Propylene-Ethylene Blends for High Gloss Blown Films
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Solution Overview
Problem
Existing thermoplastic compositions for air-quenched blown films made solely from ethylene-based polymers lack high gloss and exhibit inferior heat sealing properties, while incorporating additional layers or compatibilizers can complicate the manufacturing process and reduce physical properties like tear and toughness.
Innovation Solution
A composition comprising 2-15% propylene-based copolymer with substantially isotactic propylene sequences and 85-98% ethylene-based copolymer, which enhances gloss and heat sealing without compromising physical properties, and can be processed on standard equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If films are made solely from ethylene-based copolymer, then manufacturing process is simple, but gloss value is insufficient
Solution Approach 1:
The patent creates a composite polymer blend combining ethylene-based copolymer (85-98% by weight) with propylene-based copolymer (2-15% by weight). This composite material achieves high gloss values (greater than 60° at 60° angle) while maintaining manufacturing simplicity, as the blend can be processed on standard blown film equipment without complex modifications.
2Illumination intensity
If additional layers or compatibilizers are added to improve gloss, then gloss value increases, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the functions of multiple layers or compatibilizers into a single-layer blend composition. By combining ethylene-based copolymer and propylene-based copolymer in specific ratios, the invention achieves high gloss properties without requiring multi-layer coextrusion equipment or separate compatibilizer layers, thus reducing structural complexity.
3Illumination intensity
If additional layers or compatibilizers are added to improve gloss, then gloss value increases, but physical properties like tear and toughness are reduced
Solution Approach 1:
The patent optimizes the compositional parameters by controlling the weight ratio of propylene-based copolymer (2-15%) to ethylene-based copolymer (85-98%). This parameter optimization achieves high gloss values while maintaining adequate physical properties including tear strength and toughness, avoiding the degradation that occurs with higher propylene content or multi-layer structures.
4Strength
If ethylene-based copolymer is used alone, then physical properties are maintained, but heat sealing behavior is inferior
Solution Approach 1:
The patent applies local quality by introducing a small amount of propylene-based copolymer (2-15% by weight) specifically to improve heat sealing behavior, while the majority ethylene-based copolymer (85-98% by weight) maintains the overall physical properties. This localized modification achieves lower hot tack initiation temperature without compromising tear and toughness.
Data Source
AI summary
The invention is directed to a composition suitable for high gloss air quenched blown films. The films are comprised of from 2 to 15 percent by weight of a substantially isotactic propylene-based copolymer having a melt flow rate of at least 5 g/10 minutes and having from 8 to 21 mole percent units derived from an alpha olefin; and from 85 to 98 percent by weight of an ethylene-based copolymer having a melt index of from 0.1 to 9 g/10 minutes. An air quenched blown film made from the inventive composition exhibits a value for gloss greater than the value for gloss exhibited by an air quenched blown film made solely from the ethylene-based copolymer.