Abstract: The invention relates to a process for working up particulate crude polyoxymethylene, which comprises the following steps: (a) introduction of the particulate crude polyoxymethylene into an extraction column (13) operated at a pressure in the range from 1 to 6 bar, (b) introduction of a polar extractant into the extraction column (13) with a temperature in the range from 95 to 140° C. and a pressure in the range from 1 to 6 bar, wherein from 10 to 1000 ppm, based on the amount of polar extractant introduced, of a buffer substance which buffers in the pH range from 7.5 to 11.5 are introduced into the extraction column (13).

Abstract: The invention relates to a polyoxymethylene (POM) powder for use in a selective laser sintering process and having the following parameters: Isothermal crystallization time (at 152° C.) >3 min Mn from 22 000 to 25 000 g/mol Mw from 60 000 to 140 000 g/mol Mw/Mn from 3 to 5 MVR from 15 to 70 [cm3/10 min] d50 average particle size 60 ?m Particle size from 30 to 130 ?m. A process for producing the powder, and also moldings produced from this powder by a selective laser sintering process, are also described.

Abstract: The invention relates to a process for working up particulate crude polyoxymethylene, which comprises the following steps: (a) introduction of the particulate crude polyoxymethylene into an extraction column (13) operated at a pressure in the range from 1 to 6 bar, (b) introduction of a polar extractant into the extraction column (13) with a temperature in the range from 95 to 140° C. and a pressure in the range from 1 to 6 bar, wherein from 10 to 1000 ppm, based on the amount of polar extractant introduced, of a buffer substance which buffers in the pH range from 7.5 to 11.5 are introduced into the extraction column (13).

Abstract: Polyamide containing a compound which bears at least one hydroxy group and has chemical bonding by way of an amide group to the end of the polymer chain, process for preparing this polyamide, and also fibers, films, and moldings, comprising at least one such polyamide.

Abstract: The invention relates to a polyoxymethylene (POM) powder for use in a selective laser sintering process and having the following parameters: Isothermal crystallization time (at 152° C.) >3 min Mn from 22 000 to 25 000 g/mol Mw from 60 000 to 140 000 g/mol Mw/Mn from 3 to 5 MVR from 15 to 70 [cm3/10 min] d50 average particle size 60 ?m Particle size from 30 to 130 ?m. A process for producing the powder, and also moldings produced from this powder by a selective laser sintering process, are also described.

Abstract: Thermoplastic molding materials comprising A) 10 to 99.99% by weight of a polyoxymethylene homo- or copolymer, B) 0.01 to 5% by weight of an imidazole of the general formula where the R1 to R4 radicals are each independently defined as follows: R1 is an alkyl radical having 1 to 5 carbon atoms, R2 to R4 are each hydrogen, an alkyl radical having 1 to 5 carbon atoms, C) 0 to 5% by weight of an alkaline earth metal oxide, D) 0 to 80% by weight of further additives, where the sum of the percentages by weight of components A) to D) adds up to 100%.

Abstract: The present invention relates to coated polyoxymethylene moldings comprising at least one polyoxymethylene homo- or copolymer A), and also, if appropriate, further additives B), which has been coated on the surface with at least one binder C) and one formaldehyde scavenger D), wherein the binder C) used comprises a polyalkylene oxide C1 or a polyvinyl ester C2 or a graft polymer C3 composed of C1 and C2 or a mixture of these, and the formaldehyde scavenger D) used comprises at least one imidazolidin-2-one compound.

Abstract: The present invention relates to coated polyoxymethylene moldings comprising at least one polyoxymethylene homo- or copolymer A), and also, if appropriate, further additives B), which has been coated on the surface with at least one binder C) and one formaldehyde scavenger D), wherein the binder C) used comprises a polyalkylene oxide C1 or a polyvinyl ester C2 or a graft polymer C3 composed of C1 and C2 or a mixture of these, and the formaldehyde scavenger D) used comprises at least one imidazolidin-2-one compound.

Abstract: A continuous process for producing polyamides, their oligomers or mixtures thereof, if appropriate with further reaction products, comprises reaction of aminonitriles or dinitriles and diamines or mixtures thereof, if appropriate together with further polyamide-forming monomers and/or oligomers, with an aqueous medium composed of aqueous monomer and oligomer extracts obtained from polyamide production by extraction of the polymer with water in a reactor which has a vertical longitudinal axis and through which there is a flow substantially in the longitudinal direction wherein water and/or the aqueous medium are introduced into the reactor at two or more different locations along the vertical longitudinal axis, wherein the aqueous medium is introduced at one or more locations.

Abstract: Polyamide, whose main chain contains a chemically bound amine selected from the group consisting of 2-methyl-1,5-diaminopentane and 1-amino-2-R-cyclopent-1-ene, where R is a functional group capable of combining with an amino group to form an amide group, and processes for preparing such a polyamide and fibers, films and moldings comprising such a polyamide.

Abstract: Polyamide whose main chain contains a chemically bound N-alkyllactam, and processes for preparing such a polyamide and fibers, films and moldings comprising such a polyamide.

Abstract: The invention relates to an initiator composition for anionic polymerization, comprising at least one alkali metal hydride selected from LiH, NaH, and KH, and at least one organylaluminum compound, and to a process for the anionic polymerization of styrene monomers or of diene monomers using the initiator composition.

Abstract: In a process for distillatively removing ammonia and water from mixtures obtained in the preparation of polyamides which comprise a lactam and/or diamines, and, if appropriate, an aminonitrile and/or dinitrile, and also a cyclopentanone impurity in two stages: 1) the mixture is distilled at from 11 to 35 bar to give, as the top product T1, water, ammonia and cyclopentanone, and, as the bottoms B1, water, the lactam and/or diamines, and, if appropriate, the aminonitrile and/or dinitrile, and 2) T1 is distilled at from 11 to 35 bar to give, as the top product T2, ammonia and cyclopentanone, and, as the bottoms B2, water.

Abstract: A continuous process for producing polyamides, their oligomers or mixtures thereof, if appropriate with further reaction products, comprises reaction of aminonitriles or dinitriles and diamines or mixtures thereof, if appropriate together with further polyamide-forming monomers and/or oligomers, with an aqueous medium composed of aqueous monomer and oligomer extracts obtained from polyamide production by extraction of the polymer with water in a reactor which has a vertical longitudinal axis and through which there is a flow substantially in the longitudinal direction wherein water and/or the aqueous medium are introduced into the reactor at two or more different locations along the vertical longitudinal axis, wherein the aqueous medium is introduced at one or more locations.

Abstract: Polyamide whose main chain contains a chemically bound N-alkyllactam, and processes for preparing such a polyamide and fibers, films and moldings comprising such a polyamide.

Abstract: Polyamides, oligomers thereof or mixtures thereof, if required with further reaction products, are prepared by reacting aminonitriles or dinitriles and diamines or a mixture containing aminonitrile, dinitrile and diamine, and, if required, further polyamide-forming monomers and/oligomers with water in a reactor (1) having a vertically oriented longitudinal axis, by a process in which, in the reactor (1), the reaction product is removed from the bottom and ammonia formed and any further low molecular weight compounds formed and water are taken off via the top (2), wherein the reactor (1) has at least two chambers (4) arranged one on top of the other in the longitudinal direction, the chambers (4) being separated from one another by liquid-tight trays (5), each chamber (4) being connected by a liquid overflow (6) to the chamber (4) directly underneath and a liquid product stream being taken off by the liquid overflow (6) of the lowermost chamber (4), the gas space (7) above the liquid level in each chambe

Abstract: Polyamide, whose main chain contains a chemically bound amine selected from the group consisting of 2-methyl-1,5-diaminopentane and 1-amino-2-R-cyclopent-1-ene, where R is a functional group capable of combining with an amino group to form an amide group, and processes for preparing such a polyamide and fibers, films and moldings comprising such a polyamide.

Abstract: An apparatus for making polyamides oligomers thereof mixtures thereof, the apparatus comprising a material selected from the group consisting of a) an austenitic steel comprising from 15 to 25% by weight of chromium, from 3 to 35% by weight of nickel and from 0 to 10% by weight of molybdenum, and iron, b) a duplex steel comprising from 20 to 30% by weight of chromium, from 3 to 10% by weight of nickel and from 0 to 5% by weight of molybdenum, and iron, and c) a nickel-based alloy comprising from 12 to 25% by weight of chromium and from 12 to 20% by weight of molybdenum, and nickel

Abstract: Polyamide containing a compound which bears at least one hydroxy group and has chemical bonding by way of an amide group to the end of the polymer chain, process for preparing this polyamide, and also fibers, films, and moldings, comprising at least one such polyamide.

Abstract: The invention relates to an initiator composition for anionic polymerization, comprising at least one alkali metal hydride selected from LiH, NaH, and KH, and at least one organylaluminum compound, and to a process for the anionic polymerization of styrene monomers or of diene monomers using the initiator composition.