EP0318204A1

EP0318204A1 - Machine dishwashing compositions

Info

Publication number: EP0318204A1
Application number: EP88310845A
Authority: EP
Inventors: Jakob Van Dijk; Hidde Frankena; Hendrik Simon Kielman
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 1987-11-19
Filing date: 1988-11-17
Publication date: 1989-05-31
Also published as: ZA888565B; AU2562488A; GB8727135D0; WO1989004863A1; BR8807311A; JPH02501489A

Abstract

A detergent composition adapted for machine dishwashing in tablet form comprising in combination at least two tablet types, incompatible components being distributed amongst said tablets such that no substantially incompatible ingredients are formulated within the same tablet type.

Description

The present invention relates to machine dishwashing products in tablet form. More particularly it relates to tablet systems wherein incompatible ingredients are formulated into separate tablets, the tablets then being mixed to provide a product having all the desired ingredients.
The most common type of machine dishwashing cleanser is a powder or granulate. The average particle size varies between approximately 0.05 and 2mm diameter. The formulations usually contain alkali-metal polyphosphates, alkali-metal silicates, a bleach and a detergent. The silicates, usually sodium metasilicate, are hygroscopic, and consequently they are difficult to formulate into a spray-dried powder. Compositions are instead produced by a mixing and absorption technique.
In use, the powder is dosed into a small dispenser in the dishwashing machine. During the washing cycle, it is flushed out by a water flow. However, due to the hygroscopicity, the powder can form lumps in the dispenser, resulting in low dosage into the wash. Anticaking ingredients such as paraffin have been added, but without complete success.
As a solution to the problem of caking and uneven dispensing, it has been proposed to use thixotropic liquids, e.g. as described in GB 1 527 706 and GB 2 140 450. However, the cleaning power of such compositions is not in general as good as conventional powder forms.
A third form of machine dishwashing product comprises tablets. Such forms have been disclosed in, e.g. FR 1 472 680, DE-OS-2 857 001 and DE-OS-3 315 950. These tablets may contain conventional ingredients. The disadvantages caused by caking and lump-formation can be substantially eliminated by production of a high relative mass solid tablet.
The formulation of high relative mass tablets does encounter other problems. For example, there are proposals to incorporate enzymes such as proteases and amylases into machine dishwashing compositions (e.g. GB 1 579 946). Enzymic mixtures have been shown to have a greater cleaning performance on soiled dishes and cookware. However, enzymes are not compatible with the hign pH resulting from incorporation of silicates that are usually included to build and to protect glazing.* Thus, the high pH's resulting from metasilicates have been shown to deactivate enzymes, particularly amylase. Furthermore, enzymes and bleaches often included to assist stain removal are incompatible. Solutions to the problem proposed include coating bleach components with soluble polymers such as methacrylates. Such treatments are very difficult when forming tablets.
There is therefore a need for a machine dish-washing composition which is free from such problems as caking and enzyme degradation and which will deliver a suitable cleaning ability.
Accordingly, there is now provided a detergent composition in tablet form comprising in combination at least two tablet types, incompatible components being distributed amongst said tablets such that no substantially incompatible ingredients are formulated within the same tablet type.
For example, the basic composition of all the tablets may be the same. However, silicate components may be incorporated into half the tablets, enzyme components into the other half. Likewise, substantially incompatible ingredients such as bleaches and dyes could be kept separate. After manufacture, the tablets would be mixed to give a final product containing all the required ingredients. The mixture of tablets, generally a random mixture, may be filled directly from a package into the dishwashing machine cup dispenser.
There is a surprising benefit which accompanies the formulation of the machine dishwashing compositions described below in the tablet form: i.e., the enzymes present in tablet formulations contribute substantially more activity than enzymes in powder. It is believed this benefit is due to the differing rates of tablet versus powder dissolution: the silicate component of the tablet composition dissolves more slowly than in powder, or at a rate relative to any buffering builder salts present which is slower than that in powders. In either case, the pH of the washing liquid would not rise as quickly to an enzyme-inactivating value as when a powder is used.
The dissolution rate of silicate with respect to buffering builder salts and/or enzymes seems to play an important role. This is because the first few minutes of a wash cycle using machine dishwash powder seems to inactivate a substantial amount of enzyme.
It is believed this phenomenon of improved enzyme activity from a dishwashing composition in tablet form may be further exploited. If the slower dissolution of silicate from a tablet relative to builder results in improved enzyme activity, then means for speeding up dissolution of builder may be incorporated in the tablet containing the builder. Such means are well known to the art and include incorporating in the tablet, an effervescent agent; an agent which expands upon contact with water; an agent which enhances water solubility of the tablet; or a mixture of such agents. Where one or more of these agents is incoporated in the tablet with the builder, the silicate is preferably in a tablet separate from the builder. Alternatively, one may choose to incorporate an agent in the tablet containing enzyme which delays dissolution. The purpose of this would be to prevent releasing the enzyme into the wash liquid at a time when the pH might be too high. It is clear that different combinations of the ingredients of the composition with one or more of such dissolution-accelerating or -decellerating agents may be made by a person of ordinary skill in the art.
The compositions may contain one or more alkali salts commonly used in dishwashing compositions. Thus, they may contain organic and/or inorganic builder salts such as alkali metal ortho-, pyro- and tripolyphosphates and hexametaphosphates, silicates, carbonates, borates, citrates, carboxymethyloxy-succinates, nitroloacetates and ethylenediaminetetra-acetates, polymeric polyelectrolytes such as polyacrylates, polymaleates and other known organic and inorganic builder compounds. Silicates and enzymes will usually be kept separate.
Usually, the total amount of alkali salts distributed throughout the tablets varies from 10-90% by weight, generally from 30-70% by weight.
