WO2011163162A2

WO2011163162A2 - Stabilized vinylidene chloride copolymer blend composition

Info

Publication number: WO2011163162A2
Application number: PCT/US2011/041152
Authority: WO
Inventors: Douglas Beyer; Jeffrey Bonekamp; Steven Jenkins; Michael Mounts; Kurt Olson
Original assignee: Dow Global Technologies LLC
Current assignee: Dow Global Technologies LLC
Priority date: 2010-06-24
Filing date: 2011-06-21
Publication date: 2011-12-29
Anticipated expiration: 2012-12-24
Also published as: WO2011163162A3

Abstract

The present invention relates to a formulated vinylidene copolymer composition comprising a copolymer of vinylidene chloride with an alkyl acrylate and/or vinyl chloride and a metal silicate and a metal hydroxide stabilizer represented by the formula: Cai.x.y M 2+x Aly (OH)2 wherein M2+ represents at least one bivalent metal selected from the group consisting of Mg, Zn, or Cu, preferably Mg and/or Zn, x is in the range of 0 < x < 1, preferably 0 < x < 0.4 and y is in the range of 0 < y < 0.1 an one or more of the following additives: a high density polyethylene, an epoxidized vegetable oil, an oxidized polyolefin, and/or a paraffin or polyolefin wax. The formulated vinylidene copolymer composition demonstrates substantially improved heat stability than existing compositions.

Description

STABILIZED VINYLIDENE CHLORIDE COPOLYMER BLEND COMPOSITION

CROSS REFERENCE STATEMENT

This application claims the benefit of U.S. Provisional Application Serial No. 61/358,138, filed June 24, 2010, which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to vinylidene chloride copolymer compositions and more specifically, to vinylidene chloride copolymer compositions having improved thermal stability during extrusion.

BACKGROUND OF THE INVENTION

Halogen-containing resin compositions, especially chlorine-containing resin compositions, are well known. However, different halogen-containing resin compositions demonstrate different properties and end-product usefulness. For example, copolymers of vinylidene chloride (PVDC) and vinyl chloride or methyl acrylate are known to be useful as barrier polymers while polyvinyl chloride (PVC) resins are not useful as barrier polymers.

Extruded and coextruded shaped articles, such as films, containing a barrier layer of PVDC copolymer having from 75 to 98 percent vinylidene chloride provide excellent barrier with respect to transportation of oxygen, water, carbon dioxide and flavoring for food, medical and other high barrier packaging. Vinylidene chloride copolymers and their uses are described in numerous references, such as R. A. Wessling, Polyvinylidene Chloride (Gordon & Breach Sci. Pub. 1977) and 23 Ency. Chem. Tech., Vinylidene Chloride and Poly(Vinylidene Chloride), 764 (J. Wiley & Sons 1983).

Likewise, halogen-containing resins are generally susceptible to thermal degradation during extrusion. That degradation causes specks of carbonaceous material to appear in the extruded product. The level of carbonaceous material ordinarily increases at higher extrusion rates, which produce higher temperatures in the polymer. Carbonaceous material is unsightly and may cause the customer of the extruded product to reject the product. A variety of additives have been added to halogen-containing resins to help control thermal degradation and permit extrusion at higher rates. R. A. Wessling,

Polyvinylidene Chloride at 174-76, and Johnson, Process for Imparting Stability to Particulate Vinylidene Chloride Polymer Resins, USP 4,418,168 and 5,002,989, which are incorporated herein by reference, disclose PVDC resins contain stabilizing amounts of tetrasodium pyrophosphate, magnesium hydroxide, and organic epoxides. US Publication Numbers 2009/0215947 and 2009/0215950, which are incorporated herein by reference, disclose PVC resins comprising a mixture of a metal silicate and a calcium hydroxide with one or more of a hydrotalcite and/or tin-containing stabilizer. However, it is well known that stabilizers which stabilize PVC may actually destabilize PVDC compositions, for example the tin-containing compounds of US Publication Numbers 2009/0215947 and 2009/0215950 which are useful in PVC destabilize PVDC.

It would be desirable to have a vinylidene chloride copolymer composition having improved thermal stability while demonstrating equal or better barrier properties and extrudability as compared to conventional vinylidene chloride copolymer compositions.

