Polypropylene material for paper diaper fastener and method for preparing the same

Abstract

This invention relates to a polypropylene material for diaper fasteners and its preparation method. The material is composed of polypropylene resin, a durable antistatic masterbatch, a compatibilizer, an antioxidant, and a lubricant. The antistatic masterbatch is prepared by melt-blending polypropylene grafted with maleic anhydride with an imidazolium salt-based antistatic agent. The antistatic components in this material are uniformly dispersed and have low migration, forming stable charge dissipation channels, thereby achieving durable antistatic performance while maintaining good mechanical and processing properties.

Description

Technical Field

[0001] This invention relates to the field of diaper fastener technology, and in particular to a polypropylene material for diaper fasteners and its preparation method. Background Technology

[0002] Polypropylene (PP), a typical olefin polymer material, is widely used in disposable hygiene products due to its low density, excellent mechanical properties, good chemical resistance, and stable processing performance. It is particularly prevalent in structural components such as diaper fasteners, where it is typically manufactured using injection molding or extrusion molding. However, polypropylene is a non-polar polymer material lacking polar groups in its molecular chain, resulting in low electrical conductivity. During processing, transportation, and use, it is prone to generating and accumulating static electricity due to friction, leading to problems such as product adhesion, dust adsorption, and impacting the stability of automated production.

[0003] To address these issues, existing technologies typically modify polypropylene materials by adding antistatic agents. Commonly used antistatic agents include fatty acid esters (such as glyceryl monostearate), fatty amines (such as stearylamine and ethoxylated fatty amines), quaternary ammonium salts, polyethers (such as polyethylene glycol), and conductive fillers (such as carbon black and carbon nanotubes). While these antistatic agents can reduce the surface resistivity of the material to some extent, they also have limitations in practical applications.

[0004] Among them, fatty acid esters, fatty amines, and quaternary ammonium salts are mostly small molecules that tend to migrate and precipitate onto the material surface during processing or use, causing "blooming" or surface stickiness. This not only affects the appearance of the product but may also weaken the stability and performance of the snap fastener structure. Furthermore, the continuous migration of these substances can lead to a decline in antistatic effect over time, making it difficult to achieve long-term stable antistatic performance.

[0005] Furthermore, polyether-based antistatic agents, due to their strong molecular polarity, have limited compatibility with the non-polar polypropylene matrix. At higher addition levels, they can easily cause inhomogeneity in the internal structure of the material, leading to a decrease in mechanical properties such as tensile strength and flexural modulus, and potentially causing melt flow instability during processing. While conductive filler-based antistatic materials can significantly reduce resistivity by creating conductive pathways, they typically require higher addition levels, which can easily lead to increased material rigidity and decreased toughness, while also adversely affecting the color and processing flowability of the finished product.

[0006] Therefore, while ensuring the original mechanical and processing properties of polypropylene materials, how to achieve long-term stability of antistatic properties and avoid the adverse effects of traditional antistatic agents on material properties remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] This application provides a polypropylene material for diaper fasteners, which, by weight, comprises the following components:

[0008] 70-95 parts of polypropylene resin;

[0009] 3-20 parts of durable antistatic masterbatch;

[0010] 1-8 parts compatibilizer;

[0011] Antioxidant 0.1 to 1 part;

[0012] Lubricant 0.2 to 2 parts;

[0013] The durable antistatic masterbatch is prepared by melt blending polypropylene grafted maleic anhydride (PP-g-MAH) as carrier resin with imidazolium salt antistatic agent, wherein the content of imidazolium salt antistatic agent in the masterbatch is 10-50 wt%.

[0014] It should be noted that the durable antistatic masterbatch described in this application uses polypropylene grafted maleic anhydride (PP-g-MAH) as the carrier resin. Through melt blending with imidazolium salt antistatic agents, the imidazolium salt molecules are uniformly dispersed in the PP-g-MAH matrix during processing. The polar interaction between the anhydride groups and the imidazolium cations creates an interfacial binding effect on the antistatic components, effectively inhibiting their migration and precipitation in the polypropylene system. Furthermore, the ion conduction channels provided by the imidazolium salt can form stable charge dissipation pathways within the material, allowing the polypropylene material to achieve a continuous antistatic effect without relying on surface precipitation or environmental humidity. This avoids the problems of blooming, stickiness, and performance degradation over time associated with traditional small-molecule antistatic agents, thus achieving long-term stable antistatic performance while ensuring the material's mechanical properties and processing stability.

[0015] As a preferred technical solution for polypropylene materials used in diaper fasteners, the polypropylene resin includes homopolymer polypropylene, copolymer polypropylene, and mixtures thereof.

