JPH03112647A - Film-laminated steel board with excellent heat conductivity for cooking utensil - Google Patents

Abstract

PURPOSE:To make adhesion, anticorrosio, abrasion resistivity, and baking finish excellent by giving the rear surface side of a steel plate a surface treatment in which the L value of color measurement in an L a b method shows a specific value and constituting of a fluroresin film given electric discharge machining such that the adhesion surface with the steel plate shows a specific angle in a water contact angle. CONSTITUTION:It is constituted of Al in which a post-roughening hydro-oxidized substratum is subjected to a coating treatment or an Al alloy plated steel plate, and a thermoplastic fluororesin film welded to one surface thereof. The rear surface side of the steel plate is surface-treated such that the L value of color measurement in an L a b method shows 60 or less, and it is constituted of a fluororesin film given electric discharge machining such that the adhesion surface with the steel plate shows 70 deg. or less in the water contact angle. And, between the surface roughened steel plate covered with hydro-oxide and the electric discharge machined thermoplastic fluororesin film, a thin thermoplastic fluororesin layer is disposed which can be obtained by thermoplastic fluororesin dispersion coating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a steel plate in which a thermoplastic fluororesin film is heat-sealed to an Al-plated or Al alloy-plated steel plate.

This steel plate is suitably used as a material for food cooking equipment such as baking molds and flat plates used for baking bread, cakes, confectionery, etc., particularly for heating cooking equipment.

C. Conventional technology and its problems] Heat cooking utensils, especially molds for baking bread, cakes, confectionery, etc., are heated to prevent burning and improve release properties.
Conventionally, baking molds whose inner surfaces are coated with silicone resin have often been used. Such a silicone resin coating material has good mold releasability. However, on the other hand, the abrasion resistance is poor, and since the film disappears in 2 to 3 months, scorching occurs early, resulting in poor mold release properties. Furthermore, although the mold releasability is good to some extent, the reality is that sufficient mold releasability cannot be obtained unless oil application is also used.

However, the use of such oil may generate soot, which may be removed during baking of bread, cakes, sweets, etc. Of course, products with soot removed have a lower commercial value and are also unfavorable from a food hygiene perspective. Therefore, manufacturers of bread, confectionery, and cakes must frequently clean their heating equipment.

For this reason, much research and development has been carried out on the above-mentioned materials for baking molds, which do not use oil (even if they do not burn) and have excellent mold releasability, but they have poor corrosion resistance. It has not been put into practical use due to poor adhesion.In particular,
Regarding adhesion, as a result of various practical tests, it was found that unless sufficient adhesion was maintained in the # type Erichsen test after 10 hours of boiling, it could not be put to practical use.

Below, conventional techniques developed to meet such demands will be described.

Tl) JP-A-61-137534, JP-A-6
Publication No. 1-138567: These techniques relate to materials in which stainless steel or plated steel sheets are coated with tetrafluoroethylene resin, and although the mold release property is good, there are pinholes in the coating and the coating is film-like. The problem is that it is difficult to obtain smoothness.

(2) Special Publication No. 59-16836, Special Publication No. 59-1
Publication No. 6837: These techniques relate to a material in which an A1-plated steel plate is coated with a fluororesin. This is a technique in which a plated steel plate is annealed at 150 to 600°C, the surface is mechanically roughened by sandblasting, liquid honing, etc., and this surface is coated with a fluororesin.

The reality is that these technologies also have the same problems as mentioned above, and there is still room for improvement.

(3) Special Publication No. 54-24434, Special Publication No. 59-1
No. 0304, JP-A-61126728; The techniques described in these publications are known as fluororesin film laminate materials.

First, what is described in Japanese Patent Publication No. 54-24434 is
An Al material obtained by subjecting Al or Al alloy to direct current electrolytic etching in an aqueous chloride solution, then coating the surface with a fluorocarbon resin dispersion, and hot-pressing a thermoplastic fluorocarbon resin film thereon. It is something. This technology is
Although the adhesion of the film is good, since electrolytic etching is performed, processing time and expensive equipment are required, and there are also problems in the adhesion of the film.

