JP3213609B1 - Coating composition - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To provide a coating composition capable of preventing burning. SOLUTION: A coating composition containing at least one selected from calcium bentonite and mite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition which is preferably used in a vanishing model casting method.

[0002]

2. Description of the Related Art The vanishing model casting method is also referred to as a full molding method, in which a model made of a synthetic resin foam is used as a mold while being buried in molding sand. It is rare. The residue defect is a defect of the casting due to a large amount of pyrolysis gas and residue generated by the thermal decomposition of the synthetic resin foam due to the cast molten metal. Also, baking is a phenomenon in which the molten metal breaks through the coating film at the place where the sand is cast, such as corners and grooves of the casting, and the molten metal penetrates between the sand particles of the sand mold, and especially the synthetic resin foam has strength. It is easy to occur in a part designed to have a large thickness.

To solve the former defect, Japanese Patent Application Laid-Open No. Sho 63-290647 discloses a coating composition containing a substance which generates an inert gas upon heating.
Japanese Patent Application Laid-Open No. 4-262 discloses a coating material containing a specific ratio of a refractory fine powder, a binder and glass fiber in a specific ratio.
No. 832 has a mold wash mixed with a porous incombustible material,
Japanese Patent Application Laid-Open No. 7-112238 discloses a coating composition using aggregated particles having pores for adsorbing pyrolysis gas.
No. 436 proposes a coating material containing a refractory solid powder and attapulgite at a specific ratio.

[0004]

However, it is difficult to say that the casting defects (materials) can sufficiently eliminate casting defects caused by baking. In particular, further improvement is desired for the burning of grooves and corners of castings manufactured by the vanishing model casting method.

[0005]

The present invention relates to a coating composition containing at least one selected from calcium bentonite and plum (hereinafter referred to as "component (a)").

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Among the components (a), calcium bentonite is a natural bentonite mainly composed of calcium ions and magnesium ions as exchangeable cations. It is thought that it forms and suppresses casting adhesion. Calcium bentonite is typically from Zao in Miyagi Prefecture and from Mississippi in the United States. Fraser Earth in Europe and the United Kingdom is a typical calcium bentonite.

Among the components (a), plum is also called a plum group and is an aluminosilicate containing an alkali metal (Chemical Encyclopedia, Vol. 1, July 1, 1968, No. 6).
Printing, Kyoritsu Publishing Co., Ltd.). Plums include natural plums and artificial plums, and examples of the natural plums include white plums, gold plums, and black plums, and preferably white plums. Examples of artificial muffles include fluorine muffles, such as fluorine gold muffles, fluorine tetrasilicon mounds, and teniolite.

[0008] In the present invention, the melting characteristics and shape characteristics of calcium bentonite and pumice are related to each other to form a film having a high masking property. It is considered to be suppressed.

Although the coating composition of the present invention can be used as a coating composition for various molds, it is preferable to use it as a coating composition for a vanishing model, since the effect is effectively exhibited.

In the coating composition of the present invention, calcium bentonite is added in an amount of 0.1% by weight based on 100 parts by weight of the solid content in the composition.
5 to 20 parts by weight, 2 to 10 parts by weight;
It is preferable to contain 9 parts by weight, more preferably 15 to 90 parts by weight, from the viewpoint that a better effect of the present invention can be obtained. Since an excellent effect can be obtained only by adding a small amount, it is preferable to contain calcium bentonite, and plum and calcium bentonite are preferably contained in a weight ratio of plum / calcium bentonite = 100/1 to 100/100, More preferably, they are used in combination.

The coating composition of the present invention can be used for both non-ferrous metal castings such as aluminum and iron-based castings such as cast iron and cast steel. It is preferable to use it for an iron-based casting which is liable to cause a seizure defect because it is cast because the effects of the present invention can be effectively used.

The coating composition of the present invention comprises the above-mentioned component (a) and components such as a refractory aggregate, a binder and the like which are usually blended with this type of composition. The composition may be aqueous or alcoholic.

