JPH0148103B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new and useful self-hardening binder composition for foundry molds, and more particularly, it contains as an essential component a specific acid-curable phenol-aldehyde resin initial condensate modified with bisphenol F. A high-strength self-hardening binder composition comprising: The molds used in making castings or mouldings are obtained by mixing an aggregate material based on foundry sand with the desired amount of binder and then allowing it to harden. By the way, it goes without saying that the generally required performance of such a binder is that it has high strength. As long as it has high strength, even if there is some variation in the work, a mold that meets the purpose can be obtained stably, and the amount of binder used can be reduced, making it economical. Even. In order to achieve high strength of such molds,
Measures have been taken to improve the binder's leakability into the sand, which is important, but for this purpose it must be a condensation product as early as possible and a low viscosity product. is necessary. However, the initial condensate generally has a large amount of free formalin and a high content of free phenol, and although it has high strength, it has a strong odor, so it is not desirable from the viewpoint of the working environment. Generally speaking, binder resins must be designed to strike a balance between strength and odor, which naturally have a contradictory relationship. However, the current situation is that a binder with a perfect balance between strength and odor has not yet been found. However, the present inventors have conducted intensive studies to further improve the strength performance of commonly commercially available acid-curing self-hardening phenolic resin binders, which are designed based on a balance between low odor performance and strength performance. As a result of further research, it was discovered that this type of phenolic resin binder modified with bisphenol F can significantly improve the strength of casting molds, and the present invention was completed. That is, the present invention uses phenols and formaldehydes as essential components in the presence of an alkali metal and/or alkaline earth metal compound catalyst in a molar ratio of 1:1.15 to 1.65, and furthermore, the initial stage of the resulting resin is 5 to 12 based on condensate
It contains a bisphenol F-modified acid-curing phenol-aldehyde resin initial condensate obtained by modifying it with % by weight of bisphenol F, and has a non-volatile content of 55 to 85% by weight at 25°C. Provides a self-hardening binder composition for foundry molds having a viscosity of 150 centipoise (cps) or less,
The subject of the present invention is a resol type phenolic resin initial condensate that follows almost the usual resin design for self-hardening binders, and the resin initial condensate is modified with a specific dinuclear compound called bisphenol F. Therefore, the nonvolatile content (NV) and viscosity of the target binder composition obtained are within the specific ranges listed above, are suitable for acid curing, have a balance between strength performance and low odor performance, and have a high strength The present invention provides a binder composition with improved properties. Here, first, the molar ratio of phenols and aldehydes is usually within the range of 1:1.15 to 1:1.65, preferably within the range of 1:1.30 to 1.55. As the phenol, phenol is most preferred, but it may be partially replaced with other phenols such as resorcinol, xylenol or cresol, and as the aldehyde, formaldehyde is most preferred, but other aldehydes such as acetaldehyde or glyoxal may be substituted. Of course, some of them may be replaced. Next, examples of the reaction catalyst mentioned above include oxides, hydroxides, or weak acid salts of alkali metals such as sodium or potassium, or alkaline earth metals such as calcium or barium, and these may be used singly or Of course, it may be used as a mixture of two or more types, or it may be a compound spanning both of these alkali metals and alkaline earth metals. These reaction catalysts are generally neutralized and deactivated after the reaction is completed. In order to prepare a bisphenol-modified acid-curable phenol-formaldehyde resin initial condensate, which is an essential binder component of the composition of the present invention, using the above-mentioned raw materials, the following various methods can be considered. . That is, a method in which bisphenol F is simultaneously added at the beginning of the initial reaction and each raw material is reacted according to a conventional method, and a method in which the reaction is proceeded according to a conventional method and bisphenol F is added in the middle of the reaction to cause a partial reaction. After proceeding with the reaction according to a conventional method, bisphenol F is added at the end of the reaction,
There are methods that cause almost no reaction. Among these methods, when the above method is used, the reaction does not substantially proceed and the mixture is merely mixed, but the denaturation effect is large and the reaction control is easy. ,
It can be said that the above method is the most preferable. Such modification of bisphenol F is carried out in an amount of 5 to 12% by weight, preferably 5 to 12% by weight, based on the resulting binder product, that is, the initial condensate of acid-curing phenol formaldehyde resin modified with bisphenol F.
