JP2804419B2 - Binder composition for 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 resin composition for a mold which is excellent in curability and working environment and is used for a gas-curable mold. More specifically, the present invention relates to a high-strength, fast-curing binder composition for a carbon dioxide gas-curable mold, in which the molecular weight distribution is narrowed by suppressing the content of the mononuclear component to a small amount.

[0002]

2. Description of the Related Art Conventionally, in the field of the casting industry, a room-temperature-curable mold molding method includes a method using various types of organic and inorganic binders. The method of hardening the inorganic binder using water glass or the like with carbon dioxide gas has less harmful gas during casting, but the mold disintegration after casting is poor, and it takes more man-hours than the organic binder, Another drawback is that it is difficult to collect and regenerate sand. On the other hand, molding methods using an organic binder include a method of curing a furan resin, a urea-modified furan resin and a peroxide with an organic sulfonic acid, sulfuric acid, or sulfurous acid gas, and a mixture of a benzylic ether type phenol resin and a polyisocyanate. Is cured with a liquid or gaseous tertiary amine. Although these mold making methods have good mold disintegration properties after casting, many problems in metallurgy have been pointed out, such as adverse effects on castings such as gas defects, soot defects, and vaning defects. Further, the generated S
It has been pointed out that Ox and NOx gases cause deterioration of the working environment and air pollution causes acid rain, which has become a social problem.

For the purpose of solving such a drawback, Japanese Patent Application Laid-Open No. 1-224263 has been proposed as a method of manufacturing a mold using carbon dioxide from the viewpoint of a working environment.
However, such a molding technique is effective in improving the working environment and the like as compared with other organic binders, but has a drawback that the production efficiency is remarkably reduced because the molding strength is low and the curing speed is very slow. As a practical matter, high strength, fast curing performance and improvement of the working environment are contradictory from the viewpoint of binder production. For this reason, performance has been conventionally designed on the basis of a balance between the two.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to produce a carbon dioxide-curing mold having excellent harmful gas generation and excellent working environment as well as excellent mold strength and curing speed. Agent composition.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the problems of achieving high strength, fast curing and a good working environment, and as a result, have reacted phenol and formaldehyde at a high molar ratio. Thereafter, a mononuclear component which hardly contributes to the development of strength during curing and promotes thickening of the binder is removed and reduced to obtain a phenol resin, and a binder composition containing a boron compound therein. It has been found that a binder composition having a high working strength and a good working environment can be obtained by using. That is, the present invention uses phenol and formaldehyde in a molar ratio of 1: 1.6 to 3.0 using an alkali catalyst such as an oxide or hydroxide of an alkali metal and / or alkaline earth metal as a reaction catalyst. After the reaction, the mixture is neutralized with an organic acid or an inorganic acid, and then washed with water to reduce the mononuclear component to 7% by weight or less.
It is intended to provide a binder composition for a carbon dioxide gas-curable mold in which a boron compound is added to a phenol resin obtained by setting the composition to 9.

The details of the present invention will be described below. First, the molar ratio of formaldehyde to phenol is usually 1.
It is 6-3.0, preferably 1.8-2.6. Whether this molar ratio is low or high does not give good results in strength and working environment. Here, the above-mentioned phenol can be mostly or partially modified with other phenols such as cresol, xylenol, bisphenol A, bisphenol F and resorcinol. Also, urea,
A monomer capable of being condensed with formaldehyde such as melamine and cyclohexanone may be co-condensed to such an extent that it does not become a main constituent unit by weight ratio. Acetaldehyde, benzaldehyde, glyoxal, and the like can be used as the aldehyde, but formaldehyde is preferred because it is inexpensive and has good performance. Next, as the reaction catalyst, an oxide of an alkali metal such as sodium or potassium,
Hydroxides or weak acid salts, oxides, hydroxides or weak acid salts of alkaline earth metals such as barium, calcium, magnesium. Either one or both of these alkali metal and alkaline earth metal compounds may be used, but they are finally removed after neutralizing the reaction product.
Inexpensive ones are preferred. In general, the use amount of such a reaction catalyst is preferably as large as possible with respect to phenol. An appropriate amount is at least 05 mol, preferably 0.08 to 0.20 mol.

There is no restriction on the neutralizing acids other than that a combination should be selected so that the salt of these with the alkali as a reaction catalyst should be water-soluble.
It is preferable to be able to neutralize the pH to 4.5 to 7.0 and to remove substantially the whole amount in the form of a hydrated salt. Organic acids such as carbonic acid, acetic acid and oxalic acid, and inorganic acids such as hydrochloric acid and phosphoric acid are preferred. Can be generally used. In obtaining the composition of the present invention, the degree of reaction between phenol and formaldehyde is particularly important. It is necessary to control the reaction as quickly as possible so that a large number of 2- to 4-nuclear products are produced. Since these improve the strength and the quick-curing property, it is preferable to use as many as possible. However, a high molecular compound is not preferable because it increases the viscosity of the binder too much and adversely affects the kneading properties. Also, 1
The study of the present invention has revealed that nucleus components such as phenol, monomethylolphenol, dimethylolphenol, and trimethylolphenol increase the viscosity of the binder but hardly contribute to the mold strength performance.

[0008] From the above, from the viewpoint of industrial control, the reaction temperature is naturally restricted, and a suitable temperature range is 70 to 100 ° C, more preferably 75 to 95 ° C.
If the reaction temperature is high, it is difficult to control the reaction, which is dangerous. On the other hand, if it is too low, the amount of mononuclear compounds increases, and the yield decreases due to the removal. Further, the end point of the reaction needs to be controlled by an apparatus capable of measuring the molecular weight distribution in some form. The end point of the reaction between phenol and formaldehyde in obtaining the composition of the present invention is "High Performance Liquid Chromatograph HLC-8020" (manufactured by Toyo Soda Kogyo, hereinafter HL).
(Referred to as C). However, since this method requires a certain amount of time, it is generally possible to perform alternative control by previously setting the correlation between the water ratio or the viscosity of the reaction product and HLC as a simple method. As described above, the mononuclear component is unnecessary from the viewpoint of mold strength performance. As the reaction proceeds further, the content of binuclear or higher components increases, but the viscosity increases sharply as the polymer becomes more advanced.

On the other hand, when the reaction is stopped, the high molecular weight components of two or more nuclei lose their water solubility by being neutralized when the reaction is stopped, but the mononuclear components of phenol, monomethylol phenol, dimethylol phenol, Trimethylolphenol and the like remain water-soluble and can be separated from each other.
As a method of separation, a reduced pressure steam distillation method and a water washing method can be considered, but removal by water washing that can be carried out simply and at room temperature is preferable. The remaining amount of the mononuclear component can be controlled by adjusting the number of times of washing, but from the viewpoint of the balance between mold strength characteristics and economic efficiency, it is 7% by weight or less, preferably 5% by weight or less in mold performance. is there. Next, the polymer component having two or more nuclei becomes water-soluble again by adding and mixing the alkali metal compound again with the one having the mononuclear component removed. The alkali metal compound is added to at least PH9, preferably PH11 to 13. As such an alkali metal compound, sodium hydroxide or potassium hydroxide is preferably used alone or in combination.

As the boron compound, boric acid or borate salts such as sodium tetraborate decahydrate, potassium borate decahydrate, sodium metaborate, potassium pentaborate and sodium pentaborate are preferred. The boron compounds may be used alone or in combination of two or more. The addition amount of the boron compound is in the range of 1 to 75 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of the resin, and good results can be obtained. Further, a silane coupling agent may be added for the purpose of improving the mold performance. Preferred silane coupling agents include γ-aminopropyltriethoxysilane and γ
-(2-aminoethyl) aminopropyltrimethoxysilane and the like.

[0011]

The present invention will be described below with reference to examples. However, the present invention is not limited by the examples. Further, “parts” and “%” shown in Examples and Comparative Examples are all “parts by weight” and “% by weight”. << Example 1 >> Phenol was added to a reaction vessel equipped with a cooler and a stirrer.
470 parts (5.00 moles), 730 parts (9.00 moles) of 37% formalin, and 40 parts (0.50 moles) of 50% sodium hydroxide were gradually heated. The mixture was refluxed at 85 ° C., kept at this temperature for 2 hours from the start of reflux, and reacted to a water magnification of 480%. Immediately after cooling was started, 50% acetic acid (temperature of 50 ° C.) was added to neutralize to pH 5.5. After neutralization, the mixture was stirred at 40 ° C. or lower while adding 500 parts of water for washing, and cooled. After sufficient stirring, the mixture was allowed to stand for 30 minutes. During this time, high molecular components of two or more nuclei precipitated. The separated water containing the mononuclear body was removed, water was added again, and this washing step was repeated three times. Next, 200 parts of 50% sodium hydroxide is added while cooling, and the pH is adjusted to 12 and the viscosity is 80 CPs / 25 ° C., and then the aminosilane coupling agent is added.
The desired resin composition was obtained by adding 0.5%. This resin composition has a viscosity of 80 CPs / 25 ° C., a nonvolatile content of 50%, a free phenol of 1.2%, a content of a mononuclear component containing free phenol of 7.0%, and a high molecular component of three or more nuclei. Content of 64.2
%, The remaining 28.8% being binuclear components (see FIG. 1). Sodium tetraborate decahydrate 1
0% by weight was added and mixed to obtain a binder composition of the present invention.

90 parts by weight of this binder is added to 3000 parts by weight of flattery silica sand, and the mixture is mixed for 1 minute.
It was placed in a mold of × 50 mm and molded. Next, after the carbon dioxide gas was ventilated to cure the mold, the mold was taken out of the mold and the compressive strength was measured over time. Molding was performed using the compounded sand that had passed 2 hours after kneading, and after 24 hours standing, the working strength was determined. The fluidity of the sand affects the quality of the workability, and the packing density is used as a measure for measuring the workability. This is obtained by dividing the weight of a cured 50 mm x 50 mm mold by volume. A pouring test was performed using a mold 24 hours after the molding. Furthermore, 28φ x 50m
Using the m mold, a mold was prepared in the same manner as described above, and a hot compression strength test was performed.

Example 2 In a reaction vessel equipped with a condenser and a stirrer, 470 parts (5.00 mol) of phenol, 811 parts (10.00 mol) of 37% formalin, 40% sodium hydroxide 40
(0.50 mol), and the temperature was gradually raised. Reflux at 80 ° C., hold at this temperature for 2 hours from the start of reflux,
Reacted to 00%. Immediately after cooling was started, 50% acetic acid (temperature of 50 ° C.) was added to neutralize to pH 5.5. After neutralization, the mixture was stirred at 40 ° C. or lower while adding 500 parts of water for washing, and cooled. After sufficient stirring, the mixture was allowed to stand for 30 minutes. During this time, high molecular components of two or more nuclei precipitated. The separated water containing the mononuclear body was removed, water was added again, and this washing step was repeated five times. Then 50% sodium hydroxide 2
Add 00 parts while cooling, PH12, viscosity 70C
After adjusting to Ps / 25 ° C., 0.5% of an aminosilane coupling agent was added to obtain a target resin composition. This resin composition has a viscosity of 70 CPs / 25 ° C., a non-volatile content of 53%,
The free phenol content is 0.9%, the content of mononuclear components containing free phenol is 4.8%, the content of high molecular components with three or more nuclei is 67.2%, and the remaining 28.0% is dinuclear. It is a body component. To this resin composition, 5% by weight of potassium pentaborate decahydrate was added and mixed to obtain a binder composition of the present invention. The mold characteristics were evaluated in the same manner as in Example 1 using this binder.

Example 3 470 parts (5.00 mol) of phenol, 730 parts (9.00 mol) of 37% formalin, and 56 parts (0.50 mol) of 50% potassium hydroxide were placed in a reaction vessel equipped with a cooler and a stirrer. The temperature was gradually increased during the preparation. Reflux at 85 ° C., hold at this temperature for 2 hours from the start of reflux,
Reacted to 0%. Start cooling immediately and at the same time
0% acetic acid (temperature of 50 ° C.) was added to neutralize to pH 5.5. After neutralization, the mixture was stirred at 40 ° C. or lower while adding 500 parts of water for washing, and cooled. After sufficient stirring, the mixture was allowed to stand for 30 minutes. During this time, high molecular components of two or more nuclei precipitated. The separated water containing the mononuclear body was removed, water was added again, and this washing step was repeated three times. Then 50% sodium hydroxide 2
Add 00 parts while cooling, PH12, viscosity is 90CP
After adjusting to s / 25 ° C., 0.5% of an aminosilane coupling agent was added to obtain a target resin composition. This resin composition has a viscosity of 90 CPs / 25 ° C., a non-volatile content of 50%, a free phenol content of 1.4%, a mononuclear component content of 6.0% including free phenol, and a trinuclear or higher polymer. With a component content of 66.2%, the remaining 27.8% is a binuclear component. Sodium tetraborate decahydrate 10% by weight was added to this resin composition.
And 10% by weight of potassium pentaborate decahydrate were added and mixed to obtain a binder composition of the present invention. Next, mold characteristics were evaluated in the same manner as in Example 1 using this binder.

Example 4 A reaction vessel equipped with a cooler and a stirrer was charged with 470 parts (5.00 mol) of phenol, 811 parts (10.00 mol) of 37% formalin, and 56 parts (0.50 mol) of 50% potassium hydroxide gradually. The temperature rose. Reflux at 80 ° C., hold at this temperature for 2 hours from the start of reflux, and use a water magnification of 35
Reacted to 0%. Start cooling immediately and at the same time
0% acetic acid (temperature of 50 ° C.) was added to neutralize to pH 5.5. After neutralization, the mixture was stirred at 40 ° C. or lower while adding 500 parts of water for washing, and cooled. After sufficient stirring, the mixture was allowed to stand for 30 minutes. During this time, high molecular components of two or more nuclei precipitated. The separated water containing the mononuclear body was removed, water was added again, and this washing step was repeated five times. Then 50% potassium hydroxide 20
0 parts are added while cooling, PH12, viscosity is 75CPs /
After adjusting the temperature to 25 ° C., 0.5% of an aminolane coupling agent was added to obtain a target resin composition. This resin composition has a viscosity of 75 CPs / 25 ° C., a non-volatile content of 51%, a free phenol content of 0.8%, a mononuclear component containing free phenol of 4.5%, and a trinuclear or higher content. Polymer component content 6
8.3% and the remaining 27.2% are binuclear components. To this resin composition, 10% by weight of sodium tetraborate decahydrate and 5% by weight of potassium pentaborate were added and mixed to obtain a binder composition of the present invention. Next, the same mold properties as in Example 1 were evaluated using this binder.

Comparative Example 1 In a reaction vessel equipped with a cooler and a stirrer, 470 parts (5.00 mol) of phenol, 730 parts (9.00 mol) of 37% formalin, and 40% sodium hydroxide 40
(0.50 mol), and the temperature was gradually raised. Reflux at 85 ° C., hold at this temperature for 2 hours from the start of reflux, and use a water
Reacted to 90%. Then 50% sodium hydroxide 2
10 parts were added while cooling, PH12, viscosity was 180
After adjusting to CPs / 25 ° C., 0.5% of an aminosilane coupling agent was added to obtain a resin composition. This resin composition has a viscosity of 180 CPs / 25 ° C., a non-volatile content of 53%,
With a free phenol content of 1.9%, a mononuclear component containing free phenol of 18.5%, and a trinuclear or higher polymer component of 56.2%, with the remaining 25.3% remaining It is a binuclear composition. To this resin composition, 10% by weight of sodium tetraborate decahydrate was added and mixed to obtain a binder composition. Next, the same mold properties as in Example 1 were evaluated using this binder.

[0017]

[Table 1]

[0018]

As is evident from the above results, the mold binder composition of the present invention has a better working environment, higher strength, faster curability and higher production efficiency than conventional compositions. It has excellent effects such as being able to do.

[Brief description of the drawings]

FIG. 1 shows an HLC chart of a resin binder of Example 1.
G.

[Explanation of symbols]

 A region of a high molecular component having three or more nuclei B region of a two-nucleus component C region of a one-nucleus component.

Claims (1)

(57) [Claims] 1. A phenol and formaldehyde:
The reaction is carried out at a molar ratio of 1.6 to 3.0 using an alkali metal and / or alkaline earth metal compound as a reaction catalyst, and then neutralized with an organic acid or an inorganic acid. An aqueous solution of an alkali metal compound was added to the resin obtained by washing with water so that the content of the core component was 7% by weight or less, and the system was adjusted to at least PH.
9. A binder composition for a carbon dioxide gas-curable mold comprising a phenolic resin and a boron compound obtained by setting the composition to 9.