JP6767121B2 - Chromium-free alloyed hot-dip galvanized steel sheet and its manufacturing method - Google Patents

Description

In the present invention, a surface treatment layer containing no hexavalent chromium, which has a high environmental load, is formed on at least one surface of a metal plate. In addition to performances such as temporary rust prevention, lubricity, and adhesion, contradictory electricals are provided. Regarding chromium-free alloyed hot-dip zinc-plated steel sheet and its manufacturing method, which achieves both good electrodeposition coating property and good weldability, which are the characteristics, and has excellent corrosion resistance that surpasses the currently widely used zinc phosphate treatment. ..

Generally, as a technique for imparting corrosion resistance and fingerprint resistance to the surface of a metal material, which has excellent adhesion to the surface of the metal material, the surface of the metal material contains chromic acid, dichromic acid or a salt thereof as a main component. Known methods include a method of applying chromate treatment with a treatment liquid, a method of applying a phosphate treatment, a method of applying an organic resin film treatment, and the like, which are put into practical use. Among them, for automobile steel sheets, in addition to zinc phosphate treatment, zinc-based plated steel sheets that have been previously treated with an organic resin film have also been put into practical use.

Conventionally, as a rust-preventive steel sheet for automobiles, a rust-preventive coated steel sheet (gincrometal) in which a zinc powder-containing coating film is formed with a film thickness of 10 to 20 μm, as in Patent Document 1, has been used. However, in the zinc powder-containing coating film of this rust-preventive coated steel sheet, remarkable film peeling occurs during press molding, which accumulates on the mold and causes defects and press cracks, as well as a portion where the rust-preventive film has peeled off. There was a problem that the corrosion resistance of the steel was deteriorated.

Therefore, in recent years, European automobile manufacturers have already formed a chromate film on the surface of galvanized steel sheets with the aim of reducing or omitting auxiliary materials such as sealers and waxes, and further containing conductive metal powders such as zinc powder. In some cases, an organic coated steel sheet having a coating film of about 4 to 7 μm is used. However, the fact is that the need for chromate treatment containing hexavalent chromium, the peeling of the film during press working, and the problem of corrosion resistance after peeling have not been solved.

Recently, as rust-preventive steel sheets applied to automobiles and the like, for example, those shown in Patent Documents 2 to 4 have been proposed, and in Patent Document 5, organic resin and phosphorus are provided on the surface of a galvanized steel sheet. A rust-preventive steel sheet is shown in which a chemical conversion treatment mainly composed of an acid or a fluoride is performed and an organic coating film composed of an organic resin, a conductive pigment and a rust-preventive pigment is formed on the surface thereof. However, since the rust-preventive steel sheets of Patent Documents 2 to 4 are all subjected to chromate treatment or use hexavalent chromium-based rust-preventive pigments, there is a problem in terms of the environment. Further, although the rust-preventive steel sheet of Patent Document 5 is a chromium-free type, it still does not have sufficient corrosion resistance and weldability.

Special Publication No. 47-6882 JP-A-10-44307 Japanese Patent Application Laid-Open No. 9-276785 JP-A-10-043677 Japanese Unexamined Patent Publication No. 2005-288730

In the present invention, a surface treatment layer containing no hexavalent chromium, which has a high environmental load, is formed on at least one surface of a metal plate. In addition to performances such as temporary rust prevention, lubricity, and adhesion, contradictory electricals are provided. To provide a chromium-free alloyed hot-dip zinc-plated steel sheet that achieves both good electrodeposition coating properties and good weldability, which are the characteristics, and has excellent corrosion resistance that surpasses the currently widely used zinc phosphate treatment. The purpose.

In the present invention, a silane coupling agent (A) containing an amino group in the molecule and a silane coupling agent (B) containing a glycidyl group in the molecule are blended on at least one surface of the alloyed hot-dip zinc-plated steel sheet. A film-forming component (X) containing an organosilicon compound (C) having a cyclic siloxane bond in the structure obtained by reaction and a cationic polyurethane resin (D), phosphoric acid (J) and magnesium phosphate (K). It has a surface treatment layer (Z) containing an inhibitor component (Y) composed of
Among the components contained in the surface treatment layer (Z), the cationic polyurethane resin (D) has a maximum peak temperature (T1) of a loss elastic modulus E ″ of −50 ° C. to −15 ° C., and a storage elastic modulus E ′. Two or more dispersion peaks of loss positive tangent tan δ represented by the ratio of loss elastic modulus E ″ are not observed, and the dispersion peak temperature (T2) of the loss positive tangent is −50 ° C. to 0 ° C., and the film-forming component The solid content weight ratio of the cationic polyurethane resin (D) in (X) is 40% to 80%, and the solid content weight ratio C / D of the organic silicon compound (C) and the cationic polyurethane resin (D) is 0. A chrome-free alloyed hot-dip zinc-plated steel plate characterized by having a ratio of .25 to 1.5.
Further, the solid content weight of phosphorus derived from the phosphoric acid (J) and magnesium phosphate (K) may be 0.1 to 12.0% of the total weight of the surface treatment layer (Z).
Further, the surface treatment layer (Z) formed on the chromium-free alloyed hot-dip galvanized steel sheet may have a film amount of 0.5 to 5.0 g / m ² .
Further, the surface treatment layer (Z) contains at least one functional particle (E) selected from the group consisting of extender pigments, rust preventive pigments and conductive pigments having an average particle diameter of 0.05 μm to 10 μm. However, the amount of adhesion per type of the functional particles (E) may be 30 mg / m ² to 2000 mg / m ² .
Further, the functional particles (E) are obtained from fine particles obtained by subjecting the surface of the fine particles to a functional surface treatment with one of the metal phosphate fine particles, carbon black fine particles, silica and these fine particles as the nucleus. It may be at least one selected from the group.
Further, in the present invention, a chromium-free alloyed hot-dip galvanized iron having the surface treatment layer is applied in a step of applying an aqueous surface treatment agent containing a component contained in the surface treatment layer and drying at an ultimate temperature of 50 to 250 ° C. This is a method for manufacturing a plated steel sheet.

