GB2048931A - Dimensionally Stable Detergent Bars - Google Patents

Abstract

Detergent bars intended for laundry use contain a water resistant matrix which reduces the sogginess and rate of wear in extreme climatic conditions. The matrix is formed within the bars by cross-linking a film forming material by use of a cross- linking agent or heat. Gelatine is a suitable film forming agent. The bars are preferably built and are dimensionally stable.

Description

SPECIFICATION Detergent Bars and Methods of Preparation Field of the Invention This invention relates to improved detergent bars and methods for their preparation.

Detergent bars used for fabric washing, personal washing, or for other cleaning e.g. of hard surfaces are required to have certain desirable properties during use and storage in that they should not become soggy in use, they should not wear out excessively and they should have an agreeable smooth texture and feel. Those properties can be difficult to achieve. When stored and used under adverse conditions of temperature and humidity detergent bars can become soggy and wear out excessively. In addition there is scope to make their texture and feel more agreeable. This invention is directed to improving both built and unbuilt detergent bars.

General Description of Invention According to the invention an effective amount of film forming agent/agents is incorporated in the bar during the preparative stages with or without corresponding crosslinking agent/agents, so as to form in situ, a water resistant matrix within the bar which modifies the bar properties/characteristics such as sogginess, rate of wear, texture and feel. The extent of modification of the characteristics depends upon the film forming agent and its level of incorporation; the cross linking agent (when employed and its level of incorporation; and the process of preparation of the bar. The invention relates both to bars and methods for preparing them. The water resistent matrix is substantially water insoluble but is dispersible as the bar is used. To provide the desired properties the matrix must be formed in situ.Addition of the cross linked materials as a separate component distributes the material throughout the bar in discrete particles; in this form the cross linked material is unable to protect the other components and thereby provide the desired improvements in bar properties.

The present invention provides modification of the above characteristics of detergent bars so that in general they have reduced sogginess and/or a lower rate of wear and, in certain cases, they are smooth in feel.

The invention is of particular application to built detergent bars intended for fabric washing. Bars of this class will contain typically from about 5% to about 60% by weight of each of detergent active and builder material. Built detergent bars contain a variety of components to ensure the bar is able to function efficiently in the fabric washing process. The presence of these several components can make the bar susceptible to a reduction of desirable bar properties, in particular in climatic extremes of humidity and temperature.

The bars formed by the present invention are non-deformable, i.e. dimensionally stable and structurally consistant. The bar is required to be dimensionally stable so that it has utility for laundry and other washing procedures. The use of gelatine, which is optionally cross linked, has been suggested previously to provide an elastic detergent bar intended for childrens use; this formulation is disclosed in German Specification 2,753,850 (Colgate-Palmolive Co.).

The matrix which provides the reduction in sogginess and wear extends substantially throughout the bar in a concentration dependant on the amounts of starting materials used.

Components of the Formulation: A) Film forming agents of use in the present invention are proteins for example gelatin, casein and soyabean extract; amino resins for example urea formaldehyde and melamine formaldehyde; phenolic resins for example resorcinol formaldehyde; cellulose derivatives for example methyl cellulose and carboxy methyl cellulose; epoxy resins polyvinyl acetate, polyvinyl alcohol and other polyfunctional resins; starches, obtained for example from corn, tapioca, potato and sorgham; and starch derivatives for example dextrin, gums and phosphoxylated starch, which are capable of forming, in situ, in the bar, a water resistant matrix of macro molecules by heating to an elevated temperature or by reaction with one or more chemical cross-linking agents.

The cross linkable film forming component will preferably be present in an amount of from about 0.1% to about 50% by weight more preferably about 0.5% to about 10% by weight. This range includes amounts which provide an effect in the final product after the cross-linking step has progressed. When gelatine is used as the film forming material it will preferably be present in the range from about 0.5% to about 25% more preferably about 1% to about 6% by weight of the formulation, more preferably about 2% to about 4% by weight. The gelatine can be used in purified form or in an impure form, for example a gelatine containing glue obtained from animal sources. The gelatine used is required to have sufficient purity to form a gel. Use of gelatine as the film forming material gives the bar a smooth feel.

In general use of the cross linkable material below about 0.5% will not provide the benefit at a consistent level suitable for commericai use and above the upper limit the bar is unlikely to have suitable properties.

The heat treatment induces reaction between the reactive centres of the molecules of certain film forming agents such as amino resins, phenolic resins to form a physical link and/or expedites the effect of a chemical crosslinking agent. The cross linkable component is required to be film forming so that it can coat the particles of the bar components at least in part.

B) The chemical crosslinking agent (when employed) can function as a physical link between two reactive centres on the film forming material or as an agent inducing reaction between two centres. It will usually be present in an amount of about 0.01% to about 100% by weight of the film forming material.

There will be different chemical cross linking agents for different film forming materials. For example, proteins can be crosslinked with aldehydes such as formaldehyde, paraformaldehyde, acetaldehyde, furfural, urea formaldehyde and melamine formaldehyde. Other chemicals such as ketene, dihydroxy acetone, tannins, basic chromium sulphate, salts of zinc, aluminium; quinones, nitroso compounds, polyhydric alcohols and polybasic acids as discussed in the particle "Cross Linkages in Protein Chemistry" published in 'Advances in Protein Chemistry', vol VI, (Academic Press Inc., 1 951) may be used as cross linking agents for proteins. Thus gelatine can be cross linked with formaldehyde (and its polymers), acetaldehyde, glyoxal, furfural, basic chromium sulphate, urea and melamine formaldehyde resins and sodium hypochlorite.

The gelatine may be plasticised, for example with glycerol, before addition; the use of a plasticiser assists distribution of gelatine in the mass. When aldehydes are used to cross link gelatine their preferred level is 0.1% to 5% on the weight of gelatine.

Amino resins can be crosslinked with proteins such as gelatine or casein or in presences of catalysts such as ammonium sulphate.

Phenolic resins can be crosslinked with proteins, paraformaldehyde and hexamine.

Cellulose derivatives such as methyl cellulose and carboxymethyl cellulose can be crosslinked with aldehydes such as formaldehyde, urea formaldehyde and by polyvinyl acetate.

Epoxy resins can be crosslinked with amideamines and polyamines.

Polyvinyl alcohol or polyvinyl acetate can be crosslinked with borax and proteins.

Dextrin can be cross linked with hexametaphosphates and trimetaphosphates, epichlorohydrin and phosphorus oxychloride are cross-linking agents of general utility. The amount of cross linking agent is selected to give a slow reaction with the cross linkable material so the mixed mass could be formed into bars, for example by plodding or pressure tabletting. The usual amount of cross-linking agent is in the range of about 0.5% to 10% by weight of the cross linkable material.

C) Builder and detergent active components are well characterised in the field of detergent bar technology. Examples of these components are listed hereafter and full descriptions of these and other examples of these components will be found in "Surface Active Agents" by Schwartz s Perry published by lnterscience (1949) and volume II by Schwartz, Perry s Berch published by Interscience (1958). Examples of detergent actives usable in both built and unbuilt compositions, the latter including those used for personal washing bars, are present in the general classes of anionic, nonionic, amphoteric, betaine and cationic actives.Specific classes of value are: (a) isethionates containing an alkyl group having from 8 to 1 8 carbon atoms, such actives are termed "Igepon A" and may be derived from, for example, coconut fatty acids; (b) alkali metal salts of alkane sulphonates having an alkyl chain length of from 11 to 17, these actives are prepared by the reaction of a bisulphite ion species with an olefin; (c) sulphates of branched chain alcohols having chain lengths from 1 2 to 1 5, these alcohols are obtainable under the trade name "Dobanol"; (d) alkylaryl sulphonates having an alkyl chain from C,O to C15; (e) dialkali metal salts of sulphonated saturated fatty acids having a chain length from C,2 to C20;; (f) ethoxylated alcohols (C12 to C20) having a degree of ethaxylation between 10 and 20; (g) alkyl (C,2 to Css8) sulphates, having a degree of branching at the alpha position of up to 25%; (h) alkene sulphonates having a chain length from C,4 to C24; (i) alkali metal salts of C8 to C22 long chain fatty acids; and (j) nonionic detergent actives, for example polyoxyalkylene derivatives of alcohols, alkyl amides and alkanolamides, polyoxyalkyiene esters of acids, alkylene oxide block polymers (e.g. Pluronics), polyol esters and acyl alkanolamides.

(k) alkyl (C12 to Crs) ether (1 to 20 EO) sulphates.

Specific examples of the builder component are: Water soluble phosphate salts, e.g. sodium tripoly phosphate, pyrophosphate and orthophate; Water soluble carbonate salts e.g. sodium carbonate; Organic builders e.g. sodium nitrilotriacetate, sodium ethylene diamine tetra-acetate, sodium citrate, sodium tartarate, trisodium carboxymethyloxysuccinate, sodium hydrofuran tetracarboxylate, sodium oxydiacetate, sodium oxydisuccinate and sodium sulphonated long chain (C,4 to C20) fatty acids.

Other ingredients, for example fillers sodium alkaline silicates, starch, sodium carboxymethylcellulose, colouring materials, fluorescors, opacifiers, germicides perfumes, bleaching agents and abrasives are optionally added.

Methods of Preparation It is believed the method of preparation provides the desirable properties of the bar by producting a water resistant matrix cross-linked film forming material encapsulating some or all of the bar components in a subdivided state.

The method of preparation of the bar consists of four steps, viz: i) Mixing the film forming material with the rest of the ingredients in such manner that the film forming material is completely dispersed throughout the mixture, ii) Incorporation of the cross linking agents (when employed) in the mixture of bar ingredients and the film forming material in a well dispersed manner, optionally steps (i) and (ii) can be performed in a single mixing step, iii) Forming of the resultant mass obtained from step (ii) into bars of desired shape, and, optionally, iv) Heat treatment of the shaped bars.

Two examples of step (i) are: A) All the bar ingredients are obtained as a mixture of powdered form. A solution of the film forming material is sprayed on it. The resultant mass is converted into a homogenous mixture by using a signa mixer, a rolling mill or other mixing device.

B) A solution of the film forming material is thoroughly emulsified with a paste of the detergent actives. A small amount of other ingredients (up to 20%) may be present in the paste of detergent actives before the addition of the solution of film forming material. The bulk of the other ingredients are added to the emulsion of detergent actives and film forming material. The mass is then converted into a homogeneous mixture by using a Sigma mixer and/or a rolling mill or other device.

Step (ii) may be accomplished by four methods depending upon the rate of reaction of the cross linking agent with the film forming material, the form in which it is available, and its solubility behaviour.

A) A solid, powdered slow reacting cross linking agent may be added in premixed form with a powder component at any stage of step (i).

B) If the cross linking agent is fast reacting then it is mixed at the stage in step (i) when the final homogeneous mixture is formed.

C) If the cross linking agent is in liquid or solution form there are two options. If it is slow reacting so that it does not gel or precipitate the solution of film forming material then these two components can be mixed and the mixture can replace the solutions of the film forming agent used in step (i).

D) If the cross-linking agent in liquid or solution form is fast reacting, then it can be added to the final mixed mass and thoroughly homogenised using a Sigma mixer and/or a rolling mill or other device so that a mixed mass is obtained which can be processed further.

Step (iii) may be accomplished by normal methods of plodding or compression moulding of the mixed mass to obtain formed bars.

Step (iv) is accomplished (when employed) by exposing the formed bars to a source of heat, for example an oven, for the desired time interval.

These process steps are provided to exemplify but not limit the invention. Thus a modification is to add the cross linking agent to the components before the film forming material.

The overall composition ranges of the various ingredients of the bar are: Detergent active/actives 2% to 95% by weight Detergent builder/builders 0% to 90% by weight Detergent filler/fillers 0% to 90% by weight Other additives etc. 0% to 15% by weight Moisture 0% to 80% by weight Film forming agent 0.1% to 50% by weight Cross linking agent (when present) 0.1% to 100% by weight of film forming agent.

The bar product may be prepared in a container or having an attachment for example a plate, so that not all surfaces can be contacted in use. When a bar is formed in an open-topped container the user can extract the product by rubbing the exposed surface with, for example a moist cloth. The presence of a plate or other holding device would assist in gripping the bar in use.

Specific Examples In use the bars had reduced sogginess with some reduction in the lather achieved. The in-use rate of wear was also reduced. Examples of the detergent bars according to the invention and methods for manufacturing them will now be given to illustrate but not limit the invention.

Sogginess of test bars was measured by storage of a sample of five bars, after a three week ageing period, in humid conditions (95% relative humidity) at constant ambient temperature (320C) for 32 days. Rate of wear in-use was also measured. Sogginess was measured by ranking the samples on a scale from 0 to 24 and in-use wear by subjecting bars to a fabric wash down over 3 days under the above temperature and humidity conditions. The rate of wear is given as % loss on original weight.

The formulations are quoted as parts by weight of the components calculated as the anhydrous materials.

Example I The control bars (A) were made from the formulation: Parts by weight Alkyl (C12) benzene sulphonic acid 25 sodium carbonate 5 sodium tripolyphosphate 20 sodium orthophosphate 6 sodium carboxymethylceliulose (SCMC) 2 talc 9 starch 15 moisture 10 paraffin wax 5 The components were dry mixed, being added together in the order sulphonic acid, carbonate, orthophosphate, wax and then remainder. The formulation was plodded and stamped, after thorough mixing, to form bars.

Test bars B, C, D, E and F were prepared using the above control formulation but with the orthophosphate omitted and the talc level increased. The test bars included an alkali soluble (isoelectric point in acidic pH) gelatine with a bloom strength of 400 as film forming material. This was added as an aqueous solution to the formulation components. The addition of components during the mixing stage was sulphonic acid, carbonate, SCMC, gelatin solution, cross linking agent, wax and remainder of components. The amounts of the components: gelatine (neglecting the water in the solution) and cross linking agent are given in Table I together with the measurements of wear and in-use sogginess.

Table I Components in Parts by Weight Cross linking wear sogginess agent (% (% weight (scale formulation talc gelatine on gelatine) loss) value) A (Control) 9 none none 38.8 7.37 B 1 5 2 Acetaldehyde 19.2 6.0 3% C 15 2 Furfural 22.4 6.1 15% D 1 5 2 Urea 19.2 5.3 Formaldehyde 5% E 15 2 Melamine 24.7 5.1 Formaldehyde 5% F 15 4 Glyoxal 18.7 3.9 4% It is believed the gelatine first acts by coating the powder components and is then cross linked to form a matrix. The improvement in properties follows from the coating provided for the separate particles in the mixture. This data shows the bars of the invention had reduced sogginess and in-use wear; additionally the bars had a smooth feel.

Example II Control bars were prepared by mixing 10 parts by weight of water with 100 parts by weight of a powder of detergent ingredients passing through 100 mesh B S sieve and using following compositions: Powder Ingredients % Weight Detergent active (sodium dodecyl benzene sulphonate) 25.00 Detergent builder (Soda Ash) 3.00 Detergent Filler (Talc) 66.00 Additive (Colour etc.) 4.00 Moisture 2.00 Total 100.00 The mixture was made homogeneous in a Sigma mixer and compressed into bars in a punch and die set.

The test bars were made by the following procedure.

The epoxy resin 'Araldite' (made by CIBA) was mixed with its slow reacting cross linking agent, the commercial 'Hardener' (made by CIBA). The crosslinking agent was employed at 100% on weight of the resin. The mixture was mixed and homogenised with the powder of detergent ingredients mentioned above in a Sigma mixer. The mixer of epoxy resin and its cross linking agent (50/50) was employed at 20% level on the weight of the powder of detergent ingredients. The resultant mass was compressed into bars using a die and punch set. The formed bars were cured by heat treating them at 90"C in an oven for 8 hours.

The test bars were subjected to a qualitative test for sogginess and rate of wear in comparison with the control bars.

The test bars had a far less sogginess and rate of wear as compared to the Control.

Example Ill Ten bars were prepared using the formulations 1 to 10 listed in Table II. Formulation 1 acted as the control bar while formulations 2 to 10 contain amounts of crosslinked film forming materials. The components were dry mixed, being added together in the order sulphonic acid, carbonates tripoly phosphate and then the remainder. The formulation was plodded and cut, after thorough mixing, to form bars.

The bars were subjected to a rate of wear test. The cloth was placed on a smooth surface which was inclined to extend below the surface of water in a trough. A detergent bar was placed on the cloth, contracting it at a face having an area of 5 cm by 3 cm with the 5 cm dimension positioned across the slope. The bar was moved up and down the plane under a force of about 1 90 g tracing a path of 6.5 cm of which about half extended below the water level.

The bar was subjected to 125 cycles (a cycle being two strokes, one in each direction) with a new cloth being used for each period of 25 cycles.

The loss in weight after the bar had been dried at ambient overnight is the rate of wear (R) in grams.

The bars were subjected to an accelerated test to measure the sogginess of the bars. Each bar was weighed and immersed in water at ambient temperature for 2 hours; the resulting surface sog was removed without excess pressure being applied and weighed. The sog was dried in ambient to constant weight and the percentage amount of water in the sog calculated.

The Rate of wear and % bar in sog layer as a percentage of the total weight of bar immersed are given for each formulation in Table II. From these results it will be seen bars 2 to 10 have reduced sogginess compared to the control bar and all bars, with the exception of the lowest level of sodium carboxymethyl cellulose, have reduced rate of wear.

