DE69710315T2 - LIQUID CLEANER - Google Patents

Description

Field of the invention

This invention relates to an acidic liquid crystal cleaning composition. More particularly, it relates to an acidic liquid crystal cleaning composition in a liquid crystalline state which is superior to other liquid cleaning compositions in cleaning power and other physical properties when brought into contact with oily soil.

Background of the invention

Liquid, aqueous, synthetic, organic detergent compositions have long been used in human hair shampoos and as dishwashing detergents for washing dishes by hand (as opposed to washing dishes in automatic dishwashers). Liquid detergent compositions have also been used as hard surface cleaners such as in pine oil liquids for cleaning floors and walls. Recently, they have also proven successful as laundry detergents, apparently because they are convenient to use, are immediately soluble in wash water, and can be used in "stain pretreatment" applications to aid in the removal of soils and stains from laundry during subsequent washing. Liquid detergent compositions contain anionic, cationic and nonionic surfactants, builders and adjuvants, including lipophilic materials as adjuvants that can act as solvents for lipophilic soils and stains. The various liquid, aqueous, synthetic, organic detergent compositions mentioned serve to emulsify lipophilic materials including oily soils in aqueous media such as wash water by forming micelle dispersions and emulsions.

Although emulsification is a method of soil removal, it has only been relatively recently discovered how to prepare microemulsions that are much more effective than normal emulsions in removing lipophilic materials from substrates. Such microemulsions are described in GB-B-2 190 681 and US-A-5 075 026, US-A-5 076 954 and US-A-5 082 584 and US-A-5 108 643, most of which deal with acidic microemulsions useful for cleaning hard surfaced objects such as baths and wash basins, the microemulsions being particularly effective for removing soap scum and limescale. However, as in US-A-4,919,893, the microemulsions must be substantially neutral and are also taught to be effective for microemulsifying lipophilic soils from substrates. US Application No. 7/313,664 describes a light-duty microemulsion liquid detergent composition useful for washing dishes and removing greasy deposits therefrom, both in neat and diluted form. Such compositions include complexes of anionic and cationic detergents as surface-active components of the microemulsions.

The various microemulsions referred to contain a lipophile which may be a hydrocarbon, a surfactant which may be an anionic and/or a non-ionic detergent, a cosurfactant which may be a poly-lower alkylene glycol lower alkyl ether, e.g. tripropylene glycol monomethyl ether, and water.

Although the preparation and use of cleaning compositions in microemulsion form significantly improves the cleaning power and the removal of greasy soils compared to the ordinary emulsions, the present invention further improves these and increases the ability of the cleaning compositions to adhere to surfaces to which they are applied. Thus, they drip or run significantly less than cleaning compositions of "similar" cleaning power that are in microemulsion or normal liquid detergent form. Because they spontaneously form microemulsions with lipophilic soil or stain material, essentially without the need for the input of any energy, either thermal or mechanical, they are more effective cleaners than ordinary liquid detergents at room temperature and at the higher and lower temperatures normally used in cleaning operations, and they are also more effective than cleaning compositions in microemulsion form.

The present liquid crystal cleaning compositions may be either clear or slightly cloudy or milky (opalescent) in appearance, however both forms are stable upon storage and their components do not separate or become ineffective even when stored at slightly elevated temperatures for periods of up to 6 months and up to 1 year. The presence of cosurfactant in the liquid crystal cleaning compositions helps such compositions to resist freezing at low temperatures.

According to the present invention, an acidic liquid cleaning composition, suitably at room temperature or below, for pretreating and cleaning materials soiled with lipophilic soil or soap scum is in liquid crystalline form and comprises synthetic organic surfactant, cosurfactant, organic acid, solvent for the soil and water. The invention also relates to a method of treating objects and materials soiled with soap scum and/or lipophilic soil with compositions according to the invention to dissolve or remove such soil by applying to the site of such soil on such material a soil-dissolving or removing amount of the composition according to the invention. In another aspect of the invention, lipophilic soil from the soiled surface is absorbed into the liquid crystal.

In recent years, general purpose liquid cleaners have been widely adopted for cleaning hard surfaces, e.g., painted wood and paneling, tiled walls, wash basins, bathtubs, linoleum or tiled floors, washable wallpaper, etc. Such general purpose liquids contain clear or opaque aqueous mixtures of water-soluble synthetic organic detergents and water-soluble detergent builder salts. In order to achieve cleaning effectiveness comparable to granular or powdered general purpose cleaner compositions, preference has been given to using water-soluble inorganic phosphate builder salts in the previously known general purpose liquids. For example, such early phosphate-containing compositions are described in US-A-2 560 839, US-A-3 234 138, US-A-3 350 319 and GB-B-1 223 739.

In response to efforts by environmentalists to reduce phosphate levels in groundwater, improved general-purpose fluids have emerged that contain reduced concentrations of inorganic phosphate builder salts or nonphosphate builder salts. A particularly useful self-clouding fluid of the latter type is described in US-A-4,244,840.

