PLS HELP - CLEAR (TRANSPARENT) RIGID PVC FORMULATION

[ijekic]

Dear all,
can You help me? We are PVC compounder from Serbia. Besides all types that we have, we want to make clear rigid PVC compound. It will be very helpfully if You can give me some exsample of that formulation, and conditions.
We use Ca-Zn stabiliser, PVC 58, 67 and 70, DOP...
Thanfull in advance
Isidora

[Dr. Dick]

Isidora,
You need to provide some additional information for anyone to help you. What molding process will be used? Calendering, Extrusion, Injection, Rotational Molding? Does end use involve outdoor or indoor use? Will the product involve Medical or Food contact use? Temperature range of end product use, any exposure limitations? (solvents, gases, humidity, etc.) Any oxygen or other vapor permeability requirements or limitations?

There are a number of books in English that review PVC compounding and give starting formulations, but bear in mind that some formulations have patents or are considered proprietary by their users.

Skip may have some additional input when he sees this post.

Also have you searched the PVC resin producers for technical data sheets on rigid transparent PVC compounding?

[ijekic]

Dear Dr.Dick,

Our customers ask from us to produce rigid PVC compound for transparent roller shuter (we have grade for white roller shuter but they also want to produce transparent, clear PVC roller shuter), so it will be extrusion process. So end use involve outdoor use.
I think that it will be SPVC K57 (is it possible to be K67 or 70), ESBO, wax, Ca-Zn stabilizer (because we don't use Sn stabilizer, only Ca-Zn), MBS impact modif....what else....

Thanks,
Isidora

[Dr. Dick]

Isodora,

In Theory and practice of Vinyl Compounding, Argus Chemical, 1968 Victor Struber gives two Formulations

Rigid formulation for Outdoor use 1 .........................................................Formula 2
Medium M.W. Homopolymer........................100.0.....................................100.0
Chlorinated PE Impact Modifier.....................0.0 - 10.0............................... 0.0 - 10
Acrylic Processing Aid................................0.0 - 5.0............................... 0.0 - 5.0
Mark 235 or Mark 99(reqd for crystal clarity).....2.0 - 3.0......................Mark 445 3.0
Mark C.................................................0.5 - 1.0......................... omit
Drapex 3.2 ...........................................2.0 - 3.0.................................... 2.0
Mark 446 ...(UV STABILIZER).......................0.25 - 1.0................................... 0.25 - 1.0
Lubricant .............................................0.0 - 0.5..................................... 0.25 - 1.0

He also notes a three component system that is not as good as Formula 1 for out door use
A specialty organo SN stabilizer Mark 445, An Epoxy Plasticizer Drapex 3.2, and a UV absorber Mark 446
He references Argus Laboratory Reports A-449 and A-533

Since this work was done in the early 1960's , I expect there are newer improved formulations for CaZn stabilizer systems

[ijekic]

Dear Dr. Dick,

I have some information that for transparent rigid profiles can be used also this kind of formulation:

PVC K57...........................100
Ca-Zn stabil.......................2.0-3.0.......from Bearlocher, Reagens
MBS (impact.modif.).............4-5.........like Paraloid, Clearstrenght, or MB880 from LG...
processing aid.....................1-2
ESBO................................2-4
int./ext. lubrikant...............0.5.......like Loxiol + 0.15 PE oxidized wax
UV absorber.......................0.5
ultramarine........................0.1

MBS as impact modifier, because it gives transparency. Is it necessary to add also chelating agent like trifenil phosphite for transparency, besides MBS?
What do You think about this formulation, and Is it possible to use this formulation also for transparent spirals ?

Thanksss,
Isidora

[Skip]

Not knowing the extruder type, whether single screw or twin screw (which affects lube balance), your formulation sounds reasonable. My only comment is that Ca/Zn ESO stabilization, while satisfactory for the most part, is still a marginally effective system compared to a good methyltin stabilizer, especially if you are striving for higher output rates. Why choose Ca/Zn's? If you feel the need for a "food-contact" approved stabilizer, the methyltin TM181FS has USFDA sanction. Methyltins provide better melt flow properties and better stabilzation than Ca/Zn's. Use 0.5phr for twin screw, or 1.2 phr for single screw.

[ijekic]

Dear Mr. Skip,
we have Bandera twin screw extruder, and we use only Ca/Zn stabilizer.
purveyance of raw materials is always complicated, we need a lot of time to find a supplier / distributor / representative. And we need to make the compound as soon as possible as , we have Ca / Zn stabilizers always in stock. Therefore, we plan to create a formulation with Ca / Zn stabilizer and not with Sn.
Thanks,
Isidora

[Dr. Dick]

By staying with the CaZn stabilizer you increase the possibility of producing scrap material and lost production time. Even given your time to find and get a Sn stabilizer and maybe even pay a premium delivery charge it may be cost effective to make the change. Given the internet you should be able to find the right Sn stabilizer source near you. The low levels required might allow the initial stabilizer to be air freighted to your site.

Compounding is still more art than science in PVC even given the history of PVC.