Method of laundering fabric

Abstract

A method of laundering fabric is provided, the method comprising: A) providing fabrics to which invisible stains are attached; B) treating the fabric with a detergent composition comprising either anionic surfactant, or a graft copolymer or both.

Description

[0001] METHOD OF LAUNDERING FABRIC

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method of laundering fabric.

[0004] BACKGROUND OF THE INVENTION

[0005] As detergent products are evolving, consumer needs in the term of cleaning have been well met. However, there are still some other unmet consumer needs in the field of laundry . Particularly, one of the unsolved issues is that most clothes become grayer / darker and less colorful after a period of usage. Even though clothes look very clean after washing, they do not look as new and colorful as the original ones. In other words, clothes look “old” as time passes.

[0006] The reasons that underly the issue as mentioned above are quite complex. Without wishing to be bound by theory, it is believed that one of the reasons is the presence of some invisible stains deposited inside the interstices of fabrics or yarns or even penetrating fibers of clothes which cannot be easily removed during washing process. Such invisible stains are often located deeply within the fabric or strongly adhered to fibers or within crenulations of fibers or in internal pores of fibre. Accordingly, some detergent composition products may not be very efficient for removing them from clothes. Furthermore, these invisible stains cannot be seen under the common conditions of usage. As such, it is quite difficult to assess whether these invisible stains are removed in a washing process. Without wishing to be bound by theory, invisible stains that are not removed with washing become problematic over time due to oxidation or other degradation such as by heat often ruining garments.

[0007] Therefore, there is a need for developing a method of laundering clothes which is capable of efficiently removing such invisible stains. Also, it is desired to provide a method for detecting invisible stains.

[0008] SUMMARY OF THE INVENTION

[0009] It is a surprising and unexpected discovery of the present invention that some detergent compositions are very useful in removing invisible stains.

[0010] Correspondingly, the present invention in one aspect relates to a method for laundering fabric, the method comprising the steps of:

[0011] A) providing fabrics to which invisible stains are attached;

[0012] B) treating the fabrics with a detergent composition comprising from about 1% to about 70%, by weight of the composition, of a surfactant system, wherein the surfactant system comprises from about 51% to about 100%, by weight of the surfactant system, of an anionic surfactant; and

[0013] C) optionally, detecting the invisible stains in the fabrics under a transmitted light source.

[0014] In one embodiment according to the present application, the surfactant system may further comprise from about 1% to about 49%, by weight of the surfactant system, of a nonionic surfactant.

[0015] In another embodiment according to the present application, the weight ratio of the anionic surfactant to the nonionic surfactant may be from 1.05 to 10, preferably from 1.1 to 5, more preferably from 1.15 to 3, e.g., 1.1, 1.5, 2, 3 or any ranges therebetween.

[0016] In another embodiment according to the present application, the detergent composition may further comprise from about 0.05% to about 15%, preferably from about 0.1% to about 5%, more preferably from about 0.2% to about 3%, by weight of the detergent composition, of a polyalkylene oxide graft copolymer comprising: a) polyalkylene oxide component as a graft base in which the polyalkylene oxide has a number average molecular weight of from 1000 to 20,000 Daltons and is based on ethylene oxide, propylene oxide, butylene oxide or mixtures thereof, b) polyvinyl ester component as side chains in which the polyvinyl ester is derived from a saturated monocarboxylic acid containing from 1 to 6 carbon atoms and / or a methyl or ethyl ester of acrylic or methacrylic acid, and c) polyvinylpyrrolidone as side chains, wherein the weight ratio of (a):(c) is from 1 :0.1 to 1 :2, and wherein the amount, by weight, of (a) is greater than the amount of (b).

[0017] In one embodiment according to the present application, in the graft copolymer, a) the polyalkylene oxide comprises and preferably consists of ethylene oxide units or ethylene oxide and propylene oxide units, and b) the polyvinyl ester comprises and preferably consists of vinyl acetate.

[0018] In one embodiment according to the present application, in the graft copolymer, the polyalkylene oxide has a number average molecular weight of from 2000 to 15,000 Daltons; and / or, the weight ratio of (a):(b) is from 1.0:0.1 to 1.0:0.99, preferably from 1.0:0.3 to 1.0:0.9; and / or, the polyalkylene oxide graft polymer has a weight average molecular weight of from 4,000 Da to 100,000 Da.

[0019] In one embodiment according to the present application, the composition may further comprise a treatment adjunct which is preferably selected from the group consisting of a surfactant system, fatty acids and / or salts thereof, enzymes, encapsulated benefit agents, soil release polymers, hueing agents, builders, chelating agents, dye transfer inhibiting agents, dispersants, enzyme stabilizers, anti-oxidants, catalytic materials, bleaching agents, bleach catalysts, bleach activators, polymeric dispersing agents, soil removal / anti-redeposition agents, polymeric grease cleaning agents, amphiphilic copolymers, brighteners, suds suppressors, dyes, hueing agents, perfume, encapsulated perfume, structure elasticizing agents, fabric softeners, carriers, fillers, hydrotropes, solvents, anti-microbial agents and / or preservatives, neutralizers and / or pH adjusting agents, processing aids, rheology modifiers and / or structurants, opacifiers, pearlescent agents, pigments, anti -corrosion and / or anti-tarnishing agents, and mixtures thereof.

[0020] In one embodiment according to the present application, the composition is in the form of a liquid composition, a granular composition, a single-compartment pouch, a multi-compartment pouch, a sheet, a pastille or bead, a fibrous article, a tablet, a bar, flake, or a mixture thereof.

[0021] In one embodiment according to the present application, the detergent composition comprises: from about 2% to about 20%, by weight of the detergent composition, of C6-C20 LAS, from about 0% to about 10%, by weight of the detergent composition, of C6-C20 AES, from about 0% to about 10%, by weight of the detergent composition, of C6-C20 AS, from about 2% to about 20%, by weight of the detergent composition, of C12-C18 alkyl ethoxylates, and from about 0.2% to about 3%, by weight of the detergent composition, of the graft copolymer, wherein the weight ratio of the anionic surfactant to the nonionic surfactant is from 1.15 to 2.5.

[0022] In another aspect, the present application is related to a method for laundering fabric, the method comprising the steps of

[0023] A) providing fabrics to which micron-sized stains are attached;

[0024] B) treating the fabrics with a detergent composition comprising from about 1% to about 70%, by weight of the composition, of a surfactant system, wherein the surfactant system comprises from about 51% to about 100%, by weight of the surfactant system, of an anionic surfactant; and

[0025] C) optionally, detecting the micron-sized stains in the fabrics under a transmitted light source.

[0026] In one embodiment according to the present application, detecting the invisible stains and / or micron-sized stains in the fabrics under a transmitted light source is achieved by observing the fabrics at a side of the fabrics which is opposite to the transmitted light source (e.g. sunshine or D65 standard illuminant). In another aspect, the present application is related to a method for detecting invisible stains and / or micron-sized stains in fabrics, the method comprising the steps of:

[0027] A) providing a fabric to which invisible stains and / or micron-sized stains are attached;

[0028] B) measuring Transmitted Whiteness Index of the fabric under a transmitted light source.

[0029] In some embodiments, the method for detecting invisible stains and / or micron-sized stains in fabrics comprises the steps of:

[0030] A) providing a fabric to which invisible stains and / or micron-sized stains are attached;

[0031] Bl) measuring Transmitted Whiteness Index before washing (i.e. TWIbefore) of the fabric by using a spectrometer under a transmitted light source;

[0032] B2) washing the fabric with a detergent composition;

[0033] B3) measuring Transmitted Whiteness Index after washing (i.e. TWIafter) of the fabric by using a spectrometer under a transmitted light source;

[0034] B4) calculating ATWI by the following equation:

[0035] TWIafter " TWIbefore=ATWI.

[0036] In some embodiments, the method for detecting invisible stains and / or micron-sized stains in fabrics may comprise the steps of:

[0037] A) providing a fabric to which invisible stains and / or micron-sized stains are attached;

[0038] Bl) measuring Transmitted Whiteness Index before washing (i.e. TWIbefore) of the fabric by using a spectrometer under a transmitted light source and measuring Reflected Whiteness Index before washing (i.e. RWIbefore) of the fabric by using a spectrometer under a reflected light source;

[0039] B2) washing the fabric with a detergent composition;

[0040] B3) measuring Transmitted Whiteness Index after washing (i.e. TWIafter) of the fabric by using a spectrometer under a transmitted light source and measuring Reflected Whiteness Index after washing (i.e. RWIafter) of the fabric by using a spectrometer under a reflected light source;

[0041] B4) calculating ATWI and ARWI by the following equations:

[0042] TWIafter " TWIbefore=ATWI, and

[0043] RWIafter " RWIbefore=ARWI.

[0044] In some embodiments, the fabrics which are treated in the laundering method according to the present disclosure may be characterized in that:

[0045] ARWI of the fabric is from -5 to 5, preferably from -3 to 3, e.g., -3, -2, -1, 0, 1, 2, 3 or any ranges therebetween, as measured in accordance with Test 1 : Whiteness Index test; and / or ATWI of the fabric is from -5 to 5, preferably from -3 to 3, e.g., -3, -2, -1, 0, 1, 2, 3 or any ranges therebetween, as measured in accordance with Test 1 : Whiteness Index test.

[0046] In another aspect, the present application is related to a method for laundering fabric, the method comprising the steps of: i) providing fabrics to which invisible stains and / or micron-sized stains are attached; ii) treating the fabrics with a detergent composition comprising from about 0.05% to about 15%, preferably from about 0.1% to about 5%, more preferably from about 0.2% to about 3%, by weight of the detergent composition, of a polyalkylene oxide graft copolymer comprising a) polyalkylene oxide component as a graft base, and b) polyvinyl ester component as side chains, and / or c) polyvinylpyrrolidone as side chains.

[0047] DETAILED DESCRIPTION OF THE INVENTION

[0048] Definitions

[0049] As used herein, the articles including “a” and “an” when used in a claim, are understood to mean one or more of what is claimed or described.

[0050] As used herein, the terms “comprise”, “comprises”, “comprising”, “include”, “includes”, “including”, “contain”, “contains”, and “containing” are meant to be non-limiting, i.e., other steps and other ingredients which do not affect the end of result can be added. The above terms encompass the terms “consisting of’ and “consisting essentially of’.

[0051] As used herein, when a composition is “substantially free” of a specific ingredient, it is meant that the composition comprises less than a trace amount, alternatively less than 0.1%, alternatively less than 0.01%, alternatively less than 0.001%, by weight of the composition, of the specific ingredient.

[0052] As used herein, the term “laundry detergent composition” means a composition for cleaning soiled materials, including fabrics. Such compositions may be used as a pre-laundering treatment, a post-laundering treatment, or may be added during the rinse or wash cycle of the laundering operation. The laundry detergent composition compositions may have a form selected from liquid, powder, unit dose such as single-compartment or multi-compartment unit dose, pouch, tablet, gel, paste, bar, or flake. Preferably, the laundry detergent composition is a liquid or a unit dose composition. The term of “liquid laundry detergent composition” herein refers to compositions that are in a form selected from the group consisting of pourable liquid, gel, cream, and combinations thereof. The liquid laundry detergent composition may be either aqueous or nonaqueous, and may be anisotropic, isotropic, or combinations thereof. The term of “unit dose laundry detergent composition” herein refers to a water-soluble pouch containing a certain volume of liquid wrapped with a water-soluble film.

[0053] As used herein, the term "alkyl" means a hydrocarbyl moiety which is branched or unbranched, substituted or unsubstituted. Included in the term "alkyl" is the alkyl portion of acyl groups.

[0054] As used herein, the term “main surfactant” refers to a surfactant that is present in a composition at an amount that is greater than any other surfactant contained by such composition. Similarly, the term “main anionic surfactant” refers to an anionic surfactant that is present in a composition at an amount that is greater than any other anionic surfactant contained by such composition

[0055] As used herein, the term “majority surfactant” refers to a surfactant that is present in a composition at an amount that is at least 50% by weight of the total surfactant content in such composition. Similarly, the term “majority anionic surfactant” refers to an anionic surfactant that is present in a composition at an amount that is at least 50% by weight of the total anionic surfactant content in such composition.

[0056] As used herein, the term “washing solution” refers to the typical amount of aqueous solution used for one cycle of laundry washing, preferably from 1 L to 50 L, alternatively from 1 L to 20 L for hand washing and from 20 L to 65 L for machine washing.

[0057] As used herein, the term “fabric” is used non-specifically and may refer to any type of natural or man-made synthetic fibers, including natural, and synthetic fibers, such as, but not limited to, cotton, regenerated cotton, synthetically-modified cotton, linen, wool, polyester, nylon, elastane, silk, acrylic, and the like, as well as various blends and combinations.

