DE69405735T2 - DETERGENT COMPOSITIONS - Google Patents

Description

TECHNICAL AREA

The present invention relates to particulate detergent compositions of high bulk density containing anionic and nonionic surfactants and zeolite builders.

HISTORY AND STATE OF THE ART

EP 544 492A (Unilever) describes detergent powders of high bulk density containing an organic surfactant system (ethoxylated nonionic surfactant plus primary alcohol sulfate), zeolite builder and other optional ingredients. The ethoxylated nonionic surfactant, which is the predominant component (at least 60% by weight) of the surfactant system, has a degree of ethoxylation not exceeding 6.5, and preferably from 3 to 6.5, and most preferably from 4 to 5.5. This high potency surfactant provides excellent detergency and the use of relatively high levels of zeolite allows the formulation of free-flowing powders containing high levels of these highly mobile surfactants.

These compositions are typical of the recent trend of high bulk density powders, produced by processes that eliminate or do not introduce the porosity typical of conventional spray-dried powders. These include post-column densification of spray dried powders, and more preferably entirely non-column routes comprising dry blending, agglomeration, granulation and similar processes.

However, some problems have been encountered with formulations of this type in delivering the active ingredients of the powder to the laundry in an automatic washing machine. Delivery is a two-stage process: the first stage is the induction of the powder into the wash liquid, either from the washing machine's induction compartment or from an induction device (a washing ball or similar) supplied by the powder manufacturer; and the second stage is the dissolution of the powder as it enters the wash water.

It has surprisingly been found that in powders of the above mentioned type of high bulk density, delivery is significantly improved by the use of a non-ionic surfactant with a higher degree of ethoxylation, provided that a citric acid salt is also present.

Citrates are well known as detergency builders used to supplement zeolites. Their use in zeolite-built powders is disclosed, for example, in EP 313 143A, EP 313 144A, EP 448 297A and EP 448 298A (Unilever); GB-A-1 408 678, EP 1310A, EP 18538, EP 326 208A, EP 456 315A and WO 91 15566A (Procter &Gamble); DE 2 336 182C (Lion); and GB 2 095 2748 (Colgate).

EP-A-0 508 034 discloses a granular detergent composition characterized by containing polyvinylpyrrolidone to provide good dye transfer inhibition effects without impairing particulate soil removal. It is mentioned that citric acid can be used as a carboxylate chelating agent.

EP-A-0 508 358 relates to a laundry detergent composition, characterized in that it contains an alkaline cellulase and polyvinylpyrrolidone. Citrates can be used as builders.

However, the use of citrate in the presence of specific non-ionic surfactant to improve the dissolution of a detergent powder with high bulk density is not described in the literature.

DEFINITION OF THE INVENTION

Accordingly, the present invention provides a particulate detergent composition which is not the direct product of a spray drying process, the composition having a bulk density of at least 650 g/l and containing:

(a) From 15 to 50 percent by weight of a surfactant system, consisting essentially of

(i) ethoxylated nonionic surfactant which is a primary C8-18 alcohol having an average degree of ethoxylation within the range of 5.2 to 8.0,

(ii) optionally primary alcohol sulphate,

(iii) optionally not more than 25% by weight (based on the surfactant system) alkylbenzenesulfonate,

(b) from 20 to 70 weight percent (anhydrous basis) alkali metal aluminosilicate builder,

(c) from 5 to 40% by weight of a water-soluble salt of citric acid,

(d) if necessary, other detergent ingredients up to 100 percent by weight.

The invention further provides the use of a nonionic surfactant which is an ethoxylated C₈₋₁₈ primary alcohol having an average degree of ethoxylation within the range of 5.2 to 8.0 for improving the feeding and dissolution properties of a particulate detergent composition having a bulk density of at least 650 g/l, which is not the direct process of a spray drying process and which comprises:

(a) From 15 to 50 percent by weight of a surfactant system, consisting essentially of

(i) ethoxylated nonionic surfactant,

(ii) optionally primary alcohol sulphate,

(iii) optionally not more than 25% by weight (based on the surfactant system) alkylbenzenesulfonate,

(b) from 20 to 70 weight percent (anhydrous basis) alkali metal aluminosilicate builder,

(c) from 5 to 40% by weight of a water-soluble salt of citric acid,

(d) if necessary, other detergent ingredients up to 100 percent by weight.

DETAILED DESCRIPTION OF THE INVENTION

The high bulk density particulate detergent compositions of the invention contain as essential ingredients:

(a) A limited surfactant system,

(b) an aluminosilicate builder,

(c) a citric acid salt.

Other optional components may be present if necessary or desired.

