JPS5935309B2 - foundry sand binder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a foundry sand binder used in manufacturing foundry molds from foundry sand.

Conventionally, in order to melt a mold, various binders made of inorganic or organic materials are mixed with sand, and the mixture is formed into a mold.

Among these, water glass is often used as a typical inorganic binder, but when water glass is used, the mold is affected by the heat during pouring of molten metal, and the sand grains and sodium silicate sinter, forming the mold. The collapsibility of the material deteriorates, making work such as demolding and removing sand difficult.

In order to improve such water glass-based binders, it is known to mix appropriate amounts of spherical pinch, graphite, wood powder, magnesium oxide, etc. into water glass, but this method does not have a sufficient effect on improving collapsibility. However, the surface stability of the mold and the strength of the mold decrease.

In recent years, as improvements to such methods, as disclosed in, for example, Japanese Patent Publication No. 51-39604, Japanese Patent Application Laid-open No. 51-87124, and Japanese Patent Application Laid-open No. 51-88426, ethylene glycol, urea, etc. It has been proposed to use organic substances such as resins and polystyrene solutions in combination with water glass.

However, these are of the sequential addition type with poor workability, or even if they are of the one-liquid type, they are of the emulsion type with poor storage stability, which poses practical problems.

Also, according to JP-A-52-152820, α-olefin i
It has also been proposed to use mannic anhydride copolymer with water glass, but in this case, the viscosity as a binder becomes too strong, and when the mold is removed during mold production, sand may be deposited in the mold. This adhesion causes a phenomenon called staining, in which the surface of the mold becomes rough.

On the other hand, organic binders such as phenolic resins are superior to water glass in terms of disintegration, but they are not only more expensive than water glass, but also emit a bad odor and generate significant gas when hardening or pouring. In addition, they have the disadvantage of poor storage stability due to gradual polymerization during storage.

The present invention has been made for the purpose of solving the above-mentioned drawbacks of foundry sand binders and providing a foundry sand binder that has excellent disintegrability, strength, workability, and storage stability. It consists of a foundry sand binder consisting of arabinogalactan and water glass.

The arabinogalactan used in the present invention is a water-soluble natural high-molecular polysaccharide composed of arabinose and galactose, which can be extracted from Western larch trees and manufactured by Steinhall, USA. 5T
One commercially available under the trademark RACTANI+ can be used.

In addition, in the present invention, the filter water glass is a general formula Na2O which has been conventionally used as a molding sand binder.

n5io2 (molar ratio n is 1.8 to 3.2).
Water glass having a specific gravity (Be' number at 20° C.) of 34 to 55 is preferably used.

The foundry sand binder of the present invention is a mixture of the arabinogalactan and the water glass.

The mixing ratio is based on 100 parts by weight of water glass solids,
50-400 parts by weight of water, 0.5-2 arabinogalactan
．． It is preferable to use a proportion of 0 parts by weight.

This means that arabinogalactan is 0.5 in the above case.
This is based on the fact that if the amount is less than 20 parts by weight, the effect of improving collapsibility tends to decrease, and if it is more than 20 parts by weight, the strength after curing the mold, for example, after passing carbon dioxide gas through it, tends to decrease.

In the foundry sand binder of the present invention, it is generally preferable to increase the solid content and keep the viscosity low, so that mixing into the foundry sand is good and the caking performance is satisfactory. .

Therefore, the solid content concentration and viscosity generally suitably adopted in the present invention are approximately 25 to 50% by weight and 500 to 100% by weight.
00 centiboise.

Furthermore, in order to manufacture a mold using the foundry sand binder of the present invention, the binder is added to foundry sand and mixed.
The amount of binder used in this case is preferably 2 to 10 parts by weight per 100 parts by weight of the foundry sand, and the resulting mixture is then molded into a mold.

Conventional methods may be used for the above-mentioned mixing method and mold forming method. For example, to harden the mold formed, known methods such as carbon dioxide gas spraying, heating, and use of curing chemicals may be used. It's okay to be.

In the present invention, it is preferable to use carbon dioxide gas to harden the mold, and as in the case of water glass alone, it is hardened by carbon dioxide gas spraying or blowing to impart strength as a mold.