However, these previously known general purpose liquid cleaners containing detergent builder salts or other equivalents tend to leave films, stains or streaks on cleaned unrinsed surfaces, especially on glossy surfaces. Therefore, such liquids require thorough rinsing of the cleaned surfaces, which represents a time-consuming effort for the user.

In order to overcome the above-mentioned disadvantage of the previously known general-purpose fluid, US-A-4 017 409 teaches that a mixture of paraffin sulfonate and a reduced concentration of inorganic phosphate builder salt should be used. However, such compositions are not suitable for use in the not entirely acceptable from an environmental point of view. On the other hand, another alternative to achieve phosphate-free general purpose fluids is to use a larger proportion of a mixture of anionic and nonionic detergents with smaller amounts of glycol ether solvent and organic amine, as shown in US-A-3 935 130. This approach is again not entirely satisfactory and the high levels of organic detergents necessary to achieve cleaning cause foaming which in turn leads to the need for thorough rinsing, which has proven to be undesirable for today's consumers.

Another way to formulate liquid cleaning compositions for hard surfaces or any purpose where product homogeneity and clarity are important issues involves the formation of oil-in-water (O/W) microemulsions containing one or more surface-active cleaning compounds, water-immiscible solvent (typically a hydrocarbon solvent), water and a "cosurfactant" compound that provides product stability. By definition, an O/W microemulsion represents a spontaneously forming colloidal dispersion of "oil" phase particles having a particle size in the range of 25-800 Å in an aqueous dispersion medium.

Due to the extremely small particle size of the dispersed oil phase particles, microemulsions are translucent and clear and usually highly stable against phase separation.

Patent disclosures relating to the use of soil removal solvents in O/W microemulsions include, for example, EP-A-0 137 615 and EP-A-0 137 617 to Herbots et al., EP-A-0 160 762 to Johnston et al., and US-A-4 561 991 to Herbots et al. Each of these patents also teaches the use of at least 5 wt.% soil removal solvent.

It is also known from GB-A-2 144 763 to Herbots et al., published on 13 March 1985, that magnesium salts increase the soil removal performance of organic soil removal solvents such as terpenes in O/W microemulsion liquid cleaning compositions. The compositions of this invention described by Herbots et al. require at least 5% of the soil removal solvent and magnesium salt mixture and preferably at least 5% solvent (which may be a mixture of water-immiscible, non-polar solvent with sparingly soluble, weakly polar solvent) and at least 0.1% magnesium salt.

The following exemplary prior art patents also relate to liquid detergent cleaning compositions in the form of O/W microemulsions: US-A-4 472 291 - Rosario, US-A-4 540 448 - Gauteer et al., US-A-3 723 330 - Sheflin et al.

Liquid cleaning compositions containing terpenes such as D-limonene or other soil removal solvents, although not disclosing that they are in the form of O/W microemulsions, are the subject of the following exemplary patents: EP-A-0 080 749, GB-B-1 603 074 and US-A-4 414 128 and US-A-4 540 505. For example, US-A-4 414 128 generally discloses an aqueous liquid cleaning composition characterized by, by weight:

(a) 1% to 20% synthetic anionic, nonionic, amphoteric or zwitterionic surfactant or a mixture of these,

(b) 0.5% to 10% mono- or sesquiterpene or a mixture of the same, in a weight ratio of (a) : (b) in the range from 5 : 1 to 1 : 3 and

(c) 0.5% to 20% polar solvent having a solubility in water at 15°C in the range of 0.2% to 10%. Other ingredients present in the formulations disclosed in this patent include 0.05% to 10% by weight alkali metal, ammonium or alkanolammonium soap of C3 to C24 fatty acid, 0.5% to 13% by weight calcium sequestrant, up to 10% by weight non-aqueous solvent, e.g. alcohols and glycol ethers, and up to 10% by weight hydrotropes, e.g. urea, ethanolamines and salts of lower alkylaryl sulfonates. All formulations shown in the examples of this patent contain relatively high amounts of detergent builder salts which are detrimental to the surface gloss.

US-A-5 035 826 teaches liquid crystal compositions, but these compositions exhibit thermal stability in the limited temperature range of 19ºC to 36ºC.

Hard surface cleaners such as bathroom cleaners and scouring cleaners have been around for many years. Scouring cleaners typically contain a soap or synthetic organic detergent or surfactant and an abrasive. Such products can scratch relatively soft surfaces and ultimately cause them to appear dull. These products are not effective in removing limescale deposits (usually encrusted calcium and magnesium carbonates) under normal use. Because limescale deposits can be removed by chemical reactions with acidic media, various acidic cleaners have been manufactured and have proven to be of varying success. In some cases, such cleaners have failed because the acid used was too strong and damaged the surfaces being cleaned. Sometimes the acid component of the cleaner has reacted undesirably with other components of the product, negatively affecting the detergent or perfume. Some cleaners required rinsing to avoid leaving unwanted deposits on the cleaned surfaces. As a As a result of research conducted in an attempt to overcome the disadvantages mentioned, an improved liquid cleaning composition in stable microemulsion form has recently been prepared which is an effective cleaner for removing soap scum, limescale and greasy soils from hard surfaces such as bathroom surfaces and which does not require rinsing after application. One such product is described in US-A-5 076 954, which is hereby incorporated by reference. In particular, Example 3 of the document discloses an acidic, clear, oil-in-water microemulsion which is therein described as being successfully used for cleaning shower wall tiles of limescale and soap scum which had adhered to them. Such cleaning was effected by applying the cleaner to the walls followed by wiping or minimal rinsing, after which the walls were allowed to dry to give a good shine.

