JP2001179882A - Polyester resin laminated steel plate - Google Patents

Abstract

(57) [Summary] [PROBLEMS] As a steel plate used for container materials such as 18L cans and pail cans, it has excellent workability and impact resistance, and is made of a highly corrosive substance such as a surfactant and soy sauce as a filler. To provide a polyester resin laminated steel sheet having excellent corrosion resistance even in a case thereof. A steel sheet and a lower layer formed on at least one surface of the steel plate, and a lower layer of 40 to 200 mg / m per side.
A chromium metal layer having an adhesion amount of ² and an upper layer having an adhesion amount of 3 to 25 mg / m ^{2 in} terms of metal chromium per side, and an electrolytic chromate treated layer of a hydrated chromium oxide layer; A first resin layer formed mainly of a polyester-based resin and a phenolic and / or cresol-based resol-type phenolic resin, and a thermoplastic polyester-based resin formed on the first resin layer and formed on the first resin layer A polyester resin laminated steel sheet having excellent corrosion resistance, comprising: a second resin layer having a thickness of 10 to 200 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester resin laminated steel sheet used for 18L cans, pail cans, etc., and has excellent corrosion resistance even when the content is a highly corrosive substance such as a surfactant or soy sauce. And can processability,
The present invention relates to a polyester resin laminated steel sheet having excellent impact resistance.

[0002]

2. Description of the Related Art Conventionally, as a container material used for general can applications, a thermosetting resin is coated on a metal material such as a tin-plated steel plate, a chromium-treated steel plate (TFS), and a nickel-plated steel plate for the purpose of preventing corrosion. That is used.
However, these thermosetting resins contain a large amount of solvent, and it takes time to evaporate the solvent and cure the resin, and consume a large amount of thermal energy. In addition, there is a problem such as environmental pollution caused by using a large amount of solvent. In addition, from the viewpoint of corrosion protection, coating and
It is necessary to repeat baking, and there is a problem in terms of productivity and energy saving.

As a method of solving these problems, a laminated steel sheet in which the above metal material is coated with a thermoplastic resin film has been developed. As the resin film material, polyethylene resin (PE), polypropylene resin (P
P), polyethylene terephthalate resin (PET) and the like. For example, a steel sheet laminated with PE is disclosed in JP-A-5-200961,
JP-A-6-99543 discloses a steel sheet laminated with PET, and JP-A-7-113 describes a steel sheet laminated with PET.
8387 and JP-A-8-1862.

However, when these laminated steel sheets are subjected to an impact at a low temperature, micro cracks are generated in the film. In addition, when molding is performed as a can, cracks may occur in the resin layer of the processed portion. When a crack occurs in the resin layer as described above, particularly, a surfactant,
When the container is filled with a highly corrosive substance such as soy sauce, the corrosion of the steel plate progresses rapidly, and thus there is a problem when used as a container material for 18L cans, pail cans and the like.
Further, in a steel sheet laminated with a PE or PP resin, the melting point of the resin is low, so that heat resistance to heating during printing is also insufficient.

As a technique for solving such a problem, Japanese Patent Publication No. 63-13829 discloses a method of laminating an organic resin film on which a polymer composition composed of an epoxy resin and a curing agent thereof has been coated in advance. JP-A-1-249331, JP-B-4-74176, JP-B5-71035, JP-A-2-704
No. 30, for example. Further, a method of applying an epoxy-phenol-based, epoxy-urea-based adhesive primer on one or both surfaces of a steel plate is disclosed in Japanese Patent Application Laid-Open No. 4-344.
No. 231 is disclosed. However, these materials contain bisphenol A, which is one of the suspected endocrine disrupters, and according to these methods, the corrosion resistance is improved to some extent, but the contents are corrosive beverages such as acidic beverages. In the case of the above, it cannot be said that it is sufficient from the viewpoint of corrosion resistance as compared with a painted can or the like.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been accomplished in view of the above problems, and has excellent workability and impact resistance as a steel sheet used for container materials such as 18L cans and pail cans. It is another object of the present invention to provide a polyester resin laminated steel sheet having excellent corrosion resistance even when a highly corrosive substance such as a surfactant and soy sauce is used as a filler.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors investigated the corrosion resistance of a laminated steel plate when it was subjected to can processing or impact, and found the following organic materials not available in conventional materials. The introduction of a resin layer was found. That is,
An organic resin layer (hereinafter, referred to as a first resin) that improves the adhesion at the interface between the conventional resin film and TFS and that prevents metal exposure and metal ion elution without breaking by can processing or impact. A surface-treated steel sheet having excellent corrosion resistance that achieves the intended purpose can be obtained.

