Dealcoholization Organopolysiloxane Composition for Metal-Free Curing
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Solution Overview
Problem
Existing room-temperature curable organopolysiloxane compositions face challenges with poor reactivity, toxicity, and inadequate adhesiveness to materials like polyphenylene sulfide resin and nylon 66, necessitating the use of metal catalysts that are restricted or slow-curing, and are costly to synthesize.
Innovation Solution
A room-temperature curable organopolysiloxane composition using a partial (co-)hydrolytic condensation of specific hydrolysable organosilane compounds with a hydrolysable organosilane having a phenylene backbone and two or more amino groups, along with a guanidine group-containing organic catalyst, to achieve curability and adhesiveness without metal catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an organotin catalyst or titanium chelate catalyst is used to improve curability, then sufficient curability is achieved, but toxicity increases and environmental restrictions apply
Solution Approach 1:
The patent introduces a silane compound as an intermediary substance that mediates the curing reaction between the organopolysiloxane and moisture. The silane compound (e.g., vinyltrimethoxysilane, allyltrimethoxysilane) acts as a catalyst-free curing agent that enables sufficient curability without requiring toxic metal catalysts, thus resolving the contradiction between achieving curability and avoiding toxicity
Solution Approach 2:
The patent extracts and eliminates the toxic organotin catalyst or titanium chelate catalyst from the composition while maintaining curability through the use of silane compounds. By removing the harmful catalytic component and replacing it with a non-toxic silane-based curing mechanism, the invention achieves curability without the associated toxicity and environmental restrictions
2Reliability
If an organotin compound is used to achieve curability, then curing is sufficient, but cracking occurs due to main chain cleavage and hardness decreases with time
Solution Approach 1:
The silane compound serves as an intermediary curing agent that enables crosslinking without causing main chain cleavage. The silane-based curing mechanism proceeds through hydrolysis and condensation reactions that form stable siloxane bonds, avoiding the degradation pathways associated with organotin catalysts, thus maintaining hardness over time while achieving sufficient curability
Solution Approach 2:
The patent removes the organotin compound from the system to eliminate the cause of main chain cleavage. By replacing the organotin catalyst with a silane compound-based curing system, the invention prevents the degradation reactions that lead to cracking and hardness loss, thereby maintaining structural integrity while achieving curability
3Reliability
If an organotitanium compound is used to achieve curability, then curing is possible, but curing rate is slow and cured product discolors with time
Solution Approach 1:
The silane compound acts as an intermediary that enables rapid curing through moisture-induced hydrolysis and condensation reactions. This silane-based curing mechanism proceeds much faster than organotitanium-catalyzed curing, achieving practical cure times while also preventing the discoloration issues associated with titanium compounds
Solution Approach 2:
The patent extracts the organotitanium compound from the composition to eliminate both the slow curing rate and discoloration problems. The replacement silane compound system provides rapid curing kinetics and maintains color stability over time, resolving both productivity and reliability concerns
4Reliability
If conventional organopolysiloxane composition is used to achieve curability, then curing is possible, but adhesiveness to polyphenylene sulfide resin and nylon 66 is insufficient
Solution Approach 1:
The patent creates a composite curing system that combines the organopolysiloxane base polymer with specific silane compounds (vinyltrimethoxysilane, allyltrimethoxysilane, or phenyltrimethoxysilane). This composite composition provides both sufficient curability and enhanced adhesiveness to difficult-to-bond substrates like polyphenylene sulfide resin and nylon 66, overcoming the limitations of conventional single-component systems
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
The composition provides a silicone rubber cured product with favorable adhesion to polyphenylene sulfide resin and nylon 66, as well as other resins, while being non-toxic, environmentally friendly, and cost-competitive.
Implementation Method 1
a compound obtained by partial (co-)hydrolytic condensation of specific hydrolysable organosilane compounds (siloxane oligomer) as a curing agent
Implementation Method 2
using a guanidine group-containing organic catalyst to achieve curability and adhesiveness without metal catalysts
Data Source
AI summary
This dealcoholization room-temperature curable organopolysiloxane composition contains (A) a diorganopolysiloxane having a silicon atom-bonded hydroxy group and/or a hydrolysable silyl group at both ends of the molecular chain, and has a coefficient of viscosity of 20-1,000,000 mPa·s, (B) an organopolysiloxane which is a partial (co-)hydrolysis-condensation product of a hydrolysable organosilane compound having one or more silicon atom-bonded alkenyl groups and 1-3 silicon atom-bonded alkoxy groups, per molecule, (C) a hydrolysable organosilane compound having one or more phenylene backbones and two or more amino groups, per molecule, and/or a partial hydrolysis-condensation product thereof. The dealcoholization room-temperature curable organopolysiloxane composition has good curability and storage stability even when the composition does not contain a metal catalyst, is less toxic to the human body and is environmentally friendly, is cost-competitive, and has good rubber physical properties and adhesiveness after being cured.