JP7213872B2 - Cleaning agent for scale and method for removing scale using the cleaning agent - Google Patents

Description

The present invention relates to a scale cleaning agent comprising ammonium citrates, a trialkyl citrate, and water, and a method for removing scale using the cleaning agent.

Stainless steel is used in various fields such as construction, home appliances, kitchens, transportation, and industry, and is used in situations where corrosion resistance, heat resistance, strength, formability, etc. are required. Among them, SUS316, which is a stainless steel with particularly excellent corrosion resistance, is sometimes used for equipment and piping in the chemical and food industries in order to prevent corrosion or contamination by metal pieces (foreign matter) due to severe use conditions.

Acid cleaning agents and alkaline cleaning agents are used to clean equipment and piping using stainless steel. When such equipment and pipes are washed repeatedly, scale is formed by combining ions such as magnesium ions and calcium ions contained in water with acidic and alkaline components contained in acidic and alkaline cleaning agents. A water-insoluble inorganic salt called , may adhere to the surface of the stainless steel. These scales cause equipment and piping failure, functional deterioration, and foreign matter contamination.

As a method for removing scale, a method of using an aqueous cleaning agent is generally known. , Patent Document 1, etc.). However, the above method uses deleterious substances such as hydrochloric acid and hydrofluoric acid, which are highly corrosive and toxic. rice field.

As a substitute for the above-mentioned cleaning agent containing hydrochloric acid or hydrofluoric acid, a cleaning agent for removing fluorine-based scales has been proposed that uses both an ammonium salt of alkylenepolyaminepolyacetic acid and an ammonium salt of a carboxylic acid that may have a hydroxyl group. (for example, Patent Document 2, etc.). However, although the cleaning agents described above are effective in removing fluorine-based scale, scale formed by other metals such as magnesium, sodium, iron, and chromium and acid components such as phosphoric acid or carboxylic acid, etc. It was found to be inadequate in removing various other scale species.

In addition, stainless steel is known to cause discoloration (temper color: a thin scale layer containing iron oxide components) in heated or welded parts due to iron concentration and component changes, and rusting due to a decrease in corrosion resistance. ing. Products manufactured using equipment and piping in the chemical and food industries with such discoloration components attached may be contaminated with foreign substances, degraded or discolored. There has also been a need for a cleaning agent that removes encrusted scale.

JP-A-62-260081 Japanese Patent Application Laid-Open No. 2005-206620

Therefore, the problem to be solved by the present invention is to provide a cleaning agent that does not corrode stainless steel, its passive film, and anticorrosion coating layer and that can remove scale containing iron components that cause discoloration. is.

Accordingly, the inventors of the present invention conducted intensive studies and found a scale cleaning agent containing specific amounts of ammonium citrates and trialkyl citrates, resulting in the present invention. That is, the present invention provides a scale cleaning agent comprising (A) at least one ammonium citrate, (B) at least one trialkyl citrate, and (C) water. A cleaning agent for scale containing 0.1% to 60% by mass of component (A) and 0.25% to 10% by mass of component (B) relative to the total amount.

The cleaning agent for scale of the present invention does not corrode stainless steel, its passive film, and anticorrosion coating layer, and can remove scale containing iron components that cause discoloration. Equipment and pipes using stainless steel that have been cleaned with the cleaning agent for scale of the present invention can prevent the occurrence of failures and functional deterioration, and the metals in products manufactured with such equipment can be prevented. Contamination of foreign matter such as pieces can be suppressed. In addition, the wettability to stainless steel is also good, and the amount of cleaning agent required for cleaning scale can be reduced, which is economically advantageous.

Ammonium citrates, which are the component (A) of the present invention, act on metal components contained in the scale to form an ammonium citrate metal complex. This metal complex can be dissolved in the cleaning liquid when the trialkyl citrate, which is the component (B) described later, is present.

The ammonium citrates of the present invention include monoammonium citrate, diammonium citrate, and triammonium citrate. Among these, in the present invention, triammonium citrate is preferred from the viewpoint of cleaning of scale. Triammonium citrate can be obtained by neutralizing citric acid and aqueous ammonia, and can also be obtained by neutralizing monoammonium citrate or diammonium citrate and aqueous ammonia. In addition, commercially available products sold by Kanto Kagaku Co., Ltd., Fuji Film Wako Pure Chemical Co., Ltd., etc. can be used.

The content of ammonium citrates is 0.1% by mass to 60% by mass with respect to the total amount of the scale cleaning agent of the present invention, and from the viewpoint of compatibility with other components, it is 0.1% by mass to 25% by mass. %, and more preferably 5% by mass to 12.5% by mass from the viewpoint of dissolution rate.

