Printing composite PE film for sanitary bag

Abstract

The invention relates to the technical field of preparation of composite PE (polyethylene) films, and discloses a printing composite PE film for a sanitary bag, which comprises 94.0-99.0 parts by mass of polyethylene matrix resin; 0.5 to 5.0 parts by mass of hyperbranched polyolefin; 0.1 to 0.5 part by mass of polyethylene wax; 0.1 to 0.3 part by mass of a composite antioxidant; the preparation method comprises the following steps: synthesizing the functionalized hyperbranched polyolefin, and mixing the polyethylene resin and the additive; extruding, blending and granulating by using double screws; carrying out multi-layer co-extrusion film blowing molding; controlling air temperature to cool the film bubbles; and adjusting the tension and rolling to form the film. The hyperbranched polyolefin with a specific terminal functional group is introduced into the polyethylene matrix resin, and the hyperbranched polyolefin is promoted to migrate to the surface of the film in the melting processing process, so that a stable interface layer with relatively high surface energy is formed, and the adhesion fastness and the composite peel strength of the ink are improved.

Description

Technical Field

[0001] This application relates to the field of composite PE film preparation technology, specifically a printed composite PE film for sanitary packaging. Background Technology

[0002] Polyethylene film, with its excellent flexibility, economy, and ease of processing, has become an indispensable material in the packaging industry, especially in the hygienic packaging of food, daily chemical, and medical products. Its lightweight, transparent, and moisture-proof properties make it the preferred packaging form for many commodities.

[0003] In practical applications, PE film is often used for printing and lamination. For example, as a printing substrate, PE film needs to support various texts, patterns, and logos to convey product information and showcase the brand. As a layer in composite packaging, PE film is usually bonded to other materials with adhesives to form a multi-layer structure, meeting the product's comprehensive requirements for barrier properties, mechanical strength, and heat-sealing performance.

[0004] However, the low surface energy of existing PE films results in poor wetting properties of printing inks, insufficient ink adhesion after printing, and easy peeling. During the lamination process, the weak bonding force between the PE film and the adhesive leads to poor interlayer peel strength and delamination. Furthermore, existing technologies often use surface modification methods such as corona treatment or flame treatment to improve the surface polarity of PE films, but the effectiveness of these treatments is limited and decays over time. Therefore, this invention provides a printable composite PE film for sanitary packaging to address the shortcomings of existing technologies. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this application is to provide a printable composite PE film for sanitary pads, which solves the problems of insufficient ink adhesion and unstable composite strength in existing PE films.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of the present invention provides a printed composite PE film for sanitary napkins, the PE film being made of components comprising the following parts by weight: Polyethylene base resin: 94.0-99.0 parts by weight; Hyperbranched polyolefins: 0.5-5.0 parts by weight; Polyethylene wax: 0.1-0.5 parts by weight; Compound antioxidant: 0.1-0.3 parts by weight; Stearate anti-blocking agent: 0.05-0.2 parts by weight.

[0007] In the PE film provided by this invention, the bulk properties of the film material are controlled by introducing hyperbranched polyolefins with specific molecular structures. The hyperbranched polyolefins possess a three-dimensional branched structure and terminal functional groups. During melt processing, the hyperbranched polyolefins can form a stable blend system with the polyethylene matrix resin, and some of their terminal functional groups can migrate to the PE film surface, thereby forming an interface layer with high surface energy. This interface layer can enhance the interaction with active components in printing inks or composite adhesives, thereby improving the printability and composite strength of the PE film.

[0008] In a preferred embodiment, the polyethylene host resin is selected from any combination of low-density polyethylene, linear low-density polyethylene, and high-density polyethylene.

[0009] Furthermore, to achieve precise control over the surface properties of the PE film, the hyperbranched polyolefin has an average branching degree of 0.6-0.8, terminates with reactive functional groups, and a density of 0.1-1.0 mmol / g. These reactive functional groups are selected from hydroxyl, carboxyl, maleic anhydride, or epoxy groups. This specific branching degree and functional group density ensure the dispersibility of the hyperbranched polyolefin within the polyethylene matrix and the effectiveness of its migration to the surface.

