GB2318800A - Detergent composition - Google Patents

Abstract

Tablets of detergent composition incorporate particles which contain sodium tripolyphosphate with a high proportion of the phase I form, and desirably from 2 to 4% prehydration. This promotes rapid disintegration and dissolution at the time of use, even when a large proportion of further, detergent-containing particles is present.

Description

2318800 DETERGENT COMPOSITION This invention relates to cleaning

compositions in the form of tablets, e. g. for use in fabric washing.

Detergent compositions in tablet form are described,.for example, in GB 911204 (Unilever), US 3953350 (Kao), JP 60015500A (Lion), JP 60-135497A (Lion) and JP 60-135498A (Lion); and are sold commercially in Spain. Tablets have several advantages over powdered products: they do not require measuring and are thus easier to handle and dispense into the washload, and they are more compact, hence facilitating more economical storage.

Detergent tablets are generally made by compressing or compacting a detergent powder, which includes detergent.

is active and detergency.builder. It is desirable that tablets have adequate strength when dry, yet disperse and dissolve quickly when added to wash water.

It is known to include materials whose function is to enhance disintegration of tablets when placed in wash 2.0 water. Some tablets which are sold commercially incorporate urea for this purpose. Urea has a very high solubility in water exceeding 10Ogms per 100m1 water at 20C.

2 Sodium tripolyphosphate is very well known as a sequestering builder in detergent compositions.

It exists in a hydrated form and two crystalline anhydrous forms. These are the normal crystalline anhydrous form, known as phase II which is the low temperature form, and phase I which is stable at high temperature. The conversion of phase II to phase I proceeds fairly rapidly on heating above the transition temperature, which is about 420C, but the reverse reaction is slow. Consequently phase I sodium tripolyphosphate is metastable at ambient temperature.

Phase I material is known to hydrate to the hexahydrate more rapidly than phase IT material. It is also known to dissolve somewhat more rapidly when there is no obstacle to dispersion in the solution. However, during dissolution, this phase I material can form a viscous or solid mass which, in a confined space can hinder dissolution. For instance when making a slurry for spray drying, phase I tripolyphosphate can form so-called "grit", which is a mass of interlocked crystals.

GB-A-1375131 includes a comparison of the dissolution of sodium tripolyphosphate samples containing 38-h and 75k phase I material. Each also containing 5% water of hydration. The sample with 38% of phase I sodium tripolyphosphate dissolved very slightly faster, but both 3 formed a viscous mass during dissolution. A sample with 4% phase I and 12% water of hydration dissolved even more slowly. This document teaches that a powdered dishwasher composition should contain partially hydrated sodium tripolyphosphate with a'phase I content which is between 4 and 14k of the anhydrous tripolyphosphate.

EP-A-178986 teaches that sodium tripolyphosphate intended for incorporation into a spray-dried detergent powder should have over 50% phase I material, with some water of hydration present.

US-A-4362641 teaches that granular sodium tripolyphosphate for a dishwasher composition should contain some phase I material to enhance absorption of free water during manufacture and packing.

is EP-A-219314 and EP-A-220024 teach that phase I anhydrous tripolyphosphate should be avoided in a spray-dried component of a particulate detergent composition which is formulated to dissolve rapidly.

For tablets, where speed of dissolution of the entire tablet is an important objective, it is important that water should penetrate into the tablet and dissolve material from the tablet interior, as well as at the tablet exterior. It would therefore seem desirable that any material incorporated as an aid to dissolution should have 4 high solubility and should not impede contact with water by the formation of a poorly mobile mass which could block pores in the tablet.

Surprisingly, we have now found that the speed of disintegration of tablets can be enhanced by including sodium tripolyphosphate with a substantial content of phase Broadly, the present invention provides a tablet of compacted particulate composition containing sodium tripolyphosphate, in which the tablet or a region of the tablet comprises particles containing sodium tripolyphosphate with more than 20% (by weight of the tripolyphosphate in the particles) of the anhydrous phase I form. The amount of anhydrous phase I form will often be is greater, such as at least 25% or 301-., preferably these particles contain an even higher proportion of the phase I form of sodium tripolyphosphate, e.g. at least 40%, 50% or 55% by weight of the tripolyphosphate in the particles.

