JP3092983B2 - Casting sand mold manufacturing method - 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 sand mold for a casting used in a self-hardening mold and a gas-curing mold molding method.

[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 mold molding method has already become a general-purpose molding method in place of the inorganic type from the viewpoint of production method, casting quality, and safety and health mainly in the field of mechanical casting. On the other hand,
So-called coated sand, in which phenolic resin is coated on granular refractories to produce molds at high speeds
A cloning method of producing a template by heat-curing is widely used. However, energy saving during mold production,
In order to improve mold production speed, mold and casting quality, cold box mold method of curing at room temperature with gaseous or aerosol-like material has been seriously introduced in the casting industry as a mold production method that replaces the cloning method. Is coming.

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. 58-154434. In the mold making method using this binder, unlike conventional acid-curable binders, the binder composition does not contain sulfur elements or nitrogen elements, so the operation by the generation of sulfurous acid gas during pouring There is no environmental pollution, or the casting has the feature that there are few casting defects due to sulfur and nitrogen elements, but the reproducibility of the casting sand when using the binder is extremely poor, It is well known that its use is limited, and there is a strong demand for improvement.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems. Conventionally used water-soluble phenolic resin has low strength of the resulting mold,
In order to obtain the required casting strength for molding, the amount of resin added had to be increased. One of the major drawbacks of this binder is that it is more difficult to secure the mold strength with the use of recovered sand intended for reuse after casting or regenerated sand that has been repeatedly used several times. 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, in order to remove residual organic substances and alkalis 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 The current situation is to deal with disposable sand. For this reason, when foundry sand is used for recycling, the maximum sand recycling rate is about 85% (FoundryTrade
Journal-8/22 December 1989) The difference between this recycled sand and the acid-curable furan resin, which is widely used, becomes even more apparent. That is, in the case of an acid-curable furan resin, generally, the use of recycled sand can set the strength of the mold higher than that of fresh sand, so that the amount of the binder added can be somewhat reduced in the recycled sand system. Further, the recovery rate of the reclaimed sand is about 95% or more because no mechanical polishing and reclaiming treatment is required. Sand regeneration 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 broken apart by mechanical vibration or decomposition,
Break up clumps or aggregates and collect 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.

When the recycled sand thus obtained is used, a sufficient mold strength cannot be obtained by a binder process using a water-soluble phenol resin as a binder and an organic ester as a curing agent. There are disadvantages inherent in this process, such as: This is a completely different phenomenon from the widely used acid-curable furan resin, and improvement is strongly desired. Recently, for the purpose of improving the strength of a mold using recycled sand, a method for lowering the resin solid content concentration in a binder is disclosed in JP-A-1-262042, and a method for pre-treating the recycled sand with a silane solution in advance is disclosed. It 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.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, in the step of reacting phenols with an excess of aldehyde, the reaction was carried out at pH 7 or less in the presence of a divalent metal ion catalyst. After the initial reaction, a water-soluble phenol resin obtained by resolving in the presence of an excess of an alkaline catalyst is used as a binder, and an organic ester is used as a curing agent. By using recovered sand or reclaimed sand for the purpose of reuse especially as a granular material, a water-soluble phenol resin conventionally used, i.e., in the step of reacting phenols with an excess of aldehyde, It is made from a resol in the presence of an excess alkaline catalyst without initial reaction at pH 7 or less in the presence of a metal ion catalyst. It found that the strength of the mold can be greatly improved, in which the present invention has been accomplished. That is, the present invention uses a divalent metal element compound in a step of condensing a phenol and an aldehyde in an acidic region, and performs an alkali metal catalyst in an alkaline region in a preceding stage and / or a subsequent stage. A water-soluble phenolic resin produced by performing the above reaction is used as a binder, and an organic ester is used as a curing agent. The present invention provides a method for producing a casting sand mold, characterized by using recovered sand or recycled sand.

The binder composition itself used in the method for producing a sand mold for castings of the present invention is known in Japanese Patent Application Laid-Open No. Hei 2-261815. There is no description about using the target recovered or recycled sand to form a sand mold for casting.
Further, in the above-mentioned Japanese Patent Application Laid-Open No. 2-261815, it is described that the mold strength is improved by obtaining a benzyl ether type resin, but this is because the refractory granular material is made of fresh sand as described in the Examples. In some cases, gas-curable molds are effective. However, when the present inventors mold a sand mold for casting using the above-mentioned reclaimed sand or the like as a refractory granular material, the resin structure does not crucially govern the mold strength, and the catalyst used in the synthesis thereof is not used. That is, they have found that divalent metal ions have the effect of further improving the strength of the mold when the mold is formed using the above-mentioned recycled sand or the like. Recovered or reclaimed sand intended for reuse is quartz sand, chromite sand, zircon sand, olivine sand,
Alumina sand and the like are mentioned, but in the present invention,
In particular, the effect of improving the mold strength when such reclaimed sand is used is remarkable, and among these reclaimed sands, silica sand containing quartz as a main component is particularly effective, and SiO ₂ which is a silica sand component is effective.
Those having a weight percentage of 97% by weight or more exhibit a particularly remarkable effect. When reclaimed sand is used, a reclaimed sand obtained by an ordinary abrasion method or a roasting method is used, but the method for producing the reclaimed sand is not particularly limited.

In the method for producing a sand mold for castings of the present invention, a conventionally known silane coupling agent can be used. Specific examples thereof include γ-aminopropyltriethoxysilane and γ- (2
-Aminoethyl) aminopropyltrimethoxysilane,
γ-glycidoxypropyltrimethoxysilane and the like. In the present invention, these silane coupling agents can be used together at the time of kneading the binder or the regenerated sand.

