Thermoplastic Polyolefin Composition Without Peroxide Crosslinking
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Solution Overview
Problem
Conventional polyolefin polymerization processes using Ziegler-Natta catalysts face limitations in achieving enhanced melt strength and rheological properties due to constraints on molecular weight and viscosity, which can negatively impact mechanical and impact resistance properties.
Innovation Solution
Reacting a polyolefin resin with a functional agent acting as a rheology modifier, free from peroxide initiators, under specific conditions of temperature (180°C to 300°C) and specific energy (0.15 kWh/kg) to form a thermoplastic polyolefin composition with improved rheological properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If peroxide crosslinking is used to improve rheological properties, then melt strength increases, but uncontrollable side reactions and oxygen-containing by-products occur
Solution Approach 1:
The invention extracts and eliminates the peroxide initiator from the polymerization system, replacing it with controlled radical polymerization using alternative initiators (azobisisobutyronitrile, 2,2'-azobis(2-methylpropionamidine) dihydrochloride) that do not produce oxygen-containing by-products or uncontrollable crosslinking side reactions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process significantly increases viscosity at a constant shear stress, reduces melt flow rate, broadens shear thinning indices and flow rate ratios, and enhances melt strength and die swell, while maintaining thermal and mechanical properties.
Implementation Method 1
modification of the polyolefin backbone utilizing free radical chemistry such as high energy radiation or peroxide crosslinking
Implementation Method 2
heating the reactive polyolefin composition to a temperature of 180°C to 300°C and subjecting the reactive polyolefin composition to a specific energy of equal to or more than 0.15 kWh/kg
Data Source
Figure 1
AI summary
The present invention relates to process for preparing a thermoplastic polyolefin composition comprising a) providing a reactive polyolefin composition comprising a polyolefin resin and a rheology modifier, which is free of peroxide initiator; b) heating the reactive polyolefin composition to a temperature of 180°C to 300°C; and c) subjecting the reactive polyolefin composition to a specific energy of equal to or more than 0.15 kWh/kg to obtain the thermoplastic polyolefin composition, the thermoplastic polyolefin composition obtainable by said process, an article comprising said thermoplastic polyolefin composition and the use of a rheology modifier, which is free of peroxide initiator, in said reactive polyolefin composition for increasing the viscosity at a constant shear stress of 747 Pa of the thermoplastic polyolefin composition, eta747 (Comp), by reacting the polyolefin resin and the rheology modifier at a temperature in the range of from 180°C to 300°C and a specific energy equal to or greater than 0.15 kWh/kg.