MXPA99000242A - Closure of plastic with interior coating of barrier molded by compres - Google Patents

Abstract

The present invention relates to a plastic closure that includes a lid (22) having a base (30) with a peripheral edge (30) with a peripheral edge (32) defining an interior of the lid and cords (34) on the edge to ensure closure to a container. An inner liner (20a, 20b or 20c) is secured to the inside of the lid, preferably by compression molding it consists essentially of a mixture of a matrix polymer, a particulate barrier polymer and a compatibilizer. The compression heat and pressure form the particles of the barrier polymer in the platelets that are oriented essentially parallel to the plane of the

Description

PLASTIC CLOSURE WITH INTERIOR COATING OF COMPRESSED MOLDED BARRIER FIELD OF THE INVENTION The present invention is directed to closures of plastic containers for beverage, food, juice, pharmaceutical applications and the like, and more particularly to an improved process for providing closures with interior sealing coatings having resistance to gas transmission, water vapor. and / or flavorings (loss of flavor). Reference is made to the application currently filed Serial No. (Record 17155) entitled "Plástic Closure with Compression Molded Sealing / Barrier Liner "and assigned to the assignee hereof.

BACKGROUND AND OBJECTIVES OF THE INVENTION Therefore, it has been proposed to provide a plastic closure for a container comprising a plastic cap with an inner liner for the sealing coupling with the sealing surface of the container. For example, the North American patent REF .: 29178 No. 4,984,703 discloses a plastic closure comprising a lid having a base with a peripheral edge and ropes for securing the lid to a container, and an internal compression liner molded by compression in situ within the interior of the container. base of the lid. The interior sealing liner comprises a mixture of ethylene vinyl acetate (EVA) and an elastomeric, thermoplastic material such as olefin or styrene-butadiene-styrene. U.S. Patent No. 5,451,360 discloses a method and apparatus for compression molding inner liners in situ within the lids. Therefore, it has also been proposed to form an interior barrier coating for a plastic closure in an operation of injection molding or extrusion of a blend of a thermoplastic olefin homopolymer or copolymer such as ethyl vinyl acetate (EVA) or a thermoplastic elastomer, and a barrier polymer for the transmission of oxygen and carbon dioxide such as ethyl vinyl alcohol (EVOH, for its acronym in English). The blend also typically includes a compatibilizer material to promote adhesion between the EVOH particles and the EVA carrier material. In general, the particles of the EVOH barrier material force the gases that penetrate the EVA carrier either to follow a tortuous path around the EVOH particles or to penetrate through the EVOH polymer, thereby decreasing the velocity of the EVOH polymer. the transmission of gases. The EVOH particles are generally spherically dispersed in the EVA carrier since these materials are not miscible. As a general proposition, the percentage reduction in gas transmission corresponds to the content percentage -of EVOH in the mixture. The results of this technology to date have not provided high barrier properties at an acceptable cost and sealing performance. Therefore, it is a general object of the present invention to provide an inner liner for a plastic closure that combines the functions of a seal for coupling with the sealing surface of the container and an improved barrier against the transmission of gases, absorption of flavor (loss of flavor) and / or permeation of water vapor. Another more specific objective of the present invention is to provide an inner liner of the described character that is easily moldable and inexpensive in composition. Still another object of the invention is to provide an interior liner that satisfies the above objectives and is of clear or translucent construction to allow reading through the inner printing liner on the closure. A further object of the present invention is to provide a method of manufacturing such an inner liner, and a plastic closure including such a liner.

