Biodegradable Polyurethane Adhesive for Home Compostable Labels
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Solution Overview
Problem
Current biodegradable adhesive solutions for labels face challenges in achieving simultaneous stability during use and rapid degradation under home composting conditions, with existing polyurethane-based adhesives not meeting the requirements of high tackiness, adhesive strength, and rapid biodisintegratability at ambient temperatures.
Innovation Solution
Development of adhesive labels using an aqueous polyurethane dispersion pressure-sensitive adhesive, composed of at least 60% diisocyanates, polyesterdiols, and bifunctional carboxylic acids, with a glass transition temperature below 20°C and no melting point or a melting point with low enthalpy, ensuring rapid decomposition into CO2 and water within 360 days at home composting conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyacrylate pressure-sensitive adhesives are used, then high adhesive strength and stability during use are achieved, but biodegradability and compostability are not achieved
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive by using polyurethane polymers with specific molecular structures containing hydrolyzable bonds (ester, amide, or carbamate linkages) instead of conventional polyacrylate adhesives. This parameter change enables the adhesive to maintain required adhesive properties while being biodegradable and compostable under home composting conditions.
Solution Approach 2:
The patent employs composite material design by creating polyurethane adhesives that combine multiple functional components: polyol segments providing adhesive properties, diisocyanate segments providing structural integrity, and hydrolyzable linkage groups enabling biodegradability. This composite structure allows simultaneous achievement of adhesive strength, stability during use, and compostability.
2Object-generated harmful factors
If biodegradable adhesive materials are used, then compostability is improved, but adhesive strength and stability during use deteriorate
Solution Approach 1:
The patent applies local quality principle by designing the polyurethane adhesive with different segments having different functions: some segments (polyol chains) provide adhesive strength and stability, while specific linkage regions (ester, amide, or carbamate bonds) provide biodegradability. This localized functional differentiation allows the adhesive to exhibit both strong bonding during use and controlled degradation after use.
Solution Approach 2:
The patent implements dynamics by creating an adhesive system that transitions from a stable state during use to a degradable state after use. The polyurethane adhesive maintains structural integrity and adhesive properties under normal conditions but dynamically transforms through hydrolysis and microbial degradation when exposed to composting environments, converting from a functional adhesive to decomposable organic matter.
3Object-generated harmful factors
If aqueous polyurethane dispersion is used, then environmental friendliness is improved, but rapid degradation under home composting conditions deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the polyurethane structure by incorporating specific hydrolyzable linkage groups (ester, amide, or carbamate bonds) at controlled proportions (0.1-10 mol% based on total polymer moles). This parameter optimization enables the aqueous dispersion to degrade rapidly under home composting conditions (temperatures below 50°C) while maintaining environmental friendliness through water-based formulation without organic solvents.
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 solution provides adhesive labels with high tackiness and adhesive properties while ensuring rapid and complete biodegradability under home composting conditions, meeting the criteria for both stability and biodisintegratability, as demonstrated by compliance with Australian Standard AS 5810-2010 and ISO 14855-1 standards.
Implementation Method 1
the adhesive polymer should undergo rapid degradation under home compost conditions... complete and final microbial degradation
Implementation Method 2
the ester bonds in polyester polyurethanes may promote degradation by hydrolyzing due to reaction with water
Data Source
AI summary
An adhesive label is described comprising a backing material, a pressure-sensitive adhesive layer attached to the backing material and either a release liner attached to the adhesive layer or a release coating on the other side of the backing material. The backing material is made of paper or home compostable and biodegradable polymer film, and the pressure-sensitive adhesive layer is made from an aqueous polyurethane dispersion pressure-sensitive adhesive. At least 60% by weight of the polyurethane is composed of diisocyanates, polyesterdiols, and at least one bifunctional carboxylic acid selected from di hydroxy carboxylic acids and diamino carboxylic acids, wherein the polyurethane has no melting point above 20° C. or wherein the polyurethane has a melting point above 20° C. with an enthalpy of fusion lower than 10 J/g, and wherein a film of the polyurethane adhesive preferably decomposes at home compost conditions to more than 90% by weight into CO2 and water within 360 days.