FR2539106A1 - THERMOPLASTIC FOOD CONTAINER AND PROCESS FOR PRODUCING THE SAME - Google Patents

Abstract

The present invention relates to a thermoplastic container as well as its manufacturing process. The thermoplastic container 101 is formed from a sheet of a multilayer thermoplastic material which is thermoformed. The container 101 comprises a frustoconical upper body 102 comprising a filling opening, and a frustoconical lower body 103 whose bottom is closed, these two bodies being welded together by friction. The container is particularly advantageous as a packaging for food products which are susceptible to spoilage by passage of oxygen through the walls of the container. This container is suitable for hot filling. (CF DRAWING IN BOPI)

Description

The present invention relates to containers

  thermoplastics intended to receive food In parti-

  The present invention relates to thermoplastic containers consisting of several layers of thermoplastic materials. In the current state of food packaging, many food products such as soups and juices are still packed mainly in containers

metal.

  Due to the high acidity and high susceptibility to oxygen spoilage, many food products have to be packed in containers

  which offer additional chemical resistance

  silencing acidity as well as impermeability and

  hermetic closure This implies, in the case of

  metal pillars, the establishment of an internal liner

  on the metal container in order to prevent the acidity of the

  food dude to attack the metal of the container.

  Other types of food containers include glass containers with a metal cap. The glass container not only offers chemical resistance to acidity but also provides an impermeable barrier to the entry of oxygen. in the container Unfortunately, the glass container is

  costly and breakable and in addition the glass debris constitut

  risk of accidents-for consumers

  can also be said that both the metal containers

  With their internal coating, glass containers are more expensive to manufacture and therefore less desirable than thermoplastic containers for packaging.

the same food products.

  However, the majority of plastic containers, authorized to be brought into contact with foodstuffs, and used as packaging have the disadvantage, in particular, that they do not have all the characteristics of a container. For example, one of the materials strongly desired to pack food is polyethylene terephthalate (PET), which is a hard and transparent plastic, with good resistance properties, -2-

  but moderate barrier properties However, this

  The material does not have sufficient impermeability to protect products that are susceptible to deterioration in the presence of oxygen. Thus, soups and juices rapidly deteriorate when placed in PET containers because of the relative porosity of the product. PET vis-à-vis the penetration of oxygen Therefore, PET is not very suitable as a packaging container for

foodstuffs.

  The present invention aims to avoid the disadvantages of the containers that currently exist, using a container with multiple layers; this container is highly impervious to the transmission of gases such as C 02 and oxygen, it is hard and resistant,

and inexpensive to manufacture.

  The thermoplastic container of the present invention, intended to be filled with hot materials, is characterized in that it comprises: a frustoconical upper body comprising a filling opening at the top and an open bottom, of a larger diameter than that the filling aperture-e ge, and a frustoconical lower body whose bottom is closed and an open top adapted for a suitable fit with the frustoconical upper body; and of which at least one of these bodies comprises a multilayer thermoplastic material at least one layer of which is constituted by a barrier polymer having a low gas permeability, and these two bodies being welded together by

  friction to form a single container.

  The container of the present invention is made by coextruding barrier polymer between two layers of the polymer of the container with foil formation and then by thermoforming to obtain both

  separate sections or the two bodies which are then

friction dice.

  The present invention is also described with the aid of the accompanying drawings in which FIG. 1 represents a profile view, in partial section, of a container manufactured according to an embodiment of the invention; Figure 2 shows an axial view of one end of the container of Figure 1, taken along the line 2-2; Figure 3 shows an axial view of the bottom of the container of Figure 1; FIG. 4 represents a profile view, in section

  of the container of Figure 1 after the container

  neur has been filled; FIG. 5 represents a profile view, in section, of an embodiment different from the closure lid of the container of FIG. 1; Figure 6 shows a sectional view of the lid of Figure 5 after filling with a hot material; Figure 7 shows a partial sectional view of the assembly of the upper and lower parts of the container.

