JPS6310038A - Composition for molding sand - Google Patents

Abstract

PURPOSE:To obtain a compsn. for molding sand which does not generate harmful emitting malodors during production of a casting mold by compounding an alkaline resol type phenolic resin and alkylene carbonate expressed by the specific formula respectively at specific ratios with the molding sand. CONSTITUTION:The alkaline resol type phenolic resin obtd. by bringing monophenols and formaldehyde into reaction is compounded at 0.5-2pts.wt. and the alkylene carbonate expressed by the formula (R and R' are respectively a hydrogen atom or alkyl group of 1-8C) is compounded at 5-7pts.wt. per 100pts.wt. said phenolic resin, with 100pts.wt. molding sand. The resol resin is prepd. by using phenol, cresol, etc. for the monophenols, using about 1-5mol formaldehyde per mol of the monophenols and bringing the same into an addition condensation reaction for 1-10hr at about 4-100 deg.C in the presence of an alkaline catalyst. The casting mold formed of the compsn. for molding sand obtd. in the above-mentioned manner has the substantial strength and does not generate the gases having the malodors during pouring of a molten metal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a novel foundry sand composition, more specifically, a low-odor foundry sand composition that does not generate harmful gases accompanied by bad odors when manufacturing molds. It is a knowledgeable thing.

Conventional technology Recently, organic self-hardening molds made from foundry sand containing an organic binder have come into widespread use in the production of castings, as they are advantageous in terms of shortening work time and ensuring uniform quality. Next time.

This organic self-hardening mold uses, for example, a foundry sand composition in which foundry sand is blended with a binder such as a phenolic resin or a furan resin, and an acidic curing agent such as aromatic sulfonic acid, and is molded into a predetermined shape. A method of molding and then curing at room temperature,
It is manufactured by molding a composition made by adding a binder consisting of a phenol resin solution and a polyisocyanate solution to foundry sand, and curing it at room temperature with a basic catalyst.

However, molds manufactured by this method usually produce bad odors such as sulfur dioxide gas generated by thermal decomposition of aromatic sulfonic acid contained in the mold during casting, or hydrocarbon solvents that volatilize without being completely burned. When used industrially, it is necessary to take measures such as installing local exhaust equipment and wearing protective equipment. This inevitably leads to an increase in expenses and a decrease in work efficiency.

Therefore, in the field of casting technology, there has been a long-awaited desire for a foundry sand composition that does not generate bad odors or harmful gases.

Problems to be Solved by the Invention It is an object of the present invention to provide a foundry sand composition that does not generate bad odors or harmful gases during mold production and can provide molds with sufficient strength.

Means for Solving the Problems The present inventors have conducted extensive research in order to develop such a desirable foundry sand composition, and have found that certain alkaline resol type phenolic resins and certain alkylene carbonates harden at room temperature. The resulting mold is significantly superior to conventional molds in terms of low odor and has sufficient strength, and this strength can be further improved by adding a specific silane coupling agent. Based on this finding, the present invention was completed.

That is, the present invention provides 0.5 to 20 parts by weight of an alkaline resol type phenolic resin obtained by reacting monophenols and formaldehyde to 100 parts by weight of foundry sand, and 95 to 70 parts by weight per 100 parts by weight of the phenolic resin. General formula % Formula % (R and R' in the formula are each a hydrogen atom or a carbon number of 1 to 1% by weight)
A low-odor foundry sand composition containing an alkylene carbonate represented by the alkyl group (8), and further comprising 0.01 to 10 parts by weight per 100 parts by weight of the phenolic resin.
It is characterized by containing at least one silane coupling agent selected from a trifunctional epoxy silane coupling agent, a trifunctional amino silane coupling agent, and a trifunctional mercapto silane coupling agent. The present invention provides a low-odor foundry sand composition.

The present invention will be explained in detail below.

There are no particular restrictions on the foundry sand in the composition of the present invention, but usually silica sand, olivine sand, chromite sand,
Zircon sand, Ashland no-peque recycled sand, roasted recycled sand mixed with green sand, furan recycled sand, etc. are used.

