WO2016103491A1 - Paint for hot-dip galvanized steel sheet, method for treating hot-dip galvanized steel sheet, process for producing surface-treated hot-dip galvanized steel sheet, and surface-treated hot-dip galvanized steel sheet - Google Patents

Abstract

The present invention provides a paint for hot-dip galvanized steel sheets which is for use in imparting, to a hot-dip galvanized steel sheet, excellent appearance properties, excellent rubbing resistance, and excellent corrosion resistance. The paint for hot-dip galvanized steel sheets according to the present invention contains a cationic polyurethane resin (A) having at least one kind of cationic functional groups selected from among primary to tertiary amino groups and quaternary ammonium salt groups, wherein the cationic polyurethane resin (A) includes a polycarbonate structural unit and bisphenol structural units, the loss modulus E" of the cationic polyurethane resin (A) shows a maximum peak value at a temperature (Tg1) in the range of -60ºC to -5ºC, and the loss tangent tanδ, which is the ratio of the loss modulus E" to the storage modulus E' of the cationic polyurethane resin (A), has one peak.

Description

Paint for hot dipped galvanized steel sheet, processing method for hot dipped galvanized steel sheet, method for manufacturing surface dipped hot dip galvanized steel sheet, and surface-treated hot dip galvanized steel sheet

The present invention relates to a coating for hot pickled hot dip galvanized steel sheet, a processing method for hot pickled hot dip galvanized steel sheet, a manufacturing method of surface treated hot dipped galvanized steel sheet, and a surface treated hot dip galvanized steel sheet.

Conventionally, zinc-based plated steel sheets including hot-dip galvanized steel sheets, hot-dip zinc-5% aluminum alloy-plated steel sheets, and hot-dip zinc alloy-plated steel sheets have been widely used for home appliances and building materials. In addition, as a method of producing a zinc-based plated steel sheet, for example, a steel sheet which is an object to be treated is immersed in a hot dip zinc bath, and plating is performed on the entire surface by a soaking method (so-called “soaked zinc plating”). The method of hot-dip galvanizing is mentioned, and the obtained steel plate is also called a soaked hot-dip galvanized steel plate. In addition, in the soaking method by soaking (hereinafter also referred to as the soaking method), the zinc adhesion amount control by an air knife or the like performed in CGL (continuous hot dip galvanizing plate line) is not performed.
In galvanized steel sheets, steel sheets subjected to chromate treatment with a treatment liquid containing chromic acid, dichromic acid or salts thereof as main components are widely used for the purpose of improving corrosion resistance.
However, since the chromate-treated film usually contains hexavalent chromium having a high environmental load, in recent years, there has been an increasing demand for the hexavalent chromium-free treatment film, and various techniques have been proposed.

For example, Patent Document 1 discloses a method of preventing corrosion of a steel material surface by bringing an aqueous solution containing a vanadate and a water-soluble acrylic resin into contact with the surface of the galvanized steel material.

JP 2002-146554 A

On the other hand, in recent years, zinc-based plated steel sheets have been developed for various uses, and not only further improvement of corrosion resistance but also improvement of other characteristics is required. For example, improvement of the appearance characteristics of galvanized steel sheets and coatings for the work of wiping off oil-based magic that has been marked as an assemblage with a cloth soaked in alcohol (films placed on galvanized steel sheets) ) Of the film, which is difficult to peel off (hereinafter referred to as rubbing resistance). In particular, with respect to the hot dipped galvanized steel sheet, there is a strong demand for improvement of the above characteristics (corrosion resistance, appearance characteristics, rubbing resistance).
The inventors of the present invention have evaluated the above-mentioned various properties with respect to the steel plate obtained by applying the method described in Patent Document 1 to the hot dipped galvanized steel plate. As a result, appearance characteristics, rubbing resistance, and It was found that the corrosion resistance could not be satisfied at the same time as the recent required level, and further improvement was necessary.

In view of the above circumstances, the present invention imparts excellent appearance characteristics, excellent rubbing resistance, and excellent corrosion resistance to hot dipped galvanized steel sheets (or hot dip galvanized steel sheets or galvanized steel sheets). It is an object of the present invention to provide a coating for a hot dipped galvanized steel sheet (or a hot-dip galvanized steel sheet or a galvanized steel sheet).

The inventors of the present invention have made extensive studies on the above problems and have found that a desired effect can be obtained by using a paint containing a cationic polyurethane resin exhibiting predetermined characteristics.
More specifically, the present inventors have found that the above object can be achieved by the following configuration.

(1) A cationic polyurethane resin containing a cationic polyurethane resin (A) having at least one cationic functional group selected from the group consisting of primary to tertiary amino groups and quaternary ammonium bases (A) has a polycarbonate structural unit and a bisphenol structural unit, and the temperature (Tg1) showing the maximum peak value of the loss elastic modulus E ″ of the cationic polyurethane resin (A) is in the range of −60 ° C. to −5 ° C. The coating material for hot dipped galvanized steel sheet, wherein the loss tangent tan δ, which is the ratio of the loss elastic modulus E ″ and the storage elastic modulus E ′ of the cationic polyurethane resin (A), has one peak.
(2) The paint for hot dipped galvanized steel sheets according to (1), wherein the peak temperature (Tg2) of the loss tangent tan δ is in the range of −50 ° C. to −2 ° C.
(3) The paint for hot dipped galvanized steel sheets according to (1) or (2), which further contains a phosphoric acid compound (B).
(4) The soaked hot-dip galvanized steel sheet according to (3), wherein the phosphoric acid compound (B) contains at least one selected from the group consisting of orthophosphoric acid, condensed phosphoric acid, and salts thereof paint.
(5) The coating material for hot dipped galvanized steel sheets according to any one of (1) to (4), wherein the cationic polyurethane resin (A) has an amine value (AV) of 2.0 to 5.0 mgKOH / g. .
(6) The content ratio (% by mass) (BV) of the phosphoric acid compound (B) to the solid content of the cationic polyurethane resin and the amine value ((BV) / (AV)) is 0.1 to 9. The paint for hot dipped galvanized steel sheets according to (5), which is 5.
(7) The paint for hot dipped galvanized steel sheets according to any one of (1) to (6), further comprising a trivalent chromium compound (C).
(8) A method for treating a soaked hot dip galvanized steel sheet, wherein the soaked hot dip galvanized steel sheet is treated using the paint for a soaked hot dip galvanized steel sheet according to any one of (1) to (7).
(9) The paint for hot dipped galvanized steel sheet according to any one of (1) to (7) is brought into contact with the hot dipped galvanized steel sheet and placed on the hot dipped galvanized steel sheet and its surface. A method for producing a surface-treated soaked hot-dip galvanized steel sheet having a coated surface.
(10) A surface-treated hot-dip galvanized steel sheet obtained from the production method according to (9).

According to the present invention, it is used for imparting excellent appearance characteristics, excellent rubbing resistance, and excellent corrosion resistance to hot dipped galvanized steel sheets (or hot-dip galvanized steel sheets or galvanized steel sheets). It is possible to provide a coating material for hot-dip galvanized steel sheets (or hot-dip galvanized steel sheets or galvanized steel sheets).
Furthermore, the paint is used to treat the soaked hot dip galvanized steel sheet (or hot dip galvanized steel sheet or galvanized steel sheet). The processing method of the plated steel sheet, and its paint and the hot-dip galvanized steel sheet (or hot-dip galvanized steel sheet or galvanized steel sheet) are brought into contact with each other, and the hot-dip galvanized steel sheet (or hot-dip zinc) A method for producing a surface-treated dip galvanized steel sheet (or a hot-dip galvanized steel sheet or a galvanized steel sheet) having a coating disposed on the surface thereof and a steel sheet thereof are provided. can do.
Moreover, although the paint for hot-dip galvanized steel sheets of the present invention is a hexavalent chromium-free technique, the performance is greatly improved by containing trivalent chromium. Moreover, even if it is a form which does not contain trivalent chromium, there exists a desired effect.

