EP2734482A1

EP2734482A1 - Method for producing a spinnable silica sol material

Info

Publication number: EP2734482A1
Application number: EP12735551.9A
Authority: EP
Inventors: Ekkehard Barth; Bastian MAHR
Original assignee: Bayer Innovation GmbH
Current assignee: JIANGSU SYNECOUN MEDICAL TECHNOLOGY CO., LTD.
Priority date: 2011-07-21
Filing date: 2012-07-17
Publication date: 2014-05-28
Also published as: US20140161707A1; US9518345B2; WO2013011016A1; CN103796971B; CN103796971A

Abstract

The invention relates to a method for the production of a spinnable silica sol material, in which a viscosity value that the spinnable silica sol material should show after maturation, V_s, is defined, and a viscosity value which the silica sol material shows prior to maturation, V_R, is determined which corresponds to V_s. An aqueous acid solution and a hydrolysable silicon compound are combined, and this combined mixture is concentrated by evaporation to obtain a single-phase solution, with the viscosity of said mixture being measured and the evaporation process being stopped once the viscosity value V_R has been reached. The single-phase solution that has been obtained in this manner is subsequently matured to obtain a silica sol material of the viscosity value V_s. The method is characterised in that waste is reduced and the spun sol characteristics are able to be reproduced more precisely during the synthesis, and in that an increased space-time yield is obtained in the production of biodegradable and/or resorbable fibres and nonwoven fabrics.

Description

Process for producing a spinnable gravel closol material

The present invention relates to a process for producing a spinnable Kiesclsol- M aterials taking into account viscosities as process parameters. It further relates to a process for producing a fiber or a nonwoven fabric based on such a material and a fiber or a nonwoven fabric obtained thereby.

Biologically degradable and / or absorbable fibers and nonwovens obtained from a spinnable silica sol material are known in the art. The fibers and nonwovens can be used, for example, in medical technology and / or human medicine, in particular in wound treatment. Thus, WO 2008/086970 A I describes a silica sol material and its use for the production of biodegradable kieselgei material. The materials such as fibers, nonwovens, powders, in monolithic form or as a coating can be used, for example, in medical technology and / or human medicine, in particular for wound treatment. The production of such fibers and nonwovens can be divided into four steps:

1. Hydrolysis-condensation of a hydrolyzable silicon compound

2. Solvent removal

3. maturation

4. spinning

In the patent DE 196 09 551 Cl a process for the production of biodegradable / bioabsorbable fiber structures is disclosed by way of example. This document relates to biodegradable and / or bioabsorbable (endless) fibers and processes for their production. The oil phases are obtained by partial or complete hydrolytic condensation of one or more hydrolytically condensable silicon compounds and / or precondensates derived therefrom The hydrolytic condensation is achieved by the action of water and optionally in water The presence of a catalyst and / or a solvent, and preferably a sol-gel process, is carried out by this partial or complete hydrolytic condensation to give a dope which is prepared by conventional methods into continuous and / or long and / or short fibers can be worked out.

According to one embodiment, the method has the following features: - Producing a dope by hydrolytic (partial (condensation of one or more silicon compounds SiX-s (which is defined previously) and / or derived from these precondensates;

- It performs the hydrolytic isch condensation ion, optionally in the presence of a catalyst and or a solvent, by the addition of water; the amount of water used is such that the molar ratio SiX.;: H 0 is between 1: 1 and 1:10, preferably between 1: 1.5 and 1: 2.5;

a phase transfer catalyst or such a large amount of a water-soluble solvent (LM) or solvent mixture is used that the molar ratio LM: SiX4>! , preferably> 1; After completion of the hydrolysis and adjustment of a dynamic equivalent weight, the LM is removed until the resulting mixture at room temperature and a shear rate of 20 s has a viscosity between 0.05 and 50 Pas, preferably between 0.5 and 2 Pas having;

after removal of the solvent, the resulting mixture is subjected to filtration; - After filtration, the resulting mixture is allowed to stand until it reaches the spinnability;

- Filaments are drawn from the dope and dried if necessary.

In WO 2008/086970 A1 a similar process is disclosed in which, however, the hydrolysis-condensation step is carried out over a period of at least 16 hours at a temperature of 0 ° C to 80 ° C with acid catalysis. By subsequent vapor deposition, a single-phase solution with a viscosity in the range of 0.5 to 2 Pa s at a shear rate of 10 s ^~! be generated at 4 ° C. This solution is subsequently cooled and subjected to a kinetically controlled ripening to form a homogeneous sol.

WO 2008/148384 A1 discloses a further process for producing a polyethoxysilane (PES) material. The material can be obtained by:

(A) a first hydrolysis Kondensationsreakt ion (HKR) of at most one radical X of one or more different Si compounds of formula S1X ₄ , in which the radicals e X are g eich or different and hydroxy, hydrogen or ethoxy (EtO), acid catalyzed at an initial pH of 0 to <7, in the presence of ethanol (EtO Fl) or an ethanol-water Mixture as a solvent, over a period of 1 to 24 li at a temperature of 0 ° C to

78 ° C (boiling point of ethanol) is performed,

(B) a second HKR of the material obtained in step (a) with simultaneous removal of the solvent by successive evaporation in a gas-tight container at a pressure of 100 to 1013 mbar, preferably at a slight suppression of 300 mbar to 800 mbar, a temperature of 50-78 ° C, preferably from about 70 ° C, b to ei ne r drastic increase in viscosity (at a shear rate of 10 s ^"1 at 4 ° C) to 0.5 to 2, preferably 1 Pa-s, to to constant weight and to the formation of a cyclotetrasiloxane of general formula ((SiO (OH) o,? 5 (OEt) i, 25 x 1/64 FfcO ^ and the molecular weight of 4 * about 1 14 g = about 456 g, is carried out;

(C) this PES material is cooled in a closed, preferably gas-tight container over a period of a few (2 to 5) minutes to a few (0.2 to 5, preferably 0.5) hours, and

(D) the PES material obtained from (c) is converted by a third HKR in a rPES material. In WO 2009/077104 A I, a similar process is disclosed as in WO2008 / 148384A1, in which the evaporation in a closed apparatus is optionally carried out by continuous supply of a chemically inert drag gas stream.

It is noted in all of these disclosures that the ripened silica sol material should have a viscosity in a preferred range in order to be able to spin it. However, all of the above-mentioned prior art methods can not provide a concrete statement as to the viscosity of the spinnable material at specification loss after maturation, but indicate a relatively wide viscosity range (between 30 and 100 Pa.s). This has the following disadvantages in the synthesis and spinning of the sol:

• The measurement of the loss factor, in contrast to the measurement of the dynamic viscosity, can not be realized inline or online without considerable effort. Therefore, it is imperative to measure the loss factor offline. Since the viscosity of the sol changes within a very short time, depending on the selected ripening temperature, especially at the end of ripening, this often leads to the loss of the batch. This loss of sol can be prevented only by an increased measurement and resulting staff costs. • The operating parameters of the spinning system must be adjusted for each new sol in order to obtain a specification-compatible nonwoven, which is biodegradable.

• Adjusting the operating parameters results in a time lag (reduction in space-time yield) as well as a loss of spinnable sol. · If the spinnable material has a high viscosity (> 65 Pa-s), the space-time

Yield in the spinning, if you want to continue to get specification-appropriate nonwovens.

The object of the present invention was therefore to address the objects of the prior art and to provide an improved process for the preparation of silica sol materials, in particular with regard to the termination criterion after reactive vaporization, the spinnability and the spatial properties. Time yield in the spinning, to provide. The method is intended to allow reproducible production of virgin silica sol materials. The method should be scalable to an industrial scale and allow a more accurate prediction of the viscosity of the spec sol.

The object is achieved by a method for producing a silica sol material in which the viscosity is detected during the removal of the solvent, for example by means of suitable probes and the removal of the solvent immediately upon reaching a desired viscosity, which also correlated with the loss factor is canceled. Furthermore, it is a process in which, after the determination of a complete substance data set, the measurement of the loss factor during the maturation of the sol can be dispensed with. Instead, the dynamic viscosity, easily accessible by means of measuring probes inline or online, is used as a termination criterion.

Surprisingly, it has been found that the viscosity of the silica sol material after the removal of the solvent correlates with the viscosity of the ripened mass.

The prior art (see, for example, WO 2008/086970 Al and WO 2008/148384 Al) discloses that it is necessary to obtain a spinnable sol having a viscosity between 30 and 100 Pa.s at a shear rate of 10 s ⁴ is that the single-phase solution after removal of the solvent preferably has a dynamic viscosity η in the range of 0.5 to 2 Pa s at a shear rate of 10 s ^-1 at 4 ° C. However, it does not describe what effect the viscosity after removal of the solvent has on the viscosity of the v-spinnable material. Surprisingly, however, the viscosity of the sol according to the invention can be predicted to ± 10 Pa-s with the aid of a precise adjustment of the viscosity after removal of the solvent.

A first subject of the present invention is therefore a process for the preparation of a spinnable silica sol material comprising the steps of: (a) establishing a viscosity value Vs which the spinnable silica sol material should have after maturation,

(b) determining the viscosity value VR corresponding to Vs which the silica sol material has before maturing,

(c) combining an aqueous acid solution and a hydrolyzable silicon compound,

(d) evaporating the mixture combined in step (c) to a single-phase solution while measuring the viscosity of the mixture and stopping the evaporation process when the viscosity value VR is reached,

(e) ripening the single-phase solution obtained in step (d) into a silica sol material having the viscosity value Vs.

The present invention will be described below inter alia in consideration of preferred embodiments. The embodiments can be combined as desired, unless the contrary results from the context.

The designation of the individual steps of the method according to the invention with the letters (a) to (e) does not mean that the individual steps must necessarily take place in the order indicated. If I have the steps (c), (d) and (e) must be carried out in the order given. Step (a) must be done before step (b) and step (b) must be done before step (d). Otherwise, the order can also be varied; For example, the order (c), (a), (b), (d), (e) is conceivable. In step (a) of the process according to the invention, the properties which the spinnable silica sol material should have are determined. More specifically, a viscosity value Vs to be determined by the spinnable silica sol-materiai is set. This viscosity value is the value of a physical quantity that provides information about the ideological properties of the spinnable silica sol material. The physical size (viscosity) can be, for example, the dynamic shear viscosity of the silica sol material which can be used with a rotational viscometer is measurable. Those skilled in the rheology are the corresponding physical quantities that indicate the theological behavior th, and their dependencies known among each other. Which physical variable is used to determine the viscosity value depends inter alia on their measurability in step (d) of the method according to the invention. Sinnvoilerweise one will use a physical size that can be measured easily, quickly and reproducibly.

In a preferred embodiment, the viscosity data Vs and V _{R are} dynamic viscosities measured by probes within the mixture. In this way, an online or inline monitoring of the viscosities is possible. These sizes are each determinable on the basis of DI EN ISO 3219.

The defined viscosity value Vs (DIN EN ISO 321 9) is preferably in the range from 30 to 100 Pas, more preferably in the range from 35 to 70 Pas, most preferably from 40 to 55 Pas at a shear rate of 10 s ^"1 at 4 ° C., or in the corresponding regions of another physical variable which can be deduced from the dynamic viscosity or has a mathematical relationship with it.

In step (b) of the process according to the invention, the viscosity value VR of the ice-oil material corresponding to this viscosity value Vs after the removal of the solvent and before maturing is determined on the basis of the viscosity value Vs of the silica sol material. The correlation between the value Vs and VR can be determined empirically in a series of experiments. In my own experiments, it has been found that a linear or at least well calculable relationship can be produced, so that the determination of the viscosity values can be done easily. Of course, this determination can be implemented in a process control system or in another data processing system.

In step (c) of the process according to the invention, an aqueous acid solution and a hydrolyzable silicon compound are combined.

Instead of the rapid addition described in the prior art (WO 2008/086970 A1, page 4, line 24) of an aqueous acid to the hydrolyzable silicon compound, the present invention preferably provides a controlled combination of these components. A controlled merger is understood to mean that the merger does not take place quickly, not quickly, but over a given length of time. The merge is such that the temperature of the mixture remains within a predetermined temperature range. The combination in step (c) is preferably carried out over a period of at least 15 minutes, more preferably at least 30 minutes and more preferably at least 1 hour. The shorter the period of time for metering, the more likely additional equipment measures will be required to remove the heat generated during the reaction and to maintain the temperature of the reaction mixture in a predetermined range.

It is surprising that, in comparison with the state of the art, the combination of hydrolyzable silicon compound and aqueous acid solution, which has been extended over a relatively long period of time, does not lead to a noticeably changed mass distribution of the polymers. If, for example, the synthesis method described in WO 2008/086970 A1 is modified such that the addition of the aqueous acid solution to the hydrolyzable silicon compound does not take place rapidly but over a period of 1 hour, this has no appreciable effect on the end of the process (after maturation ), for example, as measured by gel permeation chromatography. However, controlled merging has significant advantages, particularly with regard to an industrial scale process such as safety compliance, process control and reproducibility.

It is conceivable to carry out the combination in step (c) of the method according to the invention at a constant rate. It is likewise conceivable to carry out the combination in such a way that the temperature of the reaction mixture develops within a predetermined range. In the latter case, therefore, there is a control loop in which the combination of the components is controlled by the temperature and / or temperature change in the reaction mixture.

In a preferred embodiment of the process according to the invention, the combination in step (c) takes place under quasi-isothermal conditions. By the term "quasi-isothermal conditions", it is understood that a chemical reaction is carried out at as constant a temperature as possible In the present process at step t (c), the reaction under quasi-isothermal conditions would preferably be within a sump temperature range (ie, measured within the Reaction mixture) of ± 5 ° C, preferably from ± 2 ° C, more preferably from ± 0.5 ° C expire.

In a further preferred embodiment of the process according to the invention, the components are combined in step (c) in such a way that the components produced by the hydrolysis Condensation released heat is used to heat up the synthesis approach. It is thus possible to avoid overheating of the synthesis approach, for example in the case of low-performance or inert heat exchangers, and the hydrolysis-condensation reaction can be carried out in a controlled manner at the desired temperature. The hydrolysis-Kondensationsreakl ion in step (c) is preferably carried out with stirring.

The term "hydrolyzable silicon in the compound" preferably refers to a silicon compound of the formula (I)

SiX., (I) in which the radicals X are identical or different and are hydroxy, hydrogen, halogen, amino, alkoxy, acyloxy, alkylcarbonyl and or alkoxycarbonyl and of alkyl radicals. which optionally represent substituted straight-chain, branched or cyclic radicals having 1 to 20 carbon atoms, preferably having 1 to 10 carbon atoms, and can be interrupted by oxygen or sulfur atoms or by amino groups. In a preferred embodiment according to the invention, X in the formula (I) represents a given case-substituted straight-chain, branched and or cyclic alkoxy radical having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms.

X in the formula (I) particularly preferably represents an optionally substituted straight-chain and or branched C 1 -C 5 -alkoxy radical. More particularly preferred are substituted, but preferably unsubstituted, straight-chain and or branched C 2 - C 3 -alkoxy radicals, such as, for example, ethoxy, N-propoxy and / or isopropoxy. Very particular preference according to the invention is given to using tetraethoxysilane (TEOS) as hydrolyzable Si compound in the process according to the invention.

The term "aqueous acid solution" describes mixtures and / or solutions which have a pH of 0 to <7, preferably of 0 to 2. In addition to water and a proton donor, the aqueous acid solution may comprise one or more further substances Preferably, a water-soluble solvent is added, and ethanol is particularly preferred. The aqueous acid solution preferably comprises water and ethanol in a molar ratio of 1 to 1.27 to 1 to 1.59 preferably in the molar ratio of 1 to 1, 41. The proton donor used is preferably nitric acid. In addition to a preferably ethanolic aqueous salaric acid solution, aqueous or alcoholic (preferably an aqueous dilute ethanolic) solution of a physiologically tolerated acid (for example citric, succinic, acetic or ascorbic acid) and at least one essential (for example Arginine, more preferably L-valine, L-leucine, L-isoleucine, [.phenylalanine, [.-Thyroxine, L-methionine, L-lycin or L-tryptophan) or non-essential amino acid (for example L-glutamine , L-Giutaminsäure, L-asparagine, L-aspartic acid, L-cysteine, L-Giycin, L-alanine, L-proline, L-histidine, L-tyrosine). Such mixtures and / or solutions form in a physiological environment with molecular oxygen enzymatically (mitteis a nitroxide synthase, NOS) nitric oxide (NO). In addition, it is also possible to use organic nitrates or nitrate esters (so-called NO donors), for example ethyl nitrate, which form NO with the aid of an organic nitrate eductase. Thiol groups (cysteine) are required for this enzymatic release of NO.

For hydrolysis of Siiiziumverbindung such a large amount of water is used that the molar ratio of SiX: water in the range of 1: 1, 5 to 1: 2.5, preferably in the range of 1: 1.7 to 1: 1, 9, more preferably in the range of 1: 1, 7 to 1: 1, 8.

The assembly of the components in step (c) can take place in various ways. It is conceivable to introduce the hydrolyzable silicon compound in the reactor and to add the aqueous acid solution. It is conceivable to present the hydrolyzable silicon compound in a suitable solvent (for example ethanol in the case of TEOS). In a further preferred embodiment, in step (c), both the acid and the hydrolyzable silicon compound are added in parallel to a solvent in a controlled manner. Preferably, the hydrolyzable silicon compound is pre-mixed with a portion of the solvent, preferably 35 to 38% of the solvent. Insges amt the amount of solvent preferably does not change. However, at the beginning there is proportionately less solvent in the reaction vessel to which the acid and the described mixture of a part of the solvent and the hydrolyzable silicon compound are added in a controlled manner. This embodiment is particularly important in terms of a continuous manufacturing process (on a large scale) of importance. In this embodiment, the acid and the hydrolyzable silicon compound can be added independently of each other (for example via different reaction vessel openings and pump systems) over different periods of time. Preferably, however, the same period of time for metering is selected in proportion to the volume flow. The added hydrolyzable amount of silicon compound or the amount of acid added per unit of time is preferably constant. This embodiment of the invention will preferably under quasi-isothermal conditions. Preferably, the hydrolyzable silicon compound or the acid is metered in over a period of at least 15 minutes, preferably at least 30 minutes and more preferably at least 1 hour.

In a further preferred embodiment, in step (c) a hydrolyzable silicon compound is added to an acid present in a solvent. This controlled combination, also referred to below as "inverse dosing", surprisingly leads to a novel sol which is reproducible and can be prepared in a controlled manner, but whose physical properties differ from those described in the prior art Sol can be spun into a fiber and is also biodegradable and / or resorbable.This sol has a lower viscosity at the same loss factor as compared to those described in the prior art.

In the inverse dosage, the hydrolyzable Siiiziumverbindung is preferably not previously or only in a small portion of a solvent, preferably 0 to 5%, dissolved. Overall, the amount of solvent thus preferably does not change. However, at the beginning of the reaction, there is no or proportionately less solvent in the reaction vessel to which the silicon compound or the mixture of a part of the solvent and the hydrolyzable silicon compound is metered in in a controlled manner. The inverse dosage is preferably carried out under quasi-isothermal conditions. Preferably, the amount of hydrolyzable Siiiziumverbindung added per unit time is constant or approximately constant. Preferably, the hydrolyzable silicon compound is metered in over a period of at least 15 minutes, preferably at least 30 minutes and more preferably at least 1 hour. Surprisingly, it was also found in the inverse dosage compared to the other in the prior art and the embodiments described so far that the reaction accelerates overall. At a temperature of 37 ° C and otherwise the same conditions, the reaction lasts only 4 hours instead of 1 8 in the other controlled metering methods. Even with the inverse dosage, the reaction also accelerates with increasing temperature.

After combining the components in step (c) and before evaporation in step (d), the reaction mixture is preferably stirred for some time until a dynamic equilibrium has been established.

The duration of the reaction depends on the selected temperature and the period of the controlled metered addition. For example, the reaction lasts at a temperature of 55 ° C and a - II - controlled metered addition of the acid to the present in the solvent hydrolyzable silicon compound over a period of one hour, a total of about 5 hours on a laboratory scale. At a temperature of 37 ° C and otherwise the same conditions, the reaction takes about 18 hours. The hydrolysis condensation is preferably carried out without pressure (ie without overpressure at about 101325 Pa), preferably at a temperature of 0 ° C to 78 ° C. By appropriate pressure regulation and the implementation of the reaction at temperatures above the boiling point of ethanol (ie 78 ° C) is possible.

In step (d), the removal of the solvent takes place. This step is also referred to here as Reaktivindampfen. During reactive evaporation, the viscosity of the mixture is measured. When a viscosity value VR is reached, the evaporation process is stopped. The viscosity can be measured "online", "inline" or "offline." In the online or inline measurement, the viscosity is measured continuously by means of a sensor in the mixture. The on-line or in-line measurement is preferred, and those skilled in the art of rheology are familiar with corresponding measurement methods and measuring devices for measuring on, in, and offline.

In a preferred embodiment of the invention, step (d) is carried out in a closed apparatus in which mixing is possible and at the same time also an existing solvent (ie, for example, water, ethanol) can be evaporated. Preferably, the bottom temperature is maintained constant (ie, ± 5 ° C, preferably ± 2 ° C) by pressure regulation (time variable adjustment preferably between 500 to 120 mbar) so as to continuously add solvent with gentle boiling from the batch until the viscosity value is reached V _{R is} removed. The reaction temperature may be selected as described in the prior art, ie preferably between 30 ° C to 78 ° C, and more preferably between 60 ° C and 75 ° C. Preferably, step (d) is carried out with gentle mixing of the reaction system.

The single-phase solution resulting from step (d) is subjected to ripening in step (e). In contrast to the prior art (WO 2008/148384 AI, page 9, line 3 1), the single-phase solution is preferably stirred in this maturation process. Mixing the system with agitation causes the ripening to be slightly accelerated. In addition, the mixing of the single-phase solution leads to a degradation of temperature gradients, which in turn causes a better temperature control and thus an easier scalability of the process. It For example, it is preferable to use a stirrer which does not cause bubbles in the single-phase solution. In this case, those based on the principle of a helix, have proven to be particularly suitable. Also, the speed of the stirrer is chosen so that no bubbles can arise in the single-phase solution. There are speeds of 4 to 50 U / min, especially of less than 25 U / min, especially those which are smaller than 10 U / min, made sense.

It is also possible by intermingling the single-phase solution during ripening. Pharmaceutical agents homogeneous in the sun! contribute. In particular, the introduction of temperature-sensitive active substances is suitable for use at the point where reactive evaporation (combined with the higher reaction temperatures required for evaporation) has already been completed.

For the purposes of the invention, "active substances" are defined as substances which produce a specific action, a reaction, in a small dose in an organism Temperature-sensitive active substances or pharmaceutical substances are those whose degradation is markedly accelerated at temperatures below 8 ° C., preferably below 2 ° C.

Of course, in step (e), a check can be made as to whether the loss factor corresponding to Vs is within the specification limits.

An important factor influencing maturation (step (e)) is the temperature. In principle, the ripening can be carried out at temperatures of up to -80 ° C to 78 ° C and with regulation of the pressure also above it. At all temperatures, a S l known in the art may be prepared. However, it has proved to be particularly favorable when the ripening in step (e) at temperatures of 25 ° C to 35 ° C is performed. On the one hand, the production time at these temperatures is significantly shortened (from 2 to 3 weeks when ripening is carried out at 4 ° C compared to 2 days when the reaction is carried out at 31 ° C). The temperature should ideally not exceed 45 ° C during ripening.

It has surprisingly been found that the individual reaction steps (c) to (e) obey a simple Arrhenius equation. The pre-exponential factor and the activation energy can be determined empirically by the methods known to the person skilled in the art. Thus, it is possible either to predict the time for a given reaction temperature when the reaction will be completed or to determine the required reaction temperature for a given reaction time. In contrast to the prediction methods described in the prior art, which allow only a very inaccurate prediction (prediction within a range of ± 2 days), it is possible with the present method to determine the end of the production of the specified silica material within a range of ± 2 hours to predict. This makes it possible to predict the time of maturation until reaching a spinnable Kieselsii- material with the viscosity value Vs without determining the loss factor.

Preferably, the viscosity value is in the range of 30 to 100 Pa · s (shear rate 10 s at 4 ° C) preferably in the range of 35 to 70 Pa ^■ s (shear rate 10 s at 4 ° C) (with a loss factor at 4 ° C, Shear rate 10 s, 1% deformation) of 2 to 5, preferably from 2.5 to 3.5 and particularly preferably from 2.8 to 3.2, or in the corresponding ranges of another from the dynamic viscosity derivable or with her in one mathematical relationship standing physical size.

The silica sol material produced by the process according to the invention can be further processed into a fiber or a nonwoven. In principle, the further processing of the material into powders, monoliths and / or coatings is also conceivable. Further processing is known to the person skilled in the art.

Spun processes of such silica sol-mate rials to fibers or non-wovens are described, for example, in US Pat

DE 196 09 551 C1 and DE 10 2004 063 599 A I have been described. The production of powder, monolith and / or a coating starting from the silica sol material according to the invention has been described, for example, in WO 2008/086970 A1, WO 2008/148384 A1 and WO 2009/077104 A1.

Accordingly, another aspect of the present invention is a spinnable silica sol material obtained by a process of the invention.

Furthermore, the invention thus relates to a method for the manufacture of a fiber or a nonwoven, comprising the preparation of a spinnable Kieselsoi material according to the present invention and additionally the step

(f) drawing threads from the ripened silica sol material from step (e) and, in the case of a nonwoven, collapsing the threads into a nonwoven fabric.

Finally, the present invention also relates to a fiber or web obtained by a method as described above. The present invention will be further described by the following examples taken in conjunction with the figures, but not limited thereto.

Show it:

FIG. Figure 1 shows the relationship between the dynamic viscosity of a silica sol material before and after maturation

In all examples, the viscosity values were determined on the basis of DIN ISO EN 3219.

example 1

As starting materials for the hydrolysis condensation, 5.4 mol TEOS (tetraethoxysiloxane) in ethanol (6.8 mol) were placed in a closed reaction vessel. 9.6 moles of water in the form of a 0.006 N HNO 2 solution were mixed in advance and then added to the ethanol TEOS mixture rapidly at 19 ° C. The reaction solution was stirred for 17 hours. Thereafter, the solvent was separated by a chemically inert Schleppgasstrom to a viscosity of 1 Pa · s at a shear rate of 10 s ^" at 4 ° C. The maturation of the silica sol material standing at a temperature of 4 ° C to a Viscosity of 52 Pa · s at a shear rate of 10 s at 4 ° C and a loss factor of 3. By analogous experiments with the corresponding values for the viscosity after the reactive evaporation or for the loss factor after Rei tion of the sol are the Points shown in Figure 1 have been determined.

FIG. Figure 1 exemplifies the relationship between the dynamic viscosity of a silica sol material before and after maturation. In the present example, a compensation gcradc was determined which provides a mathematical relationship between Vs and VR. The figure shows a good linear approximation between the viscosity VR before the maturation of the silica sol (η ΐ, determined at a shear rate of 10 s at 4 ° C) and the viscosity Vs after ripening (η2, determined at a shear rate of 10 s ^"1 at 4 ° C.) The measured values were determined for three different loss factors tan δ (2.9, 3.0 and 3, 1) A rounded straight line equation for the compensatory gcradc through all measuring points is ηΐ = 12, 5 · η2 + 36.

Example 2

As starting materials for the hydrolysis condensation, 5.4 mol of TEOS (tetraethoxysiloxane) in ethanol were initially charged with 6.8 mol in a closed reaction vessel. 9.6 mol of water in the form of a 0.006 N HNO; solution were mixed orally and then the ethanol / TEOS mixture over a period of 1 hour at constant temperature (isothermal mode) of 37 ° C kontrol added. The reaction solution was stirred for 17 hours until an ethanol concentration of about 68% by weight was reached. Thereafter, the single-phase solution was evaporated at a constant bottom temperature of 62 ° C and a pressure between 500 to 120 mbar successively to a viscosity of 1 Pa · s at a shear rate of 10 s at 4 ° C. The maturation of the silica sol-materiais was carried out with stirring at a temperature of 28.1 ° C up to a viscosity of 55 Pa · s at a shear rate of 10 s at 4 ° C and a loss factor of 3.

Example 3

Ethanol (2.6 mol, 100%) was placed in a closed reaction vessel. The remaining ethanol (4.2 mol, 100%) was metered in together with 5.4 mol of TEOS via an access to the ethanol in the reaction vessel over a period of one hour in a controlled manner. At the same time 9.6 mol of water in the form of a 0.006 N HNCh solution over a period of one hour were added via another access to the reaction vessel. The reaction was carried out so that the bottom temperature in the reaction vessel during the entire reaction was 37 ° C (isothermal mode). The further process steps were carried out as described in Example 2, with the exception of the ripening temperature. The ripening temperature here was 4 ° C.

Example 4

Ethanol (6.8 mol, 100%) was charged together with 9.6 mol of water in the form of a 0.006 N HNCh solution in a closed reaction vessel. 5.4 mol of TEOS were added to the mixture in the reaction vessel in a controlled manner over a period of one hour. The reaction was carried out so that the bottom temperature in the reaction vessel during the entire reaction was 7 ° C (isothermal mode). The further process steps were carried out as described in Example 2. The maturation of the silica sol-Materiais was carried out with stirring at a temperature of 7 ° C to a viscosity of 30 Pa · s at a shear rate of 10 s at 4 ° C and a loss factor of 3, 1.

Claims

claims

A method of making a spinnable silica sol material comprising the steps of:

(a) determining a viscosity value Vs which the spinnable silica sol material should have after ripening, (b) determining the viscosity value VR corresponding to Vs which the silica sol material has before ripening,

(c) combining an aqueous acid solution and a hydrolyzable silicon compound,

(d) evaporating the mixture combined in step (c) to a single-phase solution, measuring the viscosity of the mixture and stopping the evaporation process

Reaching the viscosity value VR,

The method of claim 1, wherein the viscosity values Vs and VR are dynamic viscosities measured by probes within the mixture.

A method according to any one of the preceding claims, wherein the predetermined viscosity value Vs is in the range of 30 to 100 Pa-s at a shear rate of 10 s ^-1 at 4 ° C.

4. The method according to any one of the preceding claims, wherein the combination in step (c) takes place over a period of at least 15 minutes.

5. The method according to any one of the preceding claims, wherein the combination in step (c) takes place under quasi-isothermal conditions

6. The method according to claim any one of the preceding claims, wherein the combination of the components in step (c) is carried out so that the heat released by the hydrolysis-condensation reaction is used to heat the synthesis approach.

7. The method according to any one of the preceding claims, wherein the hydro lysie b silicon compound is a silicon compound of the formula (I)

SiX »(I) and X in formula (I) is an optionally substituted straight chain and or branched G - C5 alkoxy radical.

8. The method according to any one of the preceding claims, wherein in step (c), both the acid and the hydrolyzable silicon compound are added in parallel to a solvent controlled metered.

9. The method according to any one of claims 1 to 7, wherein in step (c) a hydrolyzable silicon compound is added to a solvent located in a solvent.

1 0. A method according to any one of the preceding claims, wherein i step (d) is carried out in a closed apparatus in which a mixing is possible and at the same time also an existing solvent can be evaporated.

1 1. Process according to any one of the preceding claims, wherein in step (e) the single-phase solution is stirred.

12. The method according to any one of the preceding claims, wherein the maturation in step (e) is carried out at temperatures of 25 ° C to 35 ° C.

13. A spinnable silica sol material obtained by a process according to any one of claims 1 to 12.

14. A process for producing a fiber or a nonwoven comprising the preparation of a spinnable silica sol material according to any one of claims 1 to 12 and additionally the step

(f) drawing threads from the rippled silica sol material of step (e) and in the case of a nonwoven, folding the threads into a nonwoven fabric.

1 . A fiber or nonwoven obtained by a process according to claim 14.