To improve the adhesion at the interface between the conventional outermost resin film (hereinafter, also referred to as a second resin film layer) and TFS by interposing the first resin layer,
For each of the TFS and the second resin film layer,
It is necessary that the first resin layer has excellent adhesion and that the material itself does not cause cohesive failure.

In order to prevent cohesive failure, it is preferable that the organic component forming the first resin layer is a high molecular weight substance to some extent. Further, in order to achieve excellent adhesion with TFS, it is preferable to improve the hydrogen bond with TFS or to cause a covalent bond or a coordination bond. It is preferable to introduce a polar group such as a hydroxyl group or a carboxyl group in order to improve hydrogen bonding, and it is preferable to introduce a hydroxyl group or a carboxyl group in order to form a coordination bond.

[0010] In order to improve the adhesion with the second resin film layer, it is preferable to improve the secondary bonding force by increasing the compatibility with the resin film.
For example, when the second resin film layer is a polyester-based resin, it is effective to introduce an aromatic ring or the like into the organic component forming the first resin layer to bring the solubility parameter closer to that of the polyester-based resin. In order to prevent the metal from being exposed without being broken by can processing or impact, the first resin layer needs to withstand the elongation during processing and cover the electrolytic chromate treatment film. It is necessary that the organic substance forming the resin layer is a high molecular weight substance and has a flexible skeleton. In addition to the covering, the material itself needs to have corrosion resistance, and for that purpose, the organic substance needs to have a rigid skeleton such as an aromatic ring. In order to prevent elution of metal ions, it is desirable to introduce a hydroxyl group, a carboxyl group, or the like, which may form a coordination bond with the metal ions. In summary, as the organic substance forming the first resin layer, a balance between a rigid structure (for example, an aromatic ring) and a flexible structure is required, and it is necessary to introduce a polar group such as a hydroxyl group or a carboxyl group. Becomes The present invention has been made based on such knowledge, and has the following features.

That is, according to the present invention, a steel sheet is formed on at least one surface of the steel sheet, and the lower layer has a thickness of 4% per side.
A metal chromium layer having an adhesion amount of 0 to 200 mg / m ² , and the upper layer is 3 to 25 mg /
an electrolytic chromate-treated layer of a hydrated chromium oxide layer having an adhesion amount of m2, and a ^second layer formed on the electrolytic chromate-treated layer and mainly composed of a polyester-based resin and a phenolic resin and / or a cresol-based resol-type phenol resin. Excellent corrosion resistance, comprising: a first resin layer; and a second resin layer formed on the first resin layer and having a thickness of 10 to 200 μm and containing a thermoplastic polyester resin as a main component. To provide a polyester resin laminated steel sheet.

In the present invention, the first resin layer has a thickness of 0.1 to 10 μm, and the polyester resin of the resin composition has a number average molecular weight of 3,000 to 3,000.
0, a hydroxyl value of 5 to 30, an acid value of 0 to 50, and a glass transition temperature of 5 to 110 ° C.
Or a total of 1 with cresol-based resole phenolic resin
It is preferably contained in the range of 60 to 99 parts by weight with respect to 00 parts by weight.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the film-laminated steel sheet according to the present invention, the lower layer is formed on at least one surface of the base steel plate at 40 to 2 per side.
A metallic chromium layer having a deposition amount of 200 mg / m ^2, and electrolytic chromate treatment layer of hydrated chromium oxide layer having a deposition amount of 3~25mg / m ² layer is in per side reckoned as metal chromium, the electrolytic chromate treatment A first resin layer mainly formed of a polyester-based resin and a phenolic and / or cresol-based resol-type phenol resin; and a thermoplastic polyester-based resin formed on the first resin layer. And a second resin layer having a thickness of 10 to 200 μm as a component.

In the present invention, the base steel sheet is not particularly limited, and any steel sheet usually used for this type of surface-treated steel sheet can be used. For example, ordinary low-carbon cold-rolled steel sheet having a thickness of 0.1 to 0.5 mm, low-carbon Al
A killed steel plate or the like can be used.

At least one surface of such a base steel sheet is directly or after chromium plating and has a lower layer comprising a metal chromium layer and an upper layer comprising a hydrated chromium oxide layer as a surface treatment film.
A layer of electrolytic chromated film is formed. As the electrolytic chromate treatment method at this time, a commonly used known method can be adopted, a one-liquid method for simultaneously depositing chromium metal and hydrated chromium oxide, and hydrated chromium oxide after forming the chromium metal layer. May be any of the two-component methods for precipitating the compound.

Here, the amount of deposited metal chromium in the lower layer is 40 to 200 mg / m ² per one side. Adhesion amount is 40mg
If it is less than / m ² , the corrosion resistance at the processed and impacted parts is reduced. On the other hand, if it exceeds 200 mg / m ² , there is no problem in performance at all, but it is not preferable from an economic viewpoint. A more preferred range is 95~150mg / ^{m 2.} The amount of adhesion of the upper chromium oxide layer was 3 in terms of chromium metal per side.
２５25 mg / m ² . If the adhesion amount is less than 3 mg / m ² , the chromium metal layer is not uniformly covered with the chromium oxide, the exposed area of the chromium metal layer becomes large, and the corrosion resistance in processing and impact parts is reduced. On the other hand, if it exceeds 25 mg / m ² , the TF caused by the chromium oxide layer being too thick
The surface color of S deteriorates, and the adhesion to the resin film decreases. As a result, the corrosion resistance at the processing and impact portions decreases.

On the electrolytic chromate treatment film, a first resin layer mainly composed of a polyester resin and a phenolic resin and / or a cresol resol type phenol resin is formed. These resin compositions can be obtained either in an organic solvent system or in an aqueous system, and any form can be used in the present invention.

Examples of the polyester resin constituting the resin composition include succinic acid, maleic acid, fumaric acid, phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, 1,4
Dibasic acids such as cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid; polybasic acids such as trimellitic acid and pyromellitic acid; ethylene glycol;
-Propylene glycol, 1,3-propanediol,
1,4-butanediol, 1,5-pentanediol,
Diols such as neopentyl glycol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, and polyethylene glycol, and polyhydric alcohols such as glycerin and pentaerythritol are used without a catalyst or in the presence of a catalyst such as dibutyltin oxide and titanium tetrabutoxide. A linear and / or branched product obtained by condensation can be used.

For the purpose of controlling the molecular weight of the resin to be produced, monobasic acids such as acetic acid, benzoic acid, 4,4-bis (4'-hydroxyphenyl) pentanoic acid, cetyl alcohol, decyl alcohol, lauryl A monohydric alcohol such as an alcohol can be used as appropriate. Further, in order to lower the melting point of the material and promote a smooth condensation reaction, isophthalic acid, terephthalic acid and the like can be used as an ester such as dimethyl ester and diethyl ester.

The polyester resin thus obtained may be used in an aromatic solvent such as toluene and xylene, an alcohol solvent such as methanol, ethanol, isopropanol and n-butanol, acetone, methyl ethyl ketone and the like.
Known organic solvents such as ketone solvents such as methyl isobutyl ketone, isophorone and cyclohexanone; ether alcohol solvents such as methyl cellosolve, ethyl cellosolve and butyl cellosolve; ether ester solvents such as methyl cellosolve acetate, ethyl cellosolve acetate and butyl cellosolve acetate; It can be dissolved and used. Alternatively, as another embodiment, a polyester resin dissolved in a small amount of a water-compatible organic solvent is dropped into warm water containing an amine such as ammonia, triethylamine, or dimethylethanolamine under pressure to form an aqueous dispersion. Can also be used. As water-soluble organic solvents,
Examples thereof include alcohol solvents such as methanol, ethanol, isopropanol and n-butanol; ketone solvents such as acetone and methyl ethyl ketone; and ether alcohol solvents such as methyl cellosolve, ethyl cellosolve and butyl cellosolve.

