Dextrin-Based Coating Slips for Paper Stability
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Solution Overview
Problem
Current coating compositions for paper and cardboard, primarily based on styrene polymers, face issues with stability, high production costs due to non-renewable resources, and poor water retention, leading to inefficiencies in the coating process and suboptimal paper properties.
Innovation Solution
A coating color comprising a mixture of dextrins with specific weight-average molecular weights (between 30 and 90% of dextrin A with <500 kDa and 10 and 70% of dextrin B with >MA+50 kDa) is used, along with pigments and water, to enhance gloss, water retention, and machinability, improving the coating process and paper quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If styrene polymer-based coating compositions are used, then the coating process can be carried out with conventional materials, but the production costs increase due to non-renewable resources and stability issues
Solution Approach 1:
The patent changes the chemical composition parameters by replacing styrene polymers with dextrin-based binders. This substitution fundamentally alters the coating composition from petroleum-derived to renewable plant-based materials, thereby reducing production costs associated with non-renewable resources while improving stability through the natural properties of dextrin
Solution Approach 2:
The patent employs dextrin, a renewable and cost-effective binder derived from plant starches, to replace expensive styrene polymers. This approach uses readily available, biodegradable materials that reduce both production costs and environmental impact while maintaining coating performance
2Reliability
If styrene polymer-based coating compositions are used, then the coating can be applied, but water retention is poor leading to inefficiencies in the coating process
Solution Approach 1:
The patent modifies the water retention properties by incorporating dextrin-based binders that inherently possess superior water-holding capabilities compared to styrene polymers. This parameter change in binder chemistry directly improves water retention, allowing the coating composition to maintain optimal viscosity and application properties throughout the coating process without premature drying
3Ease of operation
If low molecular weight dextrins are used, then the coating composition becomes more fluid and easier to apply, but the gloss and quality of the coated paper decrease
Solution Approach 1:
The patent creates a composite dextrin binder system combining multiple dextrin fractions with different molecular weights. This composite approach integrates low molecular weight dextrins (providing fluidity and ease of application) with high molecular weight dextrins (providing gloss and quality), achieving a synergistic effect that satisfies both processing and performance requirements
Solution Approach 2:
The patent applies the concept of local quality by assigning different molecular weight dextrins to different functional roles within the coating composition. Low molecular weight dextrins are utilized for their flow properties during application, while high molecular weight dextrins are leveraged for their film-forming and gloss-enhancing properties in the final coating layer
4Manufacturing precision
If high molecular weight dextrins are used, then the gloss and paper quality improve, but the coating composition becomes more viscous and difficult to apply
Solution Approach 1:
The patent formulates a composite dextrin binder system that combines high molecular weight dextrins (for gloss and quality) with low molecular weight dextrins (for fluidity). This composite structure balances the opposing viscosity and performance requirements, creating a coating composition that is both easy to apply and produces high-quality results
Solution Approach 2:
The patent optimizes the molecular weight distribution parameters of the dextrin binder to achieve the desired balance between viscosity and performance. By carefully controlling the proportion and range of molecular weights in the dextrin mixture, the formulation achieves optimal flow characteristics for application while maintaining the gloss and quality benefits of higher molecular weight components
Data Source
AI summary
A coating slip including at least one pigment, water and: between 30% and 90% by weight of dextrin (A) of at least one dextrin having a weight-average molecular weight MA of less than 500 kDa; between 10% and 70% by weight of dextrin (B) of at least one dextrin having a weight-average molecular weight MB; the weight amounts of dextrins being relative to the total amount of the mixture of dextrins (A) and (B) in the composition, characterized in that MB is greater than MA+50 kDa. Also, a process for coating paper including a step of coating with this slip, and also to the paper obtained at the end of this process.