JPH08327512A - Resin film-peeling liquid for resin coated steel plate and resin film-peeling method - Google Patents

Abstract

PURPOSE: To obtain a required amount of a resin sample for analysis by subjecting a galvanized steel plate to an anode dissolving process in a peeling liquid made of an electrolyte containing a specified concentration of iodide ions, and a chelating agent containing a specified concentration of maleic anhydride, using methanol as a solvent, and then electrolying the solution at hydrogen generating potential. CONSTITUTION: The resin film-peeling liquid uses methanol as a solvent, and contains 0.02 to 5mol/l of iodide ions as an electrolyte, and 0.1 to 10wt.% of maleic anhydride as a chelating agent. Methanol is liable to infiltrate to an interface between a resin film and a plated layer, and a quick dissolution process can be provided. Also, maleic anhydride is well soluble in methanol and no colored even in the formation of chelate with a metal such as zinc, thereby allowing a peeling state to be easily observed. At the final electrolytic process, the resin film is cathode-polarized and treated at a hydrogen generating potential for a short time. As the result, bubbles are generated and keep the film afloat, thereby allowing the film to be peeled off without any damage thereto.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for collecting an organic resin film formed on a steel sheet, and more specifically, to analyze the components of the resin film of an organic resin-coated plated steel sheet, the resin film is melted and damaged. The present invention relates to a stripping solution and a stripping method for stripping from a base plated steel sheet without performing.

[0002]

2. Description of the Related Art Automotive steel sheets exhibiting high corrosion resistance are required in regions where rock salt is sprayed as a snow-melting agent to prevent road freezing in winter, and resin coated with chromate and resin coating is required for plated steel sheets. The coated steel sheet was developed,
It's being used. Currently, many resin-coated steel sheets are being researched and developed, but they are formed on steel sheets in order to satisfy various properties such as rust resistance, adhesion, and weldability, and to develop products that are cheaper and easier to handle. It is necessary to analyze and observe the molecular structure of the resin film to be applied, the amount of adhesion, the cross-sectional shape of the adhesion surface to the plating layer, or to measure physical properties such as elongation, hardness, strength and the like.

Infrared spectroscopy (IR) and photoelectron spectroscopy (E) are available as methods for analyzing the resin film without peeling it from the steel sheet.
SCA), etc., but there is a limit in obtaining a measurement value representative of the entire sample, since only local information of the surface layer and a part thereof can be obtained. To know more detailed molecular structure, nuclear magnetic resonance analysis and pyrolysis gas chromatography (pyrolysis G
It is necessary to apply an analysis method such as C), and for that purpose, it is necessary to peel off the resin film on the steel plate and use only the resin as an analysis sample.

In order to obtain only a resin film as an analysis sample from these steel plates, a method of shaving off the surface with a blade or the like has been conventionally used. However, recent resin films are thinned to ensure weldability, and it requires a great deal of labor and technology to obtain a sample of resin only, and it is difficult to obtain a sufficient amount of resin for analysis. there were. Further, in the case of a thin resin film, the metal layer is often scraped off and coexists with the resin sample, and analysis using such a sample may adversely affect the apparatus or subsequent analysis.

On the other hand, there is also a method of obtaining a resin film by completely dissolving the underlying metal using a chemical such as an acid, but since the dissolution of the metal is performed preferentially from the portion without the resin film, it takes a long time. However, a sufficient amount of sample cannot be obtained. Also,
Since the treatment takes time, it may be modified by chemicals such as acid depending on the type of resin.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and solves the problems of the prior art to obtain a sample for analysis of a resin film coated, pressure-bonded or adhered on a steel plate. Method, that is, a resin film stripping solution for a resin-coated steel sheet capable of easily obtaining a sufficient amount of a resin sample without mixing a metal layer and without causing a change in the composition and chemical structure of the resin film, and An object is to provide a resin film peeling method.

[0007]

The present invention is preferably applied to the preparation of a sample for analysis of a resin film coated, pressure-bonded or adhered on a plated steel plate, more preferably a resin thin film applied on a plated steel plate. It That is, the first invention of the present invention uses methanol as a solvent and 0.02 to 5 as an electrolyte.
A resin film stripping solution for a resin-coated steel sheet, which contains mol / l iodine ions and 0.1 to 10% by weight of maleic anhydride as a chelating agent.

The second aspect of the present invention is to use methanol as a solvent, 0.02 to 5 mol / l of iodine ion as an electrolyte, and 0.1 to 10 maleic anhydride as a chelating agent.
A resin film stripping method for a resin-coated steel sheet, which comprises subjecting a resin-coated plated steel sheet to anodic dissolution in a stripping solution containing wt% and further electrolyzing at a hydrogen generation potential.

The plating in the present invention is preferably applied to both electroplating and hot dipping. The plating components include Al, Zn, Cr, Fe,
One or more selected from the group consisting of Co, Ni, Sn, Mo and Cu are preferable, and zinc-based plating containing Zn, which is an electrochemically base metal, as a main component is preferable.

