Microdomained Emulsion Polymers for Pressure-Sensitive Adhesives
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Solution Overview
Problem
Current methods for synthesizing microdomain structured polymer particles for pressure-sensitive adhesives are limited in achieving high poly-styrenic microdomain content without compromising adhesive properties, and existing processes face challenges in controlling morphology, especially in large batch preparations.
Innovation Solution
An aqueous emulsion polymer comprising a first domain with a low glass transition temperature and a non-crosslinked second domain with a high styrenic monomer content, where the second domain ranges from 50 to 100 wt% styrenic monomer, is synthesized through emulsion polymerization without the use of crosslinking monomers, allowing for a continuous addition of the second monomer emulsion with a cofeed of initiator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If swelling polymerization technique is used to synthesize microdomain structured polymer particles, then adhesive properties are maintained, but microdomain content cannot be increased due to inability to control morphology in microdomain forming stage
Solution Approach 1:
The polymerization process is divided into two distinct stages: first stage polymerization to form the continuous matrix, and second stage polymerization to form discrete microdomains. This segmentation allows independent control of each stage, enabling high microdomain content while maintaining morphology control through sequential monomer addition and initiator feeding.
Solution Approach 2:
The continuous matrix is formed first through first stage polymerization before the microdomain forming stage. This preliminary action establishes the continuous phase structure that will embed the subsequent microdomains, ensuring proper morphology control while allowing high microdomain content to be introduced in the second stage.
2Quantity of substance
If high poly-styrenic microdomain content is achieved, then adhesive properties are enhanced, but control of morphology becomes difficult in large batch preparation
Solution Approach 1:
The second monomer emulsion is continuously added to the reactor during the second stage polymerization, maintaining continuous useful action throughout the process. This continuous addition method, combined with cofeed of initiator, ensures uniform distribution and controlled morphology even in large batch preparations, making the process scalable and easy to manufacture.
3Quantity of substance
If crosslinking monomer is used to form microdomains, then microdomain content increases, but core/shell structures are generated which adversely affect domain structure properties
Solution Approach 1:
The harmful crosslinking monomer is completely removed from the system. Instead, the invention uses a non-crosslinking approach where the second monomer emulsion (50-100 wt% styrenic monomer) is continuously added with cofeed of initiator, forming microdomains without crosslinking. This extraction of the harmful component eliminates core/shell structure formation while maintaining high microdomain content and stable domain structure.
4Quantity of substance
If high styrenic monomer content is used, then microdomain content increases, but safety issues arise
Solution Approach 1:
The styrenic monomer is continuously added in controlled amounts during the second stage polymerization rather than introduced all at once. This continuous addition method, combined with cofeed of initiator, maintains safe handling conditions while achieving the desired high styrenic monomer content (50-100 wt%) in the final polymer product, eliminating safety issues associated with high monomer concentrations during processing.
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 approach enables the formation of polymer particles with a high content of poly-styrenic microdomains, enhancing adhesive properties such as shear resistance and water resistance while reducing raw material costs and avoiding safety issues associated with high styrenic monomer content.
Implementation Method 1
emulsion polymerization in a reactor of a first monomer feed comprising from acrylic monomer selected from the group consisting of (meth)acrylic acid, alkyl (meth)acrylate, (meth)acrylamide, (meth)acrylonitrile, hydroxyalkyl (meth)acrylate, and mixtures thereof; and continuous addition of a second monomer emulsion comprising from 50 to 100 wt% of a styrenic monomer to the reactor with cofeed of initiator
Data Source
AI summary
A microdomained aqueous emulsion polymer is provided. The polymer comprises a first domain having a Tg of from -80 to -10°C and comprising from 80 to 100 wt% of acrylic monomer; and a non-crosslinked second domain having a Tg of from 50 to 120°C and comprising, as polymerized unit and based on the weight of the second domain, from 50 to 100 wt% of styrenic monomer; wherein the content of the second domain ranges from greater than 6 wt% to 30 wt% of the total weight of the first domain and the second domain.. The polymer is suitable for applications including adhesives and binders, especially for pressure sensitive adhesives.