Note: Descriptions are shown in the official language in which they were submitted.
1~2~
Background of the Invention
Field of the Invèntion
This invention relates to the preparation of (1) homopolymers and
copolymers of a vinyl halide such as vinyl chloride characterized by the
properties of small particle size, higher bulk density, reduced plasti-
cizer absorption and easy processability and (2) copolymers of a vinyl
halide such as vinyl chloride having improved impact strength properties.
The viscosity of plastisols which utilize extender resins is affected
not only by the plasticizer absorption characteristics of the polymers,
but also by the average particle size, thè particle size distribution and
the bulk density of the particles. Certain polymers of the invention are
particularly useful as extender polymers for this application. These
polymers are also useful for the manufacture of films and as coatings for
fabrics. The high impact strength polymers of the invention are used in
the preparation of moldings.
Description of the Prior Art
In an article entitled "Vapor Phase Polymerization of Vinyl Chloride"
in the Journal of Applied Polymer Science, Vol. 15, Pages 445-451, 1971,
by Kahle et al., a process is disclosed for the polymerization of vinyl
chloride utilizing a liquid bulk polymerized polymer as a seed for a sub-
sequent vapor phase polymerization process. The product is said to have
reduced plasticizer absorption. In the process, general purpose grade
polyvinyl chloride powder is ground to a suitable size to produce small
particle size polymer product. Similar processes are disclosed in U. S.
3,595,840 and U. S. 3,622,553.
French Patent 1,588,381 discloses the addition of fresh vinyl
chloride and initiator to a vinyl chloride reaction mixture which has
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already been bulk polymerized to a substantial extent in a single stage
reactor and the submission of this mixture to bulk polymerization in order
to obtain polyvinyl chloride granules having excellent plasticizer absorp-
tion in the cold and in various sizes according to the duration of their
dwelling under polymerization conditions.
U.S. 3,583,956 relates to a process for producing vinyl chloride
copolymers having a lower softening point than polyvinyl chloride comprising
initially polymerizing vinyl chloride to at least 40% conversion, adding a
different vinyl monomer in an amount less than remaining unreacted vinyl
chloride and continuing the polymerization at a temperature at least 5
degrees centigrade higher than the first polymerization temperature, prefer-
ably 10 to 35 degrees centigrade. The specification discloses that the
reaction can be carried out in bulk, solution, emulsion or suspension poly-
merization processes, but only suspension polymerization processes are
described in the Examples.
U.S. 3,725,367 relates to the use of a vinyl chloride latex as a seed
polymer in a bulk polymerization process to obtain small particle size vinyl
chloride particles having a narrow granular size distribution within the
range of 10-50 microns.
U.S. 3,687,923 relates to a process for the polymerization of vinyl
chloride in bulk comprising polymerizing a portion of the monomer so as to
form seeds, and subsequently adding a larger portion of liquid monomer and
continuing the polymerization with mild agitation. The amount of monomer
used in the first stage of the polymerization should be at least 1/3 by
weight of the total qua~tity of monomer, ~hich is to undergo reaction. An
Example shows a product containing 73% pa~ticles between 100 and 200 microns
in size.
1~2~6
U.S. 3,230,206 relates to a process for the suspension polymerization
of copolymers having an heterogeneous structure, good flow properties, and
low temperature impact strength by polymerizing acrylic acid esters and
vinyl chloride. A portion of the vinyl chloride is added after 5-20 per-
cent of the copolymer is formed.
U.S. 2,961,432 relates to a process for the bulk polymerization ofhomopolymers and copolymers whereby mixtures of liquid monomers and
polymer powders are formed and polymerization carried out. The monomer
used corresponds to the same monomer used to form the polymer powder.
Summary of the Invention
This invention relates to a method of obtaining a high bulk density
vinyl halide polymer having reduced plasticizer absorption when compounded
as an extender resin in a polyvinyl halide plastisol and to a method of
obtaining unusual polymers of vinyl halide by polymerization with other
ethylenically unsaturated monomers to provide, in addition to properties
such as low plasticizer absorption and higher bulk density, such polymer
properties as reduced melt viscosity, lower glass transition temperature
and greater impact strength. By the process of the invention, particles of
a vinyl halide polymer or copolymer in powder form can be used as seed as
produced from conventional emulsion, suspension, or bulk polymerization
methods. Preferably, such seeds are utilized in a post polymerization in
the liquid state under bulk polymerization conditions wherein further
polymerization takes place within the particles rather than on the surface
of the particles used as seed. The post polymerization process of the
invention can be integrated with a two-stage liquid bulk polymerization
process comprising high speed agitation during a first stage in which
about 3 to about 20 percent, preferably about 7 to about 12 percent by
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weight of the monomer or monomers are converted, followed by polymerization
in a second stage with low speed agitation. By the two-stage polymerization
process of the invention, additional monomer is incorporated into the product
during the second state reaction after partial conversion of monomer or
monomers to polymer. Reactor productivity can be increased about 25 percent
by the method of the invention. Usually, additional initiator is used,
together with the additional monomer. Alternately, a higher temperature
reactive additional initiator may be added at the beginning of said second
stage reaction and the post polymerization conducted at a higher reaction
temperature suitable to activate the additional initiator.
By the method of the invention wherein a polyvinyl halide polymer or
copolymer is prepared in a two-stage liquid phase bulk process and the post
polymerization is conducted during some portion of the second state, high
bulk density, low plasticizer absorption products can be obtained by the
incorporation of additional amounts of the same vinyl halide monomer or co-
monomers. It is not necessary to isolate the resin produced prior to post
polymerization, but only to polymerize the vinyl halide monomer or comonomers
to the powder form prior to the addition of the same monomer or a different
monomer. Where the same process is used, but dissimilar monomers are used
in the post polymerization step, besides reduced plasticizer absorption,
reduced melt viscosity and increased impact strength can be obtained.
When it is desired to produce small particle size vinyl halide polymers
by the bulk process of polymerization, seed particles can be utilized from
emulsion polymerized or suspension polymerized vinyl halide polymers in the
liquid phase post bulk polymerization process of the invention. Alternately,
the liquid phase bulk polymerization process described in Belgian Patent
787,046, published February 1, 1973, and U.S. Patent 4,029,863, issued
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l~;)Z~4S
June 14, 1977, can be utilized to produce a small particle
size seed particle as a base for the post polymerization pro-
cess of the invention. Still further, alternatively, the
liquid phase bulk polymerization process of U.S. Patent
3,933,771, or of Belgian Patent 799,263, published November 8,
1973, discussed below, can be used to produce said small
particle size seed particle.
