Hygienic product high-tensile composite film and preparation method thereof

Abstract

The invention relates to the technical field of polymer composite materials, provides a high-tensile composite film for hygienic products and a preparation method of the high-tensile composite film, and solves the problems that an existing bottom film for the hygienic products cannot give consideration to high tensile strength, high elongation at break, high barrier property and high moisture permeability, the bottom film is poor in softness, leftover materials of the film are difficult to recycle, and the production cost is low. And low-temperature and high-speed industrial production cannot be adapted. The film is prepared from the following raw materials: matrix resin, a difunctional core-shell reinforcing agent, a superfine fiber reinforced phase and a processing aid, the matrix resin is prepared from 40 to 70 parts by weight of polyethylene and 20 to 40 parts by weight of polypropylene, the difunctional core-shell reinforcing agent is 10 to 25 parts by weight, the superfine fiber reinforced phase is 5 to 15 parts by weight, and the processing aid is prepared from 0.2 to 0.5 part by weight of antioxidant and 0.3 to 0.8 part by weight of slipping agent.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and in particular to a high-strength composite film for hygiene products and its preparation method. Background Technology

[0002] As a key component of sanitary napkins, diapers, and other products, the bottom film of hygiene products must simultaneously meet multiple stringent performance requirements: In terms of mechanical properties, it needs high tensile strength to withstand the pulling forces during high-speed production, and high elongation at break to accommodate deformation during product use; in terms of performance, it needs high hydrostatic pressure to prevent leakage of bodily fluids, i.e., high barrier properties; and high moisture permeability to avoid stuffiness, i.e., high comfort; in terms of user experience, it needs to maintain high softness to improve fit; and in terms of environmental protection and cost control, it needs to be recyclable to reduce waste. However, existing technologies exhibit significant contradictions in these performance requirements, making it difficult to simultaneously achieve both.

[0003] (1) The contradiction between strength and elongation: When the strength of the film is improved by adding rigid particles (such as nano SiO2), the elongation at break will decrease and the brittleness of the film will increase; while when the elongation is improved by adding elastomers (such as POE), the strength and rigidity will decrease.

[0004] (2) The contradiction between barrier and permeability: Improving the barrier properties of the film (such as increasing the thickness or adding barrier particles) usually sacrifices the permeability, resulting in stuffy products; while pursuing high permeability (such as using a porous structure) will reduce the barrier properties and increase the risk of leakage.

[0005] (3) The contradiction between softness and performance: The reinforcing phase (such as fibers and rigid particles) introduced to improve strength and barrier properties can easily lead to a decrease in film softness and a harder feel; while simply pursuing softness (such as reducing the addition of reinforcing phases) will result in mechanical properties and barrier properties failing to meet requirements.

[0006] (4) The contradiction between recyclability and performance: Most existing films adopt irreversible cross-linking structure or blend of incompatible components. After the waste is recycled, the performance is severely degraded and it is difficult to recycle, which does not conform to the trend of green manufacturing.

[0007] Chinese Patent Publication No. CN102690512B discloses a glass fiber reinforced and toughened nylon 6 composite material, its preparation method, and its application. The composite material comprises the following components (by weight): 50-75 parts PA6 resin, 20-40 parts alkali-free glass fiber, 1-8 parts grafted elastomer, 1-3 parts grafted polyolefin, 0.1-1.2 parts glass fiber dispersant, and 0.1-0.6 parts antioxidant. It is prepared using a twin-screw extruder and can be used in automotive cooling fans, etc. The advantages of this invention are excellent mechanical properties, high and low temperature resistance, and uniform material composition distribution, especially the uniform dispersion of glass fiber in the matrix resin (PA6), which solves the problems of uneven glass fiber dispersion and exposure. This results in fans with excellent dynamic balance performance and a bright surface free of glass fiber flow marks and exposure. However, its application scenarios are for thick-walled products (thickness > 50μm), with processing temperatures as high as 230℃ or more, resulting in high energy consumption and an inability to meet the ultra-thin (12-30μm) requirements of sanitary product bottom films. At the same time, this technology has not solved the interfacial compatibility problem between PA6 fibers and polyolefin matrix, which easily leads to fiber agglomeration and interfacial defects in ultra-thin films, resulting in unstable mechanical properties of the film and a significant decrease in softness and moisture permeability.

[0008] Chinese Patent Publication No. CN111440269B discloses a self-healing rubber based on the Diels-Alder reaction and its preparation method. First, hydroxyl-containing ethylene monomers are modified with furfural using acetal, then grafted onto rubber, and finally, a crosslinking agent, bismaleimide, is added to prepare a self-healing and recyclable rubber. This invention introduces the Diels-Alder reaction into rubber, giving it good mechanical properties, heat resistance, and high self-healing efficiency. The preparation method is simple, efficient, practical, and easy to promote. This technical solution achieves self-healing and recyclability through dynamic covalent bonds, but it does not involve the synergistic effect of rigid nanoparticles and fiber reinforcement. This technology has not been applied to ultrathin film structures and cannot solve the problems of orientation control and performance balance during film forming.

