JPH0317578B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a resin-coated sand for shell molds suitable for casting metals such as aluminum and magnesium, which have a lower melting point than iron. [Prior Art] In order to reduce weight, light metals such as aluminum and magnesium are increasingly used in automobile casting parts instead of conventional iron.
In casting these low melting point metals, the internal temperature of the shell mold during pouring remains at a low temperature of 300 to 400°C, so the decomposition of the phenolic resin in the shell mold is insufficient, and the shell mold still has a low temperature. Because it maintains its strength, it may be extremely difficult to efficiently remove the shell core from complex casting shapes. In such a case, in order to remove the cast shell core, it is necessary to heat it in a kiln for a long time and then apply an impact to cause it to collapse. This is a major obstacle to improving productivity and saving energy. Various methods have been reported for improving the disintegrability of the mold by adding and mixing substances that promote the thermal decomposition of the phenolic resin in the shell mold during the production of resin-coated sand when casting light alloys. For example, in JP-A-58-77738, a, b,
a, b, a, a, a, b, a,
There are examples of carboxylates of elements selected from groups b. Although this method has the advantage that the shell mold has high collapsibility and cold strength and does not cause corrosion of the mold during casting, it has the disadvantage that the curing speed of the phenolic resin is reduced. Furthermore, Japanese Patent Publication No. 15417/1983 provides examples of brominated inorganic compounds. According to this method, although the cold strength of the shell mold is high and the collapsibility is good, it has the disadvantage that corrosion of the mold is likely to occur during casting. If even a slight amount of corrosion occurs in the mold, the surface of the resulting casting deteriorates and the mold becomes unusable. [Object of the Invention] The present inventors have discovered that when making a shell mold, the curing speed of the phenolic resin is fast, and the resulting mold has high cold strength, and when casting a light alloy, the mold has excellent collapsibility, and As a result of research in an effort to create resin-coated sand that would not corrode the mold, we discovered that the monocarboxylate of a specific element and the bromide of a specific element coexist in the phenolic resin, and the phenolic resin contains a lubricant. The inventors have discovered that this is possible by using resin-coated sand, and have completed the present invention. [Structure of the Invention] The present invention provides a resin-coated sand in which foundry sand grains are coated with a phenolic resin.
b, a, b, a, a, a, b,
0.6 to 15 parts by weight of a monocarboxylate of an element selected from groups a, b, and selected from groups b, a, b, a, b in the periodic table. 0.3 to 10 parts by weight of elemental bromide and 0.3 to 4 parts by weight of lubricant in the phenolic resin.
The gist is a resin-coated sand containing 1% by weight. The lubricant-containing phenolic resin used in the present invention is a solid novolac-type phenolic resin obtained by reacting phenols and aldehydes in the presence of an acid catalyst and using a lubricant in combination, or a solid novolac-type phenolic resin obtained by reacting phenols and aldehydes in the presence of an acid catalyst, or This is a solid resol type phenolic resin obtained by reacting in the presence of a catalyst and using a lubricant in combination. As the lubricant for carrying out the present invention, ordinary lubricants can be used, but in particular, ethylene bisstearamide, oxystearamide, stearamide, methylolstearamide,
Carnauba wax, montan wax, paraffin wax, polyethylene wax and the like are preferred. A lubricant content of 0.3 to 4% by weight is particularly effective in improving mold strength and disintegrability. If the lubricant content is less than 0.3% by weight, the effect of improving mold strength and collapsibility is poor, and if it exceeds 4% by weight, hot strength will decrease. Further, even if these lubricants are added at any time during the production of the phenolic resin, before the start of the reaction, during the reaction, or after the completion of the reaction, a phenolic resin containing the lubricant can be obtained. Phenols used as raw materials during the production of the phenolic resin of the present invention include phenol, cresol, xylenol, etc.
