摘要:
Polytetrahydrofuran or C.sub.2 -C.sub.10 -alkylene oxide/tetrahydrofuran copolymers having a molecular weight of from 250 to 20,000 Dalton are prepared by the cationic polymerization of tetrahydrofuran or tetrahydrofuran and C.sub.2 -C.sub.10 -alkylene oxides in the prsence of a promoter by a process in which the catalyst used is a mixture of one or more C.sub.2 -C.sub.6 -di- or tricarboxylic acids with boric acid.
摘要:
The invention relates to a process for preparing hydroxyl-containing polymers, in particular for preparing polytetrahydrofuran with terminal hydroxyl groups, from the corresponding acyloxy-containing polymers by transesterification with alcohols in the presence of a sodium-containing catalyst. In this process the polytetrahydrofuiran solution is passed in the presence of a catalytic amount of water directly through at least one ion exchanger following the transesterification in order to remove the sodium cations.The novel process makes it possible to remove the sodium cations from the sodium-containing catalyst in an economic manner and with little complexity. The residual sodium content can be reduced to values of less than 0.5 ppm.
摘要:
Tetrahydrofuran/but-2-yne-1,4-diol copolymers containing C--C triple bonds and having an average molecular weight M.sub.n of from 500 to 3500 Dalton and a content of from 0.5 to 3 mol of triple bonds/mol of copolymer and blends of these copolymers with polytetrahydrofuran having an average molecular weight M.sub.n of from 500 to 3500 Dalton, processes for their preparation and their use.
摘要:
Crude water-containing tetrahydrofuran is purified by distillation by a process in which the crude tetrahydrofuran is passed through three distillation columns, water being removed from the bottom of the first column, water-containing tetrahydrofuran being recycled from the top of the second column into the first column, the top product of the third column being recycled to the first column, a distillate being removed at the top of the first column, and pure tetrahydrofuran being distilled off from the bottom product of the second column, in the third column, and the pure tetrahydrofuran being removed from the side take-off of the third column.
摘要:
A process is disclosed for separating a mixture of methanol and tetrahydrofuran into its components. The separation is carried out in the liquid or gaseous phase through an organophilic membrane, for example, a plasma polymerization membrane.
摘要:
Tetrahydrofuran is prepared from a crude alkaline aqueous solution of butane-1,4-diol, as obtained by reaction of acetylene with aqueous formaldehyde and catylytic hydrogenation of the resulting but-2-yne-1,4-diol solution by a process in which the alkaline solution is first neutralized with sulfuric acid and water is then eliminated in the liquid phase at from 200.degree. to 260.degree. C., under superatmospheric pressure and in the presence of phosphoric acid.