The thickened microemulsion cleaner described in US-A-5 076 954 is effective and easy to use for removing limescale and soap scum from hard surfaces. However, it has been found that its mixture of acidic agents (succinic, glutaric and adipic acids) can damage the surface of some hard bodies, such as those made of materials which are not acid resistant. One of these materials is an enamel which is widely used in Europe as a coating for bathtubs and which is referred to here as European enamel. It has been referred to as zirconium white enamel or zirconium white powder enamel and has the advantage of being resistant to cleaning agents, which makes it suitable for use on bathtubs, sinks, shower tiles and enamelled objects in bathrooms. Such enamel, however, is sensitive to acids and is severely damaged by the use of the acidic microemulsion cleaner based on the three organic carboxylic acids mentioned above. This problem has been solved in EP-A-0 336 878 by providing additional acidic materials have been included in the cleaner with the organic acids. Rather than exacerbating the problem, they protect such European enamel surfaces from damage caused by such organic acids. Also, a mixture of these additional acids, namely phosphonic and phosphoric acids, surprisingly improves the safety of the aqueous cleaner when used on such European enamel surfaces, and it reduces the cost of the cleaner.

The present compositions according to the invention allow the cleaning of European enamel surfaces as well as any other acid-resistant surfaces of bathtubs and other surfaces in bathrooms. The product can be used on various other materials that are particularly sensitive to attack by acidic media, such as marble. In addition, the present compositions are stable for at least 3 months at 25°C and are shear-thinning.

The present invention relates to a thickened, acidic, aqueous liquid crystal cleaner for bathtubs and other hard surface objects that are acid-resistant or made of zirconium white enamel, the cleaner having a pH in the range of 1 to 4 and the cleaner removing limescale, soap scum and greasy dirt from the surfaces of these objects without damaging these surfaces.

US-A-5 035 826 teaches liquid crystal compositions, but these compositions have thermal stability in the limited temperature range of 19ºC to 36ºC.

Summary of the invention

The present invention provides an improved acidic liquid crystal cleaning composition having improved interfacial tension which improves cleaning of a hard surface, in the form of a liquid crystal which is useful for cleaning hard surfaces such as plastic, enamel and metal surfaces with a glossy finish, polished floors, vehicle engines and other engines. In particular, due to the improved interfacial tensions, the improved cleaning compositions exhibit good properties in removing greasy soils and leaving shiny surfaces without any additional rinsing or wiping or which require only minimal additional rinsing or wiping. This latter characteristic is demonstrated by little or no visible residue on the unrinsed cleaned surfaces and overcomes one of the disadvantages of the prior art products.

Surprisingly, these desired results are achieved even in the absence of polyphosphate or other inorganic or organic detergent builder salts and even in the complete absence or substantially complete absence of soil removal solvents.

The invention provides a stable liquid crystal hard surface cleaner composition which is particularly effective in removing oily and greasy oil. The liquid crystal composition contains by weight:

(a) 1% to 15% ethoxylated C8-18 alkyl ether sulfate surfactant or ethoxylated C8-18 alkyl phenyl ether surfactant with 2 to 6 moles of EO or sodium lauryl sulfate,

(b) 1% to 30% of a water-miscible cosurfactant having either only limited or substantially no ability to dissolve oily or greasy soils, which is a C1-6 alkyl mono-, di-, tri- or tetraethylene or propylene glycol or a mono-C16 alkyl mono-, di- or tributylene glycol,

(c) 1% to 30% ethoxylated nonionic surfactant,

(d) 0.48% to 8% magnesium salt such as magnesium sulfate heptahydrate and/or magnesium chloride,

(e) 0.6% to 10% water-insoluble organic compound selected from perfume, essential oil or water-insoluble hydrocarbon, preferably having 6 to 18 carbon atoms,

(f) 1% to 5% aliphatic carboxylic acid having 2 to 10 carbon atoms,

(g) 0.1% to 3% weak base and

(h) the balance water, wherein the acidic liquid crystal detergent composition does not contain a sulfonic surfactant and the liquid detergent composition has a storage modulus of equal to or greater than one Pascal (1 Newton/m2), preferably greater than 10 Pascal, at a temperature of 20°C to 40°C at a strain of 0.1% to 5% and a frequency of 10 rad/s, as determined on a Carr-Med® CS Rheometer, which is thermally stable and exists as a liquid crystal at a temperature in the range of 8°C to 43°C, preferably 4°C to 43°C.

