JP4481839B2 - Organic binder for mold, foundry sand composition obtained using the same, and mold - Google Patents

Description

  The present invention relates to an organic binder for a mold used for molding a phenol-urethane gas-curing mold or a self-hardening mold used in sand mold casting, a casting sand composition and a mold obtained using the same. .

  Conventionally, as one of the typical organic molds used in sand mold casting, phenols and polyisocyanate compounds are used as binders, and phenols are molded using their polyaddition reaction (urethanization reaction). Urethane molds are known. The phenol-urethane mold includes a mass-produced gas-cured mold produced by the amine cold box method that does not require heating during molding, and a non-mass-produced self-hardened mold produced by the room temperature self-hardening method. Widely known.

  Specifically, the gas-curing mold by the amine cold box method is usually an organic caking mold for a mold composed of a granular refractory casting sand, a phenol resin solution using an organic solvent as a solvent, and a polyisocyanate compound solution using a mixer. After producing a foundry sand composition by coating the surface of the foundry sand with an organic binder by kneading with an agent, the foundry sand composition is blown into a predetermined mold to mold a mold, It is manufactured by passing an amine-based catalyst gas through this and performing curing. In addition, a self-hardening mold by the room temperature self-hardening method is used when a granular refractory casting sand is kneaded with an organic binder for a mold comprising a phenol resin solution and a polyisocyanate compound solution using an organic solvent as a solvent. And the resulting mixture is immediately formed into an initial shape.

  In such a phenol-urethane mold obtained by using a polyaddition reaction (urethanization reaction) between a phenol resin and a polyisocyanate compound, it is caused by a long curing time particularly in winter molding. Thus, the strength (initial strength) of the manufactured mold is low, and there is a problem that the mold is damaged due to the release resistance at the time of mold release.

  On the other hand, such a phenol resin and a polyisocyanate compound have a possibility that a polyaddition reaction (urethanization reaction) gradually proceeds and begins to harden at the mixing stage when producing a foundry sand composition. In the field, when the casting mold is formed using the foundry sand composition accommodated in the sand hopper for a long time, the strength (initial strength) of the manufactured casting mold is significantly lower than the desired strength. In some cases, problems such as various molding defects are caused. For this reason, even when a casting mold is made using a casting sand composition that has been manufactured for a long time, the casting sand composition can provide sufficient strength (initial strength). Therefore, the development of an organic binder for molds that can exhibit such characteristics is desired.

  Therefore, in JP-A-6-210390 (Patent Document 1), a granular refractory aggregate coated with a binder containing a phenol resin, an alkyd resin or a modified alkyd resin, a polyisocyanate compound, and a solvent is used. There is proposed a method for producing a mold characterized in that it is introduced into a frame and molded, and then a curing catalyst is introduced into the mold and cured. It is said that the tensile strength (initial strength) of a mold obtained using the binder-coated sand (casting sand composition) can be effectively improved.

  However, a desired mold using a binder-coated sand (casting sand composition) prepared by kneading a binder containing an alkyd resin and a refractory aggregate as in the previously proposed technique. It is recognized that the strength (initial strength) of the obtained mold is somewhat better than the strength of the mold obtained using a conventional binder that does not contain an alkyd resin or the like. However, its strength was still insufficient. In addition, in the case of the granular refractory aggregate (casting sand composition) coated with the binder containing the alkyd resin previously proposed, when a mold is manufactured using a material after a certain time has passed since kneading. Inherent in the problem of low strength

JP-A-6-210390

  Here, the present invention has been made in the background of such circumstances, and the problem to be solved is a mold formed using a casting sand composition immediately after production, and a certain time elapsed from production. In any of the molds molded using the foundry sand composition later, an organic binder for a mold that can exhibit excellent strength (initial strength), and an organic binder for this mold The object of the present invention is to provide a foundry sand composition obtained by use, and a gas-curing mold and a self-hardening mold produced using the foundry sand composition.

  And in order to solve this problem, the present invention is an organic binder used for molding a phenol-urethane-based gas-curing mold or a self-hardening mold, and includes a phenol resin, a polyisocyanate compound and an organic solvent, A) a compound having at least two nitrogen atoms in a five-membered ring, b) a hydrazine compound substituted with at least one aromatic functional group, c) a formamide compound substituted with two alkyl groups, d) at least one aromatic At least one organic nitrogen compound selected from the group consisting of an acetamide compound substituted with a group functional group, e) an amide compound having at least one unsaturated bond, and f) a compound having at least two amide groups An organic binder for molds characterized in that it is contained as an essential constituent, and its gist is .

