GB2266100A - Fabric softening compositions - Google Patents

Abstract

A fabric softening composition which comprises more than 2 wt% of a cationic fabric softener, 0.5-5 wt% of a water soluble organic deposition agent and being substantially free from anionic detergent active.

Description

FABRIC CONDITIONING COMPOSITION This invention relates to a fabric conditioning composition which is substantially free of anionic detergent and is particularly suitable for the conditioning (e.g. softening) of fabrics in the rinse step of a fabric laundering process. The invention particularly relates to softening in the presence of anionic detergent carried over from the washing step of the fabric laundering process.

It is known to add fabric conditioning agents comprising cat ionic materials such as quaternary ammonium salts or imidazolinium salts to the rinse step of a fabric laundering process. As a result of the use of anionic materials for soil removal from fabrics in a preceding wash step, anionic materials find their way into the rinse water. This problem is common in countries where water is used sparingly and will become more common as machine manufacturers move to lower water consumption machines for increased energy efficiency. Anionic 'carry-over' can have disadvantageous effects on cat ionic fabric softening materials added to the rinse water. The anionic and cationic materials react together to form a neutral complex and thereby to reduce the quantity of cat ionic charged material available for deposition on the wash load.

Several proposals have been made to solve this problem.

GB 2039 556 discloses the use of a soluble monoalkyl quaternary ammonium salt in conjunction with the more usual dialkyl softening quaternary. Unfortunately the benefit of this solution is small relative to the increased formulation cost.

A second solution, which also seeks to providesincreased cationic charge to neutralise the anionic, is described in US 4179382. This patent specification suggests that use of cationic polymers which provide a high density of positive charge will improve softening performance. The problem with such polymers is that they give rise to product stability problems when used at high enough levels to be of practical use and they are uneconomic.

EP 063 899 suggests a different approach. An inorganic polymer such as aluminium chlorohydrate precipitates metal hydroxide or hydrated oxide at a pH of less than 7.5. The precipitate is said to facilitate deposition of the softener. The disadvantage of this solution is that the inorganic polymer has to be used at very high levels (12.5 to 37.5% of the cationic level) to be effective. This makes it unattractive from an economic and an environmental viewpoint.

GB 2 195 652 teaches that anionic/cationic complexes provide a softening effect when deposited on fabric. The problem with such complexes is that they need to preformed and administered in special ways if grease spot formulation is to be avoided. The extent of softening is also rather limited.

EP 426304 describes a rinse conditioner containing polysiloxane, a cellulose ether and an optional fabric softener material. Soap is the preferred fabric softener material and is deposited with the polysiloxane to give the softening effect.

According to the present invention there is provided a fabric softening composition comprising more than 2% of a cationic fabric softener and being substantially free from anionic detergent active, characterised in that the composition contains from 0.05 - 5% by weight of a watersoluble organic deposition agent. The deposition agent is advantageously nonionic and is preferably a cellulose ether having an HLB between 3.0 and 4.3, and a gel point of less than 580C, at least 95% of the cellulose ether containing no hydroxyalkyl groups having 3 or more carbon atoms.

The deposition agent is preferably present in an amount 0.1 - 2% by weight. The advantage of such a composition is that it may be used in rinse steps where there is anionic detergent active resulting from carry-over from the wash steps. In such circumstances the cationic reacts with the anionic to form a complex and the cellulose ether deposits the complex onto the fabric to give an improved deposition of softening agent and perfume delivery.

Preferably the composition contains more than 3.5% cationic fabric softener.

The cellulose ethers useful in the present invention are nonionic cellulose ethers, of which some or-all of the three hydroxyl sites per anhydroglucose ring of the polymer have been substituted with a nonionic substituent group.

Preferably the substituent groups are selected from the C2-C3 alkyl and -C2-C3 mono- or polyhydric hydroxy alkyl groups, or combinations thereof. Especially the use of alkyl and hydroxyalkyl substituted cellulose ethers are preferred. Most preferred are the use of ethyl and hydroxyethyl substituted cellulose ethers. The choice and percentage of substituent groups has a direct influence on the HLB value of the cellulose ether.

The useful substituted cellulose ethers are defined in part by their HLB. HLB is a well known measure of the hydrophilic-lyophilic balance of a material and can be calculated from its molecular structure.

A suitable estimation method for emulsifiers is described by J T Davies, 2nd Int Congress of Surface Activity 1957, I pp 426-439. This method has been adopted to derive a relative HLB ranking for cellulose ethers by summation of Davies's HLB assignments for substituent groups at the three available hydroxyl sites on the anhydroglucose ring of the polymer. The HLB assignments for substituent groups include the following: Residual hydroxyl 1.9 Methyl 0.825 Ethyl 0.350 Hydroxy ethyl 1.63 The cellulose ether derivatives useful herein are polymers which are water-soluble at room temperature. The gel point of polymers can be measured in a number of whys.In the present context the gel point is measured on a polymer solution prepared by dispersion at 60/700C and cooling to 200-250C at lOg/l concentration in deionised water. 50ml of this solution placed in a beaker is heated, with stirring, at a heating rate of approximately 5 C/minute.

The temperature at which the solution clouds is the gel point of the cellulose ether being tested and is measured using a Sybron/Brinkmann colorimeter at 80% transmission/450nm.

Provided that the HLB and gel point of the polymer fall within the required ranges, the degree of substitution (DS) of the anhydroglucose ring may be any value up to the theoretical maximum value of 3, but is preferably from about 1.7-2.9, there being a maximum of 3 hydroxyl groups on each anhydroglucose unit in cellulose. The expression 'molar substitution' (MS) is sometimes also used in connection with these polymers and refers the number of hydroxyalkyl substituents per anydroglucose ring and may be more than 3 when the substituents themselves carry further substituents.

The most highly preferred polymers have an average number of anhydroglucose units in the cellulose polymer, or weight average degree of polymerisation, from about 50 to about 1,200. For certain product forms, e.g. liquids it may be desirable to include polymers of relatively low degree of polymerisation to obtain a satisfactory product viscosity.

A number of cellulose ether derivatives suitable for use in the present invention are commercially available, as follows: Trade Name Gel Point HLB alkyl/hydroxyalkyl OC (Davies) BERMOCOLL CST035 35 3.40 ) 1.4 ethyl (ex Berol Nobel) ) 0.5 hydroxyethyl DVT 88004 37 3.11 ) 1.5 ethyl (ex Berol Nobel) )1.0 hydroxyethyl TYLOSE MHB 1000 54 3.52 ) 2.0 methyl (ex Hoechst) ) 0.1 hydroxyethyl A number of other cellulose ether derivatives are known from the prior art, but have been found to be unsuitable for use in the present invention. Thus, British Specification No.GB 2 038 353B (COLGATE-PALMOLIVE) discloses TYLOSE MH 300 (ex Hoechst) which has a gel point of 580C and METHOCEL XD 8861 (ex Dow Chemical Company, now coded METHOCEL HB12M) which contains about 0.1 hydroxybutyl substituents per anhydroglucose ring, while Japanese Patent Specification No. 59-6293 (LION KK) discloses KLUCEL H (ex Hercules Chemical Corp) which has an HLB of about 4.4, METHOCEL K4M (ex Dow Chemical Company) which has a gel point of about 690C, and NATROSOL 250H (ex Hercules Chemical Corp) which has an HLB of about 6.9.

Preferred cellulose ethers for use in compositions of the present invention have an HLB of between 3.3 and 3.8 and a gel point of between 30 and 560C. Especially preferred is the use of Bermocoll CST035.

The cationic fabric softener may be any suitable cationic surfactant which has fabric softening properties.

Suitable fabric softening materials and mixtures thereof are well known in the art, particularly from Schwartz, Perry and Berch, "Surface active Agents" (Vol I and II), from Davidson and Milwidsky, "Synthetic Detergents" John Wiley and Sons and "Household Industrial Fabric Conditioners" (Noyes Data Corporation).

Cat ironic materials which are most useful are quaternary ammonium salts, wherein at least one higher molecular weight group and two or three lower molecular weight groups are linked to a common nitrogen atom to produce a cation and wherein the electrically balancing anion is a halide, acetate or lower alkosulphate ion, such as chloride or methosulphate. The higher molecular weight substituent on the nitrogen is preferably a higher alkyl group, containing 12 to 18 or 20 carbon atoms, such as coco-alkyl, tallowalkyl, hydrogenated tallowalkyl or substituted higher alkyl, and the lower molecular weight substituents are preferably lower alkyl of 1 to 4 carbon atoms, such as methyl or ethyl, or substituted lower alkyl.One or more of the said lower molecular weight substituents may include an aryl moiety or may be replaced by an aryl, such as benzyl, phenyl or other suitable substituent. A preferred quaternary ammonium salt is a do higher alkyl, di-lower alkyl ammonium halide, such as di-tallowalkyl dimethyl ammonium chloride or dihydrogenated tallowalkyl dimethyl ammonium chloride, and other quaternary ammonium chlorides will also usually be preferred. For biodegradability the higher molecular weight group may be linked to the nitrogen atom via an ester group.

In addition to the cat ionic compounds previously mentioned, other suitable cationic surfactants include the imidazolinium salts, such as 2-heptadecyl-l-methy1-1-[(2- stearoylamido) ethyl]-imidazolinium chloride; the corresponding methyl sulphate compound; 2-methyl-1-(2hydroxyethyl)-l-benzyl imidazolinium chloride; 2-cQco-l- (2-hydroxyethyl)-l-benzyl imidazolinium chloride; 2-coco-1- (2-hydroxyethyl) -1-octadecenyl imidazolinium chloride; 2 heptadecenyl-l- (2-hydroxyethyl) -1- (4-chlorobutyl) imidazolinium chloride; and 2-heptadecyl-l- (hydroxyethyl) - l-octadecyl imidazolinium ethyl sulphate.Generally, the imidazolinium salts of preference will be halides (preferably chlorides) and lower alkylsulphates (alkosulphates).

Others of the mentioned quaternary ammonium salts and imidazolinium salts having fabric softening properties may also be employed in the present invention and various others of such compounds are described in U.S. Patent 4,000,077.

The fabric softening composition may also include other cationic fabric conditioning materials, such as cationic anti-static materials, and non-cationic fabric softening materials such as nonionic fabric softening materials.

When nonionic fabric softening materials are included, the weight ratio of the cationic fabric softening material to the nonionic fabric softening material should be at least about 1:1, preferably at least about 3:1. The fabric softening composition may also include fatty acid.

The fabric conditioning compositions according to the invention may be in liquid or granular solid form.

When in liquid form, the product may be in the form of a dilute rinse conditioner (containing say up to about 10% by weight total active material) or in concentrated form.

Suitable formulations for concentrated rinse conditioners will include viscosity control agents such as are disclosed in GB 2 053 249 (Unilever Limited) wherethe compositions contain materials such as polyethylene glycol and US 4 149 978 (Goffinet assigned to Procter & Gamble Company) where the compositions contain hydrocarbons, these disclosures being incorporated herein by reference.

An alternative viscosity control agent is lanolin.

In dilute liquid fabric softening compositions the concentration of the fabric conditioning agent may be from about 0.5% to about 10% by weight, preferably from about 1.5% to about 10 by weight. In concentrated liquid fabric softening compositions the concentration of the fabric softening agent may be from about 10% to about 60% by weight, preferably from about 10% to about 50% by weight.

When in liquid form, the fabric softening composition will contain, in addition to the fabric conditioning agent and the cellulose ether a liquid carrier such as an aqueous base which may consist only of water or of a mixture of water with other materials such as those referred to below.

The pH of the products of the invention may lie between about 3 and about 10, although products having a pH about 2 and about 3 are also possible. Suitable products can be prepared having a pH between about 3 and about 6. On dilution in the rinse liquor the pH will generally change to about 6 to about 8.

The compositions according to the invention may further include materials conventionally added to fabric conditioning compositions such as buffering agents, organic solvents, emulsifiers, colouring materials, bactericides, antioxidants, perfumes, perfume carriers, bleaches and hydrotropes.

When the fabric softening composition is in solid eg granular form, it may be prepared either by dry bleaching the ingredients or by adsorbing the ingredients on a solid carrier, such as silica. Alternatively the composition may be formed in to a slurry which is subsequently spray dried.

The compositions 'of the present invention may be prepared by a variety of methods. One suitable method, in the case of dilute liquid fabric softening compositions, is to form a molten premix consisting of the fabric conditioning agent, water and optionally a solvent and adding the cellulose ester to this molten premix in the presence of sufficient water to give the desired dilution in the product.

The invention may be used to provide a softening effect in conjunction with any anionic detergent active or any detergent composition containing mixtures of anionic detergent active with other components, such as non-ionic detergents.

The invention'also comprises a method of rinse conditioning laundry items including the step of adding a fabric conditioning composition containing a cat ionic fabric softener and a water-soluble nonionic cellulose ether, having an HLB between 3.0 and 4.3 and a gel point of less than 580C, at least 95% of the cellulose ether containing no hydroxyalkyl groups having 3 or more carbon atoms, to a wash liquor containing the laundry items and anionic surfactant carried over from an earlier washing step.

The invention will now be described by way of example only and with reference to the following non-limiting examples.

In all examples the anionic used was Petrelab 550, an alkyl benzene sulphonate from Petresa.

Example 1 An ethyl hydroxyethyl cellulose ether with an ethyl substitution of 1.4 and a hydroxyethyl substitution of 0.5, gel point 350C was used in rinse conditioner compositions having the following formulations.

2HT = Arquad 2HT = 6.33% Prist= Pristerine 4916 = as indicated below Berm = Bermocoll CST035 = 0.2% if present.

Water = to 100% A wash liquor was prepared using 60FH US water. 40g standard 11 terry towelling monitors were washed in the liquor for 10 minutes in a laboratory scale "Tergo" apparatus using 2g of rinse conditioner (product) in 1 litre of liquor. The formulation contained varying levels of the hard tallow fatty acid Pristerine 4916 from Unichema. The cationic was Arquad 2HT a dihardened tallow dimethyl ammonium chloride from Akzo. In all cases a molar ratio of 1:1.5 cationic to anionic was used.

Articles washed in each formulation were ranked in softness against each other and against standards by an expert panel. The results are given below.

Pairs Comparison Total Scores (max 36) V Stds A 6.33% 2HT/Prist 1.58%/Berm 0.2% 25 9 B 6.33% 2HT/Prist 0.42%/Berm 0.2% 22 9 C 6.33% 2HT/Prist 0 /Berm 0.2% 25 9 D 6.33% 2HT/Prist 0.42%/Berm 0 0 11 It can be seen that compositions containing Bermocoll gave good softening with varying levels of fatty acid.

Claims (8)

1. A fabric softening composition comprising more than 2% of a cationic fabric softener and being substantially free from anionic detergent active, characterised in that the composition contains from 0.05 - 5% by weight of a water-soluble organic deposition agent.

2. A composition according to claim 1 in which the deposition agent is nonionic.

3. A composition according to claim 2 in which the deposition agent is a cellulose ether having an HLB between 3.0 and 4.3, and a gel point of less than 580C, at least 95% of the cellulose ether containing no hydroxyalkyl groups having 3 or more carbon atoms.

4. A composition according to any preceding claim in which the deposition agent is present in an amount 0.1 - 2% by weight.

5. A composition according to any precding claim in which the composition contains more than 3.5% cationic fabric softener.

6. A composition according to any preceding claim in which the weight ratio of deposition agent to cationic fabric softener lies in the range 1:4 to 1:50.

7. A composition according to any one of claims 3 to 8 in which the cellulose ether has an HLB of between

3.3 and 3.8 and a gel point of between 30 and 560C.

8. A method of rinse conditioning laundry items including the step of adding a fabric.conditioning composition containing a cat ionic fabric softener and a water-soluble nonionic cellulose ether, having an HLB between 3.0 and 4.3 and a gel point of less than 580C, at least 95% of the cellulose ether containing no hydroxyalkyl groups having 3 or more carbon atoms, to a wash liquor containing the laundry items and anionic surfactant carried over from an earlier washing step.