Bis[3-(3,5-dialkyl-4-hydroxyphenyl)propyl]monoand disulfides as the sevilen stabilizers

Article abstract of DOI:10.1134/S1070363211060144

The effect of the shielding degree of the phenol hydroxy group on the hydrolytic and thermal stability of ethylene-vinyl acetate copolymer (Sevilen) was studied on a series of phenols containing one or two sulfur atoms in the aliphatic chain of the para-s

Full text of DOI:10.1134/S1070363211060144

ISSN 1070-3632, Russian Journal of General Chemistry, 2011, Vol. 81, No. 6, pp. 1159–1162. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.P. Krysin, T.B. Khlebnikova, 2011, published in Zhurnal Obshchei Khimii, 2011, Vol. 81, No. 6, pp. 966–969.
Bis[3-(3,5-dialkyl-4-hydroxyphenyl)propyl]mono-
and Disulfides as the Sevilen Stabilizers
A. P. Krysina and T. B. Khlebnikovab
a Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences,
ul. Akad. Lavrent’eva 9, Novosibirsk, 630090 Russia
e-mail: benzol@nioch.nsc.ru
b Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
e-mail: chleb@catalysis.nsk.ru
Received June 3, 2010
Abstract—The effect of the shielding degree of the phenol hydroxy group on the hydrolytic and thermal
stability of ethylene–vinyl acetate copolymer (Sevilen) was studied on a series of phenols containing one or
two sulfur atoms in the aliphatic chain of the para-substituent. Among the synthesized compounds a group of
disulfides was found with a high antioxidant efficiency, which increase the Sevilen hydrolytic stability. The
most effective are the 6-tert-butyl-2-methylphenol derivatives.
DOI: 10.1134/S1070363211060144
Sevilen, a copolymer of vinyl acetate with ethylene,
is widely used: from the transparent goods of medical
purpose, toys, and packaging, appropriate for the use
in contact with the human body and food, to polymer
composites used for the manufacture of the products
for the technical application. The known handbooks
listing the additives for polymers do not contain
information on the Sevilen stabilizers.
as Phenozan-23 or Agydol-23) as a stabilizer for the
Sevilen, the problems appeared related to the
hydrolytic instability of both the copolymer and the
antioxidant. At heating a composition stabilized with
Irganox 1010 a rapid decrease occurred in the
copolymer molecular mass detected by an increase in
the melt flow index (MFI) (see the table). Such a
stabilized polymer can be thermally processed only
once. At its recycling the certified performance charac-
teristics could not be achieved.
While studying the thermal degradation of Sevilen
the processes with different mechanisms have been
observed, including radical and hydrolytic degradation
[1]. Hence, the Sevilen stabilizers should be
multifunctional, as well as non-toxic and not colorizing
the copolymer. The number of such substances among
those permitted for the use in polymer processing is
very limited.
COOCH2
C
4
HO
I
Sevilen differs from many polymers by its low
hydrolytic stability. There is no published information
of compounds improving hydrolytic stability of
polymers, in particular, of Sevilen, that is essential for
the creation of its compositions. By our knowledge, the
set of complex antioxidant additives definitely includes
a sulfur-containing stabilizer of technical purpose TAB
[2], but it is not listed among the low-toxic additives.
For the creation of more stabilized Sevilen com-
positions we decided to use the effect of synergesis
that usually occurs at the combined use of sulfur-
containing compounds and sterically hindered phenols
[3]. To reduce the number of additives introduced into
Sevilen, we synthesized a single compound II, con-
taining a fragment of 2,6-dimethylphenol and sulfur
atom in the aliphatic chain of the para-substituent to
use it instead of two substances showing synergism. Its
When we used the non-toxic and not colorizing
phenol thermostabilizer Irganox 1010 (I) (also known
1159

1160
KRYSIN, KHLEBNIKOVA
application allowed us to reach the required stabiliza-
tion of the Sevilen at producing various commodities
[4]. However, a group of commodities produced from
Sevilen required higher stability at their exploitation.
containing fragment located in the aliphatic chain of
the para-substituent of the same molecule. We decided
to leave unchanged the distance between the sulfur
atoms and the aromatic ring of phenol: three methylene
groups between the sulfur and the aromatic ring. By
the data of [5], this distance is optimal for the sulfur-
containing polymer stabilizers both due to the
availability of the methods of their synthesis, and their
performance.
In this regard, for the creation of more effective
stabilizers we initiated an investigation of the influence
of the degree of shilding in the sterically loaded
phenols on their ability to interact with the sulfur-
R2
HO
CH2
S
R2
R1
R2
R1
R1
R2
Na2S
2
II, IV, V
HO
Cl
HO
OH
Na2S + S
HO
S
XI−XIII
VIII−X
R1
2
III, V, VII
R1 = R2 = CH3 (II, III, VIII, XI); R1 = CH3, R2 = t-Bu (IV, V, IX, XII); R1 = R2 = t-Bu (VI, VII, X, XIII).
Effectiveness of stabilizing additives I–VII to Sevilena
The derivatives of 2,6-di-tert-butylphenol, sulfide
VI and disulfide VII (see the scheme) have been
Content of stabilizer in Sevilen, wt %
prepared by us earlier [6, 7]. The sulfur-containing
derivatives of 6-tert-butyl-2-methylphenol, sulfide IV
0.1
0.2
0.3
τ, min
Comp. no.
and disulfide V, were synthesized in this work, based
on the accessible 4-(3-hydroxypropyl)-6-tert-butyl-2-
methylphenol [8]. A new disulfide III was synthesized
using the method of [7] based on compound XI.
τ, min MFI τ, min
MFI
MFI
21
–
95
95
70
105
55
55
–
40
100
300
100
300
65
>30
7.7
7.7
7.7
7.9
5.1
7.7
75
120
300
150
330
80
I
The compounds obtained were tested at the Plast-
polymer facility, Ochta Branch (St. Petersburg). For
the tests the Sevilen was used of widely known brand
11306-75 that contains co-polymerized 15% of vinyl
acetate and 85% of ethylene. On this basis 21 com-
positions were prepared containing as antioxidant a
sulfide (II, IV, VI) or a disulfide (III, V, VII), or
Irganox 1010 as a control, at a concentration 0.1, 0.2,
or 0.3%. Table 1 shows the physico-mechanical
properties measured after processing the compositions
at a temperature of 180°C.
8.8
8.8
8.8
8.7
7.1
8.8
7.0
7.0
7.0
7.0
0.3
7.0
II
III
IV
V
VI
VII
90
140
a
τ, min. specifies the induction period for each composition of the
stabilized Sevilen, as defined after maintaining it at a tempera-
ture of 180°C, according to the time of its hydrolytic stability.
MFI is melt flow index, determined at the end of the induction
period. (MFI of the original composition is 7.0).
As follows from the table, any of the additives
except Irganox 1010 stabilize the MFI (melt flow
index) value of the composition at the content of 0.2–
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 6 2011