Next, what is described in Japanese Patent Publication No. 59-10304 is
3 μm on an Al or A1 alloy plate with a surface roughness of 2 μm or less
This invention relates to an Al material formed by forming the following anodic oxide film and bonding a thermoplastic fluororesin film to the surface by thermocompression. Since this technology is applied to electrical parts that utilize the dielectric constant of a thin film of fluororesin film, the adhesion of the film is not much of an issue. It is unsuitable for use.

In the method described in JP-A-63-126728, a hydrated oxide film is formed on an Al or A1 alloy plate, and then a thermoplastic fluororesin layer is coated, and then a tetrafluoroethylene An Al material formed by coating a resin film, and an Al material formed by thermally fusing the thermoplastic fluororesin and 47 fluoroethylene resin film after forming a hydrated oxide film and treating with an aminosilane compound. It is. Because this technology does not consider physical adhesion, the adhesive strength is low, and peeling of the film was observed in boiling water tests.

[Problem to be solved by the invention]

As explained above, each of the conventional technologies still has issues to be solved in terms of film adhesion, abrasion resistance, processability, etc., which are necessary conditions for materials for heating cooking utensils such as bread, confectionery, and cakes. was left behind.

Furthermore, the common problem to be solved for the materials manufactured by each of the above-mentioned conventional techniques "(11 to (3))" is that when these materials are cooked in a baking mold, under normal heating conditions, One example of this is the phenomenon of bread, cakes, and confectionery being half-cooked.Therefore, as far as heating cooking equipment using these conventional materials is concerned, in order to expect normal baking, the heating temperature should be 10 to 10 degrees higher than the normal temperature. The problem was that the temperature had to be set 20 degrees Celsius higher and the baking time had to be increased by 5 to 10 minutes.Thus, these materials still require improvement in terms of temperature and time, and have not been put into practical use. The reality is that there is no such thing.

The purpose of the present invention is to develop and propose a material that is suitable for use as a material for heating cooking utensils for bread, confectionery, cakes, etc., which has good adhesion, corrosion resistance, abrasion resistance, and is also economical in baking bread, etc. It's there.

[Means to solve the problem]

In order to achieve the above-mentioned purpose, the following are the basic baking mold materials for bread, confectionery, cakes, etc. that can be used in the food industry.
The present inventors have come up with the idea that an Al-plated or A1 alloy-plated steel plate may be used as the target material in terms of strength and corrosion resistance. As a coating applied to the surface of steel sheets, fu-no-resin emulsion coating has corrosion resistance,
Since it has poor abrasion resistance, we focused on a heat-sealable film made of fluororesin film. In order to prevent premature burning, which is the most important thing to be careful about with this type of baking mold material, we decided to improve the surface finish on the back of the material.

That is, the gist of the present invention consists of an Al or A1 alloy plated steel sheet whose surface is roughened and then coated with a hydrated oxide layer, and a thermoplastic fluororesin film heat-sealed to one surface of the Al or A1 alloy plated steel sheet. The back side of the steel plate has a surface finish showing an L value of 60 or less in color measurement by the Lab method, and the fluororesin film has a surface that is bonded to the steel plate in a manner that is free from water. A film-laminated steel sheet for cooking utensils having excellent heat transfer properties, characterized in that it is constructed of a steel sheet that has been subjected to electric discharge machining so as to have a contact angle of 70" or less.

Further, the present invention provides a thin thermoplastic film obtained by dispersion coating of a thermoplastic fluororesin between the roughened copper plate covered with a hydrated oxide and the thermoplastic fluororesin film subjected to electrical discharge machining. The gist of this invention is a film-laminated steel plate for cooking processing that has excellent heat transfer properties and is characterized by having a fluororesin layer interposed therebetween.

Below, the steel plate of the present invention will be explained in more detail.

Now, materials for heating cooking utensils used as molds for baking bread, confectionery, cakes, etc. are required to have a certain degree of rigidity to prevent deformation due to impacts during handling. By the way, conventional material techniques that have been subjected to fluororesin treatment have used Al or A1 alloy plates in order to facilitate surface roughening such as anodic oxidation and electrolytic etching. However, this Al or A1 alloy plate has the disadvantage that it has low rigidity and is easily deformed during handling.For example, if a dent occurs during manufacturing, it has the disadvantage that it loses its commercial value.

Therefore, in the present invention, we have decided to use a steel plate plated with Al or A1 alloy, which has not been considered in the past, so that the material itself already has rigidity.

Next, the present inventors studied pretreatment for effectively performing thermal fusion between the A1 or A1 alloy plated steel sheet and the thermoplastic fluororesin film.

As a result, the following findings were found.

(2) It was confirmed that it is effective to roughen the front and back surfaces of an Al or A1 alloy plated steel plate by jet blasting, etc., and then form a hydrated oxide film.

■The present inventors have determined that in order to improve the heat transfer characteristics of the thermoplastic fluororesin film, the L value of the coated steel sheet (this L value is based on the Hunter Lab system of JIS Z 8730) It has been found that it is effective to reduce the As for the thermoplastic fluororesin film to be bonded to the steel plate, a film that has been treated by electric discharge machining so that the contact angle of water to the film is 70 degrees or less is heat-sealed to the bonding surface. It has been found that this is important in maintaining excellent adhesion over a long period of time.

■Furthermore, the present inventors applied a thin layer of thermoplastic fluororesin dispersion before heat-sealing the resin film, and then heated it above the melting point of the resin to completely melt the resin on the surface of the steel plate. By forming the thermoplastic fluororesin layer, the contact angle of water with the film can be reduced by 70°.
It has been found that this method is effective in obtaining stable adhesion when heat-sealing films with a temperature of less than 100 °C.

The reason for such limitations regarding the steel plate of the present invention based on the above-mentioned findings will be explained in detail below.

First of all, the reason why the back surface of the steel plate is roughened by shot blasting or the like is that it has a great effect on lowering the glossiness of the surface and is also effective in promoting the reaction for producing hydrated oxides. On the other hand, regarding the roughening treatment on the back side of the steel plate, there is no need to impose any strict restrictions on the surface, just to make sure that a new surface appears and to make the surface uniformly rough to maintain low gloss. The roughness of the steel plate surface is determined in consideration of the promotion of the hydrated oxide production reaction and the degree of physical adhesion between the hydrated oxide and the thermoplastic fluororesin film to be thermally fused thereto.

Next, the reason why the L value of the back surface of the steel sheet should be set to 60 or less due to surface roughening treatment and generation of hydrated oxides will be explained.

According to the research conducted by the present inventors, when a baking mold for bread, etc. is made using temporary plating M such as Al to which a fluororesin film is adhered, and bread, confectionery, cakes, etc. are baked under normal conditions, the baking of the aluminum-plated steel sheet Only the food baked in the mold was half-cooked.

Therefore, the present inventors considered the cause. As a result, we found that this premature burning phenomenon was caused more by the heat absorption rate of the outer surface not covered with resin film than by the thermal conductivity of the inner surface coated with resin film. . Further research revealed that the factor that greatly influences the heat absorption rate from the outer surface of the steel sheet is the heat emissivity of the outer surface.If the degree of blackening on the outer surface is low, the heat absorption rate decreases, and the heat absorption rate from the inner surface increases. It is thought that the heat transfer of the product is significantly reduced, resulting in undercooked bread, sweets, cakes, etc.

Therefore, by changing the degree of blackening on the outer surface of the steel plate, that is, the L value,
In addition, a bread baking test was conducted. As a result, it was found that when the L value of color measurement by the Lab method is 70 or less, the bread is baked to a good degree.

As explained above, one of the features of the present invention is that the surface treatment of the steel plate for heat absorption is already completed before the resin film is bonded to the steel plate, and after the film is bonded, There is no need to apply black heat-resistant paint after molding.

Note that a generally known method is sufficient for generating the hydrated oxide as part of the surface treatment of the steel sheet. for example,
The roughened Al-plated steel sheet was placed in a boiling aqueous solution containing a basic organic compound heated to 90°C or higher.
By soaking for ~20 minutes, hydrated oxides are generated on the front and back surfaces. As the basic organic compound, triethanolamine, jetanolamine, monoethanolamine, ammonium acetate, etc. are used.

