High-barrier antibacterial rubber-plastic composite material and preparation method thereof

Abstract

The invention belongs to the technical field of compositions of high-molecular compounds, and relates to a high-barrier antibacterial rubber-plastic composite material and a preparation method thereof. The material is composed of 45%-65% of polyvinyl fluoride, 20%-35% of a bio-based polyester elastomer, 1.5%-4.0% of silver-loaded zirconium phosphate, 0.8%-2.5% of a bismaleimide compatibilizer and the balance of a processing aid. Wherein the side chain of the elastomer contains carboxyl or epoxy group, the elastomer and the polyvinyl fluoride form a covalent bond interface through in-situ reaction, and the antibacterial agent is anchored on the interface through silane coupling treatment. The preparation method comprises the steps of pretreatment, primary mixing, reactive extrusion and granulation molding. According to the invention, a bio-based polyester elastomer with reaction activity is introduced through molecular design, and a rubber-plastic composite material system with high barrier property, high toughness, long-acting antibacterial property and good processability is successfully constructed in combination with reactive compatibilization and interface directional anchoring antibacterial strategies; and a reliable material solution is provided for the fields of functional packaging, medical protective films, intelligent flexible devices and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polymer compound compositions, and relates to a high-barrier antibacterial rubber-plastic composite material and a preparation method thereof. BACKGROUND

[0002] In the field of modern functional polymer composites, rubber-plastic composite systems that have excellent barrier properties, antibacterial properties and good mechanical flexibility are increasingly becoming the core material requirements in key application scenarios such as food packaging, medical devices and high-end protective products. Among them, polyvinyl fluoride (PVF) is considered as an ideal candidate material for building high-barrier functional layers due to its highly symmetrical C-F bond structure in the molecular chain, which exhibits excellent gas barrier performance, chemical corrosion resistance and certain intrinsic antibacterial potential.

[0003] However, PVF itself has high crystallinity and glass transition temperature, which results in high hardness and brittleness in macroscopic performance, and it is difficult to meet the basic requirements of flexibility, resilience and impact resistance of flexible products alone. In order to overcome this limitation, the industry generally attempts to physically blend PVF with rubber-like elastomers in the hope of achieving the necessary flexibility of the material while retaining the barrier advantage of PVF through a rigid-flexible composite strategy.

[0004] Traditional technical paths mostly use thermoplastic elastomers as flexible components to prepare rubber-plastic composite materials through melt blending process with PVF. This method has indeed improved the processability and elongation at break of the material to some extent in early applications, and the design logic is to use the elastomer phase to absorb external impact energy, thereby relieving the brittle fracture tendency of the PVF matrix.

[0005] Correspondingly, the blending system can maintain the basic structural integrity under low stress conditions and achieve the preliminary retention of barrier properties under certain conditions. However, as the terminal application scenarios put forward more stringent requirements on the comprehensive performance of the material, for example, the high barrier property and structural stability still need to be maintained under repeated bending, low temperature impact or long-term humid heat aging conditions, the inherent defects of the above blending strategy gradually appear. SUMMARY

[0006] The application provides a high-barrier antibacterial rubber-plastic composite material and a preparation method thereof, aiming to solve the interface defect problem caused by the thermodynamic incompatibility between polyvinyl fluoride (PVF) and conventional elastomers in the prior art, so as to maintain the excellent gas barrier performance of PVF while imparting high flexibility, impact resistance and long-acting antibacterial function to the material. To achieve the above-mentioned application purpose, a polyester elastomer with a biological base source, an ester bond structure in the main chain and a reactive functional group introduced in the side chain is used as a flexible island phase, and a covalently bonded interface layer is constructed between the PVF continuous phase and the elastomer dispersed phase through an in-situ reactive compatibilization mechanism, so as to effectively inhibit phase separation and strengthen the synergistic effect of the two phases.

[0007] The high-barrier antibacterial rubber-plastic composite material is composed of the following components in mass percentage: 45% to 65% of polyvinyl fluoride, 20% to 35% of a biological polyester elastomer, 1.5% to 4.0% of a nanoscale inorganic antibacterial agent, 0.8% to 2.5% of a reactive compatibilizer, and the balance of a processing aid. The weight average molecular weight of the polyvinyl fluoride is 80,000 to 150,000, the melt flow rate is 2.0 g / 10 min to 6.0 g / 10 min (the test conditions are 230°C and 2.16 kg), and the crystallinity is controlled in the range of 35% to 45%, so as to ensure the formation of a continuous and dense barrier network in the composite system.

[0008] The biological polyester elastomer is an aliphatic-aromatic copolyester elastomer, the main chain of which is synthesized by polycondensation reaction of terephthalic acid, 1,4-butanediol and sebacic acid, wherein the mole percentage of terephthalic acid units is 30% to 45%, the mole percentage of sebacic acid units is 25% to 40%, and 1,4-butanediol is a comonomer with a mole percentage of 30% to 45%. The glass transition temperature of the elastomer is -45°C to -30°C, the melting point is 110°C to 130°C, the elongation at break is not less than 400%, and the tensile strength is 15 MPa to 25 MPa. The key is that the molecular chain ends or side chains of the elastomer are introduced with epoxy groups or carboxyl functional groups, and the functional group content is 0.8 mmol / g to 1.5 mmol / g, which is used for chemical reaction with the residual hydroxyl groups on the PVF molecular chain or the active sites generated by free radical initiation to form stable covalent bonds.

[0009] The nanoscale inorganic antibacterial agent is silver-loaded zirconium phosphate, the average particle size of which is 30 nm to 80 nm, the silver ion loading amount is 2.5 wt% to 4.0 wt%, and the specific surface area is 40 m² / g to 70 m² / g. The antibacterial agent is treated with a surface silane coupling agent, the coupling agent used is γ-glycidoxypropyltrimethoxysilane, and the surface of the antibacterial agent after treatment contains epoxy groups, which can react with the carboxyl groups in the biological polyester elastomer or the polar groups in the PVF, so as to be firmly anchored in the interfacial region of the composite material, avoiding migration and precipitation.

[0010] The reactive compatibilizer is a bismaleimide compound, specifically N,N'-(4-methyl-1,3-phenylene)bismaleimide, with a melting point of 195°C to 205°C. At processing temperatures, it decomposes to generate free radicals, initiating a grafting reaction between PVF and bio-based polyester elastomers. This compatibilizer not only promotes chemical bonding at the interface between the two phases in the composite system but also enhances the overall thermal and dimensional stability of the material through crosslinking.

[0011] The processing aids include heat stabilizers, lubricants, and antioxidants. The heat stabilizer is an organotin compound; the lubricant is calcium stearate; and the antioxidant is a complex system of hindered phenols and phosphites.

[0012] The preparation method of the high-barrier antibacterial rubber-plastic composite material of the present invention includes the following steps: Step 1, Pretreatment: Polyvinyl fluoride particles are vacuum dried at 80℃ for 12 hours, with the moisture content controlled below 0.05%; bio-based polyester elastomer is granulated and vacuum dried at 60℃ for 8 hours; silver-loaded zirconium phosphate is dried at 100℃ for 2 hours and mixed with γ-glycidoxypropyltrimethoxysilane at a mass ratio of 100:3 in a high-speed mixer, and reacted at 120℃ for 30 minutes to complete the surface modification.

[0013] Step 2, Initial mixing: Add the dried polyvinyl fluoride, bio-based polyester elastomer, surface-modified silver-loaded zirconium phosphate, bismaleimide compatibilizer and all processing aids into a high-speed mixer and mix for 8 minutes at a speed of 800 r / min and a temperature of 40℃ to obtain a uniform premix.

[0014] Step 3, Melt Blending and Reactive Extrusion: The premixed material is fed into a twin-screw extruder with a screw length-to-diameter ratio of 40:1. The temperature zones are set as follows: feeding section 160℃, compression section 180℃, metering section 200℃, and die section 195℃; the screw speed is 200 r / min. During extrusion, bismaleimide decomposes above 180℃ to generate free radicals, initiating a grafting reaction between the PVF molecular chains and the bio-based polyester elastomer molecular chains. Simultaneously, the epoxy groups on the surface of the silver-loaded zirconium phosphate undergo ring-opening addition reactions with the carboxyl groups in the elastomer, forming a three-dimensional network interface structure. The material residence time in the extruder is 2.5 to 3.5 minutes to ensure complete reaction.

[0015] Step 4, Granulation and Molding: The extruded material is water-cooled, stretched, and granulated to obtain composite material masterbatch; this masterbatch can be directly used for injection molding, blown film molding, or calendering to obtain the final product.

[0016] As a preferred embodiment of the present invention, the method for synthesizing the bio-based polyester elastomer is as follows: Terephthalic acid, sebacic acid and 1,4-butanediol were added to an esterification reactor in a molar ratio of 0.35:0.35:0.30 and the esterification reaction was carried out at 180°C to 220°C for 2 hours under nitrogen protection to generate oligomers. The temperature was then raised to 240°C, and tetrabutyl titanate (0.05% of the total monomer mass) was added as a catalyst. Polycondensation reaction was carried out for 3 hours under a vacuum of less than 100 Pa to obtain a copolyester with an intrinsic viscosity of 1.2 dL / g to 1.6 dL / g. Finally, maleic anhydride was added in the molten state at an amount of 1.2% of the copolyester mass, and the mixture was reacted at 230°C for 20 minutes to convert some of the terminal hydroxyl groups into carboxyl groups, thereby obtaining a bio-based polyester elastomer with carboxyl groups in the side chain.

[0017] In another preferred embodiment of the present invention, the method for preparing the silver-loaded zirconium phosphate is as follows: Zirconium phosphate powder was dispersed in deionized water, silver nitrate solution was added, and the mixture was stirred at 60°C for 4 hours to allow silver ions to exchange into the interlayer of zirconium phosphate. After filtration, washing, and drying, the mixture was calcined in air at 300°C for 2 hours to obtain silver-loaded zirconium phosphate with a silver ion loading of 3.2 wt%. Subsequently, silane coupling treatment was performed as described above.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Bio-based polyester elastomers, due to the presence of terephthalic acid units in their main chain, exhibit a certain degree of polarity matching with PVF, reducing initial interfacial tension. Simultaneously, the carboxyl or epoxy groups introduced into their molecular chains can form C–O–C or C–C covalent bonds with PVF under free radical initiation, constructing a robust chemical interface and significantly enhancing the bonding strength between the two phases. Scanning electron microscopy observation revealed that the elastomer phase in the composite material cross-section was uniformly dispersed in spherical shapes, with a particle size distribution ranging from 0.5 μm to 2.0 μm, exhibiting no obvious debonding or pores, indicating good compatibility.

[0019] 2. Silver-loaded zirconium phosphate is oriented and anchored in the interface region between the two phases, which avoids agglomeration caused by enrichment in a single phase, and allows it to continue to release silver ions when the material surface is worn or microcracks are generated, thus achieving long-lasting antibacterial effect.

[0020] 3. The integrity of the PVF continuous phase is maintained, the gas barrier performance is not significantly deteriorated due to the introduction of the elastomer, and the mechanical properties of the material are significantly improved.

[0021] 4. The material has good processing stability and thermal stability, and is suitable for conventional plastic processing equipment. Detailed Implementation

[0022] This invention provides a high-barrier antibacterial rubber-plastic composite material and its preparation method, aiming to solve the interfacial defect problem caused by thermodynamic incompatibility between polyvinyl fluoride (PVC) and conventional elastomers in the prior art. This allows the material to maintain the excellent gas barrier properties of PVC while possessing high flexibility, impact resistance, and long-lasting antibacterial function. To achieve this objective, this invention uses a polyester-type elastomer with a bio-based origin, an ester-bonded main chain, and reactive functional groups introduced into the side chains as a flexible dispersed phase. Through an in-situ reactive compatibilization mechanism, a covalently bonded interfacial layer is constructed between the PVC continuous phase and the elastomer dispersed phase, effectively suppressing phase separation and enhancing the synergistic effect between the two phases.

[0023] The technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples, so as to ensure that those skilled in the art can fully understand and implement the present invention.

[0024] The specific parameters for the embodiment are as follows: Serial number Polyvinyl fluoride mass ratio Bio-based polyester elastomer mass ratio Nanoscale inorganic antibacterial agent mass ratio Reactive compatibilizer mass ratio Processing aid mass ratio Example 1 45% 35% 4.0% 2.5% 13.5% Example 2 65% 20% 1.5% 0.8% 12.7% Example 3 50% 30% 2.0% 1.2% 16.8% Example 4 55% 25% 3.0% 1.8% 15.2% Example 5 60% 28% 2.5% 2.0% 7.5% Example 6 48% 32% 3.5% 1.5% 15.0% Example 7 52% 22% 1.8% 2.2% 22.0% The specific parameters for the comparison are as follows: Serial number Polyvinyl fluoride mass ratio Flexible component mass ratio Antibacterial agent type and mass ratio Reactive compatibilizer mass ratio Processing aid mass ratio Comparative Example 1 55% Thermoplastic polyurethane 25% Modified silver-loaded zirconium phosphate 3.0% 1.8% 15.2% Comparative Example 2 55% Bio-based polyester elastomer 25% Modified silver-loaded zirconium phosphate 3.0% 0% 17.0% Comparative Example 3 55% Bio-based polyester elastomer 25% Unmodified silver-loaded zirconium phosphate 3.0% 1.8% 15.2% In all examples and comparative examples, the processing aids included organotin heat stabilizers, calcium stearate lubricants, and hindered phenolic and phosphite compound antioxidants in the same proportions; the bio-based polyester elastomers conformed to the structural and performance parameters of the present invention; and the reactive compatibilizers were all N,N'-(4-methyl-1,3-phenylene)bismaleimide.

[0025] Test method: Oxygen permeability: Tested according to the American Society for Testing and Materials (ASTM) standard D3985, under test conditions of 23 degrees Celsius and 50% relative humidity.

[0026] Water vapor transmission rate: Tested according to the American Society for Testing and Materials (ASTM) E96 standard, under test conditions of 38 degrees Celsius and 90% relative humidity.

[0027] Antibacterial rate: Tested according to the International Organization for Standardization 22196 standard, the test species are Escherichia coli and Staphylococcus aureus, and the antibacterial rate is tested simultaneously after 50 water washes and 1000 bends.

[0028] Tensile strength and elongation at break: Conventional polymer tensile testing methods were used, with a test rate of 50 mm per minute.

[0029] Tear strength: The conventional polymer material tear test method was used.

[0030] Low-temperature notched impact strength: Tested using conventional notched impact test methods at -20 degrees Celsius.

[0031] Thermal stability: Thermogravimetric analysis was performed under a nitrogen atmosphere at a heating rate of 10 degrees Celsius per minute, with the 5% weight loss temperature being tested.

[0032] Test data comparison table 1: Serial number Oxygen transmission rate Water vapor transmission rate Initial antibacterial rate Antibacterial rate after washing Antibacterial rate after bending Example 1 0.8 0.5 99.95% 99.90% 99.85% Example 2 1.2 0.5 99.90% 99.85% 99.80% Example 3 0.9 0.5 99.92% 99.88% 99.83% Example 4 1.0 0.5 99.93% 99.89% 99.84% Example 5 1.1 0.5 99.91% 99.87% 99.82% Example 6 0.85 0.5 99.94% 99.89% 99.85% Example 7 1.05 0.5 99.92% 99.88% 99.83% Comparative Example 1 3.0 1.2 95.00% 90.00% 88.00% Comparative Example 2 2.8 1.1 96.00% 92.00% 90.00% Comparative Example 3 2.6 1.0 97.00% 85.00% 82.00% Test data comparison table 2: Serial number Tensile strength (MPa) Elongation at break (%) Tear strength (kN / m) Low-temperature notched impact strength (kJ / m2) 5% weight loss temperature (℃) Example 1 28 410 110 58 325 Example 2 35 320 85 45 330 Example 3 30 380 95 52 328 Example 4 32 350 100 50 326 Example 5 34 330 90 48 329 Example 6 29 400 105 55 327 Example 7 31 360 98 53 328 Comparative Example 1 20 250 60 30 300 Comparative Example 2 22 280 65 35 305 Comparative Example 3 24 300 70 38 310 Note: Oxygen transmission rate is measured in cubic centimeters per mil (100 square inches per day at standard atmospheric pressure), and water vapor transmission rate is measured in grams per mil (100 square inches per day).

[0033] The oxygen permeability of all embodiments was controlled between 0.8 and 1.2, and the water vapor permeability was consistently between 0.5, far superior to the 1.0 to 1.2 of the comparative examples, demonstrating excellent gas barrier performance. Regarding antibacterial performance, the initial antibacterial rate of the embodiments all exceeded 99.9%, and remained above 99.8% after 50 washes and 1000 bends, exhibiting outstanding long-lasting effectiveness; while the antibacterial rate of the comparative examples was only a maximum of 97%, and decreased significantly after environmental testing.

[0034] In terms of mechanical properties, the tensile strength of the examples ranges from 28 to 35 MPa, the elongation at break ranges from 320% to 410%, the tear strength ranges from 85 to 110 kN / m, and the cryogenic notched impact strength ranges from 45 to 58 kJ / m², fully meeting the requirements of flexible products for high toughness and low-temperature impact resistance. Regarding thermal stability, the 5% weight loss temperature of the examples is not lower than 325 degrees Celsius, demonstrating good processing stability.

[0035] Comparative Example 1, due to the use of conventional thermoplastic polyurethane instead of bio-based polyester elastomer, has poor compatibility with polyvinyl fluoride, resulting in a significant decrease in barrier properties and mechanical properties; Comparative Example 2 lacks reactive compatibilizers, and there are no covalent bonds connecting the two phases at the interface, resulting in obvious phase separation, and all its properties are inferior to those of the examples; Comparative Example 3 uses unmodified antibacterial agents, which cannot be anchored at the interface between the two phases, and the antibacterial components are prone to migration and precipitation, resulting in insufficient long-term antibacterial properties.

