Aqueous Polymer Dispersion for Paper Coating
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Solution Overview
Problem
Existing aqueous polymer dispersions used in paper coating applications suffer from high squeegee pressure, insufficient binding power, and undesirable by-products, limiting their use in high-purity applications and requiring complex cleaning processes.
Innovation Solution
Aqueous polymer dispersions are produced through radically initiated emulsion polymerization of vinyl aromatic compounds, acrylate monomers, and ethylenically unsaturated acids in the presence of seed latex and degraded starch, optimizing the composition and process conditions to achieve high binding force, low viscosity, and low doctor pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If starch degradation products with Mw of 2500 to 25,000 are used in emulsion polymerization, then the polymer dispersions can be produced, but they generate high squeegee pressure and cannot be used on modern high-speed paper coating systems
Solution Approach 1:
The patent changes the molecular weight parameter of the starch degradation products from the conventional range of 2500-25,000 Mw to a lower range of 500-2500 Mw. This parameter change reduces the viscosity and molecular size of the polymer chains, thereby reducing squeegee pressure during high-speed paper coating while maintaining the ease of manufacture through emulsion polymerization
2Ease of manufacture
If styrene and butadiene copolymers are used as binders, then the polymer can be produced, but undesirable by-products such as 4-PCH and 4-VCH arise during production
Solution Approach 1:
The patent extracts and eliminates the butadiene component from the monomer mixture, removing the source of harmful by-products (4-PCH and 4-VCH) that form through Diels-Alder reactions. The formulation uses only vinyl aromatic compounds, acrylate monomers, and ethylenically unsaturated acids, which do not generate these harmful by-products during polymerization
Solution Approach 2:
The patent converts the harmful Diels-Alder reaction pathway into a beneficial outcome by selecting monomers that undergo clean radical polymerization without forming cyclic by-products. The chosen monomer system (vinyl aromatic + acrylate + ethylenically unsaturated acid) provides excellent binding properties while eliminating contamination issues
3Ease of operation
If existing binder compositions are used, then the paper coating can be applied, but the binding power is insufficient
Solution Approach 1:
The patent creates a composite polymer system by copolymerizing three types of monomers: vinyl aromatic compounds (for adhesion), acrylate monomers (for flexibility and binding), and ethylenically unsaturated acids (for polarity and surface interaction). This composite approach achieves superior binding power while maintaining ease of coating application
4Object-affected harmful factors
If complex cleaning processes are implemented to remove by-products, then product purity can be improved, but the process complexity and cost increase
Solution Approach 1:
The patent takes preliminary action by selecting a monomer formulation that prevents the formation of harmful by-products from the start. By using vinyl aromatic compounds, acrylate monomers, and ethylenically unsaturated acids without butadiene, the harmful Diels-Alder reactions are prevented before they can occur, eliminating the need for complex post-production cleaning processes
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 polymer dispersions exhibit enhanced binding strength, high pick resistance, and reduced viscosity at high shear, enabling their use in high-speed paper coating systems with improved application properties and purity.
Implementation Method 1
radically initiated emulsion polymerization of (a) 19.9 to 80 parts by weight of at least one vinyl aromatic compound, (b) 19.9 to 80 parts by weight of at least one acrylate monomer selected from C1 to C10 alkyl acrylates and C1 to C10 alkyl methacrylates, (c) 0.1 to 10 parts by weight of at least one ethylenically unsaturated acid
Implementation Method 2
the emulsion polymerization taking place in an aqueous medium in the presence of initiators, seed latex and at least one carbohydrate compound
Data Source
AI summary
Aqueous polymer dispersions and processes for preparing them are described. The polymer dispersions can be obtained by free-radically initiated emulsion polymerization of from 19.9 to 80 parts by weight of vinylaromatic compounds, from 19.9 to 80 parts by weight of acrylate monomers selected from among C1-C10-alkyl acrylates and C1-C10-alkyl methacrylates, from 0.1 to 10 parts by weight of ethylenically unsaturated acids and from 0 to 20 parts by weight of other ethylenically unsaturated monomers, wherein the emulsion polymerization is carried out in an aqueous medium in the presence of free-radical-forming initiators, seed latex and at least one carbohydrate compound in the form of a degraded starch. The polymer dispersions are particularly suitable for producing paper coating compositions.