JP2004105982A - Binder composition for amine gas hardening type mold, molding sand composition obtained from this binder and sand core for casting light alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide collapsibility of a sand core which is improved compared with the conventional sand core, which contributes to reduction of energy cost and improvement of working environments. <P>SOLUTION: A binder composition for amine gas hardening type mold, is composed essentially of an orthocresol modified phenol resin, polyisocyanate compound, organic solvent and silicic ester and/or its hydrolysate. Molding sand composition and the sand core for casting a light alloy are obtained by using the above binder composition. <P>COPYRIGHT: (C)2004,JPO

Description

【００３４】
【発明の効果】
以上説明したとおり、本発明によれば、オルソクレゾール変性フェノール樹脂とケイ酸エステル及び／又はその加水分解生成物との併用により、従来のフェノール樹脂ベースより、大幅に改善された砂中子の崩壊性を提供できるため、軽合金鋳物製造でのエネルギーコストの低減及び作業環境の改善に寄与することができる。
【図面の簡単な説明】
【図１】図１は砂中子の崩壊性評価のための鋳造試験用砂型の縦断面図である。
【図２】図２は使用済み砂中子を内包した鋳物の縦断面図である。
【符号の説明】
１…溶湯注入口
２…幅木固定部
３，３′…主型
４…砂中子
４′…砂中子の幅木
５…鋳造試験用砂型
６…使用済み砂中子
７…排出口
８…鋳物[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a gas-hardening mold produced by an amine cold box method, particularly to a molding sand composition suitable for producing a sand core suitable for light alloy casting, and a binder composition used therefor.
[0002]
[Prior art]
In recent years, the amine cold box method, which has been gaining importance as a competitive technology of the shell mold method, uses an organic solvent solution (phenol resin component) of a phenol resin, which is a component of a two-component reaction-curable binder, and a polyisocyanate. A compound or an organic solvent solution thereof (polyisocyanate component) is added to and kneaded with molding sand, and after kneading sand, that is, a molding sand composition is filled in a molding die, a tertiary amine (curing catalyst) is actuated. This is a method for producing a mass-producable gas-hardening mold capable of promoting the reaction between a phenolic resin and a polyisocyanate compound to form a molding sand composition into a sand mold (main mold or sand core) for casting in a short time.
[0003]
By the way, in the field of the automobile industry, it is inevitable to switch from castings made of iron to products made of light alloys such as aluminum alloys from the viewpoint of weight reduction and improvement of fuel efficiency. However, when a light alloy casting was manufactured by a sand casting method of pouring a light alloy molten metal such as an aluminum or magnesium alloy having a low pouring temperature after setting a sand core in a casting mold, the obtained result was obtained. As-cast castings are generally subjected to sand removal operations such as high-temperature heat treatment and chipping treatment to discharge used sand cores remaining in the castings. As described above, sand cores used for light alloy casting have been focused on the ability to discharge used sand cores from as-cast castings (hereinafter referred to as "disintegration"). It is not sufficient, and in addition, the thinning of castings and the complicated structure due to the high performance of the engine require further collapse of the sand core.
Japanese Patent Application Laid-Open No. 2000-84643 describes a binder composition for a mold that does not include a silicate ester and / or a hydrolysis product thereof as a constituent element. A low-viscosity binder with low viscosity and excellent weighability while reducing organic solvents, especially non-polar solvents, thereby improving the working environment and improving the adhesion to the mold. It is stated to provide. However, according to this document, by providing a silicate ester and / or a hydrolysis product thereof as a constituent element as in the present invention, it is possible to provide a significantly improved disintegration property of a sand core. There is no description or suggestion that it has the effect of reducing energy costs and improving the working environment in casting production.
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-84643
[Problems to be solved by the invention]
Therefore, an object of the present invention is to provide a binder composition used for producing a gas-hardening mold by the amine cold box method, particularly a sand core excellent in disintegration suitable for light alloy casting. Another object of the present invention is to provide a molding sand composition for an amine gas-curable mold capable of providing a sand core for light alloy casting having such characteristics.