Detailed description of the invention

The present invention relates to a stable acidic liquid crystal detergent composition comprising approximately, by weight, 1 to 15% ethoxylated alkyl ether sulfate surfactant, 1% to 30% cosurfactant, 1% to 30% ethoxylated nonionic surfactant, 0.6 to 10% water insoluble hydrocarbon, essential oil or perfume, 1% to 5% aliphatic carboxylic acid, 0.1% to 3% weak base, 0.48% to 8% magnesium salt and the balance water, wherein the acidic liquid crystal composition does not contain a sulfonic surfactant and the liquid detergent composition has a Has a storage modulus of equal to or greater than one Pascal (1 Newton/m²), preferably greater than 10 Pascal, as determined on a Carr-Med CS rheometer, is thermally stable and exists as a clear liquid crystal in the temperature range of 8ºC to 43ºC, preferably 4ºC to 43ºC.

According to the invention, the role of the water-insoluble hydrocarbon can be taken by a non-water-soluble perfume. Typically, in water-based compositions, the presence of a solubilizer is necessary for perfume dissolution, such as an alkali metal lower alkylaryl sulfonate hydrotrope, triethanolamine, urea, etc., particularly at perfume levels of 1% or above, because perfumes are generally a mixture of essential fragrance oils and aromatic compounds, which are generally not water-soluble.

The term "perfume" is used here and in the appended claims in its normal meaning and refers to and includes any water-soluble fragrance substance or mixture of substances, including natural (i.e., obtained by extraction from flowers, herbs, blossoms or plants), artificial (i.e., a mixture of natural oils or oil constituents) or synthetically produced substances as odoriferous substances. Typically, perfumes are complex mixtures of mixtures of various organic compounds such as alcohols, aldehydes, ethers, aromatic compounds or varying amounts of essential oils (e.g., terpenes), e.g., 0 to 80% by weight, normal 10 to 70% by weight, the essential oils themselves being volatile odoriferous compounds and also serving to dissolve the other components of the perfume.

Although the perfume is not a solvent for greasy or oily dirt from the outset - although some perfumes actually contain up to 80% terpenes, which are known to be good fat solvents - the compositions according to the invention, in diluted form, quite surprisingly have the ability to To dissolve 10 times the weight of the perfume of oily or greasy dirt which is removed or dissolved from the hard surface as a result of the action of the anionic and non-ionic surfactants, this dirt being absorbed into the oil phase of the O/W microemulsion.

In the present invention, the precise composition of the perfume is not of particular importance for the cleaning performance, as long as it is water-immiscible and has a pleasant odor. Of course, especially for cleaning compositions intended for use in the home, the perfume, like all other ingredients, should be cosmetically acceptable, i.e. non-toxic, hypoallergenic, etc.

The hydrocarbon, e.g. a perfume, is contained in the liquid crystal composition in an amount of 0.6 to 10 wt%, preferably 0.8 to 8 wt%, particularly 1 to 6 wt%. If the amount of hydrocarbon (perfume) is less than 0.6 wt%, it becomes difficult to form the liquid crystal. If the hydrocarbon (perfume) is added in amounts of more than 10 wt%, the cost is increased without any additional cleaning effect; the cleaning performance is actually somewhat reduced because the total amount of greasy or oily dirt that can be absorbed into the oil phase of the microemulsion is proportionally reduced.

Furthermore, although better soil removal performance is achieved with perfume compositions that do not contain terpene solvents, it is obviously difficult for perfumers to formulate sufficiently inexpensive perfume compositions for products of this type (i.e. very cost-sensitive consumer products) containing less than 20%, typically less than 30%, of such terpene solvents.

Thus, from a practical and economic point of view, the liquid crystal cleaning composition according to the invention contains considerations, often up to 0.2 to 7% by weight, based on the total composition, of terpene solvents incorporated therein via the perfume component. However, even when the amount of terpene solvent in the cleaning formulation is less than 1.5% by weight, such as up to 0.6% by weight or 0.4% by weight or less, satisfactory soil removal and oil removal ability is provided by the compositions of the invention.

Instead of the perfume, either in the microemulsion composition or in the all-purpose hard surface cleaner composition, one can use, in the same predefined concentrations as the perfume was used in either the microemulsion composition or in the all-purpose hard surface cleaner composition, an essential oil or a water-insoluble organic compound such as a water-insoluble hydrocarbon having 6 to 18 carbon atoms, such as a paraffin or isoparaffin such as IsoparH, isodecane, alpha-pinene, beta-pinene, decanol and terpineol.

Suitable essential oils are selected from the group consisting of: natural anethole 20/21, anise seed oil Chinastar, anise seed oil Globebrand, linseed (Peru), basil oil (India), black pepper oil, black pepper oleoresin 40/20, bois de rose (Brazil) FOB, borneo flakes (China), white camphor oil, synthetic technical camphor powder, ylang-ylang oil (Java), cardamom oil, cinnamon blossom oil (China), cedarwood oil (China) BP, cinnamon bark oil, cinnamon leaf oil, citronella oil, clove germ oils, clove leaves, coriander (Russia), coumarin 69ºC (China), cyclamen aldehyde, diphenyl oxide, ethyl vanillin, eucalyptol, eucalyptus oil, eucalyptus citriadora, fennel oil, geranium oil, ginger oil, ginger oleoresin (India), White Grapefruit Oil, Guaiac Wood Oil, Gurjun Balsam, Heliotropin, Isobornyl Acetate, Isolongifolene, Juniper Berry Oil, L-Menthyl Acetate, Lavender Oil, Lemon Oil, Lemongrass Oil, Distilled Lime Oil, Litsea Cubeba Oil, Longifolene, Menthol Crystals, Methyl Cedryl Ketone, Methyl Chavicol, Methyl Salicylate, Ambrette Musk, Ketone Musk, Xylene Musk, Nutmeg oil, orange oil, patchouli oil, peppermint oil, phenylethyl alcohol, allspice berry oil, allspice leaf oil, rosalin, sandalwood oil, sandenol, sage oil, clear sandalwood oil, sassafras oil, peppermint oil, spike lavender, marigold, tea tree oil, vanilin, vetiver oil (Java), gaultheria oil.

The nonionic surfactant is contained in amounts of 1 to 30%, preferably 3 to 18%, based on the liquid crystal composition, and provides better performance in removing oily dirt as well as mildness to human skin.

The water-soluble ethoxylated nonionic surfactants used in the present invention are commercially known and include the ethoxylates of primary aliphatic alcohol and the ethoxylates of secondary aliphatic alcohol. The length of the polyethyleneoxy chain can be adjusted to achieve the desired balance between the hydrophobic and hydrophilic elements.

The class of nonionic surfactants includes the condensation products of higher alcohol (i.e. alkanol having 8 to 16 carbon atoms in straight or branched chain configuration) condensed with about 4 to 20 moles of ethylene oxide, e.g. B. lauryl or myristyl alcohol condensed with about 16 moles of ethylene oxide (EO), tridecanol condensed with about 6 moles of EO, myristyl alcohol condensed with about 10 moles of EO per mole of myristyl alcohol, the condensation product of EO with a coconut fatty alcohol cut containing a mixture of fatty alcohols with alkyl chains varying in length from 10 to about 14 carbon atoms, the condensate containing either about 6 moles of EO per mole of total alcohol or about 9 moles of EO per mole of alcohol, and tallow alcohol ethoxylates containing from 6 EO to 11 EO per mole of alcohol.

A preferred group of the nonionic surfactants mentioned are the Neodol® ethoxylates (Shell Company), which are higher aliphatic, primary alcohols with 9 to 15 carbon atoms, such as C₄-C₁₁ alkanol are condensed with 4 to 10 moles of ethylene oxide (Neodol® 91-8), C₁₂₋₁₃-alkanol condensed with 6.5 moles of ethylene oxide (Neodol 23-6.5), C₁₂₋₁₅-alkanol condensed with 12 moles of ethylene oxide (Neodol 25-12), C₁₄-ls-alkanol condensed with 13 moles of ethylene oxide (Neodol® 45-13), and the like. Such ethoxamers have an HLB (hydrophobic lipophilic balance) value of about 8 to 15 and give good O/W emulsification, while ethoxamers with HLB values below 7 contain less than 4 ethylene oxide groups and tend to be poor emulsifiers and poor detergents.

Additional satisfactory water-soluble alcohol-ethylene oxide condensates are the condensation products of secondary aliphatic alcohol having 8 to 18 carbon atoms in straight or branched chain configuration condensed with 5 to 30 moles of ethylene oxide. Examples of commercially available nonionic detergents of the type mentioned are C11-C15 secondary alkanol condensed with either 9 EO (Tergitol 15-S-9) or 12 EO (Tergitol® 15-S-12) offered by Union Carbide.

The anionic surfactants that can be used in the cleaning compositions of the present invention are water-soluble salts and include the sodium, potassium, ammonium, triethanolamine and ethanolammonium salts of C8-18 ethoxylated alkyl ether sulfate surfactants having the structure:

R-(OCH2 CH2 )nOSO3 -M+ ,

wherein n is about 0 (if n = 0 then it is sodium lauryl sulfate [SLS]) to about 5 and R is an alkyl group having 8 to 18 carbon atoms, preferably 12 to 15 and natural cuts, e.g. C₁₂₋₁₄, C₁₂₋₁₅, and M is an ammonium cation or a metal cation, especially sodium. The ethoxylated alkyl ether sulfate is present in the composition in a concentration of about 1 to about 20% by weight, especially 2 to 15% by weight.

The ethoxylated alkyl ether sulfate can be prepared by sulfating the condensation product of ethylene oxide with C8-10 alkanol and neutralizing the resulting product. The ethoxylated alkyl ether sulfates differ from each other in the number of carbon atoms in the alcohols and the number of moles of ethylene oxide reacted with one mole of such alcohol. Preferred ethoxylated alkyl ether polyethylene oxysulfates contain 12 to 15 carbon atoms in the alcohols and in their alkyl groups, e.g. sodium myristyl (3 EO) sulfate.

Ethoxylated C8-18 alkyl phenyl ether sulfates containing from 2 to 6 moles of ethylene oxide in the molecule are also suitable for use in the compositions of the invention. These cleaning agents can be prepared by reacting alkyl phenol with from 2 to 6 moles of ethylene oxide and sulfating and neutralizing the resulting ethoxylated alkyl phenol. The concentration of the ethoxylated alkyl ether sulfate is from about 1 to about 8% by weight.

The cosurfactants are mono-C₁-C₆ alkyl ethers of ethylene glycol and propylene glycol with the structural formula R(X)nOH, in which R is a C₁-C₆ alkyl group, X is (OCH₂CH₂) or (OCH₂(CH₃)CH) and n is a number from 1 to 4, as well as mono-C₁-C₆ alkyl ethers of mono-, di- or tributylene glycol.

Exemplary polypropylene glycols include dipropylene glycol and polypropylene glycol having a molecular weight of 200 to 1000, e.g. polypropylene glycol 400. Other satisfactory glycol ethers are ethylene glycol monobutyl ether (butyl cellusolv), diethylene glycol monobutyl ether (butyl carbitol), triethylene glycol monobutyl ether, mono-, di-, tripropylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, mono-, di-, tripropylene glycol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, propylene glycol tert-butyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, ethylene glycol monopropyl ether, ethylene glycol monopentyl ether, diethylene glycol monomethyl ether, Diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monopentyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monopentyl ether, triethylene glycol monohexyl ether, mono-, di-, tripropylene glycol monoethyl ether, mono-, di-, tripropylene glycol monopropyl ether, mono-, di-, tripropylene glycol monopentyl ether, mono-, di-, tripropylene glycol monohexyl ether, mono-, di-, tributylene glycol monomethyl ether, mono-, di-, tributylene glycol monoethyl ether, mono-, di-, tributylene glycol monopropyl ether, mono-, di-, tributylene glycol monobutyl ether, mono-, di-, tributylene glycol monopentyl ether and mono-, di-, Tributylene glycol monohexyl ether. Tripropylene glycol n-butyl ether is the preferred cosurfactant due to its hydrophobic character.

The amount of cosurfactant necessary to stabilize the liquid crystal compositions will, of course, depend on such factors as the surface tension characteristics of the cosurfactant, the type and amounts of primary surfactants and perfumes, and the type and amounts of any other additional ingredients that may be included in the composition and that have an impact on the thermodynamic factors enumerated above. The amounts of cosurfactant used in the liquid crystal composition range from 1 to 30 wt.%, preferably from 2 to 20 wt.%, especially from 3 to 16 wt.%, and provide a stable liquid crystal composition for the levels of primary surfactants and perfume described above and any other additional ingredients described below.

The aliphatic carboxylic acid having about 2 to about 10 carbon atoms is contained in the composition in a concentration of 1 wt.% to 5 wt.%, in particular about 1.25 wt.% to about 4 wt.%.

Exemplary aliphatic carboxylic acids include monovalent C₃-C₆ alkyl and alkenyl acids such as acrylic acid and propionic acid and divalent acids having 2 to 10 carbon atoms such as glutaric acid and mixtures of glutaric acid with adipic acid and succinic acid, as well as mixtures of the acids mentioned. In general, weight ratios of adipic acid: glutaric acid: succinic acid of 1-3: 1-8: 1-5, preferably 1-2: 1-6: 1-3, such as 1: 1: 1, 1: 2: 1, 2: 2: 1, 1: 2: 1.5, 1: 2: 2, 2: 3: 2, etc. can be used with equally good results.

Of the dicarboxylic acids of 2 to 10 carbon atoms, from oxalic to sebacic, suberic, azelaic and sebacic acids have lower solubility and are therefore not as useful in the present emulsions as the other aliphatic fatty diacids, all of which are preferably saturated and straight chain. Oxalic and malonic acids, although also useful as reducing agents, may be too strong for cleaning delicate hard surfaces. Preferred diacids are those in the middle of the range of acids of 2 to 10 carbon atoms, namely succinic, glutaric, adipic and pimelic acids, particularly the first three, which are fortunately commercially available, in a mixture. Citric acid can also be used as a diacid.

The preferred aliphatic carboxylic acid is an aliphatic alpha-hydroxy acid that is strong enough to lower the pH of the microemulsion to the range of 1 to 4. Various such carboxylic acids can serve this purpose, but those that have been found to best remove soap scum and limescale from bath surfaces without stabilizing the emulsion are the aliphatic hydroxy acids having the structure

in which Y is selected from the group consisting of hydroxy or a COOH group, and X is (CH₂)nW, where W is selected from the group consisting of CH₃ or COOH, and n is 0, 1 or 2. Preferred aliphatic alpha-hydroxy acids are citric acid, Lactic acid and malic acid, wherein a mixture of lactic acid with malic acid is preferred and the weight ratio of lactic acid to malic acid is preferably 5:1 to 1:1, in particular 4:1 to 1:1. The at least one aliphatic alpha-hydroxy acid is contained in the composition in an amount of 1 to 9 wt.%, preferably 2 to 7 wt.%.

