JPH0142979B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a chipping-resistant coating composition that is coated on the surface of a metal product to protect the metal product from chipping. The chipping-resistant coating composition of the present invention is used, for example, to coat the surface of an automobile gasoline tank. [Prior Art] Steel materials coated with lead-tin alloy plating are called turnsheets and are highly extensible. Therefore, since it does not impair sheet metal workability, it has been widely used for automobile gasoline tanks and the like. This lead-tin alloy plating has extremely excellent anti-rust properties. However, if the plating surface is damaged by impact from small stones or the like, corrosion will progress from that area.
Therefore, in order to prevent such scratches on the plated surface, the plated surface has conventionally been coated with a chipping-resistant coating composition as a protective material. As seen in JP-A-58-187469, this conventional chipping-resistant coating composition generally uses a water-dispersible acrylic resin as a binder and contains powdered fillers such as talc and calcium carbonate. Paint is used. Then, it is painted using airless painting, etc., and is then dried and coated. [Problems to be Solved by the Invention] In order to improve the chipping resistance, it is possible to reduce the amount of powder filler blended. That is, the amount of water-dispersible acrylic resin blended may be relatively increased to provide strength. However, conventional chipping-resistant coating compositions have been applied to gasoline tanks and the like and then dried at high temperatures of 80°C to 120°C. Therefore, when the amount of resin component is large as mentioned above, film formation occurs early, so the surface dries quickly, and the water vapor evaporated by the heat during drying presses the resin film, causing swelling of the coating film. There was a problem that occurred. That is, when the amount of powdery filler is small, chipping resistance is improved, but swelling occurs. On the other hand, when there is a large amount of powdery filler, water that has turned into steam easily escapes from the coating film to the outside and no blistering occurs, but there is a problem in that the chipping resistance is poor. The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a chipping-resistant coating composition that suppresses the occurrence of swelling during drying and has excellent chipping resistance. [Means for Solving the Problems] The chipping-resistant coating composition of the present invention includes a water-dispersible acrylic resin in a solid content of 100 parts by weight, and a yellow iron oxide powder of 10 to 300 parts by weight, It is characterized by being coated on the surface of the product to protect the metal product from chipping. The water-dispersible acrylic resin used in the present invention is
It refers to a product obtained by polymerizing various vinyl monomers using an emulsion polymerization method, and the types of monomers include, for example, styrene, alkylstyrene, alkyl acrylic acid or methacrylate, acrylonitrile, acrylamide, N-methylol acrylamide, methacrylonitrile, Hydrocarbon esters having an alicyclic ring or a benzene ring such as acrylic acid or methacrylic acid are used, and a homopolymer or copolymer resin thereof can be used. Preferred monomer combinations include, for example, ethyl acrylate, isopropyl acrylate, n-propyl acrylate, isobutyl acrylate, n-butyl acrylate, and 2-acrylate.
Examples include homopolymers or copolymers of monomers such as ethylhexyl. The chipping-resistant coating composition of the present invention may optionally contain other water-dispersible resins, such as styrene-butadiene rubber latex, nitrile-butadiene rubber latex, butyl rubber latex, vinyl acetate emulsion, vinyl acetate copolymer. A resin such as an emulsion or a water dispersion of polyurethane may be mixed with the water-dispersible acrylic resin. As a result of intensive research into the protection performance against chipping of various powder raw materials using the above acrylic resin as a binder, the present inventor found that the use of yellow iron oxide dramatically improves the chipping resistance and blister prevention performance. This discovery has led to the completion of the present invention. This yellow iron oxide is hydrated ferric oxide (α-FeO,
A yellow pigment containing OH), which can be either naturally occurring or synthesized. The blending amount is 10 to 300 parts by weight per 100 parts by weight of the solid content of the acrylic resin. If it is less than 10 parts by weight, the effect will not be readily apparent, and if it is more than 300 parts by weight, the binder amount will be relatively small and the various properties of the resulting coating film will deteriorate. This yellow iron oxide is used in the form of needles, and its particle size is not particularly limited, and can be 1 to 50 microns, similar to those used in ordinary paints. It is also preferred to use black iron oxide powder together with yellow iron oxide. The present inventor also studied black iron oxide and found that when black iron oxide is blended with the above acrylic resin, there is little effect on chipping resistance, but the ability to prevent blistering is significantly improved. On the other hand, the raw material cost for yellow iron oxide is relatively high. Therefore, it is preferable to use low-cost black iron oxide in combination with yellow iron oxide to reduce costs. Note that it is desirable that the blending amount of black iron oxide be smaller than the blending amount of yellow iron oxide. If the amount exceeds the amount of yellow iron oxide, the chipping resistance will decrease. Powder fillers can be added to the composition of the present invention in the same manner as in the past. As the powder filler, the same ones as those conventionally used can be used, such as talc, calcium carbonate, diatomaceous earth,
Mica, kaolin, barium sulfate, graphite, alumina, iron oxide, titanium oxide, silica, rubber powder, glass flakes, and the like can be used singly or in combination of two or more. The shape of this powder filler is not particularly limited, but
If the particle size becomes too large, clogging may occur during coating or unevenness may occur on the surface after coating, so particles having a particle size of 1 to 50 μm are preferable. The above powder filler contains water-dispersible acrylic resin solids.
