JP3249010B2 - Manufacturing method of casting 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 casting mold and a method for producing a core (hereinafter, abbreviated as a mold throughout the present specification) which are particularly excellent in compressive strength.

[0002]

2. Description of the Related Art Conventionally, as a binder for quickly and efficiently producing a casting mold that does not generate irritating acid gas during casting, it can be cured with, for example, a gaseous or liquid ester-based curing agent. A resin composition containing a potassium alkaline phenol / formaldehyde resin as an essential component is known (see JP-A-58-154434 and JP-A-1-40136).

[0003]

However, a mold manufactured using such a binder has low performance such as compressive strength, which causes deterioration of casting quality. In addition, when such a binder is mixed with granular refractory aggregate (casting sand) and allowed to stand by for a long period of time, when a mold is manufactured, the compressive strength of the manufactured mold is remarkably reduced, and the binder of the binder is reduced. The pot life is short, which is inconvenient for industrially producing a casting mold.

[0004]

Means for Solving the Problems In order to solve the problems of a casting mold manufactured using a conventionally known binder, the present inventor focused on a synthesis reaction of a water-soluble phenol resin,
Maximizes the production of binuclear compounds of phenols at a specific reaction ratio between phenols and aldehydes and renders them water-soluble, resulting in long pot life when mixed with granular refractory aggregate. Agent is obtained and found that the casting mold manufactured using it has high compressive strength,
The present invention has been completed.

That is, in the method for producing a casting mold of the present invention, an aldehyde is used in an amount of 1.6 to 1 mol per phenol.
The novolak reaction is performed under an acidic condition based on an acidic substance having a pKa of 2.0 or less at a ratio of 2.5 mol, and when the amount of the binuclear compound of phenols becomes maximum, the reaction solution is made alkaline, Further, a binder containing a water-soluble phenol resin obtained by performing a resolving reaction under an alkaline condition as an essential component, and a granular refractory aggregate are mixed, and the mixture is housed in a mold frame and molded. Then, the molded product is cured by passing a gaseous organic acid ester-based curing agent.

Further, in the method for producing a casting mold of the present invention, an aldehyde is added in an amount of 1.6 to 1 mol per phenol.
The novolak reaction is performed under an acidic condition based on an acidic substance having a pKa of 2.0 or less at a ratio of 2.5 mol, and when the amount of the binuclear compound of phenols becomes maximum, the reaction solution is made alkaline, Further, a binder containing a water-soluble phenol resin obtained by performing a resolving reaction under an alkaline state as an essential component, and a liquid organic acid ester-based curing agent,
It is characterized in that it is mixed with a granular refractory aggregate, this mixture is housed in a mold frame, molded and cured.

The binder in the present invention contains, as an essential component, a water-soluble phenol resin which can be cured with a gaseous or liquid organic acid ester-based curing agent to produce a casting mold. Such water-soluble phenol resins include, for example, phenol, cresol, resorcinol, xylenol, bisphenol A, cumylphenol, nonylphenol, butylphenol, phenylphenol,
Phenols including ethylphenol, octylphenol, amylphenol, naphthol, bisphenol F, bisphenol C, catechol, hydroquinone, pyrogallol, phloroglucin, lignin, bisphenol A residue, cresol residue, chlorophenol, dichlorophenol, and other substituted phenols, It is a resol-novolak type water-soluble phenol resin obtained by a novolak reaction with aldehydes such as formaldehyde, acetaldehyde, and furfural, and a subsequent resolation reaction. In order to increase the compressive strength and the like of the mold to be produced, it is necessary to use aldehydes in a ratio of 1.6 to 2.5 mol per 1 mol of phenols. The novolak reaction is a known reaction in which phenols form a novolak resin in which phenols are linked by aldehydes. The novolak reaction is traced by gas chromatography or the like, and the amount of a binuclear compound of phenols is maximized. The resolelation reaction that is subsequently carried out at this point is a known reaction for producing a resole resin by hydroxyalkylating the product of the novolak reaction. The weight-average molecular weight of the resulting water-soluble phenolic resin is preferably in the range of more than 2,000 to 3,000 or less. Usually, the water-soluble phenol resin has a solid content of 50 to
It is used as a 75% by weight solution, especially as an aqueous solution. Suitable acidic substances used in the novolak reaction are pKa
2.0 or less, specifically, for example, p-toluenesulfonic acid (pKa1.7), oxalic acid (pKa1.
3) and hydrochloric acid (pKa-8).
1.3 to 1.7 p-toluenesulfonic acid, oxalic acid and the like are preferred. When the pKa of the acidic substance exceeds 2.0, the performance such as the compressive strength of a mold produced using a water-soluble phenol resin obtained becomes insufficient, and when the pKa is too small, the reaction apparatus is limited, and thus it is preferable. Absent. This acidic substance is preferably used in the novolak reaction at a molar ratio of 0.001 to 0.1 with respect to phenols.
Suitable alkaline substances used in the resolelation reaction are sodium hydroxide, potassium hydroxide, lithium hydroxide or mixtures thereof, with potassium hydroxide being most preferred.

