EP1761435A1

EP1761435A1 - A container for liquid with a lightweight bottom

Info

Publication number: EP1761435A1
Application number: EP05753046A
Authority: EP
Inventors: Cyrille Durand; Gérard Denis
Original assignee: Nestle Waters Management and Technology SAS
Current assignee: Nestle Waters Management and Technology SAS
Priority date: 2004-06-23
Filing date: 2005-06-23
Publication date: 2007-03-14
Also published as: WO2006000408A1

Abstract

The present invention relates to a container comprising a substantially ovoid or cylindrical wall (2) and a hemispherical bottom (3) type continuing that wall (2) from which originate at least three feet (5) spaced from each other characterized in that the ratio of the weight of the wall (2) to the weight of the bottom (3) is at least 4.

Description

A container for liquid with a lightweight bottom

The invention relates to containers with a hemispherical bottom obtained by blow molding an injected preform. The invention relates in particular to improvements to the weight of the bottom of the containers .

It has been known for many years how to produce containers having the above-mentioned type of base. Diverse thermoplastic materials have been used hitherto: by way of example, reference can be made to polyethylene terephtalate (PET) , polyethylene naphtalate (PEN) , polyacrylonitrile (PAN) et alia. It is further known to use those materials singly, or mixed with one another or with various additives (binding agents, colorants) , or in superimposed layers.

A known problem with thermoplastic containers, whatever their method of manufacture and intended contents, is the mechanical strength of their base, the latter tends to deteriorate, lose shape or burst when the full container falls or undergoes internal overpressure. These characteristics relate to the methods of manufacture, which are such that the material in the base zone is less stretched than it is in other zones of the container. It is known that the more the material is stretched during blow molding, the stronger it becomes. Stretching (or blow molding) in fact induces a change in the cristallinity of the material : an unstretched zone remains amorphous after blowing, whereas as far as stretched zone is concerned, the greater the stretching the greater the crystallization, and consequent strength.

Now, the preforms used in the injection blow molding processes, and similarly the parison used in the extrusion blow molding processes, are in the form of tubes which are either blow molded, or stretched then blow molded.

The longitudinal axis of the preform or parison corresponds to that of the final container: as a result, during either a stretching or a blow molding operation the stretching of the material is practically nil at the center of the base, and increases as the side wall of the container is approached.

It has been envisaged that those disadvantages could be corrected by making containers with a thick base, hence with a large amount of material at the base. That solution is unsatisfactory because owing to the significant amount of the material in their base, those containers have a high retail price, because the cost of material is the dominant factor in price. It was then proposed to lighten the bases of the containers to give them an acceptable retail price. This gave rise to the idea of making containers with petaloid bases.

This type of container comprises a cylindrical part forming the body of the container, and in its lower portion a bottom wall generally convex in shape and from which feet (typically 4 to 6 feet) originate, formed from protuberances distributed uniformly around the base, in pairs separated by a portion of the convex bottom wall.

The base is made so that when the empty container is upright there is a sufficient gap between the central part of the convex wall and the support plane of the base of the feet. This gap is such that when the full container becomes deformed, owing either to the mass of its contents or the internal pressure inside the container (when the latter is, for example, filled with a carbonated drink) , the container remains stable, even if the central part approaches the support plane upon deformation. However, the petaloid bases known hitherto have the disadvantages that, eventually, when acted upon by the internal pressure possibly present in the container, they occasionally burst. This is the result of the shape of the convex portion and/or connection of the feet to the said convex portion and to the cylindrical wall of the container. Hence, in certain cases, the convex portion displays variations or inversions of curvature between its connection to the container wall and its central point. By way of example, the central zone of the convex portion can be a circular flat disk: in such a case, under the influence of internal pressure, that zone tends sometimes to deform and to be pushed towards the bottom of the container, so that microfissures appear in that zone, or else the disk separates from the rest of the base. By way of further example, the central zone of the generally convex portion can present as an outwardly concave dome: the border around the central portion is a fracture zone.

Another problem is that with known structures having a petaloid base the height of the base, and hence of the feet, must increase proportionally with the diameter. As a result, for large-diameter short containers the feet are rather ugly.

Generally, the ratio in weight between the wall and the bottom is from 2.8 to 3.9. These ratios are for containers with a non-plate bottom and particularly for containers with petaloid bottom. In case of a container with a plate bottom, the ratio is quite different but another problem exists because a plate bottom does not have high strength. Indeed, if the internal pressure of these containers increased, the bottom often turns out and the containers cannot stand up. So this kind of containers cannot contain sparkling water with a high level of carbonation. After that, when containers with plate bottoms are filled with still water, there is another problem because during the transport, the containers are usually on pallets and thus undergo a high vertical pressure which can deform the wall or the bottom of the container. To answer this problem, these containers usually have some reinforcing zones but the said zones require more materials. Another possible answer is to add in the container, a quantity of an inert gas after the filling, but it is not possible to add too much gas because of the insufficient strength of the plate bottom.

Patent FR 2 772 720 pertains to a container with a base of the petaloid type from which originate feet wherein the base and the wall are connected by a peripherical zone displaying an inflected curvature. This connection is effected in a substantially tangential manner. Then, the upper end of each foot is linked to the cylindrical wall. This kind of container solves some problems cited above but it needs the same quantities of material as the containers described in the prior art and the shape of the container has to be modified due to the peripherical zone. Moreover, the base of the feet is plane to allow the container to stand.

It is an object of the invention to provide a container which can resist to the internal pressure using less material than a standard container without increasing the thickness of the bottom while at the same time having comparable or higher mechanical properties. Another object of the present invention is to provide a container with a lightweight bottom. A futher object of the invention is to provide a resistant bottom with an acceptable appearance. Yet a further object of the invention is to provide a containers to be filled with still drinks which allows a good transportation resistance without reinforcing structures . The invention relates to a container comprising a substantially ovoid or cylindrical wall and a hemispherical bottom continuing from that wall from which originate at least three feet spaced from each other characterized in that the ratio of the weight of wall to the weight of the bottom is at least 4.

The bottom of the present container has generally a positive convex shape. Then, the connection of the feet to the hemispherical bottom occurs in a substantially tangential fashion. The said feet also have a substantially hemispherical shape and their thickness is less than the thickness of the bottom. In a preferred embodiment, the container is made by PET and the ratio of the weight of the wall to the weight of the bottom is comprised between 5 and 8. This kind of container can contain any flowable products but is generally filled with carbonated drinks because this kind of product needs a container, which can resist to high internal pressure; the container according to the present invention can resist an internal pressure up to 12 bars.

This kind of container is strong because the hemispherical shape of the wall allows uniform distribution of the stresses due to internal pressure or the mass of the contents. Accordingly, there is no longer any particular zone favoring the onset of fracturing.

Under bottom in the present description, we understand all the part of the body comprising the space of said body outside the feet, said feet being taken from their most external position.

Under hemispherical bottom we understand a non-plate bottom, which can be substantially shaped as a semi-sphere or can have the shape of part of a sphere . Under wall we understand the substantially ovoid or cylindrical part located between the neck and the bottom of the container.

Semi-crystalline PET means in the present specification a PET having a crystallinity comprised between 10 and 60 %. More preferably, the crystallinity is comprised between 20 and 40 %.

One specificity of the invention is that the container has feet at the bottom, which are integral with said body. The presence of three feet is a good solution, but the presence of 4 or 5 feet can be preferred to improve the stability of the bottle. The geometry of said feet is not critical. Preferably, these feet have a hemispherical geometry. Concerning the bottom of the container, it has preferably a non-flat form. The bottom of the present container has generally a positive convex shape. Then, the connection of the feet to the hemispherical bottom occurs in a substantially tangential fashion. The said feet have also a substantially hemispherical shape and their thickness is less than the thickness of the bottom.

According to a feature of the invention, the container can optionally comprise on its outside a printing made by pad printing. The advantage of this solution is that it suppresses the need of having a paper stuck around the container.

The volume of the container used according to the invention can have all type of capacity, comprised between 6 cl and 51iters capacity, preferably between 25 cl and 5 liters capacity. The container is intended to contain all types of product, like pasty, dairy products, liquid, semi-liquid, granular or powdered product. Under liquid products, we understand water or a still liquid beverage, particularly still mineral waters, carbonated water or a carbonated liquid beverage, particularly sparkling mineral water. Other types of liquid products are also possible, like chemical products, oil, essence, perfumes, pharmaceutical products. Under pasty products, we understand food and non- food products, like mayonnaise, cosmetic compounds and others.

The means of closing are either a cap, or sealed membrane. The caps can be used for any diameter of opening of the neck. In a preferred embodiment, the mean of closing is a cap.

