CH717332A1 - Reusable polyester container for filling with dairy products. - Google Patents

Abstract

The invention relates to a reusable polyester container (11) for filling with milk products with a container body (13) which is closed at its lower end by a base (15) and at its upper end a neck (17) with an opening (19) for filling or removing milk products. The areas of the container (11) which come into contact with the milk product are free of edges, corners and elevations on which the milk product can be deposited.

Description

Field of invention

The invention relates to a reusable polyester container for filling with dairy products according to the preamble of claim 1, a preform for producing a reusable polyester container according to the preamble of claim 15 and a tool for producing a preform according to the preamble of claim 16.

State of the art

Different packaging for dairy products, in particular for milk, are known from the prior art: milk packaging made of cardboard is usually made of multiple layers of paper, plastic and metal and is generally known under the generic name "Tetra Pak" or "Tetra Brik". The recycling of these multi-layer structures is difficult and therefore inadequate as a rule. Only a small part is sent for sustainable recycling.

Milk bottles made of glass are very heavy and, combined with the high melting point of glass, pose an environmental problem, since a lot of energy is required to manufacture, heat, transport, recycle and wash the packaging.

Milk bottles made of PET (polyethylene terephthalate) are light and easy to recycle. As a result, such milk bottles are environmentally friendly, but they can only be filled once and cannot be used as reusable bottles. This is because the temperatures during the washing process are 80 to 100 ° C above the softening point of the PET material. In the soft drink and water sector, returnable PET bottles are already state of the art, but the temperature of the washing process is well below the softening point of PET. Typical are 55 to 65 ° C with a 1 to 3% NaOH lye. For reasons of hygiene, the washing temperature must be much higher to remove milk product deposits. In contrast to water and soft drink products, the microbiological purity of dairy products is much more important, as the carbonic acid limits microbiological growth or the nutrient medium, e.g. water, is not ideal for germ growth. If the PET milk bottles are used once, the energy required to manufacture the bottles cannot be used optimally.

For milk bottles made of polycarbonate, Tritan or similar niche plastics, it is difficult to build a recycling cycle because the quantities are too small.

Object of the invention

The disadvantages of the described prior art result in the object of creating a polyester container for filling with dairy products, which can be filled several times and still meets the hygiene requirements for refilling.

description

The solution to the problem posed is achieved in a reusable polyester container for filling with dairy products through the features cited in the characterizing section of claim 1. Further developments and / or advantageous design variants are the subject of the dependent claims.

The invention is preferably characterized in that the areas of the container which come into contact with milk product are free of edges, corners and elevations on which milk product can be deposited. The deposits usually dry up and are therefore difficult to remove from the surface of the container. Proteins in milk can form glue-like caseins that stick to the PET bottle like glue. In particular, injection burrs or separating seams, which inevitably arise in the injection molding process for producing the preform serving as the basis for the container, do not come into contact with the milk product. There are also no reinforcing ribs formed on the container to reinforce the container bottom. The present container is therefore optimized for multiple filling, since milk product cannot collect in any hygienically problematic places. The front side of the container on which the opening is located is also free of spray burrs. This makes it easier to seal the opening and a plastic lid without a sealing ring with added plasticizers is sufficient to seal the container. Existing spray burrs are formed on the outside of the container. If these become dirty, although contact with milk product is largely prevented, they are very easy to clean as they are easily accessible.

In a further particularly preferred embodiment of the invention, the container is made from a preform and injection burrs, which arise during the production of the preform, are present in areas of the container which are free from milk product contact. A deposit of milk product on such spray burrs is impossible, as a result of which the cleaning of the container before refilling is significantly improved. In the stretch blow molding of the preform to form the container, no further undesirable, hygienically questionable elevations or edges arise.

In a further preferred embodiment of the invention, the container is made from a preform and injection burrs, which arise during the production of the preform, are formed on the outside of the container. The arrangement of the spray burrs on the outside of the container reliably prevents hygienically questionable contact with milk products filled in the container. Should the external spray burrs nevertheless become soiled (for example during filling or pouring), these spray burrs are easily accessible and can accordingly be cleaned with little effort.

In a further particularly preferred embodiment of the invention, the polyester of the container is mixed with a copolymer, the softening temperature increases to temperatures above 87 ° C measured according to DIN EN ISO 11357-2: 2014-07 and the container washing temperatures of more than 70 ° C. The container can therefore be cleaned with the necessary cleaning or washing processes in order to completely remove milk product residues from the container. The container is therefore suitable for multiple filling. In addition, the container is resistant to strong oxidizing agents such as peroxides. By using strong oxidizing agents, the cleaning process of the container can be further improved or microorganisms can be killed.

