Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
  • B01J2/10—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic in stationary drums or troughs, provided with kneading or mixing appliances
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
  • B01J2/12—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic in rotating drums

Definitions

• TITLE A METHOD FOR IMPROVING PARTICLE COMPOSITIONS
• the present invention relates to a method for improving the properties of a particulate starting material or composition by high shear treatment.
• the method comprises subjecting a particulate starting material and a liquid to high shear treatment optionally followed by separating a desired fraction of particles, wherein the treated particles in particular the desired fraction of particles obtained by separation is smoother and has a higher average particle strength compared to the particulate starting material, in particular the same fraction obtained from the starting particulate material.
• a problem may occur when the particles are exposed to shear or impact, as the particles may generate dust due to abrasion, which especially is a problem if the surface roughness of the particles is high. If furthermore the particles are weak they will also be sus- ceptible to breaking due to the forces imposed upon them thus resulting in further formation of dust. As dust may be harmful to man it is desirable to obtain particles with high particle strength which exhibits resistance to breakage and/or to obtain particles which have smooth surfaces to avoid dust formation when they get exposed to shear and impact.
• the present invention is useful whenever it is desired to improve particle strength and/or smoothness of a composition of particles.
• the high shear treatment destroys the weak- est particles of the particulate starting material to be improved are.
• Particles for which this invention is of interest may be particles comprising active compounds in particular enzyme containing granules.
• said process is useful to produce tough smooth inert particle fractions to be used as carrier materials, cores or seeds in a number of applications, within pharmaceutical industry, baking industry, candy industry, food industry, feed industry, fertilizer industry etc.
• Inert particles used as carrier materials, cores or seeds are known e.g. from the so called non-pareil seeds, which are characterised by spherical particles that have been prepared by agglomeration.
• the inert particles of the present invention differ from ordinary non-pareil seeds by not being agglomerated into particles but comprise a dense homogenous matrix optionally covered with a layer of binder-matrix. Furthermore, this preparation method is a much more cost effective production method compared to the production method of non-pareil seeds. Furthermore the particles are readily dispersible or soluble in water, preferably fully soluble in water.
• one object of the present invention is to provide a method for preparing and/or selecting particles which have improved particle strength and/or satisfactory surface smoothness and/or which release low amounts of dust during handling.
• the present invention provides a method for preparing particu- late composition having improved average strength of particles comprising contacting a particulate starting material with a liquid and subjecting the mixture to high shear at a rate substantially avoiding agglomeration of particles.
• the invention provides a particulate composition obtainable by the method of the invention.
• the strain is greater than the forces upholding the integrity of the solid particle (the yield point) the solid particle is no longer able of counteracting the strain, and the strain will cause damage to the physical integrity of the solid particle, which may release dust from the solid particle. This may happen when the particle is exposed to shear or impact, especially particles with high surface roughness cause friction and the edges and comers on the surface of the particle will act as weak areas which are susceptible to breaking off as fragments of the particle or to induce breakage of the entire particle.
• Particles for which this is of particularly high relevance are granules containing active compounds such as enzyme granules or .granules comprising pharmaceutical agents or granules known from the fertilizer industry and feed industry, where the formation of dust is an issue of great importance.
• Other particles for which it is important not to form dust and to have smooth surfaces are inert particles which are being used as seeds in further granulation proc- esses, it is important the particles are able of withstanding the strain exposed to them during further processing to avoid breakage and as a result formation of dust.
• Another issue is to increase the amount of useful seeds which end up as finished granules, which is done by removing weak particles, which are likely to break during further processing.
• the particles are smooth, as sharp edges and corners may act as weak areas, which are especially exposed to rupture or abrasion in which dust is formed. Furthermore, if particles with high surface roughness are coated, the coating has to be of a certain thickness to avoid edges and corners of the particle from sticking out of the coating. If the coating is too thin corners will stick out of the coating and act as weak areas on the finished granule which are susceptible to breaking off or even induce breakage of the entire granule and by that generate dust. Therefore as a first object it is desirable to provide a process for preparing particles with high particle strength and/or smoothness.
• inert particles such as seeds for enzyme granulation
• coating/granulation processes such as in fluid bed processes
• large particle sizes of the particulate material may cause problems, especially if the method is used to produce seeds which have to be below a certain size, so that the end product does not become too large. It may therefore be desirable to work with particulate materials with high densities to be able to keep the small particle sizes.
