WO1999019393A1

WO1999019393A1 - Extrudable vinylidene chloride polymer compositions

Info

Publication number: WO1999019393A1
Application number: PCT/US1998/018335
Authority: WO
Inventors: Eric K. Lee; Mark W. Vansumeren; Michael L. Mounts
Original assignee: The Dow Chemical Company
Priority date: 1997-10-14
Filing date: 1998-09-04
Publication date: 1999-04-22
Also published as: ID21062A; AU9219198A; ZA989331B

Abstract

A vinylidene chloride polymer composition comprises a vinylidene chloride polymer and an acylated hydroxy acid type compound, a lactate compound or combination thereof, present in an amount sufficient to improve the extrudability of the vinylidene chloride polymer.

Description

EXTRUDABLE VINYLIDENE CHLORIDE POLYMER COMPOSITIONS

This invention relates to vinylidene chloride polymer (PVDC) compositions having improved extrudability.

To control the generation of PVDC degradation products during melt processing, processing aids such as lubricants (for example, internal and external types), olefinic waxes and oils have been blended with the vinylidene chloride interpolymer prior to fabrication into a final product. However, it has been found that, after exposure to desirable processing temperatures, a certain lag time exists before the blended processing aids function effectively. It is during this lag time in the melt processing equipment that the vinylidene chloride interpolymer is particularly susceptible to decomposition.

It would be desirable to produce a vinylidene chloride polymer composition which is capable of being extruded, in either powder or pellet form, without having an unacceptable level of degradation products in the extrudate.

In a first aspect, the present invention is a vinylidene chloride polymer composition comprising a vinylidene chloride polymer and an acylated hydroxy acid type compound, a lactate compound, or combination thereof, in an amount sufficient to improve the extrudability of the vinylidene chloride polymer.

In a second aspect, the present invention is a monolayer structure comprising a vinylidene chloride polymer and an acylated hydroxy acid type compound, a lactate compound or combination thereof, in an amount sufficient to improve the extrudability of the vinylidene chloride polymer.

In a third aspect, the present invention is a multilayer structure comprising (1 ) one or more layers of an organic polymer or a blend of two or more different organic polymers, the organic polymer of one layer being the same as or different from the organic polymer of another layer and (2) one or more layers of a vinylidene chloride polymer composition comprising a vinylidene chloride polymer and an acylated hydroxy acid type compound, a lactate compound or combination thereof, in an amount sufficient to improve the extrudability of the vinylidene chloride polymer.

The inventors have discovered that adding an acylated hydroxy acid type compound, a lactate compound, or combination thereof, to PVDC improves the extrudability of the PVDC. As used herein, the term "improved extrudability" means that, if subjected to desirable elevated processing temperatures, the polymer composition is less thermally sensitive and, consequently, the extrudate possesses a reduced level of carbonaceous material contamination on the melt processing equipment, for example, on the surface of extruder screw and die, reduced discoloration or less hydrogen chloride evolvement and a lower mechanical energy to extrude, that is, amount of energy expended to extrude the polymer due to friction and the viscosity of the polymeric composition, than a PVDC composition which does not contain an acylated hydroxy acid type compound, a lactate or combination thereof. It has also been found that adding an acylated hydroxy acid type compound, a lactate compound, or combination thereof, to PVDC allows extrusion of the PVDC without air entrapment resulting in the elimination of air bubbles and voids in the extrudate.

Vinylidene chloride polymers suitable for use in the present invention are well-known in the art. See, for example, U.S. Patents 3,642,743; and 3,879,359. The most common PVDC resins are known as Saran™ resins, Trademark of The Dow Chemical

Company. As used herein, the term "vinylidene chloride polymer" or "PVDC" encompasses homopolymers of vinylidene chloride, and also copolymers and terpolymers thereof, wherein the major component is vinylidene chloride and the remainder is one or more monoethylenically unsaturated monomer copolymerizable with the vinylidene chloride monomer. Monoethylenically unsaturated monomers which can be employed in the practice of the present invention for preparing the vinylidene chloride polymers include vinyl chloride, alkyl acrylates, alkyl methacrylates, acrylic acid, ethacrylic acid, itaconic acid, acrylonitrile, and methacrylonitrile,. Preferred ethylenically unsaturated monomers include vinyl chloride, acrylonitrile, methacrylonitrile, alkyl acrylates, and alkyl methacrylates. More preferred ethylenically unsaturated monomers include vinyl chloride, acrylonitrile, methacrylonitrile, and the alkyl acrylates and alkyl methacrylates having from 1 to 8 carbon atoms per alkyl group. Most preferred ethylenically unsaturated monomers are vinyl chloride, methylacrylate, ethylacrylate, and methyl methacrylate.

