Aqueous Polymer Dispersion for Paper Coating
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Solution Overview
Problem
Existing aqueous polymer dispersions based on copolymers of vinyl aromatics and conjugated aliphatic dienes, used as binders in paper coating slips, exhibit inadequate running behavior on high-speed machines and insufficient binding power.
Innovation Solution
Aqueous polymer dispersions with a mean particle size of 80 to 150 nm, obtained through free radical emulsion copolymerization of vinyl aromatic compounds, conjugated aliphatic dienes, ethylenically unsaturated acids, and other monoethylenically unsaturated monomers, in the presence of degraded starch with low intrinsic viscosity, using specific initiators and process conditions to enhance binding power and prevent coagulant formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If aqueous polymer dispersions with larger particle sizes (209-407 nm) are used, then the dispersions can be prepared with conventional processes, but the running behavior on high-speed machines is inadequate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size of polymer dispersions to the range of 80-150 nm, which is a significant reduction from conventional particle sizes (209-407 nm). This parameter optimization directly improves running behavior on high-speed machines while maintaining manufacturing feasibility through controlled emulsion polymerization processes.
2Strength
If polymer dispersions are prepared with conventional starch degradation products, then the preparation process is simplified, but the binding power is insufficient
Solution Approach 1:
The patent employs parameter changes by optimizing the degree of starch hydrolysis to achieve specific viscosity ranges (0.5-2.0 dL/g) and by controlling the monomer composition ratios. These parameter optimizations enhance binding power while keeping the emulsion polymerization process manageable and industrially feasible.
Solution Approach 2:
The patent creates composite materials by forming copolymers from multiple monomer components including styrene, butadiene, and vinyl aromatic compounds in specific ratios. This composite approach combines the advantages of different monomers to achieve superior binding power that cannot be obtained with single-monomer systems.
3Quantity of substance
If polymer dispersions are prepared with higher monomer concentrations, then the solids content is improved, but coagulant formation increases
Solution Approach 1:
The patent applies parameter changes by optimizing the starch to monomer ratio and controlling the hydrolysis degree of starch to achieve the desired solids content while preventing coagulation. By adjusting these parameters within specific ranges, the patent achieves high solids content dispersions with minimal coagulant formation.
Solution Approach 2:
The patent uses degraded starch as an intermediary substance that facilitates polymerization and stabilizes the emulsion system. The starch acts as a protective colloid and nucleation site, enabling high solids content to be achieved without coagulation by mediating between the monomers and the aqueous phase.
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 solution provides polymer dispersions with improved binding power and running behavior on high-speed machines, ensuring high pick resistance and solids content, while minimizing coagulum formation, thus enhancing their suitability as binders in paper coating slips.
Implementation Method 1
obtainable by free radical emulsion copolymerization of (a) from 19.9 to 80 parts by weight of at least one vinyl aromatic compound, (b) from 19.9 to 80 parts by weight of at least one conjugated aliphatic diene, (c) from 0.1 to 10 parts by weight of at least one ethylenically unsaturated acid
Implementation Method 2
in the presence of at least one degraded starch having an intrinsic viscosity ηi of less than 0.07 dl/g
Data Source
AI summary
Aqueous polymer dispersions based on copolymers of vinyl aromatics and conjugated aliphatic dienes having a mean particle size of from 80 to 150 nm, obtained by free radical emulsion copolymerization of(a) from 19.9 to 80 parts by weight of at least one vinyl aromatic compound,(b) from 19.9 to 80 parts by weight of at least one conjugated aliphatic diene,(c) from 0.1 to 10 parts by weight of at least one ethylenically unsaturated acid, and(d) from 0 to 20 parts by weight of at least one other monoethylenically Unsaturated monomer,the sum of the parts by weight of the monomers (a), (b), (c) and (d) always being 100, in an aqueous medium in the presence of at least one degraded starch having an intrinsic viscosity ηi of less than 0.07 dl/g with the use of at least 0.9% by weight, based on the monomers used altogether, of initiators selected from peroxodisulfates, peroxosulfates, azo initiators, organic peroxides, organic hydroperoxides and hydrogen peroxide, at least 30% by weight of the initiators being initially taken together with the degraded starch in the aqueous medium and the monomers and the remaining initiators being metered into this initially taken mixture under polymerization conditions.