DE891185C - Process for the production of molded articles from fiber suspensions - Google Patents

Description

Process for the production of moldings from fiber suspensions It is known to suspend molded bodies made of fibrous material by molding, dewatering, To produce dry, hardened and hardened hardnesses in the presence of hardenable binders. In such a way one can preferably feltable., Fibrous materials such as wood pulp, Defibrator material as well as straw, asbestos and similar materials on the one hand and phenoplasts, aminoplasts, or other thermally curable binders, on the other hand and any other additives, such as fillers, colors, etc., to molded fibrous articles of various specific weights, such as synthetic cork, synthetic wood or other plastic-like ones Products. In general, this involves deformation and drainage, made, which is followed by the actual drying. For drying and hardening is done using the usual hot air or steam drying process, which lead to the desired results, but are imperfect because they require relatively long treatment times and lead to irregularities, which result in layering and tension within the dried and hardened. Express moldings.

According to the invention, the method can be improved in that the Drying and, if necessary, also the hardening completely or partially in the high tension electric alternating field made will, in which the wet Fittings are introduced. Here, the moldings are not only within Warmed up in the shortest possible time, eon # also heated evenly and continuously, so that the drying and hardening takes place faster and to more uniform products. leads than was previously possible; also -being, stratification and tensioneu avoided within the products.

depending on the final density desired for the products, one can. included the fittings during treatment in a high-tension alternating electric field also press together under constant or variable pressure.

The method according to the invention is particularly advantageous for you the corresponding production of specifically suffering bodies, in the case of weldhen im Within the well-known hot air and steam drying process, the removal of the mostly up to about 8o () / o constituting fluid antefles besontderis langiam I go unid, the hacking takes a considerable amount of time.

The method also offers particular advantages for denser and very thick panels as a result of the uniform and rapid heating, as well as for molded pieces, in which the shortening of the hardening process leads to a more effective use of the often teners Shape leads.

The treatment according to the invention is carried out by the Electrodes of the high-tension electrical alternating field; it on. the wet moldings and the field is turned on, whereupon the temperature quickly increases required height increases.

It is particularly advantageous, within the framework of the method according to the invention a part of the drying and or or curing with Hi - lfe of RF fields to perform, wherein the first drying Stufeder kn change Feild, final drying is carried out with ultra-short waves. During the pre-drying, an average of 30 to 700/0 of the water is evaporated. The use of these two temperature treatment stages further shortens the drying times.

Furthermore, the action of the high-tension electric alternating field and / or the high-frequency field can also be carried out completely or partially under negative pressure or vacuum avoided. As long as the suspending agent has not yet evaporated, the temperature is kept below its boiling point. Hardening of the binder must not yet occur at this temperature, since otherwise the strength of the molded body is reduced or it is not achieved at all. A corresponding voting the curing temperature and curing, speed of the binder can take place in a known manner. Only after evaporation of the floating agent is the temperature increased to such an extent that hardening is thereby brought about.

Claims (2)

PATENT CLAIMS-. i. Process for the production of moldings from Fibers suspensions through forming, dewatering, drying and curing in the presence of curable binders, characterized in that drying and optionally also curing completely or partially in a high-tension alternating electric field: is made. 2. The method according to claim i, characterized in that part of the drying and / or hardening is carried out with the aid of high-frequency fields, preferably in such a way that the first stage is carried out in an alternating field and the second stage in a high-frequency field. 3. The method according to claim 1 and 2, characterized in that the action of the high-tension alternating electric field and / or the high-frequency field is carried out completely or partially under negative pressure, the temperature below this respective one in the case of the use of negative pressure during drying The boiling point of the suspending agent is maintained and then preferably increased beyond this point.