A plurality of microcapsules and use thereof in polymers

Abstract

A plurality of microcapsules, said microcapsules having a cross-linked polymeric shell encapsulating an active ingredient, wherein said plurality of microcapsules has a glass transition temperature of from 70°C to less than 120°C.

Description

A plurality of microcapsules and use thereof in polymers

[0001] The present invention concerns a plurality of microcapsules which allows for targeted release of an active ingredient under environmentally acceptable conditions and is useful in particular for improving the processing and the properties of polymers. The invention also concerns the use of the plurality of microcapsules in polymer processing, premixes comprising a polymer and the plurality of microcapsules and polymer compositions comprising the plurality of microcapsules. The invention finally concerns novel copolymers useful for providing the shell of the microcapsules

[0002] The encapsulation of active ingredients has been developed as a technical option to protect such active ingredients from undesired and premature interactions with other components of formulations or reaction mixtures. The encapsulation is useful in particular to provide formulations, e.g. cosmetic, pharmaceutical and agricultural formulations, having an improved efficiency of use of the active ingredients and reaction mixtures, for example polymerization mixtures or polymer processing mixtures, which allow for improved processes and final products due to a better controlled use of active ingredients such as e.g.: catalysts. WO-A-2018 / 172431 in the name of the applicant discloses a series of microcapsules having a polymeric shell with a pore size less than 1 nm which are generally suitable for such purpose.

[0003] US-A-2005 / 0153839 discloses inter alia a microcapsule having a polyurethane and / or polyurea wall, wherein the capsule wall comprises, via a covalent bond, a polymer obtained by radically polymerizing in the presence of a chain transfer agent comprising active hydrogen at least a vinyl monomer comprising a polymerizable compound comprising a particular polyether. It is discussed that a homopolymer of the vinyl monomer should have a glass transition temperature of at least 120¨C, preferably at least 130°C.

[0004] US2004195711A1 discloses a microcapsule comprising a disperse system, in which a colored particle is dispersed in an oil phase, and a wall encapsulating the disperse system, wherein the wall is formed by a resin having an acid group or a salt thereof. The resin may be cross-linked. The microcapsules are used as toner particles in electrophoresis.

[0005] The invention now makes available a plurality of microcapsules which allows for protection of active ingredients, in particular during storage and to release the active ingredient under improved conditions of energy consumption.

[0006] The invention consequently relates to a plurality of microcapsules having a cross-linked polymeric shell encapsulating an active ingredient, wherein said plurality of microcapsules has a glass transition temperature of from 70°C to less than 120°C.

[0007] It has been found, surprisingly, a plurality of microcapsules which solves this problem, in spite of the cross-linking of the polymeric shell and the presence of the active ingredient. The plurality of microcapsules according to the invention allows to efficiently protect an active ingredient during storage at room temperature and initial stages of use while being capable of releasing the active ingredient beyond a threshold temperature, in a range which is lower than for known microcapsules. Namely, the plurality of microcapsules according to the invention allows to release the active at temperature ranges between 70°C to less than 120°C. This responds to a need in industry.

[0008] The glass transition temperature is commonly abbreviated Tg,which abbreviation is used interchangeably with the full expression glass transition temperature in this patent application.

[0009] The measurement of the glass transition temperature Tgof polymeric materials is well known to the skilled person and is generally carried out by differential scanning calorimetry (DSC). This analytical measure can be applied to the plurality of microcapsules according to the invention. A detailed description of the method which can be generally used for the determination of the Tgof the plurality of microcapsules according to the invention is given in the example section.

[0010] For the purposes of the present invention, « monodisperse » is understood to denote with reference to a series of droplets or a series of capsules, that the standard deviation of the distribution of the diameter of said droplets or said capsules is less than 50%, in particular less than 25%, or less than 1 μm. For the purposes of the present invention, the diameter of said droplets or said capsules is determined by light scattering technique using a Mastersizer 3000 (Malvern Instruments) equipped with a Hydro SV measurement cell.

[0011] For the purpose of the present invention « plurality » refers to a significant number of microcapsules, for example a quantity of microcapsules obtained from a synthesis of microcapsules or a quantity of microcapsules suitable for application, in particular industrial application in the intended use of the microcapsules, generally, a plurality of microcapsules comprises at least 50, preferably at least 100 microcapsules.

[0012] In the plurality of microcapsules according to the invention, the glass transition temperature is often from 80°C to 110°C. A glass transition temperature from greater than 80°C to equal to or lower than 100°C is preferred. Particular examples of the plurality of microcapsules according to the invention have a glass transition temperature of about 76°C or about 85°C. In a certain aspects, the glass transition temperature of the plurality of microcapsules according to the invention is equal to or lower than 119°C,or equal to or lower than 118°C. It has been found that when the plurality of microcapsules is heated for a sufficient time above the glass transition temperature, the release of the active ingredient is facilitated. Without wishing to be bound by any theory, it is believed that the heating above the glass transition temperature alters the permeability and porosity of the polymeric shell such that the active ingredient can be released more easily.

[0013] In a particular embodiment, the plurality of microcapsules is heat-treated in the absence of a polymer matrix or any other surrounding medium. Typically, the heat treatment is carried out at a temperature higher than 120°C. Without wishing to be bound by any theory, it is believed that the foregoing heat treatment allows to increase the conversion of any optionally present reactive groups in the shell of the microcapsules, thereby providing a plurality of microcapsules having a further adapted, generally higher Tg than the untreated plurality of microcapsules. It has been found that it is possible to carry out the aforesaid heat treatment with limited albeit no degradation of the microcapsules and their active ingredient. Preferably, the plurality of microcapsules according to the invention is heat-treated, in this embodiment for less than 10 minutes, for example 3 minutes, at 200°C. This glass transition temperature would be stable over the life of the capsule. With the same material, a person skilled in the art can can have access to different glass transition temperatures as a function of the time of the heat treatment. The Tg can be maximized by maximizing the heating time to achieve the highest possible level of a combination of cross-linking and reorganization of the co-polymer network

[0014] Typically the Tg of the microcapsules according to the invention is characterized by differential scanning calorimetry.