Trialkyl citrate, which is the component (B) of the present invention, is a compound in which all three carboxylic acids contained in citric acid are esterified, and contributes to scale cleaning. The alkyl group in the esterified moiety in the trialkyl citrate includes alkyl groups having 1 to 6 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a secondary butyl group, a tertiary butyl group, an isobutyl group, a pentyl group, an isopentyl group, a secondary pentyl group, and a tertiary pentyl group. , a hexyl group, and the like. Among these, an alkyl group having 1 to 4 carbon atoms is preferable, and a methyl group, an ethyl group, a propyl group, and an isopropyl group are more preferable, from the viewpoint that the ammonium citrate metal complex described above can be dissolved more. Ethyl group is particularly preferred from the viewpoint of safety that it can be used as

Trialkyl citrate, which is the component (B) of the present invention, can be a commercially available product. For example, trimethyl citrate, triethyl citrate, etc. are available from Kanto Chemical Co., Ltd. are sold at.

The content of the trialkyl citrate, which is the component (B) of the present invention, is 0.25% by mass to 10% by mass with respect to the total amount of the scale cleaning agent, and from the viewpoint of surface activity, it is 0.5% by mass to 10% by mass. It is preferably 10% by mass, and more preferably 1% by mass to 2.5% by mass from the viewpoint of compatibility with other components.

The blending ratio of the components (A) and (B) of the present invention is not particularly limited as long as each component is within the above concentration range. is contained in the scale cleaning agent in an amount of 5 to 50 parts by mass, preferably 10 to 40 parts by mass, more preferably 10 to 25 parts by mass.

Water, which is the component (C) of the present invention, refers to tap water, distilled water, ion-exchanged water, pure water, ultrapure water, RO water (reverse osmosis water), and the like. Among these, it is preferable to use distilled water or ion-exchanged water.

The amount of component (C) used in the present invention includes (A) component, (B) component, and optionally used (D) pH adjuster, thickener, surfactant, chelating agent, etc. Combined with the total amount of other components, it is used as a cleaning agent for scale so as to be 100% by mass.

In the present invention, (D) a pH adjuster may also be used. (D) By using a pH adjuster, the detergency of scale can be improved. (D) Examples of pH adjusters include inorganic acids, organic acids, and bases.

Examples of the inorganic acids include sulfuric acid, nitric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid.
Examples of the organic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n- Heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, diglycolic acid, 2-furancarboxylic acid, 2,5-furandicarboxylic acid, 3-furancarboxylic acid, 2-tetrahydrofurancarboxylic acid, methoxyacetic acid, methoxyphenyl Acetic acid, phenoxyacetic acid, hydroxyethylidene diphosphonic acid, nitrilotris (methylene phosphonic acid), phosphonobutanetricarboxylic acid, ethylenediamine tetra (methylene phosphonic acid) and the like.

Examples of the bases include organic bases such as amines and quaternary ammonium hydroxides, hydroxides of alkali metals such as sodium and potassium, hydroxides of alkaline earth metals such as magnesium and calcium, and ammonia. mentioned.

Among the pH adjusters (D) listed above, ammonia, citric acid, and lactic acid are preferably used, and ammonia and citric acid are more preferably used, from the viewpoints of safety, cost, and scale detergency. . Moreover, the (D) pH adjusting agent exemplified above may be used alone or in combination of two or more.

The content of the pH adjuster (D) mentioned above is 0.0001% by mass to 15% by mass in the scale cleaning agent from the viewpoint of the balance between the detergency of the scale, the viscosity of the cleaning solution, and the cost. preferably 0.05% by mass to 10% by mass, and even more preferably 0.05% by mass to 5% by mass.

Although the pH of the cleaning agent for scale of the present invention is not particularly limited, it is preferably 4 to 12 from the viewpoint of detergency of scale, and 6 to 8 from the viewpoint of safety in handling. is more preferred.

The scale cleaning agent of the present invention may contain a thickening agent, a surfactant, and a chelating agent, if necessary.
Examples of the thickening agent include guar gum, ethyl cellulose, xanthan gum, carbomer, carrageenan, chitosan, hydroxyethyl cellulose, microcrystalline cellulose, high molecular weight solid polyethylene glycol, alginic acid, sodium alginate, calcium carboxymethyl cellulose, magnesium aluminum silicate, Colloidal silicon dioxide and the like can be mentioned.

