JPH0638971B2 - Binder composition for mold - Google Patents

Description

TECHNICAL FIELD The present invention relates to an acid-curable binder composition for molds. More particularly, it relates to an improved binder composition for use in a self-hardening and gas-curing cold box in which a refractory granular material is reacted with an acid-curing resin and an acid catalyst to produce a mold.

[Conventional technology]

Conventionally, when manufacturing cores and main molds in a foundry, there are various advantages such as reduction of pollution of industrial waste, rationalization of productivity, quickness, etc. Was adopted instead of the manufacturing method that uses an inorganic binder such as glass and cement.

As a method of manufacturing a mold using an organic self-hardening and gas-curable cold box, a method of curing an acid-curable resin typified by a furan resin with an acid catalyst and a method of curing a polyol and a polyisocyanate with an amine catalyst. Some are made of urethane resin.

Among these, a mold using a urethane resin has drawbacks such as poor disintegration property of sand during production of a casting, and sand casting, scooping, pinholes, soot defects and other casting defects. On the other hand, an acid-curing process using a furan resin is becoming mainstream in recent years as a method for solving the above-mentioned problems.

[Problems to be solved by the invention]

The acid-curable mold is energy-saving during mold production, the mold production speed is fast, the speed control is easy, and the quality of the produced mold, the dimensional accuracy of the casting, and the quality are excellent. Although it has many advantages over the resin-based method, it also has the following drawbacks.

That is, hot cracking occurs in the case of cast steel castings.
What is hot cracking of cast steel casting? When the molten metal is cast into the mold, the thermal energy of the molten metal causes the mold to undergo rapid thermal expansion.
Further, the molten metal shrinks as it solidifies while releasing thermal energy to the mold. At that time, forward and reverse stress concentration occurs at the interface between the casting and the mold. In particular, in a corner portion where the change in wall thickness is large and the angle is small, the strength on the casting side loses the strength on the casting side to cause cracks in the casting. When this hot cracking occurs, it causes casting defects and increases the number of finishing processes such as repairs in order to commercialize it, or increases the defective rate because it can not be commercialized, which is a cause of impairing casting productivity .

[Means for solving problems]

As a result of intensive research to solve the above problems, the present inventors have significantly improved hot cracking of cast steel castings, and as an acid-curable mold binder composition for further improving casting productivity. The inventors have found that the above-mentioned problems can be improved by using an acid-curable binder composition comprising a specific ketone resin and an acid-curable resin, and have reached the present invention.

That is, the present invention is a binder composition used in a mold manufacturing method using an acid-curable resin as a binder, wherein the acid-curable resin 40
~ 90% by weight, and ketone (A) and aldecht (B) shown below
The present invention provides a binder composition for a mold, which is characterized by being mixed with 60 to 10% by weight of a ketone resin having a number average molecular weight in the range of 300 to 1,500.

Ketone (A): One or more ketones selected from the group consisting of methyl ethyl ketone, methyl isobutyl ketone, acetophenone, cyclohexanone and methyl cyclohexanone.

Aldehyde (B): formaldehyde (including polymer forms such as paraformaldehyde and trioxane), acetaldehyde, propionaldehyde, butyraldehyde,
One or more aldehydes selected from the group consisting of acrolein, crotonaldehyde, benzaldehyde, anisaldehyde and cinnamaldehyde.

Examples of the ketone (A) used in the present invention include those shown above, but cyclohexanone is preferable.

Examples of the aldehyde (B) used in the present invention include those shown above, but aliphatic aldehydes are preferable, and formaldehyde and paraformaldehyde are more preferable.

The ketone resin used in the present invention is obtained by reacting the above-mentioned ketone (A) and aldehyde (B) by a conventional method.

The number average molecular weight of the ketone resin used in the present invention is Vapo
Chloroform solution (0.7 ~
The number average molecular weight measured at 40 ° C for 14.3 g /) is 30.
Must be in the range 0-1,500, preferably 400-1,0
The range is 00. When a ketone resin having a molecular weight smaller than this range or a ketone resin having a large molecular weight is used, sufficient mold strength cannot be obtained.

