JPS583744A - Recovered and reconditioned sand, microwave hardenable molding sand made of said sand and its production - Google Patents

Abstract

PURPOSE:To produce molding sand of superior microwave curing performance inexpensively by dry washing recovered sand under application of impact and frictional effect by circulation of said sand in a rotary vessel then adding a thermosetting resin thereto and kneading these. CONSTITUTION:Recovered sand is charged from a hopper 6 into a rotary vessel 1, and under circulation by rotation of the vessel 1, it is scrubbed by the impact and frictional effect of a high speed revolving agitator 4. The impurities on the surfaces of the sand grains are moderately removed by this dry washing, and the sand contg. 0.5-6% clay components and 0.3-5% carbonaceous org. materials is reconditioned. The reconditioned sand is classified, and a thermosetting resin is added at 2-5% to 100pts.wt. reconditioned sand, then these are kneaded. In this way, a large amt. of the reusable reconditioned sand is obtained in a large amt. with low energy. From this reconditioned sand, the microwave curable molding sand having uniform and quick microwave curing performance and having sufficient shell strength without addition of dielectric materials such as carbon black is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to recycling treatment of recovered sand generated in large quantities in foundries, microwave-curable foundry sand using the recovered recycled sand as a raw material, and a method for producing the same. be.

The applicant first irradiates the mold material with microwaves,
We are proposing a method of manufacturing molds using self-heating of the mold material, and the mold materials used in this process include fresh sand and thermosetting resin (a thermosetting resin made by blending a hardening agent with a thermoplastic resin). proposed a microwave-curable foundry sand made by mixing dielectric materials such as carbon fibers and graphite (% patent application No. 53-114046).

However, this foundry sand has problems in terms of cost due to the high cost of materials such as graphite, and when this foundry sand is used, there are also problems such as separation of graphite and uneven hardening.

In order to solve the above problems, the applicant has further proposed microwave-curable foundry sand, which is a mixture of thermosetting resin and fresh sand with carbonized sand that acts as a dielectric substance against microwaves. (Patent Application No. 53-156924),
If the surface of the sand grains is coated with resin in advance and then heated to carbonize the resin to obtain carbonized sand, manufacturing costs are high, and if carbonized sand generated from a molding line such as a shell mold is used, However, there is a problem in that it is difficult to obtain suitably carbonized raw material sand of large IkK. In addition, in order to increase the transverse rupture strength of the mold and shorten the curing time, it is required that the sand grains be uniformly coated with carbide, but in this case, an additional surface conditioning process for the carbonized sand is required. , resulting in an increase in processing costs. 1 more
．． Carbonized sand is used as a dielectric substance and is mixed with fresh sand, and it is difficult to replace it with raw sand due to the above-mentioned problems and quality issues.

By the way, it would be extremely advantageous if the recovered sand, which is generated in large quantities in foundries, could be recycled as raw material sand for microwave-curable foundry sand, as it would greatly reduce manufacturing costs and increase productivity. The recovered sand that is generated in large quantities contains a large amount of clay and fine powder, and has been caked and solidified, so it cannot be used as it is. It is impossible to obtain raw sand for this purpose.

In other words, the conventionally known recycling and recovery method involves magnetic separation (
The recovered sand obtained by removing iron pieces), cooling, and sieving (further pulverizing coarse particles, removing glass, and sieving) is washed with water, dried, cooled, and further classified to remove fine particles. Alternatively, the recovered sand obtained by K as described above is roasted at a high temperature of about 800°C, and after cooling, the surface of the roasted sand grains is scrubbed with a stirrer or the like (washing fIP).
There is a roasting scrubbing method that classifies and removes fine powder. However, when regeneration treatment is performed using such a method, most of the carbonaceous organic matter that coats the surface of the sand grains is washed away when using the water washing method, or burnt out when using the roasting scrubbing method. , recycled sand is obtained in which no carbonaceous organic matter remains as a dielectric substance for microwaves. Therefore, when using such recycled sand as microwave-curable foundry sand, it is necessary to add dielectric substances such as carbon black and iron oxide, which makes it difficult to achieve the intended purpose of reducing manufacturing costs. I can't.

