EP1341736A2

EP1341736A2 - Lamellar pressed body

Info

Publication number: EP1341736A2
Application number: EP01986867A
Authority: EP
Inventors: Stefan Dr. Dick; Arthur Schepf; Tteshi Kimura; Andrew Robertson; Mike Gaffney
Original assignee: Sued Chemie AG
Current assignee: Sued Chemie AG
Priority date: 2000-12-12
Filing date: 2001-12-12
Publication date: 2003-09-10
Also published as: KR100585542B1; WO2002048025A3; WO2002048025A8; WO2002048025A2; DE10065946A1; AU2002238423A1; CN1282623C; JP2004515443A; KR20030067700A; CN1484623A; JP4142951B2

Abstract

The invention relates to a lamellar pressed body (wafer), based on an inorganic sorbent and a binding agent, with a thickness of less than 700 mu m. Said wafer is obtained by pressing a mixture of the inorganic sorbent, binding agent, water and optionally auxiliary pressing agents at a pressure of at least 70 Mpa, whereby the weight ratio of the dry sorbent and the dry binding agent in the mixture lies between approximately 4 and 0.7 and the water content of the mixture, determined at 160 DEG C, lies between approximately 8 and 20 %. The green pressed body thus obtained is then calcined at temperatures of at least approximately 500 DEG C, until a considerable amount of the water content has been removed.

Description

Patent application

Platelet-shaped pressed body

Description-

The invention relates to platelet-shaped pressed bodies (wafers) based on an inorganic sorbent and a binder, with a thickness of less than 700 μm, which are characterized by high mechanical strength and low brittleness and which are capable of inorganic and organic Effectively sorb gases or vapors.

The production of compacts, in particular tablets, on the basis of zeolites and binders is already known. According to JP-A-61 15 5216, zeolite tablets are produced by mixing a zeolite, a binder and a lubricant and extruding the mixture. It is obviously tablets with the same dimensions in all directions. From JP-A-56063818 the production of zeolite tablets for use as gas adsorbents is known, powdered and dried at 105 to 110 ° C zeolite mixed with 8.1 wt .-% bentonite powder and kneaded with a 4% aqueous urea solution. The mixture is tableted, dried and calcined at 510 ° C. The increase in compressive strength is due to the urea content.

From JP-A-55 16 5144 it is known to knead zeolite powder for cooling units in powder form with bentonite and water, to extrude the mixture and to form round particles with a diameter of 0.8 to 10 mm.

According to JP-A-55 10 4913, zeolite is mixed in the Na form with 25% by weight of clay, kneaded with water, extruded, calcined at 650 ° C., immersed in a calcium chloride solution, washed, at 110 ° C. dried and activated at 400 ° C. The tablets are used as desiccants.

According to JP-A-4 603 2572, zeolite powder is mixed with kaolin and Na (or NH ₄ -) hydroxyethyl cellulose, molded, dried and calcined at 650 ° C. in order to increase the strength of the zeolite tablets.

According to JP-A-21 44 121, deodorants are extruded by extruding zeolite powder or grains with calcium chloride or bentonite and water, whereupon the mixture is tabletted and the tablets are calcined.

According to JP-A-63 218 234, drying agents are produced by extruding a mixture of microporous particles (for example gypsum, cement, ceramic 'ulver) and an inorganic or organic filler, such as CaCl, LiCl, bentonite, zeolites, PVA or other water-soluble polymers , The mixture is tabletted and then cured. According to JP-A-60 132 643, zeolite tablets are produced as drying agents using 20% sepiolite as a binder. The mixture is kneaded with water, tabletted, dried at 150 ° C. and calcined at 550 ° C. The tablets have an improved drying effect compared to bentonite tablets.

The tablets produced according to the state of the art are unsuitable for use in confined spaces and under mechanical stress, since they are too thick and too heavy and, based on mass and surface area, have too little sorption power for harmful gases and vapors. With the methods and mixtures according to the prior art, brittle compacts are obtained which crumble in particular after firing.

It is known that electroluminescent devices only function properly over a long period of time if a desiccant is present. This is due to the sensitivity of the electrodes, especially the cathodes, e.g. due to moisture (the cathodes are made of Ca or Mg alloys). That is why these devices are sealed as well as possible under protective gas.

