GB2296919A - Detergent composition - Google Patents

Abstract

A detergent composition which contains a surfactant system having alkyl sulfate and nonionic surfactant components, and a detergency builder comprising zeolite P having a silicon to aluminium ratio not greater than 1.33 (zeolite MAP). Granular and liquid detergent compositions are preferred.

Description

DETERGENT COMPOSITION The present invention relates to a detergent composition comprising a surfactant system and a zeolite component as a sequestering agent for water hardness.

Detergent compositions containing synthetic detergents, particularly linear alkyl benzene sulfonate salts are well known in the art and are in widespread commercial use. Conventionally the linear alkyl benzene sulfonate salt forms part of a surfactant mixture in association with one or more other anionic or nonionic surfactants.

Current environmental concern has focused on the undesirability of deriving detergent components from non-renewable hydrocarbon sources.

Interest has therefore increased in the formulation of well-performing detergent compositions comprising surfactant systems which are environmentally compatible and preferably derived from renewable natural sources.

An example of an anionic surfactant which is readily derivable from renewable natural sources and which could replace the alkyl benzene sulfonate component either partially or in total is alkyl sulfate surfactant.

Detergent compositions including alkyl sulfate surfactant derived from naturally occurring fats and oils are known in the art. For example, GB-A1,399,966, in the name of the Procter & Gamble Company, discloses a detergent composition containing alkyl sulfate surfactant derived from tallow oil, or from coconut oil.

The detergency performance characteristics of surfactants having alkyl chains are known to depend on the nature and length of the alkyl chain.

For example, EP-A-342,917 describes a surfactant system, derived preferably from natural feedstock material, comprising an anionic surfactant the major ingredient of which is an alkyl sulfate of mixed alkyl chain length such that at least 10% by weight of the alkyl chains present in the alkyl sulfate are C 12 chains and at least 20% by weight of the alkyl chains are C 18 chains.

It has been recently established that good detergency performance over a range of laundry wash temperatures may be obtained for surfactant systems containing an alkyl sulfate surfactant having a high proportion of alkyl chain lengths greater than C 14, in combination with a nonionic surfactant.

A surfactant system containing alkyl sulfate surfactant of mixed alkyl chain length such that the level of C 12 and C 18 alkyl chain lengths is minimised, and wherein the C14 and C16 alkyl chain lengths form the major part, in combination with a nonionic surfactant, which provides particularly good detergency performance over a wide range of temperatures, is described in the Applicant's copending PCT Application No. US94/06943.

It has however, now been found that for the above described alkyl sulfate and nonionic containing surfactant systems to perform satisfactorily as components of a detergent composition designed primarily for laundering purposes it is important for the composition to contain a builder system providing effective control of hardness ions, particularly calcium ions.

Conventionally, water soluble inorganic phosphates, such as sodium tripolyphosphate, have been used as builders for laundry detergents.

More recently, alkali metal aluminosilicate ion-exchangers, particularly crystalline water insoluble sodium aluminosilicate zeolites, have been proposed as replacements for the inorganic phosphates.

For example, EP 21 491 A (Procter & Gamble) discloses detergent compositions containing a builder system which includes zeolite A, X or P (B) or a mixture thereof. EP 384070A (Unilever) discloses specific zeolite P materials having an especially low silicon to aluminium ratio not greater than 1.33 (hereinafter referred to as zeolite MAP) and describes their use as detergency builders.

However, it is known that there are certain problems in the use of water insoluble zeolites as detergency builders, as compared with water soluble builders such as phosphates. In particular, most zeolites, including zeolite A, act relatively slowly to sequester the calcium ions.

It has been found that this slow sequestration of calcium ions can compromise the effective working of surfactant systems which require more rapid control of water hardness. In particular, the performance of the hereinabove described surfactant systems containing alkyl sulfate and nonionic surfactants have been found to be compromised when used in a detergent composition employing a builder system having a significant zeolite A content. Performance is particularly compromised under hard feed water conditions.

