U.S. patent application number 10/810158 was filed with the patent office on 2004-09-16 for tack free surface cures of polymers by organic peroxides in the presence of air.
Invention is credited to Gullo, Gary J., Novits, Michael F., Palys, Leonard H..
Application Number | 20040180985 10/810158 |
Document ID | / |
Family ID | 32328655 |
Filed Date | 2004-09-16 |
United States Patent
Application |
20040180985 |
Kind Code |
A1 |
Novits, Michael F. ; et
al. |
September 16, 2004 |
Tack free surface cures of polymers by organic peroxides in the
presence of air
Abstract
Compositions are disclosed which comprise mixtures of at least
one compound selected from silicone elastomers, bis-, tri- or
higher polymaleimides and/or bis-, tri- or higher
polyciraconimides, and at least one compound selected from
p-phenylene-diamine based antiozonants, sulfur compounds capable of
accelerating sulfur vulcanization of polymers capable of being
crosslinked by sulfur and polysulfide polymers which when
compounded into polymers curable by free radical initiators in the
presence of free radical initiators permit substantially tack free
surface cure of the polymers by decomposition of the free radical
initiator in the presence of molecular oxygen. Compositions
containing the above ingredients and at least one free radical
initiator, curable compositions containing the combination and
processes for making and using the compositions are also
disclosed.
Inventors: |
Novits, Michael F.;
(Buffalo, NY) ; Palys, Leonard H.; (Eagle, PA)
; Gullo, Gary J.; (Barrington, NH) |
Correspondence
Address: |
ATOFINA Chemicals, Inc.
Patent Department
26th Floor
2000 Market Street
Philadelphia
PA
19103
US
|
Family ID: |
32328655 |
Appl. No.: |
10/810158 |
Filed: |
March 26, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10810158 |
Mar 26, 2004 |
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09869251 |
Jun 26, 2001 |
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6747099 |
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09869251 |
Jun 26, 2001 |
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PCT/US00/30953 |
Nov 9, 2000 |
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60164488 |
Nov 9, 1999 |
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Current U.S.
Class: |
522/172 |
Current CPC
Class: |
C08K 5/3415 20130101;
C08K 5/0025 20130101 |
Class at
Publication: |
522/172 |
International
Class: |
C08F 008/00 |
Claims
We claim:
1. A composition comprising: a) At least one compound (A) selected
from the group consisting of silcone elastomers and a compound
having the formula (I): 11Wherein n is 1, or 2 and R is divalent,
or trivalent and is selected from the group consisting of acyclic
aliphatic groups having from about 2 to 16 carbon atoms, cyclic
aliphatic groups having from about 5 to 20 carbon atoms, aromatic
groups having from about 6 to 18 carbon atoms and allyl aromatic
groups having from about 7 to 24 carbon atoms, and wherein the
divalent, or trivalent groups may contain one or more heteroatoms
selected from O, N and S, replacing a carbon atom, or carbon atoms
and each R.sub.1 is identical and is hydrogen or an alkyl group of
1 to 18 carbon atoms; and b) At least one compound (B) selected
from the group consisting of p-phenylenediamine based antiozonants
and sulfur containing organic compounds selected from the group
consisting of sulfur containing organic compounds capable of
accelerating sulfur vulcanization of a polymer capable of being
crosslinked by sulfur, polysulfide polymers and mixtures of said
sulfur containing compounds.
2. A composition as defined in claim 1 additionally containing a
free radical initiator selected from the group consisting of
organic peroxides and azo initiators.
3. A composition comprising a composition as deemed in claim 2 and
a polymer curable by free radical initiators.
4. A process comprising forming the composition of claim 3 into a
shaped article and then subjecting it in the presence of molecular
oxygen to a temperature sufficient to initiate decomposition of the
free radical initiator and thereby obtaining a cured shaped article
substantially free of surface tack.
5. A composition formed by mixing compounds (A) and (B) as defined
in claim one.
6. A composition formed by mixing compounds (A) and (B) as defined
in claim 1 and an organic peroxide in any order.
7. A composition as defined in claim 1 wherein compound (A) is
selected from bismaleimides and Compound (B) is selected from
sulfur accelerators.
8. A composition as defined in claim 1 wherein compound (A) is
selected from biscitraconimides and compound (B) is selected from
sulfur accelerators.
9. A composition as defined in claim 1 wherein compound (A) is
selected firm bismaleimides and compound (B) is selected from
polysulfide polymers.
10. A composition as defined in claim 1 wherein compound (A) is
selected from biscitraconimides and compound (B) is selected from
polysulfide polymers.
11. A composition as defined in claim 1 wherein compound (A) is
selected from silicone elastomers and compound (B) is selected from
polysulfide polymers.
12. A composition as defined in claim 1 also comprising a compound
selected from the group consisting of chlorinated polyethylene and
chlorosulfonated polyethylene.
13. A composition as defined in claim 2 wherein the free radical
initiator is selected from organic peroxides.
14. A surface tack free cured polymer cured in the presence of
molecular oxygen by free radicals generated by decomposition of the
free radical initiator in a composition as defined in claim 3.
15. A process for making a surface tack free cured polymer cured by
free radicals generated by decomposition of a free radical
initiator contained therein in the presence of molecular oxygen
which comprises compounding said polymer with a composition as
defined in claim 2 and supplying sufficient heat energy to
decompose the free radical initiator thus introduced into the
polymer.
16. A process for making a curable composition capable of being
cured to a tack free surface in the presence of molecular oxygen by
a free radical initiator which process comprises compounding a
polymer capable of being crosslinked by a free radical initiator
with a composition as defined in claim 2.
17. A process for making a curable composition capable of being
cured to a tack free surface in the presence of molecular oxygen by
a free radical initiator which comprises compounding a polymer
capable of being crosslinked by a free radical initiator containing
a composition as defined in claim 1 in the presence of a free
radical initiator.
18. A composition as defined in claim 1 wherein compound (A) is
selected from one or more bismaleimides and compound (B) is
selected from the group consisting of dialkylthiuram tetrasulfides
diarylthiuram tetrasulfides, alkylphenol disulfides,
tetraalkylthiuram monosulfides, tetraalkylthiuram monosulfides and
mixtures thereof.
19. A composition as defined in claim 2 wherein the free radical
initiator is selected from dialkyl peroxides or peroxyketals.
20. A composition as defined in claim 18 additionally containing a
free radical initiator selected from dialkyl peroxides or
peroxyketals.
21. A composition as defined in claim 1 wherein compound (A) is
selected from one or more bismaleimides and compound (B) is
selected from the group consisting of 4,4-dithiomorpholine,
acyclicalkyl-2-benzothiazole sulfenane, cyclicalky-2-benzothiazole
sulfenamides, aryl-2-benzothiazole sulfenamides, alkylphenol
disulfides and mixtures thereof.
22. A composition as defined in claim 21 additionally containing a
free radical initiator selected from dialkyl peroxides, or
peroxyketals.
23. A composition as defined in claim 2 comprising dicumylperoxide,
N,N-phenylenebismaleimide, 4,4-dithiomoropholine,
alkylphenoldisulfide and N-cyclohexyl-2-benzothiazole
sulfenamide.
24. A composition as defined in claim 2 comprising dicumylperoxide,
N,N-phenylenebismaleimide, dipentamethylene thiuram tetrasulfide,
alkylphenoldisulfide, and tetramethylthiuram monosulfide.
25. A composition as defined in claim 2 comprising dicumyl
peroxide, N,N-phenylenebismaleimide, dipentamethylenethiuram is
tetrasulfide, alkylphenol disulfide and
N-t-butyl-benzothiazole-2-sulfenimide.
26. A composition as defined in claim 1 formulated as a masterbatch
on a carrier selected from the group consisting of microcrystalline
wax, polycaprolactone, EPDM, EPM, EVA, PE and mixtures thereof.
27. A composition as defined in claim 2 formulated as a masterbatch
on a carrier selected from microcrystalline wax, polycaprolactone,
EPDM, EPM, EVA, PE and mixtures thereof.
Description
[0001] This application claims priority from provisional
application 60/164,488 filed Nov. 9, 1999.
BACKGROUND OF THE INVENTION
[0002] This invention relates to compositions of matter classified
in the art of chemistry as bis-, tri- and higher poly-maleimides,
as bis-, tri- and higher poly-citraconimides, as silicone
elastomers, as p-phenylenediamine based antiozonants and as sulfur
containing organic compounds which are accelerators for the sulfur
curing (crosslinking) of polymers which are curable/crosslinkable
by sulfur and also sulfur compounds which are polysulfide polymers.
The invention also relates to compositions containing them, to
processes for their use and to the products produced by such
processes.
[0003] Polymers and copolymers crosslinked with free radical
initiators; organic peroxides and/or azo initiators, are known to
have superior properties, particularly to polymers crosslinked by
sulfur cure. These properties include high heat ageing resistance,
low compression set, decreased staining of metal or coated metal
sheet and easy production of colored products which have color
stability during crosslinking and during long periods of use. These
properties make use of peroxide cure of great practical importance
particularly because crosslinking is through a carbon carbon bond
rather than through a sulfur containing linkage and this bonding
difference is responsible for the improved heat aging and
compression set. The drawback for cure of polymers with free
radicals from organic peroxides and azo initiators has always been
that if air is not excluded from the surface of the material during
cure, a tacky surface due to cure inhibition by the molecular
oxygen in the air results.
[0004] In order to avoid tacky surfaces on objects fabricated using
such free radical crosslinking by organic peroxides and/or azo
initiators, it has been conventional to exclude air from contact
with the surface during cure to avoid the cure inhibition caused by
the presence of the molecular oxygen found in atmospheric air.
Measures to exclude molecular oxygen add to the cost and complexity
of the cure step and sometimes it is difficult, as in the cases of
cure in steam autoclaves and in the interior of hoses, to assure
the complete exhaustion of air and its molecular oxygen component.
In some cases the manufacturer would like to switch from sulfur to
peroxide cure and use existing hot air oven curing chambers. Curing
with conventional peroxide systems under these circumstances, would
not be viable as a tacky surface would result.
[0005] In order to simplify and reduce the cost and complexity of
the cure step, various methods have been suggested for preventing
surface cure inhibition by molecular oxygen during free radical
crosslinking. These methods have, for various reasons, met with
little or no success in actual practice. In particular, none have
provided a tack free surface while providing the most desirable
physical property of peroxide (azo) cure; superior compression set
at 150.degree. C. for 70 hours, compared to about 100.degree. C.,
i.e. lower temperature performance for the prior art.
PRIOR ART
[0006] U.S. Pat. No. 4,983,685 discloses the use of compounds
selected from the following classes: (a) imidazole compounds, (b)
thiourea compounds, (c) thiazole compounds, (d) thiuram compounds,
(e) dithiocarbamate compounds, (f) phenol compounds, (g) triazole
compounds and (h) amine compounds which are accelerators for sulfur
vulcanization in the optional presence of antioxidants, anti-ageing
compounds and the like for elastomers for reducing surface tack in
the peroxide cure of elastomers in the presence of molecular
oxygen. Among optional ingredients which are suggested as possible
ingredients for inclusion in the formulations, in this case for
increased crosslinking, is N,N'-m-phenylene bismaleimide.
[0007] This is not the preferred optional coagent as a
dimethacrylate compound is actually used in the examples. There is
no recognition that this latter bismaleimide compound might provide
an enhanced effect on the ability of certain compounds of (a)
through (h) to reduce surface tack during free radical cure in the
presence of molecular oxygen. The use of the various sulfur
accelerators, in particular with peroxide, does provide tack free
or reduced tack surfaces for the cured polymers in this reference
but the important physical properties expected from a peroxide cure
are also reduced There is no recognition in U.S. Pat. No. 4,983,685
that if the silicone elastomers, bismaleimides and
biscitraconimides of the present invention are used in combination
with p-phenylene diamine based antiozonants, sulfur containing
sulfur vulcanization accelerators and antioxidants and/or
polysulfide polymers in free radical cures of polymers, that tack
free surfaces and improved physical properties will result and that
of all the crosslinking aids mentioned, only these particular
classes of compounds have that effect.
[0008] Japanese Published Patent Application No. Hei 9[1997]-169873
discloses that antioxidants of the benzimidazole type and of the
polymeric 2,2,4-trimethyl-1,2-dihydroquinoline type used in
combination with standard crosslinking aids such as methacrylate
esters, triallylcyanurates and maleimides, such as this present
invention's preferred component N,N'-m-phenylene bismaleimide, and
standard crosslinking peroxides will result in cured peroxide
crosslinkable elastomers with a tack free surface in the presence
of air. The inclusion of p-phenylene diamine based antiozonants,
silicone elastomers, sulfur accelerators of any type and/or
polysulfide polymers is not suggested.
[0009] U.S. Pat. No. 4,334,043 teaches the use of surface treatment
of curable polymer compositions with organo-metallic compounds,
inorganic metallic salts, or lanthanides prior to crosslinking with
organic peroxide crosslinking initiators in air to prevent surface
tack after crosslinking. Other means of controlling surface tack
are not mentioned except for the previously known techniques for
surface tack free curing by simply excluding air contact with the
rubber surface.
[0010] U.S. Pat. Nos. 4,814,384 and 4,973,627 disclose cures of
rubber blends for tire treads and sidewalls using a combination of
sulfur and peroxide cures. Sulfur accelerators are also employed.
Coagents of any type are not mentioned, nor is cure in the presence
of air discussed. The use of elemental sulfur is required in the
practice of these inventions. We have found, however, that the use
of elemental sulfur adversely affects the final physical properties
of the cured elastomer to the point where they are more typical of
sulfur cure than peroxide cure.
[0011] U.S. Pat. No. 4,743,656 also discloses a mixed
sulfur/peroxide cure agent for elastomers, which cure agent also
includes sulfur accelerators as well as elemental sulfur and the
peroxide. Coagents are not mentioned, nor are crosslinking in air
and surface tackiness discussed.
[0012] U.S. Pat. No. 4,575,552 claims the use of specific
combinations of hindered phenol antioxidants, metal salts of
dithiocarbamates and m-phenylene-dimaleimide to provide a peroxide
crosslinked polymer with superior hydrolytic and thermal stability
for geothermal applications. There is no mention of crosslinking in
the presence of air, air-inhibition or surface tackiness as a
result of air-inhibition.
[0013] U.S. Pat. No. 5,849,214 discloses the use of sulfur
compounds, sulfur accelerators and hydroquinones with the optional
presence of crosslinking aids (coagents) in the retardation of
scorch during compounding of free radical crosslinkable polymers in
the presence of free radical initiators. Bismaleimides, and
biscitraconimides are not specifically discussed nor is there any
mention of the possible effect on surface tackiness during cure in
the presence of molecular oxygen (air) for any of the compositions
disclosed.
[0014] In addition there are patents which use various compounds to
physically coat the surface of crosslinkable elastomers to exclude
air (oxygen) e.g., U.S. Pat. No. 4,439,388 which teaches use of
boric acid, boric acid anhydride as a surface treatment prior hot
air cure. This surface coating technique is labor intensive as it
must be removed and disposed of after the crosslinking reaction
step is completed.
[0015] None of the above references, taken singly or in
combination, suggests applicants' solution described and claimed
herein for elimination of surface tack due to air-inhibition during
free radical cure of polymers by free radical curing agents, such
as organic peroxides and azo initiators while providing the
desirable physical properties of a peroxide (azo) cure. For
example, the compression set values expected from a standard
peroxide cure and wherein the compression set is measured at
temperatures in the region about 150.degree. C. for 70 hours.
SUMMARY OF TH INVENTION
[0016] The invention provides in its first composition aspect, a
composition comprising:
[0017] a) At least one compound (A) selected from the group
consisting of silicone elastomers and a compound having the formula
(I): 1
[0018] wherein n is 1, or 2 and R is divalent, or trivalent and is
selected from the group consisting of acyclic aliphatic groups
having from about 2 to 16 carbon atoms, cyclic aliphatic groups
having from about 5 to 20 carbon atoms, aromatic groups having from
about 6 to 18 carbon atoms and alkyl aromatic groups having from
about 7 to 24 carbon atoms, and wherein those divalent, or
trivalent groups may contain one or more heteroatoms selected from
O, N and S, replacing a carbon atom, or atoms, and each R.sub.1 is
identical and is hydrogen or an alkyl group of 1 to 1 8 carbon
atoms; and
[0019] (b) at least one compound (B) selected from the group
consisting of p-phenylenediamine based antiozonants and sulfur
containing organic compounds selected from the group consisting of
sulfur containing organic compounds capable of accelerating sulfur
vulcanization of polymers capable of being crosslinked by sulfur
("sulfur accelerators"), polysulfide polymers and mixtures of said
sulfur containing compounds.
