JPH0523784A - Resin composition for producing curing mold and production of casting mold - Google Patents

Abstract

PURPOSE:To provide the binder compsn. for a curing mold used in a molding method for self-curing and gas-curing molds and the process for production of a casting sand mold. CONSTITUTION:This resin compsn. for production of the ester-curing mold is formed by incorporating a water-soluble phenolic resin which is produced by effecting reaction in an acidic region by using a bivalent or higher valency metallic ion catalyst in a stage for bringing phenols and aldehydes into reaction, effecting the reaction with an alkaline catalyst in an alkaline region in the stage before the above-mentioned stage and/or the stage thereafter and is further incorporated with metallic powder and/or alloy powder during the reaction into this compsn. This process for production of the casting mold consists in using the above-mentioned resin compsn. The strength of the casting mold formed from a reclained refractory granular material is greatly improved by using the above-mentioned resin compsn. and process for production of the casting mold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder composition for a curable mold and a method for producing a molding sand mold, which is used in a self-hardening and gas-curable mold molding method, and more specifically, a water-soluble phenol resin. As a binder, the organic ester as a curing agent, in the production of a sand mold for casting to mold the refractory granular material, the reusability of the refractory granular material is significantly improved curable mold resin composition and The present invention relates to a method for producing a foundry sand mold using this resin composition.

[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 is mainly used in the field of mechanical casting to improve productivity, casting quality,
From the viewpoint of safety and health, it has already become a general-purpose molding method in place of the inorganic type. On the other hand, conventionally, in order to manufacture a mold at medium to high speed, a cloning method in which a so-called Coated Sand in which a phenol resin is coated on a granular refractory is heat-cured to manufacture a mold is widely used. However, in order to save energy at the time of mold production, mold production speed, and further improve the quality of the mold and casting, the cold-box mold method in which the material is cooled at room temperature with a gaseous or aerosol-like substance is used as a mold manufacturing method that replaces the cloning method. The industry is trying to introduce it seriously.

Recently, as a binder composition for improving casting quality and working environment, a water-soluble phenol resin is used as a binder,
A binder composition for molding sand used in an organic self-hardening mold molding method and a gas-curable mold molding method in which it is cured with an organic ester is disclosed in JP-A-50-130627 and JP-A-58-154433.
It has come to be known from Japanese Patent Publication No. 58-154434 and Japanese Patent Publication No. 58-154434. In the mold making method using this binder, unlike the conventional acid-curable binder, since the binder composition does not contain elemental sulfur or nitrogen, the working environment due to the generation of sulfurous acid gas during pouring Contrary to the above, there is no pollution, or there are few casting defects due to elemental sulfur and nitrogen to the casting, but the reproducibility of the binder type foundry sand is extremely poor,
It is well known that its use is limited, and its improvement is strongly desired.

In such a binder composition, since the strength of the obtained mold is low, the amount of the resin added must be increased in order to obtain the mold strength required for molding. In addition, as a particularly big drawback of this binder, the more difficult it is to secure the mold strength with the use of recovered sand that is intended to be reused after casting once or reclaimed sand that has been repeatedly used a plurality of times, the more difficult it is for binder sand There was a drawback that it was easy to fall into a vicious circle, such as the amount used. Further, such an increase in the amount of the binder in the mold leads to an increase in the amount of the pyrolysis gas at the time of pouring, and also has drawbacks such as a gas defect of the casting and a deterioration of working environment. In order to reduce such drawbacks even a little, in general, to remove the residual organic matter and alkali content on the sand surface,
At the same time as the mechanical mechanical polishing and regeneration treatment, at the same time, the supply rate of fresh sand is increased or the sand is thrown away. Therefore, when the foundry sand is used for regeneration, the sand regeneration rate is limited to about 85% at most (FOUNDRY TRADE JOURNAL-8 / 22 DECEMBER 198).
9). The difference in this sand reproducibility becomes even clearer as compared with the case of acid-curing furan resin which is widely used. That is, in the case of an acid-curing furan resin, the strength of the mold is generally higher when reclaimed sand is used than when fresh sand is used. Therefore, the amount of the binder added is somewhat reduced in the reclaimed sand system.
And since it does not require a strong mechanical polishing regeneration treatment,
The recovery rate of recycled sand is about 95% or more.

