posted March 05, 2006 05:42 PM               

WE HAVE A NEW PET SHEET EXTRUSION LINE TO PROCESS PET FLAKES.FOR TWO MONTHS NOW I AM TRYING TO FIND TEMPERATURE PROFILES FOR EXTRUDER AND THE CHILL ROLLS.I HAVE BOUGHT DOZENS OF BOOKS AND READ HUNDREDS OF ARTICLES FROM INTERNET BUT STILL COULD NOT FIND SUITABLE TEMPERATUR PROFILES TO PROCESS PET FLAKES.

I SHALL BE VERY THANKFUL IF ANYBODY COULD HELP ME.

BEST REGARDS

posted March 06, 2006 02:04 AM               

Welcome to the single screw forum- Is your extruder new, or new to you? What L/D is it, how many barrel zones, is the barrel vented? what is the geometery of the screw?

You mention flake, are you trying to reprocess regrind, running virgin resin(Whose, what grade), are you predrying?

Your roll stack, three chill rolls, four/more? Does the material run upstack or down?

posted March 06, 2006 08:59 AM               

quote:

---

Originally posted by Steve H:
Greetings Ali

Welcome to the single screw forum- Is your extruder new, or new to you? What L/D is it, how many barrel zones, is the barrel vented? what is the geometery of the screw?

You mention flake, are you trying to reprocess regrind, running virgin resin(Whose, what grade), are you predrying?

Your roll stack, three chill rolls, four/more? Does the material run upstack or down?

Steve

---

posted March 06, 2006 09:14 AM               

THANK YOU FOR YOUR KIND INTEREST.

THE EXTRUDER IS NEW AND ALSO NEW TO ME AS I HAVE NO EXPERIENCE IN EXTRUSION AND THIS IS THE FIRST TIME I AM WORKING WITH AN EXTRUDER.

THE L/D IS AROUND 42.

THERE ARE 9 BARREL HEATING ZONES AND 7 DYE ZONES.
1-5 INIIAL ZONES.
6 VACUUM DEGASSING ZONE
7 HEATING ZONE
8 FILTERING ZONE
9 PUMP ZONE
10-16 DYE ZONES

I HAVE NO IDEA SCREW GEOMETRY AS I CANNOT SEE IT.

WE PROCESS PET REGRIND FROM RECYCLED PET BOTTLES.

WE HAVE A VACUUM AGLOMERATION UNIT FOR PREDRYING.

BEST REGARDS

posted March 06, 2006 09:17 AM               

AS FOR THE CHILL ROLLS:

posted March 11, 2006 01:30 PM               

What is the IV of the PET(intrinsic viscosity?)

What is the extruder diameter?

It seems like you have six barrel zones in the extruder, a filter (7), a melt pump (8), and seven die body zones (10-16.) Is this correct?

You really need a screw drawing. Ask for one from the vendor. You may need to buy it.

Suggested barrel zone temperatures.
degrees F
zones 1 and 2 475 F
zone 3 and 4 500 F
zones 5 and 6 520 F

Zones 5 and 6 will be need to be set to get the proper product temperature, 540 F???.

Filter, pump, and die should be around product temperature.

You may need to profile the die lips to get the proper sheet thickness control. Trial and error, likely. Some calculations can help if you want to pay for them. But you will still need to try and error to see if they work.

Many other questions.
Flow rate?
Screw speed?
Drive power?
Drive max speed?
PET bulk density?
Screw dimensions?
Sheet dimensions (width, thickness?)

posted April 02, 2006 01:32 PM               

i have tried the temperatures you adviced and it worked good.thank you very much!

what did you mean by product temperature 540????.i set to 520 and worked.might it be something else.

i shall be very pleased also if you would advise me the chill roll temperatures which run upstack.i tried 40,50 and the last upper roll 60.the sheet became brittle.is the brittleness due to the incorrect roll temp or incorrect tension in the pull rolls.

thanks again for your kind help.is there anything we could do for you?we shall be very pleased to show our gratitudes.

best regards

ali

posted April 04, 2006 08:58 PM               

In your chill rolls you may be crystallizing the PET. This will make it brittle. Cooling too fast is a cause for crtstallization. Also, too low of a product temperature can lead to crystallization. So, try increasing the last barrel zone to raise the product temperature to eliminate the crystallization that way.

Most of my experience is with PET. If you would like to contract for greater work (i.e. defined projects with specific deliverable goals, timeline, and cost.) I would be happy to consider it. steve@extrudertech.com

If you have a need for excellent training on the fundmentals of extrusion, I offer an in-plant course with EMMount Technologies. Training of this type is the mainstay of my company. see www.extrudertech.com for details.

Thank you,

posted April 05, 2006 06:15 AM               

thank you very much for your advices.

only i am a bit confused.we require amorphous pet(transperent) and all the articles i had read on the subject explained that the matterial should be cooled below the glass trans temp (80 deg C ) very quickly.thats why we set our chill roll temps to 40,50 and 60 deg C.

is this right?

thanks again

posted April 05, 2006 09:31 AM               

What is important is roll "wetting." This is how well the sheet thermally contacts the roll. If the sheet does not "wet" the roll, then thermal contact is poor and cooling suffers. So, there is a lower limit to temperature for good roll wetting below which cooling is poor. You should be able to see a line between sheet and roll where the "wetting contact ends."

Sheet thickness plays a big part in this, too. A slight increase in thickness has a dramatic effect on cooling of the interior sheet, on the order of square of sheet thickness.

My appologies for the misinformation. I hope it did not cause undue problems.

posted April 05, 2006 10:04 AM               

You need to download two files, one a executable and the other a working data file.

posted April 05, 2006 11:25 AM               

THANK YOU VERY MUCH FOR YOUR KIND HELP.

AS MUCH I UNDERSSTOOD

THE ROLL TEMPERATURE MUST BE BELOW THE TG WHICH IS 80 DEG C , BUT IN THE MEANTIME IT MUST BE NOT LOWER THAN THE TEMP WHERE THE WETTING OCCURS.

I FOUND A PET SHEET EXTRUSION GUIDE PUBLISHED BY EASTMAN.THERE IT IS STATED THAT THE FIRST CONTACT ROLL SHOULD BE 40,THE MIDDLE ROLL 50 AND THE FINAL ONE 65 DEG C.

COULD YOU PLEASE TELL ME YOUR IDEAS ON THE ABOVE STATED TEMPS.

BEST REGARDS

posted April 05, 2006 01:39 PM               

I believe that if the sheet or the roll is too cold, wetting is not good because the surface becomes too hard to wet the roll. The sheet surface should be warm enough to be "wet" to wet the roll. So, you can have the wheel or the sheet too cold initially.

Did you try the sheet temperature program? This might help you with the internal temperatures of the sheet as it cools. It could help you set up the three roller temperatures to promote wetting while still cooling the sheet.

You can also blow air on the other side (OS) of the sheet to help cooling.

Also, be careful that thermal steady state is obtained by the extrusion system and die. I do not know if you start up every day, but it can take some hours for steady thermal conditions to occur for a large machine. So, you could have good sheet and then have poor sheet a few hours later.

As I recall some figures, I think roll temperature of about 30 C was used ok. However, it all depends on sheet thickness, roll speed, and OS cooling. There is quite a transient in temperature in the roll surface when the sheet contacts it, too. You will need to do some trial and error to find some good settings, likely. Go up 5 or down 5 C on the roll, and notice effect. It should not take long to find out what is best.

When it is correct, it will be beautiful. It is all a very nice combination of science and art!

posted June 06, 2006 04:37 AM               

AFTER YOUR KIND ADVISES WE HAVE CHANGED OUR SCREEN CHANGER AND ADDED A STATIC MIXER TO THE EXTRUDER.YESTERDAY WE MADE A TRIAL AFTER ASSEMBLING THESE.

WE STİLL HAVE THE SAME PROBLEM OUR SHEET IS BRITTLE IN ONE DIRECTION.

THAT IS IT IS BREAKING ALONG THE WIDTH WHEN BENDED AND PRESSED.THERE IS NO BREAKING ALONG THE LENGHT SIDE.

I HAVE STUDIED A LOT OF PAPERS AND MOSTLY IT SAID THAT IT IS DUE TO MOLECULAR ORIENTATION.

THEY ADVISE THE FOLLOWINGSOLUTIONS:
REDUCE DRAW DOWN OF CHILL ROLLS
INCREASE CHILL ROLL TEMPS
INCREASE MELT TEMP
ELIMINATE MELT BANK

YESTERDAY IHAVE TRIED THESE BUT DOING THESE CAUSED OTHER PROBLEMS.

TO REDUCE DRAW DOWN OF ROLLS I HAD TO BRING THE SCREWS RPM DOWN.THIS INCREASED THE RESIDENCE TIME IN EXTRUDER AND CAUSED THE MATTERIAL TO BE BROWNISH.

INCREASING THE MELT TEMP ALSO CAUSED THE MATTERIAL TO GET BROWNISH.

TO ELIMINATE THE MELT BANK IHAD TO REDUCE THE RPM OF THE SCREW WHICH RESULTED IN INC OF RESIDENCE TIME.I ALSO TRIED TO ELIMINATE THE BANK BY INCREASING THE RPM OF CHILL ROLLS WHICH CAUSED WEB STRETCHING.

I DONT KNOW WHAT ELSE TO DO.THERE ARE NO EXPERTS IN TURKEY WHICH WOULD COME TO OUR FACTORY AND CONSULT US.

COULD YOU PLEASE ADVISE US WHAT TO DO AND SHOW US A WAY TO OVERCOME THIS SITUATION.

THANKING IN ADVISE FOR YOUR KIND INTEREST.

ALI

posted June 07, 2006 03:00 AM               

MY PREVIOUS REPLY WAS TO YOU.I AM TERRIBLY SORRY.I MIXED UP YOUR NAME AND NAMED THE LETTER AS TO PETER.

BEST REGARDS

posted June 07, 2006 07:20 AM               

Your brown polymer is not good. It is degraded badly so it is no longer pure PET.

What are you trying to make? Thickness, mm?

You can e-mail me at steve@extrudertech.com