WO2000032679A1

WO2000032679A1 - Halogen-containing vinyl polymer resins and processes for the preparation thereof

Info

Publication number: WO2000032679A1
Application number: PCT/EP1999/009372
Authority: WO
Inventors: Yves Vanderveken; Bernard Guenaire; Guy Laurent
Original assignee: Solvay (Societe Anonyme)
Priority date: 1998-12-02
Filing date: 1999-11-30
Publication date: 2000-06-08
Also published as: EP1137692A1; CN1334840A; AU1779100A; JP2002531616A; GB2344345A; BR9915884A; CA2353571A1; MXPA01005502A; GB9826524D0

Abstract

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 of processing aids, stabilisers, plasticizers and/or other polymer resins which particles are substantially homogeneously distributed throughout. These co-coagulates are substantially free of polymer dust and fines and are substantially free from lumping and crusting. These co-coagulates are further '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.

Description

Halogen-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 extruded 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 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 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 (PNDC), 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 PNDC 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 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. 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. 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 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 maleic anhydride for forming halogen-containing vinyl copolymers). Examples of such halogen-containing vinyl polymers are polyvinylidene chloride (PNDC), polyvinyl chloride (PNC) and polyvinylidene fluoride (PNDF).

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 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 maleic anhydride for forming halogen-containing vinyl copolymers). Examples of such halogen-containing vinyl polymer resins are polyvinylidene chloride (PNDC), polyvinyl chloride (PNC) 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 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 (NC).

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 (PNC) having vinyl chloride monomers, and polyvinylidene chloride (PNDC) 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 maleic anhydride for forming copolymers). Examples of such chloride-containing vinyl polymer resins are polyvinylidene chloride (PNDC) and polyvinyl chloride (PNC).

As used herein, the term "chloride-containing vinyl polymer" refers to 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 maleic anhydride for forming copolymers). Examples of such chloride-containing vinyl polymers are polyvinylidene chloride (PNDC) and polyvinyl chloride (PNC). 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 (NDC) and vinyl chloride (NC). 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/NC) resin. Particularly preferred is the NDC/NC 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 :

CH =CRιR₂ in which

R\ is selected from the group consisting of hydrogen and methyl radical and in which

R₂ is selected from the group consisting of -CΝ 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 -ΝR4R5 radicals, in which R4 and R5 are selected from the 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 (NDC/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/MA/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% (w/w) 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 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 HC1 scavengers (such as hydrotalcite-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. 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 (DO A), latexes of butadiene-styrene and polycaprolactones, such as ε-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 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 NC and/or NDC 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 emulsion, once again in particular where the formation of (co)polymer resins having NC and/or NDC 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. 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 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 form 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 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 emulsion(s) 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 blend. 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 PNDC. 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 incoφorated 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 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. Example Polymerisation

Into a 16 liter autoclave was introduced 6150 cm^ of demineralized water. Then, under agitation of 160 rpm using an impeller, 390 cm^ of a solution of 110 g/1 tetrapropylbenzene sulfonate, 4590 g of NDC monomer and 1910 g of NC monomer were added and the temperature of the autoclave was set at 46°C.

At 44°C, 110 cm^of an aqueous solution of 20 g/1 erythorbic acid was added to the solution in the autoclave followed by the successive addition of 100 cm^ of an aqueous solution of 3.5 g/1 H₂O₂.

30 minutes later, an aqueous solution (3 g/1) of erythorbic acid and an aqueous solution of 0.8 g/1 H₂O₂ were injected continuously (at respective rates of 100 cm^/hour) for about 450 minutes.

After depressurising the autoclave for about 3 hours, the autoclave was cooled to ambient temperature. Then 2500 crn^ of demineralized water was added to dilute the NDC based latex. Co-coagulation 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. 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 NDC 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 by 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 g/1) 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 NDC 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. Drying

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. Tablel

Claims

C L A I M S

1 - A halogen-containing vinyl polymer resin characterised in that the resin is comprised of co-coagulates of particles of halogen-containing vinyl polymer resins and particles chosen from the group consisting of processing aids, stabilisers (such as thermal stabilisers), plasticizers and/or other polymer resins.

2 - The halogen-containing vinyl polymer resin according to claim 1, further characterised in that the particles of halogen-containing vinyl polymer resins and the particles chosen from the group consisting of processing aids, stabilisers (such as thermal stabilisers), plasticizers and other polymer resins of the co-coagulates are substantially homogeneously distributed throughout the diameter of each co-coagulate.

3 - The halogen-containing vinyl polymer resin according to any of claims 1 to 2, further characterised in that the resin is substantially free of dust and fines of the polymer resin.

4 - The halogen-containing vinyl polymer resin according to any of claims

1 to 3, further characterised in that the particles of the halogen-containing vinyl polymer resins are particles of chloride-containing vinyl polymers.

5 - The halogen-containing vinyl polymer resin according to claim 4, further characterised in that the particles of the halogen-containing vinyl polymer resins are particles of polyvinyl chloride (PNC).

6 - The halogen-containing vinyl polymer resin according to claim 4, further characterised in that the particles of the halogen-containing vinyl polymer resins are particles of polyvinylidene chloride (PNDC).

7 - The halogen-containing vinyl polymer resin according to any of claims 1 to 3, further characterised in that the particles of the halogen-containing vinyl polymer resins are particles of copolymers of halogen-containing vinyl monomers and at least one other monomer.

8 - The halogen-containing vinyl polymer resin according to claim 7, further characterised in that the particles of the halogen-containing vinyl polymer resins are particles of copolymers of chloride-containing vinyl monomers and at least one other monomer.

9 - The halogen-containing vinyl polymer resin according to claim 8, further characterised in that the particles of the halogen-containing vinyl polymer resins are particles of copolymers of vinyl chloride monomers and at least one other monomer.

10 - The halogen-containing vinyl polymer resin according to claim 8, further characterised in that the particles of the halogen-containing vinyl polymer resins are particles of copolymers of vinylidene chloride monomers and at least one other monomer.

11 - The halogen-containing vinyl polymer resin according to any of claims 8 to 10, further characterised in that the particles of the halogen- containing vinyl polymer resins are particles of copolymers of vinylidene chloride monomers and vinyl chloride monomers.

12 - The halogen-containing vinyl polymer resin according to either of claims 8 or 10, further characterised in that the particles of the halogen- containing vinyl polymer resins are particles of copolymers of vinylidene chloride monomers and monomers of acrylates or methacrylates.

13 - The halogen-containing vinyl polymer resin according to either of claims 8 or 10, further characterised in that the particles of the halogen- containing vinyl polymer resins are particles of copolymers of vinylidene chloride monomers and glycidylmethacrylate monomers.

14 - The halogen-containing vinyl polymer resin according to any of claims 1 to 13, further characterised in that the particles of stabilisers are epoxidized soybean oil (ESO).

15 - A process for the preparation of a halogen-containing vinyl polymer resin including the steps of polymerising a halogen-containing vinyl monomer, whereby an emulsion is formed having the polymer, coagulation of the polymer in the emulsion, whereby a coagulated polymer is formed and drying of the coagulated polymer, whereby a dry halogen-containing vinyl polymer resin is formed, the process being characterised by adding to the emulsion having the polymer an emulsion including a substance selected from the group of stabilisers, processing aids, plasticizers and other polymers and co-coagulating the emulsion having the polymer and the emulsion having the substance, whereby a co- coagulated polymer resin is formed.

16 - The process according to claim 15, further characterised in that the stabiliser added to the polymer resin and co-coagulated therewith is epoxidized soybean oil (ESO).

17 - The process according talcum 15, further characterised in that the halogen-containing vinyl monomer is vinylidene chloride.

18 - The process according to any of claims 15 to 17, further characterised by the copolymerization of a halogen-containing vinyl monomer and another monomer, whereby an emulsion is formed having a halogen-containing copolymer is formed.

19 - Use of the halogen-containing polymer resins of any of claims 1 to 14, for the formation of extrudable articles.

20 - Extruded articles characterised by being formed from the halogen- containing polymer resins of any of claims 1 to 14.