GB2172300A - Laundry bars - Google Patents

Abstract

Bleach-containing bars used in the handwashing of fabrics comprise from 15-45% by weight of anionic detergent material, 5-60% of detergency builder material, 5 to 30% of sodium perborate and 0.5 to not more than 2.5% of magnesium silicate. Preferred bars contain sodium carbonate, sodium perborate monohydrate and minor amounts of a heavy metal sequestrant. The bars show improved bleach stability and cleaning performance.

Description

SPECIFICATION Laundry bars This invention relates to improved laundry bars for use in the handwashing of fabrics.

Laundry bars for use in the handwashing of fabrics, as distinct from disintegrating laundry or detergent tablets for use in washing machines or bowl washing, must have a good strength to ensure that they retain their structural integrity during handling after manufacture, transport and use. They are popular because they are economical in use, and as the bar is applied directly to the fabric surface by rubbing, they are particularly suitable for use in handwash areas, where little water is employed in the washing process.

The commonly known laundry bars of the art, such as described in GB-A-2 083 490, generally contain from about 7% to about 45% by weight of detergent-active materials and from about 5% to about 60% by weight of detergency builder materials together with a number of optional components, such as abrasives, fillers, perfumes, colouring agents and alkaline salts.

They are used under cold water or luke-warm water conditions.

In an attempt to improve the cleaning performance, it has also been proposed to include a bleaching agent in the laundry bars, but so far without much success.

German Patent Application No 1 086 214 discloses built detergent bars containing sodium perborate.

Since laundry bars for use in the handwashing of fabrics are intended for repeated use, as distinct from disintegrating detergent tablets for use in a single wash operation, the main problem of sodium perborate incorporation in laundry bars lies not only in keeping the bleach stable in the bar on storage before use, but also during use, i.e. in the bar after first and each subsequent use and contact with water.

It has now been found that an improved laundry bar for use in the handwashing of fabrics, having an improved cleaning performance and a satisfactory stability on storage before and during use can be obtained if sodium perborate is incorporated in a laundry bar formulation comprising from 15% to 45% by weight of an anionic detergent-active material and from 5% to 60% by weight of a detergency builder material, together with a minor amount of magnesium silicate (MgSiO.

The amount of magnesium silicate will depend upon the level of perborate in the bar, but in general it can be said that an amount of about 0.5% to not more than 2.5% by weight, preferably from about 1% to 2% by weight of magnesium silicate is quite sufficient to provide the required stabilisation of perborate present at a level ranging from about 5 to 30% by weight.

The stabiliser can either be added to the bar mix during manufacture as magnesium silicate or, alternatively, it can be formed in situ from, for example, magnesium sulphate and- sodium silicate.

The sodium perborate used may be in the form of its tetrahydrate (NaBO3.H202.3H20) or its monohydrate (NaBO3.H202), though the latter form is preferred. The main advantage of sodium perborate monohydrate is that it is more weight effective than sodium perborate tetrahydrate on an equal available oxygen basis. Preferred ranges are from about 6.5 to 15% by weight of sodium perborate monohydrate and from about 10 to 22% by weight of sodium perborate tetrahydrate.

Accordingly, the invention provides an improved bleach-containing laundry bar for use in the handwashing of fabrics, comprising from 15% to 45% by weight of an anionic detergent-active material, from 5% to 60% by weight of a detergency builder material, from about 5% to 30% by weight of sodium perborate and from 0.5 to not more than 2.5% by weight of magnesium silicate.

Satisfactory bars of this formula can be manufactured with a wide range of moisture levels from e.g. 3.5 to about 15%, preferably from 6-11% by weight.

A further improvement can be obtained if the bar also contains a heavy metal sequestrant, such as ethylene diamine tetraacetate, ethylene diamine tetra-(methylene phosphonates), diethylene triamine penta-(methylene phosphonates) and nitrilotriacetate.

These heavy metal sequestrants may be used in the form of their acids or their water-soluble salts, particularly their alkali metal salts, such as the sodium salts. These sequestrants are used in minor proportions with the magnesium silicate, ranging from about 0.05% to a maximum of about 0.7% by weight, preferably from about 0.1% to 0.5% by weight, based on the total bar formulation. Preferred sequestrants are ethylene diamine tetraacetate (EDTA) and nitrilotriacetate (NTA).

