MXPA00003600A - Multilayer plastic container and method of making the same - Google Patents

Abstract

The multilayer plastic container (10) comprises a neck portion (16), a body portion (20), adjacent the neck portion (16), forming a cylindrical wall (21), and a bottom portion (22) adjacent the body portion (20) and opposite the neck portion (16). The cylindrical wall (21) comprises a first layer (24) of PET, a layer (26) of EVOH adjacent the first layer (24) of PET and a second layer (28) of PET adjacent the layer (26) of EVOH. The EVOH has an average thickness which is greater near the neck portion (16) of the container than near the bottom portion (22) of the container (10).

Description

MULTICAPAS PLASTIC CONTAINER AND METHOD FOR DEVELOPING THE SAME BACKGROUND OF THE INVENTION .1 ^. Field of the Invention The invention relates in general to multilayer plastic containers. More specifically, the invention relates to improved multilayer plastic containers having at least three layers, one of the layers provides oxygen barrier protection and C02, which is useful for containing and storing beverages. 2 . Prior Art Multi-layer containers or containers having a layer of oxygen barrier material, for example EVOH, are well known in the art. The EVOH also provides a barrier protection to C02 which is useful for storing and containing carbonated beverages. These multilayer containers are made by blowing from preforms. The preforms are manufactured by a multilayer injection molding process, for example that described generally in U.S. Patent No. 4,511,528, which is incorporated herein by reference. A problem in the manufacture of these injection molded preforms is the flow control of the various materials. It is desired to make containers that have an internal layer and an outer layer of PET and a middle layer of EVOH, for products that require protection of barrier against oxygen and C02, such as carbonated beverages. EVOH is a relatively expensive material and is much more expensive than the PET that is used to make the inner and outer layers of the container. Consequently, multilayer containers that have an EVOH layer for oxygen barrier protection and C02 in general, have been used only with products that require a relatively thin layer of EVOH, approximately 0.0127-0.254 mm (0.5 to 1 thousandth of a inch). The preforms from which these generally known containers are made have an EVOH layer of approximately 0.1016-0.254 mm (4-10 mils). Containers that have thicker layers of EVOH, approximately 0.0129-0.0735 mm (2-3 mils), are thought to be cost prohibitive when compared to other types of containers, due to the cost of EVOH. The preforms for making these containers or containers must contain an EVOH layer that is approximately 0.508-0.762 mm (20-30 mils) thick. Additionally, the difficulty of controlling these relatively thicker layers of EVOH is more difficult than that of controlling relatively thin layers of EVOH. If the flow of EVOH is not exactly controlled when making the preform, the EVOH layer is not evenly distributed in the blown container. Therefore, the EVOH can be exposed to the internal or external surfaces of the bottle. If the EVOH is exposed to any of these surfaces, the EVOH that is expensive is wasted. In addition, if the EVOH is exposed to the internal or external surfaces of the containers, the EVOH can be de-scaled in the bottle, creating an undesirable appearance for a consumer. Additionally, if the EVOH is distributed unevenly around the bottom profile of the bottle, it can cause weakness in the bottom profile, which can make the bottle unstable and subject to deformation of the internal pressure. U.S. Patent No. 5,674,448 discloses a multilayer plastic preform to form multilayer plastic containers. The multilayer plastic preform has an internal layer and a barrier layer that is extruded and an outer layer that is formed on the extruded layers, by an injection molding process.

