JP2008050666A - Degreasing liquid and degreasing/cleaning method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a degreasing liquid capable of exhibiting excellent degreasing/cleaning properties at a pH value in the range of 10.5 to 12.0 without substantially comprising phosphorous compounds and nitrogen compounds causing environmental contamination, and further, capable of sufficiently maintaining the degreasing/cleaning properties even in the case oils and fats are relatively largely comprised by use over a long period. <P>SOLUTION: The degreasing liquid comprises: two or more of alkali builders including at least one alkali silicate; a first nonionic surfactant expressed by general formula (1): R<SP>1</SP>O-(C<SB>2</SB>H<SB>4</SB>O)<SB>n</SB>-H (wherein, R<SP>1</SP>denotes a 10-12C alkyl group; and n denotes the integer of 7 to 9); and a second nonionic surfactant expressed by general formula (2): R<SP>2</SP>O-(C<SB>2</SB>H<SB>4</SB>O)<SB>m</SB>-H (wherein, R<SP>2</SP>denotes a group having at least two aromatic rings in one molecule; and m denotes the integer of 6 to 10), has a pH value of 10.5 to 12.0, and does not substantially comprise phosphorous compounds and nitrogen compounds. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a degreasing liquid and a degreasing cleaning method using the same.

  In the field of metal surface treatment, particularly metal surface chemical conversion treatment, before performing chemical conversion treatment with zinc phosphate or the like on the object to be treated, fats and oils adhering to the surface of the object to be treated (for example, In general, a degreasing cleaning treatment is performed using a degreasing liquid to remove mineral oil, animal and vegetable oils, and the like. Therefore, as a component of such a degreasing liquid, it is inappropriate that the reaction product produced by reacting with itself or the component remains on the surface of the object to be treated and adversely affects the chemical conversion treatment. is there.

  As such a degreasing solution, a solution containing a builder mainly composed of acid or alkali and a nonionic or anionic surfactant as main components has been adopted. And in such a degreasing liquid, phosphates, such as an alkali phosphate and an alkali condensed phosphate, have been mix | blended as a useful builder which improves a degreasing detergency. However, recently, it has been pointed out that phosphate causes eutrophication and pollution of lake water, and as such a degreasing solution, the development of a degreasing solution containing no phosphate is required. Yes.

  As such a non-phosphate degreasing liquid, for example, in JP-A-5-125571 (Patent Document 1), an alkali silicate, a nonionic surfactant, and a water-soluble polycarboxylate And a degreasing solution contained so as to satisfy a predetermined condition. However, in the degreasing solution as described in Patent Document 1, when the pH value is 12 or less, a heavily contaminated member or product cannot always be sufficiently degreased. For this reason, when such a conventional degreasing solution is used, a strong base such as sodium hydroxide has been continuously added to adjust the pH value. The use of a large amount of base is also problematic in terms of economy. In addition, when a degreased solution having a pH value of more than 12 is used and a surface-treated steel sheet is used as an object to be processed, the coating on the surface dissolves and various performances such as corrosion resistance of the object to be processed are reduced. There was also a problem of doing.

In view of this problem, studies have been made on degreasing solutions that can exhibit excellent degreasing properties even when the phosphate is not blended and the pH value is 12 or less. For example, JP 2005-320598 A (Patent Document 2) discloses a degreasing liquid containing at least two alkali builders including at least an alkali silicate and a specific nonionic surfactant. Yes. However, even a degreasing solution as described in Patent Document 2 is not always sufficient in terms of maintaining the cleaning power when used for a long period of time.
Japanese Patent Laid-Open No. 5-125571 JP 2005-320598 A

  This invention is made | formed in view of the subject which the said prior art has, and is excellent in pH value in the range of 10.5-12.0, without containing the phosphorus compound and nitrogen compound which cause environmental pollution substantially. A degreasing solution that can exhibit a degreasing performance and that can maintain a sufficient degreasing performance even when oils and fats are contained in a relatively large amount after long-term use, and a degreasing cleaning using the same It aims to provide a method.

  As a result of intensive studies to achieve the above object, the present inventors have found that at least one alkali builder containing at least one alkali silicate and the first nonionic surface activity having a specific structure. PH value of 10.5 to 12 without substantially containing a phosphorus compound and a nitrogen compound that cause environmental pollution by the degreasing liquid containing the agent and the second nonionic surfactant having a specific structure The present invention has been completed by finding that it can exhibit excellent degreasing properties in the range of 0.0, and that it can sufficiently maintain degreasing properties even when oils and fats are contained in a relatively large amount by long-term use. It came to do.

