JP2009155708A - Method for cleaning steel strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for cleaning a steel strip by which a stable rinsing effect can be obtained even if a water solution containing a surfactant is used as a rinsing agent, and also the rinsing agent is circularly used in a rinsing stage in the method for cleaning a steel strip. <P>SOLUTION: The method for cleaning the steel strip includes: a cleaning stage (1) where stain stuck to a steel strip is cleaned with a detergent; and a rinsing stage (2) where the steel strip after being subjected to the cleaning stage (1) is rinsed with a rinsing agent W. The rinsing agent used in the rinsing stage (2) uses a water base composition containing a cationic surfactant (a) expressed by general formula (1). In the formula, R denotes a 14 to 18C hydrocarbon group; R<SP>2</SP>, R<SP>3</SP>and R<SP>4</SP>are the same or different, and denote a hydrogen atom or a 1 to 3C hydrocarbon group; and X<SP>-</SP>denotes an inorganic anion or an organic anion. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for cleaning a steel strip. The steel strip cleaning method of the present invention is suitably used for removing dirt on the surface of a cold rolled steel strip, for example, in a method for producing a cold rolled steel strip.

  Conventionally, in the manufacturing process of various industrial articles, various industrial parts to which dirt is attached are subjected to a cleaning process of cleaning with a rinse agent such as rinse water after being cleaned with a cleaning agent. In such a cleaning process, after cleaning various parts such as metal parts, plated parts, painted parts, electronic parts, etc. with a cleaning agent, the cleaning waste water used for the cleaning is treated by distillation under reduced pressure and the treated water is rinsed. It has been reported that it is circulated and used as water (for example, Patent Document 1).

On the other hand, in a steel strip cleaning process obtained by cold rolling or the like, it is reported that an aqueous solution containing water or an antirust agent is used as a rinse agent after cleaning with a cleaning agent (for example, Patent Document 2). Patent Document 3). However, compared with the metal parts etc. which are the to-be-cleaned objects in patent document 1, rolling steel, rust prevention oil, etc. have adhered to the steel strip over a large area. Therefore, in the steel strip cleaning process, a sufficient rinsing effect cannot be obtained even if the rinse water is circulated and used in the rinsing process. Therefore, in the cleaning of the steel strip, all of the rinse agents are supplied in a non-circulating manner and are treated as waste water.
JP-A-5-115857 JP-A-9-296284 JP-A-11-269678

  In the steel strip cleaning method, when water is used as a rinsing agent, if the rinsing process is performed at 25 ° C. (normal temperature), drying (drainage) shortage occurs. For this reason, in the rinsing process using water, the rinsing agent is usually heated to about 60 to 80 ° C. However, such a rinsing process requires steam costs for raising the temperature of water. In order to reduce the cost and efficiently perform the rinsing process at 25 ° C. (normal temperature), an aqueous solution containing a surfactant as a rinsing agent is used. According to the rinse agent containing such a surfactant, the surface of the steel strip can be made hydrophobic, preferably water repellent, so that all drainage on the surface of the steel strip can be improved and the drying property can be improved. However, when an aqueous solution containing a surfactant is used as the rinse agent, there is a problem that COD (chemical oxygen demand) of the waste water of the rinse agent increases. On the other hand, in response to the recent demands for strengthening environmental regulations, it is expected that the rinse agent in the rinsing process of the steel strip cleaning method will be required to circulate, but the aqueous solution containing the surfactant will be circulated. In many cases, a stable rinsing effect cannot be obtained when used.

  The present invention provides a stable rinsing effect even when an aqueous solution containing a surfactant as a specific rinsing agent is used in the rinsing step of the steel strip cleaning method and the rinsing agent is circulated. An object of the present invention is to provide a method for cleaning a steel strip that is manufactured, and to provide a method for manufacturing a cold-rolled steel strip using the method for cleaning a steel strip.

That is, the present invention includes a cleaning step (1) for cleaning dirt adhering to the steel strip with a cleaning agent, and a rinsing step (2) for rinsing the steel strip after the cleaning step (1) is performed. A method of cleaning a steel strip having
The rinse agent used in the rinse step (2) is represented by the following general formula (1):

(Wherein R ¹ represents a hydrocarbon group having 14 to 18 carbon atoms, and R ² , R ³ and R ⁴ are the same or different and represent a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms. X ^-. is a water-based composition containing a cationic surfactant represented by showing the inorganic anion or an organic anion) (a), and,
The rinsing step (2) includes at least one step of bringing a rinsing agent into contact with the steel strip, and in the step of bringing the at least one rinsing agent into contact, at least part of the rinsing agent is circulated and used. The present invention relates to a method for cleaning a steel strip.

  The present invention also includes a cold rolling step (A) for cold rolling a steel strip in the presence of rolling oil, a cleaning step (1) for cleaning the rolling oil adhering to the rolled steel strip with a cleaning agent, and A method of manufacturing a cold-rolled steel strip comprising a cleaning step (B) including a rinsing step (2) for rinsing the steel strip after being subjected to the cleaning step (1) with a rinsing agent, wherein the cleaning step In (B), it is related with the manufacturing method of the cold rolled steel strip using the cleaning method of the said steel strip.

  In the method for cleaning a steel strip according to the present invention, an aqueous composition containing a specific cationic surfactant is used in the rinsing step (2), which is practically superior to rinse agents other than the present invention. It satisfies the durability (sustainability) of the rinsing effect, and is suitable for circulating use. Furthermore, in the present invention, since at least a part of the rinse agent is circulated and used, the COD of the rinse drainage can be suppressed low.

