Double, Dual & Triple Shaft Mixers for High Viscosity

Mixing high-viscosity materials: four parameters that decide the mixer type

A high-viscosity mixer is not a bigger disperser — it is a different machine class for a different part of the viscosity range. Getting the configuration right on the first pass avoids a vessel you cannot discharge, an agitator that stalls, or a dispersion step you have to bolt on afterwards.

1. Viscosity. Below roughly 50,000 cP a high-speed disperser usually does the job. From about 50,000 cP up to around 1,500,000 cP you need a planetary, double-shaft or triple-shaft mixer where a slow agitator moves the whole batch while a high-speed head does the shear work. Above that, discharge and containment become the limiting factors rather than the agitator power.
2. Do you also need dispersion? If the product must be both mixed and wetted (pigment, filler, resin premix), a double- or triple-shaft design carries a slow agitator and a high-speed disperser in one vessel. If mixing alone is the goal, a planetary mixer without a disperser head is simpler and cheaper to clean.
3. Batch size and throughput. The range spans 1 L lab units through to 15,000 L production kettles. A 1,000–15,000 L platform triple-shaft mixer is built for large continuous-style batches; everything below that is a floor-standing or hoist unit sized to the working volume.
4. Process extras. Vacuum degassing, jacket heating or cooling, a wall-scraper, and hydraulic discharge are options, not defaults. Specify them from the material and the downstream step, not as a checklist.

What this range covers

Seven platforms span laboratory trials through to 15,000 L production. Each answers a different combination of the four parameters above.

Combined agitator + disperser platforms

• Butterfly Double Shaft Mixer — a butterfly agitator paired with a high-speed disperser for efficient shear mixing of high-viscosity sealants, adhesives and pastes. Capacity range 100–12,000 L.
• Concentric Double Shaft Mixer — a scraper agitator with a concentric high-speed disperser, offered with frame, half-frame and multi-disc agitator options for coatings and filled pastes. Capacity range 100–12,000 L.
• Powerful Three Shafts Agitator — a three-shaft arrangement for high-efficiency, multifunction mixing of heavy pastes where a single agitator cannot maintain homogeneity. Capacity range 100–12,000 L.
• Platform Triple Shaft Mixer (PSK Multi-Function Dispersing Kettle) — the large-batch platform, built in PSK-1, PSK-2, PSK-3, PSK-5, PSK-8, PSK-10 and PSK-15 models covering 1,000–15,000 L for integrated mixing, dispersion and discharge. Capacity range 1,000–15,000 L.

Planetary and dedicated mixers

• Planetary Mixer (DPL) — a planetary agitator for viscosities up to 1,500,000 cP, combining reaction, mixing and dispersion in one vessel, often under vacuum. Capacity range 100–12,000 L.
• Lacquer Mixer (PLM) — a concentric-design unit for stirring and mixing high-viscosity lacquers and coatings where uniform wet-out matters more than high shear. Capacity range 100–12,000 L.
• Hydraulic Discharging Machine (PHD) — a hydraulic extruder that discharges and transfers the finished high-viscosity product from the mixer vessel, shortening the changeover between batches. Capacity range 100–12,000 L.

Typical process routes

Three configurations cover most high-viscosity mixing work. The agitator choice matters more than the vessel size.

1. Sealants and adhesives (combined route)

Slow agitator for bulk movement plus a high-speed disperser for wet-out and de-agglomeration in one vessel, under vacuum to remove entrained air, then hydraulic discharge. This is the route for MS polymers, silicones, PU and epoxy systems.

2. Coatings and lacquers (planetary route)

A planetary or concentric mixer for homogenisation and reaction, with vacuum degassing where film appearance depends on it. Pigment dispersion, if required, is handled by the integrated high-speed head or by a separate bead mill upstream.

3. Heavy pastes and filled systems (triple-shaft route)

A three-shaft agitator keeps very high solids-loadings uniform while the disperser head does the shear work, used for heavily filled compounds, plastisols and ceramic pastes that would stall a single agitator.

