Antibacterial flame-retardant three-layer co-extrusion bopp film and preparation method thereof

Abstract

The application relates to an antibacterial and flame-retardant three-layer co-extrusion BOPP film and a preparation method thereof. On the basis of original BOPP film production processes and equipment, a diatomite / zinc oxide / silver chloride type antibacterial agent and a cobalt-based metal organic framework / ammonium polyphosphate type flame-retardant filler are used as antibacterial and flame-retardant additives, so that good antibacterial and flame-retardant effects are achieved, and the problems of poor antibacterial property and poor flame-retardant property of the BOPP film are solved in the research and development process.

Description

Technical Field

[0001] This invention relates to the field of BOPP film processing technology, specifically to an antibacterial and flame-retardant three-layer co-extruded BOPP film and its preparation method. Background Technology

[0002] The production of biaxially oriented polypropylene (BOPP) film involves first forming molten polypropylene into sheets or thick films using a narrow die head, then stretching it simultaneously or in stages in two perpendicular directions (longitudinal and transverse) at a specific temperature and speed in a specialized stretching machine. The resulting film undergoes appropriate cooling or heat treatment, or special processing (such as corona treatment or coating). BOPP film produced through biaxial stretching exhibits significantly improved mechanical properties, with changes in transparency, thermal properties, and barrier properties, better meeting the needs of various fields and making it the most widely used printing film currently available.

[0003] Due to the oriented molecular structure of BOPP film, it possesses high physical stability, high mechanical strength, toughness, and wear resistance. It also boasts advantages such as light weight, non-toxicity, odorlessness, good printability, and good transparency. However, polypropylene has a low limiting oxygen index (LOI), only around 18%, making it easily combustible and producing a large amount of smoke during combustion, posing a significant safety hazard. Furthermore, with increasing demands for healthy living, antibacterial products are becoming more popular. Traditional BOPP packaging films, however, suffer from poor air and water permeability, resulting in limited antibacterial properties and susceptibility to mold and microbial contamination.

[0004] Therefore, modifying BOPP and related products with flame retardant and antibacterial properties to prepare antibacterial and flame retardant BOPP films with integrated flame retardant and antibacterial functions is in line with market development trends and has broad application prospects. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide an antibacterial and flame-retardant three-layer co-extruded BOPP film and its preparation method. Based on the existing BOPP film production process and equipment, suitable antibacterial and flame-retardant additives are selected to achieve good antibacterial and flame-retardant effects. In the research and development process, the problems of poor antibacterial and flame-retardant properties of BOPP film were solved.

[0006] This invention discloses an antibacterial and flame-retardant three-layer co-extruded BOPP film, which consists of an upper surface layer, an antibacterial and flame-retardant layer, and a lower surface layer from top to bottom.

[0007] Furthermore, the upper, antibacterial, and flame-retardant three-layer co-extruded BOPP film is prepared by melt co-extrusion.

[0008] Furthermore, the upper surface layer is made of the following raw materials in the indicated mass fractions: 95%–99% polypropylene (PP), 0.5%–2.5% anti-adhesion agent, and 0.5%–2.5% slip agent;

[0009] Furthermore, the antibacterial and flame-retardant layer is made of the following raw materials in the indicated mass fractions: 85%–95% polypropylene (PP), 3.7%–10.5% flame-retardant filler, 1%–3% antibacterial agent, 0.1%–0.5% antioxidant, 0.1%–0.5% compatibilizer, and 0.1%–0.5% dispersant;

[0010] Furthermore, the lower surface layer is made of the following raw materials in the indicated mass fractions: 95%–99% polypropylene (PP), 0.5%–2.5% anti-adhesion agent, and 0.5%–2.5% slip agent.

[0011] Furthermore, the thickness of the antibacterial and flame-retardant three-layer co-extruded BOPP film is 40-45 μm, the thickness of the upper surface layer accounts for 2.5%-5% of the total thickness of the antibacterial and flame-retardant three-layer co-extruded BOPP film, the thickness of the antibacterial and flame-retardant layer accounts for 90%-95% of the total thickness of the antibacterial and flame-retardant three-layer co-extruded BOPP film, and the thickness of the lower surface layer accounts for 2.5%-5% of the total thickness of the antibacterial and flame-retardant three-layer co-extruded BOPP film.

[0012] Furthermore, the PP in the upper surface layer, the antibacterial and flame-retardant layer, and the lower surface layer is isotactic polypropylene.

[0013] Furthermore, the anti-adhesion agent in the upper and lower surface layers is at least one of silica, talc, and kaolin.

[0014] Furthermore, the slip agent in the upper and lower surface layers is one of vinyl bis-stearamide (EBS), erucamide, oleamide, and polyethylene wax.

[0015] Furthermore, the antioxidant in the antibacterial flame retardant layer is one or more of antioxidant 168, antioxidant 1010 and antioxidant 1330, the compatibilizer is one of ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA) and ethylene-vinyl acetate copolymer (EVA), and the dispersant is polyethylene glycol.