As described above, the first resin layer of the present invention comprises
It is formed of a resin composition containing the polyester-based resin and phenolic and / or cresol-based resol-type phenol resin as main components. As the phenolic resin and / or cresol-based resol type phenol resin, phenolic acid, o-cresol, m-cresol, p-cresol or a mixture thereof is condensed with formaldehyde using an alkali such as ammonia, triethylamine, caustic soda, caustic potash as a catalyst. Or methanol, ethanol, n
-Alkyl ethers with alcohols such as butanol can be used.

The phenolic and / or cresol-based resol-type phenol resin may be simply mixed with the polyester-based resin as it is, but a resin in which the phenolic and / or cresol-based resol-type phenol resin is reacted in advance to such an extent that it does not gelate is used. You may.

The resin composition containing the polyester resin and the phenolic and / or cresol resole type phenol resin may be further added with a melamine resin, if necessary.
An amino resin such as a urea resin, a cured product such as a block urethane resin, a urethane resin, another polyester resin, a novolak type phenol resin, and the like can also be blended. Also,
Further, if necessary, a rust preventive such as strontium chromate, calcium chromate, zinc chromate, calcium silicate, aluminum tripolyphosphate or the like can be added in order to increase the corrosion resistance.

In the present invention, the resin composition containing the polyester resin thus obtained and a phenolic and / or cresol-based resol-type phenol resin as main components is used as the first resin layer on the above-mentioned electrolytic chromate-treated film. Formed. As a forming method, there is a method of forming a first resin layer on a steel sheet, or a method of forming a first resin layer on a side surface of a second resin layer on the steel sheet side in advance. Can also be used.

As the coating method, a known method usually used can be adopted in any case.
Roll coating method, curtain flow method, die coater method, dipping method, spray coating method, curtain flow coating method, ironing coating method, blade coater coating method, rod coater coating method, air doctor coater coating method, kiss coater coating method, etc. Can be.

As a drying method, when a steel sheet is coated, any of a jacket roll method and a method using a drying furnace may be used, and the drying method may be performed by a known method. An induction heating furnace or the like can be used. The drying temperature is 10 when painted on steel plate.
When applied to a thermoplastic polyester resin film at 0 to 270 ° C, it is desirable to perform the heating at a temperature of 50 to 110 ° C or lower, which is lower than the heat resistance temperature of the polyester resin film. The drying temperature is preferably 2 seconds to 2 minutes in each case.

The preferred thickness of the first resin layer is 0.1
A preferred composition of the resin composition as the main component is 60 to 99 parts by weight of the polyester resin with respect to 100 parts by weight of the total of the polyester resin and the phenolic and / or cresol resole type phenol resin. ,
The phenolic and / or cresol-based resole phenolic resin is 40 to 1 part by weight. When the film thickness is less than 0.1 μm, sufficient coverage cannot be obtained, so that the corrosion resistance is reduced. On the other hand, when the film thickness is more than 10 μm, cohesive failure is easily caused inside the organic material layer, and as a result, can processability is reduced. And
Corrosion resistance tends to decrease.

When the amount of the polyester resin is less than 60 parts by weight, the adhesion to the thermoplastic polyester layer as the second resin layer is reduced, and as a result, the corrosion resistance is reduced. Also,
Even if it exceeds 99 parts by weight, the corrosion resistance decreases. In the present invention, the polyester resin constituting the resin composition preferably has a number average molecular weight of 3,000 to 30,000 (G
PC value), a hydroxyl value of 5 to 30, an acid value of 0 to 50, and a glass transition temperature of 5 to 110 ° C.

The number average molecular weight of both the solvent type and the aqueous polyester resin is desirably 3,000 to 30,000. If it is less than 3000, the workability of the can and the adhesion to the thermoplastic polyester layer as the second resin layer are reduced, and as a result, the corrosion resistance is reduced. On the other hand, if it exceeds 30,000, the solid content decreases to maintain the coating viscosity, and there is no improvement in corrosion resistance and the like.

