WO2018202868A1

WO2018202868A1 - Barrier encapsulation of water-based systems on the basis of uv-curable shell systems

Info

Publication number: WO2018202868A1
Application number: PCT/EP2018/061542
Authority: WO
Inventors: Thomas Ballweg; Doris Hanselmann
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2017-05-05
Filing date: 2018-05-04
Publication date: 2018-11-08
Also published as: DE102017109673A1

Abstract

The present invention relates to a method for producing capsules comprising a water-containing core material and a water-vapour-impermeable polymerised casing, wherein the capsules have a high water vapour impermeability, and relates to water-(vapour)-impermeable capsules or capsules that can be obtained by the method. The method comprises co-extruding the core material and a composition that contains a UV-polymerisable precursor material of the casing and a radical starter in such a way that the UV-polymerisable precursor material surrounds droplets of the water-containing core material, in order to obtain a co-extruded material, and subsequently passing the co-extruded material through a curing zone for a short time, wherein a polymerisation and crosslinking of the precursor material of the casing is brought about by actinic radiation, wherein the UV-polymerisable precursor material is at least one compound with two diacrylate groups and/or dimethacrylate groups respectively at the ends, which are connected by a short, rigid group, and wherein the core material contains a means for achieving interfacial compatibility between the core material and the casing.

Description

Barrier encapsulation of water-based systems based on UV-curable shell systems

The present invention relates to a process for the preparation of capsules comprising a water-containing core material and a water vapor-impermeable one

polymerized shell, the capsules having a high water vapor impermeability, as well as water (vapor) impermeable capsules or capsules obtainable by the process. The encapsulation of water, aqueous solutions, suspensions, emulsions or other aqueous or water-suspended ingredients in terms of a water and water vapor-tight hermetic and contamination-free seal in a thin-walled container is an unresolved challenge in many areas and for many applications. While the encapsulation of larger volumes in milliliters or

Literature scale (so-called macroencapsulation) usually by the filling and the

It can be achieved in the size range from 0.1 to 10 mm in diameter (nanoliter to submillitre range up to a maximum of about 1 milliliter), in which the encapsulation is not achieved by subsequent filling, but preferably by an internal situ process takes place, no viable alternative.

This is because, on the one hand, the number of suitable water vapor impermeable materials is very limited and, on the other hand, the processability of the materials must be compatible with the ingredients. Polyolefins such. B. Ultra-high molecular weight polyethylene, which is used for example for the macroencapsulation of salt hydrate-based heat storage, provide good conditions, the requirements of the

To meet water vapor barrier. However, for the processing of the materials in the context of in-situ (micro) encapsulation processes, temperatures in the melting range are

Materials beyond 100 ° C or the use of solvents required, which would lead to boiling or contamination of the aqueous content and thus are not pro-compatible. Therefore containers made of polymeric materials are prefabricated and subsequently filled and sealed. The same applies to the processing of

Metal containers. In turn, low melting waxes and fats are unsuitable for producing thin-walled, mechanically stable shells and, moreover, do not meet the barrier requirements.

Depending on the intended use, the capsules frequently still have to meet a catalog of further criteria, in particular with regard to the adjustability of the mechanical properties such as the breaking strength and the modulus of elasticity. Especially when it comes to it goes, the contents of the capsules in a defined pressure window by mechanical

Exposing and destroying the capsule walls are classic

Polymer materials (thermoplastics, "Plastics") due to their plastic deformability and impact resistance is not a suitable starting point, so that for this reason other solution concepts are required.

An adequate solution to this problem does not yet exist. In the "method for encapsulating liquid or pasty substances in a crosslinked encapsulating material" described in WO 2010/125094 A2, precrosslinked actinically curable ones are used

Compounds based on inorganic-organic hybrid polymers as shell formers for use. A concentric nozzle configuration produces droplets of the ingredient in the core and the hybrid polymeric shell material on the outside of the droplets. Hardening occurs when a UV radiation field fails. The UV-induced "cold" hardening enables temperature control and the production of largely defect-free capsules in core-shell morphology, which means that the requirements of a moderate process temperature and largely solvent-free conditions as conditions for gentle in situ encapsulation can be met. However, a water and water vapor barrier is not accessible with these materials because of the many different reasons: Firstly, the heterogeneous matrix material with its polar structural units does not meet the material requirements of a water vapor barrier material, which is defined by the combined solubility / diffusion principle second slows down the

Pre-crosslinking the shell molding with the result of a non-uniform shell thickness and poor encapsulation quality. Third, the hybrid polymers virtually inevitably always contain traces of volatile components and / or residual solvents that affect the compactness as well as the defect frequency of the shell. Therefore, due to the process, the hybrid polymers do not meet the requirements of a

Substrate material for barrier applications must be made.

The encapsulation of aqueous systems with the aid of UV-curable acrylates (hydrocapsules) is also described in US Pat. No. 6,780,507 B2. The drop formation and capsule formation takes place here by micro-extrusion using a concentric nozzle, but here in the

Contrary to WO 2010/125094 A2, in which the extrusion in air or in general

Gas atmosphere takes place - in an oil bath, which is illuminated by a UV lamp. The idea and motivation for this was to use the residence times in the radiation field in the

Range of seconds considered necessary for capsule formation and cure. The barrier aspect is not addressed in the "hydrocapsules." The shells are not defined with respect to water vapor permeability

assume that the capsules revealed there are stored in the atmosphere dry out within a short time when an aqueous core material is used. The size distribution of the capsules is wide, as the shearing by inevitable

Flows of the fluid is influenced uncontrollably. Surface quality and shape of the capsules as well as the process frequency are adversely affected by the external liquid medium.

US 2006/0071357 A1 discloses a method and an apparatus for producing microcapsules by means of ultrasonic atomization, wherein a UV-polymerizable material is used as the starting material for the envelope. Concretely, propoxylated neopentyl glycol diacrylate (SR-9003 from Sartomer) and an ethoxylated pentaerythritol tetraacrylate (SR 494 Sartomer) were used as the shell materials. Due to the shell materials used and the described preparation is not to be assumed by a water vapor impermeable envelope. On the contrary, the propoxylation and in particular the ethoxylation causes an increase in water affinity and has a particularly rapid dehydration of the capsules.