Hereinafter, the paint for hot dipped galvanized steel sheet of the present invention (hereinafter simply referred to as “paint”) will be described in detail. The reason why the desired effect can be obtained by using the paint of the present invention is presumed as follows.
First, the reason why the appearance characteristics are improved is that the temperature (Tg1) showing the maximum peak value of the loss elastic modulus E ″ of the cationic polyurethane resin is in the range of −60 ° C. to −5 ° C. The present inventors have found that the temperature (Tg1) is related to the appearance characteristics and rubbing resistance of the film. In other words, the loss elastic modulus E ″ is an index indicating the viscosity of an object. If the temperature showing the maximum peak value of the loss elastic modulus E ″ is too low, the resin exhibits good fluidity and the flatness of the film is improved. Excellent appearance characteristics can be obtained, but the hardness of the formed film is inferior and the rubbing resistance is lowered. On the other hand, when the temperature is too high, the hardness of the formed film is excellent and the rubbing resistance is excellent, but the fluidity of the resin is lowered and the appearance characteristics are poor. In the present invention, it has been found that if the temperature (Tg1) of the cationic polyurethane resin is within the above range, both appearance characteristics and rubbing resistance can be achieved. The rubbing resistance is intended to indicate the resistance of the film to the work of wiping off the oil-based magic applied as a mark during assembly work with a cloth soaked in alcohol or the like.
Further, the reason why the corrosion resistance is improved is that the loss tangent tan δ of the cationic polyurethane resin consists of one peak. Generally, a polyurethane resin tends to form a sea-island structure having two or more domains of a soft segment and a hard segment in a film form because of its resin skeleton. Therefore, when dynamic viscoelasticity measurement is performed, two or more peaks are observed at the loss tangent tan δ. On the other hand, in the cationic polyurethane resin used in the present invention, the loss tangent tan δ has one peak, the sea-island structure is hardly formed in the film, and a uniform film is formed. As a result, the corrosion resistance is estimated to be improved. Is done.

In order to ensure good top coat adhesion and impact resistance, the peak temperature (Tg2) of the loss tangent tan δ of the cationic polyurethane resin is preferably in the range of −50 ° C. to −2 ° C. Depending on the use environment of the product to which the paint of the present invention is applied, there are cases where processing is performed in a cold region. Paints containing components with high peak loss tangent tan δ used in surface treatments are hard, so when coated at low temperatures, especially in winter, adhesion to the top coat is insufficient, and coating film peeling tends to occur. . In addition, paints containing components with low peak tangent loss tan δ used in surface treatments are soft, so when they are processed at high temperatures especially in summer, the impact resistance is insufficient and the coating film peels off. It is easy to produce. In contrast, if the peak temperature (Tg2) of the loss tangent tan δ is in the range of −50 ° C. to −2 ° C., the film has sufficient flexibility and hardness at both low and high temperatures, It is presumed to exhibit top coat adhesion and impact resistance.
In order to ensure good storage stability, the amine value of the cationic polyurethane resin is preferably in the range of 2.0 to 5.0 mgKOH / g. The cationic functional group in the cationic polyurethane resin contributes to making the cationic polyurethane resin water-soluble or water-dispersible. Therefore, if the cationic functional group is small, in other words, if the amine value is low, the stability of the cationic polyurethane resin is insufficient and redispersion in the paint is possible, but the resin tends to precipitate. Therefore, in order to improve the stability of the cationic polyurethane resin, it is desirable to increase the number of cationic functional groups, in other words, to increase the amine value, but the hydrophilic group in the resin is excessively increased. On the other hand, if the viscosity is too high, the cationic urethane resin becomes water-soluble so that the viscosity becomes strong and the paint thickens, which may affect the redispersibility of the paint. In addition, the workability of coating may be affected by thickening. Therefore, it is presumed that good storage stability can be obtained by controlling the amine value of the cationic polyurethane resin in the range of 2.0 to 5.0 mgKOH / g.
Furthermore, as another effect of the coating material of the present invention, a point that the phosphate treatment property is excellent is also mentioned. The reason why the phosphate treatment property is excellent is that a cationic polyurethane resin having a predetermined functional group is used. Zinc phosphate, etc. in the phosphate treatment by interaction between the cationic functional group in the cationic polyurethane resin in the film formed on the hot dipped galvanized steel sheet and the phosphoric acid present in the phosphate compound This is the starting point for the phosphate formation reaction, and it is assumed that the phosphate processability is improved. The ratio (BV) / (AV) of the phosphoric acid compound based on the solid content of the cationic polyurethane resin (mass%) (BV) and the amine value (BV) / (AV) is not particularly limited and may be 0.05 to 20 or the like. However, it is preferably 0.1 to 9.5, more preferably 0.5 to 9.0, and still more preferably 0.5 to 6.0. When (BV) / (AV) is within the above-mentioned range (0.1 to 9.5), the starting point of the phosphate formation reaction is more favorably generated on the film, and more excellent phosphatability. I guess that you can get. In this case, when the phosphoric acid compound is relatively large, that is, when (BV) / (AV) is large, the phosphoric acid compound dissolves in the phosphating solution so that a phosphate film is formed. When the phosphate compound is relatively small, that is, when (BV) / (AV) is small, the interaction of the phosphate compound with the cationic functional group of the cationic polyurethane resin Since it becomes relatively small, the swelling and dissolution of the cationic polyurethane resin by the phosphating solution is lowered, and it is estimated that the formation of the phosphate film is likely to be delayed.
The phosphate treatment is intended to be a treatment using a phosphate treatment liquid mainly composed of zinc phosphate, manganese phosphate, magnesium phosphate or the like applied to a coating base or the like. The coating type phosphate treatment is a form of phosphate treatment. In the coating type phosphate treatment, fine and dense crystals of zinc phosphate are formed on the surface of an object to be treated (for example, a galvanized steel sheet such as a hot dipped galvanized steel sheet) by applying a coating type phosphate treatment solution. It is intended to perform a treatment for improving the slip resistance at the frictional joint surface with the high-strength bolt.

The paint of the present invention can be suitably applied to hot dipped hot dip galvanized steel sheets, hot dip galvanized steel sheets manufactured by CGL (continuous hot dip galvanized plate line), hot dip zinc-5% aluminum alloy plating. Applicable to galvanized steel sheets including steel sheets, hot dip galvanized 55% aluminum alloy plated steel sheets, galvannealed steel sheets, electrogalvanized steel sheets manufactured by EGL (electrogalvanizing line), etc. It is possible to improve the above-described various characteristics (appearance characteristics, rubbing resistance, corrosion resistance, adhesion to top coat, impact resistance, phosphate treatment, etc.). In other words, the paint of the present invention can be suitably applied to a zinc-based plated steel sheet and can also be used as a paint for a zinc-based plated steel sheet. In particular, hot dipped galvanized steel sheet, hot dip galvanized steel sheet manufactured with CGL (continuous galvanized sheet line), hot dip zinc-5% aluminum alloy plated steel sheet, hot dip zinc-55% molten aluminum alloy plated steel sheet, alloy The present invention can be suitably applied to a hot dip galvanized steel sheet obtained by performing a plating process using hot galvanized steel such as a hot dip galvanized steel sheet, and can also be used as a paint for a hot dip galvanized steel sheet.

The paint of the present invention contains at least a cationic polyurethane resin (A).
Hereinafter, the various components contained in the paint will be described in detail, and then the treatment method for the soaked hot dip galvanized steel sheet using the paint (in other words, the soaked hot dip galvanized steel sheet and the surface having the film disposed on the surface thereof) A method for producing a surface-treated soaked hot-dip galvanized steel sheet, which produces a soaked hot-dip galvanized steel sheet, will be described in detail.

