Method for preparing biodegradable microcapsules and microcapsules obtained in this manner

Abstract

Method for manufacturing microcapsules enclosing a substance referred to as the active substance, in which method: there are provided an aqueous solution of a surfactant, an oily phase comprising the active substance and at least a first monomer X, and a polar phase having at least a second monomer Y; an O/W emulsion is prepared by adding the oily phase to the aqueous solution of the surfactant; the polar phase is added to the O/W emulsion in order to obtain a polymer by polymerisation of the X and Y monomers; starting from this reaction mixture, the microcapsules are isolated and comprise a wall which is formed by the polymer and which encloses the active substance; the polymer is a poly(beta-amino ester).

1 . A method for manufacturing microcapsules containing a so-called active substance, in which method:
 an aqueous solution of a surfactant, an oily phase comprising said active substance and at least a first monomer X, and a polar phase comprising at least a second monomer Y are provided;   an O/W type emulsion is prepared by adding said oily phase to said aqueous solution of the surfactant;   said polar phase is added to said O/W emulsion, in order to obtain a polymer by polymerizing said monomers X and Y;   from this reaction mixture, said microcapsules including a wall formed by said polymer and containing said active substance are isolated;   said method being characterized in that said polymer is a poly(beta-amino ester).   
     
     
         2 . The method according to  claim 1 , characterized in that said first monomer X is selected from (multi)acrylates, and preferably (multi)acrylates of formula X′—(—O(C═O)—CH═CH 2 ) n  where n≥4 and where X′ is a molecule whereon n acrylate structural units are grafted. 
     
     
         3 . The method according to  claim 2 , characterized in that the first monomer X is selected from the group formed by:
 diacrylates;   triacrylates, particularly trimethylolpropane triacrylate, tetraacrylates, pentaacrylates, hexaacrylates, mixtures of these different acrylates of type O[CH 2 C(CH 2 OR) 3 ] 2  where R is H or COCH═CH 2 ;   polymers carrying pendant acrylate functions;   functional oligo-PBAEs, prepared for example by reacting diacrylate compounds with a functional primary amine and/or a functional secondary diamine;   the mixture of different compounds described above.   
     
     
         4 . The method according to  claim 1 , characterized in that said second monomer Y is selected from amines. 
     
     
         5 . The method according to  claim 4 , characterized in that the second monomer Y is selected from the group formed by:
 primary amines R—NH 2 ;   primary diamines of type NH 2 (CH 2 ) n NH 2  where n is an integer which can typically be between 1 and 20, and which is preferably 2 or 6;   primary diamines having an aromatic core, and preferably meta-xylylene diamine;   primary (multi)amines, and preferably tris(2-aminoethyl) amine;   (multi)amines containing primary and secondary amine functions, and preferably tetraethylene pentamine;   secondary diamines and preferably piperazine;   polymers containing primary and secondary amine functions, and preferably polyethylene imine.   
     
     
         6 . The method according to  claim 1 , characterized in that said polymerization of said monomers is performed under stirring at a temperature between 20° C. and 100° C., and preferably between 30° C. and 90° C. 
     
     
         7 . The method according to  claim 1 , characterized in that said surfactant is selected from the group formed by macromolecular surfactants, preferably in that said surfactant is selected from the group formed by polyacrylates, methylcelluloses, carboxymethylcelluloses, polyvinyl alcohol optionally partially esterified or etherified, polyacrylamide, synthetic polymers having anhydride or carboxylic acid functions, ethylene/maleic anhydride copolymers, and in that said surfactant is even more preferably polyvinyl alcohol. 
     
     
         8 . The method according to  claim 1 , characterized in that said active substance is selected from the group formed by:
 essential oils, fragrances,   inks, paints, thermochromic and/or photochromic substances, dyes, adhesives,   products with biocidal effect, products with fungicidal effect, products with antiviral effect, products with phytosanitary effect, products with cosmetic effect, pharmaceutical active ingredients,   natural and edible oils, plant and edible oils, liquid alkanes, esters and fatty acids.   
     
     
         9 . The method according to  claim 1 , characterized in that the wall of the microcapsules is modified either by a layer of polymer deposited on the surface of the microcapsule, or by adding a radical initiator in the aqueous phase and/or oily phase, or by adding in the aqueous phase a water-soluble acrylate capable of modifying the surface condition of the microcapsules. 
     
     
         10 . A microcapsules prepared according to the method of  claim 1 . 
     
     
         11 . The microcapsule according to  claim 10 , containing a so-called active substance, characterized in that the wall thereof consists of poly(beta-amino ester). 
     
     
         12 . The microcapsule according to  claim 10 , characterized in that it has a mean diameter between 100 nm and 100 μm, preferably between 1 μm and 50 μm, and even more preferably between 10 μm and 40 μm. 
     
     
         13 . The microcapsule according to  claim 10 , characterized in that said microcapsule and/or the wall thereof shows a biodegradation of at least 80%, preferably at least 83%, and even more preferably at least 85%, measured with a manometric respirometry test according to method 301 F of the “OECD Guidelines for Testing of Chemicals: Ready Biodegradability” after ten days of incubation. 
     
     
         14 . The microcapsule according to  claim 10 , characterized in that said microcapsule and/or the wall thereof shows a biodegradation of at least 90%, preferably at least 95%, and even more preferably at least 98%, measured with a manometric respirometry test according to method 301 F of the “OECD Guidelines for Testing of Chemicals: Ready Biodegradability” after 28 days of incubation. 
     
     
         15 . The microcapsule according to  claim 10 , characterized in that the wall thereof has been modified either by a polymer layer deposited on the surface of the microcapsule, or by adding a radical initiator in the aqueous phase and/or the oily phase, or by adding in the aqueous phase a water-soluble acrylate capable of modifying the surface condition of the microcapsules.