Microwave Packaging Bag Steam Venting Mechanism
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Solution Overview
Problem
Packaging bags for microwave heating often suffer thermal damage due to high internal pressure and moisture content, leading to leakage and film degradation, despite the use of heat-resistant materials like polybutylene terephthalate-based films.
Innovation Solution
A multilayer film packaging bag with a steam releasing mechanism, featuring a base layer with low moisture content (<1.0%), a welding layer, and a barrier layer, where the steam releasing portion is designed to maintain internal pressure below 115 kPa during heating, using materials like polyester and polypropylene, and a vapor-deposited or coated barrier layer to enhance heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polybutylene terephthalate-based film with high heat resistance is used for the base layer, then thermal damage is reduced, but the packaging bag still suffers thermal damage under certain heating conditions and content properties
Solution Approach 1:
The patent employs a multilayer film structure comprising a base layer, welding layer, and barrier layer. The base layer uses polybutylene terephthalate for heat resistance, the barrier layer provides moisture and oil resistance, and the welding layer ensures proper sealing. This composite structure synergistically addresses thermal damage by combining materials with complementary properties, where each layer performs its specific function to protect the packaging bag under microwave heating conditions.
2Reliability
If the internal pressure is allowed to increase during heating, then steam release is delayed, but thermal damage and leakage occur
Solution Approach 1:
The patent incorporates a pre-designed steam releasing mechanism with a steam releasing portion of specific dimensions (maximal width 3-20 mm) positioned in the packaging bag structure. This mechanism is prepared in advance to activate automatically when internal pressure reaches a critical level during microwave heating, releasing steam and pressure before thermal damage can occur. The mechanism ensures timely pressure relief without requiring external intervention.
3Stress or pressure
If the steam releasing portion is made larger, then internal pressure is released more effectively, but leakage of contents may occur
Solution Approach 1:
The patent specifies precise dimensional parameters for the steam releasing portion, with a maximal width constrained to 3-20 mm. This parameter optimization balances two opposing requirements: the opening must be large enough to effectively release steam and pressure during heating, yet small enough to prevent leakage of viscous contents. The barrier layer with specific moisture content (<1.0%) further refines this balance by controlling the properties of released steam.
4Stability of the object's composition
If the moisture content of the multilayer film is high, then the film is more flexible, but thermal damage occurs during microwave heating
Solution Approach 1:
The patent specifies that the multilayer film must have a moisture content of not more than 1.0%, with the barrier layer having a moisture content of not more than 0.6% immediately after retort sterilization. This parameter control prevents excessive moisture from causing thermal damage during microwave heating, while the multilayer structure maintains necessary flexibility through material selection and layer configuration rather than moisture content.
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 effectively prevents thermal damage and leakage by controlling internal pressure and maintaining heat resistance, even with viscous contents containing metals and oils, as demonstrated in various examples where the packaging bags remain intact without holes or leakage.
Implementation Method 1
the multilayer film has a moisture content of not more than 1.0% in a state in which the packaging bag is filled with a content
Implementation Method 2
the packaging bag can prevent effectively thermal damage irrespective of the properties of the contents
Implementation Method 3
the packaging bag has an internal pressure kept to be not more than 115 kPa during a period from the time the internal pressure is released through the steam releasing portion as a result of an increase in the internal pressure caused by heating in a microwave oven
Implementation Method 4
either a vapor-deposited layer or a coating layer arranged to face the base layer
Implementation Method 5
either a vapor-deposited layer or a coating layer arranged to face the base layer
Data Source
AI summary
A packaging bag composed of a multilayer film and having a steam releasing mechanism. The multilayer film has at least a base layer and a welding layer and has a moisture content of not more than 1.0% in a state in which the packaging bag is filled with a content. The steam releasing mechanism has at least a steam releasing portion formed to have a maximal width of 3 to 20 mm. The internal pressure of the packaging bag is kept to be not more than 115 kPa during a period from the time the internal pressure is released through the steam releasing portion as a result of an increase in the internal pressure caused by heating in a microwave oven to the time the heating in the microwave oven finishes.