  Referring to Figure 1, there is shown a

  Thermoplastic 101 is particularly advantageous for packaging hot food products, for example vegetable juices.

  upper part 102 and a lower part 103

  upper portion 102 is constituted by a truncated cone having at the top a depression in the neck 104 and a peripheral rim 105 The edge 105 has a depression 106 for the lid defining an opening

filling 107.

  The lower part or base section 103 is constituted

  killed by a truncated cone-108 extending upwardly, having at its upper end a peripheral flange

  109 of rotation welding, integrally mounted on it.

  The lower or cutting portion 103 has an edge 110 forming the bottom support of the container and a diaphragm portion 111. The diaphragm portion 111 comprises a central disc separated from the edge 110 by a pair of grooves.

alternates 112 and 113.

  The arrangement of the disc and grooves 112 and 113 allows a degree of flexibility on the volume of the container 101. A flexible metal cover 114 is used to fit over the filling pad 105. This cover 114 is made of preferably made of a material

  ductile, as for example in aluminum foil.

  The central portion 115 which can be depressed, is light-

  raised relative to the cover 114, this central portion 115 is formed to provide a space

  flexible above the product which has filled the container.

  Several recesses 116, preferably at least three, have been made in the upper part of the frustoconical body 102. These depressions 116 are preferably situated at the periphery of the upper part of the truncated body.

  the same way, another series of at least three

  ments 117 are practiced in a lower part 103.

  These recesses 116 and 117 are adapted for stacking so that several stacked containers, having the same configuration, do not lock together before

to be dislocated and used.

  The preferred material for forming the container of

  the invention consists of a multi-layer thermoplastic sheet

  layer having an inner layer and a polypropylene outer layer and an interlayer bonded to the other two and made of an ethylene-vinyl alcohol copolymer (EVAL) This sandwiche composition provides a

  impermeable polypropylene layer inside the

  and a resistant and decorative outer layer

  polypropylene, and an intermediate layer of

  EVAL copolymer between the two layers of polypropylene.

  The EVAL copolymer layer serves to form a barrier to the passage of oxygen, so as to avoid any

  oxygen penetration inside the container and

  thus protect the food from rapid deterioration.

  According to one embodiment, the thermoplastic sheet

  The multilayer tick has been coextruded through a coextrusion die; the sheet is then thermoformed for example by extrusion blowing to form the

  upper and lower end parts.

  A method of thermoforming can be applied which offers the additional advantage of

biaxial in the container.

  Other more conventional methods for thermoforming container parts such as vacuum molding, or blow extrusion can also be

used.

  After having thermoformed the upper part 102,

  a stamping machine can be used to discover

per upper opening 107.

  After thermoforming the upper and lower portions of the container into the composite sheet, each portion is placed on its respective mandrel of the rotational welding apparatus, and these parts are welded together.

  so as to form a hermetically sealed container 101.

  It is preferable to provide a slight adjustment space in the parts of the container between the flange 109 and the lower portion of the tapered portion 102. This allows slight variations in the dimensions of the two parts of the container while providing assistance in achieving

  their welding by rotation welding techniques.

  The choice of polypropylene or polyethylene terephthalate as the inner and outer layers of the container ensures a strong frictional bond between the two parts due to the ability of these polymers to be welded

by friction.

  Referring to Figure 4, we show a

  when filled and chilled The problem with previous containers was retraction, which occurred when the food, which

  had been heated or heated to sterilization

  was placed in the container (filling technique).

  wise to hot) The problem usually appears when

  hot food products at a temperature exceeding

  950 C, are placed in the container and then sealed the container As the heated food and the air above them in the container are cooled, they shrink naturally because of the temperature change in In many cases this causes warping of the outer wall or top and bottom of the container. This is particularly annoying for thermoplastic containers which have a higher flexibility than metal or glass containers. Thanks to the present invention, this problem is remedied by means of the single diaphragm 111 of the lower part, having expansion grooves 112 and 113 to allow upward bending of the lower part. In the same manner, the upper cover 114 has the possibility of compensating for the removal of the upper air space and the products as shown in

