DE102005002169B4 - Microcapsules, process for their preparation and their use - Google Patents

Abstract

Microcapsules containing an encapsulated core, wherein the core material consists of at least one inorganic salt, the salt hydrate and / or water whose melting point is in the range of 0 ° C to 100 ° C, which consists of a capsule wall of at least one in the range of 0 ° C is encapsulated to 100 ° C non-meltable duromer, wherein the capsule wall consists of an unmodified or modified organophilic melamine-formaldehyde resin.

Description

The The invention relates to microcapsules containing low-melting salts or Salt hydrates or aqueous salt solutions contain, and a process for their production with non-meltable polymeric wall materials made of a reactive resin. The particle parameters and the thermal and mechanical stability of the microcapsules can be determined by polymer-specific, such as As network density and polymer structure, and / or technological Parameter of particle formation, such. Shear and reaction conditions for the Wall formation, targeted adjustment. Salt hydrate-containing microcapsules with simple or complex particle wall are mainly for latent heat storage used. Microencapsulated water is the initial stage for easy manufacturing polymer-based hollow microspheres.

For the in All national and private sectors strive for reduction of energy consumption are a variety of technical, technological and materials management solutions to disposal, being common the combination of different variants shows the highest effects. Latent heat storage in the form of salts, salt hydrates or long-chain paraffins as a storage medium to compensate for unwanted temperature fluctuations or used as heat protection. Latent heat storage systems use thermodynamics from phase transformations to heat energy economical save and release if necessary. These are called "phase Change Material "(PCM) Heckenkamp, H. Baumann, Nachr. Chem. Tech. Lab. 45 (1997) 1075).

The use of latent heat storage requires for various reasons, such as stability of the storage capacity, protection of the storage medium from environmental influences or protection of the environment from the storage medium, their separation from other building or component components in containers of various embodiments. The use of microencapsulated PCMs is particularly flexible. They can be used as a dispersion or free-flowing powder not only in solid and liquid materials as bulk components, but also in near-surface areas. The encapsulation prevents the macroscopic and molecular transport of the PCMs from the application form or from the point of use. Microencapsulated paraffins and their application in plasterboard are used in the DE 101 391 71 and DE 102 212 22 described.

The Potential use of microencapsulated paraffins is for the sake of storage capacity, selectable Temperature ranges and the flammability of organic materials considerably limited. Inorganic salts or salt hydrates are not only non-combustible, but also have a wider storage capacity and Melting temperature spectrum on. So is the storage capacity for paraffins in the Range from 197 to 258 J / g, the melting temperature spectrum from -32 to 65 ° C, for salt hydrates from 132 to 296 J / g and 8 to 117 ° C, respectively (E. Jahns, ZAE Symposium, Würzburg, March 2004 and J. Heckenkamp, H. Baumann, Nachr. Chem. Tech. Lab. 45 (1997) 1075).

in the Unlike the paraffins are analog technical solutions in Form of microencapsulated salt hydrates not known. To the storage capacity of salt hydrates still be able to use were for example for developed the construction sector for the separation of the salt hydrates from other building materials Makrocontainerlösungen. However, these developments lack the flexible application of microencapsulated Latent heat storage and they can only limited to be used in the living and working area.

method for the preparation of polymer-based microparticles by means of reactive and non-reactive particle formation processes have been described many times. In the reactive particle formation, the formation of the wall takes place in parallel to a polymerization, polycondensation or polyaddition process. In the non-reactive processes, film-forming polymers become direct used in a thermodynamic way for phase separation and particle formation (M. Jobmann, G. Rafler, Pharm. Ind. 60 (1998) 979).

For reactive processes for the encapsulation of solid or liquid core materials melamine-formaldehyde resins are very often used ( DE 199 23 202 ), but also isocyanate / amine systems are described ( DE 101 56 672 ). Melamine-formaldehyde resins are broad and easy to use for the coating of hydrophobic core materials and they can be applied for particle formation from the aqueous phase. Reactive processes require core materials that are inert to the wall-forming monomers or oligomers, ie that they do not react with other components involved. Except for the melamine-formaldehyde resins, these reactive processes often require long reaction times of up to 24 hours. The microcapsule size may vary depending on the reaction conditions, e.g. B. emulsifier, dispersing method, from 1 to 150 microns. For a monomer concentration below 10% by mass and when using high-shear dispersing tools, sizes of around 1 μm can also be achieved ( EP 0 653 444 ).

