Polymer Blends for Nonwoven Articles
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing nonwoven articles made from propylene and ethylene copolymers lack a balanced set of properties including good processability, soft aesthetically-pleasing feel, drapeability, reduced bonding temperature, and adequate tensile and tear resistance.
Innovation Solution
A heterogeneous blend comprising 60-99% semi-crystalline polymers with specific melting points and melt flow rates, combined with 1-40% semi-amorphous polymers having controlled heat of fusion, melt flow rates, and intermolecular compositional distribution, where the semi-crystalline polymer is the continuous phase and the semi-amorphous polymer is the discontinuous phase, achieving a blend with enhanced properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If propylene and ethylene copolymers are used to make nonwoven articles, then the articles can be produced with basic structural properties, but the articles lack a balanced set of properties including processability, softness, drapeability, bonding temperature, and tensile resistance
Solution Approach 1:
The patent uses a composite material system consisting of semi-crystalline polypropylene (continuous phase) and semi-amorphous polyethylene copolymer (discontinuous phase). This composite structure allows the nonwoven article to simultaneously achieve processability from the semi-amorphous phase and mechanical strength from the semi-crystalline phase, resolving the contradiction between versatile property balance and performance consistency.
Solution Approach 2:
The invention applies local quality by creating a heterogeneous blend where different phases perform different functions: the semi-crystalline polypropylene provides structural integrity and tensile resistance in the continuous phase, while the semi-amorphous polyethylene copolymer provides processability and softness in the discontinuous dispersed phase. This spatial differentiation of material properties enables the article to exhibit multiple desirable characteristics simultaneously.
2Ease of manufacture
If conventional copolymer blends are used, then manufacturing is simplified, but the articles exhibit poor softness and drapeability
Solution Approach 1:
The patent changes the molecular parameters of the polyethylene component by specifying semi-amorphous copolymers with 20-40 weight percent ethylene content and controlled molecular weight distributions. This parameter optimization allows the material to be processed using conventional equipment while simultaneously achieving superior softness and drapeability that conventional copolymers cannot provide.
Solution Approach 2:
By combining semi-crystalline polypropylene with semi-amorphous polyethylene copolymer in a heterogeneous blend, the invention creates a composite material that maintains ease of manufacture through compatibility with existing processes while the semi-amorphous phase specifically contributes the desired softness and drapeability properties.
3Strength
If high crystallinity polymers are used, then tensile strength is improved, but bonding temperature increases and processability deteriorates
Solution Approach 1:
The invention applies local quality by distributing different crystallinity levels spatially: the semi-crystalline polypropylene (40-80% crystallinity) in the continuous phase provides tensile strength, while the semi-amorphous polyethylene copolymer (low crystallinity) in the discontinuous phase lowers the overall bonding temperature. This spatial differentiation allows the article to achieve both high strength and low processing temperature.
Solution Approach 2:
The composite material system combines high-crystallinity semi-crystalline polypropylene for tensile strength with low-crystallinity semi-amorphous polyethylene copolymer for reduced bonding temperature. The heterogeneous blend structure enables these seemingly contradictory properties to coexist, with each phase contributing its optimal characteristics to the overall material performance.
4Ease of operation
If semi-amorphous polymers with high comonomer content are used, then processability and softness improve, but tensile resistance decreases
Solution Approach 1:
The invention uses local quality by placing the semi-amorphous polyethylene copolymer (providing processability and softness) in the discontinuous dispersed phase, while the semi-crystalline polypropylene (providing tensile resistance) forms the continuous matrix phase. This spatial arrangement allows the high-comonomer content component to improve processability without compromising the overall tensile resistance provided by the continuous crystalline phase.
Solution Approach 2:
The composite material system balances the trade-off by combining semi-amorphous polyethylene copolymer with high comonomer content (for processability and softness) with semi-crystalline polypropylene (for tensile resistance). The heterogeneous blend structure ensures that the weakness of the semi-amorphous phase in tensile resistance is compensated by the strength of the semi-crystalline continuous phase, achieving overall property balance.
Data Source
AI summary
This invention relates to a nonwoven article comprising a heterogeneous blend comprising:1) from 60 to 99 weight percent of one or more semi-crystalline polymers (based upon the weight of the semi-crystalline and semi-amorphous polymers), each semi-crystalline polymer comprising propylene and from 0 to 5 weight % alpha-olefin comonomer (based upon the weight of the polymer), said semi-crystalline polymers each having a melting point between 100 and 170° C. and a melt flow rate of 2000 dg/min or less; and2) from 1 to 40 weight % of one or more semi-amorphous polymers (based upon the weight of the semi-crystalline and semi-amorphous polymers), each semi-amorphous polymer comprising propylene and from 10 to 25 weight % of one or more C2 and or C4 to C10 alpha-olefin comonomers, said semi-amorphous polymers each having:a) heat of fusion of 4 to 70 J/g;b) a Melt Flow Rate of 0.1 to 2000 dg/min;c) an intermolecular compositional distribution as determined by thermal fractionation in hexane such that 85% by weight or more of the polymer is isolated as one or two adjacent, soluble fractions with the balance of the polymer in immediately preceding or succeeding fractions; and wherein each of these fractions has a wt % comonomer content with a difference of no greater than 20 wt % relative to the average wt % comonomer content of the copolymer; andd) an Mw/Mn of 1.5 to 4, ande) a propylene triad tacticity, as measured by 13C NMR, of 75% or greater; where the blend of the semi-crystalline and semi-amorphous polymers comprises less than 5 weight % filler, based upon the weight of the polymers and the filler, and the blend has:i) an MFR greater than 10 dg/min; andii) a Permanent Set of greater than 65% (as measured on a 125 mil thick molded part); andwhere the nonwoven article has a Hand of 40 g or less at a fabric basis weight of 35 gsm.