recent candle stabilization developments at .recent candle stabilization developments at ciba

Ciba Specialty Chemicals
Business Line Coatings
Robert Waldron, June 20071
Recent Candle Stabilization
Developments at Ciba
Second World Candle Congress
June 2007

Overview of Discussion Topics
Stabilizer Additive Technology
Historical Developments and Current Needs in the Candle Industry
Soy Wax Candles Stabilization Study
The Challenge of Fragrance Oil StabilizationSome Preliminary
Observations
Candle Stabilization RefinementsIdeas for Doing It Better

Candle Stabilization
Scented candles are complex chemical systems prone to
degradation when exposed to light and heat.
Waxes: different types and blends for different candle applications
Paraffin
Microcrystalline
Vegetable> Soy
> Palm
> Cottonseed
Dyes
Fragrances: typical functional groups include
Aromatics and phenolics
Aldehydes, ketones and esters
Ethers and alcohols
Olefins

Degradation MechanismFree Radicals
Free radicalsAtomic or molecular species with unpaired
electrons on an otherwise open shell configuration. These
unpaired electrons are usually highly reactive.
FormationBy exposure of a substance to light energy or by
thermal cleavage of a chemical bond.

Bond Cleavage Due to Light Absorption
Absorption of light is the reaction of light with a material
(chromophore).
Different functional groups and molecules absorb different
wavelengths (energies) of light.
Single bonds correlate to very high energy light or shorter overall
wavelengths (less susceptible to cleavage).
Double () bonds are responsible for light absorption (more
susceptible to cleavage).
Polar groups also give rise to reactivity with light.

Bond Cleavage Due to Light Absorption

Auto-oxidation Process Induced by Light and Heat
R R* R. (alkyl radical)
R. ROO. (peroxy radical)
ROO. ROOH + R. (hydroperoxide & alkyl radical)
ROOH RO. + .OH (alkoxy & hydroxyl radicals)
This is a chain-propagating process.
h
O2
RH
h or

Stabilizer Additives to Interrupt the Auto-oxidation Process
UV Absorbers (UVA)
Prevent damage caused by free radical formation when a substrate is exposed to light.
Absorb UV light energy at specific wavelengths and dissipate this energy as heat.
Hindered Amine Light Stabilizers (HALS)
Scavenge oxygen-centered and alkyl free radicals.
Cyclic mechanism with regeneration of active chemical species.
Antioxidants (AO)
Scavenge oxygen-centered free radicals.
Phosphite Process Stabilizers
Decompose hydroperoxides.

Where Stabilizer Additives Act to Disrupt Degradation
R R* R. Counter with UVA
R. ROO. Counter with HALS
ROO. ROOH + R. Counter with HALS, AO
ROOH RO. + .OH Counter with Phosphite
h
O2
RH
h or

UVA Examples
BenzophenonesLower photo-permanence, coverage better in short wavelength
range
BenzotriazolesHigher photo-permanence, good coverage over broad
wavelength range
O OH
OR
NN
N
OH
R
R

UVA MechanismKeto-Enol Tautomerism

Hindered Amine Light Stabilizers
Substituted Tetramethyl Piperidines
NR1
R2
R1 = Head Group R2 = Backbone
Activity
Basicity
Compatibility
Solubility/compatibility
Equivalent Wt.
Basicity

HALS Examples
Amine Typehigh basicity, pKb= 5.1-5.5
Amino-ether Typelow basicity, pKb= 9.6, does not interact with acids,
metals
NH3C
H
O.CO.(CH2)8.CO.O
N
H
CH3
NC8H
17.O
H
O.CO.(CH2)8.CO.O
N
H
O.C8H
17

HALS Proposed MechanismCyclic Regeneration
N
A
XE C
RH
N
O
X
N
O
X
E
R
E C R
O
H
O
E C R
O
E C R
OH
H
A = H, alkyl, alkoxy, carbonyl
ROO.
Key initiating
step

Use of Stabilizer Additives in Candles
Conventional Technologyadequate for candles made with highly-refined
paraffin wax and with minimal fragrance component
Benzophenone and/or benzotriazole UVAs (typically in solid form)
No free radical scavenging
Advanced Technologyprompted by the destabilizing impact of increased
fragrance oil loadings
Synergistic blend of benzotriazole UVA and non-interacting HALS in liquid form
UV absorption and free radical scavenging
Latest Developments
Increased cost and decreased availability of paraffin wax
Widespread substitution of vegetable waxes for petroleum-based waxes
How well will stabilizer packages proven in paraffin wax work in vegetable wax?

Soy Wax Candles Stabilization Study
WaxNatureWax Container Candle Blend C-3 from Cargill
Hydrogenated vegetable glycerides
Mettler dropping point = 125 - 130 F
Iodine value = 50 - 56
Three representative candle formulations:
Vanilla fragrance with no dye,
Hydrangea fragrance with blue dye,
Cinnamon fragrance with red dye.
Three light stabilizer (LS) options:
No light stabilizer,
0.3% w/w of conventional LS package (1:1 blend of benzophenone and
benzotriazole UVAs)
0.3% w/w of advanced LS package (1:1 blend of benzotriazole UVA and non-
interacting HALS)

Soy Wax Candles Stabilization StudyAdditives Tested
BP1 (solid benzophenone UVA)
BZT1 (solid benzotriazole UVA)

Soy Wax Candles Stabilization StudyAdditives Tested
BZT2 (liquid benzotriazole UVA)
HALS1 (liquid, non-interacting hindered amine light stabilizer)

Accelerated Light Exposure Tests
Pre-exposure and post-exposure color measurements of all candle
samples were made with an X-Rite SP 64 spectrophotometer
(D65 illuminant, 10 degree observer).
Control samples were stored in the dark inside sealed plastic bags.
Test samples were placed in a light box:
Open upper level equipped with 3 double banks of cool-white
fluorescent tubes (34 Watts each)
Enclosed, ventilated lower level equipped with 3 double banks of
black light (UV) tubes (40 Watts each)

Equipment for Accelerated Light Stability Testing

Quantifying Color Stability
CIELAB color scale system
L* signifies lightness/darkness
a* signifies red/green color axis
b* signifies yellow/blue color axis
E* = [(L*)2 + (a*)2 + (b*)2]1/2

Soy Wax Candles Light Stability Test3 Weeks UV Light Exposure
No LS
0.3% BTZ2/HALS1
0.3% BP1/BTZ1
Vanilla, no dye
Hydrangea, blue dye
Cinnamon, red dye
0
5
10
15
20
25
30
35
40
delta E*

Soy Wax Candles Light Stability Test5 Weeks Fluorescent Light Exposure
No LS
0.3% BTZ2/HALS1
0.3% BP1/BTZ1
Vanilla, no dye
Hydrangea, blue dye
Cinnamon, red dye
0
5
10
15
20
25
30
35
40
delta E*

Fragrance Oil Impact
Impact of 330 hours UV light exposure on paraffin wax candle with blue dye in the
absence

recent candle stabilization developments at .recent candle stabilization developments at ciba

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