JP3226724B2 - Painted aluminum plated steel sheet with excellent lubricity and heat resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated aluminum-based steel sheet which is excellent in pressability of oil-free oil and can be used particularly in a heated area from room temperature to 200.degree. Used for building materials.

[0002]

2. Description of the Related Art Electrogalvanized steel sheets, hot-dip galvanized steel sheets and various types of alloy galvanized steel sheets are widely used in the fields of automobiles, home appliances and building materials. Generally, when press-forming these steel sheets, press oil is applied to reduce frictional resistance with a mold and improve workability. However, there are problems that a degreasing step of the press oil is required thereafter, and a volatile organic solvent such as specific freon or trichloroethane used in the degreasing adversely affects the environment. Therefore, from the viewpoints of saving steps, saving costs, and protecting the environment, a surface treatment method has been proposed in which good workability can be obtained without using press oil. For example, a method is known in which a resin containing an inorganic or organic solid lubricant is applied to a plated steel sheet and dried to obtain high workability and enable naked use.
Such a method is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-227178.
Gazette, Japanese Patent Publication No. Sho 62-24505,
No. 35798).

On the other hand, hot-dip aluminum-plated steel sheets are also used in the fields of automobiles, home appliances, and building materials, and the demand for development of lubricated steel sheets is increasing. The most characteristic feature of the aluminum-plated steel sheet is that it is excellent in heat resistance and weather resistance as compared with other surface-treated steel sheets such as a galvanized steel sheet. A member that requires lubrication treatment of the steel sheet, that is, a member that requires press working, is often used for parts that are usually exposed to a high temperature of 150 ° C. or higher. Therefore, a resin film that imparts lubricity needs to have properties that do not change even at high temperatures. However, although the lubricating film in the above-mentioned prior art shows effective lubricating properties in press molding, when used in a heated portion, the film is reduced or discolored, the surface becomes uneven, and the appearance is impaired during use. There is a problem.

[0004]

SUMMARY OF THE INVENTION The present invention aims at solving the above-mentioned conventional problems and at the same time, aims at developing and applying it to a product exhibiting sufficient plating characteristics. Holds and has sufficient galling resistance with molds, and has excellent heat resistance and corrosion resistance even after steel plate processing, and can be used as it is for heating parts and weather resistant materials It is intended for.

[0005]

As described above, by forming a resin film on the surface of a steel sheet, lubricity can be improved and it can contribute to good press formability. The present inventors have taken advantage of these advantages and found that a system using an isocyanate resin or a phenol resin as a curing agent for an acryl-grafted epoxy resin as an organic resin film that can be used even in a heated environment after processing is a good lubricant. The present inventors have found that characteristics and heat resistance are exhibited, and have reached the present invention.

[0006] The present invention provides a method for forming a coating layer on an aluminum-plated steel sheet or a zinc-aluminum alloy-plated steel sheet.
Chromate treatment is applied, and isocyanate resin 10-3 as a curing agent on the acrylic grafted epoxy resin.
0% by weight, or 10-30% by weight of phenolic resin,
Resin film containing 0.6 to 2.0 wt% lubricity imparting agent has excellent lubricity and heat resistance, characterized in that it is formed by coating weight 0.5 to 5.0 g / m ² It is a painted aluminum-based plated steel sheet.

Hereinafter, the resin-coated steel sheet of the present invention having excellent lubricity and heat resistance will be described in detail. In the present invention,
The chromate treatment is performed on the plating layer of the aluminum-plated steel sheet or the zinc-aluminum alloy-plated steel sheet in order to secure the adhesion of the resin film. The base resin used in the resin composition of the present invention is preferably a thermosetting resin rather than a thermoplastic resin in consideration of heat resistance. In order to maintain good press workability, a cross-linkable resin having toughness and excellent elasticity is most suitable among thermosetting resins. The acrylic-grafted epoxy-urethane resin used in the present invention, and the acrylic-grafted epoxy-phenol resin are a thermosetting cross-linkable resin obtained by reacting an epoxy resin obtained by graft polymerization of an acrylic resin with an isocyanate resin or a phenol resin. is there. This is usually used as a one-pack water-dispersible resin. The resin composition excellent in both the heat resistance and the press workability will be described below.