That is, the degreasing solution of the present invention comprises at least one alkali builder containing at least one alkali silicate,
The following general formula (1):
R ¹ O— (C ₂ H ₄ O) _n —H (1)
(In the formula, R ¹ represents an alkyl group having 10 to 12 carbon atoms, and n represents an integer of 7 to 9)
A first nonionic surfactant represented by:
The following general formula (2):
_{^{R 2 O- (C 2 H 4}} O) m -H (2)
(In the formula, R ² represents a group having at least two aromatic rings in one molecule, and m represents an integer of 6 to 10).
A second nonionic surfactant represented by:
And a pH value of 10.5 to 12.0, and is substantially free of phosphorus compounds and nitrogen compounds.

  As the degreasing liquid of the present invention, the content ratio of the first nonionic surfactant and the second nonionic surfactant in terms of solid content is from 1: 9 to 9: 1. It is preferable that

  Moreover, as said degreasing liquid of this invention, it is preferable that the said 2 or more types of alkali builder further contains water-soluble polycarboxylate.

Furthermore, as the degreasing solution of the present invention, the concentration of the alkali silicate is represented by the following formula (I) in terms of silicon element:
300 <Y <10 ^{(0.318X + 2.72)} (I)
(In the formula, X is a value obtained by subtracting 10.5 from the pH value of the degreasing solution, and Y is the concentration (unit: ppm) of the alkali silicate.)
Satisfying the condition of the inequality represented by
The concentration of the water-soluble polycarboxylate is in the range of 100 to 500 ppm, and
The total concentration of the first nonionic surfactant and the second nonionic surfactant is preferably in the range of 1400 to 2400 ppm.

  The degreasing and cleaning method of the present invention is a method characterized in that the object to be treated is degreased and cleaned using the above-described degreasing solution of the present invention.

  It is preferable that at least a part of the workpiece according to the present invention is a surface-treated steel sheet.

  Further, the object to be processed according to the present invention is preferably an automobile body.

  According to the present invention, an excellent degreasing performance can be exhibited in a pH value range of 10.5 to 12.0 without substantially containing a phosphorus compound or a nitrogen compound that causes environmental pollution. It becomes possible to provide a degreasing solution and a degreasing cleaning method using the same that can sufficiently maintain the degreasing performance even when the fats and oils are contained in a relatively large amount by using the period.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

First, the degreasing solution of the present invention will be described. That is, the degreasing solution of the present invention comprises at least one alkali builder containing at least one alkali silicate,
The following general formula (1):
R ¹ O— (C ₂ H ₄ O) _n —H (1)
(In the formula, R ¹ represents an alkyl group having 10 to 12 carbon atoms, and n represents an integer of 7 to 9)
A first nonionic surfactant represented by:
The following general formula (2):
_{^{R 2 O- (C 2 H 4}} O) m -H (2)
(In the formula, R ² represents a group having at least two aromatic rings in one molecule, and m represents an integer of 6 to 10).
A second nonionic surfactant represented by:
And a pH value of 10.5 to 12.0, and is substantially free of phosphorus compounds and nitrogen compounds.

  Two or more types of alkali builders according to the present invention include at least one type of alkali silicate. By containing alkali silicate as one kind of alkali builder, it is possible to exhibit excellent degreasing and detergency without blending phosphate. Although it does not specifically limit as such an alkali silicate, The thing which does not contain nitrogen and phosphorus from a viewpoint of environmental protection is preferable. Examples of such alkali silicate include alkali metal salts of orthosilicate such as sodium orthosilicate and potassium orthosilicate; alkali metal salts of metasilicate such as sodium metasilicate and potassium metasilicate; sodium sesquisilicate and sesquisilicate Examples thereof include alkali metal salts of sesquisilicate such as potassium. Among such alkali silicates, sodium silicate is preferable because higher degreasing power can be obtained. Such alkali silicate may be used individually by 1 type, or may mix and use 2 or more types.

  Further, the two or more types of alkali builder may include only two or more types of alkali silicate, but include one containing alkali silicate and another alkali builder other than alkali silicate. Is preferred. Thus, degreasing tends to be further improved by including alkali silicate and other alkali builder. Such other alkali builder is not particularly limited, and a known alkali builder can be used as appropriate, for example, alkali metal carbonates such as sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, sodium potassium carbonate, etc. Etc.