[0009] In addition, there are many technical obstacles to directly introducing PA6 fibers into the PE / PP base film of hygiene products: PA6 has poor compatibility with the polyolefin matrix and is prone to agglomeration, which leads to fluctuations in the mechanical properties of the film; under conventional processing technology, PA6 fiberization is incomplete, with fiber diameter >500nm, which easily deteriorates the film's softness and optical properties (increased haze); existing high-temperature processing technology (>230℃) easily leads to premature cross-linking of Diels-Alder dynamic covalent bonds, affecting the dispersibility of the core-shell reinforcing agent and the recyclability of the film.

[0010] Therefore, developing a novel composite film for hygiene products that can synergistically resolve the contradictions of "high strength-high elongation", "high barrier-high moisture permeability" and "high softness-recyclability", and is compatible with low-temperature and high-speed processing technology, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0011] Therefore, in view of the above problems, the present invention provides a high-strength composite film for hygiene products and its preparation method, which solves the problems that existing hygiene product bottom films are difficult to balance with high tensile strength and high elongation at break, high barrier properties and high moisture permeability, poor bottom film softness, difficulty in recycling film scraps, and inability to adapt to low-temperature and high-speed industrial production.

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] A high-strength composite film for hygiene products comprises the following raw materials: a matrix resin, a bifunctional core-shell reinforcing agent, a microfiber reinforcing phase, and processing aids; the matrix resin comprises 40-70 parts by weight of polyethylene and 20-40 parts by weight of polypropylene, the bifunctional core-shell reinforcing agent comprises 10-25 parts by weight, the microfiber reinforcing phase comprises 5-15 parts by weight, and the processing aids comprise 0.2-0.5 parts by weight of antioxidant and 0.3-0.8 parts by weight of slip agent;

[0014] The bifunctional core-shell reinforcing agent is a core-shell structured particle with mesoporous SiO2 nanospheres as the core layer and maleic anhydride-grafted polyolefin elastomers linked by Diels-Alder dynamic covalent bonds as the shell layer. The preparation process of the ultrafine fiber reinforcing phase is as follows: polyamide 6 fibers and polypropylene-grafted maleic anhydride are mixed in a high-speed mixer at 80-100℃ for 5-8 minutes, followed by extrusion granulation using a single-screw extruder at 210-230℃ to prepare PA6 pre-dispersion masterbatch with a concentration of 40-60%, thus obtaining the ultrafine fiber reinforcing phase. The film thickness is 12-30 μm, longitudinal tensile strength ≥100 MPa, elongation at break ≥650%, hydrostatic pressure ≥130 mmH2O, and moisture permeability ≥2800 g / (m²). 2 • 24h), softness ≤12mN; the tensile strength retention rate of the film after 3 cycles of processing is ≥95%, Hermans orientation factor is ≥0.90, haze is ≤20%, and the tensile strength retention rate after aging for 72 hours at 100℃ and 85% relative humidity is ≥90%.

[0015] In this process, polyamide 6 fibers are mixed with polypropylene grafted maleic anhydride (PP-g-MAH) in a high-speed mixer to uniformly coat PA6 particles with PP-g-MAH; the screw speed of the single-screw extruder is 150-200 rpm, and the L / D ratio is 25-30 to avoid excessive degradation of PA6 and ensure uniform masterbatch concentration.

[0016] Furthermore, the density of the polyethylene is 0.915-0.930 g / cm³. 3The melt flow rate of the polypropylene is 2-5 g / 10 min.

[0017] Among them, those with a density of 0.915-0.930 g / cm³ were selected. 3 Polyethylene (PE) possesses excellent flexibility and processing fluidity, providing basic softness and extensibility for the film. Polypropylene (PP), with a melt flow rate of 2-5 g / 10 min, has higher rigidity and strength, which can compensate for the strength deficiency of polyethylene. Pure PE has low strength, and pure PP has high brittleness. Blending PE and PP, by adjusting the ratio, achieves a "flexible-rigid" balance in the matrix, avoiding the performance defects of a single resin.

[0018] Furthermore, the mesoporous SiO2 nanospheres have a pore size of 5-15 nm and a specific surface area > 500 m². 2 / g; the surface of the mesoporous SiO2 nanospheres is modified with γ-aminopropyltriethoxysilane, and the amino content on the surface after modification is 0.8-1.2 mmol / g.

[0019] The surface of the mesoporous SiO2 nanospheres is modified with γ-aminopropyltriethoxysilane, which can enhance the interfacial bonding force with the maleic anhydride-grafted polyolefin elastomer shell.

[0020] The bifunctional core-shell reinforcing agent possesses rigidity, toughness, and recyclability. It employs a "mesoporous SiO2 nanosphere core-POE-g-MAH shell-Diels-Alder dynamic bond" structure, where POE-g-MAH is a maleic anhydride-grafted polyolefin elastomer. The components of this structure function synergistically.

