JP2633966B2 - Foundry sand composition - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a novel acid-curable molding sand composition, and more particularly to a molding having excellent moldability, improved strength and good heat resistance. It relates to a sand composition.

2. Description of the Related Art Conventionally, acid-curing molds commonly used in the casting field include:
A so-called no-bake mold or a warm box mold or a hot box, which is formed by adding a resinous binder such as phenolic resin and furan resin and an acid curing agent to a refractory aggregate and mixing the molding sand composition at room temperature or by heating. Molds and the like are known. However, molds obtained from this type of composition generally have low heat resistance. For example, when casting cast iron, cast steel, or the like, coating is performed to suppress the occurrence of casting defects such as seizure and insertion during casting. The mold is applied, and as a result, the production efficiency of the mold is reduced, resulting in an increase in cost, and furthermore, there is a drawback that economic disadvantages such as equipment cost and cost burden required for coating are inevitable.

Therefore, there have been many proposals for improving the heat resistance of a mold in order to develop such a defect. Among them, a molding sand composition using a synthetic resin binder modified with an alkyl silicate is particularly useful. (Japanese Patent Laid-Open No. 62-107840).

Problems to be Solved by the Invention However, this type of casting composition has a problem that the mold cannot be produced efficiently because the moldability greatly varies depending on the type of alkyl silicate used. That is, when using methyl silicate,
Since the hydrolysis rate of methyl silicate is very fast, and the generated methyl alcohol is very easy to volatilize,
The resulting composition does not have sufficient pot life and molding of a mold becomes difficult. On the other hand, when ethyl silicate is used, the hydrolysis rate of ethyl silicate is much slower than the former, and the generated ethyl alcohol tends to remain without volatilization. In any case, there is an inconvenience that the pot life and the removal time are not balanced. Another problem is that alkyl silicate has a very low caking force in a low-temperature region, and thus the combined use thereof causes a reduction in mold strength. An object of the present invention is to provide an acid-curing system having excellent moldability rich in the balance between the pot life and the removal time, and providing a mold with significantly improved strength and heat resistance comparable to that of the above-mentioned publication technology. An object of the present invention is to provide a molding sand composition.

Means for Solving the Problems The present inventors have conducted intensive studies on the foundry sand composition having the above-mentioned preferable properties, and as a result, completed the present invention.

That is, the present invention provides (A) a refractory aggregate, (B) an acidic curing agent, (C) an organosilicon compound having a furfuryloxy group, or a mixture of the same and furfurylfurcol, and optionally (D) An object of the present invention is to provide a molding sand composition comprising a resin binder.

 Hereinafter, the present invention will be described in detail.

In the composition of the present invention, the refractory aggregate used as the component (A) is a sand-granular refractory which forms a base material of a mold, and is generally, for example, natural silica sand, artificial silica sand, or regenerated silica sand. Special sands such as silica sand, olivine sand, zircon sand, alumina sand, chromite sand, such as sand,
Slag-based particles such as ferrochrome-based slag, ferronickel-based slag, converter slag, and porous particles such as zeolite and cerabeads are used, but are not limited thereto. One type of these refractory aggregates may be used, or two or more types may be used in combination.

In the composition of the present invention, the organosilicon compound having a furfuryloxy group (hereinafter referred to as FA-modified organosilicon compound) used as a basic element of the component (C) is represented by the following formula (I) An organosilicon compound having one or more hydrolyzable structures in a molecule in which a furfuryloxy group represented by is bonded to a silicon atom directly or via a divalent organic residue such as an alkylene group or an aryl group. is there. This is not only effective in improving heat resistance due to hydrolysis by moisture in the presence of an acidic curing agent, but also functions as a fast-setting binder having the action of a coupling agent, It has a feature in that it has high strength development. In addition, the higher the degree of furfuryloxy modification (hereinafter referred to as the degree of modification of FA), the better in terms of mold strength and high acceleration, and the improvement effect becomes remarkable even when used in combination with a resin binder, which is advantageous. used.

Such FA-modified organosilicon compounds include, for example, halogen groups, haloalkyl groups, phenoxy groups, acetoxy groups,
Reacting an organosilane or organosiloxane having one or more functional groups such as an alkoxy group in a molecule or both with furfuryl alcohol in the presence of a catalyst,
Further, it can be prepared by removing free furfuryl alcohol and neutralizing the catalyst in some cases.

