This invention relates to fabric softening compositions and, in particular, to compositions in aqueous medium having improved softening effectiveness combined with excellent physical characteristics, especially formulation stability.

Conventional rinse-added fabric softening compositions contain fabric softening agents which are substantially water-insoluble cationic materials usually having two long alkyl chains. Typical of such materials are distearyl di-methyl ammonium chloride and imidazolinium compounds substituted with two stearyl groups. These materials are normally prepared in the form of an aqueous dispersion or emulsion, and it is generally not possible to prepare such aqueous dispersions with more than about 6% of cationic material without taking special precautions to ensure acceptable viscosity and stability characteristics. Indeed, with cationic levels in excess of about 8% the problems of physical instability and high viscosity become, in the case of conventional fabric softening products, almost intractable. This, of course, limits the level of softening performance achievable with conventional compositions without using excessive amounts of product, and also adds substantially to distribution and packaging costs, because of the need to market such dilute solutions of the active ingredient.

One approach which has been taken to improve the softening performance of cationic fabric softeners has been via the incorporation of certain fatty or oily materials in the softener active system. While these adjunct materials have little intrinsic softening capability in their own right, they are apparently effective in extending the performance of conventional cationic softening materials, both in concentrated and normal softener compositions so that the cost-effectiveness of these compositions is considerably improved. Moreover, by incorporating relatively high proportions of the oily adjunct materials in relation to the cationic softener, and by adding thereto relatively high proportions of a water-soluble cationic surfactant in relation to the cationic softener, concentrated softening compositions can be prepared containing a high total level of active softening materials. Reference is made to published European Patent Application No. 0000406 and Belgian Patent No. 868934 (equivalent to DE-A 2830 173) both of which are relevant to this general approach. Note also BE-A 871 431 which relates to water-free liquid fabric softener concentrates incorporating oily materials and to dilute aqueous softener compositions prepared there from.

Formulations prepared in this manner, however, are still not entirely satisfactory. Thus, while such compositions do allow a high concentration of active ingredient, the level of softness benefit delivered by such compositions on a unit active weight basis is still much lower than for conventional dilute products and problems of physical formulation characteristics, especially phase stability and also viscosity, still remain. In particular, an important limitation of the prior art compositions is the difficulty in meeting simultaneous product stability and viscosity characteristics. Indeed, phase stability remains a problem even in the case of dilute softener compositions formulated in the manner of the above prior art references.

Other approaches have also been taken for improving the physical characteristics of softener compositions of course. Thus, it is generally known (for example in U.S. Patent No. 3 681 241 ) that the presence of ionizable salts in concentrated compositions do help reduce viscosity, but these materials do not offer the additional benefit of enhancing the softening performance of the compositions. More importantly, the quantity of ionizable salts required for significant viscosity reduction is found to be generally deleterious in terms of product stability. Dutch patent application No. 6706178 (NL-A 6706178) relates to viscosity control in fabric softening compositions with up to 12% of cationic softener, and suggests the use of low molecular weight hydrocarbons for this purpose, while German patent application No. 2503026 (DE-A 2503026) discloses a complex softener/disinfectant composition in which a long chain fatty alcohol is suggested as a solubilization aid. Finally, U.S. Patent No. 3 793 196 describes an improved viscosity softening agent in the form of an oil-inwater emulsion comprising a cationic surface-active agent, a higher fatty alcohol, a sobitan fatty acid ester and a polyethoxylated nonionic surfactant.

The present invention accordingly provides a fabric softening composition having improved softening characteristics and cost-effectiveness combined with excellent physical characteristics, especially phase stability, freeze-thaw behaviour and low viscosity; and it further provides a concentrated fabric softening composition having satisfactory characteristics for consumer use, based on cationic fabric softener as the major active component.

