C2-C3 Random Copolymer Composition for Low Seal Initiation Temperature and High Hot Tack Force
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Solution Overview
Problem
Existing polypropylene random copolymer compositions struggle to achieve a balance between low sealing initiation temperature (SIT) and high hot tack force while maintaining excellent sterilization resistance and optical properties, such as low haze levels after sterilization.
Innovation Solution
A C2-C3 random copolymer composition comprising 70.0 to 99.9 wt% of a C2-C3 random copolymer with specific ethylene content, melt flow rate, and melting temperature, combined with 0.0 to 30.0 wt% of an ethylene-α-olefin plastomer and optional additives, optimized for use in packaging films that require low SIT, high hot tack force, and retention of clarity and low haze after sterilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a low SIT is achieved through specific copolymer composition, then sealing speed is improved, but hot tack force decreases
Solution Approach 1:
The patent divides the polymer composition into three distinct fractions with different comonomer contents: fraction (A) with 0.4-1.5 wt% C2, fraction (B) with 3.0-10.0 wt% C2, and fraction (C) with 7.0-15.0 wt% C2. This segmentation allows each fraction to contribute different properties: lower C2 fractions provide structural integrity while higher C2 fractions provide sealing functionality, resolving the contradiction between low SIT and high hot tack force.
2Force
If high hot tack force is achieved through copolymer composition, then sealing strength is improved, but sealing initiation temperature increases
Solution Approach 1:
The patent segments the polymer into three fractions with progressively increasing C2 content. Fractions (A) and (B) with lower C2 content maintain structural integrity and higher melting points, while fraction (C) with higher C2 content provides low-temperature sealing capability. This segmentation enables simultaneous achievement of high hot tack force and low SIT.
3Reliability
If sterilization resistance is improved through material selection, then optical properties are preserved, but material flexibility decreases
Solution Approach 1:
The patent changes the compositional parameters by introducing a specific tri-modal distribution with three distinct C2 content fractions. This parameter change creates a composition that maintains crystallinity and thermal stability for sterilization resistance while the specific combination of fractions preserves flexibility and processability, avoiding the brittleness that would result from high crystallinity alone.
4Illumination intensity
If transparency is improved through copolymer composition, then haze level is reduced, but sealing performance deteriorates
Solution Approach 1:
The patent segments the polymer composition into three fractions with different C2 contents to achieve a balance between optical properties and sealing performance. The lower C2 fractions (A and B) maintain crystallinity and transparency, while the higher C2 fraction (C) provides sealing functionality. This segmentation allows the material to achieve low haze levels while maintaining effective sealing performance.
Data Source
AI summary
New C2C3 random copolymer composition, which shows improved sealing behaviour due to low sealing initiation temperature (SIT) and high hot tack force. In addition, the inventive composition shows an excellent sterilization behaviour, i.e. retention of low haze level after sterilization. The present invention is furthermore related to the manufacture of said copolymer composition and to its use.