DE102016117790A1 - Complex monolithic, porous SiO₂-rich glass molded body, a process for its preparation and its use - Google Patents

Abstract

The invention relates to a method for producing a complex monolithic, porous SiO 2 -rich glass body by means of selective laser sintering and / or laser fusion, as well as its use.

Description

The invention relates to a complex monolithic porous, silica-rich glass molded body, a process for its preparation and its use.

Products of porous glasses, such as microspheres or flakes, are known in the art. Microspheres are used, for example, as a packed bed in reactors. Controlled metering and control of the media flowing through the microspheres, such as liquids or gases, is limited, however. Porous glass flakes have no internal reaction spaces. The flow control of liquids or gases takes place exclusively via the bulk density and the applied volume flow. Consequently, a targeted steering of the flow is excluded. In addition, membranes of porous glasses are still known in which, however, the flowing media are exposed to a high pressure loss and low flow velocities. Finally, pipes or tube bundles of porous glasses are known from the prior art, which allow only a linear guidance of the medium.

The known products made of porous glass have the drawback that they can be implemented with them only simple and geometrically limited morphologies. Thus, with such known products, for example, no undercuts or different pore geometries can be realized in a single monolith. These limitations are detrimental in that dosage, pressure drop, and flow rate within the porous glass are limitedly adjustable.

All known structures made of porous glasses have in common that they can not be produced in any desired different geometries, both externally and internally, in order to form individual morphologies with individually adjustable properties.

Accordingly, the present invention has for its object to provide a complex monolithic molded body, which can be individually created and provides complex three-dimensional structures with arbitrarily different geometries. In particular, two pore systems in different sizes should be independently adjustable. Furthermore, it is an object of the present invention to provide a production process for a complex monolithic porous, silica-rich glass molded body, which is inexpensive, easy and quick to carry out.

This object is achieved according to the features of claim 1, of claim 12 and of claim 13.

• a. Aufbringen eines Glasausgangsmaterials auf ein Trägersubstrat, wobei das Glasausgangsmaterial wenigstens Alkaliborosilicatglaspartikel aufweist;
• b. Selektive Beaufschlagung der Alkaliborosilicatglaspartikel mit wenigstens einer Laserquelle zu Versinterung und/oder Verschmelzung der Alkaliborosilicatglaspartikel miteinander in einer vorbestimmbaren Geometrie zur Ausbildung eines Alkaliborosilicatglasformkörpers;
• c. Wärmebehandlung des selektiv versintertem und/oder verschmolzenem Alkaliborosilicatglasformkörpers zur Erzeugung einer Entmischung des Alkaliborosilicatglasformkörpers; und
• d. Saure Extraktion der boratreichen Phase aus dem Alkaliborosilicatglasformkörper zur Ausbildung eines komplexen monolithischen porösen, siliziumdioxidreichen Glasformkörpers mit einer Vielzahl an Poren und/oder Kanälen und/oder Reaktionsräumen,

wobei die Schritte a. und b. wenigstens einmal durchgeführt werden.An essential point of the invention is that the process for producing a complex monolithic porous, silicon dioxide-rich glass molded body has at least the following steps:

• a. Applying a glass starting material to a carrier substrate, wherein the glass starting material comprises at least alkali borosilicate glass particles;
• b. Selective loading of the alkali borosilicate glass particles with at least one laser source for sintering and / or fusing the alkali borosilicate glass particles together in a predeterminable geometry to form an alkali borosilicate glass molded body;
• c. Heat treatment of the selectively sintered and / or fused alkali borosilicate glass molded body to produce a demixing of the alkali borosilicate glass molded body; and
• d. Acid extraction of the borate-rich phase from the alkali borosilicate glass molded body to form a complex monolithic porous, silicon dioxide-rich glass molded body having a multiplicity of pores and / or channels and / or reaction spaces,

wherein steps a. and b. be performed at least once.

Depending on the complex monolithic porous, silicon dioxide-rich glass molded body to be produced, steps a. and b. repeated until the desired three-dimensional Alkaliborosilicatglasformkörper is produced as an intermediate. Only then are steps c. and d. executed in succession.

First, a glass raw material having at least alkali borosilicate glass particles is provided. For this purpose, it is advantageous if alkali borosilicate glass, such as, for example, sodium borosilicate glass or lithium borosilicate glass with an increased borate content, is correspondingly comminuted. In the simplest case, the comminution takes place by means of grinding process and subsequent screening process. The glass starting material is advantageously formed Partiklulär.

The glass starting material containing at least alkali borosilicate glass particles is first applied to a carrier substrate. This can be done directly or indirectly via at least one intermediate layer. The carrier substrate is arbitrary and can be formed for example of glass, ceramic, metal or plastic. Application layer thicknesses have proven to be particularly advantageous a position in the range of 10nm-5mm, advantageously 10 nm to 150 microns and more preferably proved from 10 nm to 80 microns. The layer thickness mentioned here refers to the freshly applied starting material.

Subsequently, the applied layer is at least partially, advantageously completely, sintered and / or fused. For this purpose, the glass starting material and thus also the alkali borosilicate glass particles are subjected to at least one laser source. The energy introduced by the at least one laser source into the freshly applied glass starting material is sufficient to sinter and / or fuse the particles contained in the glass starting material in a predeterminable geometry to form an alkali borosilicate glass molded body.

Due to the high energy input and the small diameter of the at least one laser spot, it is now possible to produce individual shapes, sizes and geometries, such as particle cavities, reaction spaces, channels or a mixture thereof as a first pore system within the glass starting material.