  4, the portion 116 of the cover 114 is sufficiently

  ductile to be pulled down into the container opening when the product shrinks due to cooling.

  retracted, the cross portion 115 of the lid 114 is

  downward in the area of the flange 106, 107 of the

upper tie 104 -

  It can thus be seen in this Figure 4 how the top cover 114 was pulled down during the cooling of the food product and how the diaphragm 111 of the lower part was bent upwards to compensate for the withdrawal of the liquid. The main advantages of the present invention lies in the fact that these two effects are not noticed for the consumer. One of the significant disadvantages of thermoplastic containers used previously.

  lies in the fact that the shrinkage due to cooling

  This causes the inner walls of the upper and lower parts of the container to bend inwardly. This deflection or warping of the container

  plastic is often misinterpreted by consumers

  Therefore, by virtue of the present invention, the bending of the diaphragm of the lower part is caused, and that of the closure lid of the upper part 7 to compensate for the effects of the retraction of the contents of the product.

  As a result, the warping of the side walls

  the lower part is not noticed for the average consumer and the pull down

  closing cover appears as a condition

  natural seal.

  FIGS. 5 and 6 illustrate a preferred embodiment of the invention according to which a metal sheet cover of a different construction is used. In FIG. 5, the cover 214 comprises an external circular flange 215 and a ribbed diaphragm 216. rib 216 and dome 217 sink into the container to remove most of the air contained in the container and located above the food products it contains This significant reduction of the upper space gives a reduction of the vacuum effect when the air trapped products get cooler In fact this allows a downward bending of the lid better controlled, when the

  products contained in the container are cooling down.

  Figure 6 shows the final downward position of the airtight seal system after total depression

  in the filling opening of the container.

  The present invention also relates to a process for manufacturing a thermoplastic container for drinks

  and foods from a sheet of thermoformed material

  composite plastic having a barrier inner layer, the method comprising thermoforming the upper and lower portions of the container from this multi-layer sheet, and then welding by

  rotation of these two parts to form a single container.

  The bottom of the container includes a flexible diaphragm, while the top receives a sheet capable of sinking for sealing and for compensating for the shrinkage of cooling air and products.

contained in the container.

  In addition to the advantages of the present invention, which are enumerated above, the design of the container described herein is particularly advantageous for the

transport.

  Although most prior conventional containers are formed in a single operation, they must be either formed on the site or transported empty, however, the present invention relates to a nestable container and can therefore be transported.

  for only part of the taste required for

  Conventional Containers Since most conventional containers must be transported empty, the truck

  or the wagon containing these containers is mainly filled

  For example, the average load for a semitrailer carrying normal products is around 10 tonnes, while the load

  a semi-trailer filled with plastic containers

  that empty, would be only 2 tons, ie the container carrier pays the price of an entire truck to transport air According to the present invention, the containers can be transported by separate parts, which because of their frustoconical shape can be nested in a very compact arrangement The upper parts 102 are nested together and transported in a container while the lower parts 103 can be nested together and sent into a separate container, which translates into an important saving on the cost of transport The nested parts arrive at the user who performs the filling of the container There is placed the upper and lower parts on a friction welding apparatus to form a single container

  friction welding machines which are particularly

  used to weld the containers of the invention are described in US Patents 3,800,400,

  3,799,821, 3,708,376 and in Reissue 29,448.

  Although the present invention has been described by means of preferred embodiments, it is not

  however not limited to these Thus, although the material

  cited for making the container either polyethylene

  does not terephthalate or polypropylene, it is understood that

  other thermoplastic materials can be used

  such as polyethylene, polyethylene 9

  glycol terephthalate, polyvinyl chloride, poly-

  styrene, as well as other polyolefins and polyesters.

  In the same way, other materials having barrier properties, such as polyvinylidene chloride, polyvinyl alcohol, polyvinyl chloride-polyvinylidene chloride copolymers and

  styrene-acrylonitrile copolymers.

