close

Вход

Забыли?

вход по аккаунту

?

Патент USA US2401445

код для вставки
Patented June 4, 1946
2,401,445
UNITED STATES PATENT OFFICE
2,401,445 '
POLYMERIZATION OF VINYL ACETATE
"Jesse Oris White, Arlington, N. J., assignor to E. I.
du Pont de Nemours & Company, Wilmington,
Del., a corporation of Delaware
7
No Drawing. Application July 13, 1943,
Serial No. 494,510
.
9 Claims.
1
This invention relates to the polymerization of
vinyl acetate and, more particularly, to the poly
merization of vinyl acetate while dispersed in an
aqueous medium.
_
The so-called “granular polymerization" of liq
uid monomers, as described in Crawford et a1;
U. S. Patent 2,108,044, comprises subjecting the
monomer to polymerizing conditions while sus
pended in the form of droplets in a non-solvent
medium, commonly an aqueous medium. This
process, when properly conducted, produces poly
mer in the form of small globules. The mainte
(Cl. 260-9)
2
Hydrogen peroxide is free from these objection
able characteristics but it has been found to be
a comparatively weak catalyst when used alone.
Admixture, with hydrogen peroxide, of a small
proportion ofbenzoyl peroxide has been shown
by Marks U. S. Patent 2,109,595, to increase in
surprising measure the activity of hydrogen per
oxide as a catalyst of polymerization, but the
complete exclusion of benzoyl peroxide is never
theless desirable.
'
An object of the present invention is to pro
vide improvements in the polymerization of vinyl
nance of the monomeric liquid in the form of
‘acetate in suspension in an aqueous vehicle by
‘droplets is accomplished by the combined in?u
the general method of said U. S. Patent 2,108,044,"
ences of various agitation and a dispersing agent. 16 i. e., the method of so-called granular polymer
Various dispersing agents have been proposed
ization. More speci?cally, the invention relates
for this purpose. For satisfactory service, a gran
to improvements in the selection and manner of
ulating agent must not merely be eifective as
use of starch as a dispersing agent in this proc
such, but also must be easy to prepare and in
ess, and to the provision of a feasible technique
troduce into the reaction batch, and either read 20 for the use of hydrogen peroxide as the sole added
ily removed from the particles of polymer, on
catalyst of polymerization.
which it becomes adsorbed, or else unobjection
A speci?c object of the invention is to make
able if not removed from it.
unnecessary the ancillary step’ of putting the
The use of starch as a dispersing agent in a
starch into solution in advance of adding it to
process of this type has been suggested in the 25 the other ingredents Of the polymerization batch.
above mentioned patent, but this patent, although
Another object is the preparation of granular
noting that the dispersing powers of a starch de
polyvinyl acetate of desirable and uniform par
pend on its past history, is silent with respect
ticle size. Other objects will be apparent from
to the basis for selection of a starch for optimum
the description of the invention given herein
performance. Furthermore, the method disclosed
therein for the preparation and use of the starch
presents certain practical di?iculties.
In accordance with that patent a solution of
the starch is prepared in advance of its use. This
after,
‘
In accordance with the present invention, the
above objects are accomplished by a process which
comprises heating under agitation a mixture
comprising monomeric vinyl acetate, water as
necessarily adds to the process of polymerization
vehicle, hydrogen peroxide as catalyst of poly
an ancillary step. Furthermore, in actual prac
merization, a water-soluble alkaline substance in
tice the solution of starch cannot be made up in
quantity to provide and maintain a pH between
advance in large batches, because starch solutions
4.9 and 3.8 in the mixture during the process
tend, upon standing, to be spoiled by action of
and, as dispersing agent, a requisite quantity,
molds or bacteria, and because it is not practi 40 between 0.05% and 0.25%, .by weight of the mon
cable to use preservatives for the inhibition of _ omer, of a starch of viscosiy hereinafer speci
such action since a preservative is likely to inter
?ed. In a preferred embodiment of the process,
fere with the desired progress of polymerization
the monomer is heated to about 50‘? C., to it are
of the monomer. The necessity of limiting the
added the starch, in dry comminuted form, and
size of batches of starch solution to what can be
drysodium ‘bicarbonate, or other water-soluble.