The compositions are preferably prepared by mixing and granulation processes which do not include spray drying. However, the invention also encompasses compositions which have been prepared by spray drying and subsequently subjected to granulation, compaction or a similar treatment which removes or reduces the porosity typical of a spray dried powder.

The compositions of the invention are characteristically of low particle porosity. Preferably the particles have a pore volume not exceeding 10% by weight, more preferably not exceeding 5% by weight, and desirably as low as possible. The pore volume can be measured by mercury porosity measurement.

The surfactant system

The compositions of the invention contain from 15 to 50 percent by weight, preferably from 15 to 30 percent by weight, of a defined surfactant system.

The essential component of the surfactant system is an ethoxylated alcohol nonionic surfactant having an average alkyl chain length of C8-18 and an average degree of ethoxylation within the range of 5.2 to 8.0.

The nonionic surfactant preferably has an alkyl chain length of C12-16, more preferably C12-14.

Preferably, the nonionic surfactant, whether of vegetable or petrochemical origin, is predominantly or entirely linear. Particularly preferred are nonionic surfactants derived from coconut oil. However, synthetic materials containing any branched material are also within the scope of the invention.

The average degree of ethoxylation is preferably within the range of 6 to 7.5, more preferably 6.5 to 7.5, and most preferably about 7.

The desired degree of ethoxylation can be achieved, for example, by using a single commercial material with a nominal degree of ethoxylation of 7; for example, coconut alcohol 7 EO (e.g. Kolb's Inbentin* or DAC's Lorodac*), average degree of ethoxylation 6.9; or Synperonic* A7 from ICI, degree of ethoxylation 6.9 (* indicates trademark).

Similarly, commercial materials with a nominal degree of ethoxylation of 6.5 are available and suitable for use in the present invention.

Advantageously, lower degrees of ethoxylation can be achieved within the scope of the present invention, as described in the above-mentioned EP 544 492A (Unilever), by mixing a commercial 7 EO (nominal) material with a commercial 3 EO (nominal) material in suitable proportions, provided that at least 55 Weight percent of the mixture is formed by the 7 EO (nominal) material.

Therefore, the nonionic surfactant used in the compositions of the invention may comprise commercial nonionic surfactant having a nominal average degree of ethoxylation of 7 (55 to 100 weight percent, preferably 60 to 100 weight percent), optionally in combination with commercial nonionic surfactant having a nominal average degree of ethoxylation of 3 (0 to 45 weight percent, preferably 0 to 40 weight percent).

The calculated average ethoxylation levels of some 3 EO/7 EO non-ionic blends are shown in Table I, together with the measured values for some commercial materials.

Of course, desired total average degrees of ethoxylation between 5.2 and 7 can also be obtained by using a single commercial material, or alternatively by using a mixture of three or more commercial materials. Table I

The ethoxylated nonionic surfactant may be the only surfactant in the compositions of the invention.

According to a preferred embodiment of the invention, the primary alcohol sulfate (PAS) may also optionally be present. In this embodiment, the ethoxylated nonionic surfactant preferably makes up from 30 to 90 percent by weight of the surfactant system, more preferably from 40 to 70 percent by weight; and the PAS preferably comprises from 10 to 70 percent by weight, more preferably from 30 to 60 percent by weight of the surfactant system. Preferably, the total composition contains at least 5 percent by weight PAS.

The PAS suitably has a chain length in the C8-C18 range, preferably C12-C16. If desired, mixtures of chain lengths can be used as described and claimed in EP 342 917A (Unilever).

Fully or predominantly linear PAS is preferred. PAS of vegetable origin, in particular PAS from coconut oil (cocoPAS), is particularly preferred. However, it is also within the scope of the invention to use branched PAS as described and claimed in EP 439 316A (Unilever).

The PAS is preferably present in sodium salt form.

In principle, minor amounts of other anionic surfactants may be present, provided that the surfactant system does not contain more than 25% by weight of alkylbenzenesulfonates. These materials appear to have a deleterious effect on delivery and dissolution. Preferably, the compositions of the invention contain no more than 5% by weight (based on the total composition) of alkylbenzenesulfonates, and more preferably they do not contain any alkylbenzenesulfonate.

The aluminosilicate builder

The detergent compositions of the invention contain an alkali metal, preferably sodium, aluminosilicate builder. Sodium aluminosilicates may usually be incorporated in amounts in the range of from 20 to 70% by weight (anhydrous basis), preferably from 25 to 50% by weight.