[0010] In another preferred embodiment, the hyperbranched polyolefin is reactively blended with the polyethylene matrix to form a material structure with gradient interfacial compatibility. This structure facilitates the stable dispersion of the hyperbranched polyolefin in the polyethylene matrix and promotes its efficient migration to the surface.

[0011] Preferably, the composite antioxidant is composed of antioxidant 1010 and antioxidant 168, and the mass ratio of antioxidant 1010 to antioxidant 168 is 1:1 to 1:5.

[0012] Preferably, the stearate-based anti-blocking agent is selected from calcium stearate or zinc stearate.

[0013] A second aspect of the present invention provides a method for preparing the above-mentioned printed composite PE film for sanitary packaging, comprising the following steps: S1. Synthesize hyperbranched polyolefins with specific branching degree and terminal functional groups; S2. The polyethylene base resin, polyethylene wax, composite antioxidant, stearate antiblocking agent and synthetic hyperbranched polyolefin are uniformly mixed to form a mixture for extrusion film formation. S3. The constructed mixture is fed into a twin-screw extruder for blending and granulation to form modified PE granules; S4. The formed PE granules are fed into a multi-layer co-extrusion blown film unit for extrusion, and a film bubble with a specific thickness and blow-up ratio is formed during the extrusion process. S5. Cool the formed membrane bubble and control the cooling air temperature to ensure uniform solidification of the membrane bubble; S6. The cooled film is wound up, and a flat film roll is obtained by controlling the winding tension.

[0014] The reactive blending granulation process, through specific control of temperature, shear rate, and residence time, promotes the uniform dispersion of hyperbranched polyolefins in the polyethylene matrix and may involve limited interfacial reactions, thereby forming stable modified PE granules. The multilayer co-extrusion blown film process, through the coordinated control of temperature, blow-up ratio, traction speed, and the online air ring system, ensures the uniformity and stability of the film's macroscopic dimensions and provides suitable processing conditions for the migration of hyperbranched polyolefins to the film surface.

[0015] In step S3, the barrel temperature of the twin-screw extruder is set to 160-220℃, the screw speed is 150-300 rpm, and the average residence time of the melt in the extruder is 60-180 seconds. This combination of parameters ensures thorough plasticization and homogenization of the mixture.

[0016] In step S4, the process parameters for the extrusion process are further defined as follows: The barrel temperature is set to 170-215℃, the die temperature to 190-220℃, the die annular gap to 1.8-2.5mm, the blow-up ratio to 1.8-2.2, and the traction speed to 20-40m / min; an online air ring system is used for membrane bubble control. The synergistic effect of these parameters directly determines the thickness uniformity and mechanical properties of the final membrane product.

[0017] By synergistically controlling the extrusion rate, traction speed, and blow-up ratio, and combining this with a winding tension of 100-300N, a film with a thickness of 30-40 micrometers can be prepared.

[0018] In summary, this application includes at least one of the following beneficial technical effects: 1. This invention introduces hyperbranched polyolefins with specific terminal functional groups into the polyethylene base resin and promotes their migration to the film surface during melt processing, forming a stable interface layer with high surface energy. This interface layer enhances the physicochemical interaction between the PE film and printing inks and composite adhesives, thereby effectively improving ink adhesion and composite peel strength, and solving the technical problem of unstable printing and lamination performance caused by the surface inertness of traditional PE films.

[0019] 2. This invention achieves bulk modification of the membrane material by introducing hyperbranched polyolefins into the PE matrix resin. The modification effect stems from the structural design of the material components themselves, resulting in a highly stable functional surface layer that is not easily degraded by time and environmental changes. Therefore, the resulting PE film exhibits higher aging stability and environmental tolerance in its printability and lamination properties, reducing dependence on harsh storage conditions and immediate processing.

[0020] 3. The hyperbranched polyolefin used in this invention not only serves as a stress transfer node in the PE matrix, enhancing the toughness and stiffness of the film, but also reduces the melt viscosity of the system in the molten state, improving processing fluidity. By combining specific reactive blending and extrusion processes, this invention can synergistically optimize the mechanical and processing properties of the film while improving its surface properties, thereby enhancing the stability of the production process. Attached Figure Description

[0021] Figure 1 This is a flowchart of the preparation method of this application. Detailed Implementation

[0022] The following is in conjunction with the appendix Figure 1 This application will be described in further detail below.

