JPH0632780B2 - Resin-coated steel sheet with excellent press formability, coatability after processing, and corrosion 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 resin-coated steel sheet having excellent press formability, paintability after processing and corrosion resistance, which are used in automobiles, household electric appliances, building materials and the like.

[0002]

2. Description of the Related Art Generally, when pressing a steel plate,
Press oil is applied to the surface of the steel sheet to improve its workability. However, if the press oil is applied in this manner, the press oil is scattered during the press working of the steel sheet, which deteriorates the working environment or causes pollution problems, and further requires a degreasing step after the press working. There is a problem such as.

Therefore, various steel sheet surface treatment methods have been proposed in order to obtain good press workability without using press oil. For example, a mill bond coating or a wax coating is formed on the surface of the steel sheet, or a resin emulsion or resin aqueous solution containing an inorganic or organic solid lubricant is used as a surface treatment agent, and this is applied to the surface of the steel sheet. A method of forming a resin film by drying is known. In particular, the latter method is preferably used as a surface treatment method in the case of a product that is subjected to strong processing, or in the case where degreasing is omitted after processing and the product is required to have paintability.

In this method, graphite or molybdenum disulfide is conventionally used as the solid lubricant in the inorganic system, and paraffin or polyethylene wax or metal such as calcium stearate is used in the organic system. Stone Ken is used. As described above, a method using an inorganic solid lubricant is disclosed in, for example, JP-A-61-22717.
No. 8, JP 61-227179, JP 6
It is described in JP-A No. 1-231177, JP-A No. 61-2799687 and the like.

However, when graphite or molybdenum disulfide is used as the solid lubricant, it is generally difficult to adjust the color tone of the surface of the steel sheet and, in addition, to provide a lubricating performance capable of withstanding the heavy working of the steel sheet, When a large amount of a lubricant is added to the surface treatment agent, the adhesiveness of the resin coating obtained is extremely poor and the corrosion resistance of the steel sheet after processing deteriorates. Furthermore, since graphite and molybdenum disulfide have a large specific gravity, it is difficult to disperse them uniformly in the surface treatment agent, and they easily settle in the surface treatment agent not only during storage, but also during storage, so storage stability and workability are improved. There are also difficulties.

On the other hand, when using a surface treatment agent such as a resin emulsion to which wax is added, after applying it to a steel plate,
When dried, the wax floats on the surface of the resin film, so the surface has good slipperiness, but the temperature rise of the mold due to continuous pressing causes the wax on the surface to liquefy and flow, and its lubrication Performance deteriorates, peeling of the resin coating occurs, and corrosion resistance after processing also deteriorates.

When metal soap is used as a solid lubricant, the resin coating formed on the surface of the steel sheet has high hygroscopicity, which causes tackiness and a problem in corrosion resistance. According to the surface treatment agent containing the polyethylene particles, the resulting coating film does not exhibit sufficient performance against extreme pressure during press molding, causing peeling of the coating film, resulting in poor corrosion resistance after press molding.

Recently, JP-A-63-162886 proposes a surface treatment agent in which an epoxy resin is added to a carboxylated polyolefin resin to achieve cross-linking film formation at low temperature. However, such a surface treatment agent
Since the cross-linking of the coating film starts at low temperature, the surface treatment agent in some cases lacks stability in actual operation. Therefore, the present inventors have already formed a resin coating on the surface of the steel sheet, which is mainly composed of an acrylated epoxy resin and contains a predetermined amount of fluorine-based resin particles and silica particles, thereby improving press formability. It has been found that an excellent resin-coated steel sheet can be obtained. However, even in such a resin-coated steel sheet, the fluorine-based resin particles as a lubricant do not have sufficient adhesiveness to the acrylated epoxy resin that is the base resin, and the surface of the obtained resin-coated steel sheet has Because some fluororesin particles are exposed,
Fluorine-based resin particles may be peeled off during the production of a resin-coated steel sheet and may be wound around a roll in a line, resulting in a decrease in productivity.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in order to solve the problems in the above-mentioned conventional resin-coated steel sheet, and in particular, is mainly composed of an acrylated epoxy resin, fluorine-based resin particles and silica. In the production of a resin-coated steel sheet having a resin coating formed by containing a predetermined amount of particles on each surface, the adhesiveness between the acrylated epoxy resin and the fluorine-based resin particles is improved to prevent winding around the roll during production. We provide a resin-coated steel sheet that is excellent in lubricity, can withstand extreme pressure during strong working and temperature rise of molds, and has excellent paintability and corrosion resistance after working. The purpose is to do.