The alkali metal aluminosilicate can be either crystalline or amorphous, or mixtures thereof, and have the following general formula:

0.8-1.5 Na2O. Al2 O3 . 8.8-6 SiO2

These materials contain some bound water and are required to have a calcium ion exchange capacity of at least 50 mg CaO/g. The preferred sodium aluminosilicates contain 1.5 to 3.5 SiO2 units (in the formula above). Both the amorphous and crystalline materials can be readily prepared by reaction between sodium silicate and sodium aluminate, as described in detail in the literature.

Suitable crystalline sodium aluminosilicate ion exchange detergent builders are described, for example, in GB-A-1 429 143 (Procter & Gamble). The preferred sodium aluminosilicates of this type are the well-known commercially available zeolites A and X, and mixtures thereof.

The zeolite may be the commercially available zeolite 4A, now widely used in laundry detergent powders. However, according to a preferred embodiment of the invention, the zeolite builder incorporated in the compositions of the invention is at most aluminium zeolite P (zeolite MAP) as described and claimed in EP 384 070A (Unilever). The zeolite MAP is defined as an alkali metal aluminosilicate of the zeolite P type, having a silicon to aluminium ratio not exceeding 1.33, preferably within the range of 0.90 to 1.33, and most preferably within the range of 0.90 to 1.20.

Particularly preferred is zeolite MAP having a silicon to aluminum ratio not exceeding 1.07, more preferably about 1.00. The calcium binding capacity of zeolite MAP is usually at least 150 mg CaO per g anhydrous material.

The citric acid salt

The compositions of the invention also contain as an essential ingredient a water-soluble salt of citric acid, preferably sodium citrate.

The citrate salt is present in an amount ranging from 5 to 40 percent by weight, preferably from 10 to 35 percent by weight, more preferably from 15 to 30 percent by weight. Particularly good results have been obtained with compositions containing from 20 to 25 percent by weight.

Where the citrate salt is sodium citrate, the percentages refer to the dihydrate.

Other Builders

Other builders may also be included in the detergent compositions of the invention if necessary or desired. For example, polycarboxylate polymers, more suitably polyacrylates and acrylic/maleic copolymers, may be used suitably in amounts ranging from 0.5 to 15% by weight, especially from 1 to 10% by weight.

Other ingredients

The compositions according to the invention may contain sodium carbonate to increase detergency and to facilitate processing. Sodium carbonate may generally be present in amounts ranging from 1 to 60% by weight, preferably from 2 to 40% by weight and most suitably from 2 to 13% by weight. However, compositions free of alkali metal carbonate are also within the scope of the invention.

The compositions advantageously also contain fatty acid soap, as a powder structurant, suitably in an amount in the range 1 to 5% by weight.

Other ingredients that may be included in the base powder include fluorescers; sodium silicate; and anti-graying agents such as cellulose derivative polymers, for example sodium carboxymethylcellulose.

Optional ingredients which may generally be added (dosed) to form a final product include bleaching components such as sodium perborate or percarbonate, bleach activators and bleach stabilizers; sodium carbonate; proteolytic and lipolytic enzymes; dyes, foam controlling granules; colored measles; perfumes; and fabric softening compounds. This list is not intended to be exhaustive.

Preparation of detergent compositions

As previously indicated, the compositions of the invention are of high bulk density and are preferably prepared by non-column (non-spray drying) processes in which solid and liquid ingredients are mixed and granulated together. Such powders have relatively non-porous particles and can particularly give rise to feeding, dispersion and dissolution problems in use.

According to a preferred method, mixing and granulation are carried out in a high speed mixer/granulator, both of which have an agitating and a cutting action. The high speed mixer/granulator, also known as a high speed mixer/densifier, may be a batch machine, such as the Fukae (trade mark) FS, or a continuous machine, such as the Lodige (trade mark) Recycler CB30.

Suitable processes are described, for example, in EP 544 492A, EP 420 317A and EP 506 184A (Unilever).

Generally, the inorganic builders and other inorganic materials (e.g. zeolite, sodium carbonate) are granulated with the surfactants which act as binders and granulating or agglomerating agents. Any optional ingredients as previously mentioned may be incorporated at any suitable stage of the process. Fatty acid soap may be prepared by neutralization in situ with sodium hydroxide solution during the mixing and granulation process.

In these processes, any PAS present may already be neutralized, i.e. in salt form, when it enters the high speed mixer/granulator, or it may optionally be added in acidic form and neutralized in situ. If desired, PAS and nonionic surfactant may be introduced in the form of a homogeneous liquid mixture as described in EP 265 203A and EP 507 402A (Unilever). EP 420 317A and EP 506 184A (Unilever) describe a different process wherein PAS acid, which is a liquid, is mixed and reacted with a solid inorganic alkali material such as sodium carbonate in a continuous high speed mixer. The resulting granule or "ingredient" is then dosed into another high speed mixer with the nonionic surfactants and the solid ingredients. All of these processes are suitable for the preparation of compositions of the invention.

