JPS6234645A - Production of sand mold for casting - Google Patents

Abstract

PURPOSE:To obtain a sand mold which has excellent dry strength and is used for production of a casting having high quality and high accuracy by using the alkaline (earth) metallic salt of the hydrolyzate of a butadiene/maleic anhydride copolymer having specific pH as a binder for molding sand. CONSTITUTION:The aq. soln. of the alkaline or alkaline earth metallic salt of the hydrolyzate of the butadiene/maleic anhydride copolymer having <=6pH is mixed with the molding sand in such a manner that the metallic salt of the above-mentioned hydrolyzate is incorporated at 0.1-5pts.wt. in 100pts.wt. molding sand. The sand mold for casting is produced by molding such mixture, then drying and curing the same by heating. This sand mold has all of the advantages of the conventional sand mold for which a maleic anhydride copolymer, etc. are used. The butadiene/maleic anhydride copolymer is dissolved in water to obtain the above-mentioned aq. soln., then the copolymer becomes the hydrolyzate and the aq. soln. thereof is obtd. The oxide, hydroxide, etc. of the alkaline (earth) metal are added thereto control the pH thereof to <=6.

Description

Detailed Description of the Invention 3. Revised Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing river sand for casting. For more details, see p.
An aqueous solution of an alkali or alkaline earth metal salt of a hydrolyzate of a butadiene/maleic anhydride copolymer of H5 or less is mixed with 0.1 to 5 parts by weight of the metal salt of the hydrolyzate per 100 parts by weight of foundry sand. The present invention relates to a method for producing foundry river sand, which is characterized in that it is mixed with foundry sand so as to have the following properties, and then heated and dried after molding to harden it.

[Prior art and its problems] Conventionally, in order to manufacture sand molds for foundries, an inorganic or organic binder is mixed with foundry sand such as silica sand,
This is done by molding and curing.

In this case, each of these various binders has advantages and disadvantages.

For example, in the case of water glass, if you discard the used sand mold,
Because the water glass that adheres to the sand surface is alkaline,
It may contaminate the soil around the disposal. Due to such pollution problems, there is a demand for the development of a cast iron Sunagawa binder to replace water glass.

As one solution to this problem, organic binders made from self-hardening furan resins or phenolic resins are attracting attention. These organic binders crush the sand after use,
Since the organic binder is removed by friction or combustion, there is an advantage that the foundry sand can be reused. However, operations such as crushing and friction are troublesome, and they also have drawbacks such as emitting a bad odor when burned. Furthermore, the hardening speed of the binder and the mechanical strength of the sand mold vary significantly depending on factors such as the properties of the foundry sand, water content, temperature, humidity, type of acid used as a hardening agent, and its temperature of 11 degrees, making handling difficult. Furthermore, since the polymerization of the binder raw material is gradually accelerated during storage, it has the disadvantage that it must be washed within a year after production. Copolymers of α-olefins such as isobutylene and maleic anhydride have also been proposed as organic binders. Such water-soluble polymers using maleic anhydride and the like not only eliminate the above-mentioned drawbacks, but also are desirable because they are easy to regenerate molds and are easy to mix with various other polymers. has been done. However, with the method of using a binder made of the copolymer described above, it is not possible to obtain a sand mold with great strength.Nowadays, when high-quality and high-precision castings are required, medium-sized and large-sized sand molds, J3 In sand molds for castings, which require high precision, self-hardening organic binders such as furan resins are intentionally used in hopes of improving the above-mentioned drawbacks.

[Means for Solving the Problems] An object of the present invention is to propose a new method that eliminates the drawbacks of the above-mentioned conventional methods for manufacturing foundry sand molds.

In other words, the sand mold obtained by the present invention has the advantages of conventionally proposed sand molds using maleic anhydride copolymers, etc., has excellent dry strength, and is suitable for high-quality, high-precision castings. Can be used for visiting.

The present invention will be explained in more detail below.

In the present invention, an aqueous solution of an alkali or alkaline earth metal salt of a hydrolyzate of a butadiene/maleic anhydride copolymer of 1116 or less is mixed with 0.0. The present invention relates to a method for manufacturing a foundry sand mold, characterized in that it is mixed with foundry sand in an amount of 1 to 5 parts by weight, and after molding, it is heated and dried to harden it.

The butadiene/maleic anhydride copolymer of the present invention contains approximately 50 mol% maleic anhydride units, and
Its manufacture is, for example, by combining butadiene and maleic anhydride in a polar solvent such as acetone, methyl ethyl ketone, cyclohexanone, dioxane, demethylformamide, a non-polar solvent such as benvin, or a mixture thereof. Copolymerization is carried out by a method such as solution polymerization or slurry polymerization using a radical polymerization initiator such as benzoyl oxide or azobisisobutyronitrile.

