JPS6178641A - Steel plate for canning having adhesive property excellent to ultraviolet curing paint - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a nickel-plated steel sheet that has excellent coating adhesion to ultraviolet curing paints.

The gist of it! ``i'' The purpose is to control the composition of the chromate film applied to the plated steel sheet as a post-treatment, as well as the composition of the surface oil applied thereon, so as to provide optimum adhesion to the ultraviolet curing paint.

(Prior Art) In recent years, ultraviolet curing paints (hereinafter abbreviated as UV paints), which use ultraviolet rays for curing the paint, are being applied in various fields from the viewpoint of energy saving and low public costs. Especially the outer surface coating of the can (marked t)
White coat for ii11) and the like have a thin film thickness and have few problems such as corrosion resistance, so they are the most advanced in practical use. gv
As the paint, epoxy acrylate, polyester-modified epoxy, or the like having an unsaturated double bond in the molecule is used. The biggest drawback of the υv6 material is its poor adhesion to the substrate, which is due to large volumetric shrinkage during curing. In order to overcome this drawback, efforts have been made to improve the coating composition, such as increasing the molecular weight of the prepolymer and reducing the amount of reactive diluent mixed.

On the other hand, tin-plated steel sheets and nickel-plated steel sheets are used as materials to be coated. Nickel-plated 'i@ plates have recently been developed as a material for welded cans in place of tin-plated steel sheets, and are usually produced by cathodic electrolysis from a disoqueous sulfuric acid + nickel chloride bath. Both tin-plated steel sheets and nickel-plated steel sheets undergo chromate electrolytic post-treatment for corrosion resistance and paint adhesion.

On top of this, the front surface is applied. Cottonseed oil and dioctyl sebacate are used before the surface, and acetyltributyl citrate is also used for tin-plated steel sheets.

From the perspective of the material to be coated, it is known that the adhesion of UV paint is affected by the chromate film composition and oil film, and also changes by dry baking before UV painting. For example, in the case of tin-plated steel sheets, it has been shown that triptyl nitrate exhibits more stable UV paint adhesion than cottonseed oil or dioctyl sebacate, and the conditions for forming a chromate film (pH and temperature of the electrolyte solution) that provide good adhesion have been proposed. ing. (E, J
.

He1wtg and M, J, Black;
” Effect of Tin-plate 5ur
face properties on performance
mance of UV-Cured Inks and
Lacquers”; Proc, 2ndIn
ter, Txnplate Conf, p, 40
7 (1980) London).

However, the relationship between the detailed structure of the product's surface and UV paint adhesion is not clear. Furthermore, the chromate film formed on the nickel-plated steel sheet is different from that on the tin-plated steel sheet, and it was completely unclear what type of surface layer was superior to UV and ffaK. Furthermore, in the can manufacturing field, prior to the general KUV coating (external surface), the internal coating undergoes a coating baking process (infrared rays, hot air heating, aging), so the oil and chromate film react with each other due to the heating (prebaking, dry baking) at this time. This results in a surface composition that is different from that before dry firing, and this controls adhesion, resulting in a wide difference in adhesion depending on the dry firing conditions.

For example, it has been known that adhesion is severely deteriorated at the contact area with the stainless steel support (called a wicket) that supports the nickel-plated plate during preliminary dry firing (Ul/paint peeling occurs in the shape of the wicket). The cause was unknown. In other words, U is always stable regardless of the dry firing conditions.
In order to obtain V-paint adhesion, it is necessary to accurately understand the structure of the chromate film, including the composition of the oil, but no research has been conducted from this perspective. The reason for this is that the oil film and chromate film are each extremely thin, several tens of layers thick, and there is no way to accurately know their composition and structure. However, in recent years Auger electron spectroscopy (AFS) and
With the development of surface 7-fold instruments such as line photoelectron spectroscopy (ESCA), it has become possible to quantify the chemical composition of the surface in smaller orders, and it has been utilized in a variety of fields. This circle E
SCA has an fF characteristic for analysis of the surface layer containing crystalline objects, and can be applied to the analysis of the composition of the chromate film including the pre-surface layer.