According to the present invention, there is provided an aqueous fabric softening composition comprising:

• (a) from 6% to 22% by weight of a water-insoluble cationic fabric softener,
• (b) up to 8% by weight of a water-soluble cationic or nonionic surfactant or mixture thereof, and
• (c) a C_lo-C₄₀ non-cyclic hydrocarbon, or a mixture thereof with a fatty acid ester of a monohydric alcohol, said ester having a total of 10 to 40 carbon atoms,

wherein the weight ratio of (a) to (b) is in the range from 20:1 to 5:2, and the weight ratio of (a) to (c) is in the range from 8:1 to 2:1.

The physical form of the composition is that of a dispersion of an anisotropic softener phase in an aqueous isotropic surfactant solution phase. The physical form is simply determined under a polarizing microscope. The anisotropic/isotropic phase system is highly important for achieving optimum viscosity, stability, softening and other textile benefits.

The water insoluble cationic fabric softener is preferably a di-C₁₂-C₂₄ alkyl or alkenyl 'onium salt, especially a mono- or polyammonium salt, an imidazolinium salt or a mixture of such salts. Highly preferred are mono-quaternary ammonium salts, imidazolinium salts and mixtures thereof.

The water-soluble cationic surfactant is preferably a mono-C_8-24 alkyl or alkenyl 'onium salt, especially a mono- or polyammonium salt, an imidazolinium salt, a pyridinium salt or a mixture of such salts. Highly preferred are mono-quaternary ammonium salts, imidazolinium salts and mixtures thereof.

The preferred water-soluble nonionic surfactant has the general formula RO(CH₂CH₂0)_nH wherein R is a C_8-20 alkyl or alkenyl group, and n is from 2 to 100.

From the point of view of optimum product stability and viscosity and softening performance, the weight ratio of water-insoluble cationic to water-soluble cationic and/or nonionic surfactant, falls preferably in the range from 20:1 to 4:1, especially from 15:1 to 6:1. The weight ratio of the cationic softener to the hydrophobic adjunct, on the other hand, falls in the range from 8:1 to 2:1. In terms of level, compositions of the invention preferably comprise up to 6% of the water-soluble cationic and/or nonionic surfactant, up to 6% of the non-cyclic hydrocarbon and from 0% to 6% of the fatty acid ester.

In the present specification, percentage figures given for components in a composition refer to the weight percent of that component in the composition.

With regard to the hydrophobic adjunct, highly preferred materials are C₁₂-C₂₄, especially C₁₂-C₂₀ paraffins or paraffin mixtures and mixtures thereof with esters of C₁₂-C₂₄ fatty acids with monohydric alcohols having from 1 to 8 carbon atoms in a 3:1 to 1: weight ratio.

At higher concentrations of water insoluble cationic softener, greater than 12% by weight, it is desirable to include relatively high levels of water-soluble surfactant in relation to the insoluble softener. Thus, there are two highly preferred executions:

• (A) A composition comprising:
  • (a) from 6% to 12% by weight of a water-insoluble cationic fabric softener which is a mixture of:
    • (i) a di-C₁₂-C₂₄ alkyl or alkenyl mono-quaternary ammonium salt, and
    • (ii) a di-C,₂-C₂₄ alkyl or alkenyl imidazolinium salt,
    
    wherein the weight ratio of (i) to (ii) is in the range from 1:6 to 1:1,
  • (b) a water-soluble cationic surfactant which is:
    • (i) a mono-C₈-C₂₄ alkyl or alkenyl mono-quaternary ammonium salt,
    • (ii) a mono-C₈-C₂₄ alkyl or alkenyl imidazolinium salt, or
    • (iii) a mixture thereof, and
  • (c) a C₁₂-C₂₄preferably C₁₂-C₂₀ paraffin or paraffin mixture, wherein the weight ratio of (a) to (b) is in the range from 10.1 to 5.2, and the weight ratio of (a) to (c) is in the range from 5:1 to 5:2; and
• (B) A composition comprising
  • (a) from 12% to 22% of a water-insoluble di-C₁₂-C₂₄ alkyl or alkenyl imidazolinium salt,
  • (b) up to 8% of a water-soluble cationic surfactant which is:
    • (i) a mono-C₈-C₂₄ alkyl or alkenyl mono-quaternary ammonium salt,
    • (ii) a mono-C₈-C₂₄ alkyl or alkenyl imidazolinium salt, or
    • (iii) a mixture thereof, and
  • (c) at least 6% of a 3:1 to 1:3 mixture of:
    • (i) a C₁₂-C₂₄ preferably C₁₂-C₃₀ paraffin or paraffin mixture, and
    • (ii) an ester of a C₁₂-C₂₄ fatty acid with a C₁-C₈ monohydric alcohol,

