Tin Catalyst Structure for Silicone Elastomer Storage Stability
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Solution Overview
Problem
Conventional single-component silicone elastomers face stability issues during storage due to the use of tin catalysts, leading to premature ageing and failure in crosslinking after long-term storage, with existing solutions often requiring complex mixtures of catalysts to achieve a balance between crosslinking kinetics and stability.
Innovation Solution
The use of specific tin catalysts, such as [Re2Sn(OOC—Rf)]2O or Re2Sn(OOCRf)2, in amounts ranging from 0.05 to 0.35 mmol of tin per 100 g of composition, which alone provide an excellent compromise between crosslinking kinetics and storage stability, ensuring compositions remain effective for over 6 months.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional tin catalysts (dibutyltin dilaurate, dialkyltin dicarboxylates) are used, then crosslinking kinetics are improved, but storage stability deteriorates due to premature ageing
Solution Approach 1:
The patent applies parameter changes by modifying the chemical structure of the tin catalyst, specifically using tin compounds with beta-diketonate ligands (e.g., dibutyltin bis(beta-diketonate)) instead of conventional catalysts like dibutyltin dilaurate. This structural parameter change fundamentally alters the catalyst's properties, enabling it to maintain stability during storage while preserving crosslinking activity.
Solution Approach 2:
The patent employs composite materials by creating mixed catalytic systems that combine tin compounds with beta-diketonate functionality with other organotin compounds. This composite approach leverages the complementary properties of different catalysts to achieve both stable storage and effective crosslinking, as demonstrated in the mixture described in U.S. Pat. No. 4,749,766.
2Stability of the object's composition
If mixtures of catalysts are used to improve storage stability, then stability is improved, but device complexity and production costs increase
Solution Approach 1:
The patent applies the extraction principle by isolating and utilizing the specific beta-diketonate functionality as the key stabilizing element. By focusing on this particular chemical feature and building the catalyst around it, the invention simplifies the overall system compared to complex multi-component mixtures, while maintaining the desired stability properties.
Solution Approach 2:
The tin compound with beta-diketonate functionality serves multiple functions simultaneously: it acts as a crosslinking catalyst during application and provides storage stability during shelf life. This multi-functionality eliminates the need for separate stabilizing agents or complex catalyst mixtures, thereby reducing system complexity.
3Productivity
If conventional catalysts are used, then crosslinking activity is maintained, but product reliability deteriorates after long-term storage due to premature ageing
Solution Approach 1:
The patent applies preliminary action by incorporating the beta-diketonate ligand structure into the catalyst design before the crosslinking process begins. This pre-configured structure proactively prevents premature ageing and maintains catalyst reliability throughout storage, ensuring consistent crosslinking performance when the product is eventually applied.
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
These catalysts enable single-component silicone elastomers to maintain stability and crosslinking capability after long-term storage, eliminating the need for catalyst mixtures and reducing production complexity and costs, while ensuring effective adhesion and curing at ambient temperatures.
Implementation Method 1
single-component silicone mastics which are stable on storage in the absence of moisture and which crosslink by polycondensation at ambient temperature (for example, 5 to 35° C.) in the presence of water (for example, ambient moisture) to result in elastomers
Implementation Method 2
crosslink by polycondensation at ambient temperature (for example, 5 to 35° C.) in the presence of water (for example, ambient moisture)
Data Source
AI summary
The invention relates to polyorganosiloxane monocomponent compounds (POS) which are stable when stored without humidity and crosslinking into elastomer in the presence of water. The inventive compounds comprise at least one type of crosslinkable linear polyorganosiloxane (POS), a mineral filler and a crosslinking catalyst of formula (I) which provides said compound with an excellent compromise between cross linking kinetics and a storage stability (i.e. more than 6 months).