Antifouling agent

Abstract

To provide a stain-proofing agent that reduces adsorption of an oil component to a processing object surface.SOLUTION: A stain-proofing agent contains sulfosuccinic acid branched alkyl ester (hereinafter referred to as (a) component) in which a branched alkyl group is a branched alkyl group having a carbon number of 8-13. A stain-proof method includes bringing a process liquid containing the (a) component into contact with a processing object.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an antifouling agent and an antifouling method. [Background technology]

[0002] There are many situations in which water comes into contact with hydrophobic surfaces. For example, in a typical household, when leftover bath water is stored in a unit bath for the next wash, oily components such as sebum adhere to the hydrophobic surface of the bathtub, causing the bath to become dirty. Also, when oily stains adhere to the inside of a dishwasher, the cleaning efficiency decreases. Furthermore, hydrophobic materials such as polyvinyl chloride are used in the pits and pipes that serve as water flow paths, and when oily components are present, they are adsorbed to the hydrophobic material and stain the surface of the hydrophobic material. Therefore, there is a demand for anti-fouling technology that suppresses the adsorption of oily components to hydrophobic surfaces that come into contact with water.

[0003] On the other hand, sulfosuccinates are known as surfactants having excellent cleaning properties and surface activity (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-214554 A [Patent Document 2] US Patent Application Publication No. 2007 / 0214999 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a demand for a technology that suppresses the adsorption of hydrophobic soiling components such as oil components to hydrophobic surfaces that come into contact with water. In addition, hydrophobic soiling components dissolved in water by detergents may reattach to hydrophobic surfaces. For example, when plastic tableware is washed in an automatic dishwasher, oily soiling dissolved in water during washing is transferred to the plastic tableware, which is one of the factors that reduces satisfaction with the dirt removal.

[0006] The present invention provides an antifouling agent and an antifouling method that suppress adsorption of oil components to the surface of an object to be treated. [Means for solving the problem]

[0007] The present invention relates to an antifouling agent containing (a) a branched alkyl sulfosuccinate ester (hereinafter referred to as component (a)), in which the branched alkyl group has from 8 to 13 carbon atoms.

[0008] The present invention also relates to (a) an antifouling method, which comprises contacting an object to be treated with a treatment liquid containing a branched alkyl sulfosuccinate ester, the branched alkyl group of which is a branched alkyl group having from 8 to 13 carbon atoms. Effect of the Invention

[0009] According to the present invention, there are provided an antifouling agent and an antifouling method which suppress the adsorption of oil components to the surface of an object to be treated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] As a result of extensive research, the inventors discovered that by contacting a specific compound with the object to be treated, the adsorption of oil components onto the surface of the object to be treated is suppressed, resulting in an excellent anti-fouling effect, and thus completing the present invention. Although the mechanism by which the antifouling agent of the present invention suppresses the adsorption of oil components to the surface of the object to be treated is not clear, it is believed that the antifouling agent of the present invention adsorbs to the surface of the object to be treated and controls the surface energy of the object to be treated (modifies the surface of the object to be treated), thereby preventing the adsorption of oil components to the surface of the object to be treated. According to the antifouling agent and antifouling method of the present invention, not only can an excellent antifouling effect be obtained by treating the object to be treated in advance with the antifouling agent of the present invention, but also, by including a predetermined concentration of the antifouling agent of the present invention in a cleaning solution for the object to be treated, the dirt components contained in the cleaning solution etc. are prevented from re-adhering to the object to be treated. In particular, the antifouling agent of the present invention can prevent the oil components contained in water from adsorbing to a hydrophobic surface.

[0011] <Anti-fouling agent> The antifouling agent of the present invention contains (a) a branched alkyl sulfosuccinate ester in which the branched alkyl group has from 8 to 13 carbon atoms (hereinafter referred to as component (a)).

[0012] The component (a) is a branched alkyl sulfosuccinate ester in which the branched alkyl group has 8 to 13 carbon atoms.

[0013] The component (a) may be a monoester or a diester, and is preferably a branched alkyl sulfosuccinate diester in which the branched alkyl group has 8 to 13 carbon atoms.