Compositions of the invention thus comprise three essential ingredients, a water-insoluble cationic fabric softener, a water-soluble cationic and/or nonionic surfactant and a hydrophobic adjunct selected from C₁₀-C₄₀ non-cyclic hydrocarbons and mixtures thereof with specified fatty acid esters, the water soluble surfactant and the hydrophobic adjunct acting in combination to provide compositions of optimum viscosity and stability. The essential components will now be discussed in detail.

The water-insoluble cationic fabric softener can be any fabric-substantive cationic compound which, in pure form as a strong acid salt (e.g. chloride), has a solubility in distilled water at pH 2.5 and 20°C of less than 1 g/I, or can be a mixture of such compounds. In this context, the soluble fraction of the surfactant is taken to be that material which cannot be separated from water by centrifugal action and which passes a 100 nm Nuclepore filter (Registered Trade Mark). Preferred materials are di-C₁₂-C₂₄ alkyl or alkenyl 'onium salts, especially mono- and poly-ammonium salts, and imidazolinium salts. Optionally, the two long chain alkyl or alkenyl groups may be substituted or interrupted by functional groups such as -OH, -O-, CONH-, -COO-, etc.

Well known species of substantially water-insoluble mono-ammonium compounds are the quaternary ammonium compounds having the formula: wherein R₁ and R₂ represent alkyl or alkenyl groups of from 12 to 24 carbon atoms; R₃ and R₄ represent alkyl, alkenyl or hydroxyalkyl groups containing from 1 to 4 carbon atoms; and X is the salt counteranion, preferably selected from halide, methyl sulfate and ethyl sulfate radicals. Representative examples of these quaternary softeners include ditallow dimethyl ammonium chloride; ditallow dimethyl ammonium methyl sulfate; dihexadecyl dimethyl ammonium chloride; di(hydrogenated tallow alkyl) dimethyl ammonium chloride; dioctadecyl dimethyl ammonium chloride; dieicosyl dimethyl ammonium chloride; didocosyl dimethyl ammonium chloride; di(hydrogenated tallow) dimethyl ammonium methyl sulfate; dihexadecyl diethyl ammonium chloride; di(coconut alkyl) dimethyl ammonium chloride and di(coconut alkyl) dimethyl ammonium methosulfate. Of these ditallow dimethyl ammonium chloride and di(hydrogenated tallow alkyl) dimethyl ammonium chloride are preferred.

Another preferred class of water-insoluble cationic materials are the alkyl imidazolinium salts believed to have the formula: wherein R₆ is an alkyl containing from 1 to 4, preferably 1 or 2 carbon atoms, R₇ is an alkyl containing from 12 to 24 carbon atoms, R₈ is an alkyl containing from 12 to 24 carbon atoms, and Rg is hydrogen or an alkyl containing from 1 to 4 carbon atoms and X is the salt counter-anion, preferably a halide, methosulfate or ethosulfate. Preferred imidazolinium salts include 3-methyl-1-(tallowyl- amido)ethyl-2-tallowyl-4,5-dihydroimidazolinium methosulfate and 3-methyl-1-(palmitoylami- do)ethyl-2-octadecyl-4,5-dihydroimidazolinium chloride. Other useful imidazolinium materials are 2-heptadecyl_-3-methyl-1-(2-stearylamido)-ethyl-4,5-dihydroimidazolinium chloride and 2-lau ryl-3-hydroxyethyl-1-(oleylamido)ethyl-4,5-dihydroimidazolinium chloride. Also suitable herein are the imidazolinium fabric softening components of U.S. Patent No. 4127 489.

In the present invention, the water-insoluble cationic softener is present at a level of at least 6%. The overall aim is to adjust the levels of the softening and surfactant components within the prescribed limits to provide products which are stable to separation in a centrifuge at 3000 r.p.m. for 16 hours and which have a viscosity of less than 350 mPas, preferably less than 150 mPas measured in a Brookfield Viscometer, using Spindle No. 2 at 60 r.p.m. and at 21°C. The maximum level of cationic softener in the present formulations is determined by practical considerations; thus, above a cationic softener level of 22% the problems of physical stability and product viscosity are such that it is not generally possible to formulate stable pourable emulsions based on water-insoluble cationic softener as the major softening component.

The water-soluble surfactant is a cationic or nonionic surfactant having a solubility in distilled water at pH2.5 and 20°C of greater than 1 g/I. Once again, the solubility of the cationic surfactant is defined with reference to the pure material in the form of a strong acid salt (e.g. chloride), and the soluble fraction of the surfactant is taken to be that material which cannot be separated from water by centrifugal action and which passes a 100 nm Nuclepore filter.

Preferred water-soluble cationic surfactants are mono-C_B-C₂₄ alkyl or alkenyl ammonium salts, imidazolinium salts, pyridinium salts and mixtures thereof.

Suitable water-soluble mono-ammonium compounds have the general formula: wherein R₅ represents a C_a-C₂₄ alkyl or alkenyl group, R₆ represents hydrogen, a C₁-C₁₂ alkyl, alkenyl or hydroxyalkyl group, an aryl group, a C_1-6 alkylaryl group, or a poly(ethylene oxide) group having from 2 to 20 ethylene oxide units, R₇, R₈ individually represent hydrogen, a C₁-C₄ alkyl, alkenyl or hydroxyalkyl group or a poly(ethylene oxide) group having from 2 to 20 ethylene oxide units and X is as defined above.

Highly preferred materials of this general type include the tallow trimethyl ammonium salts, cetyl trimethyl ammonium salts, myristyl trimethyl ammonium salts, coconutalkyl trimethyl ammonium salts, stearyl dimethyl ammonium salts, cetyl dimethyl ammonium salts, myristyl dimethyl ammonium salts, coconutalkyl dimethyl ammonium salts, oleyl methyl ammonium salts, palmityl methyl ammonium salts, myristyl methyl ammonium salts, lauryl methyl ammonium salts, dodecyl dimethyl hydroxyethyl ammonium salts, dodecyl dimethyl hydroxypropyl ammonium salts, myristyl dimethyl hydroxyethyl ammonium salts, dodecyl dimethyl dioxyethylenyl ammonium salts, myristyl benzyl hydroxyethyl methyl ammonium salts, coconutalkyl benzyl hydroxyethyl methyl ammonium salts, dodecyl dihydroxyethyl methyl ammonium salts, cetyl dihydroxyethyl methyl ammonium salts, and stearyl dihydroxyethyl methyl ammonium salts.

Highly preferred water-soluble imidazolinium materials are represented by the general formula or acids salts thereof, wherein R₆, R₇, R₈, R₉ and X were defined earlier. Preferred imidazolinium salts of this general formula include the compound in which R₆ is methyl, R₈ is tallowyl and Rg is hydrogen and the compound in which R₆ is methyl, R₈ is palmitoyl and R₉ is hydrogen.

Highly preferred water-soluble polyammonium 20 cation materials are represented by the general formula: wherein R₁₁ is selected from an alkyl or alkenyl group having from 12 to 24, preferably from 16 to 20 carbon atoms in the alk(en)yl chain, R₁₁CO-and R₁₁-O-(CH₂)_n-; each R₁₀ is independently selected from hydrogen, -(C₂H₄O)_pH, -(C₃H₆O)_qH, -(C₂H₄O)_r(C₃H₆O)_sH, a C_1-3 alkyl group and the group -(CH₂)_n-N(R')2, wherein R_' is selected from hydrogen, -(C₂H₄0)_PH, -(C₂H₄0)p(C₃H₆0)qH and C_1-3 alkyl; n is an integer from 2 to 6, preferably 2 or 3; m is an integer from 1 to 5, preferably 1 or 2; p, q, r and s are each a number such that the total p + q + r + s in the molecule does not exceed 25 (preferably, each p and q is 1 or 2 and each r and s is 1); and X represents one or more anions having total charge balancing that of the nitrogen atoms.

Preferred water-soluble cationic materials are alkoxylated and contain not more than one -C₂H₄0H or -C₃H₆OH group attached to each nitrogen atom, except that up to two of these groups can be attached to a terminal nitrogen atom which is not substituted by an alkyl group having from 10 to 24 carbon atoms.

Polyamine species suitable for use herein include:

• N-tallowyl,N,N' N' -tris(2-hydroxyethyl) 1,3-propanediamine di-hydrochloride or dibenzoate; N-soybean alkyl 1,3-propane diammonium sulfate;
• N-stearyI,N,N'-di(2-hydroxyethyl)-N'-(3-hydroxypropyl)-1,3-propanediamine dihydrofluoride;
• N-cocoyl-N,N,N',N',N'-pentamethyl-1,3-propane diammonium dichloride or di-methosulfate;
• N-oleyl N,N',N'-tris (3-hydroxypropyl)-1,3-propanediamine dihydrofluoride;
• N-stearyl N,N',N'-tris(2-hydroxyethyl) N,N_'- dimethyl-1,3-propanediammonium dimethylsulfate;
• N-palmityl N,N',N'-tris(3-hydroxypropyl)-1,3-propanediamine dihydrobromide;
• N-(stearyloxypropyl) N,N',N'-tris(3-hydroxypropyl)1,3-propanediammonium diacetate;
• N-tallowyl N-(3-aminopropyl)1,3-propanediamine trihydrochloride;
• N-oleyl N-[1 N",N" bis(2-hydroxyethyl)3-aminopropyl]N',N'-bis(2-hydroxyethyl)1,3-diaminopropane trihydrofluoride;
• N-tallowyl diethylene triamine trihydrochloride.

The water-soluble cationic surfactant herein can also be represented by alkyl pyridinium salts having the following formula: wherein R₁₂ is a C₁₀-C₂₄, preferably C₁₆ or C₁₈ alkyl radical and X is a suitable anion as defined hereinbefore, preferably a halide, especially chloride or bromide.

It should be understood, of course, that water-soluble cationic surfactants of the amine-salt class can be added in the form of the neutral amine followed by pH adjustment to within the range from pH4to pH8.

The hydrophobic adjunct is selected from non-cyclic hydrocarbons and mixtures thereof with fatty acid esters of monohydric alcohols, each component having a total of from 10 to 40 carbon atoms. The hydrophobic adjunct is present in an amount relative to the insoluble cationic softener and the water-soluble cationic and/or nonionic surfactant, to provide a dispersion of anisotropic softener phase in isotropic aqueous surfactant phase.

The first class of hydrophobic adjunct is represented by non-cyclic hydrocarbons having from 10 to 40, preferably from 12 to 24, more preferably from 12 to 20 carbon atoms.

Preferably, hydrocarbons useful in the present invention are paraffins or olefins, but other materials, such as alkynes and halo-paraffins, for example myristyl chloride or stearyl bromide, are not excluded. Materials known generally as paraffin oil, soft paraffin wax and petrolatum are especially suitable. Examples of specific materials are tetradecane, hexadecane, octadecane and octadecene. Preferred commercially-available paraffin mixtures include spindle oil and light oil and technical grade mixtures of C_14/C_l7 and C₁₈/C₂₀ n-paraffins.

The second class of hydrophobic adjunct is represented by fatty acid esters having a total of 10 to 40 carbon atoms. Preferred materials are esters of C_S-C₂₄ fatty acids with mono-hydric alcohols having from 1 to 8, especially from 1 to 4 carbon atoms.

