Note: Descriptions are shown in the official language in which they were submitted.
DIELS ALDER ASSISTED
POLYMER GRAFTING PROCESS
This invention relates to a method o~ grafting
an ethylenically unsaturated monomer onto a polyolefin
or polyvinyl polymer substrate and particularly to such
a method in which a Diels Alder adduct of the monomer
to be grafted is employed to provide the source of the
ethylenically unsaturated monomer through a retro Diels
Alder mechanism.
The grafting of ethylenically unsaturated
monomers onto a molten polymer substrate with or
without a free radical initiator is well known. For
example 9 methods of grafting monomers such as maleic
anhydride onto polyethylene in an extruder are
described in U. S. Patents 3,882,194 and 3,873,643.
In many applications~ however~ the monomer to
be grafted is volatile and requires elaborate,
complicated and often expensive apparatus and
techniques to prevent escape of the volatile monomer
from the polymer melt. Usually, the volatile monomer
is both toxic and flammable, posing risks to personnel
and equipment~
32,836-F -1 ~J~
~;~9~3~
6~693-~195
In addition, monomers such as acrylic acid, for example,
are too reactive to be conveniently grafted to the polymer.
Generally, such graft monomers will homopolymeri~e to an
undesirable extent and not react with the polymer to be ~rafted to
the desired extent.
Fu.rther, many monomers are not miscihle or soluble in
the polymer melt, resulting in poor disp~rsion of the monomer in
the graft polymer product and considerable quantities of the
monomer intended to be yrafted being homopolymerized.
Further still, many monomers are :Li~uid at room
temperature and are consequently difficult to mix with a normally
solid polymer substrate and too volatile to mix with a molten
polymer substrate.
The present invention avoids the foregoing problems
associated with the prior art by employing a Diels Alder adduct of
the monomer desired to be grafted which decomposes into the
monomer to be graEted and conjugated diene at the grafting
conditions.
The present invention provides a retro Diels Alder-
assisted gr~fting method, comprising the steps of:
(a) mixing polyolefin or vinyl, polymer substrate and DielsAlder adduct, said Diels Alder adduct not substantially
decomposing below about 120C. and substantially decomposing at a
temperature of ~rom about 120C. to about 300C. into conjugated
diene and ethylenically unsaturated monomer of the ~ormula
RlR2C'=CHR3 wherein Rl is hydrogen, methyl or ethyl; R2 is
hydrogen, methyl, ethyl or vinyl; and R3 is hydroxyl, cyano,
~z~
64693-4195
formyl, acetyl, propanoyl, phenyl, ~rialkoxysilyl, hydroxyphenyl~
isocyanato, pyridinyl or amino ~hen R2 is vinyl r and R3 is
hydroxyl, cyano, formyl, acetyl, propanoyl, phenyl,
trialkoxysilyl, hydroxy-phenyl, isocyanate, pyridinyl or amlno
when R2 is hydrogen, methyl or ethyl;
(b~ heating said mixture to a temperature of from about
120C. to about 300C. sufficient to substantially decompose said
Diels Alder adduct into said conjugated diene and said
ethylenically unsa~urated monomer; and
(c) inducing graft polymerization of ~aid ethylenically
unsaturated monomer onto said polymer substrate, thereby forming a
graft copolymer.
The present invention provides a process of grafting
ethylenically uns~t.urated monomer onto a polyolefin or a vinyl
polymer. The process includes the step of mixing a polyolefin or
vinyl polymer substrate with a Diels Alder adduct of the
ethylenically unsaturated monomer to be grafted. The Diels Alder
adduct is stable below 120 C and substantially decomposes into
conjugated diene and the ethylenically unsaturated monomer ~o be
~0 grafted at a temperature of from 1~0 to 300C.
The method also includes the step of heatin~ the polymer
substrate/Diels Alder adduct mixture to a
-2a-
~9~Z
temperature o~ from 120 to 300C sufficient to
substantially decompose the Diels Alder adduct into the
conjugated diene and the ethylenically unsaturated
monomer to be grafted.
The method ~urther includes the step of
inducing gra~t polymerization of the ethylenically
unsaturated monomer onto the polyolefin or vinyl
polymer substrate, thereby forming a graft polymer.