The concentration of the alkali silicate in the degreasing solution of the present invention is expressed by the following formula (I) in terms of silicon element:
300 <Y <10 ^{(0.318X + 2.72)} (I)
(In the formula, X is a value obtained by subtracting 10.5 from the pH value of the degreasing solution, and Y is the concentration (unit: ppm) of the alkali silicate.)
It is preferable to satisfy the condition of the inequality represented by: If the concentration Y of the alkali silicate is less than 300 ppm in terms of Si element, the chemical conversion treatment property is lowered, and further, the effect of suppressing the dissolution of the zinc phosphate film tends to be lowered. That is, by making the concentration of the alkali silicate within the range of the inequality represented by the formula (I), dissolution of the zinc phosphate film can be suppressed, and the degreasing solution of the present invention is coated with zinc phosphate. It becomes possible to use it more suitably for a steel plate. The lower limit value of the alkali silicate concentration is more preferably 1500 ppm.

  Furthermore, the molar ratio of alkali silicate to other alkali builder in the two or more types of alkali builder (alkali silicate: other alkali builder) is preferably 1:10 to 1: 2. More preferably, it is 1: 7 to 1: 3. If the molar ratio of such alkali silicate is less than the lower limit, sufficient degreasing properties tend not to be obtained. On the other hand, if the upper limit is exceeded, it is adsorbed on the object to be processed and unevenness occurs after the treatment. There is a tendency.

The first nonionic surfactant according to the present invention is represented by the following general formula (1):
R ¹ O— (C ₂ H ₄ O) _n —H (1)
(In the formula, R ¹ represents an alkyl group having 10 to 12 carbon atoms, and n represents an integer of 7 to 9)
It is represented by In the present invention, since the nonionic surfactant represented by the general formula (1) is contained, excellent degreasing properties are obtained, and the pH is relatively lower than that of the conventional degreasing liquid. A degreasing solution can be used within the range. Therefore, for example, even when a surface-treated steel sheet such as a zinc phosphate-coated steel sheet or an organic film-coated steel sheet is used as an object to be processed, an excellent degreasing process can be performed without impairing corrosion resistance. In addition, by using the nonionic surfactant represented by the general formula (1), it is possible to reduce the amount of strong base components such as sodium hydroxide added to the degreasing liquid as necessary. Become.

R ¹ in the formula (1) is an alkyl group having 10 to 12 carbon atoms. If the carbon number of such an alkyl group is less than 10, it becomes difficult to emulsify the oil, while if it exceeds 12, it becomes difficult to disperse in water. Further, in such a formula (1), the alkyl group represented by R ¹ may be linear or branched, and may be cyclic. . Examples of such R ¹ include a decyl group, an undecyl group, a lauryl group, and the like, and a decyl group is particularly preferable from the viewpoint of obtaining higher detergency.

  Moreover, n in said Formula (1) is an integer of 7-9. When the value of n is less than 7, it is difficult to disperse in water. On the other hand, when it exceeds 9, foaming increases and is not suitable for practical use.

In addition, as such a first nonionic surfactant, a known nonionic surfactant can be appropriately used. For example, the following commercially available products can be used.
“DKS NL-60” (polyoxyethylene alkyl ether) manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
"DKS NL-70" (polyoxyethylene alkyl ether)
"Emulgen 108" manufactured by Kao Corporation (polyoxyethylene alkyl ether)
Asahi Denka Kogyo Co., Ltd. “Adecatol UA-70” (polyoxyethylene alkyl ether).

The second nonionic surfactant according to the present invention is represented by the following general formula (2):
^{_{R 2 O- (C 2 H 4}} O) m -H (2)
(In the formula, R ² represents a group having at least two aromatic rings in one molecule, and m represents an integer of 6 to 10).
It is represented by In the present invention, since the nonionic surfactant represented by the general formula (2) is included, even if a relatively large amount of oils and fats is contained in the obtained degreasing liquid, the general formula The emulsification of the nonionic surfactant represented by (1) can be sufficiently suppressed to prevent the degreasing power from deteriorating over time.

R ² in the general formula (2) is a group having at least two aromatic rings in one molecule. When the number of aromatic rings in one molecule of the substituent represented by R ² is less than 2, when used for degreasing multiple times, the decrease in degreasing power over time tends not to be sufficiently suppressed. is there. Further, the number of aromatic rings in one molecule of the substituent represented by R ² is preferably 2 to 4. When the number of such aromatic rings exceeds 4, it tends to be difficult to dissolve in water. Examples of such aromatic rings include benzene, naphthalene, anthracene, pyrrole, furan, thiophene, pyridine, indole and the like. Such R ² is preferably other than a nonylphenol group from the viewpoint of safety and the like.

