Block Copolymer Bitumen Binder Without Crosslinking Agents
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Solution Overview
Problem
Current polymer-modified bituminous binder compositions for paving applications rely on crosslinking agents, which pose environmental and safety concerns, and fail to provide optimal mixing efficiency, storage stability, and curing time.
Innovation Solution
A process using a block copolymer composition with a high vinyl content diblock copolymer and either a high vinyl linear triblock copolymer or multiarm block copolymer, eliminating the need for crosslinking agents and enhancing compatibility and processability, resulting in improved mixing, reduced curing time, and increased storage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If crosslinking agents are used to improve polymer-bitumen bonding and curing, then bonding strength and curing speed are improved, but environmental safety and operational safety deteriorate due to hydrogen sulfide generation
Solution Approach 1:
The invention extracts and removes the harmful crosslinking agents (sulfur and sulfur-containing compounds) from the polymer-modified bitumen system. By using block copolymers with specific microstructures (high vinyl content, diblock content ≥50%, specific architecture) that enable self-crosslinking through thermal processing alone, the patent eliminates the need for external crosslinking agents, thereby removing the source of hydrogen sulfide generation while maintaining bonding strength
Solution Approach 2:
The block copolymers are designed with self-crosslinking capability through their specific microstructure. The high vinyl content and diblock architecture allow the polymer to undergo auto-crosslinking reactions during thermal processing (160-200°C) without requiring external crosslinking agents. This self-service mechanism eliminates harmful chemicals while achieving the desired bonding strength and curing performance
2Productivity
If high diblock content copolymers are used to improve mixing efficiency and dispersion, then mixing speed and homogeneity are improved, but compatibility and storage stability worsen
Solution Approach 1:
The invention applies local quality by creating specific microstructural regions within the block copolymer that serve different functions. The diblock segments (≥50% content) provide mixing efficiency and dispersion through their linear structure and compatibility with bitumen, while the high vinyl content regions (≥35 mol%) provide crosslinking sites for bonding. This spatial and functional differentiation within the polymer structure resolves the contradiction between mixing efficiency and storage stability
Solution Approach 2:
The block copolymer acts as a composite material at the molecular level, combining different structural elements (diblock segments for mixing, high vinyl content segments for crosslinking, aromatic blocks for compatibility) within a single polymer chain. This composite structure enables simultaneous achievement of mixing efficiency, compatibility, and storage stability by assigning different functional roles to different parts of the polymer architecture
3Reliability
If high vinyl content block copolymers are used to improve compatibility and bonding, then compatibility is improved, but mixing efficiency and processing time worsen
Solution Approach 1:
The invention optimizes multiple parameters simultaneously: vinyl content (≥35 mol%), diblock content (≥50%), molecular weight (30,000-200,000), and block copolymer architecture. By carefully balancing these parameters, the patent achieves a state where compatibility is improved through high vinyl content and aromatic blocks, while mixing efficiency is maintained through appropriate molecular weight and diblock structure. The self-crosslinking capability further reduces curing time despite the complex microstructure
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 achieves safer, more environmentally friendly polymer-modified bituminous binder compositions with improved properties, including reduced phase separation and faster curing, while maintaining or exceeding the performance of compositions using crosslinking agents.
Implementation Method 1
heating said bitumen and said block copolymer composition to a temperature from 160°C to 200°C for a period of time sufficient to effect crosslinking of said block copolymer composition and said bitumen
Implementation Method 2
effect crosslinking of said block copolymer composition and said bitumen
Implementation Method 3
The polymer-modified bituminous binder composition of the present invention may be used to prepare hot mix asphalts, cutbacks and emulsions
Data Source
AI summary
The present invention is directed to a process for preparing a polymer modified bituminous binder composition in the substantial absence of crosslinking agents by heating a bitumen component in a stirred tank to a temperature from 185 °C to 221 °C; adding a block copolymer composition to the bitumen component while the bitumen component is being stirred to form a homogeneous mixture of the bitumen component and the block copolymer composition; and continuing to stir the homogeneous mixture while maintaining the temperature from 185 °C to 221 °C for a period of time from 4 hours to 30 hours thereby forming a cured polymer modified bituminous binder composition. The block copolymer composition utilized in the process comprises a diblock copolymer comprising one block of a monovinylaromatic hydrocarbon and one block of a conjugated diene having a peak molecular weight from 30,000 to 78,000 and a vinyl content from 35 to 80 mol percent based on the number of repeat monomer units in the conjugated diene block, and optionally one or more block copolymers comprising at least two blocks of monovinylaromatic hydrocarbon and at least one block of conjugated diene, the block copolymer selected from linear triblock copolymers having a peak molecular weight that is 1.5 to 3.0 times the peak molecular weight of the diblock copolymer, multiarm coupled block copolymers having a peak molecular weight that is 1.5 to 9.0 times the peak molecular weight of the diblock copolymer, and mixtures thereof, wherein each block copolymer has a vinyl content from 35 to 80 mol percent based on the number of repeat monomer units in the conjugated diene block, wherein when both (i) and (ii) are present in the block copolymer composition, the ratio of (i) to (ii) is greater than 1:1. The present invention is further related to an alternative to this process, a specific class of bituminous binder compositions and concentrates and a specific class of block copolymer compositions.