MXPA99007164A - Enhanced shelf-life pressurized container with ribbed appearance - Google Patents

Abstract

Pressurized plastic container (40) having the appearance of ribs but with substantially reduced creep and without delamination, i.e., having an enhanced shelf-life compared to prior art ribbed containers. In multilayer containers, the scribe lines reduce delamination of the layer structure so as to avoid loss of transparency and/or barrier properties. The reduction in creep is particularly useful for smaller volume containers having a greater surface area to volume ratio.

Description

PRESSURIZED VESSEL WITH LIFE IN THE IMPROVED SHELL WITH A ROCKED APPEARANCE.

FIELD OF THE INVENTION The p. This invention is directed to pressurized plastic containers, such as containers for carbonated drinks, polyester, transparent, and more particularly containers that have the appearance of grooves but have a reduced tendency to diagonally shift and / or delaminate. .

BACKGROUND OF THE INVENTION Transparent polyester carbonated beverage containers are widely used around the world and have and have significantly replaced prior art glass containers for soft drinks. The plastic containers are substantially lighter in weight, and are resistant to fragmentation. The most commonly used polyester, polyethylene terephthalate (PET), provides superior clarity, recyclability and manufacturing ease at a competitive price.

REF .: 30938 Despite the substantial uniformity in the material used to manufacture plastic containers for carbonated beverages, each beverage manufacturer would prefer to distinguish the visual appearance of their bottles from competitor bottles. One way to accomplish this is by applying a distinctive label to the container. Another way is to customize the contour of the container itself to provide a distinguishable visual appearance that consumers could recognize. The accents are a feature that can be used with almost endless variations, to customize the appearance of a container. The grooves may be singular, plural, extending radially inwardly or outwardly relative to the circumference of the container, and otherwise form patterns that can make the container distinguishable. The grooves can also provide structural reinforcement to prevent deformation or warping of the container.

A problem with the contour grooves of the prior art in pressurized containers is their tendency to "elastic deformation" (movements) under pressure. This produces an increase in the volume of the container and an undesirable pressure loss in the carbonated beverage. The problem of elastic or progressive deformation is illustrated for two prior art containers in Figures 1-4. Both are representative of the containers for carbonated drinks of transparent PET, known for half a liter of volume, one has internal grooves and the other has external grooves.

Figure 1 shows the container 10 of the prior art having ten grooves 12 positioned vertically in the panel 14 and sections 16 of the flange. The grooves extend radially inward (lowered) from the circumference 18 of the container as shown in Figure 2 (a cross section through the portion 14 of the panel). The solid line of Figure 2 is the circumference 18 of the panel after blow molding, and before filling with a carbonated beverage. The 10 grooves 12 of relatively large radius are arranged symmetrically around the circumference 18 of the panel, which is defined by the radius R (the radial distance of the vertical centerline CL of the container). After filling, the panel undergoes elastic deformation in a radially outward direction, such that inwardly extending grooves tend to flatten around the circumference (i.e., the grooves are substantially removed) the panel forms a circumference 18 'of panel substantially cylindrical that has a radius R ^, which is somewhat larger than R. This is clearly undesirable from the point of view of the beverage company for at least two reasons. First, the container loses a significant contour characteristic which attempts to distinguish this container from the company from other containers in the market. Second, the increase in the diameter of the container produces an increase in volume resulting in the container, which generates a lower pressure in the upper space, that is, the volume of the pressurized air above the liquid at the upper end of the container. This reduction in the pressure of the upper space generates gases in the pressurized liquid (carbonation) that leaves the liquid and enters the upper space, resulting in an undesirable caldera at the level of carbonation. The beverage company would prefer to maintain a tighter control over the pressure of carbonation in order to provide an optimal product to the consumer. In relation to this, the company establishes a shelf life for its product, which specifies a maximum loss in carbonation pressure over time. In effect, the volume increases due to the expansion of the grooves, which reduces the shelf life of the product. This increases the cost to the manufacturer and now either selling the product in a shorter period or replacing the product whose time has expired with a fresh product on the shelves of the retail stores.

Figure 2A is an enlarged fragment of the cross-section of the panel, showing more clearly the circumference of the original outer panel 18 to Rl7 and the circumference 18 'of the enlarged outer panel in R.-after filling. The circular extension between the grooves 12 is defined as a circumferential distance in degrees between the center points of two adjacent grooves. Each groove is defined by a relatively large radius R ^, for example, 0.254 to 0.508 cm (0.100 to 0.200 in). A radius R < plus small, smooth connects the opposing edges of the groove to the circumference 18 of the container.

