JP2954396B2 - Resin composition for producing curable mold 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 method for producing a resin composition for a curable mold and a method for producing a sand mold for molding, which are used in a self-hardening and gas-curable mold molding method. As a binder, using an organic ester as a curing agent, in the production of a sand mold for casting for molding a refractory granular material, a resin composition for a curable mold in which the reusability of the refractory granular material is remarkably improved and this resin The present invention relates to a method for producing a foundry sand mold using the 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, there are a self-hardening mold method, a cold box mold method, a cloning method (shell). Method) is known. In particular, the organic self-hardening molding method is used mainly for the field of mechanical casting to improve productivity, casting quality,
It has already become a general-purpose molding method in place of inorganic type from the viewpoint of safety and health. 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, which has been coated with a phenol resin on a refractory, has been widely used. However, in order to improve energy saving during mold production, mold production speed, and quality of molds and castings, cold box mold method of curing at room temperature with gaseous or aerosol-like materials is a casting method as an alternative to cloning method. The industry has been seriously trying to introduce it.

Recently, as a binder composition for improving casting quality and work environment, a water-soluble phenol resin is used as a binder,
Binder compositions for molding sand used in organic self-hardening mold molding methods and gas-curable mold molding methods in which this is cured with an organic ester are disclosed in JP-A-50-130627 and JP-A-58-154433.
And Japanese Patent Application Laid-Open No. Sho 58-154433. In the mold making method using this binder, unlike conventional acid-curing binders, since the binder composition does not contain sulfur or nitrogen elements, the working environment due to the generation of sulfurous acid gas during pouring While there is no contamination, or the casting has the feature that there are few casting defects caused by sulfur elements and nitrogen elements, the renewability of the binder type molding sand is extremely poor,
It is well known that its use is limited, and there is a strong demand for improvement.

[0004] In such a binder composition, the strength of the resulting mold is low, so that the amount of resin added has to be increased in order to obtain the mold strength required for molding. One of the major disadvantages of this binder is that it is more difficult to secure the strength of the mold as recovered sand intended for reuse after casting or recycled sand used multiple times is repeated. There was a drawback that it was easy to fall into a vicious circle, such as an increased amount of use. Further, such an increase in the amount of the binder in the mold leads to an increase in the amount of pyrolysis gas at the time of pouring, and also has drawbacks such as gas defects in the casting and deterioration of the working environment. In order to reduce such defects as much as possible, generally to remove residual organic matter and alkali on the sand surface, perform a strong mechanical polishing and regenerating treatment and at the same time increase the proportion of fresh sand replenished, Or at present, they are dealing with disposable sand. For this reason, when the foundry sand is used for regeneration, the regeneration rate of the sand is at most about 85% (FOUNDRY TRADE JOURNAL-8 / 22 DECEMBER 198).
9). The difference in sand reproducibility becomes even more clear when compared with the case of acid-curable furan resins, which are widely used. That is, in the case of an acid-curable furan resin, the use of recycled sand generally increases the strength of the mold as compared to that of fresh sand.
In addition, since strong mechanical polishing regeneration processing is not required,
The recovery rate of recycled sand is about 95% or more.

[0005] Regeneration of sand is an important economic issue when producing molds and cores from sand bound by a curable binder. To reclaim sand from the mold or core, after removing the casting, the used mold and core are mechanically vibrated or disassembled to break up the sand, break up lumps or aggregates, and collect the sand. . Since the surface of the recovered sand contains unburned components of the binder, the sand is usually regenerated next. There are three generally accepted methods for reclaiming reclaimed sand (mechanical, wet, and thermal). Wet regeneration is a relatively unfavorable method due to the disposal problems associated with wash water and the energy costs required to dry the sand. Thermal regeneration is also a relatively unfavorable method due to the high energy costs of this method. On the other hand, the mechanical regeneration method is the most economical, so it is most commonly used in the foundry industry and is a widely used regeneration method.

