JP7032983B2 - Detergent composition for steel sheet - Google Patents

Description

The present invention relates to a cleaning agent composition for a steel sheet, a cleaning method using the cleaning agent composition, and a method for producing a steel sheet including the cleaning method in a manufacturing process.

Cleaning of the steel sheet is necessary as a pretreatment for surface treatment such as painting of the surface of the steel sheet, and is a very large factor that determines the quality of the product. Examples of the stains adhering to the surface of the steel sheet include oil stains such as rolling oil and rust preventive oil adhering during cold rolling. In recent cold rolling of steel sheets, rolling oil suitable for improving mill cleanliness and productivity has come to be used, and excellent detergency for the rolling oil is required.

Furthermore, increasing environmental awareness requires reduction of carbon dioxide emissions, which is no exception in steel production. Therefore, in order to suppress the energy cost that leads to the emission of carbon dioxide, we have tried to develop a cleaning agent that exhibits excellent cleaning performance even at a lower temperature than the conventional cleaning temperature of 70 to 90 ° C. Has been done.

On the other hand, in order to meet the diverse needs of the world, a wide variety of steel sheets have been developed that have been surface-treated such as plated steel sheets to improve the value of the steel sheets, and the production volume as steel sheets has also increased significantly. Improvement of sex is required. In order to improve productivity, it is necessary to improve efficiency in each manufacturing process, and improvements have been made to increase the processing area per unit time by widening the width of the steel sheet and increasing the processing speed. In addition, instead of renewing equipment that requires excessive costs, equipment improvements such as improving aging equipment to increase processing speed are being actively carried out. In order to improve productivity as described above, in the cleaning step, a highly detergency cleaning agent that can be cleaned in a short time by increasing the cleaning speed is required. In addition, as the speed increases and the width of the steel sheet increases, the amount of cleaning liquid taken out from the cleaning tank per unit time tends to increase, and the amount of additional cleaning liquid replenished tends to increase. As the amount of replenishment increases, the temperature of the cleaning liquid drops, the amount of energy such as steam for raising the temperature increases, and it is necessary to increase the storage amount of the cleaning agent. There is a demand for mold cleaners.

Against this background, various concentrated cleaning agents have been developed. For example, Patent Document 1 describes a strong alkaline water-soluble composition containing a strong alkaline agent and a nonionic surfactant of HLB3 to 18 and containing two specific carboxylic acids.

Patent Document 2 contains (a) an alkaline agent, (b) a nonionic surfactant and (c) a solubilizer, and the solubilizer is a carboxylic acid represented by the general formula (I) or a salt thereof. (Hereinafter referred to as solubilizer (I)), carboxylic acid represented by the general formula (II) or a salt thereof (hereinafter referred to as solubilizer (II)) and carboxylic acid represented by the general formula (III) or a salt thereof. (Hereinafter referred to as solubilizer (III)), and the blending ratios of the solubilizers (I), (II) and (III) are by weight, (I): [(II) + (III)] =. Described are alkaline aqueous composition compositions having 95: 5 to 35:65 and (II): (III) = 70:30 to 30:70.

Patent Document 3 describes (a) an alkaline agent: 10 to 50% by weight, (b) a nonionic alkylene oxide adduct: 0.1 to 10% by weight, and (c) an alkyl polyglycoside having 2 to 4 carbon atoms: Described is a detergent composition comprising 0.1 to 10% by weight, (d) an alkyl polyglycoside having 6 to 16 carbon atoms: 0.1 to 10% by weight, and (e) water: remaining amount%. There is.

Patent Document 4 contains an alkaline agent, a specific polyoxyalkylene alkyl ether, and a specific water-soluble polymer carboxylic acid, and is characterized by being liquid or slurry-like and fluid. Is described.

Japanese Unexamined Patent Publication No. 1-123622 Japanese Unexamined Patent Publication No. 2004-182801 Japanese Unexamined Patent Publication No. 2009-263560 Japanese Unexamined Patent Publication No. 11-2262887

However, in the cleaning of steel sheets, the cleaning agent compositions described in Patent Documents 1 to 3 are insufficiently concentrated at a high alkaline agent concentration, and the cleaning property at a low temperature is also insufficient. Further, the detergent composition described in Patent Document 4 can be highly concentrated and washed at a low temperature, but its low stability requires a stirring device for long-term storage, and its high viscosity makes delivery difficult, and piping. There are problems such as thickening and requiring a powerful pump. Therefore, there is a demand for a cleaning agent composition for steel sheets that can be stably stored at a high concentration while maintaining good cleaning performance at a low temperature.