SUMMARY OF THE INVENTION One of the main objects of this invention is to provide a multilayer plastic bottle having a layer of EVOH, to provide barrier protection against oxygen and C02, which is about 0.0508-0.0762 mm (2-3) thousandths of an inch) thick. Another object of the invention is to provide a multilayer plastic bottle having a middle layer of EVOH, with a variable thickness, whereby the thickness of the EVOH layer has a uniform distribution of EVOH through the upper and middle sections of the body of the bottle and thins from the middle section of the bottle to form a Thinner layer of EVOH at the bottom of it. Another object of the present invention is to provide a process for making a multilayer preform, which can be used to make a multilayer bottle having a middle layer of EVOH, with a variable thickness, whereby the thickness of the EVOH layer is evenly distributed through the upper and middle part of the body of the preform and thins forming a thinner layer of EVOH near the bottom of the preform. Yet another object of the invention is to provide a plastic bottle that is cost-effective and provides oxygen and C02 barrier protection. Still another object of the invention is to provide a package that provides improved protection against ultraviolet light for the materials contained in the package. Still another object of the present invention is to provide a bottle having a thick layer of EVOH protection and still having a good and strong bottom profile.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a multilayer container according to the present invention. Figure 2 is a cross-sectional view of the package shown in Figure 1. Figure 3 is an enlarged drawing of a portion of the cross-sectional view shown in Figure 2. Figure 4 is a perspective view of a preform multilayers of the present invention. Figure 5 is a cross-sectional view of the multilayer preform shown in Figure 4. Figure 6 is a cross-sectional view of a multilayer preform having a defective middle layer. Figure 7 is a cross-sectional view of another multilayer preform having a defective middle layer.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to Figure 1, a multilayer plastic container is shown, specifically the bottle 10, according to the teachings of this invention. The bottle 10 has an upper end 12 having a crown finish 14 for receiving a crown cap (not shown) which seals the bottle 10 after it has been filled. Below the upper end 12 of the bottle 10 is a thinned neck portion 16. The thinned neck portion 16 is thinner near the upper end 12 of the bottle 10 and widens as it runs downward. The neck portion 16 is adjacent a rounded shoulder 18 which is rounded to a body portion 20 of the bottle 10. The body portion 20 forms a cylindrical wall 21. A bottom end 22 of the bottle 10 is adjacent to the body portion 20 of bottle 10. Bottom end 22 has a profile (See Figure 2) that is designed to withstand the internal pressure of carbonated beverages. As best illustrated in the cross-sectional views of the bottle 10 shown in Figures 2 and 3, the bottle 10 is constructed of three layers, namely, an inner layer 24, a middle layer 26 and an outer layer 28.

Both the inner layer 24 and the outer layer 28 are made of polyester (PET) The middle layer 26 is made of vinyl alcohol and ethylene (EVOH) The middle layer 26 of the EVOH provides barrier resistance against oxygen and 5 C02, which allows a product to be stored inside the bottle 10, for a period of time, without spoiling However, note that the EVOH is more expensive than PET and you want to use as little as possible EVOH in order to preserve the product during its entire life of pre-designed shelves. The bottle 10 of the present invention has a relatively thick layer of EVOH as compared to the generally known commercial multilayer containers, which have EVOH and are specially designed to be used with products that require a relatively greater amount of oxygen barrier protection, for example many of the European beers. The bottle 10 is blow molded from a preform 30 (Figure 4), using techniques conventional blow molding. The preform 30 is made with an injection molding process for example the injection molding process which is described in U.S. Patent No. 4,511,528, which is incorporated herein by reference. The process used to Making the preform 30 will be described in more detail below. The preform 30 has an upper portion 31 having a crown finish 32. Beneath the crown finish 32 is a rounded neck portion 33 which thins toward a body portion 34. At the lower end 35 of the portion of body 34 there is a bottom 36 of the preform 30. A cross section of the preform 30 according to the present invention is shown in Figure 5. In Figures 6 and 7 transverse sections of the preforms 40 and 50 are shown, respectively, which do not have the thinned EVOH layers and are not made according to the present invention. Referring to Figure 5, the preform 30 has a thinned layer of EVOH 37 between two PET layers 38 and 39. The process by which this preform 30 is processed is described in more detail below. The EVOH layer 37 is uniformly thick across most of the leather portion 34 of the preform, but thins as it reaches the lower portion 35 of the body portion 34. This thinning or tapering of the layer of EVOH provides the advantage of saving on EVOH material which is expensive, while still providing an excellent barrier layer to oxygen and C02, as well as a uniform distribution of the EVOH through the bottle 10 blown from the preform 30. B _ Also, the tapering or thinned end of the EVOH near the bottom of the preform creates a bottle having a thicker layer of PET in the rounded portion 70 and the bottom 22 5 of the bottle. The thicker layer of PET creates a stronger background profile that develops greater resistance to the internal pressures of carbonated beverages that are stored there. As shown in Figure 5, the preform 30 has a total length of about 10.16 cm (4.0 inches) and has a total, generally uniform, wall thickness of approximately 4,699 mm (185 mils). The thickness of the EVOH 37 layer at point A, approximately 4.44 cm (1.75 inches) from the of the preform 30, is approximately 0.635 mm (25 mils) thick around the circumference of the preform 30. At point B, which is approximately 5.72 cm (2.25 inches), from the top of the preform 30, the EVOH is approximately 0.508 mm (20 mils) thick around the circumference of the preform 30. At point C, which is approximately 6.35 cm (2.50 inches), from the top of the preform 30, the EVOH layer 37 is approximately 0.381 mm (15 mils) of thickness around the circumference of the preform 30.