[0016] It should be noted that homopolymer polypropylene has high crystallinity and rigidity, which is beneficial to improving the mechanical strength and wear resistance of the material; copolymer polypropylene, due to the introduction of copolymer units such as ethylene, can effectively improve the toughness and low-temperature performance of the material; by using the two in a reasonable ratio or in combination, the material's strength and wear resistance can be guaranteed while also taking into account its flexibility and processing performance, thereby meeting the comprehensive performance requirements of different application scenarios.

[0017] As a preferred technical solution for polypropylene material used in diaper fasteners, the compatibilizer is an ethylene-octene copolymer grafted with maleic anhydride, with a grafting rate of 1-2 wt%.

[0018] It should be noted that the compatibilizer is an ethylene-octene copolymer grafted with maleic anhydride at a grafting rate of 1-2 wt%. Its flexible polyolefin segments can improve the toughness and resistance to repeated bending of the material, while the polar groups of maleic anhydride can enhance the interfacial compatibility between the antistatic masterbatch and the polypropylene matrix, promote the uniform dispersion of each component and inhibit precipitation, thereby taking into account antistatic stability, mechanical properties and processing performance.

[0019] As a preferred technical solution for polypropylene material used in diaper fasteners, the imidazodium salt antistatic agent is selected from at least one of 1-alkyl-3-methylimidazodium salt and 1-alkyl-3-ethylimidazodium salt, and its anion is selected from BF4. - PF6 - Cl - or Br - .

[0020] It should be noted that the imidazolium salt antistatic agent described in this application is selected from at least one of 1-alkyl-3-methylimidazolium salt or 1-alkyl-3-ethylimidazolium salt, and the alkyl chain length in its cationic structure can be adjusted, thereby improving its compatibility with the polypropylene matrix while ensuring ionic conductivity; at the same time, by selecting BF4 - PF6 - Cl - or Br - Different anions can be used to modulate the polarity, thermal stability, and ion mobility of ionic liquids, among which BF4... - and PF6 - It is beneficial for improving thermal stability and reducing volatility, while Cl - and Br - This helps to enhance ionic conductivity; the synergistic regulation of the above-mentioned cations and anions optimizes the dispersibility and stability of imidazolium salt in polypropylene grafted maleic anhydride support, forming a stable and continuous ion conduction channel inside the material, thereby achieving long-lasting and stable antistatic properties without significant migration or precipitation.

[0021] As a preferred technical solution for polypropylene material used in diaper fasteners, the weight ratio of PP-g-MAH to imidazoline salt antistatic agent in the durable antistatic masterbatch is (1-9):1.

[0022] It should be noted that the weight ratio of PP-g-MAH to imidazolium salt antistatic agent in the durable antistatic masterbatch is (1-9):1. Within this ratio range, both effective loading and stable dispersion of antistatic components can be achieved, while avoiding phase separation or decrease in mechanical properties caused by excessive antistatic agent content.

[0023] As a preferred technical solution for polypropylene materials used in diaper fasteners, the antioxidant is a mixture of hindered phenolic antioxidants and phosphite antioxidants in a weight ratio of (1-2):1. It should be noted that the use of hindered phenolic antioxidants and phosphite antioxidants in a weight ratio of (1-2):1 forms a synergistic antioxidant system, effectively inhibiting the thermo-oxidative degradation of polypropylene during processing and use.

[0024] As a preferred technical solution for polypropylene material used in diaper fasteners, the lubricant is selected from at least one of calcium stearate and ethylene bis-stearamide.

[0025] It should be noted that the lubricant is selected from at least one of calcium stearate and ethylene bis-stearamide, which can reduce frictional resistance and shear heat during melt processing, improve the processing fluidity of materials and the surface quality of products.

[0026] This application also provides a durable antistatic masterbatch, comprising, by weight parts:

[0027] 50-90 parts of polypropylene grafted with maleic anhydride;

[0028] 10-50 parts of imidazolyl salt antistatic agent.

[0029] It should be noted that the durable antistatic masterbatch described in this application uses polypropylene grafted with maleic anhydride as the carrier resin. By fully blending it with imidazolium salt antistatic agents in the molten state, the antistatic components are uniformly dispersed and effectively coated in the carrier. The polar anhydride groups in PP-g-MAH can form interfacial interactions with imidazolium salts, thereby binding and fixing them and significantly reducing their migration and precipitation tendency in the subsequent polypropylene system. At the same time, the ion conduction ability provided by imidazolium salts can build stable charge dissipation pathways within the material, enabling the masterbatch to impart durable and stable antistatic properties to the matrix material at a low addition amount, while also taking into account good processing adaptability and storage stability.

[0030] In addition, this application also provides a method for preparing polypropylene material, including the following steps:

[0031] Step S1. Preparation of durable antistatic masterbatch: Polypropylene grafted with maleic anhydride and imidazolium salt antistatic agent are added to a twin-screw extruder in proportion, melt-blended and extruded and granulated at 180-220℃ and screw speed of 200-400 rpm to obtain durable antistatic masterbatch;

[0032] Step S2. Preparation of polypropylene material: After mixing polypropylene resin, the durable antistatic masterbatch, compatibilizer, antioxidant and lubricant, the mixture is melt-blended and extruded and granulated at 190-230°C and screw speed of 300-500 rpm to obtain the polypropylene material.

