Note: Descriptions are shown in the official language in which they were submitted.
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Halosten-containing vinyl polymer resins and processes for
the preparation thereof
The present invention relates to halogen-containing vinyl polymer resins,
and in particular halogen-containing vinyl polymer resins formed by
polymerisation in aqueous emulsion, processes for the preparation of such
resins
by co-coagulation with other emulsions, the use of such resins for the
formation
of articles therefrom by extrusion and the extruded articles obtained
therefrom.
Traditionally, halogen-containing vinyl polymer resins formed by
polymerisation in aqueous emulsion are coagulated producing larger coagulated
polymer particles. The liquid portion of the emulsion is then removed from the
coagulated polymer leaving a dry coagulated halogen-containing vinyl polymer
resin.
The polymer resins formed in this fashion include fines and dust (particles
which, generally speaking, are less than about 45 microns in size) of the
resin.
To produce a polymer blend for extrusion, these dry halogen-containing
vinyl polymer resins are then normally blended with other materials, such as
stabilisers, plasticizers, processing aids and other polymers, in a blender
(mixer)
to form a polymer blend. This polymer blend is then extn~ded forming extruded
articles.
Unfortunately, the presence of fines and dust in the polymer resins is at
least partially responsible for the formation of "sticky" particles which are
the
source of several problems which occur when forming (blending) and extruding
of the polymer blends.
Due to their tendency to melt more rapidly than larger particles under the
heat, frictional and otherwise, to which they are exposed during blending,
fines
and dust tend to be "sticky", particularly when a high-speed blender is used.
These "sticky" particles tend to adhere not only to one another and to other
resin
particles, but also to the blades of the blender. The adherence of these
"sticky"
polymer fines and dust to one another is problematic in that it leads to the
formation of lumps which causes problems in the extrusion feed. The adherence
of these "sticky" polymer fines and dust to the blades of the blender is
problematic in that it encrusts them which leads to poor blending and results
in a
lower quality product (polymer blend) being obtained unless important
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investments are made and processing downtime incurred to clean the encrusted
blades.
Furthermore, fines and dust of polymer resins have limited capabilities to
absorb liquids (such as epoxidized soybean oil and liquid plasticizers) that
are
S added to the resin during blending. This results in a poorly stabilised or a
poorly
plasticized polymer resin. This is particularly problematic when the liquid
does
not fully penetrate the polymer resin being blended, such as when the resin is
that of a barrier polymer, like polyvinylidene chloride (PVDC), which resist
such
penetration.
The addition of solid additives, such as processing aids or other polymers
results in a blend which is heterogeneous by nature and which is subject to
segregation during transport and feeding during extrusion, resulting in uneven
feeding and inducing variations in the backpressure which is undesirable,
particularly where the extrusion of PVDC is involved.
Further, during extrusion, poorly stabilised.fines and dust of polymer resin
tend to segregate in the extrusion feed hopper, resulting in uneven feeding
and
inducing variations in the backpressure in the extruder. Furthermore, such
fines
and dust tend to require longer residence times in the extruder during which
time
they are exposed to heat from the extruder which turns them dark or black. The
presence of such dark or black particles in the extruded product is highly
undesirable, particularly when the final product is a film.
Solutions proposed to avoid the above-mentioned problems have, for the
most part, centered on avoiding the formation of "sticky" particles of polymer
resin (and not on avoiding the formation of the polymer fines and dust). In
_. 25 particular, resort has been made to the incorporation of stabilisers,
such as
epoxidized soybean oil (ESO), in the polymer resin during emulsion
polymerisation. However, such a solution has not been entirely satisfactory in
solving the problem in that the addition of ESO (even at concentrations as low
as
4 parts per thousand) during polymerisation, even under the form of an
emulsion,
leads to the formation of sludge in the autoclave. Such sludge detrimentally
affects the process and the products later extruded therefrom.
Thus, it can be seen that it would be highly desirable to provide a halogen-
containing vinyl polymer resin which is substantially free of dust and fines,
and
in particular, such a polymer resin which has a thermal stabiliser, such as
ESO,
incorporated therein.
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Accordingly, there remains a need to provide a solution to the above-
mentioned problems by providing a halogen-containing vinyl polymer resin, and
in particular a vinylidene chloride polymer resin, that is prepared by
polymerisation in an aqueous emulsion, which polymer resin is substantially
free
of polymer fines and dust. There remains a further need to provide such a
substantially fine and dust free polymer resin which has a thermal stabiliser,
such
as ESO, incorporated therein, so that the resin has good thermal stability,
flowability and extrudability and is less prone to lumping than conventional
polymer resins.
It is a primary object of the present invention to provide halogen-
containing vinyl polymer resins which have improved thermal stability,
flowability and extrudability and which are less prone to lumping than
conventional halogen-containing vinyl polymer resins.
In this regard, it is a further primary object to provide such resins which
have those desired additives, such as processing aids, stabilisers (such as
thermal
stabilisers, plasticizers and/or other polymers, incorporated therein, so that
such
additives do not need to be added later, so that blending of the resin is
avoided
and so that a resin which is "ready-to-use" (that is to say, a resin that may
be
directly employed without the necessity for any further treatment, mixing or
other processing) is provided.
It is a further primary object of the present invention to provide such
polymer resins in the form of a co-coagulate having a substantially
homogeneous
distribution of the halogen-containing vinyl polymer resin and of those other
substances, such as processing aids, stabilisers (such as thermal
stabilisers),
plasticizers and/or other polymers which are desired to be included therewith.
It is a still further primary object of the present invention to provide such
halogen-containing vinyl polymer resins which are substantially free of
polymer
dust and fines.
A further primary object of the present invention is to provide processes
for the preparation of such halogen-containing vinyl polymer resins and such
co-
coagulates. In this regard, it is a further primary object of the present
invention
to provide novel processes for including those desired additives, such as
stabilisers, processing aids, plasticizers and other polymers with the polymer
resin without the need for, and eliminating the step of, blending.
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It is a still further object of the present invention to provide methods and
to
use such halogen-containing vinyl polymer resins and such co-coagulates to
form
extruded articles.
A still further object of the present invention is to provide extruded
articles
formed from such halogen-containing vinyl polymer resins and such co-
coagulates.
In accordance with the teachings of the present invention, disclosed herein
are halogen-containing vinyl polymer resins in the form of co-coagulates of
particles of halogen-containing vinyl polymer resins and particles which are
chosen from the group (comprised) of processing aids, stabilisers (such as
thermal stabilisers), plasticizers and/or other polymer resins. These co-
coagulates are substantially free of polymer dust and fines and are
substantially
free from lumping and crusting. Also, by having those additives (that is to
say,
the processing aids, stabilisers (such as thermal stabilisers), plasticizers
and/or
I S other polymer resins which are desired to be included therewith) which are
desired to be included with the halogen-containing vinyl polymer resin, these
co-
coagulates have halogen-containing vinyl polymer resins which are "ready-to-
use", do not require blending or the addition of further components thereto
before being extruded, and present good flowability, thermal stability and
extrudability.
As used herein, the term "halogen-containing vinyl polymer" refers to
those (homo- and co-) polymers which are formed by the polymerisation of
halogen-containing vinyl monomers. Such polymers may be obtained by any
known means. However, preferred is the radical polymerisation in aqueous
emulsion of halogen-containing vinyl monomers (either by themselves for
forming halogen-containing vinyl homopolymers or with other copolymerizable
monomers, such as vinylic esters, vinylic ethers, acrylic acids, acrylic
esters,
acrylic nitriles, acrylic amides, methacrylic acids, methacrylic esters,
methacrylic
amides, styrene, styrenic derivatives, butadiene, olefins such as ethylene and
propylene, itaconic acid and malefic anhydride for forming halogen-containing
vinyl copolymers). Examples of such halogen-containing vinyl polymers are
polyvinylidene chloride (PVDC), polyvinyl chloride (PVC) and polyvinylidene
fluoride (PVDF).