Preferably, the vinylidene chloride polymer is formed from a monomer mixture comprising a vinylidene chloride monomer generally in the range of from 50 to 99 weight percent and the monoethylenically unsaturated comonomer in an amount of from 50 to 1 weight percent, said weight percents being based on total weight of the vinylidene chloride interpolymer. More preferably, the amount of monoethylenically unsaturated monomer is from 40 to 4 weight percent, and most preferably, from 40 to 6 weight percent, based on the total weight of the vinylidene chloride polymer.

Preferably, the acylated hydroxy acid type compounds employed in the practice of the present invention for preparing the vinylidene chloride polymer composition are those described in U.S. Patent 4,366,280, the pertinent portions of which are. Such acylated hydroxy acid type compounds have repeating units represented by the general formula:

wherein R, is hydrogen, C,-C₂₃ alkyl unsubstituted or substituted by 1 to 5 hydroxyl groups or C₂-C₂₃ alkenyl, R₂ is hydrogen, methyl, or phenyl, R₃ is hydrogen or methyl, n is 0 to 4, Me is Group I metal, Group II metal, Group III metal, lithium, potassium, sodium, calcium, magnesium, zinc, cadmium, barium, tin, lead, titanium, antimony, bismuth or vanadium and m is the valence of the metal.

Preferably, R, is C,-C₂₃ branched or unbranched alkyl, especially C₇-C₂₃ alkyl, such as methyl, ethyl, propyl, heptyl, undecyl, tridecyl, pentadecyl, heptadecyl,

2-ethyl-heptyl, and 2-hexyl-nonyl and R,CO therefore stands for a fatty acid acyl residue of 8 to 24 carbon atoms, such as stearoyl. If R, is substituted by 1 to 5 hydroxy groups, such residues contain especially as many carbon atoms as hydroxy groups, each carbon atom carrying one hydroxy group, or hydroxyalkyl is of 2 to 18 carbon atoms carrying one hydroxyl group especially in 1 -position, such as 1-hydroxyethyl, 1-hydroxypropyl or 1-hydroxy-heptyl. An example of monohydroxyalkyl carrying the hydroxyl group in a position other than 1 is 11-hydroxyheptadecyl. R, as C₂-C₂₃ alkenyl contains several double bonds, especially two double bonds and, most preferred, one double bond, and has preferably 2 to 17 carbon atoms, such as vinyl, allyl, heptenyl or hexadecenyl. Those metals which are defined as preferred include sodium, potassium, lithium, calcium, magnesium, barium, aluminum, cadmium, zinc and mixtures thereof. More preferred are potassium, sodium and calcium, and most preferred is calcium.

R₂ is preferably methyl, that is, compounds derived from lactic acid and condensed lactic acid and R₃ is preferably H. Thus, the preferred compound of the above general formula is calcium stearoyl lactate. By the term "calcium stearoyl lactate" is meant the calcium salt of the stearate ester of condensed lactic acid. In the Japanese list of chemical substances [7-2115], it is expressed as salt (calcium) of the condensate of lactic acid polycondensate (with the polymerization degree of 1 to 5) and the saturated fatty acid (C₈-C₂₂) and listed together with sodium salt and potassium salt. In the Japanese Official Compendia for Food Additives, Edition IV, in section "Calcium Lactylate", it is described as white to yellowish white powdered or flaked solids with acid value of 50 to 86 and ester value of 125 to 164, comprising calcium salts of stearoyl lactates as the main component and their related acids and their calcium salts. Calcium stearoyl 2-lactylate is commercially available from American

Ingredients Company as Pationic™ 930.

Preferably, the lactate compound is represented by the general formula :

wherein Me is Group I metal, Group II metal, Group III metal, lithium, potassium, sodium, calcium magnesium, zinc, barium, tin or lead; and m is the valence of the metal.

Those metals which are defined as preferred include lithium, sodium, potassium, calcium, magnesium, barium and mixtures thereof. More preferred are potassium, sodium and calcium, and most preferred is calcium. Thus, the preferred compound of the general formula above is calcium lactate. Calcium lactate is commercially available from American Ingredients

Company as Pationic™ 1225.

In general, the vinylidene chloride polymer composition of the present invention can be prepared by melt blending the vinylidene chloride polymer with the acylated hydroxy acid type compound, the lactate compound, or combination thereof, using conventional melt processing techniques using the conventional melt processing equipment mentioned previously.

