Note: Descriptions are shown in the official language in which they were submitted.
-- 1 --
USE OF AN ELECTROLYTE IN THE EMULSION
POLYMERIZATION PROCESS FOR PRODUCING
VINYL DISPERSION RESINS
BACXGROUND OF THE INVENTION
It is well known that vinyl resins may be
plasticized or changed from the hard, horny and stiff
state to a soft, plastic workable condition by the
addition thereto, at elevated temperatures, of certain
plasticizers, such as dioctyl phthalate, and the like.
These vinyl polymers or resins are referred to as dis-
persion resins or paste resins and are usually made
employing an aqueous emulsion polymerization technique.
In some cases, a suspension polymerization process has
been used, but emulsion polymerization is preferred.
15When the vinyl dispersion resin is mixed or
blended with a plasticizer, it is referred to as a
"plastisol". By virtue of the flowability of the plas-
tisol, it can be processed into various useful products.
For example, the plastisols can be used in making molded
products, films, coatings, and the like. Accordingly,
the vinyl dispersion resin must be capable of being
mixed with the plasticizers easily and uniformly to form
low viscosity plastisols which are stable, containing
particles of uniform and proper size, and capable of
25 producing films, and like products, of good clarity.
With the customary emulsion polymerization
processes, suitable latices have been difficult to
obtain since the latices usually conta.in particles of
varying size and are either too fine or too large.
30 Various proposals haYe heretofore been made to overcome
these difficulties but not with the ultimate success
desired. For example, the use of various different
emulsifiers and catalysts have been proposed. Also,
varying the conditions of polymerization has been
35 suggested. However, in most o these cases, too much
, 1~38~5
-- 2 --
coagulation occurred with the resulting latex containing
too much coagulum or partially agglomerated particles
which precipitate reducing the yield. Further, the
shelf~ife of such latices leave much to be desired. It
is desirable to have latices which change very little
during storage with respect to viscosity and have and
maintain good heat stability.
In U.S. Patent No. 4,076,920, issued February
28, 1978, a process for preparing vinyl dispersion
resins is disclosed and claimed which produces polymers
having unique properties for certain end uses. However,
here, as in other prior art processes, it is necessary
to spray dry the latex or polymer emulsion resulting in
aggregates of the polymer particles which requires
grinding to break them up into a size capable of being
used in plastisols. As a result of the crushing and
grinding required to reduce the polymer to a size capable
of being used in plastisols and, also because of the
varying sizes and irregular shapes of the ground frag-
ments, the plastisols produced from them have highviscosities relative to their solids content. Further,
the excessive grinding required develops excessive heat
which tends to fuse the polymer.
As opposed to "pearl" or suspension polymer-
ization, where the polymer particles are large enough to
be filtered, vinyl dispersion resins cannot be recovered
from the water emulsions by filtration and tray drying
because they go through the filters and also because the
small particles pack tightly together during tray drying
forming "cake" that even after grinding remains hard to
formulate into smooth plastisols making it practically
useless for most commercial operations. The particles
of polymer to be used in a plastisol should preferably
be spherical in shape to present as small a particle
surface as possible for minimum solvation. Also, a
dispersion of spheres provides the lowest flow viscosity
1138150
for charging molds, coating and like operations (See U.S.
Patent No. 3, 179, 646, issued April 20, 1965).
Another problem in making vinyl dispersion resins
is the formation of undesirable polymer buildup on the inner
surfaces of the reactor. This deposlt or bulldup of polymer
on sald reactor surfaces not only interferes with heat trans-
fer, but also decreases productlvity and adversely affects
polymer quallty, such as produclng finer particles than
desired with the resultant adverse effect on viscosity. Ob-
vlously, thls polymer bulldup must be removed, withlts atten-
dant dlfflcultles. It would be most deslrous to prevent or
substantially eliminate polymer bulldup ln the flrst instance.
