JP2008007645A - Rust preventive pigment composition for galvanized steel plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-pollution type rust preventive pigment composition exhibiting rust preventive performances comparable to those of a rust preventive pigment containing a toxic heavy metal such as strontium chromate for a galvanized steel plate including a galvalume steel plate. <P>SOLUTION: The rust preventive pigment composition for the galvanized steel plate comprises three components of (a) amorphous magnesium silicate at 0.025-1.0 Mg/Si atomic ratio or powder prepared by coating a dense inorganic carrier particle with the amorphous magnesium silicate, (b) a sparing water-soluble condensed aluminum phosphate or a layer phosphate of a tetravalent metal and (c) magnesium oxide. The ratio of (a):(b) is (1:0.5) to (1:40) on the weight basis and the ratio of (a):(c) is (1:0.03) to (1:3) on the weight basis. The ratio of (b):(c) is (1:0.02) to (1:0.6) on the weight basis. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rust preventive pigment composition for a galvanized steel sheet, and more particularly to a rust preventive pigment composition blended in a precoated metal (PCM) primer made of a galvanized steel sheet.

  PCM made of a galvanized steel sheet is manufactured by applying a primer and then a topcoat layer after chemical conversion treatment of the plating layer. Since PCM is subjected to machining such as cutting and bending after coating, the steel plate and the galvanized layer are exposed on the cut surface. Therefore, white rust having no sacrificial electrode effect is generated in the galvanized layer on the cut surface, and finally rust is generated from there to the steel plate portion. Therefore, the rust preventive pigment used for the galvanized steel sheet is primarily required to have a rust preventive performance for the galvanized layer.

  For this purpose, strontium chromate rust preventive pigments have been used so far. However, since this pigment contains harmful hexavalent chromium, the development of a pollution-free rust preventive pigment is desired. It was.

  In order to satisfy the above demand, for example, JP 2000-273363 A discloses a rust preventive pigment for a galvanized steel sheet made of an amorphous hydrous magnesium silicate compound having an Mg / Si atomic ratio of 0.025 to 1.0. ing. Japanese Patent Laid-Open No. 2001-192869 discloses a rust preventive for a galvanized steel sheet in which a surface of a dense inorganic carrier is coated with an amorphous hydrous magnesium silicate compound having an Mg / Si atomic ratio of 0.025 to 1.0. Pigments are disclosed.

  However, these amorphous hydrous magnesium silicate compounds themselves have rust prevention performance comparable to that of strontium chromate, but the oil absorption is high, resulting in a bulky powder, which is difficult to handle when used as a paint. There was a problem.

  Further, the present applicant's Patent No. 3004486 discloses a water-insoluble phosphate compound selected from aluminum dihydrogen triphosphate, aluminum metaphosphate, layered titanium phosphate, layered zirconium phosphate or layered cerium phosphate; In addition, a rust preventive pigment composition for a galvanized steel sheet made of a magnesium compound selected from magnesium oxide, hydrous magnesium oxide, magnesium carbonate or magnesium borate is described.

  These known rust-preventing pigment compositions for galvanized steel sheets are one-component or two-component systems, but their rust-preventing performance, particularly galvanium steel plate, which is a 55% aluminum-plated aluminum zinc alloy-plated steel plate. There is a demand for the development of a pollution-free rust-preventing pigment composition with excellent quality.

  In order to satisfy this demand, the present invention provides a rust preventive pigment composition for galvanized steel sheet comprising the following three components.

(A) Amorphous magnesium silicate having an Mg / Si atomic ratio of 0.025 to 1.0, or a powder obtained by coating dense inorganic carrier particles with this amorphous magnesium silicate;
(B) a water-soluble condensed aluminum phosphate salt or a tetravalent metal layered phosphate, and (c) a magnesium oxide three-component;
(A) :( b) is 1: 0.5 to 1:40 on a weight basis, (a) :( c) is 1: 0.003 to 1: 3, (b) :( c) Is 1: 0.02 to 1: 0.6.

  By using the above three-component system, the rust prevention performance for a galvanized steel sheet including a galvalume steel sheet is improved as compared with a known one-component or two-component rust preventive pigment composition.