[0006] In the reclaimed sand thus obtained, a binder process using a water-soluble phenol resin as a binder and an organic ester as a curing agent cannot provide sufficient mold strength as described above. It has a peculiar defect and is a phenomenon completely different from the case of the acid-curable furan resin which is widely used, and improvement is strongly desired.
Recently, for the purpose of improving the strength of a mold using recycled sand, a method by lowering the resin solid concentration in the binder is disclosed in JP-A-1-262042, and the recycled sand is pre-treated with a silane solution in advance. The method is disclosed in Japanese Patent Application Laid-Open No. 1-262043. However, some of these methods improve the strength of the reclaimed sand, but do not provide satisfactory mold strength.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, have formed a refractory granular material using a water-soluble phenol resin as a binder and an organic ester as a curing agent. and have your method of manufacturing a foundry sand mold, by using a resin composition for a specific amount containing a specific metal element, (hereinafter referred to as recycled sand), especially regenerated refractory particulate material
The present inventors have found that the strength of a mold molded from is greatly improved, and have completed the present invention. That is, in the present invention, in the step of condensing a phenol and an aldehyde, a metal powder and / or an alloy powder selected from Groups III, IV, V and VI of the periodic table are reacted in an acidic region, A resin composition for producing an ester-curable mold, comprising a water-soluble phenol resin produced by performing a reaction with an alkaline catalyst under an alkaline region in a step and / or a subsequent step, and the resin composition. It is intended to provide a method for producing a casting sand mold, which is characterized in that it is used.

The present invention will be described in more detail.
The resin composition is a metal and / or alloy powder as a periodic table.
III, IV, V, one or two or more selected from the Group VI, the water-soluble phenol resins, obtained by 5~50000ppm contained as metal elements. The metals used in the present invention include Al, Ga, In, Ta, Sc, and Y in Group III and T in Group IV.
i, Zr, Hf, Sn, Pb, etc .; V, Nb, Ta, Bi, etc. in the V group; Cr,
Mo, W, Po and the like can be mentioned. Among these metals, III
And those containing at least one metal of Group IV as a main component are preferred.

The metal and / or alloy powder used in the present invention includes Al powder, Ga powder, Ti powder, Zr powder, V powder, Cr powder, and Mo powder.
Powders, W powders, aluminum alloy powders, and alloys containing these, but are not limited thereto.
When metal and / or alloy powder is used, the particle size is preferably as small as possible, and the average particle size is usually 10,000 μm or less, preferably 2000 μm or less. If it is 10,000 μm or more, the effect of the recovered sand on mold strength recovery tends to be insufficient.

The water-soluble phenolic resin used in the present invention is a resin curable with an organic ester. For example, phenols including phenol, cresol, resorcinol, 3,5-xylenol, bisphenol A, and other substituted phenols can be used. And aldehydes such as formaldehyde, acetaldehyde and furylaldehyde or a mixture thereof in a large amount of an aqueous solution of an alkaline substance. Further, a monomer capable of formalin condensation such as urea, melamine, and cyclohexanone may be co-condensed to such an extent that it does not become a main constituent unit by weight ratio. Suitable alkaline catalysts used in the production of these water-soluble phenolic resins are alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide and mixtures thereof. Most preferred. The water-soluble phenolic resin containing a metal element is prepared by adding a metal powder and / or an alloy powder selected from groups III, IV, V and VI of the periodic table in a step of reacting a phenol with an excess of an aldehyde,
Moreover, after the initial reaction at a pH of 7 or less, a water-soluble phenol resin containing a metal element reacted with an excess of an alkaline catalyst is obtained. The amount of the metal and / or alloy powder to be added is, as a metal element, 5 to 50,000 ppm, preferably 10 to 50 ppm.
It is 30000 ppm. If the addition amount of the metal element is less than 5 ppm, the improvement of the mold strength of the reclaimed sand does not reach the desired level.
If it exceeds 000 ppm, the stability of the resin and the curing agent deteriorates, which is not preferable.

The determination of a metal element in a resin composition is generally performed as follows. The resin composition [Determination of metal element in the resin composition], thoroughly mixed and stirred, in a platinum dish for 100 ml 0.5
Weigh ~ 0.8 g. To this, 10 ml of concentrated nitric acid is added, and after acid decomposition, it is subjected to weak thermal decomposition. 10 ml of concentrated perchloric acid is added, white smoke treatment is performed, and the remaining amount of concentrated perchloric acid is reduced to 3 ml. After cooling, HCl (1 + 1) 10
ml + H ₂ O10ml is added and dissolved by heating. This is filtered (No5C
Filter paper) and wash with dilute hydrochloric acid + warm water. The residue remaining on the filter paper is ashed in a 30 ml platinum crucible at 900 to 1000 ° C., then allowed to cool, 2 g of potassium pyrosulfate is added and melted at 800 ° C. The extracted melt is combined with the above filtrate to make a 100 ml solution in a volumetric flask, and the metal element is quantified by ICP (inductively coupled plasma emission spectrometry).