used up before it spoils adds, of course, to the
alkaline substance, 'then water at 75° C.-85° C.
cost of the dispersing agent used per pound of
and ?nally hydrogen perioxide; the tempera
polymer produced.
ture of the mixture is raised by heat applied and
The polymerization of liquid monomers by the
by the heat developed in the resulting polymer- general method just described involves regularly a9 ization of the vinyl acetate, until it reaches about
the use of a catalyst, in an amount so selected
as to promote the polymerization at an eco
nomical rate and at the same time to exercise
some control upon the size of the macromolecules
_ developed by the polymerization. The most usual
catalyst is benzoyl peroxide but it is-not alto
gether a satisfactory one since not only is it ex—
92° C.
To be acceptable for use as granulating agent
in this process, the starch must exert an ~ade
quate granulating or dispersing e?ect to supple
ment the dispersing effect of the agitation in
opposition to the tendency of the suspended ma
terial to coalesce in the course of‘ its polymeriza
pensive and somewhat hazardous, but also, it is a
tion. At the beginning of the process, when the
source of discoloration in the resulting polymer. 60 vinyl, acetate exists still as a mobile liquid, and
2,401,445
again at'the end of the process, when it has been
converted practically completely into polymer,
the suspension can be adequately maintained by
means of agitation alone, at least in any reason
ably well designed equipment operated at suit
able speed. But during the intermediate stages
of the polymerization the partially polymerized
vinyl acetate is relatively adhesive and the glob
ules of it tend to coalesce and to adhere to the
equipment. It is during this stage that the dispersing in?uence of a granulating agent must
be provided to supplement the agitation in pre
venting such coalescence and adherence. In the
course of the rise in temperature during the proc
ess, which accompanies the progressive polymeri 15
4
cup is heated to 161.5° F. (:1° F.) and main
tained at that temperature by suitable adiust- ment of a voltage-regulator in the line supply
ing current to the heater.
An accurately weighed sample'of the starch
(2.02 grams, dry basis) "is slurried in exactly 20
grams of water at 28° C. in a 400 cc. beaker,
and to this suspension there is added rapidly,
with a minimum of agitation, 180 grams of water
at 80° C.
The cover of the viscosimeter isremoved, and
the mixture of starch and water is poured into
the inner cup, up to the second graduation on
the plunger. Immediately the cover is replaced,
the platform is set into rotation at 42 R. P. M.
and a stopwatch is started.
zation, a temperature, or range of temperature,
The temperature of the liquid is now about
is reached at which the tendency of the globules
69° C. It is maintained at 69° C.:0.5° Cxthrough
to coalesce is at its strongest. This temperature,
the determination by maintaining the tempera
or range of temperature, is designated herein, for
ture
of the water in the outer cup at this tem
convenience of reference, the "temperature of 20
perature.
maximum adhesiveness”; for vinyl acetate it has
The viscosity of the liquid at any time is read
a characteristic and fairly de?nite value of 67°
in “degrees M” on the graduated disc. Previous
C-'l0° C.
'
calibration of the instrument with liquids of ac
According to the present invention, the cri
terion of acceptability of a starch for use as gran 25 curately known viscosities makes it possible to
convert "degrees M" to millipoises (mp).
ulating agent is that, under specific conditions
In testing a starch for suitability for use in
of test, presently to be described, a solution of
this invention, a reading of viscosity is made at
not more than one per cent of it in water ex
hibits a viscosity of not less than 10 millipoises
after having been heated for 15 minutes at the
temperature of maximum adhesiveness of mono
meric vinyl acetate, and also after having been
heated for 120 minutes at this temperature.
