JPS5937139B2 - foundry sand binder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a binder for fixing foundry sand.

Conventionally, in order to manufacture special molds for casting, sand is mixed with various binders of inorganic or organic materials and molded.

In this case, each of these various inorganic or organic binders has advantages and disadvantages, and cannot be used for sand molds of all metal castings.

For example, in the case of gas-type water glass, when the used sand is discarded, the water glass adhered to the surface of the sand gradually dissolves and alkaline substances are eluted, making the surrounding soil alkaline.

As a result, not only do plants wither away, but also organisms living in the soil and water die.

Due to these pollution problems, there is a need for a foundry sand binder that can replace water glass.

As one solution to this problem, organic binders made from self-hardening furan or phenol are attracting attention, and such organic binders can remove organic substances by rubbing or burning sand after use. Sand can also be reused, but it produces a foul odor when burned.

Furthermore, the hardening speed of the binder and the mechanical strength of the mold vary considerably depending on factors such as the properties of the sand, water content, temperature, humidity, and the type and concentration of the acid used as a hardening agent, making handling difficult.

In addition, since the binder raw material undergoes gradual polymerization during its storage period, it has the disadvantage that it must be consumed within one year after production.

The inventor of the present invention made extensive studies to create an organic foundry sand binder that does not have the above-mentioned drawbacks, and as a result, discovered that a water-soluble styrene-maleic acid copolymer has extremely good properties as a foundry sand binder. This led to the completion of the present invention.

That is, the gist of the present invention is that the sodium salt of styrene-maleic acid copolymer is dissolved in an aqueous solution with a hydrogen ion concentration of 10-8 or less, and the content of the sodium salt is 25 to 55% by weight. A foundry sand binder characterized by:

The styrene-maleic acid copolymer used in the present invention is a copolymer of styrene and a maleic acid compound, and the maleic acid compound refers to maleic anhydride, maleic acid,
It is a general term for maleic acid esters, etc.

Any known method may be used to copolymerize styrene and a maleic acid compound. For example, styrene, a maleic acid compound, and a catalyst such as azobisisobutyronitrile are added to an organic solvent such as butyl acetate. A copolymerization reaction is carried out by heating to 95° C. for several hours, and after the reaction is completed, a styrene-maleic acid copolymer is obtained by removing with a solvent.

Next, the styrene-maleic acid copolymer is made into a sodium salt by reacting some or all of the carboxyl groups of the copolymer with sodium such as sodium hydroxide.

In addition, depending on the physical properties required for the foundry sand binder, a part of the styrene-maleic acid copolymer may be mixed with toehamethyl alcohol, ethyl alcohol, butyl alcohol, isobutyl alcohol, lauryl alcohol, β-hydroxyethyl methacrylate, Esterification may be performed with a compound having a hydroxyl group such as β-hydroxypropyl acrylate.

In the present invention, the styrene-maleic acid copolymer salt is dissolved in water, the hydrogen ion concentration of the aqueous solution is 10-8 or less, and the sodium salt concentration is 25-5.
Although the method for producing the aqueous solution is not limited in any way, for example, it is preferable to raise the water temperature to a high temperature to facilitate dissolution, and to avoid excessive hydroxylation. This is preferred because after dissolving sodium in water, the styrene-maleic acid copolymer is easily dissolved and a sodium salt is produced.

The hydrogen ion concentration of the aqueous solution is 10-8 or less because the sodium salt of styrene-maleic acid copolymer is difficult to dissolve on the acidic side, and in order to dissolve 25% by weight or more, P is required.
This is because H must be 8 or more, that is, the hydrogen ion concentration must be 10-8 or less.

In addition, the concentration of the sodium salt in the aqueous solution is 25 to 55% by weight because, in order to bond the foundry sand, about 2 parts by weight of the sodium salt is required per 100 parts by weight of the foundry sand, but when the concentration is low, In the case of an aqueous solution, a large amount of aqueous solution is required, which not only makes drying difficult, but also because the sodium salts precipitate to the bottom during drying, making it difficult to adhere uniformly. Foundry sand increases in viscosity of aqueous solution.

This is because it becomes difficult to mix uniformly with

More preferably, the concentration of the aqueous solution is 30 to 45% by weight.

Next, a method of using the binder of the present invention will be explained.

Add 3.5 to 10 parts by weight of this aqueous solution to 100 parts by weight of silica sand, mix thoroughly to obtain a mixture, pour this mixture into a mold-like mold, mold, remove the mold, and dry. to prepare a mold.

At this time, any known drying method may be used (for example, placing the mold in a drying oven, blowing hot air on it, placing it in a high-frequency heater, or leaving it to air dry after making the mold). can give.

Next, molten metal or the like is poured into the completed mold, and after cooling, the mold is destroyed to obtain a casting.

At this time, any known method may be used to destroy the mold, and since the binder of the present invention is water-soluble, the mold will easily collapse even when immersed in water.