As a rule, by means of reactive processes, primarily hydrophobic, liquid components or solids are microencapsulated, since the wall material al is deposited from the aqueous phase. This applies in particular to the domino resins which are predominant in practical application. Anhydrous applications of these resins for in situ encapsulation are not yet known. There is only a small amount of information on the use of aqueous-organic mixed phases for the encapsulation of water-sensitive core materials.

Thus, for the microencapsulation of particulate solids, which partially go into solution in aqueous environments, tend to absorb water or swell by absorbing water or react with water, in the DE 10 2004 004 107 describes a method in which organophilic amino resins are used as encapsulating materials in mixed solvents. Also in the patents EP 0 492 793 and US 5,401,577 For example, aqueous-organic mixed phases are used as solvents for organophilic amino resins and these solutions are used for microencapsulation. Under these mixed phase conditions, the acid-catalyzed amino resin condensation is not only difficult to control but also leads to incomplete reaction conversions with the result that the low network density of the amino resin wall leads to particle sticking, artifacts in the particle wall, formation of large particles, and poor mechanical and thermal stability Particle walls leads.

organic Phases as solvent for the polymers Wall materials are predominantly included the non-reactive encapsulation method with linear-chain, soluble Applied polymers. It is preferably made of organic solution by dispersing, Dropping or spraying processes or over Processes based on the principle of liquid-liquid phase separation, a drug / polymer system converted into a particulate form. Dispersing, dripping and spraying method include a solvent evaporation; In contrast, phase separation methods are based on the principle of precipitation of the Wall material, z. B. by adding an incompatible component to the polymer solution.

For technical Applications of encapsulated systems are almost exclusively amino resins as Wall materials used because the cured resins are infusible as well are thermally and chemically stable. Nonreactive encapsulation processes with soluble Polymers are economical, technological and applicative establish limited to applications in the life sciences field.

From the US 5,456,852 microcapsules for heat-storing materials are known, which include a material capable of undergoing a phase transition, the microcapsules having a component with a melting point higher by 20 to 110 ° C than the component which is capable of to perform a phase transition, have.

From the US 4,708,812 the encapsulation of phase change materials (PCM) in organic solvents with amino resins is described. This results in relatively large particles with a diameter between 50 microns and 10 mm.

The US 4,504,402 describes a pellet-shaped product for storing thermal energy having a diameter of 1/8 inch to 1 inch (about 0.32 cm to about 2.54 cm), wherein a material which can undergo a phase transition into the Encapsulated capsules present.

From the JP 2002 038136 In addition, microcapsules are known which use a melamine-formaldehyde resin or a urea-formaldehyde resin as wall materials.

outgoing It was the object of the present invention to microencapsulate To provide systems with high mechanical stability, acting as latent heat storage are suitable and under the processing and operating conditions for latent heat storage for an efficient and safe in situ encapsulation process can be produced.

These The object is achieved by the microcapsules having the features of the claim 1, and the method for their preparation with the features of the claim 15 solved. The other dependent claims show advantageous developments. In claim 23, the Use of the microcapsules according to the invention described.

According to the invention Microcapsules provided as a core material at least one inorganic salt containing salt hydrate and / or water, wherein the core material from a capsule wall of at least one Covered duromer is. It is essential with the microcapsules according to the invention that the core material has a melting point in the range of 0 to 100 ° C, wherein in this temperature range, the coated thermoset not melt is.

Thus, according to the invention the core material, the so-called PCM, encapsulated with a duromeric polymer, that the particle wall for forms the particle core of the actual latent heat storage material.

In accordance with the invention, unmodified or modified organophilic melamine-formaldehyde resins are used as capsule wall materials. It is also possible to use specially modified, non-commercially available solid resins with a modification compo ners, which increase the hydrophobicity of the resins and improve their solubility in organic phases. Preferred modification components here are 1,3-diamino-s-triazines, such as benzoguanamine, or 1,3-diamino-5-chloro-triazine, fatty amines and fatty acid amides. Likewise, it is possible that the modifying component is keto-containing, which is then particularly preferably selected from the group consisting of acetaldehyde, glutaric dialdehyde and glyoxal. In a particularly preferred variant of the microcapsules, the capsule wall consists of a phenolic / melamine mixed resin.