  The steel strip cleaning method of the present invention includes a cleaning step (1) for cleaning dirt adhering to the steel strip with a cleaning agent, and rinsing the steel strip after the cleaning step (1) is performed with a rinse agent. A rinsing step (2) is included.

  In the washing step (1), dirt such as rolling oil adhering to the steel strip is washed with a cleaning agent in accordance with conventional conditions. The steel strip may be any metal, but iron is preferable from the viewpoint of rust prevention. As the cleaning agent, for example, alkaline cleaning agents as described in JP-A-10-280179 and JP-A-10-324900 can be used. In some cases, electrolytic cleaning may be further used. Moreover, at the time of acid cleaning, the oxide film produced | generated on the steel plate surface is removed with an acid cleaning agent.

  As the alkaline detergent, an aqueous solution containing an alkaline agent is used. Any alkaline agent can be used as long as it is a water-soluble alkaline agent in order to ensure the removal of oil stains. Specific examples include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, silicates such as sodium orthosilicate, sodium metasilicate and sodium sesquisilicate, phosphates such as trisodium phosphate, disodium carbonate And carbonates such as sodium hydrogen carbonate and dipotassium carbonate, and borate salts such as sodium borate. Two or more water-soluble alkaline agents may be combined. The content of the alkaline agent is preferably 0.1 to 10% by weight in the alkaline detergent.

  In addition to the alkaline agent, the alkaline detergent is a nonionic surfactant such as polyoxyalkylene alkyl ether; acts on dirt such as iron soap to chelate iron ions, etc., and dissolves the dirt as fatty acid soap. A chelating agent that facilitates and improves detergency; from the viewpoint of ensuring stability during storage and stability of effects after storage, an aliphatic carboxylic acid or a salt thereof can be added. Furthermore, an arbitrary additive can be added to the cleaning agent of the present invention. For example, an additive such as an organic builder that improves the cleaning property that is generally used is considered in consideration of an increase in COD and cost. It is possible to mix with.

  The proportion of components other than the alkaline agent in the alkaline detergent is appropriately determined, but is 1 part by weight or less, and further 0.1 to 0.5 parts by weight with respect to 1 part by weight of the alkaline agent. Is preferred. Moreover, it is preferable that an alkali cleaning agent adjusts the ratio of components other than an alkali agent so that the ratio of the non volatile matter containing components other than an alkali agent and an alkali agent may be 1-10 weight%.

  After the cleaning step (1), a rinsing step (2) is performed to remove the cleaning agent and the remaining rolling oil. As the rinsing agent used in the rinsing step (2), the following general formula (1):

(Wherein R ¹ represents a hydrocarbon group having 14 to 18 carbon atoms, and R ² , R ³ and R ⁴ are the same or different and represent a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms. X ^- is an inorganic anion or an organic anion) cationic surfactants represented (a) an aqueous composition containing a..

In the general formula (1), R ¹ is preferably a linear or branched alkyl group or alkenyl group having 14 to 18 carbon atoms. R ¹ preferably has 16 to 18 carbon atoms. Examples include myristyl (tetradecyl) group, palmityl (hexadecyl) group, stearyl (octadecyl) group, oleyl group and the like.

R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms such as a methyl group, an ethyl group or an isopropyl group.

Specific examples of X ⁻ include halogen ions such as Cl ⁻ and Br ⁻ , organic anions obtained by removing protons from organic acids such as acetic acid, lactic acid and citric acid, alkyl sulfate ions having 1 to 5 carbon atoms (CH ₃ OSO _{^{3 -, C 2 H 5 OSO}} 3 -, C 3 H 7 OSO 3 - , etc.), alkyl carbonate ion (CH ₃ OCO ₂ ^-), can be mentioned alkyl phosphate ions, from the viewpoint of equipment rust, Organic anions obtained by removing protons from organic acids such as acetic acid, lactic acid or citric acid, alkyl carbonate ions (CH ₃ OCO ₂ ⁻ ) and alkyl phosphate ions are more preferred, and organic anions obtained by removing protons from acetic acid are more preferred.

Specifically, the component (a) is preferably an acid neutralized product of myristylamine, myristyldimethylamine, palmitylamine, palmityldimethylamine, stearylamine, stearyldimethylamine, oleylamine, oleyldimethylamine or 4 In view of maintaining rinsability with respect to cyclic use, palmitylamine, palmityldimethylamine, stearylamine, stearyldimethylamine, oleylamine, and oleyldimethylamine are more preferable, and oleylamine is still more preferable. In the case of an acid neutralized product, at least one of R ² , R ³ and R ⁴ is a hydrogen atom.

  Preferred acids for obtaining an acid neutralized product include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, formic acid, maleic acid, fumaric acid, citric acid, tartaric acid, adipic acid, sulfamic acid, toluenesulfonic acid, lactic acid, pyrrolidone -2-carboxylic acid, succinic acid and the like are mentioned. Preferred quaternizing agents for obtaining a quaternary ammonium salt include alkyl halides such as methyl chloride, ethyl chloride, methyl bromide and methyl iodide, dimethyl sulfate And general alkylating agents such as diethyl sulfate and di-n-propyl sulfate. From the viewpoint of the stability of the product (a), and the stability of the product, phosphoric acid, acetic acid, Formic acid is more preferred, and acetic acid is still more preferred.

