Abstract: A coaxial plug or coaxial socket connected to a coaxial coupler of a device that is to be calibrated, such as a measuring port of a vectorial network analyzer (VNA). The coaxial coupler has an inner conductor part and a coaxial outer conductor part, and has a short-circuit connection provided between the inner conductor part and the outer conductor part. The outer conductor part and the inner conductor part are connected to a contact coupling sleeve so that they can be axially displaced in relation to one another. A contact mechanism is located and configured to act selectively on the contact coupling sleeve, so that the latter creates the short-circuit connection in the form of a detachable electrical contact between the inner conductor part and the outer conductor part, whilst at the same time mechanically fixing the inner conductor part and the outer conductor part in their relative positions.

Abstract: This invention relates to a process for preparing a low-odor hydrogel-forming acrylic acid polymer, which comprises the steps of: a) preparing a polymeric hydrogel by free-radically polymerizing a monomer composition comprising at least 50% by weight of acrylic acid in an aqueous polymerization medium and converting said hydrogel into a particulate hydrogel or into hydrogel-forming powder; and optionally b) treating said particulate hydrogel or said hydrogel-forming powder with a crosslinking substance which, actually or latently, contain at least two functional groups capable of reacting with the carboxyl groups on the addition polymer; characterized by the acrylic acid used in step a) containing less than 400 ppm of acetic acid and propionic acid. It further relates to the hydrogel-forming addition polymers obtainable by the process and to their use.

Abstract: Basic (meth)acrylates IV are prepared by transesterification of alkyl (meth)acrylates I in the presence of a catalyst and working-up of the reaction mixture by distillation, by a process in which a gas or gas mixture which is inert under the reaction conditions is passed through the reaction zone and/or heat exchanger.

Abstract: A coaxial plug or coaxial socket connected to a coaxial coupler of a device that is to be calibrated, such as a measuring port of a vectorial network analyzer (VNA). The coaxial coupler has an inner conductor part and a coaxial outer conductor part, and has a short-circuit connection provided between the inner conductor part and the outer conductor part. The outer conductor part and the inner conductor part are connected to a contact coupling sleeve so that they can be axially displaced in relation to one another. A contact mechanism is located and configured to act selectively on the contact coupling sleeve, so that the latter creates the short-circuit connection in the form of a detachable electrical contact between the inner conductor part and the outer conductor part, whilst at the same time mechanically fixing the inner conductor part and the outer conductor part in their relative positions.

Abstract: The invention relates to a method for producing (meth)acrylic acid esters IV by means of transesterification of a (meth)acrylic acid ester I with an alcohol R2OH comprising at least one more carbon atom than the alcohol constituents (R1O—) in the (meth)acrylic acid ester I to be subjected to transesterification, in the presence of a catalyst or a catalyst mixture. Either essentially the (meth)acrylic acid ester I is separated and then the catalyst used is separated by distillation (catalyst separation), or the catalyst used is separated by distillation first (catalyst separation), and then essentially the (meth)acrylic acid ester I is separated, from the reaction product of the transesterification. Constituents from the mixture obtained, which have a lower boiling point than the (meth)acrylic acid ester IV, are essentially separated by distillation (separation of constituents at low boiling point), and the (meth)acrylic acid ester IV is then purified by distillation (purification by distillation).

Abstract: Acrylic acid is prepared from propene by means of gas-phase oxidation by a process in which a starting gas mixture which contains propene and steam and whose molar propene/steam ratio is ?1 and whose propane content is ?5% is passed at elevated temperatures through a fixed catalyst bed comprising successive catalyst part-beds A and B, the part-bed A passed through first containing, as active material, a mixed oxide containing the elements Mo, Bi and Fe and the part-bed B containing, as active material, a mixed oxide containing the elements Mo and V, in a manner such that at least 96.5 mol % of propene are converted in a single pass through part-bed A.

Abstract: In a process for preparing water-absorbent resins based on acrylic acid, crude acrylic acid is firstly isolated from the reaction gases from the catalytic gas-phase oxidation of propane, propylene and/or acrolein. This is treated with an aldehyde scavenger and pure acrylic acid is separated by distillation from the treated crude acrylic acid, and this pure acrylic acid can be subjected directly to a free-radical polymerization.

Abstract: Higher (meth)acrylates IV are prepared by transesterification of a lower (meth)acrylate I with a higher alcohol R2OH in the presence of a stabilizer or stabilizer mixture and of a catalyst or catalyst mixture, by a process in which the liberated lower alkanol R1OH is separated off and is fed at least partly to the preparation of the lower (meth)acrylate I.

Abstract: The present invention relates to a process for preparing a low-odor hydrogel-forming acrylic acid polymer, which comprises the steps of: a) preparing a polymeric hydrogel by free-radically polymerizing a monomer composition comprising at least 50% by weight of acrylic acid in an aqueous polymerization medium and converting said hydrogel into a particulate hydrogel or into hydrogel-forming powder; and optionally b) treating said particulate hydrogel or said hydrogel-forming powder with a crosslinking substance which, actually or latently, contain at least two functional groups capable of reacting with the carboxyl groups on the addition polymer; characterized by the acrylic acid used in step a) having a total acrylic acid oligomer content of less than 500 ppm, preferably not more than 400 ppm and especially not more than 300 ppm. Here and hereinafter, all ppm units are by weight based on acrylic acid.

