U.S. patent number RE30,322 [Application Number 05/969,935] was granted by the patent office on 1980-07-01 for novel elastomeric graft copolymers.
This patent grant is currently assigned to E. I. Du Pont de Nemours and Company. Invention is credited to Clarence F. Hammer, Harold K. Sinclair.
United States Patent |
RE30,322 |
Hammer , et al. |
* July 1, 1980 |
**Please see images for:
( Certificate of Correction ) ** |
Novel elastomeric graft copolymers
Abstract
6-Nylons and 12-nylons having primary amino end-groups and an
average degree of polymerization of about 5-60 are grafted onto
elastomeric trunk polymers having anhydride groups, vicinal
carboxylic groups, or carboxylic groups adjacent to alkoxycarbonyl
groups by heating a mixture of the nylon and the trunk polymer,
preferably under high shear conditions for about 1 minute or less
to 30 minutes or more above the melting temperature of the nylon.
The resulting elastomeric graft polymers are suitable for
fabricating into a variety of articles, such as, for example, wire
jacketing, hose, belts, seals, gaskets, and low pressure tires.
Inventors: |
Hammer; Clarence F.
(Wilmington, DE), Sinclair; Harold K. (Louisville, KY) |
Assignee: |
E. I. Du Pont de Nemours and
Company (Wilmington, DE)
|
[*] Notice: |
The portion of the term of this patent
subsequent to August 3, 1993 has been disclaimed. |
Family
ID: |
27061158 |
Appl.
No.: |
05/969,935 |
Filed: |
December 15, 1978 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
523465 |
Nov 13, 1974 |
04017557 |
Apr 12, 1977 |
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Current U.S.
Class: |
525/183;
525/178 |
Current CPC
Class: |
C08G
81/028 (20130101) |
Current International
Class: |
C08G
81/02 (20060101); C08G 81/00 (20060101); C08L
077/00 () |
Field of
Search: |
;525/183,178 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1074948 |
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Jul 1967 |
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GB |
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1368628 |
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Oct 1974 |
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GB |
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Primary Examiner: Danison; Walter C.
Claims
We claim:
1. An elastomeric, thermoplastic graft copolymer consisting
essentially of
A. an elastomeric trunk copolymer derived from at least two
monomers, at least one of said monomers providing amine-reactive
sites selected from the class consisting of an anhydride group, a
vicinal pair of carboxylic groups, and a carboxylic group adjacent
to an alkoxy-, phenoxy-, napthoxy-, substituted phenoxy-, or
substituted naphthoxycarbonyl group, where the alkyl of the
alkoxycarbonyl group has 1-10 carbon atoms, and the substituents of
substituted phenoxycarbonyl and naphthoxycarbonyl groups can be a
C.sub.1 -C.sub.10 alkyl, halogen, or a C.sub.1 -C.sub.10 alkoxy
group; at least one of said monomers containing no amine-reactive
sites and none of said monomers containing hydroxyl or amino
groups; and
B. a side chain polymer derived from a short chain polyamide
represented by the formula ##STR8## where Z is ##STR9## R.sup.1 and
R.sup.2 being independently selected from hydrogen, a C.sub.1
-C.sub.18 alkyl, benzyl, and C.sub.5 -C.sub.6 cycloalkyl; or taken
together, being --(CH.sub.2).sub.4 --, --(CH.sub.2).sub.5 --,
--(CH.sub.2).sub.2 --O--(CH.sub.2).sub.2 --, or ##STR10## where
R.sup.3 is a C.sub.1 -C.sub.6 alkyl; with the proviso that only one
of R.sup.1 or R.sup.2 can be hydrogen;
m is 5 and 11; and
x is a positive number having an average value of 5-60;
said side chain polymer being attached to said trunk copolymer
through amide or imide linkages resulting from a reaction of the
terminal primary amino group of said short chain polyamide with the
amine-reactive sites of said trunk copolymer;
the proportion of said elastomeric trunk copolymer in the graft
copolymer being about 45-85 weight percent.
2. A graft copolymer of claim 1 wherein m is 5.
3. A graft copolymer of claim 2 wherein R.sup.1 is hydrogen and
R.sup.2 is octadecyl.
4. A graft copolymer of claim 2 wherein R.sup.1 is hydrogen and
R.sup.2 is octyl.
5. A graft copolymer of claim 1 wherein m is 11.
6. A graft copolymer of claim 5 wherein R.sup.1 is hydrogen and
R.sup.2 is octyl.
7. A graft copolymer of claim 1 wherein the weight proportion of
the trunk copolymer is about 64.5-74%.
8. A graft copolymer of claim 1 wherein the weight proportion of
the trunk polymer is about 52.5-67%.
9. A graft copolymer of claim 1 wherein the trunk polymer is a
copolymer of an active site monomer selected from maleic anhydride,
maleic acid, fumaric acid, and monoesters of maleic or fumaric
acids with alcohols having up to about 20 carbon atoms with at
least one monomer selected from .alpha.-olefins; conjugated or
nonconjugated dienes; styrene, and its ring-substituted
derivatives; acrylic and methacrylic acids, esters, and nitriles;
vinyl esters; and vinyl ethers.
10. A graft copolymer of claim 9 wherein the trunk polymer is a
copolymer of ethylene, methyl acrylate, and monoethylmaleate.
11. A graft copolymer of claim 9 wherein the trunk polymer is a
copolymer of ethylene, vinyl acetate and maleic anhydride.
12. A graft copolymer of claim 9 wherein the trunk polymer is a
copolymer of ethylene, ethyl acrylate, allyl acrylate, and maleic
anhydride.
13. A graft copolymer of claim 1 wherein the trunk polymer is an
ethylene/.alpha.-olefin/diene monomer (EODM) polymer, having
grafted thereon at least one of maleic anhydride and ethyl hydrogen
maleate active sites.
14. A graft copolymer of claim 12 wherein the EODM polymer is an
ethylene/propylene/diene monomer (EPDM) polymer.
15. A graft copolymer of claim 13 wherein the EPDM polymer is an
ethylene/propylene/1,4-hexadiene polymer.
Description
BACKGROUND OF THE INVENTION
This invention relates to novel thermoplastic, elastomeric
polymeric materials formed by grafting short chain 6-nylons or
12-nylons onto rubbery trunk polymers.
Most elastomers can be molded or extruded into various shapes. The
fabricated articles may include, for example, automotive trim,
bumper inserts, and hoses. Usually, these elastomers have low
strength and must be crosslinked after being shaped into the
desired article. The curing step usually requires compounding with
suitable agents such as sulfur, peroxides, and the like, before
shaping. The thermal sensitivity of the compounded curable
compositions may cause premature curing ("scorch") and loss of
plasticity. Radiation cures, which do not involve compounding, are
generally only effective with thin cross sections; degradation may
compete with crosslinking. Furthermore, cured scrap and cured
shaped articles which have defects are not conveniently reused.
Accordingly, it would be desirable to have thermoplastic elastomers
which require no cure and can be shaped repeatedly by heating to
give articles having satisfactory strength and dimensional
stability at the temperatures prevailing during their use. Blends
and grafts of polymers are known in the art to give thermoplastic
products which often have improved properties.
Tutorskii et al., Journal Polymer Sc. 61, 97-106 (1962) reports
grafting of .epsilon.-caprolactam onto carboxylated
butadiene-styrene rubbers by heating the rubber and the lactam
above 200.degree. C. in the presence of boron trifluoride.
Chapman et al., Journal Polymer Sc. 34, 319-335 (1959) report the
polymerization of .epsilon.-caprolactam at elevated temperatures in
the presence of a copolymer of styrene with methyl acrylate,
acrylic acid, or maleic anhydride. Gelling was observed in several
instances, especially with styrene/maleic anhydride copolymers.
U.S. Pat. No. 3,484,403 describes certain hot melt adhesive and
coating compositions based on blends of polyamides with grafts of
unsaturated dicarboxylic acids or their anhydrides on polyolefin
backbone.
U.S. Pat. No. 3,261,885 discloses block-graft copolymers obtained
by subjecting to high shear conditions at 50.degree.-350.degree. C.
a mixture of C.sub.2 -C.sub.4 olefin or styrene copolymers with up
to 50 weight percent of another unsaturated monomer with various
synthetic linear polyamides in the presence of free radical
generators.
Yurkevich et al., Khimicheskie Volokna No. 3, 11-13 (1971) (1972,
Consultants Bureau's English translation) reports experiments with
graft copolymers of polycaproamide (6-nylon) with vinyl monomers,
such as acrylonitrile, styrene, acrylic acid, and various acrylic
esters. While no experimental details are given, it appears that
the vinyl monomers were grafted onto polycaproamide. The resulting
products were examined for possible use in melt spinning of
fibers.
U.S. Pat. No. 3,676,400 discloses melt extrusion of mixtures of
certain amino-terminated polyamides having molecular weights of at
least 2000, and preferably 10,000-40,000, with copolymers of
2-monoolefins and unsaturated mono- or dicarboxylic acids.
None of the prior art suggests grafting of amino-terminated 6- or
12-nylons on rubbery materials to produce thermoplastic elastomers
of improved mechanical properties.
SUMMARY OF THE INVENTION
According to this invention, there is provided a class of novel
thermoplastic, elastomeric compositions, which are made by grafting
short chain primary amino-terminated 6-nylons or 12-nylons onto
uncured elastomeric trunk polymers having reactive sites such as
anhydride, adjacent carboxyl and alkoxy carbonyl, or two adjacent
carboxy groups. These graft copolymers can be readily shaped and
molded at temperatures above the melting point of the nylon
component; when cooled to temperatures below 100.degree. C., they
display greatly enhanced strength relative to that of cured trunk
polymers.
For the purpose of the present invention, the term "6-nylon" means
an NH.sub.2 -terminated linear polymer of .epsilon.-caprolactam.
The term "12-nylon" means an NH.sub.2 -terminated linear polymer of
.omega.-laurolactam. Suitable short chain 6- or 12-nylons have an
average degree of polymerization of about 5-60 and contain no
primary or secondary amino groups other than one terminal NH.sub.2
group.
In the resulting graft copolymers of the present invention the
polyamide branches are believed to be attached to the trunk through
imide or amide linkages. An imide can be represented, for example,
by the following Formula (1) ##STR1## wherein
the wavy lines represent the trunk copolymer;
Z is ##STR2## or --OH,
R.sup.1 and R.sup.2 being independently selected from hydrogen, a
C.sub.1 -C.sub.18 alkyl, benzyl, and a C.sub.5 -C.sub.6 cycloalkyl;
or, taken together, being --(CH.sub.2).sub.4 --, --(CH.sub.2).sub.5
--, --(CH.sub.2).sub.2 --O--(CH.sub.2).sub.2 --, or ##STR3## where
R.sup.3 is a C.sub.1 -C.sub.6 alkyl; with the proviso that only one
of R.sup.1 and R.sup.2 can be hydrogen;
m is 5 or 11; and
x is a positive number having an average value of about 5-60.
In addition to or instead of the amide groups, such as shown in
Formula (1), amide linkages may be present in the graft copolymer.
The amide linkages may form as intermediates in the first stage of
the grafting process or may be the predominant groups if grafting
is stopped at that stage.
DESCRIPTION OF THE INVENTION
The trunk polymers useful in the present invention are elastomeric.
As applied to the trunk polymers, the term "elastomeric" is defined
to mean that when they are crosslinked, they are capable of
recovering from large deformations quickly and forcibly. Free from
diluents, the crosslinked trunk polymers retract within one minute
to less than 1.5 times their original lengths after being stretched
at 18.degree.-29.degree. C. to twice their lengths and held for one
minute before release. However, these trunk polymers are used in
the process of this invention in uncured state. The graft
copolymers of this invention are elastomeric, as defined above for
the trunk copolymers, without being subjected to vulcanization or
curing. Grafting of polyamide side chains on an uncured trunk
polymer results in an elastomeric graft copolymer.
The uncured trunk polymers may carry additional functional groups
such as, for example, carboxyl, alkoxycarbonyl, alkoxyl, and cyano.
Hydroxyl or amino groups, however, are unsuitable because they can
interact with the graft sites to form thermostable crosslinks
causing a loss of the desired thermoplasticity. The trunk
copolymers contain, on a number-average basis, about 300 to 50,000
(preferably 1,000 to 5,000) chain atoms and about one to 50
amine-reactive sites per 1000 chain atoms of the trunk copolymer.
The side-chain polymer will, in general, be shorter than the trunk
copolymer, ranging in length from about 25 to 1,000 chain atoms,
preferably about 30 to 300 chain atoms. The trunk polymers must be
sufficiently stable to withstand heating during the grafting step
and the subsequent processing into shaped articles. Such polymers
usually are copolymers of the active site-containing monomer with
at least one other monomer, for example, various .alpha.-olefins
such as ethylene, propylene, 1-butene; dienes such as butadiene,
isoprene, 1,3-hexadiene, 1,4-hexadiene, and norbornadiene; styrene,
and its ring-substituted derivatives; acrylic and methacrylic
acids, esters and nitriles; vinyl esters such as vinyl acetate and
butyrate; vinyl ethers, vinyl sulfides, and the like.
Representative trunk copolymers can be made by copolymerizing the
site-containing monomer with such other monomers as, for example,
ethylene and an alkyl acrylate; ethyl or butyl acrylate; ethylene
and vinyl acetate; ethylene and acrylonitrile; and ethylene and
methyl vinyl ether.
The amine-reactive sites on the trunk copolymers are provided by
monomers which are either copolymerized during the preparation of
the trunk copolymer or are grafted onto a previously existing
polymer.
Copolymerization of the monomer providing the amine-reactive site
will be possible when all the monomers are polymerizable by
conventional free radical catalysis. Ethylene, alkyl acrylates,
conjugated dienes, styrene, vinyl ether, vinyl sulfides,
acrylonitrile, vinyl esters, acrylic acid, methacrylic acid, and
the like, are examples of such comonomers.
Free radical-polymerizable monomers, which can be incorporated into
the trunk copolymer to provide the amine-reactive sites, frequently
have the formulae ##STR4## where X and Y are independently selected
from H, Cl, C.sub.1 -C.sub.8 alkyl, and phenyl; with the proviso
that one of X and Y must be H; and W is H, C.sub.1 -C.sub.10 alkyl,
phenyl, naphthyl, or substituted phenyl or naphthyl where the
substituents are C.sub.1 -C.sub.10 alkyl, halogen, or C.sub.1
-C.sub.10 alkoxy groups. Other possible monomers, which are not
represented by either formula (2) or formula (3), are itaconic
acid, its anhydride, and monoesters.
Compounds representative of formula (2) include maleic anhydride
and citraconic anhydride. Compounds representative of formula (3)
include maleic acid, citraconic acid, fumaric acid, mesaconic acid,
and monoesters of maleic and fumaric acids, including the methyl,
ethyl, isopropyl, propyl, butyl, tert-butyl, amyl, isoamyl, hexyl,
octyl, decyl, phenyl, 1-naphthyl, 2-naphthyl, 2-methylphenyl,
2-ethylphenyl, 2,5-dimethylphenyl, 4-isopropylphenyl,
4-butylphenyl, 3,5-dimethyl-3-propylphenyl, 3-decylphenyl,
4-tetradecylphenyl, 4-hexadecylphenyl, 4-octadecylphenyl,
2-chlorophenyl, 4-methoxyphenyl, 4-bromophenyl,
2-chloro-1-naphthyl, 4-chloro-1-naphthyl, 6-chloro-1-naphthyl,
7,8-dichloro-1-napthyl, 4-bromo-1-naphthyl, 7-chloro-2-naphthyl,
4-methyl-1-naphthyl, and 1-propyl-2-naphthyl esters.
Suitable free-radical polymerization initiators include organic
peroxides, for example, lauryl peroxide, and di-t-butyl peroxide;
peresters, such as t-butyl peracetate and t-butyl peroxypivalate;
and azo compounds, such as azobisisobutyronitrile. The
copolymerization is carried out most advantageously in a pressure
reactor at a temperature of 90.degree.-250.degree. C. and a
pressure of 1600-2200 atm. The polymerization temperature is
preferably maintained at about 145.degree. C. and the pressure at
1800-2000 atm. Usually, the polymerization process is continuous,
the monomer, optionally a solvent such as benzene, and the
initiator being introduced at a controlled rate, and the reaction
product being continuously removed. A stirred autoclave such as
described in U.S. Pat. No. 2,897,183 to Christl et al. can be
used.
A representative trunk copolymer is a random copolymer of ethylene,
methyl acrylate, and from 0.0025 to 0.077 moles/100 grams of
polymer of a monoethyl maleate, each 100 grams of copolymer having
about 0.64-0.80 moles of (--CO.sub.2 --) units. Such copolymers may
have, for example, compositions such as the following:
______________________________________ Mole % Monoethyl Ethylene
Methyl Acrylate Maleate ______________________________________ 71.2
28.7 0.1 57.8 42.1 0.1 74.4 22.0 3.6 61.4 34.4 4.2
______________________________________
Another representative trunk copolymer is an alternating copolymer
having repeating units consisting essentially of --A--B--, where B
represents ethylene units and A represents units selected from at
least one C.sub.1 -C.sub.8 alkyl acrylate, and an acrylic cure-site
monomer (2) or (3) (described above). The copolymerization is done
in solution at -10.degree. to about 200.degree. C. in the presence
of a free radical initiator and BF.sub.3 at pressures sufficient to
keep the BF.sub.3 complexed with the alkyl acrylate (generally 10
psig to 10,000 psig).
