JPS6250042A - Production of resin coated sand for shell mold - Google Patents

Abstract

PURPOSE:To provide high strength and collapsing property to titled sand by coating the sand with a lubricant, solid resol type phenolic resin, solid novolak type phenolic resin, bromide of elements and hexamethylene tetramine respectively at limited amts. of addition. CONSTITUTION:The lubricant-contg. solid resin type phenolic resin in which the content of the unmodified lubricant is 0.2-5pts.wt. by 100pts.wt. solid resol type phenolic resin and the solid novolak type phenolic resin are added at 85/15-45/55 ratios weight ratios to the heated sand. The bromide of the elements selected from the respective groups Ib, IIa, IIb, IIIa, VIIb and VII of periodic table is further added at 1-15wt% by the total weight of the resin added to said resin and the hexamethylene tetramine is added at <=8wt% by the total weight of the resin added and such resin is coated on the sand.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is for use in shell molds that have superior strength and collapsibility when casting metals with low melting points compared to iron such as aluminum and magnesium. Related to the manufacturing method of resin coated sand <Prior art> Recently, light metals such as aluminum and magnesium are used in place of the conventional iron sills for automobile casting parts in order to reduce the weight. These materials have low melting point properties. It is expected that casting of these light metals will become increasingly popular in the future.

In the case of iron-based metals, the internal temperature of the shell mold after pouring is 8.
Since the temperature is 00 to 100°C, the phenolic resin used as a binder is exposed to high temperatures and almost thermally decomposes, which naturally reduces the strength of the shell mold after pouring, so the shell mold after casting is The sand-like core is easy to remove from the casting, but when casting low melting point metals such as aluminum and magnesium, the internal temperature of the shell mold during pouring is 300 to 400°C. Stays at low temperatures. For this reason, the decomposition of the phenolic resin in the shell mold is insufficient, and the shell mold maintains sufficient strength, making it possible to efficiently remove the shell core from the casting in complex casting shapes. It can be extremely difficult. Therefore, in such a case, in order to turn the cast shell core into a sandy state and remove it, it is necessary to heat it for a long time in a kiln or the like and then apply an impact to cause it to collapse. This is a major obstacle to improving productivity and saving energy when producing large quantities of aluminum castings.

<Purpose of the Invention> As one method for causing the thermal decomposition of phenolic resin to occur at a low temperature of 300 to 400°C, it is thought to be effective to add a substance that has a catalytic effect to lower the activation energy of thermal decomposition. .

The present inventors discovered that tb in the periodic table,
It has been found that the presence of one or more bromides of elements selected from Group 6, Ila, nb, nla, and b1, promotes the disintegration of the shell mold after pouring. (Japanese Patent Application No. 58-172137) As a result of intensive research by the present inventors on a method for further improving the collapsibility after pouring while maintaining the strength of the shell mold at a high level,
This has led to the completion of the present invention. In the present invention, a solid resol-type phenolic resin containing a lubricant and a solid novolak type resin having an unmodified lubricant content of 0.2 to 5 parts by weight based on 100 parts of the solid resol-type phenolic resin are added to heated sand. Phenol resin 85/15~45155
It is added in a weight ratio, and furthermore, according to the periodic table, tb, I[atI
[1 to 15% by weight of bromide of an element selected from Group 6 of BLMA, ■b1■ based on the total amount of resin added, and 8 weight t of hexamethylenetetramine based on the total amount of resin added.
This is a method for producing resin-coated sand for shell molds, which is characterized by coating the sand with the addition of S or less, and this method has become effective for shell molds.

<Structure of the Invention> The lubricant-containing solid resol type phenolic resin used in the present invention is a solid phenol resin obtained by reacting phenols and aldehydes in the presence of an alkali catalyst, and further using a lubricant in combination. .

The solid novolac type phenol resin used in the present invention is a solid phenol resin obtained by reacting phenols and aldehydes in the presence of an acid catalyst. It is also possible to use a lubricant together with the solid novolac type phenolic resin.