EP 500 382 A2 describes the use of a moisture absorber in an electroluminescent device. The drying agent in the form of a powder or small beads is applied to a black silicone resin coating. According to the preferred embodiment, the desiccant is filled in a gas-permeable bag.

The use of a desiccant in an electroluminescent device is also described in US Pat. No. 5,882,761. BaO is used as the preferred desiccant. The sorbents known from the above publications have the disadvantage that they can only sorb water vapor. However, an attack on the cathodes can also be triggered by other gases which, in addition to water, form when the epoxy resin used for sealing sets (ammonia, volatile amines). In addition, the action of oxygen leads to the failure of the luminescent components (oxidation of the cathode).

The object of the present invention is to provide plate-shaped pressed bodies (wafers) based on an inorganic sorbent and an inorganic binder with a very small thickness (less than 700 μm) which, despite their small thickness, have great strength and thus in particular can be installed in electronic components in which only a limited space is available and which can be exposed to vibrations (eg electronic display devices in automobiles and mobile telephones).

This object is achieved according to the invention by providing platelet-shaped pressed bodies (wafers) based on an inorganic sorbent and a binder with a thickness of less than 700 μm, which can be obtained by pressing a mixture consisting of or containing at least one inorganic sorbent, at least one binder, and optionally water and pressing aids, at a pressure of at least 70 MPa, the weight ratio of the dry sorbent and the dry binder in the mixture being between about 4 and 0.7 and the water content of the mixture, determined at 160 ° C., is between about 8 and 20%; and calcining the resulting green body at temperatures of at least about 500 ° C to ^■ to substantially remove the total water content.

The pressed bodies (wafers) according to the invention have high strength, low brittleness, high sorption speed and high sorption capacities with low mass. They show a low thermal expansion, no abrasion and can easily be colored by adding pigments during manufacture.

The wafers according to the invention can be produced in automated processes in large numbers per unit of time. They are easy to handle and can be removed from a storage container, for example, using so-called “pick-and-place” machines and inserted into an electronic device.

In addition to water vapor, the wafers according to the invention are also capable of sorbing other gases (ammonia, amines, oxygen). Since they have a high sorption capacity, the electronic device in which they are used does not need to be completely airtight, i.e. the rate of diffusion for water vapor into the device may be greater than zero. In addition, the selection of a suitable material for sealing the device (e.g. an epoxy resin) is simplified, since the critical time by which this material must have reached its final lowest water vapor permeability can be extended by using the wafer.

The inorganic sorbent is preferably a natural or artificial zeolite. However, other sorbents, such as amorphous silica or aluminum hydroxide, and mixtures of two or more sorbents can also be used.

In principle, any binder which appears suitable to a person skilled in the art in this field can be used as the binder. A smectitic clay, in particular bentonite, is preferably used as the binder. It is also possible to use other inorganic binders, eg aluminum oxide hydroxide (pseudo boehmite). However, organic binders based on carbohydrates or proteins can also be used, for example starch, cellulose derivatives (such as CMC or CEC), casein or synthetic polymers such as PVA, PVP or polyphenols or tannin-containing binders (quebracho). Mixtures of different binders can also be used.

The addition of bentonite to the zeolite surprisingly does not reduce the sorption capacity of the latter. In fact, a synergetic effect can be observed, i.e. the water vapor absorption of the mixture after calcination is far less reduced than that of pure zeolite than would be expected from a purely mathematical point of view.

The thickness of the wafer is preferably not more than about 400 μm, in particular about 200 to 400 μm.

The invention further relates to a method, in particular for the production of the pressed bodies defined above, which is characterized in that a mixture consisting of or comprising at least one inorganic sorbent, at least one binder, and optionally water and pressing aids at a pressure of at least approximately 70 MPa pressed, the weight ratio of the dry sorbent and the dry binder in the mixture being between approximately 4 and 0.7 and the water content of the mixture, determined at 160 ° C., being between approximately 8 and 20%; and calcined the green compact obtained at temperatures of at least about 500 ° C. until the total water content was largely removed.

It has been found that particularly advantageous pressed bodies with very good physical and chemical properties can be obtained by this process. Particularly advantageous compacts result from a mixing ratio of dry sorbent to binder in the starting mixture of between about 1.5 and 1.

The desired water content of the mixture can be determined via the water content of the components (sorbent, binder) and / or additional water can be set.

Zeolite A, which is preferably used as sorbent, is available in powder form and has a water content of about 10 to 22%. The bentonite which is preferably used as a binder is available as a powder with a water content of about 10 to 20%. The bentonite used has a montmorillonite content of preferably> 80%, based on the dry state. A fatty acid salt of a divalent or trivalent metal, such as calcium, magnesium or aluminum stearate, is preferably used as the pressing aid.

It has been found that the best results can be achieved when the mixture is pressed into the pressed body if the mixture does not contain large proportions, i.e. contains not more than about 15%, preferably not more than about 8%, and particularly preferably 0% of particles> 250 μm, preferably> 200 μm and particularly preferably> 150 μm, and the main proportion of the particles, i.e. at least 50%, preferably at least 60%, is greater than about 45 μm.

A preferred process measure is that zeolite and bentonite powder are mixed in the desired ratio with so much water that the mixture can be granulated. An intensive mixer is preferably used for this. The amount of water that has to be added depends on the mixing ratio of zeolite and bentonite and the colloidal chemical properties of the bentonite used in each case and can easily be determined routinely by a person skilled in the art. After granulation, the mixture is adjusted or dried to a water content of about 8 to 20%, the water content being determined at 160 ° C. The mixture is then comminuted to particle sizes <250 μm, preferably <200 μm, particularly preferably <150 μm in accordance with the above information. Surprisingly, it was found that the best results can be achieved when the mixture is pressed into the green compact if the particles of the mixture have at least for the most part a largely spherical character, as obtained, for example, by spray drying. A particularly preferred process measure is therefore zeolite. and slurrying bentonite powder in water to a pumpable suspension using a high-shear stirrer, such as an Ultra-Turrax stirrer, and spray-drying this by conventional methods. By appropriately controlling the spray drying process, the water content of the mixture can be set to the preferred values between about 8 and 20% (the water content is determined at 160 ° C). The setting of the particle size distribution so that the mixture, as defined above, does not contain any larger proportions of particles> 250 μm, preferably> 200 μm and particularly preferably> 150 μm, and the main proportion of the particles is greater than approximately 45 μm can also be done by Corresponding control of the spray drying process and, if appropriate, subsequent process steps such as deagglomeration, sieving and sifting known as such in the prior art are carried out.

The compact is formed from the mixture by applying a pressure of at least about 70 MPa. The preferred pressing pressure is about 100 to 1300 MPa. The mixture can be pressed in commercially available automatic presses, the type of which is known to the person skilled in the art.

In order to ensure smooth production of the pressing bodies, it is important that the shaped bodies come off easily and without residue from the pressing tools. This can be ensured by choosing appropriate surface-modified tools (with, for example, TiN or WC-modified steel), precise adjustment of the water content of the mixture and control of temperature and air humidity at the location of the pressing process. At low water content of the mixture it is advantageous to set a relatively high absolute humidity, for example 50 to 80% relative humidity at about 25 to 35 ° C. If the mixture has high water contents, a relatively low absolute humidity is more favorable, for example 30 to 50% relative humidity at about 20 to 30 ° C. Another preferred possibility is the application of an “anti-sticking agent”, such as magnesium or calcium stearate, to the pressing tools after a predetermined number of press cycles, for example after every or every second cycle. This effectively prevents the compacts from sticking to the pressing tools.

The compacts are calcined at about 500 to 900 ° C, preferably at about 650 ° C, until constant weight is achieved and the water content is largely removed.

It has also been found, surprisingly, that the formation of curvatures and curvatures during the calcination of the pressed bodies can be largely suppressed by applying pressure to the pressed bodies during the calcining step.

According to a preferred embodiment, the application of pressure to the pressed bodies during the calcination is brought about by using a specially designed belt calcining device, with the belts being pressurized. In principle, the pressure can be applied to the compact during the calcination in any way, as long as the curvature of the compact is effectively prevented during the calcination on the one hand and the pressure does not damage the compact on the other. In general, a pressure between 10 and 30,000 Pa, in particular between 100 and 5,000 Pa, can be used. According to a further preferred possibility, a certain number of pressed bodies are stacked in tubes which, for example, consist of stainless steel or ceramic. These tubes preferably have bores, which the Allow water to escape during the calcination. This enables quick and even drying. The entire stack within the tube is subjected to a pressure sufficient to suppress the curvature of the pressed body during the calcination, but which does not lead to breakage, sticking together or sintering of the pressed body during this process step. In general, this pressure is between about 10 and 30,000 Pa, in particular between 100 and 5.00.0 Pa. The wafers calcined according to the invention under pressure are flat and show no or only minimal curvature or curvature, which is a prerequisite for use in electroluminescent devices.

According to a further preferred embodiment, the calcination temperature is approached or increased step by step in order to prevent the formation of cracks and cracks in the pressed bodies due to water escaping too quickly or unevenly.

The compacts can also be calcined and cooled under vacuum, • which enables them to sorb even permanent gases such as oxygen.

The compact can also contain coloring pigments, for example Fe 3 O ₄ .

The invention further relates to the use of the pressing bodies defined above as inserts in electronic devices or components, such as display devices, in particular in electroluminescent components, such as organic light-emitting diodes (LEDs). However, they can also be used in moisture sensitive liquid crystal display (LCD) devices.

These devices or components can be caused by inorganic or organic gases or vapors during the manufacture or during the Use are damaged in their function and have only a very small space for a sorbent due to their design.

These electronic devices or components (e.g. display devices in motor vehicles and mobile phones) are often subjected to strong vibrations, which is why it is important that the pressed bodies do not break or crumble. Because of their strength, it is not necessary to cover the pressed body with a gas-permeable film, which simplifies the manufacture of the electronic components.

Compared to BaO, the electronic component can be significantly reduced in volume and cost. For example, the wafers have a higher sorption capacity and speed for water vapor in the required temperature and humidity range within an electronic component. In addition, when using BaO, it must be taken into account that the volume of the material increases by 100% during the hydration reaction; Therefore, additional volume must be provided for the expansion of the desiccant within the component and a water vapor permeable film must be applied between BaO and the electroluminescent layer, which prevents contact between the expanding and possibly crumbling desiccant and the layer. In contrast, the wafers show no change in volume when absorbing water vapor and remain mechanically stable, so that the provision of an additional expansion volume within the component and the application of a protective film can be dispensed with.

BaO also has the disadvantage that it itself and its hydration products react strongly basic; it also heats it up very strongly when it absorbs moisture, and it tends to self-ignite if it comes into direct contact with organic compounds. This limits the choice of polymers for the above-mentioned protective film on very expensive, for example fluoropolymers, and thus increases the cost of the component. In addition, there are disposal problems with the use of BaO, since it is very difficult to disassemble, reuse and dispose of the individual parts of the electronic component as a harmful chemical.

The compacts according to the invention can also be used for other purposes, e.g. as inserts in pharmaceutical packaging, since there is only a limited volume available to hold a desiccant.

The compacts can be in any shape, e.g. be round, square, triangular or rectangular or also contain bores and / or recesses. The compacts according to the invention are dust-free and wear-resistant. They can be produced in large numbers per time unit in conventional press machines.

The invention is illustrated by the following examples:

Example 1 (comparison)

75.2 kg of zeolite 4A (water content 20%), 23.8 kg bentonite (water content 12%) and 1 kg calcium stearate are mixed in an intensive mixer for 2 minutes. Then water is added until the viscosity rises sharply and mixing is continued for a further 4 minutes. The mixture is dried at 110 ° C. to a water content of 12% and then granulated (Stokes granulator) and sieved (250 μm). 0.22 g of the material with a particle size _< 250 μm are pressed to a round wafer with a pressure of 69 MPa. The green wafers are calcined at 650 ° C for three hours, cooled with the exclusion of moisture and packed airtight. The thickness of the wafers decreases by about 15 to 25% during the calcination. Product features:

Thickness: 300 ± 50 μm

Moisture (after calcination): <1%

Production scrap:> 90%

Drop test *: 100% break, wafer crumbles on the edge

* The so-called drop test serves as a measure of the compressive strength, whereby 100 calcined pressed bodies (round disks with a diameter of 27 mm) are dropped from a height of 1 m with the flat side down. The percentage of broken test specimens is determined.

Example 2 (comparison)

57 kg zeolite 4A (water content 20%), 42 kg bentonite (water content 12%) and 1 kg calcium stearate are mixed in an intensive mixer for 2 minutes. Then water is added until the viscosity rises sharply and mixing is continued for 4 minutes. The mixture is dried at 110 ° C. to a water content of 12% and then granulated (Stokes granulator) and sieved (250 μm). 0.22 g of the material with a particle size <250μm are pressed to a wafer with a pressure of 69 MPa. The green wafers are calcined at 650 ° C for three hours, cooled with the exclusion of moisture and packed airtight.

Product features:

Thickness: 300 ± 50 μm

Moisture (after calcination): <1%

Production waste: 75%

Drop test: 80% break Example 3

57 kg zeolite 4A (water content 20%), 42 kg bentonite (water content 12%) and 1 kg calcium stearate are mixed in an intensive mixer for 2 minutes. Then water is added until the viscosity rises sharply and mixing is continued for a further 4 minutes. The mixture is dried at 110 ° C. to a water content of 12% and then granulated (Stokes granulator) and sieved on a 250 μm sieve. 0.22 g of the material with a particle size <250 μm are pressed to a wafer with a pressure of 72 MPa. The green wafers are processed as in Example 2:

Product features:

_Thickness. 300 ± 50 μm

Moisture (after calcination): <1%

Production scrap: <50%

Drop test: 60% break

Example 4

57 kg zeolite 4A (water content 20%), 42 kg bentonite (water content 12%) and 1 kg calcium stereate are mixed in an intensive mixer for 2 minutes. Then water is added until the viscosity rises sharply and mixing is continued for a further 4 minutes. The mixture is dried at 110 ° C. to a water content of 12%, then granulated (Stokes granulator) and sieved on a 250 μm sieve. 0.22 g of the material with a particle size <250 μm are pressed to a wafer with a pressure of 350 MPa. The green wafers are calcined at 650 ° C for three hours, cooled with exclusion of moisture and packaged. Product features:

Thickness: 300 ± 50 μm

Moisture (after calcination): <1%

Production scrap: <25%

Drop test: 15% break

Sorption capacity * after one hour: 5.4% by weight after 5 hours: 7.2% by weight after 24 hours: 13.0% by weight

* The sorption capacity for water vapor is determined at 25 ° C in an atmosphere with a humidity of 10%.

Example 5

The procedure of Example 4 was repeated with the difference that the green wafers were calcined in vacuo. The calcined wafers had essentially the same product properties as the wafers of Example 4, but additionally showed an oxygen absorption capacity of about 5 ml / g (determined in a dry oxygen atmosphere).

Example 6

56.5 kg of zeolite 4A (water content 20%), 41.5 kg bentonite (water content 12%), 1 kg calcium stearate and 1 kg quebracho are mixed in an intensive mixer for 2 minutes. Then water is added until the viscosity rises sharply and mixing is continued for a further 4 minutes. The mixture is dried at 110 ° C to a water content of 12% and then granulated (Stokes _Granulato. R), and sieved (250 .mu.m). 0.22 g of the material with a particle size <250 μm are pressed to a wafer with a pressure of 200 MPa. The green wafers are calcined at 650 ° C for three hours, with the exclusion of moisture cooled and packed.

Product features:

Thickness: 300 ± 50 μm

Moisture (after calcination) <1%

Production scrap: <35%

Drop test: 10% break

Example 7

The procedure of Example 4 was repeated with the difference that the pressure applied during the pressing was 1200 MPa. The drop test showed 10% break. The reject rate was <10%.

Example 8

The procedure of Example 4 was repeated with the difference that 54 kg of zeolite 4A, 40 kg of bentonite, 5 kg of Fe3Ü4 and 1 kg of calcium stereate were used. The wafers obtained were colored dark and could be used as a contrast surface in an LED display.

Example 9

110.5 kg of zeolite 4A (water content 20%), 76.0 kg of bentonite (water content 12%) and 1.9 kg of calcium stearate are slurried in so much water using a high-shear stirrer (Ultra-Turrax stirrer) that a pumpable Suspension arises. The suspension is spray dried in such a way that a powder with a water content of 9.2% (determined by drying at 160 ° C.) and a particle size division of 0%> 150 μm and 30% <45 μm. 0.17 g of this material is pressed at a pressure of 190 MPa to a wafer with a diameter of 20 mm, the water vapor partial pressure in the ambient air of the pressing tools being about 30 mbar. The green wafers are calcined at 650 ° C for three hours using pressure. For this purpose, 300 green wafers are stacked in perforated stainless steel tubes (height 120 mm, inner diameter 22 mm), and the stack is subjected to a pressure of 2550 Pa. After the calcination, the product was cooled and packaged with the exclusion of moisture.

Product features:

Thickness: 300 ± 50 μm

Vertical expansion: <350 μm

(Thickness + curvature)

Humidity: <1%

(after calcination)

Production scrap: <5%

Drop test: <! ■%

Example 10

110.5 kg of zeolite 4A (water content 20%), 76.0 kg of bentonite (water content 12%) and 1.9 kg of calcium stearate are slurried in so much water using a high-shear stirrer (Ultra-Turrax stirrer) that a pumpable Suspension arises. The suspension is spray-dried in such a way that a powder with a water content of 12.6% (determined by drying at 160 ° C.) and a particle size distribution of 0%> 150 μm and 26% <45 μm is produced. 0.17 g of this material are pressed with a pressure of 210 MPa into a wafer from the ^'diameter of 20 mm, wherein the water vapor partial pressure is mbar in the ambient air of the pressing tools about 17th The green wafers are made using Calcined pressure at 650 ° C for three hours. For this purpose, 300 green wafers are stacked in perforated stainless steel tubes (height 120 mm, inner diameter 22 mm) and the stack is subjected to a pressure of 2550 Pa. After the calcination, the product was cooled and packaged with the exclusion of moisture.

Product features:

Thickness: 300 ± 50 μm

Vertical expansion: <350 μm

(Thickness + curvature)

Humidity: <1%

(after calcination)

Production scrap: <5%

Drop test: <1%

Example 11

110.5 kg of zeolite 4A (water content 20%), 76.0 kg of bentonite (water content 12%) and 1.9 kg of calcium stearate are slurried in so much water using a high-shear stirrer (Ultra-Turrax stirrer) that a pumpable Suspension arises. The suspension is spray-dried in such a way that a powder with a water content of 15.5% (determined by drying at 160 ° C.) and a particle size distribution of 4%> 150 μm and 8% <45 μm is produced. 0.17 g of this material is pressed at a pressure of 195 MPa to a wafer with a diameter of 20 mm, the water vapor partial pressure in the ambient air of the pressing tools being approximately 12 mbar and the pressing tools being periodically sprayed with magnesium stearate. The green wafers are calcined at 650 ° C for three hours using pressure. For this purpose, 300 green wafers are stacked in perforated stainless steel tubes (height 120 mm, inner diameter 22 mm) and the stack is subjected to a pressure of 2550 Pa. After the calci- nation was cooled and packaged with the exclusion of moisture.

Product features:

Thickness: 300 ± 50 μm

Vertical expansion: <350 μm

(Thickness + curvature)

Humidity: <1%

(after calcination)

Production scrap: <5%

Drop test: <1%

Example 12

57 kg of zeolite 4A (water content 20%), 42 kg of a 50/50 mixture of attapulgite and kaolin (water content 12%) and 1 kg of calcium stearate are mixed in an intensive mixer for 2 minutes. Then water is added until the viscosity rises sharply and mixing is continued for a further 4 minutes. The mixture is dried to a water content of 12%, then granulated and sieved on a 150 μm sieve. 0.17 g of the material with a particle size <150 μm is pressed to a wafer with a pressure of 200 MPa. The green wafers are calcined at 650 ° C for three hours, cooled with exclusion of moisture and packaged.

Product features:

Thickness: 300 ± 50 μm

Moisture (after calcination): <1% ^'

Production waste: 25%

Drop test: 70% break Example 13

An organic electroluminescent component 1 (square, area 12.9 cm ² ), as shown in Figure 1, is produced using a wafer (circular, diameter 27 mm) from Example 4. After the wafer 2 has been attached to the rear wall 3 of the component, this is attached to the glass substrate 5 of the component with the aid of an adhesive 4 and sealed as far as possible with the aid of an adhesive. A microscopic photograph (magnification 50 times) of the light-emitting part 6 (consisting of the anode 7, the light-emitting layer 8 and the cathode 9) of the component is then taken. This photograph shows no dark (non-luminous) spots that would indicate an attack on the cathode 9.

The component is exposed to a temperature of 85 ° C and a relative humidity of 85% for 500 h. A microscopic photograph of the light-emitting part 6 of the component 1 is then taken again. A comparison of the two photographs shows that there are no dark spots that would indicate an attack on the cathode 9.

Example 14 (comparison)

An organic electroluminescent component 1 such as Example 9 is produced using BaO. A water-permeable Teflon film is used as a cover for the BaO, which is attached to the rear wall 3 of the component with the aid of a thin double-sided adhesive tape. The amount of BaO is adjusted so that the total mass of BaO, the Teflon film and the double-sided adhesive tape corresponds exactly to that of a wafer used in Example 9. Then, as in Example 9, wrote, enlarged photographs of the light-emitting part taken before and after storage for 500 h at 85 ° C and 85% humidity. A comparison of the two photographs shows a clearly recognizable growth of dark spots, which indicate an attack on the cathode 9.

Claims

claims

1. platelet-shaped pressed body (wafer), containing at least one inorganic sorbent and at least one binder, with a thickness of less than 700 μm, obtainable by pressing a mixture consisting of or containing the inorganic sorbent (sorbents) and the binder (s) at a pressure of at least 70 MPa, the mixture of the weight ratio of the dry sorbent (sorbents) and the dry binder (s) being between about 4 and 0.7 and the water content of the mixture, determined at 160 ° C, is between about 8 and 20%; and calcining the green compacts obtained at temperatures of at least about 500 ° C. until the water content has been largely removed.

2. Press body according to claim 1, characterized in that water and / or pressing aids, such as fatty acid salts of a di- or trivalent metal, are added to the mixture.

3. Press body according to claim 1 or 2, characterized in that the calcination is carried out to constant weight or to a residual moisture content of <2% by weight, determined at the calcination temperature.

4. Press body according to one of claims 1 to 3, characterized in that the inorganic sorbent is a natural or artificial zeolite.

5. Press body according to one of claims 1 to 4, characterized in that the binder is a smectite clay, preferably bentonite.

6. Press body according to one of claims 1 to 5, characterized in that the thickness of the wafer is about 200 to 400 microns.

7. Press body according to one of claims 1 to 6, characterized in that the weight ratio of the dry sorbent to the dry binder is between about 1.5 and 1 in the mixture.

8. Press body according to one of claims 1 to 7, characterized in that the pressure is about 100 to 1300 MPa.

9. Press body according to one of claims 1 to 8, characterized in that a fatty acid salt of a 2 or 3-valent metal is used as the pressing aid.

10. pressed body according to one of claims 1 to 9, characterized in that it has been pressed with a tannin-containing binder, preferably Quebracho.

11. Press body according to one of claims 1 to 10, characterized in that the mixture contains no larger proportions, preferably not more than 15%, particularly preferably not more than 8%, and in particular 0% of particles> 250 μm, preferably> 200 μm and particularly preferably contains> 150 μm.

12. Press body according to one of claims 1 to 11, characterized in that the main part of the particles, i.e. at least about 50%, in particular at least about 60%, in the mixture is greater than about 45 μm.

13. Press body according to one of claims 1 to 12, characterized in that the mixture mainly contains spherical particles.

14. Press body according to one of claims 1 to 13, characterized in that more than 50%, in particular more than 75%, preferably more than 80% and in particular more than 98% of the particles are substantially spherical.

15. Press body according to one of claims 1 to 14, characterized in that the mixture was obtained by spray drying.

16. Press body according to one of claims 1 to 15, characterized in that it has been calcined under vacuum.

17. Press body according to one of claims 1 to 16, characterized in that the calcination is carried out under pressure on the press body.

18. Press body according to claim 17, characterized in that the calcination of the pressed body was carried out under pressure in a pierced tube.

19. A process for the production of platelet-shaped pressed bodies (wafers), characterized in that a mixture consisting of or comprising the inorganic sorbent (s)

(Sorbents) and the binder (s), pressed at a pressure of at least 70 MPa, in the mixture the weight ratio of the dry sorbent (sorbent) and the dry binder (s) between about 4 and 0.7 and the water content of the mixture, determined at 160 ° C, is between about 8 and 20%; and calcining the green compacts obtained at temperatures of at least about 500 ° C. until the water content has been largely removed.

20. The method according to claim 19, characterized in that one or more of the constituents specified in one of claims 2 to 18 are used under the conditions specified therein.

21. Use of the pressed body according to one of claims 1 to 18 as use in electronic devices, such as display devices, in particular in electroluminescent components.