As the zinc-based plating, Zn plating, Zn-
Ni plating, Zn-Fe plating, Zn-Co plating, Z
n-Al plating, Zn-Mo plating, or Ni, F
1 selected from the group consisting of e, Co, Al, and Mo
An example is alloy plating of Zn with one kind or two or more kinds.
The Zn-Fe plating also includes Zn-Fe alloying hot-dip galvanizing.

[0011]

The present invention will be described in more detail below.
The organic composite-coated steel sheet is a cold-rolled steel sheet as an underlayer in which a zinc-based plating layer, a chromate layer, and a resin film layer are sequentially formed. However, the inventors have found that the plating layer under the resin film is zinc. It was thought that it was dissolved by electrolysis because it is the main component and has conductivity.

That is, it is considered that zinc is electrochemically base and can be dissolved quickly and in a short time by anodic dissolution, and the resin film on the upper portion of the plating layer can be peeled off. Furthermore, by electrolyzing the plated steel sheet by setting the potential between the dissolution potential of the plating layer and the dissolution potential of the base steel sheet, we believe that the plating layer alone can be selectively and rapidly dissolved without dissolving the base steel sheet at all. It was From the above viewpoints, the present inventors have conducted various studies on a stripping solution and a stripping method for selectively dissolving only the plating layer between the resin film and the base steel sheet, and uniformly separating only the resin film over the entire surface.

In this case, the stripping solution is neutral and has as little chemical action as possible, and since the dissolution proceeds from the peripheral portion of the sample in electrolysis, it is necessary to process a sample having a large area in order to obtain a large amount of sample. Therefore, it is desirable that the peeling liquid has a penetrating power to the interface between the resin film and the plating layer. Therefore, as a result of diligent study, methanol was used as a solvent and 0.02 as an electrolyte.
~ Maleic anhydride 0.1 ~ 5 mol / l iodine ion as a chelating agent to form a chelate with metal ions
It has been found that if electrolysis is performed with a stripping solution containing 10 wt%, the entire plating layer is rapidly dissolved and the resin film can be stripped.

Here, the reason why the solvent is methanol is that the stripping solution easily penetrates into the interface between the resin film and the plating layer, and as the dissolution of the plating layer metal progresses, the solvent is changed to the interface between the resin film and the plating layer. Permeation of the stripping solution allows rapid dissolution. When the stripping solution is a water-soluble electrolytic solution, electrolysis proceeds from the surroundings, but the electrolytic solution does not permeate into the interface, so that the resin film is unsuitable for peeling off the resin film in a large-area sample.

As the chelating agent, maleic anhydride is
It is preferable because it dissolves well in methanol, and even if it forms a chelate with a metal such as zinc, it is not colored and the peeling condition is easily observed. The concentration is preferably 0.1-10 wt%.
If it is less than 0.1 wt%, the rate of chelate formation with elution metal such as zinc will be slow, and the dissolution rate of the plating layer will be slow.
If it exceeds, there is no difference in the dissolution rate of the plating layer even if more is added, which is uneconomical.

In addition, although many electrolytes conventionally used for dissolving steel materials use chlorides such as lithium chloride and zinc chloride as electrolytes, zinc-based plating layers and chloride ions are used as electrolytes. It was found that when the electrolytic solution was dissolved by electrolysis, the zinc oxide containing chlorine was generated and adhered to the resin film to be analyzed, which was not preferable in the subsequent analysis operation and measurement data.

Therefore, it is preferable that the electrolyte does not form an insoluble precipitate with the dissolved metal such as zinc, and as a result of examination, iodine ions do not react with the metal such as zinc to form a precipitate, which is preferable. all right. Moreover, it is preferable to use potassium iodide or the like as an electrolyte for generating iodine ions, since it is not colored and the peeling state is easily observed. The concentration of iodine ions is preferably 0.02 to 5 mol / l.
This is because if it is less than 0.02 mol / l, the dissolution rate of the plating layer is slow and it cannot be practically used, and if it exceeds 5 mol / l, a precipitate is deposited and it cannot be used as a stripping solution.

Furthermore, in the final stage of electrolysis, the resin film is floated by the air bubbles generated by cathodic polarization and short-time treatment at the hydrogen generation potential, and the peeling is promoted so that the resin film can be peeled without damage. It has become possible.
As a result of the above, it was found that when the stripping solution and stripping method of the present invention were used, the resin film could not be dissolved at all, the plating layer could be dissolved, and the resin film could be stripped. Further, after the plating layer is dissolved by using the stripping solution and stripping method of the present invention, the stripped resin film is directly subjected to pyrolysis GC method, infrared spectroscopy, solid NM
By the R method or by dissolving a resin species that dissolves in a rich solvent such as chloroform, the detailed composition and chemical structure of the coating resin can be analyzed by a method such as the liquid NMR method. Further, according to the present invention, since it is easy to obtain a large amount of sample, it is possible to analyze a small amount of an additive or the like added to the resin. It is also possible to measure the coating amount of the coating resin by measuring the weight of the peeled resin film.

[0019]

EXAMPLES The present invention will be specifically described below based on examples. A peeling test of the coating resin on the organic composite-coated steel sheet was performed using each of the electrolytic solutions shown in Table 1.