US 2010/0126344 A1 discloses mixtures which are a component of the latent

Heat storage in the form of microcapsules contained in an organometallic matrix component.

EP 2 081 541 B1 discloses microencapsulated photoinitiators which are prepared by forming a microemulsion and subsequently the monomer droplets of the

Microemulsion are polymerized. EP 1 784 302 B1 discloses a substantially non-flowing carrier material of monomers, oligomers or polymers coated by a polymer capsule, wherein the polymeric coating material is not substantially limited.

The object of the present invention is therefore to provide a simple and highly productive process for the production of capsules, in particular in the size range up to about 10 mm in diameter with the narrowest possible size distribution and high surface quality, containing as the core material water or a water

Composition, wherein the capsule shell a high water vapor or

Has impermeability to water, the capsules have a high storage stability and the core material can be released as needed by a defined mechanical action.

This is inventively achieved by a method according to claim 1.

Preferred embodiments of the method can be found in subclaims and the following description. The present invention also relates to capsules or capsules obtainable by the method according to the invention

water vapor-resistant envelope of a polymeric material obtained from a UV-polymerizable precursor material and an aqueous core material. The capsules allow for easy release of the aqueous core material

mechanical action / stress, for example by pressure and / or

Shear stress.

It has been possible to produce spherical capsules filled with water, aqueous solutions, aqueous suspensions, aqueous emulsions, in particular aqueous oil-in-water emulsions, in the millimeter and sub-millimeter range with thin acrylate shells which are also stored under storage Ambient conditions or even the conditions of particularly dry air have long retention periods (over months and years) against water and water vapor and do not dry out. The high quality of the shells with their good mechanical and basic barrier properties also makes it possible to use the capsules z. B. by vacuum process even in the high barrier area, z. B. by sputtering technology to further refine.

This is achieved by a method according to the invention for the production of capsules with a water-containing core material and a water vapor-impermeable polymerized shell, with the steps:

Coextrusion of the core material and a composition containing a UV-polymerizable precursor material of the shell and a radical initiator, such that the UV-polymerizable precursor material contains droplets of the water-containing

Surrounding core material to obtain a co-extruded material, and

- then passing the coextruded material through a curing zone which is a gas filled area, e.g. Air or inert gas filled area wherein polymerization and crosslinking of the precursor material of the shell is effected by actinic radiation and the residence time of the coextruded material in this curing zone is 0.02 to 0.2 seconds,

wherein the UV-polymerizable precursor material is at least one compound having two respective terminal diacrylate groups and / or dimethacrylate groups joined by a short, rigid group, and

wherein the core material contains a means for achieving interfacial compatibility between the core material and the shell.

The curing zone according to the invention is in particular a zone of very high radiation intensity. This high radiation intensity can be achieved by having a Total radiation power of, for example, 140 W / cm x 15 cm = 2100 W is focused in a focal line of, for example, about 1 cm wide, which fall through the capsules. For a 1 cm wide focal line, this corresponds to a radiation intensity of 140 W / cm ² . According to the invention, the radiation intensity in the region which is precipitated by the particles is preferably 10 to 160 W / cm ² , more preferably 20 to 150 W / cm ² , more preferably 30 to 145 W / cm ² , still more preferably in the range of 50 to 140 W / cm ² . Such a radiation intensity can easily be set by the person skilled in the art. As a result, short residence times and simultaneously high degrees of crosslinking can be achieved. In the prior art, for example US 2006/0071357 A1, the radiation intensity is significantly lower.

According to the invention, the capsules are thus produced by means of a technological process which combines microextrusion, the selection of specific precursor materials, a generally vibration-induced drop generation and UV curing. In particular, it was surprising that capsules with particularly good barrier properties are obtained by certain diacrylates and methacrylates and not with higher functional building blocks (tri- / tetraacrylates or oligomers), which in principle make possible a higher crosslinking density.

The coextrusion is carried out according to the invention by means of a concentric nozzle combination with a core and ring nozzle, the most parallel possible leakage of the

The sheath precursor material and the core material enable such that the cross-linkable precursor material is extruded as an outer sheath (eg, annular) around the content material, the core material is enclosed by the precursor material, and from the core material

Outside material covered drops are formed. This ensures the clean

Separation of core (water) and shell materials at negligible

Contamination and controlled adjustable shell thickness with tight tolerances in the

Sense of maximum encapsulation efficiency. The coextrusion step is carried out in air or generally a gas, in particular an inert gas. Immediately or shortly after the extrusion step and preferably in a relatively large spatial proximity to the

Extrusion device, the particles are preferably guided by gravity through a zone in which the precursor material is polymerized and crosslinked by actinic radiation. The choice of the distances between the components is important. The distance between the extrusion device and the radiation zone is preferably to be selected such that it is just sufficient for pinching and rounding off the drops. Depending on the nozzle exit speed of the materials, the associated optimal pinch-off frequency and the resulting production speed, this distance is preferably at least 15 cm and a maximum of 150 cm, typically about 20 to 50 cm. With increasing distance between nozzles and radiator takes the Speed of the capsules due to the acceleration of gravity, so that the residence time in the radiation zone at an even greater distance for curing is not sufficient.

The resulting cross-linking product encloses as a capsule the ingredient that fills these structures. The coextrusion process for the formation of capsules is known per se and described for example in Chemie Ingenieur Technik 2003, 75, No.11, pp. 1741-1745, but without the UV curing used in this invention for encapsulating aqueous ingredients. An essential feature of the present invention is that the UV-polymerizable precursor material for the shell is at least one compound having two respective terminal groups, the terminal groups being independent of one another

Diacrylate groups, dimethacrylate groups, and combinations thereof are selected, wherein the terminal groups are linked by a short, rigid group (hereinafter also referred to as "linking group"). One skilled in the art will understand groups having low lateral and rotational mobility having steric properties and / or by stabilizing hydrogen bonds.

The term "(meth) acrylate", and terms derived therefrom, as used herein include, but are not limited to, methacrylates, acrylates or mixtures of both.