• a problem may occur if the particles to be treated with high shear start to coalesce by agglomerating during the high shear treatment. It is desirable to avoid the agglomeration of the particles.
• One way of avoiding coalescence is to control the particle sizes, the density of the particles, the amount of liquid added and the high shear rate, see the section "Coalescing theory".
• the particles are readily dispersible or soluble in water and often it is desired to have fully soluble particles, e.g. enzymes particles and inert particles used as carrier materials or seeds which are often used in products where it is desirable that the product is readily dispersible or soluble in water and often fully soluble. Therefore it may be important that the materials used to produce said particles are readily dispersible or soluble in water and preferably fully soluble in water.
• the present invention is a very cost effective way of preparing water soluble inert particles with higher particle strength than compared to ordinary non-pareil seeds.
• Granules/particles The terms “particle” and “granulate” or “granule” are intended to be understood as the same as predominantly spherical or near spherical structures of a macromolecular size.
• V r V imp /V Where V r is the relative swept volume ratio, V imp is the swept volume which is the swept area multiplied with the speed, and V is the volume of the apparatus chamber where the high shear process is taking place. See “Relative Swept Volume ratio”: ref. Ennis and Lister “The Science & Engineering of Granulation Processes", 1996.
• V r When V r is between 0.5 and 3.0 s "1 it is a high shear process.
• particle starting material is meant the particles chosen to be exposed to the method of the present invention.
• St v is the viscous Stokes number
• p the density of the granules
• v 0 the initial velocity
• a the granule radius
• ⁇ the viscosity of the liquid layer
• St v * is the critical viscous Stokes number
• e the coefficient of restitution
• h the thickness of the surface liquid layer
• h a is a characteristic length of the surface asperities.
• Ennis et al. then proceeded to state that for a successful collision between two granules to occur, the viscous Stokes number had to be less than or equal to the critical viscous Stokes number.
• substantially avoiding agglomeration of particles means that no major portions of particles of a particulate composition agglomerates.
• minor portions of individual particles may adhere to or agglomerate to each other, while, however, this particulate material may not be characterized as agglomerated.
• the skilled person would readily comprehend the meaning of the term "substantially avoiding agglomeration of particles as meaning that although in principle all particles is kept as single unagglomerated particles, insignificant levels of agglomeration of particles may still occur, without affecting the overall properties of the composition.
• substantially avoiding agglomeration of particles means that more than 80 %, in particular more than 85 %, in particular more than 90 %, in particular more than 95 %, most particular more than 98 % of the un-agglomerated particles in the particulate starting material is kept in the unagglomerated form.
• SPAN value is a measure of the breadth the particle size distribution (PSD) and is defined as:
• the mean mass diameter, D50 is the diameter at which 50% of the enzyme particles, by mass, have a. smaller diameter, while 50% by mass have a larger diameter.
• the values D10 and D90 are the diameters at which 10% and 90%, respectively, of the particles, by mass, have a smaller diameter than the value in question. The smaller the SPAN value is, the narrower the particle size distribution is.
• Fraction By the term “fraction” is meant a particular part of the entire amount of particulate material which has a desired particle size, e.g. 300 micrometer to 600 micrometer, which has been separated from the rest e.g. by sieving. By comparison of the "same fraction” is meant comparison of particles obtained before and after the particulate material has been exposed to the method of the present invention with specific particle sizes e.g. 300 to 600 micrometer.
• dust particles which may be adhering to the surfaces of the particles after the high shear treatment, is meant fragments of whole particles, which usually have a considerably smaller size than the particles of the particulate material. Dust particles typically have an irregular non- spherical a nd a brupt structure s uch as rod or flake s haped. D ust p articles a re typically m uch smaller than the average size of the particles of the particulate material, and most dust particles are, depending on the particulate material, less than 20 micrometer in diameter.
• This shape factor has a maximum value of 1 for a true spherical particle. It defines roundness and can be used to measure departures from circularity or surface smoothness.
• the shape factor is dimensionless since shape does not depend on size.
• the divisor and divi- dend must have the same units, e.g. area/length x perimeter or it may be a number, such as the number of corners per grain.
• the shape factor is also independent of the orientation of the feature.
