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EFFECTIVE VISCOSITY MODIFIER FOR POLYOLEFINS

IP.com Disclosure Number: IPCOM000215090D
Publication Date: 2012-Feb-16
Document File: 5 page(s) / 51K

Publishing Venue

The IP.com Prior Art Database

Abstract

Polymers such as polyolefins are known to have good mechanical properties particularly if the molecular weight is high enough. Unfortunately, the dynamic melt viscosity of polymers is also correlated with the molecular weight and its distribution. Since customers require specific mechanical properties for their plastic products and also want high throughput, low temperature, pressure and torque during processing, there is a need to have polymers with balanced properties. A common approach to address this issue is adding processing aids to the polymeric formulation and the most typical ones used today are low molecular weight hydrocarbons and fluoroelastomers. Addition of processing aids typically modify the molten polymer to metal contact during extrusion, thereby reducing the friction and thus allowing higher processing rates or lower torque, temperature. This is called external lubrication as opposed to internal lubrication where the influence of an additive lowers the polymer’s dynamic viscosity. The latter is far more beneficial for the mechanical versus rheological property balance which is important for many thin wall applications. Furthermore, addition of less efficient processing aids can also add substantial cost to the polymer resin which is undesirable.

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EFFECTIVE VISCOSITY MODIFIER FOR POLYOLEFINS

Polymers such as polyolefins are known to have good mechanical properties particularly if the molecular weight is high enough. Unfortunately, the dynamic melt viscosity of polymers is also correlated with the molecular weight and its distribution. Since customers require specific mechanical properties for their plastic products and also want high throughput, low temperature, pressure and torque during processing, there is a need to have polymers with balanced properties.

A common approach to address this issue is adding processing aids to the polymeric formulation and the most typical ones used today are low molecular weight hydrocarbons and fluoroelastomers. Addition of processing aids typically modify the molten polymer to metal contact during extrusion, thereby reducing the friction and thus allowing higher processing rates or lower torque, temperature. This is called external lubrication as opposed to internal lubrication where the influence of an additive lowers the polymer's dynamic viscosity. The latter is far more beneficial for the mechanical versus rheological property balance which is important for many thin wall applications. Furthermore, addition of less efficient processing aids can also add substantial cost to the polymer resin which is undesirable.

During compounding of hydroxy fatty acid or derivatives with polypropylene it was surprisingly found that the dynamic viscosity of the resin was substantially lowered. Particularly efficient was the 12 hydrostearic acid (12-HSA) which, already at a level of 0.5 wt%, gave a viscosity reduction of approximately 20%. The methyl ester of 12-HSA also demonstrated viscosity reduction albeit less efficient and hydrogenated castor oil did not show any effect on dynamic viscosity in polypropylene. On the other hand, di- and tri-hydroxystearic acid methylester revealed a viscosity increase when compounded with polypropylene. Physical properties such as melt temperature, crystallization temperature, haze, clarity, and transmission were not changed compared to the virgin polypropylene.

These data demonstrate that 12-hydroxy stearic acid or ester can be used as efficient (...