The alkali borosilicate glass particles are particularly advantageously sintered with one another, as this significantly reduces the susceptibility to cracking of the resulting complex, monolithic, porous, silicon dioxide-rich glass molded body.

Depending on the embodiment, it is conceivable to move either the at least one laser source horizontally over the applied layer of glass starting material, for example computer-controlled. On the other hand, it is also conceivable to displace the carrier substrate horizontally below the at least one laser source. For example, the shifting is line-like, grid-like, concentric or purely random. The guidance of the laser source is computer-controlled, for example, depending on the prefabricated computer model of the three-dimensional body to be created.

Depending on the desired three-dimensional structure of the complex monolithic porous, silicon dioxide-rich glass molded body as the final product, the first two steps a. and b. repeated several times. With each repetition, the intermediate product, the Alkaliborosilicatglasformkörper in addition to the first pore system, built up in layers. Thus, any geometries can be formed, such as pyramids, spheres, cuboids with a first pore system with corresponding holes, reaction spaces or channels.

To form the layered structure of the intermediate product advantageously two versions are conceivable. Thus, for example, the glass starting material can be applied directly in the form which the end product should later have. The sintering then takes place over the entire applied glass starting material.

Furthermore, however, it is also conceivable that the glass starting material applied to the substrate substrate and / or the intermediate layer in a planar manner is only partially sintered and loose starting glass material is later removed again as an option.

Consequently, it is not necessary to sinter and / or fuse the entire surface of the glass starting material, and then in turn to cut or cut out the resulting structure by physical methods. Through the targeted use of the at least one laser source, it is now possible for the first time to selectively sinter and / or fuse alkali borosilicate glass particles, for example to produce a three-dimensional structure with macroscopic holes or bends as an alkali borosilicate glass molded body as an intermediate product.

With the completion of the predetermined, geometrically free-form alkali borosilicate glass molded body, it will be completed in step c. subjected to a heat treatment. The heat treatment is advantageously carried out in a temperature range of 300-1000 ° C, more preferably 450-750 ° C and even more advantageously at 600 ° C for a time interval in the range of 0.5-90 hours, more advantageously 1-72 hours demixing the glass phases. By this heat treatment, the glass starting material of the alkali borosilicate glass molded body is demixed, so that a borate-rich phase and a silicate-rich phase is formed. Consequently, there is a phase separation within the alkali borosilicate glass molded body. Advantageously, the segregation is spinodal. However, this is of course not to be understood as limiting, so that demixing in addition to spinodal can also take place bimodal and / or multimodal.

The demixing caused by the heat treatment takes place in the wall regions of the alkali borosilicate glass molded body, which span and bound the first pore system. By means of the controlled demixing described here, a further, second pore system with a penetration structure is formed both within the wall regions and at the surface thereof.

In the simplest case, the heat treatment, for example in an oven, but is not limited thereto. So it is also conceivable that the Heat treatment is performed by the at least one laser source.

After completion of the heat treatment, the borate-rich phase can then be removed from the demixed alkali borosilicate glass molded body by acid extraction. By dissolving out the borate-rich phase, a further pore system different from the first pore system is formed in the otherwise monolithic glass wall regions of the resulting silicon dioxide-rich glass molded body. The pores of the second pore system form a pore system. Thus, a porous penetration structure is particularly advantageously formed.

Particularly advantageously, the acid extraction is carried out with 0.5-4 M hydrochloric acid, more preferably with 1-3 M hydrochloric acid, at a temperature in the range of room temperature to 100 ° C for a time interval of 4-96 hours, more preferably 8-72 hours. In particular, the temperature range up to 100 ° Celsius, advantageously <98 ° C has proved to be advantageous in this respect, since it is ensured that only the borate phase is dissolved in this temperature range. If higher temperatures are used, a part of the silicate-rich phase, ie part of the silicon dioxide, also dissolves in the borate phase and remains in the pores after the acidic extraction and clogs them. Therefore, an exact temperature setting is especially important for extraction.

As a result of the removal of the borate-rich phase, the silicate-rich phase and thus also the silicon dioxide in the shaped body itself remain or form the complex, monolithic, porous glass molded body. Silicon dioxide rich shares of silica of> 80 weight percent, more preferably> 90 weight percent, more preferably of> 97 percent by weight based on the total weight of the complex, monolithic, porous glass molded body to understand.

Under complex are advantageously complex, individual two and three-dimensional inner and outer geometries of the glass molded body to understand.

This initially relates to the targeted shaping of the external shape of the alkali borosilicate glass molded body as an intermediate product by laser sintering, whereby, for example, plates, cuboids, pyramids, spheres and other more complicated shapes can be produced.

Furthermore, at the same time complex, targeted geometries of the inner first pore system of the alkali borosilicate glass molded body, such as particle cavities, reaction spaces, channels, are produced by laser sintering.

With the heat treatment subsequently carried out, within the wall regions of the alkali borosilicate glass molded body which span and bound the first pore system, the wall material itself is demixed, advantageously spinodal and / or bimodal and / or multimodal, so that a further, second pore system is formed within the wall region of the alkali borosilicate glass molded body , In this case, pores with a penetration structure are advantageously formed, more preferably a three-dimensional, open-pore penetration structure is formed in the wall region and on its surface. This penetration structure has a size range of <1 μm. The second pore system is formed with the acidic extraction of the borate-rich phase and accessible.

This is of course not to be understood as limiting, so that it is alternatively also conceivable to carry out the extraction in the basic. The basic extraction, for example with sodium hydroxide solution, is carried out particularly advantageously as a further process step following the acidic extraction. This basic extraction serves to remove finely dispersed silicon dioxide from the pores already formed in the wall regions by the acidic extraction. In addition, the pores are again controlled by the basic extraction increases.

In addition, the method described here creates a monolithic, silicon dioxide-rich glass molded body, which allows the control of flow rates and the adjustment of the pressure loss at separation individually.

Furthermore, the present method also allows the adjustability of the geometry, size and surface roughness of the reaction spaces and / or channels and / or pores in the interior of the monolith. In particular, the adjustment of the pore size of the further, second pore system in the wall regions takes place as a function of the heat treatment for separation of the alkali borosilicate glass molded body. Thus, for example, an alkali borosilicate glass molded body which has undergone the heat treatment step at 500 ° C. and 72 hours has a significantly more pronounced segregation than an alkali borosilicate glass molded body which was subjected to the heat treatment at 500 ° C. for only 2 hours. It can be observed at 72 hours that borate-rich and silicate-rich phases increase markedly and the borate-rich phase forms size ranges of more than> 300 nm. The size ranges of the borate-rich phase result from the borate content of the glass starting material. The higher the borate content selected, the greater the segregation areas are formed.

Consequently, after the acidic extraction of the borate phase, hollow pores remain in the monolithic glass molded body, which advantageously communicate with one another. Thus, a penetrating structure is formed, which constitutes the second pore system.

Particularly advantageous is the pore size of the second pore system in the range of 1 nm to 750 nm adjustable. The pore size of the further, second pore system is adjusted by the heat treatment step and / or by the subsequent acidic and / or optionally basic extraction, as already described above.

However, this is not to be understood as limiting, so that it is also conceivable that the pore size can be extended to the range of 0.1-1000 nm if the glass starting material is varied and, if appropriate, during pseudomorphic transformation. Under pore size is to be understood here advantageously the pore diameter average.

In addition to the pores of the second pore system, channels, pores, particle cavities and reaction spaces of the first pore system within the complex monolithic silicon dioxide-rich glass molded body can also be produced and adjusted by laser sintering using the method described here.

Advantageously, the size of the channels and reaction spaces is in the range of 10 .mu.m-50 mm, particularly advantageously in the range of 500 .mu.m-5 mm. Under size of the cavities is presently advantageous to understand their diameter. Their length is limited by the overall dimensions of the molding.

In addition, with the present method, voids can be generated, which are formed by the interparticle volume. The size of the cavities is advantageously dependent on the degree of sintering and / or the fusion. Size ranges of the cavities of <250 μm have proved particularly advantageous. These cavities are formed as particle cavities. Particle cavities are to be understood as meaning those cavities which result between at least three particles sintered together. The particle cavities may be formed empty, but may also be at least partially filled with loose glass particles of different size and composition. The particle cavities are significantly smaller than, for example, the channels. Also, the particle cavities include, such as the channels and reaction spaces to the first pore system.

Under reaction chambers are advantageously closed cavities within the glass molded body to understand, which have no direct opening to the surface. A possible mass transport into or out of the reaction chambers takes place only through the porous wall regions, that is to say through the pores with the penetration structure of the second pore system and through the particle cavities of the first pore system. In contrast, channels of the first pore system have at least one opening which is arranged directly in the surface of the glass molded body.

The surface roughness within the particle cavities, reaction spaces and channels of the first pore system is predominantly dependent on the glass particle fraction and / or glass particle fraction span and the degree of sintering and / or fusion.

As a particularly advantageous glass composition has a composition of at least SiO ₂ in the range of 55 to 75 weight percent, B ₂ O ₃ in the range of 20 to 35 weight percent and Na ₂ O and / or Li ₂ O in the range of 2.5 to 10 weight percent based on the total mass of the glass composition.

Further advantageous embodiments will become apparent from the dependent claims.

In a further advantageous method step, the steps a. and b. Repeatedly repeated changing the height position of the carrier substrate, thus forming a pre-definable height and pre-definable geometry of the alkali borosilicate glass molded body. In a first pass, steps a. and b. carried out, so takes place after completion of the sintering and / or fusion, a change in the position of the carrier substrate. This can be raised as well as lowered. In the simplest case, the carrier substrate is lowered by the previously applied layer thickness of the glass starting material before a new layer of the glass starting material is applied to the previous, already sintered and / or fused monolithic layer of the glass starting material. This change in the height position of the carrier substrate thus leads to a layered structure of the alkali borosilicate molding, which then ultimately results in a three-dimensional body.

In a further advantageous method step, before step a. at least one adhesion promoter layer is applied to the carrier substrate. This is advantageous because it makes it easier to position the glass starting material on the carrier substrate and also makes it easier to hold on to it. The construction of complex, Three-dimensional moldings is simplified. Bonding agent layers made of ceramic have proved to be particularly advantageous. For this purpose, at least one filter band is arranged on the carrier substrate. At least one coating is provided on the side of the filter belt facing the carrier substrate, which coating is transferred from the filter belt to the carrier substrate upon laser irradiation. The application of this primer layer can be done both over a large area and partially. This is of course not to be understood as limiting, so that in an alternative embodiment it is also conceivable to initially apply the adhesion promoter layer as a ceramic slip. Subsequently, the ceramic slip is sintered by means of a laser source, so that a ceramic layer is formed. This layer may be formed continuously on the carrier substrate or only partially. The latter has the advantage that during the laser application only the geometry is sintered, which is then also required as a base for the future silicon dioxide-rich glass molded body. The adhesion promoter layer is produced in a layer thickness of 10 nm to 800 .mu.m, advantageously from 50 nm to 500 .mu.m, and more preferably from 800 nm to 250 .mu.m. In this layer thickness range, the adhesion promoter layer can be quickly and efficiently dissolved in the presence of at least one acid, for example hydrochloric acid, in a later process step.