[0012] It has never been known that the use of the resin composition of the present invention containing such a metal element significantly improves the strength of the recycled sand. On the other hand, a metal ion is known as a catalyst for forming a benzyl ether bond at an ortho position between phenol nuclei of phenols.
For example, Group II elements or transition elements are described in JP-B-47-50873, U.S. Patent No. 348579, JP-B-54-15797, and JP-B-60-23769.
However, the metal element in these prior arts is a catalyst necessary for causing a resolation or benzyl etherification reaction, but the obtained resole resin is classified as a thermosetting solid resole resin. Thus, the fields of use and the curing mechanisms are completely different. That is, the water-soluble phenolic resin referred to in the present invention is cured by an organic ester as a curing agent triggered by a hydrolysis reaction in a resin exhibiting strong alkalinity, and is cured with the solid resol resin described above. The mechanism is completely different. In fact, even if an organic ester is added to the resin found in the prior patent, no curing reaction is induced due to insufficient alkalinity. Therefore, these prior arts do not correspond to the prior art of the present invention. JP-A-2-261815 discloses a benzyl ether type resin obtained by subjecting a phenol and a formalin to a condensation reaction in the presence of a divalent metal ion under an acidic condition of pH 7 or less, and then reacting with an unreacted acid in excess alkali. Is reacted with formalin to convert the phenol nucleus into methylol, thereby obtaining a benzyl ether type organic ester curable water-soluble resol resin. The purpose of the metal ion in the application patent is a catalyst for the purpose of forming a benzyl ether bond between the ortho positions of the phenol nuclei, and a benzyl ether type water-soluble resol resin produced under such conditions is: The bond between phenol nuclei produced under strong alkaline conditions using an alkali metal as a synthetic catalyst is said to be stronger than a known water-soluble phenol resin having a methylene type bond. It differs fundamentally from water-soluble phenolic resins in sand.
Further, the metals of Groups III, IV, V and VI of the present invention have not been generally used as a catalyst for the production of phenolic resins. It is believed that it has never before been contained in a resin in the form of a metal powder or an alloy.

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 alone or in a mixture is used. However, in the self-hardening molding method, γ-butyrolactone, propionlactone,
It is preferable to use ε-caprolactone, ethyl formate, ethylene glycol diacetate, ethylene glycol monoacetate, triacetin, and the like, and it is preferable to use methyl formate in a gas-curable mold molding method. Examples of the refractory granular material include silica sand, chromite sand, zircon sand, olivine sand, and alumina sand mainly composed of quartz. In the present invention, as these refractory granular materials, either new sand or regenerated sand can be used, but the effect of improving the mold strength is particularly remarkable when regenerated sand is used. When reclaimed sand is used, a reclaimed sand obtained by a normal abrasion method or a roasting method is used, but the method for producing the reclaimed sand is not particularly limited. In the resin composition of the present invention,
As other additives, conventionally known silane coupling agents can be used. As a specific example,
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 resin composition.

In producing a sand mold for casting by the self-hardening molding method using the resin composition of the present invention, a well-known method is employed. For example, 100 parts by weight of recycled sand, a water-soluble phenol resin aqueous solution of the resin composition according to the present invention
0.4 to 15 parts by weight, preferably 0.6 to 5 parts by weight, and 0.05 to 9 parts by weight, preferably 0.1 to 9 parts by weight of the organic ester of the curing agent.
Five parts by weight are kneaded by a known method, and a mold can be manufactured using the conventional self-hardening mold manufacturing process as it is.

[0015]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. Synthesis Example 1 In a four-necked flask equipped with a stirrer, a reflux condenser, and a thermometer, 255 parts by weight of water, 267 parts by weight of phenol, 158 parts by weight of 92% paraformaldehyde, and a metal / alloy powder and the elements shown in Tables 1 and 2 The solution was heated to a concentration of 85 ° C. while stirring on a hot water bath, and allowed to react for 16 hours. Thereafter, 292 parts by weight of 48% potassium hydroxide was added, and when the viscosity of the resin solution reached 100 cp at 25 ° C., the mixture was cooled.
Add 4 parts by weight of γ-aminopropyltriethoxysilane and add a resin solution (solid content: about 50%, weight average molecular weight: about 2300)
I got

Synthesis Example 2 255 parts by weight of water, 267 parts by weight of phenol, 158 parts by weight of 92% paraformaldehyde and 2.7 parts by weight of zinc acetate were added to a four-necked flask equipped with a stirrer, a reflux condenser, and a thermometer. The mixture was heated on a bath, kept at 85 ° C., and reacted for 16 hours. Thereafter, 292 parts by weight of 48% potassium hydroxide was added, and when the viscosity of the resin solution reached 100 cp at 25 ° C., the mixture was cooled. Then, 4 parts by weight of γ-aminopropyltriethoxysilane was added, and the resin solution (solid content: approx. 50%, a weight average molecular weight of about 2300).

