GB2200132A - Dishwasher composition containing a stabilized enzyme system - Google Patents

Description

j 1 "DISHWASHER COMPOSITIONS CONTAINING A STABILIZED ENZYME SYSTEW'

2200132 The present invention relates to aqueous built dishwasher compositions containing a stabilized enzyme system. The stabilized enzyme system contains a boron compound,, an alpha-hydroxy carboxylic acid, casein and an enzyme. The present invention particularly relates to aqueous liquid thixotropic clay dishwasher compositions containing a stabilized enzyme system comprising a boron compound, e.g. sodium borax, an alpha-hydroxy carboxylic acid, e.g. lactic, tartaric or citric acid, casein and an enzymep e.g. a 'proteolytic or an amylolytic enzyme or a mixture thereof. The present invention specifically relates to automatic dishwashing detergent compositions containing a stabilized enzyme system having enzyme stability and physical stability and which are readily dispersible in the washing medium to provide effective Cleaning of dishware, glassware, china and the like.

The powder built dishwasher detergent compositions and the aqueous built dishwasher detergent compositions, including thixotropic dishwasher compositions that are presently available do not contain stabilized enzyme systems.

The present invention relates to built# enzymecontaining aqueous-liquid dishwasher detergent compositions suitable for cleaning of dishware, glassware, chinay utensils and the like. More particularly. the invention relates to aqueous enzyme -containing liquid dishwasher detergent compositions which contain one or more detergent builders and which are characterised by 1 2 1 being stable compositions.

The automatic dishwashing compositions,, hereinafter also designated ADD,. generally contain (1) sodium tripolyphosphate (NaTPP) to soften or tie up hard-water minerals and to emulsify and/or peptize soil; (2) sodium silicate to supply the alkalinity necessary for effective detergency and to provide protection for fine china glaze and pattern; (3) sodium carbonate, generally considered to be optional, to enhance alkalinity; (4) a chlorine-releasing agent to aid in the elimination of soil specks which lead to water spotting and to-aid in the elimination of stainy soils like tea and coffee; and (5) def oamer/ surf actant to reduce foam,, thereby enhancing machine efficiency and supplying requisite detergency. See, for example, SDA Detergents in Depth, "Formulations Aspects of Machine Dishwashing", Thomas Oberle (1974). - Cleaners approxi mating to the aforedescribed compositions are mostly liquids or powders.

The use of a chlorine releasing agent, however, in some dishwasher formulations has been found to be objectionable because the chlorine releasing agent tends to react with other chemically active ingredients, particularly surfactant (see U.S.P.

4,,115F308), thereby degrading the suspending or thixotropic agentand impairing its effectiveness. It is a feature and an advantage of the present invention that a chlorine releasing agent is not required in the dishwasher composition.

The formulation of stabilized enzyme-containing liquid dishwasher compositions has been a difficult problem. The desirability of incorporating enzymes into dishwasher detergent compositions is primarily due 3 to the ef f ectiveness of proteolytic and amylolytic enzymes in decomposing proteinaceous and starchy materials found on dirty dishes and utensils, thereby facilitating the removal of leftover food materials, such as gravy, egg,, tomato sauce, chocolate and the like during automatic machine dishwasing. However, enzymatic materials suitable for dishwasher compositions, particularly proteolytic enzymes, are relatively expensive. Moreover, enzymes are known to be unstable in aqueous built detergent laundry Compositions.

In the case of liquid laundry detergent compositions containing a phosphate builder, the problem of enzyme instability is known to be particularly acute. Primarily this is because phosphate detergent builders have a destabilizing effect on enzymes. Moreover, the incorporation of a phosphate builder into a liquid dishwasher detergent composition poses an additional problem, namely the ability to form a stable singlephase composition; the solubility of sodium tripolyphosphate, for example,, being relatively limited in aqueous compositions, and especially in the presence of anionic detergents.

The stabilization of enzymes in detergent compositions having a high alkalinity is also difficult because high alkalinity is known to deactivate enzymes. While it is possible to reduce the pH to improve enzyme stability this negates to some extent the benefit of is the builders. The stabilized enzyme system of the present invention provides enzyme stability even at relatively high pH's, up to pH 10-12. The higher pH's, e.g. pH 10-12, are known to give better detergency and are preferred. Reducing the pH of the detergent composition e.g. to pH 7.5 to 9.5 can increase the 1 P 4 stability of the enzyme, but reduces suds lif e and the benefits of the builder. i.e. detergency.

Ulrich U.S.P. 4,,431.559 discloses a thixotropic automatic dishwasher composition comprising an aqueous solvent. a thickening agent, a source of chlorine# an anionic surfactantr builder salts and a buffer system to stabilize the chlorine source.

UOS.P. 3j558,498 discloses a granular laundry detergen composition ' containing stabilized enzymest sodium perborate trihydratei anhydrous trisodium, phosphate. anhydrous calcium sulphate and soluble or dispersible proteins having a molecular weight of 5.000 to 1.000.000. e.g. casein having a molecular weight of 50, 000 to 200,000.

U.S.P. 3.560,392 (a continuation-in-part of U.S.P. 3,558,498) discloses a granular laundry detergent composition containing organic detergent, alkaline builder salt, a stabilized enzyme and a stabilizing amount of proteinaceous collagen having a molecular weight of 5.000 to 250.000.

U.S.P. 4r238,345 discloses a liquid laundry detergent composition in which the enzyme is stabilized by adding an antioxidant and a hydrophilic polyol having 2 to 6 hydroxyl groups. 'The patentee states in column 1 that calcium salts combined with proteins and glycerol combined with proteins have been used to provide enzyme stabilizing systems in aqueous liquid laundry detergents.

U.K. Patent Application G.B. 2j079#305 discloses an aqueous built liquid laundry detergent composition containing an enzyme in which the enzyme is stabilized by a mixture of a polyol and boric acid.

In accordance with the present invention there is provided a polyphosphate built aqueous liquid dishwasher composition containing a stabilized enzyme system comprising a boron compound and an alpha-hydroxy carboxylic acid, and a proteinaceous material, e.g.

casein, and an enzyme.

- The enzyme stabilization is obtained by premixing a boron and alphahydroxy carboxylic acid mixture with an enzyme and casein mixture. This is thought to block, at the same time, the enzyme catalytic sites with casein and to block the enzyme structure with the mixture of the boron compound and the alpha-hydroxy carboxylic acid.

The enzyme stabilizing system of the present invention in addition to providing very good protease stabilization exhibits a very good amylase stabilization, thus allowing the use of dual protease and amylase stabilized systems in high alkaline detergent compositions.

The effective stabilization of amylase enzyme activity is surprising since it would have been expected that any amylase activity would have been destroyed at pH above 9.

In accordance with the present invention, machine washing of dirty dishware and utensils is affected by contacting the dishware and utensils with a heavy duty built aqueous liquid dishwasher composition containing the stabilized enzyme system.

The - aqueous liquid dishwasher compositions of the present invention are capable of satisfactorily cleaning dishware and utensils containing both oily and particulate food soils. Additionally, the described compositions may be employed for the presoak of badly soiled dishes to be washed in an automatic dishwasher i 6 1 1 machine.

The present invention is based upon the discovery that a stabilizing enzyme system comprising a boron compound, an alpha-hydroxy carboxyli c acid, a proteinaceous material, e.g. casein. and an enzyme provide an e ffective and efficient enzyme stabilizing effect to the aqueous liquid dishwasher compositions.

In an embodiment of the present invention there is provided a built aqueous liquid dishwasher composition comprising a stabilized enzyme system and a suspension of a detergent phosphate builder salt in an aqueous liquid anionic surfactant detergent.

In another embodiment of the present invention there is provided an aqueous liquid thixotropic clay is dishwasher composition comprising an enzyme stabilizing system and a suspension of a detergent phosphate builder salt in the aqueous liquid anionic surfactant detergent.

- The applicants have found that a stabilized enzyme syst.em comprising a mixture of a boron compound, an alpha-hydroxy carboxylic acid, a proteinaceous material, e.g. casein and an enzyme provided stable, effective enzyme activity over relatively long periods of time in aqueous liquid dishwasher compositions. The dishwasher formulations of the present invention are physically stable compositions. The aqueous liquid detergent composition of the present invention are easily pourable, easily measured and easily put into an automatic dishwasher machine. 30 It would be desirable to provide an aqueous liquid or an aqueous liquid thixotropic clay dishwasher composition containing a stabilized enzyme system and optionally a physical stabilizing agent.

7 The present invention aims to provide an aqueous liquid dishwasher composition containing a stabilized enzyme system.

The invention also aims to provide an aqueous liquid thixotropic clay dishwasher composition containing a stabilized enzyme system.

- The invention further aims to provide a stabilized enzyme system containing a boron compound, an alphahydroxy carboxylic acid, casein and an enzyme for adding to aqueous liquid and aqueous liquid thixotropic dishwasher compositions to provide effective proteolytic andlor amylolytic enzyme cleaning activity to the dishwasher composition.

The invention also aims to improve the physical stability of aqueous liquid thixotropic gel dishwasher compositions containing stabilized enzyme systems by incorporating in a thixotropic clay dishwasher composition a small effective amount of a fatty acid metal salt, physical stabilizing agent, e.g. aluminium stearate, to inhibit the settling of suspended particles and to prevent phase separation.

According to the p resent invention there is provided an aqueous dishwasher composition containing a stabilized enzyme system which composition comprises: an alkali metal phosphate builder salt, an organic surfactant. a boron compound. a carboxylic acid, a proteinaceous material, and an enzyme.

A preferred embodiment of the invention incorporates in an aqueous thixotropic, e.g. normally gel-like, - composition a stabilized enzyme system. In order to improve the physical stability of the dishwasher composition there can be included in the composition a small effective amount of a physical i Q 1 1 t.

8 stabilizer, for example, a fatty acid or a fatty acid metal- salt. More particularly according to a particularly preferred embodiment of the inventiont there is provided a normally gel-like automatic dishwasher composition in which there is incorporated a stabilized enzyme system containing a boron compound, a n alpha-hydroxy carboxylic acid. casein and an enzymer and a physical stabilizing amount of a long chain fatty acid metal salt which is effective to inhibit settling of the suspended particles.

The present invention provides a phosphate built aqueous liquid dishwasher composition containing a relatively simple stabilized enzyme system which comprises a boron compound, an alpha-hydroxy carboxylic acid, a proteinaceous material,, e.g. casein, and an enzyme. The enzyme stabilizing systemprovides stabilization of the active ingredient enzyme over relatively long periods of time such that small amounts of the expensive enzymes can be used.

The present invention provides an aqueous liquid phosphate built anionic surfactant dishwasher composi tion containing a stabilized enzyme that can be used at effective high pHs of 10-12. The present invention also provides an effective and efficient dishwasher composition that does not require the use of a chlorine compound.

In accordance with a preferred embodiment of the present inventionthere is provided a normally gel-like aqueous automatic dishwasher composition having thixo- tropic properties which includes on a weight basis:.(a) 8 to 35% alkali metal tripolyphosphate; (b) 0 to 20%# such as 2.5 to 20% sodium silicate; (c) 0 to 9% alkali metal carbonate; 9 (d) 0 to 5%, such as 0.1 to 5% water dispersible organic detergent active material; (e) thixotropic clay thickener in an amount sufficient to provide the composition with thixotropy index of 0 to 10, such as about 2. 5 to 10; (f) 0.5-2.0% boron compound# (g) 1.5-4.0% alpha-hydroxy carboxylic acid; (h) 1-4.0% casein; (i) 0.5-2.0% enzyme; (k) (1) salt; and 0 to 5% foam depressant; 0 to 8% sodium hydroxide; 0 to 2% of a long chain fatty acid metal W the balance water.

Also related to this aspect, the invention provides a method for cleaning dishware in an automatic dishwashing machine with an aqueous wash bath containing an effective amount of the liquid automatic dishwasher detergent (LADD) composition as described above. According to this aspect of the invention, the LADD composition can be readily poured into the dispensing cup of the automatic dishwashing machine and will, within just a few seconds, prom ptly thicken to its normal gel-like or pasty state to remain securely within the dispensing cup until shear forces are again applied thereto,, such as by the water spray from the dishwashing machine.

According tothe present invention the activity of the enzyme is stabilized over a relatively long period of time such that smaller amounts of the enzyme provide effective enzyme cleaning activity. The enzyme activity is stabilized by the addition of small effective amounts of a stabilized enzyme system f 4 comprising a boron compound and an' alpha-hydroxy carboxylic acid, and a proteinaceous material, e.g. casein and an enzyme. The stabilized enzyme system is used in aqueous phosphate built anionic detergent compositions.

The stabilized enzyme system is preferably p repared separately and then added to the dishwasher composition.

The stabilize C15,>, enzyme system is preferably prepared in a three step procedure as follows.

1. A boron compound is added to an alPha-hydroxy carboxylic acid or salt to obtain a first mixture.

2. The proteinaceous material, e.g. casein is added to an aqueous alkali solution and the enzyme is added to the aqueous alkali solution to obtain a second mixture.

3. The boron and alpha-hydroxy carboxylic acid mixture obtained in step 1 is then mixed with the proteinaceous material and enzyme mixture obtained in step 2 to obtain the premix stabilized enzyme system of the present invention.

The above step 1 mixture and step 2 mixture can each separately be added to the dishwasher composition. however, the best enzyme stabilizing results are obtained by premixing the step 1 and 2 mixtures and then adding the premixed mixture to the dishwasher composition.

Though the applicant does not wish to be limited to any theory of how the stabilized enzyme system operates# it is believed that the boron compound reacts with the alpha- hydroxy carboxylic acid or the alphahydroxy polycarboxylic acid to form a boric ester. The boric acid ester is believed to react on the enzyme and 11 block its structure in the active conformation so as to protect it from denaturation. The proteinaceous material is believed to block the enzyme catalytic sites hence preventing the digestion of other enzyme molecules during Product storage.

The stabilized enzyme system preferably comprises:

Boron compoundr e.g. Borax, in an amount of 0.4 to 2.51 preferably 0.75 to 2.0 and more preferably 0.9 to 1.2 parts by weight.

Alpha-hydroxy carboxylic acid, in an amount of 1 to 5, pref erably 1.5 to 4. 0 and more pref erably 1.8 to 3.6 parts by weight.

Proteinaceous material, e.g. casein, in an amount of 1 to 6.0, preferably 1 to 4.0, for example about 1.0 to 2.0 parts by weight.

Enzyme in an amount of 0.5 to 3.0. preferably 0.5 to 2.0 and more preferably 0.5 to 1.0 parts by weight.

The weight ratio of alphahydroxy carboxylic acid to boron compound, may be 7:1 to 1:1, preferably 4:1 to 1:1,_and more preferably 3:1 to 2:1.

The weight ratio of proteinaceous material, e.g. casein, to enzyme may be 8:1 to 1: 1, preferably 4:1 to 1:1 and more preferably 4:1 to 2:1.

A preferred stabilized enzyme system for use in the compositions of the present invention comprises the following constituents in the amounts indicated.

Parts by Weiqht Borax (Na2B407.10H20) 0.75 to 2.0 Alpha-hydroxy carboxylic acid 1.5 to 4.0 Casein 1.0 to 4.0 Enzyme 0.5 tc 2.0 The stabilized enzyme system can be added to a dishwasher composition in an amount of 10 to 30 parts z 12 Z :r I- of stabilized enzyme system-to 90 to 70 parts by weight of deteregnt composition,' preferably 15 to 25 parts of stabilized system to 85 to 75 parts by weight of dishwasher composition and more preferably 15 to 20 parts of stabilized system to 85 to 80 parts by weight o-f dishwasher composition. The stabilized enzyme system is added to the dishwasher composition in a manner such that the weight percent of active ingredients of the enzyme system in the dishwasher composition are equivalent to the above mentioned parts.by weight of the active ingredients in the stabilized enzyme system.

According to the present invention the stabilized enzyme system can be used in aqueous liquid dishwasher compositions, aqueous liquid thixotropic dishwasher compositions and in powder or granular dishwasher compositions.

In a preferred embodim ent of the present invention the stabilized enzyme system is added to aqueous liquid 2,0 thixotropic dishwasher compositions.

The alpha-hydroxy carboxylic acids that are preferab ly used in the present invention are the organic carboxylic acids having 3 to 8 carbon atoms, including 1 to 3 carboxylic acid groups,, and 1 to 3 hydroxy groups.

The preferred carboxylic acids are the alphahydroxy carboxylic acids having 3 to 6 carbon atoms,, including 1 to 3. carboxylic acid groups, and 1 to 2 hydroxy groups.. Suitable alpha-hydroxy carboxylic 1 30 13 acids include malic acid (HOOCCHOHCH2COOH), tartaric acid (HOOCCHOHCHOHCOOH), lactic acid (HOOCCHOHCH3) and citric acid (HOOCCH2C(OH)COOHCH2COOH). The pref erred alpha-hydroxy carboxylic acids are tartaricf lactic and citric acids. Citric-acid is the most preferred. The alpha-hydroxy carboxylic acids per se can be used or the acids can be used as their alkali metal saltsf such as sodium and potassium salts.

The boron compounds that are used in the dishwasher compositions of the present invention are preferably those which are water soluble and when added to water form boric acid or an alkali metal salt of boric acid. The boron compounds that are used preferably include boric acid, boric oxide or an alkali metal borate. Suitable alkali metal borates are sodium and potassium ortho-, pyro- and meta-borates, polyborates and borax (Na2B407,10H20). The preferred boron compounds are boric acid,, sodium borate (Na3BO3) and borax (Na2B407,10H20).

The enzymes to be incorporated in the dishwasher compositions of the present invention may be proteolytic or amylolytic enzymes or mixtures thereof. The proteolytic enzymes suitable for the present invention include the various commercial liquid, powder or slurry enzyme preparations which have been adapted for use in detergent compositions.

Though the incorporation of the enzyme in the composition is most conveniently achieved in liquid form, enzymes in slurry form having proven to be useful. Suitable liquid enzyme preparations include "Alcalase" and "Esperase" sold by Novo Industries, Copenhagen,, Denmark, "Maxatase" and "Maxacal" sold by Gist-Brocades, Delft, The Netherlands and Optimase, 1 i 1 Maybrook, Inc. A pref erred casein protein is sold under the trade name "Sodium Caseinate" by Bridal (Prance) or Dena. A.G. (Germany). The Sodium Caseinate is a mixture of several caseins of different molecular weights. The proteins,, e.g. casein, are normally 1 available as powders. The proteins such as casein exist as long chemical chains. As powders the chains are folded upon themselves and form hydrogen bonds holding the protein in a globular form. Unravelling or denaturing the protein involves rupturing these bonds to form a looser more random structure. The proteins can be denatured by boiling, the use of acids. alkalis and various detergents. The unravelled or denatured proteins are more easily digested by enzymes. hence J_. provide a better stabilizing effect, i.e. provide better enzyme stability. The denaturing make,s the protein more effective as a stabilizer. The protein. e.g. casein, is used in an amount sufficient to effect stabilization of the enzyme activity.

Generally, the effectiveness of a thixotropic clay aqueous dishwasher composition is related to (a) alkalinity,, (b) solubility in washing medium, and (c) foam inhibition. It is preferred herein that the pH of the LADD composition be at least about 9.5,, more preferably from about 10.5 to 12.5 and most preferably at least about 11. 5. At the relatively lower pH values,, the dishwasher detergent product is too viscous, i.e. solid-like, and thus not readily fluidized under the shear-force levels created within the dispenser cup under normal machine operating conditions. Addition of NaOH is thus often needed to increase the pH to within the above ranges, and to increase flowability properties. The presence of 16 carbonate is also often needed herein, since it acts as a buffer helping to maintain the desired pH level. Excess carbonate is to be avoided, however, since it may cause the formation of needle-like crystals of carbonate# thereby impairing the stability. thixotropy andlor detergency of the LADD producti as well as impairing the dispensibility of the product fromi for example, squeeze tube bottles. Caustic soda (NaOH) serves the further function of neutralizing the phosphoric or phosphonic acid ester foam depressant when present. About 0. 5 to 3 weight percent of NaOH and about 2 to 9 weight percent of sodium carbonate in the LADD composition are typically preferred, although it should be noted that sufficient alkalinity may be provided by the NaTPP and sodium silicate. The sodium silicate can be employed in amounts of 0 to 20 weight percent, preferably 2.5 to 20 weight percent and more preferably 5 to 15 weight percent.

The NaTPP is preferably employed in the LADD 20 composition in a range of about 8 to 35 weight percent preferably about 20 to 30 weight percent. The NaTPP may be anhydrous or hydrated, including the stable hexahydrate with a degree of hydration ' of 6 corresponding to about 18% by weight of water or more. Actually, in view of the stability of the hexahydrate. the presence of some water of hydration is highly effective, serving it is thought to form seeds of the stable hexahydrate which expedites hydration and solubilization of the remaining NaTPP particles. if only the hexahydrate is used. the detergent product may be too liquid and may have little if any thixotropic character. Conversely, if only the anhydrous NaTPP is used, the product may, in some cases, be too thick and, 1 17 9 theref ore,. unsuitable. Especially preferred LADD compositions are obtained, f or example, when using a 0.5:1 to 2:1 weight ratio of anhydrous to hexahydrated. NaTPP,- values of about 1:1 being particularly preferred.

Foam inhibition is important to increase dishwasher machine efficiency and minimize destabilizing effects which might occur due to the presence 7% of excess fc?5,m within the washer during use.

Foam may be sufficiently reduced by suitable selection of the type and/or amount of detergent active material,,, the main foam-producing component. The degree of foam is also somewhat dependent on the hardness of the wash water in the machine whereby suitable adjustment of the proportions of NaTPP which has a water softening effect may aid in providing the desired degree of foam inhibition. However, there may optimally be included a foam depressant or inhibitor where a low foam LADD is desired. Particularly effective are the alkyl phosphonic acid esters of the formula 0 HO-P-R OR available, for example, from BASF-Wyandotte (PCUK-PAE).

and especially the alkyl acid phosphate esters of the formula 0 HO-P-OR 1 OR j 18 available, for example, from Hooker (SAP) and Knapsack (LPKn-158), in which one or both R groups in each type of ester may represent independently a C12-20 alkyl group. Mixtures of the two types or mixtures of mono- and di-esters of the same type,, may be employed. Especially preferred is a mixture of mono- and d'-C1618 alkyl acid phosphate esters such as monostearyl/distearyl acid phosphates 1.2/1 (Knapsack). When employed, proportions of 0.1 to 5 weight percent,, preferably about 0.1 to 0.5 weight percent of foam depressant in the composition is typical, the weight ratio of detergent active component (d) to foam depressant (j) generally ranging from about 10:1 to 1:1 and preferably about 4:1 to 1:1. Other defoamers which may be used include, for example, the known silicones.

The sodium silicate, which provides alkalinity and protection of hard surfaces, such as fine china glaze and pattern, is employed in an amount ranging from about 2.5 to 20 weight percent, preferably about 5 to 15 weight percent in the composition. The sodium silicate is generally added in the form of an aqueous solutiont preferably having an Na2o:S'02 ratio of about 1:2.2 to 1:2.8. At this point,, it should be mentioned that most of the other components of this composition, especially NaOH, foam depressant and thixotropic thickener, are also often added in the form of a preliminary prepared aqueous dispersion or solution.

Detergent active materials useful herein are preferably the organic anionic, amine oxide, phosphine oxide, sulphoxide or betaine water dispersible surfactant types. The anionic surfactants are preferred. The surfactants,, e.g. anionic surfactants are preferably used in amounts ranging from about 0.1 4 1 f t S S 19 to 5%, preferably about 0.3 to 2.0%. Particularly preferred surfactants fo r use herein are the linear or branched alkali metal mono- and/or di- (C8-14) alkyl diphenyl-oxide monoand/or di-sulphates,, e.g. those commercially available, for example, as DOWFAX (Registered Trademark) 3B- 2 and DOWFAX 2A-1. In general, the paraffin sulphonates tend to impair, if not destroy, thixotropy. We have found that at least some paraffin sulphonates unduly increase viscosity causing severe shearing force problems. In additiont the surfactant should be compatible with the other ingredients of the composition. Other suitable surfactants include the primary alkylsulphates, alkylsuphonates, alkylaryi-sulphonates, and sec.-alkylsulphates. Examples include sodium C10-C18 alkylsulphates such as sodium dodecylsulphate and sodium tallow alCoholsulphate; sodium C10-C18 alkanesulphonates such as sodium hexadecyl-1-sulphonate and sodium C12-C18 alkylbenzenesulphonates such-as sodium dodecylbenzene- sulphonates.- The corresponding potassium salts may also be employed. Examples of suitable alkyl sulphonates are the C10 to C18 primary alkyl sodium and potassium sulphonates, with the C10 to C15 primary normal alkyl sodium sulphonate salt being preferred.

As other suitable surfactants or detergents,, the amine oxide surfactants are typically of the structure R2R'N-0, in which each R represents a lower alkyl group,, for instance, methyl, and R1 represents a long chain alkyl group having from 8 to 22 carbon atoms, for instance a lauryl, myristyl,palmityl or cetyl group. Instead of an amine oxide, a corresponding surfactant phosphine oxide R2R1PO or sulphoxide RR'SO can be employed. Betaine surfactants are typically -of the structure R2R1 N-WC00-. in which each R represents a lower alkylene group having from 1 to 5 carbon atoms.

Specif ic examples of these surf actants are lauryldimethylamine oxidei myristyldimethylamine oxide,, the corresponding phosphine oxides and sulphoxides, and the corresponding betaines, including dodecyldimethylammonium acetate. tetradecyldiethylammonium pentanoater hexadecyldimethylammonium hexanoate and the like. For biodegradability, the alkyl groups in these sufactants should be linear, and such compounds are preferred.

Surfactants of the foregoing type,, all well known in the art. are described, for example. in U.S. Patents 3,985,668 and 4,271,030.

Thixotropic thickeners, i.e. thickenersor suspending agents which provide an aqueous medium with thixotropic properties, are known in the art and may be organic or inorganic water soluble, water dispersible or colloid-forming,, and monomeric or polymeric, and should of course be stable in these compositions. e.g.

stable to high alkalinity.' Those especially preferred generally comprise the inorganic, colloid-forming clays of smectite and/or attapulgite types. The organic clay thixotropic thickeners can also be used. These materials were generally used in amounts of about 1.5 to 10, pref erably 2 to 5 weight percent to conf er the desired thixotropic properties and Bingham plastic character in the assignee's prior disclosed LADD formulations disclosed in GB 2y116j199A and GB 2,140,450A. In accordance with the present invention, amounts of the inorganic colloid-forming clays of the smectite andlor attapulgite types in the range of from 1 21 about 0.25 to 5%, preferably 0.50 to 4.0%j, especially 1.0 to 3%. are generally sufficient to achieve the desired thixotropic properties and Bingham plastic character. Smaller amounts of the thixotropic agent can be used when used in combination with the fatty acid metal salt physical stabilizer.

Smectite clays include montmorillonite (bentonite) # hectorite, attapulgite. smectite p saponiter and the like. Montmorillonite clays are preferred and are available under tradenames such as Thixogel (Registered trademark) No. 1 and Gelwhite (Registered Trademark) GPi H. etc., from Georgia Kaolin Company; and ECCAGUM (Registered Trademark) GP, Ht etc., from Luthern Clay Products.. Attapulgite clays is include the materials commercially available under the tradename Attagel (Registered Trademark)i i.e. Attagel 40, Attagel 50 and Attagel 150 from Engelhard Minerals and Chemicals Corporation. Mixtures of smectite and attapulgite types in weight ratios of 4:1 to 1:5 are also ' useful herein. Thickening or'suspending agents of the foregoing types are well known in the art. being described,, for example,, in U.S. Patent No. 3,,985,,668 referredto above. Abrasives or polishing agents should b avoided in the LADD compositions as they may mar the surface of fine dishware, crystal and the like.

The amount of water contained in these compositions should, of' course, be neither so high as to produce unduly low viscosity and fluidity#, nor so low as to produce unduly high viscosity and low flowabilityi thixotropic properties in either case being diminished or destroyed. Such amount is readily etermined by-routine experimentation in any particular instance. generally ranging from about 35 to 65 weight 22 percent, preferably about 40 to 55 weight percent. The water should also be preferably deionized or softened. The description of the LADD product, except as otherwise noted, conforms generally to the compositions 5 as disclosed in the aforementioned U.K. Patent Applications GB 2,116,199A and GB 2,140,450A, which are assigned to applicants' assignee. The LADD products of the prior U.K. Patent Application GB 2,166,,199A and GB 2,140, 450A exhibit 10 improved rheological properties as evaluated by testing product viscosity as- a function of shear rate. The compositions exhibited higher viscosity at a low shear rate and lower viscosity at a high shear rate, the data indicating efficient fluidization, and gellation well 15 within the shear rates extant within the standard dishwasher machines. In practical terms, this means improved pouring and processing characteristics as well as less leaking in the machine dispenser-cup, compared to prior liquid or gel ADD products. For applied shear 20 rates corresponding to 3 to 30 rpmr viscosity (Brookfield) correspondingly ranged from about 10,000 to 30,000 cps (at 3 rpm) to about 3,000 to 7,000 cps (at 30 rpm), as measured at room temperature by means of an LVT Brookfiled viscometer after 3 minutes using a No. 4 25 spindle. A shear rate of 7.4 sec-1 corresponds to a spindle rpm of about 3. An approximate ten-fold increase in shear rate produces about a 3- to 9-fold reduction in viscosity. With prior ADD gels, the corresponding reduction in viscosity was only about 230 fold. Moreover, with such compositions, the initial viscosity taken at about 3 rpm was only about 2r500 to 2,,700_ cps. The compositions of the assignee's prior invention thus exhibit threshold fluidizations at lower

1 1 W 23 shear rates and of significantly greater extent in terms of incremental increases in shear rate versus incremental decrease in viscosity. This property of the LADD 'products of the prior invention is summarized in terms of a thixotropic index (TI) which is the ratio of the apparent viscosity at 3 rpm and at 30 rpm. The prior compositions have a TI of from 2 to 10. The LADD compositions tested exhibited substantial and quick return to prior quiescent state consistency when the shear force was discontinued.