In one aspect of the invention there is provided a
process for the preparation of small particle size polymer of
vinyl halide by bulk polymerization comprising the steps of:
(1) polymerization of a monomer composition comprising a vinyl
halide monomer or a mixture of a vinyl halide monomer with an
ethylenically unsaturated comonomer copolymerizable therewith,
in a first stage using high speed agitation at a temperature
of from about 30 to 70 degrees centigrade in the presence of
an additive selected from the group consisting of: a) an in-
organic or organic, inert, fine particle size material which
is solid at least at the reaction temperature and insoluble
in said monomer, said ma-terial having an average particle size
in the range of about 0.001 to about 50 microns and said
material being present in the amount of 0.001 to 5 percent
by weight based upon said monomer composition present in said
first stage; b) a surface active agent in an amount of 0.01
to 5 percent by weight based upon said monomer present in
said first stage, c) a mixture of said inert, fine particle
size material and said surface active agent; and d) a poly-
olefin in an amount of about 0.05 to about 4 percent by weight
based upon said monomer composition present in said first
stage' until about 3 to about 20 percent by weight of said
monomer composition has been converted to polymer particles,
(2) continuing the preparation of small particle size polymers
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by polyrneri7ation in a second stage during which the reaction
mixture is subjected to low speed agitation, until about 30
to about 95 percent by weiyht of the monomer com~osition has
been converted -to base polymer, (3) introducing additional
monomer into said second stage comprising at least one vinyl
halide monomer or at least one comonomer which copolymerizes
therewi-th or mixtures thereof, and (4) carrying out the poly-
merization of said additional monomer in said second stage
to provide non-porous polymer particules by increasing
the second stage polymerization temperature after about 30
to about 80 percent by weight of said reaction mixture has
been converted to polymer, from a range of about 30 to about
70 degrees centigrade to a range of about 60 to 80 degrees
centigrade, said increase in polymerization temperature being
about 10 to about 50 degrees centigrade.
In another aspect of the invention there is provided
: a process as defined in the preceding paragraph wherein the
second stage polymerization is carried out in the presence of
a surface active agent added to said second stage poly-
merization reaction in an amount of about 0.01 to about 0.2
percent by weight based upon the weight of monomer composition
added up to said point of surface active agent addition.
The preferred method of the invention contemplates
the addition of at least one monomer to a base polymer or
base copolymer, bulk polymerized in the liquid phase which
functions as a seed particle, followed by post polymerization
of said monomers so as to provide a polymer or copolymer
having increased bulk density, reduced plasticizer absorption,
and, by appropriate selection of additional monomer or
monomers added during the post polymerization reaction,
increased impact strength, reduced melt viscosity and lower
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glass transition ternperature. The additiona~ monomer or
monomers are added either all at once or continuously at a
stage in the bulk process where conversion of the bulk
polymerized base polymer or base copolymer to the powder form
has been obtained. This is a conversion of about 30 to 95
percent, preferably about 30 to 80 percen-t. Where the
additional monomer or monomers are added continuously, the
rate of addition is adjusted so as to provide for completion
of addition before the end of the polymerization cycle. The
proportion of monomer or monomers added is generally from
about 1 to about 200 percent by weight of the resultant
converted polymer preferably from about 2 to about 150 per-
cent by weight on the weight of the resultant converted
polymer.
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416
A less preferred method of the invention contemplates the addition
of at least one monomer to a base polymer produced by a suspension or
emulsion polymerization process. A polymer product is obtained having
increased bulk density, lower glass transition temperature, reduced melt
viscosity and improved impact strength. The polymers produced by the
process of the invention can have bulk densities of about 0.3 grams per
milliliter to about 0.9 grams per milliliter and impact strengths of
about 2 to about 30 foot pounds per inch of notch.
In the method of the invention wherein seed particles of a vinyl
halide polymer produced by emulsion, suspension or liquid phase bulk
polymerization processes are used, the additional monomer is added to the
pulverulent seed particles and a liquid bulk polymerization process is
initiated. In a preferred aspect of the process wherein an integrated
bulk polymerization process is obtained, the vinyl halide monomer can be
polymerized in either a single stage or a two-stage process of bulk poly-
merization until a monomer conversion of between about 30 percent to about
95 percent, preferably between about 30 percent to about 80 percent is
achieved and subsequently the additional monomer which is a different
monomer from the vinyl halide monomer used initially is added. Alterna-
tively, the additional monomer may be the same as, or different from,
the vinyl halide monomer used initially provided that a particle size
control additive is employed as described hereinbelow.
The preferred two-stage bulk polymerization process used in the inven-
tion is disclosed in British Patent 1,047,489, and U.S. Patent 3,522,227.
The vinyl halide monomers included within the scope of the invention
include, e.g., vinyl fluoride, vinYl chloride, vinyl bromide, vinyl iodide,
vinylidene fluoride, vinylidene chloride, vinylidene bromide, vinylidene
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iodide and the like, although vinyl chloride is preferred. It is intended
to include within the scope of the invention all alpha-halo-substituted
ethylenically unsaturated compounds which are capable of entering into an
addition polymerization reaction. The polymers of the present invention
can be formed of the same or different alpha-halo-substituted ethylenically
unsaturated materials and, thus, the invention is intended to cover homo-
polymers, copolymers, terpolymers and tetrapolymers formed by addition
polymerization. Illustrative of these copolymers is a copolymer of vinyl
chloride and vinylidene chloride. The term "vinyl halide polymer" as used
in this specification and claims is intended to include both of vinyl halide
homopolymers and copolymers prepared usin~ a vinyl halide and ethylenically
unsaturated monomers copolymerizable therewith.
While the monomer composition can be comprised totally of vinyl halide
monomer, the present invention is also intended to include copolymers formed
by the free-radical addition polymerization of a monomer composition contain-
ing a predominant amount, e.g., at least 50% of vinyl halide, preferably
80% of a vinyl halide and a minor amount, e.g. up to 50% by weight of another
ethylenically unsaturated monomer material copolymerizable therewith. Pre-
ferably, the other ethylenically unsaturated monomer material is used in
amounts of less than 20% by weight and more preferably in amounts less than
10% by weight of the total monomer compounds used in preparing the polymer.