Conventional ethylene/.alpha.-olefin/diene monomer (EODM)
copolymers, and especially EPDM (ethylene/propylene/diene monomer)
copolymers, also can be used as the trunk polymers, provided an
active site is introduced therein. These copolymers are prepared in
the presence of Ziegler (or coordination) catalysts, which are
combinations of transition metal compounds (usually vanadium or
titanium compounds such as VOCl.sub.3, VCl.sub.4, vanadium
trisacetylacetonate, and titanium tetrachloride) and Group I-II
organometallic reducing agents (such as alkylaluminum chlorides and
bromides, lithium aluminum tetraalkyls, aluminum trialkyls). EPDM
rubber is made by copolymerizing ethylene and propylene with at
least one nonconjugated hydrocarbon diene (such as, for example,
1,4-hexadiene, 5-propenyl-2-norbornene, 5-ethylidene-2-norbornene,
5-methylene-2-norbornene, or dicyclopentadiene) as described in
U.S. Pat. Nos. 2,933,480 to Gresham & Hunt; 3,000,866 to
Tarney; 3,093,620 to Gladding; 3,093,621 to Gladding et al.;
3,211,709 to Adamek et al.; and 3,151,173 to Nyce. One of the
double bonds is usually substantially less reactive than the other;
incorporation of the diene then leads to a monomer unit having the
less reactive double bond in the side-chain. After the copolymer
has been formed, active site monomers (2) or (3) (described above)
can be grafted to the EPDM by thermal addition to the unsaturated
side-chains. A typical trunk copolymer can be represented by the
following formula (4), which illustrates the case of a graft of
maleic anhydride on an ethylene/.alpha.-olefin/1,4-hexadiene
copolymer. Wavy lines represent the polymer chain. ##STR5## The
hydrocarbon copolymer may also include small amounts of units of a
direactive nonconjugated diene as in the
ethylene/propylene/1,4-hexadiene/2,5-norbornadiene copolymer (and
others) described in U.S. Pat. No. 3,819,591 to Campbell and
Thurn.
Propylene is normally selected as the .alpha.-monoolefin in
preparing side-chain unsaturated elastomeric ethylene copolymers
because of its availability and low cost. Higher
.alpha.-monoolefins (C.sub.4 -C.sub.18) also are useful; 1-butene,
-hexene, and 1-dodecene are examples.
The graft addition of amine-reactive monomers described above
(e.g., maleic anhydride and ethyl hydrogen maleate) is conveniently
accomplished by heating a blend of the copolymer and amine-reactive
monomer within a range of about 225.degree.-400.degree. C. A
process of this type is described in detail in the copending
application of Stanley William Caywood, Jr., Ser. No. 322,360,
filed Jan. 10, 1973, and now allowed in part. Internal mixers or
extruders are suitable. Exposure to maleic anhydride vapor should
be minimized on account of its toxicity and potential for causing
severe eye damage. Unchanged maleic anhydride can be extracted from
the graft product with water or separated by dissolving the product
in hexane (which will not solubilize maleic anhydride).
The proportion of the active sites in the trunk polymer can vary
within a broad range. It is closely related to the desired
proportion of the 6- or 12-nylon in the final graft copolymer. For
any given proportion of nylon grafts, there must be available a
sufficient number of graft sites. The required number of graft
sites also is related to the degree of polymerization of the
starting 6- or 12-nylon. To achieve the same final proportion of
grafted nylon, one may choose a trunk polymer having fewer graft
sites and a 6- or 12-nylon having a relatively high degree of
polymerization (for example, 45) or a trunk polymer having more
graft sites and a 6- or 12-nylon having a relatively low degree of
polymerization (for example, 7). These relationships are very
straightforward and can be readily established by a skilled chemist
or chemical engineer.
Many elastomeric polymers could be used in principle as the trunk
polymers, but some polymers are not attractive because they may
undergo undesirable side reactions. Halogenated polymers, for
example, have a tendency to thermally dehydrohalogenate.
Chlorosulfonyl groups are suitable grafting sites, but
chlorosulfonated polyethylene is not a good trunk polymer because
it does not have sufficient thermal stability. It is worth
mentioning that isolated acid groups, such as carboxylic groups,
may form quasi salt-like addition products with amino-terminated
6-nylons. Such products do not by themselves, however, have
sufficient thermal stability unless grafts also are present. Under
the usual grafting conditions, no appreciable amide formation would
occur between such carboxylic groups and the nylons.
The amino-terminated 6- or 12-nylons are prepared by thermal
polymerization of .epsilon.-caprolactam or .omega.-laurolactam
initiated by water or by amines of the formula R.sub.1 R.sub.2 NH,
where R.sub.1 and R.sub.2 have the meaning defined above in Summary
of the Invention. Representative amines include butylamine,
hexylamine, octylamine, diethylamine, dibutylamine,
cyclopentylamine, cyclohexylamine, propylamine, morpholine,
pyrrolidine, N-methylpiperazine, and piperidine. The molar ratio
range of the lactam to the amine initiator normally will be
slightly broader than the desired range of degree of polymerization
and can be about 4:1 to 65:1. It is recommended that at least about
2 weight percent of water be present for practical reaction rates;
5% is satisfactory. About three hours at 245.degree. C. are
satisfactory, but the reaction time is rather long; higher
temperatures, such as 280.degree. C., allow a shorter reaction
time.
When it is desired to prepare a carboxyl-terminated nylon, the
polymerization is initiated by water alone and is carried out in
the presence of a large amount of water, usually, about 20-50
weight percent of the starting lactam. The resulting 6- or 12-nylon
has the structure ##STR6## wherein Z is --OH and m and x have the
above-defined meaning.
The degree of polymerization of the nylon (5) can be determined by
titration of the terminal amino groups by well known methods. It is
often practical to carry out the titration in an alcoholic solution
by either the potentiometric or the conductometric method.
It is believed that under the grafting conditions the nylon reacts
with the anhydride group at the graft site, either initially
present or formed under graft conditions, to form the cyclic imide
such as that of Formula (1), above. In the preferred embodiment of
the process, the anhydride group is already present in the trunk
polymer. The next preferred is an adjacent pair of a carboxylic
group and an alkoxycarbonyl, which at higher temperature form the
anhydride, with elimination of one molecule of alcohol. A third
alternative is to use a starting trunk polymer preferably having
vicinal carboxylic groups (although 1,3-carboxylic groups allow
some grafting).
When the graft site is an adjacent pair of a carboxylic group and
an alkoxycarbonyl, these groups normally are derived from a
monoalkyl maleate, fumarate, or citraconate comonomer. Vicinal
carboxyl groups are introduced by copolymerization with fumaric,
maleic, itaconic, or citraconic acids. The size of the ester alkyl
group is at most about 20 carbon atoms. Preferred are ethyl and
methyl esters. Other esters include, for example, all isomeric
forms of propyl, butyl, hexyl, nonyl, undecyl, tetradecyl,
heptadecyl, and eicosyl.
Grafting can be accomplished in any convenient apparatus,
preferably one able to produce high shear conditions at a
temperature above the melting point of the starting nylon. Examples
include roll mills, extruders, and internal mixers having
convoluted rollers, sigma blades, and the like. Usually, the
reaction temperature will be at least about 215.degree. C. The
reaction time mainly depends on the speed of mixing because the
grafting reaction is quite rapid. The usual reaction time will be
about 1-30 minutes. Below 1 minute, adequate mixing may not be
achieved in some equipment; however, reaction times as short as,
for example, 15 seconds are possible. Above 30 minutes, no
additional grafting can be expected, while some thermal degradation
may occur. In any event, it is practical to avoid air atmosphere
during the grafting operation, for example, by maintaining a
nitrogen blanket over the reacting mass or by carrying out the
process in an extruder.
The ratio of the 6- or 12-nylon to the trunk polymer can be varied
within a rather broad range. Since it is desired to produce
elastomeric products, rather than plastics, the minimum proportion
of the elastomeric trunk polymer should be about 45 weight percent
of the final product. Above about 85 weight percent of the trunk
polymer, the mechanical properties of the graft copolymer tend to
deteriorate.
Graft copolymers having the most desirable balance of physical
properties are those in which the proportion of the 6-nylon is
about 35-55 parts per 100 parts by weight of the trunk copolymer,
the latter thus constituting about 64.5-74 weight percent of the
final graft copolymer. Graft copolymers having the highest tensile
strength contain about 50-90 parts of the 6-nylon per 100 parts by
weight of the trunk copolymer, the latter constituting about
52.5-67 weight percent of the final graft copolymer.
It is theoretically possible to graft amine-terminated 6-nylon onto
an elastomeric backbone polymer in solution, but solvents which
would dissolve nylon (mainly, phenolic solvents) are rather
inconvenient to work with. Therefore, solution grafting is less
attractive.
The progress of grafting can be followed by infrared spectroscopy.
When the starting trunk polymer contains 5-membered, cyclic
anhydride active sites, the disappearance of either one of two
characteristic absorption bands at 5.4 microns or at 5.6 microns
indicates that grafting is taking place. The proportion of the
anhydride groups in the starting trunk polymer can be determined by
forming a polymer film of known thickness and examining the
infrared spectrum of such film. It has been found experimentally
that 0.28 absorption units/mil (11 units/mm) at 5.4 microns or 2.2
absorption units/mil (87 units/mm) at 5.6 microns correspond to 10
weight percent anhydride. The absorption units are read directly
from an infrared spectrogram.
Similarly, when the starting trunk copolymer contains vicinal
carboxyl and alkoxycarbonyl groups, the characteristic infrared
absorption band lies at 5.9 microns. Assuming the vicinal carboxyl
and alkoxycarbonyl groups to be derived from ethyl hydrogen
maleate, the characteristic absorption will be 1.1 absorption
units/mil (43 units/mm) for every 10 weight percent maleate
present. Such analytical techniques would not be practical in the
case of a starting copolymer containing vicinal carboxyl groups.
