GB2221220A

GB2221220A - Laundry bars

Info

Publication number: GB2221220A
Application number: GB8916911A
Authority: GB
Inventors: William John Iley; Arthur George Leigh
Original assignee: Unilever PLC
Current assignee: Unilever PLC
Priority date: 1988-07-26
Filing date: 1989-07-24
Publication date: 1990-01-31
Also published as: GB8817827D0; GB8916911D0; MY107362A; IN170488B; PH26563A; BR8903687A

Abstract

A laundry bar comprising detergent active and builder characterised in that the bar is formed from an extruded shear mixed dough and additionally comprises chlorine bleach encapsulated with a coating material which is insoluble in water at pH 7. The bleach can be encapsulated according to the method of US 4 759 956 and has greatly improved stability in the bar.

Description

DETERGENT COMPOSITION This invention relates to the manufacture of built detergent laundry bars. Such bars comprise detergent active, builder and optionally fillers, abrasives, perfumes and silicates.

The bars are manufactured by a preferred process which requires the addition of water and customarily the bars contain alkaline ingredients so that the bar forms an alkaline solution when dissolved/dispersed in water. The preferred process of manufacture involves mixing under conditions of high temperature and shear followed by extrusion into billets.

To enhance the cleaning performance of such laundry bars it is desirable to incorporate bleaching compounds.

Bleaches are liable to decomposition when placed in intimate contact with the other constituents of the bar.

In the past the addition of bleach has been achieved by coating a bleach core with an abradable wax to isolate it from the rest of the ingredients.

GB 1 438 647 (Unilever Ltd/POTTER) discloses a method of forming a detergent bar containing a hypochlorite bleach where the detergent active is in the form of particles which are lightly mixed with wax coated hypochlorite particles and pressed into bars. The wax coating is abradable on contact with a fabric or domestic hard surface to release the bleach.

We have now found that it is possible to incorporate coated bleach particles into laundry bar compositions formed using the potentially damaging conditions of high temperature, shear and extrusion and that bars so formed mitigate the problem of bleach decomposition during storage.

Accordingly the present invention provides a laundry bar comprising detergent active and builder characterised in that the bar is formed from an extruded, shear mixed dough and additionally contains a chlorine bleach encapsulated with a coating material which is insoluble in water at pH 7.

Surprisingly, an effective encapsulating material can remain effective despite the stress of being mixed into the bar composition and extruded with it.

It is preferred that the bar composition has a water content, at the time of manufacture, of not more than 12%, preferably not more than 10% by weight of the bar composition.

The detergent active employed in the bar is preferably present in an amount of 10 to 60% by weight of the bar composition, more preferably 12 to 45% by weight.

The detergent active will normally be a non-soap detergent active such as alkyl benzene sulphonate having 8 to 22 carbon atoms in the alkyl group, C8 to C18 primary alcohol sulphate, or C8 to C18 fatty acid C1 to C4 ester sulphonate. Various other non-soap detergent actives may be used. It is also feasible to use soap as detergent active although it would be preferable to utilise an exceptionally dry soap.

The detergent builder is desirably present in an amount from 5 to 60% by weight of the bar composition, more preferably 10 to 60%, yet more preferably 12 to 45% of the composition. The builder may include hydratable phosphate (which term embraces condensed phosphates such as pyrophosphate or tripolyphosphate).

Other inorganic or organic builders can be included also. Examples are water soluble carbonate, e.g. sodium carbonate; organic builders, e.g. sodium nitrilotriacetate, sodium tartrate, sodium citrate, trisodium carboxymethyl oxysuccinate, sodium oxydisuccinate, sodium sulphonated long-chain monocarboxylic acids, polyacrylates and oxidised polysaccharides; and aluminosilicate ion exchangers; e.g.

zeolite 4A. In particular, use of phosphate builders or polyphosphate detergency builder may provide at least 3% by weight of the bar composition.

Chlorine bleach incorporated in accordance with this invention can be selected from oxygen-chlorine bleaches such as hypochlorite conveniently in the form of lithium or calcium hypochlorite, or bleaching powder. Presently preferred are nitrogen-chlorine bleaches such as sodium or potassium salts of chloroisocyanuric acids or an oxygen containing bleach such as potassium monopersulphate.

The coating material with which the bleach is encapsulated is insoluble in water at neutrality. It is preferably insoluble under acid conditions also, but soluble or swellable in aqueous alkaline solution so that when the bar is used such as bv rubbing on wet fabric, the encapsulating coating swells or dissolves, so releasing the bleach. However it would also be possible to rely on abrasion during use to expose the bleach.

Possible coating materials which are insoluble in neutral to acid aqueous solution are fatty acids.

Preferred are alkali-soluble or swellable polymers. These may have monomer units selected from acrylic and methacrylic acids, styrenes amd mixtures thereof.

Application of coating material to bleach particles is preferably carried out in a fluidised bed.

United States patent 4 759 969 and equivalents elsewhere describes in detail a technique for encapsulation of particles, which may be bleach particles, with polymer latex. The procedure disclosed therein is our preferred route for the preparation of coated bleach particles.

We have found that bleach particles coated in accordance with that application have good storage stability in laundry bars, despite the presence of water and alkaline material in a detergent bar composition. In addition to this surprising finding, we have also found that coated bleach particles survive mixing into a detergent bar dough prior to extrusion even when mixing and subsequent extrusion are carried out at temperatures well above the glass transition temperature of the polymer used to encapsulate the bleach particles.

Built laundry bars generally contain a proportion of filler which although chemically inert is significant in contributina to the properties of the bar. Such filler may be incorporated in bars of this invention and an appropriate range for such filler is 5 to 60% by weigh of the bar composition. The filler may consist of water soluble salts such as sodium sulphate but possible it includes water-insoluble filler. The filler present may even all be water insoluble and accordingly the possible amount of water insoluble filler is 5 to 60 wt%. Examples of water insoluble fillers are talc, kaolin, calcite, bentonite and aluminosilicate.

Other ingredients may also be present in the bar composition. These include silicates, e.g. alkaline sodium silicate, sodium carboxymethyl cellulose, lather enhancing agents such as coconut alkanolamides (both monoand di- derivatives) as well as coconut alcohol, colouring materials, enzymes, fluorescers, opacifiers, germicides and perfumes.

It will be appreciated that this invention is concerned with detergent bars which will generally be substantially rigid, enabling such a bar to be rubbed against an item of laundry. Of course if a bar is soaked in water or stored under conditions of excessive humidity it may lose its strength and become plastically deformable by hand pressure.

The bars according to this invention may be prepared by progressively mixing the ingredients, with water, using a high shear mixer as is conventional and then extruding.

It may be desirable to add the coated bleach particles last of all the constituents so that they are subjected to the least amount of shear.

If the bar making procedure entails neutralisation of the acid form of detergent active, it is important to complete the neutralisation before adding the bleach which reacts with strong acid.

Embodiments of this invention will now be described with reference to the accompanying examples.

Example 1 Potassium dichloroisocyanuric acid (KDCCA) from Monsanto chemicals and having a mean particle size of 560 Fm was coated with a latex polymer from National Starch under designation NSC78-6312. This polymer contained the following monomer units, by weight based on the polymer: 10% styrene 60% n-butyl acrylate 30% methacrylic acid.

The polymer had a glass transition temperature Tg of approximately 400C. Its particle size was very small, 0.2 to 0.5;. It was supplied as a latex, and used in this form, when it contained 40% w/w polymer and had a pH of 2.9.

Coating was carried out by the technique described in US 4 759 956, using a Glatt fluidized bed coating apparatus. The polymer latex was sprayed in by the Wurster spray method. The bed temperature was maintained at 42eC which was of course close to the glass transition temperature of the polymer of approximately 400C.

The coated particles contained 75% by weight of the bleach as core particles and 25% by weight polymer coating.

Example 2a Non-soap built doughs of the composition listed in Table I in which all percentages are by weight of the dough formulation (alkyl benzene sulphonic acid neutralised).

Table I (% w/w in dough) A B ABS 30.5 30.5 Soda Ash 15.7 15.7 Calcite (CaCO3) 19.4 20.65 SCMC 2.0 2.0 TSPP 4.1 4.1 STP 7.1 7.1 2 4 5.1 5.1 Water 11.0 11.0 KDCCA (coated) 5.1 KDCCA (uncoated) - 3.85 ABS denotes alkyl benzene sulphonate SCMC denotes sodium carboxymethyl cellulose TSPP denotes tetrasodium pyrophosphate STP denotes sodiumtripolyphosphate KDCCA denotes potassium dichloroisocyanuric acid The doughs were prepared in 500 gram batches in a heated lkg capacity Z-blade mixer at 750C. KDCCA particles from Example 1 were added to the dough at the final stage of mixing. The temperature was maintained at 750C for 50 minutes. Samples were analysed for percentage KDCCA remaining after 5, 25 and 50 minutes.

For a 1st series of results the KDCCA particles were mixed into the dough for 2 minutes at 75rpm and the dough was left to stand in the heated mixer for the remainder of the 50 minute period. Additional mixing for 30 seconds was carried out prior to sampling.

For a 2nd series of results the KDCCA particles were mixed into the dough for 50 minutes at 10 rpm.

For a 3rd series of results the KDCCA particles were mixed into the dough for 50 minutes at 75rpm.

Dough stability data: KDCCA Series Formulation Particle % residual KDCCA at 750C 5 mins 25 mins 50 mins 1 A coated 98 105 97 1 B uncoated 104 97 103 2 A coated 101 98 97 2 B uncoated 103 75 67 3 A coated 96 68 48 3 B uncoated 100 48 29 The results indicate that polymer coated KDCCA particles used in dough A show improved stability over the uncoated KDCCA particles used in dough B under conditions of continuous mixing.

The variations in sequential measurements are thought to reflect small differences in the uniformity of particle distribution throughout the dough.

The comparative stability of coated KDCCA particles is all the more surprising when it is realised that the polymer coating has a transition temperature of approx.

400C i.e. the coating appears to survive shear forces exerted at a temperature 350C in excess of its glass transition temperature.

Example 2b Non-soap, built detergent laundry bars were made from the ingredients listed in Table II in which all percentages are by weight of the formulation used in the manufacture of the bars (prior to neutralisation of the alkyl benzene sulphonic acid).

TABLE II NSD formulations used in the manufacture of bars % w/w in formulation Ingredient C D E Escane F 28.5 28.0 28.0 Soda Ash 6.0 20.0 20.0 Water 5.0 6.0 6.0 Calcite 16.0 23.0 24.25 SCMC - 2.0 2.0 Pyrophosphate 9.4 4.0 4.0 Sodium Tripolyphosphate - 7.0 7.0 2 4 14.1 5.0 5.0 NaHCO3 8.0 Borax 8.0 Coated KDCCA (GK54) 5.0 5.0 Uncoated KDCCA - - 3.75 100.00 100.00 100.00 pH (2.5% Sol) 8.90 10.31 10.40 Escane F is alkyl benzene sulphonic acid SCMC denotes sodiumcarboxymethyl cellulose Formulations C and D in Table II contained coated KDCCA produced as in Example 1 above. Formulation E contained KDCCA which had not been coated, and was used in an amount to provide an equal quantity of KDCCA itself.

This resulted in final bar compositions as given in Table III below, the alkyl benzene sulphonic acid having been neutralised to alkyl benzene sulphonate.

The bars were made using a Z-blade mizer and a small extruder. The sodium alkyl benzene sulphonate was made 'in situ' by neutralising alkyl benzene sulphonic acid with excess soda ash at 550C, approximately half the water being added at this stage. Sodium pyrophosphate and, where appropriate sodium tripolyphosphate were added next followed by the rest of the ingredients and remaining water. After thorough mixing the resulting dough was cooled to 40-450C and the bleach particles mixed in for 1-2 minutes. The mixture was then extruded into bars.

TABLE III NSD bar compositions % w/w in manufactured bar Ingredient C D E ABS 31.0 30.5 30.5 Soda Ash 1.4 15.75 15.75 Water 5.9 6.9 6.9 Calcite 16.2 23.4 24.7 SCMC - 2.05 2.05 Pyrophosphate 9.6 4.1 4.1 STP - 7.1 7.1 2 4 14.4 5.1 5.1 NaHCO3 8.2 Borax 8.2 Coated KDCCA 5.1 5.1 Uncoated KDCCA - - 3.8 100.00 100.00 100.00 Example 3 Some bars produced in Example 2b were wrapped in glassine paper alone, others. were wrapped in glassine paper and then enclosed in a plastic bag. Bars wrapped in each way were stored for varying periods of time under various conditions of temperature and humidity and then analysed to determine the remaining KDCCA content. It was noted that there was some uptake of moisture and a correction was made for this so the results could be expressed as percentages of the amount of KDCCA originally present. These results are set out in the following three tables. They demonstrate that the coating was very effective to increase the amount of KDCCA remaining after storage.

Storage stability data: KDCCA % KDCCA Surviving after different periods of storage under the stated conditions of temperature, humidity and method of bar wrapping A. Storage Conditions - Laboratory (220C/40% RH) Wrapping Glassine paper or glassine paper plus plastic % KDCCA Surviving* Storage Time Glassine Glassine paper (Days) Paper plus plastic C D E C D E 0 100 100 100 100 100 100 7 89.2 110.4 70.7 95.0 108.6 72.1 20 - 95.8 - - 103.9 27 90.0 - 32.6 89.7 - 35.3 50 105.8 - - 100.5 111 - 92.2 7.6 - 98.7 6.7 118 90.0 - - 96.0 * Corrected for water uptake by the bar during storage.

Results indicated that coated KDCCA used in bars C and D is substantially stable during storage whereas uncoated KDCCA as used in bar E in unstable.

Example 4 Storage stability data: KDCCA B. Storage conditions - 280C/70% RH Wrapping Glassine paper or glassine paper plus plastic 8 KDCCA Surviving* Storage Time Glassine Glassine paper (Days) Paper plus plastic C D E C D E 0 100 100 100 100 100 100 7 90.7 104.7 37.8 87.5 105.6 38.9 20 - 98.2 - - 106.2 27 89.0 - 4.4 92.2 - 4.7 50 98.2 - - 105.5 111 - 56.0 0.7 - 82.3 1.8 118 95.7 - - 92.0 * Corrected for water uptake during storage.

Results again show the comparatively high stability of coated KDCCA (as used in compositions C and D) compared with uncoated KDCCA (as used in composition E).

Example 5 C. Storage conditions - 370C/70% RH Wrapping Glassine paper or glassine paper plus plastic % KDCCA Surviving* Storage Time Glassine Glassine paper (Days) Paper plus plastic C D E C D E 0 100 100 100 100 100 100 7 93.2 94.5 6.6 90.7 94.8 11.0 20 - 72.7 - - 83.6 27 87.5 - 2.2 91.7 - 2.5 50 85.7 - - 108.3 - 111 - 16.8 1.2 - 33.1 1.5 118 56.1 - - 87.5 - * Corrected for water uptake during storage.

Coated bleach is again much more stable than uncoated bleach.

Coated bleach is less stable than at 28/70 or ambient.

Coated bleach is more stable in composition C than in D.

Coated bleach is more stable when plastic wrapped.

Example 6 Potassium dichloroisocyanuric acid (KDCCA) was coated with wax of melting point 500C according to the method of Example 1 except that the wax was applied as a molten spray from a torroidal mixer/coater. The coated particles contained 75% by weight of the bleach as core particles and 25% by weight wax coating.

Example 7 Non-soap, built detergent laundry bars were made from the ingredients listed in Table IV in which all percentages are by weight of the formulation used in the manufacture of the bars.

TABLE IV % w/w in formulation Ingredient E F Alkyl benzene sulphonic acid 28.0 27.6 Soda Ash 20.0 15.8 Water 6.0 2.0 Al2 (SO4)3 14. 5H2O - 3.5 Alkaline silicate (48% solids) - 2.0 SCMC 2.0 0.9 TiO2 - 0.5 Calcite 24.25 34.7 STP 7.0 2.4 Na4 pyrophosphate 4.0 4.8 Sodium sulphate 5.0 3.0 Perfume 0.3 Wax coated KDCCA - 2.5 Uncoated KDCCA 3.75 100.00 100.00 pH (2.5% solution) 10.4 10.3 Formulation E in Table IV contained KDCCA which had not been coated. Formulation F in Table IV contained KDCCA produced according to Example 6 above.

The bars were made according to the method of Example 2.

Example 8 The bars produced in Example 7 were wrapped in glassine paper and then enclosed in a plastic bag. The bars were stored under various conditions of temperature and humidity and then analysed to determine the remaining KDCCA content. Corrections were made for moisture uptake and the results expressed as percentages of the amount of KDCCA originally present. The results are set out in the following table. They demonstrate that the coating was very effective in increasing the amount of KDCCA remaining after storage.

Storage stability data: KDCCA Storage % KDCCA surviving* Time (Days) 220C/40% RH 28 C/70% RH 37 C/70% RH E F E F E F 0 100 - 100 - 100 1 - 82.8 - - - 4 - 83.2 7 72.1 - 38.9 - 11.0 11 - 83.6 - 88.4 - 57.2 19 - 101.2 - 76.9 - 53.2 20 - - - - - 27 35.3 - 4.7 71.2 2.5 33 - 76.8 - - - 42.4 49 - 84.8 - 62.0 - 32.4 50 - - - - - 60 - 84.0 - 69.6 - 17.6 83 - 80.8 - 82.4 - 6.4 96 - 76.4 - 54.8 - 5.2 104 - - - 56.4 - 5.2 111 6.7 - 1.8 - 1.5 118 - - - - - * Corrected for water uptake during storage.

The results indicate that coated KDCCA in bars F is substantially more stable during storage than uncoated KDCCA in bars E.

Example 9 Potassium monopersulphate (KMPS) was coated with the latex polymer of Example 1 according to the method of Example 1. The coating was applied at a nominal level of 25% w/w of the total coated particle. The average size of the particles was approximately 250ism.

Example 10 Non-soap doughs were prepared from the ingredients listed in Table V in which all percentages are by weight.

The doughs were prepared in 500 gram batches in a heated lkg capacity Z-blade mixer at 750C. KMPS particles were mixed into the dough at 5% w/w for 2 minutes at 75rpm.

The temperature was maintained at 750C and the dough was left to stand in the mixer for 50 minutes. Samples were analysed for percentage bleach remaining after 5, 25 and 50 minutes. Additional mixing for 30 seconds was carried out immediately before removal of a sample for analysis.

TABLE V Ingredient % w/w in formulation G H I J Escane F 28.0 28.0 28.0 28.0 Soda Ash 20.0 20.0 20.0 20.0 Water 6.25 6.25 5.0 6.25 Calcite 22.75 20.75 22.0 22.75 SCMC 2.0 2.0 2.0 2.0 Na4 pyrophosphate 4.0 4.0 4.0 4.0 STP 7. 0 7. 0 7. 0 7. 0 Na2SO4 5.0 5.0 5.0 5.0 Magilex 808 - 2.0 2.0 KMPS 5.0 5.0 - Coated KMPS - - 5.0 5.0 Escane F is alkyl benzene sulphonic acid.

Magilex 808 is a bleach stabiliser mixture of magnesium silicate/organic sequestrant ex Rhone Poulenc.

Dough stability data: KMPS % residual KMPS at 75OC Formulation Bleach Level of 5 mins 25 mins 50 mins Particle Coating G uncoated - 4.1 2.9 2.5 H uncoated - 5.5 4.8 3.5 I coated 20.35 - - 87.9 J coated 25.0 66.2 72.4 77.3 The results indicate that polymer coated KMPS used in doughs I and J is substantially stable whereas uncoated KMPS as used in doughs I and J is unstable. These results are all the more surprising when it is realised that the transition temperature of the coating is around 400C and the dough temperature was maintained at 750C throughout the test. A marginal improvement in stability is seen for compositions H and I which comprises Magilex 808, a bleach stabiliser.

Example 11 Non-soap, built detergent laundry bars were made from the ingredients listed in Table VI in which all percentages are by weight of the formulation used to prepare the final bar. The bars were made according to the method of Example 2.

TABLE VI t w/w in formulation Ingredient K L Escane F 28.5 28.5 Na2CO3 6.0 6.0 H2O 5.0 5.0 Calcite 16.0 18.5 SCMC Na2 pyrophosphate 3.0 3.0 Na4 pyrophosphate 6.4 6.4 STP NaHCO3 8.0 8.0 Borax 5H2O 8.0 8.0 Na2SO4 9.1 9.1 Coated KMPS 10.0 Uncoated KMPS - 7.5 100.00 100.00 pH (2.5% solution) 8.9 8.9 Example 12 The bars produced in Example 11 were wrapped in glassine paper and then enclosed in a plastic bag. The bars were then stored in various conditions of temperature and humidity and then analysed to determine the remaining KMPS content. Corrections were made for moisture uptake.

Storage stability data: KMPS Storage % KMPS surviving* Time (Days) 220C/40% RH 280C/70% RH 370C/70% RH K L K L K L 0 83.0 73.5 83.0 73.5 83.0 73.5 13 - 72.6 - 5.1 - 5.5 22 86.2 64.5 87.4 6.0 86.0 4.8 43 - 58.0 - 2.0 - 3.0 65 101.5 - 93.3 - 86.9 84 - 54.0 - 1.5 - 1.4 111 - 46.0 - 0.8 - 1.8 142 - - - - - - 148 95.5 - 69.6 - 41.9 * corrected for water uptake during storage.

The results indicate that coated KMPS in bars K is substantially more stable during storage than uncoated KMPS in bars L.

Claims

1. A laundry bar comprising detergent active and builder characterised in that the bar is formed from an extruded, shear mixed dough and additionally comprises chlorine bleach encapsulated with a coating material which is insoluble in water at pH 7.

2. A bar according to claim 1 characterised in that the coating material is soluble or swellable in aqueous alkaline solution.

3. A bar according to claim 1 or 2 characterised in that the bar comprises from 0.1% to 10% by weight of bleach, preferably 0.58 to 6%.

4. A bar according to any preceding claim characterised in that the weight ratio of bleach to coating material lies in the range from 10:1 to 1:4, preferably 5:1 to 1:1.

5. A bar according to any preceding claim wherein the bleach is selected from potassium dichloroisocyanuric acid salts thereof, and potassium monopersulphate.

6. A bar according to any preceding claim wherein the coating material is a synthetic polymer.

7. A laundry bar comprising detergent active and builder characterised in that the bar additionally comprises particles of chloroisocyanuric acid encapsulated by coating in a fluidized bed.

8. A laundry bar comprising detergent active and builder characterised in that the bar additionally comprises particles of monopersulphate salt encapsulated by coating in a fluidized bed.

9. A laundry bar as claimed in claim 7 or claim 8 characterised in that the coating material is wax.

10. A process for preparing a bar according to any of the preceding claims comprising the steps of: (i) encapsulating bleach particles by coating in a fluidised bed; and (ii) mixing detergent active and builder, subsequently adding the encapsulated bleach particles, mixing and extruding into bars.