BRIEF DESCRIPTION OF THE INVENTION According to one aspect of the present invention, there is provided a plastic closure comprising a lid having a base with a peripheral edge defining an interior of the lid and a means at the edge for securing the closure to a container. An inner lining is secured to the inside of the lid, preferably when in situ compression molding. The inner lining essentially consists of a mixture of a matrix polymer and a barrier material and a compatibilizer. The barrier material is in the form of a distributed, discontinuous phase of particles in a continuous matrix phase. It has been found that the heat and pressure of the compression molding forms the particles of the barrier polymer in substantially superjacent, thin, two-dimensional platelets which are oriented within the matrix polymer essentially parallel to the plane of the inner coating. In this way, the gas that penetrates the inner coating must follow a more tortuous path around the platelets, which increases the efficiency of the barrier. The "matrix polymer" is a thermoplastic elastomer, a mild olefin polymer, or a combination thereof. A thermoplastic elastomer is a synthetic polymer that has the processability of a thermoplastic material and the functional performance and properties of a conventional thermosetting rubber. There are six generic classes of commercially available thermoplastic elastomer, including styrenic block copolymers (SBC), polyolefin blends (TPO), elastomeric alloys, thermoplastic polyurethanes (TPU). in English), thermoplastic copolyesters and thermoplastic polyamides. Thermoplastic elastomers are described starting on page 64 in Modern Pla s ti cs in cycl opedia Handbook, published by McGraw-Hill, 1994, the description of which is incorporated by reference. Examples of thermoplastic elastomers are styrene block copolymers such as those manufactured by Shell Chemical under the trademark KRATON. These synthetic polymers consist of three discrete blocks of the linear type or A-B-A: styrene-butadiene-styrene, styrene-isoprene-styrene and styrene-ethylene / butylene-styrene-styrene. An elastomeric alloy is the ethylene-propylene-diene terpolymer (EPDM). Another elastomeric alloy consists of the EPDM / PP and butyl rubber / PP compounds as manufactured by Advanced Elastomer Systems under the trade names SANTOPRENE and TREFSIN and those described in U.S. Patent Nos. 4,130,535, 4,311,628, 4,130,534 and 4,607,074. In general, thermoplastic elastomers are characterized by a Shore A hardness of 45 to 95 and a flexural modulus of 2106.48 to 7021.6 kg / cm2 (30,000 to 100,000 psi). The mild olefin polymers are thermoplastic olefins, homopolymers and copolymers that are flexible, elastic with a Shore A hardness of less than about 100. Typical mild olefin polymers are: metallocene polyethylene, ethylene-propylene rubbers, ethylene copolymers and mixtures thereof, ethylene copolymers such as ethylene vinyl acetate, ethylenemethyl acrylate copolymers and ionomers and combinations thereof. Examples of mild olefin polymers are alpha-olefin-substituted polyethylenes made using the individual site catalyst technology (these materials are known in the art as metallocene polyethylenes); ethylene vinyl acetate (EVA) such as that manufactured by DuPont under the trademark ELVAX; polypropylene made with the technology of the individual site catalyst known in the art as metallocene polypropylenes; syndiotactic polypropylenes as marketed by Fina Oil and Chemical; the ethylene / propylene copolymers and styrene-ethylene interpolymers as sold by Dow Chemical; and ionomers such as the SURLYN product line from DuPont. The matrix polymer is typically combined with antioxidants, lubricants and other stabilization materials, as is known in the art. A "compatibilizer" is a thermoplastic material that joins two other thermoplastic materials together by a reactive bond (covalent or dipole-dipole) or a non-reactive medium (chain entanglement). Examples include maleic anhydride graft polymers or ethylene vinyl acetate graft polymers such as PLEXAR (trademark) of Quantum Chemical, ADMER (trademark) of Mitsui Petrochemical and product line BYNEL (trademark) of DuPont, ethylenemethyl acrylate and ionomers. A "barrier material" is a thermoplastic material that has a low gas transmission rate and / or water vapor and has a high barrier to odorants and essential oils. The following materials have lower gas transmission rates than the EVA, which is an interior lining material, normal in the industry: EVOH (ethylene vinyl alcohol) such as the SOARNOL product line (trademark) of Nippon Goshei and the Evaca EVAL product line (trademark), nilons such as the SELAR PA (trademark) product lines from DuPont, EMS G21 and Mitsubishi Gas MXDß, the BAREX acrylonitrile product line (trademark) from British Petroleum , mixtures of EVOH and amorphous nylon, mixtures of EVOH and an ionomer such as SURLYN (DuPont), and cyclic olefin copolymers such as those marketed by Ticona. Other suitable barrier materials and blends are described in U.S. Patent Nos. 4,977,004 and 5,064,716, the disclosures of which are incorporated herein by reference. It is currently preferred that the inner liner also includes an additive to reduce the coefficient of friction between the inner liner and the sealing surface of the container. In the art these additives are called "lubricants". Typical additive lubricants include fatty acid amides and fatty acid esters, microcrystalline waxes and polyethylene glycols. A preferred lubricant is a low molecular weight fatty acid amide material that blooms to the exposed surface of the polymeric material upon cooling from the molten state, thereby reducing the coefficient of friction between the inner liner and the sealing surface. of the container. Examples are: primary amides with the general chemical structure R-CO-NH2, where R is an alkyl group; secondary amides with the general chemical structure R-CO-NH-R '; where R, R 'are alkyl groups; secondary bis-amides with the general chemical structure R-CO-NH-A-NH-CO-R, where R, R 'are alkyl groups and A is an alkylene group Y; and mixtures of the above materials such as in U.S. Patent No. 5,306,542. The lubricant preferably comprises about 0.5% to 2.0% of the total interior coating composition by weight, more preferably about 1% by weight. The lubricant is preferably combined in the elastomeric, thermoplastic material (together with any desired colorant) by the material manufacturer. The amount of lubricant and / or colorant is not included in the calculations of the compositions in this application. In the presently preferred mixtures of the matrix polymer, the barrier material and the compatibilizer, the barrier material is in the range of about 20% to 60% by weight, the compatibilizer in the range of about 1% to 10% by weight, and the rest consists essentially of the matrix polymer (with lubricant). The percentages of the relative components will vary with the applications, and will depend on the hardness and therefore, sealability, the ability of the barrier material to form the pellets in the matrix polymer, and the desired torque of removal torque. As for hardness, it has been found that a hardness of the inner liner higher than about 94 to 95 Shore (A) is too hard for proper sealing with the container. When an elastomer that is relatively hard, such as EVA, is used, the upper limit of the barrier material may be relatively low, such as 35% EVOH. However, when a matrix polymer of relatively low hardness is used, such as a thermoplastic elastomer, the upper limit of the barrier material can be much higher, such as 50% to 60% EVOH. It has also been found that the amount of the barrier material that can be included in the mixture also depends in part on the polarity of the matrix polymer. The miscibility of the barrier material in the matrix material decreases with decreasing the polarity of the matrix material, which means that the highest percentages of the barrier material can be mixed with matrix polymers of lower polarity while still maintaining a phase of discontinuous barrier pellets. The amount of the compatibilizer also affects the ability of the barrier material to form platelets. Above approximately 10% of the compatibilizer, the barrier material becomes too well blended with the matrix polymer to form the platelets that characterize the invention. Below about 1%, the inner liner does not exhibit good mechanical properties and does not bond properly with the closure cover.

