Organopolysiloxane Composition Two-Stage Catalyst Curing

The patent divides the hydrosilylation reaction into two distinct stages using different catalysts: a first catalyst (e.g., platinum-based) for initial crosslinking and a second catalyst (e.g., organometallic complex) for subsequent crosslinking. This segmentation allows independent optimization of each reaction stage, achieving high crosslinking density and molecular weight control that single-catalyst systems cannot accomplish, thereby improving adhesiveness and mechanical strength.

The patent changes the catalytic parameters by introducing a second catalyst with different activity characteristics and temperature dependence. The second catalyst remains inactive at the first catalyst's operating temperature but becomes active at higher temperatures, enabling sequential reactions. This parameter change allows precise control over crosslinking progression, resulting in superior mechanical properties.

The patent segments the simultaneous MH and DH unit reactions into sequential steps by using a first catalyst that selectively promotes one reaction type at lower temperatures, followed by a second catalyst that promotes the other reaction type at higher temperatures. This temporal and thermal segmentation achieves precise control over molecular weight and crosslinking density that cannot be obtained when both units react simultaneously.

The patent employs periodic action through a two-stage curing process with distinct temperature profiles and catalyst activation sequences. The first stage operates under conditions favoring MH unit reaction, then the second stage activates under conditions favoring DH unit reaction. This periodic control eliminates the randomness of simultaneous reactions, achieving consistent molecular weight and crosslinking density.

The patent ensures continuity of useful action by designing a two-stage curing process where the first catalyst initiates crosslinking and the second catalyst continues and completes the crosslinking process at elevated temperatures. This continuous action ensures complete curing even for high molecular weight polymers, achieving both high adhesiveness and reliable cure completion that single-stage processes cannot achieve.

The first catalyst performs preliminary crosslinking action at lower temperatures to establish initial network formation, preparing the system for the second catalyst's high-temperature crosslinking. This preliminary action ensures that the polymer chains are sufficiently connected before the second stage, preventing incomplete curing while maintaining the ability to achieve high degree of polymerization for strong adhesiveness.