[0020] The tangible embodiments of the first composition aspect of
the invention possess the inherent applied use characteristic of
being suppressors of surface inhibition of free radical induced
cure of polymers in the presence of gaseous molecular oxygen,
(i.e., oxygen present in the atmosphere) thereby permitting tack
free cures of polymers by free radical curing agents in the
presence of air while maintaining the final physical properties
associated with a conventional peroxide cure.
[0021] The invention provides in a subgeneric aspect of the first
composition aspect of the invention, a composition formed by mixing
as the essential ingredients thereof at least one member of
compound (A) and at least one member of compound (B) of the first
composition aspect of the invention.
[0022] The invention provides in a second composition aspect, a
composition comprising a composition as defined in the first
composition aspect and a free radical initiator selected from the
group consisting of organic peroxides and azo initiators.
[0023] The tangible embodiments of the second composition aspect of
the invention possess the inherent applied use characteristic of
being curing or crosslinking agents for those polymers capable of
being crosslinked by free radical initiators and of being capable
of effecting such cares in the presence of air (molecular oxygen)
without the polymer being cured experiencing surface inhibition by
the presence of air (molecular oxygen), thus, providing a cured or
crosslinked polymer having a substantially tack free surface
without the necessity for avoiding contact of said surface with air
(molecular oxygen) during cure.
[0024] The invention provides a subgeneric aspect of the second
composition aspect of the invention. Said composition being one
prepared by mixing in any order, at least one member of compound
(A) and at least one member of compound (B) of the first
composition aspect of the invention and a free radical initiator as
defined for the second composition aspect of the invention.
[0025] The invention provides in a third composition aspect a
curable composition comprising a polymer curable by free radical
initiators and a composition as defined in the second composition
aspect of the invention.
[0026] The third composition aspect of the invention possesses the
inherent applied use characteristic of being formable into a shaped
article and then being crosslinkable while the surface of said
shaped article is in contact with air (molecular oxygen) to provide
a crosslinked shaped article having a substantially tack free
surface.
[0027] The invention provides in a subgeneric composition aspect of
the third composition aspect of the invention a curable composition
prepared by mixing in any order at least one member of compound (A)
and at least one member of compound (B) of the first composition
aspect of the invention, a free radical initiator as defined for
the second composition aspect of the invention and a polymer
crosslinkable by a free radical initiator.
[0028] The invention provides in a first process aspect a process
for the preparation of the second composition aspect of the
invention which comprises mixing in any order at least one member
of compound (A) and at least one member of compound (B) of the
first composition aspect of the invention and a free radical
initiator as defined in the second composition aspect of the
invention.
[0029] The invention provides in a second process aspect of the
invention, a process for the preparation of the third composition
aspect of the invention which comprises mixing in any order at
least one member of compound (A) and at least one member of
compound (B) of the first composition aspect of the invention, a
free radical initiator as defined in the second composition aspect
of the invention and a polymer crosslinkable by a free radical
initiator.
[0030] Special mention is made of embodiments of the several
aspects of the invention wherein compound (A) is selected from
bismaleimides and compound (B) is selected from sulfur
accelerators, where compound (A) is selected from biscitraconimides
and compound (E) is selected from sulfur accelerators, where
compound (A) is selected from bismaleimides and compound (B) is
selected from polysulfide polymers, where compound (A) is selected
from biscitraconimides and compound (B) is selected from
polysulfide polymers, where compound (A) is selected from silicone
elastomers and compound (B) is selected from polysulfide
polymers.
[0031] Special mention is also made of embodiments of the several
aspects of the invention wherein chlorinated polyethylene and/or
chlorosulfonated polyethylene are included as optional supplemental
ingredients in addition to compounds (A) and (B).
DETAILED DESCRIPTION
[0032] The best mode contemplated by the inventors for making and
using their invention will now be described in detail with
reference to a particular embodiment thereof, namely.
[0033] A mixture of dipentamethylene thiuram tetra-sulfide
(Sulfads), N,N'-m-phenylene bismaleimide (HVA-2) and
1,1-di(t-butylperoxy)3,3,5-trim- ethylcyclohexane (LUPEROX.RTM. 231
XL) used to cure ethylene propylene copolymer (VISTALON.RTM. 504)
in hot air.
[0034] To prepare the mixture of Sulfads, HVA-2 and LUPEROX 231 XL,
the ingredients, which are all in dry powder form (the LUPEROX.RTM.
231 XL is in the form of 40% by weight peroxide dispersed on
calcium carbonate), may be mixed in any order and then compounded
by standard methods (Banbury, two roll mill, extruder and the like)
into the VISTALON.RTM. polymer. The Sulfads.RTM., HVA-2 and LUPEROX
231 XL may also be compounded directly into the VISTALON either
simultaneously or sequentially in any order. Any Two of the
Sulfads, HVA-2 and LUPEROX 231 XL ingredients may be mixed and
compounded into the VISTALON separately or simultaneously with the
third ingredient. This compounding, if done separately, may also be
performed in any order of ingredient addition to the polymer, but
it is preferred if the peroxide is added last.
[0035] Once compounding with the VISTALON is complete, the
compounded mixture may be cured simply by placing it in a hot air
oven at a suitable temperature for initiating cure by decomposition
of the peroxide, conveniently, in this case, at about 365.degree.
F. (about 185.degree. C.), for a sufficient period of time to
permit the desired degree of crosslinking to take place,
conveniently, in this case, about minutes, for a thin sample at
room temperature at the start.
[0036] One of skill in the art will recognize that the other
compounds falling within the scope of Formula I of the first
composition aspect of this invention are all solid materials, are
all trimaleimides, bismaleimides, tricitraconimides, or
bis-citraconimides and can all be combined with the other starting
materials contemplated by the invention by similar conventional
methods to those described. The bismaleimides and biscitraconimides
contemplated as starting materials are all either commercially
available or can be readily synthesized by methods well known in
the art. See, for example, U.S. Pat. Nos. 5,484,948; 5,616,666,
5,292,815 and the references cited therein for more general
synthetic methods.
[0037] The trimaleimides and tricitraconimides as well as the
higher polymaleimides and citraconimides may be prepared by
analogous techniques if they are not commercially available. For
example, the trimaleimide,
N,N',N"-(1,3,5-triazine-2,4,6-triyl)trimaleimide has CAS number
CAS(67460-81-5).
[0038] Some primary amines suitable for synthesis of the di, tri-
and higher polymaleimides and analogous citraconimides are
polyfnctional primary amines such as melamine and the various
polyoxypropylene amines such as the polyoxypropylene diamines and
the polyoxypropylene triamines sold under the JEFFAMINE tradename
by Huntsman Corporation.
[0039] In addition to the N,N'-m-phenylene-bismaleimide
specifically referenced above, other bismaleimides, in addition to
those disclosed in the above referenced patents, suitable for use
in the invention, without limiting the generality of the above
general formula (I), are:
[0040] N,N'-ethylenebismaleimide, N,N'-hexamethylenebismaleimide,
N,N'-dodecamethylene-bismaleimide,
N,N'-(2,2,4-trimethylhexamethylene) bismaleimide,
N,N'-(oxy-dipropylene)bismaleimide, N,N'-(aminodipropylene)-
bismaleimide, N,N'-(ethylenedioxy-dipropylene)bismaleimide,
N,N'(1,4-cyclohexylene)bismaleimide,
N,N'-(1,3-cyclohexylene)bismaleimide- , N,N'-(methylene
1,4-dicyclohexylene) bismaleimide,
N,N'-(isopropylidene-1,4-dicyclohexylene)bismaleimide,
N,N'-(oxy-1,4dicyclohexylene)bismaleimide, N,N'-p-(phenylene)
bismaleimide, N,N'-(o-phenylene)bismaleimide,
N,N'-(1,3-naphthylene)bisma- leimide,
N,N'-(1,4-naphthylene)bismaleimide, N,N'-(1,5-naphthylene)bismale-
imide, N,N-(3,3'-dimethyl-4,4'-diphenylene)bismaleimide,
N,N'-(3,3-dichloro-4,4'-biphenylene)bismaleimide,
N,N'-(2,4-pyridyl)bisma- leimide, N,N'-2,6-pyridyl)bismaleimide,
N,N'-(1,4-anthraquinonediyl) bismaleimide,
N,N'-(m-tolylene)bismaleimide, N,N'(p-tolylene)bismaleimide- ,
N,N'-(4,6-dimethyl-1,3-phenylene)bismaleimide,
N,N'-(2,3-dimethyl-1,4-ph- enylene)bismaleimide,
N,N'-(4,6-dichloro-1,3-phenylene)bismaleimide,
N,N'-(5-chloro-1,3-phenylene) bismaleimide,
N,N'-(5-hydroxy-1,3-phenylene- )bismaleimide,
N,N'-(5-methoxy-1,3-phenylene)bismaleimide,
N,N'-(m-xylylene)bismaleimide, N,N'-(pxylylene)bismaleimide,
N,N'-(methylenedi-p-phenylene)bismaleimide,
N,N'-(isopropylidenedi-p-phen- ylene)bismaleimide,
N,N'-(oxydi-p-phenylene)bismaleimide,
N,N'-(thiodi-p-phenylene)bismaleimide,
N,N'-(dithiodi-p-phenylene)bismale- imide,
N,N'-(sulfodi-p-phenylene)bismaleimide,
N,N'-(carbonyldi-p-phenylen- e)bismaleimide,
.alpha.,.alpha.-bis-4maleimodophenyl)-meta-diisopropylbenz- ene,
.alpha.,.alpha.-bis-(4-p-phenylene)bismaleimide and
.alpha.,.alpha.-bis-(4-maleimodophenyl)-para-diisopropylbenzene.
[0041] Combination of two or more bismaleimides, or bismaleimides
with the trimaleimides, and with the higher polymaleimides in the
compositions and processes of the invention are also contemplated
as equivalents and one of skill in the art would understand that
such tri and higher polymaleimides and their substitution for the
compounds and processes specifically illustrated herein for the
practice of the invention to be such equivalents and to be well
within the scope contemplated by the invention.
[0042] Biscitraconimides, which may be substituted in whole or in
part for the N,N'-m-phenylenebismaleimide referenced above include
as representative examples:
[0043] 1,2-N,N'-dimethylene biscitraconimide;
[0044] 1,2-N,N'-trimethylene biscitraconimide;
[0045] 1,5-N,N'-(2-methyl-pentamethylene)-biscitraconimide; and
[0046] N,N'-methylphenylene biscitraconimide.
[0047] Mixtures of biscitraconimides and mixtures of bismaleimides
and biscitraconimides as well as those including the trimaleimides
are also contemplated as equivalents by the invention.
[0048] The biscitraconimides contemplated by the invention are all
well known compounds and where not commercially available, they may
be readily synthesized by methods detailed in the art. U.S. Pat.
No. 5,292,815 in column 4, provides a detailed list of such
methods. As stated above, the tri- and higher polyciraconimides may
be prepared by analogous methods and substituted in whole or in
part in the compositions of the invention and such compounds and
substitutions will be understood by one of skill in the art as
being a full equivalent to those specifically illustrated herein
and well within the scope contemplated as equivalent by the
invention.
[0049] The silicone elastomers contemplated as useful in the
aspects of the invention are the peroxide crosslinkable dimethyl
vinyl substituted silicone derivative elastomers which are well
known in the art See, for example, "Kirk Othmer Encyclopedia of
Chemical Technology", Vol. 20, pp. 943 et seq., John Wiley &
Sons, .COPYRGT.1982.
[0050] Sulfur containing organic compounds capable of accelerating
sulfur vulcanization of polymers, which are capable of being
crosslinked by sulfur contemplated for use in the invention are
well known in the art. Many different classes of these compounds
are known and all are contemplated as equivalent
[0051] The Vanderbilt Rubber Handbook, thirteenth edition, 1990, R.
T. Vanderbilt Company, Inc., publisher lists many types.
Illustrative of these are derivatives of benzothiazoles,
thiadiazoles, sulfenamides, sulfenamides, dithiocarbamates,
thiurams, imidazoles, xanthates, and thioureas. Also included in
this general class of sulfur compound sulfur accelerators are
sulfides, disulfides (e.g., diallyldisulfide) polysulfides and
arylpolysulfide compounds such as the amylphenol polysulfides e.g.
VULTAC.RTM. products from ATOFINA Chemicals, Inc. and other
sulfides such as disulfide and/or other known sulfur accelerating
polysulfide phosphate, dithiophosphates and/or phosphorous and
sulfur containing compounds. Other sulfur containing organic
compounds capable of sulfur donation at vulcanization temperatures
which are known but are not presently used for such reactions
because of cost concerns are also contemplated as equivalents.
Illustrative of these is the compound
2-(2,4cyclopentadiene-1-ylidene)-1,3-dithiolane.
[0052] More particularly, one sulfur accelerator class suitable for
use in the practice of the invention are salts of disubstituted
dithiocarbamate acid.
[0053] These salts have the general structure: 2
[0054] Wherein X is an ion derived from a metal selected from the
group consisting of nickel, cobalt, iron, chromium, tin, zinc,
copper, lead, bismuth cadmium, selenium and tellurium, or X is a
quaternary ammonium ion, n may vary from 1 to 6 and is equal to the
number of formal positive charges on the X ion, and R.sub.1 and
R.sub.2 are independently alkyl of 1 to 7 carbon atoms.
[0055] Examples of the salts of disubstituted dithiocarbamate acid
are:
[0056] bismuth dimethyldithocarbamate;
[0057] cadmium diethyldithiocarbamate;
[0058] cadmium diamyldithiocarbamate;
[0059] copper dimethyldithocarbamate;
[0060] lead diamyldithiocarbamate;
[0061] lead dimethyldithiocarbamate;
[0062] selenium diethyldithiocarbamate;
[0063] selenium dimethyldithiocarbamate;
[0064] tellurium diethyldithiocarbamate;
[0065] piperidinium pentamethylene dithiocarbamate;
[0066] zinc diamyldithiocarbamate
[0067] zinc diisobutyldithiocarbamate
[0068] zinc diethyldithiocarbamate;
[0069] zinc dimethyldithiocarbamate:
[0070] copper dibutyldithiocarbamate;
[0071] sodium dimethyldithiocarbamate;
[0072] sodium diethyldithiocarbamate;
[0073] sodium dibutyldithiocarbamate;
[0074] zinc di-n-butyldithiocarbamate;
[0075] zinc dibenzyldithiocarbamate.
[0076] A second sulfur accelerator class suitable for use in the
invention comprises the thiurams. These are prepared from secondary
amines and carbon disulfide and possess the general structure:
3
[0077] Wherein R.sub.3 is an alkyl group of from 1 to about 7
carbon atoms or the R.sub.3 groups on each particular, nitrogen
atom may be concatenated to form together with the nitrogen atom on
which they are attached, a five, six or seven membered heterocyclic
ring containing 4, 5 or 6 carbon atoms respectively and n may have
a positive value from greater than zero up to 6.
[0078] Typical examples of thiuram sulfur accelerators are:
[0079] dipentamethylenethiuram tetrasulfide and hexasulfide;
[0080] tetrabutylthiuram disulfide;
[0081] tetramethylthiuram disulfide;
[0082] tetraethylthiuram disulfide;
[0083] tetramethylthiuram monosulfide;
[0084] isobutylthiuram disulfide;
[0085] dibenzylthiuram disulfide;
[0086] tetrabenzylthiuram disulfide;
[0087] tetraisobutylthiuram disulfide;
[0088] isobutylthiuram monosulfide;
[0089] dibenzylthiuram monosulfide;
[0090] tetrabenzylthiuram monosulfide;
[0091] tetraisobutylthiuram monosulfide.
[0092] The higher multisulfides of the various thiurams are also
sulfur donors.
[0093] Derivatives of thiadiazoles: are, but not limited to,
monobenzoyl derivatives of dimercaptothiadiazole
(2,5dimethyl-1,3,4-thiadiazole); the proprietary thiadiazole of the
Vanderbilt Rubber Company identified as VANAX.RTM. 189;
1,2,4-thiadiazole, 5-ethoxy-3-(trichloromethyl) thiadiazole; and
alkyl mercaptothiadiazoles, e.g. methyl mercapto thiadiazole.