It has proven to be useful if the copolymer is isosorbide and / or naphthalene dicarboxylic acid (NDC). These copolymers bring about a reliable increase in the softening temperature.

The container expediently has a volume shrinkage of less than 3% when heated to 70 ° C. This means that the same amount of milk product can always be filled into the container even after repeated cleaning. Refilling with the corresponding filling quantity is possible for more than 10 filling cycles.

The invention is also preferably characterized in that the bottom is flat or cambered inward and is free of stiffening ribs. As a result, the inside of the base can also be cleaned particularly easily, since there are no elevations on which milk product could deposit. The visual inspection of the container and the milk product is also improved, since there are no ribs on the bottom to refract the light. In addition, the even flow through the container is improved, since there are no ribs which worsen the flow conditions when washing the container. The crowning improves the stability of the base, which reliably prevents bulging or damage due to the weight of the product.

During stretch blow molding, the preform is turned inside out into the “champagne base”, and thermal stresses remain in the bottom of the bottle. These thermal voltages attempt to bulge the floor back into the shape of a preform when it is heated up (hot washing process). The distance between the center of the floor (injection point) and the substrate becomes smaller with each washing process and is measured as the base clearance. This base clearance remains greater than 0 even after the container has been washed several times, which means that the container has a stable footprint even after repeated washing cycles.

The wall thickness of the floor is advantageously between 0.3 and 1 mm and preferably between 0.5 and 0.8 mm at its standing surface. As a result, the base does not bulge and is also not damaged by the weight of the dairy product, as it is sufficiently stable due to the increased wall thickness.

In a further particularly preferred embodiment of the invention, the opening has a diameter which is between 30 and 50 mm and preferably between 31 and 46 mm. The enlarged opening allows the washing solution to be poured in quickly and removed from the container quickly. The product filling and emptying is also facilitated by this dimensioning of the opening. In particular, the drying of the container is accelerated by the large opening. This is advantageous because the container has to be partially filled dry for hygienic reasons.

In a further particularly preferred embodiment of the invention, the container has a transparent green or brown color. As a result, the vitamin B2 contained in the milk product is protected from light decomposition and the container can still be visually checked, for example with a camera or visual inspection. The polyester can be colored using color pigments or "dyes". The color filters the light in a range from approx. 200 to 550 nm. The use of UV blockers, which filter light in a spectrum from approx. 200 to 400 nm, is also conceivable. The desired coloration filters out the UV radiation and parts of the visible light in a targeted manner (200 to 550 nm) in order to protect the vitamin B2 in the milk.

The polyester is expediently free from titanium dioxide pigments. Titanium dioxide pigments have the disadvantages that they make the polyester opaque and its surface rough. By avoiding titanium dioxide, the polyester used is therefore transparent and has a smooth, easy-to-clean surface.

It proves to be advantageous if the container has a plastic cover for closing the opening, which has a sealing ring protruding into the opening and tapering in the direction of the opening. Such closures are also known as "cone sealers". As a result, the open end face of the container neck is sealed off by the sealing ring and no milk product can penetrate the end face. The “Cone Sealer” can also compensate for dimensional deviations in the area of the opening, which means that the seal does not require any rubber-like plasticizers for a reliable seal. This also increases the efficiency of the washing process, since such softeners contaminate the detergent.

The container expediently has a filling volume between 200 ml and 1500 ml and preferably between 500 ml and 1000 ml. These volumes are widespread and common for dairy products such as milk, yogurt or cream.

It proves to be expedient if the polyester is a polyethylene terephthalate copolyester. PET is the leading plastic in the reusable filling of bottles. A reusable system for dairy products based on PET can therefore be quickly established and expanded. The PET can also be a PET with a high isosorbide content as a copolyester (PEIT).

Another aspect of the invention relates to a preform for producing a container described above. The preform is characterized by the fact that the injection burr, which occurs when the neck is injection molded at the transition between two injection molded parts, is formed on the outside of the neck. This design feature leads to the advantages described above that the milk product does not come into contact with spray burrs.

Another aspect of the invention relates to a tool for producing a preform, as described above. The tool is characterized in that the injection core is shaped in such a way that the transition between the injection core and the jaws is provided on the outside of the cavity. As a result, the spray burr or the separating seam, which occurs at the transition between the injection core and the jaws, is formed on the outside of the preform neck, where this elevation does not come into contact with the milk product.

In a particularly preferred embodiment of the invention, the open end of the cavity, at which the injection core is pushed into the outer shell, is surrounded by the injection core. This creates the injection burr at the transition between the injection core and the jaws on the outside of the preform neck and does not come into contact with the milk product filled in the container.

