JPH0647480A - Continuous production of sand mold for casting - Google Patents

Abstract

PURPOSE:To easily, economically and continuously produce sand molds for casting having high strength in a large quantity by greatly prolonging the pot life of resin coated sand without degrading its compressive strength. CONSTITUTION:This process for continuous production of the sand molds for casting consists inpetitively executing the various stages of introducing a part of the resin coated sand consisting of a binder soln. contg. water and/or org. solvent and a water-soluble phenolic resin and sand into molds for production of the sand molds, then introducing the vapor or aerosol of a hardener contg. the formate expressed by general formula HCOOR (where R denotes 1 to 3C alkyl group) into the molds. The water and/or the org. solvent are continuously and properly added to the balance of the resin coated sand.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous and large-scale method for producing a high-strength sand mold for castings by extending the pot life of the resin-coated sand.

[0002]

2. Description of the Related Art Conventionally, a method described in Japanese Patent Publication No. 3-68061 is known as an industrial method for producing a sand mold for castings using a binder solution containing a water-soluble phenol resin. That is, the method for manufacturing the sand mold for casting described in the above publication is specifically as follows. First, a resin-coated sand is prepared by mixing a binder solution containing a potassium alkaline phenol / formaldehyde resin and sand for casting with a mixer, and the sand is stored in a sand magazine (sand storage tank). The sand magazine is arranged above the molding die during sand molding, and the resin-coated sand is blown into the mold by blowing air from above. The blown resin-coated sand is then cured at room temperature by passing through a curing agent such as methyl formate to form a sand mold for casting. According to the conventional method, the amount of resin-coated sand stored in the sand magazine was in the range of several tens to several hundreds of times the mold capacity, but from the standpoint of sand mold production efficiency, this ratio is large. The higher the number, the better. However, when the amount of the resin-coated sand stored increases, the number of times air is blown into the resin-coated sand during sand molding increases and the waiting time of the resin-coated sand also increases, so that the solvent is lost and the resin-coated sand is lost. The fluidity of sand is reduced. As a result, the packing density of the resin-coated sand in the mold is reduced, and the strength of the manufactured sand mold is also reduced. Therefore, in order to efficiently manufacture a high-strength sand mold for casting, a method has been employed in which the resin-coated sand is temporarily taken out from the sand magazine during the production downtime and put in a vinyl bag or the like for storage.

[0003]

However, in particular,
When the amount of sand used per hour is small relative to the storage amount in the sand magazine, when the amount of sand used is small relative to the number of times of blowing, when the sand temperature is high and the humidity is low, the conventional casting resin is used. Even with the method for manufacturing foundry sand molds that use coated sand, increasing the amount of resin-coated sand stored in the sand magazine still lowers the packing density of the resin-coated sand and reduces the strength of the sand mold, making it suitable for practical casting. There is a problem that a large number of sand molds cannot be continuously manufactured. An object of the present invention is to solve the problems of the above-described conventional method for continuously manufacturing a sand mold for foundry, and to provide a method for continuously and mass-producing a sand mold for foundry having high strength.

[0004]

According to the present invention, a part of resin-coated sand consisting of sand and a binder solution containing water and / or an organic solvent and a water-soluble phenolic resin is used as a mold for sand mold production. To the general formula HCOOR (where R is 1
Represents an alkyl group of 3; In a continuous method for producing a sand mold for casting, which comprises repeating the steps of introducing vapor or an aerosol of a curing agent containing a formate ester into the mold as shown in (4), water and / or water is added to the remainder of the resin-coated sand. The above method is provided, which is characterized in that an organic solvent is appropriately added.

The binder solution used in the present invention is
It comprises water and / or an organic solvent and a water-soluble phenol resin. The water-soluble phenolic resin used as the binder in the present invention is a resin curable with an organic ester, and examples thereof include phenol, cresol, resorcinol, xylenol, bisphenol A, cumylphenol, nonylphenol, butylphenol, phenylphenol, ethylphenol, Octylphenol, amylphenol, naphthol, bisphenol F, bisphenol C, catechol, hydroquinone, pyrogallol, phloroglucin, lignin, bisphenol A residue, cresol residue, chlorophenol,
Examples thereof include phenol resins obtained by reacting phenols including dichlorophenol and other substituted phenols with formaldehyde, acetaldehyde, furfural aldehyde, a mixture of aldehydes and the like. Suitable alkaline substances used in the condensation of these phenolic resins are sodium hydroxide, potassium hydroxide,
Of the lithium hydroxide and mixtures thereof, potassium hydroxide is most preferred.

