Partially Laminated Thermoformable Webs for Puncture Resistance
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Solution Overview
Problem
Existing packaging methods for food products with sharp edges, such as meat containing bones, face challenges in providing adequate puncture resistance while maintaining cost-effectiveness and formability, especially in semi-automated thermoforming processes.
Innovation Solution
A partially laminated thermoplastic film structure is developed, where two films are adhesively laminated with a pattern that leaves substantial areas unlaminated, allowing for hot forming and enhanced puncture resistance without the need for expensive, annealed biaxially oriented films. This structure includes a honeycomb or dot pattern of lamination and can include an oxygen barrier for improved protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the web is increased to improve puncture resistance, then puncture resistance is improved, but the cost of packaging material increases and the ability to thermoform the web is limited
Solution Approach 1:
The web is segmented into two separate thermoplastic films that are partially laminated together. This segmentation allows each film to maintain its individual thermoformability while the combination provides enhanced puncture resistance. The films can be formed into cavities of substantial depth independently before being joined, resolving the contradiction between thickness and formability.
Solution Approach 2:
The invention uses a composite structure of two different thermoplastic films laminated together. This composite material approach provides puncture resistance comparable to much thicker single webs while maintaining the thermoformability of thinner materials. The composite structure combines the advantages of multiple materials to simultaneously achieve strength and manufacturability.
2Strength
If annealed biaxially oriented films are used to achieve puncture resistance, then puncture resistance is improved, but the cost of packaging material increases significantly
Solution Approach 1:
The invention replaces expensive annealed biaxially oriented films with a combination of cheaper thermoplastic films that are partially laminated. The cost-effective films used in this invention include polyethylene, polypropylene, and other common thermoplastics that are significantly less expensive than annealed oriented films, while still providing adequate puncture resistance for the application.
Solution Approach 2:
By creating a composite structure of two standard thermoplastic films, the invention achieves puncture resistance that would otherwise require expensive specialized materials. The composite approach allows use of economical materials while obtaining the mechanical performance of premium materials through structural design rather than material selection alone.
3Strength
If two thermoplastic films are fully laminated to each other, then puncture resistance is improved, but the web cannot be hot formed as a single unit
Solution Approach 1:
Instead of fully laminating the two films across their entire surfaces, the invention uses partial lamination where only certain areas of the films are bonded together. This partial action allows the unlaminated areas to separate and form into cavities during hot forming, while the laminated areas provide structural integrity and puncture resistance. The pattern of partial lamination balances formability and strength requirements.
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 puncture resistance comparable to annealed biaxially oriented films at a lower cost, allowing for effective packaging of hard food items with sharp edges, including bones, while maintaining the ability to form into deep cavities, thus reducing the risk of leakage and contamination.
Implementation Method 1
the partially laminated web be capable of being formed into cavities of substantial depth by being vacuum drawn into a mold
Implementation Method 2
a portion of a second thermoplastic web is heat sealed over the open mouth of the cavity
Implementation Method 3
the partially laminated web be capable of being formed into cavities of substantial depth by being vacuum drawn into a mold with it being especially preferred that the double wall web be capable of draws of about 2 inches or greater
Implementation Method 4
a portion of a second thermoplastic web is heat sealed over the open mouth of the cavity
Data Source
AI summary
The present disclosure is concerned with packages formed from thermoformable webs with improved puncture resistance suitable for use in semi-automatic horizontal form fill and seal (HFFS) packaging machines and a process for packaging hard food items with sharp angular surfaces using such webs in such machines. The webs have a double wall partially laminated structure. The structure is conveniently formed by adhesively laminating two component films in a face to face configuration using a pattern of adhesive which leaves a substantial portion of the two facing surfaces unlaminated. The lamination just needs to be sufficient that the two component films will hot form together when they are vacuum drawn into a die to form a cavity for packaging the food items. The lamination pattern can vary from just edge strips to the edge strips and a honey comb pattern or a pattern of dots over the facing surfaces between the edge strips.