Furthermore, the recycled sand obtained by each of the above methods also has a quality problem because most of the clay content, which acts as a backing layer to moderate the thermal shock that the mold receives when pouring molten metal, is also lost. .

Therefore, an object of the present invention is to recycle the sand so that it can be used as raw material sand in foundries. Similarly, an object of the present invention is to provide recycled sand of good quality and in a large quantity at a low price, which can be used as it is as raw material sand for the above-mentioned microphone four-wave curing.

Still another object of the present invention is to provide microwave-curable foundry sand with excellent qualities such as four-wave hardenability and shell strength at a low cost and with good productivity.

It is an object of the present invention to carry out the recycling treatment of recovered sand by giving circulation motion to the recovered sand stored in a rotating container by the rotation of the rotating container, and by disposing the recovered sand in a rotating container in a direction opposite to the rotating direction of the container. By the rotation of the agitator which rotates, an impact friction effect is applied to the recovered sand in the above-mentioned circulating motion state, and dry cleaning of the recovered sand is achieved.

By such dry regeneration treatment of the present invention, the clay content is reduced to 0.
5-6-1 Recycled sand containing 0.3-5-5 carbonaceous organic matter and usable as raw material sand for microwave curing is obtained, and 2-5 weight of thermosetting resin is added to the recycled sand. By slow kneading, foundry sand with excellent microwave curability can be obtained.

Explain in detail.

First, the waste sand generated after molding, pouring molten metal, and breaking the frame is magnetically sorted, cooled, and sieved according to conventional methods to obtain recovered sand.

This recovered sand is then subjected to the regeneration treatment according to the present invention.

FIG. 1 and FIG. 2 show an example of an embodiment of electricity production for carrying out the regeneration process according to the present invention.

Reference numeral 1 denotes a rotating container inclined by about 15e', which is rotated by a drive device 2 around a bottom plate 3 which can be opened and closed at a medium speed of about 50 to 100 rpm in the direction of the arrow shown in Fig. fs2. An agitator 4 is disposed at a predetermined position within the rotating container 1, and the agitator 4 is rotated by a drive device 5 at a high speed of about 500 to 2000 rpm in a direction opposite to the rotational direction of the rotating container il+.

A hopper 6 and a duct 7 are provided at predetermined positions in the upper part of the rotating container 1. In addition, since the recovered sand contains clay, it adheres to the inner wall of the rotating container 10 and forms islands. Alternatively, it is preferable to arrange it so that it slides into contact with the inner peripheral wall.
.

Further, the agitator 4 shown in Fig. 1 is a rotating disk having protrusions 9 with a circumference of I81/c11, and has a shape in which a plurality of bottles IO are fixed above and below the peripheral part, but the shape of the stirring blade is The design can be changed as appropriate.

Here, the recovered sand is put into the rotating container 1 from the hopper 6, and is circulated by the rotating container 10 times, while being subjected to a scrubbing process by being subjected to impact friction (agitator 4) rotating at high speed in the opposite direction. Processing is 5-15
This process is carried out for several minutes, and impurities on the surface of the sand grains are appropriately removed.

After the recycling treatment, the bottom plate 3 disposed at the bottom of the one-rotation container is opened with a hammer to recover the recycled sand. Although fine powder is generated during the regeneration process, this fine powder is removed by suction from the duct 7. Note 1
As shown in the figure, it is preferable that the rotating container 1 is tilted to a certain degree because the recovered sand undergoes a combined circulation movement in the circumferential direction and the radial direction, so that the scrubbing process is performed more effectively.

Further, as shown in the figure, when the axis of the agitator 4 is disposed at a position slightly displaced from the center of the rotating container IO, the scrubbing effect on the recovered sand is more effective.

By recycling in this manner, recycled sand having the optimum properties as raw material sand for microwave curing can be obtained.

