JPH0396337A - Resin-coated steel sheet excellent in press moldability - Google Patents

Abstract

PURPOSE:To obtain the resin-coated steel sheet which is excellent in lubricating properties and is sufficiently durable against the extremely pressurizing in severe working on the elevated temperature of a mold and has no necessity of degreasing in coating process by forming the resin coating film containing the specified wt.% of fluorine plastic particles and silica particles and composed of acrylic epoxy resin as main material on the surface of a steel sheet in a specified amount of coating build up. CONSTITUTION:In a resin-coated steel sheet, the resin coating film composed of acrylic epoxy resin as main material and containing 2.5-30wt.% of fluorine plastic particles and 1-20wt.% of silica particles in the state of SiO2, is formed on the surface of the steel sheet at the coating build up of 0.1-5g/m<2>. Especially, since the acrylic epoxy resin which is the main component constituting surface- treating agent is thermosetting resin, it has high glass transition point relatively to that of thermoplastic resin, whereby said epoxy resin is not softened at the elevated temperature of a mold, and since the coating film is kept on the surface of the steel sheet even in extremely pressurizing, the resin-coated steel sheet excellent in press moldability may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resin-coated steel sheet with excellent breathability for use in automobiles, home appliances, building materials, etc. In general, when pressing a steel plate, press oil is applied to the surface of the steel plate to improve workability.

However, if press oil is applied in this way, the press oil will scatter during the press working of the steel plate, worsening the working environment or causing pollution problems, and furthermore, a degreasing process is required after the press working. There are other problems.

Therefore, various methods of surface treatment of steel sheets have been proposed in order to obtain good press workability without using press oil.
For example, a Milbond film or a wax film is formed on the surface of a steel plate, or a resin emulsion or aqueous resin solution containing an inorganic or organic solid lubricant is used as a surface treatment agent and applied to the surface of the steel plate. A method of forming a resin film by drying is known. In particular, the latter method is suitably used as a surface treatment method for products that undergo heavy processing or for products that require paintability without degreasing after processing. In this method,
Conventionally, graphite and molybdenum disulfide have been used as the solid lubricants for inorganic systems, and for organic systems,
Metal soaps such as paraffin, polyethylene-based Wanx, and calcium stearate are used. In this way, methods using inorganic solid lubricants are disclosed, for example, in JP-A-61-227178 and JP-A-61-2271.
79, JP-A-61-231177, JP-A-61-279687, etc. However, when graphite or molybdenum disulfide is used as a solid lubricant, it is generally difficult to adjust the color tone of the steel plate surface, and in order to provide lubrication performance that can withstand heavy working of the steel plate, surface treatment agents are required. If a large amount of lubricant is added to the steel sheet, the adhesion of the resulting resin coating will be extremely poor, and the corrosion resistance of the steel sheet after processing will deteriorate. Furthermore, graphite and molybdenum disulfide
Due to its high specific gravity, it is difficult to disperse uniformly in the surface treatment agent, and it tends to settle in the surface treatment agent not only during storage but also during use, resulting in problems in storage stability and workability.

On the other hand, when using a surface treatment agent such as a resin emulsion containing wax, the wax stands out on the surface of the resin coating when it dries after being applied to the steel plate, so the surface slipperiness is good, but As the temperature of the mold increases due to continuous pressing, the wax on the surface liquefies and flows, reducing its lubricating performance and causing peeling of the resin coating, which also deteriorates the corrosion resistance after processing.

In addition, when using metal soap as a solid lubricant, the resin film formed on the surface of the steel plate is highly hygroscopic, so
In addition to being sticky, it also has problems with corrosion resistance. If a surface treatment agent containing polyethylene particles is used, the resulting coating will not exhibit sufficient performance against the extreme pressure during pressing, resulting in peeling of the coating and poor corrosion resistance after pressing. .

Recently, JP-A-63-162886 has proposed a surface treatment agent in which an epoxy resin is added to a carboxylated polyolefin resin to form a crosslinked film at low temperatures. However, with such surface treatment agents, the coating film begins to crosslink at low temperatures. However, the stability of the surface treatment agent during actual operation is lacking.

! The present invention was made in order to solve the above-mentioned problems with conventional resin-coated steel sheets, and has excellent lubricity, and is suitable for extreme pressure and mold temperature during heavy machining. The purpose of the present invention is to provide a resin-coated steel plate that can sufficiently withstand rising temperatures, has high corrosion resistance even after the steel plate is processed, and does not require degreasing even during subsequent painting. .

The resin-coated steel sheet with excellent press formability according to the present invention is
A resin coating mainly composed of acrylated epoxy resin and containing 2.5 to 30% by weight of fluororesin particles and 1 to 20% by weight of silica particles as SiO2 has an adhesion amount of 0.5%. 1-5
It is characterized by being formed on the surface of a steel plate at a g/rd.

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-component water-dispersible resin.

The acrylic resin is a copolymer of an ethylenically unsaturated carboxylic acid as a first monomer and a second monomer copolymerizable therewith, and is usually an ethylenically unsaturated carboxylic acid. It can be obtained by copolymerizing an acid and a second monomer having copolymerizability with the acid in a solvent using a common radical polymerization initiator such as azobisisobutyronitrile or penzoyl peroxide. can. In this copolymerization, the ethylenically unsaturated carboxylic acid accounts for 1 of the total monomers.
It is used in an amount of 2% by weight or more. When the ethylenically unsaturated carboxylic acid is less than 12% by weight of the total monomers, it can be reacted with an epoxy resin as described below to improve its dispersion stability in an aqueous medium as an acrylated epoxy resin. Inferior.

Examples of the ethylenically unsaturated carboxylic acids include (
One or more of meth>acrylic acid, maleic acid, itaconic acid, etc. is preferably used.

Examples of the second monomer include (meth)acrylic esters such as methyl (meth)acrylate, ethyl (meth)acrylate, and probyl (meth)acrylate, styrene, vinyltoluene, and chlorostyrene. Styrenic monomer, (meth)hydroxyethyl acrylate, (meth)
Hydroxyalkyl (meth)acrylates such as hydroxybyl acrylate, N-1-substituted (meth)acrylamide such as N-methylol (meth)acrylamide, (meth)
One or more types of epoxy group-containing (meth)acrylic esters such as glycidyl acrylate and (meth)acrylonitrile are used.

Acrylated epoxy resin is obtained by subjecting the acrylic resin and epoxy resin to an esterification reaction in a hydrophilic organic solvent in the presence of a basic compound, for example, a tertiary amine compound such as dimethylethanolamine. can be obtained by

Acrylic resin has a weight average molecular weight of 2000 to 100.
It is preferably in the range of 00. When the molecular weight is too small, emulsifying dispersibility in an aqueous dispersion medium is insufficient, and when the molecular weight is too large, gelation tends to occur during reaction with Epoquin resin.

Examples of the epoxy resin include shrimp chlorohydrin/
Bisphenol type epoxy resins are preferably used, and in particular, those having an average of 1.1 to 2.0 epoxy groups in the molecule and an average molecular weight of 800 or more are preferably used.

In the reaction between acrylic resin and epoxy resin, the weight ratio of acrylic resin/epoxy resin is 1.
A range of 9/1 to 1/1O is preferable.

In addition, acrylated epoxy resin is produced by reacting an epoxy resin with an ethylenically unsaturated carboxylic acid, and then copolymerizing this with the same ethylenically unsaturated carboxylic acid and other copolymerizable monomers using a polymerization initiator. It can also be obtained by letting

The resin-coated steel sheet according to the present invention is produced by dispersing the above-mentioned acrylated epoxy resin, fluororesin dispersion, and silica particles in an aqueous dispersion medium within the predetermined range, and further having a pH of 4 to 11. A resin-coated steel sheet according to the present invention can be obtained by preparing a surface treatment agent by adding ammonia or an organic amine, applying the surface treatment agent to a steel sheet, and drying it.

The aqueous dispersion medium may be water or at least IO wt%
A mixture of water and a hydrophilic organic solvent is used. Examples of the hydrophilic organic solvent include lower aliphatic alcohols such as methanol, ethanol, and n-probanol; glycol ethers such as ethylene glycol methyl ether; glycol esters such as ethylene glycol acetate; ethers such as tetrahydrofuran and dioxane;
Dimethylformamide, diacetone alcohol, etc. are used.

Examples of the organic amine include trimethylamine,
Alkylamines such as triethylamine, alkanolamines such as diethanolamine, morpholines, and polyvalent amines such as ethylene diagonal and diethylene triamine are preferably used.

Furthermore, the surface treatment agent may contain, for example, an aqueous Abaynoblast resin, a Phenoplast resin, or the like as a curing agent, if necessary.

The resin-coated steel sheet according to the present invention has a resin coating mainly composed of the above-mentioned acrylated epoxy resin and containing 2.5 to 30% by weight of fluororesin particles and 1 to 20% by weight of silica particles as Si (h) with an adhesion amount of 0.5%. It is formed on the surface of the steel plate at 1 to 5 g/tri.

When the amount of fluororesin particles in the resin coating is less than 2.5% by weight, the resulting resin coating still has poor lubricity 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 resulting coating to the steel plate deteriorates, and during press working, the coating force < il1 separates, resulting in poor corrosion resistance after processing. . Furthermore, with regard to paintability, the adhesion between the film and the paint decreases. In particular, in the present invention, the amount of fluororesin particles in the resin coating is preferably 15 to 25% by weight.

In the present invention, the fluororesin particles have a particle size of 0.
The thickness is preferably in the range of 0.01 to 2 μm.

When the particle size exceeds 2 μm, it becomes difficult to uniformly disperse the particles in the resin dispersion, and as a result, the adhesion of the resulting coating to @temporary and paint deteriorates. On the other hand, when the particle size of the fluororesin is smaller than 0.01 μm, the effect of improving the lubricity and corrosion resistance of the coating cannot be obtained by adding the fluororesin.

Examples of the above-mentioned fluororesin include tetrafluoroethylene resin (PTFE), trifluorochloroethylene resin, vinylidene fluoride resin, vinyl fluoride resin, ethylene/tetrafluoroethylene copolymer resin, and tetrafluoroethylene resin.・Hexafluorinated propylene copolymer resin, etc. can be mentioned.

Furthermore, if the amount of silica particles in the resin coating is less than 1% by weight as SiOz, the resulting coating will not have sufficient corrosion resistance, while if it exceeds 20% by weight, the silica may act as a lubricant. This increases the coefficient of friction of the coating, lowers the lubricity, and further deteriorates the corrosion resistance after processing.

In order to obtain the maximum effect of silica, the particle size of silica is preferably in the range of 1 to 20 mμ. As the particle size of silica becomes smaller, the corrosion resistance and paintability of the coating improve, and in particular, the corrosion resistance after processing improves significantly. This effect of silica appears to be due to the fact that the resin coating is dense and has excellent adhesion, thereby further enhancing the corrosion resistance of the resin coating. From this perspective,
The smaller the particle size of the silica used, the better; however, even if extremely small particles are used, the above effects will not be particularly enhanced, so in the present invention, the silica is It is sufficient if the particle size is 1 mμ or more. On the other hand,
When it exceeds 20 mμ, the surface of the coating becomes rough and the lubricity decreases. In particular, in the present invention, the silica used preferably has a particle size in the range of 3 to 10 mμ.

Such silica is usually known as colloidal silica, and can be obtained commercially as, for example, Snowtex XS or SS (Nissan Chemical Industry Co., Ltd. (!)).

In the present invention, when the amount of such a resin coating attached to the steel plate is less than 0.1 g/m2, the required lubrication effect and post-working corrosion resistance cannot be obtained during heavy working. However, when the amount of adhesion exceeds 5 g/d, the amount of peeling of the film increases during press working of a steel plate, and for example, during press forming, the peeled film accumulates on the mold, causing problems in pressing.

In the present invention, the steel sheet material is not particularly limited, but for example, zinc or zinc alloy plated steel sheets, or those steel sheets subjected to chemical conversion treatment such as chromate treatment or phosphate treatment, etc. are preferably used. .

As described above, according to the present invention, a surface treatment agent consisting of an aqueous dispersion of an acrylated epoxy resin containing fluororesin particles and silica particles is applied to a steel plate and dried. It is possible to form a resin coating that can be subjected to strong processing without applying press oil and has excellent corrosion resistance, especially corrosion resistance after processing.

Particularly, according to the present invention, since the acrylated epoxy resin, which is the main component constituting the surface treatment agent, is a thermosetting resin, it has a higher glass transition point than a thermoplastic resin. During shaping, the coating does not soften due to the rise in temperature of the mold, and the coating is maintained on the steel plate surface even under extreme pressure, so a resin-coated steel plate with excellent pressability can be obtained.

Furthermore, since the above-mentioned surface treatment agent is a one-component resin, it is easy to handle, and the crosslinking initiation temperature is approximately 14
Because it is as high as 0°C, it has excellent stability during operation.

A treated steel sheet having such a highly lubricating and highly corrosion-resistant resin coating can be used not only as a coated steel sheet but also as a bare steel sheet after press working.

Although the present invention will be described below with reference to Examples, the present invention is not limited to these Examples in any way. Example 1 An electrogalvanized steel sheet subjected to chromate treatment (zinc coating amount: 20 g/m, chromium coating amount: l3/1) was used as a material steel sheet.

Dimethylethanolamine was added to a carboxyl group-containing acrylated epoxy resin to give a final product pi of 6 to 7. O ~ 30% by weight of polytetrafluoroethylene resin (particle size 0.1-4 μm) dispersion and collodyl silicone with particle size 4-6 μm SiOz
A surface treatment agent was obtained by adding and dispersing 10% of Seikai.

This surface treatment agent was applied to the surface of the steel plate using a squeezing roll so that the dry coating amount was Ig/1, and dried to form a resin film to obtain a resin-coated steel plate.

The obtained resin-coated steel sheets were subjected to a sliding test, a cylindrical deep drawing test, and a salt water spray n test to examine the dynamic friction coefficient, limit drawing ratio, die galling resistance, and corrosion resistance. The limiting drawing ratio was determined by the single blank method using a blank diameter of 100 tm and a punch diameter of 50 m. In addition, the dynamic friction coefficient is a pressing force of 150k
It was determined from the sliding load in g. The results are shown in Figures 1 and 2. Salt spray test is JIS Z 237
It was carried out after Erichsen extrusion processing according to the method described in 1.

The results are shown in Figure 3.

Example 2 The same water-dispersible acrylated epoxy resin as in Example 1 was coated with 20% by weight of tetrafluoroethylene resin (particle size 0.1 to 4 μm) in terms of total solid content after film formation, and the particle size 10% by weight of colloidal SiOz of 4 to 6 mμ, 10 to 20 mμ, and 40 to 50 mμ was added and dispersed to obtain a surface treatment agent.

This surface treatment agent was applied to the surface of the steel plate in a dry adhesion amount Ig/r.
It was coated with a squeeze roll so that it would be .rl, dried, and a resin coating was formed to obtain a resin-coated steel plate.

The properties of the treated steel sheet were investigated in the same manner as in Example 1. The results are shown in Table 1.

Example 3 Same water-dispersible acrylated epoxy tree as Example I? 0 to 30% by weight (calculated as total solids) of tetrafluoroethylene resin (particle size 0.1 to 4 μm) dispersion in the form of a film, and colloidal silica with a particle size of 4 to 6 μm as SiO ~20% by weight was added and dispersed to obtain a surface treatment agent.

This surface treatment agent was applied to the surface of the steel plate in a dry amount of 1 g.
/rd using a squeeze roll, dried, and formed a resin film to obtain a resin-coated steel plate.

The properties of the treated steel sheet were investigated in the same manner as in Example 1. The results are shown in Table 2.

Example 4 The same water-dispersible acrylated epoxy resin as in Example 1 was coated with tetrafluoroethylene resin (particle size 0.1 to 4 μm) disbursed so that the total solid content after film formation was 20%. Along with adding digon, colloidal silica with a particle size of 4 to 6 mμ was added in an amount of 0 to 20% by weight as SiOt, and dispersed.
A surface treatment agent was obtained.

This surface treatment agent was applied to the surface of the steel plate in a dry adhesion amount Ig/r.
It was applied with a squeezing roll so that it would be RF, dried, and a resin coating was formed to obtain a resin-coated mesh board.

The properties of the treated steel sheet were investigated in the same manner as in Example I. The results are shown in Table 3.

For comparison, a surface treatment agent was prepared using urethane modified polyethylene, urethane modified polypropylene, carboxylated polyethylene, and acrylic resin as resin components in the surface treatment agent, and a resin-coated steel sheet was obtained in the same manner. .

The properties of the treated steel plate were investigated in the same manner as in Example 1. The results are shown in Table 3.

According to the present invention, it is possible to obtain a resin-coated steel sheet that is excellent in press formability, corrosion resistance, and paintability.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the amount of PTFE added in the surface treatment agent and the coefficient of dynamic friction of the obtained resin-coated steel sheet,
FIG. 2 is a graph showing the relationship between the amount of PTFE added in the surface treatment agent and the limiting drawing ratio of the obtained resin-coated steel sheet;
FIG. 3 is a graph showing the relationship between the amount of PTFE added in the surface treatment agent and the corrosion resistance of the obtained resin-coated steel sheet. Fig. 1 Fig. 2 PTFE main aero greeting (WC ζ) Fig. 3 PTFE concentration (“t curse”)

Claims (3)

[Claims] (1) Mainly acrylated epoxy resin, 2.5 to 30% by weight of fluororesin particles and silica particles are SiO_
The resin coating containing 1 to 20% by weight of 2 has an adhesion amount of 0.
A resin-coated steel sheet with excellent press formability, characterized by being formed on the surface of the steel sheet at a thickness of 1 to 5 g/m^2. (2) The resin-coated steel sheet according to claim 1, wherein the fluororesin 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 mμ.