However, the concentration of carboxyl groups can be readily
determined by simple titration.
The graft copolymer product can be characterized by several
techniques, which show the presence of polyamide side chains, the
degree of polymerization of the polyamide side chains, and the
chemical identity of the polyamide, to name a few. Certain physical
characteristics often are also helpful to show that a graft
copolymer has been obtained.
The presence of polyamide is shown by infrared absorption at 6.0
microns (amide carbonyl). Other useful wavelengths include 6.4
microns (--NH bending) and 3.0 microns (--NH stretching). The
proportion of polyamide is determined by Kjeldahl analysis for %
N.
The polyamide can be chemically identified by heating a sample of a
graft copolymer with a mineral acid, for example, sulfuric or
hydrochloric acids, to about 200.degree. C. or more. Under these
conditions, the polyamide chain degrades to the starting lactam.
Both .epsilon.-caprolactam and .omega.-laurolactam are volatile.
They can be isolated and identified by any convenient technique of
qualitative analysis.
Direct measurement of graft efficiency by extraction of unbound
polyamide is difficult since solvents for polyamides also attack
trunk and graft copolymers. Reactive function titration results on
graft copolymers provide no more than rough estimates of graft
efficiency.
Determination of the increase of molecular weight due to grafting
is a convenient technique. This is usually done by gel permeation
chromatography of 0.5% graft copolymer solutions in m-cresol at
100.degree. C. on porous polystyrene-packed columns.
A good indication that grafting has taken place is the torsion
modulus of the products, especially at 100.degree.-150.degree. C.
While the grafted copolymer will have a fairly high modulus (e.g.,
10.sup.7 -10.sup.8 dynes/cm..sup.2), ungrafted material will flow
in that temperature range.
Ungrafted blends of trunk copolymers and polyamides (within the
proportions capable of giving elastomeric graft copolymers) display
negligible strengths and compression set resistance, acting like
typical uncured compositions. After grafting, the strength,
clarity, hardness, compression set resistance, and solvent
resistance increase. Strength at elevated temperatures, e.g., at
100.degree. C., is significantly better than displayed by the
physical blends before grafting.
Knowing the degree of polymerization (DP) of each starting 6- or
12-nylon, it is possible to plot DP versus the peak melting point
of each resulting graft copolymer, as determined with a
differential scanning calorimeter (DSC). It has been observed that
the peak melting point increases as the DP of the polyamide side
chains increases. Such a plot can serve as a calibration curve
which can be used for the determination of the DP of the polyamide
grafts in the copolymers of the present invention.
The graft copolymers must be conditioned for testing by first
heating to 250.degree. C., then cooling at the rate of 10.degree.
C. per minute to 50.degree. C. During the test, the sample is
heated at the rate of 10.degree. C. per minute.
DSC techniques are discussed in Thermoanalytical Methods of
Investigation, by P. D. Garn, Academic Press, New York, 1965.
Another convenient and somewhat related technique for correlating
the DP of the grafted polyamide with its melting point is
differential thermal analysis (DTA). The sample also must be
preconditioned and is heated during the test at the rate of
20.degree. C. per minute. The details of the DTA technique are
described in Differential Thermal Analysis, R. C. MacKenzie,
Editor, Academic Press, New York, 1970; especially in Chapter 23,
by C. B. Murphy, dealing with polymers, Vol. I, pp. 643-671.
It is to be noted that the above techniques relying on polymer
melting point determination, DSC and DTA, can only be used for
polymers having a high degree of crystallinity. In the present
case, only the crystalline polyamide side chains will have well
defined melting points, and those will be recorded. The elastomeric
trunk polymers are usually noncrystalline at the test temperatures
and will not produce any melting point peaks on DSC or DTA graphs.
In the case of trunk copolymers containing a substantial proportion
of ethylene (for example, certain ethylene/propylene/diene monomer
copolymers having active site monomers grafted thereon), their
crystallinity may be sufficiently high to produce a distinct
melting point peak. This, however, will be well below the
temperature range of interest and thus will not interfere with the
determination.
The thermoplastic graft copolymers made by the process of this
invention can be made into a wide variety of useful shaped articles
by techniques and in equipment familiar to those skilled in the
art. Conventional casting and compression and injection molding are
suitable fabricating techniques. A reciprocating screw type
injection molding machine in which shearing provides additional
heating is the preferred apparatus; typically a machine having a
4.5 kg charge can exert a clamping pressure of 1.225 million kg.
Injection pressures of 900-1200 kg/sq.cm. and cycles times (mold
closing to mold closing) of 150 seconds can be used.
The thermoplastic elastomeric compositions of the instant invention
can be used in a wide variety of industrial applications including
wire jacketing, hose, belts, miscellaneous molded boots, seals and
gaskets; they can be also employed to make low speed, low pressure
tires for off-the-road application; and they can be melt spun to
give elastic fibers.
The preparation of representative starting trunk copolymers and
6-nylons and of the graft polymers of this invention is now
illustrated by the following examples of certain representative
embodiments thereof, wherein all parts, proportions, and
percentages are by weight unless indicated otherwise.
The determination of physical and/or chemical properties of the
starting trunk copolymers was carried out as follows:
a. inherent viscosity, deciliters per gram, was measured at
30.degree. C. on a solution of 0.1 g of polymer in 100 ml. of
chloroform, unless a different solvent is shown.
b. neutralization equivalent was determined by acid-base titration
using standard aqueous sodium hydroxide, the anhydride being
titrated as diacid,
c. Wallace plasticity at 100.degree. C. was determined according to
the following procedure:
The Wallace plasticity is a measure of the amount of flow or
deformation under load of unvulcanized elastomeric materials. The
sample to be tested is sheeted and cut into pellets having a
thickness in the range of 3.18 mm to 7.62 mm (0.125 to 0.300 inch).
The test is done with a Wallace Plastimeter, manufactured by H. W.
Wallace and Co., Ltd., London. Initially, for a 15-second period,
the test pellet is compressed to a thickness of exactly one
millimeter and heated to 100.degree. C. Then the test pellet is
subjected to a 10-kilogram load for exactly 15 seconds at
100.degree. C. The final thickness of the test piece, expressed in
units of 0.01 millimeter, is the plasticity reading.
d. melt index was measured at 190.degree. C. under a 2160 g. load -
ASTM Method D 1238-70, Condition E.
The degree of polymerization (DP) or molecular weight of the
starting 6-nylons can be readily determined by end group analysis.
The aminio end groups are determined by titration with a strong
acid, either in the presence of an indicator or by a potentiometric
orconductometric method. Acid end groups are determined by
titration with a strong base. These techniques are discussed in
Nylon Plastics, M. I. Kohan, Editor, pp. 38 and 105, John Wiley and
Sons, New York (1973), and in Encyclopedia of Polymer Science and
Technology. Vol. 10, pp. 542 and 543, John Wiley and Sons, New York
(1969).
EXAMPLES
Preparation of Trunk Copolymers
A. Preparation of Ethylene/Methyl Acrylate/Monoethyl Maleate
Copolymer
A terpolymer containing 46.6% ethylene, 50% methyl acrylate, and
3.6 weight percent monoethyl maleate and displaying a melt index of
3.6 g/10 min was prepared in a 0.72-liter stirred autoclave.
A mixture of methyl acrylate, monoethyl maleate, and benzene
(weight ratio: 68.28/2.46/29.26) was pressured to about 422 kg/sq
cm; ethylene was separately pressured to about 422 kg/sq cm.
Separate streams of this mixture (0.91 kg/hr) and ethylene (6.35
kg/hr) were joined and pressured to 1900 kg/sq cm. The resulting
feed stream then entered the autoclave. Simultaneously, a catalyst
solution, made by adding 50 ml of tert-butyl peroxypivalate to 4.5
kg of benzene was introduced at the rate of 0.00204 kg/hr to keep
the temperature at 170.degree. C. The effluent from the autoclave
passed through a let-down valve to a chamber at atmospheric
pressure where most of the residual monomers and solvent flashed
off. The ethylene/methyl acrylate/monoethyl maleate terpolymer thus
isolated was freed from the small amount of residual volatiles by
heating for 16 hours at 80.degree. C. in a nitrogen stream.
Acid-base titration indicated that 0.25 meq. of acid groups was
present per gram of terpolymer, corresponding to 3.6 weight %
monoethyl maleate in the copolymer.
B. Preparation of Ethylene/Vinyl Acetate/Maleic Anhydride
Copolymer
A terpolymer containing 60.3% ethylene, 38 weight percent vinyl
acetate, and 1.7% maleic anhydride, and displaying a melt index of
220 g/10 min was prepared at the rate of 0.68 kg/hr in a continuous
0.72-liter stirred autoclave by the following procedure. Monomers
were mixed, pressured to 1900 kg/sq cm, and fed at these rates:
______________________________________ Ethylene 4.54 kg/hr Vinyl
acetate 2.29 kg/hr Maleic anhydride 0.015 kg/hr
______________________________________
A solution of azobis(isobutyronitrile) in benzene was
simultaneously introduced at a rate sufficient to keep the reactor
temperature at 170.degree. C. (about 0.587 g/hr corresponding to
0.86 kg catalyst per 1000 kg of terpolymer). The total benzene feed
rate was 1.04 kg/hr. The terpolymer produced was isolated by a
procedure similar to that described in Example A.