The structure of the present invention is as described above, and since the binder is made of a specific water-soluble polymer, this binder aqueous solution is very stable and will not change in any way even if left for one year. Furthermore, it has almost no odor or toxicity and is very easy to handle.

Further, since the concentration is as high as 25 to 55% by weight, uniform mixing with silica sand is easy, and drying is also easy, resulting in good workability.

In addition, there is almost no sand attached to the castings during the manufacturing process.
Furthermore, since the mold after casting can be immersed in water and disintegrated, there is no generation of dust and the working environment is improved.

In addition, the sand in the mold after destruction can be easily reused by washing with water, burning, etc., and when burning, SOx, NOx, and HCI are removed.
There is no generation of toxic gases such as

Next, examples of the present invention will be described.

Note that the counter pressure was measured according to JIS-Z-2604 (strength testing method for foundry sand).

Further, hereinafter, the term "parts" simply means "parts by weight."

Example 1 After heating an aqueous solution obtained by dissolving 30 parts of granular sodium hydroxide in 300 parts of water to 80°C, 250 parts of a styrene-maleic acid copolymer was gradually added with stirring, and then 280 parts of water was added. An aqueous solution containing 32 parts of granular sodium hydroxide dissolved therein was added thereto, and 100 parts of a styrene-maleic acid copolymer was gradually added thereto, followed by stirring at 80° C. for about 2 hours.

Thereafter, the mixture was allowed to cool to obtain a foundry sand binder having a sodium salt concentration of styrene-maleic acid copolymer of 40% by weight, a viscosity of 4000 centipoise, and a hydrogen ion concentration of 10-10.

5 parts of the above binder was added to 100 parts of silica sand and mixed thoroughly so that the binder would adhere uniformly to the surface of the silica sand.The resulting mixture was poured into a mold and tamped.

After tamping, the mold was removed to obtain a mold, and the resistance pressure of the mold was measured and found to be 100 P/c4.

This mold was dried by supplying it to a hot air dryer to obtain a dry mold, and the resistance pressure of this mold was measured and was 9/20.
It was CVT.

1300 in the mold after drying obtained by the above method.
℃ molten pig iron was poured and then cooled.

After cooling, this mold was immersed in water, and the mold collapsed easily, yielding a casting with a beautiful surface.

Almost no dust was generated during this work, and the borax in the water could be reused by washing with water.

Example 2 After heating an aqueous solution obtained by dissolving 4 parts of granular sodium hydroxide in 700 parts of water to 80°C, 300 parts of a sodium salt of styrene-maleic acid copolymer was gradually added while stirring.

After the addition, the mixture was stirred for 2 hours and then allowed to cool to obtain a foundry sand binder having a sodium salt concentration of styrene-maleic acid copolymer of 30%, a viscosity of 800 centipoise, and a hydrogen ion concentration of 10-9.

Example 1: 6 parts of the above binder was added to 100 parts of silica sand.
A mold was obtained in the same manner as in .

Is the resistance pressure before drying 90? /cwt, the counter pressure after drying is 1
It was 5 kg/crA.

Molten pig iron at 1300°C was poured into the mold, and then cooled.

After cooling, when this mold was sprayed with a small amount of water, everything collapsed except for the blackened part.

When the blackened part was peeled off, a casting with a beautiful surface was obtained.

Almost no dust was generated during this process, and the parts that had not turned black could be reused by simply adding a small amount of binder.

Furthermore, the blackened parts could be reused by processing them with a recycling machine.

Example 3 After heating an aqueous solution obtained by dissolving 40 parts of granular sodium hydroxide in 300 parts of water to 85°C, 250 parts of a styrene-maleic acid copolymer was gradually added with stirring, and then 230 parts of water was heated to 85°C. An aqueous solution containing 23 parts of granular sodium hydroxide dissolved therein was added thereto, and 150 parts of a styrene-maleic acid copolymer was gradually added thereto, followed by stirring at 85° C. for about 3 hours.

Thereafter, the mixture was allowed to cool to obtain a foundry sand binder having a sodium salt concentration of styrene-maleic acid copolymer of 45% by weight, a viscosity of 10,000 centipoise, and a hydrogen ion concentration of 1 ()-10.

Three parts of the above binder heated to 50° C. was added to 100 parts of silica sand, and a mold before drying was obtained in the same manner as in Example 1.

Is the counter pressure 300? /cfL.

When the mold was supplied to a microwave oven and dried, the resistive pressure of the dried mold was 20 kg/crA.

Molten pig iron was poured into this mold at 1.300°C, and then cooled.

After cooling, when the mold was broken down with a hammer, it collapsed easily and a casting with a beautiful surface was obtained.

The collapsed sand could be reused in the same manner as in Example 2.

Claims (1)

[Claims] 1. An aqueous solution in which a sodium salt of a styrene-maleic acid copolymer is dissolved and the hydrogen ion concentration is 10-8 or less, and the content of the sodium salt is 25 to 55% by weight. A foundry sand binder characterized by: 2. The foundry sand binder according to claim 1, wherein the sodium salt concentration is 30 to 45% by weight.