Omnibearing easy-to-tear composite film and preparation process thereof

Abstract

The invention relates to the field of packaging bag materials, and particularly discloses an all-dimensional composite film easy to tear and pull and a preparation technology of the all-dimensional composite film easy to tear and pull. An all-dimensional composite film easy to tear comprises polyester layers, polyethylene layers, paper and aluminum foil, the polyester layers and the aluminum foil are arranged on the two sides of the paper, and the polyethylene layers are arranged on the two sides of the aluminum foil respectively. The polyester layer is prepared from the following raw materials in parts by weight: 30 to 40 parts of polyethylene glycol terephthalate, 1 to 3 parts of isocyanate, 1 to 3 parts of bio-based cross-linking agent, 10 to 20 parts of polylactic acid and 8 to 10 parts of natural inorganic filler; through blending modification of polyethylene glycol terephthalate and polylactic acid, under the synergistic effect of the bio-based cross-linking agent and isocyanate, the prepared composite film has a good tearing effect.

Description

Technical Field

[0001] The present application relates to the field of packaging bag materials, and in particular to an all-round easy-tear composite film and a preparation process thereof. Background Art

[0002] As living conditions improve, people's requirements for quality of life are getting higher and higher. Solid beverages such as coffee, soy milk, milk tea, fruit and vegetable tea, etc., have gradually replaced traditional bottled beverages and are favored by consumers. However, there is a problem. When the solid beverage packaging is opened for use, it is often difficult to tear the packaging bag, the bag can only be torn at a specified position, or it requires a lot of force to tear it, which brings a bad experience to consumers and limits user satisfaction.

[0003] At present, the common composite films on the market mainly include single-layer or multi-layer structures. In order to improve the easy-tear performance of the composite film, a tear line is set at a certain part of the composite film, and the easy-tear effect is achieved through a preset weakened area, or a tiny gap or interface is introduced between different layers of the composite film to facilitate tearing. Although these methods can improve the easy-tear performance of the composite film to a certain extent.

[0004] However, the setting of the tear line is relatively complicated, the production process is relatively high, and in actual use, problems such as incomplete tearing or deviation of the tearing position are prone to occur. At the same time, the interface bonding strength between different layers is not ideal, which makes the composite film easy to delaminate or peel off during use. Summary of the invention

[0005] In order to improve the easy-tear performance of the composite film, the present application provides a comprehensive easy-tear composite film and a preparation process thereof.

[0006] In the first aspect, the present application provides an all-round easy-tear composite film, adopting the following technical scheme: an all-round easy-tear composite film, comprising a polyester layer, a polyethylene layer, paper and aluminum foil, wherein the two sides of the paper are polyester layers and aluminum foils, and the two sides of the aluminum foil are each provided with a polyethylene layer; the polyester layer comprises the following raw materials in parts by weight: 30-40 parts of polyethylene terephthalate, 1-3 parts of isocyanate, 10-20 parts of polylactic acid, and 8-10 parts of natural inorganic filler.

[0007] By adopting the above technical scheme, polyethylene terephthalate and polylactic acid are blended and modified, and at the same time, under the synergistic effect of bio-based cross-linking agent and isocyanate, the cross-linking degree of the polymer is increased, the problem of strong ductility and easy deformation of polyethylene terephthalate is reduced, the rigidity of the polyester layer is enhanced, and the prepared composite film is easy to tear. Aluminum foil has good barrier properties, ensuring that the items in the package are not easily affected by moisture and deterioration. At the same time, aluminum foil has certain rigidity and strength, and has an easy-to-tear effect. At the same time, the flexibility of polylactic acid is conducive to the composite film to form a smoother tearing path when tearing, reducing the resistance during the tearing process, and thus improving the easy-to-tear effect of the composite film. Adding an appropriate amount of natural inorganic filler to the polyester layer raw material can form tiny stress concentration points in the composite film system. These stress concentration points can become the starting point of tearing when subjected to external force, thereby guiding the tearing path and achieving the easy-to-tear effect of the composite film.

