JP3351995B2 - Heat-resistant non-adhesive design steel sheet and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant and non-adhesive design steel sheet suitable for food cooking utensils, cooking utensils, and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Fluororesins have been used as composites with steel sheets by utilizing their excellent properties such as heat resistance, non-adhesion and stain resistance. BACKGROUND ART A steel sheet in which a fluororesin is compounded is widely used as a heating cooker such as a food cooker such as a pan and a cake baking pan, a frying pan, an inner plate of a microwave oven, an inner pot of an electronic control jar, and a top plate for a gas table. I have. By the way, about the top plate of the gas table, about 70% of them are fluororesin coated products. At present, non-adhesive fluororesin coatings have become widely used, and in order to increase product value, differentiation is required, and the design, including the pattern, is better than monotone, such as gray, silver, and black. There is a demand for an excellently designed steel sheet. Therefore,
Gravure printing is performed on a transparent perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer film (hereinafter, referred to as a PFA film) in order to express print design, and the printed surface is placed on the steel plate side, and the printed PFA film is laminated. Laminated steel sheets, which provide a printable design through the transparent PFA film layer, have begun to be used for gas table tops and the like. In Japanese Patent Application Laid-Open No. Hei 7-112517, in order to print and display on a heating container, a primer layer and a printing display layer are applied to a molded heating container, and a polytetrafluoroethylene layer containing a brilliant component is further sprayed on the upper surface thereof. After coating, a perfluoroalkoxyethylene copolymer is powder-coated.

[0003]

However, when a printed PFA film is laminated on a steel plate, the unit cost of the resin of the PFA film used as a base material for printing is expensive.
In order to obtain printability on the film, a thick film having a thickness of at least 40 μm or more is required. However, the unit price per square meter of the PFA film exceeds the unit price of the SUS430 stainless steel plate as the material to be laminated. Further, in order to laminate the printed PFA film on the steel plate with sufficient adhesiveness, the heating method, the heating time and the like are restricted, and the processing becomes complicated. Therefore, the obtained laminated steel sheet is significantly more expensive than the heat-resistant and non-adhesive coated steel sheet which is a conventional pre-coated steel sheet.

[0004] On the other hand, in Japanese Patent Application Laid-Open No. Hei 7-112517, a heating container which has been molded by tampo printing or the like is marked with a scale or the like, and then a fluororesin paint is sprayed and powder-coated. Since the fluororesin paint used here takes a form in which the fluororesin is not dissolved in a solvent, a roll coating method, a curtain flow coating method, and the like, which are widely used for the production of a precoated steel sheet, cannot be adopted. Of course, tampo printing cannot also be performed in a continuous coating facility for the production of precoated steel sheets. The present invention has been devised to solve such a problem, and a fluorinated resin-based heat-resistant printing ink layer having a surface of 70% or less is formed by gravure offset printing on a colored coating film made of a heat-resistant resin. After providing the coating at the coverage, a transparent heat-resistant and non-adhesive coating consisting of the same heat-resistant resin and tetrafluoride resin as the resin forming the colored coating is provided, so that continuous coating equipment for the production of pre-coated steel sheets can be used and printing An object is to easily obtain a heat-resistant and non-adhesive design steel sheet having excellent design properties.

[0005]

