Metallocene Polypropylene Nonwoven Weldability
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Solution Overview
Problem
Lightweight spunbonded thermoplastic nonwovens with low surface mass face challenges in reproducibility and mechanical weakness at bonding zones, leading to delamination and increased permeability, which affects the weldability and durability of hygiene products like diapers.
Innovation Solution
A nonwoven comprising at least 95% by weight of two polypropylene polymers A and B, with polymer A obtained using a metallocene-based catalyst, achieving improved mechanical and thermal welding properties, and a surface mass of less than 35 g/m², enhancing filament distribution and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If the surface mass of nonwovens is reduced to lower production costs, then manufacturing cost decreases, but filament distribution becomes less homogeneous and mechanical strength decreases
Solution Approach 1:
The patent changes the chemical composition parameters of the polypropylene polymer by using a metallocene-based catalyst system with specific comonomer content (0.1-10 mol% of 1-butene or hexene), which fundamentally alters the polymer's molecular structure and intermolecular forces, enabling low surface mass nonwovens to maintain high mechanical strength
Solution Approach 2:
The patent creates a composite polymer material by copolymerizing propylene with small amounts of comonomers (1-butene or 1-hexene) using metallocene catalysts, producing a polypropylene copolymer that combines the structural integrity of polypropylene with enhanced bonding characteristics from the comonomer units
2Weight of stationary object
If the surface mass of nonwovens is reduced to lower production costs, then manufacturing cost decreases, but weldability deteriorates
Solution Approach 1:
The patent modifies the thermal and chemical parameters of the polypropylene by controlling the comonomer type and content in the copolymerization process, which changes the polymer's melting behavior and molecular weight distribution, thereby improving weldability even at low surface masses
Solution Approach 2:
The patent introduces local compositional variations by incorporating specific comonomer units at controlled concentrations within the polypropylene chains, creating regions with enhanced bonding capability that locally improve weldability without compromising the overall lightweight structure
3Strength
If hotmelt glue is used to join nonwovens, then joining strength improves, but glue may pierce through low surface mass nonwovens and damage the product
Solution Approach 1:
The patent enables the nonwoven material itself to provide the bonding function through its inherent polymer properties. The metallocene-catalyzed polypropylene copolymer exhibits self-bonding capability during thermal processing, eliminating the need for external hotmelt glue and thus preventing glue piercing issues
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 solution improves the mechanical and thermal welding properties of the nonwoven, ensuring stronger bonding zones and reduced delamination, while maintaining a lightweight structure, thus enhancing the durability and performance of hygiene products.
Implementation Method 1
a) at least 88% by weight of a polypropylene polymer A obtained by polymerization in the presence of a metallocene-based polymerization catalyst
Implementation Method 2
The securing zones, in particular with regard to hygiene articles, are subject to numerous efforts when said articles are worn
Implementation Method 3
Nonwovens can be assembled according to bonding zones by thermal welding
Implementation Method 4
a nonwoven of spun-bonded thermoplastic filaments
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to a nonwoven of spun-bonded thermoplastic filaments characteristically comprising at least 95% by mass (g) of its surface mass (g/m2) of at least two polypropylene polymer(s) A and B, said filaments having a density less than or equal to 1.3 dtex, said nonwoven having a surface mass less than or equal to 35 g/m2, the bonding ratio being at least 10% and at most 25% and at least 88% by mass (g) of its surface mass (g/m2) of said polypropylene polymer A obtained by polymerization in the presence of at least one metallocene-based polymerization catalyst and at most 12% by mass (g) of its surface mass of said polypropylene polymer B.