<Cationic polyurethane resin (A)>
The paint of the present invention includes a cationic polyurethane resin (A) having at least one cationic functional group selected from the group consisting of primary to tertiary amino groups and quaternary ammonium bases.
Anionic resins used in the prior art generally have poor alkali resistance and tend to be excellent in acid resistance. When it is inferior in alkali resistance, the film is easily dissolved and peeled off by an alkali degreasing step after the film is formed, which causes a decrease in corrosion resistance. Moreover, since it is excellent in acid resistance, it is often difficult to perform phosphate treatment. On the other hand, since the cationic polyurethane resin (A) is excellent in alkali resistance, it is excellent in corrosion resistance even after the alkali degreasing step. In addition, the polyurethane resin has a strong film due to hydrogen bonding by urethane bonds in the molecule, leading to improved corrosion resistance. Furthermore, since it may have a cationic functional group relatively, and acid resistance is low, it is easy to perform a phosphate process also as a characteristic of resin.

(Cationic functional group)
Examples of the cationic functional group contained in the cationic polyurethane resin (A) include an amino group, a methylamino group, an ethylamino group, a dimethylamino group, a diethylamino group, a trimethylamino group, and a triethylamino group. There is no particular limitation as long as it is a primary to tertiary amino group or a quaternary ammonium base.
The cationic functional group in the cationic polyurethane resin (A) contributes to making the cationic polyurethane resin (A) water-soluble or water-dispersible. The dissolution or dispersion of the cationic polyurethane resin (A) in water may be achieved based on the self-solubility or self-dispersibility of the cationic polyurethane resin (A) in water. It may be achieved with the help of activators (eg alkyl quaternary ammonium salts) and / or nonionic surfactants (eg alkyl phenyl ethers).

(Temperature (Tg1) showing maximum peak value of loss elastic modulus E ″)
The temperature (Tg1) showing the maximum peak value of the loss elastic modulus E ″ of the cationic polyurethane resin (A) is in the range of −60 ° C. to −5 ° C., appearance characteristics, rubbing resistance, corrosion resistance, phosphate -55 ° C to -10 ° C in that at least one of processability, top coat adhesion, impact resistance, and storage stability is superior (hereinafter also referred to simply as “the point where the effect of the present invention is more excellent”). Is preferable, and −50 ° C. to −15 ° C. is more preferable.
When the temperature (Tg1) is less than −60 ° C., the rubbing resistance is inferior, and when it exceeds −5 ° C., the film appearance characteristics are inferior.
In addition, the said maximum peak value is in the loss elastic modulus curve (temperature dependence curve of the loss elastic modulus in the graph which made the horizontal axis temperature and the vertical axis | shaft loss elastic modulus) obtained from the dynamic-viscoelasticity measurement mentioned later. The maximum peak value among the observed peak values is intended. The peak value can be said to be a so-called maximum value.

(Loss tangent tan δ)
The loss tangent tan δ, which is the ratio (loss elastic modulus E ″ / storage elastic modulus E ′) of the loss elastic modulus E ″ and the storage elastic modulus E ′ of the cationic polyurethane resin (A), consists of one peak ( It has only one peak). That is, a loss tangent tan δ curve (temperature dependence curve of loss tangent tan δ in a graph in which the horizontal axis is temperature and the vertical axis is loss tangent tan δ) obtained from dynamic viscoelasticity measurement described later consists of one peak ( Intended to have only one peak). In other words, it is intended that there are no more than two peaks. As described above, when two or more peaks are observed, the formed film is microscopically uneven and inferior in corrosion resistance.

(Peak temperature of loss tangent tan δ (Tg2))
The range of the peak temperature (Tg2) of the loss tangent tan δ is not particularly limited, but −50 ° C. to −2 ° C. is preferable from the viewpoint of more excellent effects of the present invention (particularly adhesion to the top coat and impact resistance). 48 ° C to -5 ° C is more preferable, and -45 ° C to -10 ° C is more preferable.
As a method for measuring dynamic viscoelasticity, a dynamic viscoelasticity measuring device “RSAG2” manufactured by TA Instruments was used, and a film of a cationic polyurethane resin (A) (sample area: grip length × width = 20 mm × 5 mm) was used. In the transverse direction (TD), the storage elastic modulus E ′ and the loss elastic modulus E ″ are measured from −100 ° C. to 200 ° C. at a temperature rising rate of 5 ° C./min at a vibration frequency of 10 Hz and a strain of 0.1%. The loss tangent tan δ is calculated.

The above characteristics (loss elastic modulus E ″, loss tangent tan δ) of the cationic polyurethane resin (A) contained in the paint of the present invention can be appropriately adjusted by controlling the structure and synthesis method.
For example, the temperature (Tg1) can be controlled by the amount and molecular weight of the polyol that forms the soft segment of the cationic polyurethane resin (A), and the temperature during polymerization. When the amount of polyol is large, the temperature (Tg1) tends to be low, and when the amount is small, the temperature (Tg1) tends to be high.
In order to prevent two or more peaks of the loss tangent tan δ from being observed, for example, there is a method of controlling the molecular weight of the polyol that constitutes the soft segment of the cationic polyurethane resin (A) and the temperature during polymerization. .

(Structure of urethane resin)
The cationic polyurethane resin (A) has a polycarbonate structural unit and a bisphenol structural unit. In other words, the cationic polyurethane resin (A) has a polycarbonate structure repeating unit and a bisphenol structure repeating unit as a repeating unit constituting the resin.
The carbonate structural unit is flexible and has excellent adhesion, but tends to be inferior in hydrolysis resistance of the film when wet with water. Bisphenol structural units are excellent in hydrolysis resistance, but are hard and inferior in flexibility, and tend to be damaged by rubbing.
That is, if the polycarbonate structural unit and the bisphenol structural unit are not included, the corrosion resistance and the rubbing resistance are inferior to those having the polycarbonate structural unit and the bisphenol structural unit.
In the present invention, excellent corrosion resistance and rubbing resistance are obtained by combining the two and controlling the temperature (Tg1) at which the loss elastic modulus E ″ shows the maximum peak value to be in the range of −60 ° C. to −5 ° C. And excellent appearance characteristics can be obtained at the same time.

The polycarbonate structural unit is a repeating unit having a plurality of carbonate bonds (—O—C (═O) —O—) in the structure. Usually, a polyurethane resin is produced by reaction of a polyol and a polyisocyanate. Then, as a method of introducing a carbonate structural unit into the cationic polyurethane resin (A), a method of producing the cationic polyurethane resin (A) using a polycarbonate polyol can be mentioned.
Examples of the polycarbonate polyol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 1,8-nonanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol-A, or hydrogenated bisphenol-A Examples thereof include polycarbonate polyol having a hydroxyl group at the terminal obtained by reacting polyol such as dimethyl carbonate, diphenyl carbonate, ethylene carbonate, or phosgene.

Examples of the bisphenol structural unit include structural units derived from bisphenol A, bisphenol F, or bisphenol S. Examples of the method for introducing the bisphenol structural unit into the cationic polyurethane resin (A) include a method for producing the cationic polyurethane resin (A) using a polyol having a bisphenol structure.
Examples of the polyol having a bisphenol structure include bisphenol A type, bisphenol F type, bisphenol E type, polyol in which alkylene oxide is added to bisphenol A type, polyol in which alkylene oxide is added to bisphenol F type, and alkylene oxide in bisphenol E type. Hydrogenated bisphenol A type, hydrogenated bisphenol A type, hydrogenated bisphenol F type, polyol obtained by adding alkylene oxide to hydrogenated bisphenol A type, polyol obtained by adding alkylene oxide to hydrogenated bisphenol F type, etc. Examples include polyols to which alkylene oxide is added.