[0010]

A resin-coated steel sheet excellent in press formability, coatability after processing and corrosion resistance according to the present invention is mainly composed of an acrylated epoxy resin and has a fluorine resin particle content of 2.5 to 30% by weight, 1 to 30% by weight of silica particles
And the amount of resin coating containing ethylene glycol mono-normal hexyl ether 1 to 20% by weight is 0.1 to 5 g
/ Square meter is formed on the surface of the steel sheet.

The acrylated epoxy resin used in the present invention is a thermosetting resin obtained by reacting an acrylic resin and an epoxy resin, and is usually used as a one-pack type water-dispersible resin. The acrylic resin is the first
Which is a copolymer of an ethylenically unsaturated carboxylic acid as a monomer of and a second monomer having a copolymerizability therewith,
Usually, an ethylenically unsaturated carboxylic acid and a second monomer having a copolymerizability therewith are copolymerized in a solvent with a usual radical polymerization initiator such as azobisisobutyronitrile or benzoyl peroxide. It can be obtained by polymerizing. In this copolymerization, the ethylenically unsaturated carboxylic acid is used in an amount of 12% by weight or more based on all monomers. Ethylenically unsaturated carboxylic acid is one of all monomers
When it is at least less than 2% by weight, it reacts with an epoxy resin as described below, and even an acrylated epoxy resin has poor dispersion stability in an aqueous medium.

As the ethylenically unsaturated carboxylic acid, for example, one kind or two or more kinds of (meth) acrylic acid, maleic acid, itaconic acid and the like are preferably used. Examples of the second monomer include (meth) acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, and propyl (meth) acrylate, styrene,
Styrene-based monomers such as vinyltoluene and chlorostyrene, hydroxyethyl (meth) acrylate such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, N-substitution such as N-methylol (meth) acrylamide One or more of epoxy group-containing (meth) acrylic acid esters such as (meth) acrylamide and glycidyl (meth) acrylate, and (meth) acrylonitrile are used.

The acrylated epoxy resin is obtained by esterifying the acrylic resin and the epoxy resin in a hydrophilic organic solvent in the presence of a basic compound, for example, a tertiary amine compound such as dimethylethanolamine. It can be obtained by reacting. Acrylic resin is
The weight average molecular weight is preferably in the range of 2,000 to 10,000. When the molecular weight is too small, the emulsifying dispersibility in the aqueous dispersion medium is insufficient, and when the molecular weight is too large, gelation tends to occur during the reaction with the epoxy resin.

As the epoxy resin, for example, an epichlorohydrin / bisphenol type epoxy resin is preferably used, and particularly, it has an average of 1.1 to 2.0 epoxy groups in the molecule and has an average molecular weight of Those having a value of 800 or more are preferably used. In the reaction between the acrylic resin and the epoxy resin, the weight ratio of the acrylic resin / epoxy resin is preferably 1.9 / 1 to 1/10.

The acrylated epoxy resin is obtained by reacting an epoxy resin with an ethylenically unsaturated carboxylic acid, and using the same ethylenically unsaturated carboxylic acid and other copolymerizable monomer as a polymerization initiator. It can also be obtained by copolymerization. In the resin-coated steel sheet according to the present invention, the dispersion of the acrylated epoxy resin, the fluororesin, and the silica particles as described above are dispersed in the aqueous dispersion medium within the above-mentioned predetermined range, and further the pH becomes 4 to 11. Like this, after adding ammonia or organic amine,
A resin-coated steel sheet according to the present invention can be obtained by adding a predetermined amount of ethylene glycol mononormal hexyl ether to prepare a surface treatment agent, applying the surface treatment agent to a steel sheet, and drying.

As the aqueous dispersion medium, water or a mixture with a hydrophilic organic solvent containing at least 10% by weight of water is used. Examples of the hydrophilic organic solvent include lower aliphatic alcohols such as methanol, ethanol, isopropanol, and n-propanol, glycol ethers such as ethylene glycol methyl ether, glycol esters such as ethylene glycol acetate, tetrahydrofuran, ethers such as dioxane, and the like. Dimethylformamide, diacetone alcohol and the like are used.