  Here, in one of the preferable embodiments of the organic binder for a mold according to the present invention, the phenol resin is an orthocresol-modified phenol resin, and in another preferable embodiment, the organic nitrogen compound is used. Is a triazole-based compound.

  Further, the present invention provides a casting sand composition obtained by kneading the organic binder for a mold as described above with respect to the foundry sand, or by bringing a catalyst gas into contact with the foundry sand composition. A gas-curing mold obtained by curing the foundry sand composition, and further a self-hardening mold formed by kneading the foundry sand together with a curing catalyst and a mold organic binder as described above. Each of them has its gist.

  Thus, in the organic binder for molds according to the present invention, in addition to the phenolic resin, polyisocyanate compound and organic solvent that have been widely used as constituents of the organic binder, a) five members A compound having at least two nitrogen atoms in the ring, b) a hydrazine compound substituted with at least one aromatic functional group, c) a formamide compound substituted with two alkyl groups, d) at least one aromatic functional group An acetamide compound substituted with e) at least one organic nitrogen compound selected from the group consisting of e) an amide compound having at least one unsaturated bond, and f) a compound having at least two amide groups Because it is contained as a component, such a component is a polyaddition reaction between a phenol resin and a polyisocyanate compound. This effectively contributes to (urethanization reaction), and kneading the organic binder for mold and foundry sand to produce a foundry sand composition, and using the foundry sand composition immediately after the production, When manufactured, the obtained mold exhibits excellent strength (initial strength).

  Moreover, in the foundry sand composition manufactured using such an organic binder for molds, the mold was molded using a product that had been used for a long time since its manufacture (mixing with foundry sand). Even in this case, since the strength (initial strength) of the obtained mold is sufficiently high, it can be advantageously used in an actual molding site.

  In particular, when an ortho-cresol-modified phenol resin is used as the phenol resin, or when a triazole compound is used as the organic nitrogen compound, the excellent effects as described above can be enjoyed advantageously.

  By the way, in such an organic binder for a mold according to the present invention, the phenol resin used as one of the main components is not particularly limited, and when a phenol urethane mold is conventionally formed. Various known phenol resins used can be appropriately used. Specifically, in the presence of a reaction catalyst, phenols and aldehydes are generally in a ratio of 0.5 to 3.0 moles with respect to 1 mole of phenols, Examples of the benzyl ether type phenolic resin, resol type phenolic resin, novolac type phenolic resin, and modified phenolic resins thereof, which are obtained by addition / condensation reaction, and mixtures thereof, can be exemplified. Of these, one or more of them are appropriately selected and used. Among these, in particular, an ortho-cresol-modified phenol resin modified with ortho-cresol, more preferably a benzyl ether-type ortho-cresol-modified phenol resin, and a mixture thereof include solubility in an organic solvent and polyisocyanate. In addition to being excellent in compatibility, the present invention is suitably used in the present invention because it effectively improves the strength (initial strength) of the obtained mold.

  The catalyst used in the addition / condensation reaction of the above-described phenols and aldehydes is not particularly limited, and depending on the type of phenol resin desired, an acidic catalyst, a basic catalyst, Various catalysts conventionally used for the production of phenol resins are appropriately used. Examples of such a catalyst include metal salts having metal elements such as tin, lead, zinc, cobalt, manganese, nickel, and more specifically, lead naphthenate, zinc naphthenate, lead acetate. In addition to zinc chloride, zinc acetate, zinc borate, lead oxide, and combinations of acids and bases that can form such metal salts. Moreover, when employ | adopting such a metal salt as a reaction catalyst, the usage-amount is although it does not specifically limit, Generally, it will be 0.01-5 weight part with respect to 100 weight part of phenols. It will be used at a rate.

  Examples of the phenols that give the phenol resin include alkylphenols such as phenol, cresol, xylenol, p-tert-butylphenol, and nonylphenol, polyhydric phenols such as resorcinol, bisphenol F, and bisphenol A, and mixtures thereof. On the other hand, examples of aldehydes include formaldehyde, formalin, paraformaldehyde, polyoxymethylene, glyoxal, furfural, and mixtures thereof.

  Further, as described above, orthocresol-modified phenol resin, which is one of the phenol resins that can be advantageously employed in the present invention, includes, for example, ortho-cresol and phenol in the presence of a reaction catalyst such as a metal salt. In addition to (1) a co-condensation type ortho cresol modified phenol resin of ortho cresol and phenol, (2) a mixed type ortho cresol modified phenol resin of ortho cresol resin and phenol resin obtained by reacting with aldehydes, 1) and (2) resins modified with a modifier (modifier), (3) modified orthocresol modified phenolic resin, and 2 of (1), (2) and (3) Examples thereof include a mixture obtained by combining more than one species.

