JPH0292536A - Coated metallic sheet - Google Patents

Abstract

PURPOSE:To improve adhesion, nonadhesion, lubricity and heat resistance, by a method wherein a dry thickness of a film and a mean particle diameter or a median particle diameter of olefin fluoride resin powder are put within specific ranges. CONSTITUTION:A coating consisting mainly of a mixture of olefin fluororesin powder and the other resin is applied onto a metallic sheet and baked to form a film. A dry thickness of a film (T) and a mean particle diameter or a median particle diameter (R) fall within a range of T/R=0.6-2. When a form of a film of a coating obtained by mixing up at least two kinds of resin which are different in their facial free energy from each other and not compatible with each other is taken into consideration, it is considered that a form where the resin whose facial free energy is low is stretched to an upper layer and covers the surface in the most stabilized state from a view point of thermodynamics. Therefore, formation of a fluororesin rich layer and that of a binder resin rich layer are attained respectively to places close to a surface layer and a metallic sheet and a coated metallic sheet whose nonadhesion, lubricity, adhesion and heat resistance are favorable can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to polytetrafluoroethylene resin (PTFE) or polytetrafluoroethylene hexafluoropropylene copolymer resin (F
The present invention relates to a coated metal plate coated with a paint containing a fluorinated olefin resin such as EP), which has excellent non-adhesion and lubricity and is used for home appliances, containers, etc.

The present invention also relates to a coated metal plate suitable for heat-resistant applications coated with a paint containing a heat-resistant resin such as polysulfone in addition to the above-mentioned fluororesin.

BACKGROUND OF THE INVENTION Conventionally, fluororesins have been widely used for high-grade painted metal plates because of their good weather resistance and corrosion resistance.

In particular, among fluororesins, tetrafluoroethylene resin (hereinafter referred to as PTFE) and tetrafluoroethylene/hexafluoropropylene copolymer resin (hereinafter referred to as FEP) have low surface energy and low coefficient of friction. It is widely used in fields that require adhesiveness and lubricity (processability), and is often used in paints as a mixture of PTFE and FEP with various resins (hereinafter referred to as binder resins). (Special Publication No. 55-44785. Japanese Patent Publication No. 6l-11137
8).

For fields that require non-adhesion and lubricity.

Examples include household cooking containers and frozen food containers that require adhesion prevention, and fields that require oil-free molding that requires lubricity.

In a coating film formed from a paint mainly composed of PTFE or FEP and a binder resin, PTFE,
Is FEP non-adhesive? 11 lubricity, the binder resin needs to exhibit the functions of adhesion with the base material and flexibility, so the membrane structure is made of PTFE as the upper layer.
, FEP ideally has a layer-separated structure in which the base material side is enriched with binder resin.

However, with ordinary coating systems containing PTFE and FEP, extremely thin PTFE and FEP are applied to the surface during the baking process.
Although a layer with a high concentration of EP is formed, it does not form a large-scale layer, and it is difficult to obtain good adhesion and processability, as well as stable non-adhesiveness and lubricity that can withstand long-term use. there were.

Conventionally, the method of improving non-adhesion and lubricity was to increase the content of (+)PTFE and FEP (Japanese Patent Laid-Open No. 8
1-1131359).

(2) Baking increases the temperature.

(3) Roll down the coating surface (# open/close 131-138
567).

Problems to be Solved by the Invention However, although the method (1) improves non-adhesiveness and lubricity, it leads to a decrease in adhesion and workability;
In method (3), although it is recognized that non-adhesiveness and lubricity are improved to some extent by leveling, it cannot be said to be sufficient as it does not result in a good layer separation structure.

The present invention has been made to solve these problems, and it focuses on the effects of dry coating thickness and PTF in the coating on layer separation behavior.
E. By considering the particle size of FEP and increasing its average particle size or radian particle size compared to conventional fluororesin powder, a layer rich in fiber resin can be created in the upper layer of the coating film. The present invention has been completed based on the discovery that this is the case.

Means for Solving the Problems The present invention provides the following methods: (1) A paint film mainly composed of a mixture of fluorinated olefin resin powder and other resins is applied onto a metal plate and baked to form a paint film. In a coated metal plate made of a metal sheet, the dry coating thickness (T) of the coating film and the average particle size or median particle size (R) of the fluorinated olefin resin powder are T/R=0.
．． A painted metal plate characterized in that it is within the range of 8 to 2.

(2) The fluorinated olefin resin is one or more selected from the group consisting of tetrafluoroethylene resin (PTFE) and tetrafluoroethylene/hexafluoropropylene copolymer resin (FEP). , and other resins include polyether sulfone resin (PES), polyphenylene sulfide resin (PPS), and polyamideimide resin (PAI).
The coated metal plate according to claim 1, which is one or more selected from the group consisting of:

It is.

The present invention will be explained in detail below.

Effect Generally speaking, when considering the form of a paint film made by mixing two or more mutually incompatible resins with different surface free energies, thermodynamically the resin with lower surface free energy is oriented in the upper layer and covers the surface. This is considered to be the most stable state.

Therefore, in a mixed system of PTFE or FEP, which is said to have a low surface free energy among resins, and other resins, a layer separation structure is expected in which PTFE and FEP are naturally oriented in the upper layer.

However, in reality, due to the viscosity of the resin being mixed and interference with the mixture such as pigments, baking occurs during the process of dispersing PTFE.
Diffusion due to thermal energy of FEP and FEP does not proceed sufficiently,
PTFE and FEP are used as surface layer from the beginning of coating film formation.
As a result of experiments, it was found that only the formation of a surface layer occurs, and large-scale layer separation does not easily occur.

Therefore, the inventors of the present invention have intensively investigated a method of applying the gradient of thermodynamic energy potential, which is the driving force for forming the surface layer of PTFE and FEP, to as much PTFE and FEP as possible. PTFE, FEP
It has been found that when the average particle size or median particle size of PTFE and FEP particles is set below a certain level, a large amount of PTFE and FEP particles are located near the surface when forming a coating film after solvent evaporation, and they form a surface layer. .

As a result, a layer rich in fluororesin near the surface layer and a layer rich in binder resin near the metal plate was achieved, resulting in a coated metal plate with good non-stick properties, lubricity, adhesion, and heat resistance. I was able to get it.

Here, PTFE, F to realize large-scale two-layer formation
It is necessary that the dry coating thickness is at most twice the average particle size or median particle size of EP. However, if the dry coating thickness is less than 0.8 times the average or median particle size of PTFE or FEP, the PTFE or FEP layer becomes non-uniform, resulting in a decrease in adhesion and processability.

PT to improve non-adhesiveness while maintaining coating film properties
The dry coating thickness needs to be in the range of 0.6 to 2 times the average particle size or median particle size of FE or FEP, particularly preferably in the range of 0.75 to 1.75 times. be.

In addition, as other resins to be mixed with PTFE and FEP, any resin may be used, regardless of whether it is thermoplastic or thermosetting, as long as it can be applied as a paint.1 Typical examples include polyester resins, acrylic resins, and epoxy resins. resin, urethane resin, etc.

In particular, for heat-resistant applications that require a normal heat-resistant temperature of about 200 to 260°C, polyether sulfone resin (PES)
), polyphenylene sulfide resin (PPS), and polyamideimide resin (PAI) may be used alone or as a mixture thereof.

The mixing ratio of PTFE and FEP to these resins is determined depending on the required properties, but it is preferable that the content ratio of PTFE and FEP to the total resin is 5 to 80 wt%; PTFE and FEP may be used in combination.

Pigments and solvents are not particularly limited, and those commonly used for paints can be used. It may also be used as a powder coating or a dispersion coating.

Examples of metal plates include cold rolled steel plates, Zn and Zn alloy plated steel plates, M and superalloy plated steel plates, Cr plated steel plates (T
Plated steel plates such as FS), Xi-plated steel plates, and Cu-plated steel plates, as well as aluminum plates, titanium plates, stainless steel plates, etc., are used, and after cleaning the surface by alkaline degreasing etc. as necessary, these are used directly or with a brushing roll. It is painted after surface polishing and chemical conversion treatment.

Chemical conversion treatments include chromate chemical conversion treatment, phosphate chemical treatment, and composite oxide film treatment.Chromate chemical conversion treatment includes electrolytic chromate, applied chromate, and reactive chromate treatment, and phosphate chemical treatment includes zinc phosphate. Treatments include iron phosphate treatment, and treatments containing nickel and cobalt can be applied to composite oxide film treatment.

Further, it is also possible to apply a primer as necessary for the purpose of improving corrosion resistance and adhesion.

The coating is applied by a method such as spraying, roll coating, flow coating, etc., and baking is performed under temperature conditions depending on the resin used to form a coating film.

Examples Examples 1 to 17 and Comparative Examples 1 to 10 Table 1 shows the performance confirmation results of samples coated with a bar coater according to the coating conditions of the Examples and Comparative Examples described for each of the five paint compositions.

Regarding the comparative examples (examples where the T/R value in the table is less than 0.8) in which the dry coating thickness is less than 0.6 times the average particle size of the fluororesin compared to the examples in any paint composition. It can be seen that the adhesiveness is poor, while the comparative examples (examples where the T/R value in the table is more than 2) where the T/R value exceeds 2 times have poor non-adhesiveness and lubricity.

That is, the coated metal plate obtained by the present invention has the advantage of being non-adhesive, having good lubricity, and having excellent coating film properties.

The test methods shown in Table 1 are as follows.

Cut 100 base lines on the surface of the sample using an adhesion 2NT cutter, extrude 7I using an Erichsen tester, and then tape the sample to evaluate the peeling situation. The evaluation method is as follows.

O: No flaking was observed at all, and 1 to 5 flakes occurred out of 67,100 base marks. X: 5 or more flakes occurred out of 100 base marks. Contact angle: 20 The contact angle of one drop of pure water is measured in an atmosphere of .degree. The a constant is measured five times for each sample, and the average value of the three data excluding the maximum and minimum values is used as the evaluation value.

The measurement was carried out using a dynamic friction coefficient bi-surface measuring device Model 14 (manufactured by Shinraikagakusha) using a stainless steel pole as a sliding contact object under a load of 50 g.

As described in detail, according to the present invention, adhesiveness, non-adhesiveness,
A coated metal plate with excellent lubricity could be obtained.

Furthermore, fluororesins inherently have good heat resistance, and when combined with a binder such as PES, which has good heat resistance, they are useful for heat-resistant applications.

Claims (2)

[Claims] (1) A coated metal plate in which a paint film is formed by coating a metal plate with a paint mainly composed of a mixture of fluorinated olefin resin powder and other resins and baking it. The dry coating thickness (T) and the average particle size or median particle size (R) of the fluorinated olefin resin powder are T/R=0.
A painted metal plate characterized in that it is within the range of 8 to 2. (2) The fluorinated olefin resin is one or more selected from the group consisting of tetrafluoroethylene resin (PTFE) and tetrafluoroethylene/hexafluoropropylene copolymer resin (FEP). , and other resins include polyether sulfone resin (PES), polyphenylene sulfide resin (PPS), and polyamideimide resin (PAI).
The coated metal plate according to claim 1, which is one or more selected from the group consisting of: