JPS59113953A - Molding sand for shell mold - Google Patents

Abstract

PURPOSE:To obtain molding sand for shell mold having excellent moldability, mold strength and a core collapsing property after charging by using a compd. contg. at urethane bond in a molecule or using a thermosetting resin in conjunction with said compd. as a binder for the molding sand for shell mold. CONSTITUTION:Molding sand for shell mold for casting Al alloy is prepd. by adding 3 parts a urethane bond-contg. compd. and 0.24 part hexamethylene tetramine to 100 parts molding sand heated to 90 deg.C, kneading the mixture with a mixer and further adding 0.1 part calcium stearate powder and kneading the mixture. Otherwise, a thermosetting resin such as a phenolic resin, urea resin, furan resin or the like is added to said sand at 1.5 times of the amt. of the urethane bond-contg. compd., and both are thoroughly kneaded, thereby forming the casting mold for shell mold. The shell mold formed by such molding sand has excellent moldability and strength during molding and an excellent core collapsing property after charging of an Al alloy, etc. at a charging temp. of 700-800 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to foundry sand for shell molds, and more particularly, the present invention relates to foundry sand for shell molds, and more particularly, a compound containing a urethane bond in the molecule is used as a sand binder, or a compound containing such a urethane bond is further heat-cured. Concerning foundry sand which is made by using in combination with a synthetic resin, When producing castings made of relatively low-temperature materials within the above-mentioned pouring temperature range, conventional shell mold cores have extremely poor disintegration properties when poured.
For this purpose, a lot of energy, labor, and/or time is required, such as providing a sand removal process.

However, the inventors of the present invention have considered the actual situation as described above, and have found that the present invention has the same workability as conventional foundry sand for shell molding, and is no inferior to conventional foundry sand for shell molding. We have conducted extensive research with the aim of providing molding sand for shell molds that provides moldability and casting strength, has good core collapse after pouring, and does not require a sand removal process even for aluminum alloy castings. As a result, they discovered that the above objective could be achieved by using a compound containing a specific atomic group called a urethane bond in the molecule as a sand binder and coating the sand grains with it. The present invention has now been completed.

That is, the present invention provides foundry sand for shell molds obtained by depositing a compound containing a urethane bond in the molecule, or compound A) and thermosetting resin UIBI as a sand binder on sand grains. It provides:

Here, the above-mentioned urethane bond-containing compound i1mA
) is obtained by reacting the phenol derivative (a-1) with the isocyanate compound (a-2).
Typical examples include compounds represented by the following formulas.

Next, the incyanate compound (a-2) includes all compounds having an isocyanate group at the end of the molecule, but in order to more effectively achieve the object of the present invention, at least Polyisocyanate compounds having two isocyanate groups are preferred, typical among which are hexamethylene diisocyanate, dicyclohexyl diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate or naphthalene diisocyanate, or polyisocyanate compounds thereof. Examples include polyisocyanate compounds obtained by the reaction of phosphorus and water, amines, or polyhydric alcohols.

These phenol derivatives (a-
Regarding the quantitative ratio of 1) and isocyanate compound (11-2), the equivalent weight of hydroxyl groups in derivative (a-1) is
It is necessary to select the amount far exceeding the equivalent of the 5- isocyanate group in a-2).

In addition, as for the reaction conditions at this time, solid compounds (a-1) and (a-2) are mixed in the above-mentioned quantitative ratio without a solvent or using a solvent that is not reactive with compound (a-2). It is possible to simply mix the compound (a-1) with the derivative (a-1).
Although a-2) may be added little by little, in order to shorten the reaction time, it is effective to heat the mixture to about 70 to 80°C or to add a tertiary amine catalyst.

However, if the amount of this catalyst added is too large or the reaction temperature is too high, side reactions may occur or gelation may occur, so special attention must be paid to this point.

The urethane-bonded gold-containing compound powder thus prepared can be used as it is as a sand binder, but in this case, it is necessary to also use a known and commonly used curing agent such as hexamethylenetetramine or paraformaldehyde. On the other hand, when the compound (vAA) and a thermosetting resin (UlldB) such as phenolic resin, urea resin and/or furan resin are used together as a sand binder, it is not necessary to
Such curing agents are not necessary. In any of these cases, when heated, it easily hardens to provide excellent foundry sand, but the core obtained using the foundry sand of the present invention does not disintegrate after pouring low-temperature melt such as aluminum alloy. The reason for the good properties is believed to be that the urethane bonding portion of the compound, which is a sand binder, is decomposed by heat, reducing the sand binding effect.