Figures 3-4 show a container 20 of the alternative prior art which is the same as the first container (of figures 1-2) but where the vertical grooves 22 extend radially outward (projecting), instead of into. Note that similar characteristics have been given similar number of references in relation to the first container, but in a range of 20-29 opposed to 10-19. In this mode, the circumference 28 of the original panel is in Ri. After filling, the circumference 28 'of the panel has experienced a net total radial increase to R:?. With the grooves again flat around the circumference. Again, each groove has a relatively large radius R_ and a relatively small combined radius R: j.

Another significant problem caused by the movement of the grooves in the pressurized containers of previous multiple layers, is the delamination. Often, a manufacturer will like to provide a wall of multiple layers in some portion or in the entire container to influence the total cost of the material, the thermal resistance, the barrier properties (for example the loss of C02 and / or the entry of oxygenate), the processability, and so on. In particular, small size containers, which have a high surface area to volume ratio, often can not be produced with an acceptable shelf life unless a barrier layer is included. However, in multi-layered pressurized containers with grooved contours, when the grooves move under pressure (deform) to become substantially flat around the circumference of the panel, this results in the delamination (separation) of the layers. The separation of the layers is undesirable since it can lead to loss of transparency, structural weakness, loss of barrier properties, and so on. The separation of the layers can be a particular problem in multi-layered containers without chemical bonding or adhesives for joining the layers, for example, recyclable containers in which a relatively weak diffusion of the hydrogen bonds maintains the structure of the layers during the use, but allows easy separation when cut (during the recycling process).

Then, there is a need for a pressurized container for carbonated drinks and the like which can be customized or made to taste, but which avoids the above problems of pressure loss and delamination.

WO 96/13436 (Krishnakumar) describes a hot-fill container with vacuum panels which moves to relieve the reduced pressure after hot filling. Post-grooves are provided in the grooved walls whose grooves are designed to allow a maximum opening movement of the panels to vacuum.

BRIEF DESCRIPTION OF THE INVENTION The present invention is directed to a method for manufacturing and to the resulting pressurized plastic containers having the visual appearance of grooves, but resisting elastic deformation.

The use of wide grooves that show deformation Elastic under pressure is avoided and replaced with a plurality of "striped" lines. A line of stripes is a thin band that projects or is molded into a blow mold by expanding a preform or pari is polymer into a narrow recess (groove) that has been cut ("scratched") on the wall of the mold cavity. The polymer can fill all or a portion of the groove. Alternatively, a line of stripes may be formed by expanding the polymer over a raised narrow band formed in the wall cavity to produce a recessed line in the container.

Stripe lines can withstand pressurization, or a significant reduction in elastic deformation and resist deslammation in multi-layered containers. These lines can thus provide a visual appearance of a groove, but provide superior efficiency in pressurized applications, particularly in containers of smaller volume, where elastic deformation can be a significant problem.

By way of example, three lines of parallel stripes placed in a relatively close proximity provide the visual appearance of a relatively deep contour groove. By providing the streak lines in a substantially vertical position in the container, and by deriving the upper and lower ends of the streak lines to form substantially rounded end portions, which produces a visual effect similar to a relatively deep bore groove, but without coinciding in the problem of elastic deformation, loss of pressure and / or delamination of the contour grooves, of the prior art.

As an example of the reduction of elastic deformation, a commercial, disposable, half-liter (500 cmJ) carbonated beverage container with grooves was carbonated to 4 volumes of CO; and kept at 38 ° C for 24 hours. It exhibited an increase in diameter (in the section of the panel that has the grooves) of 2.2o, producing a significant reduction in carbonation during this short period of time. In contrast, a half-liter container of similar dimensions but with lines in shapes Stripes instead of grooves, had only an increase of 1.2? in the diameter under the same conditions. That is a significant improvement in terms of extended shelf life. The loss of pressurization becomes a problem that increases with the increase in surface area in relation to the ratio of surface area to volume. As the present invention is particularly useful in providing a pressurized plastic container having a surface area at a volume ratio of at least about 720 cirr / L (c "per liter) with a loss of carbonation not greater than 17.5% during a period of 90 days.That surface area to volume ratio is typical for relatively small containers that have volumes of half a liter (1) or less.In a multi-layer container of similar size, the maximum carbonation loss of 17.5 ? It can be achieved in a period of 120 days or more.

The thickness of the container wall can have a significant effect on the amount of pressure loss over time for certain container designs. Is another one It is an aspect of the present invention to provide a pre-sized plastic container having a plurality of dashed lines of a narrow width W that gives a visual appearance of grooves in a portion of the container having a wall thickness T, wherein a proportion of W: T this in the range of approximately 1.5: 1 to 3.0: 1.