[0021] (1) Mesoporous SiO2 nanosphere core layer: Mesoporous SiO2 nanospheres with a pore size of 5-15 nm and a specific surface area > 500 m² are selected. 2 / g, its high specific surface area can increase the contact area with the matrix and improve the interfacial bonding force; the mesoporous structure can serve as a moisture permeation channel, ensuring rigidity without sacrificing moisture permeability; after modification with γ-aminopropyltriethoxysilane (KH550), the surface amino groups can react with the maleic anhydride groups of POE-g-MAH, further enhancing the core-shell interfacial bonding force.

[0022] (2) POE-g-MAH shell: POE-g-MAH with a grafting rate of 5-15% and a glass transition temperature ≤-40℃ is selected. Its elastomer properties can improve the elongation at break and flexibility of the film; maleic anhydride groups can react with the matrix PP, PE and polyamide 6 fibers to improve interfacial compatibility; at the same time, POE-g-MAH and the mesoporous SiO2 nanosphere core layer are connected by Diels-Alder dynamic covalent bonds.

[0023] (3) Diels-Alder dynamic covalent bond: It remains stable during low-temperature processing (≤200℃) to ensure the integrity of the core-shell structure; during high-temperature recycling (240-260℃), it undergoes a reverse reaction to de-crosslink, allowing scrap materials to be reprocessed and achieving recyclability; at the same time, the dynamic bond can break and recombine when the film is under stress, playing a role in energy dissipation and improving the toughness and impact resistance of the film.

[0024] Furthermore, the maleic anhydride-grafted polyolefin elastomer has a grafting rate of 5-15% and a glass transition temperature ≤-40℃.

[0025] Furthermore, in the PA6 predispersed masterbatch, the grafting rate of polypropylene grafted with maleic anhydride is 1.0-2.0%, and the mass ratio of polyamide 6 fiber to polypropylene grafted with maleic anhydride is 1:(1-2).

[0026] Furthermore, the polyamide 6 fiber has a relative viscosity of 2.0-2.4, and its morphology in the film is microfiber with a diameter of 50-300 nm and an aspect ratio greater than 50.

[0027] Among them, polyamide 6 fibers with a relative viscosity of 2.0-2.4 are selected. The polyamide 6 is PA6. This viscosity range can ensure that PA6 can be fully melted and stretched into fibers under low temperature shear, while avoiding incomplete fiberization due to excessive viscosity. The diameter of PA6 fibers in the film is controlled to be 50-300nm and the aspect ratio is >50. Nanoscale fibers can reduce the impact on the flexibility of the film, while the high aspect ratio can give full play to the reinforcing effect of "nano steel bars".

[0028] PA6 fibers are grafted with polypropylene maleic anhydride (PP-g-MAH) to prepare PA6 pre-dispersed masterbatch with a concentration of 40-60%. PP-g-MAH is used as a compatibilizer. Its maleic anhydride groups can react with the amino groups of PA6, and the polyethylene segments can be compatible with the matrix PE / PP, effectively solving the interfacial compatibility problem between PA6 and the matrix and avoiding fiber agglomeration. At the same time, the pre-dispersed masterbatch can reduce the difficulty of dispersing PA6 in the matrix and ensure uniform fiberization.

[0029] Furthermore, the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and the slip agent is erucamide.

[0030] The antioxidant can prevent the film from oxidative degradation during processing and aging, improve aging resistance, and ensure that the tensile strength retention rate of the film is ≥90% after aging for 72 hours at 100°C and 85% relative humidity. The slip agent can reduce the surface friction coefficient of the film, avoid film adhesion during high-speed production, and does not affect the moisture permeability and softness of the film.

[0031] The above-described method for preparing a high-strength composite film for hygiene products includes the following steps:

[0032] S1. Raw material preparation: including polyethylene, polypropylene, bifunctional core-shell reinforcing agent, PA6 predispersed masterbatch, antioxidant and slip agent;

[0033] S2. Blending and granulation: Add each raw material to a high-speed mixer and mix at 60-80℃ for 3-5 minutes. Then feed it into a twin-screw extruder with an aspect ratio ≤35 and melt blend and granulate at a melt temperature of 180-200℃ to obtain composite masterbatch.

[0034] S3. Casting and Online Micro-stretching: The composite masterbatch prepared in step S2 is fed into a casting extruder and cast into a film at a die temperature of 190-200°C. Then, it is immediately subjected to 2-6% online micro-stretching through two sets of traction rollers to obtain a preliminary film.

[0035] S4. Post-processing: The initial film obtained in step S3 is subjected to corona treatment to make the surface tension of the film ≥42dyn / cm and the water contact angle ≤65°. Then it is wound up to obtain a high tensile composite film for hygiene products.

[0036] The high-stretch composite film for hygiene products is prepared by low-temperature high-shear melt blending and online micro-stretching process, which uniformly disperses the bifunctional core-shell reinforcing agent and forms a dynamic energy dissipation network, while simultaneously enabling polyamide 6 fibers to form in situ and be highly oriented.

[0037] In step S2, a twin-screw extruder with an aspect ratio ≤35 is used to shorten the melt residence time to ≤30 seconds, thereby avoiding material degradation and premature cross-linking of Diels-Alder bonds caused by long-term high-temperature processing.