The cationic polyurethane resin (A) may have a structural unit other than the polycarbonate structural unit and the bisphenol structural unit.
For example, you may use together other polyols other than polycarbonate polyols, such as polyether polyol and polyester polyol, at the time of manufacture of a cationic polyurethane resin (A).
Further, in the production of the cationic polyurethane resin (A), an alcohol compound having a cationic functional group such as a (substituted) amino group (preferably a polyol compound having a cationic functional group such as a (substituted) amino group). (For example, N-methyldiethanolamine, N, N-dimethylaminodimethylolpropane, etc.) and an amine compound having a predetermined cationic functional group are used together to introduce a desired cationic functional group into the polyurethane resin. can do.
In addition, as described above, in the production of the cationic polyurethane resin (A), it is obtained by reacting the above-described polyol with a polyisocyanate (for example, aliphatic, alicyclic or aromatic polyisocyanate). .

Examples of the polyether polyol include polyethylene glycols such as diethylene glycol and triethylene glycol, and polyethylene / propylene glycol.
Polyester polyols include alkylene (for example, 1 to 6 carbon atoms) glycol (ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, hexamethylene glycol, etc.), polyether polyol, bisphenol A, hydrogenated bisphenol A, trimethylolpropane. Or a hydroxyl group at the terminal obtained by polycondensation of a polyol such as glycerin with a polybasic acid such as succinic acid, glutaric acid, adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, or trimellitic acid Examples include polyester polyols having
Examples of the aliphatic, alicyclic or aromatic polyisocyanate include tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, dicyclohexylmethane diisocyanate, cyclohexylene diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

(Amine number)
The amine value of the cationic polyurethane resin (A) is not particularly limited, but is preferably from 2.0 to 5.0 mgKOH / g, more preferably from 2.3 to 4.5 mgKOH / g in terms of better storage stability of the paint. More preferably, 2.5 to 4.0 mgKOH / g is more preferable.
The amine value is defined as the total amine value measured by the following measurement method.
About 3 g of the cationic polyurethane resin (A) is collected in terms of solid content and accurately weighed. Thereafter, dimethylformamide is added and dissolved. Next, a few drops of bromcresol green indicator are added, titrated with a 0.1 mol / L hydrochloric acid titration solution, and the amount of titrant is read with the point where the color changed from blue to yellow as the end point. The total amine value (mgKOH / g) is calculated by the following formula.
Total amine value = [(F1-F2) × f × 5.661 / S]
In the formula:
F1: 0.1 mol / L hydrochloric acid titration solution required for this test (mL)
F2: 0.1 mol / L hydrochloric acid titration solution volume required for the blank test (mL)
f: titer of 0.1 mol / L hydrochloric acid titration solution S: sampling amount (g)
It is.
In addition, the said blank test intends the test measured not using cationic polyurethane resin but using deionized water.

<Other optional components>
The coating material of the present invention may contain components other than the cationic polyurethane resin (A). Hereinafter, the optional components will be described in detail.

(Phosphate compound (B))
The paint of the present invention may contain a phosphoric acid compound (B). By including the phosphoric acid compound (B), the corrosion resistance is further improved.
Examples of the phosphoric acid compound (B) include at least one selected from the group consisting of inorganic phosphoric acid, inorganic phosphate, organic phosphoric acid, and organic phosphate.
Examples of inorganic phosphoric acid and salts thereof include phosphoric acid (orthophosphoric acid), phosphorous acid, triphosphoric acid, hypophosphorous acid, monophosphoric acid such as hypophosphoric acid, monophosphoric acid derivatives and salts, metaphosphoric acid, tripolyphosphoric acid, Examples include condensed phosphoric acid such as tetraphosphoric acid and hexaphosphoric acid, derivatives and salts of condensed phosphoric acid, and the like.
Examples of organic phosphoric acid and salts thereof include phosphoric acid monoesters (for example, monododecyl dihydrogen phosphate, monotridecyl dihydrogen phosphate) and salts thereof, phosphoric diesters (for example, didodecyl hydrogen phosphate, ditridecyl hydrogen phosphate, etc.) ) And its salts. Specific examples of the organic phosphoric acid include compounds represented by R ₁₀ O—P (═O) (OR ₁₁ ) (OR ₁₂ ). R ₁₀ represents an organic group, and R ₁₁ and R ₁₂ each independently represent a hydrogen atom or an organic group. Examples of the organic group include a hydrocarbon group (for example, an alkyl group, an aryl group, or a group obtained by combining these).
In addition, although it does not restrict | limit especially as salts, such as inorganic phosphate (salt of inorganic phosphoric acid) and organic phosphate (salt of organic phosphoric acid), For example, an alkali metal salt, ammonium salt, and an amine salt are mentioned. it can.
Especially, it is preferable that the phosphoric acid compound (B) contains at least 1 sort (s) selected from the group which consists of orthophosphoric acid, condensed phosphoric acid, and these salts at the point which the effect of this invention is more excellent.

(Trivalent chromium compound (C))
The paint of the present invention may contain a trivalent chromium compound (C). By including the trivalent chromium compound (C), the corrosion resistance is further improved.
A trivalent chromium compound (C) is a compound which can supply a trivalent chromium ion, for example, a trivalent chromium salt is mentioned. Examples of the salt include inorganic acid salts such as nitrate, sulfate, and hydrochloride, and organic acid salts such as acetate, oxalate, and succinate.
Specific examples of the trivalent chromium compound (C) include, for example, chromium (III) fluoride, chromium (III) chloride, chromium (III) nitrate, chromium (III) sulfate, and chromium (III) acetate.

(solvent)
The paint of the present invention may contain a solvent. Examples of the solvent include water and organic solvents (for example, alcohol).

(Other additives)
The paint of the present invention contains a thickener, a leveling agent, a wettability improver, an antifoaming agent, a surfactant, a water-soluble alcohol, a cellosolve solvent, etc. for the purpose of adjusting coating properties. Also good.
Moreover, you may contain antiseptic | preservative, an antibacterial agent, a coloring agent, a damage prevention agent, a lubricant, etc.
Moreover, you may contain a benzotriazole, a guanidine type compound, a hindered amine, etc.

<Dow pickled hot-dip galvanized steel sheet paint>
The paint of the present invention contains the various components described above.
The content of the cationic polyurethane resin (A) in the paint is not particularly limited, but is 1 to 40% by weight with respect to the total weight of the paint in terms of more excellent effects of the present invention and handling. Preferably, 5 to 30% by mass is more preferable.

When the phosphoric acid compound (B) is contained in the paint, the content of the phosphoric acid compound (B) is not particularly limited, but the cationic polyurethane resin (A) is added in 100 parts by mass in terms of more excellent effects of the present invention. On the other hand, 0.1 to 30 parts by mass is preferable, 0.3 to 25 parts by mass is more preferable, and 1 to 10 parts by mass is further preferable.
When the trivalent chromium compound (C) is contained in the paint, the content of the trivalent chromium compound (C) is not particularly limited, but the cationic polyurethane resin (A) 100 mass in that the effect of the present invention is more excellent. 0.5 to 20 parts by mass is preferable with respect to parts, and 1 to 10 parts by mass is more preferable.

The method for preparing the paint is not particularly limited, and for example, it can be prepared by adding the cationic polyurethane resin (A) and other optional components to a solvent such as water and mixing them.

<Manufacturing method of surface-treated dobu pickled galvanized steel sheet>
The paint of the present invention can be suitably applied to the soaked hot dip galvanized steel sheet, and is placed on the soaked hot dip galvanized steel sheet and its surface by bringing the paint of the present invention into contact with the soaked hot dip galvanized steel sheet. A surface-treated soaked hot-dip galvanized steel sheet having a film can be produced.
As described above, the paint of the present invention can also be suitably applied to galvanized steel sheets (or hot dip galvanized steel sheets) including hot dipped galvanized steel sheets.
In the following, the embodiment using the soaked hot dip galvanized steel sheet as the object to be treated will be representatively described. However, a predetermined film is formed on a galvanized steel sheet other than the soaked hot dip galvanized steel sheet under the conditions described later. It is also possible to produce a surface-treated galvanized steel sheet that is excellent in various properties. Moreover, when the above-mentioned hot-dip galvanized steel sheet is used, a hot-dip galvanized steel sheet and a surface-treated hot-dip galvanized steel sheet having a film thereon can also be produced.

