U.S. patent number RE31,103 [Application Number 06/197,660] was granted by the patent office on 1982-12-14 for crosslinking agent for polymers and wire construction utilizing crosslinked polymers.
This patent grant is currently assigned to Raychem Corporation. Invention is credited to Paul B. Germeraad, Alan J. Gotcher, Viktors Jansons.
United States Patent |
RE31,103 |
Gotcher , et al. |
December 14, 1982 |
Crosslinking agent for polymers and wire construction utilizing
crosslinked polymers
Abstract
A composition comprising a polymer having a processing
temperature of at least 200.degree. and from about 0.1 wt % up to
about 30 wt % of crosslinking agent said crosslinking agent
comprising a compound of the formula ##STR1## wherein X is hydrogen
and Y is ##STR2## and X and Y are substituents on adjacent carbon
atoms of A or wherein X and Y together form the imide ring system
##STR3## which is joined to A on adjacent carbons atoms, thereof,
wherein A is an aromatic, heteroaromatic, alicyclic, or
heterocyclic system or an open chain aliphatic moiety, where R is
vinyl, allyl, methallyl or propargyl and wherein R' is hydrogen,
C.sub.1 to C.sub.12 alkyl or R and mixtures thereof. Compounds per
se and articles manufactured from the above-indicated polymer
composition are also taught.
Inventors: |
Gotcher; Alan J. (Saratoga,
CA), Germeraad; Paul B. (Palo Alto, CA), Jansons;
Viktors (Los Gatos, CA) |
Assignee: |
Raychem Corporation (Menlo
Park, CA)
|
Family
ID: |
26893033 |
Appl.
No.: |
06/197,660 |
Filed: |
October 16, 1980 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
759473 |
Jan 14, 1977 |
04121001 |
Oct 17, 1978 |
|
|
Current U.S.
Class: |
428/35.7;
174/110FC; 174/110R; 428/36.9; 428/36.92; 428/379; 428/421;
522/117; 522/137; 525/375; 525/386; 525/460; 525/535 |
Current CPC
Class: |
C07D
207/452 (20130101); C07D 209/48 (20130101); C07D
251/34 (20130101); C07D 487/04 (20130101); C07D
487/08 (20130101); G03F 7/031 (20130101); C08K
5/3417 (20130101); Y10T 428/1352 (20150115); Y10T
428/3154 (20150401); Y10T 428/294 (20150115); Y10T
428/139 (20150115); Y10T 428/1397 (20150115) |
Current International
Class: |
C07D
209/00 (20060101); C07D 207/00 (20060101); C07D
207/452 (20060101); C07D 251/00 (20060101); C07D
209/48 (20060101); C07D 251/34 (20060101); C07D
487/08 (20060101); C07D 487/04 (20060101); C07D
487/00 (20060101); C08K 5/3417 (20060101); C08K
5/00 (20060101); G03F 7/031 (20060101); B32B
015/00 (); H01B 007/00 (); C08F 002/46 () |
Field of
Search: |
;174/11R,11FC
;204/159.17,159.18,159.19,159.2,159.15 ;428/35,36,379,421,422,411
;525/329,330,331,334,375,386,397,418,420,437,439,460,462,471,535 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Chemical Abstracts 73, 36098j, 1970. .
Chemical Abstracts 78, 135892h, 1973..
|
Primary Examiner: Dixon, Jr.; William R.
Attorney, Agent or Firm: Lyon & Lyon
Claims
We claim:
1. A composition comprising an organic crosslinkable polymer having
a melt processing temperature of at least 200.degree. and from
about 0.1 wt % up to about 30 wt % of crosslinking agent said
crosslinking agent comprising a compound of the formula ##STR24##
wherein X is hydrogen and Y is ##STR25## and X and Y are
substituents on adjacent carbon atoms of A or wherein X and Y
together form the imide ring system ##STR26## which is joined to A
on adjacent carbons atoms, thereof, wherein A is an aromatic,
heteroaromatic, alicyclic, or heterocyclic system or an open chain
aliphatic moiety, where R is vinyl, allyl, methallyl or propargyl
and wherein R' is hydrogen, C.sub.1 to C.sub.12 alkyl or R, or a
mixture of said compounds.
2. A composition in accordance with claim 1 wherein said polymer
comprises a fluorocarbon polymer .
3. A composition in accordance with claim 2 wherein said polymer
comprises ethylene-tetrafluoroethylene copolymers and terpolymers,
ethylenechlorotrifluoroethylene copolymers and terpolymer
vinylidene fluoride polymers, tetrafluoroethylene-vinylidene
fluoride copolymers, tetrafluoroethylene-hexafluoropropylene
copolymers and vinylidene fluoride-hexafluoropropylene copolymers
and mixtures thereof.
4. A composition in accordance with claim 1 wherein said polymer
comprises a polyarylene ether ketone, polyarylene ether sulfone,
polyphenylene oxide, polycarbonate, polyoxybenzoate, polyamide,
polybutylene terephthalate; polyurethane ester block copolymer,
poluurethane ether block copolymer, polyesterether block copolymers
or mixtures thereof.
5. A composition in accordance with claim 1 wherein said
composition contains from about 5 to about 15 weight percent
crosslinking agent.
6. The composition of claim 1 wherein the crosslinking agent is
N,N'-di(2-propenyl)-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic-2,3:5,
6-diimide.
7. The composition of claim 1 wherein the crosslinking agent is
N,N'-di-(2-methyl-2-propenyl)-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxy
lic-2,3:5,6-diimide.
