A plastic film for a packaging bag and a method for producing the same

Abstract

The application discloses a plastic film for packaging bags and a preparation method thereof, and relates to the technical field of polyethylene composite films.The plastic film comprises an outer nylon layer, a middle adhesive layer and an inner polyethylene layer.Polyethylene is put into a mixing device for mixing, then modified titanium dioxide is added for blending, the blended material is added into an extruder for extrusion molding to obtain a polyethylene film, the polyethylene film is coated with adhesive, and the polyethylene film and the nylon layer are compounded together to obtain the plastic film for packaging bags.The prepared composite film has excellent tensile strength and tensile strength, excellent puncture resistance, and good heat resistance, oil resistance, aging resistance and flame resistance.

Description

Technical Field

[0001] This invention relates to the field of polyethylene composite films, and more specifically to a plastic film for packaging bags and its preparation method. Background Technology

[0002] Polyethylene is a thermoplastic resin obtained by polymerizing ethylene. It is non-toxic, odorless, has good low-temperature resistance, good chemical stability, is resistant to most acids and alkalis, is insoluble in common solvents at room temperature, has low water absorption, and excellent electrical insulation properties. Therefore, polyethylene products are widely used in the packaging, construction, communications, and agriculture industries.

[0003] Based on differences in molecular weight, chain structure, and polymerization method, polyethylene can be classified into linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE). LLDPE is produced by copolymerizing α-olefins with ethylene under low pressure using a highly active catalyst with a coordination structure. Its molecular structure is linear, resulting in poor transparency but good surface gloss. It possesses advantages such as bending resistance, high modulus, resistance to stress cracking, and low-temperature toughness, as well as good impact strength at low temperatures. LDPE is typically produced using a high-pressure method, resulting in lower crystallinity and density (0.910~0.925). It exhibits good flexibility, low-temperature resistance, and impact resistance, making it widely used in the production of plastic bags and agricultural films. High-density polyethylene is typically manufactured using the Ziegler-Natta polymerization method, resulting in fewer branched chains, higher density (0.941~0.965), and higher crystallinity (85~95%). Compared with LLDPE and LDPE, HDPE has higher oil resistance, temperature resistance, vapor permeability resistance and environmental stress cracking resistance. In addition, it also has good electrical insulation, impact resistance and cold resistance. It is currently mainly used in injection molding, blow molding and other fields.

[0004] The most important raw material for various films is polyethylene, of which more than 50% is used to make films.

[0005] Chinese patent document CN109081990A discloses a durable plastic packaging bag film, composed of the following raw materials in parts by weight: 20-30 parts linear low-density polyethylene, 60-80 parts high-density polyethylene, 10-20 parts metallocene polyethylene, 15-25 parts glass fiber, 4-6 parts nano zinc oxide, 4-6 parts nano titanium dioxide, 0.5-1.5 parts compatibilizer, 1-2 parts coupling agent, and 1-2 parts antioxidant. This plastic packaging bag film possesses advantages such as chemical stability, electrical conductivity, thermal stability, non-toxicity, superhydrophilicity, and non-migratory properties. However, the nano-inorganic particles are prone to agglomeration in the resin matrix, and will precipitate after a period of use, causing performance degradation. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a plastic film for packaging bags and its preparation method. The resulting composite film has excellent tensile strength and tensile strength, excellent puncture resistance, and good heat resistance, oil resistance, aging resistance, and flame retardancy.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A plastic film for packaging bags includes an outer nylon layer, an intermediate adhesive layer, and an inner polyethylene layer, wherein the inner polyethylene layer is a polyethylene film toughened with modified titanium dioxide particles, and the mass ratio of the polyethylene to the modified titanium dioxide particles is 10:1.5~5.

[0009] Preferably, the thickness of the nylon layer is 10~30μm, and the thickness of the polyethylene layer is 40~60μm.

[0010] Specifically, the thickness of the nylon layer can be 10μm, 20μm, or 30μm; and the thickness of the polyethylene layer can be 40μm, 50μm, or 60μm.

[0011] Preferably, the polyethylene is one or more of linear low-density polyethylene, low-density polyethylene, and high-density polyethylene.

[0012] Preferably, the nylon is one or more of PA6, PA66, PA46, and PA6T, and the weight-average molecular weight of the nylon is 13000 Da to 27000 Da.

[0013] Preferably, the method for preparing the modified titanium dioxide includes the following steps:

[0014] (1) Add nano-titanium dioxide and epoxy-based POSS to xylene, sonicate, then add potassium carbonate solution dropwise, stir the reaction, filter, wash and dry the product to obtain POSS-grafted titanium dioxide.