• the perimeter p should be used with caution since its value depends on the resolution of the measuring instrument.
• Water soluble particulate materials or fractions of materials in the context of the present invention are understood to be particulate materials of fractions of materials of which at least 50 g/l and more particularly, at least 80 g/l dissolve in water at a temperature of 30°C.
• the particle density is defined as the mass of particles divided by the volume of a liquid which is displaced by particles.
• the liquid is chosen so that it does not dissolve the particles and it is preferably a viscous liquid.
• the displaced volume is measured using a pkynometer flask.
• the density of the chosen liquid is measured at the applied temperature as part of the procedure.
• the particulate starting material of the present invention can be ny composition of particulate material which average particle strength or smoothness or both needs improvement.
• the par- ticulate materials may be selected from but are not limited to granules comprising active compounds such as pharmaceutical granules, enzyme granules, fertilizer granules, and the particulate material may further be selected from inert particles, such as particles comprising a salt or a carbohydrate or a combination.
• the particulate starting material is granules comprising active compounds
• the active compounds present in the particulate starting material are enzymes.
• the particulate starting material comprises, contains or consist an inorganic or organic carrier compound.
• This compound is in particular selected from the group of salts and carbohydrates, in a more particular embodiment the particulate starting material is selected from the group of salts and sugars.
• the particulate starting materials are inert particles.
• inert particles such as salt or sugar particles are used as particulate starting material.
• the particulate starting materials are chosen from crystalline material.
• the particulate material is water soluble.
• the particulate starting material particularly has a density of at least 1.1 g/cm 3 , more particular the particulate material has a density f at least 1.3 g/cm 3 , more particular the particulate material has a density of at least 1.5 g/cm 3 , even more particular the particulate material has a density of at least 2.0 g/cm 3 and most particular the particulate material has a density of at least 2.5 g/cm 3 .
• the particulate material is characterised by having a particle size, in particular an average particle size of at least 50 micrometer, more particular of at least 100 micrometer and most particular of at least 200 micrometer.
• the particulate material is characterised by having a particle size, especially an average particle size, of less than 800 micrometer such as less than 600 ⁇ i ⁇ po ⁇ p. More particularly the particulate material is characterised by having a particle size, especially an average particle size, from 300 micrometer to 600 micrometer.
• the granules comprising enzymes which are relevant as particulate starting materials for the present invention may be any particle comprising enzymes at a ny stage during the manufacture of enzyme granules, where it is appropriate to use the method of the present invention.
• the salts suitable as particulate starting materials, and as additional materials, in the present invention may be inorganic salts, e.g. salts of sulfate, sulfite, phosphate, phosphonate, nitrate, chloride or carbonate or salts of simple organic acids (less than 10 carbon atoms e.g. 6 or less carbon atoms) such as citrate, malonate or acetate.
• inorganic salts e.g. salts of sulfate, sulfite, phosphate, phosphonate, nitrate, chloride or carbonate or salts of simple organic acids (less than 10 carbon atoms e.g. 6 or less carbon atoms) such as citrate, malonate or acetate.
• simple organic acids less than 10 carbon atoms e.g. 6 or less carbon atoms
• alkali or earth alkali metal ions ammonium ion or metal ions of the first transition series, such as sodium, potassium,
• anions include chloride, bromide, iodide, sulfate, sulfite, bisulfite, thiosulfate, phosphate, monobasic phosphate, dibasic phosphate, hypophosphite, dihydrogen pyrophosphate, tetraborate, borate, carbonate, bicarbonate, metasilicate, citrate, malate, maleate, malonate, succinate, lactate, formate, acetate, butyrate, propionate, benzoate, tartrate, ascorbate or gluconate.
• alkali- or earth alkali metal salts of sulfate, sulfite, phosphate, phosphonate, nitrate, chloride or carbonate or salts of simple organic acids such as citrate, malonate or acetate may be used.
• Specific examples include Na 2 HPO 4 , Na 3 PO 4 , (NH 4 )H 2 PO 4 , KH 2 PO 4 , Na 2 SO , K 2 SO 4 , KHSO 4 , ZnSO 4 , MgSO 4 , CuSO 4 , Mg(NO 3 ) 2 , (NH 4 ) 2 SO 4 , sodium borate, magnesium acetate and sodium citrate.
