Dual-Cure Polyolefin Composition to Minimize Scorch
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Solution Overview
Problem
Existing processes for producing crosslinked polymers face challenges in minimizing premature crosslinking (scorch) during melt mixing while achieving sufficient ultimate crosslinking, particularly in the production of articles like cables and foams.
Innovation Solution
A process involving the formation of a crosslinkable polymeric composition comprising a polyolefin with hydrolyzable silane groups, an organic peroxide, and a silanol condensation catalyst, where the composition is subjected to conditions that induce crosslinking through both the peroxide and silane groups, with water generated in situ to facilitate moisture-induced crosslinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polymeric compositions containing dialkyl peroxides are melt mixed at temperatures around 140°C and subsequently crosslinked by heating to higher temperatures, then crosslinking is achieved, but scorch (premature crosslinking) occurs during melt mixing
Solution Approach 1:
The crosslinking process is divided into two distinct stages: (1) peroxide crosslinking at elevated temperatures (180-200°C) to achieve initial network formation, and (2) moisture-induced silane crosslinking at lower temperatures (100-150°C) to complete the crosslinking. This segmentation allows each crosslinking mechanism to operate optimally without causing scorch during melt mixing, as the silane groups remain dormant until the moisture-curing stage.
Solution Approach 2:
The polyolefin is pre-modified with hydrolyzable silane groups before processing. This preliminary action prepares the polymer for dual crosslinking mechanisms, allowing the silane groups to remain stable during melt mixing and peroxide crosslinking, then activate subsequently through moisture exposure to provide additional crosslinking without causing premature reaction.
2Reliability
If heating temperature is increased to achieve sufficient crosslinking, then crosslinking degree improves, but scorch during melt mixing increases
Solution Approach 1:
The invention changes the temperature parameters of the crosslinking process by implementing a two-stage approach: first stage at 180-200°C for peroxide crosslinking, then second stage at lower 100-150°C for moisture-induced silane crosslinking. This parameter change allows achieving high crosslinking degree without requiring continuously high temperatures that would cause scorch during melt mixing.
Solution Approach 2:
The polymeric composition is made composite by combining polyolefin with hydrolyzable silane groups, organic peroxide, and silanol condensation catalyst. This composite structure enables dual crosslinking mechanisms where peroxide provides initial crosslinking at elevated temperatures and silane provides additional crosslinking at lower temperatures through moisture activation, resolving the temperature-corch contradiction.
3Reliability
If dual crosslinking mechanisms are employed, then ultimate crosslinking degree increases, but process complexity increases
Solution Approach 1:
The invention merges two crosslinking mechanisms (peroxide and moisture-induced silane) into a single integrated process. The polymeric composition contains both peroxide and silane groups that work sequentially: peroxide crosslinking first at elevated temperatures, then moisture-induced silane crosslinking at lower temperatures. This merging achieves high ultimate crosslinking degree while consolidating the process into one continuous operation rather than separate steps.
Solution Approach 2:
The silane crosslinking mechanism is self-service in that it automatically activates through moisture exposure after the peroxide crosslinking stage. The water generated in situ during peroxide decomposition and/or added as steam or humid atmosphere triggers the silane condensation reaction without requiring additional catalysts or complex processing equipment. The catalyst present in the composition facilitates this self-service moisture-curing process.
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 process effectively minimizes scorch during melt mixing and achieves a high degree of crosslinking, as demonstrated by increased torque values and gel content in the crosslinked polymeric compositions, maintaining performance even at elevated temperatures.
Implementation Method 1
subjecting said crosslinkable polymeric composition to conditions sufficient to induce crosslinking in at least a portion of said crosslinkable polymeric composition via said organic peroxide
Implementation Method 2
subjecting said crosslinkable polymeric composition to conditions sufficient to induce crosslinking in at least a portion of said crosslinkable polymeric composition via said hydrolyzable silane groups
Implementation Method 3
a silanol condensation catalyst selected from the group consisting of Bronsted acids
Implementation Method 4
wherein said water is generated in situ
Data Source
Figure 1~3
Figure 4~5
AI summary
Crosslinkable polymeric compositions comprising a polyolefin having hydrolyzable silane groups, an organic peroxide, and optionally a silanol condensation catalyst. Such crosslinkable polymeric compositions are crosslinkable via a combination of peroxide crosslinking and moisture curing. Such crosslinkable polymeric compositions can be employed in the production of various articles of manufacture, such as coated conductors.