Next, electric discharge machining treatment on the adhesive surface of the thermoplastic fluororesin film will be explained. Although this treatment itself is generally known, no examples of its application to steel plates, particularly Al-plated steel plates, have been found. The electric discharge machining treatment carried out in the present invention is preferably a corona electric discharge machining treatment carried out at atmospheric pressure or a glow electric discharge machining treatment carried out in a low pressure atmosphere. The purpose of this treatment is to improve the wettability of the adhesive surface of the fluororesin film. In the present invention, this wettability is evaluated by the contact angle of water. In other words, as a condition for good thermal fusion, the contact angle of water with the film should be 70°.
Good results were obtained when the temperature was set to less than 60°, more preferably 60° or less.

The reason why the adhesive surface of the thermoplastic fluororesin film is subjected to the required electric discharge machining treatment is that the thermoplastic fluororesin film itself is inherently difficult to adhere to objects.

In this respect, the thermoplastic fluororesin film subjected to such electrical discharge machining treatment decomposes the heat-sealed outer surface to form functional groups thereon, thereby causing the aforementioned hydration that has already been generated on the Al-plated steel sheet. Effectively acts to form strong chemical bonds with oxides. Note that the chemical bonds are thought to be mainly hydrogen bonds.

Furthermore, in addition to the above-mentioned configuration, the present invention provides a method in which, in the above-mentioned process, after the hydrated oxide is formed, a thermoplastic fluororesin dispersion is applied thinly and heated to a temperature higher than the melting point of the resin to completely coat the surface of the steel sheet. melting, thereby pre-forming their resin layers. It may then be a steel plate on which the thermoplastic fluororesin film is heat-sealed. The steel sheet obtained in this way can completely melt the resin layer generated by heat treatment after applying the thermoplastic fluororesin dispersion during the formation process, and can also be used to roughen the surface of the steel sheet, hydrate and oxidize it. It can be penetrated into the material film. Therefore, the adhesion between the two is further improved. In other words, the fluororesin film heat-sealed to the upper layer fuses with the lower resin layer generated by heat treatment after coating, resulting in stronger and always stable adhesive force.

Next, the heat fusion treatment in the present invention involves heating the steel plate to a temperature higher than the melting point of the thermoplastic fluororesin film, and heat-sealing the thermoplastic fluororesin film to the heated surface by roll crimping, press crimping, etc. conduct. The conditions for this heat fusion may be set to suit each thermoplastic fluororesin film by controlling the temperature, pressure, and time.

The thermoplastic fluorine resin film used in this example is a tetrafluoroethylene-perfluoroalkodiethylene copolymer resin (PFA) film, a tetrafluoroethylene-67
Propylene fluoride copolymer resin (FEP) film, 4
One or more types selected from fluorinated ethylene-ethylene copolymer resin (ETFE) films may be used. The thickness of the film does not need to be particularly limited, and is 10 to 100 μm for use in baking molds for bread, confectionery, cakes, etc.
Preferably.

[Examples and comparative examples]

Next, the present invention will be explained in more detail based on Examples and Comparative Examples.

Example-■ A1-plated steel plate was prepared for Y$, and its front and back surfaces were made uniformly roughened by shot blasting, and then degreased with a weak alkaline type degreasing solution and washed with water.
% of triethanolamine for the required time. Through this pretreatment, the steel plates coated with hydrated oxides had different L values on their back surfaces.

Next, after washing and drying, the pretreated steel sheet was coated with a fluorinated ethylene-perfluoroalkodiethylene copolymer resin film whose heat-sealed surface was treated with glow electrical discharge machining to make the contact angle of water to the film 65°. were prepared and heat fused to obtain a product steel plate. The obtained product steel plate was processed into a bread baking mold, and bread was actually baked.

The bread baking conditions were 23 minutes in an atmosphere of 230°C.

Judgments were made based on the color of the outside of the bread and the degree of doneness of the center of the bread.

Judgment Criteria: ○: The outside has a good brown color and the center of the bread is baked well.

△: The outside color is slightly brown or pale, and the bread is well baked to the center.

×: The outside color is whitish and the center of the bread is undercooked.

The results are shown in Table 1. It has been found that when the L value is 60 or less, the bread is baked well.

