EP0586447A1 - Compositions polymeres particulaires et leur production - Google Patents

Compositions polymeres particulaires et leur production

Info

Publication number
EP0586447A1
EP0586447A1 EP92910542A EP92910542A EP0586447A1 EP 0586447 A1 EP0586447 A1 EP 0586447A1 EP 92910542 A EP92910542 A EP 92910542A EP 92910542 A EP92910542 A EP 92910542A EP 0586447 A1 EP0586447 A1 EP 0586447A1
Authority
EP
European Patent Office
Prior art keywords
temperature
polymer
particles
tri
depressant
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP92910542A
Other languages
German (de)
English (en)
Inventor
John Graham Manderley Thorpe Lane Langley
Kenneth Charles 4 Silk Mill Drive Symes
Kishor Kumar 69 Beckside Lane Mistry
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ciba Specialty Chemicals Water Treatments Ltd
Original Assignee
Allied Colloids Ltd
Ciba Specialty Chemicals Water Treatments Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Allied Colloids Ltd, Ciba Specialty Chemicals Water Treatments Ltd filed Critical Allied Colloids Ltd
Publication of EP0586447A1 publication Critical patent/EP0586447A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K8/00—Cosmetics or similar toiletry preparations
    • A61K8/02—Cosmetics or similar toiletry preparations characterised by special physical form
    • A61K8/11—Encapsulated compositions
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K8/00—Cosmetics or similar toiletry preparations
    • A61K8/18—Cosmetics or similar toiletry preparations characterised by the composition
    • A61K8/72—Cosmetics or similar toiletry preparations characterised by the composition containing organic macromolecular compounds
    • A61K8/81—Cosmetics or similar toiletry preparations characterised by the composition containing organic macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
    • A61K8/8141—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
    • A61K8/8158—Homopolymers or copolymers of amides or imides, e.g. (meth) acrylamide; Compositions of derivatives of such polymers
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61Q—SPECIFIC USE OF COSMETICS OR SIMILAR TOILETRY PREPARATIONS
    • A61Q13/00—Formulations or additives for perfume preparations
    • 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
    • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
    • B01J13/02—Making microcapsules or microballoons
    • B01J13/06—Making microcapsules or microballoons by phase separation
    • B01J13/08—Simple coacervation, i.e. addition of highly hydrophilic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • B41M5/124—Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components
    • B41M5/165—Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components characterised by the use of microcapsules; Special solvents for incorporating the ingredients
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K2800/00—Properties of cosmetic compositions or active ingredients thereof or formulation aids used therein and process related aspects
    • A61K2800/40—Chemical, physico-chemical or functional or structural properties of particular ingredients
    • A61K2800/41—Particular ingredients further characterized by their size
    • A61K2800/412—Microsized, i.e. having sizes between 0.1 and 100 microns
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K2800/00—Properties of cosmetic compositions or active ingredients thereof or formulation aids used therein and process related aspects
    • A61K2800/40—Chemical, physico-chemical or functional or structural properties of particular ingredients
    • A61K2800/54—Polymers characterized by specific structures/properties