[0014] The branched alkyl group of component (a) preferably has 8 to 11 carbon atoms, and particularly preferably has 9 or 10 carbon atoms. The branched alkyl group of component (a) is preferably a branched alkyl group having a main chain of 6 or 7 carbon atoms and one or more side chains. The branched alkyl group of component (a) is preferably a branched alkyl group having a main chain of 6 or 7 carbon atoms and one or more side chains, the total number of carbon atoms in the side chains being 3 or 4. The branched alkyl group of the component (a) is preferably a branched alkyl group selected from a 2-propylheptyl group and a 3,5,5-trimethylhexyl group.

[0015] Examples of the component (a) include branched alkyl sulfosuccinate esters represented by the following general formula (a1).

[0016] [ka]

[0017] [In the formula, R 1a , R 2a are each independently a branched alkyl group having 8 to 13 carbon atoms. 1 , A 2 are each independently an alkylene group having 2 to 4 carbon atoms, and x and y are each independently the average number of moles added, and are each independently 0 to 6. 1 is a hydrogen atom or a cation.

[0018] Further, the component (a) may be a branched alkyl sulfosuccinate ester represented by the following general formula (a1-1): This compound is a compound in which x=0 and y=0 in general formula (a1).

[0019] [ka] [In the formula, R 1a , R 2a are each independently a branched alkyl group having 8 to 13 carbon atoms. 1 is a hydrogen atom or a cation.

[0020] The following explanation applies to both general formula (a1) and general formula (a1-1).

[0021] R 1a , R 2a may be the same or different. In the present invention, the branched chain hydrocarbon group includes a hydrocarbon residue obtained by removing a hydroxyl group from a secondary alcohol.

[0022] In the present invention, R 1a , R 2aAmong the branched chain hydrocarbon groups, the hydrocarbon chain having the largest number of carbon atoms counted from the carbon atom bonded to the oxygen atom is the main chain, and the hydrocarbon chains branched from the main chain and bonded to the main chain are side chains. When two or more main chains are considered, that is, when there are two or more hydrocarbon chains with the largest number of carbon atoms (hereinafter also referred to as the longest hydrocarbon chain), the main chain is determined in the following order. 1. The side chain branching off from the longest hydrocarbon chain has the larger number of carbon atoms and is considered the main chain. 2. Next, if the number of carbon atoms in the side chains branching off from the longest hydrocarbon chain are the same, the chain with the greater number of side chains branching off from the longest hydrocarbon chain is determined to be the main chain. 3. Next, if the number of side chains branching off from the longest hydrocarbon chain is the same, the one having a side chain on the carbon atom closer to the oxygen atom, counting from the carbon atom bonded to the oxygen atom, is considered to be the main chain. 4. Next, if the positions of the carbon atoms having side chains closest to the oxygen atom are the same, the one with the greater number of carbon atoms in the side chain closest to the oxygen atom is considered to be the main chain. When two or more longest hydrocarbon chains have the same symmetrical structure, either one may be used as the main chain.

[0023] R 1a , R 2a In each of the branched alkyl groups, the total number of carbon atoms in the branched chain hydrocarbon group may be the same or different, and from the viewpoint of suppressing adsorption of oil components to hydrophobic surfaces, is 8 or more, preferably 9 or more, and 13 or less, preferably 11 or less, and more preferably 10 or less.

[0024] R 1a , R 2a In each of the branched alkyl groups, the number of carbon atoms constituting the main chain may be the same or different, and is preferably 6 or 7 from the viewpoint of suppressing adsorption of oil components to hydrophobic surfaces.

[0025] R 1a , R 2aIn each of the branched alkyl groups, the total number of carbon atoms constituting the side chains may be the same or different, and is 2 or more, preferably 3 or 4, from the viewpoint of suppressing adsorption of oil components to hydrophobic surfaces. In the present invention, the total number of carbon atoms constituting the side chains refers to the total number of carbon atoms in all side chains other than the main chain in one branched alkyl group, and when there are multiple side chains, it refers to the total number of carbon atoms in all of those side chains.

[0026] R 1a , R 2a The number of side chains may be the same or different, and from the viewpoint of suppressing adsorption of oil components to hydrophobic surfaces, is 1 or more and preferably 3 or less. When the side chain has 2 or more carbon atoms, the number of side chains is preferably 1, and when the side chain has 1 carbon atom, the number of side chains is 2 or more, preferably 3 or 4. In the present invention, the number of side chains refers to the number of side chains branching from the main chain, and the number of side chains does not change even if the side chain has a side chain branching from the side chain. However, from the viewpoint of suppressing the adsorption of oil components to the hydrophobic surface, the side chain may have a side chain branching from the side chain.