[0036] The reactive functional groups of bio-based polyester elastomers, the free radical initiation effect of reactive compatibilizers, and the surface modification treatment of antibacterial agents synergistically solve the thermodynamic incompatibility problem between polyvinyl fluoride (PVC) and elastomers. By constructing a covalently bonded interface, the high-barrier framework of PVC is preserved while imparting high toughness to the material, and the antibacterial agent is directionally anchored, ultimately achieving the synergistic performance goals of high barrier properties, high toughness, and long-lasting antibacterial effect.

[0037] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. 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 high-barrier antibacterial rubber-plastic composite material, characterized in that, Composed of the following components by mass percentage: 45% to 65% polyvinyl fluoride, 20% to 35% bio-based polyester elastomer, 1.5% to 4.0% nano-sized inorganic antibacterial agent, 0.8% to 2.5% reactive compatibilizer, and the balance of processing aids.

2. The high-barrier antibacterial rubber-plastic composite material according to claim 1, characterized in that, The bio-based polyester elastomer is an aliphatic-aromatic copolyester elastomer, the main chain of which is formed by the condensation polymerization of terephthalic acid, sebacic acid and 1,4-butanediol, and carboxyl or epoxy functional groups are introduced at the ends of the molecular chain or on the side chain, with a functional group content of 0.8 mmol / g to 1.5 mmol / g.

3. The high-barrier antibacterial rubber-plastic composite material according to claim 1, characterized in that, The nanoscale inorganic antibacterial agent is silver-loaded zirconium phosphate surface-treated with γ-glycidoxypropyltrimethoxysilane, with an average particle size of 30 nm to 80 nm and a silver ion loading of 2.5 wt% to 4.0 wt%.

4. The high-barrier antibacterial rubber-plastic composite material according to claim 1, characterized in that, The reactive compatibilizer is N,N'-(4-methyl-1,3-phenylene)bismaleimide.

5. The high-barrier antibacterial rubber-plastic composite material according to claim 1, characterized in that, In the bio-based polyester elastomer, the molar percentage of terephthalic acid unit is 30% to 45%, the molar percentage of sebacic acid unit is 25% to 40%, and the molar percentage of 1,4-butanediol is 30% to 45%.

6. The high-barrier antibacterial rubber-plastic composite material according to claim 5, characterized in that, The bio-based polyester elastomer is obtained by adding 1.2% by mass of maleic anhydride to the copolyester melt obtained by polycondensation and reacting it at 230°C for 20 minutes to convert the terminal hydroxyl groups into carboxyl groups.

7. The high-barrier antibacterial rubber-plastic composite material according to claim 3, characterized in that, After surface silane coupling treatment, the silver-loaded zirconium phosphate has a surface epoxy group density of 0.6 to 1.0 groups / nm², a specific surface area of ​​40 m² / g to 70 m² / g, and is oriented and anchored to the two-phase interface region of polyvinyl fluoride and bio-based polyester elastomer.

8. The high-barrier antibacterial rubber-plastic composite material according to claim 1, characterized in that, The processing aids include: organotin heat stabilizers, calcium stearate lubricants, and hindered phenolic and phosphite compound antioxidants.

9. The high-barrier antibacterial rubber-plastic composite material according to claim 8, characterized in that, The organotin heat stabilizer is dibutyltin dilaurate, the hindered phenol is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and the phosphite is tris(2,4-di-tert-butylphenyl)phosphite, with a mass ratio of 1:

1.

10. A method for preparing a high-barrier antibacterial rubber-plastic composite material as described in any one of claims 1 to 9, characterized in that, Includes the following steps: S10: Drying and surface modification treatments were performed on polyvinyl fluoride, bio-based polyester elastomer and silver-loaded zirconium phosphate, respectively. S20: Mix the components at 40℃ and 800r / min for 8 minutes to obtain a premix; S30: The premixed material is fed into a twin-screw extruder with a length-to-diameter ratio of 40:

1. Melt blending and reactive extrusion are carried out under the following conditions: feeding section 160℃, compression section 180℃, metering section 200℃, die section 195℃, and screw speed 200r / min. The material residence time is 2.5 to 3.5 minutes. S40: The extrudate is water-cooled, stretched, and pelletized to obtain composite material masterbatch.