JPH0970640A - Parting material for green sand molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain clean sand molds simply by applying a parting material on metal molds and using even if the metal molds are not subjected to metal plating at a large contact angle by dissolving polymethocarbosilane into a nonpolar org. solvent. SOLUTION: This parting material for green sand molding is prepd. by dissolving the polymethocarbosilane into the nonpolar org. solvent. Toluene, xylene, hexane, cyclohexane, industrial gasoline, petroleum benzene, thinner for paints, methanol, ethanol, etc., are usable as the nonpolar org, solvent. The polymethocarbosilane is used by diluting it to properly concn., generally 3 to 30wt.%. While the parting material is obtd. simply by dissolving the polymethocarbosilane into the nonpolar org. solvent, a surfactant, inorg, fillers, etc., may be properly added thereto. The parting material prepd. in such a manner is used by applying the material on the metal molds prior to molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold release agent which is applied to a mold (model) for molding a green mold.

[0002]

2. Description of the Related Art Green molds are still the mainstream of molds because they can be poured immediately after molding, the mold sand can be easily recycled, and the mold cost is low.

[0003] Conventionally, in a mold used for molding a green mold, molding sand for molding the green mold is apt to adhere to the mold, which makes it difficult to obtain a clean green mold. The reason is that the green sand (mold) is made of aggregate, clay, water and other additives, whereas the mold is usually made of iron (for example, cast iron) whose contact angle with water is substantially 0 °. Because there is.

For this reason, conventionally, the surface of the mold has been treated by plating with nickel, chromium or the like, which has a larger contact angle with water than iron (usually electroplating).

[0005]

However, in the case of green molding, there are many cases in which a mold is partially modified (especially in the trial production stage) and used because of the simplicity of the mold. On this occasion,
It had to be plated again, which was troublesome. Further, depending on the composition of the raw sand, that is, the type of the binder and the additive, there is a possibility that the action of preventing the raw sand from adhering cannot be sufficiently exerted.

In view of the above, the present invention makes it possible to form a neat green mold only by applying it to the mold without using metal plating having a large contact angle on the mold. The purpose is to provide a mold release agent.

[0007] Another object of the present invention is to provide a mold release agent for green molding which can sufficiently exert the effect of preventing the adhesion of green sand.

[0008]

The mold release agent for green molding according to the present invention solves the above problems by the following constitution.

A mold release agent for molding a green mold, which is used by coating a model mold when molding a green mold, wherein polymetallocarbosilane as a mold releasing component is dissolved in a nonpolar organic solvent. Is characterized by.

[0010]

[Detailed Description of Means] Next, each component of the above means will be described in detail.

(1) In the release agent for green molding of the present invention, polymetallocarbosilane is dissolved in a non-polar organic solvent as a release component.

(2) The polymetallocarbosilane used herein is composed of (A) carbosilane bond unit described below and at least one (B) metalloxane bond unit described below, (In the formula, R ¹ and R ² may be the same or different and each independently represents an alkyl group having 1 to 4 carbon atoms, a phenyl group or a hydrogen atom.) (B): (-MO-) ( In the formula, M represents at least one element selected from the group consisting of Ti, Zr, Mo and Cr, and in some cases, at least a part of each element is an alkoxyl group having 1 to 4 carbon atoms or a phenyl group as a side chain group. A polymer in which the respective bonding units of (A) and (B) are randomly bonded in the main chain skeleton, and / or at least a part of the silicon atoms of the bonding unit of (A) is The polycarbosilane moiety, which is bonded to each of the metal elements of the bonding unit of (B) via an oxygen atom, and thereby the polycarbosilane moiety obtained by the chain of the bonding unit of (A) is bonded to the bonding unit of (B) via oxygen. Is a cross-linked polymer.

Total number of bonding units of (A) above (B)
It is preferred that the ratio of the total number of binding units of is in the range of 1: 1 to 10: 1. The number average molecular weight of the polymetallocarbosilane is preferably 400 to 50,000.

(3) Further, as the non-polar organic solvent,
Toluene, xylene, hexane, cyclohexane, industrial gasoline, petroleum benzine, paint thinner, methanol, ethanol and the like can be used. A polar organic solvent cannot dissolve polymetallocarbosilane.

(4) The polymetallocarbosilane is used by diluting it with the above nonpolar organic solvent to an appropriate concentration, usually 3 to 30 wt% (desirably 5 to 15 wt%). If it is less than 3%, it is difficult to impart a mold releasing action (water repellency that does not adhere to green sand) to the mold, and if it exceeds 30 wt%, the mold releasing action (water repellency imparting effect) is not further increased and the viscosity is high. If it is too high, the workability of coating the mold may be adversely affected.

At this time, usually, the polymetallocarbosilane can be used as a release agent simply by dissolving it in a non-polar organic solvent, but a surfactant, an inorganic filler or the like may be appropriately added. it can.

(5) The release agent thus prepared is used by coating it on a mold before molding. In this application, the green sand to be reused is usually heated to about 40 ° C. due to the influence of the molten metal, so it is desirable to heat the mold to about 40 ° C. This is to prevent dew condensation on the mold surface.