The hydroxyl value is preferably from 5 to 30. If it is less than 5, the crosslink density will be insufficient, it will not be able to withstand can processing, and the corrosion resistance will decrease. Further, even if it exceeds 30, the corrosion resistance decreases. The glass transition temperature is preferably from 5 to 110C.
If the temperature is lower than 5 ° C., the corrosion resistance is reduced. On the other hand, if the temperature is higher than 110 ° C., the workability and the adhesion to the second resin layer are reduced, and as a result, the corrosion resistance is reduced. The desired range of the acid value differs between the solvent type and the aqueous type. In the case of a solvent type, 0 to 50 is desirable. 50
If it exceeds, the corrosion resistance is reduced. In the case of aqueous, 5 to 50 is desirable. If it is less than 5, the water dispersibility will be insufficient, and if it exceeds 50, the corrosion resistance will decrease. In the laminated steel sheet of the present invention, a thermoplastic polyester resin layer is laminated as a second resin layer on the first resin layer from the viewpoint of corrosion resistance and the like.
As the thermoplastic polyester resin, polyethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, ethylene terephthalate / isophthalate copolymer, or the like can be used.

The thickness of the second resin layer is preferably 1
0 to 200 μm. If the thickness is less than 10 μm, scratch resistance is poor and pinholes and the like are liable to occur during film production, resulting in poor corrosion resistance. If it exceeds 200 μm, it is not economically preferable.

As a method for forming the second resin layer, a general method for forming a thermoplastic resin into a film can be used. For example, a method in which a resin extruded and melted is formed into a film by a T-die method is used. can do. Further, the film may be used as it is in a non-stretched state or in a state subjected to a stretching treatment such as biaxial stretching.

As a method of laminating the second thermoplastic polyester resin film, there are a method of laminating a film in advance and a method of laminating a resin extruded and melted by a T-die as it is. Any method may be used for lamination. When the thermoplastic polyester resin film is laminated by heat welding, a method is generally used in which the steel sheet is heated to a temperature equal to or higher than the melting point of the second thermoplastic polyester resin film and the film is pressed using a roll. The laminating technique can be performed by a publicly known method that has been disclosed in a large number. For example, a technique for laminating an organic resin film on a metal plate is disclosed in Japanese Patent Application Laid-Open No. 57-1824.
No. 28, Japanese Patent Publication No. 61-3676 and the like disclose a method in which a metal plate side of a film is heated to a temperature equal to or higher than the melting point of the film and bonded by heat fusion.

[0034]

Next, specific examples of the present invention will be described.

[Specimens] (1) Surface-treated steel sheets All examples and comparative examples were produced by subjecting a cold-rolled steel sheet having a thickness of 0.32 mm to a surface treatment shown in Table 1 below.

(2) Organic material for coating <Organic substance type A> Terephthalic acid 47 mol%, isophthalic acid 48 mol%, fumaric acid 5 mol as dicarboxylic acid components
%, 1,4-butanediol 50mo as diol component
A copolymerized polyester resin having a composition ratio of 1% to 50 mol% of ethylene glycol was synthesized. 300 parts by weight of the copolymerized polyester resin and 700 parts by weight of methyl ethyl ketone were mixed to obtain a polyester resin having a number average molecular weight of 18,000 (according to GPS), a hydroxyl value of 10, an acid value of 5, and a glass transition temperature of 68 ° C.

Next, 80 parts by weight of the polyester resin and a phenolic resole type phenol resin obtained by dissolving a thermosetting type carbonic acid / formaldehyde resin in methyl ethyl ketone (viscosity 5000 cP, gel time 160 seconds [15
0 ° C.], a nonvolatile content of 51% [105 ° C./3 hours], 20 parts by weight of a brown liquid) were mixed to obtain a resin composition as a main component of the first resin layer (organic substance type A).

<Organic substance types BR to SA, SA to SJ, Y> Similarly, the number average molecular weight, hydroxyl value, and the like of the polyester resin synthesized by changing the monomer or the production method (solvent type, aqueous).
Acid value, glass transition temperature and composition of phenolic and / or cresol-based resole type phenolic resin or resin composition (organic material type BR, SA-SJ, Y) used as a main component of an organic material layer composed of these materials The composition ratios are summarized in Table 2 below.