Representative examples of the organosilane include, for example, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetrapentyloxysilane, trimethoxyethoxysilane, triethoxymethoxysilane, trimethoxymethylsilane,
Triethoxymethylsilane, tributoxymethylsilane, triethoxyphenylsilane, triethoxybenzylsilane, vinyltrimethoxysilane, glycidoxymethyltrimethoxysilane, dimethoxydimethylsilane,
Alkoxysilanes such as diethoxydimethylsilane, diethoxydiethylsilane, diethoxydiphenylsilane, methoxytrimethylsilane, ethoxytrimethylsilane, and trichloroethoxymethylsilane; tetraphenoxysilane, diphenoxydiphenylsilane, phenoxytriphenylsilane, phenoxytrimethylsilane, etc. Phenoxysilane; triacetoxymethylsilane,
Acyloxysilanes such as triacetoxyethylsilane, triacetoxyphenylsilane, diacetoxydimethylsilane, diacetoxydiethylsilane, acetoxytrimethylsilane, acetoxytriethylsilane and acetoxytripropylsilane; trichloromethylsilane, trichlorophenylsilane, dichlorodiethylsilane, Halogen silanes such as dichlorofluoropropyl silane are exemplified. Among them, an alkoxysilane, which is particularly advantageous in terms of cost and availability, is preferably used. Further, in consideration of reactivity, moldability, template characteristics, and the like, polyalkoxysilanes having an alkoxy group having 1 to 5 carbon atoms, particularly trialkoxysilane and tetraalkoxysilane, are preferred. As the organosiloxane, for the same reason as above, a condensate obtained by partial hydrolysis of alkoxy silane, for example, ethyl silicate
40, ethyl silicate 45, M-silicate 51 (trade name, manufactured by Tama Chemical Industry Co., Ltd.) and those having a higher SiO ₂ content (for example,
60-80%) is preferably used. Incidentally, the organosilane or organosiloxane applied in the present invention,
It is not necessarily limited to the representative examples described above, and includes those having a functional group capable of forming a furfuryloxy group in the above reaction.

Examples of the reaction catalyst include titanium compounds such as tetra-i-propoxytitanium, tetra-n-butoxytitanium, tetrakis (2-ethylhexoxy) titanium and di-i-propoxybis (acetylacetonato) titanium; Tin compounds such as acetate, tin acetate, tin naphthenate and tin stearate; zinc-2-
Zinc compounds such as ethylhexoate, zinc acetate, zinc salicylate, zinc naphthenate; aluminum compounds such as aluminum acetate; sodium hydroxide, potassium hydroxide, lithium hydroxide, strong basic ion exchange resins, calcium hydroxide, water Basic or alkaline compounds such as barium oxide, magnesium oxide, sodium aluminate, ammonia, triethylamine and triethanolamine are used. Among them, particularly preferred are basic or alkaline compounds which control side reactions such as self-condensation of furfuryl alcohol and organosilicon compounds and have good reactivity (catalytic activity), especially caustic alkali and strongly basic ion exchange resins. Can be The reaction conditions are not particularly limited, and may be appropriately selected according to the types of raw materials and the mixing ratio, the types and amounts of catalysts, the reaction environment (normal pressure, reduced pressure), the degree of reaction (degree of modification, degree of condensation), and the like. But usually 30 ~
It is about 0.5-10 hours at a temperature of 100 ° C.

The FA-modified organosilicon compound thus obtained is
The component (A) is used in an amount of 0.1 part by weight or more, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the refractory aggregate. If the amount is less than 0.1 part by weight, practical improvement in heat resistance cannot be obtained.

The component (C) in the present invention also includes a mixture of the FA-modified organosilicon compound and furfurylfurcol in addition to the FA-modified organosilicon compound. The furfurylfurcol may remain as an unreacted substance in the above reaction, or may be artificially added, for example, to reduce the viscosity.

In the composition of the present invention, a resin binder is optionally used as the component (D). This has the function of hardening at room temperature or heating in the presence of an acidic curing agent to firmly bind the refractory aggregate. Examples of such a material include a resole type phenol formaldehyde resin (hereinafter referred to as a phenol resin). Unia-modified phenolic resin, melamine-modified phenolic resin, epoxy-modified phenolic resin, furan-modified phenolic resin, polyester-modified phenolic resin, furfurylfurcol resin, furfurylfurcol-formaldehyde resin (hereinafter referred to as furan resin), urea-modified furan resin, Phenol-modified furan resin, urea-phenol-modified furan resin, polyester-modified furan resin and the like,
Of course, it is not limited to these.

