EP3292191B1

EP3292191B1 - Alkaline dishwash composition

Info

Publication number: EP3292191B1
Application number: EP16716636.2A
Authority: EP
Inventors: Punam Bandyopadhyay; Kingshuk Dutta
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 2015-05-07
Filing date: 2016-04-18
Publication date: 2019-06-05
Anticipated expiration: 2036-04-18
Also published as: ZA201706983B; WO2016177563A1; AR104527A1; EP3292191A1

Description

Field of the invention

The invention relates to dishwash compositions.

Background of the invention

Aqueous dishwash liquids are fast gaining popularity in D&E markets. Usually the pH of such products is neutral to slightly acidic. However, such acidic/neutral compositions are considered mild, especially against greasy soil.
One of the ways to enhance grease-cutting is to increase pH of the compositions by including an alkali like sodium carbonate. It is believed that inclusion of an alkali, in particular, sodium carbonate, helps in two ways. First, it results in a significantly higher pH by its buffering action which in turn helps remove fatty soil by breaking it down into more soluble species. Second, it serves as a builder and thereby makes more surfactant available for cleaning. However, inclusion of high amount of an alkali, in particular, sodium carbonate, often destabilises such compositions because they turn hazy or turbid. Adverse effects of the alkali are less prominent at lower amounts e.g., about 2 to 4 wt% but they become more prominent as its amount increases. It is believed that instability is, at least in part, due to phase separation of surfactants from the surrounding medium and the presence of other common additives which lead to crystallization of sodium carbonate.
Nevertheless, there is demand for alkaline compositions and formulation scientists want to make products, which contain more and more alkali so as to capitalize on its grease cutting property. This demand cannot be fulfilled without overcoming few formulation challenges. Aqueous liquid dishwash compositions need to be homogeneous and clear, i.e. non-turbid.
One of the common methods to make liquid compositions more stable, homogeneous, and clear is to incorporate hydrotropes to solubilise some of the ingredients in the compositions. Commonly used hydrotropes include urea, ethyl alcohol, and toluene-, cumene- and xylene sulphonates. However, while such hydrotropes may produce desired effects, often the amount required to produce a perceivable and non-transient effect is too high. Inclusion of higher amounts of hydrotrope(s) lead to technical problems in to escalation of raw material costs.
GB1577140 A (Unilever, 1980 ) discloses the use of a combination of hydrotropes in an aqueous detergent composition which is homogenous. The composition contains a surfactant, sodium tripolyphosphate and sodium orthophosphate. The first hydrotrope is from the group consisting of toluene/xylene/cumene sulphonates, urea, lower aliphatic alcohols and mixtures thereof. The second hydrotrope is a fatty acid alkylolamide, a calcium soap of C₁₀-C₂₂-fatty acids or calcium soap of dimerised C₁₀-C₂₂ fatty acids.
US4126572 A (Unilever, 1978 ) discloses built liquid detergent compositions containing a different pair of hydrotropes. The first hydrotrope is of the sulphonate-type and the second is a monoalkane phosphonic acid or salt thereof. This combination provides improved stability, clarity and homogeneity.
EP1107673 A2 (P&G, 2001 ) discloses laundry powders containing non-alkoxylated anionic surfactant and about 30 % by weight sodium carbonate. The compositions, especially, example 3 formulations II and VI, also contain sulphonate-type hydrotrope.
EP0896998 A1 (P&G, 1999 ) also discloses laundry powders containing non-alkoxylated anionic surfactant and weight sodium carbonate. The compositions contain sulphonate-type hydrotrope.
There is a lot of non-patent and patent literature, which discloses the use of combination of hydrotropes in cleansing compositions. However, the present inventors could not find a practical solution to the problem described earlier and at least some of the reported combinations failed to provide a useful solution.
There is an unmet need for clear and non-turbid. aqueous cleansing compositions which contains non-alkoxylated anionic surfactant and significant amount of alkali metal carbonate.

Summary of the invention

It has been determined that this problem can be solved by the composition in accordance with claim 1.
Disclosed is an aqueous cleansing composition comprising:

(i) 5 wt% to 30 wt% of a non-alkoxylated anionic surfactant;
(ii) 5 wt% to 15 wt% alkali metal carbonate;
(iii) a first hydrotrope in the range of 1 to 8 wt%; and,
(iv) a second hydrotrope in the range of 1 to 8 wt%;

The invention is described in details in the following paragraphs.

