JPH062298B2 - Binder resin composition for foundry sand - Google Patents

Description

The present invention relates to a binder resin composition for foundry sand.
More specifically, the present invention is a so-called acid-curable method for producing a mold by adding an acid-curable resin and an oxidizing agent to a refractory granule and kneading the mixture and molding it into a mold and then injecting sulfur dioxide in a gaseous or aerosol form. The present invention relates to an improved binder resin composition for foundry sand used in a cold box.

[Conventional technology]

Conventionally, in order to manufacture a mold at medium to high speed, a cloning method in which a so-called coated sand obtained by coating a granular refractory with a phenol resin is heat-cured to manufacture a mold is widely used.

However, in order to save energy during mold manufacturing, mold production speed, and further improve the quality of the mold and casting, the cold box mold manufacturing method in which it is cured at room temperature with a gaseous or aerosol substance is a mold manufacturing method that replaces the cloning method. It has been seriously tried to be introduced in the foundry industry.

In the cold box method, an acid-curable cold box in which an acid-curable resin typified by a furan-based resin is cured by sulfur dioxide using a peroxide as an oxidizing agent, and a polyol and polyisocyanate are mixed with a tertiary amine in an aerosol form. There is a urethane cold box that cures as a catalyst.

Among them, the mold using urethane cold box is
There are drawbacks such as poor disintegration property of the casting sand during the production of castings, and sand casting, scooping, pinholes, soot defects and other casting defects.

On the other hand, the acid-curing cold box has been rapidly attracting attention in recent years as a method for solving the above-mentioned problems.

[Problems to be solved by the invention]

The acid-curing cold box has many advantages over the conventional cloning method and urethane cold box method, such as energy saving at the time of mold production, high mold production speed, excellent quality of the produced mold, and excellent casting quality. It is also desired to solve these problems to be improved and further improve these excellent characteristics.

In particular, the present invention relates to a binder resin composition having a significantly improved mold production rate and improved storage stability.

Conventionally, automatic molding machines have been used to manufacture medium and large quantities of molds, and acid-curable resin and peroxide are added and kneaded to the refractory granular material to coat the surface of the refractory granular material, pneumatic pressure, etc. Automatically fills, molds, and takes out continuously in a cycle of less than 1 minute. Therefore, in the cold box method, in order to further improve mold productivity,
It is desired to improve the initial strength so that the mold can be mechanically handled within 1 minute after molding.

Factors that improve the mold production rate in the acid-curable cold box method include factors in the molding technology such as the gassing method and factors in the binder such as reaction rate. Various studies have been made in terms of molding technology,
There are many restrictions due to differences in molds and molding machines. Therefore, under the present circumstances, there is a strong demand for improvement from the viewpoint of the binder with respect to the above problems.

[Means for solving problems]

As a result of intensive studies, the present inventors have found that in the acid-curable cold box method, an alkali metal, an alkaline earth metal, or a mixture thereof (hereinafter referred to as alkali metal) contained in a resin composition mainly containing an acid-curable resin. And / or alkaline earth metal) and the curing rate and storage stability are closely related to each other, and the content of alkali metal and / or alkaline earth metal in the resin composition is clarified. It was found that the curing rate is significantly improved and the storage stability is also improved by reducing the amount, and thus the present invention has been completed.

That is, the present invention is a binder resin composition for molding sand, which is used when molding a mold with sulfur dioxide using an acid-curable resin as a binder and a peroxide as an oxidant, which is acid-curable. A metal in a composition based on at least one resin,
The content of alkali metal and / or alkaline earth metal contained as a metal ion, a metal salt or a mixture thereof (hereinafter abbreviated as metal, metal ion and / or metal salt) per metal atom is 2% (weight basis). The same shall apply hereinafter), and a binder resin composition for foundry sand characterized by the following.

With the binder resin composition of the present invention, it is possible to significantly improve the curing speed and practically significantly increase the mold production speed with little increase in viscosity over time.

