PROCESS FOR PREPARING GRANULAR DETERGENT COMPOSITIONS

Abstract: The present invention relates to a process for preparing a granular detergent composition with good powder properties. More particularly, the invention is directed to a process in which a liquid binder is contacted with a solid particulate material in a gas fluidisation granulator, the temperature conditions in the fluidisation granulator being elevated during the process.

Description: PROCESS FOR PREPARING GRANULAR DETERGENT COMPOSITIONS FIELD OF THE INVENTION The present invention relates to a process for preparing a granular detergent composition with good, powder properties. More particularly, the invention is directed to a process in which a liquid binder is contacted with a solid particulate material in a gas fluidisation granulator under controlled process conditions. BACKGROUND OF THE INVENTION In recent years, there has been much interest in the production of detergent products by processes which employ mainly mixing, without the use of spray-drying. In this type of process, the various components are dry-mixed and optionally granulated with a liquid binder. Liquid binders typically used in such granulation processes are anionic surfactants, acid precursors of anionic surfactants, nonionic surfactants, or any mixture thereof. If substantially mechanical mixing is employed in the granulation process, then granular detergent products having a high bulk density, typically greater than 700 or 800 g/1, tend to be produced. If however the granulation process involves mixing by means of gas fluidisation, then products with medium to low bulk densities tend to be generated, for example from 300 to 750 g/1. Liquid binders are generally pumped into the mixer to contact the solid particulate material. Liquid binders must therefore be of low enough viscosity to allow for ready pumping. It is also important that the liquid binder is properly adsorbed and absorbed by the solid particulate material and that the liquid binder does not "bleed" from the product granules, especially upon storage. When powders to be formulated contain particulate components with low liquid carrying capacities, mixing processes employing liquid binders can have a deleterious effect on the requirement to produce free-flowing powders with good granularity and low moisture content. Soft granules tend to be formed in the resultant product with poor powder behaviour due to the low adhesive forces of wet particle surfaces and hence poor granule structure. Problems can also be encountered with the build-up of hard lumps due to brisk exothermic hydration and crystal bridge formation. PRIOR ART Such problems have been addressed by using a liquid binder containing a structurant as described in W098/11198 (Unilever) . This document discloses formulating a liquid binder with a structurant so as to remain pumpable at a temperature at which the liquid binder is formed and then admixing the liquid binder with a solid component at a lower temperature at which the structurant causes solidification of the mixture. WO98/58048 (Unilever) describes a granulation process in which a liquid binder is sprayed onto a fluidising particulate material in a gas fluidisation granulator. During the process, the temperature of the fluidising gas, and preferably also the bed temperature, is lowered or elevated. However, WO98/58048 fails to make any correlation between the temperature of the fluidising gas and/or the bed temperature and the nature of the liquid binder being sprayed onto the fluidising particulate material. Surprisingly, we have found that when a liquid binder is being contacted with a solid particulate material in a gas fluidisation granulation process, the resulting powder properties are significantly improved if the temperature in the granulator is controlled relative to viscosity properties of the liquid binder. More specifically, we have found that the powder flow properties and storage properties, in particular cohesiveness levels, are improved. DEFINITION OF THE INVENTION In a first aspect, this invention provides a process for preparing a granular detergent product comprising contacting a particulate solid material with a spray of liquid binder whilst fluidising the solids in a gas fluidisation granulator, wherein the temperature of the fluidisation gas is elevated so as to be within 35°C, preferably within 25°C and more preferably within 15°C, of the pumpable temperature (as hereinafter defined) of the liquid binder. In a second aspect, this invention provides a process for preparing a granular detergent product comprising contacting a particulate solid material with a spray of liquid binder whilst fluidising the solids in a gas fluidisation granulator, wherein the bed temperature is elevated so as to be within 35°C, preferably within 25°C and more preferably within 15°C, of the pumpable temperature (as hereinafter defined) of the liquid binder. In a third aspect this invention provides a granular detergent product of bulk density less than 900 g/1 obtained according to the process of the invention. The "pumpable temperature" of the liquid binder is defined herein as the temperature at which the liquid binder exhibits a viscosity of 1 Pa.s at 50 s -1 . DETAILED DESCRIPTION OF THE INVENTION Definitions Hereinafter, in the context of this invention, the term "granular detergent product" encompasses granular finished products for sale, as well as granular components or adjuncts for forming finished products, e.g. by post-dosing to or with, or any other form of admixture with further components or adjuncts. Thus a granular detergent product as herein defined may, or may not contain detergent-active material such as synthetic surfactant and/or soap. The minimum requirement is that it should contain at least one material of a general kind of conventional component of granular detergent products, such as a surfactant (including soap) , a builder, a bleach or bleach-system component, an enzyme, an enzyme stabiliser or a component of an enzyme stabilising system, a soil anti-redeposition agent, a fluorescer or optical brightener, an anti-corrosion agent, an anti-foam material, a perfume or a colourant. However, in a preferred embodiment of this invention granular detergent products contain detergent-active material such as synthetic surfactant and/or soap at a level of at least 5 wt%, preferably at least 10 wt% of the product. As used hereinafter, the term "powder" refers to materials substantially consisting of grains of individual materials and mixtures of such grains. As used hereinafter, the term "granule" refers to a small particle of agglomerated smaller particles, for example, agglomerated powder particles. The final product of the process according to the present invention consists of, or comprises a high percentage of granules. However, additional granular and or powder materials may optionally be post-dosed to such a product. As used herein, the terms "granulation" and "granulating" refer to a process in which, amongst other things, particles are agglomerated. For the purposes of this invention, the flow properties of the granular product are defined in terms of the dynamic flow rate (DFR) , in ml/s, measured by means of the following procedure. A cylindrical glass tube of internal diameter of 35 mm and length of 600 mm is securely clamped with its longitudinal axis in the vertical position. Its lower end is terminated by a cone of polyvinyl chloride having an internal angle of 15° and a lower outlet orifice of diameter 22.5 mm. A first beam sensor is positioned 150 mm above the outlet, and a second beam sensor is positioned 250 mm above the first sensor. To determine the dynamic flow rate, the outlet orifice is temporarily closed and the cylinder filled with the granular detergent product to a point about 10 cm above the upper sensor. The outlet is opened and the flow time t (seconds) taken for the powder level to fall from the upper sensor to the lower sensor measured electronically. This is repeated 2 or 3 times and an average time taken. If V is the volume (ml) of the tube between the upper and lower sensors, the DFR is given by V/t. The unconfined compressibility test (UCT) provides a measure of the cohesiveness or "stickiness" of a product and can provide a guide to its storage properties, for example, in silos. UCT may be measured on both fresh and weathered powders but the UCT value is of especial significance in indicating the likely storage behaviour of a powder. The principle of the test is to compress the granular detergent product into a compact and then measure the force required to break the compact. This is carried out using an apparatus comprising a cylinder of diameter 89 mm and height 114 mm (3.5 x 4.5 inches), a plunger and plastic discs and weights of predetermined weight as follows. The cylinder, positioned around a fixed locating disc and secured with a clamp, is filled with granular detergent product and the surface leveled by drawing a straight edge across it. A 50 g plastic disc is placed on top of the granular product, the plunger lowered and a 10 kg weight placed slowly on top of the upper plunger disc. The weight is left in position for 2 minutes after which time the 10 kg weight is removed and plunger raised. The clamp is removed from the cylinder and the two halves of the cylinder carefully removed to leave a compact of granular product. If the compact is unbroken, a second 50 g plastic disc is placed on top of the first and left for approximately ten seconds. If the compact is still unbroken, a 100 g disc is placed on top to the plastic discs and left for ten seconds. If the compact is still unbroken, the plunger is lowered very gently onto the discs and 250 g weights added at ten second intervals until the compact collapses. The total weight of plunger, plastic discs and weights at collapse is recorded. The cohesiveness of the powder is classified by the weight required to break the compact as follows. The greater the weight required, the higher the UCT level and the more cohesive ("sticky") the powder. "Fines", according to this invention, are defined as particles with a diameter of less than 180 microns. "Coarse" material, according to this invention, is defined as those particles with a diameter greater than 1400 microns . Levels of fine and coarse particles can be measured using sieve analysis. Unless specified otherwise, values relating to powder properties such as bulk density, DFR, moisture content etc, relate to the weathered granular detergent product. The Process The process of this invention is carried out using a gas fluidisation granulator. A gas fluidisation granulator is sometimes called a "fluidised bed" granulator or mixer. This is not strictly accurate since such mixers can be operated with a gas flow rate so high that a classical "bubbling" fluid bed does not form. The gas fluidisation granulation and agglomeration process step is preferably carried out substantially as described in WO98/58046 and WO98/58047 (Unilever), the contents of which are hereby incorporated by way of reference. The gas fluidisation apparatus basically comprises a chamber in which a stream of gas (hereinafter referred to as the fluidisation gas) , usually air, is used to cause turbulent flow of particulate solids to form a "cloud" of the solids and liquid binder is sprayed onto or into the cloud to contact the individual particles. As the process progresses, individual particles of solid starting materials become agglomerated, due to the liquid binder, to form granules . The gas fluidisation granulator is typically operated at a superficial air velocity of about 0.1-1.2 ms "1 , either under positive or negative relative pressure and with an air inlet temperature (ie fluidisation gas temperature) ranging from - 10°C or 5°C up to 100°C. It may be as high as 200°C in some cases. The fluidisation gas temperature, and thus preferably the bed temperature, may be changed during the granulation process as described in WO98/58048. It may be