STABILISED QUATERNARY AMMONIUM COMPOSITIONS

Abstract: Stabilised compositions comprising quaternary ammonium material containing at least one ester group characterised in that they further comprise one or more stabilising agents containing at least one ester group via the steps of adding at least one stabilising agent to the quaternary ammonium material, wherein the stabilising agent is a strong hydrogen bond donor is also provided.

Description: STABILISED QUATERNARY AMMONIUM COMPOSITIONS Technical Field The present invention relates to the stability of quaternary ammonium materials, in particular it relates to maintaining stable quaternary ammonium materials containing at least one ester group in the raw material form or as a solution in a suitable solvent . Background and Prior Art Quaternary ammonium materials both solid or liquid are used extensively in fabric softener compositions. Typically such compositions contain a water insoluble quaternary ammonium fabric softening agent dispersed in water at a level of quaternary ammonium softening agent up to 8% by weight in which case the compositions are considered dilute or at levels from 8 to 50% in which case the compositions are considered concentrates. A problem associated with quaternary ammonium materials containing at least one ester group is their instability on storage . The problem is particularly noticeable in the storage of these materials at variable temperatures over time. The instability of both such solid and liquid quaternary ammonium material manifests itself by the discolouration of such material during storage at various temperatures . The amount of discolouration is generally an indication of the level of decomposition occurring over time. This decomposition is of greatest concern when quaternary ammonium material is stored at temperatures above their melting points . In the past, stability of quaternary ammonium compounds has been improved by the storage of compounds at low temperatures, i.e. temperatures well below the melting points of the compounds being stored. Also, the addition of anti-oxidants have been used to counteract decomposition. EP 299 176 (Kao) discloses soft-finishing agents comprising a di-long chained quaternary ammonium salt containing a single ester group and a decyldimethyl amine. US 4 937 008 (Kao) discloses concentrated fabric softening agents comprising one or more quaternary ammonium salts and a di or tri-valent polyol with 2 to 3 carbon atoms. Surprisingly, we have found that low and high temperature stability of solid or liquid quaternary ammonium compounds containing at least one ester group may be improved by the addition of one or more of a select group of stabilising agents which act to prevent the extent of decomposition of the quaternary ammonium material . Definition of the Invention Thus according to one aspect of the invention there are provided improved stable compositions comprising quaternary ammonium material containing at least one ester group characterised in that they further comprise one or more stabilising agent, wherein the one or more stabilising agent (s) are strong hydrogen bond donors. In a second aspect of the present invention there is provided a process of stabilising quaternary ammonium material containing at least one ester group via the steps of adding at least one stabilising agent to the quaternary ammonium material, wherein the stability agent is a strong hydrogen bond donor. In a third aspect of the present invention, the composition as defined is incorporated into a solid and/or liquid rinse conditioner. Also provided is a method of reducing the level of discolouration of quaternary ammonium material containing at least one ester group over time by the addition of a stabilising agent as defined herein. As used herein the term v ester group' in the quaternary ammonium material includes an ester group which is a linking group in the molecule . References herein to quaternary ammonium material are to those having at least one ester group in their structure. It has surprisingly been found that compounds which readily donate hydrogen bonds to the aforementioned quaternary ammonium material assist in maintaining a high level of quaternary ammonium material and avoiding high levels of the decomposition products . Detailed Description of the Invention Preferably the stabilising agent (s) are chosen from one or more of the following group comprising, a) urea b) urea derivative c) primary or secondary amides, and/or d) polyhydric alcohols . Such compositions show improved stability at varying temperatures . The quaternary ammonium compounds containing at least one ester group are referred to herein as ester-linked quaternary ammonium compounds. It is preferred if the quaternary ammonium compounds contain two or more ester groups . In both the monoester and the diester quaternary ammonium compounds of the invention it is preferred if the ester group (s) is a linking group between the nitrogen atom and an alkyl group. The ester groups (s) are preferably attached to the nitrogen atom via another hydrocarbyl group. The invention is most useful for quaternary ammonium compounds containing at least one ester group, preferably two, wherein at least one higher molecular weight group containing at least one ester 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 28, preferably 12 to 22, eg 12 to 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 substituents . Preferably the quaternary ammonium material used in the invention is a compound having two C 12 -C 22 alkyl or alkenyl groups connected to a quaternary ammonium head group via at least one ester link, preferably two ester links or a compound comprising a single long chain with an average chain length equal to or greater than C 20 . More preferably the invention is useful for quaternary ammonium material comprising a compound having two long chain alkyl or alkenyl chains with an average chain length equal to or greater than C 14 . Even more preferably each chain has an average chain length equal to or greater than C 16 . Most preferably at least 50% of each long chain alkyl or alkenyl group has a chain length of C 18 . It is preferred if the long chain alkyl or alkenyl groups are predominantly linear. The problems referred to above have found to be particularly associated with quaternary ammonium compounds having an ester link and wherein the compound has two or three electron withdrawing groups connected to the quaternary nitrogen atom by one or two carbon atoms on different substituents, and, a