INTERNAL MIXERSINTERNAL MIXERS AND MIXING
PARAMETERS
Richard Jorkasky II
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MIXING
Early Mixers B d P tBody Parts
Finger, Hand, Arm, FootDisadvantages: Temp PowerDisadvantages: Temp., Power
Advanced Mixer DesignsAdvanced Mixer DesignsStick: Wider Temp. RangeRocks: More Power, Crush, etc., ,
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MECHANICAL MIXING
• Single Rotor MixingEarly as 1820sEarly as 1820s
• Two Roll MillsTwo Roll Mills 1835 - Chaffee → Mill, Wood Roll1854 - Iron Replace Wood Rollsp
• Mills Still Used Todayy
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MECHANICAL MIXING
• Mill DrawbacksTime Consuming/Low OutputTime Consuming/Low OutputInter-Batch VariationsLabor IntensiveDirtySafety
• Two Rotor Mixing1865 N R bb1865 - Non Rubber1916 - Fernley H. Banbury
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Internal Intensive Mixer
CHAMBER
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Hopper (Floating Weight)
● Pneumatic – Compressed Air Most Common (US)Cost Effective (US)Inconsistent Pressure: Fluctuations
● Hydraulic More Common (Asia)( )Cost Effective (Asia)Consistent Pressure, Less NoiseG t I iti l C t B k EGreater Initial Cost, Break EvenNeeds 1’-2’ More Head Space
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Types of Intensive Mixers
Internal Intensive Mixers:Chamber Volume: 0 3 - >700 LitersChamber Volume: 0.3 - >700 Liters1000 L., but chamber is not full (550 L)Batch Wt.: 0.5 - 1150 Lbs*Stationary Chamber
Tilt Discharge Mixers:Tilt-Discharge Mixers:Chamber Vol.: 4 - 300 Liters (common) Batch Wt : 6 - 500 Lbs*Batch Wt.: 6 - 500 LbsMoveable Chamber
* Based on a Specific Gravity of 1 Based on a Specific Gravity of 1
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BB-270 Internal Intensive Mixer
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Tilt Mixer: Economix™
Chamber in Full Discharge PositionChamber in Full Discharge Position
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Factors Affecting MixingRotorsRotors
Tangential20+ T f T ti l (2 6 Wi )20+ Types of Tangential (2 - 6 Wing)Master Batch, 2nd Pass, Re-Mill and FinalEven or Friction SpeedThroughput, Dispersion, MooneyThroughput, Dispersion, Mooney
Intermeshing12+ Types of Intermeshing (3, 4 Lobe)Tandem (500 → 1000 L), Adjustable Clear.Master Batch & 2nd Pass with AdditivesEven SpeedEven SpeedHigher Ram Pres. (Stiff Materials 150 psi)Decreased Fill Factor (Stiff Materials 54%)Temp. Sensitive, Dispersion, Mooney
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Tangential vs. IMPath of Rotors in the Mix Chamber
Tangential Rotor Paths
Intermeshing Rotor Paths
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Material Pull-InIM Hi h R PIM: Higher Ram Pressure
Intermeshing MixerTangential Mixer
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Types of Mixing
● Dispersive Mixing
● Distributive Mixing
● Reactive Mixing
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Types of Mixing
● Dispersive MixingReduction of Additives from Pellet/ Granule to Aggregate/Particle Size
Agglomerates AggregatesGranule/Pellet
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Types of Mixing
• Distributive MixingDistribution of Additive Aggregates/Distribution of Additive Aggregates/Particles Throughout the Matrix
Poor Distribution Good Distribution
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Tangential Rotor Mixing
Dispersive Mixing: Distributive Mixing:
WeightRotor Tip to Chamber Wall
gRotor Body to Wall
Rotor Rotor
Drop Door
Dispersive Mixing:Rotor Tip to Rotor Tip
Distributive Mixing: Between Rotors
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Intermeshing Rotor Mixing
Dispersive Mixing: Rotor Wing (Nog) to Rotor Body
Dispersive Mixing: Rotor Edge to Chamber Wall
Dispersive Mixing: Rotor Edge to Chamber Wall
Distributive Mixing: Rotor Body to Wall