Surprisingly, the Applicant has now found that good detergency performance is obtained when zeolite MAP is used, particularly as a substitute for zeolite A, in combination with the surfactant system containing alkyl sulfate surfactants having a high proportion of alkyl chain lengths greater than C 14, in combination with nonionic surfactant.

According to the present invention there is provided a detergent composition containing (a) an alkyl sulfate surfactant system comprising a mixture of alkyl chain lengths wherein the weight distribution of the alkyl chain lengths is such that less than 20% by weight of the alkyl chains are of chain length less than C14; (b) a nonionic surfactant; and (c) a zeolite builder comprising zeolite P having a silicon to aluminium ratio of not greater than 1.33 (zeolite MAP) In a preferred aspect of the present invention the alkyl sulfate surfactant system is derived from natural sources and comprises a mixture of alkyl chain lengths wherein the weight distribution of the alkyl chain lengths is such that from 30% to 80% by weight ofthe alkyl chain lengths are C14, from 30% to 50% by weight of the alkyl chain lengths are C16 and less than 10% by weight of the alkyl chain lengths are C 18 In another preferred aspect of the present invention the composition contains an alkyl ethoxysulfate surfactant as an anionic cosurfactant.

In a further preferred aspect of the present invention the nonionic surfactant is a hydrohobic nonionic surfactant, preferably an alkoxylated nonionic surfactant, having a hydrophilic lipophilic balance (hlb) value of less than 9.5.

The composition is preferably free of alkyl benzene sulfonate.

Detalled descnption of the invention Alkyl sulfate surfactant The first essential component of the detergent compositions of the invention is an alkyl sulfate surfactant system comprising a mixture of alkyl chain lengths wherein the weight distribution of the alkyl chain lengths is such that less than 20% by weight of the alkyl chain lengths are of chain length less than C14.

The alkyl sulfate surfactant system is preferably present in the detergent compositions at a level of from 1% to 50%, preferably from 3% to 30%, most preferably from 5% to 20% by weight of the compositions.

Preferably the alkyl sulfate surfactant system is derived from natural sources, and in a particularly preferred execution comprises a mixture of alkyl chain lengths wherein the weight distribution of the alkyl chain lengths is such that from 35% to 70%, most preferably from 40% to 60% ofthe alkyl chains are C14, from 30% to 50%, preferably from 30% to 40%, most preferably from 32% to 38% of the alkyl chains are C 16, less than 10%, preferably less than 5%, most preferably less than 3% of the alkyl chains are Cl8.

By derived from natural sources it is meant herein that the alkyl chain portion of the surfactant is derived from naturally occurring fats and oil.

Natural oils and fats provide feedstock material encompassing a range of alkyl chain lengths. The alkyl chains are predominantly linear, in contrast to the branched nature of feedstock obtained from synthetic sources. For example, tallow fat contains a high proportion (typically about 70%) of C 18 alkyl chains. Coconut and palm oil on the other hand contain a high proportion of C 12 alkyl chains (typically about 55%) and lesser proportions of C 14, C 16 and C 18 alkyl chain lengths.

Alkyl chains derived from natural oils and fats typically have chains with even numbers of carbon atoms, most typically C12, C14, C16 and C1 8.

The alkyl chains may contain a small proportion of unsaturated, e.g.: alkenyl, chains which if desired may be hydrogenated, or "hardened" to minimize these impurity levels. Typically the alkyl sulfate surfactant is produced from alcohols obtained by reduction ofthe natural oils and fats.

Examples of natural oils and fats include those derived from coconut, babassu, palm kernel, beef tallow, kapok, olive, peanut, sesame and teaseed.

Alkyl sulfate surfactant of the desired alkyl chain length distribution is obtained from natural feedstock, meaning natural oils or fats, or any mixtures thereof, or the natural alcohols derived therefrom, by any suitable physical process which allows for the separation of such feedstock into different components with the desired alkyl chain length distributions.