8. The composition of claim 1 wherein the crosslinking agent is
N,N'-di-(2-propynyl)-bicyclo[2.2.2oct-7-ene-2,3,5,6-tetracarboxylic-2,3:5,
6-diimide.
9. The composition of claim 1 wherein the crosslinking agent is
N,N'-diethenyl-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic-2,3:5,6-dii
mide.
10. The composition of claim 1 wherein the crosslinking agent is
N,N'-di-(2-propenyl)-1,2,4,5-benzenetetracarboxylic-1,2:4,5-diimide.
11. The composition of claim 1 wherein the crosslinking agent is
2-methyl-2-propenyl
2-(2-methyl-2-propenyl)-2,3-dihydro-1,3-dioxo-1H-isoindole-5-carboxylate.
12. The composition of claim 1 wherein the crosslinking agent is
2-propenyl
2(2-propenyl)-2,3-dihydro-1,3-dioxo-1H-isoindole-5-carboxylate.
13. A composition in accordance with claim 1 wherein said
crosslinking agent contains about 5 to 50 wt percent of a compound
selected from the group consisting of triallylcyanurate,
triallylisocyanurate, triallyl trimellitate, triallyl trimesate,
tetraallyl pyromellitate, diallyl-4-4'-oxydibenzoate,
diallyl-4,4'-sulfonyldibenzoate and 2-propenyl
2,3-dihydro-3-[4-(2-propenoxycarbonyl)phenyl]-1,1,3-trimethyl-1H-indene-5-
carboxylate.
14. The composition of claim 13 wherein said crosslinking agent
comprises a mixture of
N,N'-di-(2-propenyl)-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic-2,2:5
,6-diimide and .[.1,3,5-tri-(2-propenyl)-s-triazine-2,4,6(1H, 3H,
5H)-trione..]. .Iadd.triallylisocyanurate..Iaddend.
15. The composition of claim 13 wherein said crosslinking agent
comprises a mixture of
N,N'-di(2-propenyl)-1,2,4,5-benzenetetracarboxylic-2,3:5,6-diimide
and .[.1,3,5-tri-(2-propenyl)-s-triazine-2,4,6(1H, 3H,
5H)-trione..]. .Iadd.triallylisocyanurate. .Iaddend.
16. The composition of claim 13 wherein said the crosslinking agent
comprises a mixture of 2-propenyl
2,3-dihydro-1,3-dioxo-1-H-2-(2-propenyl)-isoindole-5-carboxylate
and .[.1,3,5tri-(2-propenyl)-s-triazine-2,4,6(1H, 3H,
5H)-trione..]. .Iadd.triallyisocyanurate. .Iaddend.
17. A formed article comprising an electrical conductor having as
an insulating coating thereover the product of the process of
crosslinking the composition of claim 1.
18. An article in accordance with claim 17 wherein said article has
been subjected to ionizing radiation at a dose level of about 1 to
40 megarads to cause said crosslinking.
19. A shaped article comprising the composition of claim 1 in
elongate substantially tubular form.
20. The article of claim 19 wherein the composition has been
subjected to ionizing radiation at a dose level of about 1 to 40
megarads.
21. An injection molded hollow shaped article comprising the
composition of claim 1.
22. The article of claim 21 wherein the composition has been
subjected to ionizing radiation at a dose level of about 1 to 40
megarads.
23. A substantially planar extruded shaped article comprising the
composition of claim 1.
24. The article of claim 23 wherein the composition has been
subjected to ionizing radiation at a dose level of about 1 to 40
megarads.
25. The product of the process of crosslinking the composition of
claim 1.
26. The product of claim 25 wherein said crosslinking is by
exposure to ionizing radiation at a dose level of from about 1 to
40 megarads. .Iadd. 27. A composition according to claim 1 wherein
said composition contains from 1-10 weight percent crosslinking
agent. .Iaddend.
Description
BACKGROUND OF THE INVENTION
A large number of high melting fluorocarbon polymers possess a
combination of mechanical, dielectric and chemical properties which
make them particularly useful as electrical insulation materials.
In order to maximize utilization of these fluorocarbon polymers
under high temperature or overload conditions, crosslinking of the
fluorocarbon polymers is required. Crosslinking of high temperature
resistant fluorocarbon polymers is particularly difficult since the
polymers are normally processed at temperatures which are too high
for most chemical crosslinking agents. As an alternative to
chemical crosslinking, irradiation crosslinking of these polymers
has been tried. However, to achieve a suitable level of
crosslinking without degradation, it is necessary to add a
crosslinking agent or coreactant to the fluorocarbon polymers, a
so-called "prorad".
The prior art teaches the existence of a variety of prorads. See
for example U.S. Pat. Nos. 3,970,770, 3,985,716, 3,911,192,
3,894,118, 3,840,619, 3,763,222 and 3,995,091.
However, all of these prior art crosslinking agents suffer from one
or more shortcomings in comparison with the crosslinking agents of
the present invention.
DESCRIPTION OF THE INVENTION
This invention relates to certain imide containing compounds which
are novel compositions of matter. This invention also relates to
polymeric compositions comprising high processing temperature
polymers, especially fluorocarbon polymers, containing one or more
imide containing crosslinking agents (prorads) including inter alia
the aforesaid novel compositions of matter. This invention also
relates to wire insulated with, and cable jacketed with, the
aforesaid polymeric compositions in crosslinked form.
The prorads of the present invention are particularly useful for
enhancing the crosslinking of fluorocarbon polymers which are
processed, that is, extruded and/or molded at temperatures of
200.degree. or greater, especially 250.degree. or greater.
