JPS5934456B2 - Binder for foundry sand - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an acid-curing binder composition for foundry sand.

Furthermore, the present invention relates to a binder for foundry sand having a long shelf life, which is made by adding a certain type of silane coupling agent to an acid-curable resin.

Phenol resins, furan resins, urea resins, melamine resins, and their modified products have been known as binders used in the production of molds and cores, and modified products with furfuryl alcohol are particularly widely used for this purpose. It is in use.

However, these binders have various drawbacks that occur during casting.

For example, when bonded with urea resin or urea furan resin, pinholes and blowholes may occur due to the decomposition of the resin and the gas generated at that time.

Phenol resins are excellent in this respect, but due to their low terminal strength and brittleness, mold mesh and core breakage sometimes occur, which poses many practical difficulties.

In order to improve this, if the amount of resin added is increased, a large amount of gas is unavoidably generated, causing a bad odor, and furthermore, it becomes an economical problem.

It is known that addition of small amounts of silane compounds is effective in solving these difficulties.

For example, according to Japanese Patent Publication No. 43-15161, the silane compound has the general formula [where R1 is a lower aliphatic group, and the activity of phenol resin, urea resin, melamine resin, furan resin, or a mixture thereof, which is cured with acid. Those having the ability to react with groups, such as amine groups, epoxy groups, mercapto groups, hydroxy groups, carbo lower alkoxy groups, hydroxy lower alkylamino groups such as dihydroxyethyl, amino lower alkylamino groups such as aminoethylamino, or A lower alkenylcarboxylene group such as acrylate or methacrylate, or an alkylene group having 2 to 6 carbon atoms having lower alkenyl such as vinyl, and R is a lower alkyl group such as methyl or ethyl, or a lower alkylene group such as methoxyethyl. 0.1 of a silane compound represented by alkoxy lower alkyl group
The strength of molds and cores manufactured by the room temperature self-hardening method using resins manufactured with ~3% by weight can be increased by 100 to 400% compared to cases where the silane compound is not used. Although this is a possible and useful technique, there are drawbacks to the storage stability of the resin.

In other words, resins to which these silane compounds have been added exhibit sufficient effects immediately after addition, but the effects gradually decrease during preservation and storage, and eventually the effects of the addition of silane compounds disappear. It is.

Under such circumstances, the present invention solves this difficulty without impairing the effect of adding a silane compound.

That is, the present invention solves these drawbacks by adding a silane coupling agent represented by the general formula to an acid-curing resin instead of the silane compound exemplified in conventionally known techniques.

However, in the formula, R and R2 are groups selected from the group consisting of alkyl, aryl, substituted aryl, and heteroalkyl groups, and may be the same or different.

R3 is a short chain alkylene group having about 2 to 6 carbon atoms;
and X is amine, epoxy, mercapto, ureido,
A reactive group selected from the group consisting of glycidoxy or amine lower alkylamino groups.

Examples of the silane coupling agent of the present invention include γ-aminopropylethyljethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-mercaptopropylethyljethoxysilane, γ-mercaptopropylmethyldimethoxysilane, NΩβ- Aminoethyl γ-amino/propylethyljethoxysilane, γ-
Examples include aminopropylphenyldiphenoxysilane, γ-ureidopropylethyljethoxysilane, N)β-aminoethyldiγ-aminopropylmethyldimethoxysilane, and the like.

As a preferable silane coupling agent, in the above general formula, R1 and R2 are an alkyl group having 1 to 3 carbon atoms, R3 is an alkylene group having 2 to 4 carbon atoms, and X is an amino group or Mention may be made of silane compounds having an aminoalkylamino group having 2 to 4 carbon atoms.

More preferred silane coupling agents are γ-aminopropylethyljethoxysilane, N-(β-aminoethyl)-
γ-aminopropylmethyldimethoxysilane.

