JPS62142048A - Production of acid curing type organic self-curing sand - Google Patents

Abstract

PURPOSE:To prevent casting defects, to reduce the cost of casting and to improve working environment by adding and mixing an acid curing agent to and with org. binder-coated molding sand formed by adding the org. binder to the molding sand. CONSTITUTION:This process is applied to the acid curing type org. self-curing sand of >=5ml/50g, more preferably 10ml/50g acid consumption. A phenolic resin, modified phenolic resin, furan resin or modified furan resin which cures at a room temp. when mixed together with the acid curing agent is used for the org. binder and such binder is added to the molding sand to coat the molding sand. The acid curing agent prepd. by adding a methanol or ethanol to an aq. soln. of an inorg. acid or arom. sulfonic acid is then added and mixed to and with such molding sand. The cost of casting and casting defects are reduced by producing the molding sand in the above-mentioned manner.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing acid-curing organic self-hardening sand used for making molds. In more detail,
The present invention is particularly advantageous when using foundry sand that consumes a large amount of acid.
The company patents a method for producing acid-curing organic self-hardening sand that has significantly improved hardening performance.

Conventional technology Conventionally, acid-curing organic self-hardening sands used for making molds at room temperature are usually foundry sand and phenolic LQ.
The main ingredients used are organic binders such as fat, 7-run resin, and furfuryl alcohol, and acidic curing agents such as phosphoric acid and aromatic sulfonic acids. For example, first, molding sand and an acidic hardener are thoroughly mixed, and then an organic binder is added to this mixture for coating, or an organic binder and an acidic hardener are simultaneously added to the foundry sand. A method of mixing and coating is generally adopted.

However, as foundry sand, the acid consumption is 5 m (!/
When using S Og (JACT Test Method S-4, Acid Consumption Test Method for Foundry Sand), organic self-hardening sand produced according to the above method has an extremely slow curing speed.
When a mold is produced using this, in particular, problems such as poor molding and decreased productivity occur due to insufficient hardening of the inside of the mold.

Therefore, in order to solve this problem, methods such as increasing the amount of acidic curing agent or using a stronger acidic curing agent have been tried, but these methods also reduce mold cost. At present, problems such as casting defects due to rising and sulfurization of the casting, and deterioration of the working environment due to SO and gas due to thermal decomposition of the acidic hardening agent are unavoidable.

Problems to be Solved by the Invention In view of the above circumstances, the purpose of the present invention is to reduce the amount of acid consumed by 5.
The reduction in hardening speed associated with the use of foundry sand of ml-/S It is an object of the present invention to provide a method that does not involve an increase in mold cost, casting defects due to sulfurization, and deterioration of the working environment due to SO□ gas.

Means for Solving the Problems The inventors of the present invention have conducted intensive research to achieve the above-mentioned object, and as a result, when manufacturing acid-curing type Uiso Jiko Patent, we used pre-coated foundry sand with an organic binder. It was discovered that the objective could be achieved by coating and then adding an acidic curing agent thereto, and based on this knowledge, the present invention was completed.

Nineteenth, the present invention is an acid-curing type molding sand whose main components are foundry sand with an acid consumption of 5 pi/50 g or more, an organic binder, and a 1J acid hardener (in the process of manufacturing the Daijiko patent). , Acid-curing type Aisoji, which is characterized by first adding an organic binder to foundry sand to form foundry sand coated with an organic binder, and then adding and mixing an acid hardener to this. It provides a method for distributing hard patents.

The foundry sand used in Method 1 of the present invention has an acid consumption rate measured according to the foundry sand acid consumption test method IAcTAc method 5-4) established by the Foundry Technology Promotion Association Shell Mode Division. 5, zn/ 50g or more, preferably 110lN150 or more, Sx1150g
If it is less than that, the effect of the present invention will not be recognized.

Examples of such foundry sand include recycled sand containing green sand, recycled sand containing alkaline coated core sand, and C.
Recycled sand containing 02 sand, recycled sand containing heat generating sleeve residue,
Examples include recycled zirconand sand, recycled taromite sand, recycled cold box sand, recycled pepcent sand, olivine sand, and Zuker sand.

The organic binder used in the method of the present invention is one that cures at room temperature without heating by mixing with an acidic curing agent. Furan-modified 7-el resin, urea-modified phenol resin, melamine-modified phenol (
3 (modified phenol LQ such as fat) fat, furan (31 fat, phenol-modified furan resin, modified furan resin such as urea-modified 7 run 11 fat, furfuryl alcohol, urea resin, and liquid resin such as 131 fat, a mixture of these fats, etc.) In addition, the binder may contain silicone-based or nathanate-based camping agents, mold release agents such as fatty acid amide, urea, guanidino, etc. to improve adhesiveness and moisture resistance. Known substances such as formaldehyde scavengers can be added.

