JPH07102420B2 - Method for producing composition for foundry sand caking - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is a composition for casting sand caking used in the production of molds or cores, especially high strength at the time of baking and molding the molds or cores. The present invention also relates to a method for producing a molding sand caking composition used for producing a mold or core having good thermal disintegration after pouring.

(Prior Art) Regarding conventional casting molds and cores, regardless of the type of alloy used as the casting material, for example, as described in “Plastic Technology Complete Book 15” issued by the Industrial Research Institute, Inc. The shell mold method using a phenol resin as a binder is widely used as the manufacturing method.

In particular, most cores are manufactured by the shell mold method because of their excellent productivity and dimensional accuracy.

(Problems to be solved by the invention) However, when it is applied to a mold for a low-melting light metal casting such as an aluminum alloy, especially a core, a part of the phenol resin undergoes a thermal change due to the heat of the molten metal and is extremely strong. The residual strength of the core is significantly increased due to the change to a simple graphitized structure,
After casting, the casting was heated at a high temperature of about 500 ° C. for 5 to 10 hours for a long time called “sand baking”, and the binder residue that had changed to the graphitized structure was burned and collapsed. It discharges sand and has the drawback of requiring a great deal of energy.

Therefore, it has been desired to develop a mold material for the shell mold method, which is easily thermally decomposed by the heat of molten metal and mechanically disintegrates.

Based on the results of research that the heat resistance of phenolic resin, which is a drawback when used as a mold core, is due to the benzene ring, a thermosetting resin that does not contain a benzene ring was searched for. However, no sufficiently satisfactory ones have been found yet, and when a resin that causes thermal decomposition easily due to the heat of the molten aluminum alloy and is liable to mechanically collapse is used as the binder. Has a drawback that the strength of the mold or core during firing is weak, and that the molding core may break due to heat due to rapid thermal decomposition during aluminum alloy casting, or gas defects may occur in the casting. there were.

The present invention significantly improves the problems of the prior art, has a high strength during warming, and has a good thermal disintegration property after pouring, and in particular, a composition for casting sand caking that is suitable for casting an aluminum alloy or the like. A manufacturing method is provided.

(Structure of Invention) That is, the present invention is [In the formula, R ₁ is an organic compound residue having ₁ active hydrogen.
n1, n2 ... nl is 0 or an integer of 1 to 99, and the sum is 1 to 9
9, l represents an integer of 1 to 100, A is the following formula: (X in the formula is -CH = CH ₂ or, When a plurality of A's are contained in the formula (I), Xs in the formula (I) may be different groups or the same groups, At least one is contained in the resin represented by the formula (I).

R ₂ represents a hydrogen atom, an alkyl group, an alkylcarbonyl group, or an arylcarbonyl group) and has an oxycyclohexane skeleton having a substituent represented by]] and a phenol formaldehyde resin reacted with the epoxy resin represented by Is a method for producing a composition for caking foundry sand.

In the epoxy resin represented by the formula (I) used in the production method of the present invention, the organic compound residue having an active hydrogen of R ₁ includes alcohols, phenols, carboxylic acids,
Represents the residue of amines.

Examples of the alcohols include fatty acid alcohols such as methanol, ethanol and octanol, aromatic alcohols such as benzyl alcohol, and polyhydric alcohols such as ethylene glycol, trimethylolpropane and dipentaerythritol.

Examples of phenols include phenol, cresol, catechol, bisphenol S, phenol resin, and cresol novolac resin.

Examples of carboxylic acids include formic acid, acetic acid, fumaric acid, adipic acid, polyacrylic acid and the like.

Examples of amines include methylamine, ethylamine, hexamethylenediamine, ethanolamine and the like.

Nl in the general formula (I) is 0 or an integer of 1 to 99, and the sum thereof is 1 to 99, but if it is 100 or more, it becomes a resin with a high melting point and it becomes difficult to handle, so it is a binder for casting sand. Cannot be used as a drug. l is an integer from 1 to 100. X in formula (I) is -CH = CH _2, Or When a plurality of A's are contained in the formula (I), Xs in the formula (I) may be different groups or the same groups.

Further, among the substituents X of A in formula (I), It is essential to include at least one or more The larger the amount, the more preferable. In particular The less, the more preferable.

That is, in the present invention, the substituent X is Is the main one.

