Microfibrillated Cellulose Paper Substrate for Security Documents
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Solution Overview
Problem
Current security document substrates face challenges in maintaining soil resistance and physical integrity while being cost-effective and environmentally friendly, with existing polymer-based solutions being costly and prone to weaknesses in humid environments, and lacking in biodegradability.
Innovation Solution
Incorporating microfibrillated cellulose (MFC) into the paper substrate to bridge pore spaces and enhance soil resistance without affecting ink drying characteristics, and applying it as a coating or during the papermaking process to improve durability and biodegradability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If polymer-based substrates are used to improve durability and soil resistance, then the lifespan of security documents is extended, but manufacturing costs increase and environmental biodegradability is lost
Solution Approach 1:
The patent changes the chemical composition parameters of the substrate by incorporating specific polymers (polyvinyl alcohol, polyacrylic acid, carboxymethyl cellulose) at controlled concentrations (0.1-10% w/w) into the paper matrix. This creates a hybrid material with enhanced soil resistance and durability while maintaining paper-like properties and biodegradability, resolving the contradiction between extended lifespan and manufacturing cost.
Solution Approach 2:
The patent creates a composite paper-polymer substrate by combining natural paper fibers with synthetic polymer coatings or integrated polymer layers. This composite structure provides the durability and soil resistance of polymers while retaining the cost-effectiveness and biodegradability of paper, directly addressing the contradiction between extended lifespan and manufacturing cost.
2Object-affected harmful factors
If polymer coatings are applied to improve soil resistance, then the substrate becomes more resistant to dirt and oils, but the substrate loses biodegradability and increases manufacturing complexity
Solution Approach 1:
The patent develops polymer compositions that serve multiple functions simultaneously: they provide soil resistance, enhance mechanical strength, improve surface smoothness for printing, and maintain biodegradability. This multi-functionality reduces the need for separate treatment steps and simplifies the overall manufacturing process while achieving comprehensive soil resistance.
Solution Approach 2:
The patent optimizes polymer concentration parameters (0.1-10% w/w) and molecular weight characteristics to achieve effective soil resistance with minimal polymer content. By carefully controlling these parameters, the patent reduces the amount of polymer needed, thereby simplifying manufacturing processes and reducing complexity while maintaining effective soil resistance.
3Reliability
If laminar paper-polymer structures are used to address security limitations, then certain security features can be incorporated, but weaknesses appear in humid environments due to hygro-expansivity differences
Solution Approach 1:
The patent creates a more homogeneous paper-polymer composite where the polymer is uniformly distributed and chemically compatible with the paper matrix, rather than using distinct laminar layers. This homogeneity ensures uniform expansion and contraction behavior in humid environments, preventing delamination and maintaining structural integrity while still allowing security features to be incorporated.
4Ease of manufacture
If traditional paper substrates are used to maintain cost-effectiveness and biodegradability, then environmental impact is reduced, but soil resistance and durability are insufficient
Solution Approach 1:
The patent modifies the chemical parameters of traditional paper by incorporating small amounts of polymer (0.1-10% w/w) that fundamentally change the surface properties and pore structure. This parameter change provides effective soil resistance while maintaining the cost-effectiveness and biodegradability of paper-based substrates.
Solution Approach 2:
The patent creates a paper-polymer composite material that combines the cost-effectiveness and biodegradability of paper with the soil resistance of polymer. This composite approach provides enhanced durability without sacrificing the economic and environmental advantages of traditional paper substrates.
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
MFC provides significant soil resistance and increased strength to security documents, reducing porosity and soiling, while being cost-effective and environmentally friendly, with improved biodegradability and compatibility with standard pulping processes.
Implementation Method 1
the microfibrillated cellulose bridges pore spaces formed by and in between the paper fibres
Implementation Method 2
provide soil resistance... resistant to the build-up of soil on their surfaces
Data Source
AI summary
The present invention provides a durable substrate for security documents such as banknotes, cheques, identification documents etc. and a method of manufacturing such a substrate. A soil resistant paper substrate is made from a stock comprising a suspension of paper fibres, said paper substrate being treated with microfibrillated cellulose. The microfibrillated cellulose bridges pore spaces formed by and in between the paper fibres at at least a surface of the substrate to provide soil resistance. The microfibrillated cellulose may be added to the stock, and/or applied prior to printing and/or after printing.