C. Preparation of Ethylene/Vinyl Acetate/Maleic Anhydride
Copolymer
A terpolymer containing 65.6% ethylene, 32% vinyl acetate, and 2.4%
maleic anhydride, and displaying a melt index of 125 g/10 min was
prepared at the rate of 0.63 kg/hr in a continuous 0.72-liter
stirred autoclave by the following procedure. Monomers were mixed,
pressured to 1900 kg/sq cm and fed at these rates:
______________________________________ Ethylene 4.54 kg/hr Vinyl
acetate 1.80 kg/hr Maleic anhydride 0.0258 kg/hr
______________________________________
A solution of azobis(isobutyronitrile) in benzene was introduced
into the reactor at the same time and at a rate sufficient to keep
the reactor temperature at 170.degree. C. (about 1.00 g/hr
corresponding to 1.58 kg/1000 kg of terpolymer). The total benzene
feed rate was 0.67 kg/hr. The terpolymer produced was isolated by a
procedure similar to that described in Example A. Acid-base
titration with standard aqueous sodium hydroxide indicated that
0.49 meq of diacid derived from anhydride groups was present per
gram of terpolymer, corresponding to 2.4 weight % maleic anhydride
in the copolymer.
D.sub.(1) Preparation of Alternating Ethylene//Ethyl Acrylate/Allyl
Acrylate/Maleic Anhydride Tetrapolymer
A 7.57-liter stirred autoclave was charged under nitrogen with 4000
ml of methylene chloride, 400 grams of ethyl acrylate, 20 grams of
maleic anhydride, 1.2 grams of allyl acrylate, and 1.0 gram of
azobis(isobutyronitrile). It was then sealed, charged with 300
grams of boron trifluoride, and pressured to 21 kg/sq cm with
ethylene. The subsequent copolymerization at 25.degree. C. was
continued until pressure measurement indicated that ethylene uptake
had ceased (about two hours later). The reaction was quenched by
addition of one liter of diethyl ether. Volatiles were removed by
steam-stripping in a well-ventilated hood. The terpolymer thereby
obtained was dissolved in acetone, precipitated in water in a
blender, and oven-dried. Yield: 415 grams.
This product had about 50 mole percent ethylene units and was
slightly branched because of the use of the direactive allyl
acrylate. The polymer chain consisted principally of alternating
units -(E)-(B)-, where E is ethylene and B is selected randomly
from ethyl acrylate, allyl acrylate, and maleic anhydride.
D.sub.(2) Preparation of Alternating Ethylene//Ethyl
Acrylate/Ethylene Diacrylate/Maleic Anhydride Tetrapolymer
The procedure of D.sub.(1), above, was repeated except that 1.2
grams of ethylene diacrylate was used in place of the allyl
acrylate. Yield: 479 grams. The branched alternating tetrapolymer
obtained had about 50 mole percent of ethylene units. The polymer
chain consisted principally of alternating units -(E)-(B')-, where
E is ethylene and B' is randomly selected from ethyl acrylate,
ethylene diacrylate, and maleic anhydride.
D.sub.(3) Preparation of Alternating Ethylene/Ethyl
Acrylate/Ethylene Diacrylate/Maleic Anhydride Tetrapolymer
The procedure of D.sub.(1) above was repeated except that 0.75 gram
of ethylene diacrylate was used in place of the allyl acrylate, and
the amount of maleic anhydride was increased to 30 grams: Yield:
417 grams. The branched alternating tetrapolymer had about 50 mole
percent of ethylene units, the units being arranged -(E)-(B')-, as
in D.sub.(2). D.sub.(4) Blend of Branched Alternating
Copolymers
The branched alternating copolymers made by procedures D.sub.(1),
D.sub.(2), and D.sub.(3) were blended on a rubber roll mill. Table
I gives the properties of the blend and its components.
TABLE I ______________________________________ Parts Weight % Neut.
Eq. Copolymer in maleic Inh. Wallace meq. D Blend anhydride Visc.
Plast. g ______________________________________ (1) 397 2.5 1.91
16.8 0.52 (2) 479 3.8 1.33 15 0.77 (3) 417 3.9 1.21 15 0.80 Blend
(4) -- 3.4 1.75 14 0.70 ______________________________________
E. Preparation of Alternating Ethylene//Ethyl Acrylate/Allyl
Acrylate/Maleic Anhydride Tetrapolymer
The procedure of Part D.sub.(1) was repeated except that the
pressure of ethylene was 42.2 kg/sq cm. Yield: 233 grams. The
tetrapolymer had an inherent viscosity of 2.37 deciliters/gram, a
Wallace Plasticity of 24.4, and a neutralization equivalent of 0.49
meq/gram, corresponding to 2.4 weight % maleic anhydride in the
copolymer.
F.sub.(1), (2) Preparation of Alternating Ethylene//Ethyl
Acrylate/Allyl Acrylate/Maleic Anhydride Tetrapolymers
The procedure of Part D.sub.(1) was twice repeated except that the
amount of maleic anhydride was decreased each time to 10 grams.
Yields: 481 grams and 497 grams.
F.sub.(3) Preparation of Alternating Ethylene/Ethyl
Acrylate/Ethylene Diacrylate/Maleic Anhydride Tetrapolymer
The procedure of Part D.sub.(1) was repeated except that 0.75 gram
of ethylene diacrylate was used in place of allyl acrylate. Yield:
476 grams.
F.sub.(4) Preparation of Blends of Branched Alternating
Copolymers
A trunk copolymer composition was prepared by blending copolymers
F.sub.(1), F.sub.(2), and F.sub.(3) on a rubber roll mill. Table II
gives characteristic properties.
TABLE II ______________________________________ Parts Weight %
Neut. Eq. in maleic Inh. Wallace meq. Component Blend anhydride
Visc. Plast. g ______________________________________ F.sub.(1) 336
1.8 1.97 15.5 0.36 F.sub.(2) 292 2.1 1.78 13.3 0.42 F.sub.(3) 241
2.3 1.52 14 0.46 Blend F.sub.(4) -- 2.1 1.44 13.5 0.43
______________________________________
G. Preparation of Ethyl Acrylate/Monoethyl Fumarate Copolymer
In a 3-neck round-bottom flask, a mechanically stirred mixture of
500 ml of benzene, 100 ml of inhibited ethyl acrylate, 7.2 grams of
monoethyl fumarate, and 0.25 gram of azobis(isobutyronitrile) was
sparged with nitrogen for 30 minutes, then heated at 50.degree. C.
under a nitrogen blanket for 24 hours. The copolymer was isolated
by steam-stripping in a well-ventilated hood and dried overnight in
a nitrogen-bled vacuum oven at 70.degree. C. Conversion was 86%.
Prior to analysis and use, the copolymer was purified by
dissolution in acetone, precipitation in water in a blender, and
vacuum oven drying. Properties are given in Table III, below.
H.sub.(1), (2) preparation of Ethyl Acrylate/Maleic Anhydride
Copolymers
1. The reactor was a two-liter resin flask fitted with an agitator,
a condenser and a dropping funnel. A 710-ml charge of ethyl acetate
and 0.2 gram of benzoyl peroxide was added and stirred under
nitrogen while being heated to reflux. A mixture of 500 grams of
inhibitor-free ethyl acrylate, 10 grams of maleic anhydride, and
one gram of benzoyl peroxide was placed in the dropping funnel. A
50-ml charge of this monomer feed was added all at once to the
stirred refluxing solution in the flask; the rest was added over a
period of 3.5 hours. After additional two hours at reflux, the
reaction mixture was steam-distilled in a hood with good
ventilation to remove solvent and residual monomers. The copolymer
thus isolated was washed with water on a wash mill, partially dried
on a hot rubber roll mill, and then heated in a nitrogen bled
vacuum oven for 22 hours at 130.degree. C. to remove residual
volatiles. Yield: 448 grams.
2. The same equipment was used as in H.sub.(1) above. The ethyl
acrylate/maleic anhydride copolymer was prepared as follows. A
mixture of 500 grams of ethyl acrylate, 10 grams of maleic
anhydride, and 0.5 gram of benzoyl peroxide was added to 490 grams
of refluxing ethyl acetate over a 4-hour period. After about 85% of
this feed mixture had been introduced, 140 ml of cyclohexane and 35
ml of ethyl acetate were added. When all the feed was in, 80 ml
more of ethyl acetate were added. Reflux continued for one hour.
Heat was then removed and the mixture was allowed to stand for 36
hours. Finally, 0.5 gram of hydroquinone was added and the
copolymer was isolated by steam-stripping the volatiles in a
well-ventilated hood. Mill drying and vacuum oven drying (20 hours
at 130.degree. C.) followed. Yield: 364 grams.
Properties of the copolymers prepared as described in Section G,
H.sub.(1) and H.sub.(2) are given in Table III.
