Paper Coating Slip Additive for Rheology and Water Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Paper coating compositions with high solids content face challenges in maintaining optimal rheology and water retention, leading to issues like rapid water absorption and stripy coating due to excessive viscosity and inadequate polymer content for binding.
Innovation Solution
A paper coating slip additive is developed through free-radical polymerization using a combination of acid monomers, associative monomers, and nonionic copolymerizable monomers, with tert-dodecyl mercaptan as a chain transfer agent to achieve a low weight average molecular weight, ensuring minimal viscosity increase and excellent water retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high solids content is used in paper coating composition, then productivity and cost efficiency are improved, but viscosity increases excessively and water retention deteriorates
Solution Approach 1:
The patent changes the molecular weight parameter of the polymeric thickener to below 200,000 (preferably not more than 150,000) by using tert-dodecyl mercaptan as chain transfer agent during polymerization. This parameter change allows the thickener to provide adequate water retention at lower concentrations, solving the contradiction between high solids content and water retention.
Solution Approach 2:
The patent uses a composite additive system comprising a polymeric thickener with specific low molecular weight characteristics combined with associative thickeners. This composite approach enables the coating composition to maintain optimal rheology and water retention even at high solids content, resolving the contradiction between productivity and reliability.
2Ease of operation
If polymeric thickener is added to adjust viscosity in high solids content coating slip, then rheology is improved, but water binding capacity becomes insufficient
Solution Approach 1:
The patent changes the molecular weight parameter of the polymeric thickener to below 200,000 by controlling the polymerization process with tert-dodecyl mercaptan as chain transfer agent. This low molecular weight configuration increases the number of polymer chains per unit mass, enhancing water binding capacity while maintaining adequate rheological control.
Solution Approach 2:
The patent creates local quality differences in the coating composition by using a specifically designed low molecular weight polymeric thickener that concentrates water binding functionality where needed, rather than relying on high molecular weight polymers that provide bulk viscosity but insufficient water binding at the molecular level.
3Productivity
If coating slip is applied to paper, then coating is deposited, but rapid water absorption occurs causing filter cake formation and stripy coating
Solution Approach 1:
The patent applies preliminary action by incorporating a low molecular weight polymeric thickener with superior water binding capacity into the coating composition before application. This pre-bound water remains available during the coating process, preventing rapid water absorption from the paper and subsequent filter cake formation, thereby ensuring uniform coating even at high application speeds.
4Ease of operation
If associative thickeners are used to establish rheological properties, then viscosity control is improved, but water retention is adversely affected
Solution Approach 1:
The patent creates a composite thickener system combining low molecular weight polymeric thickeners with associative thickeners. The low molecular weight component provides superior water binding capacity while the associative component contributes to rheological control. This composite approach resolves the contradiction between rheological properties and water retention by leveraging the complementary strengths of both thickener types.
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 additive maintains stable rheology and enhances water retention, preventing rapid water absorption and ensuring uniform coating, even in high-speed paper coating processes.
Implementation Method 1
The additive is formed by free-radical polymerization of (a) at least one acid monomer, (b) at least one associative monomer and (c) nonionic copolymerizable monomers
Implementation Method 2
tert-dodecyl mercaptan is used as chain transfer agent
Implementation Method 3
Associative monomers are monomers useful for preparing hydrophilic, water-soluble or water-swellable polymers having hydrophobic end or side groups. The interaction between hydrophobic end or side groups results in a high viscosity at low shear.
Data Source
AI summary
A paper coating slip additive obtainable by free-radical polymerization, its preparation and its use in paper coating compositions are described. The additive is formed from (a) acid monomers selected from ethylenically unsaturated C3 to C8 carboxylic acids, (b) associative monomers of the general formula H2C═CR1—COO-(EO)n—(PO)m—R2 where R1 is hydrogen or methyl, n is at least two, m is from zero to 50, EO is an ethylene oxide group, PO is a propylene oxide group and R2 is a C8-C30 alkyl group or a C8-C30 alkaryl group, and (c) nonionic copolymerizable monomers other than a) and b), wherein said additive has a weight average molecular weight of below 200 000 and wherein tert-dodecyl mercaptan is used as chain transfer agent.