In addition, the strength can be increased by further drying if necessary.

As such a drying method, methods using hot air, infrared heating, high frequency heating, etc. can be appropriately employed.

Since the foundry sand binder of the present invention is composed of arabinogalactan and water glass as described above, it can be used as an -i type, and therefore has excellent workability and good storage stability. Furthermore, the binder imparts good strength to the mold, and
It will be possible to impart excellent disintegration properties, and when the binder of the present invention is used, molds with good surface conditions can be manufactured.

Next, examples of the present invention will be described.

Example 1 No. 2 water glass (molar ratio 2.3, water content 54%, specific gravity 51.
7Be') 195 parts by weight, arabinogalactan (
Product name: Straftane AF2 (manufactured by Steinhall) 4
5 parts by weight of aqueous solution No. 5 was added and stirred thoroughly to form a uniform solution.

Five parts by weight of this solution were added to 100 parts by weight of crushed sand and mixed well, and the resulting mixture was placed in a mold and tamped.

Thereafter, carbon dioxide gas was blown into the mold, the pouring mold was removed, and a mold was made.The mold had good moldability, and a good mold with no sand adhering to the mold, that is, no oozing was obtained.

This mold resistance pressure (hereinafter, the strength in this case will be referred to as gas type strength).

) was measured based on JIS-22604 "Strength Testing Method for Molding Sand" and found to be 17.6 @/- - This mold was placed in a hot air dryer and dried at 180°C for 30 minutes, and then the resistive pressure was (Hereinafter referred to as dry strength.

, ) was measured and found to be 36.5Ay/cr? It was 1. Next, to check the collapsibility, the above mold was placed in an electric furnace for 700 min.
After heating to ℃° for 10 minutes, it is cooled and subjected to pressure (hereinafter referred to as residual strength).

) was measured and 4. It was OK/-.

Example 2 A mold was made in the same manner as in Example 1, except that a solution prepared by adding 2 parts by weight of the same arabinogalactan aqueous solution as in Example 1 to 198 parts by weight of the same water glass as in Example 1 was used, and various strengths were tested. measurements and a visual stain test was conducted at the same time.

These results are shown in Table 1.

Example 3 In place of the water glass and arabinogalactan used in Example 1, No. 3 water glass (molar ratio 3.1, water content 60.1%, specific gravity 44Be') and arabinogalactan (trade name Straftane 10, A mold was made in the same manner as in Example 1, except that a mold (manufactured by Stein Hall) was used, and various strengths etc. were measured, and the results shown in Table 1 were obtained.

Example 4 A mold was made in the same manner as in Example 3, except that the amount of No. 3 water glass used was 198 parts by weight and the amount of Group 45 arabinogalactan aqueous solution was 2 parts by weight, and various strengths etc. were measured. The results shown in Table 1 were obtained.

Comparative Example 1 Other than using a binder solution prepared by mixing 15 parts by weight of a solution of 4 parts by weight of inbutin-maleic acid copolymer dissolved in 11 parts by weight of a 10-force seiso soda solution with 185 parts by weight of No. 3 water glass. A mold was made in the same manner as in Example 1, and various strengths etc. were measured and the results shown in Table 1 were obtained.

Comparative Example 2 A binder prepared by mixing 27 parts by weight of a solution of 8 parts by weight of the same inbutylene-maleic acid copolymer as in Comparative Example 1 dissolved in 19 parts by weight of 10-coefficient seiso soda with 177 parts by weight of No. 3 water glass. The same procedure as Comparative Example 1 was carried out except that a solution was used.

Comparative Example 3 The same procedure as Comparative Example 1 was carried out except that No. 3 water glass was used as it was/as a binder solution.

Claims (1)

[Claims] 1. A foundry sand binder comprising arabinogalactan and water glass. 2 50 to 40 parts by weight of water per 100 parts by weight of solid water glass
The foundry sand binder according to claim 1, wherein 0 parts by weight and 0.5 to 20 parts by weight of arabinogalactan are used. 3. The foundry sand binder according to claim 1, wherein the total solid content of water glass and arabinogalactan is about 25 to 50% by weight. 4. The foundry sand binder according to claim 1, which has a viscosity of 500 to 10,000 centipoise.