As the solvent for the binder, any solvent used in the preparation of the binder solution containing the water-soluble phenolic resin can be used in the present invention. Specifically, in addition to water, JP-A-4-118144, JP-A-4-118145, and JP-A-4-118146
Japanese Unexamined Patent Publication No. 4-118147, Japanese Unexamined Patent Publication No. 4-1
Organic solvents such as aliphatic or aromatic ketone-based, ester-based, ether-based and alcohol-based organic solvents described in JP-A-18148, JP-A-4-118149, and JP-A-4-118150 are used alone or in combination. Alternatively, they can be used as a mixture with water. Temperature and solvent toxicity during manufacturing process of resin-coated sand and sand mold, odor,
From the economical point of view, it has a relatively high boiling point (for example, 100 ° C).
It is preferable to use the aliphatic or aromatic alcohol-based, ether-based, glycol-based, and ketone-based hydrophilic organic solvents described above) alone or in combination, or in combination with water.

Examples of alcohol organic solvents include propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, isoamyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, Capryl alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol, ularyl alcohol, allyl alcohol, crotyl alcohol, propargyl alcohol, cyclopentanol, cyclohexanol, benzyl alcohol, cinnamyl alcohol, furfuryl alcohol, etc. it can. Examples of ether-based organic solvents include anisole, phenetole, butyl phenyl ether, pentyl phenyl ether, methoxytoluene, dibenzyl ether, diphenyl ether, benzyl ethyl ether, veratrol, tetrahydrofuran and glycidyl phenyl ether. As the glycol-based organic solvent, ethylene glycol dimethyl ether, ethylene glycol diethyl ether,
Ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether,
Propylene glycol dipropyl ether, propylene glycol dibutyl ether, butylene glycol dimethyl ether, butylene glycol diethyl ether,
Butylene glycol dipropyl ether, butylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether,
Examples thereof include diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, polyethylene glycol, polypropylene glycol and polybutylene glycol. As the ketone-based organic solvent, methyl ethyl ketone, methyl propyl ketone, isopropyl methyl ketone, butyl methyl ketone,
Isobutyl methyl ketone, pinacolone, diethyl ketone, dipropyl ketone, diisopropyl ketone, mesityl oxide, methylheptenone, cyclobutanone, cyclopentanone, cyclohexanone, methylcyclohexanone, phorone, isophorone, acetophenone, propiophenone, butyrophenone, valerophenone, benzophenone, di Benzyl ketone, 2-acetonaphthone, 2-
Acetofuron, diacetyl, acetylbenzoyl, benzyl, acetylacetone, benzoylacetone, dibenzoylmethane, acetonylacetone, phenacylacetone, 2,6-heptanedione and the like can be mentioned.

The binder solution may optionally contain other components such as a deterioration inhibitor and a drying inhibitor. The sand used in the present invention is all kinds of sand including fine powdery sand, viscous sand, reclaimed sand and the like, and normal foundry sand is preferable, and sand having a particle size of about 50 to 600 μm is particularly preferable. From the viewpoint of the strength of the sand mold, the mixing ratio of the binder solution (solid content of binder 50% by weight) to sand is preferably 0.01 to 10% by weight, and particularly 0.1 to 5%. A range of 0% by weight is preferred.

The resin-coated sand is prepared, for example, by kneading the binder solution and sand at a temperature preferably in the range of -10 to 50 ° C. by a mixer so that the respective components are uniformly mixed. Can be done. Usually, a water-soluble phenol resin and water and / or an organic solvent are mixed in advance to prepare a binder solution, and this solution and sand are kneaded. The prepared resin-coated sand is stored in a sand magazine, and a desired amount of resin-coated sand is introduced into a sand mold manufacturing die by, for example, blowing with air, and then the general formula H
Introducing into the mold a vapor or aerosol of a curing agent containing a formate ester represented by COOR (wherein R represents an alkyl group having 1 to 3 carbon atoms) in an amount sufficient to cure the sand mold. To produce a sand mold for foundry. Next, water and / or an organic solvent are continuously added to the unused resin-coated sand remaining in the sand magazine by an oiler or the like, preferably in the form of fine particles such as mist or steam, and the whole is uniformly permeated. By introducing the desired amount of the resin-coated sand into the sand mold manufacturing die and then repeating the steps of introducing the curing agent, the sand mold for casting can be continuously manufactured. The solvent used here is preferably the same type as the solvent for the binder described above, but may be the same as or different from the solvent used in the preparation of the resin-coated sand. The amount of water and / or organic solvent in the resin-coated sand remaining at any point in the continuous production of the foundry sand mold, the type of water and / or organic solvent used, the temperature during the sand mold manufacturing process, Since it varies depending on various conditions such as the operating method and the weight of the sand mold to be produced, it is necessary to adjust the amount of the solvent added accordingly. From the standpoint of extending the pot life of resin-coated sand and ensuring the strength of the sand mold, approximately 150
1 of the water and / or organic solvent content immediately after the preparation of the resin-coated sand (that is, the initial content of water and / or organic solvent in the resin-coated sand) per 120 g sand mold production.
It is preferable to add water and / or organic solvent in an amount of 0 to 80% evenly to the resin-coated sand in the continuous sand-making process, and to add water and / or organic solvent in an amount of 15 to 50%. Is particularly preferable. Water and / or an organic solvent can be added to the remaining resin-coated sand by spraying the solvent directly onto the resin-coated sand from the upper opening of the sand magazine, or when introducing the resin-coated sand into the mold. There is a method of using air containing solvent vapor or atomizing solvent.

[0010]

When the water and / or the organic solvent in the resin-coated sand is lost in the process of manufacturing the sand mold for casting, its fluidity is impaired. Therefore, when water and / or an organic solvent is appropriately added to the resin-coated sand in the production of the second and later foundry sand molds in the continuous production of the sand mold, its fluidity immediately after the preparation of the resin-coated sand is almost ensured. Therefore, the resin-coated sand is introduced into the mold at a sufficient packing density, and a high-strength sand mold for casting is manufactured by curing. That is, by adding water and / or an organic solvent to the resin-coated sand in the continuous production of the sand mold for casting, the time when the resin-coated sand prepared in a large amount at a time can be used for the continuous mass production of the sand mold, It has become possible to extend it significantly.

[0011]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. Hereinafter, all "parts" are "weight parts",
All "%" mean "% by weight". Example 1 Solid content 5 in 25,000 parts of Fremantle silica sand for casting
While adding 500 parts of a 0% water-soluble phenolic resin aqueous solution, the product was kneaded for 90 seconds at 140 rpm with a Shinagawa mixer to prepare 25,500 parts of resin-coated sand. The prepared resin-coated sand was transferred into a sand magazine. 2 air with a gauge pressure of 3.0 kg / cm ^{2 in} the sand magazine
Blow twice for 2 seconds each to get resin coated sand with a diameter of 50 mm,
It was blown into a mold for producing a mold having a length of 50 mm. next,
Methyl formate at a gauge pressure of 0.5 kg / cm ² for 1 second 1.
0.5 kg after vaporizing 7 parts, gassing with a generator, permeating into the mold and curing
Air purging was carried out at a gauge pressure of / cm ² to produce one core sand mold for casting mold test having a weight of 165 g and a diameter of 50 mm and a length of 50 mm. Further, the blow, gassing, and air purging steps were repeated 19 times at intervals of 30 seconds to manufacture 19 core sand molds for mold testing (20 cores in total). The working temperature and sand temperature are both about 20 ° C and the relative humidity is 56.
%, And the machine used is a cold box machine manufactured by Naniwa Seisakusho Co., Ltd. Blowing resin-coated sand into the mold, curing the series of steps described above,
After 30 minutes, 1 hour, 2 hours, 3 hours, 5 hours, and 8 hours after preparing the resin-coated sand, 20 times each, a total of 120 times, were repeated continuously, and 12 hours after the first sand mold was manufactured. 1
A total of 140 test core sand molds weighing 65 g were manufactured. Here, in the step of blowing the resin-coated sand into the mold (8 hours described above), the air was passed through an oiler containing water to atomize the water to contain the resin-coated sand. 30 minutes, 1 hour, 2 hours after preparation,
After 3 hours, 5 hours, 8 hours, 10 copies each, total 60
A series of the above-mentioned continuous steps were carried out so that a part of water was uniformly added to the resin-coated sand. Immediately after the resin-coated sand is prepared, 3
0 minutes, 1 hour, 2 hours, 3 hours, 5 hours, 8 minutes
The average of the compressive strength of the sand mold produced after 24 hours after production was 42 kgf / cm ² and 41 kg respectively.
f / cm ² , 43 kgf / cm ² , 40 kgf / cm
² , 41 kgf / cm ² , 42 kgf / cm ² , 41k
It was gf / cm ² . That is, it is within the range of 40 to 43 kgf / cm ² for all 140 pieces, and all have a compressive strength of 42 kg of the sand mold produced immediately after the preparation of the resin-coated sand.
It was almost equal to f / cm ² and was sufficiently practical.

Example 2 In the step of blowing resin-coated sand into a mold, except that air containing a mixed solution of water and butyldiglycol (mixing ratio 9: 1) in the form of mist was used. In the same manner as in 1, a series of the above-mentioned continuous steps such as blowing of resin-coated sand and curing were carried out to manufacture a total of 140 test piece sand molds weighing 165 g. Immediately after the resin-coated sand is prepared, 3
0 minutes, 1 hour, 2 hours, 3 hours, 5 hours, 8 minutes
The average of the compressive strength of the sand mold produced after 24 hours after production was 42 kgf / cm ² and 44 kg respectively.
f / cm ² , 44 kgf / cm ² , 46 kgf / cm
² , 44 kgf / cm ² , 43 kgf / cm ² , 43k
It was gf / cm ² . That is, it is in the range of 42 to 46 kgf / cm ² for all 140 pieces, and all have a compressive strength of 42 kg of the sand mold produced immediately after the preparation of the resin-coated sand.
It exceeded f / cm ² and was sufficiently practical.

Example 3 Example 1 was repeated except that air containing a mixed solvent of water and phenoxyethanol (mixing ratio 9: 1) in an atomized state was used in the step of blowing the resin-coated sand into the mold. Similarly, a series of the above-mentioned continuous steps such as blowing of resin-coated sand and curing were carried out to manufacture a total of 140 camshaft core sand molds weighing 165 g. Immediately after the resin-coated sand preparation, 30 minutes, 1 hour, 2 hours, 3 hours,
The sand molds manufactured after 5 hours and 8 hours have an average compressive strength of 42 kgf / cm after 24 hours.
² , 46 kgf / cm ² , 45 kgf / cm ² , 47k
gf / cm ² , 46 kgf / cm ² , 45 kgf / cm
² , 46 kgf / cm ² . That is, it was within the range of 42 to 47 kgf / cm ² for all 140 pieces, and all exceeded the compressive strength of 42 kgf / cm ² of the sand mold produced immediately after the preparation of the resin-coated sand, which was sufficiently practical.

Comparative Example 1 In the step of blowing the resin-coated sand into the mold, the solvent was not contained in the air.
In the same manner as above, a camshaft core sand mold having a weight of 165 g was continuously manufactured. However, immediately after the resin-coated sand preparation,
30 minutes, 1 hour, 2 hours, 3 hours, 5 hours,
The average compressive strength of the sand mold produced after 8 hours after production for 24 hours was 42 kgf / cm ² and 38 k, respectively.
gf / cm ² , 35 kgf / cm ² , 30 kgf / cm
^{2, 27kgf / cm 2, 25kgf} / cm 2, 20k
gf / cm ² , and the one produced more than about 1 hour after the first sand mold production has a significantly reduced compressive strength,
It could not be put to practical use.

[0015]

As described above, according to the method of the present invention, the pot life of the resin-coated sand can be greatly extended without lowering the compressive strength. Therefore, a high-strength sand mold for casting can be easily and economically produced. It has become possible to continuously manufacture in large quantities.

Claims (1)

[Claims] 1. A part of a resin-coated sand consisting of a binder solution containing water and / or an organic solvent and a water-soluble phenolic resin and sand is introduced into a sand mold making mold, and then a general formula HCOOR is used.
(However, R represents an alkyl group having 1 to 3 carbon atoms.) A continuous sand mold for casting, which is obtained by repeating various steps of introducing a vapor or an aerosol of a curing agent containing a formic acid ester into the mold. In a typical manufacturing method, water and / or an organic solvent is appropriately added to the rest of the resin-coated sand,
The method as described above.