Fabric softening composition

Abstract

 An aqueous fabric softening composition comprises:

a) a water insoluble, quaternary ammonium material comprising at least one ester link and two C_12-28 alkyl or alkenyl groups, and

b) a nonionic stabilising agent present in an amount from 0.1 wt% to 2.5 wt% of the total composition

wherein the nonionic stabilising agent is a sucrose ester, the composition comprises an aqueous dispersion of the water insoluble quaternary ammonium material and the ratio of quaternary ammonium material to nonionic stabilising agent is in the range from 5:0.5 to 5:0.1.

Description

Field of the Invention

[0001] The present invention relates to a fabric softening composition, in particular the invention relates to aqueous dispersions of fabric softening compositions comprising a water insoluble quaternary ammonium material and a nonionic stabilising agent suitable as rinse-added fabric softener compositions.

Background of the Invention

[0002] Rinse added fabric softeners are known. Typically such compositions contain a water insoluble quaternary ammonium fabric softening agent dispersed in water at a level of softening agent up to about 7 wt%, in which case the compositions are considered dilute, or at levels from 7 wt% to 50 wt%, in which case the compositions are known as concentrates.

[0003] The viscosity of fabric softener may be seen by the consumer as an important attribute. For this reason thickening polymers are added to compositions, for example EP 0 331 237 (Unilever) discloses the use of hydrophobically modified nonionic cellulose ether for use as a thickener for fabric conditioning compositions containing quaternary ammonium cations.

[0004] There are however negative attributes associated with many polymeric thickeners in that they are not biodegradable, their addition to the rinse product is technically difficult and the viscosity of such polymer thickened products tends to increase with time.

[0005] In US 4 137 180 (Lever Brothers Company) discloses cationic di-esters of the formula

wherein R₁, R₂ and R₃ are each an alkyl or hydroxyalkyl group containing from 1 to 4 carbon atoms, or a benzyl group, R₄ and R₅ are each alkyl chains containing from 11 to 23 carbon atoms and X^- is a water soluble anion.

[0006] One of the problems associated with fabric softening compositions containing cationic di-esters as disclosed in US 4 137 180 is the physical instability of these compounds, the problem is exacerbated at temperatures above or below ambient.

[0007] EP 280 550 and EP 507 478 (Unilever) discloses the use of selected nonionic stabilising agents to overcome the poor stability. However we have found that many nonionic stabilising agents create a further problem in that their presence destroys the viscosity of these fabric softening compositions.

[0008] We have now found that selected nonionic stabilising agents do not destroy the viscosity of fabric softening compositions containing a biodegradable quaternary ammonium material.

Description of the Invention

[0009] Accordingly the present invention relates to a fabric softening composition comprising:

a) a water insoluble, quaternary ammonium material comprising one ester link and two C_12-28 alkyl or alkenyl groups;

b) a nonionic stabilising agent;

characterised in that the nonionic stabilising agent is a sucrose ester or an alkyl polyglucoside.

[0010] Further disclosed is a process for making a liquid fabric softening composition comprising the steps of selecting the following ingredients:

a) a water insoluble, quaternary ammonium material having at least one ester link and two C_12-28 alkyl or alkenyl groups;

b) a nonionic stabilising agent which is either a sucrose ester or an alkyl polyglucoside;

c) other optional ingredients;

mixing the ingredients whilst heating to form a melt, followed by dispersing the melt in hot water to give the rinse conditioner.

Detailed Description of the Invention

[0011] The present invention is a way of controlling the viscosity of a fabric conditioner composition containing a biodegradable quaternary ammonium material and a nonionic stabilising agent. Suitable nonionic stabilising agents include the sucrose esters such as sucrose distearate and sucrose monostearate, and the alkyl polyglucosides such as stearyl monoglucosides and stearyl triglucoside.

[0012] Without wishing to bound by theory, this invention is thought to operate in that the interaction of the hydrogen bonding elements of the molecules of the nonionic stabilising agent are essential to maintain a vesicular structure. A vesicular structure in the context of this invention can be defined as a spherical structure having onion ring shaped bilayers. The presence of such vesicular structures are an important factor in the formation of a composition with a commercially acceptable viscosity.

[0013] The preferred level of nonionic stabilising agent present is 0.1 to 2.5 % by weight.

[0014] Most preferred nonionic stabilising agents are the sucrose esters. The sucrose esters have the additional benefit that they impart additional softening benefits over the cationic softening agent. Examples of suitable sucrose esters include the Crodesta (Trademark (ex Croda)) series. Crodestas are sucrose esters esterified with 70/30 mixture of stearic/palmitic acid to form a mixes of mono-ester, di-ester and triester. According to the manufacturer the levels of mono-ester are as follows:

Trade Name	wt % monoester
Crodesta F10	3
Crodesta F20	10
Crodesta F50	29
Crodesta F70	56
Crodesta F110	52
Crodesta F140	57
Crodesta F160	75

[0015] We have found that these combination of mono-esters and di-esters and triesters of sucrose give particularly good softening benefits. Especially preferred are combinations of mono-ester, di-ester and triester that contain 56-75% monoester, in particular Crodesta F160, Crodesta F140, Crodesta 110 and Crodesta F70.

[0016] The fabric softening compound is suitably a substantially water insoluble quaternary ammonium material comprising a polar head group and two alkyl or alkenyl chains each having an average chain length greater than or equal to C₁₄, and at least one ester group.

[0017] Preferably the fabric softening compound of the invention has two long chain alkyl or alkenyl chains, each having an average chain length greater than or equal to C₁₆. Most preferably at least 50% of each long chain alkyl or alkenyl group has a chain of C₁₈.

[0018] It is preferred if the long chain alkyl or alkenyl groups of the fabric softening compound are predominantly linear.

[0019] The fabric softening compounds used in the compositions of the invention are molecules which provide excellent softening, and characterised by a chain melting -Lβ to Lα - transition temperature greater than 25°C, preferably greater than 35°C, most preferably greater than 45°C. This Lβ to Lα transition can be measured by DSC as defined in "Handbook of Lipod Bilayers, D Marsh, CRS Press, Boca Raton Florida, 1990 (Pages 137 and 337).

[0020] Substantially insoluble fabric softening compounds in the context of this invention are defined as fabric softening compounds having a solubility less than 1 x 10^-3 wt% in demineralised water at 20°C. Preferably the fabric softening compounds have a solubility less than 1 x 10^-4. Most preferably the fabric softening compounds have a solubility at 20°C in demineralised water from 1 x 10^-8 to 1 x 10^-6.

[0021] It is especially preferred if the fabric softening compound is a water insoluble quaternary ammonium material which comprises a compound having two C_12-18 alkyl or alkenyl groups connected to the molecule via at least one ester link. It is more preferred if the quaternary ammonium material has two ester links present. An especially preferred ester-linked quaternary ammonium material for use in the invention can be represented by the formula:

wherein each R1 group is independently selected from C_1-4 alkyl, hydroxyalkyl or C_2-4 alkenyl groups; and wherein each R² group is independently selected from C_8-28 alkyl or alkenyl groups; X^- is any suitable anion.
T is

and
n is an integer from 0-5.

[0022] Di(tallowyloxyethyl) dimethyl ammonium chloride is especially preferred.

[0023] A second preferred type of quaternary ammonium material can be represented by the formula:

wherein R¹,X^-,n and R² are as defined above.

[0024] Preferred materials of this class such as 1,2 bis[hardened tallowoyloxy]-3- trimethylammonium propane chloride and their method of preparation are, for example, described in US 4 137 180 (Lever Brothers). Preferably these materials comprise small amounts of the corresponding monoester as described in US 4 137 180 for example 1-hardened tallowoyloxy-2-hydroxy-3- trimethylammonium propane chloride.