  More specifically, the cocondensation-type orthocresol-modified phenol resin (1) described above is a cocondensation resin obtained by reacting orthocresol and phenol with aldehydes simultaneously or stepwise, Depending on the reaction conditions such as the type of reaction catalyst used, a novolak type, a resol type, a benzyl ether type, and a co-condensation type ortho cresol modified phenolic resin combining these types can be obtained. In addition, a benzyl ether type co-condensation type ortho-cresol-modified phenol resin is preferably used. The blending ratio of orthocresol and phenol is preferably orthocresol / phenol (weight ratio) = 10/90 to 90/10, more preferably 20/90, from the viewpoint of improving the initial strength of the mold. 80-80 / 20 is desirable.

  The mixed orthocresol-modified phenol resin (2) described above is at least one selected from the group of novolak-type, resol-type and benzylether-type orthocresol resins obtained by reacting orthocresol and aldehydes. Obtained by mixing a kind of ortho-cresol resin and at least one phenol resin selected from the group of novolak-type, resol-type and benzyl ether-type phenol resins obtained by reacting phenol with aldehydes Is. Among these, in the present invention, a benzyl ether type mixed ortho cresol-modified phenol resin obtained by mixing a benzyl ether type ortho cresol resin and a benzyl ether type phenol resin is preferably used. Even in such a mixed type ortho-cresol-modified phenol resin, from the viewpoint of improving the initial strength of the mold, etc., the ortho-cresol resin and the phenol resin are mixed so that the blending ratio of ortho-cresol and phenol falls within the range described above. However, it is preferably mixed at a ratio of orthocresol resin / phenol resin (weight ratio) = 10/90 to 90/10, more preferably 20/80 to 80/20.

  In addition, the modified orthocresol-modified phenolic resin (3) described above may be added to any resin during or after the production of the co-condensed orthocresol-modified phenolic resin, orthocresol resin, or phenolic resin. Modifiers (modifiers) such as alkyd resins, epoxy resins, melamine resins, urea resins, xylene resins, vinyl acetate resins, polyamide resins, urea compounds, melamine compounds, epoxy compounds, furfuryl alcohol, polyvinyl alcohol , Urea, amides, linseed oil, cashew nut shell liquid, rosin, starches, monosaccharides, etc., selected from the group of novolak, resole and benzyl ether resins modified by mixing or reacting At least one modified ortho-cresol modified phenolic resin That. Among these, in the present invention, a modified ortho-cresol-modified phenol resin of benzyl ether type is advantageously used.

  Thus, in the organic binder for molds of the present invention, the phenol resin used as one of the main components is reduced in viscosity, compatible with the polyisocyanate solution described later, coating property to foundry sand, mold From the viewpoint of physical properties and the like, generally, a solution (hereinafter referred to as “phenol resin solution”) having a concentration of about 30 to 80% by weight dissolved in an organic solvent formed by combining a polar organic solvent and a nonpolar organic solvent. ")").

  On the other hand, in the organic binder for molds according to the present invention, the polyisocyanate compound used as another of the main components is obtained by polyaddition reaction with the active hydrogen of the phenol resin as described above, thereby converting the foundry sands to phenol. It is a compound having in its molecule two or more isocyanate groups that can be chemically bonded with urethane. Specific examples of such polyisocyanate compounds include aromatic, aliphatic or cycloaliphatic polyisocyanates such as diphenylmethane diisocyanate, polymethylene polyphenylene polyisocyanate (hereinafter referred to as “polymeric MDI”), and hexamethylene diisocyanate. In addition to 4,4'-dicyclohexylmethane diisocyanate, various conventionally known polyisocyanates such as prepolymers having two or more isocyanate groups obtained by reacting these polyisocyanate compounds with polyols can be mentioned. You may use, or may use it in combination of 2 or more types.

  Further, even in such a polyisocyanate compound, for the same reason as the phenol resin as described above, generally, a nonpolar organic solvent or a mixed solvent of a nonpolar organic solvent and a polar solvent is used as a solvent. , It will be used as a solution in which the concentration is about 40 to 90% by weight. In addition, it is not always necessary to dissolve in an organic solvent depending on the type of polyisocyanate compound to be used, and the undiluted solution can be used. Hereinafter, the polyisocyanate compound stock solution and a solution obtained by dissolving the polyisocyanate compound in an organic solvent are referred to as a polyisocyanate solution.