Examples of the surfactant include general anionic surfactants and nonionic surfactants, primary amine salts, secondary amine salts, tertiary amine salts, quaternary amine salts and pyridinium salts. Cationic surfactants such as betaine type, sulfate ester type and sulfonic acid type amphoteric surfactants, and the like can be used.
Examples of the anionic surfactant include alkyl sulfates such as sodium dodecyl sulfate, potassium dodecyl sulfate and ammonium dodecyl sulfate; polyoxyethylene ether sulfates such as sodium dodecyl polyglycol ether sulfate and ammonium polyoxyethylene alkyl ether sulfate; Alkylsulfonates such as ricinoleate, alkali metal salts of sulfonated paraffin and ammonium salts of sulfonated paraffin; Fatty acid salts such as sodium laurate, triethanolamine oleate and triethanolamine abietate; sodium benzene sulfonate, alkali phenol hydroxy Alkylaryl sulfonates such as the alkali metal sulfate of ethylene can be used. In addition, high alkyl naphthalene sulfonates, naphthalene sulfonic acid formalin condensates, dialkyl sulfosuccinates, polyoxyethylene alkyl sulfate salts, polyoxyethylene alkyl aryl sulfate salts, polyoxyethylene ether phosphates, polyoxyethylene alkyl ether acetic acids Salts, N-acyl amino acid salts, N-acyl methyl taurine salts, and the like can also be used.

As the nonionic surfactant, fatty acid partial esters of polyhydric alcohols such as sorbitan monolaurate and sorbitan monooleate, polyoxyethylene glycol fatty acid esters, and polyglycerol fatty acid esters can be used. Furthermore, ethylene oxide and/or propylene oxide adducts of alcohols having 1 to 18 carbon atoms, ethylene oxide and/or propylene oxide adducts of alkylphenols, ethylene oxide and/or propylene oxide adducts of alkylene glycol and/or alkylenediamine, etc. can be used.

Examples of alcohols having 1 to 18 carbon atoms that constitute the nonionic surfactant include methanol, ethanol, propanol, 2-propanol, butanol, 2-butanol, tertiary butanol, amyl alcohol, isoamyl alcohol, tertiary amyl alcohol, hexanol, octanol, decane alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, and stearyl alcohol;

Examples of the alkylphenol include phenol, methylphenol, 2,4-di-tert-butylphenol, 2,5-di-tert-butylphenol, 3,5-di-tert-butylphenol, 4-(1,3-tetramethylbutyl)phenol , 4-isooctylphenol, 4-nonylphenol, 4-tertiary octylphenol, 4-dodecylphenol, 2-(3,5-dimethylheptyl)phenol, 4-(3,5-dimethylheptyl)phenol, naphthol, bisphenol A, and bisphenol F and the like.

Examples of the alkylene glycol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol and the like is.

The above alkylenediamine is, for example, a compound in which the alcoholic hydroxyl group of the alkylene glycol described above is substituted with an amino group. Both random adducts and block adducts can be used as the ethylene oxide and propylene oxide adducts.

Examples of cationic surfactants include lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, distearyldimethylammonium chloride, didecyldimethylammonium chloride, laurylbenzyldimethylammonium chloride, didecyldimethylammonium chloride, alkylpyridinium bromide and imidazolinium. Laurate and the like can be used.

Examples of the amphoteric surfactant include coconut oil fatty acid amidopropyldimethylacetate betaine, lauryldimethylamino acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxymethylimidazolinium betaine, laurylhydroxysulfobetaine, lauroylamideethylhydroxyethyl. Betaine-type amphoteric surfactants such as carboxymethylbetaine and hydroxypropyl phosphate metal salts, amino acid-type amphoteric surfactants such as β-laurylaminopropionic acid metal salts, sulfate ester-type amphoteric surfactants, and sulfonic acid-type amphoteric surfactants Surfactants can be used.

Examples of the chelating agent include nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, aspartic acid diacetic acid, ethylenediaminedisuccinic acid, or alkali metal salts or ammonium salts of these aminopolycarboxylic acid type chelating agents; Carboxymethyl oxysuccinate, oxydisuccinate, tartaric acid monosuccinate, tartaric acid disuccinate, or their alkali metal salts or oxycarboxylic acid type chelating agents such as ammonium salts, nitrilotrimethylene phosphonic acid, ethylenediaminetetramethylene phosphonic acid, hydroxyl Phosphonic acid-type chelating agents such as ethylidene diphosphonic acid, or alkali metal salts or ammonium salts thereof, and the like.

