WO2003035485A1 - Plastic container - Google Patents

Abstract

The invention relates to a plastic container, especially a plastic bottle, comprising a neck part (23) which is provided with a pouring opening (25). Said neck part (23) sits on a container body (30) which has a central region (21) having a smooth outer surface, and a closed container bottom (22). The container body (30) comprises at least one especially axially deformable section (27) in the longitudinal direction thereof.

Description

 Plastic container

The invention relates to a plastic container, in particular a plastic bottle, according to the preamble of claim 1.

The containers made of tin or colored sheet, glass or ceramic, which were common in the past, are increasingly being replaced by containers made of plastic. In particular for the bulk packaging of fluid substances, for example beverages, oil, cleaning utensils, personal care products, cosmetics, etc., plastic contents are mainly used. The low weight and the lower costs certainly play a significant role in this substitution. The use of recyclable plastic materials and the overall lower overall energy balance in their manufacture also help to promote the acceptance of plastic containers, in particular plastic bottles, by the consumer. Plastic containers are manufactured in mass production, for example in an injection molding process, a stretch blow molding process or in a continuous or discontinuous extrusion blow molding process.

The plastic containers produced in this way are used in a variety of ways. In the case of foodstuffs in particular, it is often the case that mostly liquid or pulpy contents are filled into the plastic containers in warm or hot form. After filling, the containers are closed and the contents cool down. In the case of foodstuffs in particular, care is taken to ensure that the plastic container has a very good seal so that the contents of the container retain their quality and do not spoil, at least during a guaranteed shelf life. For this purpose, for example, the application of a sealing foil prevents atmospheric oxygen, for example, from entering the closed container. In addition, sealed bottles are also given a cap. However, design variants are also known in which one applied cap seals the bottle content gas-tight. Especially with hot or hot filled plastic containers, this good tightness of the closure means that the container can become deformed when the filling material cools down. This deformation is a result of the pressure difference between the atmospheric pressure acting on the outside of the container walls and the negative pressure which arises as a result of the cooling inside. Particularly in the case of plastic bottles, which usually have an elongated, essentially cylindrical shape, this leads to deformations, in particular indentations, in the central region of their axial extension. This deformation of the plastic container has no effect on the quality of the filling material. For the consumer, however, the external appearance of a sales item is often decisive for his choice. A plastic container that has deformations can therefore often lead to the erroneous assumption of the customer that the product contained in the container no longer has the required quality properties despite a shelf life limit that still lies in the future.

This tendency to deform when the filling is warm or hot can be counteracted by increasing the wall thickness of the plastic container. Due to the increased material requirements, the production of these plastic containers becomes more expensive and their weight increases. Solutions are also known in which stiffeners are provided along the axial extent of the plastic container. The mechanical stiffeners usually require specially shaped extrusion nozzles or a special process control in the manufacture of the plastic containers.

The object of the present invention is therefore to remedy these disadvantages of the plastic containers of the prior art. The aim is to create a plastic container which allows hot or hot contents to be filled and which essentially maintains its outer shape when the contents cool down. In particular, noticeable indentations in the. central area of the plastic container can be avoided. In the central, cylindrical region of its longitudinal extent, the plastic container should have the smoothest possible outer surface for the application of lettering and / or labels. The plastic container is said to be in one of the known technical manufacturing processes, especially in the extrusion blow molding process. It should be possible to dispense with specially trained extrusion tools or a special extrusion process.

The solution to these problems consists in a plastic container which has the features stated in the characterizing section of patent claim 1. Preferred embodiments and / or further developments of the invention are the subject of the dependent claims.

A plastic container, in particular a plastic glass film, according to the invention has a neck part with a pouring opening. The neck part sits on a container body which has a central area with a smooth outer surface and a closed container bottom. The container body has at least one, in particular axially deformable, section along its axial extent.