  In addition, as an organic solvent for dissolving the phenol resin and polyisocyanate compound mentioned above here, it is non-reactive with the polyisocyanate compound and is a solute (phenol resin or polyisocyanate compound) to be dissolved. Although it is not particularly limited as long as it is a good solvent, in general, i) a polar solvent for dissolving the phenol resin and ii) a polyisocyanate compound in an amount that does not cause separation of the phenol resin. In combination with a non-polar solvent.

  More specifically, the polar solvent of i) is, for example, an aliphatic carboxylic acid ester, and particularly, from the viewpoint of environmental safety, a dicarboxylic acid methyl ester mixture (manufactured by DuPont; trade name: DBE; Dicarboxylic acid alkyl esters such as dimethyl glutarate, dimethyl adipate and dimethyl succinate), vegetable oil methyl esters such as rapeseed oil methyl ester, ethyl oleate, ethyl palmitate, mixtures thereof, fatty acid monoesters, etc. In addition to esters, for example, ketones such as isophorone, ethers such as isopropyl ether, furfuryl alcohol and the like can be mentioned. Examples of the nonpolar solvent ii) include petroleum hydrocarbons such as paraffins, naphthenes, and alkylbenzenes. Specific examples include ipsol 150 (manufactured by Idemitsu Kosan Co., Ltd .; petroleum solvent), HAWS. (Shell Chemicals Japan Co., Ltd .; petroleum solvent) can be exemplified.

  By the way, in the organic binder for a mold according to the present invention, in addition to the above-described phenol resin solution and polyisocyanate solution, a) a compound having at least two nitrogen atoms in a five-membered ring, b) at least A hydrazine compound substituted with one aromatic functional group, c) a formamide compound substituted with two alkyl groups, d) an acetamide compound substituted with at least one aromatic functional group, e) at least one unsaturated bond And at least one organic nitrogen compound selected from the group consisting of compounds having at least two amide groups is used as an essential component. With such a specific organic nitrogen compound, the produced mold is excellent both in the case of using a foundry sand composition immediately after production and in the case of using a foundry sand composition after a certain period of time has elapsed since production. High strength (initial strength) is exhibited. Among such specific organic nitrogen compounds, in particular, a) compounds having at least two nitrogen atoms in the five-membered ring are preferably used.

  Among the organic nitrogen compounds that contribute to the expression of such excellent effects, the above-mentioned a) is not particularly limited as long as it is a compound having at least two nitrogen atoms in a five-membered ring. Even if it is a thing, it can be used, for example, an imidazole type compound, a triazole type compound, a tetrazole type compound etc. can be mentioned.

  Specifically, examples of the imidazole compound include a compound having an imidazole skeleton, a derivative thereof, and a metal salt thereof, and are not particularly limited. For example, imidazole, benzimidazole, 2-methyl Examples include imidazole, 2-ethylimidazole, 2-phenylimidazole, 1-isobutyl-2-methylimidazole, and metal salts thereof. Among these, 1-isobutyl-2-methylimidazole is particularly preferably used in the present invention.

  Further, the triazole compounds include compounds having a triazole skeleton, derivatives thereof and metal salts thereof, such as 1,2,3-benzotriazole, 5-methylbenzotriazole, benzotriazole-5-carboxylic acid. Benzotriazole such as 4-nitrobenzotriazole, 5-nitrobenzotriazole, 4-aminobenzotriazole, 5-aminobenzotriazole, 1-hydroxy-benzotriazole, 2- (5-methyl-2-hydroxyphenyl) benzotriazole Compounds, 1,2,4-triazole, 3-mercapto-1,2,4-triazole, 3-amino-1,2,4-triazole, 4-amino-1,2,4-triazole, 5-amino -3-Mercapto-1,2,4-triazole, 3-Nito 1,2,4-triazole and can illustrate these metal salts.

  Furthermore, examples of the tetrazole-based compound include compounds having a tetrazole skeleton, derivatives thereof and metal salts thereof, and are not particularly limited. For example, 1H-tetrazole, 5-amino-1H-tetrazole, 5 -Methyl-1H-tetrazole, 5-phenyl-1H-tetrazole, 1-methyl-5-ethyl-1H-tetrazole, 1-methyl-5-mercapto-1H-tetrazole, 1-phenyl-5-mercapto-1H-tetrazole Etc. can be illustrated.

  Among the compounds having at least two nitrogen atoms in the five-membered ring as described above, in the present invention, by using a triazole-based compound, improvement of the initial strength of the template can be advantageously achieved, Among such triazole compounds, benzotriazole compounds, 1,2,4-triazole, and 3-mercapto-1,2,4-triazole are preferable, and 1,2,3-benzotriazole, and 3 are more preferable. -Mercapto-1,2,4-triazole is preferably used.