  The compound represented by the component (a) is, for example, myristylamine acetate, myristyltrimethylammonium chloride, palmitylamine acetate, palmityltrimethylammonium chloride, stearylamine acetate, stearyltrimethylammonium chloride, oleylamine And the like, and oleylamine acetate is more preferred.

  The rinse agent used in the present invention is an aqueous composition containing the component (a), and water is used as the aqueous medium. As water, deionized water, ion-exchanged water, tap water, industrial water and the like are preferably used. From the viewpoint of productivity, industrial water is preferred.

  The content of the component (a) in the aqueous composition is sufficient to make the steel strip surface sufficiently hydrophobic, preferably water repellent, and excessive (a) component adheres to the steel strip, From the viewpoint of not hindering the annealing process and the plating process, the content is preferably 0.003 to 0.1% by weight, more preferably 0.005 to 0.08% by weight, and still more preferably 0.01 to 0.05% by weight.

In order to improve the adsorption of the cationic surfactant on the steel strip in addition to the component (a), the aqueous composition used as a rinse agent in the present invention has the following general formula (2):
R ⁵ —O — {(EO) _m / (AO) _n } H (2)
(Wherein R ⁵ is a linear or branched alkyl or alkenyl group having 12 to 18 carbon atoms, EO is an ethyleneoxy group, AO is an alkyleneoxy group having 3 to 4 carbon atoms, and m is an average addition mole of EO. N represents an average added mole number of AO, and is 0 to 35. (EO) _m / (AO) _n is m of EO and _n of AO. It is possible to contain a nonionic surfactant (b) represented by the following formula. In the rinse agent of the present invention, one or more kinds of the component (b) can be used. From the viewpoint of securing the adsorptivity of the cationic surfactant to the steel strip and the foam suppression property, m is preferably 3 to 30, and more preferably 5 to 20. n is preferably 3 to 30, more preferably 5 to 25.

In the general formula (2), AO means an alkyleneoxy group having 3 to 4 carbon atoms such as a propyleneoxy group (hereinafter abbreviated as PO) and a tetramethylene group. AO may be the same or different. In the general formula (2), {(EO) _m / (AO) _n } indicates that the arrangement of the EO and the AO is not limited, and may be a block body or a random body.

  The component (b) preferably has a critical micelle concentration (25 ° C.) of 0.01% by weight or less in order to exhibit the effect of promoting the adsorption of the component (a) in a small amount.

The critical micelle concentration of the component (b) is measured by the following method. The surface tension of an aqueous surfactant solution of 0.0001%, 0.001%, 0.01%, 0.1%, 1%, 10% by weight is measured by the Wilhelmy method (at 25 ° C.). . When the decrease rate of the surface tension when any concentration is multiplied by 10 is 5% or less, the surface of the surfactant aqueous solution having a concentration obtained by dividing the concentration and the (1/10) concentration into 9 equal parts The tension is measured by the Wilhelmy method (at 25 ° C.). The surface tensions of the concentration divided into nine equal parts are compared, and the lowest concentration and the low concentration are selected for the combination of adjacent concentrations, and this is set as the critical micelle concentration (weight basis). For example, when the surface tension of C ₁₄ H ₂₉ O (EO) ₇ (PO) ₂ (EO) ₇ H (block addition) is measured by the Wilhelmy method (at 25 ° C.), 58.5 mN /% at 0.0001 wt% m, 0.001 wt%, 42.3 mN / m, 0.01 wt%, 35.4 mN / m, 0.1 wt%, 35.3 mN / m, 1 wt%, 35.3 mN / m. When the concentration is increased by 10 times, the decrease rate of the surface tension is 5% or less is 0.01% by weight. It was 36.0 mN / m at 004 wt%, 35.4 mN / m at 0.005 wt%, and 35.4 mN / m at 0.006 wt%. Therefore, when the amount is 0.005% by weight, the decrease rate of the surface tension is the lowest at 0% and the lowest concentration, so the critical micelle concentration is 0.005% by weight in this case.

  In addition, the component (b) preferably has an HLB of 1 to 3 according to the Davis method from the viewpoint of obtaining good foam suppression. In addition, HLB by Davis method is a value represented by the following formula, and the number of hydrophilic groups and the number of lipophilic groups in the following formula are “new edition surfactant handbook”, Engineering Books Co., Ltd., 1996. On May 1, the values listed in Table 5-1-3 on page 235 are adopted.

  HLB = Σ [number of hydrophilic groups in general formula (2)] + Σ [number of lipophilic groups in general formula (2)] + 7

In the general formula (2), R ⁵ is a linear or branched alkyl group or alkenyl group having 12 to 18 carbon atoms, preferably a linear or branched alkyl group or alkenyl group having 14 to 18 carbon atoms. is there. Examples of the alkyl group include lauryl (dodecyl) group, sec-lauryl group, myristyl group, cetyl group, stearyl group and the like.

  The average addition mole of the component (b) was measured using a sample prepared by dissolving 3% by weight of a predetermined nonionic surfactant in isopropyl alcohol under the following apparatus and column measurement conditions.

GC device: 6850 SERIES II manufactured by Agilent Technologies
Column: Agilent 19091A-102E ULTRA 1 methylsiloxane Measurement conditions: Initial: 60 ° C., hold for 2 minutes, Rate of temperature increase: 10 ° C./min, 300 ° C .: hold for 20 minutes

  Specifically, the general formula (2) having a critical micelle concentration (25 ° C.) of 0.01% by weight or less includes one or more selected from the following.