Regeneration of sand is an important economic problem when making molds and cores from sand bound by a curable binder. To regenerate sand from a mold or core, after removing the casting, mechanically vibrate or decompose the used mold and core to break up the sand, destroy the lumps or agglomerates, and collect the sand. . Since the unburned component of the binder is present on the recovered sand surface, it is usually regenerated next. Three generally accepted methods for reclaiming recycled sand (mechanical,
Wet and thermal). The wet regeneration method is a relatively unfavorable method because of the waste problems associated with wash water and the energy costs of drying sand. The thermal regeneration method is also a relatively unfavorable method because of the high energy cost of this method. On the other hand, since the mechanical regeneration method is the most economical, it is the most commonly used and popular regeneration method in the foundry industry.

In the reclaimed sand thus obtained, a binder process using a water-soluble phenolic resin as a binder and an organic ester as a curing agent does not provide sufficient mold strength. This is a phenomenon which has a unique defect and is completely different from the case of the widely used acid-curable furan resin, and improvement is strongly desired.
Recently, for the purpose of improving the strength of a mold using reclaimed sand, a method of lowering the resin solid content concentration in the binder is disclosed in JP-A 1-262042, and reclaimed sand is pretreated with a silane solution in advance. The method is disclosed in JP-A 1-262043. However, although some of these methods improve the strength of reclaimed sand to some extent, satisfactory mold strength cannot be obtained.

[0007]

As a result of intensive studies to solve the above problems, the inventors of the present invention mold a fire-resistant granular material using a water-soluble phenol resin as a binder and an organic ester as a curing agent. In a binder composition used in a method for producing a sand mold for casting, by using a binder composition containing a specific amount of a specific metal element, molding is particularly performed from a refractory granular material (hereinafter referred to as recycled sand) The inventors have found that the strength of the cast mold is significantly improved and have completed the present invention. That is, according to the present invention, in the step of reacting a phenol with an aldehyde, the reaction is carried out in an acidic region using a metal ion catalyst having a valence of 2 or more, and the alkaline catalyst is used in an alkaline region in the preceding stage and / or the subsequent stage. And a resin composition for producing an ester-curable template, which comprises a water-soluble phenolic resin produced by containing a metal powder and / or an alloy powder during the reaction, and the resin composition. The present invention provides a method for producing a foundry sand mold characterized by being used.

To explain the present invention in more detail, the binder composition of the present invention comprises a metal powder and / or an alloy powder containing one or more selected from Group IB to VIII of the Periodic Table and a water-soluble phenol. It can be obtained by incorporating 5 to 50,000 ppm as a metal element into a resin and / or an organic ester.

The metals used in the present invention include Cu, Ag, Au, etc. in the group IB, Mg, Ca, Sr, Ba, Zn, Cd, etc. in the group II, Al, Sc, Ga, etc. in the group III, IV Ti, Zr, Sn, etc. in group C, V, Bi, etc. in group V, Cr, Mo, W, etc. in group VI, Mn, Tc in group VII
Etc. In the Group VIII, Fe, Co, Ni and the like can be mentioned. Among these metals, those containing at least one metal of Group II, III, IV, and VIII as a main component are preferable.

The metal and / or alloy powder used in the present invention includes Al powder, Zr powder, Zn powder, Ni powder, Fe powder, Mn powder and Cu.
Powders, Ti powders, Sn powders, duralumin, magnarium, ferromagnesium, magnesium silicon, ferromanganese and the like can be mentioned, but not limited to these.
When the metal and / or alloy powder is used, its particle size should be as small as possible, and the average particle size is usually 10,000 μm or less, preferably 2000 μm or less. If it is 10000 μm or more, the effect of recovering the mold strength with reclaimed sand tends to be insufficient.

