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Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles that are visible to the naked eye or can be seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. On the other hand, a solution is a homogeneous mixture in which no settling occurs and in which the dissolved...
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Esferas de poliolefina de metallocenos apoyadas en poliestireno que no interactúa.

Roscoe1, Frechet, Walzer

  • 1S. B. Roscoe and J. M. J. Frechet, Department of Chemistry, University of California, Berkeley, CA 94720, USA. J. F. Walzer and A. J. Dias, Baytown Polymer Center, Exxon Chemical Company, 5200 Bayway Drive, Baytown, TX 77520, USA.

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Resumen

Un nuevo soporte de poliestireno evita la desactivación del catalizador en la polimerización de olefinas, permitiendo sitios catalíticos homogéneos dentro de las cuentas de polímero. Este método produce cuentas de poliolefina uniformes con tamaños controlables.

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Área de la Ciencia:

  • Química de Polímeros La Química de Polímeros es la química de los polímeros.
  • La catálisis de la catálisis.
  • Ciencia de los materiales Ciencia de los materiales.

Sus antecedentes:

  • Los catalizadores de metaloceno ofrecen una alta actividad para la polimerización de olefinas, pero son propensos a la desactivación por soportes de sílice tradicionales.
  • Los catalizadores con soporte proporcionan ventajas de manejo sobre los sistemas homogéneos, pero las interacciones de soporte pueden ser perjudiciales.

Objetivo del estudio:

  • Desarrollar un soporte no interactuante para catalizadores de metaloceno para evitar interacciones destructivas.
  • Para retener los beneficios de los catalizadores soportados al tiempo que mejora su estabilidad y rendimiento en la polimerización de olefinas.

Principales métodos:

  • Se sintetizó un soporte de poliestireno clorometilado no interactuante, ligeramente reticulado y sin interacción.
  • Se prepararon catalizadores de metalloceno con soporte mediante el tratamiento secuencial de las cuentas de poliestireno con reactivos específicos.
  • Los sitios del catalizador se distribuyeron de manera homogénea dentro de las cuentas de poliestireno.

Principales resultados:

  • El soporte de poliestireno desarrollado evita efectivamente las interacciones destructivas con los catalizadores de metaloceno.
  • La polimerización ocurre dentro de las cuentas de soporte, lo que lleva a sitios catalíticos homogéneos.
  • La copolimerización del etileno y el 1-hexeno produjo cuentas de poliolefina discretas y esféricas (0,3-1,4 mm).
  • El tamaño de las cuentas de poliolefina era controlable ajustando el tiempo de polimerización.

Conclusiones:

  • Un nuevo sistema de soporte de poliestireno es efectivo para la polimerización de olefinas catalizadas por metaloceno.
  • Este enfoque supera las limitaciones de los soportes basados en sílice, ofreciendo una mejor estabilidad del catalizador.
  • El método permite la producción de cuentas de poliolefina uniformes con tamaños ajustables.