Technical Field

The present invention relates to an aqueous neutral cleaning composition.

Background Art

Aqueous neutral cleaning compositions have been used to remove organic substances including fats and oils, such as mechanical oils, cutting oils, grease, and waxes, adhering to the hard surfaces of mechanical parts, precision fixtures, electronic parts, industrial parts, tools, etc., since they cause fewer problems regarding environmental safety, biological safety, flammability, metal corrosiveness, etc.

JP 2009-084390A discloses such an aqueous neutral cleaning composition for hard surfaces, comprising an organic acid and an amine, and additionally a non-ionic surfactant.

Summary of Invention

It is known that an aqueous neutral cleaning composition that contains a non-ionic surfactant having polyoxyalkylene chain(s) in its hydrophilic moiety can have insufficient thermal stability. More specifically, such a cleaning composition is known to undergo phase separation when the temperature exceeds a certain level and thereby becomes cloudy.

An object of the present invention is to prevent an aqueous neutral cleaning composition comprising an organic acid, an amine, and a non-ionic surfactant having polyoxyalkylene chain(s) in its hydrophilic moiety from undergoing phase separation when the temperature increases; and to improve thermal stability.

To solve the above problems, the present inventor conducted extensive research and found that phase separation that occurs in response to a temperature increase is suppressed, and thermal stability is improved, when a compound having a specific structure, i.e., an alkylamine alkoxylate, is selected as the non-ionic surfactant having polyoxyalkylene chain(s) in its hydrophilic moiety. The present invention has been completed as a result of further research based on the above findings. The present invention encompasses the following embodiments. Item ! An aqueous neutral cleaning composition comprising:

(a) an alkylamine alkoxylate as a non-ionic surfactant;

(b) an organic acid; and

(c) an amine.

Item 2.

The aqueous neutral cleaning composition according to Item 1 , wherein the alkylamine alkoxylate (a) is represented by the following formula (I): wherein R ¹ represents linear or branched alkyl having 6 to 30 carbon atoms, linear or branched alkenyl having 6 to 30 carbon atoms, or linear or branched alkynyl having 6 to 30 carbon atoms,

R ² and R ³ are identical or different, and each represents alkylene, and the total of n and n' is 2 to 30.

Item 3.

The aqueous neutral cleaning composition according to Item 1 or 2, wherein the organic acid (b) is a linear or branched, saturated or unsaturated carboxylic acid having 1 to 30 carbon atoms.

Item 4.

The aqueous neutral cleaning composition according to any one of Items 1 to 3, wherein the amine (c) is represented by the following formula (II): wherein Xs are identical or different, and each represents hydrogen, alkyl having 1 to 6 carbon atoms, alkenyl having 2 to 6 carbon atoms, or alkynyl having 2 to 6 carbon atoms,

R ⁴ s are identical or different, and each represents alkylene having 1 to 6 carbon atoms, and m is an integer of 0 to 3. Item 5.

The aqueous neutral cleaning composition according to any one of Items 1 to 4, wherein the amine (c) is an alkanolamine.

Item 6.

The aqueous neutral cleaning composition according to any one of Items 1 to 5, which has a pH of 6 to 8 at 25°C.

Item 7.

The aqueous neutral cleaning composition according to any one of Items 1 to 6, for use in cleaning hard surfaces.

Item 8.

Use of an aqueous neutral cleaning composition comprising:

(a) an alkylamine alkoxylate as a non-ionic surfactant;

(b) an organic acid; and

(c) an amine, in cleaning of a hard surface.

Item 9.

A method for cleaning a hard surface, comprising applying an aqueous neutral cleaning composition comprising:

(a) an alkylamine alkoxylate as a non-ionic surfactant;

(b) an organic acid; and

(c) an amine, to a hard surface.

The present invention can provide an aqueous neutral cleaning composition exhibiting excellent thermal stability.

Detailed Description

1 . Aqueous Neutral Cleaning Composition

The aqueous neutral cleaning composition of the present invention comprises:

(a) an alkylamine alkoxylate as a non-ionic surfactant; (b) an organic acid; and

(c) an amine.

1.1 Alkylamine Alkoxylate (a) In the present invention, an alkylamine alkoxylate is used as a non-ionic surfactant. There is no limitation on the alkylamine alkoxylate, as long as it is usable as a non-ionic surfactant.

The alkylamine alkoxylate as used herein is preferably represented by the following formula wherein R ¹ represents linear or branched alkyl having 6 to 30 carbon atoms, linear or branched alkenyl having 6 to 30 carbon atoms, or linear or branched alkynyl having 6 to 30 carbon atoms; R ² and R ³ are identical or different, and each represents alkylene; and the total of n and n' is 2 to 30. In formula (I) above, R ¹ preferably has 6 to 20 carbon atoms, more preferably 8 to 16 carbon atoms, and still more preferably 10 to 14 carbon atoms.

In formula (I) above, R ¹ is preferably linear. In formula (I) above, R ¹ is preferably alkyl.

In formula (I) above, R ¹ is preferably linear alkyl having 6 to 20 carbon atoms, more preferably linear alkyl having 8 to 16 carbon atoms, and still more preferably linear alkyl having 10 to 14 carbon atoms.

In formula (I) above, R ² and R ³ are identical or different, and each preferably represents linear or branched alkylene having 2 to 4 carbon atoms, more preferably linear or branched alkylene having 2 to 3 carbon atoms, and most preferably ethylene (i.e., the compound of formula (I) above is alkylamine ethoxylate).

In formula (I) above, n and n' may be integers from 0 to 30. In formula (I) above, the total of n and n' is preferably 4 to 20, more preferably 6 to 18, and still more preferably 8 to 16.

The alkylamine alkoxylate of formula (I) above may comprise a mixture of two or more types of compounds, rather than a single-type compound. In this case, the numbers of carbon atoms of R ¹ , R ² , and R ³ , and the total of n and n' represent an average value, and the structure thereof (whether it is linear, whether it is alkyl, etc.) represents a dominant structure in the entire mixture. When the total average value of n and n' is low, this mixture can contain a compound in which either n or n', or both, are 0.

The alkylamine alkoxylate can be obtained by alkoxylation of an alkylamine.

Examples of the alkylamine alkoxylate of formula (I) above include hexylamine ethoxylate, octylamine ethoxylate, decylamine ethoxylate, undecylamine ethoxylate, tridecylamine ethoxylate, tetradecylamine ethoxylate, pentadecylamine ethoxylate, hexadecylamine ethoxylate, heptadecylamine ethoxylate, octadecylamine ethoxylate, nonadecylamine ethoxylate, icosylamine ethoxylate, henicosylamine ethoxylate, docosylamine ethoxylate, tricosylamine ethoxylate, tetracosylamine ethoxylate, oleylamine ethoxylate, palmitinamine ethoxylate, stearylamine ethoxylate, laurylamine ethoxylate, coco amine ethoxylate, tallow amine ethoxylate, soya amine ethoxylate, and the like.

The aqueous neutral cleaning composition of the present invention preferably comprises the alkylamine alkoxylate in a total amount of 0.01 to 20 wt%, and more preferably 0.1 to 10 wt%, based on the entire aqueous neutral cleaning composition.

1.2 Organic Acid (b)

In the present invention, an organic acid is incorporated mainly for the purpose of imparting chelating activity and antirust properties to the aqueous neutral cleaning composition.

The organic acid is preferably a linear or branched, saturated or unsaturated carboxylic acid having 1 to 30 carbon atoms.

The organic acid may be a hydroxy acid. The organic acid preferably has 2 or more carbon atoms in terms of antirust properties, and preferably has 20 or fewer carbon atoms in terms of solubility in water. The organic acid more preferably has 4 to 12 carbon atoms, and still more preferably 6 to 10 carbon atoms.

Examples of linear organic acids include formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, lauric acid, tridecyl acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, arachidic acid, and the like.

Examples of branched organic acids include (1 ) isodecanoic acids, (2) isononanoic acids, (3) isooctanoic acids, (4) isoheptanoic acids, (5) isohexanoic acids, and the like.

Examples of (1 ) isodecanoic acids include methylnonanoic acid, ethyloctanoic acid, dimethyloctanoic acid, trimethylheptanoic acid, butylhexanoic acid, diethylhexanoic acid, and the like.

Examples of (2) isononanoic acids include methyloctanoic acid, ethylheptanoic acid, dimethylheptanoic acid, trimethylhexanoic acid, propylhexanoic acid, butylpentanoic acid, and the like.