[0020]

[Table 1]

Example 1 A coating material using an epoxy resin as a resin species was applied to the surface of a galvanized steel sheet.
The test piece (50 mm × 50 mm, resin film thickness 1 μm) of the obtained organic composite coated steel sheet was set on the table installed in the electrolytic cell, and the resin film near the center of the test piece was partially scraped off to expose the exposed metal surface. The anode was brought into contact with, the electrolytic solution was injected into the cell, and current was supplied while introducing nitrogen gas. Electrolysis starts from around the test piece in the water-soluble electrolytic solution, but the resin film does not peel off because the electrolytic solution does not penetrate into the interface between the resin film and the plating layer due to the progress of dissolution of the plating layer metal. It was inappropriate. In addition, in the case of the methanol-based electrolyte solution, which used acetylacetone as the chelating agent, the dissolution of the plating layer proceeded sequentially and the dissolution rate was sufficient, but at the same time iron chelate was generated and the solution was colored and the peeling condition was observed. Was impossible. The system using methyl salicylate had the same problem.

On the other hand, 5% maleic anhydride-1% potassium iodide-methanol solution (containing iodine ion: 0.060 mol /
When l) was used as the stripping solution, these problems did not occur and the resin film could be stripped uniformly. (Example 2) A test piece similar to the test piece used in Example 1 was set on a stand installed in an electrolytic cell, and a resin film near the central portion of the test piece was partially scraped off to expose an exposed metal surface. The anode was brought into contact with the cell, 5% maleic anhydride-1% potassium iodide-methanol solution was injected into the cell, and the electrolytic potential was kept at -1.3 V vs SCE while introducing nitrogen gas, and electricity was supplied. 20
After a minute, electrolysis was terminated, the potential was adjusted to generate hydrogen gas, and the resin film was peeled off. The sheet-shaped organic resin film that had been peeled off and floated in the electrolytic solution was scooped with tweezers or the like, further washed with methanol for cleaning prepared in another container, and dried to obtain a resin film for analysis. This resin film is pyrolyzed GC / M
The result of analysis by the S method is shown in FIG.

As a result of mass spectrum analysis, the peaks in FIG. 1 can be identified as phenol, isopropylphenol, isopropenylphenol, bisphenol A, and the peaks of bisphenol A can be identified as a decomposition component of bisphenol A type epoxy resin. The resin was identified in accordance with the typical pyrolysis GC pattern of (Example 3) On the surface of a zinc-nickel alloy plated steel sheet,
Test piece of organic composite coated steel sheet coated with paint using acrylic resin as resin type (50mm x 50mm, resin film thickness 1μ
m) was treated in the same manner as in Example 1 to obtain a resin film for analysis. The result of analysis of this resin film by the pyrolysis GC / MS method is shown in FIG.

As a result of mass spectrum analysis, the peak in FIG. 2 is methyl methacrylate, which shows a typical pyrolysis GC pattern of acrylic resin. In addition, the peak can be identified as octyl acrylate,
It was possible to analyze that it consisted of various kinds of acrylic. (Comparative Example) A sample obtained by scraping off a resin film from a test piece of an organic composite-coated steel sheet coated with the same resin as in Example 2 using a cutter knife as in the conventional case was analyzed by a pyrolysis GC / MS method, and the results are shown in FIG. As shown in FIG. 3, a spectrum sufficient for analysis is not obtained. It is considered that this is because the amount of the sample that can be introduced into the analyzer is limited, and the sample in which the plating layer metal is mixed is introduced, and as a result, the amount of the resin sample to be analyzed becomes insufficient.

[0025]

As described in detail above, according to the present invention,
An organic resin thin film formed on a steel plate, which has been difficult to achieve in the past, because it is possible to quickly obtain the required amount of resin sample for analysis without dissolving or damaging the resin film and changing the resin composition or chemical structure. It has become possible to easily analyze the composition, chemical structure, etc.

[Brief description of drawings]

FIG. 1 is a graph showing a total ion chromatogram obtained by thermal decomposition GC / MS analysis of a resin film obtained in the present invention.

FIG. 2 is a graph showing a total ion chromatogram obtained by thermal decomposition GC / MS analysis of the resin film obtained in the present invention.

FIG. 3 is a graph showing a total ion chromatogram obtained by thermal decomposition GC / MS analysis of a resin film obtained by a conventional method.

Claims (3)

[Claims] 1. Methanol as a solvent and an electrolyte of 0.1.
A resin film stripping solution for a resin-coated steel sheet, which contains 02 to 5 mol / l iodine ion and 0.1 to 10 wt% of maleic anhydride as a chelating agent. 2. Methanol as a solvent and an electrolyte of 0.1.
In a stripping solution containing 02 to 5 mol / l iodine ion and 0.1 to 10 wt% of maleic anhydride as a chelating agent, the resin-coated plated steel sheet is subjected to anodic dissolution and further electrolyzed at a hydrogen generation potential. A method for peeling a resin film from a resin-coated steel sheet, comprising: 3. The resin film peeling method for a resin-coated steel sheet according to claim 2, wherein the plating is zinc-based plating.