The chrome-free alloyed hot-dip galvanized steel sheet of the present invention achieves both good electrodeposition coating property and good weldability, which are contradictory electrical characteristics, in addition to performances such as temporary rust prevention, lubricity, and adhesion. Moreover, it has excellent corrosion resistance that surpasses the currently widely used zinc phosphate treatment.

It is a perspective view which shows the four-sheet box used when evaluating the turnability with painting. It is explanatory drawing which shows the evaluation method of the turnability with painting. It is another explanatory drawing which shows the evaluation method of the turnability with a coating. It is a chart of loss tangent tan δ / temperature of D3 (1 dispersion peak) and D11 (2 dispersion peak).

The present invention will be described in detail in the following order.
・ Chrome-free alloyed hot-dip galvanized steel sheet (each component, composition, adhesion amount)
・ Manufacturing method of chromium-free alloyed hot-dip galvanized steel sheet ・ Applications of chromium-free alloyed hot-dip galvanized steel sheet

≪Chromium-free alloyed hot-dip galvanized steel sheet≫
In the present invention, a silane coupling agent (A) containing an amino group in the molecule and a silane coupling agent (B) containing a glycidyl group in the molecule are blended on at least one surface of the alloyed hot-dip zinc-plated steel sheet. A film-forming component (X) containing an organosilicon compound (C) having a cyclic siloxane bond in the structure obtained by reaction and a cationic polyurethane resin (D), phosphoric acid (J), and magnesium phosphate (K). It has an inhibitor component (Y) containing and a surface treatment layer (Z) containing
Among the components contained in the surface treatment layer (Z), the cationic polyurethane resin (D) has a maximum peak temperature (T1) of a loss elastic modulus E ″ of −50 ° C. to −15 ° C., and a storage elastic modulus E ′. Two or more dispersion peaks of loss positive tangent tan δ represented by the ratio of loss elastic modulus E ″ are not observed, and the dispersion peak temperature (T2) of the loss positive tangent is −50 ° C. to 0 ° C., and the film-forming component The solid content weight ratio of the cationic polyurethane resin (D) in (X) is 40% to 80%, and the solid content weight ratio C / D of the organic silicon compound (C) and the cationic polyurethane resin (D) is 0. A chrome-free alloyed hot-dip zinc-plated steel plate characterized by having a ratio of .25 to 1.5. Hereinafter, each component and composition constituting the surface treatment layer (Z) will be described in detail.

<Each ingredient>
{Film formation component (X)}
(Organosilicon compound (C))
One essential component of the film-forming component (X) is an organosilicon compound (C). The organosilicon compound (C) is obtained by blending a silane coupling agent (A) containing an amino group in the molecule and a silane coupling agent (B) containing a glycidyl group in the molecule and reacting them to obtain a structure. It has a cyclic siloxane bond inside.

First, the silane coupling agent (A) and the silane coupling agent (B), which are one raw material of the organosilicon compound (C), will be described. First, the silane coupling agent (A) is not particularly limited as long as it has at least one amino group in the molecule, and examples thereof include 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane. Can be done. Next, the silane coupling agent (B) is not particularly limited as long as it has at least one glycidyl group in the molecule, but 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane. Etc. can be exemplified.

Preferably, the organosilicon compound (C) is a silane coupling agent (A) containing an amino group in the molecule and a silane coupling agent (B) containing a glycidyl group in the molecule in terms of solid content weight ratio [(A). ) / (B)] is a compound obtained by blending and reacting at a ratio of 0.5 to 1.7. When the solid content weight ratio [(A) / (B)] of the silane coupling agent (A) and (B) is less than 0.5, the hydrophobicity and self-crosslinking property of the organosilicon compound (C) become high. Therefore, the stability of the aqueous treatment agent for forming the surface treatment layer (Z) is lowered, which is not preferable. When the solid content weight ratio [(A) / (B)] exceeds 1.7, the hydrophilicity and cationicity of the organosilicon compound (C) become too high, and the water resistance and water resistance of the obtained surface treatment layer (Z) and It is not preferable because it reduces corrosion resistance. The solid content weight ratio [(A) / (B)] is more preferably 0.6 to 1.5, and most preferably 0.7 to 1.3.

In addition, the organosilicon compound (C) has a cyclic siloxane bond in its structure. The "cyclic siloxane bond" contained in the structure of the organosilicon compound (C) has a structure in which Si—O—Si bonds are continuous, and is composed only of Si and O bonds, and Si—O is repeated. Refers to an annular structure with a number of 3-8. The "chain siloxane bond" has a structure in which Si—O—Si bonds are continuous, and is composed only of Si and O bonds, and the number of repetitions of Si—O is between 3 and 8 and is cyclic. Refers to something that does not have a structure. The organosilicon compound (C) according to the present invention is essential to have a cyclic siloxane bond in its structure. If the structure does not have a cyclic siloxane bond, it is presumed that the barrier property of the film-forming component is lowered and the corrosion resistance is lowered.

The abundance ratio of the cyclic siloxane structure is the ratio of the absorbance (c1) of 1090-1100 cm ^-1 showing a cyclic siloxane bond by the FT-IR reflection method to the absorbance (c2) of 1030-1040 cm ^-1 showing a chain siloxane bond. c1 / c2] is most preferably 1.0 to 2.0. When the ratio [c1 / c1] is 1.0 to 2.0, both the barrier property due to the cyclic structure and the flexibility due to the chain structure can be provided in a well-balanced manner, and all the performances such as corrosion resistance and film adhesion can be obtained. improves. Further, a tougher and denser film is formed by the entanglement of the resin molecule and the cyclic siloxane bond portion.

The organosilicon compound (C) is preferably contained in the molecule by the following general formula [1].
(Equation 1)

(In the formula, R ₁ , R ₂ and R ₃ independently represent an alkoxy group or a hydroxyl group, and at least one represents an alkoxy group), and two or more functional groups (a) represented by the hydroxyl group ( It contains at least one hydrophilic functional group (b) selected from an amino group (which is separate from the one contained in the functional group (a)).

When the number of functional groups (a) is two or more in the molecule of the organosilicon compound (C), the adhesion between the surface of the metal plate and the surface treatment layer (Z) and the self-crosslinking property of the organosilicon compound (C) are improved. It is improved and the film forming ability is enhanced. The carbon number of the alkoxy group in the definition of R ₁ , R ₂ and R ₃ of the functional group (a) is not particularly limited, but is preferably 1 to 6, more preferably 1 to 4, or 1 or. It is most preferably 2.

When one or more functional groups (b) are present in the molecule of the organosilicon compound (C), the adhesion between the surface treatment layer (Z) and the upper coating film such as electrodeposition coating is improved, and the surface treatment layer ( The stability of the organosilicon compound (C) in the aqueous treatment agent for forming Z) is improved.

The abundance ratio of the cyclic siloxane structure of the organosilicon compound (C) and the functional groups (a) and (b) are, for example, a Fourier transform infrared spectrophotometer IRPrestique-21 manufactured by Shimadzu Corporation and nuclear magnetic resonance manufactured by JEOL Ltd. It can be measured by a resonator (NMR) JNM-ECX series or the like.

The organosilicon compound (C) also preferably has a weight average molecular weight of 1000 to 10000. The weight average molecular weight referred to here is not particularly limited, but may be measured by either direct measurement by the TOF-MS method or conversion measurement by the chromatography method. Preferably, the weight average molecular weight is measured using GFC (Gel Filteration Chromatography) and ethylene glycol as the molecular weight reference material. When the weight average molecular weight obtained by this method is less than 1000, the water solubility of the organosilicon compound (C) becomes high, so that the water resistance and corrosion resistance of the formed surface treatment layer (Z) tend to decrease. .. On the other hand, when the weight average molecular weight exceeds 10,000, the solubility or dispersibility of the organosilicon compound (C) in water tends to decrease, and the stability of the aqueous treatment agent for forming the surface treatment layer (Z) May be impaired. The weight average molecular weight of the organosilicon compound (C) is preferably 1300 to 6000.

The method for producing the organosilicon compound (C) is not particularly limited, but as an example, the silane coupling agent (A) and the silane coupling agent (B) are sequentially added to water having a pH adjusted to 4. , A method of stirring for a predetermined time can be mentioned. Since the aqueous solution generates heat when the silane coupling agent (A) is added, the organosilicon compound (C) is produced by cooling the water in advance, continuing to cool it for a predetermined time after the addition, and producing it in a certain temperature range. ), The abundance ratio of the cyclic siloxane bond and the chain siloxane bond can be controlled.

(Cationic Polyurethane Resin (D))
One essential component of the film-forming component (X) is the cationic polyurethane resin (D). The "cationism" in the cationic polyurethane resin (D) blended in the aqueous surface treatment agent for forming the surface treatment layer (Z) of the present invention is expressed in the following general formulas (I) to (IV) in the molecular structure. It means having the indicated cationic functional group. The amount of the cationic functional group may be any amount as long as the cationic polyurethane resin (D) can be stably present in the metal surface treatment agent of the present invention in a dissolved or dispersed state.

In the formulas of the groups represented by the general formulas (I) to (IV), R ¹ , R ² , R ³ , R ⁶ and R ⁷ are independent hydrogen atoms and have 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms. Represents an alkyl group of a linear or branched chain or a hydroxyalkyl group of a linear or branched chain having 1 to 10 carbon atoms, preferably 1 to 6, and R ⁴ and R ⁵ preferably have 2 to 10 carbon atoms independently of each other. Represents 2 to 6 linear or branched alkylene groups, and A ⁻ and B ⁻ represent hydrogen or acid ions.

In the general formulas (I) to (IV), the alkyl groups having 1 to 10 carbon atoms represented by R ¹ , R ² , R ³ , R ⁶ and R ⁷ include methyl group, ethyl group and propyl group. Isopropyl group, butyl group, isobutyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group and the like, and hydroxyalkyl groups having 1 to 10 carbon atoms include hydroxymethyl group and 2-hydroxyethyl group. , 1-Hydroxyethyl group, 3-Hydroxypropyl group, 4-Hydroxybutyl group, 5-Hydroxypentyl group, 6-Hydroxyhexyl group, 7-Hydroxyheptyl group, 8-hydroxyoctyl group, 9-hydroxynonyl group, 10 -Hydroxydecyl group and the like can be mentioned.

Further, in the general formulas (III) and (IV), the alkylene groups having 2 to 10 carbon atoms represented by R ⁴ and R ⁵ include an ethylene group, a propylene group, a trimethylene group, a tetramethylene group, a pentamethylene group and a hexa. Examples thereof include a methylene group, an octamethylene group, a 2-ethyl-hexylene group and a decamethylene group.

Further, in the general formulas (II) and (IV), the acid ions represented by A ⁻ and B ⁻ include halogen ions (chlorine ion, bromine ion, fluorine ion, etc.), sulfate ion, nitrate ion, phosphate ion and the like. Examples thereof include organic acid ions such as inorganic acid ions, acetate ions and formate ions. The cationic polyurethane resin (D) used in the present invention is a water-soluble resin or an aqueous emulsion form.

The cationic polyurethane resin (D) is one of the polyols used in a urethane resin which is a polycondensation polymer of a polyol such as a polyether polyol, a polyester polyol, or a polycarbonate polyol and an aliphatic, alicyclic or aromatic polyisocyanate. As a part, it is obtained by using a polyol having a (substituted) amino group (for example, N, N-dimethylaminodimethylol propane, etc.). Examples of the polyether polyol include polyethylene glycol such as diethylene glycol and triethylene glycol, and polyethylene / propylene glycol. Examples of the polyester polyol 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, trimethylol propane, and the like. Polyester polyols having a hydroxyl group at the terminal obtained by polycondensation of polyols such as glycerin with polybasic acids such as succinic acid, glutaric acid, adipic acid, sebatic acid, phthalic acid, isophthalic acid, terephthalic acid and trimellitic acid Illustrated. Examples of the aliphatic, alicyclic or aromatic polyisocyanate include tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, dicyclohexylmethane diisocyanate, cyclohexylene diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

Further, the maximum peak temperature (T1) of the loss elastic modulus E "of the cationic polyurethane resin (D) is -50 ° C to -15 ° C. Here, the maximum peak temperature (T1) of the loss elastic modulus E". Refers to the temperature at which the loss elastic modulus (E ″) reaches its peak at a frequency of 10 Hz and a heating rate of 20 ° C./min using a dynamic viscoelasticity measuring device (Rheogel-E4000, manufactured by UBM). When is in this range, the flowability of the resin is improved, and a phenomenon occurs in which the film thickness of the surface treatment layer (Z) is different between the convex portion and the concave portion of the surface of the alloyed hot-dip zinc-plated steel plate, and hydrogen during electrodeposition coating occurs. Since it is the starting point of occurrence, electrodeposition coating property, particularly circling property is improved. A more preferable range of T1 is −45 ° C. to −20 ° C.

Further, in the cationic polyurethane resin (D), two or more dispersion peaks of the loss tangent tan δ represented by the ratio of the storage elastic modulus E'and the loss tangent E'are not observed, and the dispersion peak of the loss tangent is not observed. The temperature (T2) is preferably −50 ° C. to 0 ° C., where the dispersion peak temperature (T2) at the tangent loss is defined by the dynamic viscoelastic modulus measuring device, having a frequency of 10 Hz and a heating rate of 20 ° C./. The storage elastic modulus (E') and the loss elastic modulus (E ") in minutes are measured, and it means the peak temperature of the loss tangent (tan δ). Further, the definition that the dispersion peak temperature of the loss tangent tan δ is one in the above range (T2) means that there are no two or more tan δ changes of 0.05 or more with respect to the baseline. When the dispersion peak temperature (T2) of the loss tangent tan δ is one in the above range, the sea-island structure does not appear in the film formed, and the resistance of the entire film is reduced by eliminating partial high resistance sites. Therefore, the weldability is significantly improved. In addition, when the solid content weight ratio of the cationic polyurethane resin (D) in the film-forming component (X) is 40% to 80%, the tan δ peak temperature of the film-forming component (X) is the resin (D). ) Depends on it. Therefore, the weldability and electrodeposition coating property are improved without losing the physical properties suitable for the surface treatment layer (Z) of the present invention. A more preferable range of T2 is −40 ° C. to −10 ° C.

{Inhibitor component (Y)}
The surface-treated layer (Z) of the present invention contains phosphoric acid (J) and magnesium phosphate (K) as inhibitor components. As phosphoric acid as a counter anion of phosphoric acid (J) and magnesium phosphate (K), for example, orthophosphoric acid, metaphosphoric acid, polyphosphoric acid (particularly orthophosphoric acid multimers such as pyrophosphoric acid and triphosphoric acid) Etc.) and so on.

<Mixing>
Next, the composition of the surface treatment layer (Z) will be described in detail.

{Film formation component (X)}
(Amount of film-forming component (X))
The amount of the film-forming component (X) in the surface treatment layer is preferably 50% to 99.7% in terms of solid content weight ratio.

(Amount of cationic polyurethane resin (D))
The ratio of the cationic polyurethane resin (D) in the film-forming component (X) is 40% to 80% by weight of the solid content, preferably 40 to 70%. When the ratio of the cationic polyurethane resin (D) in the film-forming component (D) is in this range, the organosilicon compound which is the other essential component is not lost without losing the excellent properties of the cationic polyurethane resin (D). (C) improves the adhesion to the material, and the effect of improving the film density due to the entanglement effect improves the corrosion resistance.

(C / D ratio)
The solid content-weight ratio C / D of the organosilicon compound (C) and the cationic polyurethane resin (D) is 0.25 to 1.5, and preferably 0.4 to 1.5. When the solid content weight ratio C / D is in this range, adhesion is imparted by the organosilicon compound (C), corrosion resistance is imparted by increasing the density of the film, and an appropriate cationic polyurethane resin (D) is blended. The characteristics of the cationic polyurethane resin (D) of the present invention are exhibited, and a film having excellent electrodeposition coating properties and weldability can be obtained.

{Inhibitor component (Y)}
(Amount of inhibitor (Y))
In the content ratio of phosphoric acid (J) and magnesium phosphate (K) contained in the surface treatment layer (Z) of the present invention, the total phosphorus derived from the phosphoric acid (J) and the magnesium phosphate (K). The solid content weight of is preferably 0.1 to 12% of the total surface treatment layer (Z). Further, 0.11 to 9.6% is more preferable, and 0.7 to 6.4% is most preferable. When the content ratio is in this range, the corrosion resistance is improved. If it is less than 0.1%, the addition effect is not exhibited, and if it is more than 12.0%, the water resistance tends to decrease and the corrosion resistance tends to decrease.

(J / K ratio)
The solid content weight ratio J / K of phosphoric acid (J) and magnesium phosphate (K) is preferably 0.2 to 1.5. When the solid content weight ratio J / K is in this range, it is possible to suppress a decrease in water resistance due to phosphoric acid and a decrease in stability of the treatment liquid due to magnesium phosphate, so that the effect of imparting corrosion resistance can be sufficiently obtained. ..

{Functional particles (E)}
The surface treatment layer (Z) contains at least one functional particle (E) selected from the group consisting of extender pigments, rust preventive pigments and conductive pigments having an average particle diameter of 0.05 μm to 10 μm. Is preferable. Here, the average particle size of the pigment is the result of measurement with a laser diffraction / scattering type particle size distribution measuring device (model name: LA-920, manufactured by Horiba Seisakusho Co., Ltd.), and the particle size of 5 measured particles. The average value was taken as the average particle size. Examples of such extender pigments include water-dispersible silica, fumed silica, calcium carbonate and the like. By containing such an extender pigment, the film strength is increased and the workability is improved, but the resistance of the film is increased and the weldability tends to be decreased. Examples of such rust preventive pigments include (1) phosphoric acid-based rust preventive pigments such as zirconium phosphate, zinc phosphate, iron phosphate, and aluminum phosphate, and (2) calcium molybdate, aluminum molybdate, and barium molybdate. Examples thereof include molybdic acid-based rust preventive pigments such as (3) vanadium-based rust preventive pigments such as vanadium oxide. By containing such a rust preventive pigment, the corrosion resistance of the scratched portion after painting is improved, but the resistance of the film tends to increase and the weldability tends to decrease. On the other hand, examples of the conductive pigment include carbon black fine particles and the like. By adding such a conductive pigment, the resistance of the film is lowered and the weldability is improved, but the corrosion resistance may be lowered.

Further, the functional particles (E) are obtained from fine particles obtained by subjecting the surface of the fine particles to a functional surface treatment with one of the metal phosphate fine particles, carbon black fine particles, silica and these fine particles as the nucleus. It is preferable that it is at least one selected from the group. The above-mentioned effects are most effectively exhibited as the metal phosphate fine particles as a rust preventive pigment, the carbon black fine particles as a conductive pigment, and silica as an extender pigment. Further, the ones in which the shape of each particle is optimized is for the purpose of suppressing the harmful effects of each particle, and the one in which the shape is optimized is more preferable. Examples of such shape optimization include chain formation treatment and the like. Here, the chain shape means a state in which the conductive pigment of the spherical particles and the conductive pigment of the rod-shaped particles are connected, and the chain formation process means a process of forming a chain.

<Adhesion amount>
(Amount of film)
The surface-treated layer (Z) formed on the chromium-free alloyed hot-dip galvanized steel sheet preferably has a film amount of 0.5 to 5.0 g / m ² . When the film weight of the surface treatment layer (Z) is in this range, all of corrosion resistance, weldability, and electrodeposition coating property can be satisfied, but it may be 1.0 to 3.0 g / m ^2. It is more preferable because these performances are the best.

(Adhesion amount of functional particles (E))
Since the functional particles (E) have an adverse effect due to addition, the adhered weight of the functional particles (E) is preferably 30 mg / m ² to 2000 mg / m ² , and 100 mg / m ² to 500 mg / m. and more preferably ^2. When the adhered weight of the functional pigment (E) is in this range, the effects of each are exhibited, and the harmful effects are tolerable.

≪Manufacturing method of chrome-free alloyed hot-dip galvanized steel sheet≫
In the chromium-free hot-dip galvanized steel sheet of the present invention, an aqueous surface treatment agent containing a component contained in the surface treatment layer is applied to the surface of the alloyed hot-dip galvanized steel sheet and dried at an ultimate temperature of 50 to 250 ° C. It can be manufactured in the process. Here, the alloyed hot-dip galvanized steel sheet referred to in the present invention means that an iron plate is dipped in a hot-dip zinc bath, the texture is adjusted with an air wiper or the like, and then the iron plate is heated in a furnace to form iron in the plated layer. A steel sheet that is alloyed with zinc to improve the corrosion resistance of the plating layer itself. The coating method is not particularly limited, and generally known coating methods such as roll coating, curtain flow coating, air spray, airless spray, and immersion can be used. It can be formed by drying at an ultimate temperature of 50 to 250 ° C. If the ultimate temperature for drying is less than 50 ° C., the solvent of the base treatment agent does not completely volatilize, which is not preferable. If the temperature exceeds 250 ° C., a part of the organic chains of the film formed by the surface treatment agent is decomposed, which is not preferable. The ultimate temperature is more preferably 70 ° C. to 150 ° C., and most preferably 100 ° C. to 140 ° C.

As the surface treatment agent used in the present invention, a leveling agent, a water-soluble solvent, a metal stabilizer, an etching inhibitor, etc. for improving coatability can be used as long as the effects of the present invention are not impaired. Is. Examples of the leveling agent include polyethylene oxide or polypropylene oxide adduct, acetylene glycol compound and the like as a nonionic or cationic surfactant. Examples of the water-soluble solvent include alcohols such as ethanol, isopropyl alcohol, t-butyl alcohol and propylene glycol, cellosolves such as ethylene glycol monobutyl ether and ethylene glycol monoethyl ether, esters such as ethyl acetate and butyl acetate, and acetone. Ketones such as methyl ethyl ketone and methyl isobutyl ketone can be mentioned. Examples of the metal stabilizer include chelate compounds such as EDTA and DTPA. Examples of the etching inhibitor include amine compounds such as ethylenediamine, triethylenetetramine, guanidine and pyrimidine. In particular, those having two or more amino groups in one molecule are also effective as a metal stabilizer and are more preferable. As the galvanized steel sheet used in the present invention, it is preferable to use an alloyed hot-dip galvanized steel sheet having excellent workability and rust prevention ability.

≪Applications of chrome-free alloyed hot-dip galvanized steel sheets≫
The chromium-free alloyed hot-dip galvanized steel sheet having the surface treatment layer of the present invention is useful for applications such as cationic electrodeposition coating and welding.

Next, the present invention will be further described with reference to Examples. However, the present invention is not limited to the following examples.

An alloyed hot-dip galvanized steel sheet (with a basis weight of 45 g / m ² ) was used in the experiment. A mild steel plate having a thickness of 0.5 mm was used as the base material of the plated metal plate. The alloyed hot-dip galvanized steel sheet is spray-treated with fine cleaner 4336 (manufactured by Nippon Parkering Co., Ltd.), which is a silicate-based alkaline degreasing agent, at a concentration of 20 g / L and a temperature of 60 ° C. for 2 minutes, and then sprayed with pure water for 30 seconds. The one that was washed with water and then dried was used.

Table 1 shows the organosilicon compound (C) used. The organosilicon compound (C) was prepared by sequentially adding the silane coupling agents shown in Table 1 to ion-exchanged water adjusted to pH 4 with acetic acid in the combinations and blending ratios described, and at a predetermined temperature (at the time of production). The starting temperature and the maximum temperature are also described), and the mixture was stirred to obtain an aqueous solution of an organosilicon compound having a solid content of 20%. The average molecular weight of the obtained organosilicon compound, and the absorbance (c1) of 1090-1100 cm- ¹ showing a cyclic siloxane bond by the FT-IR reflection method and the absorbance (c2) of 1030-1040 cm- ¹ showing a chain siloxane bond. The ratio [c1 / c2] of is shown in Table 1. [C1 / c2] was controlled by the reaction temperature when the silane coupling agent was reacted. By lowering the maximum temperature during production, the abundance ratio of c1 / c2, that is, the cyclic siloxane bond becomes high. The maximum manufacturing temperature can be controlled by the manufacturing start temperature.

Table 2 shows the details of the commercially available cationic polyurethane resin (D) used. The loss elastic modulus (E ") and loss tangent tan δ of the cationic polyurethane resin (D) are determined by using a dynamic viscoelasticity measuring device (Rheogel-E4000, manufactured by UBM) (filming conditions), a frequency of 10 Hz, and a temperature rise rate of 20. Calculated using ° C./min. The phosphoric acid compound (J) used in Table 3 is shown in the functional pigment (E) used in Table 4. Here, FIG. 4 shows D3 (1 dispersion peak). It is a chart of loss tangent tan δ / temperature of D11 (two dispersion peaks).

Tables 5 and 6 show the composition of the surface-treated layer (Z) of the chromium-free alloyed hot-dip galvanized steel sheet of the present invention and the composition of the comparative surface-treated layer not included in the scope of the present invention prepared as a comparison. Note that E1 and E7 in Table 4 are surface treatments according to WO2010 / 07072. Further, E6 in Table 4 is a surface treatment according to Special Table 2009-503182.

Table 7 shows the combination of the alloyed hot-dip galvanized steel sheet and the surface-treated layer (Z) or the comparative surface-treated layer, the film weight, and the temperature reached during baking after coating. The amount of the pigment adhered from G40 to G48 is 300 mg / m ² , G51 and G54 are 100 mg / m ² , G52 and G55 are 300 mg / m ² , and G53 and G56 are 1000 mg / m ² .

Evaluation test <adhesion>
The portion cut into a 1 mm grid was extruded by 7 mm with an Eriksen tester, and then the tape was peeled off, and the adhesion was evaluated by the remaining number ratio (remaining number / cut number: 100).
<Evaluation criteria>
◎ = 100%
○ = less than 20% 95% or more △ = 90% or more, less than 95% × = less than 90%

<Workability>
Cut the test piece to a size of 30 mm x 300 mm, perform a draw bead test (bead tip 1 mmR, load 500 kgf, bead height 4 mm, die shoulder 1 mmR, temperature 30 ° C.), observe the state of scratches on the sliding part, and observe the following. It was evaluated according to the criteria of.
◎ = No scratches ○ = Some scratches △ = Full surface scratches × = Break

<Weldability>
Using a CF type Cr-Cu electrode with a tip diameter of 5 mm and R40, a continuous spot welding test was conducted with a pressing force of 1.96 kN, a welding current of 8 kA, and an energization time of 12 cycles / 50 Hz, and the nugget diameter was 3√t (nugget diameter). The number of hit points immediately before cutting (t is the plate thickness) was obtained. The superiority and inferiority of spot weldability was evaluated using the following evaluation points.
Evaluation ◎: Number of hit points is 3000 points or more ○: 200 points or more and less than 3000 points △: Less than 200 points ×: Nugget is not generated and no point can be welded

<Electrodeposition coating property>
The test material is cut into 70 mm x 150 mm and subjected to alkaline degreasing (Nihon Parkerizing, FC-E2001 at 40 ° C for 3 minutes) and chemical conversion treatment (Nihon Parkerizing, PB-SX35 at 40 ° C for 3 minutes). Then, four of them were prepared, and three of them were formed with circular holes having a diameter of 8 mm. The position of the hole is the center in the short side direction of the metal plate, 50 mm in the vertical direction from one short side in the long side direction (the shortest distance between the center of the hole and one short side is 50 mm), and vertical from the other short side. The position was set to 100 mm in the direction. Then, using these four metal plates and three vinyl chloride plates, the four-sheet box shown in FIG. 1 was formed. In FIG. 1, the four metal plates 12, 13, 14, and 15 are parallel, the clearances between them are all 20 mm, and the metal plates 12, 13, and 14 have holes 10, and the metal plate 15 Has no holes. Here, the surface of the metal plate 12 opposite to the metal plate 13 was designated as the A surface. Further, the surface of the metal plate 15 on the side of the metal plate 14 was designated as the G surface.

Then, as shown in FIG. 1, each of the two vinyl chloride plates (21, 22) is adhered with an adhesive tape so as to be in contact with all the long sides of the four metal plates, and further to all of one short side. One vinyl chloride plate (23) was adhered with an adhesive tape so as to be in contact with each other. In this way, the four-sheet box 1 was formed. This four-sheet box corresponds to the "metal material having a bag structure" in the present invention.