Suitable ethylenically unsaturated monomer materials which can be used to
form base copolymers, terpolymers, interpolymers and the like, are illustrated
by the following monoolefinic hydrocarbons, i.e., monomers containing only
carbon and hydrogen, including such materials as ethylene, propylene, butene-
1, 3-methyl-butene-1, 4-methylpentene-1, pentene-l, 3,3-dimethylbutene-1,
4,4-dimethylbutene-1, octene-l, decene-l, styrene and its nuclear alpha-
alkyl or aryl substituted derivatives, e.g., o-, m- or p-methyl, ethyl,
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propyl or butyl styrenei alpha-methyl, ethyl, propyl or butyl styrenei
phenyl styrene, and halogenated styrenes such as alpha-chlorostyrenei
monoolefinically unsaturated esters including vinyl esters, e.g., vinyl
acetate, vinyl propionate, vinyl butyrate, vinyl stearate, vinyl laurate,
vinyl benzoate, vinyl caprate, vinyl hexanoate, vinyl-p-chlorobenzoates,
alkyl methacrylates, e.g., methyl, ethyl, propyl and butyl methacrylatei
octyl methacrylate, lauryl methacrylate, stearyl methacrylate, alkyl
crotonates, e.g., octyl; alkyl acrylates, e.g., methyl, ethyl, propyl,
butyl, 2-ethyl hexyl, stearyl, n-hexyl, n-octyl, hydroxyether and tertiary
butylamino acrylates, 2-ethoxy ethyl acrylate, 2-methoxy ethyl acrylate,
isopropenyl esters, e.g., isopropenyl acetate, isopropenyl propionate,
isopropenyl butyrate and isopropenyl isobutyratei isopropenyl halides,
e.g., isopropenyl chloride; vinyl esters of halogenated acids, e.g., vinyl
alpha-chloroacetate, vinyl alpha-chloropropionate and vinyl alpha-bromo-
propionatei allyl and methallyl esters, e.g., allyl chloride, allyl cyanideiallyl chlorocarbonate, allyl nitrate, allyl formate and allyl acetate and
the corresponding methallyl compoundsi esters of alkenyl alcohols, e.g.,
beta-ethyl allyl alcohol and beta-propyl allyl alcohol; halo-alkyl acrylates,
e.g., methyl alpha-chloroacrylate, and ethyl alpha-chloroacrylate, methyl
alpha-bromoacrylate, ethyl alpha-bromoacrylate, methyl alpha-fluoroacrylate,
ethyl alpha-fluoroacrylate, methyl alpha-iodoacrylate and ethyl alpha-iodo-
acrylatei and alkyl alpha-cyanoacrylates, e.g., methyl alpha-cyanoacrylate
and ethyl alpha-cyanoacrylatei itaconates, e.g., monomethyl itaconate,
monoethyl itaconate, diethyl itaconate, the mono- and diesters of itaconic
acid with C-3 to C-8 alcohols; maleates, e.g., monomethyl maleate, monoethyl
maleate, dimethyl maleate, diethyl maleate, the mono- and diesters of maleic
acid with C-3 to C-8 alcoi,ols; and fumarates, e.g., monomethyl fumarate,
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mono-ethyl fumarate, dimethyl fumarate, d;ethyl fumarate, the mono- and
diesters of fumaric acid with C-3 to C-8 àlcohols, and diethyl glutaconate;
monoolefinically unsaturated organic nitriles including, for example,
fumaronitrile, acrylonitrile, methacrylonitrile, ethacrylonitrile, 1,1-
dicyanopropene-l, 3-octenenitrile, crotonitrile and oleonitrile; mono-
olefinically unsaturated carboxylic acids including, for example, acrylic
acid, methacrylic acid, crotonic acid, 3-butenoic acid, cinnamic acid,
maleic, fumaric and itaconic acids, maleic anhydride and the like. Amides
of these acids, such as acrylamide, are also useful. Vinyl alkyl ethers
and vinyl ethers, e.g., vinyl methyl ether, vinyl ethyl ether, vinyl propyl
ether, vinyl n-butyl ether, vinyl isobutyl ether, vinyl 2-ethylhexyl ether,
vinyl 2-chloroethyl ether, vinyl cetyl ether, and the like; and vinyl
sulfides, e.g., vinyl beta-chloroethyl sulfide, vinyl beta-ethoxyethyl
sulfide and the like can also be included as can diolefinically unsaturated
hydrocarbons containing two olefinic groups in conjugated relation and the
halogen derivatives thereof, e.g., butadiene-1,3i 2-methylbutadiene-1,3;
2,3-dimethylbutadiene-1,3; 2-chlorobutadiene-1,3; 2,3-dichlorobutadiene-1,3i
and 2-bromobutadiene-1,3 and the like.
Specific monomer compositions for forming the base copolymers can be
illustrated by vinyl chloride and/or vinylidene chloride and vinyl acetate,
vinyl chloride and/or vinylidene chloride and maleic or fumaric acid esters,
vinyl chloride and/or vinylidene chloride and acrylate or methacrylate
ester, vinyl chloride and/or vlnylidene chloride and vinyl alkyl ether.
These are given as illustrative of the nu~erous combinations of monomers
possible for the formation of copolymers. The present invention is intended
to cover all such combinations which fall within the scope of the present
invention. While such combinations are intended to be included within the
2~6
scope of the present invention, it is preférred that the base polymer be
formed from vinyl halide monomer alone and most preferably vinyl chloride.
- The monomer or monomers added subsequent to the partial conversion
of monomer or monomers can be the same or different than the vinyl halide
polymer used to form the base polymer as described hereinabove, and where
different, the monomer or monomers are preferably selected from those classes
of monomers which polymerize at the same or a faster rate as compared to said
vinyl halide polymer. Examples of monomers useful in the post polymerization
process of the invention are those listed above. Where impact strength is
desired in the product of the process, monomers are used such as l-olefins
of 2 to 10 carbon atoms, e.g., ethylene, propylene, pentene-l, butene-l,
octene-l, decene-li vinyl esters such as vinyl butyrate, vinyl stearate, vinyl
laurate, vinyl caprate, vinyl hexanoatei alkyl methacrylates such as octyl
methacrylatej alkyl acrylates such as ethyl acrylate, propyl acrylate, butyl
acrylate, 2- ethyl hexyl acrylate, stearyl acrylate, n-hexyl acrylate, n-octyl
; acrylate; hydroxyether acrylates such as 2-methoxy ethyl acrylate, 2-ethoxy
ethyl acrylate; maleates, fumarates and itaconates such as monomethyl maleate,
monoethyl maleate, dimethyl maleate, diethyl maleate, monomethyl itaconate,
monoethyl itaconate, dimethyl itaconate, diethyl itaconate, monomethyl
fumarates, monoethyl fumarate, dimethyl fumarate, diethyl fumarate, alkyl
maleates, fumarates and itaconates having an alkyl group chain length of C-3
to C-8; vinyl alkyl ethers and vinyl ethers, such as vinyl methyl ether, vinyl
ethyl ether, vinyl propyl ether, vinyl n-butyl ether, vinyl isobutyl ether,
vinyl 2-ethylhexyl ether, vinyl cetyl ether; diolefinically unsaturated
hydrocarbons containing two olefinic groups in conjugated relation, such as
butadiene-1,3; 2-methylbutadiene-1,3; 2,3-dimethylbutadiene-1,3; 2-chloro-
butadiene-1,3. Impact strength values for the polymers of the invention
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11~2~g6
are about 2 to about 30 foot pounds per inch at ambient temperature.
Where copolymers having good impact strength at temperatures below
ambient temperature as well as impact strength at room temperature are
desired to be produced by the process of the invention, a vinyl halide
monomer alone or in admixture with other monomers are used to form the
base polymer, and the post polymerization process step utilizes a monomer
or monomers such as the acrylates which can be polymerized alone to form
rubbery homopolymers having glass transition temperatures of 10C or below.
Acrylic acid esters are particularly desirable as monomers for use in
providing vinyl halide copolymers having good impact strength. The acrylic
acid esters found useful are those which contain about 2 to about 15 carbon
atoms in the alkyl group preferably about 2 to about 11 carbon atoms and
most preferably about 4 to about 8 carbon atoms. Such monomers are added
either all at once or continuously to the bulk polymerization process of
the invention when conversion of the base vinyl halide polymer has been
obtained of between about 30 to about 95 percent, preferably about 50 to
about 95 percent conversion at a time when the base polymer is in the powder
form. Preferred acrylic acid ester comonomers for producing polymers having
low temperature impact strength are 2-ethyl hexyl acrylate, n-hexyl acrylate,
and n-octyl acrylate.