(Problems to be Solved by the Invention) In order to solve the problem of insufficient dense layer of UV paint, the present inventors applied the above-mentioned FiSCA to clarify the influence of material surface on adhesion. Based on this, we have developed a steel plate for can making that has excellent adhesion to UV paint.

(Means for solving half-tone spots) The present invention provides that the adhesion of UV paint to a chromate-treated nickel-plated steel sheet depends on the degree of hydration of the chromate film and the degree of flatness of the oil applied to the surface. Because it is influenced by
U ■In order to improve the adhesion of the paint, the hydration degree N of the chromate film (represented by the general formula Cr2O3.NH2O) is 15 or more, and the concentration of polar groups (ester carbonyl groups) in front of the surface, nco is a nonpolar group (carbon hydrogen group) flu
ff, at least 8% or more with respect to nCH, and 0.24N + 2.6 (ΩCo/IIIcH)≧1 between the degree of hydration N and the polar group concentration ratio (neo/ncH)
The surface is designed to satisfy the following relationship.

(Function) First, the present inventors investigated a good material that causes poor adhesion of UV paint.

The steel plates for can manufacturing that are coated with UV paint are chromate-treated nickel-plated steel plates, or multi-layer plated steel plates with a nickel base and a thin tin plating on top. Used in a coated state. Therefore, after applying and curing TJV paint,
ES the peeled interface O coating side and metal side respectively.
Investigation by CA revealed that peeling occurs at the interface between the chromate film containing the oil film and the paint film, and that both the oil film and the chromate film composition can affect adhesion.

Next, we focused on the degree of hydration and coverage of the chromate film composition and the concentration of polar groups in the oil film. A large number of samples with different conditions and compositions were prepared and the relationship with adhesion was investigated. the result,
It has been found that adhesion is determined by the concentration of swimming groups in the oil and the degree of hydration of the chromate film, and that the higher the concentration of polar groups and the higher the degree of hydration, the better the adhesion. This relationship is shown in FIG.

In the present invention, the degree of hydration of the chromate film and the concentration of polar groups in the oil are determined based on the above-mentioned ESCA measurement data. The present invention quantitatively determines the surface composition of a material to be coated, and therefore, the method of quantifying it has an important meaning and will be described in detail below.

When the surface of a chromate-treated nickel-plated steel sheet is measured using gsCA, four elements, Cr, O, Ni, and C, are detected, but as shown in Figure 2, C is a hydrocarbon group (ICH) and an ester carbonyl group, depending on its peak shape. group (rco
), and Cr and N1 can be separated into trivalent hydrated chromium oxide (Cr2O3・NH
2O) and nickel oxide/l/ (Ni203). The reason why the oil film is made of a compound containing an ester bond is that dioctyl sebacate or cottonseed oil, which has an ester carbonyl group in the molecule, is generally used as the surface oil.

Now, the surface element concentration is determined as follows according to the usual quantitative analysis procedure. In other words, when the peak intensity (height or area is used) of the three elements is 11,■, the ratio of the atomic concentration (number of atoms per unit volume), n/n, is given by equation (1). Given.

Here, σ1 and σ3 are the ionization cross sections of l and 3 elements.

