Polyester Hotmelt Adhesive Low VOC Cyclic Dimer Control
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Solution Overview
Problem
Conventional hotmelt adhesives based on crystalline or semicrystalline polyester polyols often exceed VOC and FOG limits due to the formation of volatile cyclic dimers, posing health concerns and fogging issues, especially in the automotive and food packaging sectors.
Innovation Solution
The use of polyesters formed from long-chain linear dicarboxylic acids and diols with specific molecular ratios, which result in solid, crystalline or semicrystalline polyols with low VOC and FOG values, preventing the formation of volatile cyclic dimers after curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyester polyols are used in hotmelt adhesives, then good adhesion and polymer properties are achieved, but VOC and FOG values exceed regulatory limits due to volatile cyclic dimers
Solution Approach 1:
The invention changes the chemical parameters of the polyester polyol by specifying exact molecular weight ranges (500-2000 g/mol), hydroxyl number ranges (30-100 mg KOH/g), and acid number ranges (0.1-5.0 mg KOH/g). These parameter changes ensure low cyclic dimer formation while maintaining adhesive performance, directly resolving the contradiction between bond reliability and VOC emissions
Solution Approach 2:
The invention creates a composite adhesive system combining polyester polyol with specific molecular weight and hydroxyl number characteristics, polyisocyanate, and optional additives. This composite formulation achieves both low VOC/FOG values and reliable adhesive bonding through synergistic component selection and配比
2Object-generated harmful factors
If polyester polyols with specific molecular weight and hydroxyl number are used, then cyclic dimer formation is reduced, but adhesive strength may be compromised
Solution Approach 1:
The invention optimizes the molecular weight parameter to 500-2000 g/mol and hydroxyl number to 30-100 mg KOH/g, which reduces cyclic dimer formation while maintaining sufficient reactive groups for strong bonding. The acid number is controlled at 0.1-5.0 mg KOH/g to ensure proper curing without excessive byproducts
Solution Approach 2:
The adhesive combines polyester polyol with controlled parameters with polyisocyanate in specific ratios to achieve both low cyclic dimer concentration and high bond strength. The composite system compensates for any potential strength reduction through synergistic interactions between components
3Object-generated harmful factors
If the adhesive is designed for low VOC values, then emissions are reduced, but the formulation complexity increases to maintain performance
Solution Approach 1:
The invention establishes specific parameter ranges for polyester polyol (molecular weight 500-2000 g/mol, hydroxyl number 30-100 mg KOH/g, acid number 0.1-5.0 mg KOH/g) that inherently limit cyclic dimer formation. These standardized parameters simplify formulation development while ensuring low VOC emissions and consistent performance
Solution Approach 2:
The adhesive uses a composite system of polyester polyol, polyisocyanate, and optional additives in controlled ratios. This composite approach achieves low VOC emissions through component selection while maintaining simple processing and application characteristics
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 described polyester-based hotmelt adhesives meet the stringent VOC and FOG limits of the automotive industry, ensuring low emissions and improved safety and performance by maintaining low cyclic dimer concentrations even after storage and curing.
Implementation Method 1
reactive hotmelt adhesives which, after application, additionally crosslink and thus cure irreversibly to form a thermoset
Implementation Method 2
the ester groups can bind to the substrate surface via hydrogen bonds
Implementation Method 3
They are solid at room temperature and are melted by heating, and are applied to the substrate in substance at elevated temperature
Implementation Method 4
In the course of cooling, they solidify again and thus ensure a firm adhesive bond after only a short time
Data Source
AI summary
The invention relates to hotmelt adhesives based on polyesters, having low VOC and fogging values. In particular, the invention is directed to a polyester based on polycarboxylic acids and di- or polyols, wherein the polyester including dicarboxylic acids of the formula HOOC—(CH2)x-COOH with x>10 and diols of the formula HO—(CH2)y-OH, with the proviso that at least 50 mole percent of the dicarboxylic acids, based on the total amount of polycarboxylic acid components, and at least 50 mole percent of the diols, based on the total amount of di- or polyols, satisfy the condition x+y>18, in hotmelt adhesives.