The free radical bulk polymerization can take place in accordance with
the process of the invention at temperatures between 0 and 90 degrees centi-
grade. The polymerization reaction is conducted in the presence of a free
radical initiator. Useful free-radical initiators are organic or inorganic
peroxides, persulfates, ozonides, hydroperoxides, peracids and percarbonates,
azo compounds, diazonium salts, diazotates, peroxy sulfonates, trialkyl
borane-oxygen systems, and amine oxides. Azobisisobutyronitrile is
~Z~46
particularly useful in the present invention. The catalyst is used in
concentrations ranging from about 0.01 to about 1.0% by weight based on
the total weight of the monomers. For use in mass, suspension, and
solution polymerization, the catalysts which are soluble in the organic
phase, such as benzoyl peroxide, diacetyl peroxide, azobisisobutyronitrile,
diisopropyl peroxydicarbonate, azobis (alpha-methyl-gamma-carboxybutyro-
nitrile), caprylyl peroxide, lauroyl peroxide, azobisisobutyramidine
hydrochloride, t-butyl peroxypivalate, 2,4-dichlorobenzoyl peroxide,
azobis (alpha, gamma-dimethylvaleronitrile), and 2,2'-azobis(2,4-dimethyl
valeronitrile) are generally used. Preferably, the initiator which is
used is chosen from a group of initiators known in the prior art as the
"hot catalysts" or those which have a high degree of free-radical initia-
ting activity. Initiators with a lower degree of activity are less desir-
able in that they require longer polymerization times. Also, long
polymerization times may cause preliminary product degradation evidenced
by color problems, e.g., pinking.
The polymerization products of the present invention can be admixed
with various conventional inert additives, such as fillers, dyes, and
pigments. In addition, the polymerization products can be admixed with
plasticizers, lubricants, thermostabilizers and ultraviolet light stabil-
izers as desired.
In the post liquid phase bulk polymerization method of the invention,
all other conditions and measures are those conventionally employed in the
previously known processes for bulk polymerization of vinyl chloride com-
prising a two-stage polymerization as disclosed in British Patent 1,047,489
and U.S. Patent 3,522,227. In an integrated post polymerization process
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of the invention with a two-stage bulk polymerization process for vinyl
halide, the reaction is conducted in a fi~st stage reactor with means
chosen to agitate the monomer or monomers of a type capable of providing
high shear and commonly referred to aS a "radial turbine type" agitator.
At the start of the first stage reaction, the vessel is charged with a
monomer composition to which a catalyst has been added. Any polymerization
catalyst generally used in bulk polymerization methods, that is those
hereinabove described can be used to an extent which is usual for bulk
polymerization processes. After addition of the vinyl chloride monomer to
the first stage reactor, a small amount of monomer is vented in the process
of removing the air from the first stage reactor vessel. The speed of the
turbine type agitator generally lies between 500 and 2,000 revolutions per
minute or a tip speed of about 2 to 7 meters per second in the first stage
reactor. A tip speed of about 0.5 to abo~t 2 meters per second is used in
the second stage reactor. These figures should not be regarded as limiting
values. As soon as a conversion of at least about 3 to about 20 percent
of the monomer composition has been obtained in the first stage reactor,
the contents of the vessel are transferred to a second stage polymerization
vessel equipped to provide slow speed, low shear agitation so as to insure
proper temperature control of the reaction medium.
By the method of the invention, a small particle size polymer can be
obtained. The size of the polymer particles is reduced over methods of
the prior art by the incorporation of an additive or a surfactant or mixture
thereof to the first stage of the bulk polymerization process. Thus, there
is incorporated with the monomer or monomers in a first stage polymerization
reactor 0.001 percent to 5 percent by weight, based on the monomer or
monomers present in the first stage of the vinyl chloride polymerization
1~2~6
of an additive to control polymer particle size, said additive having an
average particle size in the range of about 0.001 to about 50 microns. A
suitable additive is fumed silica sold by Degussa under the tradename
"Aerosil". The silica can be treated with an agent to render it hydro-
phobic. Such a treating agent is dichlorodimethylsilane which is used toproduce a fumed silica sold under the tradename "Aerosil R-972" by Degussa.
The silica used preferably is a fumed silica having an average particle
- size below lO l microns.
It is contemplated that both organic and inorganic solid particulate
matter which is both insoluble in vinyl chloride monomer and solid at
temperatures at least up to reaction temperatures can be used in conjunction
with monomers disclosed in the invention in a bulk polymerization process
to provide a reduction in particle size of the polymers produced. The
average particle size of the solid, inert, particulate matter can be in the
range of 0.001 micron to about 50 microns preferred. An example of an
organic solid particulate material useful in the process of the invention
is emulsion polymerized vinyl chloride having an average particle size of
two microns. Examples of inorganic solid particulate materials other than
fumed silica useful in the process of the invention are carbonates such as
calcium, magnesium, zinc, cadmium, and barium carbonates, aluminum silicates,
and talc. When large quantities of solid inert matter can be added to the
monomer without adding excessively to the cost or detracting from the
physical properties of the polymers obtained, it is possible to use organic
or inorganic solid inert particulate matter having an average particle size
range up to 50 microns. An operable amaunt of useful solid inert particulate
matter may thus be obtained from materials having greater than the above
preferred average particle size.
The surfactants, or surface active agents, used in combination with
vinyl chloride monomer or monomers can be of the nonionic, cationic, or
anionic type and are present in the first reaction stage in the range of
0.01 percent to S percent by weight based upon the monomer or monomers
present in the first stage polymerization.
The surface active agents are organic agents having structurally
unsymmetrical molecules containing both hydrophilic and hydrophobic
moieties. The non-ionics do not ionize but may acquire hydrophilic
character from an oxygenated side chain, usually polyoxyethylene. The
oil-soluble part of the molecule can be aliphatic or aromatic in nature.
The cationics ionize so that the oil-soluble portion is positively charged.
Principal examples are quaternary ammonium halides such as benzethonium
chloride and cetalkonium chloride. The anionics form negatively charged
ions containing in the oil-soluble portion of the molecule. The ioniz-
able group is the hydrophilic portion. Examples are sodium salts of or-
ganic acids, such as stearic acid and sulfonates or sulfates such as
alkylaryl sulfonates, i.e., sulfonates of dodecylbenzene and sulfates
of straight chain primary alcohols either fatty alcohols or products of
the Oxo process, i.e., sodium lauryl sulfate. Examples of non-ionic sur-
factants that have proven effective are octylphenoxy polyethoxyethanols
sold under the trade-name "Triton X-lO0" and "Triton X-35" by the Rohm
& Haas Company, Philadelphia, Pennsylvania. Examples of anionic sur-
factants are as follows: calcium, zinc, magnesium, and nickel stearates.
An example of an effective cationic surfactant is a quaternized amine
sold under the tradename "Quaternary 0" by the Ciba-Geigy Corporation.
Additional examples of suitable surfactants and more detailed
descriptions of their composition are presented in McCutcheon's
Detergents and Emulsifiers, N. American Ed., 1975 Annual, p. 35-265.
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Further details of the use of the above-described particle size
control additives and surfactants can be obtained from aforementioned
US Patent 4,029,863.
The use of a polyolefin additive in the first stage of a two stage
vinyl halide polymerization according to the invention provides especial-
ly good control of product particle size and also inhibits formation of
reactor scale. When any of the particle size control agents of the in-
vention are employed, it is advantageous to add to the reaction additional
polyolefin, preferably at the beginning of the second reaction stage, to
inhibit scale formation.
Advantageously, when a polyolefin is employed in the second stage
of the polymerization according to a preferred mode of the invention de-
scribed above, a surfactant of the type described hereinbefore may be
added with said second stage polyolefin~ the amount of surfactant being
about 0.01 to about 0.2 percent based on the weight of vinyl halide mon-
omer added up to that point.
The aforementioned presence of the surface active agent in the second
stage of the polymerization process of the invention results in more com-
plete filling in of intercises in the polymer product particles, i.e.,
diminishes the porosity of polymer product particles. Said diminution
of the product particle porosity beneficially reduces the viscosity of
plastisol formulations incorporating the present product as an extender
resin. Accordingly, the addition of the surface active agent to the
second stage of the polymerization in conjunction with any of the par-
ticle size control additives of the invention is beneficial even whenno polyolefin is added to the second stage of the polymerization.
- 18 -
3,1~2~?46
The polyolefin add;tives of the 1nvention are homopolymers, copolymers
or terpolymers of aliphatic hydrocarbon olefins of 2 to 8 carbon atoms.
Polymers of the aforementioned olefins wh;ch also contain monomer residues
of aliphatic hydrocarbon polyenes e.g. dienes or trienes, of 4 to 18 carbon
atoms can also be used. While advantageously the olefin polymers used in
the invention contain only hydrogen as substituents, halogenated olefin
polymers such as chlorinated, brominated and fluorinated polyolefins can
also be employed. The weight average molecular weight of the olefin polymers,
copolymers, and terpolymers employed as additives can vary from about 50,000
to about 300,000 and higher, up to l,000,000 and higher. Preferably the
polyolefin additive employed in the first stage of the present process has
a weight average molecular weight of about 50,000 to about l,000,000 while
preferably the polyolefin additive added in the second stage has a weight
average molecular weight of about 50,000 to about 300,000. Preferably also,
the first stage polyolefin additive is a polyene-modified olefin polymer of
the type described above whereas the second stage polyolefin additive is
advantageously free of polyene monomer residues.
In general the amount of polyolefin added in the first stage of poly-
merization according to the invention is about 0.05 to about 4 weight percent,
preferably about 0.1 to about 2 weight percent based on the weight of monomer
or monomers employed in the first reaction stage. The amount of polyolefin
charged to the reaction at the beginning of the second stage can be as low
as about 0.05 to about 0.5 percent by weight based upon vinyl halide monomer,
but more usually is about 0.05 to about 3 weight percent, preferably about
0.1 to about 2 weight percent, based on the weight monomer charged up to one
point of the addition of the polyolefin at the beginning of the second
reaction stage of the polymerization.
19
1'1~2~P46
The use of olefin polymers in bulk vinyl halide polymerization processes
is described more particularly in Belgian Patent 799,263, published November
8, 1973.
It is thus an object of the present invention to provide a bulk polym-
erization process for the production of highly molecular weight vinyl chloridepolymers or copolymers having small particle size and the individual particle
or agglomerate characterized as being non-porous. The porous particles are
believed to be filled in with a low molecular weight polyvinyl chloride which
renders such particles of polyvinyl chloride polymer or copolymer more resis-
tant to solvation at ambient temperature as compared to polymers and copoly-
mers of the prior art.
The reaction temperature in both first and second stage reactors is
generally in the range from about 25 degrees centigrade to about 80 degrees
centigrade, preferably about 30 to about 70 degrees centigrade. The reac-
tion pressure in the first stage reactor is generally in the range from
about 130 pounds per square inch to about 210 pounds per square inch, pref-
erably about 150 to about 190 pounds per square inch and corresponds to and
results from the temperature used in the process. The reaction pressure in
the second stage reactor is generally from about 80 to about 180 pounds per
square inch, preferably from about 90 to about 105 pounds per square inch,
and also corresponds to and results from the temperature used in the
process.
During the po~t polymerization, the temperature of the reactor con-
tents can be raised from about 30 degrees to about 70 degrees centigrade
to about
- 20 -
~2Y?~L~
60 degrees to about 80 degrees centigrade, said increase in polymerization
temperature being about 10 to about S0 degrees centigrade, and the pres-
sure raised from about 115 to about 215 pounds per square inch to about
160 to 265 pounds per square inch in order to initiate the reaction where
a higher temperature initiator is added at the beginning of the second
stage of a two stage bulk polymerization reaction process. Further de-
tails can be obtained of a process of bulk polymerization in two stages
in which the temperature of the reactor contents is raised during the
second stage of the process by reference to an earlier filed, commonly
owned U.S. Patent 3,933,771, issued January 20, 1976.
When the post polymerization is conducted at a higher reaction
temperature than is used initially in the second stage of the polymer-
ization process, said post polymerization results in the particles pro-
duced being non-porous, being less susceptible to solvation when in
contact at room temperature with a primary plasticizer for polyvinyl
chloride or polyvinyl chloride copolymers. The polymers also fuse at
a lower temperature.
In the process of the invention, additional monomer is added during
the second stage part of the bulk polymerization process. In addition to
the aforesaid advantaaes of the post polymerization the addition of mono-
mer during the second stage has the advantage of increasing the yield of
polymer since by the addition of monomer during the second stage, a greater
yield is obtained of product from the reaction vessel used. Reactor pro-
ductivity can thus be increased by about 25 percent.
- 21 -
~ ,
Z~4s~
In order to further illustrate this invention but without being limited
thereto, the following examples are given. [n this specification and claims,
all parts and percentages are by weight, all pressures are gauge pressures,
and all temperatures are in degrees centigrade unless otherwise specified.
5 Example 1 - Control
In a vertical type first stage reactor of 2 1/2 gallon capacity and
stainless steel construction, equipped with a radial turbine type agitator
were added 5.2 grams of fumed silica treated with dichlorodimethyl silane,
5.0 9. Triton X-100, 2.0 g. of a 29 percent solution of acetyl cyclohexane
10 sulfonyl peroxide in dimethyl phthalate sold under the trademark "Lupersol
228P" by the Lucidol Division of the Pennwalt Company and 1.0 g. of a 40
percent solution of di-2, ethyl-hexyl peroxy dicarbonate in mineral spirits
sold under the trademark "Lupersol 223M" by the Lucidol Division of the
Pennwalt Company. 11.0 pounds of vinyl chloride were added to the reactor
; 15 at a temperature of 20 degrees centigrade and 1.0 pounds of the vinyl
chloride monomer were vented to the atmosphere to remove air from the
reactor. The mixture in the reactor was slowly raised in temperature while
agitating using a radial turbine type agitator at a high agitation speed
of 2,000 revolutions per minute to a temperature of 67 degrees centigrade
20 over a period of 1 hour and maintained at this temperature for a period
of 15 minutes at a reaction pressure of 167 pounds per square inch.
The mixture was then transferred to a 5-gallon stainless steel reaction
vessel containing 2.2 9. of "Lupersol 223M" and 3.0 9. lauroyl peroxide and
7 pounds of vinyl chloride agitated at a low agitation speed. 1.5 pounds
25 of vinyl chloride were vented in order to clear ~the air from the reactor.
The mixture was heated at 50 degrees centigrade and the pressure raised
to 105 pounds per square inch. These conditions were maintained over a
- 22 -
Z~4~i
period of 4.5 hours. Then the mixture was heated and pressure of 170 psi
was maintained for 2.0 hours. The monomer that has not reacted is blown
off and collected in a condensing circuit incorporating a filter so as
to separate any particles of polymer carried over. The final traces of
residual monomer absorbed by the particles of polymer are eliminated by
placing the polymerizer under vacuum twice in succession and changing
over to a nitrogen atmosphere in between. All the polymer composition
is then passed through screening equipment. In this way, a powdery polymer
is obtained in a yield of 13 pounds of polymer. The polymer has an average
particle size of 48 microns as indicated by Coulter Counter measurements.
Example 2
A bulk polymerized polyvinyl chlor;de homopolymer was made by the
process of this invention using the same proportions of ingredients as in
Example 1, but 10.0 pounds of degassed monomer was added after 4.5 hours
polymerization time in the second stage and polymerization carried on for
an additional 4 hours. In this way, a powdery polymer is obtained in a
yield of 20 pounds. The polymer has an average particle size of 51 microns
as indicated by Coulter Counter measurements.
Using the resins prepared in Examples 1 and 2 above, plastisols were
made up using the following formulation. Seventy parts of an emulsion
polymerized polyvinyl chloride homopolymer sold under the trademark "Geon
121" by B. F. Goodrich Chemical Company, 30 parts of the bulk polymerized
polyvinyl chloride resin produced in the Examples above, and 60 parts of
dioctylphthalate. The plastisols were prepared in the usual manner by
combining the ingredients, blending until uniform using high speed
agitation and deaerating to remove entrapped air. Viscosity was evaluated
- 23 -
~1~2~4~
using a Brookfield Viscometer Model LVT with the plastisol being maintained
at a temperature of 25 degrees centigrade - 0.3 degrees centigrade. A No.
3 spindle was used and viscosity was determined as follows after aging the
plastisol two hours:
5Plastisol Made UsingBrookfield Viscosity
the Resin of (Centipoises)
Example 1 5350
Example 2 3700
Example 3
To a one-liter glass autoclave equipped with a spiral stirring blade
was added 180 grams of a polyvinyl chloride bulk polymerized polymer. The
reactor was evacuated to .05 millimeters mercury pressure and then press-
urized to 100 pounds per square inch gauge with nitrogen. This procedure
was repeated and then 0.5 millimeters of a 21 percent solution of acetyl
cyclohexane sulfonyl peroxide in mineral spirits. The reactor was evacuated
and cooled to 5 to 10 degrees centigrade and 345 grams of vinyl chloride
- were added and 30 grams vented off. The reactor jacket was heated with 80
degree water and the slurry was heated to a temperature of 72 degrees cent-
igrade within the reactor. After a period of two hours at this temperature,
the reactor was cooled to 30 degrees centigrade and the vinyl chloride was
distilled from the reactor over a two hour period. A 310 gram yield of
polymer was obtained after drying at 50 degrees centigrade for 16 hours.
Examination of the vinyl chloride by optical microscope showed an
average particle size of about 56 microns. The bulk polymerized starting
polymer had an average particle size of 49 microns. In order to evaluate
plasticizer absorption properties, a standard plastisol was made up of 70
parts of emulsion polymerized polyvinyl chloride sold under the trademark
- 24 -
~1~2~46
"Geon 121" by the B. F. Goodrich Chemical Company, 30 parts of the post-
polymerized polymer to be evaluated and 60 parts of diisooctyl phthalate.
A plastisol made up using the polyvinyl chloride bulk polymerized starting
polymer showed a viscosity of 4350 centipoises as measured by a LVT
Brookfield Viscometer, spindle Number 3, speed 12 rpm at 25 degrees
centigrade and 2 hours aging time. A similar plastisol prepared using
the product of the post polymerized process of the invention showed a
viscosity of 2805 centipoises.
In a similar manner, polyvinyl chloride powders prepared by suspension
polymerization and alternately emulsion polymerization were substituted for
the bulk polymerized polymer used above to produce extender resins useful
in the preparation of plastisols.
Example 4 - Control
A two stage bulk polymerized vinyl chloride was made using a one liter
stainless steel reactor by adding a mixture of 0.10 milliliters of acetyl
cyclohexane sulfonyl peroxide as a 29 percent solution in dimethyl phthalate
and 0.25 milliliters of di(2-ethylhexyl) peroxy dicarbonate as a 40 percent
solution in mineral spirits. The reactor was alternately evacuated and
pressurized with nitrogen to a pressure of 150 psig. The reactor was
charged with 500 grams of vinyl chloride monomer and the polymerization
was run for 20 minutes at 70 degrees centigrade. The contents of the
reactor were then transferred to a tubular reactor containing 250 grams of
vinyl chloride, 0.20 milliliters of acetyl cyclohexane sulfonyl peroxide as
a 29 percent solution in dimethyl phthalate and 0.5 milliliters di(2-ethyl
hexyl) peroxy dicarbonate as a 40 percent solution in mineral spirits. The
polymerization in this second stage reactor was run for 5 hours at 65 degrees
- 25 -
2~4f~;
centigrade. The polymer was then isolated by venting off excess vinyl
chloride and the polymer obtained as a dry polymer.
Examples 5 and 6
In the following Table, methyl acrylate was added during a second stage
vinyl chloride bulk polymerization reaction having the same ingredients,
proportions of ingredients and reaction conditions as in Example 4, except
that 2 hours after the start of the second stage polymerization, a monomer
was added to the polymerization mixture by placing the monomer in a steel
bomb pressurized to 200 pounds per square inch gauge of nitrogen. At the
moment of addition, two valves were opened, connecting the pressurized
bomb and reactor to complete the addition.
- 26 -
ll(~Z~46
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~1~2~46
Examples 7 and 8
To a one-liter glass autoclave equipped with a spiral stirring blade
were added 180 grams of a polyvinyl chloride bulk polymerized polymer made
as in Example 4. The reactor was evacuated to .05 millimeters mercury
pressure and then pressurized to 100 pounds per square inch gauge with
nitrogen. This procedure was repeated and then 0.5 milliliters was added
of a 21 percent solution of acetyl cyclohexane sulfonyl peroxide in mineral
spirits. The reactor was evacuated and cooled to 5 to 10 degrees centigrade
and 345 grams of vinyl chloride were added and 30 grams vented off. The
; 10 reactor jacket was heated with 80 degrees centigrade water and the slurry
was heated to a temperature of 72 degrees centigrade within the reactor.
After a period of two hours at this temperature, the reactor was coo1ed
to 30 degrees centigrade and the unreacted vinyl chloride was distilled
from the reactor over a two-hour period. This procedure was repeated to
produce a second batch of polymer. The extent of post-polymerization as
indicated by the effect on loose bulk density and flow times is shown
in the following Table:
-
TABLE 11
Effect of Post-Polymerization on
Loose Bulk Density and Flow Time
g Post Particle Loose Bulk Flow Time
ResinPolymerization Size Density (q/cc) (sec.)
- Example 4 0 115 ,u0.52 7.2
Example 754 133 y0,58 5.6
Example 855 129 y0.59 4.2
- 28 -
~1~2~46
Examples 9-19
In the following examples, bulk polymerizations were conducted using
the same proportions and ingredients and process conditions as in Example
4, except that during the first stage reaction, the reactor is loaded with
450 grams of vinyl chloride monomer and the contents of the first stage
reactor are transferred under pressure to a two-liter glass reactor con-
stituting the second stage reactor and the procedure modified as indicated
- below so that an acrylate monomer is added during the second stage of the
process at various specified times as indicated below. In Examples 9-19,
the amount of vinyl chloride in the second stage reactor was less than
shown in Example 4, the control, and corresponds to a total amount of 650
grams of vinyl chloride monomer, including polymer in the second stage
reactor made up of 450 grams of vinyl chloride added in the first stage
reactor and 200 grams of vinyl chloride added in the second stage reactor.
In Table III below, there is set out the results of polymerization in which
an acrylate monomer is added during a portion of the second stage polymer-
ization. The monomer is added all at once in these examples at the speci-
fied time subsequent to the start of the second stage polymerization reaction.
Samples of the polymer obtained in Examples 9-19 were compression
molded and tested for fusion time, heat distortion and notched Izod impact
strength. The compression molding procedure used was as follows: 105.6
~` grams of polymer were mixed with 2.i grams of dibutyltin, S,S'-bis(isooctyl
mercapto acetate), 3.76 grams of acrylic polymer processing aid, 0.52 grams
of a low molecular weight polyethylene wax, and 1.58 grams of glycerol mono-
stearate. The mixture of ingredients was compounded by milling on a two-roll
mill heated to 410F. Fusion of the mixture was found to occur within 30-60
- 29 -
11~2~g6
seconds of the start of the milling operation. The milled formulations
were molded at a temperature of 370F. in a mold measuring 6" x 6" x 1/8"
using a time interval of 3 minutes and a pressure of 1,000 pounds per
square inch. After molding, the samples are allowed to remain in the mold
for an additional 2 minutes and then the pressure raised to 3200 pounds
per square inch and this pressure held for 2 minutes. Samples were then
cooled 2 minutes and removed from the mold. These samples were then
tested for heat distortion according to ASTM Test Procedures D-648 for
heat distortion and D-256 for notched Izod, impact strength. A special
test procedure was used to determine fusion time which is defined as the
D maximum fusion torque measured using a Brabender Plastigraph. The procedure
for measuring fusion time is as follows: Into the Brabender bowl, heated
to 204C., were added 55 grams of polymer, together with 2 parts of an
organic stabilizer sold under the trademark Thermolite T-31 by M&T Chemicals,
and 1 part of an organic stabilizer sold under the trademark Thermolite T-187
by the N&T Chemicals Corporation. The maximum fusion torque is determined
by measuring the time from the addition of the above-described mixture of
polymer and stabilizer into the Brabender Plastigraph with the rotors
activated to the time when maximum torque is obtained as indicated by
subsequent reduction in torque. Test results are shown in Table IV below.
- 30 -
11~2~46
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Example 20
To a one liter glass autoclave equipped with a spiral stirring blade
there was added 300 grams of a polyvinyl chloride bulk polymerized polymer
made as in Example 4. The reactor was evacuated to .05 millimeters of
mercury pressure and then pressurized to 100 psi gauge with nitrogen. This
procedure was repeated and then there was added 0.5 milliliters of a 21
percent solution of acetyl cyclohexane sulfonyl peroxide in mineral spirits.
The reactor was evacuated and cooled to 5 to 10 degrees centigrade and 70
grams of n-butyl acrylate and 100 grams of vinyl chloride were added.
After polymerization for 2 hours at 72 degrees centigrade, an impact grade
polyvinyl chloride copolymer was obtained useful in the preparation of
moldings.
Example 21
A vertical stainless steel first stage reactor of 2-1/2 gallon capacity
as described in Example 1, equipped with a radial turbine type agitator of
3-1/4 inch outside diameter was charged with an air-free mixture of about
4540 9. of vinyl chloride, 0.38 ml of 50-53% solution of diisobutyryl
peroxide initiator in odorless mineral spirits (Lupersol 227, Lucidol
Division of the Pennwalt Company), 2.20 ml of a 40% solution of di (2-
ethylhexyl) peroxydicarbonate initiator in mineral spirits (Lupersol 223M,Lucidol Div. of Pennwalt Ço.), 0.776 9. of odorless mineral spirits, 1.081
9. of epoxidized soybean oil and 30 grams (corresponding to 1.15% of the
vinyl chloride monomer reactant) of an ethylene-propylene-ethylidene
norbornene terpolymer of weight average molecular weight of about 180,000
which had previously been dispersed in 1iquid vinyl chloride. Over a period
of 55 minutes, with high speed agitation employing an agitator speed of
~1~2~6
2000 rpm, the mixture was heated from 20 to 70 under autogenous super-
atmospheric pressure and then was maintained at 70 for 15 minutes.
The reaction mixture was then transferred to a second stage reactor
as described in Example 1 equipped with a spiral agitator of 11-1/8 inch
5 outside diameter, which contained an air-free mixture of about 2270 9.
of vinyl chloride monomer, 3.80 ml of the diisobutyryl peroxide initiator,
5.5 9. of lauroyl peroxide initiator, O. 776 9. of odorless mineral spirits,
5.48 9. of octylphenoxy polyethyoxy ethanol (a liquid surface active agent
manufactured under the trademark Triton X-100 by Rohm and Haas Co. ) and
91.0 9. (corresponding to 1.34% of the vinyl chloride monomer added to
the polymerization reaction up to this point) of ethylene-propylene co-
polymer of a weight average molecular weight of about 160,000. The
resulting mixture was agitated at a low speed of agitation of 63 rpm for
three hours at 49 and then an additional 4540 9. of vinyl chloride were
15 added to the mixture over a 30 minute period. On completion of the addition
the reaction mixture was agitated at 49 for 15 minutes. Over a 15 minute
period the agitated reaction mixture was heated from 49 to 60 and then
maintained at the latter temperature for 15 minutes to insure that all
of the diisobutyryl peroxide initiator was consumed. Over about a 20
20 minute period, the agitated reaction mixture was heated from 60 to 72
and agitation of the reaction mixture was continued at the latter temp-
erature until a drop in the reaction pressure indicated that polymer-
ization was substantially complete (or no longer than about 8 hours for
the total duration of reaction in the first and second stage reaction
25 zones).
