Silane-Grafted Polyolefin Flame Retardant Systems
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Solution Overview
Problem
The existing processes for producing crosslinked wire and cable products with brominated flame retardant additives are inefficient and costly, often requiring a two-step process that distracts from process efficiency and increases costs.
Innovation Solution
A composition comprising polyolefin, hydrolysable unsaturated silane, a free radical generator, and halogenated polyaryl alkane flame retardant, which is processed in a single step by contacting these components in a reaction zone under grafting conditions to create a silane-grafted polyolefin that is then crosslinked upon exposure to moisture, allowing for the production of crosslinked wire or cable sheaths with integrated flame retardancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a two-step process is used to produce crosslinked wire and cable products with brominated flame retardant additives, then the flame retardant properties are achieved, but the process efficiency decreases and costs increase
Solution Approach 1:
The patent combines the silane grafting process and flame retardant additive introduction into a single simultaneous operation within the extruder. Both the hydrolysable unsaturated silane and brominated flame retardant additive are introduced together with the polymer, allowing crosslinking and flame retardancy to be achieved in one step rather than requiring separate processing steps.
Solution Approach 2:
The patent performs preliminary silane grafting and flame retardant incorporation during the extrusion process itself, before the material is formed into the final wire or cable product. The crosslinking reaction is initiated during extrusion through the use of a free-radical generator, so that the material is pre-crosslinked and pre-flame-retardant before leaving the extruder.
2Reliability
If brominated flame retardant additives are introduced during silane grafting, then flame retardancy is achieved, but the grafting process is interfered with and crosslinking is prevented
Solution Approach 1:
The patent uses a free-radical generator as an intermediary substance that facilitates both the silane grafting to the polymer and the incorporation of the brominated flame retardant additive. The free-radical generator initiates simultaneous reactions: grafting silane groups to the polymer backbone and incorporating the flame retardant additive, thereby mediating between these two processes and preventing interference between them.
Solution Approach 2:
The patent changes the reaction parameters during extrusion, specifically controlling temperature and the amount of free-radical generator, to optimize simultaneous silane grafting and flame retardant incorporation. The temperature is raised sufficiently to effect grafting while limiting direct free-radical crosslinking to levels that will not prevent extrusion, allowing both processes to proceed without mutual interference.
3Ease of operation
If direct free-radical crosslinking is limited to low levels, then extrusion is enabled, but crosslinking efficiency decreases
Solution Approach 1:
The patent performs preliminary silane grafting during the extrusion process itself, so that the crosslinking reaction begins while the material is still in the extruder. This preliminary crosslinking action occurs at controlled levels that allow extrusion to proceed, while the remaining crosslinking completes after extrusion when the material is exposed to moisture, thereby maximizing overall crosslinking efficiency without compromising extrusion capability.
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
This approach enables the production of crosslinked wire and cable products with integrated flame retardancy in a single step, improving process efficiency and reducing costs by minimizing interference from additives during the grafting process, while maintaining desired mechanical and chemical properties.
Implementation Method 1
a free-radical generator and a silanol condensation catalyst. These ingredients are blended with the polymer in the barrel of the extruder, and the temperature is raised sufficiently to effect grafting of silane groups to the polymer
Implementation Method 2
the cure is continued and completed outside the extruder by the action of moisture
Data Source
AI summary
Silane-grafted polyolefin composition comprising a brominated, flame retardant additive is prepared by a process comprising the step of contacting within a reaction—extrusion zone operated at grafting conditions: A. A polyolefin, B. A hydrolysable unsaturated silane, C. A free radical generator, and D. Halogenated polyaryl alkane, e.g., decabromodiphenyl ethane, such that at least a portion of the hydrolysable unsaturated silane is grafted to the polyolefin. The silane-grafted polyolefin is crosslinked after extrusion from the zone, typically as a wire and cable coating, upon exposure to moisture.