As the lubricant for carrying out the present invention, ordinary lubricants can be used, and in particular, ethylene bisstearamide, oxystearamide, stearamide, methylolstearamide, Kakaru Eiwa wax, Montan wax, and )Z rough-in wax. , ethylene wax, etc. are preferred. When the lubricant content of the solid resol is 0.2 to 5 parts by weight, it is particularly effective in improving the strength and collapsibility of the shell mold. If the lubricant content is less than 0.2 parts by weight per 100 parts of the solid resol, the effect of improving the strength and collapsibility of the shell mold is poor, and if it exceeds 5 parts by weight, the hot strength decreases. Further, even if these lubricants are added at any time during the production of the solid resol type phenolic resin, before the start of the reaction, during the reaction, or after the completion of the reaction, a solid resol type phenol resin containing the lubricant can be obtained.

Phenols used as raw materials for producing the phenolic resin of the present invention include phenol, cresol, xylenol, etc., including resorcinol, ? F7:r-
It is also possible to use oils containing silica, hydroquinone, aniline, urea, melamine, cashew nut shell oil, etc. Further, as the aldehyde, an aldehyde substance selected from formalin, noraformaldehyde, trioxane, etc. can be used. Basic substances such as ammonia, triethylamine, sodium hydroxide, and barium hydroxide are generally used as reaction catalysts for resol type phenolic resins. Further, reaction catalysts for novolac type phenolic resins are generally acidic substances such as oxalic acid, hydrochloric acid, and sulfuric acid, and organic acid metal salts. The ratio of solid resol type phenolic resin containing lubricant to solid novolak type phenolic resin is 85/15 to 4.
5155 weight ratio. When this ratio exceeds 85/15, the strength of the shell mold decreases, and when it is less than 45155, the collapsibility of the shell mold decreases.

In the present invention, the bromide used in particular is Ib in the periodic table.
, I[a, nb111a1■b, ■Bromides of elements selected from the 6 groups of copper,
These include zinc bromide and aluminum bromide.

More than 1aI of these bromides can be used.

The amount of these bromides added is 1 to 15 times the total amount of the lubricant-containing solid resol type phenolic resin and the solid novolac type phenol resin added. If the amount of bromide added is less than 1 weight, the collapsibility of the shell mold will decrease, and if it exceeds 15 weight, the strength will decrease. The bromide can be added during the resin-coated sand production process before, after, or simultaneously with the addition of the phenolic resin. Further, the bromide may be blended as it is or after being dispersed or dissolved in a medium.

In the present invention, the amount of hexamethylenetetramine added is 8% by weight or less based on the total amount of resin added.

Hexamethylenetetramine provides fast hardening of resin-coated sand and high strength of shell molds.

If the amount of hexamethylenetetramine added exceeds 8 weight St, the disintegrability of the shell mold decreases.

In order to carry out the present invention more effectively, it is desirable that the solid novolac type phenolic resin contains a silane coupling agent and an amide having a molecular weight of less than 500. Their inclusion further improves the strength and collapsibility of the shell mold.

Silane coupling agents include aminosilane, epoxysilane and vinylsilane, and have a molecular weight of 5.
Amides less than 00 include acrylamide, dimethylacrylamide, acetoacetanilide, formamide,
Dimethylformamide, N-methylbenzamide, N-
7enylpropionamide, methylolstearamide, N-7enylacetamide, dimethylacetamide,
Acetamide, stearylamide, propionamide, etc. are preferred.

<Effects of the Invention> According to the method of the present invention, it is possible to achieve both high strength and good disintegration properties of the shell mold, which was impossible with conventional methods.
This method is suitable as a method for producing resin-coated sand for industrial light metal shell molds.

<Examples> The present invention will be explained below with reference to Examples, but the present invention is not limited by these Examples.

