JP2504660B2 - Organic ester-curable molding sand curing agent composition and method for producing mold using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an improved organic ester-curable molding sand for use in a molding method in which a water-soluble phenolic resin is used as a binder for a refractory granular material and is cured with an organic ester. TECHNICAL FIELD The present invention relates to a hardener composition for use and a method for producing a mold using the same.

[0002]

2. Description of the Related Art As a molding method for manufacturing a mold such as a main mold or a core using an organic binder, a self-hardening mold method, a cold box mold method, a cloning method (shell Method) is known. In particular, the organic self-hardening mold making 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 centering on the field of mechanical casting. On the other hand, conventionally, in order to manufacture a mold at medium to high speed, a cloning method has been widely used in which a so-called coated sand in which a phenolic resin is coated on a granular refractory is heat-cured to manufacture a mold. However, energy saving during mold production, mold production speed, further mold, in order to improve the quality of the casting, cold box mold method to cure at room temperature with a gaseous or aerosol-like substance, as a method of producing a mold that replaces the cloning method, It has been seriously tried to be introduced in the foundry industry.

Further, as a binder used in the organic self-hardening mold making method and the gas-curing mold making method, a water-soluble phenol resin is used as a binder, and the binder composition for foundry sand is hardened with an organic ester. The products are known from JP-A-50-130627, JP-A-58-154433 and JP-A-58-154434. Mold molding method using this binder, since it does not contain a sulfur atom in the binder, while having a feature that the influence of vulcanization is less compared to the mold molding method using an acid-curable resin, Compared with the acid-curable mold making method, it has drawbacks such as low mold strength, short pot life, and poor sand reclaimability, and further improvement is desired.

[0004]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, have found that a refractory granular material and a water-soluble phenolic resin are used as a binder and are cured by an organic ester. In the curing agent composition for foundry sand used in the molding method, by containing a specific ratio of the phenol compound monomer in the organic ester, the pot life is significantly extended without lowering the final strength of the mold. The present invention has been completed and the present invention has been completed. That is, the present invention is a curing agent composition used in a template molding method in which a water-soluble phenolic resin is used as a binder and is cured with an organic ester, wherein the organic ester and one of phenol compound monomers or A hardener composition for organic ester-curable foundry sand, which comprises two or more kinds.

The content of the phenol compound monomer in the curing agent composition used in the present invention is 2 to 2 in the organic ester.
The amount is 50% by weight, preferably 3 to 40% by weight, and the phenol compound monomer is preferably a compound having 2 or 3 phenolic hydroxyl groups in one molecule. A compound having one phenolic hydroxyl group has substantially the same pot life as that containing no phenol compound monomer, and the final strength is lowered. A compound having 4 or more phenolic hydroxyl groups is costly and economically unfavorable. According to the present invention, the pot life can be extended by incorporating the phenol compound monomer into the organic ester, and the content of the phenol compound monomer in the organic ester is 2 to 50% by weight. Within the range, a sufficient effect of extending the pot life is exhibited from the viewpoint of the final strength of the mold. Phenolic compound monomer content 2% by weight
If it is less than 50% by weight, the effect of extending the pot life is not sufficient, while if it exceeds 50% by weight, the final strength of the mold is lowered and it is not practical.
The phenol compound monomer used in the present invention,
For example, resorcin, bisphenol A, bisphenol F, bisphenol C, catechol, hydroquinone,
Examples include pyrogallol and phloroglysin, and further compounds having 2 or 3 phenolic hydroxyl groups in one molecule such as resorcin residue, bisphenol A residue, butylphenol, phenol, cresol, xylenol,
Compounds such as cumylphenol, nonylphenol, phenylphenol, ethylphenol, octylphenol, amylphenol, naphthol, chlorophenol, dichlorophenol and phenols including other substituted phenols can also be used.

The reason why the pot life can be greatly extended without lowering the final strength of the mold by the method for producing a mold using the curing agent composition used in the present invention is presumed as follows. That is, by allowing a specific proportion of a phenol compound monomer to be present in an organic ester, the activation and polymerization of the water-soluble phenol resin due to the hydrolysis of the ester was delayed and the pot life was extended and activated. Since the phenol compound monomer is incorporated into the water-soluble phenol resin, it is considered that the final strength of the mold does not decrease. Further, it is considered that the phenolic hydroxyl group is deeply involved in the delaying effect and the ease of incorporation into the resin, and it is considered that two or more phenolic hydroxyl groups are contained than one having one phenolic hydroxyl group in one molecule. The one having a phenolic hydroxyl group is more effective. As a form in which the organic ester and one or a mixture of two or more phenol compound monomers in the above-mentioned specific proportions are used in combination, the phenol compound monomer may be mixed with stirring in the organic ester, or they may be mixed. May be separately added to the refractory granular material. At this time, it is also possible to add it after diluting it with a known solvent to improve the kneading property.

