Basefilm capable of automatically exhausting air after being heated for food packaging and preparation method of base film

Abstract

The invention belongs to the technical field of packaging films, and particularly relates to a food packaging base film capable of exhausting automatically after being heated and a preparation method of the food packaging base film. Through the design of inner and outer surface layer materials of the base film and the heat sealing performance of POP and LLDPE, the heat bonding strength and low-temperature heat sealing performance of the base film are improved, and the problem of leakage after heat sealing caused by thickness difference is avoided; due to the improvement of the easy-to-tear strength, the situation that when non-vacuum food is packaged, the package is easily extruded and broken by external force, and the integrity of a product cannot be guaranteed can be avoided, and due to the fact that the heat sealing strength is poor, heat sealing of a non-base film area belongs to dead sealing, the strength is controlled to be 25 N / 15 mm or above, and the heat sealing strength of a base film area is controlled to be 10-15 N / 15 mm; in this way, the base film area has enough heat sealing strength to support stress caused by extrusion of a product, and bag breaking is avoided.

Description

Technical Field

[0001] This invention belongs to the field of packaging film technology, specifically relating to a heating and automatic exhaust base film for food packaging and its preparation method. Background Technology

[0002] The heating and automatic venting base film for food packaging can automatically regulate the internal air pressure during the heating process to prevent the packaging from expanding and breaking, while maintaining the freshness and safety of the food. Its core function relies on the synergistic effect of high-temperature resistant materials and special venting structure.

[0003] The base film needs to possess heat resistance, barrier properties, and flexibility. The venting mechanism is achieved through microstructural innovation, such as using nanoscale micropore technology to embed venting channels invisible to the naked eye in the sealing film. When heated, the internal gas pressure reaches a threshold, and the gas is slowly released through the micropores to avoid pressure buildup. Alternatively, laser perforation or other technical means can be used.

[0004] Current venting methods take into account the influence of film thickness and perforation depth, which affect the venting effect and make it impossible to control the venting volume. Venting is achieved by changing the shape of the heat seal and reducing the width of the heat seal. However, due to the limitation of product moisture content, the venting volume may be insufficient to open the packaging for venting 100%. Food packaging films produced by traditional easy-open methods that automatically vent and lock in moisture through heating are easily damaged by external pressure when packaging non-vacuum foods, and the integrity of the product cannot be guaranteed. Summary of the Invention

[0005] The purpose of this application is to provide a heating and automatic exhaust base film for food packaging and its preparation method, so as to solve the above-mentioned technical problems.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows: The first aspect of this application is to provide a heated and automatically venting base film for food packaging, the base film comprising a multi-layer structure, the layer structure including a support layer, an adhesive layer, a heat-adhesive layer, and an easy-peel layer; The support layer is connected to the adhesive layer on both sides; Any one of the adhesive layers is bonded to the thermal adhesive layer, and the other adhesive layer is bonded to the easy-peel layer; the thickness of the base film is 25–30 µm; The support layer is polyamide, and the thickness of the support layer is 10-30% of the thickness of the base film.

[0007] In some embodiments, the adhesive layer is a vinyl maleic anhydride graft.

[0008] In some embodiments, the heat-adhesive layer is a mixture of polyolefin plastomer and linear low-density polyethylene in an 8 / 2 mass ratio.

[0009] In some embodiments, the easy-peel layer is a mixture of poly(1-butene), polyolefin plasmon, and metallocene polyethylene in any mass ratio.

[0010] In some embodiments, a filler layer may be provided between the easy-peel layer and the adhesive layer.

[0011] In some embodiments, a filler layer may be provided between the heat-adhesive layer and the adhesive layer.

[0012] In some embodiments, the filler layer is low-density polyethylene.

[0013] In some embodiments, the base film is attached to the film by localized adhesive bonding or by heat sealing of a single strip at an unwinding tension of 1 to 5 N, wherein the heat sealing temperature is 130 to 150 °C, and stretching deformation or wrinkling is avoided during the process by controlling the unwinding tension.