[0015] The determination of the glass transition temperature by DSC may be carried out as follows: a modulated DSC measurement using Texas Instruments Discovery DSC 2, equipped with a modulated DSC function

[0016] The samples for the measurement are prepared as follows : approximately 10 mg of the capsules are prepared in contact with the crucible. Methods to do so are well known to a person skilled in the art and art furthermore detailed in for instance ASTM D3418-15 – Standard Test Method for Transition Temperatures, Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry.

[0017] The following temperature program is applied:

[0018] Amplitude of 3°CPeriod of 60sHeating rate of 3°C / minEquilibration at 30°C over 10minRamp from 30°C to -90°C at a rate of 3°C / minEquilibration at -90°C over 10minRamp from -90°C to Tmax°C at a rate of 3°C / minRamp from Tmax to -90 °CEquilibration at -90°C during 10 minRamp from -90°C to Tmax°C at a rate of 3°C / minThe window of temperature ranges -Tmin°C / Tmax can be adapted as a function of the predicted glass transition temperature. The Tmax is limited by the potential loss of mass arising from the thermogravimetric analysis or degradation of the sample.

[0019] The principle behind the determination of the glass transition temperature using differential scanning calorimetry is as follows: the material is subjected to a steadily increasing temperature and its heat release is measured. Because the glass transition temperature will create a change in the properties of the material, the polymer chains reorient, requiring a change in energy to heat. This shows as an inflection on the curve of heat as a function of temperature. Three points may be selected and reported: the onset, which is the lowest value at which inflection is observed, the mid-point and end point. This analytical method is described in detail in ASTM D3418-15 and is a well established method for determining Tg known to those skilled in the art.

[0020] In one embodiment the plurality of microcapsules according to the invention has a difference in value between the Tg onset and midpoint below 20 C, more preferably below 10 C and most preferably below 5 C. It has been found that the plurality of microcapsules according to this embodiment, having a relatively narrow range of temperature between onset and mid-point is advantageous for controlling the thermally activated release of the active ingredient from the plurality of microcapsules.

[0021] In the plurality of microcapsules according to  the invention, the microcapsules generally have an average diameter of equal to or greater than 1 micrometer, preferably equal to or greater than 3 micrometer. In the plurality of microcapsules according to  the invention, the microcapsules generally have an average diameter of equal to or smaller than 30 micrometer, preferably equal to or smaller than 20 micrometer.

[0022] In the plurality of microcapsules according to  the invention, the microcapsules generally have a shell thickness of equal to or greater than 0.1 micrometer, preferably equal to or greater than 0.2 micrometer. In the plurality of microcapsules according to  the invention, the microcapsules generally have an shell thickness of equal to or smaller than 20 micrometer, preferably equal to or smaller than 8 micrometer. Shell thickness can also be denoted as wall thickness and refers to the thickness of the, generally solid, envelope of cross-linked polymer which encloses the inner space of a microcapsule.

[0023] In a first particular aspect of the plurality of microcapsules according to  the invention, the microcapsules have an average diameter of 1 to 30 micrometer and a wall thickness from 0.1 to 20 micrometer.

[0024] The plurality of microcapsules according to  the invention is often monodisperse.

[0025] In a second particular aspect of the plurality of microcapsules according to  the invention, the microcapsules have mean diameter between 1 μm and 30 μm, the thickness of the solid enveloping shell is between 0.2 μm and 8 μm and the standard deviation of the distribution of the diameter of microcapsules is less than 50%, or less than 1 μm.

[0026] In a preferred aspect of the plurality of microcapsules according to the invention, the crosslinked polymeric shell is obtained by photopolymerization of a photopolymerizable composition which comprises reactive groups. If appropriate, a photoinitiator may be added to initiate the conversion of the reactive groups at the desired wavelength. In one embodiment, the reactive groups may be (meth)acrylates. In this aspect, the conversion of reactive groups of the photopolymerizable composition is generally at least 80%, preferably at least 90%.

[0027] The conversion of reactive groups can be determined by the monitoring of the disappearance of one band representative of a functional group under FTIR, the absorption of IR bands being proportional to the amount of the functional group, therefore the reduction of peak height corresponds to the reduction of the amount of the functional group, further indicating successful polymerization. The standard method of doing this is comparison of the FTIR absorption of the emulsion before and after cross-linking, in particular by photopolymerization. For the purpose of the present invention this can be done using the method disclosed in Barszczewska-Rybarek,Materials2019, 12(24), 4057. By way of example, the conversion of reactive groups of an acrylate over the course of radical polymerization can be observed as a function of the reduction in FTIR absorption of the signature spectrum thereof, which for acrylates falls between 2900 and 3000 µm wavelength.

[0028] The invention consequently also concerns a plurality of microcapsules having a cross-linked polymeric shell encapsulating an active ingredient, wherein the cross-linked polymeric shell has a degree of cross-linking defined as the number of polymerizable groups which are effectively polymerized. The number of polymerizable groups is defined as the average functionality per unity of molar weight (f / Mw) of the shell. The number of polymerizable groups is multiplied with the conversion rate of polymerizable groups, determined by observation of the reduction of FTIR absorption of a characteristic FTIR absorption band of a cross-linkable precursor group of the cross-linked polymeric shell.

[0029] The conversion rate is usually equal to or greater than 80%, preferably equal to or greater than 90%. Generally, this conversion rate is lower than 100%, in particular equal to or lower than 95%. In the case wherein the cross-linking is carried out by photopolymerization, the degree of cross-linking is correlated to the degree of conversion of photopolymerizable groups.

[0030] The conversion rate maximization enables, if appropriate, a stable value of the temperature of release of active ingredient from the plurality of microcapsules. Without wishing to be bound by any explanation, it is believed that this is achieved by assuring that the microcapsule structure does not change upon exposure to elevated temperatures until reaching the target release temperature.

[0031] In the plurality of microcapsules according to the invention, the crosslinked polymeric shell generally comprises or consists of a copolymer of at least two monomers at least one monomer having a crosslinkable functionality, said monomers having different glass transition temperatures. It is understood that if only one of the monomers has a determined glass transition temperature there will be a difference in the glass-transition temperatures with the other monomer.

[0032] In the plurality of microcapsules according to the invention, usually, all monomers have more than one polymerizable function and are then called cross-linkers, or is equal to one, leading to the formation of linear chains which may be cross-linked by addition of a cross-linker. In one aspect, at least one of the two monomers is a crosslinker. In this case the monomers are preferably linear with the polymerizable groups in terminal position. In another aspect, one monomer is a cross-linker with two polymerizable functionalities and at least one monomer is a cross-linker with more than two polymerizable functionalities, for example 3, 4, 5 or 6 crosslinkable functionalities. In this case the monomer having two crosslinkable functionalities is preferably linear with the crosslinkable groups in terminal position and he monomer having more than two crosslinkable functionalities is preferably branched with the crosslinkable groups in terminal position.

[0033] The plurality of microcapsules according to the invention generally comprises spacer groups between cross-linkable groups of the cross-linked polymeric shell. The average molecular weight of said spacer groups is usually from 200 to 500 g / mole, preferably from 300 to 400 g / mol.

[0034] Suitable spacer groups may comprise for example, carbon chains, in which one or more catenary atoms are optionally replaced by oxygen or nitrogen. Generally the chains have from 2 to 20 atoms, more preferably from 6 to 10 atoms. Other suitable spacer groups include for example (hetero)aromatic cycles and (hetero)aliphatic cycles which may be substituted by a cross-linkable group or linked to a cross-linkable group through an optionally substituted methylene group or through a carbon chain as described here before. It is understood that the description of the spacer groups in the polymer also applies to the monomers discussed here before.

[0035] Another way of describing in a non-limitative way the polymeric shell and a fortiori the monomers used therein is the distance between two crosslinkable groups which is generally from 1 to 4 nm, preferably from 2 to 3 nm.

[0036] In one preferred aspect, the plurality of microcapsules according to the invention comprises at least acrylate functions. Acrylate functions are cross-linkable functionalities in the sense of this patent application, including notably acrylate and methacrylate functions. The plurality of microcapsules according to the invention often comprises acrylate and methacrylate functions. Referring to monomers used to provide the cross-linked polymeric shell, often, each monomer comprises at least one acrylate and / or methacrylate function. Preferably each monomer comprises at least two acrylate and / or methacrylate functions.

[0037] In a particular aspect of the plurality of microcapsules according to the invention, the cross-linked polymeric shell comprises acrylate and methacrylate functions and the molar ratio of acrylate to methacrylate is from 1:1 to 5:1, preferably from 1:1 to 2:1.

[0038] In still another aspect of the plurality of the microcapsules according to the invention, the cross-linked polymeric shell comprises urethane functions. Particularly, the cross-linked polymeric shell comprises urethane functions in addition to crosslinkable functionalities as described herein before, notably acrylate and / or methacrylate.

[0039] In a particular aspect of the plurality of microcapsules according the invention, the crosslinked polymeric shell is essentially free of nitrile functional groups. « Essentially free of nitrile functional groups » is understood to denote in particular a content of nitrile functional groups lower than 1 weight %, preferably less than 0.5 weight % relative to the total weight of the cross-linked polymeric shell. Preferably, the cross-linked polymeric shell is free of nitrile functional groups. This is in particular the case when no nitriles have been used as monomers, polymers or cross-linking agents for the production of the cross-linked polymeric shell.

[0040] When all of the monomers have a determined glass transition temperature, it could be attempted to extrapolate the glass transition temperature of the co-polymer using the Flory-Fox equation. However, it has been found that generally, the Tg of the microcapsules according to the invention does not follow the Flory-Fox equation.

[0041] Formula 1

[0042] wherein Tg is the glass transition temperature of the co-polymer and Tgistands for the glass transition temperature of the homopolymer of a monomer i incorporated into the co-polymer and xistands for the weight percentage of the monomer i relative to the total weight of the copolymer.

[0043] This further illustrates the advantages of the invention which makes available microcapsules tailored to an advantageous range of release temperatures in spite of the presence of cross-linking and the active ingredient.

[0044] The invention also concerns a copolymer in accordance with the description of the co-polymer forming the crosslinked polymeric shell, as described here before.

[0045] In a first particular aspect, the polymeric shell has a ratio of rigid moieties to flexible moieties between 0,90 and 3,00, preferably between 1,00 and 2,50 and more preferably between 1,05 and 2,30.

[0046] Rigid moieties are defined as functional groups comprising insaturations and / or cyclic systems. Particular classes of such functional groups are selected from olefinic double bonds, triple bonds, ester groups, urethane groups, aromatic rings, heteroaromatic rings, aliphatic rings or heteroaliphatic rings. More particularly, aromatic rings can be selected from, optionally substituted, benzene rings, naphtyl, anthracenyl, p-biphenyl and o-biphenyl. More particularly, heteroaromatic rings can be selected from optionally substituted, furanyl, pyridyl and pyrrolyl, More particularly, aliphatic rings can be selected from, optionally substituted, cyclopropyl, cuclobutyl, cyclohexyl, cyclyheptyl, cyclooctyl and norbornyl. More particularly, heteroaliphatic rings can be selected from, optionally substituted, epoxy, oxetanyl and tetrahydrofuranyl.