Abstract: A tert-C4–C8-alkyl (meth)acrylate is prepared by reacting (meth)acrylic acid with an olefin of the formula where R1 and R2, which may be identical or different, are methyl or ethyl and R3 is H, methyl or ethyl, in homogeneous phase in the presence of an acidic catalyst and isolating the tert-C4–C8-alkyl (meth)acrylate from the reaction mixture, by a process in which the catalyst is separated off as residue by a two-stage distillation of the reaction mixture and the tert-C4–C8-alkyl (meth)acrylate is isolated from the distillates. The novel process makes it possible to use acetic acid-containing (meth)acrylic acid. The danger of cleavage of the ester and of polymerization of (meth)acrylic compounds is reduced.

Abstract: This invention relates to a process for preparing a low-odor hydrogel-forming acrylic acid polymer, which comprises the steps of: a) preparing a polymeric hydrogel by free-radically polymerizing a monomer composition comprising at least 50% by weight of acrylic acid in an aqueous polymerization medium and converting said hydrogel into a particulate hydrogel or into hydrogel-forming powder; and optionally b) treating said particulate hydrogel or said hydrogel-forming powder with a crosslinking substance which, actually or latently, contain at least two functional groups capable of reacting with the carboxyl groups on the addition polymer; characterized by the acrylic acid used in step a) containing less than 400 ppm of acetic acid and propionic acid. It further relates to the hydrogel-forming addition polymers obtainable by the process and to their use.

Abstract: In a process for preparing an ester of an unsaturated carboxylic acid by reacting an ester of the unsaturated carboxylic acid and a C1-C4-alkanol with an alcohol R3OH, where R3 is a C4-C20-alkyl radical, a C5-C7-cycloalkyl radical, a phenyl-C1-C4-alkyl radical or a C2-C12-alkyl radical substituted by at least one NR5R5 group or by from 1 to 3 hydroxyl groups or C1-C4-alkoxyl groups or interrupted by one or more oxygen atoms, where the radicals R5 are, independently of one another, C1-C6-alkyl or together with the nitrogen atom form a 5- to 7-membered heterocyclic ring which may contain a further nitrogen or oxygen atom, in the presence of a transesterification catalyst, the transesterification catalyst used is at least one metal alkanolate containing at least one OR1 group, where R1 is a 2,2,6,6-tetraalkyl-1-oxylpiperidin-4-yl radical.

Abstract: Mixtures containing monomers having at least one ethylenically unsaturated group are chemically and/or physically treated in the presence of the reaction products of alkylsuccinic anhydrides and stable N-oxyl radicals having a hydroxyl group.

Abstract: The present invention relates to novel tocopherol-containing superabsorbents, to a process for preparing them using tocopherol-containing acid-functional monomers, especially acrylic acid, and to their use for absorbing aqueous fluids.

Abstract: Acrylic acid is prepared from propene by means of gas-phase oxidation by a process in which a starting gas mixture which contains propene and steam and whose molar propene/steam ratio is ≧1 and whose propane content is ≦5% is passed at elevated temperatures through a fixed catalyst bed comprising successive catalyst part-beds A and B, the part-bed A passed through first containing, as active material, a mixed oxide containing the elements Mo, Bi and Fe and the part-bed B containing, as active material, a mixed oxide containing the elements Mo and V, in a manner such that at least 96.5 mol % of propene are converted in a single pass through part-bed A.

Abstract: In a process for preparing water-absorbent resins based on acrylic acid, crude acrylic acid is firstly isolated from the reaction gases from the catalytic gas-phase oxidation of propane, propylene and/or acrolein. This is treated with an aldehyde scavenger and pure acrylic acid is separated by distillation from the treated crude acrylic acid, and this pure acrylic acid can be subjected directly to a free-radical polymerization.

Abstract: (Meth)acrylates are prepared by reacting (meth)acrylic acid with an alcohol in the presence of at least one acidic catalyst and at least one polymerization inhibitor in a reaction zone b) consisting of at least one reactor b1) having at least one connected distillation unit b2), by a process in which

Abstract: The invention relates to a method for producing (meth)acrylic acid esters by transesterification of the (meth)acrylic acid with a higher alkanol in the presence of an acid catalyst, at least one polymerization inhibitor and one organic solvent that forms an azeotropic mixture with water. The reaction mixture is heated to the boiling point of the mixture in a reactor that comprises a distillation unit with a column and a condenser. The content of the reactor is recirculated via an external evaporator and heated to the boiling point, and the azeotropic mixture is distilled off. The organic solvent forms a reflux and at least a part of the solvent reflux is recirculated between the reactor and the evaporator. The inventive method allows for the production of higher (meth)acrylic acid esters in a reactor with a circulation evaporator without using copper salts as the polymerization inhibitors.

Abstract: Polymerizable compounds are prepared and/or worked up using at least one liquid ring pump by a process in which a working liquid which contains a material stream from the preparation and/or working-up of the polymerizable compound is used in a liquid ring pump.

Abstract: In a process for rectificative isolation of (meth)acrylic acid from a mixture containing, as main components, (meth)acrylic acid and an organic liquid having a higher boiling point than (meth)acrylic acid, the rectification is carried out with the addition of a surfactant.