15 minutes after the start. If the viscosity is
too low at this time, the determination may
be discontinued and the starch rejected as un
suitable. If the viscosity at 15 minutes is above
the required minimum, then the test is continued.
If at the end of 105 minutes additional (120
In characterizing the starches which are op
minutes
total) the reading is still above the re
erative in the present invention, the term "vis 35 quired minimum,
the starch is acceptable. If
cosity" is used herein, as a matter of convenience
before that time the reading falls. below the
in language, to designate a property of solutions
required minimum, the test may be stopped, and
of starch in which viscosity in the strict sense of
the starch rejected.
the word is complicated by at least one other
If, on the other hand, the one per cent solu
factor. Starches are not homogeneous in struc 40 tion of a starch, made up as described, is too “vis
ture or behavior, in that each granule is made
cous” or jellylike to be handled satisfactorily by
up of a relatively insoluble capsule (amylopectin)
the
test apparatus, then a less concentrated solu
and its relatively soluble contents (amylose) . At
"; tion may be used instead and, if this latter passes
the temperatures of use of starch in this inven
test at both points of time, the starch is obvi
tion, the material of the interior of the granule 45' the
ously
acceptable as being of well over minimum
is readily soluble in water and, once it is released
acceptable viscosity and behavior.
upon the swelling and bursting of the capsules,
The failure of a starch to pass this test may
this material goes smoothly into solution. The
be due to de?ciency in one or both of the factors
material of the capsule, however, is merely swoll
en and gelled, and persists as fragments suspend
ed in the solution. In a viscosimeter these frag
ments in suspension contribute to the reading of
what is designated as viscosity. And because
these fragments are fragile and become subdi
vided by agitation of the solution, the magnitude
which contribute viscosity, 1. e. to de?ciency in
the inherent viscosity of the relatively easily solu
ble amylose, to failure of the amylopectin to be
effectively gelatinized at the temperature of the
test, to excessive fragility of the gelatinized
amylopectin, or to a combination of these de
of their in?uence upon the‘ viscosity depends in 55 ?ciencies. Thus a starch of which the amylopec
tln fails to gel adequately at 69° C. is not satis
part upon the manner in which the solution has
facory, even though it may become well gela
been prepared.
'
tinized at a somewhat higher temperature, for it
Accordingly, it is necessary that the viscosity
is at or near this temperature of maximum ad
of a starch, for the purposes of describing the
hesiveness of vinyl acetate that its granulating
invention, be de?ned in terms of the apparent
effect is required. And failure of a‘ starch to hold
viscosity of a solution of it prepared in a speci?c
its viscosity above the set minimum in the two
manner and measured in a speci?c manner in a
hours of gentle agitation in the test apparatus is
speci?c viscosimeter.
'
'
evidence that the gelatinized amylopectin is too
A starch for use in the present invention is
65 fragile to maintain the viscosity of the starch
tested as follows:
under the more vigorous agitation encountered
The instrument used is the Mac Michael vis
cosimeter, as described in bulletin No. 560 of
in the commercial reaction of polymerization.
Elmer and Amend, New York city.
As has been pointed out in the aforementioned
Into the outer cup of this instrument is placed
U. S. Patent 2,108,044, the amount of dispersing
120 cc. of water, and the inner cup (No. 32,788c) 70 agent should be, on the one hand, adequate to
is inserted. The cylindrical plunger of 1 cm. di
supplement the dispersing effect of the agitation
ameter (No. 32,788!) is suspended by the wire of
provided, so as to prevent coalescence of the dis
gauge No. 34 B. and 8., the instrument is lev
persed globules during the polymerization, but
elled, the pointer is adjusted to zero, and the
also should be, on the other hand, not so great
cover is put into place. The water in the outer
5
2,401,445
6
as to make the dispersed globules obiectionably
small. Other factors being constant, the amount
used of a given dispersing agent serves to con
trol the size of the particles of the polymer pro
duced. The amount to be used of a given starch
of some acidity by hydrolysis of vinyl acetate.
and a further addition of alkaline substance will
‘
The following examples, wherein all propor
tions are given by weight unless otherwise stated,
illustrate speci?c embodiments of the invention.