The amount of the silane coupling agent used in the present invention is usually 0.015 to 1.5% by weight in the binder, preferably 0.015 to 1.5% by weight.
．． 0.05 to 0.5% by weight.

As the resins used in the present invention, furan resins, phenolic resins, furfuryl alcohol, urea resins, each singly or in combination, are effective, and those used in general acid-curing binders for foundry sand are particularly effective. Furanurea resin or furanphenol resin produced by adding furfuryl alcohol is preferably used.

Further, those resins modified with urea, phenol, and furan are included in the resins according to the present invention.

Due to the effect of the silane coupling agent of the present invention, the binder of the present invention can reduce the amount of binder added in castings without compromising mold strength, compared to binders made of corresponding types of resins used up to now. It is possible to reduce the amount of gas by 50 to 100% compared to sand, in other words, it is possible to reduce the amount of gas generated during casting, and therefore it is possible to greatly reduce casting defects caused by it, and it is also possible to reduce costs. Ta.

Furthermore, compared to the technology disclosed in Japanese Patent Publication No. 43-15161, the present invention has less decrease in the effect caused by the silane compound during storage and preservation of the binder composition, and is extremely useful in different industries. It's technology.

Generally, to manufacture molds and cores using the present composition,
It is manufactured by kneading refractory particles such as silica sand, zircon sand, chromite sand, etc. together with a hardening agent.

Curing agents include known inorganic and organic acids (for example, inorganic acids include aqueous or non-aqueous solutions such as sulfuric acid and phosphoric acid; examples of organic acids include benzenesulfonic acid, toluenesulfonic acid, Typically, an aqueous solution or a non-aqueous solution of a sulfonic acid such as xylene sulfonic acid is used, but the solution is not particularly limited thereto.

Acid-curable binder compositions modified with silane coupling agents according to the present invention have extremely long shelf lives.

While the shelf life of acid-curing binders modified with conventionally known silane compounds due to the effect of silane was about 2 to 3 months at most, The shelf life of acid-curing binders is 2 to 5.
Furthermore, when making a mold using a binder that has been stored for the same period of time, the silane compound-modified binder of the present invention can be It can be reduced by about 50 to 100% by changing the amount of binder added.

This means that it is possible to reduce the cost of making a mold, and furthermore, it is possible to reduce the amount of gas generated during casting, which is useful for reducing casting gaps caused by generated gas.

As described above, the present invention can be said to be an extremely useful invention for molds and casting, as it has greatly improved the sustainability of the effect due to the addition of a silane coupling agent to the binder compared to conventionally known techniques.

The present invention will be further explained in detail with reference to Examples below.

In addition, in the examples, [parts 1] are all "parts by weight." Example 1
~3 and Comparative Example 1 100 parts of 85% paraformaldehyde in 100 parts of urea,
After adding 800 parts of furfuryl alcohol and carrying out a heating reaction using 1.5 cc of 20% sodium hydroxide as a catalyst at 90°C for 1 hour using a conventional method, 5 cc of a 5% aqueous solution of para-toluenesulfonic acid was added to adjust the pH value to 5. A binder composition was produced by adding 0.3 wt% of the silane compound according to the present invention and a known silane compound to a furanurea resin prepared by adjusting the silane compound to about .1 and then heating and polymerizing it at the same temperature for 2 hours. Immediately after addition of the silane compound, and after storage for one month in a constant temperature room at 35° C., mold resistance pressure was measured using the binder composition.

The specimen for resistance pressure measurement was A at 25°C and 55% R and H.
Australian silica sand 20 with FS particle size index 39.8
00 parts and 15 parts of a 70% aqueous solution of toluenesulfonic acid were kneaded for 1 minute in advance, 30 parts of a binder was added and kneaded for 1 minute, molded into a mold of 50 mm x 50 mmφ, and measured after being left for a predetermined time.

The results are shown in Figure 1.

