Note: Descriptions are shown in the official language in which they were submitted.
1077043
The invention pertains to the field of controlled-
rubber vulcanization art. The applicable U.S. patent
classification defines the invention as "retarders".
In the manufacture of vulcanized rubber products,
crude rubber is combined with various other ingredients such
as fillers, accelerators, and antidegradants to alter and
improve processing of the rubber and to improve the properties
of the final product. The crude rubber is put through several
steps in the plant before it is ready for the final step of
vulcanization. Generally, the rubber is mixed with carbon
black and other ingredients except the vulcanizing agent and
accelerator. Then the vulcanizing and~ccelerating agents
are added to this masterbatch in a Banbury mixer or a mill.
Scorching, viz., premature vulcanization, can occur at this
stage of the processing, during the storage period before
vulcanizing, and during the actual vulcanization. After the
vulcanizing and accelerating agents are added, the mixture of
crude rubber is ready for calendering or extruding and vul-
canization. If premature vulcanization occurs during the
storage of the crude mixture or during processing ~ior to
vulcanization, the processing operations cannot be carried out
because the scorched rubber is rough and lumpy, consequently,
useless. Premature vulcanization is am~jor problem in the
- 2 -
- . :. . .. -
: : .: ,,,, . ::.; . ' ' :
,
1~77043
rubber industry and must be prevented in order to allow the
rubber mix to be preformed and shaped before it is cured or
vulcanized.
There are several reasons offered for premature vul-
canization. The discovery of the thiazolesulfenamide accele-
rators constituted a major breakthrough in the vulcanization
art, because thiazolesulfenamides delayed onset of the vul-
canizing process; but, once it started, the built-in amine
activation of the thiazole resulted in strong, rapid curing.
Mercaptobenzothiazole is a valuable organic vulcanization
accelerator but by present standards would be considered
scorchy. It has been largely replaced by the delayed-action
accelerators. The development of high pH furnace blacks
which lack the inherent inhib~ing effect of the acidic
channel blacks and popularity of certain phenylenediamine
antidegradants which promote scorching have placed
increasingly stringent demands on the accelerator system.
Retarders have long been available to rubber com-
pounders. These include N-nitrosodiphenylamine, salicyclic
acid, and a terpene-resin acid blend. See Editors of Rubber
World, "Compounding Ingredients for Rubber", 125-128 (3rd Ed.,
1965). Acids as retarders are generally ineffective with
thiazolesulfenamide accelerators or adversely affect this
vulcanizing process. Nitrosoamines as retarders are only
of limited effectiveness with thiazolesulfenamides derived
from primary amines.
Summary
We have discovered a class of sulfenimides which
are extremely valuable inhibitors of premature vulcanization.
The characteristic nucleus is R-S-N-C - where the dangling
-- 3 --
2-51-0811 ~
1077043
valence on the nitrogen ls linked to a second carbonyl and
R is alkyl, aryl, or cycloalkyl. Aryl is used ln the usual
generic sense to mean any univalent organlc radlcal where rree
valence belongs to an aromatlc carbocyclic nucleus and not to
a side chain. The term includes radlcals substltuted in the
carbocyclic nucleus, for example, by alkyl, alkoxy, nltro,
chloro, bromo, fluoro, lodo, and hydroxy. Alkyl is used in
the usual generic sense to mean univalent aliphatic radicals
of the Series C H2n+l. Primary, secondary~ and tertlary
alkyls are lncluded, for example, stralght or branched chalns.
The term cycloalkyl lncludes cycloalkyl radicals o~ 5 to 8
carbon atoms in the rlng. The R may be substltuted to give
a bls-sulfenimlde of the formula R'_S-R-S-R' where R i9 an
alkane, arylene, or cycloalkane and R' ls an lmide. A com-
blnatlon of an accelerator and an lnhlbltor of thls lnventlonls an lmproved rubber addltive whlch allows longer and sa~er
processing tlme.
Descri tlon of the Preferred Embodiments
P - -- .
Our invention is that bls-sulfenimldes havlng the
formula
R'-S-R-S-R'
are excellent premature vulcanizatlon lnhlbitors for a vul-
canlzable diene rubber where R ls an alkane, arylene, or
cycloalkane and R~ 18 an imide. Examples of the compounds
useful in this inventlon are as ~ollows~
l,l-bls(2-thlophthalimldo)methane
l,2-bis(2-thiophthalimido)ethane
1,3-bls(2-thiophthalimido)propane
l,2-bis(2-thlophthalimido)i~opropane
1,4-bls(2-thiophthallmldo)butane
,' - ' :.,
2-51-0~11
10 7 70 43
1,3-bls(2-thiophthallmido)-3-lsobutane
1,5-bis(2-thlophthallmldo)pentane
1,6-bis(2-thiophthallmldo)hexane
1,7-bls(2-thlophthallmldo)heptane
1,8-bis(2-thlophthallmldo)octane
1,4-bls(2-thlophthallmldo)cyclohexane
1,4-bls(2-thlophthalimldo)benzene-
1,4-bis(2-thlophthallmldo)nltrobenzene
1,4-bl8(2-thlophthallmldo)toluene
1,1-bls(2-thlosucclnimldo)methane
1,2-bls(2-thlosucclnlmldo)ethane
1,3-bls(2-thlosucclnimldo)propane
1,2-bls(2-thlosucclnlmldo)lsopropane
1,4-bls(2-thlosucclnimldo)butane
1,3-bls(2-thlosucclnlmldo)-3-lsobutane
1,5-bls(2-thlosuccinlmido)pentane
; 1,6-bls(2-thlosucclnlmldo)hexane
1,7-bls(2-thlosucclnlmldo)heptane
1,8-bls(2-thiosucclnlmldo)octane
1,4-bls(2-thlosucclnlmldo)cyclohexane
1,4-bls(2-thlosucclnlmldo)benzene
1,4-bls(2-thlosucclnlmldo)nitrobenzene
1,4-bls(2-thlosucclnlmldo)toluene
1,1-bls(2-thloglutarlmldo)methane
1,2-bls(2-thloglutarlmldo)ethane
1,3-bls(2-thloglutarlmldo)propane
1,2-bls(2-thloglutarlmldo)lsopropane
1,4-bls(2-thloglutarlmldo)butane
1,3-bls(2-thioglutarlmldo)-3-lsobutane
1,5-bls(2-thloglutarlmido)pentane
`~
~ ~ 7 ~ ~ ~3
1,6-bl~(2~thloglutarimido)hexane
1,7-bls(2-thioglutarimido~heptane
1,8-bis(2-thiogl~tarimido)octane
1,4-bis(2-thioglutarimido)cyclohexane
1,4-bls(2-thioglutarim~do)benzene
1,4-bis(2-thioglutarimido)nitrobenzene
1,4-bis(2-thioglutarimido)toluene
1,1-bis(2-thiomaleimldo)methane
1,2-bl~(2-thlomalelmldo)ethane
1,3-bi~(2-thiomalelmido)propane
1J2-bis(2-thlomalelmldo~lsopropane
1,4-bis~2-thiomalei-u_do)butane
1,3-bls(2-thiomaleimido)-3-isobutane
1,5-bl~(2-thiomaleimido)pentane
1,6-bis~2-thiomalelmido)hexarle
1,7-bis(2-thiomaleimido)heptane
1,8-bi~(2-thiomaleimido~octane
1,4-bis(2-thiomalelmido)cyclohexane
1,4-bis(2-thiomaleimldo)benzene
1,4-bis(2-thlomalelmldo)nitrobenzene
1,4-bls(2-thiomalelmldo)toluene
1,1-bls(2-thionaphthalimldoJmethane
1,2-bls(2-thlonaphthalimido)ethane
1~3-bis(2-thionaphthalimido)propane
1,2-bis(2-thionaphthalimido)isopropane
1,4-bls(2-thlonaphthal'mido)butane
1,3-bi~(2-thionaphthalimldo)-3-lsobutane
1,5-bls(2-thlonaphthalimido)pentane
1,6-biq(2-thionaphthalimido)hexane
1,7-bis(2-thionaphthalimido)heptane
.-
!