[0038] In step S3, the two sets of traction rollers include a front traction roller and a rear traction roller. The rotation speed of the front traction roller is 120-200 m / min, and the rotation speed of the rear traction roller is adjusted synchronously according to the stretching ratio. The production line speed is controlled at 120-250 m / min, and the die head gap of the cast extruder is 0.2-0.5 mm.

[0039] In step S4, the power of the corona treatment is 3-5kW; the tension of the winding is controlled at 50-80N to ensure that the film is wrinkle-free and that the finished film is flat; to improve the composite adhesion with other layers of the sanitary products; at the same time, the corona treatment can slightly etch the film surface, increase the moisture permeability channels, and further improve the moisture permeability.

[0040] Furthermore, the twin-screw extruder is equipped with a high-shear element, with a maximum melt shear rate ≥1500s. -1The melt residence time is ≤30 seconds, and the rotation speed is 280-320 rpm.

[0041] Among them, a high-shear element is configured to ensure that the maximum shear rate of the melt is ≥1500s. -1 This promotes the full stretching of PA6 fibers in the PA6 pre-dispersed masterbatch into fibers with a diameter of 50-300nm, while ensuring uniform dispersion of the core-shell reinforcing agent with a particle size ≤500nm.

[0042] The temperature zones of the twin-screw extruder are set as follows: feeding zone 180-185℃, compression zone 185-190℃, melting zone 190-195℃, homogenization zone 195-200℃, and die head temperature 195-200℃. This ensures that the melt temperature is stable and there is no excessive degradation. It also ensures that the melt temperature is stable at 180-200℃, which meets the melting requirements of PE / PP / PA6 and avoids excessively high temperatures from affecting the core-shell structure and fiber morphology.

[0043] The temperature of the casting rollers for film casting is controlled at 20-25℃, and the cooling air velocity is 0.5-1.0m / s to ensure rapid film setting and uniform thickness, avoiding elastic shrinkage of PA6 fibers. The temperature of the casting die is controlled at 190-200℃, and the die gap is 0.2-0.5mm to ensure uniform film thickness, with a film thickness deviation of ≤±5%. The online micro-stretch rate is controlled at 2-6%. By adjusting the speed of the front and rear traction rollers, the PA6 fibers are induced to be highly oriented longitudinally (Hermans orientation factor ≥0.90), thereby improving longitudinal tensile strength. At the same time, moderate stretching can open the micropore channels inside the film, increase moisture permeability, and avoid excessive stretching that leads to increased film brittleness.

[0044] Furthermore, after step S4, scrap material recycling is carried out. The scrap material generated during the production process is heat-treated at 240-260℃ for 10-15 minutes, crushed to a particle size of 2-5mm, and then mixed into the raw material of step S2 at a mass ratio of no more than 30% for re-blending and granulation.

[0045] The scrap recycling process employs a twin-screw extruder with the following temperature zones: feeding zone 200-210℃, compression zone 220-230℃, melting zone 240-260℃, homogenization zone 240-260℃, and die head temperature 230-240℃. This ensures that the Diels-Alder dynamic covalent bonds are fully decrosslinked, restoring the material's processing fluidity. The recycled material is crushed to a particle size of 2-5mm and mixed into virgin material at a ratio not exceeding 30%, then re-participates in blending and granulation. After three cycles of processing, the performance retention rate is ≥95%, significantly reducing waste.

[0046] Through the synergy of the above material system and processes, a three-level structure of "rigid load-bearing - dynamic dissipation - orientation enhancement" is formed inside the thin film, and the functions of each level work together as follows:

[0047] I. Rigid bearing layer: Mesoporous SiO2 cores and highly oriented PA6 nanofibers form a rigid framework to bear external loads and improve the tensile strength and hydrostatic pressure (barrier properties) of the film.

[0048] II. Dynamic dissipation layer: The POE-g-MAH shell and Diels-Alder dynamic covalent bonds form an elastic network. When the film is subjected to stress, deformation and bond breakage-reorganization occur, absorbing energy and improving the elongation at break and toughness.

[0049] III. Orientation Reinforcement Layer: Online micro-stretching induces high orientation of PA6 fibers, further strengthening the load-bearing capacity of the rigid skeleton. At the same time, the orientation structure can guide the direction of the moisture permeability channel and improve the moisture permeability.

[0050] The interaction of the three-level structure not only solves the performance defects of the single structure, but also achieves the synergy of "high strength, high elongation, high barrier, high moisture permeability and high flexibility".

[0051] By adopting the aforementioned technical solution, the beneficial effects of the present invention are as follows:

[0052] 1. The interfacial compatibility problem between PA6 and the polyolefin matrix is ​​solved by pre-dispersion treatment with polypropylene grafted maleic anhydride (PP-g-MAH), resulting in a film free of fiber agglomeration and interfacial defects; after modification, the interfacial bonding force between the mesoporous SiO2 nanosphere core and the maleic anhydride grafted polyolefin elastomer (POE-g-MAH) shell is increased by more than 30%, and the core-shell structure remains stable during processing and use.