We have unexpectedly found that when the emulsion
polymerizatlon of vlnyl dlsperslon reslns ls conducted ln the
presence of an electrolyte, such as, for example, the
"fugltlve" ammonium carbonate ((NH4)2CO3), whlch evaporates
durlng drylng, the resultlng aqueous polymer emulslon can be
tray drled lnto friable aggregates of lndividual spheres of
polymer particles which can be separated into lndivldual
spherical polymer particles by simple light rubbing or crush-
ing. In the process of the present lnventlon, whereln tray
drying is employed, in additlon to the electrolyte, the poly-
merlzatlon reaction of the vlnyl monomer or monomers ls con-
ducted in an aqueous alkallne medlum uslng a free radlcal
yleldlng polymerlzation initlator, at a temperature of about
30C to about 70C, ln the presence of an emulslfier for the
polymerization system, for example an ammonlum salt of a
hlgh fatty acld containing from 8 to 20 carbon atoms, and at
least one long straight chain alcohol contalnlng from 14 to
24 carbon atoms, wherein the ratio of alcohol to emulsifier is
equal to or greater than 1.0 and whereln the reaction ingre-
dients are thoroughly mixed, and preferably homogenized, prior
to polymeriza-
.~
,'
:
: :
:; : : :
-- 4 --
tion. When employing the process of the invention, thepolymer buildup in the reactor is reduced and multiple
polymerizations can be run in the reactor without open-
ing the same thereby substantially reducing the amount
5 of unreacted monomer in the surrounding atmosphere.
DETAILED DESCRIPTION
In the present invention, "vinyl dispersion
resin" refers to polymers and copolymers of vinyl and
vinylidene halides such as vinyl chloride, vinylidene
chloride, and the like. The vinyl halides and vinyl-
idene halides may be copolymerized with one or more
vinylidene monomers having at least one terminal CH2=C
grouping. As examples of such vinylidene monomers may
be be mentioned the ,~-olefinically unsaturated car-
boxylic acids, such as acrylic acid, methacrylic acid,-cyanoacrylic acid, and the like; esters of acrylic
acids, such as methyl acrylate, ethyl acrylate, butyl
acrylate, octyl acrylate, cyanoethyl acrylate, and the
like; esters of methacrylic acid, such as methyl meth-
acrylate, butyl methacrylate, and the like; nitrilessuch as acrylonitrile and methacrylonitrile; acrylamides,
such as methyl acrylamide, N-methylol acrylamide, N-
butoxyl methacrylamide, and the like; v nyl ethers, such
as ethyl vinyl ether, chloroethyl vinyl ether, and the
like; the vinyl ketones; styrene and styrene derivatives
including a-methyl styrene, vinyl toluene, chloro-
styrene, and the like; vinyl naphthalene, allyl and
vinyl chloroacetate, vinyl acetate, vinyl pyridine,
methyl vinyl ketone, and other vinylidene monomers of
the types known to those skilled in the art. The present
invention is particularly applicable to the manufacture
of vinyl dispersion resins or pastes made by the poly-
merization of vinyl chloride or vinylidene chloride
alone or in admixture with one or more vinylidene
monomers copolymerizable therewith in amounts as great
as about 80~ by weight, based on the weight of the
~i38~50
-- 5 --
monomer mixture. The most preferred vinyl dispersion
resin is polyvinyl chloride (PVC) and the invention, for
simplicity and convenience, will be described in connec-
tion therewith, it being understood that this is merely
intended in an illustrative and not a limitative sense.
The important aspect of the instant invention
is the provision of a process for producing vinyl dis-
persion resins wherein, after the formulation of the
polymer latex or aqueous polymer emulsion, the same can
10 be dried into friable aggregates of individual spheres
of polymer particles by simple tray drying. This elim-
inates the troublesome spray drying and grinding which
very often results in undesirable polymer quality. The
inventive concept which enables one to tray dry the
15 polymer emulsion is in the use of an electrolyte in the
polymerization recipe. The electrolytes useful in the
present invention are ammonium carbonate ((NH4)2CO3),
calcium chloride (CaC12), calcium carbonate (CaCO3),
ammonium phosphate, the bicarbonates, the sodium salts
20 such as carbonates, bicarbonates and phosphates, and the
like. The amount of electrolyte suitable for use in the
present invention will vary from about 0.05% to about
6.0% by weight, based on the weight of the monomer or
monomers being polymerized. Preferably an amount in the
25 range of 0.1% to 2.0% by weight is employed.
