AU616218B2 - Machine dishwashing composition - Google Patents

Description

i

AUSTRALIA

PATENTS ACT 1952 COMPLETE SPECIFICATION Form 616218

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art: TO BE COMPLETED BY APPLICANT a a a oa o Q~ Qo a aao 6o )Ia a o~ Name of Applicant: Address of Applicant: UNILEVER PLC UNILEVER HOUSE

BLACKFRIARS

LONDON EC4

ENGLAND

Actual Inventor: Address for Service: GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

a ,aa 0 90 ol o 0s o 0 a 0 ,o Complete Specification for the invention entitled: MACHINE DISHWASHING COMPOSI'ION a 0 The following statement is a full description of this invention including the best method of performing it known to me:- SI 00 11 4000oo aL t 4 0r, A A E. _-1 3A- C.3203 MACHINE DISHWASHING COMPOSITION The present invention relates to machine dishwashing liquid detergent compositions suitable for use in cleansing food soils from cooking utensils, dishes and glasses. More particularly, the present invention relates to an aqueous thixotropic structured system comprising an alkaline source and builder salts.

The use of liquid forms of detergent for machine dishwashing offers several advantages over powdered or granular forms. These advantages include greater ease of handling in dispensing and dosing, the elimination of lump a; .formation, "caking" and dust, and improved solubility.

However, liquid detergents must meet certain requirements. Firstly, the liquid detergent must be a uniform mixture of ingredients to deliver the optimum combination of active components to the wash with each dose. In most current formulations, this requires that the liquid be shaken before each use to remix the components. A preferred product should be stable against physical separation and segregation of its active components. High viscosity at low shear rate contributes t" 2 C.3203 to physical stability of the liquid and protects against separation of the active components.

Physical stability can be achieved through the use of suspending or viscosifying systems to enhance the liquid rheological properties. These agents must maintain viscosity at low shear rate under the high ionic strength conditions present in a well-built liquid detergent, and must be chemically compatible with the other components of the formula, especially the chlorine bleach used to assist stain removal.

The liquid dishwashing detergent must be compatible with the dishwashing equipment presently available. Home dishwashing machines use a detergent cup which has been designed to house powdered or granular solid detergent and deliver it to a specific wash cycle. The cups are nct 00 o°0 designed to contain low viscosity liquids. Consequently, a oo liquids for use as machine dishwashing detergents must 0 20 possess high viscosity to be effectively retained in the oa cup and avoid leakage into the machine during cycles which a°o precede the wash. Excessive leakage will lead to under-dosing in the wash cycle and may affect cleaning performance.

to 0 Although high viscosity is desirable under storage conditions or while the material is in the detergent cup, the liquid must readily and conveniently dispense from its i container. Therefore, a liquid that undergoes a viscosity decrease under the influence of applied shear such that the decrease is reversible with time after the *a(o removal of shear is preferable for this application.

This behaviour is termed "rhear-thinning" and is desirable for liquid dishwashing detergents. Agitation of the liquid in the container, such as squeezing or shaking, will supply sufficient shear strain to initiate 4 i i i 3 3 C.3203 shear-thinning behaviour and increased liquid flow.

Optimum flow properties would allow for easily pourable fluids which maintain sufficient viscosity at higher shear rates to prevent or minimise excessive spillage. The liquid should quickly regain its structure after dispensing. This liquid characteristic is termed "thixotropy".

There is now disclosed a thixotropic liquid detergent composition suitable for use in a machine dishwasher which is structured by interaction between the components, giving a positive effect on the rheology of the components, without the need to include a conventional thickening agent. This effect is shown in viscosity increases and in yield point enhancement.

0 The prior art has disclosed a number of systems for thickening of machine dishwashing compositions.

o" GB 1 527 706 discloses a slurry structured by the addition 20 of synthetic polymers. However, it is thought that the 000I o low yield point in liquids containing, eg polyacrylate as the only structuring agent causes poor cup retention.

GB 2 140 450 discloses liquids structured with clay. The clay lowers the amount of active component which can be C.o. 25 delivered in each dosa. Furthermore, the presence of insoluble clay minerals at levels used for structuring can negatively affect glass spotting and filming performance.

00 The use of biopolymers or cellulosics within a liquid detergent base has also been proposed to provide thickened systems, eg US 4 226 736 and US 4 260 528. Since most biopolymers react readily with hypochlorite, these systems are unstable and exhibit a gradual loss in viscosity if hypochlorite is present.

Micellar structured liquids are known in other areas, eg in thickened bleach systems (GB 1 466 560), usually 4containing over 90 wt% hypochlorite solution and no builder. Systems thickened by synergistic action with urea (eg GB 1 579 668) are also known. GB 2 185 037 describes aqueous, thixotropic machine dishwashing detergents which are structured by fatty mono- or polycarboxylic acid.

