Патент USA US2054483

Patented Sept. 15, 1936
2,054,483
UNITED STATES
PATENT OFFICE
2,054,483
RUBBER COMPOSITION
George D. Martin, Nitro, W. Va., assignor, by
mesne assignments, to Monsanto Chemical
Company, Wilmington, Del., a corporation of v
Delaware
No Drawing. Application June 4, 1934,
Serial No. 728,854,
20 Claims.
The present invention relates to the art of
rubber manufacture, and particularly relates to
the preparation of rubber compositions which
5
resist deterioration due to aging or to exposure
to the atmosphere. It has long been known that
such deterioration can be greatly retarded by
treating the rubber either before or after vul
canization with certain substances known as age
resisters or antioxidants. One object of this in
10 vention is to provide a new and superior class
of antioxidants for rubber.
.
(01. 18-50)
?ex cracking resistance to the vulcanized rub
ber product. The compounds herein disclosed as
imparting such desirable properties to vulcanized
rubber comprise a reaction product of a diaryl
amine, an aliphatic aldehyde and an aromatic
hydroxide.
'
5
'
It is thought the principal reactions involved
in the preparation of the preferred antioxidants
of the present invention may be represented as '
A further object of
this invention is to provide a new and superior
class of materials which when incorporated into
rubber, preferably before the vulcanization there
15 of, imparts thereto properties markedly resist
ant to tear and cracking when portions thereof
have been repeatedly and alternately stretched
and the tension removed. Such a process is
analogous to the ?exing of an automobile tire
20 in actual road service.
The age resisting characteristics of a vulcan
ized rubber product can be readily ascertained
by subjecting samples of the vulcanized product
in a bomb to the action of oxygen under elevated
25 pressure and at an elevated temperature. The
aged rubber samples are then examined and test
ed and the test data compared with the results
obtained on testing the unaged rubber samples.
The deterioration in properties effected as a re
30 sult of the oxidation treatment is indicative of
the result that would normally be expected of
that particular stock during actual service. Such
a test is known as the Bierer-Davis aging test
and produces an effect on a vulcanized rubber
35 stock comparable with that resulting from sev
eral years of natural aging of the rubber de
pending upon the condition of the test. In all
the oxygen bomb tests hereinafter set forth, the
aging was carried out at temperatures of 70° C.
40 and an oxygen pressure of 300 pounds per square
inch.
The ?ex cracking resistance of the vulcanized
rubber products was determined on a flexing ma
chine as set forth by L. V. Cooper, Analytical Edi
45 tion of Industrial and Engineering Chemistry,
vol. 2, No. 4, 1930, pages 391-394.
According to the present invention, a new class
of antioxidants or age-resistors has been found
which, upon incorporating into a rubber stock,
50 “imparts
exceptional age resisting qualities'and
wherein R1, R.2 and R4 are aryl radicals, R3 is an 15
alkylidene radical and R5 is hydrogen or an alkyl
radical (see McLeod and Robinson, Journal of
the Chemical Society,’ volume 119, part 2, (1921)
page 1471).
a
For example, the following reaction products 20
are typical members of the preferred class of
materials outlined above: Reaction product of
substantially ‘equi-molecular proportions of di- ,
phenylamine, formaldehyde and cyclohexanol;
reaction product of substantially equi-molecular 25
proportions of diphenylamine, acetaldehyde and
cyclohexanol; reaction product of substantially
equi-molecular proportions of diphenylamine,
butyraldehyde and phenol; reaction product of
substantially equi-molecular proportions of di- 30
phenylamine, formaldehyde and phenol; reac
tion product of substantially equi-molecular pro
portions of diphenylamine, formaldehyde and
beta naphthol; reaction product of substantially
equi-molecular proportions of beta betadinaph- 35
thylamine, formaldehyde and phenol; reaction
product of substantially equi-molecular propor
tions of ditolylamine, heptaldehyde and cresol
and their chemical equivalents.
Any one or a mixture of the above enumerated 40
substances or of these substances with other
antioxidants maybe incorporated into rubber
with good effect on the properties thereof.
The following are tov be understood as illus
trative of the invention and not limitative of the 45 '
scope thereof.
7 ,
Example I
50 parts by weight of 'diph'enylamine (substan
tially 0.3 a molecular proportion), 23 parts by 60,.
2,054,483
weight of 40% formaldehyde solution (substan
tially 0.3 a molecular proportion), 33 parts by
prising a brown oil, was incorporated in a rubber
stock comprising
weight of cyclohexanol (substantially a 10% ex
cess over 0.3 a molecular proportion)
and 25
Parts
Smoked sheet rubber __________________ __ 100
parts by weight of sodium carbonate were placed
Carbon black _________________________ __
50
in a suitable reactor and heated with agitation
at a convenient temperature, for example 60 to
70° C., until the reaction was completed. The
'undissolved sodium carbonate was then removed
10 preferably by ?ltration and the excess unreacted
cyclohexanol removed by distillation. The resid
Zinc oxide ____________________________ __
5
Benzothiazyl ester of thiobenzoic acid_____
0. 8 10
Diphenyl guanidine ________ __,_____>_____,_
0. 2
ual liquid comprising the crude reaction product
The reaction product of diphenylamine,
may be employed as‘ an antioxidant without fur
ther puri?cation. If convenient or desirable, the
15 crude reaction product may be puri?ed by dis
tillation under reduced pressure, whereupon a
liquid product distilling at substantially 204-206"
C. at 5 mm. pressure is obtained. A'portion of
the puri?ed product described above was incor
Sulfur _______________________________ __
3
Pine tar ______________________________ __
2
Stearic acid _____________________________ __3
formaldehyde and phenol ____________ __
The stock so compounded was vulcanized and 15
the cured rubber product aged in the oxygen
bomb. A comparison between the physical prop
erties of the aged and unaged cured rubber
product is given in Table II.
porated in the usual manner in a typical tread
stock comprising
V
.
.
Parts
Carbon black _________________________ __
Cute
.
50
Zinc oxide ____________________________ __
5
Sulfur‘ _______________________________ __
3
Pine tar ______________________________ __
Stearic acid __________________________ c_
2
3
Benzothiazyl ester of thiobenzoic acid_ ____
0. 8
Diphenyl guanidine ___________________ __
0. 2
Lbs
.
'
Mrns.
Hrs.
steam
aged
Modulus of
elasticity in
Tensile at
Ult.
lbs/in.” at
elongation of
break in
lbs/in.z
along.
percent
300
pressure
3.0
The reaction product of diphenylamine,
formaldehyde and cyclohexanol____r____ 1. 0
The rubber stock so compounded was then vul
35 canized by heating in a press maintained at 30
pounds of steam pressure per square inch, and
portions of the cured rubber product aged by
heating in the Bierer-Davis oxygen bomb for 96
hours at 70° C. and under 300 pounds oxygen
pressure per square inch. A comparison between
40 the physical characteristics of the aged and un
aged rubber products is given in Table I.
Table I
45
' Cure
Mins
‘_
of
el‘dodulu's
asticity in
Lbs. steam
pressure
Hrs.
aged
lbs/in) at
elongation of
'
300%
break in “11:52:35
lbs/m.
'
30
30
30
30
30
30
0
96
0
96
0
96
2400
1090
2330
2010
2440
2105
2
4665
2780
4470
2615
4300
2550
75
30
30
75
90
30
'
0
96
0
2330
2020
2245
25
‘
2750
4510
4580
530
440
520
>410
r 500
90
105
30
30
96
2025
2480
2665 '
4550
105
30
96
2050
2455
375
Flexing tests carried out as described on stocks
wherein the reaction product of diphenylamine,
formaldehyde and phenol was incorporated 35
showed them also to possess desirable anti-?ex
cracking properties.
As a third speci?c embodiment of the present
invention, a reaction product of substantially
equi-molecular proportions of diphenylamine,
formaldehyde and beta naphthol was prepared
in a manner analogous to that employed in Ex
ample I. The product prepared as described,
comprising a solid, was milled in the well known
45:
manner into a tread stock comprising
, Parts.
T ensi 1 e at
Smoked sheet rubber _____ _'__'_ _________ __ 100
Carbon
50'
75
75
90
90
105
105
20
Table II
.
Smoked sheet rubber ____________ _r ____ __r 100
25
1. 0
535
450
500
410
480
385
black _________________ __. ______ __
50
Zinc oxide ___________________ __' _______ __
5
Sulfur ________________________ __'____'__._
'3
Pine tar ______________________________ __
Stearic acid __________________________ __
2
3
Benzothiazyl ester of thiobenzoic acid_____
0. 8
Diphenyl
0.2
guanidine___'_ _______________ __ '
The‘ reaction product of diphenylamine,
55
formaldehyde and beta naphthol _____ __
1. 0
Portions of the unaged stock were ?exed in the
mannerrhereinbefore set forth before aging and
after 3 days’ aging in the Well known Geer oven
60 at 70°C., and found to be markedly resistant to
the deteriorating influence of ?ex cracking and
far superior to the same'stock containing no anti
oxidant. It is thus shown that the preferred
class of materials, for example the reaction prod
.65 uct of diphenylamine, formaldehyde and cyclo
The stock so compounded was vulcanized and
the vulcanized rubber product aged in the Bierer
Davis oxygen bomb. A comparison between the 60
physical properties of the aged and unaged vul
canized rubber product follows in Table'III.
Table. III
Cure
. hexanol comprise an important ‘class of vulcani
zation antioxidants or age-resistors.
I '7
Ming
Lbs. steam
Hrs.
pressure
aged
Modulus of
elasticity in
Tensile at
lbs./in.’_ at
elongation
break in
lbs/in.i
of 300% "
Ult.
elong.
percent
"
Example II '
70 ..
Substantially equi-molecular proportions of
diphenylamine, formaldehyde and phenol were
reacted in a manner analogous to that employed
in Example I._ The product so obtained,_com-'
75
75
30
30
0
96
2370
1705
4600
2155
525
390
485
90
30
0
2320
' 4255
90
105
'30
30
96
0
1745
2435
1990
4550
355
500
105
30
96
1805 >
1840
305 .
70
2,054,483
kaline inorganic catalyst substantially equi-mo
lecular proportions of diphenylamine, formalde
Stocks wherein the reaction product of diphenyl
amine, formaldehyde and beta naphthol was in
corporated also showed marked resistance to de
terioration due to ?ex cracking.
.
.
.
hyde and phenol.
.
From the speci?c examples hereinbefore set
forth, it is shown that rubber compositions con
tainable by reacting in'the presence of an alkaline
of materials markedly resist the deterioration in
inorganic catalyst substantially equi-molecular
proportions of diphenylamine,formaldehyde and
?uences due to' heat, oxidation and ?exing.
beta naphthol.
taining small proportions‘of the preferred class
10
"
6. The method of preserving rubber which com
prises treating rubber with a reaction product ob
,
Obviously, practice of the’ present invention is
not limited to the speci?c compositions given
above, such compositions being merely illustra
tive of the manneruof employing the antioxidants
or age-resisters of this invention.
The anti
15 oxidants or age-resisters may be employed in con
junction with other vulcanizing agents than those
speci?cally disclosed, for this invention is ap
plicable generally to pure rubber or rubber com
positions of the most varied nature. Further
20 more, the preferred class of materials may be em
ployed in rubber ‘stocks in‘conjunction with other
accelerators than the one speci?cally shown with
varying differences in tensile and modulus prop
erties but still exhibiting the desirable qualities
25 of the class.
It is to be understood that the term “treat
ing” as employed in the appended claims is used
in a generic sense to include either the incor
porating of the preferred class of materials into
30 the rubber by milling or similar process, or their
addition to the rubber latex before its coagulation,
.
.
'7. A composition comprising rubber and a re
presence of an alkaline inorganic catalyst sub
stantially equi-molecular proportions of a diaryl
amine, an aliphatic aldehyde and a mono hydric
phenol consisting in carbon, hydrogen and oxy
gen atoms only.
8. A composition comprising rubber and a
reaction product obtainable by reacting in the
presence of an alkaline inorganic catalyst sub
stantially equi-molecular proportions of diphenyl
phenol consisting in carbon, hydrogen and oxygen
atoms only.
9. A composition comprising rubber and a re
action product obtainable by reacting in the pres
ence of an alkaline inorganic catalyst substan
10. A composition comprising rubber and a re
action product obtainable by reacting in the pres
ence of an alkaline inorganic catalyst substan
natural or synthetic, reclaimed rubber, balata,
gutta percha, rubber isomers and like products
whether or not admixed with ?llers, pigments or
speci?cation.
What is claimed is:
1. The method of preserving rubber which
45 comprises treating rubber with a reaction prod
uct obtainable by reacting in the presence of an
alkaline inorganic catalyst substantially equi
molecular proportions of a diarylamine, an ali
phatic aldehyde and an aromatic mono hydroxide
50 consisting in carbon, hydrogen and oxygen atoms
only.
2. The method of preserving rubber which
comprises treating rubber with a reaction prod
uct obtainable by reacting in the presence of an
55 alkaline inorganic catalyst substantially equi
molecular proportions of diphenylamine, an ali
phatic aldehyde and a monohydric phenol con
sisting in carbon, hydrogen and oxygen atoms
only.
3. The method of preserving rubber which com
prises treating rubber with a reaction product
obtainable by reacting in the presence of an al
kaline inorganic catalyst substantially equi-mo
lecular proportions of diphenylamine, formalde
65 hyde ‘and a mono hydric phenol consisting in
carbon, hydrogen and oxygen atoms only.
11. A composition comprising rubber and a re
action product obtainable by reacting in the pres
12. A vulcanized rubber product possessing age‘
resisting properties comprising the vulcanization
product of a rubber stock containing prior to
the vulcanization thereof a product obtainable
by reacting in the presence of an alkaline inor
ganic catalyst substantially equi-molecular pro
portions of a diarylamine, an aliphatic aldehyde 45
and a mono hydric phenol consisting in carbon,
hydrogen and oxygen atoms only.
13. A vulcanized rubber product possessing age
resisting properties comprising the vulcanization
product of a rubber stock containing prior to the 50
vulcanization thereof a product obtainable by re
acting in the presence of an alkaline inorganic
catalyst substantially equi-molecular proportions
of diphenylamine, an aliphatic aldehyde and a
mono hydric phenol consisting in carbon, hydro
gen and oxygen atoms only.
14. A vulcanized rubber product possessing age
resisting properties comprising the vulcanization
product of a rubber stock containing prior to the
vulcanization thereof a product obtainable by 60
reacting in the presence of an alkaline inorganic
catalyst substantially equi-molecular proportions
of diphenylamine, formaldehyde and cyclohex
anol.
15. A vulcanized rubber product possessing age 65
resisting properties comprising the vulcanization
product of a rubber stock containing prior to the
prises treating rubber with a reaction product
vulcanization thereof a product . obtainable by
obtainable by reacting in the presence of an al
35
tially equi-molecular proportions of diphenyl
amine, formaldehyde and beta naphthol.
4. The method of preserving rubber which com
70 kaline inorganic'catalyst substantially equi-mo
lecular proportions of diphenylamine, formalde
hyde and cyclohexanol.
5. The method of preserving rubber which com
prises treating rubber with a reaction product
75 obtainable by reacting in the presence of an al
25
tially equi-molecular proportions of diphenyl
amine, formaldehyde and cyclohexanol.
ence of an alkaline inorganic catalyst substan
The present invention is limited solely by the
claims attached hereto as part of the present
20
amine, an aliphatic aldehyde and a mono hydric
tially equi-molecular proportions of diphenyl
amine, formaldehyde and phenol.
accelerating agents.
15
-
or to the application thereof to the surface of a
mass of crude or vulcanized rubber. The term
“rubber” is likewise employed in the claims in
35 a generic sense to include caoutchouc, whether
40
10
action product obtainable by reacting in the
reacting in the presence of an alkaline inorganic
catalyst substantially equi-molecular proportions 70
of diphenylamine, formaldehyde and phenol.
16. A vulcanized rubber product possessing age
resisting properties comprising the vulcanization
product of a rubber stock containing prior to the
vulcanization thereof a product obtainable by 75
4
2,054,483
reacting in the presence of an alkaline inorganic
where R‘, It2 and R4 are aryl hydrocarbon‘radi
catalyst substantially equi-molecular proportions
of diphenylamine, formaldehyde and vbeta naph
cals and ‘R3 is a. methylene group.
thol.
.
‘
‘
.
.19. A composition comprising rubber and a
product possessing the formula
1'7. The method of preserving rubber which
comprises treating rubber with a product possess
ing the formula
.
\N—Rl——-0R4
R1
R"
\N—R'V—-OR4
10
R1
R‘
'
where R1 and R2 are aryl radicals, R3 is an alkyli
.
where R1 and R2 are aryl radicals, R3 is an
alkylidene radical and R4 is an aromatichydro
carbon radical.
18. The method of preserving rubber which
comprises treating rubber with a product possess
ing the formula
dene radical and R‘ is an aromatic hydrocarbon 110.
radical.
’
20. A composition comprising rubber and a
product possessing the formula
R1
\N-R¥-—OR4
'15
R:
where R1, R2 and R‘ are aryl hydrocarbon radi
20
cals and R.3 is a methylene group.
7
GEORGE D. MARTIN.
20'