JPH02133142A - Binder composition for casting mold - Google Patents

Abstract

PURPOSE:To obtain the casting mold having high strength by forming a phenolic resin of a resol type phenolic resin, the catalyst of which is lithium hydroxide. CONSTITUTION:The phenolic resin of the binder compsn. used for a cold curing type molding method using the phenolic resin and org. ester is formed of the resol type phenolic resin, the catalyst of which is the lithium hydroxide. The resol type phenolic resin consisting of the lithium hydroxide is usable as the resol type phenolic resin, the catalyst of which is the hydroxide of other alkaline metals. This resin additionally accelerates curing. The casting mold which has high strength and contains less blowhole defects is, therefore, obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a binder composition that has excellent mold strength and is used in a cold-curing mold making method.

[Prior art]

Room temperature curing mold forming methods include methods using various organic or inorganic binders.

A mold using an inorganic binder has poor sand disintegration properties after casting, and it is difficult to recover the sand.

As a modeling method using an organic binder, there is a method in which a urea-modified furan resin or a resol type phenol resin is used with a strong acidic substance such as xylene sulfonic acid as a hardening agent. Although this method has good disintegration properties of the casting after casting, it has the disadvantage that the sulfonic acid group in the hardening agent decomposes during casting and generates sulfur dioxide gas, etc., which worsens the working environment.

Another method using an organic binder is a modeling method in which a benzylic ether type phenol resin and a polyisocyanate liquid are hardened with amines, which shortens the molding time and has good workability, but the nitrogen content caused by the polyisocyanate increases. becomes nitrogen gas during casting, which tends to cause pinholes in the casting.

Further, as a method that does not contain nitrogen, a mold forming method using a resol type phenol resin and an organic ester as a binder is disclosed in Japanese Patent Publication No. 61-43132 and Japanese Patent Publication No. 61-37032. However, this method has a problem in that the obtained mold has low strength, requires a large amount of binder, and its uses are limited.

[Purpose of the invention]

As a result of various studies on phenolic resins for mold making methods that use organic esters as curing catalysts, the present inventor found that resol type phenolic resins synthesized using lithium hydroxide as catalysts are particularly effective in obtaining molds with excellent strength. I got it.

Furthermore, based on this knowledge, we proceeded with studies and completed the present invention.

[Structure of the invention]

The present invention provides a binder composition for use in a cold-curing mold forming method using a phenolic resin and an organic ester,
A binder composition for molds, wherein the phenol resin is a resol type phenol resin using lithium hydroxide as a catalyst.

The phenol resin used in the present invention is preferably phenol alone, but alkyl-substituted phenols such as cresol and xylenol, and polyhydric phenols having two or more hydroxyl groups such as catechol and resorcinol can also be used in combination.

The formaldehyde used in the present invention is formalin, paraformaldehyde, trioxane, etc., and the molar ratio of formaldehyde to phenol is 0.5 to 1.
It is 3.0.

The molar ratio of lithium hydroxide used as a catalyst to phenol is 0.2 to 1.0. If the molar ratio of lithium hydroxide is less than 0.2, a mold with high strength cannot be obtained, and if it exceeds 1.0, the strength of the mold tends to decrease during storage.

Alkali metal hydroxides other than lithium, such as potassium hydroxide and sodium hydroxide, can be used in combination with lithium hydroxide.

Furthermore, by adding and mixing silane coupling agents such as γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane in an amount of 0.2 to 3.0% by weight, a mold with even higher strength can be obtained. .

The resol type phenolic resin using lithium hydroxide of the present invention can be used in combination with a resol type phenol resin using another alkali metal hydroxide as a catalyst.

Organic esters used as curing catalysts include methyl formate, ethyl formate, propyl formate, butyrolactone, ethylene glycol diacetate, triacetin, and the like. The organic ester can be added at the time of mixing the sand and resin, or it can be gasified and added to the mixture of sand and resin.

The ratio of organic ester to phenol resin is suitably 0.1 to 0.5 in terms of weight ratio. If it is less than 0.1, the curing of the phenol resin will be insufficient, and if it exceeds 0.5, the degree of curing will not increase.

As the foundry sand, silica sand, zircon sand, chromite sand, oripin sand, and recycled sand thereof can be used.

The appropriate weight ratio of the resin and organic ester to the foundry sand is 0.001 to 0.02.

〔Effect of the invention〕

According to the present invention, a mold with high strength and few gas defects can be obtained, so it is extremely suitable as an industrial mold making method.

[Example] Hereinafter, the present invention will be explained with reference to Examples. The invention is not limited by the examples. Further, "parts" and "%" shown in Examples, Comparative Examples, and Application Examples are all parts by weight and weight %.

11 Add phenol 100 to a reaction vessel equipped with a condenser and stirrer.
0 parts and 153 parts of lithium hydroxide were charged and heated to 60°C.

Then, 1725 parts of 37% formalin was added over 30 minutes. The temperature of the reaction solution was raised to 75-80°C, and the reaction was carried out until the resin viscosity reached 2.2-2.7 poise/25°C.

After reaching a predetermined viscosity, it was quickly cooled to below 30°C, and 30 parts of γ-aminopropylethoxysilane was added and mixed to obtain 2900 parts of a resol type phenolic resin with a viscosity of 2.6 boids/25°C. .

11. Phenol 100 in a reaction vessel equipped with a condenser and a stirrer.
0 parts and 1725 parts of 37% formalin were charged and heated to 60°C.

Next, 715 parts of a 50% potassium hydroxide aqueous solution was added over 30 minutes, and the temperature of the reaction solution was increased to 75 to 80°C.
After the reaction was carried out until the resin viscosity reached 0.8-1.2 voids/25°C, 250 parts of water was removed under reduced pressure of 70 Torr.

Thereafter, the temperature was quickly cooled to below 30°C, 32 parts of γ-aminopropyltriethoxysilane was added and mixed, and the viscosity was 3.
．． 0 voids/25℃ resol type phenolic resin 320
I got 0 copies.

[3000 parts of Fremantle silica sand and 15 parts of triacetin were put into a table-top mixer for previous products, and after mixing for 30 seconds, 60 parts of each of the resins of Examples or Comparative Examples were added and mixed for 60 seconds to create mixed sand. was prepared.

Immediately after mixing, the blended sand was placed in a wooden mold having a shaped part with a diameter of 50 mm and a height of 50 mm, and the mold was struck three times with a plastic hammer, and the excess sand was removed to smooth the upper surface of the shaped blended sand.

After the mixed sand had hardened in the wooden mold, the mold was taken out and the compressive strength was measured.

The results are shown in Table 1.

Table 1 As shown in Table 1, the binder composition for molds of the present invention provides molds with high strength.

Claims (2)

[Claims] (1) A binder composition used in a cold-curing mold making method using a phenolic resin and an organic ester, wherein the phenolic resin is a resol type phenolic resin using lithium hydroxide as a catalyst. binder composition for use. (2) The binder composition for molds according to claim 1, wherein the molar ratio of lithium hydroxide to the phenolic resin is 0.2 to 1.0.