A range of 10% by weight is appropriate. If the amount of bisphenol F used for such modification is less than 5% by weight, the modification effect will not be significant, and if it exceeds 12% by weight, it will be used as a mere contaminant. Perhaps because of this, the effects become progressively worse, so neither is preferable. The non-volatile content of the bisphenol-modified acid-curing phenol-formaldehyde resin initial condensate obtained in this way is preferably within the range of 55 to 75% by weight, and the viscosity of the condensate at 25°C is 150cps or less is appropriate. The composition of the present invention thus obtained is, so to speak, a mixture of an acid-curable phenol-formaldehyde resin initial condensate and unreacted bisphenol F, and due to the synergistic effect of these two components, the composition of the present invention as described above can be obtained. While this objective is achieved, the compositions of the present invention may also include acid curing agents such as organic acids such as xylene sulfonic acid or benzene sulfonic acid or inorganic acids such as sulfuric acid. The compositions of the invention are used in the preparation of foundry molds for cast steel, cast iron, ductile iron and various alloys such as aluminum or copper. Next, the present invention will be specifically explained with reference to Examples and Comparative Examples. In the following, all parts and percentages are based on weight unless otherwise specified. Example 1 470 parts of phenol, 116 parts of bisphenol F, and 536 parts of 42% formalin were charged into a flask equipped with a thermometer, a condenser, and a stirrer, and 23.5 parts of a 48% aqueous potassium hydroxide solution was added as a reaction catalyst. The temperature was raised to 80°C over 1 hour, and the reaction was allowed to occur until the water dilution ability (water tolerance) at the same temperature reached 500%, and the mixture was immediately cooled. Neutralize to ~7.0, then vacuum distillate,
A bisphenol F-modified phenol-formaldehyde resin initial condensate solution having an NV of 68.5% and a viscosity of 110 cps was obtained. The bisphenol F modification rate of this resin initial condensate was 10%, the water dilutability of the condensate was 100%, and the free formalin content was 0.3%. Example 2 470 parts of phenol and 536 parts of 42% formalin
23.5 parts of 48% potassium hydroxide aqueous solution was added to the flask equipped with a thermometer, condenser and stirrer, and the temperature was gradually raised to 80°C over 1 hour until the water dilution ability at the same temperature was 300°C. % and immediately cooled, then neutralized with a 70% aqueous solution of balatoluenesulfonic acid to a pH of 6.5 to 7.0, and then vacuum distilled. Next, the obtained acid-curing bisphenol formaldehyde resin initial condensate was mixed with methanol.
A bisphenol F solution dissolved to a concentration of 70% was mixed at a ratio of 10% in terms of solid content based on this resin initial condensate to form a resin liquid. The properties of the resin liquid obtained here, that is, the acid-curing phenol-formaldehyde resin initial condensate solution modified with bisphenol F, have an NV of 68.0%.
Viscosity is 80cps, free formalin content is 0.3%,
Moreover, the water dilution ability was 100%. Example 3 470 parts of phenol and 482 parts of 42% formalin
of barium hydroxide into a flask equipped with a thermometer, condenser and stirrer, add 18.8 parts of barium hydroxide,
The temperature was gradually raised to 80°C over 1 hour, and then the reaction was allowed to occur until the water dilution ability at the same temperature reached 300%, after which it was cooled and the pH was adjusted to 6.5 to 7.0 with a 70% aqueous para-toluenesulfonic acid solution. The mixture was neutralized and then vacuum distilled to obtain an acid-curing phenol-formaldehyde resin initial condensate solution. Thereafter, a bisphenol F solution dissolved in methanol to a concentration of 70% was mixed with the resin solution at a ratio of 10% in terms of solid content to obtain a resin liquid, that is, the composition of the present invention. . The property value of the resin liquid thus obtained was NV of 70.0.
%, viscosity is 75cps, free formalin content is 0.2%,
Moreover, the water dilution ability was 180%. Comparative Example 1 Same as Example 1 except that the use of bisphenol F was completely omitted, the water dilution ability at 80% was changed to 290%, and the pH was neutralized to 7.0 with 70% para-toluenesulfonic acid. A control resin composition was obtained in the same manner. The resin composition thus obtained had an NV of 70.0%,
The resin solution had a viscosity of 120 cps, the free formalin content of this resin was 0.6%, and the water dilution ability was 200%. Comparative Example 2 An unmodified acid-curable phenol-formaldehyde resin initial condensate was obtained in the same manner as in Example 3, except that the step of mixing bisphenol F was completely omitted. This control resin solution has an NV of 69.1% and a viscosity of
110 cps, free formalin content was 0.5%, and water dilutability was 220%. Performance evaluations of the respective resin compositions obtained in the above Examples and Comparative Examples were compared and examined using the following method in order to determine their suitability as acid-curing self-hardening binders for foundry molds. The locations are summarized in Table 1. That is, 3000 parts of Freemantle new sand was placed in a small multi-arm mixer of 90 cpm, and 80% para-toluenesulfonic acid methanol solution was added as an acid hardener.
Add 9.6 parts (50% to resin) and mix for 45 seconds.
Then 24 parts of each resin composition (0.8% to sand)
and knead for an additional 45 seconds, immediately reducing the diameter to 50 mm.
The molds were molded individually by hand into molds made of polyvinyl chloride with a height of 50 mm, and 0.5 hours, 1.0 hours, and 3.0 hours after the mold filling,
The compressive strength in the normal state was measured after 5.0 hours and 24 hours by removing the mold immediately before the measurement.Also, as shown above, each resin composition was kneaded separately and then left for 10 minutes before being measured by hand. The usable strength is determined by molding the product by hand molding, removing it from the mold 24 hours after the manual molding process, and measuring the usable strength.

[Table] As is clear from these results, the composition of the present invention has a higher initial strength (rising strength) than conventional unmodified phenol formaldehyde resins when applied to a self-hardening mold binder. ), that is, the initial strength is remarkable, and the final strength (strength after 24 hours) is very high.In addition, it is known that it is a binder with excellent workability.

Claims (1)

[Claims] 1. Using an alkali metal and/or alkaline earth metal compound as a reaction catalyst, using phenols and aldehydes in a molar ratio of 1:1.15 to 1.65, and based on the resulting resin initial condensate, Contains as an essential component an acid-curing phenol-aldehyde resin initial condensate modified with bisphenol F obtained by modifying with 12% by weight of bisphenol F, and has a non-volatile content of 55 to 85% by weight. A self-hardening binder composition for foundry molds having a viscosity of 150 centipoise or less at 25°C.