Additionally, the crosslinking agents of the present invention
improve the elevated temperature mechanical properties of the
crosslinked polymers, especially elevated temperature elongation,
abrasion and deformation resistance. Fluorocarbon polymers with
which the crosslinking agents of the present invention may
advantageously be utilized include homopolymers, copolymers and
terpolymers such as ethylene-tetrafluoroethylene copolymers,
ethylene-chlorotrifluoroethylene copolymers, polyvinylidene
fluoride homopolymers, tetrafluoroethylenevinylidene fluoride
copolymers, tetrafluoroethylene-hexafluoropropylene copolymers,
vinylidene fluoride hexafluoropropylene copolymers, vinylidene
fluoride hexafluoropropylene tetrafluoroethylene terpolymers and
the like. Mixtures of any of the above enumerated polymers may also
be advantageously crosslinked using the crosslinking agents of the
present invention.
The crosslinking agents of the present invention are suitably
present in the polymer in an amount ranging from 0.1 to 30 weight
percent, .Iadd.for example, from about 5-15 weight percent,
.Iaddend.but will normally be employed in the range of 1-10 percent
by weight. The polymer or polymers and crosslinking agents are
blended, that is processed in the melt at an elevated temperature
for a period of time sufficient to melt-process, but insufficient
to crosslink. This mixture is then formed as desired, cooled to
ambient temperature, and the formed cooled article irradiated to
effect crosslinking of the polymer.
The crosslinking agents of the present invention can, if desired,
be utilized in conjunction with one or more of the crosslinking
agents taught by the prior art, especially those taught in U.S.
Pat. Nos. 3,970,770, 3,985,716, 3,911,192, 3,894,118, 3,840,619,
3,763,222 and 3,995,091.
When a composition, according to the present invention, is employed
as an insulation coating, as for example, on wire, the composition
is extruded by conventional techniques directly onto the surface of
the conductor, preferably as a relatively thin wall coating.
Thereafter, the extruded composition, while on the surface of the
conductor, is subjected to a dose of radiation sufficient to
provide the desired degree of crosslinking without substantially
degrading the material. It has been determined that a radiation
dose in the range of about 1-40 megarads, and preferably about 3-20
megarads, most preferably 5-10 megarads, is suitable to provide the
desired degree of crosslinking.
Additional adjuvants such as fillers including silica and carbon
black, stabilizers, antioxidants, coloring agents and additional
plasticizers and/or crosslinking agents may suitably be
incorporated into the fluorocarbon polymers in addition to the
crosslinking agents of the present invention.
The crosslinking agents of the present invention comprise compounds
of the following generic formula ##STR4## wherein X=hydrogen and Y=
##STR5## on adjacent carbons of A or wherein X and Y together form
the ring system shown below: ##STR6## which is joined to moiety A
on adjacent carbon atoms thereof, wherein R is vinyl, allyl,
methallyl, or propargyl, where R' is hydrogen, C.sub.1 to C.sub.12
alkyl or R and wherein A is an aromatic, heteroaromatic, alicyclic,
or heterocyclic ring system or an open chain aliphatic moiety. The
following list is representative of a few starting materials
suitable to provide moiety A:
1,2,4,5-benzenetetracarboxylic acid
ethylene tetracarboxylic acid
ethane-1,1,2,2-tetracarboxylic acid
decahydronaphthalene-1,4,5,8-tetracarboxylic acid
4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic
acid
cyclopentane-1,2,3,4-tetracarboxylic acid
pyrrolidine-2,3,4,5-tetracarboxylic acid
pyrazine-2,3,5,6-tetracarboxylic acid
butane-1,2,3,4-tetracarboxylic acid
cyclobutane-1,2,3,4-tetracarboxylic acid
thiophene-2,3,4,5-tetracarboxylic acid
furan-1,2,3,4-tetracarboxylic acid
cyclohexane-1,2,3,4,5,6-hexacarboxylic acid
cyclohexa-3,5-diene-1,2-dicarboxylic acid
bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid
1,4-dimethyl-7,8-diphenyl-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic
acid
1,4,7,8-tetrachloro-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic
acid
1,8-dimethyl-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic
acid
3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene-succinic
dianhydride
thianthrenetetracarboxylic acid-5,5,10,10-tetroxide
1,3-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride
1,2,4-benzenetricarboxylic anhydride
The preferred compounds of the present invention have the following
structural formulae: ##STR7##
Compound I wherein R is allyl .Iadd.,
N,N'-di(2-propenyl)-1,2,4,5-benzenetetracarboxylic-1,2:4,5-diimide,
.Iaddend.is taught by the prior art (Chem. Abstr. 73, 36098,
Akiyama et al., Japan 70 09,547) as coreacting with
N-ethylmaleimide to afford a thermoset resin; similarly, compound
III wherein R is allyl .Iadd., 2-propenyl 2,3-dihydro-1,3-dioxo-1
H-2-(2-propenyl)-isoindole-5-carboxylate, .Iaddend.has been
reported to be useful as a monomer for the synthesis of heat
resistant resins (Chem. Abstr. 78, 135895b, Hara, Japan 73 05,586).
All the other compounds comprehended by the formulae I through VIII
are believed to be unknown to the art. .Iadd.Compound II, R=allyl
is
N,N'-di(2-propenyl)-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic-2,3:5,
6-diimide; Compound II, R=methallyl is
N,N'-di-(2-methyl-2-propenyl)-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxy
lic-2,3:5,6-diimide; Compound II, R=propargyl is
N,N'-di(2-propynyl)-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic-2,3:5,
6-diimide; Compound II, R=vinyl is
N,N'-diethenyl-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic-2,3:5,6-dii
mide; Compound III, R=methallyl is 2-methyl-2-propenyl
2-(2-methyl-2-propenyl)-2,3-dihydro-1,3-dioxo-1H-isoindole-5-carboxylate.