[0023] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0024] Low-density polyethylene (LDPE), CAS No.: 9002-88-4, density is 0.910-0.925 g / cm³. 3 .

[0025] Linear low-density polyethylene (LLDPE), CAS No.: 9002-88-4, density between 0.918-0.935 g / cm³. 3 between.

[0026] High-density polyethylene (HDPE), CAS No.: 9002-88-4, density is 0.940-0.976 g / cm³. 3 .

[0027] Maleic anhydride-functionalized hyperbranched polyolefins were prepared in-house, as shown in Preparation Example 1.

[0028] Polyethylene wax (PEWax), CAS No.: 9002-88-4, density: 0.92-0.98 g / cm³ 3 .

[0029] Calcium stearate, CAS No.: 1592-23-0.

[0030] Zinc stearate, CAS No.: 557-05-1.

[0031] Preparation Example 1: Preparation of Hyperbranched Polyolefin (HBPO): Preparation steps: Synthesis of the HBPO backbone: In a high-pressure reactor, 2000 mL of toluene was added, and dissolved oxygen was removed by bubbling under nitrogen for 30 minutes. Under nitrogen protection, 1 mmol of zirconium dichloroethylene and 100 mmol of methylaluminoxane were added to the reactor. The reaction system was heated to 60 °C, and 300 mL of 1,7-octadiene monomer was continuously added dropwise at a rate of 10 mL / min using a metering pump, while maintaining the pressure inside the reactor at 0.5 MPa. After the addition was complete, the reaction was continued at 60 °C for 6 hours. After the reaction was completed, the reactor was cooled to room temperature, and 100 mL of acidified ethanol (containing 5 vol% hydrochloric acid) was slowly added to terminate the reaction and deactivate the catalyst. The reaction solution was poured into a large amount of ethanol to precipitate, and the white solid product was collected by filtration. The obtained solid was washed three times with ethanol and then dried in a vacuum oven at 60 °C for 24 hours to obtain the HBPO backbone with terminal double bonds.

[0032] Terminal functionalization of HBPO: 100 parts by mass of the prepared HBPO backbone, 5 parts by mass of maleic anhydride (MAH), and 0.1 parts by mass of dicumyl peroxide (DCP) were premixed uniformly in a high-speed mixer. The mixture was then added to a twin-screw extruder with an L / D ratio of 40 for reactive grafting. The temperatures of each zone of the twin-screw extruder were set to 150℃, 170℃, 180℃, 180℃, and 175℃. The screw speed was set to 200 rpm. After extrusion through a die, the melt was water-cooled, pelletized, and dried to obtain a maleic anhydride-functionalized hyperbranched polyolefin. The terminal functional group density was determined to be 0.48 mmol / g, and the average degree of branching was 0.72, by acid-base titration.

[0033] Please see the appendix Figure 1 : Example 1: Raw material components (by mass parts): Low-density polyethylene (LDPE): 40.0; Linear low-density polyethylene (LLDPE): 57.5; Maleic anhydride-functionalized hyperbranched polyolefin: 2.0; Polyethylene wax (PEWax): 0.2; Antioxidant 1010:0.1; Antioxidant 168:0.1; Calcium stearate: 0.1g.

[0034] Preparation steps: S1. Mix the components in the formula in a high-speed mixer at 1000 rpm for 5 minutes to obtain a uniform mixture.

[0035] S2. The mixture is fed into a twin-screw extruder with an L / D ratio of 40 for blending and granulation. The temperatures of each zone of the twin-screw extruder are set to 170℃, 185℃, 200℃, 210℃, and 205℃, and the screw speed is set to 200 rpm. By controlling the feed rate, the average residence time of the melt in the extruder is made to be 120 seconds. The extruded strips are then water-cooled and pelletized to obtain modified PE granules.

[0036] S3. The obtained modified PE granules are fed into the outer extruder of a three-layer co-extrusion blown film unit, while LLDPE is added to the inner and middle extruders. The temperatures of each zone of the outer extruder are set to 180℃, 195℃, and 205℃, and the die temperature is set to 210℃. The annular gap of the die is set to 2.2mm, the blow-up ratio to 2.0, and the upper traction speed to 30m / min.

