JP2005138294A - Coated metal sheet excellent in lubricity and processability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated metal sheet capable of being formed into a product shape enhanced in dimensional precision by press processing without requiring a lubricant. <P>SOLUTION: This coated metal sheet is constituted by dispersing polyethylene resin particles 3 and polyethylene-fluoroplastic resin particles 4 in the resin coating film 2 provided on a substrate metal sheet 1 in a compounded dispersed state. The polyethylene resin particles 3 are melted in a resin coating drying/baking process to become a bled polyethylene resin 5 to cover the surface of the resin coating film 2. The wax action of the bled polyethylene resin 5 and the rolling action of the polyethylene-fluoroplastic resin particles 4 cooperate to improve the lubricity and processability of the coated metal sheet. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a coated metal plate excellent in lubricity and workability that can be pressed into a product shape without the need to separately apply lubricating oil.

Various metal plates used for interior materials, exterior materials, cover materials, and the like are formed into target shapes by press working. If the metal plate material does not slide smoothly with respect to the mold during pressing, surface defects such as rubbing flaws are likely to occur in the processed product, and the mold life is shortened. Moreover, when the steel plate provided with the chemical conversion treatment film which is hard and inferior in lubricity is press-worked, the defect part from which the chemical conversion treatment film peeled becomes a starting point of corrosion generation.
Generation | occurrence | production of a surface defect and the fall of a metal mold | die lifetime can be prevented by apply | coating a highly viscous lubricating oil and providing lubricity to a raw material metal plate. When using a lubricating oil, the lubricating oil is applied to the material metal plate prior to the press working, and the lubricating oil is removed from the processed product by degreasing after the pressing. Lubricating metal plates that do not require lubricating oil have been developed because the application and removal of lubricating oil can be omitted if the press working property of the material metal plate is good, and the number of press working steps is reduced.

As a lubricated metal plate that can be pressed into a product shape without oil coating, a coated metal plate in which an organic coating film excellent in lubricity and workability is provided on the entire surface of the material metal plate is known. The present applicant also introduces in Patent Document 1 a coated metal plate provided with a discontinuous organic coating film in which an organic resin powder having a high melting point is dispersed. In the coated metal plate, the entire surface of the zinc or zinc alloy plated steel plate is chromated, and then a urethane discontinuous resin coating film in which a high melting point resin powder such as polyethylene or polypropylene is dispersed is provided on the chromate coating. Many coated steel sheets that can be pressed without lubrication by providing a continuous resin coating have been reported (Patent Documents 2 and 3).
JP-A-5-305266 JP-A-1-301333 Japanese Unexamined Patent Publication No. 4-313368

  In a coated metal plate with lubricity provided by a discontinuous resin coating, the discontinuous resin coating is thin, and depending on the particle size of the resin powder dispersed in the resin coating, powdery deposits can easily accumulate on the mold. , Frequent maintenance of the mold is required. The surface color tone may fluctuate with damage to the resin coating. Even with a coated metal plate provided with a continuous resin coating film, powdering may occur due to the relationship between the film thickness and the resin powder. When a large number of metal cutting plates are continuously pressed, processing defects such as powdering and deposition of powdery deposits on the mold are further promoted. In addition, when a processed product with high dimensional accuracy tends to be desired, there is a strong demand for a metal plate that has much better lubricity and workability than conventional lubricated steel plates.

  By improving the lubricant dispersed in the resin coating, the present invention does not require the application of a lubricant, and even when pressed at a high degree of processing, there is no reduction in processing defects and mold life, and dimensional accuracy is improved. The object is to provide a coated metal plate that can be pressed into a high product shape.

  The coated metal plate of the present invention is provided with a resin coating film in which polyethylene-fluororesin particles in which fluororesin fine powders are bonded to the surfaces of polyethylene resin powder and polyethylene resin particles are combined and dispersed as a lubricant on the surface of the base metal plate. Yes. It is preferable that the polyethylene-fluororesin particles protrude from a part of the surface of the resin coating, and the remaining part or all of the surface of the resin coating is covered with a reflowed polyethylene resin powder.

In the coated metal plate according to the present invention, a resin coating film 2 is provided on the surface of the base metal plate 1, and polyethylene resin particles 3 and polyethylene-fluorine resin particles 4 are compositely dispersed in the resin coating film 2. The polyethylene-fluororesin particle 4 is a particle in which a fluororesin fine powder is bonded to the surface of the polyethylene resin particle, heat resistance is imparted by the fluororesin fine powder bonded to the particle surface, and the specific gravity is slightly higher than that of the polyethylene resin powder. However, the dispersion stability in an aqueous solution is also improved as compared with a conventional fluororesin particle alone, which has a large specific gravity and does not stably disperse in the liquid.
In the state in which the resin coating containing the polyethylene resin particles 3 and the polyethylene-fluorine resin particles 4 is applied to the base metal plate 1, the polyethylene resin particles 3 and the polyethylene-fluorine resin particles 4 are suspended in the wet resin coating film 2. (FIG. 1a).