[0027] R 1a , R 2a The number of branched carbons may be the same or different, and from the viewpoint of suppressing adsorption of oil components to a hydrophobic surface, is 1 or more, and preferably 3 or less, and even more preferably 2 or less. In the present invention, the number of branched carbon atoms means the total number of tertiary carbon atoms and quaternary carbon atoms in the branched chain hydrocarbon group.

[0028] R 1a , R 2a A preferred embodiment of the formula is R 1a , R 2a the total number of carbon atoms in the chain branched hydrocarbon groups is independently 9 or 10, preferably 10; the number of carbon atoms in the main chain is independently 6 or 7, preferably 7; the number of carbon atoms constituting the side chains is independently 3; and the number of side chains is independently 1 or more and 3 or less, preferably 1.

[0029] R1a , R 2a Specific branched alkyl groups may be the same or different, and are preferably branched alkyl groups selected from a 2-ethylhexyl group, a 2-propylheptyl group, and a 3,5,5-trimethylhexyl group, and more preferably branched alkyl groups selected from a 2-propylheptyl group and a 3,5,5-trimethylhexyl group.

[0030] In general formula (a1), A 1 , A 2 are each independently an alkylene group having 2 or more carbon atoms and 4 or less, preferably 3 or less, carbon atoms. In general formula (a1), x and y are the average number of moles added, and from the viewpoint of suppressing adsorption of oil components to a hydrophobic surface, each of them independently is preferably 0 or more and preferably 6 or less, more preferably 4 or less, even more preferably 2 or less, and even more preferably 0. In addition, from the viewpoint of suppressing adsorption of oil components to the hydrophobic surface, x+y is preferably 0 or more and preferably 12 or less, more preferably 6 or less, even more preferably 3 or less, and even more preferably 0.

[0031] M 1 is a hydrogen ion, an inorganic cation such as a sodium ion, an ammonium ion, a potassium ion, or a magnesium ion, or an organic cation such as a monoethanolammonium ion, a diethanolammonium ion, a triethanolammonium ion, or a morpholinium ion, and is preferably an inorganic cation selected from the group consisting of a sodium ion, an ammonium ion, a potassium ion, and a magnesium ion.

[0032] R 1a , R 2a The method for preparing the compound in which R is the same is not particularly limited. For example, the compound can be prepared by referring to the method described in U.S. Pat. No. 2,028,091. 1a , R 2aAs a method for preparing an asymmetric compound having different carbon atoms, for example, JP-A-58-24555 can be referred to. As the raw material of component (a), an alkylene oxide added to an alcohol having a predetermined carbon number can also be used. Suitable alcohols for use in the preparation of component (a) of the present invention include: (1) Primary alcohols such as 2-ethylhexanol, 3,5,5-trimethylhexan-1-ol, and 2-propylheptan-1-ol, (2) Secondary alcohols such as 5-nonanol and 2,6-dimethyl-4-heptanol Examples include:

[0033] In the present invention, by using the component (a), it is possible to provide an antifouling agent that is excellent in inhibiting the adsorption of oil components to hydrophobic surfaces.

[0034] The object to be treated with the antifouling agent of the present invention is not particularly limited, but is preferably a hard article, and more preferably a hard article having a hydrophobic surface. Examples of the object to be treated include articles made of glass, metal, resin, etc. The hydrophobic surface may be a surface that comes into contact with dirt and has a critical surface energy of 50 mN / m or less, and may be a surface that is coated with a polymer, etc. Specifically, for example, it is known that the surface energy of polyethylene is 35 mN / m, that of polypropylene is 21.0 to 28.5 mN / m, and that of polystyrene is 44 mN / m (Physical Chemistry of Polymer Surface, Vol. 17, No. 196, 1968, 680-687), and the present invention can effectively impart an antifouling effect to hydrophobic surfaces having such surface energies.

[0035] The antifouling agent of the present invention is suitable for use in bathrooms, sinks, washtubs, tableware cooking utensils, etc., and is particularly suitable as an antifouling agent for tableware, and more particularly as an antifouling agent for preventing adhesion of oily stains (solid grease, etc.) to tableware. Furthermore, when the antifouling agent of the present invention is used as an antifouling agent when washing tableware with an automatic dishwashing machine, it is preferable because it can prevent re-adhesion of oily stains to tableware having a hydrophobic surface and adhesion of oily stains inside the automatic dishwashing machine. The antifouling agent of the present invention may be contained in a liquid detergent composition for automatic dishwashing machines.

