JP3221802B2 - Binder composition for mold, mold composition and method for producing mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder composition used for producing a mold. The present invention also relates to a mold composition containing the binder composition, and a method for producing a mold using the binder composition.

[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 molding method is already a general-purpose molding method in place of the inorganic type from the viewpoint of productivity, casting quality, safety and health mainly in the field of mechanical casting.

On the other hand, a cloning method for producing a mold by heating and curing a so-called coated sand in which a phenolic resin is coated on a granular refractory, that is, a phenol resin is conventionally widely used for producing a mold at a medium and high speed.

[0004] However, in order to save energy during mold production, improve mold production speed, and further improve the quality of molds and castings, the cold box mold method of curing at room temperature with a gaseous or aerosol-like material is a method of producing a mold that replaces the cloning method. It has been seriously attempted in the foundry industry as a law.

[0005]

As a binder composition used in an organic self-hardening mold molding method and a gas-curable mold molding method, a water-soluble phenol-formaldehyde resin aqueous solution is used as a binder, and this is an organic ester. The binder composition for molding sand to be cured is disclosed in JP-A-50-130627 and JP-A-50-130627.
It is known from JP-A-58-154433 and JP-A-58-154434. Further, a phenolic resin obtained by polycondensation of bisphenol and formaldehyde is used as a binder (JP-A-62-40948, JP-A-63-40636).
It is also known to use a potassium-alkaline bisphenol-phenol copolymer type resole resin as a binder (Japanese Patent Application Laid-Open No. H5-123818).

[0006] Recently, a process using carbon dioxide has been proposed as a gas curing mold molding method (Japanese Patent Publication No. 1-224263). This is particularly noted from the viewpoint of health and safety because it uses carbon dioxide gas, which has less adverse effect on the human body than organic ester gas.

[0007] The mold making method using these binders has advantages such as a lower tendency of sulfuration as compared with the mold making method using an acid-curable resin because no sulfur atom is contained in the binder. However, they have drawbacks such as low mold strength, short pot life, and poor sand recyclability as compared with the acid-curable mold molding method, and further improvements are desired.

JP-A-4-118144 and JP-A-5-200481
Japanese Patent Application Laid-Open Publication No. H11-139,086 discloses a method for producing a sand mold for castings containing a water-soluble phenol resin and a phenol compound monomer as essential components, but has a problem that the strength of a mold obtained is low.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a phenol / aldehyde-modified resin is used as a binder and this is cured with an organic ester and / or carbon dioxide gas. In the binder composition for,
By using a specific ratio of a phenolic compound monomer in the phenol-aldehyde-modified resin, it was found that the strength of the template was greatly improved, and that the pot life could be greatly extended, and the present invention was completed. Things.

That is, the present invention relates to a binder composition for a mold, comprising a phenol-aldehyde-modified resin and at least one phenol compound monomer as essential components.

The present invention also provides a mold composition obtained by kneading a mixture comprising 0.1 to 15 parts by weight of the binder composition for a mold with 100 parts by weight of a refractory aggregate. About things.

Further, the present invention relates to a method for producing a mold, comprising using the above binder composition for a mold and using an organic ester and / or carbon dioxide gas as a curing agent.

The phenolic compound monomer used in the present invention includes, for example, phenol, cresol, xylenol, cumylphenol, nonylphenol, butylphenol, phenylphenol, ethylphenol, octylphenol, amylphenol, naphthol, resorcinol, bisphenol A, Phenol compounds including bisphenol F, bisphenol C, catechol, hydroquinone, pyrogallol, phloroglysin, resorcinol residue, cresol residue, bisphenol A residue, chlorophenol, dichlorophenol and other substituted phenols can be mentioned.

