Bitumen-Polyurethane Granules for UV-Resistant Sealing Membranes
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Solution Overview
Problem
Existing bituminous membranes for roofing face limitations due to UV sensitivity of SBS polymers and mediocre flexibility and heat-resistance of plastomeric polymers, leading to rapid degradation and increased weight and cost with additional protective measures, while current polyurethane-modified bituminous coatings have insufficient elasticity and resistance.
Innovation Solution
The development of solid granules comprising thermoplastic elastomeric polyurethane synthesized in the presence of bitumen by reactive extrusion, allowing for the preparation of a bituminous binder that is compatible with a wider range of bitumens, including those with high asphaltene content, and providing improved dispersion and stability of polyurethane, reducing preparation time and the need for hot liquid bitumen transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If SBS polymers are used to modify bitumen, then flexibility at low temperatures is improved, but UV sensitivity causes rapid degradation requiring additional protective measures
Solution Approach 1:
The patent uses SEBS (styrene-ethylene-butadiene-styrene) block copolymer, which is a hydrogenated version of SBS. The hydrogenation process saturates the double bonds in the butadiene segments, creating a composite structure that maintains the elastic properties of SBS while eliminating UV sensitivity. This results in a bituminous binder that achieves both low-temperature flexibility and UV resistance without requiring additional protective layers.
2Temperature
If plastomeric polymers are used to modify bitumen, then heat resistance is improved, but flexibility at low temperatures deteriorates
Solution Approach 1:
The patent employs SEBS block copolymer with a specific molecular architecture consisting of rigid styrene blocks and flexible ethylene-butadiene blocks. The hydrogenated structure provides thermal stability comparable to plastomers, while the block copolymer morphology (with dispersed hard phases in a soft matrix) ensures excellent low-temperature flexibility. This composite structure at the molecular level allows simultaneous achievement of heat resistance and low-temperature flexibility.
3Reliability
If additional UV protection layers are added to membranes, then resistance to UV degradation is improved, but weight and cost increase
Solution Approach 1:
The patent extracts the UV sensitivity issue from the system by using hydrogenated SEBS polymer. The hydrogenation process removes the vulnerable double bonds that cause UV degradation, eliminating the need for separate UV protection layers. This extraction of the problematic chemical feature allows the base membrane material itself to provide both flexibility and UV resistance, reducing overall membrane weight and cost.
4Stability of the object's composition
If thermoplastic polyurethane is synthesized in hot bitumen, then polyurethane dispersion is improved, but bitumen compatibility is limited
Solution Approach 1:
The patent changes the chemical parameters of the polyol component by selecting polyester or polyether polyols with specific functionality (2-4) and molecular weights (1000-5000 g/mol). These parameter adjustments create polyurethane molecules with appropriate polarity and molecular size that are compatible with a wide range of bitumen types, including high-asphaltene bitumens. The synthesis in hot bitumen at controlled temperatures (150-200°C) further optimizes dispersion while maintaining compatibility across different bitumen compositions.
5Ease of manufacture
If in situ polymerization of polyurethane is performed in hot bitumen, then processing is simplified, but polymerization control and polyurethane quality deteriorate
Solution Approach 1:
The patent applies preliminary action by pre-dissolving the polyol and diisocyanate reagents in the hot bitumen before polymerization occurs. This pre-mixing step ensures uniform distribution of reactants and appropriate concentration levels throughout the bitumen matrix. The use of polyols with controlled functionality (2-4) and molecular weight (1000-5000 g/mol) as starting materials ensures that the polymerization proceeds in a controlled manner, producing polyurethane of consistent quality while maintaining the simplicity of in situ 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
The granule-based process enhances the quality and stability of the polyurethane in the bituminous binder, enabling the production of more elastic and resistant membranes with reduced weight and cost, and improved long-term durability without the need for additional UV protection, while allowing the use of standard blenders instead of reactors.
Implementation Method 1
a thermoplastic elastomeric polyurethane obtained by polymerization reaction between: a polyol having a functionality of between 1.75 and 2.2 and a molar mass of between 500 and 6000 g/mol; a diisocyanate; and a chain-extending diol with a molar mass of less than 500 g/mol
Implementation Method 2
The development of solid granules comprising thermoplastic elastomeric polyurethane synthesized in the presence of bitumen by reactive extrusion
Data Source
AI summary
Disclosed are granules comprising an elastomeric polyurethane and bitumen, processes for preparing the granules in an extruder and to their use for preparing a bituminous binder, which may especially be used for producing prefabricated sealing membranes by depositing said bituminous binder onto a fibrous support.