(A) Amorphous magnesium silicate compound having a component Mg / Si atomic ratio of 0.025 to 1.0, and a powder obtained by coating a dense inorganic carrier such as titanium dioxide with this compound is used for a galvanized steel sheet. The rust pigments are disclosed in Japanese Patent Application Laid-Open Nos. 2000-273363 and 2001-192869 of the present applicant. Therefore, although details of the production method thereof are not described here, amorphous magnesium silicate is an alkali metal silicate, a water-soluble magnesium salt, and an Mg / Si atomic ratio of 0.025 to 1.0 in an aqueous solution. It is obtained by reacting. The Mg / Si atomic ratio is preferably 0.025 to 0.8. The produced precipitate can be used as the component (a) of the rust preventive pigment composition of the present invention by filtering, washing with water, drying and grinding.

  When this amorphous hydrous magnesium silicate compound is coated on inorganic carrier particles, it can be produced by carrying out a synthesis reaction of amorphous hydrous magnesium silicate in an aqueous solution in the presence of carrier particles.

  If carrier particles are present in the reaction solution, the produced amorphous hydrous magnesium silicate coats the carrier particles. After completion of the reaction, this is filtered and separated from the reaction solution, washed with water, dried and pulverized to obtain the composition used in the present invention.

  Substances that can be used as a carrier are inorganic compounds that are insoluble in water and have a dense structure. In general, they are crystalline. Furthermore, since the amorphous hydrous magnesium silicate itself is white, the carrier is preferably white to gray or yellowish white. Non-limiting examples of such materials are titanium oxide, talc, aluminum hydroxide, barium sulfate, clay, kaolin, aluminum oxide and the like.

  Generally, the average particle size of the pigment is in the range of 0.1 to 10 μm. Accordingly, the particle size of the carrier is selected so that the particle size of the pigment after coating is within this range. Since the specific surface area of the carrier is inversely proportional to the particle size, the amount of amorphous hydrous magnesium silicate that can be coated per unit weight of the carrier is a function of the particle size. For this reason, the coating amount of the amorphous hydrous magnesium silicate can vary in the range of 1/10 to 10/1 expressed by the weight ratio of the carrier / coating layer.

Component (b) The component (b) is a condensed aluminum phosphate salt hardly soluble in water or a layered phosphate of a tetravalent metal.

  Typical examples of the former are aluminum dihydrogen triphosphate and aluminum metaphosphate. Aluminum dihydrogen triphosphate is commercially available mainly as a rust preventive pigment for steel sheets, and is sold, for example, under the trade name K-Fresh # 100P by the applicant company. Aluminum metaphosphate can be produced, for example, by calcining and grinding aluminum dihydrogen triphosphate at a high temperature, and is commercially available, for example, from the applicant company under the trade name K-Bond # 90.

Instead of the condensed aluminum phosphate salt, a tetravalent metal layered phosphoric acid can be used as the component (b). This is one of the components of the rust preventive pigment composition described in Japanese Patent No. 3004486 of the present applicant, and its production method is also described in the publication. They can generally be produced by reacting tetravalent metal oxides, hydroxides, etc. with orthophosphoric acid, and the product is a secondary phosphorus in the form of M (IV) (HPO ₄ ) ₂ .nH ₂ O. Takes the salt form. Ti, Zr or Ce is preferable as the tetravalent metal.

Component (c) Commercially available magnesium oxide can be used as component (c).

Antirust pigment composition Generally, the antirust pigment composition of the present invention corresponds to a three-component system by adding the component (a) to the two-component composition of Japanese Patent No. 3004486. The mixing ratio is (a) :( b) from 1: 0.5 to 1:40, (a) :( c) is from 1: 0.03 to 1: 3, and (b) : (C) is 1: 0.02 to 1: 0.6.

The mixing method of the three components is arbitrary, and the order of mixing and the type of apparatus to be used are not limited. Typically, the three components are charged into a mixer at a predetermined ratio and mixed dry until uniform. At that time, it is preferable to finely grind the composition simultaneously with mixing using a mixing apparatus having a grinding function, such as a jet mill, a sand glide mill, an atomizer, a supermicron mill, a Fitz mill, a Raymond mill, or a ball mill.
In PCM, a primer having a fine particle diameter is more suitable because an undercoat paint containing a rust preventive pigment is generally used in a very thin film of 3 to 10 μm.
Not only the paint suitability but also the ultra-fine size with a jet mill etc. increases the specific surface area of the rust-preventive pigment composition, which makes it easier for the active ingredients to elute, and the presence of the anti-corrosion pigment in the coating uniformly corrodes it. The presence of the rust preventive pigment composition in the vicinity of the local area increases the reaction rate of the rust preventive pigment composition during corrosion and improves the rust preventive performance.

  The method of making the pigment composition of the present invention into a paint and coating the galvanized steel sheet is the same as the method disclosed in JP 2001-192869 cited above.

