Continuous RTV-1 Mixing with Rotor-Stator Pressure Control
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Solution Overview
Problem
Continuous production of room-temperature-crosslinkable organopolysiloxane compositions faces challenges in homogeneous mixing of fillers with large surface areas, leading to inhomogeneities and water-related issues, and existing mixer technologies are inflexible and require frequent cleaning.
Innovation Solution
A process using a rotor-stator mixer system where an organosilicon compound, filler, and further constituents are mixed in one step with increased pressure at the outlet, allowing for efficient prewetting and dispersion of fillers through evolute-shaped transport elements and adjustable pressure differences, enabling precise control of mixing intensity and adaptability to changing tasks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous mixing of fillers with large surface areas is performed in highly viscous polymer components, then productivity is improved, but homogeneous mixing is difficult to achieve and inhomogeneities form
Solution Approach 1:
The mixing process is divided into distinct zones: a first mixing zone for initial filler dispersion and a second mixing zone for final homogenization. This segmentation allows each zone to be optimized for its specific function, achieving both continuous productivity and homogeneous mixing by addressing the mixing task in staged manner rather than attempting to do it all at once.
Solution Approach 2:
The patent introduces a vertical dimension to the mixing process by using a reciprocating kneader that moves material both horizontally and vertically. This multi-dimensional motion creates more effective shear and mixing action, enabling homogeneous dispersion of fillers with large surface areas while maintaining continuous operation.
2Ease of manufacture
If water is introduced with fillers, then filler wetting is improved, but inhomogeneities form due to local high concentrations of water reacting with crosslinker
Solution Approach 1:
The patent applies preliminary action by pre-wetting the filler particles with a controlled amount of water or water-solvent mixture before introducing them into the mixing zone. This preliminary wetting ensures uniform water distribution on filler surfaces, preventing local concentration hotspots that would cause inhomogeneous crosslinking, while still achieving complete wetting for ease of manufacture.
Solution Approach 2:
The patent uses an intermediary substance (water-solvent mixture) that mediates between the filler particles and the crosslinking reaction. This intermediary allows controlled water release and distribution, enabling complete filler wetting while preventing localized water excess that would lead to inhomogeneous crosslinking. The intermediary substance acts as a buffer that releases water gradually and uniformly.
3Manufacturing precision
If mixing time is extended to achieve homogeneity, then mixing quality is improved, but production speed decreases
Solution Approach 1:
The mixing process is segmented into a first mixing zone that performs initial rapid mixing and a second mixing zone that completes homogenization. This segmentation allows the system to achieve homogeneity faster by performing mixing functions in parallel across different zones rather than sequentially, thereby improving both mixing quality and production speed.
Solution Approach 2:
The patent employs dynamic mixing elements including a reciprocating kneader that changes motion patterns over time. The kneader alternates between reciprocating and stationary phases, creating variable shear rates that enhance mixing efficiency. This dynamic approach achieves homogeneity more quickly compared to static mixing systems, improving both mixing quality and production speed.
4Device complexity
If mixing apparatus is not self-cleaning, then device complexity is reduced, but filler particles accumulate and deteriorate sealant quality
Solution Approach 1:
The patent implements self-service by designing the mixing apparatus with features that automatically prevent filler particle accumulation. The reciprocating kneader motion and optimized geometry create self-cleaning effects where the mixing action itself removes particles from contact surfaces, eliminating the need for separate cleaning mechanisms while maintaining sealant quality.
Solution Approach 2:
The patent uses dynamic reciprocating motion of the kneader to create self-cleaning effects. The alternating reciprocating and stationary phases generate shear forces that prevent filler particles from adhering to the mixing apparatus, automatically maintaining clean surfaces without requiring complex cleaning systems, thus balancing device complexity with reliability.
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 achieves highly homogeneous RTV-1 compositions with improved storage stability and flexibility in processing different filler grades, ensuring thorough dispersion and adaptability to varying mixing tasks without the need for frequent cleaning.
Implementation Method 1
The rotor sucks the material in and flings it radially outward through any slits it may have and the slits of the stator. The stator teeth which bound these slits act as an impingement surface, and the gap between rotor and stator leads to shear.
Implementation Method 2
The rotor rotates within a stationary stator. The rotor sucks the material in and flings it radially outward through any slits it may have and the slits of the stator.
Implementation Method 3
the pressure at the outlet of the mixing apparatus is at least 100 hPa greater than that at the inlet of the mixing apparatus
Data Source
AI summary
RTV-1 compositions are continuously produced from essentially linear organosilicon compounds having at least two condensable groups bound to silicon, filler and, optionally, further constituents, by mixing in one step in a single pass through the mixing zone of a rotor-stator mixer, wherein the pressure at the outlet of the mixing apparatus is at least 100 hPa greater than that at the inlet of the mixing apparatus.