AU3651495A - High active granular detergent compositions and process for making them - Google Patents

Description

HIGH ACTIVE GRANULAR DETERGENT COMPOSITIONS AND PROCESS FOR MAKING THEM

This is a continuation-in-part of copending application

S/N 08/083,115, filed June 25, 1993, which is a continuation-in-part of application S/N 07/980,856, filed November 24, 1992, and now abandoned, which is a continuation-in-part of copending application S/N 07/816,408, filed December 31, 1991 and now abandoned.

TECHNICAL FIELD

The present invention relates to a process for making a high active granular detergent composition and in particular a high bulk density granular detergent composition, that is, one having a bulk density higher than 600 grams per liter and at least 40% by weight of surfactants. Preferably the granular detergent composition has good powder properties. More particularly the invention relates to a process for the preparation of a granular detergent composition, especially one with a high proportion of surfactant.

BACKGROUND AND PRIOR ART

Granular detergent compositions with high surfactant levels of about 40% by weight or higher have several advantages over compositions with lower concentrations, particularly in working environments using lower amounts of water. In addition, high bulk density granular detergent compositions have several advantages over low bulk density compositions. The packing volume of the granules is lower, meaning that packaging can be smaller which facilitates storage and transport of products. Factors which govern the bulk density of detergent granules are the bulk density of the starting materials, for those granules produced by dry-mixing, and the chemical composition of the slurry for those granules produced by spray drying. Given the constraints that formulating effective compositions place on using either of these factors to vary bulk density, substantial increases in bulk density can mostly only be achieved by mechanical processing.

In view of increased environmental concern, it is desirable to reduce water consumption thereby saving water as well as the energy employed to heat it. Accordingly, high active powders suitable for use with low water washes are highly beneficial.

In the main, commercial high bulk density granules are produced by mechanical densification of a spray dried powder. This route to high bulk density detergent granules is an energy and capital intensive one. The equipment used to produce spray dry is expensive and the process itself removes 30-40% by weight of water from the slurry which is energy intensive. Since spray drying is a hot process it also places restrictions on what can be included in the formulation, in particular nonionic surfactants which can give rise to unwanted emissions, and sensitive or volatile components such as enzymes and perfumes which could be degraded or lost. After spray drying, additional equipment and energy are needed for further mechanical processing to density the powder.

EP-A-337,330 (Henkel) relates to a continuous process for obtaining high bulk density detergent powder containing a considerable amount of anionic and nonionic surfactant material, said process comprising treating spray-dried detergent material in a high-speed mixer under addition of nonionic material, whereby the mean residence time in the mixer is from 10-60 seconds.

In US Patent No. 4,923,636 and US Patent 4,826,632 to Blackburn et al and US 5,324,455 to Dumas et al., there are disclosed liquid surfactant compositions that can be sprayed onto spray-dried powders to increase the bulk density. While these "densified" spray dried powders have not been produced by mechanical densification, the disadvantages of using a spray dried powder as a starting point remain. In addition only a limited level of liquid surfactant can be sprayed-on if powder properties are not to suffer and the spray-on process relies on an absorbent powder base.

There are many prior art non spray drying processes which produce detergent granules. These have drawbacks as well. Most, in a first stage, form a dough which is de-agglomerated in a second stage to form granules. Usually the granules are then coated and dried in further stages. An example of such a process is disclosed in US Patent No. 5,045,238, Jolicoeur. Such multi-stage processes require more than one mixer and a separate granulation operation. Other processes require use of the acid form of the surfactant to work. Some others require high temperatures which degrade the starting materials.

In US Patent No. 4,925,585 Strauss et al., issued May 15, 1990, it is disclosed that certain high bulk density detergent compositions can be made by a process of fine dispersion mixing a surfactant paste and a detergency builder to form a tacky, dough like intermediate. To form granules from this dough it is necessary to cool it for example with dry ice to temperatures as low as -25°C following which further mixing forms large granules. To reach the desired moisture content the granules are dried in a separate drying step in, for instance, a fluid bed dryer. This process, involving at least three steps, is lengthy and costly due to the cooling and drying requirements.