In order to improve the cohesiveness of the mold, the silane compound which can be blended in the present invention is usually preferably in the range of 0.05 to 3% by weight with respect to the resin solution. , Γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane and the like.

The granular refractory aggregate used in the production of the casting mold according to the present invention includes, for example, refractory granules used for the production of conventional molds such as silica sand, chromite sand, zircon sand and olivine sand. In addition to sand, clay sand and recycled sand can be mentioned.

The organic acid ester as a curing agent used in the production of a casting mold in the present invention is a gaseous or liquid organic acid ester compound. The gaseous organic acid ester-based curing agent is a vapor or aerosol such as methyl formate, ethyl formate, and propyl formate. The liquid organic acid ester has a boiling point of 100 ° C. or higher at room temperature, and specifically, an ester compound of a monohydric or polyhydric alcohol and a carboxylic acid, particularly a monohydric or polyhydric alcohol having 1 to 10 carbon atoms. Examples thereof include an ester compound of a hydric alcohol and a carboxylic acid having 2 to 10 carbon atoms, a lactone compound, and a carbonate compound. More specifically, for example, ethyl acetate, dimethyl adipate, dimethyl succinate, ethylene glycol diacetate, monoacetin, diacetin, triacetin, ethylene carbonate, γ-butyrolactone, propiolactone, ε-caprolactone, or a mixture thereof. . The amount of the gaseous or liquid organic acid ester-based curing agent used is preferably in the range of 5 to 110% by weight, particularly 20 to 60% by weight, based on the binder solution.

The production of a casting mold using a gaseous hardener is carried out by mixing a granular refractory aggregate and a binder by a conventional method and molding. For the core and mold frame having good air permeability, the conventional ones used in the conventional gas curing method can be used. A gaseous organic acid ester such as methyl formate is usually added to a mold in which a mixture of a granular refractory aggregate and a solution of an organic solvent for a binder and water is molded. As a vapor or aerosol at room temperature or at a temperature slightly higher than that, and is cured. The time required for absorption of the curing agent depends on the size and shape of the mold and the type of resin, but in most cases ranges from several seconds to several minutes. When removing the mold from the frame after absorbing the hardener, it is preferable to leave the mold for a sufficient time before removing the mold from the frame in order to prevent damage to the mold. This time can be reduced by passing a heated inert carrier gas through the mold.

The production of a casting mold using a liquid hardening agent is carried out by mixing and molding a solution of a granular refractory aggregate, a binder and a liquid organic acid ester by a conventional method. A mold formed by mixing a mixture of a granular refractory aggregate, a solution of a binder in an organic solvent, water or the like, and a liquid organic acid ester is allowed to cure at room temperature or a slightly higher temperature for a certain period of time. The curing time depends on the size and shape of the mold and the type of the resin, but is usually in the range of 1 hour to 24 hours. The binder (as a 50% solution) in the present invention is used for a granular refractory aggregate,
It is preferable to mix in the range of 0.5 to 8% by weight. From the viewpoint of the compressive strength of the molding mold and the like, it is particularly preferable to mix in a range of 1 to 3% by weight.

