DD266976A1 - METHOD FOR PRODUCING AMINO-FRACTURE MICRO-CAPSULES - Google Patents

Abstract

The invention relates to a process for the preparation of smooth-walled amino resin microcapsules with gleichmaessiger Wandstaerke. It is used in various fields where the delayed release of active substances and their long-term effects is required, for example in the field of plant protection.

Description

Ti tel of the invention

Process for the preparation of amino resin microcapsules

Field of application of the invention

The invention relates to a process for the preparation of amino resin microcapsules which contain water-insoluble or sparingly water-soluble substances as core material and can be used in various fields of industry, agriculture, pharmacy, medicine and hygiene. "

Characteristic of the known state of the art

For the preparation of amino resin microcapsules, on the one hand methods for the polycondensation of the monomers at the phase boundary of Möhrphaoensystemen have been described (US Pat. No. 4,221,710, DE-PS 2,832,637, US Pat. No. 4,001 HO, US Pat. No. 4,089,802 U.S. Patent 4,333,849, Japanese Patent Publication No. 80/99,337). On the other hand, methods have been known in which an amino resin precondensate with simultaneous use of additional components (homopolymers, copolymers, poly electrolytes, protective colloids) is reacted in a multi-phase system corresponding to microcapsules (DD-PS 129 107> DE-PS 3 008 390, US-PS 4 2I> 3 178, DE-PS 3 008 658, DE-PS 3 512 565, US-PS 3,516,846, EP-PS 46 415) · The daboi mentioned, mostly significant addition of polyelectrolytes takes place factohlohllioh under the aspect of a Effect as a binding or viscosity-enhancing agent for the particular intended use of the microcapsules. , .

In addition to the additional economic burden, a larger addition of polyelectrolytes av.oh is technically suitable for the preparation of microcapsules present in dispersion in an isolated form, since the tendency to coagulate or counteract by adducts of unreacted cationic amino resin and anionic polyelectrolytes increases greatly ., the uptake of the product of the roughening may not be possible with the capsules present in insulating form.

To u.a. In order to get around this Naohttfil, DD-PS 241 556 and DD-PS 240 843 have proposed processes which are based on partially etherified, water-soluble amino resins and in which such additives can be dispensed with In order to produce the microcapsules, DD-PS 241 556 uses, in addition to the aqueous phase of the particular amino resin solution for forming the second phase, a water-immiscible organic solvent.

In DD-PS 240 843, which describes the encapsulation insecticidal phosphoric acid ester, the formation of the second Phaae either alone by each nloht - to be encapsulated, or only slightly water-soluble liquid active ingredient in the form of the respective phosphoric acid ester itself or in admixture with an organic solvent causes.

However, studies have shown that the majority of the microcapsules prepared by the latter methods have strong inconveniences in terms of the wall thickness of individual absorbent sections of the individual capsules. This problem and its associated effects have not received any attention in all known processes so far. Such wall thicknesses may occur both during the manufacturing process and in particular during the subsequent use of the corresponding active ingredients

(In particular, liquid active substances) containing microcapsules in various hinsioht prove disadvantageous «

Microcapsules, which have the abovementioned wall thickness ingleighing conditions, are susceptible to bruoh to high and fluctuating degrees in processes occurring under high shear forces. This applies both to corresponding production methods (for example according to DD-PS 241 556 and DD-PS 240 843) for producing the concentrated ones Capsule dispersions as in particular for solohe applications in which the diluted capsule dispersion eg duroh VerdUsen or spraying is used in pest control.

From this uncontrollable premature, or in their reproducibility z.T. only controllable release of active substances takes place and any necessary, exact prior determination of the desired active substance release and long-term action of the microcapsules may be carried out. become impossible. In addition, this unfavorable behavior can be exacerbated when most of the capsule wall surfaces do not have a smooth texture, but as frequently noted - these show particulate elevations.

Another Naohteil is that such microcapsules, in the erforderliohen in many cases, high dilution levels of the microcapsules In. Water condition a strongly fluctuating diffusion rate of the encapsulated drug out of the capsules out, which may also affect the reproducibility of the microcapsule approach in terms of controllable drug release and Langzeltwirkung.

Finally, another shortcoming of capsules having pronounced wall thickness properties is that amine resin microcapsules having too thin local wall thickness ranges often result in an undesirable reduction in dry weight.

Have strength, i. after drying (deliquescing on a base and thereby possibly releasing the active substance in an undesired and uncontrolled manner)

The mentioned in DD-PS 240 843 high Raeohanisohe stability of the microcapsules and maintain a high Wirkstofffkonzentration even after several days, therefore, taking into account the above-mentioned problems probably only apply to a portion of the respective microcapsules obtained from a reaction mixture.

Aim of the invention;

The aim of the invention is the development of a technically advantageous and economically advantageous process for the production of amino resin microcapsules, which have an improved morphological structure of the cladding walls and the advantages of application technology.

Explanation of the essence of the invention

The object of the invention is to develop a qualitatively new process by a simple addition or modification of the process parameters to well-known methods for the production of Arainoharz microcapsules, which results in Arainoharz microcapsules with an improved morphological structure of the capsule walls. leads to superficially smooth capsules with significantly 'increased uniformity of the wall thickness of the capsules.

According to the invention, the object could surprisingly be solved daduroh that in the preparation of the amino resin microcapsules, the reaction components are reacted in a 0.01 to 0.2 mass percent aqueous solution of carboxymethylcellulose.

Ale wall-forming materials are used on solvent-known partially methanol-etherified, cationically-modified water-soluble high melamine-formaldehyde or melamine-urea-formaldehyde resins in which 25 to 75 % of the hydroxymethyl groups have been etherified, and AIb cation-like modifiers are preferably alkanolamines (Mono-, di- and triethanolamine u »a») used #

The amino resin microcapsules are prepared by the following process according to the invention:

A water-soluble imino resin in a concentration of 0, for the wall formation, is added to an aqueous 0.01 to 0.2% by mass aqueous solution of carboxycarbonyl oxychloride (0M3 solution), which is adjusted to a pH of 2.5 to 6.0. 5 to 20 g / 100 ml of GMö solution are dissolved and a pHadduroh changed pH of the solution is again adjusted to a value between 2.5 and 6.0 as Reaktlons pH value. However, it is also possible, first CMC To mix solution and Amlnoharz solution and adjust the reaction pH danaoh directly · In this solution, the following substances are dispersed as core materials:

a) water immiscible liquids

b) solutions of non-water-soluble pesticides in water-immiscible liquids

o) solid at room temperature, not soluble in water substances with melting points up to 95 ⁰ O in solid form or as a melt

d) non-water soluble solids

The constituents used must have a boiling temperature which is above the encapsulation temperature.

The dispersing takes place depending on the desired degree of distribution of these substances, using low and / or residual soother forces by means of a conventional dispersing device.

Pesticides can also be used as finely dispersed substances prepared beforehand. Before and / or during and / or after the dispersion of the core materials which gewünsohte Reaktlonstemperatur between 20 ⁰ O 100 ⁰ O is adjusted · The dispersion is stirred for 0.25 to 24 hours in this temperature range, also used various agitators during the reaction After completion of the reaction, the resulting capsule dispersion is applied according to the intended use of the capsules in catfish known per se. processed ". The resulting amino resin microcapsules have a smooth surface and, depending on the ratio of Wan''material used to core material and the other manufacturing conditions (pH, dispersion, retention temperature), diameter zwisohen 2 and 50 / um, wall thicknesses between 20 and 500 nm , whereby individual sections of the capsule wall do not deviate more than + 25 % from the average thickness of the capsule walls of the respective approach determined by electron microscopy.

The microcapsules also have the following performance advantages:

- high dry strength of virtually all capsules

good mechanical stability during spraying or atomization of the capsule dispersion diluted with water (high), it being surprising that even microcapsules prepared by the process according to the invention, even thin-walled but uniform wall thicknesses, prove to be much more stable than thick-walled ones produced by well-known processes, but uneven wall thickness microcapsules

- uniform long-term effect of the capsules over several days

The erfindungsgeiniiße method is to be further illustrated by the following examples, wherein for Verkapselnfyii ^ ^ ioiiioioh known partially prepared methanol-etherified cationically modified water-soluble melamine ~ formaldehyde or melamine-urea form-Fonnaldehyd resins are used:

Haratype I: crude product of 1 mole of melamine with 6 moles of formaldehyde cationically modified after etherification with methanol by ethanolic ethanolamine and having 1.23 moles of free methylol moiety per mole of melamine *

Haratyp IX »He & ctionsprodukt of 1 mol of melamine with 5 * 6 moles of formaldehyde, which was cationically modified by etherification with methanol duroh triethanolamine and has 1.58 moles of free methylol groups per mole of melamine ·

Bei p 1 iel (Vergleiohsbeispiel)

Mischungηο mixture of 60 ml of water and 5 g of a 50% by mass aqueous solution of a partially methanolverethort'en cationically modified melamine-formaldehyde resin (resin type I) is adjusted with 2 ml of 2 N aqueous citric acid solution to pH 4.1 high Sohertmg with a Turborilhrer and equilateral heating to 60 ⁰ O 30 g of liquid technical methyl parathion (active ingredient content of thiophosphoric acid-0,0-dimethyl-0-p-nitrophenylesteri 82.1 mass%) are emulsified in this mixture · llaoh a Ruhr time of The resulting microcapole dispersion is optionally carried out in wells prepared in a manner known per se for 30 minutes with a high degree of soution and 3.5 hours with a rotary stirrer. The mean diameter of the capsules is 16 μm, the average wall thickness is 66 nm, the wall thickness of absorptive branches of the single cap styles being between 20 μm and 130 w & waver.

Example 2

The procedure is as in Example 1, with dom difference that instead of the 60 ml of water, the glelohe amount of 0.1 mass% aqueous OMO solution with 5 g of the aqueous 50 mass% solution of the gielohen Melamlnharzes In Example 1 diluted and adjusted to pH 4.1. The capsules obtained have a mean diameter of 14 * 7 / va and an average thickness of 65 nm, with the wall thickness of the absorptions of the individual capsules ranging between 56 and 77 nm.

Example 3

100 ml of a 0.2% by mass aqueous solution of oMO and 6 g of a 50% by mass aqueous solution of a methanol-etherified, modified gelatin-formaldehyde resin (resin type II) are mixed with 3 ml of 1N formic acid pH 3 * 8 and heated to the reaction temperature of 60 ⁰ . 37 g of teohnisoher 2,4-Diohlor-4-nitro ~ diphenylei ago with a melting point of λ * 50 ⁰ O are added aufgesohmolzon urd under high Soherung in the solution and a total of 25 τηΐη under high Soherung (Turborilhrer) dlspergiert. The Misohung is stirred for another 3.5 hours. After cooling, the capsules have a solid core, an average Durohmesser of 27 / Um and an average wall thickness of 95 nm, the wall thickness of Absamentenitten the individual capsules varies between 80 and 120 nm.

Example 4

60 ml of a 0.03 mass% aqueous CMO solution are vermisoht with 5 g of Amlnoharzlösung type II used in Example 3 and adjusted with 0.5 η phosphoric acid to pH 4.1. In the resulting solution v / ground untor stirring and heating to 65 ⁰ O 30 g of 2-Ohlor-4,6-bis- (isopropylamtno) -1,3,5-trla55in

(Pp 212-2H ⁰ C, mean particle size 25 / um) added with stirring with a paddle stirrer. Naoh 5 hours Gesamttratktlonszelt at 65 ⁰ C microcapsules are obtained with a solid core. The average capsule diameter is 25 μm and the average wall thickness is 130 nm, with the wall thickness of sections of the single-capsule fluctuating between 110 and 150 nm.

Example 5

In a 30 l-Olashängegefäß with stirrer 14 400 ml of a 0.03 mass # lgen aqueous CMC solution at 65 ⁰ C are heated and at this temperature 630 g of Amlnoharzlfeung Harz.typ II, 420 ml of 2 η citric acid to adjust to a pH of 3.9 and under high shear 6 817 g of 70% methylparathion solution in chlorobenzene was added. Naoh a clock time of 60 min under high Soherung and further 4-stündlgen stirring with a flights] rlüirer at 60 ⁰ C a Diepereion of capsules with buckets average diameter of 10 / um and an average thickness of 41 nm is obtained, wherein the wall thickness of Sections of the individual capsules between 33 and 50 nm sohwankt.

Claims (1)

Patentanspru ch Process for the preparation of amino resin microcapsules based on partially methanol-etherified, cationic modlflzlertor, water-soluble melamic-pormaldehyde resins or · melamine-hairastack-formaldehyde resins, under sioh known other reaction conditions, daduroh characterized in that the reaction of all reaction components in a 0, 01 to 0.2 masseproζentigen Öarboxymethyloöllulose solution at a concentration of 0.5 to 20 g per 100 ml Aminohf _k ra Carboxymethyloellulose-Lb'sung takes place ·