The mixing ratio of the acid-curable resin and the ketone resin used in the present invention is 40 to 90% by weight of the acid-curable resin and 60% of the ketone resin.
Is 10 to 10% by weight, preferably 50 to 20% by weight of ketone resin with respect to 50 to 80% by weight of acid-curable resin. If the mixing ratio of the ketone resin is less than the above range, the effect of mixing the ketone resin is not recognized, and if it is more than the above range, sufficient mold strength cannot be obtained.

It is already known from JP-B-51-26368 that a ketone resin is mixed with an acid-curable resin and used as a binder for a self-hardening mold. However, the inventors of the present invention use various ketones and aldehydes as ketones. As a result of detailed examination of mixing a resin with an acid-curable resin, it is possible to impart sufficient template strength only to a ketone resin which is a condensate of a specific ketone and an aldehyde having a number average molecular weight in a certain range, and They have found that they are effective in reducing hot cracking of cast steel.

The methylol% of the ketone resin used in the present invention is 4 to.
Methylol% is preferably 16%, and the ketone resin was oxidized with iodine in the presence of alkali, and then unreacted iodine was titrated with sodium thiosulfate solution under acidic condition.

When the methylol% of the ketone resin is smaller than the above range, the mold strength is low. On the other hand, when it is larger than the above range, the effect of mixing the ketone resin is small.

When a ketone resin composed of an aromatic ketone and / or an aromatic aldehyde is used, the effect of mixing the ketone resin on the reduction of hot cracking of the cast steel casting is small.

In the present invention, by using the specific ketone resin as described above, it has become possible to significantly improve the hot cracking of the cast steel in the case of the conventional acid-curable mold. Assuming the reason for this, the crosslink density of the acid-curable resin is adjusted to an appropriate crosslink density by the specific ketone resin used in the present invention, and therefore, it is appropriately softened by the heat energy during pouring, It is considered that the result of improving the bending property was that the local stress strain generated at the interface between the mold and the casting, which is a cause of hot cracking, was absorbed by the bending property on the casting side.

In the present invention, the acid-curable resin is a furan-based resin,
A phenolic resin, a urea resin, a melamine resin, or a copolymer resin of one or more of these is used, but it is not particularly limited.

To produce a mold using the binder composition of the present invention,
First, a refractory granular material is kneaded with a binder composition of the present invention comprising a ketone resin and an acid-curable resin and an acidic catalyst by a known method to obtain a self-hardening mold composition, and then the self-hardening mold composition is obtained. A conventional self-hardening mold manufacturing process can be used as it is to manufacture a mold from the composition for a hard mold.

The amount of the binder composition of the present invention is 100% refractory granular material.
Usually 0.4 to 10 parts by weight, preferably 0.6 to 2 parts by weight
Parts by weight. The amount of the acidic catalyst used depends on the binder composition.
Usually 5 to 80 parts by weight, preferably 20 to 7 parts by weight per 100 parts by weight
0 parts by weight.

As the acidic catalyst used when producing a mold using the binder composition of the present invention, directly used as an acid curing agent, sulfuric acid, inorganic acids such as phosphoric acid, and toluenesulfonic acid, xylenesulfonic acid Inorganic peroxides such as sulfurous acid gas and hydrogen peroxide, or organic peroxides such as methyl ethyl ketone peroxide (MEKPO), which are used by forming a curing agent in a template, such as organic sulfonic acids.

As the refractory granular material, inorganic refractory granular materials such as silica sand, chromite sand, zircon sand and olivine sand are used.