[0094] Derivatives of benzothiazoles have the general structure:
4
[0095] Wherein M is a direct bond between two sulfur atoms, H, or
an ion derived from a metal selected from the group consisting of
nickel, cobalt, iron, chromium, tin, zinc, copper, lead, bismuth,
cadmium, selenium and tellurium; and when M is H, x is 1; when M is
a direct bond between two sulfur atoms, x is 1 or 2; and when M is
an ion derived from a metal, x is equal to the formal valence of
the metal ion; and if M is a direct bond between two sulfur atoms
and x is 1, then the second sulfur atom to which the M bond is
attached is also bonded to a 4-morpholinyl radical.
[0096] Illustrative compounds are: 2-(4-morpholinodithio)
benzothiazole; benzothiazyl disulfide; 2-mercapto-benzothiazole;
2-mercaptobenzothiazole disulfide;
sodium-2-mercaptobenzothiazolate; zinc-2-mercapto-benzothiazol- e;
copper-2-mercaptobenzothiazolate; 2-N-cyclohexylaminobenzothiazole;
N-cyclohexylamino-2-benzothiazole polysulfide;
2-bisbenzothiazole-2,2-pol- ysulfide and
2-bisbenzothiazole-2,2-disulfide; bis(2,2'-benzothiazyldisluf-
ide).
[0097] The sulfenamides accelerators are also well known.
Illustrative examples are: N-oxydiethylene-2-benzothiazole
sulfenamides; N-oxydiethylene thiocarbamyl-N-oxydiethylene
sulfenamide; N-cyclohexyl-2-benzothiazole sulfenamide;
N-t-butyl-2-benzothiazole sulfenamide;
N-cyclohexyl-2-benzothiazylsulfeneamide; N,N-dicyclohexyl
benzthiazyl sulphenamide; N-t-butyl-2-benzothiazole sulfenamide.
There are also sulfenamide compounds, e.g.,
N-t-butyl-benzothiazole-2-sulfenimi- de.
[0098] Typical imidazoles are: 2-mercaptobenzimidazole,
2-mercaptomethylbenzimidazole; and the zinc salt of
2-mercaptobenzimidazole.
[0099] Zinc isopropyl xanthate is a typical xanthate sulfur
accelerator.
[0100] Typical thioureas are: trimethylthiourea;
1,3-diethylthiourea and 1,3-dibutylthiourea; ethylene thiourea,
blend of dialkyl thioureas; diphenyl thiourea; diorthotolyl
thiourea; dimethyl thiourea, diethyl thiourea; dibutyl thiourea
[0101] Alkylphenoldisulfide types of sulfur accelerators are
illustrated by the compounds available from ATOFINA Chemicals,
Inc., under the designation VULTAC.RTM. 2, VULTAC 3 and VULTAC
5.
[0102] Thiophosphate sulfur accelerators are illustrated by such
compounds as copper dialkyidithiophosphate; zinc
dialkyldithiophosphate; zinc amine dithiophosphate; zinc
dibutyldithophosphate; copper O,O-diisopropyl-phosphorodithiolate;
zinc O,O-diisopropylphosphorodithiol- ate.
[0103] Other miscellaneous sulfur accelerators include
4,4-dithiodimorpholine; N,N'-caprolactam disulfide;
dibutylxanthogen disulfide.
[0104] The polymers which can be cured (crosslinked) in the
presence of molecular oxygen include all those natural and
synthetic polymers capable of being crosslinked either by
abstraction of hydrogen (or other extractable atoms, such as with
iodo and bromo substituted fluoroelastomers) or by polymerization
trough double bonds.
[0105] Polymers which are currently understood to not be
crosslinkable by these mechanisms and which undergo degradation in
the presence of free radicals generated from organic peroxides and
the azo initiators defined herein below and whose presence should
be substantially avoided in the curable compositions of this
invention include: poly(vinyl chloride), poly-(propylene), butyl
rubber, epichlorohydrin polymers and epichlorohydrin ethylene oxide
polymers. When used herein and in the appended claims when
referring to polymers suitable for use in connection with the
invention any reference to a group of polymers using the terms
"comprising," "consisting essentially" and "consisting of"
expressly excludes more than minor insignificant amounts (1% by
weight or less) of the non free radical crosslinkable polymers in
the absence of an express statement to the contrary.
[0106] Polymers crosslinkable by free radicals from organic
peroxides and azo initiators as defined herein below include
ethylene-propylene terpolymer (EPDM), ethylene-propylene copolymer
(EPM) natural polyisoprene rubber (NR), styrene butadiene rubber
(SBR), polybutadiene rubber (BR), synthetic polyisoprene rubber
(IR), poly(ethylene) (PE), ethylene-vinyl acetate (EVA),
acrylonitrile-butadiene-styrene (ABS), unsaturated polyester,
styrene-butadiene-styrene block copolymers (SBS),
styrene-isoprene-styrene block copolymers (SIS), neoprene rubber
(CR), nitrile rubber (NBR), polysulfide rubber (T) chlorinated
poly-(ethylene) (CM), polyurethane (AU, EU), vinylidene fluoride
copolymers (CFM), silicone rubber (PMQ), vinyl silicone rubber
(VMQ, PVMQ), polyacrylate (ACM), chlorosulfonated poly(ethylene)
(CSM) and fluorosilicone rubber (FVMQ).
[0107] The free radical initiators (organic peroxides and azo
initiators) suitable for use in the invention include all those
classes of organic peroxides and azo initiators suitable for curing
(crosslinking) polymers, both thermoplastics and elastomers.
[0108] The azo initiators are those known in the art, such as
2,2'-azobis-(2-acetoxypropane), to generate free radicals on heat
decomposition capable of inducing the desired curing (crosslinking)
reaction. The azo initiators of U.S. Pat. Nos. 3,862,107 and
4,129,531, the disclosures of which are incorporated herein by
reference, are also suitable.
[0109] With the exception of hydroperoxides and liquid
peroxydicarbonates, all those organic peroxides known to undergo
decomposition by heat to generate radicals capable of initiating
the desired curing (crosslinking) reactions are contemplated as
suitable for use in the invention. Dialkyl peroxides,
diperoxyketals, mono-peroxy carbonates, cyclic ketone peroxides,
diacyl peroxides, organosulfonyl peroxides, peroxyesters and solid,
room temperature stable peroxydicarbonates are the preferred
initiators. The most preferred initiators are dialkyl peroxides,
peroxyketals, cyclic ketone peroxides and diacyl peroxides.
[0110] A good reference which provides important peroxide names and
physical properties for all these classes of organic peroxides can
be found in "Organic Peroxides" by Jose Sanchez and Terry N. Myers;
Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Ed., Volume
18, (1996).
[0111] Illustrative dialkyl peroxide initiators are:
[0112] di-t-butyl peroxide;
[0113] t-butyl cumyl peroxide;
[0114] 2,5-di(cumylperoxy)-2,5-dimethyl hexane;
[0115] 2,5-(cumylperoxy)-2,5-dimethyl hexyne-3;
[0116] 4-methyl-4-(t-butylperoxy)-2-pentanol;
[0117] 4-methyl-4-(t-amylperoxy)-2-pentanol;
[0118] 4-methyl-4-(cumylperoxy)-2-pentanol;
[0119] 4-methyl-4-(t-butylperoxy)-2-pentanone;
[0120] 4-methyl-4-(t-amylperoxy)-2-pentanone;
[0121] 4-methyl-4-(cumylperoxy-2-pentanone;
[0122] 2,5-dimethyl-2,5-di(t-butylperoxy)hexane;
[0123] 2,5-dimethyl-2,5-di(t-amylperoxy)hexane;
[0124] 2,5-dimethyl-2,5-(t-butylperoxy)hexyne-3;
[0125] 2,5-dimethyl-2,5-di(t-amylperoxy)hexyne-3;
[0126] 2,5-dimethyl-2-t-butylperoxy-5-hydroperoxyhexane;
[0127] 2,5-dimethyl-2-cumylperoxy-5-hydroperoxy hexane;
[0128] 2,5-dimethyl-2-t-amylperoxy-5-hydroperoxyhexane;
[0129] m/p-alpha, alpha-di[(t-butylperoxy)-isopropyl]benzene;
[0130] 1,3,5-tris(t-butylperoxyisopropyl)benzene;
[0131] 1,3,5-tris(t-amylperoxyisopropyl)benzene;
[0132] 1,3,5-tris(cumylperoxyisopropyl) benzene;
[0133] di[1,3-dimethyl-3-(t-butylperoxy)butyl]carbonate;
[0134] di[1,3-dimethyl-3-(t-amylperoxy)butyl]carbonate;
[0135] di[1,3-dimethyl-3-(cumylperoxy)butyl]carbonate;
[0136] di-t-amyl peroxide;
[0137] t-amyl cumyl peroxide;
[0138] 2,4,6-tri(butylperoxy)-s-triazine;
[0139] 1,3,5-tri[-(t-butylperoxy)-1-methylethyl]benzene
[0140] 1,3,5-tri-[(t-butylperoxy)-isopropyl]benzene;
[0141] 1,3,-dimethyl-3-(t-butylperoxy)butanol;
[0142] 1,3-dimethyl-3-(t-amylperoxy)butanol; and mixtures
thereof.
[0143] Illustrative solid, room temperature stable
peroxydicarbonates are, but not limited to:
[0144] di(2-phenoxyethyl) peroxydicarbonate;
di(4-t-butyl-cyclohexyl) peroxydicarbonate; dimyristyl
peroxydicarbonate; dibenzyl peroxydicarbonate; di(isobornyl)
peroxydicarbonate.
[0145] Another preferred class of dialkylperoxides which may be
used singly or in combination with the other free radical
initiators contemplated by the invention are those selected from
the group represented by the formula 5
[0146] Wherein R.sub.4 and R.sub.5 may independently be in the meta
or para positions and are the same or different and are selected
from the group hydrogen or straight or branched chain alkyl of from
1 to 6 carbon atoms. Dicumyl peroxide and isopropylcumyl cumyl
peroxide are illustrative.
[0147] Other dialkyl peroxides are:
[0148] 3-cumylperoxy-1,3-dimethylbutyl methacrylate;
[0149] 3-t-butylperoxy-1,3-dimethylbutyl methacrylate;
[0150] 3-t-amyperoxy-1,3-dimethylbutyl methacrylate;
[0151] tri(1,3-dimethyl-3-t-butylperoxy butyloxy)vinyl silane;
[0152] 1,3-dimethyl-3-(t-butylperoxy)butyl
N-[I-{3-(1-methylethenyl)-pheny- l}-1-methylethyl]carbamate;
[0153] 1,3-dimethyl-3-(t-amylperoxy)butyl
N-[I-{3-(1-methylethenyl)-phenyl- }-1-methylethyl]carbamate;
[0154] 1,3-dimethyl-3-(cumylperoxy))butyl
N-[I-{3-(1-methylethenyl)-phenyl- }-1-methylethyl]carbamate.
[0155] In the group of diperoxyketal initiators, the preferred
initiators are:
[0156] 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane;
[0157] 1,1-di(t-butylperoxy)cyclohexane;
[0158] n-butyl 4,4di(t-amylperoxy)valerate,
[0159] ethyl 3,3-di(t-butylperoxy)butyrate;
[0160] 2,2-di(t-amylperoxy)propane;
[0161]
3,6,6,9,9-pentamethyl-3-ethoxycarbonyl-methyl-1,2,4,5-tetraoxacyclo-
nonane;
[0162] n-butyl-4,4-bis(t-butylperoxy)valerate;
[0163] ethyl-3,3-di(t-amylperoxy)butyrate; and mixtures
thereof.
[0164] Other peroxides falling within the general class defined as
useful in the invention include benzoyl peroxide,
00-t-butyl-0-hydrogen-monopero- xy-succinate and
00t-amyl-0-hydrogen-monoperoxy-succinate.
[0165] Illustrative cyclic ketone peroxides are compounds having
the general formulae (II), (III) and/or (IV). 6
[0166] Wherein R.sub.1 to R.sub.10 are independently selected from
the group consisting of hydrogen, C.sub.1 to C.sub.20 alkyl,
C.sub.3 to C.sub.20 cycloalkyl, C.sub.6 to C.sub.20 aryl, C.sub.7
to C.sub.20 aralkyl and C.sub.7 to C.sub.20 alkaryl, which groups
may include linear or branched alkyl properties and each of R.sub.1
to R.sub.10 may be substituted with one or more groups selected
from hydroxy, C.sub.1 to C.sub.20 alkoxy, linear or branched
C.sub.1 to C.sub.20 alkyl C.sub.6 to C.sub.20 aryloxy, halogen,
ester, carboxy, nitride and amido, preferably, at least 20% of the
total active oxygen content of the peroxide mixture used for a
crosslinking reaction will be from compounds having formulas (II),
(III) and/or (IV).
[0167] Some examples of suitable cyclic ketone peroxides are:
[0168] 3,6,9, triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane (or
methyl ethyl ketone peroxide cyclic trimer) and methyl ethyl ketone
peroxide cyclic dimer;
[0169] 3,3,6,6,9,9-hexamethyl-1,2,4,5-tetraoxacyclononane;
[0170] Illustrative suitable peroxy esters are:
[0171] 2,5-dimethyl-2,5-di(benzoylperoxy) hexane;
[0172] t-butylperbenzoate;
[0173] t-butylperoxy acetate;
[0174] t-butylperoxy-2-ethyl hexanoate;
[0175] t-amyl perbenzoate;
[0176] t-amyl peroxy acetate;
[0177] t-butyl peroxy isobutyrate;
[0178] 3-hydroxy-1,1-dimethyl t-butyl peroxy-2-ethyl hexanoate;
[0179] 00-t-amyl-0-hydrogen-monoperoxy succinate;
[0180] 00-t-butyl-0-hydrogen-monoperoxy succinate;
[0181] di-t-butyl-diperoxyphthalate;
[0182] t-butylperoxy (3,3,5-triethylhexanoate);
[0183] 1,4-bis (t-butylperoxycarbo) cyclohexane;
[0184] t-butylperoxy-3,5,5-trimethylhexanoate;
[0185] t-butyl-peroxy-cis-3-carboxy) propionate;
[0186] allyl 3-methyl-3-t-butylperoxy butyrate.
[0187] Illustrative monoperoxy carbonates are:
[0188] 00-t-butyl-0-isopropylmonoperoxy carbonate;
[0189] 00-t-butyl-0-(2-ethyl hexyl) monoperoxy carbonate;
[0190]
1,1,1-tris[(2t-butylperoxy-carbonyloxy)ethoxymnethyl]propane;
[0191]
1,1,1-tris[(2-t-amylperoxy-carbonyloxy)ethoxymethyl]propane;
[0192]
1,1,1-tris[(2cumylperoxycarbonyloxy)ethoxymethyl]propane;
[0193] OO-t-amyl-O-isopropylmonoperoxy carbonate.
[0194] Illustrative diacyl peroxides are:
[0195] di(4methylbenzoyl) peroxide;
[0196] di(3-methylbenzoyl) peroxide;
[0197] di(2-methylbenzoyl) peroxide;
[0198] didecanoyl peroxide; dilauroyl peroxide;
[0199] 2,4-dibromo-benzoyl peroxide;
[0200] succinic acid peroxide;
[0201] dibenzoyl peroxide;
[0202] di (2,4-dichloro-benzoyl) peroxide.
[0203] Imido peroxides of the type described in PCT Application
publication WO9703961 A1 6 Feb. 1997 are also contemplated as
suitable for use by the invention.
[0204] One of skill in the art will readily be able to select
suitable quantities of the, various ingredients for use in the
invention and will quickly and easily be able to optimize the
concentrations through a series of bench scale trials employing
increasing amounts of the ingredients in samples of the polymer to
be cured (crosslinked). The optimum processing (compounding) time
and temperatures and the like may also be determined from the same
trials as will the optimum cure time and temperature.
[0205] Typically, one will employ the compounds of formula (a) (the
bismaleimides and biscitraconimides) in the composition of the
invention in quantities which will provide from about 0-2 parts by
weight per part of polymer by weight (phr) to about 10.0 phr,
preferably from about 1.0 phr to about 5.0 phr, most preferably
from about 1.5 phr to about 3.0 phr.
[0206] Typically, one will employ the sulfur containing organic
compound capable of accelerating sulfur vulcanization in polymers
capable of being crosslinked by sulfur in compositions of the
invention in quantities which will provide from about 0.01 phr to
about 20 phr, preferably from about 0.1 phr to about 1.0 phr, most
preferably from about 0.1 phr to about 0.5 phr. It is understood by
those of skill in the art that these compounds are of two types.
Those that donate sulfur to the vulcanization and those which
simply accelerate sulfur vulcanization. Either class of compound or
mixtures thereof are contemplated as equivalents by the
invention.
[0207] Alkyl phenol disulfide polymers of the VULTAC.RTM. type are
preferably used at from about 0.5 phr to 20 phr when used alone or
at from about 0.1 phr to about 10 phr when in combination with
other sulfur accelerators.
[0208] Typically, one will employ the free radical initiator
(organic peroxide and/or azo initiator) in quantities of from about
0.04 to about 10 phr preferably from about 1 to about 4 phr.
[0209] The time-temperature conditions necessary for curing largely
depend on the structure of the free radical curing agent. For the
azo initiators, suitable conditions are detailed in U.S. Pat. Nos.
3,632,107 and 4,129,531.
[0210] For the compositions of the invention, appropriate time and
temperature conditions may be determined for crosslinking a
particular polymer composition by running a small number of well
controlled rheometer studies and selecting values from the results
of those studies where the time/temperature relationship is from
five to fifteen times the half life value for the free radical
initiator in the system.
[0211] The invention contemplates that other conventional additives
such as anti-oxidants (hindered phenols and polymeric quinoline
derivatives are preferred), aliphatic process oils, and other
process aids, pigments, dyes, tackifiers, waxes, reinforcing aids,
UV stabilization agents, blowing agents and activators and
antiozonants may also be present in the compositions before, after
and during the curing step.
[0212] The polysulfide polymers contemplated by the invention are
those known polysulfide polymers which are prepared by the reaction
of an .alpha., .omega.-dihaloalkyl (or dihaloheteroalkyl) compound
with a metallic, preferably an alkali metal, polysulfide. The
common commercially available polysulfide polymers are either
liquids or solids, are either thiol or hydroxy terminated and are
derived from materials produce by the reaction of 1,2-chloroethane,
2,2'-dichloro-diethyl ether or bis(2-chloroethyl)formal with an
alkali metal polysulfide (MSx.sub.x) wherein M is an alkali metal
ion, preferably derived from sodium and x is a number greater than
1 up to about six.
[0213] The invention contemplates that polysulfide polymers may be
used in place of or in admixture with the other compounds (B) in
equal quantities to those previously specified for those compounds.
Since an excess of polysulfide polymer is not contemplated as
detrimental to the practice of the invention, it is also
contemplated that they may be preblended with the compound(s) (A)
and optionally with the free radical initiator(s) to form
masterbatches, either solid or liquid. The polysulfide polymers may
also be preblended into the polymer to be cured and and the
compound(s) (A) and also the free radical initiator(s) blended in
simultaneously or subsequently at the option of the operator. Use
of the polysulfide polymers in combination with the other sulfur
accelerators contemplated by the invention permits reduction of the
amount of sulfur accelerator required by the invention.
[0214] Similarly it will be obvious to one of skill in the art that
polysulfide polymers themselves may be cured to tack free surfaces
with free radical initiators in the presence of molecular oxygen if
a compound (A) is present in the curable composition even if
another compound (B) is not present. Thus, the invention
contemplates such a curable composition as an equivalent to the
second composition aspect of the invention as defined above.
[0215] Certain crosslinkable elastomer compositions which are
highly filled with oil and/or carbon black (commonly referred to as
highly extended elastomer formulations) are normally cured using
sulfur vulcanization rather than free radical initiators. Free
radical cure is more difficult because the radicals generated lack
specificity and react with the filler and oil as well as the
elastomer. This reduces efficiency of the free radical
initiator.
[0216] It has been found that the use of chlorinated polyethylene
and/or chlorosulfonated polyethylene as supplemental ingredients to
all the compositions of the various composition aspects of the
invention surprisingly increases free radical cure efficiency in
highly extended elastomer formulations and allows free radical cure
of the systems with reduced or no surface tack. The amount of
chlorinated and/or chlorosulfonated polyethylene as supplemental
ingredients in the: compositions of the first composition aspect of
the invention may be from about 1% to about 50% by weight,
preferably 15% to 40% by weight and more preferably from 20% to 35%
by weight.
[0217] The inclusion of these two polymers as supplemental
ingredients in some cases has been found to permit use of lower
concentrations of the compositions of the first composition aspect
of the invention in formulation of the compositions of the second
composition aspect of the invention.
[0218] The following examples further illustrate the best mode
contemplated by the inventors for the practice of their invention
and are to be construed as illustrative and not in limitation
thereof.
EXAMPLES
Example 1
Evaluation of Prior Art Compositions for Crosslinking EPM in the
Presence of Air and their Effect on Surface Tack and Level of
Crosslinking
[0219] In the example, various known co-curing agents, e.g.,
unsaturated monomeric crosslinking coagents, elemental sulfur, or
sulfur donor compounds, were evaluated in a cure with an organic
peroxide. The elastomer used in this example was an ethylene
propylene copolymer (EPM) marketed by Exxon, VISTALON.RTM. 504.
Prior art (U.S. Pat. No. 4,983,685) claims that use of high levels
(2.5 to 20 parts) of specific sulfur containing compounds with or
without optional unsaturated monomers can be used to crosslink
elastomers with peroxide in the presence of air and produce a
non-tacky surface. Other references employ sulfur. In this example,
low levels of sulfur or sulfur donor compounds were evaluated alone
or with some monomeric coagents. The data in Table 1 shows these
formulations produced a sticky surface, but also provided a
crosslinked product with good physical properties (higher MH
torque). A blend (as taught by the prior art) of an optional
monomeric coagent, a high level of sulfur compound and peroxide was
also evaluated. This produced a non tacky surface when crosslinking
elastomers in the presence of air, however, the physical properties
were unacceptable compared to a conventional peroxide monomeric
crosslinking formulation.
[0220] In the formulation of Table 1, a standard carbon black
formulation was used. Carbon black (N774), Sunpar.RTM. LW150
process oil from sun, zinc oxide, an antioxidant (AgeRite MA) were
compounded into the EPM. In addition, all formulations included E
parts of a 40% assay organic peroxyketal peroxide, LUPEROX.RTM.
231XL [40% 1,1-di(butylperoxy)-3,3,5-t- rimethylcyclohexane]
dispersed on calcium carbonate, marketed by ATOFINA Chemicals, Inc.
The level of cross listing was determined using a Flexsys MDR.RTM.
2000E moving die rheometer. Samples were also cured in hot air at
365.degree. F. for ten minutes and judged for surface tackiness by
placing a paper towel on the surface, immediately after removal
from the oven using moderate and consistent pressure. Surface tack
was rated from 1-10, where 1 is considered non-tacky and 10 is very
tacky.
[0221] A combination of peroxide and a low level of elemental
sulfur, 0.3 parts (a typical EPM cure), (Table 1, run #1) provided
a good level of crosslinking based on the M.sub.H but a sticky
surface when cured in hot air. Use of 2 parts HVA-2 (N,N'-phenylene
bismaleimide, marketed by Dupont) coagent together with peroxide
(Table 1, run #2) provides an expected improved level of
crosslinking (based on M.sub.H), but the surface tackiness is,
unfortunately, poor. Note: in each case, 1 part of an antioxidant,
AgeRite MA (a polymerized quinoline marketed by R.T. Vanderbilt),
is used, a standard level which does not affect the surface. A
combination of 0.3 parts elemental sulfur and 2 parts of HVA-2
(Table 1, run #5) provides further improvement in the level of
crosslinking, (compared to run #2 using HVA-2 alone), but,
unfortunately, provides high surface tackiness (7 out of 10). Thus,
blends of coagent with low levels of elemental sulfur can improve
crosslinking, but not surface tackiness. Prior art teaches 2.5 to
20 parts of sulfur accelerator or its equivalent is required. The
use of the coagent HVA-2 and peroxide in the carbon black EPM
formulation containing oil and antioxidant provided good
crosslinking, but, unfortunately, also produced a sticky surface
when curing in hot air. Using 4 parts of monomeric coagent
SR-350.RTM. together with 0.3 parts of elemental sulfur provided
the highest level of crosslinking, but poor surface tackiness (see
Table 1, run #4). SR-350 is trimethylolpropanetrimethacrylate,
marketed by Sartomer.
[0222] Table 1, run #3, 1,2 parts of Sulfads.RTM. in combination
with peroxide, provided an unacceptable surface tackiness of 6 out
of 10, and an undesirable level of cure based on M.sub.H. Sulfads
is 98% dipentamethylene thiuram tetrasulfide, marketed by R T.
Vanderbilt; thus, the amount of dipentamethylene thiuram
tetrasulfide actually added was 1.2.times.0.98-1.18 parts. Finally,
using 1.2 parts of Sulfads in combination with 2 parts HVA-2 and
peroxide results in a good surface when cured in the presence of
air, unfortunately, the desired crosslinked physical properties are
reduced, as shown by the low M.sub.H value attained.
[0223] This example illustrates that one cannot predict the effect
of blending dissimilar co-curing agents such as peroxide, monomeric
coagents and elemental sulfur or sulfur containing compounds with
the objective of maintaining an acceptable level of crosslinking
together with low surface tackiness when curing in the presence of
air. One may postulate that if the overall level of crosslinking
can be improved with various coagents and peroxide, the surface
tackiness in the presence of air can be improved. However, our data
shows that one can improve the level of crosslinking while not
improving the surface tackiness when curing in the presence of
air.
[0224] In addition, when the surface tack was finally reduced using
teaching from the prior art, it was found that the overall
crosslinking was undesirable. Crosslinking within the sample
(excluding air) and crosslinking the surface in the presence of air
are two separate processes. Increasing or decreasing the level of
crosslinking coagents or use of the various co-curing agents in
combination with peroxide leads to unpredictable results.
Crosslinking coagents such as HVA-2 help to increase the level of
crosslinking with peroxides cures, but appear to provide a poor
surface tack in air cure. When using monomeric coagents, e.g.,
HVA-2 or SR 350 in combination with other co-curing agents, such as
elemental sulfur or sulfur donor/accelerator compounds, as taught
in the art, we find that the final physical properties are severely
reduced, thus negating the advantages of a monomeric
coagent-peroxide cure system
1 TABLE 1 Run # 1 2 3 4 5 6 VISTALON .RTM. 100 100 100 100 100 100
504 EPM elastomer The various components below were added as (phr)
parts by weight per 100 parts of rubber, "as is," without
correcting for assay. N 774 (phr) 75 75 75 75 75 75 Carbon Black
LW150 Oil phr 10 10 10 10 10 10 ZnO (phr) 5 5 5 5 5 5 AgeRite MA 1
1 1 1 1 1 (antioxidant) LUPEROX .RTM. 8 8 8 8 8 8 231XL 40%
Peroxide SR-350 .RTM. -- -- -- 4.0 -- -- (phr) HVA-2 -- 2.0 -- --
2.0 2.0 Sulfur 0.3 -- -- 0.3 0.3 -- Sulfads .RTM. -- -- 1.2 -- --
1.2 (98%) Crosslinking, MDR 2000E Moving Die Rheometer at
150.degree. C. M.sub.H in.-lb. 29 39 20 44 43 29 Curing in hot air
for 10 minutes at 365.degree. F. to determine surface tack Surface
Tack* 7 7 6 10 7 1 *Surface Tackiness Rating: 1-10 where 10 is very
tacky and 1 is no tack.
Example 2
Compounding of Prior Art Peroxide Formulations Versus Novel
Peroxide Formulations for Crosslinking fully Saturated (no Double
Bonds within the Polymer Chains) Elastomers
[0225] The novel peroxide formulation provides good physical
properties associated with a conventional peroxide cure, plus an
unexpected non-tacky surface when crosslinking in the presence of
air.
[0226] In this example, 40% assay dicumyl peroxide dispersed on
clay, was used to crosslink EPM (polyethylene propylene copolymer)
VISTALON.RTM. 707 (Exxon). Table 2, run #1, dicumyl peroxide
blended with SR 206 (ethylene glycol dimethacrylate) was evaluated
for crosslinking in the MDR, % compression set and in hot air cure
for surface tack. Note: prior art (U.S. Pat. No. 4,983,685) used SR
206 as an optional monomeric coagent in their examples. This
peroxide and coagent blend produced a good cure (M.sub.H) and %
compression set, with a very sticky surface upon hot air cure at
400.degree. F. Addition of Sulfads.RTM. (98% dipentamethylene
thiuram tetra sulfide) at the prior art claimed levels of 2.5 parts
to the peroxide SR 206 blend improved the surface but totally
destroyed % compression set; Table 2, run #2.
[0227] Using prior art levels in the specification of U.S. Pat. No.
4,983,685 of 0.8 parts of Sulfads, Table 2, run #4 together with an
optional 2.2 parts HVA-2 coagent, 5parts DC40 provided good
surface, but very poor % compression set. Note: percent compression
set values of 100% to 60% would be expected for sulfur
vulcanization, not peroxide crosslinking.
[0228] Table 2, run #3, prior art taught levels of 5 parts Vanox
ZMTI (93% Zinc 2-mercapto-toluimidazole) with optional SR-206
coagent, improved compression set but gave a very sticky,
unacceptable surface.
[0229] Unexpectedly, Table 2, run #5, low levels of
dipentamethylene thiuram tetra sulfide (at 0.4 parts which falls
outside of U.S. Pat. No. 4,983,685), 0.4 parts of Durax (98%
N-yclohexyl-2-benzothiazolesulfeamide- ) and 5 parts DC40 (40%
dicumyl peroxide), provides a tack free surface when cured in a hot
air oven with an improved 41% compression set and. better level of
crosslinking.
[0230] Table 2, run #6, shows that, unexpectedly, 0.4 parts Durax,
0.4 parts of Vanax A (98% 4,4'-dithiodimorpholine), 2.2 parts HVA-2
monomeric coagent and 5 parts DC40 (40% dicumyl peroxide), provided
a tack free surface with 31% compression set. The use of the Durax
and/or Vanax A, with peroxide and bismaleimide type coagent, for
use in hot air cure of elastomers, has not been taught in the prior
art. Table 2, run 7, use of 0.8 parts of Durax, instead of the
Durax/Vanax blend, provided a further unexpected outstanding %
compression set value of 21% with a non-tacky surface upon hot air
cure at 400.degree. F.
[0231] Lastly, Table 2 run #8, unexpectedly outstanding results
were obtained; an excellent, tack free surface with very desirable,
extremely low 18% compression set using the novel blend of 2.2
parts HVA-2, 0.4 parts VULTAC 5, 0.4 parts Durax and 5 parts DC40.
VULTAC 5 (75% alkyl phenol disulfide polymer from Elf Atochem) has
not been taught by the art for use in hot air cure of elastomers
together with peroxide and bismaleimide type coagent. Note that 0.4
parts of VULTAC 5 is equivalent to adding 0.3parts of the alkyl
phenol disulfide polymer, due to the 75% assay.
[0232] This example shows that prior art formulations using
peroxide and high levels of select compounds, such as
dipentamethylene thiuram tetra sulfide, blended with optional
monomeric coagents do, in fact, produce a tack-free surface but
provide very poor final physical properties for the crosslinked
elastomer. Using 0.8 parts of a thiuram preferred compound taught
by the prior art's U.S. Pat. No. 4,983,685 disclosure, but less
than the 2.5 to 20 part levels claimed, produced a crosslinked
elastomer with very poor heat aging properties for a peroxide cure
formulation.
[0233] The high 60%+ compression set values show that the prior art
crosslinked polymer permanently deformed under applied pressure
over 70 hours at 150.degree. C., a standard test (ASTM D-395-61)
for a peroxide cure. A tack free surface can be obtained in hot air
by sulfur vulcanization for unsaturated polymers, but results in
poor heat aging properties. There is no advantage to a peroxide
cure system cured in hot air over a sulfur vulcanization if there
are no significant differences in physical properties, e.g., low
M.sub.H and/or high (poor) percent compression set values. Peroxide
cures have been traditionally the choice for a number of high
temperature and high performance applications. Peroxide
crosslinking provides carbon-carbon bonds which allow the
crosslinked polymer manufacturer to use the full engineering
capabilities of the elastomer.
2 TABLE 2 Run # 1 2 3 4 5 6 7 8 VISTALON 707 100 100 100 100 100
100 100 100 EPM The various components below were added as (phr)
parts by weight per 100 parts of rubber, "as is," without
correcting for assay. N774 Carbon Black 75 75 75 75 75 75 75 75
LW150 process oil 30 30 30 30 30 30 30 30 ZnO 5 5 5 5 5 5 5 5
Stearic acid 1 1 1 1 1 1 1 1 AgeRite MA 1 1 1 1 1 1 1 1 DC40 8.0
8.0 8.0 5.0 5.0 5.0 5.0 5.0 SR-206 2.0 2.0 2.0 -- -- -- -- -- HVA-2
-- -- -- 2.2 2.2 2.2 2.2 2.2 Sulfads (98%) -- 2.5 -- 0.8 0.4 -- --
-- ZMTI (93%) -- -- 5.0 -- -- -- -- -- Vanax A (98%) -- -- -- -- --
0.4 -- -- VULTAC 5 (75%) -- -- -- -- -- -- -- 0.4 Durax (98%) -- --
-- -- 0.4 0.4 0.8 0.4 MDR Cure at 170.degree. C. M.sub.H in-lb 17 9
16 17 18 17 16 16 T.sub.S1 min 1.04 1.56 1.06 1.20 1.11 0.61 0.58
0.63 T.sub.C90 min 5.8 7.5 5.5 6.6 5.2 5.9 4.1 4.2 Cure in
400.degree. F. air for 12 min. Surface 10 1.5 7 1.5 2 2.5 2.5 2
Compression Set 70 hr. at 150.degree. C. % Compression Set 25 100
35 63 41 31 21 18
Example 3
Novel Peroxide-Additive Compositions Produce Solid or Foamed
Crosslinked Elastomer in Hot Air, with Outstanding Physical
Properties, e.g. Percent Compression set, while also Producing a
non Tacky Surface when Curing in the Presence of Air
[0234] The elastomer used in this example was Uniroyal.RTM. X3378
EPDM containing 4% dicyclopentadiene as the tenmonomer. Peroximon
DC 40KEP (40% dicumyl peroxide on clay) was used as the peroxide
crosslinking agent. In this example the levels of Sulfads.RTM. 98%
dipentamethylene thiuram tetra sulfide), VULTAC.RTM. 5 (75% alkyl
phenol disulfide polymer) and Durax.RTM. (98%
N-cyclohexyl-2-benzothiazolesulfenamnide) were varied, keeping the
peroxide and HVA-2 coagent constant (Table 3, runs #2 to #6).
[0235] Note: adding 0.5 parts (phr) Sulfads is equivalent to 0.49
parts of dipentamethylene thiuram tetra sulfide, per 100 parts of
rubber. Referring to runs #2, #3 and #4, unexpectedly, excellent
compression set and a tack free surface were found when using
dipentamethylene thiuram tetra sulfide below 0.5 phr, on a pure
basis with HVA-2 and peroxide.
[0236] When the Sulfads (98% dipentamethylene thiuram tetra
sulfide), VULTAC 5 and Durax concentration were varied, it was
unexpectedly discovered that both solid and foamed crosslinked
elastomers could be produced by hot air cure using our novel
peroxide/additive composition. Foamed crosslinked elastomer with a
tack free surface was obtained when using <0.5 phr pure
dipentamethylene thiuram tetra sulfide, with either VULTAC 5 or
Durax; see Table 3, runs #2, #3 and #4. Using VULTAC 5 or a blend
of VULTAC 5 with Durax provided solid crosslinked EPDM, Table 3,
runs #5 and #6. Unexpectedly in each case (Table 2, runs #2 to #6)
outstanding percent compression set values were obtained, virtually
equivalent to a conventional peroxide cure, provided in Table 2,
run #1.
[0237] Sulfur vulcanization compression sets are measured at
approximately 100.degree. C. -120.degree. C. and rarely determined
at 150.degree. C. due to constant poor performance at elevated
temperature. The present 150.degree. C., 70 hour desirable
compression set data proves that these novel peroxide-additive
compositions illustrated in the practice of this invention produce
crosslinked EPDM with unexpectedly good heat aging properties. In
addition, the novel peroxide-additive compositions surprisingly
provide a way to produce both solid and foamed articles.
[0238] Although not wishing to be bound, it is thought that faster
scorch times related to the unexpected crosslinked network sets up
faster than gas evolution from the cure system early in the cure to
provide solid cured articles, which is more difficult under low
pressure conditions in an oven as opposed to a closed mold. When
that scorch time is delayed, the gas evolution may coincide with
the crosslink network formation. Furthermore, in addition to these
various unexpected processing and engineering advantages, these
novel peroxide formulations provide a completely tack free surface
when cured in the presence of air.
3 TABLE 3 Run # 1 2 3 4 5 6 Uniroyal 100 100 100 100 100 100 X3378
EPDM The various components below were added as (phr) parts by
weight per 100 parts of rubber, "as is," without correcting for
assay. N774 Carbon 100 100 100 100 100 100 Black Sunpar 2280 30 30
30 30 30 30 Oil ZnO 4 4 4 4 4 4 Stearic acid 0.5 0.5 0.5 0.5 0.5
0.5 AgeRite D 1 1 1 1 1 1 DC40KEP 40% 8.0 5.2 5.2 5.2 5.2 5.2
Dicumyl Peroxide HVA-2 -- 2.0 2.0 2.0 2.0 2.0 Sulfads (98%) -- 0.5
0.3 0.3 -- -- VULTAC 5 -- -- -- 0.5 0.8 0.5 (75%) Durax (98%) --
0.3 0.5 -- -- 0.3 MDR at 170.degree. C. M.sub.H in-lb 24 30 30 31
32 31 T.sub.S1 min .53 .83 .76 .69 .55 .54 T.sub.C90 min 7.9 5.9
5.6 5.5 4.9 4.7 Compression set 70 hrs. at 150.degree. C. %
Compression 21 30 24 27 22 19 Set Air cure at 400.degree. F. for 10
min. Surface 10 1 1 1 1 1 Gassing No Yes Yes Yes No No
Example 4
Novel Peroxide-Additive Compositions are Studied using a Fast Cure,
Higher Ethylene EPDM (Rovalene 509 EPDM) using Dicumyl Peroxide and
HVA-2 in Table 4.
[0239] The prior art formulations (Table 4, runs #2 and #3)
provided a good surface after hot air cure, but unfortunately,
resulted in very poor 150.degree. C./70 hour compression set
physical properties and exhibited a highly undesirable odor. These
61% and 71% compression set values are similar to what one would
obtain from a sulfur vulcanization, not a peroxide cure. In
addition, the prior art samples #2 and #3 which used 2.5 parts of
Sulfads.RTM., had large gas bubbles trapped at the center of the
cured part; considered an unacceptable cure defect.
[0240] In contrast, all the samples (runs #5 to #12) using the
novel peroxide-additive composition taught by this invention,
provided outstanding physical properties, i.e., very low
compression set values at 150.degree./70 hours, very similar to
that obtained by the use of the peroxide control reaction with no
coagent or sulfur additive (Table 1, run #1). In that control
reaction a 15% compression set was obtained, despite the very
sticky surface (10 out of 10) for the hot air cure study. The blend
of HVA-2 coagent with peroxide (run #4) and the antioxidant AgeRite
D (typically incorporated as standard practice in rubber
formulations) provided a good compression set value at the reduced
120.degree. C./70 hour test temperature, but unfortunately, a poor
surface (7 out of 10) when crosslinking in the presence of air. All
samples included in this invention, runs #5 to #12, provided
excellent physical properties associated with a peroxide cure, plus
a tack free surface when cured in the presence of air.
4 TABLE 4 1 2 3 4 5 6 7 8 9 10 11 12 Royalene 521 100 100 100 100
100 100 100 100 100 100 100 100 EPDM The various components below
were added as (phr) parts by weight per 100 parts of rubber, "as
is," without correcting for assay. N550 50 50 50 50 50 50 50 50 50
50 50 50 N 990 25 25 25 25 25 25 25 25 25 25 25 25 LW150 oil 20 20
20 20 20 20 20 20 20 20 20 20 ZnO 4 4 4 4 4 4 4 4 4 4 4 4 Stearic
Acid 1 1 1 1 1 1 1 1 1 1 1 1 AgeRite D 1 1 1 1 1 1 1 1 1 1 1 1 DC40
KEP 40% 7.2 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 HVA-2 --
2.2 -- 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.2 SR-206 -- -- 2.2 -- --
-- -- -- -- -- -- -- Sulfads 98% -- 2.5 2.5 -- 0.5 0.3 0.3 -- 0.3
0.3 0.3 0.3 Vanax A 98% -- -- -- -- -- -- -- 0.3 -- -- -- -- M.
Tuads 98% -- -- -- -- -- 0.2 -- -- -- -- -- -- Durax 98% -- -- --
-- -- -- 0.2 0.2 -- -- -- -- Unads 98% -- -- -- -- -- -- -- -- 0.2
-- -- -- M. Zimate 98% -- -- -- -- -- -- -- -- -- 0.2 -- -- M.
Niclate 98% -- -- -- -- -- -- -- -- -- -- 0.2 -- M. Curnate 98% --
-- -- -- -- -- -- -- -- -- -- 0.2 MDR at 170.degree. C., 1 degree
arc M.sub.H 39 43 27 45 40 38 40 42 38 38 41 37 T.sub.S1 .45 .68
.75 .38 .60 .62 .58 .42 .65 .46 .56 .53 T.sub.C90 7.1 4.3 2.5 4.6
4.8 5.3 4.6 4.9 4.8 5.1 4.8 5.2 Cure in air at 400.degree. F. for
12 min. Surface 10 1 1 7 1 1 1 1 1 1 1 1 Percent Compression set
120.degree. C. for 70 hours % Set 11 46 -- 8 16 18 14 -- 15 -- --
-- Percent Compression set 150.degree. C. for 70 hours % Set 15 61
71 -- -- -- 19 17 -- 21 17 21
Example 5
Evaluation of Common Classes of Coagents to Demonstrate the
Uniqueness of the use of Bismaleimide Coagents with Selected
Additives, for Utility in Providing Good Overall Peroxide-Type
Physical Properties with the Ability to Cure the Surface of a
Rubber (Tack-Free Surface) in the Presence of Air
[0241] The bismaleimide is evaluated in combination with
Sulfads.RTM. and VULTAC.RTM. 5 together with dicumyl peroxide for
crosslinking a fast cure type EPDM (Royalene.RTM. 509 EPDM).
[0242] The prior art teachings use various coagents both monomeric
and non-monomeric to improve crosslinking efficiency, but have no
relation to their effect with air contact. We found that the use of
these various coagents are just as likely to increase reactions
with oxygen and make the rubber surface more tacky after curing in
the presence of air, versus the bismaleimide type.
[0243] In Table 5, the HVA-2 (bismaleimide de-type coagent)
provided a tack free surface with the blend of 0.3 pans Sulfads and
0.2 parts of VULTAC 5. Use of other agents provided a sticky
surface, e.g., TAC (triallyl cyanurate), SR-350 (trimethylolpropane
trimethacrylate), 1.2 BR (1,2 liquid butadiene rubber), Santolink
XI-100 (allyl glycidyl ether alcohol resin), TAP (triallyl
phosphate) and pBQ (para benzoquinone).
5 TABLE 5 Run # 1 2 3 4 5 6 7 8 9 Royalene 509 EPDM 100 100 100 100
100 100 100 100 100 The various components below were added as
(phr) parts by weight per 100 parts of rubber, "as is," without
correcting for assay. N550 50 50 50 50 50 50 50 50 50 N990 25 25 25
25 25 25 25 25 25 LW150 oil 20 20 20 20 20 20 20 20 20 ZnO 4 4 4 4
4 4 4 4 4 Stearic acid 1 1 1 1 1 1 1 1 1 AgeRite D 1 1 1 1 1 1 1 1
1 DC 40KEP 5.4 5.4 5.4 5.4 5.4 5.4 5.4 5.4 5.4 Sulfads 98% -- 0.3
0.3 0.3 0.3 0.3 0.3 0.3 0.3 VULTAC 5 98% -- 0.2 0.2 0.2 0.2 0.2 0.2
0.2 0.2 HVA-2 -- -- 2.0 -- -- -- -- -- -- TAC -- -- -- 3.0 -- -- --
-- -- SR-350 -- -- -- -- 4.0 -- -- -- -- 1,2 BR -- -- -- -- -- 6.0
-- -- -- Santolink XI-100 -- -- -- -- -- -- 4.0 -- -- TAP -- -- --
-- -- -- -- 4.0 -- pBQ -- -- -- -- -- -- -- -- 1.0 MDR Cure at
170.degree. C. M.sub.H in-lb 32 27 42 26 32 27 19 23 22 T.sub.C90
min 7.7 6.6 4.5 7.6 6.7 8.2 7.0 7.2 9.5 Cure in air at 200.degree.
C. Surface 10 4 1 7 7 4 4 4 4
Example 6
Use of Low Levels of Prior Art Sulfur Accelerators Blended with
HVA-2 and Dicumyl Peroxide does not Provide Tack Free Surface.
Unexpectedly use of Low Level Prior Art Compounds with HVA-2 and
Select Compounds Provide a Tack-Free Surface when Crosslinking a
Fast Cure EPDM (Rovalene.RTM. 509) in the Presence of Air
[0244] Using 0.2 parts of Methyl Zimate (98% zinc
dimetiylditeiocarcamate) or 0.2 parts Unads (98% tetramethylthiuram
monosulfide) wh HVA-2 provided poor surface cure (sticky surface)
when curing in the presence of air. Thus, it is not obvious to use
very low levels of the prior art compounds in combination with
HVA-2 (N,N'phenylene bismaleimide) coagent and peroxide to provide
a tack-free surface for crosslinked elastomers in the presence of
air.
[0245] Unexpectedly, when VULTAC.RTM. 5 (75% alkyl phmnol disulfide
polymer) or Vanax.RTM. A (98% 4,4'dithiodimorpholine) is blended
with these low levels of prior art compounds, e.g., Methyl Zimate
or Unads, one obtains a tack-free surface when crosslinking in the
presence of air.
[0246] Thus, a unique blend of peroxide, HVA-2 coagent, and low
levels of dithiocarbamates or thiurams with VULTAC 5 or Vanax A
provides a crosslinked polymer with a cured surface in the presence
of air. In addition, no gassing was noted, thus, solid crosslinked
parts can be formed with these novel blends.
6 TABLE 6 Run # 1 2 3 4 5 6 7 8 9 Royalene 509 EPDM 100 100 100 100
100 100 100 100 100 The various components below were added as
(phr) parts by weight per 100 parts of rubber, "as is," without
correcting for assay. N774 75 75 75 75 75 75 75 75 75 Sunpar 2280
Oil 20 20 20 20 20 20 20 20 20 ZnO 5 5 5 5 5 5 5 5 5 Stearic acid
0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 DC40KEP 40% 7.0 5.0 5.0 5.0 5.0
5.0 5.0 5.0 5.0 HVA-2 -- 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 M. Zimate
98% -- 0.2 0.2 0.2 0.2 -- -- -- -- Unads 98% -- -- -- -- -- 0.2 0.2
0.2 0.2 Vanax A 98% -- -- 0.5 -- -- -- 0.5 -- -- Sulfur -- -- --
0.15 -- -- -- 0.15 -- VULTAC 5 75% -- -- -- -- 0.67 -- -- -- 0.67
MDR at 170.degree. C. M.sub.H in-lb 43 42 41 43 41 43 40 42 41
T.sub.S1 min 0.38 0.34 0.45 .042 0.40 0.47 0.50 0.47 0.49 T.sub.C90
min 7.2 4.6 4.8 4.4 4.4 4.5 5.3 4.7 4.5 Cure in air at 420.degree.
F. for 8 min. Surface 10 7 1 4 1 7 1 4 1 Gassing No No No No No No
No No No
Example 7
The Use of Low Levels of Prior Art Elemental Sulfur with Low Levels
of Prior Art Sulfads.RTM., with or Without Optional HVA-2 Monomeric
Coagent, Provides Good Surface Cure in Hot Air, However, Poor
Physical Properties (61% and 49% Compression Set)
[0247] Thus, the concept of using low levels of known prior art
sulfur compounds with suggested coagent and peroxide does not
readily lead to a combination of good surface cure and desired
physical properties expected.
7 TABLE 7 1 2 3 4 Keltan 4906 EPDM 100 100 100 100 The various
components below were added as (phr) parts by weight per 100 parts
of rubber, "as is," without correcting for assay. N 774 80 80 80 80
N 330 20 20 20 20 LW 150 Oil 40 40 40 40 ZnO 6 6 6 6 Stearic Acid 1
1 1 1 AgeRite D 1 1 1 1 DC40P (40%) 5 5 5 5 HVA-2 -- -- 1.8 1.8
Sulfur -- 0.2 -- 0.2 Sulfads (98%) -- 0.4 -- 0.4 420.degree. F. for
8 min. cure in 10 1 10 1 air Surface (1 to 10) 10 = Sticky
Compression set 120.degree. C./70 hrs. Percent Compression Set 25%
61% 12% 49%
Example 8
In this Example, it is Shown that the Novel Peroxide-Additive
Composition Performs well in Filled and Non-Filled EBDM
Formulations
[0248] Run #2 contains only EPDM and the novel peroxide-additive
formulating, i.e.; no oil, carbon black, ZnO or stearic acid. Note:
the novel-formulation, as taught in the practice of the invention,
provides a completely tack free surface when cured in the presence
of air, (1 out of 10) where 10 is tacky. Addition of normal levels
of carbon black and oil (run #4) provides excellent tack free
surface in the presence of air. Use of very high levels of carbon
black (that exceed the amount of EPDM used) and high levels of oil
as shown in Table 8, runs #6 and #8, show the expected reduction in
the level of crosslinking (M.sub.H) for an organic peroxide type
cure. However, the resulting surface cure in the presence of air is
surprisingly good (4 out of 10) as shown in run #8, when the level
of peroxide-additive blend was increased. It is well known that
peroxide cures are adversely affected by high levels of oil and
carbon black. The peroxide radicals can be readily abstract
hydrogens from the oil as well as from the rubber. When the oil
concentration is increased, this significantly reduces the peroxide
cure efficiency. This is shown by the reduction in M.sub.H for the
two peroxide controls, with no additives (compare normal levels of
oil and carbon black run #3 to high levels of oil and carbon black
run #5).
8 TABLE 8 Run # 1 2 3 4 5 6 7 8 Royalene 509 EPDM 100 100 100 100
100 100 100 100 The various components below were added as (phr)
parts by weight per 100 parts of rubber, "as is," without
correcting for assay. N774 carbon black -- -- 75 75 130 130 130 130
Sunpar 2280 oil -- -- 20 20 60 60 60 60 ZnO -- -- 5.0 5.0 5.0 5.0
5.0 5.0 Stearic acid -- -- 0.5 0.5 0.5 0.5 0.5 0.5 DC40KEP 40% 7.00
5.00 7.00 5.00 7.00 5.00 10.5 7.50 HVA-2 -- 1.50 -- 1.50 -- 1.50 --
2.25 VULTAC 5 75% -- 0.67 -- 0.67 -- 0.67 -- 1.00 B. Zimate 98% --
0.20 -- 0.20 -- 0.20 -- 0.30 Crosslinking MDR Cure at 170.degree.
C., 1.degree. arc M.sub.H in-lb 40 31 43 41 18 24 26 31 T.sub.S1
min 0.45 0.46 0.38 0.40 0.54 0.50 0.43 0.44 T.sub.C90 min 8.3 5.8
7.2 4.4 7.0 4.2 6.6 3.8 Cure in air at 375.degree. F. for 14 min.
Surface 7 1 10 1 10 6 10 4
Example 9
Novel Peroxide-Additive Blends are used to Hot Air Cure a very
Highly Filled EPDM
[0249] This highly filled EPDM contains a large amount of carbon
black and oil. Such formulations are only used for sulfur
vulcanization, and are not typically used in peroxide cure. The
successful use in these examples shows the unexpected tremendous
utility of these novel peroxide-additive blends. In addition, the
effectiveness of this system is illustrated by providing examples
using four different organic peroxides. These are LUPEROX.RTM.
231-XL=40% 3,3,5-trimethyl-1,1-di(t-butylperoxy)cyclohexane;
LUPEROX 230-XL=40% n-Butyl-4,4-di(t-butylperoxy)valerate; Peroximon
DC40KEP=40% dicumyl peroxide and Peroximon F40KEP 40%
di(t-butylperoxy)diisopropylbenzene.
[0250] The peroxide controls (Table 9, runs #1, #3, #5 and #7) are
all tacky due to an under cured surface when crosslinking in the
presence of air. They also contain some gas bubbles in the interior
of the sample. The novel peroxide-additive formulations used in
this invention provide a fully cured surface (non-tacky) when
crosslinking in the presence of air, see Table 9, runs #2, #4, #6
and #8. Unexpectedly, these formulations cure to a higher level of
crosslinking to the point that there was no foaming (gas bubbles).
Thus, the novel peroxide formulations provide a desirable, solid,
crosslinked part with a non-sticky surface upon hot air cure. The
cure times vary because of the different peroxides used, but
unexpectedly the surfaces are always tack-free, despite the large
amount of filler and oil used.
9 TABLE 9 Run # 1 2 3 4 5 6 7 8 Nordel 2470 EPDM 100 100 100 100
100 100 100 100 The various components below were added as (phr)
parts by weight per 100 parts of rubber, "as is," without
correcting for assay. N 762 100 100 100 100 100 100 100 100 N 650
100 100 100 100 100 100 100 100 2280 oil 100 100 100 100 100 100
100 100 Lup 231 KE 40% 16.0 10.0 -- -- -- -- -- -- Lup 230 XL 40%
-- -- 16.0 10.0 -- -- -- -- Per DC40P 40% -- -- -- -- 16.0 10.0 --
-- Per F40P 40% -- -- -- -- -- -- 16.0 10.0 HVA-2 -- 4.0 -- 4.0 --
4.0 -- 4.0 Vanax A 98% -- 0.3 -- 0.3 -- 0.3 -- 0.3 Durax 98% -- 0.2
-- 0.2 -- 0.2 -- 0.2 VULTAC 5 75% -- 1.5 -- 1.5 -- 1.5 -- 1.5 MDR
Temp. 150.degree. C. 165.degree. C. 170.degree. C. 180.degree. C.
M.sub.H in-lb 11 26 11 23 14 26 20 29 T.sub.S1 min .50 .48 .53 .49
.52 .56 .38 .38 T.sub.C90 min 4.6 5.4 4.4 4.5 7.0 5.0 5.4 3.1 Cure
in air for 14 min. 360.degree. F. 390.degree. F. 400.degree. F.
415.degree. F. Surface 10 2 10 1 10 1 10 1 Gassing V.sli No Sli. No
Sli. No Sli. No
Example 10
ADA (Azodicarbonamide) is a Blowing Agent which is used to Create
Foamed Articles
[0251] In Table 10, ADA is used to produce hot air cured,
free-rise, crosslinked EPDM sponge using our novel
peroxide-additive formulations to create a tack free surface. The
peroxide control with no additive or ADA is provided in Table 10,
run #1. Note: the level of crosslinking was M.sub.H=9.8 inch-lbs,
as per the Moving Die Rheometer (MDR 2000E, at,200.degree. C. and
1.degree. arc). Note, however, the surface was very sticky when
crosslinking in the presence of air. The Tangent delta for run #1
(peroxide control) was 0.064, a desirable low value. The MDR can
measure tan .delta. (tangent delta) which can be determined by
dividing the viscous moduli by the elastic moduli. A cured compound
with a very low tangent delta will be very resilient and exhibit
low hysteresis. A higher tangent delta value means that the polymer
chains can undergo permanent movement or deformation, after an
applied stress. Table 10, run #2, peroxide and ADA with no other
additives provided and M.sub.H=17.6 inch-lbs, so the ADA appears to
reduce the level of crosslinking, although gas pressure can also
affect the reading, compared to run #1 while continuing to provide
a sticky surface.
[0252] Table 10, run #3, use of peroxide, ADA and coagent blend
N,N'-m-phenylene bismaleimide (HVA-2) and
1,3-bis(citraconimidomethyl)ben- zene (Perkalink 900) provided
improved crosslinking performance, based on the higher M.sub.H of
24.9 in-lbs, but the surface was very sticky (7 rating out of 10)
after hot air cure. Coagents with peroxide helps to improve the
cure, but continue to provide poor surface due to air
inhibition.
[0253] Table 10, run #4, low levels of certain additives, ADA and
no coagent with peroxide improves the surface (4 to 5 out of 10)
after hot air cure, but the crosslinking is very low (M.sub.H=14.9
in-lbs) with an undesirable Tangent Delta of 0.095.
[0254] Unexpectedly the use of a coagent blend (HVA-2 and Perkalink
900) with low levels of select additives, peroxide and ADA blowing
agent as per our invention provided excellent crosslink density
(M.sub.H of 22.2 in-lbs) and a very *good surface (2 out of 10)
when cured in hot air (Table 10, run #5). Note: a uniform foamed
EPDM with a density of 30 lbs/cu. ft was produced.
[0255] As taught in prior art, Table 10 run #7, use of Vanox ZMTI
(93% Zinc 2-mercapto-toluimidazole) at 5 phr peroxide plus ADA
provides a non tacky surface in hot air cure with unfortunately a
low M.sub.H of only 16.9 in-lbs and a corresponding poor tangent
delta, compared to run #5.
[0256] Use of Captax (98% 2-mercaptobenzothiazole) as per prior
art, Table 10 run #8, provides a non-tacky surface as well,
however, with further degradation in final crosslinked physical
properties (M.sub.H and tangent delta).
10 TABLE 10 Run # 1 2 3 4 5 6 7 8 Royalene X3378 EPDM 100 100 100
100 100 100 100 100 The various components below were added as
(phr) parts by weight per 100 parts of rubber, "as is," without
correcting for assay. N774 carbon black 100 100 100 100 100 100 100
100 Sunpar 228 oil 40 40 40 40 40 40 40 40 ZnO 2 2 2 2 2 2 2 2
Stearic acid 2 2 2 2 2 2 2 2 DC40KEP 40% 9.0 9.0 9.0 9.0 9.0 4.5
9.0 9.0 HVA-2 -- -- 0.5 -- 0.5 2.0 -- -- Perkalink 900 -- -- 1.5 --
1.5 -- -- -- Sulfads 98% -- -- -- 0.3 0.3 0.3 -- -- Unads 98% -- --
-- 0.2 0.2 0.2 -- -- Vanox ZMTI 93% -- -- -- -- -- -- 5.0 -- Captax
98% -- -- -- -- -- -- -- 5.0 Azodicarbonamide -- 4.0 4.0 4.0 4.0
4.0 4.0 4.0 ADA Crosslinking in an MDR at 200.degree. C., 1.degree.
arc M.sub.H in-lb 19.8 17.6 24.9 14.9 22.2 19.6 16.9 6.7 Tangent
Delta .064 .068 .037 .095 .046 0.64 .093 .247 T.sub.S5 min 0.34
0.36 0.26 0.39 0.33 0.38 0.39 -- T.sub.C90 min 0.78 0.78 0.57 0.69
0.60 0.61 0.75 0.98 Hot Air Cure at 400.degree. F. for 7 min.
Surface 10 5 7 4 1 1 1 4 Density lbs/cu. ft. 74 21 48 22 30 26 29
43 Hot Air cure @ 400.degree. F. for 12 min. Surface 9 9 9 5 2 1 1
1 Density lbs/cu. ft. 71 24 54 22 30 28 29 41
Example 11
Common Coagents are Evaluated by Adding them to a Sulfur
Donor--Accelerator Blend Together with LUPEROX.RTM. 101-XL [45%
2,5-dimethyl-2,5-di(t-butylperoxy)hexane].
[0257] These peroxide-coagent-accelerator blends are used to cure
standard EPDM to show that the maleimide type coagent, HVA-2 or
Vanax MBM is the only one of those tested which is capable of
providing the all important combination of good cure with tack-free
surface when crosslinking EPDM in the presence of air.
[0258] Coagents in general are more efficient in Royalene.RTM. 521
EPDM compared to Royalene 509 in Example 4/Table 4. Referring to
Table 11, run #5 only HVA-2 provides a tack-free surface when used
in the practice of our invention, in the presence of air, and has a
higher MDR torque than the peroxide control in Table 11, run #1.
Although a few of the coagents provide some less reproducible
improvement, only the bismaleimide-type coagent, together with the
select additives at low levels, unexpectedly provide an outstanding
balance of surface cure and physical properties.
[0259] In addition, the previous data in Table 5 and in Table 11
show HVA-2 to have the fastest cure time of all the coagents, while
working well with the low levels of additives in the practice of
our invention to provide a reduced cure time in air, a tack free
surface with excellent final physical properties. The shortened
cure time should help the manufacturer with improved productivity
as well as producing a more superior product.
[0260] Various Components used in Table 11
[0261] LUPEROX 101-XL (45% 2,5Admethyl-2,5-di(t-butylpemxy)
hexane
[0262] Sulfads (98% dipentamethylene thiuram tetra sulfide)
[0263] Santocure TBSI (N-t-butyl-2-benzothiazolesulfenimide)
[0264] TAIC (Triallylisocyanurate)
[0265] SR-350 (trimethylolpropane trimethacrylate)
[0266] HVA-2 (N,N'-m-phenylenebismaleimide)
[0267] DAM (diallyl mellitate)
11 TABLE 11 1 2 3 4 5 6 7 8 9 10 Royalene 521 100 100 100 100 100
100 100 100 100 100 EPDM The various components below were added as
(phr) parts by weight per 100 parts of rubber, "as is," without
correcting for assay. N660 80 80 80 80 80 80 80 80 80 80 2280 Oil
10 10 10 10 10 10 10 10 10 10 Stearic Acid 1 1 1 1 1 1 1 1 1 1 Lup
101XL 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 45% Sulfads 98% --
0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 TBSI -- 0.15 0.15 0.15
0.15 0.15 0.15 0.15 0.15 0.15 TAIC -- -- 2.00 -- -- -- -- -- -- --
SR-350 -- -- -- 2.00 -- -- -- -- -- -- HVA-2 -- -- -- -- 2.00 -- --
-- -- -- ZnDMA -- -- -- -- -- 2.00 -- -- -- -- DAM -- -- -- -- --
-- 2.00 -- -- -- SR-206 -- -- -- -- -- -- -- 2.00 -- -- Perkalink
-- -- -- -- -- -- -- -- 2.00 -- 900 Sulfur -- -- -- -- -- -- -- --
-- 0.20 MDR at 185.degree. C. M.sub.H 37 27 32 35 41 27 32 33 31 28
T.sub.S1 0.34 0.40 0.39 0.41 0.37 0.31 0.40 0.44 0.41 0.42
T.sub.C90 4.2 3.7 4.3 3.4 2.4 3.7 4.2 4.0 3.6 3.5 Cure in air at
420.degree. F. for 8 min. Surface 10 5 4 2 1 1 4 4 4 1
Example 12
Various Peroxide--Sulfur Cure Blends used for other Applications
are Rated for Surface Tack (Quality) in Air Cure and Percent
Compression set Properties Compared to the Novel Blends of this
Invention and to Standard-Peroxide and Sulfur Cures
[0268] The novel peroxide cure system in Table 12, run #2
unexpectedly gives an excellent, tack-free surface in air (1 out of
10) with an outstanding compression set equal to the peroxide cures
in Table 12, runs #1, #3 and #6. which are very tacky (10 out of
10) after curing in air. Sulfur additives in Table 12, runs #4 and
#5, without HVA-2, produces a poor surface with higher, less
desirable compression set valued. A semi EV (semi-efficient sulfur
vulcanization system) which uses low levels of elemental sulfur in
Table 12, runs #7 and #8, provide expected improved surface
(non-tacky) but exhibit the poor compression set values of such EV
sulfur cures. The poor compression set values of 77% and 71% for
the standard sulfur vulcanization systems, Table 12, runs #9 and
#10, provide good, tack-free surfaces, unlike the peroxide controls
of Table 12, runs #1, #3 and #6 which provide excellent 14-16
percent compression set but a very sticky surface.
12TABLE 12 Comparison of a novel blend (Run #2) of this invention,
compared to a various peroxide-sulfur cure systems (Runs #4, #5, #7
and #8), and to standard peroxide (Runs #1, #3 and #6) and standard
sulfur cure (Runs #9 and #10). Royalene 521 EPDM 100 N 660 Black 75
2280 Oil 20 Stearic Acid 1 Run # 1 2 3 4 5 6 7 8 9 10 ZnO 1.00 1.00
1.00 1.00 1.00 3.00 3.00 3.00 3.00 3.00 DC40KEP 6.00 6.00 7.50 7.50
7.50 8.00 6.00 4.00 -- -- SR-206 2.00 -- -- -- -- -- -- -- -- --
HVA-2 -- 2.00 -- -- -- -- -- -- -- -- Sulfads 98% -- 0.24 -- -- --
-- 0.70 1.40 -- 2.80 M. Niclate 98% -- 0.24 -- -- -- -- -- -- -- --
Altax -- -- -- -- -- -- 0.40 0.80 1.00 1.60 Unads -- -- -- -- -- --
0.40 0.80 1.50 1.60 Durax -- -- -- 0.10 0.20 -- -- -- -- -- Sulfur
-- -- -- 0.20 0.40 -- 0.10 0.20 2.00 0.40 MDR at 170.degree. C.
M.sub.H (in-lbs) 26 31 26 25 25 27 21 26 31 29 T.sub.S1 (mins) 0.74
0.50 0.47 0.45 0.50 0.47 0.85 0.99 1.02 0.93 T.sub.C90 (mins) 7.1
4.1 7.2 5.3 5.1 7.1 4.3 3.4 3.0 2.6 Compression set 70 hrs. at
150.degree. F. Percent (%) 14 16 16 28 42 15 62 73 77 71
Compression Set Cure in air at 400.degree. F. for 8 to 12 min.
Surface 10 1 10 10 7 10 2 1 1 1
Example 13
Storage Stability of Novel Peroxide Formulations
[0269] The powdered forms of these compositions can be premixed and
stored for later use without loss of activity. In Table 13, runs #3
and #5 were Mixture 1 and Mixture 2 respectively, which were aged
at room temperature for 3 months. These aged mixtures were compared
to freshly prepared peroxide mixtures as shown in Table, 13, run #2
and run #4. The rheometer torque versus time curves, and the
quality of the crosslinked surfaces which were cured in hot air,
are the same for both compounds, within experimental error. MDR
torques, times and surface would be closer to the control (run #1)
if components reacted during aging. In the practice of the
invention,.one can add the various ingredients then add the
peroxide, however, premixing the various additives makes it more
practical and/or easier to use.
13TABLE 13 The novel peroxide compositions can be premixed and
stored for later use without loss of activity or performance. Two
different peroxide formulations were stored for three months.
Mixture 1 Mixture 2 DC40P 64.6% 64.6% HVA-2 27.8 22.8 Sulfads 3.8
-- Unads 3.8 -- VULTAC 5 -- 8.8 Durax -- 3.8 Keltan 4506 EPDM 100 N
660 Black 50 N 550 Black 50 2280 Oil 35 ZnO 3.0 Stearic Acid 1.5
Run # 1 2 3 4 5 Age of Mixture 0 0 3 mos. 0 3 mos. DC40P 8.0 -- --
-- -- Mixture 1 -- 7.9 -- -- -- Mixture 1 -- -- 7.9 -- -- Mixture 2
-- -- -- 7.9 -- Mixture 2 -- -- -- -- 7.9 Crosslinking Using the
MDR @ 170.degree. C., 1.degree. arc M.sub.H (in-lbs) 21.3 25.0 24.6
25.6 25.2 T.sub.S4 (mins) 0.38 0.56 0.55 0.38 0.39 T.sub.C90 (mins)
6.8 4.6 4.5 4.4 4.3 Cure in air at 400.degree. F. for 14 min.
Surface 10 2 1.5 3 2
Example 14
Use of Low Levels of Antioxidants (Phenolic, Metal
Dimethyldithiocarbamate Type) in Combination with Bismaleimide
Coagents and Low Levels of Sulfur Donors Provide Excellent
Tack-Free Surfaces when Curing Elastomers in the Presence of Air
and also Provides Desirable Final Physical Properties (i.e. low %
Compression Set)
[0270] The novel peroxide air curing formulations which consist of
peroxide(s), bismaleimide coagents(s), sulfur donor--sulfur
accelerator system can also include low levels of antioxidants.
Previously, in Example 4, Table 4, run #11, (M. Niclate, i.e.,
Methyl Niclate) nickel dimethyldithiocarbamate was used at a low
level of 0.2 phr, along with others, e.g., zinc (M. Zimate) and
copper (M. Cumate) type dimethyldithiocarbamates along with
Sulfads.RTM. to successfully produce a tack-free surface with good
physical-properties (compression set). The Methyl Niclate, whose
chemical name is nickel dimethyldithiocarbamate, is sold as
antioxidant.
[0271] In this present Example 14 and Table 14, a low level of 0.28
phr of Methyl Niclate is used in run #3 compared to a phenolic
antioxidant and a sulfenamide accelerator; see run #6 MBPC
(2,2'-methylene bis-4-methyl-6-t-butylphenol), and run #7,
Santocure TBSI (N-t-butyl-2-benzothiazolesulfenimide). In each case
HVA-2 and Sulfads are also included in the formulation, as per the
present invention.
[0272] Methyl Niclate (nickel dimethyldithiocarbamate) with Sulfads
(98% dipentamethylene thiuram tetrasulfide) or Morfax (98%
4-morpholinyl-2-benzothiazble disulfide) is an acceptable
combination as per Table 14, runs #2, #3 and #4. Substituting MBPC
(2,2'-methylene bis-4-methyl-6-butylphenol) or Santocure TBSI
(N-t-butyl-2-benzothiazoles- ulfenemide) for Niclate (nickel
dimethyldithiocarbamate) gives an excellent surface with desirable
low compression set physical properties. Thus, low levels of
phenolic antioxidants and sulfenamide class of accelerator work,
well with HVA-2 and low levels of other sulfur accelerators in the
novel peroxide compositions of this invention It is not obvious
that low levels of these compounds would be effective, based on the
teachings of the prior art Examples of prior art formulations which
use the acrylic coagent SR-206 (ethylene glycol dimethacrylate) are
provided in table 14, run #9 and run #10, where much higher amounts
of antioxidants, Vanox MBPC (99% 2,2'-methylene
bis-4-methyl-6-t-butylphenol- ) and Vanox ZMTI (93% Zinc
2-mercapto-toluimidazole) appear to have a poor effect on the
surface cure in this formulation, along with undesirable higher
compression set values, particularly for run #10.
14 TABLE 14 Royalene 521 EPDM 100 N 660 Black 75 2280 Oil 20 ZnO 1
Stearic Acid 1 Run # 1 2 3 4 5 6 7 8 9 10 DC40KEP 7.5 6.0 5.0 5.0
5.0 5.0 5.0 6.0 6.0 6.0 SR-206 -- -- -- -- -- -- -- 2.0 2.0 2.0
HVA-2 -- 2.0 2.0 2.0 2.0 2.0 2.0 -- -- -- Sulfads -- 0.24 0.20 --
-- 0.20 0.20 -- -- -- Methyl Niclate -- 0.24 0.28 0.28 -- -- -- --
-- -- Morfax -- -- -- 0.20 0.48 -- -- -- -- -- TBSI -- -- -- -- --
-- 0.28 -- -- -- MBPC -- -- -- -- -- 0.28 -- -- -- 2.5 ZMTI -- --
-- -- -- -- -- -- 2.5 -- MDR at 170.degree. C. M.sub.H 26 31 29 28
28 29 30 26 26 13 T.sub.S1 0.47 0.50 0.51 0.42 0.43 0.55 0.54 0.74
0.73 1.44 T.sub.C90 7.2 4.1 3.7 3.8 3.9 3.9 4.1 7.1 6.7 11.6 Cure
in air at 400.degree. F. for 12 min. Surface 10 1.5 2 2 4 1 1 10 8
10 Compression set 150.degree. C./70 hrs. % Comp. Set 16 16 16 15
19 17 19 14 22 49
Example 15
Crosslinking Fully Saturated Elastomer (ethylene-octene
copolymer)
[0273] An ethylene-octene (24%) copolymer G8100 from Dupont Dow, is
cured with 2 levels of dicumyl peroxide with and without
HVA-2--VULTAC.RTM. 5-Butyl Zimate in the rheometer and thin samples
in hot air. This extended formulation is rubbery, but slightly
thermoplastic and not sulfur curable.
[0274] In Table 15, run #3 and run #4 are only slightly tacky after
curing which is a major improvement because most thermoplastic
ethylene polymers would be very sticky in this test, simply because
these polymers melt/soften at these temperatures. The oil is added
to reduce stiffness but can make the surface more tacky. The oil
can be left out at this low filler level. When cooled to room
temperature, these samples (runs #3 & #4) were not tacky.
15TABLE 15 Crosslinking a Fully Saturated Elastomer
(Ethylene-Octene Copolymer) EG8100 100 N 660 black 60 2280 oil 5
ZnO 3 Stearic Acid 1 AgeRite MA 0.5 Run # 1 2 3 4 DC40P 7.0 10.0
4.00 5.72 HVA-2 -- -- 1.50 2.14 VULTAC 5 -- -- 0.55 0.79 B. Zimate
-- -- 0.25 0.36 MDR at 170.degree. C. M.sub.H in lb 22 30 30 37
T.sub.S.4 min 0.43 0.39 0.49 0.44 T.sub.C90 min 7.6 6.9 5.3 5.0
Cured in air Surface tackiness rating 420.degree. F./8 min 10 10 5
5 375.degree. F./18 min 10 10 4 4
Example 16
Evaluation of Different Bismaleimide Compounds for use in Novel
Peroxide Formulations which can Crosslink Elastomers with a
Tack-Free Surface in the Presence of Air
[0275] In Table 16, several different bismaleimide compounds were
evaluated in the practice of this invention. Unexpectedly, all of
these bismaleimide compounds provided good crosslinking efficiency
plus tack-free surfaces when tested immediately upon removal from a
hot air cure profile of 410.degree. F. for eight minutes. The
various coagents were evaluated on an equivalent molar bases
(taking into account the number of unsaturated functionality)
compared to 2 phr of m-phenylene-bismaleimide (MBM). Structures for
these various compounds are provided below: 7
[0276] The rubber formulation which was used for these experiments
is provided below:
16 The rubber formulation Parts Keltan 2506 EPDM (DSM Copolymer)
100 N660 carbon black (Huber) 75 Sunpar 2280 (Sun Oil) 15 Peroximon
DC40KEP 5 Coagent Molar Equivalent to 2.0 phr of MBM* Vanax A
(.RTM.. T. Vanderbilt) 0.2 VULTAC 5 (Elf Atochem) 0.7 Durax (R.T.
Vanderbilt) 0.1 *Taking into account the number of unsaturated
groups for each coagent compound.
[0277]
17 TABLE 16 Run # 1 2 3 4 Coagent Used None .sctn. MBM MPBM MMBM
Crosslinking DSM Copolymer Keltan 2506 EPDM in an MDR 2000E at
170.degree. C., 1.degree. arc M.sub.L (lb-in) 2.270 2.280 2.140
2.180 M.sub.H (lb-in) 34.90 32.47 27.51 30.08 M.sub.H - M.sub.L
(min) 32.63 30.19 25.37 27.90 T.sub.S 0.2 (min) 0.310 0.330 0.370
0.345 T.sub.S 0.4 (min) 0.350 0.370 0.430 0.390 T.sub.S 1.0 (min)
0.440 0.465 0.550 0.490 T.sub.C90 (min) 6.850 4.870 5.890 5.260
Crosslinking in a hot air oven at 410.degree. F. for 8 minutes
Surface Tack, 1-10 10 1 3 2 (10 worst) % Compression Set @ -- 27 46
36 150.degree. C./70 hours .sctn. Note: When no coagent was used,
30% more dicumyl peroxide was used in the formulation in an attempt
to reduce surface tack. However, even with the increase in peroxide
for run #1, surface tack was very poor (10 out of 10).
[0278] After the MDR2000E testing was completed, the AIR Cure
Surface Tack test was performed. All of the samples were heated in
the press oven at 410.degree. F. for eight minutes. After the eight
minutes, the samples were removed and paper towels were pressed
onto the hot samples. After cooling, the paper towel was removed at
a uniform rate to check for tackiness. Note that after the hot air
crosslinked samples had cooled to room temperature, there was very
little tack on the surface (except for the control run #1 peroxide
cure), with all samples having very similar, low surface tack. All
of the samples also displayed their own foaming height, meaning
each AIR Cured sample did internally foam to a certain degree. This
is partially dependent on the low Mooney Viscosity EPDM used
Example 17
Further Evaluations of Different Bismaleimide Compounds for use in
Novel Peroxide Formulations which can Crosslink elastomers with a
Tack-Free Surface in the Presence of Air
[0279] The 1,2; 1,3 and 1,4 (ortho, meta, para) isomers of
N,N'-phenylene bismaleimide were evaluated for use in novel
peroxide compositions which allow crosslinking elastomers in the
presence of air and provide a fully cured tack-free surface. The
elastomer used in this present example is Nordel.RTM.IP EPDM
NDR-4640. This is one of the new Dupont Dow metallocene type EPDM
elastomers.
[0280] The various bismaleimide coagents performed well to provide
a good tack free surface, as per Table 17, runs #5, #6 and #7, when
used with low levels of select additives as per this invention. All
of these novel compositions use a unique blend of sulfur containing
additives (Sulfads.RTM., VULTAC.RTM. 5 and Unads.RTM.) at low
levels together with the bismaleimide coagent and peroxide.
[0281] Note that poor surface cure was obtained when the separate
components of the peroxide formulations are used individually, see
Table 17, runs #1, #2, #3, #4, and #8. Run #1 was the peroxide
alone, runs #2 to #4 were the coagents and peroxide, run #8 was the
peroxide and s accelerator blend In each case the surface of these
formulations were tacky -upon hot air cure at 400.degree. F.
cure.
18TABLE 17 Crosslinking Nordel IP NDR-4640 EPDM in Hot Air Oven
Evaluation of various bismaleimide compounds in the practice of
this invention. Run # 1 2 3 4 5 6 7 8 DCKEP 7.00 4.20 4.20 4.20
4.20 4.20 4.20 7.00 1,2 PDM -- 2.10 -- -- 2.10 -- -- -- 1,3 PDM --
-- 2.10 -- -- 2.10 -- -- 1,4 PDM -- -- -- 2.10 -- -- 2.10 --
Sulfads -- -- -- -- 0.28 0.28 0.28 0.28 VULTAC 5 -- -- -- -- 0.28
0.28 0.28 0.28 Unads -- -- -- -- 0.14 0.14 0.14 0.14 MDR2000E
175.degree. C., 1.degree. arc M.sub.H (lb-in) 33.8 27.6 37.2 43.3
24.1 34.5 36.2 24.8 T.sub.S.4 (min) 0.29 0.29 0.26 0.27 0.45 0.44
0.44 0.37 T.sub.C90 (min) 4.59 5.26 3.06 2.94 4.59 3.26 5.18 4.22
140.degree. C. M.sub.L 3.26 3.28 3.32 3.30 3.28 3.29 3.29 3.15
T.sub.S.4 2.01 2.04 1.79 1.99 3.37 3.32 3.29 2.67 T.sub.S.1 3.33
2.91 2.39 2.72 4.85 4.76 4.78 3.97 195.degree. C. M.sub.H 30.5 23.5
34.1 39.7 20.5 31.7 34.2 22.7 M.sub.L 2.47 2.45 2.71 2.63 2.14 2.14
2.16 2.19 T.sub.S.4 0.19 0.20 0.17 0.17 0.26 0.25 0.25 0.22
T.sub.C90 1.01 1.08 0.75 0.75 1.00 0.81 1.09 0.96 Hot Air Cure @
400.degree. F. at 12 minutes Tacky Surface 10 8 8 8 4 1 3 10 Rating
Hardness 60 60 62 65 60 62 62 58 Formulation: Nordel 4640 100 *
Surface Tackiness Ratings N 774 80 1 no, 4 slight, 7 moderate, 10
yes N 990 20 Sunpar 2280 25 ZnO 1 Stearic Acid 1 PDM = N,N-(1,2 or
1,3 or 1,4)-phenylenedimaleimide
Example 18
Further Evaluation of Various Bismaleimide Compounds in the
Practice of this Invention
[0282] Table 18 shows the results of the evaluation of four coagent
bismaleimide compounds for their effectiveness to provide a cured
elastomer with tack-free surface upon curing, in a hot air oven,
when used with peroxides and select low levels of sulfur
accelerators, as per the practice of this present invention in this
example, Dupont Dow Nordel IP NDR-4640 metallocene EPDM was chosen
as the elastomer for evaluation work.
[0283] The monomeric compounds are:
1,1'-(3,3-dimethyl-1,1'-biphenyl-4,4'-- diyl)-bismaleimide;
N,N-(1,1'-biphenyl-4,4'-bismaleimide; 1,2-bismaleimidoethane and
1,6-bismaleimidohexane. They were compared no
N,N'-1,3-phenylenebismalemide or Vanax MBM, in Table 18. Using our
preferred formulation consisting of dicumyl peroxide, Sulfads,
VULTAC 5 and Unads, unexpectedly we found that the various
bismaleimide coagents provided excellent tack-free surfaces, Table
18, run #2 to run #6, compared to the peroxide control run #1 which
provided a very sticky surface. 8
19TABLE 18 Air Cure - Nordel NDR 4640 - Coagent Blend Study Run # 1
2 3 4 5 6 DC 40 KEP 7.00 5.00 5.00 5.00 5.00 5.00 Vanax MBM -- 1.50
1.00 1.00 1.00 1.00 DMBPDB -- -- -- 0.25 -- -- BPDP -- -- -- 0.25
-- -- BE -- -- -- -- 0.50 -- BH -- -- -- -- -- 0.50 Sulfads -- 0.28
0.28 0.28 0.28 0.28 VULTAC 5 -- 0.48 0.48 0.48 0.48 0.48 Unads --
0.14 0.14 0.14 0.14 0.14 MDR2000E 175.degree. C. M.sub.H (in-lb)
44.0 40.8 36.9 40.1 40.2 39.8 T.sub.S.4 min 0.27 0.38 0.38 0.38
0.39 0.39 T.sub.C90 4.53 3.05 3.15 3.51 3.20 3.07 MDR 195.degree.
C. M.sub.H 40.2 38.0 34.3 37.0 36.6 36.9 M.sub.L 2.94 2.62 2.55
2.60 2.57 2.60 T.sub.S.4 0.18 0.23 0.23 0.22 0.22 0.23 T.sub.C90
1.02 0.79 0.80 0.83 0.78 0.79 MDR 140.degree. C. M.sub.L 3.85 3.95
3.81 3.91 3.90 3.85 T.sub.S.4 1.74 2.86 2.85 2.83 2.82 2.79
Evaluation of the surface of crosslinked EPDM, cured in a hot air
oven at 400.degree. F. for 8 to 12 minutes. Tackiness rating 1 to
10; 10 = sticky surface 8 minutes 10 2.5 4 2.5 3 4 12 minutes 10 1
2.5 1 1 1 Shore 65 67 66 66 66 66 Formulation: Nordel 4640 100
DMBPDB: 1,1'(3,3-dimethyl- N 774 60
1,1'-biphenyl-4,4-diyl)-bismaleimide N 990 60 BPDB:
N,N'-(1,1'-biphenyl-4,4'-diyl)- 2280 20 bismaleimide ZnO 1 BE:
1,2-bismaleimidoethane Stearic Acid 1 BH:
1,6-bismaleimidohexane
Example 19
Evaluation of 2-(2,4-cyclopentadien-1-ylidene)-1,3-dithiolane as an
Additive for use in a Novel Peroxide Formulation, for use in the
Crosslinking of Elastomers in Hot Air Ovens to Provide a Good
Surface Cure (Tack-Free Surface) with Good Physical Properties
[0284] An unsaturated sulfur containing compound was evaluated in
combination with a bismaleimide coagent and peroxide. The compound
2-(2,4-cyclopentadien-1-ylidene)-1,3-dithiolane was substituted for
the blend of Durax, Vanax A and VULTAC 5 which was used in
combination with N,N'-m-phenylene bismaleimide (HVA-2) coagent and
dicumyl peroxide as per the data in table 19, this unique
formulation provided efficient crosslinking with an excellent
tack-free surface upon hot air cure at 410.degree. F. for eight
minutes. 9
[0285] In addition to the good crosslinking performance in the
presence of air, thus overcoming the air (oxygen) inhibition, it
was found that the final crosslinked elastomer had excellent final
physical properties, based on the desirable, low percent
compression set number which was obtained after heat aging the
crosslinked EPDM for 70 hours at 150.degree. C.
20 TABLE 19 Run # 1 2 DSM 2506 EPDM 100 100 N660 Carbon black 75 75
Sunpar 2280 15 15 Dicumyl Peroxide 40% on clay 5 5 N,N'-m-phenylene
bismaleimide 2 2 Vanax A 0.2 -- VULTAC 5 0.7 -- Durax 0.1 --
2-(2,4-cyclopentadien-1-ylidene)- -- 1.0 1,3-dithiolane MDR2000E at
170.degree. C., 1.degree. arc M.sub.H - M.sub.L (in-lbs) 32 30
T.sub.S4 min 0.36 0.34 T.sub.C90 5.23 5.44 Hot Air Cure at
400.degree. F. Tacky Surface Rating 2 1 % Compression set,
150.degree. C., 70 hrs. 27% 14%
Example 20
Use of Polysulfide in Combination with Select Halogenated Polymers
or Silicone Rubber, used as Additives with Peroxide, Sulfur
Accelerators and Bismaleimide Coagents, to Produce a Tack-Free
Surface in Highly Extended EPDM Formulations
[0286] Nordel IP 4520 (Dupont Dow Elastomers) blended with equal
weight of carbon black and high levels of oil would be difficult to
cure with ordinary peroxides and is representative of a sulfur
cured hose compound formulation. The highly extended EPDM
formulations where carbon black and or oil levels are nearly the
same as the EPDM usage, represents a formulation which is difficult
to cure well with organic peroxides. When curing a highly filled
EPDM in the presence of air, the peroxide radicals will attack the
oil and carbon black as if it were rubber, so obtaining a good
level of cure and maintaining a tack-free surface in the presence
of air is very difficult.
[0287] Using our novel blend of sulfur accelerators and
bismaleimide, we also incorporated small amounts of (FA)
polysulfide polymer and (SE6160) silicone rubber as novel additives
for use in our invention. We found that the blend of polysulfide
polymer and silicone rubber or chlorinated polyethylene or hypalon.
(chlorosulfonated polyethylene) with peroxide, bismaleimide coagent
and low levels of select sulfur accelerators will produce a
suitably tack-free cured surface in the presence of air. So this
novel blend provides a means to cure these highly extended EPDM
formulation which are commonly cured with sulfur vulcanization.
Note that the various sulfur vulcanization systems used in the art,
are not sensitive to higher concentrations of oil and carbon black
and are capable of fully curing highly extended rubber
formulations.
[0288] Thus we envision that a polymeric masterbatch of peroxide,
select sulfur accelerators, bismaleimide coagent, polysulfide could
be prepared wherein chlorinated polyethylene and or
chlorosulfonated polyethylene could be incorporated as additional
additives, as part of our invention.
[0289] Note the use of silicone rubber without the polysulfide
polymer produces a moderately tacky surface. Use of a
fluoroelastomer as an additive in our invention in combination with
polysulfide does not produce a suitable surface.
21TABLE 20 AIR Cure - Nordel IP 4520 --Effect of Polymer Additives
1 2 3 4 5 6 4520 EPDM 100 100 100 100 100 100 N660 100 100 100 100
100 100 N990 60 60 60 60 60 60 LW150 oil 60 60 60 60 60 60 stearic
acid 0.50 0.5 0.50 0.50 0.50 0.50 DCKE 40% 10.0 8.0 8.0 8.0 8.0 8.0
M3M -- 1.35 1.35 1.35 1.35 1.35 Vanax A -- 0.15 0.15 0.15 0.15 0.15
VULTAC 5 -- 0.45 0.45 0.45 0.45 0.45 Durax -- 0.05 0.05 0.05 0.05
0.05 Polysulfide -- -- 1 1 1 1 Silicone -- 4.00 4.00 -- -- --
Rubber CPE -- -- 4.00 -- -- Hypalon -- -- -- 4.00 -- Fluoroelas. --
-- -- -- 4.00 RPA 170 C, 0.2.degree. arc, 60 cpm Max S' inlb 4.57
5.66 5.82 6.41 7.61 5.94 T.sub.S.5 0.64 0.46 0.44 0.41 0.35 0.46
T.sub.C90 7.46 4.36 4.69 4.89 3.88 4.63 Surface Tacky MOD SLI NO NO
MOD Surface: TACKY - very sticky; SLI = only slightly tacky; NO =
no tack; MOD = moderate tack
[0290] Surface:
[0291] TACKY--very sticky; SLI=only slightly tacky;. NO=no tack,
MOD=moderate tack
Example 21
In this Example we Show More Data for Curing the "Difficult to Cure
by Peroxide" highly Filled EPDM Formulations
[0292] In this particular formulation we use more carbon black (a
total of 180 parts) than EPDM rubber (used at a total of 100
parts). The use of the novel blend of peroxide, MBM and select
sulfur accelerators (listed as blend 1) provides a good surface
(run 2) when crosslinking in the presence of air, compared to the
standard peroxide (run 1) and at a lower overall curative
concentration. Again this is a highly filled EPDM formulation which
is very difficult to cure with organic peroxides. One skilled in
the art would not consider such a formulation for use with organic
peroxides, and would only use sulfur vulcanization cure
systems.
[0293] When crosslinking in the presence of hot air, further
improvement in surface cure was attained when using a small amount
of a chlorosulfonated polyethylene (Hypalon--from Dupont Dow) as a
novel additive to be used in the practice of our invention (run 3).
Further improvements in surface cure were noted when the blend of
polysulfide and Hypalon (run 4) were used as novel polymeric
additives in the practice of our invention.
22TABLE 21 Use of Chlorosulfonated Polyethylene and Polysulfide as
novel additives to crosslink a highly filled EPDM in the presence
of air to provide a tack-free surface using organic peroxides 1 2 3
4 DCKEP 15.00 -- 4.00 4.00 Blend 1 -- 10.00 8.00 8.00 AgeRite MA --
-- -- -- MTBHQ -- -- -- -- *Hypalon 40 -- -- 5.00 5.00 Polysulfide
-- -- -- 1.00 RPA cure at 170 C, 0.2 degree arc, 60 cpm Max S'
in-lbs 5.77 6.75 8.72 8.32 T.sub.S.5 min 0.42 0.53 0.35 0.35
T.sub.C90 min 6.07 4.41 3.46 3.69 Hot Air Cure at 400 F. for 8 to
12 minutes Surface Tack: Tacky Slight Very Slight None Rubber
Formulation Blend 1 4570 EPDM 80* DCKE 60% 4770 EPDM 20 MBM 27% N
660 120 Vanax A 3% N 990 60 VULTAC 5 9% LW 150 80 Durax 1% Stearic
acid 0.8 *a small portion of Hypalon (amount listed above) replaces
an equal amount of 4570 EPDM
Example 22
In this Example we Illustrate Several New Chemical and Polymeric
Additives which are Useful in Developing a Peroxide Formulation for
Crosslinking elastomers in the presence of Hot Air
[0294] In particular these are: Vanax 6H
(N-cyclohexyl-N'-phenyl-p-phenyle- nediamine) CAS 101-87-1, an
antiozonants for diene based polymers; Polysulfide (PTE) and
silicone rubber (VMQ).
[0295] Vanax 6H (R. T. Vanderbilt) 10
[0296] We show that the antiozonant serves as a replacement for the
sulfur containing compounds in the practice of this invention. The
invention contemplates such substitution of this antioxidant and
those of similar structure as full equivalents to the other
compounds included within the scope of the definition of compound
(B). In addition polysulfide (PTE) also serves this same
purpose.
[0297] Lastly, by an unexpected blend of two polymers PTE and VMQ
as polymeric additives one can produce a tack-free surface with
peroxides in the presence of hot air. Note no bismaleimide and
sulfur compounds or antiozonant additives were used.
23TABLE 22 Crosslinking Royalene 501 EPDM Use of polysulfide and
silicone rubber as well as the use of an anitiozonant
N-cyclohexyl-N'-phenyl-p-phenylene diamine (V anax 6H). Basic
Elastomer Formulation: 100 parts of Royalene 501 EPDM, 70 parts
N550 carbon black, 30 parts N-990 carbon black, 20 parts Sunpar
LW150 oil, 1 part zinc oxide, 1 part stearic acid Additive 1 2 3 4
5 6 7 DCP 40KE 7.5 4.6 4.6 4.6 4.6 4.6 7.5 MBM -- 2.2 2.2 2.2 2.2
2.2 -- Vanax A -- -- 0.7 -- -- -- -- Vanax 6H -- -- -- 0.7 -- -- --
Polysulfide -- -- -- -- 0.7 2.2 3.0 VMQ -- -- -- -- -- -- 7.0
Crosslinking using an MDR 2000E 175.degree. C., 1.degree. arc
M.sub.H (in-lbs) 35.6 37.8 40.1 36.1 33.3 36.0 27.7 T.sub.S0.4
(min) 0.3 0.26 0.29 0.34 0.26 0.26 0.30 T.sub.C90 (min) 4.39 2.98
3.46 3.63 2.51 2.89 3.98 Hot Air Cure at 400.degree. F. (8 to 12
minutes) Tacky Yes Yes No No No No No Surface (tested hot)
Example 23
Examples of Using Various other Dialkyl Type Peroxides
[0298] In this example we crosslink a metallocene based EPDM
(Nordel IP 4640) using different organic peroxides. Note that in
each case the peroxide without the various additives, was not able
to provide a2tack-free surface when crosslinking the EPDM elastomer
formulation in the presence of hot air. The peroxides listed in
Table 23 are:
24 Peroxide Chemical Name Lup 101
2,5-dimethyl-2,5-Di(t-butylperoxy)hexane MTBPP
4-methyl-4-(t-butylperoxy)-2-pentanone Luperox F/R
Di(t-butylperoxy) diisopropyl benzene DAPDIB Di(t-amylperoxy)
diisopropyl benzene
[0299] This example is provided to illustrate that other dialkyl
peroxides can be used in the practice of this invention, besides
the most commonly used dialkyl peroxide, dicumyl peroxide, which
was extensively evaluated in the previous examples.
25TABLE 23 Use of other Dialkyl Peroxides for Hot Air Cure
Crosslinking of Nordel IP 4640 EPDM 1 2 3 4 5 6 7 8 Nordel 4640 100
100 100 100 100 100 100 100 N330 60 60 60 60 60 60 60 60 N990 40 40
40 40 40 40 40 40 LW150 35 35 35 35 35 35 35 35 ZnO 1 1 1 1 1 1 1 1
Stearic Acid 1 1 1 1 1 1 1 1 Lup 101 92.8% 3.60 2.20 -- -- -- -- --
-- MTBPP 84.4% -- -- 4.90 3.00 -- -- -- -- Luperox F/R -- -- -- --
3.60 2.20 -- -- DAPDIB 79.7% -- -- -- -- -- -- 4.90 3.00 Vanax MBM
-- 2.40 -- 2.40 -- 2.40 -- 2.40 Sulfads -- 0.32 -- 0.32 -- 0.32 --
0.32 Vultac 5 -- 0.32 -- 0.32 -- 0.32 -- 0.32 Unads -- 0.16 -- 0.16
-- 0.16 -- 0.16 Crosslinking using an MDR2000E @ 200.degree. C.
1.degree. arc M.sub.H 27.4 30.9 21.1 30.7 32.7 34.9 26.3 29.9
T.sub.S.4 0.18 0.24 0.19 0.24 0.17 0.22 0.17 0.21 T.sub.C90 1.07
0.76 1.16 0.85 0.91 0.72 0.79 0.58 HOT AIR Cure @400.degree. F.:
Surface Tack Rating Tacky Surface? Yes No Yes No Yes No Yes No
(Tested hot) Peroxide Chemical Name Lup 101
2,5-dimethyl-2,5-Di(t-but- ylperoxy)hexane MTBPP
4-methyl-4-(t-butylperoxy)-2-pentanone Luperox F/R
Di(t-butylperoxy) diisopropyl benzene DAPDIB Di(t-amylperoxy)
diisopropyl benzene
[0300] One of skill in the art will also recognize that th
compositions of the inventions may also be formulated as
masterbatches for convenience in handling and compounding into the
polymers for crosslinking in the presence of molecular oxygen.
Typical masterbatch carriers include, for example, microcrystalline
wax, polycaprolactone, Ethylene propylene diene monomers polymers
(EPDM), ethylene propylene monomers polymers (EPM), ethylene vinyl
alcohol polymer (EVA), polyethylene (PE), or mixtures thereof.
[0301] The subject matter which applicants regard as their
invention is particularly pointed out and distinctly claimed as
follows:
* * * * *