High-Yield Cyclic Polysiloxane Synthesis via Halogen-Capped Precursors
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Solution Overview
Problem
Existing methods for producing cyclic polysiloxanes are limited by the use of toxic catalysts, result in low yields, and produce a mixture of cyclic trimers, tetramers, and pentamers, making it difficult to obtain a single constituent in high purity and yield.
Innovation Solution
A method involving the reaction of cyclic siloxane with dihalosilane in the presence of Lewis base compounds, phosphorus compounds with a P=O bond, quaternary ammonium salts, or quaternary phosphonium salts to form a linear polysiloxane capped with halogen atoms, followed by hydrolysis to produce cyclic polysiloxane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional catalysts (acid or alkali) are used for producing cyclic polysiloxane, then the reaction can proceed, but toxic substances are generated and environmental pollution occurs
Solution Approach 1:
The patent introduces a solid acid catalyst as an intermediary substance that enables the cyclization reaction without using toxic liquid acids or alkalis. The solid acid catalyst mediates between the hydrolyzed linear polysiloxane and water to form cyclic polysiloxane, and can be easily separated from the reaction mixture, thus eliminating the harmful effects of conventional catalysts while maintaining reaction feasibility
Solution Approach 2:
The patent employs a disposable solid acid catalyst that can be used in small amounts and then discarded or regenerated. This approach eliminates the need for complex catalyst recovery systems required by conventional catalysts, reducing both toxicity and manufacturing complexity
2Manufacturing precision
If conventional synthesis methods are used, then cyclic polysiloxane can be produced, but a mixture of cyclic trimers, tetramers, and pentamers is formed making it difficult to obtain high purity single constituent
Solution Approach 1:
The patent applies local quality control by carefully controlling the molecular weight distribution of the linear polysiloxane precursor and the hydrolysis conditions to ensure that only cyclic polysiloxane with the desired ring size is formed. This selective approach ensures high purity of the target cyclic polysiloxane constituent
Solution Approach 2:
The patent utilizes parameter changes in the hydrolysis process, specifically controlling temperature, pH, and reaction time, to favor the formation of a specific cyclic polysiloxane ring size. By optimizing these parameters, the reaction selectively produces the desired cyclic trimer, tetramer, or pentamer with high purity and yield
3Productivity
If existing synthesis methods are used, then cyclic polysiloxane can be produced, but the process is complex and yield is low
Solution Approach 1:
The patent merges the hydrolysis and cyclization steps into a single integrated process. The solid acid catalyst simultaneously facilitates both the hydrolysis of the linear polysiloxane and the subsequent cyclization reaction, eliminating the need for separate processing steps and simplifying the overall synthesis process while improving yield
Solution Approach 2:
The solid acid catalyst serves multiple functions: it catalyzes the hydrolysis reaction, catalyzes the cyclization reaction, and can be easily separated from the product. This self-service capability of the catalyst reduces the need for additional reagents and processing steps, thereby improving productivity and 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
This method allows for the production of cyclic polysiloxane in high yield and purity without toxic catalysts, enabling improved properties in high-molecular-weight silicone oils, silicone rubbers, and other applications.
Implementation Method 1
reacting a starting cyclic siloxane of general formula (1) below with a dihalosilane of general formula (2) below, accompanied by ring opening of the cyclic siloxane of general formula (1) and in the presence of one or more catalyst selected from phosphorus compounds having a P=O bond with the exception of phosphoric triamides, to obtain a linear polysiloxane capped at both ends of the molecular chain with halogen atoms
Implementation Method 2
reacting the resulting linear polysiloxane capped at both ends of the molecular chain with halogen atoms with water to obtain a cyclic polysiloxane
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A method for producing a cyclic polysiloxane that includes a step for reacting a raw material cyclic siloxane and a dihalosilane in association with ring-opening of the cyclic siloxane in the presence of at least one catalyst selected from Lewis base compounds having a carbonamide bond represented by -C(=O)N<, phosphorus compounds having a P=O bond, quaternary ammonium salts, and quaternary phosphonium salts to obtain a linear polysiloxane with both ends of the molecular chain blocked by halogen atoms and a step for obtaining a cyclic polysiloxane by reacting the linear polysiloxane with both ends of the molecular chain blocked by halogen atoms with water makes it possible to provide a method for producing a cyclic polysiloxane that obtains a cyclic polysiloxane at high yield and high purity by simple steps and under moderate conditions.