  In addition, among the organic nitrogen compounds in the present invention, the “hydrazine compound substituted with at least one aromatic functional group” of the above b) includes the hydrazine compound itself substituted with at least one aromatic functional group. , Derivatives thereof and metal salts thereof, and specifically, 2,4-dinitrophenylhydrazine is advantageously used.

  Furthermore, among the organic nitrogen compounds of the present invention, examples of the “formamide compound substituted with two alkyl groups” in the above c) include N, N-dimethylformamide, N, N-diethylformamide and the like. In the present invention, N, N-dimethylformamide is advantageously used.

  Furthermore, among the organic nitrogen compounds of the present invention, the “acetamide compound substituted with at least one aromatic functional group” in the above d) includes an acetamide compound substituted with at least one aromatic functional group, and derivatives thereof. And a metal salt thereof, and the like, although not particularly limited, acetanilide or the like is preferably used.

  In addition, among the organic nitrogen compounds of the present invention, the “amide compound having at least one unsaturated bond” in the above e) means an amide compound itself having at least one unsaturated bond, its derivative and its metal. Salts are also included, and for example, N, N-dimethylacrylamide and the like are advantageously used.

  Among the organic nitrogen compounds of the present invention, as the “compound having at least two amide groups” of f), a compound itself having at least two amide groups, a derivative thereof, a metal salt thereof, and the like can be used. Although not particularly limited, compounds having the target structure such as succinic acid diamide, adipamide, and biurea are preferably used.

  In addition, such an organic nitrogen compound may be used independently and can also be used in combination of 2 or more type.

  Then, the organic binder for mold according to the present invention is formed by the predetermined organic nitrogen compound as described above, the phenol resin solution and the polyisocyanate solution that form phenol urethane, and this organic viscosity is formed. For binders, if necessary, it can be used as an organic binder for molds, such as a pot life extender different from the above organic nitrogen compounds, mold release agents, strength deterioration inhibitors, and drying inhibitors. It is also possible to appropriately select and mix known various additives used. However, it goes without saying that these various additives can be used in a quantitative range that does not impair the effects that can be enjoyed by the present invention.

  For example, among various additives as described above, a pot life extender (curing retarder) is conventionally used as a component for suppressing the urethanization reaction and extending the pot life of the foundry sand composition. In the present invention, it can be used to further assist the above-described effects of the organic nitrogen compound. Preferable specific examples include isophthalic acid chloride, salicylic acid, benzoic acid, phosphoric acid, acidic phosphate ester, phosphorus chloride, boric acid and the like.

  Further, the mold release agent reduces the resistance when the mold obtained using the organic binder according to the present invention is removed from the mold, and a part of the molding sand composition blown and filled into the mold is used. It is an additive used to obtain a mold having a uniform molding surface and high accuracy, which prevents a stain caused by adhering to the mold when the mold is removed. Suitable examples include, for example, long-chain fatty acids. Long chain fatty acid ester, tall oil fatty acid, alkyd resin, liquid polybutadiene and the like. In general, these can be used in a proportion of about 0.01 to 100 parts by weight, preferably about 0.1 to 10 parts by weight with respect to 100 parts by weight of the phenol resin.

  Furthermore, the strength deterioration preventing agent is used for preventing deterioration of the mold strength in a humid environment and improving the adhesion between the resin component of the organic binder and the foundry sand. Specific examples include amino-based silanes such as N-β (aminoethyl) -γ-aminopropyltrimethoxysilane and γ-aminopropyltriethoxysilane, and epoxy-based materials such as γ-glycidoxypropyltrimethoxysilane. Examples include silane coupling agents such as silane. In addition, as a usage-amount of this intensity | strength deterioration inhibitor, generally the ratio used as about 0.01-5 weight part with respect to 100 weight part of a phenol resin, Preferably it is about 0.05-2.5 weight part. Adopted.

  Thus, an organic binder for a mold according to the present invention is constituted by various components as described above, and a phenol urethane-based gas curing mold or a self-hardening mold is formed using the organic binder.

  Specifically, when molding a gas-curing mold by the cold box method, first, an organic binder for mold is kneaded with the molding sand to coat the surface of the casting sand with the organic binder for mold. The resulting casting sand composition (kneaded sand) is produced. That is, a phenol resin solution, a polyisocyanate solution, a predetermined organic nitrogen compound, and, if necessary, various other additives are sufficiently kneaded and mixed with the foundry sand as an organic binder. Thus, the molding sand composition is manufactured by coating the molding sand surface with the organic binder for casting. At this time, the organic nitrogen compound and various additives are added to either or both of the separately prepared phenol resin solution and polyisocyanate solution so that they can be uniformly mixed with the foundry sand composition. Or mixed in a suitable organic solvent and mixed with a molding resin together with a phenol resin solution or a polyisocyanate solution during kneading, or a phenol resin is produced. It is also possible to add and mix after completion of the condensation.

