JPS5846377B2 - Binder composition for foundry sand - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a binder composition for foundry sand that is self-hardening at room temperature or quickly hardens by contacting with an amine-containing gas.

Binder compositions for foundry sand for manufacturing sand molds are very useful in the foundry industry.

The binder (
There are inorganic and organic binders, but each has advantages and disadvantages, and no one has been found that is fully satisfactory.

A typical method for producing foundry sand molds using an inorganic binder is to make a sand mold with water glass adhered to the surface, and then harden it by blowing carbon dioxide gas into it.

This method has a problem in that when iron or aluminum hot water is poured into a sand mold to form a casting and then taken out, the sand mold has poor collapsibility and workability is significantly reduced.

The remaining foundry sand cannot be reused and alkali pollution becomes a problem, so there are also problems such as there is no place to dump it, gas defects occur during casting, and it is difficult to obtain a beautiful casting surface.

Examples of methods for manufacturing foundry sand molds using organic binders include methods using furan resins, phenolic resins, and the like.

However, if a sand mold is made by curing furan resin or resol-type phenolic resin with strong acids such as para-toluenesulfonic acid or phosphoric acid, the remaining acid may corrode the surface of the casting or the curing rate may increase due to temperature changes. There is a problem with fluctuations.

There is also a known method of curing the phenolic resin by reacting it with an organic isocyanate compound (for example, Japanese Patent Publication No. 45-32820, Japanese Patent Publication No. 48-25431, etc.), but in this case as well, the casting after molding is There is a problem that the sand mold disintegrates poorly when taken out.

The present invention provides a novel binder composition that solves the above problems.

That is, the present invention is a binder composition for foundry sand containing the following components a and b.

(a) Organic polyisocyanate compound.

(b) A polyol compound obtained by reacting a mixture of bisphenols and a cyclic ketone in which the carbon atom adjacent to the carbonyl group has at least two hydrogen atoms with formaldehyde.

The binder composition of the present invention has an excellent balance of fast curing properties, strength during molding, heat resistance during casting, and disintegrability of sand molds after casting, and can be used for cast iron, but is particularly suitable for aluminum. It is suitable as a binder composition for light alloy castings such as.

The organic polyisocyanate compound as component a used in the present invention can be appropriately selected from organic polyisocyanate compounds that are generally widely used as raw materials for polyurethane, and di- or triisocyanates are preferred.

Suitable organic polyisocyanate compounds include aliphatic incyanates such as hexamethylene diisocyanate; cycloaliphatic incyanates such as 4,4-one/chlorohexylmethane diisocyanate, inphorone diisocyanate; 2,4i- and 2.6 tolylene diisocyanate,
Aromatic polyisocyanates such as diphenylmethane diisocyanate, triphenylmethane triisocyanate, (1), 5-naphthalene diisocyanate, polymethylene polyphenylene isocyanate, and chlorophenylene-2,4-diisocyanate: xylylene diisocyanate button and its methyl derivatives.

Among these, aromatic polyisocyanates are preferred, and diphenylmethane diisocyanate, triphenylmethane triisocyanate, and mixtures thereof are particularly preferred.

These organic polyisocyanate compounds include toluene,
It may be used by dissolving it in an aromatic hydrocarbon such as xylene, ethylbenzene, diethylbenzene, cumene, diisopropylbenzene, heavy oil produced as a by-product during the production of ethylbenzene, or heavy oil produced as a by-product during the production of cumene.

Component b is used to generate polyurethane by reacting with an organic polyisocyanate compound and to harden foundry sand.

The polyol compound of component b is obtained by reacting a mixture of bisphenols and a cyclic ketone in which the carbon atom adjacent to the carbonyl group has at least two hydrogen atoms with formaldehyde.

Examples of bisphenols used in the present invention include bisphenol A1, bisphenol F, bisphenol C, and bisphenol H.

Cyclic ketones used in the present invention include cyclopentanone, methylcyclopentanone, cyclohexanone, methylcyclohexanone, isophorone, camphor, etc.
Cyclohexanone is especially heavy.

As the formaldehyde source, formalin aqueous solution, paraformaldehyde, trioxane, etc. can be used.

The reaction between a mixture of bisphenols and cyclic ketones and formaldehyde is usually carried out in the presence of a metal naphthenate catalyst such as zinc naphthenate or lead naanthenate, or an alkali catalyst such as sodium hydroxide, potassium acetate, or sodium acetate. , normal temperature to 150℃, preferably 50 to 130℃
℃ for 1 to 7 hours.

Thereafter, water and unreacted cyclic ketone in the reaction system are removed under reduced pressure.

When the reaction is carried out in a non-aqueous solution using a naphthenic acid metal salt catalyst and paraformaldehyde, the reaction temperature is
The temperature is 70 to 140°C, preferably 80 to 130°C.

When the reaction is carried out using an aqueous formalin solution and an alkali catalyst, the reaction temperature is 40 to 95°C, preferably 50 to 80°C.

In both of the above reactions, if the reaction temperature is too low,
Unreacted formalin tends to remain, and on the other hand, if the reaction temperature is too high, the methylolated cyclic ketone and methylolated bisphenols will react further, and dehydration condensation between these products will occur, resulting in a polynuclear product. This is not good or bad because it becomes the main subject.