[0053] 2. Achieve a balance of five core properties in the base film of hygiene products: high tensile strength, high elongation at break, high barrier properties, hydrostatic pressure, moisture permeability, softness, and excellent aging resistance.

[0054] 3. Based on the thermally reversible properties of Diels-Alder dynamic covalent bonds, scrap materials can be recycled up to 3 times with a performance retention rate of ≥95%. Compared with the existing technology, the performance retention rate after recycling is 70%-75%, which significantly improves the recycling rate, conforms to the trend of green manufacturing, and reduces production costs.

[0055] 4. Develop a low-temperature short-path processing technology below 200℃, with a melt residence time of less than 30 seconds, which significantly reduces energy consumption compared to the existing high-temperature process above 230℃; the process parameters are compatible with the existing high-speed casting production line, requiring no equipment modification, resulting in low industrialization costs and enabling rapid large-scale production. Detailed Implementation

[0056] Example 1

[0057] A high-strength composite film for hygiene products comprises the following raw materials: a matrix resin, a bifunctional core-shell reinforcing agent, a microfiber reinforcing phase, and processing aids; the matrix resin comprises 55 parts by weight of polyethylene and 25 parts by weight of polypropylene, the bifunctional core-shell reinforcing agent comprises 18 parts by weight, the microfiber reinforcing phase comprises 10 parts by weight, and the processing aids comprise 0.3 parts by weight of antioxidant and 0.5 parts by weight of slip agent;

[0058] The bifunctional core-shell reinforcing agent is a core-shell structured particle with mesoporous SiO2 nanospheres as the core layer and maleic anhydride-grafted polyolefin elastomers linked by Diels-Alder dynamic covalent bonds as the shell layer. The preparation process of the ultrafine fiber reinforcing phase is as follows: polyamide 6 fibers and polypropylene-grafted maleic anhydride are mixed in a high-speed mixer at 90°C for 5 min, and then extruded and granulated at 220°C using a single-screw extruder to prepare a 50% concentration PA6 pre-dispersion masterbatch to obtain the ultrafine fiber reinforcing phase.

[0059] The density of the polyethylene is 0.920 g / cm³. 3 The melt flow rate of the polypropylene is 3 g / 10 min;

[0060] The mesoporous SiO2 nanospheres have a pore size of 10 nm and a specific surface area of ​​550 m². 2 / g; The surface of the mesoporous SiO2 nanospheres is modified with γ-aminopropyltriethoxysilane, and the amino content on the surface after modification is 1.0 mmol / g;

[0061] The maleic anhydride-grafted polyolefin elastomer has a grafting rate of 10% and a glass transition temperature of -45°C.

[0062] In the PA6 predispersed masterbatch, the grafting rate of polypropylene grafted with maleic anhydride is 1.5%, and the mass ratio of polyamide 6 fiber to polypropylene grafted with maleic anhydride is 1:1.

[0063] The polyamide 6 fiber has a relative viscosity of 2.2 and its morphology in the film is a microfiber with a diameter of 100 nm and an aspect ratio greater than 50.

[0064] The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and the slip agent is erucamide.

[0065] The above-described method for preparing a high-strength composite film for hygiene products includes the following steps:

[0066] S1. Raw material preparation: including polyethylene, polypropylene, bifunctional core-shell reinforcing agent, PA6 predispersed masterbatch, antioxidant and slip agent;

[0067] S2. Blending and Granulation: All raw materials are added to a high-speed mixer and mixed at 80°C for 3 minutes. Then, the mixture is fed into a twin-screw extruder with an aspect ratio of 32, and melt-blended and granulated at a melt temperature of 200°C to obtain composite masterbatch. The twin-screw extruder is equipped with a high-shear element, with a maximum melt shear rate of 1600 s⁻¹. -1 The melt residence time is 25 seconds and the rotation speed is 300 rpm; the temperature zones of the twin-screw extruder are set as follows: feeding zone 182℃, compression zone 187℃, melting zone 192℃, homogenization zone 197℃, and die head temperature 197℃.

[0068] S3. Casting and Online Micro-stretching: The composite masterbatch obtained in step S2 is fed into a casting extruder and cast into a film at a die temperature of 195°C. Immediately afterwards, it undergoes 5% online micro-stretching through two sets of traction rollers to obtain a preliminary film. The die gap is 0.3 mm, the casting roller temperature is 30°C, the cooling air velocity is 0.8 m / s, the front traction roller speed is 180 m / min, the rear traction roller speed is 189 m / min, and the production line speed is 180 m / min.

[0069] S4. Post-processing: The initial film obtained in step S3 is subjected to corona treatment to make the surface tension of the film 43dyn / cm and the water contact angle ≤65°. Then it is wound up to obtain a high tensile composite film for hygiene products; wherein the corona power is 4kW and the winding tension is 65N.

