JPS61127887A - Acidic galvanizing bath - Google Patents

Abstract

PURPOSE:To form a highly lustrous and fine galvanized surface on which fingerprints are hardly left by adding polyacrylamide having a specified structure having cationic groups to a prescribed galvanizing bath. CONSTITUTION:Acrylamide is copolymerized with 1-20mol% cationic monomer, and the resulting polyacrylamide represented by general formula I is added to a prescribed acidic galvanizing bath by 0.2-20g/l. Polyacrylamide represented by general formula II may be added to the bath by 0.2-20g/l. The polyacrylamide is obtd. by copolymerizing acrylamide with 1-20mol% cationic monomer and >=20mol% vinyl monomer. When the galvanizing bath contg. the copolymer represented by the formula I or II is used, a highly lustrous galvanized surface on which fingerprints are hardly left can be formed under various galvanizing conditions.

Description

[Detailed Description of the Invention] <Field of Industrial Application> The present invention relates to an acid plating bath for obtaining electrogalvanized plating that has high gloss and does not easily attract fingerprints. <Prior Art and its Problems> Electric galvanized:! ! Steel sheets are increasingly being used as parts of panels for audio equipment, amplifier cassette decks, tuners, and speakers. In such cases, galvanized steel sheets are
Products are often assembled with the whole or part of the product unpainted, and there is a problem in that if a worker touches the galvanized surface during this assembly process, his or her fingerprints will remain dark and clear.

This fingerprint adhesion phenomenon is clearly noticeable because skin secretions are embedded in the four parts of the fine irregularities of the zinc crystal, and as a result, diffuse reflection does not occur in those parts, light is absorbed, and the surface appears dark. This phenomenon occurs regardless of the presence or absence of chromate treatment for the purpose of rust prevention on the galvanized surface.

Fingerprints once attached to the surface cannot be easily removed using organic solvents and the like, and they significantly impair the aesthetic appearance and commercial value.

It has been found that polishing the plated surface with a slurry of sodium bicarbonate to increase the gloss is effective in obtaining electrogalvanized coatings that are less likely to attract fingerprints (Japanese Patent Application Laid-Open No. 57-8
5990% reference).

Again, meh! ! It is known that adding brighteners such as thiourea, gum arabic cresol, dextrin, glucose, and coumarin to the plating bath is effective in increasing coating surface gloss.

On the other hand, in electrogalvanizing steel strip.

Sulfates, because they can be plated at high speed by increasing the current density.
pH approx. 1 with municipal substances or mixtures thereof as main components
~4 acidic plating baths are used. In this acidic bath, even if conventional brighteners are added, they are only effective in a narrow current density range, and defects such as plating fading are likely to occur at high current densities.Also, the brighteners have poor stability in the bath. In particular, there was a strong tendency for the effect to decrease when the bath temperature was high.

Under these circumstances, one type of brightener that exists in a stable solution state during plating is polyacrylic
Its use is shown in 8888.

However, this polyacrylamide also has a concentration of 2 g
/ l or less, the effect as a brightening agent is insufficient, and l Og/9. If it exceeds , the plating surface tends to become gray to black depending on the plating conditions. Also,
There were disadvantages such as the influence of the flow rate on the plating appearance was large and the uniform electrodeposition was poor.

<Purpose of the Invention> In view of the above-mentioned current situation, the present invention provides an acidic electrogalvanizing bath for stably obtaining electrogalvanizing that is highly glossy, beautiful, and resistant to fingerprints over a wide range of plating conditions. The purpose is to provide.

<Structure of the invention> According to the first aspect of the invention, a general formula consisting of acrylamide as a main component and 1 to 20 mol% of a cationic monomer copolymerized, provided that Y: 0 or NH X, halogen, inorganic or organic acid anion R,,R2,
The above objective can be achieved by dissolving 02 to 20 g/polyacrylamide containing a cationic group represented by R3: H or CH3 or C2H3 n:l~2 in an acidic electrogalvanizing bath. .

According to the second aspect of the present invention, the main component is acrylamide, 1 to 20 mol % of a cationic monomer, and 20 mol % or less of - in vinyl 7. halogen, inorganic or organic acid anion R+,
The above purpose can be achieved by dissolving 0.2 to 20 g of polyacrylamide containing a cationic group represented by R, 2, R3・H or CH3 or c2H5 n・1 to 2 V, W:H, CNt or COOH. can be achieved.

Next, the acid bright electrogalvanizing bath of the present invention will be explained in detail.

The electrogalvanizing bath used in the present invention contains zinc sulfate, zinc chloride, or a mixture thereof as a main component.
To this, add alkali metal sulfates, chlorides, borates, nitrates, other conductive aids, and pH buffers,
This is an acidic bath whose pH has been adjusted to a range of approximately 1 to 4. This bath contains 0.2 to 20 g of polyacrylamide copolymerized with a cationic group.

Cationic group Y20 or NHX of the present invention, halogen inorganic or organic acid anion R,,R2,R
3: Polyacrylamide copolymerized with H or CH3 or C2R5 n:l~2 is different from polyacrylamide that does not contain a cationic group.

It exhibits a brightening effect even at a concentration as low as 0.2 g/l, is stable against changes in current density and plating solution flow, has excellent uniform electrodeposition, and exhibits its effectiveness under a wide range of plating conditions.

It is generally believed that the brightener adsorbs to the metal deposited on the cathode surface and inhibits crystallization, resulting in a smooth and glossy plating surface. The reason why it exhibits such excellent effects as described above is thought to be that the brightener molecules 4RF-electrify cations in the bath and concentrate on the cathode surface, thereby controlling the metal precipitation reaction more effectively. .