According to the present invention there is provided an aqueous, thixotropic liquid cleaning composition comprising an alkali-metal builder and an alkali metal silicate characterized in that it comprises 0.5-2 wt of Laponite clay to reduce spot formation on glassware and a stabilizer comprising from 0.05 to 5 wt of a C 10

-C

22 alkyl phosphate, phosphite, phosphonate, sulphate, sulphonate or alkylarylsulphonate, the composition having a yield point of between 5-50 Pa, a 15 viscosity of between 500-5000 mPas at a shear of 20 s- on o a Haake RV2 at 20°C with a MV2 rotor.

#4a4 The present invention is based upon the discovery that the alkyl derivatives named may be used as liquid stabilisers. Alkyl phosphates have previously been i 20 described for use in machine dishwashing compositions as 4. foam depressors, but we do not believe that their use as liquid stabilisers has previously been described.

Structuring occurs independently of the presence of active detergent.

The compositions according to the present invention may also preferably incorporate a bleach, eg. a hypochlorite. The system is stable when these bleaches are included in comparison to some systems of the prior art, wherein the presence of hypochlorite destroys system stability.

The composition according to the present invention has improved rheology and stability and can deliver a high and uniform dosage of active ingredients to the machine wash cycle. An improvement of the structuring also results in easier dispensing from the product container to the dispenser and from the dispenser to the 8 1 1(11 W 5 machine wash at the appropriate time.

The system of the present invention has good stability against physical separation upon storage, providing a more uniform product. Poor physical stability can lead to development of a stratified liquid through separation of a fluid layer and a solids layer. This requires remixing by the end user through vigorous shaking of the container.

The structuring system of the invention may also be adjusted to develop optimum fluid rheology in terms of low shear rate attributes, giving physical stability, cup retention and moderate shear rate flow behaviour during dispensing into the wash cycle, 8 The product according to the present invention is s a thixotropic machine dishwashing detergent in the form of O a slurry-like paste. The product possesses a yield point of between 5-50 Pa and a viscosity between 500-5000mPas at s (Haake RV2 at 20 0 C, MV2 rotor).

The stabilisers according to the present invention are long chain alkyl, ie C 10

C

22 sulphates, sulphonates, phosphates, phosphites, phosphonates or 0. alkylarylsulphonates, Preferred are phosphorous based compounds. Particularly preferred are compounds selected from those listed in Table 1 below, or mixtures thereof: i 6 C. 3203 Table I Formula R 0 P (O H) 2 (RO) 2

POH

R P (OH) 2 R 2P OH R 0 P (OH) 2 (RO).Z P OH R IP(O) (O H) 2 R P (OH) H R 2 P (OH) R 0 S (OH) 2 (RO) (R 1 0) S (OH) R S (OH) H R S (OHi) IR 0 so 3 Recommended Name Alkyl phosp1bite Dialky. phosphite Alkyl phosphorous acid Dialkyl phosphorous acid Alkyl dihydrogen phosphate Dialky. hydrogen phosphate Alkyl. phosphonic acid Alkyl phosphanic acid Dialkyl phosphonic acid Alkyl sulphate DiaJlkyl sulphate Alkyl suiphonate Dialkyl suiphonate Alkylbenzene sulphonates and wherein

R/R

1 represent C1 C2 the same or different.

alkyl, chain5 which may be Most preferred is the mixture of C 6 1 alkyl dihydrogen phosphate and dialkyl, hydrogen phosphate, referred to hereafter as ALF-5 (Lancro Chemicals Limited).

The higher alkyl phosphates and phosphonic, acids are also preferred due to their tendency to reduce corrosion of metals and erosion of vitreous enamel surfaces.

1 7 C.3203 If sulphates or sulphonates are to be used, such as alkyl benzene sulphonates, it is preferred to additionally use a phosphate or phosphonate.

An alkali-metal condensed phosphate may be present in the formula as a water hardness sequestering agent or builder. Tripolyphosphate is the preferred sequestrant although pyrophosphate, hexametaphosphate, or other condensed phosphates may be used. The sequestrant should be present in the formula from 0.1 to 35 wt% with 15 to wt% preferred. Use of the sequestrant, such as sodium tripolyphosphate, in excess of its solubility limit within the formula requires that the solid be present as fine particles which are suspended by the structuring system.

The presence of solids will affect the viscosity of the liquid and may modify the range of the structurants needed Sto deliver the proper rheology. Zeolites may also be used as builders.

20 The sources of alkalinity are used in combination in 'oo the more preferred embodiments of this invention. An S alkali-metal carbonate may be used as an alkaline buffering agent and may be present from 0 to 30 wt%, or more preferably from 2 to 10 wt%.

Pure alkali-metal metasilicates or alkali-metal f" fsilicates with a molar ratio of SiO 2 /Na20 and/or K20 of from 1.0 to 3.25 (or mixtures of 2 or more metasilicate S and/or silicates) may be used as alkaline sources and as anti-corrosion agents to protect metal and china surfaces against the harshly alkaline environments present in the wash. The silicate may be used in the form of an aqueous liquor or a solid and may be present in the formula from 0.1 to 30 wt%, more preferably from 2 to 20 wt%.

i' 8 C.3203 An alkali-metal hydroxide may be used as an alkaline source and as a means to boost the pH of the liquid detergent concentrate to stabilise the hypochlorite.