The reason why the use of the binder composition of the present invention can greatly improve the mold strength and further extend the pot life can be presumed as follows. That is, by causing a specific ratio of the phenol compound monomer to be present in the organic ester, activation and polymerization of the phenol-aldehyde-modified resin due to hydrolysis of the ester are delayed, so that the pot life is extended and activated. Since the phenol compound monomer is incorporated into the phenol / aldehyde-modified resin, it is considered that the strength of the template is improved. or,
It is considered that the phenolic hydroxyl group is deeply involved in the retardation effect and the ease of incorporation into the resin.
Those having at least two phenolic hydroxyl groups are more effective.

The phenol-aldehyde-modified resin and the phenol compound monomer may be used in combination in a phenol-aldehyde-modified resin or an aqueous solution, or may be mixed by stirring in an organic ester. Alternatively, they may be separately added to the refractory granular material.
At this time, it may be added by diluting it with a known solvent to improve the kneading property.

In order to produce the binder composition for a mold of the present invention, the phenol compound monomer of the present invention is usually added to the phenol-aldehyde-modified resin in an amount of from 2 to 2% based on the solid content of the phenol-aldehyde-modified resin. It is used in an amount of 40% by weight, preferably 3 to 30% by weight. As the phenol compound monomer, various phenol compound monomers can be used, but it is preferable that one molecule has two or three phenolic hydroxyl groups. According to the present invention, the pot life can be extended by including the specific phenol compound monomer. When the phenol compound monomer is less than 2% by weight, the effect of the pot life extension is reduced. On the other hand, if it exceeds 40% by weight, the final strength of the mold is reduced, which is not practical.

When mixed in an organic ester,
The content of the phenol compound monomer in the organic ester is 2 to 50% by weight, preferably 3 to 40% by weight,
As the phenol compound monomer, a compound having two or three phenolic hydroxyl groups in one molecule is preferable.
According to the present invention, the pot life can be extended by including the phenol compound monomer in the organic ester, and the content of the phenol compound monomer in the organic ester is 2 to 50% by weight. Within this range, a sufficient effect can be obtained to extend the pot life. If the content of the phenolic compound monomer is less than 2% 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, which is not practical.

In order to produce a mold by a self-hardening molding method using the binder composition for a mold of the present invention, 100 parts by weight of the refractory granular material is added to the binder composition for a mold of the present invention in an amount of 0.1 to 100 parts by weight.
15 parts by weight, preferably 0.3 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 as a curing agent are kneaded by a known method, and the conventional self-hardening mold production process is used as it is. To produce a mold.

In the present invention, in order to produce a mold by a gas-curable mold molding method, first, a refractory granular material is used.
To 100 parts by weight, 0.1 to 15 parts by weight of the binder composition for a mold of the present invention, preferably 0.3 to 5 parts by weight of kneading sand added, or filled into a model by blowing with pressurized air. Then, 0.05 to 9 parts by weight of a gaseous or aerosol organic ester is blown to cure the phenol-aldehyde-modified resin mixture to produce a mold.

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 may be used alone or as a mixture. However, in the self-hardening molding method, it is preferable to use γ-butyrolactone, propionlactone, ε-caprolactone, ethyl formate, ethylene glycol diacetate, ethylene glycol monoacetate, triacetin, dimethyl glutarate, etc. In the method, it is preferable to use methyl formate. Further, when the binder composition for a mold is cured by using carbon dioxide gas instead of the gaseous organic ester, an appropriate amount of boric acid, borate, aluminate is contained in the binder composition. A phenol-aldehyde-modified resin can be cured by the synergistic action of a compound having an oxyanion and a carbon dioxide gas (Japanese Patent Application Laid-Open No. 1-224263).
The binder composition for a mold of the present invention is not particularly limited, regardless of whether it is a self-hardening mold molding method or a gas-curable mold molding method.

The phenol-aldehyde modified resin used in the present invention is obtained by co-condensing at least one compound selected from bisphenols represented by the following general formula (1), an aldehyde compound, and an alcohol. those obtained or, with one or more compound selected from bisphenol represented by one or more compound selected from phenols and above formula (1), an aldehyde compound, Al
A call such is obtained by co-condensing.

