Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
-l- A-2544
EMULSION PROCESS FOR PREPARING ELASTOMERIC
VI~Y. ~0~1~5~ ~r~Y~a~ coP LYMERS _
Vinyl acetate-ethylene (VAE) copolymers constitute
a well known class of synthetic resins demonstrating a broad
range of properties d.epending upon the relative quantities
5 of copolymerized ethylene and vinyl acetate (and other
ethylenic monomers which may be present~ in the copolymer
chain. Elastomeric amorphous VAE gum stocks contain from
about 40~ to about 70% vinyl acetate by weight randomly
distributed throughout the copolymer chain and, when cross-
1~ linked, for example, by a peroxide crosslinking agent,
-: possess properties which make them especially useful as
elastomers for rubber compounding, as base copolymers for
adhesive formulations and as impact modifiers for polyvinyl
chloride (PVC). Among the physical and chemical.properties
15 which make the rubbery VAE copolymers attractive or such
applications are the ollowing: heat aging resistance; oil
and solvent resistance; low compression set, good low
temperature performance; excellent weatherability and ozone
resistance; resistance to natural light; transparent or
: 20 white-to-black vulcanizates; high loadability; -receptance
to dielectric heating; and high dampening characteristics.
Thus, the elastomeric VAE copolymers are excellent
candidates for such automotive applications as gaskets,
seals and O-rings, wire insulation, radiator tubing and
: ~5 hose, bumper strips and auto body filler panels and are
ideal for other demanding applications as well such as
- machinery mounts, weather stripping, washing machine hose,
refrigeratox gaskets, and the like.
,: 30
..;
: .~
--2--
1 In accordance with the present invention, VA~
elastomers are obtained in the ~orrn of latices employing
an improved emulsion copolymerization process and the
elastomers are recovered therefrom employiny such con~
5 ventional techni~ues as coagulation. In general, a VAE
copolymer latex is prepared by first charging an aqueous
phase containing water, surfactant, buffer, catalyst or
catalyst system of the free radical type, and usually a
protective colloid such as polyvinyl alcohol (PVA), to a
10 reactor as, for example, described in U. S. Patent No.
3,708,38a. In some procedures, an initial charge of
vinyl acetate monomer, and in others, the entire amount
of vinyl acetate monomer, is also charged to the reactor.
The reactor is flushed with nitrogen, sealed,and stirring
15 is commenced. Ethylene is then pumped to the reactor
until the desired pressure is attained. The reactor can
be repressurized one or more times if the batch is
carried out under variable ethylene pressure, or a con-
stant pressure can be maintained automatically employing
20 techniques which are well known in the art. After reactor
pressure has stabilized, the contents thereof are heated
to the polymerization temperature, usually by circulating
hot water or steam through a jacket ~urrounding the reactor.
When the desired polymerization temperature (commonly ~rom
25 about 120 to about 165E'.) is reached, temperature is
maintained at this level by automated controls. Thereafter,
a co-catalyst such as sodium hydrogen sulfite ~NaH~O3) can
.L.~'33L~
1 be added t~ the reactor (if a catalyst system employing
a reducing agent to generate free radicals by a redox
reaction is used) followed by any remaining vinyl
acetate monomer. The completion of polymerization is
5 indicated by cessation of ethylene demand and stabilization
of the reactant coolant temperature at about 6 - 8F.
above the reactor tempera~ure~ Upon completion of
polymerization, the reactor contents are cooled and
discharged through a pressure l~t-down valve to areceiving
tank at atmospheric pressure from which unreacted ethylene
is vented. The finished VAE copolymer latex is passed
through a screen of desired mesh to complete the manu-
facturing process.
Various manipulations of both the amount and
nature of the components of a ~AE copolymerization medium
and the copolymerization process variables have heretofore
been attempted in order to optimize one or a few properties
of the resulting latex. U. S. Patent No. 3,6~4,262
describes a copolymerization which by regulating the
addition of vinyl acetate to an aqueous emulsifying
composition containing a free-radical initiator at a
rate which will maintain the concentration of unpolymerized
vinyl acetate at a level not exceeding about 3.5% by
weight of emulsifying composition and, optionally by
delaying the addition of surface active agent, permits
the introduction of substantially more ethylene into the
copolymer for a given pressure and temperature than would
,1 ~"~ 7~
be o-therwise attainable. The resulting high ethylene
content VAE copolymer latices are said to be better
adapted to their end uses than the latices of relatively
low ethylene content. A different approach to improved
VAE copolymer latices is described in U.S. Patent NoO
3,423,352 in which high solids content VAE copolymer
latices of reduced viscosity and improved freeze-thaw
stability are obtained by controlling the addition of
monomer, catalyst and surfactant. According to this
patent, relatively large amounts of surfactant, i.e.,
from about 3% to about 10% by weight, and catalyst are
added to a conventionally pr~pared polyvinyl acetate
latex, having a solids content of up to about 52% and con-
taining relatively large amounts of vinyl acetate, at
specified times once polymerization has proceeded to a
certain extent. This is said to resul-t in a marked
reduction in the viscosity of the emulsion. Frequently,
these and other prior art techniques for preparing VAE
copolymer latices achieve an improvement in one or two
performance characteristics but at the expense of one
or more other vital performance characteristics.
In accordance with an emulsion copolymerization
process, VAE copolymer latices are prepared by copolymer-
izing from about 40% to about 70% by weight of vinyl acetate
with from about 60% to about 30% by weight of ethylene in an
~ r~
1 emulsion reaction meclium containing a su~face active
a~ent in an amount of not less than abou~ 1.0'~ by weight,
and no-t more than ahout 2.0~ by weiyht, of the total
monomer, a catalyst and a protective colloid, the total
5 weight of the surface active agent and vinyl acetate being
introduced into the reaction medium in delayed increments
prior to and after the commencement of copolymerization.