  Moreover, m in the said General formula (2) is an integer of 6-10 (more preferably 7-9). When m is less than 6, it is difficult to disperse in water. On the other hand, when m exceeds 10, foaming becomes large and it is not suitable for practical use.

As the second nonionic surfactant, a known nonionic surfactant can be appropriately used. For example, the following commercially available products can be used.
“Adecatol PC-6” manufactured by Asahi Denka Kogyo Co., Ltd. (special phenol ethoxylate, cloud point 10 ° C., HLB value 11.1)
“Adecatol PC-8” (special phenol ethoxylate, cloud point 51 ° C., HLB value 12.4)
“Adecatol PC-10” (special phenol ethoxylate, cloud point 67 ° C., HLB value 13.5)
Rhodia Nikka Co., Ltd. “Sanmor MP-80N” (polyoxyethylene aromatic derivative, pH value: about 6, active ingredient 99% by mass)
Further, the total concentration of the first nonionic surfactant and the second nonionic surfactant in the degreasing solution of the present invention is preferably in the range of 1400 to 2400 ppm. When the concentration of such a nonionic surfactant is less than 1400 ppm, the degreasing detergency does not sufficiently improve, and the degreasing detergency tends to decrease over time when used multiple times, while 2400 ppm. If it exceeds, not only the improvement of the effect cannot be obtained, but also the economy tends to decrease.

  Moreover, as a content ratio by mass conversion of solid content of said 1st nonionic surfactant and said 2nd nonionic surfactant, it is preferable that it is 1: 9-9: 1, It is more preferable that it is 3: 7-7: 3. When the content ratio of the first nonionic surfactant is less than the lower limit, sufficient degreasing power tends to be hardly obtained, and when the upper limit is exceeded, it is difficult to maintain the degreasing power with time. Tend to be.

  Moreover, the pH value of the degreasing solution of the present invention is in the range of 10.5 to 12.0. If such a pH value is less than 10.5, it causes deterioration of the degreasing power over time and deterioration of the chemical conversion property and paintability of the object to be processed. Damaged. That is, the degreasing solution of the present invention has a pH value within the above-mentioned range, and therefore can be suitably used for a metal substrate surface-treated by zinc phosphate treatment or the like. Furthermore, the pH value of such a degreasing solution is more preferably in the range of 10.9 to 11.7.

  The method for adjusting the pH value is not particularly limited, and a known method can be appropriately employed. For example, in addition to the above essential components, a basic compound for raising the pH is appropriately blended, and the pH value is adjusted. A method of making it within the range of 10.5 to 12.0 can be employed. Examples of such basic compounds include, but are not limited to, alkali bicarbonates such as sodium bicarbonate and potassium bicarbonate; alkali carbonates such as sodium bicarbonate, sodium carbonate, potassium bicarbonate and potassium carbonate; Examples thereof include caustic alkalis such as potassium and sodium hydroxide. Moreover, as such a basic compound, the compound which does not contain nitrogen and phosphorus from a viewpoint of environmental protection is preferable, and sodium hydrogencarbonate, sodium carbonate, and sodium hydroxide are preferable from an economical viewpoint. In addition, such a basic compound may be used individually by 1 type, or may mix and use 2 or more types.

  Moreover, in the degreasing liquid of the present invention, the total alkali amount contained in the basic compound added to adjust the two or more alkali builders and the pH value is in the range of 9000 ppm to 16000 ppm. It is preferable. When the total alkali amount is less than 9000 ppm, good degreasing properties tend not to be exhibited. On the other hand, when it exceeds 16000 ppm, the dissolution inhibiting effect of the zinc phosphate film tends to be lowered. Moreover, as such total alkali amount, it is more preferable that it exists in the range of 10000 ppm-13000 ppm.

  Furthermore, in the degreasing solution of the present invention, the free alkalinity (FA) is preferably in the range of 10 to 15 points. When the free alkalinity is less than 10 points, the pH of the degreasing solution is less than 10.5, which tends to cause deterioration of the degreasing power and deterioration of chemical conversion properties and paintability of the object to be processed. If it exceeds 15 points, no further effect is obtained and the consumption of the components of the degreasing liquid tends to increase unnecessarily. Here, the free alkalinity is a point indicating the amount [ml] of 0.1N hydrochloric acid (or sulfuric acid) solution required to neutralize 10 ml of the degreasing solution using phenolphthalein as an indicator.