[0022]

Embedded image

Specific examples of the bisphenols represented by the general formula (1) include bisphenol A, bisphenol F, bisphenol C, bisphenol E, bisphenol Z, bisphenol S, bisphenol AF, bisphenol AP, di-sec-butyl- Bisphenol A, di-isopropyl-bisphenol A, 1,1-ethylidene-bisphenol, methyl-ethyl-methylene-
Bisphenol A, methyl isobutyl-methylene-bisphenol, methyl-hexyl-methylene-bisphenol, methyl-phenyl-methylene-bisphenol,
4,4'-thiodiphenol and the like are used alone or as a mixture.

The phenols are represented by the following general formula (2)
One or more compounds selected from the compounds represented by (4) to (4) are used.

[0025]

Embedded image

(In the formula, R ₅ and R ₆ represent a hydrogen atom or a hydrocarbon group having 2 or less carbon atoms.)

[0027]

Embedded image

(In the formula, R ₇ represents a hydrogen atom, a hydroxyl group or a hydrocarbon group having 2 or less carbon atoms.)

[0029]

Embedded image

(In the formula, R ₈ represents an aliphatic hydrocarbon group or an aromatic hydrocarbon group having 3 or more carbon atoms.)

Among the phenols, specific examples of the compound represented by the general formula (2) include phenol, cresol,
3,5-xylenol and the like. The compound represented by the general formula (3) is a polyhydric phenol, and specific examples include resorcinol and catechol. The compound represented by the general formula (4) is mainly a compound in which an alkyl group having 3 or more carbon atoms or a phenyl group is bonded to the para position, and specific examples thereof include nonylphenol and p-tert.
-Butylphenol, isopropenylphenol, phenylphenol and the like. Also, a mixture of various phenols such as cashew nut shell liquid can be used. Particularly, as the phenols, a mixture of phenol and cresol is preferable.

As the aldehyde compound, formaldehyde, paraformaldehyde, furfural, glyoxal and the like are used alone or in combination.

When co-condensing bisphenols or phenols and bisphenols with aldehyde compounds, the molar ratio of each compound is preferably as follows. That is, the ratio of the number of moles of the aldehyde compound to the number of moles of the bisphenols or the total number of moles of the phenols and the number of moles of the bisphenols is 1.
0 to 5.0 [(mol number of bisphenols or mol number of phenols + mol number of bisphenols): mol number of aldehyde compound = 1: 1.0 to 5.0]. In particular, the molar ratio of the aldehyde compound is 1.5 to
3.0 is more preferred. When the ratio of the number of moles of the aldehyde compound is less than 1.0, there is a tendency that the strength of the mold is not sufficiently improved even when molding is performed using the obtained phenol / aldehyde-modified resin. Conversely, if the ratio of the number of moles of the aldehyde compound exceeds 5.0, the obtained phenol / aldehyde-modified resin has a strong odor of aldehyde, which may deteriorate the working environment. When phenols and bisphenols are used in combination, the ratio of the number of moles of bisphenols to the number of moles of phenols is about 0.001 to 1000 (the number of moles of phenols: the number of moles of bisphenols = 1: 0.001 to 1000 ) Is preferred. In particular, the ratio of the number of moles of bisphenols is more preferably 0.01 to 90.
When the number of moles of the bisphenol is less than 0.001 or more than 1,000, the strength of the obtained mold tends not to be sufficiently improved.

