Propylene Random Copolymer Transparency Mechanical Strength
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Solution Overview
Problem
Existing propylene random copolymers fail to achieve a balance between transparency, mechanical performance, and thermal stability, particularly in sealing layers of multi-layer films, often resulting in insufficient transparency and high haze due to inadequate comonomer content and melting temperature.
Innovation Solution
A propylene random copolymer with a specific ethylene content range of 5.3 to 9.0 wt.%, a melt flow rate of 0.8 to 25.0 g/10min, and a melting temperature of 128 to 138°C, featuring a monophasic structure and controlled relative content of isolated to block ethylene sequences, is developed to enhance transparency and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If propylene copolymer has high comonomer content to achieve low melting temperature and good transparency, then transparency is improved, but mechanical strength deteriorates
Solution Approach 1:
The patent precisely controls the comonomer content within 3.5-7.0 wt.% and ethylene content within 5.3-9.0 wt.% to achieve the optimal balance between transparency and mechanical strength. By adjusting these compositional parameters, the polymer attains both good optical properties and sufficient mechanical performance for film applications
Solution Approach 2:
The patent creates a composite polymer system by incorporating ethylene as a comonomer into propylene polymer chains. This composite structure at the molecular level allows the material to exhibit properties of both propylene (mechanical strength) and ethylene (transparency and flexibility), resolving the contradiction between these two properties
2Temperature
If propylene copolymer has low melting temperature to achieve low sealing initiation temperature, then sealing performance is improved, but thermal stability deteriorates
Solution Approach 1:
The patent optimizes the comonomer content (3.5-7.0 wt.%) and ethylene content (5.3-9.0 wt.%) to achieve a melting temperature range of 128-138°C. This precise parameter control allows the polymer to have low enough melting point for easy sealing while maintaining sufficient thermal stability through the controlled copolymer structure
Solution Approach 2:
The patent creates local structural variations by controlling the distribution of ethylene sequences (isolated vs block sequences) within the propylene matrix. This local quality variation allows different regions of the polymer to contribute differently to sealing behavior and thermal stability, achieving both low SIT and adequate thermal resistance
3Ease of operation
If propylene copolymer has high ethylene content to achieve good flexibility and low SIT, then sealing performance is improved, but phase separation occurs resulting in high haze
Solution Approach 1:
The patent precisely controls the ethylene content within 5.3-9.0 wt.% and the relative content of isolated to block ethylene sequences (I(E)) within 45.0-69.0%. This parameter optimization ensures sufficient flexibility and low SIT while preventing excessive phase separation that would cause high haze
Solution Approach 2:
The patent promotes homogeneous distribution of ethylene sequences within the propylene matrix by controlling the polymerization process to achieve a balanced I(E) ratio. This homogeneity prevents macroscopic phase separation and maintains good optical properties (low haze) while still providing the flexibility benefits of ethylene incorporation
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 propylene random copolymer achieves a combination of low sealing initiation temperature, high hot tack force, and excellent optical properties, making it suitable for flexible and transparent films suitable for packaging applications.
Implementation Method 1
The finding of the present invention is to produce a propylene random copolymer with rather high ethylene content having a moderate to low randomness, a low melting temperature and being monophasic, i.e. having a single glass transition temperature.
Implementation Method 2
a melting temperature Tm as determined by DSC according to ISO 11357 of from 128 to 138°C
Data Source
AI summary
Propylene copolymer having a comonomer content in the range of 5.0 to 9.0 wt.-% and a melt flow rate MFR2 (230°C) in the range of 0.8 to 25.0 g/10min, wherein said propylene copolymer is suitable for film applications featured by good sealing properties.