JPS6114042A - Production of casting mold - Google Patents

Abstract

PURPOSE:To improve remarkably the collapsing property of a casting mold after casting by heating and curing resin-coated sand for casting coated with a compsn. contg. a specific ammonia resol resin. CONSTITUTION:The compsn. contg. the ammonia resol resin obtd. by bringing 1.5-4.0mol formaldehyde and 0.01-0.5mol ammonia or hexamethylene tetramine into reaction with a block isocyanate compd. and 1mol bisphenol A is coated on sand for casting. The coated sand is cured by heating, by which a casting mold is produced. The collapsing property after casting is thus improved and the operation equal to the operation of the present shell mold method is made possible. The strength of the casting mold is particularly remarkably improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a mold, and in particular to a method for manufacturing molds, particularly for reducing the collapsibility of molds after casting, which are used for castings with relatively low Komagome temperatures, such as aluminum castings and alloy castings. This invention relates to a significantly improved method for manufacturing molds.

[Conventional technology]

Traditionally, there are various processes for manufacturing molds, but among them, the shell molding method using phenolic resin has been widely used mainly in the automobile industry because it has excellent mold dimensional stability, has good mold skin, and has a fast curing speed. However, when used in molds with low casting temperatures such as aluminum castings,
The mold has poor disintegration properties and requires heat treatment at a high temperature of about 500° C. for 6 to 12 hours, making it extremely costly and labor intensive to remove sand after casting. In order to improve the disintegration properties of the mold, a method was developed in which polyisocyanate and polyol were mixed with foundry sand and cured with amine gas, but this method had problems with the toxicity and odor of amine gas. A self-hardening mold manufacturing method has also been developed in which foundry sand is blended with polyisocyanate and amine polyol, but there is a problem in that it takes a long time to harden.

Therefore, there is a strong demand in the foundry industry for the development of a mold manufacturing method that can perform operations similar to the shell molding method and has excellent mold disintegration properties.

[Problem that the invention seeks to solve]

The present invention provides a method for manufacturing a mold that reduces post-casting heat treatment, easily disintegrates, and allows operations equivalent to the current sealed mold method.

Formaldehyde 1.5 per mole of bisphenol A
A mold is produced by hardening the sand coated with a composition containing an ammonia resol resin obtained by reacting ~4.0 mol and 0.01 to 0.5 mol of ammonia or hexamethylenetetramine by heating. It has been found that this method significantly improves the disintegration properties after casting, enables operations equivalent to the current shell molding method (sand fluidity, hardening speed), and in particular greatly improves mold strength.

That is, according to the present invention, when the above-mentioned foundry resin @ sand-covered mold is filled into a mold heated to 150°C to 650°C, the blocking agent of the blocked isocyanate compound dissociates, and the isocyanate compound and ammonia resol resin are generated. The methylol groups, amino groups, imino groups, hydroxyl groups, etc. of the template react, and the urethane bonds make the template strong and reach a level where it can be removed from the mold. Furthermore, the disintegration properties of the mold are significantly improved. This seems to be due to the use of urethane bonding in forming the template.

As the polyisocyanate compound of the composition used in the present invention, an addition reaction product of a polyisocyanate compound and an isocyanate blocking agent is used. As the polyisocyanate compound, any of the conventionally known isocyanate compounds having two or more isocyanate groups can be used, and these polyisocyanate compounds can be combined with ethylene glycol, propylene glycol, trimethylolpropane, glycerin,
A terminal inocyanate group-containing compound obtained by reacting an active hydrogen compound such as polyether polyols may also be used.

As the incyanate blocking agent, any conventionally used incyanate blocking agent can be used, including phenol-based incyanates such as phenol, cresol, xylenol, and nonylphenol. Tertiary alcohols such as t-butyl alcohol, active methylene compounds such as acetylacetone and diesterate matetra, aromatic amines such as methylaniline and diphenylamine, imides such as phthalic acid imide, and ε-caprolactam. These include lactams, imines such as ethyleneimine, ureas, oximes, bisulfites, and boric acids. The blocked isocyanate compound used in the present invention is obtained by reacting the above-mentioned incyanate compound and an isocyanate blocking agent by a conventionally known method.