Examples 2 to 7, Comparative Examples 1 to 3 Al-plated steel plates were prepared, and the front and back surfaces thereof were made uniformly roughened by shot blasting, and then degreased with a weak alkaline degreasing liquid. , after washing with water, 0.
It was immersed in a boiling aqueous solution containing 5% triethanolamine for the required time. Through this treatment, the m-plate covered with the hydrated oxide layer became a steel plate whose back surface exhibited various L values. Next, after washing and drying the pretreated steel sheet, a thermoplastic fluororesin film with various contact angles of water to the film was prepared by glow discharge machining on the heat-sealed surface of the film, and this was heated. It was fused. In this way, thermoplastic fluororesin film-laminated Al-plated steel sheets were produced in which the hydrated oxide generation conditions of the pretreatment and the type of film were varied.

Details of the manufacturing conditions for these examples and the test results are shown in Table 2.

Examples 8 to 12 Al-plated steel plates were prepared, and a uniformly roughened surface was formed on the front and back surfaces by shot blasting, and then this was degreased with a weak alkaline degreasing solution and washed with water. , immersed in a boiling aqueous solution containing 0.5% triethanolamine for the required time.

As a result of this pretreatment, the steel plates coated with hydrated oxides had different L values on their back surfaces. Next, this pretreated steel sheet was washed with water, dried, and further coated with a thermoplastic fluororesin dispersion, and subjected to an intermediate treatment of heating it above its melting point to form a thermoplastic fluororesin layer.

Afterwards, the adhesive surface of the film is treated with glow electrical discharge machining.
Thermoplastic fluororesin films with varying water contact angles were prepared and heat-sealed. In this way, thermoplastic fluororesin film-laminated Al-plated steel sheets were produced in which the conditions for producing the hydrated oxide in the pretreatment and the type of film were varied.

Details of the manufacturing conditions and the test results are shown in Table 3.

Test items, test methods, and judgment methods ■1 Suita adhesion test of film Prepare a test piece according to JIS K 6744 # Erichsen test method, extrude it with an Erichsen tester, and then cut the cut end of the extruded part of the film with a knife. Grasp it with tweezers and forcibly peel off the film.

Evaluation criteria ○: The film cannot be faded. △: The film can be made to last, but the film cannot be peeled. After making adjustments, use a knife to cut the film at the extrusion section, and use Vincent to forcefully peel off the film.

Evaluation criteria O: The film cannot be washed away △: The film is made thin, but the film cannot be peeled ×: The film is peeled ■ Abrasion test 150 On the surface-F of
Fix 0X120■l, apply a load of 2kg to the scrubber,
Rotate the turntable at a speed of 63 rpm. Moisten the Scotch scrubber with water. The judgment was based on the number of rotations until the film was removed by rubbing with a Scotch scrubber and the substrate was exposed.

From the above results, the L value of the surface of the baking mold should be 70 or less, preferably 60 or less, and when treating a fluororesin film, the contact angle between water and the film should be 70° or less for good adhesion. It is clear that the material has excellent abrasion resistance, and it was also confirmed that it is effective to provide a resin layer made of thermoplastic fluorine resin dispersion as an intervening layer.

〔Effect of the invention〕

As explained above, the steel sheet according to the present invention does not require the application of edible oil at all, has excellent mold releasability, and in particular, the film-laminated steel sheet of the present invention has an L value of 60 or less. Since the heat transfer properties have been improved, it is possible to supply materials for baking molds such as bread, cakes, and sweets that bake well.

Claims (1)

[Claims] 1. A obtained by coating with a hydrated oxide layer after roughening the surface
1 or Al alloy plated steel plate and a thermoplastic fluororesin film heat-sealed to one side thereof, the back side of the steel plate has an L value of 60 when measured by the Lab method. With a surface finish that shows the following,
The fluororesin film is for cooking utensils with excellent heat transfer properties, characterized in that the adhesive surface with the steel plate is electrical discharge machined so that the contact angle with water is 70 degrees or less. Film laminated steel plate. 2. A thin thermoplastic fluororesin layer obtained by coating a thermoplastic fluororesin dispersion is applied between the roughened steel sheet covered with hydrated oxide and the thermoplastic fluororesin film subjected to electrical discharge machining. 2. The film-laminated steel sheet for cooking utensils having excellent heat transfer properties as claimed in claim 1.