The resulting VAE copolymer latices, which are employed
as such as bases for paints and other surface coatings,
10 as adhesives, textile treatiny agents, and the like,
possess high inherent viscosity, i.e., not less than
about 1.90, and demonstrate superior performance in the
Time of Set Test and Vinyl Wetting Test.
Such properties are especially desirable attribute.s
15 of a VAE polymer latex. ~owever, where as here VAE elastomers
are concerned, other physical properties, significantly,
Mooney viscosity and gel content, are dominant considerations
in the acceptability of the resins for rubbery articles such
as enumerated above.
The emulsion copolymerization process of this
invention provides a relatively simple procedure for
obtaining VAE elastomers having high Mooney viscosity and
low gel content which are ideally suited materials for
25 fabrication into rubber-like articles meeting fairly
demanding performance criteria. The expressions"hiyh
Mooney viscosity" and "low gel content" contemplate VAE
'
-6~
1 e]astomers havi.ng a Mooney vi.scosi.ty at 212F. o from
about 30 MI. (1 ~ to about ~0 ML (1 -I 4) and preferably
from about 30 ML (1 -~ 4) to about 70 ML (1 -~ 4), and a gel
content as measured by insolubility in xylene at 80C.
5 of not more than about 2 %, preferably not more than
1 % by weight insolubles.
Broadly stated, the process herein comprises:
a) copolymerizing from about 40~ to about 70~ by
weight of vinyl acetate monomer with from about
60% to about30% by weight of ethylene monomer in
an aqueous emulsion reaction mediu~ to provide
a latex, the reaction medium for VAE elastomer
containing:
(i) at least one surface active agent in an
amount above about 2.0% by weight of the
total monomer,
(ii) a polymerization catalyst, and
(iii) at least one protective colloid in an
amount of less than about one part for
each part by weight of total surface active
agent, with the total weight of the surface
active agent and vinyl acetate being present
in the reaction medium at the commencement
of copolymerization; and
b) recovering the ~'AE elastomer from the latex.
Recovery of the VAE elastomer from the latex can
be readily accomplished employing well known methods such
--7--
1 as coa~ulatlnc3 the ela.stomer by freezlncJ the latex or
by adding a coagulatiny amount of a salt such as sodiurn
chlorlde to the latex and thereafter filteriny the
coagulum. The VAE elastomer can then be subiec-ted to
5 further processlng, e.g., crosslinking, compounding with
antioxidants, stàbili~ers, fillers, other modifying
polymers, etc.
The amount of vinyl acetate monomer copolymerized
~ with ethylene monomer will vary from about 40% up to about
70~ by weight of the total comonomer charge, the balance
of said charge being made up of ethylene, and if desired,
small quantities, i.e., up to about 15%, of one or more
other ethylenically unsaturated comonomers not exceeding
5 the weight ~uantity of ethylene. Included among such
additional comonomers are monoethylenically unsaturated
aliphatic hydrocarbons such as propylene and isobutylene;
monoethylenically unsaturated substituted aliphatic hydro-
carbons such as vinyl fluoride, vinyl chloride, vinyl
20 bromide, vinylidene fluoride, l-chloro-l-fluoroethylene,
chlorotrifluoroethylene and tetrafluoroethylene; unsaturated
acids such as acrylic acid, methacrylic acid, crotonic acid
and itaconic acid, as well as polymerizable derivatives
thereof, e.g. alkyl acrylates and methacrylates such as
methyl acrylates, ethyl acrylate, n-propyl acrylate, n-butyl
acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, methyl
methacrylate, ethyl methacrylate, n-propyl-methacrylate,
5~
--8--
1 1,6-hexanediol diacrylate and isobutyl methacrylate,
- acxylonitrile, methacrylonitrile, acrylamide, meth-
acrylamide, N-methylolacrylamide, alkylated N-methylol-
acrylamides such as N-methoxymethylacrylamide and
5 N-butoxymethylacrylamide~ and acrolein; aliphatic vinyl
esters such as vinyl formate, vinyl propionate and vinyl
butyrate; aliphatic vinyl e-thers such as methyl vinyl
ether, ethyl vinyl ether and n-butyl vinyl ether; vinyl
ketones such as methyl vinyl ketone, ethyl vinyl ketone
. ,.
~0 and isobutyl vinyl ketone; allyl esters of saturated
monocarboxylic acids, e.g. allyl acetate~ allyl propionate
and allyl lactate; and, alkyl esters o~ monoethylenically
unsaturated dicarboxylic acids, e.g., diethyl maleate,
dibutyl maleate, dioctyl maleate, dipropyl fumaxate,
15 dibutyl fumarate, dioctyl ~umarate, dodecyl ~umarate,
dibutyl itaconate and dioctyl itaconate.
The surface active agents contemplated by this
invention include any of the known and conventional surfac-
tants and emulsifying agents, principally the nonlonic
20 and anionic materials, and mixtures thereof heretofore
employed in the emulsion copolymerization of vinyl acetate
and ethylene. One group of nonionic surface active agents
which can be employed has a water-insoluble polyoxyalkylene
glycol (other than ethylene glycol) nucleus with a molecular
25 weight of more than 900 which has been extended with water-
soluble polyoxyethylene groups at each end. The water-
soluble portion of the molecule should constitute at least
3~
_9_
1 50~ by weight of the total. The polyoxyalkylene glycol
can be aliphatic, aromatic or alicyclic in nature, can be
saturated or unsaturated, and can be represented by the
formula:
HO~C2H4O)y(cm~lno)x(c2 4 )y
wherein x, y, m and n are integers. When (CmHnO)x is
saturated aliphatic, n-2m.
Compounds in this class are described in U. S.
10 Patent Nos. 2,674,619 and 2,677,700.
The polyoxyalkylene compounds of U. S. Patent
No. 2,674,619 which can be used herein are defined by the
formula:
Y[(C3H6O)n E H]x
15 wherein Y is the residue of an organic compound containing
therein x active hydrogen atoms, n is an integer, and x
is an integer greater than 1.