<Organic substance type Z> Organic solvent-based phenolic resole type phenolic resin (viscosity of 6000 c) synthesized from 80 parts by weight of a bisphenol-type organic solvent-based epoxy resin having a molecular weight of about 7,000 and carbonic acid / formaldehyde resin
P, gel time 140 seconds [150 ° C], nonvolatile content 52%
[105 ° C./3 hours], 20 parts by weight of a brown liquid) were blended to obtain a resin composition (organic substance type Z).

(3) Film lamination The steel sheet on which the first resin layer was formed was cut into a 200 × 300 mm plate, and a commercially available polyester film was laminated on both sides under the following conditions.

Film: Biaxially oriented polyester film (copolymer of polyethylene glycol and terephthalic acid / isophthalic acid) Film thickness: 25 μm Crystal melting temperature of film: 229 ° C. Steel sheet temperature immediately before lamination: 235 ° C. Laminating speed: 2 m / Seconds Cooling after lamination: water cooling (rapid cooling) [Evaluation method] (1) Evaluation of scratch corrosion resistance A laminated steel sheet is cut into a square of 50 mm x 50 mm, and then a cutter knife is used to reach from the top of the square to the film surface to the steel plate surface. The wound was cut in a cross cut (x) shape. Then, the scratched laminated steel sheet was immersed in a commercial neutral detergent (product name: Rypon F) at 50 ° C. for 1 month, and the degree of film peeling from the scratched portion was evaluated in five steps based on the peeling width.

5 points: less than 2 mm, 4 points: 2 mm or more and 5 m
m, 3 points: 5 mm or more and less than 10 mm, 2 points: 10 mm or more and less than 15 mm, 1 point: 15 mm or more (2) Evaluation of corrosion resistance after processing 0 for a laminated steel sheet having a width of 50 mm and a length of 100 mm.
T-shaped bending tests of T, 1T, 2T, and 3T were performed. Put the sample in a commercial neutral detergent (product name: Raipon F)
It was immersed at 10 ° C. for 10 days, and the corrosion of the processed portion was visually observed. 5 without corrosion in all processes
The point where corrosion was observed at 0T was evaluated as 4 points, and the evaluation was sequentially performed on a 5-point scale from 3 points to 1 point.

(3) Evaluation of corrosion resistance after impact At -20.degree.
A DuPont impact test (load: 1 kg, drop height: 8 cm) based on 00 was performed. The sample was immersed in a commercial neutral detergent (product name: RIPON F) at 50 ° C. for one month, and the degree of film peeling was evaluated in five steps based on the peel width.

5 points: less than 2 mm, 4 points: 2 mm or more and 5 mm
Less than, 3 points: 5 mm or more and less than 10 mm, 2 points: 10 mm or more and less than 15 mm, 1 point: 15 mm or more. (4) Comprehensive evaluation of corrosion resistance As comprehensive evaluation of corrosion resistance, evaluation of scratch resistance, evaluation of corrosion resistance after processing, evaluation of corrosion resistance after impact of 5 Good grades of 5 or 4 were evaluated as ○, normal grades of 3 were evaluated as Δ, and others were evaluated as ×.

[0045] (Example 1) to the surface treatment the original sheet, as shown in Table 1, the metal chromium layer of metallic chromium coating weight 126 mg / ^{m 2,} the hydration of the coating weight 16 mg / ^{m 2} in metal chromium conversion chromium oxide After the material layer is subjected to electrolytic chromate treatment, a resin composition (organic material type A) comprising the polyester resin and the phenolic resole type phenol resin is applied by a reverse roll coater, and dried to have a thickness of 2.0 μm. A first resin layer was formed. A polyester film was laminated on the surface-treated steel sheet under the conditions described above, and then the corrosion resistance was evaluated by evaluation of scratch corrosion resistance, evaluation of corrosion resistance after processing, and evaluation of corrosion resistance after impact.
These evaluation results are also shown in Table 1. As a result, it was found that the polyester resin-laminated steel sheet according to the present invention was excellent in any of scratch resistance after film lamination, corrosion resistance after processing, and corrosion resistance after impact.