Most of the alkali metals and alkaline earth metals in the resin composition of the present invention are usually contained in the composition as a catalyst during resin production or a neutralizing agent thereof. In the acid-curable cold box method, the curing rate is greatly affected by the contents of alkali metal and alkaline earth metal in the composition. Captures sulfur dioxide, which is a reaction aid,
It has not been clarified about its action whether it exhibits an inhibitory action such as salt exchange or an effective action of peroxide, but it is significantly hardened by reducing the content to 2% or less. Speed is improved. More preferably, the content is 1% or less.

On the other hand, by simultaneously reducing the contents of the alkali metal and the alkaline earth metal in the composition, the viscosity increase with time is improved, and particularly in the case of the phenol resin and the phenol furan resin, the influence is great. Thickening with time has an adverse effect on the wettability of the binder to the molding sand and the filling property of the molding sand in which the binder is kneaded. Particularly in the cold box method, since molding sand is blown into a mold together with pressurized air to fill it, the wettability of the binder and the filling property of the kneading sand have a great influence on the mold strength.

As described above, in the acid-curable cold box method, the binder resin in which the content of the alkali metal and the alkaline earth metal in the resin composition is reduced in order to improve the curing rate without lowering the wettability and the filling property The composition is extremely important.

As the acid-curable resin in the present invention, a furan-based resin,
Phenolic resin, urea resin, melamine resin, resorcin resin, and the like, preferably furan resin,
A mixture or co-condensate of at least one selected from the group consisting of a phenol resin and a urea resin is mainly used. Further, at least one kind of conventionally known modifier may be mixed or co-condensed. Its denaturation rate is 20
% Or less is preferable. Specific examples of the modifier include coumarone / indene resin, petroleum resin, polyester, alkyd resin, polyvinyl alcohol, epoxy resin, ethylene / vinyl acetate, polyvinyl acetate, polybutadiene, polyether, polyethyleneimine, polyvinyl chloride, and poly (vinyl chloride). Acrylic ester, polyvinyl butyral, phenoxy resin, cellulose acetate,
Polymers and oligomers such as xylene resin, toluene resin, polyamide, styrene resin, polyvinyl formal, acrylic resin, urethane resin, nylon, lignin, lignin sulfonic acid, rosin, ester gum, vegetable oil, bitumen, heavy oil, cashew nut shell liquid, Natural products such as vanillin and tannins, starch, corn starch,
Glucose, sugars such as dextrin and derivatives thereof,
Resorcin residue, cresol residue, 2,2,4-trimethyl-4
-Reaction residues and by-products such as reaction by-products of (hydroxyphenyl) coumarone and isopropenylphenol, reaction by-products of terephthalic acid and ethylene glycol, polyhydric alcohols such as polyethylene glycol, ketones such as acene, cyclohexanone, and acetophenone. Condensates with compounds and aldehydes, dicyandiamide, acrylamide, amino or imino compounds such as thiourea and their aldehyde condensates, furfural, aldehyde compounds such as glyoxal, and isocyanuric acid esters,
Examples thereof include ester compounds such as unsaturated fatty acid esters.

Further, the binder resin composition of the present invention may be mixed with a diluent within a range that does not adversely affect other properties in order to improve mold strength and handleability. The blending amount is preferably 20% or less. Specific examples of the diluent that can be used include aromatic hydrocarbons such as benzene and xylene, alcohols such as methanol, ethanol, and furfuryl alcohol, and ethers such as diethyl ether, anisole, and acetal, and acetone. Ketones such as methyl ethyl ketone, tetrahydrofuran,
Heterocyclic hydrocarbons such as dioxane, esters such as methyl acetate and ethyl acetate, polyhydric alcohols such as ethylene glycol and glycerin, 2-methoxyethanol, 2-
Cellosolves such as ethoxymethanol, cellosolve acetates such as 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate, 2-phenoxyethyl acetate, carbitol acetates such as diethylene glycol monoethyl ether acetate, etc. Is mentioned.

Further, a silane coupling agent may be added for the purpose of further improving the mold strength. Examples of the silane coupling agent include γ- (2-amino) aminopropylmethyldimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and γ
-Mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane and the like can be mentioned.