These particles may contain sodium tripolyphosphate as their only ingredient, or at least as a high proportion of the particles, such as at least 80% or 90% by weight. However, it is conceivable that they could contain sodium tripolyphosphate mixed with some other constituent of the overall tablet composition.

The tablets, or region thereof, might consist solely of the said particles.

Generally, however, the composition within the tablets or region thereof, will contain one or more detergent active compounds together with other detergent ingredients. For this, the tablet or region thereof may contain a spray dried or granulated detergent composition, plus the sa-id particles containing phase I sodium tripolyphosphate, possibly accompanied by further particulate ingredients of the overall composition.

Sodium tri-polyphosphate with high phase I content As mentioned.above, sodium tripolyphosphate can be converted to the phase I form 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 420C is given in US-A453637.

Suitable material is commercially available. Suppliers include Rhone-Poulenc, France and Albright & Wilson, UK. The sodium tripolyphosphate may be partially hydrated, but the phase I anhydrous form should also be present.

Some hydration of the sodium tripolyphosphate may be beneficial. Thus, the sodium tripolyphosphate in the 6 particles may incorporate up to 5% (by weight of the sodium tripolyphosphate in these particles) of water of hydration. The extent of hydration is likely to be at least 0.2% and more probably at least 0.5% by weight. It may lie in a 5 range from 0.5% to 4% by weight.

The remainder of the tablet composition may include additional sodium tripolyphosphate. This may be in any form, including anhydrous sodium tripolyphosphate with a high content of the phase II form, hydrated sodium tripolyphosphate or some combination of the two.

Preferably the said particles containing sodium tripolyphosphate with more than 20% of phase I material provide this phase I tripolyphosphate as at least 3% by weight of the whole tablet composition. It is also preferable that they provide sodium tripolyphosphate, including the phase I tripolyphosphate, in a quantity which is at least 8%, e.g. 8 to 30-0k, by weight of the overall tablet composition.

The total quantity of sodium tripolyphosphate, in all forms, present in the tablet composition will generally lie in a range from 15 to 60% by weight of the tablet. Therefore it will be appreciated that the overall quantity of sodium tripolyphosphate may be provided at least partially by other material in addition to the said particles.

7 Detergent-active Compounds Tablet compositions of this invention generally contain one or more detergent-active compounds. Preferably these provide from 5 to 50% by weight of the overall tablet composition, more preferably from 8 or 9% by weight of the overall composition up to 40% or 50% by weight. Detergentactive material may be anionic (soap or non-soap), cationic, zwitterionic, amphoteric, nonionic or a combination of these.

Anionic detergent-active compounds may be present in an amount from 0.5 to 5056 by weight, preferably from 2% or 4% up to 30% or 40% by weight of the tablet composition.

Synthetic (i.e. non-soap) anionic surfactants are well known to those skilled in the art. Examples include alkylbenzene sulphonates, particularly sodium linear alkylbenzene sulphonates having an alkyl chain length of C,-C,.; olefin sulphonates; alkane sulphonates; dialkyl sulphosuccinates; and fatty acid ester sulphonates.

Primary alkyl sulphate having the formula ROS03- m+ in which R is an alkyl or alkenyl chain of 8 to 18 carbon atoms especially 10 to 14 carbon atoms and M' is a solubilising cation, is commercially significant as an 8 anionic detergent active. Linear alkyl benzene sulphonate of the fgrmula R M S03- m+ where R is linear alkyl of 8 to 15 carbon atoms and M+ is a solubilising cation, especially sodium, is also a commercially significant anionic detergent active.

Frequently, such linear'alkyl benzene sulphonate or primary alkyl sulphate of the formula above, or a mixture thereof 10 will be the desired anionic detergent and may provide 75 to loowto-. of any anionic non-soap detergent in the composition.

In some forms of this invention the amount of non-soap anionic detergent lies in a range from 0.5 to 15 wto-. of the is tablet composition.

It may also be desirable to include one or more soaps of fatty acids. These are preferably sodium soaps derived from naturally occurring fatty acids, for example, the fatty acids from coconut oil, beef tallow, sunflower or 20 hardened rapeseed oil.

Suitable nonionic detergent compounds which may be used include in particular the reaction products of compounds 9 having a hydrophobic group and a reactive hydrogen atom, for example, aliphatic alcohols, acids, amides or alkyl phenols with alkylene oxides, especially ethylene oxide ether alone or with propylene oxide.

Specific nonionic detergent compounds are alkyl (C,-2) phenol-ethylene oxide condensates, the condensation products of linear or branched aliphatic C8-20 primary or secondary alcohols with ethylene oxide, and products made by condensation of ethylene oxide with the reaction products,of propylene oxide and ethylene-diamine. Other nonionic detergent compounds include long-chain amine oxides, tertiary phosphine oxides, and dialkyl sulphoxides.

Especially preferred are the primary and secondary alcohol ethoxylates, especially the C,_11 and C12-1. primary,and is secondary alcohols ethoxylated with an average of from 5 to 20 moles of ethylene oxide per mole of alcohol.

In certain forms of this invention the amount of nonionic detergent lies in a range from 4 to 400k, better 4 or 5 to 30?k by weight of the composition.

Many nonionic detergent-active compounds are liquids. These may be absorbed onto particles of the composition.

Detergent Builder A tablet composition will generally contain from 15 to 800k, more usually 15 to 60-. by weight of detergency builder. This may be provided solely by sodium tripolyphosphate, or part of it may be provided by other material with watersoftening properties.

Conceivably this could be a.water-insoluble aluminosilicate or a layered sodium silicate as described in GB-A-1429143 and US-A-420439 respectively.

More probably it will be a water-soluble builder.

Water-soluble builders may be organic or inorganic. Inorganic builders that may be present include alkali metal (generally sodium) carbonate; while organic builders include polycarboxylate polymers, such as po. lyacrylates, is acrylic/maleic copolymers, and acrylic phosphonates, monomeric polycarboxylates such as citrates,, gluconates, oxydisuccinates, glycerol mono- di- and trisuccinates, carboxymethyloxysuccinates, carboxymethyloxymalonates, dipicolinates and hydroxyethyliminodiacetates.

Tablets may include polycarboxylate polymers, more especially polyacrylates and acrylic/maleic copolymers which can function as builders and also inhibit unwanted deposition onto fabric from the wash liquor.

Tablets of this invention may include an organic watersoluble polymer, applied as a coating to some of the constituent particles, and serving as a binder when the particles are compacted into tablets. This polymer may be 5 a polycarboxylate such as those mentioned above.

It is preferred that such a binder material, if present, should melt at a temperature of at least 350C, better 400C or above, which is above ambient temperatures in many temperate countries. For use in hotter countries it will be preferable that the melting temperature is somewhat above 400C, so as to be above the ambient temperature.

For convenience the melting temperature of the binder material should be below 800C.

Preferred binder materials are synthetic organic polymers is of appropriate melting temperature, especially polyethylene glycol. Polyethylene glycol of average molecular weight 1500.(PEG 1500) melts at 450C and has proved suitable. Polyethylene glycol of higher molecular weight, notably 4000 or 6000, can also be used.

Other possibilities are polyvinylpyrrolidone, and polyacrylates and watersoluble acrylate copolymers.

The binder may suitably be applied to the particles by spraying, e.g. as a solution or dispersion. If used, the 12 binder is preferably used in an amount within the range from 0.1 to 10% by weight of the tablet composition, more preferably the amount is at least 1% or even at least 3% by weight of the tablets. Preferably the amount is not over 8% or even 6% by weight unless the binder serves some other additional function.

Tablets may include other ingredients which aid tableting. Tablet lubricants include calcium, magnesium and zinc soaps (especially stearates)., talc, glyceryl behapate, sugar Myvatex (Trade Mark) TL ex Eastman Kodak, polyethylene glycols, and colloidal silicas (for example, Alusil (Trade. Mark) ex Crosfield Chemicals Ltsd).

Bleach System Tableted detergent compositions according to the invention may contain a bleach system. This preferably comprises one or more peroxy bleach compounds, for example, inorganic persalts or organic peroxyacids, which may be employed in conjunction with activators to improve bleaching action at low wash temperatures. If any peroxygen compound is present, the amount is likely to lie in a range from 10 to 25% by weight of the composition.

Preferred inorganic persalts are sodium perborate monohydrate and tetrahydrate, and sodium percarbonate, advantageously employed together with an activator. Bleach activators, also referred to as bleach precursors, have 13 been widely disclosed in the art. Preferred examples include peracetic acid precursors, for example, tetraacetylethylene diamine (TAED), now in widespread commercial use in conjunction with sodium perborate; and perbenz.oic acid precursors. The quaternary ammonium and phosphonium bleach activators disclosed in US 4751015'and US 4818426 (Lever Brothers Company) are also of interest. Another type of bleach activator which may be used, but which is not a bleach precursor,.is a transition metal catalyst as.disclosed in EP-A-458397, EP-A-458398 and EP-A- 549272. A.bleach system may.also include a bleach stabiliser (heavy metal sequestrant) such as ethylenediamine tetramethylene phosphonate and diethylenetriamine pentamethylene phosphonate.

is As indicated above, if a bleach is present and is a watersoluble inorganic peroxygen bleach, the amount may well be from 10% to 25% by weight of the composition.

Other Detergent Ingredients The detergent tablets of the invention may also contain one of the detergency enzymes.well known in the art for their ability to degrade and aid in the removalof various soils and stains. Suitable enzymes include the various proteases, cellulases, lipases, amylases, and mixtures thereof, which are designed to remove a variety of soils and stains from fabrics. Examples of suitable proteases are Maxatase (Trade Mark), as supplied by Gist-Brocades 14 N.V., Delft, Holland, and Alcalase ATrade Mark), and Savinase (Trade Mark), as supplied by Novo Industri A/S, Copenhagen, Denmark. Detergency enzymes are commonly employed in the form of granules or marumes, optionally with a protective coating, in amount of from about 0.1% to about 3.0%.by weight of the composition; and these granules or marumes present no problems with respect to compaction to form a tablet.

The detergent tablets of the invention may also contain a fluorescer (optical brightener), for example, Tinopal (Trade Mark) DMS or Tinopal CBS available from Ciba-Geigy AG, Basel, Switzerland. Tinopal DMS is disodium 4,41bis (2-morpholino-4-anilino-s-:triazin-S-ylamino) stilbene disulphonate; and.Tinopal CBS is disodium 2,21-bis-(phenyl is styryl) disulphonate.

An antifoam material is advantageously included, especially if the detergent tablet is primarily intended for use in front-loading drum-type automatic washing machines. Suitable antifoam materials are usually in granular form, 20 -such as those described in EP 266863A (Unilever). Such antifoam granules typically comprise a mixture of silicone oil, petroleum jelly, hydrophobic silica and alkyl phosphate as antifoam active material, sorbed onto a porous absorbed water-soluble carbonate-based inorganic carrier material. Antifoam granules may be present in an amount up to 5% by weight of the composition.

It may also be desirable that a detergent tablet of the invention includes an amount of an alkali metal silicate, particularly sodium ortho- , metaor disilicate. The presence of such alkali metal silicates at levels, for example, of 0.1 to 10 wt%, may be advantageous in providing protection against the corrosion of metal parts.in washing machines, besides providing some measure of building and giving processing benefits in manufacture of the particulate material which is compacted into tablets.

Further ingredients which can optionally be employed in the detergent tablet of the invention include anti-redeposition agents such as sodium carboxymethylcellulose, straightchain polyvinyl pyrrolidone and the cellulose ethers such as methyl cellulose and ethyl hydroxyethyl cellulose, is fabric-softening agents; heavy metal sequestrants such as EDTA; perfumes; and colorants or coloured speckles.

Particle Size and Distribution A detergent tablet of this invention, or a discrete region, of such a tablet, is a matrix of compacted particles.

Preferably the particulate composition has an average particle size in the range from 200 to 2000 gm, more preferably from 250 to 1400 gm. Fine particles, smaller than 180 gm or 200 gm may be eliminated by sieving before tableting, if desired, although we have observed that this 25 is not always essential.

16 While the starting particulate composition may in principle have any bulk density, the present invention is especially relevant to tablets made by compacting powders of relatively high bulk density, because of their greater tendency to exhibit disintegration and dispersion problems. Such tablets have the advantage that, as compared with a tablet derived from a low bulk density powder, a given dose of composition can be presented as a smaller tablet.

Thus the starting particulate composition may suitably have 10 a bulk density of at least.400 g/litre, preferably at least 500 g/litre, and advantageously at least 700 g/litre.

Granular detergent compositions of high bulk density prepared by granulation and densification in a high-speed mixer/granulator, as described and claimed in EP 340013A (Unilever), EP 352135A (Unilever), and EP 425277A (Unilever), or by the continuous granulation/densification. processes described and claimed in EP 367339A (Unilever) and EP 390251A (Unilever), are inherently suitable for use in the present invention.

A tablet of the invention may be either homogeneous or heterogeneous. In the present specification, the term "homogeneous" is used to mean a tablet produced by compaction of a single particulate composition, but does not imply that all the particles of that composition will 25 necessarily be of identical composition.

17 It is envisaged that the particles with a high content of phase 1, sodium tripolyphosphate will preferably be distributed throughout the whole tablet. However, it is possible that they will be contained within one or more discrete regions of the tablet, such as a layer or an insert large enough to constitute from 10 to 90% of the weight of the whole tablet. The presence of such a layer or insert could assist break up of the entire tablet when placed in water..

Tableting Tableting entails compaction of a particulate composition. A variety of tableting machinery is known, and can be used. Generally it will function by stamping a quantity of the particulate composition which is confined in a die.

Tableting may be carried out at ambient temperature or at a temperature above ambient which may allow adequate strength to be achieved with less applied pressure during compaction. In order to carry out the tableting at a temperature which is above ambient, the particulate composition is preferably supplied to the tableting machinery at an elevated temperature. This will of course supply heat to the tableting machinery, but the machinery may be heated in some other way also.

If any heat is supplied, it is envisaged that this will be supplied conventionally, such as by passing the particulate 18 composition through an oven, rather than by any application of microwave energy.

Exam,Ple 1 Tablets for use in fabric washing were made, starting with a spray-dried base powder of the following composition:

Sodium linear alkylbenzene sulphonate 11.8306 Sodium tripolyphosphate, type 1A.44.83-,; Nonionic detergent 2 7.88-0,5 Sodium silicate 11.8306 Soap 1.130-15 Sodium carboxymethyl cellulose 0.90-5 Acrylate/maleate copolymer 3.2015 Sodium sulphate and minor ingredients 3.00k Water balance to 100% 1. This contained less than 30% of the phase I form of anhydrous sodium tripolyphosphate.

2. C.3-1. fatty alcohol 7E0.

This powder was mixed with particles of sodium tripolyphosphate specified to contain 70% phase I form and contain 3.5% water of hydration (Rhodia-Phos HPA 3.5 available from Rhone-Poulenc) and other detergent ingredients as tabulated below. As a comparative composition the base powder was mixed with urea and other detergent ingredients.

19 The two compositions thus contained the following percentages by weight:

m le 1, 1Comparative A Base powder 63.25 63.25 Sodium perborate tetrahydrate 10.4 10.4 TAED granules 4.0 4.0 Anti-foam granule 2.0 2.0 Enzymes 0.85 0.85 Phosphonate 0.5 0.5 Sodium carbonate 3.6 3.6 HPA tripolyphosphate 15.0 -- Urea --- 15.0 35g portions of each composition were made into cylindrical tablets of 44 mm diameter, using a Carver hand press.

The strength of these tablets was measured using an Instron universal testing machine to compress a tablet until fracture. The value of diametral fracture stress (DFS) was then calculated using the equation 2P 7rDt where a is the diametral fracture stress in Pascals, P is the applied load in Newtons to cause fracture, D is the tablet diameter in metres and t is the tablet thickness in metres.

The break-up, dispersion and dissolution of tablets was measured by a test procedure in which a tablet is placed on a plastic sieve with 2mm mesh size which was immersed in 9 litres of demineralised water at ambient temperature of 22C and rotated at 200 rpm. The water conductivity was 5 monitored until it reached a constant value.

The time for break up and dispersion of the tablets was taken as the time (T90) for change in the water conductivity to reach 90% of its final magnitude. This was also confirmed by visual observation of the material remaining on the rotating sieve.

The results were:

-F Example 1 TC-0-Mparative A Tablet strength (kP,a). 19.5 21.9 Tablet dissolution T90 (min) 3.35 13.4 This shows that tablets of this Example dissolved much is faster than the comparative tablets of similar strength made with urea.

Examle 2 Further tablets were prepared using the same spray dried base powder as in Example 1. Tablets embodying the invention and comparative tablets were prepared with a formulation as follows:- 21 Ingredient -j by weicrht Base powder 62 Sodium perborate tetrahydrate 12.6 TAED granules 3.0 Anti-foam granule 2.0 Enzymes 0.85 Phosphonate 0.5 Perfume 0.45 Variable, soluble ingredient 18.6 Various soluble materials were used as the variable, soluble ingredient, as set out in the table below. Tablets were made as in Example 1, using varying levels of compaction force. The resulting DFS and T9. values are also given in the table below.

3 22 Variable Compaction DFS (kPa) T9Wk Soluble force (kN) dissolution Ingredient (minutes) HPA 2 11.0 4.55 (high phase 1) 3 16.0 5.0 4 24.7 9.0 Empiphos D 2 6.0 7.0 (low phase 1) 3 11.4 16.0 Empiphos E 4 20.0 7.0 (high phase 1) Urea 2 14.8 4.55 3 25.2 8.0 Na-sulphate 2 10.4 18.9 fine granular HPA grade sodium tripolyphosphate (as used also in Example 1) is specified to contain 709j of phase I, and to contain 3.5% water of hydration.

Empiphos D, available from Albright & Wilson, has a very high content of phase II tripolyphosphate. The content of phase I is 10% and the water content is 0.2%.

Empiphos E, available from Albright & Wilson is specified as having 50% of phase I, and to contain 1% water of hydration.

23 These results show that sodium tripolyphosphate of high phase I content enhance dissolution, compared to similar tablets containing sodium sulphate and sodium tripolyphosphate of low phase I content. Unlike urea, it functions as a detergency builder in the wash liquor..

24

Claims (11)

CLAIMS:

1. A tablet of compacted particulate detergent composition, containing one or more detergent-active compounds together with sodium tripolyphosphate and other ingredients characterised in that the tablet or a region thereof comprises particles in which sodium tripolyphosphate has a content of the phase 1 form which is more than 20% by weight of the sodium tripolyphosphate in the said particles.

2. A tablet according to claim 1, wherein the sodium tripolyphosphate in the said particles has a content of the phase I form which is more than 40% by weight of the sodium tripolyphosphate in the said particles.

is

3. A tablet according to claim 1, wherein the sodium tripolyphosphate in the said particles has a content of the phase I form which is more than 60% by weight of the sodium tripolyphosphate in the said particles.

4. A tablet according to any one of the preceding claims, in which the sodium tripolyphosphate in the said particles contains water of hydration in an amount between 0.5 and 5% by weight of the sodium tripolyphosphate in the particles.

5. A tablet according to claim 4, where the amount of water of hydration lies in a range from 1 to 4% by weight of the sodium tripolyphosphate in the particles.

6. A tablet according to any one of the preceding claims, wherein said particles provide phase I sodium tripolyphosphate as at least 5% by weight of the tablet composition.

7. A tablet according to any one of the preceding claims, wherein sodium tripolyphosphate in said particles provides at least 12% by weight of the overall tablet composition.

8. A tablet according to any one of the preceding claims, wherein the composition includes other sodium tripolyphosphate, in addition to said sodium tripolyphosphate in said particles.

9. A tablet according to any one of the preceding claims, is which contains from 5 to 50% by weight of detergent-active and 10 to 80% by weight of detergency builder.

10. A tablet according to claim 9, which contains from 10 to 80% by weight of water-soluble detergency builder.

11. A tablet according to any one of the preceding claims, 20 wherein the tablet contains from 2 to 30% by weight of water-soluble polycarboxylate.