Copolycondensation of bisphenols or phenols and bisphenols with aldehyde compounds is generally carried out in an aqueous solution to obtain a phenol-aldehyde-modified resin. For example, it is preferable to obtain by co-condensation polymerization while gradually adding a predetermined amount of an aldehyde compound to an aqueous solution in which a predetermined amount of a bisphenol or a phenol and a bisphenol are dissolved. At this time, as a reaction catalyst, an alkali catalyst such as potassium hydroxide (KOH), sodium hydroxide (NaOH), and lithium hydroxide (LiOH) is used.In particular, potassium hydroxide (KOH) is used. Is preferred. Since the phenol-aldehyde-modified resin in the present invention is adjusted to an alkaline aqueous solution, a predetermined amount of potassium hydroxide may be used at the time of copolycondensation, or a minimum amount of potassium hydroxide is used as a reaction catalyst. After completion of the copolycondensation, a predetermined amount of potassium hydroxide may be added. After the completion of the copolycondensation, sodium hydroxide (NaOH) or lithium hydroxide (LiOH) may be used in combination with potassium hydroxide so as to have a predetermined alkalinity. Further, after co-condensation polymerization using an acid catalyst, co-condensation polymerization may be subsequently advanced using an alkali catalyst such as potassium hydroxide. In the aqueous alkali solution of the phenol-aldehyde-modified resin, the ratio of the number of moles of the total alkali to the total number of moles of the hydroxyl group of the bisphenol or the number of moles of the hydroxyl group of the phenol and the number of moles of the hydroxyl group of the bisphenol is 0.2 ~
Preferably it is 1.2. The concentration of the phenol-aldehyde-modified resin in the aqueous alkali solution is 30 to
Preferably it is 75% by weight.

The phenol-aldehyde-modified resin is further co-condensed with an alcohol, so that when kneaded with the refractory granular material, the kneaded sand becomes excellent in fluidity and filling in a model. As the alcohols, monohydric alcohols having 2 to 10 carbon atoms are preferable. For example, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, isoamyl Alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, caprylic alcohol, nonyl alcohol, decyl alcohol and the like can be mentioned. In particular, as monohydric alcohols, propyl alcohol, isopropyl alcohol,
Most preferably, butyl alcohol, isobutyl alcohol, sec-butyl alcohol or tert-butyl alcohol is used. The mixing ratio is preferably 0.0001 to 0.5 times the mole number of the bisphenols or the total number of moles of the phenols and the bisphenols. In particular, it is more preferable that the amount of the alcohol is 0.01 to 0.2 times mol. The number of moles of alcohols is 0.
If the molar ratio is less than 0001 times, there is no effect of adding alcohols, and if it exceeds 0.5 times, the strength of the mold tends to be not sufficiently improved.

As the refractory granular material, inorganic refractory granular materials such as chromite sand, zircon sand, olivine sand, alumina sand and the like are used in addition to quartz sand having quartz as a main component. is not.

Further, a silane coupling agent may be added for the purpose of further improving the mold strength. Preferred silane coupling agents include γ-aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and the like.

The solid content of the water-soluble phenol resin aqueous solution in the present invention can be determined by weighing a sample (2.0 ±
0.1 g) was heated to 100 ° C. for 3 hours.

[0039]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

[Preparation of aqueous solution of binder composition for mold 1] 50
The phenols, bisphenols, and alcohols in the amounts shown in Table 1 were added to a 1% aqueous potassium hydroxide solution and stirred to dissolve. While maintaining this solution at 80 ° C., an amount of the aldehyde compound determined by the molar ratio shown in Table 1 was gradually added. Then, the reaction was continued at 80 ° C. until the weight average molecular weight of the phenol-aldehyde-modified resin in the reaction solution reached 2500. The determination when the weight average molecular weight reached 2500 was performed by measuring the viscosity of the reaction solution. After the reaction was completed, the reaction mixture was cooled to room temperature, and then a 50% aqueous solution of potassium hydroxide was added so that the ratio of the number of moles of potassium hydroxide to the total number of moles of phenols and bisphenols was 0.85. Was. As described above, the binder composition aqueous solution 1 for a mold, which is an aqueous alkaline solution of a phenol / aldehyde-modified resin, was prepared. The content of the binder composition (phenol / aldehyde-modified resin, aliphatic compound or surfactant) in the aqueous solution of the binder composition was 50% by weight.

