Solventless Silicone PSA Composition With Low-Viscosity Coating
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Solution Overview
Problem
The preparation of solventless pressure sensitive adhesive (PSA) compositions is hindered by the difficulty in blending polyorganosilicate resin with other ingredients homogeneously due to its solid form at room temperature, leading to high viscosity and the need for solvent use, which results in residual solvent and inadequate coating on substrates.
Innovation Solution
A process involving the preparation of a silicone base part with a viscosity of less than 5,000 mPa·s at room temperature by mixing specific polyorganosilicate components with aliphatically unsaturated polydiorganosiloxane and polydiorganosiloxane gum, followed by admixing with polyorganohydrogensiloxane and a hydrosilylation reaction catalyst to form a solventless PSA composition suitable for direct application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If polyorganosilicate resin is used in solid form without solvent, then residual solvent content is reduced, but viscosity becomes too high for direct coating
Solution Approach 1:
The patent changes the molecular weight parameter of the polyorganosilicate resin to 500-8000 g/mol and controls the ratio of capped to uncapped resin units, thereby reducing viscosity while maintaining solventless formulation. This allows the adhesive to be directly coatable without solvents.
Solution Approach 2:
The patent creates a composite adhesive system combining polyorganosilicate resin with specific silicone polymers and crosslinking agents. This composite formulation achieves low viscosity and good coatability while remaining solventless, resolving the contradiction between residual solvent reduction and ease of operation.
2Ease of operation
If polyorganosilicate resin is dissolved in solvent, then viscosity is reduced for easier coating, but residual solvent remains in the composition
Solution Approach 1:
The patent extracts and eliminates the solvent component entirely from the adhesive formulation, achieving a solventless composition. This removes the harmful residual solvent while maintaining coatability through alternative viscosity control methods using specific resin molecular weights and compositions.
Solution Approach 2:
The patent changes the physical state parameter of the adhesive from solvent-based liquid to solventless meltable solid, with controlled viscosity through molecular weight selection. This allows direct coating without solvent while eliminating residual solvent content.
3Object-affected harmful factors
If solvent removal step is added to eliminate residual solvent, then residual solvent content is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts and removes the solvent removal step from the manufacturing process by formulating a solventless adhesive from the beginning. This eliminates the need for complex solvent stripping equipment and processes while achieving zero residual solvent content.
Solution Approach 2:
The patent performs preliminary formulation design to create a solventless adhesive composition before manufacturing, preventing the need for subsequent solvent removal steps. This simplifies the manufacturing process and reduces equipment complexity while ensuring low residual solvent content.
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 process enables the production of a solventless PSA composition with desired coating appearance and adhesion strength, suitable for protective films, achieving peel adhesion of 20 g/in or less without the need for solvent dilution.
Implementation Method 1
mixing starting material (A) with starting material (B) and optionally starting material (C) at a temperature of 100° C. or higher
Implementation Method 2
cooling the mixture obtained from step (ii) to form a silicone base part with a viscosity of less than 5,000 millipascal-seconds (mPa·s) at room temperature
Implementation Method 3
The resulting solventless PSA composition can be directly applied to a substrate and cured to form pressure sensitive adhesives (PSAs)
Data Source
AI summary
A process for preparing a solventless pressure sensitive adhesive composition comprising mixing (A) a solid polyorganosilicate resin component with (B) an aliphatically unsaturated polydiorganosiloxane (B-1), a branched polyorganosiloxane (B-2), or a mixture of (B-1) and (B-2), at certain temperatures, followed by cooling. The solventless pressure sensitive adhesive composition prepared by the process has a low viscosity and can be cured to form pressure sensitive adhesives. The pressure sensitive adhesives are suitable for protective film applications.