Our -prior unpublished application US Serial No.

903,924 corresponding to GB ApplicationNo.

8720698 Serial No. is based upon the discovery that the physical stability,, i.e.. resistance to phase separationj settling, etc.i of the U.K. Patent Applications GB 2,116,199A and GB 2,140,450 liquid aqueous ADD compositions can be significantly improved, without adversely affecting, and in some cases, advantageously affectingr their rheological properties by adding to the composition a small but effective amount of a metal salt of a long Chain fatty acid.

As an example of the improvement in rheologiCal propertiesil it has been found that at low shear rates, e.g 0 at a spindle rpm of about 31 apparent viscosity may often be increased by 2- to 3-fold with the incorporation of as little as 0.2% or less. e.g. 0.16%. of the _fatty acid metal salt stabilizer. At the same time, the physical.stability may be improved to such an extent that even after a long time, twelve weeks. over 30temperature ranges extending from near freezing to 400C,, the compositions containing the fatty acid metal salt stabilizers do not undergo any visible phase separation.

1 j 24 The pref erred long chain f atty acid metal salts are those disclosed in the above mentioned application U.S. Serial No. 903,924. which is incorporated herein by reference. Suitable fatty acid metal salts are the higher aliphatic fatty acid metal salts having from about 8 to about 22 carbon atoms# more preferably from about 10 to 20 carbon atoms, and especially preferably from about 12 to 18 carbon atoms, inclusive of the carbon atom of the carboxyl group of the fatty acid.

The aliphatic radical may be saturated or unsaturated and may be straight or branched. Straight chain saturated fatty acids are preferred. Mixtures of fatty acids may be used, such as those derived from natural sources, such as tallow fatty acid, coco fatty acid,, soya fatty acid, etc., or from synthetic sources available from industrial manufacturing processes.

Thus. examples of the fatty acids from which the polyvalent metal salt stabilizers can be formed include, for example, decanoic acid, dodecanoic acid, palmitic acid, myristic acid. stearic acid, oleic acid, eicosanoic acid, tallow fatty acid, coco fatty acid, soya fatty acid, and Mixtures of these acids. Stearic acid and mixed fatty acids are preferred.

The preferred metals are the polyvalent metals, such as magnesium, calcium, aluminium and zinc.

Many of these metal salts are commercially available. For example, the aluminium salts are available in the triacid form, e.g. aluminium stearate as aluminium tristearate, Al(C17H35C00)3 The monoacid salts,, e.g. aluminium monosterate, Al(O%(C17H35COC)) and didcid salts, e. g. aluminium distearate, Al(OH)C17H35C00)2), and mixtures of two or three of the mono-, di- and tri-acid salts can be used for those t, L metals. e.g. Ali with valences of +3p and mixtures of the mono- and di- acid salts can be used for those metals, e.,g. Zn, with valences of +2.

Calcium stearate, i.e. calcium distearate, magnesium stearate,, i.e. magnesium distearate# aluminium stearatey i.e. aluminium tristearatei and zinc stearate, i.e. zinc distearate. are the preferred polyvalent fatty acid salt stabilizers.

Naturally, for LADD compositions. as well as any other applications where the composition of the present invention will or may come into contact with articles used for the handling, storage or serving of food products or which otherwise may come into contact with or be consumed by people or animals, the use of the 1,5 fatty acids as the stabilizing agent are of particular advantage because of their known low toxicity. For this purpose, the calcium stearate, e.g. calcium disteratei magnesium stearate,, e.g. magnesium distearate are especially preferred as generally safe food additives.

The amount of the fatty acid metal salt stabilizers to achieve the desired enhancement of physical stability will depend on such factors as the nature of the fatty acid salt. the nature and amount of the thixotropic agent. detergent active compound, inorganic salts, especially TPP,, other LADD ingredients. as well as the anticipated storage and shipping-conditions.

Generally, however, amounts of the fatty acid metal salt stabilizing agents in the range of f rom about 0.2 to 2%, preferably from about 0.5 to 1.0%, especially -preferably from about 0.5 to 0.8%, provide the long term stability and absence of phase separation 26 upon standing or during transport at both low and elevated temperatures as are required for a commercially acceptable product.

Depending on the amountsi proportions and types of physical stabilizers and thixotropic agents, the addition of the fatty acid metal salt not only increases physical stability but also provides a simultaneous increase in apparent viscosity. Ratios of fatty acid to thixotropic agent in the range of from about 0.08 to 0.4 weight percent fatty acid and from about 1.3 to 2.5 weight percent thixotropic agent are usually sufficient to provide these simultaneous benefits and,, therefore, the use of these ingredients in these ratios is most preferred..

According to one method of making compositions in accordance with the present invention, one should dissolve or disperse first all the inorganic salts, i.e. carbonate (when employed), silicate and tripolyphosphate, in the aqueous medium. Thickening agent (when employed) is added just before the stabilized enzy me system. The foaT depressor (when employed) is preliminarily prepared as,an aqueous dispersion, as is the thickening agent. The foam depressant dispersion. caustic soda (when employed) and inorganic salts are first mixed at elevated tempertures in aqueous solution (deionized water) and, thereafter, cooled, using agitation throughout. Surfactant. fatty acid stabilizer and thickener dispersion at room temperature are thereafter added to the cooled (20- 250q) solution." The stabilized enzyme system of the present invention is added last. The total salt concentration (NaTPP,, sodium silicate and carbonate) is generally about 20 to 50 weight percent,, preferably about 30 to 40 weight i 27 1 i, percent in the composition. The stabilized enzyme system is generally about 15 to 25 parts by weight,, preferably about 15 to 20 parts by weight of the composition.

Another method f or mixing the ingredients of the LADD f ormulations involves f irst f orming a mixture of the water, foam suppressor (when employed), detergent, physical stabilizert e.g. fatty acidj, (when employed) and thixotropic agent, e.g. clay, (when employed).

These ingredients are mixed together under high shear conditions, preferably starting at room temperature, to form a uniform dispersion. To this premixed portion, the remaining ingredients are introduced under lo w shear mixing conditions. For instance, the required amount of the premix is introduced into a low shear mixer and thereafter the remaining ingredients are added, with mixing, either sequentially or simultaneously. Preferably, the ingredients are added sequentially, although it is not necessary to complete the addition of all of one ingredient before beginning to add the next ingredient. Furthermoret one or more of the ingredients can be divided. into portions and added at different times. Good results have been obtained by adding the remaining ingredients in the following sequence: sodium hydroxide, alkali metal carbonate, sodium silicate, alkali metal tripolyphosphate (hydrated), alkali metal tripolyphosphate (anhydrous or up to 5% Water), sodium hydroxide and the stabilized enzyme system last.

Other conventional ingredients may be included in these compositions in small amounts,, generally less.

than about 3 weight percent, such as perfume, hydro tropic agents such as the sodium benzene, toluene, 28 xylene and cumene sulphonates, perservatives, dyestuffs and pigments and the likei all of course being stable to high alkalinity (properties of all the components). Especially preferred for colouring are the chlorinated phthalocyanines and polysulphides of aluminosilicate which provide, respectively, pleasing green and blue t ints. T'02 may be employed for whitening or neutralizing off-shades.

The liquid ADD compositions of the present invention are readily employed in known manner for washing dishes, kitchen utensils and the like in an automatic dishwasher, provided with a suitable detergent dispenser, in an aqueous wash bath containing an effective amount of the composition.

While the invention has been particularly described in connection with its application to aqueous thixotropic clay automatic dishwasher detergents it will be readily understood by one of ordinary skill in the art that the benefts which are obtained by the addition of the stabilized enzyme system will apply equally well to aqueous liquid dishwasher compositions and powder dishwasher compositions.

The invention may be put into practice in various ways and a number of specific embodiments will be described to illustrate the invention with reference to the accompanying examples.

All amounts and proportions referred to herein are by - w eight of the composition unless otherwise indicated.

EXAMPLE 1

A stabilized enzyme system for use in the present invention was prepared using the following procedure.

(1) 12.6 grams of sodium borate (Na3B03) was 1 1 1 29 i d m added to 56.1 grams of tartaric acid in 90 grams of water with stirring. The mixture was neutralized to_ about pH 7 with 56.1 grams NaOH (50% solution).

(2) 60 grams of casein, supplied by Bridel. were added -to 270 grams of water containing 1.8 grams Na0Hp U nder stirring and heating. After complete dissolu tion. 15 grams Esperase 8.OL were added at 500C. and 9 grams Termamyl 120L were added at room temperature to jg obtain a'casein enzym%.mixture.

(3) The mixtures obtained in steps (1) and (2) above are mixed together to obtain the premixed stabilized enzyme system for use in the present invention.

The entire premixed stabilized enzyme system. i.e.

about 570.6 grams, can be incorporated in an aqueous liquid dishwasher composition or in an aqueous liquid thixotropic clay dishwasher composition to obtain about 3000g of dishwasher composition in accordance with the present invention in which the stabilized enzyme system is present in the amounts given in Table 1. TABLE 1 Weiqht Percent Na.)BO.) j.A Tartaric Acid Casein Esperase 8.OL Termamyl 120L 0.4 1.9 2.0 0.5 0.3 Dishwasher compositions containing the stabilized enzyme system of the present invention are found to ef f iciently clean dirty dishes even in the absence of compounds that supply active chlorine. EXAMPLE 2 A stabilized enzyme system was prepared following 1 1 the procedure of Example 1 containing the ingredients given in Table 2.

TABLE 2

Partsby weight Na2B407. 1 0H20 Citric Acid Casein 0.8 2.6 2.0 Esperase 8.OL 0.5 Termamyl 120L 0.3 A thixotropic clay dishwasher detergent composi- tion was prepared and about 19 parts by weight of the above stabilized enzyme system were added to about 81 parts by weight of a dishwasher detergent composition to obtain the following d ishwasher detergent composition having the ingredients given in Table 3. TABLE 3 Inqredients Deionized water Caustic Soda Solution (50% NaOH) 20 Sodium Carbonate (anhydrous) Sodium Silicate (47.5% solution of Na20:S'02 ratio 1:2.4) Sodium TPP (substantially anhydroust i.e. 0-5%, preferably 3% moisture) (Thermphos NW) Sodium TPP (hexahydrate) (Thermphos N hexa) Na2B407.10H20 Citric Acid Casein Esperase 8.OL Termamyl 120L Monostearyl Phosphate Weiqht Percent 43.7 2.2 5.0 15.74 12.0 12.0 0.8 2.6 2.0 0. 5 0.3 0.16 R T i 31 DOWFAX 3B-2-(45% Na monodecylldidecyl diphenyl oxide disulphonate aqueous solution) Aluminium Stearate Pharmagel H (Thixotropic Clay) 0.80 0.20 2.0 100.00 The aqueous liquid thixotropic dishwasher composition of Example 2 containing the stabilized enzyme systemcomprising 0.5 weight percent Esperase 8.OL and 0.3 weight percent Termamyl 120L enzymes was tested for proteolytic activity and for amylolytic activity after ageing at 40C,, room temperature and 350C. for 1. 4 and 8 weeks. The dishwasher detergent,composition had a pH of about 11.7.. The results obtained are reported in the following Table 4.

TABLE. 4

Ageing Temperature_ 40C Aqeina Time (Weeks) 1 2 4 Room Temp. 350C 1 2 4 1 2 4 Prot.eolytic Activity 77 -- 58 AMylolytic Activity -- 50 -- -- 22 --- 4 -- The borax-citric acid and casein-Esperase and Termamyl stabilized enzyme system not only allows stabilization of amylase under very detrimental conditions (amylase is normally destroyed at pH 9) but also allows an observed amylolytic activity at highly alkaline pH. The dishwasher detergent composition in fact exhibited an.amylolytic activity in the dishwasher composition after 5 months storage at room temperature.

On further testing it was found that the efliciency of the above formulation on hard wastes was higher than for ADD's on the marketj especially at low concentration of 5g/1 in the dishwasher machine.

v i 32 EXAMPLE 3

In accordance with the present invention an aqueous liquid dishwasher detergent composition was prepared which is suitable for handwashing dishes and for presoaking especially dirty dishes prior to machine washing. The composition has the ingredients in the amount indicated in Table 5.

TABLE 5 Inqredients Deionized Water Caustic Soda Solution (50% NaOH) Sodium Carbonate (anhydrous) Sodium Silicate (47.5% solution of Na20:S'02 ratio 1:2.4) Sodium TPP (Thermphos NW) Sodium TPP (Thermphos N hexa) Na2B407.1 0H20 Lactic Acid Casein Esperase 8.OL Monostearyl Phosphate DOWFAX 3B-2 (45% Na monodebylldidecyl diphenyl oxide disulphonate aqueous solution) Aluminium Stearate Weiqht Percent 46.1 2.2 5.0 15.74 12.0 12.0 0.9 1.8 2.0 0.8 0.16 0.80 0.50 100.00 The dishwasher detergent compositions of the present invention containing a stabilized enzyme system 30 can also be formulated as powder dishwasher compositions.

In the above formulating procedure the ingredients and the proportions thereof can be varied by those J k 41 0 1 i skilled in the art to obtain desired dishwashwer detergent. compositions of specific ingredients and proportions.

It is understood that the foregoing detailed description. is given merely by way of illustration and that variations may be made therein without departing from the spirit of the invention.

1 v 1 01 1 34

Claims (21)

1. A dishwasher composition containing a stabilized enzyme system which composition comprises:an alkali metal phosphate builder salt. an organic surfactanty a boron compound, a carboxylic acid. a proteinaceous material, and an enzyme.

2. A dishwasher composition as claimed in Claim 1 in which the said boron compound is borax (Na2B407.10H20), sodium borate (Na3B03), boric acid,, boric oxide or a mixture thereof.

3. A dishwasher composition as claimed in Claim 1 or Claim 2 in which the said proteinaceous material is casein.

4-. An aqueous liquid dishwasher composition containing a stabilized enzyme system which composition comprises in % by weight: water 35-65, an alkali metal phosphate builder salt 8-35. sodium silicate 0-20, an organic surfactant 0-

5. boron compound 0.4-2, carboxylic acid 1-5, proteinaceous material 1-6. and an enzyme 1-6, the total of all the ingredients being 100%by weight.

# 41 1 k Sil 5. An aqueous liquid dishwasher composition as claimed in any one of Claims 1 to 4 comprising a thixotropic clay thickener in an amount up to 5% by weight.

6. A dishwasher composition as claimed in any one of the preceding claims in which the said boron compoun& is borax (Na2B407.10H20), sodium borate (Na3B03), boric acid, loric oxide or a mixture thereof.

7. A dishwasher composition as claimed in any one of the preceding claims in which the said carboxylic acid is an alpha-hydroxy carboxylic acid.

is

8. An aqueous liquid dishwasher composition comprising in percent by weight:

water 40-55, sodium tripolyphosphate (TPP) 20-30p an organic surfactant 0-5, sodium silicate 0-20, sodium carbonate 0-9, an anti-foam agent 0-5.

borax (Na2B407.10H20) 0.75 to 2.0. an alpha-hydroxy carboxylic acid 1.5 to 4.0, casein 1.0 to 4.0. and an enzyme 0.5 to 2.0, the total of all the ingredients being 100% by weight.

9. An aqueous liquid dishwasher composition comprising in percent by weight:

water 40-55.

sodium tripolyphosphate 20-30.

36 is a thixotropic clay thickener 0.25-5.0, an anionic surfactant 0.1-5. sodium silicate 0-20, sodium carbonate 2-9, an anti-foam agent 0.1-0.5. borax (Na2B407.10H20) 0.75 to 2.0, an alpha-hydroxy carboxylic acid 1.5 to 4.0j, casein 1.0 to 4.0, and an enzyme 0.5 to 2.0,, the total of all the ingredients being 100% by weight.

10. An aqueous thixotropic automatic dishwasher composition containing a stabilized enzyme system which composition comprises in percent by weight:

water 40-55, sodium tripolyphosphate 20-30p a thixotropic clay thickener 0.5 to 4.0, sodium silicate 2.5-20.

sodium carbonate 2-9, an anionic surfactant 0.3-2.01 borax (Na2B407.10H20) 0.75 to 2.0r an alpha-hydroxy carboxylic acid 1.5 to 4.0, casein 1.0 to 4.0, and an enzyme 0.5 to 2.0,, the total of all the ingredients being 100% by weight.

11. A dishwasher composition as claimed in any one of the preceding claims in which the anionic surfactant is sodi um linear tridecylbenzene sulphonate.

12.A dishwasher composition as claimed in any one of the preceding claims in which the alpha-hydroxy carboxylic acid is lactic acidy tartaric acid, citric a J i. 1a 37 acid, a sodium salt thereof or a mixture thereof.

z; '

13. A dishwasher composition as claimed in any one of the preceding claims in which the alpha-hydroxy carboxylic acid comprises citric acid or the sodium salt thereof or a mixture thereof.

-

14. An aqueous thixotropic automatic dishwasher composition as claimed in any one of Claims 9 to 13 which contains a long chain fatty acid metal salt physical stabilizing agent in an amount sufficient to increase the physical stability of the composition.

15. A composition as claimed in Claim 14 in which the physical stabilizing agent is aluminium stearate.

16. A composition as claimed in Claim 14 or Claim 15 in which the physical stabilizing agent is present in an amount of about 0.1-2.

17. A composition as claimed in any one of Claims 9 to 16 in which the thixotropic thickener is an inorganic or organic, colloid-forming clay.

18. A composition as claimed in any one of Claims 9 to 17 in which the clay is a montMorillonite clayo, an attapulgite clay, a hectorite clay or a smectite clay.

19. A composition as claimed in any one of the preceding claims which contains 0.1 to 0.5 of an antifoam agent.

20. A composition as claimed in Claim 1 _Z 4.

p 38 substantially as specifically described herein with reference to the examples.

11

21. A method for cleaning soiled dishware which comprises contacting the soiled dishware with an effective amount of a dishwasher composition as claimed in any one of the preceding claims.

Published 198B at The Patent Office, State House, 66?'71 High Holborn, London WClR 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3F.D. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Con. 1/87. m j3aai7 L;ray, urpingTon, rentbitb 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent. 00n. 1157.