The organic amine may be, for example,
Alkylamines such as trimethylamine and triethylamine, alkanolamines such as diethanolamine, polymorphic amines such as morpholines, ethylenediamine and diethylenetriamine are preferably used. Furthermore, the surface treatment agent may contain, for example, a water-based aminoplast resin or phenoplast resin as a curing agent, if necessary.

The resin-coated steel sheet according to the present invention is mainly composed of the above-mentioned acrylated epoxy resin, and has fluorine resin particles of 2.5.
~ 30 wt%, 1-30 wt% of silica particles and 1-20 wt% of ethylene glycol mono-normal hexyl ether, a resin coating is formed on the surface of the steel sheet with an adhesion amount of 0.1-5 g / square meter. . In the resin coating, when the amount of the fluorine-based resin particles is less than 2.5% by weight, the lubricity of the obtained resin coating is still poor, and the press formability of the resin-coated steel sheet is not sufficiently improved. When it exceeds%, there is no particular problem in terms of lubrication performance, but the adhesion of the obtained coating film to the steel sheet deteriorates, the coating film peels off during press working, and the corrosion resistance after working becomes poor. Further, with respect to paintability as well, the adhesion between the coating film and the paint is reduced. Particularly, in the present invention, the amount of the fluororesin particles is 15 to 25% by weight in the resin coating.
Is preferred.

In the present invention, the fluororesin particles preferably have a particle size in the range of 0.01 to 2 μm.
When the particle size exceeds 2 μm, it becomes difficult to uniformly disperse in the resin dispersion liquid, and as a result, the adhesion of the resulting coating film to the steel sheet and the adhesion to the coating material deteriorate. On the other hand, when the particle size of the fluorine-based resin is smaller than 0.01 μm, the effect of improving the lubricity and corrosion resistance of the coating film by adding the fluorine-based resin cannot be obtained.

Examples of the above-mentioned fluororesin include tetrafluoroethylene resin (PTFE), trifluoroethylene chloride resin, vinylidene fluoride resin, vinyl fluoride resin, ethylene / tetrafluoroethylene copolymer resin, tetrafluoroethylene resin Examples thereof include ethylene fluoride / hexafluoropropylene copolymer resin. Furthermore, in the resin coating, when the silica particles are less than 1% by weight as silicon dioxide, the corrosion resistance of the obtained coating is insufficient, while when it exceeds 30% by weight, silica acts as a lubricant. Therefore, the coefficient of friction of the coating film is increased, the lubricity is lowered, and the corrosion resistance after processing is also deteriorated.

In order to maximize the effect of such silica, the particle size of silica is preferably in the range of 1 to 20 nm. The smaller the particle size of silica, the more improved the corrosion resistance and coatability of the coating, and especially the significantly improved corrosion resistance after processing. The effect of such silica is considered to be due to the fact that the resin coating is dense and has excellent adhesiveness, and the corrosion resistance of the resin coating is further enhanced. From this point of view, the smaller the particle size of the silica used, the better, but even if extremely fine particles are used, the above-mentioned effect is not correspondingly enhanced, and therefore,
In the present invention, silica may have a particle size of 1 nm or more. On the other hand, when the thickness exceeds 20 nm, the surface of the coating is roughened to reduce the lubricity. In particular, in the present invention, the silica used preferably has a particle size of 3 to 10 nm.

Such silica is generally known as colloidal silica, for example, Snowtex-X.
S, SS, Snowtex-40 (Nissan Chemical Co., Ltd.)
A commercially available product can be obtained. The resin-coated steel sheet according to the present invention contains ethylene glycol mononormal hexyl ether in its resin coating. In the present invention, the fluorine-based resin particles used as a lubricant have an inactive surface and originally have poor adhesiveness with various resins. Therefore, the fluorine-based resin particles are not only those exposed on the surface of the resin coating, but those embedded in the resin coating are It is easy to cause problems such as wrapping the steel sheet around a roll and adhesion of resin to a press die or product. Therefore, according to the present invention, the surface treatment agent is blended with ethylene glycol mononormal hexyl ether,
By forming a resin coating containing this on the surface of a steel sheet, not only the film-forming property of the resin coating is improved, but also the adhesiveness of the fluorine-based resin particles to the resin coating is increased, and thus, the roll of the steel sheet. It is possible to solve the problems such as peeling from the resin coating during contact with or pressing, winding around a roll, and sticking to a press die or product.