The alkaline resol type phenolic resin (hereinafter referred to as resol resin) used in the uninvented composition is a reaction mixture produced by an addition condensation reaction of monophenols and formaldehyde in the presence of an alkali catalyst, and the solid content concentration is adjusted as desired. It is provided as an aqueous solution adjusted to 40 to 70M food %, or as an organic solvent solution dissolved in methanol, amethane, etc., or a mixture of these organic solvents and water, but it is generally provided according to the Fire Service Act. An aqueous solution type is preferably used because it is not bound by legal regulations and is advantageous in terms of cost. (9) In general, the resol resin in the composition of the present invention tends to have a slow curing speed when its number average molecular weight is small, and exhibits a property that it cannot impart sufficient strength to the mold. When using a resol resin, it is necessary to further add an alkaline compound, such as an alkali metal hydroxide, which promotes the curing reaction to the composition of the present invention to adjust the curing speed. Therefore, in order to avoid such complications, it is desirable to adjust the number average molecular weight of the resol resin to usually 200 or more, preferably 300 or more.

Examples of monophenols used in the production of the resol resin according to the present invention include phenol, cresol,
xylenol, cumylphenol, nonylphenol,
Examples include furfural and phenylphenol.

These monophenols may be used alone or in combination of two or more, and if necessary, it is also possible to use by-products, such as cresol residue, which are produced during the preparation of monophenols.

In addition, an aqueous solution such as formalin is usually used as the formaldehyde to be subjected to the addition condensation reaction with these monophenols, but there are also other substances that can generate formaldehyde during the reaction, such as paraformaldehyde, trioxane, hexamethylenetetramine, etc. can also be used, optionally replacing f7' with glyoxal,
It is also possible to use furfural etc. in combination.

The amount of formaldehyde to be used is usually selected within the range of 0.8 to 6 moles, preferably 1 to 5 moles per mole of monophenols.

The resol resin according to the present invention uses the above-mentioned monophenols and formaldehyde in the above-mentioned ratio, and is prepared in the presence of an alkali catalyst at a temperature of usually 40-1001:1.
It is obtained by reacting for about hours.

As the alkali catalyst, for example, an inorganic alkali compound such as an alkali metal hydroxide, oxide, carbonate, hydrogen carbonate, an alkaline earth metal hydroxide or oxide, or an amine compound may be used alone or in combination. Although the above may be used in combination, alkali metal compounds are particularly preferably used.

The amount used is b per mole of monophenols, in the case of non-alkaline compounds, usually 0.01 to 1.5 moles, preferably 0.1 to 1.2 moles, and in the case of amine compounds is usually 0.01 to 0.5 mol, preferably 0.01 to 0.5 mol.
A range of 0.02 to 0.4 mol is practical.

In particular, alkali metal hydroxides or oxides are used not only as catalysts for the production of resol resins but also as water-solubilizing agents for hydrophobic resol resins prepared as necessary, or as curing rate regulators as described above. It is also possible to blend it into the resol resin after preparation.

Typical examples of this alkali catalyst include, for example, KO
H, NaOH%LiOH, Ca(OH)2, Ba(OH
)2.5r(oH)2, K2O, Na20, OaO,
MgO%Na2CO3, K2O05, KHC! 05,N
aHCO3, ammonia, hexamethylenetetramine,
Examples include triethylamine, triethanolamine, ethylenediamine, quaternary ammonium hydroxide salt, N,N-dimethylethanolamine, and the like.

In the composition of the present invention, this resol resin is
It is blended in an amount of 0.5 to 20 parts by weight, preferably 1 to 10 parts by weight.

The alkylene carbonate used in the composition of the present invention is a carbonic ester having a cyclic structure represented by the general formula % (in which R and R' have the same meanings as above).

Preferred specific examples of this alkylene carbonate include dioxolone-2 (commonly known as ethylene carbonate),
4-Methyldioxolone (commonly known as propylene carbonate), 4-ethyldioxolone, 4-butyldioxolone, 4,5-dimethyldioxolone, 4-pentyldioxolone 4,4'-dimethyldioxo Examples include Ron.

Among these alkylene carbonates, each can be used alone or as a mixture of two or more, but ethylene carbonate and propylene carbonate are particularly preferably used because they are inexpensive and commercially available.