Further advantages and features emerge from the following description of an exemplary embodiment of the invention with reference to the schematic representations. These show, in a representation not true to scale: FIG. 1: a side view of a container for filling with milk products; FIG. 2: a side view of a tool with an injection-molded preform according to the prior art; and FIG. 3: a side view of a tool with an injection-molded preform, in which the injection burr is created on the outside of the preform neck.

In FIG. 1, a reusable polyester container, in particular a reusable bottle, is shown, which is designated as a whole by the reference numeral 11. The container 11 has a container body 13 which is closed at its lower end by a base 15. A neck 17 with an opening 19 adjoins its upper end. The container 11 can be filled with milk products and emptied via the opening 19. The container 11 has a longitudinal axis 21.

Since it is a reusable container, it must be ensured that the container 11 can be completely freed or cleaned of residues and deposits of the milk product before refilling. Product residues, which are very difficult to remove, accumulate on edges, corners and elevations. The present container 11 is therefore free of such elevations in its areas which come into contact with milk product. The container is stretch-blown from an injection-molded preform 23b with a preform body 24. In particular, injection burrs 25, which are unavoidable during the production of the preform 23, are arranged in areas of the container 11 which do not come into contact with milk products. There is also no injection burr on the open end face of the neck 17. In the case of the novel container 11, therefore, it is reliably avoided that product residues are deposited on spray burrs 25. The bottom 15 does not have any reinforcing ribs which absorb the increased weight load caused by the product. Instead, the base 15 is cambered inwards so that the base is not deformed or even damaged under the weight of the product. Deposits on reinforcing ribs are therefore avoided in the case of the container 11. To avoid deformations, the base 15 preferably has an increased wall thickness between 0.5 and 0.8 mm in addition to the crown.

In addition to avoiding product deposits, another point for the implementation of reusable containers is the possible cleaning according to the hygiene standards for milk product packaging. For this purpose, the container 11 has to endure washing solutions with a temperature of up to 90 ° C. and pH values between 12 and 14 without becoming softened or exhibiting a volume loss of more than 3%. In order to be able to withstand these washing conditions, the softening point of the polyester, in particular of the PET, must be increased. This is achieved with the addition of copolymers, in particular isosorbide or naphthalene dicarboxylic acid. This allows the softening point of the polyester used to be increased up to 90 ° C. In addition, the container can also be disinfected with strongly oxidizing detergents such as peroxide. The opening 19 has a diameter between 31 and 46 mm so that the washing solution can be injected into the container and emptied in a simplified manner.

In many cases, disposable PET milk bottles are colored white with titanium dioxide pigments in order to ensure that the milk product is protected from light. In particular, the vitamin B2 contained in dairy products must be protected from light in order not to be broken down with the formation of unpleasant odors. Titanium dioxide pigments, however, are responsible for the formation of a rough surface on which deposits and germs can easily hold. The polyester used to manufacture the present container 11 is therefore free of titanium dioxide. To achieve the necessary light protection, the container is colored green or brown, but is nevertheless transparent so that optical controls can be carried out. "Dyes" or color pigments are used for coloring.

These allow the inside of the container to remain smooth and easy to clean. The light protection extends from approx. 200 to 550 nm. UV blockers with a protection range between 200 and 400 nm are also conceivable.

On the outside of the neck 17, an external thread 27 and an underlying support ring 29 are formed. The external thread 27 can interact with an internal thread 31 of a plastic cover 33 in order to close the opening 19. PVC plasticizers or epoxy coatings in the seal of the lid can compensate for irregularities on the front side of the container and thus enable reliable seals. However, such seals provided with auxiliary substances contaminate the detergent. In order to avoid such auxiliary substances in the seal, the face of the neck17 is free of burrs. In addition, on its side facing the opening 19, the cover 33 has a sealing ring 35 which protrudes into the opening 19 and tapers in the direction of the opening. Such a sealing ring, also known as a “conesealer”, reliably seals the opening 19 without the need for chemical auxiliaries.

In Figures 2 and 3 tools 36a, 36b for producing a preform 23a, 23b are shown, wherein in Figure 2, a tool 36a is shown according to the prior art. Both tools have an injection core 39, two jaws 41a, 41b for shaping the neck 17 and the support ring 29 and a two-part outer shell 43. A cavity 44 for forming the preform 23a, 23b is formed by the injection core 39, the jaws 41 and the outer shell 43 and represents a negative shape of the preform 23a, 23b.

In FIG. 2 it is shown that the transition between the injection core 39a and the jaws 41a, 41b lies on the end face of the neck 17 and therefore an injection burr is formed on the end face of the neck 17. This is undesirable for the hygienic reasons described in detail above.

Therefore, in the tool 36b, as shown in FIG. 3, the injection core 39b is shaped in such a way that the transition between the injection core 39b and the jaws is provided on the outside of the cavity 44 or the neck 17. As a result, the splash burr 25 no longer comes into contact with the milk product and the splash burr 25 cannot become soiled. This shaping of the injection core 39b can be realized in that the injection core 39b surrounds the cavity 44 or the preform 23b at the open end. The injection core 39b therefore everts the opening 19. The position of the injection burr 25 on the outside of the neck 17 is shown in FIG.

Legend:

11 reusable polyester container, reusable bottle 13 container body 15 bottom 17 neck 19 opening 21 longitudinal axis 23a, 23b preform 24 preform body 25 injection burrs 27 external thread 29 support ring 31 internal thread 33 plastic lid 35 sealing ring 36a, 36b tool 39a, 39b injection core 41a, 41b Jaws 43 Two-part outer shell 44 Cavity

Claims (17)

1. Reusable polyester container (11) for filling with milk products - A container body (13) which is closed at its lower end by a base (15) and at its upper end has a neck (17) with an opening (19) for filling or removing milk products, characterized in that, that the areas of the container (11) which come into contact with milk product are free of edges, corners and elevations on which milk product can deposit. 2. Container according to claim 1, characterized in that the container (11) is made from a preform (23b) and injection burrs (25) which arise during the production of the preform (23b) are present in areas of the container (11) which are free from dairy product contact. 3. Container according to claim 1 or 2, characterized in that the container (11) is made from a preform (23b) and injection burrs (25), which arise during the production of the preform (23b), on the outside of the container (11 ) are formed. 4. Container according to one of the preceding claims, characterized in that the polyester of the container (11) is mixed with a copolymer, whereby the softening temperature rises to temperatures above 87 ° C measured according to DIN EN ISO 11357-2: 2014-07 and the container (11) can withstand washing temperatures of more than 70 ° C. 5. Container according to claim 4, characterized in that the copolymer is isosorbide and / or naphthalene dicarboxylic acid (NDC). 6. Container according to one of the preceding claims, characterized in that the container (11) has a volume shrinkage of less than 3% when heated to 70 ° C. 7. Container according to one of the preceding claims, characterized in that the bottom (15) is flat or cambered inward and is free of stiffening ribs. 8. Container according to one of the preceding claims, characterized in that the wall thickness of the base (15) is between 0.3 and 1 mm and preferably between 0.5 and 0.8 mm at its standing surface. 9. Container according to one of the preceding claims, characterized in that the opening (19) has a diameter which is between 30 and 50 mm and preferably between 31 and 46 mm. 10. Container according to one of the preceding claims, characterized in that the container (11) has a transparent green or brown color. 11. Container according to one of the preceding claims, characterized in that the polyester is free from titanium dioxide pigments. 12. Container according to one of the preceding claims, characterized in that the container (11) has a plastic lid (33) for closing the opening (11), which has a protruding into the opening (19) and extends in the direction of the opening (19) has tapered sealing ring (35). 13. Container according to one of the preceding claims, characterized in that the container (11) has a filling volume between 200 ml and 1500 ml and preferably between 500 ml and 1000 ml. 14. Container according to one of the preceding claims, characterized in that the polyester is a polyethylene terephthalate copolyester. 15. Preform (23b) for producing a container (11) according to the preceding claims - a preform body (24), - A neck (17) adjoining the preform body (24), which neck can have an external thread (27) and - A support ring (29) which is formed on the outside of the neck (17) at the transition from the neck (17) to the preform body (24), characterized, that the injection burr (25), which occurs during the injection molding of the neck (17) at the transition between two injection molded parts (39, 41), is formed on the outside of the neck (17). 16. A tool (36b) for producing a preform (23b) according to claim 15 having - an injection core (39b), - two jaws (41a, 41b) for shaping the neck (17) and the support ring (25), - A two-part outer shell (43) and - a cavity (44) which is formed by the injection core (39b), the jaws (41a, 41b) and the outer shell (43) for forming the preform (23b) and which represents a negative shape of the preform (23b), characterized, that the injection core (39b) is shaped in such a way that the transition between the injection core (39b) and the jaws (41a, 41b) is provided on the outside of the cavity (44). 17. Tool according to claim 16, characterized in that the open end of the cavity (44), at which the injection core (39b) is inserted into the outer shell (43), is surrounded by the injection core (39b).