Aqueous Vinyl Aromatic–Diene Polymerization to Reduce 4-Phenylcyclohexene
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Solution Overview
Problem
Existing processes for producing aqueous polymer dispersions of vinylaromatic compounds and conjugated aliphatic dienes are unsatisfactory due to the formation of strong-smelling Diels-Alder adducts and the need for sulfur- or halogen-containing chain transfer agents, which affect performance and odor.
Innovation Solution
A process involving the continuous metering of inorganic and organic peroxides during polymerization, with the organic peroxide addition starting after a certain percentage of the vinyl aromatic compound has been introduced, and the use of a monomer feed process to minimize the formation of 4-phenylcyclohexene and eliminate the need for chain transfer agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chain transfer agents (peroxides) are used to prevent excessive crosslinking, then polymer performance is improved, but strong inherent odor is introduced
Solution Approach 1:
The patent removes sulfur- and halogen-containing chain transfer agents from the polymerization process, extracting the harmful components that cause odor while maintaining the necessary polymerization control through alternative means (monitoring and controlling monomer feed rates)
Solution Approach 2:
The patent employs temporary, non-persistent control mechanisms (monitoring monomer feed rates and using mild regulators like hydroperoxides that decompose easily) instead of persistent sulfur- or halogen-containing chain transfer agents, eliminating odor issues while maintaining polymerization control
2Quantity of substance
If heating to high temperatures is applied to reduce residual monomer content, then monomer conversion is improved, but crosslinking reactions increase
Solution Approach 1:
The patent implements dynamic control of the polymerization process by continuously monitoring monomer feed rates and adjusting conditions in real-time, allowing the process to adapt between polymerization and termination phases without requiring high-temperature heating that would cause crosslinking
Solution Approach 2:
The patent employs feedback mechanisms to monitor monomer consumption and feed rates, enabling precise control of polymerization progression and allowing termination to occur at optimal points before crosslinking can occur, without requiring high-temperature treatment
3Productivity
If oil-soluble radical initiators are introduced initially, then polymerization initiation is improved, but high proportion of 4-phenylcyclohexene is formed
Solution Approach 1:
The patent performs preliminary characterization of monomers and controls their introduction sequence, ensuring that polymerization initiates properly while preventing the formation of 4-phenylcyclohexene by controlling the timing and conditions of monomer addition
Solution Approach 2:
The patent changes key process parameters including monomer feed rates, temperature profiles, and initiator addition timing to optimize polymerization initiation while suppressing the formation of unwanted 4-phenylcyclohexene side products
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 process results in aqueous polymer dispersions with reduced 4-phenylcyclohexene content, minimal odor, and improved performance characteristics, suitable for applications such as binders, adhesives, and paper coating slips.
Implementation Method 1
a process for producing an aqueous polymer dispersion by radically initiated aqueous emulsion polymerization by reacting in an aqueous medium (a) 40 to 75 parts by weight at least one vinyl aromatic compound and (b) 24.9 to 59.9 parts by weight at least one conjugated aliphatic diene
Implementation Method 2
polymerized by a monomer feed process in the presence of at least one inorganic peroxide and at least one organic peroxide
Data Source
AI summary
The present invention relates to a method for preparing an aqueous polymer dispersion by means of radical-initiated aqueous emulsion polymerisation, by polymerising (a) 40 to 75 parts by weight of at least one vinyl aromatic compound and (b) 24.9 to 59.9 parts by weight of at least one conjugated aliphatic diene, (c) 0.1 to 10 parts by weight of at least one monomer containing acid groups and (d) 0 to 20 parts by weight of at least one other monoethylenically unsaturated monomer, wherein the amounts of the monomers (a) to (d) add up to 100 parts by weight, in an aqueous medium according to a monomer feed process in the presence of at least one inorganic peroxide and at least one organic peroxide, with the proviso that: - the continuous metering of the inorganic peroxide starts at the same time as the continuous metering of the vinyl aromatic compound; - the metering of the organic peroxide is started at a time at which at least 5% and at most 20% of the vinyl aromatic compound have already been added in a continuous mass flow under polymerisation conditions; and - optionally a partial quantity of the inorganic peroxide is provided. The invention also relates to the aqueous polymer dispersions prepared according to the method and to the use thereof as a binder, adhesive, sizing agent for fibres, for producing coatings, or for producing a paper coating slip.