methyl group also attached to said nitrogen atom. This arrangement is shown in the following formula (A) . Such compounds having a chloride counterion have been found to particularly benefit from the present invention in terms of stability. Without wishing to be bound by theory the applicant believes that the problems of discolouration/instability are most common in quaternary ammonium compounds containing an ester linking group and having a methyl group attached to the nitrogen and a chloride counter-ion and two or three electron withdrawing groups separately attached to the quaternary nitrogen atom. Whilst the quaternary ammonium compounds of general formula (B) below may suffer from discolouration and instability these problems have found to be most prevalent in the compounds of type (A) below and especially in those compounds referred to immediately above. Thus especially preferred ester-linked quaternary ammonium material for use in the invention can be represented by the formula: R x (A) R ^ N (CH 2 ) n -T-R 2 X (CH 2 ) n -T-R 2 wherein each R 1 group is independently selected from C 1-4 alkyl, hydroxyalkyl or C 2 . 4 alkenyl groups; and wherein each R 2 group is independently selected from C 8-28 alkyl or alkenyl groups; X " is any suitable counterion, i.e. a halide, acetate or lower alkosulphate ion, such as chloride or methosulphate. T is -O-C- or -C-0-; and n is an integer from 1-5 or is 0 It is especially preferred that each R 1 group is methyl and each n is 2 as such compounds are found to be particularly susceptible to the stability problems referred to above. Di (tallowyloxyethyl) dimethyl ammonium chloride, available from Hoechst, is especially preferred, also Di (hardened tallowyloxyethyl) dimethyl ammonium chloride, ex Hoechst. Another preferred type of ester-linked quaternary ammonium material that can be used according to the invention is represented by the formula: OOCR 2 (B) (R^ a N * - (CH 2 ) n CH CH 2 OCOR 2 wherein R , n R and X " are as defined above. However it has been found that these materials do not show such a tendency to instability, particularly at high temperatures eg 60-70°C, as the compounds of the preceding formula. It is advantageous for environmental reasons if the quaternary ammonium material is biologically degradable. 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. Accordingly it is especially preferred that the quaternary ammonium material according to the invention comprises at least one methyl group attached to the quaternary nitrogen atom, with two or three nitrogen atom substituents containing electron withdrawing groups and having a chloride counter-ion. It is especially preferred that such compounds falling within general formula A are used, and even more preferred that such compounds have two methyl substituents on the nitrogen and in the remaining radicals n is 1 or 2 and R 2 is C 12 -C 22 , especially C 16 -C 22 e.g. tallow. It is also preferred that the quaternary ammonium compound used in the present invention is substantially anhydrous, meaning containing less than 10% water in the context of the present invention. The quaternary ammonium material may contain optional additional components, as known in the art, in particular, low molecular weight solvents, for instance isopropanol and/or ethanol, and co-actives such as nonionic softeners, for example fatty acid or sorbitan esters . The types of stabilising agent that may be used are any that are strong hydrogen bond donors . The stabilising agent may be urea or a derivative thereof, a primary or secondary amide or a polyhydric alcohol, or mixtures thereof . Two or more stabilising agents may be used. The stabilising agent is preferably added to the composition of the present invention at levels of 0.05 to 10% by weight of the weight of the quaternary ammonium material. However, lower amounts than this are preferred, more preferably 0.1 to 7.5% is added based on the weight of the quaternary ammonium material, especially 0.5 to 6.0% and even more preferably 0.5 to 4%. The stabilising agent may be introduced to the quaternary ammonium material at any stage during the manufacture of the quaternary ammonium material or after manufacture i.e. on storage. The stabilising agent may be added in any form, as a powder direct to the molten quaternary ammonium material or as a solution in a suitable solvent, for instance iso propanol . The addition step can take place during the synthesis of the quaternary ammonium material, preferably following the quaternisation step. The addition may take alternatively, or additionally, place during storage of the quaternary ammonium material . The stabilising agent is most effectively introduced at any stage following the quaternisation step of the synthesis of the quaternary ammonium material . An example of amide to be used in the present invention is acetomide. Polyhydric alcohols such as glycerol may be used as stabilising agents. Another preferred stabilising agent is urea. A combination of glycerol and a quaternary ammonium compound of general formula (A) is particularly preferred, especially wherein both R 1 are CH 3 , n is 2 and R 2 is tallow. The stabilised composition may be in a liquid, molten or semi-solid form containing less than 10% by weight water. Also provided according to the invention is a solid rinse conditioner comprising a stabilised composition as defined above, preferably a composition in a granular or powdered form. Another type of rinse conditioner provided by the invention is a liquid rinse conditioner comprising a stabilised composition as defined above. The invention will now be illustrated by the following example. Further examples within the scope of the invention will be apparent to the person skilled in the art . Example Urea was added to the quaternary ammonium material as a powder and heated to 82°C. The combined material was stored for three days . The reflectance was measured on a datacolor international Spectraflash SF600 plus reflectometer after 3 days storage at 82°C. DEQ is di (2- [hardened tallow] oxyl oxyethyl) dimethyl ammonium chloride ex Hoechst . It includes approximately 10% mono ester and minor amounts of unquaternised amine/amine salt as well as approximately 2% fatty acid and 14% isopropanol. These results show that addition of urea to compositions comprising a quaternary ammonium compound counteracts decomposition at high temperature. This is indicated by the greatly increased R540 reflectance values found for samples of quaternary ammonium compound stored in admixture with urea.