[0047] Flexible moieties are defined as saturated linear carbon chains in which carbon can be partially replaced by oxygen. Generally, the linear chain has at least two member atoms having a covalent bond, preferably at least 5 member atoms. In certain aspects, the linear chain has equal to or greater than 6 member atoms. Generally, the linear chain has at most 30 member atoms, preferably at most 20 member atoms. When carbon is partially replaced by oxygen, usually, each third or fourth member atom of the linear chain is replaced by oxygen. Particular examples of suitable flexible moieties include n-propylene, n-butylene, n-amylene, n-hexylene, n-heptylene, n-octylene, n-nonylene, n-decylene, n-undecylene, n-dodecyclene, n-tridecylene, n-tetradecylene, n-pentadecylene, n-hexadecylene, n-heptadecylene, n-octadecylene, n- nonadecylene and n-eicosadecylene. When carbon is partially substituted by oxygen, the flexible moiety generally corresponds to formula (I)

[0048] - [(CH2)n-O]p- (I)

[0049] wherein n is 2, 3 or 4 and p is 1, 2, 3, 4, 5 or 6.

[0050] In another embodiment, flexible moieties include saturated linear carbon chains in which carbon can be partially replaced by oxygen.and / or nitrogen. The number of atoms in the linear chain in this embodiment is generally as described here before.

[0051] The flexible moieties can be part of the main backbone of the polymer chain and / or can be present as non cross-linkable ramifications.

[0052] To calculate the number % of each functional group, the weight% of each oligomer and monomer is converted in number % knowing the molar mass and the Avogadro number. Knowing the molar mass of each functional group and the number of recurrences of each group in each monomer and oligomer, the number percentage of rigid moieties and flexible moieties respectively can be determined. The ratio between rigid moieties and flexible moieties is then calculated.

[0053] In a second particular aspect, the cross-linking density of the copolymer network formed in the polymeric shell is advantageously from 0,1 mmol / g to 10 mmol / g, preferably from 0,5 mmol / g to 7 mmol / g, and more preferably from 1 mmol / g to 5 mmol / g. It has been found that providing a cross-linked polymeric shell having a cross-linking density in the above range allows to improve the retention of the active ingredient within the capsule up to a given release temperature. The maximal cross-linking density is calculated by dividing the number of polymerizable groups by the molar mass. The experimental cross-linking density, named cross-linking density in the following text, is the maximal cross-linking density weighted by the conversion rate of the polymerizable functions according to the following formula:.

[0054] Formula 2

[0055] The active ingredient is usually released from the microcapsules through a change in temperature within the range of glass transition temperature of the microcapsules. Other specific external stimulus, including but not limited to a change in pH, and exposure to ultra-violet radiation, and / or any combination thereof can optionally be applied in addition. In order to achieve said release by external stimulus, certain components of the shell may be selected, as disclosed in for instance EP 3548529.

[0056] In certain aspects, the release of the active ingredient is further facilitated by the interaction of the microcapsules with an active material different from the microcapsules. Examples of suitable active materials include but are not limited to solvents and solid matrices, such as in particular polymer matrices. Air and inert gas atmospheres are not to be considered active materials according to this aspect. Active materials suitable for this purpose include also polymer surfaces. Particular examples of polymer surfaces and / or polymer matrices comprise or consist of epoxy resins, acrylic resins, vinyl resins or polyesters. In another aspect, the aforesaid active material includes premixes such as in particular the premixes according to the invention described below. Consequently, the invention also relates to a composition comprising a plurality of microcapsules, preferably in accordance with the plurality of microcapsules according to the invention, and an active material, wherein the active ingredient is released from the microcapsules at a temperature from 70°C to 120°C. The invention also concerns a polymer composition comprising a plurality of microcapsules according to the invention.

[0057] In the plurality of microcapsules according to the invention, the shell encapsulates an active ingredient. The active ingredient can be a solid at 25°C. The active ingredient can also be a liquid at 25°C and 1013,25 kPa pressure.

[0058] In the plurality of microcapsules according to the invention the active ingredient can be suitably selected from, for example: a crosslinking agent, a hardener, an organic or metal catalyst (such as an organometallic or inorganometallic complex of platinum, palladium, titanium, molybdenum, copper, zinc) used for polymerising polymer-, elastomer-, rubber-, paint-, adhesive-, sealant-, mortar-, varnish-, or coating formulations;

[0059] a dye or pigment intended for elastomer-, paint-, coating-, adhesive-, sealant-, mortar-, or paper formulations

[0060] a fragrance (in accordance with the list of molecules established by the International Fragrance Association (IFRA) and available on the website www.ifraorg.org) intended for detersive products such as cleaning / washing products, home care products, cosmetic and personal care products, textiles, paints, coatings;

[0061] an aroma / flavouring agent, a vitamin, an amino acid, a protein, a lipid, a probiotic, an antioxidant, a pH corrector, a preservative for food compounds and animal feed;

[0062] a softener, a conditioning agent for detersive products, cleaning / washing products, cosmetics and personal care products. In this regard, the active agents that may be used are for example as listed in the US patents U.S. Pat. No. 6,335,315 and U.S. Pat. No. 5,877,145;

[0063] an anti-discolouration or anti-fading agent (such as an ammonium derivative), an antifoaming agent (such as an alcohol ethoxylate, an alkylbenzene sulfonate, a polyethylene ethoxylate, an alkylethoxysulfate or alkylsulfate) intended for detersive products and cleaning / washing products and home care products;

[0064] a brightening agent, also referred to as a colour activating agent (such as a stilbene derivative, a coumarin derivative, a pyrazoline derivative, a benzoxazole derivative, or a naphthalimide derivative) intended for detersive products, cleaning / washing products, cosmetics and personal care products;

[0065] a biologically active compound such as an enzyme, a vitamin, a protein, a plant extract, an emollient agent, a disinfecting agent, an antibacterial agent, an anti-UV agent, a medicament intended for cosmetic and personal care products, and textiles. Among these biologically active compounds the following may be mentioned: vitamins A, B, C, D and E, para-aminobenzoic acid, alpha hydroxy acids (such as glycolic acid, lactic acid, malic acid, tartaric acid, or citric acid), camphor, ceramides, polyphenols (such as flavonoids, phenolic acid, ellagic acid, tocopherol, ubiquinol), hydroquinone, hyaluronic acid, isopropyl isostearate, isopropyl palmitate, oxybenzone, panthenol, proline, retinol, retinyl palmitate, salicylic acid, sorbic acid, sorbitol, triclosan, tyrosine;

[0066] a disinfecting agent, an antibacterial agent, an anti-UV agent, intended for paints and coatings;

[0067] a fertiliser, a herbicide, an insecticide, a pesticide, a fungicide, a repellent, or a disinfecting agent intended for agrochemical products;

[0068] a fire resistant agent, also known as a flame retarding agent, (for example a brominated polyol such as tetrabromobisphenol A, a halogenated or non-halogenated organophosphorus compound, a chlorinated compound, an aluminum trihydrate, an antimony oxide, a zinc borate, a red phosphorus, a melamine, or a magnesium dihydroxide) intended for use in plastic materials, coatings, paints, and textiles;

[0069] a photonic crystal or a photochromophore intended for use in paints, coatings, and in polymer materials that form curved and flexible screens;

[0070] a product known to the person skilled in the art under the accepted nomenclature Phase Change Materials (PCMs) that is capable of absorbing or releasing so-called ‘latent’ heat when going through a change in a phase, intended for the storage of energy. Examples of PCMs and the applications thereof are described in “A review on phase change energy storage: materials and applications”, Farid et al., Energy Conversion and Management, 2004, 45(9-10), 1597-1615. By way of examples of PCMs, mention may be made of molten salts of aluminum phosphate, ammonium carbonate, ammonium chloride, cesium carbonate, cesium sulfate, calcium citrate, calcium chloride, calcium hydroxide, calcium oxide, calcium phosphate, calcium saccharate, calcium sulfate, cerium phosphate, iron phosphate, lithium carbonate, lithium sulfate, magnesium chloride, magnesium sulfate, manganese chloride, manganese nitrate, manganese sulfate, potassium acetate, potassium carbonate, potassium chloride, potassium phosphate, rubidium carbonate, rubidium sulfate, disodium tetraborate, sodium acetate, sodium bicarbonate, sodium bisulfate, sodium citrate, sodium chloride, sodium hydroxide, sodium nitrate, sodium percarbonate, sodium persulfate, sodium phosphate, sodium propionate, sodium selenite, sodium silicate, sodium sulfate, sodium tellurate, sodium thiosulfate, strontium hydrophosphate, zinc acetate, zinc chloride, sodium thiosulfate, paraffinic hydrocarbon waxes, polyethylene glycols.

[0071] In one embodiment of the plurality of microcapsules according to the invention, the active ingredient does not consist of a foaming agent. In this embodiment, the active ingredient does often not comprise a foaming agent. Generally, the microcapsules in the plurality of microcapsules according to the invention of this embodiment are not expandable.

[0072] The plurality of microcapsules according to the invention is obtainable, for example, by a process which comprises (a) providing a double emulsion comprising droplets of at least one active ingredient (C1) dispersed in a photopolymerizable composition C2, said droplets being dispersed in a composition C3, the compositions C2 and C3 being immiscible with each other; (b) inducing a controlled shear rate in said double emulsion to provide a mixed double emulsion (C4); and (c) irradiating the mixed double emulsion (C4) to prepare the microcapsules.

[0073] In a particular embodiment of the preferred aspect of the plurality of microcapsules according to the invention, the active ingredient is a lubricant. Examples of suitable lubricants include but are not limited to oils such as mineral oils, polyalphaolefins, polyglycols, synthetic esters, phosphate esters, triglyceride esters, polyol esters, fatty acids, vegetal oils, silicone oils, polyethers, perfluoropolyethers, as well as solid lubricants, such as notably amides, such as erucamide or ethylene bis(stearamide), and synthetic or natural waxes (paraffins).

[0074] The invention consequently also concerns the use of the plurality of microcapsules according to this particular embodiment to enhance the wear resistance or the scratch resistance of a polymeric surface and the use of the plurality of microcapsules according to this particular embodiment to enhance the water resistance of a polymeric surface. Such polymeric surfaces include for example an epoxy-resin surface or an acrylic resin surface. Such surfaces may further be applied to objects such as e.g coatings, textiles and gaskets.

[0075] The invention consequently also concerns the use of the plurality of microcapsules according to this particular embodiment for the self-lubrication of an elastomer. Preferably, the lubricant is a polyol ester.

[0076] The invention also concerns the use of the plurality of microcapsules according to the invention, for the supply of an active ingredient to a polymerization process or to a polymer processing process.

[0077] It has been found that the plurality of microcapsules according to the invention and in particular according preferred aspect is particularly advantageous to protect active ingredients such as catalysts. In the aspect wherein the microcapsules include air or a gas, the plurality of microcapsules allows for an efficient and stable reduction of the density of the produced polymer. The use according to the invention may be for example, for the production of a thermoset polymer. It may also be for the production of a molded, extruded or cast thermoplastic article or thermoset article. It may also be for the production of a compression molded or an injection molded thermoplastic article or thermoset article.

[0078] The invention also concerns a premix for manufacturing a thermoset polymer, comprising the plurality of microcapsules according to the invention. The premix according to the invention preferably comprises an epoxy resin which is combined with the plurality of microcapsules according to the invention containing an anionic or cationic catalyst as the active ingredient. Another embodiment may be a premix in the form of acrylic resins, vinyl resins and polyesters which are combined with the plurality of microcapsules according to the invention containing an unsaturated monomer diluent such as: acrylic acid, acrylamide, acryloyl chloride, and methyl methacrylate as the active ingredient.

[0079] In another embodiment the premix according to the invention comprises an isocyanate resin which is combined with the plurality of microcapsules according to the invention containing at least a polyol as the active ingredient.

[0080] It has been found that the storage and process stability of the premix according to the invention is improved. The premix according to the invention is capable of surviving extreme conditions to which the premix may be exposed during standard processing conditions, such as extrusion and / or injection molding.

[0081] In a particular aspect, the premix according to the invention comprises an epoxy resin and the plurality of microcapsules according to the invention wherein the active ingredient is a latent accelerator of curing of the epoxy resin. Suitable latent accelerators may be selected, for example, from amine latent accelerators, in particular polyamine latent accelerators. Particular examples are selected from modified polyamines, e.g. Ancamine2014 FG.

[0082] The invention also concerns a mixture comprising a thermoplastic polymer and the plurality of microcapsules according to the invention.

[0083] The examples here after are intended to illustrate the invention without however limiting it.

[0084] EXAMPLESMeasurement of Tg1

[0085] The glass transition temperature (Tg) of the capsules is obtained by modulated differential scanning calorimetry DSC (TA Instruments, DSC25 DSC2-01527). The sample is put in an aluminum receptacle with or without a cap. The reference is an empty aluminum receptacle. The sample is composed of a determined quantity of microcapsules in powder form. The sample and a reference are firstly cooled until reaching an equilibrium at – 90 °C. Secondly, a modulation of 2 °C for 60 s is applied before applying an isotherm for 10 min. Then, the temperature is increased from – 90 °C to 200 °C at a speed of 3 °C / min. The glass transition temperature Tg2 is determined as follows: two inflection points are observed in the curve of heat release as a function of temperature. These two inflection points correspond to the onset and endpoint of the glass transition and may be determined mathematically through a peak in the first-order differentiation of the Heat vs. temperature curve. The glass transition temperature Tg is defined as the midpoint between the onset and endpoint temperatures described above.Heat treatment and determination of Tg2

[0086] A sample of microcapsules is treated as for the measurement of Tg 1. When reaching 200 °C, the temperature is maintained for 3 min. Afterwards, the sample and the reference are cooled down up to -90 °C at 10 °C / min where another isotherm is maintained for 3 min. The sample and the reference are heated again from – 90 °C to 200 °C at a temperature ramp of 10 °C / min. The glass transition temperature Tg2 is determined as follows: two inflection points are observed in the curve of heat release as a function of temperature. These two inflection points correspond to the onset and endpoint of the glass transition and may be determined mathematically through a peak in the first-order differentiation of the Heat vs. temperature curve. The glass transition temperature Tg is defined as the midpoint between the onset and endpoint temperatures described above.Preparation examples

[0087] Manufacture of Microcapsules

[0088] The following process was applied to produce a plurality of microcapsules according to the invention, using the starting materials indicated below in then tables for each example:

[0089] The composition Cl is an active ingredient. The composition C2 is a mixture of oligomers and monomers and a photoinitiator of composition described in the tables. The composition C3 is a solution of cellulose derivatives at 8 % by weight

[0090] A mechanical stirrer (IKA 2000) equipped with a 3 cm diameter deflocculating stirring propeller is used to carry out all the emulsification steps.

[0091] Step a). the composition Cl is added dropwise to the composition C2 at a ratio C1:C2=40:60 by weight with stirring at 2000 rpm with a mechanical stirrer (IKA 2000) equipped with a stirring anchor for 5 min.

[0092] Step b): the emulsion (E1) obtained in the preceding step is added dropwise to the composition C3 at a ratio E I C3=10:90 by weight with stirring at 3050 rpm with a mechanical stirrer Supertest from VMI with a 3 cm diameter deflocculating stirring propeller.

[0093] Step c): The emulsion (E2) thus obtained is stirred at 3050 rpm for 5 minutes.

[0094] Step d): the monodisperse emulsion (E3) thus obtained is irradiated for 2 minutes using a UV UV lamp emitting at 365nm having a maximum light intensity of 1 W / cm2 to allow cross-linking of the capsules. The plurality of microcapsules is then recovered and dried to powder form.

[0095] Example 1 -

[0096] ComponentsRatio in each phaseRatio in capsuleComposition C1Solid urea derivative100 %40 %Composition C2CN109 (polyepoxy acrylate, Sartomer)75 %45%Genomer 1121 M (isobornyl methacrylate, Rhan)24 %14,4 %Darocur 1173 (photoinitiator BASF)1 %0,6 %Composition C3Cellulose derivative8 %Deionized water92%

[0097] Example 2

[0098] ComponentsRatio in each phaseRatio in capsuleComposition C1Solid urea derivative100 %40 %Composition C2Ebecryl 4859 (polyurethane acrylate, Allnex)56 %33,6 %Photomer 4127 (neopentyl glycol diacrylate, IGM Resins)43 %25,8 %Darocur 1173 (photoinitiator, BASF)1 %0,6 %Composition C3Cellulose Derivative8 %Deionized water92 %

[0099] Example 3:

[0100] ComponentsRatio in each phaseRatio in capsuleComposition C1Solid urea derivative100 %40%Composition C2Ebecryl 4859(polyurethane acrylate, Allnex)73 %44.4%Sarbio 710126%15.6%Darocur 1173 (photoinitiator, BASF)1 %0.6%Composition C3Cellulose Derivative8 %Deionized water92 %

[0101] Properties of the plurality of microcapsules

[0102] The table here after shows the properties of the plurality of microcapsules determined as described above.

