WO2013041257A1

WO2013041257A1 - Aerosol photopolymerization

Info

Publication number: WO2013041257A1
Application number: PCT/EP2012/062099
Authority: WO
Inventors: Wolfgang Gerlinger; Michael Wörner; Erlan AKGÜN
Original assignee: Basf Se; Karlsruher Institut Für Technologie (Kit)
Priority date: 2011-09-23
Filing date: 2012-06-22
Publication date: 2013-03-28
Also published as: EP2758439A1; KR20140078630A; CN103842391A; JP2014526588A

Abstract

The present invention relates to a method for producing nanoparticles containing at least one polymer and/or copolymer by providing an aerosol containing droplets of at least one monomer and at least one photoinitiator in a gas stream, irradiating this aerosol stream with light so that the monomers present are polymerized, and separating the nanoparticles that have formed from the gas flow; the invention also relates to nanoparticles that can be produced by this method and to the use of these nanoparticles according to the invention in optical, electronic, chemical or biotechnology systems, or for application of active substances.

Description

The present invention relates to a process for producing nanoparticles containing at least one polymer and / or copolymer by providing an aerosol containing droplets of at least one monomer and at least one photoinitiator in a gas stream, irradiating this aerosol stream with light so that the present monomers polymerize , and separating the nanoparticles formed from the gas stream, nanoparticles producible by this method and the use of these nanoparticles according to the invention in optical, electronic, chemical, biotechnological systems or for the application of active ingredient.

Methods for producing nanoparticles from polymeric organic materials are already known from the prior art.

US 2007/0142589 A1 discloses a process for the preparation of polymeric microparticles. For this purpose, a liquid containing corresponding monomeric compounds is atomized in order to obtain a droplet cloud of polymerization-initiated monomer droplets in a gas-filled reaction zone. Under the action of gravity, these liquid droplets fall through a reaction zone and begin to polymerize. The particles are then collected and removed from the reaction zone. According to the example, neutralized acrylic acid is sprayed in aqueous solution by means of a spray bottle in a reaction chamber at 50 to 80 ° C against a gas plate. After about one minute, corresponding microspheres can be detected on this gas plate.

Morita et al. disclose methods of making nanoparticles from organic materials, see, for example, Journal of Photopolymer Science and Technology, Volume 12, Number 1 (1999), 95-100, Journal of Photopolymer Science and Technology, Volume 12, Number 1 (1999) 101-106 , Journal of Photopolymer Science and Technology, Volume 13, Number 1 (2000), 159-162, Journal of Photochemistry and Photobiology, A: Chemistry, 150 (2002), 7-11, or Journal of Photochemistry and Photobiology, A: Chemistry, 103 (1997), 27-31. The processes mentioned in these documents involve the preparation of nanoparticles from organic monomers. These monomers, for example acrolein, carbon disulfide and / or trimethylsilylacetylene, are evaporated and the gaseous monomer mixture is then polymerized. The radical polymerization is by irradiation with high-energy Laser beams initiated. The polymerization of liquid monomers is not mentioned in these documents.

US 2008/0187663 discloses a method for depositing polymeric materials on certain surfaces. For this purpose, a mixture containing polymerizable components is evaporated and deposited on the corresponding surfaces under reduced pressure.

The processes known from the prior art for the preparation of polymer particles have the disadvantage that the particle size can not be reliably predicted. Furthermore, the prior art methods are not accessible to particles which are characterized by a high uniformity, for example by a narrow particle size distribution or uniform particle shape or uniform particle composition. Also, the methods of the prior art are not suitable to produce nanoparticles with diameters smaller than 3 μηη. Furthermore, the prior art methods are not necessarily suitable for continuous driving.

It is therefore an object of the present invention over the prior art to provide a process for producing nanoparticles comprising at least one polymer and / or copolymer which makes these particles accessible with predeterminable diameters. Furthermore, the process should be able to be operated continuously, making it easier to implement industrially. By changing the length of the reactor, it is preferable to be able to adjust the residence time, so that the reaction of the monomers to a large extent can take place.

These objects are achieved by the method according to the invention for producing nanoparticles comprising at least one polymer and / or copolymer by providing an aerosol containing droplets of at least one monomer and at least one photoinitiator in a gas stream, irradiating this aerosol stream with light so that the present monomers polymerize , and separating the formed nanoparticles from the gas stream.

The method according to the invention will be explained in detail below.

The process according to the invention is preferably carried out continuously.

Nanoparticles containing at least one polymer and / or copolymer are accessible by the process according to the invention. According to the invention, the term " noparticles "particles with a diameter, ie the longest particle present in the distance, from 40 to 3000 nm, preferably 50 to 1000 nm, more preferably between 50 to 400 nm and 50 to 200 nm. According to the invention, the particles produced contain at least one polymer and The term "copolymer" is understood according to the invention to mean a polymer which is made up of at least two different monomers. In a preferred embodiment, the nanoparticles produced according to the invention consist of at least one polymer and / or copolymer. In further preferred embodiments, the nanoparticles prepared according to the invention additionally contain at least one nanoparticulate additive.

In principle, larger particles than the particles produced according to the invention can also be produced with the nebulizer or atomizer used according to the invention. The direction of flow of the gas stream within the reactor is not crucial according to the invention.

The nanoparticles produced according to the invention may generally have any shape, preferably the nanoparticles are spherical, shell-shaped or hollow spheres or gel-like spheres.

The present invention therefore preferably relates to the method according to the invention, wherein the nanoparticles are spherical, shell-shaped or hollow spheres or gel-like spheres. In the context of the present invention, "cup-shaped" means that a particle is formed which has the above-mentioned diameter as outer diameter d _a and has a concave indentation with a smaller inner diameter, this inner diameter d being the diameter of the largest sphere. which fits into the indentation without this ball protruding beyond the indentation, see also FIG. 3.

In the method according to the invention, an aerosol is provided comprising droplets of at least one monomer and at least one photoinitiator in a gas stream. The use according to the invention of an aerosol has the advantage over the emulsion-based processes of the prior art that a surfactant-free system, ie a pure batch of monomer plus photoinitiator, can be used. According to the invention, the gas stream may be an inert gas stream, for example selected from the group consisting of nitrogen (N ₂ ), carbon dioxide (CO ₂ ), argon (Ar), helium (He) and mixtures thereof, or air. If the polymerization according to the invention is initiated and carried out by free radicals, it is preferred to use an inert gas stream. If the polymerization according to the invention is initiated and carried out cationically, an air or inert gas stream is preferably used.

The present invention therefore preferably relates to the process according to the invention, wherein the gas stream is an inert gas stream, for example selected from the group consisting of nitrogen (N ₂ ), carbon dioxide (C0 ₂ ), argon (Ar), helium (He) and mixtures thereof, and the polymer is formed by radical polymerization.

The present invention furthermore preferably relates to the process according to the invention, wherein the gas stream is an air stream or an inert gas stream, for example selected from the group consisting of nitrogen (N ₂ ), carbon dioxide (CO ₂ ), argon (Ar), helium (He) and mixtures thereof, and the polymer is formed by cationic polymerization.

In general, all monomers can be used according to the invention, which are characterized by a high reactivity, ie. H. a high polymerization rate under the reaction conditions of the invention, distinguished.

Since, in a preferred embodiment, the polymerization reaction takes place up to a residual monomer content in the particle of not more than 30%, preferably not more than 20%, more preferably not more than 10% within a time of less than 2 minutes, preferably less than 1.5 minutes, more preferably less than 1 minute is to be used, monomers are particularly preferably used in the process according to the invention, which have a correspondingly high rate of polymerization under the reaction conditions of the invention.

As a measure of the reaction rate of a polymerization reaction can generally serve the chain growth rate coefficient K _p . The determination of K _p is known to those skilled in the art and, for example, in Beuermann, S .; Buback, M. Prog. Polym. Be. 2002, 27, 191.

According to the invention, the chain growth rate coefficient K _{p of} the polymerization reaction is preferably greater than 500 mol / l / s, particularly preferably greater than 1 .000 mol / l / s, very particularly preferably greater than 2,000 mol / l / s, in particular greater than 5,000 mol / l / s , more preferably greater than 10,000 mol / l / s. The present invention therefore preferably relates to the process according to the invention, wherein the chain growth rate coefficient K _{p of} the polymerization reaction is greater than 500 mol / l / s, preferably greater than 1 .000 mol / l / s, more preferably greater than 2,000 mol / l / s, very particularly preferably greater than 5,000 mol / l / s, in particular greater than 10,000 mol / l / s, is.

Furthermore, the reaction rate can also be described by the so-called Damköhler number Da, which forms the ratio of residence time in the reactor and reaction time:

Da = K _p ^* Co * τ

The reaction time results from the product of chain growth rate coefficient K _p and average initial concentration of the mixture of monomer and crosslinker c ₀ .

The residence time in the reactor τ is calculated from the internal volume of the reactor divided by the aerosol volume flow.

The initial concentration is the weighted average of monomer and crosslinker concentration in the drop.

In the process according to the invention, the Damköhler number Da of the polymerization reaction is preferably greater than 200,000, particularly preferably greater than 500,000, very particularly preferably greater than 1,000,000.

The present invention therefore preferably relates to the process according to the invention, wherein the Damköhler number Da of the polymerization reaction is greater than 200,000, preferably greater than 500,000, particularly preferably greater than 1,000,000.

In the process according to the invention, preference may be given to using at least one monomer selected from the group consisting of olefinically unsaturated, preferably α, β-unsaturated, monomers, epoxides, cyclic ethers, acetals and mixtures thereof.

The present invention therefore preferably relates to the process according to the invention, wherein the at least one monomer is selected from the group consisting of olefinically unsaturated, preferably α, β-unsaturated, monomers, epoxides, cyclic ethers, acetals and mixtures thereof.

In general, α, β-unsaturated monomers are known in the art. According to the invention preferred α, β-unsaturated monomers are selected from the group consisting of acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, styrene, styrene derivatives, vinylic monomers, acrylamides, methacrylamides and mixtures thereof. Preferably used acrylic esters and methacrylic esters are compounds of general formula (I)

in which

R ^{1 is} hydrogen (acrylic acid) or methyl (methacrylic acid) and

R ^{2 is a} linear or branched, optionally substituted alkyl group having 1 to

12 carbon atoms, linear or branched, optionally substituted alkenyl group having 2 to 12 carbon atoms, optionally substituted aryl group having 5 to 18 carbon atoms, or optionally substituted heteroaryl group having 4 to 18 carbon atoms.

The groups mentioned may optionally have further functional groups, for example alcohol, keto, ether groups or heteroatoms, for example N, O, P or S. The said aryl and heteroaryl groups may optionally be attached via a saturated or unsaturated, optionally substituted carbon chain having 1 to 12 carbon atoms, preferably one or two carbon atoms, to the oxygen atom of the acid functionality. Examples of optionally present heteroatoms are selected from the group consisting of N, O, P, S and mixtures thereof. Styrene is known per se to the person skilled in the art and corresponds to the following formula (II)

Derivatives of styrene are, for example, corresponding compounds which are derived from styrene and carry further substituents on the aromatic ring and / or on the double bond, for example methyl. A preferred styrene derivative is methyl styrene.

Epoxides are known per se to those skilled in the art and, for example, selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, styrene oxide and mixtures thereof. According to the invention, the at least one monomer is preferably selected from the group consisting of acrylic acid, butyl acrylate (butyl acrylate), benzyl acrylate (benzyl acrylate), hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl methacrylate (HPMA), alkyl 2-cyanoacrylates such as ethyl cyanoacrylate (E-CA), methacrylic acid, methyl methacrylate (methyl methacrylate, MMA) butyl methacrylate (butyl methacrylate), benzyl methacrylate (benzyl methacrylate), styrene, α- Methyl styrene, 4-vinylpyridine, vinyl chloride, vinyl alcohol, vinyl ethers, N-iso-propylacrylamide (NIPAM), acrylamide, methacrylamide, and mixtures thereof.

For a cationic, photoinitiated polymerization, preference is given to using vinyl ethers and / or isopropenylbenzene (α-methylstyrene). For a cationic photoinitiated (ring-opening) polymerization, preference is given to using epoxides, cyclic ethers and / or acetals. differential

For an anionic, photoinitiated polymerization, preference is given to using alkyl-2-cyanoacrylates, acrylonitrile, styrene (derivatives), acrylates and / or epoxides.

The provision of an aerosol containing droplets of at least one monomer and at least one photoinitiator in a gas stream can generally be carried out by any method known to the person skilled in the art, or using the apparatuses generally known to the person skilled in the art. Particularly preferably, the provision of the aerosol takes place in a nebulizer or atomizer, for example by Spraying of the monomer or of the monomer solution (containing monomers, photoinitiator, optionally additives such as nanoparticles, optionally crosslinker, optionally solvent, optionally cosolvent) by means of a two-fluid nozzle or with an electrospray or with an ultrasonic nebulizer.

An advantage of the photopolymerization according to the invention over thermally induced polymerization is that in the latter case the temperature is increased. In this case, the monomers or a part thereof evaporate, so that the adjustment of the particle diameter can not be done simply by adjusting the droplet diameter. If necessary, the droplet then does not polymerize at all. At the same time, the material parameters change as the temperature increases (eg, surface tension and viscosity), which also adversely affects the stability of the drops. In particular, by evaporating monomer, it is not possible by thermally induced polymerization to produce a 1: 1 copy (i.e., particle diameter = drop diameter). Compared to a thermally initiated polymerization, the inventive method can be carried out at lower temperatures, so that a smaller proportion of the monomers evaporated. As a result, the droplet size more accurately determines the particle size. According to the invention, it is further possible, by choice of the atomizer, to set particularly narrow particle size distributions, e.g. by classifying the drops using a differential mobility analyzer (DMA).

The gas stream generally has a flow rate of 0.1 to 100 cm / s, preferably 0.5 to 10 cm / s, more preferably 0.5 to 2 cm / s, at the location of the reactor where the polymerization reaction takes place ,

The aerosol provided by the invention contains droplets of at least one monomer and at least one photoinitiator in a gas stream. The erfindungsge- Permitted method is preferably carried out so that a droplet concentration in the gas stream of preferably 10 ⁶ to 10 ¹⁰ droplets / cm ^3, preferably 10 ⁶ to 10 ⁸ droplets / cm ^3, most preferably 1 x 10 ⁷ to 1 x 10 ⁸ Droplets / cm ³ , for example 5 x 10 ⁷ droplets / cm ³ , is present. The droplet concentration can be determined, for example, using a Scanning Mobility Particle Sizer (SMPS) or a condensation particle counter.

According to the invention, N ₂ (nitrogen) is used to form the gas stream. This nitrogen may be from any source known to those skilled in the art, for example, from commercially available storage bottles, from the distillation of air etc. The other inert gases mentioned may also originate from the sources known to the person skilled in the art. The air used is preferably ambient or compressed air.

The pressure in the gas stream is according to the invention preferably at atmospheric pressure or slightly elevated atmospheric pressure. In the context of the present invention, "slightly elevated atmospheric pressure" means a pressure which is, for example, 1 to 500 mbar above atmospheric pressure. This preferably slightly elevated pressure serves, in particular, for the gas flow to overcome the resistance of a filter or a separating liquid.

The process according to the invention is preferably carried out at a temperature of from 10 to 80 ° C., preferably from 20 to 35 ° C., for example 30 ° C. The advantage of the photopolymerization carried out according to the invention is that it can be carried out at low temperatures and thus fewer chain transfers take place.

The droplets contained in the aerosol provided according to the invention contain, in addition to the at least one monomer, at least one photoinitiator. According to the invention, it is possible to use all photoinitiators known to the person skilled in the art which comprise a free-radical or ionic, ie. H. cause cationic or anionic polymerization reaction of the at least one monomer used. Since the monomer mixture is irradiated with light for polymerization, it is preferred according to the invention to use photoinitiators which release a sufficiently large amount of (primary) radicals by irradiation with light. In the context of the present invention, "light" means UV light or visible light, ie electromagnetic radiation with a wavelength of 150 to 800 nm, preferably 180 to 500 nm, particularly preferably 200 to 400 nm, in particular 250 to 350 nm UV light is preferably used according to the invention.

Examples of inventively preferred photoinitiators for a radical polymerization are selected from the group consisting of 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (for example, available under the trade name Irgacure ^® 907), 2, 2'-azobisisobutyronitrile (AIBN) and other non-symmetrical azo derivatives, benzoin, benzoin alkyl ethers, benzoin derivatives, acetophenones, benzil ketals, α-hydroxyalkylphenones, α-aminoalkylphenones, O-acyl-a-oximinoketones (Bi) acylphosphine oxides, thioxanthone (derivatives) and Mixtures thereof. Examples of photoinitiators for cationic photopolymerization which are preferred according to the invention are selected from the group consisting of substituted diaryliodonium salts, substituted triarylphosphonium salts and mixtures thereof. Examples of inventively preferred photoinitiators for anionic photopolymerization are selected from the group consisting of transition metal complexes, N-alkoxypyridinium salts, N-Phenylacylpyridiniumsalzen and mixtures thereof. According to the invention, it is also possible to carry out a so-called living anionic polymerization in the pure polymer mixture, optionally comprising secondary functionalization by means of a termination reagent, for example by injection of a gaseous or vaporizable chemical compound into the aerosol space, preferably in the outlet section.

According to the invention, certain nanoparticles, for example ZnO and / or TiO ₂ in nanoparticulate form, can also be used as the photoinitiator. These are also preferably used according to the invention as an additive. Therefore, in a preferred embodiment of the process according to the invention, at least one nanoparticle, for example ZnO and / or TiO ₂ in nanoparticulate form, is used simultaneously as a photoinitiator and as an additive.

The amount of photoinitiator in the droplets present in the aerosol provided according to the invention is, for example, 0.1 to 10% by weight, preferably 0.5 to 8% by weight, particularly preferably 0.8 to 6% by weight. , in each case based on the amount of the at least one monomer present.

In a preferred embodiment, the present invention relates to the method according to the invention, in which the droplets contain no solvent and nanoparticles are formed which have a spherical shape.

In a further preferred embodiment of the method according to the invention, the droplets additionally contain at least one solvent. In the preferred embodiment according to the invention, which contains at least one solvent in the droplets, it is preferred according to the invention to form nanoparticles which have a cup-shaped form. Furthermore, by adjusting the monomer solution containing at least one solvent, it is also possible to produce hollow spheres or gel-like spheres. The present invention therefore relates, in a preferred embodiment, to the method according to the invention, wherein at least one solvent is contained in the droplets and nanoparticles are formed which have a shell-shaped or hollow-spherical form.

Solvents which are preferred according to the invention are those in which the at least one monomer is soluble but the polymer formed is insoluble. Examples of preferred solvents according to the invention are polar organic solvents such as alcohols, ketones, esters of carboxylic acids or mixtures thereof or polar aprotic organic solvents such as acetonitrile. Other possible solvents are hexane, (methyl) cyclohexane, cyclic ethers such as THF, dioxane or ionic liquids. Mixtures of the solvents mentioned are also possible.

Suitable alcohols are, for example, selected from the group consisting of methanol, ethanol, propanols, such as n-propanol, isopropanol, butanols, such as n-butanol, isobutanol, tert-butanol, pentanols and mixtures thereof. Suitable ketones according to the invention are for example selected from the group consisting of acetone, methyl ethyl ketone and mixtures thereof.

Suitable esters of carboxylic acids according to the invention are, for example, selected from the group consisting of ethyl acetate, methyl acetate and mixtures thereof.

In a further possible embodiment of the process according to the invention, the at least one monomer can also function as solvent. For this purpose, the process parameters are set so that not all monomer is converted. Not everything is implemented, for example, up to a residual monomer content in the particle of not more than 30%, preferably not more than 20%, particularly preferably not more than 10%, and the remainder evaporates, so that the residual monomer content in the finished particles can nevertheless be very low. Ethanol or 1-propanol (n-propanol) is particularly preferably used as the solvent according to the invention.

The at least one solvent according to the invention, for example, in an amount of 10 to 80 vol .-%, preferably 30 to 70 vol .-%, particularly preferably 40 to 60 vol .-%, each based on the amount of at least one monomer used.

In a further preferred embodiment, the droplets additionally contain at least one crosslinker.

The present invention therefore preferably relates to the process according to the invention, wherein the droplets additionally contain at least one crosslinker. Crosslinkers which can be used according to the invention are known per se to the person skilled in the art. The crosslinkers bring about in the polymerization reaction of the monomers provided a crosslinking and thus an increase in the molecular weight of the polymers obtained. Examples of suitable crosslinkers are selected from the group consisting of 1,6-hexanediol diacrylate (HDDA), diethylene glycol dimethacrylate (EGDMA), allyl methacrylate (AMA), trifunctional acrylates such as trimethylolpropane trimethacrylate (PMPTMA), and mixtures thereof.

The at least one crosslinker is used according to the invention, for example, in an amount of from 2 to 80% by volume, preferably from 2 to 20% by volume, particularly preferably from 3 to 15% by volume, based in each case on the amount of the at least one monomer.

According to the invention, at least one cosolvent can additionally be added to the droplets. By way of example, this co-solvent serves to positively influence the particle structure by changing the physical, chemical or mechanical properties during the polymerization, for example solution properties of monomers and polymers, surface tension, vapor pressure, drop stability or viscosity. The cosolvent is selected, for example, from the group consisting of glycerol, glycol, polyethylene glycol, EO / PO copolymers, silicone oils and mixtures thereof.

The present invention therefore preferably relates to the process according to the invention, wherein the droplets additionally comprise at least one cosolvent selected from the group consisting of glycerol, glycol, polyethylene glycol, EO / PO copolymers, silicone oils and mixtures thereof.

In a further preferred embodiment, the droplets additionally contain at least one further additive. The present invention therefore preferably relates to the process according to the invention, wherein the droplets additionally contain at least one further additive.

In principle, all additives can be used which appear to be suitable for the person skilled in the art. Preferred examples of corresponding additives are inorganic materials and / or active substances, for example pharmaceutical, biological, insecticidal, pesticidal active substances. It is essential for the optionally present additives that they do not absorb all the radiation which is made available when irradiating the gas stream with light, preferably UV light. The additives mentioned are preferably in nanoparticulate or dissolved form.

In a preferred embodiment, the optionally additionally present additives are metals or metal and / or semi-metal oxides, for example selected from the group consisting of ZnO, Ti0 ₂ , Fe oxides such as FeO, Fe ₂ 0 ₃ , Fe ₃ 0 ₄ , Si0 ₂ and Mixtures of it.

In a preferred embodiment, the at least one additive, in particular the metal and / or semimetal oxide, is in nanoparticulate form, ie. H. with a diameter of 1 to 400 nm, preferably 5 to 100 nm, in particular 10 to 50 nm, before. The nanoparticles may be of any shape, e.g. B. spherical, cube-shaped, rod-shaped.

The at least one additive according to the invention, for example, in an amount of 0.1 to 40 wt .-%, preferably 0.5 to 25 wt .-%, particularly preferably 0.6 to 22 wt .-%, each based on the amount of at least one monomer used.

If, according to the invention, the abovementioned additives are additionally added, according to the invention hybrid nanoparticles containing at least one polymer and / or copolymer and at least one additive are obtained. These are preferably in spherical form. The hybrid nanoparticles according to the invention may also preferably be shell-shaped.

According to the invention, the droplet diameter is preferably set by the choice of operating conditions of the atomizer, for example by the pre-atomizer pressure, gas / liquid ratio, etc. In the electrospray method, for example, the voltage can be varied, for an ultrasonic atomizer the energy input , In addition, according to the invention, a specific size fraction can be selected by a differential mobility analyzer (DMA) The amount of at least one monomer and at least one photoinitiator, which are introduced into the gas stream, according to the invention is such that a corresponding number of particles per volume is obtained. By the amount of at least one monomer, according to the invention, the size of the liquid droplets formed in the aerosol and thus the size of the nanoparticles obtained after the polymerization can be calculated. Preferred diameters of the droplets present in the aerosol are, for example, 40 to 3000 nm, preferably 50 to 1000 nm, particularly preferably 50 to 400 nm or 50 to 200 nm.

Thus, according to the invention, the size of the nanoparticles to be produced can be adjusted in a targeted manner. The size of the nanoparticles produced according to the invention is therefore for example 40 to 3000 nm, preferably 50 to 1000 nm, more preferably 50 to 400 nm or 50 to 200 nm.

In the process according to the invention, the gas stream containing an aerosol containing droplets of at least one monomer and at least one photoinitiator, optionally containing at least one solvent, at least one additive, for example an inorganic material, and / or at least one crosslinker, with light, preferably UV Light, so that the present monomers polymerize. The irradiation of the gas stream with light according to the invention can generally be carried out in any device known to the person skilled in the art. UV light is preferably used according to the invention. This can be produced by all devices known to the person skilled in the art, for example LEDs, excimer radiators, for example with xenon chloride (XeCl, 308 nm), xenon fluoride (XeF, 351 nm), krypton fluoride (KrF, 249 nm), krypton chloride (KrCl, 222 nm ), Argon fluoride (ArF, 193 nm) or Xe ₂ (172 nm) as a laser-active medium, for example with 10 mW / cm ² on the radiator surface, or with a UV fluorescence tube, for example with 8 mW / cm ² on the radiator surface , The use of an excimer radiator is advantageous since it can be dimmed by pulsed operation, for example to 10 to 100%. As a result, an optimization of the polymerization process is relatively easy.

In a preferred embodiment of the method according to the invention, the reactor inner wall is flushed with an inert gas, for example with N ₂ , Ar, He, CO ₂ or mixtures thereof. This serves, for example, to suppress wall losses through polymer film formation. In a further preferred embodiment of the method according to the invention, it is additionally possible to inject a reactive gas for the secondary functionalization of the nanoparticles formed. Thus, after leaving the irradiation chamber preferably used according to the invention, the polymerization within the nanoparticles is substantially complete, so that corresponding nanoparticles are obtained which have a solid surface and thus no longer change in the further process steps, for example separation of the nanoparticles formed. This results according to the invention the advantage that almost completely spherical, or shell-shaped nanoparticles are formed. Another advantage is that the size of the droplets largely predefines the size of the particles produced. With the setting of the droplet size over the Zertäuber can thus be adjusted directly the resulting particle size. The molecular weight of the at least one polymer and / or copolymer produced according to the invention is generally from 1 000 to 1 000 000 g / mol, preferably from 10 000 to 100 000 g / mol.

In a last process step, the nanoparticles formed are separated off. The separation can be carried out in principle according to all methods known in the art. In a preferred embodiment, the separation of the nanoparticles formed takes place by deposition on the surface of a filter or by introduction into a liquid medium. The present invention therefore preferably relates to the process according to the invention, wherein the separation of the nanoparticles formed takes place by deposition on a surface of a filter or by introduction into a liquid medium.

Suitable filters are known per se to those skilled in the art, for example polyamide, polycarbonate filters, PTFE filters, for example with pore sizes of 50 nm, electrostatic precipitators.

The deposition in a liquid can be done for example with a wash bottle or a wet electrostatic precipitator. The optionally used liquid medium may be selected from the group consisting of water, ethanol, organic solvents, for example the abovementioned, non-polar solvents of all kinds, for example alkanes, cycloalkanes and mixtures thereof. After introduction of the nanoparticles produced, it is preferable to form a suspension of the particles in the liquid medium. Erfindungsge- measure this suspension can be further processed, for example by separating the particles from the suspension. In a further embodiment, this suspension is the desired process product according to the invention and can be introduced directly into the corresponding application.

The present invention also relates to nanoparticles producible by the method according to the invention. These are characterized by a particularly uniform shape, either shell-shaped or spherical, hollow sphere or gel-like spheres, and / or by a particularly narrow particle size distribution.

Due to their size, structure, composition and uniformity, the nanoparticles prepared according to the invention are particularly suitable for applications in optical, electronic, chemical, biotechnological systems or for drug application.

The present invention therefore preferably relates to the use of the nanoparticles according to the invention in optical, electronic, chemical, biotechnological systems or for the application of active ingredient. The present invention therefore preferably relates to the use according to the invention, wherein the nanoparticles are used as photosensitizers and / or photoinitiators.

characters

FIG. 1 shows a scanning electron micrograph of crosslinked PMMA polymer particles which have been produced by the process according to the invention.

FIG. 2 shows photographs of nanostructured polymer particles. On the left are nanoshells (scanning electron micrograph), on the right are hybrid nanoparticles consisting of ZnO nanoparticles and a polymer (transmission electron micrograph).

FIG. 3 shows a schematic illustration of a shell-shaped particle. In this case, d _{a is} the outer diameter and d, the inner diameter, d, results from the diameter of the largest ball, which finds place in the recess, without this ball protrudes beyond the recess. FIG. 4 shows a characteristic particle size distribution according to the invention. The x-axis shows the diameter of the particles in nm, the y-axis describes the number of particles per cm ³ . FIG. 5 shows a scanning electron micrograph of nanoshells with benzyl methacrylate as monomer according to Example 23.

FIG. 6 shows a scanning electron micrograph of hybrid nanoshells with methyl methacrylate as monomer and ZnO as nanoparticles according to Example 24.

FIG. 7 shows a transmission electron micrograph of hybrid nanoshells with methyl methacrylate as monomer and ZnO as nanoparticles according to Example 24.

FIG. 8 shows a scanning electron micrograph of copolymer particles formed with butyl acrylate (BA) and methyl methacrylate (MMA) as monomers according to Example 29.

Examples

The built-up laboratory facilities consist essentially of a commercially available atomizer and a self-constructed photoreactor. To form nanoscale, spherical (co) polymer particles, a solution is first prepared. This solution includes one or more monomers, the photoinitiator and optionally a crosslinker. The prepared solution is added to the atomizer with two-fluid nozzle and atomized with the aid of nitrogen (N ₂ ). The nitrogen-borne droplet aerosol from nanoscale monomer droplets is passed through the flow-through photoreactor, where the photo-initiated polymerization of the monomer droplets to nanoscale polymer particles or copolymer particles takes place. The gas-borne particles are then either deposited on a filter or transferred to the liquid phase. The following emitters are used: Excimer XeCI emitter (10 mW / cm ² on the emitter surface)

UV fluorescence tube (8 mW / cm ² on the radiator surface)

Further structures by means of aerosol photopolymerization: Before the atomization, the starting solution can be mixed with a solvent and / or cosolvent to obtain To form nanoshells (nanoshells) in the photoreactor (Figure 2, left). Hybrid nanoparticles can be prepared by suspending inorganic particles in the starting solution and atomising them with the solution (Figure 2, right). The following examples give the composition of the solutions used.

example 1

For the production of the particles shown in FIG. 1, a solution with methyl methacrylate (MMA) as monomer is used. The crosslinker is 1,6-hexanediol diacrylate (HD DA, 5% by volume with respect to MMA) and the photoinitiator 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 1% by weight in MMA).

Example 2

For the preparation of the nanoshells shown on the left in FIG. 2, a solution of methyl methacrylate (MMA) as monomer and ethanol (45.45% by volume in MMA) as solvent is prepared. Therein, 1,6-hexanediol diacrylate (HDDA, 10% by volume with respect to MMA) as crosslinker, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 5 wt .-% in MMA) as a photoinitiator and glycerol (26.18 wt .-% in MMA). Nanoparticles in the size range of 100 to 400 nm (more than 75% of the particles in this range) are obtained. It is generated to a proportion of> 95% shell-shaped particles.

Example 3 For the preparation of the nanoscale hybrid particles, a suspension of zinc oxide particles in ethanol (40% by weight ZnO in ethanol / 1, 74% by weight in MMA) and methyl methacrylate (MMA) is used as the monomer. The crosslinker used is 1,6-hexanediol diacrylate (HDDA, 10% by volume with respect to MMA) and the photoinitiator 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 1 % By weight in MMA). It is generated in a proportion of> 98% hybrid particles.

Example 4: For the preparation of the other homopolymers of polymethyl methacrylate, a solution with methyl methacrylate (MMA) is used as a monomer. The crosslinker is 1,6-hexanediol diacrylate (HD DA, 10% by volume with respect to MMA) and the photoinitiator 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 1% by weight in MMA). Nanoparticles in the size range of 60 to 350 nm are obtained (more than 75% of the particles in this range).

Example 5:

For the preparation of the other homopolymers of polymethyl methacrylate, a solution with methyl methacrylate (MMA) is used as a monomer. The crosslinker used is 1,6-hexanediol diacrylate (HD DA, 20% by volume with respect to MMA) and the photoinitiator 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 1% by weight in MMA).

Example 6: For the preparation of the homopolymers of polybutyl acrylate, a solution with butyl acrylate (BA) is used as the monomer. The crosslinker used is 1,6-hexanediol diacrylate (HD DA, 10% by volume with respect to MMA) and the photoinitiator 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 1% by weight in MMA).

Example 7:

For the preparation of the homopolymers of polybutyl acrylate, a solution with butyl acrylate (BA) is used as monomer. No crosslinker is used and 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 1% by weight in MMA) is used as the photoinitiator. Nanoparticles in the size range of 60 to 350 nm are obtained (more than 75% of the particles in this range).

Example 8:

For the preparation of the homopolymers of polybenzyl methacrylate, a solution with benzyl methacrylate (BzMA) is used as a monomer. The crosslinker is 1,6-hexanediol diacrylate (HD DA, 10% by volume with respect to MMA) and the photoinitiator 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 1 wt .-% in MMA) used. Nanoparticles in the size range of 60 to 300 nm are obtained (more than 75% of the particles in this range).

Example 9:

For the preparation of the nanoscale hybrid particles, a suspension of zinc oxide particles in ethanol (40% by weight ZnO in ethanol / 21, 01% by weight in MMA) and methyl methacrylate (MMA) is used as the monomer. The crosslinker used is 1,6-hexanediol diacrylate (HDDA, 10% by volume with respect to MMA) and the photoinitiator 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 1 % By weight in MMA).

Example 10:

For the preparation of the nanoscale hybrid particles, a suspension of zinc oxide particles in ethanol (40% by weight ZnO in ethanol / 0.64% by weight in BzMA) and benzyl methacrylate (BzMA) is used as the monomer. The crosslinker used is 1,6-hexanediol diacrylate (HDDA, 10% by volume with respect to BzMA) and, as photoinitiator, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 1 % By weight in BzMA). It is generated in a proportion of> 98% hybrid particles.

