EP0507478B1 - Fabric softening composition - Google Patents

Description

• The present invention relates to fabric softening compositions, in particular the invention relates to aqueous dispersions of biodegradable fabric softening compositions comprising a water insoluble cationic fabric softening agent and a nonionic stabilising agent suitable as rinse-added fabric softener compositions.
• Rinse added fabric softener compositions are well known. Typically such compositions contain a water insoluble quaternary ammonium fabric softening agent dispersed in water at a level of softening agent up to 7% by weight in which case the compositions are considered dilute, or at levels from 7% to 50% in which case the compositions are considered concentrates. In addition to softening, fabric softening compositions desirably have other benefits. One is the ability to confer soil release properties to fabrics, particularly those woven from polyester fibres.
• One of the problems associated with fabric softening compositions is the physical instability of such compositions when stored. This problem is accentuated by having a concentrated composition and by storage at low temperatures.
• Concentrates and storage stability at low temperatures are however desired by the consumer. Physical instability manifests as a thickening on storage of the composition to a level where the composition is no longer pourable and can even lead to the formation of an irreversible gel. The thickening is very undesirable since the composition can no longer be conveniently used.
• In the past physical stability of rinse added fabric softener compositions has been improved by the addition of viscosity control agents or anti-gelling agents. For example in EP 13780 (Procter and Gamble) viscosity control agents are added to certain concentrated compositions. The agents may include C₁₀-C₁₈ fatty alcohols. More recently in EP 280550 (Unilever) it has been proposed to improve the physical stability of dilute compositions comprising biodegradable, ester-linked quaternary ammonium compounds and fatty acid by the addition of nonionic surfactants.
• With concentrated compositions comprising biodegradable ester-linked quaternary ammonium compounds the problem of physical instability is more acute than with traditional quaternary ammonium compounds.
• In EP 0 040 562 (Lesieur Cotelle) a nonionic emulsifier/stabiliser is added to a concentrate comprising an ester-linked quaternary ammonium compound to form a viscous gel. The stabiliser is a C₁₂ to C₁₄ alcohol ethoxylated with 9 molecules of ethylene oxide. The degree of branching of the alcohol is not, however, mentioned.
• EP-A-0,293,953 discloses mono-ester analogs of ditallow dimethyl ammonium chloride as fabric softeners. The presence of only one ester group is said to provide hydrolytic stability to the softeners. The softeners may be stabilized with standard emulsifiers, including nonionics.
• EP-A-0,309,052 discloses fabric softening compositions comprising a quaternary ammonium salt which has at least one ester linkage and a linear alkoxylated alcohol to stabilize against settling. The alcohol is alkoxylated with between about 1 and 10, preferably 2 to 5, moles of ethylene or propylene oxide.
• EP-A-0,346,634 discloses a liquid laundry conditioner containing a quaternary ammonium compound with two 2-acyloxyalkyl groups, and a fatty acid. The composition may also include nonionic dispersing agents such as the condensation products of C_10-20 alcohols with from 4 to 40 moles of ethylene or propylene oxide. The degree of branching of the alcohols is not mentioned.
• EP-A-0,331,237 discloses an aqueous fabric conditioning composition comprising a fabric softener (which may be an ester-containing quaternary ammonium compound) and a hydrophobically modified nonionic cellulose ether. Nonionic fabric softening agents may also be included.
• Certain nonionic stabilising agents not only stabilise concentrated compositions comprising biodegradable quaternary ammonium compounds but are also environmentally friendly, in that they show acceptable biodegradability and are not substantially toxic in aquatic systems.
• Soil release properties are generally imparted to fabrics by the use of separate soil-release agents, usually a high molecular weight polymer, in a detergent composition or separate treatment. For example in EP 0 398 133A (Procter & Gamble) there is disclosed a cationic polymeric soil release agent for use in a fabric conditioning composition.
• A disadvantage of such compositions is that the soil release agent increases the number of components in the formulation, increasing cost and making the product less environmentally acceptable.
• We have now found that fabric softening compositions comprising biodegradable ester-linked quaternary ammonium compounds may confer improved soil release properties to fabrics.
• Thus, according to one aspect of the invention there is provided a fabric softening composition comprising a water insoluble cationic fabric softening agent and a nonionic stabilising agent characterised in that the water insoluble cationic fabric softening agent is a biodegradable quaternary ammonium material as defined below and the nonionic stabilising agent is
• i. a linear C₈ to C₂₂ alcohol alkoxylated with 10 to 20 moles of alkylene oxide
  or
• ii. a C₁₀ to C₂₀ alcohol or mixtures thereof.
• Advantageously the nonionic stabilising agent is a linear C₈ to C₂₂ alcohol alkoxylated with 10 to 20 moles of alkylene oxide
• preferably the compositions of the invention are liquids comprising an aqueous base.
• The ester-linked quaternary ammonium material for use in the compositions according to the invention can be represented either by the formula:

  

  wherein each R₁ group is independently selected from C_1-4 alkyl, alkenyl or hydroxyalkyl groups; each R₂ group is independently selected from C_8-28, preferably C_12-28, alkyl or alkenyl groups;
  T is

  

  and n is an integer from 0-5,
  or by the formula:

  

  wherein R₁, n and R₂ are as defined above.
• Preferred materials of this class 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-tallowoxy, 2-hydroxytrimethyl ammonium propane chloride.
• According to another aspect of the invention, there is provided the use, in a fabric softening composition comprising a water insoluble cationic fabric softening agent which is a biodegradable quaternary ammonium material having at least one ester link, of a nonionic stabilising agent which is either:
• i) a linear C₈ to C₂₂ alcohol alkoxylated with 10 to 20 moles of alkylene oxide, or
• ii) a C₁₀ to C₂₀ alcohol or mixture thereof,
in order to improve the stability of the composition below ambient temperature.
• Preferably the level of ester linked quaternary ammonium compounds, in the compositions of the invention, is at least 1% by weight of the composition, more preferably more than 3% by weight of the composition; especially interesting are concentrated compositions which comprise more than 7% of ester-linked quaternary ammonium compound. The level of ester-linked quaternary ammonium compounds preferably is between 1% and 80% by weight, more preferably 3% to 50%, most preferably 8% to 50%.
• Suitable nonionic stabilisers which can be used include the condensation products of C₈ - C₂₂ primary linear alcohols with 10 to 20 moles of ethylene oxide. The term linear alcohol means a primary alcohol attached directly to a hydrocarbon backbone structure. Use of less than 10 moles of ethylene oxide, especially when the alkyl chain is in the tallow range, leads to unacceptably high aquatic toxicity. Since the aquatic toxicity is related to both the number of moles of ethylene oxide and the length of the alkyl chain we have found that the HLB value can be used as an indication of likely aquatic toxicity. An HLB of greater than about 12 gives rise to an acceptable acute aquatic toxicity value of >1mg/l;EC₅₀ 48 hours for daphnia and algae and EC₅₀ 96 hours for fish. The selection of linear alcohols and the use of 20 moles or less of ethylene oxide gives acceptable biodegradability to the nonionic stabiliser. However the use of nonionic stabilisers with more than 20 ethylene oxide units will also provide the stability benefit .The alcohols may be saturated or unsaturated. In particular Genapol T-110, Genapol T-150, Genapol T-200, Genapol C-200 (all Trade Marks, all ex Hoechst AG), Lutensol AT18 (Trade Mark) ex BASF, Genapol 0-100 and Genapol 0-150 (Trade Marks) ex Hoechst, or fatty alcohols for example Laurex CS (Trade Mark), ex Albright and Wilson or Adol 340 (Trade Mark) ex Sherex. Preferably the nonionic stabiliser has an HLB of between 10 and 20, more preferably 12 and 20. Preferably, the level of nonionic stabiliser is within the range from 0.1 to 10% by weight, more preferably from 0.5 to 5% by weight, most preferably from 1 to 4% by weight. The mole ratio of the quaternary ammonium compound to the nonionic stabilising agent is within the range from 40:1 to about 1:1, preferably within the range from 18:1 to about 3:1.
• The composition can also contain fatty acids 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.
• The level of fatty acid material is preferably more than 0.1% by weight, more preferably more than 0.2% by weight. Especially preferred are concentrates comprising from 0.5 to 20% by weight of fatty acid, more preferably 1% to 10% by weight. The weight ratio of quaternary ammonium material to fatty acid material is preferably from 10:1 to 1:10.
• The compositions of the invention preferably have a pH of more than 2.0, more preferably less than 5.
• The composition can also contain one or more optional ingredients, selected from non-aqueous solvents, pH buffering agents, perfumes, perfume carriers, fluorescers, colourants, hydrotropes, antifoaming agents, antiredeposition agents, enzymes, optical brightening agents, opacifiers, anti-shrinking agents, anti-wrinkle agents, anti-spotting agents, germicides, fungicides, anti-oxidants, anti-corrosion agents, drape imparting agents, antistatic agents and ironing aids.
• The composition may also contain nonionic fabric softening agents such as lanolin and derivatives thereof.
• The invention will now be illustrated by the following examples. In the examples all percentages are expressed by weight.
Example 1
• Liquid fabric softening compositions were made as follows.
• The cationic fabric softening agent, fatty acid and 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.
• The viscosity of the compositions was measured by Haake rotoviscometer following 21 days storage at ambient temperature or at 5°C.