[0036] The antifouling agent of the present invention can be contained in a bathtub cleaning agent or bath additive, for example, to suppress adhesion of sebum stains and the like to the bathtub. Also, the antifouling agent of the present invention can be contained in a fluid flowing through a pipe to suppress adhesion of dirt components to the inside of the pipe.

[0037] When the antifouling agent of the present invention is used for tableware, the effects of the present invention can be obtained, for example, by adding it to the treatment liquid before, during, or during rinsing of the tableware, and the redeposition of soiling components (e.g., oily soils such as solid grease and liquid oil) onto the tableware can be inhibited.

[0038] In the antifouling agent of the present invention, the concentration of component (a) during use is preferably 1 ppm (by mass, the same applies hereinafter) or more, more preferably 10 ppm or more, even more preferably 20 ppm or more, and preferably 500 ppm or less, more preferably 300 ppm or less, even more preferably 200 ppm or less, from the viewpoint of suppressing adsorption of oil components to hydrophobic surfaces. In the present invention, the description of the amount of the component (a) (ppm or mass %) refers to the mass of the compound converted into a sodium salt, for example, M 1 is based on the mass assuming it is sodium.

[0039] In general, it is known that surfactants have surface activity at a concentration equal to or higher than the critical micelle concentration (hereinafter referred to as cmc). 1a , R 2aIn the case of a compound in which the carboxyl group is 2-propylheptyl, the cmc (measured in pure water) of this compound is about 500 ppm, but as shown in the examples described later, it is surprising that this compound has an excellent antifouling effect even at a concentration lower than the cmc of the compound. Therefore, in the antifouling agent of the present invention, the concentration of component (a) during use may be lower than the cmc of component (a). In the present invention, the cmc is the equilibrium value obtained by using a surface tension measurement method. The cmc may be the equilibrium value at 25° C. and atmospheric pressure (1013 hPa).

[0040] The stainproofing agent of the present invention may contain optional components other than component (a) to the extent that the effects of the present invention are not impaired. The optional components include surfactants, solvents, hydrotropes, dispersants, pH adjusters, thickeners, viscosity adjusters, fragrances, colorants, antioxidants, preservatives, foam inhibitors, bleaching agents, bleaching activators, and other components (however, those not included in component (a)).

[0041] The antifouling agent of the present invention can be produced by mixing a predetermined amount of component (a) and water. In this case, a precursor composition containing component (a) can be diluted with water to obtain the antifouling agent composition of the present invention. For example, the antifouling agent of the present invention may be prepared by such dilution immediately before use of the antifouling agent of the present invention. Examples of the precursor composition include a composition containing component (a) in an amount of preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and preferably 5% by mass or less, more preferably 3% by mass or less, and further containing water.

[0042] From the viewpoint of irritation to the skin of the hands, the soil-proofing agent of the present invention has a pH at 25° C. of preferably 2 or more, more preferably 4 or more, even more preferably 5 or more, and preferably 10 or less, more preferably 9 or less, even more preferably 8 or less. The pH can be measured by a glass electrode method.

[0043] The antifouling agent of the present invention has a viscosity at 25° C. of preferably 3 mPa s or more, more preferably 10 mPa s or more, and preferably 5,000 mPa s or less, more preferably 2,500 mPa s or less, although this varies depending on the application, etc. The viscosity can be adjusted with commonly used thickeners, solvents, hydrotropes, etc.

[0044] In the present invention, the antifouling agent is preferably diluted with water 10 to less than 10,000 times, preferably 50 to less than 5,000 times, to prepare an antifouling agent composition (treatment liquid), which is then used to treat the object to be treated.

[0045] <Anti-stain method> The present invention provides an antifouling method, which comprises contacting an object to be treated with a treatment liquid containing component (a). The object to be treated is an article to be treated with the antifouling agent of the present invention. The treatment liquid of the present invention can be obtained by mixing the antifouling agent of the present invention with water. The treatment liquid of the present invention can also be obtained by diluting the precursor composition containing the component (a) with water. The treatment liquid of the present invention may also be one in which the antifouling agent of the present invention is used as is. The matters described for the antifouling agent of the present invention can be appropriately applied to the antifouling method of the present invention. Specific examples of the component (a), preferred embodiments, and antifouling treatment targets in the antifouling method of the present invention are the same as those of the antifouling agent of the present invention.