Example 1 1:

For the preparation of the nanoscale hybrid particles, a suspension of zinc oxide particles in ethanol (40% by weight ZnO in ethanol / 0.74% by weight in BA) and butyl acrylate (BA) is used as the monomer. The crosslinker is 1,6-hexanediol diacrylate (HDDA, 10% by volume with respect to BA) and, as photoinitiator, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 1 % By weight in BA).

Example 12:

For the preparation of the nanoscale hybrid particles, a suspension of zinc oxide particles in ethanol (40% by weight ZnO in ethanol / 0.74% by weight in BA) and butyl acrylate (BA) is used as the monomer. There is no crosslinker used and as a photoinitiator 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 1 % By weight in BA). Nanoparticles in the size range of 70 to 400 nm are obtained (more than 75% of the particles in this range). It is generated to a share of> 95% hybrid particles.

Example 13:

For the preparation of the nanoscale hybrid particles, a suspension of zinc oxide particles in ethanol (40% by weight ZnO in ethanol / 0.74% by weight in BA) and butyl acrylate (BA) is used as the monomer. The crosslinker used is 1,6-hexanediol diacrylate (HDDA, 10% by volume with respect to BA). The zinc oxide particles serve as photoinitiator. It is generated to a share of> 95% hybrid particles.

Example 14:

For the preparation of the nanoscale hybrid particles, a suspension of zinc oxide particles in ethanol (40% by weight ZnO in ethanol / 0.74% by weight in BA) and butyl acrylate (BA) is used as the monomer. There is no crosslinker used. The zinc oxide particles serve as photoinitiators. It is generated in a proportion of> 98% hybrid particles.

Example 15:

For the preparation of the other homopolymers of polymethyl methacrylate, a solution with methyl methacrylate (MMA) is used as a monomer. There is no crosslinker used and as a photoinitiator 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1 -οη (Irgacure 907, 1 wt .-% in MMA) is used. This will not produce any particles.

Example 16: For the preparation of the nanoshells, a solution of methyl methacrylate (MMA) as monomer and 1-propanol (45.45% by volume in MMA) as solvent is prepared. Therein are 1,6-hexanediol diacrylate (HDDA, 10% by volume with respect to MMA) as crosslinking agent, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 5% by wt .- % in MMA) as photoinitiator and glycerol (26.18 wt% in MMA). The proportion of particles in shell form is greater than 98%.

Example 17:

For the preparation of the nanoshells, a solution of methyl methacrylate (MMA) as a monomer and ethanol (45.45% by volume in MMA) as a solvent is prepared. Therein are 1,6-hexanediol diacrylate (HDDA, 20% by volume with respect to MMA) as crosslinker, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 5% by wt .-% in MMA) as a photoinitiator and glycerol (26.18 wt .-% in MMA). The proportion of particles in shell form is greater than 98%.

Example 18:

For the preparation of the nanoshells, a solution of methyl methacrylate (MMA) as a monomer and 1-propanol (45.45% by volume in MMA) as solvent is prepared. Therein are 1,6-hexanediol diacrylate (HDDA, 20% by volume with respect to MMA) as crosslinker, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 5% by weight in MMA) as photoinitiator and glycerol (26.18% by weight in MMA).

Example 19:

For the preparation of homopolymers of polystyrene, a solution with styrene as a monomer is used. The crosslinker is 1,6-hexanediol diacrylate (HDDA, 10% by volume with respect to styrene) and, as photoinitiator, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 5 % By weight in styrene).

Example 20:

For the preparation of the copolymers of styrene and methyl methacrylate, a solution with styrene and methyl methacrylate (MMA) is used as the monomer. The volume ratio of MMA to styrene is 3. The crosslinker used is 1,6-hexanediol diacrylate (HDDA, 10% by volume with respect to MMA + styrene) and, as photoinitiator, 2-methyl-1 [4- (methylthio) phenyl] -2 -morpholinopropan-1-one (Irgacure 907, 5 wt .-% in MMA + styrene) used. Example 21: Nanoshells with Butyl Acrylate as Monomer For the preparation of nanoshells, a solution of butyl acrylate (BA) as a monomer and ethanol (45.45% by volume in BA) as solvent are prepared. Therein are 1,6-hexanediol diacrylate (HDDA, 10% by volume in BA) as crosslinker, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 5% by weight). % in BA) as photoinitiator and glycerol (27.07% by weight in BA).

Example 21b: Nanoshells with butyl acrylate as monomer

For the preparation of nanoshells, a solution of butyl acrylate (BA) as a monomer and ethanol (45.45% by volume in BA) as solvent is prepared. No crosslinker is used and the solution is 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-o (Irgacure 907, 5 wt .-% in BA) as a photoinitiator and glycerol (15, 65% by weight in BA).

Example 22: Hybrid particles with MMA as monomer and without Irgacure 907

For the preparation of the nanoscale hybrid particles, a suspension of zinc oxide particles in ethanol (40% by weight of ZnO in ethanol / 6.62% by weight in MMA) and methyl methacrylate (MMA) is used as the monomer. The crosslinker used is 1,6-hexanediol diacrylate (HDDA, 10% by volume with respect to MMA). The ZnO particles serve as photoinitiator.

Example 23: Nanoshells with benzyl methacrylate as monomer

For the preparation of nanoshells, a solution of benzyl methacrylate (BzMA) as a monomer and ethanol (45.45 vol% in BzMA) as a solvent is prepared. Therein, 1,6-hexanediol diacrylate (HDDA, 20% by volume with respect to BzMA) as crosslinker, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907, 5 wt % in BzMA) as a photoinitiator and glycerol (24.27% by weight in BzMA).

Example 24: Hybrid nanoshells with methyl methacrylate as monomer For the preparation of the hybrid nanoshells, the monomer used is methyl methacrylate (MMA). The crosslinker is 1,6-hexanediol diacrylate (HD DA, 10% by volume with respect to MMA) and the photoinitiator is 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907 , 5 wt .-% in MMA) dissolved in the monomer. This solution is dissolved in ethanol (45.45% by volume of ethanol in MMA). Glycerol is also dissolved in this solution (26.18 wt% in MMA). The resulting solution is mixed with a suspension of zinc oxide particles in ethanol (40% by weight ZnO in ethanol / 0.50% by weight in MMA) to form a monomer suspension.

