JPH0780599A - Casting method for casting mold - Google Patents

Abstract

PURPOSE:To produce a casting mold which is rapid in improvement of casting mold strength, has the high casting mold strength and has the good surface stability of the casting mold. CONSTITUTION:System sand is obtd. by uniformly kneading an aq. soln. of a resol type water-soluble phenolic resin which is a binder and a compd. having an epoxy group which is a hardener into a refractory granular material. This system sand is packed into a molding flask for gas curing. Gaseous or aerosol org. ester is thereafter sprayed to the system sand to bring the org. ester into contact with the compd. having the epoxy group. As a result, the compd. having the epoxy group is activated, by which the curing reaction of the binder (resol type water-soluble phenolic resin) is accelerated. Then, the effect of rapidly improving the casting mold strength and improving the productivity of the casting mold is obtd. The degree of curing of the binder is increased and the casting mold having the high casting mold strength and the good surface stability is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a mold by adding and kneading a binder made of a resole-type water-soluble phenolic resin to a refractory granular material and curing the binder. is there.

[0002]

2. Description of the Related Art Conventionally, a mold is prepared by filling a mold (model) with kneading sand obtained by kneading a refractory granular material and a binder, and then hardening the binder with a predetermined curing agent. Is manufactured by. For example, in the field of cast steel, a water glass / CO ₂ method and a water glass / dical method using a binder mainly composed of water glass are used. In recent years, various organic curable resins such as furan-based resins, resol-type water-soluble phenolic resins and urethane-based resins have been developed and started to be used as binders in place of water glass. Among these, the resol-type water-soluble phenolic resin, which is cured with a gaseous or aerosol organic ester, can prevent the deterioration of the working environment during the production of the gas-curable mold, and is suitable as a binder in place of water glass. (Japanese Patent Laid-Open No. 50-130627
Japanese Patent Publication, Japanese Patent Publication No. 61-43132, Japanese Patent Publication No. 61-37022).

However, when a binder made of the resol-type water-soluble phenolic resin and a refractory granular material are kneaded to produce a mold by a gas curing method, and a binder made of a furan resin is used. However, there were the following drawbacks. That is, there is a defect that the strength of the obtained mold is low and the surface stability of the obtained mold is poor. All of these drawbacks are caused by the weak binding force of the cured resol-type water-soluble phenolic resin. Further, the resol-type water-soluble phenol resin has a drawback that the curing speed is slow. Therefore, after the mold has been manufactured by the gas curing method, the mold may not be used for producing a casting unless it is left for a relatively long time.

[0004]

Therefore, in the present invention, a compound having an epoxy group is added to a binder composed of a resol-type water-soluble phenolic resin to prepare a gaseous or aerosol organic ester and the epoxy compound. By contacting the compound having a group, the compound having an epoxy group is activated to accelerate the curing speed of the resol-type water-soluble phenolic resin and increase the degree of curing to enhance the cohesive strength of the resol-type water-soluble phenolic resin. It is to improve.

In order to improve the cohesive strength of the resol-type water-soluble phenolic resin, a two-component system of a mixture of the resole-type water-soluble phenolic resin and a compound having an epoxy group such as a hydrophilic epoxy resin oligomer is used. It is known that a binder may be used (JP-A-4-298591). However, it is not known to contact the hydrophilic epoxy resin oligomer with a gaseous or aerosol organic ester to accelerate the curing rate of the resol-type water-soluble phenol resin. The present invention has been made based on such novel findings.

[0006]

That is, according to the present invention, a refractory granular material is uniformly kneaded with an aqueous solution of a resol type water-soluble phenolic resin which is a binder and a compound having an epoxy group which is a curing agent. After obtaining the kneading sand by filling the kneading sand in a mold for gas curing, spraying a gaseous or aerosol organic ester, by contacting the organic ester with the compound having the epoxy group, The present invention relates to a method for producing a mold, which comprises accelerating a curing reaction of a binder.

The binder used in the present invention is generally a resol type water-soluble phenol resin. The resol-type water-soluble phenol resin is obtained by condensing phenols and an aldehyde compound in the presence of an alkaline catalyst such as potassium hydroxide. Phenols include phenol, cresol,
Alkylphenols such as 3,5-xylenol, nonylphenol, p-tert-butylphenol, isopropenylphenol, phenylphenol, polyphenols such as resorcinol, catechol, hydroquinone, phloroglysin, bisphenol A, bisphenol F, bisphenol C, bisphenol E, etc. Bisphenols and the like are used. In addition, cashew nut shell liquid, lignin,
A mixture of phenolic compounds such as tannin can also be used as the phenols. For these various phenols, one kind of substance may be used alone, or two or more kinds of substances may be mixed and co-condensed with the aldehyde compound.