In dependence From the requirement profile to the microcapsules, the particle wall be simple or complex. Under a complex particle wall construction this is understood to mean a multilayer structure of the capsule wall. In the case of complex wall construction, the individual layers both from the same material and from different materials getting produced. For structure-different materials are in addition to the previously mentioned Duromers preferably layers of linear chain polymers or from low molecular weight organic or inorganic substances selected. As linear chain polymers here are in particular polyacrylates, Polyacrylonitriles, polyethylene glycols, ethylcelluloses, starch-fatty acid esters and Stärkecarbamate long-chain isocyanates are preferred. As low-molecular substances are waxes, fatty acid derivatives, Silicones, siloxanes or silicates are preferred.

When Core material for the microcapsules are preferably alkali, alkaline earth or Aluminum salts.

As well their hydrates are preferred. As the core material particularly preferred are calcium chloride hexahydrate, manganese sulfate tetrahydrate, manganese sulfate pentahydrate, Sodium aluminum sulfate dodecahydrate, sodium hydrogen phosphate dodecahydrate, lithium nitrate trihydrate and potassium magnesium chloride hexahydrate.

Preferably The microcapsules have an average particle size in the range of 3 to 30 microns, especially preferably from 5 to 20 microns on. The thickness of the capsule wall is in the range of 20 to 300 nm, more preferably from 50 to 200 nm. The proportion of the core material in the microcapsule amounts preferably 75 to 98 wt .-%, based on the microcapsule.

According to the invention as well a process for the preparation of the microcapsules according to the invention is provided, in which an unmodified or modified organophilic melamine-formaldehyde resin in a solvent, which is immiscible with water under the reaction conditions, in a for this suitable solvent is initially solved to form a continuous phase. The solvent used is under the prevailing reaction conditions with water immiscible. In this continuous phase then becomes the core material dispersed, wherein at the phase interface between nuclear material and continuous phase by thermally and / or catalytically initiated Polymerization, polycondensation and / or polyaddition of the capsule wall is trained. The reaction temperature in the production is while above the melting point of the core material.

The Production of the microcapsules is thus achieved by for the Microencapsulation process relevant to thermodynamic and kinetic controlled processes of capsule wall formation are combined.

• • Partielle Hydrolyse des veretherten Melaminharzes an der Phasengrenze „organische Melaminharzlösung/geschmolzenes bzw. gelöstes PCM” mit parallel ablaufender Kondensation im organischen Medium in Gegenwart des aciden Katalysators
• • Anreicherung kolloidaler Primärkolloide des kondensierenden Aminoharzes an der Phasengrenze ”organische Melaminharzlösung/geschmolzenes bzw. gelöstes PCM” durch abnehmende Löslichkeit in der organischen Phase mit Reduktion der Accessibilität des Kernmaterials
• • Belegung der Oberfläche des dispergierten PCM mit dem Melaminharz
• • Thermisch und sauer katalysierte Polykondensation der auf den PCM-Kernen abgeschiedenen Aminoharze und Bildung des wandbildenden polymeren Netzwerks.

Crucial for a successful microencapsulation with production of artifact-free capsule walls is that the organic solvents used are immiscible with water in the process-relevant concentration range. According to the process of the invention, the formation of the particle wall on the molten PCM surface is controlled by the kinetics of the amino resin condensation and the thermodynamics of the amino resin deposition by the following parallel and subsequent processes:

• Partial hydrolysis of the etherified melamine resin at the phase boundary "organic melamine resin solution / molten or dissolved PCM" with parallel condensation in the organic medium in the presence of the acidic catalyst
• Enrichment of colloidal primary colloids of the condensing amino resin at the phase boundary "organic melamine resin solution / molten or dissolved PCM" by decreasing solubility in the organic phase with reduction of accessibility of the core material
• • Occupancy of the surface of the dispersed PCM with the melamine resin
• • Thermally and acid catalyzed polycondensation of the amino resins deposited on the PCM cores and formation of the wall-forming polymeric network.

