阅读说明：本技术 用于评价织物调理剂的方法 (Method for evaluating fabric conditioners ) 是由 C·博德曼 沈帆 S·B·乔伊斯 许丹萍 于 2018-07-11 设计创作，主要内容包括：一种评价织物调理剂的中和效果的方法,所述方法包括以下步骤：a)将第一片或段的吸收性材料浸入包含洗衣洗涤剂组合物的水中；b)将所述第一片或段的吸收性材料浸入包含织物调理组合物的水中；c)向所述吸收性材料施加阳离子染料；和d)评价所述织物的颜色。(A method of evaluating the neutralization effectiveness of a fabric conditioner, the method comprising the steps of: a) immersing a first sheet or section of absorbent material in water comprising a laundry detergent composition; b) immersing the first sheet or section of absorbent material in water comprising a fabric conditioning composition; c) applying a cationic dye to the absorbent material; and d) evaluating the colour of the fabric.)

1. A method of evaluating the neutralization effectiveness of a fabric conditioner, the method comprising the steps of:

a) immersing a first sheet or section of absorbent material in water comprising a laundry detergent composition, wherein the detergent composition comprises an anionic surfactant;

b) immersing the first sheet or section of absorbent material in water comprising a fabric conditioning composition, wherein the fabric conditioning composition comprises a cationic surfactant;

c) applying a cationic dye to the absorbent material; and

d) the color of the absorbent material is evaluated,

wherein the fabric conditioner neutralizes detergent residues.

2. The method of claim 1 wherein a first sheet or section of absorbent material is compared to a second sheet or section of absorbent material, the second sheet or section of absorbent material being treated according to the steps of:

a) immersing in water comprising a laundry detergent composition;

b) optionally immersed in water or water containing a fabric conditioning composition;

c) applying a cationic dye to the absorbent material; and

d) the color of the absorbent material was evaluated.

3. The method of claim 2, wherein the concentration of laundry detergent composition is constant for both the absorbent material of the first sheet or section and the absorbent material of the second sheet or section.

4. The method of claim 2, wherein the absorbent material of the first sheet or section and the absorbent material of the second sheet or section are treated with the same laundry detergent composition.

5. The method of claim 2 wherein the absorbent material of the first sheet or section and the absorbent material of the second sheet or section are the same absorbent material.

6. The method of claim 2, wherein two sheets of absorbent material are used, and the difference in height of the two sheets of absorbent material is less than 10cm, the difference in width of the two sheets of absorbent material is less than 10cm, and in a related case, the difference in depth of the two sheets of absorbent material is less than 10 cm.

7. The method of claim 2, wherein step b) comprises rinsing the second sheet or section of absorbent material in:

-water;

-water comprising the same fabric conditioner composition as used for the first sheet of fabric, but in a different concentration; or

-water comprising the same concentration of fabric conditioner composition as used for the first sheet of fabric, but a different fabric conditioner composition.

8. The method according to any preceding claims, wherein the laundry detergent composition comprises anionic and nonionic surfactants.

9. The method of any preceding claim, wherein the fabric conditioning composition comprises a quaternary ammonium compound.

10. The method of any preceding claim, wherein the cationic dye is in an aqueous solution at a concentration of 1 x 10 of the aqueous solution^-9To 1X 10^-3And (3) weight percent.

11. The method of any of the preceding claims, wherein the one or more pieces of absorbent material are synthetic materials.

12. The method according to any one of the preceding claims, wherein the one or more pieces of absorbent material are in the shape of an article of clothing.

13. The method of any of the preceding claims, wherein the one or more pieces of absorbent material are selected from a sheet of acrylic, polyester, or nylon, or a three-dimensional polyurethane sponge.

14. The method according to any one of the preceding claims, wherein the evaluation of color is a visual evaluation.

15. Use of a method according to any preceding claim for demonstrating the neutralising effect of a fabric conditioner on residues from a laundry detergent.

Technical Field

The present invention is in the field of evaluating the neutralising effect of fabric conditioning compositions.

Background

Laundry detergent compositions leave residues on fabrics. When these residues come into contact with the skin of the consumer, they can cause skin irritation.

WO 00/17297 discloses the use of cationic materials such as cationic fabric conditioning materials and compositions to reduce skin irritation. Methods of evaluating fabric conditioners for reduced skin irritation are disclosed. However, these methods require human panelists willing to participate in patch tests or to be able to perform titrations in a laboratory setting.

There is a need for a method for rapid and easy evaluation of the neutralization effectiveness of fabric conditioners.

Disclosure of Invention

A method of evaluating the neutralization effectiveness of a fabric conditioner, the method comprising the steps of:

a) immersing a first sheet or section of absorbent material in water comprising a laundry detergent composition, wherein the detergent composition comprises an anionic surfactant;

b) immersing the first sheet or section of absorbent material in water comprising a fabric conditioning composition, wherein the fabric conditioning composition comprises a cationic surfactant;

c) applying a cationic dye to the absorbent material; and

d) the color of the absorbent material is evaluated,

wherein the fabric conditioner neutralizes detergent residues.

Also disclosed is the use of the method for validating fabric conditioners and detergent residues.

Detailed Description

These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims. For the avoidance of doubt, any feature of one aspect of the invention may be used in any other aspect of the invention. The word "comprising" is intended to mean "including", but not necessarily "consisting of. In other words, the listed steps or options need not be exhaustive. It should be noted that the examples given in the following description are intended to illustrate the present invention, and are not intended to limit the present invention to these examples per se. Similarly, all percentages are weight/weight percentages unless otherwise indicated. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word "about". Numerical ranges expressed as "x to y" are understood to include x and y. When multiple preferred ranges are described in the form of "x to y" for a particular feature, it is to be understood that all ranges combining the different endpoints are also contemplated.

Step a) immersion in water containing a laundry detergent composition

In the first step of the process, one or more absorbent materials are immersed in water containing a laundry detergent composition. The detergent composition comprises a surfactant. The detergent composition used in the process comprises at least one anionic surfactant, preferably the composition comprises a nonionic surfactant and an anionic surfactant.

The nonionic surfactant, if present, preferably comprisesAn alcohol ethoxylate. Alcohol ethoxylates are formed from the reaction of primary or secondary alcohols with ethylene oxide. Typically, aliphatic C₈To C₁₈Linear or branched primary or secondary alcohols are reacted with ethylene oxide in the desired molar amounts to produce alcohol ethoxylates. Preferred alcohol ethoxylates have from 2 to 40, preferably from 3 to 30, more preferably from 5 to 20 ethylene oxide units attached to the aliphatic chain.

The surfactant may be selected from the group consisting of surfactants described in "Surface Active Agents", volume 1, Schwartz Perry, Interscience 1949, volume 2, Schwartz, Perry 205 Berch, Interscience 1958, the current version of "McCutcheon's Emulsifiers and detergents" published by the Manufacturing conditioners Company, or "Tenside Taschenbuch", H.Stache, 2 nd edition, Carl HauserVerlag, 1981. Preferably, the surfactant is saturated.

Suitable nonionic detergent compounds which may be used include in particular the reaction products of compounds having a hydrophobic group and a reactive hydrogen atom, for example aliphatic alcohols, acids or amides or alkyl phenols with alkylene oxides, especially ethylene oxide alone or together with propylene oxide. A specific nonionic detergent compound is C₆To C₂₂Alkylphenol-ethylene oxide condensates, usually 5 to 25EO, i.e. 5 to 25 ethylene oxide units, per molecule, and aliphatic C₈To C₁₈Condensation products of linear or branched primary or secondary alcohols with ethylene oxide, typically 5 to 40 EO.

Suitable anionic detergent compounds which may be used are water-soluble alkali metal salts of organic sulphuric and sulphonic acids having an alkyl group containing from about 8 to about 22 carbon atoms, the term alkyl being used to include the alkyl portion of higher acyl groups. Examples of suitable synthetic anionic detergent compounds are sodium and potassium alkyl sulphates, especially by reacting a higher C₈To C₁₈Alcohols (e.g. derived from tallow or coconut oil) sulphated, alkyl C₉To C₂₀Sodium and potassium benzene-sulphonates, especially linear secondary alkyl C₁₀To C₁₅Sodium benzenesulfonate; and sodium alkyl glyceryl ether sulfates, particularly higher alcohols and derivatives derived from tallow or coconut oilThose ethers of synthetic alcohols from petroleum. Preferred anionic detergent compounds are C₁₁To C₁₅Sodium alkyl benzene sulfonate and C₁₂To C₁₈Sodium alkyl sulfate. The sulfonate salt contained as a hydrotrope can additionally be considered an anionic surfactant as defined herein. Also suitable are surfactants such as those described in EP-A-328177 (Unilever), which exhibit resistance to salting out, alkylpolyglycoside surfactants as described in EP-A-070074, and alkylmonoglycosides.

The total amount of surfactant present in the laundry detergent composition may be from 5 to 40 wt%. The surfactant content is preferably at least 6 wt%, more preferably at least 10 wt%, more preferably the total amount of surfactants is from 12.5 to 40 wt%, preferably from 14 to 35 wt%.

Preferred nonionic surfactants are C with an average of 7 to 9 moles of ethoxylation₁₂-C₁₅An alkyl chain. Preferred anionic surfactants are: linear alkyl benzene sulfonates, sodium lauryl ether sulfonate with 1 to 3 moles (on average) of ethoxylation, primary alkyl sulfonates, methyl ether sulfates and secondary alkyl sulfonates or mixtures thereof.

In addition to the aforementioned nonionic and anionic surfactants, other surfactants such as amphoteric, zwitterionic and cationic surfactants may also be present.

The laundry detergent composition added to the water may be in powder or liquid form and should be well mixed/dissolved in the water.

The concentration of the laundry detergent in water is preferably from 2 to 20 g/litre, more preferably from 3 to 15 g/litre, most preferably from 3 to 10 g/litre.

When comparing two or more pieces or segments of absorbent material, the detergent compositions may be the same or different compositions depending on the variables evaluated by the method. For example, the effectiveness of a particular fabric conditioner can be evaluated for different laundry detergent compositions. Alternatively, the effectiveness of different fabric conditioners can be evaluated for a particular laundry detergent composition.

Likewise, if the fabric conditioner composition is evaluated for effectiveness with different concentrations of laundry detergent, the concentration of laundry detergent may be different. Preferably, the concentration of laundry detergent is the same for all of the tablets or segments of absorbent material used in the process.

When two or more sheets or sections of absorbent material are used in the process, the laundry detergent composition is the same, and the sheets or sections of absorbent material are immersed simultaneously or sequentially in the same water containing the laundry detergent composition.

A single piece of material can be immersed in water containing detergent and then separated into two separate pieces for the remaining steps. For example, two halves are cut and treated differently in the following method steps.

Step b) immersion in water containing a fabric conditioning composition

In the second step of the process, the first and optionally second sheets or sections of absorbent material are immersed in water containing the fabric conditioning composition. The fabric conditioning composition comprises a cationic softening active.

The preferred cationic softening active for use in the process is a Quaternary Ammonium Compound (QAC). Preferred quaternary ammonium compounds for use in the process compositions of the invention are so-called "ester quats" comprising ester linkages. A particularly preferred material is an ester-linked Triethanolamine (TEA) quaternary ammonium compound comprising a mixture of mono-, di-, or tri-ester linked components. Most preferably, the ester-linked quaternary ammonium compound is an ester-linked triethanolamine quaternary ammonium compound comprising an unsaturated fatty chain.

Typically, TEA-based fabric softening actives comprise a mixture of mono-, di-and tri-ester forms of the compound, wherein the diester linkage component comprises no more than 70% by weight of the fabric softening compound, preferably no more than 60% (e.g. 55% or 45%) of the fabric softening compound, and at least 10% of the monoester linkage component, e.g. 11% monoester. One preferred hardening type of active agent has the following typical monoester: triester distribution: 18 to 22 monoester, 58 to 62 diester, 18 to 22 triester; such as 20:60: 20. A soft TEA quaternary ammonium compound can have the following typical monoester: triester distribution: 25 to 45%, preferably 30 to 40%, monoester, 45 to 60%, preferably 50 to 55%, diester and 5 to 25%, preferably 10 to 15%, triester; for example 40:50: 10.

A first group of Quaternary Ammonium Compounds (QACs) suitable for use in the method of the present invention is represented by formula (I):

wherein each R is independently selected from C_5-35An alkyl or alkenyl group; r¹Is represented by C_1-4Alkyl radical, C_2-4Alkenyl or C_2-4A hydroxyalkyl group; t is typically O — CO (i.e., an ester group bound to R via its carbon atom), but may alternatively be CO — O (i.e., an ester group bound to R via its oxygen atom); n is a number selected from 1 to 4; m is a number selected from 1,2 or 3; and X is an anionic counterion, such as a halide or an alkyl sulfate, for example chloride or methyl sulfate. Diester variants of formula I (i.e., m ═ 2) are preferred, typically with monoester and triester analogs associated therewith.

Particularly preferred agents are preparations of diesters rich in triethanolammonium methylsulfate, otherwise known as "TEA ester quats".

Commercial examples include Stepandex^TMUL85 (from Stepan), Prapagen^TMTQL (from Clariant) and Tetranyl^TMAHT-1 (from Kao) (both of which are di hardened tallow ester of triethanolammonium methylsulfate]) AT-1 (Di [ tallow ] ester of triethanolammonium methylsulfate]) And L5/90 (di [ palmityl ester of triethanolammonium methylsulfate)]) (both from Kao), and Rewoquat^TMWE15 (with C-derived)₁₀-C₂₀And C₁₆-C₁₈Diester of triethanolammonium methylsulfate of fatty acyl residues of unsaturated fatty acids) (from Evonik). Also suitable are soft quaternary ammonium actives such as StepantexVK90, Stepantex VT90, SP88 (from Stepan), Ceca Noramine, Prapagen TQ (from Clariant), Dehyquat AU-57 (from Cognis), Rewoquat WE18 (from Degussa) and Tetranyl L190P, Tetranyl L190 SP and Tetranyl L190S (both from Kao).

A second group of QACs suitable for use in the method of the present invention is represented by formula (II):

wherein each R¹The groups are independently selected from C_1-4Alkyl, hydroxyalkyl or C_2-4An alkenyl group; and wherein each R²The groups are independently selected from C_8-28An alkyl or alkenyl group; and wherein n, T and X are as defined above.

Preferred materials of this second group include 1, 2-bis [ tallowoyloxy ] -3-trimethylammonium chloropropane, 1, 2-bis [ hardened tallowoyloxy ] -3-trimethylammonium chloropropane, 1, 2-bis [ oleoyloxy ] -3-trimethylammonium chloropropane and 1, 2-bis [ stearoyloxy ] -3-trimethylammonium chloropropane. Such materials are described in US 4,137,180(Lever Brothers). Preferably, these materials also contain a certain amount of the corresponding monoester.

A third group of QACs suitable for use in the present invention is represented by formula (III):

(R¹)₂-N⁺-[(CH₂)_n-T-R²]₂X^-(III)

wherein each R¹The groups are independently selected from C_1-4Alkyl, hydroxyalkyl or C_2-4An alkenyl group; and wherein each R²The groups are independently selected from C_8-28An alkyl or alkenyl group; and n, T and X are as defined above. Preferred materials of this third group include bis (2-tallowoyloxyethyl) dimethylammonium chloride and hardened forms thereof.

The iodine value of the quaternary ammonium fabric softening material is preferably from 0 to 80, more preferably from 0 to 60, most preferably from 0 to 45. The iodine number may be selected as desired. Soft, hard or partially hardened materials are suitable for use in the method of the invention.

The iodine value used in the context of the present invention relates to the fatty acids used to produce the QAC, and the measurement of the unsaturation present in the material is by methods such as NMR spectroscopy as described in anal. chem.,34,1136(1962) Johnson and Shoolery.

Another class of softening compounds can be non-ester quaternary ammonium materials represented by formula (IV):

wherein each R¹The groups are independently selected from C_1-4Alkyl, hydroxyalkyl or C_2-4An alkenyl group; each R²The groups are independently selected from C_8-28An alkyl or alkenyl group; and X is as defined above.

The total amount of fabric softening active present in the fabric conditioning composition may be from 1 to 40 wt%. The active agent content is preferably at least 3 wt.%, more preferably at least 4 wt.%. More preferably, the total amount of surfactant is from 2 to 25 wt%, preferably from 4 to 18 wt%.

The concentration of fabric conditioning agent in water is preferably from 10 to 100g of fabric conditioning composition per 1 litre of water, more preferably from 20 to 75g of fabric conditioning composition per 1 litre of water, most preferably from 30 to 60g per litre of water.

When comparing two or more sheets or sections of absorbent material, depending on the variables evaluated by the method, the second and any successive sheets or sections of absorbent material may optionally be dipped into:

-the same concentration of fabric conditioning composition as the absorbent material of the first sheet or section;

-a different concentration of the same fabric conditioning composition as the absorbent material of the first sheet or section;

-the same concentration of a fabric conditioning composition different from the absorbent material of the first sheet or section; or

-water.

Alternatively, the absorbent material of the comparative sheet or section may not be subjected to step b) of the method. The comparator can be immersed in water containing the detergent composition and then the cationic dye applied without an intermediate step.

Step c) applying a cationic dye

Cationic dyes are dyes that can dissociate in aqueous solution into positively charged ions. The dye may be of any color. Examples of classes of cationic dyes include, but are not limited to: azo dyes, triarylmethane dyes, anthraquinone dyes, heterocyclic compounds, methine (methane) dyes, trisdiphenylmethane dyes, and azomethine (azomethine) dyes.

Examples of cationic dyes include, but are not limited to: methylene blue, crystal violet, methyl violet, safranin O, bismark brown Y, toluidine blue, thionine, azure A, B or C. Particularly preferably, for transparency results, the cationic dye is toluidine blue.

The dye is preferably in aqueous solution. The concentration of the dye in the aqueous solution is preferably 1X 10^-9To 1X 10^-3Wt.%, more preferably 1X 10^-8To 1X 10^-4Wt.%, most preferably 1X 10^-7To 1X 10^-5And (3) weight percent. When two or more sheets or sections of absorbent material are used in the process, the same concentration of cationic dye should be applied to both.

The dye may be applied by any suitable method. Non-limiting examples of suitable methods include dipping, spraying, or dripping (e.g., with a pipette). Preferably, the absorbent material is sprayed with or immersed in an aqueous solution of the cationic dye.

When two or more sheets of absorbent material are used in the process, the same amount of cationic dye should be applied to two or all sheets or sections of absorbent material. For example, if the absorbent material is immersed in an aqueous solution of the dye, each sheet or segment should be immersed for the same period of time. If a cationic dye is sprayed, the same amount of spray should be sprayed directly onto the absorbent material of each patch or section.

Step d) evaluation of the color

The color evaluation can be performed visually or using a suitable device.

The visual evaluation may be performed, for example, by comparing the color of two differently treated sheets of absorbent material. Alternatively, the visual assessment may be made by comparison to a colorimetric chart or any other such reference point.

The evaluation by means of a suitable device can be carried out, for example, using a spectrometer, for example a spherical spectrophotometer.

Preferably, the evaluation method is visual inspection.

Visual comparison between two or more sheets of absorbent material may be improved by placing the two or more sheets of absorbent material on a dark surface.

The darker the color of the dye on the fabric, the less the absorbent material is neutralized. This indicates the presence of residues that can cause skin irritation. The lighter the dye is on the fabric, the less residue.

Absorbent material

The absorbent material may be of any size or shape. The absorbent material may be a sheet of fabric (sheet) or a three-dimensional article such as a sponge. The absorbent material may be in any shape, and it may be preferred that the absorbent material is in the shape of an article of clothing, such as a T-shirt, a pair of trousers, a jersey (jumper), an undergarment, a shirt, a dress, etc. This provides a method by which the consumer can distinguish.

The absorbent material may be any material or mixture of materials, however, for best results, the material is preferably a synthetic material. When the absorbent material is a sheet of fabric, more preferably the material is selected from: acrylic, polyester, or nylon. Most preferably, the material is polyester, and the effect is particularly pronounced when polyester is used. When the absorbent material is a three-dimensional article, the material is preferably a polyurethane sponge.

When making a comparison, two or more pieces or sections of absorbent material will be used. A comparison may be made between the materials of two separate sheets or more separate sheets that have been treated differently, or a comparison may be made between different sections of absorbent material of the same sheet that have been treated differently.

Preferably, when comparing between two different compositions, the absorbent materials of the two pieces or sections are the same material, however, if it is desired to compare the effect of detergent in fabric conditioner and on different types of fabrics, two different types of materials may be used.

If the sheet of absorbent material is a web, it will have a height and a width. If the sheet of absorbent material is three-dimensional, it will have a height, width and depth. A sheet of absorbent material may have a wide variety of shapes that do not have a noticeable height, width, or depth. Thus, the height is considered to be the largest dimension in the y-direction, the width is considered to be the largest dimension in the x-direction, and the depth is considered to be the largest dimension in the z-direction. Preferably, the height, width and, in the relevant case, the depth are between 1cm and 100cm, preferably between 5cm and 50cm, most preferably between 8cm and 25 cm.

If a comparison is made between two sheets of absorbent material, it is preferred that the sheets of absorbent material have substantially the same dimensions, i.e. the difference in height between the two sheets of absorbent material is less than 10cm, the difference in width between the two sheets of absorbent material is less than 10cm, and in the relevant case the difference in depth between the two sheets of absorbent material is less than 10 cm. More preferably, the difference in each dimension is less than 5cm, most preferably less than 2 cm. In a most preferred embodiment, the sheets of absorbent material are of the same size, i.e. have the same dimensions.

Preferably, the absorbent material should have the same color as the color on which the dye is detectable. For example, the value of L should preferably be between 60 and 100, more preferably between 75 and 100, even more preferably between 85 and 100, most preferably between 92 and 100. The value of L may be measured using a spectrometer, such as a spherical spectrophotometer.

L axis represents brightness. This is vertical; 0 from the bottom, which has no brightness (i.e., absolute black); through the middle 50 to the top 100, which is the maximum brightness (i.e., absolute white).

Additional method steps

Although the claimed method describes two sheets or sections of absorbent material, it is not intended to exclude a third and consecutive sheet or section treated according to the method steps and compared to the first two.

In each of steps a), b) and c), the immersion in the liquid composition may be for any period of time, i.e. the piece of absorbent material may simply be dipped in the liquid or may be left to soak. When two or more sheets or sections of absorbent material are used in the process, they are preferably immersed in the respective steps for the same time period, i.e. both are immersed in step a) for the x time period, both are immersed in step b) for the y time period and both are immersed in step c) for the z time period. The immersion times (i.e., time periods x, y, and z) for the different steps may be the same or different. For example, time periods x, y, and z may each be 1 minute, or x may be 5 minutes, y may be 1 minute, and z may be 10 seconds.

In each of steps a), b) and c), the sheet of absorbent material may be agitated in the liquid composition.

Between each of steps a) to d), the sheet of absorbent material may be squeezed or ring pressed (crushing out) to remove excess liquid. For example:

-between steps a) and b), pressing one or more pieces of absorbent material to remove excess liquid

-between steps b) and c), pressing one or more pieces of absorbent material to remove excess liquid

-between steps c) and d), pressing one or more pieces of absorbent material to remove excess liquid

Method steps a) to d) can be carried out on a sheet of absorbent material. Alternatively, method steps a) to d) may be performed on two or more pieces or sections of absorbent fabric and a comparison made between them.

Preferably, if the process is carried out on more than one piece or section of fabric, the resulting color of the absorbent material of two or more pieces or sections may be compared. When testing multiple pieces or sections of absorbent material, the process may be performed sequentially or simultaneously, preferably simultaneously.

When comparing two or more pieces or sections of absorbent material, the method can be used to test the neutralization of fabric conditioners in a number of different ways. For example, by varying the type or concentration of the laundry detergent in step a) and keeping the type and concentration of the fabric conditioner the same in step b), the effectiveness of the fabric conditioner can be compared for different laundry detergents or different concentrations of laundry detergent.

Alternatively, by keeping the type and concentration of the laundry detergent the same in step a), the effect of using fabric conditioner versus no fabric conditioner, a different type of fabric conditioner, or a different concentration of fabric conditioner can be evaluated.

Preferably, when comparing two or more pieces or sections of absorbent material, each respective step a) involves the same laundry detergent composition at the same concentration, the pieces of absorbent material being immersed for the same period of time.

Preferably, in step b), a first sheet or section of absorbent material is immersed in the fabric conditioner composition and a second sheet or section of absorbent material and a continuous sheet or section are immersed in:

-water; or

-water comprising the same fabric conditioner composition as used for the first sheet of fabric, but in a different concentration; or

-water comprising the same concentration of fabric conditioner composition as used for the first piece of fabric, but a different fabric conditioner composition;

-or untreated.

Preferably, the absorbent material of each sheet or segment is immersed for the same period of time.

Most preferably, the second and continuous sheets or lengths of absorbent material are immersed in water or water containing the same concentration of a different fabric conditioning composition.

Use of the method

The method of the present invention can be used to demonstrate the use of fabric conditioners and laundry detergent residues. In particular, the neutralizing effect of fabric conditioners is associated with a reduction in skin irritation caused by laundry detergents.