Propylene Random Copolymer Sealing Layer with 1-Butene
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Solution Overview
Problem
Current polyolefin compositions for packaging films, particularly those based on propylene ethylene random copolymers, face challenges in achieving a low sealing initiation temperature without compromising optical and hot tack properties, and often require high amounts of expensive additives or terpolymers, which are costly and inefficient.
Innovation Solution
A polyolefin composition comprising a random copolymer of propylene with ethylene and a polymer of 1-butene, where the random copolymer has a specific comonomer content and molecular weight distribution, and the polymer of 1-butene has a weight average molecular weight of 100,000 to 300,000 g/mol, reducing the sealing initiation temperature while maintaining important properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a random copolymer of propylene with ethylene is used as the sealing layer, then the film provides good strength, stiffness, and transparency, but the sealing initiation temperature is too high for high-speed packaging lines
Solution Approach 1:
The patent uses a composite material system consisting of a propylene-ethylene random copolymer matrix combined with a specific polymer of 1-butene. This composite approach allows the sealing layer to inherit the strength and transparency of the propylene copolymer while the 1-butene polymer component provides the necessary low-temperature sealing properties, achieving both mechanical performance and low sealing initiation temperature
Solution Approach 2:
The patent changes the chemical composition parameters of the sealing layer by incorporating a polymer of 1-butene with specific molecular weight characteristics (weight average molecular weight of 100,000 to 300,000 g/mol and molecular weight distribution Mw/Mn of below 6.0). This parameter change in the polymer structure directly lowers the sealing initiation temperature from typical propylene copolymer temperatures above 110°C to the target range of around 105°C or lower, enabling high-speed packaging operations
2Temperature
If high amounts of additives or terpolymers are added to reduce sealing initiation temperature, then the sealing temperature decreases, but the cost increases and other properties deteriorate
Solution Approach 1:
Instead of adding high amounts of additives or terpolymers, the patent achieves low sealing initiation temperature by carefully controlling the molecular weight parameters of the 1-butene polymer component. The specific range of weight average molecular weight (100,000 to 300,000 g/mol) and molecular weight distribution (Mw/Mn below 6.0) provides optimal sealing performance without requiring high additive concentrations, thus maintaining cost-effectiveness and avoiding property deterioration
Solution Approach 2:
The patent applies local quality by introducing a specific polymer of 1-butene with controlled molecular weight characteristics into the propylene-ethylene copolymer matrix. This localized modification with precise molecular weight control provides the necessary low-temperature sealing functionality without uniformly compromising the overall material properties or requiring excessive additive amounts throughout the entire sealing layer
Data Source
AI summary
The present invention is directed to a polyolefin composition which is suitable as sealing layer of a multilayer film providing improved, i.e. reduced sealing initiation temperature. The polyolefin composition comprises a random copolymer of propylene and a polymer of 1-butene. The present invention is also directed to oriented and non-oriented films comprising the polyolefin composition and to the use of a polymer of 1-butene in a polyolefin composition comprising a random copolymer of propylene for reducing the sealing initiation temperature of an oriented or non-oriented film comprising the polyolefin composition. The present invention allows the application of a random copolymer of propylene based polyolefin composition as sealing layer of a multilayer film for higher speed packaging lines and at the same time also provides good hot tack and optical properties.