[0008] Preferably, the natural inorganic filler is at least one of bamboo charcoal, wood powder and rice husk ash.

[0009] By adopting the above technical solution, bamboo charcoal, wood powder and rice husk ash have good environmental protection and hardness, can reduce the ductility of the composite polyester layer, and make the prepared composite film easy to tear. Bamboo charcoal, wood powder and rice husk ash can enhance the rigidity and toughness of the composite film, form a uniform stress concentration point in the composite film system, and then make the prepared composite film have a comprehensive easy-to-tear effect.

[0010] Preferably, the paper is one of kraft paper and coated paper.

[0011] By adopting the above technical solution, kraft paper and coated paper have good bidirectional tearing effect, further improving the all-round tearing effect of the composite film.

[0012] Preferably, the bio-based cross-linking agent is rosin resin.

[0013] Preferably, the polyethylene layer comprises the following raw materials in parts by weight: 15-25 parts of low-density polyethylene, 60-80 parts of high-density polyethylene, 10-20 parts of ethyl acrylate, 0.5-3 parts of anti-blocking agent, 0.5-3 parts of lubricating agent, 1-5 parts of antistatic agent, and 3-8 parts of tearing aid.

[0014] By adopting the above technical solution, low-density polyethylene has high flexibility, high-density polyethylene has good strength and rigidity, and the combination of low-density polyethylene and high-density polyethylene can balance the flexibility and strength of the composite film, maintain the integrity of the structure, and easily control the tearing path, thereby improving the tearing effect of the composite film. On the other hand, the high-density polyethylene has a compact molecular structure, which improves the structural stability and strength of the composite film and reduces the delamination of the composite film.

[0015] Adding ethyl acrylate to the polyethylene layer can enhance the bonding performance between the polyethylene layer and the aluminum foil and paper, reduce the delamination of the composite film, and at the same time, ethyl acrylate can improve the antistatic property of the composite film.

[0016] Preferably, the tear aid is at least one of calcium carbonate, zinc oxide and titanium dioxide.

[0017] By adopting the above technical solution, calcium carbonate, zinc oxide, and titanium dioxide as tear aids can reduce the tearing force, form a weak stress concentration point in the polyethylene system, and guide the tearing path when subjected to force, making the composite film easier to tear and improving the tearing effect of the composite film. Calcium carbonate, zinc oxide, and titanium dioxide added to the polyethylene layer can form tiny mechanical locking points, enhance the adhesion between the polyethylene layer and other layers, and reduce the delamination or peeling of the composite film caused by external forces.

[0018] In a second aspect, the present application provides a comprehensive process for preparing an easy-to-tear composite film, which adopts the following technical solution: A preparation process of a comprehensive easy-tear composite film comprises the following specific steps: Polyethylene terephthalate, polylactic acid and natural inorganic filler are mixed and heated to melt to obtain a polyester mixture, and isocyanate is added under the protection of nitrogen for mixed reaction, and then extruded and granulated, and then biaxially stretched by casting to obtain a polyester layer; After printing on one side of the polyester layer, the polyester layer is dried, and then glue is applied to the printed surface of the polyester layer, and after heating and drying, the printed surface is bonded to the paper to obtain a composite film semi-finished product; The paper surface of the composite film semi-finished product is corona treated, the dark side of the aluminum foil is bonded to the paper surface through the polyethylene layer mixture, and then the molten polyethylene layer mixture is coated on the bright side of the aluminum foil and dried to form a polyethylene layer on each side of the aluminum foil to obtain an all-round easy-to-tear composite film.

[0019] By adopting the above technical solution and combining various processes, the prepared composite film has an all-round easy-tear effect, and the package can be opened smoothly by applying force from all angles. At the same time, there is a strong bonding force between the layers, which reduces the stratification phenomenon of the composite film.