Definitions

  • This invention relates to processes of encapsulating particles by coacervation and to products made by coacervation processes.
  • Coacervation techniques for encapsulating a variety of materials are well known and are described in, for instance, GB 1,275,712, 1,475,229 and 1,507,739 and DE 3,545,803.
  • the particulate material is provided as a dispersion in a solution of coacervating polymer or polymer blend and the polymer or polymer blend is then caused to precipitate out from solution so as to form a coacervate coating around the individual particles. If the coacervation technique merely involves precipitation, the coating will tend to be reasonably permeable to water, and may even be readily soluble in water.
  • EP 351,162 it is proposed to precipitate a water soluble polymer generally in the presence of an aqueous solution of enzyme. It is possible that some of the techniques described in EP 351,162 may give some form of coacervation but again it is difficult to form a coacervate shell that both protects the enzyme adequately during storage of the liquid detergent and releases it adequately upon dilution of the liquid detergent in wash water. For instance polyvinyl alcohol has been proposed as a matrix or a coating for enzyme particles but it is difficult to achieve a suitable balance of insolubility during storage and release when required.
  • the coacervate coating by this technique tends to be rather weak and so it is proposed in U.S. 3,244,640 to add a cross linking agent to harden the coacervate polymeric coating that is formed, and then to recover and dry the encapsulated particles. It is also stated in U.S. 3,244,640 that it can be desirable to include inorganic salts such as alkali metal sulphate in the aqueous solution of the LCST polymer before heating so as to reduce the temperature of coacervation, and that it is possible to induce coacervation solely by the addition of inorganic salts. However it is stated to be preferable not to add the salts because the capsules then have to be washed after recovery to remove residual salt. Also, when coacervation is brought about by adding a material to the coacervating solution, there is a tendency for agglomeration of polymer to occur in preference to uniform coacervation.
  • inorganic salts such as alkali metal sulphate
  • Coacervation techniques have been used for encapsulating a wide variety of particulate materials, often including solutions or dispersions of an active ingredient in a solid or liquid matrix.
  • known techniques have not proved entirely satisfactory for the situation where the coating must provide an impermeable barrier in one liquid environment and a permeable barrier in another liquid environment.
  • present techniques have tended to be inadequate for the encapsulation of some compositions. For instance some herbicides or other agriculturally useful, water insoluble, active ingredients that at present normally have to be delivered to the user as emulsifiable concentrates (that is to say emulsions in oil that have to be dispersed into water to make a sprayable composition) are difficult to encapsulate satisfactorily to give release when required.
  • a process according to the invention for forming encapsulated particles comprising a core surrounded by a coacervate coating comprises providing an aqueous solution of a LCST polymer that has a temperature of reversible insolubilisation (TRI) in that solution of Tl, forming a dispersion of the particles in that solution at a temperature T2 that is below Tl, heating the dispersion to a temperature above Tl and thereby precipitating the LCST polymer as a coacervate around the particles, then adding a TRI depressant to the solution and thereby reducing the temperature of reversible insolubilisation of the LCST polymer in that solution to a temperature T3 that is lower than Tl, and either cooling the dispersion to a temperature between T3 and Tl and maintaining the dispersion at a temperature between T3 and Tl, or separating the particles from the
  • the invention also provides a particulate composition
  • a particulate composition comprising encapsulated particles each comprising a core surrounded by a coacervate coating that comprises an LCST polymer and a water-removable TRI depressant, wherein the composition either is in the form of dry particles or is an aqueous dispersion at a temperature that is below the temperature of reversible insolubilisation of the polymer in the absence of the TRI depressant but above the temperature of reversible insolubilisation of the polymer in the presence of the TRI depressant, whereby the coating dissolves when the composition is mixed with water.
  • the particulate composition may be a dispersion in an aqueous solution of the TRI depressant (for instance a liquid detergent) or may be a dry powder that can be added to water.
  • the invention also includes methods of protecting an active ingredient by providing it within such particles and then mixing the particulate composition into sufficient water to dilute the concentration of TRI depressant sufficient to raise the temperature of reversible insolubilisation to a value at which the polymer coating will dissolve and release the active ingredient into the dilution of water.
  • the TRI depressant and its amount are selected to give the desired depression in the temperature of reversible insolubilisation.
  • it is an electrolyte.
  • electrolytes A wide variety of electrolytes can be used but since satisfactory results are obtained with simple inorganic salts it is generally preferred to use them as part or all of the electrolyte.
  • Suitable salts include sodium, potassium, ammonium, calcium, magnesium and aluminium salts, particularly of carbonate, sulphate, chloride and nitrate.
  • Some or all of the electrolyte can be anionic surfactant, for instance of the type conventionally present in a liquid detergent concentrate.
  • Typical amounts of salt that should be added are 2 to 30% based on the aqueous composition, or such as to give a 15:1 to 1:15 weight ratio of polymer:salt.
  • the amount is preferably sufficient for T3 to be at least 5°C below the anticipated lowest temperature of storage.
  • some electrolyte can be present in the initial solution, typically in an amount of 0 to 5% based on the initial solution, provided this does not depress Tl too much.
  • Tl is at least 5°C higher than the anticipated temperature of usage, for instance the temperature of the dilution water into which the particles are to be dissolved.
  • any other material that has the desired depressant effect can be used.
  • they can all be characterised as being water-miscible non-solvents (in the absence of significant amounts of water) for the relevant LCST polymer.
  • examples include organic liquids such as lower alcohols, glycols and non-ionic surfactants.
  • Particular examples are ethanol, glycerol, ethylene glycol, mono propylene glycol and ethoxylated octyl or nonyl phenol surfactants.
  • the LCST polymer can be a naturally occurring polymer such as certain cellulose derivatives, such as the methyl, hydroxy propyl, and mixed methyl/hydroxy propyl cellulose ethers. However it is generally preferred for the LCST polymer to be a synthetic polymer formed by polymerisation of what can be termed an LCST monomer either as a homopolymer or as a copolymer with a hydrophilic monomer that is present in an amount insufficient to cause Tl to be unacceptably high.
  • Suitable LCST monomers include N- alkylacrylamide, N,N-dialkylacrylamide, diacetone acrylamide, N-acryloylpyrrolidine, vinyl acetate, certain (meth) acrylate esters (especially hydroxypropyl esters) , styrene, and various other vinyl monomers, especially N- vinylimidazoline and the like.
  • the comono er is usually hydrophilic and can be non-ionic or ionic.
  • Suitable non-ionic monomers include acrylamide, hydroxyethyl acrylate, vinyl pyrollidone, or hydrolysed vinyl acetate.
  • Anionic or cationic monomer can be used in place of or in addition to the non-ionic comonomer to form a copolymer or terpolymer with the LCST monomer respectively.
  • Suitable anionic monomers include ethylenically unsaturated carboxylic or sulphonic acid monomers, for example (meth) acrylic acid and alkaline salts thereof, and 2-acrylamido methyl propane sulphonic acid.
  • Suitable cationic monomers include dialkylaminoalkyl (meth)acrylates and acrylamides as acid addition or quaternary ammonium salts, for example dialkylaminoethyl (meth)acrylate acid addition salts.
  • the method of the invention relies upon the reversible insolubilisation by temperature change of an LCST polymer to form a coacervate coating, followed by the addition of a TRI depressant to modify the properties of the coating in a beneficial manner. Since the initial insolubilisation is by temperature change, this can be conducted homogeneously througout the composition and so can yield very uniform coacervation.
  • An essential modification of the coating is that the TRI depressant reduces the temperature of reversible insolubilisation of the coating. This means that the temperature of the solution can be cooled below the temperature at which the coacervate coating was first formed without the coating being solubilised. This permits handling, storage and recovery at ambient temperatures.
  • the addition of the TRI depressant can tend to change other physical properties of the coating of the LCST polymer.
  • the addition of the electrolyte will generally both reduce the temperature of reversible insolubilisation of the polymer and will render the coating much harder and less permeable than it would be in the absence of the electrolyte.
  • the coating may tend to revert to its original softer and more permeable texture.
  • This reversibility, and the maintenance of a non-cross linked polymer structure, is advantageous as it promotes subsequent release of the core upon dilution in water, but if desired the coating can be cross linked after its formation.
  • Suitable methods for cross linking coacervate polymer coatings are known.
  • the process can be conducted to form dry particles that are separated from the medium in which they were formed. Separation can be by, for instance filtration or centrifuging or decanting, often followed by fluid bed or other drying.
  • One benefit of the process is that the presence of the TRI depressant means that the particles can be separated at conveniently low temperatures and will have a sufficiently hard texture during separation and drying to facilitate handling.
  • TRI depressant Sufficient TRI depressant will be trapped in the coacervate coating to maintain this structure even after separation of the particles from the aqueous solution of TRI depressant (usually an electrolyte) in which they are formed. However when the dry particles are subsequently dispersed into water, the water will dissolve the TRI depressant from the coating so as to reduce the concentration of TRI depressant in the vicinity of the coacervate polymer.
  • TRI depressant usually an electrolyte
  • This dissolution must occur to a sufficient extent to allow the coating to be softened and rendered permeable to the core or active ingredient in the core and often full dissolution occurs at the prevailing temperature. For instance this is valuable when the particles contain an active ingredient that is to be distributed into water, since the dry particles can be stirred into sufficient water to dilute the TRI depressant content sufficiently for the shell to dissolve and to release the active ingredient into water. This is particularly valuable for agricultural active ingredients such as herbicides or pesticides that, prior to the invention, might have had to be formulated as e ulsifiable concentrates because they are insoluble or poorly soluble in water.
  • a particularly valuable aspect of the invention arises when the particles are to be maintained in the dispersion at a temperature between Tl and T3. As a result, provided the amount of electrolyte is such that T3 is below the normal ambient temperature, and therefore below the storage temperature of the dispersion, the coacervate coating will tend to provide a hard impermeable barrier during normal storage.
  • the TRI depressant comprises electrolyte or other component in a liquid detergent concentrate.
  • the presence of this electrolyte or other component tends to maintain the coacervate coating in an impermeable form in the final dispersion containing the particles.
  • the concentration of electrolyte or other TRI depressant is diluted sufficiently to raise the temperature of reversible insolubilisation above the temperature of the wash water, with the result that the coacervate coating dissolves sufficiently to allow the release of the encapsulated material or active ingredient into the wash water. This is particularly valuable when the encapsulated particles contain a detergent enzyme.
  • the temperature Tl of reversible insolubilisation of the LCST polymer is the temperature at which the polymer will become insoluble if the solution containing the polymer is heated past Tl or will become soluble if insoluble polymer in that aqueous solution is cooled below that temperature.
  • the temperature of reversible insolubilisation is generally reasonably abrupt, but may extend over a few degrees or more.
  • T3 must be sufficiently low that any range for Tl does not significantly overlap the range for T3, which is the corresponding temperature for the polymer in the aqueous solution containing the TRI depressant. It should be noted that Tl and T3 relate to the polymer in the particular aqueous solution in which it exists.
  • the initial aqueous solution can contain some electrolyte or other TRI depressant in which event Tl in that solution will generally be lower than it would be if the initial solution had been free of electrolyte or other depressant, but additional electrolyte or other depressant is then added to reduce the temperature of reversible insolubilisation to T3.
  • Tl is generally at least 25°C and often at least 30°C and frequently is in the range 45 to 80°C but can be as high as 100°C.
  • Some polymers require the presence of some electrolyte in order to bring Tl in the initial solution down to a convenient value, eg below 100°C.
  • T3 is generally at least 5°C lower than Tl and is preferably at least 10°C and often at least 20°C below Tl.
  • T3 should be below the probable storage temperature.
  • T3 is 0°C, that is to say the coating will never dissolve in liquid water, but higher values of T3, such as 5°C or even 10°C, can be acceptable in many instances.
  • the particles that are to serve as the core to be encapsulated can consist of a single component or a blend of components, typically a blend of an active ingredient in a carrier.
  • the particles must be water-insoluble and capable of being dispersed in the aqueous solution of coacervating polymer. Accordingly the particles can be formed by dispersion of a water-insoluble oily solution or melt or by dispersion of water-insoluble finely divided solid.
  • the core particles comprise or consist of an oily liquid or solution
  • they may include, for instance, paraffinic, napthenic or aromatic hydrocarbons, triglyceride oils or fats, silicone oils or phthalic esters. If such materials have a melting point above ambient, they may be included as a melt.
  • an active ingredient is present in the core within a polymer, for instance being dispersed throughout a matrix polymer. If the polymer is relatively water impermeable, i ⁇ may protect a water soluble or water sensitive active ingredient from dissolution into the aqueous coacervating solution.
  • an enzyme may be distributed within particles of a matrix polymer, for instance as described in EP 356,239.
  • Active ingredients that may be included, either alone or in solvents, melts or polymer solid particles, include leuco dyes (that may be present as solutions for pressure- sensitive paper) , agricultural chemicals, perfumes, flavours, condiments, essential oils, bath oils, enzymes and bleaching agents.
  • leuco dyes that may be present as solutions for pressure- sensitive paper
  • agricultural chemicals perfumes, flavours, condiments, essential oils, bath oils, enzymes and bleaching agents.
  • the invention is of particular value with agricultural chemicals, and especially water insoluble agricultural chemicals.
  • Such chemicals may be growth promoters, nutrients or pesticides, including herbicides, insecticides (including pheromones) , fungicides, nematocides, etc.
  • compositions Prior to the invention, a normal way of supplying such compositions was as an emulsifiable concentrate, i.e., a solution of the active ingredient in an organic solvent that could be emulsified into water to form a sprayable composition.
  • the organic solvents are undesirable.
  • Naturally suitable emulsifying agent may be required to maintain it in emulsion in the spray solution.
  • the active ingredient when the active ingredient is in a matrix polymer it can be preferred for the polymer to be in a water insoluble form within the particles so as to reduce still further the risk of solubilisation of the active ingredient through the coacervate coating, but preferably the matrix polymer should dissolve at the pH of the dilution water, so as to release the active ingredient.
  • the core particles comprise active ingredient dispersed in a matrix polymer, these particles will preferably have initially been formed as a dispersion of polymer particles in hydrophobic oil (as in EP 356,239) and this dispersion is then dispersed into the aqueous coacervating solution.
  • the matrix polymer is sufficiently hydrophobic that it will partition into the oil in preference to the aqueous solution of the coacervating material.
  • the core particles comprise one or more matrix polymer particles surrounded by the oil, and the oil is surrounded by the coacervate shell.
  • It can be an LCST polymer and the matrix can include a TRI.
  • the invention is performed by dispersing the desired particles into the aqueous solution of the coacervating, LCST, polymer at a temperature below Tl and under conditions that will provide a dispersion having the desired particle size.
  • the dispersion is formed by dispersing an oil phase containing an active ingredient into the aqueous solution of LCST polymer, the act of dispersing the oil phase into the aqueous solution is generally conducted with sufficient agitation to form particles of the desired size.
  • the dispersion is formed in the absence of an emulsifying agent.
  • a homogenising system such as a Silverson mixer, it is possible to easily achieve a desired small particle size that is typically below 20 ⁇ m and usually below lO ⁇ m, for instance down to l ⁇ m or even
  • an entropic stabilising polymer such as carboxymethyl cellulose, sodium alginates or starch
  • LCST polymeric component can be mixed with the LCST polymeric component prior to encapsulation.
  • Such polymers can act as dispersants in conditions of high salt concentration, eg in certain detergent environments.
  • Diacetone acrylamide (1 part) and acrylamide (0.4 part) were dissolved in 1% aqueous sodium acetate at pH 6.5
  • An oil phase (33 parts) comprising a 5% solution of leuco-dye (Pergascript blue in Santosol oil from Ciba-Geigy and Monsanto UK respectively) was added with high shear mixing to 100 parts of an aqueous solution of Polymer A from Example 1.
  • sample 2D were, respectively, 21, 35 and 51% by weight based on amount of polymer in the original solution and in each instance a stable emulsion was formed.
  • the amount of polymer added to the composition was less than the amount required to give the 21% absorption of sample
  • the emulsion was unstable, and it was not possible to measure the polymer in the particles.
  • the average particle size in samples 2B to 2D was between 1 and 2 ⁇ m with more than 95% by weight of the particles being below 5 ⁇ m. Microscopic examination of the products of samples 2B to 2D under an optical microscope demonstrated the presence of distinct capsules having core regions and wall regions.
  • aqueous compositions of samples 2B to 2D are each added to liquid detergent concentrates comprising: Alkyl benzene sulphonates 10% Fatty alcohol ether sulphate 5% Soap 1%
  • Polymer B A polymer similar in composition to Polymer A was made by the procedure described in Example 1, but with a diacetone acrylamide:acrylamide weight ratio of 60:40. This polymer (Polymer B) had a TRI of about 50°C.
  • the 25% aqueous solution of Polymer B (1 part) was diluted with water (1.5 parts) and warmed to 45°C.
  • a melt of technical Trifluralin (mp 40°C) (0.5 part) was added to the warm polymer solution and dispersed by high shear mixing into tiny drops of a dispersed phase. This mixture was then warmed to 6'5°C (a temperature above the polymer TRI) with low shear stirring.
  • Sodium sulphate solution in water (10%; 0.25 part) was then added and the mixture allowed to cool slowly to 20°C) .
  • Example 5 Microencapsulation by simple coacervation of
  • An oil phase (33 parts) comprising a 5% solution of leuco-dye (Pergascript blue in Santosol oil from Ciba-Geigy and Monsanto UK respectively) was added with high shear mixing to 100 parts of an aqueous solution of poly-N- isopropyl acrylamide.
  • the temperature was held below 20°C.
  • the resultant smooth white O/W emulsion was warmed in a water-bath to 40°C and held at this temperature for 15 min.
  • Glycerol was added to 10% concentration based on the aqueous phase, and the mixture then allowed to cool slowly to 20°C.
  • a stable microcapsule suspension in water was obtained.
  • the dye was released upon dilution with water.