By choosing a short connection group, the mobility of one of the

Limited precursor material formed polymer chain. The rigidity or chain stiffness of the linking group is determined by the spatial structure of the linking group and the chemical nature of the bonds occurring therein. Since the shell material serves as a water or water vapor barrier, it is preferable according to the invention to choose a nonpolar compound group. The crosslinking and polymerization takes place according to the invention substantially via the terminal (meth) acrylate groups. The linking group should preferably not or not significantly contribute to crosslinking and therefore preferably contains no double bonds. Moreover, double bonds can be cleaved during UV curing and should therefore preferably be avoided according to the invention within the compound group.

The linking groups are groups derived or derived from compounds having terminal OH groups (diols, bisphenols). By "derived from" or "derived from" it is meant that in the precursor material at the terminal OH groups of these compounds, the hydrogen atoms through the acrylate or

Methacrylate residues are replaced. Preferably, the short, rigid group (linking group) is derived from or derived from at least one compound selected from the group consisting of: a. aliphatic bicyclic or tricyclic ring diol systems obtained by

Alkyl groups with 1 to 3 carbon atoms may be substituted,

b. Bisphenol A or derivatives thereof in which one or both of the phenyl radicals

Alkyl groups are substituted by 1 to 3 carbon atoms, and

c. Diurethanes formed from a branched Cs to Cio-alkyl diisocyanate or Cs to C10 cycloalkyl diisocyanate and monoethylene glycol, wherein the molar ratio is preferably from about 1: 1.5 to about 1: 3 (alkyl diisocyanate: ethylene glycol).

The under a. mentioned compounds are particularly preferred according to the invention and can be prepared from diols of bicyclic compounds such as bicycloheptanes (for example bicyclo [3.2.0] heptane),

Bicyclooctaene (eg bicyclo [2.2.2] octane), bicyclononanes (eg bicyclo [3.3.1] nonane or bicyclo [4.3.0] nonane), bicyclodecanes (eg bicyclo [4.4.0] decane), bicycloundecanes (e.g. B. bicyclo [3.3.3] undecane), and the like, or bridged bicyclics (ie, tricycles), such as Diols of tricyclodecanedimethane.

The under a. mentioned compounds may be unsubstituted according to the invention or substituted with alkyl groups each having 1 to 3 carbon atoms. As preferred

Substituents are methyl groups in question. The number of optional

Alkyl substituents are preferably 1 to 5, more preferably 2 to 4. In further

preferred embodiments, no further substituents are present. As concrete and particularly preferred examples of precursor materials, the compounds of category a. Tricyclodecanedimethanol diacrylate (TCDDA, more particularly tricyclo [5.2.1.0] decanedimethanol diacrylate) and tricyclodecanedimethanol dimethacrylate (TCDMDA, more particularly tricyclo [5.2.1.0] decanedimethanol dimethacrylate) may be mentioned, with tricyclodecanedimethanol diacrylate (TCDDA) being most preferred.

The under b. The compounds mentioned are in particular derived from bisphenol A (2,2-bis (4-hydroxyphenyl) propane) or from derivatives of bisphenol A in which one or both phenyl radicals are substituted by alkyl groups having 1 to 3 carbon atoms. Preferred substituents are methyl groups. The total number of optional alkyl substituents on the phenyl radicals is preferably from 1 to 4, more preferably from 2 to 3. In further preferred embodiments, there are no substituents on the aromatic rings, ie, bisphenol A. Examples of alkyl substituents Derivatives are bisphenol C (4,4 '- (1-methylethylidene) bis [2-methylphenol]) or bisphenol G (4,4' - (1-methylethylidene) bis [2- (1-methylethyl) phenol]).

As concrete and particularly preferred examples of precursor materials, the compounds of category a. may be mentioned bisphenol A diacrylate and bisphenol A dimethacrylate.

The under c. The compounds mentioned are preferably derived from diurethanes which are formed from a branched Cs to Cio-alkyl diisocyanate or Cs to Cio-Cycloalkyldiisocyanat and monoethylene glycol. In this case, the molar ratio is preferably from about 1: 1, 5 to about 1: 3 (alkyl diisocyanate: monoethylene glycol), more preferably about 1: 2.

These compounds are compounds with two terminal ones

Monoethylenglycolgruppen, which are each connected via a urethane group with a central, branched alkylene group. The branched alkylene group preferably has 5 to 10 carbon atoms, more preferably 6 to 9 carbon atoms. The main chain of the branched alkylene group preferably has 4 to 7, more preferably 5 or 6

Carbon atoms on. As the branching group, in particular, methyl groups are preferable. Most preferably, the branched alkylene group is a 2-methyl-4,4-dimethylhexylene group. Cycloalkyl groups are also suitable according to the invention, the cycles preferably having 5 to 6, in particular 6, ring carbons and furthermore being able to be substituted by alkyl groups, in particular methyl groups.

As concrete and particularly preferred examples of precursor materials, the compounds of category c. are urethane dimethacrylate (UDMA) of the following formula, which is usually a mixture of isomers, called, or

corresponding urethane diacrylate:

This is commercially available under the name UDMA (HEMATMDI), for example, from the company Evonik and has a viscosity of 0.33 Pas (60 ° C) (manufacturer). As already mentioned, a coextrusion of the core material and the

Precursor material of the shell such that the precursor material surrounds the core material. This is achieved by means of a nozzle combination of a generally annular nozzle and a central, usually concentric inner nozzle. The resulting coextruded material is then solidified by actinic radiation. The

achievable forms can merge into each other, d. H. Depending on the process, it is possible to produce essentially spherical capsules, or rather drop-shaped or egg-shaped capsules. A particular advantage, however, is that according to the invention capsules with high

Sphericity and possible monomodal size distribution can be achieved.

As far as possible a monomodal size distribution are typical

According to the invention, dmax / dmin values of less than 1, 1, less than 1, 05, or also achievable in the range of 1:01 or smaller, where dmax and dmin are the diameters of individual particles of an ensemble of, for example, 20 or 50 particles , The diameters of the individual particles can be determined by means of a caliper or with small particle sizes by a light or scanning electron microscope.