[0005]
[Means for Solving the Problems]
The present inventors have been able to provide a sand core which is more excellent in disintegration than the sand core manufactured by the shell mold method, and is also advantageous in improving energy cost and working environment in the above-mentioned technological evolution. As a result of intensive studies focusing on the amine cold box method, it was found that the combination of ortho-cresol-modified phenolic resin and silicate ester and / or its hydrolysis product is extremely effective in improving the disintegration of sand cores. As a result, the present invention has been completed.
[0006]
That is, the present invention (claim 1) provides an amine gas-curable mold characterized by comprising an ortho-cresol-modified phenol resin, a polyisocyanate compound, an organic solvent, a silicate ester and / or a hydrolysis product thereof as essential components. It is a binder composition. Another aspect of the present invention (claim 2) is a molding sand composition for an amine gas-curable mold, comprising the binder composition according to claim 1 and a molding sand. In particular, a preferred embodiment (claim 3) is one selected from the group consisting of alumina sand, mullite sand and a mixture thereof as the molding sand. Further, another aspect of the present invention (claim 4) is that the molding sand composition is cured by contacting the molding sand composition according to claim 2 with a tertiary amine. Sand core for alloy casting.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
The binder composition for an amine gas-curable mold according to the present invention (hereinafter simply referred to as “binder composition”) functions as at least a two-part reaction-curable binder for molding sand (A) a phenolic resin. Component and (B) a polyisocyanate component, and (C) a silicate ester functioning as a disintegrant for a used sand core, a hydrolysis product thereof, and one selected from the group consisting of a mixture thereof. The components (A) and (B) are generally used as a solution whose concentration is appropriately adjusted with an organic solvent from the viewpoint of coating properties on molding sand.
[0008]
The component (A) is an organic solvent containing an ortho-cresol-modified phenolic resin, which reacts with the polyisocyanate compound in the component (B) to cause the strength between molding sands to be developed, at a ratio of about 40 to 80% by mass. Although it is a solution, the component contains a silane coupling agent such as γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, etc. A pot life extending agent, for example, a carboxylic acid chloride such as isophthalic acid chloride, or a phosphonic acid chloride or the like may be added at a ratio of 0.01 to 5% by mass.
[0009]
The organic solvent used herein can be used without any particular limitation as long as it is non-reactive with the polyisocyanate compound and a good solvent for the phenolic resin. A polar solvent for dissolving the compound, for example, an aliphatic carboxylic acid ester, especially from the viewpoint of environmental safety, a mixture of dicarboxylic acid methyl esters (trade name: DBE manufactured by DuPont: a mixture of dimethyl glutarate, dimethyl adipate and dimethyl succinate) In addition to alkyl esters of dicarboxylic acids, methyl esters of vegetable oils such as rapeseed oil methyl esters, esters such as fatty acid monoesters such as ethyl oleate and ethyl palmitate, and mixtures thereof, ketones such as isophorone, isopropyl ether and the like Ethers, furfuryl alcohol, etc. And a non-polar solvent for dissolving a polyisocyanate compound in such an amount that resin separation does not occur, for example, petroleum hydrocarbons such as paraffins, naphthenes and alkylbenzenes, specifically, for example, Ipsol 150 (product Name, petroleum solvent, Idemitsu Sekiyu KK, and Hisol (trade name, petroleum solvent, Showa Shell Sekiyu KK) and the like.
[0010]
Examples of the orthocresol-modified phenol resin include orthocresol and / or phenol and aldehydes (for example, formalin, paraformaldehyde, polyoxymethylene, glyoxal, furfural, and the like) in the presence of a reaction catalyst such as an acid, a base, and a divalent metal salt. Or a mixture of ortho-cresol and phenol resin, and (2) a mixed ortho-cresol-modified phenol resin of ortho-cresol and phenol resin. And (3) a modified ortho-cresol-modified phenol resin obtained by modifying these resins with a modifier, or an arbitrary mixture of (1), (2) and (3).
[0011]
(1) The co-condensed ortho-cresol-modified phenolic resin is preferably obtained by converting ortho-cresol (oCr) and phenol (P) from the viewpoint of the disintegration of the sand core, preferably oCr / P (mass ratio) = 30 / 70- At least one selected from the group of co-condensation resins of novolak type, resol type and benzyl ether type obtained by reacting with aldehydes simultaneously or stepwise in the range of 90/10, preferably 50/50 to 90/10. Is a type of co-condensed ortho-cresol-modified phenolic resin. Generally, it is a benzyl ether type co-condensation type ortho-cresol-modified phenol resin.
[0012]
Further, (2) the mixed ortho-cresol-modified phenol resin is at least one ortho-cresol resin selected from the group of novolak-type, resol-type and benzyl ether-type ortho-cresol resins obtained by reacting ortho-cresol with aldehydes. (X) at least one phenolic resin (Y) selected from the group of phenolic resins of the novolak type, resole type and benzyl ether type obtained by reacting phenol with aldehydes, and the disintegration of sand core In view of the above, a mixed orthocresol-modified phenol resin obtained by mixing at a ratio of X / Y (mass ratio) = 3/7 to 9/1, preferably 5/5 to 9/1. Generally, it is a mixed-type ortho-cresol-modified phenol resin of benzyl ether type.
[0013]
Also, (3) the modified orthocresol-modified phenolic resin may be further modified at any time after or after the production of the co-condensation resin, the orthocresol resin or the phenolic resin, for example, an alkyd resin, an epoxy resin, a melamine resin, a urea resin, Modified novolak type, resol type and benzyl obtained by mixing or reacting with xylene resin, vinyl acetate resin, polyamide resin, urea compound, melamine compound, epoxy compound, polyvinyl alcohol, amides, linseed oil, etc. It is at least one modified orthocresol-modified phenol resin selected from the group of ether type resins. Generally, it is a benzyl ether type modified orthocresol-modified phenol resin.
[0014]
The polyisocyanate component used as the component (B) is an organic solvent solution containing about 65 to 90% by mass of a polyisocyanate compound having two or more isocyanate groups in a molecule having reactivity with an ortho-cresol-modified phenol resin. In some cases, the polyisocyanate compound is in the form of a stock solution. Examples of such polyisocyanate compounds include, for example, aromatic polyisocyanates such as diphenylmethane diisocyanate and polymethylene polyphenylene polyisocyanate (hereinafter referred to as "crude MDI"), aliphatic polyisocyanates such as hexamethylene diisocyanate, and 4,4'-dicyclohexyl. Examples thereof include alicyclic polyisocyanates such as methane diisocyanate, prepolymers having isocyanate groups obtained by reacting these polyisocyanates with polyols, and mixtures of these polyisocyanates.
[0015]
The silicate used as the component (C), a hydrolysis product thereof, and a mixture thereof (hereinafter, referred to as “silicate ester or the like”) function effectively for improving the disintegration of the sand core, for unknown reasons. Examples of such silicates include silicates, for example, methyl silicate, ethyl silicate, propyl silicate, butyl silicate, and the like, hydrolysis products of silicates, such as those manufactured by Colcoat Co., Ltd. Examples thereof include methyl silicate 51, ethyl silicate 40, and a mixture thereof. Since the component (C) generally has a high degree of hydrolyzability, it is preferably added and mixed when preparing the (B) polyisocyanate component or molding sand composition.
[0016]
The amine gas-curable molding sand composition for a mold according to the present invention is kneaded sand obtained by adding and kneading (A) a phenol resin component, (B) a polyisocyanate component, and (C) a silicate ester to the molding sand. As described above, the kneaded sand is first formed into a sand core shape in a molding die, and a tertiary amine (eg, triethylamine, dimethylethylamine, dimethylisopropylamine, etc.) as a curing catalyst is aerated therethrough. Thereby, the hardening of the kneaded sand due to the contact between the kneaded sand and the tertiary amine proceeds to form a sand core. The obtained sand core has excellent disintegration properties after casting, and is particularly useful as a casting mold for light alloys. This molding sand composition is generally kneaded with molding sand and the component (A) in a batch type or continuous mixer, and then the components (B) and (C) are added and then re-kneaded. It is prepared by a method in which the components (A), (B) and (C) are simultaneously added to the foundry sand and kneaded.