The coating method may be any of spraying, brushing, dipping and the like, but spraying is preferable from the viewpoint of workability. The coating thickness is 10 in the dry state.
˜100 μm (preferably 40 to 60 μm).

Further, after application, it is desirable to heat-dry mainly to accelerate the evaporation of the solvent, but if there is time, it may be naturally dried.

The mold with the release film thus formed can be repeatedly used for green molding. By the way, when a 10 wt% toluene solution of polytitanocarbosilane was spray applied 3 times, green molding was carried out 300 times, but adhesion of green sand to the mold was not observed.

[0021]

The release agent for green molding of the present invention is obtained by dissolving polymetallocarbosilane in a non-polar organic solvent as described above, and is applied to a mold during green molding. Only by doing so, it is possible to impart a green sand adhesion preventing effect to the surface of the mold, as will be supported in the test examples described later.

Therefore, even if the metal plating having a large contact angle is not applied to the mold, it is possible to form a neat green mold simply by applying it to the mold and using it.

Further, the contact angle is remarkably high as compared with the conventional nickel plating, and very high water repellency can be imparted to the mold surface. That is, regardless of the composition of the raw sand, that is, the types of the binder and the additive, the effect of preventing the raw sand from adhering can be sufficiently exerted.

In Japanese Patent Laid-Open No. 63-12672, there is disclosed a coating composition (release agent) which is used by coating a base material such as iron with the polymetallocarbosilane used in the present invention as an essential component. It is disclosed.

However, the known release agent is different from the release agent of the present invention and does not affect the inventive step of the present invention.

The mold release agent of the present invention is a mold release agent for green molding, and is intended to have mold release property for green molding sand containing a large amount of water and having a temperature of about 40 ° C. at the time of molding. On the other hand, the known release agent has a high temperature (usually 500
The purpose is to releasability from a metal melt such as aluminum or a glass melt which is higher than or equal to (° C.), and the two purposes are completely different.

In the component having the releasing action, the present invention is "polymetallocarbosilane", whereas the known releasing agent is mainly "boron nitride powder" (see the above-mentioned page 2, page 2). (1st row in the left column). Polymetallocarbosilane has only been suggested to be mainly responsible for the adhesion to the substrate (the above-mentioned publication, page 2, lower left column, fourth stage),
It is not suggested in the above-mentioned publication that polymetallocarbosilane has a releasing effect.

[0028]

[Test Example] A water repellency test, which is an indirect test conducted to confirm the effect of the present invention, will be described below.

(1) Test pieces prepared by treating a 70 × 70 × 5 mmt iron plate or cast iron (FC) plate with a release agent by the following method were placed horizontally as shown in FIG. A water drop 2 was dropped on a heated test piece 1 kept at 40 ° C., and a contact angle Θ immediately after was dropped, and an average of 3 points was taken.

In the release agent treatment, a release agent (polytitanocarbosilane 10 wt% toluene solution) was applied three times by brush coating, and naturally dried for 60 minutes → 200 ° C. × 30 minutes → 25.
Drying was carried out under the condition of 0 ° C. × 15 minutes (dry film thickness: about 5
0 μm). As the polytitanocarbosilane, "Tyrannocoat VN110" manufactured by Ube Industries, Ltd. was used.

The results are as follows: Iron plate: 83.7 ° (normal temperature), 74.7 ° (40 ° C.), FC plate: 84.3 °
(Normal temperature) and 74.7 ° (40 ° C.). The contact angles of iron and nichrome with water at room temperature are 0 ° and 6.5 °, respectively (“Chemical Handbook Basic Edition II”).
Maruzen, p. 541).

It can be seen that the product treated with the release agent of the present invention exhibits far superior water repellency than the nickel plating process.

[Brief description of drawings]

FIG. 1 is a model cross-sectional view of a water repellency test of the present invention.

[Explanation of symbols]

 1 Test piece 3 Water drop Θ Contact angle

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Nakamura 1 Toyota-cho, Toyota-shi, Aichi Prefecture Toyota Motor Corporation (72) Inventor Tsujihiko Yasuda 230 Okita-machi, Nakamura-ku, Nagoya, Aichi Chubu Sukegawa Kogyo Incorporated (72) Inventor Akiyoshi Hanno 230 Okita-cho, Nakamura-ku, Nagoya, Aichi Chubu Sukegawa Kogyo Co., Ltd. (72) Inventor Tamuro Ito 230 Okita-cho, Nakamura-ku, Nagoya, Aichi Chubu Sukegawa Kogyo Co., Ltd.

Claims (3)

[Claims] 1. A mold release agent applied to a mold when molding a green mold, wherein a polymetallocarbosilane, which is a mold release component, is dissolved in a non-polar organic solvent. A mold release agent for green molding. 2. The mold releasing agent for green molding according to claim 1, wherein the concentration of the polymetallocarbosilane is 3 to 30 wt%. 3. The mold releasing agent for green molding according to claim 1 or 2, wherein the polymetallocarbosilane is the polytitanocarbosilane.