In order to achieve the object, the heat-resistant and non-adhesive design steel sheet of the present invention comprises one kind of heat-resistant resin selected from polyethersulfone resin, polyphenylsulfide resin and polyamideimide resin. A colored coating film as a main component is formed on the surface of the steel sheet, and at least one kind of fluororesin of polytetrafluoroethylene resin, perfluoroalkylvinylether-tetrafluoroethylene copolymer and at least one of acrylic resin, polyurethane resin and polyester resin A heat-resistant printing ink layer based on a mixture with one or more water-soluble or water-dispersible resins is formed on the colored coating with a surface coverage of 70% or less;
Further, a transparent heat-resistant and non-adhesive coating mainly comprising a mixture of the same heat-resistant resin as the colored coating film and at least one kind of fluororesin of polytetrafluoroethylene resin and perfluoroalkylvinylether-tetrafluoroethylene copolymer. A film is formed on a non-printed portion of the heat-resistant printing ink layer and the colored coating film. This heat-resistant and non-adhesive design steel sheet is a heat-resistant printing ink based on a mixture of a tetrafluoride resin and a water-soluble or water-dispersible resin after applying a colored coating mainly composed of a heat-resistant resin to the steel sheet surface. The layer is subjected to gravure offset printing on the colored coating at a surface coverage of 70% or less, and then a transparent heat-resistant and non-adhesive resin mainly composed of a mixture of the same heat-resistant resin and tetrafluoride resin as the colored coating. It is manufactured by forming a coating film on the heat-resistant printing ink layer and the non-printed portion of the colored coating film.

[0006]

The present inventors have developed a base color tone with a colored coating made of a heat-resistant resin, developed a printing design on the colored coating by a direct printing method on a steel plate, and furthermore applied a four-floor coating on the upper surface. By providing a transparent heat-resistant and non-adhesive coating layer made of a heat-resistant resin and a heat-resistant resin, the present inventors have conducted intensive studies on a product configuration that exhibits heat-resistant and non-adhesive properties while maintaining the printing design of the lower layer. In this product configuration, attention was paid to gravure offset printing for the possibility of exhibiting a print design property close to gravure printing in which a PFA film exhibits a design.

With respect to the basic gravure offset ink, polyether sulfone resin, polyphenyl sulfide resin, polyamide imide resin and the like were investigated as base resins having excellent heat resistance. Then, the same polyether sulfone resin,
A gravure offset printing of a heat-resistant printing ink composed of polyphenylsulfide resin, polyamide-imide resin, etc., and a transparent heat-resistant and non-adhesive coating film is provided on the upper surface. The printing pattern formed by the heat-resistant printing ink layer has an outline. The print design was unclear. It is considered that the blurred print pattern is caused by the heat-resistant printing ink flowing and partially mixing with the colored coating film. In this method, although excellent heat-resistant and non-adhesive properties are obtained, the printed PFA film laminate is used. It turned out that printing design property like a steel plate cannot be expressed.

[0008] Therefore, when a gravure offset printing is performed on a colored coating film using a heat-resistant ink based on a polytetrafluoroethylene resin or a perfluoroalkylvinyl ether-tetrafluoroethylene copolymer having excellent heat resistance, the printed pattern is obtained. Became clear, and excellent print design was obtained. However, there was a problem in non-adhesion at high temperature, that is, heat-resistant non-adhesion. The heat-resistant and non-adhesive property is as follows. Specifically, a mixed solution of soy sauce / sugar / egg = 1/1/1 and milk are placed on the surface of the coating film, left in a heating furnace at 260 ° C. for 1 hour, and sufficiently cooled. Later, soy sauce / sugar / egg, which is a pollutant, is 1 /
The evaluation is made based on whether or not 1/1 mixed liquid and milk can be removed without scorching on the coating film surface.

A transparent heat-resistant and non-adhesive coating is directly provided on a colored coating without using a heat-resistant printing ink layer based on a polytetrafluoroethylene resin or a perfluoroalkylvinylether-tetrafluoroethylene copolymer. In this case, excellent heat-resistant and non-adhesive properties can be obtained. In addition, even if a heat-resistant printing ink based on a heat-resistant resin with a blurred outline of the printed pattern is gravure offset printed with a transparent heat-resistant and non-adhesive coating, excellent heat-resistant and non-adhesive properties can be obtained. Obtained. This phenomenon was discovered for the first time by the present inventors' research and research,
It cannot be predicted from the conventional product configuration. The designed steel sheet of the present invention has been completed on the basis of such knowledge, and by adopting the specified layer structure as described in the claims, has excellent printing design properties, heat resistance and heat-resistant non-adhesion. It has sex.