When the ionization cross section of C, σC, is 1.00, σ. =2
85 σ(r = 7.60 (JH4 = 1392 λ□, λ.

is the escape depth of the electron and is determined from λc-CEO%, '75 (EK is the kinetic energy of the electron). S is the detection efficiency (a between devices) that depends on the kinetic energy of electrons, and in this device (ESCAI manufactured by 'Jt3), S (= 1.3.
5Cr=185.50=18, SN, = 2.6. Using these protections, nwork/n can be obtained from equation (1). However, regarding C, hydrocarbon accumulation (28s,
OeV ) and an ester group (,5s6ev), the sum of h and D peak intensities (ICH+
Take Ico = Ic). no/n(=k
, ncr/nc = kt, nNx/nC=, then n(+ n."nCr" nN+:
Since l, we can find the atomic @ degree percent of all elements as . Also, a W (ncH) of hydrocarbon C and ester C
The concentration of (nco) is ncH” nCX (IC
H/IC), neo = nc x (ICO/
IC).

Now, once we know the atomic percent of each element (and component) that makes up the surface through the above procedure, we can calculate the degree of hydration (N) and coverage (α) of hydrated chromium oxide using the following method. can. That is, the surface structure is generally αCr2O3NH2O+ (1-α)N120. -(6
). In this molecular formula, the atomic concentration of oxygen (n,') is given by the value obtained from equation (4).
There are fewer ester bonds, so no ” no -2
It becomes nCO. Here no'/ nCr ”X, nN
When i/nCr=Y, N and α are as follows (7), (
8) can be obtained from Eq.

N = 2X-3Y-3-(7) α= −-(8) Y+1 According to the above calculation, the water-containing chromium layer on the nickel-plated steel sheet is characterized by the degree of hydration (N) and the coverage rate (α). I found out. - Manly characteristics can be evaluated by its polar group concentration ratio (nco/ncH). /
ICH) is defined by the degree of hydration (N) of the chromate film and its coverage (α). n and α
varies depending on the chromate treatment conditions and 9 firing conditions, and N=1
5 to 4.6, α=075 to 091. Although N and α generally decrease due to dry firing, there is an interaction with surface oil.

In addition, n(Q/n cH generally increases during dry baking (oil oxidation), but nco/ncH increases in areas with poor air circulation in the oven (corresponding to the contact area with the stainless steel wick mentioned above). does not change, and oil oxidation is less likely to occur.In addition, pretreatment such as flame heating
/ncHits increases, but does not change much with UV pre-irradiation or solvent cleaning. When we investigated the layer properties of UV coating N by changing the surface composition under the various conditions listed above, we found that
Adhesion is determined by the degree of hydration (N) and the polarity V (nco/neH).
), and the chromate coverage (α) is 075~
There was almost no relationship within the 091 range.

This result is shown in the relationship shown in Figure A1 mentioned above. In FIG. 1, the horizontal axis shows the polar group concentration of the oil, and the vertical axis shows the degree of hydration of the chromate film, where 0 indicates good adhesion and X indicates poor adhesion. When the degree of hydration is low, the adhesion becomes poor because of the all bond (-〇H) that increases the adhesion through hydrogen bonding.
...) decreases, and even if the polar group concentration of the oil is somewhat high, adhesion will be poor. This lower limit is approximately N=15. On the other hand, even if the degree of hydration is above this value, if the polar group concentration of the oil is low, good adhesion cannot be obtained. Taking into account that it changes depending on the dry firing conditions, the polar group concentration (nc
It is necessary to secure 8 or more as o/neHX 100). The broken line in the figure is 0.24N+260 (
nco/neH) = 1, but N≧15
, ncm/n (HX IOO ≧8%), the adhesiveness is still poor in the range below the broken line to the left.

Therefore, the surface composition to obtain good layer properties regardless of the firing conditions is N≧15 and nco/neH≧0.
08 and 0.24 N + 2.60 (nco/n
cH)≧1 or more.

That is, a chromate-treated nickel-plated steel sheet having a surface composition within the above range exhibits good UV coating density regardless of the presence or absence of dry firing and the presence or absence of wicket contact. Examples of the present invention will be described below.