elevated for a first period, e.g. at up to 100°C or even up to 200°C and then at one or more other stages (before or after) , it may be reduced to just above, at, or below ambient, e.g. to 30°C or less, preferably 25°C or less or even as low as 5°C or less or -10°C or less. When the process is a batch process, the temperature variation will be effected over time. If it is a continuous process, it will be varied along the "track" of the granulator bed (i.e. in the direction of powder flow through the granulator bed) . In the latter case, this is conveniently effected using a granulator of the "plug flow" type, ie one in which the materials flow through the reactor from beginning to end. In a batch process, the fluidisation gas temperature may be reduced over a relatively short period of time, for example 10 to 50% of the process time. Typically, the gas temperature may be reduced for 0.5 to 15 minutes. In a continuous process, the gas temperature may be reduced along a relatively short length of the "track" of the granulator bed, for example along 10 to 50% of the track. In both cases, the gas may be pre-cooled. Preferably, the fluidisation gas temperature, and preferably also the bed temperature, is not lowered until agglomeration of the fluidising particulate solid material is substantially complete. In addition to the fluidisation gas, a gas fluidisation granulator may also employ an atomising gas stream. Such an atomising gas stream is used to aid atomisation of the liquid binder from the nozzle onto or into the fluidising solids. If an atomising gas stream is employed, it may generally be operated at a pressure of from 2 to 5 bar. The atomising gas stream, usually air, may also be heated. According to one aspect of the invention, the temperature of the fluidisation gas is elevated so as to be within (plus or minus) 35°C, preferably within 25°C, more preferably within 15°C, most preferably within 10°C and advantageously within 5°C, of the pumpable temperature (as defined) of the liquid binder. In a preferred embodiment, the atomisation gas temperature is also elevated so as to be within (plus or minus) 35°C, preferably within 25°C, more preferably within 15°C, most preferably within 10°C and advantageously within 5°C, of the pumpable temperature of the liquid binder. Alternatively, in another aspect of the invention, the bed temperature in the gas fluidisation chamber is elevated so as to be within (plus or minus) 35°C, preferably within 25°C, more preferably within 15°C, most preferably within 10°C and advantageously within 5°C, of the pumpable temperature of the liquid binder. It is highly preferred that the temperature of the fluidising gas, and preferably also the atomising gas, and/or the temperature of the bed be elevated for at least part of the time and preferably for substantially the entire time the liquid binder is being sprayed onto the fluidising solids. - li ¬ lt is especially preferred that the temperature of the fluidising gas, and preferably also the atomising gas, and/or the temperature of the bed be elevated and maintained at around or near the pumpable temperature of the liquid binder. The elevation in temperature, relative to the pumpable temperature of the liquid binder, of the fluidising gas, and preferably also the atomising gas, and/or the temperature of the bed, has been found to be especially beneficial when the liquid binder is a structured blend. As used herein, the term "bed temperature" refers to the temperature of the fluidising gas around the solid particulate material. The bed temperature can be measured, for example, using a thermocouple probe. Whether there is a discernible powder bed or no discernible powder bed (ie because the mixer is being operated with a gas flow rate so high that a classical "bubbling" fluid bed is not formed) , the "bed temperature" is taken to be the temperature as measured at a point inside the fluidisation chamber about 15 cm from the gas distributor plate. Whether the gas fluidisation granulation process of the present invention is a batch process or a continuous process, solid particulate material may be introduced at any time during the time when liquid binder is being sprayed. In the simplest form of process, solid particulate material is first introduced to the gas fluidisation granulator and then sprayed with the liquid binder. However, some solid particulate material could be introduced at the beginning of processing in the gas fluidisation apparatus and the remainder introduced at one or more later times, either as one or more discrete batches or in continuous fashion. The gas fluidisation granulator may optionally be of the kind provided with a vibrating bed, particularly for use in continuous mode. Optional Drying and/or cooling For use, handling and storage, the granular detergent product must be in a free flowing state. Therefore, in a final step, the granules can be dried and/or cooled if necessary. This step can be carried out in any known manner, for instance in a fluid bed apparatus (drying and cooling) or in an airlift (cooling) . Drying and/or cooling can be carried out in the same fluid bed apparatus as used for the final agglomeration step simply by changing the process conditions employed as will be well-known to the person skilled in the art. For example, fluidisation can be continued for a period after addition of liquid binder has been completed and the air inlet temperature can be reduced. Other optional process steps In a refinement of the process of the present invention, the solid particulate material may be treated in one or more mixers and/or granulators prior to the gas fluidisation granulator. For example, a solid particulate material may be mixed and optionally contacted with a liquid binder, in a separate premixing step, e.g. in a low-, moderate- or high- shear mixer. If liquid binder is added in a premixing step, then a partially granulated material is formed. The latter can then be sprayed with further liquid binder in the gas fluidisation granulator, to form the granulated detergent product . In this respect, it is possible to precede the fluid bed granulation step with one or more separate mixing or granulation steps. Suitable mixers and granulators will be well-know to the person skilled in the art. For example, solid particulate material may first be treated with liquid binder in a high-speed mixing step, which is then followed by a moderate-speed mixing step, prior to the gas fluidisation step. Examples of suitable pre-granulation processes are described in EP 367339, EP 420317, WO96/04359, WO98/58046 and WO98/58047 (Unilever) , but other granulation and mixing processes are equally as appropriate as will be evident to the person skilled in the art. The process of the invention can be carried out either in a batchwise or continuous manner. In a preferred embodiment, the entire process is continuous. The liquid binder In the process of this invention, liquid binder is added during the gas fluidisation granulation step, and also may be added in other optional preceding process steps. If there is more than one granulation step, or more than one point of addition or time of addition, then the liquid binder added at each step or point or time may be the same or different and more than one liquid binder may be added in any one step or at any one point or time. The liquid binder is sprayed into the gas fluidisation granulator. The liquid binder can comprise one or more components of the granular detergent product. Suitable liquid components include anionic surfactants and acid precursors thereof, nonionic surfactants, fatty acids, water and organic solvents . The liquid binder can also comprise solid components dissolved in or dispersed in a liquid component, such as, for example, inorganic neutralising agents and detergency builders. The only limitation is that with or without dissolved or dispersed solids, the liquid binder should be pumpable and capable of being delivered to the mixer and/or granulator in a fluid, including paste-like, form. It is preferred that the liquid binder comprises an anionic surfactant. The content of anionic surfactant in the liquid binder may be as high as possible, e.g. at least 98 wt% of the liquid binder, or it may be less than 75 wt%, less than 50 wt% or less than 25 wt%. It may, of course constitute 5 wt% or less or not be present at all. Suitable anionic surfactants are well-known to those skilled in the art. Examples suitable for incorporation in the liquid binder include alkylbenzene sulphonates, particularly linear alkylbenzene sulphonates having an alkyl chain length of C 8 -Cι 5 ; primary and secondary alkyl sulphates, particularly Cι 2 -Cιs primary alkyl sulphates; alkyl ether sulphates; olefin sulphonates; alkyl xylene sulphonates; dialkyl sulphosuccinates; and fatty acid ester sulphonates. Sodium salts are generally preferred. It is very much preferred to form some or all of any anionic surfactant in situ in the liquid binder by reaction of an appropriate acid precursor and an alkaline material such as an alkali metal hydroxide, e.g. NaOH. Since the latter normally must be dosed as an aqueous solution, that inevitably incorporates some water. Moreover, the reaction of an alkali metal hydroxide and acid precursor also yields some water as a by-product. However, in principle, any alkaline inorganic material can be used for the neutralisation but water-soluble alkaline inorganic materials are preferred. Another preferred material is sodium carbonate, alone or in combination with one or more other water-soluble inorganic materials, for example, sodium bicarbonate or silicate. If desired, a stoichiometric excess of neutralising agent may be employed to ensure complete neutralisation or to provide an alternative function, for example as a detergency builder, e.g. if the neutralising agent comprises sodium carbonate. Organic neutralising agents may also be employed. Of course, if the liquid binder contains an acid precursor of an anionic surfactant, the acid precursor can be neutralised or neutralisation completed in situ in the mixer and/or granulator by either contacting with a solid alkaline material or adding a separate liquid neutralising agent to the mixer and/or granulator. However, neutralisation in the mixer and/or granulator is not a preferred feature of this invention. The liquid acid precursor may be selected from linear alkyl benzene sulphonic (LAS) acids, alphaolefin sulphonic acids, internal olefin sulphonic acids, fatty acid ester sulphonic acids and combinations thereof. The process of the invention is especially useful for producing compositions comprising alkyl benzene sulphonates by reaction of the corresponding alkyl benzene sulphonic acid, for instance Dobanoic acid ex Shell. Linear or branched primary alkyl sulphates (PAS) having 10 to 15 carbon atoms can also be used. In a preferred embodiment, the liquid binder comprises an anionic surfactant and a nonionic surfactant. The weight ratio of anionic surfactant to nonionic surfactant is in the range from 10:1 to 1:15, preferably from 10:1 to 1:10, more preferably 10:1 to 1:5. If the liquid binder comprises at least some acid precursor of an anionic surfactant and a nonionic surfactant, then the weight ratio of anionic surfactant, including the acid precursor, to nonionic surfactant can be higher, for example 15:1. The nonionic surfactant component of the liquid binder may be any one or more liquid nonionics selected from primary and secondary alcohol ethoxylates, especially C 8 -C 20 aliphatic alcohols ethoxylated with an average of from 1 to 20 moles ethylene oxide per mole of alcohol, and more especially the C 1 0-C 15 primary and secondary aliphatic alcohols ethoxylated with an average of from 1 to 10 moles of ethylene oxide per mole of alcohol. Non-ethoxylated nonionic surfactants include alkylpolyglycosides, glycerol monoethers, and polyhydroxyamides (glucamide) . In a preferred embodiment the liquid binder is substantially non-aqueous. That is to say, the total amount of