The aliphatic alpha-hydroxy acid, after being incorporated into the acidic emulsion, can easily be partially neutralized to yield efficacy.

Phosphoric acid can be used at a concentration of 0 to 1 wt.% and is one of the additional acids that helps protect the acid-sensitive surfaces cleaned with the present emulsion cleaner. Because it is a triacid, it can also be partially neutralized to maintain an emulsion pH in the desired range. For example, it can be partially neutralized to the bisphosphate, e.g. NaH2PO4 or NH4H2PO4.

Phosphonic acid, used in a concentration of 0 to 1% by weight, can also be used to protect the acid-sensitive surfaces from the dissolving action of the dicarboxylic acids of the present thickened emulsions. It obviously exists only theoretically, but its derivatives are stable and useful in the practice of the present invention. These are considered to be phosphonic acids and this term is used in the description. The phosphonic acids have the structure

wherein Y is any suitable substituent, but Y is preferably alkylamino or N-substituted alkylamino. For example, a preferred phosphonic acid component of the present thickened acidic emulsions is aminotris(methylenephosphonic) acid, which has the formula N(CH₂PHxO)₃. Among the other Useful phosphonic acids are ethylenediaminetetra(methylenephosphonic) acid, hexamethylenediaminetetra(methylenephosphonic) acid, and diethylenetriaminepenta(methylenephosphonic) acid. The compounds of this class may be referred to as aminoalkylenephosphonic acids containing 1 to 3 amine nitrogen atoms, 3 or 4 lower alkylenephosphonic acid groups in which the lower alkylene consists of 1 to 2 carbon atoms, and 0 to 2 alkylene groups each having 2 to 6 carbon atoms, the alkylene(s) being present and connecting amino nitrogen atoms when a plurality of such amino nitrogen atoms are present in the aminoalkylenephosphonic acid. It has been found that such aminoalkylenephosphonic acids, which may also be partially neutralized at the desired pH of the microemulsion cleaner, have a desired stabilizing and protective effect in the cleaner according to the invention, especially when they are present together with phosphoric acid, and prevent damaging attack by the dicarboxylic acid(s) components of the cleaner on surfaces made of European enamel. When salts of the phosphorus-containing acids are present, they are normally monosalts of the phosphorus and/or phosphonic acid groups present.

The liquid crystal composition contains a weak base such as diethylanolamine or triethanolamine in a concentration of 0.1 wt% to 3 wt%. The weak base is used in the composition to adjust the pH of the composition.

The present composition contains 0.48 to 8 wt.%, preferably 1 to 6 wt.% magnesium salt such as magnesium chloride and/or magnesium sulfate heptahydrate and mixtures thereof.

The ability to formulate neutral and acidic products without builders that have soil removal capabilities is a feature of the present invention because the prior art O/W microemulsion formulations are usually highly alkaline or contain a lot of builder or both.

In addition to their excellent ability to clean greasy and oily soils, the low pH liquid crystal formulations also demonstrate excellent cleaning performance and the removal of soap scum and limescale when used undiluted or diluted.

The last necessary ingredient in the acidic liquid crystal compositions of the present invention having improved interfacial tension properties is water. The proportion of water in the liquid crystal cleaning composition is generally in the range of 20 to 97 wt.%, preferably 70 to 97 wt.%.

A composition according to the invention is in the liquid crystalline state when it has a lipotropic structure, is transparent or slightly opalescent but not opalescent and has a storage modulus, measured at a temperature of 20-40°C, at a frequency of 10 rad/s and a load of 0.1 to 5%, of equal to or greater than one Pascal (1 Newton/m²). The rheological behavior of the compositions according to the invention was determined at 25°C using a Carm-Med® CS rheometer. In carrying out the measurements, a cone and a plate at a cone angle of 2°, 0', 0" with a cone diameter of 6.0 cm, a measuring system gap of 52.0 µm and a measuring system inertia of 17.02 microNm·s⊃min;² were used.

The preparation of the liquid crystal compositions of the invention is relatively simple because they tend to form spontaneously, with little need for energy input to promote the formation of the liquid crystalline state. However, to promote uniformity of the composition, mixing is normally carried out and it has been found preferable to first mix the surfactants and cosurfactant with water, followed by admixture of the lipophilic component, normally a hydrocarbon (although esters or mixtures of hydrocarbons with esters may also be used). It is not necessary to use heat and most mixing operations are preferably carried out at about room temperature (20-25ºC).