The mono-hydric alcohol portion of the ester can be represented by methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, t-butanol, 2-ethyl-hexanol and iso-octanol.

Examples of such materials are methyl laurate, ethyl stearate, isopropyl myristate, isopropyl pal- mitate, iso-butyl stearate, isopropylstearate, 2-ethylhexyl laurate and isooctyl myristate. Of the above, iso-butyl stearate is highly preferred.

Of all the above, paraffins having from 12 to 20 carbon atoms constitute the preferred adjunct. However, mixtures of paraffins and fatty acid esters in a 3:1 to 1:3 weight ratio are also effective.

Apart from enhancing the phase stability of the composition, the hydrophobic adjunct acts to lower the viscosity of the composition and because each of the materials has a long fatty chain, the agent does contribute to some extent to the softening performance of the composition, a feature which is not shared by other known viscosity control agents, for example electrolytes and low molecular weight solvent materials. Compositions of the present invention also have enhanced dispersibility in cold water and exhibit less dispenser residues than conventional fabric softening composition based solely on a cationic fabric softener.

In addition to the above-mentioned components, the compositions may contain other textile treatment or conditioning agents. Such agents include silicones, as for example described in DE-A2631419.

The optional silicone component can be used in an amount of from 0.1% to 6%, preferably from 0.5% to 2% of the softener composition.

A further optional component of the present composition is a fatty acid ester of a polyhydric alcohol, for instance a C₁₂-C₂₂ fatty acid ester of ethylene glycol, propylene glycol, glycerol, diglycerol, xylitol, sucrose, erythritol, pentaerythritol, sorbitol or sorbitan. These esters, specific examples of which include ethyleneglycol monostearate, propyleneglycol monostearate, glyceryl monostearate and glyceryl distearate, can provide an additional softening facility. However, in as much as such fatty acid esters are relatively hydrophilic and indeed are emulsifying materials in their own right, it is desirable to include such materials in a level of no more than 4% by weight or in a weight ratio with respect to the cationic softener of no more than 2:3.

The compositions herein can contain other optional ingredients which are known to be suitable for use in textile softeners at usual levels for their known functions. Such adjuvants include emulsifiers, perfumes, preservatives, germicides, colorants, dyes fungicides, stabilizers, brighteners and opacifiers. These adjuvants, if used, are normally added at their conventional low levels.

The composition of the invention can also comprise additional viscosity control agents, such as 1% to 10% of lower alcohols, especially ethanol and isopropanol, and electrolytes, for example calcium chloride, at levels of from 100 to 1000 ppm. It is a feature of the invention, however, that such materials can be reduced or eliminated completely from the instant compositions.

The compositions can normally be prepared by mixing the ingredients together in water, heating to a temperature of about 60°C and agitating for 5-30 minutes.

The pH of the compositions is generally adjusted to be in the range from 3 to 8, preferably from 4 to 6. In this preferred pH range, it will be understood that the neutralization of amines or polyamines in the composition can be incomplete.

When compositions of the present invention are added to the rinse liquor, a concentration from 10 ppm to 1000 ppm, preferably from 50 ppm to 500 ppm, of total active ingredient is appropriate.

The following examples illustrate the invention. In the Examples, the following abbreviations are used:

Concentrated liquid fabric softeners were prepared having the compositions indicated below, by dispersing the active ingredients in water at about 60°C.

The above compositions had good phase stability, low viscosity, good dispersibility and excellent softening characteristics compared with compositions containing no hydrophobic adjunct or no water-soluble cationic or nonionic surfactants or with compositions in which the active system contains a major proportion of hydrophobic adjunct and/or soluble surfactant.

Concentrated fabric softeners were prepared in analogous manner with the compositions indicated below.

The above composition was a stable dispersion with low viscosity, good dispersibility and excellent softening characteristics compared with compositions containing no hydrophobic adjunct or soluble surfactant or with compositions in which the active system contains a major proportion of the hydrophobic adjunct and/or soluble surfactant.