JPS5948062B2 - How to cure binder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for curing acid-curable liquid binders such as phenolic resins, furan resins, and furfuryl alcohol.

More specifically, when these binders are used to bind or adhere powder or granular materials to produce a molded product, the hardening of the molded product is accelerated without adversely affecting the final strength of the molded product,
The present invention also relates to an improved method for curing a binder, which has the characteristic that it does not adversely affect the storage stability of each component of the binder. Conventionally, acid-curing liquid resins such as phenol resins, furan resins, and furfuryl alcohol have been used to manufacture molds, resinoid grindstones, and other molded products of powdered materials such as wood, metals, and minerals. A common method is to add a curing agent to the curing agent and cure it, but even with this method, a sufficient curing speed cannot be obtained. For example, to explain the case of caking of foundry sand when manufacturing molds, the sand temperature is increased to promote hardening, water is removed by reduced pressure, etc.
Methods such as using large amounts of hardening agents have been taken. However, there are many negative effects such as economical efficiency, complexity of operation, and deterioration in the strength of the sand mold and the accompanying decrease in surface stability, and other methods have been desired. Among these, phenolic resins have a slower curing speed than furan resins, and a curing method that can quickly develop strength has been desired in order to shorten mold removal time and improve work efficiency for small and medium-sized castings. Generally, resol type phenolic resins have poor storage stability and are known to gradually increase in viscosity through condensation polymerization. Therefore, in order to improve the curing speed, a method of adding a curing accelerator such as a phenol derivative to the binder can be considered, but although such a method can accelerate the initial curing speed to some extent, Due to the accelerating effect of the curing accelerator itself, the viscosity increases significantly during storage, making it impossible to store it stably, and surprisingly, the strength of the molded product obtained is significantly reduced. In view of the above circumstances, the present inventors have conducted various studies and examinations in order to solve these shortcomings. The inventors have discovered that the above-mentioned drawbacks can be solved all at once by adding the above ingredients to the powder material in the following order and kneading them together with a binder, thereby completing the present invention.

That is, in the present invention, when curing a binder made of an acid-curable liquid resin using a curing agent, a phenol derivative having a substituent that increases the charge density at the ortho position or distal position relative to the hydroxyl group is added in advance. The present invention relates to a method for curing a binder of powder or granular material, characterized in that the binder is added to the powder material and then the binder is added. Acid curing type binders used in the present invention include phenol type, furan type,
There are phenolfuran resins, furfuryl alcohol, etc., but all of them generally need to be low molecular weight liquids with a viscosity of 5,000 centipoise or less.

By using these binders and kneading them together with a curing agent and a curing accelerator according to the method of the present invention, curing can be effected at room temperature without particular heating. In addition, as the curing agent, it is particularly necessary to use aromatic sulfonic acid, and if necessary, an aqueous solution of this aromatic sulfonic acid or methanol,
It is also possible to use an ethanol solution or a mixture of this with a small amount of inorganic acid such as phosphoric acid or sulfuric acid added thereto. Examples of such aromatic sulfonic acids include para-toluenesulfonic acid (hereinafter abbreviated as PTS), xylene sulfonic acid, benzenesulfonic acid, naphthalenesulfonic acid, phenolsulfonic acid, and the like. Among these, PTSl xylene sulfonic acid and benzenesulfonic acid are most preferred. Further, in the present invention, as a curing accelerator, a phenol derivative having a substituent that increases the charge density at the ortho or para position relative to the hydroxyl group can be used, and specifically, for example, resorcinol, cresol,
Examples include xylenol, catechol, hydroquinone, methylenebisphenol, phloroglucinol, and preferably zorcinol, xylenol, cresol, phloroglucinol, and methylenebisphenol. In actual use, each of them may be used alone, or a mixture thereof, or a composition containing them. The amount of the phenol derivative is 0.1 to 40% by weight relative to the curing agent. It is preferable to add it to the curing agent so that it is preferably contained in an amount of 2 to 15% by weight. Further, the amount of the curing agent added is 5 to 100% by weight based on the binder. The most notable feature of the method of the present invention is that the phenol derivative, which is a curing accelerator, is not added to the binder but is added to the curing agent, and that such curing agent is first added to the powder material. Then, a binder is added and kneaded.

By such a method, the initial hardening speed when producing a molded product can be significantly improved, and, for example, in the case of mold production, the time required for demolding can be significantly shortened and the mold can be used efficiently. Moreover, the final strength and surface stability of the molded product after a day or night of use are not deteriorated, and the binder itself is not adversely affected, making it possible to store the molded product stably for a long period of time. In this case, when the phenol derivative is added to a binder, the initial curing speed is improved to some extent, but the final strength is reduced, and the viscosity of the binder itself increases significantly when stored for a long period of time. However, the method of adding a binder to the powder material and then adding a curing agent and kneading it does not provide sufficient final strength.

Next, the present invention will be explained with reference to Examples.

Note that parts and percentages in the examples are based on weight. Example 1 A predetermined amount of a curing agent composition consisting of a 70% aqueous solution of PTS, which is a curing agent, and metacresol, which is a curing accelerator, was added to 1000 parts of sand (Freemantle) and kneaded for 1 minute. Free phenol 4%, free formaldehyde (0.4%, viscosity 4000ps125℃
] was added in a predetermined amount and kneaded for 1 minute.

