Tin-Free Silane Polymer Coating Catalyst System
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Solution Overview
Problem
Current curable compositions, particularly those used in sealants and adhesives, face challenges with the use of organotin compounds due to environmental regulations and the need for alternatives that maintain catalytic activity, storage stability, and adhesion properties, while achieving rapid curing and thick-section curing without premature gelation.
Innovation Solution
A catalyst composition comprising a combination of metal amidine complexes with amine carboxylate salts is used, which acts as a catalyst for polymers with reactive silicon groups, providing a tin-free, non-toxic solution that enhances cure speed, adhesiveness, and storage stability, similar to organotin compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If organotin compounds are used as catalysts, then curing speed and adhesion are improved, but environmental safety and storage stability deteriorate due to toxicity and regulatory restrictions
Solution Approach 1:
The patent changes the chemical composition parameters by replacing organotin compounds with alternative catalyst systems comprising organometallic compounds (such as organozinc, organoaluminum, or organotitanium compounds) combined with co-catalysts like carboxylic acids or esters. This parameter change maintains catalytic activity for silicon-bond formation while eliminating the toxicity associated with organotin compounds, thereby resolving the contradiction between curing speed and environmental safety
Solution Approach 2:
The patent employs catalyst systems with appropriate half-lives that are active during the curing process but decompose or become inactive afterward, leaving no toxic residue. The organometallic catalysts and co-catalyst combinations are designed to complete the curing reaction efficiently and then degrade into harmless byproducts, effectively replacing persistent toxic organotin compounds with transient, non-toxic catalytic systems
2Loss of time
If moisture curing is accelerated, then production time is reduced, but premature gelation and loss of storage stability occur
Solution Approach 1:
The patent incorporates a co-catalyst (such as a carboxylic acid or ester) in advance within the composition that remains dormant during storage. Upon exposure to moisture during the curing process, the co-catalyst activates the organometallic catalyst, initiating rapid silicon-bond formation. This preliminary preparation allows the composition to remain stable during storage while enabling fast curing when needed, resolving the contradiction between curing speed and storage stability
Solution Approach 2:
The patent creates a dynamic catalytic system where the organometallic catalyst and co-catalyst exist in a balanced state during storage with minimal reactivity. When moisture is introduced, the system dynamically shifts to high catalytic activity, accelerating the curing reaction. This dynamic behavior allows the composition to maintain stability during storage while achieving rapid curing when activated, effectively managing the trade-off between storage stability and curing speed
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 metal amidine complex and amine carboxylate salt combination achieves rapid curing with a tack-free surface and complete bulk curing in thick sections, while maintaining storage stability and adhesion on various substrates, effectively replacing organotin compounds in RTV compositions.
Implementation Method 1
polymers having a reactive silicon group can polymerize with the formation of siloxane bond by hydrolysis and/or condensation reactions aided by moisture and suitable catalysts
Implementation Method 2
polymers having a reactive silicon group can polymerize with the formation of siloxane bond by hydrolysis and/or condensation reactions
Implementation Method 3
catalysts for reactions of one or more organic polymers having a reactive-silicon-containing group
Data Source
AI summary
There is a tin-free curable composition having (A) one or more organic polymers having a reactive-silicon-containing group, wherein at least one polymer has a main chain skeleton selected from the group consisting of polyoxyalkylene polymers, saturated hydrocarbon polymers, and (meth)acrylic acid ester polymers; (B) from 0.001 to 20 parts by weight for 100 parts by weight of the organic polymer(s) (A) of a silanol condensation catalyst consisting of one or more metal amidine complexes and one or more amine carboxylate salts, (C) a crosslinker or chain extender chosen from an alkoxysilane, an alkoxysiloxane, an oximosilane, an oximosiloxane, an epoxysilane, an epoxysiloxane, an aminosilane, a carboxysilane, a carboxysiloxane, an alkylamidosilane, an alkylamidosiloxane, an arylamidosilane, an arylamidosiloxane, an alkoxyaminosilane, an alkaryaminosiloxane, an alkoxycarbamatosilane, an alkoxycarbamatosiloxane, and combinations of two or more thereof; and (D) at least one adhesion promoter chosen from a silane or siloxane other than the compounds listed under (C). There is also a cured polymer formed from the tin-free curable composition.