Next, the four-box box 1 and the counter electrode 2 were arranged as shown in FIGS. 2 and 3. That is, the four boxes were arranged so that the metal plate 12 having the hole 10 formed on the side close to the counter electrode 2 was placed. Then, wiring was performed so as to short-circuit all four metal plates. FIG. 2 shows a cross section at the center of the metal plate in the short side direction, and FIG. 3 is a perspective view. Note that FIG. 3 does not show vinyl chloride plates (21, 22, 23). As the counter electrode 2, a 70 × 150 × 0.5 mm stainless steel plate (SUS304) having one side (the side opposite to the four-sheet box side) sealed with insulating tape was used. Then, the liquid level of the paint (“GT-10HT” manufactured by Kansai Paint Co., Ltd.) was controlled to a position where the metal plate and the counter electrode were immersed by 90 mm. The temperature of the paint was maintained at 28 ° C. and the paint was stirred with a stirrer.

In such a state, the coating film was electrolytically deposited on the surface of the metal plate of the four-sheet box by the cathode electrolysis method using the counter electrode as the anode. As a specific electrolysis condition, a rectifier was used, and cathode electrolysis was performed at a predetermined voltage for 180 seconds. The voltage was adjusted so that the film thickness of the coating film on the A side of the four-sheet box was 20 μm. Then, after electrolysis, each metal plate was washed with water and then baked at 170 ° C. for 20 minutes to form a coating film. Then, the film thickness of the coating film formed on the A surface and the G surface was measured using an electromagnetic film thickness meter, G / A was obtained, and the film thickness was evaluated according to the following criteria.
⊚ = G / A is 0.7 or more ○ = G / A is 0.5 to less than 0.7 Δ = G / A is 0.3 to less than 0.5 × = G / A is less than 0.3

<Corrosion resistance after electrodeposition>
The test material was cut into 70 mm x 150 mm, alkaline degreased (Nihon Parkerizing, FC-E2001 at 40 ° C for 3 minutes), chemical conversion treatment (Nihon Parkerizing, PB-SX35 at 40 ° C, 3 minutes), Cationic electrodeposition coating (GT-10HT manufactured by Kansai Paint Co., Ltd., film thickness 20 μm, baking at 170 ° C. for 20 minutes) was performed. After performing a salt warm water immersion test for 1000 hours, salt spraying was performed for 2 hours and drying was performed for 4 hours. A cycle corrosion test was carried out with a total of 8 hours of 2 hours of wetting as one cycle. The conditions of salt spraying were based on JIS-Z2371. The drying conditions were a temperature of 60 ° C. and a humidity of 30% RH or less, and the wet conditions were The temperature was 50 ° C. and the humidity was 95% RH or more. The area where red rust was generated was examined and evaluated according to the following criteria.
◎ = Red rust area less than 10% ○ = Red rust area less than 10 to 30% △ = Red rust area 30 to less than 50% × = Red rust area 50% or more

<Stability>
After storing the treatment agents of each Example and Comparative Example in an oven at 40 ° C. for a predetermined time, the corrosion resistance and electrodeposition coating property were evaluated using the treatment agents, and the treatment agents within 7 days at room temperature after the liquid preparation were used. Compared with the case, the maximum storage time in which no deterioration in performance was observed was evaluated by the following evaluation criteria.
◎ = No deterioration in performance is observed after a storage time of 2 months.
◯ = Performance deteriorated when the storage time was 2 months, but no deterioration was observed when the storage time was 1 month.
Δ = Performance deteriorated when the storage time was 1 month, but no deterioration was observed when the storage time was 14 days.
× = Performance (score) deteriorated after a storage time of 14 days.

Tables 8 to 15 show the evaluation test results of the examples and comparative examples shown in Table 7.

From Table 8, those containing no one of the organosilicon compound (C), the cationic polyurethane resin (D), and the phosphoric acid compound (J), which are essential components of the present invention (Comparative Example 1, Comparative Example 2, and Comparison, respectively). Example 3), the organosilicon compound (C) does not contain the two essential silane coupling agents (Comparative Example 4), and the organosilicon compound (C) does not contain a cyclic siloxane bond (Comparative Example 5). At least one of corrosion resistance, adhesion, processability, and electrodeposition coating property was inferior to that of Example 1, which is within the scope of the present invention.

From Table 9, regarding the physical properties of the cationic polyurethane resin, in Examples 1 to 9, in which both the peak temperature (T1) of the loss elastic modulus and the loss tangent tanδ dispersion peak temperature (T2) are in a preferable range, T1 is −50. Corrosion resistance and workability are excellent as compared with Comparative Example 6 below. Similarly, when compared with Comparative Example 7 in which two T2 appear, the weldability is lower than -50 in T1, and when compared with Comparative Example 8 in which two T2 appear, the workability and weldability are two, and T2 is -15. Compared with Comparative Example 9, the electrodeposition coating property is excellent, and the peak temperature (T1) of the loss elastic modulus of the cationic polyurethane resin (D) and the loss tangent tanδ dispersion peak temperature (T2) are within the range of the present invention. It can be seen that it has excellent performance. As described above, when T1 is within the preferable range of the present invention, the flowability of the resin is improved, and the film thickness of the surface treatment layer (Z) at the convex portion and the concave portion of the surface of the alloyed hot-dip galvanized steel sheet is increased. It is presumed that a different phenomenon occurs and it becomes the starting point of hydrogen generation during electrodeposition coating, so that the electrodeposition coating property, especially the turning property, is improved. It is presumed that if the number is one in the preferable range, the sea-island structure does not appear in the film formed, and the resistance of the entire film is reduced by eliminating the partially high resistance portion, so that the weldability is remarkably improved.

From Table 10, it can be seen that the cationic polyurethane resin (D) has excellent performance within the preferable range of the present invention in the blending ratio. When the blending ratio of the cationic polyurethane resin (D) is small, the electrodeposition coating property is slightly lowered, but the corrosion resistance is improved. On the contrary, when the blending ratio of the cationic polyurethane resin (D) is large, the corrosion resistance is slightly lowered. Comparative Example 10 in which this blending ratio is outside the range of the present invention has extremely poor adhesion and electrodeposition coating property, and Comparative Example 11 has extremely poor processability and electrodeposition coating property.

