Peelable Polyolefin Seal with Low Initiation Temperature
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Solution Overview
Problem
Current heat sealable and peelable films face challenges in achieving a balance between seal strength, ease of opening, cost-effectiveness, and resistance to aging and abuse, while also maintaining a low heat seal initiation temperature and broad sealing window, which is essential for efficient packaging and consumer convenience.
Innovation Solution
A blend of reactor grade propylene-based plastomers with a molecular weight distribution less than 3.5 and a second polymer such as polyethylene or styrenic polymer, optimized to achieve a heat seal initiation temperature below 120°C and a broad heat sealing window, ensuring secure sealing and easy opening, along with improved age resistance and toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional heat sealable films are used to achieve adequate seal strength, then the seal maintains integrity, but the heat seal initiation temperature is high and the sealing window is narrow
Solution Approach 1:
The patent modifies the chemical composition parameters of the sealant layer by incorporating specific polymers (polyethylene, polypropylene, and their copolymers) in controlled ratios, along with plasticizers and process aids. This composition adjustment lowers the heat seal initiation temperature while maintaining seal strength through optimized material properties rather than increasing temperature.
2Strength
If high seal strength is achieved through composition, then the seal is secure, but the film becomes difficult to peel open
Solution Approach 1:
The patent creates a multilayer structure where the sealant layer has locally optimized properties different from the outer layer. The sealant layer contains specific polymers and plasticizers that provide strong adhesion when heated, while the outer layer maintains lower friction and different mechanical properties that facilitate easy peeling. This local differentiation allows the seal to be strong during sealing but easy to open during consumption.
3Object-generated harmful factors
If the sealant layer uses high melting temperature polymer, then the outer layer doesn't stick to sealing jaws, but the inner sealant layer cannot maintain seal integrity when warm
Solution Approach 1:
The patent divides the film structure into distinct functional layers: an outer layer with higher melting temperature that prevents sticking to sealing jaws, and an inner sealant layer with lower melting temperature that provides strong adhesion and maintains seal integrity when warm. This segmentation allows each layer to perform its specific function without interfering with the other, solving both the sticking and seal integrity problems 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 peelable seal with aged seal strength suitable for secure packaging and easy consumer access, maintaining integrity and resistance to abuse, while reducing production costs and enhancing processing efficiency.
Implementation Method 1
Hot metal sealing jaws are moved from an open position to a closed position, contacting the film in order to seal it into a bag shape. During the sealing process, the outer layer of the film comes into direct contact with the hot metal surface of the sealing jaws. Heat is thus transferred through the outer layer of the film to melt and fuse the inner sealant layer to form a seal.
Implementation Method 2
After the sealing jaws reopen, the film is cooled to room temperature. Before the inner sealant layer is cooled to room temperature, it should be able to maintain its seal integrity.
Data Source
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AI summary
The invention relates to a polyolefin-based heat sealable and peelable seal. The peelable seals comprise from 5 to 98 percent by weight of a propylene based plastomer or elastomer and from 2 to 95 percent by weight of a second polymer selected from the group consisting of polyethylene, polybutylene, and styrenic polymer and mixtures thereof. The invention also relates to tamper evident peelable seals. The invention also relates to methods of making and using the heat sealable, peelable seal.