JPS6116213B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing light alloy casting products such as aluminum. According to the method of the present invention, it is possible to obtain a cast product that exhibits excellent self-hardening properties and moldability using the cold box method, and has a beautiful appearance, and it is easy to remove sand after taking out the cast product. Binder compositions for foundry sand for making sand molds are very useful in the foundry industry. Conventionally, there are inorganic and organic binders used in the production of foundry sand molds, but each type of binder used in the production of aluminum foundry sand molds has advantages and disadvantages and is fully satisfactory. Nothing that can be done has been found. 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. Also, the foundry sand cannot be reused. Since alkali pollution is a problem, there are 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, phenol 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-toluene sulfonic acid or phosphoric acid, the remaining acid may corrode the surface of the casting, or the curing speed may increase depending on the temperature. There is a problem with fluctuations. Also known is a method of manufacturing a sand mold by curing foundry sand by reacting a phenol resin having a benzyl ether group or a methylol group represented by the following formula (I) with an organic isocyanate compound (Japanese Patent Publication No. 45-32820 No. 48-25431, Japanese Unexamined Patent Publication No. 1983-
Publication No. 128526). [In the formula, R is H or a phenol substituent at the meta position to the phenolic hydroxyl group, the sum of m and n is at least 2, the ratio of m and n is at least 1, and X is H
or methylol end groups, the molar ratio of methylol to hydrogen end groups being at least 1]. 1200 using a sand mold obtained using this binder
When casting cast iron at a high temperature of ℃ or higher, the above formula ()
The phenolic resin represented by is highly heat resistant, and since phenolic resin is easily carbonized, the above
Even at casting temperatures of 1200°C or higher, the molding sand in the part of the mold that comes into contact with the iron molten metal is bound by the carbide of phenolic resin, making it possible to obtain castings with beautiful casting surfaces, and the molding sand used also remains at the above-mentioned high temperature. As the phenolic resin is exposed and beautified, it becomes more easily disintegrated, and the foundry sand has the advantage of being reusable. However, this binder can be used with aluminum etc.
When used as a binder for molding sand in molds of light alloys cast at temperatures below 760°C, there is a drawback that the molding sand used has poor collapsibility (see JP-A-56-4621). This is because, when producing castings of the same volume, iron has a specific gravity approximately 2.5 times that of aluminum, and the temperature of the molten metal is as high as 1200°C or higher, resulting in a very large heat capacity for the sand mold. Therefore, the binder is required to have the strength to withstand such heat capacity until the end of pouring. Moreover, since the large heat capacity conversely requires a long cooling time, the carbonization of the phenolic resin progresses during that time, and the foundry sand becomes easily disintegrated. However, when this binder is used as a binder for molding sand for light alloy casting molds, the heat capacity is considerably lower than that of iron molten metal, and the cooling time of the molten metal is also short, so the progress of carbonization is small and the foundry sand is It is presumed that it has poor disintegration properties because it is strongly bonded. Further, a self-hardening binder comprising a resol type phenolic resin or a benzyl ether type phenolic resin, a polyisocyanate, and a basic catalyst such as γ picoline is also known. (Unexamined Japanese Patent Publication No. 53-128526
issue). Although the examples in this publication do not include examples in which a resol type phenolic resin is used as a binder component, the resol type phenolic resin obtained from phenol and paraform has poor compatibility with polyisocyanate, and the strength of the resulting sand mold is poor. is weak [the resistance pressure of compaction strength (after 1 day) is about 10 to 15
Kg/cm ² G] and the disintegrability of the foundry sand is also poor. In order to improve the disintegrability of the foundry sand after casting, instead of using phenolic resin, [In the formula, R ₁ and R ₂ are each H, CH ₃ or C ₂ H ₅ , R ₃ is C ₂ H ₄ or C ₃ H ₉ , m + n = 1
~20] Using polyether polyols shown in
A casting method using a binder containing these polyether polyols, polyisocyanate, and amine polyol (reactive curing catalyst) was proposed (Japanese Patent Application Laid-open Nos. 103734-1982 and 107427-1982).
