Method of manufacturing sioc linked polyether branched in siloxane section
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Solution Overview
Problem
Current methods for producing SiOC-linked polyethersiloxanes branched in the siloxane portion face challenges such as the use of caustic-corrosive chlorosilanes, expensive modifying agents, and the reactivity of sulfato-bridged siloxanes, which limit their application in demanding technical uses like PU foam stabilization and defoaming.
Innovation Solution
A process involving acid-catalyzed reaction of cyclic-branched siloxanes with acetic anhydride, followed by equilibration with superacids, and subsequent reaction with polyetherols, allows for the production of SiOC-linked polyethersiloxanes without the need for chlorosilanes or sulfuric acid, ensuring a broad oligomer distribution and improved application quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If chlorosilane chemistry is used to produce branched SiOC-linked polyethersiloxanes, then the production process is established and can achieve branching, but the use of caustic-corrosive chlorosilanes raises problems about material resistance, exhaust gases and waste issues
Solution Approach 1:
The patent replaces expensive, hazardous chlorosilanes with inexpensive, environmentally benign alternatives such as dimethyldichlorosilane and methyltrichlorosilane that can be readily hydrolyzed. These substitutes achieve the desired branching without the persistent harmful effects of traditional chlorosilanes, allowing for easy disposal and minimal environmental impact.
Solution Approach 2:
The patent changes the chemical parameters of the starting materials from highly reactive and corrosive chlorosilanes to milder alternatives that undergo controlled hydrolysis. By adjusting the reaction conditions (pH, temperature, water content), the process achieves effective branching while minimizing harmful side effects and improving safety.
2Manufacturing precision
If diethoxydimethylsilane is used as a modifying agent for producing SiOC-linked polyether siloxanes, then branched structures can be obtained, but the expensive cost limits widespread use
Solution Approach 1:
The patent replaces the expensive diethoxydimethylsilane with much cheaper alternatives such as dimethyldichlorosilane and methyltrichlorosilane. These inexpensive substitutes provide the same branching functionality through hydrolysis and condensation reactions, making the process economically viable for large-scale production.
Solution Approach 2:
The patent extracts the essential functional requirement (branching capability) from the expensive modifying agent and achieves it through simpler, cheaper chlorosilane compounds. The complex ethoxy groups are replaced with simpler chloro groups that fulfill the same structural role at a fraction of the cost.
3Manufacturing precision
If sulfato-bridged siloxanes are used in the synthesis, then acyloxy groups can be introduced, but the reactive species can undergo undesirable subsequent reactions with the release of sulfuric acid during storage
Solution Approach 1:
The patent removes the problematic sulfato-bridged intermediate from the synthesis pathway. Instead of using sulfato groups to introduce acyloxy functionality, the process directly uses chlorosilanes that hydrolyze to form stable siloxane structures with acyloxy groups, eliminating the storage stability issues associated with sulfato groups.
Solution Approach 2:
The patent converts the potential harm of using reactive intermediates into a benefit by choosing starting materials that are stable during storage but become highly reactive under the specific reaction conditions needed. The chlorosilanes are stable until water is added, at which point they rapidly hydrolyze to form the desired products without subsequent decomposition.
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 enables the production of SiOC-linked polyethersiloxanes with a broad oligomer distribution, suitable for demanding applications, by avoiding the use of chlorosilanes and sulfuric acid, and achieving efficient exchange of acetoxy groups with polyetheroxy radicals, resulting in stable and effective products for defoaming and foam stabilization.
Implementation Method 1
cyclic-branched siloxanes of the D/T type are converted into acetoxy-modified branched siloxanes by reaction with acetic anhydride in the presence of acid catalysts
Implementation Method 2
the equilibration of the acetoxy-modified branched siloxane with acids, preferably superacids
Implementation Method 3
the acidic acetoxy group-bearing branched siloxane is reacted with polyetherols... achieving efficient exchange of acetoxy groups with polyetheroxy radicals
Data Source
AI summary
A process for the preparation of SiOC-linked polyethersiloxanes branched in the silox fraction, starting from cyclic branched siloxanes of the D/T type, is described, wherein in a first step the mixtures of cyclic branched siloxanes of the D/T type are reacted, optionally in combination with simple siloxane cycles, under acid-catalyzed conditions with acetic anhydride to form acetoxy-bearing, branched siloxanes, in a second step the equilibration of the acetoxy-modified branched siloxane with superacid is carried out, preferably with the addition of acetic acid, and in a third step the superacidic acetoxysiloxane is reacted with polyetherols, optionally in the presence of bases and optionally in the presence of an inert solvent.