SUMMARY OF THE INVENTION

The present invention is such a vinylidene chloride copolymer composition. In one embodiment, the present invention is a formulated vinylidene copolymer composition comprising:

i) a copolymer of vinylidene chloride and a comonomer chosen from the group consisting of:

(a) 8 to 25 weight percent vinyl chloride,

(b) 3 to 10 weight percent alkyl acrylate, or

(c) a mixture of those comonomers;

and

ii) 0.05 to 3 parts of a metal silicate and a metal hydroxide stabilizer represented by the formula 1 :

C_ai._x._yM ²⁺ _x Al_y (OH)₂ 1 wherein M²⁺ represents at least one bivalent metal selected from the group consisting of Mg, Zn, or Cu, preferably Mg and/or Zn, x is in the range of 0 < x < 1, preferably 0 < x < 0.4 and y is in the range of 0 < y < 0.1, wherein parts are based on hundred parts of the formulated vinylidene copolymer composition. In one embodiment of the herein above described invention, the metal silicate and metal hydroxide stabilizer is produced by thermally hydrating a metal silicate represented by the formula 2:

(Al₂0₃)_a(M²⁺ 0)_bSi0₂(H₂0)_{m 2} wherein M²⁺ is at least one bivalent metal selected from the group consisting of Zn, Mg, or Ca, a is in the range of 0.1 < a < 0.5, b is in the range of 0.1 < b < 1, provided that a+b is in the range of 0 < a+b < 1, and m is in the range of 0.1 < m < 2, with calcium oxide or a solid solution comprised of calcium oxide and M²⁺ and/or Al in an aqueous medium.

In another embodiment of the herein above described present invention, further comprising: iii) a mixture of one or more of the following additives: (a) 0.45 to 1.05 parts high density polyethylene; (b) 0.1 to 7 parts epoxidized vegetable oil; (c) 0.05 to 0.25 parts oxidized polyolefin; (d) 0.20 to 0.55 parts polyethylene or paraffin wax, and (e) 0.05 to 2.5 parts magnesium hydroxide, wherein parts are based on hundred parts of the formulated vinylidene copolymer composition.

In another embodiment of the herein above described invention, the alkyl acrylate of the formulated vinylidene copolymer composition is methyl acrylate.

Another embodiment of the present invention is the herein above described formulated vinylidene copolymer composition in the form of a container, a package, a fiber, a mono-layer film, a multi-layer film, or a multi-layer sheet.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plot of mixing time versus torque for Examples 1 and 2 and Comparative Examples A to C;

FIG. 2 is a plot of mixing time versus Z-average molecular weight for Examples 1 and 2 and Comparative Examples A to C;

FIG. 3 is a plot of mixing time versus Z-average molecular weight for Examples 3 and 4 and Comparative Examples D and E; and

FIG. 4 is a plot of mixing time versus Z-average molecular weight for Example 6 and Comparative Example F. DETAILED DESCRIPTION OF THE INVENTION Formulated vinylidene copolymer compositions of the present invention comprise a vinylidene chloride copolymer, an inorganic stabilizer, and one or more of a high density polyethylene (HDPE), an epoxidized vegetable oil, acrylic process aids, plasticizers, an oxidized polyolefin and/or a paraffin or polyethylene wax. The major component is vinylidene chloride copolymer. The minor components are in an amount suitable to provide a composition which demonstrates improved thermal stability during extrusion and has high barrier with respect to oxygen and other permeants.

Vinylidene chloride copolymers suitable for use in the present invention are those vinylidene chloride copolymers formed from a monomer mixture of vinylidene chloride monomer and a comonomer which is vinyl chloride and/or an alkyl acrylate. The alkyl acrylates are generally selected to have from about 1 to about 8 carbon atoms per alkyl group. Preferably, alkyl acrylates are selected to have from about 1 to about 4 carbon atoms per alkyl group. The alkyl acrylate is more preferably ethyl or methyl acrylate. The comonomer is most preferably methyl acrylate. Of course, vinylidene chloride copolymers useful in formulated vinylidene copolymer compositions may also contain small amounts (usually less than about 1 to 2 percent) of other ethylenically-unsaturated monomers which do not substantially reduce the extrudability or increase the permeability of the copolymer.

The amount of vinyl chloride or alkyl acrylate comonomer in the copolymer is low enough to preserve the semicrystalline character of the copolymer and high enough to provide a commercially extrudable polymer. By "semicrystalline character" it is meant that the copolymer has between about 5 percent and about 95 percent crystallinity. Crystallinity values depend upon the measuring technique, and as used herein crystallinity is defined by the commonly used density method. See, for example, the discussion by R. Wessling, in Chapter 6 of Polyvinylidene Chloride. Vol. 5, Gordon and Breach Science Publishers, New York, 1977, the teachings of which are incorporated herein by reference. Vinyl chloride comonomer is preferably equal to or greater than about 8 percent, more preferably equal to or greater than about 10 percent, and even more preferably equal to or greater than about 12 percent of the copolymer: it is preferably equal to or less than about 25 percent, more preferably equal to or less than about 20 percent, and even more preferably equal to or less than about 17 percent of the copolymer. Methyl acrylate comonomer is preferably equal to or greater than about 3 percent, more preferably equal to or greater than about 4 percent, and even more preferably equal to or greater than about 5 percent of the resulting copolymer; it is preferably equal to or less than about 10 percent, more preferably equal to or less than about 9 percent, and even more preferably equal to or less than about 8 percent of the resulting copolymer.

The vinylidene chloride copolymer of the present invention preferably has a melting point of from 130°C to 185°C and more preferably of from 140°C to 175°C.