The single-layer or multi-layer containers of this invention are generally transparent and have a major polymer component which will typically be a polyester, such as polyethylene terephthalate (PET) and / or polyethylene naphthalate (PEN), which includes homopolymers, copolymers and mixtures thereof. In a multi-layer container, PET and / or PEN polymers commonly form inner and outer layers with one or more internal layers of recycled polymer (such as PET that have already been consumed), a barrier layer of CO and / or oxygen , a resistant thermal layer, etc. Recyclable multi-layer containers are made from these polymers with diffusion of hydrogen bonds to maintain the adhesion of the layers during use (as opposed to adhesive or chemical bonds). The lines of line are particularly useful in such recyclable containers to prevent delamination.

Magnetically flexible thin-walled containers made of polyesters and other orientable polymers typically have a mat thickness in a section of the panel in a range from about 0.02 to 0.040 cm (0.008 to 0.016 in), where the panel section has been biaxially oriented at an average stretch ratio in a range of 10: 1 to 18: 1. In such containers, the lines of individual stripes may have a width in a range from about 0.030 to 0.100 cm (0.012 to 0.040 in). Stripe lines may have a radial depth, extending outwardly from the circumference of the outer panel (or alternatively extending radially inwardly from the circumference of the inner panel) or from about 0.00254 to 0.0254 cm (0.001 to 0.010 in.) . Three lines of substantially parallel and closely spaced stripes provide a particularly pleasing appearance, the three sets of lines may have an angular extent, measured as a distance between the lines. central points of the two outer lines in a range from approximately 3 to 10 °.

Stripe lines can be provided in one or more lines, with several alignments (vertical, horizontal, diagonal) and with several spacings between the lines, to provide an almost infinite variety of personalized details in a given container.

These and other features and advantages of the present invention will be described more particularly with respect to the following detailed descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS. Figure 1 is a front elevational view of a prior art container with grooves in the form of recesses; Figure 2 is a schematic cross-sectional plan view taken along line 2.2 of Figure 1, showing the circumference of the panel before (solid line) and after (dashed lines) filling it with a carbonated liquid: Figure 2A is an enlarged fragmentary cross-sectional view of a portion of the section of the panel seen in Figure 2; Figure 3 is a front elevational view of a prior art container with projecting grooves; Figure 4 is a schematic cross-sectional plan view taken along line 4-4 of figure 3, showing the panel circumference before (solid lines) and after (broken lines) filling with a carbonated liquid; Figure 4A is an enlarged fragmentary cross-sectional view of a portion of the panel section seen in Figure 4; Figure 5 is a front elevational view of a container according to a first embodiment of the present invention. Figure 5A is a fragmentary, fragmentary, cross-sectional view of a portion of the panel section of the container of Figure 5, showing multiple layers; Figure 6 is a plan view of the schematic cross section taken along the line 6-6 of figure 5 showing the circumference of the panel that does not change substantially before and after filling; Figure 6A is a fragmentary, enlarged, cross-sectional view of a portion of the panel section seen in Figure 6; Figure 6A 'is a fragmentary, enlarged, cross-sectional view of a portion of the panel section of an alternative embodiment; 6A "is a fragmentary, enlarged, cross-sectional view of a portion of the panel section of another alternative embodiment; Figure 7 is a front elevational view of a container according to a second embodiment of the present invention, having a central part contoured and separated from the groups of three lines of vertical stripes, the lines of stripes in a set have different lengths which provides a rounded contour at the ends; Figure 8 is a front elevational view of a container according to another embodiment of the invention, having single, separate, vertical stripes lines fusing with the rim and the base portions of the container; Figure 9 is a front elevational view of a container according to another embodiment of the invention, having separate sets, spaced from three lines of stripes placed horizontally in the section of the panel; Figure 10 is a front elevation view of a container according to another embodiment, having a pair of dashed lines, which form a spiral around the section of the panel; and Figure 11 is a cross-sectional view of a blow mold of the container.

DETAILED DESCRIPTION OF THE INVENTION Figure 5-6 illustrate a first embodiment of the multi-layer container of the present invention. This container 40 has a visual appearance very similar to the containers 10 of the prior art, 20 of figures 1-4 but without the large diameter grooves 12, 22 (of the previous containers) which deform elastically and result a loss of pressurization that leads a reduced life on the shelf. Instead of this the container 40 has a set of lines of vertical stripes in separate groups of three, which converge at their upper and lower ends to provide a contour similar to that of the grooves. The circumference of the container (which includes lines of stripes) undergoes a less significant elastic deformation and thus the container has an improved shelf life. In addition, the multilayer container 40 resists delamination.

