JPS61235034A - Binder composition for casting mold - Google Patents

Abstract

PURPOSE:To improve the curing speed, strength, etc. of a casting mold by forming a compd. having >=1 aldehyde groups in a molecule of a saccharide, etc. then subjecting the compd. to the reaction with an acid-setting resin, etc. CONSTITUTION:The saccharide such as glucose and starch are oxidized by using an oxidizing agent such as periodic acid or lead chromate to form the compd. contg. >=1 aldehyde groups having high reactivity in the molecule. Such compd. is mixed with or brought into reaction with the acid-setting resin at 2-50wt% ratio, by which the binder compsn. for a casting mold is obtd. The curing speed of the casting mold is increased by the incorporation of the aldehyde having high reactivity in the binder curing reaction in the stage of molding when such binder is used. The surface stability and strength are further improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improved self-hardening binder composition for molds.

[Conventional technology and problems]

It is a well-known fact that aromatic dialdehyde is mixed with furfuryl alcohol or aromatic alcohol and used as a binder for molds to obtain high strength (Japanese Unexamined Patent Application Publication No. 1983-1999).
124543). However, aromatic dialdehydes have a problem in solubility in furan resins. Furthermore, aromatic dialdehydes are difficult to produce and are problematic for general use.

Furthermore, although it is a well-known fact that tl [or starches, etc.] can be used as a furan-based binder, there is a drawback that the curing speed and mold strength are reduced.

[Means for solving problems]

The present inventors have conducted intensive research to improve the curing speed and mold strength reduction caused by sugars. By mixing or reacting a compound having one or more aldehyde groups in the molecule with an acid-curing resin such as a furan-based resin or a phenol-based resin, the curing speed is fast and the mold is The inventors have discovered that a binder composition for molds with excellent surface stability and high strength can be obtained, leading to the present invention.

That is, the present invention provides a method for use in acid-curing molds, which is made by mixing or reacting an acid-curing resin with a compound having one or more aldehyde groups in the molecule obtained from saccharides or starch. A binder composition is provided.

The compound having an aldehyde group used in the present invention is preferably mixed or reacted in an amount of 2 to 50 parts by weight, more preferably 5 to 20 parts by weight, based on 100 parts by weight of the acid-curing resin.

Furthermore, for the mold binder composition of the present invention, γ-aminopropyltriethoxysilane, γ-(2-aminoethyl)
Various known silane coupling agents such as aminopropylmethyldimethoxysilane or water may be added in an amount of 1 to 20% by weight, preferably 5 to 15% by weight.

In addition, when oxidizing sugars, starch, etc., not only aldehyde groups but also ketone groups and carboxyl groups are generated at the same time. Although the inclusion of these by-products does not particularly significantly adversely affect the curing rate or mold strength, it is preferable that the amount of these ketone groups and carboxyl groups produced is 30 equivalent % or less. Moreover, it is preferable that there are two or more aldehyde groups.

Examples of class IIi and starches used in the present invention include monosaccharides such as glucose, galactose, sucrose, fructose, and maltose;
Small #Ms, polysaccharides, etc., dextrin, soluble starch,
Any sugar or starch may be used, including natural starches such as corn starch, sweet potato starch, rice starch, and wheat starch, and modified starches. In addition, the oxidizing agents used to oxidize these sugars and starches include periodic acid, lead tetraacetate, chromic acid,
Hydrogen peroxide, nitric acid, oxygen, etc. are used.

〔Effect of the invention〕

In the present invention, one or more highly reactive aldehyde groups are added in the molecule obtained by oxidizing a compound containing one or more α-diols in the molecule, such as Group III or starch. By mixing or reacting the contained compound with an acid-curing resin, the curing speed can be increased by incorporating the highly reactive aldehyde into the curing reaction in the binder curing reaction during mold making. A mold with high mold strength and excellent surface stability can be obtained.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples. In the examples, furan resin was used as the acid-curable resin.

Production Example 1 A mixed aqueous solution of 50 parts by weight of periodic acid and 200 parts by weight of water was placed in a beaker, 40 parts by weight of cornstarch was added thereto, stirred and reacted, filtered and washed with water to obtain the desired compound (^
) was obtained.

Examples 1 to 4, Comparative Example 1 At 10°C, 0.4% of a 75% aqueous solution of para-toluenesulfonic acid was added as a curing catalyst to 100 parts by weight of foundry sand.
After adding parts by weight and mixing for 1 minute, 1.0 parts by weight of a binder composition prepared by mixing and dissolving the above compound (^) in the acid-curing resin at the compounding ratio shown in Table 1 was added and further mixed for 1 minute. . A test piece of 50 mmφ x 50 mmh was prepared from this kneaded sand, and its mold strength and surface stability were measured.

The results are shown in Table 1. Moreover, a system in which compound (A) was not added was shown as Comparative Example 1.

The strength of the test piece was determined by measuring the compressive strength, and the surface stability was determined by placing the test piece on a 10-mesh sieve, treating it with a rotary tube vibrator for 2 minutes, and determining the weight ratio before and after the treatment.

Table 1 Examples 5 to 8, Comparative Examples 2 to 6 At 25°C, 0.4% of a 75% aqueous solution of para-toluenesulfonic acid was added as a curing catalyst to 100 parts by weight of foundry sand.
After adding 5 parts by weight and mixing for 1 minute, 1.0 parts by weight of a binder composition prepared by mixing and dissolving the above compound (A) in the acid-curing resin at the mixing ratio shown in Table 2 was added, and further mixed for 1 minute. did.

A test piece of 50 mmφ x 50 mmb was prepared from this kneaded sand, and its mold strength was measured.

The results are shown in Table 2. Moreover, a system in which compound (A) was not mixed and a system in which sugar was mixed and dissolved were shown as Comparative Examples 2 to 6.

Table 2 As is clear from Table 2, by mixing and dissolving compound (A), both the curing speed and the 24-hour standing strength are significantly improved.

Production Example 2 A mixed aqueous solution of 50 parts by weight of periodic acid and 200 parts by weight of water was placed in a beaker, 40 parts by weight of dextrin was added thereto, stirred and reacted, filtered and washed with water to obtain the target compound (B).
I got it.

Examples 9 to 12, Comparative Example 7 At 25°C, 0.4% of a 75% aqueous solution of para-toluenesulfonic acid was added as a curing catalyst to 100 parts by weight of foundry sand.
After adding 5 parts by weight and mixing for 1 minute, 1.0 parts by weight of a binder composition prepared by mixing and dissolving the above compound (B) in the acid-curing resin at the mixing ratio shown in Table 3 was added, and further mixed for 1 minute. did.

A test piece of 50 m + *φ x 50 mn + h was prepared from this kneaded sand, and its mold strength was measured.

The results are shown in Table 3. Moreover, a system in which compound (B) was not mixed was shown as Comparative Example 7.

Table 3 Production Example 3 A mixed aqueous solution of 50 parts by weight of periodic acid and 200 parts by weight of water was placed in a beaker, 40 parts by weight of glucose was added thereto, stirred and reacted, and then filtered to obtain the target compound (C). Ta.

Examples 13 to 16, Comparative Example 8 At 25°C, 0.4% of a 75% aqueous solution of para-toluenesulfonic acid was added as a curing catalyst to 100 parts by weight of foundry sand.
After adding 5 parts by weight and mixing for 1 minute, 1.0 parts by weight of a binder composition prepared by mixing and dissolving the above compound (C) in the acid-curing resin at the mixing ratio shown in Table 4 was added, and further mixed for 1 minute. did.

A test piece of 50 mttrφ×50 mmb was prepared using any of the mixed sands, and the mold strength thereof was measured.

The results are shown in Table 4. Moreover, a system in which compound (C) was not mixed was shown as Comparative Example 8.

Table 4

Claims (1)

[Claims] 1. A binder composition for acid-curing molds, which is made by mixing or reacting an acid-curing resin with a compound having one or more aldehyde groups in the molecule obtained from saccharides or starch. thing.