Detergent composition for automatic dishwashing machines

Abstract

To provide an automatic dishwasher detergent composition that has both corrosion inhibition ability against aluminum, and cleaning performance and scale formation inhibition ability.SOLUTION: Provided is an automatic dishwasher detergent composition that contains the following components (A) to (E). (A) an alkali metal silicate having M2O / SiO2=1 / 1 (mole ratio) (M indicates an alkali metal). (B) a bicarbonate. (C) a water-soluble chelating agent. (D) a water-soluble antioxidant. (E) potassium hydroxide.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a detergent composition for automatic dishwashers, which is used when cleaning hard surfaces of tableware, various containers, utensils, etc., with an automatic dishwasher. [Background technology]

[0002] Conventionally, automatic dishwashers have been widely used to efficiently wash used tableware in hotels, restaurants, schools, hospitals, eating and drinking establishments, food service companies, company cafeterias, etc. In addition to washing tableware, various automatic dishwashers are also used in various manufacturing plants, processing plants, etc. to wash utensils, containers, plastic containers used in distribution, etc.

[0003] The detergent compositions used in such automatic dishwashers and the like generally contain an alkaline agent and a chelating agent as main components. However, when aluminum or anodized aluminum is included in the materials constituting the above-mentioned tableware, utensils, containers, etc., corrosion by the alkaline agent becomes a problem. For this reason, various formulations have been studied to prevent corrosion of aluminum and the like.

[0004] For example, in Patent Document 1, the compounding ratio of silicate and carbonate is specified to suppress aluminum corrosion. In Patent Document 2, methylglycine diacetate (MGDA) and carbonate are compounded to suppress aluminum corrosion while cleaning calcium-based scale on the surface. Furthermore, Patent Document 3 combines an alkali metal metasilicate with a specific alkali silicate to achieve both aluminum corrosion inhibition and cleaning power. And, in Patent Document 4, the alkali agent, chelating agent, and metal corrosion inhibitor are set within specific ranges to achieve both aluminum corrosion inhibition and cleaning power. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2006-296470 A [Patent Document 2] JP 2004-175871 A [Patent Document 3] JP 2000-186297 A [Patent Document 4] JP 2020-050781 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the case of Patent Document 1, the chelating agent is not considered, so the chelating effect cannot be fully exerted, and there is a risk that sufficient cleaning power cannot be obtained when cleaning is performed under high hardness conditions. In the case of Patent Document 2, although the corrosion of aluminum can be reduced, there is a risk that sufficient cleaning power cannot be obtained at low concentrations, and furthermore, there is a risk that scale formation cannot be suppressed when cleaning is performed under high hardness conditions. And, in the case of Patent Document 3, although the corrosion of aluminum can be reduced, a phosphorus-free cleaning agent cannot be realized because a phosphate is used as a chelating agent. In addition, since no consideration is given to scale formation, the effect of suppressing scale formation cannot be expected. Furthermore, in the case of Patent Document 4, since an alkali hydroxide is used as an alkaline agent, the corrosion of copper can be suppressed, but the corrosion of aluminum cannot be sufficiently suppressed.

[0007] As described above, no conventional cleaning agent composition has both an aluminum corrosion inhibiting effect, high detergency, and an effect of inhibiting scale formation, and therefore there is a demand for a cleaning agent composition having all of these properties.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a detergent composition for automatic dishwashers which has both an ability to inhibit corrosion of aluminum, cleaning performance and an ability to inhibit scale formation. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides the following [1] to [4]. [1] A detergent composition for automatic dishwashers, comprising the following components (A) to (E): (A)M2O / S i An alkali metal silicate in which O2=1 / 1 (molar ratio) (M represents an alkali metal). (B) Bicarbonate. (C) A water-soluble chelating agent. (D) Water-soluble antioxidant. (E) Potassium hydroxide. [2] The detergent composition for automatic dishwashers according to [1], wherein the bicarbonate salt of component (B) is at least one of sodium bicarbonate and potassium bicarbonate. [3] The detergent composition for use in automatic dishwashers according to [1] or [2], wherein the component (C) contains an aminocarboxylate. [4] The detergent composition for automatic dishwashers according to any one of [1] to [3], wherein a 0.05% by mass aqueous solution has a pH of 10.5 or more at 25° C.

[0010] That is, as a result of intensive research by the present inventors to solve the above problems, they found that by using a bicarbonate and a water-soluble antioxidant in combination with a specific alkali metal silicate, a water-soluble chelating agent, and potassium hydroxide, even a cleaning composition that is strongly alkaline and contains a large amount of a water-soluble chelating agent can inhibit aluminum corrosion, achieve high detergency, and inhibit scale formation, and thus completed the present invention. Effect of the Invention

[0011] The detergent composition for automatic dishwashers of the present invention (hereinafter sometimes abbreviated as "detergent composition") contains the following components (A) to (E). (A)M2O / S i An alkali metal silicate in which O2=1 / 1 (molar ratio) (M represents an alkali metal). (B) Bicarbonate. (C) A water-soluble chelating agent. (D) Water-soluble antioxidant. (E) Potassium hydroxide.

[0012] The above-mentioned detergent composition has corrosion-inhibiting ability against aluminum, and therefore has high versatility and is easy to use, for example, by eliminating the need to check in detail the material of the tableware to be washed. In addition, since phosphate is not an essential component, a phosphorus-free product can be realized, and it is excellent in environmental consideration. Furthermore, since it has excellent cleaning performance and scale formation-inhibiting ability, it can achieve a consistent cleaning finish even at a low concentration. In the present invention, "low concentration" means a concentration of 0.05% by mass or less, and usually means a concentration of 0.02% by mass or more.

[0013] In the present invention, when the bicarbonate salt of component (B) is at least one of sodium bicarbonate and potassium bicarbonate, the handling properties during production of the detergent composition (hereinafter sometimes referred to as "handling properties") are improved, and the storage stability and cost performance are excellent.

[0014] Furthermore, when the component (C) contains an aminocarboxylate, the cleaning properties and the effect of inhibiting scale formation are improved.

[0015] Furthermore, if the pH of a 0.05% by mass aqueous solution at 25° C. is 10.5 or higher, higher detergency can be obtained even when used at a low concentration. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Next, an embodiment of the present invention will be described in detail.

[0017] The cleaning composition of the present invention comprises (A) M2O / S iIt contains an alkali metal silicate (M represents an alkali metal) with a molar ratio of O2=1 / 1, (B) a bicarbonate, (C) a water-soluble chelating agent, (D) a water-soluble antioxidant, and (E) potassium hydroxide, each in a predetermined range. Each component will be explained below.

[0018] <Component (A)> (A) Component, MO / S i Alkaline metal silicates with a molar ratio of 1 / 1 (M indicates an alkali metal) are blended to improve cleaning properties. In the above-mentioned alkali metal silicates, if there is a large amount of M2O, there is a tendency for aluminum to be corroded, and if there is a large amount of S i Since there is a tendency for silicate scale to be easily formed when there is a large amount of O2, one of the features of the present invention is to use a molar ratio of the two at 1 / 1. i Among alkali metal silicates (M represents an alkali metal) having O2=1 / 1 (molar ratio), sodium metasilicate is preferably used from the standpoint of storage stability and cost. In addition, the above (A)M2O / S i The alkali metal silicate (M represents an alkali metal) having a molar ratio of O2=1 / 1 may be used either hydrous or anhydrous, and may also be used as a silicate such as sodium silicate or potassium silicate. These may be used alone or in combination of two or more kinds.

[0019] The content of the above component (A) is preferably 10 to 60% by mass, more preferably 25 to 45% by mass, based on the total mass of the detergent composition. That is, if the content of the component (A) in the detergent composition is too low, the cleaning ability tends to decrease due to a decrease in alkaline strength, whereas if the content of the component (A) is too high, the balance of the detergent composition system tends to deteriorate, resulting in a decrease in storage stability and silicate scale formation inhibitory ability. In addition, the above component (A) is preferably used in the form of a powder or granule, from the viewpoint of good handling and concentration.

[0020] <(B) component> The bicarbonate salt as component (B) is not particularly limited, but for example, sodium bicarbonate, potassium bicarbonate, etc. are preferably used, and sodium bicarbonate is particularly preferably used in terms of storage stability, handling, and cost. These can be used alone or in combination of two or more. The above component (B) exhibits the effect of suppressing aluminum corrosion by containing a specific amount of the above component (C) described in detail later. The above component (B) is also used as a reinforcement and buffer for alkaline strength, and is also used as an extender when the detergent composition is in the form of a solid or powder.

[0021] The content of the (B) component is preferably 1 to 20% by mass, more preferably 5 to 15% by mass, based on the total mass of the detergent composition. That is, if the content of the (B) component in the detergent composition is too low, the effect of inhibiting aluminum corrosion tends to decrease, whereas if the content of the (B) component is too high, the alkaline strength increases, and conversely, the effect of inhibiting aluminum corrosion and the ability to inhibit carbonate scale formation tend to decrease. In addition, the (B) component is preferably used in the form of a powder or granule, from the viewpoint of good handling and concentration.

[0022] <(C) component> The water-soluble chelating agent (C) is effective in suppressing aluminum corrosion by being contained in a specific amount together with the above-mentioned (B) component. In the present invention, a phosphorus-free water-soluble chelating agent is preferably used as the water-soluble chelating agent, but a phosphorus-based agent may also be used. In other words, when a phosphorus-free water-soluble chelating agent is used as the water-soluble chelating agent, the resulting cleaning agent composition can be a phosphorus-free product, which is preferable as it is a more environmentally friendly product.

[0023] Examples of the phosphorus-free water-soluble chelating agent include aminocarboxylic acids such as ethylenediaminetetraacetic acid, nitrilotriacetic acid, iminodiacetic acid, diethylenetriaminepentaacetic acid, N-hydroxyethylethylenediamineacetic acid, ethylenediaminetetrapropionic acid, methylglycinediacetic acid (MGDA), triethylenetetraaminehexaacetic acid, ethyleneglycoldietherdiaminetetraacetic acid, hydroxyethyliminodiacetic acid, cyclohexane-1,2-diaminetetraacetic acid, dienkol acid, hydroxyethylethylenediaminetriacetic acid, ethylenediaminedisuccinic acid (EDDS), L-glutamic acid diacetic acid (GLDA), 3-hydroxy-2,2'-iminodisuccinic acid (HIDS), and L-aspartic acid-N,N-diacetic acid (ASDA); dicarboxymethylglutaric acid, heptogluconic acid, taurine-N,N-diacetic acid, gluconic acid, citric acid, and / or water-soluble alkali metal salts thereof such as sodium salts and potassium salts, ethanolamine salts, and ammonium salts thereof. Among these, aminocarboxylic acids and their salts are preferably used, and ethylenediaminetetraacetic acid, nitrilotriacetic acid, L-glutamic acid diacetic acid, methylglycine diacetic acid and / or their water-soluble alkali metal salts such as sodium salts and potassium salts, ethanolamine salts, ammonium salts, and methylglycine diacetic acid are more preferably used, and in particular, sodium salts are advantageously used in terms of cleaning power and cost. These can be used alone or in combination of two or more kinds.

[0024] Examples of the phosphorus-based water-soluble chelating agent include alkali metal phosphates. Examples of the phosphoric acid include orthophosphoric acid, polyphosphoric acid, pyrophosphoric acid, metaphosphoric acid, and hexametaphosphoric acid. Examples of the alkali metals to be combined with these include sodium and potassium. In the present invention, when a phosphorus-based aqueous solution chelating agent is used, sodium tripolyphosphate is preferably used among the alkali metal phosphates. These can be used alone or in combination of two or more.

[0025] The content of the above component (C) is preferably 20 to 60% by mass, more preferably 35 to 45% by mass, based on the total mass of the detergent composition. That is, if the content of the component (C) in the detergent composition is too low, the cleaning ability, especially for oily stains, tends to decrease, while if the content of the component (C) is too high, the balance of the detergent composition system tends to be poor, and the effect of inhibiting corrosion of aluminum tends to decrease. In addition, the above component (C) is preferably used in the form of a powder or granule, from the viewpoint of good handling and concentration.

[0026] In the present invention, "phosphorus-free" means not only those that do not contain phosphorus at all, but also those that contain less than 0.5 mass% phosphorus (as elemental phosphorus). When the cleaning composition of the present invention is "phosphorus-free", the content is preferably less than 0.2 mass%, more preferably less than 0.1 mass%, and even more preferably does not contain detectable phosphorus. The above mass% is the proportion of the dry mass in the cleaning composition, and is calculated excluding any water that may be present in the cleaning composition.

[0027] <(D) component> As the water-soluble antioxidant, which is the component (D), for example, sulfite (sodium salt, potassium salt), ascorbic acid or its salt, sodium nitrite, sodium hydrogen sulfite, erythorbic acid or its salt, cysteine ​​hydrochloride, cysteine, potassium dichloroisocyanurate, sodium thioglycolate, thioglycerol, sodium formaldehyde sulfoxylate, pyrosulfite (sodium salt, potassium salt), polyphenols such as catechin, etc. Among them, it is preferable to use pyrosulfite and ascorbate. These can be used alone or in combination of two or more kinds.

[0028] The content of the above component (D) is preferably 0.5 to 30 mass %, and more preferably 1 to 20 mass %, based on the total mass of the detergent composition. That is, if the content of the component (D) in the detergent composition is too low, the effect of inhibiting aluminum corrosion tends to decrease, whereas if the content of the component (D) is too high, the balance of the detergent composition system tends to deteriorate, resulting in decreased storage stability and detergency.

[0029] <(E) component> Although potassium hydroxide, which is component (E), has been known to cause aluminum corrosion, its use together with the above components (A) to (D) can improve cleaning properties and silicate scale formation inhibitory ability. The content of component (E) is preferably 0.5 to 10 mass % and more preferably 1 to 5 mass % based on the total mass of the detergent composition. That is, if the content of component (E) in the detergent composition is too low, cleaning properties and silicate scale formation inhibitory ability tend to decrease, whereas if the content of component (E) is too high, the effect of inhibiting aluminum corrosion tends to decrease.

[0030] The cleaning composition of the present invention is prepared using the above components (A) to (E) as essential components, but may further contain various optional components, such as nonionic surfactants, organophosphorus chelating agents, polyelectrolyte polymers, rust inhibitors, colorants, fragrances, pH adjusters, germicides, preservatives, deodorants, antistatic agents, etc.

[0031] <Optional ingredient: nonionic surfactant> The nonionic surfactants are blended for the purpose of improving cleaning properties, prevention of oil re-adhesion to the object to be cleaned, and foam suppression properties, and examples thereof include polyoxyethylene polyoxypropylene alkyl ethers, Pluronic (registered trademark) type block polymers, reverse Pluronic type block polymers, EO,PO adducts of polyhydric alcohols, EO,PO adducts of glycerin, glycerin fatty acid esters, polyglycerin fatty acid esters, sorbitan fatty acid esters, etc. These can be used alone or in combination of two or more kinds.

[0032] As the polyoxyethylene polyoxypropylene alkyl ether, a polyoxyethylene polyoxypropylene alkyl ether in which 1 to 20 moles of EO and 1 to 20 moles of PO are added to a linear or branched alcohol having 6 to 18 carbon atoms, and in which the mass ratio of EO / PO is in the range of 0.5 to 2, or a polyoxyethylene polyoxypropylene alkyl ether in which 1 to 15 moles of EO and 1 to 50 moles of PO are added to a linear or branched alcohol having 6 to 18 carbon atoms, and in which the mass ratio of EO / PO is in the range of 0.05 to 0.5, is preferably used. As the above-mentioned Pluronic block polymer, a Pluronic block polymer having an average molecular weight in the range of 500 to 10,000 and an EO / PO mass ratio in the range of 0.5 to 4.0, a Pluronic block polymer having an average molecular weight in the range of 500 to 10,000 and an EO content in the range of 5% to 80% of the total average molecular weight, a Pluronic block polymer having an average molecular weight in the range of 500 to 10,000 and an EO / PO mass ratio in the range of 0.05 to 0.5, etc. are preferably used. As the reverse Pluronic block polymer, a reverse Pluronic block polymer having an average molecular weight in the range of 500 to 10,000 and an EO / PO mass ratio in the range of 0.05 to 1 is preferably used. As the EO,PO adduct of the polyhydric alcohol, an adduct of 3 to 45 mol of EO and 15 to 120 mol of PO to trimethylolpropane is preferably used. As the EO,PO adduct of glycerin, one in which 3 to 45 mol of EO and 15 to 120 mol of PO are added to glycerin is preferably used. Preferred examples of the monoglycerol fatty acid ester include glycerol monocaproate, glycerol monocaprylate, glycerol monocaprate, glycerol monolaurate, glycerol monomyristate, glycerol monopalmitate, glycerol monostearate, glycerol monobehenate, glycerol monooleate, glycerol monoelaidate, glycerol monoricinoleate, and glycerol monocondensed ricinoleate.

[0033] The polyglycerol fatty acid ester is a partial ester of a fatty acid having 6 to 22 carbon atoms and a polyglycerol having an average degree of polymerization of glycerol of 2 to 10. Specifically, esters of diglycerol, triglycerol, tetraglycerol, pentaglycerol, hexaglycerol, heptaglycerol, octaglycerol, nonaglycerol, decaglycerol, or the like, with caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, ricinoleic acid, linoleic acid, linolenic acid, or a mixture thereof are preferably used.

[0034] Specific examples of the polyglycerol fatty acid ester include diglycerol monocaprylate, triglycerol monocaprylate, tetraglycerol monocaprylate, pentaglycerol monocaprylate, hexaglycerol monocaprylate, heptaglycerol monocaprylate, octaglycerol monocaprylate, nonaglycerol monocaprylate, decaglycerol monocaprylate, tetraglycerol monolaurate, tetraglycerol monostearate, tetraglycerol monooleate, hexaglycerol monolaurate, hexaglycerol monostearate, hexaglycerol tristearate, hexaglycerol monooleate, decaglycerol monolaurate, and decaglycerol monooleate. Preferred examples of the sorbitan fatty acid ester include sorbitan caproate ester, sorbitan caprylate ester, sorbitan caprate ester, sorbitan laurate ester, sorbitan myristate ester, sorbitan palmitate ester, sorbitan stearate ester, sorbitan behenate ester, sorbitan oleate ester, sorbitan elaidate ester, sorbitan ricinoleate ester, condensed sorbitan ricinoleate ester, and / or their EO 10 to 100 mole adducts.

[0035] The nonionic surfactants are preferably used in the following combinations (1) to (6) from the viewpoints of cleaning performance, foam suppression, and prevention of oil re-adhesion to the object to be cleaned. (1) Three combinations consisting of a polyoxyethylene polyoxypropylene alkyl ether obtained by adding 1 to 20 moles of EO and 1 to 20 moles of PO to a linear or branched alcohol having 6 to 18 carbon atoms, the mass ratio of EO / PO being in the range of 0.5 to 2; a polyoxyethylene polyoxypropylene alkyl ether obtained by adding 1 to 15 moles of EO and 1 to 50 moles of PO to a linear or branched alcohol having 6 to 18 carbon atoms, the mass ratio of EO / PO being in the range of 0.05 to 0.5; and an EO, PO adduct of a polyhydric alcohol obtained by adding 3 to 45 moles of EO and 15 to 120 moles of PO to trimethylolpropane. (2) Three combinations consisting of polyoxyethylene polyoxypropylene alkyl ethers obtained by adding 1 to 20 moles of EO and 1 to 20 moles of PO to a linear or branched alcohol having 6 to 18 carbon atoms, where the mass ratio of EO / PO is in the range of 0.5 to 2; polyoxyethylene polyoxypropylene alkyl ethers obtained by adding 1 to 15 moles of EO and 1 to 50 moles of PO to a linear or branched alcohol having 6 to 18 carbon atoms, where the mass ratio of EO / PO is in the range of 0.05 to 0.5; and an EO, PO adduct of glycerin obtained by adding 3 to 45 moles of EO and 15 to 120 moles of PO to glycerin. (3) Three combinations consisting of a polyoxyethylene polyoxypropylene alkyl ether having 1 to 20 moles of EO and 1 to 20 moles of PO added to a linear or branched alcohol having 6 to 18 carbon atoms, with an EO / PO mass ratio in the range of 0.5 to 2, a Pluronic block polymer having an average molecular weight in the range of 500 to 10,000 and an EO / PO mass ratio in the range of 0.05 to 0.5 or a reverse Pluronic block polymer having an average molecular weight in the range of 500 to 10,000 and an EO / PO mass ratio in the range of 0.05 to 0.5, and an EO, PO adduct of a polyhydric alcohol having 3 to 45 moles of EO and 15 to 120 moles of PO added to trimethylolpropane. (4) Three combinations consisting of a polyoxyethylene polyoxypropylene alkyl ether having an EO / PO mass ratio in the range of 0.5 to 2, in which 1 to 20 moles of EO and 1 to 20 moles of PO are added to a linear or branched alcohol having 6 to 18 carbon atoms; an EO, PO adduct of a polyhydric alcohol having 3 to 45 moles of EO and 15 to 120 moles of PO added to trimethylolpropane; and an EO, PO adduct of glycerin having 3 to 45 moles of EO and 15 to 120 moles of PO added to glycerin. (5) A combination of three types of polyoxyethylene polyoxypropylene alkyl ethers in which 1 to 20 moles of EO and 1 to 20 moles of PO are added to a linear or branched alcohol having 6 to 18 carbon atoms, with an EO / PO mass ratio in the range of 0.5 to 2; an EO, PO adduct of a polyhydric alcohol in which 3 to 45 moles of EO and 15 to 120 moles of PO are added to trimethylolpropane; and at least one type selected from sorbitan fatty acid esters, polyglycerin fatty acid esters, and glycerin fatty acid esters. (6) A combination of two types of polyoxyethylene polyoxypropylene alkyl ethers obtained by adding 1 to 20 moles of EO and 1 to 20 moles of PO to a linear or branched alcohol having 6 to 18 carbon atoms, wherein the mass ratio of EO / PO is in the range of 0.5 to 2, and polyoxyethylene polyoxypropylene alkyl ethers obtained by adding 1 to 15 moles of EO and 1 to 50 moles of PO to a linear or branched alcohol having 6 to 18 carbon atoms, wherein the mass ratio of EO / PO is in the range of 0.05 to 0.5.

[0036] When the nonionic surfactant is used, its content is preferably set within the range of 1 to 10% by mass relative to the total mass of the detergent composition, and more preferably within the range of 2 to 5% by mass from the viewpoints of cleaning performance and cost. That is, if the content of the nonionic surfactant is too small, it tends to be difficult to obtain the desired effect of improving cleaning performance, and as a result, it is difficult to make the detergent composition compact, which may be disadvantageous in terms of cost, while if the content of the nonionic surfactant is too high, the balance as a whole becomes poor and there is a tendency that no further synergistic effect with other components can be obtained.

[0037] <Optional ingredient: organophosphorus chelating agent> As the organic phosphorus chelating agent, for example, ethane-1,1-diphosphonic acid salt, ethane-1,1,2-triphosphonic acid salt, ethane-1-hydroxy-1,1-diphosphonic acid salt and its derivatives, ethanehydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, and other phosphonic acid compounds, or their alkali metal salts, alkaline earth metal salts, ammonium salts, or ethanolamine salts, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, α-methylphosphonosuccinic acid, and other phosphonocarboxylic acid compounds, or their alkali metal salts, alkaline earth metal salts, ammonium salts, or ethanolamine salts. Among them, alkali metal salts are preferably used. These can be used alone or in combination of two or more.

[0038] <Optional component: Polyelectrolyte polymer> The above-mentioned polyelectrolyte polymers are used for the purpose of improving the sequestering ability, threshold effect, dispersibility of water-insoluble substances, prevention of dirt redeposition, and cleaning performance, and examples thereof include acrylic acid polymers and their salts, maleic acid polymers and their salts, acrylic acid-maleic acid copolymers and their salts, poly-α-hydroxyacrylic acid and its salts, acrylic acid-maleic acid-polyethylene glycol copolymers and their salts, and olefin-maleic acid copolymers and their salts. Examples of the salts include sodium salts, potassium salts, ammonium salts, and ethanolamine salts, and among these, sodium salts and potassium salts are preferably used. In particular, from the viewpoints of sequestering ability, prevention of redeposition of dirt, and cleaning performance, sodium polymaleate, sodium polyacrylate, sodium salt of acrylic acid-maleic acid copolymer, sodium poly-α-hydroxyacrylate, acrylic acid-maleic acid-polyethylene glycol copolymer, and sodium salt of olefin-maleic acid copolymer are preferably used. These may be used alone or in combination of two or more kinds.

[0039] The salts of maleic acid polymers, acrylic acid polymers, and copolymers of maleic acid and acrylic acid may be commercially available products, but for example, sodium polymaleate can be appropriately prepared by adding sodium hydroxide to polymaleic acid in advance (neutralization reaction). Therefore, when sodium hydroxide and potassium hydroxide are added, a mixture of sodium polymaleate and potassium polymaleate can be obtained in any ratio. The average molecular weight of the maleic acid polymer, acrylic acid polymer, and salts thereof is preferably 600 to 15,000, and more preferably 1,000 to 15,000. The average molecular weight of the maleic acid / acrylic acid copolymer, and salts thereof is preferably 1,000 to 100,000, and more preferably 3,000 to 80,000. The salts of the polymers and copolymers may be fully neutralized salts or partially neutralized salts.

[0040] When the polyelectrolyte polymer is used, its content is preferably set within the range of 0.2 to 10% by mass relative to the total mass of the cleaning composition, and more preferably set within the range of 0.5 to 7% by mass in terms of sequestering ability, threshold effect, dispersibility of water-insoluble substances, dirt redeposition prevention effect, and cleaning performance in balance with other components. That is, if the content of the polyelectrolyte polymer is too low, it tends to be difficult to obtain the desired redeposition prevention effect and cleaning performance, and if the content of the polyelectrolyte polymer is too high, the balance as a whole becomes poor, storage stability decreases, and a synergistic effect with other components tends not to be obtained any more.

[0041] <Optional ingredient: Rust inhibitor> The rust inhibitor is not particularly limited, but is preferably a corrosion inhibitor for copper or copper alloy, and is preferably at least one selected from the group consisting of triazole or its derivatives, benzimidazole or its derivatives, and benzothiazole or its derivatives. Examples of such an inhibitor include benzotriazole, tolyltriazole, 5-dodecylbenzotriazole, 5-octylbenzotriazole, 5-hexylbenzotriazole, 5-butylbenzotriazole, 5-methylbenzotriazole, carboxybenzotriazole (4-carboxybenzotriazole, 5-carboxybenzotriazole), carboxybenzotriazole methyl ester, carboxybenzotriazole butyl ester, carboxybenzotriazole hexyl ester, benzotriazole octyl ester, dicarboxypropylbenzotriazole, benzimidazole, 2-mercaptobenzimidazole, thiazolylbenzimidazole, thiabendazole, benzothiazole, 2-methylbenzothiazole, 2-aminobenzothiazole, and 2-mercaptobenzothiazole. These can be used alone or in combination of two or more.

[0042] When the rust inhibitor is used, its content is preferably set within the range of 0.2 to 10 mass % relative to the total mass of the cleaning composition, more preferably set within the range of 0.1 to 2.0 mass %, and even more preferably set within the range of 0.5 to 1.0 mass %. That is, if the content of the rust inhibitor is too small, there is a tendency that the rust-preventing effect on copper and copper alloys is not sufficiently obtained, whereas if the content of the rust inhibitor is too high, there is a tendency that the balance with other components becomes poor, and the stability during storage is deteriorated.

[0043] The detergent composition of the present invention can be prepared by using the essential components (A) to (E) and other components blended as necessary, according to a method for preparing a normal detergent composition. The final form of the composition may be a lump solid, or may be a powder or granule. It can also be prepared as a liquid detergent composition by adding water. When the detergent composition of the present invention is prepared as a liquid detergent composition, water is usually blended to adjust the balance of the system, and is one of the components.

[0044] The thus obtained cleaning composition of the present invention contains the following components (A) to (E). (A)M2O / S i An alkali metal silicate in which O2=1 / 1 (molar ratio) (M represents an alkali metal). (B) Bicarbonate. (C) A water-soluble chelating agent. (D) Water-soluble antioxidant. (E) Potassium hydroxide.

[0045] According to this configuration, bicarbonate and antioxidant are used in combination with a specific alkali metal silicate, a water-soluble chelating agent, and potassium hydroxide, so that even a strong alkaline detergent composition containing a large amount of water-soluble chelating agent can suppress corrosion of aluminum, and it is easy to use because there is no need to check the material of the tableware to be washed in detail. Moreover, since it can achieve high cleaning power and suppress scale formation, it can achieve a consistent finish even at low concentrations. In addition, since phosphate is not an essential component, it is possible to realize a phosphorus-free product, which is excellent in environmental consideration.

[0046] The detergent composition of the present invention is not only suitable for washing tableware made of glass, ceramics, metal, plastic, etc., but can also be used for washing utensils and containers in various manufacturing plants, processing plants, etc., plastic containers used in distribution, etc. In particular, it can be suitably used in automatic dishwashers in hotels, restaurants, schools, hospitals, eating and drinking establishments, food service companies, company cafeterias, etc.

[0047] The detergent composition of the present invention is usually supplied to an automatic dishwasher as a 0.02 to 0.5 mass % aqueous solution (aqueous detergent solution) taking into consideration the type and amount (level) of dirt, the quality of the water used for washing, etc., thereby providing an excellent finishing effect on the objects to be washed.

[0048] Incidentally, the pH of a 0.05% by mass aqueous solution of the detergent composition of the present invention is preferably 10.5 or more, and more preferably 10.8 or more and less than 11.8. That is, the higher the pH, the higher the cleaning power can be expected, and the lower the pH, the lower the cleaning power and the more likely it is to have a negative effect on the sanitary environment inside the dishwasher. However, if the pH is 11.8 or more, the more likely it is to have a stronger effect on aluminum. In the present invention, the pH of a 0.05% by mass aqueous solution at 25°C is a value measured according to JIS (Z-8802 "pH measurement method"). EXAMPLES

[0049] Next, examples will be described together with comparative examples. Note that the present invention is not limited to the following examples. Prior to the Examples and Comparative Examples, the following components were prepared. Details of each prepared component and its effective pure content (%) are as follows, and the values ​​in Tables 1 to 5 indicate the purity of each component. Ion-exchanged water was used.

[0050] <(A) Alkali metal silicate> a-1: Anhydrous sodium metasilicate (purity 96%)Na2O / SiO2=1 / 1 Product name: Anhydrous sodium metasilicate (manufactured by Nippon Chemical Industry Co., Ltd.) a-2: Sodium metasilicate (purity 57%) Na2O / SiO2=1 / 1 Product name: Metaace 5 (manufactured by Sanbo Chemical Industry Co., Ltd.) <Alkali metal silicate other than (A)> a'-3: Sodium orthosilicate (65% pure)Na2O / SiO2=2 / 1 Product name: Neo Ortho 65 (manufactured by Koei Chemical Industry Co., Ltd.) a'-4: No. 1 sodium silicate (77% pure content)Na2O / SiO2=1 / 2 Product name: Powdered sodium silicate No. 1 (manufactured by Nippon Chemical Industry Co., Ltd.) <(B) Bicarbonate> b-1: Sodium bicarbonate (99% pure) Product name: Sodium bicarbonate (Tokuyama Corporation) b-2: Potassium bicarbonate (99.3% pure) Product name: Potassium bicarbonate (manufactured by Nacalai Tesque) <(C) Water-soluble chelating agent> c-1: Sodium nitrilotriacetate (purity 92%) Product name: Clewat PC-C3 (manufactured by Nagase ChemteX Corporation) · c-2: Sodium methylglycine diacetate (76% pure) Product name: Trilon M Granules SG (manufactured by BASF) · C-3: Trisodium citrate (99% pure) Product name: Sodium citrate H (Fuso Chemical Co., Ltd.) · C-4: Sodium tripolyphosphate (purity 97%) Product name: Sodium tripolyphosphate (manufactured by Shimonoseki Mitsui Co., Ltd.) <(D) Water-soluble antioxidant> d-1: Dipotassium disulfite (100% pure) Product name: Metakari (manufactured by Daito Chemical Co., Ltd.) d-2: Sodium disulfite (100% pure) Product name: Anhydrous sodium bisulfite (manufactured by Daito Chemical Co., Ltd.) d-3: Sodium L-ascorbate (98% pure) Product name: Sodium L-ascorbate (Nacalai Tesque) <(E) Potassium hydroxide> e-1: Potassium hydroxide (95% pure) Product name: Flake caustic potash (manufactured by Toagosei Co., Ltd.)

[0051] <Optional ingredients> Nonionic surfactant: A mixture of polyoxyethylene polyoxypropylene linear alkyl (ether) and polyoxyethylene polyoxypropylene block polymers. ·Organophosphorus chelating agent: 1-hydroxyethylidene-1,1-diphosphonic acid tetrasodium salt (85% pure) Product name: Dequest 2016D (manufactured by Italmatch Japan) Polyelectrolyte polymer: Sodium polyacrylate (92% pure) Product name: Acusol 445NG (Dow Chemical Company) Rust inhibitor: A mixture of 1-bis(2-hydroxyethyl)aminomethyl-4-methyl-1H-benzotriazole and 1-bis(2-hydroxyethyl)aminomethyl-5-methyl-1H-benzotriazole (80% pure). Product name: Belzon TT-250A (manufactured by Yamato Kasei Co., Ltd.)

[0052] [Examples 1 to 22, Comparative Examples 1 to 11] Detergent compositions having the compositions shown in Tables 1 to 5 below (the units of values ​​in each table are mass%) were prepared, and their cleaning properties (cleaning performance of artificial soil using a commercial automatic dishwasher), scale prevention properties (scale inhibition test using artificial hard water), and corrosion prevention properties for aluminum (corrosion test using test pieces) were evaluated. In addition, 0.05 mass% aqueous solutions of each of the compositions were prepared, and their pH was measured. These results are also shown in Tables 1 to 5 below. The test and evaluation methods for each item are as follows.

[0053] [Cleaning ability] Testing Method The prepared detergent composition was applied to a commercial automatic dishwasher (DW-DR61, manufactured by Sanyo Electric Co., Ltd.). The washing performance was evaluated based on the following criteria: Two types of stains, beef tallow stains and egg yolk stains, were prepared and cleaning evaluation was performed for each stain. *Operating conditions Detergent concentration: 0.05% by mass Washing temperature: 60℃ Rinse temperature: 80℃ Washing course: Standard wash cycle (wash: 43 seconds, rinse: 15 seconds) Tap water hardness: (as CaCO3) 60mg / L Beef tallow stains: Beef tallow was prepared to evaluate oily stains, and refined beef tallow was applied to a porcelain dish having a diameter of 25 cm so that 4 g of the refined beef tallow was applied to each dish. Egg yolk stains: Egg yolk was prepared to evaluate protein stains. 4 g of chicken egg yolk was attached to a porcelain dish with a diameter of 25 cm, dried at room temperature for 1 hour, and then immersed in 40°C hot water for 30 minutes immediately before cleaning. Evaluation criteria For beef tallow stains, an oil red liquid was applied to the porcelain dish after cleaning, and for egg yolk stains, the degree of stain removal was judged visually as follows. ◎: Removes more than 90% of dirt. ○: More than 70% but less than 90% of dirt removed. △: More than 50% but less than 70% of dirt removed. ×: Less than 50% of dirt removed.

[0054] [Scale prevention: Scale formation inhibition test using artificial hard water] Testing Method The detergent composition was diluted to a concentration of 0.05% by mass with artificial hard water (hardness 150 ppm) to prepare a test solution. 50 mL of this test solution was poured into a color comparison tube with a capacity of 100 mL, and kept at 60°C for 4 hours in an incubator (IS800, manufactured by Yamato Scientific Co., Ltd.). The test solution and the color comparison tube were then visually observed, and the scale prevention properties were evaluated based on the following criteria. Note that scale can be classified into two types: one that floats in the test solution and one that adheres to the bottom and sides of the color comparison tube, and both were evaluated. Evaluation criteria ⊚: Very good (no scale formation at all). ○: Good (almost no scale formation). △: Passable (scale formation was observed, but not at a level that caused any problems). ×: Poor (the adhesion of scale was significant and at a problematic level).

[0055] [Aluminum corrosion resistance] Testing Method Water was added to the cleaning composition to prepare a 0.10% by mass aqueous solution, and 100 ml of the 0.10% by mass aqueous solution was poured into a 200 ml polypropylene bottle. An aluminum test piece [A1050P (0.8 mm × 20 mm × 50 mm)] was immersed in the solution and held at 60°C for 1 hour. The loss in mass per unit area was then calculated to obtain the corrosion rate (g / m 2 ·h) was obtained and the aluminum corrosion resistance was evaluated based on the following criteria. Evaluation criteria ◎ Less than 0.8 (g / m 2 ·h): No effect on aluminum. ○…0.8 or more and less than 1.5 (g / m 2 ·h): Almost no effect on aluminum. △…1.5 or more and less than 3.3 (g / m 2 ·h): Has an effect on aluminum. ×…3.3 or more (g / m 2 ·h): The effect on aluminum is significant.

[0056] [pH (0.05% by mass, 25℃)] ·Measurement method Using a pH meter (pH METER F-12, manufactured by Horiba, Ltd.), the pH value at 25° C. of an aqueous solution having a concentration of 0.05% by mass of the prepared cleaning composition was measured in accordance with JIS Z-8802:1984. ◎: 10.5 or more and less than 11.8 ○: 11.8 or higher ×: Less than 10.5

[0057] [Table 1]

[0058] [Table 2]

[0059] [Table 3]

[0060] [Table 4]

[0061] [Table 5]

[0062] From the above results, it can be seen that Examples 1 to 22 were generally rated as excellent in all the evaluation items. On the other hand, Comparative Examples 1 to 11, which did not contain any of the components (A) to (E), were rated as "x" in all the evaluation items, indicating that there was a problem in either the detergency, the ability to inhibit scale formation, or the ability to inhibit corrosion of aluminum. [Industrial Applicability]

[0063] INDUSTRIAL APPLICABILITY The present invention can be used for a detergent composition for automatic dishwashing machines that combines corrosion inhibition ability for aluminum with cleaning performance and anti-scale formation ability.

Claims

1. A detergent composition for automatic dishwashing machines, comprising the following components (A) to (E): (A) M 2 O / S i O 2 = 1 / 1 (molar ratio) of an alkali metal silicate (M represents an alkali metal). (B) Bicarbonate. (C) A water-soluble chelating agent. (D) A water-soluble antioxidant comprising at least one of a pyrosulfite and an ascorbate. (E) Potassium hydroxide.

2. 2. The detergent composition for automatic dishwashers according to claim 1, wherein the bicarbonate salt of component (B) is at least one of sodium bicarbonate and potassium bicarbonate.

3. 3. The detergent composition for use in an automatic dishwashing machine according to claim 1, wherein the component (C) contains an aminocarboxylate.

4. The detergent composition for automatic dishwashers according to any one of claims 1 to 3, wherein a pH of a 0.05% by mass aqueous solution at 25°C is 10.5 or more.

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