[0015] (2) POSS-grafted titanium dioxide was dispersed in xylene, 4-tert-butylphenyl salicylate was added, potassium carbonate solution was added dropwise, the reaction was heated, and the product was filtered, washed and dried to obtain modified titanium dioxide.

[0016] Preferably, step (1) includes a nano-titanium dioxide pretreatment step: treating the nano-titanium dioxide with water vapor at 130~150℃ for 30~90min.

[0017] Specifically, the steam temperature can be 130℃, 135℃, 140℃, 145℃, or 150℃; the treatment time can be 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, or 90 min.

[0018] Preferably, in step (1), the structural formula of the epoxy group POSS is as follows: ,

[0019] R is 2,3-epoxypropoxypropyl.

[0020] Preferably, in step (1), the ratio of nano-titanium dioxide, epoxy-based POSS, and potassium carbonate solution is 10g:8~14g:0.5~3mL; and the concentration of potassium carbonate solution is 10~20wt%.

[0021] Preferably, in step (1), the stirring reaction conditions are 110~130℃ for 3~6h.

[0022] Specifically, the stirring reaction temperature can be 110℃, 120℃, or 130℃; the reaction time can be 3h, 4h, 5h, or 6h.

[0023] Preferably, in step (2), the ratio of POSS-grafted titanium dioxide, salicylic acid-4-tert-butylphenyl ester, and potassium carbonate solution is 10g:4.6~11.3g:0.5~3mL; and the concentration of potassium carbonate solution is 10~20wt%.

[0024] Preferably, in step (2), the heating reaction conditions are 120~150℃ for 2~6h.

[0025] Specifically, the heating reaction temperature can be 120℃, 130℃, 140℃, or 150℃; the reaction time can be 2h, 3h, 4h, 5h, or 6h.

[0026] The present invention also claims a method for preparing the plastic film for packaging bags, comprising the following steps: placing polyethylene into a mixing device for mixing, then adding modified titanium dioxide for blending, adding the blend to an extruder for extrusion molding to obtain a polyethylene film, coating the polyethylene film with an adhesive, and laminating the polyethylene film with a nylon layer to obtain the plastic film for packaging bags.

[0027] Preferably, the blending temperature is 180~260℃, the blending time is 2~5min, the blending speed is 50~80r / min, and the blending time is 5~10min.

[0028] Specifically, the blending temperature can be 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, or 260℃; the blending time can be 2 min, 3 min, 4 min, or 5 min; the blending speed can be 50 r / min, 60 r / min, 70 r / min, or 80 r / min; and the blending time can be 5 min, 6 min, 7 min, 8 min, 9 min, or 10 min.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) This invention provides a plastic film for packaging bags, with an outer nylon layer and an inner polyethylene layer, which are laminated together with an adhesive. Modified nano-titanium dioxide inorganic particles are used to toughen the polyethylene layer. The modified nano-titanium dioxide particles can be uniformly dispersed in the polyethylene matrix, which significantly improves the mechanical properties of the composite film, giving it excellent tensile strength and tensile strength, excellent puncture resistance, and good heat resistance, oil resistance, aging resistance and flame retardancy.

[0031] 2) This invention provides a modified titanium dioxide. First, nano-titanium dioxide is pretreated with water vapor to increase the hydroxyl content on its surface. Then, under the catalysis of potassium carbonate, the hydroxyl groups on the titanium dioxide surface undergo a ring-opening reaction with the epoxy groups on the surface of epoxy-based POSS, grafting POSS onto the nano-titanium dioxide surface. Subsequently, the antioxidant 4-tert-butylphenyl salicylate is grafted onto the POSS surface through the reaction of the hydroxyl groups in 4-tert-butylphenyl salicylate with the epoxy-based POSS. Titanium dioxide and 4-tert-butylphenyl salicylate are then combined using polysilsesquioxane (POSS) to prepare modified titanium dioxide. This modified titanium dioxide is then blended with polyethylene to obtain a modified nano-titanium dioxide-toughened polyethylene film, which imparts the following beneficial properties to the film. Effects: Titanium dioxide grafted with epoxy-based POSS and 4-tert-butylphenyl salicylate can transform its hydrophilic surface into a hydrophobic surface, improving its dispersibility in polyethylene systems and enhancing the beneficial effects of modified titanium dioxide on polyethylene films. Titanium dioxide possesses strong UV shielding capabilities, abrasion resistance, thermal stability, and antibacterial properties, while POSS improves the material's mechanical properties, thermal stability, puncture resistance, and flame retardancy. POSS and nano-titanium dioxide synergistically enhance the tensile strength, tensile strength, and puncture resistance of polyethylene films, while the antioxidant 4-tert-butylphenyl salicylate works synergistically with nano-titanium dioxide to provide excellent UV aging resistance, significantly improving the service life and applicability of polyethylene films. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some schematic diagrams of certain embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A plastic film for packaging bags provided by the present invention;

[0034] In the diagram, 1 is the nylon layer; 2 is the adhesive layer; and 3 is the polyethylene layer. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Of course, the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0036] Unless otherwise specified, all chemical reagents and materials in this invention are purchased from the market or synthesized from raw materials purchased from the market.