(Examples 2 to 5, Comparative Examples 1 to 3) In these, as shown in Table 1, the conditions for electrolytic chromate treatment were variously changed, and the other operations were performed in the same manner as in Example 1 to obtain the surface. A treated steel sheet was obtained. Table 1 shows the results of these corrosion resistance evaluations.
It is described together. As is clear from Table 1, all of Examples 2 to 5 in which the lower layer chromium metal adhesion amount is 40 mg / m ² or more per one side and the upper layer hydrated chromium oxide adhesion amount is 3 to 25 mg / m ^2. Excellent in scratch resistance, corrosion resistance after processing, and corrosion resistance after impact.

On the other hand, when the amount of deposited metal chromium in the lower layer is 4
Comparative Example 1 with less than 0 mg / m ² was inferior in corrosion resistance.
The Comparative Examples deposition amount is less than 3 mg / m ² of the upper hydrated chromium oxide 2 also corrosion resistance was inferior. Further, in Comparative Example 3 in which the amount of the deposited upper layer hydrated chromium oxide exceeded 25 mg / m ² , the appearance was deteriorated and the corrosion resistance was poor.

(Examples 6 to 9, 33 and 34) In these, as shown in Table 1, the film thickness of the resin composition (organic substance type A) composed of a polyester resin and a carboxylate resol type phenol resin was determined. Various changes were made, and otherwise the same operation as in Example 1 was performed to obtain a surface-treated steel sheet. These evaluation results are also shown in Table 1. As is clear from Table 1, in all cases, favorable evaluations were obtained in all of the scratch resistance, the corrosion resistance after processing, and the corrosion resistance after impact. In particular, in Examples 6 to 9 in which the thickness of the first resin layer was 0.1 to 10 µm, all were particularly excellent in scratch corrosion resistance, corrosion resistance after processing, and corrosion resistance after impact.

(Examples 10 to 15, 35, 36) In these, as shown in Table 1, the resin composition (organic substance type A) was prepared by mixing the polyester resin constituting the resin composition with phenolic and / or A surface-treated steel sheet was obtained by performing the same operation as in Example 1 except that the composition or composition ratio of the cresol-based resol-type phenol resin was changed (see Table 2). These evaluation results are also shown in Table 1. As is clear from Table 1, Examples 10 to 15
Was particularly excellent in all of scratch resistance, corrosion resistance after processing, and corrosion resistance after impact.

(Examples 16 to 26, 37 to 44) In these, as shown in Table 1, the resin composition (organic substance type A) was prepared by changing the number average molecular weight of the polyester resin constituting the resin composition, A surface-treated steel sheet was obtained by performing the same operation as in Example 1 except that the resin composition was changed to a hydroxyl value, an acid value and a glass transition temperature (see Table 2). These evaluation results are also shown in Table 1.

As is clear from Table 1, Examples 16 to 2
No. 6 was particularly excellent in all of scratch resistance, corrosion resistance after processing, and corrosion resistance after impact.

(Comparative Examples 4 to 6) In Comparative Example 4, as shown in Table 1, the same operation as in Example 1 was performed except that the first resin layer, which is a feature of the present invention, was not formed. A treated steel sheet was obtained. Further, in Comparative Example 5, the resin composition (organic substance type A) was changed to a resin composition (organic substance type Y) consisting only of a copolymerized polyester resin (see Table 2), and otherwise the same as in Example 1 The operation was performed to obtain a surface-treated steel sheet. In Comparative Example 6, the resin composition (organic substance type A)
Was changed to a resin composition (organic substance type Z) in which a polyester resin was changed to an epoxy phenol resin (see Table 2), and otherwise the same operation as in Example 1 was performed to obtain a surface-treated steel sheet. These corrosion resistance evaluation results are also shown in Table 1. As is clear from Table 1, the corrosion resistance was poor in all cases.

(Example 27) In this example, a resin composition (organic substance type A) comprising the polyester resin and a phenolic resole type phenol resin was applied to a polyester film to be a second resin layer by a reverse roll coater. By drying, an organic layer having a thickness of 2.0 μm to be a first resin layer was formed. The polyester film was laminated on a surface-treated steel sheet under the conditions described above, and otherwise the same operation as in Example 1 was performed to obtain a surface-treated steel sheet. These evaluation results are also shown in Table 1.

