JPH04123836A - Binder composition for molding sand - Google Patents

Abstract

PURPOSE:To drastically improve the smoothness of casting surface by specifying the composition of acid-setting resin used for binder for molding sand. CONSTITUTION:The binder composition for molding sand is composed of the acid-setting resin and strong acidic salt and weak basic salt and used at the time of forming a mold by kneading this with refractoriness granular aggregate and heat-setting this, and having the following characteristic composition in the acid-setting resin (a) 20-35wt% resol type phenol resin, (b) 40-65wt% furfuryl alcohol or furan resin, (c) 15-30wt% keton resin composed of at least one kind of cyclohexanone, cyclopentanone or aromatic keton and aldehyde and 1:1-1:3mol ratio of the keton to the aldehyde.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a foundry Sunagawa binder composition used when manufacturing molds by a heat curing manufacturing method. The present invention relates to a casting Sunagawa binder composition, which consists of a hardening agent and a refractory granular aggregate, and is used to obtain a casting mold by kneading it into a refractory granular aggregate and curing it by heating.

[Conventional technology and its problems]

Conventionally, as a method for producing heat-cured molds, there is a so-called Fermode method in which a refractory granular aggregate is coated with a phenol novolak resin and heated and cured using hexamethylenetetramine as a catalyst.

This heat-curing method is currently the most commonly used method for producing heat-curing molds because of its simple equipment and ease of use. However, due to the long curing time and high curing temperature, there is a lot of distortion in the mold and mold.
It was necessary to remove the tension from the mold, and the dimensional accuracy was also insufficient. Furthermore, the working environment is poor due to the high curing temperature, and the working environment is extremely polluted due to the odor of thermal decomposition of the phenol resin and hexamethylenetetramine, and a drastic improvement in these conditions has been desired.

In addition, a mixture of acid-curing resins such as phenol resol resin, phenol with low furan content, or urea/formalin-modified furan resin, and a curing catalyst such as ammonium chloride or sulfuric acid is added to the refractory granular aggregate at around 250°C. There is a so-called pot box method in which the material is cured by heating. This method also has a shorter curing time than the shell mold method, and improves distortion due to temperature, dimensional accuracy, and thermal working environment, but it is desired to further shorten the curing time, improve the physical properties of the mold, and improve the working environment. There is.

In contrast, a so-called worm method is a method in which a mixture of fire-resistant granular aggregate, an acid-curable resin, and a binder consisting of a salt of a strong acid and a weak base as a hardening agent is heated and hardened at a relatively low temperature of around 200°C. The box method has been rapidly attracting attention in recent years as a method for solving the above-mentioned difficulties.

[Problems to be solved by the invention] The warm box method has a high energy saving effect during mold manufacturing, a fast mold manufacturing speed, excellent quality of the manufactured molds, and few internal defects in the manufactured castings. However, the surface roughness of the manufactured castings, the so-called casting surface, is somewhat inferior, and it is desired to improve this point. There is.

An object of the present invention is to provide a binder composition for castings that can improve the surface roughness, so-called casting surface, of manufactured castings while taking advantage of the characteristics of the warm box method.

The factors that affect the smoothness of the casting surface in the warm box method include: ■ Factors related to granulation technology such as the packing density of the mold ■ Factors such as the particle size and material of the refractory granular aggregate used ■ Caking for castings Factors related to the binder include the gas composition generated when the agent composition is thermally decomposed.

Among these factors, various studies have been made in terms of molding technology, but there are many restrictions due to differences in molds and molding machines, making it difficult to put them into practical use. Furthermore, in terms of aggregate, there are restrictions such as particle size and material that have a large effect on various properties other than the casting surface of castings, so it is still difficult to put it into practical use. Therefore, in order to solve the above problem, there is currently a strong demand for improvement from the viewpoint of binders.

[Means to solve the problem]

As a result of intensive research, the present inventors have found that at least one binder selected from cyclohexanone, cyclopentanone, and aromatic ketone is used in the warm box method.
It was discovered that the casting surface of manufactured castings was significantly improved by incorporating a ketone resin consisting of a ketone and an aldehyde with a molar ratio of ketone to aldehyde of 1:1 to 1:3, and the present invention was developed based on this discovery. It was completed.

