Polydiorganosiloxane Polyoxamide Block Copolymers for Adhesives
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Solution Overview
Problem
Siloxane polymers lack tensile strength, making it difficult to produce high-degree polymerization siloxane-based polyamides with larger polyorganosiloxane segments, and polydiorganosiloxane polyureas tend to degrade at elevated temperatures.
Innovation Solution
The development of polydiorganosiloxane polyoxamide block copolymers with a high fraction of polydiorganosiloxane segments, combined with a tackifier, which can be formulated as either pressure-sensitive or heat-activated adhesives, to enhance mechanical strength and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polydiorganosiloxane segments are increased in size and fraction to improve tensile strength, then mechanical strength is improved, but solubility parameters become significantly different making high degree of polymerization difficult to achieve
Solution Approach 1:
The patent changes the chemical parameters of the reaction system by introducing oxalate esters as coupling agents and using specific catalysts (tin octoate, dibutyltin dilaurate) to enable polymerization reactions between polydiorganosiloxane segments and diamines despite solubility parameter differences. This allows achieving high degrees of polymerization (n≥40) that were previously unattainable.
Solution Approach 2:
The patent uses oxalate esters as intermediary compounds that facilitate the coupling between polydiorganosiloxane segments and diamines. The oxalate ester acts as a bridge, enabling the formation of stable amide bonds while maintaining solubility and allowing high molecular weight copolymers to form despite the inherent solubility parameter mismatch between the polymer components.
2Reliability
If polydiorganosiloxane polyurea block copolymers are used to improve adhesive properties, then adhesive performance is improved, but thermal stability deteriorates at elevated temperatures (250°C or higher)
Solution Approach 1:
The patent changes the chemical structure parameter by replacing the urea linkage (—NH—CO—NH—) with an amide linkage (—NH—CO—) derived from oxalate ester coupling. This structural modification maintains the adhesive performance while significantly improving thermal stability, allowing the copolymers to withstand temperatures of 250°C or higher without degradation.
3Reliability
If known siloxane-based polyamide copolymers are used, then adhesive properties are achieved, but the fraction of polydiorganosiloxane soft segments is relatively low (no greater than about 30 units)
Solution Approach 1:
The patent employs a block copolymer architecture with well-defined segments: polydiorganosiloxane soft segments (n≥40) and polyamide hard segments. This segmentation allows the soft segments to provide adhesive properties and flexibility while the hard segments provide structural integrity, enabling a higher fraction of polydiorganosiloxane content than previously achieved in known copolymers.
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 polydiorganosiloxane polyoxamide copolymers exhibit improved mechanical strength, thermal stability, and resistance to degradation at high temperatures, while maintaining desirable properties like low glass transition temperature and resistance to ultraviolet radiation.
Implementation Method 1
The siloxane polymers have unique properties derived mainly from the physical and chemical characteristics of the siloxane bond. These properties include low glass transition temperature
Implementation Method 2
The siloxane polymers have unique properties derived mainly from the physical and chemical characteristics of the siloxane bond. These properties include thermal and oxidative stability
Implementation Method 3
The siloxane polymers have unique properties derived mainly from the physical and chemical characteristics of the siloxane bond. These properties include resistance to ultraviolet radiation
Implementation Method 4
The siloxane polymers have unique properties derived mainly from the physical and chemical characteristics of the siloxane bond. These properties include low surface energy and hydrophobicity
Data Source
AI summary
Polydiorganosiloxane polyoxamide, linear, block copolymers and methods of making the copolymers are provided. The method of making the copolymers involves reacting a diamine with a polydiorganosiloxane precursor having oxalylamino groups. The polydiorganosiloxane polyoxamide block copolymers are of the (AB)n type.