JPS5812095B2 - Foundry sand composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a foundry sand composition used in forming a foundry mold, and more particularly to a composition that exhibits good disintegration properties after casting.

In order to obtain a casting mold using such foundry sand, for example, when using a shell molding method, the sand is generally hardened and molded with a binder containing a phenolic resin as a main component.

Incidentally, the mold thus obtained has good disintegration properties after casting when the molten metal temperature exceeds 1,000°C, such as cast iron, but when the molten metal temperature exceeds 700°C, such as aluminum. This disintegration property is poor at relatively low temperatures such as

Therefore, if the core has poor collapsibility, a part of the mold may remain attached to the inside of the casting.
Although the collapsibility of such molds has been improved by sand baking after casting, using coarse silica sand with high SiO2 purity, and reducing the amount of binder added, Firing requires a large amount of thermal energy, and when coarse silica sand is used to reduce the amount of binder, there are drawbacks such as the casting surface becoming more likely to become rough.

In addition, various studies have been made to create molds with good disintegration properties after casting, but no means that are sufficiently effective have yet been found.

In the first place, in order for the core surrounded by molten metal to collapse after pouring, the binder in the sand must decompose in a reducing atmosphere and lose its bonding strength, but this binder is an organic substance such as a cured phenolic resin. In some cases, they are more likely to decompose in an oxidizing atmosphere than in a reducing atmosphere.

To this end, a method has been proposed in which the binder is oxidized and decomposed by adding a substance that releases oxygen through thermal decomposition to bring it closer to an oxidizing atmosphere, thereby improving the collapsibility of the mold.

There have been several reports on the use of such substances; for example, there is an example of the use of zinc carbonate in Japanese Patent Publication No. 54-162622. (b) Scales that easily collapse when external force is applied to the mold after pouring, even when cast at a relatively low temperature, such as in aluminum alloys. (c) The baked sand after disintegration should not contain harmful substances, and (c) When the temperature of the mold increases during casting or immediately after casting, large amounts of gases that are undesirable to the human body, such as bad odors, will not be emitted. It is stated that the following conditions are satisfied.

However, the disintegration properties of the mold after casting using zinc carbonate are good only when a specific organic material such as polyester resin is used as a binder. For phenolic resins, the disintegration promoting effect of zinc carbonate is extremely small.

However, the present inventors have found that foundry sand using a specific dicarboxylic acid derivative as an organic binder has excellent mold disintegration properties after casting, and particularly when using a phenolic resin as a binder, mold sand does not disintegrate after casting. We have discovered that it is possible to create molds with excellent disintegration properties.

That is, the present invention uses an organic substance as a binder, and adds a dicarboxylic acid metal having a carbon number of 4 or less to 100 parts by weight of the binder to foundry river sand that can be hardened by heating to form a mold. The present invention provides a foundry sand composition comprising 0.5 to 30 parts by weight of a salt, a metal hydrogen salt, or a hydrate thereof.

Here, representative examples of the metal salts or metal hydrogen salts of the above-mentioned dicarboxylic acids or their hydrates include lead oxalate, lead oxalate, potassium oxalate, nickel oxalate, strontium oxalate, potassium oxyhydrogen, potassium tartrate or sodium hydrogen tartrate, and their hydrates,
Among these, particularly preferable ones are
It is a compound that has a decomposition point of 00°C or less.

These dicarboxylic acid derivatives can be used alone or in combination of two or more.

The reason why dicarboxylic acid derivatives are limited to compounds having 4 or less carbon atoms is thought to be that the compounds that act as a type of oxygen supplying agent contain a large proportion of oxygen atoms in the molecule.

In fact, not only dicarboxylic acids, but even monocarboxylic acids, if the number of carbon atoms exceeds 5, their ability as oxygen supplying agents decreases, making them unsuitable for the purpose of the present invention. Although there are 4 compounds that contain many oxygen atoms in their molecular structure, such as 4 compounds, they cannot be used because they generate highly toxic decomposition gas.

On the other hand, typical organic substances that are binder components of the composition of the present invention include novolac type phenolic resins, resol type phenolic resins, polyester resins, furan resins, urea resins, polyisocyanates, and starch. etc.

The composition of the present invention comprises as main components each of the above-mentioned organic binders and dicarboxylic acid derivatives such as metal salts, metal hydride salts or hydrates of dicarboxylic acids, and the dicarboxylic acid derivative to be used depends on the hardening temperature of the foundry sand, and it is necessary to use a compound with a decomposition point higher than this hardening temperature.By doing this, the decomposition of the dicarboxylic acid derivative during molding can proceed. This ensures that the mold collapses sufficiently after casting.

Although various methods can be used to obtain the composition of the present invention, the following methods are suitable.

(1) Either the dicarboxylic acid derivative is dissolved or dispersed in the organic binder in advance and sand is mixed therein, or the binder obtained by dissolving or dispersing the dicarboxylic acid derivative is added to the sand. (2) A method of mixing an organic binder and sand or adding a dicarboxylic acid derivative during the process of coating the sand with the binder; (3) A method of adding a dicarboxylic acid derivative to sand to which dicarboxylic acid derivative 6 has been added in advance. (4) a method of coating or mixing an organic binder; and (4) a method of mixing a dicarboxylic acid derivative with foundry river sand containing an organic binder.

The amount of the dicarboxylic acid derivative used in obtaining the composition of the present invention by these various methods is 0.5 to 3 parts by weight per 100 parts by weight of the organic binder described above.
A suitable amount is 0 parts by weight, preferably 2 to 10 parts by weight.

If the amount of this dicarboxylic acid derivative used is too small, the collapsibility of the mold after casting will be poor, while if it is too large, the fusion point of the foundry sand will be lowered and the strength of the mold after molding will be reduced. Neither is preferable.

It goes without saying that a known and commonly used filler can be added to the thus obtained composition of the present invention, and the composition of the present invention is mainly used for casting aluminum and furthermore copper alloys.

Next, the present invention will be explained in detail with reference to Examples and Comparative Examples, as well as application test results obtained on each side. In the following, parts mean parts by weight unless otherwise specified. .

Example 1 SiO2 purity is 99 which was heated to 150°C in advance
% or more, and the AFS particle size index is 60±3 (hereinafter referred to as
This is simply abbreviated as silica sand.

), 100 copies of “Found Lets TD-3402
2.5 parts of "-B" (novolac type phenolic resin manufactured by Inu Nippon Ink Chemical Industry ■) and 0.0 parts of silver oxalate 1/2 hydrate.
15 parts and kneaded for 1 minute using a whirl mixer.

Next, hexamethylenetetramine (hereinafter abbreviated as hexamine) was added to this.

) A hexamine solution prepared by dissolving 0.375 parts in 1.5 parts of water was added and kneaded for 1 minute, and then 0.1 part of calcium stearate was added and kneaded for 20 seconds to obtain a foundry sand composition. Ta.

Example 2 2.5 parts of Foundrez TD-3402-Bj was added to 100 parts of silica sand preheated to 150°C and kneaded for 1 minute using a whirl mixer, and then 0.375 parts of hexamine was added to the mixture. A solution of 0.15 parts of potassium hydrogen oxalate and 0.15 parts of potassium hydrogen oxalate dissolved in 1.5 parts of water was added and kneaded for 1 minute, and then 0.1 part of calcium stearate was added and kneaded for 20 seconds to obtain the foundry sand composition. I got something.

Example 3 100 parts of "Found Drets TD-3402-B" was heated to 150°C to melt it, then 6 parts of nickel oxalate dihydrate was added, stirred well to mix uniformly, and cooled. A resin composition was obtained.

Separately, 2.65 parts of the resin composition was coarsely crushed so as to pass through a 3-mesh sieve and remain on a 20-mesh sieve, and added to 100 parts of silica sand preheated to 150°C. The mixture was kneaded with a mixer for 1 minute.

Thereafter, the same operations as in Example 1 were repeated to obtain a foundry sand composition.

Example 4 Except that potassium hydrogen oxalate was added by using 0.15 parts per 103 parts of resin-coated sand obtained after performing the same operation as in Example 2 up to the addition of calcium stearate. A foundry composition was obtained in the same manner as in Example 2.

Example 5 100 parts of phenol, 120 parts of 37% formaldehyde aqueous solution and 12 parts of 25% ammonia aqueous solution were mixed into 65%
After reacting at 150°C for 2 hours, low-boiling substances such as water and unreacted substances present in the reaction solution were removed by vacuum distillation, and the mixture was taken out when the gelation time at 150°C reached 90 seconds. The mixture was immediately cooled to obtain a solid resol type phenol resin having a softening point of 85°C.

Separately, 2.5 parts of solid resol type phenolic resin was crushed into 100 parts of silica sand that had been heated to 150°C in advance so that it passed through a 3-mesh sieve and remained on a 20-mesh sieve. The mixture was added and kneaded for 1 minute using a whirl mixer.

Next, 1.5 parts of water and 0.15 parts of silver oxalate 1/2 hydrate were added and kneaded for 1 minute, and further 0.1 part of calcium stearate was added and kneaded for 20 seconds to form a casting. A sand composition was obtained.

Example 6 To 100 parts of silica sand preheated to 170°C, 3
．． 0 parts polyester resin and 0.15 parts silver oxalate 1
/dihydrate and kneaded for 1 minute using a whirl mixer.

Then, tert-butyl perbenzoate 0
．． 3 parts by adding 0.03 parts and 0.09 parts of dicumyl peroxide.
The mixture was kneaded for 30 seconds, and 0.1 part of calcium stearate was further added and kneaded for 20 seconds to obtain a foundry sand composition.

The above polyester resin used in this example was a mixture of 95 parts of "Panolac BA-223" (polyester resin manufactured by Dainippon Ink & Chemicals) and 5 parts of diallyl phthalate, and the resulting mixture was sieved through 3 meshes. passing through 20
It is coarsely crushed so that it remains on the mesh sieve.

Comparative Example 1 A foundry sand composition was obtained by repeating the same operation as in Example 1, except that no silver oxalate hemihydrate was used.

Comparative Example 2 A foundry sand composition was obtained in the same manner as in Example 1, except that the same amount of basic zinc carbonate was used in place of silver oxalate hemihydrate.

Comparative Example 3 A foundry sand composition was obtained in the same manner as in Example 5, except that the use of silver oxalate hemihydrate was completely omitted.

Comparative Example 4 A foundry sand composition was obtained in the same manner as in Example 6, except that no silver oxalate hemihydrate was used.

Comparative Example 5 A foundry sand composition was obtained in the same manner as in Example 6, except that the same amount of basic zinc carbonate was used instead of silver oxalate hemihydrate.

Using the various foundry sand compositions obtained in Examples 1 to 6 and Comparative Examples 1 to 5, applied tests were conducted on the following items: fusion point, bending strength, and collapsibility.

The test procedures are shown below, and the test results are summarized in Table 1.

The melting point was measured according to JACT (Japan Manufacturing Technology Association) test method C-1.

Bending strength was measured according to JIS K-6910, but in Example 1
For the foundry sand compositions obtained in ~5 and Comparative Examples 1 to 3, test pieces were prepared with a mold temperature of 250°C and a firing time of 60 seconds; For the compositions obtained in steps 4 and 5, the mold temperature was
A test piece was prepared at a temperature of 90° C. and a firing time of 150 seconds.

For the foundry sand compositions obtained in Disintegration Examples 1 to 5 and Comparative Examples 1 to 3, each composition was individually heated at 230°C.
After pouring into a mold heated to
A test piece of 85 parts Mtφ×10 m was prepared by firing in a furnace at 0° C. for 1 minute.

On the other hand, it was obtained in Example 6 and Comparative Examples 4 and 5.

For compositions, each composition separately, 190
After pouring into a mold heated to ℃ and holding for 3 minutes,
Baked for 2 minutes in a 50℃ oven to 85mmφX10mm
A test piece was prepared.

The 11 types of test pieces thus obtained were individually wrapped in aluminum foil and placed in a furnace at 500°C for 20 minutes.
After leaving the heat-treated test piece in this way, the sand was removed using a rotary sieve on a 10-mesh sieve. For each test piece, either measure the amount of sand (in seconds) or measure the ratio (% value) of the amount of sand falling 4 minutes after sand removal starts to the weight of the test piece before sand removal starts. The test was carried out four times and the average value was taken as the disintegration value.

Example 7 100 parts of silica sand and 0.5 parts of "Catalyst PD-2"
(Hardening agent manufactured by Inu Nippon Ink Chemical Industry ■) in a Whirl mixer for 1 minute, and then 0.08 parts of potassium tartrate and [Foundrets TD-807-2.0 parts were added to give 1. The mixture was kneaded for a minute to obtain a cast river sand resin composition.

Comparative Example 6 A foundry river sand resin composition was obtained by repeating the same operation as in Example 7 except that potassium tartrate was not used at all.

Using each of the foundry sand compositions obtained in Example 7 and Comparative Example 6, applied tests were conducted on the items of bending strength and collapsibility.

The test was carried out by first blowing each sand composition into a mold heated to 230°C at a blowing pressure of 5 kg/crA.
A test piece with a size of 20 m x 20 mm x 120 mm was prepared by firing for seconds, and the bending strength was measured using the test piece thus obtained in accordance with JISK-6910. Wrapped in double aluminum foil and placed in an oven at 500℃
After heating and holding for 0 minutes, the Rotatub sieve is removed using a machine on a 10-mesh sieve, and the time until no test pieces remain on the sieve, that is, the time required for disintegration (in seconds). ).

The test results are summarized in Table 2.

Claims (1)

[Claims] 1 Add 100% of the above binder to foundry river sand that can be hardened by heating to form a mold by using an organic substance as a binder.
0.5 to 0.5 to parts by weight of metal salts or metal hydride salts of dicarboxylic acids having 4 or less carbon atoms, or hydrates thereof.
A foundry sand composition characterized in that it is used in a proportion of 30 parts by weight.