BIS[3-(3,5-DIALKYL-4-HYDROXYPHENYL)PROPYL]MONO- AND DISULFIDES
1161
0.3 wt %. Note a much higher antioxidant efficiency of
disulfides III, V, and VII in comparison with mono-
sulfides II, IV, and VI.
the filtrate to obtained 13.55 g of brown oil. The oil was
dissolved in 10 ml of boiling chloroform, to the solu-
tion was added 10 ml of hexane, and the mixture was
kept in a refrigerator for 1 h. The precipitate formed
was filtered off and washed with cold hexane. White
crystals of disulfide III (8.37 g, 67%) was isolated, mp
95.5–97.0°C. Found, %: C 66.99, H 7.68, S 16.52.
C22H30O2S2. m/z 390.1691 (mass-spectrometrically). Cal-
culated, %: C 67.45, H 7.74, S 16.42. m/z 390.1687.
The most attractive for the stabilization of Sevilen
is disulfide V. This compound is a low-toxic derivative
of 2-methyl-6-tert-butylphenol (LD/50 = 8000 mg kg–1,
mice), and all other parameters at its application at the
concentration up to 0.2% satisfy all the requirements
for the Sevilen stabilizers. The effect-tiveness of 2,6-
di-tert-butylphenol derivatives I, VI, and VII was low
compared to this compound. The sulfur-containing
derivatives of 2,6-dimethylphenol are more effective,
but currently their use is limited by the lack of
1H NMR spectrum (in CDCl3) δ, ppm: 1.70–2.12 t
(2H, ArCH2CH2, J = 6 Hz); 2.16 s (6H, ArCH3); 2.55–
2.58 m (2H, CH2S, J = 8 Hz), 2.64–2.87 t (2H, ArCH2,
J = 7 Hz), 4.22 s (1H, OH); 6.66 s (2H, ArH). UV
spectrum (in ethanol): λmax 280 nm, log ε 3.64. IR spec-
trum (in CCl4): 3625 cm–1 (OH).
domestic
production
of
2,6-dimethylphenol.
Nevertheless, as is seen from the data of this work, the
effectiveness of non-toxic derivatives of 2,6-di-tert-
butylphenol is not enough to stabilize the critical parts
made of this polymers. Now a new basis is required for
the production of non-toxic phenol-based antioxidants.
3-(6-tert-Butyl-2-methyl-4-hydroxyphenyl)-1-
chloropropane (XII). In a reactor with stirrer was
placed 7.4 g of 96% 3-(6-tert-butyl-2-methyl-4-hyd-
roxyphenyl)propanol (0.032 mol) and 4.55 g (0.0383
mol) of distilled SOCl2. The mixture was heated while
stirring for 3.0 h at a temperature in the reactor 80°C.
Then into the reactor were injected in succession 30 ml
of cold water and 30 ml of methyl tert-butyl ether. The
organic layer was separated, washed with water, and
dried over anhydrous CaCl2. The desiccant was filtered
off, the solvent was evaporated in a vacuum, and 7.79 g
of black oil was obtained. The oil was placed in a
column with 77 g of silica gel of 140–315 mesh. The
product was eluted with a hexane–chloroform mixture,
2:1. Compound XII (5.52 g) was isolated as a yellow
oil, bp 120–125°C (1–2 mm Hg) Found: m/z 240.1283
(mass spectrometry). C14H21ClO. Calculated: m/z
240.1281. IR spectrum in CCl4: 3610 and 3650 cm–1
(OH). UV spectrum, λmax 278 nm, log ε 3.32. 1H NMR
spectrum (in CDCl3) δ, ppm: 1.39 s (4H, C4H9-t),
1.81–2.21 m (2H, ArCH2CH2), 2.62 t (2H, ArCH2, J =
7 Hz), 3.44 t (2H, CH2Cl, J = 6 Hz); 4.44 s (1H, OH);
6.7 and 6.9 m (2H, ArH).
EXPERIMENTAL
1H NMR spectra were taken on a Bruker AV-300
instrument (300.13 MHz) from solutions in CCl4. As
internal references were used TMS and CDCl3. The
UV spectra were recorded on a Specord UV VIS
instrument from 1×10–4 molar solutions in ethanol. The
IR spectra were recorded on a Bruker Vektor-22
spectrometer from KBr pellets and 1% solutions in
CCl4. The mass spectra were obtained on a high-
resolution instrument Finnigan MAT-8200, the ele-
mental compositions were calculated from the spectra
with a resolution of 10000. The melting points were
measured on a Köffler device.
For the preparation of the compositions Sevilen TU
6-05-1636-97 brand 11306-75 was used, whose
practical properties are listed on the site http://
www.sevilen.ru/sev.html.
Bis-[3-(2-tert-butyl-6-methyl-4-hydroxyphenyl)-
propyl]sulfide (IV). In a three-neck flask with a stirrer
and reflux condenser was mixed 1.43 g (0.013 mol) of
crude 74% aqueous Na2S, 5.6 g (0.023 mol) of
chloride XII, and 20 ml of isopropyl alcohol, and the
mixture was stirred for 7 h at 100ºC. The hot reaction
mixture was filtered to remove the NaCl precipitate,
and the solvent was evaporated. The resulting oil was
purified by column chromatography on silica gel
eluting with a mixture of hexane-chloroform, 2:1, and
then with chloroform. The fractions containing sulfide
IV were combined and evaporated. 4.32 g of oil (yield
Bis-3-[(3,5-dimethyl-4-hydroxyphenyl)propyl]di-
sulfide (III). A mixture of preliminary triturated sulfur
(1.22 g, 0.038 mol) and 4.35 g of 74% aqueous Na2S
(0.041 mol) was loaded to the reactor containing 50 ml
of isopropyl alcohol. The reaction mixture was heated
to boiling and maintained at vigorous stirring for 3 h
till it became transparent. Then to the reactor a solution
was added of 12.99 g (0.064 mol) of compound XI
(content of the main product 98%) in 6 ml of isopropyl
alcohol, and the stirring was continued for 4 h at
reflux. From the hot reaction mixture the precipitate of
salt was filtered off, the solvent was evaporated from
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 6 2011

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KRYSIN, KHLEBNIKOVA
70%) containing, according to the NMR spectrum,
97% of sulfide IV, was isolated. Found: m/z 442.2903
(mass spectrometry). C22H42O2S. Calculated: m/z
ArH). UV spectrum (ethanol): λmax 280 nm, log ε 3.69.
IR spectrum (in CCl4): 3610 and 3650 cm–1 (OH).
1
ACKNOWLEDGMENTS
442.2906. H NMR spectrum (in CDCl3) δ, ppm: 1.37
s (9H, C4H9-t), 1.56–2.06 m (CH2CH2Ar), 2.14 s (3H,
CH3), 2.22–2.68 m (2H, ArCH2), 4.28 s (ArOH), 6.67
and 6. 84 m (2H, ArH).
We are grateful to L.I. Lugovaya, V.M. Demidova
and I.G. Zaveleva, for their active participation in this
work on the creation of effective Sevilen stabilizers.
Bis[3-(2-tert-butyl-6-methyl-4-hydroxyphenyl)-
propyl]disulfide (V). A triturated mixture of 0.4 g
(0.013 mol) sulfur and 1.43 g of Na2S containing 74%
of the main substance (0.013 mol) was placed in the
reactor, and 20 ml of isopropyl alcohol was added. The
mixture was refluxed with stirring for 4 h, until the
solution became clear. Then in the reactor was added a
solution of 5.6 g (0.023 mol) of chloride XII in 5 ml of
isopropyl alcohol, and the mixture was maintained at
reflux over another 4 h. The hot solution was filtered
from the residue of salt, and the solvent was
evaporated. The resulting oil, 5.0 g, was placed in a
column with silica gel (60 g) and eluted with a
hexane–chloroform mixture, 2:1. The fractions con-
taining compound V were combined, and the solvent
was evaporated. 3.82 g (yield 80%) of compound V
was isolated as oil. Found: m/z 474.2623. C28H42O2S2
(mass spectrometry). Calculated: m/z 474.2626.
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1H NMR spectrum (in CDCl3), δ, ppm: 1.37 s (9H,
C4H9-t), 1.7–2.2 m (2H, CH2CH2S), 2.17 s (3H,
ArCH3), 2.4–2.7 t (Hz, 2H, ArCH2, J = 7 Hz), 2.7–3.0
m (2H, CH2S), 4.42 s (OH), 6.76 and 6.84 m (2H,
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 6 2011