[0046] The treatment target of the antifouling agent of the present invention is preferably the surface of a hard article, and is preferably a hard article having a hydrophobic surface. The treatment target of the antifouling agent of the present invention may be, for example, a hydrophobic surface of tableware. The object to be antifouled may also be, for example, a bathtub, a pipe, a medical instrument, an optical instrument, etc. In the present invention, it is preferable to treat tableware with the antifouling agent when washing tableware using an automatic dishwasher, and further when washing tableware with oily stains including solid fat.

[0047] The automatic dishwashing machine may be any automatic dishwashing machine generally available on the market, and may be, for example, either a household automatic dishwashing machine or a commercial automatic dishwashing machine. The washing conditions are not particularly limited, and the washing temperature, washing time, etc. can be in accordance with known washing conditions for an automatic dishwasher.

[0048] From the viewpoint of suppressing the adsorption of oil components to the hydrophobic surface, the treatment liquid of the present invention contains component (a) at a concentration of preferably 1 ppm or more, more preferably 10 ppm or more, even more preferably 20 ppm or more, and preferably 500 ppm or less, more preferably 300 ppm or less, even more preferably 200 ppm or less. The treatment liquid of the present invention may contain component (a) at a concentration less than the cmc of component (a).

[0049] From the viewpoint of irritation to the skin of the hands, the treatment liquid of the present invention has a pH of preferably 2 or more, more preferably 4 or more, even more preferably 5 or more, and preferably 10 or less, more preferably 9 or less, even more preferably 8 or less. This pH is the pH at the washing temperature.

[0050] In the cleaning method of the present invention, the cleaning temperature is preferably 40° C. or higher, more preferably 50° C. or higher, from the viewpoint of cleaning performance, and is preferably 80° C. or lower, more preferably 70° C. or lower, from the viewpoints of cleaning performance and productivity. This cleaning temperature may be the temperature of the cleaning solution of the present invention.

[0051] The above-mentioned content of component (a), washing time and washing temperature are also preferable conditions when washing tableware in an automatic dishwasher, for example.

[0052] After being washed in an automatic dishwasher, dishes are usually promptly rinsed in the same automatic dishwasher with water, warm water or hot water, for example, hot water of 70° C. to 90° C., for 5 to 15 seconds.

[0053] The method for contacting the object to be treated with the antifouling agent of the present invention is not particularly limited, and can be by coating, immersion, spraying, etc. While the object to be treated is immersed in the treatment liquid containing the antifouling agent of the present invention, mechanical force such as stirring, shaking, water flow, etc., or mechanical force may be applied using a tool generally used for cleaning such as a brush or sponge. EXAMPLES

[0054] The following component (a) or (a') was dissolved in 3.5°DH water to prepare the treatment solutions shown in Tables 1 to 3. Component (a') is a comparative component to component (a). The pH of the treatment solution was measured by the glass electrode method. cmc is the value of pH 7 in pure water at 25°C under atmospheric pressure.

[0055] (a) Ingredients The number in parentheses indicates the number of carbon atoms in the branched alkyl group. a-1 is a branched alkyl sulfosuccinate ester (carbon number 12 / carbon number 13=37-48 / 52-63 (mass ratio), branching rate 92 mass% or more (SASOL catalog value)) synthesized using a branched alcohol commercially available as Isalchem123 (manufactured by SASOL). a-1 Sodium di-(C12 / C13, branched alcohol) sulfosuccinate (one alkyl group has 12 or 13 carbon atoms) A-2 Sodium di-(2-propylheptyl)sulfosuccinate (one alkyl group has 10 carbon atoms), CMC: approx. 500 ppm A-3 Sodium di-(3,5,5-trimethylhexyl) sulfosuccinate (one alkyl group has 9 carbon atoms), CMC: approx. 600 ppm A-4 Sodium di-(2-ethylhexyl) sulfosuccinate (one alkyl group has 8 carbon atoms), CMC: approx. 1100 ppm

