Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2001-09-28
2003-09-09
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S403000, C428S402200, C428S407000, C427S212000, C427S213000, C427S213310
Reexamination Certificate
active
06617026
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to particles comprising an active comprised in a liquid visco-elastic liquid matrix. The invention also relates to processes for the manufacture of such particles and to compositions and the use of such particles in a number of applications.
BACKGROUND OF THE INVENTION
It is known to the art to incorporate actives such as enzyme into dry solid particles and thereby protect the active from inactivation and/or protect the environment form the active. Such products have usually been applied to other dry products such as dry granular detergents compositions to improve their performance. Such particles containing an active are prepared by applying the active to a mixture of solids. Among actives, which suitably may be incorporated in dry solid particles are enzymes.
Known enzyme granule formulation technologies include:
a) Spray dried products, wherein a liquid enzyme-containing solution is atomised in a spray drying tower to form small droplets which during their way down the drying tower dry to form an enzyme-containing particulate material. Very small particles can be produced this way (Michael S. Showell (editor);
Powdered detergents;
Surfactant Science Series; 1998; vol. 71; page 140-142; Marcel Dekker).
b) Layered products, wherein the enzyme is coated as a layer around a pre-formed inert core particle, wherein an enzyme-containing solution is atomised, typically in a fluid bed apparatus wherein the pre-formed core particles are fluidised, and the enzyme-containing solution adheres to the core particles and dries up to leave a layer of dry enzyme on the surface of the core particle. Particles of a desired size can be obtained this way if a useful core particle of the desired size can be found. This type of product is described in e.g. WO 97/23606.
c) Absorbed core particles, wherein rather than coating the enzyme as a layer around the core, the enzyme is absorbed onto and/or into the surface of the core. Such a process is described in WO 97/39116.
d) Extrusion or pelletized products, wherein an enzyme-containing paste is pressed to pellets or under pressure is extruded through a small opening and cut into particles which are subsequently dried. Such particles usually have a considerable size because of the material in which the extrusion opening is made (usually a plate with bore holes) sets a limit on the allowable pressure drop over the extrusion opening. Also, very high extrusion pressures when using a small opening increase heat generation in the enzyme paste, which is harmful to the enzyme. (Michael S. Showell (editor);
Powdered detergents;
Surfactant Science Series; 1998; vol. 71; page 140-142; Marcel Dekker).
e) Prilled products, wherein an enzyme powder is suspended in molten wax and the suspension is sprayed, e.g. through a rotating disk atomiser, into a cooling chamber where the droplets quickly solidify (Michael S. Showell (editor);
Powdered detergents;
Surfactant Science Series; 1998; vol. 71; page 140-142; Marcel Dekker). The product obtained is one wherein the enzyme is uniformly distributed throughout an inert material instead of being concentrated on its surface. Also U.S. Pat. Nos. 4,016,040 and 4,713,245 are documents relating to this technique.
f) Mixer granulation products, wherein an enzyme-containing liquid is added to a dry powder composition of conventional granulating components. The liquid and the powder in a suitable proportion are mixed and as the moisture of the liquid is absorbed in the dry powder, the components of the dry powder will start to adhere and agglomerate and particles will build up, forming granulates comprising the enzyme. Such a process is described in U.S. Pat. No. 4,106,991 (NOVO NORDISK) and related documents EP 170360 B1 (NOVO NORDISK), EP 304332 B1 (NOVO NORDISK), EP 304331 (NOVO NORDISK), WO 90/09440 (NOVO NORDISK) and WO 90/09428 (NOVO NORDISK). In a particular product of this process wherein various high-shear mixers can be used as granulators, granulates consisting of the enzyme, fillers and binders etc. are mixed with cellulose fibers to reinforce the particles to give the so-called T-granulate. Reinforced particles, being more robust, release less enzymatic dust (vide infra).
Known enzyme formulations are to day either “dry formulations”, i.e. consisting of agglomerates of solid particles or “liquid formulations”, i.e. liquids containing solutions or suspensions of enzymes/enzyme particles.
WO 00/10700 disclose a method for producing particle-shaped immobilizates of a substrate in a supporting material, according to which the substrate and supporting material form a moderately to highly viscous and possibly viscoelastic mixture and the structure of the immobilizates is fixed in a liquid medium only after preparation of the mixture of supporting material and substrate.
WO 00/21504 disclose encapsulation of sensitive liquid components into a matrix to obtain discrete shelf-stable particles.
WO 01/25323 disclose elastic articles comprising a polymeric matrix and an active.
SUMMARY OF THE INVENTION
One object of the present invention is to provide new and safer ways to use and handle active substances, such as enzymes. For actives it is generally desired to separate them from their surroundings until the moment when they are to be used in an application. This has generally been achieved by incorporating the active in discrete particles. Incorporation of the active in a particle also serves the purpose of lowering the amount of potentially harmful active dust, which may be generated from the active. The present invention relates to such improved particles and provide a particle comprising an active dispersed in a visco-elastic liquid matrix, wherein the visco-elastic parameters &eegr;′ and &eegr;″ are between 10
3
to 10
14
Pa measured in a cone-and-plate rheometer at 25° C. and a sinusoidal frequency, &ohgr;, of 1 Hz.
The invention also provides methods for preparation of the particles and compositions comprising the particles.
DETAILED DESCRIPTION OF THE INVENTION
When handling dry solid compositions comprising an active, one of the major problems is the formation of dust from the active, which may be harmful to persons handling the dry solid composition. This problem does usually not occur when an active is present in a liquid composition because the surrounding liquid effectively suppresses dust formation. However, for other properties, such as stability of the active, dry solid compositions are usually far superior to liquid compositions because an active may more effectively be separated from other ingredients and dry compositions does not usually provide a medium in which the active may be degraded.
Although the active may be incorporated in dry solid particles as known to the art, which may inhibit the formation of active dust it is a fact that active dust may still be released from the particles, e.g. as measured by the known Heubach Method.
We have found that is possible to prepare liquid particles incorporating an active, wherein the particles, although being liquid, at certain conditions may be processed and prepared as solid particle. The reason why the proposed particles have a very low dust release is that a liquid never or rarely develop dust as long as the liquid does not atomise, which will be impossible due to the extreme high viscosities and the visco-elastic properties. It is contemplated that the viscosity needs to be below 100-500 mPa to be atomised, whereas the visco-elastic liquid matrix of the present invention have viscosities above 10
3
Pa.
The particle of the invention has in particular a shell core configuration, wherein the core is a particle comprising an active dispersed in a liquid visco-elastic matrix having a &eegr;′ and a &eegr;″ between 10
3
to 10
14
Pa at 25° C. and the coating is any coating material.
Definitions
The term “solid” as used in the context of this invention is to be understood as a property of a material. A solid material is defined as a material for which a certain amount of stress, i.e
Garbell Jason
Kiliman Leszek
Lambiris Elias
Novozymes A/S
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