A solution of 1.2 9. of 2,6 di-t-butyl p-cresol antioxidant color
stabilizer in a mixture of 22.7 9. of epoxidized soybean oil and 2.33 9.
- 34 -
4~i
of odorless mineral spirits was added under pressure to the polymerized
product in the reactor and the resultant mix~ure was agitated for 15
minutes at 72. Unreacted vinyl chloride monomer was vented from the
reactor and about 9040 9. of product (corresponding to a conversion of
5 about 79.6% based on the total vinyl chloride monomer charged to the
reaction) was recovered. As determined by gel permeation chromatography
the weight average molecular weight and the number average molecular
weight of the product were, respectively, about 72~800 and about 25~600
with the ratio of weight average molecular weight to number average
molecular weight being about 2~84~ The product contained 12.6% of scale
(i.e. particles greater than about 0~5 inch size) 11.1% of particles
greater than 20 mesh size but less than 0.5 inch size, 2~0% of particles
greater than 40 mesh size but less than 20 mesh size, 16.6% of particles
greater than 70 mesh size but less than 40 mesh size and 57~7% of particles
15 less than 70 mesh size.
As determined by Coulter Counter analysis of the latter predominant
fraction of the product, 84% of the fraction had an average particle of
less than 44.1 microns, 50% of the fraction had an average particle size
of less than 37.9 microns and 16% of the fraction had an average particle
20 size of less than 31~6 microns.
The bulk density of the aforementioned fraction of product having an
average particle size less than 70 mesh was 0~55 9. per cc. The plastisol
viscosity of this fraction was 2960 centipoises as measured on a Brookfield
Viscometer at 25 + 3~, this value being about 8% lower than the corresponding
25 viscosity of a proprietary conventional vinyl chloride homopolymer extender
resin (Borden 260SS~ Borden Chemical Co.) prepared by the suspension mode
of polymerization.
~ 35 ~
4~
It will be appreciated by those skilled in the art that procedural
modifications of the above-described experimental technique can be made
without departing from the spirit and scope of the invention. For example,
the staged raising (i.e. ramping) of the reaction temperature from 49 to
72 (which follows post-polymerization addition of additional monomer in
the second reaction stage) can be accomplished more rapidly than by direct
heating of the reaction mixture as described, i.e. by preheating the
monomer, before its addition, to above 72 and then adding the hot monomer
to the reaction mixture at 49 (by incremental addition, if desired),
thereby raising the temperature of the resultant mixture from 49 to the
desired final reaction mixture temperature of 72.
Example 22
A vertical stainless steel reactor equipped with a radial turbine type
agitator and a marine propeller type agitator was charged with an air-free
mixture of about 3506 Kg. of vinyl chloride, 340.00 grams of 2,2' azobis
(2,4-dimethyl-4-methoxy-valeronitrile) containing approximately 35% H20,
857.14 ml of a 75% solution of di(2-ethylhexyl) peroxy dicarbonate in-
mineral spirits, 750 ml of mineral spirits, 750 ml of epoxidized soybean
oil and 24.33 Kg. (corresponding to 0.694% of the vinyl chloride monomer
reactant) of an ethylene-propylene-ethylidene norbornene terpolymer of
weight average molecular weight of about 180,000 which had previously been
dispersed in liquid vinyl chloride. Over a period of 55 minutes, with
high speed agitation, the mixture was heated from 20 to 70 under auto-
genous superatmospheric pressure and then maintained at 70C. for 15
minutes.
The reaction mixture was transferred to a horizontal, reactor
equipped with three paddle-type agitator vanes, which contained an air-free
- 36 -
2C~
mixture of about 1724 Kg. of vinyl chloride monomer, 10.2 Kg. of the 2,2'
azobis (2,4-dimethyl-4-methoxyvaleronitrile) initiator, 750 ml of regular
mineral spirits and 3.9 liters of octylphenoxy polyethoxy ethanol ta
liquid surface active agent manufactured under the trademark Triton X-100
by Rohm and Haas Co.). The resulting mixture was agitated at low speed
of agitation for approximately 4.5 hours at 47 and then an additional
2268 Kg. of vinyl chloride monomer containing 2.5 Kg. of lauroyl peroxide
intiator were added to the mixture over a 30 minute period. On completion
of the addition the reaction mixture was agitated at 47 for 15 minutes.
Over a 15 minute period the agitated reaction mixture was heated from 47
to 60 and then maintained at the latter temperature for 15 minutes to
ensure that all of the low temperature initiator had been consumed. Over
about a 15 minute period the reaction mixture was then heated from 60 to
72 and agitation of the reaction mixture was continued at the latter
temperature until a drop in pressure indicated that polymerization was
substantially completed (or no longer than about ten hours for the total
duration in the first and second stage reaction zones).
Twelve liters of epoxidized soybean oil were added to the reaction
mixture upon completion of reaction as a color and heat stabilizer. After
the additlon of the epoxidized soybean oil, the reaction mass was agitated
for 15 minutes at 72.
Unreacted vinyl chloride monomer was vented from the reactor and about
4899 Kg. (corresponding to a conversion of about 66.7% based on the total
vinyl chloride monomer charged to the reaction) was recovered. As deter-
mined by gel permeation chromatography the weight average molecular weightand the number average molecular weight of the product were, respectively,
- 37 -
about 102,000 and about 35,300 with the ratio of weight average molecular
weight to number average molecular weight being about 2.88. The product
contained 85.3% of particles less than 70 mesh size.
As determined by Coulter Counter analysis of the latter predominant
fraction of the product, 84% of the fraction had an average particle of
less than 84.0 microns, 50% of the fraction had an average particle size of
less than 56.7 microns and 16% of the fraction had an average particle size
of less than 38.7 microns.
The bulk density of the aforementioned fraction of product having an
average particle size less than 70 mesh was 0.65 9. per cc. The plastisol
viscosity of this fraction was 3438 centipoises as measured on a Brookfield
Viscometer at 25 - 3, this value being about 3% lower than the corres-
ponding viscosity of a proprietary conventional vinyl chloride homopolymer
extender resin (Borden 260SS, Borden Chemical Co.) prepared by the sus-
pension mode of polymerization.
It will be appreciated by those skilled in the art that proceduralmodifications of the above-described process can be made without departing
from the spirit and scope of the invention. For example, the staged
raising (i.e. ramping) of the reaction temperature from 47 to 72 (which
follows post-polymerization addition of additional monomer in the second
reaction stage) can be accomplished more rapidly than by direct heating of
the reaction mixture as described, i.e. by preheating the monomer, before
its addition, to above 72 and then adding the hot monomer to the reaction
mixture at 47 (by incremental addition, if desired), thereby raising the
temperature of the resultant mixture fram 47 to the desired final reaction
mixture temperature of 72.
- 38 -
l~Z~
The invention has been described in the above specification and
illustrated by reference to specific embodiments in the illustrative ex-
amples. However, it is to be understood that those embodiments are not
intended to limit the invention since, as ~llustrated, changes and modif-
ications in the specific details disclosed hereinabove can be made withoutdeparting from the scope or spirit of the invention.
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