In addition, "parts" and rll described in each example and comparative example all indicate "parts by weight" and "% by weight."

Production Example 1 A flask with a condenser and a stirrer was prepared, and 1000 parts of phenol, 1840 parts of 37% formalin, and then 2
120 parts of 8 thiammonia water and 50 parts of IJium aqueous solution (50% hydroxide) were added. The temperature gradually rises to 96℃
After refluxing for 25 minutes, 50 parts of ethylene bisstearamide was added, and a dehydration reaction was carried out under vacuum, followed by discharging and quenching to obtain 1160 parts of a solid resol type phenolic resin containing a lubricant, which was solid at room temperature. Obtained.

Production Example 2 A flask equipped with a condenser and a stirrer was prepared, and 1000 parts of phenol, 640 parts of 37-thiformin, and then 10 parts of oxalic acid were charged therein. The temperature was gradually raised, and after the temperature reached 96° C., a reflux reaction was performed for 30 minutes, followed by dehydration reaction under vacuum, followed by discharging and quenching to obtain 670 parts of a novolac type phenol resin that was solid at room temperature.

Production Example 3 A flask with a condenser and a stirrer was prepared, and 1000 parts of phenol, 1840 parts of 37-thiformin, and then 2
120 parts of 8 thiammonia water and 50 parts of IJium aqueous solution (50% hydroxide) were added. The temperature gradually rises to 96℃
After refluxing for 25 minutes, the mixture was dehydrated under vacuum, discharged, and rapidly cooled to obtain 110 parts of a solid resol type phenol resin that was solid at room temperature.

Production Example 4 Prepare a flask with a condenser and a stirrer, and add 7 ml to it.
1000 parts of x, 640 parts of 37cs formaly, and then 10 parts of oxalic acid were charged. The temperature was gradually raised, and after the temperature reached 96°C, a reflux reaction was carried out for 30 minutes, and then a dehydration reaction was carried out under vacuum. Methylene bisstearamide 35 parts, r
3 parts of -aminozolopyltriethoxysilane and 6 parts of propionamide were added, and the mixture was quenched by discharging a mixed wave to obtain 714 parts of a novolac type phenol resin that was solid at room temperature.

Example 1 Kyusanei No. 6 silica sand 7000 heated to a temperature of 130 to 140°C
105 parts of the lubricant-containing solid resol-type phenolic resin obtained in Production Example 1 and 70 parts of the solid novolac-type phenolic resin obtained in Production Example 2 were added and kneaded for 45 seconds. Then manganese bromide 1
4 parts were added and kneaded for 10 seconds. Further, an aqueous hexamethylenetetramine solution prepared by dissolving 7 parts of hexamethylenetetramine in 16 parts of water was added, and after mixing until the coated sand collapsed, 7 parts of calcium stearate was added. The mixture was mixed for 30 seconds, the sand was discharged, and aeration was performed to obtain resin coated sand.

Example 2 Sanei No. 6 silica sand 7000 heated to a temperature of 130 to 140°C
96 parts of the lubricant-containing solid resol-type phenolic resin obtained in Production Example 1 and 79 parts of the solid novolac-type phenolic resin obtained in Production Example 4 were added, followed by kneading for 30 seconds. Then zinc bromide 18
An aqueous solution of zinc bromide dissolved in 18 parts of water was added and kneaded for 15 seconds. Further, an aqueous hexamethylenetetramine solution prepared by dissolving 9 parts of hexamethylenetetramine in 21 parts of water was added, and after kneading the coated sand until it collapsed, 7 parts of calcium stearate were added.

After mixing for 30 seconds, the sand was removed and aeration was performed to obtain resin coated sand.