Sodium or potassium hydroxide in the form of an aqueous liquor or as a solid may be used in the formula at from 0.1 to 25 wt%, preferably from 0.5 to 15 wt%.

Polymers may be added to the system to provide a further building effect. The polymer used should be of a synthetic type and be water-soluble. Examples of applicable polymers are polyacrylic acid and its alkali-metal salts, polymethacrylic acid and its alkali-metal salts, and copolymers of these with alkyl acrylates and alkyl methacrylates, copolymers of these with maleic anhydrides, polyacrylamide and partially hydrolysed polyacrylamide, polyacrylonitrile and its o* ,o partially hydrolysed forms, polymethacrylonitrile and its 0o opartially hydrolysed forms, polystyrenesulphonic acid and its alkali-metal salts, polymaleic anhydride and its a s o 20 alkali-metal salts, poly n-vinyl lactams (poly-vinyl 0 pyrrolidone, poly(N-vinyl caprolactam, etc), and polymers S% of N-substituted acrylamides or mixtures thereof. These polymers have a weight average molecular weight of from 1,000 to 15,000,000 with a molecular weight of from 10,000 to 400,000 preferred, and 100,000 to 250,000 most preferred. These polymers may be used in the acid or the neutralised form. The polymers should be of a hypochlorite-stable type with polyacrylate and polymethacrylate being most preferred. The polymer should be of a purity such that it contains a minimum of unsaturated monomers, chemically reactive initiators, .0oo terminators, or surfactants present which will hasten the rate of hypochlorite decomposition. The polymer may be present in the formula from 0.05 to 10 wt%, preferably 3- 0.1-0.5 wt%.

i I i. I 9 To reduce spot formation on glassware 0,5-2 wt of Laponite, a synthetic hectorite clay, is included in the claimed cleaning composition.

The system may incorporate a bleach generating system, such as a hypochlorite, at from 0,5 to 5 wt% active chlorine. Actives may optionally be included within the system. Preferred are nonionic actives.

However, low levels of anionic actives such as secondary alkyl sulphates may be included.

10 0 Conventional additives such as colourants and perfumes may be present in the composition in amounts not exceeding 5 wt%. Other foam depressors may be included, The product according to the invention may be prepared by initial formulation of a premix comprising the stabilising component and water, the addition of this premix to a silicate and alkali-metal hydroxide mixture, and the subsequent addition of builder and hypochiorite.

The process is preferably carried out at above 40 0

C,

The product according to the invention has been shown to possess a high degree of stability at room temperature, whilst also demonstrating a suitably low viscosity to assist dispensing. The pH of the composition may range 10 10 from 10-14, preferably 12-13.5. It also demonstrates an improved washing performance in comparison to other thickened machine dishwashing systems.

The invention will now be further illustrated by means of the following non-limiting Example.

:oo t @1 6 t! C t S0 Example The incorporation of different levelL Q1L o\i intc a liquid cleaning composition was carried out in order to examine any increased stability.

Base system; wt% STP (anhydrous) 20.5 Na-disilicate 11 .0 Na-carbonate Na-OH 1.2 Hypochlorite (AvCl 2 Laponite clay Water to 100,0 4, t0 I a, a 44 4 0 44 4 44 4444 44 4S .4 a 44~ *4~t 4, a, ALF-5 Viscosity (20 sec- 1 (mPas) 15 0 1645 0.1 1805 0.i5 2375 S'pparation 4 week 371C RT 12 weok .I2LC RT 12 6 17 3 5 7 6 3 0 7 3

Claims (2)

1. An aqueous thixotropic liquid cleaning composition comprising an alkali-metal builder and an alkali-metal silicate characterized in that it comprises 0.5-2 wt of Laponite clay to reduce spot formation on glassware and a stabiliser uomprising from 0.05 to 5 wt of a C10-C22 alkyl phosphate, phosphite, phosphonate, sulphate, sulphonate or alkylarylsulphonate, the composition having a yield point of between 5-50 Pa, a viscosity of between

500-5000 mPas at a shear of 20 s 1 on a Haake RV2 at 20 0 C with a MV2 rotor. The composition according to claim 1 further 0 comprising a bleaching agent providing 0.5-5 wt% available chlorine. 3. The composition according to claim 2 consisting essentially of: 0.1-35 wt alkali-metal phosphate; 0.1-3C wt alkali-metal silicate; 0.1-25 wt NaOH; 4 0 0-30 wt alkali-metal carbonate; 0.05-5 wt alkyl phosphate, phosphite, phosphonate, sulphate or sulpi .ate; a il on o ewe -0 a icsiyo ewe N 0-50 Otsa ha f2 1 o ak V t2° 4 0.50-5 wt available chlorine; 0.5-2 wt Laponite clay; and balance water. DATED THIS 14TH DAY OF MAR~CH 1991 UNILEVER PLC By its Patent Attorneys: GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia. 4 44 44 4 4 go I. 4 04 I~4* I 4, 44 4 44.44 4444 0*4 0 4 44 4 44 4 444444 4 .4 4440 4 44 44 4 44 44 44 4 4 4 44 44 4 444 4 4 444444 4 4