JP6119611B2 - Resin coated sand fluidity improver - Google Patents

Description

  The present invention relates to a fluidity improver for resin-coated sand. Specifically, the present invention improves the fluidity of the resin-coated sand when pouring the resin-coated sand into the mold at the time of mold production, can suppress blocking of the resin-coated sand, remarkably increase the strength of the mold, The present invention relates to a fluidity improver for resin-coated sand that can improve the casting surface.

  The mold is made by combining refractory aggregates for molds such as cinnabar with a binder such as phenol resin, and then adding resin-coated sand obtained by adding a fluidity improver to the mold and raising the temperature to cure. Since it has excellent characteristics such as good dimensional accuracy, it has been widely used in the past.

  And as this fluidity improver, fatty acid metal salts are generally used. Mix the refractory aggregate and the binder to cover the surface of the refractory aggregate, and then add a fatty acid metal salt to prepare a resin-coated sand, and then apply this resin-coated sand to a heated mold. The shell mold is formed by pouring and filling and melting and curing the binder. Here, the fluidity improver improves the workability by improving the fluidity when molding the resin-coated sand into the mold, and blocking occurs until the resin-coated sand is used. It is used to prevent.

  Thus, when manufacturing the resin coated sand which coat | covered the binder and the fluidity improver on the refractory aggregate, it carries out as follows, for example. First, a thermosetting resin such as a solid phenol resin is added as a binder to a refractory aggregate heated to about 120 to 180 ° C., mixed with a mixer, and the resin is heated and melted with the heat of the refractory aggregate. The resin is coated on the surface of the refractory aggregate. Next, in order to lower the temperature below the softening point of the thermosetting resin while maintaining this mixing, water for cooling or an aqueous solution in which a curing agent such as hexamethylenetetramine is dissolved as necessary is added. At this time, as the cooling progresses, the refractory aggregate in the mixer increases in viscosity and becomes cocoon-like, and then suddenly disintegrates to a smooth state. After this, a fluidity improver such as a fatty acid metal salt is added in a state where the inside of the mixer is at about 70 to 90 ° C., and the mixture is mixed in a short time of about 10 to 60 seconds and under mild conditions. Resin coated sand can be obtained by paying off In the production of resin-coated sand, binders such as phenolic resin that has been coated with refractory aggregate and cooled and solidified are peeled off from refractory aggregate by adding and mixing a fluidity improver under mild mixer stirring conditions. Can be prevented.

As a fluidity improver (lubricant) for resin-coated sand, for example, Patent Document 1 uses calcium stearate (paragraphs [0034] and [0046]).
However, the conventional calcium stearate does not sufficiently exhibit the lubricity action by the fluidity improver, and the effect of improving the fluidity becomes insufficient, which may reduce the strength of the mold. In particular, when manufacturing a complex mold having a shape such as a core, it may be difficult to pour the resin-coated sand into a complicated and dense mold, and there is a possibility that quality may be deteriorated due to insufficient strength. Further, the conventional calcium stearate has a problem that the workability of molding is lowered or blocking occurs before the resin-coated sand is used. These problems have not been solved yet.

  Furthermore, when casting of a casting is performed using such a mold, when bath water, which is a high-temperature molten metal, is in contact with the surface of the mold, the so-called “hot water bath” is formed at the interface between the mold and the bath water. “Insertion” and “crack” may occur, and the casting skin (surface state) may be roughened, or sand removal failure may occur on the casting surface.

JP 2007-275988 A

  The present invention has been made in view of the above problems, and can improve the fluidity of the resin-coated sand when casting the resin-coated sand into a mold during mold production, and can suppress blocking of the resin-coated sand. An object of the present invention is to provide a fluidity improver for resin-coated sand that can remarkably increase the strength of the mold and improve the casting surface.

  As a result of intensive studies to solve the above problems, the present inventors have found that resin-coated sand containing fatty acid metal salt particles having a specific particle size summary value and agglomeration degree exhibits excellent performance, The present invention has been completed.

That is, the present invention comprises divalent fatty acid metal salt particles having 8 to 24 carbon atoms, the particle size summary value A represented by the following formula (1) satisfies the relationship of A ≦ 2.0, and is an environment at 80 ° C. in the fatty acid metal salt particles allowed to stand for 10 minutes under, cohesion B (%) shown by the following equation (2) as measured by a powder tester meets the relation B ≦ 20, said divalent fatty acid metal A fluidity improver for resin-coated sand , wherein the divalent metal constituting the salt particles is calcium .

Particle size summary value A = (D90−D10) / D50 (where 1.0 ≦ D50 ≦ 40.0) (1) Formula D10: 10% integrated diameter (μm) of fatty acid metal salt particles based on volume
D50: Median diameter (μm) of fatty acid metal salt particles based on volume
D90: 90% integrated diameter (μm) of fatty acid metal salt particles based on volume

  Aggregation degree B = [(mass of fatty acid metal salt particles remaining on sieve with 350 μm sieve) / 2] × 100 × (1/1) + [(mass of fatty acid metal salt particles remaining on sieve with 250 μm sieve) / 2] × 100 × (3/5) + [(mass of fatty acid metal salt particles remaining on a sieve having a mesh size of 150 μm) / 2] × 100 × (1/5)] (2) formula

  Moreover, this invention is resin coated sand containing a fireproof aggregate, a binder, and the fluidity improving agent for resin coated sands of this invention.

  The fluidity improver for resin-coated sand of the present invention can impart excellent fluidity to the resin-coated sand and can suppress the occurrence of blocking of the resin-coated sand. Therefore, the bulk density of filling can be increased, and the effect of remarkably improving the strength of a mold such as a complicated and dense mold can be sufficiently obtained. When the resin coated sand is poured into the mold at the time of mold production, the resin coated sand is easily poured, and the mold is easily released from the mold, so that the workability of molding is improved. Furthermore, the occurrence of so-called “insertion” or “crack” in the bath water can suppress the roughening of the casting skin (surface condition) or the occurrence of sand removal defects on the casting surface.

Hereinafter, embodiments of the present invention will be described. The flowability improver for resin-coated sand of the present invention (hereinafter also simply referred to as flowability improver), the refractory aggregate, the binder and the resin-coated sand used for the resin-coated sand will be described in order.
In the present invention, the numerical value sandwiching the symbol “to” is included in the range defined by “to”. For example, “10-30” represents a range of 10 or more and 30 or less.

(1) Fluidity improver The fluidity improver used in the present invention comprises divalent fatty acid metal salt particles having 8 to 24 carbon atoms. This fatty acid metal salt particle is a metathesis method in which a fatty acid alkali compound salt obtained by reacting a monovalent alkali compound with a fatty acid having 8 to 24 carbon atoms and a divalent metal salt are reacted in an aqueous solution. Can be prepared.

  The fatty acid used as the raw material for the fatty acid alkali compound salt is not particularly limited as long as it is a fatty acid having 8 to 24 carbon atoms. That is, any of naturally occurring fatty acids and synthetic fatty acids may be used, either saturated fatty acids or unsaturated fatty acids may be used, and either linear or branched fatty acids may be used. Furthermore, a functional group such as a hydroxyl group, an aldehyde group, or an epoxy group may be included in the structure of the fatty acid. Preferably, it is a linear saturated fatty acid having 12 to 22 carbon atoms. When the number of carbon atoms is less than 8, the effect as a fluidity improver of the obtained fatty acid metal salt particles cannot be obtained. On the other hand, fatty acids having more than 24 carbon atoms are difficult to obtain industrially, and the solubility of the resulting fatty acid alkali compound salt in water is significantly reduced, resulting in low productivity.

  Examples of the fatty acid include caprylic acid, capric acid, lauric acid, myristic acid, myristoleic acid, palmitic acid, palmitooleic acid, stearic acid, oleic acid, linoleic acid, arachidic acid, behenic acid, erucic acid, Examples thereof include hydroxystearic acid and epoxy stearic acid, among which stearic acid is preferred. When using a mixed fatty acid, a mixed fatty acid having a stearic acid content of preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more is used.

  Examples of the monovalent alkali compound used as the raw material for the fatty acid alkali compound salt include hydroxides of alkali metals (sodium, potassium, etc.) and amines such as ammonia, monoethanolamine, diethanolamine, and triethanolamine. From the viewpoint of high solubility in water when a fatty acid alkali compound salt is used, an alkali metal hydroxide such as sodium or potassium is preferred.

  The fatty acid alkali compound salt used in the present invention generally has a monovalent alkali compound and a fatty acid at a temperature that is not lower than the melting point of the fatty acid and does not decompose the fatty acid, preferably 100 ° C. or lower, more preferably 50 to It is obtained by reacting at 100 ° C., more preferably 60 to 95 ° C., particularly preferably 70 to 95 ° C.

As the divalent fatty acid metal salt particles used in the present invention, it is preferable to use fatty acid metal salt particles obtained by reacting the fatty acid alkali compound salt obtained above with a divalent metal salt in an aqueous solution. The divalent metal salt is specifically a salt of a divalent inorganic metal and an inorganic acid or an organic acid. Examples of divalent inorganic metals include alkaline earth metals such as magnesium, calcium and barium, transition metals such as titanium, zinc, iron, manganese, cadmium, mercury, zirconium, lead, copper, cobalt, aluminum and nickel. It is done. Among these, calcium and magnesium are preferable because they are less burdensome on the environment and are easily available industrially. Particularly preferably calcium der terms of fluidity of the resin-coated sand is, Ru calcium as divalent metal constituting a divalent fatty acid metal salt particles used in the present invention.

  Examples of the divalent metal salt include calcium chloride, calcium acetate, magnesium chloride, magnesium sulfate, zinc chloride, zinc sulfate, and aluminum sulfate. In particular, chlorides such as calcium and magnesium, sulfates, and nitrates are preferable because they have high solubility in water and efficiently react with fatty acid alkali compound salts.

Specifically, the above reaction is performed by separately preparing a divalent metal salt-containing aqueous solution and a fatty acid alkali compound salt-containing aqueous solution, and then mixing them. For example, the divalent metal salt-containing aqueous solution is added to the fatty acid alkali compound salt-containing aqueous solution, or both are added to another reaction tank.
When mixing the fatty acid alkali compound salt-containing aqueous solution and the divalent metal salt-containing aqueous solution, for example, when the divalent metal salt-containing aqueous solution is added at once to the fatty acid alkali compound salt-containing aqueous solution, the resulting fatty acid metal salt particles There is a possibility that the shape of the material becomes non-uniform and the particle size distribution becomes wide. Therefore, in the present invention, it is preferable that the divalent metal salt-containing aqueous solution is gradually dropped at an appropriate rate with respect to the fatty acid alkali compound salt-containing aqueous solution.

  The concentration of the fatty acid alkali compound salt during the production of the fatty acid metal salt is usually 1% by mass to the productivity of the fatty acid metal salt and the handling property of the fatty acid alkali compound salt-containing aqueous solution or the resulting fatty acid metal salt slurry. 20% by mass, preferably 5% by mass to 15% by mass. When the concentration of the fatty acid alkali compound salt is less than 1% by mass, the productivity of the fatty acid metal salt may decrease, which is not practically preferable. When the amount exceeds 20% by mass, the viscosity of the fatty acid alkali compound salt-containing aqueous solution or the resulting fatty acid metal salt slurry increases, so that it may be difficult to perform a uniform reaction. The concentration of the divalent metal salt in the divalent metal salt-containing liquid is determined from the viewpoint of the productivity of the fatty acid metal salt, and the handling property of the fatty acid alkali compound salt-containing aqueous solution or the obtained fatty acid metal salt slurry. Usually, it is 10 mass%-50 mass%, Preferably it is 10 mass%-40 mass%.

  The reaction between the fatty acid alkali compound salt and the divalent metal salt is performed under temperature conditions that are usually performed by those skilled in the art in consideration of the solubility of the fatty acid alkali compound salt. Preferably it is 50-100 degreeC, More preferably, it is 60-95 degreeC. When reaction temperature is less than 50 degreeC, there exists a possibility that the reaction rate of a fatty-acid alkali compound salt and a bivalent metal salt may fall.

  Polyalkylene glycol ethers, especially oxypropylene blocks, are the oxyethylene blocks for the purpose of stabilizing the fatty acid metal salt slurry during the reaction between the fatty acid alkali compound salt and the divalent metal salt and improving the productivity of the fatty acid metal salt. It is preferable that a triblock ether having a structure sandwiched between (EO-PO-EO) is present in the fatty acid metal salt slurry. The content of the polyalkylene glycol ether in the fatty acid metal salt slurry is usually 0.01 to 5 parts by mass, preferably 0.05 to 2 parts by mass with respect to 100 parts by mass of the fatty acid alkali compound salt. is there. The polyalkylene glycol ether may be present in the reaction system before reacting the monovalent alkali compound with the fatty acid, or the reaction system before the reaction between the fatty acid alkali compound salt and the divalent metal salt. May be present.

  By the above method, a fatty acid metal salt slurry is obtained. This fatty acid metal salt slurry is used as it is or after separating the solvent by a centrifugal dehydrator, filter press, vacuum rotary filter, etc., and if necessary, washing and removing by-product inorganic salts, Drying is performed by an air dryer, an aeration dryer, a spray dryer, a fluidized bed dryer or the like. The drying method may be continuous, batch, normal pressure or vacuum. Furthermore, the dried fatty acid metal salt is pulverized as necessary. The pulverization method is not particularly limited, and for example, a pin mill, a jet mill, an atomizer or the like can be used. The pulverized fatty acid metal salt particles are classified. That is, classification is performed using a multistage sieving apparatus or the like that applies vibrations and performs sieving to adjust the particle size distribution. In this way, the fatty acid metal salt particles as the fluidity improver for the resin-coated sand of the present invention can be obtained.

  By making the fatty acid metal salt particles used in the present invention narrow in particle size distribution, it is possible to make the fatty acid metal salt particles uniformly present in the resin-coated sand, and the effects of the present invention (especially the core strength improvement) can be further improved. It is easy to express stably. Specifically, the particle size summary value A represented by the following formula (1) of the fatty acid metal salt particles is set to 2.0 or less. In the present invention, the particle size summary value A is calculated from the particle size measured by the microtrack laser diffraction method. If the particle size summary value A exceeds 2.0, the resin coated sand fluidity becomes unstable due to variations in the particle size of the fatty acid metal salt particles present in the resin coated sand. Therefore, there is a possibility that a casting having the intended strength cannot be manufactured. Accordingly, when the particle size summary value A exceeds 2.0, the so-called “insertion” or “crack” of the bath water causes the casting's skin (surface state) to become rough, or cause the sand removal failure on the casting's surface. there is a possibility.

  More preferably, the particle size summary value A satisfies the relationship of 1.0 ≦ A ≦ 1.8. When the relationship of 1.0 ≦ A ≦ 1.8 is satisfied, the effects of the present invention can be obtained more stably. When the particle size summary value A is less than 1.0, it may be difficult to produce industrially, for example, the yield may be significantly reduced.

  The particle size summary value A is adjusted by adjusting the concentration of the fatty acid alkali compound salt, the temperature during the reaction between the fatty acid alkali compound salt and the divalent metal salt, and dropping the divalent metal salt-containing aqueous solution into the fatty acid alkali compound salt-containing aqueous solution. It can carry out by adjusting the dripping speed | rate at the time of carrying out suitably, respectively. In addition, those having a wide particle size distribution, that is, a particle size summary value A having a large value can be obtained by classification using a sieve of 100 mesh, 200 mesh, 330 mesh or the like in post-processing.

  The microtrack laser diffraction method used here is a method for obtaining a particle size distribution using scattered light obtained by irradiating particles with laser light. In the present invention, the measurement is performed by a wet method in which an organic solvent in which fatty acid metal salt particles are not dissolved, for example, an organic solvent such as ethanol or isopropyl alcohol is circulated, and the sample is put as it is. Moreover, the measurement object in this invention is the range of a particle diameter of 0.1 micrometer-200 micrometers, and let the value represented by the following (1) formula be the particle size summary value A. In the present invention, measurement can be performed using, for example, Microtrack MT-3000 manufactured by Nikkiso Co., Ltd.

Particle size summary value A = (D90−D10) / D50 (where 1.0 ≦ D50 ≦ 40.0) (1) Formula D10: 10% integrated diameter (μm) of fatty acid metal salt particles based on volume
D50: Median diameter (μm) of fatty acid metal salt particles based on volume
D90: 90% integrated diameter (μm) of fatty acid metal salt particles based on volume

  In the production of resin-coated sand, refractory aggregate and binder are added and heated to around 120 to 170 ° C with cooling water or, if necessary, an aqueous solution in which a curing agent is dissolved. The mixture is cooled to around 70 to 90 ° C., and when the material is released and the fluidity is obtained, a predetermined amount of the fluidity improver is added, and the resin is mixed for about 10 to 60 seconds with gentle stirring. The coated sand can be discharged.

  According to the study of the present inventors, the aggregation degree B (%) represented by the following formula (2) measured by a powder tester when the fatty acid metal salt particles are left in an environment of 80 ° C. for 10 minutes is B ≦ By satisfying the relationship of 20, the fatty acid metal salt particles can be easily released even under mild mixing conditions of the resin-coated sand, and can be quickly and uniformly dispersed in the resin-coated sand. Therefore, the bulk density can be increased with the improvement of the fluidity of the resin-coated sand, and the strength of the mold such as the core can be improved. Moreover, it can suppress that the quality defect of a casting_mold | template arises. Furthermore, the occurrence of so-called “insertion” or “crack” in the bath water can suppress the roughening of the casting skin (surface condition) or the occurrence of sand removal defects on the casting surface.

  The adjustment of the degree of aggregation B is performed by carrying out the reaction between the fatty acid alkali compound salt and the divalent metal salt under mild conditions and preventing aggregation of the fatty acid metal salt particles in the slurry obtained by the reaction. Can do. That is, for example, the reaction can be performed at a mild temperature that does not decrease the reaction rate during the reaction between the fatty acid alkali compound salt and the divalent metal salt, or by shortening the aging time. By appropriately adjusting these factors during the reaction, the degree of aggregation B can be adjusted within the range specified in the present invention.

  The degree of aggregation B (%) is more preferably 2 ≦ B ≦ 18, further preferably 2 ≦ B ≦ 15, and particularly preferably 2 ≦ B ≦ 13. When 2 ≦ B ≦ 13 is satisfied, the operational effects of the present invention can be obtained more stably. On the other hand, when the aggregation degree B is less than 2%, the handling property of the fatty acid metal salt particles is deteriorated when added to the resin-coated sand, and the workability may be lowered.

  Aggregation degree B = [(mass of fatty acid metal salt particles remaining on sieve with 350 μm sieve) / 2] × 100 × (1/1) + [(mass of fatty acid metal salt particles remaining on sieve with 250 μm sieve) / 2] × 100 × (3/5) + [(mass of fatty acid metal salt particles remaining on a sieve having a mesh size of 150 μm) / 2] × 100 × (1/5)] (2) formula

The aggregation degree B of the fatty acid metal salt particles by the powder tester used here is a value obtained by the following measuring method. That is, for example, the following steps (a) to (f) are performed using a powder tester (manufactured by Hosokawa Micron Corporation, PT-N type).
(A) The fatty acid metal salt particles to be measured are left for 10 minutes in a thermostat set to 80 ° C.
(B) Sieves of 350 μm, 250 μm, and 150 μm are sequentially set from the upper layer on the vibrating table of the powder tester.
(C) Immediately place 2.0 g of fatty acid metal salt particles after step (a) gently on a sieve having a sieve size of 350 μm.
(D) Vibrate the sieve with an amplitude of 1 mm for 105 seconds.
(E) The mass of the fatty acid metal salt particles remaining on each sieve is measured.
(F) A value obtained by multiplying each mass obtained in the step (e) by a weight of 1/1, 3/5, and 1/5 in order, and adding these to calculate the percentage by the above equation (2). Is a degree of aggregation B (%).
The above steps (a) to (f) are repeated five times, and the average value is taken as the measured value.

  Furthermore, the fatty acid metal salt particles used in the present invention preferably have a loose bulk density (Da) (g / cc) of 0.110 ≦ Da ≦ 0.180, and 0.135 ≦ Da ≦ 0.160. More preferably. By being 0.110 ≦ Da ≦ 0.180, when added to the resin-coated sand, high slipperiness is obtained in the fatty acid metal salt particles, and fluidity can be further imparted to the resin-coated sand.

  The loose bulk density (Da) is a value obtained by the following measuring method. First, for example, a powder tester (made by Hosokawa Micron Corporation, PT-N type) is used, and a sieve with a mesh size of 710 μm is set on a vibration table. Collect the dropped sample in the measuring cup. Using the attached blade, scrape excess fatty acid metal salt particles on the cup, and then weigh the cup containing the sample. In the present invention, this operation / measurement is repeated five times, and the average value is taken as the measurement value of the bulk density (Da). In the PT-N type, the measured value is automatically displayed.

  Loose bulk density (Da) (g / cc) = weight of cup containing sample (g) / volume of cup (cc) (3)

  The fatty acid metal salt particles used in the present invention have an average circularity C of a particle group of 10% particle diameter to 90% particle diameter of 0.810 to 1.000 as measured by a flow particle image analyzer. Is preferable, 0.820 to 0.950 is more preferable, and 0.830 to 0.920 is particularly preferable. If average circularity C is the said range, the coating property to the resin coated sand particle at the time of fatty acid metal salt particle addition in a resin coated sand manufacturing process can further be improved.

  The average circularity C is adjusted by performing the reaction between the fatty acid alkali compound salt and the divalent metal salt under mild conditions, and the particle shape of the fatty acid metal salt particles in the slurry obtained by the reaction becomes nonuniform. Can be done by preventing. That is, for example, the reaction is performed at a mild temperature that does not reduce the reaction rate during the reaction between the fatty acid alkali compound salt and the divalent metal salt, or the divalent metal salt-containing aqueous solution is changed to the fatty acid alkali compound salt-containing aqueous solution. The dropping can be performed by slowing the dropping speed or adding the above-mentioned polyalkylene glycol ether to stabilize the slurry. By appropriately adjusting these factors during the reaction, the average circularity C can be adjusted within the range specified in the present invention.

  The average circularity in the present invention is used as a simple method for quantitatively expressing the shape of the fatty acid metal salt particles, and can be defined as follows. First, for example, using a flow type particle image analyzer “FPIA-3000” manufactured by Sysmex Corporation, particles within a circle equivalent diameter of 0.5 μm to 200 μm are measured, and the circularity (ai) of each particle measured there. Are obtained by the following equation (4).

Circularity (ai) = (perimeter of a circle having the same area as the projected image of the particle) / (perimeter of the projected image of the particle)
... (4) formula

  The average circularity in the present invention is an index indicating the degree of unevenness of the particle shape of the fatty acid metal salt. As the surface shape of the fatty acid metal salt particle becomes closer to a circle, it approaches 1.000, and the surface shape of the particle becomes complicated. The average circularity becomes a small value. “FPIA-3000”, which is a measuring apparatus that can be used in the present invention, calculates the circularity of each particle, and classifies the circularity of particles from 0.4 to 1.0 into 61 by the obtained circularity. A calculation method is used in which the average circularity is calculated using the center and frequency of the division points.

  In the present invention, the average circularity C (hereinafter, also simply referred to as “average circularity C”) of a particle group having a particle size of 10% to 90% is a particle size among all particles measured by the measuring device. This is a value obtained by dividing the total circularity of particles in the range of 10% particle diameter to 90% particle diameter from the small particle diameter side of the distribution by the number of particles.

  The average circularity C of a particle group having a particle size of 10% to 90% is measured, for example, as follows. 30 ml of ion-exchanged water from which impure solids and the like have been removed in advance is prepared in a container, and a surfactant, preferably polyoxyethylene nonylphenyl ether (trade name: Nonion NS-, manufactured by NOF Corporation) is used as a dispersant therein. After adding 210), 20 mg of a measurement sample is further added and dispersed uniformly. As a dispersing means, for example, an ultrasonic dispersing machine UH-50 type (manufactured by SMT Co., 20 kHz, 50 W) equipped with a titanium alloy chip having a diameter of 5 mm as a vibrator is subjected to a dispersion treatment for 5 minutes. The concentration is set to 3,000 / 20,000 to 20,000 / ml to obtain a dispersion for measurement. At that time, the measurement is performed while cooling appropriately so that the temperature of the dispersion liquid for measurement does not become 40 ° C. or higher. Thereafter, measurement is performed using a flow type particle image analyzer “FPIA-3000”, and the average circularity C is obtained by processing the obtained data.

As described above, the fatty acid metal salt particles used in the present invention have powder physical properties in which each of the particle size summary value A and the aggregation degree B is in a specific range. The smaller the particle size summary value A, that is, the more uniform the particle size distribution of the fatty acid metal salt particles, the easier it is to loosen the degree of aggregation B when a certain external force is applied. At this time, it is preferable that the arithmetic average specific surface area is less than 0.70 m ² / cc, more preferably not more than 0.60 m ² / cc. Such fatty acid metal salt particles are rapidly and uniformly dispersed even at the addition conditions during the production of the resin-coated sand, such as a gentle mixing at 70 to 90 ° C. for a short time of about 10 to 40 seconds, with respect to the resin-coated sand particles. It is preferable in that it can be effectively coated and can impart high fluidity to the resin-coated sand. Along with the provision of high fluidity, the strength of the mold is improved and the occurrence of quality defects can be suppressed. Moreover, it is possible to suppress the occurrence of so-called “insertion” or “crack” of the bath water from causing the casting to have a rough skin (surface state) or causing a sand drop defect to occur on the casting surface. Furthermore, the blocking resistance during storage of the resin-coated sand is also good.

When the present inventors use the obtained fatty acid metal salt particles as a fluidity improver for resin-coated sand, among the obtained powder physical properties, the average circularity of a particle group having a particle size of 10% to 90% It has been found that the numerical relationship between C, the particle size summary value A in the formula (1), and the degree of aggregation B in the formula (2) has a great influence on the fluidity imparted to the resin-coated sand. In other words, the present inventor designed the fatty acid metal salt particles having powder properties satisfying the following relational expression, thereby providing excellent dispersibility with respect to the resin-coated sand even under mild mixing conditions. And found that fatty acid metal salt particles can be obtained that more efficiently improve the coating on the resin-coated sand particles.
That is, 3.0 <{(particle size summary value A × aggregation degree B) / average circularity C} ≦ 37.0 is preferable, and 5.0 <{(particle size summary value A × aggregation degree B) / average. More preferably, the circularity C} ≦ 35.0.
The smaller the {(particle size summary value A × aggregation degree B) / average circularity C} value is within the above range, the smaller the particle size distribution of the fatty acid metal salt particles becomes, and the smaller the degree of aggregation. The shape of each particle becomes close to a circle. Accordingly, it is possible to obtain a resin-coated sand which is quickly and uniformly dispersed in the resin-coated sand at the time of addition, further increases the coating property to the resin-coated sand particles, and has high fluidity.

  The fluidity improving agent for resin-coated sand of the present invention may be used by mixing with a nonionic surfactant. As the nonionic surfactant, an ether type nonionic surfactant is desirable, and polyoxyethylene alkyl ether and / or polyoxyethylene alkylphenyl ether is more desirable. This is because it is better to use the fatty acid metal salt particles and the nonionic surfactant in combination in the stability of the formation of fatty acid metal salt particles in the slurry and the flowability of the resin-coated sand of the obtained fatty acid metal salt particles. This is because.

(2) Refractory aggregate The refractory aggregate used in the present invention is an aggregate for a mold, typically a refractory granular material. Examples of such refractory granular materials include silica sand, chromite sand, zircon sand, olivine sand, mullite sand, synthetic mullite sand, magnesia, special sand, and recovered sand, reclaim, and the like mainly composed of quartz. In the present invention, various refractory granular materials such as fresh sand, recovered sand, reclaimed sand, or mixed sand thereof can be used without particular limitation. Further, the particle size distribution and the particle shape of the refractory granular material can be selected without any particular limitation as long as the refractory granular material is suitable for casting and forming a mold.

(3) Binder The binder used in the present invention includes bentonite, water glass, starch and the like. In general, one or a combination of two or more thermosetting resins such as a phenolic resin such as a resol type, a novolak type, or a benzylic ether type, a furan resin, a urethane resin, an amine polyol resin, or a polyether polyol resin is used. be able to. In addition, these binders are blended with hexamethylenetetramine, isocyanate, organic esters, phosphate esters, etc. as curing agents as necessary, and tertiary amines, sulfur dioxide, pyridine derivatives, organic as curing accelerators. A sulfonic acid etc. can be mix | blended and it can be used after making it thermosetting self-curing property.

(4) Resin coated sand The resin coated sand of the present invention contains the fluidity improver, fireproof aggregate and binder of the present invention. The resin-coated sand can be produced by putting refractory aggregate heated to a predetermined temperature into, for example, a mixer, melt-coating the above-mentioned binder on the refractory aggregate, and then kneading. More specifically, the fire-resistant granular material which is a fire-resistant aggregate is heated to, for example, 130 to 160 ° C., the heated fire-resistant granular material and the binder are kneaded, and then the curing agent is, for example, hexamethylenetetramine. Aqueous solution containing is added and kneaded until the mass of the refractory granular material collapses. Furthermore, it cools to 70-90 degreeC, the fatty-acid metal salt particle | grains by this invention are thrown in as a fluidity improver, and it disperse | distributes on mild conditions for about 10 to 60 second, and obtains the resin coated sand of this invention.

  The compounding quantity of a binder is 0.1-100g with respect to 1kg of fireproof aggregates, Preferably it is 0.1-50g. Moreover, the compounding quantity of the fatty-acid metal salt particle | grains which are the fluidity improvers of this invention is 0.1-50g with respect to 1 kg of fireproof aggregates, Preferably it is 0.1-30g.

  The resin-coated sand obtained as described above is distributed or filled into a mold heated to about 300 ° C. according to a known method, and a binder such as a thermosetting resin is melted and cured. By making it, a casting_mold | template can be manufactured by the bonding action of sand through a binder. And casting can be manufactured by pouring bath water heated at about 900-1900 degreeC into this casting_mold | template.

  By using the fluidity improver of the present invention, the fluidity of the resin-coated sand is improved, and accordingly, a strong mold is obtained. Therefore, it is possible to suppress the occurrence of so-called “insertion” or “crack” in the bath water from causing the casting skin (surface state) to become rough or to cause a sand drop defect on the casting surface.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.

  (Preparation of fluidity improver)

Example 1
A 3 L separable flask was mixed with mixed fatty acids (2.1% by weight myristic acid, 30.3% by weight palmitic acid, 66.5% stearic acid, 0.8% by weight arachidic acid, and 0.3% behenic acid. 250 g, polyethylene glycol / polypropylene glycol / block ether (manufactured by NOF Corporation, trade name: Pronon # 104) was charged with 0.75 g and water 2500 g, and the temperature was raised to 90.degree. Subsequently, 77.2g of 48 mass% sodium hydroxide aqueous solution was added, and it stirred at the same temperature (90 degreeC) for 1 hour, and obtained fatty-acid alkali compound salt aqueous solution. Then, 151.2g of 35 mass% calcium chloride aqueous solution was dripped at the fatty-acid alkali compound salt aqueous solution over 10 minutes, hold | maintaining at 90 degreeC. After completion of dropping, the mixture was kept at 90 ° C. and stirred for 10 minutes for aging. 1500 g of water was added to the obtained mixed fatty acid calcium salt aqueous solution slurry and cooled to 65 ° C. or lower. Thereafter, the mixture was filtered with a suction filter, washed twice with 1000 g of water, and the obtained cake was dried and ground with a micron dryer to obtain fatty acid calcium salt particles.

(Example 2)
In a 3 L separable flask, mixed fatty acids (2.1% by mass of myristic acid, 30.3% by mass of palmitic acid, 66.5% by mass of stearic acid, 0.8% by mass of arachidic acid, and 0.8% of behenic acid were added. 3% by mass) 250 g and 2500 g of water were charged, and the temperature was raised to 80 ° C. Subsequently, 77.2 g of 48 mass% sodium hydroxide aqueous solution was added, and it stirred at the same temperature (80 degreeC) for 1 hour, and obtained fatty-acid alkali compound salt aqueous solution. Then, 151.2 g of 35 mass% calcium chloride aqueous solution was dripped at the fatty-acid alkali compound salt aqueous solution over 30 minutes, hold | maintaining at 80 degreeC. After completion of dropping, the mixture was kept at 80 ° C. and stirred for 30 minutes for aging. 1500 g of water was added to the obtained mixed fatty acid calcium salt aqueous solution slurry and cooled to 65 ° C. or lower. Thereafter, the mixture was filtered with a suction filter, washed twice with 1000 g of water, and the resulting cake was dried, pulverized and classified with a micron dryer to obtain fatty acid calcium salt particles.

(Example 3)
In a 3 L separable flask, mixed fatty acids (myristic acid 1.6% by mass, palmitic acid 24.0% by mass, stearic acid 73.4%, arachidic acid 0.7% by mass, and behenic acid 0.3% 250 g, polyethylene glycol / polypropylene glycol / block ether (manufactured by NOF Corporation, trade name: Pronon # 104) was charged with 0.75 g and water 2500 g, and the temperature was raised to 70.degree. Subsequently, 76.5g of 48 mass% sodium hydroxide aqueous solution was added, and it stirred at the same temperature (70 degreeC) for 1 hour, and obtained fatty-acid alkali compound salt aqueous solution. Then, 150.1g of 35 mass% calcium chloride aqueous solution was dripped at the fatty-acid alkali compound salt aqueous solution over 1 hour, hold | maintaining at 70 degreeC. After completion of the dropwise addition, 1500 g of water was immediately added to the obtained mixed fatty acid calcium salt aqueous solution slurry and cooled to 65 ° C. or lower. Thereafter, the mixture was filtered with a suction filter, washed twice with 1000 g of water, and the obtained cake was dried and ground with a micron dryer to obtain fatty acid calcium salt particles.

(Comparative Example 1)
Calcium stearate (trade name “AFCO CHEM CS-S”, manufactured by ADEKA Corporation)

(Comparative Example 2)
Calcium stearate (trade name “Calcium stearate C” manufactured by NOF Corporation)
(Comparative Example 3)
Calcium stearate (manufactured by Tamnan Chemical Co., Ltd., trade name “Calcium stearate”)

(Comparative Example 4)
Calcium stearate (manufactured by NOF Corporation, trade name “Nissan Electol MC-2”)
(Comparative Example 5)
Calcium stearate (manufactured by Tianjin Shirako Chemical Co., Ltd., trade name "CALCIUM STEARATE")

  About the fatty acid metal salt particles of Examples 1 to 3 and Comparative Examples 1 to 5, the particle size summary value A [10% integrated diameter D10 (μm) on volume basis, median diameter D50 (μm) on volume basis, 90% on volume basis Value calculated from integrated diameter D90 (μm)], loose bulk density Da (g / cc), cohesion degree B (%) and average circularity C were measured by the methods described above using the following apparatuses. The results are shown in Table 1.

(1) Particle size (D10, D50, D90) / specific surface area It was measured with a particle size distribution measuring device (device name “Microtrack MT-3000” manufactured by Nikkiso Co., Ltd.) (principle: laser diffraction / scattering method).
When the cumulative curve was determined with the total volume of the group of powders to be measured as 100%, the particle diameter at the point where the cumulative curve was 10%, 50%, and 90% was 10% diameter (D10) and 50% diameter, respectively. (D50), 90% diameter (D90) (μm). The specific surface area represents the value of the measurement result when the particles are assumed to be spherical.

(2) Loose bulk density The loose bulk density was measured with a powder property evaluation apparatus (device name “Powder Tester PT-N type” manufactured by Hosokawa Micron Corporation).

(3) Aggregation degree It measured with the powder characteristic evaluation apparatus (Equipment name "powder tester PT-N type" Hosokawa Micron Corporation make). A sample obtained by leaving the fatty acid metal salt particles in an environment at 80 ° C. for 10 minutes was used as a measurement sample.

(4) Average circularity Using a flow particle image analyzer “FPIA-3000” (manufactured by Sysmex Corporation), measurement was performed in an aqueous dispersion system.

(Examples 1-3 and Comparative Examples 1-5; Production and Evaluation of Resin Coated Sand)
Using the fatty acid metal salt particles of Examples 1 to 3 and Comparative Examples 1 to 5 as fluidity improvers, resin coated sands were produced as follows. First, 100 g of phenol resin (2.0 wt% / refractory aggregate) as a binder was kneaded with 5 kg of fresh sand heated to 150 ° C. as a refractory aggregate for 45 seconds using a speed mixer, and then 15 g (15.0 wt. % / Resin) of hexamethylenetetramine (reagent) and 100 g of water were mixed and dissolved, and 115 g of an aqueous solution of hexamethylenetetramine was added and kneaded until the lump of sand collapsed. When the temperature reached about 80 ° C., 2.5 g (0.10 wt% / refractory aggregate) of each fatty acid metal salt was added, mixed and kneaded for 30 seconds, and then discharged from the mixer to obtain resin-coated sand. Using the resulting resin-coated sand, the bulk specific gravity, the falling speed, the angle of repose, and the casting surface were measured. Moreover, the obtained resin-coated sand was fired to prepare a test piece, and the bending strength was measured.
The formulation of the resin-coated sand used and the measurement method of each characteristic of the resin-coated sand are shown below, and the results are shown in Table 2.

(Bulk specific gravity)
The bulk specific gravity was measured according to JIS K6721-1995 using a bulk specific gravity measuring machine A type manufactured by Kyowa Rika Kogyo Co., Ltd. The number of measurements was N = 5, and the average value was taken as the value. The unit is g / cc.

(Falling speed)
The drop speed was measured using a Ford cup defined in JIS K5402-1995 according to JACT test method S-5. The number of measurements was N = 5, and the average value was taken as the value. The unit is seconds.

(Repose angle)
The angle of repose was measured using an “AOD powder property measuring instrument” manufactured by Tsutsui Riken Kikai Co., Ltd. The number of measurements was N = 5, and the average value was taken as the value. The unit is degrees.

(Drag strength)
The bending strength was measured by a three-point bending strength test according to JACT (Japan Foundry Technology Association) test method SM-1. The test piece was measured according to JIS K6910-1995 4.9.2 Test piece preparation method (drop method). That is, the fired resin-coated sand test piece was supported at both ends, and the maximum bending stress when a concentrated load was applied from the top to the center was defined as the bending strength (MPa). The molding conditions of the test piece are a mold temperature of 250 ° C. and baking for 60 seconds. The number of measurements was N = 30, and the average value was taken as the value. The unit is kgf / cm ² .

(Cast surface)
The resin-coated sand obtained in Examples 1 to 3 and Comparative Examples 1 to 5 was poured into a mold heated to 300 ° C. and baked for 60 seconds, thereby forming a crucible-like shape having an inner diameter of 100 mm, a height of 100 mm, and a wall thickness of 20 mm. A mold was made. Then, a casting was cast by pouring a bath of 1,400 ° C. ductile cast iron into the mold and cooling, the resulting casting was taken out of the mold, and the surface of the casting was visually observed. “◎” indicates that the cast surface is very good, “◯” indicates that the casting surface is good, “△” indicates that the casting surface is normal, and “×” indicates that the casting surface is bad.

  From the results in Table 2, No. 1 in Table 1 was obtained. 1, no. 2 and no. The resin-coated sand using the fatty acid calcium salt particles of No. 3 has a large bulk specific gravity, a good fall time, a good repose angle, and a small angle of repose. 1-No. No. 3 fatty acid calcium salt particles are No. 3 obtained by the direct method. No. 4 fatty acid calcium salt particles and No. 4 5-No. It can be seen that higher fluidity can be imparted to the resin-coated sand as compared with 8 conventional fatty acid calcium salt particles. In addition, as the fluidity of the resin-coated sand was improved, the filling property was also improved, and it was confirmed that the bending strength of the test pieces obtained by firing these resin-coated sands could be remarkably improved. Furthermore, along with the improvement in bending strength, there was a tendency that the defective product generation rate could be reduced even with a complex mold such as a core. No. Resin coated sand No. 3 has the highest bulk specific gravity, the shortest drop time, the smallest angle of repose, and extremely high fluidity. It was very good.

On the other hand, No. using the fatty acid calcium salt obtained by the direct method. In No. 4, since the particle size summary value A is large, the dispersibility when added to the resin-coated sand is extremely low. Therefore, the bulk specific gravity, the falling time, and the angle of repose were inferior, and accordingly the bending strength was low. Furthermore, the condition of the casting surface was also bad.
No. In No. 5, since the particle size summary value A was large, the particle size was not uniform, and the aggregation degree B was large, the bulk specific gravity, the falling time and the angle of repose were inferior, and accordingly the bending strength was also low.
No. In No. 6, since the particle size summary value A and the aggregation degree B are remarkably high, the dispersibility in the resin-coated sand is low. Therefore, the bulk specific gravity, the falling time, and the angle of repose were inferior, and accordingly the bending strength was low.
No. In No. 7, although the particle size summary value A is small and the average circularity C is high, the cohesion degree B is remarkably high, so that the dispersibility in the resin-coated sand is poor. Therefore, the bulk specific gravity, the falling time, and the angle of repose were inferior, and accordingly the bending strength was low.
No. In No. 8, although the aggregation degree B is low, the particle size summary value A is large and the particle size distribution is broad, and the average circularity C is low, so the dispersibility in the resin-coated sand is extremely poor. Therefore, the bulk specific gravity, the falling time, and the angle of repose were inferior, and accordingly the bending strength was low. Furthermore, the condition of the casting surface was also bad.

  The fluidity improver for resin-coated sand of the present invention has a specific particle size distribution and low cohesiveness. Therefore, by adding the resin-coated sand to the resin-coated sand when casting the resin-coated sand into the mold, it is added to the resin-coated sand. The fluidity of the sand can be remarkably improved as compared with conventional fluidity improvers, and the occurrence of blocking of the resin-coated sand can be suppressed. Therefore, the bulk density of filling can be increased, and the effect of remarkably improving the strength of a mold such as a complicated and dense mold can be sufficiently obtained. When the resin coated sand is poured into the mold at the time of mold production, the resin coated sand is easily poured, and the mold is easily released from the mold, so that the workability of molding is improved. Furthermore, the occurrence of so-called “insertion” or “crack” in the bath water can suppress the roughening of the casting skin (surface condition) or the occurrence of sand removal defects on the casting surface.

Claims (3)

It consists of divalent fatty acid metal salt particles having 8 to 24 carbon atoms, the particle size summary value A represented by the following formula (1) satisfies the relationship of A ≦ 2.0, and left in an environment of 80 ° C. for 10 minutes. in the fatty acid metal salt particles, the secondary aggregation of B represented by the following equation (2) as measured by a powder tester (percent) meets the relation B ≦ 20, constituting the divalent fatty acid metal salt particles A fluidity improver for resin-coated sand, characterized in that the valent metal is calcium .

Particle size summary value A = (D90−D10) / D50 (where 1.0 ≦ D50 ≦ 40.0) (1) Formula D10: 10% integrated diameter (μm) of fatty acid metal salt particles based on volume
D50: Median diameter (μm) of fatty acid metal salt particles based on volume
D90: 90% integrated diameter (μm) of fatty acid metal salt particles based on volume

Aggregation degree B = [(mass of fatty acid metal salt particles remaining on sieve with 350 μm sieve) / 2] × 100 × (1/1) + [(mass of fatty acid metal salt particles remaining on sieve with 250 μm sieve) / 2] × 100 × (3/5) + [(mass of fatty acid metal salt particles remaining on a sieve having a mesh size of 150 μm) / 2] × 100 × (1/5)] (2) formula   The average circularity C of a particle group having a particle size of 10% to 90% is 0.810 to 1.000 when the divalent fatty acid metal salt particles are measured by a flow type particle image analyzer. The fluidity improving agent for resin-coated sand described in 1. A resin-coated sand containing a refractory aggregate, a binder, and a fluidity improver for resin-coated sand according to claim 1 or 2 .