Polyolefin Film Softness and Transparency Balance
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Solution Overview
Problem
Films made from propylene copolymers or terpolymers face challenges in achieving a balance between softness and optical properties, particularly when high xylene-soluble fractions are present, which can make them unsuitable for food contact applications and result in unsatisfactory sealing initiation temperature and optical properties.
Innovation Solution
A polyolefin composition comprising a propylene/ethylene copolymer and a propylene/ethylene/1-butene terpolymer, obtained using a specific heterogeneous catalyst system, with a balanced ratio of ethylene and 1-butene units and a controlled xylene-soluble fraction, which results in a film with low sealing initiation temperature, improved transparency, and a regular thickness profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If high amount of xylene soluble fractions are used to achieve softness, then softness is improved, but the film becomes unsuitable for food contact applications and optical properties deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition parameters of the polyolefin mixture, specifically maintaining xylene soluble fraction between 3-13 wt% and using a specific ratio of propylene/ethylene copolymer (19-50 wt%) to propylene/ethylene/1-butene terpolymer (50-81 wt%). This controlled parameter approach achieves the desired softness while maintaining food contact suitability and optical properties.
Solution Approach 2:
The patent uses composite materials by creating a multi-component polyolefin system comprising propylene homopolymer, propylene/ethylene copolymer, and propylene/ethylene/1-butene terpolymer in specific proportions. This composite approach allows balancing contrasting properties - the homopolymer provides structural integrity while the copolymer and terpolymer components provide softness and flexibility, achieving food contact suitability with improved optical properties.
2Ease of operation
If high amount of xylene soluble fractions are used to achieve softness, then softness is improved, but sealing initiation temperature and optical properties become unsatisfactory
Solution Approach 1:
The patent controls the xylene soluble fraction within 3-13 wt% and adjusts the polyolefin composition ratios to achieve optimal sealing initiation temperature between 85-105°C. By changing these parameters, the patent simultaneously achieves softness and satisfactory sealing temperature without the trade-off present in conventional single-polymer films.
Solution Approach 2:
The multi-component polyolefin composite allows independent optimization of different properties: the propylene/ethylene/1-butene terpolymer component (50-81 wt%) provides softness and flexibility, while the propylene/ethylene copolymer (19-50 wt%) and homopolymer provide structural support and control sealing temperature. This composite structure resolves the contradiction between softness and sealing initiation temperature.
3Ease of operation
If high amount of xylene soluble fractions are used to achieve softness, then softness is improved, but transparency deteriorates
Solution Approach 1:
The patent optimizes the xylene soluble fraction parameter within 3-13 wt% and controls the composition ratios to achieve both softness and high transparency. This parameter optimization ensures that the film maintains excellent optical clarity while providing the desired softness, eliminating the trade-off between these properties.
Solution Approach 2:
The patent employs a composite polyolefin system where the propylene homopolymer and copolymer components maintain crystalline structure for transparency, while the controlled amount of terpolymer (containing 1-butene units) provides softness. The specific composition ratios ensure that the composite material achieves both high transparency and softness simultaneously.
4Strength
If propylene copolymers or terpolymers are used to improve impact and transparency, then impact resistance and transparency are improved, but rigidity decreases and balance between contrasting properties becomes difficult to achieve
Solution Approach 1:
The patent creates a composite polyolefin system comprising propylene homopolymer (providing rigidity and structural integrity), propylene/ethylene copolymer (providing impact resistance), and propylene/ethylene/1-butene terpolymer (providing flexibility and softness). The specific composition ratios - homopolymer plus copolymer making 80-97 wt% and terpolymer making 3-20 wt% - are optimized to achieve the perfect balance between rigidity and impact resistance.
Solution Approach 2:
The patent applies local quality by assigning different functional roles to different components within the polyolefin mixture. The homopolymer and copolymer components provide structural support and rigidity in certain aspects, while the terpolymer component provides localized softness and impact absorption. This functional differentiation within the composite allows achieving both rigidity and impact resistance simultaneously.
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 provides a film with a low xylene-soluble fraction, low sealing initiation temperature, and enhanced transparency, while maintaining a regular thickness profile, making it suitable for food contact applications and improving the balance between contrasting properties.
Implementation Method 1
component A) of the polyolefin composition being obtained by polymerizing propylene and ethylene in the presence of a catalyst comprising the product of the reaction between: (i) a solid catalyst component comprising Ti, Mg, Cl, and an internal electron donor compound characterized by the fact that it contains from 0.1 to 50%wt of Bi with respect to the total weight of said solid catalyst component; (ii) an alkylaluminum compound and, (iii) an electron-donor compound (external donor)
Data Source
Figure 1
AI summary
A polyolefin composition comprising: A) from 19 wt% to 50 wt% of a propylene ethylene copolymer having an ethylene derived units content ranging from 1.5 wt% to 6.0 wt% B) from 50 wt% to 81 wt% of a propylene ethylene 1-butene terpolymer having an ethylene derived units content ranging from 1.5 wt% and 6.0 wt% and 1-butene derived units content of between 4.8 wt% and 12.4 wt%; the sum of the amount of component A) and B) being 100.