The item A in Table 1 indicates the number of moles of the aldehyde compound relative to the number of moles of the phenol, the number of moles of the bisphenol, or the total number of moles of the phenol and the bisphenol. Is the ratio of That is, [mol number of aldehyde compound / (mol number of phenols + mol number of bisphenols)]. Item B is the ratio of the number of moles of bisphenol to the number of moles of phenol when phenols and bisphenols are used in combination. That is, [mol number of bisphenol / mol number of phenol]. Further, item C is the ratio of the number of moles of alcohol to the number of moles of phenols, the number of moles of bisphenols, or the total number of moles of phenols and bisphenols. That is, [mol number of alcohols / (mol number of phenols + mol number of bisphenols)].

[Preparation of aqueous solution of binder composition for mold 2] 50
The phenols, bisphenols, and alcohols in the amounts specified by the molar ratios shown in Example 6 in Table 1 were added to a 5% aqueous potassium hydroxide solution, and the mixture was stirred and dissolved. While maintaining this solution at 80 ° C., a 50% aqueous formaldehyde solution in an amount determined by the molar ratio shown in Example 6 in Table 1 was gradually added. Then, the reaction was continued at 80 ° C. until the weight average molecular weight of the phenol-aldehyde-modified resin in the reaction solution reached 1800. The determination at the time when the weight average molecular weight reached 1800 was performed by measuring the viscosity of the reaction solution. After the reaction is completed, the reaction mixture is cooled to room temperature, and then subjected to 50% hydroxylation so that the ratio of the number of moles of potassium hydroxide to the total number of moles of hydroxyl groups of phenols and the number of moles of hydroxyl groups of bisphenols becomes 0.85. An aqueous potassium solution was added. Then, γ-glycidoxypropyltrimethoxysilane was added to 0.5 parts by weight of the aqueous solution based on 100 parts by weight of the aqueous solution. The content of the binder composition (phenol-aldehyde-modified resin and silane coupling agent) in the aqueous solution of the binder composition adjusted as described above was 50% by weight.

[Preparation of aqueous solution of binder composition for mold 3] In the preparation of aqueous solution of binder composition for mold 2, 90 parts by weight of an aqueous solution of a phenol-aldehyde-modified resin obtained after completion of the reaction was added. 5 parts by weight of sodium borate decahydrate, 95%
5 parts by weight of potassium hydroxide were mixed to prepare an aqueous solution of the binder composition for a mold.

Examples 1 to 13 and Comparative Examples 1 to 3 The pot life of the mold strength was evaluated in the self-hardening mold making method. That is, with respect to 100 parts by weight of silica sand, 0.38 parts by weight of dimethyl glutarate was added. In Examples 1 to 10 , various phenol compound monomers shown in Table 1 were added to dimethyl glutarate by weight% shown in Table 1. A mixture obtained by adding and kneading 1.5 parts by weight of an aqueous solution 1 of the binder composition for a mold was added to a mixture of 50 mmφ × 50
Compressive strength (temperature 35 ° C, humidity 60%) immediately after kneading and after standing for 30 minutes
(Under RH conditions). At the same time,
The filling properties were measured. That is, inner diameter 50mm, inner effective length 100mm
Attach a pedestal to the bottom of the test tube, pass through a 3 mm sieve, and roughly fill the test tube with kneaded sand. Next, the excess kneading sand at the top was scraped off and applied to a “Compactability tester manufactured by George Fisher Co.”, and pressurized with a squeeze pressure of 10 kg / cm ² . After this, the decrease in the height of the kneading sand was measured, and the reduced height X mm [= C. B. (Compactability)] was used as an index for the fluidity and filling properties of the kneaded sand. The smaller the value of X, the better the fluidity and filling properties of the kneaded sand. In Examples 11 to 13 , the phenol compound monomer was added to the aqueous solution of the binder composition for template 1 in an amount of 5 to the solid content.
The addition was performed by weight%. Table 1 shows the results.