According to normal detergent powder manufacturing practice, bleaching ingredients (bleaching agents, bleach precursors, bleach stabilizers), proteolytic and lipolytic enzymes, colored grains, perfumes and foam control granules are admixed (postdosed) in a particularly suitable manner to the dense homogeneous granular product - the base powder - after it has left the high-speed mixer/granulator.

The citrate salt may suitably be among the postdosed ingredients.

Powder properties

The particulate detergent compositions of the invention have bulk densities of at least 650 g/l, preferably of at least 770 g/l, and most preferably of at least 800 g/l.

As previously stated, powder porosity is typically low: preferably the pore volume does not exceed 10% by weight, and more preferably it does not exceed 5% by weight. Such low values are not exhibited by powders which are the direct products of spray drying processes.

Advantageously, the content of "fine particles", that is to say particles smaller than 180 micrometers, does not exceed 10% by weight, and more preferably not exceed 5% by weight.

Examples

The invention is further illustrated by the following non-limiting examples in which parts and percentages are by weight unless otherwise indicated.

Test methods used in the examples

The laundry delivery, dispersion and dissolution properties were determined using three different tests.

Test 1: Case test

The feeding characteristics of the powders were compared using a model system that simulates the feeding of a powder into an automatic washing machine under more adverse conditions (low temperature, minimal agitation) than those normally encountered in a natural washing process.

For this test, a cylindrical container with a diameter of 4 cm and a height of 7 cm was used, made of stainless steel wire mesh with a pore size of 600 microns, with a top cap made of Teflon and a bottom cap made of the mesh just described. The top cap contained a 30 cm long metal rod inserted into it, which served as a holder, and this holder was attached to an agitator arm set over 1 liter of water at 20ºC in an open container. By means of this agitator, the cylindrical container, held at 45º, could be rotated through a circle with a radius of 10 cm for a period of 2 seconds. and then the container was allowed to rest for 2 seconds before the next rotation-rest cycle began.

A 50 g powder sample was introduced into the cylindrical container, which was then sealed. The container was attached to the stirring arm, which was then moved to a position where the head of the cylindrical container was just below the water surface. After a 10 second break, the apparatus was operated for 15 rotation-rest cycles.

The cylindrical container and holder were removed from the water and the container was detached from the holder. Surface water was carefully drained off and any powder residue was transferred to a pre-weighed container and dried at 100ºC for 24 hours. The weight of the dried residue as a percentage of the initial powder weight (50 g) was then calculated.

Test 2: Feeder test

Feeding characteristics of the powders were also compared using a model system simulating the feeding of a powder into an automatic washing machine from a flexible feeder of the type supplied with Lever's Persil (Trade Mark) Micro System powder in the UK: A spherical container made of flexible plastic material with a diameter of approximately 4 cm and a head opening with a diameter of approximately 3 cm.

In this test, the feeder was mounted in an upright position (opening at the top) on a stirring arm positioned above the water. This apparatus allowed the device to be moved vertically up and down over a distance of 30 cm, with the lowest 5 cm of this movement being underwater. Each up or down movement lasted 2 seconds, allowing the device to remain 5 cm underwater for 4 seconds at the lowest position, and in the highest position to be rotated through 1000 and to rest in the resulting inclined position for 2 seconds before moving downwards. 5 liters of water at a temperature of 20ºC were used.

A pre-weighed powder sample was introduced into the device at its highest position and the apparatus was then allowed to operate for six cycles, stopping when the device was again at its highest position. Surface water was carefully drained off and any residual powder transferred to a pre-weighed container. The container was then dried at 100ºC for 24 hours and the weight of the dried residue calculated as a percentage of the initial powder weight.

Test 3: Black pillowcase test

A washing machine test was also used to determine the extent to which insoluble residues are deposited on washed items. The machine used was a Siemens Siwamat (trade mark) Plus 3700 automatic front-loading washing machine.

A 100 g powder dose was placed in a flexible feeder as described above. The feeder was placed inside a black cotton pillowcase measuring 30 cm by 60 cm, ensuring it was kept upright, and the pillowcase was then zipped closed. The pillowcase containing the feeder (upright) was then placed at the head of a 3.5 kg dry cotton laundry load in the drum of the washing machine.