The capsules or the capsules of the present invention prepared by the method according to the invention are so-called microcapsules and are in a range of an average particle size of preferably 0.1 to 10 mm, preferably 0.2 to 8, more preferably 0.3 to 5 mm, most preferably in the range 1 to 5 mm. The resulting portioning of the water is advantageous for many applications, since large quantities can be applied with good mixing at the same time. The mean particle size can be determined, for example, by means of a caliper, the diameter of 20 or more, for example 50 or 100 particles, determined and then the average is formed. For smaller particle sizes, the particle size determination can also be determined by means of light or scanning electron microscope, also by averaging 20 or more, for example 50 or 100 particles. In the case of high sphericity and monomodal particle size distribution, 20 particles are generally sufficient to determine the mean diameter. As a rule, ideal spherical particles are desired according to the invention, but oval shapes of the particles are also included. In the case of oval, elongated particle shapes, the particle diameter can first be determined for each individual particle by measuring the long and the short diameter and using the mean value thereof as the particle diameter. From these particle diameters, the average particle diameter is then calculated as in the case of round particles. It is possible with the method according to the invention, capsules with compared to

Capsule size thin wall thicknesses. In general, the

Capsules produced according to the invention have an average wall thickness of 10 μm to 2 mm, preferably 50 μm to 200 μm. A wall thickness of the capsules in the range of 50 to 200 μηη provides an optimal compromise of capsule efficiency and strength, in the extended range are also range 10 μηη adjustable to 2 mm.

Due to the high shell strength and thus achievable low shell thickness charge capacities of up to 50 to 90% or more than 90% can be achieved, wherein the charge capacity is defined as the ratio of mass of core material to the total mass of the capsules.

The wall thickness is set by adjusting the ratio of the

Material flows for the core and shell material. This is done at the beginning of a

Production series a material flow ratio of core to shell material z. From 5: 1 w / w. specified. For a defined outer diameter of the capsule z. B. of 4 mm, which is set by the choice of the nozzle geometry, is thus under

Consideration of density for core and shell material defines the wall thickness. Control of the average wall thickness of a capsule batch is accomplished by first weighing a representative ensemble of about 20 water-filled capsules of defined size, then crushing, drying and weighing again. About the density of nuclear and

Shell material with a defined outer diameter, the average wall thickness is calculated. By way of example, on individual capsules of the series, the control of the shell thickness and its uniformity and freedom from defects also take place with the aid of light and light

Scanning electron micrographs of the shell surface and the break edges.

The compressive strength resulting from the dimensions (uniaxial load) is dependent on the variable diameter of the capsule diameter and the shell thickness

Use adjustable in the range of 0.1 N to 200 N. This corresponds to the

Categories Eggshell morphology to practical (by hand) indestructible. For capsules in which the capsule contents are made by crushing the cups between the fingers, compressive strength in the range of about 5 N to 25 N is particularly advantageous. The uniaxial compressive strength is determined using a Zwick universal testing machine based on representative sample sizes of 20 capsules. The capsules are between two planar test stamps made of stainless steel with a

Forward speed from 3 mm / min to total failure (break) crushed. The data acquisition and evaluation is carried out with a 100 N load cell and the software testXpert ^® . The capsule wall thickness is a significant factor not only for the compressive strength but also for the water vapor transmission rate. A reduction of the wall thickness reduces the pressure resistance and thus the force required for the release, but on the other hand increases the water vapor transmission rate. Depending on the field of application, a compromise can be found here and an adjustment made.

As already mentioned, the capsules can be produced in monomodal, uniform size with a very low tolerance range. This is beneficial for achieving a

uniform wall thickness and prevents falling below a minimum value as a prerequisite for barrier applications and further processing in a vacuum process.

In the method according to the invention, the rheological behavior of the

Precursor material can be adjusted so that it prefers the constriction and the formation of spherical capsules as possible and favors a smooth running on the core material. Preferably, the viscosity of the UV-polymerizable precursor material at the process temperature, ie during extrusion, 0.001 to 50 Pa-s, more preferably 0.01 to 10 Pa-s, even more preferably 0.1 to 1 Pa-s. The

Viscosity values thus relate to the particular used in the extrusion

Temperature of the precursor material. The viscosity is measured with a pair of MCR 102 rheometer according to the cone-and-plate principle with cone dimensions of 60 mm / 4 ° and a measuring gap of 150 μm. For estimation of a suitable process temperature can be measured by default in the speed range from 0.1 to 100 1 / s at 20, 40 and 60 ° C. The respective desired viscosities can be controlled or readjusted via the temperature at which the encapsulation takes place.

Furthermore, only non-processable (or non-processable at a given temperature) higher-viscosity precursor materials can also by mixing with

low-viscosity components, for example, the tri-, tetra- or higher-functional acrylates described below, are processed. With regard to the water or water vapor impermeability of the sheaths of

Capsules according to the invention aim for a capsule shell which is as defect-free as possible. In order to achieve this, it is particularly advantageous according to the invention if the precursor material contains no organic solvents or other volatile constituents which could escape during the production process or storage and thus could damage the casing. Technical grade systems with impurities and low vapor pressure fractions favor shell defects due to bubble formation

less suitable according to the invention. In preferred embodiments, the composition which is extruded as a shell material preferably consists of Precursor material and the radical initiator, in further preferred embodiments, the sum of precursor material and free-radical initiator is at least 98 wt .-%, ideally greater than 99 wt .-% of the composition, which is extruded as a shell material. In further embodiments of the invention, the composition which is extruded as a shell material consists of the precursor material, the radical initiator and an agent for improving interfacial compatibility.

The precursor material which is at least one compound having two respective terminal diacrylate groups and / or dimethacrylate groups joined by a short, rigid group may be partially replaced by tri-, tetra- or higher-functionality acrylates, in particular to adjust the viscosity of the precursor material, as mentioned above. The present invention thus also encompasses embodiments in which the di (meth) acrylate precursor material contains up to 30% by weight, for example up to 25% by weight or up to 20% by weight, of such tri-, tetra - or higher functional

Acrylates is replaced. An example of such inventively applicable

trifunctional acrylate is trimethylolpropane triacrylate (TMPTA).

According to the invention, an extrusion in a gas atmosphere, i.d.R. Air or inert gas, carried out to a maximum surface tension of the shell over the

External medium to produce, so that a sufficiently good, defect-free and smooth surface is obtained as a condition for a pinholefreie barrier. Suitable gases besides air, e.g. Nitrogen or noble gases such as argon. By the drop formation in air or

Gas atmosphere gives the best possible surface quality with low roughness comparable to that of the substrates for barrier films, as shown by AFM images. This is favorable with regard to an optional further refinement and improvement of the barrier properties of the capsules z. B. by subsequent metallization or metal oxide coating.

