EP1661815A1 - Plastic container having multilayered side walls - Google Patents

Abstract

Plastic containers with a base (2) and side walls (3), in which the sides (3) comprise a double- or multi-layer sandwich structure with individual layers (6, 7) having a thickness such that the layer is dimensionally stable under production conditions during and after binding the layers, the required mechanical stability of the wall being provided by the sandwich structure. An independent claim is also included for a method for the production of such containers by injection moulding the container with a first layer (7) of side wall, making a second layer (6) independently of the first and then binding the two layers together.

Description

The present invention relates to a container made of plastic and in particular bottle crates according to the preamble of claim 1 and a method for their preparation.

Plastic containers enjoy in many areas of great popularity z. B. in the form of crates for storage and transport of beverage bottles u. etc. ..

Such plastic containers usually have joints in certain areas of the side walls, in which webs or reinforcing ribs are connected to the side wall regions. Due to the different cooling conditions of the plastic after injection molding at these junctions, so-called sink marks occur, which cause a disadvantageous appearance even with very small depth of incidence on large wall areas.

In order to solve this problem, various approaches have been taken in the prior art, such as. B. the two-component syringes or the successive spraying of outer frame and inner box. However, these methods are complex and therefore unsuitable for solution.

Furthermore, attempts were made to conceal the sink marks by lacquering the outer surface, the problem here being that the lacquer layer would have to be applied unevenly in order to compensate for the sink marks. However, this is technically hardly feasible, so that also eliminates this possibility.

As a further solution, it has been proposed to form air chambers in the so-called air-mold process by blowing in air at the critical joints where there is a risk of the formation of sink marks, which are intended to counteract the formation of sink marks. Similarly, attempts have been made by the addition of blowing agents in the plastic foaming of the plastic to be achieved by pore formation also the formation of sink marks to be counteracted. But even these procedures are very complex, especially if the desired success is to be achieved.

Moreover, it is also known to produce multilayer plastic container walls by the so-called. In-mold process, in which a layer of the container wall structure, in particular the decorative surface or a so-called label during injection molding of the plastic container inserted into the injection mold as an insert and the plastic then This insert is injected (injection molding). However, this method has the disadvantage that due to the high and large-surface temperature load during the back-injection, the insert is softened in the usual dimensions for plastic container walls such that a deformation of the label and thus a replica of the sink marks is possible. In addition, there is the problem that due to the common cooling of insert and molded plastic it comes to deformations due to different thermal expansions. This problem can not be counteracted by the formation of correspondingly thick inserts, since then further problems due to the different thickness ratios of the surrounding plastic occur during cooling.

It is therefore an object of the present invention to eliminate the disadvantages of the above-described prior art and to provide plastic containers, in particular large-scale side wall areas in which sink marks are avoided by joints of inner walls, reinforcing webs or ribs and the like., To a pleasing external appearance guarantee. In addition, a variable design of the container with simple production should be possible, in particular containers with areas of different properties, such as different materials, colors, etc. should be possible. Overall, the design of the container should be very variable.

This object is achieved by a plastic container having the features of claim 1 and a method for producing a container with the Features of claim 16. Advantageous embodiments are the subject of the dependent claims.

