# US 2008/0185758 A1 · Pellet Treatment Unit

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- Number: US 2008/0185758 A1
- Document ID: US20080185758A1
- Status: Published application
- Kind: A1
- Application number: 11/793,582
- Filed: 2005-12-20
- Published: 2008-08-07
- Earliest claimed: 2004-12-20
- Inventors: Eric Damme
- Web page: https://patentgrep.com/patent/US20080185758A1

## CPC

- B29B 9/16: Auxiliary treatment of granules
- B29B 7/78: by gravity, e.g. falling particle mixers
- B29B 7/82: Heating or cooling
- B29B 7/826: {Apparatus therefor}
- B29B 7/845: {Venting, degassing or removing evaporated components in devices with rotary stirrers}
- B29B 9/065: {under-water, e.g. underwater pelletizers}
- C08F 6/005: {from solid polymers}
- B29B 7/38: rotary (B29B7/52 takes precedence)
- B29B 2009/161: {Absorbing, i.e. introducing a gas, a liquid or a solid material into the granules}
- B29B 2009/168: {Removing undesirable residual components, e.g. solvents, unreacted monomers; Degassing}
- B29K 2023/06: {PE, i.e. polyethylene}
- B29B: PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- B29K: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR {MOULDS, } REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS

## Abstract

The present invention discloses a continuous process for producing polymer pellets having reduced volatiles.

## Claims

### Claim 1

A method for reducing volatiles in polyethylene pellets that comprises the steps of:
a) retrieving the pellets from the extruder (1) and pushing them through a cooling pipe (3) with a stream of cooling water and with a residence time sufficient to reach the desired temperature;
b) separating the pellets from the water in a dryer (4), returning the water to the cooling system via a cooling device (5) and pushing the cooled pellets through a pipe (9) into the heating silo (10);
c) keeping the pellets for a period of time of from 5 to 50 hours in the heating silo under a stream of hot gas (11) entering near the lower end of the heating silo and escaping through the upper open surface;
d) continuously retrieving pellets through the bottom part of the heating silo via a valve (24) that allows control of the exiting flow of material in order to keep the heating silo constantly full;
e) feeding the pellets to the cooling device (25);
f) keeping the cooling device at room temperature to bring the pellets' temperature down to the desired level of from 60 to 70° C.;
g) sending the cooled pellets to the homogenisation silos.

### Claim 2 (depends on 1)

The method of claim 1 wherein the stream of hot gas of step c) is air.

### Claim 3 (depends on 1, 2)

The method of claim 1 or claim 2 wherein the cooling device is a cooling silo kept under a stream of gas, preferably air, at room temperature (26).

### Claim 4 (depends on 3)

The method of claim 3 wherein the warmed-up cooling gas exiting the cooling silo is recycled back to the heating unit (11).

### Claim 5 (depends on 1, 2)

The method of claim 1 or claim 2 wherein the cooling device is a set of vertical plates cooled by water at room temperature between which the pellets fall under gravitational acceleration.

### Claim 6 (depends on 1, 2, 3, 4, 5)

The method of any one of claims 1 to 5 wherein the desired temperature of step a) is of 60 to 70° C., said temperature being achieved for a residence time of 10 to 20 seconds in a stream of cooling water kept at a temperature between 40 and 105° C., preferably between 50 and 90° C., most preferably between 55° C. and 80° C.

### Claim 7 (depends on 1, 2, 3, 4, 5)

The method of any one of claims 1 to 5 wherein the desired temperature of step a) is of about 100° C., said temperature being achieved for a residence time of 3 to 10 seconds in a stream of cooling water kept at a temperature between 50 to 80° C.

### Claim 8 (depends on 1, 2, 3, 4, 5)

The method of any one of claims 1 to 5 wherein the desired temperature of step a) is of about 100° C., said temperature being achieved for a residence time of 10 to 20 seconds in a stream of cooling water kept at about 100° C.

### Claim 9 (depends on 7, 8)

The method of claim 7 or claim 8 wherein the cooled pellets are pushed through a pipe (9) into the heating silo by a stream of gas at a temperature between 20 and 60° C.

### Claim 10 (depends on 7, 8)

The method of claim 7 or claim 8 wherein the cooled pellets are pushed through a pipe (9) into the heating silo by a stream of water at a temperature of about 100° C., and wherein the dryer is moved to the end of pipe (9) and before the heating silo.

### Claim 11

The method of any one of the preceding claims wherein the heating silo is kept at a temperature of from 80 to 130° C. and the residence time of the pellets therein is of from 5 to 50 hours.

### Claim 12

Use of the system according to any one of the preceding claims to produce pellets having organoleptic properties.

### Claim 13 (depends on 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11)

Use of the system according to any one of claims 1 to 11 to produce pellets having low volatiles content.