[0037] S4. An online air circulation system is used to cool the membrane bubble, and the cooling air temperature is controlled at 20℃.

[0038] S5. The cooled and formed film is wound up, with the winding tension controlled at 150N. The final product is a 35-micron thick printed composite PE film for sanitary packaging.

[0039] Example 2: Raw material components (by mass parts): Low-density polyethylene (LDPE): 40.0; Linear low-density polyethylene (LLDPE): 55.0; Maleic anhydride-functionalized hyperbranched polyolefins: 4.5; Polyethylene wax (PEWax): 0.2; Antioxidant 1010: 0.1; Antioxidant 168: 0.1; Calcium stearate: 0.1.

[0040] Preparation steps: S1. Mix the components in the formula in a high-speed mixer at 1000 rpm for 5 minutes to obtain a uniform mixture.

[0041] S2. The mixture is fed into a twin-screw extruder with an L / D ratio of 40 for blending and granulation. The temperatures of each zone of the twin-screw extruder are set to 170℃, 185℃, 200℃, 210℃, and 205℃, and the screw speed is set to 200 rpm. By controlling the feed rate, the average residence time of the melt in the extruder is made to be 120 seconds. The extruded strips are then water-cooled and pelletized to obtain modified PE granules.

[0042] S3. The obtained modified PE granules are fed into the outer extruder of a three-layer co-extrusion blown film unit, while LLDPE is added to the inner and middle extruders. The temperatures of each zone of the outer extruder are set to 180℃, 195℃, and 205℃, and the die temperature is set to 210℃. The annular gap of the die is set to 2.2mm, the blow-up ratio to 2.0, and the upper traction speed to 30m / min.

[0043] S4. An online air circulation system is used to cool the membrane bubble, and the cooling air temperature is controlled at 20℃.

[0044] S5. The cooled and formed film is wound up, with the winding tension controlled at 150N. The final product is a 35-micron thick printed composite PE film for sanitary packaging.

[0045] Example 3: Raw material components (by mass parts): Low-density polyethylene (LDPE): 40.0; Linear low-density polyethylene (LLDPE): 57.5; Maleic anhydride-functionalized hyperbranched polyolefin: 2.0; Polyethylene wax (PEWax): 0.2; Antioxidant 1010:0.1; Antioxidant 168:0.1; Calcium stearate: 0.1g.

[0046] Preparation steps: S1. Mix each component in a high-speed mixer at 1000 rpm for 5 minutes to obtain a uniform mixture.

[0047] S2. The mixture is fed into a twin-screw extruder with an L / D ratio of 40 for blending and granulation. The temperatures of each zone of the twin-screw extruder are set to 175℃, 190℃, 210℃, 215℃, and 210℃, and the screw speed is set to 250 rpm. By controlling the feed rate, the average residence time of the melt in the extruder is made to be 100 seconds. The extruded strips are then water-cooled and pelletized to obtain modified PE granules.

[0048] S3. The obtained modified PE granules are fed into the outer layer extruder of a three-layer co-extrusion blown film unit, while LLDPE is added to the inner and middle layer extruders. The temperatures of each zone of the outer layer extruder are set to 185℃, 200℃, and 210℃, and the die temperature is set to 215℃. The annular gap of the die is set to 2.0mm, the blow-up ratio to 2.2, and the upper traction speed to 25m / min.

[0049] S4. An online air circulation system is used to cool the membrane bubble, and the cooling air temperature is controlled at 18℃.

[0050] S5. The cooled and formed film is wound up, with the winding tension controlled at 180N. The final product is a 38-micron thick printed composite PE film for sanitary packaging.

[0051] Comparative Example 1: Compared to Example 1, the difference is that maleic anhydride-functionalized hyperbranched polyolefins are not added to the formulation, but all other aspects are the same.

[0052] Comparative Example 2: Compared with Example 1, the difference is that maleic anhydride-functionalized hyperbranched polyolefin is not added to the formulation, but linear polyethylene grafted with maleic anhydride (PE-g-MAH) is used, and the rest are the same.

[0053] Comparative Example 3: Compared with Example 1, the difference is that maleic anhydride-functionalized hyperbranched polyolefins are not added to the formulation, but non-functionalized hyperbranched polyolefins are used instead, all other aspects are the same.

[0054] Experiment 1: Experimental objective: To compare the performance of each sample in terms of ink adhesion fastness.

[0055] Experimental steps: The test was conducted according to the national standard GB / T9286-1998 "Cross-cut test for paint and varnish films". The specific operating steps are as follows: Place the prepared PE film sample under standard laboratory conditions (temperature 23±2℃, relative humidity 50±5%) for at least 24 hours.

[0056] Prepare the printing ink for testing, and print a uniform layer of ink on the surface of the PE film sample using flexographic printing. After printing, cure the printed film in a 60℃ oven for 2 hours.

[0057] After curing, the printed film is cooled to room temperature. Using a scribing tool (1mm blade spacing, 6 blades), 6 cuts are made on the surface of the printed film in two directions: perpendicular to the printing direction and parallel to the printing direction, forming 25 small squares.

[0058] Use transparent pressure-sensitive tape (24mm wide) conforming to GB / T25227 standard to stick it on the marked area. Press the tape with your finger to ensure that the tape is in full contact with the film surface and there are no air bubbles.

[0059] Within 5 minutes of applying the tape, quickly peel it off perpendicular to the film surface.

[0060] Inspect the ink peeling in the gridded areas and rate it according to the percentage of ink peeling area in accordance with the GB / T9286-1998 standard (0 is no peeling, 5 is peeling of more than 65% of the area).

[0061] The experimental results are shown in Table 1.

[0062] Table 1: Ink Adhesion Fastness Test Results Sample number Ink adhesion strength (grade) Example 1 0 Example 2 0 Example 3 1 Comparative Example 1 4 Comparative Example 2 3 Comparative Example 3 3 As shown in Table 1, the samples from Examples 1, 2, and 3 achieved a rating of 0 or 1 in the ink adhesion test, indicating that the printing ink adhered tightly to the film surface with minimal or no ink detachment. This is attributed to the introduction of hyperbranched polyolefins with specific terminal functional groups during the PE film preparation process, which migrate to the film surface during processing, thereby forming an interface layer with high surface energy. This interface layer can enhance the interaction with the polar components in the printing ink, promoting the anchoring of the ink during wetting, spreading, and curing processes on the film surface, thus effectively improving the ink adhesion.

[0063] In contrast, the sample in Comparative Example 1, lacking hyperbranched polyolefins, exhibited an ink adhesion rating of 4, demonstrating significant ink detachment. This indicates that in the absence of components in the polyethylene matrix that can effectively improve surface properties, the inherent non-polar characteristics of the PE film surface lead to poor compatibility with the ink, preventing the formation of a strong interfacial bond. The samples in Comparative Examples 2 and 3, although using linear polyethylene grafted with maleic anhydride or non-functionalized hyperbranched polyolefins respectively, had ink adhesion ratings of 3 and 3 respectively, inferior to the embodiments of this invention. This demonstrates that the unique three-dimensional branched structure of hyperbranched polyolefins and the synergistic effect of their terminal functional groups offer advantages in constructing high surface energy interfacial layers that linear polymers or non-functionalized polymers lack. This verifies the importance of the reactive blending and blown film process parameters in the preparation method of this invention for the dispersion, migration, and final surface property construction of hyperbranched polyolefins in the polyethylene matrix.

[0064] Experiment 2: Experimental objective: To compare the performance of each sample in terms of composite peel strength.

[0065] Experimental steps: The test was conducted according to the national standard GB / T8808-1988 "Peel Test Method for Flexible Composite Plastic Materials". The specific operating steps are as follows: Place the prepared PE film sample under standard laboratory conditions (temperature 23±2℃, relative humidity 50±5%) for at least 24 hours.

[0066] Prepare another substrate, such as a BOPP (biaxially oriented polypropylene) film with a thickness of 20 micrometers.

[0067] Prepare a polyurethane-based two-component composite adhesive and mix it thoroughly according to the recommended ratio.