The present invention relates to at least one organic acid selected from the group consisting of an inorganic alkaline agent (component A), gluconic acid and ethylenediaminetetraacetic acid or a salt thereof (component B), and a nonionic surfactant represented by the following formula (1) (1). It contains a component C), an alkyl glucoside (component D) represented by the following formula (2), a fatty acid or a salt thereof (component E) represented by the following formula (3), and water (component F), and the content of the component A is Detergent composition for steel plates, 25% by mass or more and 34% by mass or less, the content of component D is 0.3% by mass or more and 2.9% by mass or less, and the content of component F is 57% by mass or more and 74% by mass or less. Provided are a product, a cleaning method using the detergent composition, and a method for producing a steel plate including the cleaning method in the production process.
R ¹ -O-{(EO) n / (PO) m} -H (1)
(In the formula (1), R ¹ is an alkyl group or an alkenyl group having 8 or more and 18 or less carbon atoms in a linear or branched chain, EO is an ethyleneoxy group, PO is a propyleneoxy group, and n is an average addition molar of EO. The number and m are the average number of moles of PO added, n is 2 or more and 20 or less, m is a number satisfying 0 or more and 20 or less, and the addition form of PO and EO in {} is either a random sequence or a block sequence. May be.)
R2-Gx ( ² )
(In the formula (2), R ² represents an alkyl group or an alkenyl group having 5 or more and 8 or less carbon atoms in the linear or branched chain, G represents a residue derived from glucose, and x represents a residue derived from glucose. Indicates the average degree of condensation of 1 or more and 5 or less.)
R ³ -COM (3)
(In the formula (3), R ³ represents an alkyl group or an alkenyl group having 5 or more and 9 or less carbon atoms in a linear or branched chain, and M represents a cation or a hydrogen atom.)

According to the present invention, a detergent composition for steel sheets, a cleaning method using the detergent composition, and the cleaning method that can be stably stored at a high concentration while maintaining good detergency at low temperatures are used in the manufacturing process. It is possible to provide a method for manufacturing a steel sheet containing a steel sheet.

<Cleaning agent composition for steel sheet>
The cleaning agent composition for steel plates of the present embodiment is at least one organic acid selected from the group consisting of an inorganic alkaline agent (component A), gluconic acid and ethylenediaminetetraacetic acid or a salt thereof (component B), and the following formula (1). Contains a nonionic surfactant (component C) represented by the following formula (component C), an alkyl glucoside represented by the following formula (2) (component D), a fatty acid represented by the following formula (3) or a salt thereof (component E), and water (component F). However, the content of component A is 25% by mass or more and 34% by mass or less, the content of component D is 0.3% by mass or more and 2.9% by mass or less, and the content of component F is 57% by mass or more and 74% by mass or less. Is.
R ¹ -O-{(EO) n / (PO) m} -H (1)
(In the formula (1), R ¹ is an alkyl group or an alkenyl group having 8 or more and 18 or less carbon atoms in a linear or branched chain, EO is an ethyleneoxy group, PO is a propyleneoxy group, and n is an average addition molar of EO. The number and m are the average number of moles of PO added, n is 2 or more and 20 or less, m is a number satisfying 0 or more and 20 or less, and the addition form of PO and EO in {} is either a random sequence or a block sequence. May be.)
R2-Gx ( ² )
(In the formula (2), R ² represents an alkyl group or an alkenyl group having 5 or more and 8 or less carbon atoms in the linear or branched chain, G represents a residue derived from glucose, and x represents a residue derived from glucose. Indicates the average degree of condensation of 1 or more and 5 or less.)
R ³ -COM (3)
(In the formula (3), R ³ represents an alkyl group or an alkenyl group having 5 or more and 9 or less carbon atoms in a linear or branched chain, and M represents a cation or a hydrogen atom.)

Although the details of the action mechanism of the effect in the detergent composition for steel sheets of the present embodiment are unknown, it is presumed as follows. That is, in water (component F) in which the inorganic alkaline agent (component A) is dissolved at a high concentration, water molecules are immobilized near the cations of the inorganic alkaline agent, the number of free water molecules is small, and the water molecules are relatively hydrophilic. The non-ionic surfactant (component C) having a low content cannot stably exist in water and separates. It is presumed that by adding a specific alkyl glucoside (component D) at a specific ratio (concentration), the component D acts between the nonionic surfactant (component C) and water (component F) to solubilize the substance. Will be done. In addition, it is presumed that a specific fatty acid or a salt thereof (component E) assists the action of component D and improves stability. On the other hand, the inorganic alkaline agent (component A) has an action of saponifying oily stains such as rolling oil adhering to the steel sheet and changing the form so that it can be easily removed from the surface of the steel sheet such as soap, and is a nonionic surfactant (component). C) is not affected by the salt and acts on hydrophobic oily stains to become hydrophilic and promote the action of the alkaline agent, so that the detergency can be improved. However, if a large amount of the component D is present, the affinity with the component C is strong, so that it is presumed that the surface activity of the component C is lowered and the detergency is lowered. Therefore, it is presumed that high concentration and high detergency can be achieved at the same time by setting the components A, D and F to specific concentrations. However, the present disclosure may not be construed as being limited to this mechanism.