[0025] It is preferred if the quaternary ammonium compound is biodegradable. Biodegradable in the context of this invention should be interpreted as meaning degrades to materials that are not known to be harmful to the environment.

[0026] The ratio of quaternary ammonium material to nonionic stabilising agent is in the range from 5:0.5 to 5:0.1.

[0027] The composition may also contain long chain fatty acid material for example C₈ - C₂₄ alkyl or alkenyl monocarboxylic acids or polymers thereof. Preferably saturated fatty acids are used, in particular hardened tallow C₁₆ - C₁₈ fatty acids. Preferably the fatty acid is non-saponified, more preferably the fatty acid is free for example oleic acid. lauric acid or tallow fatty acid.

[0028] The level of fatty acid material is preferably more than 0.1%, more preferably more than 0.2% by weight. Especially preferred are dilutes in which the fatty acid material is present from 0.25 wt% to 20 wt%. The weight ratio of quaternary ammonium compound to fatty acid material is preferably from 1:10 to 10:1.

[0029] It is desirable if the viscosities of these fabric compositions lie in the range from 15 mPa.s to 120 mPa.s at a shear rate of 110s^-1.

[0030] The compositions of the invention preferably have a pH of more than 2, more preferably between 2 and 5.

[0031] The composition can also contain one or more optional ingredients, selected from the group consisting of nonaqueous solvents, pH buffering agents, perfumes, perfume carriers, fluorescers, colorants, hydrotopes, antifoaming agents, antiredeposition agents, enzymes, optical brighteners, opacifiers, antishrinking agents, drape imparting agents, antistatic agents and ironing aids.

[0032] The composition may also contain nonionic fabric softening agents such as lanolin and derivatives thereof.

[0033] The invention will now be illustrated by the following nonlimiting examples.

EXAMPLES

[0034] In the examples all percentages are expressed by weight.

[0035] Comparative examples are represented by a letter while examples of the invention are represented by a number.

[0036] In the Examples HEQ is 1,2 bis[hardened tallowoyloxy]-3-trimethylammonium propane chloride ex Hoechst.

Preparation of Fabric Conditioning Composition

[0037] Liquid fabric softening agents were made up as follows:

[0038] The cationic fabric softening agent and/or fatty acid and/or nonionic stabilising agent where appropriate were premixed and heated together to form a clear melt. The molten mixture thus formed was added over a period of at least one minute to water at 70°C to 80°C with constant stirring to form a dispersion.

Viscosity Measurements

[0039] Viscosity was measured using the Haake RV20 Rotoviscometer. Viscosity is quoted at a shear rate of 10s^-1. The Casson data are obtained by using the Casson relationship:

Where:

τ 2= Shear Stress (Pa)

τ₀ 3= Yield Stress (Pa)

η_infinity 4= Infinite shear rate viscosity (mPa.s)

D ₅= Shear rate (s^-1)

[0040] The Casson data were generated using the Haake RV20 Rotoviscometer with a range of shear rates from 0-1000s^-1.

Examples 1-2 Comparative Examples A-D

[0041] Compositions were prepared in which an aqueous dispersion of 5% 6:1 HEQ:fatty acid, 0.5% of the following nonionics were added:

Table 1

Example	Nonionic
A	No nonionic
B	Genapol T-150
C	Tween 80
D	Tween 85
1	Crodesta F50
2	Crodesta F110

Genapol, Tween and Crodesta are trademarks.

[0042] The effect of nonionic type on viscosity of a dilute quaternary ammonium compound is shown in Table 2.

Table 2

Example	η110(mPa.s)	η∞(mPa.s)	Comments
A	66	14.2	Vesicular
B	26	4.6	No vesicles
C	15	5.4	No vesicles
D	16	8.4	No vesicles
1	87	22.0	Vesicles
2	48	12.3	Vesicles

[0043] It can be seen that in the absence of nonionic the composition has a vesicular structure and accordingly has an acceptable viscosity. However the presence of nonionics stabilising agents which are not as specified by this invention, such as Genapol T-150, Tween 80 and Tween 85, do not allow vesicle formation and hence the viscosity of the composition is unacceptably low. The examples according to the invention allow vesicle formation and so have an acceptably high viscosity.

