CN115771319A - Recyclable high-barrier puffed food packaging film and preparation method thereof - Google Patents

Abstract

The invention discloses a recyclable high-barrier expanded food packaging film which is formed by compounding a printing layer, a barrier layer and a heat sealing layer, wherein the printing layer is an SOPP (biaxially oriented heat-sealing polypropylene film), the barrier layer is an MOPP (biaxially oriented aluminized polypropylene film), and the heat sealing layer is an ultralow-temperature heat-sealing CPP (ultralow-temperature heat-sealing cast polypropylene film); the printing layer and the blocking layer are compounded through an extrusion compounding middle layer, and the blocking layer and the heat sealing layer are compounded through a solvent-free compounding process. The packaging film structure contains SOPP, MOPP and CPP, so that the packaging film structure has good tensile strength, impact strength and toughness and good transparency, and the three materials are good environment-friendly materials.

Description

Recyclable high-barrier puffed food packaging film and preparation method thereof

Technical Field

The invention relates to the field of food packaging, in particular to a high-barrier green printing and environment-friendly film.

Background

Puffed food is a novel food appearing at the end of the sixties, and is also called extruded food, spray puffed food, light food and the like abroad. It is made up by using cereal, potato and bean as main raw material, and making them undergo the processes of pressurization and heating treatment to make the volume of raw material self-expand and change internal tissue structure, and making them pass through the processes of processing and forming. The food has a porous and fluffy texture structure, is crispy and sweet in taste, and has certain nutritional value which is very popular with children. Puffed food is easy to oxidize and is not sensitive to light, and a plastic composite pillow type bag is generally used as a package of the product. The plastic composite bag has good product protection effect. The plastic composite packaging material has various varieties and can be compounded and combined in various ways, including plastic-plastic compounding, paper-plastic compounding, aluminum-plastic compounding and the like. Composite materials for food packaging require three layers. The inner layer is required to have no toxicity, no odor, good oil resistance and chemical resistance and good heat sealability. The outer layer is required to have good optical performance, good printability, wear resistance, heat resistance, strength and rigidity. The middle layer is required to have barrier properties (gas barrier, fragrance barrier, moisture barrier, and light blocking). The packaging material of the general puffed food is OPP/aluminized/CPP, wherein the OPP ensures the strength of the material and the printing effect of the package, the aluminized material has good effects of air resistance, light resistance and the like, and the CPP layer plays a role in heat sealing. The composite technological process includes 3 kinds of coating process, laminating process and co-extruding process, and may be used alone or in combination. A vertical packing machine for packing puffed snack food features that the coiled film is used as packing material and a single machine can perform a series of functions including making bags, filling materials, filling nitrogen gas, sealing, cutting off and printing date.

Today, where people pay great attention to the ecological environment, green and environment-friendly packaging of food is also a necessity. The reduction, the reuse, the recovery and the degradation are taken as the targets and means of ecological environment-friendly packaging in all countries in the world. Many countries have regulations for the recycling of packaging materials. The packaging material of the puffed food is also environment-friendly. The aluminizer in the prior art is MPET, cannot be recycled, is simply replaced by MOPP, and has great influence on the machine moving performance of packaging.

Disclosure of Invention

In order to solve the technical problems, the invention provides a recyclable high-barrier puffed food packaging film and a preparation method thereof, which have the advantages of high barrier, high recoverability, high-speed vertical packaging machine adaptability and the like.

In order to realize one of the purposes of the invention, the invention provides a recyclable high-barrier expanded food packaging film which is formed by compounding three layers of structures, namely a printing layer, a barrier layer and a heat sealing layer, wherein the printing layer is an SOPP (biaxially oriented heat-seal polypropylene) film, the barrier layer is an MOPP (biaxially oriented aluminized polypropylene) film, and the heat sealing layer is an ultralow-temperature heat-seal CPP (ultralow-temperature heat-seal cast polypropylene) film; the printing layer and the blocking layer are compounded through an extrusion compounding middle layer, and the blocking layer and the heat sealing layer are compounded through a solvent-free compounding process.

Preferably, the formulation mass ratio of the extruded middle layer is LDPE: MLLDPE: EMAA = 2.

Preferably, the thickness of the printing layer is 15-20 μm, the thickness of the extrusion intermediate layer is 8-15 μm, the thickness of the barrier layer is 13-18 μm, and the thickness of the heat sealing layer is 18-30 μm.

Preferably, in the printing layer, a heat sealing surface and a corona surface are arranged on one surface for printing, so that the peeling strength of the ink and the extrusion interlayer is improved.