  

  
• The results show that while known fabric softening compositions comprising conventional quaternary ammonium compounds do not show physical instability on short term storage at 5°C (composition A) a problem is experienced with compositions comprising ester-linked quaternaries and fatty acid (composition E). The results also show that addition of selected nonionic stabilising agents counteract destabilisation to give stable concentrated compositions.
Example 2
• Liquid fabric softening compositions as given below were made as described in Example 1. The soil release properties imparted to polyester test pieces by treatment with the compositions was assessed by measuring the change in reflectance following staining and a subsequent wash in a proprietary detergent composition. The pieces were first rinsed for 5 minutes in 1 litre of 14°FH water containing 0.67 ml of either composition. The pieces were then line dried and stained with 100 micro litres of olive oil containing 0.06% sudan red dye. The stain was allowed to spread for a minimum of two days following which the reflectance of the stained piece (R₁) was measured using an ICS micromatch. The pieces were then washed, rinsed and line dried using 5g/1 New System Persil Automatic (Trade Mark) ex Lever in 14°FH water for a 15 minute wash cycle. The reflectance of the pretreated, washed piece (R₂) was measured and the percentage detergency calculated according to the following equation: $$\text{\% Detergency =}\frac{{\text{Ks}}_{\text{1}}{\text{- Ks}}_{\text{2}}}{{\text{Ks}}_{\text{1}}}\text{x 100}$$

  

  where $${\text{Ks}}_{\text{1}}\text{=}\frac{{\text{(1 - R}}_{\text{1}}{\text{)}}^{\text{2}}}{{\text{2R}}_{\text{1}}}$$

  

  and $${\text{Ks}}_{\text{2}}\text{=}\frac{{\text{(1 - R}}_{\text{2}}{\text{)}}^{\text{2}}}{{\text{2R}}_{\text{2}}}$$

  
• The higher the percentage detergency, the greater the soil release benefit.

  Composition	% by weight
  	A	B
  Arquad 2HT1 (Trade Mark)	-	12.8
  HT TMAPC2	11.6	-
  Fatty acid3	1.9	3.2
  Tallow 11EO4	2.5	-
  Water and minors to balance % Detergency	30	21

Notes
• Formulation B corresponds to a commercially available fabric softening composition, currently sold in the UK by Lever under the trade mark COMFORT. 1, 2, 3 and 4 are as in Example 1.
• These results show that known compositions comprising conventional quaternary ammonium compositions (Composition B) show a smaller soil release benefit than compositions according to the invention (Composition A).
Example 3
• Preferred compositions according to the invention are as follows:

  Composition	% by weight
  	A	B	C
  HTTMAPC2	11.6	11.6	11.6
  Fatty acid3	1.9	1.9	1.9
  Tallow 11EO4	-	2.5	-
  Tallow Alcohol7	1.5	-	-
  Tallow 15EO8	-	-	1.5
  Isopropyl alcohol	1.6	1.6	1.6
  Glycerol	1.6	1.6	1.6
  Perfume, Dye + minors	0.8	0.8	0.8
  Water to balance
  Notes 2, 3, 4 and 7 are as in Example 1 8. is tallow alcohol ethoxylated with 15 moles of ethylene oxide.

Claims (13)

1. A fabric softening composition comprising a water insoluble cationic fabric softening agent and a nonionic stabilising agent characterised in that the water insoluble cationic fabric softening agent is a biodegradable quaternary ammonium material represented either by the formula:

   

   wherein each R₁ group is independently selected from C_1-4 alkyl, alkenyl or hydroxyalkyl groups; each R₂ group is independently selected from C_8-28 alkyl or alkenyl groups;
   T is

   

   and n is an integer from 0-5,
   or by the formula:

   

   wherein R₁, n and R₂ are as defined above, and in that the nonionic stabilising agent is

   i. a linear C₈ to C₂₂ alcohol alkoxylated with 10 to 20 moles of alkylene oxide, or

   ii. a C₁₀ to C₂₀ alcohol, or mixtures thereof.
2. A composition as claimed in claim 1 wherein the nonionic stabilising agent is a linear C₈ to C₂₂ alcohol alkoxylated with 10 to 20 moles of alkylene oxide.
3. A composition as claimed in claim 1 or claim 2 characterised in that the composition comprises at least 1% by weight of the quaternary ammonium material.
4. A composition as claimed in any preceding claim characterised in that the composition comprises from 0.1 to 10% by weight of the nonionic stabilising agent.
5. A composition as claimed in any preceding claim characterised in that the composition also comprises more than 0.1% by weight of a fatty acid material.
6. A composition as claimed in any preceding claim characterised in that the composition comprises from 3% to 50% by weight of the quaternary ammonium material, from 0.5% to 5% by weight of the nonionic stabilising agent and from 0.5 to 20% by weight of fatty acid material.
7. A composition as claimed in any preceding claim characterised in that the nonionic stabilising agent has an HLB of between 10 and 20.
8. A composition as claimed in claim 7 wherein the nonionic stabilising agent has an HLB of between 12 and 20.
9. A process for making a liquid fabric softening composition as claimed in any of claims 1 to 8 comprising the steps of

   i. mixing and heating the cationic fabric softening agent and nonionic stabilising agent to form a melt and

   ii. dispersing the melt in water.
10. Use, in a fabric softening composition comprising a water insoluble cationic fabric softening agent which is a biodegradable quaternary ammonium material having at least one ester link, of a nonionic stabilising agent which is either:

    i. a linear C₈ to C₂₂ alcohol alkoxylated with 10 to 20 moles of alkylene oxide, or

    ii. a C₁₀ to C₂₀ alcohol or mixtures thereof,

    in order to improve the stability of the composition below ambient temperature.
11. Use according to claim 10, wherein the nonionic stabilising agent is a linear C₈ to C₂₂ alcohol alkoxylated with 10 to 20 moles of alkylene oxide.
12. Use according to claim 10 or claim 11, wherein the nonionic stabilising agent is used in the composition at a concentration of between 0.1 and 10% by weight.
13. Use according to any one of claims 10-12, wherein the cationic fabric softening agent is represented either by the formula:

    

    wherein each R₁ group is independently selected from C_1-4 alkyl, alkenyl or hydroxyalkyl groups; each R₂ group is independently selected from C_8-28 alkyl or alkenyl groups;
    T is

    

    and n is an integer from 0-5,
    or by the formula:

    

    wherein R₁, n and R₂ are as defined above.