Coated Paper for Wet Labels with Controlled Moisture and Fiber Structure
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Solution Overview
Problem
Coated papers used for wet labeling of bottles face issues with label alignment, adhesion, and reliability due to their inherent rigidity and low compression, leading to incomplete contact and potential slippage, especially on curved surfaces like bottle necks.
Innovation Solution
A process for producing coated paper with a high proportion of long fiber pulp, controlled water absorption, and specific wet elongation properties, combined with a cast-coating process that includes a high-gloss press treatment and optional metal layer application, to enhance label flexibility and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If coated paper with low compression and high fiber integrity is used, then paper strength and structural stability are improved, but label flexibility and adaptability to curved surfaces deteriorate
Solution Approach 1:
The invention changes the physical-chemical parameters of the paper by controlling the moisture content during production (2.5-7% absolute moisture) and specifying water absorption capacity (Cobb 10: 5-20 g/m²). This creates a paper that maintains structural integrity while having controlled flexibility when wet, allowing it to adapt to curved bottle surfaces without compromising strength.
Solution Approach 2:
The invention uses a composite structure with a base paper containing specific fiber compositions (at least 25% long fiber pulp) combined with a coating layer. This composite structure provides both the strength from the fiber network and the controlled flexibility from the coating, resolving the contradiction between rigidity and adaptability.
2Stability of the object's composition
If label paper with high rigidity is used, then structural stability is improved, but label adhesion and contact completeness on curved surfaces deteriorate
Solution Approach 1:
The invention applies parameter changes by controlling the paper's moisture content (2.5-7% absolute moisture) and water absorption capacity (Cobb 10: 5-20 g/m²). The paper is produced with controlled moisture to maintain stability, but absorbs water during the labeling process to become more flexible and adhesive, ensuring complete contact with curved surfaces while maintaining structural integrity.
3Productivity
If conventional coating processes are used, then production efficiency is improved, but label alignment precision and wrapping behavior deteriorate
Solution Approach 1:
The invention modifies the coating process parameters by controlling the absolute moisture content (2.5-7%) and water absorption capacity (Cobb 10: 5-20 g/m²) of the paper. These parameter changes enable the paper to exhibit specific wrapping behavior and alignment precision during labeling while maintaining production efficiency, as the controlled moisture content allows for standard coating processes without requiring additional precision steps.
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 resulting paper ensures improved label alignment and adhesion on bottles, reducing slippage and downtime in labeling systems, while maintaining strength and preventing wrinkles, thus increasing the reliability of the labeling process.
Implementation Method 1
The coating improves the water absorption of the back, so that water penetration reduces the rigidity of the base material
Data Source
AI summary
Disclosed is a method for producing a coated paper. Said method comprises the following steps: a) a raw paper is provided that has a minimum long-fiber cellulose content of 25 percent by weight, a minimum absolute humidity of 2.5 percent according to ISO 287, a water absorptiveness, according to ISO 535, of 5 bis 20 g/m2 following a test period of 10 s (Cobb10), and a maximum wet expansion (according to Fenchel) of 0 percent parallel to the direction of the machine and 3 percent perpendicular to the direction of the machine; b) ten to 40 g/m2 (oven-dry) of an aqueous coating material are applied to at least one face of the raw paper so as to obtain a coated raw paper; and c) the coated paper obtained in step b) is conditioned.