UPW - rPVC

[nutter]

Hello again,
We use a twin screw TP140 extruder with UWP to pelletize rigid compounds.
I am currently struggling with "burning" in the adapter & die when compounding clear rigid with 9 phr Clearstrength 320 impact modifier.
I have compounded other clears in the past using KM334 with no problems.
The burning has not affected the pellets at this point, I suspect mostly because I have never run more than 10K at a time.
Does anyone have experience with this and can steer me in the right direction with temperature changes that may need to be made when using this?
I currently am running
ZONE 1 385
ZONE 2 380
ZONE 3 375
ZONE 4 370
ZONE 5 360
SCREW OIL 360
ENTRY ADAPTER 360
GALA ADAPTER 365
DIE 370

As I mentioned earlier - This profile works well when using other impact modifiers

Jay

[Len]

Jay,

You do not mention process aids in your post. And, your formulation details are lacking for a anything beyond educated guesses. But, I think you should compare your two impact modifiers. 1.) It the only thing you mention changing. 2.) They may not be direct drop in rerplacements for one another. Some of these impact modifiers are "one-packs" which contain processing aids, other are straight impact modifiers which in th elatter case need processing aids to function properly. I'm not familiar w/ the CS 320, in this regard.

I also suspect you may be dealing w/ some other issues; a metal release issue or poor lubricity w/in the melt and a possilbe under stabilized situation in your compound when Clearstrength is used. It's not uncomon to encounter slight differences in processing when 1:1 additive replacements are made to good running compounds, even if the replacement is from a similar family of modifiers.

I little more information on the content (additives listed by phr) between the KM 334 and CS 320 formulations would be helpful.

Regards,

Len

[nutter]

Hi Len,

I do hesitate to post exacts although I certainly benefit when others do.

PhR Component Description
100 GG 2082
2 ESO,
1 Advalube F-1060LN
2 TM 181FS / Mark 1900
2 Paraloid K175, Pstrength 770
1 Paraloid K120ND, Pstrength 550
9 Clearstrength 320
0.6 Advalube E-2100
0.008 Blue
0.03 Violet

Hopefully this will help you guide me through this problem.

Jay

[Len]

Hi Len,

I do hesitate to post exacts although I certainly benefit when others do.

PhR Component Description
100 GG 2082
2 ESO,
1 Advalube F-1060LN
2 TM 181FS / Mark 1900
2 Paraloid K175, Pstrength 770
1 Paraloid K120ND, Pstrength 550
9 Clearstrength 320
0.6 Advalube E-2100
0.008 Blue
0.03 Violet

Hopefully this will help you guide me through this problem.

Jay

Thank you.

And, let me be sure, you don't change a thing when switching from KM 334 to CS 230, or back to KM 334?

Are you sure you use the PS 550 and PS 770 in those ratios? Interesting, as most PVC compounds reverse this ratio, favoring the fusion inhancer over lubrication.

Len

[nutter]

Len,
I checked my history and yes the phr levels have been reversed from original. I have been working with our formulator & apparently he reversed this in an effort to help stop the burning.
On a side note - I had the die changed today because I was suspicious of water getting behind it. We have 2 other UWPs on single screws so I am experienced with the havoc this can cause.
We are currently running 10K of this formula so I will know in the morning if the burning has stopped.
Thank you so much for working with me & I will report the results of this run in the morning.

Jay

[Len]

Jay,

Your stabilizer level looks good. You may bump it up by 0.5 phr w/out over stablizing if you think that its level is related to the burning. I would also suggest a re-look at the lubricants.

Advalube designations F and E are generally related to their function in the compound. Designation E = external and F = internal lubricant in general (although there are exceptions). The actual function is sometimes a mixed bag internal/external/balanced and is related to the additive's chemical structure. External lubricants can aid metal release, stickiness, and thus reduce burning due to hang-up. They generally have a limited compatability in the PVC compound. If you over do them and they can act as plasticizers or haze and surface exudation can increase. Internal lubricants tend to work w/ the stabilizer to reduce burning due to process shear, adn they tend to aid polymer flow.

I'm not sure, is one of these lubricants is Ca. Stearate? If it's not already in the compound, I'd add about 1.5 phr of Ca. stearate and lower the existing internal lubricant accordingly in the compound. Just a suggestion!

All these are general guidelines, the actual lubricant action is subject to its structure and the effect of other ingredients in the formulation.

Good luck w/ the run. Keep us posted, please.

Thanks,

Len

[nutter]

Finally returning to update the results of our last campaign.
We successfully produced 10K pounds of the above formula. We continue to have carbon buildup on the adapter between extruder & die but less than in the past.
Ca Stearate is not in this formula - Is this an acceptable ingredient for clear compounds?

Jay

[Len]

Finally returning to update the results of our last campaign.
We successfully produced 10K pounds of the above formula. We continue to have carbon buildup on the adapter between extruder & die but less than in the past.
Ca Stearate is not in this formula - Is this an acceptable ingredient for clear compounds?

Jay

Ca. St. is not normally recommended in clears.

Len

[aria78]

Hello Jay

From your original problem I can comment that the heat stability would be enough for this application but I think the problem coming from over gelled material as it possible that one impact modifier bring more energy to the system than other.
My solution for you is to check the turque level for both impact modifers if the new one brings more turque try to reduce the barel temp which are already very high to my belief.
If this do not help try using external lubricants like synthetic PE waxes , but this also may not be very good for transparency.
the other solution is to use amid wax as external lubrication that reduce the gelation.
Also reducing the Advalub 1060 and ESBO may Help

Aria