[0017]
In the preparation of such a molding sand composition, (A) the phenolic resin component and (B) the polyisocyanate component are each 0.01 to 5.0 parts by mass, preferably 0.1 to 2 parts by mass, per 100 parts by mass of the molding sand. 0.0 parts by mass. The mixing ratio of the two components is not particularly limited, but is generally (A) / (B) = 70/30 to 30/70 on a mass basis. In addition, from the viewpoint of the effect of improving the disintegration of the sand core, the amount of the component (C) generally needs to be 0.1 part by mass or more based on 100 parts by mass of the phenol resin component (A). Considering the cost, it is preferably 1 to 20 parts by mass. Examples of the foundry sand include silica sand, olivine sand, zircon sand, chromite sand, alumina sand, ferrochrome slag, ferronickel slag, converter slag, and mullite artificial particles (for example, Niigai commercially available from ITOCHU CERATECH CORPORATION). Cerabeads) and their recycled sands. Among them, mullite-based artificial particles which are spherical and have excellent crush resistance are preferred from the viewpoint of polishing and regenerating treatment after the recovery of the mold. These may be used alone or in combination of two or more.
[0018]
【Example】
Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In addition, "part" and "%" all mean "part by mass" and "% by mass". In addition, the obtained molding sand composition was subjected to measurement of mold strength (strength of punching and standing strength after 24 hours) and evaluation of disintegration of the sand core by the following test methods.
[0019]
1. Measurement of mold strength (stretching strength and standing strength after 24 hours) After the casting sand composition was charged into a sand magazine of a cold box molding machine, this was placed in a bending strength test piece forming mold at a gauge pressure of 0.3 MPa. Filled. Next, triethylamine was passed through the mold from a gas generator (gauge pressure: 0.2 MPa × 1 second), air purged (gauge pressure: 0.2 MPa × 10 seconds), the mold was removed, and a bending test piece (width 30 mm × length) was removed. 85 mm x thickness 10 mm). The bending strength (N / cm ² ) of the obtained test piece was measured immediately or after standing at room temperature for 24 hours using a digital molding sand strength tester (manufactured by Takachiho Seiki Co., Ltd.). Of the standing strength.
[0020]
2. Evaluation of the disintegration of the sand core In FIG. 1, the molten metal injection port 1 was prepared in advance using room temperature self-hardening sand, and the sand core fixing part 2 was used in the lower part (this part was used from an aluminum casting after casting). And a circular empty core 4 made of a molding sand composition in a main mold 3 (width 80 mm × length 125 mm × thickness 75 mm) having a space in the middle. A test piece: 47 mm in diameter × 49 mm in height) was bonded and fixed at the baseboard fixing portion 2, and then the main mold 3 ′ was bonded and fixed to prepare a sand mold 5 for casting test.
[0021]
Next, an aluminum alloy (temperature: 710 ± 5 ° C.) is poured from the molten metal injection port 1 of the sand mold 5 for casting test, and left to cool to room temperature. A circular casting 8 made of an aluminum alloy and having an outlet 7 (diameter 16 mm) of the used sand core 6 was obtained. The casting 8 thus obtained was first measured for the amount of sand core discharged by oscillating (0 seconds) before chipping, and then repeatedly chipped every 3 seconds with an air hammer (pressure 0.1 MPa). The amount of the sand core discharged from the outlet 7 was measured. This operation was repeated until almost all of the used sand core 6 was discharged. The disintegration of the sand core was expressed as a percentage (%) obtained by dividing the amount discharged every 0 seconds and 3 seconds by the total amount of discharge, and it was judged that the shorter the time to reach the 100% discharge rate, the better the disintegration.
