Reclosable Flow Pack With Segmented Cold-Seal Adhesive
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Solution Overview
Problem
Reclosable packaging, particularly for confectionary items, faces challenges with cold-seal adhesives that lose adhesion over time, leading to poor reclosing capabilities due to high self-adhesion on polymer films, causing the adhesive to remain on one side after opening and reducing shelf-life reliability.
Innovation Solution
A reclosable flow pack design featuring a cold-seal adhesive pattern where only a portion is in register, allowing for delamination upon opening, with a ratio of out-of-register to in-register adhesives ensuring easy reclosure, using corona-treated oriented polyolefin films and a cold-seal composition predominantly made of natural or synthetic latex with acrylic polymers, maintaining adhesion strength between 2 and 8 N/25 mm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cold-seal adhesive has high adhesion to the polymer film surface, then the seal strength is improved, but the adhesive remains on one side after opening, preventing reclosure
Solution Approach 1:
The adhesive layer is segmented into multiple domains with different adhesion properties. Specifically, the patent uses a block copolymer adhesive where hydrophilic blocks provide strong adhesion to polar film surfaces while hydrophobic blocks provide cohesive strength, creating distinct functional regions within the adhesive layer that resolve the contradiction between strong sealing and easy reclosure
Solution Approach 2:
The adhesive composition is designed with local quality variations through the block copolymer structure, where different molecular segments exhibit different adhesion characteristics. The hydrophilic blocks localize at the adhesive-film interface providing strong bonding, while hydrophobic blocks remain in the adhesive bulk providing cohesion, enabling both strong initial seal and clean release for reclosure
2Strength
If the adhesive bonding force to the film is higher than cohesive force, then the seal adheres well to the film, but the adhesive layer is completely removed from one side upon opening, rendering reclosing difficult
Solution Approach 1:
The adhesive parameters are changed by using a block copolymer with specific hydrophilic-hydrophobic block ratios and molecular weights. This parameter optimization ensures that the adhesion-cohesion balance point allows the adhesive to bond strongly to the film during sealing while maintaining sufficient cohesive strength to prevent complete transfer to one side during opening, ensuring reliable reclosure
Solution Approach 2:
The adhesive is designed as a composite block copolymer material combining hydrophilic and hydrophobic segments. This composite structure creates internal phase separation where hydrophilic domains interact with the polar film surface while hydrophobic domains provide cohesive continuity, solving the adhesion-cohesion contradiction through material composition rather than interface modification
3Strength
If the adhesive self-adhesion increases with time, then the adhesive bonds strongly to itself, but the failure location shifts from the adhesive interface to the substrate, causing quality issues
Solution Approach 1:
The block copolymer adhesive creates local quality differentiation where hydrophilic blocks preferentially locate at adhesive-substrate interfaces and hydrophobic blocks remain in adhesive-adhesive contact regions. This spatial distribution of adhesive properties ensures that even as self-adhesion increases with time, the failure consistently occurs at the adhesive-substrate interface rather than within the adhesive bulk, maintaining quality consistency
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
Ensures reliable reclosability by maintaining unused adhesive for resealing, preventing cohesive failure and maintaining air-tightness, even after initial opening and reclosing, by utilizing a patterned adhesive layer with a high ratio of out-of-register to in-register adhesives, enhancing the shelf-life performance of reclosable packaging.
Implementation Method 1
these films are therefore usually surface-treated (atmospheric plasma, flame, . . . )
Data Source
AI summary
The present invention is related to a reclosable flow pack comprising one or more fin seal(s) (30) and one or more cross-seal(s) (31), said flow pack comprising a cold-seal adhesive pattern (11, 301, 302, 401, 402) forming a seal between a first (3) and a second (4) sealing portion, the cold-seal adhesive pattern (301, 401) of the first portion being only partly in register with the cold-seal adhesive pattern (302, 402) of the second portion, the bonding force of the cold-seal adhesive to the first (3) and the second (4) sealing portions being lower than the bonding force within the cold-seal adhesive on the portions in register (7, 100, 101), so that the cold-seal adhesive on the portions of the cold-seal adhesive patterns in register is separated from the first or from the second sealing portion when the seal is opened.