Paper Food Packaging Primer for Crack-Resistant Barrier
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Solution Overview
Problem
Paper-based packaging materials face challenges in maintaining high barrier performance under mechanical stress due to the rough surface of paper, which allows gas penetration, and the hygro-expansion of paper during PVD coating, leading to defects and cracks in the inorganic layer.
Innovation Solution
A composite packaging material is developed with a primer based on an aqueous polymer dispersion applied directly to the paper substrate, combined with a metal oxide layer and/or a hybrid polymer layer made of organically modified silica, which enhances barrier performance while being flexible and environmentally friendly, allowing for folding and kinking without cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PVD coating is applied to paper substrates to increase barrier performance, then the barrier performance is improved, but the coating contains defects due to the rough paper surface that allow gas penetration
Solution Approach 1:
A pre-coating layer is applied to the paper substrate before the PVD metal oxide coating to smooth the rough surface. This preliminary action creates a uniform base that enables the subsequent barrier coating to be applied without defects, resolving the contradiction between achieving high barrier performance and maintaining coating quality.
Solution Approach 2:
The pre-coating layer acts as an intermediary between the rough paper substrate and the PVD metal oxide coating. This intermediate layer bridges the surface irregularities, allowing the barrier coating to form a continuous, defect-free layer that maintains high barrier performance.
2Reliability
If PVD coating is applied under dry conditions to increase barrier performance, then the barrier performance is improved, but the paper shrinks and expands after coating causing tension and cracks in the inorganic layer
Solution Approach 1:
The pre-coating layer serves as a cushioning layer that absorbs and compensates for the dimensional changes of the paper substrate during hygro-expansion. This beforehand cushioning prevents the transmission of stress to the brittle metal oxide coating, avoiding cracks and maintaining layer integrity.
Solution Approach 2:
The pre-coating layer acts as a flexible buffer between the paper substrate and the rigid metal oxide coating. This flexible layer accommodates the expansion and contraction of the paper without transmitting damaging stresses to the inorganic barrier layer, maintaining its integrity.
3Ease of operation
If the metal oxide layer is made thin to avoid cracks and chips, then the flexibility is improved, but the barrier performance may be compromised
Solution Approach 1:
The invention uses a composite structure combining a pre-coating layer with a thin metal oxide barrier layer. The pre-coating provides mechanical support and flexibility, while the thin metal oxide layer provides barrier performance. Together, they achieve both flexibility and effective barrier properties without requiring a thick, brittle coating.
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 composite maintains high barrier performance under mechanical stress, is flexible, and prevents gas penetration, making it suitable for food packaging and other applications, with improved adhesion and crack resistance due to the buffer layers and covalent bonding between the layers.
Implementation Method 1
The roughness of the paper can be reduced by pre-coatings. A hybrid polymer layer made of inorganic-organic polymers based on silanes can serve as a smooth planarization layer. The low viscosity of the paints and the effects of drying result in very smooth surfaces
Implementation Method 2
The barrier performance can be increased for polymeric substrate films by applying e.g. B. metal oxides can be increased by physical vapor deposition (PVD)
Implementation Method 3
A hybrid polymer layer made of inorganic-organic polymers based on silanes can serve as a smooth planarization layer
Implementation Method 4
The network must be sufficiently flexible for aspects [1-1] to [1-5]. The composite is flexible, so that the barrier performance is largely retained under mechanical stress
Implementation Method 5
with improved adhesion and crack resistance due to the buffer layers and covalent bonding between the layers
Data Source
AI summary
Composite as food packaging material, comprising a substrate consisting of a paper carrier and a primer based on an aqueous polymer dispersion, and a barrier layer comprising a metal oxide layer and/or a hybrid polymer layer of an organically modified silica (hetero)polycondensate; method for producing the composite; and use of the composite as food packaging.