[0068] A dry laminator is used to laminate PE film and BOPP film together using the aforementioned adhesive. The lamination coating amount is controlled at 3.0 ± 0.2 g / m³. 2 The compound speed is set to 30 m / min.

[0069] The composite sample was cured in a 50°C oven for 48 hours to ensure that the adhesive was fully cured.

[0070] The cured composite membrane was cooled to room temperature. The composite membrane was then cut into samples with a width of 15 mm and a length of 200 mm.

[0071] The specimen is clamped in the upper and lower fixtures of the electronic tensile testing machine, and the peel angle is set to 180°. The test speed is set to 200 mm / min.

[0072] Record the average peel force during the peeling process, expressed in N / 15mm. Test at least 5 parallel samples for each sample and take the average value.

[0073] The experimental results are shown in Table 2.

[0074] Table 2: Composite Peel Strength Test Results As shown in Table 2, the composite peel strength of the samples from Examples 1, 2, and 3 is all above 2.5 N / 15 mm, indicating that a stable interlayer bond has been formed between the PE film and the composite substrate. This is attributed to the introduction of hyperbranched polyolefins with specific terminal functional groups into the PE film. These hyperbranched polyolefins form high surface energy regions on the PE film surface, increasing the wettability and chemical interaction between the film surface and the active groups in the polyurethane composite adhesive. This improves the wetting and anchoring strength of the adhesive on the PE film surface during wetting and curing, ultimately enhancing the peel strength between the composite layers.

[0075] In contrast, the sample in Comparative Example 1, without the addition of hyperbranched polyolefin, exhibited a composite peel strength of only 0.51 N / 15 mm, indicating that the composite layer was easily separated. This demonstrates that the inherently low surface energy of the PE film limits its bonding ability with the composite adhesive. The samples in Comparative Examples 2 and 3, although using linear polyethylene grafted with maleic anhydride or non-functionalized hyperbranched polyolefin, respectively, showed composite peel strengths of 1.35 N / 15 mm and 0.98 N / 15 mm, significantly lower than the embodiments of this invention. This illustrates the advantage of the unique three-dimensional branched structure and terminal functional groups of hyperbranched polyolefin in enhancing interfacial compatibility. This verifies the importance of the reactive blending and extrusion blown film processes in this invention for the distribution of hyperbranched polyolefin in the polyethylene matrix and the construction of the final interfacial bonding strength.

[0076] Experiment 3: Experimental objective: To compare the mechanical properties of different samples.

[0077] Experimental steps: The procedure was performed according to the national standard GB / T1040.3-2006, "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". The specific operating steps are as follows: The prepared PE film samples were placed under standard laboratory conditions (temperature 23±2℃, relative humidity 50±5%) for at least 24 hours.

[0078] Using a standard cutting knife, cut the PE film sample along both the longitudinal (MD) and transverse (TD) directions into dumbbell-shaped samples conforming to the GB / T1040.3-2006 standard (e.g., Type I sample, clamp spacing 50 mm, mark spacing 25 mm, width 4 mm). Cut at least 5 parallel samples in each direction.

[0079] Clamp the dumbbell-shaped specimens in the upper and lower grips of the electronic tensile testing machine. Ensure that the specimen axis is aligned with the center line of the grips and that there is no twisting.

[0080] The testing speed of the tensile testing machine is set to 200 mm / min.

[0081] Start the test until the specimen breaks. The tensile testing machine automatically records the tensile strength (in MPa) and elongation at break (in %).

[0082] Calculate the average values ​​of longitudinal and transverse tensile strength and elongation at break, respectively.

[0083] The experimental results are shown in Table 3.

[0084] Table 3: Test data on extrusion stability and molding accuracy As shown in Table 3, the samples from Examples 1, 2, and 3 exhibited relatively superior tensile strength and elongation at break in both the longitudinal (MD) and transverse (TD) directions. This indicates that introducing hyperbranched polyolefins into the polyethylene matrix not only achieves the control of membrane surface properties but also synergistically optimizes the bulk mechanical properties. Hyperbranched polyolefins possess a three-dimensional branched structure, which can act as stress transfer nodes within the polyethylene matrix, effectively dispersing and absorbing external forces, thus improving the overall toughness and load-bearing capacity of the material, manifested as increased tensile strength and elongation at break.