  Moreover, when manufacturing this foundry sand composition, the phenol resin solution and the polyisocyanate solution constituting the organic binder are gradually subjected to a polyaddition reaction (urethanization reaction) from the stage of mixing them. Therefore, they are prepared separately and prepared in advance, and are usually mixed at the time of kneading with foundry sand. Furthermore, the kneading / mixing operation is preferably performed in the range of −10 to 50 ° C. using a continuous or batch mixer similar to the conventional one.

  Next, the molding sand composition obtained as described above is shaped in a molding die that gives a desired shape, and then a catalyst gas for curing is vented to the casting. Curing of the sand composition is promoted to produce a gas curing mold. Examples of the catalyst gas include various conventionally known tertiary amine gases such as triethylamine, dimethylethylamine, and diisopropylamine, as well as cyclic nitrogen compounds, pyridine, and N-ethylmorpholine. At least one kind is appropriately selected and used in an ordinary quantitative range.

  On the other hand, when molding a self-hardening mold by a room temperature self-hardening method, as in the case of the gas-curing mold, first, a casting sand composition in which the surface of the casting sand is coated with an organic binder is manufactured. However, the molding sand composition used in the room temperature self-hardening method is further mixed with a curing catalyst together with the organic binder at the time of kneading. Examples of the curing catalyst include bases, amines, metal ions and the like that are usually used in the known Ashland method.

  The obtained foundry sand composition is immediately shaped in a molding die giving a desired shape from where the curing proceeds by the added curing catalyst, and a self-hardening mold is produced. It will be.

  In addition, in the preparation of the foundry sand composition that gives the gas curing mold and the self-hardening mold described above, the blending amounts of the phenol resin solution and the polyisocyanate solution are the blending amounts of the phenol resin and the polyisocyanate compound, which are active ingredients, respectively. The ratio of 0.01 to 5.0 parts by weight, preferably 0.1 to 2.0 parts by weight, can be suitably employed for 100 parts by weight of the foundry sand. Further, the blending ratio of the phenol resin and the polyisocyanate compound is not particularly limited, but in general, the phenol resin: polyisocyanate compound = 80: 20 to 20:80 on a weight basis. A solution or a polyisocyanate solution is used in combination.

  Moreover, the blending amount of the predetermined organic nitrogen compound with respect to the foundry sand is not generally limited, and can be appropriately set according to the type of the organic nitrogen compound used, etc. In consideration, generally, a ratio of 0.0001 to 1 part by weight, preferably 0.001 to 0.1 part by weight with respect to 100 parts by weight of foundry sand can be suitably employed.

  Further, the foundry sand used in the present invention may be natural sand or artificial sand as long as it is fire-resistant conventionally used for casting molds, and is not particularly limited. . For example, silica sand, olivine sand, zircon sand, chromite sand, alumina sand, ferrochrome slag, ferronickel slag, converter slag, mullite artificial particles (for example, trade names “available from ITOCHU CERATECH CORPORATION” Cerabeads ”) and regenerated sand of these, and the like, and one of these or two or more of them can be used in combination. Of these, mullite artificial particles that are spherical and have excellent crush resistance are more suitably employed from the viewpoint of polishing regeneration treatment after recovery of the mold.

  Thus, the gas-curing mold and the self-hardening mold manufactured as described above are effectively improved in strength (initial strength), and as a result, there is no risk of damaging the surface due to mold release resistance at the time of mold release. Therefore, it is advantageously used for casting a casting product made of various metals such as an aluminum alloy, a magnesium alloy, and iron as a sand mold such as a sand core with high accuracy.

  Some examples of the present invention will be shown below to clarify the present invention more specifically. However, the present invention is not limited by the description of such examples. Needless to say. In addition to the following examples, the present invention includes various changes and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention, in addition to the above specific description. It should be understood that improvements and the like can be added. In this example, the measurement of the mold strength (initial strength) immediately after the mold release was performed as follows.