C _j H 2 _{j + 1} −O (EO) _{pH
C j H2 j + 1 -O (} EO) q (PO) r H, ( provided that EO and PO are block addition)
C _j H2 _{j + 1} -O (PO) _s (EO) _t H (however, EO and PO block added)
C _j H 2 _{j + 1} −O (EO) _u (PO) _v (EO) _w H (however, EO and PO are added as a block)
_{C j H2 j + 1 -O (} EO) x (PO) y H ( provided that EO and PO is randomly added)

(Wherein j is a number from 12 to 18, p, q, r, s, t, u, v, w, x, y, z are average added mole numbers, respectively, and p is a number from 1 to 35. , Q, t and x are numbers from 1 to 35, t and y are numbers from 1 to 35, and q + r, s + t and x + y are all preferably 40 or less, and u is a number from 1 to 30. , V is preferably a number from 1 to 30, and w is preferably a number from 1 to 30, provided that the value of u + v + w is preferably 40 or less.

More preferably, 1 or more things chosen from the following are mentioned.
C ₁₈ H ₃₅ O (EO) ₄ H, C ₁₂ H ₂₅ O (EO) ₅ (PO) ₂ (EO) ₅ H, C ₁₄ H ₂₉ O (EO) ₇ (PO) ₂ (EO) ₇ H, C ₁₆ H ₃₃ O (EO) ₇ (PO) ₂ (EO) ₇ H, C ₁₆ H ₃₃ O (EO) ₁₀ (PO) ₁₂ H, C ₁₈ H ₃₇ O (EO) ₁₀ (PO) ₉ H, C ₁₈ H ₃₇ O (EO) ₉ (PO) ₆ H (however, random addition of EO and PO), C ₁₈ H ₃₇ O (EO) ₁₂ (PO) ₂₁ H (however, random addition of EO and PO) ).

As a general formula (2) having a critical micelle concentration (25 ° C.) of 0.01% by weight or less and an HLB (Davis method) of 1 to 3, C ₁₈ H ₃₅ O (EO) ₄ H, C ₁₈ H ₃₇ O (EO) ₁₂ (PO) ₂₁ H (provided that EO and PO are randomly added).

  In the specific example, (EO) and (PO) indicate that blocks are added in the display order unless otherwise specified.

  When the component (b) is blended in the aqueous composition, the content of the component (b) in the aqueous composition promotes adsorption of the component (a) and makes the steel strip hydrophobic. From the viewpoint of promoting, it is preferably 0.1% by weight or less, more preferably 0.003 to 0.1% by weight, still more preferably 0.005 to 0.08% by weight, and 0.005 to 0.05. Weight percent is particularly preferred.

  When the component (b) is blended in the aqueous composition, the weight ratio of the component (a) to the component (b) is (a) / (b) in order to sufficiently hydrophobize the steel strip surface. ) = 3/7 to 10/1 is preferable, and 5/5 to 8/2 is more preferable.

  Further, the aqueous composition which is the rinse agent of the present invention may contain an antifoaming agent, a chelating agent, a preservative and the like. The aqueous composition used as the rinsing agent of the present invention preferably has a pH of 3 to 10, more preferably 5 to 10, from the viewpoint of hydrophobicity of the steel strip surface, preferably water repellency. Furthermore, it is preferable that pH is 6-9.

  In this invention, the rinse process (2) is given to the steel strip in which the washing process (1) was given using the rinse agent. In the rinse step (2), a rinse agent is brought into contact with the steel strip. As the contact step, for example, a step (21) of rinsing the steel strip with the rinse agent while brushing, a step (22) of rinsing the steel strip without spraying the rinse agent and brushing, etc. A rinsing step of immersing the steel strip in a rinsing agent is exemplified. As the contacting step, it is preferable to perform the brush rinsing step (21) and / or the spray rinsing step (22) from the viewpoint of providing efficient rinsing properties. The rinsing line is made compact and provided between existing lines. It is more preferable to perform the spray rinsing step (22) from the viewpoint of possible. As the contact step, after the brush rinsing step (21) and / or the spray rinsing step (22), and further the spray rinsing step (22), the finishing rinsing step (23) can be performed. . The finishing rinsing step (23) is preferable in terms of removing excess rinsing agent.

In the brush rinsing step (21), the rinsing agent is brought into contact with the steel strip by spraying the steel strip and the brush roll while transporting the steel strip between the brush rolls or between the brush roll and the transport roll. The rotation speed of the brush roll is preferably 100 to 1200 rotations / minute, more preferably 500 to 1000 rotations / minute. The spraying conditions are preferably a spray head pressure of 0.05 to 1 MPa, and more preferably 0.1 to 0.5 MPa. Spray volume is preferably 1 to 100 m ³ / time, 5~60m ³ / time is more preferable. The spray time is preferably from 0.01 to 30 seconds, more preferably from 0.1 to 10 seconds, still more preferably from 1 to 10 seconds. The contact time of the brush is preferably from 0.01 to 30 seconds, more preferably from 0.1 to 10 seconds.

