摘要:
A process for the preparation of polyoxymethylene copolymers, wherein 1,3,5-trioxane is polymerized with generally known comonomers in the presence of a strong protonic acid initiator and in the presence of a formaldehyde dialkyl acetal, and wherein the initiator is dissolved in the formaldehyde dialkyl acetal before admixing to the trioxane and the comonomers.
摘要:
Use of a polymer containing maleimide units of the formula I ##STR1## in which R.sup.1 is hydrogen, an acyclic or cyclic, aliphatic, aromatic or araliphatic radical which is chiral or achiral, can be monosubstituted or polysubstituted by functional groups and in which one or more CH.sub.2 groups can be replaced by functional groups, as alignment layer in liquid-crystal displays.Alignment layers containing a polymer conforming to the formula I effect, in particular, a suppression of twist states and ghost images and thus an improvement in the optical contrast.
摘要:
Process for preparing polyoxymethylene homo- and copolymers and apparatus suitable for this purpose An apparatus is described for preparing polyoxymethylene homo- and copolymers. This has the following elements: A) reactor (1) encompassing a polymerization zone (2) and a deactivation zone (3) directly downstream thereof for polymerizing and deactivating polyoxymethylene homo- and copolymers in a homogeneous phase in a manner known per se, B) depressurizing assembly (4), which, if appropriate, has a metering apparatus (5) for additives for the polymer, C) pelletizer (6), D) extraction apparatus (7), and E) if appropriate, a drying apparatus (8). Use of the apparatus and of the polymerization process carried out therein can achieve particularly low residual monomer contents in a simple manner which saves energy.
摘要:
The present invention relates to a process for preparing 2,2'-bis(diphenylphosphinylmethyl)-1,1'-binaphthyls by reacting a reaction mixture prepared in a solvent by reaction of 2,2'-dimethyl-1,1'-binaphthyl with a brominating agent to produce a mixture comprising 2,2'-bis(bromomethyl)-1,1'-binaphthyl and further brominated binaphthyls and optionally further comprising unreacted brominating agent, reacted brominating agent and solvent, with an alkyl diphenylphosphinite of the formula RO--P(Ph--(R').sub.n).sub.2, where R is an alkyl radical having from 1 to 5 carbon atoms, Ph is phenyl, R' is an alkyl radical having from 1 to 4 carbon atoms, CF.sub.3, fluorine, chlorine or bromine and n is 0, 1 or 2, at from 70.degree. to 180.degree. C. optionally in the presence of a further solvent.
摘要:
An initiator for cationic polymerization comprises a salt of a protic acid as well as a protic acid. The molar ratio of protic acid to salt is in the range from 1:0.01 to 1:2000. The initiator is used for example for cationic homo- or copolymerization of trioxane, and permits stable and flexible operation of the polymerization.