DE4009407A1 - METHOD FOR PRODUCING BINDER-FREE INORGANIC MIXED FIBER PRODUCTS - Google Patents

Description

There are two types of ceramic fibers in the form of wool or mats known:

• - The glassy (amorphous) fiber based on Al₂O₃, SiO₂, Cr₂O₃ and / or ZrO₂,
• - Polycrystalline fiber based on Al₂O₃, SiO₂, ZrO₂ or mixtures of the aforementioned oxides, also with changing proportions of Cr₂O₃, MgO etc.

Glassy fibers are formed by melting raw materials high levels of Al₂O₃, SiO₂ and with low proportions of TiO₂, Fe₂O₃, alkaline earths and alkalis prepared by the Melt jet by supplying large amounts of air across or parallel to the direction of the beam or by impact is defibrated on rapidly rotating disks or drums.  

The resulting fibers are in the appropriate Collectors collected, are wool and can through compaction and needling also as mats, fleece be preformed.

The polycrystalline fibers are the Starting materials through chemical processes (e.g. sol-gel or precursor), the spinning solution is defibrated and subject these fibers to a subsequent firing process, in which the X-ray amorphous starting products in crystalline Forms such as mullite, corundum, transition alumina etc. being transformed.

The classification temperatures of glassy fibers are included maximum 1400 to 1450 ° C. The application limit temperatures however, these products are much lower on what's on the high shrinkage of a maximum of 4% Classification temperature is attributable. Are against both the KT and the AGT of the polycrystalline fibers significantly higher and can e.g. B. for a fiber with 95% Al₂O₃ and 5% SiO₂ are settled at approx. 1850 ° C. But because of the much higher price for that Polycrystalline fibers are their increased use - too in terms of possible energy savings - in many Cases not economically justifiable.

For glassy fibers, the application temperatures can be through z. B. do not raise the increase in Al₂O₃ content, because it changes the melting behavior and a Fiber production is no longer possible. Numerous Industrial furnaces (e.g. in the fine ceramic industry, Oxide ceramics industry, refractory industry), however Operating temperatures above 1300 ° C. In such ovens  would be an energy-saving lining only with the expensive polycrystalline fibers possible.

The task of registration is the production of wool and Ceramic fiber mats with higher Application temperature limits than that of conventional ones glassy fibers.

This object is achieved in that polycrystalline and glassy fibers are mixed together. to make wool out of it and mats with which ovens of the like kind can be lined easily.

During the production of the glassy fiber, the polycrystalline fibers in the fiber stream of the former blown in and by correspondingly high amounts of air optimally mixed before the fibers on the Remove the collector belt. The quantitative control of the Mixing components are made by gravimetric dosing of the polycrystalline fibers in relation to the melting rate of the glassy fibers.

Another solution to the problem is the lining ovens with vacuum formed parts where glassy and polycrystalline fibers in various proportions in aqueous Mixed solutions, mixed with binders and fillers, molded in special shapes by suction technology and be thermally treated. The so obtained Fiber products are much heavier than fiber mats and require careful anchoring.

example

Production of a fiber mat consisting of ² / ₃ glassy Fibers and ¹ / ₃ polycrystalline fibers.

Composition of the glassy fiber:
15% ZrO₂, 35% Al₂O₃, 50% SiO₂

Composition of the polycrystalline fiber:
80% Al₂O₃, 20% SiO₂ (corundum, mullite)

The polycrystalline fiber was fed through a conveyor line, which widens trapezoidally at the end (corresponding to the Chamber width), pneumatically into the collector and into the Blown fiber stream. Both types of fibers were used mixed and made mats of 1 '' thickness. Out the mats were tested according to the 41st PRE recommendation removed and checked for their shrinkage behavior. In the The following table shows the results with the compared to conventional products:

In another experiment, the mixed fiber and the glassy fiber baked at 1400 ° C for 100 hours. After that 10% vibration was determined for the glassy fiber, only 4% for the mixed fiber.

Claims (6)

1. A process for the preparation of binder-free inorganic mixed fiber products, consisting of changing proportions of glassy fibers or changing proportions of glassy and polycrystalline fibers in order to improve the properties of use at the respective application temperature, characterized in that in the manufacture of the glassy fibers via a metering system, inorganic foreign fibers, which were previously rolled up, conveyed into the fiber collector and swirled into a mixed fiber wool there. 2. The method according to claim 1, characterized characterized in that the mixed fiber wool then to mat webs in different thicknesses be assembled. 3. The method according to claim 1 or 2, characterized characterized in that the glassy fibers are ceramic fibers based on Al₂O₃ / SiO₂ / ZrO₂. 4. The method according to claim 1 or 2, characterized characterized in that the glassy fibers Mineral fibers are known composition.   5. The method according to any one of the preceding claims, characterized in that the Foreign fibers based on polycrystalline fibers Al₂O₃ / SiO₂ / ZrO₂ are. 6. The method according to any one of claims 1 to 4, characterized in that the Foreign fibers are mineral fibers of known compositions.