Multylayered oriented tubular film for food packing

FIELD: film for food packing.

SUBSTANCE: claimed tubular film contains at least three polyamide layers, wherein each layer consists mixture of (mass parts) polyamide 6 70-77; polycaprolactam-hexamethylenediamine-adipic acid copolymer 5-11; amorphous resin 20-25; aromatic polyamide containing hexamethylene diamine and terephthalic acid units in molecule 3-8; and mixture of acid modified copolymers 0.3-5.

EFFECT: film of improved barrier properties, moldability, abrasive and oil resistance.

3 cl

The invention relates to food industry, namely the production of a multilayer film packaging materials on polyamide basis for long-term storage of various food products and can be used for conventional or vacuum packing of perishable products such as fresh meat, meat products, cooked sausages, sausage cheese, and meats of these products, and bulk products such as various cereals and pasta.

Artificial multilayer oriented tubular film based on synthetic polyamides are widely used in the food industry for the packaging of perishable products. However, this type of films, in some cases, do not provide the required length of storage products. Therefore, further improvement of the blown film aimed primarily at improving their barrier and optical properties, strength properties.

Known, for example, a multilayer oriented heat shrinkable film for packaging food products, which has high rigidity, good shrinkage when heated, high optical properties and good barrier properties against oxygen. The film has a thickness of 12-50 μm and contains more than seven symmetrical layers. The main layer of multi-stakeholder who oinoi film made of a copolymer of ethylene and vinyl alcohol. The intermediate layer is made of polyamide, which includes a copolymer of nylon 6 and nylon 12. Two outer film layer made of a mixture of synthetic materials, the mixture can be accomplished in two ways. The first option is a mixture containing a linear low-density polyethylene (40-60%), linear medium-density polyethylene (20-30%) and a copolymer of ethylene and vinyl acetate (20-30%). The second option is a mixture containing a copolymer of ethylene and propylene (85-96%) and polypropylene (4-15%). In addition, the composition of this multilayer film includes two adhesive layer located between the intermediate and outer layers, which consist of linear low density polyethylene and linear medium-density polyethylene modified with acid or acid anhydride (for the case of mixture of the outer layer on the second version). This film, according to its developers, provides sufficient, in terms of storage, food preservation (see U.S. patent No. 4755419 class 32 In 27/08, published in 1988).

This multi-layer film has at least three major drawbacks. Firstly, the composition of the polymeric materials comprising the layers of the film, it is not possible to obtain a tubular film with high mechanical strength, therefore, a well-known film has sklon is here to damages due to various external mechanical influences. Secondly, this film has a low barrier properties against moisture, which reduces the duration of storage of the Packed product and leads to rapid deterioration of her. Thirdly, the high rigidity of the film affects its elasticity, therefore, this film is totally unsuitable for vacuum packaging of food products, that is, the scope of application of the known film is severely limited.

Also known thermoplastic multi-layer protective packaging film, which is used for making bags. This multi-layered heat-shrinkable film made by coextruding protective layer of a copolymer of vinylidenechloride, to which is adjoined directly (without using glue) on the one hand the outer layer made of polyamide, which used nylon 6 or nylon 12 with a melting point of more than 160°and containing more than 10% of the adhesive, and on the other side heat sealable layer of the following composition: copolymer of ethylene and vinyl acetate, linear low density polyethylene, polyethylene, very low, low, medium and high density copolymer of ethylene butyl acrylate copolymer α-olefin of the formula RHC=CH₂and α,β-Ethylenediamine carboxylic acids. This film made of biaxially-oriented and has a high interlayer adhesion. Bags made from this film (with Nar is mportant polyamide layer) used for packing pork (see U.S. patent No. 4755402 class b 65 D 65/02, 32 In 27/34, published in 1988).

The disadvantages of this multilayer films should include low formability given polymeric composition and a low resistance to mechanical damage, in particular to punctures. Another significant disadvantage of this multilayer film is that as a protective layer are copolymers of vinylidenechloride. These copolymers according to European standard is not recommended for use in contact with food, as they are under the influence of elevated temperatures and/or when exposed to liquid environments are able to release toxic substances, in particular vinyl chloride.

Another example of artificial casings used for food packaging unequal and irregular, is a multilayer heat-shrinkable bag film containing gazoballonnyj, outer and intermediate layers, between which is located the adhesive layer. The thickness gatbering layer is more than 30% of the total film thickness, and the thickness of the intermediate layer is in the range 5-40% of the total film thickness. Gazoballonnyj layer of this film made from a copolymer of vinylidenechloride, the intermediate layer is made of polyamide or thermoplastic polyethylene terephthalate with a melting point of the crystalline phase Bo is its 240° C, and the outer layer is made of a copolymer of ethylene and vinyl acetate with a melting point 80-103°C, linear low density polyethylene with a melting point of 110-130°or from a mixture of the same copolymers with a content of linear low density polyethylene, more than 40%, or from mixtures containing more than 60% of these same copolymers and linear low density polyethylene with a density of 0,915-0.930 g/cm³. The film is produced as follows. The materials of the layers together ekstragiruyut through an annular cylinder with adiabatic zones and, after cooling water with a temperature of 15-25°receive laminated sleeve. In the flattened condition, laminated sleeve has a width of 120 mm and a thickness of 540 μm. Then the sleeve is passed through the water bath, heated to 96°where he is within 12 seconds. This time is sufficient to heat the material of the multilayer film. Next, the sleeve is pulled in an atmosphere of air with a temperature of 80-120°between the two pairs of rolls, rotating at speeds of 20 and 60 m/min, the Degree of drawing of the sleeve in the longitudinal direction is equal to three. The same degree of stretching in the radial direction to receive the next blow of the sleeve from the inside air. So, bring the dimensions of the sleeve in the flattened condition to 350 mm width and 60 μm in thickness (see U.S. patent No. 4883693 class 32 In 27/08, 32 27/32 IN 32V 27/34, published in 1989).

One of the major drawbacks of this multilayer film is that for the manufacture of its outer layer applied linear low-density polyethylene or copolymers based on ethylene. As is known, these materials may not give the desired film strength, which limits its scope, for example, you cannot use the machine for stuffing sausage meat. Another drawback of this multilayer film is used in its gazobetona layer copolymers vinylidenechloride that during processing and operation of the finished product, as already noted, secrete toxic substances that adversely affect the human body.

These shortcomings in the packaging laminated film of a thickness of 50-150 μm, obtained by coextruding and containing the Central inner layer of a thickness of 5-15 μm of low density polyethylene, two inner layer of a thickness of 5-15 μm each of polyolefin or a copolymer of ethylene and vinyl acetate and two outer layer thickness 8-35 μm each of ionomer - copolymer of ethylene and methacrylic acid, neutralized with sodium ions. The film may contain additional layer of polymer that is impermeable to oxygen, which is made from polyvinylidenechloride or copolymer of ethylene and vinyl alcohol. The film may b the th completed oriented and crosslinked radiation method. In the example below the following composition of the multilayer film. Coextruded film containing layers ionomer Surlyn 1605 thickness of 21 μm, a copolymer of ethylene and vinyl acetate of a thickness of 8 μm, linear low density polyethylene with a thickness of 9 μm, a copolymer of ethylene and vinyl acetate 4 µm thick, low-density polyethylene of a thickness of 13 μm, a copolymer of ethylene and vinyl acetate with a thickness of 4 μm and ionomer Surlyn 1601 thickness of 11 μm. Oriented film of the above composition has a total thickness of 71 μm, shrinkage in the longitudinal and transverse directions 29 and 42%, respectively (see application great Britain No. 2233934 class 32 27/32 In, 32 In 27/08, 32 In 27/30, published in 1991).

The main disadvantage of this multilayer tubular film is that it does not have sufficient strength, because it consists mainly of polyolefins that do not have high strength characteristics. In addition, in this multilayer film as a protective layer used grades, which for sanitary-chemical properties of the plastics are not suitable for food contact.

Most similar in its essence and the achieved effect, taken as a prototype, is oriented multilayer blown film for packaging food products that at the time of placement in the film Il is after placement in the film may be subjected to heat treatment, containing at least three polyamide layers, each of which consists of a mixture of nylon 6, copolymer polycaprolactam with hexamethylenediamine were and adipic acid, aromatic polyamide containing links diamine and terephthalic acid, and mixtures kislotoobrazovanie copolymers. Between the polyamide layers are layers of Homo - or copolymers of olefins. The polyamides may consist of different amide units, in particular to contain 70-95% of aliphatic polyamide and/or a mixture of polyamide and partially aromatic polyamide and/or olefinic copolymers such as ethylene vinyl acetate, ionomer polymers, modified acid copolymers and/or polyesters. The inner and/or outer layers of this multilayer film can be made of a partially aromatic polyamide, in particular, obtained by polycondensation of m-xylylenediamine and adipic acid, and the layers of the polyolefin may contain adhesive based on a polymer of ethylene and/or propylene. The total thickness of this multilayer film is in the range 35-70 µm, with one of the polyamide film layers may consist of a mixture of all extrudable components as product recycling-known films (see application Germany No. 4130486 class And 22 With 13/00, 32 In 27/08, published 25.02.93 year).

The main disadvantages of e is th a multilayer oriented tubular film for packaging food products are its low optical indicators, insufficient formability and low strength characteristics. These shortcomings, in General, reduce the attractiveness of packaged products, restrict the use of film in some ways its completion and require more delicate handling of products, so there is a high probability of damage. In addition, the known multi-layer film, despite the presence of at least three polyamide layers, still has a fairly low barrier properties against moisture and against gases, which greatly reduces the duration of pre-storage products.

The basis of the invention is the task of creating a multilayer oriented tubular film for packaging food products (sausages, cheese, fresh meat, meat products, pasta and other paste-like and solid foods)with high formability, transparency, strength, resistance to puncture, elasticity, and barrier properties, as well as a reliable tightness of the seam during welding by changing the chemical composition of each polyamide layer by introducing into the composition additional materials, giving the film layers of various listed properties depending on where each layer with respect to the products, p is displaced in film.

The solution of this problem is achieved by the fact that in the known multilayer oriented tubular film for packaging food products containing at least three polyamide layers, each of which consists of a mixture of nylon 6, copolymer polycaprolactam with hexamethylenediamine were and adipic acid, aromatic polyamide containing links diamine and terephthalic acid, and mixtures kislotoobrazovanie copolymers in the composition of the outer layer additionally introduced amorphous resin Selar 3426 in the amount of 20-25 wt. hours from the total weight of the mixture components at the next General ratio of components (wt. PM): polyamide 6 70-77, a copolymer of polycaprolactam with hexamethylenediamine were and adipinic acid 5-11, amorphous resin Selar 3426 20-25, aromatic polyamide containing links diamine and terephthalic acid, 3-8, a mixture kislotoobrazovanie copolymers of 0.3-5.

Introduction to the composition of the amorphous resin Selar 3426 helps to give the film the necessary strength and transparency.

To improve the barrier properties of the multilayer films of its barrier layer has the following composition of the mixture of the copolymer with the following General ratio of components (parts by weight): a copolymer of ethylene with vinyl alcohol 57-78, a copolymer of ethylene and propylene 18-22, food dyes 0.5 to 3.

To ensure the high transparency and the possibility of cooking in the film meat products in its inner polyamide layer is introduced a mixture of ionomer resins, Surlyn 1855 with zinc ions, Surlyn 1601 ions with sodium salts of the following quantities of these component (wt. PM): ionomer resin Surlyn 1855 3,

ionomer resin Surlyn 1601 4.

Introduction to the composition of the outer layer of the amorphous resin Selar 3426, even in small quantities (up to 20%), allows mixing with the polyamide 6 and copolymers of polyamides to create a polymer material having the characteristics of amorphous polyamide. Such mixtures retain all the advantages of resin Selar 3426, but at the same time gain some valuable mechanical properties of semi-crystalline polyamide. Primarily amorphous resin provides ease of extrusion. Due to the fact that the treatment temperature of the amorphous resin is within 221-327°S, it can be successfully used in coextruded structures. Mixtures of polyamide resins Selar 3426 and polyamide 6 can be obtained by a simple method of dry mixing. Adding resin Selar 3426 in the polyamide composition improves the optical properties of the film and increases its share of vagueness. This composition combines the ability to process low-temperature extrusion and impact resistance, the heat generated during the manufacture of tubular film, that is, the composition is characterized by improved processability of the film production process and its welding if necessary. Introduction to the composition of the resin Selar 3426 provides good barrier properties of the film in relation to sour the ode, carbon dioxide and water vapor, even in conditions of high relative humidity (95-100%). At zero relative humidity barrier characteristics of the resin Selar 3426 with respect to oxygen and carbon dioxide are similar to those same characteristics of polyamide 6.

Layer multilayer films with water steam barrier properties is preferably made from polyethylene or polypropylene or copolymers based on a mixture of ethylene and propylene. For layer in a multilayer shell having barrier properties against oxygen, use, basically, a copolymer of ethylene with vinyl alcohol. The sharing option in the composition of the named polymers as a middle layer of a multilayer shell is ideal to maximize the barrier properties of the film. Therefore, the proposed film barrier layer consists mainly of a copolymer of vinyl alcohol and a copolymer of ethylene and propylene in the above mass parts.

The use of a barrier layer to the above-mentioned polymer composition allows to obtain a multilayer film with high barrier properties, due to their ability to be used in the composition of the polymers to protect the packaged product from the influence of moisture and gases simultaneously. Kislotonepronitsaemost copolymer of ethylene with vinyl alcohol IU the remote control waterproof layers better and use them in a single composition, that is, the joint extrusion, allows you to create complex layer film with improved barrier properties. In addition, a copolymer of ethylene with vinyl alcohol gives the film transparency, hygroscopicity and excellent barrier to the penetration of gases. A copolymer of ethylene with propylene creates excellent protection from moisture, improves the optical properties of the film. Therefore, the combination of these properties provides long-term preservation packaged in foil food products.

As the inner layer in the proposed multi-layer film is used ion meter - derivatives of copolymers of ethylene and methacrylic acid. When used as the inner layer of ionomer type Surlyn you can get the film to cook meat in it. When cooking the inner surface of the film sticks to the meat, tightly hugs him and prevents the allocation of a liquid component; therefore, the output of the cooked product and its quality increases. Surlyn gives the film a good formability, durability, less leakage, caused by good formability (a smaller deformation of meat) and strength, especially in freezing conditions. Distinctive properties of Surline are impact resistance at low temperatures, resistance to puncture and abrasion resistance, high the th strength of the melt, high elasticity, high adhesive strength, resistance to oils, solvents, greases and high transparency. In the proposed multi-layer film, allowing packaging of various food products, inner layer made of a mixture of two ionomer resins: Surlyn 1855, Surlyn 1601, each of which has a number of useful properties. Surlyn 1855 with zinc ions is a material with a low melt flow index and is designed to wrap the sliced pieces of fresh meat with bones for coextrusion, mainly with nylon and polyethylene. At the same time, Surlyn 1855 can be used in conjunction with other brands of Surline for food packaging. Its optical properties are inferior to other ionomers, so it is advisable to add to it, Surlyn 1601, the fundamental characteristics of which are high stickiness and strength when heated, good formability, oil resistance, excellent optical properties for both films being formed by molding, and blown. We offer a blend of ionomer resins allows you to create the inner layer of the multilayer film with the desired combination of properties required for packaging cheese, fresh meat and other food products.

For the manufacture of the proposed multilayer tubular film all the components are thoroughly mixed and poured into bankeroctober. In the extruder mixing and homogenization of the melt, which is then filtered through a set of filter meshes and is served in the multi-head extruder. The melt passing through the forming channels, sandwiches and exits through the annular gap in the forming head. After this primary sleeve is water-cooled. This cooling method allows to obtain an amorphous film structure, which provides it with excellent optical properties and reduces stiffness. Then the sleeve is subjected to biaxial orientation and heat-setting. The finished sleeve is wound on a cardboard sleeve.