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Veterinary Medicine (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Birds (AREA)
  • Epidemiology (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Dispersion Chemistry (AREA)
  • Manufacturing Of Micro-Capsules (AREA)
  • Agricultural Chemicals And Associated Chemicals (AREA)

Abstract

Particules encapsulées comprenant un noyau entouré par une enrobage de coacervat qui comporte un polymère de température de solution critique faible et un dépresseur permettant de retirer l'eau pour la température d'insolubilisation de ce polymère. Sa composition se présente soit sous forme de particules sèches soit dans une dispersion aqueuse à une température inférieure à la température d'insolubilisation réversible du polymère en l'absence du dépresseur mais supérieure à la température d'insolubilisation en présence du dépresseur. L'enrobage se dissout lorsque la composition est mélangée avec l'eau. La composition est constituée par formation du noyau dans une solution du polymère, par échauffement de la solution de façon à provoquer sa précipitation comme coacervat, et ensuite par adjonction du dépresseur. La composition peut être constituée d'une dispersion aqueuse ou de particules sèches.
EP92910542A 1991-05-14 1992-05-14 Compositions polymeres particulaires et leur production Withdrawn EP0586447A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB919110407A GB9110407D0 (en) 1991-05-14 1991-05-14 Particulate polymeric compositions and their production
GB9110407 1991-05-14

Publications (1)

Publication Number Publication Date
EP0586447A1 true EP0586447A1 (fr) 1994-03-16

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EP92910542A Withdrawn EP0586447A1 (fr) 1991-05-14 1992-05-14 Compositions polymeres particulaires et leur production

Country Status (7)

Country Link
EP (1) EP0586447A1 (fr)
AU (1) AU1794892A (fr)
CA (1) CA2102128A1 (fr)
GB (1) GB9110407D0 (fr)
MX (1) MX9202248A (fr)
WO (1) WO1992020441A1 (fr)
ZA (1) ZA923509B (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL1007696C1 (nl) † 1997-05-01 1998-11-03 Inst Voor Agrotech Onderzoek Omhulde stof met gecontroleerde afgifte.
DE10006538C2 (de) 2000-02-15 2002-11-28 Forsch Pigmente Und Lacke E V Verfahren zur Beschichtung von Partikeln mit LCST-Polymeren
DE10140246A1 (de) 2001-08-09 2003-03-06 Forsch Pigmente Und Lacke E V Verfahren zur Behandlung von Oberflächen von Substraten
DE102006058200A1 (de) 2006-12-11 2008-06-12 Merck Patent Gmbh Redispergierbare oberflächenmodifizierte Partikel
US8557288B2 (en) * 2008-08-15 2013-10-15 Washington University Hydrogel microparticle formation in aqueous solvent for biomedical applications

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1254126B (de) * 1961-06-20 1967-11-16 Henkel & Cie Gmbh Einkapselung von Fluessigkeiten
US3594326A (en) * 1964-12-03 1971-07-20 Ncr Co Method of making microscopic capsules
US3567650A (en) * 1969-02-14 1971-03-02 Ncr Co Method of making microscopic capsules
CA1040018A (fr) * 1974-06-19 1978-10-10 Dale R. Shackle Microcapsules d'hydroxypropylcellulose reticulee
DE3615043A1 (de) * 1986-05-03 1987-11-05 Hoechst Ag Verfahren zur verkapselung von biologisch aktivem material

Non-Patent Citations (1)

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Title
See references of WO9220441A1 *

Also Published As

Publication number Publication date
ZA923509B (en) 1993-05-17
GB9110407D0 (en) 1991-07-03
MX9202248A (es) 1992-11-01
CA2102128A1 (fr) 1992-11-15
WO1992020441A1 (fr) 1992-11-26
AU1794892A (en) 1992-12-30

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