The heat-resistant resin contained in the transparent heat-resistant and non-adhesive coating film according to the present invention is specified as the same resin as the heat-resistant resin forming the colored coating film. Further, the surface coverage of the heat-resistant printing ink layer provided on the colored coating film is specified to be 70% or less, and the printed appearance is such that the colored coating film as the underlying coating film is exposed to 30% or more. Polyether sulfone resin, polyphenyl sulfide resin, and polyamide imide resin, which are heat-resistant resins, are strictly different from tetrafluoride resins such as polytetrafluoroethylene resin and perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer. Although it does not dissolve, high adhesive strength can be obtained at each resin interface. Therefore, the heat-resistant printing ink layer provided on the colored coating film is firmly bonded to the colored coating film, and the transparent heat-resistant and non-adhesive coating film provided on the upper surface is also strongly bonded to the heat-resistant printing ink layer. Is done.

The polytetrafluoroethylene resin and the perfluoroalkylvinyl ether-tetrafluoroethylene copolymer contained in the transparent heat-resistant non-adhesive coating film have a small surface tension and are thermodynamically stable when the coating film is baked. Transfer to the surface of the coating film. As a result, heat-resistant non-adhesiveness is exhibited. Further, the transparent heat-resistant and non-adhesive coating film is a thin layer as compared with the PFA film having a thickness of 40 μm, and can exhibit heat-resistant and non-adhesiveness at low cost. However, when the coverage of the heat-resistant printing ink layer on the surface of the colored coating film exceeds 70%, the tetrafluoride resin contained in the transparent heat-resistant and non-adhesive coating film mainly migrates to the lower heat-resistant printing ink layer. As a result, the amount of tetrafluoride resin migrating to the surface is drastically reduced, and the heat-resistant and non-adhesive property is not exhibited. For example, when a polyamideimide resin is used as a colored coating with a transparent heat-resistant and non-adhesive coating containing a polyether sulfone resin as a heat-resistant resin, a cross-sectional photograph, EPMA (electron probe micropart analysis),
The migration ratio of the tetrafluoride resin to the surface of the transparent heat-resistant and non-adhesive coating film estimated from infrared spectroscopy and the like is that the surface coverage is 60%
Is about 60/40 on the surface / heat-resistant printing ink layer side, but at a surface coverage of 80%, the transition ratio is about 20/80.

Further, in the transparent heat-resistant and non-adhesive coating film, a heat-resistant resin such as a polyether sulfone resin, a polyphenyl sulfide resin, a polyamide imide resin, etc. may be used in combination with a polytetrafluoroethylene resin, a perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer. Simultaneous with the transfer of tetrafluoride resin such as coalescence. When the heat-resistant resin in the transparent heat-resistant and non-adhesive coating is the same resin as the lower colored coating in the portion where the colored coating is exposed on the heat-resistant printing ink surface, that is, in the non-printing portion, The heat-resistant resin in the transparent heat-resistant and non-adhesive coating film is unevenly distributed near the heat-resistant printing ink layer due to high compatibility. As a result, the development of heat-resistant and non-adhesive properties is accelerated. In other words, the uneven distribution of the heat-resistant resin contained in the transparent heat-resistant and non-adhesive coating film in the vicinity of the heat-resistant printing ink layer may be caused by a tetrafluoroethylene resin, a perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer or the like. Transfer of the activated resin to the heat-resistant printing ink layer is suppressed. Specifically, when the heat-resistant resin in the transparent heat-resistant and non-adhesive coating film is the same as the resin of the lower colored coating film, at a surface coverage of 60%, the tetrafluoride resin is applied to the surface of the transparent heat-resistant and non-adhesive coating film. The transition ratio is about 90/10. On the other hand, when the surface coverage is 80%, the transfer of the tetrafluoride resin to the heat-resistant printing ink layer is not substantially suppressed.

When the heat-resistant resin is a mixture of two or more, the effect of suppressing the transfer of the polytetrafluoroethylene resin or the perfluoroalkylvinylether-tetrafluoroethylene copolymer to the heat-resistant printing ink layer is not sufficient. For this reason, it is necessary that the heat-resistant resin in the colored coating film and the transparent heat-resistant and non-adhesive coating film is one kind of single resin. On the other hand, if the heat-resistant resin is a mixture of two or more kinds, the two cannot be strictly compatible with each other, so that the phase separation form (including microphase separation) between the formed resins is caused through the non-printed portion. Inhibits the compatibility of the heat-resistant resin between the colored coating and the transparent heat-resistant and non-adhesive coating.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION As a steel sheet to be coated according to the present invention, a 55% Al-Zn coated steel sheet, an Al-plated steel sheet, a stainless steel sheet, etc., which have been subjected to a phosphate treatment, a coating type chromate treatment or the like as necessary. . First, a colored paint made of a heat-resistant resin is applied to the original coating plate and baked. One kind of resin selected from polyether sulfone resin, polyphenyl sulfide resin and polyamide imide resin is used as the heat resistant resin which is a component of the coloring paint. The coloring paint has a heat-resistant coloring pigment such as titanium oxide, carbon black, chromium oxide, iron oxide, etc., because it exhibits a base color to express the printing design in combination with the concealment of the steel sheet base and the printed pattern. Is done. In addition, rust-preventive pigments, extender pigments and the like can be added as necessary.

The colored coating layer has a dry coating thickness of 2 to 20 μm.
m is applied to the steel sheet surface. A paint in which a heat-resistant resin is dissolved in a solvent is applied to a steel plate by a roll coating method, a curtain flow method, or the like, and baked at a temperature exceeding the melting point of the resin contained in the paint. A heat-resistant printing ink layer is printed on the steel sheet coated with the heat-resistant coloring by a gravure offset method.
In gravure offset printing, a necessary production line is constructed simply by replacing an applicator roll of a roll coater used in a continuous coating facility for manufacturing a precoated steel sheet with an offset roll and disposing a gravure roll. As a result, there is no need to use an expensive printed PFA film, and the complicated processing required for laminating the printed PFA film on the steel plate with sufficient adhesiveness is omitted. Therefore, a heat-resistant non-adhesive design steel plate can be manufactured inexpensively and easily at a low manufacturing cost.

The printing ink used for the gravure offset printing is at least one kind of polytetrafluoroethylene resin, at least one kind of perfluoroalkylvinylether-tetrafluoroethylene copolymer, and an acrylic resin, a polyurethane resin, and a polyester resin. An aqueous printing ink composition based on a mixture with at least one water-soluble or water-dispersible resin. The tetrafluoride resin, which is a component of the printing ink, has poor pigment dispersibility, and proper gravure offset printability cannot be obtained using the tetrafluoride resin alone. In this regard, acrylic resin, polyurethane resin,
When an ink is formed by mixing at least one or more water-soluble or water-dispersible resins of a polyester resin, the dispersibility of the pigment can be remarkably improved. The compounding ratio of the tetrafluoride resin and the water-soluble or water-dispersible resin is in the range of 99: 1 to 95: 5 by weight since the heat resistance decreases as the amount of the water-soluble or water-dispersible resin increases. It is preferable to adjust to.

A pigment having good heat resistance, such as titanium oxide, carbon black, chromium oxide or iron oxide, is dispersed in a resin composition obtained by mixing a tetrafluororesin and a water-soluble or water-dispersible resin. And made into an ink with additives such as a pigment dispersant. This ink is usually 0.5 to
10 μm thick and 70% coverage on the colored coating surface
% Or less for gravure offset printing. The thickness of the formed heat-resistant printing ink layer is determined by the thickness of the polytetrafluoroethylene resin, perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer or other tetrafluoride resin and polyether sulfone contained in the transparent heat-resistant and non-adhesive coating film. It does not adversely affect the transfer of heat-resistant resins such as resins, polyphenylsulfide resins, and polyamide-imide resins. After printing, it is dried and, if necessary, baked.