[0016] Furthermore, the specific steps for preparing the flame-retardant filler in the antibacterial flame-retardant layer are as follows:

[0017] S1, a certain amount of cobalt nitrate, triethylamine, 4,4'-diaminodiphenylmethane, salicylaldehyde, ammonium polyphosphate, and anhydrous ethanol are measured into a reaction vessel and reacted at 70-90℃ for 8-10 hours. After cooling to room temperature, solution A is obtained.

[0018] S2, solution A is sequentially filtered and washed, and then dried at 50-70℃ for 12-14h to obtain a cobalt-based metal-organic framework / ammonium polyphosphate flame retardant filler.

[0019] Furthermore, in step S1, the mass ratio of cobalt nitrate, triethylamine, 4,4'-diaminodiphenylmethane, salicylaldehyde, ammonium polyphosphate, and anhydrous ethanol is (15-20):(30-40):(50-60):(90-100):(15-20):(110-120).

[0020] Furthermore, the specific steps of the preparation method of the antibacterial agent are as follows:

[0021] (1) A certain amount of diatomaceous earth, zinc chloride, potassium hydroxide and deionized water are placed in a reaction vessel and reacted at 90-110℃ for 8-12 hours. After filtration, a solid precipitate is obtained. The solid precipitate is dried at 50-70℃ for 10-12 hours and then calcined at 110-140℃ for 16-20 hours to obtain diatomaceous earth / zinc oxide.

[0022] (2) Measure a certain amount of diatomaceous earth / zinc oxide, potassium chloride, silver nitrate and deionized water, place them in a reactor dish, react at 80-100℃ for 10-12h, filter the product obtained from the reaction, and dry the solid obtained after filtration at 50-60℃ for 10-12h to obtain an antibacterial agent of the diatomaceous earth / zinc oxide / silver chloride type.

[0023] Furthermore, the mass ratio of diatomaceous earth, zinc chloride, potassium hydroxide, and deionized water in step (1) is (35-40):(5-8):(10-16):(125-135).

[0024] Furthermore, in step (2), the mass ratio of diatomaceous earth / zinc oxide, potassium chloride, silver nitrate, and deionized water is (24-28):(11-14):(18-22):(100-120).

[0025] This invention also provides a method for manufacturing an antibacterial and flame-retardant three-layer co-extruded BOPP film, specifically including the following steps:

[0026] (1) Mixing: Mix the raw material components in the upper surface layer, antibacterial flame retardant layer and lower surface layer according to the proportion, and disperse them evenly by high-speed mixer;

[0027] (2) Extrusion: The raw material of the uniformly dispersed antibacterial and flame-retardant layer is added to the main extruder for melt extrusion, and then filtered through a filter screen to obtain the melt of the antibacterial and flame-retardant layer; the raw material of the upper surface layer is added to the first auxiliary extruder and the raw material of the lower surface layer is added to the second auxiliary extruder for melt extrusion, and then filtered through a filter screen to obtain the melt of the upper surface layer and the melt of the lower surface layer respectively.

[0028] (3) Casting: The upper surface melt, antibacterial and flame retardant layer melt, and lower surface melt are combined and extruded in the lip of the die of the three-layer extruder in the order from top to bottom, and cast onto the surface of the chilling roller. Under the action of the chilling roller, water bath, and guide roller, a cast sheet is formed.

[0029] (4) Stretching: The cast film is drawn out and stretched longitudinally under the action of stretching rollers with different speeds at the front and rear of the longitudinal stretching machine and the heating roller in the middle; then it passes through the transverse stretching machine, where the two sides of the film are clamped by chain clamps and moved forward along the gradually widening track, passing through the heating zone and the shaping zone to increase the width of the film.

[0030] (5) Traction and winding: After edge trimming, thickness measurement and corona treatment, the film is rolled into a cylindrical film roll.

[0031] Furthermore, in step (2), the melt extrusion temperature of the main extruder is 225-235℃, the melt extrusion temperature of the first auxiliary extruder is 215℃-225℃, and the melt extrusion temperature of the second auxiliary extruder is 220℃-230℃.

[0032] Furthermore, in step (3), the surface temperature of the chilling roller is 15–35°C;

[0033] Furthermore, in step (4), the longitudinal stretching temperature is 65-75℃ and the transverse stretching temperature is 145-155℃.

[0034] Furthermore, in step (4), the longitudinal stretching ratio is 1.5-2.5 times, and the transverse stretching ratio is 6.5-7.5 times;

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) Highly effective antibacterial and flame-retardant properties. Testing showed that the prepared diatomaceous earth / zinc oxide / silver chloride type antibacterial agent exhibits highly effective antibacterial activity against Escherichia coli and Staphylococcus aureus, with significant antibacterial effects. Meanwhile, the cobalt-based metal-organic framework / ammonium polyphosphate type flame-retardant filler demonstrates excellent flame-retardant properties, achieving a V-0 rating in the vertical burning test (UL94). The resulting product is safe and non-toxic, the preparation method is simple, the raw materials are readily available, and mass production is possible. It can also be combined with polymer materials to prepare packaging materials with antibacterial and flame-retardant properties.

[0037] (2) The antibacterial mechanism of the antibacterial agent of the present invention is as follows: The antibacterial agent uses diatomaceous earth as a carrier. Silver chloride in diatomaceous earth / zinc oxide / silver chloride is positively charged when it comes into contact with water, and exhibits positive affinity when it encounters negatively charged Escherichia coli. This facilitates the induction of bacteria to aggregate on the surface of the material, and then releases Ag. +It disrupts the cell membrane of E. coli, thus killing the bacteria. ZnO, as an inorganic antibacterial agent, has high thermal stability and resistance to UV aging, making it one of the safest inorganic antibacterial agents. Diatomaceous earth-supported ZnO releases more reactive oxygen species under the same conditions, resulting in better antibacterial effects. In summary, the synergistic antibacterial properties of diatomaceous earth, zinc oxide, and silver chloride give it excellent antibacterial performance.

[0038] (3) The flame-retardant mechanism of the flame-retardant filler described in this invention is as follows: The porous structure of the cobalt-based metal-organic framework can restrict the diffusion of the matrix from the interior to the combustion surface, thereby inhibiting combustion. In the solid phase, the heat-resistant cobalt-based metal-organic framework acts as a thermal barrier, as its decomposition requires a large amount of heat. The porous metal oxides generated during combustion can not only delay the diffusion of heat but also inhibit the release of the matrix from the solid phase to the combustion zone. Ammonium polyphosphate can not only inhibit the volatilization of flammable substances and the formation of new free radicals but also reduce the diffusion of oxygen. Therefore, ammonium polyphosphate plays a flame-retardant role in both the solid and gas phases. This synergistic effect gives the cobalt-based metal-organic framework / ammonium polyphosphate type flame-retardant filler high-efficiency flame-retardant performance. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the structure of the antibacterial and flame-retardant three-layer co-extruded BOPP film of the present invention. In the figure: 1 is the upper surface layer, 2 is the antibacterial and flame-retardant layer, and 3 is the lower surface layer. Detailed Implementation

[0040] To better understand the content of this invention, it will be further described below with reference to specific embodiments and accompanying drawings. The following embodiments are based on the technology of this invention and provide detailed implementation methods and operating steps, but the scope of protection of this invention is not limited to the following embodiments.

[0041] The materials used in the following embodiments and comparative examples:

[0042] Isotactic polypropylene, Daqing Refining & Chemical Co., Ltd., China National Petroleum Corporation; cobalt nitrate, Shandong Changyao New Materials Co., Ltd.; triethylamine, Shandong Duoju Chemical Co., Ltd.; 4,4'-diaminodiphenylmethane, Shandong Chenyu Chemical Co., Ltd.; anhydrous ethanol, Shanghai Fangye Chemical Co., Ltd.; salicylaldehyde, Jinan Wenzhu Chemical Co., Ltd.; ammonium polyphosphate, Jiangsu Xinsu New Materials Co., Ltd.; zinc chloride, Shandong Desheng New Materials Co., Ltd.; diatomaceous earth, Chongqing Shihuan Mining Co., Ltd.; silver nitrate, Shandong Xuxiang Chemical Co., Ltd.; potassium chloride, Jinan Qinghai Chemical Co., Ltd.; silver nitrate, Shandong Xuxiang Chemical Co., Ltd.; antioxidants (antioxidant 168, antioxidant 1010, antioxidant 1330), BASF. Other raw materials, unless otherwise specified, were either commercially available or prepared using conventional methods in the art.

[0043] Example 1:

[0044] The antibacterial and flame-retardant three-layer co-extruded BOPP film described in this embodiment is composed of an upper surface layer, an antibacterial and flame-retardant layer, and a lower surface layer arranged from top to bottom. The upper surface layer, the antibacterial and flame-retardant layer, and the lower surface layer are prepared by melt co-extrusion.

[0045] The antibacterial and flame-retardant three-layer co-extruded BOPP film composition, by mass fraction, comprises: an upper layer of 95% isotactic polypropylene, 2.5% silica, and 2.5% EBS; an antibacterial and flame-retardant layer of 85% isotactic polypropylene, 10.5% flame-retardant filler, 3% antibacterial agent, 0.5% antioxidant 168, 0.5% EAA, and 0.5% polyethylene glycol; and a lower layer of 95% isotactic polypropylene, 2.5% silica, and 2.5% EBS.

[0046] The antibacterial and flame-retardant three-layer co-extruded BOPP film has a total thickness of 40 μm, with the upper surface layer accounting for 5% of the total thickness, the antibacterial and flame-retardant layer accounting for 90% of the total thickness, and the lower surface layer accounting for 5% of the total thickness.

[0047] In this embodiment, the preparation method of the flame-retardant filler in the antibacterial flame-retardant layer includes the following specific steps:

[0048] S1. A certain amount of cobalt nitrate, triethylamine, 4,4'-diaminodiphenylmethane, salicylaldehyde, ammonium polyphosphate, and anhydrous ethanol were measured and placed in a reaction vessel. The reaction was carried out at 70°C for 8 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain solution A. The mass ratio of cobalt nitrate, triethylamine, 4,4'-diaminodiphenylmethane, salicylaldehyde, ammonium polyphosphate, and anhydrous ethanol was 15:30:50:90:15:110.

[0049] S2, solution A was sequentially filtered and washed, and then dried at 50℃ for 12h to obtain a cobalt-based metal-organic framework / ammonium polyphosphate flame retardant filler;

[0050] In this embodiment, the specific steps of the preparation method of the antibacterial agent are as follows:

[0051] (1) A certain amount of diatomaceous earth, zinc chloride, potassium hydroxide and deionized water were measured and placed in a reaction vessel. The reaction was carried out at 90°C for 8 hours. After filtration, a solid precipitate was obtained. The solid precipitate was dried at 50°C for 10 hours and then calcined at 110°C for 16 hours to obtain diatomaceous earth / zinc oxide. The mass ratio of diatomaceous earth, zinc chloride, potassium hydroxide and deionized water was 35:5:10:125.

[0052] (2) Take a certain amount of diatomaceous earth / zinc oxide, potassium chloride, silver nitrate and deionized water obtained in step (1), place them in a reactor dish, react at 80°C for 10 h, filter the product obtained from the reaction, and dry the solid obtained after filtration at 50°C for 10 h to obtain an antibacterial agent of the diatomaceous earth / zinc oxide / silver chloride type, wherein the mass ratio of diatomaceous earth / zinc oxide, potassium chloride, silver nitrate and deionized water is 24:11:18:100.

[0053] The manufacturing method of the antibacterial and flame-retardant three-layer co-extruded BOPP film in this embodiment specifically includes the following steps:

[0054] (1) Mixing: Mix the raw material components in the upper surface layer, antibacterial flame retardant layer and lower surface layer according to the proportion, and disperse them evenly by high-speed mixer;

[0055] (2) Extrusion: The uniformly dispersed antibacterial and flame-retardant layer raw material is added to the main extruder for melt extrusion, and filtered through a filter screen to obtain an antibacterial and flame-retardant melt; the raw material of the upper surface layer is added to the first auxiliary extruder and the raw material of the lower surface layer is added to the second auxiliary extruder for melt extrusion, and then filtered through a filter screen to obtain the upper surface melt and the lower surface melt, respectively; wherein, the melt extrusion temperature of the main extruder is 230℃, the melt extrusion temperature of the first auxiliary extruder is 220℃, and the melt extrusion temperature of the second auxiliary extruder is 225℃;

[0056] (3) Casting: The upper surface melt, antibacterial and flame retardant layer melt, and lower surface melt are combined and extruded in the die lip of a three-layer extruder in the order from top to bottom, and cast onto the surface of the chilling roller. The surface temperature of the chilling roller is 25°C. Under the action of the chilling roller, water bath, and guide roller, a cast sheet is formed.

[0057] (4) Stretching: The cast film is drawn out and stretched longitudinally under the action of stretching rollers with different speeds before and after the longitudinal stretching machine and the heating roller in the middle; then it passes through the transverse stretching machine, where the two sides of the film are clamped by chain clamps and moved forward along the gradually widening track, passing through the heating zone and the shaping zone to increase the width of the film; the longitudinal stretching temperature is 70℃ and the transverse stretching temperature is 150℃.

[0058] (5) Traction and winding: After edge trimming, thickness measurement and corona treatment, the film is rolled into a cylindrical film roll, with a longitudinal stretching ratio of 1.5 times and a transverse stretching ratio of 6.5 times.

[0059] Example 2:

[0060] The antibacterial and flame-retardant three-layer co-extruded BOPP film described in this embodiment is composed of an upper surface layer, an antibacterial and flame-retardant layer, and a lower surface layer arranged from top to bottom. The upper surface layer, the antibacterial and flame-retardant layer, and the lower surface layer are prepared by melt co-extrusion.

[0061] The antibacterial and flame-retardant three-layer co-extruded BOPP film composition, by mass fraction, comprises: an upper layer of 96% isotactic polypropylene, 2% silica, and 2% EBS; an antibacterial and flame-retardant layer of 87.5% isotactic polypropylene, 8.8% flame-retardant filler, 2.5% antibacterial agent, 0.4% antioxidant 168, 0.4% EAA, and 0.4% polyethylene glycol; and a lower layer of 96% isotactic polypropylene, 2% silica, and 2% EBS.

[0062] The antibacterial and flame-retardant three-layer co-extruded BOPP film has a total thickness of 40 μm, with the upper surface layer accounting for 5% of the total thickness, the antibacterial and flame-retardant layer accounting for 90% of the total thickness, and the lower surface layer accounting for 5% of the total thickness.

[0063] In this embodiment, the preparation method of the flame-retardant filler in the antibacterial flame-retardant layer includes the following specific steps:

[0064] S1. A certain amount of cobalt nitrate, triethylamine, 4,4'-diaminodiphenylmethane, salicylaldehyde, ammonium polyphosphate, and anhydrous ethanol were measured and placed in a reaction vessel. The reaction was carried out at 75°C for 8.5 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain solution A. The mass ratio of cobalt nitrate, triethylamine, 4,4'-diaminodiphenylmethane, salicylaldehyde, ammonium polyphosphate, and anhydrous ethanol was 16:32:52:92:16:112.

[0065] S2, solution A was subjected to suction filtration and washing operations in sequence, and then dried at 55℃ for 12.5h to obtain a cobalt-based metal-organic framework / ammonium polyphosphate type flame retardant filler;

[0066] In this embodiment, the specific steps of the preparation method of the antibacterial agent are as follows:

[0067] (1) A certain amount of diatomaceous earth, zinc chloride, potassium hydroxide and deionized water were measured and placed in a reaction vessel. The reaction was carried out at 95℃ for 8.5h. After filtration, a solid precipitate was obtained. The solid precipitate was dried at 55℃ for 10.5h and then calcined at 110℃ for 17h to obtain diatomaceous earth / zinc oxide. The mass ratio of diatomaceous earth, zinc chloride, potassium hydroxide and deionized water was 36:6:12:130.

[0068] (2) Take a certain amount of diatomaceous earth / zinc oxide, potassium chloride, silver nitrate and deionized water obtained in step (1), place them in a reactor dish, react at 85°C for 10.5 h, filter the product obtained from the reaction, and dry the solid obtained after filtration at 55°C for 10.5 h to obtain an antibacterial agent of the diatomaceous earth / zinc oxide / silver chloride type, wherein the mass ratio of diatomaceous earth / zinc oxide, potassium chloride, silver nitrate and deionized water is 25:12:19:112.

[0069] The manufacturing method of the antibacterial and flame-retardant three-layer co-extruded BOPP film in this embodiment is the same as that in Embodiment 1.

[0070] Example 3:

[0071] The antibacterial and flame-retardant three-layer co-extruded BOPP film described in this embodiment is composed of an upper surface layer, an antibacterial and flame-retardant layer, and a lower surface layer arranged from top to bottom. The upper surface layer, the antibacterial and flame-retardant layer, and the lower surface layer are prepared by melt co-extrusion.

[0072] The antibacterial and flame-retardant three-layer co-extruded BOPP film composition, by mass fraction, comprises: an upper layer of 97% isotactic polypropylene, 1.5% silica, and 1.5% EBS; an antibacterial and flame-retardant layer of 90% isotactic polypropylene, 7.1% flame-retardant filler, 2% antibacterial agent, 0.3% antioxidant 168, 0.3% EAA, and 0.3% polyethylene glycol; and a lower layer of 97% isotactic polypropylene, 1.5% silica, and 1.5% EBS.

[0073] The antibacterial and flame-retardant three-layer co-extruded BOPP film has a total thickness of 40 μm, with the upper surface layer accounting for 5% of the total thickness, the antibacterial and flame-retardant layer accounting for 90% of the total thickness, and the lower surface layer accounting for 5% of the total thickness.

[0074] In this embodiment, the preparation method of the flame-retardant filler in the antibacterial flame-retardant layer includes the following specific steps:

[0075] S1. A certain amount of cobalt nitrate, triethylamine, 4,4'-diaminodiphenylmethane, salicylaldehyde, ammonium polyphosphate, and anhydrous ethanol were measured and placed in a reaction vessel. The reaction was carried out at 80°C for 9 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain solution A. The mass ratio of cobalt nitrate, triethylamine, 4,4'-diaminodiphenylmethane, salicylaldehyde, ammonium polyphosphate, and anhydrous ethanol was 18:35:55:95:18:115.

[0076] S2, solution A was sequentially filtered and washed, and then dried at 60℃ for 13h to obtain a cobalt-based metal-organic framework / ammonium polyphosphate flame retardant filler;

[0077] In this embodiment, the specific steps of the preparation method of the antibacterial agent are as follows:

[0078] (1) A certain amount of diatomaceous earth, zinc chloride, potassium hydroxide and deionized water were measured and placed in a reaction vessel. The reaction was carried out at 100℃ for 10h. After filtration, a solid precipitate was obtained. The solid precipitate was dried at 60℃ for 11h and then calcined at 120℃ for 18h to obtain diatomaceous earth / zinc oxide. The mass ratio of diatomaceous earth, zinc chloride, potassium hydroxide and deionized water was 37:7:15:130.

[0079] (2) Take a certain amount of diatomaceous earth / zinc oxide, potassium chloride, silver nitrate and deionized water obtained in step (1), place them in a reactor dish, react at 90°C for 11 h, filter the product obtained from the reaction, and dry the solid obtained after filtration at 55°C for 11 h to obtain an antibacterial agent of the diatomaceous earth / zinc oxide / silver chloride type, wherein the mass ratio of diatomaceous earth / zinc oxide, potassium chloride, silver nitrate and deionized water is 26:13:20:110.

[0080] The manufacturing method of the antibacterial and flame-retardant three-layer co-extruded BOPP film in this embodiment is the same as that in Embodiment 1.

[0081] Example 4:

[0082] The antibacterial and flame-retardant three-layer co-extruded BOPP film described in this embodiment is composed of an upper surface layer, an antibacterial and flame-retardant layer, and a lower surface layer arranged from top to bottom. The upper surface layer, the antibacterial and flame-retardant layer, and the lower surface layer are prepared by melt co-extrusion.

[0083] The antibacterial and flame-retardant three-layer co-extruded BOPP film composition, by mass fraction, comprises: an upper layer of 98% isotactic polypropylene, 1% silica, and 1% EBS; an antibacterial and flame-retardant layer of 92.5% isotactic polypropylene, 5.4% flame-retardant filler, 1.5% antibacterial agent, 0.2% antioxidant 168, 0.2% EAA, and 0.2% polyethylene glycol; and a lower layer of 98% isotactic polypropylene, 1% silica, and 1% EBS.

[0084] The antibacterial and flame-retardant three-layer co-extruded BOPP film has a total thickness of 40 μm, with the upper surface layer accounting for 5% of the total thickness, the antibacterial and flame-retardant layer accounting for 90% of the total thickness, and the lower surface layer accounting for 5% of the total thickness.

[0085] In this embodiment, the preparation method of the flame-retardant filler in the antibacterial flame-retardant layer includes the following specific steps:

[0086] S1. A certain amount of cobalt nitrate, triethylamine, 4,4'-diaminodiphenylmethane, salicylaldehyde, ammonium polyphosphate, and anhydrous ethanol were measured and placed in a reaction vessel. The reaction was carried out at 85°C for 9.5 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain solution A. The mass ratio of cobalt nitrate, triethylamine, 4,4'-diaminodiphenylmethane, salicylaldehyde, ammonium polyphosphate, and anhydrous ethanol was 15:40:55:100:20:115.

[0087] S2, solution A was subjected to suction filtration and washing operations in sequence, and then dried at 65℃ for 13.5h to obtain a cobalt-based metal-organic framework / ammonium polyphosphate type flame retardant filler;

[0088] In this embodiment, the specific steps of the preparation method of the antibacterial agent are as follows:

[0089] (1) A certain amount of diatomaceous earth, zinc chloride, potassium hydroxide and deionized water were measured and placed in a reaction vessel. The reaction was carried out at 105℃ for 11 hours. After filtration, a solid precipitate was obtained. The solid precipitate was dried at 65℃ for 11.5 hours and then calcined at 130℃ for 19 hours to obtain diatomaceous earth / zinc oxide. The mass ratio of diatomaceous earth, zinc chloride, potassium hydroxide and deionized water was 35:8:15:130.

[0090] (2) Take a certain amount of diatomaceous earth / zinc oxide, potassium chloride, silver nitrate and deionized water obtained in step (1), place them in a reactor dish, react at 95°C for 11.5 h, filter the product obtained from the reaction, and dry the solid obtained after filtration at 55°C for 11.5 h to obtain an antibacterial agent of the diatomaceous earth / zinc oxide / silver chloride type, wherein the mass ratio of diatomaceous earth / zinc oxide, potassium chloride, silver nitrate and deionized water is 27:14:21:115.

[0091] The manufacturing method of the antibacterial and flame-retardant three-layer co-extruded BOPP film in this embodiment is the same as that in Embodiment 1.

[0092] Example 5:

[0093] The antibacterial and flame-retardant three-layer co-extruded BOPP film described in this embodiment is composed of an upper surface layer, an antibacterial and flame-retardant layer, and a lower surface layer arranged from top to bottom. The upper surface layer, the antibacterial and flame-retardant layer, and the lower surface layer are prepared by melt co-extrusion.

[0094] The antibacterial and flame-retardant three-layer co-extruded BOPP film composition, by mass fraction, comprises: an upper layer of 99% isotactic polypropylene, 0.5% silica, and 0.5% EBS; an antibacterial and flame-retardant layer of 95% isotactic polypropylene, 3.7% flame-retardant filler, 1% antibacterial agent, 0.1% antioxidant 168, 0.1% EAA, and 0.1% polyethylene glycol; and a lower layer of 99% isotactic polypropylene, 0.5% silica, and 0.5% EBS.

[0095] The antibacterial and flame-retardant three-layer co-extruded BOPP film has a total thickness of 40 μm, with the upper surface layer accounting for 5% of the total thickness, the antibacterial and flame-retardant layer accounting for 90% of the total thickness, and the lower surface layer accounting for 5% of the total thickness.

[0096] In this embodiment, the preparation method of the flame-retardant filler in the antibacterial flame-retardant layer includes the following specific steps:

[0097] S1. A certain amount of cobalt nitrate, triethylamine, 4,4'-diaminodiphenylmethane, salicylaldehyde, ammonium polyphosphate, and anhydrous ethanol were measured and placed in a reaction vessel. The reaction was carried out at 90°C for 10 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain solution A. The mass ratio of cobalt nitrate, triethylamine, 4,4'-diaminodiphenylmethane, salicylaldehyde, ammonium polyphosphate, and anhydrous ethanol was 15:40:60:100:20:120.

[0098] S2, solution A was sequentially filtered and washed, and then dried at 70℃ for 14h to obtain a cobalt-based metal-organic framework / ammonium polyphosphate flame retardant filler;

[0099] In this embodiment, the specific steps of the preparation method of the antibacterial agent are as follows:

[0100] (1) A certain amount of diatomaceous earth, zinc chloride, potassium hydroxide and deionized water were measured and placed in a reaction vessel. The reaction was carried out at 110℃ for 12 hours. After filtration, a solid precipitate was obtained. The solid precipitate was dried at 70℃ for 12 hours and then calcined at 140℃ for 20 hours to obtain diatomaceous earth / zinc oxide. The mass ratio of diatomaceous earth, zinc chloride, potassium hydroxide and deionized water was 40:5:15:125.

[0101] (2) Take a certain amount of diatomaceous earth / zinc oxide, potassium chloride, silver nitrate and deionized water obtained in step (1), place them in a reactor dish, react at 100℃ for 12h, filter the product obtained from the reaction, and dry the solid obtained after filtration at 60℃ for 12h to obtain an antibacterial agent of the diatomaceous earth / zinc oxide / silver chloride type, wherein the mass ratio of diatomaceous earth / zinc oxide, potassium chloride, silver nitrate and deionized water is 25:12:20:120.

[0102] The manufacturing method of the antibacterial and flame-retardant three-layer co-extruded BOPP film in this embodiment is the same as that in Embodiment 1.

[0103] Comparative Example 1:

[0104] Following the structure of the antibacterial and flame-retardant three-layer co-extruded BOPP film in Example 1, the antibacterial and flame-retardant layer in this comparative example is made from the following raw materials by mass fraction: 98.5% isotactic polypropylene, 0.5% antioxidant, 0.5% compatibilizer, and 0.5% dispersant; the rest is the same as in Example 1.

[0105] The antibacterial and flame-retardant three-layer co-extruded BOPP film in this comparative example is manufactured using the same method as in Example 1.

[0106] Comparative Example 2:

[0107] Following the structure of the antibacterial and flame-retardant three-layer co-extruded BOPP film in Example 1, the antibacterial and flame-retardant layer in this comparative example is made from the following raw materials in the following mass fractions: 88% isotactic polypropylene, 10.5% flame-retardant filler, 0.5% antioxidant, 0.5% compatibilizer, and 0.5% dispersant; the rest is the same as in Example 1.

[0108] The antibacterial and flame-retardant three-layer co-extruded BOPP film in this comparative example is manufactured using the same method as in Example 1.

[0109] Comparative Example 3:

[0110] According to the structure of the antibacterial and flame-retardant three-layer co-extruded BOPP film in Example 1, the antibacterial and flame-retardant layer in this comparative example is made from the following raw materials in the following mass fractions: 95.5% isotactic polypropylene, 3% antibacterial agent, 0.5% antioxidant, 0.5% compatibilizer, and 0.5% dispersant; the others are the same as in Example 1.

[0111] The antibacterial and flame-retardant three-layer co-extruded BOPP film in this comparative example is manufactured using the same method as in Example 1.

[0112] The antibacterial and flame-retardant three-layer co-extruded BOPP films prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to performance tests, and the test results are shown in Table 1:

[0113] Table 1. Performance test results of antibacterial and flame-retardant three-layer co-extruded BOPP films in Examples 1-5 and Comparative Examples 1-3.

[0114]

[0115] As shown in Table 1, Examples 1-5 exhibit superior antibacterial properties compared to Comparative Examples 1 and 2, achieving an antibacterial rate of over 99% against Staphylococcus aureus and over 98% against Escherichia coli. Examples 1-5 also demonstrate superior flame-retardant properties compared to Comparative Examples 1 and 3, achieving a flame-retardant rating of V-0. In summary, the antibacterial and flame-retardant BOPP film prepared by the method provided by this invention possesses excellent antibacterial and flame-retardant properties and can be extended to various application fields of antibacterial and flame-retardant BOPP films.

[0116] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. The present invention can also have other embodiments based on the above structure and function, which will not be listed hereafter. Therefore, any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An antibacterial and flame-retardant three-layer co-extruded BOPP film, characterized in that, It consists of an upper surface layer, an antibacterial and flame-retardant layer, and a lower surface layer, which are prepared by melt co-extrusion. The antibacterial and flame-retardant layer is made from the following raw materials in the indicated mass fractions: 85%–95% polypropylene, 3.7%–10.5% flame-retardant filler, 1%–3% antibacterial agent, 0.1%–0.5% antioxidant, 0.1%–0.5% compatibilizer, and 0.1%–0.5% dispersant. The specific steps for preparing the flame-retardant filler in the antibacterial and flame-retardant layer are as follows: S1. A certain amount of cobalt nitrate, triethylamine, 4,4'-diaminodiphenylmethane, salicylaldehyde, ammonium polyphosphate, and anhydrous ethanol are measured and placed in a reaction vessel. The reaction is carried out at 70-90℃ for 8-10 hours. After cooling to room temperature, solution A is obtained. The mass ratio of cobalt nitrate, triethylamine, 4,4'-diaminodiphenylmethane, salicylaldehyde, ammonium polyphosphate, and anhydrous ethanol is (15-20):(30-40):(50-60):(90-100):(15-20):(110-120). S2, solution A is sequentially filtered and washed, and then dried at 50-70℃ for 12-14h to obtain a cobalt-based metal-organic framework / ammonium polyphosphate flame retardant filler. The specific steps for preparing the antibacterial agent are as follows: (1) A certain amount of diatomaceous earth, zinc chloride, potassium hydroxide and deionized water are measured into a reaction vessel and reacted at 90-110℃ for 8-12h. After filtration, a solid precipitate is obtained. The solid precipitate is dried at 50-70℃ for 10-12h and then calcined at 110-140℃ for 16-20h to obtain diatomaceous earth / zinc oxide. (2) Measure a certain amount of diatomaceous earth / zinc oxide, potassium chloride, silver nitrate and deionized water, place them in a reactor dish, react at 80-100℃ for 10-12h, filter the product obtained from the reaction, and dry the solid obtained after filtration at 50-60℃ for 10-12h to obtain an antibacterial agent of the diatomaceous earth / zinc oxide / silver chloride type.

2. The antibacterial and flame-retardant three-layer co-extruded BOPP film as described in claim 1, characterized in that, The upper surface layer is made of the following raw materials by mass fraction: 95%–99% polypropylene, 0.5%–2.5% anti-adhesion agent, and 0.5%–2.5% slip agent; the lower surface layer is made of the following raw materials by mass fraction: 95%–99% polypropylene, 0.5%–2.5% anti-adhesion agent, and 0.5%–2.5% slip agent.

3. The antibacterial and flame-retardant three-layer co-extruded BOPP film as described in claim 1, characterized in that, The thickness of the antibacterial and flame-retardant three-layer co-extruded BOPP film is 40-45 μm. The thickness of the upper surface layer accounts for 2.5%-5% of the total thickness of the antibacterial and flame-retardant three-layer co-extruded BOPP film, the thickness of the antibacterial and flame-retardant layer accounts for 90%-95% of the total thickness of the antibacterial and flame-retardant three-layer co-extruded BOPP film, and the thickness of the lower surface layer accounts for 2.5%-5% of the total thickness of the antibacterial and flame-retardant three-layer co-extruded BOPP film.

4. The antibacterial and flame-retardant three-layer co-extruded BOPP film as described in claim 2, characterized in that, The polypropylene in the upper and lower surface layers is isotactic polypropylene, the anti-adhesion agent is at least one of silica, talc and kaolin, and the slip agent is one of vinyl bis-stearamide, erucamide, oleamide and polyethylene wax.

5. The antibacterial and flame-retardant three-layer co-extruded BOPP film as described in claim 1, characterized in that, The polypropylene in the antibacterial and flame-retardant layer is isotactic polypropylene, the antioxidant is one or more of antioxidant 168, antioxidant 1010 and antioxidant 1330, the compatibilizer is one of ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, and the dispersant is polyethylene glycol.

6. The method for preparing the antibacterial and flame-retardant three-layer co-extruded BOPP film according to any one of claims 1 to 5, characterized in that, Specifically, the following steps are included: (1) Mixing: Mix the raw material components in the upper surface layer, antibacterial flame retardant layer and lower surface layer according to the proportion, and disperse them evenly by high-speed mixer; (2) Extrusion: The raw material of the uniformly dispersed antibacterial and flame-retardant layer is added to the main extruder for melt extrusion, and filtered through a filter screen to obtain the melt of the antibacterial and flame-retardant layer; the raw material of the upper surface layer is added to the first auxiliary extruder and the raw material of the lower surface layer is added to the second auxiliary extruder for melt extrusion, and then filtered through a filter screen to obtain the melt of the upper surface layer and the melt of the lower surface layer respectively. (3) Casting: The upper surface melt, antibacterial flame retardant layer melt, and lower surface melt are combined and extruded in the lip of the die of the three-layer extruder in the order from top to bottom, and cast onto the surface of the chilling roller. Under the action of the chilling roller, water bath, and guide roller, a cast sheet is formed. (4) Stretching: The cast film is drawn out and stretched longitudinally under the action of stretching rollers with different speeds before and after the longitudinal stretching machine and the heating roller in the middle; then it passes through the transverse stretching machine, where the two sides of the film are clamped by chain clamps and moved forward along the gradually widening track, passing through the heating zone and the shaping zone to increase the width of the film. (5) Traction and winding: After edge trimming, thickness measurement and corona treatment, the film is rolled into a cylindrical film roll; The mass ratio of diatomaceous earth, zinc chloride, potassium hydroxide and deionized water in step (1) is (35-40): (5-8): (10-16): (125-135); the mass ratio of diatomaceous earth / zinc oxide, potassium chloride, silver nitrate and deionized water in step (2) is (24-28): (11-14): (18-22): (100-120).

7. The preparation method according to claim 6, characterized in that, In step (2), the melt extrusion temperature of the main extruder is 225-235℃, the melt extrusion temperature of the first auxiliary extruder is 215℃-225℃, and the melt extrusion temperature of the second auxiliary extruder is 220℃-230℃; in step (3), the surface temperature of the quench roll is 15-35℃; in step (4), the longitudinal stretching temperature is 65-75℃, the transverse stretching temperature is 145-155℃, the longitudinal stretching rate is 1.5-2.5 times, and the transverse stretching rate is 6.5-7.5 times.

Images