BLEACHING COMPOSITIONS

Abstract: Thickened bleaches of enhanced viscosity consist of water, alkali metal hypochlorite and a thickening agent consisting of a mixture of straight chain C₁₄ amine oxide with a mixture comprising branched chain and straight chain C₁₅ amine oxides.

Description: THE PRESENT INVENTION relates to bleaching and cleaning compositions containing hypochlorite and in particular to thickened bleach compositions, that is compositions having an increased viscosity as compared with straight aqueous solutions of alkali metal hypochlorite. Thickened bleach compositions have a number of advantages over unthickened bleach compositions in that the more viscous compositions adhere more readily and for a longer time to vertical and inclined surfaces than do the unthickened compositions. The performance of thickened bleach compostions is therefore superior to that of unthickened bleach compositions for vertical and inclined surfaces such as are found in lavatory pans, urinals, drains, waste pipes and the like. In recent years a number of proposals have been made which provide thickened bleach compositions, for example compositions having viscosities at 25°C of greater than 10 dm²/s, by the addition of suitable thickening agents. Viscosity can be further enhanced by the inclusion in such compositions of other components, for example caustic alkali, alkali metal salts. British Patent Specification No 1,329,086 describes thickened aqueous alkali metal hypochlorite compositions which contain in addition to the hypochlorite, an alkali metal salt of a C₈ to C₁₈ fully saturated fatty acid and a hypochlorite-soluble surface active agent, the latter being exemplified by an amine oxide containing a C₈ to C₁₈ alkyl group. The amine oxides described in the specification are those commercially available which are derived from naturally occuring C₈ to C₁₈ fatty acids, for example coconut acids, lauric acid and myristic acid. British Patent Specification No 2,051,162A describes thickened aqueous alkali metal hypochlorite compositions which contain, in addition to the hypochlorite, an amine oxide and an alkali metal alkyl sulphate. British Patent Specification No 2,003,522A describes thickened aqueous alkali metal hypochlorite compositions which contain a C₈ to C₂₀ branched chain amine oxide or a mixture of such amine oxides with or without the presence of an alkali metal salt of a fatty acid. Our European Patent Application 0147943 describes thickened bleach compositions comprising water, alkali metal hypochlorite and a thickening component comprising at least one amine oxide and at least one amine. Our European Patent Application 0110544 describes thickened bleach compositions comprising water, alkali metal hypochlorite and a thickening agent consisting solely of a straight chain amine oxide or a mixture of straight chain amine oxides wherein the or at least one amine oxide has at least 14 carbon atoms in the straight chain. European Patent Application No 079 697 suggests that as the alkyl chain length of an amine oxide increases its effectiveness as a thickening agent also increases. In general, the prior art teaches that the viscosity of a thickened sodium hypochlorite cleaning formulation increases in proportion to the amine oxide content of the formulation. This is especially the case in formulations in which amine oxide is the sole thickening agent and is illustrated in Table A and Fig A accompanying this specification. European Patent Application No 079 697 claims that the thickening effect shown by amine oxides is a function of the alkyl chain length up to the solubility of the amine oxide component. Furthermore, the prior art teaches that in a mixture of amine oxides the ability to thicken aqueous solutions of an alkali metal hypochlorite is a function of the individual thickening performance of the component amine oxides. In such a case viscosity would increase in proportion to the content of the longer linear alkyl chain amine oxides. Table B and Fig B accompanying this specification illustrate how the viscosity of a cleaning formulation containing sodium hypochlorite increases in proportion with nC₁₅ alkyl amine oxide content. Conversely it also illustrates that viscosity decreases with an increase in nC₁₄ alkyl amine oxide content. Figure C and Table C illustrate that this effect is also observed with mixtures of linear and branched alkyl dimethyl amine oxides. The amine oxide used to produce the data given in Table C consisted of a mixture of amine oxides with the following structural formulae: The C₁₃ amine oxide used in the formulations shown in Table C consisted of 50% amine oxides with structure (a), 40% with structure (b), and 10% with structure (c). We have now surprisingly found that certain mixtures of amine oxides do not display the expected linear relationship between alkyl chain length and viscosity. According to the present invention a thickened bleach composition of enhanced viscosity comprises water, an alkali metal hypochlorite and a thickening agent comprising a mixture of straight chain C₁₄ amine oxide with a mixture comprising branched chain and straight chain C₁₅ amine oxides. By the terms "C₁₄" and "C₁₅" we mean that in the amine oxide formula the total number of carbon atoms in R₁ is 14 or 15 respectively. In this formula R₂ and R₃ are preferably selected from lower ie C₁ to C₄ alkyl radicals, more preferably each of R₂ and R₃ being methyl. In a preferred embodiment of the composition of this invention the thickening agent comprises 10 to 60% w/w, more preferably 20 to 40% w/w of straight chain C₁₄ amine oxide. The C₁₅ amine oxide component of the thickening agent preferably comprises at least 25 % w/w of branched chain material, more preferably at least 40% w/w, most preferably 45 to 55 % w/w. Over a range of concentrations the compositions of the invention have unexpectedly enhanced viscosities compared with the following prior art systems: (a) C₁₅ amine oxide alone, (b) a mixture of straight chain C₁₅ amine oxide and straight chain C₁₄ amine oxide, and (c) a mixture of straight chain C₁₄ amine oxide with a mixture of C₁₃ branched and straight chain amine oxides. This is graphically illustrated by the non-linear appearance of Figure 1 accompanying this specification when compared with Figures A, B and C. The enhanced viscosity provided by the compositions of this invention has the considerable advantage that appreciably less thickening agent is required to achieve a commercially acceptable viscosity than is the case with prior art compositions. Optionally, the compositions of this invention may also contain an alkali metal salt of a fatty acid, for example sodium laurate, as an additional component to aid thickening. The effect of enhanced viscosity is maintained in the compositions which contain such a salt. Optionally, thickened bleaches according to this invention can contain additional components frequently incorporated in such compositions including caustic alkali, alkali metal salts, perfume and colourants. The bleach compositions of this invention preferably contain an amount of available chlorine in the range 1 to 15%, preferably 5 to 10% by weight. The compositions of this invention preferably have a viscosity of at least 10⁻⁵m²s⁻¹ at 25°C, measured with a Brookfield RT viscometer using a No 3 spindle at 100 rpmin, and a cloud point in excess of 40°C. The following examples, in which all parts and percentages are by weight and all viscosities are measured at 25°C with a Brookfield viscometer, further illustrate thickened bleach compositions according to this invention. Examples 1 to 3 Five thickened bleach compositions were prepared by mixing in water sufficient sodium hypochlorite to give an amount of available chlorine of 8% and a thickening agent consisting of dimethyl C₁₄ straight chain amine oxide and a mixture of branched and straight chain C₁₅ amine oxides, in amounts as set out in Table 1. The C₁₅ amine oxides had the following structural formulae: The mixture of C₁₅ amine oxides used in the compositions of Table 1 comprised 50% amine oxide with structure (a), 40% amine oxide with structure (b), and 10% structure (c). In Table 1, compositions 1 to 3 are according to this invention and compositions D and E are comparative compositions according to the prior art. The full line in Figure 1 is a plot of viscosity against percentage C₁₅ amine oxide in the thickening agent for the compositions of Table 1. For comparative purposes, the substantially straight line plot which would be expected from a consideration of prior art compositions is included as the dotted line in Figure 1. The enhanced viscosity of the compositions according to this invention is clearly shown. Example 4 to 6 A further five compositions were prepared identical to those shown in Table 1 except that each additionally contained 0.05 wt% sodium laurate. The compositions and their viscosities and cloud points are shown in Table 2, compositions F and G again being comparative compositions not according to the invention. Figure 2 is a plot of the viscosities of these five compositions against their C₁₅ amine oxide content, again illustrating the enhanced viscosity effect.