  In addition, although the container described is cylindrical to be friction welded, it is understood that other geometric shapes may be used,

  such as oval, elliptical or poly-

  gonales, and instead of the friction welding it is possible to practice oscillation welding; the latter technique and the appropriate apparatus are described in the French patent application No. 83 06630 filed on the 22

April 1983.

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Claims (11)

claims:   Composite thermoplastic container for filling with hot materials, characterized in that it comprises: a frustoconical upper body 102 comprising a filling aperture 107 at the upper end and a lower end of a larger diameter   that of the filling opening; -   a frustoconical lower body 103 whose bottom is closed and having an open upper end,   adapted for a proper fit with the upper body   and at least one of these co-rps comprises a multilayer thermoplastic material of which at least one layer is constituted by a barrier polymer having a low gas permeability, these two upper and lower bodies being   welded together by friction to form a single container.   Composite thermoplastic container according to the invention   1 characterized in that the container comprises   inner and outer layers of a thermoplastic material   resistant, these layers being coextruded with a   intermediate layer of a barrier polymer.   3 thermoplastic composite container according to claim 2 characterized in that the thermoplastic material is polypropylene and the polymer   barrier is an ethylene-polyvinyl alcohol copolymer.   4 Composite thermoplastic container according to one   any of claims 1 to 3, characterized in that   it comprises at its lower end a vacuum compensation device comprising a flexible diaphragm 111 adapted to curve inwardly of the container in response to the vacuum created therein during the cooling of the filling material, at its end a vacuum compensation device having a sheet cover 114 sealed to the filler opening 107, this being   lid having a diiagma 115 which can sink.   Container according to claim 4, characterized in that it comprises a flexible cover 114 adapted for the removal of the closure film over the filling opening, said cover having a diaphragm 115 which can push inward   container in response to the vacuum created in the container.   Container according to any one of the claims   1 to 5 characterized in that the diaphragm 111 has the shape of a circular disc surrounded by a U-shaped flange. 7 Container according to claim 5 characterized in that the flexible cover 114 is constituted by a metal foil.   Process for preparing a thermoplastic, expandable container having barrier properties, for filling with hot products, and having vacuum compensation systems, the process being characterized by the steps of -coextruding a sheet of thermoplastic material composite having at least one layer of a resistant polymer and at least one layer of a barrier-barrier polymer; thermoforming from this sheet a frustoconical upper body having an open end, wider and a narrower end with a filling opening; thermoforming from this sheet a frustoconical lower body having an open upper end, wider and a lower closure, the latter being thermoformed so as to contain a flexible diaphragm 111 which curves inwardly of the container in response to the vacuum created In this one; friction welding the upper body 102 and   lower 103 together to form a single container 101.   Process for forming a thermoplastic container according to claim 8, characterized in that it comprises a step of placing a hermetic lid   114 on the container, this lid comprising a device   tive to curve into the container in response to to emptiness created in this one.   Process for forming a thermoplastic container   according to any one of claims 8 and 9   Characterized in that at least three polymer layers are coextruded, the outer layers being of resistant polymer, the intermediate layer being of barrier polymer. Process for forming a thermoplastic container according to Claim 8, characterized in that the polymer   resistant is selected from the group consisting of   propylene, polyethylene, polyethylene terephthalate, polyethylene glycol terephthalate, polystyrene,   polyvinyl chloride, and copolymers thereof.   12 Process for forming a thermoplastic container,   according to claim 8, characterized in that the polymer   The barrier is selected from the group consisting of   ethylene-polyvinyl alcohol, polyvinyl alcohol, polyvinylidene chloride, polyvinylidene polyvinylchloride chloride copolymers and styrene-acrylonitrile copolymers. 13 Process for forming a thermoplastic container   according to any of claims 8 to 12, characterized   in that the friction welding of the upper and lower bodies of the container is effected by rotation or oscillation.