[0037] The nano-titanium dioxide was purchased from Xuancheng Jingrui New Materials Co., Ltd., model number JR05, with an average particle size of 5nm.

[0038] The low-density polyethylene was purchased from Sinopec Yangzi Petrochemical Co., Ltd., and the model was 2426K.

[0039] High-density polyethylene was purchased from Dongguan Shunyu Chemical Co., Ltd., and its grade was LH606.

[0040] The nylon resin is PA6 resin, purchased from Suzhou Aoxuan Engineering Plastics Co., Ltd., with product number YH3400.

[0041] A method for preparing a plastic film for packaging bags includes the following steps:

[0042] (1) Treat nano-titanium dioxide with steam at 130~150℃ for 30~90min, then add 10g of pretreated nano-titanium dioxide and 8~14g of epoxy-based POSS to 100mL of xylene, sonicate for 10~30min, then add 0.5~3mL of 10~20wt% potassium carbonate solution dropwise, stir and react at 110~130℃ for 3~6h, filter, wash and dry the product to obtain POSS-grafted titanium dioxide;

[0043] (2) Disperse 10g of POSS-grafted titanium dioxide into 100mL of xylene, add 4.6~11.3g of salicylic acid-4-tert-butylphenyl ester, and then add 0.5~3mL of 10~20wt% potassium carbonate solution dropwise. Heat the mixture at 120~150℃ for 2~6h. Filter, wash and dry the product to obtain modified titanium dioxide.

[0044] (3) Weigh polyethylene and modified titanium dioxide at a mass ratio of 10:1.5~5, set the blending temperature to 180~260℃, and after the set temperature is reached, put polyethylene into the mixing equipment for 2~5 min and then add modified titanium dioxide. Blend at 50~80 r / min for 5~10 min, add the blend to the extruder and extrude to obtain a polyethylene film, coat the polyethylene film with an adhesive, and combine the polyethylene film with the nylon layer to obtain the plastic film for the packaging bag.

[0045] The present invention will be further described below through specific embodiments.

[0046] Example 1

[0047] A method for preparing a plastic film for packaging bags includes the following steps:

[0048] (1) Treat nano-titanium dioxide with water vapor at 150℃ for 30 min, then add 10 g of pretreated nano-titanium dioxide and 14 g of epoxy POSS to 100 mL of xylene, sonicate for 30 min, then add 3 mL of 10 wt% potassium carbonate solution, stir and react at 130℃ for 3 h, filter, wash and dry the product to obtain POSS-grafted titanium dioxide;

[0049] (2) Disperse 10g of POSS-grafted titanium dioxide into 100mL of xylene, add 11.3g of salicylic acid-4-tert-butylphenyl ester, then add 3mL of 10wt% potassium carbonate solution, heat at 150℃ for 2h, filter, wash and dry the product to obtain modified titanium dioxide.

[0050] (3) Weigh high-density polyethylene and modified titanium dioxide at a mass ratio of 10:5, set the blending temperature to 220°C, and after the set temperature is reached, put the polyethylene into the mixing equipment for 3.5 min of mixing, then add the modified titanium dioxide and mix at 60 r / min for 7.5 min. Add the blend to the extruder and extrude to obtain a polyethylene film. Coat the polyethylene film with an adhesive and combine the polyethylene film with the nylon layer to obtain the plastic film for the packaging bag.

[0051] Example 2

[0052] A method for preparing a plastic film for packaging bags includes the following steps:

[0053] (1) Treat nano-titanium dioxide with water vapor at 140℃ for 60 min, then add 10 g of pretreated nano-titanium dioxide and 12 g of epoxy group POSS to 100 mL of xylene, sonicate for 20 min, then add 2.5 mL of 10 wt% potassium carbonate solution dropwise, stir and react at 125℃ for 5 h, filter, wash and dry the product to obtain POSS grafted titanium dioxide;

[0054] (2) 10g of POSS-grafted titanium dioxide was dispersed in 100mL of xylene, 9.4g of salicylic acid-4-tert-butylphenyl ester was added, and then 2.5mL of 10wt% potassium carbonate solution was added dropwise. The mixture was heated at 140℃ for 3h. The product was filtered, washed and dried to obtain modified titanium dioxide.