[0058] As used herein, the term “invisible stain” means any stain attached to fabrics but is invisible to naked eyes under the circumstances of daily use. Particularly, invisible stain refers to any stain attached to fabrics but is invisible to observers who are located at a side of fabrics which is the same with a light source (e.g. sunshine or D65 standard illuminant). More particularly, invisible stain refers to any stain attached to fabrics which is visible to observers who are located at an opposite side of fabrics to a light source (e.g. sunshine or D65 standard illuminant) but is invisible to observers who are located at a side of fabrics which is the same with the light source. Particularly, the invisible stain may have a micron-sized dimension (e.g. from 1 to 500 microns, preferably from 1 to 100 microns, more preferably from 1 to 50 microns, most preferably from 1 to 20 microns). In some embodiments, the invisible stain may comprise stains which are deposited within the fabric or strongly adhered to fibers or within internal pores of fibre. Preferably, the invisible stain may comprise sweat stain, urine stain, desquamed skin cells, dander, sebum, sugar, polysaccharides, guar or any combinations thereof which are deposited within the interstices of fabrics or yarns or internal pores of fibre. The laundering method according to the present disclosure may be capable of efficiently removing invisible stains.

[0059] As used herein, the term “micron-sized stain” means any stain attached to fabrics which is in the form of particles and / or spots having a micron-sized dimension (e.g. from 1 to 500 microns, preferably from 1 to 100 microns, more preferably from 1 to 50 microns, most preferably from 1 to 20 microns). Particularly, the micron-sized stain is invisible to naked eyes under the circumstances of daily use. In some embodiments, the micron-sized stain may comprise stains which are deposited within the interstices of fabrics or yams or internal pores of fibre. Preferably, the micron-sized stain may comprise sweat stain, urine stain, desquamed skin cells, dander, sebum, sugar, polysaccharides, guar or any combinations thereof which are deposited within the interstices of fabrics or yarns or internal pores of fibre. The laundering method according to the present disclosure may be capable of efficiently removing micron-sized stains.

[0060] As used herein, the term “transmitted light source” means a light source which is located at an opposite side of fabrics to the observer. Preferably, the transmitted light source is a D65 illuminant. In some embodiments, TWI is measured by using spectrometer under the following conditions: D65 illuminant at an opposite side of fabrics to the observer, an observing angle of 10°.

[0061] As used herein, the term “reflected light source” means a light source which is located at a side of fabrics which is the same with the observer. Preferably, the reflected light source is a D65 illuminant. In some embodiments, RWI is measured by using spectrometer under the following conditions: D65 illuminant at a side of fabrics which is the same with the observer, an observing angle of 10°.

[0062] Composition

[0063] The compositions of the present disclosure may be selected from the group of detergent powder compositions, light duty liquid detergents compositions, heavy duty liquid detergent compositions, detergent gels commonly used for laundry, bleaching compositions, laundry additives, fabric enhancer compositions, unit dose articles, and mixtures thereof.

[0064] The composition may be in any suitable form. The composition may be in the form of a liquid composition, a granular composition, a single-compartment pouch, a multi -compartment pouch, a sheet, a pastille or bead, a fibrous article, a tablet, a bar, flake, or a mixture thereof. The composition can be selected from a liquid, solid, or combination thereof.

[0065] The composition can be an aqueous liquid laundry detergent composition. For such aqueous liquid laundry detergent compositions, the water content can be present at a level of from 5.0 % to 95 %, preferably from 25 % to 90 %, more preferably from 50 % to 85 % by weight of the liquid detergent composition.

[0066] The pH range of the detergent composition may be from 2.5 to 9, e.g., from 3.0 to 5.0, from 4.0 to 7.0, from 6.0 to 8.9, preferably from pH 7 to 8.8.

[0067] The detergent composition can also be encapsulated in a water-soluble film, to form a unit dose article. Such unit dose articles comprise a detergent composition of the present invention, wherein the detergent composition comprises less than 20%, preferably less than 15%, more preferably less than 10% by weight of water, and the detergent composition is enclosed in a water- soluble or dispersible film. Such unit-dose articles can be formed using any means known in the art. Suitable unit-dose articles can comprise one compartment, wherein the compartment comprises the liquid laundry detergent composition. Alternatively, the unit-dose articles can be multicompartment unit-dose articles, wherein at least one compartment comprises the liquid laundry detergent composition.

[0068] Polyalkylene oxide graft copolymers

[0069] The detergent composition may comprise one or more polyalkylene oxide graft copolymers. The graft copolymer can be present at a level of from about 0.01% to about 15%, preferably from about 0.05% to about 10%, more preferably from about 0.1% to about 5%, and most preferably from about 0.2% to about 3%, e.g. 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, 0.45%, 0.50%, 1%, 2%, or 3%, by weight of the composition.

[0070] In a particular embodiment, the polyalkylene oxide graft copolymer comprises: (a) polyalkylene oxide which has a number average molecular weight of from 1000 to 20,000 Daltons and is based on ethylene oxide, propylene oxide, and / or butylene oxide, (b) polyvinyl ester component as side chains, and (c) polyvinylpyrrolidone as side chains. Particularly, the polyvinyl ester component is derived from a saturated monocarboxylic acid containing from 1 to 6 carbon atoms and / or a methyl or ethyl ester of acrylic or methacrylic acid.

[0071] In a particular embodiment, the weight ratio of component a) to component b) is from 1 :0.1 to 1 :0.99, preferably from 1 :0.3 to 1 :0.9.

[0072] In a particular embodiment, the weight ratio of component a) to component c) is from 1 :0.1 to 1 :2, preferably from 1 :0.3 to 1 : 1.

[0073] In a particular embodiment, in the polyalkylene oxide graft copolymer, from 1.0 mol% to 60 mol%, preferably from 20 mol% to 60 mol%, more preferably from 30 mol% to 50mol% of the grafted-on monomers of component (b) are hydrolyzed. In a particular embodiment, the polyalkylene oxide comprises or consists of ethylene oxide units or ethylene oxide units and propylene oxide units.

[0074] In a particular embodiment, the polyvinyl ester comprises vinyl acetate.

[0075] Suitable polyalkylene oxides may be based on homopolymers or copolymers, with homopolymers being preferred. Suitable polyalkylene oxides may be based on homopolymers of ethylene oxide or ethylene oxide copolymers having an ethylene oxide content of from 40 mol% to 99 mol%. Suitable comonomers for such copolymers may include propylene oxide, n-butylene oxide, and / or isobutylene oxide. Suitable copolymers may include copolymers of ethylene oxide and propylene oxide, copolymers of ethylene oxide and butylene oxide, and / or copolymers of ethylene oxide, propylene oxide, and at least one butylene oxide. The copolymers may include an ethylene oxide content of from 40 to 99 mol%, a propylene oxide content of from 1.0 to 60 mol%, and a butylene oxide content of from 1.0 to 30 mol%. The graft base may be linear (straight-chain) or branched, for example a branched homopolymer and / or a branched copolymer.

