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.
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:
Oxymethylene polymers having a bimodal distribution or having a distribution of higher modality and having a targeted content of a low molecular weight fraction of from 1 to 5 percent by mass are described. Moldings of these polymers are distinguished by high low-temperature notched impact strength associated with a high modulus of elasticity.
摘要:
An initiator for cationic polymerization comprises a salt of a protic acid as well as a protic add. 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.
摘要:
The present invention relates to a process for the preparation of oxymethylene polymers as well as oxymethylene polymers obtainable therefrom. The process includes polymerization of a monomer, which forms —CH2—O— units in the presence of an acetal of formaldehyde or a polyhydric alcohol and an initiator for cationic polymerization. The initiator may be a heteropoly acid or an acid salt thereof which is dissolved in an alkyl ester of a polybasic carboxylic acid.
摘要:
Oxymethylene polymers having a bimodal distribution or having a distribution of higher modality and having a targeted content of a low molecular weight fraction of from 1 to 5 percent by mass are described. Moldings of these polymers are distinguished by high low-temperature notched impact strength associated with a high modulus of elasticity.
摘要:
An apparatus is described for preparation of oxymethylene homo- and copolymers. This encompasses heterogeneous polymerization of a monomer which forms oxymethylene groups in the presence of an acetal of formaldehyde and of an initiator for cationic polymerization, followed by the deactivation of the polymer in a homogeneous phase via treatment with a basic aprotic solvent or with an aprotic solvent which comprises a base. Oxymethylene homopolymers with very high stability are also described.
摘要:
Oxymethylene polymers having a bimodal distribution or having a distribution of higher modality and having a targeted content of a low molecular weight fraction of from 1 to 5 percent by mass are described. Moldings of these polymers are distinguished by high low-temperature notched impact strength associated with a high modulus of elasticity.
摘要:
Oxymethylene copolymers having a high proportion of terminal alkyl ether groups and having terminal hydroxyalkylene groups are described. These polymers are distinguished by high thermal stability and high hot water resistance. Furthermore, a process for the preparation of oxymethylene copolymers is described in which the polymerization of at least one monomer forming —CH2—O— units is effected in the presence of at least one acetal of formaldehyde and of at least one initiator of cationic polymerization and the initiator of cationic polymerization is used in an amount of less than or equal to 10−4 mol %, based on the amount of the monomers present at the beginning of the polymerization and forming —CH2—O— units, in which starting materials of the polymerization are used such that the content of water and formic acid at the beginning of the polymerization is less than or equal to 40 ppm, and in which the initiator and/or the active polymer chains are deactivated by treatment of the prepared polymer with a base-containing protic 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.