Drop generation is vibration-assisted in the frequency range from 20 to 2000 Hz depending on capsule size. For a capsule size of 4 mm diameter is the

Frequency range of 40 to 200 Hz preferred, equivalent to a capsule amount of 40 to 200 capsules per second or approx. 150,000 to 720,000 capsules per hour. This results in a highly scalable and commercializable process. Short exposure times are inventively a necessary condition for the

Production of capsules with barrier quality. By the short and high-intensity

Exposure pulse, the hardening of the shells is initiated, which after the subsequent dark reaction very high conversion rates of the monomers used, for example. Significant above 90%, so that the curing reaction is largely complete when the capsules hit the collecting container or a collecting device and the capsules have a tack-free surface. The exposure time is

According to the invention about 0.02 to 0.2 seconds, preferably about 0.05 to 0.1 seconds.

This results in a maximum, not yet reached or reported degree of crosslinking. The conversion rate is for example in the range of 93-95% z. For TCDD (M) A, but at least 85%.

The initiation of the starter reaction takes place in a UV radiation field, which consists of a

Mercury spectrum or metal-doped (eg Fe) mercury silver is obtained. Specifically, for example, iron-doped mercury vapor radiators which generate a radiation spectrum of the D-type can be used as the radiator. This is characterized by the fact that, in addition to the short-wave Hg spectrum, it also has a strong output in the longer-wave UV range of 350 to 400 nm. An emitter usable according to the invention is 15 cm long and emits a maximum of 200 watts of total radiation power per cm length (IR, visible, UV). The radiation can be brought together via an elliptical reflector in a focal line which will fall through the capsules. For example, about 50 to 140 W per cm arc length or, in the case of an about 1 cm wide focal line, about 50 to 140 W / cm ² can be used as suitable radiation intensities

Total area intensity. In the present invention, the radiation intensity in the region / focal line which is precipitated by the particles is preferably 10 to 160 W / cm ² , more preferably 20 to 150 W / cm ² , more preferably 30 to 145 W / cm ² , still more preferably in the range of 50 to 140 W / cm ² . Such a radiation intensity can be adjusted by the person skilled in the art with the aid of the abovementioned radiators. As a result, short residence times and simultaneously high degrees of crosslinking can be achieved. In the prior art, for example US 2006/0071357 A1, the radiation intensity is significantly lower.

The composition containing a UV-polymerizable precursor material according to the invention also contains a radical initiator. Commercial free-radical initiators known to those skilled in the art, such as, for example, benzophenones, acylphosphine oxides, o-hydroxyketones or the like, in particular Lucirin® TPO (BASF) or Irgacure® 184 (Ciba), can be used as radical initiators.

According to the invention, the residual monomer content of the monomers used after curing is preferably 15% by weight or less, more preferably from 2 to 10% by weight, even more preferably from 1 to 5% by weight. This corresponds to a high conversion rate, i. a high degree of conversion of the monomers used and thus a minimization of the

Residual monomer content of the shell. At the same time, the amount of the required Radical starters reduced. As a result, the migration of residual monomers and starter molecules into the core material can be pushed into the detection limit range even during prolonged storage. As a result, new qualities are achieved which enable the use of materials in the consumer product sector as well. It is also particularly advantageous that the aqueous content is sterilized in situ by the high-intensity UV irradiation and sterilized in this way. The conversion rate and, correspondingly, the residual monomer content of the shells can be determined in a simple manner, for example using the Dynamic Scanning Calorimetry (DSC) method, and used for quality assurance purposes. Here, a representative amount (typically 0.1 g) of hardened shell fragments in a crucible is heated continuously at a rate of 10 K min, thereby causing the remaining double bonds to react and quantifying the remaining double bonds by evaluating the resulting exothermic signal.

The conversion rate may be significantly greater than 85%, typically even significantly greater than 90%, corresponding to the low residual monomer content.

To provide interfacial compatibility between the polar, aqueous dominated content and significantly less polar shell material, the addition of a process additive to the core material is envisioned. As such, means for achieving a

Interfacial compatibility is, for example, neutral surfactants (eg Tween 80) or water-soluble polymers such as polyethylene oxide having a molecular weight in the range of about 1,000 to 10,000,000, especially 50,000 to 3,000,000 or 100,000 to 2,000,000 (e.g. PEO with molar mass 1 million or 2 million daltons). The additive PEO has the additional advantage over the surfactant effect that it increases the viscosity of the core material, thereby reducing the vibration behavior of the droplet and thus favors the capsule formation in terms of sphericity.

The concentration is preferably in the range of about 0.05 to 2 wt .-%, based on the core material. Also, the composition containing the UV-polymerizable precursor material may be added with an agent for achieving interfacial compatibility, for example, an ethoxylated acrylate, but is preferable in the present invention if the

Means for achieving interfacial compatibility is added only to the core material.

Due to the high degree of conversion that can be achieved during curing, it is in

Embodiments of the invention are not required to carry out an active postcuring, optionally such postcuring, in particular UV curing, but according to the invention may be advantageous in order to further reduce the residual monomer content. If the capsules produced are not shielded, for example in the collecting container by the stray light of the radiator, An automatic post-crosslinking takes place without further measures having to be taken.

The capsule walls of the capsules according to the invention or inventively prepared already have unmodified barrier properties up to the middle range at shell thicknesses in the range of 150 μηη. Water vapor transmission rates (WVTR) are thus obtained in the range from 1 to 10 g / m ² d under standard measuring conditions (23 ° C., 80% relative humidity difference). The water vapor transmission rate can according to the invention with a predetermined number of particles, typically 20 particles, with a known wall thickness (eg about 150 μηη simple wall thickness), resulting in a

Environment with a relative humidity of 20% can be determined. In this case, over a predetermined period of time, for. B. 2 weeks, the weight loss followed gravimetrically. The high degree of crosslinking is an essential prerequisite for or favors the barrier property of the capsule.

