Alkoxysilane Polymer Stabilization Against Viscosity Increase
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Solution Overview
Problem
Existing methods fail to effectively control the increase in Mooney viscosity and molecular weight of alkoxysilane terminated polymers over time, leading to coupling and instability during aging and storage.
Innovation Solution
The process involves reacting conjugated diolefin polymers with alkoxy and/or aryloxy silane terminal functionalizing groups, followed by the addition of dialkoxysilane stabilizing agents and a base, and subsequent desolvatization, which stabilizes the polymer by preventing Si—O—Si bond formation between polymer chains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If alkoxysilane termination is used to impart advantageous properties to polymers, then polymer functionality is improved, but Mooney viscosity increases and coupling occurs during aging
Solution Approach 1:
A base metal stabilizer (such as calcium stearate, zinc stearate, or other metal soaps) is introduced as an intermediary substance that interferes with the hydrolysis reaction of alkoxysilane end groups. The stabilizer binds to the hydrolyzed silane groups or the hydroxyl groups formed during hydrolysis, preventing the condensation reaction that would otherwise lead to Si-O-Si bond formation and polymer coupling. This intermediary action blocks the harmful reaction pathway while preserving the desired polymer functionality.
Solution Approach 2:
The invention changes the chemical environment parameters by introducing basic substances (metal soaps with carboxylate groups) that alter the pH and reactivity conditions. The base metal stabilizer creates a less favorable environment for acid-catalyzed hydrolysis and condensation reactions, thereby slowing down the rate of Mooney viscosity increase and polymer coupling during storage and aging.
2Ease of manufacture
If steam or heated water desolventization is used to process alkoxysiloxane terminated polymers, then solvent removal is achieved, but hydrolysis of end groups occurs leading to increased Mooney viscosity
Solution Approach 1:
The base metal stabilizer is added to the polymer system before the desolventization step. This preliminary action ensures that the stabilizer is already present and active when the steam or heated water contact occurs during solvent removal. The stabilizer pre-positioned in the system immediately begins to inhibit hydrolysis reactions as water is introduced, preventing the unwanted increase in Mooney viscosity that would otherwise occur during the necessary desolventization process.
3Loss of time
If attempts are made to reduce the rate of hydrolysis reaction, then coupling rate is slowed, but polymer coupling continues over time during storage
Solution Approach 1:
The base metal stabilizer acts as a continuous intermediary that maintains its protective function throughout the entire storage period. Unlike methods that merely slow hydrolysis, the stabilizer actively binds to reactive species (hydroxyl groups or hydrolyzed silane end groups) as they form, preventing the condensation reaction pathway. This ongoing intermediary action ensures long-term reliability and prevents polymer coupling even during extended storage times.
Solution Approach 2:
The base metal stabilizer provides continuous protection against polymer coupling throughout storage and aging. The stabilizer remains active and continues to interfere with the hydrolysis-condensation mechanism as long as moisture is present, ensuring uninterrupted protection. This continuous useful action maintains polymer stability over time, preventing the gradual coupling that occurs with conventional methods.
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 maintains stable Mooney viscosity and molecular weight over long periods, including during storage, preventing the increase in viscosity and coupling of polymer chains, thus ensuring the polymer's stability and performance.
Implementation Method 1
an even larger increase in Mooney viscosity often occurs during the hydrolysis of the alkoxysiloxane end groups such as pendant —SiOR groups, thereby leading to coupling of the polymer via formation of Si—O—Si bonds
Data Source
AI summary
A method of making a polymer with stable Mooney viscosity and molecular weight is described. A conjugated diolefin is reacted in a hydrocarbon solvent in the presence of an initiator to form a polymer. After forming the polymer, alkoxy silane terminal functionalizing groups are bonded to the polymer. A dialkoxysilane stabilizing agent is then added to the polymer in combination with a base material. The polymer is then desolvatizing, resulting in a polymer with stable Mooney viscosity and molecular weight, even over prolonged periods of time. Compositions and articles containing the polymer are also described.