• the soluble salt may also be a hydrated salt, i.e. a crystalline salt hydrate with bound water(s) of crystallization, such as described in WO 99/32595.
• hydrated salts include magnesium sulfate heptahydrate (MgSO 4 (7H 2 O)), zinc sulfate heptahydrate (ZnSO 4 (7H 2 O)), copper sulfate pentahydrate (CuSO 4 (5H 2 O)), sodium phosphate dibasic heptahydrate (Na 2 HPO 4 (7H 2 O)), magnesium nitrate hexahydrate (Mg(NO 3 ) 2 (6H 2 O)), sodium borate decahydrate, sodium citrate dihydrate and magnesium acetate tetrahydrate.
• Suitable carbohydrates of the present invention may be selected from but are not limited to pectin, starch, modified starch, cellulose, modified cellulose, carrageenan, gum Arabic, acacia gum, xanthan gum, locust bean gum, guar gum, sugars such as monosaccharides e.g. glucose an fructrose, disaccharides e.g. sucrose, polysaccharides e.g. Hyaluronic acid and dextrin. As employed, in the.
• modified starch de. ⁇ _ notes a s tarch ( native s tarch), w hich h as u ndergone s ome kind o f a 1 1 east p artial c hemical modification, enzymatic modification, and/or physical or physicochemical modification, and which - in general - exhibits altered properties relative to the "parent" starch.
• Relevant c hemical m odifications i n include, b ut a re n ot I imited to: e sterification of h y- droxy groups (achieved, e.g. via acetylation); etherification of hydroxy groups; oxidation (achieved, e.g. via reaction with chlorine or hypochlorite); and cross-linking (achieved, e.g. by reaction with formaldehyde or epichlorohydrin).
• Relevant enzymatic modifications include, for example, treatment with a starch- degrading or starch-modifying enzyme, e.g. an amylase, such as an ⁇ -amylase or glucoamy- lase.
• gelatinisation in particular, so-called gelatinisation.
• gelatinised in the context of starch, is used herein in accordance with usage in the art (see, e.g. A. Xu and P.A. Seib, Cereal Chem. 70 (1993), pp. 463-470).
• Starches naturally occurring starches from a wide variety of plant sources appear to be suitable in the context of the invention (either as starches per se, or as the starting point for modified starches), and relevant starches include starch from: rice, corn, wheat, potato, oat, cassava, sago-palm, yuca, barley, sweet potato, sorghum, yams, rye, millet, buckwheat, arrowroot, taro, tannia, and may for example be in the form of flour.
• Cassava starch is among preferred starches in the context of the invention; in this connection it may be mentioned that cassava and cassava starch are known under various synonyms, including tapioca, manioc, mandioca and manihot.
• the particulate material is a carbohydrate, in a more particular embodiment of the present invention the particulate material is a sugar.
• the particles a re soluble in water. This applies to large number of particles such as enzyme granules, fertilizer granules, detergent granules, inert particles used as seed in production of enzyme granules or pharmaceutical granules etc.
• a liquid may be added to the high shear process.
• a liquid may be added to the high shear treatment.
• the amount of liquid and the high shear rate is adjusted to suppress agglomeration.
• the control is obtained by adjusting the high shear rate and/or the amount of liquid added and/or the viscosity of liquid added.
• the liquid can be a liquid or a liquid composition, such as a dispersion, a solution or an emulsion.
• the liquid can be but is not limited to water and oils particularly vegetable oils.
• the liquid is water.
• the liquid is an aqueous composition.
• the liquid is an emulsion.
• Additional materials may be added to the liquid to form a liquid composition. Suitable additional materials may be but are not limited to salts, carbohydrates, binders, fibres, fillers, or other conventional coating materials.
• the liquid is a saturated solution of one or more or compounds present in the particulate material.
• the additional material added to the liquid of the present invention is found to improve the process either by improving the smoothness of the particulate material or by controlling the dissolving of the particulate material.
• the amount of liquid added to the high shear treatment is of great importance. If a too high amount of liquid is added to the particulate material, the composition exposed to the high shear process will become too sticky and the particulate material will start agglomerating.
• the amount of liquid added to the high shear treatment is not exceeding 20 % by weight, in a more particular embodiment the amount of liq- uid added to the high shear treatment is not exceeding 15% by weight, in an even more particular embodiment of the present invention the amount of liquid added to the high shear treatment is not exceeding 10 % by weight.
• Additional materials Components which may be additionally added to the high shear treatment process e.g. to improve the smoothness of the obtained granules are salts, polysaccharides, binders, fibres, fillers including anti-dusting or anti-caking materials such as cellulose fibres or finely divided silicium dioxide or other conventional coating materials. These materials may be added to the liquid or on their own. We have further found that addition of certain components on their own to the high shear treatment process has a positive influence on the smoothness of the obtained granules. Salts and carbohydrates are mentioned above.
• Binders include materials with a high melting point or no melting point at all and which are of a non waxy nature e.g. polyvinyl pyrrolidon, dextrins, polyvinylalkohol, cellulose derivatives, for example hydroxypropyl cellulose, methyl cellulose or CMC.
• a suitable binder is a carbohydrate binder such as Glucidex 21 D available from Roquette Freres, France.
• wax as used herein is to be understood as a compound having a melting point b etween 20-150°C.
• P referred waxes a re o rganic compounds o r s alts of o rganic compounds having a melting point in the said range.
• wax as used herein also encompasses mixtures of two or more different waxes.
• an important feature of the wax or mixture of waxes is that the wax should be water soluble or water dis- persible, particularly in neutral and alkaline solution, so that when the coated particles of the invention are introduced into an aqueous solution, i.e.
• the wax should disintegrate and/or dissolve providing a quick release and dissolution of the active compound incorporated in the particles to the aqueous solution.
• water soluble waxes are poly ethylene glycols (PEG's). Accordingly amongst water soluble waxes the solubility of wax in water should in particular be up to 75 parts wax to 25 parts water.
• the wax of the invention may be any wax, which is chemically synthesized. It may also equally well be a wax isolated from a natural source or a derivative thereof. Accordingly, the wax of the invention may be selected from the following non limiting list of waxes:
• Poly ethylene glycols abbreviated PEG, type of wax. Different PEG waxes are com- briefly available having different molecular sizes, polypropylene or polyethylene or mixtures thereof.
• Nonionic tensides which are solid at room temperature such as ethoxylated fatty alcohols having a high level of ethoxy groups such as Lutensol AT80 from BASF having 80 units of ehtyleneoxide per molecule ⁇ -
• polymers of ethyleneoxide, propyle-- neoxide or copolymers thereof are useful, such as in block polymers, e.g. Pluronic PE
• Waxes isolated from a natural source such as Carnauba wax, Candelilla wax and bees wax.
• Other natural waxes or derivatives thereof are waxes derived from animals or plants, e.g. of marine origin.
• - Fatty acid alcohols such as the linear long chain fatty acid alcohol NAFOL 1822 (C18,
• waxes which are useful in the invention can be found in CM. McTaggart et. al., Int. J. Pharm. 19, 139 (1984) or Flanders et.al., Drug Dev. lnd. Pharm. 13, 1001 (1987) both incorporated herein by reference.
• Polypeptide may be selected from gelatin, collagen, casein, chitosan poly aspartic acid and poly glutamatic acid.
• Synthetic polymers may be selected from polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), polyvinyl acetate, polyacrylate, polymethacrylate, poly-acrylamide, polysulfonate, polycarboxylate, and copolymers thereof, in particular water soluble polymers or copolymers.
• PVP polyvinyl pyrrolidone
• PVA polyvinyl alcohol
• PV acetate polyacrylate
• polymethacrylate poly-acrylamide
• polysulfonate polycarboxylate
• copolymers thereof in particular water soluble polymers or copolymers.
• Fibre materials can be but are not limited to pure or impure cellulose in fibrous form. This can be sawdust, pure fibrous cellulose, cotton, or other forms of pure or impure fibrous cellulose. Also, filter aids based on fibrous cellulose can be used. Several brands of cellulose in fibrous form are on the market, e.g. CEPO TM and ARBOCELL TM . Pertinent examples of fibrous cellulose filter aids are Arbocel BFC200 TM and Arbocel BC200 TM . Also synthetic fibers may be used as described in EP 304331 B1 and typical fibers may be made of polyethylene, polypropylene, polyester, especially nylon, polyvinylformate, poly(meth)acrylic compounds. In a particular embodiment of the present invention the fraction obtained in (d) is water soluble.