.Iaddend.
Although, as heretofore indicated, a wide variety of prima facie
suitable radiation crosslinking agents (prorads) for fluorocarbon
polymers are known to the prior art, all such known materials pose
problems when the polymer must be processed at a high temperature,
e.g., greater than 200.degree., especially greater than
250.degree., prior to being subjected to irradiation.
Conventionally, the polymer plus prorad plus other additives (e.g.,
fillers, antioxidants, etc.) are blended together a homogeneously
as possible and then formed, as by molding or extrusion such as
extrusion coating of conductor to form a jacketed wire. The formed
article, e.g., the jacketed wire, is then irradiated to crosslink
the polymer insulation. Unfortunately, some of the most desirable
polymers from a general property standpoint require relatively high
temperatures (e.g., in excess of 250.degree.) for effective
extrusion or molding. Subjecting most of the prior art prorads to
such temperatures causes severe problems, i.e., much of the prorad
is lost through evaporation and/or the prorad undergoes thermally
induced homopolymerization or degradation. In either case the
prorad is no longer available to effect radiation induced
crosslinking of the polymer. Also, where thermally induced
homopolymerization has occurred, this prorad homopolymer is present
as an undesirable and frequently marginally stable impurity. The
compounds of the present invention are uniquely superior in having
both a low volatility and a limited tendency to homopolymerize when
subjected to temperatures even in excess of 250.degree.. They are,
however, highly effective as crosslinking agents for fluorocarbon
polymers when subjected to ionizing radiation. The compounds of the
present invention are therefore particularly useful for high
melting fluorocarbon polymers such as polyvinylidene fluoride
(e.g., Pennwalt Kynar), ethylene chlorotrifluoroethylene copolymers
(e.g., Allied Chemical Halar), and ethylenetetrafluoroethylene
copolymers (e.g., duPont Tefzel).
The crosslinking agents of the present invention are made by
efficient and economical synthetic routes:
To form compounds I and II the dianhydride of moiety A, that is the
compounds ##STR8## when A is a benzene or bicyclooctene ring
system, respectively, are reacted with at least twice as many moles
of RNH.sub.2 wherein R is allyl, methallyl, or propargyl. Compounds
I and II are diimides and the preparation thereof is by synthetic
methods generally known, per se. That is, the reaction of
dianhydrides with two or more molar equivalents of an amine to form
a diimide is well known.
The preparation of Compounds III, IV, V and VI is effected by a
similar reaction sequence. The compounds ##STR9## are reacted with
RNH.sub.2, preferably in molar excess, to afford (using for
illustrative purposes A=phenyl): ##STR10##
This intermediate is further reacted with, for example, PCl.sub.5
or SOCl.sub.2 to afford the corresponding acid chloride ##STR11##
which is then reacted with at least one mole of ROH or RR'NH to
afford: ##STR12## Where it is desired that R be a vinyl group it is
not possible to prepare the compounds of the invention directly
using ROH or RNH.sub.2 since these compounds are not stable.
Alternative synthetic methods are available such as formation of
the unsubstituted vinyl ester anhydride which is then reacted with
allylamine to give the desired ester imide. A similar synthetic
sequence is suitable for other A moieties.
Of course, mixtures of amines and/or alcohols and/or anhydrides can
be used to form the compounds of the present invention, or instead
or likewise, mixtures of all or any of said compounds can be
incorporated into the fluorocarbon polymer to serve as the
crosslinking agent.
Although the previous description of this invention has been stated
in terms of crosslinking fluorocarbon polymers, it should be
understood that the compounds of the present invention are also
useful to effect or enhance the radiation crosslinking of other
polymers including halogenated polymers such as polyvinyl chloride
and polyvinylidene chloride, polyolefins such as polyethylene,
polypropylene and ethylene-propylene copolymers, copolymers and
terpolymers of ethylene with other olefinic monomers such as vinyl
acetate and ethyl acrylate, high performance polymers such as
polyarylene ether ketone (e.g., Raychem Stilan), polyarylene ether
sulfone (e.g., Union Carbide Udel or Radel), polyphenylene oxide
(e.g., General Electric PPO), polyesters such as polyoxybenzoate
(e.g., Carborundum Exxel) and polybutylene terephthalate (e.g.,
Eastman Tenite), polyamides (e.g., Dynamit Nobel Trogamid),
polycarbonates (e.g., General Electric Lexan), and high performance
thermoplastic elastomers such as polyester ether block copolymers
(e.g., duPont Hytrel) and polyurethane ether block copolymers. The
conditions of radiation and amount of prorad used in such polymers
are substantially the same as for the fluorocarbon polymers. It
should be noted that the compounds of the present invention can
under certain circumstances be advantageously used in conjunction
with other prorads to effect or enhance the radiation crosslinking
of polymers. In addition, the compounds of the present invention,
mixtures thereof, or mixtures thereof with from about 5 to 50 wt %
of other prior art prorads, have been found to plasticize polymers,
especially at elevated temperatures such as the polymer processing
temperature. It is apparent to those skilled in the art that the
degree of plasticization is dependent upon the amount of prorad
introduced into the polymer formulation, that is, higher levels of
prorad impart substantially greater levels of plasticization to the
polymer as to allow a reduction to be made in the processing
temperature of the polymer composition. These compositions can
thereafter be crosslinked to impart superior mechanical properties
to the end product. .Iadd.
