Hydroxyalkylcellulose Rheology Modifier for Coating Misting
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Solution Overview
Problem
The pigmented metering size press method for applying paper coatings often experiences severe misting issues, leading to wasteful depletion of coating and cleanup challenges, which has hindered its large-scale industrial adoption due to the ineffectiveness of commonly used rheology modifiers in reducing this problem.
Innovation Solution
Incorporating water-soluble hydroxyalkylcellulose (HAC) or alkylhydroxyalkylcellulose (AHAC) into the coating formulation at a specific dosage, applied via roller metering size press, significantly reduces misting and enhances fiber coverage, opacity, and brightness of the coated paper.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional rheology modifiers (CMC, guar gum, sodium alginate, HEC) are used in pigmented metering size press coating, then the coating can be applied to paper web, but severe misting occurs during application
Solution Approach 1:
The patent changes the chemical parameters of the rheology modifier by using hydroxypropylcellulose (HPC) with specific substitution degrees (0.2-0.8) and molecular weights (50,000-500,000), which fundamentally alters the coating's rheological behavior and reduces misting compared to traditional modifiers like CMC or HEC
Solution Approach 2:
The invention uses composite coating formulations that combine HPC with specific binders (styrene-butadiene latex, acrylic latex, or polyvinyl acetate) and pigments (kaolin, calcium carbonate) to create a synergistic system that controls misting while maintaining coating quality
2Object-generated harmful factors
If coating formulation is strictly controlled to minimize misting, then misting is reduced, but equipment complexity and processing control requirements increase
Solution Approach 1:
The HPC-based coating formulation is self-regulating in terms of misting control, eliminating the need for complex equipment adjustments or strict processing controls. The rheological properties of HPC automatically maintain optimal coating behavior under varying operating conditions
3Force
If hydroxyethylcellulose (HEC) is used as rheology modifier, then coating viscosity is controlled, but misting is not significantly reduced
Solution Approach 1:
The patent changes from HEC to HPC, altering the chemical structure parameters (hydroxypropyl substitution vs. hydroxyethyl substitution) which fundamentally changes the rheological response and misting behavior while maintaining viscosity control capabilities
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 use of HAC or AHAC in the coating formulation effectively minimizes misting, improves runnability, and enhances optical properties of the coated paper, making the process more commercially viable and efficient compared to traditional methods.
Implementation Method 1
adding a water-soluble hydroxyalkylcellulose (HAC) with an alkyl moiety of 1 to 4 carbons, or water soluble alkylhydroxyalkylcellulose (AHAC) with an alkyl hydrophobe of 1 to 24 carbons to a wet coating formulation in a n amount equal to or greater than 0.15 parts HAC or AHAC based on pigment content of the coating
Data Source
AI summary
Pigmented coated paper is prepared by adding a water-soluble hydroxyalkylcellulose (HAC) with an alkyl moiety of 1 to 4 carbons, or water soluble alkylhydroxyalkylcellulose (AHAC) with an alkyl hydrophobe of 1 to 24 carbons to a pigmented wet coating formulation in an amount equal to or greater than 0.15 parts HAC or AHAC based on pigment content of the coating and applying the pigmented wet coating formulation to a moving paper web via roller metering size press, wherein the use of HAC or AHAC in the pigmented coating significantly reduce misting of the coating during application as compared to the control condition with no HAC or AHAC added.