Further, the type of cast product as the final product is not limited to the cast steel, but is also limited to the cast material such as general cast iron or special steel.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 3 and Comparative Examples 1 to 3 By a conventional method, various ketones and aldehydes are reacted in the presence of a predetermined amount of sodium hydroxide catalyst for a predetermined time, after completion of the reaction, neutralized with an acetic acid aqueous solution, and then concentrated under reduced pressure. Thus, various ketone resins shown in Table 1 were obtained. The number average molecular weight of the ketone resin was measured using a Vapor Pressure Osmometer.

35% by weight of the various obtained ketone resins were dissolved in 65% by weight of urea-modified furan resin to prepare a binder composition.

A self-hardening mold was produced using the obtained binder composition, and the compression strength was measured and the cast steel cracking and casting test was performed by the following methods.

The results are shown in Table 1.

<Measurement method of compressive strength> 75 parts as a curing agent for 100 parts by weight of Fremantle silica sand
% P-toluenesulfonic acid aqueous solution 0.4 parts by weight, 1 part by weight of the above binder composition was added and kneaded, and the mixture for a mold was immediately filled into a 50 mmφ × 50 mmh test piece model, and the compressive strength after 24 hours at room temperature was measured. did.

<Cast steel cracking and casting test conditions> I. Manufacturing method for self-hardening molds for testing 100 parts by weight of Fremantle silica sand is used as a hardening agent.
% P-toluenesulfonic acid aqueous solution and 1 part by weight of the above-mentioned binder composition, and the mixture was kneaded and cast into a cast steel test piece model.

II. Casting conditions (1) Casting temperature: 1550 to 1560 ℃ (melting water 1600 ℃) (2) Steel type: SC-42 (3) Casting weight: Approx. 145kg (as cast 90kg) (4) Casting time: 11 to 15 Second (5) Charged tapping amount: 11 tons (6) Elapsed time from tapping to casting: about 15 minutes (7) Molten metal components: C0.20%, Si0.36%, Mn0.69%, P0.016
%, S 0.009% III. Shape of cast steel test piece 600 × 300 × 300mm, 20mm thick box type Examples 4 to 6 and Comparative Examples 4,5 Ketone resin dissolved in urea-modified furan resin (Example 2
Using the binder composition in which the mixing ratio of the (ketone resin used in 1) was changed as shown in Table 2, the compressive strength was measured and the cast steel cracking and casting test was performed in the same manner as in Examples 1 to 3.

The results are shown in Table 2.

Examples 7 to 9 Various reaction amounts of cyclohexanone and 37% formalin were reacted in the presence of a predetermined amount of sodium hydroxide catalyst for a predetermined time by a conventional method. After completion of the reaction, the solution was neutralized with an aqueous acetic acid solution and then concentrated under reduced pressure. 35% by weight of various ketone resins obtained
Was dissolved in 65% by weight of urea-modified furan resin to obtain a binder composition. By the same method as in Examples 1 to 3, the compressive strength was measured and the cast steel cracking and casting test was performed.

The results are shown in Table 3.

Claims (3)

[Claims] 1. A binder composition for use in a mold manufacturing method, wherein an acid-curable resin is used as a binder.
%, And 60% by weight of a ketone resin which is a condensate of the following ketone (A) and aldehyde (B) and has a number average molecular weight in the range of 300 to 1,500. Binder composition for molds. Ketone (A): One or more ketones selected from the group consisting of methyl ethyl ketone, methyl isobutyl ketone, acetophenone, cyclohexanone and methyl cyclohexanone. Aldehyde (B): formaldehyde (including polymer forms such as paraformaldehyde and trioxane), acetaldehyde, propionaldehyde, butyraldehyde,
One or more aldehydes selected from the group consisting of acrolein, crotonaldehyde, benzaldehyde, anisaldehyde and cinnamaldehyde. 2. The number average molecular weight of the ketone resin is 400 to 1,0.
The binder composition for a mold according to claim 1, which has a range of 00. 3. The binder composition for a mold according to claim 1, which comprises 50 to 80% by weight of an acid-curable resin and 50 to 20% by weight of the ketone resin.