Among suitable prior art prorads useful in such mixtures may be
mentioned triallylcyanurate (Compound B, Table I),
triallylisocyanurate (Compound D, Table I), i.e.,
1,3,5-tri-(2-propenyl)-s-triazine-2,4,6(1H, 3H, 5H)-trione,
triallyl trimellitate (Compound E, Table I), triallyl trimesate
(Compound F, Table I), tetraallyl pyromellitate, diallyl-4,4'l
-oxydibenzoate (Compound G, Table I),
diallyl-4,4'-sulfonyldibenzoate (Compound A, Table I) and
2-propenyl 2,3-dihydro-3-[4-(2-propenoxycarbonyl)
phenyl]-1,2,3-trimethyl-1H-indene-5 -carboxylate.
Suitable mixtures include mixtures of triallylisocyanurate with
N,N'-di-(2-propenyl)-bicyclo[2.2.2.]oct-7-ene-2,3,5,6-tetracarboxylic-2,3:
5,6-diimide (Compound II, R=alkyl);
N,N'-di-(2-propenyl)-1,2,4,5-benzenetetracarboxylic-2,3:5,6-diimide,
or 2-propenyl
2,3-dihydro-1,3-dioxo-1H-2-(2-propenyl)-isoindole-5-carboxylate
(Compound III, R=allyl). .Iaddend.
This invention is further illustrated by examples which serve to
illustrate specific details, aspects and embodiments of the
invention. All parts are by weight unless otherwise indicated. All
temperatures throughout the specification and claims are in degrees
centigrade. All tests unless otherwise indicated were carried out
at 23.degree.. The term melting point or crystalline melting point
is defined as that temperature at which the last traces of
crystallinity as measured by differential scanning calorimetry is
observed. The polymer processing temperature as that term is used
herein is defined as a temperature above the crystalline melting
point of any polymeric component at which temperature the polymer
melt has a viscosity of not more than 2.times.10.sup.6 poise. The
majority of polymeric components useful in the practice of the
present invention, however, have melt viscosities of less than
10.sup.5 poise at the processing temperature. The term wire can
connote either bared conductor or jacketed conductor as is apparent
from the context.
Certain of the tests utilized are first described.
MODULUS MEASUREMENT
To determine the relative level of crosslinking in these polymeric
resins, a modulus test conducted at 320.degree. was used because
conventional methods to determine crosslinking levels by gel
analysis require the polymer to be soluble. In the case of ethylene
tetrafluoroethylene copolymers, there are no known solvents below
200.degree.. This modulus test measures the stress required to
elongate a resin by 100% at a temperature of 320.degree.. High
values obtained from this test indicate increasing resistance to
elastic deformation or development of a significant amount of a
three-dimensional network. The 320.degree. temperature was chosen
as it is intermediate between the decomposition temperature
(.about.350.degree.) and the crystalline melting point
(.about.280.degree.) for ethylene tetrafluoroethylene copolymers.
The modulus measurement expressed as the M.sub.100 value can be
calcuated by: ##EQU1## Should the sample rupture prior to 100%
elongation, the M.sub.100 is calculated using the equation:
##EQU2##
CUT THROUGH TEST
A sample of the wire is placed between an anvil and a 90.degree.
included angle wedge shaped weighted knife blade having a 5 mil
flat at the knife edge. The anvil is hung by means of a stirrup
from the load cell of an Instron tensile tester and the knife blade
mounted on the movable bar of said tensile tester also by a stirrup
so that the blade edge lies transversely over the wire specimen.
The knife edge is advanced towards the wire conductor at a speed of
0.2 in per minute. Failure occurs when the knife edge contacts the
conductor. The resulting electrical contact causes the tensile
tester to stop advancing the blade. The peak reading from the load
cell is taken to be the cut through resistance of the wire. This
cut through test is not to be confused with a cut through test
identified by Bowers et al., IEC Product R&D 1, 89 (1962). The
latter test simulates an accelerated creep test in which the
viscoelastic flow of a polymeric resin is altered by radiation
crosslinking. Further information pertaining to enhancement of
polymer creep resistance through crosslinking can be found in
"Mechanical Properties of Polymers and Composites," by L. E.
Nielsen, Vol. 1, p. 87, 1974.
EXAMPLE I
To a stirred slurry of 49.6 parts of
bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic-2,3:5,6-dianhydride
in 200 parts of glacial acetic acid was added dropwise with cooling
(ice bath) 26.2 parts of allylamine over a period of 5-10 min. The
reaction mixture was gradually heated and held at reflux for 30
min, resulting in a clear amber solution. Upon cooling, a
crystalline material precipitated, was collected by filtration and
was recrystallized from toluene to give 58.5 parts (90%) of
colorless crystals: mp 202.degree.-3.degree.. Thinlayer
chromatography indicated one compound (SiO.sub.2 /CHCl.sub.3 as
eluent). Nuclear magnetic resonance and infrared spectral analysis
confirmed the formation of the desired diimide
.Iadd.N,N'-di(2-propenyl)-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic-
2,3:5,6-diimide (Compound II, R=allyl).Iaddend.: nmr:
.delta.(CDCl.sub.3) ppm, 2.9-3.2 (multiplet, 4H,
--CH--CH--C.dbd.O), 3.6-3.9 (multiplet, 2H, --CH--CH-- C.dbd.O),
4.05 (doublet, 4H, --CH.sub.2 --CH.dbd.CH.sub.2). 4.9-6.0
(multiplet, 6H, --CH.sub.2 --CH.dbd.CH.sub.2), 6.15 (triplet, 2H,
--CH--CH.dbd.CH--CH--); ir: (KBr)cm.sup.-1, 3130 (w) and 3020 (m)
[unsat. CH], 1770 (s) and 1705 (vs) [imide--C.dbd.O].