The compositions of the invention can be applied to such surfaces by pouring them on, by application with a cloth or sponge, or by various other contact means, but it is preferred to apply them in the form of a spray by spraying them onto the substrate from a hand or finger pressure operated sprayer or pressure bottle. Such application can be to hard surfaces such as dishes, walls or floors from which a lipophilic (usually greasy or oily) soil is to be removed, or can be to fabrics such as laundry which have previously been stained with lipophilic soils such as motor oil. The compositions of the invention can be used as cleaning agents and can be used in the same way that liquid cleaning agents are normally used in dishwashing, floor and wall cleaning and laundry washing, but it is preferred that they also be used as stain pre-treatment agents, in which applications they have proven to be extremely useful in loosening the adhesions of lipophilic soils to substrates and thereby promote much easier cleaning by applying more of the same cleaning compositions of the invention or by applying different commercial cleaning compositions, in liquid, block or particulate form.

The various advantages of the invention have already been described in some detail and will not be repeated hereafter. However, it should be reiterated that the invention relates to the important discovery that effective liquid cleaning compositions can be prepared in the liquid crystalline state and that, because they are in this state, they are particularly effective in removing lipophilic soils from substrates and also for removing non-lipophilic materials from substrates. These advantageous properties of the liquid crystal cleaning compositions of the invention make them ideal for use as stain pre-treatment agents and cleaning agents for removing difficult-to-remove soils from substrates in various cleaning applications on hard and soft surfaces.

The following examples illustrate the invention but do not limit it. Unless otherwise indicated, all parts in the examples, specification and appended claims are by weight and all temperatures are in degrees Celsius. Example 1 The following formulations (wt.%) were prepared at 25ºC by simple mixing.

The cleaning ease number is given as:

[1-(wiping number of sample A)/wiping number of the special bath product)].

If the number of strokes of the sample = number of strokes of the reference, then the number is zero (equivalent cleaning effect between sample and comparison),

if the number of wipes of the pattern > number of wipes comparison, then the number has a negative value (the more negative the value the less effective the pattern is) and

if the number of strokes of the pattern < number of strokes comparison, then the number has a positive value (the more positive the value the more effective the pattern).

The soap scum residue is produced by spraying sodium oleate and a stoichiometric amount of calcium chloride directly onto ceramic tiles.

The cleaning ease index of A compared with the various comparison products was calculated by an indirect comparison between the neutral sample (A) and the comparisons. In other words, A and the comparisons were not tested on the same tile.

The formulation of the gel bath is:

% by weight

Xanthan solution 5.0

Paraffin sulfonate 4.0

non-ionic Plurafac LF400 3.0

H₃PO₄(85%) 0.26

Aminotrimethylphosphonic acid 0.05

Perfume 0.75

Water Rest

The Ajax® AME 1:1 formulation has the same formulation as the gel bath, except that no xanthan solution is included and 1.5 wt% MgSO₄·7H₂O has been added.

Claims (7)

1. An acidic liquid crystal cleaning composition comprising, by weight: (a) 1 to 30% ethoxylated nonionic surfactant containing ethylene oxide groups, (b) 1 to 5% aliphatic carboxylic acid having 2 to 10 carbon atoms, (c) 1 to 15% water soluble salt of ethoxylated C8-18 alkyl ether sulfate surfactant or ethoxylated C8-18 alkyl phenyl ether sulfate surfactant with 2 to 6 moles of EO or sodium lauryl sulfate, (d) 0.1 to 3% weak base, (e) 0.6 to 10% water-insoluble organic compound selected from the group consisting of perfumes, essential oils and water-insoluble hydrocarbons, (f) 1 to 30% water-miscible glycol ether cosurfactant which is a mono-C₁₋₆ alkyl mono-, di-, tri- or a tetraethylene or propylene glycol or a a mono-C₁₋₆ alkyl mono-, di- or tributylene glycol, (g) 0.48 to 8% magnesium salt and (h) the balance being water, wherein the liquid crystal cleaning composition does not contain a sulfonate surfactant and has a storage modulus, measured at a temperature between 20ºC to 40ºC at a load of 0.1% to 5% and a frequency of 10 radians/second, of equal to or greater than one Pascal, thermally is stable and exists as a liquid crystal at a temperature of 8 to 43ºC. 2. The composition of claim 1 wherein the nonionic surfactant is a condensation product of 1 mole of higher fatty alcohol having from about 9 to about 11 carbon atoms with 2 to 5 moles of ethylene oxide groups. 3. The composition of claim 2 wherein the water-soluble salt of the ethoxylated C8-18 alkyl ether sulfate surfactant comprises a cation selected from the group consisting of sodium, potassium and ammonium. 4. A composition according to claim 3, wherein the aliphatic carboxylic acid is citric acid. 5. The composition of claim 3, wherein the water-insoluble hydrocarbon is selected from the group consisting of d-limonene, α-terpineol, α-pinene and β-pinene and mixtures thereof. 6. The composition of claim 1, wherein the carboxylic acid is citric acid. 7. A method for removing one or more of limescale, soap scum and greasy dirt from bath tubs or other hard surfaced objects which are acid resistant or made of zirconium white enamel, comprising applying to such a surface a composition according to claim 1 and removing said composition and the limescale and/or soap scum and/or greasy dirt from the surface.