The scale cleaning agent of the present invention can remove scale containing metal components. The metal component contained in the scale is a metal ion capable of forming a salt with the acid component or base component contained in the scale. Metal elements in such metal ions include, for example, sodium, potassium, magnesium, chromium, manganese, iron, nickel, copper, silver, zinc, aluminum, and titanium. Scale containing metal ions composed of these metal elements is insoluble in generally known cleaning solutions, but ammonium citrates, which are the component (A) contained in the cleaning agent for scale of the present invention, are effective for scaling. Ammonium citrate metal complexes are formed by acting on the metal ions in the scale and exchanging salts with the metal components in the scale. Furthermore, the metal complex can be dissolved in the trialkyl citrate which is the component (B). Therefore, the scale can be efficiently removed by using the scale cleaning agent of the present invention. It is particularly effective for removing scale from stainless steel, and is particularly effective for removing scale from equipment using SUS316.
In addition, among the above metal elements, scale containing iron in particular can be efficiently removed.

In the method of removing scale with the cleaning agent for scale of the present invention, the amount of the cleaning agent for scale used may be 10 parts by mass to 10,000 parts by mass of the cleaning agent for scale per 1 part by mass of scale. .

EXAMPLES The present invention will be specifically described below with reference to examples. In the following examples and the like, % is based on mass unless otherwise specified.
The raw materials used for the examples are as follows.
Triammonium citrate: Fuji Film Wako Pure Chemical Co., Ltd. Monoammonium citrate: Fuji Film Wako Pure Chemical Co., Ltd. Diammonium citrate: Fuji Film Wako Pure Chemical Co., Ltd. Triethyl citrate: Fuji Film Wako Pure Chemical Pharmaceutical Co., Ltd. Trisodium citrate: Fuji Film Wako Pure Chemical Co., Ltd. Citric acid: Fuji Film Wako Pure Chemical Co., Ltd. Ammonia water: Fuji Film Wako Pure Chemical Co., Ltd.

[Examples 1 to 5, Comparative Examples 1 to 5]
Raw materials as shown in Table 1 were added to a 200 ml beaker and stirred at 25° C. until the raw materials were completely dissolved to obtain cleaning agents.

[Scale solubility evaluation]
99.8 parts by mass of each cleaning agent and 0.2 parts by mass of condensed polyvalent metal phosphate scale powder were added to a 200 ml beaker, and the solution was allowed to stand at 45°C for 24 hours. Check to see if the powder is dissolved. When the solution was green and transparent, it was judged to be acceptable, and when the scale powder was not dissolved but dispersed in water and observed as a suspension, it was judged to be unacceptable.

The scale powder was adhered to the inner wall of the SUS316 vaporization equipment for hydrogen peroxide containing phosphoric acid. 15 kV, low vacuum 10 Pa), the composition was confirmed by component analysis. Cr: 3.2 wt%, Mn: 0.3 wt%, Fe: 20.8 wt%, Ni: 2.5 wt% (average value of five measurements).

[Wettability evaluation]
50 μL of each of the cleaning agents obtained above was dispensed with a micropipette, dropped onto the surface of a 50×50×1 mm SUS316 test piece (manufactured by Nippon Test Panel Co., Ltd.), and the droplets spread on the stainless steel surface. (Circular droplet diameter) was measured with a ruler. The larger the spread, the better the wettability to the stainless steel surface, which is advantageous in that the amount used can be reduced when spraying and cleaning the oil-contaminated part or the uneven part. In this evaluation, cleaning agent droplets with a diameter of 9 mm or more were considered acceptable. Table 1 shows the results.

As can be seen from Table 1, the scale cleaning agent of the present invention is capable of efficiently dissolving scale, which is a condensed phosphate containing iron, and is excellent in detergency of scale adhering to stainless steel. rice field. The detergents other than the present invention gave low scores in terms of both scale solubility and wettability to stainless steel.

Claims (6)

(A) at least one ammonium citrate;
(B) at least one trialkyl citrate; and (C) water, comprising:
A cleaning agent for scale containing 0.1% to 60% by mass of component (A) and 0.25% to 10% by mass of component (B) relative to the total amount of said cleaning agent for scale. 2. The cleaning agent for scale according to claim 1, further comprising (D) a pH adjuster in an amount of 0.0001% by mass to 15% by mass relative to the total amount of the cleaning agent for scale. The cleaning agent for scale according to claim 2, wherein (D) the pH adjuster is at least one selected from the group consisting of ammonia, citric acid, and lactic acid. The scale cleaning agent according to any one of claims 1 to 3, wherein the (B) trialkyl citrate is triethyl citrate. The cleaning agent for scale according to any one of claims 1 to 4, wherein the cleaning agent for scale has a pH of 6 to 8. A method for removing iron-containing scale adhered to stainless steel using the scale cleaning agent according to any one of claims 1 to 5.