JPH11323079A - Binder composition and production of molded article using the composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the quick-curing molding, the improvement in the working environment, the decrease in defects in cast material, etc., at the same time in the molding by carbon dioxide gas curing method. SOLUTION: The objective binder composition is produced by reacting a phenolic compound with formaldehyde in the presence of an acidic catalyst to obtain a novolak phenolic resin and adding an alkali metal hydroxide and a chelating agent forming a stable complex with the above resin to the obtained novolak phenolic resin. The alkali metal hydroxide is preferably potassium hydroxide or a mixture of potassium hydroxide and sodium hydroxide and the chelating agent is preferably derived from sodium borate, potassium borate or ammonium borate.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a binder composition for producing a molded body such as a casting main die, a core or a refractory container for steel, and the like, and mixing the binder with a refractory aggregate to form a desired shape. After that, a method of manufacturing a molded article, characterized by passing carbon dioxide gas and thereby curing the binder resin.

[0002]

2. Description of the Related Art Conventionally, room temperature gas curing mold molding in the casting industry and the like includes inorganic and organic methods. The method of hardening an inorganic binder using water glass with carbon dioxide gas can be easily molded into a mold and generates little harmful gas when pouring, but it has poor finishability of the mold after pouring and requires an organic finish. It has a disadvantage that it is higher than a binder and that it is difficult to collect and regenerate sand. On the other hand, as a gas curing molding method using an organic binder, a hardening method of curing a mixed sand of a furan resin or a urea-modified furan resin and a peroxide with a sulfurous acid gas, or a benzylic ether type phenol resin and a polyisocyanate Is cured with a gaseous tertiary amine. These molding methods have excellent mold strength and good mold disintegration after pouring.However, metallurgy such as giving harmful gas leakage problems during molding, gas defects, soot defects, vaning defects, etc. Many problems have been pointed out above. Furthermore, it has been pointed out that the working environment is deteriorated by the generated SO _X and NO _X gases, and acid rain is caused by air pollution, which is a social problem.

For the purpose of solving such disadvantages, there has been a demand for a technique for producing a binder using a metallurgically excellent basic substance as a binder. As a molding technique, there is a method of manufacturing a resol-type phenol resin using a methyl formate gas mold (Japanese Patent Publication No. 61-37022). However, care must be taken when handling because the flash point of methyl formate is low and it corresponds to special flammability. is necessary. In addition, there is a method in which an oxyanion is contained in an alkaline aqueous solution of a resol-type phenol resin and the mixture is cured with carbon dioxide using a binder (Japanese Patent Application Laid-Open No. 1-222463). The casting industry is supposed to collect and recycle aggregates due to cost and environmental issues. However, these resole-based systems require the use of a large excess of alkali metal hydroxide. At high temperatures such as pouring molten metal, the alkali metal has a defect that acts as a fusion agent for the mold aggregate, sintering the aggregates, and hindering the recovery and regeneration of the aggregates. Is required. Furthermore, these methods are excellent in terms of working environment and are improved compared to other organic binders, but have the drawback of low mold release strength and mold strength immediately after production, which is a feature of the gas curing method.

[0004]

DISCLOSURE OF THE INVENTION The present invention does not include components which lead to the improvement of the working environment in steel-related workplaces and the like mainly in a conventional foundry, and which do not contain components which may lead to metallurgical casting defects. An object of the present invention is to provide a binder composition capable of producing a clean casting. Further, important requirements of the present invention are raw material availability and cost. The present inventors have conducted intensive research to solve such problems as rapid curing molding of a mold, improvement of a working environment, and reduction of casting defects, and as a result, a novolak-type phenol resin was used as a particulate refractory aggregate. By reducing the alkali metal and improving the mold strength by blowing carbon dioxide gas into the mold, which is made to be water-soluble in the metal and mixing it with a binder containing a chelating agent, and hardening it, As a result, the present invention has been completed.

[0005]

SUMMARY OF THE INVENTION The present invention provides an alkali metal hydroxide and a stable complex with a novolak-type phenol resin obtained by reacting a phenol and formaldehyde with an acid catalyst. The present invention relates to a binder composition obtained by adding a chelating agent.

The phenols used in the present invention include, for example, phenol, cresol, resorcinol, catechol, dimers of isopropenylphenol, cumylphenol, nonylphenol, butylphenol, octylphenol, amylphenol and other substituted phenols. . Aldehydes include, but are not limited to, formalin, balaformaldehyde, furfural, α-polyoxymethylene, acetaldehyde, and the like. The reaction molar ratio of formaldehydes and phenols is 0.5 / 1 to 2.4 / 1,
More preferably, it is in the range of 0.7 / 1 to 2.0 / 1. Oxalic acid, hydrochloric acid, phosphoric acid,
Inorganic or organic acids such as sulfuric acid, boric acid, palladium toluene sulfonic acid, phenol sulfonic acid, xylene sulfonic acid, and the like, or a mixture of two or more thereof. In the novolak-type phenolic resin, the present invention also includes replacing a part of phenols with urea, melamine, lignin or other compounds capable of reacting with aldehydes.

