KR20080087698A - Stain-resistant electrogalvanized steel sheet - Google Patents

Abstract

A high stain-resistant electrogalvanized steel sheet is provided to confirm that white rust resistance and stain resistance of the steel sheet are improved by increasing strength of a chromate free resin thin film through Na. A high stain-resistant electrogalvanized steel sheet has an electrogalvanized layer. A resin thin film containing 0.05 to 5% of Na without Cr is installed on the electrogalvanized layer. Pb and T1 of the electrogalvanized layer are restricted by less than Pb:5ppm and less than T1:10ppm. The electrogalvanized layer has at least one of a group having Ni, Fe, Cr, Mo, Sn, Cu, Cd, Ag, Si, Co, In, Ir, and W, in which Ni:60~6000ppm, Fe:60~600ppm, Cr:0.5~5ppm, Mo:30~500ppm, Sn:0.6~20ppm, Cu:8~3000ppm, Cd:0.0001~0.02ppm, Ag:1.0~400ppm, Si:30~2000ppm, Co:0.0003~0.3ppm, In:0.1~30ppm, Ir:0.01~10ppm, and W:0.1~50ppm are contained.

Description

Electroplated steel plate with excellent stain resistance {STAIN-RESISTANT ELECTROGALVANIZED STEEL SHEET}

The present invention relates to an electric Zn plated steel sheet excellent in stain resistance, and a method for producing the same, and in particular, an electric Zn plated steel sheet having a resin film substantially free of Cr, which is stained due to Na in the resin film. It relates to a technique for improving stain resistance that can effectively suppress (not noticeable) poor appearance of contamination. The electrical Zn-plated steel sheet of the present invention can be suitably used for applications mainly used indoors, such as chassis, case parts, steel furniture, etc., such as home appliances and OA appliances.

In view of the regulation of the use of harmful substances, an electric Zn plated steel sheet (non-chromate electric Zn plated steel sheet) having a chromate-free chemical conversion coating containing no hexavalent chromium has been widely used. Since such non-chromate electroplated Zn coated steel sheets are often used without coating at the request of omission of coating from the user, such as during storage of coils after manufacture, processing at home appliance manufacturers or OA equipment manufacturers, and during user use. In some cases, it may be exposed for a long time in an environment of high temperature and high humidity.

By the way, when the non-chromate electroplated Zn plated steel sheet is left for more than half a month or a long time (for example, about 504 hours (21 days)) under a high temperature and high humidity environment, appearance defects (differences in color tone) appear on the surface of the steel sheet in the form of spots (spots). Phenomenon of discoloration in shape) was found by the inventors' experiment.

Such a phenomenon (hereinafter sometimes referred to as "stain contamination") was not seen in the electroplated Zn plated steel sheet subjected to the chromate treatment. In addition, stain contamination is a white rust generated under the corrosive phenomenon reported so far, typically in a humid environment in which chlorine ions are present (typically 96 hours (4 days) after the salt spray test specified in JIS Z2371). In contrast to black stools that occur under relatively mild corrosive conditions seen before or after the development of white rust [typically after 72 hours (three days) at constant temperature and humidity of 95% relative humidity at 50 ° C]. It has been found that the non-chromate electroplated Zn plated steel sheet containing Na in the coating can be seen by exposing it to about half a month or more in an extremely high temperature and high humidity environment for a very long time.

However, the appearance defect improvement technique of the electroplated Zn-plated steel sheet proposed so far is a method of preventing blackening phenomenon before white blue or white blue occurrence (for example, Japanese Patent No. 304336, Japanese Patent No. 3499544, Japanese Patent No. 3499543, Japanese Patent) Japanese Patent Application Laid-Open No. 2004-263252, Japanese Patent Application Laid-Open No. 2000-355790, and Japanese Patent Application Laid-Open No. 2003-55790).

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is not only excellent in whiteness resistance but also excellent in stain stain resistance, and is suitable for producing a non-chromate electroplated Zn plated steel sheet and a method for manufacturing the same, and a non-chromate electroplated Zn plated steel sheet. It is to provide an electric Zn plating bath to be used.

The electrical Zn plated steel sheet of the present invention, which has solved the above problems, is substantially free of Cr on the electrical Zn plating layer, and is provided with a resin film containing 0.05 to 5% of Na (% means mass%, hereinafter, the same). As a Zn plated steel sheet, Pb and Tl in the said electroplated Zn plating layer are suppressed to Pb: 5 ppm (ppm means mass ppm. Or less, the same) or less, and Tl: 10 ppm or less in atomic conversion.

In a preferred embodiment, the electroplated Zn plating layer is at least one selected from the group consisting of Ni, Fe, Cr, Mo, Sn, Cu, Cd, Ag, Si, Co, In, Ir, and W in atomic terms Ni: 60-6000 ppm, Fe: 60-600 ppm, Cr: 0.5-5 ppm, Mo: 30-500 ppm, Sn: 0.6-20 ppm, Cu: 8-3000 ppm, Cd: 0.0001-0.02 ppm, Ag: 1.0-400 ppm, Si: 30-2000 ppm, Co: 0.0003-0.3 ppm, In: 0.1-30 ppm, Ir: 0.01-10 ppm, W: 0.1-50 ppm.

In a preferred embodiment, the resin film contains a carboxyl group-containing resin and an Si-based inorganic compound. Representative examples of the Si-based inorganic compound include colloidal silica, for example.

In a preferred embodiment, the resin film further contains a silane coupling agent.

The method for producing an electroplated Zn plated steel sheet according to the present invention, which can solve the above problems, (1) electroplated Zn plating using an acidic plating solution in which Pb and Tl in a plating solution are suppressed to Pb: 0.08 ppm or less and Tl: 0.2 ppm or less. The process of performing and (2) forming the resin film containing 0.05-5 mass% of Na are included.

In a preferred embodiment, the acidic plating solution is Ni: 20 to 2000ppm, Fe ^{2 +} : 50 to 5000ppm, Fe ^{3 +} : 50 to 5000ppm, Cr: 5 to 2000ppm, Mo: 50 to 2000ppm, Sn: 0.05 to 20ppm, Cu : 0.05 to 50 ppm, Cd: 0.05 to 5 ppm, Ag: 0.05 to 5 ppm, Si: 20 to 2000 ppm, Co: 0.05 to 50 ppm, In: 0.5 to 50 ppm, Ir: 0.05 to 5 ppm, and W: 0.5 to 50 ppm It contains at least one element selected from.

Moreover, in this invention, the electric Zn plating bath in which Pb and Tl in a plating liquid were controlled to Pb: 0.08 ppm or less and Tl: 0.2 ppm or less is also included in the scope of the present invention.

In a preferred embodiment, the electric Zn plating bath is Ni: 20 to 2000ppm, Fe ^{2 +} : 50 to 5000ppm, Fe ^{3 +} : 50 to 5000ppm, Cr: 5 to 2000ppm, Mo: 50 to 2000ppm, Sn: 0.05 to 20ppm , Cu: 0.05-50 ppm, Cd: 0.05-5 ppm, Ag: 0.05-5 ppm, Si: 20-2000 ppm, Co: 0.05-50 ppm, In: 0.5-50 ppm, Ir: 0.05-5 ppm, and W: 0.5-50 ppm It contains at least one element selected from the group consisting of.

Since the electrical Zn-coated steel sheet of this invention is comprised as mentioned above, the white-blue rust resistance and the stain-resistant dirt of a non-chromate-treated steel plate are improved significantly.

Implement the invention  Best form for

The "stain contamination" phenomenon (phenomena in which appearance defects (color difference) occurs due to spot shape) has not been recognized in conventional chromate-treated steel sheets and, according to the experiments of the present inventors, contains Na in the chromate-free resin film. It has been found that the Zn plated steel sheet is observed by exposing it for a long time (about 504 hours) under a high temperature and high humidity environment. Na is mainly added for the purpose of increasing the strength of the chromate-free resin film to improve abrasion resistance (scratch resistance) (details will be described later), and the non-chromate resin film containing Na is widely used in the field of non-chromate-treated steel sheets. It became.

Therefore, the inventors of the present invention particularly provide a technology capable of preventing (not noticeable) appearance defects of "stain contamination" caused by long-term storage of non-chromate electroplated Zn plated steel sheets in a high temperature and high humidity environment. Attention has been focused on the impurity elements inevitably present in Zn and impurity elements inevitably introduced into the Zn plating layer due to elution of an anode material or the like during electroplating Zn.

As a result, when the (A) Pb and Tl are suppressed to a predetermined level among the impurity elements included in the plating layer, the stain resistance is improved, and (B) Ni, Fe, Cr, Mo, Sn, Cu, Cd, If the content of at least one element selected from the group consisting of Ag, Si, Co, In, Ir, and W (hereinafter, collectively referred to as "staining stain resistance improving element") is controlled within a predetermined range, The stain contamination was found to be further improved, and the present invention was completed. In the above (A), Tl is an element that has not been noticed at all in the field of the non-chromate electroplated Zn plated steel sheet of the present invention, and the present invention includes various unavoidable impurities that may be included in the Zn plating raw material. After a careful examination exceeding the normal detection limit level, it was found for the first time that it was an element to be controlled (suppressed) in the improvement of stain resistance, similar to Pb.

As detailed below, Pb and Tl prescribed | regulated by said (A) are the elements which have a bad influence on the improvement of stain-resistant contamination (referred to as a stain element in relationship with stain-resistant contamination, and improves stain-resistant contamination of said (B) Element may be referred to as a stain resistant deterioration element). If neither of these elements is suppressed below a predetermined range, desired characteristics cannot be obtained. The fewer these elements are, the better and ultimately 0 ppm is most preferable. On the other hand, the element which contributes to further improvement of stain resistance by adding all the above-mentioned stain stain resistance improving elements of (B) which is an optional component in this invention (a useful element in the relationship of stain stain resistance) The addition effect is different from Pb and Tl of the above-mentioned (A).

Moreover, although it is not the technique of improving the stain stain resistance like this invention, each prior patent document mentioned above proposes the method of aiming at the improvement of white-blue blueness resistance by controlling content of the predetermined | prescribed element in an electric Zn plating layer. However, even if these patent documents are examined closely, there is no description regarding Tl. If Tl is not controlled to the level of the present invention, the desired stain resistance is not obtained. Moreover, although the said patent document has the example which controlled Pb in an electroplated Zn plating layer, it is inadequate only to suppress only Pb in the scope of the present invention, and desired staining is not desired if both Pb and Tl are not controlled within the scope of the present invention. Contamination is not obtained as described in Examples later.

Further, regarding the stain resistance improving element (selective component) specified in the present invention, for example, Japanese Patent No. 304336, Japanese Patent No. 3499544, Japanese Patent No. 3499543, and Japanese Patent Laid-Open No. 2004-263252 describe the present invention. Some of the elements in which part of the content is overlapped are disclosed as staining resistance improving elements used. Specifically, in order to prevent appearance defects such as white and blue, Japanese Patent No. 304336, Japanese Patent No. 3499544, and Japanese Patent No. 3499543 have elements that are more precious than Zn in the plating bath (Ni, In, Cu, Ag, Co). ) Is disclosed, and Japanese Patent Laid-Open No. 2004-263252 discloses elements (Fe, Co, Ni, Mn, Mg, Al, Ce, In that form poorly soluble hydroxides in an alkali region in which Zn is dissolved). And a method of adding an element (Si, Ti, V, Mo, Zr) which is stable in a neutral region and stably even in a corrosive environment, to a plating bath.

However, as described below, the appearance defects targeted by both are different, and it is inferred that the cause of occurrence thereof is different and the mechanism of occurrence (mechanism) is also different.

That is, the appearance defect of the "stain contamination" which is object of this invention arises only by exposing the non-chromate electroplated Zn plated steel sheet for extremely long time under high temperature, high humidity, and it is generated by white blue which arises in a salty atmosphere, or short time exposure in high temperature, high humidity. It is thought that the generation mechanism differs from the appearance defect of the black side. In addition, the "stain contamination" mentioned above is a phenomenon seen only when Na is contained in a non-chromate chemical conversion coating film, and it is thought that a generation mechanism differs from the appearance defect of white blue and black side. Even if these patent documents are examined closely, the use of a Na-containing non-chromate film is not described at all.

Moreover, as shown in the Example mentioned later, the kind and content of the stain-resistant contamination improvement element used for this invention may differ from the kind and content of the white-blue improvement element which the effect was confirmed by the above-mentioned patent document realistically, It was also found that it is difficult to apply the method described in the patent document to a stain resistance improvement technique as it is.

Although the mechanism by which stain contamination is produced by Na contained in the non-chromate film is unclear in detail, it is inferred as follows. When the Zn-plated steel sheet containing Na in the non-chromate film is placed in a humid atmosphere of a high temperature and high humidity environment, water condenses on the surface of the film first. Soluble Na in the coating is eluted from the dew condensation portion, and when Na-containing water is dried, Na agglomerated portion where Na is agglomerated and Na agglomerated portion where Na is not agglomerated are formed. In the Na agglomerated portion, since the corrosion reaction of zinc is promoted by Na ions, an amorphous oxide deviating from the stoichiometric composition of Zn _x O _1-x is formed on the surface of the Zn plating under the coating, and the plating surface is darkened. It becomes discolored. On the other hand, in the Na non-aggregated part, the above discoloration does not occur. In this way, the stain contamination phenomenon is thought to be due to the appearance of spots such as spots on the entire coating because only the Na-aggregated portion is discolored.

EMBODIMENT OF THE INVENTION Hereinafter, the electrical Zn plating steel plate of this invention is demonstrated in detail.

The electroplated Zn plated steel sheet of the present invention is an electroplated Zn plated steel sheet provided with a resin film containing 0.05 to 5% Na and substantially free of Cr on the electroplated Zn plated layer, wherein Pb and Tl contained in the electroplated Zn plated layer are atoms. In terms of conversion, Pb: 5 ppm or less and Tl: 10 ppm or less are suppressed. As shown in Examples described later, even if only one of Pb or Tl is suppressed in the above range, the desired characteristics are not exerted. Only when both Pb and Tl are suppressed in the above range, the desired characteristics are exhibited. The smaller the content of Pb and Tl, the better. The content of Pb and Tl is preferably 1.0 ppm or less and Tl: 1.0 ppm or less, more preferably Pb: 0.3 ppm or less and Tl: 0.5 ppm or less.

The electroplated Zn plating layer is at least one element selected from the group consisting of Ni, Fe, Cr, Mo, Sn, Cu, Cd, Ag, Si, Co, In, Ir, and W (staining stain resistance improving element) In terms of atoms, Fe: 60 to 600 ppm, Cr: 0.5 to 5 ppm, Mo: 30 to 500 ppm, Sn: 0.6 to 20 ppm, Cu: 8 to 3000 ppm, Cd: 0.0001 to 0.02 ppm, Ag: 1.0 to 400 ppm, Si It is preferable to contain in the range of: 30-2000 ppm, Co: 0.0003-0.3 ppm, In: 0.1-30 ppm, Ir: 0.01-10 ppm, W: 0.1-50 ppm.

Although the mechanism which can effectively prevent stain contamination by the addition of the stain resistance improving element is unclear, by providing an electric Zn plating layer containing a predetermined amount of the above element, the crystal form of Zn plating or the oxide of the surface (such as Zn Since it affects the hydroxide layer etc. of Zn containing said additional element which unavoidably produces on the plating surface, it is thought that it becomes possible to almost eliminate the difference of the color tone of a Na aggregate part and a Na non-aggregate part. As a result, appearance defects due to stain contamination can be eliminated.

All of the above elements have a stain resistance improvement effect, but in general, they are (1) more precious than Zn (Ni, Fe, Sn, Cd, Ir, In, Cu, Ag, Co) and (2) more precious than Zn Although not divided into the elements forming the oxide (Cr, Mo, Si, W). These elements may be used independently and may use 2 or more types together.

In order to effectively exhibit the stain resistance improvement effect by the said element, 60 ppm or more (preferably 600 ppm or more) of Ni and 60 ppm or more of content of each element contained in an electroplated Zn plating layer in atomic conversion, respectively. (Preferably 80 ppm or more), Cr 0.5 ppm or more (preferably 0.8 ppm or more), Mo 30 ppm or more (preferably 100 ppm or more), Sn 0.6 ppm or more (preferably 1.5 ppm or more), Cu 8.0 ppm or more (preferably 100 ppm or more), Cd 0.0001 ppm or more (preferably 0.01 ppm or more), Ag 1.0 ppm or more (preferably 30 ppm or more), Si 30 ppm or more (preferably 80 ppm or more), 0.0003 ppm or more of Co (preferably 0.001 ppm or more), 0.1 ppm or more of In (preferably 1.0 ppm or more), 0.01 ppm or more of Ir (preferably 0.1 ppm or more), and 0.1 ppm or more of W (preferably Is 1.0 ppm or more) (see Examples described later).

However, when added excessively, the following problems arise. First, when Fe and Si are added excessively, the stain | pollution resistance improvement effect will fall, and corrosion resistance (especially white-blue-blue resistance) will also fall. On the other hand, when an excessive amount of staining resistance improving elements other than Fe or Si is added, staining resistance is good, but whitening resistance is lowered. In order to satisfy both of the stain resistance and the white-rust resistance, and to obtain an excellent surface appearance, the content of each element included in the electroplated Zn plating layer is 6,000 ppm or less Ni, 600 ppm or less Fe, 5.0 ppm or less Cr, respectively. 500 ppm or less Mo, 20 ppm or less Sn, 3000 ppm or less Cu, 0.02 ppm or less Cd, 400 ppm or less Ag, 2000 ppm or less Si, 0.3 ppm or less Co, 30 ppm or less In, 10 ppm or less Ir, 50 ppm W It is set as follows.

Among the above-mentioned elements, Ni, Fe, Cr, Mo, Si, Cu, Co, W, In, Cu, Ag are particularly preferred as the element having excellent staining resistance improving action, and more preferably Ni, Fe, Mo, Cr, W.

The amount of stain resistance improving elements contained in the electroplated Zn plating layer can be analyzed using methods such as atomic absorption spectrometry, inductively coupled plasma emission spectroscopy (ICP), or inductively coupled plasma mass spectrometry (ICP-MS). The detailed analysis method is described in the column of the following Example. In the analysis, in order to eliminate measurement errors caused by matrix elements such as Zn, Na, and S contained in the plating solution, it is preferable to carry out after diluting the plating layer using hydrochloric acid or the like. What is necessary is just to control a dilution ratio to a suitable range suitably according to the density | concentration of a matrix element, the addition amount of the stain-resistant contamination improvement element which is a measurement object, etc. In the Example mentioned later, after diluting a plating layer with 2 times diluted hydrochloric acid, content of the element in a plating layer is analyzed.

In consideration of the crystal size of the Zn single crystal deposited on the surface of the plating layer, the deposition amount of the electroplated Zn plating is preferably about 40 g / m ² or less, and more preferably 30 g / m ² or less. In addition, the lower limit is, in view of the above is not particularly limited, in consideration of the victim way (防食) action of Zn, and preferably from about 3g / m ^2, more preferably from 10g / m ^2.

The electrical Zn plating layer should just be provided at least on the predetermined surface of the steel plate which is a base material, may be provided only in the single side | surface of a steel plate, and may be provided in both surfaces.

The resin film (nonchromate resin film) contains Na about 0.05 to 5% (preferably 0.1% or more and 3% or less, more preferably 1% or less). Na is usually added to the carboxyl group-containing resin or colloidal silica for the purpose of improving the strength of the non-chromate resin film (preferably containing Si-based inorganic compounds such as carboxyl group-containing resin and colloidal silica). It is. If the content of Na is less than 0.05%, for example, Na crosslinking is not sufficiently produced between the carboxyl group and Na in the carboxyl group-containing resin, and the strength of the film is lowered, while when the content of Na exceeds 5%, The amount of soluble Na increases, and wear resistance falls. The amount of Na contained in the resin film is represented by the total amount of Na in the solid content of each component (resin component, Si-based inorganic compound, silane coupling agent, etc. included as necessary) constituting the resin film.

The resin film does not substantially contain Cr. Here, "it does not contain substantially" means the Cr amount of the grade unavoidably mixed in the manufacturing process of a resin film can be tolerated. For example, in the present invention, a small amount of Cr may be added to the plating layer as a staining resistance improving element, but Cr in the plating layer may be mixed in the resin film. In addition, when a small amount of Cr compound is eluted from the production container, the coating device, or the like during the preparation and application of a treatment liquid that can be used for the non-chromate resin film, for example, Cr may be mixed in the resin film. . Even in such a case, the amount of Cr contained in the resin film is preferably in the range of approximately 0.01% or less.

It is preferable that the resin film contains the resin component of carboxyl group-containing resin, and Si type | system | group inorganic compound (typically colloidal silica). By using these as a resin film containing these, the corrosion resistance, alkali degreasing resistance, coating property, etc. of a film improve.

The carboxyl group-containing resin is not particularly limited as long as it has a carboxyl group, for example, a polymer synthesized by polymerization using a monomer having a carboxyl group such as unsaturated carboxylic acid as part or all of the raw material, or a resin modified by carboxylic acid using a functional group reaction. Can be mentioned.

A carboxyl group-containing resin may use a commercial item, for example, high-tech S3141 (made by Tohogagaku) etc. is mentioned.

The resin component may contain organic resins other than the carboxyl group-containing resin mentioned above.

Examples of the Si-based inorganic compound include silicate and / or silica. These may be used independently and may use 2 or more types together.

Among these, potassium silicate, lithium silicate, etc. are mentioned as a silicate, for example.

Typical examples of the silica include colloidal silica and flaky silica. In addition, dry silica such as pulverized silica, vapor phase silica, silica sol or fumed silica, and the like can also be used.

Among these, use of colloidal silica is especially preferable. As a result, in addition to being able to increase the strength of the resin film, silica is concentrated in the scratches of the film under a corrosive environment, and the corrosion of Zn is suppressed and the corrosion resistance is further improved.

The colloidal silica may use a commercial item, for example, Snowtex series "ST-40", "ST-XS", "ST-N", "ST-20L", "ST-UP" made by Nissan Chemical Industries, Ltd. "," ST-ZL "," ST-SS "," ST-O "," ST-AK ", etc. are mentioned. These usually contain Na.

It is preferable that the mass ratio of the resin component constituting the resin film and the Si-based inorganic compound (typically colloidal silica) is approximately within the range of resin component: Si-based inorganic compound = 5 parts to 45 parts: 55 parts to 95 parts. When there is little content of a resin component, corrosion resistance, alkali degreasing resistance, coating property, etc. tend to fall, while when there is much content of a resin component, wear resistance, electroconductivity, etc. will fall. Moreover, when there is little content of Si type inorganic compound, there exists a tendency for abrasion resistance, electroconductivity, etc. to fall, and when there is much content of Si type inorganic compound, since the resin component becomes small, the film-forming property of a resin film falls and corrosion resistance falls. Will be.

The resin film may further contain a silane coupling agent. By the addition of the silane coupling agent, the bond between the carboxyl group-containing resin and the Si-based inorganic compound described above is strengthened, so that elution of Na ions is reduced and staining resistance is further improved.

It is preferable that a silane coupling agent has lower alkoxy groups, such as a C1-C5 alkyl group, an allyl group, and an aryl group, for example. Specifically, for example, γ-glycidoxypropyl trimethoxysilane, γ-glycidoxypropylmethyl dimethoxysilane, γ-glycidoxypropyl triethoxysilane, γ-glycidoxymethyl dimeth Glycidoxy group-containing silane coupling agents such as oxysilane; γ-aminopropyl trimethoxysilane, γ-aminopropyl triethoxysilane, N- (β-aminoethyl) -γ-aminopropyl trimethoxysilane, N- (β-aminoethyl) -γ- Amino group-containing silane coupling agents such as aminopropylmethyl dimethoxysilane; Vinyl group-containing silane coupling agents such as vinyl trimethoxysilane, vinyl triethoxysilane, and vinyl tris (β-methoxyethoxy) silane; methacryloxy group containing silane coupling agents such as γ-methacryloxypropyl trimethoxysilane; mercapto group-containing silane coupling agents such as γ-mercaptopropyl trimethoxysilane and γ-mercaptopropylmethyl dimethoxysilane; Halogen group containing silane coupling agents, such as (gamma) -chloropropyl methoxysilane and (gamma) -chloropropyl trimethoxysilane, etc. are mentioned. These silane coupling agents may be used independently and may use 2 or more types together.

Among the above, the glycidoxy group-containing silane coupling agent is particularly preferably used because of its high reactivity and excellent corrosion resistance and alkali resistance.

A silane coupling agent can also use a commercial item, For example, (gamma)-glycidoxy propyl trimethoxysilane "KBM403" (made by Shin-Etsu Chemical Co., Ltd.) etc. are mentioned.

It is preferable that content of a silane coupling agent is the range of about 5 mass parts or more and 25 mass parts or less with respect to a total of 100 mass parts of a resin component and a Si type inorganic compound. When the content of the silane coupling agent is small, in addition to the effect of improving stain resistance, the reactivity of the carboxyl group-containing resin and the Si-based inorganic compound is lowered, and the wear resistance, paintability, corrosion resistance, and the like are lowered. do. On the other hand, when there is much content of a silane coupling agent, stability of the film preparation liquid used for preparation of a resin film falls, and there exists a possibility of gelatinizing. Moreover, since the quantity of the silane coupling agent which does not contribute to reaction increases, there exists a possibility that the adhesiveness of a Zn plating layer and a resin film may fall.

Hereinafter, the case where the following resin films are used as a typical non-chromate resin film used for this invention is demonstrated. Although the structure and preparation method of the said resin film are demonstrated easily below, the resin film used for this invention is not limited to this.

In addition, this resin film is a urethane resin improvement film disclosed by the applicant of this application, and the detail is as having been described in Unexamined-Japanese-Patent No. 2006-43913 (for example, see paragraphs [0020]-[0071)).