In the present invention, in order to manufacture a sand mold for casting by a self-hardening molding method, 0.05 to 9 parts by weight of an organic ester as a curing agent is added to 100 parts by weight of a refractory granular material,
Preferably, 0.1 to 5 parts by weight of one or a mixture of two or more phenol compound monomers is contained in an amount of 2 to 50% by weight, preferably 3 to 40% by weight, and a water-soluble phenol resin aqueous solution. (Solid content concentration: 40-80% by weight) 0.4-
It is possible to knead 15 parts by weight, preferably 0.6 to 5 parts by weight by a known method, and use the conventional self-hardening mold manufacturing process as it is to manufacture a mold.

The water-soluble phenolic resin used in the present invention is a resin curable with an organic ester, such as phenol, cresol, resorcinol, 3,5-xylenol, bisphenol A, and phenols including other substituted phenols. Phenolic resins obtained by reacting with a mixture of formaldehyde, acetaldehyde, furfural aldehyde and aldehyde in a large amount of an aqueous solution of an alkaline substance. or,
A monomer capable of formaldehyde condensation such as urea, melamine, and cyclohexanone may be co-condensed with these to such an extent that they do not become the main constituent units in a weight ratio. Suitable alkaline substances used in the production of these water-soluble phenolic resins are sodium hydroxide, potassium hydroxide, lithium hydroxide and mixtures thereof, with potassium hydroxide being particularly preferred.

As the organic ester used in the present invention, a lactone or an organic ester derived from a monohydric or polyhydric alcohol having 1 to 10 carbon atoms and an organic carboxylic acid having 1 to 10 carbon atoms is used alone or in a mixture. However, in the self-hardening molding method, γ-butyrolactone, propionolactone,
It is preferable to use ε-caprolactone, ethyl formate, ethylene glycol monoacetate, ethylene glycol diacetate, triacetin, dimethyl glutarate and the like. As the refractory granular material, in addition to silica sand containing silica as a main component, inorganic refractory granular materials such as chromite sand, zircon sand, olivine sand, and alumina sand are used, but are not particularly limited.

Conventionally, a silane coupling agent has been widely used as a part of a curing agent because it is effective for improving the mold strength. Known silane coupling agents are used in the present invention,
Preferred are γ-aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane and the like. In the present invention, it is preferable to use this silane coupling agent together with the curing agent composition.

[0011]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Examples 1 to 13 and Comparative Example 1 The pot life of the mold strength in the self-hardening mold making method was evaluated. That is, 0.38 parts by weight of dimethyl glutarate was added to 100 parts by weight of silica sand, and various phenol compound monomers shown in Table 1 were added to dimethyl glutarate in the weight percentages shown in Table 1. Add a mixture of 1.5 parts by weight of a water-soluble phenolic resin (weight%), and knead it to give a mixture
A test piece model having a size of 50 mm and a height of 50 mm was filled, and the compression strength of the molded product was measured immediately after kneading and after standing for 30 minutes. Table 1 shows the results. In addition, the solid content of the water-soluble phenolic resin aqueous solution was measured in the air circulation furnace (2.
00 ± 0.1 g) was heated at 100 ° C. for 3 hours.

[0012]

[Table 1]

* 1 Compressive strength: The compressive strength of a mold after molding and standing for 24 hours, measured under conditions of a temperature of 35 ° C. and a humidity of 60% RH. * 2 Evaluation result: ◎ = The pot life is very long and the final compressive strength does not decrease. ◯ = The pot life is long and the final compressive strength does not decrease. × = Short pot life. From the results in Table 1, the molded product made of the mixture obtained by kneading the curing agent composition used in the present invention has a difference in compressive strength between the molded product immediately after kneading and the molded product after being left for 30 minutes, as compared with the comparative product. It can be seen that there is almost no value and the evaluation of the pot life is good.

[0014]

As is apparent from the above examples, the method for producing a mold using the curing agent composition of the present invention yields a mold having a longer pot life than the mold obtained by the conventional composition. be able to. As a result, in summer and when the sand temperature is high,
Also, when a longer working time is required, such as when molding a large mold or a mold with a complicated shape, it becomes possible to mold the mold without lowering the mold strength, which is practically useful. .

Claims (5)

(57) [Claims] 1. A curing agent composition used in a template molding method in which a water-soluble phenolic resin is used as a binder and is cured with an organic ester, wherein the organic ester and one of a phenol compound monomer or A hardener composition for organic ester-curable foundry sand, which comprises two or more kinds. 2. The hardening agent composition for organic ester-curable foundry sand according to claim 1, wherein the phenolic compound monomer is contained in the organic ester in an amount of 2 to 50% by weight in advance. 3. The phenol compound monomer is 2 in one molecule.
3. The hardener composition for organic ester-curable foundry sand according to claim 1, which has one or three phenolic hydroxyl groups. 4. A method for producing a mold, which comprises using the organic ester-curable molding sand curing agent composition according to any one of claims 1 to 3. 5. A template molding method in which a water-soluble phenolic resin is used as a binder and is cured with an organic ester, and the organic ester and phenol compound monomer
A method for producing a mold, which comprises the step of separately adding one or more kinds to the refractory granular material.