As is clear from Table 1, the surface-treated steel sheet according to the present invention is excellent in all of the scratch resistance, corrosion resistance after working, and corrosion resistance after impact.

(Examples 28 to 30, Comparative Example 7) In these, the thickness of the laminate film as the second resin layer was 10 μm (Example 28) and 200 μm (Example 2).
9), 30 μm (Example 30) and 8 μm (Comparative Example 7), except that the same operation as in Example 1 was performed to obtain a surface-treated steel sheet. These corrosion resistance evaluation results are also shown in Table 1. As is clear from Table 1, Examples 28 to 30
Had excellent scratch resistance, corrosion resistance after processing, and corrosion resistance after impact. On the other hand, when the film thickness is 10 μm
Comparative Example 7 with less than m was inferior in corrosion resistance.

(Examples 31 and 32, Comparative Examples 8 and 9) In Example 31, the laminated film was changed from copolymerized polyester to homo-PET.
The same operation as described above was performed to obtain a surface-treated steel sheet. Further, in Example 32, the same copolymerized polyester resin as in Example 1 extruded and melted by the T-die method was directly laminated on the first resin layer to form a second resin film layer of 25 μm. Otherwise, the same operation as in Example 1 was performed to obtain a surface-treated steel sheet. In Comparative Examples 8 and 9, surface-treated steel sheets were obtained by performing the same operations as in Example 1 except that the laminated film was changed to 25 μm polypropylene (Comparative Example 8) and nylon 6 (Comparative Example 9). These corrosion resistance evaluation results are also shown in Table 1. As is clear from Table 1, Examples 31 and 32 were excellent in all of the scratch resistance, the corrosion resistance after processing, and the corrosion resistance after impact. On the other hand, Comparative Examples 8 and 9 in which the film was other than polyester were inferior in corrosion resistance.

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

[Table 3]

[0060]

[Table 4]

[0061]

As described above, according to the present invention,
A surface-treated steel sheet having excellent corrosion resistance even when subjected to severe processing and impact after film lamination is provided. They are also excellent in workability as a steel sheet used for 18L cans, pail cans, etc., and can be used without problems even when highly corrosive substances such as surfactants and soy sauce are used as fillers. Having.

As described above, according to the present invention, since excellent corrosion resistance can be obtained without going through complicated steps, its economic value is extremely high.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akihiko Furuta 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. F-term (reference) 4F100 AA22C AB03A AB13B AK33D AK41D AK41E AR00C BA05 BA07 BA10B BA10E EJ69C GB16 JA07D JA20D JA20E JB02 JB16E JK10 JL00 YY00B YY00C YY00D YY00E 4K026 AA02 AA08 AA12 AA22 BA06 BA12 BB08 BB09 BB10 CA02 CA16 CA20 CA39 DA01 DA16 EB08 EB11

Claims (2)

[Claims] 1. A steel sheet, wherein the lower layer is formed on at least one surface of the steel plate and has a lower layer of 40 to 200 mg / m2 per side.
A chromium metal layer having an adhesion amount of ² and an upper layer having an adhesion amount of 3 to 25 mg / m ^{2 in} terms of metal chromium per side, and an electrolytic chromate treated layer of a hydrated chromium oxide layer; A first resin layer formed mainly of a polyester-based resin and a phenolic and / or cresol-based resol-type phenolic resin, and a thermoplastic polyester-based resin formed on the first resin layer and formed on the first resin layer A polyester resin laminated steel sheet having excellent corrosion resistance, comprising: a second resin layer having a thickness of 10 to 200 μm. 2. The method according to claim 1, wherein the first resin layer has a thickness of 0.1 to 10.
μm, and the polyester resin of the resin composition has a number average molecular weight of 3,000 to 30,000 and a hydroxyl value of 5 to 3
0, an acid value of 0 to 50, a glass transition temperature of 5 to 110 ° C., and 6 to 100 parts by weight of the polyester resin and the phenolic and / or cresol resole type phenol resin in total.
The polyester resin laminated steel sheet having excellent corrosion resistance according to claim 1, which is contained in the range of 0 to 99 parts by weight.