Since the method of the present invention is directed to curing at room temperature, it is preferable to use these alkylene carbonates as a liquid in combination with an aqueous solution or liquid carbonate, and if necessary, alcohols, ketones, etc. Dilution with organic solvents is also possible.

The blending amount of this alkylene carbonate is 5 to 70 parts by weight, preferably 10 parts by weight, per 100 parts by weight of the resol resin.
-50 parts by weight.

As a method for preparing the foundry sand composition of the present invention, methods generally employed in the technical field can be applied as they are, such as a method in which foundry sand and alkylene carbonate are mixed in advance and then resol resin is mixed, Examples include a method of mixing both components simultaneously, or a method of mixing the resol resin with the foundry sand and then mixing the alkylene carbonate.

The binder composition comprising the combination of resol resin and alkylene carbonate in the composition of the present invention has the property of causing a rapid curing reaction at room temperature through the catalytic action of an alkaline compound to form a practical cured product. , when using the above amine compound alone as a catalyst, a resol resin produced using a small amount of an inorganic alkali compound, or a highly acidic foundry sand such as furan recycled sand, it is generally However, since the curing rate tends to be slow, another method to replace the above method is to use an inorganic alkali compound such as an alkali metal hydroxide or an amine compound such as a tertiary amine when preparing a foundry sand composition. It is also possible to adjust the curing rate.

In the composition of the present invention, a specific silane coupling agent is blended as desired in order to improve mold properties such as curing speed and mold strength, but this agent is an organosilicon compound having different reactive groups. One of the reactive groups is a reactive group such as a methoxy group, an ethoxy group, or a phenoxy group that chemically bonds with an inorganic substance such as silica sand, and the other reactive group chemically bonds with an organic substance such as a resol resin. It is a reactive group such as an epoxy group, an amino group, or a mercapto group to be bonded.

As such a silane coupling agent, for example, γ
-glycidoxyprobyltrimethoxysilane, β-(3
, 4-epoxycyclohexyl)ethyltrimethoxysilane, N-β-(aminoethyl)γ-aminopropyltrimethoxysilane, γ
-aminopropyltriethoxysilane, N-phenyl-
Examples include trifunctional amino silanes such as γ-aminopropyltrimethoxysilane, and trifunctional mercapto silanes such as γ-mercaptopropyltrimethoxysilane.

These silane coupling agents may be used alone or in combination of two or more, and the amount added is 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, per 100 parts by weight of the resol resin. selected within the range.

When preparing the foundry sand composition of the present invention, there are no particular restrictions on the method or timing of blending the silane coupling agent. For example, (1) adding and dissolving the silane coupling agent in resol resin or alkylene carbonate; Method of mixing in advance and then adding and mixing this to foundry sand% (2
) A method in which foundry sand and silane coupling agent tK are added and mixed in advance, and then a binder component is added and mixed; (3) A method in which a silane coupling agent is added and mixed into foundry sand at the same time as a binder component. Adopted.

Note that when the trifunctional amino-based 7-run coupling agent is dissolved and mixed in the alkylene carbonate, a cloudy white precipitate is generated over time, so it is preferable to dissolve and mix it in the resol resin.

Furthermore, in addition to the above-mentioned components, the foundry sand composition of the present invention may contain any additives commonly used in the past.
For example, mold disintegration improvers such as iron sand, red iron, wood flour, halogen-containing organic compounds, and alkali metal salts of aromatic carboxylic acids may be incorporated within the scope of the present invention.

In addition, the mold obtained from the composition of the present invention may be coated with graphite-based, zircon-based, silica-based, magnesium oxide-based coatings, etc., which are commonly used in the technical field, as necessary for casting. It is also possible to provide

Function The reason why a practically usable low-odor organic mold can be obtained by adding and mixing alkaline resol resin and alkylene carbonate to foundry sand in the present invention is not necessarily clear, but it is presumed as follows. Ru.

In other words, carbon dioxide generated by the room-temperature decomposition of alkylene carbonate based on the catalytic action of the alkaline component bonded to the resol resin excites the resol resin during the neutralization reaction with the alkali component. In combination with the reaction heat generated by the resol, a complex curing reaction with the resol resin itself or organic residues generated by the decomposition, or the formation and solidification of carbonized metal salts due to the neutralization reaction causes the resol. A mold is formed by a type of coagulation effect such as condensation thickening or solidification of the resin, and the silane coupling agent used greatly improves the bonding force between the foundry sand and the binder, resulting in excellent mold strength, etc. It is thought that this provides a strong template with ft.

Furthermore, since the mold obtained from the composition of the present invention undergoes thermal history during casting, the curing reaction of the resol resin progresses further, improving the heat resistance of the mold and making it suitable for practical use. ``Also, as is clear from the above explanation, there is no generation of harmful gases such as those caused by aromatic sulfonic acids and hydrocarbon solvents in conventional technology, and the organic solvents used as needed are easily combusted. Therefore, it is presumed that the odor will be significantly reduced compared to using molds of the prior art, and that deterioration of the working environment will be prevented.

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

The number average molecular weight of the resol resin was measured as follows.

That is, after adjusting the resol resin to pH 5 to 6 using formic acid, tetrahydrofuran was added and dissolved to prepare a sample. Regarding this sample, high performance liquid chromatography [manufactured by Toyo Soda, column G1000 H [l, G 20
00 H8] was used to measure the number average molecular weight.

Production Example 1 Phenol 1000F and potassium hydroxide 50% by weight aqueous solution 7 were placed in a Yotsuro flask equipped with a cooler and a stirring device.
After adding 1358 f of a 47 wt % formaldehyde aqueous solution dropwise using a separating funnel, the temperature was raised to 75°C and reacted for 1 hour, 3 hours, 5 hours, and 7 hours. Binder A is a type phenolic resin.

B, C, and D were obtained. Table 1 shows the properties of each binder.

Table 1 Production Example 2 A Yotsuro flask equipped with a cooler and a stirrer, phenol 100(1,47]ii-% formalde L aqueous solution 135111. Add triethylamine 32f and react at 75°C for 3 hours to form a binder. E was obtained.The number average molecular weight of this binder E was 180, the solid content was 62% by weight,
The viscosity was 50 cp/25°C.

Examples 1 to 6 After weighing Iwami No. 5 sand 3000 F and 36 tons of 50% by weight ethylene carbonate aqueous solution (actual blending amount 18f, 30% by weight/resol resin), they were mixed for 30 seconds in a Shinagawa table mixer. Next, the binder A60F obtained in Production Example 1 was added, and the mixture was further mixed for 30 seconds to prepare a foundry sand composition.

(Foundry Sand Compositions for Example 1) In the same manner as in Example 1, five types of foundry sand compositions were prepared according to the combinations of alkylene/carbonate and binder shown in Table 2. (Foundry sand composition for Examples 2 to 6) The obtained foundry sand composition was
Immediately prepare a large number of anti-pressure test pieces (diameter 5010I x height 50
M11 (hereinafter referred to as mold) was manually filled into a wooden mold that could be made at the same time and left at room temperature. Thereafter, the mold was removed at predetermined intervals and its strength (resistance pressure) was measured, and the results are shown in Table 2.

As shown in Table 2, as the number average molecular weight of Luzole resin decreases, the curing speed tends to slow and mold strength also tends to decrease. The propylene carbonate molding sand composition (Example 3) had a higher initial strength of the mold, that is, a faster curing speed, but the final strength tended to be slightly lower, indicating a rapid hardening property. It was recognized that the

Examples 7-17 Iwami No. 5 sand 30009, propylene carbonate 13.
After weighing out 5r (30% by weight/resol resin), they were mixed for 30 seconds in a Shinagawa table mixer, and then the silane cup shown in Table 3 was added to the binder C obtained in Production Example 1. 4. Mixed with 0.5% by weight of ring agent.
Ten types of foundry sand compositions were prepared by adding 59% of the total amount and mixing for an additional 30 seconds. In addition, a foundry sand composition without using a silane coupling agent was also prepared in the same manner.

Table 3 shows the results of measuring the resistive pressure of molds made using these foundry sand compositions according to the methods described in Examples 1 to 6.

As shown in Table 3, trifunctional epoxy silane coupling agents (Examples 7 and 8), trifunctional amine silane coupling agents (Examples 10 and 11), trifunctional mercapto silane cups, The ring agent (Example 13) is a foundry sand composition (Example 17) that does not use a silane coupling agent.
And trifunctional epoxy silane coupling agent (Example 9), Ninomiya functional amino silane coupling agent (Example 12), methacryloxy silane/coupling agent (Example 14), ureido silane coupling agent agent (Example 15), vinyl silane coupling agent (Example 16)
Provides a mold with extremely superior mold properties,
It was found to be effective in improving mold strength.

Note that when the mercapto-based silane coupling agent was used, a slight odor was felt compared to other silane coupling agents, but the odor was not a problem for practical purposes.

Examples 18-23 Iwami No. 5 sand 300C1, 0.23 t of γ-glycidoxyprobyltrimethoxysilane (approximately 0.5 weight width/resol resin), and an equal weight mixture of ethylene carbonate/propylene carbonate (weight ratio) For binder C, the fourth
After weighing the proportions shown in the table, they are mixed for 30 seconds in a Shinagawa tabletop mixer, then the binder C452 obtained in Production Example 1 is added, and the foundry sand is obtained by further mixing for 30 seconds. Composition T-6 types of results.

All of these foundry sand compositions were used and molds were prepared based on the methods described in Examples 1 to 6, and the results of measuring the resistive pressure of the molds obtained were shown in Table 4.

As shown in Table 4, it was observed that molds obtained from foundry sand compositions in which the blending ratio of the carbonate to the resol resin was less than 5% by weight were extremely low in strength (Example 18).

Example 24.25 Iwami No. 5 sand 3000PK, propylene carbonate to about 1 r-glycidoxyprobyltrimethoxysilane
．． 7% by weight added and mixed 14? (equivalent to 0.5% by weight of silane/binder E, approximately 30% by weight of carbonate/binder E), mixed for 30 seconds in a Shinagawa table mixer, and then manufactured. The binder E452 obtained in Example 2 was added and mixed for an additional 30 seconds to obtain a foundry sand composition. This composition was molded in the same manner as in Examples 1 to 6, and the counter pressure was measured at predetermined intervals (Example 24).

Further, an experiment was conducted in the same manner as in Example 24 above, except that after adding and uniformly mixing binder E, 50% by weight potassium hydroxide aqueous solution 182 was added (Example 25).
. These results are shown in Table 5.

Table 5 As shown in Table 5, even if a binder with a number average molecular weight of less than 200 is used, if an inorganic alkaline compound is added at the time of mixing foundry sand, the curing speed and casting mold can be maintained without any practical problems. It can be seen that strength can be obtained.

Effects of the Invention As is clear from the above explanation, the mold obtained from the foundry sand composition of the present invention has a mold strength that does not pose a problem in practical use, and does not produce bad odor when pouring molten metal, unlike the prior art. Since no gas is generated, a comfortable working environment is maintained. Furthermore, along with such improvements in the working environment, not only work efficiency is improved, but also economic losses such as pollution control costs can be reduced, which is an excellent effect.

Claims (1)

[Scope of Claims] 1. 0.5 to 20 parts by weight of an alkaline resol type phenolic resin obtained by reacting monophenols and formaldehyde to 100 parts by weight of foundry sand, and 5 to 20 parts by weight per 100 parts by weight of the phenolic resin. 70 parts by weight General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, R and R' each represent a hydrogen atom or a carbon number of 1 to
A low-odor foundry sand composition characterized in that it contains an alkylene carbonate represented by: 2 0.5 to 20 parts by weight of an alkaline resol type phenolic resin obtained by reacting monophenols and formaldehyde to 100 parts by weight of foundry sand, and 5 to 70 parts by weight of the general formula per 100 parts by weight of the phenolic resin. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (R and R' in the formula each represent a hydrogen atom or a carbon number of 1 to 1)
8 alkyl group) and 0.01 to 10
parts by weight of a trifunctional epoxy silane coupling agent;
A low-odor foundry sand composition comprising at least one silane coupling agent selected from trifunctional amino-based silane coupling agents and trifunctional mercapto-based silane coupling agents.