  Moreover, the degreasing solution of the present invention is substantially free of phosphorus compounds and nitrogen compounds. Here, the phrase “substantially free of phosphorus compound and nitrogen compound” in the present invention means that the phosphorus compound and nitrogen compound are not included to the extent that they act as components in the degreasing liquid, The content of the nitrogen compound is preferably less than 10 ppm, and more preferably no phosphorus compound or nitrogen compound is contained. Thus, since the degreasing solution of the present invention does not substantially contain phosphorus compounds and nitrogen compounds, it can reduce environmental loads such as eutrophication and pollution of lake water.

  The degreasing solution of the present invention preferably further contains a chelating agent. By containing such a chelating agent, the chelating agent binds to the calcium salt or magnesium salt. Therefore, when the calcium salt or magnesium salt is mixed in the degreasing solution, the calcium salt or magnesium salt is converted into the alkali silica according to the present invention. Bonding with an acid salt can be prevented, and this tends to more sufficiently suppress a reduction in degreasing power. Such a chelating agent is not particularly limited, and a known chelating agent can be used as appropriate. However, it is particularly preferable to use a water-soluble polycarboxylate since it can prevent a reduction in degreasing power more highly. That is, the degreasing solution of the present invention preferably further contains a water-soluble polycarboxylate.

  Although it does not restrict | limit especially as such water-soluble polycarboxylate, The polycarboxylate which melt | dissolves 0.01 g / L or more in the water of 0 degreeC or more is preferable. Such water-soluble polycarboxylates include homopolymers and copolymers of unsaturated carboxylic acids having one polymerizable double bond, and the carboxyl group is an alkali such as sodium or potassium. Metal neutralized salts are more preferred.

  Moreover, although it does not restrict | limit especially as a mass average molecular weight of such water-soluble polycarboxylate, It is preferable to exist in the range of 5000-100000, and it is more preferable to exist in the range of 10000-100000. When such a mass average molecular weight is less than 5000 or exceeds 100,000, the degreasing power is not sufficiently improved, and the degreasing power may be deteriorated with time.

  The concentration of the water-soluble polycarboxylate in the degreasing solution of the present invention is preferably maintained in the range of 100 to 500 ppm (more preferably 150 to 400 ppm). When the concentration of such a water-soluble polycarboxylate is less than 100 ppm, the degreasing cleaning power is not sufficiently improved, and the degreasing cleaning power tends to deteriorate with time. On the other hand, when the concentration of the water-soluble polycarboxylate salt exceeds 500 ppm, the degreasing solution becomes thickened, and the amount consumed by adhering to the object to be processed increases, and the improvement of the effect becomes insufficient. Tend to decrease.

Moreover, well-known water-soluble polycarboxylate can be used suitably as such water-soluble polycarboxylate, for example, the following commercial products can be used.
“SOCARAN CP-5” manufactured by BASF (resin solution containing 40% by mass of sodium salt of maleic acid-acrylic acid copolymer having a mass average molecular weight of 70,000)
“Socaran CP-7” (resin solution containing 40% by mass of sodium salt of maleic acid-acrylic acid copolymer having a mass average molecular weight of 50,000)
“Socaran PA-40” (resin liquid containing 40% by mass of polyacrylic acid sodium carbonate having a mass average molecular weight of 15000)
“Poise 520” manufactured by Kao Corporation (resin liquid containing 40% by mass of special polycarboxylate)
"Poise 521" (resin liquid containing 40% by mass of special polycarboxylate)
"Poise 531" (resin solution containing 40% by weight of special polycarboxylate)
“Adeka Coal W-193” manufactured by Asahi Denka Kogyo Co., Ltd. (resin solution containing 25% by mass of a soda salt of diisobutylene / olefin / maleic anhydride copolymer)
“Adeka Coal W-304” (resin liquid containing 40% by mass of polyacrylic acid soda)
“Adekacol W-370” (resin solution containing 40% by mass of sodium salt of maleic acid-acrylic acid copolymer).

  Moreover, in the degreasing liquid of this invention, you may further contain other nonionic surfactants other than said 1st and 2nd nonionic surfactant. Such other nonionic surfactants are not particularly limited and include conventionally known ones. Among these other nonionic surfactants, from the viewpoint of excellent detergency and low fish toxicity, a monoalkyl ether of polyethylene oxide is preferred, which has excellent detergency, low fish toxicity and low consumption. From the viewpoint of excellent foamability (low foamability), a monoalkyl ether of polyethylene oxide polypropylene oxide is preferable.

  In addition, water can be used suitably as a solvent used in the degreasing solution of the present invention. Furthermore, in the degreasing liquid of the present invention, other additives that can be used in the degreasing liquid as long as the effects thereof are not impaired may be appropriately used. Examples of such additives include kerosene.

  The degreasing liquid of the present invention has been described above. Next, the degreasing cleaning method of the present invention will be described.