Suitable physical processes would include, for example, distillation processes. The separation of feedstock material into different components of desired composition is often referred to in the industry as "cutting" of the feedstock (into desired "cuts"). The different components (or cuts) may then be used as such, or blended, as appropriate to allow for derivation of the alkyl sulfate surfactant with the desired alkyl chain length distribution.

Alkyl ethoxvsulfate surfactant In addition to the alkyl sulfate surfactant the detergent compositions preferably also contain an alkyl ethoxysulfate surfactant. The weight ratio of the alkyl sulfate surfactant to the alkyl ethoxysulfate surfactant is preferably from 2:1 to 19:1 more preferably from 3:1 to 12:1 and most preferably from 3.5:1 to 10:1.

The alkyl ethoxysulfate surfactant is preferably a water soluble C12-Cl8 alkyl ethoxysulfate surfactant containing an average of from 1 to 7 moles ethylene oxide per mole derived from the condensation product of a C12 C 18 alcohol wherein said C1 2-C 18 alcohol is most preferably derived from natural sources. Examples of naturally occurring materials from which the alcohols can be derived are coconut oil and palm kernel oil and the corresponding fatty acids.

Preferred are C 12-C14 alkyl ethoxysulfate salts with an average of from one to five ethoxy groups per mole, and most preferably with an average of from one to three ethoxy groups per mole.

Noni onic surfactant The second essential component of the detergent composition according to the present invention is a nonionic surfactant.

The nonionic surfactant is preferably present in the detergent compositions at a level of from 1% to 50%, preferably from 2% to 20%, most preferably from 3% to 10% by weight of the compositions.

The nonionic surfactant is preferably a hydrophobic nonionic surfactant, particularly an alkoxylated nonionic surfactant, having a hydrophilic lipophilic balance (hlb) value of < 9.5, more preferably < 10.5.

Examples of suitable hydrophobic alkoxylated nonionic surfactants include alkoxylated adducts of fatty alcohols containing an average of less than 5 alkylene oxide groups per molecule.

The alkylene oxide residues may, for example, be ethylene oxide residues or mixtures thereof with propylene oxide residues.

Preferred alkylene oxide adducts of fatty alcohols useful in the present invention can suitably be chosen from those of the general formula: R-O-(CnH2nO)yH wherein R is an alkyl or alkenyl group having at least 10 carbon atoms, most preferably from 10 to 22 carbon atoms, y is from 0.5 to 3.5andnis2Or3.

Preferred nonionic surfactants include primary C 11-C15 aliphatic alcohols condensed with an average of no more than five ethylene oxide groups per mole of alcohol, having an ethylene oxide content of less than 50% by weight, preferably from 25% to less than 50% by weight.

A particularly preferred aliphatic alcohol ethoxylated is a primary alcohol having an average of 12 to 15 carbon atoms in the alkyl chain condensed with an average of three ethoxy groups per mole of alcohol.

Specific examples of suitable alkoxylated adducts of fatty alcohols are Synperonic A3 (ex ICI), which is a C13-C15 alcohol with about three ethylene oxide groups per molecule and Empilan KB3 (ex Marchon), which is lauric alcohol 3EO.

Another class of nonionic sufactants comprises alkyl polyglucoside compounds of general formula RO(CnH2nO)tZx wherein Z is a moiety derived from glucose; R is a saturated hydrophobic alkyl group that contains from 12 to 18 carbon atoms; t is from 0 to 10 and n is 2 or 3; xis from 1.1 to 4, the compounds including less than 10% unreacted fatty alcohol and less than 50% short chain alkyl polyglucosides. Compounds of this type and their use in detergent compositions are disclosed in EP-B 0070074, 0070077, 0075996 and 0094118.

