RU2766908C1 - Method of producing multilayer composite material for packaging liquid or fluid food products, material and container made therefrom - Google Patents

Abstract

FIELD: packing and storage.

SUBSTANCE: invention relates to production of multilayer composite materials without use of foil and packaging for food products of long-term storage, in particular, intended for packing liquid or fluid food products, such as milk, milk and cultured milk products, juices, nectars, soups, baby food products, puree-like products, cereals. Method envisages production of a multilayer material by extrusion-laminator technology on an extrusion-laminator installation, wherein the material includes four successively arranged layers of polyethylene, paper or cardboard, polyethylene and a metallised polyethylene film. Finished containers are formed from the obtained material.

EFFECT: using the proposed new technology, it is possible not only to exclude expensive foil and the inner layer of polyethylene, which is sensitive to oxidation, from production, but also to simplify the technology and reduce units of equipment.

14 cl, 4 dwg

Description

The invention relates to the field of production of multilayer combined film materials without the use of foil and packaging for food products with a long shelf life. In particular, intended for packaging liquid or flowing food products, such as milk, dairy products, fermented milk products, juices, purees, cereals, soups, nectars, baby food.

There are a significant number of patents in the prior art, owned mainly by Tetra Laval Holdings and Finance S.A., and containing information on methods for the production of multilayer and combined film materials based on aluminum foil using extrusion and laminator technologies: RU 2483932 C1, RU 2529522 C1, RU 2316427 C1, RU 2669866 C1; RU 2453439 C1; RU 2353523 C1, RU 2654037 C1; US 4657614 A, US 6551434 B1; EP 0575703A1.

The closest analogue, according to the applicant, for the claimed method is the description of the classical extrusion-laminator technology for producing multilayer films in article D1: http://plastweb.ru/ekstruzionnoe-laminirovanie/ (11.04.2014). Extrusion lamination is carried out by connecting two or more basic layers (for example, aluminum foil and paper), using a plastic film as an adhesive between them. This often involves preheating as well as surface treatment of these base layers (eg corona), which significantly increases the strength of the bond to the plastic film.

An extruded sheet or film can be laminated with a film on one or both sides. The most suitable materials for lamination are aluminum foil, metal or plastic mesh, paper. In the process of extrusion lamination, various structures of film or sheet products (paper / cardboard) can be obtained. The web to be laminated is unwound from a reel, then bonded to a plastic film, and then guided into a nip between several chill, pressure and pinch rolls. At the end of the lamination process, the multilayer or composite film material is wound into a roll and used as a packaging material in the usual manner.

However, the disadvantages of this (D1) and other known extrusion-laminator methods for producing multilayer films with aluminum foil are: the use of expensive aluminum foil, the specific gravity of which significantly exceeds the specific gravity of other materials used, problems with transporting the foil, because its rolls are easily damaged and must be moved in a suspended state; increased consumption of polyethylene, which forms a heat-sealable layer of material (because an additional adhesive polyethylene layer is required); the complexity of the technological process, the need to install a large amount of equipment, and, consequently, significant energy costs for servicing the installation and large areas for production.

Packages made of multilayer combined materials by Tetra-Pak are widely represented on the market. The material consists of 6 layers (see the figure 1 container of this material), located in the following sequence, starting with the outer and ending with the inner surface of the container formed from it: 1) - polyethylene; 2) - paper with a print applied to the surface facing outward; 3) - polyethylene; 4) - aluminum foil; 5) - oxidized polyethylene, 6) - unoxidized polyethylene. The weight of the layers is distributed as follows: paper (cardboard) - 75%; polyethylene - 20%; aluminum - 5%.

The disadvantages of this material are: the use of expensive aluminum foil, the specific gravity of which (2700 kg / m ³ ) significantly exceeds the specific gravity of the other materials used, the inability of the material to noticeable deformations - here it is inferior even to paper; increased consumption of polyethylene, which forms a heat-sealed layer of material. In addition, the presence of an inner layer of oxidized polyethylene, which is in direct contact with the food product, is an unsafe factor for the consumer, because. can give packaged products an unpleasant odor and taste due to the fact that during the manufacture of the material this layer is heated to over 270 ° C.

At the same time, the layer of aluminum foil in the packaging laminate creates gas barrier properties far superior to those of most polymeric materials. The classic aluminum foil packaging material for aseptic liquid food packaging is the most cost-effective packaging material. Any other competing material should be more cost effective in terms of raw materials, have comparable food protection performance, and have relatively low processing complexity into the final packaging laminate.

Currently, there are hardly any paper or paperboard-based packaging for long-term food storage on the market, made from an inexpensive packaging laminate without the use of foil and comparable to aluminum foil laminates, which have a reliable level of barrier properties and characteristics. food preservation for more than 3 months. There are some polymeric materials that provide good barrier performance, but either have poor mechanical properties in a laminate or are difficult to process into thin layers in laminates, such as requiring costly coextruding of the layers. Or, they can be significantly more expensive at an acceptable thickness than aluminum and therefore not economically viable for packaging eg milk or juice. When laminating packaging materials, such as liquid packaging, it is common practice to start with a paper or cardboard web, one or both sides of which are coated with different types of films or layers of material in order to achieve the desired properties of the final packaging material.

According to the applicant, a close analogue to the proposed material, according to the present invention, is patent RU 2487065 C1 (D2). It describes a packaging laminate without the use of foil for packaging liquid food products, a method for producing it, and a packaging container made from this material. The packaging material comprises a middle layer of paper or cardboard, a first outer liquid-impervious heat-sealable polyolefin layer, a second internal liquid-impervious heat-sealable polyolefin layer and an oxygen barrier layer. The packaging laminate has good gas barrier properties suitable for long-term aseptic packaging and good adhesion between layers to ensure package integrity, which is also important for long-term storage of liquid food products.

However, a disadvantage in the production of this packaging material is that complex equipment is required for applying the coating by vacuum evaporation, metal sputtering or ionic intrusion of the material forming such a coating.

Also close in technical essence to the proposed material according to the invention is patent RU 2519451 C1 (D3). It describes a non-foil packaging material for aseptic packaging of a liquid food product. The material includes a middle layer of paper or cardboard, outer liquid-impervious heat-sealable layers of polyolefin and an oxygen-impermeable layer applied to the inner side of the paper or cardboard layer. In this case, the liquid composition contains a polymeric binder dispersed or dissolved in a liquid medium. The material additionally includes a layer of a polyolefin-based matrix polymer together with inorganic filler particles distributed therein, and inorganic particles dispersed also in the gas-tight layer of the liquid gas-tight composition.

A disadvantage in the manufacture of these packaging materials is that the particulate polyolefin blend requires special process control, thorough mixing and complex extrusion equipment.

In the prior art, the Applicant did not find any mention of the possibility of using any equivalent replacement instead of aluminum foil, in particular proposals to replace it with a metallized polyethylene (PE) film. Especially in combination with paper or cardboard in the production of multilayer composite materials. At the same time, there is no information anywhere that it is expedient to use polyethylene as a connecting adhesive layer to create such film combinations.

Thus, on the one hand, there is a need in the market to create an inexpensive packaging multilayer composite material without the use of foil, and on the other hand, this material must have optimal barrier properties for packaging and storage of liquid or fluid food products, and at the same time acceptable mechanical and technological properties that meet the requirements of production.

The objective of the present invention is to meet the above needs in the market by creating an inexpensive packaging material through a technologically simpler method for the production of multilayer, composite film materials without the use of foil and the inner layer of oxidation-sensitive polyethylene, based on classical extrusion-laminator technology.

The problem is solved by the fact that the method of obtaining a multilayer combined material for packaging liquid or flowing food products provides for the production of a multilayer material by extrusion-laminator technology at an extrusion-laminator installation, while the material includes four consecutive layers of polyethylene, paper or cardboard, polyethylene and metallized polyethylene (PE) film.

The method according to the first embodiment provides for completing the extrusion-laminator installation with two laminators and two extruders (each with one flat die extrusion head) as shown in figure 3, instead of three units of laminators and three to four units of extruders according to known technology. In this case, the roll of paper / cardboard enters the first laminator. In the laminator 1, a layer of PE is applied to the surface of the cardboard through a flat-slot die of the extruder, which is then pressed against the cooling roller by a roller. This two-layer material then enters the second laminator. In the second laminator, a second layer of PE melt is applied to the two-layer material from the second extruder, which here is connected to the surface of the metallized polyethylene film being unwound from the roll. The metallized PE film enters the second laminator in such a way that the metallized surface faces the polyethylene melt connecting the layers. At the output, the finished combined material has 4 layers "PE - cardboard / paper - PE - metallized PE film".

Or, alternatively, the method can be carried out as shown in Figure 4. In this case, the extrusion laminating machine may include one laminator and one extruder with a double flat die. In the second embodiment of the method, the rolled material - paper or cardboard - enters the laminator, passing between the heated surfaces of the double extrusion head. In the laminator, two layers of molten polyethylene are applied to both surfaces of the paper through a double flat die extruder. Moreover, one of these layers covers one of the surfaces of the paper, and the second surface of the paper is connected by the second layer of PE to the metallized surface of the polyethylene film. And in this case, as in the first variant, the metallized polyethylene film enters the laminator in such a way that the metallized surface faces the polyethylene melt connecting the layers. At the output, a ready-made combined material "PE - paper - PE - metallized PE film" is obtained.

In addition, to increase the adhesion of the material layers, before feeding into the extrusion-laminator installation, the surface of paper or cardboard, as well as metallized PE film, is, if necessary, treated with a corona discharge in a coronator. Additionally, the installation may include a coronator(s).

In the resulting multilayer material, the layers are distributed approximately in the following ratio: polyethylene - 10-15%, paper / cardboard - 70-80%, metallized polyethylene film - 10-15%. The resulting multilayer material includes a metallized polyethylene film of 30-50 µm thickness required for the heat-sealing layer.

In the present method, a finished metallized polyethylene film is used. Metallized polyethylene films are widely known in the domestic market (for example, from the company "Galileo Nanotech", etc.). They are obtained by sleeve extrusion at temperatures not exceeding 170-190°C. They are not oxidized and do not impart flavors or odors to packaged products, unlike standard films with foil and high temperature extruded polyethylene. The barrier properties of films made of metallized polyethylene (with aluminum) are comparable to the barrier properties of aluminum foil, and are at a level that provides the required shelf life of packaged products from 3 months or more (up to 1-3 years).

The method according to the present invention is suitable for producing a multilayer composite packaging material for liquid or flowable food products, such as milk, milk, sour milk products, juices, soups, baby foods, nectars, purees, cereals.

Brief description of the figures

On FIG. 1 shows a packaging for food products, mainly milk and dairy products, made of a Tetra-Pak multilayer material. The composition of the Tetra Pak package using the example of Tetra Brik 1000 ml. List of layers and their functions: 1 - The outer layer of polyethylene protects the packaging and the design applied to the cardboard base from moisture. 2 - The cardboard frame gives the package shape and rigidity. 3 - Polyethylene connects cardboard with aluminum foil. 4 - Aluminum foil protects the product from oxygen, odors and light penetration. 5 - Another bonding layer of polyethylene. 6 - A layer of food-grade polyethylene for sealing the package.

On FIG. 2 shows a multilayer composite food packaging material according to the invention. List of layers: 1 - polyethylene; 2 - paper / cardboard with a print applied to the surface facing outward; 1a - polyethylene; 3 - metallized polyethylene film.

On FIG. 3 shows a block diagram of the first embodiment of the method according to the claimed invention. List of designations: 1 - roll cardboard/paper (layer 2) and PE granules (layer 1) arrive; 2 - cardboard / paper with a PE layer, PE granules (layer 1a) and metallized PE film (layer 3) arrive; 3 - finished roll material "PE - cardboard / paper - PE - metallized PE film".

On FIG. 4 is a block diagram of a second embodiment of the method according to the claimed invention. List of symbols: 1 - rolled cardboard / paper arrives (layer 2), then PE granules (layers 1 and 1a) are applied to paper from both sides and layer 1a is combined with a metallized PE film (layer 3); 2 - finished roll material "PE-paper-PE - metallized PE film".

Thus, according to the proposed method, the obtained multilayer composite material for packaging liquid or fluid food products includes four layers arranged in series - polyethylene, paper or cardboard, polyethylene and metallized polyethylene film (see Fig. 2).

The purpose of the first layer of polyethylene (1) is to protect the paper from the effects of external moisture and to provide the possibility of thermal welding during the formation of containers. The purpose of the second layer of paper or cardboard (2) is to provide a frame for the future formed container and apply the necessary printing design. The purpose of the third layer of polyethylene (1a) is the connection of the second layer and the metallized polyethylene film. The purpose of the fourth layer (3) is to provide the necessary gas barrier properties, namely the protection of products from the effects of oxygen and UV radiation, and the provision of the possibility of thermal welding during the formation of containers.

These 4 layers are distributed approximately in the following ratio: polyethylene - 10-15%, paper / cardboard - 70-80%, metallized polyethylene film - 10-15%. The multilayer material contains a metallized polyethylene film with a thickness of 30-50 microns required for a heat-sealed layer.

Such a composition of the layers makes it possible to reduce the weight of one square meter of material by 16.2 g by eliminating the use of aluminum foil and by another 15-20 g by eliminating the use of an inner layer of oxidation-sensitive polyethylene. Thus, there is a saving of consumables in comparison with the known classical production method while maintaining and even improving the safety and quality characteristics of the finished multilayer material.

A multilayer composite material is obtained by the claimed method on an extrusion-laminator installation in the configuration and sequence as shown in Fig. 3 according to the first block diagram (see also Example 1) or the second block diagram in FIG. 4 (see also Example 2).

The rolled four-layer material is then used to form packaging containers suitable for liquid or flowable foodstuffs. In packaging containers, mainly milk, dairy, sour-milk products, juices, nectars, soups, baby food, puree products, cereals are packed in appropriate or aseptic conditions directly at the factory.

As reported above, the Applicant did not find in the prior art any mention of the possibility of using metallized PE films instead of aluminum foil in combination with paper or cardboard in the production of multilayer composite materials. At the same time, there is no information anywhere that polyethylene can be used as an adhesive layer in the molten state for this purpose. Moreover, this polyethylene layer does not come into direct contact with the food product itself, but is needed only as a connecting adhesive between the layers - paper / cardboard and metallized PE film.

Thus, the technical result of the proposed invention is the creation in a simple technological process of an inexpensive, but high-quality and safe for the health of the consumer four-layer combined film material without the use of aluminum foil. This excludes the possibility of direct contact of the surface of the polyethylene layer with the food product. The material according to the invention is resistant to deformation, to undesirable oxidation, has optimal mechanical properties for production, acceptable gas barrier properties for long-term storage of liquid or flowing food products. This reduces the number of pieces of necessary technological equipment in the extrusion-laminator installation due to the fact that one (or several) extrusion-laminator(s) node(s), which forms a heat-sealable polyethylene layer, is dispensed with. That is, the production of highly demanded multilayer composite packaging materials is simplified and cheaper, and at the same time their quality and safety for food consumers are improved. With the help of the new proposed technology, it became possible not only to exclude expensive foil and the inner layer of polyethylene sensitive to oxidation from production, but also save on all consumables and equipment used, reduce energy and resource consumption for servicing only the necessary equipment, and reduce production areas. Thus, there is a simplification of technology and an expansion of the range of inexpensive, safe for the consumer food multilayer composite films and, accordingly, packaging from them.

The possibility of carrying out the present invention is illustrated by the following examples.

Example 1

An example is illustrated in the block diagram in Fig. 3. If necessary, the surface of the rolled material (for example, cardboard) is preliminarily treated in the “coronator” with a corona discharge to increase the adhesive ability, and then it enters 1 laminator. In the laminator 1, a layer of PE heated to a temperature of 300-320°C is applied to the treated surface of the cardboard through a flat-slot die of the extruder, which is then pressed against the cooling roller with a roller. This two-layer material then enters the second laminator.

In the second laminator, the two-layer material, if necessary, is subjected to corona treatment from the uncoated side and then a second layer of PE is applied to it from the second extruder. Here, the second PE melt connects the two-layer material with the metallized polyethylene film. If necessary, it can also be treated with a corona discharge. The metallized PE film enters the second laminator in such a way that the metallized surface faces the polyethylene melt connecting the layers. After that, the finished combined material "PE - cardboard / paper - PE - metallized PE film" is wound into rolls and delivered to the warehouse. Finished containers (containers) are formed from the material directly at the factory.

Example 2

An example is illustrated in the block diagram in Fig. 4. According to this scheme, the roll material, such as paper, enters the laminator, passing between the heated surfaces of the dual extrusion head. If necessary, the paper can be pre-treated in the coronator on both sides. This technique further increases the adhesive ability of the paper. In the laminator, 2 layers of polyethylene melt heated to a temperature of 300-320°C are applied to both surfaces of the paper through a double flat-slotted extruder head. Moreover, one of these layers covers one of the surfaces of the paper, and the second surface of the paper is connected by the second layer of PE to the metallized surface of the polyethylene film. Pre-metallized PE film, if necessary, is treated with a corona discharge. After that, the finished combined material "PE - paper - PE - metallized PE film" is wound into rolls and delivered to the warehouse. Finished containers/containers are formed from the material directly at the factory under suitable conditions.

These examples are not limiting to the present invention, but merely illustrate preferred embodiments of the invention in practice.

Thus, once again it is worth emphasizing the advantages of the claimed invention:

- instead of expensive aluminum foil, an inexpensive metallized polyethylene film is used;

- ready-made containers are safe for consumers of liquid or flowing food products due to the absence of an inner layer of oxidized polyethylene and the use of a neutral metallized PE film facing directly to the food product;

- layers of polyethylene are used as an adhesive for layers of material, while they do not come into direct contact with the food product;

- the claimed combination of layers provides optimal technological properties of the material and long-term storage of the food product;

- production is carried out using well-known and proven extrusion-laminator technology on well-known equipment (laminator, extruder, coronator), but according to a simplified scheme and with a smaller number of installed equipment, reducing the energy and auxiliary materials consumed in the production (for example, water cooling laminators) ;

- due to the improvement of the method, the dimensions of the process plant are reduced, and hence the area of production facilities;

- there is an improvement in the sanitary and hygienic characteristics of the packaging material;

- the specific gravity (mass of one square meter) of the finished material decreases;

- ease and convenience of maintenance of the technological line;

- production according to the new technology is inexpensive, high-quality and efficient.

Claims (14)

1. An extrusion-laminator method for producing a multilayer combined foil-free material for packaging liquid or fluid food products, characterized in that the multilayer material is obtained in an extrusion-laminator installation at a polyethylene melt temperature, preferably 300-320 ° C, the finished material includes four successively arranged a layer of polyethylene, paper or cardboard, polyethylene and metallized polyethylene film, while the polyethylene layer is used as a connecting adhesive between the paper/cardboard layers and the metallized polyethylene film, which is not in contact with the food product. 2. The method according to claim 1, characterized in that the extrusion-laminator installation includes two laminators and two extruders with one flat-slot extrusion head. 3. The method according to claim 1, characterized in that the extrusion-laminator installation includes one laminator and one extruder with a double flat die extrusion head. 4. The method according to claim 1, characterized in that the surface of paper or cardboard, as well as the metallized PE film, is additionally treated with a corona discharge. 5. The method according to claim 1, characterized in that the resulting multilayer material includes a metallized polyethylene film of 30-50 µm thickness required for the heat-sealable layer. 6. The method according to claim 1 or 5, characterized in that in the obtained multilayer material the layers are distributed in the following ratio: polyethylene - 10-15%, paper / cardboard - 70-80%, metallized polyethylene film - 10-15%. 7. The method according to claim 1, characterized in that milk, dairy, sour-milk products, juices, soups, baby food, nectars, puree products, cereals are packaged as liquid or fluid food products. 8. Multilayer combined non-foil material for packaging liquid or fluid food products, characterized in that it is obtained by the method according to any of claims 1-7, and includes four layers arranged in series - polyethylene, paper or cardboard, polyethylene and metallized polyethylene film. 9. Multilayer material according to claim 8, characterized in that its layers are distributed in the following ratio: polyethylene - 10-15%, paper / cardboard - 70-80%, metallized polyethylene film - 10-15%. 10. Multilayer material according to claim 8 or 9, characterized in that it contains a metallized polyethylene film with a thickness of 30-50 microns required for a heat-sealable layer. 11. A multilayer material according to claim 8, characterized in that milk, dairy, sour-milk products, juices, soups, baby food products, nectars, puree products, cereals are packaged as liquid or fluid food products. 12. A packaging container for liquid or flowable food products, made from a combined multilayer non-foil material according to any one of paragraphs. 8-11. 13. Packaging container according to claim 12, characterized in that it includes four consecutive layers of polyethylene, paper or cardboard, polyethylene and metallized polyethylene film. 14. A packaging container according to claim 12 or 13, characterized in that it is intended for packaging milk, dairy, sour-milk products, juices, nectars, soups, baby food, puree products, cereals.

Images