Optionally, the method may also include the
step of devolatilizing the gra~t copolymer to remove
unreacted Diels Alder adduct, conjugated diene and
ethylenically unsaturated monomer therefrom.
In the practice of the present invention , a
polymer substrate is mixed and heated with a Diels
Alder adduct which decomposes upon heating into
conjugated diene and ethylenically unsaturated monomer.
The ethylenically unsaturated monomer produced by the
decomposition o~ the Diels Alder adduct is then grafted
onto the polymer substrate. If desired, any unreacted
Diels Alder adduct and decomposition products thereof
may be removed by devolatilizing the gra~t polymer.
The polymers contemplated as suitable
substrates in the present method include polyolefins
and vinyl polymers. Polyolefins include, ~or example,
homopolymers and copolymers of one or more olefins such
3 as ethylene, propylene, 1-butene, 1-pentene, 3-methyl-
1-pentene, 1-hexene and 1-octene. Fur-ther, the
polyolefins also include olefins copolymerized with
relativey minor amounts of monomers copolymerizable
therewith, such as, for example: vinyl aryls such as
styrene, substituted styrenes, vinyl naphthalene, vinyl
32 9 836-F -3-
~ 2 ~ d
and vinylidene halides such as vinyl chloride and
vinylidene bromide; vinyl esters such as vinyl acetate,
vinyl propionate and vinyl chloroacetate; acrylic and
~-alkyl acrylic acids, and the alkyl esters, amides and
nitriles thereof, such as acrylic acid, chloroacrylic
acid, methacryliac acid, methyl acrylate, acrylamide,
N-methyl acrylamide, acrylonitrile9 choroacrylonitrile
and methacrylonitrile; alkyl esters of maleic and
fumaric acid such as dimethyl maleate and diethyl
fumarate; vinyl alkyl ethers and ketones such as vinyl
methyl ether, vinyl ethyl ether, 2-chloroethyl vinyl
ether, methyl vinyl ketone and ethyl vinyl ketone; and
other copolymerizable monomers such as carbon
mono~ide
Preferred polyolefins include low density
polyethylene, high density polyethylene, linear low
density polyethylene, ethylene-propylene rubbers and
plYPrOpylene
Suitable vinyl polymers include, for example,
homopolymers and copolymers of one or more vinyl
compound such as: vinyl aryls such as styrene,
substituted styrenes and vinyl napthalene; vinyl and
vinyldene halidss such as vinyl chlorlde, vinylidene
chloride and vinylidene bromide; vinyl esters such as
vinyl acetate, vinyl propionate and vinyl
chloroacetate; acrylic and ~-alkyl acrylic acids, and
the alkyl esters, amides and nitriles thereof, such as
acrylic acid, chloroacrylic acid, methacrylic acid,
methyl acrylate, acrylamide, N-methyl acrylamide,
acrylonitrile, chloroacrylonitrile and
methacrylonitile; and vinyl alkyl ethers and ketones
such as vinyl methyl ether, vinyl ethyl ether, 2-
chloroethyl ether, methyl vinyl ketone and ethyl vinyl
32,836-F -~-
~ ~ ~ 9 3
--5--
ketone. Further, the vinyl polymers also include vinyl
compounds copolymerized with relatively minor amount of
monomers copolymerizable therewith such as, for
example: olefins such as ethylene, propylene and 1-
butene; alkyl esters of maleic and fumaric acid such asdimethyl maleate and diethyl fumarate; and other
copolymerizable monomers such as carbon monoxide.
Preferred vlnyl polymer3 include polystyrene
and block copolymers of styrene and butadiene.
The Diels Alder adducts contemplated as
suitable in the method include those which decompose
upon heating into conjugated diene and ethylenically
unsaturated monomer. The Diels Alder adduct must not
substantially decompose below 120C in order to permit
adequate mixing of the Diels Alder adduct with the
polymer substrate before grafting, and must
substantially decompose below 300C to avoid degradation
of the substrate polymer. As used herein with respect
to the Viels Alder adduct 9 the phrase "not
substantially decomposed" means that not more than
about lO percent decomposed into the diene and carbonyl
monomer constituents, and the phrase "substantially
decomposed" means that at least 90 percent of the
adduct is so decomposed.