[0085] In contrast, the sample in Comparative Example 1, lacking hyperbranched polyolefin, exhibited lower tensile strength and elongation at break. This indicates that the mechanical properties of the PE film were not fully optimized without the modification effect of hyperbranched polyolefin. Although samples in Comparative Examples 2 and 3 used linear polyethylene grafted with maleic anhydride or non-functionalized hyperbranched polyolefin, respectively, their mechanical properties were still lower than those of the embodiments of this invention. This demonstrates that the specific three-dimensional branched structure of the hyperbranched polyolefin, and the interfacial compatibility formed between it and the polyethylene matrix, play a crucial role in synergistically improving the mechanical properties of the film. This verifies the importance of the reactive blending and blown film process parameters in the preparation method of this invention for the effective dispersion of hyperbranched polyolefin in the polyethylene matrix and the final construction of the film's mechanical properties.

Claims

1. A printable composite PE film for sanitary pads, comprising the following components in parts by weight: Polyethylene base resin: 94.0-99.0 parts by weight; Hyperbranched polyolefins: 0.5-5.0 parts by weight; Polyethylene wax: 0.1-0.5 parts by weight; Compound antioxidant: 0.1-0.3 parts by weight; Stearate anti-blocking agent: 0.05-0.2 parts by weight.

2. The printed composite PE film for sanitary napkins according to claim 1, characterized in that, The polyethylene main resin is selected from any combination of low-density polyethylene, linear low-density polyethylene and high-density polyethylene.

3. The printed composite PE film for sanitary pads according to claim 1, characterized in that, The hyperbranched polyolefin has an average degree of branching of 0.6-0.8, includes reactive functional groups at the ends, and has a density of 0.1-1.0 mmol / g. The reactive functional groups are selected from hydroxyl, carboxyl, maleic anhydride, or epoxy groups.

4. The printed composite PE film for sanitary pads according to claim 1, characterized in that, The hyperbranched polyolefin is reactively blended with the polyethylene host resin to form a material structure with gradient interfacial compatibility.

5. The printed composite PE film for sanitary napkins according to claim 1, characterized in that, The composite antioxidant is composed of antioxidant 1010 and antioxidant 168, and the mass ratio of antioxidant 1010 to antioxidant 168 is 1:1 to 1:

5.

6. The printed composite PE film for sanitary pads according to claim 1, characterized in that, The stearate-based anti-blocking agent is selected from calcium stearate or zinc stearate.

7. A method for preparing a printed composite PE film for sanitary ware, used to prepare the printed composite PE film for sanitary ware as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Synthesize hyperbranched polyolefins with specific branching degree and terminal functional groups; S2. The polyethylene base resin, polyethylene wax, composite antioxidant, stearate antiblocking agent and synthetic hyperbranched polyolefin are uniformly mixed to form a mixture for extrusion film formation. S3. The constructed mixture is fed into a twin-screw extruder for blending and granulation to form modified PE granules; S4. The formed PE granules are fed into a multi-layer co-extrusion blown film unit for extrusion, and a film bubble with a specific thickness and blow-up ratio is formed during the extrusion process. S5. Cool the formed membrane bubble and control the cooling air temperature to ensure uniform solidification of the membrane bubble; S6. The cooled film is wound up, and a flat film roll is obtained by controlling the winding tension.

8. The method for preparing a printed composite PE film for sanitary ware according to claim 7, characterized in that, In step S3, the barrel temperature of the twin-screw extruder is set to 160-220℃, the screw speed is 150-300rpm, and the average residence time of the melt in the extruder is 60-180 seconds.

9. The method for preparing a printed composite PE film for sanitary ware according to claim 7, characterized in that, In step S4, the extrusion process includes: Set the barrel temperature to 170-215℃, the die head temperature to 190-220℃, the die head annular gap to 1.8-2.5mm, the blow-up ratio to 1.8-2.2, and the traction speed to 20-40m / min. An online air circulation system is used for membrane bubble control.

10. The method for preparing a printed composite PE film for sanitary pads according to claim 7, characterized in that, In step S6, the winding tension is controlled at 100-300N to obtain a film with a thickness of 30-40 micrometers.

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