Silazane Catalyst Silicone Resin Handling Viscosity
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Solution Overview
Problem
Condensation-curable organopolysiloxane compositions face challenges in achieving high heat resistance and light resistance due to catalyst residue, viscosity issues, and poor handling properties, particularly with conventional catalysts that degrade and leave behind color or remain in the cured product.
Innovation Solution
A condensation-curable silicone resin composition using a silazane compound as a catalyst, which reacts quickly with organopolysiloxanes having branched or network structures and terminal hydrolyzable groups, preventing viscosity increase during handling and ensuring high heat and light resistance without residual catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large amount of condensation catalyst is used to improve reactivity, then the curing rate increases, but the heat resistance and light resistance of the cured product deteriorate due to accelerated resin degradation and catalyst residue
Solution Approach 1:
The patent uses a silazane compound as an intermediary catalyst that mediates the condensation reaction between the organopolysiloxane components. The silazane compound enables the reaction to proceed at a practical rate while being completely consumed in the reaction, unlike conventional metal catalysts that remain as residues. This intermediary approach allows achieving both fast curing and excellent heat/light resistance by replacing persistent catalysts with a consumable catalytic agent.
Solution Approach 2:
The patent changes the chemical parameter of the catalyst from conventional metal-based catalysts (such as tin, zinc, or aluminum compounds) to a silazane compound. This parameter change fundamentally alters the catalyst's behavior: it becomes a reactant that is completely consumed rather than a persistent residue, thereby eliminating the trade-off between curing rate and long-term stability. The silazane compound reacts to form part of the cured network, ensuring both speed and durability.
2Productivity
If conventional metal catalysts are used to achieve fast curing, then the productivity improves, but the transparency and color stability of the cured product deteriorate due to catalyst color and degradation
Solution Approach 1:
The silazane compound functions as a disposable catalyst that is completely consumed during the curing reaction. Unlike conventional metal catalysts that persist in the cured product and cause coloration, the silazane compound is used up in the reaction process, leaving no harmful residues. This disposable catalytic approach ensures the cured product maintains excellent transparency and color stability while still achieving fast curing rates.
3Productivity
If the organopolysiloxane has high molecular weight to reduce reaction steps, then the gelation efficiency improves, but the viscosity increases making pouring and handling difficult
Solution Approach 1:
The patent segments the organopolysiloxane system into two distinct components: a branched or network-type organopolysiloxane (which provides gelation and crosslinking) and a linear organopolysiloxane (which provides fluidity and low viscosity). This segmentation allows each component to fulfill its specific function optimally - the network-type component ensures efficient gelation while the linear component maintains low viscosity for easy handling and pouring, resolving the contradiction between gelation efficiency and operability.
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 cures quickly, maintains low viscosity during handling, and produces a cured product with high heat resistance, light resistance, and transparency, eliminating catalyst residue and degradation issues.
Implementation Method 1
a condensation-curable silicone resin composition comprising a branched or network type organopolysiloxane (A) which has two or more hydrolyzable groups each bonded to a silicon atom... (B) a linear organopolysiloxane (B) which has at least one hydrolyzable group bonded to a silicon atom at each of both terminals... (C) at least one silazane compound
Implementation Method 2
the silazane compound hydrolyzes quickly in the curing reaction to thereby form ammonia having the silazane-origin nitrogen atom and, then, the ammonia volatilizes
Implementation Method 3
the ammonia volatilizes. Therefore, the catalyst does not remain in the cured product
Data Source
AI summary
One of the purposes of the present invention is to provide a condensation-curable silicone resin composition which show a less increase of the viscosity during handling and cures quickly to provide a cured product which has a very small amount of a remaining catalyst and which has high heat resistance and high light resistance. Thus, the present invention is to provide a condensation-curable silicone composition comprising the following components (A) to (C): (A) 100 parts by mass of an organopolysiloxane which has a branched or network structure and has two or more hydrolyzable groups each bonded to a silicon atom and at least one of (R1SiO3/2) and (SiO4/2) units, wherein R1 is, independently of each other, a hydrogen atom or a substituted or unsubstituted, monovalent hydrocarbon group having 1 to 12 carbon atoms, (B) 5 to 500 parts by mass of a linear organopolysiloxane having at least one hydrolyzable group bonded to a silicon atom at each of both terminals, and (C) at least one silazane compound represented by the following general formula (3) or (5) or comprising the following units (6) in an amount of 0.02 to 30 parts by mass, relative to total 100 parts by mass of components (A) and (B):