[Inorganic alkaline agent (component A)]
As the component A, any inorganic alkaline agent can be used. Specific examples of the inorganic alkaline agent include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali metal silicates such as sodium orthosilicate, sodium metasilicate and sodium sesquisilicate, and trisodium phosphate. Alkali metal phosphates, alkali metal carbonates such as disodium carbonate, sodium hydrogencarbonate and dipotassium carbonate, alkali metal borates such as sodium borate and the like can be used. Two or more kinds of inorganic alkaline agents may be combined. From the viewpoint of ensuring the removability of organic stains and improving the detergency, alkali metal hydroxides and alkali metal silicates are preferable, sodium hydroxide, potassium hydroxide, sodium orthosilicate and sodium metasilicates are more preferable, and water. Sodium oxide and potassium hydroxide are even more preferred, and sodium hydroxide is even more preferred. When the inorganic alkaline agent contains sodium hydroxide, the sodium hydroxide concentration in the inorganic alkaline agent is preferably 50% by mass or more, more preferably 70% by mass or more, and 90% by mass or more from the viewpoint of improving detergency. Even more preferably, 100% by mass is even more preferable.

[Organic acid or salt thereof (component B)]
The component B is at least one organic acid selected from the group consisting of gluconic acid and ethylenediaminetetraacetic acid or a salt thereof in order to ensure detergency. Among these, from the viewpoint of improving the detergency of organic stains, a salt of at least one organic acid selected from the group consisting of gluconic acid and ethylenediamine tetraacetic acid is preferable, and a salt of gluconic acid is more preferable. As the salt, an alkali metal salt or a lower amine salt is preferable, an alkali metal salt is more preferable, a sodium salt and a potassium salt are further preferable, and a sodium salt is further preferable. Among them, from the same viewpoint, it is preferable to use a combination of an alkali metal salt of gluconic acid and an alkali metal salt of ethylenediamine tetraacetic acid, and a combination of sodium gluconate and sodium ethylenediamine tetraacetate is more preferable.

[Nonionic surfactant (component C)]
As the component C, any nonionic surfactant represented by the following formula (1) can be used, but from the viewpoint of improving the detergency against organic stains and the foam-suppressing property, it is represented by the following formula (4). Nonionic surfactants are more preferred. At least one type of component C may be used, and two or more types may be used in combination.
R ¹ -O-{(EO) n / (PO) m} -H (1)
(R ¹ is an alkyl or alkenyl group having 8 or more and 18 or less carbon atoms in a linear or branched chain, EO is an ethyleneoxy group, PO is a propyleneoxy group, n is the average number of moles of EO, and m is PO. The average number of added moles, n is 2 or more and 20 or less, m is a number satisfying 0 or more and 20 or less, and the addition form of PO and EO in {} may be either a random sequence or a block sequence.)
R ⁴ -O- (EO) p (PO) q (EO) r-H (4)
( ^R4 is an alkyl group or alkenyl group having 8 or more and 18 or less carbon atoms in a linear or branched chain, EO is an ethyleneoxy group, PO is a propyleneoxy group, and p, q, and r are ethyleneoxy groups and propyleneoxy, respectively. The average number of moles of groups and ethyleneoxy groups, p is 1 or more and 15 or less, q is 0 or more and 20 or less, r is 1 or more and 15 or less, and q ≦ p + r ≦ 20).

In the nonionic surfactant represented by the formula (1), EO is an ethyleneoxy group and PO is a propyleneoxy group. The ethyleneoxy group and the propyleneoxy group have a distribution depending on the number of added moles, but from the viewpoint of improving the detergency of organic stains, the average number of added moles n of the ethyleneoxy group n is 2 or more and 20 or less, and the average of the propyleneoxy groups. The number of added moles m is 0 or more and 20 or less. From the viewpoint of improving the detergency of organic stains, the average number of moles of ethylene oxy groups added is preferably 5 or more, more preferably 8 or more, further preferably 12 or more, and preferably 18 or less, more preferably 16 or less. .. The average number of moles of propyleneoxy group added is preferably 1 or more, preferably 10 or less, more preferably 5 or less, still more preferably 3 or less, from the viewpoint of improving detergency and foam suppression. Further, from the viewpoint of improving detergency, it is preferable that the average number of moles of ethylene oxy groups added is larger than the average number of moles of propyleneoxy groups added. Of the nonionic surfactants represented by the formula (1), the nonionic surfactant represented by the formula (4) is more preferable from the viewpoint of improving detergency and foam suppression.

In the nonionic surfactant represented by the formula (4), EO is an ethyleneoxy group and PO is a propyleneoxy group. The average number of moles of ethylene oxy groups p and r are 1 or more and 15 or less, respectively, and each is 1 or more, preferably 2 or more, and more preferably 4 or more, from the viewpoint of improving the detergency of organic stains. The above is more preferable, and it is 15 or less, preferably 12 or less, and more preferably 10 or less. The average number of moles of propyleneoxy groups added is 0 or more and 20 or less, preferably 1 or more, preferably 10 or less, and more preferably 5 or less, from the viewpoint of improving detergency and foam suppression. The following is more preferable. Further, from the viewpoint of improving detergency, p + r is preferably q or more and 20 or less, and is preferably larger than q.

[Alkyl glucoside (component D)]
The component D is an alkyl glucoside represented by the following formula (2).
R2-Gx ( ² )
(In the formula (2), R ² represents an alkyl group or an alkenyl group having 5 or more and 8 or less carbon atoms in a linear or branched chain, G represents a residue derived from glucose, and x represents a residue derived from glucose. Indicates the average degree of condensation of 1 or more and 5 or less.)

In the alkyl glucoside represented by the formula (2), R ² is an alkyl group or an alkenyl group having 5 or more and 8 or less carbon atoms in a straight chain or a branched chain, and is a branched chain from the viewpoint of improving detergency and storage stability. Is preferable, and an alkyl group is preferable. From the same viewpoint, R ² has 5 or more carbon atoms, preferably 6 or more, and more preferably 7 or more. x is the average degree of condensation of residues derived from glucose, which is 1 or more and 5 or less, preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and further preferably 1 or more and 2 or less. preferable.

As specific examples of the component D, n-pentyl glucoside, n-hexyl glucoside, n-heptyl glucoside, isoheptyl glucoside, n-octyl glucoside, isooctyl glucoside, 2-ethylhexyl glucoside and the like can be used. From the viewpoint of improving cleanability and storage stability, n-hexyl glucoside, n-heptyl glucoside, isoheptyl glucoside, n-octyl glucoside, isooctyl glucoside, and 2-ethylhexyl glucoside are preferable, and n-heptyl glucoside and isoheptyl glucoside are preferable. , N-octyl glucoside, isooctyl glucoside, 2-ethylhexyl glucoside are more preferred, n-octyl glucoside, isooctyl glucoside, 2-ethylhexyl glucoside are even more preferred, and isooctyl glucoside, 2-ethylhexyl glucoside are even more preferred. At least one type of component D may be used, and two or more types may be used in combination.

[Organic acid or salt thereof (component E)]
The component E is a fatty acid represented by the following formula (3) or a salt thereof.
R ³ -COM (3)
(In the formula (3), R ³ represents an alkyl group or an alkenyl group having 5 or more and 9 or less carbon atoms in a linear or branched chain, and M represents a cation or a hydrogen atom.)

In the fatty acid represented by the formula (3) or a salt thereof, R ³ is an alkyl group or an alkenyl group having 5 or more and 9 or less carbon atoms in a straight chain or a branched chain, and the branched chain is preferable from the viewpoint of improving storage stability. , Alkyl groups are preferred. From the same viewpoint, R ³ has 5 or more carbon atoms, preferably 6 or more, more preferably 7 or more, and 9 or less, preferably 8 or less. M is a cation or a hydrogen atom, and from the same viewpoint, a cation is preferable, an alkali metal ion or a lower ammonium is more preferable, a sodium ion or a potassium ion is further preferable, and a sodium ion is further preferable.

As specific examples of the component E, caproic acid, enanthic acid, neoheptanic acid, caprylic acid, 2-ethylhexanoic acid, pelargonic acid, 3,5,5-trimethylhexanoic acid, capric acid and salts thereof can be used. .. From the viewpoint of improving storage stability, caprylic acid, 2-ethylcaproic acid, pelargonic acid, 3,5,5-trimethylcaproic acid and salts thereof are preferable, and caprylic acid salt and 2-ethylhexanoic acid salt are more preferable. Preferably, sodium caprylate, sodium 2-ethylhexanoate is more preferable, and sodium 2-ethylhexanoate is even more preferable. At least one kind of component E may be used, and two or more kinds may be used in combination.

[Water (component F)]
As the component F, industrial water, tap water, deionized water and the like can be used, industrial water is preferable from the viewpoint of supply and cost, and ion-exchanged water is preferable from the viewpoint of detergency.

In one embodiment of the present invention, component A is sodium hydroxide, component B is a salt of at least one organic acid selected from the group consisting of gluconic acid and ethylenediaminetetraacetic acid, and component C is the above formula (1). It is preferable that the component D is the alkyl glucoside represented by the above formula (2) and the component E is a salt of the fatty acid represented by the above formula (3).