[0020] Preferably, the method comprises the following specific steps: Polyethylene terephthalate, polylactic acid and natural inorganic filler are mixed and heated to melt to obtain a polyester mixture, and isocyanate is added under the protection of nitrogen for mixed reaction, and then extruded and granulated, and then biaxially stretched by casting to obtain a polyester layer; After printing on one side of the polyester layer, the polyester layer is dried, and then glue is applied to the printed surface of the polyester layer to adhere to the paper, and then heated and dried to obtain a composite film semi-finished product; Mix low-density polyethylene, high-density polyethylene, ethyl acrylate, anti-blocking agent, slip agent, antistatic agent and tearing aid, stir evenly, heat and melt to form a polyethylene layer mixture, and divide the polyethylene layer mixture into two parts; The paper surface of the composite film semi-finished product is corona treated, and the dark side of the aluminum foil is bonded to the paper surface through a part of the polyethylene layer mixture. Then, the molten polyethylene layer mixture is coated on the bright side of the aluminum foil and dried to form a polyethylene layer on each side of the aluminum foil to obtain a full-range easy-to-tear composite film.

[0021] Preferably, the glue is polyurethane glue.

[0022] Preferably, the thickness of the polyester layer and the polyethylene layer are both 0.02-0.05 mm.

[0023] In summary, this application has the following beneficial effects: 1. Since the present application adopts polylactic acid and polyethylene terephthalate for blending and modification, reduces the ductility of polyethylene terephthalate, uses bio-based crosslinking agents and isocyanates to increase the crosslinking degree and rigidity of the polymer, and makes the prepared composite film easy to tear. At the same time, polylactic acid and natural inorganic fillers are compounded to form a smoother tearing path when the composite film is torn under force, thereby improving the easy tearing effect of the composite film.

[0024] 2. The combination of low-density polyethylene and high-density polyethylene in this application can make the polyethylene layer have better rigidity, and the high-density polyethylene can enhance the structural density and strength of the composite film and reduce the stratification of the composite film. At the same time, ethyl acrylate and easy-tear aids can enhance the adhesion between the polyethylene layer and other layers, reduce the stratification or peeling of the composite film caused by external forces, and form a weak stress concentration point in the polyethylene system. When subjected to force, it can guide the tearing path, make the composite film easier to tear, and improve the easy-tear effect of the composite film. DETAILED DESCRIPTION

[0025] The present application is further described in detail below with reference to the embodiments.

[0026] All raw materials in the examples are commercially available. Example

[0027] Example 1 This embodiment provides a comprehensive easy-to-tear composite film, including a polyester layer, a polyethylene layer, paper and aluminum foil, wherein the polyester layer includes the following raw materials in parts by weight: 35 kg of polyethylene terephthalate, 2 kg of isocyanate, 2 kg of bio-based cross-linking agent, 15 kg of polylactic acid, and 9 kg of natural inorganic filler. The CAS number of polyethylene terephthalate is 25038-59-9, the isocyanate is 1,5-naphthalene diisocyanate, the bio-based cross-linking agent is rosin resin, the CAS number of rosin resin is 112-84-5, the polylactic acid is LX175, the natural inorganic filler is bamboo charcoal, and the average particle size of the natural inorganic filler is 10-50 μm. The polyethylene layer includes the following raw materials in parts by weight: 20 kg of low-density polyethylene, 70 kg of high-density polyethylene, the low-density polyethylene is LDPE-5202, the high-density polyethylene is HGPE5000S, and the paper is kraft paper.

[0028] The preparation process of the all-round easy-tear composite film includes the following specific steps: S1: Polyethylene terephthalate, polylactic acid and natural inorganic filler are mixed and heated to 220°C for melting to obtain a polyester mixture. Under the protection of nitrogen, isocyanate is added and mixed for reaction for 60 minutes. After extrusion granulation, biaxial stretching is performed by casting to obtain a polyester layer with a thickness of 0.03 mm.

[0029] S2: After printing on one side of the polyester layer, it is dried at 70°C, and then polyurethane glue is coated on the printed surface of the polyester layer. The polyurethane glue model is HY-752. The glued surface of the polyester layer is sequentially dried in a three-stage oven at 65°C, 75°C, and 85°C, and then laminated to the glossy surface of the paper to obtain a composite film semi-finished product.

[0030] S3: Low-density polyethylene and high-density polyethylene are mixed and heated to 180°C to melt to form a polyethylene mixture; the paper surface of the composite film semi-finished product is subjected to corona treatment, and the dark side of the aluminum foil is bonded to the paper surface through a polyethylene layer mixture with a mass of one-third to form a polyethylene layer with a thickness of 0.02 mm, and then the remaining polyethylene layer mixture is coated on the bright side of the aluminum foil and dried to form a polyethylene layer with a thickness of 0.05 mm, thereby obtaining an all-round easy-to-tear composite film.

[0031] Example 2 The difference between Example 2 and Example 1 is that the amount of polyethylene terephthalate used in the polyester layer raw material is 30 kg, the amount of isocyanate used is 1 kg, the amount of bio-based cross-linking agent used is 3 kg, the amount of polylactic acid used is 20 kg, and the amount of natural inorganic filler used is 8 kg.

[0032] Example 3 The difference between Example 3 and Example 1 is that the amount of polyethylene terephthalate used in the polyester layer raw material is 40 kg, the amount of isocyanate used is 3 kg, the amount of bio-based cross-linking agent used is 1 kg, the amount of polylactic acid used is 10 kg, and the amount of natural inorganic filler used is 10 kg.

[0033] Example 4 The difference between Example 4 and Example 1 is that the natural inorganic filler is a mixture of bamboo charcoal, wood powder and rice husk ash, and the mass ratio of the bamboo charcoal, wood powder and rice husk ash is 1:1.

[0034] Example 5 The difference between Example 5 and Example 1 is that the paper in the omnidirectional easy-tear composite film is coated paper.

[0035] Example 6 The difference between Example 6 and Example 1 is that the polyethylene layer includes the following raw materials in parts by weight: 20 kg of low-density polyethylene, 70 kg of high-density polyethylene, 15 kg of ethyl acrylate, 2 kg of anti-blocking agent, 2 kg of lubricant, 3 kg of antistatic agent, and 5 kg of tearing aid. The anti-blocking agent is purchased from Transparent-6 of Haining Yanguan, the lubricant is purchased from 101820-K of Anpeise Masterbatch Manufacturing Co., Ltd., the antistatic agent is BOPP, the tearing aid is calcium carbonate, and the average particle size of the tearing aid is 50 nm.

[0036] The preparation process of the all-round easy-tear composite film includes the following specific steps: S1: Polyethylene terephthalate, polylactic acid and natural inorganic filler are mixed and heated to 220°C for melting to obtain a polyester mixture. Under the protection of nitrogen, isocyanate is added and mixed for reaction for 60 minutes. After extrusion granulation, biaxial stretching is performed by casting to obtain a polyester layer with a thickness of 0.03 mm.

[0037] S2: After printing on one side of the polyester layer, it is dried at 70°C, and then polyurethane glue is coated on the printed surface of the polyester layer. The polyurethane glue model is HY-752. The glued surface of the polyester layer is sequentially dried in a three-stage oven at 65°C, 75°C, and 85°C, and then laminated to the glossy surface of the paper to obtain a composite film semi-finished product.

[0038] S3: low-density polyethylene, high-density polyethylene, ethyl acrylate, anti-blocking agent, lubricant, antistatic agent and tearing aid are mixed and heated to 180°C to melt to form a polyethylene mixture; the paper surface of the composite film semi-finished product is subjected to corona treatment, and the dark side of the aluminum foil is bonded to the paper surface through a polyethylene layer mixture with a mass of one-third to form a polyethylene layer with a thickness of 0.02 mm, and then the remaining polyethylene layer mixture is coated on the bright side of the aluminum foil and dried to form a polyethylene layer with a thickness of 0.05 mm, thereby obtaining a full-range easy-to-tear composite film.

[0039] Example 7 The difference between Example 7 and Example 6 is that, in the raw material of the polyethylene layer of the all-round easy-to-tear composite film, the amount of low-density polyethylene used is 15 kg, the amount of high-density polyethylene used is 80 kg, the amount of ethyl acrylate used is 10 kg, the amount of opening agent used is 0.5 kg, the amount of lubricant used is 3 kg, the amount of antistatic agent used is 1 kg, and the amount of easy-to-tear aid used is 8 kg.

[0040] Example 8 The difference between Example 8 and Example 6 is that, in the raw material of the polyethylene layer in the all-round easy-to-tear composite film, the amount of low-density polyethylene used is 25 kg, the amount of high-density polyethylene used is 60 kg, the amount of ethyl acrylate used is 20 kg, the amount of opening agent used is 3 kg, the amount of lubricant used is 0.5 kg, the amount of antistatic agent used is 5 kg, and the amount of easy-to-tear aid used is 3 kg.

[0041] Example 9 The difference between Example 9 and Example 6 is that the tearing aid is a mixture of zinc oxide and titanium dioxide, and the mass ratio of zinc oxide to titanium dioxide is 1:1.

[0042] Comparative Example Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the polyester layer comprises the following raw materials in parts by weight: 35 kg of polyethylene terephthalate and 15 kg of polylactic acid.

[0043] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the raw material of the polyester layer is polyethylene terephthalate.

[0044] Performance testing The following performance tests were conducted on the omnidirectional easy-tear composite films and packaging bags made of the composite films provided in Examples 1-9 and Comparative Examples 1-2 of the present application. The specific test results are shown in Table 1.

[0045] Detection Methods 1. Elongation at break With reference to the standard of GB / T1040-2006 "Tensile Properties of Plastics", the elongation at break of the composite film prepared in the present application was tested.

[0046] 2. Right Angle Tear Strength The right-angle tear strength of the packaging bag prepared from the composite film of the present application was tested with reference to the standard of QB / T1130-1991 "Test method for right-angle tear performance of plastics".

[0047] 3. Tearability in all directions Direction A is to tear from the left side of the packaging bag, and tear to the right side at a uniform speed of 30mm / s. Direction B is to tear from the right side of the packaging bag, and tear to the left side at a uniform speed of 30 mm / s. Observe whether the tearing path is smooth or straight.

[0048] 4. Peel strength A 180° peel test was performed with a test length of 200 mm and a width of (15±1) mm at a peeling speed of 100 mm / min. Five specimens were taken in the transverse and longitudinal directions, and the average of the five test values ​​was taken as the result to detect the peel strength between the polyethylene layer in the composite film of the present application and the composite film semi-finished product.

[0049] Table 1: Performance test results data table It can be seen from the performance test results that the packaging bag made of the composite film prepared in the present application can be smoothly opened from any direction, and at the same time, the layers of the composite film have strong peeling strength, which reduces the phenomenon of composite film delamination.

[0050] By comparing Comparative Examples 1-2 with Example 1, it can be seen that the polyester layer raw materials in Comparative Example 1 only use polyethylene terephthalate and polylactic acid, and the polyester layer raw materials in Comparative Example 2 only use polyethylene terephthalate. From the performance test results, it can be seen that the tearing effect of the composite film is significantly reduced, and a greater force is required to tear the packaging bag. It further shows that the single polyethylene terephthalate has a high ductility, thereby increasing the difficulty of tearing the packaging bag. At the same time, although the combination of polyethylene terephthalate and polylactic acid can improve the rigidity of the composite film, the degree of crosslinking in the composite film system is limited, which leads to a low tearing effect of the composite film.

