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(19)
Europaisches
Patentamt
European
Patent Office
Office
europeen
des brevets
(12)
peen
des brevets
E P 0 5 6 9 9 9 5 B 1
EUROPEAN PATENT SPECI FICAT ION
(45)
Date of
publication
and mention
of the
grant
of the
patent:
16.12.1998 Bulletin 1998/51
(21)
Application
number: 93107840.6
(22)
Date of
filing:
13.05.1993
(51)
intci.6:
C 0 8 K 5 / 0 0 , C 0 8 K 5 / 4 4 ,
C08L 21/00
(54)
Scorch retardant
compositions
for
peroxide
curable elastomers
Mischungen zur Verzogerung
der Vorvulkanisation fur
peroxidhartbare
Elastomere
Melanges anti-grilleurs
pour
des elastomeres durcissables
par
les
peroxides
DO
lO
O)
O)
O)
CO
LO
o
a .
LU
(84)
Designated Contracting
States:
BE DE ES FR GB IT NL SE
(30)
Priority:
14.05.1992 US 883333
(43)
Date of
publication
of
application:
18.11.1993 Bulletin 1993/46
(73)
Proprietor:
CRAY VALLEY SA
92800 Puteaux
(FR)
(72)
Inventors:
Knowles,
Eric
Thornton
Cleveleys,
Lanes. FY5 3JD
(GB)
Cornforth,
David Arthur
Rochdale,
Lancashire OL12-7RU
(GB)
Carney,
Francis Michael
Crumpsall,
Manchester M8 7WR
(GB)
(74)
Representative:
Chaillot,
Genevieve
Cabinet
CHAILLOT,
16-20,
avenue
de L
Agent
Sarre,
B.P. 74
92703 Colombes Cedex
(FR)
(56)
References cited:
EP-A- 0 346 863
US-A- 3 993 633
EP-A- 0 504 920
Note: Within nine months from the
publication
of the mention of the
grant
of the
European
patent,
any person may
give
notice
to
the
European
Patent Office of
opposition
to
the
European
patent
granted.
Notice of
opposition
shall be filed in
a
written reasoned
statement.
It shall
not
be deemed
to
have been filed until the
opposition
fee has been
paid. (Art.
99(1) European
Patent
Convention).
Printed
by
Jouve,
75001 PARIS
(FR)
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Description
FIELD OF THE INVENTION
5
This invention is directed
to
scorch retardant
compositions
suited for the vulcanization of elastomers.
DESCRIPTION OF THE PRIOR ART
The
use
of
polyunsaturated
monomers,
and
particularly polyfunctional (meth)acrylate monomer
systems,
for the
10
curing
and vulcanization of
peroxide-curable
elastomers
to
enhance
physical properties
of the
resulting
elastomers is
known. Such
property
enhancements include
high
hardness,
resistance
to
attack
by sunlight, hydrocarbon
solvents
as
well
as water, physical strength
and
aging.
Free-radical reaction of the
polyunsaturated monomers
with the elasto-
meric
compositions
is conducted
at
elevated
temperatures
wherein the
polyunsaturated compositions
crosslinkth
rough
an
abstractable
hydrogen
atom
on
the elastomer.
is
Scorching
is
a problem
associated with the
curing
of the elastomers in the
presence
of
peroxide
and
scorching,
in
effect,
is the result of
prevulcanization
of the elastomer. In
prevulcanization
the
monomer
crosslinks with the elas-
tomer at
low
temperature
resulting
in
products
which have
a rough texture, a
shriveled
appearance
and its surface
appearance
is
lumpy.
Thus,
they are unacceptable.
To combat the
problem
of
prevulcanization
and
scorching
of the
elastomer,
it has been
customary
to
add scorch retardants
to
the
polyunsaturated monomer
which in
turn
retard the
20
rate
of
crosslinking
between the elastomer and
polyunsaturated monomer
at
low
temperature.
Although
many
types
of scorch retardants have been incorporated into the polyunsaturated monomers for subsequent peroxide curing of
elastomers,
there have been
problems.
In
terms
of elastomer
properties,
the addition of the scorch retardants have
been
relatively
ineffective
during high
temperature
vulcanization
or
too
effective in that
they
have retarded vulcanization
to
the
extent
that the
resulting
elastomers do
not
have the
required physical properties.
For
example
many
have reduced
25
elastic modulus and increased
elongation.
In
terms
of
processing
the
elastomers,
the scorch retardants often have
extended the
cure
times
to
such
an
extent
that
costs
become
prohibitive
or,
because of their
volatility,
present
envi-
ronmental
problems
in the
workplace
due
to
odor and
toxicity.
Several
patents
which disclose scorch retardant
systems
for
inhibiting prevulcanization
of elastomers
including
rubber and rubber
type
compositions are as
follows:
30
U.S.
3,751 ,378
discloses
a
mechanism for
inhibiting prevulcanization
of rubber crosslinked with
a polyfunctional
methacrylate
in the
presence
of
peroxide.
Ascorch retardant of
N-nitrosodiarylamine or
N,N'-dinitrosodiphenyl-j>phe-
nylenediamine
is shown.
U.S.
4,857,571
discloses
a
method for the
inhibiting
the
prevulcanization during
free-radical
curing
of rubbers. The
prior art
section of the
patent
discloses that it
was
known
to use
acidic materials such
as phthalic anhydride, salicylic
35
acid and sodium
acetate
which
act
as
retarders in sulfur vulcanization
systems.
Other known retarders include nitroso
and nitroaromatic amines
as
well
as
various
quinones
e.g.
p-benzoquinone
and
naphthoquinone.
Retarders used
by
the
patentees
include modified
alkyl-substituted aminoalkylphenols, an example
of which is
2,6-di-t-butyl-4-[methyl
(phenyl)amino]-n-propylphenol.
U.S.
954,907
discloses
a
method for
avoiding scorching
of
ethylene polymer
based
compositions
vulcanized in
40
the
presence
of
organic peroxide.
The
patentees
disclose the
use
of monofunctional
vinyl compositions as a
scorch
retarding
agent.
Antioxidants such
as sterically
hindered
phenols are
also
suggested as an adjuvant.
U.S.
3,578,647
discloses
a
scorch
prevention
process
for
producing ethylene-containing polymers
crosslinked
by
free radical
generating crosslinking
agents.
The
patentees
employ
the
use
of
a
chain transfer
agent
e.g.,
mercaptans
and
aldehydes as a
scorch
retarding or
scorch
preventing adjuvant.
45
U.S.
3,335,124
discloses method for
controlling
the
rate
of vulcanization of
polyethylene through
the
use
of
a
crosslinking regulator
which heretofore
were
utilized
or
antioxidants. Various
compositions having
antioxidant
activity
and suited
as a crosslinking regulator
include aromatic
amines,
phenolic compounds
and
ketone-aldehyde
condensa-
tion
products.
U.S.
3,202,648
discloses the addition of scorch
inhibiting
components
during
the free radical
peroxide crosslinking
so
of
polyethylene. Alkyl, cycloalkyl
and
arylalkyl
nitrites
having
from
5 to
18 carbon
atoms
are
used
as
the scorch
pre-
venting
additive.
EP-A-0 346 863 relates
to
a
mixture
containing
at
least
one organic peroxide
suitable for the
crosslinking
of
polymers
;
at
least
one hydroquinone
derivative
;
and
at
least
one crosslinking reinforcing
agent,
said mixture
permitting
the
crosslinking
of
polymers
while
extending
the scorch time.
55
US-A-3 993 633 describes
a
class of
2-(1 (2H)-phthalazinone)
sulfenamides useful
as
inhibitors of
premature
vul-
canization of rubber.
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SUMMARY OF THE INVENTION
This invention relates
to
a polyfunctional (meth)acrylate
based scorch retardant formulation for
use as a
crosslinker
system
for the
peroxide curing
of elastomer
compositions
vulcanizable in the
presence
of the
peroxide catalyst
and
to
5
the curable elastomer
system
itself. The
improved
scorch
retarding polyfunctional (meth)acrylate
system
comprises:
a polyfunctional (meth)acrylate
and
an
effective
amount
of
a
scorch retardant mixture
comprising hydroquinone
and
a
sulfenamide. Scorch
retarding
curable elastomers
are
formed
by incorporating
the
polyfunctional (meth)acrylate
based
scorch retardant formulations into a peroxide-curable elastomer system. There are several advantages associated
with the
polyfunctional (meth)acrylate
based scorch retardant
compositions
and the curable elastomers
prepared
there-
to
from and these include:
an ability
to
formulate
an easily
handled scorch retardant
polyfunctional (meth)acrylate
system
for
vulcanizing
peroxide-curable
elastomers;
an ability
to
formulate
storageable,
scorch retardant
polyfunctional (meth)acrylate
systems
suited for
forming
per-
15
oxide-curable
compositions;
an ability
to
retard
scorching
of
peroxide-curable
elastomers
during crosslinking
with
polyfunctional (meth)acrylate
monomers
while
maintaining
excellent
rates
of
cure
at
vulcanization
temperatures;
and
an ability
to
inhibit scorch in the vulcanization of
peroxide-curable
elastomers reacted with
polyfunctional (meth)
acrylates
without
significant
environmental
problems
due
to
offensive odors and
particularly
offensive
toxicity.
20
Afirst subject-matter of the present invention is a scorch retarding polyunsaturated monomer containing system
suited for
curing peroxide
curable elastomers and
polyethylene, polypropylene, copolymers containing ethylene
units
and
copolymers containing propylene
units,
which
comprises polyunsaturated
monomer,
0.2
to
6
weight
percent
hyd-
roquinone
based
upon
said
polyunsaturated monomer
and
1 to
50
weight
percent
sulfenamide based
upon
said
pol-
25
yunsaturated monomer.
Asecond
subject
matter
of the
present
invention is
a
curable
composition comprising an
elastomer
or polyethylene
or polypropylene or a copolymer containing ethylene
units
or a copolymer containing propylene
units
having an
ab-
stractable
hydrogen
atom
crosslinkable with
a polyfunctional (meth)acrylate, polyfunctional (meth)acrylate, organic
peroxide,
and
a
scorch
retarding
additive which
comprises
from 0.2
to 6%
by weight
of
hydroquinone
based
upon
said
30
polyfunctional (meth)acrylate
and from
1 to 50%
by weight
of
a
sulfenamide based
upon
said
polyfunctional (meth)
acrylate.
DETAILED DESCRIPTION OF THE INVENTION
35
This invention
pertains
to
compositions
suited for
inhibiting or retarding
the
prevulcanization or scorching
of
per-
oxide-curable elastomers
during cure
with
polyinsaturated monomers.
The curable elastomers which
are
crosslinked
with the
polyunsaturated monomers are
elastomeric
organic high polymers,
e.g.,
rubbers which
are
curable via free-
radical
crosslinking
with
polymerizable vinyl
unsaturated
monomers.
In
general,
the free-radical curable elastomers
are polymers having
extractable
hydrogen
atoms
which
on
reaction with the
polymerizable monomers crosslinkthrough
40
carbon-carbon bonds.
Representative examples
of
synthetic rubbery polymers
formed via the
polymerization
of
con-
jugated
dienes,
include
polyisoprene, styrene-butadiene
rubbers,
polybutadiene
rubbers,
neoprene,
and substituted
butyl
rubbers,
chlorinated
polyethylene
rubber. Other elastomers
are
based
upon
vinyl polymerization
and include
polymers
such
as ethylene-propylene
rubbers,
butadiene-acrylonitrile
elastomers,
and silicone elastomers. This inven-
tion
pertains
also
to
compositions
mited for
inhibiting or retarding
the
prevulcanization or searching
of
peroxide-curable
45
polyethylene, polypropylene
and
copolymers containing ethylene
and
propylene
units
e.g.
ethylene-vinyl
acetate
co-
polymers.
The
patents
described in the
prior
art
section herein
suggest
many
representative
elastomer
systems.
The scorch
retarding
curatives for
peroxide
curable elastomers
comprise a polyfunctional
unsaturated
monomer,
typically a polyfunctional (meth)acrylate
monomer,
and
an
effective
amount
of
a
scorch retardant inhibitor and vulcan-
izate
accelerator,
the scorch retarder
being hydroquinone
and the vulcanizate accelerator
being a
sulfenamide. The
so
polyfunctional
unsaturated
monomer generally
is admixed with the scorch retardant additives and
generally
it is
a
component
of the scorch
retarding
curative;
it is
polyfunctional
in that it has
a plurality
of unsaturation units for crosslink-
ing
with the elastomers.
Preferably
it is
a liquid
at
temperatures
below about 50C. The
use
of
polyacrylates
in the
vulcanization of
peroxide
curable elastomers is conventional.
Examples
of
polyfunctional acrylates
include those
acrylic
and
methacrylic
acid
esters
of
C2.12
polyols
and
alkoxylated
derivatives
containing
from 2-6
alkyleneoxide
units. Pref-
55
erably
the
polyols
have from 2-8 carbon
atoms
and
preferably they are
diols and triols.
Specific polyfunctional (meth)
acrylates are : trimethylolethane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethylacrylate,
glycerol trimethyacrylate, glycerol triacrylate, 1,3-butylene glycol dimethylacrylate, ethylene glycol dimethacrylate,
1,4-butylene glycol dimethacrylate, polyethylene glycol dimethacrylate.
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Other
polyunsaturated monomers
which
may
be used
by
themselves
or
in combination with the
polyfunctional
(meth)acrylates
include the
polyallyl
derivatives of
polyols,
such
as,
the
allylic
ethers of
trimethylolpropane,
pentaer-
ythritol, ethylene glycol, glycerol, polyethylene glycol
and
polypropylene glycol
;
triallylmellitate, diallylphthalate,
dial-
lylchlorendate, triallylcyanurate,
and
triallylisocyanurate,
5
One
component
of the scorch retardant
system
is
an organosulfenamide.
These
compounds
have been used in
rubber formulations
as delayed
action accelators. The sulfenamides
are represented by
the formulas:
I
10
wherein
30
RisuptoC10;
R-i
is
H,
C-|.10
aliphatic, aryl, cycloalkyl or aralkyl;
R2
is
C-_
10
aliphatic, aryl, cycloalkyl or aralkyl, or
combined with
R-,
forming a heterocyclic
group;
and,
X is
hydrogen, halogen, hydroxy,
C-,.6
lower
alkyl,
C-,.6
alkoxy.
35
Examples
include
N,N-dicyclohexylbenzothiazolesulfenamide;
N,N-diisopropyl-2-benzothiazolesulfenamide;
2-(4-morpholino)thiobenzothiazole (MTB);
40
N-t-butyl-2-benzothiazolesulfenamide;
and
N-cyclohexyl-2-benzothiazolesulfenamide.
Another
component
of the scorch retardant
system
is
hydroquinone.
In the
past,
quinones
have been used
as
shortstop
agents
in
polymerization
processes, e.g.
in the
polymerization
of olefins such
as
butadiene and
styrene.
45
Other
quinones or polymerization
inhibitor,
even though they
act to
retard the
rate
of
vulcanization,
do
not
give
the
desired result when combined with the sulfenamide
during
the
peroxide curing
of elastomer with
polyacrylates.
One
highly acceptable
method for
incorporating
the scorch retardant additive for
curing
of the elastomer involves
mixing
the
hydroquinone
and sulfenamide with the
polyacrylate
and then
coating
the
resulting liquid
mixture
onto
an
inert solid
phase
substrate. The material then
can
be
packaged
and stored for extended
periods
of time
at
ambient
so
temperatures.
Examples
of substrates suited for
coating
the mixture of
polyacrylates monomers
and scorch retardants
include
powdered
silica,
diatomaceous earth and
clays.
The scorch retardant
system
of
hydroquinone
and sulfenamide also
can
be added
separately or jointly
to
the
elastomer
during milling
with the
polyunsaturated monomer.
However,
it is
preferred
that the scorch retardant additives
be mixed with the
polyunsaturated monomer
and the resultant mixture added
to
the elastomer.
55
The scorch resistant
polyunsaturated monomer or polyf unctional(meth)acrylate
systems
for
effecting
vulcanization
of curable elastomeric
organic high polymers typically are
formulated
on
the basis of
one
hundred
weight
parts
mon-
omer,
e.g.,
polyfunctional(meth)acrylate.
The scorch retardant
system
then is
incorporated
into the curable elastomer
in conventional
amounts
from about 0.5
to
50
weight
parts
polyunsaturated monomer
per
one
hundred
weight
parts
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elastomer.
(These
values
may
be
expressed as weight percent.)
When
using polyallylic
functional
monomers,
higher
levels
may
be used than when
using polyacrylates.
For
polyfunctional(meth)acrylates
the level of
polyfunctional(meth)
acrylate
vis-a-vis the curable elastomer
generally
is from
1 to
50
parts
per
100
parts
elastomer.
Higher
levels
may
be
used but seldom
are
for
reasons
of
cost;
the addition level is
primarily
at
the discretion of the formulator and thus
5
depends on
the
nature
of the elastomer
to
be
produced.
In
formulating
the scorch retardant
system
the
range
of
hyd-
roquinone
based
upon
polyfunctional(meth)acrylate
is from 0.2
to
6
parts
by weight
per
one
hundred
parts
by weight
polyf unctional(meth)acrylate.
The sulfenamide also
present
in
a proportion
of from about
1to
30
typically
2
to
20
weight
parts per 100 weight parts of polyf unctional(meth)acrylate. When less than about 0.2 parts hydroquinone are used in
the scorch retardant
polyfunctional(meth)acrylate
system,
there
may
be insufficient inhibitor
to
prevent
even
modest
10
levels of
scorching during cure. Higher
levels
may
be
required depending
upon
vulcanization
temperatures
and vul-
canization times
as
well
as
the elastomeric
organic high polymers
and
polyunsatured momomers
themselves. Too
much
hydroquinone
may
overly
extend
cure cycles
and result in
insufficiently
cured elastomers.
Typically,
the vulcanization
or crosslinking
of the curable elastomers is effected
through
free radical initiation
by
the addition of
a
free-radical
generating compound or
via
a
radiation
source,
e.g.,
a high
energy
electron
source.
is
Although
many
systems
will
cure
at
high
temperature,
high
temperatures
may
result in
unacceptable product
if
cure
temperature
is
too
high. Generally,
then
polymerization
is effected
by initiating
reaction
through
the addition of
a
free
radical
generating compound
which is
usually an organic peroxide. Organic peroxides
suited for
abstracting hydrogen
from the elastomer
are
known and those
conventionally
used
can
be used in the
practice
of this invention for
vulcanizing
elastomers.
Organic peroxides
which
can
be used include
ditertiary peroxides
and these include
benzoyl peroxide,
20
1
,3-bis-t-butylperoxyisopropylbenzene;
1
,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane; 2,5-dimethyl-2,5-bis(t-
butylperoxy)hexane; di-a-cumyl peroxide; and ditertiary peroxides such as di(tert-peroxy)butane; tert-butyl-methylcy-
clohexyl peroxide
and
dibenzoyl peroxide.
Other
peroxides
include
tert-butyl perbenzoate
and
tert-butyl perphthalate.
Radiation of the
polymers
would be
an acceptable
method
depending on use
and
cost
over
chemical free radical
initatiors.
However,
any
conventional
process may
be used.
25
The elastomeric
compositions can
be
processed
in conventional
manner typically involving
the
milling
of
a mas-
terbatch formulations in roll mills and then
curing
the milled masterbatch in molds
or
presses.
Various additives
can
be added
to
the elastomer for
imparting
desirable
properties
thereto and
examples
of additives include carbon
black,
antioxidants,
wetting
agents
and
reinforcing pigments
and fillers.
Examples
of reinforcement and fillers include fine
particles,
zinc
oxide,
calcium
carbonate,
calcium
silicate,
amorphous hydrated
silica,
fine
clays, magnesium
carbonate
30
and carbon black. The addition of various additives
to
achieve desired
properties
is
at
the discretion of the
processor.
The
following examples are provided
and illustrate various embodiments of the invention and
provide comparisons
against
the
prior
art.
EXAMPLE
1
35
Scorch Retardant
Systems
for Elastomers Effect of Level of Scorch Retardent
Vulcanization of
butadiene-acrylonitrile
rubbers
was
carried
out
in conventional
manner
in
a
roll mill and then
placing
the milled
system
into
a
mold.
Varying
levels of scorch
retarding
additives of
hydroquinone
and sulfenamide
40
were compared.
The scorch retardant
systems
were
formulated
by mixing
the
hydroquinone
and sulfenamide with the
trimethylolpropane triacrylate
and
coating
the
resulting
mixture
onto
powdered
silica. Scorch time
to
determine
cure
characteristics
was
evaluated
on
the basis of
Mooney
scorch time
according
to
ASTM 1646-80. The formulations
were
cured
at 1
60C and
physical properties
i.e. hardness measured. The conditions and results
are
set
forth in Table
1
.
The masterbatch formulation is
as
follows:
45
Parts
(by wt)
NBR N367C70 Nitrile Rubber 100
FEF Carbon Black N550 40
Zinc Oxide
5
Stearic Acid
1
Trimethylolpropane Trimethacrylate
15
Vulcup
40KE
(peroxide)
5
N-t-butylbenzothiazolesulfenamide
TABLE
1
Hydroquinone
TABLE
1
Nitrile Rubber is
a butadiene-acrylonitrile
rubber
Vulcup
40KE is
1
,3-bis-t-butylperoxyisopropylbenzene
at 40%
activity
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TABLE
1
SULFENAMIDE* HYOROQUINONE*
SCORCH TIME AT 121 C
(min)
IRHD HARDNESS
1 1
48 76.5
0.5
1 54 74.5
1
0.5 48 79
0.5 0.5 47 78.5
1
0.25 49.5 84
0.5 0.25 43.5 85
TABLE
1
shows
a
combination of both additives
yields
desirable
products.
A level of
hydroquinone or
less than
0.5%
by weight
of the
trimethylolpropane trimethacrylate provided higher
hardness levels in the cured
elastomer,
al-
though
all levels
are acceptable.
EXAMPLE 2
(comparative)
Elastomers Cured with Trial
lylcyan
urate
(TAC)
No Sulfenamide
The
procedure
of
Example
1
was repeated using
the
following
masterbatch formulation. No sulfenamide
was
used
in the cure and delayed action was sought to be achieved through addition of hydroquinone to the methacrylate mon-
omer.
The scorch
retarding
monomer,
TAC,
was
also tested for
comparison.
Vistalon 7500 EPDM 100 PTS
FEF Carbon Black N550
1
00
Struckpar
2280 Process Oil
45
Antioxidant
TMQ 1
Trimethylolpropane trimethacrylate
2
Vulcup
40KE
(peroxide)
5
Vistalon 7500 EPDM is
an ethylene/propylene
rubber which is
commercially
avail-
able.
TMQ
antioxidant is
polymerized trimethyldihydroquinone.
Additions of
hydroquinone expressed as weight
percent
of the
trimethylolpropane trimethacrylate
co-agent
gave
results
as
follows:
TABLE 2
HQ
LEVEL TAC SCORCH TIME AT
1
31C
(min)
HARDNESS
1.07%
-
11
56
12.5%
-
12.5 56
2 27
55
As
can
be
seen
from Table
2,
when 2
parts
TAC
were
used
as
the
coagent
(with no
added scorch
retardant),
the
elastomer had
a
scorch time of 27 min and
a
hardness of
55.
When the
methacrylates were
used,
the addition of
hydroquinone as the sole scorch retarder failed to give as good as a scorch retardant.
EXAMPLE 3
Ethylene-Propylene
Rubbers
The
procedure
of
Example
2
was repeated
except
sulfenamide
was
added
along
with
polyacrylate
and
hydroqui-
none
in
forming
the
co-agent
formulation. Table 3
provides
data
at 5
parts
and 3
parts
trimethylolpropane trimethacrylate
as
follows. The masterbatch formulation
was comprised:
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Parts
(by wt)
Keltan 4802 EPDM 100
FEF Black 85
Sunpar
2280 Process Oil 30
Antioxidant
TMQ 1
N-t-butylbenzothiazole sulfenamide Table 3
Vulcup
40KE 9
Hydroquinone
1.7
Kelton 4802 is
an ethylene/propylene
rubber which is
commercially
avail-
able.
TABLE 3
20
TRIMETHYLOLPROPANE TRIMETHACRYLATE
CO-AGENT
5
PTS
SULFENAMIDE LEVEL SCORCH TIME AT 121 C
(min)
HARDNESS
0.25 19.5 71
0.5 24.5
71
CO-AGENT 3 PTS
SULFENAMIDE LEVEL SCORCH TIME AT 121 C
(min)
HARDNESS
0
14
73
0.25 19 70
0.5 19 72
30
When
comparing
the results with those of
Example
2,
it is
generally recognized
that the standard
methacrylate grades
give superior physical properties as
evidenced
by
the
high
hardness values relative
to
the TAC cured
product.
The
methacrylate grades
suffer
primarily
from the scorch
problem.
The additions of the sulfenamide
to
the
polymethacrylate
formulation resulted in
higher Mooney
scorch times.
Also,
these results show
generally longer
levels of scorch time
35
than those obtained with
hydroquinone
alone,
indicating
that both
components
are required
in order
to
confer with
desired
activity.
EXAMPLE
4
(comparative)
40
Comparison
of
Hydroquinone
to
Other
Polymerizaton
Inhibitors
The
procedure
of
Example
1
was repeated
but
using a
different masterbatch formulation
as
follows:
Nitrile Rubber BR 1042 100
pts.
Zinc Oxide
5
pts.
Stearic Acid
1
pt.
FEF Carbon Black 40 pts.
Dicumyl peroxide
4
pts.
Trimethylolpropane trimethacrylate
15
pts.
Various
potential
scorch additives
were
added
at
a
level of
5%
W/W relative
to
the
acrylate monomer.
Table
4 sets
forth the
test
results:
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TABLE
4
Scorch Retardant Additive
Mooney
Scorch
at
121 C Mins. Hardness* IRHD
None 8.33 84
Hydroquinone
60 46
Antioxidant 2246 10.06 79
Phenyl B-naphthylamine 8.48 83
Santowhite
Crystals
11.14
84
This demonstrates that
hydroquinone
is
unique
in its
ability
to
extend scorch
time,
but that it does
so
at
a
very
unacceptable
reduction of hardness when used alone
at
higher
levels.
After 60 mins
cure
at
160C.
Antioxidant 2246 is
2,2-methylene
bis
4,methyl,6-t-butyl phenol.
Santowhite
Crystals
is
a
Monsanto
product.
15
EXAMPLE
5
Diethyleneglycol dimethacrylate Comparison
with
Triallylcyanurate
Low Level
Polyunsaturated
Monomer in Cure
20
The
procedure
of
Example
1
was repeated
except
for the
use
of
a
different masterbatch formulation. One
co-agent
composition was prepared consisting
of
diethylene glycol dimethacrylate (83.3%), hydroquinone (1 .7%)
and
N-t-butyl-
benzthiazylsulfenamide (15%).
That formulation
was compared
with
an
identical masterbatch formulation in which TAC
was
substituted for the
diethylene glycol dimethylacrylate
and without the addition of scorch additives. Table
5 sets
forth the
test
results.
25
Ingredients
Parts
(by wt)
Vistalon 7500 EPDM 100
N550 Black 100
Paraffinic Oil
45
Antioxidant
TMQ 1
Coagent
Monomer 2
Vulcup
40KE
peroxide
5
35
TABLE
5
Coagent
Monomer 2 Parts
DIMETHACRYLATE TAC
Scorch Time
at
121 C
(min)
53
45
Hardness
57
60
Compression
Set
%
(22
hr
at 1
60C)
23.6 34.2
Elongation
at
break
%
360 31
5
Tensile
Strength
(MN.m-2)
14.5 15.7
The results show that the
dimethacrylate
cured
system
had
improved
scorch
time,
compression
set
and
elongation
compared to TAC. Hardness was slightly reduced and tensile strengths were approximately equivalent.
so
EXAMPLE 6
Low Level
Trimethylolpropane trimethacrylate-
TAC
The
procedure
of
Example
5
was repeated
except
only
30
pts
of
paraffinic
oil,
and
a
coagent
consisting
of trimeth-
55
ylolpropane trimethacrylate (83.55), N-t-butylbenzothiazolesulfenamide (15)
and
hydroquinone (1.45),
parts
were
used. Table 6
sets
forth the
test
results.
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TABLE 6
Coagent
2 Parts
METHACRYLATE TAC
Scorch Time
at
121 C 24.5 22.5
Hardness 70 67
Compression Set % (22 hrs at 160C) 21.9 16.2
Elongation
at
break
%
255 235
Tensile
Strength
(MN.m-2)
17.6 17.9
The results show that
even
at
low levels of
polyacrylate
addition in the form of
diacrylate
and
triacrylate
the scorch
retardant effect of the scorch retardant mixture
was
about
equivalent
to
TAC and
yet
hardness
was
better and
com-
pression
set
somewhat
poorer.
EXAMPLE
7
High
Level of Process Oil Addition
The
procedure
of
Example
6
was repeated
except
at
higher
levels of
process
oil addition. The
system
was com-
pared
to
TAC
systems.
Using
the
Example
6
trimethylolpropane trimethacrylate
co-agent
composition
in
a
rubber
com-
pound as
above
containing
65
parts
of
paraffinic
process
oil,
data
are as
follows in Table
7.
TABLE
7
Coagent
2
parts
METHACRYLATE TAC
Scorch Time
77
>120
Hardness 49
44
Compression
Set
%
(22
hrs
at
160C)
27.0 65.1
Elongation
at
break
%
480
515
Tensile
Strength
(MN.m"2)
12.0 6.9
The
advantage
of the scorch
retarding polyacrylate
systems
over
TAC
systems
is best
emphasized
at
the
highest
loading
levels of
process
oil. Hardness
was
better and tensile
strength was nearly
double.
Compression
set
was con-
siderably improved
in the
methacrylate
system.
EXAMPLE 8
(comparative)
Scorch Retardation
System
in the Absence of
Hydroquinone
The
procedure
of
Example
1
was repeated
except
hydroquinone was
omitted from the scorch
retarding polyacrylate
system.
The sulfenamide derivative failed
to
give adequate
scorch
protection.
The formulation consisted of:
Parts
(by wt)
Breon N3670 Nitrile Rubber 100
FEF Carbon Black 40
Zinc Oxide
5
Stearic Acid
1
DiCup
40C
(peroxide)
5
Trimethylolpropane trimethacrylate
15
N-t-butylbenzothiazolesulfenamide
2
A
Mooney
Scorch of
only
6 1/2 minutes and
a
vulcanisate hardness of 81
was
obtained thus
showing
the need for
the scorch
retarding
additive,
hydroquinone,
in combination with the sulfenamide.
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EXAMPLE 9
(comparative)
Vulcanization without Scorch Retardant Effect of
Acrylate Functionality
The
procedure
of
Example
1
was repeated
except
that the
following
masterbatch
was
used. No
special
addition
of scorch-retardant
agent(s) was
made. The results
are
in Table 8.
NBR B36C70 Nitrile Rubber 100
FEF Black 40
Zinc Oxide
5
Stearic Acid
1
Antioxidant
TMQ
0.5
DiCup
40C
(peroxide)
7
Polyacrylate
Monomer
(See
Table 8
)
15
TABLE 8
MONOMER FUNCTIONALITY SCORCH TIME AT 121 C
(min)
IRHD HARDNESS
TETRAHYDROFURFURYL
1
24 63
METHACRYLATE
1,3-BUTANEDIOL
2 9 81
DIMETHACRYLATE
TRIMETHYLOLPROPANE 3
7
84
TRIMETHACRYLATE
These results show that
polyunsaturated monomers
without
a
scorch
retarding
agent
scorch times
were
low. The
monounsaturated
monomer
had better scorch time but
at
the
expense
of hardness. The
appearance
of the
products
showed
severe scorching. Scorching
became
more
severe,
as expected,
with
increasing functionality
of the
polyacr-
ylate
and such scorch times
were significantly
lower for the
higher
functional
polyfunctional(meth)acrylates.
However,
the
polyunsaturated monomers
cured elastomers had better and excellent hardness.
EXAMPLE 10
(comparative)
Effect of
Hydroquinone
on
Vulcanization
-
No Sulfenamide
The
procedure
of
Example
1
was repeated
except
that the
percentage
of
hydroquinone was
varied based
on
the
trimethylolpropane methylacrylate.
No sulfenamide
was
used. The results
are
set
forth in Table 9.
Table 9
%
ADDITION OF
HYDROQUINONE
ON MONOMER SCORCH TIME AT 121 C
(min)
IRHD HARDNESS
0
7.5
84
0.5 16 82
1
.0 25 76
3.0 58 60
5.0 >60 50
The
increasing
levels of
hydroquinone
based
on
the
weight
of the
polyf unctional(meth)acrylate
extended the scorch
time with
increasing hydroquinone
levels,
but reduced the vulcanisate hardness. These results in
terms
of vulcanisate
hardness
are
is consistent with
Example
1
,
and
they
also show the
importance
of sulfenamide addition.
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EXAMPLE
11
(comparative)
Scorch Retardant
Using Tetramethyl/Thiuram
Monosulfide
The
procedure
of
Example
1
was repeated,
but
using tetramethyl
thiuram monosulfide in
place
of the sulfenamide.
The results obtained
are
set
forth in Table 10.
Monosulfide Hydroquinone Scorch Time 121 C Hardness
1 1
27.4 73
0.5
1
30.1 73.5
1
0.5 21.5
77
0.5 0.5 21.2 78
This demonstrates that the Monosulfide
system
has
an interesting
combination of
properties,
but that its
perform-
ance
is
not
as
the
preferred
sulfenamide
system.
EXAMPLE 12
(comparative)
Commercial Scorch Retardant and Effect
Two commercial scorch retardant
systems
were compared
to
the formulation of
Example
1
in order
to
provide
comparative performance requirements.
The formulation
was as
follows:
NBR N36C70 Nitrile Rubber 100
FEF Black N550 40
Zinc Oxide
5
Stearic Acid
1
Monomer
15
Vulcup
40KE
peroxide
4
TABLE 8
MONOMER SCORCHTIME
AT121C(min)
IRHD HARDNESS
EXAMPLE
1
43.5 85
TRIMETHYLOLPROPANE TRIMETHACRYLATE 6 1/2 84
COMMERCIAL PRODUCT
1 47.5
83
COMMERCIAL PRODUCT 2 40.5 83
The results show similar scorch times and hardness for the scorch retardant
systems
described herein
to
estab-
lished commercial
systems.
EXAMPLE 13
(comparative)
Effect of
N-Cyclohexylbenzothiazolesulfenamide
The
procedure
of
Example
4
was repeated using
the
same
masterbatch,
but
using N-cyclohexyl
benzothia-
zolesulfenamide
at
a
level of
5%
relative
to
the
methacrylate monomer.
This formulation
gave
a
scorch-time of 9.5
minutes
at
121C and
a
vulcanisate hardness of 83 after
cure
for 60 mins
at
160C. This further demonstrates that
sulfenamide
by
itself will
not
render the scorch
properties adequate.
EXAMPLE
14
Effect of
N-Cyclohexylbenzothiazolesulfenamide
The
procedure
of
Example
1
was repeated
except
that the
t-butyl-sulfenamide was replaced by N-cyclohexylben-
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zothiazolesulfenamide
at
a
level of
3%
relative
to
the
methacrylate monomer.
However,
the combination
was only
slightly
inferior
to
the commercial
products
of
Example
11
.
Claims
1
.
Scorch
retarding polyunsaturated monomer containing
system
suited for
curing peroxide
curable elastomers and
polyethylene, polypropylene, copolymers containing ethylene units and copolymers containing propylene units,
which
comprises polyunsaturated
monomer,
0.2
to
6
weight
percent
hydroquinone
based
upon
said
polyunsatu-
rated
monomer
and
1 to
50
weight
percent
sulfenamide based
upon
said
polyunsaturated monomer.
2. The scorch retardant
system
of Claim
1
wherein the sulfenamide is
represented by
the formulas
:
I
and
wherein
:
R is
up
to
C10;
R1
is
H,
C|_10
aliphatic, aryl, cycloalkyl or aralkyl
;
R2
is
C|_10
aliphatic, aryl, cycloalkyl or aralkyl, or
combined with
R1
forming a heterocyclic
group
;
and
X is
hydrogen, halogen, hydroxy,
C-,.6
alkyl,
C-,.6
alkoxy.
3. The scorch retardant
system
of Claim 2 wherein the
polyunsaturated monomer
is selected from the
group
of
poly-
functional
(meth)acrylates
and
polyallylic monomers.
4. The scorch retardant
system
of Claim 3 wherein the
polyunsaturated monomer
is
a polyacrylic or methacrylic
ester
of
a
C2_-2
polyol.
5. The scorch retardant
system
of Claim
4
wherein the
polyol
is
C2.8
diol
or
triol.
6. The scorch retardant
system
of Claim
5
wherein said sulfenamide is selected from the
group
consisting
of
N,N-
dicyclohexylbenzothiazolesulfenamide
;
N,N-diisopropyl-2-benzothiazolesulfenamide
;
2-(4-morpholino)thioben-
zo-thiazole
(MTB)
;
N-t-butyl-2-benzothiazolesulfenamide
;
and
N-cyclohexyl-2-benzothiazolesulfenamide.
7. The scorch retardant
system
of Claim
1
intended
to
be used in
a peroxide
curable elastomer selected from the
group
consisting
of
polyisoprene, styrene-butadiene
rubbers,
polybutadiene,
neoprene,
butyl,
chlorinated
polyeth-
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ylene, ethylene-propylene,
and
butadiene-acrylonitrile
rubbers,
and silicone
elastomers,
or
in
a peroxide
curable
ethylene
-
vinylacetate copolymer.
8. The scorch retardant
system
of Claim
7
wherein the
weight
parts
hydroquinone
per
1
00
weight
parts
polyfunctional
(meth)acrylate are
from 0.5
to 5.
9. The scorch retardant
system
of Claim 8 wherein the sulfenamide is
present
in
an
amount
from 2
to
20
parts
per
100 parts by weight polyfunctional (meth)acrylate.
10. The scorch retardant
system
of Claim 9 wherein the sulfenamide is
N-t-butylbenzothiazolesulfenamide.
11. Acurable
composition comprising an
elastomer
or polyethylene or polypropylene or a copolymer containing
eth-
ylene
units
or a copolymer containing propylene
units
having an
abstractable
hydrogen
atom
crosslinkable with
a
polyfunctional (meth) acrylate, polyfunctional (meth) acrylate, organic peroxide,
and
a
scorch
retarding
additive
which
comprises
from 0.2
to 6%
by weight
of
hydroquinone
based
upon
said
polyfunctional (meth)acrylate
and
from
1 to 50%
by weight
of
a
sulfenamide based
upon
said
polyfunctional (meth)acrylate.
12. The curable
composition
of Claim
11
wherein the sulfenamide is
represented by
the formulas
:
I
and
X
wherein
:
R is
up
to
C10;
R1
is
H,
C|_10
aliphatic, aryl, cycloalkyl or aralkyl
;
R2
is
C|_10
aliphatic, aryl, cycloalkyl or aralkyl, or
combined with
R1
forming a heterocyclic
group
;
and,
X is
hydrogen, halogen, hydroxy,
C-,.6
alkyl,
C-,.6
alkoxy.
13. The
composition
of Claim 12 wherein the sulfenamide is
represented by
formula
1
and
R-,
is
hydrogen
and
R2
is
aliphatic.
14. The curable
composition
of Claim 13 wherein the
polyfunctional (meth)acrylate
is
a polyacrylic or methacrylic
ester
of
a
C2.12
polyol.
15. The curable
composition
of Claim
14
wherein the
polyol
is
C2.8
diol ortriol.
