Polyolefin composite film and preparation method thereof

Abstract

The invention discloses a polyolefin composite film and a preparation method thereof, the polyolefin composite film comprises an A-B-C three-layer structure which is overlapped up and down, and the total thickness is 50-80 microns; the A-layer structure accounts for 25-35% of the total thickness; the B layer structure accounts for 35-45% of the total thickness; the C layer structure accounts for 25-35% of the total thickness; the A-layer structure is prepared from the following raw materials: ternary polypropylene, a nanofiller 1, hydroxypropyl methyl cellulose, a compatilizer and a nucleating agent; the B-layer structure is prepared from the following raw materials: modified polypropylene, a nano filler 2, a compatilizer, a cross-linking agent and an antioxidant; the C-layer structure is prepared from the following raw materials: low-density polyethylene, a nano filler 3, a compatilizer, an antistatic agent and a flexibilizer; the polyolefin composite film prepared by the invention is a composite film with a three-layer film structure, so that the wear resistance, the aging resistance, the strength and the elongation of the composite film are improved; according to the polyolefin composite film prepared by the invention, the haze of the composite film is reduced, and the antistatic performance of the composite film is improved.

Description

Technical Field

[0001] The invention relates to the technical field of composite material preparation, and in particular to a polyolefin composite film and a preparation method thereof. Background Art

[0002] Film is a thin, soft, transparent sheet. Made of plastic, adhesive, rubber or other materials, the scientific explanation of film is: a 2D material formed by atoms, molecules or ions deposited on the surface of a substrate, such as optical film, composite film, superconducting film, polyester film, nylon film, plastic film, etc. Film is widely used in electronics, machinery, printing and other industries. Film material refers to a thin metal or organic layer with a thickness ranging from a single atom to several millimeters. Electronic semiconductor functional devices and optical coatings are the main applications of thin film technology.

[0003] Generally, it is a multi-layer co-extruded film. Its production is to make the melt of high molecular weight polypropylene into a sheet or thick film through a narrow and long die, and then in a special stretching machine, at a certain temperature and set speed, it is stretched in two vertical directions (longitudinal and transverse) at the same time or in steps, and then properly cooled or heat treated or special processed (such as corona, coating, etc.) to make a film. Due to the orientation of the stretched molecules, this film has good physical stability, mechanical strength, air tightness, high transparency and gloss, and is tough and wear-resistant. It is a widely used printing film. The thickness is generally 20 to 40 microns, and the most widely used is 20 microns. It is widely used in the packaging of food, candy, cigarettes, tea, juice, milk, textiles, etc., and is known as the "Queen of Packaging". The wide application of BOPP film, low pollution and protection of forest natural resources make it a more popular packaging material than paper and polyvinyl chloride (PVC); the simple and reliable manufacturing process and reasonable price make it a more commonly used packaging material than biaxially oriented polyester (BOPET) film and biaxially oriented nylon (BOPA) film.

[0004] With the development of economy and the improvement of people's living standards, the film industry is developing in a diversified, differentiated and high-speed trend, and the performance of the film has become the key research object of the industry. In view of the limitations and defects of the prior art, the present invention discloses a polyolefin composite film and a preparation method thereof. Summary of the invention

[0005] The purpose of the present invention is to provide a polyolefin composite film and a preparation method thereof, so as to fill the gap in the current technology.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing a polyolefin composite film, the polyolefin composite film comprising: an ABC three-layer structure stacked up and down, with a total thickness of 50 to 80 microns;

[0008] Among them: the A layer structure accounts for 25-35% of the total thickness;

[0009] The B layer structure accounts for 35-45% of the total thickness;

[0010] The C layer structure accounts for 25-35% of the total thickness;

[0011] The raw materials of the A layer structure are terpolymer, nano filler 1, hydroxypropyl methylcellulose, a compatibilizer, and a nucleating agent;

[0012] The raw materials of the B layer structure are modified polypropylene, nano filler 2, compatibilizer, crosslinking agent and antioxidant;

[0013] The raw materials of the C layer structure are low-density polyethylene, nano filler 3, compatibilizer, antistatic agent, and toughening agent, and the density of the low-density polyethylene is 0.915-0.925;

[0014] The nano filler 1 is modified nano boron nitride, and the preparation method of the modified nano boron nitride is:

[0015] S1. The nano hexagonal boron nitride is subjected to high-temperature calcination treatment, cooled, mixed with deionized water, subjected to ultrasonic treatment, centrifugally dispersed, and then dried in a vacuum drying oven to obtain dispersed hydroxylated nano hexagonal boron nitride, wherein the average particle size of the nano hexagonal boron nitride is 300-500nm, the temperature of the high-temperature calcination is controlled to be 1000-1100°C, the heating rate is 7-9°C / min, the ratio of the nano hexagonal boron nitride after high-temperature calcination to water is 7-8:500-600; the ultrasonic treatment time is 5-6h; the ultrasonic power is 130-150W; the centrifugal dispersion time is 65-75min; the vacuum drying temperature is 70-80°C, and the drying time is 14-16h;