In US Patent No. 4,666,740 to Wixon issued May 19, 1987, it is disclosed that certain high bulk density detergent particles can be made by a process of spraying a liquid or pasty nonionic detergent onto pre-formed carbonate-bicarbonate beads. The beads are then coated with zeolite to form free-flowing particles.

European Patent Application No. 420 317 Appel discloses a three-step process for preparing a high bulk density granular detergent composition by in situ neutralization of a liquid acid precursor of an anionic surfactant. Typically, in this type of process, excess carbonate is required to assure reasonable conversion of the acid. Excess carbonate gives rise to undesirably high pH in the product. Use of the acid precursor also requires careful handling, storage and coordination with granulation.

Beerse et al., US 5,108,646 discloses a granulation process for making a granular detergent builder, rather than a complete detergent composition. Critically, applicants' invention requires at least about 40% by weight of active surfactant and in addition describes a granulation route to make a complete detergent. Applicants particles contain detergent solids such as builders and fillers, and mixed surfactant actives with a very low water content as the binder for the granulation process. Beerse et al. discloses a granulation process using an aqueous mixed active paste, but the granules must be combined with at least 1.3 times their weight of spray-dried base granules to produce a complete detergent product. Beerse's solid builder portion must be chosen from zeolites or silicates, and the size of the solids are restricted to 0.1 to 10 microns. The current invention permits any detergent solid ingredient including soda ash or sodium sulfate and in a much wider size range. Also, Beerse's ratio of anionic to nonionic surfactant is limited to 3:1 or greater, unlike the current invention. In Beerse's adjunct particle, the weigh ratio of builder to binder is 1.75:1 to 3.5:1. The maximum amount of surfactant in the adjunct is thus about 36%.

There is a need for a process to make a granular detergent composition especially of high bulk density, which does not use a spray dried powder as a starting material and mitigates the disadvantages and complexities of the prior art processes.

We have now found that it is possible to make a high active, bulk density granular detergent composition in a simple, low energy process using readily available starting materials. We have also found that it is possible to make a high active, high bulk density granular detergent composition by an environmentally friendly, low energy process preferably with a high surfactant content.

In particular, we have now found that these and other preferred objects can be achieved if a mobile surfactant system comprising anionic surfactants and an alkoxylated nonionic surfactant is added to particulate starting material during treatment of this starting material in a high speed mixer/densifier. The anionic surfactants may be linear alkyl benzene sulfonate, alkyl sulfate and the like. It has been found that a superior detergent powder can be produced containing high surfactant levels produced by granulating solid detergent ingredients with a binder composed of a low-moisture content liquid mixture of anionic and nonionic surfactants and small particulate components with high surface areas which act as granulating aids. The entire particulate mixture can have high surface area or the high surface area can be achieved by manipulating selected components of the mixture. The active (surfactant) levels that can be achieved are as high as 60% by weight of surfactants and at least 40% by weight. The advantages are the increased level of active that can be incorporated into the granulate by comparison to granulations without the high surface area components.

SUMMARY OF THE INVENTION

Accordingly, the invention provides a process and a product prepared by the process for making a high active, high bulk density detergent composition comprising the step of high shear mixing until granular with a binder component, comprising a neutralized or partially neutralized surfactant with a particulate solid component, of initial particle size from about 0.1 to about 500 microns, wherein the binder maintains the mixture in a particulate state throughout the process. The particle size of at least 15% by weight of the particulate solids must be at least 50 microns and is preferably from about 50 to 400 microns to provide seeding. It has been found that if a particulate having an appropriate particle size and surface area is added in a sufficient amount such that the total particulate employed has an average surface area of above at least 9m²/g and preferably above at least 15 m²/g as measured by the BET method then particularly high amounts of active may be employed, theoretically, as much as 60%.