At point D, which is approximately 6.99 cm (2.75 inches) from the top, the EVOH layer 37 is approximately 0.3048 mm (12 mils) thick around the circumference of the preform 30. At the point E, which is approximately 7.62 cm (3.00 inches) from the top, the EVOH layer 37 is approximately 0.254 mm (10 mils) thick around the circumference of the preform 30. At point F, which is about 8.26 cm (3.25 inches) from the top, the EVOH layer 37 is approximately 0.127 mm (5 mils) thick around the circumference of the preform 30. Note that the bottle 10, which is blown at Starting from the preform 30, it has a total, approximately uniform, total wall thickness of approximately 0.2794-0.3302 mm (11-13 mils) through the body portion 20 of the bottle 10. The EVOH layer within the bottle 10, like the c of EVOH inside the preform 30 thinly slims from the top of the body portion 20 towards the bottom 22 of the bottle 10. For example, the thickness of the EVOH layer 26 around the circumference of the bottle 10 in point A, which is approximately 16.76 cm (6.6 inches) from bottom 22 of bottle 10 (see Figure 2) is approximately between 0.055-0.0914 mm (2.2-3.6 thousandths of an inch) thick. The thickness of the EVOH layer 26 around the circumference of the bottle 10 at points B and C which are approximately 11.30 and 5.59 cm (4,450 and 2.20 inches) from the top of the bottle, respectively, is approximately 0.0305- 0.0432 mm (1.2-1.7 thousandths of an inch) thick and has an average thickness of approximately 0.0375 mm (1,475 thousandths of an inch) in thickness. The thickness of the EVOH layer 26 around the circumference of the bottle at point D, which is approximately 0.1130 cm (0.4450 inches) from the bottom 22 of the bottle 10, is approximately between 0.0279 and 0.4108 mm (1.1 and 2.0 thousandths of an inch thick) and has an average thickness of approximately 0.0343 mm (1.35 mils). The thinning or taper in the EVOH layer 26 near the bottom 22 of the bottle 10 helps to create a strong profile at the bottom, which can withstand the internal pressure created by a carbonated beverage. If there is too much EVOH 26 in a rounded portion 60 between the body portion 20 of the bottle 10 and the bottom 22, the rounded portion 60 may be weak and bulge when the bottle 10 is pressurized with a carbonated beverage. Figure 6 is a cross-sectional view of a defective preform 40 also having an EVOH layer 41 between two layers of PET 42 and 43. The EVOH layer 41 has a "tail of tail" 44 and forms a "cluster" of EVOH 46 near a bottom 45 of the preform 40. The preform 40 will not form a commercially acceptable container when blow molded and uses more EVOH than the preforms and bottles of the present invention. Figure 7 is a cross-sectional view of another defective preform 50 having an EVOH 51 layer between the two layers of PET 52 and 53. As shown, the EVOH layer 51 has a "cutter tail" 55. The preform 50 shown in Figure 7 will not form a commercially acceptable container when molded by blow. The "tail of the cutter" at the end of the EVOH stream is undesirable since when the preform is blown to form a bottle, the tail of the cutter causes inconsistencies in the blow molding process, for example the non-uniform distribution of the material. The non-uniform distribution of the material can cause a container that has a badly formed bottom profile, which in turn can cause weakness in the bottom of the bottle, being susceptible to deformation and non-uniformity. When preparing a preform by the injection molding process, one of the last stages of the process is called "packing" the preform, which includes adding more PET to the bottom of the preform without co-injecting more EVOH. Packing the preform helps distribute the EVOH and seal the EVOH inside the two PET layers. However, it has been found that with conventional co-injection molding techniques the packaging process creates the "tailings tails" 44 and 