Abstract:
Poly(vinyl pivalate) exhibiting a high syndiotacticity and a high molecular weight is prepared through suspension polymerization of vinyl pivalate at low temperatures. Furthermore, poly(vinyl pivalate) microspheres with a high syndiotacticity is prepared for use as a precursor for PVA with a high molecular weight and a high syndiotacticity through suspension polymerization of vinyl pivalate at 20 to 70 DEG C with the use of azobisdimethylvaleronitrile as an initiator. In addition, poly(vinyl pivalate) is separated using a dispersing agent and a precipitating agent to thereby prepare poly(vinyl pivalate) microspheres with various sizes and a uniform size distribution. The poly(vinyl pivalate) microspheres are suspended in an aqueous alkali solution such that only the surface thereof is saponified to PVA. In this way, embolic particles with a spherical shape are obtained to be useable as an embolic material for embolotherapy.
Abstract:
The invention relates to a method for producing adhesives having improved adhesion in the form of their aqueous dispersions or dispersion powder that can be redispersed in water. Said adhesives are produced by carrying out the emulsion polymerization of one or more monomers selected from the group of the vinyl esters of unbranched and branched carboxylic acids having 1 to 12 C atoms, of the esters of acrylic acid and methacrylic acid with branched and unbranched alcohols having 1 to 12 C atoms, of vinyl aromatic compounds, vinyl halides, dienes and alpha olefins. The emulsion polymerization is carried out in the presence of polyvinyl alcohol and the dispersion obtained thereby is optionally dried. The inventive method is characterized in that after completion of the polymerization, one or more emulsifiers selected from the group of the anionic, cationic and non-ionic emulsifiers is/are added to the dispersion in the amount of 0.3 to 3.0 wt. % with regard to the total weight of the dispersion.
Abstract:
Gegenstand der Erfindung ist ein Verfahren zur Herstellung einer wässrigen Polymerisatdispersion mittels radikalisch initiierter Emulsionspolymerisation von radikalisch polymerisierbaren ethylenisch ungesättigten Monomeren in einem Polymerisationsreaktor, wobei die damit erhaltene Polymerisatdispersion in einen Nachbehandlungsreaktor überführt wird und darin mittels physikalischer und/oder chemischer Methoden nachbehandelt wird, dadurch gekennzeichnet, dass die im Nachbehandlungsreaktor befindliche Polymerisatdispersion simultan zur Nachbehandlung in einen Kreislauf zur Filtration und Analyse gefördert wird und anschließend in den Nachbehandlungsreaktor zurückgeführt wird.
Abstract:
This invention relates to the preparation and purification of high-X ("chi") diblock copolymers. Such copolymers contain two segments ("blocks") of polymers with significantly different interaction parameters and can be used in directed self-assembly applications.
Abstract:
Gegenstand der Erfindung ist ein Verfahren zur Reduktion des Gehalts an Formaldehyd in wässrigen Polymerdispersionen mit latent Formaldehyd freisetzenden Bestandteilen, dadurch gekennzeichnet, dass zu den wässrigen Polymerdispersionen ein oder mehrere N-Oxyl-Verbindungen zugegeben werden.