Claims: A thickened bleach composition which comprises water, an alkali metal hypochlorite and an amine oxide thickening agent characterised in that the thickening agent comprises; a) 10 to 60% w/w of straight chain C₁₄ amine oxide; and b) a mixture comprising branched chain and straight chain C₁₅ amine oxides. A thickened bleach composition as claimed in claim 1 wherein the thickening agent comprises 20 to 40% w/w of straight chain C₁₄ amine oxide. A thickened bleach composition as claimed in claim 1 or claim 2 wherein the C₁₅ amine oxide component of the thickening agent comprises at least 25% w/w of branched chain material. A thickened bleach composition as claimed in claim 3 wherein the C₁₅ amine oxide component of the thickening agent comprises 45 to 55% w/w of branched chain material. A thickened bleach composition as claimed in any one of the preceding claims wherein the composition additionally contains an alkali metal salt of a fatty acid. A thickened bleach composition as claimed in any one of the preceding claims wherein the composition contains an amount of available chlorine in the range 1 to 15% by weight. A thickened bleach composition as claimed in any one of the preceding claims wherein the composition additionally contains an alkali metal salt of a fatty acid.

Inventors: MOTSON, HAROLD RUSSELL
Applicants: IMPERIAL CHEMICAL INDUSTRIES PLC
Application year: 1987
Main classification: C11D3
IPC codes: C11D1, C11D3