The container can support an internal pressure of the order of 12 bars. Preferably, the container can support an internal pressure around 10 bars and more preferably around 8 bars .

In another embodiment, the container according to the invention has a three dimensional shape convenient for gripping, a spherical, substantially spherical or cylindrical overall shape.

This is because the geometry with symmetry of revolution is particularly easy and therefore economical to manufacture and has the advantage of allowing the container to be filled with products which can emit gaseous substances, such as carbonated beverages (sparkling waters, sodas, etc.) in particular, which are widely consumed worldwide these days. Such a shape is therefore particularly well suited to these liquids in that the release of carbon dioxide or other gas has a tendency to deform the bodies of bottles which do not have symmetry of revolution, having a negative impact on their stability, grasp and ease of handling, appearance, etc.

According to a preferred embodiment of the packaging assembly, the ratio of the weight of the walls to the weight of the bottom is comprised between 4 and 12, preferably between 4 and 11 and more preferably between 5 and 11 and further more preferably between 5 and 8.

According to another feature, the plastic used to form the wall or walls is a semicrystalline plastic with a slow rate of crystallization, the glass transition temperature (T₉) of which is 70⁰C or higher and the crystallization temperature Tc is around 140 ⁰C. A slow rate of crystallization is to be understood as meaning a rate which makes it possible to have an amorphous state by quick cooling.

Advantageously, the plastic used to form the wall or walls is chosen from the group formed by PET (polyethylene terephthalate) and PEN (polyethylene naphthalate) . It has been noted that the drawing of the PET has no negative influence on the water barrier properties of the obtained container and that also a thickness of around 50 μm and less guarantees a good safety of the container itself and of the storage.

Small thicker areas or portions of walls may also be provided on the body of the said container, particularly in close proximity to the neck and/or the bottom, so as to reinforce these parts locally. Such reinforcements may in particular be useful to facilitate the filling of the said containers or to increase their stability during storage and transport. As a preference, the container is further characterized in that the body and the neck of the container are made as a single piece. This makes it possible to avoid any join or weld which may constitute a region of greater weakness.

Indeed, according to another feature, the container according to the invention is characterized in that, it has a high resistance to internal pressure. For example, for a working volume of 1.5 litre, the amount of PET used to produce the said container is about 32g. for resistance to an internal pressure up to 12 bars. This represents a significant saving in plastic, the 1.5 litre containers filled with carbonated water comprising about 6 g/L of carbon dioxide that are currently on the market requiring an amount of polymer, which, for comparable resistance, is about 37 g. When cylindrical containers of lower volumes are used, for example of the order of 50 cl, the quantity of plastic material is of the order of 22 g, in comparison with a bottle of the same volume, wherein the amount of plastic is of the order of at least 24 g.

According to another alternative form, the container according to the invention is characterized in that the neck is fitted with a closure and/or distribution means produced in the form of a distribution tap, which can be operated with one hand.

Such distribution taps, which are known per se, advantageously allow the distribution of the flowable product contained in the container to be regulated in a particularly convenient way.

Of course, the containers of the present invention are not in any way limited to flat or sparkling mineral waters but can be intended to contain all sorts of flowable products, edible or inedible liquids of greater or lesser fluidity such as, for example, fruit juices, milk-based beverages, etc., and also sauces or condiments (ketchup, mustard, dressing, etc.) or non-food liquids (deionized water, cleaning products, detergents, etc.) . The containers according to the invention can also contain a functional component. The functional component is taken from the group consisting of a fibre, plant extract, fruit extracts, vitamins and flavors. Finally, another subject of the present invention is a means to improve the manufacture of containers. Indeed, the thickness of the bottom is less important so the time of cooling during the production is decreased and thus the productivity per mold is improved. This reduces the cost of the process by improving the productivity of the machine, which is used and moreover the actual lines of production do not need to be modified.

In another embodiment, the container according to the present invention can also be filled with still water. These kinds of containers generally bottles that are on the market need some reinforcing structure to resist to the vertical pressure that occurs on the pallets during the transport. According to the present invention, there is no need to have reinforcing structures thanks to the improved resistance of the bottom. Indeed, when the container is filled with still drink, it is possible to add a predetermined quantity of an inert gas to increase the internal pressure of the container and thus the container can resist to said vertical pressure. The consequence is that it is possible to have simple shapes, which have the advantage of providing transparency and purity. This is particularly important for the consumer in the case of a container for drinking water. Furthermore, when the container is filled and then pressurized with an inert gas, deformation during transport is significantly reduced and consumers can have a final product in its original state. Optionally, reinforcing structures can be added for merchandising matters to improve the facility of gripping by consumers .