[0051] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. An all-round easy-tear composite film, characterized in that: It comprises a polyester layer, a polyethylene layer, paper and an aluminum foil, wherein the two sides of the paper are polyester layers and aluminum foils, and the two sides of the aluminum foil are each provided with a polyethylene layer; the polyester layer comprises the following raw materials in parts by weight: 30-40 parts of polyethylene terephthalate, 1-3 parts of isocyanate, 1-3 parts of a bio-based cross-linking agent, 10-20 parts of polylactic acid, and 8-10 parts of a natural inorganic filler.

2. The omnidirectional easy-tear composite film according to claim 1, characterized in that: The natural inorganic filler is at least one of bamboo charcoal, wood powder and rice husk ash.

3. The omnidirectional easy-tear composite film according to claim 1, characterized in that: The paper is one of kraft paper and coated paper.

4. The omnidirectional easy-tear composite film according to claim 1, characterized in that: The bio-based cross-linking agent is rosin resin.

5. The omnidirectional easy-tear composite film according to claim 1, characterized in that: The polyethylene layer comprises the following raw materials in parts by weight: 15-25 parts of low-density polyethylene, 60-80 parts of high-density polyethylene, 10-20 parts of ethyl acrylate, 0.5-3 parts of an opening agent, 0.5-3 parts of a slip agent, 1-5 parts of an antistatic agent, and 3-8 parts of an easy-tear aid.

6. The omnidirectional easy-tear composite film according to claim 5, characterized in that: The tearing aid is at least one of calcium carbonate, zinc oxide and titanium dioxide.

7. A process for preparing an omnidirectional easy-tear composite film as claimed in any one of claims 1 to 6, characterized in that: The specific steps include: Polyethylene terephthalate, polylactic acid and natural inorganic filler are mixed and heated to melt to obtain a polyester mixture, and isocyanate is added under the protection of nitrogen for mixed reaction, and then extruded and granulated, and then biaxially stretched by casting to obtain a polyester layer; After printing on one side of the polyester layer, the polyester layer is dried, and then glue is applied to the printed surface of the polyester layer, and after heating and drying, the printed surface is bonded to the paper to obtain a composite film semi-finished product; The paper surface of the composite film semi-finished product is corona treated, the dark side of the aluminum foil is bonded to the paper surface through the polyethylene layer mixture, and then the molten polyethylene layer mixture is coated on the bright side of the aluminum foil and dried to form a polyethylene layer on each side of the aluminum foil to obtain an all-round easy-to-tear composite film.

8. The process for preparing the omnidirectional easy-tear composite film according to claim 7, characterized in that: The specific steps include: Polyethylene terephthalate, polylactic acid and natural inorganic filler are mixed, heated and melted, and isocyanate is added under the protection of nitrogen to obtain a polyester mixture, which is then granulated and biaxially stretched by casting to obtain a polyester layer; After printing on one side of the polyester layer, the polyester layer is dried, and then glue is applied to the printed surface of the polyester layer to adhere to the paper, and then heated and dried to obtain a composite film semi-finished product; Mix low-density polyethylene, high-density polyethylene, ethyl acrylate, anti-blocking agent, slip agent, antistatic agent and tearing aid, stir evenly, heat and melt to form a polyethylene layer mixture, and divide the polyethylene layer mixture into two parts; The paper surface of the composite film semi-finished product is corona treated, and the dark side of the aluminum foil is bonded to the paper surface through a part of the polyethylene layer mixture. Then, the molten polyethylene layer mixture is coated on the bright side of the aluminum foil and dried to form a polyethylene layer on each side of the aluminum foil to obtain a full-range easy-to-tear composite film.

9. The process for preparing the omnidirectional easy-tear composite film according to claim 7, characterized in that: The glue is polyurethane glue.

10. The process for preparing the omnidirectional easy-tear composite film according to claim 7, characterized in that: The thickness of the polyester layer and the polyethylene layer are both 0.02-0.05 mm.

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