TABLE III ______________________________________ Co- Weight % poly-
Maleic monoethyl Inh. Wallace meq..sup.(a) mer Anh., % fumarate
Visc. Plast. Acidity g. ______________________________________ G --
4.3 2.32 undet'd. 30 H.sub.(1) 1.5 -- 1.24 5 31 H.sub.(2) 1.4 --
2.03 14 29 ______________________________________ .sup.(a) acidbase
titration with standard aqueous sodium hydroxide; value for
H.sub.(1) and H.sub.(2) were each 0.15 meq./g. when alcoholic
potassium hydroxide was used, proportion of maleic anhydride
calculated from sodium hydroxide values
I. Preparation of Ethyl Acrylate/Butyl Acrylate/Monoethyl Fumarate
Terpolymer
The reactor was a nitrogen-blanketed two-liter resin flask fitted
with an agitator, a condenser, and a dropping funnel.
Monomers ethyl acrylate and butyl acrylate were passed through
alumina to remove polymerization inhibitors. Then, 70 grams of the
ethyl acrylate, 70 grams of the butyl acrylate, 10.5 grams of
monoethyl fumarate, 21 grams of "Igepal Co-730"
[nonylphenoxypoly(ethylene glycol) having about 15 --O--CH.sub.2
--CH.sub.2 -- units], 1050 grams of water, and 1.0 gram of ammonium
persulfate were added to the resin flask and heated to reflux. A
mixture of 113 grams of ethyl acrylate, 113 grams of butyl
acrylate, 9.4 grams of monoethyl fumarate, and 3.8 grams of "Igepal
CO-730" was gradually introduced at a rate to keep the reaction
temperature at 89.degree. to 93.degree. C. After 1.4 hours, all the
feed had been added and stirring was becoming difficult. After
additional 20 minutes, the temperature of the reaction mixture had
risen to 96.degree. C., whereupon 0.15 gram of hydroquinone was
added, and residual monomers were removed by a 2-hour
steam-distillation in a well-ventilated hood.
Coagulated polymer was washed by chopping in a blender with water,
twice dissolved in acetone and reprecipitated in water in a
blender, then air-dried, vacuum-oven dried 3.5 hrs. at 72.degree.
C., and finally mill-dried at about 130.degree. C. Yield: 254 g.
The terpolymer produced had an inherent viscosity (chloroform,
30.degree. C.) of 1.51 deciliters/gram and an acid content of 0.24
meq/gram (titration with aqueous sodium hydroxide), or 0.23
meq/gram (titration with alcoholic potassium hydroxide). The
terpolymer had 3.3 weight % monoethyl fumarate; the remainder was
believed to be about equally divided between ethyl acrylate and
butyl acrylate.
J. Preparation of An EPDM/Maleic Anhydride Adduct
Maleic anhydride was grafted on an ethylene/propylene/1,4-hexadiene
copolymer. The ethylene/propylene/1,4-hexadiene copolymer was a
sulfur-curable elastomer haing a Mooney (ML-1+4/121.degree. C.)
viscosity of about 35 and the following monomer unit composition:
ethylene, 61.4 weight %; propylene, 32 weight %; 1,4-hexadiene, 6.6
weight %. The copolymer had about 0.5 gram mole of ethylenically
unsaturated side-chains per kilogram. Its Wallace Plasticity was
about 28 at 100.degree. C. and its inherent viscosity was about 2.0
(measured at 30.degree. C. on a solution of 0.1 gram of copolymer
in 100 milliliters of tetrachloroethylene). Copolymerization was
carried out in solution in hexane in the presence of a Ziegler
catalyst formed by mixing VCl.sub.4 and diisobutylaluminum
chloride.
A Werner and Pfleiderer 53 mm twin screw extruder was assembled by
end-to-end attachment of sixteen barrel sections of 1.27 cm (1/2
inch) diameter. Following a short feed section were four reaction
sections (zones 1-4), one vacuum port section (zone 5), a cooling
section (zone 6), and a die section. Provisions were made for the
metering of molten maleic anhydride at the forward part of zone 1.
The screws were composed of kneading blocks, reverse pitch screws,
and transport screws arranged to generate 7.0-14.1 kg/sq.cm
(100-200 psi) pressure in zones 1-4 and no pressure in zone 5. The
free volume of zones 1-5 was equivalent to 0.91 kg (two pounds) of
polymer at operating temperature. Zones 1-4 were preheated to
300.degree. C., zone 5 to 260.degree. C., and zone 6, the
cross-head, and the die to 150.degree. C.
The above ethylene/propylene/1,4-hexadiene copolymer was fed to the
extruder in the form of chips which passed a 1.27 cm (1/2-inch)
screen. Maleic anhydride was metered to the extruder at an average
feed rate of 4.8% of the polymer weight. The screw speed was 12
rpm. and the vacuum port was operated at about 63.5 cm (25 inches)
Hg.
The product, extruded at the rate of 2.79 kg/hr. (6.15 lb./hr.),
had a maleic anhydride content of 2.23%, as determined by infrared
spectroscopy, and 2.19% by weight as determined by titration in
tetrahydrofuran with 0.1 M tetrabutylammonium hydroxide in
methanol. Wallace plasticity of the product was 33, and gel content
was less than about 5%.
Following purification of a small sample by solution in
tetrahydrofuran and precipitation with anhydrous acetone, the
maleic anhydride content was 2.19% and 2.05% by weight,
respectively, by infrared and titration and determination. The gel
content was less than about 5%. The inherent viscosity was 1.5
deciliters/gram as measured on 0.1 gram of adduct dissolved in 100
milliliters of perchloroethylene at 30.degree. C.
The rest of the product was washed on a wash mill at 125.degree. C.
for 20 minutes and dried on a 15.2.times.30.5 cm (6.times.12-inch)
mill.
Preparation of H.sub.2 N-Terminated 6-Nylons
Amine-terminated polyamides were prepared by procedures K-S which
are completely summarized in Table IV below. Additional details are
provided for Procedures L, N, Q and S, which are typical
processes.
PROCEDURE L
In each of two 400-ml stainless steel rocker bombs was placed a
mixture of 120 g of caprolactam, 10 g of octadecylamine, 0.3 g of
diethyl phosphate, and 120 ml of benzene. Both bombs were flushed
with nitrogen, sealed under nitrogen, and shaken at 275.degree. C.
for 17 hours. The benzene-wet cakes of granular product were
combined and soaked in acetone for 5 days, then extracted overnight
with acetone in a Soxhlet assembly. The resulting powdery
amine-terminated nylon product was air-dried in a hood, then
vacuum-oven dried at 50.degree. C. for one hour. Analysis are in
Table IV.
PROCEDURE N
A charge of 300 g of caprolactam and 100 ml of water was sealed
under nitrogen in a 1.4-l stainless steel rocker bomb and heated
over a period of 2.1 hours to 280.degree. C., held there for 3
hours, then cooled to room temperature. After additional 650 ml of
water had been added under nitrogen, the bomb was again sealed and
shaken while being subjected to the following temperature schedule:
1.2 hours heating to reach 210.degree. C., 15 minutes at
210.degree. C., cooling over 20 minutes to 135.degree. C., 2 hours
at 135.degree. C., then cooling over 1.2 hours to room temperature.
The resulting product, a partial slurry of powder, granules, and
cake, was partly de-watered by filtration, then chopped in a
blender with fresh warm water. Acetone was added to increase slurry
volume by 50%, and the solids were isolated by filtration. After
being air-dried in a hood, then dried in a vacuum oven for 8 hours
at 100.degree. C. (nitrogen bleed), the amine-terminated nylon
product weighed 217 grams. Analyses are in Table IV.
PROCEDURE Q
A charge of 769 grams of caprolactam, 32 grams of butylamine, and
15 grams of water was sealed under nitrogen in a 1.4-liter
stainless steel rocker bomb, heated over a 2.5-hour period to
280.degree. C., shaken at 280.degree. C. for 7 hours, then cooled
over a 3.2-hour period to room temperature. The product, a brittle
cake, was mechanically chopped to a coarse granular condition. A
317.9-gram portion of the total product was rolled overnight in a
sealed 7.57-liter (2-gallon) jar with 1.42 liters (3 pints) of
methanol. Insoluble material was collected on a filter, washed in
two portions with 0.47 liter (one pint) of methanol, briefly
air-dried, and then dried in a nitrogen-bled vacuum oven for 3
hours at 75.degree. C. Dry extracted product weighed 267.6 grams.
Analyses of a smaller sample (15 grams) similarly extracted with
methanol are shown in Table IV.
PROCEDURE S
A mixture of 70 grams of caprolactam, 6 grams of 1-octadecylamine,
and 195 milliliters of diphenyl ether was placed in a 0.4-liter
stainless steel rocker bomb.