The axially deformable section of the plastic container is able to compensate for any pressure differences, such as can occur, for example, when filling contents filled in the warm or hot state. This reliably prevents the plastic container from deforming, in particular indenting, particularly in the central region of the container body. The negative pressure which occurs inside the closed container during cooling is absorbed by the axially deformable section. At most, there is a slight reduction in the total axial length of the plastic container, but this is not perceptible to the customer.

In an advantageous embodiment variant of the invention, the axially deformable section has at least one constriction running in the circumferential direction. The constriction forms a targeted weakening of the container body. This ensures that any axial deformation takes place only in the bellows-like deformable section. The constriction extends from an outer diameter of the adjacent body into the interior of the container. The wall thickness decreases up to a flexible joint area. The flexible joint area ensures that the axial deformation of the container is only controlled in one or more predetermined areas.

The formation of the flexible joint region with the at least approximately 30%, preferably approximately 35% to approximately 70% of the average wall thickness in the central region proves to be expedient. These dimensions ensure a sufficiently great flexibility and a reliable compensation of the pressure differences occurring when the filling material cools down due to an axial deformation.

The greatest depth of the constriction in the axially deformable section compared to the outer surface in the central area corresponds to approximately 1.5 times to approximately 8 times the wall thickness in the central area. This ensures bellows-like behavior of the axially deformable section of the plastic container.

So that the plastic container can also reliably compensate for larger pressure differences, the constriction has an opening width that is approximately 3 times to approximately 10 times the wall thickness in the central area.

Preferably, two or more constrictions running in the circumferential direction are provided in the axially deformable section. When a filling material filled hot or hot in the plastic container cools, each of the constrictions suffers only a relatively small axial deformation. The sum of all deformations gives the extent of the total axial deformation or shortening compared to the initial height of the plastic container produced.

The axial distance of the clinching from each other, the ahn. Measured due to the constrictions is preferably about 0.2 times to about 5 times the wall thickness in the central area. The selected distance ensures that the individual constrictions with homogeneous properties can be produced so that the same conditions are met in the event of any later axial deformation over the entire circumference of the plastic container. This ensures that axial deformation occurs essentially in the exact axial direction, and one-sided shortening is prevented.

The transition regions present between the constrictions are also each articulated. This ensures the most uniform possible axial deformation along the axial extent of the deformable section.

By arranging the axially deformable section adjacent to the central area, preferably in the vicinity of the neck part, the outer surface of the central area remains smooth, in particular in the case of containers with an essentially cylindrical container body, and, as usual, can be used for attaching a label or a label to be used.

The plastic container according to the invention can be manufactured according to the usual mass engineering manufacturing processes. However, it is preferably produced by extrusion blow molding. The axially deformable area is produced by shaping in the blow mold. This eliminates the need for specially designed extrusion nozzles or a special procedure for the extrusions. The axial height of the deformable section, the number of constrictions and the formation of the constrictions only depend on the blow mold. They can therefore be changed very easily without having to intervene in the relatively critical area of the extruder and the extrusion arrangement for the softened plastic.

The plastic container according to the invention is particularly suitable for the storage of liquid to porridge foods which are filled in warm or hot condition. The invention is explained in more detail below with reference to an exemplary embodiment shown in the schematic drawings. In a representation that is not to scale,

1 is a schematic representation of an extrusion blow molding process;

2 shows a side view of a plastic container according to the invention, in particular a plastic bottle; and

3 shows an axial section of the plastic container from FIG. 2.

The extrusion blow molding process is used for the mass production of thin-walled hollow bodies, such as bottles, canisters, drums, but also watering cans, tanks for motor vehicles and similar containers made of thermoplastic materials. For this purpose, the plastic, which is usually in the form of granules, is melted and a preform is produced from it. The preform can be in different forms. For example, it can be designed as a hose or have an elongated, cylindrical shape. The preform is then introduced into the cavity of a blow mold immediately after its production or only at a later point in time and is inflated in accordance with the mold cavity and thereby shaped into its final shape.