More specifically, the container 40 (Figure 5-6) is a half liter (1/2 L) vessel having a height of 18,415 cm (7,250 in.) And a maximum panel diameter of 7. 1628 cm (2820 in). In this embodiment, the container has multiple layers 38, 39, 41, 42, 43, (see Figure 5A) throughout its entire length that includes the inner 41 and outer 43 layers of the new bottle grade PET homopolymer, a central core layer 42 of Recycled post-consumer PET (PC-PET) and intermediate layers 38, 39 of EVOH (barrier material). The total thickness of the wall in the panel portion is 0.028 cm (0.011 in); the inner and outer layers each have a thickness of 0.0061 cm (0.0024 in), the core layer has a thickness of 0.015 cm (0.0058 in) and the barrier layers each have a thickness of 0.0005 cm (0.0002) plg). Note that in Figures 6-6A the multiple layers of the panel are not shown to simplify the drawings. The container includes a top neck finish 44 having a top opening end 45, exterior threads 46 for attaching a screw cap (shown nc) and a flange 47 projecting by marking the lower end of the neck finish. Below the neck finish there is a flange portion 48 that increases an outer diameter that moves downward to a substantially cylindrical panel section 49. Below the section of the panel there is a portion 50 of integral base, which includes 5 legs 51 projecting downwards which end at the feet 52, then on which the bottle rests. Between the legs there are substantially hemispherical portions 53. This type of bottle design for carbonated beverage containers is well known in the art.

According to the present invention there are provided substantially along the entire length of the section of the panel and in the lower half of the section of the rim, ten sets 60 of three lines 61 of vertical stripes which provide an appearance in form of custom grooves for the container. Stripe lines, best shown in the cross section in Figures 6 and 6A, are formed in the blow mold by forming (e.g. by cutting) narrow channels (or streak lines) on the surface of the metal cavity of the blow mold (see figure 11). A thermoplastic preform 2, as is known in the art, is axially heated and stretched (by the stretching rod 3) and radially expanded (by a pressurized fluid 4) in the blow mold (5), after which the walls of the expanding preform come into contact with the wall 6 of the mold cavity and assume the shape thereof. In this case, the panel 7 and the flange sections 8 adopt the narrow lines or channels 9 formed on the inner surface of the cavity, to form lines of stripes 61 projecting slightly outwardly on the outer surface 62 of the container.

In this mode the lines of vertical stripes are formed in sets of three, relatively closely spaced (proximal) and converge at their upper and lower ends 63, 64 to form an outline rounded. As shown in Figures 6 and 6A, there are ten groups 60 of dashed lines, evenly spaced around the circumference 66 of the panel; the circumference of the panel is in the radius R and the lines extend to a distance D of radial, relatively small outwardly from the circumference 66 of the panel. The angular extension A between each set of dashed lines is approximately 36 ° (360 - ^ - 10 = 36 °); A is the distance between the center lines of the adjacent sets, as shown. The distance between the center lines of the adjacent dashed lines (in a set) is defined by the angular extension B approximately 5o. The width W of a particular streak line is approximately 0.076 cm (0.030 in.). The radial depth D of the portion of the striped lines projecting on the circumference of the panel is approximately 0.013 cm (0.005 in). The thickness T of the side wall is approximately 0.028 cm (0.011 in). The dimensions identified above are representative of a particular container but do not attempt to limit it.

The present half-liter container is designed to be filled with a carbonated beverage at 4.0 volumes (initial pressure of carbon dioxide in the liquid). It has been found that this container undergoes a less significant radial elastic deformation and therefore has an extended shelf life (compared to similar prior design containers with grooves). In this case the shelf life is defined as the time it takes for the sealed and pressurized vessel to suffer a predetermined loss of maximum percentage of carbonation pressure. In addition, the container does not undergo substantially delamination which would result in a loss of pressurization or transparency, during this time. For a single-layer container, the maximum loss of carbonation pressure of not greater than 17.5% over 90 days is desirable; for multi-layer containers, the same maximum pressure loss can be achieved up to 120 days or more.

The use of dashed lines in place of the flutes of the prior art is particularly useful in containers having multiple layers and they have a surface area to volume ratio of at least about 580 cpr / L. Such containers typically have a volume of 1 liter (L) c less, and more particularly in the range of 0.75 to 0.20 L. Even more preferred is the use of striped lines in containers of half a liter or less, which have a surface area to volume ratio of approximately 720 cpr / 1 or more. The thickness of the wall of such containers made of biaxially oriented polymers such as polyester or the like, is in the range of about 0.020 to 0.040 cm (0.008 to 0.016 in.) And more preferably about 0.025 to 0.033 cm (0.010 to 0.013 in.). The average biaxial stretch ratio in the container panel portion is typically in the range of about 10-18, and more preferably about 12-15. Such containers show an increase in diameter in the portion of the container having striped lines, of at least about 25% less, and more preferably at least about 40% less compared to the same portion of the grooved container.