Next, Table 1 shows the chemical composition of the recycled sand obtained by the dry recycling treatment according to the present invention in comparison with the recycled sand and new sand obtained by the conventional recycled hair method. The apparatus shown in FIGS. 1 and 2 is used for the regeneration process according to the present invention, and the processing conditions are as follows. The rotation speed was 1500 r, p, m, and the processing time was about 10 minutes.

Margin below Table i - Chemical composition (t4) *Indicates the amount of weight loss when baked at 1000℃ for 1 hour.

By the way, the purity of foundry sand is determined by its chemical composition.
It is well known that the more SiO, the higher the purity and heat resistance. However, when molded into a mold, if the purity is too high, the amount of rapid thermal expansion will increase (see Figure 3), and casting defects such as paening, puffiness, and cracks will occur frequently in the casting, which is undesirable, and recycled sand is used repeatedly. It was confirmed that 95 to 97 g6 is the optimum range for Sl. Therefore, since the recycled sand obtained by the recycling treatment according to the present invention shown in Table 1 falls within the above range, it can be used repeatedly without causing casting defects. According to the regeneration process according to the present invention, by appropriately setting the rotational speed of the rotating container and the agitator, the processing time, etc. within the above-mentioned ranges,
The ratio of 810 m can be within the above optimal range.

Further, the upper limit of ALIIO5 and F6mOs is about 2-, and the regeneration treatment according to the present invention can suppress the value to below this upper limit, so that recycled sand of sufficiently satisfactory quality can be obtained.

Next, the particle size distribution and clay content of each sand shown in Table 1 were
Shown in the table.

As is clear from Table 2 below, the particle size of the recycled sand obtained by the dry regeneration treatment according to the present invention is approximately the same as that of recycled sand and new sand obtained by the conventional method.

By the way, as is clear from Tables 1 and 2, the recycled sand obtained by the dry recycling treatment according to the present invention is characterized by containing some clay content and loss on ignition.

As mentioned above, one clay content plays a role in moderately mitigating the thermal shock that the mold receives when pouring molten metal, while the ignition loss is mainly carbonaceous organic matter, which plays an effective role as a dielectric material that contributes to microwave heating. Fulfill. Therefore, the recycled sand obtained by the present invention can be used as it is as raw material sand for microwave curing.

The recycled sand obtained with the above 5Kt is then classified and, if necessary, mold powder removed, and then a thermosetting resin and a solvent such as white kerosene are added to the recycled sand as necessary. Knead using a mixing machine etc. for an appropriate time. In this manner, microwave curable foundry sand is obtained.

Thermosetting resins include resol type phenolic resin, resol type novolak type mixed O phenol resin, and Novo 2.
Tsuku-type phenolic resin (However, since this resin is thermoplastic, a curing agent such as hexamethylenetetramine is usually added to
It is necessary to contain about 15% to make it thermosetting). Other thermosetting resins such as furan resin can also be used. Generally, 2 to 71 parts of these thermosetting resins are added when mixed with new sand, but in the case of recycled sand obtained by the present invention, 2 to 5 parts by weight per 100 parts by weight of recycled sand is sufficient. It is. Furthermore, the resin can be used in either powder or liquid form.

Below, an example of the preparation of microwave-curable foundry sand will be shown and its properties will be explained.

Preparation of microwave-curable foundry sand 100 parts by weight of recycled sand shown in Table 1 above was mixed with a powdered phenol resin (containing 15 g of hexamethylenetetratin per resin, melting point 70-97°C, gel tie^35-67 seconds/ 15
3 parts by weight (0°C) and line treatment to obtain microwave-curable foundry sand. For comparison, microwave-curable foundry sand was prepared in the same manner as above using reclaimed sand and new sand produced by the conventional method. However, in this case, carbon black was added as a dielectric substance.

Table 3 shows the blending ratio and shell strength of each of the foundry sands obtained, and the change in rapid thermal expansion with respect to heating time (specimen size: 2 g, sl'xs).

(2) heating furnace temperature ++SO°C) is shown in Fig. 3.