1 schematically shows the sequence of an extrusion blow molding process. An extrusion blow molding machine provided with the reference number 1 is composed of an extruder 2 with an extrusion head 4 for the production of a preform 5 and an immediately following blow molding unit which has a blow mandrel 7 projecting from a blow mandrel holder and into the cavity 10 of a mold which usually consists of two halves Blow mold 9 is retractable. In the case of extrusion blow molding, the preform 5 is produced immediately before it is introduced into the blow mold 9. This can be done in a continuous or in a batch process. With the a continuous extrusion blow molding process, a mostly granular plastic P is fed via a funnel 3 to the extruder 2, melted and melted in the. Extrusion head 4 promoted. At the exit of the extrusion head 4, a hose-like preform 5 is continuously extruded, which is introduced into the cavity 10 of the blow mold 9 essentially immediately after its production. The preform 5 can be extruded or coextruded in one or more layers as required. After the preform 5 has been separated from the continuously extruded tube with the aid of a knife 6, the blow mandrel 7 is introduced in order to inflate the preform 5 to the shape predetermined by the cavity 10 in the blow mold 9. In the discontinuous extrusion blow molding process, the plastic pain is temporarily stored in the extruder head 4. The blow mold 9 is arranged directly below the extruder opening and is opened and closed in the cycle cycle. When the blow mold 9 is open, the melt is expelled into the cavity 10 of the blow mold 9 at high speed as a tubular preform 5. When the blow mold 9 is closed, the preform 5 is separated. The blow mandrel 7 can then be inserted in order to inflate the preform 9. The preform 5, which has been inflated into its final shape, cools down by being in contact with the wall of the blow mold 9 and by the blowing medium, for example air, and can be removed as a fully formed container 20. The slug pieces on the bottom and on the neck of the container 20 are separated by a punch indicated with the reference number 8. Thereafter, the container 20 is usually checked for leaks. The finished plastic container 20 is loaded with the filling material in a subsequent process, which is usually carried out separately from the customer, and then closed.

2 and 3 show an exemplary embodiment of a plastic container 20 designed in accordance with the invention, which is particularly suitable for filling contents in a warm or hot state and does not have any unsightly deformations along its circumference even after the contents have cooled. The plastic container 20 shown for example in FIGS. 2 and 3 is a plastic bottle with an essentially cylindrical container body 30 to which a neck part 23 connects. In the exemplary embodiment shown, the neck part 23 essentially consists of the actual bottle neck 24 with a pouring opening 25 and a shoulder part 26, which forms the transition to the cylindrical container body 30. The cylindrical Body 30 includes a central region 21 with a substantially smooth outer surface, which is used to attach a label or label, and a closed container bottom 22.

According to the exemplary embodiment shown, the container body 30 has an axially elastically deformable section 27 following the central region 21. Constrictions 28 extending in the circumferential direction are provided in the axially deformable section 27. The constrictions 28 extend from the outer surface of the cylindrical body into the interior of the bottle and have a base 29 at the narrowest diameter point.

The axially elastically deformable section 27 has a flexible joint region 31 at the transition to the neck part 23. In particular, there the container wall thickness m decreases to a minimum value which is at least approximately 30%, preferably approximately 35% to approximately 70% of the wall thickness t in the central region 21. According to the exemplary embodiment shown, three constrictions 28 running in the circumferential direction are arranged over the height of the deformable section 27. The constrictions are advantageously arranged at the same distance a from one another. The distance a measured over the base 29 of the constrictions is approximately 0.2 times to approximately 5 times the wall thickness t in the central region 21.

As can be seen in particular from FIG. 3, further joint-like transition regions 32 are provided at the transition from one clinching 28 to the next. These are essentially of the same design as the flexible joint region 31. According to the exemplary embodiment shown, the constrictions 28 have an approximately trapezoidal shape

Cross section, wherein the area between the constrictions 28 is approximately cylindrical. In this variant of the constrictions 28, there are two articulated transition areas 32 next to one another between the constrictions 28. The

Constrictions 28 have a depth d, measured from the outer surface of the central region 21 to the base 29 of the constriction 28, which is approximately 1.5 times to approximately 8 times the wall thickness t in the central region 21. At their furthest Lacing 28 an opening width w, which is about 3 times to about 10 times the wall thickness t in the central region 21.

