Paper Coating Composition Using Mixed Optical Whiteners
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Solution Overview
Problem
Existing paper coating compositions using optical whiteners exhibit a 'plateau' behavior where whiteness increases initially but eventually decreases due to whitener accumulation, limiting the maximum obtainable whiteness degree.
Innovation Solution
A composition comprising a mixture of tetrasulphonated and hexasulphonated triazinylaminostilbene optical whiteners, specifically formulated to achieve higher whiteness levels before the graying phenomenon occurs, with the hexasulphonated whitener present between 5% to 40% by weight, and preferred compounds having specific structural configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the concentration of optical whitener is increased to achieve higher whiteness degree, then the whiteness degree increases initially, but eventually decreases due to whitener accumulation (graying effect)
Solution Approach 1:
The patent segments the single optical whitener into a mixture of two different optical whiteners (first and second whiteners) with different saturation limits. This segmentation allows the system to exploit the different concentration-response characteristics of each whitener, extending the useful concentration range before graying occurs.
Solution Approach 2:
The patent changes the chemical parameters by selecting optical whiteners with different molecular structures and sulfonate group configurations (different formulas and substitution patterns). This parameter change results in different saturation behaviors, allowing one whitener to compensate when the other approaches saturation.
2Illumination intensity
If a single type of optical whitener is used, then the composition is simple, but the maximum obtainable whiteness is limited by the saturation point of that whitener
Solution Approach 1:
The patent merges two different optical whiteners into a single coating composition. The first and second optical whiteners work synergistically, with each contributing to the overall whiteness enhancement while having different saturation characteristics, thereby extending the maximum achievable whiteness degree.
Solution Approach 2:
The patent creates a composite optical whitening system by combining two distinct whiter compounds with different chemical structures and properties. This composite approach allows the system to achieve superior performance compared to either component alone, as the mixture maintains effectiveness across a broader concentration range.
3Illumination intensity
If the concentration of optical whitener exceeds the saturation limit, then no further improvement in whiteness is achieved, but graying or greening occurs due to accumulation
Solution Approach 1:
The patent applies preliminary action by selecting and pre-combining two optical whiteners with different saturation characteristics before application. This pre-planned combination ensures that as one whitener approaches saturation, the other is still in its effective range, preventing the graying effect before it can occur.
Solution Approach 2:
The patent implements a feedback mechanism through the differential saturation behavior of the two whiteners. As the concentration of one whitener increases and approaches its saturation point (where graying would occur), the relative contribution of the second whitener becomes more significant, effectively compensating and preventing the harmful graying effect.
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 composition achieves a higher whiteness degree than using either whitener alone, delaying the graying effect and maintaining optimal whiteness without the accumulation issues, as demonstrated by improved colorimetric coordinates in test samples.
Implementation Method 1
The present invention relates to a composition for manufacturing coated paper and cardboard having a high degree of whiteness by using optical whiteners
Data Source
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Figure 3
AI summary
The present invention relates to a coating composition for paper and cardboard comprising at least one white pigment, at least one polymeric ligand and at least one synthetic or natural co-ligand , and a mixture of optical whiteners.