JPH0890149A - Phenolic resin composition for gas curing casting mold - Google Patents

Abstract

PURPOSE: To improve the characteristics of a casting mold obtd. by using a phenolic resin compsn. and more particularly both of the heat resistance and the collapsing property after pouring, to improve working environment and to enable high-speed molding as the casting mold described above is cured by gaseous methyl formate or combined,gases of carbon dioxide and the gaseous methyl formate. CONSTITUTION: This phenolic resin compsn. for casting molds is curable by the gaseous methyl formate or combined gases of carbon dioxide and the gaseous methyl formate and is prepd. by incorporating a boric acid or borates into a phenolic resin which is prepd. by bringing phenols and formaldehydes into reaction by using a basic catalyst, then adding an alkaline metal hydroxide and having the molar ratio of this alkaline metal hydroxide to the phenols within a range of 0.5 to 5.5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a granular refractory aggregate mixed with a binder containing a water-soluble phenolic resin containing boric acid or borates to form a main mold or core for casting, and then methyl formate gas or It provides a method of molding a mold by curing by passing a gas that uses carbon dioxide gas and methyl formate gas together, and has good mold characteristics, especially heat resistance and mold collapsibility after pouring, and a working environment. The present invention relates to a phenol resin composition for gas-curing molds, which is excellent in high-speed molding.

[0002]

2. Description of the Related Art Conventionally, there is a method of using various organic and inorganic binders for room temperature curing type mold making in the field of casting industry. The method of curing the inorganic binder using water glass or the like with carbon dioxide gas is less likely to generate harmful gas during casting, but the moldability after casting is poor, and the finishing man-hour is large compared to organic binders. It has the drawback that it is difficult to collect and regenerate sand.

On the other hand, as a molding method using an organic binder, a furan resin or a urea-modified furan resin and a peroxide are cured with an organic sulfonic acid, a sulfuric acid or a sulfurous acid gas, a benzylic ether type phenol resin and a polyphenol resin. There is a method of curing a mixture of isocyanates with a liquid or gaseous tertiary amine. These molding methods have good mold collapsibility after casting, but have an odor during molding, which causes gas defects in the casting.
Many problems have been pointed out in metallurgy, such as adverse effects such as soot defects and vaning defects. Further, it has been pointed out that SOx and NOx gas generated deteriorate the working environment and cause acid rain due to air pollution, which has become a social problem.

For the purpose of solving such a drawback, there has been a demand for a technique for producing a binder by using a basic substance which is metallurgically excellent. Conventionally, as such a molding technique, a technique for producing a mold using a resol type phenolic resin and methyl formate gas is known in Japanese Patent Publication No. 61-37022, and an aqueous solution of a resol type sodium phenolate resin and an oxyanion are used. The technology is JP-A 1-224.
No. 263, and a technique for curing an alcohol-soluble phenolic resin, a polyvalent metal hydroxide and the like with carbon dioxide is known from JP-A-56-66345.
These methods are effective in improving the working environment compared to other organic binders, but the mold strength is low at the time of manufacturing the mold, and the curing speed is very slow.
It has the drawback of low production efficiency. As a practical matter, the performance of high strength and fast curing and the improvement of working environment are contradictory from the viewpoint of the production of binders. Therefore, performance design has been made in consideration of such balance.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention have earnestly studied in order to solve the problems of achieving both high strength, rapid curing and working environment, and as a result, boric acid or borate salts are water-soluble in granular refractory aggregates. It was found that the mold strength is significantly improved by blowing and curing methyl formate gas or a gas containing both carbon dioxide gas and methyl formate gas into a mold mixed with a binder contained in a phenolic resin to complete the present invention. I arrived. The purpose of the present inventor is that
Another object of the present invention is to provide a phenolic resin composition for a gas-curable mold, which has a high strength of the mold, a high curing speed, and a metallurgical property, which is excellent in the working environment with less generation of harmful gas.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to a phenol resin composition for a mold, which is curable with methyl formate gas or a gas containing carbonic acid gas and methyl formate gas, which comprises boric acid or borates in a water-soluble phenol resin. It is about. Here, the granular refractory aggregate is natural silica sand, artificial silica sand,
Examples include olivine sand, zircon sand, chromite sand, and recovered sand, recycled sand, and the like.

In the present invention, the water-soluble phenol resin is a resin obtained by dissolving a resol-type phenol resin obtained by reacting a phenol and an aldehyde with a basic catalyst in an aqueous solution of an alkali metal hydroxide. The solid content of this phenol resin is 20% in order to improve the mold strength.
˜70 wt% is preferred. If it is less than 20% by weight, the effect of improving the mold strength is not sufficient, and if it is 70% by weight or more, the curing rate becomes slow and the viscosity becomes too high, which is not practical.

The phenols used in the phenol resin are, for example, phenol, cresol, resorcinol, catechol, bisphenol A, bisphenol F, bisphenol C, bisphenol H, isopropenylphenol dimer, bisphenol A residue, cumylphenol, nonylphenol. , Butylphenol, octylphenol, amylphenol and other substituted phenols, and aldehydes include formalin, paraformaldehyde, furfural, α-polyoxymethylene and acetaldehyde, but are not limited thereto. Aldehydes are preferably used in an amount in the range of 1.1 to 3.6 mol per mol of phenols. Sodium hydroxide as a basic catalyst,
Includes alkali metal and alkaline earth metal hydroxides such as potassium hydroxide, calcium hydroxide and barium hydroxide, weak acid / strong acid / base salts such as sodium carbonate and sodium acetate, ammonia water, amines such as triethylamine and hexamine. Be done.

In such a resol type phenolic resin, a part of phenols is replaced with urea, melamine, lignin or other compounds capable of reacting with the above-mentioned aldehydes, and resinous substances such as linseed oil, Chinese laurel oil, cashew nut oil and the like. It is also included in the present invention to incorporate a substance capable of forming a product.

Next, alkali metal hydroxides added to the resol type phenol resin include sodium hydroxide, potassium hydroxide and the like. Particularly preferable alkali metal hydroxide is potassium hydroxide which gives the resin a low viscosity. is there.
The alkali metal ion in the resin is preferably in the range of 0.5 to 5.5 with respect to the molar ratio of phenol, and is 1.5.
It is more preferably in the range of to 4.7. The resol-type phenol resin obtained by the reaction becomes water-soluble by adding an alkali metal hydroxide.

The water-soluble phenolic resin of the present invention has a content of 0.2
It is desirable to include a silane coupling agent such as γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and funoltrimethoxysilane in an amount of up to 2.0% by weight for improving the mold strength. The resole-type phenol resin of the present invention is water-soluble, but if necessary, it is partially or wholly replaced with another solvent such as alcohols such as methanol, ethanol and furfuryl alcohol, ketones such as acetone and methyl ethyl ketone, and esters. It is also possible.

The boric acid or borate used in the present invention is used by dissolving it in a water-soluble phenolic resin. Examples of the borate include potassium borate, sodium borate, magnesium borate, zinc borate, silver borate, cobalt borate and boric acid. General formula xM for nickel, lead borate, copper borate, barium borate, etc.
Is a general term for _{2 O · yB 2 O 3 ·} zH compounds having ₂ O. Particularly preferred are naturally occurring sodium borate (borax), potassium borate and boric acid.

The water-soluble phenolic resin used in the present invention is used in an amount of 0.5 to 6 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of the granular refractory aggregate.
The amount of boric acid or borate is 0.2 to 50% by weight with respect to the water-soluble phenol resin, and more preferably 1 to 3%.
0% by weight. As a curing gas, methyl formate gas or a gas in which carbon dioxide gas and methyl formate gas are used in combination is passed to cure the molded mold. The amount of methyl formate used is 5 to 80% by weight, preferably 10 to 10% by weight of the phenol resin.
It is 60% by weight. When carbon dioxide gas and methyl formate are used in combination, the amount of methyl formate can be appropriately reduced depending on the amount of carbon dioxide gas used in combination. The curing gas may be used in combination with air, and in this case air is used as the purge gas.

[0014]

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

(Synthesis Example 1 of Phenol Resin) 470 parts of phenol (5.00 mol), 37% formalin 730 parts (9.00 mol), 50% in a reaction vessel equipped with a condenser and a stirrer.
40 parts (0.50 mol) of sodium hydroxide was charged, the temperature was gradually raised, and the mixture was refluxed at 85 ° C. The temperature was maintained for 2 hours from the start of reflux, and the reaction was carried out to a water ratio of 480%. Immediately after quenching and cooling, 1000 parts of 50% potassium hydroxide was added, 6% of borax was added and dissolved, and then 0.5% of γ-aminopropyltriethoxysilane was added to obtain the target water-soluble phenol resin. It was

(Synthesis example 2 of phenol resin) 456 parts of bisphenol A (2.00
Mol), 37% formalin 405 parts (5.00 mol), 50
56% (0.50 mol) of potassium hydroxide was charged and the temperature was gradually raised to reflux at 95 ° C. The temperature was maintained for 2 hours from the start of reflux, and the reaction was continued until the viscosity reached 100 cp / 25 ° C. Immediately after quenching and cooling, 700 parts of 50% potassium hydroxide was added, 6% of potassium borate was further added and dissolved, and γ-aminopropyltriethoxysilane 0.5 was added.
% Was added to obtain the desired water-soluble phenolic resin.

(Molding) 2.5 parts of these water-soluble phenolic resins were added to 1000 parts of silica sand and mixed for 1 minute. The compound sand was molded into a test piece of 50φ × 50 mm in a mold, and subsequently, methyl formate gas or a gas in which carbon dioxide gas and methyl formate gas were used in combination was aerated to cure. The cured mold was taken out of the mold and the mold compressive strength was measured with time. Further, molding was similarly performed using the compounded sand 24 hours after kneading, and the mold compressive strength was measured, and this was defined as the usable strength.

Further, as a comparative example, the same silica sand as above was prepared by using Sumilite resin PR-51670 (phenol resin) which is a resin of cold box method in phenol urethane amine curing method and HP-31 (polymeric MDI) curing agent. And molded with triethylamine gas.
The aeration conditions of methyl formate gas or a combined gas of carbon dioxide gas and methyl formate gas were as follows. Methyl formate gas: 30% (against resin) Carbon dioxide gas: 0.5 Kg / cm ² , 10 L / min, aeration time: 20 seconds The characteristics of the obtained mold are shown in Table 1.

[0019]

[Table 1]

[0020]

The mold obtained by using the phenol resin composition of the present invention is cured by methyl formate gas or a combined gas of carbon dioxide gas and methyl formate gas.
In particular, both heat resistance and mold disintegration after pouring are excellent, the working environment is excellent, and high-speed mold molding is possible.

Claims (4)

[Claims] 1. A phenolic resin composition for a mold, which is curable by a gas containing methyl formate gas or a combination of carbon dioxide gas and methyl formate gas, which comprises boric acid or a borate compound contained in a water-soluble phenol resin. 2. A water-soluble phenolic resin is obtained by reacting phenols and formaldehyde with a basic catalyst, and then adding an alkali metal hydroxide. The molar ratio of alkali metal hydroxide to phenols is 0.5 ~
The phenolic resin composition according to claim 1, which is in the range of 5.5. 3. The phenolic resin composition according to claim 1, wherein the content of boric acid or borates is 0.2 to 50 parts by weight with respect to the water-soluble phenolic resin. 4. Mixing 0.5 to 6 parts by weight of the water-soluble phenolic resin according to claim 1, 2 or 3 with 100 parts by weight of the granular refractory aggregate and molding the mixture to use methyl formate gas or carbon dioxide gas and methyl formate gas together. A method for molding a main mold or a core mold, which comprises venting gas.