EP1041138A1

EP1041138A1 - Household cleaning compositions

Info

Publication number: EP1041138A1
Application number: EP99302849A
Authority: EP
Inventors: Terry Unilever Research Port Sunlight Instone; Martin Unilever Research Port Sunlight Sharples; Claire Frances Unilever Res.Port Sunlight Stanley
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 1999-04-02
Filing date: 1999-04-02
Publication date: 2000-10-04

Abstract

Cleaning compositions in tablet form intended for hard surface cleaning are disclosed. The tablets comprise a detergent surfactant and a solid water-soluble carrier material having a liquid carrying capacity of at least 6% of its own weight. Preferably the carrier material is chosen from sodium tripolyphosphate and crystal growth modified sodium sesquicarbonate (Na₂CO₃.NaHCO₃.2H₂O), sodium carbonate (Na₂CO₃.H₂O), sodium carbonate/sodium sulphate double salt (Na₂CO₃.(Na₂SO₄)₂burkeite) and mixtures thereof.

The tablets may additionally comprise a disintegrant, such as a swelling clay, and a hygiene agent such as a quaternary ammonium salt.

Description

Field of the invention

The invention relates to household cleaning compositions in unit dose form. More particularly the invention concerns solid household cleaning compositions in tablet form. One or a few of such tablets when added to a prescribed amount of water provide a detergent solution suitable to perform a common household cleaning operation such as cleaning of floors, walls, or bathroom or kitchen surfaces.

Background of the invention

Cleaning or detergent compositions in unit dose form, especially tablets, are well known in the art, particularly for automatic dish washing. Recently they have received renewed attention for use in laundry washing machines. They provide a clear advantage in ease of dispensing a standard amount of cleaning composition for a given cleaning job. Although they have been reported as useful for manual cleaning as well, so far for this purpose they do not appear to have gained any importance in the marketplace.
On the one hand detergent tablets must be strong to prevent them from breaking and crumbling under the mechanical treatment involved in packaging, handling, distribution and the like. On the other hand they should easily and quickly disintegrate once brought into contact with water. These two requirements are to a large extent contradictory and difficult to meet at the same time in one tablet. For tablets suitable for manual cleaning rapid disintegration and dissolution is even more difficult to attain because of the absence of the forceful agitation encountered in laundry and dish washing machines.
For manual cleaning the right amount of cleaning active substances for a limited quantity of water, usually a bucket or a bowl full, should be contained in one or a few whole tablets and yet the tablets should be of a sufficient size to be easily handled by the consumer and to be individually packed if desired.
Furthermore, tablets should preferably maintain their strength as well as their easy dissolution properties during storage under conditions of high ambient temperature and/or humidity.
Most detergent tablets basically comprise three main ingredients: a carrier material, one or more detergent surfactants and a disintegration aid. The carrier material may also be active in the wash process in some way, e.g. as a builder. If these three components, and any other components which may be present cannot be compacted to a tablet of the required strength, a binding agent may be present as well.
The disintegration aid causes the tablet to fall apart on contact with water. It performs this function in one or more of the three following ways:
a) By causing gas evolution on contact with water. Well known examples are combinations of a carbonate or bicarbonate salt and an acid, particularly an organic acid such as citric acid.
b) By quickly dissolving thereby providing inroads for water into the body of the tablet. Well known examples are easily soluble salts such as alkali metal acetates and urea.
c) By swelling on contact with water thereby forcing apart the particles which make up the tablet.
Tablets are conventionally made by compressing discrete amounts of particulate solids which solids should be such that they do not stick to the tablet mould. For this reason the solids should preferably be free flowing and non-pasty. Many detergent surfactants are either liquids or pasty solids and therefore need a carrier material to convert them into the required free flowing form. Various carrier materials such as aluminosilicates and zeolites are known in the art, see e.g. JP-A-10183199. However, for manual cleaning purposes carrier materials should preferably be completely water soluble so as to leave no unsightly residue in the bucket or on the cleaned surface.
In EP 0 221 776 a powder suitable for use as a detergent powder is described which contains as one of its components crystal-growth-modified sodium carbonate monohydrate and/or sodium carbonate/sodium sulphate double salt (Burkeite). The powder is prepared by spray drying a slurry containing the components, among which may be anionic and/or nonionic detergent actives and is said to be free flowing in spite of the presence of the detergent active. A polycarboxylate material is used as the crystal growth modifier.

Brief description of the invention

The present invention provides solid cleaning compositions in tablet form comprising one or more detergent surfactants and a solid water-soluble carrier material having a liquid carrying capacity of at least 6% of its own weight.