The ammonia aresol 6J resin used in the present invention is preferably solid at room temperature in order to maintain the dryness of the sand, and an ammonia aresol resin of bisphenol A is used to improve the disintegrability.

Ammonia resol resin of bisphenol A contains 1.5 to 4.0% formaldehyde per mole of bisphenol A.
0 mole, ammonia or hexamethylenetetramine 0
．． The amount obtained by reacting 0.01 to 0.5 mol is used. If the amount of formaldehyde is less than 1.5 moles, the number of methylol groups will decrease and the curing rate will become uneven, which is not preferable.

Further, if the formaldehyde content exceeds 4.0 moles, the formaldehyde odor will be strong and the sand mold will not come out easily when heated and cured.

If ammonia or hexamethylenetetramine is less than 1 mole of aQ, the effect of improving mold strength will be small, and if it exceeds 0.5 mole, the pattern fat will become too polymeric and the strength of the mold will decrease, which is undesirable. There are no particular limitations on the method of synthesizing the ammonia aresol resin.

The resin-coated sand for foundries of the present invention is heated to 90 to iso'c, and the foundry sand is coated with a solid or solution blocked isocyanate compound and a solid or solution ammonia reso-/I.
/resin is stirred and kneaded, and the solvent is evaporated as required during this kneading step. If the temperature of the foundry sand exceeds 180° C., the blocked isocyanate compound begins to dissociate, which not only shortens the life of the foundry resin-covered sand but also reduces the strength of the sand mold, which is undesirable. If the temperature is less than 90° C., the resin will not be sufficiently removed or the solvent will not evaporate sufficiently, and the melting point of the foundry resin sand will be low (and blocking will occur), which is not preferable.

In addition, the blending ratio (weight ratio) of the block isocyanate compound and ammonia resol resin used is 95:5 to 5:
The ratio is preferably 85:15 to 50:0.

If there is too much blocked isocyanate, curing will be slow (and if there is too much ammonia resol position/1 fat), the collapsibility of the sand mold will deteriorate.

Further, the heating temperature when manufacturing the mold is preferably 150 to 350°C. At 150℃, the hardening of the mold slows down to 350℃.
If the temperature exceeds ℃, the strength of the mold will decrease or the surface of the mold will deteriorate.

The total amount of the blocked isocyanate compound and the resol type phenol resin in the composition to be kneaded with the sand and coated is 4.0 to 0.5% by weight based on the foundry sand, preferably 50% by weight.
~1.0%. If the total amount of resin added exceeds 4%, it will not only cause gas defects during casting manufacturing but also increase the price (which is not good).If it is less than 0.5%, the strength of the sand mold will be low and it will not be suitable for practical use. do not have.

In addition, any of the conventionally known dissociation catalysts for blocked isocyanate compounds can be used for the foundry resin-coated sand obtained in the present invention, such as dibutyltin dilaurate, stannic chloride, cobalt naphthenate, calcium octylate, cobalt octylate, etc. The amount of the catalyst that may be added is α01 to 20% by weight based on the solid content of the resin.

Stairs are also used in the shell molding method to improve the fluidity of resin-coated sand for foundries.
fart,.

A lubricant such as galsium phosphate may be added, and the amount of the lubricant added is 105 to 0.2% by weight based on the foundry sand.

In addition, when manufacturing resin-covered sand for foundries, there are no particular restrictions on the method of block isocyanate formation or mixing of the metal and resol type phenolic resin (both components may be mixed in advance before stirring and mixing with the sand). They may also be added separately during mixing.

The foundry sand used in the present invention may be any of those commonly used in foundry traps, and zircon sand and oripin sand can also be used.

〔Example〕

Examples of the present invention will be shown below. .