Formalin, paraformaldehyde, furfural, glyoxal and the like are used as aldehyde compounds for condensation with phenols. The amount of the aldehyde compound used is 1 to 3 mol, preferably 1.5 to 2 mol, per 1 mol of the phenol. If the amount of the aldehyde compound used is less than 1 mol, even if the obtained binder of the resol-type water-soluble phenolic resin is cured, the binding force is insufficient and the mold strength tends not to be improved. On the other hand, when the amount of the aldehyde compound used exceeds 3 mol, the aldehyde odor from the resol-type water-soluble phenol resin is strong and the working environment tends to deteriorate.

Condensation of phenols and aldehyde compounds is generally carried out in an aqueous alkaline solution to obtain a resol-type water-soluble phenol resin. At this time, it is preferable to use potassium hydroxide (KOH) as a reaction catalyst, and therefore it is preferable to condense it in an aqueous solution of potassium hydroxide. In addition, since the resol-type water-soluble phenolic resin is generally supplied in the form of an aqueous alkaline solution, a predetermined amount of potassium hydroxide may be used during the condensation, or a minimum amount of hydroxide as a reaction catalyst may be used. After using potassium to complete the condensation, a predetermined amount of potassium hydroxide may be added. Further, after the condensation is completed, potassium hydroxide may be used together with amines such as sodium hydroxide (NaOH), lithium hydroxide (LiOH), or hexamethylenetetramine so as to have a predetermined alkalinity. . In the alkaline aqueous solution of the resol-type water-soluble phenolic resin, the number of moles of alkali (base) is preferably 0.03 to 1 mol per 1 mol of the phenolic hydroxyl group. Here, the phenolic hydroxyl group
All the O contained in the resol-type water-soluble phenolic resin
The H group, that is, both the OH group directly bonded to the aromatic ring and the OH group bonded to the aromatic ring through the methylene group are included. The number of moles of alkali (base) is 0.03
When the amount is less than the molar amount, the cohesive force of the cured resol-type water-soluble phenol resin tends to decrease. On the other hand, if the number of moles of alkali (base) exceeds 1 mole, it becomes a strong alkaline aqueous solution, which is dangerous in handling.

A silane coupling agent may be contained in the resol type water-soluble phenolic resin aqueous solution in order to improve the strength of the obtained template. As the silane coupling agent, various conventionally known ones can be used, and particularly γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ- (2
-Aminoethyl) aminopropyltrimethoxysilane, N-
Glycidyl-N, N-bis [3- (trimethoxysilyl) propyl] amine and the like are preferably used. The viscosity of the resol type water-soluble phenolic resin aqueous solution containing or not containing the silane coupling agent is 25 ° C.
Is preferably 800 cps or less, especially 200 cps
The following is preferable. If this viscosity exceeds 800 cps, it tends to be difficult to uniformly knead the refractory granular material. The viscosity is measured by a B-type viscometer. Further, the solid content of this resol type water-soluble phenolic resin aqueous solution, that is, the content excluding water is 35 to 75
It is preferable that it is wt%. If the solid content is less than 35% by weight, the resulting mold tends to have insufficient strength. On the contrary, when the solid content exceeds 75% by weight, the viscosity tends to exceed 800 cps, and it tends to be difficult to uniformly knead with the refractory granular material. In addition, this solid content is 3 in a hot air dryer using a weighed sample (2.0 ± 0.1 g).
By heating to 105 ° C for an hour to evaporate water,
(Weight of sample after evaporation of water / weight of sample to be weighed) × 100 =
It is calculated by the formula of solid content.

On the other hand, as the compound having an epoxy group to be kneaded into the refractory granular material together with the resol-type water-soluble phenolic resin, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl are used. Polyepoxy compounds such as ether, triglycidyl tris (2-hydroxyethyl) isocyanurate, glycerol polyglycidyl ether, ethylene-
Propylene glycol diglycidyl ether, propylene-polypropylene glycol diglycidyl ether,
Polytetramethylene glycol diglycidyl ether,
Diepoxy compounds such as resorcin diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol S diglycidyl ether, phenol (EO) ₅ glycidyl ether, p-tert-butylphenyl glycidyl ether, 2 -A monoepoxy compound such as ethylhexyl glycidyl ether can be used.

Further, as a gaseous or aerosol organic ester for contacting a compound having an epoxy group, methyl formate, triacetin, γ-butyrolactone,
Ethylene glycol monoacetate, ethylene glycol diacetate and the like can be used. The amount of the organic ester in the form of gas or aerosol that is brought into contact with the compound having an epoxy group is 30 to 300 parts by weight of the organic ester based on 100 parts by weight of the total amount of the compound having an epoxy group and the resol-type water-soluble phenolic resin. It is preferably a part ratio. If the proportion of contact with the organic ester is less than 30 parts by weight, the curing rate of the binder composed of the resol-type water-soluble phenol resin tends not to be sufficiently high.
Further, even if the proportion of the organic ester to be contacted exceeds 300 parts by weight, there is a tendency that the curing speed of the binder made of the resol-type water-soluble phenol resin is no longer high.

The binder prepared from the aqueous solution of resol type water-soluble phenolic resin and the compound having an epoxy group prepared as described above are uniformly added to the refractory granular material and kneaded to obtain kneading sand. Then, this kneading sand is filled in a gas curing mold, and the above-mentioned gaseous or aerosol organic ester is sprayed onto the kneading sand. Then, the organic ester comes into contact with the compound having an epoxy group in the kneading sand,
The compound having this epoxy group is activated. Then, the bonding (polymerization) reaction between the resol-type water-soluble phenolic resin and the compound having an epoxy group is promoted, the resol-type water-soluble phenolic resin is cured, and a template can be obtained. In the production of such a mold, the addition amount of the resole-type water-soluble phenolic resin or the compound having an epoxy group in the binder is preferably as follows with respect to the refractory granular material. That is, with respect to 100 parts by weight of the refractory granular material, the resole-type water-soluble phenolic resin is added so as to be 0.5 to 6 parts by weight, and the compound having an epoxy group is added.
It is preferable to add 0.05 to 3 parts by weight. Further, the amount of gas or aerosol-like organic ester aeration to the kneading sand is, as described above, 30 to 300 parts by weight with respect to the total amount 100 parts by weight of the compound having an epoxy group and the resol-type water-soluble phenol resin. A degree is preferable. As the refractory granular material to be used, various conventionally known materials can be used. For example, silica sand, chromite sand, zircon sand, olivine sand, alumina sand, mullite sand containing synthetic silica as a main component, synthetic sand Mullite sand or the like can be used. Further, as the refractory granular material, those mainly composed of these reclaimed sand and recovered sand can be used.
Needless to say.

Further, in the binder made of the resol type water-soluble phenolic resin aqueous solution used in the present invention or in the solution made of the compound having an epoxy group, a nonionic surfactant,
Kneading and kneading with refractory granular materials by incorporating various surfactants such as cationic surfactants, anionic surfactants and amphoteric surfactants, or organic nitrogen compounds such as urea, urea compounds and amide compounds It is possible to improve the fluidity of sand and the filling property into a mold for gas hardening. Furthermore, when using recycled sand as a refractory granular material,
By incorporating various polyvalent metal salts such as calcium chloride and aluminum oxide, the strength of the obtained template can be improved.

[0015]

【Example】

Examples 1 to 7 and Comparative Examples 1 and 2 Into a 50% KOH aqueous solution, phenol was added in an equimolar ratio to KOH and stirred and dissolved. While maintaining this aqueous solution at 80 ° C, 50% formalin aqueous solution was gradually added to 1 mol of phenol so that the amount of formalin was 2 mol,
The condensation reaction of phenol and formalin was allowed to proceed. Then, the reaction was continued at 80 ° C. until the viscosity of the reaction solution reached 110 cps (25 ° C.). When this viscosity is reached, the reaction solution is cooled to room temperature and phenolic hydroxyl group 1
50 mol, so that the number of moles of KOH is 0.70
% KOH aqueous solution was added to obtain an aqueous resin solution. To 100 parts by weight of this resin aqueous solution, 0.5 part by weight of γ-glycidoxypropyltrimethoxysilane was added, and the viscosity was 50 cps (25
A binder comprising an aqueous solution of resol type water-soluble phenolic resin (° C.) Was obtained. The solid content of the resol-type water-soluble phenolic resin aqueous solution was 50% by weight.