The amount of acylated hydroxy acid type compound, lactate compound or combination thereof in the vinylidene chloride polymer composition of the present invention depends on the composition of the vinylidene chloride polymer and the processing conditions to which the vinylidene chloride polymer composition is exposed. In general, the amount of acylated hydroxy acid type compound, lactate compound or a combination thereof present in the vinylidene chloride polymer composition is from 0.01 to 10.0, preferably from 0.4 to 1.2 and most preferably 0.8 weight percent. The vinylidene chloride polymer composition of the present invention can be melt processed and extruded into any suitable final product, for example, a variety of films or other articles. As is well known in the art, the films and articles are fabricated with conventional coextrusion; for example, feedblock coextrusion, multimanifold die coextrusion, or combinations of the two; injection molding; co-injection molding; extrusion molding; casting; blowing; blow molding; calendering; and laminating.

Exemplary articles include blown and cast, mono and multilayer, films; flexible containers; rigid containers thermoformed from rigid sheet; 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; that is, whereby self-sustaining lamina are bonded together by applications of heat and pressure; wet combining, that is, whereby two or more plies are laminated using a tie coat adhesive, which is applied wet, the liquid driven off, and in one continuous process combining the plies by subsequent pressure lamination; or by heat reactivation, that is, 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.

The vinylidene chloride polymer compositions of the present invention are particularly suited for fabrication into rigid and flexible containers, both as monolayer or multilayer structures, used for the preservation of food, drink, medicine and other perishables. Such containers should have good mechanical properties, as well as low gas permeabilities to, for example, oxygen, carbon dioxide, water vapor, odor bodies or flavor bodies, hydrocarbons or agricultural chemicals.

The monolayer structures comprise the vinylidene chloride polymer composition of the present invention. The multilayer structures comprise one or more layers of an organic polymer or a blend of two or more different organic polymers and one or more layers of the vinylidene chloride composition of the present invention.

The multilayer structure can have three layers comprising a first outer layer of the organic polymer or blend of two or more different organic polymers, a core layer of the vinylidene chloride polymer composition and a second outer layer of an organic polymer which is the same as or different from the organic polymer of the first outer layer. Several variations of the three-layer structure include the following:

(a) A three-layer structure comprising a first outer layer of the vinylidene chloride polymer composition; a core layer of the organic polymer or blend of two or more different organic polymers and a second outer layer of an organic polymer which is the same as or different from the organic polymer of the core layer.

(b) A three-layer structure comprising a first outer layer of the vinylidene chloride polymer composition; a core layer of the organic polymer or blend of two or more different organic polymers and a second outer layer of a vinylidene chloride polymer composition which is the same as or different from the vinylidene chloride composition of the first outer layer.

The multilayer structure can also have five or seven layers comprising one or more layers of the vinylidene chloride polymer composition of the present invention, and the remaining layers comprising an organic polymer or a blend of two or more different organic polymers, the organic polymer of one layer being the same as or different from the organic polymer of another layer.

Adhesive layers may be interposed between contiguous layers of the multilayer structures, depending on the composition and method of preparing the multilayer structure. Organic polymers which can be used in the practice of the present invention for preparing the multilayer structure include polyolefins, polyamides, polyolefins based on aromatic monomers, and chlorinated polyolefins.

Polyolefins which can be employed in the practice of the present invention include, for example, low density polyethylene, linear low density polyethylene, very low density polyethylene, polypropylene (PP), polybutene, ethylene/vinyl acetate copolymers, ethylene/propylene copolymers ethylene/butene-1 copolymers and polyethylene terephthalates and copolymers thereof.

Polyolefins based on aromatic monomers which can be employed in the practice of the present invention include polystyrene, polymethylstyrene, polyethylstyrene, styrene/methylstyrene copolymer, and styrene/chlorostyrene copolymer.

Polyamides which can be employed in the practice of the present invention include the various grades of nylon, such as nylon 6, nylon 66 and nylon 12. Adhesive materials which can be employed in the practice of the present invention for preparing the adhesive layer include ethylene vinyl acetate copolymers, ethylene/ethyl acrylic acid ester copolymers, ionomers, modified polyolefins as described in U.S. Patent 5,443,874, acrylic-based terpolymer adhesives as described in U.S. Patent 3,753,769 and adhesives formed by reacting an epoxy resin and an acidified aminoethylated vinyl polymer as described in U.S. Patent 4,447,494. The more preferred adhesive materials are maleic anhydride grafted polyethylene or polypropylene such as ADMER™ (trademark of Mitsui Petrochemicals) adhesive resins, or ethylene-vinyl acetate copolymer resins such as ELVAX™ (trademark of DuPont). The most preferred adhesive material is ELVAX™ 3175, which is a 6 Melt Index, 28 percent vinyl acetate copolymer.

The thickness of the monolayer and multilayer structures of the present invention is variable within wide limits, depending on the contemplated application. In general, the monolayer structure of the present invention has a thickness of from 0.05 to 10 mils, preferably, from 0.2 to 6 mils, most preferably, from 0.4 to 1.8 mils. In general, the multilayer structure of the present invention has a thickness of from 0.05 to 200 mils, preferably from 1 to 100 mils, most preferably, from 2 to 80 mils, with the PVDC polymer layer having a thickness of from 0.005 to 20 mils, preferably from 0.2 to 10 mils, most preferably, from 0.2 to 8.0 mils.

The present invention is illustrated in further detail by the following examples. The examples are for the purposes of illustration only, and are not to be construed as limiting the scope of the present invention. All parts and percentages are by weight unless otherwise specifically noted.

EXAMPLE 1

Calcium stearoyl 2-lactylate (CSL) (0.8 percent), epoxidized soy bean oil (0.7 weight percent), oxidized polyethylene wax (0.2 weight percent), polyethylene wax (0.5 weight percent), high density polyethylene (1.0 weight percent) and a base resin comprising a copolymer of 92 weight percent vinylidene chloride and 8 weight percent methyl acrylate composition were blended in a high intensity mixer by a sequence of first adding the solid ingredients to the resin and then followed by the liquid components. This formulation was then run on a 3.5 inch (89 mm) 24:1 plasticating extruder.

Extruder detail: Compression ratio: 3:1

Extruder temperature profile:

Zone 1 : 168°C; Zone 2: 165°C; Zone 3: 163°C; Zone 4: 160°C; Zone 5: 157°C; Feed Throat: 43°C; Die: 152 mm slit. The performance of the CSL as a thermal stabilizer and its ability to allow extrusion without air entrapment was measured visually by monitoring the extrudate.

The vinylidene chloride polymer formulation was extruded at a rate of 136 to 145 kilograms per hour on an 89 mm diameter extruder without thermal degradation or air entrapment.

Example 2

The procedure of Example 1 was followed in preparing a vinylidene chloride formulation except that calcium lactate was used instead of calcium stearoyl 2-lactylate.

This formulation was then run on a 3.5 inch (89 mm) 24:1 plasticating extruder.

Extruder detail:

Compression ratio: 3:1

Extruder temperature profile:

Zone 1 : 168°C; Zone 2: 165°C; Zone 3: 163°C; Zone 4: 160°C; Zone 5: 157°C; Feed Throat: 43°C; Die: 152 mm slit. The performance of calcium lactate as a thermal stabilizer and its ability to allow extrusion without air entrapment was measured visually by monitoring the extrudate.

The vinylidene chloride polymer formulation was extruded at a rate of 136 to 145 kilograms per hour on an 89 mm diameter extruder without thermal degradation.

Claims

CLAIMS:

1. A vinylidene chloride polymer composition comprising a vinylidene chloride polymer and an acylated hydroxy acid type compound, a lactate compound or combination thereof, in an amount sufficient to improve the extrudability of the vinylidene chloride polymer.

2. The composition of Claim 1 wherein the vinylidene chloride polymer is formed from a monomer mixture comprising from 60 to 99 weight percent vinylidene chloride monomer and from 40 to 1 weight percent of a monoethylenically unsaturated comonomer copolymehzable therewith.

3. The composition of Claim 2 wherein the monoethylenically unsaturated comonomer is present in an amount of from 40 to 4 weight percent, based on the total weight of the vinylidene chloride polymer.

4. The composition of Claim 2 wherein the monoethylenically unsaturated monomer is vinyl chloride, alkyl acrylate, alkyl methacrylate, acrylic acid, methacrylic acid, itaconic acid, acrylonitrile, or methacrylonitrile.

5. The composition of Claim 1 wherein the acylated hydroxy acid type compound has repeating units represented by the general formula:

and the lactate compound has repeating units represented by the general formula:

wherein R, is hydrogen, C,-C₂₃ alkyl unsubstituted or substituted by 1 to 5 hydroxyl groups or C₂-C₂₃ alkenyl, R₂ is independently hydrogen, methyl, or phenyl, R₃ is hydrogen or methyl, n is 0 to 4, Me is Group I metal, Group II metal, Group III metal, lithium, potassium, sodium, calcium, magnesium, zinc, cadmium, barium, tin, lead, titanium, antimony, bismuth or vanadium and m is the valence of the metal.