The advantages of this process and product are that it is simple in that only one mixer and a single stage is necessary, operating costs are low and the process can be operated at ambient temperature. Accordingly, there are less environmental concerns and the energy requirements are also less. There is no need for a drying step for most formulations. The process is flexible in that sensitive components can be included with the solid and binder components at the beginning of the process obviating the need for post dosing.

The process is essentially an agglomeration process, wherein the solid component is agglomerated by the binder component, resulting in detergent particles containing the solid component and a surfactant phase. The use of sufficient high surface area solids allows more liquid surfactant to be adsorbed per weight of solid.

The advantage of this agglomeration process over a process wherein a mobile surfactant composition is absorbed into a particulate starting material is the fact that by agglomerating, much higher levels of mobile surfactant material can be incorporated in the composition while maintaining good powder properties.

This agglomeration process can be carried out either as a continuous or a batch process. A continuous process is, however, preferred.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is concerned with a process for making a high active, high bulk density detergent composition as well as the composition itself, the process comprising the steps of (i) introducing a binder component, comprising a neutralized or partially neutralized surfactant, and a solid component of initial particle size from submicron to about 500 microns into a high shear mixer to thereby form a particulate mixture and (ii) subjecting said mixture to high shear mixing and thereby granulating the components to form granules of a size within the range of from 1 to 1200 microns. Preferably after this mixing a coating agent such as zeolite is added to the mixer.

The detergent composition is suitably a complete detergent composition. The term "complete" is used to refer to a detergent composition comprising sufficient surfactant, builder, and alkalinity source to function as an effective fabric washing powder. Alkalinity source refers to soda ash or phosphates. The term "complete" does not restrict the addition of certain minor components in conventional amounts for example at weights of less than 5%. Such minor components include enzymes, bleach, perfume, anti-deposition agent, or dye, to enhance the performance of the washing powder.

The particulate detergent composition may, if desired, be used as a feedstock in a detergent production process. For example, a liquid component surfactant such as nonionic surfactant may be sprayed onto the composition and it may then be coated with for example zeolite. If the detergent composition is used as a feedstock, it is preferred that it be the direct product of the process of the present invention. That, is, additional components are not incorporated into the detergent particles prior to their use as a feedstock. However, if desired, the particles may be admixed with separate particles comprising other materials. This provides the advantage of allowing the detergent composition to be produced at one location by a single-step process and optionally admixture with separate particles and then transported to a remote location for storage or further processing as desired.

For use as a feedstock, the detergent composition is in suitably substantially pure form. By "substantially pure form" we mean that the composition may contain up to 10% by weight of other particulate material but is preferably substantially free of any such other material.

The particulate to solid component must have at least

15% of the solids with a particle size of 50 microns and the average surface area of the solid must be at least 9m²/g.

An important characteristic of the present process is that the mixture remains in particulate or granular form throughout the process. A dough is not formed meaning that no de-agglomeration step is required. For this reason the process is simple and the final product can be made in a single step.

In the context of the present invention "by particle size" is meant the average particle size as determined by Rosin-Rammler calculation.

It is important that the process is a well controlled, robust process resulting in detergent powder with a desired particle size range and with powder properties which are comparable to those of detergent powders currently on the market. To obtain detergent powder with good powder properties, it is advantageous to add, in addition to the binder, one or more components with such a composition that a significant viscosity increase of the resulting total binder is obtained. The addition of these components raises the aforementioned viscosity generally by at least a factor 5, preferably by at least a factor 10, a viscosity increase by at least a factor 100 being most preferred (when measured in a Haake viscometer at a shear rate between 0.1 and 20 inverse seconds (S^"1) .

As a result of this viscosity increase, the process appears to be more easily controlled resulting in better powder properties for the detergent composition.

Examples of such viscosity raising components are water and, particularly, fatty acid in combination with a stoichiometric amount of alkaline material (such as caustic soda) sufficient to neutralize the fatty acid which obviously results in the formation of soap.

In the process a solid component, which can comprise detergency builders such as water-soluble alkaline inorganic materials (for example sodium carbonate seeded with calcium carbonate) , zeolite, sodium tripolyphosphate, other water-soluble inorganic materials, for example, sodium bicarbonate or silicate, fluorescers, polycarboxylate polymers, anti-redeposi ion agents and fillers, is mixed with a binder component which in addition to a neutralized or partially neutralized surfactant can comprise water, silicate solution, liquid polymer components, polyethylene glycols, perfumes, fatty acids and other materials. In the context of the present invention, the term binder component includes any component which is plastically deformable under conditions encountered during the process.

This invention allows higher surfactant levels to be incorporated into detergent powders produced by granulation. Unexpectedly, the addition of a small weight fraction of particles that possess high surface area sufficient so that the average surface area of the particulate solids is at least about 9m²/g and preferably at least about 15m²/g greatly improves the amount of surfactant that can be added. At least 15% by weight of the particulate solids must have a particle size of at least 50 microns, preferably 50 microns to 400 microns to provide a site for seeding. In addition, the high surface area solids preferably have an average diameter that differs from the other standard solid components. This leads to a marked increase in the surfactant to solids weight ratio. Specifically, the inclusion of additional, high surface area particulate components, which result in a total solid surface area exceeding 9m²/g, preferably at least 12 m²/g, and most preferably at least 15m²/g, extends the attainable surfactant weight levels to 60% by weight.

High surface area may be achieved by employing porous particles, such as zeolite MAP, Sipernat, or by using very small (sub-micron) particles, such as Cabot Cab-O-Sil. Other porous particles are also suitable. The high surface area of the resulting particle mixture then allows more liquid active to be adsorbed per weight of solid. In addition, the multi-modal distribution of particles resulting from the mixture of different components imparts greater strength in the granulate. The small particles in the distribution serve to increase the yield stress and viscosity of the liquid active binder mixture, thereby promoting efficient agglomeration of the larger particulate components. The multi-modal distribution of particles also results in more efficient packing of the solids, which strengthens the granulate. Although more efficient packing eliminates some void space in the agglomerate which liquid active could fill, this loss is more than compensated for by the void space gained by employing porous particles.

Examples of materials which may be postdosed to the composition include enzymes, bleaches, bleach precursors, bleach stabilizers, lather suppressors, perfumes and dyes. Liquid or pasty ingredients may conveniently be absorbed on to solid porous particles, generally inorganic, which may then be postdosed to the composition obtained by the process of the invention. The process is very flexible with respect to the chemical composition of the starting materials. Phosphate as well as zeolite built compositions may be made. The process is also suitable for preparing calcite/carbonate containing compositions.

The particulate solid component has an initial particle size of 0.1 to 500 microns, preferably 1 to 350 microns, more preferably from 0.1 to 300 microns. The solid component preferably comprises from 5 to 95% of detergent builders, more preferably from 10 to 80%, most preferably from 20 to 60% by weight.

The neutralized or partially neutralized surfactant may comprise anionic, nonionic or zwitterionic surfactants. By "partially neutralized" is meant a surfactant that may be selected from the linear alkyl benzene sulfate or sulfonate C₁₂ to C_lβ linear alkyl benzene sulfate, alpha-olefin sulfate or sulfonate, internal olefin sulfate or sulfonate, fatty acid ester sulfate or sulfonate, primary alkyl sulfate or sulfonate, primary and secondary alcohol sulfates or sulfonates and water soluble salts of the fatty acids for example tallow or coconut soaps.

The nonionic surfactant may be selected from those compounds produced by the condensation of alkylene oxide groups with an organic hydrophobic compound for example alkyl phenols or alcohols. Preferred nonionics are the water soluble condensation products of aliphatic alcohols with 8 to 30 carbon atoms in the molecule with 3 to 15 moles of ethylene oxide per mole of alcohol. Other nonionics include water soluble amine oxides containing one alkyl moiety of about 10 to 18 carbon atoms and 2 moieties selected from the groups of alkyl and hydroxyalkyl moieties with from 1 to 3 carbon atoms and those nonionics derived from sugars, for example the alkyl poly glycosides.

The zwitterionic surfactants include derivatives of aliphatic quaternary ammonium phosphonium and sulphonium compounds in which one of the aliphatic substituents contains an anionic water-solubilizing group.

Preferably the binder component comprises a mixture of neutralized or partially neutralized surfactants for example a mixture of linear or primary alkylbenzene sulfonate containing from 11 to 14 carbon atoms and a C₁₂ to C₁₅ primary alcohol ethoxylated with 3 to 7 moles of ethylene oxide per mole of alcohol in a weight ratio of anionic to nonionic of 3 to 1 or a mixture of a C₁₄ to C₁₇ primary or secondary alcohol sulphate with a C₁₂ to C₁₅ primary alcohol ethoxylated with 3 to 7 moles of ethylene oxide per mole of alcohol in a weight ratio of 2 to 1.

Preferably the neutralized surfactant comprises less than 20% by weight of water, more preferably less than 10% most preferably less than 5% by weight and is made by the method described in US 4,923,636 and US 4,826,632 to Blackburn, or US 4,052,342 to Fernley or US 5,324,455 to Dumas et al., incorporated herein by reference.

The surfactant content of the binder is preferably from 50% to 100%, more preferably from 55% to 90% most preferably from 60% to 80%. Preferred surfactant mixtures contain 20 to 80% by weight of anionic surfactant, 20 to 80% by weight of nonionic surfactant and no water.

Preferably the binder component comprises less than 30% by weight of water, more preferably between 0.5% and 25%, most preferably between 5% and 15%. The high shear mixer advantageously used to carry out the process is preferably a Littleford ^|TM1 FM 130D mixer. This apparatus consists essentially of a large, static hollow cylinder with its longitudinal axis horizontal. Along this axis is a rotating shaft with several different types of blades mounted thereon. Preferably, when used to carry out the process of the present invention the shaft tip speed is between 1 /sec and 20 m/sec, more preferably 1 m/sec and 12 m/sec. The mixer can be equipped with one or more high speed cutters and preferably these are operated at tip speeds from 15 m/sec to 80 m/sec, more preferably from 20 m/sec to 70 m/sec. Other suitable mixers for the process of the invention are the Lodige¹™¹, Eirich¹™¹ RV02, Powrex'™¹ VG100, Zanchetta^(TM), Schugi'™¹ and Fukae'™¹.

In the process according to the invention, the solid component is fed into the mixer followed by the binder component which is either sprayed on to the solid component or pumped into the mixer. The components are mixed for a total residence time preferably of from 0.2 to 8 minutes, more preferably of from 0.25 to 5 minutes. Optimally after this mixing time a coating agent such as zeolite can be added to the mixer and the mixer operated with only the main shaft for 20 to -60 seconds. The granules made by the process preferably have a bulk density of from 600 g/liter to 1150 g/liter and a particle size (measured by Rosin-Rammler) of from 300 to 1,200 microns more preferably from 400 to 800 microns.

The ratio of binder component to solid component is preferably in a weight ratio of from 3:2 to 2:3, more preferably 1:1 to 2:3.

The process is preferably operated at a temperature from ambient to 60°C, more preferably from ambient to 40°C. The invention is further illustrated by the following non-limiting examples in which parts and percentages are by weight unless otherwise indicated.

In the examples the following abbreviations are used for the employed materials:

Zeolite Zeolite 4A (Wessalith ex Degussa) and Zeolite MAP (ex Crosfield)

Carbonate Sodium carbonate G100 (ex FMC)

LAS Linear alkyl benzene sulfonate

Nonionic Nonionic surfactant, ethoxylated alcohol,

Neodol 25-7 ex Shell

SiL90 Fumed silica produced by Cabot and fully described in bulletin CGEN-8

2/90

Sip 50s A silicate produced by Degussa and fully described in bulletin PT 71-

16-1-391-HC.

TABLE 1

1 1/1 HAM¹¹¹ 3 4 binder type 1/1 HAM⁽¹¹ 1/1 HAM^U) 2/1 HAM⁽²⁾ 2/1 HAM granulating siL90 sip50s siP50s siP50s aid type

SOLIDS MIX % zeolite 4A 30 0 0 0 zeolite MAP 0 60 58 58

G100 soda ash 40 40 39 38

granulating 30 0 3 4 aid surface 32.2 7.2 20.5 25.0 area(m²/g)

% active in 48 38 41 45 product equipment _Fpl3) BL^,4) BL FP

(1) 1/1 HAM combination of 1 part LAS to 1 part 7E.0 C_12-15 alcohol (nonionic) high active mixture

121 2/1 HAM combination of 2 parts LAS to 1 part 7E.0 C₁₂.₁₅ alcohol (nonionic) high active mixture

(3) FP food processor

14) BL Batch Lodige mixer

Examples 1-4 were prepared on a 45kg (1001b) scale in a high speed Batch Lodige (Littleford FM 130D) mixer or on a smaller scale in a 300-500 gm scale in the General Model VC- 4 food processor. Solid and binder were added to the mixer before starting the granulation, and the duration of the granulation ranged from 30 seconds to two minutes. The granulation was halted when most of the particles appeared to be between 100 and 500 microns in diameter. The resulting powders were free flowing.

Examples 1, 3 and 4 demonstrate formulations in which the surfactant level of the granule exceeds 40% by weight. The mixture of solids employed, the resulting specific surface areas, and the amount of active in the product are reported in Table 1. The specific surface areas are measured in square meters per gram of particles, and the values for a given mixture are calculated on a weight average basis using the BET measured surface areas. BET surface areas employed for individual components are listed in Table 2 below.

Example 2 serves as a comparative to illustrate that a surfactant level lower than 40% is achieved when the solid mixture has a relatively small specific surface area.

Other mixers are also suitable,

TABLE 2 PROPERTIES OF SOLIDS

BET area (m²/g) Average Diameter (microns)

G100 Soda Ash 0.00157 300

Zeolite 4A 7.4 4

Zeolite MAP 35 1.6 siL90 100 > 1 siP50s 450 ~ 4

Claims (10)

1. Process for making a detergent composition having at least 40% by weight of surfactant and a bulk density of at least 650 g/1, the process comprising the single step of high shear mixing until granular at a temperature from ambient to 60°C, a binder component comprising said surfactant and less than 20% water, with a particulate solid component, of initial particle size from 0.1 to about 500 microns, said particulate solid component having at least about 15% by weight of particles with a particle size of at least about 50 microns and a sufficient amount of smaller particles so that the average surface area of the particulate component is at least about 9m²/g as measured by the BET method, and wherein the binder maintains the mixture in a particulate state throughout the process.

2. Process according to claim 1 wherein the binder comprises from 20 to 80% anionic and from 20 to 80% nonionic surfactant.

3. Process according to claim 1 or 2 wherein the binder component comprises:

(a) a sodium or potassium salt of an alkyl sulfate or sulfanate in an amount from 20 to 80% by weight;

(b) an alkoxylated nonionic surfactant in an amount from 20 to 80% by weight;

(c) the balance being water in an amount from 0 to less than 20% by weight.

4. Process according to any preceding claim wherein the binder comprises less than 10% water.

5. Process according to claim 1 wherein the binder comprises fatty acid in combination with a stoichiometric amount of alkaline material sufficient to neutralize the fatty acid.

6. Process according to any preceding claim wherein the solid component comprises from 5 to 95% by weight of a detergency builder.

7. Process according to any preceding claim wherein the binder and solid components are mixed until the granules are from 300 to 1200 microns in diameter.

8. Process according to any preceding claim wherein the composition comprises binder and solid components in a weight ratio of binder to solid of from 3:2 to 2:3.

9. A particulate detergent composition obtainable directly by a process as defined in any preceding claim.

10. A composition according to claim 9 which is in substantially pure form.