Detailed description of the invention.

The solid cleaning compositions in tablet form according to the invention (hereinafter for brevity referred to as "detergent tablets") may be of the self-disintegrating type or of the crumbling type.
In the former case they spontaneously disintegrate and dissolve on contact with water. Such tablets will normally contain a disintegrating aid as hereinafter more fully explained. In the latter case they need mechanical crumbling before or after being put in water in order to dissolve within a reasonable time. Normally such tablets will be crumbled by hand force just before being put in water.
The water soluble carrier material is preferably an inorganic water-soluble salt which has a porous crystal structure so as to be able to absorb at least 6% of its own weight of a liquid component without loosing its free flowing properties. It should also be compatible with the surfactant which means that it should not react therewith to produce an insoluble compound. An example of a suitable carrier material is sodium tripolyphosphate.
Very suitable and preferred carrier materials are crystal growth modified sodium sesquicarbonate (Na₂CO₃.NaHCO₃.2H₂O), sodium carbonate (Na₂CO₃.H₂O), sodium carbonate/sodium sulphate double salt (Na₂CO₃.(Na₂SO₄)₂ burkeite) and mixtures thereof. Such compounds may be prepared by preparing a solution or slurry of the salt and a crystal growth modifier followed by drying such solution or slurry by any suitable means known in the art, such as spray drying. Suitable crystal growth modifiers are polycarboxylate compounds. These may be salts of monomeric polycarboxylic acids such as EDTA, NTA and citrate. However, preferred crystal growth modifiers are polymeric polycarboxylates such as homopolymers and copolymers of acrylic acid and/or maleic acid. Crystal growth modified sodium carbonate, burkeite and mixtures thereof and their preparation have been fully described in EP-A-0 221 776. The crystal growth modifiers and the procedure described therein are also applicable to the preparation of sodium sesquicarbonate.
Preferred carrier materials are crystal modified burkeite and mixtures of crystal modified burkeite and crystal modified sodium carbonate. A slurry or solution comprising sodium sulphate as well as sodium carbonate and crystal growth modifier will on drying crystallize as much as possible in the form of crystal modified burkeite in which the carbonate to sulphate weight ratio is 0.37:1. Any excess sulphate will crystallize as sulphate; any excess carbonate will crystallize as crystal modified carbonate. To obtain sufficient porosity in the crystal mass the slurry or solution of sodium carbonate and sodium sulphate should have a carbonate to sulphate weight ratio of at least 0.03:1, preferably at least 0.1:1 and most preferably between 0.3:1 and 0.45:1.
The polymeric polycarboxylates are generally used in an amount of 0.1-20% by weight, preferably 0.2-10% of the total amount of sesquicarbonate or carbonate or carbonate + sulphate.
The minimum amount of carrier material per tablet is of course determined by the amount of liquid or pasty solid one wishes to put into one unit dose and the carrying capacity needed to accommodate this dose and the carrying capacity per gram of the carrier material. The maximum amount is largely determined by the maximum desirable size of the tablet from a practical point of view. Taking these practical constraints into account a tablet will generally contain at least 10% by weight of carrier material, more preferably at least 30%, even more preferably at least 50% or even 70%. On the other hand a tablet comprising more than 99% of carrier material will contain so little detergent active material that it will need an unpractically large tablet in order to supply a useful dose of detergent active in a bucket or bowl of water. Generally, the amount of carrier material will seldom exceed 95% by weight.
The surfactant or surfactants in the tablets may be of the anionic, cationic, nonionic, amphoteric or zwitterionic type. Preferably, the tablets contain at least one anionic or nonionic detergent surfactant.
Suitable anionic surfactants are water-soluble salts of organic sulphuric acid esters and sulphonic acids which have in their molecular structure an aliphatic group containing from 8 to 22 carbon atoms.
Suitable examples thereof are the following water-soluble salts:

long chain aliphatic alcohol sulphates, especially those obtained by sulphating the higher alcohols produced by reducing the glycerides of vegetable or animal oils or fats such as tallow or coconut oil;
alkylbenzene sulphonates, such as those in which the alkyl group contains from 6 to 20 carbon atoms;
secondary alkanesulphonates;
alkyl glyceryl ether sulphates, especially those ethers of the higher alcohols derived from tallow and coconut oil;
fatty acid monoglyceride sulphates;
ethoxylated fatty alcohol sulphates containing 1-6 EO units in the molecule
ethoxylated alkylphenol sulphates containing 1-8 EO units and in which the alkyl radicals contain 4-14 C-atoms
the reaction product of fatty acids, e.g. those derived from coconut oil, esterified with isethionic acid and neutralised with sodium hydroxide;
and mixtures thereof.