The epoxy resin represented by the formula (I) used in the present invention is, for example, an organic compound having active hydrogen as an initiator,
It can be produced by epoxidizing a polyether resin obtained by ring-opening polymerization of vinylcyclohexene-1-oxide with an oxidizing agent of peracid such as peracetic acid, perbenzoic acid, or formic acid.

4-Vinylcyclohexene-1-oxide is obtained by partially epoxidizing vinylcyclohexane obtained by the dimerization reaction of butadiene with peracetic acid.

Such an epoxy resin is described in JP-A-60-161973 and is sold, for example, by Daicel Chemical Industries, Ltd. under the name EHPE.

On the other hand, the phenol-formaldehyde resin, which is the reaction curing agent used in the production method of the present invention, is phenol, cresol, xylenol, paratertiary butylphenol, catechol, resorcinol, phenylphenol, bisphenol A, bisphenol F, bisphenol S, isopropenylphenol. Resins obtained by condensation of formaldehyde with a monophenol compound or diphenol compound, such as, are roughly classified into novolac type phenol formaldehyde resin and resol type phenol formaldehyde resin, both of which are used in the production method of the present invention. You can

Other curing accelerators may be used in combination in order to adjust the reaction rate with the phenol formaldehyde resin which is reacted as a curing agent. For example, aminophenol such as dimethylaminophenol, cyanazabicycloundecene and salts thereof, for example, , 3 (P-Chlorophenyl) -1,1
Derivatives such as dimethylurea, eg organic acid dihydrazides such as succinic dihydrazide, adipic dihydrazide, etc. are used as curing accelerators.

Other curing agents to be added are compounded at a compounding ratio of a phenol formaldehyde resin to be reacted as a curing agent with the epoxy resin represented by the above formula (I) which is the main component of the composition for casting sand caking produced by the production method of the present invention. The optimum value varies depending on the core and core molding conditions, but the conditions required to cure ordinary epoxy resin, for example, 5/1 to 1/5, preferably 2/1
~ 1/2.

The total addition amount of the resin component when adjusting the resin-coated sand using the caking composition made by the production method of the present invention,
1-10% by weight, preferably 1.5-3% by weight, based on silica sand
Is.

If the total amount of this resin component is less than 1% by weight with respect to silica sand, sufficient strength cannot be obtained during firing molding of the mold or core, while if it exceeds 10% by weight, the strength becomes too large.
The disintegration property after pouring is lowered, which is not preferable.

Further, in the composition for foundry sand caking obtained by the production method of the present invention, in addition to the resin component described above, not only the various curing accelerators and reaction accelerators described above, but also polyepoxy resin, melamine, for example. Other resins such as resins, furan resins, urea resins, xylene resins, polyester resins and the like may be mixed within the range not impairing the object of the present invention.

In addition, auxiliary agents for the purpose of improving the slipperiness of the resin-coated sand,
Silane coupling agent that improves the adhesion between sand and binder
It is also possible to use an auxiliary agent such as a titanium coupling agent or an inorganic filler other than silica sand in combination.

Additives such as auxiliaries and fillers are usually contained within about 5% by weight of the entire composition.

In order to produce a resin-coated sand using the casting sand caking composition obtained by the production method of the present invention, the caking composition obtained by the production method of the present invention is usually added to a sufficiently preheated silica sand. A method is used in which the binder is added and mixed, cooled, and the binder is fused to the sand surface.

The resin-coated sand obtained by the above method can be blown into a mold heated to usually 150 ° C. or higher, preferably 180 ° C. to 270 ° C., and demolded after 1 minute to 3 minutes to obtain a core.

(Example) Next, the present invention will be described with reference to Examples, Comparative Examples and Test Examples.

Example 1 4 kg of Nikko No. 6 silica sand (manufactured by Kawatetsu Mining Co., Ltd.) preheated to 250 ° C.
Was put into a speed mixer, and when it reached 130 ° C,
Pre-mixed epoxy resin EHPE3150 having cyclohexane ring (manufactured by Daicel Chemical Industries, Ltd., epoxy equivalent 172, softening point 72 ° C) 36g, phenol formaldehyde resin PS-41 mixed with resole type and novolac type
13 (Gunei Chemical Industry Co., Ltd.) 24g and imidazole derivative 2
2 g of fine powder of P4MHZ (manufactured by Shikoku Kasei Co., Ltd.) was added, and 1 minute later, 60 cc of water was added.

The resin component was melt-coated on the surface of the silica sand grains, and when the silica sand grains started blocking, add 3 g of calcium stearate.
After 30 seconds, it was taken out from the speed mixer to obtain the resin-coated sand of Example 1.

Example 2 4 kg of Nikko No. 6 silica sand (manufactured by Kawatetsu Mining Co., Ltd.) preheated to 250 ° C.
Was put into a speed mixer, and when it reached 150 ° C,
Epoxy resin having cyclohexane ring EHPE3150 (manufactured by Daicel Chemical Industries, Ltd., epoxy equivalent 169, softening point 70)
36 g), and when the temperature reached 130 ° C., the novolac type phenol formaldehyde resin PS-2207 (manufactured by Gunei Chemical Industry Co., Ltd., softening point 80) was mixed in advance.
24g) and imidazole derivative 2P4MHZ (manufactured by Shikoku Kasei)
3 g of the fine powder of was added, and 1 minute later, 60 cc of water was added.

The resin component was melt-coated on the surface of the silica sand particles, and when the silica sand particles started blocking, 3 g of calcium stearate was added, and after 30 seconds, it was taken out from the speed mixer, and Example 2
Of resin-coated sand was obtained.

Example 3 4 kg of Nikko No. 6 silica sand (manufactured by Kawatetsu Mining Co., Ltd.) preheated to 250 ° C.
Was put into a speed mixer, and when it reached 130 ° C,
Premixed epoxy resin EHPE1150 (manufactured by Daicel Chemical Industries, Ltd., epoxy equivalent 169, softening point 70)
℃) 30g and resol type phenol formaldehyde resin P
30 g of S-2176 (manufactured by Gunei Chemical Industry Co., Ltd., softening point: 80 ° C.) and 15 g of adipic dihydrazide were added, and 1 minute later, 60 cc of water was added and mixed.

The resin component was melt-coated on the surface of the silica sand grains, and when the silica sand grains started blocking, add 3 g of calcium stearate.
After 60 seconds, it was taken out from the speed mixer to obtain the resin-coated sand of Example 3.

Example 4 4 kg of Nikko No. 5 silica sand (manufactured by Kawatetsu Mining Co., Ltd.) preheated to 250 ° C.
Was put into a speed mixer, and when it reached 140 ° C,
36 g of epoxy resin EHPE1150 (manufactured by Daicel Chemical Industries, Ltd.) that had been mixed in advance was added, and then novolac type phenol formaldehyde resin PSM-4448 (manufactured by Gunei Chemical Industry Co., Ltd.) that had been mixed in advance at 130 ° C. , Softening point 84 ° C) 24 g, and at 110 ° C, 3 g of fine powder of imidazole derivative 2PHZ (manufactured by Shikoku Kasei Co., Ltd.)
It was dispersed in cc of water and added and mixed.

The resin component was melt-coated on the surface of the silica sand particles, and when the silica sand particles started blocking, add 4 g of calcium stearate.
After 30 seconds, it was taken out from the speed mixer to obtain the resin-coated sand of Example 4.

Comparative Example 1 4 kg of Nikko No. 6 silica sand (manufactured by Kawatetsu Mining Co., Ltd.) preheated to 250 ° C
Was put into a speed mixer, and when it reached 130 ° C,
60 g of epoxy resin EHPE3150 (manufactured by Daicel Chemical Industries, Ltd.) and dicyandiamide g which had been mixed in advance were added, and 1 minute later, 60 cc of water was added.

A resin component was melt-coated on the surface of the silica sand particles, and when the silica sand particles started blocking, 3 g of calcium stearate was added, and after 30 seconds, it was taken out from the speed mixer, and Comparative Example 1
Of resin-coated sand was obtained.

Comparative Example 2 4 kg of Nikko No. 6 silica sand (manufactured by Kawatetsu Mining Co., Ltd.) preheated to 250 ° C
Was put into a speed mixer, and when it reached 150 ° C,
60 g of novolac type phenol resin PSM-2207 (manufactured by Gunei Chemical Industry Co., Ltd.) was added, and then 9 g of hexamethylenetetramine was dissolved in 60 g of water at 100 ° C. and mixed.

A resin component was melt-coated on the surface of the silica sand particles, and when the silica sand particles began to block, 3 g of calcium stearate was added and taken out from the speed mixer after 30 seconds, and Comparative Example 2
Of resin-coated sand was obtained.

Evaluation method <Warm strength test> The resin-coated sand produced in Examples 1 to 4 and Comparative Examples 1 and 2 was molded at 250 ° C for 60 seconds using a shell mold high-temperature tensile tester, and immediately at a temperature of 250 ° C. The warm strength underneath was measured.

The results obtained are shown in Table 1.

<Heat disintegration test> In this test, the resin-coated sand obtained in each of Examples 1 to 4 and Comparative Examples 1 and 2 was poured into a mold preheated to 250 ° C., and the core 1 (upper part) shown in FIG. ; Diameter 10mm x length 20mm,
Lower part; diameter 50 mm × length 30 mm) was prepared.

Then, as shown in FIG. 2, the lower end of the core 1 is located 10 mm above the bottom surface of the metal melting crucible 2 having a recess having an inner diameter of 100 mm and a depth of 70 mm, and is located at the center of the metal melting crucible 2. Then, the core 1 is fixed with the core mounting jig 3.

Then, 700 ° C AC2A molten aluminum 4 was poured up to 10 mm below the upper end of the core.

After solidification and cooling, the jig 3 was removed from the core 1, and then the casting was taken out from the metal melting crucible 2.

The casting thus obtained is fixed to a jig for a low-tap tester with the upper part of the core facing downward, and shock-vibrated by a low-tap tester manufactured by Tokuju Seisakusho Co., Ltd., resulting in collapse of the upper part of the core. The amount of sand discharged from the discharge port was measured, and the thermal disintegration property was determined by the ratio with the initial core weight.

The time of impact vibration was 1 minute, 3 minutes, 5 minutes, and 10 minutes, and the judgment was cumulative.

The obtained results are also shown in Table 1.

<Evaluation of Gas Defects> The castings obtained in the above thermal disintegration test were cut, and the presence or absence of gas defects inside the castings was visually evaluated.

The obtained results are also shown in Table 1.

(Effects of the Invention) As described above, when the composition for casting sand caking obtained by the production method of the present invention is used, it has a warm strength equivalent to that of the phenol resin of Comparative Example 2 alone, and is further cast. The ease of discharging the core afterward, that is, the thermal disintegration property, is remarkably improved in each Example as compared with Comparative Example 2.

The core is ejected just by giving impact vibration to the casting,
It is shown that the heat treatment after casting which was conventionally required can be omitted.

Further, when only the epoxy resin of Comparative Example 1 is used, the heat disintegration property is excellent, but gas defects may occur.

However, in the evaluation of the gas defect of each example, the gas defect does not occur like the phenol resin of Comparative Example 2.

Further, the composition for casting sand caking produced by the method of the present invention is particularly a molded product having a complicated uneven shape, for example,
It is effective for cores used when molding engine cylinder heads and the like.

Therefore, by using the composition for casting sand caking obtained by the production method of the present invention has excellent warm strength, it is difficult to generate gas defects in the obtained casting, and a good thermal disintegrating mold, Alternatively, it becomes possible to obtain a core, and it is clear that the effect of the present invention is very large as a binder for a mold or core of a low melting point casting such as an aluminum alloy in the future.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a core used in a thermal decay test and gas defect evaluation, and FIG. 2 is a casting apparatus for thermal decay test and gas defect evaluation. 1 ... core 2 ... crucible for melting metal 3 ... core mounting jig 4 ... molten aluminum

Claims (1)

[Claims] 1. The following general formula [In the formula, R ₁ is an organic compound residue having ₁ active hydrogen.
n1, n2 ... nl is 0 or an integer of 1 to 99, and the sum is 1 to 9
9, l represents an integer of 1 to 100, A is the following formula: (X in the formula is -CH = CH ₂ or, When a plurality of A's are contained in the formula (I), Xs in the formula (I) may be different groups or the same groups, At least one is contained in the resin represented by the formula (I). R ₂ represents a hydrogen atom, an alkyl group, an alkylcarbonyl group, or an arylcarbonyl group) and has an oxycyclohexane skeleton having a substituent represented by]] and a phenol formaldehyde resin reacted with the epoxy resin represented by A method for producing a composition for caking foundry sand, comprising: