Dual-Polymer Barrier Coating for Flexible Paper and Board
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Solution Overview
Problem
Conventional surface treatments using polymers with high crystallinity for paper and board result in brittle coatings that break easily, while those with low crystallinity compromise barrier properties and cause equipment contamination, and biobased/biodegradable polymers exacerbate these issues with blocking and tackiness.
Innovation Solution
A dual-coating method where a biobased/biodegradable polymer with low crystallinity is protected by a second polymer with higher crystallinity, applied simultaneously without intermediate drying, followed by impingement drying to form a non-tacky, durable barrier layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polymer with high crystallinity is used for surface treatment, then barrier properties are improved, but the coating becomes brittle and breaks easily during converting steps
Solution Approach 1:
The invention uses a composite coating system with multiple layers: a first layer comprising a biobased/biodegradable polymer (providing flexibility and sustainability) and a second layer comprising a different polymer (providing barrier properties). This composite structure allows each layer to contribute its strengths, resolving the contradiction between barrier performance and flexibility.
2Strength
If a polymer with low crystallinity is used for surface treatment, then coating flexibility is improved, but barrier properties are reduced and equipment contamination increases
Solution Approach 1:
The dual-layer coating system assigns the low-crystallinity biobased polymer to the first layer for flexibility and the higher-crystallinity polymer to the second layer for barrier properties, thus achieving both flexibility and effective barrier protection without equipment contamination.
3Adaptability or versatility
If biobased/biodegradable polymers are used for surface treatment, then sustainability is improved, but blocking tendency and tackiness increase causing process disruptions
Solution Approach 1:
The invention combines a biobased/biodegradable polymer in the first layer with a complementary polymer in the second layer that provides anti-tack and anti-blocking properties. This composite approach maintains the sustainability benefit while eliminating the harmful blocking tendency through the synergistic effect of the two polymer layers.
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 coating with enhanced barrier properties, prevents equipment contamination, and increases the use of sustainable materials without process disruptions.
Implementation Method 1
at least a first coating layer and a second coating layer are applied on the first large surface of the substrate by curtain coating
Implementation Method 2
the coating layers are applied simultaneously by curtain coating on the first large surface of the substrate, without an intermediate drying between the first coating layer and the second coating layer
Data Source
AI summary
The invention relates to a sheet-like product, such as paper, board or the like, which comprises a substrate comprising cellulosic fibres and having a first large surface, wherein at least a first coating layer and a second coating layer are applied on the first large surface of the substrate by curtain coating to form a barrier coating. The second coating layer forms the surface of the sheet-like product. The first coating layer comprises a first polymer having a first crystallization degree and a first melting point, and the second coating layer comprises a second polymer having a second crystallization degree and a second melting point. The second crystallization degree and/or the second melting point is higher than the first crystallization degree and/or the first melting point of the first polymer.