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20
1.
25
2.
30
35
40
45
50
55
3.
i.
The curable
composition
of Claim
15
wherein said sulfenamide is selected from the
group
consisting
of
N,N-
dicyclohexylbenzothiazolesulfenamide
;
N,N-diisopropyl-2-benzothiazolesulfenamide
;
2-(4-morpholino)thioben-
zo-thiazole
(MTB)
;
N-t-butyl-2-benzothiazolesulfenamide;
and
N-cyclohexyl-2-benzothiazole-sulfenamide.
'. The curable
composition
of Claim
1
6 wherein the elastomer is selected from the
group
consisting
of
polyisoprene,
styrene-butadiene
rubbers,
polybutadiene,
neoprene,
butyl,
chlorinated
polyethylene ethylenepropylene,
and buta-
diene-acrylonitrile
rubbers,
and silicone
elastomers,
or
wherein the
copolymer containing ethylene
units is
ethylene
- vinyl acetate copolymer.
The curable
composition
of Claim
17
wherein the
weight
parts
hydroquinone
per
100
parts
polyfunctional (meth)
acrylate are
from 0.5
to 5.
i.
The curable
composition
of Claim 18 wherein the sulfenamide is
present
in
an
amount
from 2
to
20
parts
per
100
weight
parts
polyfunctional (meth)acrylate.
i.
The curable
composition
of Claim 19 wherein the sulfenamide is
N-t-butylbenzothiazolesulfenamide.
Mehrfach ungesattigtes Monomer enthaltendes Scorchschutzsystem fur die Hartung von peroxidhartbaren Ela-
stomeren
und
Polyethylen, Polypropylen,- Ethyleneinheiten
enthaltenden
Copolymeren
und
Propylen
enthalten-
den
Copolymeren,
enthaltend mehrfach
ungesattigtes
Monomer, 0,2
bis 6
Gewichtsprozent Hydrochinon, bezogen
auf das mehrfach
ungesattigte
Monomer,
und
1
bis 50
Gewichtsprozent
Sulfenamid,
bezogen
auf das mehrfach
ungesattigte
Monomer.
Scorchschutzsystem
nach
Anspruch
1,
wobei das Sulfenamid durch die Formeln:
dargestellt
wird,
worin:
R fur bis
zu
C10
steht;
R-,
fur
H,
C-|.10-Aliphat,
-Aryl, -Cycloalkyl
oder
-Aralkyl
steht;
RgfiirC-i.-io-Aliphat,
-Aryl, -Cycloalkyl
oder
-Aralkyl
steht oder
gemeinsam
mit
R1
eine
heterocyclische Gruppe
bildet;
und
Xfur
Wasserstoff,
Halogen, Hydroxy,
C-|.6-Alkyloder C-|.6-Alkoxy
steht.
Scorchschutzsystem
nach
Anspruch
2,
wobei das mehrfach
ungesattigte
Monomer
aus
der
Gruppe
der
polyfunk-
tionellen
(Meth)acrylate
und
Polyallylmonomere
stammt.
Patentanspriiche
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EP 0 569 995 B1
Scorchschutzsystem
nach
Anspruch
3,
wobei
es
sich bei dem mehrfach
ungesattigten
Monomer
urn
einen
Poly-
acryl-
oder
Methacrylsaureester
eines
C2_12-Polyols
handelt.
Scorchschutzsystem
nach
Anspruch
4,
wobei
es
sich bei dem
Polyol urn
ein
C2.8-Diol
oder -Triol handelt.
Scorchschutzsystems
nach
Anspruch
5,
wobei das Sulfenamid
aus
der
Gruppe
bestehend
aus N,N-Dicyclohexyl-
benzothiazolsulfenamid;
N,N-Diisopropyl-2-benzothiazol-sulfenamid; 2-(4-Morpholino)
thiobenzothiazol
(MTB);
N-t-Butyl-2-benzothiazolsulfenamid und N-Cyclohexyl-2-benzothiazolsulfenamid stammt.
Scorchschutzsystem
nach
Anspruch
1
zur Verwendung
in einem
peroxidhartbaren
Elastomer
aus
der
Gruppe
bestehend
aus Polyisopren, Styrol-Butadien-Kautschuken, Polybutadien-, Neopren-, Butyl-, Chlorpolyethylen-,
Ethylen-Propylen-
und
Butadien-Acrylnitril-Kautschuken
sowie Silicon-Elastomeren oder in einem
peroxidhartba-
ren Ethylen-vinylacetat-copolymer.
Scorchschutzsystem
nach
Anspruch
7,
worin
Hydrochinon
in einer
Menge von
0,5
bis
5
Gewichtsteilen
pro
100
Gewichtsteile
polyfunktionelles (Meth)acrylat vorliegt.
Scorchschutzsystem
nach
Anspruch
8,
worin das Sulfenamid in einer
Menge von
2 bis 20 Gewichtsteilen
pro
100
Gewichtsteile
polyfunktionelles (Meth)acrylat vorliegt.
Scorchschutzsystem nach Anspruch 9, wobei es sich bei dem Sulfenamid urn N-t-Butylbenzothiazolsulfenamid
handelt.
Hartbare
Zusammensetzung
mit einem Elastomer oder
Polyethylen
oder
Polypropylen
oder einem
Ethyleneinhei-
ten
enthaltenden
Copolymer
oder einem
Propyleneinheiten
enthaltenden
Copolymer,
das ein abstrahierbares
Wasserstoffatom
aufweist,
das mit einem
polyfunktionellen (Meth)acrylat
vernetzbar
ist,
polyfunktionellem (Meth)-
acrylat,
organ
ischem Peroxid und einem
Scorchschutz-additiv,
enthaltend
0,2
bis 6
Gew.-%
Hydrochinon, bezogen
auf das
polyfunktionelle (Meth)acrylat,
und
1
bis 50
Gewichtsprozent
Sulfenamid,
bezogen
auf das
polyfunktionelle
(Meth)acrylat.
Hartbare
Zusammensetzung
nach
Anspruch
11,
wobei das Sulfenamid durch die Formeln:
I
und
dargestellt
wird,
worin:
R fur bis
zu
C10
steht;
R-,
fur
H,
C-|.10-Aliphat,
-Aryl, -Cycloalkyl
oder
-Aralkyl
steht;
R2furC-|_10-Aliphat,
-Aryl, -Cycloalkyl
oder
-Aralkyl
steht oder
gemeinsam
mit
R-,
eine
heterocyclische Gruppe
bildet;
und
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EP 0 569 995 B1
Xfur
Wasserstoff,
Halogen, Hydroxy,
C-|.6-Alkyloder C-|.6-Alkoxy
steht.
13.
Zusammensetzung
nach
Anspruch
12,
wobei das Sulfenamid die Formel Iaufweist und
R-,
fur Wasserstoff steht
und
R2
aliphatisch
ist.
14. Hartbare
Zusammensetzung
nach
Anspruch
13,
wobei
es
sich bei dem
polyfunktionellen (Meth)acrylat urn
einen
Polyacryl-
oder
Methacrylsaureester
eines
C2_12-Polyols
handelt.
15. Hartbare
Zusammensetzung
nach
Anspruch
1
4,
wobei
es
sich bei dem
Polyol urn
ein
C2_8-Diol
oder -Triol handelt.
16. Hartbare
Zusammensetzung
nach
Anspruch
15,
wobei das Sulfenamid
aus
der
Gruppe
bestehend
aus
N,N-
Dicyclohexylbenzothiazolsulfenamid; N,N-Diisopropyl-2-benzothiazolsulfenamid;
2-
(4-Morpholino)
thiobenzot-
hiazol
(MTB); N-t-Butyl-2-benzothiazolsulfenamid
und
N-Cyclohexyl-2-benzothiazolsulfenamid
stammt.
17. Hartbare
Zusammensetzung
nach
Anspruch
16,
wobei das -Elastomer
aus
der
Gruppe
bestehend
aus Polyisopren,
Styrol-Butadien-Kautschuken, Polybutadien-, Neopren-, Butyl-, Chlorpolyethylen-, Ethylen-Propylen-
und Butadi-
en-Acrylnitril-Kautschuken
sowie Silicon-Elastomeren
stammt
oder
es
sich bei dem
Ethyleneinheiten
enthaltenden
Copolymer urn Ethylen-vinylacetat-copolymer
handelt.
18. Hartbare
Zusammensetzung
nach
Anspruch
17,
worin
Hydrochinon
in einer
Menge von
0,5
bis
5
Gewichtsteilen
pro 100 Gewichtsteile polyfunktionelles (Meth)acrylat vorliegt.
19. Hartbare
Zusammensetzung
nach
Anspruch
18,
worin das Sulfenamid in einer
Menge von
2 bis 20 Gewichtsteilen
pro
100 Gewichtsteile
polyfunktionelles (Meth)acrylat vorliegt.
20. Hartbare
Zusammensetzung
nach
Anspruch
19,
wobei
es
sich bei dem Sulfenamid
urn N-t-Butylbenzothiazolsul-
fenamid handelt.
Revendications
1.
Systeme anti-grilleur
contenant
un monomere polyinsature, approprie
pour
durcir des elastomeres durcissables
par
un peroxyde
et
le
polyethylene,
le
polypropylene,
des
copolymeres
renfermant des motifs
ethylene
et
des
copolymeres
renfermant des motifs
propylene, qui comprend un monomere polyinsature,
de
0,2 a
6
pour cent en
poids d'hydroquinone,
par
rapport
audit
monomere polyinsature,
et
de
1
a
50
pour
cent
en poids
de
sulfenamide,
par
rapport
audit
monomere polyinsature.
2.
Systeme anti-grilleur
selon la revendication
1
,
dans
lequel
le sulfenamide
est
represents
par
les formules
:
I
et
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EP 0 569 995 B1
I I
5
10
dans
lesquelles :
R
est
jusqu'en
C10
;
R-i
est
H,
un aliphatique, un aryle, un cycloalkyle ou un aralkyle en
C-|.10
;
is
-
R2
est
un aliphatique, un aryle, un cycloalkyle ou un aralkyle en
C-|.10,
ou
combine
avec
R-,
en
formant
un
groupe
heterocyclique
;
et
X
est
un hydrogene, un halogene, un hydroxy, un alkyle en
C g,
un alcoxy en
C^g.
3.
Systeme anti-grilleur
selon la revendication
2,
dans
lequel
le
monomere polyinsature
est
choisi
parmi
le
groupe
20
de
(meth)acrylates polyfonctionnels
et
de
monomeres polyallyliques.
4.
Systeme anti-grilleur
selon la revendication
3,
dans
lequel
le
monomere polyinsature
est
un
ester
polyacrylique
ou methacrylique
d'un
polyol en
C2_12.
25
5.
Systeme anti-grilleur
selon la revendication
4,
dans
lequel
le
polyol
est
un
diol
ou
triol
en
C2.8.
6.
Systeme anti-grilleur
selon la revendication
5,
dans
lequel
ledit sulfenamide
est
choisi
parmi
le
groupe
constitue
du
N,N-dicyclohexylbenzothiazolesulfenamide
;
du
N,N-diisopropyl-2-benzothiazolesulfenamide
;
du
2-(4-mor-
pholino)thiobenzothiazole (MTB)
;
du
N-t-butyl-2-benzothiazolesulfenamide
;
etdu
N-cyclohexyl-2-benzothiazole-
30
sulfenamide.
7.
Systeme anti-grilleur
selon la revendication
1,
destine
a
etre
utilise dans
un
elastomere durcissable
par
un
pe-
roxyde,
choisi
parmi
le
groupe
constitue d'un
polyisoprene,
de caoutchoucs
styrene-butadiene,
d'un
polybutadiene,
d'un
neoprene,
d'un
butyle,
d'un
polyethylene chlore,
de caoutchoucs
ethylene-propylene et butadiene-acryloni-
35
trile,
et
d'elastomeres
a
la
silicone,
ou
dans
un copolymere ethylene-acetate
de
vinyle
durcissable
par
un peroxyde.
8.
Systeme anti-grilleur
selon la revendication
7,
dans
lequel
les
parties en poids d'hydroquinone
pour
100
parties
en poids
de
(meth)acrylate polyfonctionnel
sont
de
0,5
a
5.
40
9.
Systeme anti-grilleur
selon la revendication
8,
dans
lequel
le sulfenamide
est
present
en une quantite
allant de 2
a
20
parties
pour
100
parties en poids
de
(meth)acrylate polyfonctionnel.
10.
Systeme anti-grilleur
selon la revendication
9,
dans
lequel
le sulfenamide
est
le
N-t-butylbenzothiazolesulfenami-
de.
45
11.
Composition
durcissable
comprenant
un
elastomere,
ou
du
polyethylene,
du
polypropylene, un copolymere ren-
fermant des motifs
ethylene ou un copolymere
renfermant des motifs
propylene,
ayant
un
atome
d'hydrogene
pouvant
etre
elimine,
et
reticulable
avec un (meth)acrylate polyfonctionnel, un peroxyde organique
et
un
additif
anti-grilleur,
et
qui comprend
de
0,2
a
6%
en poids d'hydroquinone,
par
rapport
audit
(meth)acrylate polyfonctionnel,
so
et
de
1
a
50%
en poids
d'un sulfenamide
par
rapport
audit
(meth)acrylate polyfonctionnel.
12.
Composition
durcissable selon la revendication
11,
dans
laquelle
le sulfenamide
est
represents
par
lesformules
:
55
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