  The following examples are for purposes of illustration and not limitation. In these, parts and% are based on weight unless otherwise specified.

Production Example 1 Production of magnesium silicate-coated titanium oxide with Ti / Mg / Si = 8.0 / 1.0 / 9.9 400 mL of water was placed in a 1 L beaker, and 2.4 g of magnesium chloride anhydride was dissolved. To this was added 16.0 g of titanium oxide. In another 300 mL beaker, 51.7 g of No. 3 water glass (29% as SiO _{2 and} 9.4% as Na ₂ SO ₃ ) was added, and diluted by adding 100 mL of water. This solution was added dropwise to the magnesium chloride solution with stirring for 10 minutes. After the dropwise addition, the mixture was stirred for 30 minutes, and then 11.2 g of concentrated hydrochloric acid was added to a 200 mL beaker and diluted by adding 100 mL of water. The mixture was added dropwise over 10 minutes and stirred for 30 minutes after the addition. The resulting reaction precipitate was filtered, washed with water, dried at 110 ° C. overnight, and pulverized to obtain 31.7 g of a white powder. As a result of X-ray fluorescence analysis, this was Ti / Mg / Ti = 8.0 / 1.0 / 9.9. This white powder is referred to as (a1).

Production Example 2 Production of Amorphous Magnesium Silicate with Mg / Si = 0.1 400 mL of water was placed in a 1 L beaker, and 2.4 g of anhydrous magnesium chloride was dissolved. In another 300 mL beaker, 51.7 g of No. 3 water glass (29% as SiO _{2 and} 9.4% as Na ₂ Si ₃ ) was added and diluted with 100 mL of water. This solution was added dropwise to the above magnesium chloride solution over 10 minutes with stirring. Stirring was continued for 30 minutes after the dropping, and then 11.2 g of concentrated hydrochloric acid was put into a 200 mL beaker, and diluted with 100 mL of water was added dropwise to the above mixture over 10 minutes. After dropping, the mixture was stirred for 30 minutes, and the resulting reaction precipitate was filtered, washed with water, dried at 110 ° C. overnight, and pulverized to obtain 16 g of a white powder. As a result of fluorescent X-ray analysis, this was Mg / Si = 0.096, and the result of X-ray diffraction was amorphous. Let this white powder be (a2).

Production Example 3 Crystalline titanium phosphate 11.6 g of titanium hydroxide Ti (OH) ₄ and 34.6 g of 85% phosphoric acid (P ₂ O ₅ / TiO ₂ molar ratio 1.5) were stirred and mixed in a magnetic crucible. Then, the mixture was placed in an electric furnace whose temperature was set to 210 ° C. together with the crucible, heated steam at 210 ° C. was blown, and reacted at 210 ° C. for 5 hours in the presence of water vapor. The reaction product was washed with water, dehydrated, dried and then powdered to obtain a white powder. As a result of X-ray diffraction, this was a crystalline layered titanium phosphate having the composition formula Ti (HPO ₄ ) ₂ .2H ₂ O, and the interlayer distance of the layered titanium phosphate was measured by powder X-ray diffraction. It was 6 angstroms. This was designated as (b2), and Teika's aluminum dihydrogen tripolyphosphate, trade name K-Fresh # 100P was designated as (b1).

Production Example 4 Aluminum Metaphosphate 500 g of aluminum tripolyphosphate (trade name K-Fresh # 100P) manufactured by Teika Co., Ltd. was placed in a box-shaped electric furnace, calcined at 500 ° C. for 2 hours, and pulverized to obtain 409.3 g of white powder. Obtained. X-ray diffraction revealed that this was aluminum metaphosphate. This is defined as (b3).

Example 1-20
(A) component shown in Tables 1-3, (b) component, magnesium oxide (Kyowa Chemical Industry Co., Ltd. magnesium oxide T), and mixing (pulverization) using the apparatus described in the weight part shown in the table And the rust preventive pigment composition of this invention was obtained.

Comparative Example 8
Commercially available Ca ion exchange silica (Grace Shieldex C303) was used.

Comparative Example 9
A commercially available strontium chromate (manufactured by Kikuchi Color) was used.

Paint test Preparation of paint and preparation of test plate Using the pigments of the production examples and comparative examples, a baking type polyester resin-based paint (undercoat) having the composition shown in the table below is prepared. After coating and baking on both the front and back surfaces of the coated plate, The following Table 2. A baking type polyester resin paint (top coating) having the composition shown in FIG. Both sides of this coated plate were cut into end surfaces (rounded up and down), and the top was bent at a thickness of 2T was used as a test plate, and a rust prevention test was performed.