[0022]
Production Example 1 <Preparation of phenol resin component (1)>
A three-necked reaction flask equipped with a reflux condenser, a thermometer, and a stirrer was charged with 50 parts of orthocresol, 50 parts of phenol, 49 parts of 92% paraformaldehyde, and 0.32 part of lead naphthenate as a divalent metal salt. , And concentrated by heating to obtain a benzyl ether-type co-condensed ortho-cresol-modified phenol resin. Next, an effective amount of γ-glycidoxypropyltrimethoxysilane and an organic ester solvent (trade name: mixture of DBE dimethyl glutarate, dimethyl adipate and dimethyl succinate, DuPont) Of a cocondensation-type ortho-cresol-modified phenolic resin having a concentration of 50% by adding 25 parts of a petroleum solvent (trade name, Solvesso 100, manufactured by ExxonMobil Co., Ltd.) to the organic solvent solution, that is, the phenolic resin component (1). ) Was prepared.
[0023]
Production Examples 2 and 3 <Preparation of phenol resin components (2) and (3)>
In Production Example 1, the mixing ratio (oCr / P, mass ratio) of orthocresol (oCr) and phenol (P) was 30/70, 50 parts of 92% paraformaldehyde, and the reflux time was 5 hours (Production Example 2). Or co-condensed orthocresol-modified phenol having a concentration of 50% in the same manner as in Production Example 1 except that oCr / P was 70/30, 47 parts of 92% paraformaldehyde, and the reaction time was changed to 5 hours (Production Example 3). An organic solvent solution of the resin, that is, phenolic resin components (2) and (3) were prepared.
[0024]
Production Examples 4 to 5 <Preparation of phenol resin components (4) and (5)>
100 parts of orthocresol, 39 parts of 92% paraformaldehyde, and 0.32 part of lead naphthenate as a divalent metal salt were charged into a three-neck reaction flask equipped with a reflux condenser, a thermometer, and a stirrer, and reacted at a reflux temperature for 6 hours. After that, the mixture was concentrated by heating to obtain a benzyl ether type ortho-cresol resin. Also, 100 parts of phenol, 52 parts of 92% paraformaldehyde and 0.32 part of lead naphthenate as a divalent metal salt were charged, reacted at reflux temperature for 1 hour, and then concentrated by heating to obtain a benzyl ether type phenol resin. . Next, an effective amount of γ-glycidoxypropyltrimethoxysilane and 50 parts of the above-mentioned organic solvent (DBE and Solvesso 100) were added to 50 parts of each resin in the same manner as in Production Example 1, and a 50% concentration of orthocresol was added. A resin organic solvent solution and a phenol resin organic solvent solution having a concentration of 50% were prepared. Further, 50 parts of the former and 50 parts of the latter were mixed to prepare an organic solvent solution of a mixed type orthocresol-modified phenol resin having a concentration of 50%, that is, a phenol resin component (4). The solution of the phenol resin in the organic solvent was used as it is as the phenol resin component (5).
[0025]
Production Example 6 <Preparation of polyisocyanate component>
In a mixing tank equipped with a stirrer, 80 parts of polymethylene polyphenylene polyisocyanate (trade name: Cosmonate M200, manufactured by Mitsui Chemicals, Inc.) and 20 parts of Solvesso 100 are mixed and a polyisocyanate component having a concentration of 80% is mixed. Was prepared.
[0026]
Example 1
After kneading 1000 parts of NAIGAI CERABEADS # 550 (trade name: manufactured by ITOCHU CERATECH CORPORATION) and 1.0 part of the phenolic resin component (1) prepared in Production Example 1 for 30 seconds in an experimental article river mixer, Production Example 6 1.0 part of the polyisocyanate component prepared in the above and 0.05 part of a hydrolysis product of a silicate ester (trade name: methyl silicate 51, hydrolysis product of methyl silicate, manufactured by Colcoat Co., Ltd.) and further 30 parts The mixture was kneaded for 2 seconds to prepare a kneaded sand, a so-called foundry sand composition (1). The obtained molding sand composition (1) was subjected to measurement of mold strength and evaluation of disintegration of the sand core by the following test methods. Table 1 shows the results.
[0027]
Examples 2 and 3
A molding sand composition (2) was prepared in the same manner as in Example 1 except that the phenol resin component (2) or (3) was used instead of the phenol resin component (1) in the preparation of the molding sand composition of Example 1. Or (3) was prepared. The obtained molding sand composition was measured for mold strength and evaluated for disintegration of the sand core by the following test methods. Table 1 shows the results.
[0028]
Examples 4 to 6
In the preparation of the molding sand composition of Example 1, the compounding amount of methyl silicate 51 used as the component (C) was 0.05 part (5%), and 0.02 part (2%) and 0.1 part (10% ) Or 0.2 parts (20%), except that a molding sand composition (4), (5) or (6) was prepared in the same manner as in Example 1. The obtained molding sand composition was measured for mold strength and evaluated for disintegration of the sand core by the following test methods. Table 1 shows the results.
[0029]
Example 7
In the preparation of the molding sand composition of Example 1, the same procedure as in Example 1 was conducted, except that methyl silicate 51 used as the component (C) was changed to ethyl silicate (trade name: ethyl silicate 28, manufactured by Colcoat Co., Ltd.). A casting sand composition (7) was prepared. The obtained molding sand composition was measured for mold strength and evaluated for disintegration of the sand core by the following test methods. Table 1 shows the results.
[0030]
Example 8
A molding sand composition (8) was prepared in the same manner as in Example 1 except that the phenol resin component (4) was used instead of the phenol resin component (1) in the preparation of the molding sand composition of Example 1. The obtained molding sand composition was measured for mold strength and evaluated for disintegration of the sand core by the following test methods. Table 1 shows the results.
[0031]
Comparative Example 1
A comparative molding sand composition (9) was prepared in the same manner as in Example 1 except that methyl silicate 51 was not used in the preparation of the molding sand composition of Example 1. The obtained molding sand composition was measured for mold strength and evaluated for disintegration of the sand core by the following test methods. Table 1 shows the results.
[0032]
Conventional example 1
A conventional casting was prepared in the same manner as in Example 1 except that the phenolic resin component (5) was used in place of the phenolic resin component (1) and the methyl silicate 51 was not used in the preparation of the molding sand composition of Example 1. A sand composition (10) was prepared. The obtained molding sand composition was measured for mold strength and evaluated for disintegration of the sand core by the following test methods. Table 1 shows the results.
[0033]
[Table 1]

[0034]
【The invention's effect】
As described above, according to the present invention, the combined use of an ortho-cresol-modified phenol resin and a silicate ester and / or a hydrolysis product thereof significantly improves the disintegration of a sand core compared to a conventional phenol resin base. Therefore, it is possible to contribute to reduction of energy cost and improvement of working environment in the production of light alloy castings.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a sand mold for a casting test for evaluating the collapse property of a sand core.
FIG. 2 is a vertical sectional view of a casting including a used sand core.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Molten injection port 2 ... Baseboard fixing part 3, 3 '... Main mold 4 ... Sand core 4' ... Sand core skirting board 5 ... Casting test sand mold 6 ... Used sand core 7 ... Discharge port 8 …casting

Claims (4)

A binder composition for an amine gas-curable mold, comprising an orthocresol-modified phenol resin, a polyisocyanate compound, an organic solvent, a silicate ester and / or a hydrolysis product thereof as essential components. A molding sand composition for an amine gas-curable mold, comprising the binder composition according to claim 1 and a molding sand. 3. A molding sand composition for an amine gas-curable mold according to claim 2, wherein the molding sand is one selected from the group consisting of alumina sand, mullite sand and a mixture thereof. A sand core for casting a light alloy, wherein the molding sand composition according to claim 2 or 3 is cured by contacting the molding sand composition with a tertiary amine.

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