Note: Descriptions are shown in the official language in which they were submitted.
7845
FIELD OF Tl113 INVISNTION
This invention concerns the polymerization of ethylenic-
ally unsaturated polymerizable monomers susceptible to free radica 1
polymerization. Specifically the invention concerns novel methods
for initiating polymerization of such monomers and monomer systems
containing inactive initiators which initiators may be activated
to polymerize the system.
DESCRIPTION OF TI~E PRIOR ART
Polymerization of ethylenically unsaturated monomers
may be initiated by several methods well known to the art. Some
of these include the use of high energy electromagnetic radiation
such as gamma radiation and x-rays, ultraviolet light radiation,
chemical initiators, and thermal means. Many polymerization
reactions depend upon the formation of free radicals to cause the
initiation of the polymerization. The use of free radical
producing agents containing an acetic acid group has been disclos ~d
in Chambers' U.S. 3,479,185. The Chambers patent discloses for
example the use of a system of N-phenyl glycine or
N,N,N',N',-ethylenediamino tetraacetic acid in combination with a
2,4,5-triphenylimidazolyl dimer as a photopolymerization catalyst.
It has now been discovered however that certain
N-substituted aromatic imino monoacetic compounds produce free
radicals and provide for excellent and versatile initiators
without the additional presence of a dimer.
An additional advantage of the initiators of the
present invention is their versatility in that they can cause
polymerization in presence or absence of air, oxygen, heat, visibl~
or ultraviolet light. While such sources of radiation energies arel
therefore not required, the presence of them as promoters will tend
to increase the activity of the initiator and consequently the ratc
of polymerization.
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i SUMM~r~Y OE 'l~llE II~VENTION
According to the invention there is therefore provided
a metllod of polymerizing ~ monomer system containing one or more
ethylenically unsaturatcd compounds susccptiblc to free radical
¦polymerization which comprises initiating polymcriza~ion ~y
¦contactiny thc systcm with an effectivc amount of a dissolved
¦initiator consistiny essentially of a compound of the formula:
¦ R ~ 2 ,
l ~ H2COOH
¦where Rl is a substituted or unsubstituted aryl radical and R2
is hydrogen, alkyl or an alkoxy group provided that the ethylenica: ,ly
unsaturatc~ compounds do not contain any grou~ witll wllich tl~c
acid group of the initiator will preferentially react chemically
(as hereinafter deined). Accor~ing to the invention there is als~ \
provide~ a monomer system susceptible to free radical polymerizati n
which comprises one or more ethylenically unsaturated monomers
and a dissolved initiator consisting essentially of a compound of
the formula ~N2 wherein ~ is a substituted or unsubstitu ed
Rl- -Cll2COoH
'aryl radical and R2 is hydrogen, alkyl or an alkoxy group, or a sa~ ,t
of sai~ compound which salt upon acidification will yield said
, compound, provided that the ethylenically unsaturated monomers'do
,~ not contain any yroup with which the acid group of the compound
will preferentially react chemically. By aryl is meant a
monovalent radical containing an aromatic ring wherein the free
valence is on a carbon atom of the aromatic ring.
DESCRIPTION OF T~E INVENTION
-~ An important aspect of the invention requires that the
_ initiator must be soluble in at least one phase of the polymerizab: e
system. This polymerizable system maybe an emulsion suspension
, or solution polymerizable system Often the initiator is soluble
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"7845 ~ :
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in the polymerizable monomer or monomers and no additional solvent
is required. ~lternatively in a polymerizable system whcre the
initiator is not directly soluble in the monomer, the system must
comprise a solvent such as for example, water or methanol for the
initiator. The term "dissolved initiator" is ~herefore meant to
includc initiators dissolved in the polymerizable monomer and
initiators dissolved in a solvent. -
The initiators which are useful in the practice oE theinvention includc:
~3~4-~ _4_
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7845
~ ~ - N-CU2COOII N- ( Carboxymethyl~-N-ethylanlline
:~ ~ HO- ~ N-CU2COOli N- (carboxymethyl)-4-hydroxyaniline
C1- ~ N-CH2COOH N-(carboxymethy1)-4-Chloroani1ine
CH30- ~ -N-CH2COOH N-(carboxymethyl)-4-methoxyaniline
~ ( 3 3 ~ -N -CH2COOH N- (oarboxymethyl)-4-t-butylanili~e
: ~ -N-CH2COOH N-(carboxymethyl)aniline
~ ~ (l-naphthylimino)acetic acid
/~\ /~\
I ~ -N-CH2cOoH
~ J [(l,l'-biphenyl)-4-ylimino]acetic acid
; I Preferred initiators are those wherein R has the formula
R wherein R is hydrogen, alkyl, alkoxy,
~1 I phenyl, aralkyl or alkaryl.
j~ R ~ ~ x
R R
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Tlle initi~tors use~ul in tllo proc~ss of ~ inv~ ion ma
be prepared by reacting in an aqueous solution the corresponding
arnine component with a slight excess of sodium chloroacetate at
elevated temperatures. During the reaction, which is usually
complete in 2 hours at reflux, the pH of the reaction mixture is
carefully controlled at about 7 by the addition of sodium hydroxid .
After the reaction is completed the product may usually be obtaine
as the inactive sodium salt by stripping or alternatively as an
active precipitate by acidification such as with hydrochloric acidl
In instances where precipitation will not occur after acidificatiol ,
extraction procedures may be employed to obtain thc product.
Monomer
The unsaturated materials which may be polymerized by
the practice of this invention are ethylenically unsaturated
compounds susceptible to free radical polymerization. These
compounds include esters, nitriles and organic halogen compounds
which are olefinically unsaturated compounds of both aromatic and
aliphatic types. By way of illustration, vinyl esters such as
vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate
and other vinyl esters containing as many as 18 or more carbon
atoms in the acid moiety, may be polymerized in accordance herewit~ .
Other vinyl derivatives such as vinyl chloride, vinyl
fluoride, chlorotrifluoroethylene, tetrafluoroethylcne, butadiene
¦ nitroethylene, methyl vinyl ketone, methyl isopropenyl ketone, but~ 1
¦vinyl sulfone, vinyl triethoxy silane, ethyl vinyl sulfoxide, styr~ ne
¦nuclear substituted styrenes including o-methyl, m-methyl,
¦p-methyl styrene, divinylbenzene, and other related compounds may
¦also be polymerized in accordance herewith. Vinylidine
¦derivatives, viz., vinylidene chloride, and vinylidene carbonate
¦respond to this polymerization also.
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The acrylates respond particularly well to the tech-
niques disclosed herein and the invention extends to include
acrylates and methacrylates containin~ up to 18 or more carbon
atoms such as ethyl acrylate, propyl acrylate, butyl acrylate,
cyclohexo acrylate, cyclohexo methacrylate, isobutyl acrylate,
decyl acrylate, dodecyl methacrylate, methyl methacrylate, benzyl
acrylate, tetrahydrofurfuryl acrylate, 2-methoxyethyl acrylate,
methyl chloroacrylate, pentaerythritol triacrylate, neopentylglyco 1
diacrylate, e~hylene~lycol acrylate phthalate, 2-hydroxypropyl
methacrylate, 2-hydroxyethyl acrylate and other related compounds
such as acrylamide, acrylic acid, methacrylic acid respond to
treatment set forth herein.
; Other materials susceptible to the practice hereof
include: acrylonitrile, methacrylonitrile, 2-chloroacrylonitrile,
and allyl esters, such as the bisallyl biscarbonate ester of
diethylene ~lycol.
Copolymers of the aforementioned unsaturated materials
may be obtained. Among the copolymers which may be prepared in
accordance herewith are: copolymers of butadiene, acrylonitrile,
vinyl acetate, vinylidene chloride, methyl acrylate, and
divinylbenzene with styrene, and one another. Copolymers of
butadiene with styrene, butadiene with acrylonitrile, acrylic acid
with acrylamide, vinyl acetate with vinylidene chloride, styrene
with methyl acrylate, and styrene with divinylbenzene, are
examples of specific copolymers which may be prepared pursuant to
this invention. Terpolymers prepared in accordance herewith are
often of special utility, such as those derived from butadiene,
acrylonitrile, styrene mixtures and other mixtures wherein vinyl
acetate, or methyl methacrylate may be components of the terpolyme -s.
PrcEerrcd monomor systoms of thc proscnt invcl-tioll aro
those containing water soluble monomers such as acrylamide, diacet ~ne
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acrylamide, acrylic acid, methacrylic acid; monomcrs such as
diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate o~
dimethylaminoethyl acrylate and their derivatives; vinyl monomer
systems containing unsaturated maleate and fumarate polyesters;
monomers containing acrylate or methacrylate unsaturation either
separately or in combin~tion with comonomers such as styrene,
methyl methacrylate, acrylonitrile, vinyl acetate or vinylidene
chloride, and latex forming systcms containing butadiene either
alone or in combination with copolymerizable vinyl monomers such
as styrene, acrylonitrile, vinyl acetate or vinylidene chloride.
The initiators of the invention have different
effectiveness in different polymerization media, which may be
aqueous or organic in nature. Most of the initiators are soluble
in organic media. However, in aqueous media the selection of
the best initiator is best determined experimentally. In general
the least substituted aromatic monoacetic acid initiator is water
soluble. As groups are substituted on the molecules, initiators
may lose water solubility. N-phenylglycine was found soluble
in aqueous solutions whereas N-carboxymethyl-4-t-butyl aniline
was not found soluble in aqueous media.
The ethylenically unsaturated monomers which are
polymerizable according to the method of the invention should not
contain any gxoup with which the acid group of the initiator will
preferentially react chemically. For example, monomer substituent ,
such as for example, amines, isocyanate or vinyl epoxy groups are
highly reactive with the acid groups of the initiator. Such
substituents, if present, will derivatise the acid groups to
amides or esters. While amine substituents may cause derivation
reactions which may be reversible by acidification, substituents
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such as iso~yanate or vinyl epoxy groups will cause irreversible
reactions which will perm~nently diminish or terminate the
ability of the initiators to generate free radicals. By the
phrase "groups with which all the acid groups of the initiator
will preferentially react chemically" is therefore meant those
highly reacti~e groups which will non-reversibly derivatise all
the acid groups of the initiator.
As is well known to those skilled in the art, free
radical polymerization refers to those polymerization reactions w ich
take place through intermediates having an odd number of
electrons and, consequently, an unpaired electron. It is these
intermediates which are generally referred to as frce radicals.
The free radicals are normally generated in one or more of a
variety of ways such as by the decomposition of a chemical initia or
added to the polymerizable mixture or by the application of heat
or ionizing radiation to the composition. If the free radical is
gene~ated in the presence of an ethylenically unsaturated monomer
described above, the radical will add to the double bond with the
regeneration of another radical. This radical will, in turn, reac t
with another monomer and in the course of the reaction generate
another free radical resulting in growth of the polymer chain
through the addition of one chain to another. Free radical
polymerization is described in detail in, for example, the
Encyclopedia of Polymer Science and Technology,Vol. 7, pages
361-~31, Interscience Publishers, 1967, and in the Textbook of
Polymer Science, Billmeyer, Interscience Publishers, 1962, pages
262-290.
In addition to growth of the polymer chain, several sid~
reactions can also take place during the course of the
polymerization reaction. One of th~se, identified as chain
transfer refers to the transfer of an atom from a molecule to a
free radical in the reaction mixture. Depending upon the
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1-04-1 j
097845- 1
nature of the other material, this can rc~lt in thc formation of~
additional polymer molecules, the formation of branch ch~in polymers,
or in termination of the polymerization reaction on a growing
radical chain.
Chain transfer agents do not terminate the polymerization
reaction entirely but merely terminate a growing chain and allow
the polymerization to start elsewhere. If premature termination of
the growing polymer chain occurs, a reduced molecular weight results
and other pol~mer properties are achieved. It is~ for this reaso ,
desirable to include in a free radical polymerization system a
chain transfer agent which would function in this manner allowing
molecular weight control.
The concentration of the various components utilized in
the production of polymers in accordance with the invention may b
varied over extremely wide ranges and appears to be not narrowly
critical. The concentration of the initiator is dependent on the
activity of the initiator used; the type and concentration of othe r
components SUCh as solvent and monomer; and promoters such as hea
and light. Although a concentration range of from .01 to 2% is
economically preferred for optimum monomer conversion, under
favorable conditions shown hereafter in the examples, any amounts
which are effective ~ay be used eg. initiator concentration of as
low as 0.01~ by weight of monomer system and as high as 9~ or mor
by weight of monomer system may be used successfully. For exampl
in nonaqueous systems the activity of p-toluidine acetic acid is
greater than an initiator having an unsubstituted aromative ring
such as aniline acetic acid. Hence the concentration of a greatl
active initiator may be less than those of less active initiators.
In general in the presence of air, oxygen or other polymerization
inhibitors, 1arge~ra~ounts of initiator may bc requircd.
The temperature used in the practice hereof may vary
widely and are only limited by the freezing and boiling point of t
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1~7845
pol~merizable system. In aqueous systems the polymerization
may be conducted between about 0 and 100C. Nonaqueous
media such as styrene or isopropyl methacrylate may allow
for polymerization temperatures as high as about 125 C~
Other nonaqueous media may allow for polymerization temper-
atures of 200C or higher.