In the process of raising the temperature during drying and baking, moisture evaporates from the resin paint, and the film thickness of the resin coating film 2 decreases. As the film thickness decreases, polyethylene resin particles 3 and polyethylene-fluorine resin particles 4 protrude from the surface of the resin coating film 2 (FIG. 1b).
The plate temperature is usually set in the range of 150 to 200 ° C. when the resin coating is dried and baked, and the polyethylene resin has a melting point in the range of 100 to 130 ° C. although it varies depending on the type and molecular weight. When the heating temperature at the time of drying and baking exceeds the melting point of the polyethylene resin particles 3, the polyethylene resin particles 3 protruding from the resin coating 2 are reflowed, and the surface of the resin coating 2 is covered with the bleed polyethylene resin 5 ( FIG. 1c). Since the polyethylene-fluorine resin particles 4 have high heat resistance because the fluororesin fine powder is bonded to the surface of the polyethylene resin powder, the initial particle shape does not bleed even at a high temperature exceeding the melting point of the polyethylene resin particles 3. To maintain.

  Since the polyethylene-fluororesin particles 4 protrude from the resin coating 2 and part or all of the surface of the resin coating 2 is covered with the bleed polyethylene resin 5, the lubricity and workability of the coated metal plate are greatly improved. Is done. The improvement in lubricity and workability is achieved by the polyethylene-fluorine resin particles 4 protruding from the resin coating 2 in addition to the polyethylene concentration on the surface of the resin coating 2 being increased by the polyethylene-fluororesin particles 4 and the bleed polyethylene resin 5. It is inferred that No. 4 exhibits the function of a roller during press working. A part of the polyethylene-fluorine resin particles 4 is partially crushed as the processing deformation progresses, but the crushed polyethylene-fluorine resin particles 4 became a supply source of polyethylene resin, and a high surface pressure was applied during press working. Excellent lubrication can be expected even at times.

As the base metal plate 1, various metal plates such as ordinary steel, low alloy steel, various plated steel plates, stainless steel, aluminum, aluminum alloy, copper plate and the like are used. Prior to the formation of the resin coating film 2, coating film adhesion may be improved by applying chemical conversion treatment such as chromate treatment, phosphate treatment, and Cr-free treatment to the base metal plate 1. Among these, Cr-free treatment, which forms a chemical conversion film with valve metal oxide, hydroxide, fluoride, etc., is a promising chemical conversion method because of its low environmental impact.
The resin coating film 2 is formed from a resin paint in which polyethylene resin particles 3 and polyethylene-fluorine resin particles 4 are blended.

Resin coatings are based on water-soluble types and water-dispersed emulsions that can be processed even on production lines that do not have an explosion-proof oven. Various additives such as anti-rust pigments, colored pigments, extender pigments, metallic pigments, and coloring pigments are available. It is blended according to the application. Examples of the base resin include acrylic resin, urethane resin, epoxy resin, and polyolefin resin.
The polyethylene resin particles 3 preferably have a melting point usually in the range of 100 to 130 ° C. and have a particle size that protrudes from the surface of the resin coating film 2. When heated to a drying temperature (usually 150 ° C. or higher) in order to improve the water resistance and alkali resistance of the resin coating film 2, the portion protruding from the resin coating film 2 is melted and becomes a bleed polyethylene resin 5. This type of polyethylene resin particle 3 includes HYTEC E-9016, HYTEC E-1000 (Toho Chemical Co., Ltd.), CJ-172B, CJ-137 (Koyo Chemical Co., Ltd.), Permarine KUE-4, Permarine KUE Commercially available resin particles such as -5 (manufactured by Sanyo Chemical Industries, Ltd.) can be used.

The blending amount of the polyethylene resin particles 3 with respect to the base resin is preferably adjusted so that the ratio of the bleed polyethylene resin 5 in the surface of the resin coating film 2 is 0.2 area% or more. When the occupation area ratio of the polyethylene resin 5 is less than 0.2 area%, the lubricating action of the polyethylene resin 5 tends to be insufficient.
The polyethylene-fluorine resin particles 4 are particles obtained by adsorbing fluororesin fine powder to polyethylene resin particles by bringing fluororesin fine particles into contact with heated and softened polyethylene resin particles. The adsorption of the fluororesin fine powder increases the specific gravity of the resin particles and thus improves the dispersion stability in the aqueous solution. Since the heat resistance is also improved, the initial grain shape is maintained at a normal drying temperature of about 150 ° C. The polyethylene resin powder preferably has a particle size capable of projecting from the surface of the resin coating film 2, and the fluororesin adsorbed on the polyethylene resin powder preferably has a particle size of 0.3 μm or less so as to cover the surface of the polyethylene resin powder.

Compared with polyethylene resin powder, fluororesin powder has excellent heat resistance with a melting point of 300 ° C. or higher, and it does not bleed like polyethylene resin particles 3 in the process of drying and firing the resin coating applied to base metal plate 1. Maintain the grain shape. However, the specific gravity is large compared to water-based resins such as urethane and acrylic, and the dispersibility in water-based emulsions is poor. By making the fluororesin fine powder, it can be uniformly dispersed in the aqueous emulsion. However, it is difficult to expect the fine powder fluororesin to protrude from the resin coating film 2.
On the other hand, polyethylene resin particles combined with fluororesin powder have the same heat resistance as fluororesin powder and dispersibility equivalent to polyethylene resin particles 3, and after initial drying and baking without coagulation sedimentation in the resin coating. Maintain the grain shape. Therefore, when the formed resin coating film 2 is observed, the polyethylene-fluororesin particles 4 protruding from the resin coating film 2 are detected.

  In order to project the polyethylene-fluorine resin particles 4 from the resin coating film 2 and to cover the surface of the resin coating film 2 with the bleed polyethylene resin 5, the polyethylene resin particles 3, having a particle size protruding from the coating film surface 3, It is preferable to blend the polyethylene-fluorine resin particles 4 into the base resin of the resin coating film 2. The polyethylene-fluororesin particles 4 have a specific gravity slightly larger than that of the polyethylene resin particles 3 because the fluororesin powders are bonded. The particle size distribution of the fluororesin powders bonded to the polyethylene resin powders, individual polyethylene resin particles 3 It can be adjusted to an appropriate specific gravity by controlling the amount of the fluororesin powder attached to.

The polyethylene resin particles 3 and the polyethylene-fluorine resin particles 4 have an average particle size of 0.8 to 3.0 × t when the film thickness of the resin coating film 2 is t so as to protrude from the resin coating film 2 after firing. It preferably has a diameter. When the average particle size is less than 0.8 × t, the ratio of the polyethylene-fluorine resin particles 4 embedded in the resin coating film 2 increases, and the number of polyethylene-fluororesin particles 4 protruding from the resin coating film 2 is ensured. It is necessary to add an excessive amount of polyethylene-fluororesin particles 4. Conversely, when polyethylene-fluorine resin particles 4 having a large particle size exceeding 3.0 × t are dispersed in the resin coating film 2, the amount of protrusion of the polyethylene-fluorine resin particles 4 becomes too large, and the polyethylene-fluorine during press working The resin particles 4 are easily removed.
The blending ratio of the polyethylene-fluororesin particles 4 to the resin coating is adjusted so that the ratio of the polyethylene-fluororesin particles 4 protruding from the resin coating film 2 to the surface of the resin coating film 2 is 0.1 area% or more. It is preferable. The polyethylene-fluorine resin particles 4 exhibit a remarkable roller action with an occupied area ratio of 0.1 area% or more.

  The coated metal plate of the present invention exhibits excellent workability due to the roller action of the polyethylene-fluorine resin particles 4 and the lubrication action of the bleed polyethylene resin 5, but the mass ratio of polyethylene-fluorine resin particles 4: polyethylene resin particles 3 is When set in the range of 0.05 to 0.8, lubricity and workability are further improved. If the mass ratio is less than 0.05, the lubricity is insufficient when processing at a high surface pressure. If the mass ratio exceeds 0.8, the contact area of the mold / resin powder decreases, and the lubricity of the bleed polyethylene resin 5 is reduced. descend.

  A coating composition containing polyethylene resin particles 3 and polyethylene-fluorine resin particles 4 is applied to the base metal plate 1 by spin coating, spraying, etc., and then dried to form a resin coating film having a predetermined performance. Formed. The resin coating film preferably has a dry film thickness of 0.3 μm or more in order to completely cover the base metal plate 1. If the resin coating film is too thin, the holding power of the resin powder will be insufficient. However, if it exceeds 5 μm, the quality improvement due to the thick film becomes saturated, which is economically disadvantageous. In bleeding the polyethylene resin particles 3, the drying temperature is set to a temperature of 100 ° C. or higher that exceeds the melting point of the polyethylene resin particles 3. However, heating at a high temperature exceeding 300 ° C. tends to bleed up to the fluororesin, impairing the action of the rollers, and easily lowering the lubricity.

Using the hot-dip Zn-Al-Mg alloy plated steel sheet forming the Zn-6 mass% -3 wt% Mg alloy plating layer at a coverage of one side per 45 g / m ² in a weak deoxidized steel having a thickness of 0.8mm to the original sheet did. Treatment liquid in which silica sol, phosphate and zirconium salt are added as inorganic rust preventives, and various polyethylene-fluorine resin particles 4 and polyethylene resin particles 3 (melting point 108 ° C.) as lubricants are added to urethane resin emulsions in various amounts. (Table 1) was prepared.

The treatment liquid was directly applied to the original plate, and dried and fired at a temperature of 150 ° C., thereby forming a resin coating film 2 having a thickness of 2 μm in which polyethylene-fluorine resin particles 4 and bleed polyethylene resin 5 were dispersed.
A test piece was cut out from each coated plated steel sheet after the resin coating 2 was formed, and the lubricity and workability were investigated under the following conditions, and the stability of the treatment liquid was investigated.

[Lubricity under low surface pressure]
A SUS304 stainless steel plate BA finish was used as a reference plate, and was placed on the test piece. The dynamic friction coefficient was measured when the reference plate was slid along the surface of the test piece at a sliding speed of 160 mm / min while applying a load of 200 gf. Coefficient of dynamic friction: ◎ for 0.10 or less, ○ for 0.15 or less, △ for 0.20 or less, and x for a test piece exceeding 0.20 were evaluated for lubricity under low surface pressure.
[Lubricity under high surface pressure]
Measure the pulling force when the SKD11 mold is brought into contact with both sides of the test piece with a width of 30 mm and a length of 300 mm, and the test piece is pulled out at a pulling speed of 100 mm / min while applying a load of 600 kgf through the mold. did. Pulling force: 250 kgf or less was evaluated as ◎, 300 kgf or less as ◯, 400 kgf or less as Δ, and pulling force exceeding 400 kgf as x.

[Processability]
Using a punch having an outer diameter of 40 mm, cylindrical drawing was performed at a drawing ratio of 2.35, and the outer diameter ratio (ratio of the outer diameter and the blank diameter at which the material fractured during the drawing process) was investigated. Outer diameter ratio: The workability was evaluated with ９５ being 0.95 or less, ○ being 0.96 or less, Δ being 0.97 or less, and × being a test piece exceeding 0.97.
[Treatment solution stability]
The chemical conversion solution was stirred and allowed to stand for 24 hours, and then the chemical conversion solution was observed. Evaluate the stability of the treatment liquid with ◎ as the treatment liquid with the same properties as immediately after preparation, △ with the treatment liquid with some sedimentation or floating resin particles observed, and x with the treatment liquid with significant sedimentation or suspension of resin particles. did.

As can be seen from the results of the investigation in Table 2, the treatment liquid in which polyethylene resin particles and polyethylene-fluorine resin particles are added in combination has excellent lubricity and workability without causing sedimentation or floating of the resin particles even after standing for 24 hours. An excellent coating film could be formed. The lubricity improves as the bleed amount of the polyethylene resin and the dispersion amount of the polyethylene-fluorine resin particles increase, and the lubricity and workability under high surface pressure due to the roller effect of the polyethylene-fluorine resin particles are also improved. It is improved according to the increase of resin particles. In addition, when the particle size of polyethylene resin particles and polyethylene-fluorine resin particles is properly selected in relation to the film thickness of the resin coating film, the bleed effect and roller effect greatly affect the lubricity and workability under high surface pressure. Was exerting.
On the other hand, the processing liquid (Comparative Examples 13 to 16) containing polyethylene resin particles and fluororesin fine powder lacks lubricity and processability, and the processing liquid (Comparative Example 15) with fluororesin fine powder added alone. Was inferior in stability and could not be used for uniform processing.

  As described above, since the bleed polyethylene resin 5 and the polyethylene-fluororesin particles 4 are compositely dispersed in the resin coating 2, the sliding action of the polyethylene resin 5 and the polyethylene- Due to the roller action of the fluororesin particles 4, excellent lubricity and workability are exhibited, and the product shape that requires high dimensional accuracy is also pressed. Since it is not necessary to apply the lubricant prior to the press working or remove the lubricant after the press working, the number of press working steps is small, and the productivity can be improved.

Schematic diagram explaining the process of forming a resin coating film from a resin coating containing polyethylene resin powder and polyethylene-fluorine resin powder

Explanation of symbols

1: Underlying metal plate 2: Resin coating film 3: Polyethylene resin particles 4: Polyethylene-fluorine resin particles 5: Bleed polyethylene resin

Claims (3)

  Lubricity characterized by a composite dispersion of a polyethylene-fluororesin powder in which a polyethylene resin powder and a fluororesin fine powder are bonded to the surface of a polyethylene resin particle as a lubricant on a resin coating provided on a base metal plate, Painted metal plate with excellent workability.   2. The coated metal plate according to claim 1, wherein polyethylene-fluororesin particles protrude from a part of the surface of the resin coating, and a part or all of the remaining surface of the resin coating is covered with a bleed polyethylene resin.   The coated metal plate according to claim 1 or 2, wherein a resin coating is provided on the base metal plate via a chemical conversion coating.

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