DE102004004107A1 - Micro-encapsulation of hydrophilic or water-sensitive solid particles, e.g. catalysts or other modifiers for use in paint, involves forming the capsule wall from amino resin precondensate in an aqueous-organic solvent mixture - Google Patents

Abstract

A method for the micro-encapsulation of hydrophilic and/or water-sensitive solid particles involves depositing a capsule wall on the particles (A) in a continuous phase comprising an aqueous-organic solvent mixture, starting from an amino resin precondensate (B) in the form of solid resin particles. An independent claim is also included for micro-encapsulated solid particles with a hydrophilic and/or water-sensitive solid core and a capsule wall of hydrophobic amino resin.

Description

The The invention relates to a process for the microencapsulation of particulate solids with hydrophilic and / or water-sensitive properties. For this counting such particulate Solids that are in aqueous Ambient media partially in solution tend to tend to absorb water or swell by water absorption or react with water. Likewise, the invention relates to microencapsulated particulate solids from hydrophilic and / or water-sensitive solid cores and capsule walls hydrophobic amino resin.

Enveloped microparticulate solids are used in many industrial and consumer products. Known are applications in agriculture and forestry, in products the food, cosmetics, packaging, construction, paints and coatings industries, in plastic additives, etc. They are used as dispersions, free flowing Powder or by direct incorporation into other materials, especially in various thermoplastic, elastic and thermosets Polymer materials.

The Microencapsulation with polymeric materials is e.g. from Encyclopedia of Polymer Science, J. Wiley & Sons, 1968, Vol. 8, pp. 719-7361 W. Sliwka, Angew. Chem. Boarding school. Edit. 14 (8) 1975, p. 539 et seq., Acta Polymerica 40 (1989) 4, p 243 ff; Drugs Pharm. Sci. 73 (1996) Microencapsulation 1-19 and Encyclopedia of Chemical Processing and Design (J.J. McKetta, Microencapsulation from R.E. Sparks), pp. 162-180 known.

Microencapsulation by means of amino resins is also known from the scientific and patent literature. In particular, the use of microencapsulated with amino resins substances in the field of production of carbonless paper (see. EP 0 017 386 ; DE 34 47 298 ).

Emphasis of these methods are often specific modifications of the wall-forming amino resin, which are made primarily related to nuclear material (see, for example DE 19 835 114 , WO 03/035245). The combination with respect to the amino resin inert additives is known (see. EP 0 532 462 and EP 0 772 395 ).

In According to the literature, the rule is usually liquid components microencapsulated and this applies in particular to reactive encapsulation processes in which amino resins are used as wall materials.

A particular method with organosoluble amino resins is disclosed in the patents EP 0 492 793 and US 5,401,577 described. Here, working with a water-insoluble amino resin precondensate in the organic phase, wherein the aqueous external phase with water-miscible organic media are added. Under these nonaqueous process conditions, the acid catalyzed amino resin condensation is not only difficult to control, it also leads to incomplete reaction conversions with the consequence that the low network density of the amino resin wall leads to particle sticking, artifacts in the particle wall, large particle formation, and little mechanical and thermal stable particle walls leads.

In further encapsulation processes, amino resins are also described several times as co-components for the crosslinking of highly functionalized linear polymers ( US 4,454,083 . US 4,898,696 ). Incomplete reaction conversions also act in the same way in these processes since the polymer component is then not completely integrated into the wall and can interact with the surrounding medium in a variety of reactive or nonreactive ways. The result of this incomplete installation are again artifacts, agglomerations and aggregate formation.

issues in the microencapsulation of solid substances by means of reactive or non-reactive Prepare dispersing process using high-shear stirrers their hydrodynamic behavior, especially when dealing with irregular shapes or geometrically highly anisotropic, crystalline products. In the exposed areas of these substances (needle points, sharp fe Edges on crystals, cavities or pores or similar) form high flow rates and eddies made a sufficient coating of the core material in these Areas frequently limit or prevent. Due to the high flow rates by lowering the solubility accumulating prepolymer colloids quickly eroded again. A reduction in the flow rate is usually not possible because then reinforced Agglomeration, aggregation and coalescence are observed.

For microencapsulation of solids is therefore usually used coating processes, which are based primarily on physical principles, such as the Wurster technique and other Spühcoating-, drageeing or granulation (see BH Kaye "Microencapsulation" KONA 10 (1992) 65), or technologically and technically complicated processes using supercritical solvents are also used ( EP 0 865 819 ).

Based on this, it was an object of the present invention to develop a process for the microencapsulation of hydrophilic particulate solids ckeln, with the partially water-soluble, water-swelling, ion-releasing, water-reacting or even by salt formation during the encapsulation process going into solution core materials can be coated efficiently and artifact-free with an amino resin wall.

These The object is achieved by the method having the features of the claim 1 and by the microencapsulated particulate solids having the characteristics of claim 17 solved. In claim 20, the use of the method according to the invention described. The other dependent claims show advantageous developments.

According to the invention is a Process for the microencapsulation of particulate solids with hydrophilic and / or water-sensitive properties, in which in an aqueous-organic solvent mixture as a continuous phase on the particulate solids starting from at least one amino resin precondensate in the form of a particulate solid resin a capsule wall is deposited.

Surprisingly succeeded in that for the microencapsulation process relevant thermodynamically and kinetically to combine controlled processes of capsule wall formation with amino resins. These Combination succeeds through the use of an aqueous-organic medium as continuous phase in the encapsulation process and the use of a unetherified amino resin precondensate as wall material.

• • Verlangsamte Auflösung des Festharzes im wässrig/organischen Medium
• • Einwirkung der organischen Komponenten auf den zu verkapselnden Wirkstoff durch hydrophob/hydrophob-Wechselwirkung mit Reduktion der Accessibilität des Wirkstoffs für Wasser
• • Langsame Belegung der Oberfläche der Wirkstoff partikel mit dem gelösten Anteil des Festharzes
• • Thermisch oder acid iniziierte Polykondensation der auf den Wirkstoffpartikeln abgeschiedenen Aminoharzanteile unter Bildung räumlicher Aminoharznetzwerke.

According to the process of the invention, the formation of the particle wall is controlled by the kinetics of the amino resin condensation and the thermodynamics of the Aminoharzabscheidung by the following parallel and subsequent processes:

• • Slowed dissolution of the solid resin in the aqueous / organic medium
• • Influence of the organic components on the active substance to be encapsulated by hydrophobic / hydrophobic interaction with reduction of the accessibility of the active substance for water
• • Slow occupancy of the surface of the active ingredient particles with the dissolved portion of the solid resin
• Thermally or acidically initiated polycondensation of the amino resin portions deposited on the active ingredient particles to form spatial amino resin networks.

Preferably are the particular Solids at least partially soluble in water, by water absorption swelling and / or in aqueous Phase reactive compounds. It is preferred that the particulate solids have a crystalline or amorphous structure. Decisive for a successful encapsulation is that not the chemical structure of the amino resin, but its morphology. A Artifact-free serving of the hydrophilic or partially soluble Solid and formation of singular particles is possible, when the amino resin is particulate Solid resin can be used and directly in the form of a powder supplied to the encapsulation process becomes. A previous resolution of the resin in the continuous phase leads to that in the prior art described problem, especially incomplete wrapping, generation no further usable large Particles, the formation of agglomerates ect. That's why it is particularly advantageous directly from the core material to be encapsulated and the solid resin to produce a powder mixture and use this or the products within a limited time window the medium supply.

The Solvent mixture is preferably water and at least one hydroxyl or keto-containing organic solvent containing water is miscible. It is particularly preferred that the added organic Solvent components with water in the process-relevant concentration ranges infinitely miscible are.

When organic solvent component for the continuous Phase are especially aliphatic compounds with hydroxy or Keto group, such as alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, methylbutanols, 2-propen-1-ol) and ketones (2-propanone, 4-hydroxy-4-methyl-2-pentanone, 2-butanone, and the like) can be used, depending on from the boiling temperature of the respective solvent a corresponding Reaction temperature is to choose. At selected Applications may be detrimental to the use of ketones, in other cases However, again be beneficial because a partial installation of solvent molecules in the Amino resin wall could be detected, resulting in a reduction the crosslink density and thus increased flexibility of the wall structure led.

It has been found that the mixing ratio of water and organic component is of crucial importance for a successful application of the process. The optimum composition of the continuous phase is determined by several factors, with hydrophilicity of the core material, reactivity of the resin and its interfacial activity dominating as process determining parameters. Reactivity of the amino resin condensation and hydrophobing of the solid surface require careful coordination of the composition, wherein certain minimum amounts of water or organic phase is not below can be taken. The deposition of the amino resin structures at hydrophilic / hydrophobic phase boundaries is not affected by the organic solvent, if the minimum of organic phase dependent on the resin structure is not exceeded. It has been found that with a solvent content of> 18% by volume many core materials according to the invention can be easily encapsulated with commercial solid resins.

About the used amount of solid resin is the thickness of the capsule wall in relative wide limits of 20-80 nm controllable. The amount of solid resin depends on the used Amount of drug to be encapsulated and its fineness or its specific surface. The finer the drug particle population is, the higher it must be the amount of solid resin chosen become. In the usual application if the upper limit of the amount of solid resin to be used is 30% by mass, based on the core material. higher Amounts require particulate Proportions of pure amino resin material in the final product. The lower one Limit is in the range of 5 mass% of solid resin, based on the Nuclear material mass. Insufficient amounts lead to incomplete encapsulations or artifacts in the capsule wall.

In dependence of the core material used and the organic solvent is to choose an appropriate reaction temperature, which is usually in the range from 50 to 100 ° C lies. Advantageous but not necessarily working in the Range of the boiling temperature of the solvent mixture using a reflux condenser. The Amino resin precondensates polymerize thermally under these conditions. To accelerate the process, the use of acidic catalysts is also possible. For this are primarily organic and inorganic acids or their Abmi mixtures suitable, which buffer the encapsulation system noticeably to the Control deposition and the formation of pure amino resin particles to avoid. Suitable are acetic acid, formic acid, citric acid, ascorbic acid, sulfamic acid, polymethacrylic u. a. or mixtures thereof, wherein a pH in the range of 2.5 to 6.0, preferably from 3.5 to 5.0 should be set.

The Reaction times arise from the reaction temperature used and the eventual catalyst use and are in the range of 30 minutes and 24 hours. For example, at a reaction temperature from 60 ° C requires a minimum reaction time of 60 minutes without the use of a catalyst. Under same Conditions reduces the reaction time at catalyst addition to 35 min.

Independent of the reaction in the mixed phase in the liquid medium is at all Aminoharzverkapselungen a thermal post-crosslinking at temperatures in the range of 110 to 180 ° C possible, if the nuclear material or drug component allows this.

The Procedure is for to use the microencapsulation of water-sensitive particulate solids, wherein the nature of the interaction with water is immaterial. The ingredients can swell in water, partially dissolve in water or with water Education disturbing gaseous, liquid or solid products. The wide variability of the mixing ratio allows a simple adaptation of the parameters of the encapsulation process to the sensitivity across from Water or the intensity the interaction with water. The more sensitive to or more intense With water, an active substance reacts, the higher the hydrophobicity of the Set encapsulation medium.

When Water-sensitive core materials are plastic additives for a wide variety of application-specific reasons. such as phosphorus-based flame retardants or stabilizers, water-sensitive Components of reactive resin systems, controlled release Catalysts or polymerization initiators, etc. with melamine resins according to the procedure according to the invention verkapselbar.

The The following examples are intended to show the essence of the invention, but do not restrict them.

The procedure is as follows:
The reaction components are introduced in a reaction vessel with reflux cooling. In this case, the observance of a certain order is not absolutely necessary. However, it is advantageous to avoid sticking and lumping or adhesion in the reactor, to enter the powdery components in the liquid phase. It is then heated to boiling temperature and the reaction is carried out under moderate stirring. It is then cooled to room temperature and the dispersion of a solid-liquid separation (filter chute, separator o. Ä.) Is supplied. Depending on the application, a wash may be required, in which case it is advantageous first to wash briefly with water and then with the organic solvent used or else with a low-boiling alcohol (methanol, ethanol).

The Products can as free-flowing Powders, pastes or dispersions are formulated.

example 1

In one with heating, agitator, Reflux cooling and 45 ml of water and water Submitted to 55 ml of methanol and heated to 50 ° C. In this solvent mixture becomes a powdery Mixture of 40 g of N-phenylthiourea, 0.5 g of amidosulfonic acid and 7 g of melamine-formaldehyde solid resin (Lamelite 200) and heated to boiling. After a Reaction time of 120 min cools to room temperature and filtered through a suction filter. To the laundry with 50 ml of water and 50 ml of methanol is the separated product 20 h at 50 ° C dried in a convection oven. This gives 44.2 g of a finely divided Powder. The determination of sulfur results in a thiourea content of 37.4 g. The FTIR spectrum shows the typical material next to the core material Gangs for crosslinked melamine resins.

Example 2

In the reaction vessel from Example 1, 35 ml of water and 65 ml of 2-propanol are introduced and heated to 60.degree. In this you solve 0.5 g of a 20% by mass aqueous solution of polymethacrylic acid and mixed with 5 ml of a 2 N aqueous Citric acid solution. After that you wear 10 g of melamine-formaldehyde solid resin (Lamelite 200) and heated at boiling temperature. While of the heating, the encapsulation are 55 g of 1,4-diazabicyclo [2,2,2] octane added. You leave 35 min at boiling temperature, cool slowly to room temperature and filter the encapsulated product from. After the wash with 2-propanol and subsequent mild drying at 30 ° C receives 58.8 g of a finely divided free-flowing powder. The FTIR spectrum clearly shows the bands of the crosslinked melamine resin.

Example 3

In one with heating, agitator, Reflux cooling and 45 ml of water and water Submitted to 55 ml of methanol and heated to 50 ° C. In this solvent mixture becomes a powdery Mixture of 40 g of N-phenylthiourea, 0.5 g of amidosulfonic acid and 7 g of a melamine-benzoguanamine [formaldehyde solid resin (benzoguanamine content: 30 mol%) and heated to boiling. After a reaction time from 120 min cools to room temperature and filtered through a suction filter. To the laundry with 50 ml of water and 50 ml of methanol is the separated product 20 h at 50 ° C dried in a convection oven. This gives 47.0 g of a finely divided Powder. The determination of sulfur results in a thiourea content of 38.0 g.

Example 4

In one with heating, agitator, Reflux cooling and 45 ml of water and water Submitted to 55 ml of methanol and heated to 50 ° C. In this solvent mixture becomes a powdery Mixture of 40 g of N-phenylthiourea, 0.5 g of amidosulfonic acid and 7 g of a melamine-dicyandiamide-formaldehyde solid resin (Dicyandiamidgehalt: 20 mol%) is added and heated to boiling. To a reaction time of 120 min is cooled to room temperature and filtered over a filter slide off. After washing with 50 ml of water and 50 ml of methanol, the separated product for 20 h at 50 ° C in a convection oven dried. You get 43.1 g of a finely divided powder. From the determination of sulfur results a thiourea content of 39.4 g.

Example 5

In a suitable stirred reactor be with reflux condenser 28 l of water and 12 l of 2-methyl-2-propanol introduced and heated to 80 ° C. Then you wear one Mixture of 6 kg of 2-phenylimidazole and 1.8 kg of melamine-formaldehyde solid resin and leaves the approach 180 min at this temperature. Then it is slow to room temperature cooled, filtered, washed with methanol and then at 60 ° C in a convection oven until dried to constant weight. This gives a free-flowing powder of microencapsulated benzimidazole.

With Epoxy resins, a one-component system was prepared, the one good stability and was activated only at temperatures above 120 ° C.

Example 6

In a stirred reactor according to Example 3, 28 l of water and 12 l of 2-propanone Heated to 80 ° C. Then you wear one Mixture of 6 kg of 2-phenylimidazole and 1.8 kg of melamine-formaldehyde solid resin and leaves the Batch for 180 min at this temperature. After working up analogously to Example 3 receives a free-flowing one Powder of microencapsulated 2-phenylimidazole with comparable Catalyst properties for One-component epoxy systems.

Example 7

In a stirrer reactor equipped according to Example 3, 25 l of water and 10 l of methanol are added, heated to 60 ° C. and, after heating, a mixture of 20 kg of ammonium polyphosphate and 2 kg of melamine-formaldehyde solid resin is introduced, heating continues until the start of boiling and leaves 120 minutes at this temperature. It is then cooled with stirring to room temperature, the dispersion is filtered and washed with 5 l of methanol. After drying at 110 ° C in a convection oven to obtain 20.8 kg of finely divided product with only according to the Melaminharzbeladung reduced phosphorus content. The analytical data showed a wall content of 6.7 mass%.

so microencapsulated ammonium polyphosphate is for the flameproofing of Room textiles and plastic compounding suitable. It shows at the textile equipment from aqueous dispersions not the for uncapsulated material usual Swelling and the pH remains at high dilution in the Range from 5.5 to 6.5.

encapsulated Ammonium polyphosphate is thermally stable up to 240 ° C and stable against shear stress. The thermal and mechanical stability of the amino resin wall is a prerequisite for trouble-free Compounding of polyolefins and PA 6 with ammonium polyphosphate in twin-screw extruder. Microencapsulated ammonium polyphosphate possesses high compatibility to various due to the melamine resin wall thermoplastic and duromeric plastic matrices.

Example 8

Analogous Example 5, 15 kg of finely divided red phosphorus are encapsulated with melamine-formaldehyde solid resin. After drying at 110 ° C received in the convection oven 15.5 kg of finely divided product with only according to the Melaminharzbeladung reduced phosphorus content. The analytical data yielded one Wall proportion of 4.6% by mass.

so microencapsulated red phosphorus is like microencapsulated ammonium polyphosphate for the Flame test equipment of home and vehicle textiles as well as plastic compounding suitable. Due to the density of the capsule wall it shows at the textile equipment aqueous Dispersions are not those for uncapsulated material usual Phosphinbildungsrate. The thermal and mechanical stability of the amino resin wall is a prerequisite for a easy compounding of polyolefins and PA 6 with red phosphorus.

Example 9

Analogous Example 5, 15 kg of ground sulfur with melamine-formaldehyde solid resin encapsulated. The sulfur-containing microparticles are separated and in filter-moist condition in a similar manner a second time encapsulated. After drying at 110 ° C and thermal post-curing at 180 ° C in a convection oven receives 17 kg of finely divided product with a wall content of 11.9% by mass.

15 kg of the double-encapsulated sulfur particles are in filter-moist Condition with 600 g paraffin wax, dissolved in 10 l gasoline, coated at 70 ° C.

so microencapsulated millbase is used for hot vulcanization of synthetic and natural rubbers used. The encapsulation gives you one up to 120 ° C stable sulfur, which is controlled only at temperatures above 150 ° C by destroying the Capsule wall is released.

Example 10

to Improvement of redispersibility are 5 kg analogously to Example 7 micro-encapsulated ammonium polyphosphate in filter-moist state with 800 g of polyethylene glycol (molecular weight 2000), dissolved in 2 l of methanol, at room temperature coated. After drying at 110 ° C in a convection oven to obtain 5.4 kg of finely divided product with only according to the melamine resin and Polyethylene glycol loading reduced phosphorus content. The analytical Data showed a share of coated wall of 8.6 mass%.

Example 11

to Improvement of compatibility to hydrophobic Kunststoffmatrices be 5 kg analogously to Example 7 microencapsulated ammonium polyphosphate in filter-moist condition with 400 g paraffin wax, dissolved in 5 liters of petrol, coated at room temperature. After air drying receives 5.2 kg of finely divided product with only the melamine resin and wax loading reduced phosphorus content. The analytical Data showed a share of coated wall of 7.6% by mass.

According to the invention likewise microencapsulated particulate Solids of hydrophilic and / or water-sensitive solid cores and capsule walls provided from hydrophobic amino resin. These are preferably capsule walls with a thickness between 20 and 80 nm. Particularly preferred it that the microencapsulated particulate solids through the process according to one of the claims 1 to 16 can be produced.

use finds the method according to the invention for the preparation of initiators, catalysts, fire retardants, Modifiers for polymers End products in the form of workpieces and films, modifiers, crosslinkers and the like in paints and varnishes, such as B. the production of one-component systems in epoxy resins.

Claims (20)

Method for microencapsulation of particulate matter Laren solids having hydrophilic and / or water-sensitive properties, in which in an aqueous-organic solvent mixture as a continuous phase on the particulate solids starting from at least one amino resin precondensate in the form of a particulate solid resin, a capsule wall is deposited. Method according to claim 1, characterized in that that the particulate Solids at least partially soluble in water, by water absorption swelling and / or in aqueous Phase reactive compounds are. Method according to one of the preceding claims, characterized characterized in that the particulate solids are crystalline or amorphous structure. Method according to one of the preceding claims, characterized characterized in that the particulate solids and the at least an amino resin precondensate in particulate form, in particular as Powders that are fed to the continuous phase. Method according to the preceding claim, characterized characterized in that the particulate solids and the at least an amino resin precondensate in the form of a powder mixture of the continuous Phase supplied become. Method according to one of the preceding claims, characterized characterized in that the solvent mixture from water and at least one hydroxyl or keto group-containing organic solvent which is miscible with water. Method according to the preceding claim, characterized characterized in that the organic solvent is an alcohol and / or a ketone is used. Method according to one of the preceding claims, characterized characterized in that the solvent mixture other additives, in particular catalysts, protective colloids, stabilizers and / or Surfactants, contains. Method according to one of the preceding claims, characterized in that at least one modified amino resin precondensate is used. Method according to one of the preceding claims, characterized characterized in that, based on the particulate solid, 5 to 30% by mass of the at least one amino resin precondensate are used. Method according to one of the preceding claims, characterized characterized in that the reaction temperature is in the range of 50 to 100 ° C is located. Method according to one of the preceding claims, characterized characterized in that the reaction temperature in the boiling range of Solvent mixture is located and the encapsulation is carried out under reflux. Method according to one of the preceding claims, characterized characterized in that the reaction time ranges from 30 min to 24 h is. Method according to one of the preceding claims, characterized characterized in that acidic catalysts having a buffer effect, in particular formic acid, Acetic acid, Citric acid, ascorbic acid, sulfamic acid, polymethacrylic and / or mixtures thereof are used. Method according to one of the preceding claims, characterized characterized in that the capsule wall of the microencapsulated particulate solids in connection with Temperatures of 110 to 180 ° C thermally is postcrosslinked. Method according to one of the preceding claims, characterized characterized in that the microencapsulated particulate solids after treatment, in particular by a second encapsulation or a coating. Microencapsulated particulate solids of hydrophilic and / or water-sensitive solid cores and capsule walls hydrophobic amino resin. Microencapsulated particulate solids according to claim 17, characterized in that the capsule walls have a thickness between 20 and 80 nm. Microencapsulated particulate solids after one of claims 17 or 18, characterized in that these by the method according to one of the claims 1 to 16 can be produced. Use of the method according to one of claims 1 to 16 for the preparation of initiators, catalysts, fire retardants, Modifiers and / or crosslinkers, especially in colors or Paints.