Zeolite MAP builder According to the present invention the detergency builder system is based on zeolite MAP, optionally in conjunction with one or more supplementary builders. The amount of zeolite MAP employed may range, for example, from 5 to 60 wt.%, more preferably from 15 to 40 wt.%.

Zeolite MAP is described in EP 384070A (Unilever). It is defined as an alkali metal alumino-silicate of the zeolite P type having a silicon to aluminium ratio not greater than 1.33, preferably within the range from 0.9 to 1.33 and more preferably within the range of from 0.9 to 1.2.

Of particular interest is zeolite MAP having a silicon to aluminium ratio not greater than 1.15 and, more particularly, not greater than 1.07.

Zeolite P having a Si:Al ratio of 1.33 or less may be prepared by the following steps: (i) mixing together a sodium aluminate having a mole ratio Na2O:A1203 within the range of from 1.4 to 2.0 and a sodium silicate having a mole ratio SiO2:Na2O within the range of from 0.8 to 3.4 with vigorous stirring at a temperature within the range of from 25"C to boiling point usually 950C, to give a gel having the following composition;A1203: (1.75-3.5) SiO2 : (2.3-7.5) Na2O :P (80-450)H20; (ii) ageing the gel composition for 0.5 to 10 hours, preferably 2 to 5 hours, at a temperature within the range of from 70"C to boiling point, usually to 950C, with sufficient stirring to maintain any solids present in suspension; (iii) separating the crystalline sodium aluminosilicate thus formed, washing to a pH within the range of from 10 to 12.5, and drying, preferably at a temperature not exceeding 1 50"C, to a moisture content of not less than 5 wt.%.

Preferred drying methods are spray-drying and flash drying. It appears that oven drying at too high a temperature may adversely affect the calcium binding capacity ofthe product under certain circumstances.

Commercial sodium metasilicate pentahydrate dissolved in water and commercial sodium silicate solution (waterglass) are both suitable silica sources for the production of zeolite P in accordance with the invention. The reactants may be added together in any order either rapidly or slowly. Rapid addition at ambient temperature, and slow addition at elevated temperature (90-950C) both give the desired product.

Vigorous stirring of the gel during the addition of the reactants, and at least moderate stirring during the subsequent ageing step, however, appear to be essential for the formation of pure zeolite P. In the absence of stirring, various mixtures of crystalline and amorphous materials may be obtained.

Zeolite MAP generally has a calcium binding capacity of at least 150 mg CaO per g of anhydrous aluminosilcate, as measured by the standard method described in GB 1473201 (Henkel). The calcium binding capacity is normally 160 mg CaO/g and may be as high 170 mg CaO/g.

Although zeolite MAP like other zeolites contains water of hydration, for the purposes of the present invention amounts and percentages of zeolite are expressed in terms of the notional anhydrous material.

The amount of water present in hydrated zeolite MAP at ambient temperature and humidity is generally about 20 wt.%.

According to one embodiment of the invention the zeolite MAP detergent builder is in powder form.

Addltlonal detergent components In addition to the essential alkyl sulfate and nonionic surfactant components, the detergent composition according to the invention can include one or more other surfactants selected from anionics, zwitterionics, ampholytics and cationics.

Many suitable detergent-active compounds are available and fully described in the literature (for example "Surface Active Agents and Detergents" Volumes I and II by Schwartz, Perry and Berch).

Examples of suitable additional anionic surfactants include olefin sulphonates, alkyl xylene sulphonates, dialkylsulphosuccinates, and fatty acid ester sulphonates. Sodium salts are generally preferred.

In addition to zeolite MAP, the builder system may contain an organic or inorganic cobuilder.

Suitable organic cobuilders can be monomeric or polymeric carboxylates such as citrates or polymers of acrylic, methacrylic and/or maleic acids in neutralised form. Suitable inorganic cobuilders include carbonates and amorphous and crystalline lamellar sodium silicates.