[0070] S5. Scrap material recycling: The scrap materials generated during the production process are heat-treated at 250℃ for 12 minutes, crushed to a particle size of 3mm, and then mixed into the raw materials of step S2 at a mass ratio of 30% for re-blending and granulation.

[0071] The film prepared in Example 1 has a thickness of 20 μm, a longitudinal tensile strength of 105 MPa, an elongation at break of 680%, a hydrostatic pressure of 135 mmH2O, and a moisture permeability of 2900 g / (m²). 2 The film has a softness of 11 mN after 24 hours of aging. The tensile strength retention rate after three cycles is 97%, the Hermans orientation factor is 0.90, the haze is 2.5%, and the tensile strength retention rate after aging for 72 hours at 100°C and 85% relative humidity is 92%.

[0072] Example 2

[0073] The difference from Example 1 is as follows:

[0074] A high-strength composite film for hygiene products comprises the following raw materials: a matrix resin, a bifunctional core-shell reinforcing agent, a microfiber reinforcing phase, and processing aids; the matrix resin comprises 60 parts by weight of polyethylene and 20 parts by weight of polypropylene, the bifunctional core-shell reinforcing agent comprises 12 parts by weight, the microfiber reinforcing phase comprises 8 parts by weight, and the processing aids comprise 0.2 parts by weight of antioxidant and 0.3 parts by weight of slip agent;

[0075] The density of the polyethylene is 0.925 g / cm³. 3 The melt flow rate of the polypropylene is 2 g / 10 min;

[0076] The mesoporous SiO2 nanospheres have a pore size of 8 nm and a specific surface area of ​​580 m². 2 / g; The surface of the mesoporous SiO2 nanospheres is modified with γ-aminopropyltriethoxysilane, and the amino content on the surface after modification is 0.8 mmol / g;

[0077] The maleic anhydride-grafted polyolefin elastomer has a grafting rate of 8% and a glass transition temperature of -42°C.

[0078] In the PA6 predispersed masterbatch, the grafting rate of polypropylene grafted with maleic anhydride is 1.0%, and the mass ratio of polyamide 6 fiber to polypropylene grafted with maleic anhydride is 1:1.5; the concentration of the PA6 predispersed masterbatch is 45%.

[0079] The polyamide 6 fiber has a relative viscosity of 2.0 and its morphology in the film is a microfiber with a diameter of 100 nm and an aspect ratio greater than 50.

[0080] The above-described method for preparing a high-strength composite film for hygiene products includes the following steps:

[0081] S1. Raw material preparation: including polyethylene, polypropylene, bifunctional core-shell reinforcing agent, PA6 predispersed masterbatch, antioxidant and slip agent;

[0082] S2. Blending and Granulation: All raw materials are added to a high-speed mixer and mixed at 80°C for 4 minutes. Then, the mixture is fed into a twin-screw extruder with a length-to-diameter ratio of 30, and melt-blended and granulated at a melt temperature of 180°C to obtain composite masterbatch. The twin-screw extruder is equipped with a high-shear element, with a maximum melt shear rate of 1500 s⁻¹. -1 The melt residence time is 28 seconds and the rotation speed is 280 rpm; the temperature zones of the twin-screw extruder are: 180°C for the feeding zone, 185°C for the compression zone, 190°C for the melting zone, 195°C for the homogenization zone, and 195°C for the die head.

[0083] S3. Casting and Online Micro-stretching: The composite masterbatch obtained in step S2 is fed into a casting extruder and cast into a film at a die temperature of 192°C. Then, it is immediately subjected to 3% online micro-stretching through two sets of traction rollers to obtain a preliminary film. The production line speed is 220 m / min.

[0084] Other technical solutions are the same as in Example 1.

[0085] The film prepared in Example 2 has a thickness of 18 μm, a longitudinal tensile strength of 101 MPa, an elongation at break of 660%, a hydrostatic pressure of 132 mmH2O, and a moisture permeability of 2850 g / (m²). 2 The film has a softness of 11.5 mN after 24 hours of aging. The tensile strength retention rate after three cycles is 96%, the Hermans orientation factor is 0.90, the haze is 2.8%, and the tensile strength retention rate after aging for 72 hours at 100°C and 85% relative humidity is 91%.

[0086] Example 3

[0087] The difference from Example 1 is as follows:

[0088] A high-strength composite film for hygiene products comprises the following raw materials: a matrix resin, a bifunctional core-shell reinforcing agent, a microfiber reinforcing phase, and processing aids; the matrix resin comprises 45 parts by weight of polyethylene and 35 parts by weight of polypropylene, the bifunctional core-shell reinforcing agent comprises 22 parts by weight, the microfiber reinforcing phase comprises 13 parts by weight, and the processing aids comprise 0.5 parts by weight of antioxidant and 0.8 parts by weight of slip agent;

[0089] The density of the polyethylene is 0.918 g / cm³. 3 The melt flow rate of the polypropylene is 5 g / 10 min;

[0090] The mesoporous SiO2 nanospheres have a pore size of 15 nm and a specific surface area of ​​520 m². 2 / g; The surface of the mesoporous SiO2 nanospheres is modified with γ-aminopropyltriethoxysilane, and the amino content on the surface after modification is 0.8 mmol / g;

[0091] The maleic anhydride-grafted polyolefin elastomer has a grafting rate of 15% and a glass transition temperature of -48°C.

[0092] In the PA6 predispersed masterbatch, the grafting rate of polypropylene grafted with maleic anhydride is 2.0%, and the mass ratio of polyamide 6 fiber to polypropylene grafted with maleic anhydride is 1:2; the concentration of the PA6 predispersed masterbatch is 60%.

[0093] The polyamide 6 fiber has a relative viscosity of 2.4 and its morphology in the film is a microfiber with a diameter of 100 nm and an aspect ratio greater than 50.

[0094] The above-described method for preparing a high-strength composite film for hygiene products includes the following steps:

[0095] S1. Raw material preparation: including polyethylene, polypropylene, bifunctional core-shell reinforcing agent, PA6 predispersed masterbatch, antioxidant and slip agent;

[0096] S2. Blending and Granulation: All raw materials are added to a high-speed mixer and mixed at 80°C for 5 minutes. Then, the mixture is fed into a twin-screw extruder with an aspect ratio of 35, and melt-blended and granulated at a melt temperature of 180°C to obtain composite masterbatch. The twin-screw extruder is equipped with a high-shear element, with a maximum melt shear rate of 1700 s⁻¹. -1 The melt residence time is 22 seconds, and the rotation speed is 320 rpm. The temperature zones of the twin-screw extruder are: 185°C for the feeding zone, 190°C for the compression zone, 195°C for the melting zone, 200°C for the homogenization zone, and 200°C for the die head.

[0097] S3. Casting and Online Micro-stretching: The composite masterbatch obtained in step S2 is fed into a casting extruder and cast into a film at a die temperature of 198°C. Then, it is immediately subjected to 6% online micro-stretching through two sets of traction rollers to obtain a preliminary film. The production line speed is 150 m / min.

[0098] Other technical solutions are the same as in Example 1.

[0099] The film prepared in Example 3 has a thickness of 25 μm, a longitudinal tensile strength of 108 MPa, an elongation at break of 645%, a hydrostatic pressure of 138 mmH2O, and a moisture permeability of 2780 g / (m²). 2 The film has a softness of 12 mN after 24 hours of aging. The tensile strength retention rate after three cycles is 95%, the Hermans orientation factor is 0.90, the haze is 2.6%, and the tensile strength retention rate after aging for 72 hours at 100°C and 85% relative humidity is 93%.

[0100] Comparative Example 1

[0101] The difference from Example 1 is as follows:

[0102] Raw materials: 60 parts PE, 30 parts PP, 8 parts nano SiO2, 10 parts POE, 0.3 parts antioxidant 1010, and 0.5 parts slip agent; the nano SiO2 is unmodified and has a particle size of 50nm.

[0103] Preparation process: The film is directly cast after conventional twin-screw blending at a blending temperature of 220℃. The casting process does not involve online micro-stretching.

[0104] The properties of the film prepared in Comparative Example 1 are as follows: tensile strength 75 MPa, elongation at break 450%, hydrostatic pressure 110 mmH2O, and moisture permeability 2500 g / (m²). 2 • 24h), softness 25mN, strength retention rate after one cycle 75%. It can be seen that its various properties are significantly lower than those of the high tensile composite film prepared by the technical solution of this application.

[0105] Comparative Example 2

[0106] The difference from Example 1 is that PA6 is not prepared as PA6 pre-dispersed masterbatch, but added in granular form. All other technical aspects are the same as in Example 1.

[0107] The performance results of the film prepared in Comparative Example 2 are as follows: PA6 fiberization is incomplete, fiber diameter is 800-1200 nm, agglomeration occurs, and fisheyes are present on the film surface; tensile strength is 85 MPa, elongation at break is 520%, softness is 18 mN, and moisture permeability is 2400 g / (m²). 2 • 24h), performance drops significantly, and the film breakage rate during production is as high as 15%.

[0108] Comparative Example 3

[0109] The difference from Example 1 is that no bifunctional core-shell reinforcing agent is added; instead, an equal amount of nano-SiO2 and POE are simply blended together. All other technical solutions are the same as in Example 1.

[0110] The performance results of the film prepared in Comparative Example 3 were as follows: tensile strength 88 MPa, elongation at break 550%, hydrostatic pressure 115 mmH2O, and strength retention rate after 3 cycles 82%, which could not achieve synergistic performance.

[0111] This technical solution, through the innovative design of a three-component material system of "matrix-core-shell reinforcing agent-ultrafine PA6 fiber" and combined with the "low-temperature short-path shearing-online micro-stretching-dynamic recycling" process, constructs a three-level synergistic structure of "rigid load-bearing-dynamic dissipation-orientation reinforcement" within the film, achieving a breakthrough in the synergistic performance of multiple core properties of hygiene product bottom films for the first time. The performance results of Examples 1 to 3 and Comparative Examples 1 to 3 demonstrate that the material combination and process parameters of this application are non-obvious, the prepared film has significantly better overall performance than existing technologies, and is suitable for high-speed production lines and green recycling requirements, possessing extremely high industrialization potential.