The invention also aims to provide a preparation method of the recyclable high-barrier puffed food packaging film, which comprises the following steps:

(1) Printing the SOPP by using a printing device of a printing machine, and drying to obtain an SOPP/INK layer;

(2) Extruding the SOPP/INK layer and the MOPP layer together by adopting an extrusion process to form a first composite layer;

(3) And compounding the composite layer I and the ultralow-temperature heat-sealing CPP by adopting solvent-free compounding equipment to form a composite layer II.

Preferably, in the step (1), when producing the SOPP (biaxially oriented heat-sealed polypropylene film), the heat-seal surface and the corona surface are made on one surface for printing, so as to improve the interlayer peel strength.

Preferably, in the step (2), the SOPP/INK layer obtained in the step (1) is taken as a first unreeled base material, then the first unreeled base material enters a coating system in a transversely-correcting and flatly-flattening manner under a certain tension condition, and a coating roller applies pressure through a rubber roller so that the AC agent is uniformly transferred to the printing surface of the SOPP/INK layer; and flattening the second unreeled substrate MOPP in parallel under a certain tension condition, melting PE resin through an extruder, and combining the SOPP/INK layer and the MOPP by using the molten resin as an adhesive layer or a coating layer.

Preferably, in the step (3), the low-temperature CPP material is used as a first unreeling base material, and then the first unreeling base material is coated with 100% of solid polyurethane adhesive on the base material through a 5-roll gluing system under a certain tension condition; flattening the composite layer I obtained in the step (2) in parallel under a certain tension condition, and bonding the materials together through a composite compression roller; in the process, a secondary corona discharge machine is started to carry out corona on the inner side adhesive surface of the MOPP film.

Preferably, in the step (2), when the material width is 550-750mm, the first unwinding tension is 10.0 +/-3.0 kgf, the second unwinding tension is 7.0 +/-2.0 kgf, the oven tension is 5.0 +/-1.0 kgf, and the winding tension is 11.0 +/-3.0 kgf; when the width of the material is 750-1050mm, the first unreeling tension is 10.0 +/-3.0 kgf, the second unreeling tension is 9.0 +/-2.0 kgf, the oven tension is 5.0 +/-1.0 kgf, and the rolling tension is 11.0 +/-3.0 kgf.

Preferably, in the step (2), the pressure applied by the rubber pressing roller is 3.0 +/-1.0 bar, and the gluing amount of the AC agent is 0.1-0.4 g/m < 2 >; in the extrusion and re-extrusion process, the temperature of a screw and a die head is 210-335 ℃, the combined pressure is 3.0 +/-1.0 bar, and the stripping pressure is 0-4.0bar; the extrusion compounding machine in the step (2) filters PE by using a 300-mesh filter screen, and controls crystal points; the cooling temperature of the cooling smooth roller in the step (2) is controlled to be 22.0 +/-2.0 ℃.

In the extrusion process, the extrusion intermediate layer is prepared from LDPE, MLLDPE, EMAA =2 in a specific mixing mass ratio.

Preferably, in the step (3), the unwinding tension of the first winding is 25 to 35N, and the unwinding tension of the second winding is 80 to 120N; the composite compression roller bonds the materials together at 50 ℃ under the pressure of 2.0-3.0 bar; the corona value of the secondary discharge corona machine is 2.5-3.0KW, the winding tension is 100-80N, and the winding taper is 20% in a hyperbolic mode.

Compared with the prior art, the invention has the beneficial effects that:

the packaging film structure contains SOPP, MOPP and CPP, so that the packaging film structure has good tensile strength, impact strength and toughness and good transparency, and the three materials are good environment-friendly materials.

According to the invention, the multilayer packaging film is obtained by adopting an extrusion compounding-solvent-free compounding method, so that the use of an adhesive can be reduced, and meanwhile, the solvent-free polyurethane adhesive is used, so that the harm of an organic solvent is reduced, the discharge of VOC in the production process is reduced, and the environment-friendly effect is achieved.

According to the invention, the polyolefin elastomer with a certain proportion is added into the ultralow temperature CPP heat-sealing layer, so that the strength of the heat-sealing layer can be improved and the heat-sealing temperature can be reduced.

Drawings

FIG. 1 is a diagram of the recyclable high barrier puffed food packaging film of the present invention;

fig. 2 is a process flow chart for manufacturing the recyclable high-barrier puffed food packaging film.