Examples 1 to 7 The metal / alloy powder shown in Table 1 was added according to Synthesis Example 1 to obtain a resin solution containing a metal element, and a test piece for self-hardening withstanding pressure test was prepared according to a predetermined method. The mold strength was measured 24 hours after the preparation. Examples 8 to 14 The metal / alloy powders shown in Table 2 were added according to Synthesis Example 1 to obtain a resin solution containing a metal element, and a test piece for gas-curable anti-pressure test was prepared and prepared according to a predetermined method. After
The mold strength after 24 hours was measured. Comparative Example 1 According to the example described in JP-A-2-261815, a resin solution was obtained according to Synthesis Example 2, and a test piece for self-hardening pressure test was prepared according to a predetermined method. Of the mold was measured. Comparative Example 2 According to the example described in JP-A-2-261815, a resin solution was obtained according to Synthetic Example 2, and a test piece for gas-curable pressure resistance test was prepared according to a predetermined method. The strength of the subsequent mold was measured.

[0018]Measuring method of mold strength  The mold strength in the self-hardening mold making method is evaluated as follows
did. That is, the type of sand is Fremantle silica sand
0.375 parts by weight of triacetin per 100 parts by weight of sand
The water-soluble phenolic resins of Examples and Comparative Examples of the invention
A 50 mmφ × 50 mmh test pipe
The mixture was filled in a source model, and the pressure resistance after 24 hours was measured. Moth
The mold strength in the hardening mold making method is evaluated as follows
did. That is, the type of sand is Fremantle quartz sand
For 100 parts by weight of sand, the aqueous solution of Examples and Comparative Examples of the present invention
Mixture of 2.5 parts by weight of water-soluble phenol resin
Into a 50mmφ × 50mmh test piece for gas curing
did. 3.0 parts by weight of gaseous methyl formate in this model
The injection was performed, and the anti-pressure 24 hours later was measured.

[0019]Preparation method of recycled sand  Hardening agent for 100 parts by weight of fresh sand of Fremantle silica sand
0.375 parts by weight of triacetin, γ-aminopropyl
0.5% by weight of triethoxysilane (based on phenol resin)
Water-soluble phenol resin contained (solid content 49%, weight average
Molding from a mixture obtained by adding and kneading 1.5 parts by weight of a molecular weight of 2300)
Using a molded mold, FC-25 (S / M = 3.5) was cast and recovered.
Sand is crushed by a Japanese cast M-type rotary
Reproduction (A reproduction, 2 passes) was performed using a reamer. More than
The reclaimed sand obtained by repeating the process five times is used for the above mold strength.
Used for preparation for testing.

Tables 1 and 2 show the measurement results of the particle diameter and the coercive pressure of Examples 1 to 14 and the coercive pressure of Comparative Examples 1 and 2.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

By using the resin composition and the method for producing a mold of the present invention, the strength of a mold molded from regenerated refractory granular material can be greatly improved.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B22C 1/00-1/26

Claims (5)

(57) [Claims] In the step of condensing a phenol and an aldehyde, a metal powder and / or an alloy powder selected from groups III, IV, V and VI of the periodic table are reacted in an acidic region. A resin composition for producing a curable mold, comprising a water-soluble phenol resin produced by performing a reaction with an alkaline catalyst under an alkaline region in a step and / or a subsequent step. 2. The resin composition according to claim 1, wherein the content of the metal powder and / or the alloy powder is 5 to 50,000 ppm as a metal element. 3. The recovered or reclaimed sand intended for reuse
3. The method according to claim 1, which is used for a refractory granular material as a main component.
The resin composition for producing a curable mold according to the above . 4. A method for producing a refractory granular material using the resin composition for producing an ester-curable mold according to claim 1 or 2 and an organic ester. 5. The method for producing a mold according to claim 4, wherein the refractory granular material is mainly composed of recovered sand or recycled sand intended for reuse.