These resin-based binders may be used alone or in combination of two or more, and the amount thereof is appropriately selected according to the type of the mold and the required characteristics. Per 100 parts by weight of the refractory aggregate of component (A)
Used in the range of ~ 10 parts by weight. It should be noted that a silane coupling agent useful for improving the strength of the mold can be added to these resin binders as desired. Suitable silane coupling agents include, for example, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, N
Amino-based silanes such as -β (aminoethyl) -γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropylethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, β- ( Epoxy silanes such as 3,4-epoxycyclohexyl) ethyltrimethoxysilane, and mercapto silanes such as γ-mercaptopropyltrimethoxysilane.

In the composition of the present invention, the acidic curing agent used as the component (B) has a property of accelerating the hydrolysis reaction of the FA-modified organosilicon compound or the curing reaction of furfurylfurcol or a resin binder. Examples thereof include inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid; organic acids such as benzenesulfonic acid, xylenesulfonic acid, toluenesulfonic acid, phenolsulfonic acid, dodecylbenzenesulfonic acid, and chloroacetic acid; and aluminum chloride. Metal chlorides such as, tin chloride, copper chloride, and iron chloride; and acid salts represented by acidic ammonium salts such as ammonium chloride, ammonium phosphate, ammonium nitrate, ammonium sulfate, and ammonium hydrogen sulfate. It is not something to be done.

One of these acid curing agents may be used alone, or two or more thereof may be used in combination. The amount of the acid curing agent is appropriately selected according to the type and required characteristics of the mold, the type of the acid curing agent, and the like. Is generally used in the range of 5 to 100 parts by weight per 100 parts by weight of the total amount of the component (C) and the optional component (D). Note that these acidic curing agents are usually used as a solution using water or alcohol as a solvent.

The composition of the present invention comprises, for example, (I) refractory aggregate (A component)
A method of mixing and mixing an acidic curing agent (component B) with an FA-modified organosilicon compound (component (C)) and optionally a resin binder (component (D)). (2) In addition to refractory aggregate, Can be prepared by, for example, mixing the components while simultaneously adding them.

In the composition of the present invention, the FA-modified organosilicon compound undergoes hydrolysis at an appropriate rate in the presence of an acidic curing agent to produce furfuryl alcohol and organosilanol. The furfuryl alcohol functions as a binder for the refractory aggregate and rapidly develops its strength. Therefore, the furfuryl alcohol causes a significant increase in strength as compared with the conventional composition, as well as the removal time (high acceleration) and the pot life. This has a subtle effect on the balance with the composition and imparts excellent moldability. On the other hand, the latter organosilanol is self-condensed and polymerized, and at the time of pouring, is turned into a ceramic to exhibit high heat resistance.Therefore, it is necessary to prevent the occurrence of casting defects such as sintering with metal melt and insertion. Can be.

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The properties of the foundry sand composition were measured by the following method.

(1) Mold strength and removal time The compositions obtained in Examples and Comparative Examples were manually filled into a plurality of strength test piece molding wooden molds, allowed to stand at room temperature, and then left for a predetermined time (leaving time from molding to removal from the mold). ) 50mm in diameter, height for each
A 50 mm test piece was demolded, and its compressive strength was measured. The mold strength is indicated by the ultimate strength after 24 hours, and the demolding time (a measure of the curing speed) is determined from the graph of compressive strength-standing time created based on the obtained data.
The standing time at which it becomes 5 kg / cm ² was obtained and shown.

(2) Pot life After performing the molding work of the above (1), the remaining sand is stored and sealed in a polyvinyl bag and allowed to stand at room temperature, and the polyvinyl bag is taken every predetermined time (waiting time from immediately after kneading to molding). A test piece was prepared by taking out the composition, and the mold strength was measured. And the pot life, from the graph of mold strength-standby time prepared based on the obtained data, the mold strength of the composition stored in the polyvinyl bag is the strength of the strength immediately after kneading.
The waiting time to be 80% is shown and shown.

(3) Moldability of the mold The moldability of the mold between compositions of the same type was evaluated by calculating the ratio of the mold removal time / the pot life based on the data measured in the above items (1) and (2). However, it was determined that the smaller the value, the better the moldability.

(4) Heat resistance The compositions obtained in Examples and Comparative Examples were hand-filled into a wooden mold for molding a heat-resistant test piece, and then left at room temperature for 24 hours to have a diameter of 30 m.
Test pieces having a height of 50 mm and a height of 50 mm were prepared. Next, the test piece was heat-treated for 2 minutes in a furnace (temperature: 1100 ° C.) of a high-temperature sand tester manufactured by Deart, and then taken out and cooled to room temperature. Was determined.

○: no change, Δ: partial collapse, ×: complete collapse Production Example 1 832 g of ethyl silicate 28 (trade name, Colcoat Co., tetraethoxysilane) was placed in a reactor equipped with a thermometer, a stirrer, and an alcohol separator. 156g frill alcohol
And 1.7 g of sodium hydroxide, and then heated and heated while reducing the pressure in the reactor and stirring the mixture.
C., the reaction time was about 90 minutes), and the temperature was raised to 160 ° C. while removing free furfuryl alcohol, and then cooled to room temperature to remove the FA-modified organosilicon compound (hereinafter referred to as solution a). ) Got. About the obtained liquid a, the amount of free furfuryl alcohol (%), the degree of FA modification, the viscosity (cp / 25 ° C.) and the like were measured by the following methods. Table 1 shows the results.

(1) Amount of free furfuryl alcohol High-performance liquid chromatography [HLC-801 manufactured by Tosoh Corporation]
0, column TSKG2000HXL × 2, RI detector].

(2) Degree of FA modification After dissolving the FA-modified organosilicon compound in deuterated chloroform, tetramethylsilane was added as an internal standard to prepare a sample for measurement, which was analyzed by nuclear magnetic resonance analysis ( ¹ H-NM).
R). The NMR spectrum is shown in FIG. Is a peak attributed to a methylene proton of a furfuryloxy group bonded to a silicon atom, is a methylene proton of a furfuryl alcohol, and is a peak attributed to a methyl proton of an ethoxy group bonded to silicon. The chemical shifts also [delta] ¹ value attributable to these furfuryl group (approximately 4.
After chemical shifts [delta] ² values attributed to the area X and the free ethoxy methylene protons 7 ppm) and the area Y of the methyl protons (about 1.2 ppm) determined from the integral curve, the formula: degree of modification = 3X / 3
The degree of FA denaturation was calculated from X + 2Y.

(3) The viscosity was measured using a B-type viscometer.

Production Examples 2 to 5 In Production Example 1, except that the charged amount of furfuryl alcohol was changed to the amount shown in Table 1, in the same manner as in Production Example 1
FA-modified organosilicon compounds (hereinafter referred to as solution b, solution c, solution d, and solution e) were produced, and their characteristics were also analyzed. The results are shown in Table 1.

Production Example 6 In Production Example 1, the amount of furfuryl alcohol charged was
A mixture of an FA-modified organosilicon compound and furfuryl alcohol (hereinafter referred to as solution f) was produced in the same manner as in Production Example 1 except that the amount was changed to 1568 g and the operation of removing free furfuryl alcohol was not performed. Characteristic analysis was also performed. Table 1 shows the results.

Production Example 7 In Production Example 6, FA was used in the same manner as in Production Example 6 except that 600 g of ethyl silicate 40 was used instead of ethyl silicate 28, and the charged amount of furfuryl alcohol was 960 g.
A modified organosilicon compound (hereinafter referred to as g solution) was produced, and its characteristics were also analyzed. Table 1 shows the results.

Examples 1 to 7 and Comparative Examples 1 to 3 Shinagawa type tabletop mixer, flattery sand (component A)
32.5 kg xylene sulfonic acid solution (component B) 22.5 g
Was added and mixed for 30 seconds, and then 45 g of the liquid a (component C) obtained in Production Example 1 was added and mixed again for 30 seconds to obtain a molding sand composition (hereinafter referred to as Example 1).

Further, in the same manner, instead of solution a, solution b, solution c,
Six types of molding sand compositions (Examples 2 to 7) were obtained using the liquid d, the liquid e, the liquid f, and the liquid g. For comparison, ethyl silicate 28 (x), an amino-based product manufactured by Nippon Yunika Co., Ltd. Silane A
Using 45 g each of furfuryl alcohol (y) containing 0.5% by weight of -1100 and a mixture thereof (x: y = 1: 2 by weight), three types of molding sand compositions were obtained (Comparative Examples 1 to 3). .

About the obtained molding sand composition, various characteristics were measured according to the above-mentioned test method. Table 1 shows the difference.