The low WVTR of the unmodified capsules is a prerequisite for a

Refining / improvement of capsules in the field of high and

Ultrahigh barrier, since it allows the adjustment of the process conditions required for the vacuum process. The invention or according to the invention

produced capsules are vacuum-tight, i. mechanically sufficiently stable and sufficiently close to water vapor, so that they can be further processed in vacuum process without damaging the shell and in this way can be further refined. These methods include the standard methods of the

Barrier film technology such as vacuum coating by vapor deposition, sputtering,

Plasma method and the like Due to their stability and impermeability, the capsules also permit chemical and / or galvanic metallization.

The present invention also relates to capsules and capsules which can be prepared by the process according to the invention and which are defined as follows: capsules having a

A water-vapor-tight envelope of a polymeric material obtained from a UV-polymerizable precursor material, wherein the UV-polymerizable

Precursor material is at least one compound having two terminal diacrylate and / or Dimethacrylatgruppen each, which are connected by a short, rigid group, and a water-containing core material, wherein the capsules have an average particle size of 0.1 to 10 mm, preferably 1 to 5 mm, and an average wall thickness of 10 μηη to 2 mm, preferably 50 μηη to 200 μηη. The advantageous embodiments described with regard to the method also apply mutatis mutandis expressly for the capsules according to the invention or can be prepared according to the invention.

Accordingly, for example, the capsules preferably have a WVTR (measured at 23 ° C. and a relative humidity difference of 80%) of 0.005 to 50 g / m ² d, in particular 0.1 to 10 g / m ² d or 1 to 10 g / m ² d, up.

With the method according to the invention it was possible to prepare capsules which have a high loading capacity of preferably 50 to 90%, the loading capacity being defined in% as (weight of the core material / total weight of the microcapsules) ^* 100 [%]. The present invention thus encompasses capsules having a loading capacity of 50 to 90% or even more than 90%, more preferably 60 to 80%. The loading capacity can be determined, for example, as an average of 100 or 1000 particles by mechanically destroying the shells of the particles and determining the weight of the liquid core materials and the solid shell materials.

Due to the choice of material and also the high degree of crosslinking, the capsules according to the invention or inventively produced have a brittle breaking shell, so that the water-containing core material can be removed by mechanical action,

For example, a compressive stress (eg impact load) and / or

Shear stress, releasable.

The capsules according to the invention or produced according to the invention can be used in various fields, e.g. in the cosmetics, automotive, textile, chemicals, DIY and home improvement, consumer products sectors

(Household, cleaning), agriculture and environment.

The capsules according to the invention or prepared according to the invention are suitable, for example, as storage for salts, salt hydrates, carbohydrates, proteins, vitamins, amino acids, nucleic acids, lipids, medicaments, thickeners, emulsifiers, surfactants, dyes, cell material, sperm, flavorings and / or fragrances. The

Core material may be present, for example, in the form of aqueous solutions, oil-in-water emulsions, water-in-oil emulsions or aqueous suspensions. The capsules according to the invention or produced according to the invention are likewise suitable as integrated or separate components of latent heat accumulators,

Dry mixes for the construction sector, moisture-activatable

Adhesive compositions, in particular one-component adhesives. The uses of capsules of said size range with water vapor barrier properties, which make it possible to retain the aqueous content for months or years, are manifold. An application example would be the encapsulation and long term sealing of salt hydrated phase change materials, which require a barrier over a 10 year period. encapsulated

Water solutions also allow dry blends z. B. for the construction sector, wherein the release of water or water-soluble agents can be done during mixing by destroying the capsules. Water-filled capsules could be used for the precise curing of adhesives (cyanoacrylate, silicone, 1 K polyurethane) by their triggered release "at the touch of a button".

The capsules according to the invention or inventively prepared can be used in dry blends for the construction chemical sector, z. For example, for mortar / concrete with integrated liquid components that are released during mixing.

According to the invention, the encapsulation of sensitive products (cell material, sperm) is possible and also preferred, since the content is preferably sterilized in the production of the capsules.

For applications in which the capsule contents should not be released as far as possible during the product life, for example, for the function of storing salt hydrates in latent heat accumulators, naturally thicker ones are suitable

Wall thicknesses that have a high compressive strength of, for example, 100 N or more, z. B. can deliver 150 to 200 N more of the capsules. Wall thicknesses in a ratio of simple wall thickness to capsule diameter of about 1:10 to 1:50 can be favorable here.

In other cases in which a release of the aqueous content is to take place under pressure, the wall thickness can be, for example, in a ratio of simple wall thickness to capsule diameter of, for example, 1:50 to 1: 120.

The production process for water (vapor) impermeable capsules according to the invention is described in more detail below.

The technical procedure of the crosslinking reaction (hardening reaction) is shown in FIG. 1

exemplified. The production of the capsules by means of an annular nozzle with preferably concentric inner nozzle, as already mentioned above. That too Containing encapsulating, water and additive containing core material and the composition containing the precursor material for the encapsulation material and the radical initiator are separately by means of a suitable conveyor (eg. By

Pumps or by pressurization) from the storage containers in the

Nozzle design led. The diameter of the outer nozzle is not specifically limited; it is typically in the range of about 5 mm to 0.1 mm, but can still be an order of magnitude smaller to achieve even smaller capsules. Of the

Diameter of the inner nozzle is harmoniously matched to the outer diameter, so therefore, for example, at 2: 3. However, the fine adjustment of the wall thicknesses of the capsules is mainly determined by other parameters than those of the nozzle geometry, z. B. by the selected delivery pressures, which may be in a favorable manner in the range of 0.1 to 5 bar overpressure compared to the ambient pressure. It is preferred that the storage container and nozzle are separately tempered. As a result, relatively higher-viscosity resins may optionally be used as the shell material in the desired

Viscosity range are transferred without it (due to the short-term

Temperature load) to damage or unwanted side effects. With appropriate adjustment of the process parameters (eg a temperature in the range of about 5 to 50 ° C and / or a delivery rate of about 10 ^"4 cm ³ / min to about 10 cm ³ / min for the resin and / or the ingredient - depending on the desired size / thickness of the capsules and desired relation of encapsulated material to wall thickness) balls, consisting of the shell material with the ingredient in the interior, can be generated The setting of a ratio of wall thickness to capsule diameter of 1: 100 is basically possible according to the invention, so that stable capsules of, for example, 4 mm diameter with wall thicknesses of 40 μm can be produced.