-Measurement of mold strength (initial strength) immediately after mold removal-
In a sand magazine of a cold box molding machine, a casting sand composition having a waiting time of 0 minutes, 2 hours or 4 hours after kneading is put, and the foundry sand composition is placed in a mold for producing a bending strength test piece. Gauge pressure: 0.3 MPa. Next, after triethylamine was aerated with a gas generator at a gauge pressure of 0.2 MPa for 1 second in the mold, air purge was performed at a gauge pressure of 0.2 MPa for 14 seconds, the mold was removed, and the width was 30 mm × A bending test piece having a length of 85 mm and a thickness of 10 mm was produced. Then, the bending strength (N / cm ² ) of the obtained test piece was immediately measured using a digital foundry sand strength tester (manufactured by Takachiho Seiki Co., Ltd.). Except for the foundry sand composition immediately after kneading (immediately after preparation) with a waiting time of 0 minutes, in a polyethylene bag under the environment of temperature: 25 ° C. × relative humidity: 60%, a predetermined time (2 The casting sand composition was allowed to stand for 2 hours and 4 hours.

  A phenol resin solution A, a phenol resin solution B, and a polyisocyanate solution were prepared and prepared as follows. Then, using these phenol resin solution A or phenol resin solution B and the polyisocyanate solution, casting sand compositions according to Examples 1 to 14 and Comparative Examples 1 and 2 were prepared.

-Preparation of phenol resin solution A-
In a three-necked reaction flask equipped with a reflux, a thermometer and a stirrer, as shown in Table 1 below, 50 parts by weight of phenol and 50 parts by weight of orthocresol (phenol / orthocresol = 50/50), First, 51.9 parts by weight of paraformaldehyde (92% by weight) and 0.32 parts by weight of lead naphthenate as a divalent metal salt were charged, reacted at the reflux temperature for 90 minutes, and then concentrated by heating to obtain a water content of 1 An ortho-cresol-modified benzyl ether type phenolic resin (phenolic resin A) having a weight percent or less was obtained. Next, the phenol resin A was diluted with an organic solvent of DBE: Ipsol 150: HAWS = 45: 45: 10, and 0.5% by weight of γ-glycidoxypropyltrimethoxy with respect to the phenol resin A was obtained. Silane was added to prepare a phenol resin solution A having a phenol resin content of 50% by weight.

-Preparation of phenol resin solution B-
In a three-neck reaction flask equipped with a reflux, a thermometer and a stirrer, as shown in Table 1 below, 100 parts by weight of phenol, 55.5 parts by weight of 92% by weight paraformaldehyde, and a divalent metal salt As a starting material, 0.32 parts by weight of lead naphthenate was added, reacted at a reflux temperature for 90 minutes, and then concentrated by heating to obtain a benzyl ether type phenol resin (phenol resin B) having a water content of 1% by weight or less. It was. Next, the phenol resin B was diluted with an organic solvent of DBE: Ipsol 150: HAWS = 45: 45: 10, and 0.5% by weight of γ-glycidoxypropyltrimethoxy with respect to the phenol resin A. Silane was added to prepare a phenol resin solution B having a phenol resin content of 50% by weight.

-Preparation of polyisocyanate solution-
Polymeric MDI, which is a polyisocyanate compound, was diluted with an organic solvent of Ipsol 150: HAWS = 60: 40, and phthalic acid chloride was added so as to be 0.93% by weight of the polymeric MDI. A 75% by weight polyisocyanate solution was prepared.

<Example 1>
First, 1 part by weight of 1,2,4-triazole was added to 100 parts by weight of the phenol resin solution A, and dissolved by heating and stirring. Next, 1000 parts by weight of flattery quartz sand left in an atmosphere of temperature: 25 ° C. × relative humidity: 60% and 1,2,4-triazole in Dalton Co., Ltd. product river type table mixer in advance. 10 parts by weight of the phenol resin solution A contained and 10 parts by weight of the polyisocyanate solution were added, and then stirred and kneaded for 40 seconds, which was coated with an organic binder, that is, a molding sand composition. A product was prepared.

  Then, with respect to the obtained molding sand composition, the mold strength was measured according to the above test method using the one with a waiting time of 0 minutes (immediately after kneading), 2 hours, and 4 hours, and the results are shown in the following table. Also shown in FIG.

<Example 2 to Example 11>
Foundry sand in the same manner as in Example 1 except that in the preparation of the foundry sand composition of Example 1, organic nitrogen compounds listed in Table 2 below were used in place of 1,2,4-triazole, respectively. The composition was prepared, and the mold strength was measured using the obtained foundry sand composition. The results are also shown in Table 2 below. In Example 4 using 1,2,3-benzotriazole as the organic nitrogen compound, the amount added was 0.8 parts by weight with respect to 100 parts by weight of the phenol resin solution A.

<Comparative example 1>
In the preparation of the foundry sand composition of Example 1, in place of the phenol resin solution A containing 1,2,4-triazole, a phenol resin containing no organic nitrogen compound such as 1,2,4-triazole. A foundry sand composition was prepared in the same manner as in Example 1 except that the solution A was used. And the mold strength was measured using the obtained foundry sand composition, and the results are shown in Table 2 below.

