JPS6259664A - Resin composition for organic self-curing mold - Google Patents

Abstract

PURPOSE:To provide a resin compsn. for org. self-curing molds, which has excellent curing rate, mold strength, etc. and is suitable for use as a binder for the production of molds by a negative pressure mold forming method, by blending a urea resin with a phenol-modified furan resin. CONSTITUTION:A phenol-modified furan resin having a phenol component content of 50wt% or below is prepd. by co-condensing a phenol (e.g., phenol or bisphenol A), furfuryl alcohol and formaldehyde (e.g., formalin or paraformaldehyde). 1-15pts.wt. urea resin is blended with 100pts.wt. phenol- modified furan resin to obtain the desired resin compsn. for org. self-curing molds. By adding the urea resin to the quick-curing phenol-modified furan resin, the mold strength can be improved without detriment to the quick curability.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an organic self-hardening resin composition for molds, and more specifically, it is used as a binder suitable for manufacturing molds by pressure molding. The present invention relates to an organic self-hardening resin composition.

[Conventional technology]

Conventionally, in the casting field, a method for manufacturing an organic self-hardening mold in which a mold is manufactured at room temperature by applying the self-hardening function of an organic binder using an acidic catalyst is widely known and is used in many foundries.

However, in this molding method, the filling of kneaded sand consisting of foundry sand, a binder, and an acidic catalyst into a model frame such as a wooden mold is often a manual process, and it takes a long time to harden from filling the kneaded sand to mold removal. Since it takes a long time of 15 to 60 minutes, the mold productivity cannot necessarily be said to be superior to other molding processes. In particular, for molds with a size that requires high productivity, we have recently developed a cold box that is characterized by high productivity and can manufacture molds by aerating tertiary amine or S02 gas to instantly harden the binder. Attempts have also been made to replace this method with a gas-curing mold making method, which is known as a gas-curing mold making method, but this method uses highly toxic tertiary amines, SO, gas, etc., which poses the problem of deteriorating the working environment.

However, in the production of such organic self-hardening molds, the @-type manufacturing method, which provides high productivity without impairing the working environment, that is, the method of filling the mold frame with the kneaded sand, replaces the conventional manual work. An intraocular pressure mold making method has been developed in which the material is instantly filled using the physical means of reduced pressure and then cured in a short period of about 2 to 5 minutes.

When conventional urea-furan resins, phenolic resins, etc. are used as binders in the plate pressure molding method, the curing speed is insufficient. When the acidic catalyst is increased, the curing rate is improved, but there are disadvantages such as deterioration of the working environment due to decomposed gas and a decrease in the ultimate strength of the mold (hereinafter referred to as mold strength).

Furthermore, in the case of phenolfuran resin, although the curing speed is satisfactory, it has the problem of low mold strength.

[Problem that the invention seeks to solve]

The present invention was made in view of the above-mentioned problems, and its purpose is to provide a binder that has a suitable curing speed and mold strength at the same time when manufacturing molds using the plate pressure mold making method. An object of the present invention is to provide a useful organic self-hardening resin composition for molding. [Means for solving the problems] As a result of the inventors' intensive research to solve the problems of the above-mentioned prior art, In this type of plate pressure molding method,
After the mixing sand is filled into the model frame, the removal time until the mold is taken out from the model frame, that is, the curing time is 2 to 5 minutes, compared to 15 to 60 minutes in the conventional manual method. In order to increase the production speed, we found that it is necessary to delicately adjust the pot life, which is the time during which molds can be produced without any practical problems using kneaded sand consisting of foundry sand, a binder, and an acidic catalyst. Based on this knowledge, the present inventors used a resin composition in which a specific amount of urea resin was blended with a phenol-modified furan resin as a binder in the plate pressure molding process, and found that a practical curing speed was achieved. The present invention was completed based on the discovery that the mold strength is as follows.

That is, the gist of the present invention is that the phenol component in the phenol-modified 7-run resin is 50% by weight or less), and that 1 to 15 parts by weight of the urea resin is blended with 100 parts by weight of the phenol-modified furan resin. This is an organic self-hardening mold resin composition suitable for the plate pressure mold making method. below,
The present invention will be explained in detail.

Phenols modified 7 mg used in the present invention
W is a combination of phenols and furfuryl alcohol.
It is a phenol-modified furan resin modified with 50% by weight or less of 7 enols, and 50% by weight of phenols.
Exceeding the weight is undesirable because mold strength and curing speed decrease.

Normally, phenol-modified 7-run resin is produced by, for example, condensing phenols and formaldehyde, then concentrating under reduced pressure, further adding furfuryl alcohol, mixing or co-condensing, and then further concentrating under reduced pressure if necessary.
It can be obtained by co-condensing phenols, furfuryl alcohol and formaldehyde, then concentrating under reduced pressure, adding furfuryl alcohol if necessary, mixing or co-condensing, and then concentrating under reduced pressure. It is not limited.

Further, the phenols are L types or a mixture of two or more types selected from phenol, cresol, xylenol, resorcinol, catechol, bisphenols, bisphenol A, etc., and the formaldehyde is formalin or paraformaldehyde.