[0014] A second aspect of this application is to provide a method for preparing the heating and automatic exhaust base film for food packaging, the method comprising the following steps: (1) Heat-bonded layer: Polyolefin plasmid and linear low-density polyethylene are added to the hopper of the extruder and melted at a temperature of 170-220℃ and then enter the die; (2) Adhesive layer: The vinyl maleic anhydride graft is added to the hopper of the extruder and melted at a temperature of 190-220°C, and then enters the die; (3) Support layer: Polyamide is added to the hopper of the extruder and melted at a temperature of 220-250℃, and then enters the die; (4) Adhesive layer: The vinyl maleic anhydride graft is added to the hopper of the extruder and melted at a temperature of 190-220°C, and then enters the die; (5) Easy-to-remove layer: Poly-1-butene, polyolefin plasmon, and metallocene polyethylene are added to the hopper of the extruder and melted at a temperature of 180-220°C before entering the die; (6) The film bubble of the multilayer co-extruded film is extruded through the die, cooled and stabilized, and then the film thickness distribution is controlled by the rotating traction and herringbone clamp. The film is then transported to the winding device through the traction roller, cut into sheet film, and then wound up to obtain the base film for food packaging with heating and automatic exhaust.

[0015] In some embodiments, the preparation method further includes setting a filler layer between step (1) and step (2) and / or between step (4) and step (5): adding low-density polyethylene into the hopper of an extruder, melting it at a temperature of 180-220°C, and then entering the die.

[0016] Beneficial effects: (1) By designing the inner and outer surface materials of the base film, the heat-sealing properties of POP and LLDPE are utilized to increase their heat-bonding strength and low-temperature heat-sealing performance, thus avoiding leakage problems caused by thickness difference after heat sealing. (2) The improved ease of opening can prevent the packaging of non-vacuum food from being easily crushed by external forces, thus ensuring the integrity of the product. By forming a heat seal strength difference, the heat seal of the non-base film area is a dead seal with a strength controlled above 25N / 15mm, while the heat seal strength of the base film area is controlled at 10-15N / 15mm. This ensures that the base film area has sufficient heat seal strength to support the product under pressure and prevent the packaging from breaking. (3) The addition of polyamide improves the tensile strength of the material, facilitates the design of base films with wider widths, and is suitable for production processes such as online printing or online heat sealing. Detailed Implementation

[0017] Unless otherwise specified, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In case of any discrepancy, the definitions in this specification shall prevail.

[0018] Unless otherwise stated, all percentages, portions, proportions, etc. are by weight.

[0019] The terms “comprising,” “including,” “having,” “containing,” “or any other variation thereof” as used herein are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may also include elements not expressly listed or other elements inherent to such composition, process, method, article, or apparatus.

[0020] When quantities, parts by weight, or other numerical values ​​or parameters are given as ranges, preferred ranges, or a series of upper and lower preferred values, it should be understood that they specifically disclose all ranges formed by any pair of values ​​of any larger or preferred range limit and any smaller or preferred range limit, regardless of whether the ranges are disclosed separately. For example, when describing a range of "1 to 5", the described range should be understood to include ranges such as "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. Unless otherwise stated, where numerical ranges are described herein, the range is intended to include the range endpoints as well as all integers, fractions, decimals, etc., within that range.

[0021] Furthermore, the indefinite articles “a” and “an” preceding the elements or components of this disclosure are intended to indicate that there is no limitation on the number of times the said element or component appears (i.e., occurs). Therefore, “a” or “an” should be understood to include one or at least one, and unless the quantity is explicitly stated to be singular, the singular form of the said element or component also includes the plural case.

[0022] Unless otherwise specified, the materials, methods, and examples described herein are exemplary and not limiting. While similar or equivalent methods and materials may be used in implementing or testing this disclosure, suitable methods and materials are also described herein.

[0023] This disclosure is described in detail below.

[0024] Example 1 A heated, automatically venting base film for food packaging, comprising multiple layers, including a support layer, an adhesive layer, a thermally adhesive layer, and an easy-peel layer; the support layer is connected to the adhesive layer on both sides; any one adhesive layer is bonded to the thermally adhesive layer, and the other adhesive layer is bonded to the easy-peel layer; the thickness of the base film is 25–30 µm; the support layer is polyamide, and its thickness is 10–30% of the base film thickness; the adhesive layer is a vinyl maleic anhydride graft; the thermally adhesive layer is a mixture of polyolefin plastide and linear low-density polyethylene in an 8 / 2 mass ratio; the easy-peel layer is a mixture of poly-1-butene, polyolefin plastide, and metallocene polyethylene in an equal mass ratio; a filler layer may be provided between the easy-peel layer and the adhesive layer; a filler layer may be provided between the thermally adhesive layer and the adhesive layer; the filler layer is low-density polyethylene.

