Pellet Polypropylene Resin High Flow Oxidation Stability
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Solution Overview
Problem
Existing polypropylene resin compositions used for fine denier fiber production face challenges in achieving high flow without using decomposition accelerators, while also maintaining excellent heat resistance and oxidation stability.
Innovation Solution
A pellet type polypropylene resin composition is developed, comprising homo polypropylene with a high melt index (400 g/10 min or more) and an antioxidant, meeting specific conditions for melt index, melting temperature, recrystallization temperature, xylene solubles, molecular weight distribution, and oxidation induction time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If peroxide based decomposition accelerator is used to increase flowability during extrusion process, then flowability is improved, but heat resistance and oxidation stability deteriorate
Solution Approach 1:
The invention extracts and removes the harmful peroxide-based decomposition accelerator from the extrusion process. By developing a resin composition that inherently provides high flowability through controlled molecular weight distribution and catalyst system optimization, the need for decomposition accelerators is eliminated, thereby preserving heat resistance and oxidation stability while maintaining ease of operation.
Solution Approach 2:
The invention changes the molecular weight distribution parameters of the polypropylene resin to achieve a balance between flowability and thermal stability. By controlling the molecular weight distribution to be within a specific range (Mw/Mn ≤ 2.4), the resin exhibits sufficient flow characteristics during extrusion without requiring decomposition accelerators that would compromise heat resistance and oxidation stability.
2Ease of manufacture
If Ziegler-Natta catalyst is used for homo polypropylene production, then production cost is reduced, but melt index remains low requiring decomposition accelerator
Solution Approach 1:
The invention employs a composite catalyst system that combines Ziegler-Natta catalyst with metallocene catalyst. This composite approach leverages the cost advantage of Ziegler-Natta catalyst while incorporating the high hydrogen reactivity and narrow molecular weight distribution control of metallocene catalyst, thereby achieving both economical production and high melt index without requiring decomposition accelerators.
Solution Approach 2:
The dual catalyst system performs multiple functions: Ziegler-Natta catalyst provides cost-effective bulk polymerization, while metallocene catalyst contributes to narrow molecular weight distribution and high hydrogen reactivity. This multi-functional catalyst system simultaneously addresses production cost and melt index requirements.
3Manufacturing precision
If metallocene catalyst is used to achieve high flow and narrow molecular weight distribution, then fiber quality is improved, but resin composition becomes powder shape making antioxidant addition difficult
Solution Approach 1:
The invention performs preliminary action by incorporating the antioxidant into the resin composition during the polymerization process itself, rather than attempting to add it to powder form afterward. The master batch method allows antioxidant to be pre-mixed with the polymerizing resin, ensuring uniform distribution in the final pellet form while maintaining the narrow molecular weight distribution and high flow characteristics achieved by the metallocene catalyst.
4Productivity
If homo polypropylene with high melt index is produced to enable fine denier fiber production, then fiber fineness is improved, but flowability control becomes challenging without decomposition accelerator
Solution Approach 1:
The invention optimizes multiple parameters simultaneously: molecular weight distribution (Mw/Mn ≤ 2.4), hydrogen to propylene ratio during polymerization, and catalyst composition. These parameter changes collectively achieve high melt index (≥400 g/10min) for fine denier fiber production while maintaining controllable flowability without decomposition accelerators through inherent resin characteristics.
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 composition exhibits excellent heat resistance, oxidation stability, and high flowability, enabling the production of fine denier fiber without decomposition accelerators, thus improving filter efficiency and durability.
Implementation Method 1
an antioxidant, and fulfilling the following conditions a1) to a6): a6) oxidation induction time, measured under conditions of 200° C. and 50 ml/min of oxygen according to ASTM D3985: 30 minutes or more
Implementation Method 2
conducting polymerization of propylene monomers while introducing hydrogen gas, in the presence of a catalyst composition comprising a metallocene compound
Data Source
AI summary
There are provided a pellet type polypropylene resin composition that exhibits excellent heat resistance and oxidation stability, and exhibits high flow without using a decomposition accelerator, and thus, can be used to prepare fine denier fiber, and a method for preparing the same.