C2C3 Random Copolymer Composition for Sealing and Sterilization
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Solution Overview
Problem
Current polypropylene random copolymer compositions face challenges in achieving a balance between low sealing initiation temperature (SIT) and high hot tack force (HTF) while maintaining excellent sterilization resistance and optical properties, such as low haze levels after sterilization.
Innovation Solution
A C2C3 random copolymer composition comprising 70.0 to 95.0 wt % of a C2C3 random copolymer with specific ethylene content, melt flow rate, and melting temperature, combined with 5.0 to 30.0 wt % of a propylene-1-butene plastomer, optimized for low SIT, high HTF, and retention of clarity and low haze after sterilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the sealing initiation temperature (SIT) is reduced to enable fast sealing, then sealing speed is improved, but the hot tack force (HTF) decreases
Solution Approach 1:
The patent uses a composite material system consisting of a C2C3 random copolymer base polymer combined with an ethylene-vinyl acetate (EVA) copolymer additive. The C2C3 copolymer provides the base sealing properties, while the EVA additive (containing 10-40 wt% vinyl acetate) specifically enhances hot tack force without significantly increasing sealing initiation temperature. This composite approach allows simultaneous achievement of fast sealing and high hot tack strength.
2Temperature
If the ethylene content in C2C3 copolymer is increased to reduce SIT, then sealing initiation temperature is improved, but hot tack force decreases
Solution Approach 1:
The patent optimizes the ethylene content parameter in the C2C3 copolymer to a specific range of 2.0-6.0 wt%, which is relatively low compared to conventional approaches. This controlled parameter change prevents excessive reduction in SIT while maintaining adequate HTF. The low ethylene content is compensated by the addition of EVA copolymer, creating a balanced performance profile.
3Reliability
If sterilization treatment is applied to ensure safety in medical applications, then sterilization resistance is improved, but optical properties (haze level) deteriorate
Solution Approach 1:
The patent modifies the chemical composition parameters by incorporating EVA copolymer with specific vinyl acetate content (10-40 wt%). This compositional change enhances the polymer's thermal stability and resistance to sterilization degradation. The vinyl acetate groups provide thermal stability that prevents excessive haze formation during steam sterilization at 121°C, maintaining optical clarity while ensuring sterilization resistance.
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.