According to another aspect of the present invention, therefore, there is provided a method for making an inner liner for a plastic closure comprising the steps of forming a pellet consisting essentially of a mixture of a thermoplastic elastomer, a polymer having high barrier properties and a compatibilizer to promote adhesion between the elastomer and the barrier polymer and between the inner liner and the closure cover. The pellet is then compression molded, preferably within a cover of the closure, to form an inner liner disc attached to the closure cover, and within which the heat and pressure of the compression molding form the polymer of barrier in the platelets that are oriented essentially parallel to the plane of the disk. The resulting inner liner exhibits a greatly decreased gas transmission rate when compared to an inner liner formed of a similar mixture different from a compression molding operation. According to a third aspect of the invention, there is provided an inner sealing liner for a plastic closure comprising a disk consisting essentially of a matrix polymer within which a platelet dispersion of a barrier material for the transmission of Gases are placed essentially in planes parallel to the disk. The inner sealing liner is preferably molded by in situ compression into a plastic closure from a compression pellet or pellet in which the matrix polymer, barrier material and a compatibilizer are mixed such that the material The barrier consists of discrete particles that flatten on the platelets during the compression molding operation.

BRIEF DESCRIPTION OF THE DRAWINGS The invention, together with the objects, features and additional advantages thereof, will be better understood from the following description, the appended claims and the accompanying drawings in which: FIGURE 1 is a schematic diagram illustrating the molding by compressing interior barrier coatings in a plastic closure according to a presently preferred implementation of the invention; FIGURE 2 is a sectional elevation view, on an enlarged scale of a plastic closure with internal barrier coating, integral made in accordance with the process schematically illustrated in FIGURE 1; FIGURES 3A and 3B are photomicrographs at 50X of portions of the inner lining within circles 3A and 3B in FIGURE 2; FIGURE 3C is a 100X photomicrograph of the portion of the inner liner illustrated in FIGURE 3B; FIGURE 4 is a photomicrograph at 100X of a loading pellet; FIGURE 5A is a photomicrograph at 50X of the edge portion of another embodiment of the invention; FIGURE 5B is a 100X photomicrograph of a center portion of the inner liner illustrated in FIGURE 5A; and FIGURES 6 and 7 are views similar to that of FIGURE 2 but showing modified geometries of the inner lining.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES FIGURE 1 is a schematic diagram of a process 10 for manufacturing plastic closures according to the present invention. An extruder 12 has a hopper 14 to receive the starting materials. The outlet of the extruder 12 is fed to a pellet slicing machine 16 from which the individual loading pellets 20 are provided. The pellet 20 is placed inside a prefabricated plastic closure cap 22 in the female nozzle 24 of a compression mold 26. A section of the male nozzle 28 is closed against the pellet 20, the cap 22 and the nozzle 24 for compression molding the pellet 20 in an inner liner that is welded or bonded to the inner surface of the base the lid. This is, with reference to FIGURE 2, the loading pellet is molded by in situ compression against the base 30 of the lid 22 to form an inner liner 20a. This can be done by hand, or more preferably with the machine described in U.S. Patent No. 5,451,360 noted above. The lid 22 also includes an edge 32 extending axially from the base periphery 30, which has internal cords 34 to secure the lid 22 to a container. Alternatively, the pellet 20 can be compression molded separately to form the inner liner 20, which can then be secured with adhesive within the lid 22 against the base 30. Such an operation requires additional and expensive steps, and for therefore it is not preferred. As a second alternative, interior coatings can be formed in the closures as described in U.S. Patent No. 4,518,336. See also U.S. Patent Nos. 3,674,393, 3,702,148, 3,877,497 and 4,518,336. FIGURE 6 illustrates an alternative interior liner 20b having a flat geometry, as opposed to the interior liner 20a of FIGURE 3 having a thick periphery. FIGURE 7 illustrates an inner liner 20c having a flat periphery and a thick middle section to hold the additional barrier material. For the manufacture of plastic closure barrier inner liners according to the presently