The method for producing the surface-treated dip galvanized steel sheet using the above-mentioned paint is not particularly limited, but usually, the above-mentioned paint is brought into contact with the dip galvanized steel sheet and, if necessary, heated and dried. It has a step of forming a film on the hot-dip galvanized steel sheet and obtaining a surface-treated hot-dip galvanized steel sheet.
In the following, first, the soaked hot-dip galvanized steel sheet that is the object to be processed will be described in detail, and the procedure of the subsequent process will be described in detail.

(Dow pickled hot dip galvanized steel sheet)
The soaked hot dip galvanized steel sheet is a steel sheet obtained by a dipping method in which a steel sheet, which is the object to be treated, is immersed in a hot dip galvanized tank, and the object is slowly pulled up from the plating tank as it is. As described above, in the soaking method, the amount of zinc attached is not controlled by an air knife or the like performed in CGL, and the object to be processed is pulled up from the plating tank and left as it is (cooled).
There are no particular restrictions on the type of steel sheet that is galvanized, such as H steel, guardrails, corrugated pipes, building columns and beams, soundproof wall columns, sign columns, lighting columns, large bridge girder bridges, and overpass bridges. All building materials that are galvanized, such as bridges, rebars, overhead metal fittings used for power towers, small parts such as bolts and nuts, mounts for solar cells and small wind power generators, outdoor exposed steel frames, etc. For example, a cut plate steel material or a coil steel material may be used.

If oil, dirt, etc. are adhered to the surface of the hot dipped galvanized steel sheet, wash it with an alkaline degreasing agent, neutral degreasing agent, or acidic degreasing agent, and then wash with hot water or water. It is preferable to clean the surface state.

(Paint contact method)
There are no particular restrictions on the method of contacting the paint with the hot-dip galvanized steel sheet, and examples include immersion treatment, spray treatment, brush coating treatment, and electrostatic coating treatment performed in the cooling step after plating. In addition, when the dip galvanized steel sheet is coiled, a conventionally used method can be applied, for example, roll coating, shower ringer roll drawing, spraying, dipping, curtain coating, flow coating, Examples include spin coating.

(Drying method of paint)
The most economical method for drying the paint is to use preheating after the plating process. It can be dried by dipping the hot dipped galvanized steel sheet in the paint and leaving it as it is. In addition, you may send the wind for flying away the water | moisture content adhering to the surface of the hot-dip galvanized steel plate dripped at the time of drying efficiently.
When it is difficult to use preheating after the galvanizing process, it is preferable to use a drying facility that can evaporate water contained in the paint. In this case, the type of drying equipment is not particularly limited, and examples thereof include hot air drying equipment, induction heating drying equipment, infrared heater drying equipment, and near infrared heater drying equipment. The drying temperature when these drying facilities are used is not particularly limited, but is preferably 60 ° C. to 200 ° C., more preferably 80 ° C. to 180 ° C. as the ultimate temperature on the surface of the hot dipped galvanized steel sheet.

(Amount of paint film attached)
By carrying out the above treatment, a surface-treated hot-dip galvanized steel sheet having a hot-dip hot-dip galvanized steel sheet and a film disposed on the surface thereof is produced.
The amount of the coating film is not particularly limited, but is preferably 0.3 to 5.0 g / m ^{2 and} more preferably 0.5 to 3.0 g / m ² from the viewpoint that the effect of the present invention is more excellent.
The manufactured surface-treated soaked hot-dip galvanized steel sheet can be suitably applied to various uses, and examples thereof include members for home appliances and building materials.
Moreover, you may apply | coat to the surface treatment soaked hot dip galvanized steel plate of this invention. In that case, the coating plate may be further processed.

Hereinafter, the present invention will be specifically described with reference to examples and comparative examples of the present invention, but the present invention is not limited to these examples.

1. Test materials The test agents (materials) used are listed below. Usually, most of the pickled galvanized products are shaped, but in this test, a plate was used as the material. It should be noted that even if the shape of the material changes, the effect of the present invention is not affected.
The hot-dip galvanized steel sheet represented by M1 below corresponds to the above-described hot-dip galvanized steel sheet produced by soaking. M1 to M3 correspond to hot-dip galvanized steel sheets (note that M2 and M3 do not correspond to hot-dip galvanized steel sheets).
M1: Hot-dip galvanized steel sheet (according to JIS H8641 HDZ35), small spangle, dimensions: 700 mm × 150 mm × 1.6 mm (plate thickness), double-sided plating adhesion amount: 360 g / m ²
M2: Hot-dip galvanized steel sheet (according to JIS G 3302 SGCC Z06), dimensions: 700 mm × 150 mm × 0.8 mm (plate thickness), double-sided plating adhesion amount: 60 g / m ²
M3: Hot-dip zinc-5% aluminum alloy plated steel sheet (according to JIS G 3317 SZACCY08), dimensions: 700 mm × 150 mm × 0.8 mm (plate thickness), double-sided plating adhesion amount: 80 g / m ²

2. Pretreatment (degreasing treatment)
Using the silicate alkali degreasing agent Fine Cleaner E6406 (manufactured by Nippon Parkerizing Co., Ltd.), the test material was sprayed for 10 seconds under the conditions of a concentration of 20 g / L and a temperature of 60 ° C., and further with pure water for 30 seconds. What was dried after being washed with water was used in the following tests.

3. Paint Table 1 shows the details of the used cationic polyurethane resin (A). The manufacturing method will be described in detail later.
The loss elastic modulus E ″ and loss tangent tan δ of the cationic polyurethane resin (A) were measured by the following procedure. First, the film (thickness: 300 to 500 μm) of the cationic polyurethane resin (A) was left at room temperature for 15 hours, then dried at 80 ° C. for 6 hours, and further dried at 120 ° C. for 20 minutes.
Next, using a dynamic viscoelasticity measuring device “RSAG2” manufactured by TA Instruments, with respect to the transverse direction (TD) of the obtained film (sample area: grip length × width = 20 mm × 5 mm), the vibration frequency is 10 Hz, the strain is Measurements were made from -100 ° C. to 200 ° C. at a rate of temperature rise of 5 ° C./min at 0.1%, and storage elastic modulus E ′, loss elastic modulus E ″ and loss tangent tan δ were calculated. In addition, the distance between grips (chuck) was set to 10 mm.
The method for measuring the amine value is as described above.

In Table 1, Tg1 represents the temperature indicating the maximum peak value of the loss elastic modulus E ″ obtained from the above measurement, and Tg2 represents the peak temperature of the loss tangent tan δ obtained from the above measurement.
The number of peaks is intended to be the number of peaks in the temperature dependence curve of the loss tangent tan δ, which is the ratio of the loss elastic modulus E ″ and the storage elastic modulus E ′.

(Production Example 1: Cationic polyurethane resin (A1))
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube was charged with 1000 parts by mass of polycarbonate polyol (Nipporan 981R, manufactured by Tosoh Corporation, Mw = 2,000), bisphenol A-bis (hydroxy). Ethyl ether) (BPE20T, manufactured by Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g) 100 parts by mass, N-methyldiethanolamine 100 parts by mass, hexamethylene diisocyanate 400 parts by mass, methyl ethyl ketone 800 parts by mass and added at 75 ° C. for 4 hours By reacting, a methyl ethyl ketone solution of urethane prepolymer having a free isocyanate group content of 3.0% by mass relative to the nonvolatile content was obtained. The solution was cooled to 40 ° C., 103 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 1 containing a cationic polyurethane resin (A1) having a nonvolatile content of about 35% by mass.