Example I
The following ingredients are used:
will be selected on that basis and will ordinarily
be not more than about 0.25 per cent of the weight
of the monomer nor less than 0.05 per cent.
More frequently, when the starch is of. really su
perior type, the amount will be of the order of
0.08 to 0.2 per cent of the weight of the monomer,
preferably between 0.10 and 0.15 per cent. The
selection of the precise optimum amount must
be based upon accumulated experience and spe
ci?c trials, since various factors must be taken
into account.
In general, the more effective the agitation of
the mixture of monomer and aqueous vehicle, the
less will be the amount of starch needed to sup
plement the agitation itself in maintaining the
monomer suspended in droplets of desired size
in the vehicle. Thus the design of the reaction
kettle and its agitator, and the speed of the lat
ter, will in?uence the amount of starch to be
used. The greater the ratio of aqueous vehicle
to suspended monomer, the less is the amount of
starch required to supplement the effect of agita
tion in keeping the monomer in suspension. The
type of polymer being made is also a factor, in
that when polymer of low viscosity is being made
.the globules of monomer in the course of being
converted into granules of polymer remain longer
in a soft and sticky condition, which promotes
their coalescence, than is the case in the manu
facture of polymer of higher viscosity. Finally,
of course, the amount of starch required depends
inversely upon the viscosity of the starch selected
for use.
The viscosity characteristics of a starch con
not be needed.
10
. Parts
Vinyl acetate monomer _______________ __ 100
Water
_
'
131
Aqueous hydrogen peroxide (27.56% by
weight) ___________________________ __,
0.23
15 Sodium bicarbonate ____________ __'______
0.13
Potato starch _______________________ _..,
0.35
In the viscosity test described above, an 0.34%
solution of this starch gives a reading of 15.5 M. P.
at 15 minutes and a reading of 21.5 M. P. at 120
20 minutes. A one per cent solution would, of
course, give still higher readings.
The vinyl acetate is introduced into a stain
less-steel kettle provided with an agitator, re
flux condenser, and jacket for heating by steam
25 or hot water. The vinyl acetate is heated to about
50° C. and then the starch and sodium bicar
bonate are added, dry, and stirred with it to a
slurry. To this slurry is now added the water,
which has been preheated to about 80° C. Then
30 the hydrogen peroxide is added. With agitation
continuing, the mixture is heated until re?ux
ing-begins, at about 66° C. When the tempera
ture of the charge reaches about 92° C., after
about 52 minutes, the reaction is considered to be
complete. The pH 'of the aqueous vehicle is
slightly below 4.85 at the start of the reaction,
' and falls not below 3.8 at its conclusion.
The liquid monomeric vinyl acetate, suspended
in droplets in the aqueous vehicle by action of
stitute the only criterion of its suitability, other 40 the agitation and the dispersing agent, has been
than that it be free;.from objectionable con
converted into solid globules of polyvinyl acetate,
taminants. The source of the starch is imma
of substantially uniform size. '
terial. For example, cornstarch; tapioca starch,
The polyvinyl acetate thus made carries ad
potato starch, and others have been used with - scrbed starch, which is removed or not according
success, as has also methyl starch. As will be
to the purpose for which the-polyvinyl acetate
seen, the process of the invention serves to gelat
is to be used. If the polyvinyl acetate is to be
inize and dissolve the raw starch.