<Example 12>
In the preparation of the foundry sand composition of Example 1, instead of the phenol resin solution A containing 1,2,4-triazole, 1,2,4-triazole was added to 100 parts by weight of the phenol resin solution B. A foundry sand composition was prepared in the same manner as in Example 1 except that the phenol resin solution B contained at a ratio of 1 part by weight was used. And the mold strength was measured using the obtained foundry sand composition, and the results are shown in Table 3 below.

<Example 13 and Example 14>
In the preparation of the foundry sand composition of Example 12, 3-mercapto-1,2,4-triazole was used in Example 13 instead of 1,2,4-triazole, and 1 in Example 14. , 2,3-benzotriazole, except that each was used in the same manner as in Example 12, a casting sand composition was prepared, and the mold strength was measured using the obtained casting sand composition. The results are shown in Table 3 below.

<Comparative example 2>
In the preparation of the foundry sand composition of Example 12, the foundry sand composition was the same as Example 12 except that the phenol resin solution B containing no organic nitrogen compound such as 1,2,4-triazole was used. Was prepared. And the mold strength was measured using the obtained foundry sand composition, and the results are shown in Table 3 below.

  As apparent from the results in Table 2 above, when the phenol resin A (orthocresol-modified benzyl ether type phenol resin) is used, the foundry sand compositions of Examples 1 to 11 according to the examples of the present invention are used. Then, immediately after kneading, after 2 hours from kneading and after 4 hours from kneading, it is superior to the foundry sand composition of Comparative Example 1 in which no organic nitrogen compound is blended. It was recognized that the strength (initial strength) was exhibited. Among these, when looking at the foundry sand composition after 2 hours or 4 hours from kneading, the foundry sand compositions of Examples 1 to 11 were compared with the foundry sand composition of Comparative Example 1. From the fact that it shows high strength (initial strength), when the organic binder for molds according to the present invention is used, it can be obtained even if the mold is molded with a foundry sand composition after a certain time has passed since kneading. It was confirmed that the mold exhibited high strength (initial strength).

Further, as apparent from the results of Table 3 above, even when phenol resin B (benzyl ether type phenol resin) was used, the foundry sand compositions of Examples 12 to 14 were immediately after kneading. It can exhibit strength (initial strength) superior to the foundry sand composition of Comparative Example 2 in which no organic nitrogen compound is blended in any of two hours after kneading and four hours after kneading. In particular, with respect to the foundry sand composition after 2 hours or 4 hours from kneading, Examples 12 to 14 show strength (initial strength) superior to that of Comparative Example 2 as well. Therefore, when a mold organic binder containing a predetermined organic nitrogen compound is used, the resulting mold has a high strength even when the mold is molded using a molding sand composition that has passed for a certain period of time after kneading. (initial It is the has been confirmed to exhibit a degree).

Claims (6)

An organic binder used for molding a phenol-urethane-based gas-curing mold or a self-curing mold, and includes a) an imidazole compound, a triazole compound, and a tetrazole compound together with a phenol resin, a polyisocyanate compound, and an organic solvent. a compound having at least two nitrogen atoms in the five-membered ring, b) at least one aromatic function hydrazine compound is substituted with a group, c) formamide compounds substituted with two alkyl groups, d) at least one aromatic acetamide compound substituted with group functionality,及 beauty, e) at least one organic nitrogen compound selected from the group consisting of compounds having at least two amide groups, by containing as essential components An organic binder for molds characterized by An organic binder used for molding a phenol-urethane-based gas-curing mold or self-hardening mold, together with an ortho-cresol-modified phenol resin, a polyisocyanate compound, and an organic solvent, and a) at least two nitrogen atoms in the five-membered ring B) a hydrazine compound substituted with at least one aromatic functional group, c) a formamide compound substituted with two alkyl groups, d) an acetamide compound substituted with at least one aromatic functional group, e It contains at least one organic nitrogen compound selected from the group consisting of a) an amide compound having at least one unsaturated bond, and f) a compound having at least two amide groups, as an essential component. An organic binder for molds characterized by The organic binder for molds according to claim 2 , wherein the organic nitrogen compound is a triazole compound.   A foundry sand composition obtained by kneading the molding binder according to any one of claims 1 to 3 with a foundry sand.   A gas-curing mold formed by curing a foundry sand composition by bringing a catalyst gas into contact with the foundry sand composition according to claim 4. A self-hardening mold formed by kneading an organic binder for a mold according to any one of claims 1 to 3 with a curing catalyst together with a molding sand.