Table II Components in Parts by Weight 1 Bar No. (control) 2 3 4 5 6 7 8 9 10 Alkyl (C12) benzene sulphonic acid 25 25 25 25 25 25 25 25 25 25 Sodium tripoly phosphate 20 20 20 20 20 20 20 20 20 20 Sodium carbonate 10 10 10 10 10 10 10 10 10 10 Calcite 27 25 23 17 23 17 25 19 23 16.6 Sodium sulphate 3 3 3 3 3 3 3 3 3 3 Gelatin - 2 4 10 - - - - - Polyvinyl alcohol - - - - - - 2 6 - Sodium carboxy methyl cellulose - - - - 4 10 - - - Epoxy Amide Resin - - - - - - - - 4 10.4 Borax - - - - - - 0.1 0.5 - Formaldehyde - 0.02 0.04 0.1 0.2 0.5 - - - Water 15 15 15 15 15 15 15 15 15 15 Rate of Wear (gms) 3.5 3.3 2.6 1.3 4.1 3.1 2.6 1.0 2.1 1.6 % Bar in sog layer 8.9 7.7 6.3 4.5 7.6 8.4 7.6 6.4 4.7 4.6 Example IV Three formulations were prepared using starch or dextrin as the film forming material.

Ingredient Formulation (% weight) A B C Sodium lauryl sulphate 18.0 18.0 18.0 Sodium dodecyl benzene sulphonate 7.0 7.0 7.0 Coconut mono-ethanolamide 1.0 2.0 1.0 Sodium tripolyphosphate 12.0 nil 12.0 Raw corn starch 28.0 40.0 26.0 Talc 18.0 17.0 17.0 Sodium sulphate 5.0 5.0 5.0 Titanium dioxide/colour/perfume 1.0 1.0 1.0 Film forming agent (precooked starch 2.0 2.0 nil (white dextrin nil nil 4.0 Water 7.9 7.9 8.0 Epichlorohydrin 0.1 0.1 nil Sodium hexametaphosphate nil nil 1.0 100.0 100.0 100.0 Bars A and C were prepared by first neutralising the sulphonic acid feedstock with soda ash, then adding sodium tripolyphosphate, the film forming material, the remaining components and finally the cross linking agent. The resulting dough was mixed thoroughly, extruded, cut into billets and stamped to form bars. Bars B used the neutralised sulphonate in powder form as feedstock and the above method followed.

Bars B and C were tested for sogginess using the test method of Example I and were found to give values well below a standard commercial bar. Each bar had a texture and fell comparable to a soap bar.

Claims (19)

Claims

1. A dimensionally stable detergent bar comprising a water resistant matrix in an amount sufficient to reduce the sogginess and/or rate of wear of the bar, the matrix being a cross-linked film forming material.

2. A detergent bar according to claim 1, comprising from about 5% to about 60% by weight of detergent active material and from about 5% to about 60% by weight of detergent builder material.

3. A detergent bar according to claim 1 or 2, wherein the matrix contains from about 0.1% to about 50% by weight of the cross linkable film forming material with respect to the total bar.

4. A detergent bar according to claim 3 wherein the matrix contains at least about 0.5% by weight of the film forming material with respect to the total bar.

5. A detergent bar according to claim 3 or 4 wherein the matrix contains up to about 10% by weight of the film forming material with respect to the total bar.

6. A detergent bar according to any preceding claim wherein the matrix contains about 0.01% to about 100% by weight of the crosslinking agent with respect to the amount of film forming material.

7. A detergent bar according to any of claims 1 to 6 wherein the matrix is formed by reaction in situ of a cross-linkable film forming material and a cross-linking agent.

8. A detergent bar according to any of claims 1 to 6 wherein the matrix is a heat cross-linked film forming material.

9. A detergent bar according to any of claims 1 to 8 wherein the cross linked material includes a film forming protein selected from the group gelatin, casein and soyabean extract.

10. A detergent bar according to any of claims 1 to 8 wherein the cross-linked material includes a film forming amine resin selected from the group urea formaldehyde and melamine formaldehyde.

11. A detergent bar according to any of claims 1 to 8 wherein the cross-linked material includes a film forming cellulose derivative selected from the group methyl cellulose and carboxy methyl cellulose.

12. A detergent bar according to any of claims 1 to 8 wherein the cross-linked material includes a film forming poly functional resin selected from the group polyvinyl acetate and polyvinyl alcohol.

13. A process for preparing a detergent bar according to any preceding claim wherein a cross linkable film forming material is mixed with the bar components together with a cross linking agent and the bar formed to allow reaction to occur in situ to form a matrix.

14. A process for preparing a detergent bar according to any preceding claim wherein a cross linkable film forming material is mixed with the bar components, the bar is formed and heated to cross link the film forming material to form a matrix.

1 5. A detergent bar according to claim 1 substantially as herein described.

1 6. A detergent bar substantially as described in any of Examples I, II, Ill and IV.

17. A process for preparing a detergent bar according to claim 13 or 14 substantially as herein described.

18. A process for preparing a detergent bar substantially as described in any of Examples I, II, Ill, and IV.

19. Detergent bars prepared by the process claimed in any of claims 13, 14, 17 and 18.