Comparing the mixer variants

Type	Typical viscosity	Integrated disperser	Best fit
Planetary mixer (DPL)	Up to 1,500,000 cP	Optional	Very high-viscosity pastes, reaction and vacuum mixing
Butterfly double-shaft	High viscosity	Yes (butterfly + disperser)	Sealants, adhesives, shear mixing of pastes
Concentric double-shaft	High viscosity	Yes (scraper + disperser)	Coatings and filled pastes, frame / multi-disc options
Powerful three-shafts agitator	High viscosity	Yes	Heavy, multifunction pastes needing homogeneity
Lacquer mixer (PLM)	High viscosity	Concentric	Lacquers and coatings where wet-out matters
Platform triple-shaft (PSK)	Large-batch	Yes	1,000–15,000 L integrated mixing and discharge
Hydraulic discharging machine	Finished paste	No (extruder)	Transfers and discharges high-viscosity product

Viscosity figures describe the working range these platforms are built for on typical formulations, not a guarantee for every material. Solids loading, filler shape and temperature all shift the practical limit — which is why we recommend a trial on your own material before a vessel size is fixed.

Frequently asked questions

When should I use a high-viscosity mixer instead of a disperser?

Use a high-viscosity mixer when the material sits above roughly 50,000 cP, when it must be both mixed and wetted in one vessel, or when it is too thick to be pumped and fluidised by a bead mill. A high-speed disperser alone is the right tool below that range; above it, the agitator cannot move the batch and a planetary or multi-shaft design is required.

What viscosity can these mixers actually handle?

Indicative working ranges: planetary mixers are built for viscosities up to about 1,500,000 cP; double- and triple-shaft units cover the high-viscosity band from roughly 50,000 cP upward; the platform triple-shaft kettle is sized for large batches of similar materials. The practical ceiling depends on solids loading, filler type and temperature rather than on the agitator nameplate, so a trial on your own paste confirms the real limit.

Double-shaft or triple-shaft — which do I need?

Choose a double-shaft mixer when one slow agitator plus one high-speed disperser maintains homogeneity. Move to a triple-shaft design when the batch is so heavy or filled that a single agitator cannot keep it uniform, or when you need separate control of bulk movement and shear. The third shaft is there to prevent stratification, not to add marketing spec.

Do I need vacuum degassing?

If entrained air would show as bubbles, pinholes or a soft film in the final product — typical of coatings, sealants and adhesives — vacuum degassing during mixing is worth specifying. For non-critical pastes it can be omitted, which simplifies the vessel and shortens cycle time.

Can these mixers also disperse pigments?

The combined double-, triple- and planetary-with-disperser designs wet out and de-agglomerate pigments through their high-speed heads, which is enough for many premixes. For sub-micron fineness you still need a bead mill upstream or downstream; the mixer handles bulk homogeneity and premix, not nanometre grinding.

How is the finished product discharged?

Lower-viscosity batches are pumped or drained; high-viscosity pastes are pushed out by the hydraulic discharging machine (PHD), an extruder that transfers the product from the vessel and shortens the gap before the next batch. Specifying discharge method up front avoids a mixer you cannot empty.

What custom options are available?

Jacket heating or cooling, vacuum-rated construction, a wall-scraper, and alternative agitator geometries (frame, half-frame, multi-disc, saw-tooth) are all configurable. The vessel, drive and agitator are usually specified to the material rather than taken from a catalogue, so send the process detail and we size the rest.

How do I estimate the vessel size I need?

Start from working volume per batch and required cycle time, then confirm the agitator power and disperser speed needed for your viscosity. A useful planning anchor: a 12,000 L double-shaft mixer covers large sealant and adhesive production, while 100–1,000 L units suit pilots and mid-volume runs. Batch size, not a headline litre figure, sets the right vessel.

Related technical guides

• High Viscosity Mixer Selection Guide — how viscosity, dispersion and discharge drive the configuration.
• High Viscosity Mixer Specs and Selection Guide — vessel, agitator, jacket and drive specification in detail.
• Types of Paint Mixing Machines — which mixer family fits which coating process.
• Planetary Mixer vs Ribbon Blender — viscosity and mixing-action differences.
• Dual Shaft vs Triple Shaft Mixer for Sealants — when the third shaft earns its place.
• Industrial Dispersers for High-Viscosity Materials — where a disperser stops and a mixer begins.