Examples 4 to 6 and Comparative Example 2 Phenol 315@L80% Paraformaldehyde 18
500 parts of furfuryl alcohol and 10 cc of 40% sodium hydroxide as a catalyst at 70° C. for 3 hours to react in a conventional manner. The test was conducted in the same manner as in Comparative Example 1.

The results are shown in Table 2.

Examples 7 to 9 and Comparative Example 3 Using 1 part of magnesium hydroxide as a catalyst, 100 parts of phenol and 125 parts of a 37% formalin aqueous solution were reacted by heating at 80°C for 4 hours in a conventional manner, and then the temperature was lowered to 50'C. Tests were conducted in the same manner as in Examples 1 to 6 and Comparative Examples 1 to 2, except that a phenol-formalin resin prepared by dehydrating the resin under reduced pressure until the water content became 15%±1% was used.

The results are shown in Figure 3.

Example 10 and Comparative Example 4 A furfuryl alcohol urea resin mixture having a ratio of furfuryl alcohol to a commercially available urea-formalin aqueous resin solution having a resin concentration of 75% was 9228, and a silane compound according to the present invention and a known silane were prepared. compound to resin 0.2
The storage properties of binders with varying amounts of addition such as , 0.4 and 0.6% by weight were observed.

The evaluation was carried out in the same manner as in Examples 1 to 9 and Comparative Examples 1 to 3, after storing the binder for a certain period of time, under the conditions of 25 ° C. and 50 to 60% RH. 10 parts of a 70% methanol solution of benzenesulfonic acid (instead of the 70% aqueous toluenesulfonic acid solution) was kneaded and produced, and after being left to stand for a certain period of time, the mold resistance pressure was compared.

The results are shown in Figure 4. Example 11 and Comparative Example 5 Using the binders of Example 10 and Comparative Example 4, a comparison was made by changing the amount of binder added to foundry sand.

However, the amount of silane compound added is 0.4% by weight, and the amount of silane compound added is 0.4% by weight.
The amount of binder was 10 parts, 15 parts, and 20 parts relative to 00 parts.

The amount of hardening agent was 50% by weight based on the binder, that is, 5 parts, 7.5 parts, and 10 parts, respectively.

Claims (1)

[Scope of Claims] 1 An acid-curing resin having the general formula (wherein R1 and R2 are the same or different, alkyl,
a group selected from the group consisting of aryl, substituted aryl, and heteroalkyl groups, where R3 is a short chain alkylene group of about 2 to 6 carbon atoms, and X is amino, mercapto, ureido, glycidoxy, or amino lower. A reactive group selected from the group consisting of alkylamino groups. ) An acid-curing binder composition for foundry sand with improved storage stability, which is obtained by adding a silane coupling agent represented by the following formula. 2. The binder composition according to claim 1, wherein the acid-curing resin is a furan resin, a phenol resin, a furfuryl alcohol, or a urea resin, each singly or in a mixture. 3 In the silane coupling agent represented by the above general formula, R1 and R2 are an alkyl group having 1 to 3 carbon atoms, R3 is an alkylene group having 2 to 4 carbon atoms, and X is an amine/group or The binder composition according to claim 1, wherein the binder composition is an amino lower alkylamino group having 2 to 4 carbon atoms. 4 The silane coupling agent is γ-aminopropylethyljethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-mercaptopropylethyljethoxysilane, γ-mercaptopropylmethyljethoxysilane, N-(β-aminoethylna γ-aminopropylethyljethoxysilane, γ-aminophylphenyldiphenoxysilane, γ-ureidopropylethyljethoxysilane or N-(, β-aminoethyl γ-aminopropylmethyldimethoxysilane) Binder composition according to item 1 or 3. 5 The amount of the silane coupling agent added is 0.015 to 1.
．． 5% by weight of the binder composition according to claim 1. 6 The amount of silane coupling agent added is 0.05 to 0.
5% by weight of the binder composition according to claim 1.