Blown Polyolefin Films with Uniform Gauge
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Solution Overview
Problem
Blown films produced from traditional polyethylene resins often lack consistent mechanical properties, particularly in terms of tensile strength and elongation at break, which can lead to mechanical weaknesses and increased production costs due to the need for edge trimming and recycling in the cast film process.
Innovation Solution
A polyolefin composition comprising 40-75 weight percent of a polyethylene with a density of 0.920-0.940 g/cm³ and 25-60 weight percent of an ethylene copolymer, where the polyethylene has a low xylene solubility and the copolymer is more soluble, providing improved tensile properties and eliminating the need for edge trimming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional polyethylene resins are used in blown film production, then production efficiency is maintained, but mechanical properties such as tensile strength and elongation at break are inconsistent
Solution Approach 1:
The patent uses a composite polyolefin composition combining polyethylene (40-75 wt.%) with an ethylene copolymer containing polar groups (25-60 wt.%). This composite structure provides consistent mechanical properties including tensile strength and elongation at break, while maintaining production efficiency in blown film extrusion.
Solution Approach 2:
The patent specifies precise compositional parameters: polyethylene content of 40-75 wt.% and ethylene copolymer content of 25-60 wt.%, with the copolymer containing 2-15 wt.% polar groups. These parameter controls ensure consistent mechanical properties in the blown film while maintaining extrusion efficiency.
2Productivity
If cast film process is used with high fluidity resins, then production efficiency is achieved, but mechanical weakness occurs due to strong orientation in machine direction
Solution Approach 1:
The patent employs a polyolefin composition with controlled molecular weight and comonomer content, achieving optimal balance between fluidity for efficient extrusion and mechanical strength. The ethylene copolymer with 2-15 wt.% polar groups provides this balance, enabling high production efficiency without mechanical weakness.
Solution Approach 2:
The patent introduces polar groups specifically in the ethylene copolymer component (25-60 wt.%) to enhance intermolecular forces and mechanical strength in critical areas, while maintaining overall processability through the polyethylene base material.
3Productivity
If cast film process is used, then production is efficient, but edge trimming is required due to gauge variations, increasing cost and complexity
Solution Approach 1:
The patent uses a polyolefin composition that produces blown films with uniform gauge and consistent properties across the transverse direction. This homogeneity eliminates the need for edge trimming and associated recycling systems, reducing both cost and process complexity while maintaining production efficiency.
4Reliability
If multi-layered barrier films containing non-polyolefinic resins are produced by cast film process, then barrier properties are achieved, but edge trim cannot be recycled due to quality considerations
Solution Approach 1:
The patent produces multi-layered barrier films with uniform composition and properties across the entire film width, eliminating edge trim waste. The polyolefin composition with ethylene copolymer (25-60 wt.%) containing polar groups ensures consistent barrier properties without requiring edge trimming, thus preventing material loss.
Data Source
AI summary
A blown film comprising a polyolefin composition (I) comprising: A) from 40 to 75 wt.% of a polyethylene having a density of 0.920-0.940 g/cm3 and a fraction soluble in xylene (XSA) of less than 10% wt.%; and B) from 25 to 60 wt.% of a copolymer of ethylene with one or more comonomers selected from α-olefins having formula HC2=CHRI, where RI is an alkyl radical, linear or branched, having from 1 to 8 carbon atoms, comprising from 50 to 70 wt.% of ethylene and having a fraction soluble in xylene (XSB) of at least 50 wt.%.