converted into a polyvinyl acetal resin, the starch
The water-soluble alkaline substance, serves
will be destroyed in the natural course of the re
two purposes, namely, (1) to promote the solu
actions involved in this conversion, and there is
bilization of the starch, and thus to render it ef 50 - therefore
no need to remove it from the granules
fective as a granulating agent, and (2) to pro-‘
of polyvinyl acetate. However, if the starch is
vide a pH which is favorable to the polymeriza
not to be removed, it is advisable to add a lubri
tion under the catalytic in?uence of the hydro
cant before the isolation of the resin from the
gen peroxide. The amount of alkaline substance
to be used is such as to develop and maintain in 55 aqueous slurry, as shown in Example IV. If, on
the other hand, the polyvinyl acetate is to be
the aqueous vehicle a pH between about 3.8 and used as such, and if the slight haziness contrib
' 4.9. Sodium bicarbonate, sodium phosphate, and
uted by the starch will be found objectionable.
sodium hydroxide are convenient substances to
then the granules of polyvinyl acetate are freed
use for this purpose but obviously other alkaline
from starch by a treatment with a suitable deter
substances can be employed.
60
gent, such-as a fatty alcohol sulfate. beforebe
In the absence of the added alkaline substance,
ing washed and dried.
the system would be more strongly acid than this,
by reason of hydrolysis of the vinyl acetate both
Example II
before and during polymerization. ‘This acidity
The
following
ingredients
are handled in the I
must be reduced in order to promote the poly 66
same manner as were those of Example I.
merization, because hydrogen peroxide does not
Parts
function effectively as a catalyst at a pH below
Vinyl acetate
__
____
100
about 3.8. On the other hand, the pH should
Water
____
___
100
be kept below about 4.9 in order to avoid excessive
Hydrogen peroxide (aqueous solution
,
hydrolysis of the vinyl acetate.
70 27.56% by weight) _________________ __ 0.4
If the amount of alkaline substance added is
Potato starch
____
1
0.4
sufficient to bring the pH at the start into the
Sodium bicarbonate ___________________ _..
0.1
upper part of the range 3.8-4.9, the pH will or
dinarily remain within the range throughout the
This starch is the same as that used ln'Ex
reaction of polymerization despite the. release 75 ample I.
v
‘
9,401,445
7
The pH is within the same stated range
throughout the reaction of polymerization.
Example III
8
maintained at a temperature of 45' C.-55° C. in
the reaction‘ vessel and the mixture is thoroughly
_ stirred to distribute the starch in suspension.
There is then added, with stirring, the amount of
The followinglingredients are handled in the 5 water at 75° C.-80° C.. required to constitute the
aqueous vehicle; the amount of water can be
same manner as were those of Example I.
varied widely but normally is at least equal in
weight to the monomer. An alkalizing agent
.Vinyl acetate ______________ __.. ______ __ 100
Water _____________________________ _.. 200
Hydrogen peroxide
(aqueous solution
27.56% by weight) _________________ -_
Sodium bicarbonate __________________ .._
.
0.13
Sando tapioca‘ starch _________________ __
0.5
such as sodium bicarbonate is introduced either
10 with the starch or with the water, and the cata
lyst is introduced ‘in any convenient manner.
The starch becomes‘ converted into‘ a water-solu- .
ble product which serves as the dispersing agent '
and this, together with continuous ‘active agita
In the viscosity test, a 0.88% solution of this
tion, keeps the liquid monomer suspended in
starch gives readings of 14.8 and 17.5 M. P. at 15 15 droplets in the aqueous vehicle. The joint action
and 120 minutes, respectively.
Example IV
of heat and catalyst gradually effect the poly
merization whereby the droplets of vliquid mono
mer are converted into globules of polymer. The
A glass lined reaction vessel equipped with an
reaction vessel is provided with a reflux. con
20
e?icient stirrer is charged with 120 parts of mono
denser to prevent loss of monomer by volatiliza
meric vinyl acetate. While this material is
tion. Alternatively, the starch may be intro
gently agitated, 0.12 part of sodium bicarbonate
duced into the water instead of into the monomer
followed by 0.3 part of starch are added. These
but the water should not be hot enough to cause
ingredients are allowed to admix for five minutes
gellation of the starch which would result in its
after which 135.5 parts of water followed by 0.3 25 becoming lumpy. Slurrying the starch with the
part of hydrogen peroxide"(2'l.56% aqueous solu
monomer, as in the preferred procedure, provides
tion) are introduced into the reaction mixture.
a uniform distribution of it and guards against
The entire mixture is then heated to re?ux by
its lumping when it becomes gelled after contact
the circulation of steam in an external heating
with the hot water.
30
jacket. Gentle re?uxing is allowed to continue
Obviously, it is preferred to use hydrogen per
for 45 minutes by supplying external heating as ' oxide as the polymerization catalyst since one of
necessary. As the reaction mixture continues to
the advantages of this invention is that it per
re?ux, the temperature gradually rises from about
mits hydrogen peroxide to be used effectively.
60° C. to a peak temperature of about 96° C.
However, other polymerization catalysts such as
When the temperature of the reaction mixture 35 benzoyl peroxide and the like may be used if de
is at 80° C., 0.24 part of sorbitan monopalmitate
sired. The proportion of, catalyst isnot critical
are admixed with reaction mixture. After the
although the amount of hydrogen peroxide will
mixture is re?uxed for the 45 minutes, the tem
usually be between 0.04% and 4.0%, by weight
perature is adjusted to 90° C. and maintained
of the monomer.
at this value for 10 minutes. The mixture is then 40
An advantage of the present invention is that
cooled to 20° C. and the polymeric vinyl acetate
it provides an improved method for using starch
is isolated as satisfactory granules of substan
as the dispersing agent in the granular polymeri
tially uniform size by centrifuging the slurry.
zation of vinyl acetate. Further, it provides a
In the indicated viscosity test, a 0.34% solution
means for the selection of a satisfactory starch
in water of the starch used in this example pos
for the purpose and a procedure which makes un
sessed a viscosity of 12.5 M. P. and 17.0 M. P. at 15
necessary the heretofore necessary and undesir
minutes and 120 minutes respectively.
able step of preparing the solution of starch in
The sorbitan monopalmitate employed in this
advance. Further, the invention provides a pro
example serves to lubricate the particles to poly 60 cedure for effectively using hydrogen peroxide as
meric vinyl acetate during the steps of isolating
the polymerization catalyst;‘- while hydrogen per
the resin from the aqueous slurry. Other mate
oxide has heretofore been recognized as desir
rials may be employed for this purpose. The long
able because of its absence of bad effect on color
chain fatty acid partial esters of hexitol anhy
of the resulting monomer, it has seldom been
drides and the polyoxyalkene derivatives of hex 55 used because of its weakness as a catalyst. A
itol anhydride have been found especially useful
further and important speci?c advantage of the
for this purpose.
invention, resulting from its effective use of
It will be understood that the above examples
starch as a granulating agent, is the unusual uni
are merely illustrative and that in its broad phase
formity of the size and shape of the granules of
the invention comprises heating under agitation no the polymerized product. Such uniformity is of
a mixture of vinyl acetate monomer, water as a
great value in commercial operations such as cen
vehicle, a polymerization catalyst, a, water-solu
trifuging, drying, and dissolving the polymer.
ble alkaline substance in quantity to provide and
As many apparently widely different embodi
maintain throughout the reaction a pH between
ments of this invention may be made without de
4.9 and 3.8 in the mixture, and, as a dispersing 65 parting- from the spirit and scope thereof, it is
agent a starch having viscosity characteristics
to be understood that the invention is not limited
such that a solution of 1%. by weight, of the . to
the speci?c embodiments thereof except as de- '
starch in water has a viscosity of notless than
?ned
in the appended claims. ,
10 millipoises after having been heated for- 15
'I claim:
minutes at approximately 67° C.-'70° C. and also
1. Process of polymerizing vinyl acetate which
after having been heated for 120 minutes at that
comprises
heating under agitation a mixture of
temperature.
vinyl acetate monomer, water as a vehicle, a per
In carrying out the invention in its preferred
oxide polymerization catalyst, a water-soluble al
form both the liquid monomer and the water are
kaline substance in quantity to provide and main
pre-heated. The starch, in finely divided-form,
is added in dry condition to the liquid monomer " tain a pH between 4.9 and 3.8 in the mixture and,
2,601,445
10
as a dispersing agent, a starch having viscosity
‘characteristics such that a solution of 1%. by
weight. of said starch in water has a viscosity oi‘
not less than 10 millipoises after having been
heated for 15 minutes at approximately 69° C.
and also after having been heated for 120 min‘
utes at that temperature.
2. Process of polymerizing vinyl acetate which
comprises heating under agitation a mixture of
resulting mixture under active agitation until
polymerization of said vinyl acetate is substan
tially complete, the water-soluble alkaline sub‘
stance being so apportioned-that the pH of the
water phase of the reaction mixture is main
tained between 4.9 and 3.8 throughout the pe
riod oi.’ heating.
vinyl acetate monomer, water as a vehicle, a per
6. Process of polymerizing vinyl acetate which
comprises heating vinyl acetate monomer to 45°
‘0.45’ (2., adding thereto with stirring between
oxide polymerization catalyst, a water soluble al
kaline substance in quantity to provide and main
0.05% and 0.25%, by weight thereof, of a dry
comminuted starch having viscosity characteris
tain a pH between 4.9 and 3.8 in the mixture and,
tics such that a solution of 1%, by weight, of said
as a dispersing agent,-between 0.05% and 0.25%.
starch in water has a viscosity of not less than
by weight of said monomer. of a starch having 15 10. millipoises‘aafter having been heated for 15
viscosity characteristics such that a solution, of
minutes at approximately 69° .C. and also after‘
1%, by weight, of said starch in water has a vis
having been heated for 120 minutes at that tem
cosity of not less than 10 millipoises after having
perature, and dry comminuted sodium bicar
been heated for 15 minutes at approximately 69°
bonate, then adding thereto water at 75° C.-85°
C. and also after having been heated for 120 min 20 C. in an amount at least equal to the weight of
utes at that temperature.
said monomer, and finally hydrogen peroxide in
3. Process of polymerizing vinyl acetate which
catalytic amounts, and heating the resulting mix- .
comprises ‘heating under agitationa mixture of
ture under active agitation until polymerization
vinyl acetate monomer, ‘water as a vehicle, hy
of said vinyl acetate is substantially complete.
drogen peroxide as a polymerization catalyst, a 25 the sodium bicarbonate being so apportioned that
water-soluble alkaline substance in quantity to
the pH of the water phase of the reaction mix
provide and maintain a pH between 4.9 and 3.8 in
ture is maintained between 4.9 and 3.8 through
the mixture and, as a dispersing agent, between
out the period of heating.
0.05% and 0.25%, by weight of said monomer,
7. Process of polymerizing vinyl acetate which‘
of a starch having viscosity characteristics such 30 comprises heating under agitation a mixture of
that a solution of 1%, by weight, of said starch in
vinyl acetate monomer, water as a vehicle, a
water has a viscosity of not less than 10 milli-‘
peroxide polymerization catalyst, a water-soluble
poises after having been heated for 15 minutes
alkaline substance in quantity to provide ‘and
at approximately 69° C. and also after having
maintain a pH between 4.9 and 3.8 in the mix
been heated for 120 minutes at that tempera 35 ture, a long chain fatty acid partial ester of a
ture.
hexitol anhydride as a lubricant, and, as a dis
4. Process of polymerizing vinyl acetate which
persing agent, a starch having viscosity char
comprises heating vinyl acetate monomer, add
acteristics such that a solution of 1%, by weight,
ing thereto with stirring between 0.05% and
of said starch in water has a viscosity of not less
0.25 %, by weight thereof, of a dry comminuted 40 than 10 millipoises after having been heated for
starch having viscosity characteristics such that
15 minutes at apprordmately 69° C. and also after
a solution of 1%, by weight, of said starch in
having been heated for ‘120 minutes at that tem
water has a viscosity of not less than 10 milli
perature,
.