When the amount of ethylene glycol mono-n-hexyl ether in the resin coating is less than 1% by weight, the film forming property of the resin coating is not improved and the resin coating formed on the steel plate is cracked. In addition to being easy to do, the amount of fluororesin particles exposed on the surface of the resin coating increases. On the other hand, when the amount of ethylene glycol mononormal hexyl ether in the resin coating is more than 20% by weight, the amount in the resin coating becomes too large and the corrosion resistance and paintability deteriorate. In order to obtain the above effects to the maximum, the amount of ethylene glycol mononormal hexyl ether in the resin coating is preferably in the range of 2 to 10% by weight.

In the present invention, when the amount of such resin coating adhered to the steel sheet is less than 0.1 g / square meter, the required lubrication effect and corrosion resistance after working cannot be obtained in heavy working. However, when the adhesion amount exceeds 5 g / square meter, the peeling amount of the coating film increases in the press working of the steel sheet, and for example, in the press molding, the peeling coating film accumulates in the mold, which causes trouble in the press molding.

In the present invention, the steel sheet material is not particularly limited, but for example, zinc or zinc alloy plated steel sheet, those obtained by subjecting these steel sheets to chemical conversion treatment such as chromate treatment or phosphate treatment, and the like. It is preferably used.

[0026]

As described above, according to the present invention, a steel sheet is coated with a surface treatment agent comprising an aqueous dispersion of an acrylated epoxy resin containing fluorine resin particles, silica particles, and ethylene glycol mononormal hexyl ether. Then, by drying, the adhesiveness between the acrylated epoxy resin as the base resin and the fluorine-based resin particles as the lubricant can be enhanced, and winding around the roll during production can be prevented. In addition, it is possible to form a resin film which can be subjected to strong working and is excellent in corrosion resistance, particularly in coatability and corrosion resistance after processing, without applying a press oil.

Further, according to the present invention, since ethylene glycol mono-normal hexyl ether is blended in the surface treatment agent, its film forming property is improved, and a resin coating having a resin film excellent in lubricity, coatability and corrosion resistance is provided. A steel plate can be obtained. Further, according to the present invention, since the acrylated epoxy resin, which is the main component that constitutes the surface treatment agent, is a thermosetting resin, the glass transition point is higher than that of the thermoplastic resin, and therefore the press molding is performed. At times, the film is not softened by the temperature rise of the mold, and the coating film is retained on the surface of the steel sheet even under extreme pressure, so that a resin-coated steel sheet having excellent press formability can be obtained.

Further, since the surface treatment agent as described above is a one-pack type resin, it is easy to handle, and since the crosslinking initiation temperature is as high as about 140 ° C., the stability during operation is also high. Be excellent. The treated steel sheet having such a highly lubricious and highly corrosion-resistant resin coating film can be used not only as a coated steel sheet but also as a bare sheet after press working.

[0029]

The present invention will be described below with reference to examples.
The present invention is not limited to these examples. Example 1 A chromate-treated electrogalvanized steel plate (zinc adhesion amount 20 g / square meter, chromium adhesion amount 20 mg / square meter) was used as a material steel plate.

Dimethylethanolamine was added to the carboxyl group-containing acrylated epoxy resin so that the final product had a pH of 6
A dispersion of 20% by weight of tetrafluoroethylene resin (particle size 0.1 to 4 μm) in terms of total solid content after forming a film on the water-dispersible acrylated epoxy resin obtained by adding 10% by weight of colloidal silica having a particle size of 10 to 20 nm as silicon dioxide is added and dispersed, and then,
0 ethylene glycol mono-normal hexyl ether
-25 wt% was added to obtain a surface treatment agent.

This surface treatment agent was applied to the surface of the steel sheet with a squeezing roll so that the dry adhesion amount was 1 g / square meter, and dried to form a resin film, thereby obtaining a resin-coated steel sheet. For the obtained resin-coated steel sheet, a sliding test, a cylindrical deep drawing test, a press test, a salt spray test and a coating test were performed, and the releasability of the fluorine-based resin particles, the dynamic friction coefficient,
The limiting drawing ratio, mold galling resistance, corrosion resistance and coating adhesion were investigated.

The peelability of the fluorine-based resin particles was determined by sliding the steel sheet with a rubber sheet of the same material as the roll material under a pressure of 150 kg using a sliding tester. I asked. The dynamic friction coefficient was determined from the load due to sliding at a pressure of 150 kg using a sliding tester. The limit drawing ratio is a blank diameter of 110 mm and a punch diameter of 5
It was obtained by the single blank method of 0 mm. The mold gall resistance was determined by visually observing the mold gall on the sliding surface of the molded product after press molding using a single press tester. Corrosion resistance is JIS
The salt spray test was performed according to the method described in Z-2371. As for the coating film adhesion, after coating with an acrylic-based and miramine alkyd-based coating, the adhesiveness of the coating film was examined by cross-cutting and cross-cutting Erichsen. The results are shown in Table 1.

[0033]

[Table 1]

Example 2 A dispersion of 20% by weight of tetrafluoroethylene resin (particle size 0.1 to 4 μm) in terms of total solid content after forming a film on the same water-dispersible acrylated epoxy resin as in Example 1 was used. 10% by weight of colloidal silica having a particle size of 4 to 6 nm, 10 to 20 nm and 40 to 50 nm as silicon dioxide.
After the addition and dispersion, 5% by weight of ethylene glycol mononormal hexyl ether was further added to obtain a surface treating agent.

[0035] This surface treatment agent was applied to the surface of the steel sheet with a squeeze roll so that the dry adhesion amount was 1 g / square meter, and dried to form a resin film, thereby obtaining a resin-coated steel sheet. The properties of the treated steel sheet were examined in the same manner as in Example 1. The results are shown in Table 2.

[0036]

[Table 2]

Example 3 The same water-dispersible acrylated epoxy resin as that used in Example 1 was used to disperse tetrafluoroethylene resin (particle size 0.1 to 4 μm) in an amount of 0 to 35% by weight in terms of total solid content after film formation. John and
Colloidal silica having a particle diameter of 10 to 20 nm was added as silicon dioxide in an amount of 0 to 35% by weight and dispersed to obtain a surface treating agent.

This surface treatment agent was applied to the surface of the steel sheet with a squeeze roll so that the dry adhesion amount was 1 g / square meter, and dried to form a resin film, whereby a resin-coated steel sheet was obtained. The properties of the treated steel sheet were examined in the same manner as in Example 1. The results are shown in Tables 3 and 4.

[0039]

[Table 3]

[0040]

[Table 4]

Example 4 The same water-dispersible acrylated epoxy resin as in Example 1 was used so that the content of the tetrafluoroethylene resin (particle size: 0.1 to 4 μm) was 20% by weight based on the total solid content after film formation. 20% by weight of dispersion and colloidal silica having a particle size of 10 to 20 nm as silicon dioxide were added and dispersed, and then 5% by weight of ethylene glycol mononormal hexyl ether was further added to obtain a surface treating agent.

This surface treatment agent was applied to the surface of the steel sheet by a squeezing roll so that the dry adhesion amount was 1 g / square meter, and dried to form a resin film, thereby obtaining a resin-coated steel sheet. The properties of the treated steel sheet were examined in the same manner as in Example 1. The results are shown in Table 5. For comparison, as the resin component in the surface treatment agent, urethane modified polyethylene, urethane modified polypropylene, carboxylated polyethylene and acrylic resin were used instead of the acrylated epoxy resin, and ethylene glycol mononormal hexyl ether was added at 5% by weight. In addition, a surface treating agent was obtained.

These surface treatment agents were applied to the surface of the steel sheet by a squeezing roll so that the dry adhesion amount was 1 g / square meter, and dried to form a resin film, to obtain a resin-coated steel sheet. The properties of the treated steel sheet were examined in the same manner as in Example 1. The results are shown in Table 4. According to the present invention, the adhesiveness between the acrylated epoxy resin that is the base resin and the fluorine-based resin particles that is the lubricant is improved, while preventing winding around the roll during production, press moldability, corrosion resistance and It is possible to obtain a resin-coated steel sheet having excellent paintability.

[0044]

[Table 5]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C09D 163/00 PJM 8830-4J PKD 8830-4J // (C09D 163/00 127: 12) 9166- 4J

Claims (3)

[Claims] 1. Acrylic epoxy resin as a main component, fluorine resin particles 2.5 to 30% by weight, silica particles 1 to 3
A resin coating containing 0% by weight and 1 to 20% by weight of ethylene glycol mononormal hexyl ether has an applied amount of 0.
A resin-coated steel sheet having excellent press formability, which is formed on the surface of the steel sheet at 1 to 5 g / square meter. 2. The resin-coated steel sheet according to claim 1, wherein the fluorine-based resin particles have a particle diameter of 0.01 to 2 μm. 3. The resin-coated steel sheet according to claim 1, wherein the silica particles have a particle diameter of 1 to 20 nm.