Suitable lamellar silicates have the composition: NaMSix02x+l. vH20 where M is sodium or hydrogen, preferably sodium; x is a number from 1.9 to 4; and y is a number from 0 to 20. Such materials are described in US Patents No. 4664839; No. 4728443 and No. 4820439 (Hoechst AG). Especially preferred are compounds in which x = 2 and y = O. The synthetic material is commercially available from Hoechst AG as 6 -Na2 Si205 (SKS6) and is described in US Patent No. 4664830.

The total amount of detergency builder in the granular composition typically ranges from 10 to 80 wt.%, more preferably from 15 to 60 wt% and most preferably from 10 to 45 wt.%.

Detergent compositions according to the invention may also suitably contain a bleach system. This preferably comprises one or more peroxy bleach compounds, for example, inorganic persalts or organic peroxyacids, which may be employed in conjunction with bleach precursors to improve bleaching action at low temperatures.

The bleach system preferably comprises a peroxy bleach compound, preferably an inorganic persalt, optionally in conjunction with a precursor. Suitable persalts include sodium perborate monohydrate and tetrahydrate and sodium percarbonate, with sodium percarbonate being most preferred.

Preferred bleach precursors are peracetic acid precursors, such as tetraacetylethylene diamine (TAED); peroxybenzoic acid precursors.

Other materials which may be present in the detergent compositions of the invention include, for example, fluorescers, antiredeposition agents, inorganic salts such as sodium sulphate, other enzymes, lather control agents, fabric softening agents, pigments, coloured speckles and perfumes.

The detergent composition according to the invention may be of any physical type, for example powders, liquids and gels. However, granular and liquid compositions are preferred.

The detergent compositions of the invention may be prepared by any suitable method. The particulate detergent compositions are suitably prepared by any tower (spray-drying) or non-tower process.

In processes based around a spray-drying tower, a base powder is first prepared by spray-drying a slurry and then other components unsuitable for processing via the slurry can be sprayed on or admixed (postdosed). The lipase enzyme will generally be post-dosed.

The zeolite MAP is suitable for inclusion in the slurry, although it may be advantageous for processing reasons for part of the zeolite MAP to be incorporated post-tower. The lamellar silicate, where this is employed, is also incorporated via a non-tower process and is preferably postdosed.

Alternatively, particulate detergent compositions in accordance with the invention may be prepared by wholly non-tower processes such as granulation.

The granular detergent compositions of the invention may be prepared to any suitable bulk density. The compositions preferably have a bulk density of at least 400 gIl preferably at least 550 g/l, most preferably at least 700 g and, with particular preference at least 800 1.

The benefits of the present invention are particularly evident in powders of high bulk density, for example, of 700 g/l or above. Such powders may be prepared either by post-tower densification of spraydried powder, or by wholly non-tower methods such as dry mixing and granulation; in both cases a high-speed mixer/granulator may advantageously be used. Processes using high-speed mixer/granulators are disclosed, for example, in EP340 013A, EP 367 339A, EP 390 251A and EP 420 317A (Unilever).

The detergent composition of the invention may be formulated as a liquid detergent composition which may be aqueous or anhydrous.

The term "liquid" used herein includes pasty viscous formulations such as gels. The liquid detergent composition generally has a pH of from 6.5 to 10.5.

The total amount of detergency builder in the liquid composition is preferably from 5 to 70% of the total liquid composition.

Illustrative compositions according to the present invention are presented in the following Examples.

In the detergent compositions, the abbreviated component identifications have the following meanings: 246AS : Sodium alkyl sulfate surfactant containing a alkyl chain length weight distribution of 15% C12 alkyl chains, 45% C14 alkyl chains, 35% C16 alkyl chains, 5% C18 alkyl chains TAS Sodium alkyl sulfate surfactant containing predominantly C 16 - C 18 alkyl chains derived from tallow oil.