[0013]

EXAMPLES The present invention will be described in more detail with reference to Synthesis Examples, Synthesis Comparative Examples, Examples and Comparative Examples, where "parts" means "parts by weight" and "%" means all parts by weight. It means "% by weight". Synthesis Example 1, Synthesis Comparative Examples 1 to 3 564 parts (6.0 mol) of 100% phenol and 295 of water
Parts in an aqueous solution consisting of 92% paraformaldehyde 3
53 parts (10.8 mol-formaldehyde conversion, the same applies hereinafter) were added (the molar ratio of paraformaldehyde: phenol was 1.8: 1). When the mixture solution was heated to 50 ° C. while stirring, 6.3 parts (0.06 mol) of 35% concentrated hydrochloric acid was added, and a novolak reaction was performed at the same temperature for a certain period of time. With respect to the novolak reaction, the binuclear compound of phenol as a raw material and phenol as a product (total of ortho and para forms) was neutralized and analyzed by gas chromatography using methanol as an internal standard substance. A graph showing the results is shown in FIG. Next, 25.0 parts (0.3 mol) of a 48% aqueous sodium hydroxide solution was added to the novolak reaction solution to make it alkaline, and
Further, 554 parts (4.8 mol) of a 48.6% aqueous solution of sodium hydroxide was gradually added over 1 hour, and the temperature of the reaction solution was reduced to 50%.
The temperature was raised from 85 ° C to 85 ° C, and the mixture was stirred at the same temperature for 3 hours. When the viscosity of the resolation reaction solution reaches 200 cps, the solution is cooled, and 3-glycidoxypropyltrimethoxysilane is added in a ratio of 0.5 part to 100 parts of the reaction solution to prepare a binder solution. did. Table 1 shows the amounts of raw materials charged and the reaction conditions.

[0014]

[Table 1]

Synthesis Examples 2-4 564 parts (6.0 mol) of 100% phenol and water 328
Parts in an aqueous solution consisting of 92% paraformaldehyde 3
92 parts (12.0 mol) were added (paraformaldehyde: phenol molar ratio 2.0: 1). When the mixture solution was heated to 50 ° C. with stirring, an acidic substance (0.06 mol) was added as a catalyst, and the mixture was heated at the same temperature for 2 hours (the amount of the phenol binuclear compound produced by gas chromatography was maximized). (When it became) Novolak reaction was performed. Next, 25.0 parts (0.3 mol) of a 48% aqueous sodium hydroxide solution was added to the novolak reaction solution to make it alkaline, and 554 parts (4.8 mol) of a 48.6% aqueous sodium hydroxide solution were gradually added over 1 hour. And the temperature of the reaction solution was increased from 50 ° C. to 85 ° C., and the mixture was stirred at the same temperature for 3 hours. When the viscosity of the resolation reaction solution reaches 200 cps, the solution is cooled, and 3-glycidoxypropyltrimethoxysilane is added in a ratio of 0.5 part to 100 parts of the reaction solution to prepare a binder solution. did. Table 2 shows the amounts of raw materials charged and the reaction conditions.

[0016]

[Table 2]

Comparative Synthesis Examples 4 and 5 564 parts (6.0 mol) of 100% phenol and 295 water
A predetermined amount of 92% paraformaldehyde was added to the aqueous solution consisting of parts. This mixture solution was heated with stirring and 5
When the temperature reaches 0 ° C., 6.3 parts (0.06 mol) of 35% concentrated hydrochloric acid is added, and the mixture is heated at the same temperature for 1.5 hours (when the amount of the phenol binuclear compound produced by gas chromatography becomes maximum) ) A novolak reaction was performed. Then 48
25.0 parts (0.3 mol) of an aqueous sodium hydroxide solution were added to the novolak reaction solution to make it alkaline, and then 92%
Add a predetermined amount of paraformaldehyde, and further add 48.6%
554 parts (4.8 mol) of an aqueous solution of sodium hydroxide was gradually added over 1 hour, the temperature of the reaction solution was raised from 50 ° C. to 85 ° C., and the mixture was stirred at the same temperature for 3 hours. When the viscosity of the solution for the resolation reaction reaches 200 cps, the solution is cooled and the reaction solution 100
To each part, 3-glycidoxypropyltrimethoxysilane was added in a ratio of 0.5 part to prepare a binder solution. Table 3 summarizes the raw material charge amounts and reaction conditions.

Comparative Example 6 In an aqueous solution consisting of 500 parts (5.3 mol) of 100% phenol, 67.5 parts (0.68 mol) of 37% concentrated hydrochloric acid and 325 parts of water, 73 parts of 37% formalin water (73 parts) 0.9 mol)
Was added dropwise at 30 ° C. over 1 hour. After the dropwise addition, the reaction solution was allowed to stand for 1.5 hours, and then the oil layer was separated. To 250 parts of the separated oil layer were added 250 parts of water and 300 parts (5.3 moles) of potassium hydroxide, and 173 parts (5.3 moles) of 92% paraformaldehyde were added over 1 hour. The temperature of the reaction solution was gradually raised while stirring, and the mixture was stirred at 85 ° C. for 2 hours. When the viscosity of the reaction solution reached 150 cps, it was cooled, and 3-glycidoxypropyltrimethoxysilane was added at a ratio of 0.5 part to 100 parts of the reaction solution to prepare a binder solution. Table 3 summarizes the raw material charge amounts and reaction conditions.

Synthesis Comparative Example 7 564 parts (6.0 mol) of 100% phenol and water 328
Parts in an aqueous solution consisting of 92% paraformaldehyde 3
92 parts (12.0 mol) were added (paraformaldehyde: phenol molar ratio 2.0: 1). The mixture solution was heated with stirring, and 554 parts (4.8 mol) of a 48.6% aqueous solution of sodium hydroxide was added gradually at 50 ° C. over 2 hours, and the temperature of the reaction solution was raised from 50 ° C. to 85 ° C. The mixture was stirred at the same temperature for 3 hours. When the viscosity of the reaction solution reached 200 cps, the solution was cooled, and 3-glycidoxypropyltrimethoxysilane was added at a ratio of 0.5 part to 100 parts of the reaction solution to prepare a binder solution. Table 3 summarizes the raw material charge amounts and reaction conditions.

[0020]

[Table 3]

Examples 1 to 4 and Comparative Examples 1 to 7 To 3000 parts of Mikawa V6 silica sand, 60 parts of the binder solution prepared in each of the Synthesis Examples and Comparative Examples was added and mixed for 90 seconds to obtain a kneaded sand. Prepared. The kneaded sand is immediately or after 24 hours, housed in a wooden form and molded, and a methyl formate-air mixed gas containing 30 parts of methyl formate is allowed to act on the molded product at room temperature to obtain a diameter of 50 mm and a height of 50 mm. 50mm
Was prepared. Tables 4, 5 and 6 show the compressive strengths of the manufactured mold test pieces. [Compression strength test method] After manufacturing a mold test piece, after 5 minutes of curing at room temperature (20 ° C) and 50% relative temperature, after 1 hour, or after curing 2
After 4 hours, the compressive strength (kgf /
cm ² ).

[0022]

[Table 4]

[0023]

[Table 5]

[0024]

[Table 6]

[0025]

As described above, according to the present invention, a binder having a long pot life when mixed with a granular refractory aggregate is obtained, and a casting mold manufactured using the same has a compressive strength. The remarkable effect of high shrinkage and small shrinkage can be obtained.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a graph showing the results of analyzing, by gas chromatography, a change in a binuclear compound of phenol as a raw material and phenol as a product over time in a novolak reaction.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Morio Shiokawa 7-43, Oguro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Hodogaya Ashland Co., Ltd. Technical Research Institute (56) References JP-B 35-17247 (JP, B1 (58) Field surveyed (Int. Cl. ⁷ , DB name) B22C 1/00-1/26

Claims (2)

(57) [Claims] 1. A novolak reaction is carried out in an acidic state based on an acidic substance having a pKa of 2.0 or less at a ratio of 1.6 to 2.5 moles of an aldehyde to 1 mole of a phenol,
At the time when the amount of the binuclear compound of phenols is maximized, the reaction solution is made alkaline, and a binder containing a water-soluble phenol resin obtained by performing a resolving reaction under an alkaline condition as an essential component is further included. Mixed with a granular refractory aggregate, housed in a mold frame and molded, and then cured by passing a gaseous organic acid ester-based curing agent through the molded product. Manufacturing method of casting mold. 2. A novolak reaction is carried out in an acidic state based on an acidic substance having a pKa of 2.0 or less at a ratio of 1.6 to 2.5 moles of aldehyde to 1 mole of phenol,
At the time when the amount of the binuclear compound of phenols is maximized, the reaction solution is made alkaline, and a binder containing a water-soluble phenol resin obtained by performing a resolving reaction under an alkaline condition as an essential component is further included. Mixing a liquid organic acid ester-based curing agent and a granular refractory aggregate, storing the mixture in a mold frame, and molding and curing the mixture.