The relative dimensions of the striped lines will depend on the circumference of the panel section, the thickness of the wall, the level of the initial pressurization, and the desired shelf life. In a preferred embodiment a polyester container of the type described preferably has dashed lines having a width W in the range of about 0.030 to 0.076 cm. (0.012 to 0.030 in.) And a depth D in the range of about 0.005 to 0.010 cm (0.002 to 0.004 in.), In a panel section having a wall thickness T in a range of about 0.025 to 0.030 cm (0.010 a) 0.012 in).

Figure 6A 'shows a cross sectional portion of an alternative panel section 49', wherein the lines 61 'of stripes have a rounded or wavy profile, opposite the substantially rectangular profile in Figure 6A. The rounded profile in Figure 6A 'will typically be a result of blow molding an orientable polymer such as PET, at a relatively high level of orientation, such as a biaxial stretch ratio of at least 12: 1. The striped lines are rounded even when the Narrow grooves in the mold cavity are substantially rectangular, because the polymer resists full filling of the corners of the grooves and has a tendency to meet at some rate when the blowing pressure is released. For example, narrow channels in the mold cavity can have a width of 0.066 cm (0.026 in) and a depth of 0.015 cm (0.006 in) while the resulting striped lines have a width of less than 0.061 cm (0.024 in). and a depth less than 0.005 cm (0.002 in.), for a panel section having a wall thickness of 0.030 cm (0.012 in.). A rounded contour is more typically achieved with a width / thickness ratio of approximately 2; if the width / thickness ratio is increased to 6 or 7 it is more likely to have a rectangular profile (ie, a more complete filling of the corners) as shown in Figure 6A. However, in addition to the stripe line dimensions and the mold, the resulting shape also depends on the process conditions and the particular polymer.

Figure 6A '' shows another profile 61 '' of lines of alternative stripes, in section 49 '' of panel, where Stripe lines have a multiple-sided shape. In this example, the striped lines have three faces c flat surfaces, a lower surface and two opposite side wall surfaces, each at an acute angle with respect to the bottom surface; This provides three reflective surfaces for improved light reflection.

Several other alternative modalities are shown in Figure 7-10.

Figure 7 shows an alternative container 70 having an outline in the middle part, i.e. a constriction 71 in the circumference 72 of the panel at approximately the average height of the panel of the container. This type of feature is commonly used to customize a visual appearance of the container. This container also includes ten sets 74 of line 75 of vertical stripes arranged in a set of three, similar to the embodiment of figure 5. However in this case, the upper and lower ends 76, 77 of each group of dashed lines do not converge, instead the central line 75b line extends vertically more - l l ¬ beyond the terminal ends of the two outer striped lines 75A, 75C in the group. This longitudinal profile in scalar form at the upper and lower ends provides the visual appearance of a rounded end portion.

Figure 8 shows another embodiment in which a container 80 has a slightly recessed side wall portion 81 extending from the middle portion of the rim to a top base portion (upper and lower limit, 82, 83). Within that recessed portion there are separate, unique striped lines 85 that extend vertically from one end of the recessed portion to the other. The striped lines are in the same circumference as the adjacent flange 86 and the upper base portions 87.

In yet another embodiment shown in Figure 9 the container 90 has three sets 92 of lines of horizontal stripes with three lines 93 of stripes per set. Again, these provide the visual appearance of a wider groove, but with reduced delamination and elastic deformation.

Figure 10 shows yet another embodiment of the container 100 having a pair 102 of lines 103 of stripes which are spirally around the panel outline, are positioned at an angle with respect to the central line CL of the container.

As shown, the striped lines have a variety of alignments of horizontal, vertical or diagonal alignments, groupings and patterns, resulting in different visual effects. In a substantially transparent container, the lines of narrow stripes refract the light passing through the side wall of the container, to a different degree than the adjacent portions of the side wall. This difference in refraction gives striped lines the appearance of a shadow, which can be used to form the visual appearance of either a projection, of either a groove of a wide angle of projection or of a recess. Because the striped lines are radially outward (or inward) with respect to the circumference of the panel, the refractive point is different with respect to the adjacent portions of the circumference of the panel. As is known, refraction describes the deflection from a straight path suffered by a ray of light or wave chosen when it passes obliquely from one medium (like air) to another (like plastic) in which its speed is different.

CONSTRUCTIONS AND ALTERNATIVE MATERIALS There are numerous preform and container constructions, and many different injection moldable materials (thermoplastics) which can be adapted for a particular food product and / or for packaging, filling and manufacturing processes. Additional representative examples are given below.

The thermoplastic polymers useful in the present invention include polyesters, polyamides and polycarbonates. Suitable polyesters include homopolymers, copolymers or blends of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polypropylene terephthalate (PPT), polyethylene naphthalate (PEN) and a cyclohexane / PET dimetanol copolymer, known as PETG (available from Eastman Chemical, Kingsport, TN). Suitable polyamides (PA) include PA6, PA6, 6, PA6.4, PA6, 10, PA11, PA12, etc. Others Useful thermoplastic polymers include acrylic / imide polymers, amorphous nylon, iPAN ^ polyacrylonitrile, polystyrene, cpstallable nylon (MXD-6), polyethylene (PE) polypropylene (PP), and polyvinyl chloride (PVC) c) Polyesters based on terephthalic acid and isophthalic are commercially available and convenient.The hydroxylic compounds are typically ethylene glycol and 1,4-d- (hydroxymethyl) -cyclohexane.The intrinsic viscosity for phthalate polyesters is typically in the range of 0.6 to 1.2 and more particularly from 0.7 to 1.0 (for the o-chlorophenol solvent), 0.6 corresponds to a viscosity for a molecular weight of 59,000 and 1.2 at a viscosity for an average molecular weight of 112,000.In general, the phthalate polyester may include polymeric bonds , side chains and end groups not related to the formal precursors of a phthalate polyester previously specified Conveniently, at least 90% 0 in mol terephthalic acid and at least 90% in mol are a glycol or aliphatic glycols, especially ethylene glycol.

Post-consumed PET (PC-PET) is a type of recycled PET prepared from PET and other recyclable plastic containers that have been or have been returned by consumers for a recycling operation, and has now been approved by the FDA for used in certain food containers. It is known that PC-PET has a certain level of intrinsic viscosity (ID), moisture content and contaminants, for example, typical PC-PET (which has a flake size of about half an inch maximum) has an average intrinsic viscosity of approximately 0.66 dl / g a relative humidity of less than 0.25% and the following levels of contaminants: PVC < lOOppm Aluminum < 50 ppm Olefin Polymers (HDPE, LDPE, PP): < 500 ppm Paper and level: < 250 ppm colored PET: < 2000 ppm Other contaminants: < 500 ppm The PC-PET can be used alone or in one or two layers to reduce the cost of other benefits.

Also useful as a base (structural) polymer and as an oxygen barrier layer and / or thermally resistant is a packaging material with physical properties similar to PET, called polyethylene naphthalate (PEN). The PEN provides an improvement of 3-5X times the barrier property and an improved thermal resistance at some additional cost. Polyethylene naphthalate (PEN) is a polyester produced when the dicarboxylate of dimethyl-2,6-naphthalene (NDC) is reacted with ethylene glycol. The PEN polymer comprises repeated units of ethylene 2,6 naphthalate. The PEN resin is available and has an inherent viscosity of 0.67 dl / g and a molecular weight of about 20,000 from Amoco Chemical Company, Chicago Illinois. The PEN has a transition temperature of Tq of about 123 ° C and a melting temperature Tr of about 267 ° C.

Oxygen barrier layers include ethylene / vinyl alcohol (EVOH), PEN, polyvinyl alcohol (PVOH), polyvinyl chloride (PVDC), nylon 6, crystallizable naylon (MXD-6), LCP (liquid crystal polymer), nylon amorphous, polyacrylonitrile (PAN) and styrene acrylonitrile (SAN).

The intrinsic viscosity (I.V.) has an effect on the processability of the resins. Polyethylene teftalate having an intrinsic viscosity of about C.8 is widely used in the carbonated beverage industry (CSD). Polyester resins for various applications may vary from about 0.55 to about 1.04, and more particularly from about 0.65 to 0.85 dl / g. The intrinsic viscosity measurements of the polyester resins are made according to the procedure of ASTM D-2857, employing 0.0050 ± 0.0002 g / ml of the polymer in a solvent comprising o-chlorophenol (melting point 0 ° C), respectively 30 ° C The intrinsic viscosity (IV) is given by the following formula: I.V. = (ln (V, _ J! l./V.1 L) / C Where: Vso? N. It is the viscosity of the solution in any unit: Vso :. It is the viscosity of the solvent in the same units; C is the concentration in grams of the polymer per 100 ml of solution.

The blown body of the container should be substantially transparent. A measure of transparency is the percentage of optical clarity for the light transmitted through the wall (HT) which is given by the following formula: Where Y is the diffuse light transmitted by the specimen, and Y5 is the specular light transmitted by the specimen. The diffuse and specular light transmission values are measured according to ASTM method D 1003, using any standard color difference measurement such as model D25D3P manufactured by Hunterlab, Inc. The body of the container shall have a percentage of clarity optical (through the panel wall) of less than about 10% and more preferably less than about 5%.

The body forming portion of the preform should also be substantially amorphous and transparent, having a percentage of optical clarity through the wall of not more than about 10 'and more preferably not more than 5%.

The container will have varying levels of crystallinity in various positions along the height of the bottle from the neck finish to the base. The percent crystallinity can be determined according to ASTM 1505 as follows: % crystallinity = [(ds-da) / (dc-da)] X 100 where ds = density of the sample in g / cirr, da = density of an amorphous film of 0% crystallinity and dc = density of the calculated crystal of the parameters of the unit cell. The portion of the container panel is usually stretched as much as possible and therefore will have the highest percentage of average crystallinity.

Additional increments in crystallinity can be achieved by adjusting the heating to provide a combination of thermally induced and stress induced crystallization. The thermally induced glass is achieved at low temperatures to preserve transparency, ie to keep the container in contact with a blow mold at or at a temperature. In some applications, a high level of crystallinity on the surface of the side wall is sufficient.

As a further alternative embodiment, the performa may include one or more layers of a material that extracts or removes oxygen. Suitable oxygen scavenging materials are described in U.S. Patent No. 08 / 355,703 filed on December 14, 1994 by Collette et al., Entitled "Oxygen Scavengmg Composition For Multilayer Preform And Container." Which is incorporated here as a reference in its entirety. As described therein, the oxygen scavenger or scavenger can be an oxidizable organic polymer, catalyzed with metal, such as a polyamide or an antioxidant such as phosphite or phenolic. The oxygen scrubber can be mixed with PC-PET to accelerate the activation of the scrubber. The oxygen scavenger can advantageously be combined with other thermoplastic polymers to provide the desired injection molding and the characteristics of blow-molding and drawing to make substantially amorphous injection-molded preforms and substantially biaxially oriented, substantially transparent polyester containers. The oxygen scavenger can be provided as an inner layer to retard the migration of the oxygen scavenger or its byproducts and to prevent premature activation of the scavenger.

It is described in US Pat. No. 4,609,516 to Krishna umar et al., A method for forming multiple layer preforms into a single injection molding cavity. In this method, successive injections (sequential) of different thermoplastic materials are made in the bottom of the mold cavity. The materials flow up to fill the cavity and for example form a five-layer structure through the side wall. This five-layer structure can be made with either two materials (ie the first and third injected materials are the same) or three materials (it is say the first and third injected materials are different). Both structures are of wide commercial use for containers for beverages and other foods.

An example of a 5M, 5L * five-layer structure of two materials has inner, outer and core layers of virgin polyethylene terephthalate (PET) and intermediate barrier layers of ethylene vinyl alcohol (EVOH). An example of a five-layer structure of three materials (3M, 5L) has inner and outer layers of virgin PET, intermediate barrier layers of EVOH, and a core layer of recycled polyethylene terephthalate (PC-PET). Two reasons for the commercial success of these containers are that: (1) the amount of the relatively expensive barrier material (n for example EVOH) can be minimized by providing very thin intermediate layers and (2) the resistant content of delammation of the layers without the use of bonding of dissimilar materials. Using PC-PET in the core layer, the cost of each container can be reduced without a significant change in quality.

The ability to withstand pressure with reduced elastic deformation and without delamination can be particularly useful in containers exposed to high temperatures, such as pasteurizable containers and filled with hot beverages and refilled.

These and other modifications of the present invention will be apparent to those skilled in the art, and are intended to be included within the scope of the present invention.

Claims (29)

1. A method for reducing the elastic deformation in a pressurized plastic container, characterized in that it comprises: eliminating any groove in the whole width which shows an elastic deformation under pressure and the blow molding in the at least one line of line which of a visual appearance of a groove while providing a substantially reduced elastic deformation, wherein at least one line of line has a width in the range of about 0.030 to 0.100 cm (0.012 to 0.040 in).

2. A plastic container for carbonated drinks having at least one line of strip blow molded which gives a visual appearance of a groove, characterized in that at least one line of line has a width in the range of 0.030 to 0.100 cm (0.012) to 0.040 in).

3. The container according to claim 2, characterized in that it has an area ratio surface to volume of at least approximately 720 c? r2 / L and a maximum pressure loss of 17.5 during a period of 90 days based on an initial pressure of 4.1 volumes.