The Diels Alder adduct is preferably also
substantially nonvolative below 120C to further
facilitate blending of the adduct with the polymer
substrate. As used herein, the term "nonvolatile"
means having a vapor pressure of about 0O5 atm or less
at the specified temperature.
32,836-F ~5-
3~
The thermal decomposition products of the Diels
Alder adduct include conjugated diene and ethylenically
unsaturated monomer. Contemplated suitable diene
decomposition constituents include, for example:
acyclic diens such as 1,3-butad ene, isoprene, 1,3-
pentadiene, 1,3-hexadiene, 2,4-hexadiene and 1,3,5-
hexatriene; cyclic dienes such as l,3-cyclopentadiene,
1,3-cyclohexadiene, 1-methyl-1,3-cyclohexadiene, and 5-
methyl-1,3-cyclohexadiene; and heterocyclic dienes such
as furan and thiophene.
Contemplated ethylenically unsaturated monomers
produced from thermal decomposition of the Diels ~lder
adduct generally conform to the formula RlR2C-CHR3
wherein Rl is hydrogen, methyl or ethyl, R2 is
hydrogen, methyl, ethyl or vinyl, and R3 is hydroxyl,
carboxyl, cyano, ~ormyl, acetyl, propanoyl, phenyl9
trialkoxysilyl, hydroxyphenyl, isocyanato, pyridinyl or
amino.
Specific representative examples of
ethylenically unsaturated monomers produced from the
thermal decomposition of the Diels Alder adduct
include: conjugated ethylenically unsaturated
carboxylic acids such as acrylic acid, methacrylic
acid, ethacrylic acid, chloroacrylic acid, crotonic
acid, angelic acid, senecoic acid, ~-vinylacrylic acid,
fumaric acid9 itaconic acid and glutaconic acid;
conju~ated ethylenically unsaturated carboxylic acid
anhydrides such as maleic anhydride, itaconic anhydride
and glutaconic anhydride; and alkyl vinyl ketones such
as methyl vinyl ketone and ethyl vinyl ketone.
The Diels Alder adduct may generally be
prepared by reacting the conjugated diene and the
32,836-F -6-
~2.9~3g;~
--7--
ethylenically unsaturated monomer under reaction
conditions effective to form the adduct.
Specific representative examples of suitable
Diels Alder adducts and their respective conjegated
diene and ethylenically unsaturated monomer thermal
decomposition products are listed in Table I.
TA8LE I
Decom~osition Products
Adduct
Diene Monomer
5-norbornene-2- cyclopentadiene ~-vinylacr~lic acid
ac~ylic acid
15 l-~ethoxybicyclo- 1-methi~y-1,3- vinyl methyl ket~ne
[2.2.2~ oct-5-en-2- cyclohexadiene dimer
yl methyl ketone
5-norbornene-2- 1,3-cy~lopentadiene ac~ylic acid
carboxylic acid dimer
The mix.~.ng of the polymer substrate and the
Diels Alder adduct may be accomplished in either solid
or molten form as by, for example, dry blending,
Banbury mixing, in a roll mill or in a mixing extruder.
Masterbatches which contain a relatively high
percentage of the Diels Alder adduct in a polymer
substrate may also be employed by mixing the materbatch
with the polymer substrate to obtain the desired
proportion of Diels Alder adductO Preferably, the
3 mixing is done at a temperature below which the Diels
Alder adduct is volatile and below which the Diels
Alder adduct is not substantially decomposed.
The mixture is then heated to a temperature at
which the Diels Alder adduct substantially decomposes
into the diane and monomer constituents, but not above
32,836-F -7-
300C in order to avoid degradation of the polymer
substrate. Preferably, the temperature to which the
mixture is heated is from 150 to 250C.
Graft polymerization of the monomer onto the
polymer substrate in the molten mixture is then induced
by the heating alone, but is preferably induced by the
heating in the presence of a free-radical eatalyst such
as air, peroxides or actinic light, and more preferably
also under high shear conditions.
The mixing, heating and inducing graft
polymerization is preferably done simultaneously,
either on a batch or continuous basis~ In a preferred
embodiment, the process is ef~ected with a screw~type
extruder.
Generally, from 0.2 to 5 parts by weight of the
D els Alder adduct are mixed with 100 parts by ~leight
of the polymer substrate, preferably from 1 to 3 parts
by weight of the adduct per 100 parts polymer
substrate.
ExamDle 1
Using a Haake Buchler Rheocord System 40 mixing
device, 40 g of an ethylene-octene LLDPE having a
density of about 0.920 g/cc and a mel~ index o~ 6.6
were fluxed in the mixing head at 50 rpm at a
temperature of 220C. Over a period of 1 minute, 8.2
mg-moles of 5-norborene-2-carboxylic acid and 30 ~l
(2.~ mg) of 2,5-dimethyl-2,5-di~t-butyl peroxy)hex-3-
yne were added to the fluxing LLDPE with a syringe
through an injection ram modified for this purpose.
The mixer speed was then increased to 200 rpm ~or 6
32,836-F ~8-
3~J2
g
minutes. The graft copolymer product was then removed
from the mixer and cooled.
The graft copolymer product was dissolved in
xylene at 10C, precipitated with acetone~ filtered, and
dried in a vacuum oven at 60C ~or 14 hours to remove
residual low molecular weight materials. By titration
in 3:1 xylene/butanol with tetra-n-butyl ammonium
hydroxide (1.OM in methanol) using thymol blue as an
indicator, the graft copolymer product had an acrylic
acid content of 0.27 weight percent.
The above procedure was repeated except that
8.2 mg-moles of acylic acid were used instead of 5-
norborene-2-carboxylic acid. The resulting g graft
copolymer had an acrylic acid content of 0.24 weight
percent. This example demonstrates that equivalent
grafting of a conjugated ethylenically unsaturated
carbonyl such as acrylic acid may be achieYed by using
a Diels Alder adduct thereo~.
ExamDle 2
Using a Brabender mixer capable of mixing
aliquots of up to 50 g of polymer, 40 g of HDPE (0.962
g/cc, melt index 10) were added to the mixing head and
allowed to melt for about 30 seconds at 175C at 200
rpm. Over a period of 30 seconds, 21.7 mg-moles of 5-
norbornene-2-carboxylic acid were injected into the
3 mixing chamber~ After allowing 15 seconds for mi~ing,
50 ~l of a 50 weight percent solution of dicumyl
peroxide In methyl ethyl ketone were injected. After
mixing an additional 3 minutes, the grafted copolymer
was removed from the chamber and allowed to cool.
The graft copolymer product was dissolved in
xylene at 100C, precipitated with aeetone, filtered and
$~ h~PrR~
32,836-F -9-
z
- l o -
dried in a vacuum oven 70C for 14 hours to remove
residual low molecular weight materials. By infrared
spectroscopy, the incorporated acylic acid content was
determined to be about 0.14 percent by weight. The
graft copolymer had a melt index of ~.08.
The above procedure was repeated except that
21.7 mg-moles of acrylic acid were used instead of the
5-norbornene-2-carboxyic acid. The resulting graft
copolymer had an acrylic acid content determined by
infrared spectroscopy of about 0.27 weight percent.
However, the melt index of this material was 0.88,
indicating that substantially more crosslinkage
occurred when acrylic acid was used instead of the
Diels Alder adduct thereof.
ExamDle 3
The procedure of Example 2 was repeated with
24.9 mg-moles of 1-methoxybicyclo[2.2.2]oct-5-ene-2-yl
methyl ketone irlstead of 5-norbornene-2-carboxylic
acid, and 100 ~l of 2,5-dimethyl-2,5-di~t-butyl-
peroxy)hex-3-yne were added in place of the 50 weight
percent dicumyl peroxide in methyl ethyl ketone. By IR
spectroscopy,-the resulting graft copolymer contained
about 0.15 percent vinyl methyl ketone by weight.
Exam~le ~
To demonstrate that various Dlels Alder adducts
are suitably employed in the present method, the IR
absorption of various Diels Alder adducts were
determined and compared with the saturated Diels Qlder
adduct and with graft HDPE copolymers thereof. The
monomers were grafted to high density polyethylene
(0.954 gcc, 5 melt index) in a Haake Buchler System ~0
32~36-F -10-
3~
mixing device by introducing 38 g of the HDPE into the
mixing head at 300C.
Following a one minute melt time, 2Q4 mg~moles
of the Diels Alder adduct (or maleic anhydride monomer)
to be examined were added to the mixing head and mixed
with the HDPE for 15 minutes at 250 rpm rotor speed.