The molar ratio of the mixture of bisphenols and cyclic ketone in the above reaction is 10/1 to 115, preferably 5/1.
~1/3.

The amount of formaldehyde to be reacted is 0.3 or more, preferably 1.0 in molar ratio to bisphenols.
~4.0, and the molar ratio to the total amount of the mixture of bisphenols and cyclic ketone is 0.2 or more, especially 0.
．． 3 to 2.0 is preferable.

The polyol compound obtained by the above reaction consists of a compound in which a methylol group is added to a bisphenol and a cyclic ketone, respectively, and a polynuclear body obtained by partially dehydrating condensation of these themselves and/or both.

In the past, products obtained by partially reducing or oxidizing the carbonyl group of a cyclic ketone may also be included.

The above polyol compound may be one of the above, or a polar solvent such as cyclohexanone, ethyl cellosolve acetate, ethylene glycol diacetate, triethylene glycol diacetate, isophorone, butyl 3-methoxyacetate, butyl cellosolve acetate, and/or the above-mentioned organic polyisocyanate compound. It is used by dissolving it in an aromatic hydrocarbon solvent similar to that used for dissolving.

Of course, it is also possible to use other polyol compounds other than component b, such as polyether polyols and alkylresorcinols.

When other polyol compounds other than component b are not used in combination, the amount of component a to component b is such that the amount of incyanate group in component a is 0 per equivalent of hydroxyl group in component b.
．． It is appropriate to mix it in an amount of 3 to 3 equivalents, preferably 0.6 to 1.5 equivalents.

Note that when component b and another polyol compound are used together, the amount of isocyanate groups in component a is 0.
It is appropriate to mix it so that it becomes 3-3, preferably 0.6-1.5.

Component a, component b, and other polyol compounds used as necessary are 0.5 to 5 parts by weight per 100 parts by weight of foundry sand.
It is blended in the proportion of parts by weight.

The foundry sand may be any sand or inorganic powder used for foundries, and its particle size, type, etc. may be selected as appropriate.

The composition of the present invention is used in combination with foundry sand.

When molding a sand mold at room temperature using foundry sand mixed with a binder composition, a catalyst can be added to perform rapid curing in order to accelerate the strength development of the sand mold.

Examples of the catalyst include metal salts such as cobalt naphthenate, tin octylate, dibutyltin dilaurate, and tertiary salts such as N-ethylmorpholine, 4-phenylpropylpyridine, ethyl morpholinpropionate, tetramethyldiaminopropane, and triethylenediamine. Grade amines etc. can be used.

The amount used is suitably 5 parts by weight or less per 100 parts by weight of the total of the polyol compound containing component a and component b.

In addition, when molding a sand mold by uniformly mixing foundry sand and a binder composition, filling a mold, and then bringing the mixture into contact with an amine-containing gas at room temperature for rapid curing, amines as catalysts can be used. As such, tertiary amines are preferred, and trimethylamine, triethylamine, dimethylamine, dimethylethanolamine, N-ethylmorpholine, etc. are particularly heavy.

These tertiary amines are introduced into the mold using an inert gas such as nitrogen or air as a carrier gas, usually at a concentration of about 5 volumes or less.

In addition, in the present invention, if necessary, a silane treatment agent such as γ-aminopropyltriethoxysilane, N-β(aminoethyl γ-aminopropyltrimethoxysilane) is added to a and Total amount of b component 10
It can also be added in an amount of 0.02 to 0.5 parts by weight relative to 0 parts by weight.

Next, the present invention will be explained in more detail with reference to Examples.

In addition, "part" and "mine" in Examples and Reference Examples are based on weight.

Reference Example 1 Production Example of Polyol Compound Cyclohexanone 98.2.9 (1 mol), Bisphenol A228. , l (1 mol), paraformaldehyde 75.0 & zinc naphthenate 2.1 were placed in four flasks equipped with a stirrer, and reacted at 120°C for 4 hours.

Next, lower the temperature inside the flask to 100'C, and
Unreacted cyclohexanone and water were removed under reduced pressure of Hg.

To this, 350 g of ethylene glycol diacetate was added and uniformly dissolved to form a polyol compound (hereinafter referred to as polyol A).

) was obtained.

The product was analyzed by GPC, IR, and NMR, and it was confirmed that polyol A consisted of methylolated bisphenol A and cyclohexanone, themselves, and a condensate of both.

Reference Example 2 Production Example of Polyol Compound 228 g (2.33 mol) of cyclohexanone, 228.3 g (1 mol) of bisphenol A, 65 g of paraformaldehyde, 1 3.0 g of zinc naphthenate were placed in four flasks equipped with a stirrer, and reacted at 100°C for 4 hours. I let it happen.

Then, at the same temperature, water and unreacted cyclohexanone 1
20. ! li' was removed under reduced pressure.

120 g of butyl 3-methoxyacetate and 90 g of isopropylbenzene were added to this, dissolved uniformly, and cooled in a room temperature cabinet to form a polyol compound (hereinafter referred to as polyol B).

) was obtained. The product polyol B was analyzed in the same manner as in Reference Example 1, and was confirmed to be component b of the present invention.

Reference Example 3) Production Example of Polyol Compound Cyclohexanone 98. :l (1 mol), reaction time 5
The reaction was carried out in the same manner as in Reference Example 2 except for changing the time.

Then, at the same temperature, water and unreacted cyclohexanone 4
5g was removed under reduced pressure.

To this, 133 g of butyl 3-methoxyacetate and 71 aromatic fractions of 09 or higher produced at an aromatic plant were added,
The polyol compound (hereinafter referred to as polyol C) is uniformly dissolved and cooled to room temperature 1.

) was obtained. The product polyol C was analyzed in the same manner as in Reference Example 1, and was confirmed to be component b of the present invention.

Example 1 9°5 parts of the solution of polyol A obtained in Reference Example 1 was added to 1000 parts of Ayaragi Silica Sand No. 6 and mixed uniformly.

Furthermore, 10.5 parts of a solution consisting of 70 parts of commercially available polymethylene polyisocyanate and 30 parts of diisopropylbenzene were added and mixed uniformly.

The foundry sand composition thus prepared was mixed with a diameter of 5 crI.
The mixture was placed in a cylindrical mold having a height of 13 cIrL and compacted using a standard compaction tester to a height of 5 crIL, and then brought into contact with nitrogen gas containing triethylamine for 15 seconds.

Immediately after taking the molding sand test piece out of the mold, its compressive strength is 43.6 kg/cI? LG, the compressive strength after 1 hour was 47,2 kg/ia.

Furthermore, a mold for a car cooler was made using the same foundry sand composition, and nitrogen containing triethylamine was passed through the mold for 30 seconds to harden it.

A molten aluminum alloy at 760° C. was cast into this mold.

The disintegration of the sand mold was good when the cast product was taken out after cooling, and the cast product had a beautiful surface.

Example 2 10.0 parts of polyol B obtained in Reference Example 2 was used as component a of the present invention, and PAPI~ manufactured by Kasei Upjohn Co., Ltd.
135 (mixture of diphenylmethane diisocyanate and triphenylmethane triisocyanate) 75%
A foundry sand composition was prepared in the same manner as in Example 1 except that 10.0 parts of a mixed solution consisting of 22.5% diisopropylbenzene and 2.5 parts of butyl 3-methoxyacetate was used, and then a foundry sand test piece was prepared. was molded.

The compressive strength of this test piece immediately after taking it out from the mold, 1 hour later, and 1 day later was 43.11 t and g.
/ant,,58.3kg/ffl,61,3 kg
/ffl.

Furthermore, the test piece after 1 day was placed in an electric furnace heated to 700'C for 2 minutes, and the compressive strength immediately after being taken out was measured to be 3.8 kg/i, indicating low heat resistance.

Further, the same foundry sand composition was filled into a core wooden mold for an automobile intake manifold, and triethylamine, which had been vaporized by blowing nitrogen, was passed through it for 30 seconds to harden it.

This core was set in a mold for an intake manifold, and molten aluminum at 760° C. was cast into it.

After cooling, the sand from the core of the cast product is slightly removed by resin...
This was possible by hitting it with a hammer.

Furthermore, no casting defects such as roughness or sand spots were observed.

Example 3 10.0 parts of the solution of polyol C obtained in Reference Example 3 and 1.0 part of a 30% cellosolve acetate solution of N-ethylmorpholine were added to 1000 parts of Ayaragi Silica Sand No. 6 and mixed uniformly. .

Next, 10.0 parts of a solution consisting of 70% polymeric polyisocyanate (a mixture of diphenylmethane diisocyanate and triphenylmethane triincyanate), 26% diisopropylbenzene, and 4 parts butyl 3-methoxyacetate was added to this and mixed uniformly. Prepared.

This foundry sand composition was 771 mm in diameter 5 CrI'L and height 5.
After quickly filling a 6-cavity wooden mold with a space of
After a certain period of time, the molding sand test piece was taken out and the compressive strength of the test piece was measured.

The results are shown in the table below.

Moreover, the test piece after 1 day was placed in an electric furnace heated to 7000C for 2 minutes, and the compressive strength immediately after taking it out was measured, and it was found to have a high heat resistance of 15.4 kg.

Additionally, the same foundry sand composition as above was filled into a wooden mold for an intake manifold core for a truck, and the mold was removed after 15 minutes.

This core was set into an outer mold made of mountain sand, and molten aluminum at 760° C. was cast two hours later.

The mold was removed after 30 minutes, but no core sand was found to be mixed with the green sand of the outer mold when the product was taken out.

Sand from the core could be removed from the product by hitting it 3 to 5 times with a resin hammer.

Claims (1)

[Scope of Claims] 1. A binder composition for foundry sand containing the following components a and b. (a) Organic polyisocyanate compound. (b) A polyol compound obtained by reacting a mixture of bisphenols and a cyclic ketone in which the carbon atom adjacent to the carbonyl group has at least two hydrogen atoms with formaldehyde.