[0045]

[Table 1]

* Evaluation result: ＝= Working time is very long and final compressive strength does not decrease. ＝= The pot life is long and the final compressive strength does not decrease. × = The pot life is short.

From the results shown in Table 1, it can be seen that the molded article made of the mixture obtained by kneading the binder composition used in the present invention has a high mold strength, and the molded article immediately after kneading after 30 minutes as compared with the comparative article. It can be seen that there is almost no difference in the compressive strength between the molded product after standing and the evaluation of the pot life is good.

Examples 14 to 25 and Comparative Example 4 The change over time of the mold strength in the gas-curable mold making method was evaluated. That is, a mixture obtained by adding and kneading 2.0 parts by weight of the aqueous solution of the binder composition for a mold 2 and 100 parts by weight of the various phenolic compound monomers shown in Table 2 with respect to 100 parts by weight of silica sand is 50 mmφ × 50.
The test piece was filled into a mmh gas-hardening test piece model. Inject 1.5 parts by weight of gaseous methyl formate into this model,
The compressive strength after time was measured. Table 2 shows the results.

[0049]

[Table 2]

Examples 26 to 37 and Comparative Example 5 3.5 parts of an aqueous solution 3 of a binder composition for a mold containing a phenolic compound monomer having a concentration shown in Table 3 was added to 100 parts by weight of silica sand as a refractory granular material. 50 parts by weight of the kneaded mixture
A gas test piece frame of mmφ × 50 mmh was filled, carbon dioxide gas was passed at a flow rate of 10 liter / min for 2 minutes, and a mold was formed by a gas-curable mold manufacturing method. At this time, the compressive strength after 24 hours was measured. Table 3 shows the results.

[0051]

[Table 3]

[0052]

As is clear from the above embodiments, according to the production method of the present invention, a mold having a longer pot life and a higher strength can be obtained as compared with the mold obtained by the conventional production method. As a result, when longer pot life is required, such as in summer or when sand temperature is high, or when molding large or complex molds, molds can be molded without reducing mold strength. Becomes Further, since it is possible to reduce the amount of the binder used, it is easy to recover the molding sand,
Since the amount of gas generated from the casting mold at the time of casting can be reduced, generation of gas defects can be suppressed and a sound casting can be manufactured, which is practically useful.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B22C 1/00-1/26

Claims (7)

(57) [Claims] 1. A phenol-aldehyde-modified resin (A) obtained by co-condensing at least one compound selected from bisphenols represented by the following general formula (1), an aldehyde compound and alcohols: ) And one or more phenolic compound monomers (B) as essential components. Embedded image 2. An aldehyde compound and an alcohol which are co-condensed with at least one compound selected from phenols and at least one compound selected from bisphenols represented by the following general formula (1): Phenol obtained by
A binder composition for a mold, comprising an aldehyde-modified resin (a) and one or more phenol compound monomers (b) as essential components. Embedded image 3. The binder composition for a mold according to claim 1, wherein bisphenol A or bisphenol F is used as the bisphenol. 4. The binder composition for a mold according to claim 2, wherein a mixture of phenol and cresol is used as the phenol. 5. The binder composition for a mold according to any one of claims 1 to 4 , wherein the binder composition is 0.1 to 100 parts by weight of the refractory aggregate.
A mold composition obtained by kneading a mixture consisting of 15 parts by weight. 6. The organic ester curing agent of 0.05 to 9 parts by weight, based on 100 parts by weight of the refractory aggregate, any one of claims 1 to 4
A mold composition obtained by kneading a mixture consisting of 0.1 to 15 parts by weight of a binder composition for a mold as described in Item. 7. A method for producing a mold, comprising using the binder composition for a mold according to any one of claims 1 to 4 and using an organic ester and / or carbon dioxide as a curing agent. .