[0076] Branched copolymers may be prepared by addition of ethylene oxide with or without propylene oxides and / or butylene oxides onto polyhydric low molecular weight alcohols, for example trimethylol propane, pentoses, or hexoses.

[0077] The alkylene oxide unit may be randomly distributed in the polymer or be present therein as blocks.

[0078] The polyalkylene oxides of component (a) may be the corresponding polyalkylene glycols in free form, that is, with OH end groups, or they may be capped at one or both end groups. Suitable end groups may be, for example, Cl-C25-alkyl, phenyl, and Cl-C14-alkylphenyl groups. The end group may be a Cl -alkyl (e.g., methyl) group. Suitable materials for the graft base may include PEG 1000, PEG 2000, PEG 4000, PEG 6000, PEG 8000, PEG 10000, PEG 12000, and / or PEG 20000, which are polyethylene glycols, and / or MPEG 2000, MPEG 4000, MPEG 6000, MPEG 8000 and MEG 10000 which are monomethoxypolyethylene glycols that are commercially available from BASF under the tradename PLURIOLand / or block copolymers made from ethylene oxi de-propylene oxide-ethylene oxide (EO-PO-EO) or from propylene oxide-ethylene oxidepropylene oxide (PO-EO-PO) such as PE 6100, PE 6800 or PE 3100 commercially available from BASF under the tradename PLURONIC.

[0079] The polyalkylene oxides may be grafted with N-vinylpyrrolidone as the monomer of component (b). Without wishing to be bound by theory, it is believed that the presence of the N- vinylpyrrolidone (“VP”) monomer in the graft copolymers according to the present disclosure provides water-solubility and good film-forming properties compared to otherwise-similar polymers that do not contain the N-vinylpyrrolidone monomer. The vinyl pyrrolidone repeat unit has amphiphilic character with a polar amide group that can form a dipole, and a non-polar portion with the methylene groups in the backbone and the ring, making it hydrophobic.

[0080] The polyalkylene oxides may be grafted with a vinyl ester as the monomer of component (c). The vinyl ester may be derived from a saturated monocarboxylic acid, which may contain 1 to 6 carbon atoms, or from 1 to 3 carbon atoms, or from 1 to 2 carbon atoms, or 1 carbon atom. Suitable vinyl esters may be selected from the group consisting of vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl iso-valerate, vinyl caproate, or mixtures thereof. Preferred monomers of component (c) include those selected from the group consisting of vinyl acetate, vinyl propionate, or mixtures thereof, preferably vinyl acetate.

[0081] Conventionally, molecular weights are expressed by their “K-values,” which are derived from relative viscosity measurements. The graft copolymers may have a K value of from 5.0 to 200, optionally from 5.0 to 50, determined according to H. Fikentscher in 2% strength by weight solution in dimethylformamide at 25C.

[0082] Particularly preferred graft copolymers of the present invention have a polyethylene oxide backbone grafted with one or more side chains of polyvinyl acetate. More preferably, the weight ratio of the polyethylene oxide backbone over the polyvinyl acetate side chains ranges from about 1 :0.2 to about 1 : 10, or from about 1 :0.5 to about 1 :6, and most preferably from about 1 : 1 to about 1 :5. One example of such preferred amphiphilic graft copolymers is the Sokalan™ HP22 polymer, which is commercially available from BASF Corporation. This polymer has a polyethylene oxide backbone grafted with polyvinyl acetate side chains. The polyethylene oxide backbone of this polymer has a number average molecular weight (Mn) of about 6,000 g / mol (equivalent to about 136 ethylene oxide units), and the weight ratio of the polyethylene oxide backbone over the polyvinyl acetate side chains is about 1 :3. The number average molecular weight (Mn) of this polymer itself is about 13,000 g / mol.

[0083] Surfactant system

[0084] The composition according to the present disclosure may comprise from 1% to 99%, preferably from 4% to 80%, preferably from 6% to 50%, more preferably from 10% to 30%, e.g., 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80%, 90% or any ranges therebetween, by weight of the composition, of a surfactant system. Particularly, the surfactant system may comprise an anionic surfactant and a nonionic surfactant.

[0085] Particularly, the anionic surfactant may comprise linear alkylbenzene sulfonate (LAS), alkyl ethoxylated sulfates (AES), alkyl sulfates (AS), methyl ester sulfonates (MES), alkyl ether carboxylates (AEC), or any combinations thereof, preferably the anionic surfactant is selected from the group consisting of C6-C20 linear alkylbenzene sulfonate (LAS), C6-C20 alkyl ethoxylated sulfates (AES), C6-C20 alkyl sulfates (AS), and any combinations thereof; and / or

[0086] Particularly, the nonionic surfactant may comprise alkyl alkoxylated alcohols, alkyl alkoxylated phenols, alkyl polysaccharides, polyhydroxy fatty acid amides, alkoxylated fatty acid esters, and any combinations thereof, preferably the nonionic surfactant is selected from the nonionic surfactants represented by Formula (1):

[0087] R12-X-[(EO)s / (PO)t]-R13... (1) wherein, R12is linear or branched alkyl having from 8 to 18 carbon atoms, X is -O- or - C(O)O-, R13is hydrogen or alkyl having from 1 to 6 carbon atoms, s represents average repeats of EO, t represents average repeats of PO, s is from 3 to 20, t is from 0 to 6, EO represents ethylene oxide, PO represents propylene oxide, EO and PO may be arranged in mixture.

[0088] The anionic surfactant suitable for the composition in the present invention may be selected from the group consisting of C6-C20 linear alkylbenzene sulfonates (LAS), C6-C20 alkyl sulfates (AS), C6-C20 alkyl alkoxy sulfates (AAS), C6-C20 methyl ester sulfonates (MES), C6-C20 alkyl ether carboxylates (AEC), and any combinations thereof. For example, the laundry detergent composition may contain a C6-C20 alkyl alkoxy sulfates (AAXS), wherein x is about 1-30, preferably about 1-15, more preferably about 1-10, most preferably x is about 1-3. The alkyl chain in such AAXS can be either linear or branched, with mid-chain branched AAXS surfactants being particularly preferred. A preferred group of AAXS include C12-C14 alkyl alkoxy sulfates with x of about 1-3. In some embodiments, the composition comprises from 1% to 30%, preferably from 2% to 25%, more preferably from 3% to 20%, for example, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%, 16%, 18%, 20%, or any ranges therebetween, by weight of the composition of the anionic surfactant.