water therein is not more than 15 wt% of the liquid binder, preferably not more than 10 wt%. However, if desired, a controlled amount of water may be added to facilitate neutralisation. Typically, the water may be added in amounts of 0.5 to 2 wt% of the final detergent product. Typically, from 3 to 4 wt% of the liquid binder may be water as the reaction by-product and the rest of the water present will be the solvent in which the alkaline material was dissolved. The liquid binder is very preferably devoid of all water other than that from the latter-mentioned sources, except perhaps for trace amounts/impurities. Alternatively, an aqueous liquid binder may be employed. This is especially suited to manufacture of products which are adjuncts for subsequent admixture with other components to form a fully formulated detergent product. Such adjuncts will usually, apart from components resulting from the liquid binder, mainly consist of one, or a small number of components normally found in detergent compositions, e.g. a surfactant or a builder such as zeolite or sodium tripolyphosphate . However, this does not preclude use of aqueous liquid binders for granulation of substantially fully formulated products. In any event, typical aqueous liquid binders include aqueous solutions of alkali metal silicates, water soluble acrylic/maleic polymers (e.g. Sokalan CP5) and the like. The liquid binder may optionally comprise dissolved solids and/or finely divided solids which are dispersed therein. The only limitation is that with or without dissolved or dispersed solids, the liquid binder should be pumpable and sprayable at temperatures of 50 °C or greater or at any rate, 60°C or greater e.g. 75°C. Preferably it is solid at below 50°C, preferably at 25°C or less. The liquid binder is preferably at a temperature of at least 50°C, more preferably at least 60°C when fed into the mixer or gas fluidisation granulator. According to the present invention, liquid binders are considered readily pumpable if they have a viscosity of no greater than 1 Pa.s at a shear rate of 50 s "1 and at the temperature of pumping. Liquid binders of higher viscosity may still in principle be pumpable, but an upper limit of 1 Pa.s at a shear rate of 50 s "1 is used herein to indicate easy pumpability. The viscosity can be measured, for example, using a Haake VT500 rotational viscometer. The viscosity measurement may be carried out as follows. A SV2P measuring cell is connected to a thermostatic waterbath with a cooling unit . The bob of the measuring cell rotates at a shear rate of 50 s _1 . Solidified blend is heated in a microwave to 95 °C and poured into the sample cup. After conditioning for 5 minutes at 98°C, the sample is cooled at a rate of +/- 1°C per minute. The temperature at which a viscosity of 1 Pa.s is observed, is recorded as the "pumpable temperature". The "pumpable temperature" of the liquid binder is therefore defined herein as the temperature at which the liquid binder exhibits a viscosity of 1 Pa.s at 50 s _1 . A definition of solid can be found in the Handbook of Chemistry and Physics, CRC Press, Boca Raton, Florida, 67th edition, 1986. Structured blends In a preferred embodiment of this invention, the liquid binder contains a structurant and liquid binders which contain a structurant are referred to herein as structured blends. All disclosures made herein with reference to liquid binders apply equally to structured blends. In the context of the present invention, the term "structurant" means any component which enables the liquid component to achieve solidification in the granulator and hence good granulation, even if the solid component has a low liquid carrying capacity. Structurants may be categorised as those believed to exert their structuring (solidifying) effect by one of the following mechanisms, namely: recrystallisation (e.g. silicate or phosphates) ; creation of a network of finely divided solid particles (e.g. silicas or clays); and those which exert steric effects at the molecular level (e.g. soaps or polymers) such as those types commonly used as detergency builders. One or more structurants may be used. Structured blends provide the advantage that at lower ambient temperatures they solidify and as a result lend structure and strength to the particulate solids onto which they are sprayed. It is therefore important that the structured blend should be pumpable and sprayable at an elevated temperature, e.g. at a temperature of at least 50°C, preferably of at least 60°C, and yet should solidify at a temperature below 50°C, preferably below 35°C so as to impart its benefit. Typically, in the high-speed and moderate- or low-speed mixers the temperature is more than 10 °C, preferably more than 20 °C below the temperature at which the blend is prepared and pumped into the granulator. The structurants cause solidification in the liquid binder component preferably to produce a blend strength as follows, The strength (hardness) of the solidified liquid component can be measured using an Instron pressure apparatus. A tablet of the solidified liquid component, taken from the process before it contacts the solid component, is formed of dimensions 14 mm in diameter and 19 mm in height. The tablet is then destroyed between a fixed and a moving plate, the moving plate moving towards the fixed plate. The speed of the moving plate is set to 5 mm/min, which causes a measuring time of about 2 seconds. The pressure curve is logged on a computer. Thus, the maximum pressure (at the moment of tablet breaking) is given and the E-modulus is calculated from the slope. For the solidified liquid component, P ma χ at 20 °C is preferably a minimum of 0.1 MPa, more preferbaly 0.2 MPa, e.g. from 0.3 to 0.7 M Pa. At 55 °C, a typical range is from 0.05 to 0.4 M Pa. At 20°C, E mod for the liquid blend is preferably a minimum of 3 M Pa, e.g. from 5 to 10 M Pa. The structured blend is preferably prepared in a shear dynamic mixer for premixing the components thereof and performing any neutralisation of anionic acid precursor. Soaps represent one preferred class of structurant, especially when the structured blend comprises a liquid nonionic surfactant. In many cases it may be desirable for the soap to have an average chain length greater than the average chain length of the liquid nonionic surfactant but less than twice the average chain length of the latter. It is very much preferred to form some or all of any soap structurant in situ in the liquid binder by reaction of an appropriate fatty acid precursor and an alkaline material such as an alkali metal hydroxide, e.g. NaOH . However, in principle, any alkaline inorganic material can be used for the neutralisation but water-soluble alkaline inorganic materials are preferred. In a liquid binder comprising an anionic surfactant and soap, it is preferred to form both the anionic surfactant and soap from their respective acid precursors. All disclosures made herein to formation of anionic surfactant by in situ neutralisation in the liquid binder of their acid precursors equally apply to the formation of soap in structured blends. If desired, solid components may be dissolved or dispersed in the structured blend. Typical amounts of ingredients in the essential structured blend component as % by weight of the structured blend are as follows: preferably from 98 to 10 wt% of anionic surfactant, more preferably from 70 to 30%, and especially from 50 to 30 wt%; preferably from 10 to 98 wt% of nonionic surfactant, more preferably from 30 to 70 wt%, and especially from 30 to 50 wt%; preferably from 2 to 30 wt% of structurant, more preferably from 2 to 20%, yet more preferably from 2 to 15 wt%, and especially from 2 to 10 wt%. In addition to the anionic surfactant or precursor thereof, nonionic surfactant and structurant, the structured blend may also contain other organic solvents. Solid particulate material The solid particulate materials of this invention may be powdered and/or granular. As such, the solid particulate material may be any component of the granular detergent product that is available in particulate form. Preferably, the solid particulate material with which the liquid binder is admixed comprises a detergency builder. In a particularly preferred embodiment of this invention, the solid starting material comprises builders selected from crystalline and amorphous aluminosilicates . Product The present invention also encompasses a granular detergent product resulting from the process of the invention (before any post-dosing or the like) . Granular detergent products according to the invention have a bulk density of less than 900 g/1, preferably less than 800 g/1, more preferably less than 750 g/1, and yet more preferably less than 700 g/1. The bulk density may be as low as 300 g/1, however it is preferably greater than 400 g/1. Preferably it is in the range of 400-800 g/1, more preferably 400-750 g/1, and yet more preferably 400-700 g/1. The product will have a bulk density determined by the exact nature of the process but can be controlled to a certain degree by selecting appropriate premixing steps, as will be evident to the person skilled in the art. The granular detergent products of the process of this invention are low in fines, possess good flow properties and have low UCT levels. Preferably less than 15 wt%, and more prefertably less than 10 wt% of the granules have a diameter of less 180 microns, more preferably less than 8 wt%, and most preferably less than 5 wt%. The granular product is considered to be free flowing if it has a DFR of at least 80 ml/s. Preferably the granular products of this invention have DFR values of at least 80 ml/s, preferably at least 90 ml/s, more preferably at least 100 ml/s, and most preferably at least 110 ml/s. The granular detergent product preferably has a UCT level of less than 1500 g, more preferably less than 1000 g, yet more preferably less than 900 g, yet more preferably less than 700g, and most preferably less than 500 g. Finally, the granules may be distinguished from granules produced by other methods by using mercury porosimetry. The latter technique is ideal for characterising granules that have been prepared by a process involving gas fluidisation agglomeration. Detergent compositions and ingredients As previously indicated, a granular detergent product prepared by the process of the invention may itself be a fully formulated detergent composition, or may be a component or adjunct which forms only a part of such a composition. This section relates to final, fully formed detergent compositions. The total amount of detergency builder in the final detergent composition is suitably from 10 to 80 wt%, preferably from 15 to 60 wt%. The builder may be present in an adjunct with other components or, if desired, separate builder particles containing one or more builder materials may be employed. This invention is especially applicable to use where the solid starting material comprises builders selected from crystalline and amorphous aluminosilicates, for example zeolites as disclosed in GB-A-1 473 201; amorphous aluminosilicates as disclosed in GB-A-1 473 202; and mixed crystalline/amorphous aluminosilicates as disclosed in GB 1 470 250; and layered silicates as disclosed in EP-B-164 514. Aluminosilicates, whether used as layering agents and/or incorporated in the bulk of the particles may suitably be present in a total amount of from 10 to 60 wt% and preferably an amount of from 15 to 50 wt% based on the final detergent composition. The zeolite used in most commercial particulate detergent compositions is zeolite A. Advantageously, however, maximum aluminium zeolite P (zeolite MAP) described and claimed in EP-A-384 070 may be used. Zeolite MAP is an alkali metal aluminosilicated of the P type having a silicone to aluminium ratio not exceeding 1.33, preferably not exceeding 1.15, and more preferably not exceeding 1.07. Other suitable builders include hydratable salts, preferably in substantial amounts such as at least 25% by weight of the solid component, preferably at least 10% by weight. Hydratable solids include inorganic sulphates and carbonates, as well as inorganic phosphate builders, for example, sodium orthophosphate, pyrophosphate and tripolyphosphate . Other inorganic builders that may be present include sodium carbonate (as mentioned above, an example of a hydratable solid) , if desired in combination with a crystallisation seed for calcium carbonate as disclosed in GB-A-1 437 950. As mentioned above, such sodium carbonate may be the residue of an inorganic alkaline neutralising agent used to form an anionic surfactant in situ. Organic builders that may be present include polycarboxylate polymers such as polyacrylates, acrylic/maleic copolymers, and acrylic phosphinates; monomeric polycarboxylates such as citrates, gluconates, oxydisuccinates, glycerol mono-, di- and trisuccinates, carboxymethyloxysuccinates, carboxymethyloxymalonates, dipicolinates, hydroxyethyliminodiacetates, aminopolycarboxylates such as nitrilotriacetates (NTA) , ethylenediaminetetraacetate (EDTA) and iminodiacetates, alkyl- and alkenylmalonates and succinates; and sulphonated fatty acid salts. A copolymer of maleic acid, acrylic acid and vinyl acetate is especially preferred as it is biodegradable and thus environmentally desirable. This list is not intended to be exhaustive. Especially preferred organic builders are citrates, suitably used in amounts of from 2 to 30 wt%, preferably from 5 to 25 wt%; and acrylic polymers, more especially acrylic/maleic copolymers, suitably used in amounts of from 0.5 to 15 wt%, preferably from 1 to 10 wt%. The builder is preferably present in alkali metal salt, especially sodium salt, form. The granular detergent compositions may contain, in addition to any anionic and/or nonionic surfactants of the liquid binder, one or more other detergent-active compounds which may be chosen from soap and non-soap anionic, cationic, nonionic, amphoteric and zwitterionic surfactants, and mixtures thereof. These may be dosed at any appropriate stage before or during the process. Many suitable detergent-active compounds are available and are fully described in the literature, for example, in "Surface-Active Agents and Detergents", Volumes I and II, by Schwartz, Perry and Berch. The preferred detergent-active compounds that can be used are soaps and synthetic non-soap anionic and nonionic compounds. The detergent compositions may also contain a bleach system, desirably a peroxy bleach compound, for example, an inorganic persalt or organic peroxyacid, capable of yielding hydrogen peroxide in aqueous solution. The peroxy bleach compound may be used in conjunction with a bleach activator (bleach precursor) to improve bleaching action at low wash temperatures. An especially preferred bleach system comprises a peroxy bleach compound (preferably sodium percarbonate optionally together with a bleach activator) . Usually, any bleach and other sensitive ingredients, such as enzymes and perfumes, will be post-dosed after granulation along with other minor ingredients. Typical minor ingredients include sodium silicate; corrosion inhibitors including silicates; antiredeposition agents such as cellulosic polymers; fluorescers; inorganic salts such as sodium sulphate, lather control agents or lather boosters as appropriate; proteolytic and lipolytic enzymes; dyes; coloured speckles; perfumes; foam controllers; and fabric softening compounds. This list is not intended to be exhaustive . Optionally, a "layering agent" or "flow aid" may be introduced at any appropriate stage in the process of the invention. This is to improve the granularity of the product, e.g. by preventing aggregation and/or caking of the granules. Any layering agent flow aid is suitably present in an amount of 0.1 to 15 wt% of the granular product and more preferably in an amount of 0.5 to 5 wt% . Suitable layering agents/flow aids include crystalline or amorphous alkali metal silicates, aluminosilicates including zeolites, citrates, Dicamol, calcite, diatomaceous earths, silica, for example precipitated silica, chlorides such as sodium chloride, sulphates such as magnesium sulphate, carbonates such as calcium carbonate and phosphates such as sodium tripolyphosphate . Mixtures of these materials may be employed as desired. Zeolite MAP, as well as being a preferred builder, is especially useful as a layering agent. Layered silicates such as SKS-6 ex Clariant are also useful as layering agents . Powder flow may also be improved by the incorporation of a small amount of an additional powder structurant, for example, a fatty acid (or fatty acid soap) , a sugar, an acrylate or acrylate/maleate polymer, or sodium silicate which is suitably present in an amount of from 1 to 5 wt% . In general, additional components may be included in the liquid binder or admixed with the solid starting material at an appropriate stage of the process. However, solid components can be post-dosed to the granular detergent product. The granular detergent composition may also comprise a particulate filler (or any other component which does not contribute to the wash process) which suitably comprises an inorganic salt, for example sodium sulphate and sodium chloride. The filler may be present at a level of 5 to 70 wt% of the granular product. The invention will now be described in more detail in the following non-limiting Examples, in which parts and percentages are by weight unless otherwise stated. Examples denoted by a number are in accordance with the invention, while those denoted by a letter are comparative. EXAMPLES Example 1 and Comparative Example A A granular detergent product base powder of the following formulation was prepared: wt% Sodium linear alkylbenzene sulphonate (Na-LAS) 12.40 Nonionic surfactant 7EO 12.81 Soap 1.73 Zeolite MAP 36.10 Light soda ash 24.96 SCMC 0.81 Sodium citrate 3.33 Moisture, salts, NDOM 7.86 100.00 The base powder in Example 1 was prepared as follows: (i) mixing and granulating the solid particulate materials with a liquid binder in a high-speed mixer (Lδdige Recycler CB 30) for about 15 seconds, (ii) transferring the material from step (i) to a moderate- speed mixer (Lδdige Ploughshare KM 300) for about 3 minutes, (iii) transferring the material from the step (ii) to a fluid bed operating as a gas fluidisation granulator, adding further liquid binder and granulating, and (iv) finally drying/cooling the product in the fluid bed. The fluid bed in step (iii) was operated under the following conditions during the period when the liquid binder was being sprayed into the fluidising solids. Fluidisation gas temperature: 75°C Atomisation gas temperature : hot Atomisation air pressure : 3.5 bar. The liquid binder used in steps (i) and (iii) was a structured blend comprising the anionic surfactant, nonionic surfactant and soap components of the base powder. The blend was prepared by mixing 38.44 parts by weight of LAS acid precursor and 5.20 parts by weight fatty acid precursor of the soap in the presence of 41.60 parts by weight nonionic surfactant in a blend-loop and neutralising with 14.75 parts of a sodium hydroxide solution. The blend temperature in the loop was controlled by a heat-exchanger. The neutralising agent was a sodium hydroxide solution. The resulting blend had the following composition : Sodium linear alkylbenzene sulphonate 39.9 Nonionic surfactact (7EO) 41.6 Soap 5.6 Water 12.9 The pumpable temperature of the structured blend was 75°C. The weight ratio of blend added in the recycler and gas fluidisation granulator was 67:33. The base powder of Comparative Example A was prepared in the same way except that the fluidisation gas and atomisation gas temperatures were ambient. The resulting powder properties as recorded in Table 1 clearly demonstrate the benefit of elevating the temperature of the fluidising gas and atomising gas when spraying on a liquid binder. The UCT level of Example 1 is considerably better than that of Example A. - Table 1 Example 1 Comparative Example A BD (g/1) 652 593 DFR (ml/s) 131 117 UCT (g) 200 950 Example 2 and Comparative Example B A granular detergent product base powder of the following formulation was prepared: wt% Na-LAS 12.9 Nonionic 7EO 14.5 Soap 2.0 Zeolite A24 51.7 Light soda ash 9.1 SCMC 0.95 Moisture, salts, NDOM 8.85 100.00 The base powder of Example 2 was prepared as in Example 1 except that the weight ratio of blend added in the recycler and gas fluidisation granulator was 80:20. The formulation of the blend was as follows Sodium linear alkylbenzene sulphonate 39.7 Nonionic surfactant (7EO) 44.7 Soap 6.0 Water 9.6 Its pumpable temperature was 73°C. The base powder of Comparative Example B was prepared by the same method as Example 2 except that the fluidisation gas temperature was at ambient (the atomisation gas temperature remaining hot) . Details of the powder properties are given in Table 2. Comparing Example 2 with Example B, it can clearly be seen that elevating the fluidising gas temperature leads to a clear improvement in the UCT levels of the powder. The visible properties of powders also showed a marked improvement. Example B appeared quite sticky, whereas Example 2 appeared to be very well granulated, not coarse and not sticky. Table 2 Examplf a 2 Comparative Example B BD (g/1) 663344 554 DFR (ml/s) 113311 130 UCT (g) 445500 1950 Example 3 The procedure of Example 2 was repeated with both the fluidising and atomising air temperatures elevated. The powder had the following properties : BD (g/1) 648 DFR (ml/s) 132 UCT (g) <200

Claims: CLAIMS A process for preparing a granular detergent product comprising contacting a particulate solid material with a spray of liquid binder whilst fluidising the solids in gas fluidisation granulator, wherein the temperature of the fluidisation gas is elevated so as to be within 35°C, preferably within 25°C and more preferably within 15°C, of the pumpable temperature of the liquid binder. 2. A process according to claim 1, in which the atomisation gas temperature is elevated so as to be within 35°C, preferably within 25°C and more preferably within 15°C, of the pumpable temperature of the liquid binder. 3. A process according to claim 1 or claim 2, in which the temperature of the fluidising gas, and preferably also the atomising gas, is elevated for at least part of the time and preferably for substantially the entire time over which the liquid binder is being sprayed onto the fluidising solids. 4. A process according to any preceding claim, in which the temperature of the fluidising gas, and preferably also the atomising gas, are elevated and maintained near the pumpable temperature of the liquid binder. 5. A process according to any preceding claim, in which the liquid binder comprises one or more anionic surfactants or acid precursors thereof. 6. A process according to any preceding claim, in which the liquid binder comprises one or more nonionic surfactants. 7. A process according to any preceding claim, in which the liquid binder is a structured blend. 8. A process according to any preceding claim, in which the solid particulate material is treated in one or more mixers and/or granulators prior to the gas fluidisation granulator. 9. A process for preparing a granular detergent product comprising contacting a particulate solid material with a spray of liquid binder whilst fluidising the solids in gas fluidisation granulator, wherein the bed temperature is elevated so as to be within 15°C of the pumpable temperature of the liquid binder 10. A granular detergent product of bulk density less than 900 g/1 obtained according to the process of the invention.

Inventors: BAKKER VERA JOHANNA, GROOT ANDREAS THEODORUS JOHANN, KAESS ANDRE, KLAVER MARCO, VAN POMEREN ROLAND WILHELMUS J, BAKKER, VERA, JOHANNA, GROOT, ANDREAS, THEODORUS, JOHANNES, KAESS, ANDRE, KLAVER, MARCO, VAN POMEREN, ROLAND, WILHELMUS, JOHANNES
Applicants: LEVER HINDUSTAN LTD, UNILEVER NV, UNILEVER PLC, HINDUSTAN LEVER LIMITED
Application year: 2000
Main classification: C11D11
IPC codes: C11D11, C11D17