Examples of (3) isooctanoic acids include methylheptanoic acid, ethylhexanoic acid, dimethylhexanoic acid, and the like.

Examples of (4) isoheptanoic acids include methylhexanoic acid, ethylpentanoic acid, and the like.

Examples of (5) isohexanoic acids include methylpentanoic acid, ethylbutanoic acid, and the like.

Examples of hydroxy acids include lactic acid, glycolic acid, citric acid, tartaric acid, and the like.

Octanoic acid, nonanoic acid, decanoic acid, isodecanoic acid, isononanoic acid, isooctanoic acid, and citric acid are particularly preferred as the organic acid.

The organic acid may comprise a single-type compound, or a combination of two or more types of compounds. The aqueous neutral cleaning composition of the present invention comprises the organic acid in a total amount of preferably 0.1 to 50 wt%, more preferably 0.5 to 30 wt%, and still more preferably 1 to 15 wt%, based on the entire aqueous neutral cleaning composition. 1 .3 Amine (c)

In the present invention, an amine is incorporated mainly for the purpose of neutralizing an acid and adjusting the pH to neutral. Inorganic bases, such as ammonium hydroxide and inorganic alkalis (e.g., sodium hydroxide and potassium hydroxide), can also be used to adjust the pH to neutral by neutralizing an acid. However, the use of an amine, which does not easily cause precipitation and separation of non-ionic surfactants by salting-out, is advantageous in terms of thermal stability.

The amine is preferably represented by the following formula (II): wherein Xs are identical or different, and each represents hydrogen, alkyl having 1 to 6 carbon atoms, alkenyl having 2 to 6 carbon atoms, or alkynyl having 2 to 6 carbon atoms; R ⁴ s are identical or different, and each represents alkylene having 1 to 6 carbon atoms; and m is an integer of 0 to 3.

In formula (II) above, Xs are identical or different, and each preferably represents a hydrogen atom, alkyl having 1 to 3 carbon atoms, alkenyl having 2 to 3 carbon atoms, or alkynyl having 2 to 3 carbon atoms; more preferably a hydrogen atom or alkyl having 1 to 2 carbon atoms; and still more preferably methyl.

In formula (II) above, R ⁴ is preferably alkylene having 1 to 4 carbon atoms, more preferably alkylene having 1 to 3 carbon atoms, and still more preferably alkylene having 2 to 3 carbon atoms.

The amine is preferably an alkanolamine. Examples of amines include monoethanolamine, monopnopanolamine, monoisopnopanolamine, diethanolamine, triethanolamine, N-methylethanolamine, N- methylpropanolamine, N,N-dimethylethanolamine, and the like. The amine may comprise a single-type compound, or a combination of two or more types of compounds.

The aqueous neutral cleaning composition of the present invention comprises the amine in a total amount of preferably 0.1 to 50 wt%, more preferably 0.5 to 30 wt%, and still more preferably 1 to 15 wt%, based on the entire aqueous neutral cleaning composition.

1 .4 Other Components

In addition to the components (a) to (c) above, the aqueous neutral cleaning composition of the present invention may further comprise at least one component selected from the group consisting of surfactants, chelating agents, antifoaming agents, anti-rust agents, preservatives, pH adjusters, builders, and other additives.

The surfactant may be at least one surfactant selected from the group consisting of anionic surfactants, cationic surfactants, and non-ionic surfactants other than the alkylamine alkoxylates mentioned above.

Examples of the builders include phosphoric acid salts and the like.

1 .5 Physical Properties and Usage

The aqueous neutral cleaning composition of the present invention preferably has a pH of 6 to 8 at 25°C. In terms of cleaning ability, the pH is more preferably 7 to 8, and still more preferably 7.5 to 8. In the present invention, pH is measured by a glass-electrode method. For this measurement, a pH meter, such as Model F-51 , produced by Horiba, Ltd., or an equivalent product, calibrated with a standard pH buffer solution, can be used.

The aqueous neutral cleaning composition of the present invention is preferably used for cleaning a hard surface. Examples of the hard surface include the hard surfaces of mechanical parts, precision fixtures, electronic parts, industrial parts, tools, and the like. The aqueous neutral cleaning composition of the present invention is preferably used for removing organic substances including fats and oils, such as mechanical oils, cutting oils, grease, and waxes, adhering to the hard surface.