In the figure: 1. printing layer; 2. a barrier layer, 3, a heat sealing layer; 4. and extruding the middle layer.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly apparent, the following embodiments are further detailed, and all other embodiments obtained by those skilled in the art without any creative effort based on the embodiments of the present invention belong to the protection scope of the present invention.

The present invention employs the following abbreviations:

and (3) SOPP: biaxially stretching a heat-sealed polypropylene film;

MOPP: biaxially oriented aluminized polypropylene film;

CPP: casting a polypropylene film;

BOPP: biaxially oriented polypropylene film;

PE: polyethylene;

PET: polyethylene terephthalate;

LDPE: low density polyethylene;

MLLDPE (mixed Low-Density polyethylene): a metallocene polyethylene;

EMAA: ethylene-methacrylic acid copolymer.

As shown in fig. 1, the recyclable high-barrier expanded food packaging film is formed by compounding a three-layer structure including a printing layer 1, a barrier layer 2 and a heat-sealing layer 3, wherein the printing layer 1 is an SOPP (biaxially oriented heat-sealed polypropylene film), the barrier layer 2 is an MOPP (biaxially oriented aluminized polypropylene film), and the heat-sealing layer 3 is an ultra-low temperature heat-sealed CPP (ultra-low temperature heat-sealed cast polypropylene film); the printing layer 1 and the blocking layer 2 are compounded through an extrusion compounding middle layer 4, and the blocking layer 2 and the heat sealing layer 3 are compounded through a solvent-free compounding process.

As shown in fig. 2, the preparation method of the recyclable high-barrier puffed food packaging film of the invention comprises the following steps: (1) Printing the SOPP by using a printing device of a printing machine, and drying to obtain an SOPP/INK layer; (2) Extruding the SOPP/INK layer and the MOPP layer together by adopting an extrusion process to form a first composite layer; (3) And compounding the composite layer I and the ultralow-temperature heat-sealing CPP by adopting solvent-free compounding equipment to form a composite layer II.

The following examples and comparative examples further illustrate the specific preparation and technical effects of the packaging film.

Example 1

The preparation method comprises the following steps:

(1) Printing the SOPP film by using a printing device of a printing machine, and drying to obtain an SOPP/INK layer; when producing SOPP (biaxially oriented heat-sealing polypropylene film), a heat-sealing surface and a corona surface are made on one surface for printing, so that the interlayer peeling strength is improved.

(2) Extruding the SOPP/INK layer and the MOPP layer together by adopting an extrusion process to form a first composite layer; in the step (2), the SOPP/INK layer obtained in the step (1) is taken as a first unreeled base material, then the first unreeled base material enters a coating system in a parallel and flat manner after being transversely corrected under a certain tension condition, and a coating roller applies pressure through a rubber pressing roller so that the AC agent is uniformly transferred to a printing surface of the SOPP/INK layer; the second unreeled base material MOPP is flatly laid in parallel under a certain tension condition, PE resin is melted through an extruder, and the SOPP/INK layer and the MOPP are combined together by using the melted resin as an adhesive layer or a coating layer. The PE resin comprises the following ingredients in parts by mass of LDPE, MLLDPE, EMAA = 2; in the step (2), the width of the material is 550mm, and the first unreeling tension is set to be 10.0kgf, the second unreeling tension is set to be 7.0kgf, the oven tension is set to be 5.0kgf, and the rolling tension is set to be 11.0kgf; in the step (2), the pressure applied by the rubber pressing roller is 3.0bar, and the gluing amount of the AC agent is 0.2g/m < 2 >; in the extrusion and recovery process, the temperature of a screw and a die head is 300 ℃, the composite pressure is 3.0bar, and the stripping pressure is 3.0bar; the extrusion compounding machine in the step (2) filters PE by using a 300-mesh filter screen, and crystal points are controlled; the cooling temperature of the cooling smooth roller in the step (2) is controlled to be 22.0 +/-2.0 ℃.

(3) And compounding the first composite layer and the ultralow-temperature heat-sealing CPP to form a second composite layer by adopting solvent-free compounding equipment. In the step (3), the ultralow-temperature CPP material is used as a first unreeling base material, and then 100% of solid-contained polyurethane adhesive is coated on the base material through a 5-roller gluing system under a certain tension condition; flattening the SOPP/PE/MOPP composite layer I obtained in the step (2) in parallel under a certain tension condition, and bonding the materials together through a composite compression roller; in the process, a secondary corona discharge machine is started to carry out corona on the inner side adhesive surface of the MOPP film. In the step (3), the first unreeling tension is 30N, and the second unreeling tension is 100N; the composite compression roller bonds the materials together at 50 ℃ and under the pressure of 2.5 bar; the corona value of the secondary discharge corona machine is 3.0KW, the winding tension is 100N, and the winding taper is 20% in a hyperbolic mode.

(4) And curing: and (4) feeding the composite layer two SOPP/PE/MOPP/CPP composite film roll obtained in the step (3) into a curing chamber for curing at the temperature of 40 ℃ for 24-36h.

(5) And slitting: and cutting the cured SOPP/PE/MOPP/CPP composite membrane into a required width.

(6) And inspecting, packaging and warehousing.

Wherein the thickness of the SOPP layer of the obtained composite film is 18 mu m, the thickness of the PE layer is 10 mu m, the thickness of the MOPP layer is 18 mu m, and the thickness of the ultralow-temperature heat-sealing CPP layer is 18 mu m.

Example 2

In comparison with example 1, in the step (2) described in example 2, the material width was 750mm, the primary unwinding tension was 10.0kgf, the secondary unwinding tension was 9.0kgf, the oven tension was 5.0kgf, and the winding tension was 11.0kgf.

Wherein the thickness of the SOPP layer of the obtained composite film is 18 micrometers, the thickness of the PE layer is 10 micrometers, the thickness of the MOPP layer is 18 micrometers, and the thickness of the ultralow-temperature heat-sealing CPP layer is 30 micrometers.

Example 3

In comparison with example 1, in the step (2) described in example 3, the material width was 1050mm, the primary unwinding tension was 10.0kgf, the secondary unwinding tension was 9.0kgf, the oven tension was 5.0kgf, and the winding tension was 11.0kgf.

Wherein the thickness of the SOPP layer of the obtained composite film is 18 mu m, the thickness of the PE layer is 10 mu m, the thickness of the MOPP layer is 18 mu m, and the thickness of the ultralow-temperature heat-sealing CPP layer is 25 mu m.

Comparative example 1

Compared with example 3, comparative example 1 replaces the ultra-low temperature heat-sealing CPP with the ordinary CPP.

Comparative example 2

In comparison to example 3, comparative example 2 uses BOPP instead of SOPP.

Comparative example 3

Compared with example 3, comparative example 3 adopts ordinary CPP to replace ultralow-temperature heat-sealing CPP and adopts BOPP to replace SOPP.

TABLE 1 test of the properties of the examples and comparative examples

As can be seen from the test results in the table above, the peel strength, heat seal strength and puncture strength of the product of the eco-friendly structure SOPP// PE/MOPP/CPP in the examples meet the performance requirements of the existing product BOPP// PE// PET/CPP, and all the materials are recyclable. In addition, no solvent is discharged in the two compounding processes, the residual solvent of the product is low, and the method is more environment-friendly, more sanitary and safer.

Compared with the comparative example 1, the low-temperature CPP is adopted to replace the common CPP in the example 3, the heat seal strength of the comparative example is 2876g/25mm under the heat seal conditions of 150 ℃ and 2bar,1s, while the heat seal strength of the example 3 is 4045g/25mm, the heat seal strength is greatly improved, and the performance requirement that the heat seal strength of a product is more than 3000g/25mm is met. Example 3 compared to comparative example 2, SOPP was used instead of BOPP. The peel strength of the SOPP/PE layer of the comparative example 2 is 66g/25mm, the peel strength of the SOPP/PE layer of the example 3 is 321g/25mm, and the performance requirement that the peel strength of the SOPP/PE of the product is more than 75g/25mm is met. Compared with a comparative example 3, in the example 3, the low-temperature CPP is adopted to replace the common CPP, the SOPP is adopted to replace the BOPP, and the heat sealing strength and the peeling strength are both greatly improved. The embodiment of the invention takes the using performance and the environmental protection requirement into consideration by selecting the combination of the environment-friendly materials, particularly the selection of the printing layer and the heat sealing layer materials, and makes great progress compared with the traditional packaging material.

In summary, although the present invention has been described with reference to the preferred embodiments, the above-described preferred embodiments are not intended to limit the present invention, and those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, therefore, the scope of the present invention shall be determined by the appended claims.

Claims (11)

1. The recyclable high-barrier expanded food packaging film is characterized by being formed by compounding a printing layer, a barrier layer and a heat sealing layer, wherein the printing layer is an SOPP (biaxially oriented heat-seal polypropylene film), the barrier layer is an MOPP (biaxially oriented aluminized polypropylene film), and the heat sealing layer is an ultralow-temperature heat-seal CPP (ultralow-temperature heat-seal cast polypropylene film); the printing layer and the blocking layer are compounded through an extrusion compounding middle layer, and the blocking layer and the heat sealing layer are compounded through a solvent-free compounding process.

2. The recyclable high-barrier expanded food packaging film as claimed in claim 1, wherein the compound mass ratio of the extruded middle layer is LDPE to MLLDPE to EMAA = 2.

3. The recyclable high barrier puffed food film according to claim 1 or 2, wherein the printed layer has a thickness of 15 to 20 μm, the extruded intermediate layer has a thickness of 8 to 15 μm, the barrier layer has a thickness of 13 to 18 μm, and the heat seal layer has a thickness of 18 to 30 μm.

4. The recyclable high barrier expanded food packaging film according to claim 1 or 2, wherein the heat sealing side and corona side of the printing layer are formed on one side for printing to improve the peel strength of the ink and the extrusion interlayer.

5. The method of making the recyclable high-barrier expanded food packaging film of any one of claims 1 to 4, comprising the steps of: (1) Printing the SOPP by using a printing device of a printing machine, and drying to obtain an SOPP/INK layer; (2) Extruding the SOPP/INK layer and the MOPP layer together by adopting an extrusion process to form a first composite layer; (3) And compounding the composite layer I and the ultralow-temperature heat-sealing CPP by adopting solvent-free compounding equipment to form a composite layer II.

6. The method for preparing recyclable high-barrier expanded food packaging film according to claim 5, wherein in the step (1), the heat-seal side and the corona side are printed on one side for improving interlayer peel strength when producing SOPP (biaxially oriented heat-seal polypropylene).

7. The method for preparing the recyclable high-barrier expanded food packaging film as claimed in claim 5, wherein in the step (2), the SOPP/INK layer obtained in the step (1) is taken as a first unreeled substrate, then the first unreeled substrate is transversely rectified under certain tension and then flatly laid in parallel to enter a coating system, and a coating roller applies pressure through a rubber press roller so that the AC agent is uniformly transferred to the printing surface of the SOPP/INK layer; and flattening the second unreeled substrate MOPP in parallel under a certain tension condition, melting PE resin through an extruder, and combining the SOPP/INK layer and the MOPP by using the molten resin as an adhesive layer or a coating layer.

8. The method for preparing the recyclable high-barrier expanded food packaging film as claimed in claim 5, wherein in the step (3), the ultralow-temperature heat-sealing CPP material is used as a first unreeled substrate, and then the polyurethane adhesive with 100% of solid content is coated on the substrate through a 5-roll gluing system under a certain tension condition; flattening the composite layer I obtained in the step (2) in parallel under a certain tension condition, and bonding the materials together through a composite compression roller; in the process, a secondary corona discharge machine is started to carry out corona on the inner side adhesive surface of the MOPP film.

9. The method for preparing the recyclable high barrier expanded food packaging film as claimed in claim 7, wherein in the step (2), when the material width is 550 to 750mm, the first unwinding tension is set to 10.0 ± 3.0kgf, the second unwinding tension is set to 7.0 ± 2.0kgf, the oven tension is set to 5.0 ± 1.0kgf, and the winding tension is set to 11.0 ± 3.0kgf; when the width of the material is 750-1050mm, the first unreeling tension is 10.0 +/-3.0 kgf, the second unreeling tension is 9.0 +/-2.0 kgf, the oven tension is 5.0 +/-1.0 kgf, and the rolling tension is 11.0 +/-3.0 kgf.

10. The method for preparing the recyclable high barrier puffed food packaging film according to claim 7 or 9, wherein in step (2), the pressure applied by the glue roller is 3.0 ± 1.0bar, and the amount of the ac agent applied is 0.1 to 0.4g/m2; in the extrusion and re-extrusion process, the temperature of a screw and a die head is 210-335 ℃, the combined pressure is 3.0 +/-1.0 bar, and the stripping pressure is 0-4.0bar; the extrusion compounding machine in the step (2) filters PE by using a 300-mesh filter screen, and controls crystal points; the cooling temperature of the cooling smooth roller in the step (2) is controlled to be 22.0 +/-2.0 ℃.

11. The method for preparing the recyclable high-barrier puffed food packaging film according to claim 8, wherein in the step (3), the first unwinding tension is 25-35N, and the second unwinding tension is 80-120N; the composite compression roller bonds the materials together at 50 ℃ under the pressure of 2.0-3.0 bar; the corona value of the secondary corona discharge machine is 2.5-3.0KW, the winding tension is 100-80N, and the winding taper is 20% in a hyperbolic curve mode.

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