The detergent-active and builder components usable in the present invention are well characterised in detergent bar technology. These components are characterised in "Surface Active Agents" Volume I, by Schwartz and Perry (lnterscience, 1958). Usable detergent actives are found in the general class of anionic actives, and can be used in admixture with nonionic, amphoteric, betaine and zwitterionic actives.

A preferred detergent-active component comprises linear or branched-chain alkyl benzene sul phonates (having from 8 to 16 ca'rbon atoms in the alkyl chain), either alone or in admixture with other actives, preferably in minor amounts to the alkyl benzene sulphonate. Specific examples of detergent actives usable in admixture with alkyl benzene sulphonates are alkane sulphonates, alcohol sulphates, olefin sulphonates, monocarboxylic acid salts, ethoxylated alcohols and fatty acid ester sulphonates.

Examples of builder components are: water-soluble phosphate salts, e.g. pentasodium triphosphate, tetrasodium pyrophosphate and sodium orthophosphate; water-soluble carbonates, e.g.

sodium carbonate; organic builders, e.g. sodium nitrilotriacetate, sodium tartrate, trisodium carboxymethyl oxysuccinate, sodium oxydisuccinate and sodium sulphonated long-chain monocarboxylic acids.

Preferred detergency builders for use in the laundry bar of the invention are builder mixtures comprising water-soluble carbonates. Examples of such preferred builder mixtures are: sodium triphosphate/sodium carbonate; tetrasodium pyrophosphate/sodium carbonate; and sodium triphosphate/tetrasodium pyrophosphate/sodium carbonate mixtures.

Fillers such as calcite, various types of clays (e.g. kaolin and bentonite) and sodium sulphate are non-essential ingredients, the amounts and choice of which are adaptable to volume and economical considerations.

Other ingredients, such as silicates, e.g. sodium alkaline silicate; starch, sodium carboxymethylcellulose, colouring materials, fluorescers, opacifiers, germicides, perfumes, including deoperfumes, etc., may also be incorporated as desired.

The laundry bar of the invention can be and is preferably prepared by a process comprising the steps of neutralising the anidnic-active acid, e.g. alkyl benzene sulphonic acid, with alkali, e.g. sodium carbonate, adding all or the major part of the formulation water during or after neutralisation, followed by mixing therewith the appropriate builders and fillers to form a dough, e.g. in a high shear "Z" blade mixer, and adding the sodium perborate, magnesium silicate (or magnesium sulphate+sodium silicate) and other minor ingredients at the final mixing stage.Heat is normally generated during neutralisation, hydration and by the high shear rate, but, if not sufficient, heat can be applied to adjust the temperature to about 60-65"C. Since the temperature required for successful perborate incorporation is critical, the dough temperature during the perborate addition should not exceed 50"C, and should preferably be less than 45"C. This is also the temperature at which other sensitive ingredients, e.g. perfume, fluorescent agent, are incorporated to minimise loss. Remaining water may also be added to adjust the moisture level.

After this final mixing operation, the dough is passed through a roller-mill, before plodding.

Examples l-IV Laundry bars of the following compositions were prepared: Composition (% by weight) I II Ill IV A Sodium branched C12- alkylbenzene sulphonate 31.0 31.0 31.0 31.0 31.0 Tetrasodium pyrophosphate 6.0 6.0 6.0 6.0 6.0 Sodium triphosphate 2.0 2.0 2.0 2.0 2.0 Sodium carbonate 18.0 18.0 18.0 18.0 18.0 Calcite 19.01 14.01 22.41 19.01 19.86 Kaolin - - - - 9.0 Bentonite - - - - 2.0 Sodium sulphate 4.5 4.5 4.6 4.5 4.5 Perfume 0.3 0.3 0.3 0.3 0.3 Fluorescent agent 0.24 0.24 0.24 0.24 0.24 Titanium dioxide - - - - 0.15 Water 6.5 6.5 6.5 6.5 6.5 Sodium perborate tetrahydrate 10.0 - - 10.0 Sodium perborate monohydrate - 15.0 6.5 - Magnesium silicate + EDTA 2.0 2.0 2.0 - Magnesium silicate - - - 2.0 Non-detergent organic matter 0.45 0.45 0.45 0.45 0.45 I, II, Ill and IV were compositions of laundry bar products of the invention; A was a composition of a control laundry bar without bleach.

Although the filler systems of the laundry bars I, II, Ill and IV of the invention differ somewhat from that of the control bar A and the bars were extruded at relatively low temperatures, because of the presence of perborate, no problems were encountered during processing. Fur thermore, penetrometer measurements taken immediately after extrusion shown that perborate incorporation tends to harden the bar.