Detailed description of the invention

The term "dishes" as used herein means any utensils involved in food preparation or consumption which may be required to be washed to free them from food particles and other food residues, greases, proteins, starches, gums, dyes, oils and burnt organic residues.
While compositions in accordance with the invention are meant for cleaning dishes, they may, alternatively, be used to clean any equivalent inanimate surface, in particular any hard surface.
By hard surface is meant any kind of surface typically found in and around home or office houses like kitchens, bathrooms, e. g. floors, walls, tiles, windows, cupboards, sinks, showers, shower plasticized curtains, wash basins, WCs, fixtures and fittings and the like made of different materials like ceramic, vinyl, no-wax vinyl, linoleum, melamine, glass, Inox, Formica®, vitroceramic, plasticised wood, metal or any painted or varnished or sealed surface and the like. Home or office hard surfaces also include household appliances including, but not limited to refrigerators, freezers, washing machines, automatic dryers, ovens, microwave ovens, dishwashers and so on. Such hard surfaces may be found both in private households as well as in commercial, institutional and industrial environments. Home or office hard surfaces include dish surfaces.

Non-alkoxvlated anionic surfactant

Compositions in accordance with the invention comprise 5 wt% to 30 wt% of a non-alkoxylated anionic surfactant. More than 30 wt% of this surfactant could present formulation challenges while at the same time could also make the composition too expensive.
The surfactant assists in removing soil and grease from soiled utensils and also assists in maintaining the soil in solution or suspension in the wash liquor.
The term "non-alkoxylated" is used to distinguish the surfactants from their alkoxylated counterparts which are described in details.
Suitable anionic surfactants are water-soluble salts of organic sulphuric acid monoesters and sulphonic acids which have in the molecular structure a branched or straight chain alkyl group containing from 6 to 22 carbon atoms in the alkyl part. Preferred anionic surfactants are water soluble salts of (primary) long chain (e.g. 6-22 C-atoms) alcohol sulphates (hereinafter referred to as PAS), especially those obtained by sulphating the fatty alcohols produced by reducing the glycerides of tallow or coconut oil; alkyl benzene sulphonates, such as those in which the alkyl group contains from 6 to 20 carbon atoms; secondary alkane sulphonates; and mixtures thereof.
Other preferred anionic surfactants are the olefinsulphonates (AOS) and alkyl sulphates, and the fatty acid mono-glyceride sulphates. The particularly preferred non-alkoxylated anionic surfactants are alkylbenzene sulphonates containing from 6 to 22 carbon atoms in the alkyl group in a straight or branched chain, particular example of which is sodium salt of alkylbenzenesulphonate. Generally the counter ion for anionic surfactants is an alkali metal, typically sodium, although instead of alkali metals, other amine based counter ions may also be present.

Alkali metal carbonate

The compositions according to the invention comprise 5 to 15 wt% of alkali metal carbonate. Preferably the alkali metal carbonate is at least one of sodium carbonate or potassium carbonate. It is preferred that the alkali metal carbonate is sodium carbonate. Preferably, the amount of sodium carbonate is 8 to 12 wt%.
The carbonate, in particular sodium carbonate provides high pH and high reserve alkalinity useful for degreasing.