24AE3S . C12-C14 alkyl ethoxysulfate containing an average of three ethoxy groups per mole 35E3 A C13-15 primary alcohol condensed with an average of 3 moles of ethylene oxide 25E3 : A C12-C15 primary alcohol condensed with an average of 3 moles of ethylene oxide Carbonate Anhydrous sodium carbonate Perborate Sodium perborate tetrahydrate Percarbonate Sodium percarbonate TAED Tetra acetyl ethylene diamine Silicate Amorphous Sodium Silicate (SiO2:Na2O ratio normally follows) Zeolite MAP Hydrated sodium aluminosilicate zeolite MAP having a silicon to aluminium ratio of 1.07 MA/AA Copolymer of 1:4 maleic/acrylic acid, average molecular weight about 80,000.

Enzyme Proteolytic enzyme sold by Novo Industries AS of activity 4.0 KNPU.

Example The following granular laundry detergent compositions were prepared (parts by weight) in accordance with the invention.

A B C D E 246AS 7.6 6.5 4.8 6.8 TAS - - - - 8.6 24AE3S 2.4 - 1.2 1.7 25E3 3.26 - - - 6.3 35E3 - 5.0 5.0 5.0 Zeolite MAP 20.0 25.0 20.0 25.0 31.0 Carbonate 15.0 15.0 20.0 10.0 12.0 MA/AA 4.25 4.25 4.25 4.25 2.0 Perborate - 16.0 - 16.0 20.0 Percarbonate 20.0 - 20.0 - TAED 5.0 5.0 5.0 5.0 6.7 Enzyme 1.4 1.4 1.4 1.4 1.4 Silicate (2.0 4.0 - - 4.0 3.0 ratio) Water and miscellaneous (Including suds suppressor, sodium sulphate, perfume) to balance

Claims (9)

1. CLAIMS 1. A detergent composition containing (a) an alkyl sulfate surfactant system comprising a mixture of alkyl chain lengths wherein the weight distribution of the alkyl chain lengths is such that less than 20% by weight of the alkyl chains are of chain length less than C14; (b) a nonionic surfactant; and (c) a zeolite builder comprising zeolite P having a silicon to aluminium ratio of not greater than 1.33 (zeolite MAP).
2. 2. A detergent composition according to Claim 1 wherein said alkyl sulfate surfactant system is derived from natural sources and comprises a mixture of alkyl chain lengths wherein the weight distribution of the alkyl chain lengths is such that from 30% to 80% by weight of the alkyl chain lengths are C14, from 30% to 50% by weight of the alkyl chain lengths are C 16 and less than 10% by weight of the alkyl chain lengths are C 18.
3. 3. A detergent composition according to either of Claims 1 or 2 wherein said alkyl sulfate surfactant is present at a level of from 5% to 20% by weight of the composition
4. 4. A detergent composition according to any of Claims 1 to 3 containing an alkyl ethoxysulfate surfactant as an anionic cosurfactant.
5. 5. A detergent composition according to Claim 4 wherein said alkyl ethoxysulfate is present at a level such that the weight ratio of the alkyl sulfate surfactant to the alkyl ethoxysulfate surfactant is from 3:1 to 12:1.
6. 6. A detergent composition according to any of Claims 1 to 5 wherein said nonionic surfactant has a hydrophiltc lipophilic balance (hlb) value of less than 9.5.
7. 7. A detergent composition according to Claim 6 wherein the nonionic surfactant is an alkoxylated nonionic suifactant.
8. 8. A detergent composition according to Claim 7 wherein said alkoxylated nonionic surfactant is selected from the alkylene oxide adducts of fatty alcohols having the general formula: R-O-(CnH2nO)yH wherein R is an alkyl or alkenyl group having at least 10 carbon atoms, preferably from 10 to 22 carbon atoms, y is from 0.5 to 3.5 and n is 2 or 3.
9. 9. A detergent composition according to any of Claims 1 to 8 wherein said zeolite builder is present at a level of from 5% to 60% by weight of the composition.