Polypropylene Copolymer Blend for Non-Woven Bonding
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Solution Overview
Problem
The production of non-woven fabrics faces challenges with high solubles polypropylene materials, which require specific catalyst systems and handling, leading to issues like smoke generation, agglomeration, and poor processability, while also compromising the barrier properties due to high bonding temperatures.
Innovation Solution
A polypropylene copolymer blend comprising 82% to 88% of a low solubles polypropylene homopolymer with a crystallinity of at least 55% and 12% to 18% of an ethylene/propylene copolymer, allowing for a wider bonding window and lower bonding temperatures without the drawbacks of high solubles materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high solubles polypropylene is used to improve processability and lower bonding temperatures, then bonding window widens and process performance improves, but smoke generation increases and agglomeration problems occur
Solution Approach 1:
The patent changes the chemical composition parameters of polypropylene by incorporating specific amounts of ethylene (3-10 wt%) and dibenzoxazole (0.1-5 wt%) to modify the polymer's bonding characteristics, achieving low bonding temperature without high solubles content
Solution Approach 2:
Dibenzoxazole acts as an intermediary substance that facilitates bonding at lower temperatures by modifying the polymer's thermal properties, allowing the polypropylene to bond effectively without requiring high solubles content that would otherwise be needed to lower the bonding temperature
2Strength
If high bonding temperature is used to bond spunbond material, then bonding strength improves, but meltblown fibers partially melt causing pinholes that compromise barrier properties
Solution Approach 1:
The patent changes the thermal parameters of the polypropylene by incorporating ethylene and dibenzoxazole, which lowers the melting point and bonding temperature, allowing bonding to occur at temperatures that do not damage the meltblown fibers
Solution Approach 2:
The patent creates a dynamic bonding process where the polypropylene's thermal properties are optimized to bond at a temperature window that is high enough to ensure strong bonding but low enough to prevent meltblown fiber degradation, achieving both bonding strength and barrier property preservation
3Ease of manufacture
If polypropylene with high xylene solubles is produced to improve processability, then bonding temperature decreases and bonding window widens, but production complexity increases due to specific catalyst requirements and powder handling
Solution Approach 1:
The patent changes the composition parameters by incorporating ethylene and dibenzoxazole into polypropylene, achieving the desired low bonding temperature and wide bonding window through a simpler production process that doesn't require high solubles content
Solution Approach 2:
The patent uses a conventional Ziegler-Natta catalyst system that is already widely available and well-understood in the industry, avoiding the need for specialized catalyst systems required for producing high solubles polypropylene, thereby simplifying production
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 blend provides improved processability, tensile strength, coefficient of friction, haze, gloss, and stiffness, enabling the production of non-woven fabrics with enhanced properties and reduced smoke generation, while avoiding the limitations of high solubles polypropylene.
Implementation Method 1
molten polymer is extruded through a many holed die
Implementation Method 2
a polypropylene homopolymer, that has less than 3% by weight xylene solubles and a crystallinity of at least 55%
Implementation Method 3
The web thus formed is then bonded by heating it to soften the polymer fibers
Implementation Method 4
passing the web through smooth or engraved calendar rollers to bond the fibers
Data Source
Figure 1~2
Figure 3~5
Figure 6~8
AI summary
Polypropylene resin compositions are provided that are useful in the production of thermoformed articles and biaxially oriented polypropylene films (BOPPs), tapes and fibers. The resins of the present invention are blends of high crystalline (low solubles) polypropylene homopolymer and an ethylene/propylene random copolymer (RCP). These blends can be used to replace standard high solubles BOPP grade polypropylene homopolymers. In addition, the use of high crystalline polypropylene homopolymers in the blends imparts improved stiffness to the finished films while maintaining good processability of the blends. Such polypropylene compositions are effectively produced by in-reactor blending of a high crystalline propylene homopolymer and a propylene/ethylene random copolymer.