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. It is obtained by reacting with aldehydes such as formaldehyde, acetaldehyde, furyl aldehyde or a mixture thereof in an aqueous solution of a large amount of alkaline substance. Further, a formalin-condensable monomer such as urea, melamine, or cyclohexanone may be co-condensed with them to such an extent that they do not become the main constituent units in a weight ratio. Suitable alkaline catalysts used in the production of these water-soluble phenolic resins are the alkali metal hydroxides sodium hydroxide, potassium hydroxide, lithium hydroxide and mixtures thereof, with potassium hydroxide being Most preferred. The water-soluble phenol resin containing a metal element can be obtained by adding a metal and / or alloy powder containing a metal element at any stage of producing the resin. That is, it can be obtained by dissolving or mixing a metal powder and / or an alloy powder containing a metal element when the reaction is carried out at a pH of 7 or less and / or when the reaction is carried out after the addition of an alkaline catalyst, or it is cured. It can also be obtained by mixing a metal and / or alloy powder containing a metal element with the organic ester as the agent. The addition amount of the metal and / or alloy powder is 5 as the metal element.
˜50,000 ppm, preferably 10˜30,000 ppm. If the amount of the metal element added is less than 5 ppm, the improvement of the mold strength of the reclaimed sand will not reach the desired level, while if it exceeds 50,000 ppm, the stability of the resin and the curing agent will deteriorate, which is not preferable.

The metal element in the binder is generally quantified as follows. [Quantitative determination of metal element in binder] The binder is thoroughly mixed and stirred, and 0.5 to 0.8 g is weighed in a 100 ml platinum dish. To this, 10 ml of concentrated nitric acid was added, followed by acid decomposition and then mild thermal decomposition. Add 10 ml of concentrated perchloric acid and treat with white smoke to make the residual amount of concentrated perchloric acid 3 ml. After allowing to cool, 10 ml of HCl (1 + 1) +10 ml of H ₂ O is added and dissolved by heating. This is filtered (No5C filter paper) and washed with dilute hydrochloric acid + warm water. The residue left on the filter paper is 90 ml in a 30 ml platinum crucible.
After ashing at 0 to 1000 ° C, let stand to cool, add 2 g of potassium pyrosulfate and melt at 800 ° C. The melted product is combined with the above filtrate to make a 100 ml solution in a volumetric flask, and then the metal element is quantified by ICP (Inductively Coupled Plasma Emission Spectroscopy).

It has not been known at all that the strength of the reclaimed sand is remarkably recovered by using the binder composition of the present invention containing such a metal element. On the other hand, a metal ion is known as a catalyst for forming a benzyl ether bond at the ortho position between the phenol nuclei of phenols. For example, Japanese Examined Patent Publication No. 47-50873, U.S. Pat.
Group II elements or transition elements are described in Japanese Patent Publication No. 7, Japanese Patent Publication No. 54-15797, Japanese Patent Publication No. 60-23769, and the like.

Further, in JP-A-2-261815, phenols and formalin are subjected to a condensation reaction in the presence of a divalent metal ion under an acidity of pH 7 or less to obtain a benzyl ether type resin, and then under an excess of alkali. By reacting unreacted formalin and converting the phenol nucleus into methylol, a benzyl ether type organic ester curable water-soluble resol resin is obtained. The purpose of the metal ion in the patent application is a catalyst for forming a benzyl ether bond between the ortho positions of the phenol nuclei, and the benzyl ether type water-soluble resol resin produced under such conditions is The strength is higher than that of a known water-soluble phenolic resin having a methylene type bond between phenol nuclei produced under strong alkaline conditions using an alkali metal as a synthetic catalyst. Thus, a phenol resin having a benzyl ether bond can be obtained by carrying out a polymerization reaction in the acidic region using a divalent or higher valent metal ion catalyst. In the present invention, the hardness of the mold is further improved by incorporating the metal powder and / or the alloy powder in the resin production stage (before the reaction, during the reaction, and / or after the reaction). In particular, when the recycled sand or the recovered sand is used, the hardness increasing effect is remarkably improved as compared with the case where the conventional binder is used.

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 as a mixture. However, in the self-hardening molding method, γ-butyrolactone, propionolactone,
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 the gas curable molding method.