[0056] Component (a') · a'-1 Sodium di-(1, 3-dimethylbutyl) sulfosuccinate (one alkyl group has 6 carbon atoms), CMC: 3000 ppm or more A'-2 Sodium dodecyl sulfate, CMC: approx. 2800 ppm · a'-3 1-dodecanesulfonic acid sodium salt, CMC: approx. 3000 ppm A'-4 Sodium laurate, CMC: approx. 6000 ppm a'-5 Polyoxyethylene lauryl ether (product name Emulgen 106, manufactured by Kao Corporation), average number of moles of ethyleneoxy groups added: 5, CMC: approx. 20 ppm a'-6 7EO adduct of secondary alcohol having 12 to 14 carbon atoms (trade name Softanol 70, manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.), EO represents an ethyleneoxy group. cmc: about 40 ppm

[0057] (1) Antifouling rating: 1 A clean polypropylene plate (8 cm × 3 cm, surface energy 26 mN / m) was placed in 300 mL of the treatment solution with the composition shown in Table 1, and 0.5 g of liquid paraffin was poured into it while stirring the treatment solution. 60 seconds after pouring in the liquid paraffin, the plate was pulled out and dried, and the mass of the plate with the liquid paraffin attached was measured. The amount of oil attached (mg / cm 2 The increase in the mass of the plate before and after it was coated with liquid paraffin was divided by the area of ​​the front and back surfaces of the plate to calculate the mass loss. The results are shown in Table 1.

[0058] (2) Antifouling rating 2 1 μL of triolein was applied to a polypropylene plate, and the plate with triolein applied was immersed in a treatment liquid having the composition shown in Table 2. This treatment liquid was heated to 50°, and the contact angle of triolein was measured. The results are shown in Table 2. The results in Table 2 show that a high contact angle can be obtained by contacting a treatment liquid containing an antifouling agent with a polypropylene plate. From these results, it is believed that the antifouling agent of the present invention reduces the solid-liquid interfacial energy on the hydrophobic surface, making it difficult for oily stains such as liquid oil to be adsorbed onto the hydrophobic surface. In particular, it is apparent that the treatment solution containing the stain-proofing agent of the present invention can provide an anti-staining effect even in a very dilute solution having a concentration lower than the cmc.

[0059] [Table 1]

[0060] [Table 2]

[0061] (3) Antifouling rating: 3 A clean polypropylene plate (8 cm × 3 cm) was immersed for 1 minute in a treatment solution with the composition shown in Table 3. After removing the plate from the treatment solution, a portion of the plate from the bottom end, 3 cm in length, was immersed in triolein and immediately removed. The amount of oil (mg / cm) adhering to the portion immersed in triolein was measured. 2 Specifically, the mass of oil attached to the plate was calculated from the difference in mass of the plate before and after immersion in triolein, and this mass of oil was divided by the area of ​​both sides of the plate (3 cm × 3 cm × front and back) to obtain the amount of oil attached (mg / cm 2 ) was calculated. The results are shown in Table 3. From these results, it is considered that by treating a hydrophobic surface in advance with the antifouling agent of the present invention, it becomes difficult for oily stains such as liquid oil to adhere to the hydrophobic surface thereafter.

[0062] [Table 3]

Claims

1. (a) An antifouling agent for preventing adhesion of oily stains to a hydrophobic surface, comprising a branched alkyl sulfosuccinate ester (hereinafter referred to as component (a)), the branched alkyl group having a main chain containing 6 or 7 carbon atoms and one or more side chains, and the total number of carbon atoms in the side chains being 3 or 4.

2. 2. The stainproofing agent according to claim 1, wherein the branched alkyl group of the component (a) is a branched alkyl group selected from a 2-propylheptyl group and a 3,5,5-trimethylhexyl group.

3. The stain-proofing agent according to claim 1 or 2, which is for use in an automatic dishwasher.

4. (a) An antifouling method comprising contacting an object to be treated having a hydrophobic surface with a treatment solution containing 1 ppm to 500 ppm of a branched alkyl sulfosuccinate ester (hereinafter referred to as component (a)), the branched alkyl group having a main chain containing 6 or 7 carbon atoms and one or more side chains, and the total number of carbon atoms in the side chains being 3 or 4.

5. 5. The stain-proofing method according to claim 4, wherein the branched alkyl group of the component (a) is a branched alkyl group selected from a 2-propylheptyl group and a 3,5,5-trimethylhexyl group.

6. The stain-preventing method according to claim 4 or 5, wherein the object to be treated is tableware.

7. The stain-preventing method according to any one of claims 4 to 6, wherein the treating solution is brought into contact with the object to be treated using an automatic dishwasher.

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