On the other hand, the compounds having an epoxy group shown in Table 1 were prepared. Then, the compound having this epoxy group and the above-mentioned aqueous solution of resol type water-soluble phenolic resin (Table 1
Inside, it was simply expressed as "phenolic resin aqueous solution". ) And 100% by weight of silica sand (flattery), which is a refractory granular material, so that the total amount of the compound having an epoxy group and the resol-type water-soluble phenolic resin is 2.0 parts by weight in the proportions shown in Table 1. Kneading was carried out for each part. The obtained kneading sand is immediately filled in a test piece frame for gas curing of 50 mmφ × 50 mmφ, methyl formate which is a gaseous organic ester, the total amount of the epoxy group-containing compound and the resol-type water-soluble phenol resin is 100% by weight. The test mold was obtained by venting 60 parts by weight with respect to parts. However, for Comparative Example 3, a test template was obtained without passing the gaseous organic ester. Note that this curing test was performed at an ambient temperature of 25
℃, sand temperature 25 ℃, humidity 60% RH.

[0017]

[Table 1]

Then, the compression strength of the obtained test mold after 1 minute [kg / cm ² ] and the compression strength after 30 minutes [kg / c]
m ² ], and the compressive strength after 24 hours [kg / cm ² ] were measured and are shown in Table 2. The surface stability (SSI) of the obtained template is also shown in Table 2.

[0019]

[Table 2]

The SSI (%) in Table 2 indicates the surface stability of the mold, and the test mold prepared immediately after kneading was used to test the “testing method of organic mold [multi-product small-quantity production high-efficiency casting technology contact]. Conference report (February 1986)] 104 Surface stability test method of organic mold p7 ”. That is, the test mold is shaken for 60 seconds on a sieve, and the weight after shaking is measured. Then, the weight of the test mold before shaking is W
SSI (%) is calculated by the following equation, where ₁ (g) and the weight of the test mold after shaking are W ₂ (g). That is,
SSI (%) = (W ₂ / W ₁ ) × 100. Therefore, S
The SI (%) shows that the larger the value, the better the surface stability of the mold.

As is clear from the results in Table 2, when the compound having an epoxy group was brought into contact with a gaseous organic ester to cure the binder, the compound having an epoxy group was not used. It can be seen that the mold strength (compressive strength) is improved more rapidly than in the case where the binder is cured using only the organic ester of (Comparative Example 2).
That is, it can be seen that the curing speed of the binder (resol-type water-soluble phenolic resin) is high. Further, when the resol type water-soluble phenolic resin is not used (Comparative Example 1)
It can be seen that since the substantial binder does not exist, the required mold strength (compressive strength) cannot be obtained at all. Furthermore, when the resol-type water-soluble phenolic resin and the compound having an epoxy group are cured without using a gaseous organic ester (Comparative Example 3), the mold strength (compressive strength) is slowly improved. You can see that it will not progress. That is, it can be seen that the curing speed of the binder is very slow. Furthermore, as in the embodiment,
It can be seen that the surface stability is improved when the binder is cured by bringing the compound having an epoxy group into contact with a gaseous organic ester and curing the binder.

[0022]

INDUSTRIAL APPLICABILITY As described above, the present invention is a compound having an epoxy group in the binder in order to rapidly cure the binder (resole type water-soluble phenolic resin) used in producing a mold. Is added and mixed, and the gaseous or aerosol organic ester is brought into contact with the compound having an epoxy group to activate the compound having an epoxy group. Therefore, the compound having an activated epoxy group is bonded (polymerized) with the binder, so that the speed of this bonding (polymerization) reaction is accelerated, the curing of the binder is accelerated, and the binder is bonded. The degree of (polymerization) also increases,
The binding power of the binding agent is further improved. Therefore, if a mold is manufactured by the method according to the present invention, a mold having a high mold strength can be rapidly obtained, and the productivity of the mold can be remarkably improved. Furthermore, since the curing of the binder sufficiently proceeds, the surface stability of the obtained mold is also significantly improved.

Claims (2)

[Claims] 1. A refractory granular material is uniformly kneaded with an aqueous solution of a resol type water-soluble phenolic resin which is a binder and a compound having an epoxy group which is a curing agent to obtain kneading sand, and then the kneading. To accelerate the curing reaction of the binder by filling sand with a gas-curing mold and spraying a gaseous or aerosol organic ester to bring the organic ester into contact with the compound having the epoxy group. And a method for producing a mold. 2. The method for producing a mold according to claim 1, wherein the organic ester is methyl formate.