Claims: CLAIMS 1. Stabilised compositions comprising quaternary ammonium material containing at least one ester group characterised in that they further comprise one or more stabilising agent (s) wherein the one or more stabilising agents are strong hydrogen bond donors. 2. A composition according to claim 1 wherein the stabilising agent is chosen from one or more of the group comprising: a) urea, b) urea derivative c) primary or secondary amides, and/or d) polyhydric alcohols, 3. A composition according to either claim 1 or claim 2 which is in a liquid, molten or semi-solid form containing less than 10% by weight water. 4. A composition according to any preceding claim wherein the quaternary ammonium material is represented by the formula : R x (A) N ( CH 2 ) n -T-R^ X ( CH 2 ) n -T-R^ wherein each R 1 group is independently selected from C 1-4 alkyl, hydroxyalkyl or C 2 . 4 alkenyl groups; and wherein each R 2 group is independently selected from C 8 _ 28 alkyl or alkenyl groups; X " is any suitable counter-ion. O 0 II II T is -O-C- or -C-0-; and n is an integer from 1-5 or is 0 or OOCR 2 (B) (R X ) 3 N + - (CH 2 ) n CH X " CH 2 OCOR 2 wherein R 1 , n R 2 and X " are as defined above. 5. A composition according to any one of the preceding claims where the stabilising agent is present at levels of 0.05 to 10% of the weight of the quaternary ammonium material, preferably 0.5 to 6.0%, even more preferably 0.5 to 4%. 6. Process of stabilising quaternary ammonium material containing at least one ester group via the steps of adding at least one stabilising agent to the quaternary ammonium material, wherein the stabilising agent is a strong hydrogen bond donor. 7. A process according to claim 6 wherein the stabilising agent is chosen from one or more of the group comprising a) urea, b) urea derivative c) primary or secondary amides, and/or d) polyhydric alcohols . 8. Process according to either claim 6 or 7 wherein the step of adding at least one stabilising agent occurs during the manufacture of the quaternary ammonium material, preferably following the quaternisation step in the synthesis of the quaternary ammonium material. 9. Process according to either claim 6 or 7 wherein the step of adding at least one stabilising agent occurs after manufacture of the quaternary ammonium material, preferably during storage of the quaternary ammonium material . 10. A process according to any one of the preceding claims wherein the stabilising agent is added in amounts of 0.05-10% by weight of the quaternary ammonium material, preferably 0.5-6.0%. 11. A solid rinse conditioner comprising a composition as defined in any one of claims 1 to 5. 12. A liquid rinse conditioner comprising a composition as defined in any one of claims 1 to 5. 13. Method of reducing the level of discolouration of quaternary ammonium material containing at least one ester group over time by the addition of a stabilising agent as defined in claim 1 or claim 2.

Inventors: THORNTHWAITE DAVID WILLIAM, WHALEY CHRISTOPHER, THORNTHWAITE, DAVID, WILLIAM, WHALEY, CHRISTOPHER
Applicants: LEVER HINDUSTAN LTD, THORNTHWAITE DAVID WILLIAM, UNILEVER NV, UNILEVER PLC, WHALEY CHRISTOPHER, HINDUSTAN LEVER LIMITED, THORNTHWAITE, DAVID, WILLIAM, UNILEVER N.V., WHALEY, CHRISTOPHER
Application year: 1999
Main classification: C11D1
IPC codes: C11D1, C11D3, D06M13