• the method of the invention is a method for preparing a particu- late composition having improved average strength of particles comprising contacting a particulate starting material with a liquid and subjecting the mixture to high shear at a rate substantially avoiding agglomeration of particles.
• the high shear treatment destroys weak particles leaving the stronger particles, meaning that the weaker particles break into minor particles which can be separated from the intact stronger particles.
• the method further includes isolating a fraction of the treated particulate composition so as to remove any remains of broken particles and/or oversized portions of agglomerated particles from the resulting product.
• the isolated fraction comprises, contains or consists of unbroken or whole particles f rom the particulate starting material and have a higher average particle strength that the particles of the particulate starting material.
• the method of the invention is a method for improving average particle strength of a particulate material comprising: (a) providing a particulate starting material to be improved (b) providing a liquid
• a fraction of the particulate starting material is chosen or selected for the high shear treatment for example by screening or sieving to obtain the right parti- cle size. Too small particle sizes may result in agglomeration of the particles during high shear treatment which is undesired as agglomerated particles are porous and less tough compared to the product obtained by the present invention. On the other hand it is in some cases important that the particle sizes of the starting materials are not too large, as the end product then will be too large. This is especially relevant when employing the method of the present inven- tion on inert particles which are to be used as seeds in further processing, e.g. for use in manufacturing of enzyme containing granules or pharmaceuticals.
• the lower sieve being used is a 200 micrometer sieve in a more particular embodiment the lower sieve being used is a 300 micrometer sieve.
• the upper sieve being used is an 800 micrometer sieve, in a more particular embodiment the upper sieve being used is a 600 micrometer sieve.
• the particulate starting material fractioned or un-fractioned, is added to the high shear apparatus, simultaneously, before or after adding the liquid to the high shear apparatus.
• the particulate materials and liquid are exposed to high shear treatment until a desired low level of weak particles has been reached or a desirable amount of weak particles has been destroyed.
• the particulate starting material and liquid is exposed to high , shear until at least 5 %, in particular at least 10 %, more particu- larly at least 15 % of the particles are destroyed or broken down to a size outside the size distribution of the particulate starting material
• the high shear treatment may be in a high shear mixer apparatus such as in a L ⁇ dige mixer or similar drum type mixers.
• the high shear treatment is taking place in a high shear mixer and the high shear is measured to be in the range of 0.5 s "1 and 3 s "1 .
• the particulate material may be dried in an apparatus suitable for drying particles, e.g. a fluid bed apparatus, flash dryer, ring flash dryer or other convective drying apparatuses.
• a high amount of dust may be formed. Some of that dust may still adhere to the surface of the finished particulate material after the high shear step. The removal of such dust particles present on the particles happens during the drying step.
• the treatment comprise the step of drying the particulate material, in particular before any steps sifting or screen- ing the product into desired fractions.
• the finished particulate materiel is screened with a lower size sieve of 300 micrometer and an upper size sieve of 600 micrometer to obtain a desired fraction, or a lower sieve of 250 micrometer and an upper sieve of 500 micrometer.
• the particle size of the fraction obtained during the separation step of the present invention is particularly 200 to 800 microme- ter with a mean particle size of 450 micrometer, in a more particular embodiment the particle size of the fraction obtained during the separation step of the present invention is particularly 300 to 600 micrometer.
• a desired fraction of particles obtained by separation after the high shear treatment has a higher average particle strength compared to a comparable fraction obtained from the particulate starting material. Furthermore the particles of such desired fraction are smoother than comparable particles of the particulate starting material.
• the high shear treatment may be done any number of times until no more improvement can be achieved.
• the i mprovement i n particle strength is measured by comparing of the high shear treated product with the particulate starting material, especially comparable fractions thereof, on the ability to withstand stress without breaking.
• the invention also provides a particulate composition obtainable from the method of the inven- tion.
• the particle strength of the particles can be tested by a standard Attrition Shear Cell where it is tested how much stress the particles can withstand before breakage.
• the average particle strength of a particulate composition can be measured and compared to that of another composition.
• the first composition have a higher average particle strength.
• the particles of the particulate composition have a strength so that at least 95 wt % of the particles are capable of withstanding 20 kPa in an AJAX stan- dard attrition shear cell, more particularly at least 95 wt % of the particles are capable of withstanding 25 kPa in an AJAX standard attrition shear cell.
• the particulate composition if the invention is enzyme granules
• at least 97 wt % of the granules are preferably is capable of withstanding 20 kPa in an AJAX standard attrition shear cell.
• An attrition shear cell is described by Neil and Bridgwater "Attrition of particulate solids under shear", Powder Tech-nology, vol 80, pp. 207-219, 1994.
• the extent of breakage is in particular below 6 wt % when exposed to normal stresses of 0 to at least 30 kPa in an AJAX standard attrition shear cell, more par- ticular the extent of breakage is in particular below 5 wt % when exposed to normal stresses of 0 to at least 30 kPa in an AJAX standard attrition Cell.
• the smoothness of the particles can be described by a shape factor, ⁇ , see the section "Definitions".
• One way of determining the perimeter p is by use of following equipment and software:
• a picture of the particles is digitalized using Photoshop, which subsequently calculates A and p.
• the particles of the particulate starting material will typically have a shape factor ⁇ ⁇ 0.5 while the particles of the composition if the invention will have a shape factor ⁇ > 0.5.
• the shape factor, ⁇ , of the particulate starting material is less than 0.5 before the high shear treatment and the shape factor, ⁇ , of the particles obtained by the method is greater than 0.5, such as 0.6 or 0.7 after the high shear treatment.
• the shape factor of the particulate starting material is improved by at least 0.1 , such as least 0.2 for example least 0.3 during the high shear treatment.
• Example 1 A mixture of:
• the processed wet product is subsequently dried in a fluid bed using an inlet temperature of 90 °C until the product temperature reaches 60 °C.
• the dried product is screened using a lower (fines) sieve of 300 micrometers and an upper (coarse) sieve of 600 micrometers.
• the physical yield was found to be:
• Table 1 is given the extent of breakage of three different fractions of particulate material when exposed to increasing levels of stress.
• the first fraction is the produced particulate material, Na 2 SO , which has been exposed to the high shear treatment
• the second fraction is untreated particulate starting material, "raw salt”
• the third fraction is a commercial avail- able non-pareil core.
• the comparison was made on sieved fractions with particle sizes of 300 to 600 micrometer.
• An AJAX standard Attrition Shear Cell was used.
• the industrial relevant normal stresses the inert particles used as seeds or cores have to resist are above 15 - 20 kPa. It is seen from table 1 that the fraction of the treated material on an average has improved significantly compared to the untreated "raw salt” and that the parti- cle strength of the treated particles is much higher than the particle strength of the non-pareil cores.
• a mixture of 900 g Maltose dextrin and 5000 g water is prepared. T his mixture is added to a batch of 20 kg of Sodium sulphate crystals in the size range 250 to 500 microns using a 50 L L ⁇ dige high shear mixer. The shovels are run at a speed of 80 rpm and the chop- per is run at 800 rpm. The dosing is done in 60 sec. using a total amount of 10 % by wt of the dry cores added. Processing of the batch continues for 120 sec. after the dosing step using a shovel speed of 100 rpm and a chopper speed of 1000 rpm.
• the processed wet product is subsequently dried in a fluid bed using an inlet temperature of 90°C until the product temperature reaches 60°C.
• the dried product is screened using a lower (fines) sieve of 250 microns and an upper
• a mixture of 3000 g Sodium Sulphate and 7000 g water is pre-pared. This mixture is added to a batch of 20 kg of Sodium sulphate crystals in the size range 250 to 500 microns using a 50 L ⁇ dige high shear mixer.
• the shovels are run at a speed of 80 rpm and the chop- per is run at 800 rpm.
• the dosing is done in 60 sec. using a total amount of 10 % by wt of the dry cores added. Processing of the batch continues for 120 sec. after the dosing step using a shovel speed of 100 rpm and a chopper speed of 1000 rpm.
• the processed wet product is subsequently dried in a fluid bed using an inlet tempera- ture of 90°C. until the product temperature reaches 60°C.
• the dried product is screened using a lower (fines) sieve of 250 microns and an upper (coarse) sieve of 500 microns.

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• Enzymes And Modification Thereof (AREA)
• Glanulating (AREA)
• Detergent Compositions (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

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• 2003
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