JPH07204776A - Solidifying method of sand - Google Patents

Abstract

PURPOSE:To reuse molding sand by solidifying particles of-sand by using an inorg.-org. composite formed by bringing a water-soluble inorg. compd. and org. high polymer compd. into reaction as a binder, thereby repetitively attaining solidifying and softening. CONSTITUTION:The inorg.-org. composite having a binding effect is formed and is made into a sol state. This composite is uniformly mixed with the sand and thereafter, the moisture of the system is controlled, by which the composite is collected the contact points of the particles of the sand. The hard sand mold is formed by changing the composite to a gel state to exhibit the binding force. Next, the water content of the hard sand mold is increased, by which the gel of the composite is changed to the sol state and the binding force is lost. The sand restores the sate before molding. The composite is produced by bringing water-soluble inorg. compd., for example, magnesium chloride and the org. high polymer compd., for example, sodium polyacrylate into reaction with an aq. system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is mainly used for hardening sand for casting.

[0002]

2. Description of the Related Art Many patents have been filed for manufacturing sand molds for casting. For example, the patent application publication Sho 28-
6259, Sho 42-25527, Patent Application Publication Sho 52
-152820, Sho 53-68619, Sho 54-137
There are 429 etc. In particular, the latter patent application publication shows that sand for casting is mixed with a divalent or trivalent metal oxide or hydroxide in advance, and dicarboxylic acid or polycarboxylic acid is added to the sand for sand removal. It is a method of hardening. However, the methods currently used, unlike these, use the furan-sulfonic acid system. There are various reasons for this, but the workability is not good. In addition, the strong point of the furan type is that when sand that has been once solidified is used again, it is necessary to crush the solidified sand and remove the furan resin, which causes the generation of fine powder. This is becoming a big problem recently due to the environment inside the factory. In addition, the fact that the once solidified furan resin cannot be reused is a cost issue. However, it is a fact that no system superior to the furan-sulfonic acid system existed despite these problems.

[0003]

The object of the present invention is to solve the problems of the furan system and the problems of the conventional polycarboxylic acid system, and to establish a more effective method for producing a sand mold for casting.

[0004]

In order to solve the above-mentioned problems, the present inventor re-tested the conventionally proposed methods, and as a result of earnestly devoting himself to the research of a new method that eliminates the problems, Arrived That is, the means adopted by the present invention to solve the problem is to employ a compound which has not been used in the conventional method and a work procedure which has not been carried out in the conventional method. More specifically, for example, a water-soluble polymer compound such as sodium polyacrylate and an inorganic compound such as magnesium chloride are previously reacted in an aqueous system to prepare an inorganic-organic composite. This step was not used in the conventional method, and of course magnesium chloride was not used in the conventional method. Then, the resulting inorganic-organic composite system is mixed with sand and subjected to predetermined molding. The water content of the system may be suitable for the molding operation. Furthermore, by controlling the water content of the system, it became possible to freely control the hardness of the sand mold from a maximum of 88 kg / cm ² in compressive strength to a level at which it can be easily broken with a fingertip. As a result, the sand mold that was used once could easily be used repeatedly by simply controlling the water content of the system and adding the amount of the complex burned out by contact with hot water. That is, the problems of the conventional method of manufacturing a sand mold for foundry can be solved by the present invention. Of course, what is shown here is only a specific example, and the present invention is not limited to this example.

[0005]

The operation of the means adopted by the present invention to solve the problems will be described. The basic action is to make an inorganic-organic composite having a binding effect, make it into a sol state and mix it uniformly with sand, and then collect the composite at the contact points of sand particles by controlling the water content of the system. The solidifying action is to create a solid sand mold by changing the sol to a gel state and exerting the binding force. Next, by increasing the water content of the solid sand mold, the gel of the complex at the contact point of the sand particles changes to the sol state and the binding force disappears, and the sand returns to the state before molding. What the present inventor has adopted as an inorganic-organic composite having a binding effect is a composite prepared by reacting a water-soluble inorganic compound and an organic polymer compound in an aqueous system. In particular, one or more of magnesium chloride, magnesium nitrate, and magnesium sulfate as an inorganic compound is reacted with one or more of polyalginic acid, polyacrylic acid, polymethacrylic acid, and its soda salt as an organic polymer compound in an aqueous system. The complex made by the method is effective. An example will be described below.