In this case, if the cationic group occupying less than 1 mol% in the brightener agent, the cationic nature of the brightener molecule is insufficient;
Its efficacy as a brightener is not much different from that of polyacrylamide, which does not contain cationic groups.Moreover, when the concentration exceeds 20 mol%, its effectiveness hardly changes even if its concentration is increased, and it becomes an economical cost-effective item. Not preferred, therefore the content of cationic groups in the brightener is defined as 1-20 mol%.

It is also possible to copolymerize a third component into the uninvented brightener.

Its general formula can be expressed as follows.

General formula % formula % X halogen, inorganic or organic acid anion R1, R2,
By containing 1tCOOH vinyl monomer such as R3H or CH3 or C2H3 n:l~2V, W:H, CNt, it increases the stability as a brightening agent in a plating bath, and is suitable for plating at high temperatures or in a bath. effective for long-term use.

If the t1♀ content of the vinyl monomer is too large, the apparent molecular weight of the brightener increases and the viscosity increases in the bath.
The amount of vinyl monomer added must be 20 mol% or less.

The required concentration of the two brighteners having the above composition in the plating bath is from 0.2 to 20 g/cross. If it is less than 0.2 g/cross, the gloss improvement effect will be small, and if it exceeds 20 g/9°, the plating surface will become dark and coarse crystals at high current density, which is likely to cause so-called discoloration.

The brightener in the present invention is synthesized using acrylamide monomer CH2:CHCONH2 as a main ingredient, and the cationic monobodies are diethylaminoethyl acrylate, trimethylacryloxyethylammonium chloride, trimethylmethacryloquine ethylammonium chloride, diethylaminoethyl acrylate, and triethyl acryloxyethyl. It is made by copolymerizing one or more selected from among ammonium chloride, dimethylaminomethylacrylamide, acrylamide ethyltrimethylammonium chloride, etc. When adding a vinyl monomer as a third component, one or more of acrylic acid (CH2: CHCOOH), acrylonitrile (CH2.CHCN), etc. may be selected and copolymerized.

The molecular weight of the brightener synthesized as described above is 100,000~
A value in the range of 1.5 million is preferred.

<Examples> Hereinafter, preferred examples and comparative examples of the present invention will be described.

SP with a thickness of 0.8 mm, degreased and pickled using conventional methods.
ZnSO4 ・7H2 0 300g/ on CC steel plate
1. Contains Na2 504 60g/text, below A-D
20 in a pH 2.0 agate bath with the addition of a brightener of
g/rn' electroplated. Note that among these, the polishing agent is a brightening agent for comparative examples.

Brightener A: 90 mol% acrylamide, 10 mol% dimethylaminoethyl acrylate, copolymer with a molecular weight of about 900,000. Brightener C: 85 mol% diacrylamide, 10 mol% dimethylaminoethyl acrylate, 10 mol% acrylic acid. , Copolymer brightener C with a molecular weight of about 800,000 85 mol% Niacrylamide, 15 mol% of trimethylacryloxyethylammonium chloride, Copolymer brightener D with a molecular weight of about 500,000, Polyacrylamide, a molecular weight of about 500,000 The amount added was changed to levels 2 to 3 within the range of 0.1 to 25 g/ml as shown in Table 1. The plating bath temperature is 55℃.
and the current density is 20.

4 0, 8 OA/dm2 (7) Jun Miki. ! :L
? :． ．． 1. After washing and drying the wood and determining the uniformity and gloss of the surface appearance, we stamped the wood with an artificial juice solution mixed with lanolin, sodium hydroxide, lactic acid, etc. to make it more conspicuous. Fingerprint adhesion was evaluated.
These results are shown in Table 1.

The plating using the treatment solution of the present invention shown in Examples 1 to 6 was as follows:
All had excellent appearance uniformity, gloss, and fingerprint adhesion over a wide current density range. On the other hand, Comparative Examples 1 and 3, in which the brightener concentration was too low, lacked gloss (and fingerprint adhesion was also poor). Comparative Example 2, in which the brightener concentration was too high, improved in appearance uniformity, gloss, and fingerprints as the current density increased. Both adhesiveness deteriorated.
Furthermore, in Comparative Example 4.5, in which polyacrylamide containing no cationic group was used as a brightener. When the concentration is Ig/view, the gloss effect is significantly less than in the example.

In addition, the fingerprint adhesion was poor, and when the lbg/Q was increased, discoloration occurred at high current density, and both gloss and fingerprint adhesion were poor.

<Effect of the invention> Instead of adding only polyacrylamide to the acidic electrogalvanizing bath as in the past, a copolymer of acrylamide and a cationic monomer or a copolymer of acrylamide and a cationic monomer/vinyl monomer is added. By adding it, it is possible to obtain an electrogalvanizing bath that can stably obtain electrogalvanizing that is high in gloss, beautiful, and resistant to fingerprints over a wide range of plating conditions.

Claims (2)

[Claims] (1) General formula consisting mainly of acrylamide and copolymerized with 1 to 20 mol% of cationic monomer ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Y: O or NH X: Halogen, inorganic or organic acid anion R_1, R_2, R_3: An acidic electrogalvanizing bath characterized by containing 0.2 to 20 g/l of polyacrylamide containing a cationic group represented by H, CH_3, or C_2H_5 n: 1 to 2. (2) General formula consisting mainly of acrylamide, copolymerized with 1 to 20 mol% of cationic monomer and 20 mol% or less of vinyl monomer ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼ Y: O or NH X: Halogen, Inorganic or organic acid anions R_1, R_2, R_3: H or CH_3 or C_2H_5 n: 1-2 V, W: H, CN or COOH 0.2-20 g/l of polyacrylamide containing a cationic group represented by An acidic electrogalvanizing bath characterized by containing: