Compositions – Solids with solution or dispersion aids
Reexamination Certificate
1998-04-24
2001-10-09
Warden, Jill (Department: 1743)
Compositions
Solids with solution or dispersion aids
C428S402000, C428S403000, C516S931000
Reexamination Certificate
active
06299798
ABSTRACT:
The present invention relates to water-redispersible granules comprising an active ingredient in liquid form.
In some industries, such as the food, cosmetics or paint industries, formulations are prepared from active ingredients in the form of a hydrophobic liquid. One formulation possibility is to prepare oil-in-water emulsions of such ingredients.
However, such emulsions cause stability problems on storage. The phases of the emulsion constituents are seen to separate to a greater or lesser extent. Further, there may be problems with deactivation of the active ingredient to contend with, the active ingredient possibly degrading by hydrolysis during storage.
Finally, the fact that in order to be readily manipulatable and pumpable, such formulations must contain relatively low quantities of active ingredient and a large amount of water cannot be ignored.
The present invention aims to provide an original alternative to the problems mentioned above in that the formulations proposed are powders containing high concentrations of active ingredient initially in the form of a hydrophobic liquid.
Thus the invention provides water-redispersible granules, obtained by mixing then drying at least one active ingredient, at least one principal surfactant, and at least one hydrosoluble compound and comprising:
at least one active ingredient in the form of a hydrophobic liquid;
at least one principal surfactant for which the binary water-surfactant phase diagram comprises an isotropic phase which is fluid at 25° C. up to a concentration of at least 50% by weight of surfactant followed, at high concentrations, by a hexagonal, cubic or lamellar type liquid crystal phase which is stable up to 65° C.;
at least one hydrosoluble compound.
The invention also provides a process for preparing such granules consisting of carrying out the following steps:
preparing an emulsion of at least one active ingredient, at least one principal surfactant, and at least one hydrosoluble compound;
drying the emulsion obtained.
More particularly, the invention provides water-redispersible granules obtained by drying an oil-in-water emulsion comprising:
at least one active ingredient in the form of a hydrophobic liquid;
at least one hydrosoluble compound which can form a continuous solid film during drying which traps droplets of the hydrophobic active ingredient;
water
and at least one principal surfactant in which the binary water-surfactant phase diagram comprises an isotropic phase which is fluid at 25° C. up to a concentration of at least 50% by weight of surfactant followed, at high concentrations, by a hexagonal, cubic or lamellar type liquid crystal phase which is stable up to 65° C.
The granules of the present invention have a number of advantages.
Firstly, their conformation can avoid all of the problems of using emulsions. Thus problems of instability on storage are avoided, such as creaming, flocculation, ageing and coalescence. These different phenomena have been described in the “ENCYCLOPEDIA OF EMULSIONS TECHNOLOGY”, volume 1, by Paul BECHER published by MARCEL DEKKER INC., 1983.
A further advantage of the present invention is that the concentrations of active ingredients can be very high compared with emulsions. As a result, during use of these granules, a smaller quantity of granules will suffice.
Further, the conformation of the invention can overcome the problem of deactivation of the active ingredient when it is sensitive to hydrolysis.
The present invention can also provide a pre-formulation in the form of granules which are thus easier to use than emulsions, for example in the case where the pre-formulation is added to a powder formulation.
Further, the granules of the invention, prepared from an emulsion, have the advantage of redispersing spontaneously in water, to produce again an emulsion with a granulometry close to that of the initial emulsion.
Finally, the present invention provides a solution to the problems of liquid product conformations which are normally formulated by absorption on a support. The concentration of active ingredient in such formulations is often low and there may be phase separation between the support and the active ingredient by migration of the active ingredient during storage.
Further advantages and characteristics will become clearer from the following description and examples.
As indicated above, the granules of the invention comprise at least one active ingredient in the form of a hydrophobic liquid.
All active ingredients are suitable provided that at ambient temperature they are in the form of a liquid which is non miscible in or very slightly miscible with water or are dissolved in an organic solvent.
The term “slightly miscible” means active ingredients or solvents with a solubility in water not exceeding 10% by weight.
The term “active ingredient” means either pure active ingredient or active ingredient dissolved in a solvent, or a solvent.
Examples of active ingredients in the food industry are mono-, di- and tri-glycerides, essential oils, flavourings, and colorants.
Examples of active ingredients in the cosmetics industry are silicone oils, for example from the dimethicone family.
Examples of active ingredients suitable for implementing the invention in the paint industry are alkyd resins, epoxy resins, and block or non blocked isocyanates.
In the paper industry, examples are sizing resins and water repelling resins such as alkylketene dimer (AKD) or alkenyl succinic anhydride (ASA).
In the detergent industry, antifoaming agents can be mentioned as active ingredients, such as:
saturated or unsaturated aliphatic, alicyclic, aromatic or heterocyclic hydrocarbons, such as paraffins or waxes;
monostearylphosphates, monostearyl alcohol phosphates;
polyorganosiloxane oils or resins which may be combined with silica particles.
It is also possible to use active ingredients such as lubricants for working or deforming materials.
When the active ingredient is a solvent or a mixture of solvents, solvents are used which are non miscible in or slightly miscible with water, as defined above. Solvents which can be used are those used for cleaning or stripping, such as aromatic petroleum cuts, terpene compounds such as D-limonene, or L-limonene, also solvents such as SOLVESSO®. Aliphatic esters such as methyl esters of a mixture of acetic, succinic and glutaric acids (the acid mixture is a by-product of Nylon synthesis), oils such as vaseline oil, and chlorinated solvents are also suitable as solvents.
This list is, of course, given by way of indication only and is not exhaustive.
As indicated above, the active ingredients can be used as they are or in the presence of an organic solvent. More particularly, this solvent is selected from products which are insoluble in or slightly miscible with water.
Examples are mineral oils, or mono-, di- and tri-glycerides of saturated or unsaturated fatty acids; they may be natural or synthetic triglycerides, aromatic petroleum cuts, terpene compounds (D-limonene, L-limonene), aliphatic esters or chlorinated solvents.
The redispersible granules of the invention also comprise at least one principal surfactant in which the binary water-surfactant phase diagram comprises an isotropic phase which is fluid at 25° C. up to a concentration of at least 50% by weight of surfactant followed, at high concentrations, by a hexagonal, cubic or lamellar type liquid crystal phase which is stable up to 65° C.
The description of these phases is given, for example, in the publication by R. G. LAUGHLIN entitled “THE AQUEOUS BEHAVIOUR OF SURFACTANTS”—ACADEMIC PRESS—1994. Their identification by (X and neutron) ray diffusion is described in the publication by V. LUZZATI entitled “BIOLOGICAL MEMBRANES, PHYSICAL FACT AND FUNCTION”—ACADEMIC PRESS—1968.
More particularly, the liquid crystal phase of the principal surfactant is stable up to a temperature of at least 60° C. In a preferred implementation of the invention, the liquid crystal phase is stable up to a temperature of at least 55° C.
It should be noted here that the isotropic fluid phase can be cast, wh
Guerin Gilles
Morvan Mikel
LaToya Cross
Rhodia Chimi
Seugnet Jean-Louis
Warden Jill
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