The following is weight reduction: Microwave-curable foundry sand (A) according to the present invention and microwave-curable foundry sand containing 100 fi new sand (
When D) was used for the core of cast iron parts, defects such as swelling and panning occurred in the case of the foundry sand, but such defects did not occur in the case of the foundry sand A.

As described above, the regeneration treatment according to the present invention does not require water washing, drying treatment, or high temperature roasting treatment unlike conventional methods,
Since a large amount of recycled sand of reusable quality can be obtained through dry scrubbing alone, the energy costs required for recycling can be reduced, and the recycling cost is reduced to about half that of conventional methods. In addition, the Takasand that can be used in the present invention can be any Takasand discharged from various organic caking casting factories including shell mold, water glass caking casting lacrimation, raw mold, etc. ,
It is also advantageous in terms of resource saving.

Furthermore, as is clear from Table 3, the recycled sand according to the present invention does not contain dielectric substances such as carbon black.
It is possible to obtain microwave-curable foundry sand at a low cost, which has rapid and uniform microwave curing properties and has sufficient shell strength equivalent to that of recycled sand produced by conventional methods. In particular, as is clear from Figure 3, its rapid thermal expansion is less than the Ben ratio when new sand or sand recycled by the conventional method is used, which is significant in preventing defects such as puffiness, veining, and cracks in castings. You can expect good results.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view schematically showing one embodiment of a device for performing dry regeneration processing according to the present invention, and FIG.
3 is a graph showing changes in the amount of rapid thermal expansion of various types of sand with respect to heating time. 1 is a rotating container, 4 is an agitator, 16 is a hopper, 7 is a duct, and 8 is a scraper. Applicant Komatsu Ltd. Representative Patent Attorney Tadashi Yonehara Patent Attorney Tadashi Hamamoto ¥41 Figure 2 Procedural Amendment (voluntary) August 19, 1980 Commissioner of the Japan Patent Office Shima 1) * Itsuki Tono 1 Case Indication Japanese Patent Application No. 101325/1982 2 Name of the invention Recovered recycled sand, microwave-curable foundry sand using it as raw material, and method for producing the same 3 Relationship with the case of the person making the amendment Address of the patent applicant Akasaka, Minato-ku, Tokyo 2-3-6 Name (123
) Komatsu Ltd.

Claims (1)

[Claims] L Clay content: 0.5-6s and carbonaceous organic matter: 0.3-5-
A microwave cured product containing 2 to 5 parts by weight of a thermosetting resin (including those made thermosetting by blending a curing agent with a thermoplastic resin) per 100 parts by weight of dry recycled sand containing Sex foundry sand. East: The rotation of the rotating container gives the recovered sand stored in the rotating container a circular motion, and the rotation of an agitator placed in the rotating container and rotating in a direction opposite to the direction of rotation of the mosquito container allows the above-mentioned circulating motion state to be achieved. 1. A method for producing dry reclaimed sand for producing microwave-curable foundry sand, characterized in that recovered sand IC1i is given an impact friction effect and recovered sand is dry washed. 8. The method according to claim 2, wherein the rotating container is a tilting rotating container, and the rotation of the tilting rotating container imparts a compound circulation movement to the recovered sand. The method according to claim 2 or 3, characterized in that the fine powder generated is removed by suction at the same time as the recovered sand is dry washed. a Circulating motion is given to the recovered sand contained in the rotating container by the rotation of the rotating container, and the above-mentioned circulation is achieved by the rotation of an agitator that is disposed inside the rotating container and rotates in a direction opposite to the rotational direction of the container. The recovered sand is dry washed for a predetermined period of time by applying an impact friction effect to the recovered sand in a state of motion.
After classification and removal of fine particles, a thermosetting resin (including thermosetting resin made by blending a curing agent with a thermoplastic resin) is added and kneaded to the recovered sand recycled in Tonoyo 5. Features: A method for producing microwave-curable foundry sand. 6. The method according to claim 5, wherein the rotating container is a tilting rotating container, and the rotation of the scissors tilting rotating container imparts a compound circulation movement to the recovered sand. 6. The method according to claim 5 or 6, wherein the removal of fine powder is carried out during dry washing of the recovered sand.