The compositions of the invention may also contain a detergent-active compound. If a detergent-active compound is included, it usually is in an amount of from 0.5-10%, usually 1-5%. Any well known type of detergent-active compound may be used, such as soaps, synthetic anionic, nonionic, amphoteric detergent surfactant and mixtures thereof. Preferably, a nonionic detergent surfactant is used, especially a low-foaming one. Suitable examples of such nonionic detergent surfactants can easily be found in M.Schick "Nonionic Surfactants" (1967). The detergent-active compound may be present by itself in a single tablet type or in one or more tablet types having other components. Preferably the detergent-active compound is incorporated in each tablet type such that each tablet type has at least some detergent-active compound and one other component of the composition.
The tablet forms according to the present invention are of particular use in the formulation of enzymic detergents compositions. As enzymes, proteolytic, amylolytic, lipolytic and cellulolytic enzymes can be used, as well as mixtures of such enzymes. The enzymes may be of any suitable origin, such as vegetable, animal, bacterial, fungal and yeast origin. Preferably they are of bacterial and fungal origin.
Suitabie examples of proteolytic enzymes are the subtilisins which are obtained from particular strains of B. subtilis and B. licheniformis, such as the commercially available Maxatase ^(R) (ex Gist-Brocades N.V., Delft, Holland) and Alcalase ^(R) (ex Novo Industri A/S, Copenhagen, Denmark). Particularly suitable are proteases obtained from a strain of Bacillus having maximum activity in the pH range of 8-12, developed and sold by Novo Industri A/S under the registred trade-names Esperase ^(R) and Savinase ^(R). The preparation of such enzymes is described in British patent specification 1 243 784.
Suitable examples of amylolytic enzymes are conmercially available amylases such as Maxamyl ^(R) (ex Gist-Brocades) and Termamyl ^(R) (ex Novo Industri A/S). Amylases as described in British patent specification 1 296 839 are also suitable.
Typical examples of commercial lipolytic enzymes are e.g. Lipase YL, Amano CE, Wallerstein AW, Lipase MY etc. and typical examples of cellulolytic enzymes are cellulases ex Humiscola insolens as described in German patent specification 3 117 250.
The compositions of the invention preferably contain proteolytic and/or amylolytic enzymes, and especially preferably a mixture of proteolytic and amylolytic enzymes.
Usually the amount of enzymes present in the composition is dictated by the enzymatic activity of the enzymes. The higher the activity, the lower the level of enzymes required in the composition. In general, the amount will vary between 0.001 and 10%, and for most practical purposes between 0.1 and 5% by total weight of the composition.
According to the present invention, compositions may be formulated which also contain bleaching agents. The amount of bleach may be 0.02 to 15% by weight.
Layered clays may be included within the tablets in order to reduce spot and film formation. Suitable clays belong to the geological classes of the smectites, the kaolins, the illites, the attapulgites and the mixed layer clays. Particularly preferred are the hectorites, members of the smectite family. The use of clays in machine dishwashing compositions is discussed in EP 0 139 329. The clays may be present at from 0.01 to 60% by weight, preferably 0.5 to 25% by weight, most preferably 0.5 to 5% by weight of the total composition.
The compositions may furthermore contain other useful additives such as, bleaching agent activators, enzyme-stabilising agents, hydrotropes, perfumes, colouring agents, germicides, soil-suspending agents, aminopolyphosphonic acids and alkali metal or alkaline earth metal salts thereof, anti-corrosion agents such as fatty acids, benztriazole and so on, additionally, the compositions may contain filler materials; suitable fillers include alkali metal salts of sulphate and carbonate, and polymeric materials such as polyethylene glycol having molecular weight of 400-10,000.
The compositions according to the present invention are particularly useful in forming coloured compositions, dyes often being unstable in the presence of bleaches or metasilicates. Dyes may be formulated into separate tablets from incompatible components. Thus the end product would be, for example, green and white or red and white tablets.
The products of the present invention are formulated such that they provide a wash liquor with a pH of between 7 and 12, preferably between 9 and 11.
Hygroscopic materials may be coated with, e.g. water soluble resin coatings after pressing in order to prevent premature tablet decomposition.
The tablets may also incorporate effervescent compounds, such as sodium bicarbonate and citric acid. These compounds assist in dissolution of the tablets. It may also be desirable to incorporate materials which swell in contact with water, thus disrupting the tablet structure and increasing the rate of dissolution as the area in contact with the aqueous wash bath increases.
The tablets may contain from 0.2 to 40g of preformulation composition, preferably from 0.5 to 5g. They may be of various shapes, but are preferably cylindrical, about 1cm long and 0.5 cm diameter. These small sizes assist in solubility of the product.
The tablets may be made by any conventional process known in the art. They are generally made by pressing together finely divided powders of the individual components. Compaction pressures can range from 1 x 10³ to 1 x 10⁷ N m⁻², selection of a suitable pressure being made to produce a soluble tablet. Tablet densities may range from 0.5 to 2 g/ml. Conventional tabletting ingredients, such as gums, magnesium silicate and polyethylene glucol may be included within the compositions.
The tablets may be packaged after pressing into some suitable container. In general, a random mixture of tablet types will be mixed together. However, the proportions of the different tablets can be varied according to the amounts of different ingredients which are required. It could fall within the scope of the present invention that the tablet types are packaged separately, and added by the consumer to the wash. Thus, the detergent formulation can be tailored to the requirements of each wash.
According to a further aspect of this invention there is provided a pack comprising a container and, packed thereinto, a first set of tablets comprising a synthetic organic detergent component and at least one other set of tablets comprising further detergent components, components being distributed amongst said tablet sets such that no substantially incompatible ingredients are within the same tablet set.
The invention further relates to a method of cleaning dishes which comprises admixing into a wash bath a plurality of tablets, the tablets being of differing types wherein substantially incompatible components are not within the same tablet type so as to produce an aqueous washing bath of dissolved detergent composition components.
The present invention will now be described in more detail with reference to the following non-limiting Example.