(Production Example 2: Cationic polyurethane resin (A2))
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube was charged with 1500 parts by mass of polycarbonate polyol (Nipporan 981R, manufactured by Tosoh Corporation, Mw = 2,000), bisphenol A-bis (hydroxy). (Ethyl ether) (BPE20T, manufactured by Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g) 50 parts by mass, N-methyldiethanolamine 50 parts by mass, hexamethylene diisocyanate 325 parts by mass, methyl ethyl ketone 800 parts by mass were added, and 75 ° C. for 4 hours. By reacting, a methyl ethyl ketone solution of urethane prepolymer having a free isocyanate group content of 3.0% by mass relative to the nonvolatile content was obtained. This solution was cooled to 40 ° C., 47 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed under reduced pressure at 50 ° C. to obtain a polyurethane water dispersion 2 containing a cationic polyurethane resin (A2) having a nonvolatile content of about 35% by mass.

(Production Example 3: Cationic polyurethane resin (A3))
In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube, 1000 parts by mass of polycarbonate polyol (Nipporan 980, manufactured by Tosoh Corporation, Mw = 1,000), bisphenol A-bis (hydroxy) Ethyl ether) (BPE20T, manufactured by Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g), 300 parts by mass of N-methyldiethanolamine, 535 parts by mass of hexamethylene diisocyanate, 250 parts by mass of dicyclohexylmethane diisocyanate, and 800 parts by mass of methyl ethyl ketone. In addition, it was reacted at 75 ° C. for 4 hours to obtain a methyl ethyl ketone solution of a urethane prepolymer having a free isocyanate group content of 3.0% by mass with respect to the non-volatile content. This solution was cooled to 40 ° C., 95 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 3 containing a cationic polyurethane resin (A3) having a nonvolatile content of about 35% by mass.

(Production Example 4: Cationic polyurethane resin (A4))
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube was charged with 1000 parts by mass of polycarbonate polyol (Nipporan 981R, manufactured by Tosoh Corporation, Mw = 2,000), bisphenol A-bis (hydroxy). Ethyl ether) (BPE20T, manufactured by Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g) 200 parts by mass, N-methyldiethanolamine 100 parts by mass, hexamethylene diisocyanate 480 parts by mass, methyl ethyl ketone 800 parts by mass and added at 75 ° C. for 4 hours By reacting, a methyl ethyl ketone solution of urethane prepolymer having a free isocyanate group content of 3.0% by mass relative to the nonvolatile content was obtained. The solution was cooled to 40 ° C., 101 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 4 containing a cationic polyurethane resin (A4) having a nonvolatile content of about 35% by mass.

(Production Example 5: Cationic polyurethane resin (A5))
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube was charged with 1500 parts by mass of polycarbonate polyol (Nipporan 981R, manufactured by Tosoh Corporation, Mw = 2,000), bisphenol A-bis (hydroxy). Ethyl ether) (BPE20T, Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g) 100 parts by mass, N-methyldiethanolamine 50 parts by mass, hexamethylene diisocyanate 370 parts by mass and methyl ethyl ketone 800 parts by mass were added at 75 ° C. for 4 hours. By reacting, a methyl ethyl ketone solution of urethane prepolymer having a free isocyanate group content of 3.0% by mass relative to the nonvolatile content was obtained. This solution was cooled to 40 ° C., 48 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 5 containing a cationic polyurethane resin (A5) having a nonvolatile content of about 35% by mass.

(Production Example 6: Cationic polyurethane resin (A6))
In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube, 1000 parts by mass of polycarbonate polyol (Nipporan 980, manufactured by Tosoh Corporation, Mw = 1,000), bisphenol A-bis (hydroxy) Ethyl ether) (BPE20T, manufactured by Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g) 200 parts by mass, N-methyldiethanolamine 100 parts by mass, hexamethylene diisocyanate 450 parts by mass, dicyclohexylmethane diisocyanate 220 parts by mass, methyl ethyl ketone 800 parts by mass In addition, it was reacted at 75 ° C. for 4 hours to obtain a methyl ethyl ketone solution of a urethane prepolymer having a free isocyanate group content of 3.0% by mass with respect to the non-volatile content. The solution was cooled to 40 ° C., 87 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 6 containing a cationic polyurethane resin (A6) having a nonvolatile content of about 35% by mass.

(Production Example 7: Cationic polyurethane resin (A7))
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube was charged with 1500 parts by mass of polycarbonate polyol (Nipporan 981R, manufactured by Tosoh Corporation, Mw = 2,000), bisphenol A-bis (hydroxy). Ethyl ether) (BPE20T, Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g) 100 parts by mass, N-methyldiethanolamine 50 parts by mass, hexamethylene diisocyanate 260 parts by mass, dicyclohexylmethane diisocyanate 150 parts by mass, methyl ethyl ketone 800 parts by mass In addition, it was reacted at 75 ° C. for 4 hours to obtain a methyl ethyl ketone solution of a urethane prepolymer having a free isocyanate group content of 3.0% by mass with respect to the non-volatile content. This solution was cooled to 40 ° C., 49 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 7 containing a cationic polyurethane resin (A7) having a nonvolatile content of about 35% by mass.

(Production Example 8: Cationic polyurethane resin (A8))
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube was charged with 1500 parts by mass of polycarbonate polyol (Nipporan 981R, manufactured by Tosoh Corporation, Mw = 2,000), bisphenol A-bis (hydroxy). Ethyl ether) (BPE20T, manufactured by Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g) 100 parts by mass, N-methyldiethanolamine 50 parts by mass, hexamethylene diisocyanate 315 parts by mass, dicyclohexylmethane diisocyanate 80 parts by mass, methyl ethyl ketone 800 parts by mass In addition, it was reacted at 75 ° C. for 4 hours to obtain a methyl ethyl ketone solution of a urethane prepolymer having a free isocyanate group content of 3.0% by mass with respect to the non-volatile content. This solution was cooled to 40 ° C., 49 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 8 containing a cationic polyurethane resin (A8) having a nonvolatile content of about 35% by mass.

(Production Example 9: Cationic polyurethane resin (A9))
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube was charged with 1500 parts by mass of polycarbonate polyol (Nipporan 981R, manufactured by Tosoh Corporation, Mw = 2,000), bisphenol A-bis (hydroxy). Ethyl ether) (BPE20T, manufactured by Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g), 50 parts by mass of N-methyldiethanolamine, 310 parts by mass of hexamethylene diisocyanate, 35 parts by mass of dicyclohexylmethane diisocyanate, and 800 parts by mass of methyl ethyl ketone. In addition, it was reacted at 75 ° C. for 4 hours to obtain a methyl ethyl ketone solution of a urethane prepolymer having a free isocyanate group content of 3.0% by mass with respect to the non-volatile content. This solution was cooled to 40 ° C., 49 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 9 containing a cationic polyurethane resin (A9) having a nonvolatile content of about 35% by mass.

(Production Example 10: Cationic polyurethane resin (A10))
In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube, 750 parts by weight of polycarbonate polyol (Niporan 981R, manufactured by Tosoh Corporation, Mw = 2,000), bisphenol A-bis (hydroxy) (Ethyl ether) (BPE20T, manufactured by Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g) 125 parts by mass, N-methyldiethanolamine 50 parts by mass, hexamethylene diisocyanate 290 parts by mass, dicyclohexylmethane diisocyanate 35 parts by mass, methyl ethyl ketone 800 parts by mass In addition, it was reacted at 75 ° C. for 4 hours to obtain a methyl ethyl ketone solution of a urethane prepolymer having a free isocyanate group content of 3.0% by mass with respect to the non-volatile content. This solution was cooled to 40 ° C., 51 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 10 containing a cationic polyurethane resin (A10) having a nonvolatile content of about 35% by mass.