Bar type: Bar temperature Average penetration ( C) (mm) A 37 7.5 I, Ill lil and IV 36 7.1 The results of storage stability tests of the bleaching components, i.e. sodium perborate tetrahydrate and monohydrate respectively, in bars I, II and Ill, determined over a period of three months at 28"C/70% RH and 37 C/70% RH, showed that both perborate monohydrate in bars II and Ill, and perborate tetrahydrate in bars I and IV were relatively stable when stored under humid conditions, and that bars I, II, Ill and IV of the invention were clearly superior to bar A with or without EDTA alone.

Sealing the perborate bars i, II, Ill and IV of the invention in polythene bags did not appear to confer any significant stability benefits, although the appearance of the bars was much improved.

Assessments were also carried out to determine the bleach loss during use in bars 1 (10% perborate tetrahydrate) and 11 (15% perborate monohydrate).

The bars were analysed before washing and stored overnight in a soap tray at 37 C/70% RH.

This wash/store cycle was repeated and the bars re-analysed. The results are tabulated in Table 1 below: Table I Stability of the bleach systems during use (initial value normalised to 100%) Bar I Bar II % perborate % perborate tetrahydrate monohydrate Initial 100 100 After first storage 89.2 87.2 After second storage 75.8 83.8 Evaluation of bar performance using natural stains: The action of bar I was compared with bar A on a range of bleachable and proteinaceous stains.

Performance comparison after bowl wash: The effect of direct bar application to the stain site was examined in the absence of sunlight.

Stained fabrics taken from the soaping stage were rinsed and tumble-dried. The bleaching contribution resulting from high localised concentration of bar components on the fabrics could thus be isolated. The results clearly show that perborate was extremely effective on most of the stain types examined. Despite the short contact times, the laundry bar I of the invention gave a sisignificant improvement in stain removal as shown in the following Table 2.

Table 2 Stain Stain removal (bR)

Bar A Bar I Red wine 4.8 9.5 Coffee milk 25.0 35.5 Tea 4.3 10.4 Worcester sauce 32.8 40.5 Blood 3.0 5.5 Blackberry 2.8 6.5 Tea milk 14.0 20.2 Performance comparison after line drying: After washing, the fabrics were rinsed and the line-dried in the Weatherometer*.

The results are shown in the following Table 3.

Table 3 Stain Stain removal (R)

Bar A Bar I Blood 3.1 8.5 Blackberry 9.0 14.2 Tea 11.0 15.5 Red wine 8.2 11.0 Coffee milk 41.0 46.0 Weatherometer is a Registered Trademark of Atlas Electric Devices Co., Chicago, Illinois.

Example V Performance comparison was made of control bar A with bar I of the invention containing 10% sodium perborate tetrahydrate, after sunbleaching.

The results are shown in Table 4.

Table 4 Stain Stain removal (#R)

Bar A Bar I Tea 9.6 16.2 Coffee 31.5 36.0 Coffee milk 35.8 42.2 Curry 48.0 55.0 Red wine 8.7 12.4 Example VI The following Table 5 shows the perborate stability of laundry bars containing 10% sodium perborate tetrahydrate together with different stabilisers when stored at 37 , 28 and 200C in polyethylene bags.

Table 5 Time NO ADDITIVES EDTA (0.3%) DEQUEST 2041* (0.3%) MAGNESIUM SILICATE (1.0%) days) 37 C 28 C 20 C 37 C 28 C 20 C 37 C 28 C 20 C 37 C 28 C 20 C (% Perborate) (% Perborate) (% Perborate) (% Perborate) NITIAL 10.3 10.3 10.3 10.3 10.3 10.3 10.1 10.1 10.1 9.9 9.9 9.9 1 5.8 - 9.9 9.9 9.9 9.9 - - - 9.8 9.9 9.9 2 4.5 9.4 9.4 9.5 9.9 9.9 6.5 8.1 9.3 9.8 9.9 9.8 7 2.7 8.5 9.2 8.5 9.0 9.7 0.7 6.3 8.5 9.2 9.6 9.8 14 - 8.0 8.6 3.8 8.7 9.3 - 5.2 8.1 8.9 9.6 9.8 28 - 6.8 7.7 - 8.2 8.7 - 3.0 6.9 8.4 9.6 9.7 35 - 6.7 7.2 - - 7.9 - 1.3 6.2 8.0 9.5 9.8 50 - 5.6 6.4 - 7.1 6.5 - 0.6 5.8 7.8 9.5 9.9 75 - 4.2 6.0 - 5.0 6.4 - - 5.5 5.2 9.4 9.8 100 - 3.2 5.8 - 3.9 6.2 - - 5.2 4.1 9.2 9.8 * Dequest 2041 = ethylene diamine tetra-(methylene phosphoric acid).