The values of n and x are such that the molecular
weight of the compound, exclusive of E, is at least ~00
as determined by hydroxyl number; E is a polyoxyalkylene
chain wherein the oxygen/carbon atom ratio i.9 at least
0.5, and E constitutes at least 50% by weight of the
compound.
The polyoxyalkylene compounds of U. S. Patent
No. 2,677,700 , which are useful herein, are defined by
the formula:
ll l2
Y(f I--) n
R
3~ 3 4
S6~0
~10-
1 wherein Y is the residue of an orc3anic compound con-
taining therein a single hydrogen atom capabl~ of
reacting with a 1,3-alkylene oxide; Rl, R2, R3 and R4
are selected from the group consistiny of H, aliphatic
radieals and aromatic radicals, at least one sueh
substituent bein~ a radical other than hydrogen; n
is greater than 6.4 as determined by hydroxyl number
and X is a water-solubilizing group which is nonionie and
eonstitutes at least 50% by wei~ht of the total compound.
The eompounds of U. S. Patent No. 2,674,619 are
sold commercially under the trademark "Pluronic" (BASF
Wyandotte Corp.)~ The following are examples of eompounds
eorresponding to the above formula:
Name Moleeular Ethylene oxide Moleeular
weight, poly eontent in final weight of
oxypropylene produet, weight final
base percent produet
Pluronie F68 1,700 80 8,750
Pluronie P75 2,050 50 4,100
Pluronie F-98 2,700 80 13,500
Pluronie F-108 13,400 80 12,000-22,000
Another group of surface active agents which ean
be employed has a water-insoluble nueleus with a moleeular
weight of at least 900 containing an organie eompound having
a plurality of reaetive hydrogen atoms eondensed with an
alkylene oxide other than ethylene oxide and having water-
soluble polyoxyethylene groups attaehed to eaeh end. The
weight pereent of the hydrophilic portion of the moleeule
-:L1-
1 should be at least 50. These e~hylene oxide adducts of an
aliphatic diamlne such as ethylene diamine extended with
propylene oxide have the fo]lowing formula:
~(C~ O)~(C3~I60)x\ (C3f~6o)y~(c2H4o)yH
/ N -C~ CH2 -N ~
Il(C2~40)y~c3H60)x (C3Hoo)x(c2H4o)yH
Compounds in this class are described in U. S.
Patent Nos. 2,674,619 and 3,250,719 and are sold commercially
under the trademark "Tetronic" (BASF Wyandotte Corp.~. The
following are examples of compounds corresponding-to the
above formula:
Name Molecular
weight for Ethylene oxide Molecular
ethylene di content in final weight of
amine-propylene product, weight final
oxide base percent product
Tetronic 707 3,000 75 12,000
Tetronic 908 4,050 85 27,000
Another useful group of nonionics are the "Igepals"*
(GAF Corp. Chemical Products), a homologous series of
alkylphenoxypoly (ethyleneoxy) ethanols which can be
represented by the general formula:
~3-- ~CH2~20~C~2C~
--1
* Trade Mark
~12--
1 wherein R represents an alkyl radical and n represents
the number of mols of ethylene oxide employed, among
which are alkylphenoxypoly (ethyleneoxy) ethanols having
alkyl groups containing frorn about 7 to about 18 carbon
atoms, inclusive, and having from about 4 to about 100
ethyleneoxy units, such as the heptylphenoxypoly (ethyleneoxy)
ethanols; nonylphenoxypoly~ethyleneoxy) ethanols and
dodecylphenoxypoly-(ethyleneoxy) ethanols; the sodium or
ammonium salts of the sulfate esters of these alkylphenoxypoly
(ethyleneoxy) ethanols; alkylpoly(ethyleneoxy) ethanols;
alkylpoly(propyleneoxy)-ethanols; octylphenoxyethoxyethyl-
dimethylbenzylammonium chloride; and polyethylene glycol
t-dodecylthioether.
Other compounds in this class include ethylene
oxide adducts of polyhydroxy alcohols extended with
alkylene oxide, e.g., the "Tweens"*~ICI United States
Inc.), ethylene oxide adducts of polyoxyalkylene esters
of polybasic acids, ethylene oxide adducts of polyoxy-
alkylene extended amides of polybasic acids, ethylene
oxide adducts of polyoxyalkylene extended alkyl, alkenyl
and alkynyl aminoalkanols, of which the hydrophobic nucleus
should have a molecular weight of at least 900 and the
hydrophilic part of the molecule should be at least 50%
by weight of the total. It is to be understood that the
above-mentioned organic compounds having a plurality of
active hydrogen atoms as well as the polyoxyalkylene glycols
can be aliphatic, aromatic or alicyclic in nature and can
contain unsaturation.
* Trade Mark
~1 .
-~3-
1 Amon~ the many anionic s~lrface active agents which
can be used herein are 'rriton*~-200 (~ohm & ~laas Co.), a
sodium salt of an alkylaryl polyether sulfonate;Triton X~301
(Rohm ~ Haas Co.), a sodium salt of alkylaryl polyether
5 sulfate; Triton QS-9 (Rohm & ~aas Co.), a phosphate ester;
Alipal*CO 433 ~GAF), a sodium salt of sulfated nonylphenol
(ethyleneoxy) ethanol; Dupanol*ME Dry (DuPont), a sodium
lauryl sulfonate; Ultrawet*(Atlantic Refining Co.), an alkyl
aryl sulfonate; Sipon ESY*(Alcolac, Inc.), a sodium lauryl
~o ethoxylate sulfate; and the like. Sipon ESY , 25.5 percent
in aqueous solution, has been found to provide especially
good results.