54 and the cluster 46 shown in Figures 6 and 7, in the preforms that have thicker layers of EVOH (approximately 0.508-0.762 mm (20-30 mils)). In the coinjection molding techniques used in Figures 6 and 7, the EVOH flows close at their maximum flow rates at different predetermined points. The preform 40 of Figure 6 is made by closing the EVOH stream for a predetermined time in the injection molding process, before packing the preform 40 with more PET. The preform 50 of Figure 7 is created by closing the EVOH stream at a time subsequent to that of the preform of Figure 6 and only just before the preform 50 is packed with additional PET. A solution to this problem was found in the new injection molding technique that uses a continuous flow of EVOH in which the flow of EVOH slows down, but does not stop. The PET current is continuous and never completely closed until the preform is packed. Some specific parameters, for example the stroke size of EVOH or the injection speed of EVOH, during the injection process, are controlled to achieve the tapered or tapered EVOH layer. This example is described below: Total Weight of the Bottle: 28.1 grams Material 1: Hoechst 86H Color CM 84-776-1 Material 2: Evalca LC-E105A Panorama Gral. Output B (EVOH) Cycle Time: 38.6 sec Injection Delay: 0.8 sec High Clamp Adjustment Injection: 6 sec Fast: 50.80 cm / 10 in / sec Packing: 0 sec Intermediate: 25.40 cm / 10 in / sec Maintenance: 3 sec Mold Protection: 225 PSI Cooling: 12 sec Speed Decrement 1: 49.53 cm / 19.5 in Extruder Delay: 1 sec Speed Decrease 2: 43.18 cm / 17 in Closure Limit: 37.39 cm / 14.72 in Speed Profile Injection ((PPEETT)) Aperture Limit: 66.04 cm / 26 in. Cushion: 0.25 cm / 0.1 in. Decrease in Speed: 58.42 cm / 23 in. Cushion: 0.51 cm / 0.2 in. Actual Quick: 53.34 cm / 21 in. X-fer: 0.89 cm / 0.35 in. Rapid: 50.80 cm / 20 in / sec Strike size 2.29 cm / 0.9 in. Rupture: 22.86 cm / 9 in / sec Speed 2: cm / in / sec High Tone: 40 ton. Speed 1: 3.81 cm / 1.5 in / sec Low Tone: 30 ton. Output B (EVOH) Ejector Adjustment Cushion: 0 cm / inch Ejection start: 50.80 cm / 20in X-fer: 0 cm / in Pulse (s): 1 Strike Size 1.14 cm / 0.45 in Retraction Limit: 0.08 cm / 0.03 in. Speed 1: 1.27 cm / 0.5 in / sec Retraction: 10.16 cm / 4 in / sec Speed 2: cm / in / sec Intermediate: 0.25 cm / 0.1 in.% Advance Speed 1: 9.39 cm / 3.7 / in / sec Filling Time: 3.2 sec Rapid Return: 1.27 cm / 0.5 in Residence 1: 0 sec Packing and Preservation of Pressure (PET) Speed of Feed 2: 9.39 cm / 3.7 in / sec High Fill Limit: 625 PSI Return: 10.54 cm / 4.15 in Packing: 14 sec Residence 2: 0.2 sec Packing: 375 PSI Maintenance: 0 sec Temperature Adjustment Maintenance: 0 PSI Nozzle: 288 C / 550 F Nozzle Valve: 32 C / 90 F Output B (EVOH) Zone 1: 288 C / 550 F High Filling Limit: 1000 PSI Zone 2: 288 C / 550 F Packing: 0 sec Zone 3: 288 C / 550 F Packing: 0 PSI Alarm Band: 20% Maintenance: 3 sec Temp. of Oil: 43 C / 110 F Maintenance: 400 PSI Exit B Nozzle: 199 C / 390 F RPM and Pressure (PET) Zone 1: 210 C / 410 F Decompression: 0.25 cm / 0 1 in Zone 2: 210 C / 410 F Stroke Size: 2.29 cm / 0 9 in Zone 3: 207 C / 405 F Screw Speed: 50 RPM Alarm Band: 20. Back pressure: 0 PSI Temp. of Oil: 32 C / 90 F Output B (EVOH) Warm-Up Cycles Before Decompression: 0.46 cm / 0.18 in Mold: 1: 288 C / 550 F After Decompression: 0.03 cm / O.Ol / in 2: 227 C / 440 F Stroke Size: 1.14 cm / 0.45 in 3: 277 C / 530 F Screw Speed: 150 RPM Back Pressure: 0 PSI Cycle Timers (PET) Cycle Limit: 50 sec Drying to 4 hrs. @ 160 C / 320 F High Injection: 8 sec. Cooler Temperature: 4 C / 40 F Filling: 1.95 sec Ejector Blocks: 3.18 cm / 1.25 in Packing: 14 sec Ambient Temperature: 23 C / 72 F Retention: 0 sec Color Adjustment: 4.7 Cooling: 18 sec Extruder Delay: 0 sec The injection molding process and the parameters set forth below describe how to make an injection molded preform of the present invention using Hoechst 86H PET resin, Evaica LC-E105 EVOH resin and CM 84-776- Color Matrix. 4 on a Cincinnati Milacron injection molding machine, which has been modified to add a second injection unit and use the PET barrel with a diameter of 4.13 cm (1.625 inches) and an EVOH barrel with a diameter of 1.80 cm (0.71). inches). As indicated in the above process specifications, the size of the PET shot or shot is 2.29 cm (0.90 inches) and the PET is injected into a preform mold through a 0.76 cm (0.30 inch) / seconds distributor. for 1.95 seconds. Subsequently, the pressure is maintained at 375 psi for 14 seconds to pack the preform. The PET cushion is 0.51 cm (0.20 inches) and the temperature of the PET barrel is approximately 288 ° C (550 ° F). The size of the shot or shot of EVOH is 1.14 cm (0.45 inches). The EVOH injection starts 0.80 seconds after the PET injection starts. The EVOH is injected into the mold of the preform through a distributor at a speed of 1.27 cm (0.50 inches) / seconds for 3.2 seconds. Later, Error * Unknown switch argumßnt.

The pressure of 400 psi is maintained for 3.0 seconds. The EVOH cushion is 0.0 cm (0.0 inches) and the barrel temperature of EVOH is approximately 204 ° C (400 ° F). Tapering or thinning is created by selecting the appropriate size of shot or shot, the speed of injection and the pressure to create the desired taper or thinning. One way taper is created is by simply selecting a smaller stroke size or shot and allowing the material to continue to flow through the nozzle as the injection pressure of the EVOH decreases from 400 psi to 0 psi. Alternatively or together with the above, the speed at which the EVOH is injected into the mold can vary from, for example, 1.27 cm (0.5 inches) / second to 0.64 cm (0.25 inches) / second during the EVOH injection to create a tapered EVOH layer. Note that the PET flow is continuous through the injection process and never completely closes, thus causing the desired EVOH distribution. By making it slower, but not closing it completely, the EVOH flow causes the preform 30 to have an EVOH layer that is thicker near the upper body portion 39 of the preform 30, and uniform across the middle section of the preform 30. the preform and then tapers to form a thinner layer of EVOH Error! Unknown switch argumßnt. near the bottom portion of the preform 30. (T ^ The tapered distribution of the EVOH still provides a uniform color throughout the bottle Importantly, the bottle 10 has a layer of EVOH 26 5 sufficient as barrier protection against oxygen and C02 and for products that require greater amounts of oxygen and C02 barrier protection.In addition, as described above in relation to the above process data, color has was added to the PET layers 38 and 39 used to form the preform 30 of this invention. The added color is highly concentrated so that the color I of the PET 38 and 39 in the blown bottle 10 is sufficiently dark to greatly reduce the color. contents of the bottle to exposure to light. It is important that the color used be of a high concentration so that a minimum amount of color is added, which will not affect the flow or resistance characteristics of the PET 38 and 39. In the preform 30, the color that is added is produced by Color Matrix Corporation of Cleveland, Ohio, and is known as color number 84-776-4. This color is added at such a low volume that the PET stream 38 and 39 contains approximately between 0.15% to 0.25% color. From the previous description, it will be evident that the plastic container of the present invention has Error! Unknown switch argu ent. various advantages, some of which have been described above and others will be inherent in the present invention. It is also understood that modifications can be made to the plastic package of this invention without departing from the teachings thereof. Consequently, the scope of the invention is only limited according to what the accompanying claims require.