The invention does not exclude the utilization of
polymerization inhibitors, accelerators and molecular weight
modifiers. Any of these may be employed if so desired.
Inhibitors may include any free radical scavenger.
The polymerization process according to the inven-
tion may occur over a wide range of pH. The optimum pH of the
polymerizable system will be affected by the stability of
the monomer and the solubility and stability of the initiator.
It has also been discovered that the initiators
are considerably less active when not substantially in the
acid form. The activity of the initiator and thus the rate
of polymerization may therefore be regulated by adjustment of
pH. As a further advantage, the invention therefore provides
for a latent polymerizable system by having the initiators
present not in the acid form but as the inactive salt, for
example, the inactive sodium salt, or amine salt. Such a
latent system may then be activated by the simple adjustment
of pH to a point below the neutralization point of the system.
The neutralization point is hereby defined as the pH point
of the polymerizable system at which the initi2tor becomes
active due to the presence of acid group. Generally the
lower the pH of the polymerizable system, the more active the
initiator and conversely the higher the pH, the slower the rate
of poLymerization will be. It should be noted that the
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~784S
neutralization point of the polymerizable system will
vary depending on the specific initiator employed.
A particular advantage of a latent polymerizable
system 7
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is the ability to polymerize a liquid polymerizable system at any
I time in situ merely by the addition of acid to lower the pH of the
system. For example, in oil recovery operations, water soluble
monomer mixture of so~ium acrylate and acrylamide and an inactive
salt of an initiator may be introduced into an oil bearinc3
formation as a low viscosity liquid and subsequently polymerized b r
the addition of acid to activate the initiator to produce a highly
viscous polymer solution in situ.
The invention also provides for a polymerizable system
containing additionally a second free radical polymerization
initiating system such as for example, a peroxide system to cause ,
postcuring.
The invention is further illustrated by the following
lexamples in which all parts and percentages are by weight unless
otherwise specified.
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EXAMPLE 1
To a solution of 2 g of acrylamide in 8 ml of
distilled water were addsd 20 rng of N-ethyl anilineacetic acid
The solution polymerized in 14 hours at room temperature while
being exposed to laboratory day light.
EXAMPLE 2
To a solution of 2 g of acrylamide in ~ g of methanol
were added 100 mg N-phenylglycine. The solution polymerized in 9 ¦
hours at room temperature while being exposed to laboratory day
light. A sample not containiny N-phenylglycine, acting as control,
did not polymerize.
EX~LE 3
To a solution of 2 g acrylamide in 8 g of methanol
were added 50 mg N-phenylglyclne. The solution polymerized in 17
hours at room temperature while being exposed to laboratory day
ight. A sample not containing N-phenylglycine, acting as control,
id not polymerize.
EXAMPLE 4
To a solution of 1 g acrylamide in 4 g of methanol were
dded 200 mg N-phenylglycine. The solution was kept at room
emperature in the dark. A precipitate indicating polymerization
ormed within three days. A sample not containing N-phenylglycine,
acting as control, did not polymerize.
E~AMPLE S
To a solution of 1 g acrylamide in 4 g of water were
ladded 100 mg N-phenylglycine. The solution was kept at room
Itemperature in the dark. The solution polymerized within three
days. A sample not containing N~phenylglycine, acting as control,
~` id not polymerize.
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E Xl~M~ Ll~ 6
To a solution of 1 g acrylamide in 4 g of water were
~dded 100 mg N-phenylglycine. The pH was adjusted with dilute
hydrochloric acid to 1. The solution was kept at room temperature
~n the dark. The solution polymerized within 60 hours. A sample
Iot containing N-phenylglycine, ac~ing as control, did not ,
polymerize.
EXAMPLE 7
To a solution in a glass.,contai~er of 2 g acrylamide in
13 g of methanol were added 50 g N-phenylglycine, ! The p}I was
~~~~ ~djusted with dilute hydrochloric acid to 2. After exposure of the
uolution to laboratory daylight for 14 hours at room temperature
~olymerization was observed. A sample not containing
-phenylglycine, acting as control, did not polymerize.
EX~MPLE 8
To a solution containing 3 grams of acrylamide and l.S
rams of sodium chloride in 5.5 g water, were added 200 m~
~-phenylglycine. The solution was kept at room temperature in the
~ark. The solution polymerized within three days. A sample not '
containing N-phenylglycine, acting as control, did not polymerize.
~he molecular weight of the polyacrylamide produced in the presence
of sodium chloride was found to be higher than that produced
, ithout the presence of the salt.
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