The vinylidene chloride copolymer of the present invention preferably has a weight average molecular weight of from 60,000 to 150,000 and more preferably of from 75,000 to 130,000.

Vinylidene chloride copolymers are known and are commercially available.

Methods to synthesize them, such as by an emulsion or suspension polymerization process, are also familiar to persons of ordinary skill in the art. The copolymers and processes to synthesize them are described in USP 2,558,728: 3,007,903; 3,642,743; and 3,879,359; all of which are incorporated herein by reference, in R. A. Wessling, Polyvinylidene Chloride, supra, at 21-33 and 44-53; in 23 Encyclopedia of Polymer Science, supra, at 783-87; and in Yen et al., Barrier Resins, Report No. 179 of SRI International Process Economics Program 55-106 (February 1986).

Typically, the monomeric materials, for example vinylidene chloride and methyl acrylate, are emulsified or suspended in an aqueous phase. In a typical suspension polymerization, the aqueous phase contains a surface active agent capable of suspending the monomer phase in the aqueous phase. The monomer phase will contain vinylidene chloride, comonomer, initiator and optionally other additives. The polymerization of the monomeric materials is usually carried out with heating and agitation. After

polymerization, the resulting suspension of vinylidene chloride copolymer is vacuum stripped, cooled, dewatered and dried. The resultant polymer appears as a powder or bead of approximately 200 to 350 micron diameter.

The additives used in formulated vinylidene copolymer compositions of the present invention may be added during polymerization of the vinylidene chloride copolymer or to the polymerized vinylidene chloride copolymer, for example in powder form. The additives may be blended individually with the vinylidene chloride copolymer monomers/powder (e.g., one at a time); or they may be blended concurrently (e.g., all at the same time) with the vinylidene chloride copolymer, such as by physically blending the vinylidene chloride copolymer with an additive composition which has been separately prepared. Such additive compositions make up one embodiment of the present invention. They comprise the same additives as the polymer compositions described herein. The additives will ordinarily be in about the same weight ratios with respect to each other as are found in the formulated vinylidene copolymer composition. However, the inorganic stabilizer and/or the epoxidized vegetable oil may be in a lesser proportion to make up for quantities of those additives already found in the base resin. Unless otherwise stated, amounts of additive compounds are in parts per hundred parts of the formulate vinylidene copolymer composition (herein after resin).

Additives should be blended with the vinylidene chloride copolymer to form a formulated vinylidene copolymer composition of the present invention before extrusion or melt-phase processing of the vinylidene chloride copolymer. The additives are blended with the vinylidene chloride copolymer by any method which is effective to achieve substantially homogeneous dispersion of the additives without unduly heating the resin. Blending of the vinylidene chloride copolymer and the formulation package can be accomplished by conventional dry blending techniques. It preferably uses medium or high intensity blending. Suitable dry blending equipment include, medium intensity plow blenders from Littleford and/or Lodige, or high intensity blenders such as Hobart mixers, Welex mixers, Henschel High Intensity mixers, and the like.

Formulated vinylidene copolymer compositions of the present invention contain an inorganic stabilizer. Typically, inorganic stabilizers act as acid scavengers which ab 1 HC1. HC1 is detrimental to PVDC compositions as it may cause discoloration and/or gassing. Surprisingly, we have found that conventional acid scavengers can contribute to cross-linking. We have identified an inorganic stabilizer which not only reduces discoloration and gassing, but minimizes cross-linking as well. The inorganic stabilizer of the present invention is preferably a thermal stabilizer component comprising a complex (A) of a metal silicate and a metal hydroxide, preferably calcium hydroxide compound represented by the formula 1 :

C_ai._x._y M ²⁺ _x Al_y (OH)₂ wherein M²⁺ represents at least one bivalent metal selected from the group consisting of Mg, Zn, or Cu, preferably Mg and/or Zn, x is in the range of 0 < x < 1, preferably

0 < x < 0.9, and more preferably 0 < x < 0.4 and y is in the range of 0 < y < 0.5, preferably 0 < y < 0.3, and more preferably 0 < y < 0.1. In formula 1, when x = 1, there is no detectable calcium present in the metal silicate metal hydroxide stabilizer, however, even in this embodiment the stabilizer may still be referred to as a metal silicate calcium hydroxide compound.

