Polydiene Chain-Linking Chemistry for Cold Flow Resistance
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Solution Overview
Problem
Polydienes and elastomer-reinforced polymers, such as high-impact polystyrene (HIPS), experience cold flow issues during transportation and storage, leading to shape loss and increased production costs, despite existing solutions like carboxylic or thiocarboxylic esters, Lewis acid additives, and glycidic esters.
Innovation Solution
The addition of sulfur monochloride (S2Cl2) and hydroxyethyl alkenyl ether/hydroxypropyl alkenyl ether adducts to the polymerization system of 1,4-cis polydienes and styrene-butadiene polymers reduces cold flow while maintaining Mooney viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If rubber is stored in rectangular block form, then transportation and storage are facilitated, but cold flow occurs over time especially at elevated temperatures causing shape loss and material loss
Solution Approach 1:
The patent applies preliminary action by incorporating specific additives (carboxylic or thiocarboxylic esters with nitro groups, Lewis acid additives, or glycidic esters) into the rubber polymerization system before the rubber is formed into rectangular blocks. These additives pre-establish cold flow resistance properties in the rubber matrix, preventing shape loss during subsequent storage and transportation at elevated temperatures without requiring post-processing interventions.
2Shape
If additives are introduced to stop cold flow, then shape stability is improved, but Mooney viscosity may be affected which impacts processing properties
Solution Approach 1:
The patent applies parameter changes by carefully selecting and optimizing the chemical structure, concentration, and molecular weight of the additives (carboxylic or thiocarboxylic esters with nitro groups, Lewis acid additives, or glycidic esters) to achieve the desired balance. By adjusting these parameters, the invention reduces cold flow to acceptable levels while maintaining Mooney viscosity within ranges that preserve good processability and ease of operation during rubber processing.
Data Source
AI summary
A method for the synthesis of an elastomer comprising the steps of polymerizing conjugated diene monomer in presence of at least one rare earth transition metal catalyst system to generate a polydiene cement; terminating the polydiene cement with a protic organic compound; connecting polymer chains by reacting (1) a compound containing sulfur and a halogen with (2) an hydroxyethyl alkenyl ether/hydroxypropyl alkenyl ether; and adding a product of the reaction to the cement to generate a polydiene rubber.