Silane-Terminated Polymer Adhesive with High Transparency
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Solution Overview
Problem
There is a need for curable compositions based on silane-terminated polymers that exhibit improved mechanical properties, such as reduced skin formation over time, high tensile strength with acceptable elongation, and enhanced optical properties like high transparency, while meeting the requirements of modern adhesives, sealants, and coatings.
Innovation Solution
A curable composition comprising a polymer with terminal groups of the formula -A n -R-SiXYZ, where A is a divalent or trivalent bonding group, R is a hydrocarbon residue, and X, Y, Z are hydroxyl or alkyl groups, combined with a compound of the formula R 1< -Ar-n-R 2< , where Ar is an aryl group, to achieve improved mechanical and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional silane-terminated polymers are used for adhesives and sealants, then the compositions are free from isocyanate groups and show broad adhesion to various substrates, but the mechanical properties after curing are insufficient and skin formation occurs over time
Solution Approach 1:
The patent combines silane-terminated polymers with specific silicone compounds (polydimethylsiloxanes with terminal vinyl groups) and crosslinking agents to create a composite system. This composite approach allows the adhesive to benefit from both the adhesion properties of silane-terminated polymers and the mechanical strength and flexibility of silicone-based crosslinked networks, resolving the contradiction between good adhesion and insufficient mechanical properties.
Solution Approach 2:
The patent modifies the chemical composition parameters by introducing specific silicone compounds with controlled molecular weights and terminal groups, adjusting the crosslinking density and network structure. These parameter changes enable improved tensile strength and elongation while maintaining adhesion properties, addressing the mechanical property deficiencies of conventional silane-terminated polymers.
2Reliability
If conventional silane-terminated polymers are used, then the compositions show broad adhesion without surface pretreatment, but the elongation after curing is unacceptable
Solution Approach 1:
The composite system combines silane-terminated polymers with polydimethylsiloxane components that provide elastic flexibility. This composite structure maintains the primer-free adhesion capability of silane-terminated polymers while the silicone component contributes to acceptable elongation and compositional stability after curing.
Solution Approach 2:
The patent adjusts the molecular weight and terminal group composition of the silicone compounds to optimize the balance between adhesion and elongation. By controlling these parameters, the formulation achieves both reliable adhesion without surface pretreatment and acceptable elongation properties in the cured state.
3Ease of operation
If conventional silane-terminated polymers are used, then the compositions can be formulated as one-component moisture-curing systems, but the transparency and optical properties are insufficient
Solution Approach 1:
The patent selects silicone compounds with specific molecular weights and terminal group compositions that minimize light scattering and maintain high transparency. By optimizing these parameters, the formulation achieves both ease of application as a one-component moisture-curing system and superior optical clarity in the cured state.
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 demonstrates reduced skin formation, high tensile strength, and improved elongation, along with enhanced optical clarity, making it suitable for advanced adhesive, sealant, and coating applications.
Implementation Method 1
In the presence of atmospheric moisture, polymers having silyl groups with hydrolyzable substituents are already capable of condensing with one another at room temperature, splitting off the hydrolyzed residues
Implementation Method 2
polymers having silyl groups with hydrolyzable substituents are already capable of condensing with one another at room temperature
Data Source
AI summary
The invention relates to a curable composition comprising a) at least one polymer having at least one terminal group of the general formula (I) -An-R-SiXYZ (I), wherein A is a divalent or trivalent bonding group containing at least one heteroatom, R is selected from divalent hydrocarbon residues having 1 to 12 carbon atoms, X, Y, Z are, independently of one another, selected from the group consisting of a hydroxyl group and C1 to C8 alkyl, C1 to C8 alkoxy, C1 to C8 acyloxy groups and -CH2-N-R' wherein N is oxygen, nitrogen or sulfur, preferably oxygen, and R' is selected from C1 to C8 alkyl groups, preferably a methyl group, wherein X, Y, Z are substituents directly bound with the Si atom or the two of the substituents X, Y, Z form a ring together with the Si atom to which they are bound, and at least one of the substituents X, Y, Z is selected from the group consisting of a hydroxyl group, C1 to C8 alkoxy or C1 to C8 acyloxy groups, and n is 0 or 1; and b) at least one compound of the general formula (II) wherein R1 is same or different and is, independently from one another, selected from the group consisting of a hydrogen atom and hydrocarbon residues having 1 to 12 carbon atoms, R2 is same or different and is, independently from one another, selected from hydrocarbon residues having 1 to 12 carbon atoms, Ar is selected from aryl groups, and n is an integer selected from 3 to 9; and adhesive, sealant, or coating materials comprising the composition and use thereof.