(Actual example) Example 1 Cathodic electrolysis in a nickel sulfate + nickel monoxide mixed bath to achieve nickel deposition amount of 600η/rr? Chromic acid 60 ? /l was subjected to cathodic electrolysis at a current density of 2oA/ai in a treatment bath containing 400p4 of sulfuric acid, and the amount of Cr deposited was 8jI9/drr? A film mainly composed of hydrated chromium oxide was formed, washed with hot water at 90°C, and dried with hot air. Furthermore, acetyl tributyl citrate with a high ester carbonyl concentration was added as a surface oil at 4vy/rr? It was applied to. Then, as a pre-baking, the plated plate was placed upright on a stainless steel support and evacuated at 210° C. for 10 minutes. Surfaces in contact with supports (areas with poor air flow)
When measured by ESCA, the electrolytic radical concentration f(nC) of the oil film was measured using ESCA.
A surface having a composition of 20.2% (o/ΩCHx1oo) and a degree of hydration (N) of 36 was obtained. In addition, the values were 228% and 35, respectively, at locations that did not come into contact with the support. A UV prepolymer mainly composed of epoxy acrylate was applied to the surface of the plated plate at a dry weight of 1
80 m4t/dn? Roll-coated and then UV-treated
Irradiation (1 OKW, 1.3 seconds) was performed to form a coating film. The adhesion of the UV coating thus obtained was excellent at all locations, regardless of the contact with the support, and it did not peel off at all when peeled off with a scratched tape.

Example 2 A nickel-plated steel plate was obtained under the same conditions as shown in Example 1, and then 400 ppm of sulfuric acid was added to 60 y/l of chromic acid.
Cathode electrolysis was performed at a current density of 20 A/dm in a treatment bath of .Additionally, dioctyl sebacate was added as a surface oil.
my/rr? It was applied to. Then, for pre-baking, the plated plate was placed against a stainless steel support and heated at 210°C.
, baked 9 pieces in 10 minutes. Then, the part that came into contact with the shoring tool (the part with poor air circulation) was heat-treated with the flame of a gas burner.

After that, the surface of the contact area was measured using ESCA, and the concentration of polar groups in the oil film (n(0/ncHX 100 ) 22
．． A surface with a composition of 6% and a degree of hydration (N) of 26 was obtained. In addition, the surface of the part that did not come into contact with the support is 2
08%, 2B. A UV coating film was formed on the surface of the plated plate in the same manner as in Example 1. The film adhesion of this product was excellent at all locations, regardless of contact with the support. On the other hand, if gas burner treatment is not performed, the surface of the contact area with the support! 1 (nco/nc
H) X 100 = 75%, N = 2.1, and peeling of the UV coating occurred in this area.

[Brief explanation of the drawing]

Figure 1 shows the adhesion, degree of hydration (N) of chromium oxide, and surface oil group concentration ratio (ne
o/neH). In the figure, O[1,1 is 0.24 N + 2.6 On(0
/nCH=1. FIG. 2 shows the C, Cr, and N1 spectra of the surface of a chromate-treated nickel-plated steel sheet taken with an X-ray photoelectron spectrometer (ESCA). From the peak shift of C, the atomic concentration of the polar group concentration of the surface oil can be determined from the peak intensity of 285 electron volts indicating a hydrocarbon group and the peak intensity of 2886 electron volts corresponding to a carboxyl group. Figure 1 0 0.1 θ, 2
θ, 3nca/ncs Fig. 2 Cr2p%

Claims (1)

[Claims] A chromate-treated nickel-plated steel sheet, C
The degree of hydration N of the hydrated chromium oxide film represented by the general formula r_2O_3・NH_2O is 1.5 or more, and the atomic concentration (n_C_O) of polar groups (ester bonds) in the surface oil film and non-polar groups (hydrocarbons) The ratio to the concentration (n_C_H) of (
(n_C_O/n_C_H×100) is 8% or more and 0.24N+2.60(n_C_O/n_C_H)≧1
A steel plate for can manufacturing having excellent adhesion to ultraviolet curing paint, characterized by having a surface composition that satisfies the following.