In producing the foundry sand mold according to the present invention, a known method is employed. For example, with respect to 100 parts by weight of reclaimed sand, 0.05 to 9 parts by weight, preferably 0.1 to 5 parts by weight, of an organic ester of a curing agent and 0.4 to 15 parts by weight, preferably 0.6 to 5 parts by weight of a resolulated aqueous phenol resin aqueous solution. Can be kneaded by a known method, and a mold can be manufactured using the conventional self-hardening mold manufacturing process as it is.
Examples of the organic ester used in the present invention include lactones or monohydric or polyhydric alcohols having 1 to 10 carbon atoms and 1 to 10 carbon atoms.
An organic ester derived from an organic carboxylic acid of 10 alone or in a mixture is used.
-Butyrolactone, propionlactone, ε-caprolactone, ethyl formate, ethylene glycol diacetate, ethylene glycol monoacetate, triacetin, and the like are preferably used, and methyl formate is preferably used in the gas-curing molding method.

[0010]

The present invention will be described below in detail with reference to examples.
However, the present invention is not limited to only this embodiment.
No.Synthesis Example 1  Four-port fan with stirrer, reflux condenser and thermometer
Rusco water 255 parts by weight, phenol 267 parts by weight, 92%
158 parts by weight of laformaldehyde and 2.7 parts by weight of zinc acetate
And heat it on a hot water bath with stirring, maintain at 85 ° C, and add
The reaction was performed over time. Then 48% potassium hydroxide
Add 292 parts by weight, and the viscosity of the resin solution becomes 100 cp at 25 ° C.
After cooling at this point, γ-aminopropyltriethoxy
Add 4.0 g of silane and add resin solution (solid content 49%, weight average
Molecular weight 2300).

[0011]Synthesis Example 2  Four-port fan with stirrer, reflux condenser and thermometer
Lasco water 264 parts by weight, phenol 277 parts by weight, 48% water
Add 292 parts by weight of potassium oxide and add on a hot water bath while stirring.
Heated and maintained at 85 ° C. Then 92% Paraholm Aldehi
163 parts by weight were added over 1 hour. Reaction at the same temperature
Continue cooling when the viscosity of the resin solution reaches 100 cp at 25 ° C.
4 g of γ-aminopropyltriethoxysilane
Part of the resin solution (solid content 49%, weight average molecular weight 230
0).

Example 1 Using the resin solution obtained in Synthesis Example 1, a test piece for an anti-pressure test was prepared according to the following method for measuring the strength of a mold.
The time-dependent change of the mold strength after the preparation was measured.

Comparative Example 1 Using the resin solution obtained in Synthesis Example 2, a test piece for a coercive pressure test was prepared in the same manner as in Example 1, and the time-dependent change in the mold strength after preparation was measured.

[0014]Measuring method of mold strength  100% recycled sand whose sand type is Fremantle quartz sand
Parts by weight of triacetin, 0.375 parts by weight
Water-soluble phenolic resin (solid content 49%, weight
And a mixture obtained by adding and kneading 1.5 parts by weight of
After filling into a 50mmφ × 50mmh test piece model and kneading
The change over time of the coercive pressure was measured.

[0015]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
Contains Liethoxysilane 0.5% by weight (phenolic resin)
Water soluble phenolic resin (solid content 49%, weight average molecule
2300) was molded from a mixture obtained by adding and kneading 1.5 parts by weight of
Using a mold, cast FC-25 (S / M = 3.5) and collect the collected sand.
Crusher, M-type rotary made by Nippon Casting Co., Ltd.
Regeneration (A regeneration, 2 passes) was performed using a Kramer. that's all
The reclaimed sand obtained by repeating the steps of
It was used to prepare test pieces for testing. Examples and comparative examples
Table 1 shows the results of the measurement of the coercive pressure in the above.

[0016]

[Table 1]

[0017]

As is clear from the above Examples and Comparative Examples, after the initial reaction at a pH of 7 or less in the presence of a divalent metal ion catalyst, a water-soluble phenol resin which has been converted into a resol in the presence of an alkali catalyst is used. When molding a mold, by using recovered or reclaimed sand for the purpose of reuse as a refractory granular material, compared to the case where a water-soluble phenol resin that has been converted into a resol in the presence of an alkali catalyst from the beginning is conventionally used. A high strength mold is obtained. As a result, the amount of the binder used can be reduced, so that the collection and regeneration of the molding sand becomes very easy, and the amount of gas generated from the casting mold during casting can be reduced. Generation can be suppressed and a sound casting can be manufactured, which is very useful in practice.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akio Manwa 2-18-8 Fujimidai, Toyohashi-shi, Aichi (72) Inventor Shigeo Nakai 6 Higashikawa, Iimura-cho, Toyohashi-shi, Aichi Prefecture Residence Higashi 205 (56) Reference Document JP-A-2-261815 (JP, A) JP-A-1-262042 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22C 1/00-1/26

Claims (1)

(57) [Claims] 1. A step of condensing a phenol and an aldehyde using a divalent metal element compound to cause a reaction in an acidic region, and an alkali metal catalyst in an alkaline region before and / or in a subsequent stage. A water-soluble phenolic resin produced by performing the above reaction is used as a binder, and an organic ester is used as a curing agent. A method for producing a foundry sand mold, comprising using recovered sand or recycled sand.