TABLE IV
__________________________________________________________________________
Low Molecular Weight Amine-Terminated 6-Nylon Preparations K L M N
O P Q R S
__________________________________________________________________________
Nitrogen-Blanketed Polymerization Charge Compositions, g.
caprolactam 140 240 295 300 283 283 769 769 70 octadecylamine 10 20
6 octylamine 23 32.2 20.8 butylamine 32 32 .epsilon.-aminocaproic
acid 5 water 100 4 4 15 15 diethyl phosphate 0.2 0.6 195 diphenyl
ether 135 benzene 240 Post-polymerization Diluent, g.sup.(a)
benzene 300 water 650 methanol 451 451 Polymerization Conditions
Hastelloy or stainless steel 0.4 2 .times. 0.4 1 1.4 1.4 1.4 1.4
1.4 0.4 rocker tube vessel size, 1 reaction temperature,
.degree.C..sup.(b) 260 275 245, 230 280, 210 280, 230 280, 230 280
245 260, 235 reaction time, hrs..sup.(c) 19.5 17 20, .5 3, .3 3.5,
.5 3.5, .5 7 3 56 Granulation Technique.sup.(a) diluent diluent
diluent diluent diluent diluent chopping chopping diluent
Purification Technique Overnight Soxhlet extraction acetone acetone
acetone solvent Overnight reflux in 10X wt. water solvent Overnight
roller extraction, methanol solvent Blender washing, solvent (g)
(h) Centrifugation/decantation methanol(3) washing, solvent (reps.)
After filtration collection, air drying: Vacuum oven (N.sub.2
-bleed)drying: Temp/Time (.degree.C./hrs.) 50/1 100/40 100/8 100/15
100/24 75/3 Purified 6-Nylon Properties yield, g. 101.5 .about.180
.about.258 217 250 222.2 .about.652 798.3 -- NH.sub.2 end-groups,
meq./g..sup.(c) .198 .241 .428 .45 .61 .46 .about..46 .495.sup.(f)
0.383 COOH end-groups, meq./g..sup.(d) .287 .eta.inh (m-cresol,
30.degree. C.) .38 .36 .27 .30 .19 .23 .about..29 -- 0.21
Differential scanning 216 217 210 220 209.5 214 .about.217 -- --
colorimeter melting point, .degree.C..sup.(e) Mol. Wt. from
NH.sub.2 titration 5050 4150 2335 2220 1640 2170 2170 2020 2600 DP
42.4 34.5 19.5 19.5 13.5 18 18.5 17 21
__________________________________________________________________________
.sup.(a) Inert diluent provided the nylon in finelydivided form if
the polymerizate was shaken with the diluent above the melting
point of the nylon. .sup.(b) The Table does not include times
required to reach reaction temperature (usually 1.3-2.3 hour) or
cool down (.about.1-3 hours). A second pair of temperature and time
values refers to a second heating period after addition of
postpolymerization diluent. .sup.(c) A .about.0.8 gram nylon sample
is dissolved by warming in 25 ml of ocresol, and treated with 1.5
ml of water, then 7.5 ml of chloroform, cooled, and titrated
potentiometrically (Beckmann No. 39501 combination electrode) with
standard 0.03 N ethanolic potassium hydroxide. .sup.(d) A.about.0.1
gram nylon sample is dissolved by warming in 80ml mcresol. After
cooling, 10 ml of chloroform is added and the resulting composition
is titrated potentiometrically (glassmodified calomel electrode)
with standard 0.01 N 2,4dinitrobenzenesulfonic acid in acetic acid.
.sup.(e) Samples were programmed at 10.degree. C./min. through a
cycle of 50.degree. C. .fwdarw. 250.degree. C. .fwdarw. 50.degree.
C. .fwdarw. 250.degree. C., and the peak melting endotherm of the
second heating cycl taken as the melting point. A shoulder at a
lower temperature was usually observed. .sup.(f) Caprolactam
residual amine initiator, and low oligomers had not been extracted
before analysis. .sup.(g) (1) hot H.sub.2 O, (2) acetone/H.sub.2 O
(1/3). .sup.(h) (1) methanol, (2) methanol/acetone (5/2).
After the system had been evacuated and filled with nitrogen two
times, it was closed under vacuum and shaken for about 8 hours at
260.degree. C.; heating and shaking continued for two days, the
final temperature being 235.degree. C.
The resulting mixture was washed on a filter with acetone and
shaken for three days in acetone to remove diphenyl ether. The
product was collected on a filter, washed with acetone, and
extracted overnight in a Soxhlet extractor with acetone. Drying in
air and then a vacuum desiccator at 50.degree. C. gave the 6-nylon
as a powder having an inherent viscosity of 0.21 deciliters/gram
(at 30.degree. C. in m-cresol) and 0.383, 0.388 eq. --NH.sub.2
groups/kg. (corresponding to a molecular weight of about 2600 and a
D.P of about 21).
Preparation of NH.sub.2 -Terminated 12-Nylons
PROCEDURE T
A mixture of 59.6 grams of .omega.-laurolactam and 4.8 grams of
1-octadecylamine was heated in a glass polymer tube. After the
resulting melt had been allowed to crystallize, 0.16 gram of
diethyl phosphate (CH.sub.3 CH.sub.2 O).sub.2 PO.sub.2 H was added.
The tube was then evacuated and filled with nitrogen about five
times. While under vacuum the neck of the tube was sealed. The
mixture was then heated at about 285.degree. to 288.degree. C. for
about 9.5 hours. The 12-nylon obtained (yield about 45 grams) had a
melting point of about 145.degree.-150.degree. C., an inherent
viscosity of 0.34 deciliters/gram (at 30.degree. C. in m-cresol),
and 0.225, 0.226 equivalent of --NH.sub.2 groups per kg.
(corresponding to a molecular weight of 4430 and a D.P. of about
21).
PROCEDURE U
A mixture of 50 grams of .omega.-laurolactam and 10.5 ml. (13.8 g.)
of n-hexylamine was placed in a heavy stainless steel tube, which
was evacuated, flushed with nitrogen, and filled with nitrogen,
then sealed and heated sixteen hours at 255.degree. C. The
resulting nylon contained 0.492 equivalent of --NH.sub.2 groups per
kilogram. The molecular weight of the nylon thus was about 2030 and
its D.P. was about 9.5.
ADDITIONAL 12-NYLONS
Additional 12-nylons were made by method U using n-hexylamine as
the polymerization initiator. The products had D.P.'s of 5.3, 7.0,
10.2, 14.3, 15.6, 24.0, and 15.6, respectively.
EXAMPLES 1-13
Preparation of 6-Nylon Graft Copolymers
Table V below summarizes the preparation, composition, and
properties of representative 6-nylon graft polymers of the present
invention.
TABLE V
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Graft Copolymer Preparation, Composition, and Properties Example 1
2 3 4.sup.(a) 5 6 7 8 9 10 11 12 13
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Trunk E F(4) D(4) F(1) H(2) H(1) C B A A G.sup.(e) I.sup.(e) I
Copolymer E/- EA/ "type.sup.(b) Branched Blend as in as in EA/ as
in VAc/ as in E/MA/ as in EA/ BA/ as in Alt. E/ Branched Ex. 2 Ex.
1 MAnh Ex. 5 MAnh Ex.7 MAME Ex. 9 FAME FAME Ex. 12 EA/AA/ Alt. E/
MAnh EA/ MAnh "graft site MAnh as in as in as in as in as in as in
as in MAME as in FAME as as in Ex. 1 Ex. 1 Ex. 1 Ex. 1 Ex. 1 Ex. 1
Ex. 1 Ex. 9 Ex. Ex. 11 "graft site .235 .215 .35 .18 .15 .155 .245
.173 .25 .25 .29 .24 .24 conc. meq/g Nylon P Q R K L N Plasto- M O
O O O O "initiator.sup.(d) Octyl- Butyl- as in Octa- as in H.sub.2
O as in as in as in as in as in as as in amine amine Ex. 2 decyl-
Ex. 4 Ex. 1 Ex. 1 Ex. 1 Ex. 1 Ex. 1 Ex. Ex. 1 amine "NH.sub.2 conc.
.46 .about..46 .about..495 .198 .24 .45 .61 .428 .61 .61 .61 .61
.61 meq./g phr Nylon.sup.(e) 50.6 40 50 80 55 30 39 34 40 39 50 39
39 Graft Reaction Extruder Plasto-.sup.(g) Plasto- Plasto- Plasto-
Mill.sup.(g) Mill Plasto- Extrud- Mill Mill Mill Plasto- Apparatus
graph graph graph graph graph er graph Graft Reaction Conditions:
Reactor Wall T, .about.230 220 220 .about.210.sup.(i)
.about.210.sup.(i) 220 215 220 .about.230 215 210 210 220
.degree.C..sup.(h) Residence Time .about.16.4 10 10 20 20 15 15 18
.about.6.7 15 12 12 10 min. Graft Copolymer Physical
Properties.sup.(j) Shore A 83 76 81 85 77 64 91 85 67 63 92 83 71
Hardness T.sub.b,kg./sq.cm. 224 220 165 189 159 120 167 162 141 134
139 97 88 E.sub.b, % 370 460 430 300 220 270 390 330 480 500 180
210 240 M.sub.100, kg./sq.cm. 86 67 58 110 79 58 78 84 48 28 115 70
34 Comp. Set. % 23 22 35 33 26 35 32 34 28 34 37 38 43 (22
hrs./70.degree. C., Method B)
__________________________________________________________________________
.sup.(a) A small amount of (0.4 phr) of aniline was added after the
grafting reaction. .sup.(b) E.dbd.ethylene: EA.dbd.methyl acrylate;
(alt.) refers to alternating, rather than random copolymer;
VAC.dbd.vinyl acetate; MA.dbd.methyl acrylate; BA.dbd.butyl
acrylate; AA.dbd.allyl acrylate; MAnh.dbd.maleic anhydride,
MAME.dbd.monoethyl maleate; FAME.dbd.monoethyl fumarate. These
units are copolymerized in the trunk copolymer. .sup.(c) Mill
blends were treated 15 hours in a nitrogenbled 130.degree. C.
vacuum oven just before the grafting reaction. Subsequent
experiments showed that his treatment had negligible effect on
product physical properties. .sup.(d) The alkyl group of the
initiator becomes one endgroup of nearly all the polymer chains.