After the reaction is completed, the solvent is removed to obtain a copolymer. The butadiene/maleic anhydride copolymer in the present invention usually has a molecular weight of about 3,000 to 300,000. When this copolymer is dissolved in water,! ! I anhydrous base is cleaved to become a carboxyl group and a hydrolyzate is obtained. Practically speaking, in the case of solution polymerization, it is convenient to remove the reaction solvent by steam stripping because an aqueous solution of the hydrolyzate can be obtained simultaneously with the removal of the solvent. however,
To obtain an aqueous solution of the hydrolyzate, the copolymer obtained by the above method may be isolated and redissolved in water. This aqueous solution is neutralized by adding metal compounds exhibiting alkaline properties such as alkali or alkaline earth metal oxides or hydroxides, such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, and magnesium oxide. For example, 1 u of the desired aqueous solution is added. However, 1) 11 of the aqueous solution obtained at this time must be 6 or less. pH is 6
If it is larger, sufficient dry strength will not appear. The aqueous solution of the metal salt of the hydrolyzate of the butadiene/maleic anhydride copolymer of the present invention is No. 11! is 5 to 50%, preferably 1
Preferably, 5 to 40% by weight is used. 5
If the weight is less than % by weight, curing strength is insufficient and heat curing takes time, which is not preferable. Also, 50E:Ql
If the solid content exceeds 1%, the aqueous solution becomes too viscous and difficult to operate, which is also not preferred.

The aqueous solution of the present invention has a solid content of 0.1 to 5 parts, preferably 0.3 to 3 parts per 100 parts of foundry sand, and is moistened with foundry sand and placed in a mold. After that, heat and dry to harden and create a foundry sand mold! li build.

If the amount is less than 0.1 part, the curing strength will be insufficient, which is not preferable.

Further, even if more than 51 hanging parts are used, no particular increase in hardening can be expected, which may be uneconomical.

In the present invention, after mixing foundry sand and the aqueous solution, the mixture is filled into a mold and hardened. It is also possible to heat and dry the product while it is in the mold, without removing it from the mold. Further, after pressurization or compression molding, the mold may be removed and dried by heating. In this case, in order to improve the wet strength, conventionally known additives,
For example, starch, oxalic acid, sodium perborate, etc. may be appropriately mixed and used.

However, since the mixture of foundry sand and the above-mentioned aqueous solution in the present invention has better fluidity than conventional products, it can be molded by hand or by a molding device using pressurized vibration, vacuum suction pressure, etc. Further, the heating operation can be performed by any method, such as vacuum heating drying method, method using a heating furnace, method using hot air drying at a temperature of 50 to 200°C for 0.5 to 10 minutes, or Any method such as a method using microwave heating, dielectric heating, etc. can be used. In particular, heating operations using hot air drying, microwave heating, or dielectric heating are preferred because of their good dry strength and curing speed.

[Effects of the Invention] The sand mold obtained by the present invention has high dry strength and can be used for casting high-quality, high-precision castings.

Furthermore, sufficient dry strength can be obtained even if the amount of organic binder used as a solid content is small, so it is economical. The mixture of the organic binder aqueous solution and foundry sand in the present invention has better fluidity than conventional products, so it can be easily and sufficiently molded. In other words, manual or pressurized
Molding can also be performed using a molding device that uses vacuum suction pressure. In this case, there is no need for high pressure, so complex and highly accurate sand molds can be made even when molded using a model with low pressure resistance, such as a wooden mold.

Since the residual strength (after casting) of the sand mold obtained by the present invention is appropriate, it is easy to destroy the sand mold after use (after casting), and the used sand can be reused.

In addition, pollution problems caused by used sand, such as soil contamination,
It does not cause odor problems during combustion.

[Example] Next, the present invention will be explained in more detail with reference to Examples.

Example 1 (Preparation of binder) Butadiene and maleic anhydride were reacted in acetone using radical catalytic tIR (azobisisobutyronitrile) to obtain an acetone solution of a butadiene/maleic anhydride copolymer. The molecular weight of the copolymer is approximately 30,000, and the content of maleic anhydride units in the copolymer is approximately 50E-le%.
Met.

Next, water vapor was blown into the above acetone solution to distill off the acetone and cleave the acid anhydride groups in the copolymer, thereby obtaining an aqueous solution of a hydrolyzate of a butadiene/maleic anhydride copolymer. According to IR analysis, almost all of the acid anhydride groups in the copolymer were cleaved to become carboxyl groups. A tropic soda was added to this aqueous solution to neutralize a portion of the carboxyl groups to obtain an aqueous solution of the sodium salt of a hydrolyzate of a butadiene/maleic anhydride copolymer with a DH of 3.5.

(Binder Test) The concentration of the aqueous solution of the sodium salt of the hydrolyzate obtained as described above was adjusted to 25% by weight, and the solution was kneaded with silica sand at the solid proportions shown in the following table. This mixture was fluid.

Next, a SOWφX 50 jlN mold for preparing a test piece was poured into a mold, filled and molded, and the mold was heated and dried in a microwave oven (0.5 kw) for 10 minutes without demolding. After heating and drying, the test piece was taken out and its dry strength was measured. The results are shown in the table below.

Loading soda was added to an aqueous solution of a hydrolyzate of a butadiene/maleic anhydride copolymer obtained in the same manner as in Example 1 to neutralize the solution to pH 7.0. Using this aqueous solution, a binder test was conducted in the same manner as in Example 1.
Even if 1.0 part by weight of solids was used for the 0Φ hanging part, the dry strength of the test piece was only 0.5 Kg/cta culm degree.

Claims (1)

[Claims] An aqueous solution of an alkali or alkaline earth metal salt of a hydrolyzate of a butadiene/maleic anhydride copolymer having a pH of 6 or less is mixed with 0.1 to 5 parts by weight of the metal salt of the hydrolyzate per 100 parts by weight of foundry sand. A method for producing a foundry sand mold, which comprises mixing the foundry sand with foundry sand so as to give the following properties, and heating and drying it after molding to harden it.