JPS62124046A - Molding material for shell mold - Google Patents

Abstract

PURPOSE:To improve the collapsing property of a casting mold after casting by using an alkali metal salt of an arom. caroxylic acid as a collapsing property improving agent among molding materials essentially consisting of molding sand, phenolic resin and collapsing property improving agent. CONSTITUTION:The alkali metal salt of benzoic acid, salicylic acid, phthalic acid or trimellitic acid is used as the alkali metal salt of the arom. carboxylic acid. Such collapsing property improving agent is added preferably in a 2-30pts. wt. range by 100pts.wt. phenolic resin. The collapsing property improving agent is preliminarily compounded with the resin or is charged in the kneading stage for coating the resin on the molding sand. The casting mold produced of such materials has an easy tendency to collapse after pouring of a molten metal and decreases the failure of a casting product. The yield is thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to mold materials suitable for manufacturing molds by the shell molding method, particularly in the casting of low melting point metals such as aluminum and magnesium. This invention relates to a mold material for shell molds that has good sand removal properties.

Conventional technology Usually, a mold manufactured by the shell molding method has 1
It is required to have the property of easily collapsing after pouring various molten metals. However, when casting low melting point metals such as aluminum and red sea bream alloys, unlike high melting point metals such as cast iron and cast steel, sufficient heat is not provided to thermally decompose the binder in the mold. Therefore, after pouring the metal, the mold may collapse.Generally, an air hammer or the like is used to apply a strong impact to the casting to remove the sand, but even this is often insufficient, and It is necessary to perform heat treatment for 4 to 8 hours and then perform sand firing, which requires a great deal of labor and energy consumption.

Furthermore, due to the weight reduction of recent automobile-related cast parts,
There is a trend toward thinner walls or the use of light alloys such as aluminum alloys in place of conventional iron, and improving the collapsibility of molds is an important and urgent issue in this technical field.

As a method to improve the disintegration of a shell mold mold after pouring, it is possible to mix a substance that thermally decomposes at a relatively low temperature to destroy the bonding force of the M machine binder, which is mainly made of phenolic resin. As such substances, that is, disintegration improvers, organic compounds containing organic compounds, peroxides, phosphoric acid esters, inorganic chlorides, etc. have been proposed (Japanese Patent Application Laid-Open No. 139442/1983, Japanese Patent Publication No. 57-1490
43, JP-A-57-156858, JP-A-58-3745, JP-A-58-205641).

Problems to be Solved by the Invention However, among these disintegration improvers, loge-containing/organic compounds do not reduce the strength of the mold and still have the effect of significantly improving disintegration. The disadvantage is that the hydrogen halide generated during this process corrodes the mold. However, although phosphoric acid esters do not cause strength deterioration and do not have the problem of mold corrosion, they have the disadvantage that they are insufficiently effective in improving collapsibility. Furthermore, although inorganic chlorides and peroxides have a great effect on improving disintegration, they have the drawbacks of being likely to corrode with gold 1 and causing significant strength deterioration.

The present invention has been made to overcome the drawbacks of the prior art as described above, and its purpose is to improve the collapsibility of the mold after pouring without reducing the strength of the mold, Another object of the present invention is to provide a mold material for a shell mold that is free from mold corrosion.

Means for Solving the Problems As a result of repeated research on improving mold disintegration through the thermal decomposition of phenolic resin by alkaline substances, the present inventors found that an alkali metal salt of an aromatic carboxylic acid was used as a disintegration improver. A mold formed using the mold material for shell mold obtained by using the above method has excellent collapsibility after pouring, has relatively little decrease in casting strength, and does not cause corrosion of the mold. They discovered this and came up with the present invention.

That is, the present invention is characterized in that, in a molding material for a shell mold whose main components are foundry sand, a phenolic resin, and a disintegration improver, an alkali metal salt of an aromatic carboxylic acid is used as the disintegration improver. The present invention provides a mold material for shell molds.