[0089] The nonionic surfactant suitable for the composition in the present invention may be selected from the group consisting of alkyl alkoxylated alcohols, alkyl alkoxylated phenols, alkyl polysaccharides, polyhydroxy fatty acid amides, alkoxylated fatty acid esters, sucrose esters, sorbitan esters and alkoxylated derivatives of sorbitan esters, and any combinations thereof. Nonlimiting examples of nonionic surfactants suitable for use herein include: C12-C18 alkyl ethoxylates, such as Neodol® nonionic surfactants available from Shell; C6-C12 alkyl phenol alkoxylates wherein the alkoxylate units are a mixture of ethyleneoxy and propyleneoxy units; C12-C18 alcohol and C6-C12 alkyl phenol condensates with ethylene oxide / propylene oxide block alkyl polyamine ethoxylates such as Pluronic® available from BASF; C14-C22 mid-chain branched alkyl alkoxylates, BAEx, wherein x is from about 1 to about 30; alkylpolysaccharides, specifically alkylpolyglycosides; polyhydroxy fatty acid amides; and ether capped poly(oxyalkylated) alcohol surfactants. Also useful herein as nonionic surfactants are alkoxylated ester surfactants such as those having the formula R1C(O)O(R2O)nR3wherein R1is selected from linear and branched Ce- C22 alkyl or alkylene moieties; R2is selected from C2H4 and C3IL moieties and R3is selected from H, CH3, C2H5 and C3H7 moieties; and n has a value between about 1 and about 20. Such alkoxylated ester surfactants include the fatty methyl ester ethoxylates (MEE) and are well-known in the art. In some particular embodiments, the alkoxylated nonionic surfactant contained by the laundry detergent composition of the present invention is a C6-C20 alkoxylated alcohol, preferably Cs-Cis alkoxylated alcohol, more preferably C10-C16 alkoxylated alcohol. The C6-C20 alkoxylated alcohol is preferably an alkyl alkoxylated alcohol with an average degree of alkoxylation of from about 1 to about 50, preferably from about 3 to about 30, more preferably from about 5 to about 20, even more preferably from about 5 to about 9. In some embodiments, the composition comprises from 1% to 30%, preferably from 2% to 25%, more preferably from 3% to 20%, for example, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%, 16%, 18%, 20%, or any ranges therebetween, by weight of the composition of the nonionic surfactant.

[0090] The ratio of anionic surfactant to nonionic surfactant may be between 0.01 and 100, preferably between 0.05 and 20, more preferably between 0.1 and 10, and most preferably between 0.2 and 5.

[0091] In some embodiments, the anionic surfactant comprises a C6-C20 linear alkylbenzene sulfonate surfactant (LAS), preferably C10-C16 LAS, and more preferably C12-C14 LAS. In other embodiments, the anionic surfactant comprises a C6-C20 alkyl alkoxy sulfates (AAS), preferably C10-C16 AAS, and more preferably C12-C14 AAS. In other embodiments, the anionic surfactant comprises a C6-C20 alkyl sulfates (AS), preferably C10-C16 AS, and more preferably C12-C14 AS.

[0092] In some particular embodiments of the present invention, the anionic surfactant may be present as the main surfactant, preferably as the majority surfactant, in the composition. Preferably, the ratio of anionic surfactant to nonionic surfactant may be between 1.05 and 100, preferably between 1.1 and 20, more preferably between 1.2 and 10, and most preferably between 1.3 and 5. Particularly, the anionic surfactant may comprise C6-C20 linear alkylbenzene sulfonates (LAS).

[0093] In some particular embodiments of the present invention, the nonionic surfactant may be present as the main surfactant, preferably as the majority surfactant, in the composition. Preferably, the ratio of anionic surfactant to nonionic surfactant may be between 0.01 and 0.95, preferably between 0.05 and 0.9, more preferably between 0.1 and 0.85, and most preferably between 0.2 and 0.8. Particularly, the nonionic surfactant may comprise C6-C20 alkoxylated alcohol.

[0094] The laundry detergent composition of the present invention may further comprise a cationic surfactant. Non-limiting examples of cationic surfactants include: quaternary ammonium surfactants, which can have up to 26 carbon atoms include: alkoxylate quaternary ammonium (AQA) surfactants; dimethyl hydroxyethyl quaternary ammonium compounds; dimethyl diisopropyl quaternary ammonium compounds; dimethyl hydroxy ethyl lauryl ammonium chloride; polyamine cationic surfactants; and amino surfactants, specifically amido propyldimethyl amine (APA).

[0095] The laundry detergent composition of the present invention may further comprise an amphoteric surfactant. Non-limiting examples of amphoteric surfactants include: amine oxides, derivatives of secondary and tertiary amines, derivatives of heterocyclic secondary and tertiary amines, or derivatives of quaternary ammonium, quaternary phosphonium or tertiary sulfonium compounds. Preferred examples include: C6-C20 alkyldimethyl amine oxides, betaine, including alkyl dimethyl betaine and cocodimethyl amidopropyl betaine, sulfo and hydroxy betaines, such as N-alkyl-N,N-dimethylammino-l-propane sulfonate where the alkyl group can be Cs-Cis or C10- C14.

[0096] Other ingredients

[0097] The laundry detergent composition according to the present disclosure may further comprise from 0.01% to 10%, preferably from 0.1% to 5%, more preferably from 0.2% to 3%, most preferably from 0.3% to 2%, by weight of the composition, of a surfactant boosting polymer, preferably polyvinyl acetate grafted polyethylene oxide copolymer.

[0098] The laundry detergent composition herein may comprise adjunct ingredients. Suitable adjunct materials include but are not limited to: builders, chelating agents, rheology modifiers, dye transfer inhibiting agents, dispersants, enzymes, and enzyme stabilizers, anti-oxidants, catalytic materials, bleach activators, hydrogen peroxide, sources of hydrogen peroxide, preformed peracids, polymeric dispersing agents, clay soil removal / anti-redeposition agents, brighteners, suds suppressors, dyes, photobleaches, perfumes, perfume microcapsules, structure elasticizing agents, fabric softeners, carriers, hydrotropes, processing aids, solvents, hueing agents, structurants and / or pigments. The precise nature of these adjunct ingredients and the levels thereof in the laundry detergent composition will depend on the physical form of the composition and the nature of the cleaning operation for which it is to be used.

[0099] In some embodiments, the laundry detergent composition according to the present disclosure may further comprise from 0.01% to 10%, preferably from 0.1% to 5%, more preferably from 0.2% to 4%, most preferably from 0.3% to 3%, for example, 0.5%, 1%, 2%, 3%, 4%, 5% or any ranges thereof, by weight of the composition, of a fatty acid. Composition Preparation

[0100] The laundry detergent composition of the present invention is generally prepared by conventional methods such as those known in the art of making laundry detergent compositions. Such methods typically involve mixing the essential and optional ingredients in any desired order to a relatively uniform state, with or without heating, cooling, application of vacuum, and the like, thereby providing laundry detergent compositions containing ingredients in the requisite concentrations.

[0101] Method of Use

[0102] Another aspect of the present invention is directed to a method of using the laundry detergent composition to treat a fabric. Such method can deliver a benefit for removing invisible stains from fabrics. The method comprises the step of administering from 5 g to 120 g of the above-mentioned laundry detergent composition into a laundry washing basin comprising water to form a washing solution. The washing solution in a laundry washing basin herein preferably has a volume from 1 L to 65 L, alternatively from 1 L to 20 L for hand washing and from 10 L to 65 L for machine washing. The temperatures of the laundry washing solution preferably range from 5°C to 60°C.

[0103] In some embodiments, the composition is added to a washing machine via a dispenser (e.g. a dosing drawer). In some other embodiments, the composition is added to an automatic dosing washing machine via an automatic dosing mechanism. In some other embodiments, the composition is added to directly a drum of a washing machine. In some other embodiments, the composition is added directly to the wash liquor.

[0104] The dosing amount in the method herein may be different depending on the washing type. In one embodiment, the method comprises administering from about 5 g to about 60 g of the laundry detergent composition into a hand washing basin (e.g., about 2-4 L). In an alternative embodiment, the method comprises administering from about 5 g to about 100 g, preferably from about 10 g to about 65 g of the laundry detergent composition into a washing machine (e.g., about 10-45 L).

[0105] Test Method

[0106] Test 1 : Whiteness Index test

[0107] In order to determine Whiteness Index, Titanium dioxide deposition test is conducted by using Tergotometer (Model: RHLQ IV , from China Daily Chemical Industry Research Institute) as below: TiO2 (100-300 nm, available from Mery er (Shanghai) Biochemical Technology Co., Ltd.): 2 g in IL city water

[0108] Body soil (JB03 available from Sino light inspection & certification Co. Ltd.): 6g in IL city water (optional)

[0109] Water volume: IL

[0110] Water type: city water

[0111] HDL Concentration: 3000 ppm

[0112] Fabric Tracer: 10cm x 10cm with-brightener CW98 (100% Heavy Cotton, purchased from Danxin Textile Co. Beijing, China) 3 pieces, or 10cm x 10cm with-brightener PCW13(100% Heavy Cotton, purchased from Danxin Textile Co. Beijing, China), 3 pieces, or 10cm x 10cm nil-brightener CW11(100% Heavy Cotton, purchased from Danxin Textile Co. Beijing, China), which were pre-stripped with China National Standard powder detergent (from Taiyuan, China) in DI water by 6 times

[0113] Measure the L*ab (and then calculate AE which is designated as RWIbefore) and the Opacity Y (which is designated as TWIbefore) of the fabric tracers before washing according to the Titanium dioxide deposition test method below.

[0114] 1, Add city water

[0115] 2, Add HDL and dissolve for 3 minutes.

[0116] 3, Add the mixture of titanium dioxide and JB03 and dissolve for 3 minutes.

[0117] 4, Put in fabric tracers and start stirring (main wash).

[0118] 5, The main wash time is 5 minutes.

[0119] 6, Remove the fabrics from the wash container and squeeze dry

[0120] 7, Add city water, put in fabric tracers and start stirring (rinse)

[0121] 8, The rinse time is 2 minutes.

[0122] 9, Repeat steps 7 and 8 again, until the stain is completely rinsed clean, no residue.

[0123] 10, Remove the fabrics from the rinse container and dry in natural air.

[0124] 11, Polaris was used to measure L* A B and calculate AE which is designated as RWIafter, and Hunter color was used to measure the Opacity Y which is designated as TWIafter.

[0125] 12, Measurement of reflected light: Polaris, measurement of transmitted light: Hunter color

[0126] 13, Calculating ATWI and ARWI by the following equations:

[0127] TWIafter " TWIbefore=ATWI, and

[0128] RWIafter " RWIbefore=ARWI.

[0129] Test 2: Whiteness Grade test data Titanium dioxide deposition test is conducted by using Tergotometer (Model: RHLQ IV , from China Daily Chemical Industry Research Institute) as in Test 1. For Reflected Whiteness Grade (RWG), after washing, the score of from -2 to 2 was given by five panelists to observe the whiteness of the fabric between Test Sample and Reference Sample under the condition of a reflected light source, in which negative number means that panelists have a high rating for Reference Sample, positive number means that panelists have a high rating for Test Sample and 0 point means no difference between Samples.

[0130] For Transmitted Whiteness Grade (TWG), after washing, the score of from -2 to 2 was given by five panelists to observe the whiteness of the fabric between Test Sample and Reference Sample under the condition of a transmitted light source, in which negative number means that panelists have a high rating for Reference Sample, positive number means that panelists have a high rating for Test Sample and 0 point means no difference between Samples. Particularly, when observing, 6 pieces of fabric for each sample were overlapped and covered by the flashlight as the transmitted light source.

[0131] RWG TWG

[0132] Scale 0 = No difference between test product 0 = No difference between test product and reference in the aspect of whiteness and reference in the aspect of whiteness

[0133] 1 = I am sure there is a difference between 1 = I am sure there is a difference between test product and reference in the aspect of test product and reference in the aspect of whiteness, but it is small whiteness, but it is small

[0134] 2 = There is a significant difference 2 = There is a significant difference between test product and reference in the between test product and reference in the aspect of whiteness aspect of whiteness

[0135] Note = test product better than reference = test product worse than reference

[0136] EXAMPLES

[0137] Synthesis Example 1 : Synthesis of Graft Copolymer

[0138] A graft copolymer which is PVP / PVAc-g-PEG at a weight ratio of 20:30:50 ratio with a weight average molecular weight 16,800 Dalton was prepared as follows.

[0139] A polymerization vessel equipped with stirrer and reflux condenser was initially charged with 720g of PEG (6000 g / mol) and 60g 1,2-propane diol (MPG) under nitrogen atmosphere. The mixture was homogenized at 70°C. Then, 432 g of vinyl acetate (in 2 h), 288 g of vinylpyrrolidone in 576 g of MPG (in 5 h), and 30.2 g of tert.-butyl perpivalate in 196.6 g MPG (in 5.5 h) were metered in. Upon complete addition of the feeds, the solution was stirred at 70°C for 1 h. Subsequently, 3.8 g tert.-butyl perpivalate in 25.0 g MPG (in 1.5 h) were metered in followed by 0.5 h of stirring.

[0140] The volatiles were removed by vacuum stripping. Then, 676.8 g deionized water were added and a steam distillation was conducted at 100°C for 1 h.

[0141] The temperature of the reaction mixture was reduced to 80°C and 160.6 g of aqueous sodium hydroxide solution (50 %, 40 mol% respective VAc) was added with maximum feed rate. Upon complete addition of the sodium hydroxide solution, the mixture was stirred for 1 h at 80°C and subsequently cooled to ambient temperature.

[0142] The resulting graft copolymer is characterized by a K-value of 24. The solid content of the final solution is 45 %.

[0143] Example 1 : Establishment of Method for Detecting Invisible Stains

[0144] In order to establish a method of detecting invisible stains in fabrics, two sample liquid laundry detergent compositions were prepared containing the following ingredients.

[0145] Table 1

[0146] It is known that ARWI as measured can indicate overall cleaning performance (i.e., the overall stain removal), i.e. the higher ARWI indicates the worse cleaning performance, while the lower ARWI indicates better cleaning performance. The present inventors surprisingly found that the Transmitted Whiteness Index under a transmitted light source (e.g. ATWI) as measured in accordance with Test 1 : Whiteness Index test is useful for assessing the performance of invisible stains removal. The higher ATWI indicates the worse invisible stain removal, while the lower ATWI indicates improved invisible stain removal.

[0147] In order to evaluate if this method can work, an analytical test in accordance with Test 1 : Whiteness Index test (Titanium dioxide was added without body soil) and a sensory test in accordance with Test 2: Whiteness Grade test were carried out. In accordance with Test 1 : Whiteness Index test as described hereinabove (Titanium dioxide was added without body soil), ARWI and ATWI for Samples 1 and 2 were measured, in which PCW13 (a brightener-containing polycotton) and CW98 (a brightener-containing cotton) were used as white fabric tracers.

[0148] The present inventors found that invisible stains can be noticed by consumers under the transmitted light source, for example, when looking at the sun through fabrics while such invisible stains are not distinguishable under the common reflected light source. In Test 2, TWG is a direct sensory measurement for whiteness under the transmitted light source. As such, if an analytical parameter has a same trend with TWG, the analytical parameter can be a useful measurement for invisible stains removal. The results as shown in Table 2 indicates that ATWI as measured in accordance with Test 1 : Whiteness Index test is quite consistent with TWG as measured in accordance with Test 2: Whiteness Grade test. Accordingly, ATWI is a good indicator for invisible stains removal.

[0149] Particularly, in the analytical test, Samples 1 and 2 show very similar ARWI (i.e. the overall visible stain removal between Samples 1 and 2 is similar). Consistently, the scores in the sensory test for Samples 1 and 2 are near zero (i.e., RWG being -0.6 and -0.4) which means no significantly difference therebetween. On the other hand, under the transmitted light source, Sample 2 shows much lower ATWI compared to Sample 1 (3.3 vs 7.7 and -0.2 vs 4.8) in the analytical test and Sample 2 also shows better sensory scores for whiteness compared to Sample 1 (+1.4 and +2.0) in the sensory test. Furthermore, the data indicates that a laundry detergent composition containing an anionic surfactant as a main surfactant (e.g. Sample 2) is more efficient in invisible stains removal compared to a laundry detergent composition containing an nonionic surfactant as a main surfactant (e.g. Sample 1) although the overall stain removal is similar therebetween.

[0150] Table 2

[0151] Example 2: Improved Invisible Stains Removal in Laundry Detergent Composition Containing Polyalkylene Oxide Graft Copolymer Two (2) sample liquid laundry detergent compositions were prepared containing the following ingredients, in which Sample 3 contains a polyalkylene oxide graft copolymer while Sample 4 does not contain such graft copolymer.

[0152] Table 4

[0153] 1 Poly alkylene oxide graft copolymer described in Synthesis Example 1 with PVP / P VAc-g-PEG at a weight ratio of 20:30:50 ratio with a weight average molecular weight 16,800 Dalton.

[0154] In accordance with Test 1 : Whiteness Index test as described hereinabove (Titanium dioxide was added together with body soil), ATWI for Samples 3 and 4 were measured. Sample 3 containing a graft copolymer shows significantly improved invisible stains removal compared to Sample 4 without such graft copolymer, as shown in the Table 5 below.

[0155] Table 5

[0156] The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”

[0157] Every document cited herein, including any cross referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

[0158] While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

Claims

CLAIMSWhat is claimed is:

1. A method for laundering fabric, the method comprising the steps of:A) providing fabrics to which invisible stains are attached;B) treating the fabrics with a detergent composition comprising from about 1% to about 70%, by weight of the composition, of a surfactant system, wherein the surfactant system comprises from about 51% to about 100%, by weight of the surfactant system, of an anionic surfactant.C) optionally, detecting the invisible stains in the fabrics under a transmitted light source.

2. The method according to Claim 1, wherein the surfactant system further comprises from about 1% to about 49%, by weight of the surfactant system, of a nonionic surfactant.

3. The method according to Claim 1 or 2, wherein the weight ratio of the anionic surfactant to the nonionic surfactant is from 1.05 to 10, preferably from 1.1 to 5, more preferably from 1.15 to 3.

4. The method according to any of preceding claims, wherein the anionic surfactant comprises linear alkylbenzene sulfonate (LAS), alkyl ethoxylated sulfates (AES), alkyl sulfates (AS), methyl ester sulfonates (MES), alkyl ether carboxylates (AEC), or any combinations thereof, preferably the anionic surfactant is selected from the group consisting of C6-C20 linear alkylbenzene sulfonate (LAS), C6-C20 alkyl ethoxylated sulfates (AES), C6-C20 alkyl sulfates (AS), and any combinations thereof; and / or wherein the nonionic surfactant comprises alkyl alkoxylated alcohols, alkyl alkoxylated phenols, alkyl polysaccharides, polyhydroxy fatty acid amides, alkoxylated fatty acid esters, and any combinations thereof, preferably the nonionic surfactant is selected from the nonionic surfactants represented by Formula (1):R12-X-[(EO)s / (PO)t]-R13... (1) wherein, R12is linear or branched alkyl having from 8 to 18 carbon atoms, X is -O- or - C(O)O-, R13is hydrogen or alkyl having from 1 to 6 carbon atoms, s represents average repeats of EO, t represents average repeats of PO, s is from 3 to 20, t is from 0 to 6, EO represents ethylene oxide, PO represents propylene oxide, EO and PO may be arranged in mixture.

5. The method according to any of preceding claims, wherein the detergent composition further comprises from about 0.05% to about 15%, preferably from about 0.1% to about 5%, more preferably from about 0.2% to about 3%, by weight of the detergent composition, of a graft copolymer comprising: a) polyalkylene oxide component as a graft base in which the polyalkylene oxide has a number average molecular weight of from 1000 to 20,000 Daltons and is based on ethylene oxide, propylene oxide, butylene oxide or mixtures thereof, b) polyvinyl ester component as side chains in which the polyvinyl ester is derived from a saturated monocarboxylic acid containing from 1 to 6 carbon atoms and / or a methyl or ethyl ester of acrylic or methacrylic acid, and c) polyvinylpyrrolidone as side chains, wherein the weight ratio of (a):(c) is from 1 :0.1 to 1 :2, and wherein the amount, by weight, of (a) is greater than the amount of (b)6. The method according to any of preceding claims, wherein in the polyalkylene oxide graft polymer a) the polyalkylene oxide comprises and preferably consists of ethylene oxide units or ethylene oxide and propylene oxide units, and b) the polyvinyl ester comprises and preferably consists of vinyl acetate.

7. The method according to any of preceding claims, wherein in the polyalkylene oxide graft polymer the polyalkylene oxide has a number average molecular weight of from 2000 to 15,000 Daltons; and / or the weight ratio of (a):(b) is from 1.0:0.1 to 1.0:0.99, preferably from 1.0:0.3 to 1.0:0.9; and / or the polyalkylene oxide graft polymer has a weight average molecular weight of from 4,000 Da to 100,000 Da.

8. The method according to any of preceding claims, wherein the invisible stain means any stain attached to fabrics but is invisible to naked eyes under the circumstances of daily use, particularly, the invisible stain refers to any stain attached to fabrics but is invisible to observers who are located at a side of fabrics which is the same with a light source.

9. The method according to Claim 8, wherein the invisible stain comprises stain which is deposited within internal holes of fibre, preferably the invisible stain comprises sweat stain, urine stain, dander or any combinations thereof which are deposited within internal holes of fibre.

10. The method according to any of preceding claims, wherein the fabrics are characterized in that:ARWI of the fabric is from -5 to 5, preferably from -3 to 3, as measured in accordance with Test 1 : Whiteness Index test; and / orATWI of the fabric is from -5 to 5, preferably from -3 to 3, as measured in accordance with Test 1 : Whiteness Index test.

11. The method according to any of Claims 5 to 10, wherein the detergent composition comprises: from about 2% to about 20%, by weight of the detergent composition, of C6-C20 LAS, from about 0% to about 10%, by weight of the detergent composition, of C6-C20 AES, from about 0% to about 10%, by weight of the detergent composition, of C6-C20 AS, from about 2% to about 20%, by weight of the detergent composition, of C12-C18 alkyl ethoxylates, and from about 0.2% to about 3%, by weight of the detergent composition, of the graft copolymer, wherein the weight ratio of the anionic surfactant to the nonionic surfactant is from 1.15 to 2.5.

12. The method according to any preceding claim, wherein the method is capable of efficiently removing invisible stains.

13. A method for laundering fabric, the method comprising the steps of: i) providing fabrics to which invisible stains are attached; ii) treating the fabrics with a detergent composition comprising from about 0.05% to about 15%, preferably from about 0.1% to about 5%, more preferably from about 0.2% to about 3%, by weight of the detergent composition, of a polyalkylene oxide graft copolymer comprising a) polyalkylene oxide component as a graft base, and b) polyvinyl ester component as side chains, and / or c) polyvinylpyrrolidone as side chains.

14. The method according to Claim 13, wherein the polyalkylene oxide graft copolymer comprising: a) polyalkylene oxide component as a graft base in which the polyalkylene oxide has a number average molecular weight of from 1000 to 20,000 Daltons and is based on ethylene oxide, propylene oxide, butylene oxide or mixtures thereof; b) polyvinyl ester component as side chains in which the polyvinyl ester is derived from a saturated monocarboxylic acid containing from 1 to 6 carbon atoms and / or a methyl or ethyl ester of acrylic or methacrylic acid; and c) polyvinylpyrrolidone as side chains; wherein the weight ratio of component a) to component b) is from 1 :0.1 to 1 :0.99, preferably from 1 :0.3 to 1 :0.9, and wherein the weight ratio of component a) to component c) is from 1 :0.1 to 1 :2, preferably from 1 :0.3 to 1 : 1.

15. The method according to Claim 13 or 14, wherein the polyalkylene oxide graft copolymer has a weight average molecular weight of from 4,000 Da to 100,000 Da, preferably from 5,000 Da to 100,000 Da, more preferably from 5,000 Da to 50,000 Da, most preferably from 8,000 Da to 20,000 Da; and / or wherein in the polyalkylene oxide graft copolymer, from 1.0 mol% to 60 mol%, preferably from 20 mol% to 60 mol%, more preferably from 30 mol% to 50mol% of the grafted monomers of component (b) are hydrolyzed; and / or wherein the polyalkylene oxide comprises ethylene oxide units or ethylene oxide units and propylene oxide units, and / or wherein the polyvinyl ester comprises vinyl acetate.

16. The method according to Claim 13 or 14, wherein the detergent composition comprises from about 1% to about 70%, by weight of the composition, of a surfactant system, wherein the surfactant system comprises from about 51% to about 100%, by weight of the surfactant system, of a nonionic surfactant, preferably wherein the nonionic surfactant comprises alkyl alkoxylated alcohols, alkyl alkoxylated phenols, alkyl polysaccharides, polyhydroxy fatty acid amides, alkoxylated fatty acid esters, and any combinations thereof, preferably the nonionic surfactant is selected from the nonionic surfactants represented by Formula (1):R12-X-[(EO)s / (PO)t]-R13... (1)wherein, R12is linear or branched alkyl having from 8 to 18 carbon atoms, X is -O- or - C(O)O-, R13is hydrogen or alkyl having from 1 to 6 carbon atoms, s represents average repeats of EO, t represents average repeats of PO, s is from 3 to 20, t is from 0 to 6, EO represents ethylene oxide, PO represents propylene oxide, EO and PO may be arranged in mixture.

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