Composite Coating Structure for Retort Food Packaging
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Solution Overview
Problem
Conventional coating layers lack sufficient gas barrier and water vapor barrier properties, particularly deteriorating after hot-water treatment such as retorting, limiting their use in food packaging materials and requiring an inexpensive and simple production method for stable performance.
Innovation Solution
A coating liquid is formed by mixing a phosphorus compound with an aluminum compound precipitated from an aluminate solution, with a specific mole ratio and heat treatment to create a composite structure with enhanced barrier properties, maintaining performance even after retorting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coating layers are used, then the coating can be applied to packaging materials, but the gas barrier properties and water vapor barrier properties are insufficient and deteriorate after hot-water treatment
Solution Approach 1:
The patent uses a composite coating layer comprising a polyvinyl alcohol base layer and a metal orthophosphate layer (aluminum, calcium, or magnesium orthophosphate). This composite structure combines the adhesive properties of polyvinyl alcohol with the barrier properties of metal orthophosphates, achieving both gas and water vapor barrier functions while maintaining stability after hot-water treatment and retorting
Solution Approach 2:
The patent specifies precise parameter ranges: metal orthophosphate content of 1-10 mass%, aluminum ion content of 0.1-5 mass%, and phosphorus ion content of 0.1-5 mass%. By controlling these parameters within specific ranges, the coating achieves optimal barrier properties and hot-water resistance without sacrificing other performance characteristics
2Reliability
If conventional coating methods are used, then the production process is simple, but the gas barrier properties and water vapor barrier properties are insufficient
Solution Approach 1:
The patent employs a two-stage coating process: first applying a polyvinyl alcohol base layer, then applying a metal orthophosphate-containing coating layer. This preliminary structuring ensures that the base layer provides adhesion and the subsequent layer provides barrier properties, achieving excellent gas and water vapor barrier performance through a systematic, yet straightforward, manufacturing process
3Temperature
If conventional coating layers are used, then the coating can be formed on packaging materials, but the hot-water resistance is insufficient and barrier properties deteriorate during retorting
Solution Approach 1:
The patent creates a composite structure where the polyvinyl alcohol base layer is combined with a metal orthophosphate layer. This composite provides superior hot-water resistance because metal orthophosphates form a heat-stable barrier that prevents the deterioration of gas and water vapor barrier properties during retorting and other hot-water treatments
Solution Approach 2:
The patent specifies that the metal orthophosphate content should be 1-10 mass% and the ratio of aluminum ion content to phosphorus ion content should be 1:9 to 9:1. These parameter controls ensure that the coating maintains its barrier properties at elevated temperatures during retorting while preventing excessive cross-linking or degradation
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 method produces a composite structure with excellent gas and water vapor barrier properties that remain effective after retorting, suitable for food packaging and other applications, offering improved stability and appearance.
Implementation Method 1
a dispersion liquid (S) of an aluminum compound (A) formed by adding an acid to an aluminate solution
Implementation Method 2
a layer (Y) formed by a reaction at least between the aluminum compound (A) and the phosphorus compound (B)
Data Source
AI summary
The method disclosed includes: a step (I) of preparing a dispersion liquid (S) including an aluminum compound (A); a step (II) of mixing the dispersion liquid (S) and a predetermined phosphorus compound (B) so as to prepare a coating liquid (U); a step (III) of applying the coating liquid (U) onto the base (X) so as to form a precursor layer of the layer (Y); and a step (IV) of subjecting the precursor layer to heat treatment at a temperature of 110°C or more so as to form the layer (Y). The aluminum compound (A) can be formed by adding an acid to a solution including an aluminate. The number of moles (NM) of aluminum atoms derived from the aluminum compound (A) and the number of moles (NP) of phosphorus atoms derived from the phosphorus compound (B) satisfy 0.8 ≤ (NM)/(NP) ≤ 4.5.