[0103] ExampleTg1 °CTg2 °CConversion rate final capsule (%)Crosslinkingdensity final capsule (mmole / g)Ratio of rigid moieties on flexible moities – final capsule185134841.12.2327697952.31.0837096901.91.37

[0104] Example 4 – Application of the plurality of microcapsules in the presence of an active material

[0105] To assess the ability of microcapsules to release the active ingredient, the reactivity of capsules in an epoxy was assessed by DSC by measuring the enthalpy of reaction, the onset temperature and the peak temperature. The capsules were mixed  with an epoxy resin (DER 332, Sigma Aldrich) and a catalyst (DYHARD 100 S, dicyandiamide, Alzchem). For capsules having 40 % of active ingredient, the mix contained 1,5 phr of capsules, 6 phr of DYHARD 100S in DER 332. For comparison, a resin containing the free active ingredient was prepared with 0,6  phr of free DYHARD 100S in DER 332.

[0106] DSC conditions were :1- a step of equilibrium at 25 °C for 3 min2- a ramp in temperatures from 25 °C to 220 °C at 10°C / min.

[0107] For the measurement, the samples were put into aluminum crucibles with a lid.

[0108]

[0109] The reactivity for the capsules of example 1 above are displayed in the following table and compared to the sample containing free active ingredient.Enthalpy of reaction (J  / g)Onset temperature(°C)Peak temperature (°C)Free active ingredient (DYHARD UR400, Alzchem)327,4156,1163,9Ex.1329,3156,7164,4

[0110]

[0111] These results show that the release of the latent accelerator was successful with the shell after heating as the reactivity was the same for the encapsulated or the free active ingredient.