The capsules of the core material coated with the precursor material composition are not extruded into a liquid according to the invention, but after leaving the nozzle usually move in free fall to a hardening zone, so are accelerated under the impact of gravity. The larger the distance between the nozzle and the curing zone, the faster they fall through the curing zone and the shorter the residence time. The distance should be chosen so that individual capsules are formed: These usually leave only in drop form the nozzle and require a certain amount of time to form the desired (ideally spherical) geometry. This must take into account the geometry of the device, because otherwise capsules arise with unequal shell thickness, which have defects in the worst case. As a favorable compromise, a distance has been found in the range of 10 to 50 cm. Within this case distance can optionally one or more apertures (especially iris diaphragms) be attached to the nozzle from stray light from the

Curing zone to protect.

The contact time of the ingredients with the precursor material prior to curing is generally only a short overall time (eg fractions of a second, in particular 0.1 to 0.5 sec), so that the risk of contamination of the ingredients by dissolving out of shell components minimized is.

According to the invention, the curing zone is a region of high radiation intensity, which is produced by commercially available emitters such as UV emitters

Companies Hoenle or Fusion can be provided. The length of the zone is not fixed in principle; favorably it is 15-60 cm. The formation of droplets is usually induced by vibration with the aid of a vibrating device. One

Electrostatic high voltage field between the annular nozzle and a counter electrode under the collecting container may be provided to assist the tearing of the drops.

The residence time of the capsules in the curing zone is, depending on the length of the curing zone and the nozzle-curing zone distance, between about 0.05 to 0.2 seconds, preferably about 0.05 to 0.1 seconds. In particular, given a curing zone length, in particular a radiator length of 15 cm and a distance nozzle radiator (which is preferably about 10-30 cm) of about 20 cm results in a residence time of about 0.06 seconds as a typical residence time. If an inhibition by atmospheric oxygen is observed, the radiation field can optionally be purged with inert gas. In the case of particularly thick shells, the capsules can also be posthardened if necessary by placing the collecting container in the scattered light region of the emitter for full through hardening.

The curing is carried out as mentioned with the aid of actinic radiation. As a result, thermal stress on the ingredients is largely avoided (cold curing).

If the capsule formation without active Tropfenabscherung, so the

Capsule detachment from the nozzle only under the impression of the weight of the drops, the drop size is determined primarily by the surface and interfacial properties of the ingredient and the capsule material, and only to a lesser extent by the nozzle geometry. By adding surface and interfacial tension reducing substances (eg, surfactants), capsules are typically obtained from 0.5 to 5 mm in diameter. Optionally, the shearing and thus the eruption of the Droplets to achieve smaller diameter or to achieve a higher

Throughput through special nozzle design, a directed gas flow through

Vibrations (vibrations), electrostatic fields or other mechanisms known in the art are supported. In the case of the so-called laminar

Jet decay, in which the droplet formation is vibration-assisted, the capsule geometry results directly from the nozzle dimensions.

As an upscaling principle, the parallelization of the method by means of multiple nozzles is a suitable means.

Depending on whether you are working in single or parallel operation, the radiation field should be illuminated differently. In the case of a single or mono-modal operation, it is favorable, with the help of an ellipsoidal reflector or the like. To focus the radiation intensity in a focal line through which fall the capsules. In the case of a multimode operation, a parabolic reflector geometry can be advantageous, which ensures a uniform illumination of the radiation field.

Examples Application Example 1

Preparation of 4mm diameter capsules based on Sartomer® SR 833 S (Arkema) (tricyclodecanedimethanol diacrylate) Preparation Nuclear Material: 0.5 g of PEO (2 million) was dissolved in 100 ml of boiled and demineralized water (to remove dissolved oxygen) at 30 ° C ° C dissolved with stirring.

Shell preparation: 0.25 g Lucirin® TPO was stirred into 25 g SR 833 S and dissolved at 50 ° C under light shielding and argon atmosphere.

Both materials were filled into the corresponding core and shell master vessels. Both containers were heated to 25 ° C.

The drop section was flooded with argon as an inert gas. The UV lamp was set at 60% of the maximum power corresponding to 84 W / cm of radiation intensity. The frequency of the vibration generator was set to 60 Hz. Delivery pressures were set to 100 mbar (core) and 400 mbar (shell) and the extrusion through a concentric

Nozzle configuration consisting of annular nozzle (with 3.1 mm diameter) with concentric hollow needle (2.2 mm bore) has been started. The control of the drop formation took place through a stroboscope. Curing the forming capsules in free fall and collecting the capsules in containers (beaker). This resulted in capsules of uniform size (4 mm outer diameter) and an average shell thickness of approx. 145 μηη. The capsules lingered for about 5 minutes in the scattered light of the spotlight and thus experienced a post-curing.

The determination of the permeation (water (vapor) permeability) was carried out gravimetrically on the basis of the weight loss of a capsule sample consisting of 20 capsules over time when stored at 23 ° C and 20% rel. Humidity. By following the weight loss over a period of 2 weeks, a water vapor permeation of 2.7 g / m ² d was obtained for a shell thickness of 150 μηη.

From DSC measurements, a conversion rate of 93% was determined. Application Example 2:

Production of 4mm diameter capsules based on Sartomer® SR 833 S with reduced wall thickness

Preparation of core material: 0.6 g of TWEEN 80 were dissolved in 100 ml of previously boiled demineralized water.

Preparation of shell: 0.4 g Irgacure® 184 were stirred into 20 g SR 833 S and dissolved at 50 ° C under light shielding and argon atmosphere. The two materials were filled into the template vessels for core and shell. Both containers were heated to 25 ° C. The drop section was flooded with argon as an inert gas. The UV lamp was set to 70% of the maximum power corresponding to 98 W / cm of radiation intensity. The frequency of the vibration generator was set to 60 Hz. The feed pressures were set to 50 mbar (core) and 400 mbar (shell) and the extrusion through a concentric

Nozzle configuration consisting of annular nozzle (with 3.1 mm diameter) with concentric hollow needle (2.2 mm bore) has been started. Droplet control was by a stroboscope. The hardening of the forming capsules took place in free fall and the capsules were collected in a container (beaker). This resulted in capsules of uniform size (4 mm outer diameter) and an average shell thickness of approx. 120 μηη. After hardening in scattered light.