Obtained according to the invention a multilayer bag oriented film meets the requirements necessary for its use as a packaging material for food products and, in particular, as the sausage-casing shell.

The proposed multilayer blown film remains quite strong at high temperatures, food processing, up to about 120°has high elasticity and soft to the touch.

The shell is made of a film of the proposed structure, stable in caliber and durable when filling products in the process of making sausage and sausage products, sausage cheese.

Tensile fracture corrugated “dolls” allows you to use the film when the gasket headlamp who eat high-speed automatic equipment.

The proposed multilayer blown film has a low water, steam and oxygen, which, ultimately, determines the high degree of preservation of the finished product for a long time.

The essential difference between the claimed subject matter of the invention from previously known is that the barrier layer consists of a mixture of a copolymer of ethylene with vinyl alcohol and a copolymer of ethylene and propylene, and in that the inner layer contains a mixture of ionomer resin, and the amorphous resin Selar 3426. These differences, together, allow you to securely protect Packed in foil product from the influence of moisture and gases at the same time, provide good formability, oil resistance, high transparency, high strength, reduce the level of leakage. None of the known multilayer films may not have at the same time all of these properties, since it does not contain in its polyamide compositions of components that provide the desired properties of the film as a whole.

The technical advantages of the proposed multi-layer tubular film for packaging food products, compared with the prototype, include the following:

- improvement of the barrier properties of the film through the use of for this purpose a mixture of a copolymer of ethylene with vinyl alcohol and a copolymer of ethylene and propylene;

- simplify the process of manufacturing a tubular film extrusion by use of the composition of the outer layer of the amorphous resin Solar that allows you to lower the temperature and increase the resistance to heat during manufacture;

- improving the optical properties, formemost, abrazivostruynoy and the resistance due to the use in the inner polyamide layer of a mixture of ionomer resins, Surlyn 1855, Surlyn 1601.

The economic effect from implementation of the invention, compared with the use of the prototype, are due to increased sales volume as a result of increased pre-term storage of food, and improve their appearance (transparency, absence of wrinkles), and the decrease in marriage, as a consequence of the improvements in the manufacture of the film.

The social effect of implementation of the invention, compared with the use of a prototype, get by attracting buyers appearance of food products and its high quality, remains constant during long-term storage.

1. Multilayer oriented blown film for packaging food products containing at least three polyamide layers, each of which consists of a mixture of nylon 6, copolymer polycaprolactam with hexamethylenediamine were and adipic acid, aromatic polyamide, with whom containing a series of links diamine and terephthalic acid, and mixtures kislotoobrazovanie copolymers, characterized in that the composition of the outer layer additionally introduced amorphous resin Selar 3426 in the amount of 20-25 parts by weight of the entire mass of the mixture components at the next General ratio of components (parts by weight): polyamide 6 - 70-77, a copolymer of polycaprolactam with hexamethylenediamine were and adipinic acid - 5-11, amorphous resin Selar 3426 - 20-25, aromatic polyamide containing links diamine and terephthalic acid - 3-8, the mixture kislotoobrazovanie copolymer is 0.3 to 5.

2. Multilayer oriented blown film for packaging food products according to claim 1, characterized in that the barrier layer has the following composition of the mixture of the copolymer with the following General ratio of components (parts by weight): a copolymer of ethylene with vinyl alcohol - 57-78, a copolymer of ethylene and propylene - 18-22, food dyes - 0,5-3.

3. Multilayer oriented blown film for packaging food products according to claim 1, characterized in that in the inner polyamide layer is introduced a mixture of ion exchange resins, Surlyn 1855 with zinc ions, Surlyn 1601 with ions of sodium salt of the following quantities of these components (in parts by weight): ionomer resin Surlyn 1855-3, ionomer resin Surlyn 1601-4.