The time at which the binder resin composition of the present invention is added and kneaded to the foundry sand may be before or after the peroxide addition and kneading, but the addition of peroxide from the viewpoint that the kneading sand has a longer pot life. Before kneading is preferable.

To produce a mold, as a refractory granular material with the binder according to the present invention, in addition to silica sand having silica as the main component, zircon sand, chromite sand, olivine sand, etc. are used.
It is not particularly limited.

As the peroxide used as the oxidizing agent, ketone-based, aromatic-based organic peroxides and inorganic peroxides such as hydrogen peroxide are used, but the peroxides are not particularly limited.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples.

Examples 1 to 4 and Comparative Examples 1 to 2 Phenol and paraformaldehyde were reacted by a conventional method under various catalytic amounts of NaOH basic catalyst, and the viscosity of the reaction solution was changed.
After the reaction was completed at 1000 cps at 25 ° C, the mixture was neutralized to pH 7 with paratoluenesulfonic acid and adjusted with methanol so that the viscosity of the composition at 25 ° C was about 300 cps. A resin composition having a high Na content was obtained.

The resin composition thus obtained was allowed to stand at 35 ° C. for a predetermined number of days, the viscosity at 25 ° C. was measured, and the bending strength was also measured by the following method. That is, 1.2 parts by weight of the obtained resin composition was added to 100 parts by weight of Australian flattery sand and kneaded, and M
25 × 2 of kneaded sand that was kneaded by adding 0.4 parts by weight of EKPO peroxide
Blow and fill the mold of 5 × 250 m / m with pressurized air, then blow the sulfur dioxide gas into the mold filled with the kneading sand to mold the mold test piece, and after blowing the sulfur dioxide gas, 30 The mold bending strength after 2 seconds was measured. The results are shown in Table-1.

Examples 5 to 11 and Comparative Examples 3 to 4 Furfuryl alcohol, phenol and paraformaldehyde were reacted by a conventional method under various catalytic amounts of KOH or Ba (OH) ₂ basic catalyst to synthesize a phenol furan resin.
After the reaction was completed when the viscosity of the reaction solution reached 1000 cps at 25 ° C., it was neutralized to pH 7 with an aqueous paratoluenesulfonic acid solution to obtain a resin composition containing K or Ba as shown in Table 2. It was

1.2 parts by weight of the obtained resin composition was added and kneaded to 100 parts by weight of Australian flattery silica sand, and kneaded sand was added and kneaded with 0.4 parts by weight of MEKPO-based peroxide to 25 × 25 × 250 m / m.
Blow and fill the mold with pressurized air, then blow the sulfur dioxide gas into the mold filled with the kneading sand to mold the mold test piece, and bend the mold 30 seconds after blowing the sulfur dioxide gas. The strength was measured. The results are shown in Table-2.

[Effects of the Invention] As is clear from this example, in the acid-curable cold box method according to the present invention, an alkali metal and / or an alkali metal contained in a resin composition mainly containing at least one acid-curable resin and / or By reducing the content of the alkaline earth metal, the curing rate can be remarkably improved and at the same time the storage stability can be improved and the productivity of the mold can be significantly improved.

Claims (3)

[Claims] 1. A binder resin composition for molding sand, which is used when molding a mold with sulfur dioxide using an acid-curable resin as a binder and a peroxide as an oxidant, which is an acid-curable resin. 2% by weight per metal atom of an alkali metal, an alkaline earth metal or a mixture thereof, which is contained as a metal, a metal ion, a metal salt, or a mixture thereof, in a composition mainly containing at least one of A binder resin composition for foundry sand, characterized in that: 2. The composition according to claim 1, wherein the content of the alkali metal, alkaline earth gold layer or a mixture thereof per metal atom is 1% by weight or less. 3. The alkali metal is at least one selected from the group consisting of lithium, sodium or potassium, and the alkaline earth metal is at least one selected from the group consisting of magnesium, calcium, strontium or barium. The composition according to claim 1 in the range.