GB2296920A - Detergent bars - Google Patents

Abstract

A built, non soap detergent bar comprising 10 to 60% by weight of non soap anionic detergent active, 5 to 60% by weight of detergency builder, and a betaine wherein the anionic surfactant and the betaine are present in a ratio of 1 to 12:1 by weight. Improved skin mildness and physical stability is observed with such bars.

Description

DETERGENT COMPOSITION This invention relates to built, non soap detergent bars which are suitable for use in the laundering of fabrics and the cleaning of hard surfaces.

Commercially available NSD bars typically contain a detergent active component and a detergent builder together with optional components for example abrasives, fillers, perfumes, alkaline salts for example silicates, and bleaching agents.

Non soap detergent bars (hereinafter NSD bars) suitably possess good detergency and physical characteristics, for example a resistance to cracking, low mush and a low rate of wear. Suitably the bar is formulated to provide a mildness to human skin as a further performance benefit.

There remains a need to provide NSD bars having improved detergency and mildness to skin. However, such bars must also exhibit acceptable physical characteristics.

It is known to employ several detergent active components in NSD bars to provide a suitable combination of characteristics. GB 2222410 discloses a detergent bar containing primary alkyl sulphate (PAS) and alkylbenzene sulphonate (LAS) as actives and cellulose which ameliorates breakage and handling difficulties.

US 5043091 discloses laundry bars containing PAS together with LAS and alkyl polysaccharide nonionic surfactants.

Improved foam, skin mildness and fabric softening together with easier processing characteristics are claimed advantages for such bars.

US 5041243 discloses a detergent bar containing PAS, LAS and coco amido propylamine-oxide (CAPO) which provides improved foaming skin mildness and easier processing.

We have now found that the incorporation of a betaine as a further active component in addition to an anionic surfactant can enhance the detergency and skin mildness characteristics of the bar and still provide a NSD bar having acceptable physical properties, in particular, improved resistance to breakage.

According to a first aspect of the invention there is provided a built, non soap detergent bar comprising 10 to 60% by weight of non soap anionic detergent active, 5 to 60% by weight of detergency builder, and a betaine wherein the anionic surfactant and the betaine are present in a ratio of 1 to 12:1 by weight.

The betaine is preferably cocoamidopropyl betaine (CAPB) and is suitably present in an amount of up to 15%, preferably 0.5 to 15% and more preferably 1 to 10% by weight of the bar. The betaine imparts good foaming properties and skin mildness characteristics to the NSD bar. In particular, there is a reduced tendency for the bar to break, for example during transportation thus reducing losses in the production and distribution of the bar.

The anionic detergent active is suitably present in an amount of 12 to 60% and more preferably 15 to 40% by weight of the bar. Suitable anionic actives include alkyl benzene sulphonates of formula R-C6H4-SOM and primary alkyl sulphates of formula ROSO3M where in each formula, R is a linear or branched primary alkyl or alkenyl group containing 8 to 22 carbon atoms, preferably 10 to 18 carbon atoms and M is a cation such that the detergent active is a water-soluble.

Suitably the anionic detergent active comprises, and may consist essentially of, primary alkyl sulphate or alkyl benzene sulphonate. However, it is preferred that the anionic active comprises both alkyl benzene sulphonate and primary alkyl sulphate and more preferably consists essentially of cocoPAS and LAS. PAS and LAS are suitably present in a weight ratio of 9:1 to 1:9 and especially 6:1 to 1:6.

Other anionic actives which may be employed, preferably in an amount less than the PAS and/or LAS include alkane sulphonates, secondary alcohol sulphates oleo in sulphonates, for example a olefin sulphonates and fatty acid ester sulphonates. Soap may be present in the bar however, formation of lather may be inhibited and so the amount should not exceed 2% by weight of the bar.

An alcohol ether sulphate is preferably present and suitably has an alkyl chain of 10 to 18 carbon atoms and an average degree of ethoxylation of 1 to 12 and more preferably 2 to 10 for example lauryl ether sulphate.

Alcohol ether sulphates and oleo in sulphonates provide enhanced oily soil detergency and skin mildness characteristics and, in particular, improved foam formation.

Preferably PAS represents at least 30% and more preferably 40 to 70% of the total detergent in the bar. Suitably LAS represents 5 to 40% and preferably 5 to 30% by weight of the total detergent in the bar.

If present, the other anionic surfactants suitably represent 5 to 40% and especially 10 to 40% of the total detergent in the bar.

Preferably the bar comprises an alkoxylated alcohol having an average degree of ethoxylation of 1 to 20, more preferably 1 to 12 and especially 1 to 10. Suitably the alcohol alkoxylate has an alkyl chain length of 8 to 22 and preferably 10 to 18 carbon atoms.