[0006]

【Example】

1. An inorganic-organic composite was prepared by premixing 360 liters of silica sand with 16 liters of a 40% aqueous solution of sodium polyacrylate having a degree of polymerization of 400 and 15 liters of a 50% aqueous solution of magnesium chloride hexahydrate, for a total of 31 liters. Add and stir well. Next, a square with an edge of 800 mm and a depth of 400 mm has an inner side length of 300 m in the upper center part.
m, the length of the outer side was 400 mm, and the height was 250 mm. Then, silica sand mixed with the inorganic-organic composite was packed around the wooden mold. The four corners of this wood pattern have different R's and are designed to observe the occurrence of hot cracking in castings. After leaving this system in air with a relative humidity of 40% for 24 hours, remove the external mold, and after leaving it under the same conditions for 24 hours, remove the wooden mold to make a mold and inject 120 kg of hot water of Cr-Mo iron. did. After the casting has cooled down, the original mold is assembled and the relative humidity is adjusted to 10
The casting was taken out after being placed in 0% air for 5 hours, but the sand in the mold was easily broken at that time, and the casting was easily taken out. Next, we investigated in detail the shrinkage, dimensional stability, presence of hot cracks, sand seizure, surface properties, internal properties, etc. of castings, but using the furan-sulfonic acid system currently in use. It was compared with the properties of the castings cast by the mold, but there was no change.

Next, a test of reusing the sand once used was conducted. First, 17 liters of tap water alone was added to the sand used, and the mixture was agitated so as to be uniform, and a mold was prepared by the same procedure as described at the beginning of this example.
0 kg was cast. As a result of inspecting the casting process and various properties of the casting, there was no difference from the first time.

Next, the sand used twice was premixed with 1.5 liters of a 40% aqueous solution of sodium polyacrylate having a degree of polymerization of 400 and 1.5 liters of a 50% aqueous solution of magnesium chloride hexahydrate. -Add 3 liters of the organic composite made up to 17 liters by diluting it with tap water, mix well and homogenize it, then make a casting by the same procedure as described above and check its physical properties. As a result of the measurement, there was no difference from the first one. Similarly, just add the inorganic-organic composite as a binder using the same sand.
The casting test was conducted up to the number of times, and the results were all good.

2. Furthermore, 7 ml of an aqueous sol of an inorganic-organic composite made from a combination of an inorganic compound and an organic polymer compound shown in Table 1 was added to 0.5 g by weight with respect to 100 g of sand, and uniformly added. After mixing, the mixture was molded into a predetermined shape, the water content of the system was adjusted to the range of 1.9% to 0.5%, and the compression strength of the molded product was measured. To 100 g of the sample after the measurement, 6 ml of water was added, and the mixture was uniformly mixed and molded again to adjust the water content, and then the compressive strength thereof was measured. The test was repeated 7 times in the same procedure. In Table 1,
The results of the first and seventh compression strength measurements are shown as the first and seventh times. Among the organic polymer compounds shown in Table 1, those having a degree of polymerization of sodium polyacrylate of 400, those having a degree of polymerization of sodium polyalginate and polyalginic acid of about 1800, sodium polymethacrylate, polymethacrylic acid The polymerization degree of was about 2000.

[0010]

The effect of the present invention is, as shown in the above embodiment, a simpler process than the conventional method, and a sand solidification method which is superior from the environmental point of view and from the cost point of view. That's what we could provide.

Claims (2)

[Claims] 1. A mixture of an inorganic-organic complex prepared by reacting a water-soluble inorganic compound and an organic polymer compound in water with sand to cause a gel-sol change in the complex by controlling the water content of the system. The method for solidifying sand is characterized in that the cycle of solidification-softening of sand is repeatedly controlled by. 2. One or more of magnesium chloride, magnesium nitrate, and magnesium sulfate are used as the inorganic compound, and the organic polymer compound has a degree of polymerization of 50 or more.
The method for solidifying sand according to claim 1, wherein one or more kinds of polyalginic acid, polyacrylic acid, polymethacrylic acid or a soda salt of 500 or less is used to react in an aqueous system.