[0112] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A high-strength composite film for hygiene products, characterized in that, The product comprises the following raw materials: a matrix resin, a bifunctional core-shell reinforcing agent, a microfiber reinforcing phase, and processing aids; the matrix resin comprises 40-70 parts by weight of polyethylene and 20-40 parts by weight of polypropylene, the bifunctional core-shell reinforcing agent comprises 10-25 parts by weight, the microfiber reinforcing phase comprises 5-15 parts by weight, and the processing aids comprise 0.2-0.5 parts by weight of antioxidant and 0.3-0.8 parts by weight of slip agent; The bifunctional core-shell reinforcing agent is a core-shell structured particle with mesoporous SiO2 nanospheres as the core layer and maleic anhydride-grafted polyolefin elastomers linked by Diels-Alder dynamic covalent bonds as the shell layer. The preparation process of the ultrafine fiber reinforcing phase is as follows: polyamide 6 fibers and polypropylene-grafted maleic anhydride are mixed in a high-speed mixer at 80-100℃ for 5-8 minutes, followed by extrusion granulation using a single-screw extruder at 210-230℃ to prepare PA6 pre-dispersion masterbatch with a concentration of 40-60%, thus obtaining the ultrafine fiber reinforcing phase. The film thickness is 12-30 μm, longitudinal tensile strength ≥100 MPa, elongation at break ≥650%, hydrostatic pressure ≥130 mmH2O, and moisture permeability ≥2800 g / (m²). 2 • 24h), softness ≤12mN; the tensile strength retention rate of the film after 3 cycles of processing is ≥95%, Hermans orientation factor is ≥0.90, haze is ≤20%, and the tensile strength retention rate after aging for 72 hours at 100℃ and 85% relative humidity is ≥90%.

2. The high-strength composite film for hygiene products according to claim 1, characterized in that, The density of the polyethylene is 0.915-0.930 g / cm³. 3 The melt flow rate of the polypropylene is 2-5 g / 10 min.

3. The high-strength composite film for hygiene products according to claim 1, characterized in that, The mesoporous SiO2 nanospheres have a pore size of 5-15 nm and a specific surface area >500 m². 2 / g; the surface of the mesoporous SiO2 nanospheres is modified with γ-aminopropyltriethoxysilane, and the amino content on the surface after modification is 0.8-1.2 mmol / g.

4. The high-strength composite film for hygiene products according to claim 1, characterized in that, The grafting rate of the maleic anhydride-grafted polyolefin elastomer is 5-15%, and the glass transition temperature is ≤-40℃.

5. The high-strength composite film for hygiene products according to claim 1, characterized in that, In the PA6 predispersed masterbatch, the grafting rate of polypropylene grafted with maleic anhydride is 1.0-2.0%, and the mass ratio of polyamide 6 fiber to polypropylene grafted with maleic anhydride is 1:(1-2).

6. The high-strength composite film for hygiene products according to claim 1, characterized in that, The polyamide 6 fiber has a relative viscosity of 2.0-2.4 and its morphology in the film is microfiber with a diameter of 50-300 nm and an aspect ratio greater than 50.

7. The high-strength composite film for hygiene products according to claim 1, characterized in that, The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and the slip agent is erucamide.

8. The method for preparing a high-strength composite film for hygiene products according to claim 1, characterized in that, Includes the following steps: S1. Raw material preparation: including polyethylene, polypropylene, bifunctional core-shell reinforcing agent, PA6 predispersed masterbatch, antioxidant and slip agent; S2. Blending and granulation: Add each raw material to a high-speed mixer and mix at 60-80℃ for 3-5 minutes. Then feed it into a twin-screw extruder with an aspect ratio ≤35 and melt blend and granulate at a melt temperature of 180-200℃ to obtain composite masterbatch. S3. Casting and Online Micro-stretching: The composite masterbatch prepared in step S2 is fed into a casting extruder and cast into a film at a die temperature of 190-200°C. Then, it is immediately subjected to 2-6% online micro-stretching through two sets of traction rollers to obtain a preliminary film. S4. Post-processing: The initial film obtained in step S3 is subjected to corona treatment to make the surface tension of the film ≥42dyn / cm and the water contact angle ≤65°. Then it is wound up to obtain a high tensile composite film for hygiene products.

9. The method for preparing a high-strength composite film for hygiene products according to claim 8, characterized in that, The twin-screw extruder is equipped with a high-shear element, with a maximum melt shear rate ≥1500s. -1 The melt residence time is ≤30 seconds, and the rotation speed is 280-320 rpm.

10. The method for preparing a high-strength composite film for hygiene products according to claim 8, characterized in that, After step S4, scrap material recycling is carried out. The scrap material generated during the production process is heat-treated at 240-260℃ for 10-15 minutes, crushed to a particle size of 2-5mm, and then mixed into the raw material of step S2 at a mass ratio of no more than 30% for re-blending and granulation.