JPH03240981A - Discoloration preventive agent for steel sheet - Google Patents

Abstract

PURPOSE:To prevent the discoloration of a steel sheet with the surface activated and to provide the discoloration preventive agent capable of improving the quality and yield of the product by mixing an aliphatic dicarboxylic acid (salt) and the polymer (salt) of an unsaturated carboxylic acid. CONSTITUTION:An aliphatic carboxylic acid or its salt and the polymer of salt of an unsaturated carboxylic acid are mixed to prepare a discoloration preventive agent for the steel sheet. Sebacic acid, etc., are preferably used as the aliphatic carboxylic acids, and the amine salts as their salts. Acrylic acid is preferably used for the polymer of unsaturated carboxylic acid, and the sodium salts as their salts. In this case, 0.001 to 1 pt.wt. of the polymer of unsaturated carboxylic acid and 1 pt.wt. of the aliphatic carboxylic acid salt are mixed. The water solubility of both materials is increased by adding the amine. The agent is preferably dissolved in dilution water in advance.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is an anti-discoloration agent for steel plates, particularly for preventing discoloration of steel plates whose surfaces have been activated by chemical cleaning or electrolytic cleaning. This invention relates to a steel plate discoloration inhibitor for addition.

[Conventional technology]

There are many different types of steel sheets, and they are shipped as products after undergoing various processes such as hot rolling, cold rolling, annealing, plating, and painting.

In each process, chemical cleaning such as acid cleaning, alkaline cleaning, electrolytic cleaning, etc. are performed for the purpose of cleaning the steel plate surface. After cleaning, rinse with industrial water or pure water to remove impurities adhering to the surface.
be done.

Since one surface of the steel plate cleaned by the above cleaning is activated, corrosion is more likely to occur, and the product becomes discolored due to rusting. Rusted or discolored steel sheets not only reduce product value, but also cause adverse effects on subsequent processes, such as poor plating.

Rusted or discolored steel sheets cause a reduction in product yield due to cutting of defective parts (the defective rate may reach several percent) and increase in process costs due to re-cleaning, resulting in large losses. Defective products mainly occur during low-speed operation or when the line is stopped. As countermeasures against these problems, the above-mentioned problems have been alleviated by continuous pickling and cold rolling using louvers, and continuous annealing equipment called CAL and CAPL.

However, the equipment cannot handle all cases, and for example, discontinuous electrolytic cleaning is used in the production of high-grade steel. In this case, welding is required to clean the next coil, which typically shuts down the line for 3 to 5 minutes. In addition, low-speed operation may be forced due to poor welding or the like, resulting in the production of defective products.

Recently, steel sheet discoloration inhibitors that are applied to such cleaning water are being widely used. As this steel plate discoloration inhibitor, amine salts of aliphatic dicarboxylic acids, aromatic carboxylic acids, aminocarboxylic acids, oxycarboxylic acids, etc., amines alone, hydrazine, etc. are used, and among these, aliphatic dicarboxylic acids are preferable. It is widely used because it has a powerful effect.

However, when tap water, industrial water, or the like is used as dilution water, such steel plate discoloration inhibitors combine with hardness components in the water to produce sparingly soluble salts.

Since this salt has low solubility in water, it may precipitate during the process of drying the steel plate and remain on the steel plate as a white residue. For this reason, there is a problem in that the appearance of steel sheets shipped immediately after electrolytic cleaning is impaired.

[Problem to be solved by the invention]

The purpose of this invention is to solve the above-mentioned problems by preventing discoloration of steel plates whose surfaces have been activated by chemical cleaning or electrolytic cleaning, improving product quality and product yield, and making it possible to prevent tap water and industrial To provide a steel plate discoloration preventive agent that does not generate white residue even when using water.

[Means to solve the problem]

The present invention is the following steel plate discoloration inhibitor.

(1) A steel sheet discoloration inhibitor comprising an aliphatic dicarboxylic acid or its salt and an unsaturated carboxylic acid polymer or its salt.