[0033] As a preferred technical solution for the preparation method of polypropylene material, the temperature control of the twin-screw extruder in step S2 is as follows: feeding section 180~190℃, compression section 200~210℃, metering section 210~230℃, and die head 220~230℃.

[0034] It should be noted that in step S2, the twin-screw extruder adopts segmented temperature control with a feeding section of 180-190°C, a compression section of 200-210°C, a metering section of 210-230°C, and a die head of 220-230°C. This facilitates the gradual melting of each component and achieves uniform mixing, while preventing the imidazolium salt antistatic agent from decomposing or migrating due to local overheating, thereby ensuring that the material has stable processing performance and antistatic effect.

[0035] The polypropylene material for diaper fasteners provided by this invention constructs an imidazolium salt-based durable antistatic masterbatch system using polypropylene grafted maleic anhydride (PP-g-MAH) as a carrier. This system enables the antistatic components to be uniformly dispersed in the polypropylene matrix and effectively bound by interfacial polarity, thereby significantly inhibiting the migration and precipitation of the antistatic agent. Stable charge dissipation channels can be formed without relying on surface enrichment or environmental humidity, achieving long-term stable antistatic performance. At the same time, the synergistic effect of the compatibilizer ensures the uniformity of the system's dispersion, allowing the material to maintain good mechanical properties and processing stability while achieving excellent antistatic effects. This avoids the problems of blooming, performance degradation, and the adverse effects of conductive filler systems on mechanical properties and appearance associated with traditional small-molecule antistatic agents. It has significant advantages such as durable antistatic performance, low migration, and excellent overall performance. Attached Figure Description

[0036] Figure 1 This is a scanning electron microscope (SEM) cross-sectional morphology image of the polypropylene material prepared in Example 1. Detailed Implementation

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0038] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0039] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0040] Example 1

[0041] This embodiment provides a polypropylene material for diaper fasteners, which, by weight, consists of the following components: 95 parts of homopolymer polypropylene (such as T30S) with a melt index of 10 g / 10min, 3 parts of durable antistatic masterbatch, 1 part of ethylene-octene copolymer grafted with maleic anhydride (grafting rate 1%), 0.1 parts of antioxidant (Irganox 1010 and Irgafos 168 compounded in a 1:1 ratio), and 0.2 parts of calcium stearate; wherein the antistatic masterbatch is prepared from 90 parts of PP-g-MAH and 10 parts of 1-butyl-3-methylimidazolium tetrafluoroborate.

[0042] This embodiment provides a method for preparing polypropylene material for diaper fasteners, including the following steps:

[0043] Step S1: Preparation of antistatic masterbatch

[0044] First, PP-g-MAH and imidazolium salt were placed separately in a vacuum drying oven and dried at 80°C for 4 hours to reduce their moisture content to below 0.1%. Then, they were weighed at a mass ratio of 90:10 and premixed at 800 rpm for 5 minutes in a high-speed mixer to allow the liquid antistatic agent to be initially adsorbed onto the resin surface. The mixture was then added to the main feed port of a twin-screw extruder (length-to-diameter ratio 40:1), with the temperature range set at 180°C (constant temperature throughout) and the screw speed at 200 rpm. Medium shear combined screw elements were used for melt blending. After the melt was extruded from the die head, it was cooled in a 20°C water bath with a traction speed of 5 m / min. It was then cut into particles of about 2-3 mm by a pelletizer and finally dried in a 60°C forced-air drying oven for 2 hours to obtain the antistatic masterbatch.

[0045] Step S2: Preparation of polypropylene material

[0046] Homopolymer polypropylene, antistatic masterbatch, compatibilizer, antioxidant, and lubricant were added to a high-speed mixer in proportion and mixed at 600 rpm for 10 minutes at room temperature. The uniformly mixed material was then fed into a twin-screw extruder with the following temperature settings: feeding section 180℃, compression section 200℃, metering section 210℃, and die head 220℃. The screw speed was 300 rpm. After the material was fully melted and plasticized, it was extruded, water-cooled, traction (6 m / min), pelletized (3 mm), and dried at 80℃ for 4 hours to obtain the final material.

[0047] Example 2

[0048] This embodiment provides a polypropylene material for diaper fasteners, which, by weight, consists of the following components: 85 parts of homopolymer polypropylene with a melt index of 30 g / 10min, 10 parts of durable antistatic masterbatch, 4 parts of ethylene-octene copolymer grafted maleic anhydride (grafting rate 1.5%), 0.5 parts of antioxidant (hindered phenolic antioxidant and phosphite antioxidant compounded at a ratio of 1.5:1), and 1 part of ethylene bis-stearamide; wherein the antistatic masterbatch is prepared by grafting 75 parts of polypropylene with maleic anhydride and 25 parts of 1-ethyl-3-methylimidazolium hexafluorophosphate.

[0049] This embodiment provides a method for preparing polypropylene material for diaper fasteners, including the following steps:

[0050] Step S1: Preparation of durable antistatic masterbatch

[0051] First, polypropylene grafted with maleic anhydride and imidazolium salt antistatic agents were placed separately in a vacuum drying oven and dried at 80°C for 4 hours to control the moisture content below 0.1%. Then, they were weighed at a mass ratio of 75:25 and added to a high-speed mixer, where they were mixed at 1000 rpm for 8 minutes to fully wet and adsorb the liquid imidazolium salt onto the surface of the resin particles. Next, the mixture was uniformly fed into a twin-screw extruder (L / D ratio 40:1) using a loss-in-weight feeder. All temperature zones were uniformly set to 200°C, and the screw speed was set to 300 rpm. The screw structure adopted a combination of a conveyor section and a dispersing compound block to enhance shearing and dispersion effects. After the material was melted and plasticized, it was extruded from the die head and cooled in a water-cooling tank at a temperature of 20–25°C with a traction speed controlled at 6 m / min. It was then cut into 2–3 mm particles by a rotary pelletizer. Finally, the particles were placed in a 60°C forced-air drying oven and dried for 2 hours to obtain durable antistatic masterbatch.

[0052] Step S2: Preparation of polypropylene material

[0053] Homopolymer polypropylene, the aforementioned antistatic masterbatch, compatibilizer, antioxidant, and lubricant were added to a high-speed mixer in proportion and mixed at 700 rpm for 10 minutes at room temperature to ensure uniform dispersion of the components. The mixture was then fed into a twin-screw extruder for melt blending, with the following temperatures set: feeding section 185°C, compression section 205°C, metering section 220°C, and die head 225°C; screw speed 400 rpm. After thorough melting and plasticization, the material was extruded from the die head, cooled in a 20°C water bath, with a traction speed controlled at 6.5 m / min and a pellet size controlled at approximately 3 mm. Finally, the material was dried in an 80°C forced-air drying oven for 4 hours to obtain the polypropylene material.

[0054] Example 3

[0055] This embodiment provides a polypropylene material for diaper fasteners, which, by weight, consists of the following components: 75 parts of copolymer polypropylene with a melt index of 50 g / 10min, 15 parts of durable antistatic masterbatch, 6 parts of ethylene-octene copolymer grafted maleic anhydride (grafting rate 1.8%), 0.8 parts of antioxidant (hindered phenolic antioxidant and phosphite antioxidant compounded in a 2:1 ratio), and 1.5 parts of lubricant (calcium stearate and ethylene bis-stearamide compounded in a 1:1 ratio); wherein the antistatic masterbatch is prepared by grafting 67 parts of polypropylene with maleic anhydride and 33 parts of 1-butyl-3-methylimidazolium chloride.

[0056] This embodiment provides a method for preparing polypropylene material for diaper fasteners, including the following steps:

[0057] Step S1: Preparation of durable antistatic masterbatch

[0058] First, polypropylene grafted with maleic anhydride and imidazolium salt antistatic agents were placed separately in a vacuum drying oven and dried at 80°C for 4 hours to reduce the moisture content to below 0.1%. Then, they were weighed at a mass ratio of 67:33 and added to a high-speed mixer, where they were mixed at 1200 rpm for 10 minutes to ensure that the imidazolium salt was uniformly coated on the surface of the resin particles. Subsequently, the material was fed into a twin-screw extruder (length-to-diameter ratio 40:1) using a combination of side feeding and main feeding. The temperature was set at 210°C and the screw speed at 350 rpm. The screw assembly consisted of alternating conveying, shearing, and mixing sections to improve dispersion uniformity. After melt extrusion, the material was cooled in a 20°C water-cooling bath at a traction speed of 7 m / min and then cut into particles of approximately 2–3 mm by a pelletizer. Finally, the material was dried in a 60°C forced-air drying oven for 2 hours to obtain durable antistatic masterbatch.

[0059] Step S2: Preparation of polypropylene material

[0060] Copolymer polypropylene, antistatic masterbatch, compatibilizer, antioxidant, and lubricant were added to a high-speed mixer in proportion and mixed at 700 rpm for 10 minutes at room temperature to ensure uniformity. The mixture was then fed into a twin-screw extruder for melt blending, with the following temperatures set: feeding section 187°C, compression section 207°C, metering section 225°C, and die head 227°C. The screw speed was set to 450 rpm. After extrusion through the die head, the melt was cooled in a 20°C water bath with a traction speed controlled at 7 m / min. The melt was then cut into approximately 3 mm particles by a pelletizer. Finally, the material was dried in an 80°C forced-air drying oven for 4 hours to obtain the polypropylene material.