The alkoxylated alcohol nonionic surfactant provides several advantages including improved detergency for removing oily soil and skin mildness characteristics, and improved cleaning in hard water whilst requiring reduced manual effort. The alkoxylated alcohol is present in an amount of more than 4%, preferably more than 4 to 15%, and more preferably 5 to 10% by weight of the bar. Mixtures of alcohol ethoxylates may be employed as desired.

Mono, di or tri alkanolamides, for example cocomono ethanol amide, may be included in the bar composition as desired and impart an improved feel to the bar.

The detergency builder may be water-soluble, waterinsoluble or a mixture thereof. The builder is preferably present in an amount of 10 to 45% by weight of the bar.

Examples of water-soluble builder components are: watersoluble phosphate salts for example sodium tripolyphosphate, pyrophosphate and orthophosphate; watersoluble carbonates, for example sodium carbonate; organic builders for example sodium nitrolotriacetate, sodium tartrate, sodium citrate, trisodium carboxymethyl oxysuccinate, sodium oxydisuccinate, sodium sulphonated long chain mono carboxylic acids, polyacrylates and oxidised polysaccharides. Especially preferred embodiments of the invention are those in which the builder comprises water-soluble phosphate and/or polyphosphate builder in an amount which is at least 10% by weight of the bar composition.

Suitable water-insoluble builders include alumino silicates for example natural and synthetic zeolites which may be employed in an amount of up to 40% by weight of the bar.

Bars according to this invention will usually contain up to 40% by weight of water-insoluble material, notably from 2% or 5% up to 40% It is conventional that bars include water-insoluble material, customarily referred to as filler which helps to form the structure of the bar. Talc, clays, for example kaolin and bentonite, and especially calcite are conventional for this purpose. If a water-insoluble detergency builder is present, this will also contribute to the content of water-insoluble material.

Although it is not an essential feature, bars embodying this invention may include a structuring system. Suitable structuring systems may consist of a water-insoluble metal compound precipitated during manufacture of the bars. GB Patent 2099013 describes the use of aluminium salts and a soluble silicate to form aluminosilicate in situ.

GB 2234982 A describes the use of further polyvalent metal compounds and siliceous compounds to provide a structuring system. GB 2235205 A discloses the use of phosphates in the provision of water-insoluble structuring material. These prior disclosures are incorporated herein by reference.

The systems of one or other of these prior disclosures are preferably used in the bars of the present invention and contribute to the content of water-insoluble material.

When aluminium salts are incorporated with the intention that they will react to form insoluble structure enhancing compounds, it is possible that a small proportion will not react and remain in the composition as a soluble aluminium salt.

Other structuring systems include porous materials including silicas,aluminosilicate and microfine calcite.

The bars of this invention may optionally include various other materials, both soluble and insoluble. Watersoluble salts such as sodium sulphate may be included as a filler.

The water-soluble alkali metal salts of those sulphur oxo acids which are reducing agents may be included in the composition as bleaches. Preferred is to incorporate from 1 to 15% by weight of such material, better at least 2% or even at least 7.5% by weight. These materials can be used in conjunction with a photobleach such as aluminium phthalocynaine sulphonate.

Other detergent additives include antiredeposition agents such as sodium carboxymethyl cellulose, starches, colouring materials, fluorescers, polyvinyl pyrrolidones, protein hydrolysates and germicides, opacifiers, humectants such as glycerol, polyethylene glycols, perfumes and alternative bleaches such as sodium perborate and potassium monopersulphate. Enzymes may also be included, notably proteases, lipases and amylases.

Long chain alcohols which may be branched and/or linear such as coconut alcohol may be incorporated in bars according to this invention if desired. Some long chain alcohol is likely to be included in commercial supplies of nonionic detergent or primary alkyl sulphate. Notably commercial coconut alcohol sulphate invariable contains some unsulphated material, and there can also be decomposition to the alcohol during bar manufacture.

However, there is no necessity to incorporate such alcohols in addition to the nonionic detergent.

Detergent bars according to this invention may be formulated to yield an alkaline liquor when used. This may be done by including sodium carbonate and/or sodium silicate to raise the alkalinity, (typically to a pH in the range 9.8 to 11.4 when determined as below).

However, we have found that it is both possible and advantageous to formulate detergent bars so as to give a reduced alkaline pH when placed in water. Accordingly the composition of bars embodying this invention may be such that the composition generates a pH in the range from 7.0 to 9.8 when mixed with deionised water at a weight ratio of composition: water of 2.5:97.5 and allowed to dissolve as completely as possible at a temperature of 200C.

In practice the pH of a composition will not vary much with temperature, so that a pH value measured at any temperature in the range from 1500 to 300C will be adequately accurate.

It is preferred that the pH, measured at 200C as stated above, lies in a range from 7.5 to 9.6. The pH may well lie above a lower limit of pH 8.0. Alternatively, or in addition, it may not exceed pH 9.3 or even pH 9.2.