Various types of refractory aggregates in the coating composition have been conventionally used depending on the purpose of casting, and examples thereof include graphite, zircon, magnesia, alumina, and silica. In addition, water-soluble polymers and various resin emulsions such as sodium polyacrylate, starch, methylcellulose, polyvinyl alcohol, sodium alginate, and gum arabic are used as binders in the aqueous system, and various resins soluble or dispersed in the alcohol system in the alcohol system. Is preferred from the viewpoint of coating film strength. The addition amount is preferably 0.5 to 1 with respect to 100 parts by weight of the refractory aggregate.
0 parts by weight.

The mold wash composition of the present invention is used by being applied to a synthetic resin foam model as usual. As the synthetic resin foam, a foam such as polystyrene, polymethyl methacrylate, or a copolymer thereof is used. As the molding sand used for casting, in addition to silica sand mainly composed of quartz, new sand such as zircon sand, chromite sand, and synthetic ceramic sand or recycled sand is used. Foundry sand can also be used without adding a binder, in which case the fillability is good, but if strength is required, a binder is added,
It is preferable to cure with a curing agent.

[0015]

EXAMPLES Examples 1 to 4 and Comparative Example 1 (Evaluation Method 1) A model having the shape shown in FIG. 1 was prepared using expanded polystyrene (expansion ratio: 50). The aqueous coating composition of Table 1 was applied to the surface of the model, and the dried film thickness was 1 mm. 0.2 parts by weight of an organic sulfonic acid curing agent (TK-3 manufactured by Kao Quaker Co., Ltd.) was added to Fremantle silica sand (No. 5), and the mixture was kneaded.
340B) was mixed with silica sand in an amount of 0.5 part by weight. The above model was buried in the kneaded sand. Casting was performed from the weir portion at a speed at which the molten metal did not overflow (material FC-250, casting temperature 1400 ° C.), and the presence or absence of seizure at the bottom and the corner was visually evaluated. Table 1 shows the results.

[0016]

[Table 1]

The components used in Table 1 are as follows.・ Water-soluble polymer: sodium polyacrylate ・ Emulsion resin: vinyl acetate emulsion ・ Surfactant: general nonionic surfactant ・ Preservative: general commercial product

(Evaluation Method 2) An automobile mold made of expanded polystyrene (expansion ratio 50 times) (product weight 4 t, F
The aqueous coating composition of Comparative Example 1 and Example 2 was applied to the model of C-300) with a brush of 80 Be (bome), respectively. When casting was performed by a conventional method, in Comparative Example 1, seizure occurred in the casting flat part, pocket part, and corner part, but in Example 2, only small seizure occurred in a part of the corner.

(Evaluation Method 3) Polymethyl methacrylate /
The above Comparative Example 1 and Example 1 were applied to two model slide bases (product weight 300 kg, FC-300) for machine tools made of a polystyrene (75/25) copolymer foam model (expansion ratio 50 times). Of the aqueous coating composition of
It was applied with a brush with Be (Bome). When casting was carried out by an ordinary method, in Comparative Example 1, seizure occurred in the groove,
In Example 1, no seizure occurred.

[0020]

As described above, according to the present invention, it is possible to prevent the seizure occurring in the groove or the corner part of the casting, especially when the disappearing model is used.

[Brief description of the drawings]

FIG. 1 is a schematic view of a disappearance model made of a synthetic resin foam used in evaluation method 1 of an example.

Continuation of front page (56) References JP-A-5-69079 (JP, A) JP-A-1-215434 (JP, A) JP-A-4-105748 (JP, A) JP-A-62-192227 (JP) JP-A-57-94442 (JP, A) JP-A-56-131039 (JP, A) JP-A-47-38619 (JP, A) JP-A-10-34278 (JP, A) 50-14609 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22C 3/00

Claims (4)

(57) [Claims] 1. A coating agent composition containing calcium vent Nye bets. 2. A coating agent composition you containing calcium bentonite and mica. 3. The method according to claim 1 , which is for casting a vanishing model.
Coating composition described above. 4. The coating agent composition of any one of claims 1 to 3 for use in the iron castings.