poises after having been heated for 15 minutes
8. Process of. polymerizing vinyl acetate which
at approximately 69° C. and also after having been 45 comprises heating under agitation a mixture of
heated for 120 minutes at that temperature, and
vinyl acetate monomer, water as a vehicle, a
a dry comminuted water-soluble alkaline sub
peroxide polymerization catalyst, a water-soluble
stance, then adding thereto water at elevated
alkaline substance in quantity to provide and
temperature in an amount at least equal to the
maintain a pH between 4.9 and 3.8 in the mixture.
weight of said monomer, and ?nally hydrogen 60 sorbitan monopalmitate as a lubricant, and, as a
peroxide in catalytic amounts, and heating the
dispersing agent, a starch having viscosity char
resulting mixture under active agitation until
acteristics such that a solution of 1%, by weight,
polymerization of said vinyl acetate is substan
of said starch in water has a viscosity of not less
tially complete, the water-soluble alkaline sub
than 10 millipoises after having been heated for
stance being so apportioned that the pH of the 65 15 minutes at approximately 69° C. and also after ‘
water phase of the reaction mixture is main
having been heated for 120 minutes at that tem
tained between 4.9 and 3.8 throughout the period
perature.
of heating.
9. Process of polymerizing vinyl acetate which
5. Process of polymerizing vinyl acetate which
comprises heating under agitation a mixture of
comprises heating vinyl acetate monomer to 60 vinyl acetate monomer, water as a vehicle, hy
45° C.-55° (2., adding thereto with stirring be
drogen peroxide as a polymerization catalyst, a
tween 0.05% and 0.25%, by weight thereof, of a
water-soluble alkaline substance in quantity to
dry comminuted starch having viscosity char
provide and maintain a pH between 4.9 and 3.8
acteristics such that a solution of 1%, by weight,
in the mixture, 9. long chain fatty acid partial
of said starch in water has a viscosity of not less 65 ester of a hexitol anhydride as a lubricant, and,
than 10 millipoises after having been heated for
as a dispersing agent, a starch having viscosity
15 minutes at approximately 69° C. and also after
characteristics such that a solution of 1%, by
having been heated for 120 minutes at that tem
weight, of said starch in water has a viscosity of
perature, and a dry comminuted water-soluble
not less than 10 millipoises after having been
alkaline substance, then adding thereto water at 70 heated for 15 minutes at approximately 60° C.
75° C.-85° C. in an amount at least equal to the
and also after having been heated for 120 mim
weight of said monomer, and ?nally hydrogen
utes at that temperature.
-
peroxide in catalytic amounts, and heating the
JESSE CRIS WHITE.
Certificiteof ‘Correction ‘
June 4, 1946;?- I‘
‘Patent No. 2,401,445. ‘
' ‘JESSE’. oms WHITE‘
-
.
It is hereby certi?ed that errors appear in the printed speci?cation of the above .
numbered patent requiring'correotion as‘ follows: Column 1, line 15, for “various”
read vigorous; column 2, line 41, for “vi'scosiy? read viscosity; line 48, same column
for ‘l‘perioxide” read peroxide; c01u1m147, line 49; after the word “particles” strike
out “to” and insert instead of; end that the said‘ Letters Patent should be read with
glese coéréotions therein that the same may conform to the record of the case in the
atent
ce.
1
‘
'
‘
'
Signed and sealed this'13th day of August, Af ‘D. 1946.
[w]
LESLIE FRAZER,
First Assistant Oommz'asioner of Pqtenta.
.
Документ
Категория
Без категории
Просмотров
0
Размер файла
897 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа