JPS5920473A - Improvement in chemical conversion liquid for zinc phosphate coating - Google Patents

Abstract

PURPOSE:To improve the adhesion and the suitability to bending work of a chemical conversion coating in the stage of forming the chemical conversion coating of zinc phosphate on the surface of metal by incorporating a specific org. sulfonic acid compd. in treatment liquid for forming the zinc phosphate coating. CONSTITUTION:A zinc phosphate coating is formed on the surface of an iron or steel plate or the like in order to improve the corrosion resistance and paint adhesion thereof. The zinc phosphate coating is formed by dipping the iron or steel plate to be treated for several seconds beforehand in surface preparation liquid of titanium phosphate then dipping the same in chemical conversion liquid for the zinc phosphate coating kept at 60-75 deg.C or bringing the same into contact with said liquid with spraying for 3-20 seconds then bringing the steel plate into contact for several seconds in post-treatment liquid of chromic acid or the like. The org. phosphonic acid compds. expressed by the formulas [ I ], [II], [III] are incorporated in the chemi cal conversion liquid for the zinc phosphate coating at 1-1,000ppm and further the phosphate compd. of starch or the resulted product of the acid decomposition thereof is incorporated therein at 100-10,000ppm. The chemical conversion coating of zinc phosphate as a substrate for painting having excellent adhesion to the iron or steel plate and the suitability to bending work is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in zinc phosphate coating chemical conversion treatment solutions. More specifically, the present invention relates to a treatment solution that can form a zinc phosphate film having excellent properties on the surfaces of various metals such as iron, steel, zinc, and zinc alloys, and can also form the film with good workability.

Conventionally, in order to improve the corrosion resistance and paint adhesion of the above-mentioned metals, it has been widely and generally practiced to chemically form a phosphate film on the surface of the metal as a pre-painting treatment. Recently, however, various improvements have been made to this type of chemical conversion treatment liquid in order to mass produce high quality products. especially,
In the case of so-called pre-coated products, in which a phosphate film is chemically formed on a coiled metal material, this is coated, and then the metal material is molded, the coating process, including the bendability of the chemical conversion film, is Particular emphasis is placed on adhesion. In addition, in the surface treatment process for pre-coated products, metal materials are generally held and conveyed by rolls, and in particular are bent and held by accumulators, so the chemical conversion coating is easily peeled off and powdered (powder flaking), and this remains attached to the metal. When materials are subjected to coating, the coating atmosphere is often contaminated, resulting in coating defects. From this point of view as well, the chemical conversion coating is required to have good bendability.

In addition, in general phosphate film chemical conversion treatment, sludge is unavoidably generated during treatment, and its treatment (e.g., cleaning inside the treatment liquid tank, sludge disposal) is complicated. If sludge sticks to the surface of the heating means inside the liquid tank, it will reduce its thermal efficiency, and on the other hand, in the case of the liquid to be treated in the pipes in the external heating method, the pipes are likely to become clogged due to sludge adhesion, so it is necessary to clean the sludge frequently. be.

By the way, when we specifically examine the improvement proposals that have been proposed to date, the first proposal is to add phosphate esters of starch or its acid decomposition products to the general phosphate film chemical conversion treatment solution. (Special Public Interest Publication 1977-
No. 17047, No. 54-24973, No. 57-723
(See No. 2).

This is due to the refinement and densification of the crystals in the phosphate film,
It is said that the weight of the coating is reduced and the adhesion of the coating to the surface metal is increased, resulting in improved coating adhesion and corrosion resistance after painting. Furthermore, it is said that a reduction in the amount of sludge generated can be achieved. However, it has been found that the crystals of the phosphate film produced by this technique are needle-shaped and easily disintegrate during bending. Therefore, the bendability of the chemical conversion coating on pre-coated products is still insufficient, and as mentioned above, there is a risk that the chemical conversion coating will flake during the surface treatment process of pre-coated products, leading to coating defects.

Next, it has been proposed to add a reaction product of amino alcohol and phosphoric acid (see JP-A-52-43737). According to this, it is possible to provide a phosphate film with dense crystals and no needle crystals, reduce the amount of sludge generated, and modify the sludge so that it does not stick to heating means, etc. It is said that it is possible. However, according to the technology, the bendability of the phosphate film is still not satisfactory, and even if the amount of sludge generated can be reduced, the degree of reduction is still low, leaving room for improvement. There is.

Next, it has been proposed to add a phosphoric acid surfactant (see JP-A-50-143736).

According to this, it is said that the rate of sludge formation can be reduced, but the phosphate film has insufficient bendability and also has the problem that the treatment liquid foams during use. ing.

As described above, the conventional technology has a problem in that it is not possible to simultaneously satisfy the bending processability of the phosphate film and the reduction of sludge generation during chemical conversion treatment.

In addition, the prior art techniques described above require relatively large amounts of additional components to be added to the conversion solution to achieve their respective intended objectives. Specifically, for starch or its acid decomposition product phosphoric acid ester, soo ~ 5000 ppm
, preferably in an amount of 1000 to 3500 PPm. When such a large amount of additional components is added, the problem arises that the viscosity of the chemical conversion liquid increases during preparation, resulting in poor workability.

Furthermore, it is said that a reaction product of an amino alcohol and phosphoric acid or a phosphoric acid surfactant needs to be added in an amount of 200 ppm or more.

Therefore, an object of the present invention is to improve the adhesion between the crystals of the chemical conversion coating and the base metal, and to reduce the collapse of the crystals during bending, thereby improving the paint adhesion of metal materials that undergo bending. It is an object of the present invention to provide a zinc phosphate film chemical conversion treatment solution that can be improved. Another purpose is to provide a chemical conversion treatment solution that can reduce dusting of chemical conversion coatings due to bending and holding of metal materials during the surface treatment process, thereby reducing contamination of the coating atmosphere and preventing the occurrence of coating defects. There is something to do. Still another object is to reduce the amount of sludge generated during chemical conversion treatment, which can achieve the above-mentioned purposes by adding small amounts of additional components, and to provide a treatment liquid that can prevent sludge from sticking to heating means, etc. It is on offer.

This object is achieved by a zinc phosphate film chemical conversion treatment solution that is characterized in that an organic phosphonic acid compound is added to the treatment solution for chemically converting a zinc phosphate film on a metal surface.

The organic phosphonic acid compounds used in the present invention can be roughly classified into the following three types.

(1) Organic phosphonic acid compound 1 represented by the following formula [1] R, -P-(OM)2 (1) [wherein M is H
, alkali metal, NI (4 or C1-3 alkylamine or C1-3 alkanolamine, -OH, -
It is C1-5 alkyl optionally substituted with COOH or -PO(OH)2. ] Specific examples include hydroxyethylidene-1,1-diphosphonic acid represented by (e.g., "HEDPJ" manufactured by Johoku Kagaku, "DQuest 201O" manufactured by Mitsubishi Monsanto Chemical) and its di- or trisodium salt, represented by COOH OH Examples include 2-phosphono-1,2,4-butanetricarboxylic acid and its sodium salt.

(2) Organic phosphonic acid compound 1 represented by the following formula [2] [wherein, X is an integer of 3 to 11, and M has the same meaning as above. ] As a specific example, N-(5-carboxypentyl)amino di(
methylene phosphonic acid).

(3) Organic phosphonic acid compound 3 represented by the following formula [3] [In the formula, he and he may be substituted with H or C1-5 alkinope may be substituted with Hl-0H. C□-3 aliphatic carbonization Hydrogen or a group represented by the formula: (R5 is H or a group represented by the formula: 3 (M has the same meaning as above), 2 is an integer of 1 to 3), y is 0 or 1. ] Specific examples include amino tri(methylene phosphonic acid) represented by N-[CH-P-(OH)2]3 2 (e.g. "DQuest 2000" manufactured by Mitsubishi Monsando Chemical Co., Ltd.), amino tri(methylene phosphonic acid) represented by 1 Phosphonic acid) pentasodium salt (e.g., manufactured by the same company [Dequest 2006J) 1 HocH2CH2-N [-〇H2-P-(OH)2] 2
Examples include ethylenediaminetetra (methylene phosphonic acid) represented by N-hydroxyethylaminodi(methylene phosphonic acid χ ) (eg, "DQuest 2041" manufactured by the same company).