For example, it can be used in a proportion of 150 parts by weight or less per 100 parts by weight. The present inventor has previously filed an application for a chipping-resistant coating composition containing a fibrous filler. (Special request 1986
-073440) It is also preferable to use this fibrous filler in combination with the composition of the present invention. In this way, the chipping resistance when formed into a thin film becomes excellent. The fibrous filler is not particularly limited as long as it is in the form of fibers, and examples include carbon fiber, rock wool, fibrous potassium titanate, fibrous magnesium sulfate, attapulgite, wollastonite, fibrous barium sulfate, and asbestos. Can be used. This fibrous filler can be blended in an amount of, for example, 100 parts by weight or less with respect to 100 parts by weight of the solid content for the water-dispersible acrylic resin. In addition to the above ingredients, the chipping-resistant coating composition of the present invention includes coloring pigments such as carbon black and organic pigments, rust preventive pigments such as metal chromates, metal phosphates, and metal metaborates, dispersants, Additives such as thickeners and organic solvents such as ethylene glycol and butyl cellosolve can also be mixed. To coat the surface of a metal product with the chipping-resistant coating composition of the present invention, it is applied to the surface of the metal product using airless coating, air spray coating, or the like. Thereafter, a film is obtained by drying and curing, for example, at a temperature of 80° C. to 120° C. for 10 minutes to 30 minutes. [Operations and Effects of the Invention] The chipping-resistant coating composition of the present invention contains yellow iron oxide as a filler. This yellow iron oxide improves chipping resistance and prevents blistering during drying. The reason for this is not clear, but yellow iron oxide is generally in the form of needle-like crystals, and it is presumed that it is effectively distributed in the coating film to disperse the impact force. It is also speculated that the prevention of swelling is due to the high oil absorption. Therefore, according to the coating composition of the present invention, it is possible to form a good coating that has excellent chipping resistance and is free from swelling. Furthermore, if a fibrous filler is used in combination, chipping resistance similar to that of the conventional one can be obtained even if the total amount of filler blended is larger than that of the conventional one. Also, by increasing the amount of filler, the occurrence of swelling is further prevented. Therefore, even if the total blending amount is approximately the same as the conventional one, the film thickness can be made thinner while maintaining the same chipping resistance, and the swelling can be prevented to the same or better extent. Therefore, the amount of coating composition used and the number of times of coating can be reduced, and costs can be reduced. Furthermore, since the fibrous filler is oriented in a layered manner between the powder fillers,
It further improves chipping resistance by dispersing the impact force of pebbles, etc. [Example] The following is a concrete explanation using Examples. In addition, all parts mentioned below mean parts by weight. Example 1 (1) Preparation of coating composition 100 parts of water-dispersible acrylic resin (AE331, manufactured by Japan Synthetic Rubber Co., Ltd., solid content 55%) and 5 parts of Poise 530 (manufactured by Kao Corporation) as a dispersant. , and water 150
60 parts of calcium carbonate, 1 part of carbon black, 50 parts of yellow iron oxide (Todacolor Y-2, manufactured by Toda Kogyo Co., Ltd.), while stirring with a disk bar.
Black iron oxide (KN-320, manufactured by Toda Kogyo Co., Ltd.)
30 parts and wollastonite as a fibrous filler (NYAD-400, manufactured by NYCO, diameter 2 μm, length
20 to 80 μm) was gradually added thereto and sufficiently stirred to obtain the chipping-resistant coating composition of Example 1. (2) Coating plate preparation conditions Prepare a turned sheet plate made of lead-tin alloy plating on a steel plate, apply the coating composition obtained above in an airless manner, set it at room temperature for 10 minutes, and then apply it at 80°C x 10 Baking drying was carried out under the conditions of +120°C x 20 minutes. Two types of film thicknesses, 100μ and 200μ, were created. The extent to which swelling occurred during drying was also investigated when a thick coating was applied, and with the coating composition of this example, almost no swelling occurred even when a coating of 900 μm was applied. (3) Chipping resistance test The two types of coated plates having film thicknesses of 100μ and 200μ obtained above were subjected to a chipping resistance test to measure chipping resistance performance. The test method is to continuously drop nuts (N-6) from a height of 2 m at an angle of 60 degrees to the coating surface of the coated plate, and calculate the total weight of the fallen nuts when the base material is exposed. evaluated. The results are shown in the table. Example 2 A chipping-resistant coating composition was prepared in the same manner as in Example 1 except that 10 parts of wollastonite was blended without adding calcium carbonate, and a coated plate was prepared in the same manner and a chipping-resistant test was conducted. Ivy. The results are shown in the table. In the case of this example, no swelling occurred at all during baking even when a thick film of 800 μm or more was coated. Example 3 A coating composition was prepared in the same manner as in Example 1, except that 10 parts of yellow iron oxide, 10 parts of black iron oxide, 150 parts of calcium carbonate, and 5 parts of wollastonite were used. A coated plate was prepared and a chipping resistance test was conducted. The results are shown in the table. In the case of this example, the coating was applied to a thick film of 950μ or more.

[Table] No swelling occurred at all. Example 4 Yellow iron oxide was added at 30% without wollastonite.
A coating composition was prepared in the same manner as in Example 1, except that black iron oxide was changed to 10 parts, and calcium carbonate was changed to 120 parts.A coated plate was prepared in the same manner and a chipping resistance test was conducted. The results are shown in the table. In the case of this example, no swelling occurred even when a thick film of 800 μm or more was coated. Example 5 Example 1 except that wollastonite and black iron oxide were not blended and yellow iron oxide was used at 70 parts.
A coating composition was prepared in the same manner as above, a coated plate was prepared in the same manner, and a chipping resistance test was conducted. The results are shown in the table. In the case of this example, no swelling occurred even when a thick film of 800 μm or more was coated. Comparative Example 1 A coating composition was prepared in the same manner as in Example 1 except that water was used at 70 parts and yellow iron oxide, black iron oxide, and wollastonite were not added. A coated plate was prepared in the same manner and chipping resistance was determined. I conducted a test. The results are shown in the table. In addition, in the case of Comparative Example 1, the film thickness was
Swelling occurred when it exceeded 180μ. Comparative Example 2 A coating composition was prepared in the same manner as in Example 1, except that calcium carbonate was 70 parts, water was 70 parts, and yellow iron oxide, black iron oxide, and wollastonite were not mixed. A chipping resistance test was conducted using the following materials. The results are shown in the table. Although the coating composition of Comparative Example 2 contained 10 parts more calcium carbonate than Comparative Example 1, almost no swelling occurred even at a film thickness of 800 μm. Comparative Example 3 A coating composition was prepared in the same manner as in Example 1, except that calcium carbonate was 120 parts, water was 70 parts, and yellow iron oxide, black iron oxide, and wollastonite were not added. A chipping resistance test was conducted using the following materials. The results are shown in the table. The coating composition of Comparative Example 3 showed almost no swelling even when the film thickness was 800 μm or more. (Evaluation) Example 5 and Comparative Example 2 contain the same amount of filler, but Example 5 has better chipping resistance and larger swollen film thickness. This is clearly due to the effect of yellow iron oxide. Furthermore, in Comparative Examples 1 to 3, the chipping resistance decreased as the amount of filler compounded increased. However, in Example 4, although the amount of filler was increased by the amount of yellow iron oxide and black iron oxide compared to Comparative Example 3, the chipping resistance was on the contrary improved. This is clearly an effect of yellow iron oxide. On the other hand, the chipping resistance of Examples 1 to 3 was determined by the film thickness.
Although it is as thin as 100μ, it shows a value of 3.0 to 8.0Kg, and has superior performance compared to Example 4. This effect is due to the addition of wollastonite in addition to yellow iron oxide.

Claims (1)

[Claims] 1. A water-dispersible acrylic resin having a solid content of 100 parts by weight and 10 to 300 parts by weight of yellow iron oxide powder, which is coated on the surface of a metal product to protect the metal product from chipping. A chipping-resistant coating composition characterized by: 2. The chipping-resistant coating composition according to claim 1, which contains 100 parts by weight or less of black iron oxide powder per 100 parts by weight of yellow iron oxide powder. 3. The chipping-resistant coating composition according to claim 1 or 2, which contains 0 to 150 parts by weight of a powdery filler such as an extender pigment and 0 to 100 parts by weight of a fibrous filler.