Hoechst Aktiengesellschaft

Hans-Dieter Sabel

Karlheinz Burg

Gunter Sextro

Helmut Schlaf

Alwin Heller

Dietrich Fleischer

Klaus Kohlhepp

Oskar Schleith

Andreas Kirst

A polyacetal molding composition comprising, as the active additive, at least one a) ester of long-chain monocarboxylic acids (C.sub.22 to C.sub.34) with mono- or polyhydric alcohols (C.sub.2 to C.sub.8), in the presence or absence of alkali metal and/or alkaline earth metal salts of the carboxylic acids mentioned, and/or b) polyethylene wax, is distinguished by a reduced tendency toward melt fracture. Such molding compositions can advantageously be employed in the production of shaped articles which show no undesirable defects in the surface.

Polyacetal molding compositions and their use

It has been found that moldings produced from polyoxymethylene have reduced gloss if an acrylic (co)polymer is incorporated into the polyoxymethylene. The polyoxymethylene modified according to the invention gives moldings having a streak-free, uniformly matt surface which generally retain the physical properties and also the inherent color of the base material.

Polyoxymethylene composition, and its use

Oxymethylene polymers (POM) are obtained in a granular form, by cooling a POM solution or dispersion, whose temperature is above the sintering temperature of the POM, to a temperature slightly below the sintering temperature of the POM, and extracting from the suspension obtained only those POM particles which show a grain diameter of more than 70 .mu.m. As solvent or dispersing agent as well as precipitating and cooling agent there is used a mixture of methanol and water with a methanol content of at least 75% by weight. The POM obtained is suitable as engineering plastic material for the manufacture of shaped articles having improved mechanical properties.

Process for the preparation of granular oxymethylene polymers having

Granular oxymethylene polymers are prepared by cooling a solution or dispersion of an oxymethylene polymer, the temperature of the said solution or dispersion being above the sintering temperature of the oxymethylene polymer, to a temperature just below the said sintering temperature. As dissolving or dispersing agent there is used a mixture of methanol and water. The cooling of the said solution or dispersion is effected in two stages while using a liquid cooling agent or a cooling device. After precipitation the coarse-granular polymer is separated from the fine-granular portion. It is suitable as engineering plastic for preparing molded articles.

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Konigstein/Taunus, Germany

Hans-Dieter Sabel