Therefore, m degree of urethane bonding in such sand binder,
In other words, the higher the concentration of the urethane bond-containing compound, the better the disintegration properties are. Therefore, in the present invention, the compound is less likely to be present in the sand binder to coat the sand grains.
Unless both are present in an amount of 20% by weight, foundry sand with sufficiently good disintegrability cannot be obtained.

Among the various embodiments of the present invention as described above, a particularly preferable embodiment from the viewpoint of economy, performance, and safety and hygiene is one which has two or more hydroxyl groups such as resolnol or bisphenol A, and which contains phenol. Urethane bond-containing compound 11 which is a reaction product of a phenol derivative (a-1) having 1 to 2 nuclei and an isocyanate compound (a-2) with a low vapor pressure such as diphenylmethane diincyanate
One method is to coat sand grains as a sand binder consisting of a mixture of mA) in combination with a phenolic resin and hexamethylenetetramine as a hardening agent.

In order to coat the sand with the urethane-bonded metal-containing compound to obtain the foundry sand of the present invention, it is preferable to adopt a so-called dry hot marling method. There is a method in which sand grains are coated by kneading and melting the compound A), and a method in which a solution of the compound A) is mixed with sand and then the solvent is evaporated.
When using the three components together with 111BI, there is a method of mixing both of them in advance and coating the sand with such a mixture, or first coating the sand with one of the components and then coating the sand with the other component. There is a method of further coating, and a method of coating both at the same time, but any method may be used.

In the present invention, when the main ingredient is only the compound (p$AA) that can be involved in adhesion of sand grains after the mold is formed, this compound? JA), or in the case of the main component used in combination with the compound A) and the above-mentioned tree 111B), both (A) and (B) are used to further cure the sand grains by participating in the adhesion of the sand grains. When a sand binder is used in combination with a sand binder, the base component and hardener component are collectively called a sand binder, but if the sand binder consists of more components,
Of course, foundry sand can be obtained by coating sand grains by appropriately combining various aspects as described above.

Next, the present invention will be specifically explained with reference to Synthesis Examples, Examples, Comparative Examples, and Reference Examples, and unless otherwise specified, all parts and percentages are based on weight.

Note that the sand used in each example and comparative example is S10. The purity is 99% or more and the AFS (American Foundry Men's Society) particle size index is 6.
0±3 silica sand.

Synthesis Example 1 115 parts of bisphenol A, 35 parts of tolylene diisocyanate, and 150 parts of ethyl acetate were mixed with stirring in a nitrogen stream, and reacted for 8 hours while refluxing the ethyl acetate to form 600 parts of urethane bond. Containing compound vIAA)
I got it. Hereinafter, this will be abbreviated as compound (A-1).

Synthesis Example 2 [1 of Foundretsu TD-5402-BJ (Novolac type phenolic resin manufactured by Inu Nippon Ink Chemical Industry ■)
00 parts were dissolved at 130°C, and then 200 parts of the compound (A-1) obtained in Synthesis Example 1 was added little by little to dissolve the ethyl acetate, etc. in this compound (mA). When removed by distillation, 198 parts of a mixture of the bisphenol A/tolylene diisocyanate reaction product containing the urethane-bound metal compound and the phenol resin as the thermosetting resin 111 (B) was obtained.

Synthesis Example 3 110 parts of resorcinol, 68 parts of diphenylmethane diisocyanate, and 178 parts of ethyl acetate were stirred and mixed in a nitrogen stream, and reacted for 2 hours while refluxing the ethyl acetate.
The reaction was continued for 5 hours to obtain 656 parts of urethane-bonded gold compound. Hereinafter, this will be referred to as the compound (A
-2).

Synthesis Example 4 200 parts of the compound (A-2) obtained in Synthesis Example 3 was dissolved in advance at 160°C and maintained at the same temperature. Add it little by little and remove ethyl acetate etc. in this compound (A-2) by distillation to form the urethane bond-containing compound P.
199 parts of a mixture of the resorcinol diphenylmethane diisocyanate reaction product ($IAA) and the phenolic resin (thermosetting resin J]mBl was obtained.

Synthesis Example 5 The same operation as Synthesis Example 4 was repeated, except that the amounts of 1" Foundlets TD-g4o2-BJ and Compound (A-2) were changed to 80 parts and 40 parts, respectively.
A resorcinol diphenylmethane diincyanate reaction product containing a urethane-bound gold compound and a thermosetting resin Ml (
99 parts of a mixture with phenolic resin as Bl was obtained.

