Continuous Silicone Base Composition Production via Segmented Kneading

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Solution Overview

Problem

Continuous processes for producing base compositions for silicone compositions face challenges in stability, particularly with viscosity increase, SiH degradation, and additive degradation, leading to inhomogeneity and reduced storage stability, especially at elevated temperatures, and are limited by low volume flow rates and high energy consumption.

Innovation Solution

A two-stage process using a multiple-chambered kneading machine for homogeneously mixing diorganopolysiloxanes with prehydrophobized oxidic reinforcing fillers, followed by shear and devolatilization in a downstream mixing apparatus with constant surface renewal, to enhance stability and mechanical properties of the silicone elastomers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If continuous process is used for producing base compositions, then productivity is improved, but stability of the composition deteriorates

Engineering Contradiction:

ImproveproductivityVSAvoidstability

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The continuous process is divided into multiple distinct stages: a first stage for homogeneously mixing and kneading organopolysiloxanes with prehydrophobized filler in a multiple-chambered kneading machine, and a second downstream stage for aftertreatment in a mixing apparatus with constant surface renewal. This segmentation allows each stage to optimize for its specific function, maintaining high productivity while achieving the extended residence time and mixing quality needed for composition stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The filler is prehydrophobized before being introduced into the continuous process. This preliminary action ensures that the filler surface is properly treated to prevent unwanted reactions during the continuous mixing process, thereby maintaining composition stability while enabling continuous high-speed production.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If residence time is reduced in continuous process, then productivity is improved, but homogeneity of the composition deteriorates

Engineering Contradiction:

ImproveproductivityVSAvoidhomogeneity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The mixing process is segmented into a first stage in a multiple-chambered kneading machine where initial homogeneous mixing occurs, and a second downstream stage in a mixing apparatus where further homogenization takes place with constant surface renewal. This segmentation enables sufficient mixing time for homogeneity while maintaining continuous high-speed operation for productivity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second downstream stage operates continuously with constant surface renewal, ensuring that the mixing and homogenization actions continue uninterrupted throughout the process. This continuous useful action maintains homogeneity without requiring extended residence time that would reduce productivity.

Inventive Principle:

Principle #20Continuity of useful action

3Ease of manufacture

If in-situ hydrophobization is performed, then ease of manufacture is improved, but energy consumption increases

Engineering Contradiction:

Improveease of manufactureVSAvoidenergy consumption

Core Design Contradiction:

Ease of manufactureVSUse of energy by moving object

Solution Approach 1:

Instead of performing hydrophobization in-situ during the mixing process, the filler is prehydrophobized before being introduced into the continuous mixing process. This preliminary action simplifies the manufacturing process by eliminating the need for additional chemical treatment stages while reducing energy consumption associated with in-situ treatment and inert gas requirements.

Inventive Principle:

Principle #10Preliminary action

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 improved stability against viscosity increase, reactivity loss, and additive degradation, ensuring high transparency, mechanical strength, and demoldability, while allowing for volume flow rates exceeding 300 kg/h, thus addressing the limitations of prior art.

Implementation Method 1

homogeneously mixing and kneading... in a multiple-chambered kneading machine... followed by shear and devolatilization

Methodology Applied

Scientific EffectShear force: Shear Stress

Implementation Method 2

devolatized with constant renewal of the surface

Methodology Applied

Scientific EffectDevolatilization: Evaporation

Data Source

PatentUS8287174B2Continuous process for the production of base compositions for improved-stability silicone compositions

Publication Date: 2012.10.16 WACKER CHEMIE AG

AI summary

Base compositions for addition-crosslinking silicone compositions are continuously produced by, in a first stage, homogeneously mixing and kneading organopolysiloxanes and flowable prehydrophobized oxidic reinforcing fillers in a continuous kneading machine with kneading chambers arranged alongside one another. In a second, downstream, stage of the process, the compositions produced in the first stage are subjected to aftertreatment in a mixing apparatus in which the compositions have been subjected to a mixing procedure with introduction of shear force.