Further, component A is sodium hydroxide, component B is a sodium salt of at least one organic acid selected from the group consisting of gluconic acid and ethylenediamine tetraacetic acid, and component C is a nonionic interface represented by the above formula (4). It is an activator, and component D is more preferably an alkyl glucoside represented by the formula (2), component E is more preferably a sodium salt of a fatty acid represented by the formula (3), and component A is sodium hydroxide. Component B is sodium gluconate and sodium ethylenediamine tetraacetate, component C is a nonionic surfactant represented by the above formula (4), component D is an alkyl glucoside represented by the above formula (2), and component E is. It is more preferably a sodium salt of the fatty acid represented by the formula (3).

[Other ingredients]
The cleaning agent composition for a steel sheet of the present embodiment may contain components other than the components A to F generally used as a cleaning agent within a range that does not affect the performance. Examples thereof include solubilizers, dispersants, concentrates such as thickeners, defoamers, corrosion inhibitors, rust inhibitors, colorants and the like.

[Concentration of each component]
The content of the inorganic alkaline agent (component A) is 25% by mass or more and 34% by mass or less, from the viewpoint of improving the transportation efficiency and the storage efficiency, and improving the detergency when diluted and used for cleaning the steel plate. , 26% by mass or more, more preferably 27% by mass or more, further preferably 28% by mass or more, and 33% by mass from the viewpoint of improving storage stability and improving the detergency when diluted and used for cleaning the steel plate. % Or less is preferable, 32% by mass or less is more preferable, and 31% by mass or less is further preferable.

The content of at least one organic acid selected from the group consisting of gluconic acid and ethylenediamine tetraacetic acid or a salt thereof (component B) is 0.3 from the viewpoint of improving detergency when diluted and used for cleaning steel sheets. By mass or more is preferable, 0.4% by mass or more is more preferable, 0.5% by mass or more is further preferable, and from the viewpoint of improving storage stability and reducing the wastewater treatment load after diluting and using for cleaning the steel plate. , 7% by mass or less is preferable, 6% by mass or less is more preferable, and 5% by mass or less is further preferable. The content of gluconic acid or a salt thereof is preferably 0.3% by mass or more, more preferably 0.4% by mass or more, and more preferably 0.5, from the viewpoint of improving the detergency when diluted and used for cleaning the steel plate. It is more preferably 5% by mass or more, more preferably 5% by mass or less, and more preferably 4% by mass or less, from the viewpoint of improving storage stability and reducing the wastewater treatment load after diluting and using for cleaning the steel plate. More preferably, it is by mass or less.

The content of the nonionic surfactant (component C) represented by the formula (1) is preferably 0.3% by mass or more, preferably 0.3% by mass or more, from the viewpoint of improving the detergency when diluted and used for cleaning the steel plate. 4% by mass or more is more preferable, 0.5% by mass or more is further preferable, from the viewpoint of improving storage stability, improving detergency and foam suppressing property when diluted and used for cleaning steel sheets, and diluting. From the viewpoint of reducing the load of wastewater treatment after use for cleaning steel sheets and improving the foam suppression property during wastewater treatment, 1.0% by mass or less is preferable, 0.95% by mass or less is more preferable, and 0.9% by mass or less. Is more preferable.

The content of the alkyl glucoside (component D) represented by the formula (2) is preferably 0.3% by mass or more and 2.9% by mass or less, preferably 0.4% by mass or more from the viewpoint of improving storage stability. , 0.45% by mass or more is more preferable, 0.5% by mass or more is further preferable, 0.55% by mass or more is further preferable, and the cleanability is improved and diluted when diluted and used for cleaning the steel plate. From the viewpoint of reducing the wastewater treatment load after being used for cleaning the steel plate, 2.8% by mass or less is preferable, 2.6% by mass or less is more preferable, and 2.4% by mass or less is further preferable, and 2.3% by mass. % Or less is even more preferable.

The content of the fatty acid or its salt (component E) represented by the formula (3) is preferably 0.03% by mass or more, more preferably 0.04% by mass or more, and more preferably 0.05, from the viewpoint of improving storage stability. By mass or more is further preferable, 0.06% by mass or more is further preferable, and from the viewpoint of reducing the wastewater treatment load after diluting and using for cleaning the steel plate, 0.3% by mass or less is preferable, and 0.25 mass by mass. % Or less is more preferable, 0.2% by mass or less is further preferable, and 0.15% by mass or less is further preferable.

The content of water (component F) is 57% by mass or more and 74% by mass or less, preferably 58% by mass or more, more preferably 59% by mass or more, and 60% by mass or more from the viewpoint of improving storage stability. More preferably, 61% by mass or more is further preferable, 73% by mass or less is more preferable, 72% by mass or less is more preferable, and 71% by mass or less is further preferable from the viewpoint of improvement of storage stability, transportation efficiency and storage efficiency. , 70% by mass or less is even more preferable.

The content of the components other than the components A to E is preferably 0% by mass or more and 5.0% by mass or less, more preferably 0% by mass or more and 2.0% by mass or less, and 0% by mass, within a range that does not affect the performance. % Or more and 1.0% by mass or less are further preferable, and 0% by mass or more and 0.5% by mass or less are further preferable.

The detergent composition for steel sheets of the present embodiment does not require a special method for storage because it has excellent storage stability, but in an extremely low temperature environment where the temperature is kept below −5 ° C. for a long period of time, moisture is retained. Since there is a risk of freezing, it is preferable to keep the temperature at -5 ° C or higher by keeping the storage container, storage tank, transportation pipe, etc. warm.

The detergent composition for steel sheets of the present embodiment is effective when cleaning at a high speed of 500 m / min or more, and more effective when cleaning at a high speed of 800 m / min or more. In particular, it is effective when cleaning a cold-rolled steel sheet at a high speed of 1 second or less required for electrolytic cleaning. A general steel plate cleaning line has a structure of immersion cleaning → brush cleaning → electrolytic cleaning → brush cleaning → rinsing → drying, but the period from immersion cleaning to drying is about 50 m, and the entire process is performed when the line speed is 500 m / min. Cleaning is performed in an extremely short time of 6 seconds. Of these, the electrolytic cleaning step is about 10 to 20 m, and when the line speed is 500 m / min, it is calculated to be about 1.2 to 2.4 seconds. The cleaning agent composition for steel sheets of the present embodiment is effective for electrolytic cleaning in such a short time and even in a shorter time, and thereby makes it possible to increase the cleaning line speed.

<How to clean the steel plate>
In the method for cleaning a steel sheet of the present embodiment, the cleaning agent composition is diluted with component F so that the alkalinity (Na ₂ O%) is 0.7% or more and 2.5% or less, and the steel sheet is washed. Has a cleaning step to do. The alkalinity of the cleaning agent composition during steel plate cleaning is preferably 0.7% or more, more preferably 1.0% or more, from the viewpoint of improving the cleaning property and the electrical conductivity when used for electrolytic cleaning. 2% or more is further preferable, 1.5% or more is further preferable, 2.5% or less is preferable, 2.4% or less is more preferable, and 2.3% or less is further preferable from the viewpoint of improving detergency. In the present specification, alkalinity is measured by the method described in Examples.

The cleaning temperature of the steel sheet in the cleaning step is preferably 20 ° C. or higher, more preferably 30 ° C. or higher, preferably 60 ° C. or lower, more preferably 50 ° C. or lower, from the viewpoint of reducing energy cost. 40 ° C. or lower is more preferable. The detergency does not deteriorate even when used at a high cleaning temperature such as 80 ° C.

The immersion time in the cleaning step is preferably 0.1 seconds or longer, more preferably 0.5 seconds or longer, more preferably 15 seconds or less, and more preferably 10 seconds or less from the viewpoint of steel sheet productivity. preferable.

Examples of the cleaning method in the cleaning step include continuous cleaning, that is, immersion cleaning, spray cleaning, brush cleaning, electrolytic cleaning, and the like, and oil stains such as rolling oil and solid stains such as iron powder can be cleaned and removed. .. The cleaning step is preferably immersion and electrolytic cleaning, and is preferably applied when the rolled steel sheet is passed through an alkaline immersion cleaning tank and an alkaline electrolytic cleaning tank by a roll. Electrolytic cleaning is a cleaning method in which the steel sheet is made positive (or negative) in the cleaning liquid and a direct current is passed through it. Oil stains attached to the steel sheet due to physical force using oxygen (or hydrogen) bubbles generated from the steel sheet by the electric current. This is the process of removing solid stains such as iron powder and iron powder.

In the electrolytic cleaning using the steel sheet cleaning agent composition, the current density at the time of electrolytic cleaning is preferably 0.5 A / dm ² or more, more preferably 1 A / dm ² or more, preferably 30 A / dm ² or less, and 20 A. / Dm ² or less is more preferable.

After the cleaning step, a rinsing step of rinsing the steel sheet to be cleaned by immersing and cleaning with water can be provided. Conditions of temperature and immersion time in the rinsing step can be appropriately adjusted. The temperature is preferably 5 ° C. or higher, more preferably 15 ° C. or higher, preferably 70 ° C. or lower, and more preferably 60 ° C. or lower from the viewpoint of reducing energy cost. The immersion time is preferably 0.1 seconds or longer, more preferably 0.5 seconds or longer, and more preferably 15 seconds or less, more preferably 10 seconds or less, from the viewpoint of steel sheet productivity, from the viewpoint of detergency.

Preferred steel sheets targeted by the cleaning method of the present embodiment include, for example, cold-rolled steel sheets.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

<Examples 1 to 8 and Comparative Examples 1 to 10>
[Preparation of detergent composition for steel sheet]
300 g of detergent compositions for steel sheets 1 to 18 were prepared according to the following procedure with the components and blending amounts shown in Table 1. The unit of the blending amount shown in Table 1 is mass%, and is shown by the effective amount.
In a 1.300 mL glass beaker, components other than the component A, excluding the component F required for dissolving the component A, were added, and the mixture was mixed and stirred to dissolve the solid (powder) component to obtain a mixed solution.
2. 2. Component A (including component F required to dissolve component A) was added to the mixture obtained in 1 above, and the mixture was mixed and stirred to obtain a test solution.

[Each ingredient]
-Inorganic alkaline agent (component A):
A-1: Sodium hydroxide (manufactured by Tokuyama Corporation, liquid caustic soda (48%))
-Organic acid or salt thereof (component B):
B-1: Sodium gluconate (manufactured by Fuso Chemical Industry Co., Ltd., sodium gluconate)
B-2: Sodium ethylenediaminetetraacetate (manufactured by Nagase ChemteX Corporation, Clewat S2 (sodium ethylenediaminetetraacetate, tetrahydrate))
-Nonionic surfactant (component C):
C-1: sec-C ₁₂ H ₂₅ , sec-C ₁₄ H ₂₉ -O- (EO) _5- (PO) _2- (EO) ₅ -H
(A compound in which 5 mol of EO, 2 mol of PO, and 5 mol of EO are block-added in this order to a mixed alcohol of secondary dodecanol and secondary tetradecanol. When represented by the formula (1), R ¹ is an alkyl group having 12 carbon atoms and Alkyl group having 14 carbon atoms, m is 2, n is 10) (expressed by the formula (4), ^R4 is an alkyl group having 12 carbon atoms and an alkyl group having 14 carbon atoms, p is 5, q is 2, r. Is 5))
C-2: C ₁₂ H ₂₅ , C ₁₄ H ₂₉ -O- (EO) _7- (PO) _1.5- (EO) ₇ -H
(A compound in which 7 mol of EO, 1.5 mol of PO, and 7 mol of EO are block-added in this order to a mixed alcohol of lauryl alcohol and myristyl alcohol. When represented by the formula (1), R ¹ is an alkyl group having 12 carbon atoms and carbon atoms. 14 alkyl groups, m is 1.5, n is 14) (expressed by the formula (4), ^R4 is a linear alkyl group having 12 carbon atoms and a linear alkyl group having 14 carbon atoms, p is 7, q. Is 1.5, r is 7))
-Alkyl glucoside (component D):
D-1: Isooctyl Glucoside (Shanghai Fine Chemical Co., Ltd., GREENAPG IC 08)
-Fatty acid or its salt (component E):
E-1: Sodium 2-ethylhexanoate (a salt of 2-ethylhexanoic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) neutralized with sodium hydroxide)
Water (component F):
Ion-exchanged water: Pure water of 1 μS / cm or less manufactured by the pure water device G-10DSTSET manufactured by Organo Corporation Others:
D-2 (non-ingredient D): Butyl polyglucoside (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., nonioside B-15 (x = about 1.5))
D-3 (non-ingredient D): decyl glucoside (Made by Kao Corporation, My Doll 10)
D-4 (non-ingredient D): 2-ethylhexylaminodipropionate sodium salt

[Storage stability test]
100 g of the prepared detergent composition for steel sheet 1 to 18 was placed in a 110 mL borosilicate glass screw tube bottle (screw tube bottle No. 8, manufactured by Maruemu Corporation), sealed tightly, and kept at a constant temperature of 50, 25, -5 ° C. The composition was allowed to stand in a tank for 25 hours, and the state of the composition was visually confirmed. The evaluation was performed according to the following criteria. The evaluation results are shown in Table 1.
1: Uniform transparent 2: Uniform and turbid 3: Separation

<Examples 9 to 16 and Comparative Examples 11 to 20>
[Preparation of cleaning agent for steel sheet]
The steel sheet cleaning agent compositions 1 to 18 used in Examples 1 to 8 and Comparative Examples 1 to 10 were diluted to the alkalinity shown in Table 2 to prepare steel sheet cleaning agents 1 to 18. The steel sheet cleaning agent composition 1 corresponds to the steel sheet cleaning agent 1, and the steel sheet cleaning agent composition 2 and later also correspond to the steel sheet cleaning agent 2 and later.

[Steel sheet cleaning test-1]
[Steel sheet to be cleaned]
A steel sheet having a thickness of 0.2 mm, which was cold-rolled with synthetic ester-based rolling oil (containing 30% by mass of palm oil), was cut into a size of 60 mm × 25 mm and used for a steel sheet cleaning test. As a result of measuring the carbon adhesion amount of the steel sheet before cleaning by the same method as the method for measuring the residual carbon adhesion amount described later, it was 99 mg / m ² .