(2) A steel plate discoloration inhibitor comprising an aliphatic dicarboxylic acid or its salt, an unsaturated carboxylic acid polymer or its salt, and an amine.

The aliphatic dicarboxylic acid used in the present invention is a compound in which an aliphatic hydrocarbon is substituted with two carboxyl groups, and may have a hydroxyl group or other substituent. Such aliphatic dicarboxylic acids include adipic acid, pimelic acid, superric acid, azelaic acid, sebacic acid, 1,10-decanedicarboxylic acid, 1°14-tetradecanedicarboxylic acid,
Examples include 1,18-octadecanedicarboxylic acid. The water-soluble salts of these aliphatic dicarboxylic acids may be metal salts such as sodium salts and potassium salts, but amine salts are preferred.

The unsaturated carboxylic acid polymer or salt thereof used in the present invention is a homopolymer, copolymer, or copolymer of an unsaturated carboxylic acid having a polymerizable unsaturated bond such as acrylic acid, maleic acid, methacrylic acid, itaconic acid, Alternatively, they are copolymers with other monomers copolymerizable with these, or salts thereof such as sodium salts.

Other copolymerizable monomers include vinyl sulfonic acid,
Examples include allylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, 2-hydroxyethyl methacrylate, isobutylene, etc.
These are copolymerized in an amount of 50 mol% or less in the copolymer. The molecular weight of these polymers is preferably 200 to 20,000, preferably 300 to 10,000.

The steel plate discoloration inhibitor of the present invention is composed of an aliphatic dicarboxylic acid or a salt thereof as described above and a polymer of an unsaturated carboxylic acid or a salt thereof, and the blending ratio of both is 1 weight of aliphatic dicarboxylic acid or its salt. 0.001 to 1 part by weight of the unsaturated carboxylic acid polymer per part.

When the aliphatic dicarboxylic acid or its salt and/or the unsaturated carboxylic acid polymer or its salt have low water solubility, the water solubility can be increased by incorporating an amine. The amine is monoethanolamine,
Jetanolamine.

Triethanolamine, dimethylethanolamine, diethylethanolamine, 2-amino-2-methyl-1
-Alkanolamines such as propatool and 1-amino-2-propatool, polyethylene polyamines such as pentaethylenehexamine and tetraethylenepentamine, and aliphatic amines such as cyclohexylamine, propylamine and hexylamine can be used. These amines react with polymers of aliphatic dicarboxylic acids or unsaturated carboxylic acids to form amine salts and increase their water solubility. These amines are preferably blended in an amount of 5 to 5 parts by weight per 1 part by weight of aliphatic dicarboxylic acid.

In addition to the above-mentioned components, the steel plate discoloration inhibitor of the present invention may contain other rust-preventing components, modifiers, and other additives.

The steel plate discoloration inhibitor of the present invention is obtained by blending the above-mentioned components, and can be used as it is by dissolving it in cleaning water, etc., but it is preferable to dissolve it in dilution water in advance. In this case, each component may be dissolved as is in the dilution water, but it is preferable to first dissolve easily soluble components, such as amines, and then dissolve poorly soluble components.

The steel sheet discoloration preventive agent of the present invention can be used by being added to the cleaning water in each rinsing step after chemical cleaning such as acid cleaning or alkaline cleaning or electrolytic cleaning. In this case, it is usually effective to add 50 to 1,000 parts to the washing water.

The locations where steel plates rust or discolor during low-speed operation or when the line is stopped are generally the water sprinkling area after chemical or electrolytic cleaning, inside the cleaning tank, and from the outlet of the cleaning tank until drying. Therefore, in order to prevent rusting and discoloration that occur in such places, it is effective to add an anti-discoloration agent to the cleaning water, and this cleaning water can also be used for spraying chemicals or after electrolytic cleaning. is effective.

