JPH0117780B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a foundry sand binder composition for light alloys used as a binder (binding material) for manufacturing sand molds in the foundry industry. The foundry sand binder composition of the present invention has excellent collapsibility of a sand mold after casting a light alloy. Conventionally, as a foundry sand binder composition, it is known that a phenolic resin obtained by the reaction of phenol and aldehyde and a polyisocyanate are cured in a short time using an amine catalyst (for example, Japanese Patent Publication No. 32820/1983). Publication No. 49-37486, Publication No. 25431-1980, Publication No. 17141-1973
(Refer to the publication number, etc.) These foundry sand binder compositions have excellent heat resistance as a binder and excellent disintegration properties of sand molds after casting for cast iron and cast steel whose casting temperature is 1300 to 1600°C. However, the casting temperature
The heat resistance as a binder is too high for use in light alloys at temperatures below 800°C, and the collapsibility of the sand mold after casting is extremely poor. For this reason, during the casting process, the sand from the sand mold used as the core is difficult to remove, and extra steps and manpower are required to remove the sand. As a foundry sand binder for light alloys,
-7338 is also known, but this binder has a low strength level, poor heat resistance, and poor moisture resistance during high humidity such as the rainy season, so it has not been put to practical use. or,
The foundry sand binder disclosed in Japanese Patent Publication No. 51-33506 is
There was a problem with the pot life being short. The present inventor has conducted intensive research into a foundry sand binder for light alloys that does not have the above-mentioned problems.
We have succeeded in developing a foundry sand binder composition for light alloys that has an excellent balance between heat resistance and disintegration of the sand mold after casting and has a long pot life, leading to the completion of the present invention. That is, the present invention is a foundry sand binder composition for light alloys containing the following components (a), (b), and (c),
The gist is that 10 to 200 parts by weight of component (b) is blended with 100 parts by weight of component (c). (a) Organic polyisocyanate compounds (b) Oligomers having two or more phenolic hydroxyl groups obtained by the reaction of phenols and aldehydes (c) Phenols other than the above component (b) having two phenolic hydroxyl groups Compound. 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 triisocyanate, 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 phenols used as raw materials for component (b) include phenol, o-cresol, m-cresol, and p-cresol.
-cresol, para-t-butylphenol, nonylphenol, etc. Examples of aldehydes include formaldehyde, acetaldehyde, butyraldehyde, propionaldehyde, and furfurylaldehyde. The oligomer having two or more phenolic hydroxyl groups obtained by the reaction of component (b), phenols and aldehydes, is obtained by the reaction of the above-mentioned phenols and aldehydes, and includes, for example, novolac type phenol resin, resol type phenol resin, etc. There are resins, phenolic resins having methylol groups and/or methylene ether bonds. The phenolic compound having two phenolic hydroxyl groups as the component (c) is, for example, resorcinol, catechol, hydroquinone, pyrogallol, phloroglucin, alkylresorcinol, bisphenol A,
Bisphenol F, bisphenol C, bisphenol H, dihydroxybiphenyl, 4-methyl-2,4-bis(p-hydroxyphenyl)pent-1-ene, etc., and component (b) phenols and aldehydes. It does not include oligomers having two or more phenolic hydroxyl groups obtained by reaction with phenolic hydroxyl groups. By reacting with an organic polyisocyanate compound, polyurethane is produced and the proportion of components (b) and (c) used to harden the foundry sand, the size of the sand mold for casting, the type of sand, etc. Although the optimal condition changes depending on the condition, at least (c)
It is necessary to mix 10 to 200 parts by weight of component (b) with respect to 100 parts by weight of the components, from the viewpoint of the balance between heat resistance during casting and disintegration of the sand mold after casting. (b) the ingredients are
If the amount is less than 10 parts by weight, heat resistance during casting will be insufficient and the sand mold will break during casting. Moreover, if it exceeds 200 parts by weight, the heat resistance will be too high and the collapsibility of the sand mold after casting will deteriorate. The preferred blending ratio of component (b) to 100 parts by weight of component (c) is about 20 to 200 parts by weight. The amount of isocyanate groups in component (a) is 0.3 to 3 equivalents, preferably 0.6 to 2 equivalents, per 1 equivalent of hydroxyl groups contained in the total of components (b) and (c). good. Components (b) and (c) are usually dissolved in a solvent and used in an amount and viscosity that allows them to be easily mixed with component (a) or with sand. Solvents used include, for example, cellosolve acetate, ethylene glycol diacetate,
These are polar solvents such as isophorone, butyl cellosolve acetate, cyclohexanone, butyl 3-methoxyacetate, and diethylene glycol monoethyl ether acetate. Furthermore, aromatic hydrocarbons such as xylene, kyumene, and ethylbenzene can be used in combination with the above polar solvents. The binder for foundry sand of the present invention is used by mixing with foundry sand, and the (a) component,
It is preferable that the total amount of component (b) and component (c) is 0.3 to 5 parts by weight. In the present invention, γ-aminopropylethoxysilane, N-β-(aminoethyl)-γ-
A silane treatment agent such as aminopropyltrimethoxysilane or γ-mercaptopropyltrimethoxysilane is used to improve the moisture resistance of the binder.
For 100 parts by weight of the total amount of components (a), (b) and (c),
It can also be added in an amount of 0.005 to 0.5 parts by weight. When molding a sand mold at room temperature after mixing the composition of the present invention with foundry sand, a known catalyst such as a metal salt such as dibutyltin dilaurate or a tertiary amine such as N-ethylmorpholine may be added. It can be cured quickly. At this time, the amount of catalyst added is based on 100 parts by weight of the total amount of components (a), (b) and (c).
It is preferably 5 parts by weight or less. In addition, when rapidly curing by contacting with an amine-containing gas, a known tertiary amine with a low boiling point such as triethylamine can be used, and an inert gas such as nitrogen gas or air is usually used as a carrier gas. Use at a concentration of % by volume or less. Next, the present invention will be explained in more detail with reference to Examples. In addition, "part" and "%" in Examples and Comparative Examples
is based on weight. Production example 1 Phenol 2028g, paraformaldehyde 1440
g, 30 g of zinc naphthenate solution (8%) and 240 ml of benzene were placed in a three-necked flask and heated at 110° C. for 3 hours to carry out a reaction. The reaction proceeds with distillation of water and benzene. After the reaction, add 300ml of diethylene glycol diethyl ether and benzene to the reaction system.
Added 30ml. After this, reflux was performed for 1 hour, and an additional 300 ml of the above ether was added to the reaction system. 7
After a period of time, 1200 ml of cellosolve acetate was added to obtain an oligomer, which is component (b) of the present invention. This oligomer was confirmed to be a benzyl ether type phenolic resin from an infrared absorption spectrum. Examples 1 to 4, Comparative Examples 1 to 6 Cellosolve acetate solution of bisphenol A (concentration 50%) as component (b) and component (c) shown in Table 1
10 parts of the mixture was added to 1000 parts of Ayaragi Silica Sand No. 6 and mixed uniformly. Furthermore, a xylene solution of commercially available polymethylene polyisocyanate (concentration
75%) was added and mixed uniformly. This was filled into the core wooden mold of an automobile's intake manifold, and vaporized triethylamine was passed through it for 50 seconds to harden it. This core was set in an outer mold made from a green sand mold, and molten aluminum was poured into it at 760°C. After 1 hour, remove the mold,
The way in which core sand falls from a casting product was investigated by hitting the casting with a hammer and determining how many times it takes for most of the core sand to disintegrate and be removed. 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, and the resistance pressure was measured immediately and after 4 hours. The results are shown in Table 1. From Table 1, it can be seen that the foundry sand binder composition of the present invention ranges from disintegration to strength (resistance pressure).
It is clear that the balance is excellent.

【table】

[Table] Note: Phenol-formaldehyde condensate manufactured by Meiwa Kasei.
Examples 5 and 6, Comparative Examples 7 and 8 Component (b) was added to Isokyupart (manufactured by Hodogaya Chemical Co., Ltd.).
Coercive pressure and disintegration were carried out in the same manner as in Examples 1 to 4, except that component (a) was changed to Isokyuate (manufactured by Hodogaya Chemical, an organic solvent solution of polyisocyanate) in an organic solvent solution of phenol-formaldehyde resin. I looked into gender. The results are shown in Table 2. From Table 2, it is clear that the present invention is superior.

【table】

Claims (1)

[Scope of Claims] 1 A foundry sand binder composition for light alloys containing the following components (a), (b), and (c), in which 10 parts by weight of component (b) is added to 100 parts by weight of component (c). A foundry sand binder composition for light alloys, characterized in that it contains ~200 parts by weight. (a) Organic polyisocyanate compounds (b) Oligomers having two or more phenolic hydroxyl groups obtained by the reaction of phenols and aldehydes (c) Phenols other than the above component (b) having two phenolic hydroxyl groups Compound.