In the present invention, the amount of such an organic phosphonic acid compound in the total amount of the chemical conversion treatment solution is 1 o o o ppm or less, preferably 5
It may be added to the zinc phosphate coating chemical conversion treatment solution in an amount of ~100 PPm. If the amount added is too small, no effect of the addition of the compound can be expected, while if it is too much, no effect corresponding to the amount added can be expected, and conversely, it becomes difficult to form a chemical conversion film of a predetermined amount. However, the bending performance of the formed film is sufficiently good.

The zinc phosphate film chemical conversion treatment solution to which the above-mentioned organic phospho/acid compound is added may be any of the usual ones, and its standard formulation is as follows.

Zn io7 700-1800PPmN
i-ion 500-2000 #NO3
Io7 400=1200 "PO4i,
t7 7000-12000 pStF
6*in 30o-1000' total acidity x 10-25M ton free acidity'0.5-2.0# ton acid ratio x 6-20 As Q, the amount of 0, IN NaOH required for the solution to turn pink with IN NaOH.

X free acidity is 10. 0.0.nl was taken and bromophenol blue was used as an indicator. The amount of 0, IN NaOH required for the solution to turn green to blue with IN NaOH.

X acid ratio is total acidity/free acidity The chemical conversion treatment solution of the present invention further contains a phosphoric acid ester of starch or its acid decomposition product, which is also used in the above-mentioned conventional technology. However, it is advantageous in that the effects of the present invention, particularly the coating adhesion during bending, are further improved.

Such phosphoric acid esterified products are produced by esterifying starch or its acid decomposition products (e.g., dextrin, maltose, glucose) with phosphoric acid or sodium phosphate according to a conventional method (e.g., esterifying starch or its acid decomposition products (e.g., dextrose, maltose, glucose) with phosphoric acid or sodium phosphate in accordance with a conventional method (e.g., under reduced pressure or normal pressure). 190°
It is obtained by roasting at C). Note that it is preferable to remove unreacted phosphoric acid components as much as possible.

The phosphoric acid ester product thus obtained contains 0.5 to 2.5% by weight of bound phosphorus, preferably 1.2 to 1.9% by weight.
It is particularly advantageous that the content is % by weight in terms of improving the coating adhesion. Note that, as the phosphoric acid ester, a starch phosphoric acid ester that has been decomposed with an acid can also be used.

These phosphoric acid ester compounds account for 100% of the total amount of chemical conversion treatment solution.
~10000ppm, preferably 500~3500PP
It may be added in a proportion of m.

If the amount added is too small, no effect can be expected from the addition of the phosphoric acid ester compound, while if it is excessive, the effect corresponding to the amount added cannot be expected, and the viscosity of the processing liquid increases, resulting in poor workability. Deteriorate.

Examples of metal materials that can be chemically treated with the treatment solution of the present invention having the above structure include steel sheets, hot-dipped galvanized steel sheets, electrogalvanized steel sheets, alloyed heat-dipped galvanized steel sheets, and alloyed electrogalvanized steel sheets. Can be mentioned. The treatment of such metal materials with the chemical conversion treatment solution of the present invention is
This may be carried out by methods known per se. For example, a metal material is brought into contact with a titanium phosphate-based surface conditioning liquid for several seconds in advance, squeezed with a roll, and then brought into contact with a treatment liquid heated to about 60 to 75°C for 3 to 20 seconds by immersion or spraying. Then, it may be brought into contact with a chromic acid-based post-treatment agent aqueous solution (heated to about 65° C.) by immersion or spraying for several seconds, and then rolled and squeezed to dry.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples.

The standard formulation of the zinc phosphate film chemical conversion treatment solution used in these examples is as follows.

Zn io7 1000PP”Ni ion 1400 〃NO3 ion
900〃P04 ion 75001
'S I F6 ion 880 Total acidity
150 point acid ratio
80 Example 1 (1) Various organic phosphonic acid compounds as shown in Table 1 are added to the above-mentioned standard formulation treatment liquid, and the mixture is subjected to chemical conversion treatment.

(2) The metal material used is a heat-soaked galvanized steel plate (minimized spangle + skin pass) with a plate thickness of 035 mm.

(3) First, apply a titanium phosphate surface conditioner (
0.3% by weight of "Fixodine 5" manufactured by Nippon Paint Co., Ltd.
After immersing in an aqueous solution for 2 seconds at 25°C, and then removing the roll, immersing it in a chemical conversion treatment solution for 5 seconds at 65°C.
It is immersed in a 0.3% by weight aqueous solution of "Deoxylite 41J" manufactured by Nippon Paint Co., Ltd. at 65°C for 2 seconds, squeezed with a roll, and dried without washing with water.

(4) Barcode the chemically treated metal material with an epoxy primer (Superlac DIFPO1 Primer manufactured by Nippon Paint Co., Ltd.) to reach a board temperature of 190°.
Baked to C (dry coating coverage: 5 g/rrl). Next, apply an oil-free polyester top coat (“Superlac DIFF 80 Butt 23 Blue” manufactured by Nippon Paint Co., Ltd.)
) and baked to a final board temperature of 200°C (
Top coat dry coating weight 15 g/i).

(5) Table 1 shows the results of various performance tests on the chemically treated boards and painted boards thus obtained. Table 1 also shows the results of the sludge generation test in the chemical conversion treatment liquid.

= 3 Comparative Example 1 The same procedure as in Example 1 was carried out except that the various components shown in Table 2 used in the above-mentioned conventional technology were added to the above-mentioned standard combination treatment solution in place of the organic phosphonic acid compound. . The results are shown in Table 2.

[Gafack RE610J is a trade name of GAI' Co., Ltd., and is a mixture of [wherein K is C, 3o alkyl or alkylphenyl, and n is 3-15]. ].

-3( - Example 2 Aminotri(
The same procedure as in Example 1 is carried out except that different amounts of methylene phosphonic acid (methylene phosphonic acid) are added. The results are shown in Table 3.

Table 3 Example 3 Example 1 except that the organic phosphonic acid compound and starch phosphate were added to the treatment solution with the above standard formulation as shown in Table 4.
Execute in the same manner as . The results are shown in Table 4.

The starch phosphate used in this example and Comparative Example 1 was "Hyrate FN" manufactured by Nichirin Chemical Co., Ltd. (bound phosphorus content: 1.4).
weight%).

The various test methods are as follows.

(1) Reference photo of crystal form of chemical conversion coating: , Scanning electron micrograph (magnification: 750x) (2) Bending processability test of chemical conversion coating: (a) 2φ bending test: A round bar with a diameter of 2rrtrh is attached to a chemical conversion coating. After pinching and bending 180 degrees, the outer surface of the bent portion is observed using a scanning electron microscope.

○: The crystal has hardly collapsed △: The crystal has collapsed to an intermediate degree between ○ and × ×: The crystal has almost completely collapsed (b) Fabric scraping test at bent part:
The bent portion of the chemical conversion treated plate according to (a) above is rubbed several times with a cloth and then observed with a scanning electron microscope.

○: Almost all crystals remain.

Δ: Crystals remain to an extent intermediate between ○ and ×.

×: Almost no crystals remain.

(3) Paint adhesion test: (a) QT T test: The painted board was bent 180° in a constant temperature room at 20°C, crimped with a vise, and adhesive tape was attached to the bent part. Observe the state of peeling of the paint film on the bent part when peeling off.

(b) 2 T T test: Two coated plates of the same thickness are sandwiched in a constant temperature room at 20°C, bent 18o0, crimped with a vise, and then carried out in the same manner as in (a) above.

5 points: No peeling of the paint film is observed. 4.5 points: Peeling of the paint film is observed in an area of less than 5%. 4 points: Peeling of the paint film is observed in an area of less than 5 to 10 inches.