In the exemplary embodiment of an inventive plastic bottle 20 shown in axial section in FIG. 3, the wall thickness thickens from the minimum wall thickness m in the articulated transition areas to the bottom 29 of the constrictions 28. This is a consequence of the manufacturing process in the extrusion blow molding process and the blow mold with an essential cylindrical base of the clinching. During production, the extruded preform first lies against the narrowest areas of the blow mold and is then blown outwards to the nominal diameter of the plastic film. With a narrower to sharp-edged design of the base of the constrictions, a wall thickness that is reduced compared to the wall thickness in the central area can also be achieved there.

The invention has been explained using the example of an essentially cylindrical plastic glass film which has an axially elastically deformable section with three constrictions arranged axially one behind the other at the same distance. It goes without saying that the distance between adjacent constrictions need not necessarily be the same size. The depth of the constrictions can also vary. In particular, the inventive concept also includes an exemplary embodiment with only at least one constriction running in the circumferential direction. In the illustrated embodiment, the axially deformable section is arranged between the central area and the neck part. The axially deformable region can also be arranged on another section of the container body. A plurality of axially deformable sections spaced apart from one another can also be provided along the axial extent of the container body. The plastic container can also have a shape that deviates from the cylindrical shape. For example, the container can also have a truncated cone-shaped container body. In this case too, the container body has at least one axially deformable section along its axial extent. Due to the axially deformable section, the plastic container can have pressure differences, such as those filled into the container when it cools down in warm or hot condition Contents in the closed container can occur, compensate for it by axial deformation. As a result, the container remains free of deformation over its circumference.

Claims

claims Plastic container, in particular plastic bottle, with a neck part (23) having a pouring opening (25) and a container body (30) adjoining it, which comprises a central region (21) having a smooth outer surface and a closed container bottom (22), characterized in that that the container body (30) has at least one, in particular axially deformable, section (27) along its longitudinal extent. Plastic container according to claim 1, characterized in that the axially deformable section (27) has at least one constriction (28) running in the circumferential direction. 3. Plastic container according to claim 2, characterized in that the constriction (28) extends from an outer diameter of the container body (30) into the interior of the container and the container body (30) has a wall thickness that extends to a flexible joint area (31) reduced. 4. Plastic container according to claim 3, characterized in that the lowest Wall thickness (m) at the flexible joint area (31) of the constriction (28) has at least about 30%, preferably about 35% to about 70% of the average wall thickness (t) in the central area (21). 5. Plastic container according to one of claims 2 to 4, characterized in that a greatest depth (d) of the constriction (28) relative to the outer surface in the central region (21) about 1.5 times to about 8 times the wall thickness (t ) in the central area (21). Plastic container according to one of claims 2 to 5, characterized in that the constriction (28) has an opening width (w) which is approximately S times to approximately 10 times the wall thickness (t) in the central region (21) , Plastic container according to one of the preceding claims, characterized in that two or more axially consecutive constrictions (28) running in the circumferential direction are provided in the axially deformable section (28). Plastic container according to claim 7, characterized in that an axial distance (a) of the constrictions (28) measured at the base (29) of the constrictions (28) from one another is approximately 0.2 times to approximately 5 times the wall thickness (t) in Central area (21) is. Plastic container according to claim 7 or 8, characterized in that between the constrictions (28) each articulated transition areas (32) are provided. 10. Plastic container according to one of the preceding claims, characterized in that the axially deformable section (27) adjoins the neck part (23). Plastic container according to one of the preceding claims, characterized in that it is produced in the extinction blow molding process, the axially deformable section (27) being first in shape by shaping in the blow mold. 12. Plastic container according to one of the preceding claims for use for the storage of liquid to porridge foods which are filled in warm or hot condition.