Example VII The following Table 6 shows the perborate stability of laundry bars containing 10% sodium perborate tetrahydrate with 2% magnesium silicate.

Table 6 Time 2% MgSiO2 (days) 370C 280C 20"C 0 10.3 10.3 10.3 1 10.2 10.2 10.2 7 10.2 10.2 10.2 24 9:9 10.1 10.2 28 - - 35 9.9 10.0 10.2 50 9.6 9.9 10.1 75 9.5 9.8 10.1 100 9.4 9.7 10.1 Example VIII The following Table 7 shows the perborate stability of laundry bars containing 10% sodium perborate tetrahydrate together with in situ generated magnesium silicate (magnesium sulphate+sodium silicate) at 370C.

Table 7 2% 2% 2% Time in situ in situ in situ (days) Magnesium Magnesium Magnesium silicate silicate silicate + 0.3% EDTA + 0.3% NTA 0 10.2 9.9 10.2 1 10.1 9.8 10.2 7 10.0 9.8 10.2 14 9.9 9.8 10.1 24 9.6 9.7 9.9 35 9.4 9.6 9.9 50 9.4 9.7 9.9 75 8.9 9.1 9.5 100 8.6 9.0 9.6 The basic laundry bar formulation used in Examples Vl-VIII is: Ingredient % by weight Sodium DOBS 28.00 Sodium carbonate 10.00 Tetrasodium pyrophosphate 16.00 Sodium sulphate 4.86 Calcium carbonate 31.73 SCMC 2.00 Fluorescer 0.24 Flexonyl Blue 0.05 Titanium dioxide 0.15 Perfume 0.30 Water 6.50 Impurities, NDOM, etc to 100.00

Claims (12)

1. Bleach-containing laundry bar for use in the handwashing of fabrics, comprising from 15% to 45% by weight of an anionic detergent-active material, from 5% to 60% by weight of a detergency builder material, from about 5% to 30% by weight of sodium perborate and from 0.5% to not more than 2.5% by weight of magnesium silicate.

2. Laundry bar according to claim 1, characterized in that it contains from 1% to 2% by weight of said magnesium silicate.

3. Laundry bar according to claim 1 or 2, characterized in that the sodium perborate is sodium perborate monohydrate.

4. Laundry bar according to claim 1, 2 or 3, characterized in that the anionic detergent-active material is a linear or branched chain alkyl benzene sulphonate having from 8 to 16 carbon atoms in the alkyl chain.

5. Laundry bar according to any one of the claims 1-4, characterized in that the detergency builder material is a mixture comprising a water-soluble carbonate builder.

6. Laundry bar according to any of the above claims, characterized in that it comprises a heavy metal sequestrant in an amount of from about 0.05% to 0.7% by weight, based on the total bar formulation.

7. Laundry bar according to claim 6, characterized in that said amount of heavy metal sequestrant is from 0.1% to 0.5% by weight.

8. Laundry bar according to claim 6 or 7, characterized in that said heavy metal sequestrant is ethylene diamine tetraacetate (EDTA) or nitrilotriacetate (NTA).

9. A process for preparing a bleach-containing laundry bar according to any of the claims 1-8, characterized in that it comprises the steps of neutralising the anionic active acid with an alkali, adding all or the major part of the formulation water during or after neutralisation, following by mixing the detergency builder material to form a dough and adding thereto the sodium perborate and magnesium silicate at the final mixing stage, during which the dough temperature should not exceed 50"C, and finally passing the dough through a roller-mill before extrusion to form the bar.

10. A process according to claim 9, characterized in that said magnesium silicate is added in the form of magnesium sulphate and sodium silicate, which react in situ during the process.

11. A process according to claim 9 or 10, characterized in that the dough temperature during the perborate addition is less than 45"C.

12. A process according to claim 9, 10 or 11, characterized in that the alkali used for the neutralisation reaction is sodium carbonate.