Example 1 100 parts of sand preheated to 90°C was placed in a mixer, and then 3 parts of the compound (A-1) obtained in Synthesis Example 1 and 0.24 parts of hexamethylenetetramine were mixed together. The mixture was added and kneaded for 2 minutes in a mixer, and 0.1 part of calcium stearate powder was further added and mixed for 30 seconds to obtain foundry sand for shell molds.

13-Example 2 100 parts of sand preheated to 140°C was placed in a mixer, then 1.5 parts of the mixture obtained in Synthesis Example 2 was added and kneaded in the mixer for 1 minute, and then hexa A solution of 0.45 parts of methylenetetramine dissolved in 1 part of water was added and kneaded for 1 minute, and then 0.1 part of calcium stearate powder was added and mixed for 30 seconds to obtain foundry sand for shell molds.

Example 3 Instead of compound (A-1), the same amount of compound (A-2)
Molding sand for a shell mold was obtained in the same manner as in Example 1, except that Example 4. Instead of the mixture obtained in Synthesis Example 2, the same amount of Synthesis Example 4 was used.
Foundry sand for a 14-El mold was obtained in the same manner as in Example 2, except that the mixture obtained in Example 2 was used.

Example 5 Instead of the mixture obtained in Synthesis Example 2, the same amount of Synthesis Example 5 was used.
Foundry sand for shell molds was obtained in the same manner as in Example 2, except that the mixture obtained in Example 2 was used.

Example 6 100 parts of sand preheated to 120°C was placed in a mixer, and then 1Plyamine P-364-BLJ (urea resin manufactured by Dainippon Ink & Chemicals ■; non-volatile content = 67%)
After that, 1 part of compound (A-1) obtained in Synthesis Example 1 and 02 parts of hexamethylenetetramine were mixed together and kneaded for 1 minute. After that, 01 parts of calcium stearate powder was added and stirred for 30 seconds to obtain foundry sand for shell molds.

15-Example 7 100 parts of sand preheated to 140°C was placed in a mixer, and then 1.2 parts of the mixture obtained in Synthesis Example 4 was added.
Knead for a minute, then [Foundlets TD-3
0.5 part of 699 (nonvolatile content = 60%) and a solution of 0.36 parts of hexamethylenetetramine dissolved in 1 part of water were mixed for 1 minute, and then 0.1 part of calcium stearate powder was added. was added and stirred for 30 seconds to obtain foundry sand for shell molds.

Example 8 [06 instead of Foundretsu TD-3399J]
Foundry sand for shell molds was obtained in the same manner as in Example 7, except that Foundretz DA-405J (furan resin manufactured by the same company; active ingredient = 99% or more) was used.

1A- Comparative Example 1 The same procedure as in Example 2 was repeated except that the same amount of [7 Oundretz TD-5402-BJ was used instead of the mixture obtained in Synthesis Example 2, and a control conventional type Foundry sand for shell molding was obtained.

Reference Examples 1 to 9 Performance comparison tests were conducted using various foundry sands obtained in Examples 1 to 8 and Comparative Example 1.

The results are summarized in Table 1.

In addition, each test was conducted in the following manner.

The fusion point is JACT (Casting Technology Promotion Association)
It is based on test method C-1, and the bending strength is J
ISK-691Or Powder Phenol Resin E Test Method for Shell Mold", and the disintegration property was determined by heating and molding the test resin sand (foundry sand) at 80m$X10.
A test piece with a thickness of 17-10 mm (m1) was prepared, and this test piece was
After keeping it in a reducing atmosphere at ℃ for 20 minutes, it is taken out and processed in a Rotatub tester using a 10-mesh sieve. (In cases where a test was required, the test was stopped at 5 minutes.) By measuring the processing time using the testing machine, the disintegration data was obtained.

As is clear from the results in Table 1, the shorter the treatment time, the better the disintegration properties are. It was found that the disintegration properties were gradually improved, and in addition, other properties were also comparable.

Patent applicant: Dainippon Ink Chemical Industry Co., Ltd. 19-

Claims (1)

[Scope of Claims] 1. Foundry sand for shell molds obtained by coating sand grains with a compound containing a urethane bond in the molecule, or with the compound and thermosetting resin B) as a sand binder. 2 The above compound is present in the sand binder to coat the sand grains.
The foundry sand according to claim 1, characterized in that the foundry sand is present in an amount of 0% by weight or more. 5. The foundry sand according to claim 1, wherein the thermosetting resin MB) is a phenolic resin. 4. The foundry sand according to claim 1, wherein the thermosetting resin B) is a urea resin. i. The foundry sand according to claim 1, wherein the thermosetting resin mold B) is a furan resin. The foundry sand according to claim 1.