Depending on the requirements, it is also conceivable to provide more than one adhesion promoter layer. For example, two, three or four adhesion promoter layers can be provided. This can increase the stability of the intermediate and prevent cracking.

At least one adhesion promoter layer has also proved to be advantageous in that it can be applied over the entire area or even to the monolithic structure.

Furthermore, it is also conceivable to apply a correspondingly high energy to the carrier substrate and the glass particles by means of the at least one laser source so that both the carrier substrate and the glass particles melt and thereby form a connection. However, this is problematic in practice, since the different expansion coefficients of carrier substrate and glass particles often lead to breakage. In addition, changing the carrier substrate surface is often undesirable in practice. The melting of the carrier substrate and glass particles is thus advantageously applicable only if the carrier substrate and glass particles are similar or identical in their chemical nature.

In a further advantageous method step, the glass starting material is applied to the carrier substrate and / or the adhesion promoter layer by means of a decanting process, sponge printing technique, doctor blade technique, roll technique, spraying process or printing technique).

Advantageously, the nature of the application technique of the glass starting material depends on its nature. Thus, it is particularly advantageous to use the glass starting material as a glass suspension or as a glass powder, wherein the glass suspension further comprises at least one liquid phase in addition to the Alkaliborosilicatglaspartikeln. It is thus possible for the first time to build up a complex monolithic alkali borosilicate glass molded body in layers by wet application of a glass suspension and / or by dry application of a glass powder.

If a glass suspension is used, the carrier liquid is advantageously a polar solvent, for example water, monohydric, polyhydric or cyclic alcohols, for example polyvinyl alcohol or carboxylic acids and / or a mixture thereof. Ethanol and polyvinyl alcohol have proved to be particularly advantageous as the carrier liquid for the alkali borosilicate glass particles. In this carrier liquid, the alkali borosilicate glass particles are suspended. The glass suspension itself has a volume ratio between solvent, advantageously ethanol, and glass powder, ie the alkali borosilicate glass particles, in the ratio of 1: 0.3-1: 5. Particularly preferred volume ratios between ethanol and alkali borosilicate glass particles are 1: 2 or 1: 1. With these two volume ratios, it is particularly easy and effective to apply the glass suspension to the carrier substrate and / or the adhesion promoter layer using the techniques described above.

For example, it has proved to be advantageous to apply the glass suspension to the carrier substrate and / or the adhesion promoter layer by means of a decanting process. In this case, the glass suspension is added dropwise onto the adhesion promoter layer or onto the carrier substrate. It is possible that the alkali borosilicate glass particles contained in the suspension settle on the corresponding surface, without the particles being exposed to mechanical stresses, such as, for example, shearing forces. Instead of the dripping, it is also conceivable that a dipping step is carried out in which the carrier substrate is immersed in the glass suspension and at a controlled speed in the range of 0.1 .mu.m / s to 2 mm / s pulled out again.

Advantageously, the polar solvent is subsequently reduced in a controlled manner, for example by heat treatment at a temperature range of 55 to 80 ° C within a time window of 0.2 to 5 minutes.

This is followed by the selective sintering and / or fusion of the alkali borosilicate glass particles with at least one laser source. Following this, the process is repeated from the beginning, so that in turn the glass suspension is applied dropwise to the already existing monolith surface. The steps just described are repeated until the desired geometry of the Alkaliborosilicatglasformkörpers is reached.

It has proven particularly advantageous if the glass suspension with a height of 1 to 3 mm is applied to the corresponding surface, which may be the carrier substrate, the adhesion promoter layer or the monolith surface.

Furthermore, it has proven to be advantageous to carry out the application of the glass powder and / or the glass suspension as a three-dimensional printing. In this case, the glass starting material is used as a glass powder. The glass powder, which comprises at least alkali borosilicate glass particles, is stored, for example, in a feed container, in order then to be selectively applied first to the carrier substrate and / or the adhesion promoter layer. Selective in this context is to be understood as meaning that the application of the glass powder to the carrier substrate and / or the adhesion promoter layer takes place according to a predetermined geometry. This can for example be calculated in advance in a software program and deposited.

Subsequently, the sintering and / or fusion with the at least one laser source is performed. As a result, the alkali borosilicate glass particles are inseparably connected to each other. Upon completion of this fixing step of the alkali borosilicate glass particles, the glass powder is re-coated from the feed container to the sintered and / or fused layer of the alkali borosilicate glass particles according to the given geometry. The three-dimensional intermediate, the Alkaliborosilicatglasformkörper is thus printed in layers.

Thus, with the method described herein, a three-dimensional, complex monolithic glass molded article can be prepared and printed by layered application and selective sintering and / or fusing of the glass starting material.

Another alternative is the sponge printing process. In this case, a sponge is soaked with the glass suspension already described above. Sponges with a net density in the range from 25 kg per cubic meter to 32 kg per cubic meter and a dry elongation in the range of 120-350% and a cell count of 40-90 ppi have proven to be particularly advantageous sponges. With such sponges both a particularly effective absorption of the suspension and a uniform release of the particles can be ensured on the carrier substrate. In the simplest case, the suspension-impregnated sponge is spread over the substrate and / or printed on the substrate. As a result, a thin layer of suspension having a layer thickness in the range of 100 nm-300 μm, more preferably 800-100 nm, is transferred to the carrier substrate. In a further step, the solvent of the suspension is reduced, advantageously completely reduced. In the simplest case, this can be done analogously to the decantation process already described above. With this printing method powder layers can be applied, which are thinner compared to the decanting process already described in their layer thickness. The printing of the glass suspension onto the carrier substrate advantageously takes place over the entire surface of the carrier substrate, so that in the subsequent selective laser application step only the predetermined, desired geometry with the at least one laser source is traversed and sintered and / or fused. The remaining Alkaliborosilicatglaspartikel can be removed again after completion of the intermediate product, for example by means of compressed air from the carrier substrate and recycled, so used for further suspensions.

In addition, it is also conceivable to apply the glass starting material by means of doctor blade technology to the carrier substrate. In this case, the glass suspension can advantageously be spread on the carrier substrate and / or the corresponding adhesion promoter layer in order to be subsequently selectively sintered and / or fused. Again, the glass suspension is applied over a large area and allows the desired geometry by the method of at least one laser source.

Furthermore, it is also conceivable to apply the glass suspension and / or the glass powder by means of spraying to the carrier substrate and / or the adhesion promoter layer. For this purpose, suitable spray nozzles are used which allow a controlled application of the glass suspension and / or the glass powder. Alternatively, it is also conceivable to roll up the glass suspension and / or the glass powder with a roll.

In addition, screen printing or stencil printing techniques can also be used and applied in the present process.

In the present case any substrate can be used as the carrier substrate, for example on glass, metal, plastic or ceramic. The carrier substrate advantageously serves to build up the intermediate product and the glass molded body as the end product. In this context, it has also proved to be particularly advantageous to apply the printing technique of glass suspension in curved carrier substrates. This is particularly advantageous because, as a result, depending on the curvature of the carrier substrate, straight and / or convex and / or concave, the same curvature is transferred to the intermediate product and to the later glass molded body. Thus, it is possible for the first time to print and produce curved monolithic, porous, silica-rich glass moldings in layers.

Furthermore, the at least one laser source is advantageously a CO ₂ laser or a YAG laser, wherein the CO ₂ laser with a power of 4.5 to 5.5 watts plus / minus 1 watt and the YAG laser with an output of 1.5 to 2.5 watts plus / minus 0.5 watts are operated. Advantageously, the at least one laser source is movably movable in at least one plane. In this case, the horizontal mobility has proven to be advantageous, which means that the at least one laser source is movable in the xy direction. This is advantageous because it allows the laser source itself to be moved quickly and easily so that the given geometry, for example by means of a computer program, can be traversed directly and cleanly and also the sintering and / or the fusion can be carried out with high precision.

Furthermore, it is also conceivable to make the laser source movable in the vertical direction, ie in the z-direction. Of course, this is not limiting, so that two or three laser sources can be used to perform the selective sintering and / or fusion.

In a further advantageous method step, the adhesion promoter layer is simultaneously dissolved during the acidic extraction of the borate-rich phase. This is particularly advantageous because with dissolution of the adhesion promoter layer, the resulting complex, monolithic, porous, silicon dioxide-rich glass molded body is detached from the carrier substrate and is to be regarded as an independent monolith. The replacement can take place prematurely thermally or chemically. If the chemical step is carried out, the acids, bases or other organic solvents which attack and dissolve the primer layer, but do not attack the monolith itself, are conceivable as solvents. Particularly advantageous is the replacement of the complex, monolithic, porous, silica-rich glass molded body during the acid treatment, such as with hydrochloric acid shown. This acid is advantageous in that acid extraction and dissolution of the primer layer can be carried out in a single step. This saves time.

Furthermore, the present invention claims a glass starting material for the process described above, which has alkali borosilicate glass particle fractions in the range of <32 μm, <63 μm and 63 to 125 μm. These size ranges of <125 .mu.m are advantageous in that such small alkali borosilicate glass particles can be applied uniformly to the carrier substrate and / or the adhesion promoter layer with the application processes listed above. Especially when using the glass suspension, alkali borosilicate glass particles with <125 μm prove to be advantageous, since these form a homogeneous suspension in connection with the polar solvent.

In a further advantageous embodiment, the alkali borosilicate glass particles of the glass starting material have a borate content in the range from 15 to 50 percent by weight, more preferably in the range from 25 to 35 percent by weight. This borate content ensures that the heat step and the demixing, advantageously spinodal and / or bimodal and / or multimodal, also forms an alkali borate-rich phase within the alkali borosilicate glass molded body and also enriches it. By the weight percentage of the alkali borate phase of 25 to 35 weight percent, the pores of the second pore system can be selectively formed.

In a further advantageous embodiment, the alkali borosilicate glass particles furthermore have a multiplicity of homogeneously distributed absorption centers. Advantageously, the absorption centers are required for the at least one laser source, in particular if this is designed as a YAG laser. Advantageously, homogenous distribution means a uniform distribution.

These absorption centers are formed of ions and / or non-ions of one or more elements which absorb at an exciting wavelength of the laser used. Advantageous in use with the YAG laser are metal ions, wherein the proportion of metal in the total glass in the range of 0.5 to 15 weight percent, preferably ≤ 5 weight percent. In particular, the homogeneous distribution of the metal ions, as absorption centers for the YAG laser source, is important for uniform heating and sintering. By a locally larger metal ion concentration, ie an inhomogeneous distribution of the metal ions in the glass particles, in areas with an increased metal concentration, a higher energy will be transferred into the material, so that these areas stronger be melted and cracking is the result. The use of iron oxide to form the absorption centers has proven to be particularly advantageous. This is particularly advantageous since the iron is accumulated in the borate-rich phase and washed out of the monolith with the acid extraction.

In addition, the present invention claims a complex, monolithic, porous silica-rich glass molded body, which is prepared by the method described above, which has a first pore system with a plurality of particle cavities, pores and / or channels and / or reaction spaces and the first pore system Wall regions of the glass molded body is clamped and that the glass molded body has a further, second pore system which is arranged in the wall regions of the glass molded body and which has an open-pore penetrating structure. For the pore systems described here, the textures explained in detail above are applicable.

Furthermore, it has proved to be advantageous to use complex, monolithic, porous, silicon dioxide-rich, glass moldings produced in this way as membrane, membrane reactor, microreactors, optical components, filters and / or as filters in microfluidics.

The glass starting material described here can also contain other glass particles in addition to the alkali borosilicate glass particles or else be formed completely from another glass. A prerequisite for complete replacement is that at least one glass particle fraction also separates into a soluble and insoluble phase, based on the solvent used.

Advantages and expediencies can be found in the following description in conjunction with the drawing. Hereby show:

1 the schematic production of the glass particles;

2 the schematic preparation of the adhesive layer;

3a The schematic step sequence of the decantation process;

4a -D the schematic application of the suspension by means of printing technology;

5a -F the individual production steps of the process for producing a monolithic, complex glass molded body; and

6 a further schematic view of a monolithic, complex glass molded body.

In 1 the schematic is shown how the alkali borosilicate glass particles are made. The starting point is a glass in the picture above 2 of alkali borosilicate glass, more advantageously of alkaline earth alkali borate glass, even more advantageously of sodium alkali borate glass or lithium alkali borate glass. The glass 2 itself has an alkali borate content in the range of 15 to 50 weight percent, more preferably 25 to 35 weight percent. For use with YAG laser was additionally used in the manufacture of the glass 2 to the borate-enriched alkali borosilicate glass added at least one absorbent component, preferably iron (III) oxide, which is also present by reduction within the glass as iron (II) oxide. Particularly advantageous is the proportion of iron oxide in the glass ≤ 5 weight percent based on the total mass of the glass.

In 1 above is the alkali borosilicate glass 2 showing a variety of homogeneously distributed ionic and nonionic absorption centers 4 having. Nonionic absorption centers have, for example, residues of organic solvent or else carbon. Furthermore, neutral metal atoms, metal agglomerates and / or (non-) charged nanoparticles can also be used as absorption centers.

In the next step, the cooled glass is crushed, advantageously ground, so that different sized fractions arise. Fractions of <125 μm have proven particularly advantageous for the process described above. These are appropriately controlled and provided by sieving. There are different sized fractions of alkali borosilicate glass particles 18 of a size <125 microns.

In the next step, the alkali borosilicate glass particles 18 with at least one solvent, preferably in ethanol, suspended. Thus, the glass starting material is provided as a glass suspension. If only the glass powder is to be used, the ground or otherwise comminuted alkali borosilicate glass particles 18 used from the first step.

An embodiment for the preparation of a glass suspension is that, instead of the ethanol, polyvinyl alcohol (PVA), distilled water and glass powder can also be used. In a laboratory experiment, 50 ml of distilled water are heated to 80 ° C. With continuous stirring, 3 g of PVA are added. In a second batch, a suspension of 33 g of glass powder and 30 ml of distilled water is prepared. After homogenization of the PVA / H ₂ O- Mixture, the suspension of the solution of PVA / H ₂ O is added with continuous stirring. Subsequently, another 10 ml of distilled water are added to produce a sufficient volume of suspension. Finally, the resulting suspension was cooled to room temperature. The resulting suspension is then further processed according to one of the method steps described above.

In 2 schematically the coating of the substrate with ceramic is shown. So is in 2a first the carrier substrate 6 shown. For the sake of simplicity, this is a planar carrier substrate 6 shown. This can of course be in different geometry and curvature, for example, convex and / or concave. On the surface of the carrier substrate 6 becomes a ceramic slip 8th applied with a layer thickness of 100-1000 microns. The ceramic slip 8th is in 2 B by the at least one laser source 12 Sintered line by line, so that ultimately, as in 2c shown one firmly on the carrier substrate 6 adhesive ceramic layer 14 formed. In addition to the ceramic slip described above 8th However, it is also possible to use a filter belt (not shown), which has a one-sided ceramic coating. The filter belt is coated on the surface of the carrier substrate 6 applied and fixed, then also line by line with the at least one laser source 12 to be driven off. By moving the filter belt (not shown) with the at least one laser source 12 the coating is transferred from the filter belt to the carrier substrate 6 transferred and there as a ceramic layer 14 fixed. In addition to the line-wise shutdown of the laser source 12 Other geometries are conceivable, such as concentric or purely random. The ceramic layer 14 is as a primer layer between the carrier substrate 6 and alkali borosilicate glass particles 18 educated.

In 3a -D, the decantation process is shown schematically. This is done in a first step ( 3a ) the glass suspension 16 with the alkali borosilicate glass particles disposed therein 18 , which have fractions of <125 microns, on the carrier substrate 6 and / or on the ceramic layer 14 , which is designed as a primer layer applied.

After a residence time, for example 5 min, the alkali borosilicate glass particles sink 18 and accumulate on the primer layer (not shown) and / or on the carrier substrate 6 ( 3b ). The excess solvent 20 , For example, ethanol or PVA, can be reduced by means of temperature.

Is the solvent 20 at least 85 percent by weight, more preferably 90 percent by weight, are removed, the still at this time still loose alkali borosilicate glass particles 18 by means of at least one laser source 12 sintered and / or fused in a predetermined geometry ( 3c ). The laser source 12 thus fixed by the energy input, the previously loose Alkaliborosilicatglaspartikel 18 to each other as well as to the adhesion promoter layer (not shown) and / or on the carrier substrate 6 , Due to the small diameter of the laser spot of <20 μm, highly precise and accurate structures can be sintered and / or fused. In 3d is a first layer of the at least partially sintered and / or fused alkali borosilicate glass particles 18 shown.

In 4 another production possibility of the complex, monolithic, porous, silicon dioxide-rich glass molded body is shown. This is the glass suspension 16 by sponge 17 ( 4a ) on the carrier substrate 6 and / or on the primer layer 14 printed step by step ( 4b ).

As stated above, is a sponge 17 as printing medium to the effect advantageous because the suspension 16 with alkali borosilicate glass particles 18 of <125 microns well in the sponge 17 be stored, then at Druckkraftbeaufschlagung on the adhesive layer 14 to be given back to them accordingly.

In the next step ( 4c ) are in turn by means of at least one laser source 12 the applied alkali borosilicate glass particles 18 selectively with each other and / or with the primer layer 14 and / or the carrier substrate 6 sintered and / or fused, depending on the desired geometry. It has proved to be advantageous in this case that even after the printing step, the remaining solvent, for example ethanol or polyvinyl alcohol (PVA), reduced by temperature or completely removed.

In 4d is a first layer of the at least partially sintered and / or fused alkali borosilicate glass particles 18 shown which of these capable of 3d equivalent.

Finally shows 5 the further steps of the selective layer structure of the alkali borosilicate glass molded body 22 as an intermediate and the complex, monolithic, porous, silica-rich glass molded body 26 as end product. Depending on the applied application method, starting from the first layer 3d or 4d now the steps as in 3 and 4 exemplified as long as repeated until the desired monolith level of the intermediate product is reached ( 5b ).

In the next step, as soon as the desired monolith height is reached, the powder residues are removed, so that, as in 5c shown, only the intermediate 22 , So the Alkaliborosilicatglasformkörper 22 from sintered and / or fused alkali borosilicate glass particles 18 , remains.

In the in 5d illustrated embodiment have been vertically aligned, cylindrical cavities, which serve as channels 24 are formed, recessed. The channels shown here 24 each have two direct openings on the surface of the Alkaliborosilicatglasformkörpers 22 on. Instead of the channels shown here by way of example 24 are also other geometries, such as pores and / or reaction spaces (not shown) conceivable, with reaction spaces have no direct opening to the outside. The alkali borosilicate glass molded body 22 thus has a first pore system.

In the alkali borosilicate glass molded body 22 as an intermediate it is a not yet demixed, monolithic structure. This can be formed both two-dimensional and three-dimensional.

Subsequently, the Alkaliborosilicatglasformkörper 22 initially subjected to the heat treatment. The heat treatment is advantageously carried out in a temperature range of 300-1000 ° C, more preferably 450-750 ° C and more preferably at 600 ° C for a time interval in the range of 0.5-90 hours, more preferably 1-72 hours. By this heat treatment, the sintered glass raw material of the alkali borosilicate glass molded body becomes 22 demixed, forming a borate-rich phase and a silicate-rich phase. Advantageously, the separation takes place spinodal or bimodal.

In the subsequent acid extraction, advantageously with 0.5-4 M hydrochloric acid, more advantageously with 1 - M hydrochloric acid at a temperature in the range of room temperature - 100 ° C for a time interval of 4-96 hours, more preferably 8-72 hours is the extracted borate-rich phase, so that only the complex, monolithic, porous, silica-rich glass moldings 26 remains. The cavities created by extraction form the further, second pore system ( 5e ). Immediately, the primer layer (not shown) is also dissolved by the acidic extraction, thus ultimately forming the complex, monolithic, porous, silica-rich glass molded article 26 from the carrier substrate 6 is removable.

The resulting complex, monolithic, porous, silica-rich glass molded body 26 ( 5f ) has a plurality of pores with Durchdingungsstruktur and particle cavities and / or reaction spaces and / or channels, which are arranged both inside and outside and which further advantageously communicate with each other.

In addition, in the illustrated embodiments, as well as channels 24 clearly visible cavities formed, which specifically in the complex, monolithic, porous, silica-rich glass moldings 26 were introduced by the selective laser sintering and / or laser fusion.

In 6 is another schematic view of a complex, monolithic, porous, silica-rich glass molded body 26 shown. This one points beside the canal 24 which has only an upwardly directed direct opening here, also a reaction space 29 on. This is for example cuboid, but not limited to this form. The reaction space 29 has no direct opening to the surface of the glass molded body 26 on. A mass transport or exchange in the reaction space 29 in and out again, is only about the particle cavities 28 and / or the second pore system 27 possible.

By way of example, three magnified alkali borosilicate glass particles are sintered together 18 shown which has a particle cavity 28 limit. The alkali borosilicate glass particles 18 themselves form the wall regions of the complex, monolithic, porous, silica-rich glass molded body 26 and are formed by heat treatment and extraction porous and rich in silicon dioxide. The wall areas and thus also the sintered together Alkaliborosilicatglaspartikel 18 therefore have pores with Durchdringungsstruktur 27 and thus form the further, second pore system.

If the at least one laser source is provided as a CO ₂ laser for the method steps described here, the additional introduction of absorption ceases is unnecessary. The focus of the laser is adjusted at the height of the carrier substrate. After application of the first layer of the glass suspension and after reduction of the solvent, for example ethanol at 60 ° C, the loading of the alkali borosilicate glass particles with the CO ₂ laser takes place in the xy direction at a frequency of 30 kHz. Subsequently, the focal plane of the laser is raised in the z-direction, applied new material and sintered again and / or fused. In this case, it has proven to be advantageous, after ten layers of the sponge printing technique, to shift over to the decanting process, in order to avoid tearing of the edge regions and inhomogeneous layer heights. In this exemplary embodiment, a laser power of 40-100%, particle fractions of <32 μm, <63 μm and 32-63 μm, a laser feed speed of 50-300 mm / second, a laser line spacing of 25-300 μm as well as dot control and / or or line control of the laser used. The individual steps are repeated until the desired layer height is reached.

If instead of the CO ₂ laser, however, a YAG laser is used, then this is also focused initially on the surface of the carrier substrate. Subsequently, the glass suspension and / or the glass powder can be applied to the adhesion promoter layer and sintered and / or fused with the YAG laser. In this case, prior to the next layer application, due to the stationary YAG laser, the sample itself is lowered in its height position, ie in the z direction, downwards, so that the laser distance to the layer surface always remains unchanged. In this embodiment, a laser feed speed of 0.1-200 mm / second, a laser power of 30-90% at a laser frequency of 80 kHz, a line spacing of 10-100 microns and a particle size of <32 .mu.m, <63 .mu.m and 32 -63 μm used. As in the Co ₂ laser process described in parallel, the intermediate product is also subjected to the heat treatment step at 550 ° C. for 24 hours.

All disclosed in the application documents features are claimed as essential to the invention, provided they are new individually or in combination over the prior art.

LIST OF REFERENCE NUMBERS

2

 Glass

4

 absorption centers

6

 carrier substrate

8th

 surface

10

 sintered ceramic slip

12

 laser source

14

 ceramic layer

16

 glass suspension

18

 Alkaliborosilicatglaspartikel

20

 solvent

22

 Sintered alkali borosilicate glass molded body

24

 channels

26

 extracted silica-rich glass molded body

27

 Pores with penetrating structure

28

 particle voids

29

 reaction spaces

Claims (13)

Process for producing a complex monolithic porous, silicon dioxide-rich glass molded body ( 26 ) comprising at least the following steps: a. Application of a glass starting material to a carrier substrate ( 6 ), wherein the glass starting material comprises at least alkali borosilicate glass particles ( 18 ) having; b. Selective loading of the alkali borosilicate glass particles ( 18 ) with at least one laser source ( 12 ) to sintering and / or fusing the alkali borosilicate glass particles ( 18 ) with one another in a predeterminable geometry to form an alkali borosilicate glass molded body ( 22 ); c. Heat treatment of the selectively sintered and / or fused alkali borosilicate glass molded body ( 22 ) for producing a demixing of the alkali borosilicate glass molded body ( 22 ); and d. Acid extraction of the borate-rich phase from the alkali borosilicate glass molded body ( 22 ) to form a complex monolithic porous, silica-rich glass molded body ( 26 ) having a plurality of pores and / or channels and / or reaction spaces, the steps a. and b. be performed at least once. A method according to claim 1, characterized in that the resulting shaped body in step d) from the silicate-rich phase of the Alkaliborosilicatglasformkörpers ( 22 ) is formed. Method according to at least one of claims 1 and 2, characterized in that before step b) at least one adhesion promoter layer on the carrier substrate ( 6 ) is applied. Method according to at least one of the preceding claims, characterized in that the glass starting material is applied to the carrier substrate by means of a decanting process, sponge printing technique, doctor blade technique, roll technique, spraying process or printing technique (US Pat. 6 ) and / or the primer layer is applied. Method according to at least one of the preceding claims, characterized in that the steps a) and b) while changing the height position of the carrier substrate ( 6 ) are repeated several times until the sintered and / or fused alkali borosilicate glass molded body ( 22 ) has a predeterminable height and predeterminable geometry. A method according to claim 1, characterized in that the glass starting material as a glass suspension ( 16 ) or used as a glass powder, wherein the glass suspension ( 16 ) next to the Alkaline borosilicate glass particles ( 18 ) further comprises at least one liquid phase. A method according to claim 1 or 6, characterized in that when using the glass suspension ( 16 ), after application to the carrier substrate ( 6 ), at least partially reducing the volume of liquid and obtaining the alkali borosilicate glass particles ( 18 ) is dried. Method according to at least one of the preceding claims, characterized in that the at least one laser source ( 12 ) is a CO ₂ laser or a YAG laser, wherein the CO ₂ laser with a power of 4.5 to 5.5W ± 1W and the YAG laser with a power of 1.5 to 2.5W ± 0 , 5W is operated. Method according to at least one of the preceding claims, characterized in that during the acidic extraction of the borate-rich phase at the same time the adhesive layer is dissolved. Glass starting material for the process according to at least one of claims 1 to 9, characterized in that the alkali borosilicate glass particles ( 18 ) Have fractions in the range of <32μm, <63μm and 63-125μm. Glass starting material according to claim 10, characterized in that the alkali borosilicate glass particles ( 18 ) a plurality of homogeneously distributed absorption centers ( 4 ) exhibit. Complex, monolithic, porous silica-rich glass molded body ( 26 ) prepared by the process according to at least one of claims 1 to 9; characterized in that it comprises a first pore system with a multiplicity of pores and / or channels ( 24 ) and / or reaction spaces ( 29 ) and that the first pore system is formed by wall regions of the glass molded body ( 26 ) and that the glass molded body ( 26 ) has a further, second pore system, which in the wall regions of the glass molded body ( 26 ) and which has an open-pore penetrating structure ( 27 ) having. Use of a complex monolithic porous silica-rich glass molded body ( 26 ) according to at least one of claims 1 to 9 or 12 as a membrane, membrane reactor, microreactors, optical components, filters and / or filters in microfluidics.

Images