Error! Unknown switch argument.

Claims (50)

1. CLAIMS: 1. A multilayer plastic container (10) comprising: a neck portion (16); a body portion (20), adjacent to the neck portion (16) and defining a cylindrical wall (21), and a bottom portion (22) adjacent to the body portion (20) opposite the neck portion (16); wherein the cylindrical wall (21) has a substantially uniform total wall thickness and comprises an outer layer (28), an inner layer (24) and an intermediate layer (26) between the outer layer (28) and the inner layer ( 24), and characterized in that the central axis of the intermediate layer (26) is essentially parallel to the cylindrical wall (21) and wherein the average thickness of the intermediate layer (26) of the cylindrical wall (21) tapers from the greater average thickness, in a portion near the neck portion (16) of the container (10) to a lower average thickness in a second position close to the bottom portion (22) of the container (10).
2. 2. The multilayer plastic container (10) of claim 1, wherein the intermediate layer (26) comprises an oxygen barrier material responsive to the Error! Unknown switch argument. humidity.
3. 3. The multilayer plastic container (10) of claim 2, wherein the moisture sensitive oxygen barrier material is EVOH.
4. 4. The multilayer plastic container (10) of claim 3, wherein the inner layer (24) and the outer layer (28) comprise PET. The multilayer plastic container (10) of claim 1, wherein the average thickness of the intermediate layer (26) in the cylindrical wall (21) in the first position is approximately 0.0375 mm (1,475 thousandths of an inch). The multilayer plastic container (10) of claim 1, wherein the average thickness of the intermediate layer (26) in the cylindrical wall (21) in the second position is approximately 0.0343 mm (1.35 mils). The multilayer plastic container (10) of claim 6, wherein the average thickness of the substantially uniform cylindrical wall (21) is approximately 0.279-0.330 mm (11-13 mils). The multilayer plastic container (10) of claim 1, wherein the intermediate layer (26) extends toward the bottom portion (22). Error! Unknown switch argument. 9. The multi-layer plastic container (10) of claim 1, wherein the intermediate layer (26) comprises a material selected from the group consisting of: nylon, plasticized polyvinyl alcohol, polyvinyl chloride, acrylonitrile, polyvinylidene and an oxygen scavenging material 10. The multilayer plastic container (10) of claim 1, wherein the inner layer (24) and the outer layer (28) have essentially the same thickness. 10 average. The multi-layer plastic container (10) of claim 2, wherein the package (1) is a container (10) for containing liquids. 12. A multilayer plastic container (10) 15 made from a co-injected multi-layer plastic preform (30), the package (10) comprises: a neck portion (16); a body portion (20), adjacent to the neck portion (16) and defining a cylindrical wall (21); and a bottom portion (22) adjacent to the body portion (20) opposite the neck portion (16); wherein the cylindrical wall (21) has a substantially uniform total wall thickness and 25 comprises an outer layer (28), an inner layer (24) and Error! Unknown switch argument. an intermediate layer (26) between the outer layer (28) and the inner layer (24), and characterized in that the average thickness of the intermediate layer (26) in the cylindrical wall (21) tapers from a greater average thickness in one first position close to the neck portion (16) of the container (10) to a lower average thickness in a second position close to the bottom portion (22) of the container (10). 13. The multilayer plastic container (10) of claim 12, wherein the intermediate layer (26) comprises an oxygen barrier material sensitive to moisture. I 14. The multilayer plastic container (10) of claim 13, wherein the moisture sensitive oxygen barrier material is EVOH. 15. The multilayer plastic container (10) of claim 14, wherein the inner layer (24) and the outer layer (28) comprise PET. The multilayer plastic container (10) of claim 12, wherein the average thickness of the intermediate layer (26) in the cylindrical wall (21) in the first position is approximately 0.0375 mm (1,475 thousandths of an inch). 17. The multilayer plastic container (10) of claim 12, wherein the average thickness of the layer Error! Unknown switch argument. intermediate (26) in the cylindrical wall (21) in the second position is approximately 0.0343 mm (1.35 mils). 18. The multilayer plastic container (10) of claim 12, wherein the intermediate layer (26) extends toward the bottom portion (22). The multilayer plastic container (10) of claim 12, wherein the average thickness of the cylindrical wall (21) is approximately 0.279-0.330 mm (11-13 mils). The multilayer plastic container (10) of claim 12, wherein the intermediate layer (26) comprises a material selected from the group consisting of: nylon, plasticized polyvinyl alcohol, polyvinyl chloride, acrylonitrile, polyvinylidene chloride and an oxygen scavenger material The multilayer plastic container (10) of claim 12, wherein the inner layer (24) and the outer layer (28) have essentially the same average thickness. 22. The multi-layer plastic container (10) of claim 13, wherein the package (10) is a container (10) for containing liquids. 23. A preform of multilayer plastic (30) to make a plastic container (10), the preform (30) Error! Unknown switch argument. comprises: an upper portion (31), a neck portion (33) adjacent to the upper portion (31), a body portion (34) adjacent to the neck portion (33) and an adjacent bottom portion (36) to the body portion (34) opposite the neck portion (33); the body portion (34) of the preform (30) has an inner layer (39), an outer layer (38) and an intermediate layer (37) between the inner layer (39) and the outer layer (38), and characterized in that the central axis of the intermediate layer (37) is essentially parallel to the body portion (34) of the preform (30) and wherein the average thickness of the intermediate layer (37) in the body portion (34) tapers from a greater average thickness in a first portion close to the neck portion (33) of the preform (30) to a lower average thickness in a second position close to the bottom portion (36) of the preform (30) . The preform (30) according to claim 23, wherein the intermediate layer (37) comprises a moisture-sensitive oxygen barrier material .. The preform (30) according to claim 24, wherein the material of Moisture sensitive oxygen barrier comprises EVOH. Error! Unknown switch argument. 26. The preform (30) according to claim 24, wherein the body portion (34) has an average thickness of about 4.70 mm (185 thousandths of an inch) and the average thickness of the intermediate layer (37) tapers from about 0.508- 0.635 mm (20-25 mils) near the neck portion (33) to approximately 0.127 mm (5 mils) near the bottom portion (36). 27. The preform (30) according to claim 24, wherein the body portion (34) has an average thickness of about 4,699 mm (185 mils), the intermediate layer (37) has an average thickness of about 0.635 mm (25 mils) in approximately 4.45 cm (1.75 inches) from the top portion (31) and tapers to an average thickness of approximately 0.127 mm (5 mils), at a distance of approximately 8.26 cm (3.25) inches) from the upper portion (31). The preform (30) according to claim 24, wherein the intermediate layer (37) comprises a material selected from the group consisting of: nylon, plasticized polyvinyl alcohol, polyvinyl chloride, acrylonitrile, polyvinylidene chloride and a scrubber material of oxygen. 29. The preform (30) according to claim 24, Error! Unknown switch argument. wherein the inner layer (39) and the outer layer (38) comprises PET. 30. A co-injected multilayer plastic preform (30) comprising: a neck portion (33); a body portion (34), adjacent to the neck portion (33) and a bottom portion (36) adjacent to the body portion (34), opposite the neck portion (33); wherein the body portion (34) has a substantially uniform total wall thickness and comprises an outer layer (38), an inner layer (39) and I an intermediate layer (37) between the outer layer (38) and • the inner layer (39), and characterized in that the thickness of the intermediate layer (37) in the body portion (34) tapers from a greater average thickness in a first portion close to the neck portion (33) of the preform ( 30) to a lower average thickness in a second position close to the bottom portion (36) of the preform (30). 31. The plastic preform (30) of claim 30, wherein the intermediate layer (37) comprises an oxygen barrier material sensitive to moisture. 32. The plastic preform (30) of the Error! Unknown switch argument. claim 31, wherein the intermediate layer (37) comprises EVOH. 33. The plastic preform (30) of claim 30, wherein the bottom portion (36) closes the body portion (34) and the intermediate layer (37) extends continuously through the bottom portion (36). ). 34. The plastic preform (30) of claim 30, wherein the intermediate layer (37) extends substantially uniformly through the bottom portion (36). 35. The plastic preform (30) of claim 30, wherein the inner layer (39) and the outer layer (38) completely enclose the intermediate layer (37). 36. The plastic preform (30) of claim 31, wherein the average thickness of the intermediate layer (37) around the circumference of the neck portion (33) is approximately 0.635 mm (25 mils). 37. The plastic preform (30) of claim 31, wherein the average thickness of the intermediate layer (37) around the circumference of the body portion (34) in the position adjacent to the neck portion (33). is approximately 0.508 mm (20 Error! Unknown switch argument. thousandths of an inch). 38. The plastic preform (30) of claim 31, wherein the average thickness of the intermediate layer (37) around the circumference of the body portion (34) in the position adjacent to the bottom position (36). it is approximately 0.127 mm (5 mils). 39. The plastic preform (30) of claim 31, wherein the inner layer (39) and the outer layer (38) comprise PET and the intermediate layer (37) comprises EVOH: 40. The plastic preform (30) of claim 31, wherein the thickness of the intermediate layer (37) tapers from about 0.508-0.635 mm (20-25 mils) near the neck portion (33) to about 0.127 mm (5 mils) ) near the bottom portion (36). 41. The plastic preform (30) of claim 31, wherein the thickness of the intermediate layer (37) tapers from approximately 0.635 mm (25 mils) to approximately 4.45 cm (1.75 inches) from an upper part of the preform (30) to approximately 0.127 mm (5 mils) in approximately 8.26 cm (3.25 inches) from the top of the preform (30). Error! Unknown switch argument. 42. A method of injection molding a plastic preform (30) comprising a neck portion (33), a body portion (34) defining a cylindrical wall portion adjacent to the neck portion (33) and a portion bottom (36) adjacent to the body portion (34), opposite the neck portion (33), wherein each of the cylindrical wall and the bottom portion (36) comprises an outer layer (38), an inner layer (39) and intermediate layer (37) between outer layer (38) and inner layer (39), the method comprises the steps of: a) initializing a flow of a first material to form both the inner layer ( 39) as outer layer (38); b) initializing a flow of a second material to form the intermediate layer (37); and c) terminating the flow of the second material after finishing the flow of the first material. 43. The method according to claim 42, further comprising the step of continuing to apply pressure to the second material after finishing the flow of the second material. 44. The method according to claim 41, further comprising the steps of: d) terminating the application of pressure to the second Error! Unknown switch argument. material; and e) applying pressure to the first material continuously from the termination of the flow of the first material until after the application of pressure to the second material is completed. 45. The method according to claim 44, further comprising the step of varying at least one parameter of the plurality of injection parameters of at least one of the first material and the second material., for tapering the intermediate layer (37) from a position adjacent the neck portion (33) to a position adjacent the bottom portion (36). 46. The method according to claim 45, wherein the step of varying at least one parameter of the plurality of parameters of at least one of the first material and the second material comprises the step of varying a flow rate of at least one of the first and second materials. 47. The method according to claim 44, wherein the step of varying at least one parameter of the plurality of injection parameters of at least one of the first and second materials comprises the step of varying the injection pressure of at least one of the first and second materials. 48. The method according to claim 45, in Error! Unknown switch argument. wherein the step of varying at least one parameter of the plurality of injection parameters of at least one of the first and second materials comprises the step of varying a firing or discharge size of at least one of the first and second materials. 49. The method according to claim 45, wherein the step of varying at least one parameter of the plurality of parameters of at least one of the first and second materials comprises the step of varying the injection temperature of at least one of the first and second materials. 50. The method according to claim 45, wherein: d) the step of initializing a flow of the first material comprises initializing a flow of the PET material; and e) the step of initializing a flow of the second material comprises initializing a flow of the EVOH material. Error! Unknown switch argumßnt.