Hydrotropes

Hydrotropes are useful solubilizing agents. l hHdrotropes enable the cloud point of the compositions to be raised without additional anionic surfactants. Hydrotropes are ingredients which provide solubility, viscosity, clarity and stability, but it is believed that they have very little active role in performance of the composition because they are not surfactants. Examples of hydrotropes include lower aliphatic alcohols, especially ethanol; urea; lower alkylbenzene sulphonates such as sodium toluene and xylene sulphonates; and combinations thereof.
Hydrotropes are expensive and they add to the raw material cost without any significant role in cleaning, therefore it is desirable to use as little hydrotrope as possible. However, the choice of suitable hydrotropes is linked to the type of the surfactants and the builder(s). This is also dependent on other factors and properties like temperature and storage stability. For example, stability is acceptable when the product is stored at room temperature but less satisfactory results are achieved when the product is stored under fluctuating conditions, or at lower temperatures.
The first hydrotrope belongs to the class of "sulphonates", i.e., sulphonate-type hydrotrope. It is preferred that the first hydrotrope is at least one of sodium cumene sulphonate, sodium xylene sulphonate, sodium toluene sulphonate, naphthalenesulphonate, methylnaphthalenesulphonate, dimethylnaphthalenesulphonate or trimethylnaphthalenesulphonate. Known equivalents include the potassium, ammonium and substituted ammonium salts..
The second hydrotrope belongs to the class of alcohols. It is preferred that the second hydrotrope is at least one of ethylene glycol, monopropylene glycol, dipropylene glycol or glycerol. In comparison with the sulphonate-type hydrotropes alone, which would otherwise be used, the combination enables significant reduction in the total amount of hydrotrope, while simultaneously improving the overall hydrotrope effect.
Although the first hydrotrope belongs to the class of sulphonates,such hydrotropes have practically nil surface activity. Therefore the first hydrotrope has no contribution towards the amount of the non-alkoxylated anionic surfactant.
The amount of the first hydrotrope is in the range of 1 to 8 wt%.
The second hydrotrope is in the range of 1 to 8 wt%.
Preferably the amount of the first hydrotrope is in the range of 2 to 8 wt%.
Preferably the amount of the second hydrotrope is in the range of 2 to 8 wt%.

Alkoxvlated anionic surfactant

The compositions in accordance with this invention include an alkoxylated anionic surfactant. Use of such a surfactant, especially when the individual amount of the first and second hydrotropes is at the lower end of the ranges disclosed above, provides clear and stable compositions at even lower hydrotrope content.
Therefore compositions in accordance with this invention comprise 2 wt% to 15 wt% alkoxylated anionic surfactant. A preferred alkoxylated anionic surfactant is an ethoxylated anionic surfactant like sodium lauryl ether sulphate (SLES) having varying degrees of alkoxylation, which may range from 0.5 to 7 or even more.

Water:

The cleansing compositions in accordance with the invention are aqueous. It is preferred that the compositions comprise 30 wt% to 94 wt% water. The amount of water will vary depending on the total amount of other essential and preferred ingredients.

Other preferred ingredients:

Other surfactants

The aqueous cleansing compositions of the invention may further comprise other type of surfactants for better cleansing. Such surfactants could be selected from amphoteric, zwitterionic and nonionic surfactants.
In addition to the presence of alkoxylated anionic surfactant and the non-alkoxylated anionic surfactant, additional surfactant may be present in the formulation. Additional surfactants may be chosen from, for example, other anionic and/or nonionic detergent actives. It is preferred that the compositions in accordance with this invention comprise up to 1 % by weight non-ionic surfactant. In addition, It is preferred that the compositions in accordance with this invention comprise up to 1 % by weight cationic surfactants, up to 1 % by weight amphoteric surfactants and up to 1 % by weight zwitterionic surfactants.
Nonionic surfactants tend to reduce the foam produced on use of the composition. Consumers tend to associate more foam with powerful cleaning, so it is desirable to either avoid the use of nonionic surfactants altogether, or to use up to 1 % by weight. For compositions which do include a nonionic surfactant, suitable nonionic surfactants may be broadly described as compounds produced by the condensation of simple alkylene oxides, which are hydrophilic in nature, with an aliphatic or alkyl-aromatic hydrophobic compound having a reactive hydrogen atom. The length of the hydrophilic or polyoxyalkylene chain which is attached to any particular hydrophobic group may be readily adjusted to yield a compound having the desired balance between hydrophilic and hydrophobic elements. This enables the selection of nonionic surfactants with the right 'HLB' value. The HLB value is a measure of the hydrophilic/lipophilic balance of such a surfactant.
Particular examples of preferred nonionic surfactants 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 a coconut alcohol/ethylene oxide condensates having from 2 to 15 moles of ethylene oxide per mole of coconut alcohol; condensates of alkylphenols having C₆-C₁₅ alkyl groups with 5 to 25 moles of ethylene oxide per mole of alkylphenol; and condensates of the reaction product of ethylene-diamine and propylene oxide with ethylene oxide, the condensates containing from 40 to 80 % by weight of ethyleneoxy groups and having a molecular weight of from 5,000 to 11,000 Daltons.
Other classes of nonionic surfactants include for example: tertiary amine oxides of structure R₁R₂R₃N-O, where R₁ is an alkyl group of 8 to 20 carbon atoms and R₂ and R₃ are each alkyl or hydroxyalkyl groups of 1 to 3 carbon atoms, e.g. dimethyldodecylamine oxide; tertiary phosphine oxides of structure R₁R₂R₃P-O, where R₁ is an alkyl group of 8 to 20 carbon atoms and R₂ and R₃ are each alkyl or hydroxyalkyl groups of 1 to 3 carbon atoms, for instance dimethyl-dodecylphosphine oxide; dialkyl sulphoxides of structure R₁R₂S=O, where R₁ is an alkyl group of from 10 to 18 carbon atoms and R₂ is methyl or ethyl, for instance methyl-tetradecyl sulphoxide; fatty acid alkylolamides, such as the ethanol amides; alkylene oxide condensates of fatty acid alkylolamides; and alkyl mercaptans.
If one or more nonionic surfactants are used, the amount present in the compositions of the invention will generally be at least 0.1 % by weight. Preferably the amount of nonionic surfactant will be around 0.5 % by weight.
Suitable amphoteric surfactants include the derivatives of aliphatic secondary and tertiary amines containing an alkyl group of 8 to 20 carbon atoms and an aliphatic group substituted by an anionic water-solubilising group, for instance sodium 3-dodecylamino-propionate, sodium 3-dodecylaminopropane-sulfonate and sodium N-2-hydroxy-dodecyl-N-methyltaurate.
Examples of suitable cationic surfactants may be selected from quaternary ammonium salts having one or two alkyl or aralkyl groups of from 8 to 20 carbon atoms and two or three small aliphatic (for example, methyl) groups, for instance cetyl trimethyl ammonium chloride.
A specific group of surfactants is the tertiary amines obtained by condensation of ethylene and/or propylene oxide with long chain aliphatic amines. The compounds behave like nonionic surfactants in alkaline medium and like cationic surfactants in acid medium.
Examples of suitable zwitterionic surfactants include derivatives of aliphatic quaternary ammonium, sulfonium and phosphonium compounds having an aliphatic group of from 8 to 18 carbon atoms and an aliphatic group substituted by an anionic water-solubilising group, for instance betaine and betaine derivatives such as alkyl betaine, in particular C₁₂-C₁₆ alkyl betaine, 3-(N,N-dimethyl-N-hexadecylammonium)-propane 1-sulfonate betaine, 3-(dodecylmethyl-sulfonium)-propane 1-sulfonate betaine, 3-(cetylmethyl-phosphonium)-propane-1-sulfonate betaine and N,N-dimethyl-N-dodecyl-glycine. Other well-known betaines are the alkylamidopropyl betaines for example, those wherein the alkylamido group is derived from coconut oil fatty acids.
Examples of such further surfactants suitable for inclusion herein can be found in "Surface Active Agents" Vol. 1 , by Schwartz & Perry, Interscience 1949, Vol. 2 by Schwartz, Perry & Berch, Interscience 1958, in the current edition of "McCutcheon's Emulsifiers and Detergents" published by Manufacturing Confectioners Company or in "Tenside-Taschenbuch", H. Stache, 2nd Edn., Carl Hauser Verlag, 1981.

Other Optional Ingredients

The aqueous cleansing compositions of the invention may optionally comprise other ingredients, such as fragrance, colourant, foam boosting agent, preservatives (e.g. bactericide), pH buffering agent, polyelectrolyte, anti-oxidant, anti-corrosion agent and anti-static agent.