The alkali metal salt of an aromatic carboxylic acid in the present invention means a compound in which the hydrogen atoms of an aromatic carboxylic acid having one or more carboxyl groups are completely or partially substituted with an alkali metal. These include, for example, benzoic acid, salicylic acid, p-hydroquine benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, trimellisic acid, pyromellitic acid, mellitic acid, naphthalic acid, naphthoic acid, toluic acid. , cinnabar 1i, 2.3-
Lithium, sodium, potassium, rubidium, cephram of aromatic carboxylic acids such as naphthalene dipropionic acid,
Examples include alkali metal salts such as furano7ium, which may be used alone or as a mixture of two or more. Particularly preferred are lithium benzoate, sodium benzoate, potassium benzoate, potassium salicylate, sodium salicylate, lithium salicylate, dipotassium phthalate, potassium hydrogen phthalate, disodium phthalate, sodium hydrogen phthalate, dipotassium terephthalate,
Examples include tripotassium trimellitate, monopotassium trimellitate, and trisodium trimellitate.

The blending amount of these disintegration improvers is not necessarily constant depending on the type and amount of the phenolic resin, and the desired degree of disintegration, but it is usually 10% of the phenolic resin.
0 parts by weight, 1 to 30 parts by weight, preferably 2 to 30 parts by weight
The amount is selected within the range of 20 parts by weight. If it is less than 1 part by weight, no improvement in disintegrability can be expected, and if it is more than 30 parts by weight,
This is not preferable because the mold strength is significantly reduced.

The phenolic resin used in the present invention includes phenol,
Novolak-type phenol 91 obtained by reacting phenols such as cresol, bisphenol A, kylnol, catechol, resol-7, and hydroquinone with aldehydes under a catalyst. Fat, resol-type phenol tlti
llL Either an ammonia aresol type phenol resin or a benzyritta ether type phenol resin may be used, or they may be used in combination. These phenolic resins may be various modified phenolic resins modified with urea, aniline, furan, melamine, cashew nut oil, tall oil, etc.

There are no particular restrictions on the amount of phenolic resin before blending with the νf sand, but it is usually 0.2 to 10 parts by weight, preferably 0.5 parts by weight, per 100 parts by weight of the yj sand. ~
It is selected within the range of 5 parts by weight.

In the present invention, when manufacturing the i-molding material for shell molds, the method of blending the disintegration improver of the present invention is to mix it into the resin in advance, or to coat the resin on the foundry sand. The disintegrant may be added at any stage during the kneading process, or the disintegrant may be dispersed and mixed into resin-coated sand grains produced by a conventional method.

Furthermore, the finger-coated sand grains of the present invention may contain other conventionally used standard compounding agents, such as silane coupling agents, amides, organic acids, hexamethylenetetramine, calcium stearate, etc. This does not impede the essential effects of the present invention.

Function In the present invention, the mechanism of the tendency of aromatic carboxylic acids to disintegrate due to alkali metal salts is not necessarily clear, but is presumed to be as follows.

That is, when forming a mold using a mold material for a mold made using the alkali metal salt of an aromatic carboxylic acid used in the present invention as a disintegration improver,
The firing conditions are 250-300℃ for a very short time (e.g. 4
0 seconds), and since it forms a salt, it does not act as an alkali, and therefore it is thought that there is little deterioration in the strength of the mold. Furthermore, when molten metal is cast, the metal salt is thermally decomposed to form an alkali, which acts as a catalyst to promote the thermal decomposition of the phenol resin, thereby significantly degrading the strength and improving the disintegration properties.

EXAMPLES The present invention will be explained in detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these Examples.

In addition, "part" and "part" described in each example and comparative example
All "parts by weight" and "% by weight" are indicated.

Example 1 Cratery Sand 5000 heated to 140-150°C
2. Novolak type phenolic resin 5P690 (manufactured by Asahi Yokuzai Kogyo ■, resin for shell molds) 702 and potassium benzoate 2.82 (4 parts per 100 parts of phenol resin) as a disintegration improver were added. , and kneaded for about 40 seconds. Thereafter, a solution of hexamethylenetetramine 10.5F dissolved in water 752 was added and kneaded until the resin coated sand collapsed. Calcium stearate 52 was added and the sand was drained after 10 seconds to obtain resin coated sand.

Example 2.3 Resin coated sand was obtained by carrying out jfC in the same manner as in Example I, except that sodium benzoate and lithium benzoate were used as the disintegration improver in place of potassium benzoate.

These are referred to as Example 2.3.

Comparative Example 1 A resin coated sand was obtained in the same manner as in Example 1 except that potassium benzoate was not used.