[0025] Example 2 The preparation method of the base film in Example 1 includes the following steps: (1) Heat-bonded layer: Polyolefin plasmid and linear low-density polyethylene are added to the hopper of the extruder and melted at a temperature of 170°C before entering the die; (2) Adhesive layer: The vinyl maleic anhydride graft is added to the hopper of the extruder and melted at a temperature of 190°C before entering the die; (3) Support layer: Polyamide is added to the hopper of the extruder and melted at a temperature of 220°C, and then enters the die; (4) Adhesive layer: The vinyl maleic anhydride graft is added to the hopper of the extruder and melted at a temperature of 190°C before entering the die; (5) Easy-to-remove layer: Poly-1-butene, polyolefin plasmon, and metallocene polyethylene are added to the hopper of the extruder, melted at a temperature of 180°C, and then enter the die; (6) The film bubble of the multilayer co-extruded film is extruded through the die, cooled and stabilized, and then the film thickness distribution is controlled by the rotating traction and herringbone clamp. The film is then transported to the winding device through the traction roller, cut into sheet film, and then wound up to obtain the base film for food packaging with heating and automatic exhaust.

[0026] The preparation method further includes setting a filling layer between step (1) and step (2) and / or between step (4) and step (5): adding low-density polyethylene into the hopper of an extruder, melting it at a temperature of 180°C, and then entering the die.

[0027] Example 3 The preparation method of the base film in Example 1 includes the following steps: (1) Heat-bonded layer: Polyolefin plasmid and linear low-density polyethylene are added to the hopper of the extruder and melted at a temperature of 210°C before entering the die; (2) Adhesive layer: The vinyl maleic anhydride graft is added to the hopper of the extruder and melted at a temperature of 210°C before entering the die; (3) Support layer: Polyamide is added to the hopper of the extruder and melted at a temperature of 230°C, and then enters the die; (4) Adhesive layer: The vinyl maleic anhydride graft is added to the hopper of the extruder and melted at a temperature of 200°C before entering the die; (5) Easy-to-remove layer: Poly-1-butene, polyolefin plasmon, and metallocene polyethylene are added to the hopper of the extruder, melted at a temperature of 210°C, and then enter the die; (6) The film bubble of the multilayer co-extruded film is extruded through the die, cooled and stabilized, and then the film thickness distribution is controlled by the rotating traction and herringbone clamp. The film is then transported to the winding device through the traction roller, cut into sheet film, and then wound up to obtain the base film for food packaging with heating and automatic exhaust.

[0028] The preparation method further includes setting a filling layer between step (1) and step (2) and / or between step (4) and step (5): adding low-density polyethylene into the hopper of an extruder, melting it at a temperature of 200°C, and then entering the die.

[0029] Example 4 The preparation method of the base film in Example 1 includes the following steps: (1) Heat-bonded layer: Polyolefin plasmid and linear low-density polyethylene are added to the hopper of the extruder and melted at a temperature of 220°C before entering the die; (2) Adhesive layer: The vinyl maleic anhydride graft is added to the hopper of the extruder and melted at a temperature of 220°C before entering the die; (3) Support layer: Polyamide is added to the hopper of the extruder and melted at a temperature of 250°C, and then enters the die; (4) Adhesive layer: The vinyl maleic anhydride graft is added to the hopper of the extruder and melted at a temperature of 220°C before entering the die; (5) Easy-to-remove layer: Poly-1-butene, polyolefin plasmon, and metallocene polyethylene are added to the hopper of the extruder, melted at a temperature of 220°C, and then enter the die; (6) The film bubble of the multilayer co-extruded film is extruded through the die, cooled and stabilized, and then the film thickness distribution is controlled by the rotating traction and herringbone clamp. The film is then transported to the winding device through the traction roller, cut into sheet film, and then wound up to obtain the base film for food packaging with heating and automatic exhaust.

[0030] The preparation method further includes setting a filling layer between step (1) and step (2) and / or between step (4) and step (5): adding low-density polyethylene into the hopper of an extruder, melting it at a temperature of 220°C, and then entering the die.

[0031] The base film prepared in Example 3 above was tested, and the test results are as follows:

[0032] This invention, through the design of the inner and outer surface materials of the base film, utilizes the heat-sealing properties of POP and LLDPE to increase their heat adhesion strength and low-temperature heat-sealing performance, avoiding leakage problems after heat sealing due to thickness differences. The improved easy-open strength prevents packaging of non-vacuum-sealed foods from being easily damaged by external pressure, ensuring product integrity. By creating a heat-sealing strength difference, the heat-sealing strength of the non-base film area is a dead seal, controlled at above 25N / 15mm, while the heat-sealing strength of the base film area is controlled at 10-15N / 15mm. This ensures that the base film area has sufficient heat-sealing strength to support the product under pressure, preventing packaging damage. The addition of polyamide improves the tensile strength of the material, facilitating base film designs with wider widths, and is suitable for online printing or online heat-sealing production processes.

[0033] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A heat automatic deaeration base film for food packaging, characterized by, The base film comprises a plurality of layer structures, the layer structures comprising a thermal adhesive layer (or a corona layer), a support layer, an adhesive layer, a filling layer, and a peelable layer; The support layer is connected to the adhesive layer on both sides; Any one of the adhesive layers is bonded to the thermal adhesive layer or the filling layer, and the other adhesive layer is bonded to the peelable layer or the filling layer; the thickness of the base film is 25-30 µm; The support layer is polyamide, and the thickness of the support layer is 10-30% of the thickness of the base film.

2. The heat autoexhaust base film for food packaging according to claim 1, characterized by, The adhesive layer is a vinyl maleic anhydride graft.

3. The heat-activatedly venting base film for food packaging according to claim 2, characterized by The thermal adhesive layer is a mixture of polyolefin plastomer and linear low-density polyethylene in a mass ratio of 8 / 2.

4. The heat autoexhaust base film for food packaging according to claim 3, characterized by The peelable layer is a mixture of poly-1-butene, polyolefin plastomer, and metallocene polyethylene in any mass ratio, which can adjust the peel strength.

5. The heat autoexhaust base film for food packaging according to claim 1, wherein A filling layer can be provided between the peelable layer and the adhesive layer.

6. The heat autoexhaust base film for food packaging according to claim 1, wherein A filling layer can be provided between the thermal adhesive layer and the adhesive layer.

7. The heat autoexhaustible base film for food packaging according to claim 5 or 6, characterized by, The filling layer is low-density polyethylene or linear low-density polyethylene.

8. The heat autoexhaust base film for food packaging according to claim 7, wherein The base film is wound under a tension of 1-5 N, and is attached to the film by local glue compounding or by a single heat seal, and the temperature of the heat seal is 130-150 °C.

9. A method for producing a heat-activatable degassing base film for food packaging according to any one of claims 1 to 8, characterized by, The preparation method comprises the following steps: (1) Thermal adhesive layer: polyolefin plastomer and linear low-density polyethylene are added to the hopper of the extruder, melted at a temperature of 170-220 °C, and then fed into the die; (2) Adhesive layer: vinyl maleic anhydride graft is added to the hopper of the extruder, melted at a temperature of 190-220 °C, and then fed into the die; (3) Support layer: polyamide is added to the hopper of the extruder, melted at a temperature of 220-250 °C, and then fed into the die; (4) Adhesive layer: vinyl maleic anhydride graft is added to the hopper of the extruder, melted at a temperature of 190-220 °C, and then fed into the die; (5) Peelable layer: poly-1-butene, polyolefin plastomer, and metallocene polyethylene are added to the hopper of the extruder, melted at a temperature of 180-220 °C, and then fed into the die; (6) After the multi-layer co-extruded film bubble is extruded through the die, it is cooled and stabilized, and then is controlled for thickness distribution through rotary traction and herringbone clamps. The tubular film is then transported to the winding device through traction rollers, cut into a sheet-shaped film, and wound to obtain a base film for food packaging with automatic heat exhaust.

10. The method for producing a heat automatic deaeration base film for food packaging according to claim 9, wherein The preparation method further comprises providing a filling layer between step (1) and step (2) and / or between step (4) and step (5): low-density polyethylene is added to the hopper of the extruder, melted at a temperature of 180-220 °C, and then fed into the die.

Images