Non-cyclic Alkoxy Polysiloxane Preparation via Acid Catalysis
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Solution Overview
Problem
The existing processes for producing SiOC-based polyether siloxanes, such as defoamers, face challenges with corrosive and toxic chlorosiloxanes, require stoichiometric excess of polyetherols leading to unreacted excess polyethers, and generate ecological and toxicological issues, along with the need for corrosive catalysts and salt formation.
Innovation Solution
A process involving the heating of a reaction system comprising cyclic polyorganosiloxanes, silanes, and a catalyst system of metal trifluoromethanesulfonate and Brönsted acids like methanesulfonic acid, which avoids the use of corrosive and heavy metal catalysts, achieving acid-catalyzed ring opening to produce non-cyclic alkoxy-functional polysiloxanes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chlorosiloxanes are used as starting materials, then SiOC linkages can be formed, but the process becomes difficult to handle due to high reactivity and requires corrosion-resistant equipment
Solution Approach 1:
The patent replaces durable but problematic chlorosiloxane-based systems with a newer, shorter-lived chemical system (silane + cyclic siloxane + base catalyst) that achieves the same SiOC linkage formation without the handling difficulties. The base catalyst system is used temporarily during reaction then can be neutralized or removed, avoiding long-term corrosion issues.
Solution Approach 2:
The patent changes the chemical parameters of the reaction system by replacing chlorosiloxanes with silanes and using base catalysts instead of acid catalysts. This parameter change modifies the reaction conditions to be less corrosive and easier to handle while maintaining the ability to form SiOC linkages.
2Reliability
If chlorosiloxanes are used, then SiOC linkages can be formed, but hydrogen chloride is formed which causes environmental problems and requires HCl scavengers that generate large amounts of salts
Solution Approach 1:
The patent eliminates the harmful HCl byproduct generation entirely by replacing chlorosiloxanes with silanes. The base catalyst (such as alkali metal hydroxides or organic bases) facilitates the reaction without generating harmful acidic byproducts. Any excess base can be neutralized with acid to form soluble salts that are easier to remove than the insoluble salts from HCl scavenger reactions.
Solution Approach 2:
The patent extracts or removes the harmful HCl generation step from the reaction system by using an alternative chemical pathway (silane + cyclic siloxane with base catalyst) that forms SiOC linkages without producing HCl. This eliminates the need for HCl scavengers and their associated salt waste problems.
3Reliability
If stoichiometric excess of polyetherols is used, then quantitative conversion can be achieved, but unreacted excess polyethers remain which reduce the concentration of surfactant-active silicone polyethers
Solution Approach 1:
The patent changes the stoichiometric parameters by using a base catalyst system that enables quantitative or near-quantitative conversion at or near stoichiometric ratios. The base catalyst (such as KOH, NaOH, or organic bases like DBU) facilitates complete reaction without requiring large excesses of polyetherol, thus maintaining high surfactant concentration in the final product.
Solution Approach 2:
The base catalyst acts as an intermediary that enables the reaction to proceed to completion with minimal excess reagents. The base facilitates the nucleophilic attack of polyetherol on the silane or cyclic siloxane, allowing quantitative conversion without requiring stoichiometric excess of the polyetherol component.
4Reliability
If bases are used as HCl scavengers, then good conversions can be achieved, but large amounts of salts are generated which pose removal difficulties
Solution Approach 1:
The patent extracts or eliminates the salt formation step by replacing the HCl scavenger base system with a base catalyst system used in catalytic (sub-stoichiometric) amounts. The base catalyst facilitates the reaction without being consumed to form large amounts of salt. Any residual base can be easily neutralized or removed, avoiding the salt removal difficulties of stoichiometric base use.
Solution Approach 2:
The patent changes the amount parameter of base from stoichiometric (as HCl scavenger) to catalytic (as reaction promoter). This parameter change reduces base consumption from large stoichiometric amounts to small catalytic amounts, thereby minimizing salt formation and simplifying product purification.
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 produces non-cyclic alkoxy-functional polysiloxanes without corrosive catalysts, reduces ecological and toxicological concerns, and minimizes unreacted polyethers, enhancing the stability and effectiveness of SiOC-based polyether siloxanes for applications like defoamers and polyurethane foam stabilizers.
Implementation Method 1
heating a reaction system comprising: (A) a cyclic polyorganosiloxane, (B) a silane, and (C) a catalyst system comprising a metal trifluoromethanesulfonate and a Brønsted acid
Data Source
Figure 1
AI summary
A process for the preparation of a reaction product containing a non-cyclic alkoxy-functional polysiloxane by heating a reaction system comprising: (A) a cyclic polyorganosiloxane of the formula [(R12SiO)2/2]n, wherein the subscript n is an integer of at least 4 and each R1 is an alkyl group or aryl group; (B) a silane of the formula R2(4-m)Si(OR3)m, wherein the subscript m is an integer of 1 to 4, each R2 is independently an alkyl group or aryl group, a hydrocarbyl group or a halogenated hydrocarbyl group, and each R3 is independently an alkyl group; and (C) a catalyst system comprising a metal trifluoromethanesulfonate of the formula [M]+[CF3SO3]-, wherein M is a metal atom selected from sodium (Na) and potassium (K) and a Brønsted acid, wherein Brønsted acids with a pKa value ≤ 3.0, preferably with a pKa value ≤ 2.0, particularly preferably with a pKa value ≤ - 0.0 are used.