Branched Amorphous Polyamide Adhesives for Low-Temperature PSA Performance
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Solution Overview
Problem
Crystalline or semi-crystalline polyamide (co)polymers are not effective as pressure sensitive adhesives at or below 50°C due to hydrogen bonding induced crystallization, limiting their use in applications requiring adhesion at lower temperatures.
Innovation Solution
Development of branched amorphous polyamide (co)polymers using specific di-acid and di-amine monomers to create self-cohesive adhesives that can function as pressure sensitive adhesives at or below 50°C, utilizing a backbone formed by reacting a reaction mixture with at least 25 mol % of a di-amine selected from secondary di-amine, branched di-amine, or a combination thereof, and an aliphatic acid blend including a branched aliphatic di-acid and tri-acid, with a molar equivalent ratio of 0.9-1.1.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If crystalline or semi-crystalline polyamide (co)polymers are used, then strength and structural stability are improved, but adhesion performance at or below 50°C deteriorates due to hydrogen bonding induced crystallization
Solution Approach 1:
The patent changes the physical state parameter of the polyamide from crystalline/semi-crystalline to amorphous by controlling the polymerization process and selecting specific monomers. This parameter change prevents hydrogen bonding induced crystallization, allowing the material to maintain adhesion performance at or below 50°C while retaining sufficient structural stability through the amorphous network structure
Solution Approach 2:
The patent creates a composite adhesive system by combining the amorphous polyamide (co)polymer with specific tackifiers and optional modifiers. This composite approach allows the amorphous polymer matrix to provide low-temperature adhesion while the composite formulation maintains overall structural integrity and strength
2Reliability
If amorphous polyamide (co)polymers are used to achieve PSA performance at or below 50°C, then adhesion reliability is improved, but material strength deteriorates compared to crystalline polyamides
Solution Approach 1:
The patent formulates a composite adhesive comprising the amorphous polyamide (co)polymer combined with tackifiers (such as rosin esters, terpene resins, or synthetic hydrocarbon resins) and optional modifiers. This composite structure compensates for the reduced inherent strength of amorphous polymers by incorporating materials that provide additional cohesive strength and structural stability, enabling the adhesive to meet both low-temperature adhesion requirements and overall strength specifications
3Reliability
If branched amorphous polyamide (co)polymers are synthesized with specific monomers, then self-cohesiveness and PSA performance are improved, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes the polymerization parameters including maintaining a molar equivalent ratio of di-amine to aliphatic acid blend between 0.9-1.1, controlling the glass transition temperature to be below 25°C, and specifying the molecular weight range (number average molecular weight greater than 10,000 Da). These parameter specifications provide clear manufacturing guidelines that simplify the process while ensuring the desired self-cohesiveness and PSA performance
Solution Approach 2:
The patent specifies particular local compositional requirements within the polymer structure, such as incorporating at least 25 mol % of secondary di-amine or branched di-amine and using an aliphatic acid blend containing branched aliphatic di-acid and tri-acid. These localized compositional specifications ensure the amorphous structure and self-cohesiveness while providing clear, actionable manufacturing criteria
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 amorphous polyamide (co)polymers exhibit self-cohesiveness and perform well as pressure sensitive adhesives at or below 50°C, adhering to both polar and non-polar substrates, with improved shear modulus, viscosity, and glass transition temperature, and can be processed without organic solvents, offering biodegradability and low skin/respiratory sensitization risk.
Implementation Method 1
reacting a reaction mixture including at least 25 mol % of a di-amine selected from a secondary di-amine, a branched di-amine, or a combination thereof, and an aliphatic acid blend including a branched aliphatic di-acid and a branched aliphatic tri-acid
Implementation Method 2
the self-cohesiveness of these inventive polyamide (co)polymers relates to their inherent ability to hydrogen bond with polar surfaces or even other branched amorphous polyamide (co)polymers while remaining amorphous
Data Source
AI summary
Branched amorphous polyamide (co)polymers having a backbone formed by reacting a reaction mixture including at least 25 mol % of a di-amine selected from a secondary di-amine, a branched di-amine, or a combination thereof; and an aliphatic acid blend including a branched aliphatic dimer acid and a branched aliphatic trimer acid. The molar equivalent ratio of the di¬ amine to the aliphatic acid blend is 0.9-1.1. Preferably, the branched amorphous polyamide (co)polymer is not telechelic. The branched amorphous polyamide (co)polymer preferably exhibits one or more of a shear modulus of from 10,000 to 500,000 Pa at 70° C., a complex viscosity of greater than 1,000,000 mPa*s at 70° C., a glass transition temperature of less than 25° C., or a number average molecular weight of greater than 10,000 Da. Biodegradable and/or compostable adhesive articles including the branched amorphous polyamide (co)polymer also are disclosed.