preferred implementation of the invention, the entrance to the extruder 12 in the hopper 14 preferably consists essentially of one or more barrier polymers, one or more polymers of matrix (preferentially premixed with lubricant and any desired colorant), and one or more compatibilizing materials. The input materials are mixed and combined in the hopper 14. The entrance of the barrier polymer is preferably selected from the group consisting of EVOH, nylon, acrylonitrile copolymers such as styrene acrylonitrile and acrylonitrile methylacrylate, EVOH blends and amorphous nylon, mixtures of EVOH and an ionomer, acrylonitrile, cyclic olefin copolymers, and mixtures of the same. The entrance of the matrix polymer to the hopper 14 is preferably selected from the group consisting of EVA, ethylene / propylene copolymers, styrene block copolymers, terpolymers, ionomers, thermoplastic rubbers, styrene / ethylene / butadiene block copolymers / styrene, styrene / ethylene / butadiene / styrene compounds, styrene / butadiene / styrene block copolymers, EPDM, linear metallocene low polyethylene, metallocene syndiotactic polypropylene, rubbers such as butyl rubber, styrene copolymers such as styrene / ethylene and terpolymers such as styrene / ethylene / butylene, polypropylene / butyl rubber and mixtures thereof. The entrance of the compatibilizer to the hopper 14 is preferably selected from the group consisting of maleic anhydride graft polymers, ethylene vinyl acetate graft polymers, EVA, ethylenemethyl acrylate, ionomers and mixtures thereof. As noted above, a lubricant selected from the group consisting of primary amides, secondary amides, secondary bis-amides and mixtures thereof, is preferably premixed with the matrix polymer. In the current invention, the interior coating material consists of a homogeneous mixture of a matrix polymer (TPE or soft olefin) and a condensation polymer or barrier polymer, a suitable compatibilizer and lubricant. In the described examples of the invention, the matrix polymer is ethylene vinyl acetate (EVA) marketed under the trademark ELVAC 650 by Dupont), the barrier polymer is ethylene vinyl alcohol (EVOH marketed under the trade designation E105B by Evalca), and the compatibilizer is a maleic anhydride graft polypropylene (ADMER QF551) with 0.5% by weight of erucamide + 0.5% of ethylene bis-oleamides as the lubricant. Although it is not required, it is preferred that all the components of the innerliner be used in particulate form and the components mixed as particulates before extrusion. The particles should be, as a general rule, of a size such that the molten mixture of the incompatible polymers exhibits the heterogeneity necessary to achieve the barrier properties that characterize the invention. When the particles are too small in size or the mixture is well mixed, the compound will function as a homogeneous composition with the oxygen barrier properties. It is preferred that the inlet to the extruder 12 be substantially and uniformly mixed, and that the outlet of the extruder 12 be of substantially uniform composition. The substantial uniformity of the composition is important in achieving a uniformity of properties. The barrier particles must be evenly distributed - that is, substantially and homogeneously distributed - to achieve the desired barrier properties. The extruder 12 must be a low shear mixing extruder to avoid homogenization of the mixture in which the particles or domains of the discontinuous phase are too small. It has been found that it is desirable that the barrier material is not very well mixed in the matrix polymer. The barrier material should be in the form of discrete, essentially spheroidal particles, in the loading pellet, as illustrated in FIGURE 4. If the barrier material is very well mixed in the elastomer, there are no discrete particles in the matrix of the elastomer to form platelets during comparison molding. FIGURES 3A, 3B and 3C are photomicrographs of portions of the center (FIGURES 3B and 3C) and the edge (FIGURE 3A) of the innerliner 20a (FIGURE 2) formed of a mixture of 65% EVA, 3% EVOH and 1 % compatibilizer (a maleic anhydride graft polymer). The barrier material is essentially in the form of substantially two-dimensional, superjacent, flat, thin platelets (dark in the micrographs) parallel to the plane of the inner lining. It is believed that the compression molding force coupled with the radial material flow during compression molding forms and aligns these platelets parallel to the plane of the inner liner disc. FIGURES 5A and 5B are similar photomicrographs of another compression-molded inner liner of the same material blend. Several sets of test samples were manufactured in the form of compression molded interior linings within the closures. The test materials were extruded through the system of FIGURE 1 at a melting temperature of 221 to 232 ° C (430 to 450 ° F) in proportions to produce the desired weight ratios. The pellets 29 were manually cut from the extruded product and placed in the covers of the closure 22. With the pellets 20 still at or near the melting temperature, the closure and the pellet were placed in a compression mold as in FIG. , and the compression tool was activated to compress the pellet. The compression molding machine of the inner liner was that described in U.S. Patent No. 5,451,360 noted above. The interior linings were molded to the configuration of FIGURE 2, with a thickness at position 3A of 0.0635 to 0.07112 centimeters (0.025 to 0.028 inches), and a thickness at position 3B of 0.0381 to 0.04572 centimeters (0.015 to 0.018 inches) . All closures were 43mm closures, and all interior linings had a diameter of 3,909 centimeters (1,539 inches). The closures were conditioned for approximately two weeks at 100% relative humidity before further testing. Each test closure with the inner lining was then wrapped in a finished PET bottle at a torque of normal application in the industry (25 to 30 inch-pounds for a 43 mm closure). The finish was then cut from the bottle and treated with epoxy on a metal plate surrounding a hole coupled to a purging tube. The plate with the closure was then placed in a Mocon OXYTRAN oxygen permeability tester. Oxygen outside the closure was maintained at 1 atm, 23 ° C and 100% relative humidity, and nitrogen gas was used to purge the volume within the closure to measure oxygen concentration, and therefore oxygen permeation through closure. When the oxygen permeability reached steady state, the figure was multiplied by 0.21 to correct the amount of oxygen in the atmosphere, and was recorded. When EVOH is used in polymer blends, it has generally been found in the past that the percentage reduction in gas transmission corresponds approximately to the percentage of EVOH in the mixture. For example, a mixture having 20% EVOH would typically be expected to exhibit a 20% reduction in oxygen transmission as compared to the same interior coating composition without EVOH. However, it was surprisingly discovered when implementing the present invention that the reduction in the oxygen transmission rate greatly exceeds the percentage of EVOH in the test mixtures. For example, a polypropylene cap having an internal compression-molded barrier coating in place, wherein the inner coating consists of a blend of 65% EVA, 34% EVOH and 1% adhesive / compatibilizer by weight, had an oxygen transmission rate of 0.006 to 0.007 cc / closure of 43 mm / day, when compared to the speed of 0.013 cc / closure of 43 mm / day for an identical closure that has an inner lining of compression-molded EVA of the same thickness and analyzed under identical conditions. Another test was performed on the closures with compression molded inner liners consisting of 79% EVA, 20% EVOH and 1% compatibilizer. These samples exhibited an oxygen transmission rate of 0.010 cc / closure of 43 mm / day, again when compared to a speed of 0.013 cc / closure of 43 mm / day for the comparable EVA interior liners. Further tests were performed on the compression molded inner liners in 43 mm diameter polypropylene closures having an inner lining diameter of 3,909 centimeters (1,539 inches). These tests were performed at 100% relative humidity. All interior linings were 0.0381 centimeters (0.015 inches) thick: Table 1 Test Sample Oxygen Transmissivity (cc / closure of 43 mm / day) (1) 100% EVA 0.013 (2) 79% EVA, 20% EVOH, 1% comp. 0.010 (3) 65% EVA, 34% EVOH, 1% comp. 0.007 (4) 65% EVA, 34% EVOH, 1% comp. 0.010 The compatibilizer in samples (2) to (4) was the previously observed maleic anhydride graft polymer. The test sample (4) was very well mixed, and in this way it does not exhibit the good results of the sample (3). The hardness of the samples is illustrated by the following table: Table 2 Material Hardness (Shore A) 100% EVA 91 75% EVA / 25% EVOH 92-94 50% EVA / 50% EVOH 94-96 25% EVA / 75% EVOH 97 100% EVOH 100+ As noted above, the amount of the barrier material that can be used in the mixture depends in part on the hardness of the matrix polymer. For example, the following table compares the hardness and ability to seal against one mouth of the container by several mixtures of EVOH with EVA (hardness equal to 91 Shore A) and polypropylene / butyl rubber (TREFSIN, hardness equal to 65 Shore A). The polypropylene compatibilizer treated with maleic acid salt or ester and the lubricant were used in the same amounts in all samples.

Table 3 Functional Sealed Hardness Material EVA + 20% EVOH 92 Yes EVA + 34% EVOH 92 Yes EVA + 50% EVOH 94 No Polypropylene Butyl Rubber + 20% EVOH 67 Si Polypropylene Butyl Rubber + 34% EVOH 75 Si Rubber Polypropylene / Butyl + 50% EVOH 81 Si The polypropylene / butyl rubber used is sold by Advanced Elastomer Systems under the trademark TREPSIN. In this way, a greater amount of barrier material can be incorporated into a softer matrix material while maintaining the ability to function as a seal. In this way, a barrier coating, and a method of manufacturing thereof have been described as barrier coating, which fully satisfy the previously stated objects and purposes. The inner lining is easily fabricated from otherwise conventional materials, and employing other conventional techniques and equipment. The inner lining provides improved efficiency, in terms of the amount of barrier material employed against the permeation and transmission of gases such as oxygen and carbon dioxide, water vapor and essential flavor oils (loss of flavor). The combinations of the specific barrier materials has been described. Other combinations are contemplated for different applications and will be suggested by themselves for persons or ordinary experts in the art based on the principles and parameters discussed herein.

All patents and publications cited above are incorporated herein by reference.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following claims is claimed as property.

Claims (22)

1. An interior sealing liner for a plastic closure, characterized in that it comprises a disk consisting essentially of a dispersion of superjacent, discrete platelets dispersed through a matrix polymer, the platelets consisting of a barrier polymer and essentially oriented parallel to the disc.

2. The inner liner according to claim 1, characterized in that the inner liner includes a compatibilizer for promoting adhesion between the matrix polymer and the barrier platelets.

3. A plastic closure, characterized in that it comprises: a lid having a base with a peripheral edge defining the inside of a lid and a means at the edge for securing the closure to a container, and an interior lining in accordance with claim 1 or 2 secured to the interior of the base, the platelets that are oriented essentially parallel to the base.

4. The closure according to claim 3, characterized in that the inner lining is molded by compression in situ on the base.

5. The invention according to any preceding claim, characterized in that the matrix polymer is selected from the group consisting of thermoplastic elastomers, soft olefin polymers and mixtures thereof.

6. The closure according to claim 5, characterized in that the matrix polymer is a thermoplastic elastomer having a Shore A hardness of 45 to 95 and a flexural modulus of 2106.48 to 7021.6 kg / cm2 (30,000 to 100,000 psi).

7. The closure according to claim 5, characterized in that the matrix polymer is a thermoplastic elastomer selected from the group consisting of block copolymers of styrene and elastomeric alloys.

8. The closure according to claim 5, characterized in that the matrix polymer is an olefin polymer having a Shore A hardness less than 100.

9. The closure according to claim 8, characterized in that the olefin polymer is selected from the group consisting of metallocene polyethylene, ethylene-propylene rubbers, ethylene copolymers and mixtures thereof.

10. The closure according to any preceding claim, characterized in that the barrier material is selected from the group consisting of EVOH, nylon, acrylonitrile copolymers, mixtures of EVOH and amorphous nylon, mixtures of EVOH and an ionomer, acrylonitrile, cyclic olefin copolymers and mixtures thereof.

11. The closure according to any preceding claim, characterized in that the compatibilizer is selected from the group consisting of maleic anhydride graft polymers, ethylene vinyl acetate graft polymers, ethylenemethyl acrylate, ionomers and mixtures thereof.

12. The closure according to any preceding claim, characterized in that the barrier material comprises EVOH and the matrix polymer comprises EVA or polypropylene / butyl rubber.

13. The closure according to claim 12, characterized in that the barrier material is in the range of about 20% to 60% by weight, the compatibilizer is in the range of about 1% to 10% by weight, with the remainder consisting of of the matrix polymer.

14. The closure according to any preceding claim, characterized in that the barrier material is in the range of about 20% to 60% by weight, the compatibilizer is in the range of about 1% to 10% by weight, with the remainder consisting of of the matrix polymer.

15. The closure according to any preceding claim, characterized in that the inner lining has a Shore A hardness of less than 94.

16. The closure according to any preceding claim, characterized in that the inner liner contains lubricant in the amount of about 0.5% to 2.0% by weight.

17. The closure according to claim 16, characterized in that the lubricant is in the amount of about 1% by weight.

18. The closure according to claim 17, characterized in that the lubricant is selected from the group consisting of fatty acid amides, fatty acid esters, microcrystalline waxes, polyethylene glycols, primary amides, secondary amides, secondary bis-amides and mixtures thereof .

19. A method for making an inner liner for a plastic closure according to any preceding claim, characterized in that it comprises the steps of: (a) forming a pellet consisting essentially of a mixture of a matrix polymer, a barrier polymer and a compatibilizer to promote adhesion between the matrix polymer and the barrier polymer, and (b) compression molding the pellet to form an inner facing disk within which the heat and pressure of the compression molding form the polymer in the platelets that are essentially parallel to the disk.

20. The method according to claim 19, characterized in that it comprises the additional steps of: (c) providing a closure cap having a base and a peripheral edge defining an interior of the cap and a means at the edge to secure the cap to a container, and (d) securing the inner liner disc to the inside of the lid.

21. The method according to claim 20, characterized in that step (d) is carried out by compression molding the inner liner on the base.

22. The method according to claim 21, characterized in that step (a) comprises the step of forming the pellet such that the barrier polymer is substantially uniformly dispersed as a discontinuous phase of discrete particles within the matrix polymer.