In accordance with this invention, a protective
colloid is incorporated in the aqueous emulsionsO Such
15 known and conventional protective colloids as: the partially
and fully hydrolyzed polyvinyl alcohols; cellulose ethers,
e.g., hydroxymethyl cellulose, hydroxyethyl cellulose, ethyl
hydroxylethyl cellulose and ethoxylated starch derivatives;
the natural and synthetic gums, e.g., gum tragacanth and gum
20 arabic; polyacrylic acid, poly(methyl vinyl ether/maleic
anhydride), are well suited for use herein. The partially
hydrolyzed polyvinyl alcohols such as Gelvatol*20-30 (Monsanto)
are especially advantageous for use in this invention.
The catalysts used in the copolymerization reaction
25 are any of the known and conventional free radical polymeriza-
tion catalysts heretofore used for the preparation of VAE
copolymer latices and include inorganic peroxides such as
hydrogen peroxide, sodiurrl perchlorate and sodium per~orate,
inorganic persulfates such as sodium persulfate, potassium
30 persulfate and ammonium persulfate and reducing agents such
as sodium hydrogen sulfite. Catalyst (including co-catalyst
reducing agent, if employed) is generally utilized at a
* Trade Marks
3~
~ I ~
1 level oE from about O.l~ to about l'~ by weight of total
comonom~rs.
An alkaline buffering agent such as sodium bicar-
bonate, ammonium bicarbonate sodium acetate, and the like,
5 may be added to the aqueous system to maintain the p~l at
the desired value. The amount of buffer is generally about
O.Ol to 0.5% by weight, based on the monomers.
In order to obtain the hiyh Mooney viscosity, low
gel content VAE elastomers herein, it has been found
10 necessary to employ an amount of surface active agent which
is at least above about 2.0~ by weight of the total monomer
and can range as high as about 5.0% by weight of the total
monomer although amounts in excess of this are also operable.
Similarly, high levels of Mooney viscosity and low gel content
15 require that there be less than about a l.5:l weight ratio of
protective colloid to total surface active agent, and preferably
less than a ratio of about l~ ll of the surface
active agent and vinyl acetate monomer may be present in the
polymerization medium from the outset as distinguis~ed from
~0 other processes in which one or both of these ingredients are
added incrementally to the raction medium during polymerization.
The temperature and pressure of the copolymerization
reaction hcrein can be selected at levels which have heretofore
been employed in VA~ emulsion copolymerization. Accordingly,
2~ temperatures of from about 70F. to about l~OF. and pressures
of lOOO to 5000 p.s.i. can be used with good results. It is,
of course, recognized by those skilled in the art that at the
lower end of the temperature rancJe, it may be necessary to
employ a reducing agent ko generate the free radical required
30 for initiating copol~merization.
B~
-15 -
1 The VAE elastomer which is recovered fro~ the
latex produced in accordance with this invention, preferably
af~er being treated for the removal of residual surface
active agent, protective colloid and other extraneous
5 substances, can thereafter be cured with a crosslinking
(vulcanizing) agent while compounding with such optional
ingredients as fillers; antioxidants; modifying resins
(at from about 10% to about 40% by weight of VAE copolymer),
e.g., polyvinyl chloride, ethylene propylene rubber (EPR),
10 polychloroprene, polyacrylate rubber, polyurethane,
chlorinated polyethylene, polyester, ethylene-propylene
diene monomer (EPDM) terpolymer, ethylene-methyl acrylate
elastomer, ethylene butyl acrylate elastomer, and
acrylonitrile elastomer; and other known elastomer
15 additives. The foregoing can be combined with the VAE
elastomer in conventional mixing equipment, typified by
a two-roll rubber mill, a mixing extruder or preferably
a high shear internal mixer such as a ~anbury mixer,
until a homogeneous blend is obtained. Upon completion
20 of the mixing stage, the xesin blend is processed lnto
any of several forms convenient for subsequent manufacturing
operations, for example, pellets formed by an underwater
pelletizer, strand cut, etc.
The crosslinking agents which can be used herein
include such peroxides as: t-butyl perbenzoate, dicumyl
peroxide; 2,5-dimethyl 2,5-di(t-butyl peroxy) hexane;
2,5-dimethyl-2,5-di(t-butyl peroxy) hexyne-3; 1,3,5-
tris[alpha, alpha-dimethyl-alpha-(t-butyl peroxy)]-methyl
-16-
1 benzene; alpha, alpha-bis~-t-butyl peroxy) diisopropyl
benzene; and, n-butyl-4,4-bis(t-butyl peroxy) valerate.
These crosslinking agents can be used alone or in com-
bination with any of several polyfunctional auxiliary
5 crosslinking agents such as triallyl phosphate; trimethylol
propane triacrylate; diallyl fumarate; triallyl cyanurate;
triallyl isocyanurate; pentaerythritol tetraacrylate;
trimethylol propane trimethacrylate; 1,3-butylene glycol
dimethacrylate; allyl methacrylate; ethylene glycol
10 dimethacrylate; and, 1,3-butylene glycol diacrylate.
A preferred curing agent for use herein is Vul-Cup*40 KE
(~0% dicumyl peroxide on calcium carbonate) from
Hercules Inc. The amount of peroxide crosslinking agent
can range from about 1.0 to about 10.0 parts, and preferably\
15 from about 2.0 parts to about 5.0 parts per hundred parts
of EVA copolymer. The polyfunctional auxiliary cross-
linking agents are useful within the range of from about
0.1 to about 3.0 parts per hundred parts o EVA gum
stock.
Examples of fillers which can advantageously be `
employed herein are: Hydral*710, an alumina trihydrate
obtained from Alcoa; Hi-Sil*EP and Hi-Sil 233, amorphous
precipitated hydrated silicas obtained from PPG Industries,
Inc.; Cab-0-Sil* a fumed silica obtained from Cabot
25 Corporation; Mistron*Monomix,*a talc (magnesium silicate)
from Cyprus Industrial Minerals Company; Burgess KE,* a
surface treated (silane) calcined kaolin clay (anhyclrous
* ~rade Marks
-17-
1 alumlnum slllcat~) obtalned from the sur~ess Piyment
Company; and, antimony oxide. As is appreciated by those
skilled in the art, the amounts of filler incorpoxated
into a polymer blend of this invention will depend on the
5 nature of the filler and the properties desired of the
final product. Non-reinforcing fillers such as alumina
trihydrate can be used in amounts ranging from about 5.0
parts to about 400.0 parts and preferably from about
100.0 parts to about 150.0 parts, per hundred parts of
10 polymer blend. Reinforcing fillers such as hydrated
silica, carbon black and sintered colloidal silica are
useful in the range of from about S parts to about 100
parts per hundred parts of polymer blend but the useful
upper xange is limited by the high viscosity imparted
15 by fillers of this type. The preferred amounts of these
reinforcing fillers range from about 20 parts to about 80
parts per hundred parts of polymer blend for hydrated
silica and carbon black and from about 10 parts to about
50 parts per hundred parts of polymer blend for sintered
20 colloidal silica.
Any of several known and conventional antioxidants
can be incorporated into the polymer blends herein at from
about 0.1 parts to about ~.0 parts, and preferably at about
1.0 part, per hundred parts of resin. Agerite*MA
25 ~R. T. Vanderbilt Company, Inc.), a polymerized trimethyl
dihydroquinoline antioxidant, has been used with good
results.
* Trade Mark
~0
1 of the ~ollowing examples in which all percentages
are by weight, Examples l and 2 demonstra-te by way of
comparison with the remaining examples which are illustra-
tive of the invention herein, -the critical importance of
5 the presence of both the protective colloid and the surface
active agent in the polymerization medium.
L~
-19-
am~le 1
This example demonstrates that the use of a
protective colloid alone yields a polymer with high
Mooney viscosity (more than a value of 30) but high
5 gel content. The following solution was prepared:
Deionized Water 850 gm
Gelvatol 20-30 45.7 gm
Sodium Bicarbonate l.13 gm
(Gelvatol 20-30 is a Monsanto Company polyvinyl alcohol,
~7~89% hydrolyzed and of 4.7 - 5.4 cp viscosity for a 4
10 solution.) The polyvinyl alcohol and the bicarbonate
were suspended in the water and the mixture was stirred
until complete dissolution was achieved. The solution
was sparged with nitrogen-for 30 minutes and then 0.04 gm
(4 cc of a l~ solution) of ferrous sulfate heptahydrate
15 was added~ The solution and:
Vinyl acetate 800 gm
Ammonium persulfate 3.3 gm dissolved in 50 cc water
were charged to a one-gallon, stainless steel pressure
reactor equipped with external electric heating strips,
20 internal cooling coil and agitator. The reactor was then
purged with nitrogen to remove all oxygen. The charge
was heated to 120F. During the heat-up period the reactor
was stirred at 670 rpm and ethylene was added to a pressure
of 2500 psig. When the reaction conditions of pressure
25 and temperature were reached, the polymerization was
started by adding 2 gm of sodium bisulfite dissolved in
65 cc of water. The reactor temperature and pressure
~l~lB~30
,, o
1 were kept constant during the run~ The polymerization
was considered completed 7-1/2 hours after the bisulfite
addition, when the demand of ethylene ceased. The
emulsion was cooled to room temperature and then the
5 polymer was coagulated from the emulsion by freezing the
latex. The coagulated pol~ner was then dried in an air
oven at 120F.
A vinyl acetate/ethylene copo].~ner was obtained
with the following properties:
Vinyl acetate content 59.5%
Mooney viscosity, ML(1~4) at 212F. 70~5
Gel content 42~ (xylene 80C.)
-21-
1 Example 2
This example demonstrates that the use of surface
active agent(s) as the sole dispersant yields a polymer
with low Mooney viscosity (less than a value of 30) and
low gel content. The following solution, after being
sparged with nitrogen, was charged to the reactor described
in Example 1:
Deionized Water 850 gm
Pluronic F~68 51.2 gm
Sipon ESY 14 gm
Sodium Acetate 3.2 gm
Ferrous Sulfate Heptahydrate 0.04 gm
Along with this solution, the following were charged
to the reactor:
Vinyl Acetate 800 gm
Ammonium Persulfate 3.3 gm dissolved in 50 cc ~2
~5 The polym~rization was carried out in the same way as
described in Example 1.
The polymer was coagulated from the emulsion by
adding with stirring a hot saturated solution of so.dium
chloride. The coagulated polymer was washed four times
with water and then dried in an air oven at 120F. The
vinyl acetate/ethylene copolymer obtained had the following
properties:
Vinyl acetate content 55.9%
Mooney viscosity, ML(1+4) at 212F. 25
Gel content 0.32% (xylene 80C)
--22--
~3
This exa~ple demonstrates that the use of a
combination of protective colloid and surface active
agents as dispersants yield a polymex with high Mooney
5 viscosity and low gel content. The following solution,
after being sparged with nitrogen, was charged to the
reactor described in Example 1:
Deionized Water 850 gm
Gelvatol 20-30 11.6 gm
Pluronic F-68 38.4 gm
Sipon ES~ 14 gm
10 Sodium Acetate 3.2 gm
Ferxous Sulfate Heptahydrate 0.04 gm
~long with this solution the following were charged
to the reactor:
Vinyl acetate 800 gm
Ammonium persulfate 3.3 gm dissolved in 50 cc Water
The polymerization was started with 1.08 gm of sodium
bisulfite dissolved in 35 cc of waterO The remainder of
the run was carried out as described in Example 1-. The
polymer was recovered from the emulsion by coagulating
20 the latex with sodium chloride as described in Example 2.
The vinyl acetate/ethylene copolymer obtained
had the following properties:
Vinyl acetate content 57.8
Mooney viscosity, ML~1~4) at 212F. 38.5
Gel content 0.16% (xylene 80C)
Although the combination of polyvinyl alcohol and
surface active agents as practiced in this example would
be expected on the basis of prior expexience to result in
.
3~
-23-
1 high or low values of both Mooney viscosiky and gel, or at
best some average values of these in the copolymer product,
surprisingly,Mooney viscosity was maintained at a desirable
level while gel content was actually reduced. In sub-
5 sequent examples (e.g., Examples 4 and 5), it is demonstratedthat gel can be vir-tually eliminated while attractive
Mooney viscosity is achieved by proper protective colloid
to surface active agent ratios.
~2~-
1 Example 4
This example demonstrates that the ratio of
concentration of protective colloid to that of surface
active a~ent(s) used as dispersants for Example 3 may
5 be varied within certain limits without affecting sub-
stantially desirable polymeric properties of hiyh Mooney
viscosity and low gel content. I'he following solution,
after being sparged with nitrogen, was charged to the
reactor described in Example l:
Deionized Water 850 ~m
Gelva~ol 20-30 24.4 gm
Pluronic F-68 20.5 gm
Sipon ESY 14 gm
Sodium Acetate 3.2 gm
Ferrous Sulfate ~eptahydrate 0.04 gm
Along with this solution the following were charged
15 to the reactor:
Vinyl acetate 800 gm
Ammonium persulfate 3.3 gm dissolved in 50 cc Water
The polymerization was started with 25 cc of a 3~ sodium
bisul~ite solution. Then,every hour an additional lO cc
of this solution was pumped to the reactor, for~a total
of six additions. The remainder of the run was carried
out as described in Example l. The polymer was recovered
from the latex as described in Example 2.
The vinyl acetate/ethylene copolymer obtained had
the following properties:
Vinyl acetate content 61.7
Mooney viscosity, ML(1~4) at 212F. 47
Gel content -- All dissolved except for trace
of slimy material (not measurable)
(xylene ~0C.)
~3
-25-
1 Example 5
In this example, a different ratio of protective
colloid/surface active agent (5) iS employed. The following
solution after being sparged with nitrogen was charged to
the reactor described in Example 1:
Deionized Water 850 gm
Gelvatol 20-3~ 30.9 gm
Pluronic F-68 17.9 gm
Sipon ESY 14 gm
Sodium ~cetate 3.2 gm
Ferrous Sulfate Heptahydrate 0.04 gm
Along with this solution the following were charged
to the reactor: --
Vinyl acetate 800 gm
Ammonium persulfate 3.3 gm dissolved in 50 cc Water
The run was carried out following the procedure described15 in Example 1, using 2 gm of sodium bisulflte dissolved in
65 cc of water to start thè polymerization. The polymer
was recovered from the latex following the procedure
described in Example 2.
The vinyl acetate/ethylene copolymer obtained had
the following properties:.
Vinyl acetate content 62.9%
Mooney viscosity, ML(1+4) at 212F. 37.5
Gel content less than 0.05%
.. ~0
-26-
1 Example 6
This example demonstrates that the incorporation
of t-butyl alcohol in the polymerization reaction medium
has no substatial effect on -the polymer properties. The
5 following solution, after being sparged with nitrogen,
was charged to the reactor described in Example 1:
Deionized Water 760 gm
t-butyl alcohol 90 gm
Gelvatol 20-30 11.6 gm
Pluronic F-68 38.4 gm
Sipon ESY 14 gm
Sodium Acetate 3.2 gm
10 Ferrous Sulfate Heptahydrate 0.04 gm
Along with this solution the following were charged
to the reactor:
Vinyl acetate 800 gm
Ammonium persulfate 3.3 gm dissolved in 50 cc Water
15 Following the procedure described in Example l, the
polymerization was started with 2 gm of sodium bisulfite
dissolved in 65 cc of water. Then,every two hours an
additional 20 cc of this solution were pumped to the
reactor for a total of three additions.
The polymer was recovered from the latex following
the procedure described in Example 2.
The following vinyl acetate/ethylene copolymer
was obtained:
Vinyl acetate content 58.6% -
Mooney viscosity, ML(1+4) at 120F. 405 Gel content Polymer completely soluble
in xylene at 80C.
1 F~arnple 7
his example demonstrates the use of a higher
total concentration of surface active agent. The following
solution, after being sparged with nitrogen, was charged
5 to the reactor described in E~ample l:
Deionized Water 850 gm
Gelvatol 20~30 22.9 gm
Pluxonic F-68 38.4 gm
Sipon ESY 14 gm
Sodium Acetate 3.2 gm
Ferrous Sulfate Heptahydrate 0.04 gm
lO Along with this solution the following were charged
to the reactor:
Vinyl acetate 800 gm
Ammonium persulfate 3.3 gm dissolved in 50-cc Water
The polymerization was started ~ith 25 cc of a 3% sodium
15 bisulfite solution. Then, every hour an additional lO cc
of this solution was pumped to the reactor for a total of
six additions. The remainder of the run was carried out
as described in Example l. The polymer was recovered from
the latex as described in Example 2. The vinyl acetate/
20 ethylene copolymer obtained had the following properties:
Vinyl acetate content 56.8%
Mooney ViSCGSity~ ML(1~4) at 212F. 50
~0
1 E~ le 8
This example demonstrates the further processing
of the elastomers of this invention and the resulting products.
The VAE copolymers produced in Examples 3, 4, 6 and 7 were
subjected to evaluation as elastomeric products. A cor~mercial
high pressure process VAE copolymer elastomer (VYNATHENE*
EY-907, a U. S. Industrial Chemicals Co. product having
about 60 percent vinyl acetate content) was used as a
standard. To carry out this evaluation the elastomers
10 were compounded according to the following formulation:
Elastomer 100 phr
HiSil 233 55 phr
Silane A-172* 1 phr
Agerite MA 1 phr
VulCup 40 KE 3 phr
* Vinyl tris (betamethoxyethoxy) silane coupling agent
(Union Carbide)
The compounding was done on a 6"x12" two-roll rubber mill.
The compounds were then press cured into 6"x6"x0.075"
plaques in an ASTM mold. The plaques were pressed with
2000 psig pressure at 396F. for five minutes. The
results of the evaluation are indicated in Table l.
TABLE I
(1) (1)
Tensile % Swell %
Strength psi Elong. Ratio Extract
Example No. 3 2250 370 5.12 8.20
25 Example No. 4 2520 420 5.28 7.~30
Example No. 6 2320 440 5.63 7.84
Example No. 7 2270 360 5.54 7.34
Vynathene EY-907 3000 280 3.62 5.46
(1) In xylene at 80C.
30 `
* Trade Mark
-29-
~xamPle 9
This example demonstrates that the VAE elastomers
of this invention can provide cured resins having properties
such as elongation and low temperature brittleness (Compound
III) which are superior to those commercially available.
Using the reaction medium and polymerization conditions
described in Example 7, several batches of elastomer were
made. The elastomers obtained were blended and subsequently
cured using different levels of curing agent and using
10 a coagent in the compounding formulation. The blend had
the following properties:
Vinyl acetate content 62.5%
Mooney viscosity, ML(H4) at 212F. 37.5
Vynathene EY-907 was used as the standard.
The experimental resin and the commercial elastomer
were compounded as indicated in Table II as follows:
TABLE II
Compound Compound Compound
I II III
Elastomer lO0 100 100
HiSil 233 55 55 55
Silane A-172
Agerite MA
VulCup 40 KE 3.75 4.5 3
TAIC (Triallyl isocyanurate)
The amounts are given in parts/100 parts of resin.
The products were compounded and cured as indicated previously.
The results of the evaluation are indicated in Table III
below.
.
~s~
--30--
o ~ cO
E~ ~ ~ r~ r~ r~7 r~ r~
~r~ o d o o t~
~ s~ co r~ ~ co
X OJ u~
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r~ ~~ ~ ~ ~~ r~ I
~ Ocn r~ rn o
3 ~~ r~~ rf~ r~
1 0 r~
~ O
rl rdo r~ ~ cn ,
r~ ~I~ ~D D In, ~D Ln
0 3 cn
H
H
h ~ ¦ o r > o O
rt~
a) ~ ,_ ~ s~ O O
b~l ~1 ~ h o ~a
O O O O O O O :~ o r.~ Iq
~ cn ~1 ~ ~ o ~ o
s~ ~ ~ ~ D ~ ~D O O
Cl ~ Q U Q, rt~ n~
~ U ~ u~ ~
, ~ ~ rd S~
~ ~ ~ ,1
rC ; ~C lq o s~
~J) ~ r-l ~> '>1~ .4
~r-l ~ Lf~ cn1~ o r~ ~ ~
u~ ~~Y tO ~ ~
r~c~l r~ rl ~ o
E S ~q R , r~ r-l ~
rd ,Q ~~ ~ ~1 U ~P ~/
(~ rcJ r~ I r-l 3
E~ ~ E.~ ~ (d q ~1 1~1 f~ d~
,, ~,) C~ C.) 1.
.
~t.'~ D~
-31-
1 E~ple 10
This example demonstrates that the process of
5 this invention is not limited to the use of a single
catalyst system. Thus, the redox catalyst system
ammonium persulfate/sodium ~ormaldehyde sulfoxylate
reduces polymerization time in comparison to ammonium
persulfate/sodium bisulfite, yet produces an entirely
10 acceptable copolymer.
The following solution, after being sparged with
nitrogen, was charged to the reactor described in Example 1:
Deionized Water 850 gm
Gelvatol 20-30 22.9 gm
Pluronic F 68 38.4 gm
Sipon ESY 14 gm
Sodium Acetate 3.2 gm
Ferrous Sulfate Heptahydrate ' 0.04 gm
Along wi~h this solution the following was charged
to the reactor:
Vinyl acetate 800 gm
Ammonium persulfate 3.3 gm dissolYed in 50 cc
~ deionized water
A 0.25% aqueous solution o~ sodium formaldehyde
sulfoxylate was prepared and charged to the catalyst feed
tank. Following the same procedure as described in
Example 1, the reactor was heated and pressurized with
25 ethylene. When the reactor conditions of temperature and
pressure (120F., 2500 psig) were reached, the polymerization
was started by pumping the reducing agent solution to the
1 reactor. The flow was se-t at approximately 40 cc/hour.
The polymerization was considered completed when the
ethylene demand ceased, 6 hours after beginniny addition
of the reducing agent.
S The polymer was recovered from the emulsion by
coagulating the latex with sodium chloride as described
in Example 2.
The VAE copol~ner obtained had the following
properties:
10 Vinyl acetate content 56.8
Mooney viscosity, ML(1+4) at 212F. 43.5
Gel content All dissolved except for trace
slimy material not measurable
(xylene 80~.)
-33-
This e~ample demonstrates the use of the catalyst
system ammonium persulfate/sodium hydrosulfite.
The reactor described in Example 1 was charged with
5 the same solution, persulfate and vinyl acetate, as described
in Example 10. A 1.5% aqueous solution of sodium hydro-
sulfite was prepared and charged to the catalyst feed tank.
The reactor was heated and pressurized as described
in Example 1. When the reactor conditions or temperature
10 and pressure (120F.,2sO0 psig) were reached, the
polymerization was started by pumping the reducing
agent solution to the reactor. The flow was set at
approximately 60 cc/hour. The polymerizaton was con-
sidered completed when the ethylene demand ceased, 5
5 hours after beginning the addition of the reducing
agent.
The polymer was recovered from the emulsion by
coagulating the latex with sodium chloride as described
in Example 2.