Viscosity. pH and other properties

It is preferred that the aqueous cleansing compositions according to the invention have viscosity of 100 to 10,000 mPa.s, more preferably from 200 to 8000 mPa.s, even more preferably from 400 to 6,500 mPa.s, and still even more preferably from 800 to 5,000 mPa.s, as measured at a shear rate of 20 s^-1 at 25 °C.
Viscosity may be determined by using a HAAKE® Viscotester VT550 (Gebruder HAAKE GmbH, Karlsruhe, Germany), using an 18/8 stainless steel MV measuring cup and a MV2 bob. Viscosity may be increased or decreased by adding any suitable known viscosity enhancing or lowering agent.
It is preferred that pH of the aqueous cleansing compositions according to the invention is in the range of 10 to 13. The compositions in accordance with this invention may preferably comprise a buffering agent, able to maintain the pH of a formulation. Any suitable buffering agent, or a buffer-system may be used, for example, a mixture of sodium carbonate and sodium hydrogen carbonate.

Method and use:

Compositions according to the invention may be used for cleaning soiled dishes or any similar hard surface. In general, a method for use would include a step of contacting a soiled plate with an efficacious amount of the composition preferably with the help of a scrubber or implement such as sponge, scouring pad or cloth, followed by scrubbing and later by rinsing with water.
Alternatively, the compositions of the invention, or their diluted variants, may be made available in the form of a pre-impregnated implement such as a sponge.

Packaging

The aqueous cleansing compositions according to the invention may be packaged in any suitable container. It is preferred that the composition is packaged in a plastic bottle with a detachable closure /pouring spout. The bottle may be rigid or deformable.
A deformable bottle allows the bottle to be squeezed to aid dispensing. If clear bottles are used they may be formed from PET. Polyethylene or clarified polypropylene may be used. Preferably the container is clear enough that the liquid, with any visual cues therein, is visible from the outside. The bottle may be provided with one or more labels, or with a shrink wrap sleeve which is desirably at least partially transparent, for example 50% of the area of the sleeve is transparent. The adhesive used for any transparent label should preferably not adversely affect the transparency.
The invention is further described with reference to the following non-limiting examples.

Examples

Example 1

Several compositions, some within and some outside the scope of the present invention were prepared. Details are shown in Table 1. Also included is a remark on whether the compositions were stable or not (turbid/clear). Stable compositions were clear whereas turbid compositions were unstable. All compositions were tested at 25 °C.

Table 1

Composition Ref. No.	Ingredient/wt%
Composition Ref. No.	Na₂CO₃	Na-LAS	SLES 1EO	SXS	MPG	Water	Visual Observation
1	10.0	20.0	--	--	--	q.s.	Turbid
2	10.0	20.0	--	--	10.0	q.s.	Turbid
3	10.0	20.0	--	--	14.0	q.s.	Turbid

4	10.0	20.0	--	20.0	--	q.s.	Turbid
5	10.0	20.0	--	2.0	2.0	q.s.	Turbid
6	10.0	10.0	10.0	2.0	2.0	q.s.	Clear

7	10.0	15.0	5.0	2.5	2.5	q.s.	Clear
8	10.0	5.0	15.0	1.0	1.0	q.s.	Clear
9	10.0	--	20.0	1.0	1.0	q.s.	Clear
10	10.0	15.0	5.0	--	--	q.s.	Turbid
11	10.0	10.0	10.0	--	--	q.s.	Turbid
12	10.0	5.0	15.0	--	--	q.s.	Turbid




13	10.0	35.0	--	6.0	6.0	q.s.	Turbid


14	20.0	20.0	--	6.0	6.0	q.s.	Turbid
15	5.0	10.0	--	0.5	0.5	q.s.	Turbid



16	15.0	30.0	--	10.0	10.0	q.s.	Turbid
17	10.0	20.0	--	6.5	1.5	q.s.	Turbid


18	10.0	20.0	--	3.0	5.0	q.s.	Turbid
19	10.0	20.0	--	2.0	6.0	q.s.	Turbid

Note: Abbreviations/short form used on Table 1 mean the following:
(i) Na₂CO₃ is the alkali metal carbonate
(ii) Na-LAS stands for linear alkylbenzene sulfonate, sodium salt
(iii) SLES 1EO stands for sodium lauryl ether sulphate
(iv) SXS stands for sodium xylenesulphonate, which is the first hydrotrope.
(v) MPG is monopropylene glycol which is the second hydrotrope

In addition to some other inferences, the following may be drawn from Table 1.
Data pertaining to composition 1 indicates that composition which contains more amount of the non-alkoxylated anionic surfactant and the sodium carbonate, but which is devoid of any hydrotrope, is turbid. It is believed to happen due to phase-separation of the anionic surfactant and recrystallization of a significant portion of the alkali metal carbonate.
Addition of as high as 10 wt% MPG does not render the composition clear (Composition 2). Even an increase in the amount of MPG does not help (Composition 3).
Further addition of more amount of hydrotrope makes the composition turbid again (Composition 4). Therefore in order to get a clear composition at an appreciably high amount of anionic surfactant, it is necessary to use more of the first hydrotrope.
On the other hand, using less than efficacious amount of hydrotropes, even in combination, also does not provide a technical solution (MPG and SXS at 2 wt% each in Composition 5). When the total amount of the anionic surfactant is balanced with introduction of the alkoxylated anionic surfactant, the composition becomes clear. (Compositions 6, 7, 8)
The data pertaining to composition 9 indicates that a composition devoid of non-alkoxylated anionic surfactant is clear at very low hydrotrope content but such a composition would not provide the desired extent of cleansing, especially that of oily stains and such residues on soiled dishes. Such compositions would fall outside the scope of the present invention.
Data pertaining to compositions 10 to 12 indicates that those totally devoid of hydrotrope are turbid, regardless of any permutation or combination of surfactants.
Composition 13 is turbid because it contains too much non-alkoxylated anionic surfactant. Composition 14 is turbid because it contains too much sodium carbonate. Composition 15 is turbid because the individual amount of the first and second hydrotropes is less than minimum amount of each and the composition is devoid of alkoxylated anionic surfactant. Composition 16 is turbid because it contains too much hydrotrope in combination and it is devoid of the alkoxylated anionic surfactant. On the other hand, Compositions 17, 18 and 19 are turbid because the ratio of the amount of first hydrotrope to that of said second hydrotrope is outside the range of 1:1 to 3:1 parts by weight and each composition is devoid of the alkoxylated anionic surfactant.

Example 2: Compositions outside the invention [containing other hydrotropes]

Table 2

Composition Ref. No.	lngredients/wt%						Visual Observation
Composition Ref. No.	Na₂CO₃	Na-LAS	Urea	TEA	Citric Acid	Water	Visual Observation
20	10.0	20.0	4.0	4.0	--	q.s.	Turbid
21	10.0	20.0	--	4.0	4.0	q.s.	Turbid
22	10.0	20.0	4.0	--	4.0	q.s.	Turbid

Note: TEA is Triethylamine

The data in table 2 clearly indicates that in spite of there being an appreciable quantity of total hydrotrope in the compositions, none of the compositions is clear. It happens because these hydrotropes do not belong to the classes in accordance with the present invention.

Claims

An aqueous cleansing composition comprising:
(i) 5 wt% to 30 wt% of a non-alkoxylated anionic surfactant;

(ii) 5 wt% to 15 wt% alkali metal carbonate;

(iii) a first hydrotrope in the range of 1 to 8 wt%; and,

(iv) a second hydrotrope in the range of 1 to 8 wt%,
wherein said first hydrotrope belongs to the class of sulphonates and said second hydrotrope belongs to the class of alcohols and ratio between the amount of first hydrotrope to that of said second hydrotrope is in the range of 1:1 to 3:1 parts by weight and wherein said composition comprises 2 wt% to 15 wt% alkoxylated anionic surfactant.
A composition as claimed in claim 1 wherein amount of said first hydrotrope is in the range of 2 to 8 wt%.
A composition as claimed in claim 1 or 2 wherein amount of said second hydrotrope is in the range of 2 to 8 wt%.
A composition as claimed in any preceding claim 1 to 3 wherein said first hydrotrope is sodium cumene sulphonate, sodium xylene sulphonate, sodium toluene sulphonate, naphthalenesulphonate, methylnaphthalenesulphonate, dimethylnaphthalenesulphonate and trimethylnaphthalenesulphonate or a combination thereof.
A composition as claimed in any preceding claim 1 to 4 wherein said second hydrotrope is ethylene glycol, monopropylene glycol, dipropylene glycol glycerol or a combination thereof.
A composition as claimed in claim 5 wherein said second hydrotrope is monopropylene glycol.