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2 Wing Standard Rotors
• Introduced in 1916
Still Used in Many Plants• Still Used in Many Plants
• General Purpose Mixing / Final
• Slow Temperature Rise
L E C ti• Low Energy Consumption
• Best Rotor for Certain Silica
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2 Wing Standard Rotorsg
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4 Wing Rotors
Introduced in 1939 (1960s, 2011)
Advanced Rotor Designs (4, 6, IM)Require ~25% More Drive Power
Improved Mixing, But …
Poor Dispersion of Some Additives, Especially Sulfury
Modifications to Wing Angle andRotor Bodyy
4 Wing Standard Rotor: Superior to the 2 Wing Rotorp g
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4 Wing Rotor Designs
4 Wing Standard RotorStandard Rotor
(4WS)
4 Wing H Swirl Rotor
(4WH)( )
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Mixing Patterns of 4 Wing Rotors
S4 Wing Standard Rotors
4 Wing H Swirl Rotors4 Wing H Swirl Rotors
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Advantages of 4 Wing H RotorsRotors
• Material Flows and Circulates Material Flows and Circulates More Smoothly Throughout Chamber
• Mixing Pressure in the Chamber and the Material Itself is More UniformUniform
• Improved Mixing and Dispersion p g pwith 4 Wing H
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4 Wing H Swirl Rotorsg
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Typical Rotor Features
Sh t WiShort Wing
Long Wing
Typical Rotor Features: Long Wings on One End and Short Wing on Other End of Rotor. Both Short Wings and both Long Wings are identical, having the same wing angle and rotor tip to chamber wall clearances.
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4 Wing N Rotor
♦ Asia 2000, N. America 2006
♦ Designed for Final Mixing♦ Designed for Final Mixing
♦ Master Batch, Re-Mill Rotor
♦ Achieves Greater Shear
♦ Very Aggressive RubberFlow
♦ Slower Temperature Rise
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4 Wing N Rotor
One Long Wing on Each Rotor has a Small Angle
SWSW
One Long Wing on Each R t h V L A lRotor has a Very Large Angle
Short Wings Alternate Ends, not on Same End as Most Rotors
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4 Wing Mixing Patterns
4 Wing H Swirl Rotors4 Wing H Swirl Rotors
4 Wing N Rotors4 Wing N Rotors© Kobelco Kobe Steel Group 2011
4 Wing N Rotor
♦ Temp. Sensitive Materials
♦ Lower Temp / Equal Mix Time♦ Lower Temp. / Equal Mix Time
♦ 5 - 40 F (3 - 22 C) Lower
♦ Mix at Faster Speed (10 rpm)
♦ More Uniform Batch Temp.
♦ Better Mix Qualityy
♦ Lower Mooney
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6 Wing “VCMT” Rotor
• “Various Clearance Mixing Technology” (1990s)Technology (1990s)
• “VCMT” uses Various TipClearances along the Long Wings and Short Wings ofWings and Short Wings of the Rotor
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6 Wing VCMT Rotor Tips
Small Tip Width Short Wing: Small Tip Width and Clearancep
Small Tip Clearance
Large Tip Width Large Tip Clearanceg p
Medium Tip Width Medium Tip Clearance
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Advantages of the Various ClearancesClearances
Small Tip Clearances:Reduces Dead Areas on Mixer SidesImproved Cooling CapacityHigh Shear MixingHigh Shear MixingExcellent Dispersion
Large Tip Clearances:Allows Greater Movement of MaterialImproved Heat HomogeneityDecreased Frictional Heat
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Advantages of the VCMTRotors
Overall:
Fastest Cycle TimesHighest ThroughputReduced Energy ConsumptionExcellent Dispersion pGood Temperature UniformityReduced Mixing StepsReduced Mixing StepsReduced Mooney Viscosity
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Intermeshing Rotors
• Introduced in 1934 (Present)
• Lower Fill/Smaller ChamberLower Fill/Smaller Chamber
• Smaller Batch Size
• Temperature Profile ~ 2 Wing
• Longer Cycle Times, ↑ RPM
• Greater Energy Use than Tang.
• Good Excellent Dispersion• Good - Excellent Dispersion
• Lower Mooney Vis. with SBR
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Intermeshing Rotors
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Rotor Batch Size ComparisonBB-16 Mixer
2 Wing Standard 17.7 lit / 28.0 lb
4 Wing N 16.2 lit / 26.4 lb
4 Wing H “Swirl” 16.0 lit / 26.0 lbg
4 Wing Standard 15.7 lit / 25.6 lb
6 Wing VCMT 14 4 lit / 23 8 lb6 Wing VCMT 14.4 lit / 23.8 lb
Intermeshing 14.5 lit / 20.7 lb
Wt. Lbs. = (Mixer Vol.) (Spec. Grav.) (FF) (2.2)
(Based Upon a Spec. Gravity of 1)
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Other Rotor Related Items that Affect Mixingect g
Rotor Cooling
Typical Rotor Cooling: Cored Cavity
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Other Rotor Related Items that Affect MixingAffect Mixing
Rotor Orientation
• Friction Speed: No Orientation
• Even Speed
2 Wing: No Specific Orient2 Wing: No Specific Orient.
4 Wing: 0, +90, -90 (270)°
6 Wing: 0, +60, -60 (300), 180°
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4 Wing Orientation
0° Orientation
90° Orientation90 Orientation
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Factors Affecting Mixing
Rotor SpeedSingle or “Fixed”: 40 RPMSingle or Fixed : 40 RPM
Dual: 20/40, 40/60
V i bl 1 M i RPMVariable: 1 - Maximum RPM
MixingMixing“Speed Kills” Mindset
Faster Mix Speed, Poorer Prop.
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Factors Affecting Mixing
Drive Speed
Even: Both Rotors Same Speed
60 rpm X 2 = 120 Total Rev /Min60 rpm X 2 = 120 Total Rev./Min.
Friction: 1 Rotor Faster Than OtherFriction: 1 Rotor Faster Than Other
If the friction ratio is 1.15 and the faster rotor is turning at 60 rpm,faster rotor is turning at 60 rpm,60 + 52 = 112 Total Rev./Min.
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Factors Affecting Mixing
Type of Rubber
NaturalIntra- / Inter-bale Mooney VariationPre-mastication or Breakdown
SyntheticEPDM, Nitrile, PB, SBR, etc.Some May Need Breakdown, Nitrile “Tailor Made” - No Breakdown
CombinationsUp to 4 Different Rubbers in One Mix
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Factors Affecting Mixing
Water Temperaturep
Circulate Water:
Door, Chamber Sides and RotorsSometimes Through the Ram
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Water Circulation Through Chamber SideChamber Side
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Factors Affecting Mixing
Water Temperature
Circulate Water:Door, Chamber Sides and RotorsS ti Th h th RSometimes Through the Ram
Water Type:ypTemp. Controlled Water (45 - 210 F)Well: Not affected by surface cond.Cit W t (NE Ohi 35 F t 75 F)City Water (NE Ohio: 35 F to 75 F)Tower Water
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Factors Affecting Mixing
Additives
Type: Filler, Oil, Sulfur, Chemicals, Etc.
Grade: CB N-121 vs. N-330 vs. N-774CB N 121 vs. N 330 vs. N 774
Amount:<45-50 phr CB 1 Pass Add>50 phr CB 2 Pass Add
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Factors Affecting Mixing
Mixing Scheme:
Ri ht Sid URight Side UpRubber First then Additives
Up Side DownAdditives First then Rubber
Additive Addition Filler, Oil, AO, Etc.
Single Pass vs. Multiple Pass
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Factors Affecting Mixing
Silica / Silane Mixing:
1st Pass Silanization: Hold
2nd Pass Silanization: Hold2nd Pass Silanization: Hold
Numerous Passes: No Hold
Pre-Treated Silica: No HoldReaction Done During ManufacturingReaction Done During Manufacturing
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Factors Affecting Mixing
Ram Pressure / Ram Raises
High PSI: Faster Mix TimesHigh PSI: Faster Mix Times
Low PSI: Slower Mix Times
Ram Raise: Increase Mix Times
Mix With Ram Upp
IM Rotors: Higher Ram Pressure
Dust Stops
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Factors Affecting Mixing
Fill Factor:Higher FillgFaster Mix, to a PointToo High, Poor Mix/UnmixedDust Stops
Lower FillLower FillLonger Cycle TimeNormal Fill: Draws Too Much Power Stiff MaterialsSilica: 75% FF → 60% FF
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Factors Affecting Mixing
S l UScale-Up:Lab Mixer to Production Mixer
Heat RemovalRotor/Chamber WearChamber/Rotor FinishesDifferent Rotors Rotor Speeds Different PeopleDifferent People
SuccessE i With B th MiExperience With Both MixersUse of Scale Up Mixers (16 L, 35 L)Calculate Speed/Temp. Needed
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