The urea-based resin used in the present invention is a resin obtained by reacting urea such as urea and its derivatives with formaldehyde, or an alkyl etherified resin thereof, or a resin modified with phenol, melamine, etc. alone or in a mixture. Examples include, but are not limited to, modified resins and the like.

In addition, the blending amount is 1 to 15 parts by weight per ioo parts by weight of the phenol-modified furan resin. If it is less than 1 part by weight, the object of the present invention cannot be achieved, and if it exceeds 15 parts by weight, it will harden. Speed decreases.

The resin composition for organic self-hardening steel according to the present invention is preferably produced by blending the phenol-modified furan resin and the urea resin and stirring and mixing, since the viscosity will be lower, but the viscosity will be extremely increased. 5 as necessary if it is not enough.
The reaction may be carried out for a short time at a temperature of 0 to 70'C.

Furthermore, depending on the purpose of use, additives such as urea and other substances that have the same effect as silane cuff purin agents that are commonly used in the technical field may be used within the range that does not impede the performance of the resin composition. .

[Effect]

By adding a urea-based resin to a phenol-modified furan resin, we have established an action mechanism that improves mold strength, which is a drawback, without at least impairing the curing performance (fast curing) that is characteristic of the furan resin. Although it is not clear, the following is proposed.

The phenol-modified 7-run resin, which is characterized by rapid hardening, already begins a curing reaction during the process of cross-wire or cross-wire sand filling, so the strength achieved by the mold (mold strength) decreases.

On the other hand, the above-mentioned improvement effect can be achieved by adding a urea resin because it acts to subtly moderate the rapid curing reaction of the furan resin, causing cross-wire or cross-wire sand filling. It is thought that mold strength is imparted without impairing the curing speed, since the curing reaction is suppressed during the work process and then a rapid curing reaction is started to show the development of strength. .

〔Example〕

Examples of the present invention will be described below along with comparative examples, but
The technical scope of the present invention is not limited to these examples. In addition, the parts and parts described herein mean parts by weight and % by weight, unless otherwise specified.

Pheno-#1000F, 37% formalin 1 in a 3-day reaction flask equipped with a micro condenser, thermometer, and stirrer.
294f, 20% sodium hydroxide aqueous solution 252 was added and reacted at 90°C for 2 hours.
A resol type phenolic resin was obtained by dehydration under reduced pressure using HfAb.

Next, furfuryl alcohol 4000F was added to the obtained phenol resin, and the mixture was further reacted at 70'C for 30 minutes to obtain a phenol-modified 7-run resin (Binder A: Comparative Example 1). This binder A1001 was mixed with 2F, 6F, and 101 of the shiurea resin (trade name Niroid 22, manufactured by Mitsui Toatsu Chemical Co., Ltd.), respectively, to form the binders B, C, and D of the present invention.
(Examples 1 to 3) were prepared. Also, for comparison, binder A
Binder E (Comparative Example 2) was prepared by adding the urea resin 202 to 1002.

In addition, for each of the binders A to E, a silane coupling agent (trade name 5H6020, manufactured by Toray Silicone) was used.
0.5% was added.

Comparative Example 3 Phenol 100 (1,37% formalin 1294
F, 20% sodium hydroxide aqueous solution 252 gold case, 90
After reacting for 2 hours at 0C, 60-160 mHf A
Dehydration was performed under reduced pressure in b to obtain a resol type phenol resin. Then add furfuryl alcohol 5392,
The reaction was carried out at 70°C for 30 minutes to obtain a phenol-modified furan resin. The obtained furan resin 1002 and the urea resin 61 were blended, and the silane coupling agent (trade name 5) was added to the total amount of the furan resin and the urea resin.
Binder F (Comparative Example 3) was prepared by blending 5% of H6020).

In order to compare and contrast the performance of these binders, 5 f of a mixed solution of 1000F Freemantle sand and 80% xylene sulfonic acid and tobenzenesulfonic acid were added to a quick kneader, kneaded for 30 seconds, and then 122 Add and knead for 15 seconds,
This kneaded sand was immediately put into a mold with a hopper that could simultaneously produce nine 50φ x 50h test pieces with a vent hole at the bottom, and the mold was suction-filled for 30 seconds under a reduced pressure of 160 mHjAb. After completion of kneading, the test pieces were removed from the mold every 3 minutes, 5 minutes, and 24 hours, and the mold strength (resistance) was measured. Show the results to the front engineer.

Table - ■ [Effects of the Invention] As is clear from the above explanation, when the organic self-hardening resin composition for molding according to the present invention is used as a binder in the suction molding method, it is more effective than the conventional phenol 7 run resin. Compared to , the mold strength is greatly improved and the curing speed is practical, so the mold making cycle can be shortened and productivity can be greatly improved.

Further, since there is no need to manufacture a mold by venting highly toxic tertiary amine or SOt gas, the problem of deterioration of the working environment is also solved.

Claims (1)

[Claims] 1. 1 part by weight of urea resin per 100 parts by weight of phenol-modified furan resin whose phenol component is 50% by weight or less
An organic self-hardening resin composition for molding comprising 15 parts by weight.