(Production Example 11: Cationic polyurethane resin (A11))
In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube, 750 parts by weight of polycarbonate polyol (Niporan 981R, manufactured by Tosoh Corporation, Mw = 2,000), bisphenol A-bis (hydroxy) Ethyl ether) (BPE20T, manufactured by Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g) 125 parts by mass, N-methyldiethanolamine 50 parts by mass, hexamethylene diisocyanate 220 parts by mass, dicyclohexylmethane diisocyanate 110 parts by mass, methyl ethyl ketone 800 parts by mass In addition, it was reacted at 75 ° C. for 4 hours to obtain a methyl ethyl ketone solution of a urethane prepolymer having a free isocyanate group content of 3.0% by mass with respect to the non-volatile content. The solution was cooled to 40 ° C., 50 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 11 containing a cationic polyurethane resin (A11) having a nonvolatile content of about 35% by mass.

(Production Example 12: Cationic polyurethane resin (A12))
In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube, 500 parts by mass of polycarbonate polyol (Nipporan 980, manufactured by Tosoh Corporation, Mw = 1,000), polycarbonate polyol (Nipporan 981R, Tosoh Co., Ltd., Mw = 2,000) 250 parts by mass, bisphenol A-bis (hydroxyethyl ether) (BPE20T, Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g) 150 parts by mass, N-methyldiethanolamine 50 Urethane whose mass content is 275 parts by mass of hexamethylene diisocyanate, 150 parts by mass of dicyclohexylmethane diisocyanate, and 800 parts by mass of methyl ethyl ketone and is reacted at 75 ° C. for 4 hours, and the content of free isocyanate groups with respect to the nonvolatile content is 3.0% by mass. Prepoly To obtain a methyl ethyl ketone solution of the over. This solution was cooled to 40 ° C., 44 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 12 containing a cationic polyurethane resin (A12) having a nonvolatile content of about 35% by mass.

(Production Example 13: Cationic polyurethane resin (A13))
In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube, 1500 parts by mass of polycarbonate polyol (Nipporan 980, manufactured by Tosoh Corporation, Mw = 1,000), bisphenol A-bis (hydroxy) Ethyl ether) (BPE20T, manufactured by Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g) 25 parts by mass, N-methyldiethanolamine 50 parts by mass, hexamethylene diisocyanate 500 parts by mass, methyl ethyl ketone 800 parts by mass were added, and 75 ° C. for 4 hours. By reacting, a methyl ethyl ketone solution of urethane prepolymer having a free isocyanate group content of 3.0% by mass relative to the nonvolatile content was obtained. This solution was cooled to 40 ° C., 49 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 13 containing a cationic polyurethane resin (A13) having a nonvolatile content of about 35% by mass.

(Production Example 14: Cationic polyurethane resin (A14))
In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube, 1500 parts by mass of polycarbonate polyol (Nipporan 980, manufactured by Tosoh Corporation, Mw = 1,000), bisphenol A-bis (hydroxy) Ethyl ether) (BPE20T, manufactured by Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g) 25 parts by mass, N-methyldiethanolamine 50 parts by mass, hexamethylene diisocyanate 500 parts by mass, methyl ethyl ketone 800 parts by mass were added, and 75 ° C. for 4 hours. By reacting, a methyl ethyl ketone solution of urethane prepolymer having a free isocyanate group content of 3.0% by mass relative to the nonvolatile content was obtained. The solution was cooled to 40 ° C., 25 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 14 containing a cationic polyurethane resin (A14) having a nonvolatile content of about 35% by mass.

(Production Example 15: Cationic polyurethane resin (A15))
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube was charged with 1600 parts by weight of polycarbonate polyol (Nipporan 981R, manufactured by Tosoh Corporation, Mw = 2,000), bisphenol A-bis (hydroxy). 150 parts by mass of ethyl ether (BPE20T, manufactured by Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g), 50 parts by mass of N-methyldiethanolamine, 245 parts by mass of hexamethylene diisocyanate, 275 parts by mass of dicyclohexylmethane diisocyanate, and 800 parts by mass of methyl ethyl ketone. In addition, it was reacted at 75 ° C. for 4 hours to obtain a methyl ethyl ketone solution of a urethane prepolymer having a free isocyanate group content of 3.0% by mass with respect to the non-volatile content. This solution was cooled to 40 ° C., 48 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 15 containing a cationic polyurethane resin (A15) having a nonvolatile content of about 35% by mass.

(Production Example 16: Cationic polyurethane resin (A16))
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube was charged with 600 parts by mass of polycarbonate polyol (Nipporan 981R, manufactured by Tosoh Corporation, Mw = 2,000), bisphenol A-bis (hydroxy). Ethyl ether) (BPE20T, Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g) 50 parts by mass, N-methyldiethanolamine 175 parts by mass, hexamethylene diisocyanate 550 parts by mass, and methyl ethyl ketone 800 parts by mass were added at 75 ° C. for 4 hours. By reacting, a methyl ethyl ketone solution of urethane prepolymer having a free isocyanate group content of 3.0% by mass relative to the nonvolatile content was obtained. This solution was cooled to 40 ° C., 179 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 16 containing a cationic polyurethane resin (A16) having a nonvolatile content of about 35% by mass.

(Production Example 17: Cationic polyurethane resin (A17))
A four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube was charged with 1000 parts by mass of polycarbonate polyol (Kuraray Polyol C-3090, manufactured by Kuraray Co., Ltd., Mw = 3,000), bisphenol A- 20 parts by mass of bis (hydroxyethyl ether) (BPE20T, manufactured by Sanyo Chemical Co., Ltd., hydroxy value 346 mg / g), 30 parts by mass of N-methyldiethanolamine, 160 parts by mass of hexamethylene diisocyanate, and 800 parts by mass of methyl ethyl ketone were added at 75 ° C. For 4 hours to obtain a methyl ethyl ketone solution of a urethane prepolymer having a free isocyanate group content of 3.0% by mass relative to the nonvolatile content. This solution was cooled to 40 ° C., 30 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 17 containing a cationic polyurethane resin (A17) having a nonvolatile content of about 35% by mass.

(Production Example 18: Cationic polyurethane resin (A18))
In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen blowing tube, 600 parts by mass of polyethylene glycol (PEG 2000, manufactured by Sanyo Chemical Co., Ltd., Mw = 2,000), 30 parts by mass of N-methyldiethanolamine Part, 80 parts by mass of hexamethylene diisocyanate and 800 parts by mass of methyl ethyl ketone were added and reacted at 75 ° C. for 4 hours to obtain a methyl ethyl ketone solution of urethane prepolymer having a free isocyanate group content of 3.0% by mass with respect to the nonvolatile content. . This solution was cooled to 40 ° C., 30.2 parts by mass of dimethyl sulfate was added, and 2700 parts by mass of deionized water was gradually added to carry out emulsification dispersion. Thereafter, an aqueous solution in which 45 parts by mass of ethylenediamine was dissolved in 100 g of water was added, and stirring was continued for 1 hour. The solvent was removed at 50 ° C. under reduced pressure to obtain a polyurethane water dispersion 18 containing a cationic polyurethane resin (A18) having a nonvolatile content of about 35% by mass.

Table 2 shows the phosphoric acid compound (B) used, and Table 3 shows the trivalent chromium compound (C) used.

4). Preparation of coating materials In the combinations and proportions shown in Table 4, the cationic polyurethane resin (A), the phosphoric acid compound (B), and the trivalent chromium compound (C) were mixed in this order, and the solid content was determined with deionized water. A coating material was prepared by adjusting the concentration to 20% by mass. In addition, the content rate of a phosphoric acid compound (B) and a trivalent chromium compound (C) is the mass% with respect to solid content of cationic polyurethane resin (A) (in other words, cationic polyurethane resin (A) 100). The content (parts by mass) of each component with respect to parts by mass is intended).

In Table 4, “BV / AV” represents the ratio of the phosphoric acid compound (B) content ratio (% by mass) (BV) to the solid content of the cationic polyurethane resin (A) and the amine value.