Example 1 (Synthesis of ammonia resol resin) 2280 g of bisphenol A and 1620 g of 37% formalin were charged into a four-bottle flask equipped with a reflux condenser.
After adding 166 g of 5% ammonia water bath solution and reacting at 80° C. for 2 hours, dehydration and concentration were performed to obtain a solid resin.

(Method for producing resin-coated sand for foundries) - 5 kg of flattery silica sand heated to 160°C in a mixer and coronet) AP stable (manufactured by Nippon Polyurethane Co., Ltd.,
Add 120 g of a phenol-masked incyanate compound (conversion point: about 100'C) and 40 g of the ammonia resol resin obtained above, and stir until the sand disintegrates.

Thereafter, 8 g of calcium stearate was added and mixed for an additional 20 seconds to obtain resin-coated foundry sand.

This foundry resin @ cut sand was blown into a mold heated to 300 T; at a blowing pressure of 2 kg/an', cured for 2 minutes, and then removed from the mold to form a manifold jacket core weighing 5710.41 kg. There was no damage to the core and the skin of the mold was also good. Table 1 shows the sand mold characteristics of this foundry resin can-breaking sand.

Example 2 8 kg of flattery silica sand heated to 110°C in a mixer and a bath solution consisting of 100 g of AP stable and 60 g of acetone and the ammonia reso obtained in Example 1,!
A solution consisting of 100 g of L/m jt and 60 g of acetone is added, and the mixture is stirred and kneaded until the sand disintegrates. Thereafter, 8 g of calcium stearate was added and mixed for an additional 2D seconds to obtain resin-coated foundry sand.

This casting resin encrusting sand was blown into a mold heated to 250°9 at a blowing pressure of 2 kg/#, cured for 2 minutes, and then removed from the mold.
A 41 kg jacket core for a manifold was molded.

There was no damage to the core and the skin of the mold was good.

Table 1 shows the sand mold properties of this resin-coated sand for foundries.

Implementation + A13 8 kg of flattery silica sand heated to 160°C in a mixer and 100 g of fulleran cross-linking agene) U, T (manufactured by Sumitomo Bayer Urethane, incyanate compound masked with C-kabu lactam, softened Kurokoma 100°C)
After stirring and kneading for 40 seconds, a solution consisting of 60 g of the ammonia aresol resin obtained in Example 1 and 30 g of methanol was added, and the mixture was stirred and kneaded until the sand disintegrated. Thereafter, 8 g of calcium stearate was added and mixed for an additional 20 seconds to obtain resin-coated foundry sand. This resin casting sand was blown into a mold heated to 340 DEG C. at a blowing pressure of 2 kg/atp, cured for 1 minute and 50 seconds, and then removed from the mold to form a jacket core for a manifold weighing -9O and weighing 41 kg. There was no damage to the core (the surface of the mold was also good). Table 1 shows the sand mold percentage of this resin-coated sand for foundries.

Example 4 Resin-coated sand for foundry use was infused in the same manner as in Example 5, except that 1.6 g of dibutyl tin dilaure was added. Table 1 shows the physical properties of the sand mold.

This foundry bamboo 1-fat sand was blown into a mold heated to 340° C. at a blowing pressure of 2 kg/aII+, cured for 1 minute, and then removed from the mold to form a jacket core for a manifold weighing 0.41 kg. There was no damage to the core (the skin of the mold was also good).

Comparative Example 1 (Manufacture of novolac type phenolic resin) In a four-bottle flask equipped with a reflux condenser, 7 tons of enol, 1880 g, 57% formalin, 244 g,
- 488 g of 80% rose formaldehyde was added, 4 g of oxalic acid was added, and the mixture was reacted at reflux temperature for 3 hours, followed by dehydration and concentration to obtain a solid resin.

(Manufacture of resin-coated sand for foundries) 8 kg of flattery silica sand heated to 160°C and 160 g of the novolak type phenol resin obtained above were added to a mixing machine, and after stirring and kneading for 40 seconds, a mixture of 24 g of hexamethylenetetramine and 80 g of water was added. Add the solution and stir and knead until the sand disintegrates. Then calcium stearate 8
g was added and further mixed for 20 seconds to obtain resin-blocked sand for thin products. Table 1 shows the characteristics of the sand mold.

This foundry resin-coated sand was blown into a mold heated to 250°C at a blowing pressure of 2 kg/(1111), cured for 2 minutes, and then cut out to form a manifold jacket core weighing 0.41 kg. There was no damage (the skin of the mold was also good).

Comparative Example 2 100 g of flattery silica sand heated to 160°C in a kneader and 100 g of AP stable (Coronet) and 11 g of flattery silica sand heated to 160°C
Add 60g of novolak type phenolic resin and stir until the sand collapses. Thereafter, 8 g of calcium stearate was added and mixed for an additional 20 seconds to obtain resin-coated foundry sand. Table 1 shows the physical properties of the sand mold.

This resin-coated foundry sand was blown into a mold heated to 300° C. at a blowing pressure of 2 kg/an', cured for 2 minutes, and then removed from the mold, but the entire sand broke into pieces.

Comparative Example 6 (Synthesis of resol-type phenolic stool fat) Bisphenol,
2280 g of Ru A and 1620 g of 37% formalin were added, 20% NaOH4Q g was added, and the mixture was reacted for 2 hours at a low flow temperature, followed by dehydration and concentration to obtain a solid resin.

(Method for producing resin-coated sand for foundries) 8 kg of flattery silica sand heated to 160° C., 120 g of Coronate AP stable, and 40 g of the resol type phenolic resin obtained above are added to a mixer and stirred and kneaded until the sand disintegrates. Thereafter, 8 g of calcium stearate was added and mixed for an additional 20 seconds to obtain resin-coated foundry sand.

Table 1 shows the characteristics of the sand mold.

This foundry resin-coated sand was blown into a mold heated to 300° C. at a blowing pressure of 2 kg/−, cured for 2 minutes, and then cut out of the mold, but the mold was partially damaged due to its somewhat low bending strength.

*1 Bending strength: Measured by JIS-6910 method *2 Fusion point: Measured by JACT method *3 Sand mold collapse rate: 30φ x 50mm heated to 250℃
! (Create a test piece with vIi oil coating for castings in a mold heated to 500°C and cured for 3 minutes in a mountain air oven at 400°C. Enclose in a mold heated to 500°C kept in an oxygen-free condition
After baking in a furnace for 20 minutes, it is allowed to cool. This test piece was placed on a 28-mesh sieve and shaken for 1 minute+=1 using a low-tap sieve shaker, and the magnetic disintegration rate was determined from the decrease rate using the following formula.

*4 bend: flat plate mold 70X1 set to measurement temperature
40cm above knee mold inner dimensions 50 x 120mm height 5 +
After setting the nm, the casting box filled with fat sand was left in a furnace temperature of 650℃ for 40 seconds, then taken out, and after 10 seconds, placed on a holder with a distance between fulcrums of 100mm and a 500g #+' car. The amount of deflection when applied was measured. A material with a small amount of deflection at a low temperature means that it hardens quickly.

〔Effect of the invention〕

By using the method for manufacturing a mold according to the present invention, a mold was obtained that had a hardening speed and workability equivalent to that of the shell mold method, and had excellent mold disintegration properties.

Claims (1)

[Claims] 1. Foundry sand contains 1.5 to 4% formaldehyde per mole of blocked isocyanate compound and bisphenol A.
0 mole ammonia or hexamethylenetetramine 0.
1. A method for producing a mold, comprising curing resin-coated foundry sand coated with a composition containing an ammonia aresol resin obtained by reacting 01 to 0.5 moles of resin by heating. 2. The mold manufacturing method according to claim 1, wherein the heating temperature is 150 to 350°C.