In the complex (A) used in the present invention, a metal silicate has chemical interaction with a calcium hydroxide compound and as a result thereof the primary crystallite size of the calcium hydroxide compound becomes extremely small so that the reaction activity as a thermal stabilizer is improved. The complex (A) has a BET specific surface area of at least 20 m²/g, preferably at least 30 m²/g. The BET specific surface area of calcium hydroxide is about 5 to 10 m²/g. The difference in BET specific surface area is obvious. The complex (A) can be produced by thermally hydrating a metal silicate represented by the formula 2,

2

(Al₂0₃)_a(M²⁺ 0)_bSi0₂(H₂0)_m wherein M²⁺ is at least one bivalent metal selected from the group consisting of Zn, Mg, Ca and etc., preferably Zn and/or Mg, a is in the range of 0.1 < a < 0.5, b is in the range of 0.1 < b < 1, provided that a+b is in the range of 0 < a+b < 1, and m is in the range of 0.1 < m < 2, with calcium oxide or a solid solution comprised of calcium oxide and M²⁺ and/or Al in an aqueous medium. In this case, the hydration reaction is carried out at preferably 60°C or higher, particularly preferably 80°C or higher, for preferably 10 to 30 minutes with stirring. As a production process other than the above process, it is possible to add an aqueous solution of a water-soluble salt of M²⁺ and/or Al such as a chloride or a nitrate after the above hydration reaction and allow the resultant mixture to react. Thereafter, the complex (A) is preferably surface-treated with a higher fatty acid or an alkali metal salt of a higher fatty acid, a phosphoric acid ester, a silane coupling agent, a titanium coupling agent or an aluminum coupling agent in an amount of 0.1 to 10 percent by weight based on the weight of the complex (A).

Examples of the metal silicate include crystalline activated white clay, acid white clay, amorphous aluminum silicate, zinc silicate and zinc aluminum silicate. The complexing amount of the metal silicate based on the calcium hydroxide compound is 0.5 to 40 percent by weight, preferably 1 to 10 percent by weight, particularly preferably 2 to 8 percent by weight.

A preferred a metal silicate and a calcium hydroxide compound is SEASTAB™ 510 available from Mitsui Plastics, Inc. SEASTAB 510 comprises (Ca, Mg)(OH)₂, Si0₂ and may have, for example, about 67.2 weight percent CaO, 1.09 weight percent MgO, and 3.26 weight percent Si0₂. SEASTAB 510 is a white powder with an average particle size of about 2.858 microns, a specific gravity of about 2.2, a refractive index of about 1.54 to 1.57, a hardness (Mohs') of about 12.3 to 12.4, a beginning temperature of dehydration of about 340°C, a moisture content of about 1 percent at 120°C, 1H and a BET surface area of about 39 m²/g.

A preferred a metal silicate and a calcium hydroxide compound is SEASTAB 705 available from Mitsui Plastics, Inc. SEASTAB 705 comprises (Ca, Mg, Al)(OH)₂, Si0₂ and may have, for example, 40.06 weight percent CaO, 14.05 weight percent MgO, 8.54 weight percent Al₂0₃, and 2.35 weight percent Si0₂. SEASTAB 705 is a white powder with an average particle size of about 2.77 microns, a specific gravity of about 2.2, a refractive index of about 1.54 to 1.57, a hardness (Mohs') of about 12.3 to 12.4, a beginning temperature of dehydration of about 200°C, a moisture content of about 1 percent at 120°C, 1H and a BET surface area of about 23 m²/g.

The metal silicate and a metal hydroxide stabilizer compound is preferably equal to or greater than about 0.05 parts per hundred (resin), more preferably equal to or greater than about 0.1 parts per hundred (resin), more preferably equal to or greater than about 0.3 parts per hundred (resin), and more preferably at least about 0.5 parts per hundred (resin) of the copolymer: it is preferably at most about 3 parts per hundred (resin), more preferably at most about 2 parts per hundred (resin), and more preferably at most about 1 parts per hundred (resin) of the copolymer.

The complex (A) used in the present invention is believed to act as an acid scavenger. During melt processing, vinylidene chloride copolymers undergo

dehydrohalogenation leading to the formation of HC1. As an acid scavenger, complex (A) absorbs HC1 thereby preventing other adverse reactions caused by the presence of HC1. Adverse reactions to HC1 include increased degradation rates and gassing (for example, evolution of gaseous HC1). A further step in the degradation process of vinylidene chloride copolymers is crosslinking which may lead to the formation of carbonaceous material. Such crosslinking reactions can be increased due to the presence of basic inorganic acid scavengers. Surprisingly, we have found that the complex (A) minimizes this crosslinking which advantageously leads to less carbonaceous material.

Formulated vinylidene copolymer compositions of the present invention comprise one or more additive commonly used in such compositions such as epoxidized vegetable oil, such as soybean and/or linseed oil; one or more lubricant, such as high density polyethylene, a paraffin or polyethylene wax, oxidized polyolefin, amide waxes, stearate waxes, stearic acid or similar fatty acid derivatives, acrylic process aides, silicon process aides, fluorocarbon process aides, and the like; a plasticizer such as dibutyl sebacate and/or acetyl tributyl citrate, additional acid scavengers such as calcium hydroxide, magnesium hydroxide, magnesium oxide, and/or tetrasodium pyrophosphate; an antioxidant; an anti- block agent; an anti-stat; a slip aid; colorants; and the like.

When present, the concentration of additional acid scavengers (i.e., ones not described by formula 1) in the formulated vinylidene copolymer compositions of the present invention is at least about 0.05 parts per hundred (resin), preferably at least about 0.1 parts per hundred (resin), and more preferably at least about 0.2 parts per hundred (resin). When present, the concentration of additional acid scavengers (i.e., ones not described by formula 1) in the formulated vinylidene copolymer compositions of the present invention is at most about 2.5 parts per hundred (resin) and preferably at most about 1.5 parts per hundred (resin).

When used, the high density polyethylene may contain a minor amount of oxygen. These oxygen-containing polyolefins are formed by copolymerization of ethylene with some other comonomer, which may contain oxygen. For the purpose of this invention, a "minor amount" of oxygen means that the polyolefin may contain oxygen below an amount that will significantly change the properties from that of the homopolymer. High density polyethylenes are ordinarily substantially linear and preferably have a weight- average molecular weight of at least about 40,000. High density polyethylene, its properties and its synthesis are described in 16 Kirk-Othmer Ency. Chem. Tech. - 3rd Ed., Linear (High Density) Polyethylene and Olefin Polymers (Ziegler Polyethylene), at 421-51 (J. Wiley & Sons 1980).

If present, the concentration of high density polyethylene in the formulated vinylidene copolymer composition is equal to or greater than about 0.45 parts per hundred (resin), preferably equal to or greater than about 0.5 parts per hundred (resin) and more preferably equal to or greater than about 0.9 parts per hundred (resin). If present, the high density polyethylene in the formulated vinylidene copolymer composition is equal to or less than about 1.05 parts per hundred (resin) and preferably equal to or less than about 1.0 parts per hundred (resin). The formulated vinylidene copolymer compositions of the present invention may also contain epoxidized vegetable oils, such as epoxidized soybean oil and epoxidized linseed oil. The epoxidized oil should be of a type suitable to act as a plasticizer for the copolymer. The epoxidized oil is most preferably epoxidized soybean oil. Epoxidized vegetable oils are known and are commercially available compounds. They and processes to synthesize them are described in 9 Kirk-Othmer Ency. Chem. Tech. - 3rd Ed.,

Epoxidation, at 251-63 (J. Wiley & Sons 1980). If present, the concentration of epoxidized vegetable oil in the formulated vinylidene copolymer composition is equal to or greater than about 0.1 parts per hundred (resin), preferably equal to or greater than about 0.2 parts per hundred (resin), preferably equal to or greater than about 0.5 parts per hundred (resin), and even more preferably equal to or greater than about 0.8 parts per hundred (resin). If present, the concentration of epoxidized vegetable oil in the formulated vinylidene copolymer composition is equal to or less than about 7 parts per hundred (resin), more preferably equal to or less than about 5 parts per hundred (resin), more preferably equal to or less than about 3 parts per hundred (resin), and even more preferably equal to or less than about 1 part per hundred (resin).

The compositions of the present invention may also contain oxidized polyolefins, which are low molecular weight polymers which have a number average molecular weight of less than about 5,000, as determined by vapor phase osmometry. Preferably the number average molecular weight is about 1 ,000 to about 4,000, and most preferably between about 1,500 and about 2,500. The polyolefins have preferably been oxidized to an acid number of about 10 to 35, more preferably 13 to 17. These oxidized polyolefins preferably have a softening point, as determined by ASTM E-28 of about 85 °C to 145°C, more preferably 95°C to 140°C, and most preferably 98°C to 115°C. Generally, such oxidized polyolefins have a Brookfield viscosity at 140°C of about 120 to 300 centipoise (cps), and preferably 170 to 250 cps. Exemplary oxidized polyolefins including oxidized polyethylene, oxidized polypropylene, or mixtures thereof are employed. Oxidized polyethylene is preferred.

Oxidized polyethylene and oxidized polypropylene are known polymers which are commercially available, for instance under the trademark Allied 629A from Allied-Signal Corp. They can be prepared by reacting an ethylene homopolymer or copolymer with oxygen or an organic peroxide or hydroperoxide. The processes for synthesizing them are described in 16 Kirk-Othmer Ency. Chem. Tech. - 3rd Ed. Olefin Polymers (High Pressure Polyethylene), at 412 (J. Wiley & Sons 1980) and 24 Kirk-Othmer Ency. Chem. Tech. - 3rd Ed. Waxes, at 477 (J. Wiley & Sons 1980).

When present, the concentration of oxidized polyolefin in the formulated vinylidene copolymer compositions of the present invention is at least about 0.05 parts per hundred (resin), preferably at least about 0.1 parts per hundred (resin), and more preferably at least about 0.2 parts per hundred (resin). When present, the concentration of oxidized polyolefin in the formulated vinylidene copolymer compositions of the present invention is at most about 0.25 parts per hundred (resin) and preferably at most about 0.2 parts per hundred (resin).

Compositions of the present invention may also contain a paraffin or polyethylene wax. They most preferably comprise a polyethylene wax. Paraffin waxes are defined herein as having a Brookfield viscosity in the range of about 50 to about 300 cps @ 140°C, a melting point in the range of about 40°C to about 80°C, and a density in the range of about 0.85 g/cm³ to about 0.95 g/cm³. Exemplary paraffin waxes include waxes commercially available from Degussa Corporation such as VESTOWAX™ SH-105 or Hoechst AG, such as Hoechst XL-165FR, Hoechst XL- 165 SB, Hoechst XL- 165: and the like. Polyethylene waxes are defined herein as having Brookfield viscosity in the range of about 130 to about 450 cps @ 140°C: a melting point in the range of about 80°C to about 100°C; and a density in the range of about 0.85 H g/cm³ to about 0.95 g/cm³. Exemplary polyethylene waxes include waxes commercially available from Allied Chemical Co. such as Allied 617A and 6A; and the like.

Paraffin and polyethylene waxes suitable for food contact purposes are known and commercially available, as previously described. Their properties and synthesis are described in 24 Kirk-Othmer Ency. Chem. 35 Tech. - 3rd Ed., Waxes, at 473-77 (J. Wiley & Sons 1980).

When present, the concentration of paraffin and/or polyethylene wax in the formulated vinylidene copolymer compositions of the present invention is at least about 0.1 parts per hundred (resin), preferably at least about 0.2 parts per hundred (resin), and more preferably at least about 0.25 parts per hundred (resin). When present, the concentration of paraffin and/or polyethylene wax in the formulated vinylidene copolymer compositions of the present invention is at most about 0.75 parts per hundred (resin) and preferably at most about 0.55 parts per hundred (resin). The formulated vinylidene copolymer composition may contain additional additives well-known to those skilled in the art. Exemplary of additives which may be incorporated in the formulation are light stabilizers and antioxidants such as hindered phenol derivatives, pigments such as titanium dioxide and the like. Each of these additives is known and several types of each are commercially available.

The formulated vinylidene copolymer composition may be fabricated into any suitable final product, e.g., a variety of films or other articles. As is well-known in the art, the films and articles are fabricated with conventional extrusion and coextrusion: e.g., feedblock coextrusion, multimanifold die coextrusion, or combinations of the two: injection molding; extrusion molding; casting; blowing; blow molding; calendering; and lamination techniques. Such extrusion typically is carried out using a single or multiple screw extruder, most often a single screw extruder specially constructed for use with thermally sensitive copolymers such as vinylidene chloride copolymer. Such extrusion is familiar to persons of ordinary skill in the art. It is described in a number of patents and other general references, such as R. A. Wessling, Polyvinlyidene Chloride, supra, at 176-80; in 23 Ency. Poly Sci, supra, at 788-90; and in Ma et al., Plastic Films, Report No. 159 of SRI

International Process Economics Program 179-210 (February 1986).

In using conventional processing equipment for thermally sensitive polymers, three conditions should be met. Two conditions, which are interrelated, are processing time and processing temperature. In melt processing polymers, it is generally recognized that as processing temperatures increase, processing times must decrease in order to avoid undesirable results such as polymer degradation. Melt processing must be accomplished at a temperature below that at which decomposition of the vinylidene chloride copolymer becomes significant. A third condition is that sufficient mixing must be generated during melt processing to provide a visually homogeneous blend, i.e., no visible solids, within a reasonable mixing time. The most appropriate residence time and temperature conditions vary with different equipment. Persons of ordinary skill in the art can ascertain the optimum conditions for their own equipment without undue experimentation.

Articles formed therefrom include blown and cast, mono and multi-layer, films; rigid and flexible containers: rigid and foam sheet: tubes; pipes; rods; fibers: and various profiles. Lamination techniques are particularly suited to produce multi-ply sheets. As is known in the art, specific laminating techniques include fusion: i.e., whereby self-sustaining lamina are bonded together by applications of heat and pressure; wet combining, i.e., whereby two or more plies are laminated using a tie coat adhesive, which is applied wet, the liquid driven off, and combining by subsequent pressure laminating in one continuous process; or by heat reactivation, i.e., combining a precoated film with another film by heating, and reactivating the precoat adhesive so that it becomes receptive to bonding after subsequent pressure laminating.

Exemplary articles include containers, packaging, packages, fibers, mono-layered films, multi-layered films, and sheet.

The barrier provided by formulated barrier compositions of the present invention varies depending upon the particular ratio of ingredients, the proportion of vinylidene chloride in the vinylidene chloride copolymer, and the structure (rigid container or flexible film, etc.) into which the formulated barrier product is fabricated. For coextrusion applications, the rate of transmission for oxygen is on average preferably equal to or less than about 0.20 Dow Units (D.U.), more preferably equal to or less than about 0.10 D.U., and even more preferably equal to or less than about 0.05 D.U. For monolayer film applications, the rate of transmission for oxygen is on average preferably equal to or less than about 3.0 Dow Units (D.U.), more preferably equal to or less than about 2.5 D.U., and even more preferably equal to or less than about 2.0 D.U. The rate of transmission is measured on an OXTRAN™ 10/50 oxygen permeability instrument produced by Modern Controls Inc. One D.U. equals:

(1 cm³ of 0₂ at S.T.P.)(1 mil thickness PVDC) (100 in² area)(l atmosphere Pressure)(24 hours) and D.U. are reported as: cm³-mil/100 in²-atm-day.

Formulated vinylidene copolymer compositions of the present invention can be extruded under most preferred conditions for up to 24 hours, preferably 48 hours, without noticeable build up of carbonaceous material on the extrusion screw and with very few occurrences of carbonaceous material in the extruded film, sheet, or fiber. Furthermore, the formulated vinylidene copolymer compositions have superior interlayer stability in coextruded products.

Unless otherwise noted, molecular weight is the Z-average molecular weight reported in Daltons. It may measured by size exclusion chromatography using polystyrene calibration. Sample preparation includes dissolving a polyvinylidene chloride resin sample in tetrahydrofuran (THF) at 50°C. Resin samples containing more than about 94 percent vinylidene chloride do not readily dissolve at this temperature, and dissolving at elevated temperature can result in degradation of the polymer molecular weight. Therefore, resin samples containing more than about 94 percent vinylidene chloride are pre-dissolved as a 1 percent ( ) solution, in inhibited THF at 63°C. Samples can be dissolved at up to 83°C for 4 hours without loss of molecular weight, though minimizing dissolving time and temperature is desirable. The polymers are then analyzed for determination of molecular weight by gel permeation chromatography (GPC) using the Viscotek OmniSEC software on a Waters 2690 chromatograph equipped with two columns in series. These columns contain 5m Styrene/divinylbenzene copolymer beads commercially available from Polymer Laboratories under the trade designation PLGel 5μ MFXED-C. The solvent is in line vacuum degassed HPLC Grade THF. The flow rate is 1.0 milliliter/minute and the injection size is 50 microliters. The molecular weight determination is deduced by using seventeen narrow molecular weight distribution polystyrene standards (commercially available from Polymer Labs -3,000,000 to 580 Mp) in conjunction with their elution volumes.

EXAMPLES

In Examples 1 to 5 and Comparative Examples A to E the vinylidene chloride, methyl acrylate copolymer, epoxidized soybean oil, high density polyethylene, polyethylene wax, oxidized polyethylene wax, and inorganic stabilizer are dry blended then mixed in a high intensity mixer for 1 minute.

In Example 6 and Comparative Example F the vinylidene chloride-methyl acrylate copolymer containing epoxidized soybean oil and plasticizer from the polymerization step is dry blended with other additives and mixed in a high intensity mixer for 1 minute.

Examples 1 to 6 and Comparative Examples A to F are melt blended using a 200 gram sample of each dry blend composition melt mixed on a two-roll mill for 30 minutes. The rolls are heated to 180°C and rotated at 13 rotations per minute (rpm). Samples of the melt blended formulation are taken every three minutes for Z-average molecular weight determinations (degree of cross-linking). Z-average molecular weight is determined by GPC, the results are depicted in FIG 2, FIG. 3, and FIG. 4. Also, during melt mixing on the two roll mill time to visual gassing is recorded which is observed as foaming and/or the generation of bubbles in the melt. Cross-linking is monitored for Examples 1 and 2 and Comparative Examples A to C using a 60 g sample of each dry blend composition blended in a Brabender Mixer at 180°C and 60 rpm (FIG. 1).

In Table 1, the formulation content for Examples 1 to 6 and Comparative Examples A to F are given in parts based on the total weight (100 parts) of the composition. In Table 1:

"PVDC-1" is a vinylidene chloride copolymer formed through a suspension process comprising 4.8 percent methylacrylate and having a weight average molecular weight of about 87,000;

"PVDC-2" is a vinylidene chloride copolymer formed through a suspension process comprising 4.8 percent methylacrylate and having a weight average molecular weight of about 97,000;

"STAB-1" is a (Ca, Mg)(OH)₂,Si0₂ thermal stabilizer with a BET of about 39 m²/g available as SEASTAB™ 510 in the form of a white powder having an average particle size of 2.86 microns from Mitsui Plastics, Inc.;

"STAB-2" is a (Ca, Mg, Al)(OH)₂,Si0₂ thermal stabilizer with a BET of about 26 m²/g available as SEASTAB 705 in the form of a white powder having an average particle size of 2.77 microns from Mitsui Plastics, Inc.;

"TSPP" is a tetrasodium pyrophosphate;

"Mg(OH)₂" is magnesium hydroxide available as MAG-SHIELD UF™ from Martin

Marietta Magnesia Specialties, LLC;

"APA" is an acrylic processing aid available as PLASTISTRENGTH™ L 1000 from Arkema, Inc.;

"DBS" is dibutyl sebacate a plasticizer available from Vertellus Performance Materials, Inc.;

"Erucamide" is a lubricant available as KEMAMIDE™ E from Chemtura

Corporation;

"DSTDP" is distearyl thiodipropionate a stabilizer/lubricant available as

SONGNOX™ DSTDP from Songwon Industrial Co., Ltd;

"HDPE" is a high density polyethylene available as 65053N polyethylene from The

Dow Chemical Company;

"ESO" is an epoxidized soybean oil available as PLAS CHEK™ 775 from Ferro; "OPE" is an oxidized polyethylene available as A-C629A from Honeywell

International;

"WAX-1" is a polyethylene wax available as A-C617A from Honeywell

International; and

"WAX-2" is a paraffin wax available as VESTOWAX SH- 105 from Degussa

Corporation.

Molecular weight is determined by gel permeation chromatography (GPC) and is reported as Z-average molecular weight.

For Example 5, the composition is extruded using a 3.5 inch single screw Eg an extruder. Extrusion set points included; flood feeding, feed throat temperature, 25°C, barrel zones 1 to 5 temperature, 160°C, 170°C, 165°C, 160°C, 155°C, clamp, adapter and die temperature, 165°C, extruder rpm, 38.0. The extruder is equipped with an 8 inch circular die. The extrusion rate is 204 pounds per hour. Extrudate from the extruder is quenched in water and collapsed to form a tape. The resultant extruded tape is substantially free of carbon specks, white specks and gas bubbles.

Table 1

Example 1 2 3 4 5 6

Comparative Example A B C D E F

Components

PVDC-1 96.4 96.4 96.4 95.5 95.5 97.4 96.4 96.4 96.4 96.4

PVDC-2 91.2 91.2

STAB-1 1 0.5 0.4 0.4 0.35

STAB-2 1

TSPP 1 0.5

Mg(OH)2 1 0.5 0.35

HDPE 1 1 1 2 2 1 1 1 1 1

ESO 0.9 0.9 0.9 0.9 0.9 2 0.9 0.9 0.9 0.9 0.9 2

OPE 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2

WAX-1 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

WAX-2 0.5 0.5 0.5

APA 2 2

DBS 4.25 4.25

Eruc amide 0.05 0.05

DSTDP 0.15 0.15

Properties

Time to degassing, min 11.3 11.6 8.8 11 4.8 4.5 9.0 8.0 7.3 7.5 4.3

Claims

CLAIMS:

1. A formulated vinylidene copolymer composition comprising:

5 (a) 8 to 25 weight percent vinyl chloride,

(b) 3 to 10 weight percent alkyl acrylate, or

(c) a mixture of those comonomers;

and

ii) 0.05 to 3 parts of a metal silicate and a metal hydroxide stabilizer represented o by the formula 1 :

C_ai._x._y M ²⁺ _x Al_y (OH)₂ 1 wherein M²⁺ represents at least one bivalent metal selected from the group

5 consisting of Mg, Zn, or Cu, preferably Mg and/or Zn, x is in the range of 0 < x <

1 and y is in the range of 0 < y < 0.1, wherein parts are based on hundred parts of the formulate vinylidene copolymer composition.

2. The formulated vinylidene copolymer composition of Claim 1 wherein the metal silicate and a metal hydroxide stabilizer produced by thermally hydrating a metal silicate0 represented by the formula 2:

(Al₂0₃)_a(M²⁺ 0)_bSi0₂(H₂0)_m 2 wherein M²⁺ is at least one bivalent metal selected from the group consisting of Zn, Mg, or5 Ca, a is in the range of 0.1 < a < 0.5, b is in the range of 0.1 < b < 1, provided that a+b is in the range of 0 < a+b < 1, and m is in the range of 0.1 < m < 2, with calcium oxide or a solid solution comprised of calcium oxide and M²⁺ and/or Al in an aqueous medium.

3. The formulated vinylidene copolymer composition of Claim 1 wherein M²⁺ is from 0 < x < 0.4.

0 4. The formulated vinylidene copolymer composition of Claim 1 further comprising:

iii) a mixture of one or more of the following additives:

(a) 0.45 to 1.05 parts high density polyethylene;

(b) 0.1 to 7 parts epoxidized vegetable oil; (c) 0.05 to 0.25 parts oxidized polyolefin;

(d) 0.20 to 0.55 parts polyethylene or paraffin wax; and

(e) 0.05 to 2.5 parts magnesium hydroxide,

wherein parts are based on hundred parts of the formulated vinylidene copolymer composition.

5. The formulated vinylidene copolymer composition of Claim 1 wherein the alkyl acrylate is methy acrylate.

6. The formulated vinylidene copolymer composition of Claim 1 in the form of a container, a package, a fiber, a mono-layer film, a multi-layer film, or a multi-layer sheet.