MXPA97006411A - Use of hydrogels in agriculture - Google Patents

Abstract

The present invention relates to the use of aerogels as vehicle materials for active substances in agriculture and / or veterinary medicine

Description

USE OF FARMERS IN AGRICULTURE DESCRIPTIVE REFERENCE The invention relates to the use of aerogel.es, for example, in agriculture and veterinary medicine as vehicle materials for active substances »Aerogels, in particular those with porosities of more than 60% and densities of less than 0.6 g / cm3, they have a very low thermal conductivity and are therefore used as thermal insulation material as described, for example, in EP-A-0 171 722. Aerogels in the broadest sense, ie, in the sense of "gel with air as dispersion medium ", they are prepared by drying an appropriate gel. In this sense, it is considered that the term "aerogels" means aerogelee in the narrowest sense, xerogels and cryogels, a dried gel that is described as an airgel in the narrowest sense if the gel liquid is removed to a large degree. at temperatures above the critical temperature and starting from pressures above the critical pressure. If the liquid in the gel, in contrast, is removed subcritically, for example with the formation of a liquid-adip limit phase, then the resulting gel is described as a xerogel. When the term aerogels is used in the present application, it refers to aerogels in the broadest sense, that is, in the sense of "gel with air as dispersion medium" "In addition, aerogels can be divided essentially into organic and inorganic aerogels. nicos Inorganic aerogoles have been known since 1931 (S.S. Kistler, Nature 1931, .27, 741). Since then, aerogels have been prepared from a wide variety of starting materials. Thus, for example, aerogels of 2 i2, AI2O3 aerogels, TiO2 aerogels, Z2 aerogels, SnC-2 aerogels, LY2O aerogels, Ce2 aerogels, V2O5 aerogels and mixtures have been prepared. of them (HD Geeser, PC Goswarni, Chem. Rev. 1989, 89, 756 ff). Organic aerogels obtained from a wide variety of starting materials, for example to pair + ir from meralnine formaldehyde, have also been known for some years (R.U. Pekala, D. riater, Sci. 1989, 24, 3221). Inorganic aerogels can be prepared in a wide variety of ways. For example, SIOO2 aerogels can be prepared by acid hydrolysis and condensation of tetraethyl orthosilicate in ethanol. This gives a gel that can be dried by supercritical drying, retaining its structure. Preparation methods based on this drying technique are known, for example, from EP-A-0 396 076 and UO 92/03378. An alternative is provided by a method for subcritical drying of SiO2 gels, when these are reacted with a silylating agent containing chlorine, before drying. The SIO2 gel can be obtained, for example, by acid hydrolysis with water of tetraalkoxysilanes in an appropriate organic solvent. After exchanging the solvent for an appropriate organic solvent, the resulting gel is reacted with a silylating agent in an additional step. The SIOO2 gel thus obtained can then be dried from an organic solvent in air. In this way, aerogels with densities of less than 0.4 g / cm 3 and porosities of more than 60% can be obtained. The preparation process based on this drying technique is described in detail in WO 94/25149. The aforementioned gels can be further mixed before drying in the aqueous alcohol solution with tetraalkoxysilanes and aged to increase the strength of the gel structure, as described, for example, in UO 92/20623. The SIO2 gel can also be prepared using water glass. The preparation process based on this technique is known from DE-A-43 42 548. Furthermore, in the German patent application No. 19502453.2, the use of chlorine-free silylating agents is described. Depending on the specific procedure used, the aerogels obtained by supercritical drying are hydrophilic or are hydrophobic for a short time. Nevertheless, in the long term, they are hydrophilic. This hydrophilic character can be made patent by a hydrophobicization step during supercritical drying. A process of this type is known from EP-A-0 396 (176. The dried sub-chlorite stearated aerogels are permanently hydrophobic as a result of their preparation process (salilation before drying) It was an object of the present invention find new applications for aerogels Surprisingly, it has been found that aerogels are suitable, for example, as vehicle materials for active substances in agriculture and veterinary medicine.These active materials can be insecticides, fungicides, herbicides, acaricides, piscicides, rodeni i cides, rnoluscicides, nematicides, bactericides and / or parasiticides.

Also, aerogels can serve as vehicle materials for viruses, bacteria and / or bacilli, such as Bacillus thuringensis, for the biological control of undesirable organisms. The active materials can be applied on, or be absorbed by, the aerogels in dissolved and / or suspended form in a liquid carrier medium, individually or in combinations, with the result that an almost liquid phase is retained in the airgel spaces described. . The active liquid materials can also be absorbed without additional vehicle means. For this, these liquid agents can also be provided with ionic or nonionic type emulsifiers. It is also possible to add dispersing and dispersing agents to the aerogels, preferably after the active formulations have been absorbed. The particle size of the airgel is preferably greater than 0.1 μm, particularly preferably greater than 1 μm, and in particular greater than 5 μm. The charged aerogels can be applied, for example, on plants, animals, fields or areas of land or water, mixed and / or diluted with at least one additional vehicle medium, such as talc, clay, kaolin and / or preferably with water. and / or oils. Preferably, inorganic aerogels are used. It is considered for the purposes of the present application that the term "inorganic airgel" means an airgel whose preparation has been based on inorganic materials. It is also considered that the term "aerogels based on inorganic materials" means in particular those aerogels that are modified, for example, by silylation. Preference is given to aerogels which predominantly comprise S1O2, AI2O3, TiO2, Z2 or mixtures thereof. Depending on their use, they may have hydrophilic and / or hydrophobic surface groups (e.g., OH, OR, R). Aerogels having hydrophilic and / or hydrophobic surface groups can be prepared by any of the methods known to those skilled in the art. Particular preference is given to idrophilic or hydrophobic aerogels containing SiO 2, in particular SióO 2 aerogels. Surprisingly, it was also found that the selection of an appropriate hydrophilic or hydrophobic airgel can accelerate or retard the release of the corresponding materials with which the airgel has been charged. Aerogels can also be used as dispersants for dispersions of solid, liquid or gaseous materials in solid or liquid media. It is also possible to incorporate without difficulty hydrophilic or hydrophobic aerogels that are loaded with hydrophilic and / or hydrophobic materials in liquid, semi-solid or solid hydrophilic and / or hydrophobic media, in particular to introduce hydrophobic (i.e., lipophilic) materials in hydrophilic dispersion media liquids and / or semi-solids, using hydrophilic aerogels, or to introduce hydrophilic materials into liquid hydrophobic dispersion media, with the help of hydrophobic aerogels. Hydrophobic aerogels, for example, float in aqueous hydrophilic media. Even hydrophilic or hydrophobic liquid materials can also be converted into powders or free-flowing solid granules. The invention is explained below by illustrative examples, but without being restricted by them.

The preparation of, respectively, a hydrophobic and a hydrophilic airgel is described first. In each of the following examples 1 to 39 (Tables 1 to 5), both aerogels were used. In the tables, the individual constituents are in% by weight, based on the total formulation.

PREPARED EXAMPLES EXAMPLE 1 Preparation of a permanently hydrophobic airgel 1 1 of a sodium water glass solution (with a content of 7% by weight of SiO 2 and a Na 2:: Si 2 ratio of 1: 3.3) was stirred together with 0.5 1 of an acid ion exchange resin ( styrene-divinylbenzene copolymer having sulphonic acid groups, commercially available under the name "Duolite C20), until the pH of the aqueous solution was 2.3. The ion exchange resin was then filtered and the aqueous solution was adjusted to pH 5.0 using 1 molar NaOH. The resulting gel was then aged for 3 hours at 85 ° C, and then the water was exchanged with acetone using 3 1 of acetone. The gel containing the acetone was then silylated with trimethylchlorosilane (5X by weight of trimethylchlorosilane per gram of wet gel). The gel was air dried (3 hours at 40 ° C, 2 hours at 50 ° C and 12 hours at 150 ° C). The resulting transparent airgel had a density of 0.15 g / cm3 and a BET specific surface area of 480 rn2 / g, and was permanently hydrophobic.

EXAMPLE 2 Preparation of a hydrophilic airgel The permanently hydrophobic airgel prepared in Example 1 was pyrolyzed at 600 ° C for 1 hour in a moderate air flow, using a tubular furnace. The resulting transparent airgel had a density of 0.18 g / cm 3, a BET specific surface area of 450 m2 / g, and was hydrophilic.

TABLE 1 TABLE 2 TABLE 3 TABLE 4 TABLE 5

Claims (8)

NOVELTY OF THE INVENTION CLAIMS

1. - The use of modified aerogels on their surface as vehicle materials for active substances in agriculture and / or veterinary medicine.

2. The use as claimed in claim 1, wherein the modified aerogels on their surface have hydrophobic surface groups.

3. The use of aerogels as claimed in claim 1 or 2 as vehicle materials for insecticides, fungicides, herbicides, acaricides, piscicides, rodenticides, rnoluecicides, nematicides, bactericides and / or parasiticides.

4. The use of aerogels as claimed in claim 1 or 2 as vehicle materials for vi ue, bacteria and / or bacillus.

5. A formulation containing at least one airgel and therefore an active substance in agriculture and / or veterinary medicine.

6. A formulation as claimed in claim 5, wherein the active substance is present in the vehicle medium in liquid, dissolved or suede form.

7. A formulation as claimed in claim 5 or 6, wherein the formulation contains at least one emulsifier.

8. A formulation as claimed in at least one of claims 5 to 7, wherein the formulation contains at least one fermenting and dispersing agent.