[0061] Example 4

[0062] This embodiment provides a polypropylene material for diaper fasteners, which, by weight, consists of the following components: 70 parts of a mixture of copolymer polypropylene with a melt index of 60 g / 10 min and homopolymer polypropylene with a melt index of 10 g / 10 min (at a mass ratio of 1:1), 20 parts of durable antistatic masterbatch, 8 parts of ethylene-octene copolymer grafted maleic anhydride (grafting rate 2%), 1 part of antioxidant (a mixture of hindered phenolic antioxidant and phosphite antioxidant in a 2:1 ratio), and 2 parts of ethylene bis-stearamide; wherein the durable antistatic masterbatch is prepared by grafting 50 parts of polypropylene with maleic anhydride and 50 parts of 1-ethyl-3-methylimidazolium bromide.

[0063] This embodiment provides a method for preparing polypropylene material for diaper fasteners, including the following steps:

[0064] Step S1: Preparation of durable antistatic masterbatch

[0065] First, polypropylene grafted with maleic anhydride and imidazolium salt antistatic agents were placed separately in a vacuum drying oven and dried at 80°C for 4 hours to control their moisture content below 0.1%. Then, they were accurately weighed at a 50:50 mass ratio and added to a high-speed mixer, where they were mixed at 1200 rpm for 10 minutes to ensure the imidazolium salt was uniformly wetted and adsorbed onto the surface of the resin particles, forming a preliminary coating structure. Next, the mixture was fed into a twin-screw extruder (40:1 L / D ratio) through the main feed port. All temperature zones were uniformly set to 220°C, and the screw speed was set to 400 rpm. The screw structure employed an alternating combination of a conveyor section and a high-shear mixing block to improve dispersion and coating effects. After being fully melted, plasticized, and sheared dispersed within the extruder, the material was extruded from the die head and rapidly cooled in a 20°C water-cooling tank at a traction speed of 7.5 m / min. Subsequently, it was cut into approximately 2-3 pieces by a rotary pelletizer. mm particles; finally, the obtained particles were placed in a 60℃ forced-air drying oven and dried for 2 hours to remove residual moisture, thus obtaining durable antistatic masterbatch.

[0066] Step S2: Preparation of polypropylene material

[0067] A mixture of copolymer polypropylene and homopolymer polypropylene, the aforementioned durable antistatic masterbatch, ethylene-octene copolymer grafted maleic anhydride compatibilizer, antioxidant, and lubricant were added to a high-speed mixer in proportion and mixed at 700 rpm for 10 minutes at room temperature to ensure uniform dispersion of the components. The uniformly mixed material was then added to a twin-screw extruder for melt blending. The temperatures were set as follows: feeding section 190°C, compression section 210°C, metering section 230°C, and die head 230°C. The screw speed was set to 500 rpm. After thorough plasticization and mixing in the extruder, the material was extruded from the die head and cooled in a 20°C water-cooling bath. The traction speed was controlled at 7.5 m / min. The material was then cut into approximately 3 mm particles by a pelletizer. Finally, the resulting particles were dried in an 80°C forced-air drying oven for 4 hours to obtain the polypropylene material for diaper fasteners.

[0068] Compare with Example 1

[0069] The difference between Comparative Example 1 and Example 1 is that in this Comparative Example, the traditional small molecule antistatic agent glyceryl monostearate is used instead of the durable antistatic masterbatch in Example 1.

[0070] Preparation method:

[0071] Step S1: Drying the raw materials

[0072] Polypropylene resin, glycerol monostearate, and ethylene-octene copolymer grafted with maleic anhydride were placed in a vacuum drying oven and dried at 80°C for 4 hours to reduce the moisture content to less than 0.1%.

[0073] Step S2: Premixing

[0074] Add each component to a high-speed mixer according to the formula ratio, and mix at 600 rpm for 10 minutes at room temperature to ensure uniform mixing of materials.

[0075] Step S3: Melt Blending Extrusion

[0076] The mixture is added to a twin-screw extruder, with the temperature set as follows: feeding section 180℃, compression section 200℃, metering section 210℃, die head 220℃, and screw speed 300 rpm. The material is extruded after melt blending, and then granulated by water cooling, traction, and pelletizing.

[0077] Step S4: Drying

[0078] The obtained particles were dried at 80°C for 4 hours to obtain polypropylene material.

[0079] Compare with Example 2

[0080] The difference between Comparative Example 2 and Example 1 is that: in this comparative example, a durable antistatic masterbatch was not prepared, but an imidazolium salt antistatic agent was directly added to the polypropylene system.

[0081] Preparation method:

[0082] Step S1: Drying the raw materials

[0083] Polypropylene resin, imidazolium salt antistatic agent, and ethylene-octene copolymer grafted with maleic anhydride were dried at 80°C for 4 hours.

[0084] Step S2: Premixing

[0085] Polypropylene resin and imidazolium salt antistatic agent were added to a high-speed mixer and mixed at 800 rpm for 5 minutes to allow the antistatic agent to be initially adsorbed onto the resin surface. Then, compatibilizer, antioxidant and lubricant were added and mixed for another 5 minutes.

[0086] Step S3: Melt Blending Extrusion

[0087] The mixture is added to a twin-screw extruder and melt-blended under the following conditions: feeding section 180°C, compression section 200°C, metering section 210°C, and die head 220°C. The screw speed is 300 rpm. After extrusion, the mixture is water-cooled, traction-driven, and pelletized.

[0088] Step S4: Dry at 80℃ for 4 hours.

[0089] Compare with Example 3

[0090] The difference between Comparative Example 3 and Example 1 is that the carrier resin of the durable antistatic masterbatch in this comparative example is ordinary polypropylene, and polypropylene grafted with maleic anhydride is not used.

[0091] Preparation method:

[0092] Step S1: Preparation of antistatic masterbatch

[0093] Ordinary polypropylene and imidazolium salt antistatic agent were added to a high-speed mixer at a mass ratio of 90:10 and mixed at 800 rpm for 5 minutes. Then, the mixture was added to a twin-screw extruder and melt-blended and extruded at 180°C and a screw speed of 200 rpm. After water cooling and pelletizing, antistatic masterbatch was obtained.

[0094] Step S2: Preparation of polypropylene material

[0095] Polypropylene resin, the above-mentioned antistatic masterbatch, ethylene-octene copolymer grafted maleic anhydride, antioxidant and lubricant are added to a high-speed mixer and mixed at 600 rpm for 10 minutes; then the uniformly mixed material is added to a twin-screw extruder with the temperature set as follows: feeding section 180℃, compression section 200℃, metering section 210℃, die head 220℃, screw speed 300 rpm; after the material is fully melted and plasticized, it is extruded, water cooled, traction and pelletized.

[0096] Step S3: Dry at 80℃ for 4 hours.

[0097] Compare with Example 4

[0098] The difference between Comparative Example 4 and Example 1 is that no compatibilizer was added in this Comparative Example.

[0099] Preparation method:

[0100] Step S1: The preparation of antistatic masterbatch is the same as step S1 in Example 1.

[0101] Step S2: Premixing

[0102] Polypropylene resin, antistatic masterbatch, antioxidant and lubricant are added to a high-speed mixer and mixed at 600 rpm for 10 minutes.

[0103] Step S3: Melt Blending Extrusion

[0104] The mixture is added to a twin-screw extruder and melt-blended under the following conditions: feeding section 180°C, compression section 200°C, metering section 210°C, and die head 220°C. The screw speed is 300 rpm. After extrusion, the mixture is water-cooled and pelletized.

[0105] Step S4: Dry at 80℃ for 4 hours.

[0106] Performance testing methods

[0107] 1. Surface resistivity: During the test, the sample is prepared by injection molding into a specimen with a size of 100 mm × 100 mm and a thickness of 2 mm. After conditioning for 24 hours at a temperature of 23℃ and a relative humidity of 50%, the resistivity is measured using a high-resistivity meter (such as a test device conforming to GB / T 1410 standard). A test voltage of 100 V is applied to the surface of the specimen, and the surface resistivity value after stabilization is recorded. Each test group has no less than 3 parallel samples, and the average value is taken as the test result.

[0108] 2. Durability of antistatic properties: During the test, the sample was placed in an environment with a temperature of 50℃ and a relative humidity of 30% for accelerated aging treatment for 14 days. After aging, the sample was conditioned for 24 hours in a standard environment (23℃, 50% RH) and then the surface resistivity was measured according to the surface resistivity test method to compare the changes in resistivity before and after aging.

[0109] 3. Antistatic agent migration / precipitation performance (blooming observation): During the test, the sample is stored in a 50℃ constant temperature oven for 7 days. After taking it out, observe the sample surface under natural light or a polarizing microscope to see if whitening, oily precipitation, or crystal precipitation occurs. If necessary, the filter paper pressing method (covering the sample surface with filter paper and applying a certain pressure) can be used to observe whether there are migratable substances transferred to the filter paper, thereby judging the migration tendency of the antistatic agent.

[0110] 4. Tensile Properties: Tensile properties are used to evaluate the retention of mechanical properties of materials. During testing, the material is prepared into standard dumbbell-shaped specimens according to GB / T1040.2 standard, and tested using a universal testing machine at 23℃. The tensile speed is 50 mm / min, and the tensile strength and elongation at break are recorded. Each group contains no less than 5 specimens, and the average value is taken.