The aqueous neutral cleaning composition of the present invention may be a cleaner concentrate that is used by diluting with water. In this case, the aqueous neutral cleaning composition of the present invention is preferably a cleaner concentrate that is used after being diluted to 1 to 20% by volume.

2. Cleaning Method

The cleaning method of the present invention is a method for cleaning an object by using the aqueous neutral cleaning composition of the present invention. The object is preferably a hand surface.

Examples of the hand surface include the hand surfaces of mechanical pants, pnecision fixtunes, electronic pants, industnial pants, tools, and the like. The cleaning method of the pnesent invention is pnefenably a method fon nemoving, by using the aqueous neutnal cleaning composition of the pnesent invention, organic substances including fats and oils, such as mechanical oils, cutting oils, gnease, and waxes, adhering to the hand surface.

The cleaning method of the pnesent invention may be based on any cleaning system. Examples of cleaning systems include ultnasonic cleaning, showen cleaning, spnay cleaning, brush cleaning, immension cleaning, swing cleaning, single-wafen cleaning, and combinations thereof. The cleaning system is preferably immersion cleaning based on an ultrasonic system, in terms of the cleaning effect and operating efficiency. The cleaning method of the present invention comprises applying the aqueous neutral cleaning composition of the present invention to a hard surface, and cleaning the hand surface based on the cleaning system.

The cleaning method of the present invention can be conducted using the aqueous neutral cleaning composition of the present invention at various temperatures. The temperature may usually be 10 to 90°C. If the temperature is 10°C or higher, the aqueous neutral cleaning composition can be prevented from freezing. If the temperature is 90°C or lower, the aqueous neutral cleaning composition can be prevented from evaporating, and a reduction in the liquid volume can be avoided. In cleaning, the aqueous neutral cleaning composition preferably has a temperature of 40 to 80°C, in terms of the cleaning effect.

Examples

The aqueous neutral cleaning compositions having the composition shown in Table 1 were obtained by mixing each component in a transparent glass vial at room temperature.

Unless otherwise stated, the components were commercially available products that were used as is without performing further purification. The pH was measured by a glass- electrode method at 25°C using a pH meter (Model: F-51 , produced by Horiba, Ltd.). The pH meter was used after calibration with a standard pH buffer solution. The thermal stability was evaluated by visually observing the transparency of each cleaning composition.

Table 1

The product names and manufacturers of each component shown in Table 1 are shown below.

Triethanolamine: Special reagent grade, 2,2' ,2"-n itrilotriethanol , produced by FUJIFILM Wako Pure Chemical Corporation Citric acid: Wako special grade, citric acid, produced by FUJIFILM Wako Pure Chemical Corporation

POE(12)Laurylaminoether: Cocoamine ethoxylate, produced by Angene Chemical Polyoxyalkylene decylether: NOIGEN XL-70, produced by DKS Co. Ltd.

Polyoxyalkylene alkylether: NOIGEN LF-80X, produced by DKS Co. Ltd.

At a temperature of 25°C, the cleaning composition of Comparative Example 1 underwent phase separation, and was cloudy. This is believed to be because the hydrogen bonds between water molecules and the polyoxyalkylene chains of alkyl polyethoxylate incorporated as a non-ionic surfactant were disrupted, causing a reduction in the water solubility of the alkyl polyethoxylate. The other cleaning compositions were all transparent. These other cleaning compositions were individually immersed in a water bath; and, as shown in Table 1 , the temperature was increased from 30°C to 80°C in a step-wise manner. After the water temperature reached each temperature and was maintained at the same temperature for 30 minutes, the transparency of the cleaning composition was evaluated. The cleaning compositions that underwent phase separation were removed from the water bath, and no evaluation was performed thereafter.

As shown in Table 1 , the cleaning compositions of Examples 1 to 3, which contained alkylamine ethoxylate (POE(12)laurylaminoether), were transparent even at a temperature of 60°C or higher, and were stable. In contrast, the cleaning composition of Comparative Example 2, which contained alkyl ethoxylate instead of alkylamine ethoxylate, became cloudy at 40°C or lower, and were unstable.