6. The composition of Claim 5 wherein R, is C,-C₂₃ branched or unbranched alkyl.

7. The composition of Claim 5 wherein R, is methyl, ethyl, propyl, heptyl, undecyl, tridecyl, pentadecyl, heptadecyl, 2-ethyl-heptyl or 2-hexyl-nonyl

8. The composition of Claim 6 wherein R, is substituted by 1 to 5 hydroxy groups.

9. The composition of Claim 1 wherein the acylated hydroxy acid type compound is calcium stearoyl lactylate.

10. The composition of Claim 1 wherein the lactate compound is calcium lactate.

11. The composition of Claim 1 wherein the acylated hydroxy acid type compound, lactate compound or combination thereof, is present in an amount of from 0.01 to 10.0 weight percent based on the weight of the composition.

12. The composition of Claim 11 wherein the acylated hydroxy acid type compound, lactate compound or combination thereof is present in an amount of 0.4 to 1.2 weight percent, based on the weight of the composition.

13. The composition of Claim 12 wherein the acylated hydroxy acid type compound, lactate compound, or combination thereof is present in an amount of 0.8 weight percent based on the weight of the composition.

14. A monolayer structure comprising a vinylidene chloride polymer and an acylated hydroxy acid type compound, a lactate compound or combination thereof, in an amount sufficient to improve the extrudability of the vinylidene chloride polymer.

15. A multilayer structure comprising (1) one or more layers of an organic polymer or a blend of two or more different organic polymers, the organic polymer of one layer being the same as or different from the organic polymer of another layer and (2) one or more layers of a vinylidene chloride polymer composition comprising a vinylidene chloride polymer and an acylated hydroxy acid type compound, a lactate compound or combination thereof, in an amount sufficient to improve the extrudability of the vinylidene chloride polymer.

16. The multilayer structure of Claim 15 comprising a first outer layer of the organic polymer or blend of two or more different organic polymers, a core layer of the vinylidene chloride polymer composition and a second outer layer of an organic polymer which is the same as or different from the organic polymer of the first outer layer.

17. The multilayer structure of Claim 15 comprising a first outer layer of the vinylidene chloride polymer composition; a core layer of the organic polymer or blend of two or more different organic polymers and a second outer layer of an organic polymer which is the same as or different from the organic polymer of the core layer.

18. The multilayer structure of Claim 15 comprising a first outer layer of the vinylidene chloride polymer composition; a core layer of the organic polymer or blend of two or more different organic polymers and a second outer layer of a vinylidene chloride polymer composition which is the same as or different from the vinylidene chloride composition of the first outer layer.

19. The multilayer structure of Claim 15 wherein an adhesive layer is interposed between contiguous layers of the multilyer structure.

20. The multilayer structure of Claim 15 wherein the organic polymer is a polyolefin or a polystyrene.

21. The multilayer structure of Claim 20 wherein the polyolefin is low density polyethylene, linear low density polyethylene, very low density polyethylene, polypropylene, polybutene, ethylene/vinyl acetate copolymers, ethylene/propylene copolymers ethylene/butene-1 copolymers or polyethylene terephthalates or copolymers thereof.

22. The multilayer structure of Claim 15 having a thickness of from 0.05 to 200 mils.

23. A five-layer or seven-layer structure having one or more layers of a vinylidene chloride polymer composition comprising a vinylidene chloride polymer and an acylated hydroxy acid type compound, a lactate compound or combination thereof, in an amount sufficient to improve the extrudability of the vinylidene chloride polymer and (2) the remaining layers comprising an organic polymer or a blend of two or more different organic polymers, the organic polymer of one layer being the same as or different from the organic polymer of another layer.

24. The five-layer structure of Claim 23 comprising (1 ) two outer layers of the vinylidene chloride polymer composition and (2) three core layers of the organic polymer or a blend of two or more different organic polymers, the organic polymer of one layer being the same as or different from the organic polymer of another layer.

25. The five-layer structure of Claim 23 comprising two outer layers of the organic polymer or a blend of two or more different organic polymers, the organic polymer of one layer being the same as or different from the organic polymer of the other layer and three core layers of the vinylidene chloride polymer composition.

26. The seven-layer structure of Claim 23 comprising two outer layers of the vinylidene chloride polymer composition, a first core layer of the organic polymer or blend of two or more different organic polymers, a second core layer of the vinylidene chloride polymer composition, a third core layer of the organic polymer or blend of two or more different organic polymers, a fourth core layer of the vinylidene chloride polymer composition and a fifth core layer of the organic polymer or blend of two or more different organic polymers, the organic polymer of one layer being the same as or different from the organic polymer of another layer.