issue). The disintegration of molding sand in molds using this binder is extremely easy, but because the disintegration is so good, problems with large castings include sand being washed away during casting, resulting in rough casting surfaces, and softening and deformation of molds. There is. In addition, increasing the proportion of the amine-containing polyol significantly shortens the pot life, and conversely, decreasing the proportion of the amine-containing polyol reduces the curing speed, resulting in the problem that it takes a considerable amount of time to demold. Therefore, in order to increase the heat resistance, it is necessary to further add reinforcing materials such as colloidal and water glass to the binder component, but in this case, it becomes difficult to reuse the sand. In addition, this binder has a short pot life because the polyol is an aliphatic primary or secondary acid group and has tertiary nitrogen that can act as a catalyst, so it reacts with isocyanate groups in a short time even at room temperature. . Therefore, it cannot be used in the cold box method, in which a curing catalyst such as amine is blown into a sand mold using a gas to cure it. The present inventor has discovered that polyols obtained by introducing methylol groups into bisphenols not only have a long pot life, but also that polyisocyanates react with methylol groups in addition to phenolic hydroxyl groups to form a three-dimensional structure. It was discovered that the strength of the sand mold is improved, the disintegration property is good, and it has a moderate heat resistance, so there is no problem of sand being washed away and the casting surface becomes rough, and there is no softening and deformation of the mold. reached. That is, the present invention provides a polyol compound whose main component is (a) an organic polyisocyanate compound (b) a polyol represented by the following formula () having a methylol group obtained by reacting bisphenols with formaldehyde. [In the formula, R is -CH ₂ - or

[Formula], X is -H or -CH ₂ OH group, and at least one of X is -CH ₂ OH group] Foundry sand consisting of the above components (a) and (b) Provided is a method for producing a light alloy casting product, characterized in that casting is produced by pouring a light alloy molten metal such as aluminum into a sand mold obtained by hardening molding sand by hardening a binder for molding in the presence of a curing catalyst. (However, the blending ratio of component (a) and component (b) is
(b) Hydroxyl group 1 of polyol compound as component
Per equivalent, the isocyanate group of component (a) is 0.3 to
3 equivalents). The binder composition used in carrying out the present invention has high strength of the cured product, fast curing speed,
It has features such as good disintegration of the sand mold when removing the casting after casting, and although it can be used for cast iron and cast steel, it is especially suitable as a binder composition for light alloy castings such as aluminum. The organic polyisocyanate compound as component (a) used in the present invention can be appropriately selected from organic polyisocyanate compounds generally widely used as raw materials for polyurethane, and di- or triisocyanates are preferred. Suitable organic polyisocyanate compounds include aliphatic isocyanates such as hexamethylene diisocyanate; cycloaliphatic isocyanates such as 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate; 2,4 and 2,6 tolylene diisocyanate, diphenyl Aromatic polyisocyanates such as methane diisocyanate, triphenylmethane isocyanate, 1,5 naphthalene diisocyanate, polymethylene polyphenylene isocyanate, and chlorophenylene-2,4-diisocyanate; xylylene diisocyanate 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 are dissolved in aromatic hydrocarbons such as toluene, xylene, ethylbenzene, diethylbenzene, kyumene, diisopropylbenzene, by-product heavy oil during ethylbenzene production, and by-product heavy oil during kyumene production. May be used. The polyol compound of component (b) used to produce polyurethane and harden foundry sand by reacting with an organic polyisocyanate compound is a polyol compound represented by the preceding formula () obtained by reacting bisphenols with formaldehyde. It is a polyol compound whose main component is polyol. As bisphenols, bisphenol A
Alternatively, bisphenol F can be mentioned. As the formaldehyde source, an aqueous formalin solution, a hemiacetal of formaldehyde and alcohol, paraformaldehyde, trioxane, etc. can be used. The reaction between bisphenols and formaldehyde is usually carried out at room temperature to 150°C, preferably at 60°C, in the presence of a metal salt catalyst such as zinc naphthenate or lead naphthenate, or an alkali catalyst such as sodium hydroxide.
It is carried out at between 120°C and 120°C. If the reaction temperature is higher than this, the molecular weight of the condensate will further increase due to the formation of methylene ether bonds due to dehydration condensation between methylol groups added to bisphenols, or the generation of methylene bonds due to dehydration condensation and formaldehyde condensation. Undesirable. The molar ratio of bisphenols to formaldehyde is stoichiometrically 1:1 to 4, preferably
A ratio of 1:1 to 2 is suitable, but in practice, the reaction can be carried out using a smaller or larger amount of formaldehyde than the theoretical amount, as appropriate. The main component of the resulting polyol compound is a structure represented by the above formula (2), in which a methylol group is added to a bisphenol, but it is partially condensed to contain a compound having 4 or 6 benzene nuclei. generate. The above polyol compounds are usually used in polar solvents such as cyclohexanone, ethyl cellosolve acetate, ethylene glycol diacetate, triethylene glycol diacetate, etc., or in order to dissolve these polar solvents and the above-mentioned organic polyisocyanate compounds. It is used by dissolving it in a mixed solvent with a similar aromatic hydrocarbon. Of course, it is also possible to use other polyol compounds in addition to component (b). The binder composition of the present application has sufficient heat resistance for castings of light alloys such as aluminum, but in order to increase the heat resistance of pouring, noporak type phenolic resin, resol type phenolic resin, and benzyl ether type phenol are used. Oligomers such as resins can also be added. When other polyol compounds other than component (b) are not used together, the amount of component (a) to component (b) is as follows:
The amount of isocyanate group in component (a) is 0.3 to 3 equivalents, preferably 0.6 equivalent to 1 equivalent of hydroxyl group in component (b).
It is appropriate to mix it so that it becomes ~1.5 equivalent. In addition, when using component (b) and other polyol compounds together, the amount of isocyanate groups in component (a) is 0.3 to 3 per 1 of the total hydroxyl group amount of component (b) and other polyol compounds. , preferably 0.6 to 1.5. Components (a) and (b) and other polyol compounds used as necessary are blended in a proportion of 0.5 to 5 parts by weight based on 100 parts by weight of foundry sand. The foundry sand may be any sand or inorganic powder used for foundries, and its particle size, type, etc. can be selected as appropriate. This binder is used in combination with foundry sand. Foundry sand mixed with binder composition
When molding a sand mold at room temperature, a catalyst can be added to quickly harden the sand mold in order to accelerate the strength development of the sand mold. This curing catalyst includes metal salts such as cobalt naphthenate, tin octylate, dibutyltin dilaurate, N-ethylene morpholin, 4-
Phenylpropylpyridine, ethyl morpholinopropionate, tetramethyldiaminopropane,
Tertiary amines such as triethylenediamine 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,
Tertiary amines are preferred, and trimethylamine, triethylamine, dimethylethanolamine, N-ethylmorpholine and the like are particularly preferred. 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% by volume or less. The present invention is carried out by extracting the model from the sand mold that has been hardened and hardened in this way, then pouring a light alloy such as aluminum into the cavity of the sand mold, cooling it, and then taking out the cast product. Next, the present invention will be explained in more detail with reference to Examples. In addition, "part" and "%" in Examples and Reference Examples
is based on weight. Reference Example 1: Example of producing a polyol compound 228.3 g (1 mo) of bisphenol A, 60 g of paraformaldehyde, 230 g of ethylene glycol diacetate, and 3.0 g of lead naphthenate were placed in a four-necked flask (No. 1) and heated at 110°C while stirring. The reaction was allowed to proceed for 3 hours. Unreacted formaldehyde was removed under reduced pressure, and the mixture was cooled to room temperature. The product is GPC, IR and
From the results of NMR analysis, it was found to be a polyol compound mixture (2) whose main component was a bisphenol A derivative having a methylo group. Reference Example 2: Example of producing a polyol compound 228.3 g (1 mo) of bisphenol A, 42.4 g of paraformaldehyde, 228.4 g of ethylene glycol diacetate, and 1.0 g of lead naphthenate were placed in a four-necked flask, and while stirring, The reaction was carried out at ℃ for 4 hours. Unreacted formaldehyde and water were removed under reduced pressure, and the mixture was cooled to room temperature. The product is GRC,
According to the results of IR and NMR analysis, it was a mixture of polyol compounds whose main component was a bisphenol A derivative having a methylol group. 85 parts of this polyol compound mixture and 15 parts of hexylene were added and mixed uniformly to obtain a polyol compound solution (). Reference example 3: Production example of polyol compound Bisphenol F 200.3g (1mo), paraformaldehyde 39.1g, 3-methoxybutyl acetate
225.4 g of lead naphthenate and 1.0 g of lead naphthenate were placed in a four-necked flask (No. 1), reacted with stirring at 100° C. for 5 hours, and then cooled. The product was a mixture of polyol compounds whose main component was a bisphenol F derivative having a methylol group, based on the results of GPC, IR, and NMR analyses.
15 parts of diisopropylbenzene was added to 85 parts of this polyol compound mixture and mixed uniformly to obtain a polyol compound solution (2). Example 1 To 100 parts of Ayaragi Silica Sand No. 6, 0.95 part of the solution of the polyol compound () obtained in Reference Example 1 and 0.10 part of a 10% ethyl cellosoluble acetate solution of N-ethylmorpholine were added and mixed uniformly. did. Next, 1.05 parts of a 66% diisopropylbenzene solution of polymeric polyisocyanate ((a mixture of diphenylmethane diisocyanate and triphenylmethane triisocyanate)) was added, mixed uniformly, and placed into a cylindrical mold with a diameter of 5 cm and a height of 13 cm. The sample was placed at a depth of 5 cm and compacted using a standard compaction tester to prepare a test piece, and the counter pressure of the sample was measured at regular intervals.The results are shown in the table below.

[Table] A mold for a car cooler case was also created using the same foundry sand composition. The mold was removed after 15 minutes, and molten aluminum at 760°C was cast after 3 hours. The disintegration of the outer mold and core when the cast product was taken out after cooling was good, and a product with a beautiful cast surface was obtained. Example 2 0.95 parts of the solution of the polyol compound () obtained in Reference Example 1 was added to 100 parts of Ayaragi Silica Sand No. 6,
After uniformly mixing, 1.05 parts of a 66% diisopropylbenzene solution of polymeric polyisocyanate was added and uniformly mixed. A mold for a car cooler case was made using the foundry sand composition thus prepared, and triethylamine, which had been vaporized by blowing nitrogen, was passed through it for 30 seconds to harden it. to this
Molten aluminum was cast at 760℃. The disintegration properties of the sand mold, especially the disintegration properties of the core, when the cast product was taken out after cooling were good, and a product with a beautiful casting surface was obtained. In addition, after preparing the same foundry sand composition, it was immediately put into a cylindrical mold with a diameter of 5 cm and a height of 13 cm, and after being compacted to a height of 5 cm using a standard compaction tester, nitrogen gas containing triethylamine was added to the mold for 10 minutes. It was cured for seconds. Immediately after the molding sand test piece was taken out from the mold, its counter pressure was 33.9 Kg/cm ² , and after being left for 1 hour, its counter pressure was 50.2 Kg/cm ² . Furthermore, after 30 minutes had elapsed after adjusting the foundry sand composition, it was put into the cylindrical mold and compacted, and then immediately after the foundry sand test piece obtained, which had been similarly hardened with triethylamine gas, was taken out from the mold. The counter pressure is 31.4Kg/ ^cm2 , and after leaving for 1 hour it is 49.8
It was Kg/ ^cm2 . Comparative Example 1 Bisphenol A to 100 parts of Ayaragi Silica Sand No. 6
30.7 parts of a 2 mole adduct of propylene oxide, 13.5 parts of a 4 mole adduct of propylene oxide of ethylenediamine,
Aromatic solvent (Hysol: Nippon Petrochemical Co., Ltd. product)
1.33 parts of a polyol solution consisting of 54.2 parts were mixed homogeneously. Next, polymeric isocyanate
After adding 0.67 parts and mixing uniformly, this was immediately placed into a cylindrical mold with a diameter of 5 cm and a height of 13 cm to a depth of 5 cm, a tamping mold was created using a standard tamping tester, and nitrogen was added. Triethylamine, which had been blown in and vaporized, was passed through the solution for 30 seconds to cure it. Immediately after taking the molding sand test piece out of the mold, the counter pressure was 4.9Kg/cm ² (however, the sand mold was deformed).
