Cleaning Agent for Steel Plates

Abstract

To provide a detergent for steel sheet that has good detergency against solid stains such as iron powder in addition to detergency against oil stains, and to provide a method for cleaning steel sheet using the detergent for steel sheet, and a method for producing steel sheet.SOLUTION: Provided are a detergent for steel sheet that contains (A) one or more acid or a salt thereof selected from phosphonic acids and phosphoric acids, (B) a nonionic surfactant, and (C) water, in which the HLB value of the (B) nonionic surfactant by the Davis method is 5 or more and 15 or less, and the pH is 1 or more and 8 or less, and a method for cleaning steel sheet and a method for producing steel sheet using the detergent for steel sheet.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a cleaning agent for steel sheets, which is used when cleaning oil stains, iron powder, etc. adhering to steel sheets (steel strips) made of iron, aluminum, copper, etc. The present invention also relates to a method for cleaning steel sheets and a method for manufacturing steel sheets using the above-mentioned cleaning agent for steel sheets.

Background Art

[0002] Cleaning of steel sheets is necessary as a pretreatment before surface treatment such as painting on the steel sheet surface, and is a very important factor in determining the quality of products. Examples of the dirt adhering to the steel sheet surface include oil stains such as rolling oil and rust preventive oil adhering during cold rolling, and solid dirt such as iron powder.

[0003] Patent Document 1 discloses a neutral metal cleaning agent excellent in detergency, which contains at least one of a group of compounds composed of a salt of a specific sulfonic acid, a salt of a specific carboxylic acid, and a salt of an inorganic acid, a nonionic surfactant, and an anionic surfactant, and has a pH of 5.0 to 8.0.

[0004] Patent Document 2 discloses a cleaning agent composition that can clean iron-based metals and non-ferrous metals on the same cleaning line, does not require rinsing with water, can be used without separately blending a chemical for rust prevention and corrosion prevention, and has good safety and environmental compatibility. The cleaning agent composition contains a dicarboxylic acid having 10 to 12 carbon atoms, an amino alcohol-based amine, an ethylene oxide adduct of an alicyclic amine, a metal ion sequestering agent (chelating agent), an ether-type nonionic surfactant, a glycol ether, and water, and has a pH of 6.5 to 8.5. In the examples, methylglycine diacetic acid or L-glutamic acid diacetic acid is used as the chelating agent.

[0005] Patent Document 3 aims to provide an alkaline cleaning agent with good iron powder removal properties in addition to the detergency of oil. A cleaning agent for steel sheets containing an alkaline agent, maleic acid and / or oxalic acid, a nonionic surfactant with a specific structure, a chelating agent, and water is disclosed. In the examples, sodium gluconate or sodium ethylenediaminetetraacetate is used as the chelating agent.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] Although the techniques described in Patent Documents 1 to 3 have certain effects, further improvement in the detergency of oil and the iron powder removal property is desired.

[0008] An object of the present invention is to provide a cleaning agent for steel sheets that has good detergency against oil stains (hereinafter also referred to as the detergency of oil) and good detergency against solid stains such as iron powder (hereinafter referred to as the iron powder removal property). Another object of the present invention is to provide a method for cleaning steel sheets and a method for manufacturing steel sheets using the cleaning agent for steel sheets.

Means for Solving the Problems

[0009] The present invention is a cleaning agent for steel sheets containing (A) one or more acids selected from phosphonic acids and phosphoric acids or salts thereof, (B) a nonionic surfactant, and (C) water, wherein the HLB value of the (B) nonionic surfactant by the Davis method is 5 or more and 15 or less, and the pH is 1 or more and 8 or less.

[0010] The present invention also provides a method for cleaning a steel sheet, which includes a cleaning step of cleaning the steel sheet using the above-described cleaning agent for steel sheets.

[0011] The present invention also provides a method for manufacturing a steel sheet, which includes a step of cold rolling the steel sheet in the presence of rolling oil and the above-described cleaning step.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a cleaning agent for steel sheets having good iron powder removability in addition to oil detergency, a method for cleaning a steel sheet using the cleaning agent for steel sheets, and a method for manufacturing a steel sheet.

Embodiments for Carrying Out the Invention

[0013] <Cleaning Agent for Steel Sheets> The cleaning agent for steel sheets of the present embodiment contains (A) one or more acids selected from phosphonic acids and phosphoric acids or salts thereof, (B) a nonionic surfactant, and (C) water. The HLB value of the (B) nonionic surfactant by the Davis method is 5 or more and 15 or less, and the pH is 1 or more and 8 or less. According to the cleaning agent for steel sheets of the present embodiment, it is possible to provide a cleaning agent for steel sheets excellent in oil detergency and iron powder removability and a method for cleaning a steel sheet. The reason why the cleaning agent for steel sheets of the present embodiment exhibits such effects is not clear, but it is considered as follows.