. .
2~
1~77C~3
1,8-bis(2-thionaphthalimido)octane
1,4-bis(2-thionaphthalimido)cyclohexane
1,4-bls(2-thionaphthalimido)benzene
1,4-bls(2-thionaphthalimido)nitrobenzene
1,4-bis(2-thionaphthalimldo)toluene
1 J l-bis(N-thio-4-cyclohexene-1,2-dlcarboximido)methane
1,2-bis~N-thlo-4-cyclohexene-1,2-dicarboximido)ethane
1,3-bis(N-thio-4-cyclohexene-1,2-dlcarboximido)propane
1,2-bis(N-thio-4-cyclohexene 1,2-dicarboximido)isopropane
1,4-bis(N-thlo-4-cyclo~.~xene-1,2-dlcarbox~mido)butane
1,3-bis(N-thio-4-cyc'ohexene_1,2-dicarboxlmido)-3-lsobutane
1,5-bis(N-thio-4-cycl~hexene-1,2-dicarboximido)pentane
1,6-bis(N-thio-4-cyclc~-xene-1,2-dicarboximido)hexane
1,7-bis(N-thio-4-cyclohexene-lJ2-dicarboximido~heptane
1,8-bls(N-thio-4-cyclohexene-1,2-dlcarboximido)octane
1,4-bis(N-thio-4-cyclohexene-1,2-dicarboximido)cyclohexane
!` - 1,4~bis(N-thio-4-cyclohexene-1,2-dicarc),ximido)benzene
1,4-bis(N-thio-4-cyclohexene-1,2-dicarboximido)nltrobenzene
1,4-bis(N-thio-4-cyclohexene-1,2-dlcarboximido)toluene
1,1-bis(N-thio-1,4,5,6,7,7-hexachlorobicyclo[2.2.1]he~f-5-ene-
2,3-dicarboximido)me~hane
1,2-bis(N-thio-1,4,5,6,7,7-hexachlorobicyclo[2.2.1]hept-5-ene-
2,3-dicarboxlmido)ethane
1,3-bis(N-thio-1,4,5,6,7,7-hexachlorobicyclo[2.2.1]hept-5-ene-
2,3-dicarboxlmido)prop2ne
1,2-bis(N-thio-1,4,5,6J7,7~hexachloroblcyclo[2.2.1]hept-5-ene-
2,3-dicarboximido)isopropane
1,4-bis(N-thio-1,4,5,6,7,7-hexachlorobicyclo[2.2.1]hept-5-ene-
2,3,-dicarboximido)butane
: ~ .
:-5!--r)''l 1
1077~43
1,3-bls(N-thio-' ~,5,6,7,7-hexachlorobicyclo[2.2.1]hept-5-ene-
2,3-dicarboximido)-3-isobutar.e
1,5~bis(N-thio-1,4,5,o,7,7-hexacAlo~obicyclo[2.2.1]hept-5-ene-
2,3-dicarboxlmido)pentane
1,6-bis(N-thio-1,4,5,6,7~7-hexachlorobicycloL2~2.1~hept-5-ene-
2,3-dicarboximido)he~ane
1,7-bis(N-thio-1,4,5,6,7~7-hexachlorobicyclo[2.2.1]hept-5~ene-
2,3-dicarboxlmido)heptane
1,8-bis(N-thlo-1,4,5,6,7,7-hexachlorobicyclo[2.2 1]hept-5-ene-
2,3-dicarboxlmido~octane
1,4-bis~N-thio-1,4,5,6,7~7-hexachlorobicyclo[2.2.13hept-5-ene-
2,3-dicarboxlmido) CyC lohexane
1,~-bis(N-thio-1,4,5,6,7,7-hexachlorobicyclo~2.2.1]hept-5-ene-
2,3-dlcarboximldo)b2n-ene
1,4-bis(N-thio-1,4,5,6,7,7-hexachlorobicyclo~2.2.1]hept-5-ene-
2,3-dicarboximido)nitrobenzene
t- 1,4-bis(N-thio-1,4,5,6,7,7-hexachlorobi~clo[2.2.1]hept-5-ene-
2,3-dicarboximido)toluene
1,1-bis(N-thio-5,5-dimethylhydantoin)methane
1,2-bis(N-thio-5,5-dimethylhydantoin)ethane
1,3-bis(N-thio-5,5-dimethylhydantoin)propane
1,2-bis(N-thio-5,5-dimethylhydantoin)isopropane
1,4-bis(N-thio-5,5-dimethylhydantoin)butane
1,3-bis(N-thio-5,5-dimethylhydantoin)isobutane
1,5-bis(N-thio-5,5-dimethylhydantoin)pentane
1,6-bis(N-thio-5,5-dimethylhydantoin)hexane
1,7-bis(N-thlo-5,5-dimethylhydantoln)heptane
1,8-b i5 (N-thio-5,5-dimethylhydantoin)octane
1,4-bis(N-thio-5,5 - dimethylhydantoin)cyclohexane
_ ~ ~ O ~ 1
L 1
1 ,
1~77~43
1,4-bis(N-thio-5,5-dlmethylhydantoin)benzene
1,4-bis (N-thio-5J5-dim-thylhydantoin)nitrobenzene
1,4-bls(N-thio-5J5-dime~hylhydantoin)toluene
1 J l-bis(N-thiohexahydrophthalimido)methane
lJ2-bis(N-thiohexahydrophthallmido)ethane
1,3-bis(N-thiohexahydrophthalimido)propane
1 ,2-bis (N-thiohexahydrophthalimido)isopropane
1,4-bi~(N-thlohexahydrophthalimido)butane
1,3-bis(N-thiohexahydrophthalimido)i~obutane
1~5-bls~N-thiohexahydrophthalimldo)penta~e
} J 6-b~(N-thiohexanyd~ophthalimido)hexane
1,7-bis(N-thiohexahydrophthalimido)heptane
1,8-bi~(N-thiohexahydroDhthalimido)octane
1,4-bi~(N-thiohexahyd o~nthalimido)cyclohexane
1,4-bi~(N-thiohexahydrophthalimido)benzene
1 J 4-bis(N-thiohexahydrophthalimido)nitrobenzene, and ~
t. 1,4-bi~(N-thiohexahydrophthalimido)tol-~ne.
Examples o~ other new compound~ of thi~ invention
are: N-(cyclohexylthio)phthalimide, N-(cyclooctylthio)phthal-
imide, N-(benzylthio)phthalimide, N-(ethylthio)phthalimide,
N-(propylthlo)phthalimide, N-(isopropylthio)phthalimlde,
N- ~-butylthlo)phthalimide, N-(tert-butylthio)phthallmide,
N-(isobutylthio)phthalimide, N-(sec-butylthio)phthalimide,
N-(n-hexylthio)phthalimide, N-(n-octylthio)phthalimlde, N-(n-
dodecylthio)phthallmide/ N-(cyclohexylthio)adlpimlde, N-(cyclo-
octylthio)adipimlde, N-(ben~ylthio)adipimlde, N-(ethylthio)-
adlpimide, N-(propylthio)adlpimide, N-(i~opropylthlo)adipimide,
N-(n-butylthlo)adipimide, N-(tert-butylthio)adipimide, N-(iso-
butylthio)adipimide, N-(sec-butylthio)adipimide~ N-(n-pentyl-
thio)adipimide J N-(n-heptylthio)adipimide, N-(n-hexylthio)adipimlde~
N-(n-octylthio)adipimide, N-(n-dodecylthio)adipimide,~N-(phenylthlo).
adlpimide, N-(tolylthio)adipimide, N-(cyclohexylthio)glutarimide,
i
_ g _
2-51-0811
~ 077043
N-(cyclooctylthio)glutarimide J N-(benzylthio)glutarlmlde, N-
(ethylthio)glutarimide, N-(propylthio)glutarimlde, N~ opropyl-
thio)glutarimlde, N-(n-butylthio)glutarlmide, N-(t-butylthlo)-
glutarimide, ~ obutylthio)glutarlmide, N-(sec-butylthio)-
glutarimide, N-(n-pentylthio)glutarimide, N-(n-heptylthlo)glutar-
imide, N-(n-hexylthlo)glutarimide, N-(n-octylthio)glutarimlde,
N-(n-dodecylthio)~lutarimide, N-(phenylthio)glutarlmide, N-(tolyl-
thlo)glutarlmlde, N-(cyclohexylthlo)-7-oxablcyclo[2.2.1]heptane-
2,3-~lcarboxlmide, N-(cyclohexylthlo)-7-oxabicyclo[2.2.1]hept-5-
ene-2,3-dlcarboxlmlde, N-(cyclohexylthlo)hexahydrophthallmlde,
N-(cyclohexylthlo)malelmlde, N-(cyclooctylthlo)malelmlde, N-
(phenylthlo)malelmlde, N-(chlorophenylthlo)malelmlde, N-(tolyl-
thlo)malelmide, N-(nltrophenylthio)malelmide, N-(benzylthlo)-
malelmlde, N-(t-butylthlo)malelmlde, N-(ethylthlo)malelmlde,
N-(propylthlo)malelmide, N-(i~opropylthlo)malelmide, N-(n-do-
decylth$o)malelmlde, 5,5-dimethyl-3-(cyclohexylthio)hydantoin,
5,5-dlmethyl-3-(cyclooctylthlo)hydantoin, 5,5-dlmethyl-3-(phenyl-
thlo)hydantoln, 5,5-dimethyl-3-(chlorophenylthlo)hydantoln~ 5,5-
dlmethyl-3-(benzylthlo)hydantoln, 5,5-dlmethyl-3-(tolylthlo)- '
hydantoln, 5,5-dimethyl-3-(nltrophenylthlo)hydantoln, 5,5-dlmethyl-
3-(t-butylthlo)hydantoln, 5,5-dlmethyl-3-(ethylthlo)hydantoln, 5J5-
dlmethyl-3-(propylthlo)hydantoln, 5,5-dlmethyl-3-(l~opropylthio)-
hydantoln, 5,5-dlmethyl-3-(n-dodecylthlo)hydantoln, 1,4,5,6,7,7-
hexachloro-N-(cyclohexylthlo)blcyclo[2.2.1]hept-5-ene-2,3-~1-
carboxlmlde, 1,4,5,6,7,7-hexachloro-N-(cyclooctylthio)bicyclo-
[2.2.1]hept-5-ene-dlcarboximide, 1,4,5,6,7,7-hexachloro-N-(phenyl-
thio)blcyclo[2.2.1]hept-5-ene-2,3-dlcarboxlmide, 1,4,5,6,7,7-hexa-
chloro-N-(chlorophenylthio)bicyclo[2.2.1 hept-5-ene-2,3-dicarbox-
imlde, 1,4~5,6,7,7-hexachloro-N-(benzylthio)blcyclo[2.2.1]hept-
5-ene-2,3-dicarboximlde, 1,4,5J6J7J7-hexachloro-N-(tolylthlo)-
bicyclo[2.2.1]hept-5-ene-2,3-dicarboximlde, lJ4,5,6,7J7-hexachloro-
N-(nitrophenylthio)bicyclo[2.2.1]hept-5-ene-2J3-dicarboximide,
1,4,5,6,7,7-hexachloro-N-~t-butylthio)bicyclo[2.2.1]hept-5-ene-
_ 10 --
1077043
2,3-dicarboximide, l~4~5~6~7~7-hexachloro-N-(ethylthio)bicyclo-
[2.2.1]hept-5-ene-2,3-dicarboximide, N-(propylthio)bicyclo[2.2.1]-
hept-5-ene-2,3-dicarboximide, 1,4,5,6,7,7-hexachloro-N-(isopro-
pylthio)bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide, 1,4,5,6,7,7-
hexachloro-N-(_-dodecylthio)bicyclo[2.2.1]hept-5-ene-2,3-dicar-
boximide, N-(cyclohexylthio)-4-cyclohexene-1,2-dicarboximide,
N-(cyclooctylthio)-4-cyclohexene-1,2-dicarboximide, N-(phenyl-
thio)-4-cyclohexene-1,2-dicarboximide, N-(chlorophenylthio)-4-
cyclohexene-1,2-dicarboximide, N-(benzylthio)-4-cyclohexene-
1,2-dicarboximide, N-(tolylthio)-4-cyclohexene-1,2-dicarboximide,
N-(nitrophenylthio)-4-cyclohexene-1,2-dicarboximide, N-(t-butyl-
thio)-4-cyclohexene-1,2-dicarboximide, N-(ethylthio)-4-cyclo-
hexene-1,2-dicarboximide, N-(propylthio)-4-cyclohexene-1,2-
dicarboximide, N-(n-dodecylthio)-4-cyclohexene-1,2-dicarboximide,
N-(isopropylthio)-4-cyclohexene-1,2-dicarboximide, N-phenyl-
thio-3,4,5,6-tetrachlorophthalimide, N-tolylthio-3,4,5,6-
tetrachlorophthalimide, N-chlorophenylthio-3,4,5,6-tetrachloro-
phthalimide, N-benzylthio-3,4,5,6-tetrachlorophthalimide,
N-nitrophenylthio-3,4,5,6-tetrachlorophthalimide, N-n-butyl-
thio-3,4,5,6-tetrachlorophthalimide, N-n-dodecylthio-3,4,5,6-
tetrachlorophthalimide, N-cyclohexylthio-3,4,5,6-tetrachloro-
phthalimide, N-cyclooctylthio-3~4~5~6-tetrachlorophthalimide~
N-phenylthio-3,4,5,6-tetrabromophthalimide, N-phenylthio-
3,4,5,6-tetrabromophthalimide, N-(ar-tolylthio)-3,4,5,6-
tetrachlorophthalimide, N-(ar-tolylthio)-3,4,5,6-tetrabromo-
phthalimide, N-(phenylthio)naphthalimide, N-(tolylthio)
naphthalimide, N-(chlorophenylthio)naphthalimide, N-(benzyl-
thio)naphthalimide, N-(nitrophenylthio)naphthali.mide, N-(_-
butylthio)naphthalimide, N-(_-dodecylthio)naphthalimide,
N-(cyclohexylthio)naphthalimide, N-(cyclooctylthio)naphthalimide,
and N,N'-bis(ar-tolylthio)-1,2,4,5-benzenetetracarboxylic-
1,2:4,5-diimide.
1077043
Rubber stocks containing delayed action accelera-
tors can be used in the process of this invention. Cheaper,
more scorchy accelerators can also be used with an excellent
degree of improvement. The improved vulcanizing process of
this invention can be used advantageously to process stocks
containing furnace blacks as well as stocks containing
other types of blacks and fillers used in rubber compounding.
The invention is also applicable to gum stocks.
Our invention is applicable to rubber mixes con-
taining sulfur-vulcanizing agents, peroxide-vulcanizing agents,
organic accelerators for vulcanization, and antidegradants.
For the purposes of this invention, sulfur-vulcanizing agent
means elemental sulfur or sulfur-containing vulcanizing agent,
for example, an amine disulfide or a polymeric polysulfide.
The invention is applicable to vulcanization accelerators of
various classes. For example, rubber mixes containing the
aromatic thiazole accelerators which include benzothiazyl-
2-monocyclohexyl sulfenamide, 2-mercaptobenzothiazole, N-
tert-butyl-2-benzothiazole sulfenamide, 2-benzothiazolyl
diethyldithiocarbamate, and 2-(morpholinothio)benzothiazole
can be used. Amine salts of mercaptobenzothiazole accelerators,
for example, the t-butyl amine salt of mercaptobenzothiazole,
like salts of morpholine and 2,6-dimethyl morpholine, can be
used in the invention. Thiazole accelerators other than
aromatic can be used. Stocks containing accelerators, for
example, the tetramethylthiuram disulfides, tetramethyl-
thiuram monosulfide, aldehyde amine condensation products,
thiocarbamylsulfenamides, thioureas, xanthates, and guanidine
derivatives, are substantially improved using the process of
our invention. Examples of thiocarbamylsulfenamide accelera-
tors are shown in U.S. Patent 2,381,393, Smith assigned to
Firestone; 2,388,236, Cooper assigned to Monsanto; 2,424,921,
1077043
Smith assigned to Firestone; and sritish Patent 880,912,
Dodson assigned to Imperial Chemical Industries Limited.
The invention is applicable to accelerator mixtures. The
invention is applicable to stocks containing amine anti-
degradants. Rubber mixes containing antidegradants, forexample, N-1,3-dimethylbutyl-N'-phenyl-_-phenylenediamine,
N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, and
other phenylenediamines, ketone, ether, and hydroxy anti-
degradants and mixtures thereof, are substantially improved
using the process of our invention. Mixtures of anti-
degradants, for example, a mixture of N-1,3-dimethylbutyl-
N'-phenyl-_-phenylenediamine and N,N'-bis(1,4-dimethylpentyl)-
_-phenylenediamine, furnish a much improved final product
when used with the inhibitors of this invention.
The inhibitors of our invention can be used in
natural and synthetic rubbers and mixtures thereof Syn-
thetic rubbers that can be improved by the process of this
invention include c -4-polybutadiene, butyl rubber, ethylene-
propylene terpolymers, polymers of 1,3-butadiene, for example,
1,3-butadiene itself or isoprene, copolymers of 1,3-butadiene
with other monomers, for example, styrene, acrylonitrile,
and isobutylene, and methyl methacrylate. The invention
relates to diene rubbers, and the terms rubber and diene
rubber are synonymous for the purpose of this invention.
The bis(thioimido)alkanes of this invention are
synthesized according to the following equations:
HS~(CH2)n~SH +o2 C12 ClS(CH2)nSCl
.. .. ..
ClS(CH2)nSCl ~ 2H-N~ _____:~ N - S-(CH2)nS-N
O O O
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1077043
The mercaptan is dissolved in _-pentane and then
chlorine gas is passed through the resulting solution at -5
to 5C. The orange-yellow sulfenyl chloride is added dropwise
to a solution of imide and triethylamine in dimethylformamide.
The reaction mixture is allowed to stir for 30 minutes and
it is then diluted with water. The product is filtered and
recrystallized.
To prepare 1,6-(2-thiophthalimido)hexane of the
formula O O
.. ..
~ N-S-(CH2)6-S N ~ C
O O
15 grams (0.1 mole) of 1,6-_-hexanedithiol is dissolved in
100 ml. of n-pentane in a 250 ml. round-bottomed three-
necked flask equipped with a mechanical stirrer, condenser,
a thermometer, and a gas inlet tube. Chlorine gas, 16.0 grams
(0.22 mole), is passed through the solution in the flask at
-5 to 5C. over a 20-minute period. The yellow solution of
the sulfenyl chloride is added dropwise to a solution of 28
grams (0.1 mole) of phthalimide and 26 grams (0.26 mole)
of triethylamine in 150 ml. of dimethylformamide over a
period of 30 minutes. The reaction temperature rises 24
to 40C. upon this addition. The reaction mixture is stirred
for 30 minutes and then it is diluted with two liters of
cold water. The precipitate is filtered and dried. The
precipitate weighs 37.5 grams which is an 85% yield. Re-
crystallization of the product gives a white crystalline
1,6-bis(2-thiophthalimido)hexane with a melting point of .-
171 to 172C. Elemental analysis of the 1,6-bis(2-thio-
phthalimido)hexane shown 6.12% nitrogen and 14.53% sulfur.
Calculated percentages for C22H20N2O4S2 are 6-36% nitroyen
10770D~3
and 14.55% sulfur.
An 89% yield of 1,6-bis(2-thiosuccinimido)hexane ,
is obtained using the synthesis described above. The melting
point is 118-120C. Elemental analysis of the 1,6-bis(2-
thiosuccinimido)hexane shows 7.74% nitrogen and 19.15% sulfur.
Calculated percentages for C14H20N2O4S2 are 8.13% nitrogen and
18.61% sulfur.
An 85% yield of 1,4-bis(2-thiophthalimido)butane
is obtained using the synthesis described above. The
melting point is 210-213C (decomposes).
The following table illustrates the invention in
greater detail and the best mode for carrying it out, but is
not to be construed as to narrow the scope of our invention.
For the rubber stocks tested and described, infra, as
illustrative of the invention, Mooney scorch times at 121C.
are determined by means of a Mooney plastometer. The time
in minutes (t5) required for the Mooney reading to rise
five points above the minimum viscosity is recorded. Longer
times are indicative of the activity of the inhibitor.
Longer times on the Mooney Scorch Test are desirable because
this indicates greater processing safety. Percentage increases
in scorch delay are calculated by dividing the Mooney scorch
time of the stock containing the premature vulcanization
inhibitor by the Mooney scorch time of the control stock,
25 multiplying by 100, and substracting 100. These increases
show the percentage improvement in scorch delay over the
control stock which contains no inhibitor. Additionally,
curing characteristics are calculated from the time required
to cure the stocks at 144C. by means of the Monsanto
Oscillating Disc Rheometer which is described by Decker,
Wise, and Guerry in Rubber World, December 1962, page 68.
From the Rheometer data, R. M. T. is the maximum torque in
1077043
Rheometer units, t2 is the time in minutes for a rise of
two Rheometer units above the minimum reading of the rubber
sample, and tgo is the time required to obtain a torque 90%
of the maximum.
The trademarks of some compounds used in the prac-
tice of this invention are Santocure MOR and Santoflex 13.
Santocure MOR is the accelerator 2-(morpholinothio)benzo-
thiazole. Santoflex 13 is the antidegradant N-1,3-dimethyl-
butyl-N'-phenyl-p-phenylenediamine.
The table illustrates the results of using 1,6-bis-
(2-thiophthalimido)hexane and 1,4-bis(2-thiophthalimido)-
butane as premature vulcanization inhibitors in stocks of
natural rubber containing the antidegradant Santoflex 13 and
the accelerator Santocure MOR. From the data of the table
it will be noted that 1,6-bis(2-thiophthalimido)hexane and
1,4-bis(2-thiophthalimido)butane are quite active in the
presence of the accelerator as premature vulcanization
inhibitors.
The ingredients for the table are as follows.
The stocks contain:
Parts by Weight
Natural Rubber 100
Carbon ~lack 45
Zinc Oxide 3
Stearic acid 2
Hydrocarbon Softener 5
Santoflex 13 2
Santocure MOR 0.5
Sulfur 2.5
Premature Vulcanization Inhibitor as indicated
- 16 -
1077043
There are seven stocks in the table and stock 1 is
the control. Stocks 2-7 contain the following concentrations
of premature vulcanization inhibitor.
Stock InhibitorParts by Weight
2 1,6-bis(2-thiophthalimido)hexane 0.22
3 1,6-bis(2-thiophthalimido)hexane 0.44
4 1,6-bis(2-thiophthalimido)hexane 0.88
1,4-bis(2-thiophthalimido)butane 0.24
6 1,4-bis(2-thiophthalimido)butane 0.48
7 1,4-bis(2-thiophthalimido)butane 0.96
Table
I
Stock 1 2 3 4 5 6 7
Mooney Scorch at
121C.
t5 25.3 37.4 47.560.8 35.2 51.0 64.8
% Increase in
Scorch Delay - 48 88 140 39 102 156
Rheometer at 144 C.
t2 8.0 10.0 12.215.0 9.3 11.5 14.8
tgo 21.5 22.5 26.329.5 22.6 25.2 29.5
R.M.T. 56.5 58.6 60.462.0 57.5 58.0 59.0
k2 0.183 0.183 0.173 0.173 0.173 0.187 0.183
Comparable results to those in the table illustrating
utility are obtained with the inhibitors of this invention
which are not illustrated.
Concentration studies show that the inhibitors of
this invention are effective in rubber at concentrations of 0.05
to 5.0 parts per hundred. Concentrations from 0.22 to
3.0 parts per hundred are preferred.
- , ., , .,: ~ . , :
1~77043
It is intended to cover all changes and modifica-
tions of the examples of the invention herein chosen for
purposes of disclosure which do not constitute departures
from the spirit and scope of the invention.
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