[0055] (3) Weigh high-density polyethylene and modified titanium dioxide at a mass ratio of 10:4, set the blending temperature to 220°C, and after the set temperature is reached, put the polyethylene into the mixing equipment for 3.5 min and then add the modified titanium dioxide. Blend at 60 r / min for 7.5 min, add the blend to the extruder and extrude to obtain a polyethylene film. Coat the polyethylene film with an adhesive and combine the polyethylene film with the nylon layer to obtain the plastic film for the packaging bag.

[0056] Example 3

[0057] A method for preparing a plastic film for packaging bags includes the following steps:

[0058] (1) Treat nano-titanium dioxide with water vapor at 140℃ for 60 min, then add 10 g of pretreated nano-titanium dioxide and 10 g of epoxy group POSS to 100 mL of xylene, sonicate for 20 min, then add 1.5 mL of 10 wt% potassium carbonate solution dropwise, stir and react at 120℃ for 5 h, filter, wash and dry the product to obtain POSS grafted titanium dioxide;

[0059] (2) 10g of POSS-grafted titanium dioxide was dispersed in 100mL of xylene, 7.5g of salicylic acid-4-tert-butylphenyl ester was added, and then 1.5mL of 10wt% potassium carbonate solution was added dropwise. The mixture was heated at 130℃ for 5h. The product was filtered, washed and dried to obtain modified titanium dioxide.

[0060] (3) Weigh high-density polyethylene and modified titanium dioxide at a mass ratio of 10:3, set the blending temperature to 220°C, and after the set temperature is reached, put the polyethylene into the mixing equipment for 3.5 min of mixing, then add the modified titanium dioxide, and mix at 60 r / min for 7.5 min. Add the blend to the extruder and extrude to obtain a polyethylene film. Coat the polyethylene film with an adhesive and combine the polyethylene film with the nylon layer to obtain the plastic film for the packaging bag.

[0061] Example 4

[0062] A method for preparing a plastic film for packaging bags includes the following steps:

[0063] (1) Treat nano-titanium dioxide with water vapor at 130℃ for 90 min, then add 10 g of pretreated nano-titanium dioxide and 8 g of epoxy POSS to 100 mL of xylene, sonicate for 10 min, then add 0.5 mL of 10 wt% potassium carbonate solution dropwise, stir and react at 110℃ for 6 h, filter, wash and dry the product to obtain POSS-grafted titanium dioxide;

[0064] (2) 10g of POSS-grafted titanium dioxide was dispersed in 100mL of xylene, 4.6g of salicylic acid-4-tert-butylphenyl ester was added, and then 0.5mL of 10wt% potassium carbonate solution was added dropwise. The mixture was heated at 120℃ for 6h. The product was filtered, washed and dried to obtain modified titanium dioxide.

[0065] (3) Weigh high-density polyethylene and modified titanium dioxide at a mass ratio of 10:1.5, set the blending temperature to 220°C, and after the set temperature is reached, put the polyethylene into the mixing equipment for 3.5 min of mixing, then add the modified titanium dioxide and mix at 60 r / min for 7.5 min. Add the blend to the extruder and extrude to obtain a polyethylene film. Coat the polyethylene film with an adhesive and combine the polyethylene film with the nylon layer to obtain the plastic film for the packaging bag.

[0066] Comparative Example 1

[0067] A method for preparing a plastic film for packaging bags includes the following steps:

[0068] (1) Treat nano-titanium dioxide with water vapor at 150℃ for 30 min, then add 10 g of pretreated nano-titanium dioxide and 14 g of epoxy POSS to 100 mL of xylene, sonicate for 30 min, then add 3 mL of 10 wt% potassium carbonate solution, stir and react at 130℃ for 3 h, filter, wash and dry the product to obtain POSS-grafted titanium dioxide.

[0069] (2) Weigh high-density polyethylene and POSS-grafted titanium dioxide at a mass ratio of 10:5. Set the blending temperature to 220°C. After the set temperature is reached, put the polyethylene into the mixing equipment and mix for 3.5 min. Then add POSS-grafted titanium dioxide and mix at 60 r / min for 7.5 min. Add the blend to the extruder and extrude to obtain a polyethylene film. Coat the polyethylene film with an adhesive and combine the polyethylene film with the nylon layer to obtain the plastic film for the packaging bag.

