Calix[4]resorcinols as stabilizers for rubber stocks based on butadiene-acrylonitrile rubbers

Article abstract of DOI:10.1023/B:RJAC.0000018704.06786.97

Modification of tetramethylcalix[4]resorcinol with dimethylaminomethyl and 3,5-di-tert-butyl-4-hydroxybenzyl fragments was studied. The antioxidative activity of these macrocyclic stabilizers in rubber stocks based on butadiene-acrylonitrile rubber was ex

Full text of DOI:10.1023/B:RJAC.0000018704.06786.97

Russian Journal of Applied Chemistry, Vol. 76, No. 11, 2003, pp. 1867 1869. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 11,
2003, pp. 1918 1920.
Original Russian Text Copyright
Konovalov.
2003 by Bukharov, Teregulova, Nugumanova, Mukmeneva, Miryasova, Burilov, Pudovik, Nikolaeva, Kasymova,
BRIEF
COMMUNICATIONS
Calix[4]resorcinols as Stabilizers for Rubber Stocks
Based on Butadiene Acrylonitrile Rubbers
S. V. Bukharov, E. A. Teregulova, G. N. Nugumanova, N. A. Mukmeneva,
F. K. Miryasova, A. R. Burilov, M. A. Pudovik, I. L. Nikolaeva,
E. M. Kasymova, and A. I. Konovalov
Kazan State Technological University, Kazan, Tatarstan, Russia
Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences,
Kazan, Tatarstan, Russia
Received February 21, 2003
Abstract Modification of tetramethylcalix[4]resorcinol with dimethylaminomethyl and 3,5-di-tert-butyl-
4-hydroxybenzyl fragments was studied. The antioxidative activity of these macrocyclic stabilizers in rubber
stocks based on butadiene acrylonitrile rubber was examined.
Phenolic stabilizers are relatively little used in
rubber stocks, as they are apparently inferior in the
protective effect to p-phenylenediamine derivatives.
At the same time, a major advantage of phenolic sta-
bilizers is that, in contrast to amines, they do not alter
or alter only slightly the color of rubber items; also,
they are nontoxic and low-volatile and are difficultly
washed out.
where R = H (I), CH NMe (II), or CH C H (Bu-t) -
2 2 2 6 2 2
3,5-OH-4 (III).
It is known that introduction of dimethylamino-
methyl groups into the molecule of I appreciably
facilitates its oxidation [3]. Therefore, compound II
should be a much more effective trap of peroxy radi-
cals, compared to unsubstituted calixarene I.
Compound III contains phenolic groups differing
in the reactivity. This should enhance the inhibiting
performance in radical oxidation processes. Stabilizer
III was prepared by the reaction of I with 3,5-di-tert-
butyl-4-hydroxybenzyl acetate IV in the presence of
formic acid. The mixture formed in the course of the
reaction contains 70% calixarene III and 30% 2,4,6-
tris(3,5-di-tert-butyl-4-hydroxybenzyl)resorcinol V:
Macrocyclic phenolic stabilizers, in particular,
calix[4]resorcinols, are a new group of phenolic stabi-
lizers. Tetramethylcalix[4]resorcinol I appeared to be
suitable as antioxidant for vulcanized rubbers based
on butadiene acrylonitrile rubbers [1, 2].
In this work we studied the antioxidative activity
exhibited in rubber stocks based on butadiene acrylo-
nitrile rubbers by modified tetramethylcalix[4]resor-
cinols II and III containing in o-positions of the aro-
matic rings dimethylaminomethyl or 3,5-di-tert-butyl-
4-hydroxybenzyl fragments:
OH
R
+
t
-Bu
n
Bu-t
H
H
R
OH
R
,
+
I +
III
nCH COOH
3
CH2OAc
IV
where R = CH C H (Bu-t) -3,5-OH-4.
OH
V
R
OH
HO
2
6
2
2
It was shown previously [4] that, in the presence of
strong mineral acids (HClO , H SO ), the content of
III in the reaction mixture does not exceed 30%.
OH
R
HO
R
Me
Me
Me
Me
4
2
4
,
HO
OH
The compositions of commercial rubber stocks
containing as stabilizers N-isopropyl-N -phenyl-p-
phenylenediamine (Diafen FP) or its mixture with
2,2,4-trimethyl-1,2-dihydroquinoline (Acetonanil),
OH
HO
R
1070-4272/03/7611-1867$25.00 2003 MAIK Nauka/Interperiodica

1868
BUKHAROV et al.
Table 1. Composition of rubber stocks based on SKN-18
and SKN-26 rubbers
inhibit thermal oxidative degradation more effectively
than I and are comparable in this respect with Diafen
FP (Table 2).
Content, wt parts per
100 wt parts of rubber
Component*
EXPERIMENTAL
SKN-18
SKN-26
In our study, we used commercial samples of buta-
diene acrylonitrile rubbers SKN-18 and SKN-26.
Rubber stocks were prepared in two steps with a Bra-
bender plasticorder with the mixing chamber volume
Zinc oxide
4
1
2
1
1
3
0.7
Sulfenamide Ts
N,N-Dithiodimorpholine
Thiuram D
3
of 50 cm . In the first step, the rubber, carbon black,
Stearic acid
1
40
and other components, except the vulcanizing group,
were mixed at 130 C. In the second step, the vulcaniz-
ing group was added. The total mixing time was
7 min, and the rotor rotation rate, 35 rpm. The rubber
stocks based on SKN-18 and SKN-26 were vulcanized
at 143 C for 30 and 40 min, respectively.
Carbon black
EDOS plasticizer
Sulfur
120
45
1.5
2
Stabilizer
4
* Sulfenamide Ts is N-cyclohexyl-2-benzothiazolylsulfenamide;
Thiuram D, tetramethylthiuram disulfide; EDOS plasticizer,
a mixture based on dioxane alcohols; stabilizer, compounds
I III, V, III + V, Diafen FP, or Acetonanil.
Physicomechanical tests were performed with a
Tensometer T-10 tensile-testing machine (Monsanto).
1
The H NMR spectra were recorded on a Varian
Gemini-200 spectrometer (200 MHz) relative to resid-
ual protons of deuterated solvents.
calixarenes I III, benzylated resorcinol V, and a
mixture of III and V obtained in the course of the
reaction of I with IV are listed in Table 1. The results
of physicomechanical tests of these stocks are listed
in Table 2. The performance of the stabilizers was
evaluated by relative changes in the nominal tensile
strength , relative elongation at break , and elonga-
tion set , occurring upon thermal oxidative aging.
4,6,10,12,16,18,22,24-Octahydroxy-5,11,17,19-
tetra(3,5-di-tert-butyl-4-hydroxybenzyl)-2,8,14,20-
3,7 9,13 15,19
tetramethylpentacyclo[19.3.1.1 .1 .1
]octa-
cosa-1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23-
dodecaene III. Formic acid (65 ml) was added to a
solution of 3 g (5.5 mmol) of I and 6.9 g (24.8 mmol)
of IV in 55 ml of acetone. The mixture was allowed
to stand at 20 C for 1 day. Then it was poured into
Table 2 shows that, in the rubber stock of thiuram
vulcanization with a high filler content, modified
calixarenes II and III somewhat surpass II and Diafen
100 ml of water, and an NaHCO solution was added
3
FP (amine stabilizers) as regards preservation of
,
to pH 5 6. A mixture of products (7.75 g) was ob-
1
but are inferior to the latter additives with respect to
preservation of . In the rubber stock of sulfur vul-
canization with a low filler content, exhibiting better
physicomechanical properties, calixarenes II and III
tained, containing, according to the H NMR spec-
trum, compounds V and III in a molar ratio of 3 : 7.
It was dissolved in 25 ml of benzene, and 170 ml of
hexane was added. Compound III was obtained; yield
Table 2. Effect of stabilizers on properties of vulcanized rubbers based on SKN-18 and SKN-26
Stabilizer
Parameter
control*
I
II
III
V
III + V
, MPa
, %
, %
14.0 (21.2)** 13.7 (23.5)
13.3 (18.0)
117 (244)
4 (8)
12.7 (20.1)
133 (308)
4 (8)
13.2 (20.5)
156 (310)
4 (10)
14.7 (21.6)
129 (280)
3 (8)
129 (314)
4 (8)
148 (320)
3 (9)
/ ***
/ ***
0.89 (0.87)
0.95 (0.69)
0.89 (0.78)
0.98 (0.60)
0.94 (1.06)
0.75 (0.82)
0.91 (0.95)
0.80 (0.62)
0.81 (0.95)
0.81 (0.77)
0.89 (0.88)
0.62 (0.69)
* For vulcanized rubber based on SKN-18, Diafen FP : Acetonanil (1 : 3); for that based on SKN-26, Diafen FP.
** The values for SKN-26 are given in parentheses.
*** ( , ) Values obtained after thermal oxidative aging at 100 C for 72 h.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 11 2003

CALIX[4]RESORCINOLS AS STABILIZERS FOR RUBBER STOCKS
1
1869
2.6 g (33%), mp 230 C (dec.). H NMR spectrum
CDCl ), , ppm: 1.39 s (72H, CMe ), 1.77 d (12H,
starting tetramethylcalix[4]resorcinol, toward rubber
stocks based on butadiene acrylonitrile rubbers.
3
3
3
Me, J 7.0 Hz), 3.89 s (8H, CH ), 4.60 q (4H, CH,
HH
2
3
J
7.0 Hz), 5.08 s (4H, OH), 6.34 s (8H, OH),
7.00 s (8H, Ar H), 7.33 s (4H, Ar H).
HH
ACKNOWLEDGMENTS
The study was financially supported by the Russian
Foundation for Basic Research (project no. 02-03-
33037).
Found, %: C 77.65; H 8.65.
C92H120O12.
Calculated, %: C 77.97; H 8.47.
4,6,10,12,16,18,22,24-Octahydroxy-5,11,17,19-
REFERENCES
tetrakis(dimethylaminomethyl)-2,8,14,20-tetra-
3,7 9,13 15,19
1. Ehrhardt, D., Gummi, Fasern Kunststoffe, 1992, vol. 45,
no. 5, pp. 231 239.
2. Ehrhardt, D., Gummi, Fasern Kunststoffe, 1992, vol. 45,
no. 7, pp. 358 361.
3. Yanilkin, V.V., Ryzhkina, I.S., Morozov, V.I., et al.,
Zh. Obshch. Khim., 2001, vol. 71, no. 3, pp. 409 414.
methylpentacyclo[19.3.1.1 .1 .1
]octacosa-
1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23-do-
decaene II and 2,4,6-tris(3,5-di-tert-butyl-4-hy-
droxybenzyl)resorcinol V were prepared as de-
scribed in [5] and [6], respectively.
4. Bukharov, S.V., Nugumanova, G.N., Mukmeneva, N.A.,
et al., Zh. Obshch. Khim., 2002, vol. 72, no. 8,
pp. 1405 1406.
5. Yoh-ichi, M. and Tahanao, M., Tetrahedron Lett.,
1993, no. 46, pp. 7433 7436.
6. US Patent 4173541.
CONCLUSION
Modification of tetramethylcalix[4]resorcinol with
dimethylaminomethyl and 3,5-di-tert-butyl-4-hydroxy-
benzyl fragments afforded macrocyclic stabilizers with
enhanced antioxidative activity, exceeding that of the
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 11 2003