JP3123031B2 - Binder composition for mold production and method for producing mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder composition for producing a mold mainly comprising a binder made of a water-soluble phenolic resin, and using this binder or the binder composition. The present invention relates to a method of manufacturing a mold by using the method.

[0002]

2. Description of the Related Art Conventionally, various organic binders have been used as binders for producing molds.
Recently, a method of manufacturing a mold has been adopted in which a water-soluble phenol resin is used as an organic binder capable of improving casting quality and a working environment, and the binder is cured with an organic ester or carbon dioxide gas. (Japanese Patent Application Laid-Open No. 50-130627, Japanese Patent No. 1554030, and Japanese Patent No. 1554031).

[0003] However, the mold obtained using a binder made of a water-soluble phenol resin has a drawback that the mold strength is lower than the mold obtained using a binder made of a furan resin. . When the strength of the mold is low, when the molten metal is poured (poured) into the mold at the time of casting, the surface of the mold is eroded, and the quality of the obtained casting sometimes deteriorates. Also, if a large amount of binder is used to improve the mold strength, a large amount of gas is generated from the binder during pouring,
In some cases, gas defects and the like appear in the casting, which deteriorates the casting quality.

[0004]

SUMMARY OF THE INVENTION For this reason, the present applicant uses a binder composition obtained by adding a polyfunctional silane coupling agent to a water-soluble phenol resin.
It has been proposed to improve the strength of the obtained mold (JP-A-4-55037). The polyfunctional silane coupling agent used in the invention according to Japanese Patent Application Laid-Open No. 4-55037 has an epoxy group and three alkoxy groups such as methoxy group in one molecule. -Glycidoxypropyltrimethoxysilane or β- (3,4-epoxycyclohexyl)
Ethyltrimethoxysilane and the like.

The object of the present invention is to improve the strength of the obtained mold, similarly to the invention according to JP-A-4-55037. The functional silane coupling agent is intended to sufficiently improve the mold strength by adopting a polyfunctional silane coupling agent having a completely different structure.

[0006]

That is, the present invention is directed to a binder comprising a water-soluble phenolic resin and a polyfunctional silane coupling having a hydrolyzable group comprising four or more alkoxy groups per molecule. And a method for producing a mold using the binder or the binder composition.

As the water-soluble phenol resin contained in the binder composition for producing a mold according to the present invention, a water-soluble phenol resin conventionally used as a binder for producing a mold can be used. Specifically, phenol,
It is obtained by reacting phenols such as cresol, resorcinol, 3,5-xylenol, bisphenol and other substituted phenols with aldehydes such as formaldehyde and paraformaldehyde in a large amount of an aqueous solution of an alkaline substance. As a typical water-soluble phenol resin, an alkali phenol-formaldehyde resin obtained by reacting phenol and formaldehyde until a suitable molecular weight is reached using a predetermined amount of potassium hydroxide as a reaction catalyst is used. At this time, the quantitative ratio of phenol to formaldehyde is phenol: formaldehyde = 1: 1.5 to 2.5 in molar ratio.
It is preferred that When the amount of formaldehyde is less than 1.5 mol, the curing strength of the binder is low, and the strength of the resulting mold tends to decrease. Conversely, when the amount of formaldehyde exceeds 2.5 mol, unreacted formaldehyde remains in the alkali phenol-formaldehyde resin, and formaldehyde gas is likely to be generated during molding or casting, which may deteriorate the working environment. . In the water-soluble phenol resin used in the present invention, when obtained by reacting a phenol with an aldehyde, a monomer capable of condensing with an aldehyde such as urea, melamine, cyclohexanone, etc. is used so as not to be a main constituent unit. Condensed ones are also included.

On the other hand, the polyfunctional silane coupling agent used in the present invention has a structure completely different from that of the known polyfunctional silane coupling agent described in JP-A-4-55037. . That is, it has a hydrolyzable group consisting of four or more alkoxy groups in one molecule. Examples of such a polyfunctional silane coupling agent include the following. I. N, N-bis [3- (trimethoxysilyl) propyl] amine _{HN [(CH 2) 3 Si} (OCH 3) 3] 2 II. N, N-bis [3- (trimethoxysilyl) propyl] ethylenediamine _{H 2 NCH 2 CH 2 N [} (CH 2) 3 Si (OCH 3) 3] 2 III. N, N-bis [3- (trimethoxysilyl) propyl] methacrylamide

Embedded image IV. N-glycidyl-N, N-bis [3- (trimethoxysilyl) propyl] amine

Embedded image V. γ-aminopropyltetraethoxydisiloxane

Embedded image VI. N, N-bis [3- (methyldimethoxysilyl) propyl] amine _{HN [(CH 2) 3 SiCH} 3 (OCH 3) 2] 2 VII. N, N-bis [3- (methyldimethoxysilyl)
Propyl] ethylenediamine H ₂ NCH ₂ CH ₂ N [(CH ₂ ) ₃ SiCH ₃ (OC
H ₃ ) ₂ ] ₂ VIII. N, N-bis [3- (methyldimethoxysilyl)
Propyl] methacrylamide

Embedded image IX. N-glycidyl-N, N-bis [3- (methyldimethoxysilyl) propyl] amine

Embedded image

As described above, the polyfunctional silane coupling agent used in the present invention has a hydrolyzable group consisting of an alkoxy group such as a methoxy group, an ethoxy group or a propoxy group in the Si atom in one molecule. It suffices if four or more are bonded. Therefore, the other organic group bonded to the Si atom may be any, for example, an amino group, 2-
An organic group having an epoxy group such as an aminoethyl group, a 2-aminomethyl group, an aminopropyl group, a phenylaminopropyl group, a methacryl group, a glycidyl group, a vinyl group, a mercapto group, or the like may be used. In the present invention, it is particularly preferable to employ a polyfunctional silane coupling agent having six or more hydrolyzable groups consisting of alkoxy groups. As described above, the silane coupling agent having a relatively large amount of alkoxy groups firmly bonds the hardened phenol resin to a refractory granular material such as silica sand.

The binder composition for producing a mold according to the present invention comprises:
It contains the above-mentioned water-soluble phenol resin and a polyfunctional silane coupling agent, but is generally adjusted to the form of an aqueous solution and supplied as a binder aqueous solution composition. The amount of the water-soluble phenol resin in the aqueous binder composition is generally about 30 to 75% by weight. Also,
The polyfunctional silane coupling agent is preferably used in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the water-soluble phenol resin. If the amount of the polyfunctional silane coupling agent is less than 0.01 parts by weight, the adhesive strength between the cured phenolic resin and a refractory granular material such as silica sand tends to decrease, and the resulting mold strength tends to decrease. Conversely, if the polyfunctional silane coupling agent is used in an amount exceeding 10 parts by weight, the strength of the resulting mold will be saturated, which is not economical.

The binder aqueous solution composition for producing a mold according to the present invention may contain any other various substances. For example, the binder aqueous solution composition is adjusted to be alkaline, but the molar ratio between phenol and the alkaline substance is adjusted so that phenol: alkaline substance = 1: 0.3-1.2. Therefore, when an alkaline substance is insufficient with only potassium hydroxide used as a reaction catalyst when producing a water-soluble phenol resin, sodium hydroxide, lithium hydroxide, or the like may be added. Further, a borate such as borax, an aluminate such as sodium aluminate, a stannate such as sodium stannate and the like may be added to the aqueous binder solution composition. If such an aluminate or the like is added, the mold can be satisfactorily cured by carbon dioxide gas, and a mold having high strength can be obtained. Further, a conventionally known polyfunctional silane coupling agent as described in JP-A-4-55037 may be added and used in combination with the polyfunctional silane coupling agent used in the present invention. Further, in the binder aqueous solution composition, urea-aldehyde resin, melamine-aldehyde resin, cyclohexanone-aldehyde resin and the like may be mixed and added together with the water-soluble phenol resin.

In order to obtain a mold using the binder composition for producing a mold according to the present invention, a refractory granular material and a binder aqueous solution composition are kneaded, filled into a model, and then mixed with a curing agent. What is necessary is just to harden. Specifically, first, the refractory granular material
To 100 parts by weight, 0.1 to 5 parts by weight of an organic ester as a curing agent was added and kneaded, followed by adding 0.4 to 15 parts by weight of a binder aqueous solution composition, and kneading again to obtain a kneaded sand, which was used as a model. By filling and curing, a mold can be obtained (self-hardening mold forming method). Further, 0.4 to 15 parts by weight of a binder aqueous solution composition was added and kneaded to 100 parts by weight of the refractory granular material to obtain kneaded sand, and then the kneaded sand was blown with pressurized air to obtain a gas curable sand. Fill the model. Then, 0.05 to 10 parts by weight of a gaseous or aerosol-like organic ester is blown to obtain a mold (gas-curable mold making method). In this case, the organic ester to be used is preferably an alkyl formate having an alkyl group having 1 to 3 carbon atoms, and most preferably methyl formate. Further, after using a binder aqueous solution composition to which borate, aluminate, stannate and the like are added, kneaded sand is obtained, and then the kneaded sand is filled in a gas-curable model. Then, a mold can be obtained by blowing carbon dioxide gas (gas-curable mold making method).

In the present invention, a mold can be produced by the following method. That is, first, a polyfunctional silane coupling agent is brought into contact with a refractory granular material such as silica sand. Specifically, it is performed by adding an aqueous solution comprising a polyfunctional silane coupling agent to a refractory granular material such as silica sand. At this time, the addition amount (solid) of the polyfunctional silane coupling agent is preferably 0.0001 to 0.03 parts by weight based on 100 parts by weight of the refractory granular material.
If the amount of the polyfunctional silane coupling agent is less than 0.0001 part by weight, the adhesive strength between the cured phenolic resin and a refractory granular material such as silica sand tends to decrease, and the resulting mold strength tends to decrease. Conversely, even if the polyfunctional silane coupling agent is used in an amount exceeding 0.03 parts by weight, the strength of the resulting mold will be saturated, which is not economical. After the refractory granular material such as silica sand is treated with the polyfunctional silane coupling agent as described above, a binder aqueous solution composed of a water-soluble phenol resin is added. The binder aqueous solution may be added in an amount of about 0.4 to 15 parts by weight based on 100 parts by weight of the refractory granular material. After kneading, a mold can be obtained by a self-hardening mold molding method or a gas-curable mold molding method.

Further, in the present invention, a mold can be produced by the following method. That is, a binder aqueous solution composed of a water-soluble phenol resin and an aqueous solution composed of a polyfunctional silane coupling agent are separately and simultaneously added to a refractory granular material such as silica sand. Then, after kneading the refractory granular materials and these, a mold can be obtained by a self-hardening molding method or a gas-curing molding method. On this occasion,
The water-soluble phenol resin aqueous solution is preferably added in an amount of about 0.4 to 15 parts by weight based on 100 parts by weight of the refractory granular material, and the polyfunctional silane coupling agent has a solid content of 0.00%.
It is preferable to add about 01 to 0.03 parts by weight. It is preferable that the water-soluble phenol resin aqueous solution and the polyfunctional silane coupling agent have such a quantitative range for the same reason as described above.

As the refractory granular material used in manufacturing the mold, silica sand, chromite sand, zircon sand, olivine sand, alumina sand, mullite sand, synthetic mullite sand, etc., mainly composed of quartz are used. Can be Needless to say, as the refractory granular material, a material mainly composed of recovered sand or regenerated sand for the purpose of reusing them is also used.

[0016]

【Example】

[Synthesis and Preparation of Binder Composition 1] A predetermined amount of phenol was added to a 50% aqueous potassium hydroxide solution, followed by stirring and dissolution. While maintaining this solution at 80 ° C., 2 mol of formaldehyde was gradually added to 1 mol of phenol.
The formaldehyde was added in the form of a 50% aqueous formaldehyde solution. Then, phenol and formaldehyde were reacted at 80 ° C., and the reaction was continued until the weight average molecular weight of the phenol-formaldehyde resin reached 3000, that is, until the solution reached a predetermined viscosity. After the reaction is completed, cool to room temperature and add 50%
An aqueous solution of potassium hydroxide was added. As described above, an aqueous solution of a water-soluble phenol resin was obtained. To this aqueous solution, various silane coupling agents shown in Table 1 were added at the ratios shown in Table 1 to obtain various binder aqueous solution compositions. Binder composition amount (solid content) in this binder aqueous solution composition
Was 50%.

[0017]

[Table 1]

[Synthesis and Preparation of Binder Composition 2] Except that the reaction is continued until the weight average molecular weight of the phenol-formaldehyde resin reaches 2000, the procedure is the same as in [Synthesis and Preparation of Binder 1]. An aqueous solution of a water-soluble phenol resin was obtained. To this aqueous solution, various silane coupling agents shown in Table 2 were added in the proportions shown in Table 2 to obtain various binder aqueous solution compositions. The amount (solid content) of the binder composition in this binder aqueous solution composition was 50% in each case.

[0019]

[Table 2]

[Synthesis and Preparation of Binder Composition 3] 25 parts by weight of the aqueous solution of the water-soluble phenol resin obtained in [Synthesis and Preparation of Binder Composition 2] and sodium tetraborate · 1
After mixing 5 parts by weight of 0-hydrate and 5 parts by weight of 50% potassium hydroxide, various silane coupling agents shown in Table 3 were added thereto in the proportions shown in Table 3 to obtain various viscosity. A binder aqueous solution composition was obtained.

[0021]

[Table 3]

Examples 1 to 8 and Comparative Examples 1 to 5 0.3 parts by weight of triacetin as a hardening agent was added to 100 parts by weight of silica sand as a refractory granular material and kneaded. Synthesis and Adjustment], the binder composition was added and kneaded so as to be 1.5 parts by weight, and immediately thereafter, filled into a 50 mmφ × 50 mmh test piece frame to obtain a test mold by a self-hardening mold production method. . Then, the compressive strength (kg / cm ² ) of the test mold after 24 hours was measured. The results are shown in Table 1.

Examples 9 to 13 and Comparative Examples 6 to 10 The binder composition obtained in [Synthesis and preparation of binder composition 2] was mixed with 100 parts by weight of silica sand as a refractory granular material. Kneaded so as to be 2.0 parts by weight per minute, and then immediately filled in a 50 mmφ × 50 mmh gas test piece frame, and 0.8 parts by weight of methyl formate was injected with respect to 100 parts by weight of silica sand.
Test molds were obtained by gas-curing mold making. Then, the compressive strength (kg / cm ² ) of the test mold after 24 hours was measured. The results are shown in Table 2.

Examples 14 to 18 and Comparative Examples 11 to 15 The binder composition obtained in [Synthesis and preparation of binder composition 3] was added to 100 parts by weight of silica sand as a refractory granular material. .
0 parts by weight and kneaded, then immediately 50mmφ
A test piece frame for gas of 50 mmh was filled, carbon dioxide gas was ventilated (10 liters x 2 minutes), and a test mold was obtained by a gas-curable mold molding method. Then, the compressive strength (kg / cm ² ) of the test mold after 24 hours was measured. The results are shown in Table 3.

As is apparent from the above Examples and Comparative Examples, a polyfunctional silane coupling agent having a hydrolyzable group comprising four or more alkoxy groups in one molecule in a water-soluble phenol resin. When a binder composition obtained by adding a polyfunctional silane coupling agent having a hydrolyzable group having three or less alkoxy groups in one molecule is used. The compressive strength of the obtained mold can be increased as compared with the case where the composition is used.

[0026]

As described above, the binder composition mainly composed of the water-soluble phenolic resin according to the present invention contains, as a coupling agent, a hydrolyzate comprising four or more alkoxy groups per molecule. It contains a polyfunctional silane coupling agent having a decomposable group. This coupling agent is
Since there are four or more alkoxy groups in one molecule,
It is considered that the phenol resin and the silanol groups present on the surface of the refractory granular material such as silica sand are strongly bonded. Therefore, the mold obtained by using the binder composition according to the present invention has an effect that its strength is improved as compared with the conventional mold.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B22C 1 / 10,1 / 22

Claims (7)

(57) [Claims] 1. A binder comprising a binder made of a water-soluble phenol resin and a polyfunctional silane coupling agent having a hydrolyzable group consisting of four or more alkoxy groups in one molecule. Binder composition for mold production. 2. A polyfunctional silane coupling agent,
The binder composition for producing a mold according to claim 1, wherein a binder having a hydrolyzable group comprising at least 6 alkoxy groups in one molecule is used. 3. The binder composition for producing a mold according to claim 1, wherein the alkoxy group is a methoxy group or an ethoxy group. 4. The viscosity for producing a mold according to any one of claims 1 to 3, wherein the polyfunctional silane coupling agent is contained in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the water-soluble phenol resin. Binder composition. 5. A binder composition for producing a casting by kneading a refractory granular material and the binder composition for producing a mold according to any one of claims 1 to 4, and using a curing agent. And a method for producing a mold. 6. A refractory particulate material is contacted with a polyfunctional silane coupling agent having a hydrolyzable group comprising four or more alkoxy groups in one molecule, and then a caking comprising a water-soluble phenol resin. A method for producing a mold, comprising adding and kneading an agent, and curing the binder with a curing agent. 7. The method for producing a mold according to claim 5, wherein an organic ester and / or carbon dioxide gas is used as the curing agent.