The improved strength of the bottle is obtained by both reasons. On the one hand, the plastic is high stretched so an adapted cristallinity is obtained and on the other hand, the geometry allows a uniform repartition of the forces. Other features and advantages of the present invention will appear in the following description of a preferred embodiment of the container, this embodiment being given by way of non-limiting example with reference to the annexed drawings, in which:

- Figure 1 is a general view of the container in a bottle- shape; - Figure 2 is a view of the bottom of the bottle-shape container; - Figure 3 is a section view of the bottom of the bottle- shape container.

In the embodiment described and depicted on figures 1 and 2, the container for a flowable product, particularly for a beverage and, in particular, for mineral water, essentially consists of a body 1, formed by walls 2 and a bottom 3 and a neck 4. The body is made of a semi-crystalline PET. The neck presents a screw for receiving a cap (not shown) . The bottom 3 presents five feet 5. The volume of the container is of 100 cl . In this specific example, filled with a carbonated drink comprising 8 g/L of carbon dioxide, the ratio of the weight of the walls to the weight of the bottom is 11. This means that for the volume of 100 cl, there is 37 g of PET for the body. To calculate the ratio the weight of the walls on the weight of the bottom, the weight of the wall 2 is divided by the weight of the bottom 3.

Concerning the figure 3, it shows that the feet are tangentially connected to the surface 6. Hence, the absence of a change of gradient, or at most, the presence of a slight gradient at that junction between the feet 5 and the hemispherical area 6 eliminates zones of fragility. the radii of curvature Rl and R2 are calculated so that the connection of the feet with the positive convex surface 6 occurs substantially tangentially, that is without significant change of gradient in the connecting zones so as to avoid the creation of fragility at those zones. Preferably, for a container with a capacity of 1.5 L, the radius of curvature Rl is comprised between 40 and 60° and the radius of curvature R2 is comprised between 10 and 15°. The height of the feet 5 is calculated so that the gap d exists between the central pole of the hemispherical surface 6 and the plane passing through the surface of each of the feet.

When the container is filled, the hemispherical surface 6 deform to absorb the stress. The surface between each foot also undergoes some deformation. The thickness of the feet 5 is at this moment the predominant parameters. Indeed, when the bottle is completely filled, the internal pressure is high thus the gap d is decreased. If the said gap does not exist, the bottle cannot stand. So with feet having a thickness less than the thickness of the surface 6, the deformation will occur within the feet and said feet will keep their initial form or increasing their height.

The invention is further defined by reference to the following examples describing in detail the preparation of the containers of the present invention. The invention described and claimed herein is not to be limited in scope by the specific embodiments herein disclosed, since these embodiments are intended as illustrations of several aspects of the invention. Any equivalent embodiments are intended to be within the scope of this invention. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims . Example 1 Here is a comparative example between a classic petaloid bottom from the prior art and the lightweight bottom according to the present invention. Both containers are filled with sparkling water containing carbon dioxide of 6 g/L.

Claims

Claims:

l-A container comprising a substantially ovoid or cylindrical wall (2) and a hemispherical bottom (3) continuing that wall (2) from which originate at least three feet (5) spaced from each other characterized in that the ratio of the weight of the wall (2) to the weight of the bottom (3) is at least 4.

2- A container according to claim 1, wherein the bottom (3) has a positive convex shape.

3- A container according to claim 1, wherein the connection of the feet (5) to the hemispherical bottom (3) is in a substantially tangential fashion.

4- A container according to claim 1, wherein the feet (5) have a substantially hemispherical shape.

5- A container according to claiml, wherein the thickness of the feet (5) is less than the thickness of the bottom (3) .

6- A container according to claim 1, wherein the ratio of the weight of wall (2) to the weight of the bottom (3) is comprised between 4 and 12.

7- A container according to claim S, wherein the ratio of the weight of the wall (2) to the weight of the bottom (3) is comprised between 5 and 8.

8- A container according to claim 1, wherein said container (1) is made from a semi-crystalline PET.

9- A container according to claim 1, wherein said container is filled with carbonated drinks. 10- A container according to claim 1, wherein said container is filled with still drinks without the need of reinforcing structures.

11- A container according to claim 1, wherein said container (1) can resist to internal pressure up to 12 bars .