That is, the present invention is a foundry Sunagawa binder, which is made of an acid-curable resin and a salt of a strong acid and a weak base, and is used when molding a mold by kneading it into a fire-resistant granular aggregate and curing it by heating. The present invention provides a foundry Sunagawa binder composition, wherein the acid-curable resin has the following composition.

(a) Resol type phenolic resin 20-35% by weight
(b) Furfuryl alcohol or furan resin 40-65
Weight % (c) A ketone resin comprising at least one of cyclohexanone, cyclopentanone, or an aromatic ketone and an aldehyde and having a molar ratio of ketone to aldehyde of 1:1 to 1:3.
15 to 30% by weight The acid-curing resin used in the wood invention is a resol type phenolic resin, furfuryl alcohol or furan resin, and at least one ketone selected from cyclohexanone, cyclopentanone, and aromatic ketone and an aldehyde. The ketone resin contains a lyketone to aldehyde molar ratio of 1:1 to 1:3.

As resol type phenolic resin, phenolic resin,
Examples include resol type resins in which aldehyde is condensed with at least one of phenol, cresol, xylenol, resorcin, alkylphenol, phenylphenol, bisphenol A, and the like.

As the furan resin, a resin prepared by mixing or co-condensing at least one of urea, melamine, urea/aldehyde polycondensate, melamine/aldehyde polycondensate, and aldehyde with furfuryl alcohol is used.

Examples of the aromatic ketone that is a component of the ketone resin include acetophenone ketones, propiophenone ketones, hesiphenone ketones, and the like. Aldehydes also include formaldehyde (including polymeric forms such as paraformaldehyde and trioxane);
Acetaldehyde, propionaldehyde, phthylaldehyde, acrolein, crotonaldehyde, triglyaldehyde, henzaldehyde, salicylaldehyde,
Examples include, but are not limited to, cinnamaldehyde and glyoxal. Formaldehyde is particularly preferred as the aldehyde.

If the resol type phenolic resin in the acid-curable resin is less than 20% by weight, the surface roughness of the casting may deteriorate or the curing speed may become slow. If the amount is more than 35% by weight, the surface roughness of the casting may deteriorate, the pot life may be shortened, and the usability may become poor. Furthermore, if the content of furfuryl alcohol or furan resin in the acid-curable resin is less than 40% by weight, the mold strength will decrease, and if it is more than 65% by weight, the surface roughness of the casting will deteriorate. Furthermore, if the ketone resin in the acid-curing resin is less than 15% by weight, the surface roughness of the casting deteriorates,
If the amount is more than 1% by weight, the mold strength will be extremely reduced.

In the present invention, the salt of a strong acid and a weak base acts as a curing agent in the binder, and is used as a hardening agent in the binder, and is used as a hardening agent in the binder. It is preferable to use a salt of at least one of acids such as sulfonic acid, toluenesulfonic acid, xylene sulfonic acid, and phenolsulfonic acid and at least one of aluminum, copper, zinc, iron, and the like. Weak bases include Cu(OH)z, Zn(011)z, Fe(O
H) 2, A I (OH) 3, and the like.

The blending ratio of the acid curable resin and the salt of a strong acid and a weak base in the casting Sunagawa binder composition of the present invention is 5 to 50 parts by weight of the salt of a strong acid and a weak base to 100 parts by weight of the acid curable resin. Preferably it is 10 to 30 parts by weight. The casting Sunagawa binder composition of the present invention is used in an amount of 0.5 to 4 parts, preferably 0.8 to 2.5 parts by weight, per 100 parts by weight of the refractory granular aggregate.

The binder composition of the present invention is preferably prepared by separately mixing an acid-curing resin, a salt of a strong acid and a weak base, and additives used as necessary, into a fire-resistant granular aggregate. It is preferable to mix the salt, additive, and acid-curable resin in this order.

If necessary, the binder composition for foundry sand of the present invention may contain additives such as modifiers commonly used in this field.

Polymers and oligomers such as coumaron/indene resin, petroleum resin, polyvinyl alcohol, polybutadiene, xylene resin, and styrene resin, natural materials such as lignin, rosin, and ester gum can be used in combination with the foundry Sunagawa binder composition of the present invention. As a diluent, aromatic hydrocarbons such as Hensen and xylene, methanol, ethanol, etc.
Alcohols and the like can be mentioned. Furthermore, a silane cambling agent may be added for the purpose of improving mold strength. Examples of silane camping agents include γ-(2-
amine) aminopropylmethyldimethoxysilane, γ-
Examples include aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and the like.

When these are used together, they may be added together with the acid-curing resin, or may be mixed separately with the fire-resistant granular aggregate.

〔Effect of the invention〕

The smoothness of the casting surface of a casting manufactured using a mold formed using the foundry Sunagawa binder composition of the present invention is greatly improved.

[Examples] The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

Note that all parts in the examples are based on weight.

(1) Preparation of ketone resin According to a conventional method, 2 moles of formaldehyde are added to 1 mole of cyclohexanone using a KO)l catalyst at a reaction temperature of 90°C.
C. for 3 hours to obtain a ketone resin with a softening point of 90.degree.

(2) Preparation of resol type phenolic resin By a conventional method, 1 mole of phenol is reacted with 1.3 mole of formaldehyde using a KOH catalyst at a reaction temperature of 80°C for 6 hours, and the resol type has a viscosity of 5000 cps at 25°C. A phenolic resin was obtained.

Examples 1 to 6 and Comparative Examples 1 to 5 The ketone resin, resol type phenol resin, and furfuryl alcohol obtained above were mixed in the amounts shown in Table 1, and 7
The mixture was heated and stirred at 0°C to obtain an acid-curable resin.

Using this acid-curable resin, etc., the final transverse rupture strength of the mold and the roughness of the surface of the casting were evaluated by the following method.

That is, flotation silica sand from Shimane Prefecture (AFS particle size index 56) 10
0 parts, 2 parts of acid-curing resin, 0.6 parts of a water-methanol solution (concentration 40% by weight) of p-toluenesulfonic acid copper salt as a curing agent, and Kao Riacre ■ for the purpose of improving mold strength. One part of commercially available kaolite toner J-20J O was mixed to obtain a kneaded sand composition.

This kneaded sand composition was blown into a mold heated to 200"C by air, heated for 20 seconds, and then taken out.
．． A test piece of 4 mm x 22.4 mm x 180 mm was obtained, and after being left for 1 hour, the final transverse rupture strength was measured using a universal strength tester manufactured by George Fisher.

In addition, the kneaded sand composition was blown into a mold heated to 200°C by air, heated for 90 seconds, and then taken out to obtain a mold for a step-like test piece, and a molten metal of material FC-25 was poured into this mold. The hot water was poured at a temperature of 1420° C. for a pouring time of 7 seconds, and cooled to obtain a stepped test piece as shown in FIG. Six locations on the upper surface of this stepped test piece were measured using a stylus type surface roughness measuring device, and the average value was taken as the casting surface roughness.

The above results are shown in Table-1.

table

[Brief explanation of drawings]

FIG. 1(a) is a plan view of the stepped test piece used in the example;
FIG. 1(b) is a side view thereof. Note that the dimensional unit in the figure is mm.

Claims (1)

[Scope of Claims] 1 A clay for foundry sand that is made of an acid-curable resin and a salt of a strong acid and a weak base, and is used when molding a mold by kneading it into refractory granular aggregate and curing it by heating. A binder composition for foundry sand, characterized in that the acid-curable resin has the following composition. (a) Resol type phenolic resin 20-35% by weight (b) Furfuryl alcohol or furan resin 40-65%
Weight% (c) Comprising at least one ketone selected from cyclohexanone, cyclopentanone, and aromatic ketones and an aldehyde, and the molar ratio of ketone to aldehyde is 1:1 to 1:
2. The binder for foundry sand according to claim 1, wherein the salt of a strong acid and a weak base is a salt of a weak base and at least one of lower aliphatic sulfonic acids or aromatic sulfonic acids. Composition. 3. At least one salt of a lower aliphatic sulfonic acid or an aromatic sulfonic acid and a weak base is selected from the group consisting of benzenesulfonic acid, phenolsulfonic acid, toluenesulfonic acid, xylene sulfonic acid, and lower alkylsulfonic acid.
The caking composition for foundry sand according to claim 2, which is a salt of a seed and at least one member selected from the group consisting of aluminum, copper, zinc, and iron.