JPH0739991A - Film coating agent for chiller in casting - Google Patents

Abstract

PURPOSE:To prevent the blow hole defect and the melt-sticking to the casting at the time of producing a casting and improve the workability and the working efficiency by incorporating one liquid moisture-hardening type polyurethane resin or aqueous resin emulsion in a film coating agent for chiller. CONSTITUTION:The one-liquid moisture-hardening type polyurethane resin or the aqueous resin emulsion is used as the film coating agent for chiller in the casting. The one-liquid moisture-curing polyurethane resin is an isocyanate end group polyurethane prepolymer obtd. by reacting a polyhydroxy compound having two or more hydroxyl groups in a molecle and polyisocyanate compound having two or more isocyanate groups in a molecule. This film coating agent is desirable to apply, e.g. in the range of 5-100g/m <2> on the surface of the chiller as the solid material of the one-liquid moisture-curing polyurethane resin or the aqueous resin emulsion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating agent for chill metal used in producing castings using a sand mold for casting.

[0002]

2. Description of the Related Art When a cast product having a variable wall thickness is manufactured, shrinkage cavities at the time of solidification of the thick wall portion and coarsening of the composition are likely to occur. Therefore, we use a chill to prevent this, but since the chill is made of metal,
There was a blown defect on the surface of the manufactured casting due to fusion with the manufactured casting or rust and water droplets on the surface of the chill. Conventionally, soybean oil is applied to the surface of a chill in order to prevent blow defects that occur when a casting is produced using such a chill and prevent fusion between the chill and the casting. It is known to apply oil such as.

[0003]

However, when a chill coated with such conventionally known soybean oil is used in the production of a casting, the surface of the chill is sticky and its workability is deteriorated. . In order to solve the problem of stickiness, it is necessary to apply soybean oil or the like and then heat a chilled plate to dry it. The present invention is a coating for a casting chill metal which can prevent both blown defects when manufacturing a casting using a chill metal and fusion with the casting, and which is excellent in workability and work efficiency. The purpose is to provide a film agent.

[0004]

In order to achieve the above object, the coating agent for casting chill metal of the present invention is characterized by containing a one-part moisture-curable polyurethane resin or an aqueous resin emulsion. To do.

The one-component moisture-curable polyurethane resin used in the present invention is obtained by reacting a polyhydroxy compound having two or more hydroxyl groups in the molecule with a polyisocyanate compound having two or more isocyanate groups in the molecule. Isocyanate-terminated polyurethane prepolymers obtained by the above, and specific examples thereof include one-part moisture-curable polyurethane resin coatings that are generally commercially available. In the production of this isocyanate-terminated polyurethane prepolymer, the polyisocyanate compound is preferably used in an equivalent ratio range of 1.2 to 3.0 with respect to the polyhydroxy compound. This isocyanate-terminated polyurethane prepolymer can be diluted with a solvent such as xylene or toluene, if necessary, and used as the coating agent of the present invention.

Examples of the aqueous resin emulsion used in the present invention include a polyurethane emulsion, a polyvinyl acetate emulsion, a polystyrene / butadiene copolymer emulsion, or a mixture of two or more of these. Since these dispersion media are water, these aqueous resin emulsions can be suitably used even in a poorly ventilated workplace where the use of an organic solvent is inappropriate.

The coating composition of the present invention is preferably applied to the surface of a chilled gold in the range of 5 to 100 g / m ² as a solid content of a one-component moisture-curable polyurethane resin or an aqueous resin emulsion.

[0008]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. Example 1 A one-part moisture-curable polyurethane resin coating material (trade name: Millionate CB-30, manufactured by Hodogaya Kenzai Kogyo Co., Ltd.) using diphenylmethane diisocyanate as a raw material was applied to a chilled plate made of cast iron to apply an amount of about 150 g. It was applied with a brush so as to have a ratio of / m ² , and allowed to cure at room temperature. The chilled plate coated with this paint was set at a required position in a green sand mold, and molten cast iron (trade name: Ductile cast iron, manufactured by Automobile Foundry Co., Ltd.) was cast to obtain a cast product.

Example 2 A one-part moisture-curable polyurethane resin coating (trade name: Millionate CB-4) using tolylene diisocyanate as a raw material.
In the same manner as in Example 1, No. 0, manufactured by Hodogaya Kenzai Kogyo Co., Ltd., was applied to gold and cured at room temperature. A chill coated with this paint was used in the same manner as in Example 1 to obtain a cast product.

Example 3 Polyurethane emulsion (trade name Aizerax S-
1040 manufactured by Hodogaya Chemical Co., Ltd. was cooled in the same manner as in Example 1 and applied to gold, followed by room temperature curing. A chilled product coated with this emulsion was used in the same manner as in Example 1 to obtain a cast product.

Example 4 A polyvinyl acetate emulsion (trade name Pampere, manufactured by Hodogaya Kenzai Kogyo Co., Ltd.) was applied to a cold metal in the same manner as in Example 1, and was cured at room temperature. A chilled product coated with this emulsion was used in the same manner as in Example 1 to obtain a cast product.

Example 5 A polystyrene / butadiene copolymer emulsion (trade name: Millionate CR, manufactured by Hodogaya Construction Materials Co., Ltd.) was applied in the same manner as in Example 1 and cured at room temperature. A chilled product coated with this emulsion was used in the same manner as in Example 1 to obtain a cast product.

Comparative Example 1 Soybean oil (trade name: Shirashima Oil, manufactured by Nisshin Oil Co., Ltd.) was applied to a chill made of cast iron with a brush so that the amount of application was about 150 g / m ^2. And dried by heating at about 180 ° C. for 90 minutes. After cooling by standing, this soybean oil-coated chill was set at a required position in a green sand mold, and molten cast iron (trade name: ductile cast iron, manufactured by Automobile Foundry Co., Ltd.) was cast to obtain a cast product. .

Comparative Example 2 A chill made from cast iron was placed at a required position in a green sand mold as it was, and molten cast iron (trade name: Ductile cast iron, manufactured by Automobile Foundry Co., Ltd.) was cast to obtain a cast product. It was

[Performance Test] Examples 1-5, Comparative Examples 1-2
Tables 1 and 2 show the results of each performance test of the cast product obtained in 1. above with respect to blown defects, fusion, tack-free time, and whether or not chill pretreatment was performed. (1) Blown defect It was visually judged whether or not air bubbles were present on the surface of a casting produced using a chill. Judgment Criteria: ◯: No bubbles at all x: Bubbles present (2) Fusing Welding the cast product produced was impacted with a hammer to examine the releasability of the chill from the cast product. Judgment Criteria: ◯: Easily detached ×: Difficult to detach (3) Tack-free time and presence / absence of pretreatment The time and temperature until the tackiness of the surface of the chill was disappeared were measured. The presence or absence of this pretreatment is also shown.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

As described above, the coating agent for casting chill metal of the present invention does not have stickiness which occurs when soybean oil is used in the production of casting, and the heating and drying step becomes unnecessary,
It is possible to significantly reduce the working time. Therefore,
It is possible to provide a coating agent for a chilled casting which is excellent in workability and work efficiency, and can be easily used even in a workplace where there is no facility necessary for the heating and drying step. Further, by using a chill coated with the coating agent according to the present invention, rust and water droplets are unlikely to adhere to the chill, so that a cast product without blown defects or fusion of the chill is reliably produced. can do.

Claims (2)

[Claims] 1. A coating agent for a casting chill metal, which comprises a one-part moisture-curable polyurethane resin or an aqueous resin emulsion. 2. The coating agent for a casting chill metal according to claim 1, wherein the aqueous resin emulsion is a polyurethane emulsion, a polyvinyl acetate emulsion, a polystyrene / butadiene copolymer emulsion or a mixture of two or more thereof.