[Washing test procedure]
300 g of the steel sheet cleaning agent shown in Table 2 was placed in a 300 mL glass beaker and heated to 50 ° C. Next, a pair of iron electrode plates having a size of 100 mm in length × 50 mm in width (distance between electrodes is 20 mm) were installed in the cleaning agent for steel plates. The steel sheet to be cleaned was immersed at equal distances between the electrodes and in the center substantially in parallel for 1 second, and then the potential of the steel sheet was switched once from negative to positive for 0.35 seconds at a current density of 5 A / dm ² for electrolytic cleaning. After that, the steel sheet was rinsed by spraying hot water at 60 ° C. for 1 second with a spray (pressure: 2 kgf / cm ² ), and warm air was blown to dry the surface of the steel sheet.

[Method for measuring residual carbon adhesion]
A carbon / hydrogen / moisture analyzer (model number RC-612 LECO) was used as an index of the amount of dirt adhering to the surface of the steel sheet, and the amount of carbon adhering to the steel sheet (residual carbon adhering amount) was measured. The equipment conditions are that the steel sheet is heated at 500 ° C, which is below the softening temperature of iron and where dirt on the steel sheet is considered to burn, and the amount of carbon adhering to the steel sheet from CO ² generated by volatilization / pyrolysis or combustion is determined. I figured it out. The measurement was carried out until the maximum intensity (maximum amount of CO ² generated) peak was set to 100% and the intensity dropped to 1% or less. The average value of the five sheets is rounded to two digits after the decimal point, and the results are shown in Table 2.

<Examples 17 and 18>
[Preparation of cleaning agent for steel sheet]
The steel sheet cleaning agent composition 4 was diluted to have the alkalinity shown in Table 3 to prepare the steel sheet cleaning agents 17 and 18.

[Steel sheet cleaning test-2]
The same method as in the steel sheet cleaning test-1 was performed except that the steel sheet cleaning agents 17 and 18 were used. The results are shown in Table 3.

[Measurement of alkalinity (Na ₂ O%)]
20 g of the measurement solution was collected in a 100 mL glass Erlenmeyer flask, 3 drops of a phenolphthalein indicator was added, and the mixture was titrated with a 1 mol / L hydrochloric acid standard solution. The end point was a point where the color changed from red to colorless, and the alkalinity was calculated by the following formula. The results are shown in each table.
Alkaliity (Na ₂ O%) = A × f × 3.1 ÷ 20
A: Amount of 1 mol / L hydrochloric acid standard solution required for titration (mL)
f: Factor of 1 mol / L hydrochloric acid standard solution

Claims (4)

Inorganic alkaline agent (component A),
At least one organic acid selected from the group consisting of gluconic acid and ethylenediaminetetraacetic acid or a salt thereof (component B),
Nonionic surfactant (component C) represented by the following formula (1),
Alkyl glucoside (component D) represented by the following formula (2),
Fatty acid represented by the following formula (3) or a salt thereof (component E),
And water (component F),
The content of the component A is 25% by mass or more and 34% by mass or less, the content of the component D is 0.3% by mass or more and 2.9% by mass or less, and the content of the component F is 57% by mass or more and 74% by mass or less. , Detergent composition for steel sheet.
R ¹ -O-{(EO) n / (PO) m} -H (1)
(In the formula (1), R ¹ is an alkyl group or an alkenyl group having 8 or more and 18 or less carbon atoms in a linear or branched chain, EO is an ethyleneoxy group, PO is a propyleneoxy group, and n is an average addition molar of EO. The number and m are the average number of moles of PO added, n is 2 or more and 20 or less, m is a number satisfying 0 or more and 20 or less, and the addition form of PO and EO in {} is either a random sequence or a block sequence. May be.)
R2-Gx ( ² )
(In the formula (2), R ² represents an alkyl group or an alkenyl group having 5 or more and 8 or less carbon atoms in a linear or branched chain, G represents a residue derived from glucose, and x represents a residue derived from glucose. Indicates the average degree of condensation of 1 or more and 5 or less.)
R ³ -COM (3)
(In the formula (3), R ³ represents an alkyl group or an alkenyl group having 5 or more and 9 or less carbon atoms in a linear or branched chain, and M represents a cation or a hydrogen atom.) A method for cleaning a steel sheet, comprising a cleaning step of diluting the cleaning agent composition according to claim 1 to 0.7% or more and 2.5% or less in terms of alkalinity (Na ₂ O%) to clean the steel sheet. The cleaning method according to claim 2, wherein the steel sheet is a cold-rolled steel sheet. A method for manufacturing a steel sheet, which comprises the cleaning method according to claim 2 or 3 in the manufacturing process.