Comparative Example 1 Kyusanei No. 6 silica sand 7000 heated to a temperature of 130 to 140°C
105 parts of the solid resol-type phenolic resin obtained in Production Example 3 and 70 parts of the solid novolac-type phenolic resin obtained in Production Example 2 were added, and the mixture was kneaded for 45 seconds. Next, 14 parts of manganese bromide was added and kneaded for 10 seconds. Further, an aqueous hexamethylenetetramine solution in which 7 parts of 1-hexamethylenetetramine was dissolved in 16 parts of water was added, and after mixing until the coated sand collapsed, 7 parts of calcium stearate were added. 3
After mixing for 0 seconds, the sand was discharged and aeration was performed to obtain resin coated sand.

Comparative Example 2 A resin-coated sand was obtained under the same manufacturing conditions as in Comparative Example 1, except that manganese bromide and hexamethylenetetramine were not added.

Comparative Example 3 Sanei No. 6 silica sand 7000 heated to a temperature of 130 to 140°C
After adding 175 parts of the solid novolak type phenolic resin obtained in Production Example 4,
Kneaded for 5 seconds. Then hexamethylenetetramine 26
An aqueous solution of hexamethylenetetramine dissolved in 88 parts of water was added, and mixed until the coated sand disintegrated.
7 parts of calcium stearate were added. The mixture was mixed for 30 seconds, discharged, and aired to obtain resin-coated sand.

Comparative Example 4 Sanei No. 6 silica sand 7000 heated to a temperature of 130 to 140°C
After adding 175 parts of the solid resol type phenolic resin obtained in Production Example 3 to a Whirl mixer, 45 parts of
Kneaded for seconds. Next, 66 parts of water was added, mixed until the coated sand collapsed, and then 7 parts of calcium stearate was added.
part was added.

The mixture was mixed for 30 seconds, the sand was discharged, and aeration was performed to obtain resin coated sand.

Table 1 shows the characteristic values of each resin coated sand obtained in Example 1.2 and Comparative Example 1.2.3.4.

The test method is as follows.

Bending strength: Sticking point according to JACT test method 5M-1:
Hot tensile strength according to JACT test method C-1: JAC
According to T test method 5M-10.

Disintegrable Niresin coated sand with a diameter of 29% and a length of 1
Fill a 50% iron gib and pre-fire at 250°C for 30 minutes. The No. 2 tube was covered with aluminum foil and treated at 370° C. for 3 hours.

After cooling, take out the Nogubu and Apply impact using the impact testing machine shown in the figure. Take out the sand that has collapsed each time, Measure the amount of remaining sand and check that the amount of remaining sand is O. Determine the number of impacts caused. Figure 1 In this case, A is the sample and B is the sample. represents a part of the image. Part of No Nma It is an arm that rotates around a fulcrum C.

The fulcrum of some of the hammers is 30 cm high. Attached, some parts are horizontal After being lifted up by the Place the sample around the fulcrum. Nimuko adds a shock.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an impact tester for testing collapsibility. A is a sample, B is a part of a hammer,

Claims (3)

[Claims] (1) The heated sand has an unmodified lubricant content of 0.2 to 100 parts by weight of solid resol type phenolic resin.
5 parts by weight of a solid resol type phenolic resin containing a lubricant and a solid novolak type phenolic resin were mixed into 85/15-4.
Added at a weight ratio of 5/55, and further added to Ib and IIa in the periodic table.
, IIb, IIIa, VIIb, and VIII groups, from 1 to 15% by weight based on the total amount of resin added, and hexamethylenetetramine 8% by weight or less based on the total amount of resin added. A method for producing resin-coated sand for shell molds, which comprises adding resin to coat the sand. (2) The lubricant is one or more selected from the group of ethylene bisstearamide, methylene bisstearamide, oxystearamide, stearamide, methylolstearamide, carnauba wax, montan wax, paraffin wax, and polyethylene wax. A method for producing resin-coated sand for shell molds according to claim 1. (3) The method for producing resin-coated sand for shell molds according to claim 1, wherein the solid novolac type phenolic resin contains a silane coupling agent and an amide having a molecular weight of less than 500.