On the upper surface of the heat-resistant printing ink layer, a transparent coating mainly composed of a mixture of a heat-resistant resin and a tetrafluoride resin is provided. The heat-resistant resin which is a component of the transparent heat-resistant and non-adhesive coating film is specified as the same resin as the above-mentioned colored coating film.
Further, as the tetrafluoride resin, at least one or more of a polytetrafluoroethylene resin and a perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer is used. When the proportion of the tetrafluoride resin in the paint increases, the non-adhesiveness and the heat-resistant non-adhesiveness are improved. However, since the amount of the heat-resistant resin, which is a dissolved component in the paint, is reduced, the suitability of the paint for roll coating is reduced, and the coating film is apt to be scratched due to a decrease in hardness. Therefore, from the balance between coating properties and coating properties such as non-adhesion, heat-resistant non-adhesion, and coating hardness, the heat-resistant resin and the tetrafluoride resin are preferably 4
0:60 to 70:30, more preferably 50:50 to 6
They are mixed in a weight ratio of 0:40.

The heat-resistant non-adhesive coating film is required to be transparent because it has the effect of protecting the appearance of the heat-resistant colored coating film and the print design by gravure offset printing.
Various additives are added to the paint of the transparent coat as needed, unless the colored coat and the printed pattern are hidden. Further, by blending a trace amount of aluminum powder, a coloring pigment, or the like into the paint, it is possible to improve the design properties in combination with the colored coating film and the printed pattern. The transparent heat-resistant and non-adhesive coating layer is applied to the steel sheet surface so as to have a dry coating thickness of 2 to 20 μm. Since the paint used contains a heat-resistant resin soluble in a solvent, it can be applied by a roll coating method, but exhibits a thixotropic property because it contains a tetrafluoride resin insoluble in a solvent. Therefore, it is preferable to apply by a top feed full reverse type roll coating method. The applied paint is baked at a temperature exceeding the melting point of the resin having the highest melting point among the heat-resistant resin and the tetrafluoride resin contained therein.

[0020]

EXAMPLE After a SUS430 stainless steel plate having a thickness of 0.45 mm was degreased, it was subjected to a coating type chromate treatment, and a heat-resistant coating film containing titanium oxide was roll-coated with a dry film thickness of 12 μm and baked at 300 ° C. Next, a heat-resistant printing ink containing carbon black was gravure offset printed and dried at 200 ° C. Further, a transparent heat-resistant and non-adhesive coating film in which a heat-resistant resin and a tetrafluoride resin were blended at a weight ratio of 50:50 was roll-coated on the printing ink layer with a dry film thickness of 7 μm, and baked at 400 ° C. Except for Test Nos. 8 and 12, a mixture of a tetrafluoride resin and a water-soluble or water-dispersible resin in a weight ratio of 95: 5 was used.

The components of each resin used are shown in Table 1 (Example of the present invention) and Table 2 (Comparative Example) together with the properties of the obtained coating film. PES is a polyether sulfone resin, PPS
Represents a polyphenylene sulfide resin, PAI represents a polyamideimide resin, PTFE represents a polytetrafluoroethylene resin, and PFA represents a polyfluoroethylene-perfluoroalkylvinyl ether copolymer. The surface coverage was determined by examining the surface of a 100 mm × 100 mm test piece using an image analyzer and determining the area ratio of the coated portion. The coating film adhesion was examined by a cross-cut adhesion test, and the heat resistance was examined by heating to 300 ° C. for 300 hours by a cross-cut adhesion test. In addition, heat resistance and non-adhesiveness were determined by dropping 0.5 ml of a mixture of soy sauce / sugar / egg and 1/1/1 and milk on the surface of the coating film, placing the mixture in a heating furnace at 260 ° C. for 1 hour, and cooling sufficiently. Later, the determination was made based on the scoring state of the mixture of soy sauce / sugar / egg = 1/1/1 and milk on the surface of the coating film. And soy sauce / sugar / egg = 1 /
Samples from which the 1/1 mixed solution and milk could be removed without scorching were evaluated as “excellent” in terms of heat and non-adhesiveness, and evaluated as “poor” if not scorched and removed.

As is clear from the comparison between Table 1 and Table 2,
If the colored coating, the heat-resistant printing ink layer, the surface coverage of the heat-resistant printing ink layer and the transparent heat-resistant and non-adhesive coating satisfy the conditions specified in the present invention, the appearance, coating adhesion, heat resistance and heat resistance All non-adhesive properties were good. On the other hand, if any of the colored coating, the heat-resistant printing ink layer, the surface coverage of the heat-resistant printing ink layer, and the transparent heat-resistant and non-adhesive coating does not satisfy the conditions specified in the present invention, the results are shown in Table 2. As can be seen, any one or more of the appearance, coating film adhesion, heat resistance and heat resistance and non-adhesion were inferior.

[0023]

[0024]

[0025]

As described above, the heat-resistant and non-adhesive design steel sheet of the present invention has a heat-resistant colored coating film, a gravure offset printed heat-resistant printing ink layer having a surface coverage of 70% or less, and a heat-resistant resin. A transparent heat-resistant and non-adhesive coating film identical to the coating film is laminated on the steel sheet surface. By this combination, printing design is exhibited while maintaining heat-resistant non-adhesiveness. And since the printing design is developed by gravure offset printing, it can be manufactured at low cost by continuous coating equipment for the production of pre-coated steel sheets, and has high designability and high discrimination by utilizing excellent heat resistance and heat-resistant non-adhesiveness. It is used as a design steel plate suitable for food cooking utensils, cooking utensils, and the like.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI B32B 15/08 B32B 15/08 102Z 104 104Z B05D 7/14 B05D 7/14 Z (72) Inventor Kenji Koshiishi Takaya, Ichikawa-shi, Chiba 7-1 Shinmachi Inside Nisshin Steel Co., Ltd. (72) Inventor Keiji Sakamoto 2-3-13 Kyobashi, Chuo-ku, Tokyo Toyo Ink Manufacturing Co., Ltd. (72) Inventor Yasuyoshi Ogasawara Kyobashi, Chuo-ku, Tokyo No. 2-3-13, Toyo Ink Manufacturing Co., Ltd. (56) References JP-A-7-112517 (JP, A) JP-A-6-91805 (JP, A) JP-A-2-89633 (JP, A) JP-A-7-118871 (JP, A) JP-A-5-116260 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 B05D 7/00 -7/26

Claims (2)

(57) [Claims] 1. A colored coating mainly composed of a heat-resistant resin selected from the group consisting of a polyether sulfone resin, a polyphenyl sulfide resin and a polyamide imide resin is formed on the surface of a steel sheet. Heat resistant printing based on a mixture of at least one fluororesin of fluoroalkyl vinyl ether-tetrafluoroethylene copolymer and at least one water-soluble or water-dispersible resin of acrylic resin, polyurethane resin and polyester resin The ink layer is 70 on the colored coating.
%, And a mixture of the same heat-resistant resin as the colored coating film and at least one fluororesin of polytetrafluoroethylene resin and perfluoroalkylvinylether-tetrafluoroethylene copolymer. A heat-resistant and non-adhesive design steel sheet, wherein a transparent heat-resistant and non-adhesive coating mainly composed of: is formed on a non-printed portion of the heat-resistant printing ink layer and the colored coating. 2. A steel sheet is coated with a colored coating mainly composed of a heat-resistant resin selected from the group consisting of a polyether sulfone resin, a polyphenyl sulfide resin and a polyamide imide resin. Heat-resistant printing ink based on a mixture of at least one kind of alkyl vinyl ether-tetrafluoroethylene copolymer and at least one kind of water-soluble or water-dispersible resin of acrylic resin, polyurethane resin and polyester resin. 70% layer on top of the colored coating
Gravure offset printing is performed at the following surface coverage, and then the same heat-resistant resin, polytetrafluoroethylene resin, and perfluoroalkyl vinyl ether
Forming a transparent heat-resistant and non-adhesive coating film having a mixture of at least one or more fluororesins of a tetrafluoroethylene copolymer as a main component on the heat-resistant printing ink layer and the non-printed portion of the colored coating film; Manufacturing method of non-adhesive design steel sheet.