[0070] Comparative Example 2

[0071] A method for preparing a plastic film for packaging bags includes the following steps:

[0072] (1) Pretreated nano-titanium dioxide was obtained by treating nano-titanium dioxide with water vapor at 150℃ for 30 min;

[0073] (2) Weigh high-density polyethylene and pretreated titanium dioxide at a mass ratio of 10:5. Set the blending temperature to 220°C. After the set temperature is reached, put the polyethylene into the mixing equipment and mix for 3.5 min. Then add the pretreated titanium dioxide and mix at 60 r / min for 7.5 min. Add the blend to the extruder and extrude to obtain a polyethylene film. Coat the polyethylene film with an adhesive and combine the polyethylene film with the nylon layer to obtain the plastic film for the packaging bag.

[0074] Composite films prepared in Examples 1-4 and Comparative Examples 1-2 were cut to a size of 150mm × 20mm, with a nylon layer thickness of 20μm and a polyethylene layer thickness of 40μm. Accelerated aging was performed for 2000 hours in an aging chamber using a xenon lamp simulating sunlight, according to GB / T 16422.2-2022 "Laboratory Light Source Exposure Test Methods for Plastics - Part 2: Xenon Arc Lamp". Before and after aging, tensile strength and elongation at break were tested according to GB / T 1040.3-2006 "Determination of Tensile Properties of Plastics - Part 3: Test Conditions for Films and Sheets", puncture strength was tested according to GB / T 10004-2008 "Plastic Composite Films and Bags for Packaging - Dry Lamination and Extrusion Lamination", and heat shrinkage rate was tested according to GB / T 13519-2016 "Polyethylene Heat Shrinkable Films for Packaging". 31402-2015 "Test Method for Antibacterial Properties of Plastic Surfaces" tests the antibacterial properties of films, with Escherichia coli as the bacterial strain. Specific data are shown in Table 1.

[0075] Table 1. Test results of plastic film performance

[0076]

[0077] 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 plastic film for packaging bags, characterized in that, It includes an outer nylon layer, an intermediate adhesive layer, and an inner polyethylene layer, wherein the inner polyethylene layer is a polyethylene film toughened with modified titanium dioxide particles, and the mass ratio of polyethylene to modified titanium dioxide particles is 10:1.5~5. The method for preparing the modified titanium dioxide includes the following steps: (1) Add nano-titanium dioxide and epoxy-based POSS to xylene, sonicate, then add potassium carbonate solution dropwise, stir the reaction, filter, wash and dry the product to obtain POSS-grafted titanium dioxide. (2) POSS-grafted titanium dioxide was dispersed in xylene, 4-tert-butylphenyl salicylate was added, potassium carbonate solution was added dropwise, the reaction was heated, and the product was filtered, washed and dried to obtain modified titanium dioxide.

2. The plastic film for packaging bags according to claim 1, characterized in that, The polyethylene is one or more of linear low-density polyethylene, low-density polyethylene, and high-density polyethylene; the nylon is one or more of PA6, PA66, PA46, and PA6T, and the weight-average molecular weight of the nylon is 13000 Da to 27000 Da.

3. The plastic film for packaging bags according to claim 1, characterized in that, Step (1) also includes a nano-titanium dioxide pretreatment step: treating nano-titanium dioxide with water vapor at 130~150℃ for 30~90min.

4. The plastic film for packaging bags according to claim 1, characterized in that, In step (1), the ratio of nano-titanium dioxide, epoxy-based POSS, and potassium carbonate solution is 10g:8~14g:0.5~3mL; the concentration of potassium carbonate solution is 10~20wt%.

5. The plastic film for packaging bags according to claim 1, characterized in that, In step (1), the stirring reaction conditions are 110~130℃ for 3~6h.

6. The plastic film for packaging bags according to claim 1, characterized in that, In step (2), the ratio of POSS-grafted titanium dioxide, salicylic acid-4-tert-butylphenyl ester, and potassium carbonate solution is 10g:4.6~11.3g:0.5~3mL; the concentration of potassium carbonate solution is 10~20wt%.

7. The plastic film for packaging bags according to claim 1, characterized in that, In step (2), the heating reaction conditions are 120~150℃ for 2~6h.

8. A method for preparing a plastic film for packaging bags as described in any one of claims 1 to 7, characterized in that, The process includes the following steps: placing polyethylene into a mixing device for mixing, then adding modified titanium dioxide for blending, adding the blend to an extruder for extrusion molding to obtain a polyethylene film, coating the polyethylene film with an adhesive, and laminating the polyethylene film with a nylon layer to obtain the plastic film for the packaging bag.

9. A preparation method as described in claim 8, characterized in that, The blending temperature is 180~260℃, the blending time is 2~5min, the blending speed is 50~80r / min, and the blending time is 5~10min.

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