Very suitable water-soluble synthetic anionic surfactants are the alkali metal (such as sodium and potassium) and alkaline earth metal (such as calcium and magnesium) alkyl-benzenesulphonates, olefinsulphonates, alkyl sulphates, and fatty acid mono-glyceride sulphates.
One class of suitable nonionic surfactants can be broadly described as compounds produced by the condensation of alkylene oxide groups, which are hydrophilic in nature, with an organic hydrophobic compound which may be aliphatic or alkyl aromatic in nature. The length of the hydrophilic or polyoxyalkylene radical which is attached to any particular hydrophobic group can be readily adjusted to yield a water-soluble compound having the desired balance between hydrophilic and hydrophobic elements. This enables the choice of nonionic surfactants with the right HLB.
Particular examples include:

the condensation products of aliphatic alcohols having from 8 to 22 carbon atoms in either straight or branched chain configuration with ethylene oxide, such as coconut alcohol ethylene oxide condensates having from 2 to 15 moles of ethylene oxide per mole of coconut alcohol;
condensates of alkylphenols whose alkyl group contains from 6 to 12 carbon atoms with 2 to 25 moles of ethylene oxide per mole of alkylphenol;
condensates of the reaction product of ethylenediamine and propylene oxide with ethylene oxide, the condensates containing from 40 to 80% of ethyleneoxy groups by weight and having a molecular weight of from 5,000 to 11,000.

Other classes of nonionic surfactants are:

tertiary amine oxides of general structure RRRN0, where one R is an aliphatic group of 8 to 18 carbon atoms and the other Rs are each alkyl or hydroxyalkyl groups of 1 to 3 carbon atoms, for instance dimethyldodecylamine oxide;
tertiary phosphine oxides of structure RRRP0, where one R is an aliphatic group of 8 to 18 carbon atoms and the other Rs are each alkyl or hydroxyalkyl groups of 1 to 3 carbon atoms, for instance dimethyl-dodecylphosphine oxide;
dialkyl sulphoxides of structure RRS0 where one R is an alkyl group of from 10 to 18 carbon atoms and the other is methyl or ethyl, for instance methyltetradecyl sulphoxide;
fatty acid alkylolamides;
alkylene oxide condensates of fatty acid alkylolamides;
alkyl mercaptans.