The alkali metal hydroxide to be added to the novolak type phenol resin is an aqueous solution of potassium hydroxide, sodium hydroxide, lithium hydroxide or the like. Particularly preferred is potassium hydroxide which gives the resin a low viscosity. It is also preferable to use these alone or as a mixture of two or more. The molar ratio of phenol to alkali metal hydroxide is preferably from 0.8 / 1 to 2.5 / 1, particularly preferably from 1.2 / 1 to 2.2 / 1.

The chelating agent used in the present invention includes boric acid, borate, stannic acid, stannate, silicate, aluminate and the like. As borate, potassium borate, sodium borate, magnesium borate, zinc borate, barium borate,
Is a general term for the general formula _{xM 2 O · yB 2 O 3} · H compounds having ₂ O, such as boric acid ammonia. Particularly preferred are naturally occurring sodium borate (borax), potassium borate, and boric acid.
These can be used alone or as a mixture of two or more. The molar ratio of phenol to boron as a chelating agent is preferably 0.1 / 1 to 1.0 / 1.

The binder composition of the present invention comprises a particulate refractory aggregate 1
It is used in the range of 0.5 to 10 parts by weight, preferably 1 to 6 parts by weight, per 100 parts by weight. It is mixed with the binder composition and formed into a desired shape, and carbon dioxide gas is passed in, thereby hardening the novolak type phenol resin. The amount of carbon dioxide gas used is 0.0 with respect to 100 parts by weight of the particulate refractory aggregate.
1 to 40 parts by weight, preferably 0.1 to 15 parts by weight, can be formed by ventilation. If the amount of carbon dioxide used is less than 0.1 part by weight with respect to 100 parts by weight of the particulate refractory aggregate, the mold strength is low and insufficient, and if it exceeds 15 parts by weight, it does not contribute to hardening and is uneconomical. . Carbon dioxide may be used in combination with air, or air may be used as a purge diffusion gas. Examples of the particulate refractory aggregate include quartz sand, chromite sand, zircon sand, olivine sand, alumina sand, mullite sand, synthetic mullite sand, magnesia, magnesia clinker, and their recovered sand, recycled sand, etc. Is mentioned. In the present invention, as these particulate refractory aggregates, fresh sand, recycled sand, recovered sand, or mixed sand of one or more of these can be used.

[0010] The mold molding method is applicable to a VRH molding method, a suction molding method or a reduced pressure molding method in which the mixed sand is filled, the pressure is reduced, and the pressure is replaced with carbon dioxide to normal pressure to cure the mold. There is no particular limitation, and other molding methods may be used. In the binder composition of the present invention,
It is desirable to include a silane coupling agent such as γ-aminopropyltriethoxysilane, γ-glycidoxypropyltriethoxysilane, and phenoltrimethoxysilane for improving the strength of the mold. The amount of the silane coupling agent is
Usually 0.2 to 2.0% by weight based on the binder composition. Although the binder composition of the present invention is water-soluble, if necessary, a part of the solvent may be replaced with a solvent such as furfuryl alcohol, alcohols such as methanol and ethyl alcohol, ketones such as acetone and methyl ethyl ketone, and esters. It is possible.

[0011]

The present invention will be described below with reference to examples. However, the present invention is not limited by the examples. Further, “parts” and “%” shown in Examples and Comparative Examples are all “parts by weight” and “% by weight”.

Example 1 In a reaction vessel equipped with a condenser and stirring, 470 parts (5.00 mol) of phenol and 353 parts (0.8%) of 37% formalin were added.
7 mol), and 2 parts of boric acid were charged and the temperature was gradually raised, and the mixture was refluxed at 90 ° C. for 1.5 hours. Thereafter, 75 parts (0.87 mol) of 50% sodium hydroxide was added to neutralize the mixture to pH 8 to 10 to make it transparent. Further aging was carried out under these conditions for 0.5 hour.
Thereafter, the mixture was subjected to vacuum dehydration cooling, kept at 70 ° C., cooled, and 1100 parts (9.80 mol) of 50% potassium hydroxide was added. Further, 180 parts (1.88 mol) of borax was added and dissolved, followed by cooling. Thereafter, 0.5% of γ-aminopropylethoxysilane was added to obtain a binder 1.

Example 2 In a reaction vessel equipped with a condenser and stirring, 470 parts (5.00 mol) of phenol and 567 parts (7.0 parts) of 37% formalin were added.
0 mol), and 2 parts of oxalic acid were charged, and the temperature was gradually raised to 100 ° C
At reflux. This temperature was maintained for 1.5 hours from the start of reflux. Thereafter, the mixture was subjected to vacuum dehydration cooling, kept at 70 ° C., cooled, and 1100 parts (9.80 mol) of 50% potassium hydroxide was added. Further, 180 parts (1.88 mol) of borax was added and dissolved, followed by cooling. Thereafter, 0.5% of γ-aminopropylethoxysilane was added to obtain a binder 2.

Example 3 In a reaction vessel equipped with a condenser and a stirrer, 470 parts (5.00 mol) of phenol and 345 parts (4.2 parts) of 37% formalin were added.
6 mol), 2 parts of oxalic acid were charged, and the temperature was gradually raised to 100 ° C.
At reflux. This temperature was maintained for 1.5 hours from the start of reflux. Then 75 parts of 50% sodium hydroxide (0.87
Mol) and neutralized to pH 8 to 10 and aged for 0.5 hour. Then, it was subjected to vacuum dehydration cooling, and kept at 70 ° C. for 0.5 hour while cooling at 50% potassium hydroxide 1100.
Then, 180 parts (1.88 mol) of borax was added and dissolved, followed by cooling. Thereafter, 0.5% of γ-aminopropylethoxysilane was added to obtain a binder 3.

Comparative Example 1 In a reaction vessel equipped with a condenser and stirring, 470 parts (5.00 mol) of phenol and 973 parts of 37% formalin (12.
00 mol) and 40 parts (0.5 mol) of sodium hydroxide, and the mixture was gradually heated and refluxed at 90 ° C. This temperature was maintained for 2 hours from the start of reflux. Thereafter, the mixture was cooled and kept at 70 ° C., and while cooling, 1000 parts (8.91 mol) of 50% potassium hydroxide was added, 180 parts of borax was further added and dissolved, and then 0.5% of γ-aminopropylethoxysilane was added. In addition, binder 4 was obtained.

(Molding of mold) 2.5 parts of the binder obtained in Examples 1, 2, 3 and Comparative Example 1 was added to 1000 parts of silica sand and mixed for 1 minute. 50Φ × 50mm mixed sand in mold
The test piece was molded and then cured by passing carbon dioxide gas through it. The cured mold was removed from the mold and the mold compressive strength was measured over time.

Comparative Example 2 "Sumilite Resin" PR-51670 (resole type phenolic resin) manufactured by Sumitomo Durez Co., Ltd., which is a phenol urethane curing resin widely used in the market,
Using a curing agent HP-31 (Polymeric MDI), a mold was formed with the same silica sand as described above, and cured with triethylamine gas.

Table 1 shows the characteristics and the like of the molds obtained in each example.

[Table 1]

(Measurement method) Packing density: 50Φ × 50mm
After the test piece was molded, carbon dioxide gas (triethylamine gas in Comparative Example 2) was cured through the air.
Remove the cured mold from the mold. This weight is measured, and the packing density is calculated from the volume of the test piece. Compressive strength:
A test piece having a size of 50 Φ x 50 mm was formed, and subsequently, carbon dioxide gas (in Comparative Example 2, triethylamine gas) was passed and cured. Remove the cured mold from the mold. The strength is measured with a universal Amsler compression tester. Casting defects: Casting monthly magazine "JACT News 1980"
No. 20, November 20, p. 11 Casting test evaluation "Lastrust carbon" was evaluated by a method using a mold evaluation method. Cast iron 1400 ° C
Was cast and evaluated after the collapse of the cooling mold with or without carbon defects.

[0020]

The binder of the present invention has no odor such as amine odor unlike the amine cold box method widely used in the market as a gas curing method, and does not use an organic solvent or uses a small amount. Therefore, the working environment at the time of pouring is improved. Further, at the time of pouring, a clean casting can be obtained without containing a substance such as soot which may lead to defects. Further, the mold strength is improved as compared with the case of using a resol type phenol resin which is a conventional method, and high-speed mold molding can be performed.

Claims (7)

[Claims] 1. A novolak-type phenol resin obtained by reacting a phenol and a formaldehyde using an acidic catalyst is added with an alkali metal hydroxide and a chelating agent which forms a stable complex with the phenol resin. A binder composition comprising: 2. The binder composition according to claim 12, wherein the novolak-type phenol resin has a reaction molar ratio of formaldehydes to phenols of 0.5 / 1 to 2.4 / 1. 3. The binder composition according to claim 1, wherein the alkali metal hydroxide is potassium hydroxide or a mixture of potassium hydroxide and sodium hydroxide. 4. The chelating agent is boric acid, borate, stannic acid,
The binder composition according to claim 1, 2 or 3, which is a stannate, a silicate, or an aluminate alone or as a mixture of two or more. 5. The binder composition according to claim 4, wherein the chelating agent is provided by sodium borate, potassium borate, ammonium borate. 6. A novolak-type phenol resin obtained by reacting a phenol and a formaldehyde using an acidic catalyst, to which an alkali metal hydroxide and a chelating agent forming a stable complex with the resin are added. A method for producing a molded article, comprising: mixing the obtained binder composition with a particulate refractory aggregate, forming the mixture into a desired shape, and passing carbon dioxide gas through to cure the phenol resin. 7. The method according to claim 6, wherein the amount of the binder composition to be mixed is 0.5% by weight to 10% by weight based on the particulate refractory aggregate.