According to the invention, a particularly variable and diverse design of plastic containers with in particular different materials while avoiding sink marks in large wall areas with joints is achieved in that the side walls at least partially have a two- or multi-layer sandwich structure, wherein the individual layers are dimensioned in that the individual layers are inherently stable during the entire production process and thereafter and the composite of the layers in the sandwich structure for the applications of the plastic container. These technical specifications ensure that, on the one hand, different materials with different appearances can be used due to the different layers and, on the other hand, sink marks can be avoided. The dimensional stability during and after bonding of the individual layers to the sandwich structure ensures that possible defects in one layer are not transferred to the second or further layers by replication. Thus, for example, a container base structure can be produced with a first side wall layer as an injection molded part, while independently and separately therefrom, the second layer is produced in any desired manner, for example by extrusion. While sink marks can be formed in the first side wall layer by providing joints, this is avoided in the second or further layer by the separate production and dimensional stability. Since the dimension of the layers is chosen so that they are dimensionally stable on their own, there is no disadvantageous change in shape due to the production or intermediate storage of the separate semi-finished products. After production of the two separate semi-finished products, these are connected to each other by form, force and / or material connection, so that a large-area side wall area is generated by the second or further layers, which has no defects, such as sink marks on the outer surface. Since the outer layer of the sandwich structure is manufactured separately and thus any manufacturing process can be used, methods can be used which guarantee a particularly high quality surface, such as the extrusion or co-extrusion. In particular, in coextrusion, in turn, a multi-layered structure of a low-cost carrier layer and a high-quality surface layer can be produced.

The connection of the layers can be done in any suitable manner, it being important to ensure that in the usual known container wall thicknesses no deformation occurs by the connection technique.

In general, various methods can be used, such as clip connections, welding, gluing or even connections by press fit. Such a connection technique is for example possible if the outer layer of the sandwich structure is designed as a ring-like band which surrounds the container wall closed. Such a ring-like band, for example, can be elastically expanded, slipped over a container base structure and then shrunk onto the container base structure by elastic compression.

Accordingly, the term dimensional stability in this application is understood to exclude unwanted permanent shape changes.

Preferably, the layers are glued together with hot or reactive adhesive or hot melt adhesive, wherein in particular the second or further layers can be prepared by coextrusion already with the adhesive layer.

The melting of the hot or hot melt adhesive can for example be carried out advantageously by infrared irradiation of the adhesive layer, so that the effect of heat on the entire element can be kept very low overall.

The layers can be detachably or non-detachably connected to one another, wherein in the case of a detachable connection, in particular via clip connections or a hot melt adhesive layer, it is possible, for example, to replace the outer layer after damage, without the entire container being thrown away got to. In this way, simple design changes can be made, for example, if the label is to be changed.

By means of the method according to the invention, it is possible in particular to form large-area decorative surfaces on the container walls, which can be designed above all by the separate production of the individual layers and in particular of the outer layer in any manner. In particular, it is possible to realize for the different layers different materials, colors, strength and elasticity and density values or to influence the properties in a certain way, for. B. by certain treatments.

Thus, according to preferred embodiments, the outer layer is printed, provided with gloss effects, metallic effects and the like. To be designed as a decorative surface or it is possible to design the outer layer particularly scratch resistant. This can be achieved for example by a plasma treatment, which leads to a densification of the surface areas. The plasma treatment can be advantageously carried out in air and does not require a vacuum. In addition to a plasma treatment, a treatment of the layers by flaming is conceivable.

Due to the inventive design of the container, the outer layer can also be formed in three dimensions, wherein the 3-D structure can be produced by deep drawing or embossing.

The outer layer preferably has a thickness of more than 0.3 mm, in particular 0.4-0.5 mm and preferably of about 1 mm, wherein the layers are preferably made of plastic, in particular polyethylene and / or polypropylene. Preferably, the outer and inner layers have the same thickness.

In the different layers, especially the outer layer and various additional elements such. B. transponder or the like. Be embedded.

Fig. 1

eine perspektivische Ansicht eines erfindungsgemäßen Behälters;

Fig. 2

eine perspektivische Explosionsdarstellung des Behälters aus Fig. 1;

Fig. 3

eine Schnittansicht eines Behälterelements aus Fig. 2; und in

Fig. 4

eine perspektivische Darstellung eines Behälters nach dem Stand der Technik.

Further advantages, characteristics and features of the present invention will become apparent in the following detailed description of an embodiment. The figures show this in a purely schematic manner in FIG

Fig. 1

a perspective view of a container according to the invention;

Fig. 2

an exploded perspective view of the container of Fig. 1;

Fig. 3

a sectional view of a container element of Fig. 2; and in

Fig. 4

a perspective view of a container according to the prior art.

In Fig. 1 is a perspective view of a container 1 according to the invention with a bottom 2 and four side walls 3 is shown. The side walls have an upper frame portion 4 and a lower frame portion 5 and a central portion with a sandwich structure, wherein in Fig. 1, the outer layer 6 can be seen, which is designed according to a preferred embodiment as a decorative surface.

FIG. 2 shows the container 1 according to the invention in a perspective exploded view, wherein the outer layer 6 is shown lifted off the inner side wall layer 7.

Fig. 3 shows the outer layer 6 and its structure in a sectional view.

As can be clearly seen in Fig. 3, the outer layer 6 is constructed in three layers and namely of a carrier layer 9, an outer decorative layer 10 and an inner contact layer 8, which is formed in the embodiment shown as an adhesive layer.

The plate 6, which is connected as an outer layer, as can be seen in Fig. 2, with the inner side wall layer 7 is glued in the preferred embodiments on the adhesive layer 8 on the inner side wall layer 7. The adhesives used are preferably reaction adhesives or hot melt adhesives or hot melt adhesives, melt adhesion in turn being preferred.

In melt bonding, the outer layer plate 6 on the side to which the hot melt adhesive in the form of the adhesive layer 8 is applied, for example, briefly heated by infrared irradiation, so that the adhesive melts and the plate 6 is in this state on the container 1 in the inner side wall layer 7 is pressed to form there the sandwich structure. Alternatively, the adhesive layer can also be applied to the container 1 in the region of the inner side wall layer or, as a further alternative, both on the container 1 and on the outer layer plate.

Due to this method of production, the outer layer plate 6 can be formed separately from the container base structure, for example by extrusion, in particular co-extrusion, and processed in any desired manner. According to the preferred embodiment, the outer layer 6 is formed as a decorative plate, which for example by means of extrusion or co-extrusion has a high surface quality and / or can receive an attractive decorative layer 10.

In addition, the outer layer 6 can be printed in the form of the plate, embossed, deep-drawn or otherwise treated to achieve a corresponding appearance or a particular shape.

In order to increase the adhesive strength of the adhesive layer 8, for example, the inner side wall layer 7 may be pretreated prior to bonding to the plate 6 and in particular be treated by a plasma. The plasma treatment, which can be carried out under atmospheric conditions, significantly improves the adhesion.

Furthermore, a plasma treatment of the outer layer 6, for example, on the outside to improve the scratch resistance is conceivable.

The basic structure of the container 1, which is shown in Fig. 2, is prepared in a known manner by injection molding of plastic, wherein in the region of the sandwich structure of the side walls 3 a significantly reduced side cross-section, ie a lower side thickness is provided, which is referred to as (inner) side wall layer 7. Both the outer plate 6 and the inner side wall layer 7 are dimensioned so that they have sufficient stability during the manufacturing process to remain dimensionally stable, especially during the heat treatment during the melting of the hot melt adhesive or the subsequent cooling process after bonding. In this way, a certain minimum thickness of the layers, ie the separately prepared outer layer and the inner wall layer produced by injection molding with the box base frame by the manufacturing process and its processing steps is given. On the other hand, the maximum required thickness is given by the stability requirements of the container, for example, in stackable containers by the stackability, which must meet the sandwich structure with all layers, ie in the preferred embodiment with two layers of inner wall layer and outer layer.

By the construction according to the invention, as described in FIGS. 1 to 3, can be reliably avoided that as in known containers 11, one of which is shown in Fig. 4, in providing support struts o. The like large-area wall areas sink marks 14 arise due to the different cooling behavior at these joints. As can be seen in the partial sectional view of FIG. 4, line-shaped sink marks 14 are formed on side walls 12 at the joints of the reinforcing struts 13, which result from the different cooling behavior at the junctions of the side wall 12 with the reinforcing struts 13 compared to the other side wall regions ,

By the inventive, subsequent attachment of an outer layer plate 6, as shown in FIGS. 1 to 3, this problem can be overcome, since the sufficient stability of the outer layer 6 a replica of the sink marks after connection is excluded.

In addition, such a procedure offers further significant advantages, since z. B. different materials, for example, in terms of color, composition and other properties can be used. In particular, you can high-quality decorative surfaces are created, which can be supplied separately from the container base frame consuming processing processes that would either not be feasible on the entire container or would lead to significant costs, for example, in accordance with difficult processing steps with high failure rates. In addition, certain properties, such as high-quality surfaces by extrusion only with separate decorative surfaces or plates conceivable.

Furthermore, it is possible to design the sandwich structure in such a way that the layers can be separated again from one another in order to create repairable or exchangeable surfaces or decorative surfaces.

Claims (22)

Plastic container with a bottom (2) and surrounding side walls (3)
characterized in that
the side walls at least partially have a two- or multi-layered sandwich structure whose individual layers (6, 7) are dimensioned in thickness such that each layer is inherently dimensionally stable under the conditions of manufacture during and after bonding of the layers, the required mechanical stability of the side wall is provided by the sandwich structure. Container according to claim 1,
characterized in that
the layers (6, 7) are positively, positively and / or materially connected to each other. Container according to claim 1 or 2,
characterized in that
the layers (6, 7) glued together, in particular glued together with melt or reaction adhesive, welded or connected to each other via clip connections or the adhesive after solidification, the layers (6, 7) positively to each other, in particular by the formation of undercuts. Container according to one of the preceding claims,
characterized in that
the layers (6, 7) are detachably or permanently connected to one another. Container according to one of the preceding claims,
characterized in that
the layers (6, 7) are formed of identical material or have different properties, in particular with regard to material, color, density, strength, elasticity and the like. Container according to one of the preceding claims,
characterized in that
the outer layer (6) is designed as a decorative surface. Container according to one of the preceding claims,
characterized in that
the outer layer (6) has a scratch protection. Container according to one of the preceding claims,
characterized in that
the outer layer (6) is plasma treated on the outer surface. Container according to one of the preceding claims,
characterized in that
the outer layer (6) is formed as a flat plate or as a three-dimensional structure. Container according to one of the preceding claims,
characterized in that
the layers (6, 7) are made independently of each other, wherein in particular a layer (6) itself has a multilayer structure. Container according to one of the preceding claims,
characterized in that
the outer layer (6) has a thickness of more than 0.3 mm, in particular 0.4-0.5 mm, preferably 1 mm. Container according to one of the preceding claims,
characterized in that
a layer, in particular the outer layer (6) by extrusion, deep drawing and / or embossing is made. Container according to one of the preceding claims,
characterized in that
he is a bottle crate. Container according to one of the preceding claims,
characterized in that
the outer layer is shrunk as a circulating ring-like band. Container according to one of the preceding claims,
characterized in that
the layers are made of PE and / or PP. Method for producing a container, in particular according to one of the preceding claims,
characterized in that
the container with a first side wall layer (7) is produced by injection molding,
that at least one second layer (6) is produced independently of this, which is connected to the first side wall layer (7) of the container. Method according to claim 16,
characterized in that
the second (6) or further layers are produced by extrusion, in particular by coextrusion of different materials, in particular with an adhesive layer. Method according to claim 16 or 17,
characterized in that
the layer (s) (6, 7) pretreated prior to bonding, in particular treated with plasma. Method according to one of the preceding claims,
characterized in that
the layer (s) (6, 7) is heat-treated before joining, in particular heated with infrared radiation. Method according to one of the preceding claims,
characterized in that
the outer layer (6) is printed, stamped, embossed and / or deep-drawn and / or provided with additional elements prior to joining. Method according to one of the preceding claims,
characterized in that
the outer layer is made in the form of a circumferential ring-like band, preferably elastically expanded, is slipped over the container with the first side wall layer and shrunk. Method according to claim 21,
characterized in that
the tape is thermally shrunk.

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