Paint formulation (undercoat)
Super Beckolite M-6801-30 (NV = 30%) ¹⁾ 52.7%
Super Becamine L-117-60 (NV = 60%) ²⁾ 1.8%
Super Becamine L-105-60 (NV = 60%) ³⁾ 3.7%
Titanium oxide JR-603 ⁴⁾ 8.7%
Sample 13.1%
Solvent (Solvesso 100 ⁵⁾ / cyclohexanone / n-butanol / butyl cello
Solve = 60/30/6/10) 20.1%
Total 100.0%

P / B = 1.1 PVC = 26.9
1) Dainippon Ink Chemical Co., Ltd. oil-free polyester resin 2) Dainippon Ink Chemical Co., Ltd. butylated melamine resin 3) Dainippon Ink Chemical Co., Ltd. methylated melamine resin 4) Teika Co., Ltd. White pigment 5) Exxon Chemical Co., Ltd. aroma Family solvents

Paint formulation (top coating)
Super Beckolite M-6401-50 (NV = 50%) ⁶⁾ 53.3%
Super Becamine LJ820-60 (NV = 60%) ⁷⁾ 7.8%
Titanium oxide JR-603 ⁴⁾ 31.3%
Solvent (Solvesso 100 ⁵⁾ / cyclohexanone / n-butanol / butyl cello
Solve = 60/30/6/10) 7.5%
Total 100.0%

P / B = 1.0 PVC = 20.0
1) Dainippon Ink Chemical Co., Ltd. oil-free polyester resin 2) Dainippon Ink Chemical Co., Ltd. butylated melamine resin 3) Dainippon Ink Chemical Co., Ltd. methylated melamine resin 4) Teika Co., Ltd. White pigment 5) Exxon Chemical Co., Ltd. aroma Family solvents

Coating plate 1: Hot-dip galvanized steel sheet (GI) SGCC (manufactured by Nippon Test Panel)
244 g / m ² per unit weight 0.3 mm
Coating plate 2: Galvalume steel plate (GL) (manufactured by Nippon Test Panel)
Weight per unit area 150g / m ² Thickness 0.6mm
Coating: Bar coater curing conditions: Baking temperature 210 ° C (material temperature)
Film thickness: undercoat paint 5μm, topcoat paint 15μm
Dispersion: Paint conditioner

2. Rust prevention test (total 140 points)
70 points for each type of coated plate, scored separately for general galvanizing and galvalume.

2.1 Salt spray test (SST) (30 points x 2 types)
A test plate created by forming a coating film on the coated plate under the above coating conditions is cross-cut reaching the coated plate surface with a cutter knife, and statically placed in a salt spray tester in which the temperature in the tank is maintained at 35 ° C. 5% aqueous solution of sodium chloride at a pressure of 1 kg / cm ² for a predetermined time (GI 1500 hours, GL 750 hours), sprayed onto the coating film, and observed the rust generation and swelling of the coating film, and the following evaluation criteria Based on the evaluation. The corrosion state was evaluated based on the swelling area of the flat portion and the area where rust was generated, and the corrosion width of the cut portion, the end face cut-up portion, the end face cut-down portion, and the bent portion. In any evaluation, the higher the evaluation score, the better the rust prevention ability.

Evaluation standard of rust prevention effect (according to ASTM D610-68 (1970))
Flat part Rust generation area Less than 0.1%: 5 points Rust generation area 0.1% to less than 1%: 4 points Rust generation area 1% to less than 10%: 3 points Rust generation area 10% to 33% Less than: 2 points
Rust generation area 33% or more: 1 point

Evaluation criteria for the effect of preventing blistering (based on ASTM D-714-59 (1965))

Flat part 8F or less: 5 points 8M, 6F: 4 points 8MD, 6M, F: 3 points 8D, 6MD, 4M, 2F: 2 points 6D, 4MD or more, 2M or more: 1 point cut part, end face part Corrosion width 0 1 mm: 5 points Corrosion width 1-2 mm: 4 points Corrosion width 2-3 mm: 3 points Corrosion width 3-4 mm: 2 points
Corrosion width 4-5mm: 1 point

2.2 Combined cycle test (CCT) (30 points full scale x 2 types)
Neutral salt spray cycle described in the corrosion resistance test of JIS H8502 plating by leaving the test plate with the crosscut reaching the surface of the coated plate with a cutter knife in the same way as the salt spray test. Test conditions (1) Salt spray test 5% NaCl solution spray 35 ° C. 2 hours (2) Drying 60 ° C. 4 hours (3) Wet Humidity 95RH% or more 50 ° C. 2 hours (8 hours / 1 cycle) for a predetermined time ( GI 1504 hours 188 cycles, GL 752 hours 94 cycles). The state of rust generation and the swelling of the coating film were observed and evaluated based on the same evaluation criteria as in the salt spray test.

2.3 Humidity resistance test (HT) (10 points full scale x 2 types)
The test plate, which is not cross-cut, is allowed to stand in a humidity resistance tester maintained at a temperature of 50 ° C. and a relative humidity of 95% or more for 500 hours. Evaluation was performed according to the same evaluation criteria as the generation prevention effect.

3. Dispersibility test (20 points maximum)
In the above-mentioned paint preparation, dispersibility was evaluated by the time (minutes) until the pigment was dispersed to 10 μm or less by a paint conditioner. The scoring method was 10 points within 20 minutes, and 2 points were deducted every 10 minutes thereafter. [The shorter dispersion time is better.] The determination of 10 μm or less was made based on the dispersion degree (distribution map method) of JIS K 5400.

4). Gloss (20 points maximum)
The specular gloss (60 degrees) of the primer coated plate before being subjected to a rust prevention test was measured.

5. Paint viscosity (20 points maximum)
The viscosity (mPa · s) of the paint immediately after preparation was measured using a rotational viscometer (60 rpm). [Scored from the viewpoint that the lower one is preferable]
Viscosity (mPa · s)

6). Results The results are shown in Table 6.

7). Discussion All pigment compositions of the examples are comparable to strontium chromate (Comparative Example 9) in rust resistance. On the other hand, the component (a) or the component (b), which is a component of Comparative Examples 1 to 3 alone, and the composition that is not within the range in which the blending ratio of the components (a), (b), and (c) is specified, are rustproof. Neither strontium chromate nor the compositions of the examples. Moreover, the coating material which mix | blended the pigment or the composition of Comparative Examples 1-8 except the comparative example 9 tends to become higher in the initial viscosity than the coating material which mix | blended the composition of the Example. Further, the compositions of Examples 19 and 20 that are not sufficiently pulverized at the stage of blending the composition tend to have a long dispersion time in the paint as in the pigments of Comparative Examples 1 to 3. By combining these, the pigment compositions of the examples are superior to the pigments or pigment compositions of Comparative Examples 1 to 8, and do not contain harmful heavy metals.

Claims (9)

(A) Amorphous magnesium silicate having an Mg / Si atomic ratio of 0.025 to 1.0, or a powder obtained by coating dense inorganic carrier particles with this amorphous magnesium silicate;
(B) a sparingly soluble condensed aluminum phosphate salt or a tetravalent metal layered phosphate; and (c) containing three components of magnesium oxide;
(A) :( b) is 1: 0.5 to 1:40 on a weight basis, (a) :( c) is 1: 0.03 to 1: 3, (b) :( c) Is 1: 0.02 to 1: 0.6, a rust preventive pigment composition for galvanized steel sheet.   The rust preventive pigment composition according to claim 1, wherein the inorganic carrier particles of the component (a) are selected from the group consisting of titanium dioxide, talc, aluminum hydroxide, clay, barium sulfate, kaolin and aluminum oxide.   The rust preventive pigment composition according to claim 1, wherein the tetravalent metal of the layered phosphate of the component (b) is Ti, Zr or Ce.   The rust preventive pigment composition according to claim 1, wherein the Mg / Si atomic ratio of the amorphous magnesium silicate as the component (a) is 0.05 to 0.8.   2. The rust preventive pigment composition according to claim 1, wherein the carrier particles coated with the amorphous magnesium silicate of component (a) have a magnesium silicate: carrier particle weight of 10: 1 to 1:10.   The antirust pigment composition according to claim 1, wherein the condensed aluminum phosphate salt of the component (b) is aluminum dihydrogen phosphate or aluminum metaphosphate.   The rust preventive pigment composition according to claim 1, wherein the layered phosphate of the component (b) is dibasic titanium phosphate.   The rust preventive pigment composition according to any one of claims 1 to 7, wherein the components (a), (b) and (c) are mixed by a mixer having a grinding function.   The rust preventive pigment composition according to any one of claims 1 to 8, wherein the galvanized steel sheet is a galvalume steel sheet.