Further, in the spray rinsing step (22), the rinse agent is directly sprayed on the steel strip, and the rinse agent is brought into contact with the steel strip. The spraying conditions are preferably a spray pressure of 0.05 to 1.5 MPa, more preferably 0.1 to 1 MPa. Spray volume is preferably 1 to 100 m ³ / hour and more preferably 5 to 70 m ³ / time, more preferably 7~60m ³ / time. The spray time (contact time in the spray rinsing step) is preferably from 0.01 to 30 seconds, more preferably from 0.1 to 10 seconds, still more preferably from 1 to 10 seconds.

  Moreover, in a finishing rinse process (23), a rinse agent is made to contact a steel strip, for example by immersing a steel strip in a rinse agent. The immersion time of the steel strip in the rinse agent is preferably 0.1 to 30 seconds, and more preferably 1 to 10 seconds. Moreover, in the said finish rinse process (23), the process similar to the said spray rinse process (22) can also be given other than the said immersion rinse.

  In the rinsing step (2), the rinsing agent of the present invention is used in the step of contacting the at least one rinsing agent, and the rinsing agent used in the at least one contacting step using the rinsing agent is used. Use at least a part of the circulation. The contact step for circulating the rinse agent of the present invention is circulated in any one of the brush rinse step (21), the spray rinse step (22), and the finish rinse step (23) according to the above illustration. The rinsing agent of the present invention may be circulated in two or more contact steps or all contact steps. In the rinsing step in which the rinse agent of the present invention is not used, water or a rinse agent other than the present invention can be used as the rinse agent. In the present invention, in the rinsing step (2), the spray rinsing step (22) is adopted, and the rinsing agent of the present invention is circulated in the spray rinsing step (22), so that the COD of the rinsing waste liquid is reduced. This is preferable.

In the rinsing step (2), in the step of circulating the rinse agent of the present invention, at least a part of the rinse agent is circulated. That is, in the circulation, the rinse agent of the present invention may be circulated entirely or partially. When a part of the rinse agent is circulated, the rinse agent is supplied, and substantially the same amount of the rinse agent is drained. Circulation rate of the rinsing agent is preferably from 1 to 100 m ³ / time, more preferably from 3~70m ³ / time, and even more preferably 5 to 50 m ³ / hour. The circulation amount of the rinse agent is determined by a value (ab) obtained by subtracting the drainage amount (input amount: b) of the rinse agent from the (spray) flow rate (a) of the rinse agent. The circulation rate of the rinse agent is expressed as a ratio of the circulation amount to the flow rate of the rinse agent (circulation amount / (spray) flow rate of the rinse agent), and the circulation rate becomes 100% when all of the rinse agent is circulated. In the present invention, even when the circulation rate of the rinse agent is 100%, the rinse drying property at 25 ° C. can be improved, but from the viewpoint of balancing improving the rinse drying property and suppressing the COD of the rinse waste liquid. The circulation rate of the rinse agent is preferably 20 to 80%, more preferably 30 to 70%, still more preferably 40 to 60%.

  In the rinsing step (2) of the present invention, the rinsing agent is preferably used at 5 to 40 ° C., more preferably at 10 to 30 ° C., in order to reduce many steam costs required for increasing the temperature.

  In the cleaning method of the present invention, the cleaning step (1) and the rinsing step (2) are performed, but the water rinsing step (3) may be further performed after the rinsing step (2). The water rinsing step (3) is performed in order to make the component (a) more uniform on the surface of the steel strip, to make the entire surface of the steel strip hydrophobic, and to remove the excess (a) component. This water rinsing step (3) is also preferably used at 5 to 40 ° C., more preferably 10 to 30 ° C., in order to reduce the steam cost. In order to rinse the steel strip with water, it may be impregnated in water or rinsed with a shower or the like. When impregnating in the water rinsing step (3), it is usually preferably 1 to 5 seconds, and when showering, the spray pressure is 0.05 to 1.5 MPa, preferably about 0.1 to 5 seconds.

  In addition, the said washing | cleaning process (1) and the rinse process (2) are normally given as a continuous line which conveys a steel strip. The conveying speed of the steel strip is usually 30 to 1000 m / min, preferably 50 to 800 m / min. In consideration of the conveying line speed, each treatment in the washing step (1) and the rinsing step (2) is performed. Time is set.

  Hereinafter, the rinsing step (2) will be described with reference to the drawings. FIG. 1 shows a case where only the brush rinsing step (21) is performed as the rinsing step (2) on the steel strip F subjected to the cleaning step (1). FIG. 2 shows a case where only the spray rinsing process (22) is performed as the rinsing process (2) on the steel strip F subjected to the cleaning process (1). FIG. 3 shows a case where the spray rinsing step (22) and the brush rinsing step (21) are performed in this order as the rinsing step (2) for the steel strip F subjected to the cleaning step (1). . 4 and 5 show the steel strip F that has been subjected to the cleaning step (1), as a rinsing step (2), a brush rinsing step (21), a spray rinsing step (22), and a finishing rinsing step (23). ) In this order. In FIG. 1 thru | or FIG. 5, after performing the rinse process (2), a drying process can be performed. In FIG. 1, in the brush rinsing step (21), in FIG. 2, in the spray rinsing step (22), in FIG. 3, in the brush rinsing step (21) and the spray rinsing step (22), the rinsing agent can be circulated. It has become. In FIG. 4, the rinsing agent can be circulated in the brush rinsing step (21), the spray rinsing step (22), and the finish rinsing step (23), but in FIG. 5, only in the spray rinsing step (22). The rinse agent can be circulated. In the embodiment of FIG. 5, the existing non-circulating equipment having the non-circulating brush rinsing process (21) and the non-circular finishing rinsing process (23) is added to the existing non-circulating equipment by adding the circulating equipment related to the spray rinsing process (22). It is preferable in that the circulation facility can be installed in a compact manner without moving the facility, and the effect of reducing the wastewater COD is great. In the brush rinsing step (21), circulation of the rinse agent increases the circulation facility.