[0014] Since the pH of the cleaning agent for steel sheets of the present embodiment is 1 or more and 8 or less, it has an etching effect on the steel sheet surface. The cleaning agent for steel sheets of the present embodiment can slightly dissolve the steel sheet surface by the etching effect to remove oil and iron powder. In addition, since one or more acids selected from (A) phosphonic acids and phosphoric acids or salts thereof contained in the cleaning agent for steel sheets of the present embodiment have a high chelating effect, these acids can chelate the iron powder surface under the condition that the pH is 1 or more and 8 or less to be dispersed and stabilized in water, and it is considered that reattachment of the iron powder removed from the steel sheet surface can be suppressed. Therefore, according to the cleaning agent for steel sheets of the present embodiment, it is considered that a cleaning agent for steel sheets excellent in oil detergency and iron powder removability can be provided.

[0015] [[One or more acids selected from phosphonic acids and phosphoric acids or salts thereof]] From the viewpoints of the detergency of oil and the removability of iron powder, and the suppression of reattachment of oil and iron powder to the steel sheet surface, the cleaning agent for steel sheets contains (A) one or more acids selected from phosphonic acids and phosphoric acids or salts thereof (hereinafter, may also be simply referred to as "(A) component"). From the same viewpoints, the phosphonic acids are preferably organic acids having two or more acid groups. Examples of such phosphonic acids include alkylaminophosphonic acids and hydroxyalkylphosphonic acids. Specifically, aminotrimethylenephosphonic acid, hydroxyethylidenediphosphonic acid, ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, etc. can be exemplified. Examples of phosphoric acids include phosphoric acid, tripolyphosphoric acid, and polyphosphoric acid. From the same viewpoints, the (A) component is preferably one or more acids selected from the group consisting of hydroxyethylidenediphosphonic acid and phosphoric acids or salts thereof, more preferably one or more acids selected from the group consisting of hydroxyethylidenediphosphonic acid and phosphoric acids or alkali metal salts thereof, still more preferably hydroxyethylidenediphosphonic acid, polyphosphoric acid or alkali metal salts thereof, and even more preferably hydroxyethylidenediphosphonic acid or polyphosphoric acid.

[0016] From the viewpoints of the detergency of oil and the removability of iron powder, the content of the (A) component in the cleaning agent for steel sheets is preferably 0.5% by mass or more, more preferably 1.0% by mass or more. From the viewpoint of reducing the drainage treatment load, it is preferably 20% by mass or less, more preferably 10% by mass or less.

[0017] [[ (B) Nonionic surfactant]] From the viewpoints of oil detergency and iron powder removability, the steel sheet cleaning agent contains a (B) nonionic surfactant (hereinafter, may also be simply referred to as the “(B) component”) having an HLB value of 5 or more and 15 or less according to the Davis method. From the same viewpoints, the HLB value of the (B) component according to the Davis method is preferably 5.5 or more, more preferably 6 or more, and preferably 14 or less, more preferably 13 or less. In the present specification, the HLB according to the Davis method can be calculated by using the method described on pages 24 to 25 of “Surfactants: Physical Properties, Applications, and Chemical Ecology” (written by Fumio Kita et al., published by Kodansha Scientific, 7th printing on May 20, 1990).

[0018] From the viewpoints of oil detergency and iron powder removability, the (B) nonionic surfactant preferably has a structure represented by the following general formula (1). R-O-(AO)n-H (1) (In the general formula (1), R is an aliphatic hydrocarbon group having 8 or more and 16 or less carbon atoms, AO is an alkyleneoxy group, n is the average number of moles of addition of AO, and n is a number satisfying 1 or more and 40 or less.)

[0019] In the general formula (1), examples of the aliphatic hydrocarbon group as R include linear and branched chains. From the viewpoint of iron powder removability, a linear chain is preferred. Further, examples of the aliphatic hydrocarbon group of R include saturated (alkyl group) and unsaturated (alkenyl group). The number of carbon atoms of R is preferably 8 or more, more preferably 10 or more, and preferably 16 or less, more preferably 14 or less from the same viewpoints.

[0020] In the compound represented by the general formula (1), AO is an alkyleneoxy group. The alkyleneoxy group is preferably one or more selected from the group consisting of an ethyleneoxy group and a propyleneoxy group.

[0021] In the general formula (1), n represents the average number of moles of alkyleneoxy groups added. From the viewpoints of the detergency of oil and the removability of iron powder, n is preferably 2 or more, more preferably 4 or more, preferably 35 or less, and more preferably 30 or less from the same viewpoints.

[0022] When AO in the general formula (1) is an ethyleneoxy group and a propyleneoxy group, there is no restriction on the arrangement of the ethyleneoxy group and the propyleneoxy group, and it may be a block type or a random type. However, from the viewpoints of the detergency of oil and the removability of iron powder, the block type is preferred.

[0023] From the viewpoints of the detergency of oil and the removability of iron powder, the content of the component (B) in the steel plate cleaning agent is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and preferably 3.0% by mass or less, more preferably 1.0% by mass or less from the viewpoints of foam suppression and reduction of the drainage treatment load.

[0024] 〔Water〕 When the steel plate cleaning agent does not contain components other than the component (A) and the component (B), the content of water in the steel plate cleaning agent is the remainder other than the component (A) and the component (B), and is preferably 70% by mass or more and 99% by mass or less. Examples of the water include tap water, industrial water, and deionized water, and deionized water is preferred. The concentration in the steel plate cleaning agent (aqueous composition) can be controlled by water.

[0025] From the viewpoints of the detergency of oil and the removability of iron powder, the pH of the steel plate cleaning agent is 1 or more, preferably 2 or more, more preferably 3 or more, and from the viewpoint of the removability of iron powder, it is 8 or less, preferably 7.5 or less, more preferably 7 or less. Further, the steel plate cleaning agent of the present invention contains the component (A) and the component (B), and a concentrated composition with a small content of water as the component (C) can be diluted with water at the time of use to adjust the concentration and pH of each component for use. For adjusting the pH, an alkaline agent described later can be used.

[0026] 〔Other components〕 The cleaning agent for steel plates may contain components other than the components (A) to (C) within a range that does not affect the manifestation of the effects of the cleaning agent for steel plates. Examples of components other than the components (A) to (C) include alkaline agents, solubilizing agents, dispersants, thickening agents such as agents for concentration, defoaming agents, corrosion inhibitors, rust preventives, coloring agents, and the like.

[0027] From the viewpoint of the detergency of oil, the cleaning agent for steel plates preferably contains an alkaline agent. Any water-soluble alkaline agent can be used as the alkaline agent, but inorganic alkaline agents are particularly preferred. Specific examples of inorganic alkaline agents include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, silicates of alkali metals such as sodium orthosilicate, sodium metasilicate, and sodium sesquisilicate, carbonates of alkali metals such as disodium carbonate, sodium hydrogen carbonate, and dipotassium carbonate, and borates of alkali metals such as sodium borate. Two or more water-soluble alkaline agents may be combined. From the same viewpoint, hydroxides of alkali metals and silicates of alkali metals are preferred, sodium hydroxide, potassium hydroxide, sodium orthosilicate, and sodium metasilicate are more preferred, and sodium hydroxide and potassium hydroxide are even more preferred.

[0028] From the viewpoint of pH control, the content of the alkaline agent in the cleaning agent for steel plates is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and from the same viewpoint of pH control, it is preferably 10% by mass or less, more preferably 7% by mass or less.

[0029] The cleaning agent for steel plates is used as a cleaning agent for cleaning and removing dirt from steel plates to which oil stains and solid dirt such as iron powder adhere, and is preferably applied when passing a rolled steel plate through a dipping cleaning tank and an electrolytic cleaning tank by means of a roll.

[0030] <Method for cleaning steel plates> The cleaning method of the steel sheet of this embodiment has a cleaning step of cleaning the steel sheet using the above-mentioned cleaning agent for steel sheets. By having this cleaning step, the cleaning method of the steel sheet of this embodiment can clean and remove oil stains such as rolling oil and solid stains such as iron powder. As the cleaning method of the steel sheet in the above-mentioned cleaning step, continuous cleaning, that is, immersion cleaning, spray cleaning, brush cleaning, electrolytic cleaning, etc. can be mentioned, and immersion and electrolytic cleaning are preferable.

[0031] The above-mentioned electrolytic cleaning is a cleaning method in which the steel sheet is made positive (or negative) in the cleaning solution and a direct current is passed, and it uses the bubbles of oxygen (or hydrogen) generated from the steel sheet by the current, and is a step of removing solid stains such as oil stains and iron powder adhering to the steel sheet by physical force. From the viewpoints of the detergency of oil and the removability of iron powder, the temperature of the electrolytic cleaning using the above-mentioned cleaning agent for steel sheets is preferably 30 to 90°C, and more preferably 40 to 80°C. The current density during electrolytic cleaning is preferably 0.5 to 30 A / dm 2 and more preferably 1 to 20 A / dm 2 is more preferable.

[0032] <Manufacturing method of steel sheet> The manufacturing method of the steel sheet of this embodiment includes a step of cold rolling the steel sheet in the presence of rolling oil and a cleaning step of cleaning the rolling oil adhering to the rolled steel sheet with the above-mentioned cleaning agent for steel sheets. The cleaning step in the manufacturing method of the steel sheet of this embodiment is the same as the cleaning step in the cleaning method of the above-mentioned steel sheet. That is, the manufacturing method of the steel sheet of this embodiment can adopt the same method as the conventional manufacturing method of the steel sheet except for having the cleaning step in the cleaning method of the above-mentioned steel sheet.

[0033] The above-mentioned cold rolling step is a processing step of cold rolling the steel sheet in the presence of rolling oil at a steel mill or the like. In this rolling step, since a high pressure is applied to the high-temperature steel sheet by the roll, iron powder is generated on the steel sheet. The steel sheet that has undergone the cold rolling step has oil stains and iron powder adhering to it.

[0034] Preferable steel sheets targeted by the above-mentioned cleaning agent for steel sheets include, for example, steel sheets cold-rolled with a synthetic ester-based rolling oil containing palm oil.

[0035] After the cleaning process, a rinsing process can be performed. The conditions of the temperature and immersion time in the rinsing process can be adjusted as appropriate. From the viewpoints of the detergency of oil and the removability of iron powder, the temperature is preferably 5 to 95°C, more preferably 15 to 90°C. The immersion time is preferably 0.1 to 15 seconds, more preferably 0.5 to 10 seconds.

[0036] The steel sheet obtained after cleaning can be used for various applications such as steel sheets for automobiles, steel sheets for beverages such as canned foods, and steel sheets for home appliances. The amount of solid dirt such as iron powder adhering to the surface of the steel sheet after cleaning varies depending on the use of the steel sheet. However, when the iron powder adhesion weight of the steel sheet before cleaning is taken as 100%, it is preferably 14% or less, more preferably 10% or less, and still more preferably 8% or less after cleaning.

[0037] Also, although it varies depending on the use of the steel sheet, the L value corresponding to the amount of iron powder adhering to the surface of the steel sheet before cleaning, which is the value measured for the lightness of the iron powder transferred from the steel sheet to the tape remaining on the steel sheet, is preferably 80 or less, more preferably 78 or less, from the viewpoint of exerting the effect of cleaning iron powder. The L value corresponding to the amount of iron powder adhering to the surface of the steel sheet after cleaning is preferably 87 or more, more preferably 88 or more, and still more preferably 89 or more. In this specification, the L value, which is the lightness of the iron powder transferred from the steel sheet to the tape remaining on the steel sheet, is measured by the method described in the examples.

[0038] The amount of iron powder adhering to the surface of the steel sheet after cleaning varies depending on the use of the steel sheet. However, when the L value corresponding to the amount of iron powder adhering to the surface of the steel sheet before cleaning is taken as 100%, the L value corresponding to the amount of iron powder adhering to the surface of the steel sheet after cleaning is preferably 112% or more, more preferably 114% or more.

Examples

[0039] <Preparation of cleaning agent for steel sheet> The compositions used in Examples 1 to 9 and Comparative Examples 1 to 7 were prepared as described in Table 1, and a cleaning test was conducted. The active ingredient content of 5.0% by mass of a 60% aqueous solution of 1-hydroxyethane-1,1-diphosphonic acid (1-hydroxyethylidene-1,1-diphosphonic acid) is 3.0% by mass. In addition, Nonionic Surfactants 1 to 8 in Table 1 are nonionic surfactants having the following structures. · Nonionic Surfactant 1: Polyoxyethylene (14) polyoxypropylene (1.5) lauryl myristyl ether (HLB value by Davis method: 7.6) · Nonionic Surfactant 2: Polyoxyethylene (10) polyoxypropylene (1.5) lauryl myristyl ether (HLB value by Davis method: 6.3) · Nonionic Surfactant 3: Polyoxyethylene (10) polyoxypropylene (2) alkyl (sec-C12-14) ether (HLB value by Davis method: 6.2) · Nonionic Surfactant 4: Polyoxyethylene (18) polyoxypropylene (2) lauryl myristyl ether (HLB value by Davis method: 8.8) · Nonionic Surfactant 5: Polyoxyethylene (6) lauryl ether (HLB value by Davis method: 5.2) · Nonionic Surfactant 6: Polyoxyethylene (5) alkyl (sec-C11-15) ether (HLB value by Davis method: 4.9) · Nonionic Surfactant 7: Polyoxyethylene (7) polyoxypropylene (8.5) alkyl (sec-C12-14) ether (HLB value by Davis method: 4.2) · Nonionic Surfactant 8: Polyoxyethylene (41) lauryl ether (HLB value by Davis method: 16.7) In addition, sodium hydroxide or acetic acid was used to adjust the pH of the steel plate cleaner.

[0040] <Steel Plate Cleaning Test> 〔Preparation of Steel Plate to be Cleaned (Measurement Sample)〕 A steel sheet with a thickness of 0.5 mm cold-rolled with a synthetic ester-based rolling oil and cut into a size of 25 mm × 60 mm was used as the steel sheet to be cleaned. The amount of adhered oil on the steel sheet to be cleaned was 115 mg / m 2 , and the L value corresponding to the amount of adhered iron powder was 77.5.

[0041] 〔Cleaning procedure〕 300 g of the steel sheet cleaning agents according to each of the examples and comparative examples described in Table 1 were respectively placed in a 300 mL glass beaker and heated to 65°C. Next, the steel sheet to be cleaned was immersed in the steel sheet cleaning agents according to each of the examples and comparative examples for 5 seconds, and then, while spraying warm water at 60°C on the steel sheet, it was reciprocated once for 1 second between brushes moving at a rotational speed of 300 rpm, and further rinsed by spraying warm water at 60°C (pressure: 2 kgf / cm 2 ) for 2 seconds, and then hot air was blown to dry the surface of the steel sheet, and measurement samples respectively cleaned with the steel sheet cleaning agents according to each of the examples and comparative examples described in Table 1 were obtained.

[0042] 〔Method for measuring the amount of residual carbon adhered〕 As an index of the amount of dirt adhered to the surface of the steel sheet, a carbon / hydrogen / moisture analyzer (model RC-612 manufactured by LECO Corporation) was used to measure the amount of carbon (amount of residual carbon adhered) adhered to the surface of the measurement samples according to each of the examples and comparative examples. Specifically, the steel sheet was heated at 500°C, which is below the softening temperature of iron and at which the dirt on the steel sheet is considered to burn, and the amount of carbon adhered to the steel sheet was determined from the CO2 generated by volatilization, pyrolysis, or combustion. The measurement was carried out until the intensity dropped to 1% or less with the maximum intensity (maximum CO2 generation amount) peak set as 100%. The smaller the value of the residual carbon amount, the better. The average value of 5 sheets was rounded to one decimal place, and the results are shown in Table 1.

[0043] 〔Iron powder removability〕 After performing the above cleaning, a film tape was attached to the steel plate, then the tape was peeled off, and the iron powder remaining on the steel plate was transferred to the tape. The tape with the transferred iron powder was attached to an OHP sheet to obtain an iron content measurement sample. The amount of residual iron powder was measured with a color difference meter (CR-400 manufactured by Minolta Co., Ltd.) using the lightness (L value) of this sample as the amount of residual iron powder. The higher the L value, the better the iron powder removability. The results are shown in Table 1.

[0044]

Table 1

Claims

1. A cleaning agent for steel sheets, comprising: (A) one or more acids selected from phosphonic acids and phosphoric acids or alkali metal salts thereof; (B) a nonionic surfactant; and (C) water, wherein the HLB value of the nonionic surfactant (B) by the Davis method is 5 or more and 15 or less, and the pH of the cleaning agent for steel sheets is 1 or more and 8 or less.

2. The cleaning agent for steel sheets according to Claim 1, wherein the content of the nonionic surfactant (B) is 0.01% by mass or more and 3.0% by mass or less, and the content of water is 70% by mass or more and 99% by mass or less.

3. The cleaning agent for steel sheets according to Claim 1 or 2, wherein the phosphonic acids are organic acids having two or more acid groups.

4. The cleaning agent for steel sheets according to any one of Claims 1 to 3, wherein the nonionic surfactant (B) has a structure represented by the following general formula (1). R—O—(AO)n—H (1) (In the general formula (1), R is an aliphatic hydrocarbon group having 8 or more and 16 or less carbon atoms, AO is an alkyleneoxy group, n is the average number of moles of addition of AO, and n is a number satisfying 1 or more and 40 or less.)

5. A method for cleaning a steel sheet, comprising a cleaning step of cleaning the steel sheet using the cleaning agent for steel sheets according to any one of Claims 1 to 4.

6. A method for manufacturing a steel sheet, comprising a step of cold rolling the steel sheet in the presence of rolling oil and a cleaning step of cleaning the steel sheet using the cleaning agent for steel sheets according to any one of Claims 1 to 4.

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