Fluidized Bed Drying Control for Graft Copolymer
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Solution Overview
Problem
Current methods for producing thermoplastic molding compounds with reduced residual monomer content are complex and require additional degassing-extrusion steps, while existing drying processes do not effectively control constant moisture and monomer levels, leading to inconsistent product properties.
Innovation Solution
A method involving the continuous drying of graft copolymers in a fluidized bed dryer, where the drying gas temperature and flow are controlled to maintain constant water and residual monomer content, eliminating the need for additional degassing steps and ensuring consistent product properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional drying processes are used for graft copolymer, then drying can be performed, but constant moisture and monomer levels cannot be controlled, leading to inconsistent product properties
Solution Approach 1:
The patent implements a feedback control system where the drying conditions (temperature, air flow rate) are automatically adjusted based on real-time measurement of moisture content and residual monomer levels in the graft copolymer. This closed-loop control ensures constant product properties by continuously monitoring and correcting deviations from target values.
Solution Approach 2:
The patent dynamically changes drying parameters (temperature and air flow rate) based on the measured moisture and monomer content of the graft copolymer. By adjusting these parameters in response to material state changes, the system achieves reliable control over final product composition and properties.
2Object-generated harmful factors
If additional degassing-extrusion steps are added to reduce residual monomer content, then monomer content can be reduced, but process complexity increases
Solution Approach 1:
The patent extracts residual monomers from the graft copolymer during the drying process itself, using controlled evaporation and air stripping. This integrates the monomer removal function into the existing drying operation, eliminating the need for separate degassing-extrusion steps while achieving low residual monomer content (below 500 ppm for styrene, below 100 ppm for acrylonitrile).
Solution Approach 2:
The patent combines the drying function and monomer removal function into a single integrated process step. By merging these two operations, the process achieves both moisture reduction and residual monomer elimination without requiring additional equipment or process stages.
3Productivity
If higher drying temperature and air flow are used, then drying speed increases, but energy consumption increases
Solution Approach 1:
The patent employs dynamic adjustment of drying temperature and air flow rate based on real-time material moisture and monomer content. The system starts with higher energy input for rapid initial drying, then automatically reduces energy consumption as the material approaches target specifications, optimizing the balance between productivity and energy efficiency throughout the drying process.
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 method achieves a significantly reduced residual monomer content and consistent product properties by controlling the drying process, particularly in ASA and ABS molding compounds, with residual monomers below 500 ppm for styrene and 100 ppm for acrylonitrile, enhancing the mechanical and thermal properties of the thermoplastic molding compounds.
Implementation Method 1
c) continuously drying the dewatered graft copolymer B, whereby a drying gas and the dewatered graft copolymer B are fed in, the dewatered graft copolymer B is moved through the drying gas and forms a fluidized bed
Implementation Method 2
the dewatered graft copolymer B is moved through the drying gas and forms a fluidized bed
Data Source
Figure 1
AI summary
The invention relates to a process for producing a thermoplastic moulding compound comprising a thermoplastic copolymer A and a graft copolymer B (4), comprising: continuously drying the dewatered graft copolymer B (4) by supplying a drying gas (3) and the dewatered graft copolymer B (4), by moving the dewatered graft copolymer B (4) through the drying gas (3) and forming a fluidized bed (5), the drying gas (3) having a feed temperature TG,feed in the range from 50°C to 160°C, and by removing dried graft copolymer B (4) and an offgas (7), wherein i. a starting temperature Tin of the fluidized bed (5) on feeding (9) of the dewatered graft copolymer B (4) is measured, ii. a finish temperature Tout of the fluidized bed (5) on removal (11) of the dried graft copolymer B (4) and/or of the offgas (7) is measured, iii. a difference ∆Tact between the finish temperature Tout and the starting temperature Tin is formed and the difference ∆Tact is compared with a target value ∆Ttarget, and iv. the finish temperature Tout is adjusted by – increasing a mass flow rate of drying gas (3) supplied and/or the feed temperature TG,feed of the drying gas (3) when the difference ∆Tact is smaller than the target value ∆Ttarget or – reducing a mass flow rate of drying gas (3) supplied and/or the feed temperature TG,feed of the drying gas (3) when the difference ∆Tact is greater than the target value ∆Ttarget.