Application Example 3 Production of capsules with reduced diameter (2.4 mm) based on the shell material consisting of the combination UDMA: TMPTA (trimethylolpropane triacriate) = 3: 1 with comparable shell thickness to Example 2. Preparation of core material: 0.5 g of PEO (2 ml) was dissolved in 100 ml of water.

Shell preparation: 0.4 g of Lucirin® TPO was mixed in 33 g of the acrylate combination

UDMA: TMPTA = 3: 1 stirred and dissolved at 50 ° C under light shielding. The two materials were filled into the template vessels for core and shell. The tray for the tray material and the nozzle were set at 50 ° C and the core material container at 25 ° C.

The drop section was flooded with argon as an inert gas. The UV lamp was set at 60% of the maximum power corresponding to 84 W / cm of radiation intensity. The frequency of the vibration generator was set to 90 Hz. The feed pressures were set to 200 mbar (core) and 4300 mbar (shell) and the extrusion through a concentric

Nozzle configuration consisting of annular nozzle (1.75 mm diameter) with concentric hollow needle (1, 1 mm bore) has been started. Droplet control was by a stroboscope. Curing the forming capsules in free fall and collecting the capsules in containers (beaker). This resulted in capsules of uniform size (2.4 mm outer diameter) and an average shell thickness of approx. 1 10 μηη.

* * *

Claims

1 . A process for the preparation of capsules comprising a water-containing core material and a water vapor-impermeable polymerized shell, comprising the steps of:

Coextruding the core material and a composition containing a UV-polymerizable shell precursor and a radical initiator such that the UV-polymerizable precursor material surrounds droplets of the water-containing core material to obtain a coextruded material, and

passing the coextruded material through a curing zone which is an area filled with air, another gas, or in particular inert gas, wherein polymerization and crosslinking of the precursor material of the shell is effected by actinic radiation and the residence time of the coextruded material in this curing zone is 0.02 to 0.2 seconds, the UV polymerizable precursor material being at least one compound having two respective terminal diacrylate groups and / or dimethacrylate groups joined by a short, rigid group, and

2. The method of claim 1, wherein the short, rigid group of at least one

Derived or derived compound selected from the group consisting of:

a. aliphatic bicyclic or tricyclic ring diol systems obtained by

Alkyl groups with 1 to 3 carbon atoms may be substituted,

b. Bisphenol A or derivatives thereof in which one or both of the phenyl radicals are substituted by alkyl groups of 1 to 3 carbon atoms, and

c. Diurethanes which are formed from a branched Cs to Cio-alkyl diisocyanate or Cs to Cio-Cycloalkyldiisocyanat and monoethylene glycol.

3. The method according to any one of the preceding claims, wherein the UV-polymerizable precursor material is selected from bisphenol A diacrylate, bisphenol A dimethacrylate, Tricyclodecandimethanoldiacrylat, Tricyclodecandimethanoldimethacrylat and

Urethane dimethacrylate (UDMA) of the following formula, which is usually a mixture of isomers:

4. The method according to any one of the preceding claims, wherein the viscosity of the UV-polymerizable precursor material to be extruded from 0.001 to 50 Pa-s, preferably 0.1 to 10 Pa-s.

5. The method according to any one of the preceding claims, wherein the UV-polymerizable precursor material no solvent and no at room temperature and

Atmospheric pressure contains volatile substances.

6. The method according to any one of the preceding claims, wherein the residence time of the coextruded material in the curing zone 0.05 to 0.1 seconds.

7. The method according to any one of the preceding claims, wherein the intensity of the

actinic radiation is chosen so that the residual monomer content of the monomers used after curing 15 wt .-% or less, preferably 2 to 10 wt .-%, more preferably 1 to 5 wt .-%.

8. The method according to any one of the preceding claims, optionally with a through

actinic radiation induced postcuring is performed.

A process according to any one of the preceding claims, wherein the surfactant comprises nonionic surfactants and polyalkylene oxides, in particular

Polyethylene oxides having a molecular weight of 100,000 to 3,000,000 daltons, and

Combinations thereof is selected.

10. The method according to any one of the preceding claims, wherein the capsules have an average particle size of 0.1 to 10 mm, preferably 1 to 5 mm.

1 1. Method according to one of the preceding claims, wherein the capsules have an average wall thickness of 10 μηη to 2 mm, preferably 50 μηη to 200 μηη.

12. The method according to any one of the preceding claims, wherein as the core material, water, an aqueous salt solution, salt hydrate solution or dispersion or an aqueous solution or dispersion of biological material such as cells or sperm is used.

13. The method according to any one of the preceding claims, which includes an additional step of coating the capsules, wherein the coating means

Vacuum processes such as sputtering, vapor deposition or plasma processes, or by means of chemical or electroplating to obtain coated capsules.

14. Capsules or coated capsules obtainable by the method according to one of the preceding claims.

15. Capsules with a water-impermeable envelope of a polymeric material obtained from a UV-polymerisable precursor material, wherein the UV-polymerizable precursor material is at least one compound having two respective terminal diacrylate and / or dimethacrylate groups which are replaced by a short, rigid, nonpolar, non-crosslinking group, and a core material containing water, wherein the capsules have an average particle size of 0.1 to 10 mm, preferably 1 to 5 mm, and an average wall thickness of 10 μηη to 2 mm, preferably 50 μηη up to 200 μηι.

16. Capsules according to claim 14 or 15, which have a WVTR (measured at 23 ° C and a relative humidity of 80%) of 0.005 to 50 g / m ² d, in particular 0.1 to 10 g / m ² d.

17. Capsules according to any one of claims 14 to 16, wherein the water-containing

Core material is releasable by mechanical stress.

18. Capsules according to any one of claims 14 to 17, wherein the capsules a

Loading capacity, defined as the weight of the core material to the total weight of the capsules, from 50 to 90%.

19. Use of capsules according to one of claims 14 to 18 as storage for salts, salt hydrates, carbohydrates, proteins, vitamins, amino acids, nucleic acids, lipids, medicaments, thickeners, emulsifiers, surfactants, aqueous suspensions, aqueous emulsions, dyes, cell material, sperm , Flavorings, Fragrances.

20. Use of capsules according to one of claims 14 to 18 as an integrated or separate component of latent heat accumulators, dry mixes for the construction sector, moisture-activatable adhesive compositions, in particular one-component adhesives.