Catechol, hydroquinone, aniline, urea,
It is also possible to use products containing melamine, cashew nut shell oil, etc. Further, as the aldehyde, an aldehyde substance selected from formalin, paraformaldehyde, trioxane, etc. can be used. The reaction catalyst for novolac type phenolic resins is generally an acidic substance such as oxalic acid, hydrochloric acid, or sulfuric acid, or an organic acid metal salt, and the reaction catalyst for resol type phenolic resins is generally a base such as ammore, triethylamine, sodium hydroxide, or barium hydroxide. sexual substances are used. In the present invention, the monocarboxylic hydrochloric acids particularly used are a, b, a, b, a,
Monocarboxylate salts of elements selected from groups a, a, b, a, b, such as sodium formate, nickel formate, zinc formate,
These include cobalt acetate, manganese acetate, nickel acetate, magnesium acetate, calcium acetate, zinc acetate, sodium acetate, potassium acetate, and barium acetate. The amount of these monocarboxylic acids added is 0.6 to 15 parts by weight per 100 parts by weight of the phenolic resin containing the lubricant. If the amount of monocarboxylic acid added is less than 0.6 parts by weight, the disintegrability of the mold will decrease, and if it exceeds 15 parts by weight, the cold strength will decrease. The bromide used in the present invention is a bromide of an element selected from groups b, a, b, a, and b in the periodic table, such as calcium bromide, manganese bromide, iron dibromide, octairon bromide,
These include cupric bromide, zinc bromide, and aluminum bromide. The amount of these bromides added is 0.3 to 10 parts by weight per 100 parts by weight of the phenolic resin in the lubricant. If the amount of bromide added is less than 0.3 parts by weight, the collapsibility of the mold will decrease, and if it exceeds 10 parts by weight, corrosion of the mold may occur. The monocarboxylic acid and bromide can be added during the resin-coated sand manufacturing process before or after the addition of the phenolic resin, or at the same time. Furthermore, the monocarboxylic acid and bromide may be blended as they are, or after being dispersed or dissolved in a medium. [Effects of the Invention] According to the present invention, it is possible to obtain shell molds with fast hardening properties, high strength, good disintegration properties, and non-corrosion of molds, which were impossible with conventional methods. Suitable as resin coated sand for shell molds. [Examples] The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples. In addition, "parts" and "%" described in each example and comparative example all indicate "parts by weight" and "% by weight." Production example 1 Phenol 1000 in a reaction pot with a cooler and a stirrer
1 part, 650 parts of 37% formalin, and then 10 parts of oxalic acid. Gradually increase the temperature and after the temperature reaches 96℃
After carrying out a reflux reaction for 120 minutes, a dehydration reaction was carried out under vacuum. 20 parts of ethylene bisstearamide was added, and after mixing, the mixture was discharged and rapidly cooled to obtain 970 parts of a novolak type phenolic resin that was solid at room temperature. Manufacturing comparison example 1 Phenol 1000 in a reaction pot with a cooler and a stirrer
1 part, 650 parts of 37% formalin, and then 10 parts of oxalic acid. Gradually increase the temperature and after the temperature reaches 96℃
The reflux reaction was carried out for 120 minutes. After a dehydration reaction under vacuum, the mixture was discharged and rapidly cooled to obtain 950 parts of a novolak type phenolic resin that was solid at room temperature. Example 1 Flattery silica sand 7000 heated to a temperature of 130-140℃
119 parts of the solid novolac type phenolic resin obtained in Production Example 1 were added thereto, followed by 6 parts of nickel formate and 3 parts of manganese bromide and kneaded for 45 seconds. Furthermore, an aqueous hexamethylenetetramine solution prepared by dissolving 18 parts of hexamethylenetetramine in 60 parts of water was added, and after kneading the coated sand until it disintegrated,
7 parts of calcium stearate were added. The mixture was mixed for 15 seconds and discharged to obtain resin coated sand. Example 2 Flattery silica sand 7000 heated to a temperature of 130-140℃
After adding 140 parts of the solid novolak type phenolic resin obtained in Production Example 1, 4 parts of zinc formate and 4 parts of zinc bromide were added.
Kneaded for 45 seconds. Furthermore, an aqueous hexamethylenetetramine solution prepared by dissolving 21 parts of hexamethylenetetramine in 70 parts of water was added, and after kneading the coated sand until it collapsed,
7 parts of calcium stearate were added. The mixture was mixed for 15 seconds and the sand was discharged to obtain resin coated sand. Example 3 Flattery silica sand 7000 heated to a temperature of 130-140℃
140 parts of the solid novolak type phenolic resin obtained in Production Example 1 were added thereto, and then 7 parts of cobalt acetate and 2 parts of iron dibromide were added and kneaded for 45 seconds. Further, an aqueous hexamethylenetetra solution prepared by dissolving 21 parts of hexamethylenetetramine in 70 parts of water was added, and after kneading the coated sand until it collapsed, 7 parts of calcium stearate were added. The mixture was mixed for 15 seconds and the sand was discharged to obtain resin coated sand. Comparative Example 1 Flattery silica sand 7000 heated to a temperature of 130-140℃
140 parts of the solid novolak type phenolic resin obtained in Comparative Production Example 1 were added and kneaded for 45 seconds. Further, an aqueous hexamethylenetetramine solution prepared by dissolving 21 parts of hexamethylenetetramine in 70 parts of water was added, and the mixture was kneaded until the coated sand collapsed.
7 parts of calcium stearate were added. The mixture was mixed for 15 seconds and the sand was discharged to obtain resin coated sand. Comparative Example 2 Flattery silica sand 7000 heated to a temperature of 130-140℃
140 parts of the solid novolak type phenolic resin obtained in Comparative Production Example 1 were added, followed by 16 parts of zinc formate and kneaded for 45 seconds. Further, an aqueous hexamethylenetetramine solution prepared by dissolving 21 parts of hexamethylenetetramine in 70 parts of water was added, and the mixture was kneaded until the coated sand collapsed.
7 parts of calcium stearate were added. The mixture was mixed for 15 seconds and the sand was discharged to obtain resin coated sand. Comparative Example 3 Flattery silica sand 7000 heated to a temperature of 130-140℃
140 parts of the solid novolac type phenolic resin obtained in Comparative Production Example 1 were added, followed by 6 parts of zinc bromide and kneaded for 45 seconds. Further, an aqueous hexamethylenetetramine solution prepared by dissolving 21 parts of hexamethylenetetramine in 70 parts of water was added, and the mixture was kneaded until the coated sand collapsed.
7 parts of calcium stearate were added. The mixture was mixed for 15 seconds and the sand was discharged to obtain resin coated sand. Table 1 shows the characteristic values of each resin coated sand obtained in Examples 1, 2, and 3 and Comparative Examples 1, 2, and 3. The test method is as follows. Cold bending strength: Based on JACT test method SM-1. Curing speed: Based on JACT test method SM-5. Mold temperature 250℃ Collapse property: Resin coated sand with diameter 29m/m and length
It was filled into a 150m/m iron pipe and pre-fired at 250°C for 30 minutes. Cover the pipe with aluminum foil and heat to 400℃
It was baked for 3 hours. After cooling, the pipe was taken out and subjected to impact using the impact testing machine shown in Figure 1. After each impact, the collapsed sand was taken out and the amount of remaining sand was measured, and the number of times of impact until the amount of remaining sand became 0 was determined. Ta. In Figure 1, A is a sample,
B represents the hammer part. The hammer part is an arm that rotates around branch C. The fulcrum of the hammer is at the height
It is attached to a height of 30 cm, and the hammer part is lifted horizontally and then allowed to fall naturally, centering on the fulcrum.
Apply impact to the sample. Presence of mold corrosion: Resin coated sand with a diameter of 29 m/m and a length of
A 150 m/m iron pipe was filled with the material, and an iron plate with a length of 100 m/m, a width of 10 m/m, and a thickness of 3 m/m was inserted into the center of the pipe, and the mixture was pre-fired at 250°C for 30 minutes. The entire pipe was covered with aluminum foil and fired at 400°C for 3 hours.
After cooling, the iron plate inside the iron pipe was taken out. After repeating this operation 20 times, the presence or absence of corrosion on the iron plate was visually observed.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a side view of an impact tester for testing collapsibility. A is the sample, B is the hammer part, and C is the fulcrum to which the hammer part is attached.

Claims (1)

[Claims] 1. In resin coated sand in which foundry sand grains are coated with phenolic resin, phenolic resin 100%
For parts by weight, a, b, a, in the periodic table,
b, a, a, a, b, a, b,
0.6 to 15 parts by weight of a monocarboxylate of an element selected from each group of the elements b, a, and b in the periodic table.
A resin-coated sand comprising 0.3 to 10 parts by weight of a bromide of an element selected from groups b, a, and b, and 0.3 to 4 weight % of a lubricant in a phenolic resin. 2. Claim 1 in which the monocarboxylic acid salt is sodium formate, nickel formate, zinc formate, cobalt acetate, manganese acetate, nickel acetate, magnesium acetate, calcium acetate, zinc acetate, sodium acetate, potassium acetate, and barium acetate. Resin coated sand as described. 3 Bromide is calcium bromide, manganese bromide, 2
2. The resin coated sand according to claim 1, which is iron bromide, triiron octabromide, cupric bromide, zinc bromide, and aluminum bromide.