Starch-Containing Polymer Dispersions for Paper Sizing
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Solution Overview
Problem
The paper industry requires novel and efficient sizing compositions for paper, board, and cardboard that offer improved sizing effects while maintaining storage stability, which existing starch-containing polymer dispersions do not adequately provide.
Innovation Solution
Finely divided starch-containing polymer dispersions are obtained through free radical emulsion polymerization using ethylenically unsaturated monomers, redox initiators, and degraded starch, with specific monomer ratios and the inclusion of terpene-containing chain-transfer agents, optionally with aluminium compounds, to enhance sizing and storage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing starch-containing polymer dispersions are used for paper sizing, then sizing effect is provided, but storage stability is insufficient
Solution Approach 1:
The patent applies parameter changes by carefully controlling the molecular weight of starch (10,000-100,000 g/mol), the ratio of styrene to alkyl (meth)acrylate monomers (15-65% and 35-80% respectively), and the amount of chain-transfer agent (0.01-5% based on monomers). These parameter optimizations resolve the contradiction by achieving both improved storage stability and dispersion stability simultaneously
Solution Approach 2:
The patent creates a composite polymer system combining styrene, alkyl (meth)acrylate monomers, and degraded starch through emulsion polymerization. The starch acts as both a stabilizer and sizing agent, while the polymer matrix provides structural integrity. This composite approach resolves the contradiction between storage stability and dispersion stability by creating a synergistic system where each component compensates for the limitations of the others
2Reliability
If terpene-containing chain-transfer agents are used in polymerization, then sizing effect is significantly increased, but molecular weight control becomes more complex
Solution Approach 1:
The patent uses terpene-containing chain-transfer agents (such as terpinolene or α-terpinene) in controlled amounts (0.01-5% based on total monomers) to regulate molecular weight and enhance sizing effect. The specific parameter optimization of terpene content and type resolves the contradiction by achieving improved sizing performance while maintaining manageable process complexity through precise dosage control
Solution Approach 2:
The terpene-containing chain-transfer agent acts as an intermediary substance that mediates between the monomers and the growing polymer chains. It transfers chain ends between active and dormant species, controlling molecular weight and enhancing the sizing effect without requiring complex process equipment. This intermediary role resolves the contradiction by providing a simple chemical mechanism for achieving complex performance goals
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 a significantly increased sizing effect and improved storage stability, providing better performance compared to prior art, even when applied in small amounts, especially on uncoated wood-free papers.
Implementation Method 1
emulsion polymerization of ethylenically unsaturated monomers in the presence of at least one redox initiator
Implementation Method 2
free radical emulsion polymerization of ethylenically unsaturated monomers
Implementation Method 3
polymerization being carried out in the presence of at least 0.01 % by weight, based on the monomers used, of at least one chain-transfer agent
Data Source
AI summary
A finely divided, starch-containing polymer dispersion which is obtainable by free radical emulsion polymerization of ethylenically unsaturated monomers in the presence of at least one redox initiator and starch, wherein (a) from 0 to less than 40% by weight of at least one optionally substituted styrene, (b) from greater than 60 to 100% by weight of at least one C1-C12-alkyl acrylate and/or C1-C12-alkyl methacrylate, (c) from 0 to 10% by weight of at least one other ethylenically unsaturated copolymerizable monomer, are used as the ethylenically unsaturated monomers, the sum (a) + (b) + (c) being 100% and being based on the active monomer content and (d) from 15 to 40% by weight of at least one degraded starch which has a molar mass Mw of from 1000 to 65 000 g/mol, based on the total weight of solids content of components (a) + (b) + (c) + (d), are used as the starch, and the polymerization being carried out in the presence of at least 0.01% by weight, based on the monomers used, of at least one terpene containing chain-transfer agent, and in which the polymer dispersion optionally comprises an aluminium compound. The use of the finely divided, starch-containing polymer dispersions as sizes for paper, board and cardboard is also claimed.