By the partial hydrolysis will make the resin more hydrophilic and in combination the parallel condensation reduces its solubility organic phases. With progressive condensation at the interface of the lyophilic PCM phase, increasing separation of the primary colloids occurs the surface the particle with formation of dense, thin-walled films.

Particle geometry and particle size and their distribution is a function of dispersing the PCM material in the organic phase as well as the amount of resin used. The thickness of the capsule wall is thus controllable within relatively wide limits of 20 to 300 nm.

Preferably is for the duromer is a polar approtic organic solvent used. This is particularly preferably selected from the group consisting from triphenyl phosphate, halogenated benzene derivatives, esters aromatic carboxylic acids and inorganic acids, in particular phosphoric, phosphoric and sulfuric acid.

In dependence the chemical behavior of the nucleating material and the polarity of the continuous Phase are acid catalysts for the Add capsule walling, which act either in both and / or preferably at the phase interface have to. As catalyst, acidic catalysts are preferred, more preferred are organic acids, such as For example, p-toluenesulfonic acid and trichloroacetic acid or inorganic acids, like hydrochloric acid.

The the amount of capsule wall-forming thermoset used depends on the proportion of the core material and that produced by the dispersion specific surface this material. The finer the particle or droplet population, the better higher the amount of duromer chosen become. Preferably, the proportion of the duromer, based on the core material, from 0.1 to 30% by weight, preferably from 2 to 10 Wt .-%, and particularly preferably at 5 wt .-%.

Prefers is the mean particle size 3 to 30 μm at PCM levels of 75 to 98%. To avoid agglomeration in the capsule core, the primary Encapsulation in addition be carried out under ultrasound treatment.

In dependence of the core material used and the organic solvent is to choose a reaction temperature which is above the melting temperature the core materials lies. This is usually in the range of 50 to 100 ° C, particularly preferred are process temperatures between 65 and 80 ° C.

Preferably, the microcapsules can subsequently be separated from the continuous phase and provided with at least one outer further capsule wall by means of washing, spraying or dispersion processes. However, all common coating methods for finely divided solids with organic or hybrid materials are also possible since, in contrast to the core materials themselves, the encapsulated core materials are free-flowing powders and have no hygroscopicity. Particularly suitable are reactive encapsulation processes for solids, as described for example in the DE 100 49 777 and the WO 02/30556 to be discribed. Spray coating processes with suitable organic or hybrid polymers are also well suited for this secondary coating.

The Efficiency of the procedure according to the invention to the serving of inorganic PCM's is detected by analytical and morphological studies. Light microscopic leaves show themselves that the capsules in water also under pressure mechanically are stable and a leakage of the core material at room temperature is not observed. The mean particle size and its distribution, determined by means of laser diffraction in many areas the shear intensity and the viscosity control the continuous phase. Regarding handling, stability and memory effect are optimal particle sizes in the range from 5 to 20 μm. The wall thicknesses are in a range of 50 to 200 nm for these particles.

at inorganic core materials may be the proportion of the core material simple and safe elemental analysis by determination of the anion concentration (usually chloride, sulfate, phosphate or nitrate) are determined. For safety's sake - except with nitrates - too a nitrogen determination for the proportion of the primary wall.

through Differential Thermal Analysis (DSC) are the application-relevant thermal Information on melting range and enthalpy of fusion obtained.

• • Mikroverkapselung der flüssigen PCM's mit dem Reaktivharz unter hoher Scherung des Systems
• • Reifeprozess (Nachhärtung zur Ausbildung einer mechanisch stabilen Primärkapsel)
• • Separation der PCM-haltigen Primärpartikel
• • Gegebenenfalls materialspezifische Aufbringung einer Sekundärbeschichtung durch reaktive oder nichtreaktive Verkapselungsprozesse für Polymere bzw. Wäsche oder Besprühen mit der Lösung oder Dispersion einer niedermolekularen Substanz
• • Isolierung der PCM-haltigen Mikrokomposite durch übliche Trennverfahren, wie Filtration oder Zentrifugation
• • Aufbereitung und Regenerierung der kontinuierlichen Medien von Primär- und Sekundärverkapselung bzw. Nachbehandlung im Falle niedermolekularer Zweitbeschichtungsmittel

In summary, the method of producing the microcapsules is thus subdivided into the following method steps:

• Microencapsulation of the liquid PCMs with the high shear reactive resin
• Ripening process (post-curing to form a mechanically stable primary capsule)
• • Separation of PCM-containing primary particles
• If appropriate, material-specific application of a secondary coating by reactive or non-reactive encapsulation processes for polymers or laundry or spraying with the solution or dispersion of a low molecular weight substance
• • Isolation of the PCM-containing microcomposites by conventional separation methods, such as filtration or centrifugation
• • Preparation and regeneration of the continuous media of primary and secondary encapsulation or post-treatment in the case of low molecular weight secondary coating agents

According to encapsulated PCM's with single or multi-layer wall can in various which forms of application are used as latent heat storage. The application of microencapsulated PCMs can be carried out both as finely divided dispersion in heat transfer media or in surface coating systems, as well as a solid in building materials.

Based the following figure and the examples of the subject invention will be explained in more detail, without this on the specific embodiments shown here restrict to want.

The FIG. 1 shows a scanning electron micrograph of a microcapsule according to the invention according to example Second

example 1

To 500 g of triphenyl phosphate are added to 60 g of calcium chloride hexahydrate. The solution will be 2 min with 2 drops of PEG 300 at 9500 U / min by means of an Ultra-Turrax at 80 ° C dispersed. After addition of 19.25 g of a methyl-etherified melamine resin (Cymel 301) and another 2 min. intensive dispersing, 10.5 ml a 2n toluenesulfonic acid solution in Ethanol added and melamine resin separation and capsule wall formation within 10 minutes under the same high shear dispersing conditions carried out. For the complete hardening of the Capsule wall is still 2 h at 80 ° C with an anchor stirrer touched. To separate the microcapsules is mixed with 100 ml of toluene and overnight ditched. After suction, the filter cake is 2 times with toluene washed and dried the capsules at 60 to 80 ° C.

• Ausbeute: 69,9 g
• Kernanteil: 62,7 g
• Mittlere Teilchengröße. 13 μm
• Schmelzbereich des Kerns: 38 bis 41°C
• Schmelzenthalpie zwischen 25 und 40°C: 97,8 J/g

The primary particles tend to agglomerate.

• Yield: 69.9 g
• Core content: 62.7 g
• Mean particle size. 13 μm
• Melting range of the core: 38 to 41 ° C
• Enthalpy of fusion between 25 and 40 ° C: 97.8 J / g

Example 2

Analogous Example 1, 60 g of calcium chloride hexahydrate with melamine resin Cymel 301 encapsulated at 90 ° C. The workup of the microcapsule mixture is carried out by adding 500 ml of methylene chloride followed by filtration and washing the encapsulated PCM's with methylene chloride and vacuum drying at room temperature.

• Ausbeute: 61,1 g
• Kernanteil: 52,0 g
• Mittlere Teilchengröße: 15 μm
• Schmelzbereich des Kerns: 38 bis 41°C
• Schmelzenthalpie zwischen 25 und 40°C: 53,2 J/g

The halohydrocarbon is distilled off and the triphenyl phosphate purified in this way is used for further encapsulations.

• Yield: 61.1 g
• Core content: 52.0 g
• Average particle size: 15 μm
• Melting range of the core: 38 to 41 ° C
• Enthalpy of fusion between 25 and 40 ° C: 53.2 J / g

In The figure is a scanning electron micrograph of the microencapsulated Calcium chloride hexahydrate shown.

Example 3

• Ausbeute: 58,4 g
• Kernanteil: 45,5 g
• Mittlere Teilchengröße: 15 μm
• Schmelzbereich des Kerns: 38 bis 41°C
• Schmelzenthalpie zwischen 25 und 40°C: 4,9 J/g

Analogously to Example 1, 60 g of calcium chloride hexahydrate are encapsulated at 95.degree

• Yield: 58.4 g
• Core content: 45.5 g
• Average particle size: 15 μm
• Melting range of the core: 38 to 41 ° C
• Enthalpy of fusion between 25 and 40 ° C: 4.9 J / g

Claims (23)