The resin film is obtained from the following resin aqueous solution. The resin aqueous solution is 5 to 45 parts by mass of the carboxyl group-containing polyurethane resin aqueous solution and the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion as nonvolatile resin components, and 55 to 95 parts by mass of silica particles having an average particle diameter of 4 to 20 nm. Furnace 100 parts by mass, containing a silane coupling agent in a ratio of 5 to 25 parts by mass based on 100 parts by mass in total, and the non-volatile resin component (PU) of the polyurethane resin aqueous solution and the The blending ratio of the nonvolatile resin component (EC) of the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion is PU: EC = 9: 1 to 2: 1 by mass ratio.

First, the carboxyl group-containing polyurethane resin aqueous liquid is demonstrated.

As the carboxyl group-containing polyurethane resin aqueous solution, both an aqueous dispersion in which the carboxyl group-containing polyurethane resin is dispersed in an aqueous medium or an aqueous solution in which the carboxyl group-containing polyurethane resin is dissolved in an aqueous medium can be used. In addition to water, a trace amount of hydrophilic solvents such as alcohol, N-methylpyrrolidone, acetone and the like may be contained in the aqueous medium.

It is preferable that the said carboxyl group-containing polyurethane resin is obtained by chain-reacting urethane prepolymer with a chain extender, and the said urethane prepolymer is obtained by making the polyisocyanate component and polyol component mentioned later react, for example.

As polyisocyanate component which comprises the said urethane prepolymer, tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and dicyclohexyl methane diisocyanate (hydrogen addition) Preference is given to using at least one polyisocyanate selected from the group consisting of MDI). Here, as the polyol component constituting the urethane prepolymer, all three kinds of polyols such as 1,4-cyclohexanedimethanol, polyether polyol, and polyol having a carboxyl group are used, and preferably all three kinds are die It's okay. The polyether polyol is not particularly limited as long as it has at least two or more hydroxyl groups in the molecular chain and the main skeleton is composed of alkylene oxide units. Examples thereof include polyoxyethylene glycol and polyoxypropylene glycol. Kohl, polyoxytetramethylene glycol, etc. are mentioned.

Moreover, it does not specifically limit as a chain extending agent which chain-reacts the urethane prepolymer mentioned above, For example, polyamine, low molecular weight polyol, alkanolamine, etc. are mentioned.

The preparation of the aqueous solution of the carboxyl group-containing polyurethane resin may employ a known method, and for example, a method of neutralizing the carboxyl group of the carboxyl group-containing urethane prepolymer with a base, emulsifying and dispersing it in an aqueous medium, and carrying out a chain extension reaction, containing a carboxyl group And a method in which the polyurethane resin is emulsified and dispersed by a high shear force in the presence of an emulsifier to perform a chain extension reaction.

Next, the aqueous dispersion of the ethylene-unsaturated carboxylic acid copolymer will be described.

The ethylene-unsaturated carboxylic acid copolymer aqueous dispersion is not particularly limited as long as the ethylene-unsaturated carboxylic acid copolymer is a liquid dispersed in an aqueous medium, and the ethylene-unsaturated carboxylic acid copolymer is a copolymer of ethylene and ethylenically unsaturated carboxylic acid. Examples of the unsaturated carboxylic acid include (meth) acrylic acid, crotonic acid, isocrotonic acid, maleic acid, fumaric acid, itaconic acid, and the like. A copolymer is obtained by polymerizing at least one of these and ethylene by a known high temperature and high pressure polymerization method. Can be.

Said ethylene-unsaturated carboxylic acid copolymer has a carboxyl group, and can be made into an aqueous dispersion liquid by neutralizing this carboxyl group with monovalent metal ions, such as an organic base (for example, amine of boiling point 100 degrees C or less), and Na.

Here, monovalent metal ions are used for neutralization as described above, but are effective for improving solvent resistance and film hardness. As the compound of the monovalent metal, one or two or more metals selected from sodium, potassium and lithium are preferably included, and hydroxides, carbonates or oxides of these metals are preferable. Especially, NaOH, KOH, LiOH, etc. are preferable, and NaOH is the most favorable and preferable. The present invention improves the stain contamination phenomenon derived from this NaOH.

The amount of the compound of the monovalent metal is preferably in the range of 0.02 to 0.4 mol (2 to 40 mol%) with respect to 1 mol of the carboxyl group in the ethylene-unsaturated carboxylic acid copolymer. When the amount of the metal compound is less than 0.02 mole, the emulsion stability becomes insufficient. However, when the amount of the metal compound exceeds 0.4 mole, the hygroscopicity (particularly with respect to the alkaline solution) of the resulting resin film increases, and the corrosion resistance after the degreasing step is not preferable. The lower limit of the amount of the metal compound is more preferably 0.03 mol, and more preferably 0.1 mol, and the upper limit of the amount of the metal compound is more preferably 0.5 mol, and more preferably 0.2 mol.

When the total amount (neutralization amount) of the above-mentioned organic base (preferably amine of boiling point 100 degrees C or less) and monovalent metal compound is too large, the viscosity of an aqueous dispersion may rise rapidly and solidify, and the excess alkali component Since it causes corrosion resistance deterioration, since enormous energy is required for volatilization, it is unpreferable. However, if the amount of neutralization is too small, the emulsion is inferior, which is also undesirable. Therefore, it is preferable to make the total usage-amount of an organic base and a monovalent metal compound into the range of 0.3-1.0 mol with respect to 1 mol of carboxyl groups in an ethylene- unsaturated carboxylic acid copolymer.

The aqueous dispersion of the ethylene-unsaturated carboxylic acid copolymer described above is dispersed in an aqueous medium in an extremely small fine particle (drop shape) having an average particle diameter of 5 to 50 nm by emulsifying a combination of an organic base and monovalent metal ions. Is obtained. For this reason, it is estimated that the film forming property of the resin film obtained, adhesiveness with respect to a metal plate, and densification of a film are achieved and corrosion resistance improves. The aqueous medium may contain hydrophilic solvents such as alcohol and ether, in addition to water. In addition, the particle diameter of the resin particle of the said aqueous dispersion liquid can be measured by the laser diffraction method using a light scattering photometer (made by Otsuka Electronics Co., Ltd., etc.), for example.

As a method for preparing the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion, the ethylene-unsaturated carboxylic acid copolymer is added together with an aqueous medium, for example, in a homogenizer device, and, if necessary, heated to 70 to 250 ° C., having a boiling point of 100 ° C. or less. An organic base such as an amine and a compound belonging to monovalent are suitably added in the form of an aqueous solution or the like (the amine having a boiling point of 100 ° C. or less is added first, or the compound of a amine having a boiling point of 100 ° C. or less and a monovalent metal is added at about the same time Agitate with high shear force.

Subsequently, the aqueous solution of the carboxyl group-containing polyurethane resin and the aqueous dispersion of the ethylene-unsaturated carboxylic acid copolymer obtained by the above-described method are blended with silica particles and a silane coupling agent in a predetermined amount, and a wax, a crosslinking agent, and the like are blended, if desired, to obtain a desired amount. Obtain an aqueous resin solution. Silica particles, silane coupling agents, waxes, crosslinking agents and the like can be added at any stage. However, after addition of the crosslinking agent and silane coupling agent, it is preferable not to apply heat so that the crosslinking reaction proceeds and does not gel.

In the above, the typical resin film used for this invention was demonstrated.

In the resin film, in addition to the above components, components usually included (for example, an antiskinning agent, a leveling agent, an antifoaming agent, a penetrating agent, an emulsifying agent, a film forming aid, a color pigment, a lubricant, Surfactants, conductive additives for imparting conductivity, thickeners, dispersants, desiccants, stabilizers, mold inhibitors, preservatives, cryoprotectants, and the like.

It is preferable that it is in the range of about 0.1-2 micrometers, and, as for the thickness of a resin film, it is more preferable to exist in the range which is 0.2-1.0 micrometer. If the thickness of the resin film is less than 0.1 mu m, the corrosion resistance decreases, while if it exceeds 2 mu m, the conductivity decreases.

On the resin film, a film such as an organic resin film, an organic / inorganic composite film, an inorganic film, or an electrodeposition coating film may be provided for the purpose of improving the corrosion resistance (particularly, white and blue resistance) and paintability.

Here, as the organic resin film, for example, urethane resin, epoxy resin, acrylic resin, polyethylene, polypropylene, olefin resin such as ethylene-acrylic acid copolymer, styrene resin such as polystyrene, polyester or copolymers thereof or modified The film etc. which are formed by combining colloidal silica, a solid lubricant, a crosslinking agent, etc. as needed to resin known for coating materials, such as water, are mentioned.

Moreover, as an organic-inorganic composite film, the film formed by combining the said organic resin and water glass formation components, such as sodium silicate, can be mentioned typically.

As said inorganic type film, the water glass film and the film formed from lithium silicate are mentioned typically.

Next, the manufacturing method of the non-chromate electroplated Zn plated steel sheet which concerns on this invention is demonstrated.

First, the base steel plate (plating disc) used as a base material is prepared. The base steel sheet is not particularly limited as long as it is commonly used for an electric Zn plated steel sheet, and various steel sheets such as ordinary steel sheets, Al-killed steel sheets, and high tensile steel sheets can be used. It is preferable to perform pretreatment, such as degreasing and pickling, before a plating master plate performs electroplating Zn.

Next, an electric Zn plated layer is formed on the base steel sheet by an electric Zn plating method to produce an electric Zn plated steel sheet.

In the acid bath used for electroplating Zn, Pb and Tl in an acid solution such as sulfuric acid or hydrochloric acid are suppressed to a range of Pb: 0.08 ppm or less and Tl: 0.2 ppm or less so that a desired plating layer is formed. As shown in Examples later, when the addition amount of Pb and Tl exceeds the above upper limit, the desired stain resistance is not exhibited. The smaller the addition amount of Pb and Tl, the better the amount of Pb: 0.05 ppm or less, and Tl: 0.1 ppm or less are preferably suppressed, and Pb: 0.03 ppm or less, and Tl: 0.05 ppm or less. More preferred.

Moreover, in order to suppress Pb and Tl in an electroplated Zn plating layer within the range prescribed | regulated by this invention, while controlling the addition amount of Pb and Tl in an acidic liquid as mentioned above, it is used for Zn and electroplating Zn used as a raw material. It is also preferable to pay attention to the anode material and the like. Specifically, it is preferable to control Pb and Tl in Zn as a raw material to about 15 ppm or less and about 10 ppm or less, respectively. Moreover, when Pb alloys, such as a Pb-In-Ag type alloy and a Pb-Sn type alloy, are used as a positive electrode material, since the amount of Pb in an electric Zn plating layer may increase by the elution of the said positive electrode material, substantially Pb is changed. It is preferable to use an anode material (for example, iridium oxide electrode) which does not contain.

Further, in the acid libido used in electrical Zn plating, an acidic solution such as sulfuric acid or hydrochloric acid, Ni: 20 to 2000ppm, Fe ^{2 +:} 50 to 5000ppm, Fe ^{3 +:} 50 to 5000ppm, Cr: 5 to 2000ppm, Mo : 50 to 2000 ppm, Sn: 0.05 to 20 ppm, Cu: 0.05 to 50 ppm, Cd: 0.05 to 5 ppm, Ag: 0.05 to 5 ppm, Si: 20 to 2000 ppm, Co: 0.05 to 50 ppm, In: 0.5 to 50 ppm, Ir: 0.05 At least 1 sort (s) of element chosen from the group which consists of -5 ppm and W: 0.5-50 ppm can also be added, and also the stain stain resistance improves further by this. If the added amount of each element is less than the above lower limit, the stain stain resistance will not be effectively exhibited. On the other hand, if the added amount of each element exceeds the upper limit, characteristics such as stain stain resistance and white-blue rust will be deteriorated.

The preferred addition amount of each element, respectively, Ni: 200ppm over 2000ppm or less, Fe ^{2 +:} 200ppm over 2000ppm or less, Fe ^{3 +:} 500ppm over 2000ppm or less, Cr: 50ppm or more 2000ppm or less, Mo: 200ppm or more 2000ppm or less, Sn: 0.5 ppm or more and 5 ppm or less, Cu: 2 ppm or more and 50 ppm or less, Cd: 0.5 ppm or more and 5 ppm or less, Ag: 0.5 ppm or more and 5 ppm or less, Si: 50 ppm or more and 800 ppm or less, Co: 0.5 ppm or more and 5 ppm or less, In: 2 ppm or more and 20 ppm or less , Ir: 0.5 ppm or more and 5 ppm or less, W: 2 ppm or more and 50 ppm or less.

The form of addition of the above-mentioned elements (Pb and Tl, and furthermore, stain resistance improving elements) in the plating bath is not particularly limited, and may be in any form as long as the addition amount of the atomic conversion of each element satisfies the above range. . For example, it may be added to the plating liquid in a metal state such as metal powder or metal foil, or may be added in the form of metal salts such as sulfates, chlorides, phosphates, carbonates, and oxide salts. When adding in the form of a metal salt, the valence number of an element is not specifically limited, The value which can be normally taken can be employ | adopted. For example, Cr may be trivalent or hexavalent. Mo, W, or the like may be either tetravalent or hexavalent. As shown in Examples later, the above elements may be added in the form of hydrates.

In the plating liquid, other components usually added may be added in addition to the above elements. For example, conductive aids such as Na ₂ SO ₄ , (NH ₄ ) ₂ SO ₄ , KCl, and NaCl may be added in order to increase the conductivity and reduce the power consumption.

Said electric Zn plating bath used for this invention is new, and is included in the scope of the present invention. That is, (A) an electric Zn plating bath suppressed to Pb: 0.08 ppm or less and Tl: 0.2 ppm or less, or (B) in (A), further suppressed to Pb: 0.08 ppm or less and Tl: 0.2 ppm or less. It is, and also Ni: 20 to 2000ppm, Fe ^{2 +:} 50 to 5000ppm, Fe ^{3 +:} 50 to 5000ppm, Cr: 5 to 2000ppm, Mo: 50 to 2000ppm, Sn: 0.05 to 20ppm, Cu: 0.05 to 50ppm, At least 1 selected from the group consisting of Cd: 0.05 to 5 ppm, Ag: 0.05 to 5 ppm, Si: 20 to 2000 ppm, Co: 0.05 to 50 ppm, In: 0.5 to 50 ppm, Ir: 0.05 to 5 ppm, and W: 0.5 to 50 ppm. An electric Zn plating bath containing an element of species is also included in the scope of the present invention.

In the electric Zn plating bath of the present invention, the addition amount of Pb and Tl is suppressed to the above-mentioned level in the electric Zn plating bath usually used for electric Zn plating or the like, or the amount of addition of the staining resistance improving element is controlled within the above range. There is a characteristic in that there is, and the component in other plating baths is not specifically limited. In the present invention, an acidic Zn plating bath such as an electric Zn plating bath commonly used, for example, a zinc sulfate bath (such as a zinc sulfate bath containing zinc sulfate and sulfuric acid, a zinc sulfate bath containing zinc sulfate and sodium sulfate and ammonium sulfate), and the like. In addition, the above-mentioned element can be added. The electric Zn plating bath of the present invention may contain, in addition to the above elements, additional components (such as the above-described conductive aids) usually added in the electric Zn plating bath.

Specifically, the following electric Zn plating bath can be used in addition to the electric Zn plating bath described in the Example mentioned later.

(Zinc sulfate bath… 1)

ZnSO ₄ 7H ₂ O 350 g / L

H₂SO₄ 30 g / L

(Zinc sulfate bath 2)

ZnSO ₄ 7H ₂ O 350 g / L

Na₂SO₄ 70 g / L

(NH₄)₂SO₄ 30 g / L

The production method of the present invention is characterized in that the electroplated Zn plating layer is formed by using a plating liquid in which Pb and Tl in the plating liquid are suppressed to a predetermined level, and a predetermined amount of the stain resistant improving element is further added. Although plating conditions are suitably determined in the range which does not impair the effect | action of this invention, It is preferable to control as follows, for example.

The pH of the plating liquid is preferably in the range of approximately 0.5 to 4.0, more preferably in the range of 1.0 to 2.0 in consideration of the relationship between the current efficiency and the plating probe phenomenon.

It is preferable to make the temperature of a plating liquid into the range of about 50-70 degreeC.

It is preferable that the relative flow velocity of a plating liquid exists in the range of about 0.3-5 m / sec. Here, a relative flow rate means the difference of the flow direction speed of a plating liquid, and the plate passage direction speed of the steel plate which is a plating original plate.

The type of electrode (anode) used for electroplating is not particularly limited as long as it is commonly used, and is oxidized in addition to lead-based electrodes such as Pb-Sn electrodes, Pb-In electrodes, Pb-Ag electrodes, and Pb-In-Ag electrodes. Iridium electrode, a zinc electrode, etc. are mentioned.

The plating cell can use either a vertical or horizontal cell. The method of electric Zn plating is not specifically limited, For example, a constant current plating method, a pulse plating method, etc. are mentioned.

After forming a plating layer as above-mentioned, a resin film (non chromate film) is formed as follows. Before formation of the resin film, the surface of the plating layer may be subjected to a known pretreatment using, for example, amines such as Co, Ni, Mo, V, phosphate, nitrate, etc., for the purpose of improving film adhesion, improving corrosion resistance, appearance control, and the like. .

Specifically, first, a predetermined amount of a resin component and a Si-based inorganic compound of the carboxyl group-containing resin is contained, and preferably a predetermined amount of a silane coupling agent (hereinafter, simply referred to as "process liquid"). To be called). The treatment solution is obtained by dissolving and dispersing the following components in an aqueous solvent (such as hydrochloric acid or nitric acid solution) that can dissolve completely.

It is preferable that the mass ratio of the resin component and Si-type inorganic compound contained in a process liquid exists in the range of substantially resin component: Si type | system | group inorganic compound = 5 parts-45 parts: 55 parts-95 parts. When the amount of resin components, such as carboxyl group-containing resin, is small, corrosion resistance, alkali degreasing resistance, coating property, etc. tend to fall, whereas when there are many amounts of resin components, wear resistance, electroconductivity, etc. will fall. In addition, when the amount of colloidal silica is small, there is a tendency for abrasion resistance, conductivity, etc. to fall, and when the amount of colloidal silica is large, since the resin component becomes small, the film forming property of a resin film falls and corrosion resistance falls. .

The treatment liquid may further contain a silane coupling agent. It is preferable that content of the silane coupling agent contained in a process liquid is about 5-25 mass parts with respect to a total of 100 mass parts of a resin component and a Si type inorganic compound as shown in the Example mentioned later. When the content of the silane coupling agent is small, in addition to the effect of improving stain resistance, the reactivity of the carboxyl group-containing resin and the Si-based inorganic compound is lowered, and the wear resistance, paintability, corrosion resistance, and the like are lowered. On the other hand, when there is much content of a silane coupling agent, stability of the film preparation liquid used for preparation of a resin film falls, and there exists a possibility of gelatinizing. Moreover, since the quantity of the silane coupling agent which does not contribute to reaction increases, there exists a possibility that the adhesiveness of a Zn plating layer and a resin film may fall.

A wax, a crosslinking agent, etc. can also be added to a process liquid as needed in addition to the said component. In addition, within the range which does not impair the effect | action of this invention, the process liquid provides the component (for example, anti-film formation agent, leveling agent, antifoamer, penetrant, emulsifier, film forming adjuvant, coloring pigment, lubricant, surfactant, electroconductivity, etc.) normally contained. Conductive additives, thickeners, dispersants, desiccants, stabilizers, mold inhibitors, preservatives, cryoprotectants, and the like).

The treatment liquid containing the above-mentioned components may be a single side of the metal plate using a known method such as a roll coating method, spray coating method, curtain flow coater method, knife coater method, bar coating method, dip coating method, brushing method or the like. After apply | coating to both surfaces, when heated and dried, the electrical Zn plating steel plate provided with the desired resin film is obtained.

It is preferable to perform heating and drying temperature at the temperature (for example, plate | board temperature of 90-100 degreeC) in which the crosslinking reaction of carboxyl group-containing resin and Si type | system | group inorganic compound to be used fully advances. In the case of using a spherical polyethylene wax as a lubricant, it is preferable to keep the spherical shape so that the workability in the subsequent processing step is better, so that drying is performed in the range of about 70 to 130 ° C.

Example

Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not restrict | limited by the following example, It is also possible to change suitably and to implement in the range which may be suitable for the purpose of the previous and the latter, Such aspects are also included in the technical scope of the present invention.

Example  One

In this example, the effects of Pb and Tl contained in the plating layer on stain stain resistance, and also on white-blue rust resistance were examined. Here, the resin film is produced similarly to the method of Example 1 of Unexamined-Japanese-Patent No. 2004-224454.

(1) Preparation of aqueous resin solution

Here, the resin film was produced from the aqueous resin solution containing a carboxyl group-containing polyurethane resin aqueous solution, the ethylene-unsaturated carboxylic acid copolymer aqueous dispersion liquid, a silica particle, and a silane coupling agent. The specific manufacturing method is as follows.

(1-1) Preparation of carboxyl group-containing polyurethane resin aqueous solution

60 g of polytetramethylene ether glycol (average molecular weight 1000) made by Hodogaya Chemical Co., Ltd. as a polyol component in a synthesis apparatus having a content of 0.8 L equipped with a stirrer, a thermometer and a temperature controller, 1,4-cyclohexanedimethanol 14 g and 20 g of dimethyrol propionic acid were added, and 30.0 g of N-methylpyrrolidone was added as a reaction solvent. 104g of tolylene diisocyanate (hereinafter may be simply referred to as "TDI") was added as an isocyanate component, it heated up from 80 degreeC to 85 degreeC, and made it react for 5 hours. NCO content of the obtained prepolymer was 8.9%. Furthermore, 16 g of triethylamine was added to neutralize, a mixed aqueous solution of 16 g of ethylenediamine and 480 g of water was added thereto, and the mixture was emulsified at 50 ° C for 4 hours, followed by chain extension reaction to obtain an aqueous polyurethane resin dispersion (non-volatile resin component 29.1%). , Acid value 41.4).

(1-2) Preparation of Ethylene-Unsaturated Carboxylic Acid Copolymer Aqueous Dispersion

626 parts by mass of water and 160 parts by mass of an ethylene-acrylic acid copolymer (20% by mass of acrylic acid, melt index (MI)) were added to an autoclave of an emulsification facility having a stirrer, a thermometer, and a temperature controller of 0.8L in amount. 40 mol% of triethylamine and 15 mol% of sodium hydroxide were added to 1 mol of the carboxyl group of the acrylic acid copolymer, and the mixture was subjected to high speed stirring under an atmosphere of 150 ° C and 5 Pa, and cooled to 40 ° C to obtain an ethylene-acrylic acid copolymer. An aqueous dispersion was obtained. Subsequently, 4,4'-bis (ethyleneiminocarbonylamino) diphenylmethane (made by Nihon Shokubai, Chemitite DZ-22E, "Chemite" is registered trademark) as an crosslinking agent in the aqueous dispersion, ethylene It added so that it might become a ratio of 5 mass parts with respect to 100 mass parts of nonvolatile resin components of an acrylic acid copolymer.

(1-3) Preparation of aqueous resin solution

5 mass parts of the carboxyl group-containing polyurethane resin aqueous liquid obtained above, the said ethylene-acrylic-acid copolymer aqueous dispersion liquid, and colloidal silica ("ST-XS" by Nissan Chemical Co., Ltd., average particle diameter 4-6 nm): 25 parts by mass: 100 parts by mass in total in terms of nonvolatile components are added so as to have a blending ratio of 70 parts by mass, and with respect to 100 parts by mass in total, γ-glycidoxypropyl trimethoxysilane ( 10 mass parts of "KBM403" made by Shin-Etsu Chemical Co., Ltd. was added, and the aqueous resin solution was prepared.

(2) Fabrication of Electro Zn Plated Steel Sheet

As the plating original plate, an Al-killed cold rolled steel sheet produced by a conventional method was used. After degreasing and pickling this, electroplating was performed on the following conditions using the sulfate bath in the circulation type plating apparatus of plating area 180mmx300mm, and the electrical Zn plating steel plate was obtained.

(Plating amount furtherance)

The plating liquid which contained the following components and added the element (Pb / Tl) of Table 1 in the range shown in Table 1 in the form of sulfate in each case was used. Moreover, the plating liquid which did not add these elements at all was also prepared.

ZnSO ₄ 7H ₂ O 350 g / L

Na₂SO₄ 70 g / L

H ₂ S0 ₄ 20g / L

Other electroplating conditions are as follows.

Current density: 100A / dm ²

Plating bath temperature: 60 ± 5 ℃

Plating flow rate: 1.3m / sec

Electrode (anode): IrOx electrode

Plating weight: 20g / m ²

(3) Fabrication of electric Zn plated steel sheet with resin coating

The aqueous resin solution obtained in the above (1) was applied (single sided coating) on the Zn plating layer obtained in the above (2) by a roll coating method, and heated and dried at a furnace temperature of 220 ° C. and a plate temperature of 95 ° C. in a test furnace. An electric Zn-plated steel sheet was obtained, which had a resin film (nonchromate film) having a thickness of 0.4 µm.

The resin film thus obtained contains a resin component, a colloidal silica, and a silane coupling agent in a mass ratio of approximately resin component: colloidal silica: silane coupling agent = 30 parts: 70 parts: 10 parts.

Moreover, Na contained in the said resin film was 1.2 mass% when it confirmed by the atomic absorption spectrophotometry (device: SOLARA-M6 by Nippon Jarrell-Ash Co. Ltd.). Specifically, Na content contained in the resin component which comprises a resin film was 0.55 mass%, and Na content contained in colloidal silica was 1.7 mass%.

(4) Analysis of the stain resistance improving element in the plating layer

The amount of stain resistance improving elements contained in the plating layer thus obtained was analyzed by the following method.

First, an analytical sample obtained by cutting the electroplated Zn plated steel sheet obtained as described above into a size of 50 × 50 mm was prepared. The sample was placed in a two-fold diluted hydrochloric acid solution and immersed until the dissolution reaction of Zn was completed. The solution (1) was obtained. In the present embodiment, in order to eliminate the measurement error caused by substitution and deposition of the stain resistant staining-improving element once dissolved on the surface of the steel sheet serving as the base material, the sample is immediately taken up after completion of the Zn dissolution reaction, and the newly prepared hydrochloric acid solution ( Immersion liquid (2) was obtained by immersion for 30 seconds). Thereafter, the immersion liquids (1) and (2) obtained as described above were combined to a constant volume, and then, using an ICP-MS analyzer (PLASMAQUAD type manufactured by VGI), Pb and Tl, and stain resistance were improved. The amount of elements (excluding Cu) was analyzed. About Cu, it analyzed using the ICP analyzer (ICPV-1000 by Shimadzu Corporation). In addition, the detection limits of Pb and Tl in this example were Pb: 0.1 ppm and Tl: 0.1 ppm.

(5) Evaluation of stain resistance

Each of the electroplated Zn plated steel sheets obtained as described above was placed in a constant temperature and humidity test apparatus having a temperature of 50 ° C. and a relative humidity of 95% or more, and stored for 504 hours. Then, the appearance of the surface was visually observed, and the “ Stain stain resistance was evaluated based on the photographic specimen for stain contamination evaluation determination ”(5 cm × 5 cm). 1A to 1E correspond to the following evaluation criteria 1 to 5, respectively. In the present Example, it was determined that the evaluation criteria were "1" to "3", and that the "4" or "5" was rejected.

(Evaluation standard)

1: no stain contamination (FIG. 1A)

2: when some stain contamination occurs (FIG. 1B)

3: When stain contamination occurs (Fig. 1C)

4: When stain contamination occurs remarkably (FIG. 1D)

5: When stain contamination occurs violently (FIG. 1E)

Here, in contrast to FIG. 1B (evaluation 2) and FIG. 1C (evaluation 3), it can be seen that spots such as spots are clearly generated in FIG. 1C as compared with FIG. 1B. In contrast to FIG. 1C (Evaluation 3) and FIG. 1D (Evaluation 4), in FIG. 1D, the color tone is black as a whole as compared to FIG. 1C, which indicates that the degree of blackening of the Na-aggregated portion (darkened discolored region) It seems to be because it progressed, and as a result, the difference of the stain contamination of both becomes inconspicuous. In contrast to Fig. 1D (Evaluation 4) and Fig. 1E (Evaluation 5), the color tone is darker in Fig. 1E than in Fig. 1D, because the degree of blackening of the Na-aggregated portion is excessively advanced. I think. The degree of blackening is described in the method of expressing / representing numerically by dividing the color into three elements using, for example, the L value (the three-dimensional coordinate axis of the L axis, the a axis, and the b axis) by the Hunter Lab colorimetric method. Value). Thus, in this Example, stain stain resistance was comprehensively evaluated including the degree of blackening.

(6) evaluation of anti-whiteness

The salt spray test prescribed | regulated to JISZ2371 was performed about each electroplated Zn plated steel plate obtained as mentioned above, and the white blue-blue generation area ratio after 96 hours passed was determined based on the following reference | standard, and white-blue blueness resistance was evaluated. In this example, it was determined that the evaluation criteria was "◎" or "○" as the pass (example of the present invention).

◎: less than 5%

○: less than 10% 5%

△: 10% or more but less than 50%

×: 50% or more

These results are written together in Table 1. "1" in Table 1 means that it was below a detection limit (measurement limit).

From Table 1, the following can be considered.

No. 1 is an example using the plating liquid which neither Pb nor Tl was added, and both Pb and Tl in a plating layer were suppressed below the detection limit of a present Example; No. 2 to 4 are examples in which Pb in the plating solution and the plating layer is suppressed within the scope of the present invention, and Tl in the plating layer is suppressed below the detection limit of this embodiment; No. 12 to 15 are examples in which Tl in the plating liquid and in the plating layer is suppressed within the scope of the present invention, and Pb in the plating layer is suppressed below the detection limit of the present embodiment; No. 22 to 24 are examples in which both Pb and Tl in the plating solution and in the plating layer were suppressed within the scope of the present invention, and both of them improved both stain stain resistance and white-blue resistance.

In contrast, No. 5 to 11 are examples in which Tl in the plating layer is suppressed below the detection limit of the present embodiment, and the content of Pb in the plating liquid and the plating layer is high; No. 16-21 is Pb in a plating layer being suppressed below the detection limit of a present Example, but there are many examples of content of Tl in a plating liquid and a plating layer; No. 25 to 30 are examples in which both the contents of Pb and Tl in the plating solution and the plating layer are both large, and in addition to the fact that all have reduced staining stain resistance, there have been examples of lowering white-blue rust resistance.

Example  2

In this Example, the influence on the stain stain resistance and the white rust resistance by addition of the stain stain resistance improving element was examined.

Specifically, in Example 1, a resin film (non-chromate film) was prepared in the same manner as in Example 1, except that the plating solution further added the additives (staining stain resistance improving elements) shown in Tables 2 to 9 were used. An electroplated Zn plated steel sheet was produced, and the stain resistance and the white-blue resistance were evaluated in the same manner as in Example 1. As shown in these tables, among the staining resistance improving elements, all of Ni, Fe, Cr, Sn, Cu, Cd, Co, and W are sulfates, Mo is sodium molybdate, Si is colloidal silica, and Ag is As silver nitrate, In was added as a hydroxide, Ir as bromide, respectively.

These results are written together in Tables 2-9. For reference, No. The result of 1 is also written together in Tables 2-9.

 First, it considers about Tables 2-5. In these tables, Tl is suppressed to below the detection limit of the present embodiment, and summarizes the effect of adding a stain-resistant dirt-improvement element when various amounts of Pb in the plating liquid and the plating layer are varied. Here, all the stain resistance improvement elements are changed within the preferable range of this invention.

Among these, No. 31-33 (Ni containing example), No. 37 to 39 (Fe ^{+ 2} containing for example), No. 43 to 45 (Fe ^{+ 3} contains for example), No. 49 to 51 (Cr-containing example), No. 55 to 57 (Na containing example), No. 61 to 63 (Si containing example), No. 67 to 69 (Sn-containing example), No. 73 to 75 (Cu-containing example), No. 79 to 81 (Co containing example), No. 85 to 87 (W-containing example), No. 91 to 93 (In containing example), No. 97 to 99 (Cd-containing example), No. 103 to 105 (Ag-containing example), No. Examples 109 to 111 (Ir-containing examples) are examples in which the above-mentioned stain stain resistance improving element is added within a preferred range of the present invention in a plating solution in which both Pb and Tl satisfy the requirements of the present invention. Compared with the case of Example 1 without addition, stain resistance was further improved.

In contrast, No. 34-36 (Ni containing example), No. 40 to 42 (Fe ^{+ 2} containing for example), No. 46 to 48 (Fe ^{+ 3} contains for example), No. 52 to 54 (Cr-containing example), No. 58 to 60 (Mo ^{6 +} containing example), No. 64 to 66 (Si containing example), No. 70 to 72 (Sn-containing example), No. 76 to 78 (Cu-containing example), No. 82 to 84 (Co containing example), No. 88 to 90 (W-containing example), No. 94 to 96 (In containing example), No. 100 to 102 (Cd-containing example), No. 106 to 108 (Ag-containing example), No. Examples 112 to 114 (Ir-containing examples) are examples in which the above-mentioned stain-resistant staining-improving element is added within the preferred range of the present invention in a plating solution in which the amount of Pb does not satisfy the scope of the present invention. The tendency for the degree of contamination was reduced.

Next, Tables 6 to 9 will be considered. In these tables, Pb is suppressed below the detection limit of the present embodiment, and summarizes the effect of adding the stain resistance improving element when the amount of Tl in the plating liquid and the plating layer is changed in various ways. Here, all the stain resistance improvement elements are changed within the preferable range of this invention.

Among these, No. 115 to 117 (Ni containing example), No. 123 to 125 (for example, Fe ^{2 +} containing), No. 131 to 133 (Fe ^{3 +} containing example), No. 139 to 141 (Cr-containing example), No. 147 to 149 (Mo containing example), No. 155 to 157 (Si containing example), No. 163 to 165 (Sn-containing example), No. 171-173 (Cu containing example), No. 179 to 181 (Co containing example), No. 187-189 (W containing example), No. 195-197 (In containing example), No. 203 to 205 (Cd-containing example), No. 211-213 (Ag containing example), No. Examples 219 to 221 (Ir-containing examples) are examples in which the above-mentioned stain stain resistance improving element is added within a preferred range of the present invention in a plating solution in which both Pb and Tl satisfy the scope of the present invention, and stain stain resistance Compared with the case of Example 1 in which the improvement element was not added, the stain resistance was further improved.

In contrast, No. 118-122 (Ni containing example), No. 126 to 130 (for example, Fe ^{2 +} containing), No. 134 to 138 (Fe ^{3 +} containing for example), No. 142-146 (Cr containing example), No. 150 to 154 (Mo containing example), No. 158-162 (Example containing Si), No. 166 to 170 (Sn-containing example), No. 174 to 178 (Cu-containing example), No. 182 to 186 (Co containing example), No. 190-194 (W containing example), No. 198-202 (In containing example), No. 206 to 210 (Cd-containing example), No. 214-218 (Ag containing example), No. Examples 222 to 226 (Ir-containing examples) are examples in which the above-mentioned stain-resistant staining-improving element is added within the preferred range of the present invention in a plating solution in which the amount of Tl does not satisfy the scope of the present invention. The tendency for the degree of contamination was reduced.

Example  3

In the present Example, the stain | pollution resistance improvement effect by addition of a silane coupling agent was examined. Here, as shown below, the non-chromate electroplated Zn plated steel sheet which has four types of resin films from which the compounding ratio of a resin component and colloidal silica differs is produced, and the silane coupling agent with respect to each non-chromate electroplated Zn plated steel sheet Investigated the impact of.

(No. 227 to 230)

In Example 1 mentioned above, the carboxyl group-containing polyurethane resin aqueous solution, the ethylene-acrylic-acid copolymer aqueous dispersion liquid, and colloidal silica in "preparation of the (1-3) resin aqueous solution" (5 mass parts: The silane coupling agent was added within the range of 0 mass part, 10 mass parts, 20 mass parts, and 30 mass parts with respect to a total of 100 mass parts of 25 mass parts: 70 mass parts) as shown in Table 10 further. A resin film was produced in the same manner as in Example 1 except for the above.

In addition, except for using the plating liquid which contains all the elements of Table 7 in "(2) Preparation of an electrical Zn-plated steel plate" of Example 1 mentioned above, an electrical Zn-plated steel sheet was carried out similarly to Example 1 Made. Each element of Table 11 is added in the form described in Example 1 mentioned above.

Subsequently, a non-chromate electroplated Zn plated steel sheet was produced in the same manner as in Example 1, and the stain staining resistance and the whitening resistance were evaluated.

(No. 231 to 234)

In Example 1 described above, sodium hydroxide was not added in "Preparation of (1-2) ethylene-unsaturated carboxylic acid copolymer aqueous dispersion", and Colo in "Preparation of aqueous resin solution (1-3)". As this month, the compounding ratio of Nissan Chemical Co., Ltd. product "ST-AK" is used, and the carboxyl group-containing polyurethane resin aqueous liquid, ethylene-acrylic acid copolymer aqueous dispersion liquid (without Na content), and colloidal silica are used. 5 parts by mass: 30 parts by mass: 65 parts by mass, and a range of 0 parts by mass, 10 parts by mass, 20 parts by mass, and 30 parts by mass of the silane coupling agent as shown in Table 6 with respect to 100 parts by mass in total. Except having added further in the inside, it carried out similarly to Example 1, and produced the resin film.

In addition, except for using the plating liquid which contains all the elements of Table 7 in "(2) Preparation of an electrical Zn-plated steel plate" of Example 1 mentioned above, an electrical Zn-plated steel sheet was carried out similarly to Example 1 Made. Each element of Table 11 is added in the form described in Example 1 mentioned above.

Subsequently, a non-chromate electroplated Zn plated steel sheet was produced in the same manner as in Example 1, and the stain staining resistance and the whitening resistance were evaluated.

(No. 235 to 238)

In Example 1 mentioned above, 5.1 mass% of NaOH was added for the purpose of strength improvement in Nissan Chemical Co., Ltd. "ST-XS" as colloidal silica in "preparation of (1-3) resin aqueous solution." One compound was used, and the compounding ratio of the carboxyl group-containing polyurethane resin aqueous liquid, the ethylene-acrylic acid copolymer aqueous dispersion liquid, and colloidal silica was set to 6 parts by mass: 34 parts by mass: 60 parts by mass, and 100 parts by mass of these in total. Resin coating was produced like Example 1 except having added the silane coupling agent further in the range of 0 mass part, 10 mass parts, 20 mass parts, and 30 mass parts, as shown in Table 6. .

In addition, except for using the plating liquid which contains all the elements of Table 7 in "(2) Preparation of an electrical Zn-plated steel plate" of Example 1 mentioned above, an electrical Zn-plated steel sheet was carried out similarly to Example 1 Made. Each element of Table 11 is added in the form described in Example 1 mentioned above.

Subsequently, a non-chromate electroplated Zn plated steel sheet was produced in the same manner as in Example 1, and the stain staining resistance and the whitening resistance were evaluated.

These results are written together in Table 10.

In addition, in Table 10, Na content contained in the resin component and colloidal silica which comprise a resin film, and Na content contained in a resin film are written together.

As shown in Table 10, when the silane coupling agent was added in the preferred range of the present invention, all of the above characteristics were increased as compared with the case where no silane coupling agent was added. In addition, in the example which added 30 mass parts of silane coupling agents, since the process liquid gelatinized and could not apply on a plating layer, the external appearance was not able to be evaluated.

1 is a "photograph sample for stain contamination evaluation determination" corresponding to the staining resistance evaluation criteria 1 to 5 in this embodiment, and FIGS. 1A to 1E correspond to the evaluation criteria 1 to 5, respectively.

Claims (8)

As electric Zn plated steel sheet, A resin film containing 0.05 to 5% of Na (% means mass%, hereinafter, the same) without substantially containing Cr on the electroplating Zn plating layer is provided. Pb and Tl in the said electroplated Zn plating layer are electroplated Zn plated steel sheets suppressed by Pb: 5 ppm (ppm means mass ppm. Or less, the same below) and Tl: 10 ppm or less in atomic conversion. The method of claim 1, The electroplated Zn plating layer includes at least one member selected from the group consisting of Ni, Fe, Cr, Mo, Sn, Cu, Cd, Ag, Si, Co, In, Ir, and W, in terms of atomic weight: Ni: 60 to 6000 ppm, Fe: 60 to 600 ppm, Cr: 0.5 to 5 ppm, Mo: 30 to 500 ppm, Sn: 0.6 to 20 ppm, Cu: 8 to 3000 ppm, Cd: 0.0001 to 0.02 ppm, Ag: 1.0 to 400 ppm, Si: 30 to 2000 ppm , Co: 0.0003 to 0.3 ppm, In: 0.1 to 30 ppm, Ir: 0.01 to 10 ppm, W: 0.1 to 50 ppm in an electric Zn plated steel sheet. The method according to claim 1 or 2, The resin film is an electric Zn plated steel sheet containing a carboxyl group-containing resin and an Si-based inorganic compound. The method of claim 3, wherein The resin film is an electric Zn plated steel sheet further containing a silane coupling agent. As a method for producing an electrical Zn plated steel sheet, Electroplating Zn plating using an acidic plating solution in which Pb and Tl in the plating solution are suppressed to Pb: 0.08 ppm or less and Tl: 0.2 ppm or less; Process of forming resin film containing 0.05-5 mass% of Na Method for producing an electrical Zn plated steel sheet comprising a. The method of claim 5, wherein The acidic plating solution is Ni: 20 to 2000ppm, Fe ^{2 +} : 50 to 5000ppm, Fe ^{3 +} : 50 to 5000ppm, Cr: 5 to 2000ppm, Mo: 50 to 2000ppm, Sn: 0.05 to 20ppm, Cu: 0.05 to 50ppm, At least 1 selected from the group consisting of Cd: 0.05 to 5 ppm, Ag: 0.05 to 5 ppm, Si: 20 to 2000 ppm, Co: 0.05 to 50 ppm, In: 0.5 to 50 ppm, Ir: 0.05 to 5 ppm, and W: 0.5 to 50 ppm. A method for producing an electroplated Zn plated steel sheet containing an element of species. As the electric Zn plating bath, Pb and Tl in the plating bath are controlled to Pb: 0.08 ppm or less and Tl: 0.2 ppm or less. The method of claim 7, wherein Ni: 20 to 2000ppm, Fe ^{2 +:} 50 to 5000ppm, Fe ^{3 +:} 50 to 5000ppm, Cr: 5 to 2000ppm, Mo: 50 to 2000ppm, Sn: 0.05 to 20ppm, Cu: 0.05 to 50ppm, Cd: 0.05 to At least one element selected from the group consisting of 5 ppm, Ag: 0.05-5 ppm, Si: 20-2000 ppm, Co: 0.05-50 ppm, In: 0.5-50 ppm, Ir: 0.05-5 ppm, and W: 0.5-50 ppm Electric Zn plating bath containing.

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