The machine was operated in the "high performance cycle" at a washing temperature of 40ºC using water with 150 French hardness and an inlet temperature of 20ºC. At the end of the washing cycle, the pillowcase was removed, opened and turned inside out and the level of powder residue on its inner surfaces was estimated by visual using a rating system of 1 to 5: a score of 5 corresponds to a residue of approximately 75% of the powder by weight, while 1 indicates a residue. A panel of five panelists was used to evaluate each pillowcase and assign a rating. The washing procedure was repeated ten times with each powder and the ratings were averaged over the ten replicates.

EXAMPLE 1, COMPARATIVE EXAMPLES A TO C

Four high bulk density detergent powders were prepared to the formulations shown in Table II. Base powders were prepared using a high speed continuous mixer/granulator and other ingredients were postdosed as shown. The sodium citrate, where present, was postdosed as particulate sodium citrate dihydrate having an average particle size of about 800 µm.

All powders contained PAS, non-ionic surfactant and zeolite builder. Comparative Example A and Example 1 contained sodium citrate; Comparative Example A contained 7 EO and 3 EO non-ionic surfactants, while Example was a similar formulation containing only 7 EO non-ionic surfactant at the same total level. Comparative Examples B and C were two similar compositions that did not contain sodium citrate.

Table III shows the powder properties and the delivery properties of the powders. Comparison of Examples A and 1 shows that changing the nonionic surfactant to a Ganz-7 EO system in a citrate-containing formulation substantially improves the delivery properties. Comparison of Examples B and C showed that no such improvement was observed when citrate was absent. Table II Formulations Table III Properties

Example 2

A composition was prepared with a formulation corresponding to that of Example 1, but containing the following surfactant system:

CocoPAS6.37

Non-ionic 7 EO 8.65 (60 %)

Non-ionic 3 EO 5.77 (40 %)

The composition resulted in zero residues when dosed via the dispenser of three different automatic washing machines (Phillips, Zanussi, Siemens).

Examples 3 to 6

Four additional machine wash formulations according to the present invention are given below.

Claims (10)

1. A special detergent composition which is not the direct product of a spray drying process, the composition having a bulk density of at least 650 g/l and containing: (a) From 15 to 50 percent by weight of a surfactant system, consisting essentially of (i) ethoxylated nonionic surfactant which is a C8-C18 primary alcohol having an average degree of ethoxylation within the range of 5.2 to 8.0, (ii) optionally primary alcohol sulfate, (iii) optionally not more than 25% by weight (based on the surfactant system) alkylbenzenesulfonate, (b) from 20 to 70 weight percent (aqueous basis) alkali metal aluminosilicate builder, (c) from 5 to 40% by weight of a water-soluble salt of citric acid, (d) optionally other detergent ingredients up to 100 percent by weight. 2. A detergent composition according to claim 1, wherein the ethoxylated nonionic surfactant comprises commercial nonionic surfactant having a nominal average degree of ethoxylation of 7 (55 to 100 weight percent), optionally in combination with commercial nonionic surfactant having a nominal average degree of ethoxylation of 3 (0 to 45 weight percent). 3. A detergent composition according to claim 1, wherein the nonionic surfactant has an average degree of ethoxylation within the range of 6 to 7.5. 4. A detergent composition according to claim 1, wherein the surfactant system consists essentially of from 30 to 60 weight percent primary alcohol sulfate and from 40 to 70 weight percent ethoxylated nonionic surfactant. 5. A detergent composition according to claim 1, which contains at least 10% by weight (total, based on the whole composition) of ethoxylated nonionic surfactant. 6. A detergent composition according to claim 1, which contains at least 5% by weight (based on the whole composition) of primary alcohol sulfate. 7. A detergent composition according to claim 1, which contains from 10 to 35 weight percent of the citric acid salt. 8. A detergent composition according to claim 1, wherein the citric acid salt is sodium citrate. 9. A detergent composition according to claim 1, wherein the alkali metal aluminosilicate is zeolite P having a silicon to aluminum ratio not exceeding 1.33 (zeolite MAP). 10. The use of nonionic surfactant which is an ethoxylated C₈-C₁₈ alcohol having an average degree of ethoxylation within the range of 5.2 to 8.0 for improving the delivery and dissolution properties of a particulate detergent composition having a bulk density of at least 650g/l which is not the direct product of a spray drying process and which contains: (a) From 15 to 50 percent by weight of a surfactant system, consisting essentially of (i) ethoxylated nonionic surfactant, (ii) optionally primary alcohol sulfate, (iii) optionally not more than 25% by weight (based on the surfactant system) alkylbenzenesulfonate, (b) from 20 to 70 weight percent (anhydrous basis) alkali metal aluminosilicate builder, (c) from 5 to 40% by weight of a water-soluble salt of citric acid, (d) optionally other detergent ingredients up to 100 percent by weight.