Iron Catalyst for Silicone Crosslinking
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Solution Overview
Problem
The use of platinum-based catalysts in silicone composition crosslinking is problematic due to toxicity, high cost, and instability, leading to issues like precipitation and the need for inhibitors that slow down the curing process, making it challenging for industrial-scale applications.
Innovation Solution
An iron(II) complex catalyst with a specific structure, such as [Fe(L1)2], is used in place of platinum, allowing crosslinking reactions to occur in air without the need for protective atmospheres and inhibitors, using organopolysiloxane and organohydrogenopolysiloxane compounds to form a crosslinked silicone material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If platinum-based catalysts are used for silicone composition crosslinking, then the crosslinking reaction can proceed rapidly at room temperature, but the catalyst is toxic, expensive, and unstable leading to precipitation and product discoloration
Solution Approach 1:
The patent replaces expensive platinum catalysts with inexpensive iron-based catalysts that can be used in small amounts (0.001-5 mol% relative to vinyl groups). The iron catalyst system is economically viable and eliminates the need for costly platinum while maintaining effective crosslinking functionality.
Solution Approach 2:
The patent changes the chemical composition parameter of the catalyst from platinum-based to iron-based complexes with specific ligands (β-dicarbonylato anions or enolates). This parameter change transforms the catalyst properties to eliminate toxicity and cost issues while preserving catalytic activity for hydrosilylation reactions.
2Speed
If platinum catalysts are used, then rapid crosslinking occurs, but the catalyst precipitates forming insoluble colloids that reduce activity and discolor the product
Solution Approach 1:
The iron-based catalyst is used in small quantities (0.001-5 mol% relative to vinyl groups) and remains soluble throughout the reaction, avoiding the precipitation problems of platinum catalysts. The low loading and solubility characteristics prevent colloid formation and maintain product clarity.
Solution Approach 2:
The patent changes the catalyst composition from platinum to iron complexes with specific ligands (β-dicarbonylato anions or enolates), which fundamentally alters the catalyst's solubility and stability parameters. This prevents precipitation and maintains homogeneous distribution in the reaction medium throughout the crosslinking process.
3Ease of operation
If inhibitors are added to prevent premature crosslinking, then the composition remains liquid for application, but the curing rate is significantly slowed after activation
Solution Approach 1:
The iron-based catalyst system enables the use of minimal or no inhibitors, allowing the composition to remain stable during handling and application without requiring large amounts of inhibitor that would subsequently slow curing. The catalyst's stability allows for better control of the reaction timing.
Solution Approach 2:
The patent changes the catalyst system to iron-based complexes that offer improved control over reaction kinetics. This parameter change allows for better balance between stability during handling and reactivity during curing, reducing or eliminating the need for inhibitor additives that would compromise curing speed.
4Temperature
If platinum catalysts are used, then crosslinking can occur at room temperature, but the process requires protective atmospheres and inhibitor management adding complexity
Solution Approach 1:
The iron-based catalyst system eliminates the need for expensive protective atmosphere equipment and complex inhibitor management systems. The catalyst's stability allows for simpler processing conditions while maintaining effective crosslinking, reducing overall process complexity and equipment requirements.
Solution Approach 2:
The patent changes the catalyst composition to iron-based complexes with specific ligands, which fundamentally alters the reaction conditions. This parameter change allows for simplified processing without protective atmospheres and reduces or eliminates the need for inhibitor additives, thereby reducing process complexity.
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 iron-based catalyst system enables stable and efficient crosslinking of silicone compositions at controlled temperatures, reducing the need for platinum and inhibitors, thus improving the industrial feasibility and product quality by maintaining the composition's liquid state for longer before curing.
Implementation Method 1
a crosslinkable composition comprising: at least one organopolysiloxane compound (A) comprising, per molecule, at least two C2-C6 alkenyl radicals bonded to silicon atoms, at least one organohydrogenopolysiloxane compound (B) comprising, per molecule, at least two hydrogen atoms bonded to an identical or different silicon atom, at least one catalyst (C) which is a complex corresponding to the following formula: [Fe(L1)2]
Data Source
AI summary
The invention relates to a crosslinkable composition X, comprising: at least one organopolysiloxane compound A comprising, per molecule, at least two C2-C6 alkenyl radicals bonded to silicon atoms; at least one organohydrogenopolysiloxane compound B comprising, per molecule, at least two hydrogen atoms bonded to an identical or different silicon atom; at least one catalyst C which is a complex corresponding to the following formula: [Fe(L1)2] in which: the symbol Fe represents iron at degree of oxidation II; the symbols L1, which may be identical or different, represent a ligand which is a β-dicarbonylato anion or the enolate anion of a β-dicarbonylated compound; optionally at least one adhesion promoter D; and optionally at least one charge E. The invention also relates to the use of the previously described catalyst C as silicone composition crosslinking catalyst, to a silicone composition crosslinking method, wherein it comprises heating the composition X to a temperature of between 70 and 200° C., and to the resulting crosslinked silicone material Y.