5. Test plate production method The coating material of the present invention is applied onto each test material with a bar coater, heat-treated at the ultimate plate temperature shown in Table 5, a film is formed on each test material, and a test plate is produced. did. The coating amount in each example is as shown in Table 5, and the coating amount was adjusted by adjusting the concentration of the paint (diionized water dilution) and the bar coater.

6). Evaluation method (1) Appearance characteristics (film appearance)
The appearance of the obtained test plate was visually evaluated. ○ Above are practical levels.
◎ +: Almost the same as the plating appearance, and hardly changes even after the coating treatment ◎: Almost the same as the plating appearance, but there is a slight color tone unevenness depending on the viewing angle.
○: Almost the same as the plating appearance, but there is a slight color unevenness.
(Triangle | delta): There exists a site | part different from a plating external appearance, and the site | part is light white or yellow.
X: There are many parts different from the plating appearance, and clearly white or yellow.

(2) Rubbing resistance (solvent resistance)
The gauze was soaked with ethanol, the surface of the film of the obtained test plate was subjected to a rubbing test 20 times, and the surface was observed. Above Δ is a practical level.
◎ +: No change in appearance ◎: No change in appearance (no change when viewed from the front), slight change when viewed from the angle ○: Some change when viewed from the front △: Some change when viewed from the front )
×: Changed (almost completely peeled)

(3) Corrosion resistance Using the obtained test plate, a salt spray test was performed based on JIS-Z-2371, the white rust generation area ratio after 24 hours was determined and evaluated according to the following criteria. Above Δ is a practical level. However, for the examples and comparative examples using the test material M3, the white rust generation area ratio after 48 hours of the salt spray test was obtained and evaluated according to the following criteria.
◎ +: Less than 5% ◎: 5% or more and less than 10% ○ +: 10% or more and less than 20% ○: 20% or more and less than 30% Δ +: 30% or more and less than 40% Δ: 40% or more and less than 50% ×: 50% or more

(4) Phosphate treatability (application type phosphate treatability)
The test plate obtained was treated with Nippon Parkerizing Co., Ltd. phosphate treatment chemical Palbond L15C (A agent 250 g / L + B agent 250 g / L, 25 ° C., brushed), left for 5 minutes, and then brushed. The surface state of the part was observed, the gray discoloration area ratio of the brushed part was determined, and evaluated according to the following criteria. Note that the higher the gray discoloration area ratio, the part of the formed film is dissolved by the phosphate treatment, and the phosphate film is formed to exhibit a gray color tone. Above Δ is a practical level.
◎ +: 100%
◎: 95% or more and less than 100% ○: 85% or more and less than 95% Δ: 70% or more and less than 85% ×: less than 70%

(5) Top coat adhesion Adhesion of the melamine alkyd resin coating to a dry film thickness of 25 μm using a bar coater on the film of the obtained test plate, and baking at a furnace temperature of 130 ° C. for 20 minutes. A coating was produced. Next, 100 square grids with a width of 1 mm are applied to the coating film with a cutter, left in a thermostatic chamber at -20 ° C. for 5 hours or more, and immediately after removal from the thermostatic chamber, the grids are extruded by 7 mm. Eriksen processing was applied. A tape peeling test was performed on the processed parts, and the number of peeled grids was evaluated as follows. Above Δ is a practical level.
◎ +: No peeling ◎: Number of peeled 1 to less than 5 ○: Number of peeled 6 to less than 10 △: Number of peeled 11 to less than 20 ×: Number of peeled 20 or more

(6) Impact resistance A melamine alkyd resin coating was applied on the obtained test plate film using a bar coater to a dry film thickness of 25 μm, and baked at a furnace temperature of 130 ° C. for 20 minutes. A membrane was produced. Next, the test plate having the coating film is left in a constant temperature chamber at 40 ° C. for 5 hours or more, and immediately after taking out the test plate, using a DuPont impact tester, a 1 kg droop with a diameter of 1/2 inch is used. After dropping the weight with respect to the coating film from a height of 50 cm, the impact portion was peeled off with tape. The determination was made by determining the remaining area ratio of the coating film. Above Δ is a practical level.
◎ +: 100%
◎: 95% or more and less than 100% ○: 80% or more and less than 95% △: 50% or more and less than 80% ×: less than 50%

(7) Storage stability of paint When the paint used in each example and comparative example is allowed to stand in an atmosphere of 40 ° C, the storage stability is as follows in the period until gelation and precipitation occur. evaluated. Above Δ is a practical level.
◎ +: 3 months or more ◎: 2 months or more and less than 3 months ○: 1 month or more and less than 2 months △: 2 weeks or more and less than 1 month ×: less than 2 weeks

As shown in Table 6, it was confirmed that the desired effect was obtained by using the paint of the present invention.
In particular, it was confirmed from the comparison between Examples 2, 5, 12 and 21 and other examples that when the phosphate compound is used, the effect is more excellent (particularly, the phosphate treatment ability is excellent). .
Further, when the peak temperature (Tg2) of the loss tangent tan δ is within a predetermined range (−50 ° C. to −2 ° C.) by comparing Example 26 with other examples (for example, Example 25, etc.) It was confirmed that the property is superior.
Further, when the ratio ((BV) / (AV)) is within a predetermined range (0.1 to 9.5), the effect is more excellent than the comparison between Examples 7 to 8 and Examples 12 to 19. Was confirmed.
Further, from comparison between Example 20 and Examples 27 to 29, when the amine value (AV) is within a predetermined range (2 to 5 mgKOH / g), the effect is more excellent (particularly, the storage stability is excellent). confirmed.
Further, from comparison between Example 25 and Examples 30 to 32, it was confirmed that the use of the trivalent chromium compound (C) further improved the effect (particularly the corrosion resistance was excellent).

Claims (10)

1. A cationic polyurethane resin (A) having at least one cationic functional group selected from the group consisting of primary to tertiary amino groups and quaternary ammonium bases,
   The cationic polyurethane resin (A) has a polycarbonate structural unit and a bisphenol structural unit,
   The cationic polyurethane resin (A) has a temperature (Tg1) showing the maximum peak value of the loss elastic modulus E ″ in the range of −60 ° C. to −5 ° C.,
   A paint for hot dipped galvanized steel sheets, in which the loss tangent tan δ, which is the ratio of the loss elastic modulus E ″ and the storage elastic modulus E ′ of the cationic polyurethane resin (A), has one peak.
2. The paint for hot dipped galvanized steel sheets according to claim 1, wherein the peak temperature (Tg2) of the loss tangent tan δ is in the range of -50 ° C to -2 ° C.
3. The paint for hot dipped galvanized steel sheets according to claim 1 or 2, further comprising a phosphate compound (B).
4. The paint for hot dipped galvanized steel sheets according to claim 3, wherein the phosphoric acid compound (B) contains at least one selected from the group consisting of orthophosphoric acid, condensed phosphoric acid, and salts thereof.
5. The paint for hot dipped galvanized steel sheets according to any one of claims 1 to 4, wherein the cationic polyurethane resin (A) has an amine value (AV) of 2.0 to 5.0 mgKOH / g.
6. The ratio (% (BV) / (AV)) of the phosphoric acid compound (B) to the solid content of the cationic polyurethane resin (% by mass) (BV) and the amine value is 0.1 to 9. The paint for hot dipped galvanized steel sheets according to claim 5, which is 5.
7. The paint for hot dipped galvanized steel sheets according to any one of claims 1 to 6, further comprising a trivalent chromium compound (C).
8. A method for treating a soaked hot dip galvanized steel sheet, wherein the soaked hot dip galvanized steel sheet is treated with the paint for hot soaked hot dip galvanized steel sheet according to any one of claims 1 to 7.
9. The paint for hot dipped galvanized steel sheet according to any one of claims 1 to 7 is contacted with the hot dipped galvanized steel sheet, and the film disposed on the surface thereof. A method for producing a surface-treated soaked hot-dip galvanized steel sheet, which comprises:
10. A surface-treated hot-dip galvanized steel sheet obtained from the production method according to claim 9.