Examples of acid curing agents used in the method of the present invention include inorganic acids such as phosphoric acid, sulfuric acid, and Lewis acids; aromatic sulfonic acids such as p-toluenesulfonic acid, benzene or sulfonic acid, phenolsulfonic acid, and xylene sulfonic acid; or a mixture thereof. Such acid curing agents are usually used as an aqueous solution or a mixed solution containing an appropriate amount of methanol, ethanol, etc.

In addition to the above-mentioned ingredients, additives commonly used in the past, such as curing accelerators, iron sand, benzene, and wood flour, are also included in the acid-curing type patent of the present invention. It is also possible to combine the following. Examples of the curing accelerator include resorcinol, xylene/ol, catechol, cresol, bis-7er-F, and bispherol.

Function The acid-curing type organic self-hardening sand obtained by the method of the present invention has the characteristic that hardening inhibition is prevented even though foundry sand with an acid consumption of 5 zN or more is used. Although the mechanism of preventing this curing inhibition is not necessarily clear, it is inferred as follows.

That is, the foundry sand is first coated with an organic binder according to the method of the present invention, and a thin film of the binder is formed on the surface of the foundry sand, which prevents contact with the acidic curing agent added next. As a result, the neutralization reaction between the hardening agent and the surface of the foundry sand or the basic components contained therein is inhibited, and since the hardening agent is not used up, a sound hardening function is imparted. It is considered that

EXAMPLES Next, the present invention will be explained in further detail with reference to Examples and Comparative Examples. In addition, "part" and "%" written here
All values are by weight unless otherwise specified.

Example 1 and Comparative Examples 1 and 2 Norcon recycled sand (
Acid consumption 25zN150i? Particle size index (8FS) 100
) 3000 parts and phenolfuran resin, AV Light II
Put 54 parts of P100OF (manufactured by Asahi Ariisozai Kogyo Co., Ltd.) into a tabletop mixer, stir and mix for 30 seconds to obtain resin-coated sand, and then add aromatic sulfonic acid water as an acidic curing agent; 3-part AV Rai) I”13-20 (Asahi Ariisozai Kogyo (
A room-temperature self-hardening kneaded sand was prepared according to the method of the present invention, in which 22 parts of (manufactured by) Co., Ltd.) were added, mixed for an additional 30 seconds, and then taken out.

The obtained kneaded sand was immediately subjected to a large number of anti-pressure test pieces (
Diameter 50Il! I×height 5 oz. Thereafter, the mold was removed at predetermined elapsed time intervals and its strength (resistance pressure) was measured.The hardening behavior was measured based on the behavior of the initial strength (elapsed time 0.5 to 3 hours), and the final strength of the mold was measured after 24 hours. Superiority or inferiority was determined based on the strength after the test.

In addition, for comparison with the method of the present invention, conventional method A according to Example 1 was used as Comparative Example 1, except that the order of addition of the phenol furan resin and the acidic curing agent was reversed, and the phenolfuran resin and the acidic curing agent were Comparative Example 2 was the conventional method B of the pond according to Example 1 except that the agent was added and mixed at the same time. The results are also listed in Table 1.

Table 1 (Note) Mixing method (a) Inventive method Binder (b) Conventional method A Curing agent (c) Conventional method B Binder + curing agent Examples 2 to 4 and Comparative Examples 3 to 10 Room-temperature self-hardening kneaded sand was prepared according to Example 1, Comparative Example 1, or Comparative Example 2, respectively, except for using the foundry sand, organic binder, and acid hardener listed in the formulation column of Table 2. The hardening behavior of the mixed sand and the final strength of the mold were determined by the method. The results are listed in Table 2.

Effects of the invention As is clear from the above explanation, acid consumption is 5 m/11
When manufacturing acid-cured Aiso self-hardened moldings using 50g or more of foundry sand, if the method of the present invention is followed, the curing performance will be greatly improved, thereby reducing molding defects and production due to insufficient hardening inside the mold. In addition, it is not necessary to increase the amount of acidic curing agent or use a stronger acidic curing agent, which eliminates the need for increased mold costs, casting defects in castings due to sulfurization, and SO. Various problems such as deterioration of the working environment due to gas can be solved.

Claims (1)

[Claims] 1. When producing acid-curing organic self-hardening sand whose main components are foundry sand with an acid consumption of 5 ml/50 g or more, an organic binder, and an acidic hardener, first add an organic binder to the foundry sand. 1. A method for producing acid-curing organic self-hardening sand, which comprises forming foundry sand coated with an organic binder, and then adding and mixing an acid curing agent thereto.