Examples of the refractory granular material include silica sand containing silica as a main component, chromite sand, zircon sand, olivine sand, alumina sand and the like. In the present invention, either new sand or reclaimed sand can be used as these refractory granular materials, but the effect of improving the mold strength is particularly remarkable when reclaimed sand is used. When the reclaimed sand is used, the reclaimed sand obtained by an ordinary abrasion type or roasting type is used, but the method for obtaining the reclaimed sand is not particularly limited.

In the binder composition of the present invention, conventionally known silane coupling agents can be used as other additives. Specific examples thereof include γ-aminopropyltriethoxysilane and γ-aminopropyltriethoxysilane.
Examples include (2-aminoethyl) aminopropyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane. In the present invention, it is preferable to use this silane coupling agent together with the binder composition. A well-known method is adopted for producing a sand mold for casting by the self-hardening mold making method using the binder composition of the present invention. For example, to 100 parts by weight of reclaimed sand, 0.4 to 15 parts by weight, preferably 0.6 to 5 parts by weight, of an aqueous solution of a water-soluble phenolic resin, which is the binder composition according to the present invention, and 0.05 to 9 parts by weight of an organic ester of a curing agent are used. Parts, preferably 0.1 to 5 parts by weight, can be kneaded by a known method, and a conventional self-hardening mold manufacturing process can be used as it is to manufacture a mold.

[0018]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Synthesis Example 1 255 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 placed in a four-necked flask equipped with a stirrer, a reflux condenser and a thermometer.
Metal / alloy powder was added so as to have the element concentrations shown in Table 1, heated with stirring in a hot water bath and kept at 85 ° C., and reacted for 16 hours. Then, 292 parts by weight of 48% potassium hydroxide was added, and when the viscosity of the resin solution reached 100 cp at 25 ° C, 4 parts by weight of γ-aminopropyltriethoxysilane was added, and the resin solution (solid content of about 50%, weight average molecular weight about 2300) was obtained.

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, and stirred. The mixture was heated on a hot water bath and kept at 85 ° C., and reacted for 16 hours. Then 48% potassium hydroxide 292
By weight, metal and alloy powders were added so as to have the element concentrations shown in Table 2, and after cooling when the viscosity of the resin solution reached 100 cp at 25 ° C, 4 parts by weight of γ-aminopropyltriethoxysilane was added. In addition, a resin solution (solid content: about 50%, weight average molecular weight: about 2300) was obtained.

Synthesis Example 3 To a four-necked flask equipped with a stirrer, a reflux condenser, and a thermometer, 264 parts by weight of water, 277 parts by weight of phenol, and 292 parts by weight of 48% potassium hydroxide were added, and the mixture was heated on a water bath while stirring. Hold at 85 ° C. Then 92% paraformaldehyde
163 parts by weight were added over 1 hour. The reaction is continued at the same temperature, cooled when the viscosity of the resin solution reaches 100 cp at 25 ° C, 4 parts by weight of γ-aminopropyltriethoxysilane is added, and the resin solution (solid content: about 50%, weight average molecular weight: about 50%) is added. 230
0) was obtained.

Synthesis Example 4 To 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 2.7 parts by weight of zinc acetate were added, and hot water was stirred. The mixture was heated on a bath and kept at 85 ° C., and reacted for 16 hours. After that, 292 parts by weight of 48% potassium hydroxide was added, and when the viscosity of the resin solution reached 100 cp at 25 ° C, 4 parts by weight of γ-aminopropyltriethoxysilane was added, and the resin solution (solid content of about 50%, weight average molecular weight about 2300) was obtained.

Examples 1 to 13 The metal and alloy powders shown in Table 1 were added according to Synthesis Example 1 to obtain a resin solution containing a metal element, and a test piece for self-hardening pressure resistance test was prepared according to a predetermined method. The mold strength was measured 24 hours after the preparation. Examples 14 to 25 According to Synthesis Example 2, the metal / alloy powder shown in Table 2 was added to obtain a resin solution containing a metal element, and a gas-curable pressure resistant test piece was prepared and prepared according to a predetermined method. After
The mold strength after 24 hours was measured.

