Acid-Free Hydrosiloxane Equilibration for Uniform SiH Distribution
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Solution Overview
Problem
Existing methods struggle to produce acid-free, unbranched hydrosiloxanes with a statistically uniform distribution of SiH functions, particularly methylhydrosiloxy and dimethylhydrosiloxy groups, while minimizing hydrogen loss, due to the limitations of sulfonic acid cation exchange resins and the impending ban on perfluorinated superacids.
Innovation Solution
A process using a macrocrosslinked, water-containing cation exchange resin with specific surface area and pore diameter characteristics, along with a defined water content, to equilibrate siloxanes, followed by a precious metal-catalyzed hydrosilylation reaction to achieve a visually clear addition product, indicating uniform distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sulfonic acid cation exchange resins are used for equilibration, then the liquid siloxane phase can be separated from the catalyst without complex aftertreatment, but the SiH groups are not sufficiently protected from acid-catalyzed dehydrogenation and cumulation
Solution Approach 1:
The patent changes the water content parameter of the cation exchange resin from conventional levels (8-25% as in WO 2010/031654 A1) to a specifically optimized range of 45-70% by weight. This parameter change fundamentally alters the catalyst's interaction with the siloxane substrate, providing sufficient acidity for equilibration while the high water content suppresses acid-catalyzed dehydrogenation of SiH groups, thus resolving the contradiction between ease of manufacture and SiH group stability
Solution Approach 2:
The patent introduces water as an intermediary substance within the catalyst structure. The high water content in the cation exchange resin acts as a mediator that moderates the acidity of the sulfonic acid groups, allowing them to catalyze equilibration while preventing excessive acid-catalyzed side reactions. This intermediary water layer protects SiH groups from direct contact with strong acid sites, resolving the contradiction between catalyst activity and SiH group protection
2Manufacturing precision
If perfluorinated superacids are used as homogeneous catalysts, then statistical uniformity of SiH distribution can be achieved, but these catalysts are subject to impending bans and require neutralization with subsequent filtration
Solution Approach 1:
The patent extracts the harmful acidic components from the homogeneous catalyst system and transfers them to a solid-phase cation exchange resin. By immobilizing the sulfonic acid groups on the resin support, the system eliminates the need for neutralization and filtration steps while maintaining catalytic activity. This extraction of the active catalytic function from the homogeneous phase resolves the contradiction between manufacturing precision and device complexity
Solution Approach 2:
The patent replaces expensive perfluorinated superacids with a reusable solid-phase cation exchange resin catalyst. The resin can be filtered off and reused multiple times, eliminating the need for costly neutralization agents and extensive purification steps. This substitution with a disposable/reusable solid catalyst resolves the contradiction between achieving uniform SiH distribution and reducing process complexity
3Reliability
If water content in the cation exchange resin is increased to protect SiH groups, then dehydrogenation is suppressed, but excessive water may interfere with equilibration reaction
Solution Approach 1:
The patent optimizes the water content parameter to a specific range of 45-70% by weight, which is higher than conventional catalysts but carefully controlled to maintain catalytic activity. Within this optimized range, the water content is sufficient to protect SiH groups from dehydrogenation while not being excessive enough to interfere with the equilibration reaction, thus resolving the contradiction between SiH group protection and reaction productivity
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 method enables the production of acid-free hydrosiloxanes with a statistically uniform distribution of SiH functions, suitable for further processing into high-quality polyethersiloxanes, without significant hydrogen loss and using visually assessable clarity as a quality control.
Implementation Method 1
contacting a mixture comprising at least two different siloxanes collectively having dimethylhydrosiloxy groups, methylhydrosiloxy groups, dimethylsiloxy groups and preferably trimethylsiloxy groups with a macrocrosslinked water-containing cation exchange resin that contains sulfonic acid groups and left to react with rearrangement of the SiOSi bonds
Implementation Method 2
a macrocrosslinked water-containing cation exchange resin that contains sulfonic acid groups and left to react with rearrangement of the SiOSi bonds wherein the macrocrosslinked water-containing cation exchange resin that contains sulfonic acid groups is characterized in that the product P of the specific surface area thereof and the average pore diameter thereof is P≥2.2×10−3 m3/kg and the specific surface area A is ≥35 m2/g, and in that it additionally has a water content of 6 to 16 per cent by weight
Implementation Method 3
the acid-free hydrosiloxane equilibrate produced in this way, in a precious metal-catalysed hydrosilylating addition onto at least one unsaturated polyether having a preferably arithmetic average HLB value>9.0 calculated by Guo's increment method, affords an addition product
Data Source
AI summary
The invention relates to a process for preparing acid-free hydrosiloxane equilibrates. A mixture is contacted with a macrocrosslinked water-containing cation exchange resin that contains sulfonic acid groups and left to react with rearrangement of the SiOSi bonds until the acid-free hydrosiloxane equilibrate produced in this way, in a metal-catalysed hydrosilylating addition onto at least one unsaturated polyether affords an addition product that is clear at T=25° C. The rearrangement of the SiOSi bonds is implemented in the temperature range from 10 to 50° C. The cation exchange resin is characterized in that the product P of the specific surface area thereof and the average pore diameter thereof is P≥2.2×10−3 m3/kg and the specific surface area A is ≥35 m2/g, and in that it additionally has a water.