3.5 points 2 points: 3 points where paint film peeling is observed in an area of less than 10-20%: 2 points where paint film peeling is observed on an area of 20-50% or less: Paint film peeling is observed on an area of 50-80% or less 1 point 2 Paint peeling of 80-100% area is observed.

(C) Coin scratch test: Scratch the painted surface with sufficient force with a coin and observe the extent of scratches.

5 points: There is only a slight scratch at first, but then the coin slides on the painted surface. 4 points: About 10-30% of the scratched area is covered by a chemical conversion coating.
3 points where the scratched area peels off at the interface of a single layer of primer: 2 points where about half of the scratched area peels off at the interface between the chemical conversion film and a single layer of primer: Approximately half to 90% of the scratched area peels off at the interface between the chemical conversion film and a single layer of primer One point: More than 90% of the scratched area peels off at the interface between the chemical conversion film and the primer layer. Heat with an immersion heater (voltage 100
V). After maintaining the temperature at 705°C for 20 minutes while stirring, the amount of sludge generated (the total amount of sludge that adhered to the heater and that that settled in the beaker) was measured.

(b) K value: Since this value is generally used as a measure for evaluating sludge generation during chemical conversion treatment, the K value was calculated under the chemical conversion treatment conditions in Examples and Comparative Examples.

K value - Amount of etching / Amount of film Etching amount = (Weight of board before treatment - Weight of board after film removal) / Board area C'i/d) Amount of film = (Weight of board after treatment - Weight of board after film removal) / Plate area (5'/d) For chemical conversion coating removal, use a solution in which ammonium dichromate 10fj is dissolved in 28-30% ammonia water 11,
A method is adopted in which the treated plate is immersed in vaginal fluid for 5 minutes at room temperature and then wiped with a sponge.

〔supplementary explanation〕

The amount of zinc (△Zn) that can become sludge when a galvanized steel sheet is subjected to chemical conversion treatment is per unit area, ΔZ n-Z E Z c -EW-CwxO,428, where ZE is per unit area of the galvanized steel sheet Amount of zinc eluted during formation time = Etching amount (Ew) (f!/a) Zc is the amount of zinc in the film formed during formation time per unit area of galvanized steel sheet - film amount (CW) x ( 3Zn/
Zn5(PO2)2)(F/d)=Cwxo, 42s (i) Conditions for no sludge generation: K from △Zn=Q
Value - EW/Cw - 0,428 (conditions for i-resurage to occur: △Zn〉0, so value =
Ew/CW>0.42 s Therefore, the larger the K value - Ew/Cw is 0.428, the greater the amount of sludge generated.

Patent applicant: Nippon Paint Co., Ltd. Representative Patent Attorney Aoyama Aoyama and 1 other person

Claims (1)

[Scope of Claims] 1. Improvement of a zinc phosphate film chemical conversion treatment solution, characterized in that an organic phosphonic acid compound is added to the treatment solution for chemically converting a zinc phosphate film on a metal surface. 28 organic phosphonic acid compound has the formula [1] 1 R-P-(OM)2CD [wherein M is H1 alkali metal, NI (4 or C1-3 alkylamine or C1-3 alkanolamine, R1 is -0H
C1-5 alkyl optionally substituted with 1-COOH or -PO(OH)2. ] The treatment liquid according to item 1 above. 3. The organic phosphonic acid compound has the formula [2] 1 [wherein, X is an integer of 3 to 11, and M has the same meaning as above. ] The treatment liquid according to item 1 above, which is represented by: 4. The organic phosphonic acid compound has the formula [3] 3 [wherein R2 and frost are H or C1-5 alkyl, and is a C1-3 aliphatic hydrocarbon which may be substituted with H, -OH or the formula 2 (R5 is H or a group represented by the formula: (M has the same meaning as above), 2 is an integer of 1 to 3); y is 0 or 1; ] The treatment liquid according to item 1 above, which is represented by: 5. The amount of organic phosphonic acid compound added is 1 to 100 op.
The treatment liquid of item 1 above, which is pm. The treatment solution according to item 1 above, wherein the zinc hexaphosphate film chemical conversion treatment solution contains a phosphate ester of starch or its acid decomposition product.