[0111] Table 1 Performance Comparison of Examples and Control Examples

[0112] sample Surface resistivity (Ω / sq) Surface resistivity after aging (Ω / sq) Change factor Surface precipitation Filter paper test Tensile strength (MPa) Elongation at break (%) Example 1 <![CDATA[3.2×10 10 ]]> <![CDATA[4.5×10 10 ]]> 1.4 No precipitation, smooth surface No transfer 31.5 420 Example 2 <![CDATA[8.5×10 9 ]]> <![CDATA[1.2×10 10 ]]> 1.4 No precipitation No transfer 30.2 405 Example 3 <![CDATA[3.0×10 9 ]]> <![CDATA[4.8×10 9 ]]> 1.6 No obvious precipitation No transfer 28.8 390 Example 4 <![CDATA[1.2×10 9 ]]> <![CDATA[2.0×10 9 ]]> 1.7 No precipitation No transfer 27.5 360 Compare with Example 1 <![CDATA[6.5×10 10 ]]> <![CDATA[5.2×10 12 ]]> 80 Noticeably white, with an oily exudate. obvious shift 30.8 415 Compare with Example 2 <![CDATA[2.8×10 10 ]]> <![CDATA[8.6×10 11 ]]> 30 Localized oily precipitation There is a transfer 27.0 300 Compare with Example 3 <![CDATA[1.5×10 10 ]]> <![CDATA[3.2×10 11 ]]> 21 Slightly white Small amount of transfer 28.0 320 Compare with Example 4 <![CDATA[9.0×10 9 ]]> <![CDATA[1.5×10 11 ]]> 17 There was virtually no precipitation, but it was not uniform. No obvious metastasis 26.5 280

[0113] In conjunction with Example 1 and Figure 1 As can be seen from the electron microscopy images above, the cross-section of the material is generally flat and dense, and no obvious large-sized agglomerated phases or phase separation structures were observed, indicating that the antistatic component is relatively uniformly dispersed in the polypropylene matrix. A small number of micron-sized particles are uniformly distributed in the matrix with natural interface transitions and no obvious pores or debonding phenomena, indicating that the imidazole onium salt antistatic agent is effectively encapsulated and stably embedded in the matrix system under the action of the PP-g-MAH carrier. At the same time, no continuous phase precipitation or surface enrichment structure was observed, further verifying that the system has a good interfacial binding ability for the antistatic component, thus providing microscopic morphology evidence that the material in Example 1 has excellent anti-migration and long-term stable antistatic properties.