  In the brush rinsing step (21) of FIGS. 1, 3, 4, and 5, the rinsing agent is supplied from the tank T1 to the rinsing tank A1 through the line L12 by the operation of the pump P1. In the rinsing tank A1 containing the rinse agent, the steel strip F passes between a pair of the brush B and the roll R that are alternately combined, and brush rinse is performed by the supplied rinse agent W by the spray nozzle S1. The rinse agent W is drained from the rinse tank A1 through the line L13. In FIGS. 1, 3, and 4, the drained liquid is returned to the tank T1. In the tank T1, the drainage from the line L13 can be processed as it is from the line L14. In the tank T1, the liquid drained from the line L13 can be circulated and used by the line L12. In FIG. 5, the rinse agent W is drained from the rinse tank A1 through the line L13 and processed. 4 and 5, the tank T1 is also used for the drainage from the line L33 generated in the finish rinsing step (23) (not shown, but the line L24 generated in the spray rinsing step (22)). Also, the liquid can be stored once and discharged from the line L14 in the same manner as described above, or can be circulated and used in the brush rinsing step (21) through the line L12. 1, 3, and 4, the rinsing agent W is supplied to the tank T <b> 1 through the line L <b> 11, but in FIG. 5, only the drainage from the line L <b> 33 generated in the finish rinsing step (23) It is supplied to T1.

  In the spray rinsing process (22) of FIGS. 2, 3, 4, and 5, the rinsing agent W is supplied from the tank T2 to the rinsing tank A2 through the line L22 by the operation of the pump P2. The rinse agent W is supplied to the tank T2 through the line L21. In the rinsing tank A2 containing the rinsing agent W, the steel strip F is sprayed directly from the spray nozzle S2 and spray rinsed. The rinse agent is drained from the rinse tank A2 through the line L23. The drainage is returned to the tank T2. In the tank T2, part or all of the drainage from the line L23 is circulated through the line L22. On the other hand, when the rinse agent is partially circulated in the tank T2, a part of the drainage from the line L23 is processed as drainage from the line L24.

  In the final rinse step (23) of FIG. 4, the rinse agent W is supplied to the rinse tank A3 through the line L31. In the rinsing tank A3, the steel strip F is rinsed by the supplied rinsing agent W by the spray nozzle S3, and further immersed in the rinsing tank A3. The rinse agent in the rinse tank A3 is supplied to the spray nozzle S3 through the line L32 by the operation of the pump P3 and can be circulated. In FIG. 5, the rinse agent W is supplied to the rinse tank A3 by the spray nozzle S3 through the line L32 by the operation of the pump P3 through the line L30. In the rinsing tank A3, the steel strip F is rinsed by the supplied rinsing agent W by the spray nozzle S3, and further immersed in the rinsing tank A3. Moreover, in FIG. 4, FIG. 5, the rinse agent W is drained from the rinse tank A3 by the line L33. 4 and 5, the drainage liquid is guided to the tank T1. Although not shown, the liquid drained from the line L33 can be circulated and used in the same manner as the spray rinsing step (22).

  Moreover, in this invention, the process (A) which cold-rolls a steel plate in presence of rolling oil, the process (1) which wash | cleans the rolling oil adhering to the rolled steel plate with a washing | cleaning agent, and the said washing | cleaning process (1). There is provided a method for producing a cold-rolled steel strip including a cleaning step (B) including a rinsing step (2) for rinsing the steel strip after being applied with a rinse agent. In the washing step (B) in the method for producing a cold-rolled steel strip, the washing step (1) and the rinsing step of the present invention are performed on the surface of the cold-rolled steel strip that is the object to be cleaned. It can be suitably applied to (2), and the rinse agent can be circulated and used.

  In each of the following examples,% is% by weight.

Examples 1-4 and Comparative Examples 1-5
Using the following cationic surfactant (a) and nonionic surfactant (b), rinse agents having the compositions shown in Table 1 were prepared. The rinse agent is prepared as an aqueous solution diluted with deionized water to a concentration (mg / L). The component (a) and / or the component (b) are blended according to the (a) component / (b) component: weight ratio in Table 1. Table 1 shows the pH of the rinse agent in each example. About these rinse agents, after performing the following washing | cleaning process (1) and rinse process (2) about the following steel strip, 25 degreeC rinse drying property and waste water COD were evaluated with the following method. The results are shown in Table 1.

