Hoechst Aktiengesellschaft

Klaus Schmitt

Klaus-Peter Schoen

Klaus Gehrmann

Heinz Erpenbach

Engelbert Pliefke

Juergen Lingnau

Klaus-Peter Schon

Hans-Klaus Kubbeler

Manfred Gehendges

Peter Riedel

Printing forms or metallized images can be prepared electrophotographically by a process comprising the electrostatic chargeup, imagewise exposure and tonering of a photoconductor layer applied to an electroconductive base material, followed by fixing of the tonered image areas, removal of the photoconductive layer in the non-image areas by decoating and, where appropriate, etching of the bared base material surface. A recording material is used that comprises a photoconductive layer containing at least one organic n-conducting pigment in a concentration between 10 and 50 percent by weight and an organic p-conducting photoconductor in a concentration of 0 to 20 percent by weight, based on the layer weight, together with a binder which is soluble or dispersible in aqueous-alkaline solution. The decoating is carried out with an aqueous-alkaline decoater solution, which preferably contains alkali metal hydroxides and/or phosphates. The decoating is preferably carried out at an elevated temperature, for example, between about 30.degree. to 60.degree. C.

Electrophotographic process for preparing printing forms using alkaline

An original holder for a printing plate processing apparatus for rapid exchange of an original in a vacuum frame covered by a glass plate and exposed in the exposure device of a printing plate processing apparatus. The glass plate is held in its open position by a gas pressure element to facilitate insertion of the original. Two U-shaped metal sheets serve as supports for two vacuum frames which are each evacuated following insertion of an original and closing of the glass cover plate. Swivel joints are attached at the sides of the supports which enable the original holder to be pivoted through an angle of 360.degree. and which are additionally horizontally slidable in the guides of supporting and guiding arms. The vacuum frames are individually pivotably mounted in their supports by ball guides in guide tracks. When one of the vacuum frames is in the vertical exposure position in the exposure opening in the wall of the exposure device housing and its support is secured to the housing wall by locking devices, the second vacuum frame is pivoted into the horizontal position by means of a lever so that an original can be inserted therein. The second vacuum frame is thereafter folded back again to the vertical position in its support. After exposure of the original in the first vacuum frame, the entire original holder is drawn into the change position, pivoted through 180.degree., and the original in the second vacuum frame is moved into the exposure opening. In an alternate embodiment, the swivel joints are fixedly mounted adjacent the edges of the exposure opening, and the original holder pivots inside the exposure device.

Original holder for a printing plate processing apparatus

Disclosed is a cleaning device, having a cleaning roller and a scraper, which are capable of being brought into and out of contact with the photoconductive peripheral surface of a drum of a copier. The scraper further comprises a strip which is of a geometry such that in combination with the operation of the roller and scraper it allows for complete and efficient removal of the cleaning liquid from the drum surface without overflow and damage to the copier sub-assembly.

Cleaning device for cleaning the peripheral surface of a photoconductive

The invention provides a process for making acetic anhydride, wherein methyl acetate and/or dimethylether is (are) reacted with carbon monoxide under substantially anhydrous conditions, at temperatures of 350 to 575 K and under pressures of 1 to 300 bars in the presence of a catalyst system comprised of noble metals belonging to group VIII of the periodic system of the elements, or their compounds and iodine and/or its compounds. More specifically, an aliphatic carboxylic acid with 1 to 8 carbon atoms and at least one heterocyclic aromatic compound, in which at least one hetero atom is a quaternary nitrogen atom are used as promoters.

Production of acetic anhydride

The invention relates to a semi-automatic aligning and feeding device (1) for copiers, for the purpose of aligning an original (25) and feeding it from a feed table (17) to an object stage (5). Sensors (L.sub.1 to L.sub.5) are provided for scanning the original in various positions. Except for one sensor (L.sub.2), the sensors are located in or on the pivotable cover (3) of the device. The original, laid by hand onto the feed table (17), is picked up by a suction bar (11) which is equipped with spring suction heads (12, 12') and is, corresponding to its particular operating state, supplied either with vacuum or with compressed air and can be moved from a starting position into an end position and back again. In the end position, the spring suction heads are supplied with compressed air so that the original is laid down in precise alignment on the object stage.

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Wiesbaden, Germany

Klaus Schmitt