The other endgroup is nearly always NH.sub.2. .sup.(e) Parts of
nylon by weight per hundred parts of trunk polymer. .sup.(f)
Brabender Plastograph, an apparatus having a small, electrically
heated chamber with two convoluted rollers capable of shearmixng
and masticating polymer at a selected high temperature. .sup.(g) An
electricallyheated mill was used for the required temperature
.sup.(h) Polymer is not necessarily at this temperature at all
times. There is usually an initial warmup period followed by a
modest overshoot, perhaps because of an exothermic reaction.
.sup.(i) Accurate temperature readings were not obtained here.
.sup.(j) All graft products, in addition to the components listed
here, contained a mixture of stabilizers quite similar to that
described in the detailed Example (7). The following ASTM methods
were used; Shore A, D2240-68; Tensile Stress (T.sub.b), D412-68
Tensile Strain (E.sub.b), D412.68 Stress at 100% Elongation
(M.sub.100). D412-68; Compression Set after 22 hrs. at 70.degree.
C. D395-67 (all values measured at 25.degree. C.). Specimens
annealed for 4 hrs. at 135.degree. C.
For all graft products, slabs for testing could be prepared by
brief compression molding at 235.degree. C., followed by rapid
(.about.2 min.) cooling and immediate demolding. Annealing of these
slabs at 135.degree. C. for 4 to 5 hours generally improved
compression set about 20 to 35 points but had litle effect on other
properties. The grafting procedure used in Example 7 of Table V is
illustrative of the process:
Example 7
A mixture of 36 grams of the ethylene/vinyl acetate/maleic
anhydride trunk copolymer of Procedure C, 14 grams of the powdered
low molecular weight, H.sub.2 N-terminated 6-nylon of Procedure N,
0.1 gram of tris (mono- and di-nonylphenyl) phosphite stabilizer
["Polygard" from Uniroyal], 0.1 gram of stabilizer
N-phenyl-N'-(p-toluenesulfonyl)-p-phenylenediamine ["Aranox" from
Uniroyal], 0.1 gram of
1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene
["Ionol 330" from Shell], and 0.05 gram of a 7:1 weight mixture of
potassium iodide and cuprous iodide was homogenized as thoroughly
as possible on an unheated rubber roll mill. The resulting blend
was then transferred to an electrically heated mill held at
215.degree. and masticated at 215.degree. C. under a partial
nitrogen blanket for 15 minutes to effect grafting. At this point
the material was ready for fabrication.
EXAMPLES 14-22
Preparation of Additional 6-Nylon and of 12-Nylon Graft Copolymers
Based on Ethylene/Methyl
TABLE VI
__________________________________________________________________________
Experiment 14 15 16 17 18 19 20 21 22
__________________________________________________________________________
Trunk Polymer % Ethylene 36.3 36.3 40.6 40.6 42.8 42.8 42.8 42.8
40.6 % Methyl Acrylate 39.7 39.7 50.8 50.8 51.4 51.4 51.4 51.4 50.8
% MAME 24 24 8.64 8.64 5.76 5.76 5.76 5.76 8.64 Melt Index 32.8
32.8 6.6 6.6 4.5 4.5 4.5 4.5 6.6 Nylon 6 6 6 6 6 6 12 6 12 DP 7.0
7.0 10.2 14.3 24.0 24.0 15.6 39.5 5.3 End Group H.A..sup.(a)
H.A..sup.(a) COOH COOH COOH COOH H.A..sup.(a) COOH H.A..sup.(a) %
Polyamide 25 35 25 33 25 35 25 40 25 Reaction Type Roll Mill Roll
Mill Roll Mill Roll Mill Roll Mill Roll Mill Roll Mill Extruder
Extruder DTA Melt, Pt. .degree.C. Peak 158.165 180 207 209 214 212
168 208 158 End 220, 231 195 213 213 219 219 175 217 163 Flex.
Modulus, kg/cm.sup.2 552 1083 91 178 132 23 30 1019 510 Tensile
Strength, kg/cm.sup.2 61 92 68 62 61 25 44 145 98 Elongation at
break, % 190 130 400 230 120 300 620 310 190 Torsion Modulus
.times. 10.sup.-9, dynes/cm..sup.2 -180.degree. C. 12.66 14.77
14.90 16.19 15.54 15.29 27.59 14.41 14.69 -100.degree. C. 9.80
11.94 10.18 11.84 11.07 9.23 16.97 9.59 8.96 -50.degree. C. 7.41
8.42 4.76 6.65 5.42 5.60 9.39 5.54 6.20 0.degree. C. 1.57 2.13 .07
.20 .18 .05 .10 1.00 .22 20.degree. C. .90 1.64 .05 .16 .16 .04 .10
.89 .18 50.degree. C. .28 .60 .04 .11 .12 .03 .08 .65 .12
100.degree. C. .09 .20 .02 .05 .06 .01 .04 .20 .06 150.degree. C.
.04 .11 .015 .04 .04 -- -- .12 .02
__________________________________________________________________________
##STR7##
Acrylate/Monoethyl Maleate Copolymers
Copolymers of ethylene, maleic, anhydride (MA), and monoethyl
maleate (MAME were prepared according to the method A, above,
except that the proportions of the comonomers were varied. Grafting
of low molecular weight 6-nylons and 12-nylons was accomplished
either on a roll mill under nitrogen blanket at about 225.degree.
C. or in a twin screw extruder at about 225.degree. C. Detailed
information on these preparations is presented in Table VI,
below.
For testing for tensile strength and flex modulus, the specimens
were injection-molded at 225.degree.-235.degree. C. and held under
nitrogen for at least one day at 23.degree. C. The following test
procedures were used:
Tensile strength and elongation at break--ASTM D-638-72
Flex modulus--ASTM D-790-71
The determination of the torsion modulus was made in accordance
with the following reference:
ANELASTIC AND DIELECTRIC EFFECTS IN POLYMERIC SOLIDS, N. G. McCrum,
B. E. Read, G. Williams, published by John Wiley and Sons, pages
192-195 (1967).
EXAMPLES 23 AND 24
Preparation of 6-Nylon and 12-Nylon Graft Copolymers on EPDM
Copolymers
A Brabender Plastograph was used having a capacity of about 50
grams and heated by circulating oil (temperature 250.degree. C.).
Revolving cam-shaped blades kneaded and sheared. A nitrogen blanket
was maintained at all times.
After 30 grams of the EPDM copolymer-maleic anhydride adduct J,
above, had been added, an antioxidant mixture, an oil mixture, and
an amino-terminated 6- or 12-nylon (S or T, above) were added
successively as quickly as possible. Mixing then continued for 12
minutes. The resulting nylon graft copolymer was dumped. Table VII
gives the properties of a 6-nylon and a 12-nylon graft.
The antioxidant mixture employed (0.7 gram) consisted of 0.3 gram
of N-phenyl-N'-(p-toluenesulfonyl)-p-phenylenediamine ["Aranox"],
0.3 gram of
1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)
benzene [Ethyl Antioxidant 330, formerly "Ionox 330"], and 0.1 gram
of a 7:1 weight mixture of potassium iodide and cuprous iodide.
The oil mixture consisted of the antioxidant tris(mono- and
di-nonylphenyl) phosphite ["Polygard" from Uniroyal] and "Sunpar"
paraffinic oil 2280 [ASTM D-2226 type 104B, having Saybolt
Universal Viscosity values of 2907 sec. and 165 sec. at
37.8.degree. C. (100.degree. F.) and 98.9.degree. C. (210.degree.
F.), respectively; specific gravity, 0.8916 at 15.6.degree. C.
(60.degree. F.); density, 0.8879 g/cc; molecular weight, 720;
viscosity-gravity constant, 0.796; refractive index n.sub.D.sup.20,
1.4908]. All mixtures contained 0.3 gram of the antioxidant; the
oil amounted to 10.5 grams for 6-nylon grafting and 8.5 grams for
12-nylon grafting.
TABLE VII ______________________________________ 6-Nylon 12-Nylon
Poperties Graft Graft ______________________________________
Tensile Strength 97.7 79.4, 66.1 kg./sq.cm. Extension at Break, %
680 620,660 Modulus at 100% Extension, kg./sq.cm. 26.7 33.7 200%
Extension, kg./sq.cm. 36.6 40.1 300% Extension, kg./sq.cm. 47.1
46.4 Permanent Set at Break, % 40 80 Compression Set (Method B, 22
hrs./70 .degree. C.), % 77 83 Shore A hardness 66 84 Fast Tear, 127
cm./min. 11.8 21.4 kg./cm.
______________________________________
* * * * *