EXAMPLE II
A sample of
N,N'-di-(2-propenyl)-1,2,4,6-benzenetetracarboxylic-1,2:4,5-diimide
(.Iadd.Compound I, R=ally) .Iaddend.was prepared by a reaction
analogous to that of Example I from
1,2,4,5-benzenetetracarboxylic-1,2:4,5-dianhydride and allylamine
(93% yield): colorless crystals, mp 222.5.degree.-223.5.degree..
The material was shown to be one compound by thinlayer
chromatography. Its identity was established by nuclear magnetic
resonance and infrared spectral analysis: nmr: .delta.(CDCL.sub.3)
ppm, 4.35 (doublet, 4H, --N--CH.sub.2 --CH.dbd.CH.sub.2), 5.0-6.3
(multiplet, 6H, --CH.sub.2 --CH.dbd.CH.sub.2), 8.25 (singlet, 2H,
aromatic hydrogen); ir:(KBr) cm.sup.-1, 3120 (m, aromatic H), 2950
(w, aliphatic H), 1765 (s) and 1710 (vs) [imide--C.dbd.O].
EXAMPLE III
A sample of 2-propenyl
2,3-dihydro-1,3-dioxo-1H-2-(2-propenyl)isoindole-5-carboxylate
(Compound III, R-allyl) was prepared in a three-step sequence:
1,2,4-benzenetricarboxylic anhydride (57.6 parts) was treated in
the same manner as in Example I with excess allylamine (37.7 part)
to give
2,3-dihydro-1,3-dioxo-1H-2-(2-propenyl)isoindole-5-carboxylic
acid(47.4 parts); colorless crystals, mp 155.degree.-7.degree.. A
sample of 27.3 parts of this material was refluxed in 50 parts of
thionyl chloride which contained approximately 0.5 parts of
dimethylformamide. After a reaction time of 1 hour excess thionyl
chloride was removed by distillation to give a crystalline residue
of 2,3-dihydro-1,3-dioxo-1H-2-(2-propenyl)-isoindole-5-carboxylic
acid chloride. An aliquot of 5.0 parts of this material was
dissolved in 10 parts of pyridine and 1.3 parts of allyl alcohol
(excess) was added dropwise with stirring at room temperature. The
resulting mixture was briefly heated to reflux, then cooled to room
temperature followed by dilution with water to give a crystalline
precipitate. Recrystallization first from aqueous acetic acid and
then from methanol produced 3.6 parts of colorless crystals: mp
65.degree.-6.degree.. Thinlayer chromatography (SiO.sub.2
/CHCl.sub.3 as eluent) indicated one single component. Nuclear
magnetic resonance and infrared spectral analysis confirmed the
identity of the desired 2-propenyl
2,3-dihydro-1,3-dioxo-1H-2-(2-propenyl)isoindole-5-carboxylate;
nmr: .delta.(CDCl.sub.3) ppm. 4.30 (doublet, 2H, N--CH.sub.2
--CH.dbd.CH.sub.2), 4.90 (doublet, 2H, O--CH.sub.2
--CH.dbd.CH.sub.2), 5.0-6.5 (multiplet, 6H, --CH.sub.2
--CH.dbd.CH.sub.2), 7.85 (doublet, 1 H, aromatic hydrogen), 8.1-8.4
(multiplet, 2H aromatic hydrogen); ir (KBr) cm.sup.-1, 3120 (w,
aromatic H), 2950 (w, aliphatic H), 1770 (m) 1718 (vs) [imide and
ester --C.dbd.O], 1280 (s, aromatic ester--C--O).
EXAMPLE IV
A sample of
2,3-dihydro-1,3-dioxo-1H-2-(2-propenyl)isoindole-5-carboxylic acid
chloride (5 parts), whose preparation was described in Example III,
was dissolved in 10 ml of pyridine, and 2.2 parts of diallylamine
was added dropwise with stirring while cooling to maintain a
reaction temperature of approximately 10.degree.-15.degree.. The
resulting reaction mixture was heated briefly to reflux, and then
cooled and poured into water. An oil separated which was taken up
in ether and washed sequentially with aqueous hydrochloric acid,
aqueous potassium carbonate, and water. The ethereal solution was
then freed of colored impurities by treatment with charcoal and
alumina, followed by evaporation to dryness to give 5.5 parts of a
colorless oil. The material consisted of one compound as shown by
thinlayer chromatography (SiO.sub.2 /CHCl.sub.3 as eluent). Nuclear
magnetic resonance and infrared spectral analysis confirmed the
identity of the desired
2,3-dihydro-1,3-dioxo-1H-2-(2-propenyl)isoindole-5-(N,N-di-2-propenyl)carb
oxamide (.Iadd.Compound V, R.dbd.allyl) .Iaddend.; nmr:
.delta.(CDCl.sub.3) ppm, 3.7-4.3 (multiplet, 4H,
--N,N-amide--CH.sub.2 --CH.dbd.CH.sub.2), 4.30 (doublet, 2H,
N-imide-CH.sub.2 --CH.dbd.CH.sub.2), 5.0-6.3 (multiplet, 6H,
N,N,N-imide amide--CH.sub.2 --CH.dbd.CH.sub.2), 7.7-8.0 (multiplet,
2-3H, aromatic hydrogen); ir:(neat) cm.sup.-1, 1630-1640 (s)
[secondary amide--C.dbd.O], 1710 (s) and 1770 (m)
[imide--C.dbd.O].
