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3 ................................................................. UNDERWATER STRAND PELLETIZING ................................................................. PAPER PRESENTED BY: PAUL BOILEAU AUTOMATIK MACHINERY CORPORATION THERMOPLASTIC WASTE RECLAMATION DECEMBER 4-5, 1991 HOLIDAY INN-WOODLAWN * CHARLOTTE, NC

Underwater Strand Pelletizing - InfoHouseinfohouse.p2ric.org/ref/30/29431.pdf · UNDERWATER STRAND PELLETIZING BY Paul Boileau Automatik Machinery Corporation 9724 Southern Pine Blvd

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . UNDERWATER STRAND PELLETIZING

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PAPER PRESENTED BY:

PAUL BOILEAU

AUTOMATIK MACHINERY CORPORATION

THERMOPLASTIC WASTE RECLAMATION

DECEMBER 4-5, 1991

HOLIDAY INN-WOODLAWN * CHARLOTTE, NC

UNDERWATER STRAND PELLETIZING

BY

Paul Boileau

Automatik Machinery Corporation

9724 Southern Pine Blvd.

Charlotte, NC 28273

December 4, 1991

-

The Group

AUTOMATIK The Group

After manufacturing or compounding of polymers, it is

necessary to convert them into shapes and sizes that can be

easily transported, further mixed (in many cases) and

re - processed.

a

The most common methods of "size reduction", as this process

is called, are dicing and pelletizing. Exhibit 1 shows these

two methods along with the preferred polymer types and

approximate throughput rates for each.

In dicing, a continuous, uniform width and thickness "sheet"

of polymer is formed by a die or rolls after the mixing or

extrusion process. This sheet is fed, after cooling, into a

machine known as a dicer. Dicers cut the polymer sheet into

equal size "cubes" by the action of a rotating set of knives

against a fixed blade.

illustrated in Exhibit 2 , attached.

'-1 There are various types of dicers, as

Pelletizers can be categorized into two major groups, die

face or strand type.

Die face pelletizers can be further separated into either dry

or wet (underwater) cutting types. Both types cut pellets

at the die face; the dry type pelletizers (sometimes

referred to as "hot face" pelletizers) cut pellets at the die

face without having water present.

outward by centrifugal force away from the cutting point

Pellets are thrown

*.3

AUTOMATIK The Group

and are then cooled either in water ("water ring" or "water

spray" type) or air ("dry face" type). See Exhibit I11 for

some examples of these types units.

Wet, or underwater, die face pelletizers operate in a similar

principal to dry face type in their cutting action, but in

this case there is water present at the cutting point.

Pellets are actually cut under water and quenched

immediately.

machines.

See Exhibit IV for some examples of these type

Both major types of die face machines have certain advantages

and disadvantages when compared to each other or to strand

pelletizers. Pellet shape desired, polymer types/additives

to be cut, and so on, must be considered when selecting these

type units.

Strand pelletizers provide the most flexibility among all

types of size reduction equipment.

variety of configurations from a "conventional" type unit

that normally has a horizontal waterbath between the

pelletizer and die to cool strands, to various "self

stranding" types.

They are available in a

In all cases with a strand pelletizer, polymer is forced

through a die and formed into individual strands. These

strands are then pulled or guided by the pelletizer's feed

The Group

rolls to the point of cutting. A set of rotating blades

("rotor") cuts the polymer strands against a fixed blade

("bedknife").

length and generally cylindrical in shape (square or other

pellet shapes can be produced depending on the die hole shape

used). See Exhibit V for a typical strand pelletizer cutting

chamber configuration.

3

This machine produces pellets of uniform

Exhibit VI shows a typical "conventional" strand line,

including water bath, airknife, and pelletizer. The strands

from the die fall into the waterbath. To start the machine

an operator pulls these strands through the waterbath and

feeds them into the pelletizer.

pelletizer cutting head then will pull the strands in and

continuously feed them to the cutting point.

The pull rolls inside the

3

Exhibit VI1 and Exhibit VI11 illustrate two types of self

stranding pelletizers.

pelletizer will be demonstrated later today at our facility

here in Charlotte. This machine is also produced in a

vertical configuration which is particularly suited to

polymers that need very short cooling times or are of very

low viscosity. The dry cutting type ATG is used primarily

for filled polymers or polymers that should not be cut

underwater.

The USG horizontal type underwater

AUTOMATIK )

The Group

In each type, the strands are continuously and automatically

fed to the pelletizer by means of a water trough or sluice.

This trough has a water flow that both transports the strands

from the die to the pelletizer as well as cools them on the

way.

directly into the cutter where the pellets are cut

underwater. After cutting, the pellets are carried in the

resulting slurry to a dewatering dryer where the water is

removed and dry pellets are discharged to the users

collection system.

In the USG type system, the water and strands go

In the ATG dry cutting type system, the water is removed from

the sluice and the strands are vacuumed by an airknife to

remove surface moisture before they enter the cutting

chamber. Pellets are cut dry, and are transported to a

cyclone separator by an integral blower. The dry pellets are

then discharged to the users collection system at that time.

Self stranding pelletizers in general provide the benefits of

strand pelletizing in their flexibility and pellet shape,

while giving the added benefits of increasing productivity

through reduced manpower and reduced waste. These machines

are also safer to operate than conventional strand machines,

as you will see later today.

L '- E X H I M I . . d e .

. .. - . . 'SIZE REDUCTION EQUIPMENT

.. .

. . - - .

. . . . . .

. . . . . .

- . . .

. ..

. TYPE - POLY MER. APPLICATIONS CAPACITY RANGE '(LB/HR)

up t o 10,000

Underwater type Polyolefins, polystyrene U p t o 70,000

Up t o 5,000 Water Ring type ' All thermoplastics except

nylons & polyesters

Dry Cut Polyolef.ins, styrenics, engineering thermoplastics U p t o 15,000 '

I

Strand Type' . PVC, polyolefins, nylon, thermoplastic polyester, U p t o 15,000 p o 1.y c a r b o n a t e

Source: Plastics Compounding 1991/92 Redbook

. . . . . .

. ..

, .

. .

. .

. . . .

..

EXHIBIT 11

LEAOIHG AOTOR KNIFE -~ 1 A L T E R Y E ROTOR KNIFE

1 LEADING ROTOR KNIFE \ ALTERNATE ROTOR KNIFE

. FRESHLY SEVERED PELLET. " . .

Figure 42. Cuttfng prfnclple of notched-knife dfcer. (Source: Cumborland)

Figure 43. CuttingprInclple o f rutchet-tooth dlcer. (Source: Cum b e rlan d)

LENGTHWISECUT

Figure 45. Angle-feed dfcer. Figure 46. Repluceuble-knife angle-feed dicer. (5ource: cum- . . beF1und)

I21 I

i--

Figure 44. Operatfon of rlftterl chopper. (Source: Day Mixing)

ffgure 47. Integral-knife s p t rol-type angle-feed dfcer.

PLASTICS C O M I O U I I D W 1991191 \ REDWOK

.i

. . . .

C ' . . . . . .

. .

. . 2' . .

. ._. . . . . . .

i I I .i '

i

i i I

!

KNIFE HUB . .

Figure 52. Vertical undema- '

ier pelle f her. (Source: A PV ChemicalMochtnery)

WATER AND PELLETS

.

Figure 53. Horizontal unde- water pelletizer. (So wee: Werner & Pfleiderer)

f I

I . I

--

. . ,.

. . , . . .

. . 1:. .

I 1

. . ; . . . .

.. '

. . . . .