The counter pressure after standing for 1 hour was 30.1 Kg/cm ² . In addition, after 30 minutes had elapsed after mixing silica sand, the above polyol solution, and polymeric isocyanate, they were placed in a mold, compacted, and nitrogen was blown into the mold to blow a vaporized triethylamine gas into the sand mold.The anti-pressure of the sand mold was 0 kg. /cm ² and after 1 hour it is also 0
It was Kg/ ^cm2 . Example 3 Hookah sand (silica sand from Australia)
To 100 parts, 0.95 part of the solution of the polyol compound obtained in Reference Example 2 () and 0.10 part of a 30% 3-methoxybutyl acetate solution of 4-phenylpropyl pyridine were added and mixed uniformly. Next, 1.0 part of a 75% diisopropylbenzene solution of polymeric polyisocyanate (same as in Example 1) was added and mixed uniformly, and test pieces were prepared in the same manner as in Example 1 and their anti-pressure was measured. . The results are shown in the table below.

[Table] In addition, a mold for a car cooler case was made in the same manner as in Example 1 using the same foundry sand composition, and molten aluminum was cast into it to produce a cast product. The disintegration properties of the outer mold and core of the mold were shown. Example 4 Solution of polyol compound obtained in Reference Example 2
1.0 part, 74% of polymeric polyisocyanate
A mold for a car cooler case was made using a foundry composition prepared in the same manner as in Example 2, except that 1.0 part of diisopropylbenzene solution was used, and triethylamine, which had been vaporized by blowing nitrogen, was passed through it for 30 seconds. hardened. Molten aluminum at 760°C was cast into this. The disintegrability of the sand mold, especially the disintegration of the core, when the cast product was taken out after cooling was extremely good, and the surface of the cast product was also beautiful. In addition, the same foundry sand composition was made with a diameter of 5 cm and a height of 13 cm.
5 cm into a cylindrical mold and run on a standard compaction tester.
After hardening to a height of cm, nitrogen gas containing triethylamine was passed through for 10 seconds to harden.
Immediately after the molding sand test piece was taken out from the mold, its resistance pressure was 35.5Kg/cm ² , and its resistance pressure 1 hour later was 54.6Kg/cm ² . Example 5 1.0 part of a 75% diisopropylbenzene solution of polymeric polyisocyanate (same as in Example 1) was added to 120 parts of Arayagi silica sand and mixed uniformly. Next, 0.95 parts of the polyol compound solution obtained in Reference Example 3 () and 0.10 parts of a 30% 3-methoxybutyl acetate solution of 4-phenylpropylpyridine were added and mixed uniformly, followed by the same procedure as in Example 1. Test pieces were prepared and their resistance pressures were measured using the method described above.
The results are shown in the table below.

[Table] In addition, a mold for a car cooler case was made in the same manner as in Example 1 using the same foundry sand composition, and molten aluminum (760°C) was cast into it to produce a cast product. The disintegration properties of the outer mold and core of the mold were shown. Example 6 0.8 parts of the solution of the polyol compound obtained in Reference Example 3 () and 0.8 parts of the solution of the polymeric polyisocyanate
Other than using 0.8 part of 74% diisopropyl bene solution,
Using a casting composition prepared in the same manner as in Example 2,
A mold for a car cooler case was made, and the mold was cured by blowing nitrogen into it and passing vaporized triethylamine through it for 30 seconds. Aluminum molten at 760°C was cast into this. The disintegration properties of the cast product after cooling were extremely good, and the surface of the cast product was also beautiful. In addition, the same foundry sand composition was made with a diameter of 5 cm and a height of 13 cm.
5 cm into a cylindrical mold and run on a standard compaction tester.
After compacting to a height of cm, nitrogen gas containing triethylamine was passed through for 10 seconds to harden.
Immediately after taking the molding sand test piece out of the mold, its resistance pressure was 3.6Kg/cm ² , and the resistance pressure for 1 hour was
It was 54.6Kg/ ^cm2 .

Claims (1)

[Scope of Claims] 1 (a) an organic polyisocyanate compound (b) a polyol compound whose main component is a polyol represented by the following formula having a methylol group obtained by reacting bisphenols with formaldehyde [In the formula, R is -CH ₂ - or [Formula], X is -H or -CH ₂ OH group, and at least one of X is -CH ₂ OH group] (a) above Aluminum, characterized in that a casting is produced by pouring a light alloy molten metal into a sand mold obtained by hardening a foundry sand binder consisting of a component and (b) component in the presence of a curing catalyst and hardening the foundry sand. A method for producing light alloy casting products. However, the blending ratio of component (a) and component (b) is such that the isocyanate group of component (a) is 0.3 to 3 equivalents per 1 equivalent of hydroxyl group of the polyol compound of component (b).