Specifically, in the case of a spray rinse system, for example, t,
A steel plate discoloration preventive agent diluted with water to 10,000 ml/Q may be poured into the cleaning water for 1 to 5 minutes from about 30 seconds before the line stops. In addition, in the case of the Date Prince type, there is always too much steel plate discoloration prevention agent in the Date Tank.
The drug should be injected so that the concentration is maintained at oo■/Q.

Another method of use is to apply or spray an anti-discoloration agent onto the water spraying area after chemical or electrolytic cleaning. For example, methods such as pumping up and spraying washing water containing an anti-discoloration agent, or directly spraying an anti-discoloration agent can be adopted.

〔Example〕

Example 1 Cut cold rolled steel plate after electrolytic cleaning (SPCC-5B
.

The test piece was 60mm x 100mm x O, 8m++ thickness). This test piece was subjected to ultrasonic degreasing using toluene for 30 minutes, then wiped of dirt, washed with water, immersed in methanol, and dried with cold air using a hair dryer.

On the other hand, sebacic acid as the aliphatic dicarboxylic acid/monoethanolamine (MEA) as the amine/sodium polyacrylate (average molecular weight 4,000) as the polymer salt of unsaturated carboxylic acid was used in an amount of 15 parts by weight/30 parts by weight 70.1 A steel plate discoloration inhibitor mixed in parts by weight and dissolved in tap water is added to tap water heated to 80°C.
A cleaning solution was obtained by diluting the solution to a concentration of ①/Q.

After immersing the above-mentioned test piece in this cleaning solution for 1 minute, 80°C
The test piece was placed in a transparent container filled with tap water so that the lower half was immersed, the lid was closed, and the container was left for 5 minutes.

Thereafter, the test piece was taken out, dried, and visually evaluated for rusting in the portion that protruded above the liquid surface and came into contact with water vapor in the transparent container, and for the presence or absence of white residue.

Example 2 Instead of sodium polyacrylate, polymaleic acid (
The method and formulation were the same as in Example 1, except that a compound with an average molecular weight of 500 was used.

Comparative Example 1 The same method and formulation as in Example 1 were used except that benzoic acid was used instead of sebacic acid.

Comparative Example 2 Comparative example 2 was carried out using the same method and formulation as in Example 1 without using sodium polyacrylate.

Example 3 1. IO-decanedicarboxylic acid/diethylethanolamine (DEEA)/polymaleic acid (average molecular weight 500
) in a ratio of 10 parts by weight/30 parts by weight and 10.1 parts by weight, and the same method as in Example 1 was used.

Examples 4-6 1.10-decanedicarboxylic acid/jetanolamine (
DEA)/maleic acid/isobutylene copolymer (molar ratio 50/50. average molecular weight 10,000) (Example 4), acrylic acid/2-hydroxyethyl methacrylate (HEMA)/methyl acrylate terpolymer ( Molar ratio 83/16/1, average molecular weight 3,000) (Example 5), acrylic acid/2-hydroxy-3-allyloxypropanesulfonic acid ()IAPS) copolymer (molar ratio 80
/20, average molecular weight 4,000) (Example 6) in a ratio of 10 parts by weight / 30 parts by weight, 10.1 parts by weight, respectively. .

Comparative Example 3 The same method and formulation as in Example 4 were carried out without using the maleic acid/isobutylene copolymer.

Comparative Example 4 A similar test was conducted using only tap water without using a steel sheet discoloration inhibitor.

The above results are shown in Table 1.

〔Effect of the invention〕

Since the steel plate discoloration inhibitor of the present invention contains an aliphatic dicarboxylic acid or its salt and an unsaturated carboxylic acid polymer or its salt as active ingredients, it can achieve excellent rust and discoloration prevention effects and improve product quality. In addition to improving product yield, no white residue is generated even when applied to tap water or industrial water.

Claims (2)

[Claims] (1) A steel sheet discoloration inhibitor comprising an aliphatic dicarboxylic acid or its salt and an unsaturated carboxylic acid polymer or its salt. (2) A steel plate discoloration inhibitor comprising an aliphatic dicarboxylic acid or its salt, an unsaturated carboxylic acid polymer or its salt, and an amine.