartz as a main component, but is not particularly limited. As the silane coupling agent used in the present invention, known silane coupling agents can be used, and preferred ones are γ-aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane and γ-glycidoxypropyl. Trimethoxysilane etc. are mentioned. In the present invention, it is preferable to use this silane coupling agent in combination with the binder.

[0010]

The present invention is described in detail below with reference to examples, but the present invention is not limited to these examples. Examples 1 to 4 and Comparative Example 1 In the self-hardening mold making method, mold strength, mold making, and formaldehyde odor generated during casting were evaluated. That is, 0.375 parts by weight of triacetin and 0.5% by weight of γ-aminopropyltriethoxysilane (against phenolic resin) per 100 parts by weight of reclaimed sand of which the type of sand is Fremantle silica (FC-25, S / M = 3.5). ) And 10% by weight of the aromatic aldehyde compounds shown in Table 1 (based on the resin solid content), a water-soluble phenol resin (solid content 49%, weight average molecular weight 230).
The mold strength (50 mmh × 50 mmφ) was evaluated using a mold formed from a mixture obtained by adding and kneading 1.5 parts by weight of (0).
Also, the formaldehyde odor generated during the molding of the mold and 15 minutes after the completion of the casting was sensory evaluated. The results are shown in Table 1.

[0011]

[Table 1]

* Evaluation criteria for formaldehyde odor ◎ Almost no formaldehyde odor. ○ Slightly reduce formaldehyde odor. △ There is some formaldehyde odor and irritation is observed in the eyes. × Strong formaldehyde odor and sufficient irritation to eyes. Examples 5 to 6 and Comparative Examples 2 to 4 In the self-hardening mold making method, mold strength, mold making, and formaldehyde odor generated during casting were evaluated. That is, 0.375 parts by weight of triacetin and 0.5% by weight of γ-aminopropyltriethoxysilane (against phenolic resin) relative to 100 parts by weight of reclaimed sand of which the type of sand is Fremantle silica sand (FC-25, S / M = 3.5). ) And a water-soluble phenolic resin containing terephthalaldehyde at a concentration (based on resin solid content) shown in Table 2 (solid content 49%, weight average molecular weight 2300).
The mold strength (50 mmh × 50 mmφ) was evaluated using a mold molded from a mixture obtained by adding and kneading 5 parts by weight. The formaldehyde odor generated during the molding of the mold and 15 minutes after the completion of casting was sensory evaluated. The results are shown in Table 2.

[0013]

[Table 2]

[0014]

EFFECT OF THE INVENTION By using the binder composition for foundry sand of the present invention and curing with an organic ester, the formalin odor generated during molding and casting of the foundry sand mold is significantly suppressed, and the working environment is significantly improved. Can be improved.

Claims (4)

[Claims] 1. A resin composition for organic ester-curable foundry sand, which comprises a water-soluble phenolic resin and an aromatic aldehyde as essential components. 2. A resin composition for molding sand, which comprises a water-soluble phenolic resin having an aromatic aldehyde as a constituent unit as an essential component. 3. The resin composition for molding sand according to claim 1, wherein the aromatic aldehyde is terephthalaldehyde. 4. The resin composition for molding sand according to any one of claims 1 to 3, wherein the aromatic aldehyde is contained in an amount of 0.1 to 50% by weight based on the solid content of the water-soluble phenol resin.