[0008]

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[0009] The starting material is produced by addition of a polyol or polyphenol compound, polycarboxylic acid compound or polyamine compound to epichlorohydrin, followed by ring closure by dehydrochlorination. Normal bisphenol A
A synthesized from chlorobenzene and epichlorohydrin
Diglycidyl ether is generally and often used. Other polyphenol compounds include, for example, bisphenol F, bisphenol S, resorcinol, hexahydrobisphenol A, polypropylene glycol, neopentyl glycol, and the like, and polycarboxylic acid compounds such as phthalic acid and dimer acid.

As the epoxy resin satisfying the object of achieving both the lubricity and the heat resistance of the present invention, bisphenol A diglycidyl ether synthesized from bisphenol A and epichlorohydrin is preferable.
It has 0 epoxy groups and has an average molecular weight of 3000 to 15
000 is preferred. When the molecular weight is further reduced, the heat resistance of the resin increases, but a brittle resin film having poor elasticity is obtained. On the other hand, if the molecular weight is too large, a film having excellent elasticity but poor heat resistance will be obtained.

The acrylic resin includes, for example, one or more ethylenically unsaturated carboxylic acid monomers such as (meth) acrylic acid and maleic acid, and methyl acrylate and ethyl (meth) acrylate. Acrylic esters, styrene, styrene monomers such as vinyltoluene,
A copolymer resin composed of one or more monomers such as hydroxyalkyl (meth) acrylate such as hydroxyethyl (meth) acrylate and N-substituted (meth) acrylamide is used. This acrylic resin preferably has an average molecular weight in the range of 1,000 to 5,000.

By graft-polymerizing the above-mentioned acrylic resin onto an epoxy resin, it is possible to obtain a water-soluble surface hardness that can withstand a mold galling during processing. In the graft polymerization reaction of the acrylic resin to the epoxy resin, the ratio of the acrylic resin / epoxy resin is preferably in the range of 1/3 to 2/1 by weight. If the amount of the acrylic resin is too small, the emulsifying dispersibility in an aqueous solvent is insufficient,
If it is too large, the heat resistance tends to decrease, and the elasticity of the resin film (coating film) tends to decrease.

By using an isocyanate resin or a phenol resin as a curing agent for the acrylic grafted epoxy resin, a tough and highly elastic urethane resin or a phenol resin can be cross-linked. Conventionally, as a system obtained by adding an isocyanate resin or a phenol resin as a curing agent to a bisphenol-type epoxy resin, and silica as an additive, for example, Japanese Patent Application Laid-Open No. 1-111830 is known. In some cases, whitening of the sliding portion may be caused by the drawing process. In the present invention, by using an acrylic grafted epoxy resin, a uniform and tough crosslinked film can be formed, and at the same time, a film having a surface hardness that can withstand advanced processing can be formed.

As the isocyanate resin, a blocked isocyanate such as hexamethylene diisocyanate is used, and its content is 10 to 30% by weight based on the resin film (coating film). When a phenol resin is used as a curing agent, a resol-type phenol resin is used and is blended in an amount of 10 to 30% by weight. By curing these resin systems at 200 ° C. to 240 ° C., a tough resin film having high heat resistance can be formed. The reason that the content of the curing agent is within the above range is that if the amount is less than 10% of the weight of the resin film (coating), the formation of cross-linking is insufficient, the appearance after processing becomes poor, and 30% If it exceeds, the self-condensation reaction between the curing agents becomes dominant, and an efficient cross-linked coating film is not formed, and the appearance becomes poor after processing.

Next, the lubricity imparting agent will be described. Generally, as a dry lubricant, wax, molybdenum disulfide, organic molybdenum, graphite, carbon fluoride,
Metal soap, boron nitride, fluororesin and the like are known, and are used for improving lubricity as additives for bearing lubricants and greases. In a resin film as in the present invention, the addition of such a lubricity-imparting agent is very effective in maintaining lubricity. These lubricity-imparting agents are required not only to give good lubricity but also good slidability in continuous press and high-speed press (for example, JP-A-2-43040).

Therefore, in the present invention, as a result of earnestly studying a lubricity imparting agent which maintains lubricity and can be used for continuous pressing, carnauba wax, fluororesin particles, and polyethylene wax exhibit excellent characteristics. I found something. All of these waxes exhibit high lubricating properties. In particular, carnauba wax has a melting point of about 86.
Since it has a relatively high melting point of ° C., it is hardly affected by heat at the time of processing and has excellent wear resistance. In addition, it is inexpensive and has great economical advantages, so that it is preferably used.

FIG. 1 shows the relationship between the amount of carnauba wax added as a lubricity-imparting agent, LDR (critical drawing ratio in cylindrical deep drawing test) as an index of lubricity evaluation, and mold galling. As is clear from the figure, carnauba wax is 0.6 to 2.0% by weight based on the resin film (coating).
% Is optimal. This is because if it is less than 0.6%, sufficient lubricity cannot be obtained, and if it exceeds 2.0%, the resin film is softened, which hinders press working.

The coated steel sheet according to the present invention comprises a dispersion of the acryl-grafted epoxy-urethane resin or the acryl-grafted epoxy-phenol resin as described above and carnauba wax as a lubricity-imparting agent within the above-mentioned predetermined range. Disperse in aqueous solvent, and furthermore pH 7 ~
A coating solution is prepared by adding an organic amine so as to be 11, and the coating is applied to a steel plate and dried to obtain a coating solution. As the aqueous solvent, water or a mixture of water and a hydrophilic organic solvent is used. As the hydrophilic organic solvent, for example, alcohols such as methanol and butanol, glycol ethers and glycol esters are preferably used. As the organic amine, for example, an alkylamine such as trimethylamine, an alkanolamine such as dimethylethanolamine, and a polyvalent amine such as ethylenediamine are preferably used.

In the present invention, the adhesion amount of such a lubricating resin film is 0.1% by weight of the dry resin film (coating) on one side.
5 to 5.0 g / m ² . FIG. 2 shows the relationship between the amount of the resin film adhered, the LDR, and the mold galling property. As is clear from the figure, when the adhesion amount is less than 0.5 g / m ² , the effect of improving the lubricity is small, and the press moldability is reduced, and the adhesion is reduced to 5.0 g / m ^2.
If it exceeds m ² , the galling resistance in press molding is reduced, and it is not economical. In the present invention, as the steel sheet material, an aluminum-plated steel sheet and a zinc-aluminum alloy-plated steel sheet that have been subjected to a chemical conversion treatment such as a chromate treatment or a phosphate treatment are preferably used.

[0020]

EXAMPLES Under the following conditions, test pieces of the coated steel sheet of the present invention were prepared. 1. Coated steel sheet (A) Hot-dip aluminum-coated steel sheet Sheet thickness 0.6 mm Aluminum plating adhesion amount 40 g / m ² (B) Hot-dip zinc-aluminum-coated steel sheet Sheet thickness 0.6 mm Zinc-aluminum adhesion weight 40 g / m ² Aluminum content 55 % 2. Chromate treatment CrO ₃ 10 g / l, SiO ₂
A chromate treatment solution having a composition of 30 g / l (manufactured by Nissan Chemical; Snowtex) was applied with a roll coater, squeezed with a rubber roll, and dried with hot air. The amount of chromate film
It is 20 mg / m ² on one side. 3. Resin film A treatment solution having the composition shown in Table 1 was applied to both surfaces by bar coating so as to have a coating weight of 0.5 to 5.0 g / m ^{2 on} one surface, and was dried at an ultimate plate temperature of 240 ° C for 60 seconds. A film was formed.

[0021]

[Table 1]

The obtained resin-coated steel sheet was subjected to a cylindrical deep drawing test, a heat resistance test, and a salt spray test to examine a dynamic friction coefficient, a limit drawing ratio, a mold galling resistance, a heat resistance, and a corrosion resistance. The cylindrical deep drawing test was evaluated by measuring a limit drawing ratio (LDR) at a punch diameter of 50 mm and a wrinkle suppressing pressure of 500 kg / mm ² . The coefficient of kinetic friction is determined by the Bowden method (1
0mm steel ball, load 500g, sliding speed 0.5m / mi
n). In addition, the mold galling resistance was evaluated by cellophane tape peeling after cylindrical drawing.

◎: no peeling at all, Δ: light mold galling,
Δ: Powdering occurred very slightly, ×: Powdering occurred considerably. Heat resistance was as follows: weight loss after continuous heat treatment at 200 ° C., color difference,
It was evaluated by the gloss retention. Weight loss was evaluated by weighing the weight change before and after heating. ◎: 0 to 5%, Δ: 5 to 15%, Δ: 15 to 30
%, ×: 30% or more The color difference was evaluated using a SM color computer (manufactured by Suga Test Instruments) before and after heating. ◎: 0 to 5%, Δ: 5 to 10%, Δ: 10 to 20
%, ×: 20% or more The gloss retention was evaluated by using a digital gonio-gloss meter (manufactured by Suga Test Instruments) before and after heating. ：: 0 to 10%, Δ: 10 to 20%, Δ: 20 to 30
%, ×: 30% or more The corrosion resistance was evaluated by the rust generation rate after 500 hours of the salt spray test and the swollen width from the cross cut.

[0024]

[Table 2]

The results are shown in Table 2. As is clear from the table, the coated aluminum-based plated steel sheet of the present invention not only shows good press workability but also does not change much in properties even after heat treatment at 200 ° C. Further, the corrosion resistance after processing is also good.

[0026]

As described above, according to the present invention, a paint comprising an aqueous dispersion of an acryl-grafted epoxy-urethane resin and an acryl-grafted epoxy-phenol resin containing a lubricity imparting agent such as carnauba wax. Is applied to the surface of the steel sheet and dried, so that press working such as deep drawing can be performed without using press oil, and a resin film having excellent heat resistance can be formed.
In particular, according to the present invention, since the epoxy-urethane resin and the epoxy-phenol resin constituting the film are thermosetting resins, by performing a curing treatment at a high temperature, the crosslinking reaction of the resin is promoted, and complete. Can be done.
Therefore, the glass transition point is high, the lubricity is maintained without softening against a rise in the mold temperature during press molding, and the heat resistant temperature can be improved. Further, since the above-mentioned paint is a one-pack type resin, it is easy to handle. Further, since an aluminum-plated steel plate is used as a coating base plate, a steel plate coated with the above resin has excellent corrosion resistance. The coated aluminum-plated steel sheet having excellent lubricity and heat resistance according to the present invention can be used not only in a bare state after press working but also in a painted state.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the content of carnauba wax as a lubricity-imparting agent in a resin film and the limit drawing ratio and mold galling property of the obtained coated steel sheet;

FIG. 2 is a graph showing the relationship between the adhesion amount of the obtained resin film and the limit drawing ratio and mold galling property.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-180574 (JP, A) JP-A-4-330970 (JP, A) JP-A-2-266929 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C23C 22/00-22/86 C23C 28/00

Claims (2)

(57) [Claims] An aluminum-plated steel sheet or zinc-
Chromate treatment is performed on the plating layer of the aluminum alloy-plated steel sheet, and an acrylic graft-grafted epoxy resin contains 10 to 30% by weight of an isocyanate resin as a curing agent and 0.6 to 2.0% by weight of a lubricity imparting agent thereon A coated aluminum-based steel sheet excellent in lubricity and heat resistance, characterized in that a resin film to be formed is formed with an adhesion amount of 0.5 to 5.0 g / m ² . 2. An aluminum-plated steel sheet or zinc-
A chromate treatment is applied to the plating layer of the aluminum alloy-plated steel sheet, and an acrylic-grafted epoxy resin contains 10 to 30% by weight of a phenol resin as a curing agent and 0.6 to 2.0% by weight of a lubricity-imparting agent thereon. A coated aluminum-based steel sheet having excellent lubricity and heat resistance, characterized in that a resin film to be formed is formed with an adhesion amount of 0.5 to 5.0 g / m ² .