As used herein, the term "halogen-containing vinyl polymer resin" refers to
those (homo- and co-) polymer resins which are formed by the polymerisation of
halogen-containing vinyl monomers. Such polymer resins may be obtained by
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any known means. However, preferred is the radical polymerisation in aqueous
emulsion of halogen-containing vinyl monomers (either by themselves for
forming halogen-containing vinyl homopolymers or with other copolymerizable
monomers, such as vinylic esters, vinylic ethers, acrylic acids, acrylic
esters,
acrylic nitrites, acrylic amides, methacrylic acids, methacrylic esters,
methacrylic
amides, styrene, styrenic derivatives, butadiene, olefins such as ethylene and
propylene, itaconic acid and malefic anhydride for forming halogen-containing
vinyl copolymers). Examples of such halogen-containing vinyl polymer resins
are polyvinylidene chloride (PVDC), polyvinyl chloride (PVC) and
polyvinylidene fluoride (PVDF).
The co-coagulates of the present invention are further characterized in that
the particles of halogen-containing vinyl polymer resins and the particles
chosen
from the group (comprised) of processing aids, stabilisers (such as thermal
stabilisers), plasticizers and other polymer resins are substantially
homogeneously distributed throughout the diameter of each individual co-
coagulate.
Preferably, the particles of the halogen-containing vinyl polymer resins of
the co-coagulates of the present invention are formed from by radical
polymerisation in aqueous emulsion of at least one halogen-containing vinyl
monomer and at least one other monomer.
As used herein, the term "radical polymerisation in an aqueous emulsion"
is used to describe those radical polymerisation reactions which are carried
out in
an aqueous milieu in the presence of emulsifying agents and radical
initiators.
This definition specifically includes "classical" polymerisation in an aqueous
emulsion, in which one employs hydrosoluble radical initiators, as well as
microsuspension polymerisation (sometimes referred to as homogeneous
aqueous dispersions) in which one employs oleosoluble initiators.
Polymerisation in this manner provides an emulsion of monomer droplets by a
strong mechanical agitation in the presence of emulsifying agents.
As used herein, the term "aqueous dispersion" (sometimes also referred to
as "latex") is used to describe the polymer dispersion in water obtained after
radical polymerisation in an aqueous emulsion.
As used herein, the term "vinyl monomer" refers to those monomers
possessing a terminal olefin insaturation substituted by at least one other
atom.
As used herein, the term "halogen-containing vinyl monomer" refers to
those vinyl monomers possessing a terminal olefin insaturation substituted by
at
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least one halogen atom. Examples of such monomers are vinyl chloride,
vinylidene chloride, vinyl bromide, vinyl fluoride, vinylidene fluoride,
trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene and
hexafluoropropylene. Preferred are vinylidene chloride (VDC) and vinyl
chloride (VC).
It is further preferred that the particles of the halogen-containing vinyl
polymer resins of the co-coagulates of the present invention are particles of
chloride-containing vinyl polymer resins. Examples of such chloride-containing
vinyl polymer resins are polyvinyl chloride (PVC) having vinyl chloride
monomers, and polyvinylidene chloride (PVDC) having vinylidene chloride
monomers.
As used herein, the term "chloride-containing vinyl polymer resin" refers
to those (homo- and co-) polymer resins which are formed by the polymerisation
of chloride-containing vinyl monomers. Such polymer resins may be obtained
by any known means. However, preferred is the radical polymerisation in
aqueous emulsion of chloride-containing vinyl monomers (either by themselves
for forming chloride-containing vinyl homopolymers or with other
copolymerizable monomers, such as vinylic esters, vinylic ethers, acrylic
acids,
acrylic esters, acrylic nitriles, acrylic amides, methacrylic acids,
methacrylic
esters, methacrylic amides, styrene, styrenic derivatives, butadiene, olefins
such
as ethylene and propylene, itaconic acid and malefic anhydride for forming
copolymers). Examples of such chloride-containing vinyl polymer resins are
polyvinylidene chloride (PVDC} and polyvinyl chloride (PVC).
As used herein, the term "chloride-containing vinyl polymer" refers to
_, 25 those (homo- and co-) polymers which are formed by the polymerisation of
chloride-containing vinyl monomers. Such polymers may be may be obtained by
any known means. However, preferred is the radical polymerisation in aqueous
emulsion of chloride-containing vinyl monomers (either by themselves for
forming chloride-containing vinyl homopolymers or with other copolymerizable
monomers, such as vinylic esters, vinylic ethers, acrylic acids, acrylic
esters,
acrylic nitriles, acrylic amides, methacrylic acids, methacrylic esters,
methacrylic
amides, styrene, styrenic derivatives, butadiene, olefins such as ethylene and
propylene, itaconic acid and malefic anhydride for forming copolymers).
Examples of such chloride-containing vinyl polymers are polyvinylidene
chloride (PVDC) and polyvinyl chloride (PVC).
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As noted above, the particles of the halogen-containing vinyl polymer
resins of the co-coagulates of the present invention may also be particles of
halogen-containing vinyl copolymer resins having halogen-containing vinyl
monomers and at least one other monomer.
Preferred in this regard is that the particles of chloride-containing vinyl
copolymer resins are particles of copolymers comprised of chloride-containing
vinyl monomers and at least one other monomer. Examples of such particles of
copolymers are particles comprised of vinyl chloride monomers and at least one
other monomer and particles comprised of vinylidene chloride monomers and at
least one other monomer.
As used herein, the term "chloride-containing vinyl monomer" refers to
those vinyl monomers possessing a terminal olefin insaturation substituted by
at
least one chloride atom. Examples of such monomers are vinylidene chloride
(VDC) and vinyl chloride (VC).
Further preferred in this regard are particles of copolymers comprised of
two different halogen-containing vinyl monomers, and in particular vinylidene
chloride monomers and vinyl chloride monomers. In this regard, in one
embodiment, the halogen-containing vinyl copolymer resin of the present
invention includes a vinylidene chloride/vinyl chloride (VDC/VC) resin.
Particularly preferred is the VDC/VC copolymer emulsion resin.
Still further preferred in this regard are particles of copolymers comprised
of two different halogen-containing vinyl monomers (in particular vinylidene
chloride monomers and vinyl chloride monomers) and at least one other
monomer. Of particular preference is that the other monomers be monomers of
acrylates and/or methacrylates. Further particularly preferred in this regard
is
that the other monomers are monomers of glycidylmethacrylate.
As used herein, monomers of (metha)acrylates are those monomers having
the following general formula
CH2=CR1R2
in which
R1 is selected from the group consisting of hydrogen and methyl radical
and in which
R2 is selected from the group consisting of -CN radical and -CO-OR3 radical in
which R3 is selected from the group consisting of hydrogen, alkyl radicals
containing from 1 to 18 carbon atoms, alkoxyalkyl radicals having from 1 to 10
carbon atoms and -NR4R5 radicals, in which R4 and RS are selected from the
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group consisting of hydrogen and an alkyl radical containing from 1 to 10
carbon
atoms.
Alternatively, these copolymer resins of the co-coagulates of the present
invention are formed by the polymerisation in emulsion of a halogen-containing
vinyl monomer and a monomer or monomers which do not contain a halogen. In
this regard, in one embodiment, the halogen-containing vinyl copolymer resin
of
the present invention includes a vinylidene chloride/methyl acrylate (VDC/MA)
resin. Further in this regard, in another embodiment, the halogen-containing
vinyl copolymer resin of the co-coagulates of the present invention include a
vinylidene chloride/methyl acrylate/glycidylemethacrylate (VDC/NiA/GMA)
resin.
When such copolymers contain vinylidene chloride, it is preferred that the
vinylidene chloride be the majority halogen-containing vinyl monomer.
In this respect, it is preferred that the copolymer resin has at least about
50% (w/w) of vinylidene chloride. Further preferred is that the polymer resin
has
at least about 60% (w/w) of vinylidene chloride. Still further preferred is
that the
polymer resin has at least about 70% (w/w) of vinylidene chloride.
Further in this respect, it is preferred that the copolymer resin has no more
than about 95% (w/w) of vinylidene chloride. Further preferred is that the
polymer resin has no more than about 85% (w/w) of vinylidene chloride. Still
further preferred is that the polymer resin has no more about 75% (w/w) of
vinylidene chloride.
Most preferred is that the copolymer resin has about 70% (wlw) to about
75% (w/w) of vinylidene chloride, with about 72% (w/w) of vinylidene chloride
being especially preferred.
As used herein, the term "majority halogen-containing vinyl monomer"
refers to that halogen-containing vinyl monomer which comprises at least 50%
(w/w) of the halogen-containing vinyl copolymer resin of which it forms a
part.
It is contemplated herein that, in the co-coagulates of the present invention,
the particles of the halogen-containing vinyl polymer resin will be solids.
Preferably, the particles selected from the group (comprised) of processing
aids, stabilisers (such as thermal stabilisers), plasticizers and other
polymer
resins which may be included in the co-coagulates of the present invention are
also provided in aqueous emulsion.
While not being limited thereto, it is contemplated herein that examples of
particles of processing aids which may be included in the co-coagulates of the
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present invention include particles of acrylates, methacrylates, stearates,
waxes
and polyolefins.
While not being limited thereto, it is contemplated herein that examples of
particles of stabilisers (such as thermal stabilisers) which may be included
to be
included in the co-coagulates of the present invention include epoxidized
soybean oil (ESO) and HCl scavengers (such as hydrotatcite-like compounds).
If desired, the stabiliser which is incorporated into the halogen-containing
vinyl polymer resins of the co-coagulates of the present invention may be any
conventional stabiliser (or liquid processing aid) which is capable of
coagulating
with the vinyl polymer. Particularly preferred in this regard are emulsions of
epoxidized soya oil (ESO).
Preferably, the co-coagulates have approximately at least about 0.5%
(w/w) of stabiliser. Also preferred is that the co-coagulates have
approximately
at least about 2% (w/w) of stabiliser. Further preferred that the co-
coagulates
have approximately at least about 4% (w/w) of stabiliser.
It is noted that in this manner, when the stabiliser is an emulsion of ESO
and when the liquid medium is an aqueous emulsion, the stabiliser is very
homogeneously distributed throughout the individual co-coagulates.
We have found that incorporation of the stabiliser into the resin in this
manner (as a coagulation aid) significantly increases the quantity of co-
coagulates which are formed that have a diameter of at least about 45 microns.
We have further found that use of the stabiliser in this manner (as a
coagulation aid) significantly reduces the stickiness (of the resin and) of
the co
coagulates obtained.
_, 25 In addition, we believe that the presence of the emulsifier in the ESO
plays
a role in internal lubrication during extrusion of the co-coagulates of the
present
invention.
While not being limited thereto, it is contemplated herein that examples of
particles of plasticizers to be included in the co-coagulates of the present
invention are selected from the group (comprised) of debutyl sebacate, acetyl
tributyl citrate, dioctyl adipate (DOA), latexes of butadiene-styrene and
polycaprolactones, such as s-caprolactones.
While not being limited thereto, it is contemplated herein that examples of
particles of other polymer resins to be included in the co-coagulates of the
present invention are selected from the group (comprised) of homopolymers and
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copolymers having monomers of vinyl chloride, vinylidene chloride, vinylidene
fluoride, ethylene vinyl acetate and ethylene methyl acrylate.
It is contemplated herein that the particles selected from the group
(comprised) of processing aids, stabilisers (such as thermal stabilisers),
plasticizers and other polymer resins of the present invention may be either
liquids and/or solids.
In another aspect of the present invention, disclosed herein is a process for
the preparation of the halogen-containing vinyl polymer resin containing co-
coagulates of the present invention.
The process for preparing the co-coagulates of the present invention
includes the steps of (co)polymerisation, co-coagulation and drying. This
process in characterised by co-coagulating the halogen-containing vinyl
polymer
resin and the stabiliser (and, thereby avoiding the necessity for any blending
thereof).
In the step of (co)polymerisation, at least one halogen-containing vinyl
monomer is polymerised, whereby an emulsion is formed having particles of the
(co)polymer resin therein.
The step of (co)polymerisation of the process of the present invention,
involves the (co)polymerisation of at least one halogen-containing vinyl
monomer. It is contemplated herein that such (co)polymerisation may be radical
(co)polymerisation, particularly where the formation of (co)polymer resins
having VC and/or VDC and/or VDF monomers are desired. It is further
contemplated that (co)polymerisation may be radical (co)polymerisation in an
aqueous medium, and in particular radical (co)polymerisation in an aqueous
4 25 emulsion, once again in particular where the formation of (co)polymer
resins
having VC and/or VDC monomers are desired.
The invention is particularly adapted to such "classical" (co)polymerisation
in an aqueous emulsion which is performed in those conditions well-known to
those skilled in the art. It is therefor that the (co)polymerisation be
performed
with the use of emulsifying agents and hydrosoluble initiators present in
quantities well-known to those skilled in the art.
Examples of such emulsifying agents are anionic emulsifying agents and
nonionic emulsifying agents. Examples of anionic emulsifying agents are
sulfonate waxes, alkyl sulfonates, alkyl sulphates, alkylaryl mono and
disulfonates and alkylsulfosuccinates. Examples of nonionic emulsifying agents
are derivatives of alkyl- and alkylarylethoxylates.
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Examples of hydrosoluble initiators are hydrosoluble peroxides such as
persulfates of alkaline metals persulfates of ammonium, hydrogen peroxides,
perborates and t-butyl hydroperoxide used only in association with a reducer.
Radical (co)polymerizations in an aqueous emulsion are performed in
autoclaves. Monomers, initiators and an emulsifier are all introduced into the
autoclave. The temperature within the autoclave is then increased and
agitation
started. Typical temperatures range from about 30°C to about
90°C.
(Co)polymerisation time ranges from about 5 to about 15 hours. At the end of
the (co)polymerisation reaction, the autoclave is degassed and stripping is
started
to remove individual monomers which may remain. The emulsion is then
transferred to the co-coagulator for co-coagulation.
In the step of co-coagulation, the particles of the polymer resin in the
emulsion and any other particles in the emulsion are co-coagulated, whereby a
co-coagulate having the particles of the polymer resin is formed.
The step of co-coagulation of the process of the present invention involves
the addition of a salt to the anionic emulsion to provoke co-coagulation of
the
polymer and formation of a co-coagulate.
According to the teachings of the present invention, the emulsion of the
other compound is added to the aqueous emulsion including the polymer resin
during co-coagulation simultaneously with the co-coagulating salt.
In the drying step, the co-coagulates having the particles of the polymer
resin are dried, whereby co-coagulates having dry particles of the halogen-
containing vinyl polymer resin is formed.
The step of separating the liquid medium from the polymer resin of the
process of the present invention involves the elimination of a substantial
portion
of the liquid from the co-coagulate, whereby the co-coagulate in the form of a
powder is provided. Such drying step may include removal of portions of the
liquid from the co-coagulates having the polymer resin by, for example,
decanting, filtration, etc. to provide a cake. The drying step may further
include
drying the cake so as to provide the co-coagulates having the polymer resin in
the form of a powder.
The process of the present invention is particularly characterised by adding
to the emulsion, which has the particles of the halogen-containing vinyl
polymer
resin therein, at least one other emulsion having particles of a substance
selected
from the group (comprised) of stabilisers, processing aids, plasticizers and
other
polymers and co-coagulating these two emulsions (the emulsion having the
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particles of the polymer resin and the emulsion having the at least one other
emulsion having the particles of the substance selected from the group
(comprised) of stabilisers, processing aids, plasticizers and other polymers).