Ethoxylated aliphatic alcohols are particularly preferred as nonionic surfactants.
Suitable amphoteric surfactants are derivatives of aliphatic secondary and tertiary amines containing a C8-C18 alkyl group and an aliphatic group substituted by an anionic water-solubilising group, for instance sodium 3-dodecylamino-propionate, sodium 3-dodecylaminopropane sulphonate and sodium N-2-hydroxydodecyl-N-methyl taurate.
Suitable cationic surfactants are quaternary ammonium salts having at least one C8-C22 aliphatic or alkyl-aromatic group, e.g. dodecyl-trimethylammonium bromide or chloride, cetyltrimethyl-ammonium bromide or chloride, didecyl-dimethyl-ammonium bromide or chloride, octyl-benzyl-dimethyl-ammonium bromide or chloride, dodecyl-benzyl-dimethyl-ammonium bromide or chloride and (higher alkyl)-benzyldimethyl-ammonium bromide or chloride.
Suitable zwitterionic surfactants are derivatives of aliphatic quaternary ammonium, sulphonium and phosphonium compounds having a C8-C18 aliphatic group and an aliphatic group substituted by an anionic water-solubilising group, for instance 3-(N,N-dimethyl-N-hexadecylammonium)-propane-1-sulphonate betaine, 3-(dodecyl-methyl-sulphonium)-propane-1-sulphonate betaine and 3-(cetylmethyl-phosphonium)-ethane-sulphonate betaine.
Further examples of suitable surfactants are given in the well-known textbooks "Surface Active Agents", Volume I by Schwartz and Perry and "Surface Active Agents and Detergents", Volume II by Schwartz, Perry and Berch.
The amount of surfactant per tablet is again determined by the desired size of the tablet and the required amount of surfactant per unit dose. In general the amount of surfactant will be at least 1% by weight, preferably at least 3%. The maximum amount is largely determined by the carrying capacity of the carrier material. In practice it will seldom exceed 50% by weight and preferably be below 30%.
As outlined above, the preferred surfactants are anionic or nonionic or mixtures thereof. Ethoxylated alcohols are preferred nonionics, particularly those having at most 16 carbon atoms in the aliphatic chain.
If the tablets are of the self-disintegrating type they preferably contain a disintegration aid (disintegrant). This may be one of the effervescent mixtures well known in the art, such as an organic acid, particularly citric acid, in combination with a carbonate or bicarbonate salt. Other examples are described in WO 98/46715 and the literature cited therein.
Alternatively, it may be a quickly dissolving compound as is also widely known in the art. Well known examples are: sodium citrate dihydrate, potassium carbonate, urea, sodium acetate, sodium acetate trihydrate, magnesium sulphate heptahydrate, potassium acetate, sodium chloride and sorbitol. Preferred compounds have a solubility of at least 50g in 100g of de-ionised water at 20°C.
Furthermore it may be a material which swells on contact with water, or first swells and later dissolves. Known materials include various natural and synthetic polymers, such as polyethylene glycol (e.g. PEG 1500), cellulose derivatives (sodium CMC) and swelling clays such as bentonite, smectites and montmorillonites
A suitable minimum level of disintegrant is 0.5, preferably at least 1% by weight; a suitable maximum level is 50%, preferably at most 30% by weight. Preferred disintegrants are swelling clays since they not only act as a disintegrant on contact with water but also act as a binder in the dry tablet. They are conveniently used in an amount of 1.5-10%.
Optionally the detergent tablets may contain a hygiene agent which deals with microbial contamination of the surfaces to be cleaned. Particularly, many quaternary ammonium salts are known to have antimicrobial properties. Well known examples are benzalkonium salts, cetyl-trimethyl ammonium salts, didecyl-dimethyl ammonium salts. Such quaternary ammonium salts are preferably used in combination with a nonionic surfactant.
Other compounds with antimicrobial properties may be used instead of, or in addition to antimicrobially active quaternary ammonium salts. Examples are: Triclosan™ and similar antibacterials, iodine/NaI, solid chlorine bleaching agents such as the chlorinated cyanuric acid salts.
The detergent tablets according to the invention may additionally contain other ingredients known in the art to be beneficial for cleaning hard surfaces, such as components which facilitate second time cleaning or components which improve shine of the cleaned surface. Furthermore they may contain components to increase the attractiveness of the tablets and/or the cleaning solution to the consumer such as perfumes and dyes.
For the purposes of this invention tablets are defined as macroscopic shaped objects of such minimum dimensions that they can be handled individually by the consumer. Therefore the minimum dimension of such objects should preferably not be less than 2 mm. Tablets are normally flat shaped objects in which the minimum dimension (thickness) is normally substantially less than the diameter (for round shaped tablets) or the length of the sides (for tablets with a rectangular, triangular or other shape). However, for the purposes of this invention, pills, balls, bullets and similarly shaped objects are comprised in the definition of a tablet.

Examples

Example 1

A base powder was prepared having the following composition (in % by weight):

6.00%: Neodol 91-5™ (ethoxylated alcohol)
2.25%: Benzalkonium chloride
2.25%: water
2.50%: Bentonite clay
0.20%: Eriochrome black (dye)
0.60%: perfume
86.20%: Burkeite powder

The base powder was prepared by mixing all liquid components with the burkeite powder using a Forniture Sirman™ high shear mixer until a homogeneous free flowing mixture was obtained. This was mixed with the bentonite clay.
10 g tablets were stamped from this base powder using an Instron™ tensiometer Model 5566 fitted with a 10 kN load cell and a 35 mm round die.
The burkeite carrier material was prepared from a mixture of 290.6 kg water, 213.8 kg of Na sulphate, 80 kg of Na carbonate and 15.7 kg of CP5 (40% aqueous solution of maleic/acrylic acid copolymer) by spray drying according to the procedure described in Examples 2-5 of EP 0 221 776.

Claims

Solid cleaning compositions in tablet form comprising one or more detergent surfactants and a solid water-soluble carrier material having a liquid carrying capacity of at least 6% of its own weight.
Cleaning composition according to claim 1 wherein the carrier material is chosen from sodium tripolyphosphate and crystal growth modified sodium sesquicarbonate, sodium carbonate, sodium carbonate/sodium sulphate double salt (burkeite) and mixtures thereof.
Cleaning composition according to claim 2 wherein the carrier material comprises crystal growth modified burkeite.
Cleaning compositions according to claims 1-3 wherein the surfactants are anionic and/or nonionic surfactants.
Cleaning composition according to claims 1-4 which further comprises a disintegrant.
Cleaning composition according to claim 5 wherein the disintegrant is a swelling clay.
Cleaning composition according to claims 1-6 which further comprises a hygiene agent.
Cleaning composition according to claim 7 wherein the hygiene agent is a quaternary ammonium salt.