<Cationic surfactant (a)>
(A-1): Myristyldimethylamine / hydrochloride (a-2): Palmitylamine / acetate (a-3): Oleylamine / acetate (a-4): Stearyldimethylamine / phosphate <Comparison Cationic Surfactant (a ′)>
(A′-1): Decyldimethylamine hydrochloride (a′-2): Laurylamine acetate (a′-3): Dioctylamine acetate (a′-4): Lauryltrimethylammonium chloride

<Nonionic surfactant (b)>
(B-1): C ₁₄ H ₂₉ O (EO) ₇ (PO) ₂ (EO) ₇ H (block addition) (critical micelle concentration (25 ° C.): 50 ppm, HLB (Davis method, the same shall apply hereinafter): 6. 9)
(B-2): C ₁₈ H ₃₇ O (EO) ₁₀ (PO) ₉ H (block addition) (critical micelle concentration (25 ° C.): 30 ppm, HLB: 2.7)
(B-3): C ₁₈ H ₃₇ O (EO) ₁₂ (PO) ₂₁ H (random addition) (critical micelle concentration (25 ° C.): 30 ppm, HLB: 1.9)

<Washing process (1)>
A cold rolled steel strip (stain: iron powder and rolling oil) having a thickness of 7 mm cut to a length of 7 cm and a width of 10 cm is immersed in the following alkaline cleaning agent (immersion time: 2 seconds), electrolytic cleaning (electrolytic time) 0.8 seconds and a current density of 14 A / dm ² ), and was pulled up from the electrolytic cleaning layer.

  Alkaline detergent: aqueous solution containing 2% by weight NaOH and 1% by weight additive (additive composition: 1% NaOH, 15% sodium gluconate, 5% sodium ethylenediaminetetraacetate, polyoxyethylene nonylphenyl ether (EO) Average number of moles added: 13 moles) 10%, sodium polyacrylate 5%, water 64%).

<Rinse process (2)>
Subsequent to the washing step (1), the following rinsing steps were sequentially performed as shown in FIG. The cold rolled steel strip was transported at 60 m / min. The prepared rinse agent was used only in the spray rinse step (22), and industrial water was used as the rinse agent in the brush rinse step (21) and the finish rinse step (23). Each rinse agent was used after being heated to 25 ° C.

≪Brush rinsing process (21) ≫: Nozzle (standard fan nozzle 1/4 KSH 1565 EVER LOY, manufactured by Kyoritsu Alloy Co., Ltd.), spray pressure is 0.1 MPa, spray amount (flow rate) is 50 m ³ / hour While spraying rinse agent (industrial water), brush with brush roll cleaning tester (made by Showa Kogyo Co., Ltd., nylon brush, brush rotation speed 500 rpm, brush reduction 1 mm, steel plate feed speed 60 m / min) A rinse was performed.
≪Spray rinsing process (22) ≫: Nozzle (standard fan nozzle 1/4 KSH 1565 EVER LOY, manufactured by Kyoritsu Alloy Co., Ltd.), spray pressure is 0.1 MPa, spray amount is 10 m ³ / hour, spray time is The spray rinse with the rinse agent shown in Table 1 was performed in 1 second.
<< Finishing rinse process (23) >>: Using a nozzle (standard fan nozzle 1/4 KSH 1565 EVER LOY, manufactured by Kyoritsu Alloy Co., Ltd.), spray pressure is 0.1 MPa, spray amount is 50 m ³ / hour, spray time is After performing spray rinsing with a rinse agent (industrial water) in 1 second, it was immersed in a rinse agent (industrial water) for 2 seconds.

In the rinse step (2), the rinse agent was circulated only in the spray rinse step (22). The circulation rate of the rinse agent in the spray rinsing step (22) was 50% (drainage amount: 5 m ³ / hour).

<25 ° C rinse dryness>
The water wettability of the steel strip surface subjected to the above treatment was evaluated by an index (WB: water break) expressed by area. The WB was measured by taking a photograph of the steel sheet after the final rinse, and applying the area of the wetted part to a graph paper. The evaluation indicates that the smaller this value, the better the drying property.

<Drainage COD>
The COD (mg / L) of the rinsing agent drainage in the spray rinsing step (22) was measured by a factory drainage test method (JISK010217).

  In the examples, using the rinse agent containing the cationic surfactant (a) of the present invention, the drying rate at 25 ° C. rinse when the spray rinse step (22) is performed at a circulation rate of 50% is all acceptable. It is. On the other hand, since the rinsing agent of the comparative example does not contain the cationic surfactant (a) of the present invention, the concentration of the surfactant and the spray rinsing conditions are the same as those in the example, but at the time of rinsing at 25 ° C. The dryness of the is unacceptable.

Examples 3-1 and 2
In Example 3, except that the spray circulation rate of the spray rinsing step (22) was changed as shown in Table 2, the same rinse agent as in Example 3 (the pH of the rinse agent in each example is shown in Table 2. In the same manner as in Example 3, the steel strip was subjected to the washing step (1) and the rinsing step (2), and then rinsed dryness at 25 ° C. and wastewater COD were evaluated by the following methods. The results are shown in Table 2.

Comparative Examples 6-1 to 3
In Example 3, the spray rinsing step (22) was not performed. In the brush rinsing step and the finishing rinsing step, the same rinsing agent as in Example 3 (the concentration and pH of the rinsing agent in each example) was used instead of industrial water. The temperature is shown in Table 2.) After performing the washing step (1) and the rinsing step (2) on the steel strip in the same manner as in Example 3 except that the temperature is shown in Table 2, rinse drying at 25 ° C, The wastewater COD was evaluated by the following method. The results are shown in Table 2.

Comparative Examples 7 and 8
In the same manner as in Example 1, the steel strip was subjected to the washing step (1). Next, using the industrial water at 25 ° C. or 70 ° C. as the rinsing agent, after performing the rinsing step (2) by the brush rinsing step (21) and the finishing rinsing step (23), the rinsing drying property at 25 ° C., and Wastewater COD was evaluated by the following method. The results are shown in Table 2.