From Table 11, in phosphoric acid (J) and magnesium phosphate (K), the ratio J / K has an optimum range, and the most preferable is 0.6 / 2.6 to 1.9 / 1.3. It turns out that. Within this range, corrosion resistance and coating adhesion are particularly excellent, and treatment liquid stability is also good. Further, from Table 12, regarding the total amount of phosphoric acid (J) and magnesium phosphate (K), 1.6 to 6.4 is the best range, and when it is less than this, corrosion resistance, adhesion and processability are deteriorated. If it exceeds this range, the adhesion, processability, and treatment liquid stability deteriorate.

From Table 13, in the organosilicon compound (C) of the present invention, Example 1 in which the ratio of cyclic siloxane bonds (c1 / c2) is in a preferable range and Example 28 in the upper limit are Examples 24 and Comparative Examples in which the lower limit is set. Compared with 05, it is particularly excellent in corrosion resistance, and has good workability and adhesion. Further, Examples 33 to 35 in which the blending ratio A / B of the silane coupling agent (A) and the silane coupling agent (B) is within the preferable range of the present invention are below the optimum range with Examples 31 to 32. In comparison, the electrodeposition coating property and stability are excellent, and the corrosion resistance and electrodeposition coating property are excellent as compared with Examples 36 to 37 which exceed the optimum range. In addition, Example 1 having an optimum molecular weight has excellent corrosion resistance as compared with Example 38, which is the lower limit, and has excellent adhesion and stability as compared with Example 39, which has an upper limit.

From Table 14, in the functional pigments added to the surface treatment layer (Z) of the present invention, Examples 40 and 41 to which the extender pigments colloidal silica and vapor phase silica were added were compared with Example 1 in which no addition was added. As a result, the weldability and stability are slightly reduced, but the workability is improved. Further, in Examples 44 and 45 to which the conductive pigment carbon black was added, the adhesion was slightly lowered in both cases, but in Example 45 in which the shape of carbon black was optimized, the surface treatment was not performed. It has good performance without the decrease in corrosion resistance and the decrease in stability of the treatment agent seen in Example 44. When colloidal silica smaller than the optimum particle size of the present invention is used, the effect of improving workability confirmed in Example 40 is not observed. Further, in Example 47 using zinc phosphate larger than the optimum particle size of the present invention, all the performances are deteriorated.

From Table 15, it is possible that the surface-treated layer (Z) of the present invention has sufficient performance in all the evaluation items within the preferable range of the present invention in each film amount (Examples 49 to 56). Recognize.

Although preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modifications or modifications within the scope of the claims, and it is understood that they also naturally belong to the technical scope of the invention. Will be done.

1 4 box 2 counter electrode 10 holes 12, 13, 14, 15 metal plate 21, 22, 23 vinyl chloride plate

Claims (6)

From a film-forming component (X) containing an organosilicon compound (C) and a cationic polyurethane resin (D), phosphoric acid (J), and magnesium phosphate (K) on at least one surface of an alloyed hot-dip galvanized steel sheet. It has a surface treatment layer (Z) containing an inhibitor component (Y) and
Among the components contained in the surface treatment layer (Z), the cationic polyurethane resin (D) has a maximum peak temperature (T1) of a loss modulus E ″ of −50 ° C. to −15 ° C., and a storage modulus E ′. Two or more dispersion peaks of loss positive tangent tan δ represented by the ratio of loss elastic modulus E ″ are not observed, and the dispersion peak temperature (T2) of the loss positive tangent is −50 ° C. to 0 ° C., and the film-forming component The solid content weight ratio of the cationic polyurethane resin (D) in (X) is 40% to 80%, and the solid content weight ratio C / D of the organic silicon compound (C) and the cationic polyurethane resin (D) is 0. .25 to 1.5,
The organosilicon compound (C) contains an amino group and a glycidyl group, has a cyclic siloxane bond in its structure, and has an absorbance (c1) of 1090-1100 cm- ¹ showing a cyclic siloxane bond by the FT-IR reflection method. The ratio [c1 / c2] of the absorbance (c2) of 1030 to 1040 cm ^-1 showing a chain siloxane bond is 0.4 to 2.5.
The cationic polyurethane resin (D) is a polycondensation polymer of a polyol and a polyisocyanate.
The polyols are poly (hexamethylene carbonate) diol (molecular weight: 2000) and N-methyl-N, N diethanolamine.
The polyisocyanate is a chromium-free alloyed hot-dip galvanized steel sheet, which is HDI. The chromium-free product according to claim 1, wherein the solid content weight of phosphorus derived from phosphoric acid (J) and magnesium phosphate (K) is 0.1 to 12.0% of the total weight of the surface treatment layer (Z). Alloyed hot-dip galvanized steel sheet. The chromium-free alloyed hot-dip according to claim 1 or 2, wherein the surface-treated layer (Z) formed on the chromium-free hot-dip galvanized steel sheet has a film amount of 0.5 to 5.0 g / m ^2. Galvanized steel sheet. The surface treatment layer (Z) contains at least one functional particle (E) selected from the group consisting of an extender pigment having an average particle diameter of 0.05 μm to 10 μm, an anticorrosive pigment, and a conductive pigment. The chromium-free alloyed hot-dip galvanized steel sheet according to any one of claims 1 to 3, wherein the amount of adhesion per type of the functional particles (E) is 30 mg / m ² to 2000 mg / m ² . A group in which the functional particles (E) are composed of fine particles having a metal phosphate fine particle, carbon black fine particles, silica, and any one of these fine particles as a nucleus, and the surface of the fine particles is subjected to a functional surface treatment. The chrome-free alloyed hot-dip zinc-plated steel sheet according to claim 4 , which is at least one selected from. The surface treatment layer is provided in a step of applying an aqueous surface treatment agent containing a component contained in the surface treatment layer according to any one of claims 1 to 5 and drying at an ultimate temperature of 50 to 250 ° C. A method for producing a chromium-free alloyed hot-dip galvanized steel sheet.

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