This is referred to as Comparative Example 1.

Using the resin coated sand obtained in Example 1.2.3 and Comparative Example 1, based on the test method shown below,
Transverse rupture strength and disintegration properties were measured. The results will be shown to the first group.

Test method (1) Transverse rupture strength According to JIS-6910.

(2) Disintegrability A dogbone type tensile strength test piece with a width of 40, stop length of 75, and normal thickness of 25 pieces, as shown in (1) in Figure 1, was made from resin coated sand and used for the disintegration test. I had a child.

Furthermore, an outer mold [Fig. 1 (2)] with dimensions of 125 pieces x 80 mm x 75 mm and a space slightly larger than the core test piece was prepared separately, and the core test piece was set in it. 720 parts of aluminum alloy molten at 5°C is cast to form a casting 3. After cooling, vibration is applied to the casting 301 (Fig. 2) using an Eyano thermometer at a pressure of 0.5 and 9/crrl to form the casting. The weight of the sand discharged from the discharge port with a diameter of 16 mm was measured every hour [7, divided by the total weight when all the sand was discharged, and the amount was expressed as weight ffl%, and the disintegration was determined.

Example 4 Recovered sand heated to 140-150°C 5000 ? to 5
P690 to 802. Eight parts of potassium salicylate (10 parts per 100 parts of phenol resin) was added as a disintegration improver, and kneaded for about 40 seconds. Thereafter, a solution of hexamethylenetetramine 13.5+7 dissolved in water 752 was added, and the mixture was kneaded until the resin coated sand disintegrated. Stearinated calcium 52 was added and discharged after about 10 seconds to obtain a resin coated sand. .

Examples 15 to 8 As a disintegration improver, dipotassium phthalate, dipotassium terephthalate, potassium hydrogen phthalate, and tripotassium trimellitate in the formulations listed in Table 2 were used instead of potassium salicylate. Resin coated sand was obtained in the same manner as in Example 4. Example 5.6
．． 7.8.

Comparative Example 2 A resin-coated sand was obtained in the same manner as in Example 4, except that potassium salicylate was not used.

This is referred to as Comparative Example 2.

Using the resin-coated sand obtained in Example 4.5.6.7.8 and Comparative Example 2, transverse rupture strength and collapsibility were measured using the test method described above. The results are shown in Table 2.

Example 9 7 Lacrisa/dosoo heated to 140-150°C.

2, add ammonia aresol type phenol m1JLsp4F (manufactured by Asahi Yokuzai Kogyo ■) to 637.5F690 to 277
, 457 parts of potassium salicylate (5 parts per 100 parts of phenol resin) was added as a disintegration improver, and about 40 parts of potassium salicylate was added as a disintegration improver.
Kneaded for seconds. Thereafter, water 752 was added and kneaded until the resin coated sand collapsed, calcium stearate was added, and the mixture was discharged after about 10 seconds to obtain a resin coated sand.

Comparative Example 3 A resin coated sand was obtained in the same manner as in Example 9 except that potassium salicylate was not used.

This is referred to as Comparative Example 3.

Using the resin coated sand obtained in Example 10 and Comparative Example 3, transverse rupture strength and collapsibility were measured according to the test method described above. The results are shown in Table 3.

Table 3 Effects of the Invention As is clear from the above explanation, the shell mold mold material using an alkali metal salt of an aromatic carboxylic acid as a disintegration improver has relatively little decrease in mold strength when molded. Furthermore, since the collapsibility of the mold after casting is greatly improved, the time, labor, and energy costs required for collapsing the mold are greatly reduced, and productivity is significantly improved.

Furthermore, since it does not contain halides, etc., there is no problem of mold corrosion.

In addition, since the impact force required to collapse the mold can be lowered, damage to cast products is reduced and product yield is improved, and the work environment is improved by reducing noise. It has characteristics and provides industrial utility.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams for explaining the collapsibility test of a mold made from the material of the present invention. In the figure, reference numeral 1 indicates a core, 2 indicates an outer mold, and 3 indicates a casting.

Claims (1)

[Claims] 1. A shell mold mold material containing foundry sand, a phenolic resin, and a disintegration improver as main components, characterized in that an alkali metal salt of an aromatic carboxylic acid is used as the disintegration improver. material.