Microcapsules containing an encapsulated core, wherein the core material consists of at least one inorganic salt, its salt hydrate and / or water, whose melting point is in the range from 0 ° C up to 100 ° C is, consists of a capsule wall of at least one in the Range of 0 ° C to 100 ° C non-meltable Covered duromer is, wherein the capsule wall of an unmodified or modified organophilic melamine-formaldehyde resin consists. Microcapsules according to claim 1, characterized that the organophilic melamine-formaldehyde resin having an amino- and / or amido-containing or modified with a keto-containing modifying component is. Microcapsules according to claim 2, characterized the modification component contains amino and / or amido groups is and in particular selected is from the group consisting of urea, guanidine, benzoguanamine and acrylamide. Microcapsules according to claim 2, characterized that the modifying component is keto-containing and in particular is selected from the group consisting of acetaldehyde, glutaric dialdehyde and glyoxal. Microcapsules according to one of the preceding claims, characterized characterized in that the capsule wall of a phenol / melamine mixed resin consists. Microcapsules according to one of the preceding claims, characterized in that the microcapsule has at least one further outer capsule wall, which consists of the same material as the first capsule wall or a different Ma material exists. Microcapsules according to claim 6, characterized that the at least one outer capsule wall from at least one linear-chain polymer or from at least a low molecular weight organic or inorganic substance consists. Microcapsules according to claim 7, characterized that the low-molecular substance is selected from the group consisting from waxes, fatty acid derivatives, Silicones, siloxanes and silicates. Microcapsules according to claim 7, characterized the linear-chain polymer is selected from the group consisting from polyacrylates, polyacrylonitriles, polyethylene glycols, ethenylcelluloses, Strength Fettsäureestern and starch carbamates long chain Isocyanates. Microcapsules according to one of the preceding claims, characterized characterized in that the core material is an alkali, alkaline earth or Contains aluminum salt or hydrates. Microcapsules according to claim 10, characterized that the nuclear material is selected is selected from the group consisting of calcium chloride hexahydrate, manganese sulfate tetrahydrate, manganese sulfate pentahydrate, Sodium aluminum sulfate dodecahydrate, Sodium hydrogen phosphate dodecahydrate, lithium nitrate trihydrate and potassium magnesium chloride hexahydrate. Microcapsules according to one of the preceding claims, characterized characterized in that the microcapsules have a mean particle size in the range of 3 to 30 μm, in particular from 5 to 20 μm exhibit. Microcapsules according to one of the preceding claims, characterized characterized in that the capsule wall has a thickness in the range of 20 to 300 nm, in particular from 50 to 200 nm. Microcapsules according to one of the preceding claims, characterized characterized in that the proportion of the core material in the microcapsule in the range of 75 to 98% by weight, based on the microcapsule. Process for the preparation of microcapsules according to one of the claims 1 to 14, in which an unmodified or modified organophilic Melamine-formaldehyde resin in a solvent which is among the Reaction conditions are immiscible with water, under training solved a continuous phase and the core material in the continuous phase at a Reaction temperature, which is above the melting point of the core material, is dispersed, wherein at the phase interface between nuclear material and continuous phase by thermally and / or catalytically initiated Polycondensation the capsule wall is formed. Method according to claim 15, characterized in that that for the melamine-formaldehyde resin a polar aprotic organic solvent is used. Method according to claim 16, characterized in that that the solvent selected is selected from the group consisting of triphenyl phosphate, halogenated Benzene derivatives, esters of aromatic carboxylic acids and inorganic acids, in particular Phosphoric, phosphorous and sulfuric acid. Method according to claim 17, characterized in that that a catalyst, preferably an acid catalyst used is, especially strong organic acids such as p-toluenesulfonic acid and trichloroacetic acid and / or inorganic acids like hydrochloric acid. Method according to one of claims 15 to 16, characterized that the proportion of the amino resin or amino resin-containing mixed resin, based to the core material, from 0.1 to 30 wt .-%, in particular from 5 to 15 wt .-% is. Method according to one of claims 17 to 19, characterized that the encapsulation of an ultrasound treatment for avoidance the agglomeration of the core material is accompanied. Method according to one of claims 17 to 20, characterized the reaction temperature is in the range from 50 ° C to 100 ° C, in particular from 65 to 80 ° C. Method according to one of Claims 17 to 21, characterized that the microcapsules following from the continuous phase be separated and with at least one outer further capsule wall by means Washing, spraying or dispersion process. Use of the microcapsules according to one of claims 1 to 14 as latent heat storage in construction and transportation.

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