EXAMPLE V
A sample of ethenyl
2,3-dihydro-1,3-dioxo-1H-(2-propenyl)isoindole-5-carboxylate
(.Iadd.Compound III, for N-R, R.dbd.allyl, for O-R, R.dbd.vinyl)
.Iaddend.was prepared in two steps:
4-carboethenoxy-1,2-benzenedicarboxylic anhydride was synthesized
according to the procedure given in Organic Syntheses, Coll. Vol.
IV, p. 977, from vinyl acetate and 1,2,4-benzenetricarboxylic
anhydride by effecting a mercuric acetate catalyzed ester
interchange. A pale yellow crystalline material was obtained: mp
123.degree.-127.degree.;nmr:.delta.(CDCL.sub.3) ppm, 4.85 (quartet,
1H) and 5.20 (quartet, 1 H)[--CH.dbd.CH.sub.2 ], 7.48 (quartet, 1
H, --CH.dbd.CH.sub.2), 7.9-8.7 (multiplet, 3 H, aromatic hydrogen):
ir; (Nujol) cm.sup.-1, 1645 (w) [CHR.dbd.CH.sub.2 stretch], 1730
(s) [ester --C.dbd.O], 1775 (s) and 1845 (m) [anhydride --C.dbd.O].
The above compound (21.8 parts) was dissolved in 175 parts of
glacial acetic acid, and 5.7 parts of allylamine was added dropwise
with stirring at room temperature. The reaction exotherm was
controlled by cooling with water. After completing amine addition
the reaction solution was concentrated to a volume of 125 parts by
distillation of acetic acid. The resultant concentrate was allowed
to cool to room temperature. A crystalline, colorless precipitate
formed which was collected by filtration. Recrystallization from
heptane produced 13.1 parts of colorless needles (mp
91.5.degree.-93.0.degree.). Thinlayer chromatography indicated one
compound and a trace of non-moving impurity. A sample of 6.2 parts
of this material was further purified by treatment with charcoal
and alumina in chloroform solution. This process, after solvent
removal, produced 6.0 parts of colorless crystals which consisted
of one compound as shown by thinlayer chromatography (SiO.sub.2
/CHCl.sub.3 as eluent). Nuclear magnetic resonance and infrared
spectral analysis confirmed the identity of the desired ethenyl
2,3-dihydro-1,3-dioxo-1 H-(2-propenyl)isoindole-5-carboxylate; nmr:
.delta.(CDCl.sub.3) ppm, 4.30 (doublet, 2H, --N--imide--CH.sub.2
--CH.dbd.CH.sub.2), 4.6-5.1 (multiplet, 2H, --O--CH.dbd.CH.sub.2),
5.2-6.2 (multiplet, 3H, --N--imide--CH.sub.2 --CH.dbd.CH.sub.2),
7.38 (quartet, 1 H, --O--CH.dbd.CH.sub.2), 7.85 (doublet, 1 H,
aromatic H) 8.1-8.5 (multiplet 2H, aromatic H); ir:(Nujol)
cm.sup.-1, 1645 (m) [CHR.dbd.CH.sub.2 stretch], 1720 (s) [vinyl
ester --C.dbd.O], 1735 (s) and 1770 (m) [imide --C.dbd.O].
EXAMPLE VI
As previously indicated, the compounds of the present invention
possess a combination of properties which make them uniquely
superior to prior art prorads. This and the following examples
illustrate some of these advantages such as higher
homopolymerization temperatures and lower volatility without
comprising prorad response to ionizing radiation or compatibility
with polymeric resins.
The temperature at which a variety of reported prior art
fluorocarbon prorads, and also compounds according to the present
invention commence thermally induced homopolymerization, was
evaluated by differential scanning calorimetry. In all cases, the
compounds were tested in a nitrogen atmosphere at a heating rate of
20.degree./minute from 50.degree. to 400.degree.. Results are
reported in Table I.
Polymerization at 250.degree. or below drastically reduces the
usefulness of the prorad since exposure to temperatures above
250.degree. is required to process many of the most useful
fluorocarbon polymers. As is apparent from Table I, only three of
the prior art compounds, viz., Compounds F, G and H had
polymerization initiation temperatures above 250.degree.. These
results indicate that most prior art compounds, e.g., Compounds
A-E, undergo significant homopolymerization during processing. This
causes a significant reduction of crosslinking enhancement and
leads to incorporation of undesirable prorad-homopolymer into the
fluorocarbon host polymer.
TABLE I
__________________________________________________________________________
Homopolymerization Temperatures of Selected Prorads Compound
Structure Polymerization
__________________________________________________________________________
Temp.,.degree. ##STR13## 210 B ##STR14## 220 C ##STR15## 230 D
##STR16## 250 E ##STR17## 250 F ##STR18## 260 G ##STR19## 260 H
##STR20## 280 I ##STR21## 360 II ##STR22## 330 III ##STR23## 260
__________________________________________________________________________
EXAMPLE VII
The effectiveness of a prorad is dependent on its concentration in
the host polymer during irradiation. Prorads of high volatility are
expected to be lost, at least in part, during melt processing due
to evaporation. To illustrate this point a variety of known prorads
and several of the compounds of the instant invention were compared
on the basis of volatility using thermogravimetric analysis at a
heating rate of 20.degree./minute under a nitrogen atmosphere. The
results are shown in Table II. Examination of these data reveals
that the prior art compounds A, C, G, and H have volatility
comparable to compounds of the instant invention, while all other
prior art compounds manifest excessive volatility at 250.degree..