Examples 8 to 9 and Comparative Examples 4 to 5 The same procedures as in Example 1 except that the combination of the organosilicon compound and the resin binder (D component) shown in Table 2 was used instead of the liquid a. A molding sand composition was produced in the same manner, and its properties were evaluated. Table 2 shows the results.

The resin binder in Table 2 is manufactured by Asahi Organic Materials Industry Co., Ltd.
HP4021 is a furan resin and HP3000A is a phenolic resin.

Example 10, Comparative Example 6 3 kg of flattery sand and 13.5 g of a 15% by weight cupric chloride solution were charged into a Shinagawa tabletop mixer and mixed for 30 seconds, followed by a furan resin for a worm box manufactured by Asahi Organic Materials Industry Co., Ltd.
45 g of HP7100 and 30 g of the solution f obtained in Production Example 6 were added, and 30 g of
After mixing for 2 seconds, a molding sand composition was obtained (Example 10). For comparison, a molding sand composition was obtained in the same manner except that the liquid f was changed to ethyl silicate 40 (Comparative Example 6).

With respect to these foundry sand compositions, warm strength (a measure of molding) and cold strength were measured by the following test methods. Table 3 shows the results.

Test method: A test piece (length 25 mm x width) which was blow-filled with a molding sand composition into a molding die held at 180 ° C and then fired for a predetermined time
The moldability was determined based on the bending strength (strength at warming) measured 10 seconds after release from the mold.
The bending strength measured by cooling the test piece produced by the same operation to room temperature was defined as the mold strength.

Examples 11 to 14 and Comparative Examples 7 to 9 To evaluate heat resistance by a casting test, first, the liquid a in Example 1 was treated with an organosilicon compound as shown in Table 4 or a combination thereof with a resin binder. The molding sand composition was obtained in the same manner as in Example 1 except that the composition was changed to. Next, a step cone core 1 is manufactured using the obtained molding sand composition, and then the core 1 is formed into a phenol urethane-based main mold 2 which has been formed in advance, and cast iron at about 1350 ° C. The molten metal was poured. After the cooling, the core surface of the cast iron casting obtained by dispersing the mold was observed (Examples 11 to 14). FIG. 2 is a cross-sectional view showing the combined structure of the step cone core, the main mold and the step die. For comparison, a step cone core (Comparative Example 7) with a molding sand composition obtained according to Comparative Example 4;
Using a molding sand composition obtained by using a resin binder (HP4021) alone, a step cone core is coated with a MgO-based mold M manufactured by Mikawa Mining Co., Ltd.
A sample subjected to the coating treatment with TS-713 (Comparative Example 8) and a substrate not subjected to the coating treatment (Comparative Example 9) were prepared, and a pouring test was performed in the same manner to observe a baked state. Table 4 shows the results.

Effect of the Invention As described in detail above, the foundry sand composition of the present invention is:
It is superior in terms of mold strength and moldability compared to conventional compositions, which enables stable and efficient production of molds, and is a problem in casting materials because a weakly acidic curing agent can be used. Spheroidization inhibition can be reduced. Moreover, since it has heat resistance comparable to that of the conventional improved technology,
Simplification or omission of the coating process is possible, and the industrial value is extremely high, such as labor saving and cost reduction while improving the productivity of the mold.

[Brief description of the drawings]

FIG. 1 is a nuclear magnetic resonance spectrum of the FA-modified organosilicon compound prepared in Production Example 3, and FIG. 2 is a cross-sectional view of a test mold model used for a casting test using molten cast iron.
In the figure, reference numeral 1 denotes a step cone core, 2 denotes a main die, and 3 denotes an injection port of molten cast iron.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Masahiro Kinoshita 26, Niitsu, Niiyama, Fuso-cho, Niwa-gun, Aichi Prefecture Inside the Aichi Factory, Asahi Organic Materials Industry Co., Ltd. (72) Inventor Kazuo Tamemoto Uchikanda, Chiyoda-ku, Tokyo Asahi Organic Materials Industry Co., Ltd. Tokyo Branch Office

Claims (2)

(57) [Claims] 1. A composition comprising (A) a refractory aggregate, (B) an acidic curing agent, and (C) an organosilicon compound having a furfuryloxy group or a mixture of the same and furfuryl alcohol. Foundry sand composition. (A) a refractory aggregate, (B) an acid curing agent,
A molding sand composition comprising (C) an organosilicon compound having a furfuryloxy group or a mixture thereof and furfuryl alcohol, and (D) a resin binder.