In
this fashion, a co-coagulate comprised of particles of halogen-containing
vinyl
polymer resins and particles chosen from the group (comprised) of processing
aids, stabilisers (such as thermal stabilisers), plasticizers and/or other
polymer
resins is formed.
The emulsions of the above-described process, and the contents thereof,
will vary according to the various co-coagulates having the halogen-containing
vinyl polymer resin which are desired to be produced therefrom.
In still another aspect of the present invention, disclosed herein is the use
of the co-coagulates of the present invention which have the particles of
halogen-
containing polymer resins and the particles chosen from the group (comprised)
of processing aids, stabilisers (such as thermal stabilisers), plasticizers
and/or
other polymer resins for the formation of extruded articles.
The polymer/stabiliser resins of the present invention may be used to foim
articles. In this regard, it is contemplated that the polymer/stabiliser resin
will be
extruded in an extruder for forming extrudable articles, such mono- layer and
multilayer barrier films and foils. Further in this regard, it is noted that
it is
believed that the presence of the emulsifier in the ESO could play a role in
internal lubrication during extrusion.
In a still another aspect of the present invention, disclosed herein are
extruded articles which are formed from the co-coagulates of the present
invention which have the particles of halogen-containing polymer resins and
the
_. 25 particles chosen from the group (comprised) of processing aids,
stabilisers (such
as thermal stabilisers), plasticizers and/or other polymer resins.
By co-coagulating the emulsion which contains the halogen-containing
vinyl polymer (before blending) with the emulsions) having either the desired
processing aids, stabilisers (such as thermal stabilisers), plasticizers
and/or other
polymer resins in accordance with the present invention, the co-coagulates of
the
present invention are formed so that each co-coagulate is an intimate mixture
of
each component (that is to say, the particles of these various components are
substantially homogeneously distributed throughout each co-coagulate).
Accordingly, the co-coagulates of the present invention form a very homogenous
3 5 blend.
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In this fashion, stabilisers, such as ESO, which are incorporated therein, act
as an internal lubricant which is of particular interest where resins are
involved
that have poor stability, such as is particularly notable in the case of
barrier
polymers, such as PVDC.
Further, by being co-coagulated according to the process of the present
invention, the particles of the base emulsions, which are typically less than
0.5
microns in size, are formed into larger co-coagulates. A substantial portion
of
these co-coagulates are larger than about 45 microns in size, so that the
resins
comprised of such co-coagulates are substantially free of polymer dust and
fines.
As used herein, the term "emulsion resin" is used to refer to a resin that is
obtained from an aqueous emulsion prepared using radical polymerisation in an
aqueous emulsion.
The process of the present invention presents, above all, the advantage that
the polymerisation itself is not effected (no sludge formation, no problems of
residual monomers, etc.) and that the particles of those other components
(such
as the processing aids, stabilisers -- and particularly ESO --, plasticizers
and/or
other polymer resins) is always well incorporated and, therefor, well
protected.
In this regard, we note that in contrast to suspension polymerisation's (where
ESO can be placed directly into the polymerisation reactor during
polymerisation), this is not possible where emulsion polymerisation is
involved
due to the formation of sludge which such an addition provokes, even when an
emulsified ESO is used. Thus, the process of the present invention provides a
manner where such ESO can be satisfactorily incorporated into the polymer
resin.
In addition, we believe that the presence of the emulsifier in the ESO plays
a role in internal lubrication during extrusion of the co-coagulates of the
present
invention.
Other important characteristics of the co-coagulates, notably their thermal
stability, the barrier properties thereof and their extrudability, are at
least
equivalent to or superior to those in comparison to a premix. In this regard,
we
note that while premixes may tend to be not extrudable due to extensive
lumping,
the "ready-to-use" co-coagulates of the present invention give rise to very
stable
extrusion conditions.
The halogen-containing vinyl polymer resins of the co-coagulates of the
present invention may be either homopolymers or copolymers. It is
contemplated that copolymers of the co-coagulates of the present invention may
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be formed by either copolymerization or by independent polymerization and
subsequent blending.
Preferably, these copolymer resins of the co-coagulates of the present
invention are formed by the polymerisation in emulsion of at least two
different
halogen-containing vinyl monomers.
The above-described properties of the co-coagulates of the present
invention, and particularly those properties of increased particles size and
reduced stickiness, which are obtained by the process of the present invention
permits the co-coagulates having the polymer resin/stabiliser to be used
without
any blending. Further, the co-coagulates of the present invention are less
prone
to both crusting the blades of the blender and to lumping (the formation of
less
and/or smaller lumps). In this fashion, the co-coagulates of the present
invention
prESent good flowability, thermal stability and extrudability.
Having thus described the invention, the following examples are now
presented which are for illustrative purposes only are not meant to limit the
scope of the present invention.
Exam le
Polymerisation
Into a 16 liter autoclave was introduced 6150 cm3 of demineralized water.
Then, under agitation of 160 rpm using an impeller, 390 cm3 of a solution of
110 g/1 tetrapropylbenzene sulfonate, 4590 g of VDC monomer and 1910 g of
VC monomer were added and the temperature of the autoclave was set at
4b°C.
At 44°C, 110 cm3of an aqueous solution of 20 g/1 erythorbic acid
was
added to the solution in the autoclave followed by the successive addition of
__ 25 100 cm3 of an aqueous solution of 3.5 g/1 H202.
minutes later, an aqueous solution (3 g/1) of erythorbic acid and an
aqueous solution of 0.8 g/l H202 were injected continuously (at respective
rates
of 100 cm3/hour) for about 450 minutes.
After depressurising the autoclave for about 3 hours, the autoclave was
30 cooled to ambient temperature. Then 2500 cm3of demineralized water was
added to dilute the VDC based latex.
Co-coa~uiation according to the invention
Into a first 150 litre vat, regulated by a water jacket, 30 litres of
demineralized water and 0.7 litres of an aqueous solution of aluminium
sulphate
(8.6 g/1) was added.
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The vat was then put under agitation at 200 rpm and the temperature
thereof was adjusted to about 15 °C.
23 litres of the formed VDC latex along with 1 litre of an emulsion of
epoxidized Soya bean oil (at 250 g/1) were then evenly and continuously added
in
parallel to the first vat for about 20 minutes.
The first vat was then heated to 70°C and maintained at that
temperature
for 90 minutes.
The vat was then cooled to room temperature, producing a slurry having
the co-coagulate therein.
Coagulation ~ classical means (for comparison)
Into a second 150 litre vat, regulated by a water jacket, 30 litres of
demineralized water and 0.7 litres of an aqueous solution of aluminium
sulphate
(8.6 g11) was added.
The second vat was then put under agitation at 200 rpm and the
temperature thereof was adjusted to about 15°C.
23 litres of the formed VDC latex is then even and continuously added in
parallel to the second vat for about 20 minutes.
The second vat was then heated to 70°C and maintained at that
temperature
for 90 minutes.
The second vat was then cooled to room temperature, producing a slurry
having a conventional coagulate.
Dr~rlng
The slurries from the first and the second vats were then dried by, first,
separating the liquid from the solid in an ESCHER WYSS~ system. In this
fashion, a "cake" of the co-coagulates of the present invention (from vat 1)
and a
"cake" having traditional coagulates (from vat 2) are formed.
The cakes were then dried in a Munster~ fluidised bed with an air
temperature at entry of about 60°C until the volatile material content
thereof was
reduced to less than 0.3 % (w/w).
The particle sizes of the co-coagulate particles of the two cakes were then
measured and the results thereof given below in Table 1.
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Table 1
Particle
Size
of
Co-coa
ulates
(in
microns)
Sample > 850-450 450-250 250-150 150-45 <_45
850
Cake 1 662 246 64 15 8 5
Co-coagulates
Cake 2 229 208 190 212 93 28
Coagulates
