JP3453485B2 - Method for treating casting sand and method for producing mold - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating foundry sand and a method for producing a mold in carbon dioxide gas hardening.

More particularly, it relates to an improved method for treating molding sand and a method for producing a mold, which is used in a process of using a water-soluble phenolic resin as a binder and hardening it with carbon dioxide.

[0003]

2. Description of the Related Art Self-hardening mold molding method, cloning mold molding method (shell method), and cold box mold molding method are known as molding methods for manufacturing molds such as main molds and cores using organic binders. Is. In particular, the self-hardening mold molding method has already become a general-purpose molding method in place of the inorganic type from the viewpoints of productivity, casting quality, safety and hygiene mainly in the field of mechanical casting.

On the other hand, conventionally, in order to manufacture a mold at medium and high speeds, a cloning mold molding method has been widely used in which a so-called coated sand obtained by coating a granular refractory with a phenol resin is heat-cured to manufacture a mold. .

However, in the cloning template molding method, there are problems in energy saving at the time of mold manufacturing, mold production rate, and quality of the mold and casting, and in order to improve the problems, gaseous or aerosol substances are used. Cold box mold molding, which cures at room temperature as a curing agent, has been attempted seriously in the foundry industry as a mold manufacturing method that replaces the cloning mold molding method. Since the toxic gas of is used, the working environment during molding and the environment after pouring become poor,
The improvement was desired.

Therefore, a carbon dioxide curing mold molding method has been developed in recent years. This molding method has a working environment, as compared with the self-hardening mold molding method, the cloning mold molding method (shell method), and the cold box mold molding method. It has attracted attention because of its excellent casting quality and mold-making productivity. Binder compositions used in these carbon dioxide gas-curable mold making methods are disclosed in Japanese Examined Patent Publication No. 4-76947, Japanese Unexamined Patent Publication No. 4-339535, Japanese Unexamined Patent Publication No. 7185731.

Furthermore, in a mold making method in which a water-soluble phenolic resin is used as a binder and cured with an organic ester, it is possible to add an acid to the refractory granular material.
Refractory granular material reclaimed for reuse (used in organic ester curing) as described in Publication No. 6
The purpose is to improve the strength of the mold when using.

[0008]

[Problems to be Solved by the Invention] The carbon dioxide gas-curable mold molding method is an acid curing method in which a furan resin or a resole phenol resin is cured with an acid such as an organic sulfonic acid or sulfuric acid because the binder does not contain a sulfur atom. Although it has advantages such as less tendency to sulfurize than the conventional mold molding method, it has a lower mold strength than the acid-curable mold molding method, so the amount of resin required for molding is extremely low. However, the amount of gas generated during pouring is large, gas defects are likely to occur, and the economy is not good.

[0009] Further, the recovered sand once used for casting has a lower mold strength than the new sand, and the mold strength is further lowered with repeated casting and regeneration, and the usable time of the resin kneading sand is short. ing. Therefore, in order to manufacture a mold using the refractory granular material regenerated for reuse, it is necessary to increase the amount of resin used and the amount of fresh sand replenished in order to maintain the mold strength. It has, and improvement is desired.

[0010]

[Means for Solving the Problems] As a result of intensive research to solve these problems, the inventors of the present invention have found that a water-soluble phenolic resin is used as a binder and a method for producing a mold in which the binder is cured with carbon dioxide gas. in, by acid dissociation exponent pK _a is used in combination 5.0 or less acid, pot life of the mold strength and the resin kneaded sand and have completed the present invention found that greatly improved.

[0011] Namely, the present invention is molding sand, wherein the refractory particulate material used in the mold fabrication method acid dissociation exponent pK _a curing the water-soluble phenolic resin with carbon dioxide gas to impart 5.0 following acids Regarding the processing method of.

[0012] The present invention also provides a mold manufacturing method of curing a water-soluble phenolic resin with carbon dioxide gas, acid dissociation exponent pK _a refractory granular material, characterized in that it uses by applying the 5.0 following acids The present invention relates to a mold manufacturing method.

Further, according to the present invention, the refractory granular material contains 50% by weight or more of the refractory granular material regenerated for reuse (hereinafter referred to as reclaimed sand), and the reclaimed sand has a burning loss. The present invention relates to the above-mentioned method for treating foundry sand which is reclaimed sand of 5.0% by weight or less or a method for molding a mold.

[0014]

DETAILED DESCRIPTION OF THE INVENTION

Acid used in the present invention (described acid) is an acid dissociation exponent pK _a
It is less than 5.0. Among acids, the acid dissociation index pK _a is
It is presumed that those of 5.0 or less are likely to bond with the alkali remaining in the reclaimed sand and become a strong alkali salt, and at the same time the effect of decarboxylation of the alkali carbonate will be increased, and the mold strength of the reclaimed sand will be improved.

The acid dissociation index pK _a used in the present invention is 5.0.
As the following acids, both inorganic acids and organic acids can be used. Examples of the inorganic acid include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like. Organic acids include formic acid, acetic acid, oxalic acid,
Examples thereof include carboxylic acids such as benzoic acid and glycolic acid, sulfonic acids such as sulfamic acid, xylenesulfonic acid, toluenesulfonic acid and benzenesulfonic acid, and organic phosphoric acid esters such as methylphosphoric acid and ethylphosphoric acid. In the present invention, by using one kind or two or more kinds selected from these, the mold strength of the reclaimed sand is improved.

[0016] (Description of Processing method sand) processing method of imparting acid foundry sand of the present invention is particularly but not limited to, acid dissociation exponent pK _a in 100 parts by weight of the refractory particulate material 5.0 the following acids A method of kneading 0.0001 to 15 parts by weight, preferably 0.001 to 10 parts by weight is preferable. The kneading method is not particularly limited as long as the refractory granular material and the acid are mixed appropriately and uniformly. A well-known method can be applied to the production of a mold by the carbon dioxide curing method using this treated sand.

(Explanation of Mold Manufacturing Method) As a mold manufacturing method, a carbon dioxide gas curing method in which a water-soluble phenol resin is cured with carbon dioxide gas is used. In the present invention, in order to manufacture a mold by the carbon dioxide curing method, 100% refractory granular material is used.
The parts by weight of acid dissociation exponent pK _a of 5.0 the following acid 0.0001
1 part by weight, preferably 0.001 to 10 parts by weight, and 0.5 to 15 parts by weight, preferably 0.7 to 10 parts by weight of a water-soluble phenolic resin are kneaded by a known method, and stored in a model such as a wooden pattern or with pressurized air. It is filled into the model by blowing of 0.1 to 30 parts by weight of carbon dioxide with respect to the refractory granular material, preferably
A mold can be produced by aerating 0.2 to 20 parts by weight. At this time, carbon dioxide gas may be mixed with air at an arbitrary ratio, and the gas temperature of carbon dioxide gas is usually aerated at 0 to 100 ° C., but the gas is further heated (100 ° C. or more) before use. Good. The gas pressure and the air flow rate are not particularly limited.

The refractory granular material and the acid dissociation index pK _a are
As a kneading method of an acid of 5.0 or less and a water-soluble phenolic resin, as described in the description of the molding sand treatment method,
The refractory granular material previously treated with an acid and a water-soluble phenolic resin may be kneaded, or the refractory granular material, an acid and a water-soluble phenolic resin may be kneaded at the same time, and there is no particular limitation. .

(Explanation of Refractory Granular Material) The refractory granular material used in the present invention preferably contains regenerated sand in an amount of 50% by weight or more, and has a high mold strength to maintain a long pot life of the resin kneaded sand. Is preferably 5.0% by weight or less, and most preferably 2.0% by weight or less. The reclaimed sand in the present invention refers to a refractory granular material reclaimed for reuse. As recycled sand, molds made by hardening carbon dioxide with water-soluble phenolic resin as a binder are assembled and cast, and then the used molds (lumps of aggregates) taken out are separated into sand grains by mechanical vibration. The above can be used. Further, the sand thus recovered may be used in a sand reclaimer or roasting machine to reclaim the sand surface such as scrubbing. When the reclaimed sand is used, it is possible to improve the mold strength when the mold is molded with the binder. Further, the reason why the ignition loss of the reclaimed sand used in the present invention is preferably 5.0% by weight or less is that the inorganic surface of the reclaimed sand is increased,
This is because if it is 2.0% by weight or less, the hydroxyl groups on the inorganic surface are abundant and the binding force with the binder is increased. As the type of the refractory granular material, in addition to silica sand containing silica as a main component, inorganic refractory granular materials such as chromite sand, zirconia sand, olivine sand, and artificial synthetic mullite sand are used, but are not particularly limited. is not.

(Explanation of Water-Soluble Phenolic Resin) The water-soluble phenolic resin used in the present invention is a resin curable by carbon dioxide gas such as phenol, cresol, resorcinol, 3,5-xylenol, bisphenol A, and others. Mention may be made of phenolic resins obtained by reaction of phenols, including substituted phenols and mixtures thereof with aldehydes such as formaldehyde, acetaldehyde, furfural aldehyde and mixtures thereof. Suitable alkaline substances used for the condensation of these phenolic resins are sodium hydroxide, potassium hydroxide, lithium hydroxide and mixtures thereof, of which potassium hydroxide is preferred.

In the present invention, at least one selected from oxyanion compounds such as borax, sodium aluminate and sodium stannate as a curing accelerator is a water-soluble phenol resin.
You may add and use 1-10 weight part with respect to 00 weight part.

Further, in the present invention, glycol ether may be added to the water-soluble phenol resin. Normal,
The amount of glycol ether added is 1 to 100 parts by weight of the water-soluble phenol resin containing the oxyanion compound.
Add 20 parts by weight. As a glycol ether,
Diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether , Diethylene glycol monobutyl ether and the like.

Further, a compound such as a silane coupling agent may be added for the purpose of further improving the mold strength. Addition amount of silane coupling agent is water-soluble phenol resin
The amount is preferably 0.01 to 3 parts by weight, more preferably 0.1 to 1 part by weight, based on 100 parts by weight.

[0024]

By [act] acid dissociation exponent pK _a to use 5.0 or less acid, when manufacturing the mold with the reclaimed sand that has been reproduced from the mold using a water-soluble phenolic resin, the mold strength and pot life The mechanism that is significantly improved is estimated as follows. During repeated regeneration, the alkaline components (eg K ₂ CO ₃ , Na) accumulated as the regenerated sand burning loss component were accumulated.
₂ CO _{3 and} other salts and KOH, NaOH and other hydroxides) are acid dissociation indices
pK _a is recovers reactive reclaimed sand and binder by being neutralized and decarboxylation by 5.0 the following acids.

[0025]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In addition, "%" in the following examples is "% by weight".

<Preparation Method of Reclaimed Sand Used in Comparative Examples 1 to 3 and Examples 1 to 14> 0.5% of γ-aminopropyltriethoxysilane based on 100 parts by weight of new sand of domestic No. 5 silica sand.
3 parts by weight of a water-soluble phenolic resin (60% solid content) containing (relative to the resin) was added and kneaded, and the mixture was filled into a model for gas curing, and carbon dioxide gas (gas pressure 2 kg / cm ² , aeration rate 100 L).
(/ min.) per 100 parts by weight of new sand, 3 parts by weight of aerated air was used to cast a FC-250 (S / M = 3.5) equivalent product, and the recovered sand was crushed by a crusher and cast in Japan ( It was regenerated using an M type rotary reclaimer manufactured by Co., Ltd. The reclaimed sand obtained by repeating the above steps 5 times was used as the test reclaimed sand (causing loss by ignition of 0.9%).

Comparative Examples 1-2 and Examples 1-8 The mold strength in the carbon dioxide curing mold making method was evaluated. That is, the acid value (KOH
0.3 parts by weight of an aqueous solution of the acid shown in Table 1 adjusted to 500 mg / g), and 0.5% of γ-aminopropyltriethoxysilane.
Add 3 parts by weight of carbon dioxide curable water-soluble phenolic resin (60% solid content) containing (to the resin), knead, and leave the mixture in a sealed state for 3 hours, then test piece for gas curing of 50 mmφ × 50 mmh The model is filled and carbon dioxide gas (gas pressure 2 kg / cm ² , aeration rate 20 L / min.) Is aerated for 3 parts by weight with respect to 100 parts by weight of reclaimed sand, and then the test piece is immediately demolded for 24 hours. The subsequent coercive pressure was measured. The results are shown in Table 1.

[0028]

[Table 1]

* 1: From the Science Handbook Basic Edition II Revised 2nd Edition (Chemical Society of Japan) * 2: GEK Branch and M. Calvin, The Theory of Orga
nic Chemistry, Prentice Hall, Englewood Cliffs, N.
From J., 1945, p.207 * 3: J.Horyna, Collection Czech. Chem. Commun., 24,1
From 956, 2637 (1959); 27, 1324 (1961).

From the results shown in Table 1, it can be seen that the mold strength of the test pieces of Examples 1 to 8 is higher than that of the test pieces of Comparative Examples 1 and 2. That is, it is clear that the method of the present invention improves mold strength and pot life.

Comparative Example 3 and Examples 9 to 14 The mold strength in the carbon dioxide curing mold making method was evaluated. That is, with respect to the mixture of 80 parts by weight of the reclaimed sand and 20 parts by weight of the fresh sand, the acid value (KOHmg / g) was adjusted to 500, and the aqueous solution of the acid shown in Table 2 was added. Carbon dioxide curable water-soluble phenol resin containing 0.5% aminopropyltriethoxysilane (based on resin) (60% solid content)
After adding 3 parts by weight of the mixture to the mixture and leaving it in a sealed state for 3 hours, it was filled in a 50 mmφ × 50 mmh model piece for a gas curing test piece, and carbon dioxide gas (gas pressure 2 kg / cm ² , aeration rate 20
L / min.) Was aerated for 3 parts by weight with respect to a mixture of 80 parts by weight of reclaimed sand and 20 parts by weight of fresh sand, the test piece was immediately removed from the mold, and the resistance after 24 hours was measured. The results are shown in Table 2.

[0032]

[Table 2]

From the results of Table 2, it can be seen that the mold strength of the test pieces of Examples 9 to 14 is higher than that of the test piece of Comparative Example 3. That is, it is clear that the method of the present invention improves mold strength and pot life.

<Preparation Method of Reclaimed Sand Used in Comparative Examples 4 to 5 and Examples 15 to 22> 0.5% of γ-aminopropyltriethoxysilane based on 100 parts by weight of fresh sand of domestic No. 6 silica sand.
3 parts by weight of a water-soluble phenolic resin (60% solid content) containing (relative to the resin) was added and kneaded, and the mixture was filled into a model for gas curing, and carbon dioxide gas (gas pressure 2 kg / cm ² , aeration rate 100 L).
(/ min.) per 100 parts by weight of new sand, 3 parts by weight of aerated air was used to cast a FC-250 (S / M = 3.5) equivalent product, and the recovered sand was crushed by a crusher and cast in Japan ( It was regenerated using an M type rotary reclaimer manufactured by Co., Ltd. The reclaimed sand obtained by repeating the above steps 5 times was used as the test reclaimed sand (causing loss by ignition of 0.9%).

Comparative Examples 4 to 5 and Examples 15 to 22 The mold strength in the carbon dioxide curing mold making method was evaluated. That is, with respect to 100 parts by weight of the above-mentioned reclaimed sand, the acid value (KOHmg / g) was adjusted to 250 with an aqueous solution of the acid shown in Table 3.
3 parts by weight, and γ-aminopropyltriethoxysilane
After adding 3 parts by weight of carbon dioxide curable water-soluble phenolic resin (solid content 60%) containing 0.5% (based on resin) and kneading, leave the mixture in a sealed state for 3 hours, then 50 mmφ × 50 mm
The model for gas hardening test piece of h is filled and carbon dioxide (gas pressure 2 kg / cm ² , aeration 20 L / min.) is reclaimed sand 100
3 parts by weight of air was aerated with respect to parts by weight, and then the test piece was immediately removed from the mold to measure the coercive pressure after 24 hours. The results are shown in Table 3.

[0036]

[Table 3]

From the results shown in Table 3, it can be seen that the mold strength of the test pieces of Examples 15 to 22 is higher than that of the test pieces of Comparative Examples 4 to 5. That is, it is clear that the method of the present invention improves mold strength and pot life.

<Preparation Method of Reclaimed Sand Used in Comparative Examples 6 to 7 and Examples 23 to 30> 0.5% of γ-aminopropyltriethoxysilane based on 100 parts by weight of new sand of domestic No. 6 silica sand.
5 parts by weight of a water-soluble phenolic resin (60% solids content) containing (relative to the resin) was added and kneaded, and the mixture was filled into a gas curing model, and carbon dioxide gas (gas pressure 2 kg / cm ² , aeration rate 100 L).
/ min.) with 5 parts by weight of 100 parts by weight of fresh sand, and cast a FC-250 (S / M = 3.5) equivalent product using a mold, and the recovered sand is crushed by a Japanese casting ( It was regenerated using an M type rotary reclaimer manufactured by Co., Ltd. The above steps were repeated 5 times to obtain reclaimed sand with the loss on ignition (%) shown in Table 4, and this was used as test reclaimed sand.

Comparative Examples 6 to 7 and Examples 23 to 30 The mold strength in the carbon dioxide curing mold making method was evaluated. That is, with respect to 100 parts by weight of the reclaimed sand having an ignition loss (%) shown in Table 4, 0.3 parts by weight of the aqueous solution of the acid shown in Table 4 having the acid value (KOHmg / g) adjusted to 500, and γ-aminopropyl Carbon dioxide curable water-soluble phenolic resin (solid content 60%) containing 0.5% triethoxysilane (based on resin)
After adding the parts by weight and kneading, the mixture was left in a sealed state for 3 hours, then filled in a model for a 50 mmφ × 50 mmh test piece for gas curing, and carbon dioxide gas (gas pressure 2 kg / cm ² , aeration 20 L / mi).
n.) was aerated for 4 parts by weight with respect to 100 parts by weight of the reclaimed sand, and then the test piece was immediately removed from the mold to measure the coercive pressure after 24 hours. The results are shown in Table 4.

[0040]

[Table 4]

From the results shown in Table 4, it can be seen that the test pieces of Examples 23 to 30 have higher mold strength than the test pieces of Comparative Examples 6 to 7. That is, it is clear that the method of the present invention improves mold strength and pot life.

[0042]

As is clear from the above examples, in the case of manufacturing a mold using recycled sand, the method of the present invention provides a mold having a higher strength than that obtained by the conventional manufacturing method. At the same time, the pot life of the resin kneading sand is improved. As a result, since it is possible to reduce the amount of the binder used, it is easy to regenerate the casting sand, and at the same time, the amount of gas generated from the mold during casting can be reduced, so that the occurrence of gas defects is suppressed and good casting is achieved. Can be manufactured, which is useful in practice. Further, by using the acid of the present invention, it is possible to prolong the pot life at the time of producing the mold, which facilitates the practical production of the mold.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-50176 (JP, A) JP-A-8-215788 (JP, A) JP-A-6-126378 (JP, A) JP-A-6- 210391 (JP, A) JP-A-6-210392 (JP, A) JP-A-6-210393 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B22C 9/12 B22C 1 / 00-1/26

Claims (5)

(57) [Claims] 1. A processing method of casting sand, wherein a water-soluble phenolic resin acids refractory particulate material used in the mold fabrication method of curing with carbon dioxide gas dissociation exponent pK _a confer 5.0 following acid. 2. The method for treating foundry sand according to claim 1, wherein the refractory granular material contains 50 wt% or more of the refractory granular material regenerated for reuse. 3. The method for treating foundry sand according to claim 2, wherein the refractory granular material regenerated for reuse has an ignition loss of 5.0% by weight or less. 4. A method for producing a mold, which comprises using a refractory granular material with an acid having an acid dissociation index pKa of 5.0 or less in _a method of producing a mold for curing a water-soluble phenolic resin with carbon dioxide gas. . 5. The method for producing a mold according to claim 4, wherein the refractory granular material contains 50% by weight or more of the refractory granular material regenerated for reuse.