4. The container according to claim 2, characterized in that at least one line of line has a width W in a portion of the container having a wall thickness T, wherein the ratio of W: T is in the range of approximately 1.5: 1 to 3.0: 1.

5. The container according to any of claims 1 to 4, characterized in that at least one stripe line is provided in a multilayer wall portion of the container.

6. The container according to claim 5, characterized in that the container has a volume of 1 liter or less and a maximum pressure loss of 17.5% over a period of 120 days based on an initial pressure of 4.0 volumes.

7. The container according to claim 5, characterized in that the container has a volume of 1/2 liter or less and a maximum pressure loss of 1.5% over a period of 120 days based on an initial pressure of 4.0 volumes.

8. The container according to any of claims 1 to 4, characterized in that the at least one line of line has a depth in the range of about 0.005 to 0.010 cm (0.002 to 0.004 in).

9. The container according to claim 8, characterized in that the polyester is selected from the group consisting of polyethylene terphthalate (PET) and polyethylene naphthalate (PEN), which includes homopolymers, copolymers and mixtures thereof.

10. The container according to claim 8, characterized in that the container includes one or more layers of a material selected from the group consisting of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), which includes homopolymers, copolymers and mixtures thereof. same, materials of barrier, thermally resistant materials, and recycled materials.

11. The container according to claim 8, characterized in that the container has a plurality of lines of stripes grouped in a substantially parallel relationship and in proximity to each other to form an assembly that has the appearance of a groove.

12. The container according to claim 11, characterized in that the opposite ends of each set of dashed lines has the appearance of a curved contour.

13. The container according to claim 12, characterized in that the ends converge towards a central stripe line in the assembly to provide the curved contour.

14. The container according to claim 11, characterized in that the stripe lines in the set they are of different lengths to form the curved contour.

15. The container according to claim 8, characterized in that the container has a plurality of lines of stripes having opposite ends which merge with the upper and lower portions of the container placed at the same radial distance from a central line of the container.

16. The container according to claim 11, characterized in that the set includes three dashed lines.

17. The container according to claim 8, characterized in that the container has a wall thickness T in the range of approximately 0.020 to 0.040 cm (0.008 to 0.016 in).

18. The container according to claim 8, characterized in that the container portion has been biaxially oriented at an average stretch ratio of about 10 to 18.

19. The container according to claim 8, characterized in that the at least one line of line has a width in the range of approximately 0.030 to 0.076 Cm (0.012 to 0.030 in).

20. The container according to any of claims 1, 2, 3, 4 and 8, characterized in that the at least one line of line has a radial depth from about 0.00254 to 0.0254 cm (0.001 to 0.010 in).

21. The container according to claim 8, characterized in that the container has a plurality of lines of stripes which form sets of three lines of stripes, closely spaced and substantially parallel, including a central line between two outer lines and wherein each set it has an angular extent measured as a distance between the center points of the two outer lines in a range from about 3 to 10 °.

22. The container according to any of claims 1, 2, 3, 4 and 8 characterized in that has a container portion with a wall thickness of approximately 0.020 to 0.040 cm (0.008 to 0.016 pig;), the container portion has at least one line of blow molded stripe, and the container has a maximum pressure loss of 17.5C. - during a period of 90 days based on an initial pressure of 4 volumes.

23. The container according to claim 22, characterized in that the at least one line of line has a width from about 0. 030 to 0.100 cm (0.012 to 0.040 in) and a radial depth D of approximately 0.00254 to 0.0254 cm (0.001 a 0. 010 in

24. The container according to claim 23, characterized in that there are a plurality of striped lines grouped in a substantially parallel relationship and in proximity to each other to form an assembly that has the appearance of a groove.

25. The container according to claim 24, characterized in that the ends

Opposites of the set of dashed lines each have the appearance of a curved contour. 26. The container according to claim 22, characterized in that the at least one streak line has at least one width and wherein a W: T ratio is in the range from about 1.5: 1 to 3.0: 1.

27. The container according to claim 22, characterized in that the at least one line of line has a width of approximately 0.030 to 0.076 cm (0.012 to 0.030 in.) And a radial depth of approximately 0.005 to 0.010 cm (0.002 to 0.004 in.) and the wall thickness of the container portion is from about 0.025 to 0.030 cm (0.010 to 0.012 in).

28. The container according to claim 22, characterized in that the container includes layers formed of one or more of: (a) a thermoplastic structural polymer; (b) a gas barrier polymer; (c) a scrubbing polymer; Y (d) a thermally resistant polymer.

29. The conformity container cor. Claim 22, characterized in that the container includes multiple layers without adhesives, so that the layers are easily separated for recycling.