The friable aggregates resulting from the
process of the instant invention represent a distinct
advantage or improvement over prior known means for
recovering vinyl dispersion or paste resins from the
30 water for use in plastisols, for example, spray drying
and subsequent grinding. The friable aggregates of the
present process can easily be handled in the post poly-
merization stages of polymer or resin recovery. The
friable aggregates are easily formed and the individual
35 spherical particles of the vinyl dispersion resins,
of a size required for paste resins are easily formed by
-- 6 --
crushing, simple grinding or rubbing of said aggregates.
Usually, the individual spherical particles of polymer
will have a size or diameter in the range of 0.1 micron
to about 10.0 microns. For most of the commercial uses
5 of plastisols today, it is preferred to have polymer
particles in the range of 0.2 micron to 2.0 microns.
Surprisingly, there are other pluses in the
use of the electrolytes in the emulsion polymerization
process besides the ability to use tray drying and get
10 an improved quality product. For example, when employ-
ing the electrolyte in the polymerization recipe the
rate of conversion of monomer(s) to polymer is increased
resulting in an overall decrease in the time for com-
plete polymerization which in turn results in increased
15 production per unit of time thereby reducing the cost of
making vinyl dispersion resins when using the present
process.
Another surprising feature of the present
invention is that polymer buildup on the internal sur-
20 faces of the reactor is reduced. While it is not knownprecisely why such reduction in buildup occurs, it is
believed to be due in part not only to the presence of
the electrolyte in the recipe, but also to the speed of
the reaction and the lower reaction temperatures, since
25 it is known that the higher the temperature of reaction
for prolonged periods of time increases the likelihood
of excessive polymer buildup. In any event, the polymer
buildup problem is greatly improved when using th~
present invention. Further, when employing the present
30 process, the vinyl dispersion resin and the plastisol
application properties, such as heat stability, water
resistance, flow properties, and the like, are not
adversely effected and in fact, if anything, they are
improved.
When making vinyl dispersion resins by the
emulsion polymerization procedure it is necessary to
~3~1g~
-- 7 --
employ a proper emulsifier or emulsifier system. For
example, various fatty acid derivatives and salts there-
of may be employed, as well as the sulfate and sulfonate
type soaps of from C12 to C20 alkyl or aryl hydrocarbons,
5 or various combinations thereof. However, in the
present invention, in order to get the proper water
resistance and heat stability in films made from plasti-
sols of the vinyl dispersion resins, preferably the
ammonium salt of a long chain saturated fatty acid is
10 employed as the emulsifier. The saturated fatty acids
which are useful may be either natural or synthetic and
should contain from 8 to 20 carbon atoms. As examples
of such acids there may be named lauric, myristic,
palmitic, marganic, stearic, and the like, beef tallow,
15 coconut oil, and the like. The ammonium salt emulsifier
is employed in an amount in the range of about 0.5% to
about 4.0% by weight based on the weight of the monomer
or monomers being polymerized. One can also use mix-
tures of the ammonium salts of the fatty acids in the
20 emulsifier system.
The ammonium salts of the fatty acids can be
made by mixing the fatty acid and = onium hydroxide,
separating the salt and then adding the same to the
polymerization medium or polymerization premix in the
25 usual fashion. However, it is preferred to form the
ammonium salt in situ, that is, by adding the fatty acid
and ammonium hydroxide separately to the polymerization
mixture or medium wherein they react to form the salt.
An excess of ammonium hydroxide, over that necessary to
30 react with the fatty acid, should be employed in order
to maintain the reaction medium on the alkaline side.
In addition to the ammonium salt of a long
chain fatty acid emulsifier, it is often desirable to
employ a long straight chain saturated alcohol in com-
35 bination therewith, said alcohol being one containingfrom 14 to 24 carbon atoms. Examples of such alcohols
~3siso ,
are tetradecanol, pentadecanol, hexadecanol, hepta-
decanol, octadecanol, nonadecanol, eicosanol, heneico-
sanol, tricosanol, and tetracosanol. Mixtures of the
alcohols can also be employed and in many cases an
alcohol mixture is preferred, such as, for example, a
mixture of a 14 carbon alcohol and an 18 carbon alcohol.
Also, lower carbon content alcohols can be employed when
mixed with the longer chain alcohols, such as a mixture
of dodecanol and octadecanol. When employing an alcohol,
the ratio of alcohol to the ammonium salt of the fatty
acid of 1.0 can be used., However, the best results are
obtained when said ratio is greater than 1Ø
As pointed out above, the reaction medium
should be maintained on the alkaline side, and prefer-
ably at a high pH. The present process can be conductedat a pH in the range of about 7.0 to about 12Ø How-
ever, it is preferred to operate in a pH range of about
8.0 to about 10.5. If the pH is too high it takes too
much NH40H and if the pH is too low, for example, below
7.0, the polymer buildup in the reactor increases and
the coagulum increases. The amount of NH40H needed to
properly adjust the pH will depend in part on the par-
ticular emulsifier system being used in the reaction
mixture. Of course, other alkaline agents may be
employed to adjust the pH of the reaction mixture, such
as NaOH, KOH, etc. The choice of a particular alkaline
agent depends upon the ingredients in the reaction
medium.
The process of the present invention, wherein
an electrolyte is employed in the reaction mixture and
the product is tray dried, is conducted in the presence
of a compound or compounds capable of initiating the
polymerization reaction. Free radical yielding initi-
ators, normally used for polymerizing olefinically
unsaturated monomers, are satisfactory. The useful
initiators or catalysts include, for example, the
1~38~50
g
various peroxygen compounds, such as lauryl peroxide,
isopropyl peroxydicarbonate, benzoyl peroxide, t-butyl
hydroperoxide, t-butyl peroxypivalate, cumene hydro-
peroxide, t-butyl diperphthalate, pelargonyl peroxide,
5 l-hydroxycyclohexyl hydroperoxide, and the like; azo
compounds such as azodiisobutyronitrile, dimethylazo-
diisobutyrate, and the like. Also, useful initiators
are the water-soluble peroxygen compounds, such as
hydrogen peroxide, persulfates, such as potassium per-
sulfate, ammonium persulfate, and the like. The amountof initiator used will generally be in the range of from
about 0.01~ to about 0.5% by weight, based on the weight
of the monomer or monomers being polymerized, and pre-
ferably from about 0.02% to about 0.1~ by weight.
In the present process, the initiator may be
charged completely at the outset of the polymerization
or it may be added incrementally to the reactor during
the course of the polymerization reaction. However, it
is preferred to charge the initiator at the outset by
adding it to the monomer premix with the other ingredi-
ents of the reaction mixture. This is advantageous when
said premix is homogenized prior to introduction into
the reactor. When adding the initiator to the monomer
premix and then thoroughly mixing with high speed agi-
25 tation or stirring, or when homogenizing the premix,such as when an alcohol(s) is employed in the reaction
mixture, it is necessary to keep the temperature below
the minimum temperature of reactivity of the particular
initiator or initiators being employed. This minimum
30 temperature of reactivity of any one initiator is
readily determinable by one skilled in the art and very
often, is supplied by the initiator or catalyst manu-
facturer. After introduction of the monomer premix into
the reactor, the temperature is adjusted to that at
35 which the reaction is to take place.
~38~o
-- 10 --
The temperature of reaction of the instant
emulsion polymerization process is important since the
intrinsic viscosity (IV) of the resultant vinyl disper-
sion resin is a direct function of the temperature of
5 reaction. That is the higher the temperature the lower
the IV. Accordingly, the end use for the vinyl disper-
sion resin to be produced will normally dictate the
reaction temperature. For example, when producing vinyl
dispersion resins to be used in coatings or in casting
10 flexible films, a lower temperature will be employed in
order to attain a higher IV which is desirable ~or many
coating applications and film-forming operations. We
have found that for the end uses to which the vinyl dis-
persion resins of this invention are particularly
adapted, polymerization temperatures in the range of
about 30C to about 70C are satisfactory. However, it
is preferred to employ a temperature in the range of
about 30C to about 55C.
Another factor, which must be considered with
respect to the temperature of the reaction, is that of
polymer buildup in the reactor. In general, as the
temperature of reaction is increased, the polymer build-
up in the reactor increases. However, the polymer
buildup is not of the hard crusty type and can be re-
moved by rinsing or hosing down with water and withoutopening the reactor when appropriate spray nozzles are
installed in the reactor. On the other hand, even this
buildup is controlled and reduced by the presence of the
electrolyte in the reaction medium. In combination with
the electrolyte, the walls of the reactor are kept cool
during the polymerization reaction, especially during
the early stages of the reaction when most of the build-
up, if any, forms. The regulation of the temperature of
the reaction can be accomplished by normal means, such
as employing a jacketed reactor with circulating cool
water or other liquid in the jacket. It is believed
li38~o
that a synergistic effect results from the use of the
electrolyte with a cooled reaction medium in the early
stages of the reaction cycle since polymer buildup is
reduced. Repeated cycles can be run without cleaning
the inner surfaces of the reactor between charges or
cycles thus increasing the efficiency of the process and
reducing the cost of producing vinyl dispersion resins
having a wider scope of end uses.
Upon completion of the polymerization reaction,
the vinyl dispersion resin is isolated in powder form,
that is, in the form of discrete spherical polymer
particles. This is accomplished by filtering the latex
from the polymerization reactor in order to recover the
friable aggregates of polymer, tray drying the filtered
latex at a temperature in the range of about 23C to
about 100C. under atmospheric pressure during the course
of which the electrolyte comes off. The drying tempera-
ture can be lower or higher than the limits of said
range of temperature depending upon whether or not the
drying step takes place under a vacuum or under positive
pressure. The time of the tray drying step will depend
upon the particular polymer being dried. However, the
tray drying should continue until the water content of
the polymer is about 0.1% by weight or lower. The time,
25 of course, will vary with the temperature being employed.
The important thing is not to subject the polymer to
prolonged heating at elevated temperatures since such
heating may deleteriously affect the quality of the
polymer, such as discoloration, etc. After tray drying,
30 the friable aggregates of individual spheres of polymer
particles that are found are crushed lightly or rubbed
to separate the individual spheres and the dried polymer
or resin is recovered in powder form. The powdered
resin is then ready to be made into plastisols. It
35 should be pointed out that other forms or methods of
drying may be used, such as rotary dryers, air jet
~i38150
- 12 -
dryer, fluid bed dryer, etc., so long as spray drying
is not employed. Tray drying, however, is preferred.
Plastisols are made with the vinyl dispersion
resins of the present invention by uniformly blending or
5 intimately mixing, by conventional means using heat and
agitation, with 100 parts by weight of the vinyl disper-
sion resin in the form of discrete spherical polymer
particles, from about 30 to about 100 parts by weight of
one or more plasticizers. The useful plasticizers may
10 be described as the alkyl and alkoxy alkyl esters of
dicarboxylic acids or the esters of a polyhydric alcohol
and a monobasic acid. As examples of such plasticizers,
there may be named dibutyl phthalate, dioctyl phthalate,
dibutyl sebacate, dinonyl phthalate, di(2-ethyl hexyl)
phthalate, di(2-ethyl hexyl) adipate, dilauryl phtha-
late, dimethyl tetrachlorophthalate, butyl phthalyl
butyl glycollate, glyceryl stearate, and the like. The
preferred plasticizers are the liquid diesters of ali-
phatic alcohols having from 4 to 20 carbon atoms and di-
basic carboxylic acids having from 6 to 14 carbon atoms.
The plastisols made from the vinyl dispersionresins of the present invention should have the desired
yield and preferably with little or no dilatency. Yield
is simply defined as resistance to flow and is normally
determined numerically through viscosity measurements
employing well known standard techniques. Normally such
values are arrived at by calculation from viscosity
measurements using a Brookfield Model RVF Viscometer
according to ASTM method D1824-61T. Yield is determined
from viscosity measurements of the plastisols at varying
r.p.m.'s (revolutions per minute) after initial prepara-
tion and at intervals of aging. The viscosity is
measured in centipoises (cps.) at a temperature of 23C.
In the specific examples, that follow hereinafter,
viscosity measurements were made at 2 rpm. and 20 rpm.
and are expressed as V2 and V20 respectively.
- 13 -
To further illustrate the present invention,
the following specific examples are given, it being
understood that this is merely intended in an illustra-
tive and not a limitative sense. In the examples all
parts and percents are by weight unless otherwise
indicated.
EXAMPLE I
In this Example, a series of runs were made
to show the various aspects of the present invention.
The recipes used and the conditions of reaction are
set forth in the table which follows. In the table, all
figures are in parts by weight based on the weight of
the total composition.
.,
-- 14 --
,1 ~
~ ~ ~ ~ O
~ o ~ o I S~
U~ oCO Ul o o o o I O C
o Io o o I I I Io o I I I 1~ o o
o I I I I I I I I ~ o z 5.1 ~ a~
C
o O
U~
,~ t~ ~ O
_I o
~1 o O l7 o O I O C
o o o o I I I ~ I o o o I ~
~ r Z ~ ~ ~1
~r
o ~1 o ~ ~ o~ C~
o ~ ~ o I I I o I I I o I o u~
O III II I IO~
H
. ~ C~
Z ~ O ~1 ~ o ~ o o
o ~l I I o I I I o I I o I o ~ u~
E'3 o I I I I I I I I o ~
~ O
E~ _ ,~ Co
_1 '' ~ O O U~ O C ~
C ~ ~rl O
o I I I I ~ O o O I ~ r O s~
1 Z
I
.
O ~
C
~ ~ x 1~ q,, a) o
a~ ~l ~ O ~ ~1
--I ~ O X h ~1
m ~ o ~ ~ m C ~ ,~
r1 0 C ~
+ ~I S.l ~ ~ h Q Q O ~a
h~`1 'O h a5 h ~ ~ a~
_I u c~ 1 ~ o ~ N
S ~ h O ~ e ~ ~ a ~
OO ~ Q O ~ -- h aU ~rl
Z~I S ~ C ~ , C ~
~ O h O ~1 O ~ rl O ~ ~1 O C~ ~ al ~ O ~1
Z C i~ :1 ~ ~ Ei ~ h I Q ~ ~ Ei
o ~ o a~ ~1 o o ~ O
Z u~ a P~ 3 E~
o ~ O
-
:. . ~-.
. . . .
. ~ .
, .
~.~38~0
- 15 -
In runs 2 and 3 above, where alcohols were
employed in recipes, a monomer premix tank or vessel was
evacuated. The premix tank was first charged with the
water and then, under agitation, the electrolyte was
5 added followed by the emulsifier and then the alcohol
mixture. The catalyst was added next, and lastly, the
vinyl chloride. The temperature in the premix tank was
controlled at about 25C, by means of a cooling jacket.
The mixture was agitated for about 15 minutes. There-
10 after, the mixture, or monomer premix was passed througha Mantin Ganlin 2 stage homogenizer at a temperature of
25C into the polymerization reactor which had pre-
viously been evacuated. The pressure in the first stage
of the homogenizer was 600 psig. and in the second stage
15 was 700 psig. The contents of the reactor were then
heated to the reaction temperature of 45C and held
there throughout the reaction until the desired conver-
sion was obtained. The reactor was then cooled,
vented and the polyvinyl chloride (PVC) latex or slurry
20 was removed and dried~ Pertinent data is given in
Tale II below.
