EP1239028A1

EP1239028A1 - Detergent tablets

Info

Publication number: EP1239028A1
Application number: EP01301981A
Authority: EP
Inventors: Huug Lever Fabergé Europe-Development C. Euser; Alan D Lever Fabergé Europe-Develop. C. Tomlinson
Original assignee: Unilever PLC
Current assignee: Unilever PLC
Priority date: 2001-03-05
Filing date: 2001-03-05
Publication date: 2002-09-11

Abstract

A process for producing a multiphase detergent tablet comprising the steps of:

a) introducing a first composition into a mould and compacting;

b) introducing a second composition as a separate layer into the mould and compacting ;

c) introducing a further composition as a layer into a mould and compacting with the same or greater force than for step a).

Description

Technical Field

The present invention is in the field of detergent tablets. More specifically, the invention encompasses a process for preparing a multiphase tablet.

Background of the Invention

Machine dishwashing tablets are popular with the consumer as they have several advantages over powdered products in that they do not require measuring and they are compact and so easy to store.
Aesthetically and technically, it is frequently a requirement that the tablets have more than one layer. However, we have had difficulties in producing multi-layered tablets. Difficulties have also been found in handling multi-layer tablets due to separation of the layers.
The present invention provides multiphase tablets, which are easy to produce and yet do not exhibit separation of the layers.

Description of the Invention

Accordingly, the present invention provides a A process for producing a multiphase detergent tablet comprising the steps of:
a) introducing a first composition into a mould and compacting;
b) introducing a second composition as a separate layer into the mould and compacting and;
c) introducing a further composition as a layer into a mould and compacting with the same or greater force than for step

Detailed Description of the Invention

The process of the invention relate to any tablet having 3 or more phases however it is preferable if the process is for a table having 3 layers.
It is preferable if the force used for the initial compaction pressure, (step a) is 5 kN or greater, preferably 10 kN or greater.
The force used for the middle layers, (step b), is preferably 10 kN or greater more preferably 15 kN or greater, most preferably 20kN or greater.
It is preferable if the compaction pressure for the initial compaction step a) and the middle compaction step b) is 60 kN or less, more preferably 45 kN or less, most preferably 35 kN or less.
It is especially preferable if the compaction step for the middle layer is between 20 kN and 35 kN.
In a preferred form of the process, the compaction pressure of step c) is substantially the same as step a) and a further compaction step d) is undertaken proceedings step c). The force of compaction step d) is at least double the force used for compaction step a).
The final compaction step of the tablet may be conducted after the addition of the addition of the final composition. Alternatively, after the addition of the final composition, a pre-compaction step may be undertaken followed by a final compaction step.
It is preferable if the force used for the final compaction is 50kN or greater, preferably 75kN or greater. However, the final compaction force should 200 kN or less, preferably 150 kN or less. Typically, the final force for compacting the tablet is from 100 to 150 kN.
The tablets of the invention may be in any form suitable for addition to a washing or dishwasher machine.
The compositions for use with the process can be formulated such that different phases have different colors and different textures.
It is particularly preferred if the tablet of the invention is a triple phase tablet the phases being in the form of layers. In such a case, it is highly preferable if the center layer comprises differing compositions to the outer layers of the tablet.
The process of this invention works particularly well if a hydratable salt is present in center layer. It is also particularly preferred if the center layer has a polyethylene glycol present.
It is preferred if the tablet has a strength from 50 to 300 Newton's (N) as measured on a MTS Synergie 100 using a loadcell of 500 N maximum capacity. The initial -and secondary crosshead speeds being set at 25 mm/min, with a deformation limit of 200%.
The tablets of the invention preferably have a mass of greater than 8g, more preferably from 12 to 30g, most preferably 15 to 27g. Tablet with a mass of 20, 22 or 25g are particularly useful.
Polyethylene glycol if present in the tablet preferably has a molecular weight from 1500 to 10,000, more preferably 3000 to 8000.
The total level of polyethylene glycol in the tablet is from 5-wt% to 20 wt %of the total weight of the tablet, more preferably from 7 wt% to 15 wt% of the total weight of the tablet.
If polyethylene glycol is present it is preferable if at least 60 wt% of the polyethylene glycol is in a single phase, more preferably 75 wt% of the hydrocarbon ether, most preferably at least 90wt% of the hydrocarbon ether. If the tablet is a triple layer tablet it is preferable if the ratios cited in the preceding sentence apply to the middle layer.
By the term "hydratable salt", it is meant that the salt is in a state in which it may absorb additional water by hydration. That is to say that the salt is present either in its anhydrous form, or in a partially hydrated form.
The hydratable salt is preferably particulate in nature and may, for example be alkali metal carbonate, bicarbonate, (poly) phosphate, citrate (anhydrous) or sulfate. Mixtures of two or more hydratable compounds may also be used, but preferably, sodium tripolyphosphate is used.
Compositions of the invention preferably comprise a water-soluble phosphate, typically contain this phosphate at a level of from 1 to 90% by weight, preferably from 10 to 80% by weight, most preferably from 20 to 80% by weight of the composition. Specific examples of water-soluble phosphates are the alkali metal tripolyphosphates, sodium, potassium and ammonium pyrophosphate, sodium and potassium orthophosphate, sodium polymeta/phosphate in which the degree of polymerization ranges from about 6 to 21, and salts of phytic acid. Sodium or potassium tripolyphosphate is most preferred.
In a preferred composition sodium tripolyphosphate with high Phase I Content is used.
Sodium tripolyphosphate with high Phase I can be prepared by heating to above the transition temperature at which phase II anhydrous sodium polyphosphate is transformed into the phase I form. A process for the manufacture of particles containing a high proportion of the phase I form of sodium tripolyphosphate by spray drying below 420°C is given in US-A-4536377.
Suitable material is commercially available. Suppliers include Rhodia, Courbevoie, France and Albright & Wilson, Warley, West Midlands, UK. The sodium tripolyphosphate should be partially hydrated, but the phase I anhydrous form should also be present. Thus, the sodium tripolyphosphate in the particles may incorporate up to 5% (by weight of the sodium tripolyphosphate in these particles) of water of hydration. The extent of hydration is desirably from 1% to 4% or 5% by weight. This degree of hydration in general means that the sodium tripolyphosphate is partially hydrated.
The sodium tripolyphosphate in these particles is preferably hydrated by a process that leads to a homogeneous distribution of the water of hydration within the tripolyphosphate.
The bulk density of the of sodium tripolyphosphate particles is preferably 0.75 Kg/M³ or less, more preferably from 0.52 to 0.72 Kg/M³.
It is preferable if the tablet has more than one phase that from 10 wt% to 30 wt% of the total level of phosphate present in the tablet is present in the phase comprising the higher level of polyethylene glycol.
The compositions of the invention may contain a non-hydratable builder in addition to the hydratable salt. However, if the hydratable builder and the hydratable salt are present in a single phase tablet of in the same phase it is preferred if the ratio of hydratable salt to non-hydratable builder is at least 2:1, more preferably 3:1.
If the tablet has at least two phases, it is preferable if the non-hydratable builder is present in a separate phase to the solid hydrocarbon poly ether, especially if the solid hydrocarbon polyether is a polethylene glycol.
The non-hydratable builder is preferably present from 1 to 50% by weight, more preferably from 5 to 30% by weight of the composition. Suitable examples of non-phosphorus-containing inorganic builders include water-soluble alkali metal, borates, and silicates, including layered silicates such as SKS-6 ex. Hoechst, metasilicates, and crystalline and amorphous aluminosilicates, silicates including layered silicates and zeolites.
Organic detergent builders can also be used as nonphosphate builders in the present invention. Examples of organic builders include alkali metal citrates, succinates, malonates, fatty acid sulfonates, fatty acid carboxylates, nitrilotriacetates, oxydisuccinates, alkyl and alkenyl disuccinates, oxydiacetates, carboxymethyloxy succinates, ethylenediamine tetraacetates, tartrate monosuccinates, tartrate disuccinates, tartrate monoacetates, tartrate diacetates, oxidized starches, oxidized heteropolymeric polysaccharides, polyhydroxysulfonates, polycarboxylates such as polyacrylates, polymaleates, polyacetates, polyhydroxyacrylates, polyacrylate/polymaleate and polyacrylate/ polymethacrylate copolymers, acrylate/maleate/vinyl alcohol terpolymers, aminopolycarboxylates and polyacetal carboxylates, and polyaspartates and mixtures thereof. Such carboxylates are described in U.S. Patent Nos. 4,144,226, 4,146,495 and 4,686,062. Alkali metal citrates, nitrilotriacetates, oxydisuccinates, acrylate/maleate copolymers and acrylate/maleate/vinyl alcohol terpolymers are especially preferred nonphosphate builders.
The composition optionally comprises alkali metal silicates. When silicates are present, the SiO₂ level should be from 1% to 25%, preferably from 2% to 20%, more preferably from 3% to 10%, based on the weight of the ADD. The ratio of SiO₂ to the alkali metal oxide (M₂O, where M=alkali metal) is typically from 1 to 3.5, preferably from 1.6 to 3, more preferably from 2 to 2.8. Preferably, the alkali metal silicate is hydrous, having from 15% to 25% water, more preferably, from 17% to 20%.
The highly alkali metasilicates can in general be employed, although the less alkaline hydrous alkali metal silicates having a SiO₂:M₂O ratio of from 2.0 to 2.4 are, as noted, greatly preferred. Anhydrous forms of the alkali metal silicates with a SiO₂:M₂O ratio of 2.0 or more are also less preferred because they tend to be significantly less soluble than the hydrous alkali metal silicates having the same ratio.
Sodium and potassium, and especially sodium, silicates are preferred.
Enzymes may be present in the compositions of the invention. Examples of enzymes suitable for use in the cleaning compositions of this invention include lipases, peptidases, amylases (amylolytic enzymes) and others which degrade, alter or facilitate the degradation or alteration of biochemical soils and stains encountered in cleansing situations so as to remove more easily the soil or stain from the object being washed to make the soil or stain more removable in a subsequent cleansing step. Both degradation and alteration can improve soil removal.
Well-known and preferred examples of these enzymes are lipases, amylases and proteases. The enzymes most commonly used in machine dishwashing compositions are amylolytic enzymes. Preferably, the composition of the invention also contains a proteolytic enzyme. Enzymes may be present in a weight percentage amount of from 0.2 to 5% by weight. For amylolytic enzymes, the final composition will have amylolytic activity of from 10² to 10⁶ Maltose units/kg. For proteolytic enzymes the final composition will have proteolytic enzyme activity of from 10⁶ to 10⁹ Glycine Units/kg.
Bleach material may optionally and preferably be incorporated in composition for use in processes according to the present invention. These materials may be incorporated in solid form or in the form of encapsulates and less preferably in dissolved form.
In general the level of bleach material is preferably greater than 0.5 wt% of a bleaching material.
The bleach material may be a chlorine- or bromine-releasing agent or a peroxygen compound. Peroxygen based bleach materials are however preferred.
Organic peroxy acids or the precursors therefor are typically utilised as the bleach material. The peroxyacids usable in the present invention are solid and, preferably, substantially water-insoluble compounds. By "substantially water-insoluble" is meant herein a water-solubility of less than about 1% by weight at ambient temperature. In general, peroxyacids containing at least about 7 carbon atoms are sufficiently insoluble in water for use herein.
Inorganic peroxygen-generating compounds are also typically used as the bleaching material of the present invention. Examples of these materials are salts of monopersulphate, perborate monohydrate, perborate tetrahydrate, and percarbonate.
Monoperoxy acids useful herein include alkyl peroxy acids and aryl peroxyacids such as peroxybenzoic acid and ring-substituted peroxybenzoic acids (e.g. peroxy-alphanaphthoic acid); aliphatic and substituted aliphatic monoperoxy acids (e.g. peroxylauric acid and peroxystearic acid) and phthaloyl amido peroxy caproic acid (PAP).
Typical diperoxy acids useful herein include alkyl diperoxy acids and aryldiperoxy acids, such as 1,12-di-peroxydodecanedioic acid (DPDA); 1,9-diperoxyazelaic acid, diperoxybrassylic acid, diperoxysebacic acid and diperoxyisophthalic acid; and 2-decyldiperoxybutane-1,4-dioic acid.
Peroxyacid bleach precursors are well known in the art. As non-limiting examples can be named N,N,N',N'-tetraacetyl ethylene diamine (TAED), sodium nonanoyloxybenzene sulphonate (SNOBS), sodium benzoyloxybenzene sulphonate (SBOBS) and the cationic peroxyacid precursor (SPCC) as described in US-A-4,751,015.
If desirably a bleach catalyst, such as the manganese complex, e.g. Mn-Me TACN, as described in EP-A-0458397, or the sulphonimines of US-A-5,041,232 and US-A-5,047,163, is to be incorporated, this may be presented in the form of a second encapsulate separately from the bleach capsule or granule. Cobalt catalysts can also be used.
Among suitable reactive chlorine- or bromine-oxidizing materials are heterocyclic N-bromo and N-chloro imides such as trichloroisocyanuric, tribromoisocyanuric, dibromoisocyanuric and dichloroisocyanuric acids, and salts thereof with water-solubilizing cations such as potassium and sodium. Hydantoin compounds such as 1,3-dichloro-5,5-dimethyl-hydantoin are also quite suitable.
Particulate, water-soluble anhydrous inorganic salts are likewise suitable for use herein such as lithium, sodium or calcium hypochlorite and hypobromite. Chlorinated trisodium phosphate and chloroisocyanurates are also suitable bleaching materials.
Encapsulation techniques are known for both peroxygen and chlorine bleaches, e.g. as described in US-A-4,126,573, US-A-4,327,151, US-A-3,983,254, US-A-4,279,764, US-A-3,036,013 and EP-A-0,436,971 and EP-A-0,510,761. However, encapsulation techniques are particularly useful when using halogen based bleaching systems.
If the tablet has more than one phase it is highly desirable if the bleach and the bleach catalyst is in a separate phase to the colouring agent.
A surfactant system comprising a surfactant selected from nonionic, anionic, cationic, ampholytic and zwitterionic surfactants and mixtures thereof is preferably present in the composition.
Typically the surfactant is a low to non foaming nonionic surfactant, which includes any alkoxylated nonionic surface-active agent wherein the alkoxy moiety is selected from the group consisting of ethylene oxide, propylene oxide and mixtures thereof, is preferably used to improve the detergency without excessive foaming. However, an excessive proportion of nonionic surfactant should be avoided. Normally, an amount of 15% by weight or lower, preferably 10% by weight or lower, more preferably 7% by weight or lower, and preferably 0.1% by weight or higher, more preferably 0.5% by weight or higher, most preferably 1 % by weight or higher.
Examples of suitable nonionic surfactants for use in the invention are the low- to non-foaming ethoxylated straight-chain alcohols of the Plurafac® RA series, supplied by the Eurane Company; of the Lutensol® LF series, supplied by the BasF Company and of the Triton® DF series, supplied by the Rohm & Haas Company.
Other surfactants such as anionic surfactant may be used but may require the additional presence of antifoam to surpress foaming. If an anionic surfactant is used it is advantageously present at levels of 2 wt% or below.
A water-soluble polymeric polycarboxylic compound is advantageously present in the dish wash composition. Preferably these compounds are homo- or co-polymers of polycarboxylic compounds, especially co-polymeric compounds in which the acid monomer comprises two or more carboxyl groups separated by not more than two carbon atoms. Salts of these materials can also be used.
Particularly preferred polymeric polycarboxylates are co-polymers derived from monomers of acrylic acid and maleic acid. The average molecular weight of these polymers in the acid form preferably ranges from 4,000 to 70,000.
Another type of polymeric polycarboxylic compounds suitable for use in the composition of the invention are homopolymeric polycarboxylic acid compounds with acrylic acid as the monomeric unit. The average weight of such homopolymers in the acid form preferably ranges from 1,000 to 100,000 particularly from 3,000 to 10,000.
Acrylic sulphonated polymers as described in EP 851 022 (Unilever) are also suitable.
Preferably, this polymeric material is present at a level of at least 0.1%, more preferably at levels from 1 wt% to 7 wt% of the total composition.
A chelating agent may be present in the composition. If present it is preferable if the level of chelating agent is from 0.5 to 3-wt% of the total composition.
Preferred chelating agents include organic phosphonates, amino carboxylates, polyfunctionally-substituted compounds, and mixtures thereof.
Particularly preferred chelating agents are organic phosphonates such as α-hydroxy-2 phenyl ethyl diphosphonate, ethylene diphosphonate, hydroxy 1,1-hexylidene, vinylidene 1,1 diphosphonate, 1,2 dihydroxyethane 1,1 diphosphonate and hydroxy-ethylene 1,1 diphosphonate. Most preferred is hydroxy-ethylene 1,1 diphosphonate (EHDP).
Anti-tarnishing agents such as benzotriazole and those described in EP 723 577 (Unilever) may also be included.
Optional ingredients are, for example, buffering agents, reducing agents, e.g., borates, alkali metal hydroxide and the well-known enzyme stabilisers such as the polyalcohols, e.g. glycerol and borax; anti-scaling agents; crystal-growth inhibitors, threshold agents; thickening agents and perfumes and the like.
Reducing agents may e.g. be used to prevent the appearance of an enzyme-deactivating concentration of oxidant bleach compound. Suitable agents include reducing sulphur-oxy acids and salts thereof. Most preferred for reasons of availability, low cost, and high performance are the alkali metal and ammonium salts of sulphuroxy acids including ammonium sulphite ((NH₄) ₂SO₃), sodium sulphite (Na₂SO₃), sodium bisulphite (NaHSO₃), sodium metabisulphite (Na₂S₂O₃), potassium metabisulphite (K₂S₂O₅), lithium hydrosulphite (Li₂S₂O₄), etc., sodium sulphite being particularly preferred. Another useful reducing agent, though not particularly preferred for reasons of cost, is ascorbic acid. The amount of reducing agents to be used may vary from case to case depending on the type of bleach and the form it is in, but normally a range of about 0.01% to about 1.0% by weight, preferably from about 0.02% to about 0.5% by weight, will be sufficient.
It is preferable the pH of the wash liquor at ambient temperature is higher than 6.5, more preferably 7.5 or higher, most preferably 8.5 or higher. Preferably the pH is lower than 12, more preferably lower than 11.
The invention will now be illustrated by the following non-limiting Examples
A three layer for machine dishwashing.

Outer layer

	Example 1 (wt%)
Sodium tripolyphosphate (partially hydrated)	56
Sodium citrate	-
Hydrated	-
Na disilicate	9
Na carbonate	16
Nonionic detergent	6
Na perborate	17
TAED	3
Manganese Catalyst	1.1
Sodium polyacrylate	3.7
Enzyme	4.5
Minors	to 100%

A particulate composition for making the middle layer was made by mixing the following ingredients

Middle layer

	wt. %
Polyethylene glycol	49.99
PEG 4000	-
STP	47.50
Heavy Metal sequestrant	2.50
Green dye	0.01

Three layer tablets were made by
i) introducing 9g of the first composition into a mould of a tabletting press, compacting the composition with a force of 25 kN and opening the mould;
ii) putting 4g of the second composition into the mould on top of the compacted first composition, compacting the contents of the mould with a force of 25kN and opening the mould again;
iii) putting a further 9 g of the first composition into the mould, on top of the compacted second composition, then compacting the entire contents of the mould with a force of 45kN, next opening the mould and ejecting the tablet from the mould.
The tablet had identical top and bottom layer of the first composition. Sandwiched between them was a thin middle layer of the second composition.
As an alternative a tablet was prepared as above with the exception that step iii) above was replaced by the following process iv):
iv) putting a further 9 g of the first composition into the mould, on top of the compacted second composition, then compacting the entire contents of the mould with a force of 25 kN , next opening the mould, closing the mould again and compacting again at a force of 100 kN, followed by opening the mould and ejecting the tablet from the mould.
The tablets were easy to manufacture and handled well without separation of the layers.
The tablets handled well on storage and performed well in the wash.

Claims

A process for producing a multiphase detergent tablet comprising the steps of:

a)introducing a first composition into a mould and compacting;

b)introducing a second composition as a separate layer into the mould and compacting ;

c)introducing a further composition as a layer into a mould and compacting with the same or greater force than for step a).
A process according to claim 1 wherein if the compaction pressure of step c) is substantially the same as step a) a further compaction step d) is undertaken proceedings step c) wherein the force of compaction step d) is at least double the force used for compaction step a).
A process according to claim 1 or claim 2 wherein the compaction pressure for step a) is 5 kN or greater, preferably 10 kN or greater.
A process according to any preceding claim in which the compaction pressure for step a) is 45 kN or less, preferably 35 kN or less.
A process according to claim 2 wherein the compaction pressure for step d) is 50kN or greater, preferably 75kN or greater.
A process according to claim 2 wherein the compaction pressure is 200 kN or less, preferably 150 kN or less.
A process according to any preceding claim wherein the composition used for process step b) comprises a polyethylene glycol.
A process according to claim 7 in which the polyethylene glycol has a molecular weight from 3000 to 8000
A process according to any preceding claim wherein the composition used for process step b) comprises an hydratable acid or salt thereof
A process according to claim 9) wherein the hydratable acid or salt thereof is sodium tripolyphosphate.
A detergent tablet according to any preceding claim having three layers.