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New Class of Liquid Phosphite Stabilizers The Green Solution. Dr. Michael Jakupca Dr. Don Stevenson, Jacob Lance, Nina Ruegg Dover Chemical Corporation. SPE Polyolefins Conference 2011 Houston, Texas. Polyolefin Stabilizers. - PowerPoint PPT Presentation
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New Class of Liquid Phosphite StabilizersThe Green SolutionThe Green Solution
Dr. Michael JakupcaDr. Don Stevenson, Jacob Lance, Nina Ruegg
Dover Chemical Corporation
SPE Polyolefins Conference 2011Houston, Texas
Polyolefin Stabilizers
Most polyolefin stabilizer packages include a primary antioxidant (such as a hindered phenolic) and a secondary antioxidant (usually an organophosphite)
POLYMER R· ROO·ArOH Primary AO
ArO·ROH ROOH
P(OR)3 P(OR)3 Secondary AO
O
hv, heatMet. Cat.
O2
Common Antioxidants for LLDPE
C18H CO -CH2-CH2 OH
O
37
P O C9H19
3
P O
3
O P
O
O
O
P
O
O
TNPP (trisnonylphenyl phosphite) Commodity Solid Phosphite (SP-1)
High Performance Solid Phosphite (SP-2) Commodity Hindered Phenolic (AO-1)
Commodity Phosphite Stabilizers
TNPP and SP-1 are the most widely used commercially available phosphites
Good cost-performanceGood hydrolytic stabilityGlobally registeredGlobal indirect food contact clearance
TNPP is a liquid, SP-1 is a solid
Trisnonylphenyl Phosphite (TNPP)
TNPP is in many ways the ideal phosphite. It offers several advantages over SP-1
TNPP is the most cost effective phosphite availableTNPP does not show compatibility/bloom issues in LLDPE applications, especially film
• SP-1 can bloom at >1,000ppm in certain LLDPE resins/applications
The use of TNPP is often dictated by the type of additive handling unit, solid or liquid handling
Currently, TNPP is the only liquid phosphite available with global indirect food contact clearance for all polymer applications (GRAS)
TNPP Global StatusTNPP has been used safely in food contact polymers for more than 30 years. There are no governmental mandated use restrictions on TNPP
TNPP can be used in all food contact polymers in the US without limitations (21 CFR 178.2010, Antioxidants and/or Stabilizers for Polymers) - GRAS
“The quantity used shall not exceed the amount reasonably required to accomplish the intended technical effect.”
TNPP also approved for use in the EUBroad approval and high SML Specific Migration Limit (SML) = 30 mg/kg
TNPP in EU Risk Assessment
2001 European Union NP Assessment discussed TNPP. With regards to human health concerns, the EU concluded there were no consumer exposure scenarios, including for TNPP, of concern given low exposure and limited mammalian toxicity concerns
TNPP is currently in the final stages of an environmental EU risk assessment
R1=R2=R3=alkyl AlkylAlkyl PhosphitesR1=R2=R3=aryl ArylAryl Phosphites
R1R2R3=alkyl/aryl Alkyl/ArylAlkyl/Aryl
Examples R = phenyl, 2-ethylhexyl, isodecyl, nonylphenyl
RO OR
OR
P
TNPP Replacement?
There are many types of commercially available phosphites…
Phosphite : Ligand Choice
The structure of the ligand has a large effect on phosphite properties
Physical form: solid or liquidHydrolytic stabilityCompatibility in the polymerActivity-performanceVolatility-thermal stabilityCost
Hydrolytic Stability
Phosphites can be hydrolyzed/degraded when exposed to water, especially under acidic environments.
P(OR)3 + H2O
O ||HP(OR)2 + ROH
O ||HP(OR)2 + 2 H2O H3PO3 + 2 ROH
Acidic =“ Black Specks”
Hydrolytic Stability
Hydrolysis resistance trend
Alkyl < Akyl-Aryl < Aryl < Hindered Aryl
Least MostHydrolytic Stability Hydrolytic Stability
Hydrolytic Stability (Aryl>Alkyl)
(Phosphites exposed to 60°C, 85% Humidity)
P
O
O
O
H21C10O
P OC10H21
H21C10O
O
O
P OC10H21
OC10H21P
O
H21C10O
0
100
0 1 2 3 4 5 6
Exposure Time (Hours)
Per
cent
Rem
aini
ng
0
100
0 1 2 3 4 5 6
Exposure Time (Hours)
Per
cen
t R
emai
nin
g
O
O
P OC10H21
O
O
P OC10H21
OC10H21P
O
H21C10OOC10H21P
O
H21C10O
Structure of Ligands Effect Hydrolytic Stability
Phosphites exposed to 60°C, 85% Humidity
Hydrolytic Stability (Effect of Steric Hindrance)
Neat Phosphites Exposed to 40°C & 85% Humidity
Hours to Failure % Hydrolyzed
Phosphite A <10 >50%
Phosphite B ~48 >50%
Phosphite C >2000 <5%
Phosphite A
Phosphite B
Phosphite C
Phosphite Activity (Depends on Polymer)
Peroxide decompositionP(OR)3 + R’OOH O=P(OR)3 + R’OH
Arbuzov and related reactionsP(OR)3 + Cl-R’ (labile) (RO)2P(O)-R’ + RCl
P(OR)3 + HCl (RO)2P(O)H + RCl
2P(OR)3 + ZnCl2 Zn[OP(OR)2]2 + 2RCl
HydrolysisP(OR)3 + H2O (RO)2P-OH + ROH
Addition reactionP(OR)3 + -C=C- O=P(OR)2-C-C-R
MostlyFor PVC
Competitive Oxidation : Alkyl vs. ArylIn general, Alkyl Phosphites are more active at scavenging
hydroperoxides than Aryl Phosphites
Concentration versus time in paraffin solvent at 200°C
Aryl Phosphite
AlkylPhosphite
Rate ofOxidation
Phosphite Polyolefin Stabilizers
Polyolefin phosphite stabilizers are generally composed of hindered aryl ligands (alkylphenols)
Hydrolytic stability is needed to prevent black specks and poor material handling
% Phosphorus is key to performance
Two phosphites dominate the commodity market
P O C9H19
3
P O
3
Liquid Solid
Compatibility
The choice of alkylphenol also dictates the compatibility of the phosphite in the resinEspecially important is compatibility in LLDPE during cast film processing (highly amorphous)Lack of compatibility results in plate-out on equipment as well as post process bloom or surface exudationOne of drawbacks of SP-1
Compatibility By Gloss MeasurementsIt is known that SP-1 can bloom in LLDPE applications at levels above 1000ppm. The bloom can be accurately detected by this technique.TNPP does not bloom because of the greater solubility of nonylphenol.
Compatibility LimitFor SP-1 in thisResin is <1,200ppm
0
20
40
60
80
100
0 5 10 15 20
Days In Oven at 70°C
Surf
ace
Glo
ss V
alue
500ppm 800ppm 1200ppm 1500ppm
P O
3
Antibloom Packages
Antibloom agents have been developed that prevent the bloom of phosphite SP-2
Cleared for use in food contact applications
Alkylphenols in the “Spotlight”Monosubstituted para-alkylphenols as a class
Monoalkylphenols from C4 to C12 have shown low levels of petri-dish ED activity
Butyl-, octyl-, nonylphenol, (Bisphenol A)Petri dish experiments are a screening tool, and are extremely sensitive, do NOT represent in vivo activity
This is a perception issue, not a safety issue
Alkylphenols
Increasing sensitivity of analytical methods and negative perception Alkylphenols are not readily biodegradableEU is particularly sensitive to these issues
Increased Focus on Purity and Tougher Hygienic Requirements in EU
New tests methods with ppb detection limits have been developed that ensure “unsuspected substances” do not migrate into drinking water intended for human consumption (EN 15768)May include intermediates, additives and additive byproducts.
New Liquid Green Phosphite (LGP-11)
New technology, patent pendingContains no alkylphenolsComposed of non-toxic biodegradable raw materialsHigh MW, low migration/low exposureExcellent process stability (5% phosphorus), compatibility, hydrolytic stability, long term aging and resistance to gas fade
No Alkylphenols
New technology has been developed that preserves the thermal and hydrolytic stability of phosphites that previously was only obtained through the use of alkylphenols
Thermal Stability TGA Weight Loss
0
10
20
30
40
50
60
70
80
90
100
0 100 200 300 400
Temperature (°C)
Wei
gh
t P
erce
nt
Solid Phosphite SP1 TNPP LGP-11
Hydrolytic Stability
Neat Phosphites Exposed to 50°C, 85% HumidityAll Phosphites Contain 1% TIPA
0
10
20
30
40
50
60
70
80
90
TNPP LGP11 TLP
4 Hours8 Hours24 Hours
% PhosphiteRemaining
Performance EvaluationPerformance measured with multiple pass extrusion in LLDPE, MI and YI retention
Co-rotating twin screw extruderCompounding: 170-175-180-190°CMulti-pass: 180-205-225-245°C
Phosphites levels indicated, formulations also contained 500ppm AO-1
Melt Flow Index - LLDPE 2.16kg/190°C
0.2
0.4
0.6
0.8
1
1.2
0 1 2 3 4 5
Extrusion Pass
MF
I (g
/10m
in)
800ppm TNPP 800ppm LGP11 1400ppm TNPP 1400ppm LGP11
Melt Flow Index - LLDPE21.6kg/190°C
202224
2628303234
0 1 2 3 4 5
Extrusion Pass
MF
I (g
/10m
in)
800ppm TNPP 800ppm LGP11 1400ppm TNPP 1400ppm LGP11
Yellowness Index - LLDPE
-2
-1
0
1
2
3
0 1 2 3 4 5
Extrusion Pass
YI
Un
its
800-TNPP 800-LGP11 1400-TNPP 1400-LGP11
Gel Counts – LLDPE Cast Film Extrusion
0
1000
2000
3000
4000
5000
6000
7000
8000
800ppm TNPP 800ppm LGP11
< 150 µm150-300 µm300-600 µm600-1000 µm
Gas Fade Resistance in LLDPE at 60°C
05
10152025303540
0 5 10 15 20 25
Days in NOx Chamber
YI
Un
its
1400ppm TNPP 1400ppm LGP-11
0
20
40
60
80
100
0 5 10 15 20 25 30
2000ppm TNPP 2000ppm LGP-11 1500ppm Solid Phosphite SP-1
Days in Oven at 60°C
Glo
ss
Solid phosphite SP1 is not compatible at 1500ppm
Compatibility at 2000ppm in LLDPE
Migration From The Polymer
Assuming Fickian diffusion, migration rates decrease with an increase in molecular weightMolecular weight of LGP11 is >> TNPPDecreased exposure from consumer packaging, especially in food contact applications
Conclusions
LGP-11 is a high MW liquid phosphite that offers better performance than typical commodity phosphites such as TNPP and SP1
Process stability (MI/YI), compatibility, NOx and oven aging, thermal stability
LGP-11 is alkylphenol free and is based on nontoxic biodegradable raw materials, and thus avoids many of the negative perception issues associated with phenolic based antioxidants.
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