This was quickly packed into a mold and a test piece of 50m11LφX50mm was made. This was removed from the mold at predetermined intervals and the resistance pressure was measured. Table 1 shows the effect of adding metacresol. Example 2 A curing agent composition consisting of the phenolic resin and xylene sulfonic acid curing agent [80% xylene sulfonic acid aqueous solution] used in Example 1 and the curing accelerator resorcinol was used in 1000 parts of Freemantle sand. The resistance pressure was measured using a test piece made by the method of Example 1.

As in Example 1, the effect of accelerating the initial hardening due to the addition of resorcinol was observed compared to the case without the addition.

Example 3 Table 3 shows the results of the anti-pressure test of a test piece prepared according to the method of Example 1 using resorcinol instead of metacresol as a curing accelerator.

Addition of 1% resorcinol to the binder already has a curing accelerating effect, and as the amount added increases, the accelerating effect increases, but it is added due to factors such as solubility in the curing agent and economic efficiency. The upper limit of the amount is determined by each individual. Example 4 Test pieces were made according to the method of Example 1, and the effects of various additives as curing accelerators were investigated.

The results are shown in Table 4. Example 5 The effect of accelerating the initial hardening of foundry sand was investigated when a phenol-modified furan resin [composition containing 61% free furfuryl alcohol] was used as a binder.

The results are shown in Table-5. The test piece was prepared in accordance with Example 1. As is clear from this table, an early curing accelerating effect was observed for the phenol-modified furan resin composition.

Example 6 The effect of accelerating the initial hardening of foundry sand was investigated when a urea-formaldehyde-modified furan resin composition (synthesized according to the method described in Japanese Patent Publication No. 51-26122) was used as a binder.

The results are shown in Table-6. A test piece for measurement was made according to Example 1. Example 7 Regarding a curing agent to which a curing accelerator was added, the influence of the period after addition of the curing accelerator on the curing action was investigated.

That is, 5% furfuryl alcohol was added to the phenolic resin used in Example 1 as a binder,
As a curing agent composition, a phenol derivative immediately after being dissolved in a PTS solution or one that had been left for 3 months after dissolution was used, and the flotation sand was hardened according to the method of Example 1 to prepare a test piece. Pressure was measured. The results are shown in Table-7. From this result, no change was observed in the curing effect even after a long period of time after adding the curing accelerator to the curing agent. Comparative Example 1 Changes in viscosity over time were investigated with and without adding resorcinol, a curing accelerator, to a resol type phenolic resin synthesized according to Example 1.

The results are shown in Table 8. As is clear from this, when the phenol derivative is added to the resin, the viscosity of the resin increases rapidly. That is, it significantly reduces storage stability, which is undesirable. Comparative Example 2 The effects of adding resorcinol as a curing accelerator to the binder side and to the curing agent side were investigated on the resistance pressure.

The results are shown in Table-9. Although no significant difference was observed between the two in terms of the initial curing accelerating effect, a large difference in resistance pressure was observed over time. In other words, as shown in Table 9 below, the anti-pressure after 24 hours is approximately 2 to 2 times higher when resorcinol is added to the curing agent side than when it is added to the binder side.
．． It's 5 times more expensive. Creation of test piece is Example 1
I followed. Comparative Example 3 Binder 19 made of phenolic resin used in Example 1
A curing agent composition 9.09 was prepared by adding a curing accelerator resorcinol 1.09 to a 70% aqueous solution of PTS 9.09, and a curing agent composition 4.59 was added to Fremantle sand 10009 for 1 minute. Knead and then add binder 9.5
9, kneaded for 1 minute, packed this into a mold, and made a test piece as sample A. Fremantle sand 1000
First, 9.59% of the binder was added to 9.5% of the curing agent and kneaded for 1 minute, and then 4.59% of the curing agent composition was added and kneaded to form a test piece, which was designated as Sakare B.

The counter pressure of these samples was measured in the same manner as in Example 1, and the results are shown in Table 10. That is, although the method of Sample B improves the initial curing speed, sufficient final strength cannot be obtained. Example 8 Resistance pressure was measured using a test piece prepared according to the method of Example 1 using furfuryl alcohol as a binder and a 70% ethanol solution of PTS as a hardening agent.

Claims (1)

[Claims] 1. When curing a binder made of an acid-curable liquid resin using a curing agent, a phenol derivative having a substituent that increases the charge density at the ortho or distal position relative to the hydroxyl group is added in advance. A method for curing a binder of a powder or granular material, characterized in that the hardener is added to a powder material, and then a binder is added. 2 The binder made of acid-curing liquid resin has a viscosity of 5,000
2. A method for curing a powder or granular material binder according to claim 1, which is a liquid phenol resin, furan resin, or furfuryl alcohol or a mixture thereof having a centiboise or less. 3. A method for curing a binder for a powder or granular material according to claim 1, wherein the curing agent is an aromatic sulfonic acid or a compound containing aromatic sulfonic acid as a main component. 4. A method for curing a binder for powder or granular material according to claim 3, wherein the curing agent is paratol sulfonic acid, xylene sulfonic acid, benzenesulfonic acid, or an aqueous solution thereof. 5. The method for curing a powder or granular material binder according to claim 1, wherein the phenol derivative is any one or a mixture of two or more of resorcinol, xylenol, cresol, hydroquinone, phloroglucinol, or methylenebisphenol. 6 The amount of phenol derivative added is 0.1 to the hardening agent.
6. A method of curing a powder or granular material binder according to claim 5, wherein the content is 41% by weight. 7 The amount of curing agent used is 5 to 100% by weight based on the binder.
A method for curing a powder or granular material binder according to claim 4.