In runs 1, 4 and 5 the ingredients were added
to and mixed in the polymerization reactor. Further,
the emulsifier was proportioned into the reactor during
25 the course of the reaction. In the case of runs 1 and 4,
a PVC seed was added to the reactor on which the vinyl
chloride was pverpolymerized to obtain a larger
particle size. In the case of run 5, however, a small
amount of emulsifier (sodium lauryl sulfate) was added
30 initially in place of the seed (PVC). In the case of
runs 4 and 5, the temperature of the reaction mixture
was held at 40C until about 58% to 60% conversion was
reached and then the temperature was reduced to 35C and
held there until the reaction was complete. Thereafter,
35 in each case, the reactor was cooled, vented and PVC
ltex or slurry was removed and dried.
~38i~o
- 16 -
In order to determine the Brookfield Viscosity,
plastisols were made with the resin or PVC of each run
using the following recipe:
PVC 100 parts
Dioctyl phthalate 40 parts
Dioctyl adipate 30 parts
Epoxidized soybean oil3 parts
Barium-Cadmium-Zinc
Phosphite 2 parts
The data with respect to viscosity is recorded
in the following Table II.
-- 17 --
I o o
Z I U ~ ~ Z
o
o o o o
ZI '3 ~
o o o o
,1 ~ o CO o o
o ~ ~ ~ ~ ~ CO o
~ ~
H
H O O O O
Z ~ o~ ~D 'O ~ er _1
O ~ ~ O ~ ` ` ` `
E~l ~o co ~p~ o ~
~ ~ X
_1 C~ o o o O
~ ~ O O O O
~ Z I ~ O ~1 ~
U~
U~
--
~n
a) ~
~
~1 ~ ~ ~ ~a
~ o o
0-- o ~ ,, O O
8 ~ ~ ~ .
. ~ O ~ .a) .0
o ~ ~~ ~ ,, o ~ ~ ~ 0
z ~ 0 ~ ~ x ,1 a
c~ a~ ~ o
l 0 ~ :~ O H ~_
u~ a ~ E~ u~ m
O ~l
~,
- 18 -
As can be seen from the above results, the use of an
electrolyte permits tray drying to give good dry cake
break-up and superior plastisol properites.
EXAMPL~ II
In this Example, a series of runs were made
to show the effect of varying the concentration of the
electrolyte. The same polymerization procedure as in
Example I was employed with the exception that homogen-
ization was not used. The plastisols were also made as
in Example I. The results are in the following table:
o
-- 19 --
~ ~ o ~9 ~ ,~ o~ o~ ~
8~ 4 oooo
~ o Z ~ o ~
8,~ o o o o
8~ oooo
I Z o ~ ~ o "~ ~ ON ~ ~
8" ~ ~ ~ o o o o
D~D~~
D~ ~
~ o~ ~
~38.~so
- 20 -
In the above Tables, under Slurry Viscosity, the
term "Whipped Cream" is the ideal condition for the
slurry or latex. In Table No. III it is noted that the
important property of "Dry Cake Break-Up" was excellent
or very good. The results clearly show the advantage
of employing an electrolyte followed by tray drying.
It can thus be seen from the above description
and examples that employing an electrolyte in the poly-
merization medium, it is possible to filter and tray dry
emulsion polymerization latices with a resultant im-
provement in properties of the vinyl dispersion resins
so produced. More importantly, spray drying and the
harsh grinding step attendant thereto, which adversely
affects polymer quality, is eliminated by the process of
the present invention. Further, the process produces
more dispersion resin per unit of time with improved
properties and with substantial reduction of polymer
buildup on the internal surfaces of the polymerization
reactor. These factors all contribute to a low cost
vinyl dispersion resin process. Numerous other advan-
tages of the present invention will be apparent to those
skilled in the art.
While the present invention has been described
in terms of its specific embodiments, certain modifica-
tions and equivalents will be apparent to those skilledin the art and are intended to be included within the
scope of the present invention, which is to be limited
only by the reasonable scope of the appended claims.