[0114] As can be seen from Examples 1-4 and Table 1, the surface resistivity of the polypropylene material prepared by this invention is 1.2 × 10⁻⁶. 9 ~3.2×10 10 Within the Ω / sq range, the surface resistivity after aging at 50℃ for 14 days is 2.0×10⁻⁶. 9 ~4.5×10 10The surface resistivity (Ω / sq) varied by a factor of 1.4–1.7, with relatively small overall changes, indicating that the material possesses good antistatic properties and excellent long-term stability. Furthermore, no significant precipitation or migration was observed in any of the samples after storage at 50°C for 7 days, and no transfer was observed in filter paper testing, indicating that the antistatic component is stably distributed in the system and does not easily migrate. In addition, the tensile strength of the material was 27.5–31.5 MPa, and the elongation at break was 360%–420%, indicating that it maintains good mechanical properties while achieving antistatic functionality. Combining Example 1, Comparative Example 1, and Table 1, it can be seen that the surface resistivity of Example 1 is 3.2 × 10⁻⁶. 10 Ω / sq, after aging it becomes 4.5×10 10 The change factor is only 1.4 Ω / sq, while the initial surface resistivity of Comparative Example 1 is 6.5 × 10⁻⁶. 10 Ω / sq, which significantly increased to 5.2×10 after aging. 12 The resistivity of the sample after aging was 4.5 × 10⁻⁶ Ω / sq, a change of up to 80 times, with obvious whitening and oily precipitation. The glyceryl monostearate used in Comparative Example 1 is a small-molecule antistatic agent that easily migrates from the polypropylene matrix to the material surface and gradually leaches away, leading to a rapid decline in antistatic performance over time. In contrast, the imidazole onium salt antistatic agent in Example 1 is encapsulated by a PP-g-MAH carrier, forming interfacial interactions that effectively inhibit its migration, thus achieving long-term stable antistatic performance. Combining Example 1, Comparative Example 2, and Table 1, it can be seen that the resistivity of Example 1 after aging is 4.5 × 10⁻⁶ Ω / sq. 10 The resistivity changed by a factor of 1.4, while in control example 2, the resistivity increased to 8.6 × 10⁻⁶ Ω / sq after aging. 11 The resistivity of the Ω / sq decreased by a factor of 30, and localized oily precipitation also occurred. In Comparative Example 2, the imidazolium salt antistatic agent was directly added to the polypropylene system, lacking carrier coating and interfacial restraint, resulting in uneven dispersion and easy migration during processing and use. In contrast, Example 1, by pre-preparing antistatic masterbatch, enabled the imidazolium salt to be uniformly dispersed and effectively fixed in PP-g-MAH, thereby significantly improving its stability and anti-migration ability. Combining Example 1, Comparative Example 3, and Table 1, it can be seen that the resistivity of Example 1 after aging is 4.5 × 10⁻⁶. 10 The resistivity was Ω / sq, with a change factor of 1.4, while the resistivity of control example 3 after aging was 3.2 × 10⁻⁶. 11The resistivity of the antistatic masterbatch in Example 3 was 4.5 × 10⁻⁶ Ω / sq, a change of 21 times, with slight whitening and migration observed. The carrier of the antistatic masterbatch in Comparative Example 3 was ordinary polypropylene, which lacks polar groups and cannot form an effective interfacial interaction with the imidazolium salt, resulting in insufficient constraint in the system and easy migration and aggregation. In contrast, Example 1 used PP-g-MAH as the carrier, whose anhydride groups can interact polarly with the imidazolium salt, thereby enhancing interfacial bonding, improving dispersion stability, and inhibiting migration. Combining Example 1, Comparative Example 4, and Table 1, it can be seen that the resistivity of Example 1 after aging is 4.5 × 10⁻⁶ Ω / sq. 10 The resistivity changed by a factor of 1.4, while in control example 4, the resistivity increased to 1.5 × 10⁻⁶ Ω / sq after aging. 11 The change in Ω / sq was 17 times, and the tensile strength and elongation at break decreased significantly. In Comparative Example 4, no compatibilizer was added, resulting in poor interfacial compatibility between the antistatic masterbatch and the polypropylene matrix, uneven dispersion of the antistatic components, and a greater likelihood of migration or the formation of unstable conductive pathways in locally enriched areas. In contrast, Example 1, by adding an ethylene-octene copolymer grafted with maleic anhydride compatibilizer, improved the interfacial bonding and dispersion uniformity of the system, thereby enhancing the stability of the antistatic properties and maintaining good mechanical properties.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A polypropylene material for diaper fasteners, characterized in that, It consists of the following components by weight: 70-95 parts of polypropylene resin; 3-20 parts of durable antistatic masterbatch; 1-8 parts compatibilizer; Antioxidant 0.1 to 1 part; Lubricant 0.2 to 2 parts; The durable antistatic masterbatch is prepared by melt blending PP-g-MAH as the carrier resin with an imidazolium salt antistatic agent, wherein the content of the imidazolium salt antistatic agent in the masterbatch is 10-50 wt%.

2. The polypropylene material for diaper fasteners according to claim 1, characterized in that, The polypropylene resin includes homopolymer polypropylene, copolymer polypropylene, and mixtures thereof.

3. The polypropylene material for diaper fasteners according to claim 2, characterized in that, The compatibilizer is an ethylene-octene copolymer grafted with maleic anhydride, with a grafting rate of 1-2 wt%.

4. The polypropylene material according to claim 2, characterized in that, The imidazolium salt antistatic agent is selected from at least one of 1-alkyl-3-methylimidazolium salt and 1-alkyl-3-ethylimidazolium salt, and its anion is selected from BF4. - PF6 - Cl - or Br - .

5. The polypropylene material according to claim 2, characterized in that, In the durable antistatic masterbatch, the weight ratio of PP-g-MAH to imidazolium salt antistatic agent is (1-9):

1.

6. The polypropylene material according to claim 2, characterized in that, The antioxidant is a mixture of hindered phenolic antioxidants and phosphite antioxidants in a weight ratio of (1-2):

1.

7. The polypropylene material according to claim 2, characterized in that, The lubricant is selected from at least one of calcium stearate and ethylene bis-stearamide.

8. A method for preparing the polypropylene material according to any one of claims 1 to 7, characterized in that, Includes the following steps: Step S1. Preparation of durable antistatic masterbatch: Polypropylene grafted with maleic anhydride and imidazolium salt antistatic agent are added to a twin-screw extruder in proportion, melt-blended and extruded and granulated at 180-220℃ and screw speed of 200-400 rpm to obtain durable antistatic masterbatch; Step S2. Preparation of polypropylene material: After mixing polypropylene resin, the durable antistatic masterbatch, compatibilizer, antioxidant and lubricant, the mixture is melt-blended and extruded and granulated at 190-230°C and screw speed of 300-500 rpm to obtain the polypropylene material.

9. The preparation method according to claim 8, characterized in that, In step S2, the temperature control of the twin-screw extruder is as follows: feeding section 180-190℃, compression section 200-210℃, metering section 210-230℃, and die head 220-230℃.

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