Comparative Examples E-G

[0044] Compositions were prepared in which 0.5% of the following nonionic were placed in a composition containing an aqueous dispersion of 5% 6:1 dihardened tallow dimethyl ammonium chloride:fatty acid.

Example E	No nonionic
Example F	Genapol T-150
Example G	Crodesta F50

[0045] The results are shown in Table 3.

Table 3

Example	η110(mPa.s)	η∞(mPa.s)	Comments
E	184	21.8	Vesicular
F	238	10.9	Vesicular
G	---	----	Vesicular

[0046] Table 3 demonstrates that nonionic stabilising agents do not destroy the viscosity in formulations containing dihardened tallow dimethyl ammonium chloride.

Examples 3-10 Comparative Examples A-B

[0047] To a base formulation of 5% HEQ:Hardened tallow fatty acid 6:1 in water the following nonionic stabilising agents were added:

Example 3	0.25 %	Crodesta F160
Example 4	0.50 %	Crodesta F160
Example 5	0.50 %	Crodesta F10
Example 6	0.50 %	Crodesta F20
Example 7	0.50 %	Crodesta F50
Example 8	0.50%	Crodesta F70
Example 9	0.50%	Crodesta F110
Example 10	0.50 %	Crodesta F160

[0048] The softening performance of the sugar esters are demonstrated by Table 4.

Table 4

Examples	Softening Score	Total Votes
3	0.8828	31
4	1.0750	37
A	0.0000	6
B	0.5862	22

[0049] 95% significance is obtained with a difference (Δ) between products of 0.9041. 90% significance is obtained when Δ=0.7565. It is thus demonstrated that the sucrose esters exhibit a significant softening benefit.

[0050] Table 5 demonstrates the optimum level of mono-ester present to maximise the softening effect.

Table 5

Example	Softening Score	Votes
5	0.0000	17
6	0.1689	25
7	0.2136	27
8	0.9444	54
9	1.3931	71
10	0.7005	46

Claims

1. An aqueous fabric softening composition comprising:

a) a water insoluble, quaternary ammonium material comprising at least one ester link and two C_12-28 alkyl or alkenyl groups;

b) a nonionic stabilising agent present in an amount from 0.1 wt% to 2.5 wt% of the total composition.

characterised in that the nonionic stabilising agent is a sucrose ester, the composition comprises an aqueous dispersion of the water insoluble quaternary ammonium material, and the ratio of quaternary ammonium mateial to nonionic stabilising agent is in the range from 5:0.5 to 5:0.1.

2. A fabric softening composition according to Claim 1 in which the nonionic stabilising agent is a mixture of a mono-ester, a di-ester and a tri-ester.

3. A fabric softening composition according to claim 2 in which the nonionic stabilising agent comprise from 56 wt% to 75 wt% of sucrose monoester.

4. A fabric softening composition according to any preceding claim in which the viscosity of the composition is in the range from 15 mPa.s to 120 mPa.s at a shear rate of 110s-1.

5. A composition according to any preceding claim in which the composition further comprises more than 0.1 wt% of a fatty acid material.

6. A composition according to claim 5 in which the fatty acid material is present from 0.25 wt% to 20 wt%.

7. A process for making a liquid fabric softening composition comprising the steps of selecting the following ingredients:

a) a water insoluble, quaternary ammonium material having at least one ester link and two C_12-28 alkyl groups connected to a quaternary nitrogen via an ester link;

b) a nonionic stabilising agent as defined in claim 1;

c) other optional ingredients;

then mixing the ingredients whilst heating to form a melt, followed by dispersing the melt in water to form a composition as defined in claim 1.