  The degreasing and cleaning method of the present invention is a method characterized in that the object to be treated is degreased and cleaned using the above-described degreasing solution of the present invention. As described above, in the degreasing cleaning method of the present invention, since the degreasing solution of the present invention is used, it is possible to perform processing on various objects to be processed such as a metal substrate. The product can be sufficiently degreased, and excellent chemical conversion properties can be imparted to the surface of the object to be treated after the degreasing treatment.

  Further, in the present invention, a specific cleaning method is not particularly limited, and for example, a normal degreasing cleaning method such as a dipping method, a spray method, or a liquid contact method including a combination thereof can be appropriately employed. Furthermore, as processing conditions of such a degreasing cleaning method, for example, processing temperature is room temperature to 70 ° C., preferably 30 to 50 ° C., more preferably 35 to 43 ° C., and processing time is 10 seconds to 30 minutes. Can do. If the treatment temperature is lower than room temperature or the treatment time is less than 10 seconds, the degreasing power tends to be insufficient, and the treatment temperature exceeds 70 ° C. or the treatment time exceeds 30 minutes. In some cases, the chemical conversion of the zinc material tends to decrease.

  Moreover, it does not specifically limit as a to-be-processed object concerning this invention, For example, metal base materials, such as an iron-type base material, an aluminum-type base material, and a zinc-type base material, can be mentioned. The iron-based substrate, the aluminum-based substrate, and the zinc-based substrate are respectively an iron-based substrate composed of iron and / or an alloy thereof, an aluminum substrate composed of aluminum and / or an alloy thereof, zinc, and / Or a zinc-based substrate made of an alloy thereof. Furthermore, in the degreasing cleaning method of the present invention, it can be suitably used for degreasing treatment of composite structural materials composed of a plurality of metal substrates such as an iron-based substrate, an aluminum-based substrate and a zinc-based substrate. it can.

  Furthermore, it does not specifically limit as such an iron-type base material, For example, a cold-rolled steel plate, a hot-rolled steel plate, etc. can be mentioned. It does not specifically limit as said aluminum-type base material, For example, 5000 series aluminum alloy, 6000 series aluminum alloy, etc. can be mentioned. Furthermore, it is not particularly limited as the zinc-based substrate, for example, galvanized steel sheet, zinc-nickel plated steel sheet, zinc-iron plated steel sheet, zinc-chromium plated steel sheet, zinc-aluminum plated steel sheet, zinc-titanium plated steel sheet, Examples thereof include zinc-based electroplating such as zinc-magnesium-plated steel sheet and zinc-manganese-plated steel sheet, zinc such as hot-dip plating, vapor-deposited steel sheet, and zinc-based alloy-plated steel sheet.

  Moreover, as a to-be-processed object in this invention, the steel plate by which at least one part was surface-treated may be sufficient. Such surface treatment is not particularly limited, and examples thereof include zinc phosphate treatment and zirconium treatment. That is, since the degreasing cleaning method of the present invention uses the above-described degreasing solution of the present invention, it can also be applied to a surface-treated steel sheet in which a zirconium film or the like is formed at least in part. Since dissolution of the zinc oxide film can be suppressed, it can be suitably employed for a surface-treated steel sheet (zinc phosphate-coated steel sheet) at least partially coated with zinc phosphate. Such a zinc phosphate-coated steel sheet is not particularly limited and may be a commercially available product, for example, trade name “SPC P5-W” manufactured by Sumitomo Metal Industries, Ltd. Furthermore, the object to be processed of the present invention is preferably an automobile body.

  Moreover, the to-be-processed object concerning this invention may have performed the preliminary | backup degreasing process before a degreasing process. It is preferable that the object to be treated that has been degreased by the degreasing and washing method of the present invention is further washed with water after degreasing. As such a washing treatment method, after the degreasing treatment, a method of spraying or dipping treatment once or more with a large amount of washing water in order to wash the degreasing liquid with water can be employed.

  Furthermore, as a to-be-processed object degreased | defatted by this invention, you may perform a chemical conversion treatment, various coatings, etc. after a degreasing process. In the degreasing and cleaning method of the present invention, the above-described degreasing solution of the present invention exhibits excellent degreasing properties, and therefore effectively and sufficiently removes oil and dirt that are an inhibiting factor for chemical conversion treatment from the surface of the object to be processed. Can be removed. Therefore, for example, when a zinc phosphate-based chemical conversion treatment is performed on an object to be degreased by the degreasing and cleaning method of the present invention, a high-quality crystalline film of zinc phosphate (many 151-type crystal planes are obtained by X-ray diffraction). Can be formed. Thus, the degreasing cleaning method of this invention can provide favorable chemical conversion property to a to-be-processed object.

  In the case of continuously performing the degreasing method of the present invention, in order to keep the respective components and their concentrations contained in the degreasing solution of the present invention in the above-mentioned range, a replenishing agent comprising the respective components is added. Need to replenish. Such replenishment of the replenishing agent is preferably performed while maintaining the free alkalinity of 10 to 15 points and adjusting the Si concentration and pH value of the degreasing solution to be within the above-described preferable ranges. The replenishing method for such a replenishing agent is not particularly limited. For example, a replenishing agent A consisting of an alkali silicate, an alkali compound for adjusting the pH value, and a water-soluble polycarboxylate, nonionic A method of determining the replenishment ratio of the replenishment B agent to the replenishment A agent after preparing the replenishment B agent comprising a surfactant and determining the formulation of the replenishment A agent can be employed. The concentration of Si can be determined by atomic absorption analysis, the water-soluble polycarboxylate can be quantified by a liquid chromatography method, and the nonionic surfactant can be quantified by a phosphomolybdic acid method.

A suitable example of such replenishment agent A and replenishment agent B is given below.
Supplement A agent:
Alkali silicate 1-6% by mass (Si conversion for all alkali compounds)
Alkali carbonate 20-60% by mass (based on the total alkali compounds)
Caustic 10-50% by mass (based on total alkali compounds)
Supplement B agent:
5-40% by weight of water-soluble polycarboxylate,
10-60 mass% of nonionic surfactant,
0 to 85% by mass of water (mass% of agent B is a numerical value for the total of 100% by mass of the three members)
In the case of using such a replenishing agent A, the caustic content in the total alkali components in the replenishing agent A is preferably selected in the range of 10 to 50% by mass. When the caustic content is less than 10% by mass, the equilibrium pH value of the degreasing liquid is 10.5 even if the replenishing agent A is replenished so as to keep the free alkalinity of the degreasing liquid at 10 to 15 points. Since it becomes difficult to maintain the above, or it is difficult to maintain a degreasing liquid composition that satisfies the above formula (I), it causes deterioration of degreasing power with time and deterioration of chemical conversion properties and paintability of the object to be processed. There is a tendency. On the other hand, if the content of the caustic alkali exceeds 50% by mass, if the agent A is replenished to keep the free alkalinity of the degreasing liquid within the above range, the silicate concentration in the degreasing liquid decreases with time, and degreasing. Detergency tends to decrease compared to the initial level.

  Moreover, it is preferable that the said alkali silicate density | concentration which occupies in all the alkali components in the supplement A agent is selected within the range of 1-6 mass% in conversion of Si. When the alkali silicate concentration exceeds 6% by mass, it becomes difficult to maintain a degreasing liquid composition satisfying the above formula (I), and the chemical conversion property and paintability of the object to be processed tend to be deteriorated. On the other hand, when the alkali silicate concentration is less than 1% by mass, the alkali silicate concentration in the degreasing liquid is maintained even if the replenishing agent A is replenished so as to keep the free alkalinity in the degreasing liquid at 10 to 15 points. Decreases with time, and the degreasing power tends to cause deterioration over time. In addition, although each component of the replenishing agent A may be replenished to the degreasing solution alone, it is desirable that the replenishing ratio is the above ratio.

  Moreover, when using the replenishment B agent in order to maintain the water-soluble polycarboxylate concentration and the nonionic surfactant concentration in the degreasing liquid, the respective contents in the replenishing B agent are as follows. What is necessary is just to select suitably according to each management density | concentration of each. Further, the replenishment method of the replenishing agent B is not particularly limited, and the concentration of the component in the degreasing liquid may be analyzed and replenished according to the reduced amount. Replenishment may be performed at a constant ratio with respect to replenishment.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example. In the examples shown below, “part” means “part by mass” unless otherwise specified, and “%” means “% by mass” unless otherwise specified.

(Examples 1-6 and Comparative Examples 1-4)
A degreasing solution having the composition shown in Table 1 was prepared. Regarding the alkali builder, using sodium metasilicate pentahydrate _{(Na 2 O · SiO 2 ·} 5H 2 O) as the alkali silicate, and using sodium carbonate _(Na 2 CO ₃₎ as other alkaline builders . For the first nonionic surfactant, the second nonionic surfactant, and each component of the water-soluble polycarboxylate, the above-mentioned commercially available products were used. The concentration unit of each component in the table is ppm.

<Evaluation of initial degreasing cleanability>
Using each degreasing liquid obtained in Examples 1 to 6 and Comparative Examples 1 to 4, the surface of the SPC material was subjected to a stirring dip treatment for 2 minutes on a cold-rolled steel sheet (SPC material) under a temperature condition of 40 ° C. Was degreased (degreasing treatment). Subsequently, using the SPC material after degreasing, the wet area of water was confirmed visually, and degreasability (water wet characteristics) was measured. In addition, such a degreasing property (water repellency) was measured twice for each cleaning liquid for evaluation. The obtained results are shown in Table 2.

<Evaluation of degreasing performance after aging>
In order to evaluate the degreasing performance after degreasing the metal substrate a plurality of times (after time), each degreasing solution obtained in Examples 1 to 6 and Comparative Examples 1 to 4 was mixed with oil. The mixed solution was prepared, and using this, the degreasing and cleaning properties were evaluated by the same method as the above-described initial method for evaluating the degreasing and cleaning properties. The obtained results are shown in Table 2. In addition, such a liquid mixture is rust preventive oil ("Dafney oil coat RL-" made by Idemitsu Kosan Co., Ltd.) as an oil component for each of the degreasing liquids obtained in Examples 1 to 6 and Comparative Examples 1 to 4, respectively. 55 ") was mixed with 3750 ppm.

  As is clear from the results shown in Table 2, it was confirmed that the degreasing liquids of the present invention (Examples 1 to 5) exhibited high initial degreasing detergency and sufficiently high degreasing detergency after aging. On the other hand, the degreasing liquid obtained in Comparative Example 1 was not sufficient in both initial degreasing and cleaning properties after aging. Furthermore, although the degreasing liquid obtained in Comparative Examples 2 to 4 is excellent in the initial degreasing cleanability, the degreasing performance after aging is not sufficient, and the degreasing performance of the degreasing liquid may deteriorate over time. confirmed. From these results, the degreasing solution of the present invention has excellent initial degreasing properties and can sufficiently maintain the degreasing properties even when a relatively large amount of fats and oils are contained by long-term use. It was confirmed that.

  As explained above, according to the present invention, excellent degreasing performance is exhibited in a pH value range of 10.5 to 12.0 without substantially containing a phosphorus compound or a nitrogen compound causing environmental pollution. In addition, it is possible to provide a degreasing solution capable of sufficiently maintaining degreasing properties even when oils and fats are contained in a relatively large amount after long-term use, and a degreasing cleaning method using the same. It becomes.

  Therefore, the degreasing liquid of the present invention is particularly useful as a degreasing liquid used when performing a degreasing treatment on the surface of a metal substrate (for example, zinc phosphate coated steel sheet).

Claims (7)

Two or more alkali builders comprising at least one alkali silicate;
The following general formula (1):
R ¹ O— (C ₂ H ₄ O) _n —H (1)
(In the formula, R ¹ represents an alkyl group having 10 to 12 carbon atoms, and n represents an integer of 7 to 9)
A first nonionic surfactant represented by:
The following general formula (2):
_{^{R 2 O- (C 2 H 4}} O) m -H (2)
(In the formula, R ² represents a group having at least two aromatic rings in one molecule, and m represents an integer of 6 to 10).
A second nonionic surfactant represented by:
And a pH value of 10.5 to 12.0 and substantially free of phosphorus compounds and nitrogen compounds.   The content ratio of the solid content of the first nonionic surfactant and the second nonionic surfactant in terms of mass is 1: 9 to 9: 1. The degreasing solution according to 1.   The degreasing solution according to claim 1 or 2, wherein the degreasing solution further contains a water-soluble polycarboxylate. The concentration of the alkali silicate is expressed by the following formula (I):
300 <Y <10 ^{(0.318X + 2.72)} (I)
(In the formula, X is a value obtained by subtracting 10.5 from the pH value of the degreasing solution, and Y is the concentration (unit: ppm) of the alkali silicate.)
Satisfying the condition of the inequality represented by
The concentration of the water-soluble polycarboxylate is in the range of 100 to 500 ppm, and
The total concentration of the first nonionic surfactant and the second nonionic surfactant is in the range of 1400-2400 ppm;
The degreasing solution according to claim 3.   A degreasing and cleaning method, wherein the object to be processed is degreased and cleaned using the degreasing liquid according to any one of claims 1 to 4.   The degreasing cleaning method according to claim 5, wherein at least a part of the workpiece is a surface-treated steel sheet.   The degreasing cleaning method according to claim 5 or 6, wherein the object to be processed is an automobile body.