Depending on the intended pH other less alkaline salts may be introduced to provide further control of the pH. Thus for instance sodium carbonate may be at least partially replaced with bicarbonate or borax. Phosphate acid builder salts can help to buffer the pH which is developed on mixing with water.

In use, of course, the proportions of mixing with water are not controlled and deionised water is not used.

nevertheless the pH which is generated in use will be adequately related to that measured under the stated conditions, since it is largely controlled by the salts in the composition.

To prepare bars according to this invention, it is preferred to use if possible the acid form of the detergent(s) active, neutralising them in a mixer and adding other ingredients such as insoluble filler(s), phosphate builder(s) and finally minor ingredients such as perfume. Alkyl sulphate tends to decompose back to a primary alcohol which is the starting material from which primary alkyl sulphate is made and it is difficult to use the acidic form of the detergent. Therefore alkyl sulphates are added to the mixture in the form of their alkali metal salts.

Mixing can be carried out in a high shear mixer and be followed by conventional extrusion and bar stamping.

The required betaine may be added at any stage, but preferably after neutralisation. GB 2099013, 2234982 and 2235205 explain when to add materials which react in situ to form an insoluble structuring system.

Neutralisation is preferably effected by the known procedure of dry neutralisation, in which a carbonate (usually soda ash) is added to the acidic mixture.

Neutralisation in other ways, such as with very concentrated sodium hydroxide solution or a mixture of sodium hydroxide and soda ash, is also possible.

Further surfactants such as alcohol alkoxylates and alcohol ether sulphates which may decompose to produce dioxane under certain conditions are desirably incorporated into the composition after the neutralisation step by which the anionic surfactant may be produced.

The invention will be further explained and illustrated by means of the following examples, in which all proportions and percentages are by weight unless otherwise stated.

Example 1 NSD bars containing PAS and LAS (see Table 1) as the anionic detergent with a further surfactant detergent active component were manufactured on a conventional plant for the manufacture of NSD bars. This plant consisted of a sigma mixer, mill and vacuum plodder.

All mixing of ingredients took place in the mixer, as did dry neutralisation of the acid form of the anionic detergent, as indicated above. Primary alkyl sulphate was added to the mixer in pre-neutralised (i.e. sodium salt) form.

All bars were made with the same dimensions.

Compositions 1 and 2 are listed in Table 1. A comparative Example A was prepared and is listed in Table 1, in which the detergent active consisted of PAS and LAS only. Table 1

1 2 A PAS 18 18 18 LAS 9 3 12 N1 10EO 4.5 CAPB 3 4.5 Calcite 13 STP 15 Sulphite -10 Minors -94 PAS : sodium coconut alkyl sulphate EO : ethylene oxide LAS : C12 alkyl benzene sulphonate CAPB : cocoamido propyl betaine N1 : Nonionic C12,15 alcohol ethoxylate STP : sodium tripolyphosphate Example 2 The tendency of the bars produced in experiments 2 and A to fracture was tested by wrapping 4 bars together to form a quadruplet, placing 6 quadruplets in a packing case and, at 400C, dropping the case 3 times from a height of about 0.8m onto a hard surface. The quadruplets were then inspected and the breakage pattern recorded. The results are shown in Table 2, the figures represent the number of quadruplets).

Table 2

Unbroken Broken in 1 Shattered in direction all directions A 0 | 0 6 2 6 0 0 It will be observed that the bar according to the invention exhibits excellent resistance to fracture.

Example 3 The foaming characteristics of bars produced in Experiments 1, 2 and A were tested in 100FH water in the presence of sebum anti foam.

A 4% by weight solution of the bar was produced which was then mixed with 50m1 100FH water to provide a solution having a product concentration of 2.69g/l. Sebum antifoam was added to this solution to provide a oncentration of 0.5g/l.

A cylinder of the mixture was shaken 20 times and the height of foam remaining after 1 minute was measured. The results (in cm) are tabulated in Table 3.

Table 3

EXPERIMENT 1 2 A .9 12.3 9.2 The results illustrate that bars according to the invention provide improved foam characteristics as compared to a bar of the prior art.

Claims (6)

1. A built, non soap detergent bar comprising 10 to 60% by weight of non soap anionic detergent active, 5 to 60% by weight of detergency builder, and a betaine wherein the anionic surfactant and the betaine are present in a ratio of 1 to 12:1 by weight.

2. A bar according to claim 1 in which the betaine is cocoamidopropyl betaine (CAPB)

3. A bar according to claim 1 or claim 2 in which the betaine is present in an amount of up to 15% by weight of the bar.

4. A bar according to any preceding claim in which the anionic detergent active comprises an alkyl benzene sulphonate and/or a primary alkyl sulphate.

5. A bar according to any preceding claim which comprises PAS and LAS in a weight ratio of 9:1 to 1:9.

6. A bar according to any preceding claim which further comprises an alkane sulphonate, secondary alcohol sulphate, an oleo in sulphonate, an alcohol ether sulphate and/or a fatty acid ester sulphonate.