Example 1

The effect of sodium metasilicate on amylase activity was investigated.
Two powder compositions were formulated (X and Y)
Four tablet types were formulated: (A, B, C and D)
In combination, it will be seen;
Enzyme activity was measured as an integral of activity over a period of time.
Tablet combinations 1, 2 and 3 above were investigated, either crushed and added together as a powder, or added in tablet form.
Theoretical 100% activity = 159. It is seen that at high metasilicate levels, integral enzyme activity is higher (i.e. higher activity for a longer period of time) when the detergent composition is added in the form of tablets rather than as a powder.

Claims

1. A detergent composition adapted for machine dishwashing in tablet form comprising in combination at least two tablet types, incompatible components being distributed amongst said tablets such that no substantially incompatible ingredients are formulated within the same tablet type.

2. A composition as claimed in claim 1 wherein enzymes and akali metal silicates are formulated into different tablets.

3. A composition as claimed in claim 1 or claim 2 comprising at least two tablet types, one tablet comprising an alkali-metal phosphate, an amylase and a protease and excluding a silicate and a bleach compound, the second tablet comprising an alkali-metal silicate and a bleach component and excluding enzymes.

4. A composition as claimed in claim 1 or claim 2 or claim 3 comprising at least two tablet types, each of these tablets incorporating a detergent-active compound.

5. A pack comprising a container and, packed thereinto, a first set of tablets comprising a synthetic organic detergent component and at least one other set of tablets comprising further detergent components, components being distributed amongst said tablet sets such that no substantially incompatible components are within the same tablet set.

6. A method of washing dishes in a machine dishwasher comprising forming a wash bath by mixing the detergent composition in tablet form of claim 1 with water, contacting soiled plates with the wash bath, and rinsing the wash bath from the plates.

7. A machine dishwashing composition in tablet form substantially as described herein.