JPH0480119B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] This invention is a discoloration preventive agent for steel plates, particularly for preventing discoloration of steel plates whose surface has been activated by chemical cleaning or electrolytic cleaning. This is related to drugs. [Prior Art] There are a wide variety of steel plates, 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 these cleanings, the surface is cleaned (rinsed) with industrial water, pure water, etc. in order to remove impurities adhering to the surface. The surface of the steel plate that has been cleaned by the above cleaning has been activated, making it more susceptible to corrosion.
The product becomes discolored due to rust. 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 to these problems, the above-mentioned problems have been alleviated by continuous pickling and cold rolling using a looper, 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, and usually 3~
The line will be stopped for 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 can be applied to such cleaning water are being put on the market. The steel plate discoloration inhibitors include aliphatic dicarboxylic acids, aromatic carboxylic acids,
Amine salts of aminocarboxylic acids, oxycarboxylic acids, etc., amines alone, hydrazine, etc. are used, and among these, aliphatic dicarboxylic acids are frequently used because they have excellent effects. However, such steel sheet discoloration inhibitors are
If tap water or industrial water is used as dilution water, it will combine with hardness components in the water to form poorly 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 was a problem in that the appearance of steel sheets shipped immediately after electrolytic cleaning was impaired. [Problems to be Solved by the Invention] In order to solve the above-mentioned problems, the purpose of the present invention is to prevent discoloration of a steel plate whose surface has been activated by chemical cleaning or electrolytic cleaning, and to improve product quality and product yield. It is an object of the present invention to provide a steel plate discoloration preventive agent which can prevent discoloration of steel sheets and which does not generate white residue even when tap water or industrial water is used. [Means for Solving the Problems] The present invention provides the following steel plate discoloration inhibitor. (1) A steel sheet discoloration inhibitor consisting of an aliphatic dicarboxylic acid or its salt and an unsaturated carboxylic acid polymer or its salt. (2) A steel sheet 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, suberic acid, azelaic acid, sebacic acid, 1,10-decanedicarboxylic acid,
Examples include 1,14-tetradecanedicarboxylic acid and 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 vinylsulfonic acid, allylsulfonic acid, styrenesulfonic acid,
Examples include 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, 2-hydroxyethyl methacrylate, and isobutylene, which are copolymerized in an amount of 50 mol% or less in the copolymer. The molecular weight of these polymers is 200-20000, preferably 300-10000
is preferred. 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. Examples of amines include monoethanolamine, diethanolamine, triethanolamine, dimethylethanolamine, diethylethanolamine, 2-amino-2-methyl-1-propanol, 1-amino-
Alkanolamines such as 2-propanol, 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 1 to 5 parts by weight per 1 part by weight of the aliphatic dicarboxylic acid. In addition to the above components, the steel plate discoloration inhibitor of the present invention also includes:
Other antirust components, modifiers, and other additives can be blended. 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 plate 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 1000 mg/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. It is effective to do so. Specifically, in the case of a spray rinse system, for example,
A steel plate discoloration inhibitor diluted with 1,000 to 10,000 mg in water can 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 Date Prince series, there is always a steel plate discoloration inhibitor in the Date Tank.
The drug should be injected so that the concentration is maintained at 100 to 1000 mg/. 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 cleaning water containing an anti-discoloration agent, or directly spraying an anti-discoloration agent can be adopted. [Example] Example 1 A test piece was prepared by cutting a cold-rolled steel plate after electrolytic cleaning (SPCC/SB, 60 mm x 100 mm x 0.8 mm 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, as an aliphatic dicarboxylic acid, sebacic acid/
Monoethanolamine (MEA) as amine/
15 parts by weight of sodium polyacrylate (average molecular weight 4000) as a polymer salt of unsaturated carboxylic acid/30
A steel plate discoloration inhibitor mixed in a ratio of part by weight/0.1 part by weight and dissolved in tap water was added to tap water heated to 80°C and diluted to a concentration of 5000 mg/part to obtain a cleaning solution. After immersing the test piece in this cleaning solution for 1 minute, the test piece was placed in a transparent container containing tap water at 80°C 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 The same method and formulation as in Example 1 were used except that polymaleic acid (average molecular weight 500) was used instead of sodium polyacrylate. 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 The same method and formulation as in Example 1 were carried out without using sodium polyacrylate. Example 3 Conducted using a steel sheet discoloration inhibitor containing 1,10-decanedicarboxylic acid/diethylethanolamine (DEEA)/polymaleic acid (average molecular weight 500) in a ratio of 10 parts by weight/30 parts by weight/0.1 part by weight. It was carried out in the same manner as in Example 1. Examples 4 to 6 1,10-decanedicarboxylic acid/diethanolamine (DEA)/maleic acid/isobutylene copolymer (molar ratio 50/50, average molecular weight 10000) (Example 4), acrylic acid/2-hydroxyethyl methacrylate (HEMA)/methyl acrylate terpolymer (molar ratio 83/16/1, average molecular weight 3000) (Example 5), acrylic acid/2-hydroxy-3-allyloxypropanesulfonic acid (HAPS) copolymer In the same manner as in Example 1, using a steel sheet discoloration inhibitor containing 10 parts by weight, 30 parts by weight, and 0.1 part by weight of the combination (mole ratio 80/20, average molecular weight 4000) (Example 6). I went. Comparative Example 3 A test was carried out using the same method and formulation as in Example 4, but 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.

[Table] *2: ○ Not recognized, × recognized [Effect of the invention] The steel sheet discoloration inhibitor of the present invention contains as active ingredients aliphatic dicarboxylic acid or its salt, and a polymer of unsaturated carboxylic acid or its salt. Therefore, excellent rust and discoloration prevention effects are obtained, product quality and product yield are improved, and white residue is not generated even when applied to tap water or industrial water.

Claims (1)

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