Hollow Core Shell Emulsion Polymerization Using Ceiling Temperature Monomers
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Solution Overview
Problem
Existing processes for preparing hollow organic particles with a core/shell structure face challenges such as prolonged cycle times and weakening of the shell due to the use of monomers as plasticizers, which can lead to premature reactions and shell destruction.
Innovation Solution
A multistage emulsion polymerization process is employed, involving a seed, swell seed, and multiple shells with specific monomer compositions and a plasticizer monomer having a ceiling temperature below 181°C, allowing for high monomer concentrations at the time of swelling without the need for polymerization inhibitors, thereby avoiding shell destruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If monomers are used as plasticizers to facilitate swelling, then swelling is enabled, but premature reactions occur and shell strength is weakened
Solution Approach 1:
The patent introduces a ceiling temperature parameter for selecting plasticizer monomers. By choosing monomers with ceiling temperatures below the swelling temperature, the system ensures that plasticization occurs without triggering premature polymerization reactions, thus maintaining shell strength while enabling swelling.
Solution Approach 2:
The patent uses a specifically selected plasticizer monomer as an intermediary substance that facilitates swelling without causing harmful side reactions. This intermediary role is achieved by selecting monomers whose ceiling temperature is below the swelling temperature, allowing them to act as effective plasticizers without undergoing premature polymerization.
2Reliability
If polymerization inhibitors are added to prevent premature reactions, then reaction control is improved, but monomer concentration is reduced and shell stabilization is delayed
Solution Approach 1:
The patent converts the potential harm of premature polymerization into a benefit by selecting plasticizer monomers with ceiling temperatures below the swelling temperature. This ensures that these monomers remain stable during swelling and only polymerize later when they can effectively stabilize the shell, eliminating the need for inhibitors.
Solution Approach 2:
By changing the selection criterion for plasticizer monomers from general reactivity control to specific ceiling temperature requirements, the patent achieves both reaction control and high monomer concentration. The ceiling temperature parameter ensures monomers remain stable during swelling but can polymerize effectively later for shell stabilization.
3Reliability
If swelling temperature is lowered to prevent monomer reaction, then premature reactions are avoided, but plasticizing effect is not fully exploited and cycle time increases
Solution Approach 1:
The patent changes the temperature selection criterion by introducing ceiling temperature as a key parameter. By selecting plasticizer monomers with ceiling temperatures below the swelling temperature, the system can operate at higher swelling temperatures that fully exploit the plasticizing effect while preventing premature reactions through the inherent thermal stability provided by the ceiling temperature constraint.
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
This process enables efficient swelling and stabilization of the shell, maintaining high monomer concentrations at the optimal time, preventing premature reactions and ensuring the structural integrity of the hollow particles.
Implementation Method 1
the glass transition temperature, determined by the Fox equation, of the core stage polymer is between -20° C. and 150° C.
Implementation Method 2
the shell is plasticized by the addition of monomers or organic solvents
Implementation Method 3
The method that is preferred, however, on both environmental and economic grounds, is the osmotic swelling of specific core/shell particles
Implementation Method 4
it is subsequently swollen, at a temperature of or above the glass transition temperature of the shell, with ammonia or another volatile base
Implementation Method 5
there must be no notable reaction of the monomer. Measures taught in pursuit of this objective include waiting for the free-radical initiator to have been fully consumed by reaction
Data Source
AI summary
The present invention provides a process for preparing emulsion polymer particles of a hollow core/shell structure in the presence of a monomer plasticizer having a ceiling temperature less than 181° C. wherein a polymerization inhibitor or reducing agent is not added to the aqueous emulsion of the core shell particles during the neutralization and swelling stage. The obtained core shell particles are useful in paints, paper coatings, foams, and cosmetics.