  In Example 3-1, the circulation rate of the rinse agent is 100%, and there is no problem of wastewater COD. However, the amount of contamination is increased, and the rinse agent is adsorbed to iron powder and the like, and the rinsing agent is dried at 25 ° C over time. Is running out. In Example 3-2, the circulation rate is 10%, which is lower than the circulation rate of 50% in Example 3. Therefore, the 25 ° C. rinse drying property is maintained, but the COD is higher than that in Example 3. Comparative Examples 6-1 to 3-3 and Comparative Examples 7 and 8 are cases where the rinse agent is not circulated and used. Comparative Example 6-1 uses the same composition and the same concentration of rinsing agent as Example 3, and can satisfy the 25 ° C. rinsing drying property, but increases the wastewater COD. In Comparative Example 6-2, the wastewater COD is somewhat lowered due to the low concentration rinse agent having the same composition as in Example 3, but the 25 ° C. rinse drying property is insufficient. In Comparative Example 6-3, the same composition as in Example 3 and the concentration of the rinsing agent is set to be considerably lower than in Example 3. Therefore, the wastewater COD falls to the same level as in Example 3, but the 25 ° C. rinse is performed. Dryability is unacceptable. Comparative Example 7 uses water as a rinse agent, and the 25 ° C. drying property is unacceptable. In Comparative Example 8, water is used as the rinsing agent and the rinsing temperature is raised to 70 ° C., and the drying property at 25 ° C. can be satisfied. However, in some cases, energy such as steam is required to raise the temperature.

It is an example of the schematic diagram which shows the rinse process (2) which concerns on the brush rinse process (21) in the washing | cleaning method of this invention. It is an example of the schematic diagram which shows the rinse process (2) which concerns on the spray rinse process (22) in the washing | cleaning method of this invention. It is an example of the schematic which shows the rinse process (2) which has the spray rinse process (21) and the spray rinse process (22) in the washing | cleaning method of this invention. It is an example of the schematic which shows the rinse process (2) which has a spray rinse process (21), a spray rinse process (22), and a finishing rinse process (23) in the washing | cleaning method of this invention. It is an example of the schematic which shows the rinse process (2) which has a spray rinse process (21), a spray rinse process (22), and a finishing rinse process (23) in the washing | cleaning method of this invention.

Explanation of symbols

F Steel strip A Rinse tank T Tank S Spray W Rinse agent L Line

Claims (7)

Cleaning the steel strip having a cleaning step (1) for cleaning dirt adhering to the steel strip with a cleaning agent and a rinsing step (2) for rinsing the steel strip after the cleaning step (1) is performed. A method,
The rinse agent used in the rinse step (2) is represented by the following general formula (1):

(Wherein R ¹ represents a hydrocarbon group having 14 to 18 carbon atoms, and R ² , R ³ and R ⁴ are the same or different and represent a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms. X ^-. is a water-based composition containing a cationic surfactant represented by showing the inorganic anion or an organic anion) (a), and,
The rinsing step (2) includes at least one step of bringing a rinsing agent into contact with the steel strip, and in the step of bringing the at least one rinsing agent into contact, at least part of the rinsing agent is circulated and used. A method for cleaning steel strips. The rinse agent further comprises the following general formula (2):
R ⁵ —O — {(EO) _m / (AO) _n } H (2)
(Wherein R ⁵ is a linear or branched alkyl or alkenyl group having 12 to 18 carbon atoms, EO is an ethyleneoxy group, AO is an alkyleneoxy group having 3 to 4 carbon atoms, and m is an average addition mole of EO. N represents an average added mole number of AO, and is 0 to 35. (EO) _m / (AO) _n is m of EO and _n of AO. The steel strip according to claim 1, wherein the steel strip is an aqueous composition containing a nonionic surfactant (b) represented by the following formula: Cleaning method.   In the rinsing step (2), the step of bringing the rinsing agent into contact with the steel strip includes a step (21) of rinsing the steel strip with the rinsing agent while brushing and / or spraying the rinsing agent and brushing. The method for cleaning a steel strip according to claim 1 or 2, further comprising a step (22) of rinsing the steel strip without performing the step. The method of bringing the rinse agent into contact with the steel strip in the rinsing step (2) includes at least a step (22) of spraying the rinse agent to rinse the steel strip,
And in the spray rinse step (22),
Spray head pressure is 0.05 to 1.5 MPa,
Spray amount 0.5-100 m ³ / hour,
Spray time 0.01-30 seconds,
The method for cleaning a steel strip according to any one of claims 1 to 3. Wherein the rinsing step (2), circulation of the rinsing agent to be circulated, the method of cleaning steel strip according to claim 1 which is 1 to 100 m 3 ^/ hour.   The method for cleaning a steel strip according to any one of claims 1 to 5, wherein the aqueous composition used as the rinse agent has a pH of 3 to 10.   Cold rolling step (A) for cold rolling the steel strip in the presence of rolling oil, cleaning step (1) for cleaning the rolling oil adhering to the rolled steel strip with a cleaning agent, and the cleaning step (1) And a washing step (B) including a rinsing step (2) for rinsing the steel strip after being subjected to rinsing with a rinse agent, in the washing step (B), The manufacturing method of the cold rolled steel strip using the washing | cleaning method of the steel strip in any one of Claims 1-6.