The VAE copolymer that was obtained had the
following properties:
Vinyl acetate content 56.7%
Mooney viscosity, ML(1+4) at 212F. 46
Gel content All dissolved except for trace
slimy material (not measurable)
xylene 80C.
-3~~
Example 12
This example demonstrates the use of acrylic acid
as a termonomer, and the attendant production of polymer
5 with increased Mooney viscosity without increased gel.
The reac~or described in Example 1 was charged
with the same solution described in Example 10.
Along with this solution the following was charged
to the reactor:
Vinyl acetate 800 gm
Acrylic acid 18 gm
Ammonium persulfate3.3 gm dissolved in 50 cc
deionized water
A 0.25~ aqueous solution of sodium formaldehyde
sulfoxylate was prepared and charged to the catalyst
feed tank.
The reactor was heated and pressurized as described
in Example 1. When the reaction conditions of temperature
and pressure were reached the polymerization was started by
pumping the reducing agent solution to the reactor. The
flow was set at approximately 45 cc/hour. The polymerization
20 was considered completed 6-1/2 hours a~ter beginning addition
of the reducing agent. The polymer was recovered from the
emulsion by coagulating the latex with sodium chloride as
described in Example 2.
The vinyl acetate/ethylene/acrylic acid terpolymer
25 that was obtained had the following properties:
Vinyl acetate content 58.1%
Mooney viscosity, ML(1~4) at 212F. 5S
Gel content All dissolved except for trace
slimy material (not measurable)
xylene 80C.
3~
-35-
1 Example 13
~ vinyl acetate/eth~lene/1,6 hexanediol diacr~late
terpolymer having unexpec-tedly low gel content and
furnishing improved, cured elastomers is preparedO The
5 following solution was prepared:
Deionized Water 850 gm
Gelvatol 20~30 22.9 gm
Pluronic F-6~ 38.4 gm
Sipon ESY 14 gm
Sodium Acetate 3.2 gm
Ferrous Sulfate Heptahydrate 0.04 gm
10 The polyvinyl alcohol, the Pluronic and the sodium
acetate were suspended in the water. The mixture-was
- stirred approximately one and one-half hours until
complete dissolution of the components. The solution
was sparged with nitrogen for 30 minutes and then the
15 Sipon ESY and the ferrous sulfate heptahydrate (1% aqueous
solution) were added. The solution plus
Vinyl acetate
1,6 hexanediol diacrylate
Ammonium persulfate 3.3 gm dissolved in 50 cc Water
were charged to a one-gallon stainless steel pressure
20 reactor equipped with external electric heating strips,
internal cooling coil and agitator. The reactor was then
purged with nitrogen to remove all oxygen ~rom the system.
The charge was heated to 120F. During the heat-up period
the reactor was stirred at 670 rpm and the ethylene was
25 added to a pressure of 2500 psig. The polymexization was
then started by adding 30 cc of a 3% sodium bisul~ite
solution. Then, ever~ hour an additional 10 cc of this
-36~
1 solution was pumped to the reactor for a total of six
additions. The reaction temperature and pressure were
kept constant during the run. The polymerization was
considered completed when the ethylene demand ceased,
5 seven and one-halr hours after the first sodium bisulfite
addition.
The polymer was coagulaked from the emulsion by
adding under stirring a hot saturated sodium chloride
solution. The coagulated polymer was then washed four
10 times with warm water and dried in an air oven at 120F.
This procedure was used to make several runs with
increasing concentration of 1,6-hexanediol diacrylate.
Table IV below sets forth the amounts of vinyl acetate
and 1,6-hexanediol diacrylate used in each run.
TABLE IV
Gm of 1,6- % of 1,6-Hexanediol
Gm of Vinyl Hexanediol Diacrylate Based
Run No. Acetate Diacrylate on Vin~ Acetate
1 800 1 0.125
20 2 800 4 0-5
3 800 8
4 800 16 2
800 32 4
6 750 75 10
7* 670 140 20
* Product coagulated in the reactor.
Table V below summarizes the properties of the
polymers made in these runs.
B6DV
-37
1 TABLE V
Mooney Viscos- ~ 1,6 Hexanedlol
Run Vinyl Acetate ity ML(1~4) at Diacrylate in Gel Con-
No~ ~ 212F. ~ ~ tent %
1 60.4 37 --
2 59.0 34.5 -- 0
3 60.5 35 -- o
4 60.3 41 1.8 - 2.4 0
60.3 38.53.9 - 4.5 0
6 59.9 35.5 4.2 0
7 56.9 37.5 ~.8 0
The polymers made in these runs were subjected to evaluation
l0 as an elastomeric product. A commercial VAE copolymer
elastomer (VYNATHENE EY-907, Table III) was used as the
standard. To carry ~ut this evaluation, the resins were
compounded and cured according to the procedure of Example
8. Results of the evaluation are set forth in Table VI
15 as follows:
TABLE VI
Oil
Tensile Tensil Resist., Swell %
Strength Strength % % Swell Ratio Extr.
Run No. psig psig (1) Elong. Ratio(2) (3) (3)
20 EY-907 2740 710 - 280 67 3.82 7.08
1 2230 690 490 89 5.73 6.36
2 2190 690 480 94 5.97 9.12
3 2360 690 490 91 5.72 9.50
4 2370 730 480 75 5.60 8.98
2190 810 370 83 4.58 9.45
6 2380 990 410 81 5.21 8.85
(1) After aging 7 days at 350F.
(2) AST~ #3 oil, 70 hours at 302F.
(3) xylene at 80C.
3~
-38-
1It is readily seen that the terpolymer elastomers
furnish high elongation with the cured rubbers having
improved resistance to loss of tensile strength upon
heat aging at 350F. This combination of properties
5 is surprising since the diacrylate monomer, a crosslinking
monomer, would be expected to reduce elongation in the
compound.
-
~0