Claims

A plurality of microcapsules, said microcapsules having a cross-linked polymeric shell encapsulating an active ingredient, wherein said plurality of microcapsules has a glass transition temperature of from 70°C to less than 120°C.The plurality of microcapsules according to claim 1 , wherein the glass transition temperature is measured according to ASTM D3418-15, preferably using a Texas Instruments Discovery DSC 2, equipped with a modulated DSC function.The plurality of microcapsules according to claim 1 or 2, wherein the glass transition temperature is from 80°C to 110°C.The plurality of microcapsules according to any of the preceding claims, wherein the glass transition temperature is from greater than 80°C to equal to or lower than 100°C.The plurality of microcapsules according to any of the preceding claims, wherein the difference in value between the glass transition onset and glass transition midpoint is below 20 C, more preferably below 10 C and most preferably below 5 C.The plurality of microcapsules according to any of the preceding claims, wherein the plurality of microcapsules is heat-treated prior to determination of the glass transition temperature, preferably for less than 10 minutes at 200°C.The plurality of microcapsules according to any of the preceding claims, wherein the crosslinked polymeric shell comprises or consists of a copolymer of at least two monomers at least one monomer having one or more crosslinkable functionalities, said monomers having different glass transition temperatures.The plurality of microcapsules according to claim 7, wherein the glass transition temperature Tg of the microcapsules does not follow the Flory-Fox equationFormula 1wherein Tg is the glass transition temperature of the co-polymer and Tgistands for the glass transition temperature of the homopolymer of a monomer i incorporated into the co-polymer and xistands for the weight percentage of the monomer I relative to the total weight of the copolymer. The plurality of microcapsules according to any of the preceding claims  wherein the microcapsules have an average diameter of from 1 to 30 micrometer determined by light scattering technique using a Mastersizer 3000 (Malvern Instruments) equipped with a Hydro SV measurement cell.The plurality of microcapsules according to any of the preceding claims, wherein the crosslinked polymeric shell is obtained by photopolymerization of a photopolymerizable composition having reactive groups.The plurality of microcapsules according to claim 10, wherein the conversion of reactive groups of the photopolymerizable composition C2 is at least 80% by mole, preferably at least 90% by mole determined by the monitoring of the disappearance of one band representative of a functional group of the reactive group under FTIR.The plurality of microcapsules according to any of the preceding claims, wherein the cross-linked polymeric shell comprises acrylate and methacrylate functions and the molar ratio of acrylate to methacrylate is from 1:1 to 5:1, preferably from 1:1 to 2:1.The plurality of microcapsules according to any of the preceding claims , wherein the cross-linking density of the copolymer network formed in the polymeric shell is from 0,1 mmol / g to 10 mmol / g, preferably from 0,5 mmol / g to 7 mmol / g, and more preferably from 1 mmol / g to 5 mmol / g.The plurality of microcapsules according to claim 13, wherein the cross-linking density is defined as the maximal cross-linking density, calculated by dividing the number of polymerizable functions in each monomer or oligomer by the respective molar mass, weighted by the conversion rate of the polymerizable functions, according to the following formula:Formula 2said conversion rate being determined by the monitoring of the disappearance of one band representative of a functional group of the polymerizable function under FTIR.The plurality of microcapsules according to anyone of the preceding claims, which comprises spacer groups between the cross-linkable groups and the average molecular weight of said spacer groups is from 200 to 500 g / mole, preferably from 300 to 400 g / mole.The plurality of microcapsules according to anyone of the preceding claims, wherein the cross-linked polymeric shell has a molar ratio (mole / mole) of rigid moieties defined as functional groups comprising insaturations and / or cyclic systems to flexible moieties defined as saturated linear carbon chains in which carbon can be partially replaced by oxygen and / or nitrogen between 0,90 and 3,00 , preferably between 1,00 and 2,50 and more preferably between 1,05 and 2,30.The plurality of microcapsules according to claim 16 wherein the rigid moieties comprise insaturations and / or cyclic systems.and are preferably selected from olefinic double bonds, triple bonds, ester groups, urethane groups, aromatic rings, heteroaromatic rings, aliphatic rings or heteroaliphatic rings.The plurality of microcapsules according to claim 17 wherein the rigid moieties comprise at least one moiety selected from, optionally substituted, benzene rings, naphtyl, anthracenyl, p-biphenyl and o-biphenyl, furanyl, pyridyl and pyrrolyl, cyclopropyl, cuclobutyl, cyclohexyl, cyclyheptyl, cyclooctyl and norbornyl. epoxy, oxetanyl and tetrahydrofuranyl.The plurality of microcapsules according to anyone of claims 16to 18, wherein the flexible moieties comprise at least one moiety selected from saturated linear carbon chains in which carbon can be partially replaced by oxygen and / or nitrogen said linear chain having from 2 to 30 member atoms having, preferably at from 5 to 30, more preferably from 6 to 20 member atoms.The plurality of microcapsules according to claim 19 wherein the flexible moieties flexible moieties comprise at least one moiety selected from n-propylene, n-butylene, n-amylene, n-hexylene, n-heptylene, n-octylene, n-nonylene, n-decylene, n-undecylene, n-dodecyclene, n-tridecylene, n-tetradecylene, n-pentadecylene, n-hexadecylene, n-heptadecylene, n-octadecylene, n- nonadecylene and n-eicosadecylene.The plurality of microcapsules according to claim 19 or 20 wherein the flexible moieties comprise at least one moiety selected from moieties corresponding to formula (I)- [(CH2)n-O]p- (I)wherein n is 2, 3 or 4 and p is 1, 2, 3, 4, 5 or 6.The plurality of microcapsules according to any of the preceding claims, wherein all monomers have one or more crosslinkable functionalities.The plurality of microcapsules according to anyone of claims any of the preceding claims, wherein at least two monomers have two crosslinkable functionalities.The plurality of microcapsules according to claim 23, wherein one monomer has two crosslinkable functionalities and at least one monomer has more than two crosslinkable functionalities.The plurality of microcapsules according to any of the preceding claims, which comprises at least acrylate functions.The plurality of microcapsules according to claim 25, which comprises acrylate and methacrylate functions.The plurality of microcapsules according to claim 25 or 26, wherein each monomer comprises at least one acrylate and / or methacrylate function.The plurality of microcapsules according to claim 27, wherein each monomer comprises at least two acrylate and / or methacrylate functions.The plurality of microcapsules according to any of the preceding claims, wherein the cross-linked polymeric shell comprises urethane functions.The plurality of microcapsules according to claim 15, wherein the spacer groups are selected from (i) carbon chains, in which one or more catenary atoms are optionally replaced by oxygen or nitrogen and (ii) example (hetero)aromatic cycles and (hetero)aliphatic cycles which may be substituted by a cross-linkable group or linked to a cross-linkable group through an optionally substituted methylene group or through a carbon chain.The plurality of microcapsules according to any of the preceding claims, wherein the distance between two crosslinkable groups in the cross-linked polymeric shell is from 1 to 4 nm, preferably from 2 to 3 nm.The plurality of microcapsules according to any of the preceding claims , wherein the crosslinked polymeric shell is essentially free of nitrile functional groups.The plurality of microcapsules according to  a any of the preceding claims   which is monodisperse.The plurality of microcapsules according to any of the preceding claims, wherein the active ingredient is a solid at 25°C.The plurality of microcapsules according to any of the preceding claims, wherein the active ingredient is a liquid at 25°C at a pressure of 1013,25 kPa. The plurality of microcapsules according to any of the preceding claims , wherein the active ingredient is selected from a catalyst, a UV absorber, a lubricant and a flame retardant, a pigment and a liquid crystal material.The plurality of microcapsules according to any of claims any of the preceding claims, wherein the active ingredient does not consist of a foaming agent.The plurality of microcapsules according to any of the preceding claims, wherein the active ingredient is a lubricant.The plurality of microcapsules according to any of the preceding claims, which is obtainable by a process which comprises (a) providing a double emulsion comprising droplets of at least one active ingredient (C1) dispersed in a photopolymerizable composition C2, said droplets being dispersed in a composition C3, the compositions C2 and C3 being immiscible with each other; (b) inducing a controlled shear rate in said double emulsion to provide a mixed double emulsion (C4) ; and (c) irradiating the mixed double emulsion (C4) to prepare the microcapsules.Use of the plurality of microcapsules according to any of the preceding claims, for the supply of an active ingredient to a polymerization process or to a polymer processing process.Use according to claim 40, for the production of a thermoset polymer.Use according to claim 40, for the production of a molded, extruded or cast thermoplastic article.Use according to claim 40, for the production of a compression molded or an injection molded thermoplastic article. Use according to any of claims 40 to 43, wherein the plurality of microcapsules is heated above its glass transition temperature for at least 30 minutes.A premix for manufacturing a thermoset polymer, comprising the plurality of microcapsules according to anyone of claims 1 to 39.A premix according to claim 45, which comprises an epoxy resin.The premix according to claim 46, wherein the active ingredient is a latent accelerator of curing of the epoxy resin.A mixture comprising a thermoplastic polymer and the plurality of microcapsules according to anyone of claims 1 to 39. A polymer composition  comprising the plurality of microcapsules according to anyone of claims 1 to 39. .A copolymer comprising at least two monomers having one or more crosslinkable functionalities, said monomers having different glass transition temperatures, wherein said copolymer has a glass transition temperature from 70°C to 120°C.The copolymer according to claim 50, which is in accordance with anyone of claims 10 to 19.A composition comprising a plurality of microcapsules, preferably in accordance with the plurality of microcapsules according to the invention, more preferably according to anyone of claims 1 to 39 and an active ingredient, wherein the active ingredient is released from the microcapsules at a temperature from 70°C to 120°C.