Comparative Examples 1 and 5 Resin solutions were obtained according to Synthesis Example 3 and self-hardening and gas-curing test pieces for pressure resistance test were prepared according to a predetermined method.
The template strength was measured 24 hours after the preparation. Comparative Examples 2 and 6 A water-soluble phenolic resin solution (solid content: 40%) was obtained according to the examples described in JP-A 1-262042, and a self-hardening, gas-curable pressure-resistant test piece was tested according to a predetermined method. Was prepared and the mold strength was measured 24 hours after the preparation. Comparative Examples 3 and 7 Sand was treated according to the examples described in JP-A 1-262043. That is, with respect to 100 parts by weight of reclaimed sand, after being treated with 0.024 parts by weight of a 40% aqueous solution of γ-aminopropyltriethoxysilane at 25 ° C. in advance, self-hardening according to a predetermined method, a test piece for gas-curable coercive pressure test Was prepared and the mold strength was measured 24 hours after the preparation. Comparative Examples 4 and 8 Resin solutions were obtained according to Synthesis Example 4 according to the examples described in JP-A-2-261815, and self-hardening according to a predetermined method.
A test piece for gas-curable coercive pressure test was prepared, and the mold strength was measured 24 hours after the preparation.

[0024]Mold strength measurement method   The mold strength in the self-hardening mold making method is evaluated as follows.
did. In other words, 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 were mixed with 1.5
Part by weight Add and knead the mixed mixture with a 50 mmφ × 50 mmh test pie.
It was filled in a space model and the coercive pressure was measured after 24 hours. Moth
The mold strength in the sclerosing mold molding method is evaluated as follows.
did. That is, the type of sand is Fremantle silica sand
For 100 parts by weight of sand, the water solubility of the examples and comparative examples of the present invention
Mixture made by adding 2.5 parts by weight of water-soluble phenolic resin
Is filled in a 50 mmφ x 50 mmh test piece model for gas curing.
did. 3.0 parts by weight of gaseous methyl formate was added to this model.
The infusion pressure was measured 24 hours after the injection.

[0025]Method of preparing recycled sand   Hardener against 100 parts by weight of fresh sand of Fremantle silica
Triacetin 0.375 parts by weight, γ-aminopropyl
0.5% by weight of triethoxysilane (vs. phenolic resin)
Containing water-soluble phenolic resin (solid content 49%, weight average)
Molded from a mixture of 1.5 parts by weight of molecular weight 2300) and kneading
FC-25 (S / M = 3.5) was cast and recovered using the prepared mold.
Pour sand into the crusher, M-type rotary rack made in Japan
Reproduction (A reproduction, 2 passes) was performed using a Romer. More than
The reclaimed sand obtained by repeating the process 5 times was subjected to the above mold strength.
Used for test preparation.

Tables 1 and 2 show the measurement results of the particle size and coercive force of the test pieces of Examples 1 to 25 and the coercive force of the test pieces of Comparative Examples 1 to 8.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

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

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tsutomu Tanaka             6-2-1 Fujimidai, Toyohashi City, Aichi Prefecture Kao Tomi             Shimi Dormitory

Claims (5)

[Claims] 1. In the step of reacting a phenol with an aldehyde, the reaction is carried out in the acidic region using a metal ion catalyst having a valence of 2 or more, and the alkaline catalyst is used in the alkaline region in the preceding stage and / or the subsequent stage. A resin composition for producing an ester-curable mold, which comprises a water-soluble phenolic resin produced by reacting with a metal powder and / or an alloy powder during the reaction. 2. The resin composition for producing a mold according to claim 1, wherein the metal element of the metal powder and / or the alloy powder is one kind or two or more kinds selected from the groups IB to VIII of the periodic table. 3. The mold-forming resin composition according to claim 1, wherein the refractory granular material is mainly composed of recovered sand or recycled sand for the purpose of reuse. 4. A mold manufacturing method for molding a refractory granular material using the resin composition for manufacturing an ester-curable mold according to claim 1 and an organic ester. 5. The method for producing a mold according to claim 4, wherein the refractory granular material is mainly recovered sand or recycled sand for the purpose of reuse.