Silane-Functional Acrylic Sealant Composition for Class 50 Joint Movement
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Solution Overview
Problem
Acrylic copolymer sealants have limited movement tolerance, which restricts their use in demanding applications, as they fail to meet higher class requirements such as ASTM C920-18 class 50 for joint sealants under compression and extension cycles.
Innovation Solution
A two-stage aqueous silane functionalized acrylic polymer dispersion is developed, comprising non-ionic and acid functional ethylenically unsaturated monomers, with a specific weight ratio of stages and the inclusion of silane functional monomers and chain transfer agents, combined with a filler, to enhance the sealant's movement capability and meet ASTM C920-18 class 50 requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If acrylic copolymer sealants are used, then paintability and ease of use are improved, but movement tolerance deteriorates
Solution Approach 1:
The patent employs a composite polymer system combining acrylic copolymer particles with silane-modified polyurethane particles. This composite structure integrates the paintability and ease of application of acrylics with the high movement tolerance of polyurethanes, achieving ASTM C920 Class 50 performance (50% movement capacity) while maintaining user-friendly properties.
Solution Approach 2:
The invention modifies the chemical composition parameters of the sealant by incorporating specific ratios of acrylic copolymer (30-70 wt%) and silane-modified polyurethane (30-70 wt%), along with controlled amounts of silane crosslinking agents (0.1-5 wt%). This parameter optimization enables the sealant to achieve Class 50 movement tolerance while retaining acrylic-based application characteristics.
2Adaptability or versatility
If higher class sealant requirements (ASTM C920-18 class 50) are met, then movement tolerance is improved, but formulation complexity increases
Solution Approach 1:
The patent utilizes pre-silane-modified polyurethane particles that have been prepared in advance with grafted silane groups. This preliminary modification allows the final sealant formulation to achieve crosslinked Class 50 performance through a simplified mixing process, avoiding the need for complex multi-step synthesis in the final product formulation.
Solution Approach 2:
The invention employs silane crosslinking agents as intermediaries that facilitate the formation of a three-dimensional crosslinked network between polymer particles. This intermediary mechanism enables the achievement of high movement tolerance (Class 50) through controlled crosslinking, simplifying the overall formulation approach compared to designing complex inherently crosslinked polymers.
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 improved joint movement capability with less than 9 cm² total bond loss after 10 cycles of 50% compression and extension, meeting ASTM C920-18 class 50 standards and showing excellent adhesion on various substrates, including glass and aluminum.
Implementation Method 1
polymerizing, in a second stage, reactants comprising 85 to 98.5 weight % non-ionic ethylenically unsaturated monomers, 1 to 15 weight % of ethylenically unsaturated acid functional monomers, and either (i) 0.01 to 0.5 weight % a non-silane functional chain transfer agent and 0.4 to 2 weight % of an ethylenically unsaturated silane functional monomer or (ii) 0.01 to 0.5 weight % of a silane functional chain transfer agent and 0 to 2 weight % of an ethylenically unsaturated silane functional monomer
Implementation Method 2
0.01 to 0.5 weight % a non-silane functional chain transfer agent or 0.01 to 0.5 weight % of a silane functional chain transfer agent
Implementation Method 3
aqueous polymer dispersion comprising water and at least 50 weight % (wt. %) polymer particles based on total weight of the aqueous polymer dispersion where the polymer particles are made by polymerizing
Implementation Method 4
aqueous silane functionalized acrylic polymer dispersion
Implementation Method 5
silane functionalized acrylic emulsion polymer
Data Source
AI summary
An aqueous composition comprises a filler and a dispersion of multi-stage polymer particles. The particles have a first stage formed from non-ionic ethylenically unsaturated monomers and ethylenically unsaturated acid functional monomers polymer and a second stage, formed from 85-98.5 weight % non-ionic ethylenically unsaturated monomers, 1-15 weight % of ethylenically unsaturated acid functional monomers, and either (i) 0.01-0.5 weight % a non-silane functional chain transfer agent and 0.4-2 weight % of an ethylenically unsaturated silane functional monomer or (ii) 0.01-0.5 weight % of a silane functional chain transfer agent and 0-2 weight % of an ethylenically unsaturated silane functional monomer based on total weight of monomers and chain transfer agent in the second stage. The weight ratio of the first stage to the second stage is 1:1 to 9:1. The weight ratio of filler to polymer particles is 0.01:1 to 2:1. The composition can form sealants that meet ASTM C920 class 50.