The graft copolymer was then removed from the chamber9
cooled, dissolved in hot 1,2,4-trichlorobenzene at 2
weight percent, precipitated with an equal volume of 2-
butanone, filtered and dried in a vacuum oven to
substantially remove residual monomer. The graft
copolymers were then analyzed by infrared spectroscopy
to determine the peak carbonyl absorption wavelengths.
The data is presented in Table II along with the peak
carbonyl absorption values for the adduct and the
saturated adduct.
32,836-F
~2~3~2
Table II
LLDPE
Unsaturated Saturated Graft Copolymer
Monomer Adduct/ Absorption absorption Absorptions
5No. Monomer ~ (cml) tcm 1)
1 Maleic 1788, 1863 1792, 1863 1797, 1873.5
anhydride
2 Tetrahydro- 1780, 1847 1798, 1866 --
phthalic
anhydride
10 3 ~icyclo[2.2.1~ 1775, 1856 1788, 1865 1795,187
hept-5-ene-
2,3-diGar-
boxylic
anhydride
4 7-Oxabicyclo 1795, 1865 1795, 1864 1795.5, 1874
12.2.1]hept-
5-ene-2,3-
dicarboxylic
anhydride
6-Methyl- 1785, 1863 NA 1796,1873
bicyclo
[2.2.1]-hept-
5-ene-2,3-
2~ dicarboxylic
v anhydride
6 Bicyclo[2.2.2] 1788, 1865 NA 1798, 1874
oct-5-ene-
2,3-dicar-
boxylic
anhydride
25 7 6-Methyl- 1773, 1840 NA 1797, 1874
tetrahydropht
halic
anhydride
8 ~icyclo[2.2.2~ 1780, 1860 NA ~778-1788, 1857
oct-7-ene-
2,3,5,6-
tetra-
carboxylic
acid
dianhydride
Note for Table II:
NA = saturated absorptions not determined
32~v36-F -12-
~3l2~3~2
By comparing the IR absorption of various graft
copolymers of Diels Alder adducts, it is seen either
that the decomposition products (maleic anhydride) were
grafted (as with monomers 3 to 7), the Diels Alder
adduct itself was grafted (as with monomer 8), or ~he
adduct did not result in any grafting at all (as with
monomer 2), depending on the decomposition temperature
of the adduct. It is believed that monomer No. 8 did
not yield any maleic anhydride grafting because of its
relatively hi~h decomposition temperature, whereas
monomer No. 2 did not graft at all because of its
relative volatility.
ExamDle 5
A series of tests were run to demonstrate a
technique for screening the suitability of proposed
Diels Alder adducts for use in the present method. A
38.1 cm OV-17 gas chromatograph column was used in a
20~ Finnigan 3200~GC-MS at 100G. A Pyroprobe~pyrolysis
chamber was connected to the unit as the injection
point. Samples of the Diels Alder adduct to be tested
were placed in quartz tubes and pyrolysis was incurred
for a period of 10 seconds at a predetermined
temperature. Helium flowing through the Pyroprobe
chamber carried the decomposition products onto the gas
chromatrograph column and then to the mass spectrometer
for identification. The results are presented in Table
III.
~P~ R
32,836-F 13-
3~:2
-14-
TABLE III
Diels Alder Adduct Result of Pvrolvsis
5-norbornene-2~acrylic acid Decomposed into ~-vinyl
acrylic acid and
cyclopentadiene at 200C
l-methoxybicyclo[2.2.2~oct- Decomposed into vinyl methyl
5-ene-2-yl-methyl ketone ketone and the dimer of 1-
methoxycyclohex-1,3-diene at
0 300C
5-norborene-2-carboxylic acid Decomposed into acrylic acid
and the dimer of
cyclopentadiene at 200C
5-norbornene-2-carbonitrile Stable to 300C
15 5-norbornene-2-carboxaldehyde Stable to 300C
5-norbornene-2-ol Stable to 300C
cyclohex-4-ene-1,2-dicarboxylic Stable to 450C
anhydride
l-methoxybicyclo[2.2.2~oct- Stable between 100 and
20 s-ene-2-carbonitrile 300C
3o
32,836-F -14-