However, these results are far from conclusive since prorad loss
can result from homopolymerization and evaporation. Table III takes
this factor into account by analyzing weight loss below the
homopolymerization temperature. As is apparent from the data, the
prorads of the present invention again show excellent results.
However, under these experimental conditions which measure merely
evaporative loss, only two of the known prorads, i.e. compounds A
and H, demonstrate the comparably low volatility of the prorads of
the instant invention, while the other prior art prorads show a
significantly greater relative weight loss, by a factor of three or
more, under identical conditions.
TABLE II ______________________________________ Volatility of
Selected Porads by Thermal Gravimetric Analysis.sup.1 Weight % loss
at Compound 200.degree. 250.degree. 300.degree.
______________________________________ A 0 1 4 B 15 91 100 C 2 5 12
D 22 95 100 E 3 14 54 F 2 7 37 G 1 5 24 H 0 2 7 I 0 4 23 II 0 1 6
______________________________________ .sup.1 Heating rate of
200.degree./minute, N.sub.2 atmosphere
TABLE III ______________________________________ Volatility of
Selected Prorads by Isothermal Weight Loss.sup.1 Weight % loss
after exposure time (min) Compound 5 10 20 30
______________________________________ A 0.0 0.0 0.1 0.2 B 4.3 12.2
27.2 41.3 C 1.7 2.8 3.8 4.4 D 11.3 27.2 56.7 87.0 E 1.2 3.1 6.9
10.9 F 0.8 1.6 2.8 4.2 G 1.0 1.6 3.3 3.5 H 0.1 0.3 0.7 1.1 I 0.1
0.6 0.9 1.1 II 0.0 0.0 0.0 0.0
______________________________________ .sup.1 Temperature =
175.degree., N.sub.2 atmosphere
EXAMPLE VIII
Examination of the simultaneous effect of volatility and
homopolymerization can be made by processing a standard formulation
containing various prorads and comparing the resultant extrudates.
The processability of prior art prorads is compared with prorads of
the instant invention using a 3/4 inch Brabender extruder, to
produce a thin wall (10 mil) Tefzel (duPont,
ethylenetetrafluoroethylene copolymer) insulation on 20 AWG tin
plated copper conductor. The results are given in Table IV.
As is apparent from this Table, only the prorads of the instant
invention provide a commercially viable product. Prior art prorads
each demonstrate a degree after processing product discoloration,
porosity, gelation, and surface imperfections. Each of these
drawbacks magnifies the difficulty of extruding the thin wall wire
insulation required of a high performance product.
TABLE IV ______________________________________ Processing
Comparison of Several Prorads in a Standard Formulation Extrusion
Temp. Profile Extruded Insulation Properties Com- Zone Zone Zone
Surface In- pound 1 2 3 Head Color Appearance tegrity
______________________________________ B 265 310 330 330 tan v.
rough foamed D 265 310 330 330 tan v. rough foamed F 245 295 330
340 tan rough foamed G 265 310 335 345 off lumps good white H 240
300 340 370 off lumps good white I 240 300 340 380 white excellent
good II 240 300 340 370 white excellent good III 265 300 340 370
white good good ______________________________________ 4.0 Wt. %
prorad concentration in Tefzel fluoropolymer for all samples at
start of processing.
EXAMPLE IX
Each of the previous examples delineates parameters which influence
the performance of a prorad containing polymer composition when
subjected to thermal processing and subsequent ionizing radiation
in order to effect crosslinking. The ultimate choice of a prorad is
dictated by a combined consideration of processing behavior and end
product performance. The significant overall advantages accruing
from the use of prorads of the instant invention over those of the
prior art was demonstrated by conducting appropriate test
extrusions and product evaluations. Identical polymer formulations
containing none or 5% of a prior art prorad or 5% of a prorad of
the instant invention, were compared as a wire product after
extrusion from a 3/4 inch Brabender extruder to produce a thin wall
(10 mil) insulation on 20 AWG tin plated copper conductor, followed
by irradiation to 12 Mrads and annealing at 150.degree. for 1 hour.
These wire insulations were than subjected to identical analyses
for comparison. The results are provided in Table V. Examination of
these data clearly shows the advantages of the prorads of the
instant invention, as demonstrated by superior processing behavior
and significantly improved wire insulation properties. Comparison
of the cut through resistance at room temperature and at elevated
temperature shows an improvement greater than 50% over the best of
the prior art prorad containing wire compositions.
TABLE V
__________________________________________________________________________
Processing and Performance Evaluation of Prorad Formulations
Crosslinking Ultimate Cut Through Density Elongation Resistance
Compound Tp.sup.1 Volatility.sup.2 Appearance M.sub.100, psi %
25.degree. 150.degree.
__________________________________________________________________________
None N/A N/A Smooth, clear melts 160 24 3.9 D 250 50 Badly foamed E
250 11 Badly foamed Extrudate integrity was inadequate F 260 4
Foamed for testing Uneven, contained H 280 1 gel particles 97 102
29 4.1 I 360 1 Smooth, yellow 590 100 50 6.5 II 330 0 Smooth, white
220 130 42 6.3
__________________________________________________________________________
.sup.1 Polymerization temperature, .sup.2 Volatility at 175.degree.
after 30 minutes, % weight loss.
* * * * *