Example 25: Hybrid nanoshells with methyl methacrylate as monomer

For the preparation of the hybrid nanoshells, the monomer used is methyl methacrylate (MMA). The crosslinker is 1,6-hexanediol diacrylate (HD DA, 10% by volume with respect to MMA) and the photoinitiator is 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907 , 5 wt .-% in MMA) dissolved in the monomer. This solution is dissolved in ethanol (45.45% by volume of ethanol in MMA). Glycerol is also dissolved in this solution (26.18 wt% in MMA). The resulting solution is mixed with a suspension of zinc oxide particles in ethanol (40% by weight ZnO in ethanol / 1, 50% by weight in MMA) to form a monomer suspension.

Example 26: Hybrid nanoshells with methyl methacrylate as monomer

For the preparation of the hybrid nanoshells, the monomer used is methyl methacrylate (MMA). The crosslinker is 1,6-hexanediol diacrylate (HD DA, 10% by volume with respect to MMA) and the photoinitiator is 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one (Irgacure 907 , 5 wt .-% in MMA) dissolved in the monomer. This solution is dissolved in ethanol (45.45% by volume of ethanol in MMA). Glycerol is also dissolved in this solution (26.18 wt% in MMA). The resulting solution is mixed with a suspension of zinc oxide particles in ethanol (40% by weight ZnO in ethanol / 3.00% by weight in MMA) to form a monomer suspension.

Example 27: Copolymer

For the preparation of the copolymers of butyl acrylate (BA) and methyl methacrylate (MMA) is a solution with butyl acrylate and methyl methacrylate (MMA) as a monomer used. The volume ratio of MMA to BA is 1/1. There is no crosslinker used and as a photoinitiator 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1 -οη (Irgacure 907, 1 wt .-% in MMA + BA).

Example 28: Copolymer

For the preparation of the copolymers of butyl acrylate (BA) and methyl methacrylate (MMA), a solution with butyl acrylate and methyl methacrylate (MMA) is used as the monomer. The volume ratio of MMA to BA is 9/1. There is no crosslinker used and as a photoinitiator 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1 -οη (Irgacure 907, 1 wt .-% in MMA + BA).

Example 29: Copolymer

For the preparation of the copolymers of butyl acrylate (BA) and methyl methacrylate (MMA), a solution with butyl acrylate and methyl methacrylate (MMA) is used as the monomer. The volume ratio of MMA to BA is 1/9. There is no crosslinker used and as a photoinitiator 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1 -οη (Irgacure 907, 1 wt .-% in MMA + BA).

Example 30: Copolymer

For the preparation of the copolymers of butyl acrylate (BA) and methyl methacrylate (MMA), a solution with butyl acrylate and methyl methacrylate (MMA) is used as the monomer. The volume ratio of MMA to BA is 7/3. There is no crosslinker used and as a photoinitiator 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1 -οη (Irgacure 907, 1 wt .-% in MMA + BA).

Example 31: Copolymer For the preparation of the copolymers of butyl acrylate (BA) and methyl methacrylate (MMA), a solution with butyl acrylate and methyl methacrylate (MMA) as monomer is used. The volume ratio of MMA to BA is 3/7. There is no crosslinker used and as a photoinitiator 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1 -οη (Irgacure 907, 1 wt .-% in MMA + BA).

Claims

Patent claims

1 . Method for producing nanoparticles containing at least one polymer and/or copolymer by providing an aerosol containing droplets of at least one monomer and at least one photoinitiator in one

Gas stream, irradiating this aerosol stream with light so that the monomers present polymerize and separating the nanoparticles formed from the gas stream.

2. The method according to claim 1, characterized in that the gas stream is an inert gas stream and the polymer is formed by free radical polymerization.

3. The method according to claim 1, characterized in that the gas stream is air or an inert gas stream and the polymer is formed by cationic polymerization.

4. The method according to any one of claims 1 to 3, characterized in that the chain growth rate coefficient K _p of the polymerization reaction is greater than 500 mol/l/s, preferably greater than 1,000 mol/l/s, particularly preferably greater

2,000 mol/l/s, very particularly preferably greater than 5,000 mol/l/s, in particular greater than 10,000 mol/l/s.

5. The method according to any one of claims 1 to 4, characterized in that the Damköhler number Da of the polymerization reaction is greater than 200,000, preferably greater than 500,000, particularly preferably greater than 1,000,000.

6. Method according to one of claims 1 to 5, characterized in that the droplets additionally contain at least one solvent.

7. The method according to any one of claims 1 to 6, characterized in that the droplets additionally contain at least one cosolvent selected from the group consisting of glycerol, glycol, polyethylene glycol, EO / PO copolymers, silicone oils and mixtures thereof.

8. The method according to any one of claims 1 to 7, characterized in that the droplets additionally contain at least one additive.

9. The method according to any one of claims 1 to 8, characterized in that the nanoparticles are spherical, shell-shaped or hollow spheres or gel-like spheres.

10. The method according to any one of claims 1 to 9, characterized in that the at least one monomer is selected from the group consisting of olefinically unsaturated, preferably α,β-unsaturated, monomers, epoxides, cyclic ethers, acetals and mixtures of that.

1 1 . Method according to one of claims 1 to 10, characterized in that the droplets additionally contain at least one crosslinker.

12. The method according to any one of claims 1 to 1 1, characterized in that the nanoparticles formed are separated by deposition on a filter, a surface or by introduction into a liquid medium.

13. Nanoparticles, producible by the method according to one of claims 1 to 12.

14. Use of the nanoparticles according to claim 13 in optical, electronic, chemical, biotechnological systems or for active ingredient application.

15. Use according to claim 14, characterized in that the nanoparticles are used as photosensitizers and/or photoinitiators.