Background and Task
Rubber-modified polymers are plastics in which rubber-like, elastomeric materials are blended as additives to improve the properties of the base polymer, particularly its toughness, impact resistance, and elasticity.
For this purpose, the rubber (e.g., polybutadiene or SBR) must be dispersed and dissolved in a matrix polymer (e.g., polystyrene or a styrene–acrylonitrile mixture).
Modified polymers are used, for example, in plastics for the housings of electronic devices, automotive components, or toys—applications where increased flexibility and fracture resistance are required.
The most commonly used modified polystyrenes include acrylonitrile–butadiene–styrene (ABS), high-impact polystyrene (HIPS), and styrene–butadiene rubber (SBR or SB).
Challenge(s)
To modify conventional polystyrene, the rubber (typically 35 kg blocks) must be completely dissolved in a solvent. Historically, this required placing the rubber blocks into a stirrer filled with solvent and mixing them for a very long time in a batch process.
Complete solubilization required extremely long mixing times because the necessary shear forces to break down the particles were not available. As a result, residues in the form of larger particles remained, causing blockages in basket strainers.
Other problems included the risk of explosion due to the handling of solvents, high emissions caused by the open system, and the high energy consumption of the batch process.
Solution
Since 1988, HOSOKAWA Micron and CAVITRON have supplied a dissolving system for continuous rubber processing in the production of rubber-modified polymers.
This system enables the simultaneous size reduction, homogenization, and dissolution of rubber in styrene within a closed system.
Hosokawa Micron Rubber Chopper
Hosokawa Micron manufactures various versions of the well-known PB15 Rubber Chopper each year. Designed for the coarse primary size reduction of rubber bales before dissolving or blending with other chemicals, the Rubber Chopper is known for its efficiency, robust construction, and high reliability. With its energy-efficient operation and low maintenance requirements, a Rubber Chopper can remain in service for up to 30 years.
Cavitron Rubber Dissolving System
The rubber granules pre-shredded by the Rubber Chopper fall into the hopper of the rubber dissolving system and are conveyed to the Cavitron dissolver via a screw conveyor. Inside the dissolver, the granules are milled into fine particles and intensively mixed with styrene monomers to produce a 95% dissolved, uniform rubber slurry. The dissolver pumps this slurry into the curing tank, where optimal conditions ensure complete dissolution.
Overview Customer Benefits
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Fully automated and highly efficient dissolving
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Processing large quantities and high rubber concentrations
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Lower environmental impact and maximum occupational safety
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Compact, space-saving design
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Lower maintenance requirements
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High process control for guaranteed reproducible quality
Customer Benefits in Detail
- Fully automated and highly efficient dissolving
The fully automated, continuously operating system combines size reduction, homogenization, and dissolution in a single process. Throughput times are significantly reduced, while energy consumption and operating costs decrease at the same time. - Processing large quantities and high rubber concentrations
The system processes more than four tons of rubber per hour and produces highly concentrated rubber solutions. - Lower environmental impact and maximum occupational safety
Because the material is processed in a closed system, no particles or vapors are released. The system fully complies with European directives for protection against explosive atmospheres (ATEX). - Compact, space-saving design
The compact layout of the system significantly reduces the space required—an important advantage for production facilities with limited floor space. - Reduced maintenance requirements
Intensive grinding reduces residues in plant components and eliminates the need for regular cleaning of basket screens. - High process control for guaranteed reproducible quality
The system operates with precision and reliability, consistently delivering uniform product quality. This ensures that both processes and results remain reproducible.
Dissolving systems for continuous rubber processing from Hosokawa Micron & Cavitron not only enable efficient, high-quality production of thermoplastics, but also contribute to reduced production costs and improved sustainability.
This system has proven itself with numerous customers worldwide and has been an indispensable component in the production of ABS, HIPS, and SBR/SB since 1988.
General Technical Specifications
Static seals:
Viton, Teflon, Kalrez, other elastomers.
Operating pressure:
Application-dependent, up to 100 bar; standard: up to 10 bar.
Operating temperature:
Application-dependent up to 250 °C; standard: 150 °C.
Performance and energy consumption:
Type overview available for download.
Drives and power transmission:
Three-phase motors, high-frequency motors, mechanical gear units, variable-speed drives, stepless electronically controlled and monitored systems.
V-belt and Poly-V belt drives.
Intensity levels:
Application-specific, ranging from coarse mixing to dispersion in the angstrom range.
Bearings:
Tapered roller bearings, angular contact ball bearings (double).
engineered.