[0016] S2, dissolving 1,3-propylenediamine in deionized water, and stirring at room temperature after ultrasonic treatment to obtain solution 1 for standby use, placing the dispersed hydroxylated nano hexagonal boron nitride prepared in step S1 in solution 1 and continuing ultrasonic treatment, stirring the reaction, centrifuging and separating the precipitate, washing and drying to obtain the modified nano boron nitride, the ratio of the dispersed hydroxylated nano hexagonal boron nitride to the solution 1 is 2-4:25; the ultrasonic power of the ultrasonic treatment is 100-110W, and the time is controlled to be 30-50min; the stirring rate is 550-650r / min, and the stirring time is controlled to be 3-4h; the centrifugal speed is 2500-2800rpm, and the centrifugal time is 32-35min; the drying temperature is 70-80℃, and the drying time is 14-16h;

[0017] The nanofiller 2 is modified nanographene, the modified substance and preparation method of the modified nanographene are the same as those of the nanofiller 1 modified nanoboron nitride, and the average particle size of the nanographene is 200-300nm;

[0018] The nano filler 3 is modified mesoporous nano silica, and the preparation method of the modified mesoporous nano silica is:

[0019] The mesoporous nano-silica is dissolved in deionized water, and after ultrasonic treatment, the solution 2 is prepared by stirring at room temperature for standby use. Under the protection of nitrogen atmosphere, a sodium hydroxide aqueous solution is added dropwise to the solution 2 to form a mixed solution 1, and isopropoxy tris (dioctyl pyrophosphate acyloxy) phthalate is added to the mixed solution 1 for co-condensation reaction to obtain modified mesoporous nano-silica; the average particle size of the mesoporous nano-silica is 100-200nm, and the ratio of the solution 2 to the isopropoxy tris (dioctyl pyrophosphate acyloxy) phthalate is 5:10-12; the stirring rate at room temperature is 550-600r / min, and the stirring time at room temperature is controlled to be 2-3h; the co-condensation reaction conditions are 5.5-5.8Kpa , the temperature is first raised to 100-105°C, the nitrogen purge flow rate is adjusted to 1.0L / min, respectively, the polycondensation is 10-12h, the temperature is again raised to 120-125°C, the nitrogen purge flow rate is adjusted to 1.2L / min, respectively, the polycondensation is 8-10h, the temperature is further raised to 150-155°C, the nitrogen purge flow rate is adjusted to 1.5L / min, respectively, the polycondensation is 8-10h, the temperature is further raised to 180-190°C, the nitrogen purge flow rate is adjusted to 2.0L / min, respectively, the polycondensation is 12-14h; the sodium hydroxide aqueous solution is 8wt% sodium hydroxide aqueous solution; the condition of dripping the sodium hydroxide aqueous solution is: dripping at room temperature for 18-20min;

[0020] The preparation method of the polyolefin composite film:

[0021] (1) Preparation of A-layer structure masterbatch:

[0022] Hydroxypropyl methylcellulose is dissolved in deionized water and subjected to ultrasonic treatment to obtain a hydroxypropyl methylcellulose solution; 90-95 parts of terpolymer, 8-10 parts of nanofiller 1, 4-5 parts of hydroxypropyl methylcellulose, 0.5-0.8 parts of a compatibilizer, and 2-3 parts of a nucleating agent are placed in a twin-screw extruder for melt blending and extrusion granulation; the main engine speed of the twin-screw extruder is 320-350 r / min, the main engine current is 21-22 A, the temperature of the twin-screw extruder head is controlled at 240-260° C., and the melt pressure is controlled at 2-2.2 MPa;

[0023] (2) Preparation of B-layer structure masterbatch:

[0024] 105-110 parts of modified polypropylene, 8-10 parts of nanofiller 2, 0.5-0.8 parts of compatibilizer, 1-2 parts of crosslinking agent, and 0.05-0.06 parts of antioxidant are placed in a twin-screw extruder for melt blending and extrusion granulation, wherein the modified polypropylene is a polypropylene-butadiene block copolymer; the main engine speed of the twin-screw extruder is 340-360r / min, the main engine current is 21-22A, the temperature of the twin-screw extruder head is controlled at 240-260°C, and the melt pressure is controlled at 1.9-2.1MPa;

[0025] (3) Preparation of C-layer structure masterbatch:

[0026] 100-105 parts of low-density polyethylene, 5-6 parts of maleic anhydride and an initiator are placed in a twin-screw extruder, the temperature of the twin-screw extruder head is controlled to be 178-180° C., the speed of the extruder host is controlled to be 40-45 r / min, after melt blending, the temperature is increased to 240-260° C., 8-10 parts of nano filler 3, 1-2 parts of compatibilizer, 3-4 parts of antistatic agent, 3-4 parts of toughening agent are added thereto, the main engine speed of the extruder is adjusted to 340-360 r / min, the main engine current is 21-22 A, and the melt pressure is controlled to be 1.9-2.1 MPa for melt blending and then extrusion granulation;

[0027] (4) Preparation of polyolefin composite film:

[0028] The A layer structure masterbatch prepared in step (1), the B layer structure masterbatch prepared in step (2), and the C layer structure masterbatch prepared in step (3) are melted in layers, and the three layers of melt are co-extruded to form a sheet, the sheet is cooled to form a cast sheet, and the cast sheet is longitudinally stretched, transversely stretched, heat-set, cooled, and rolled to obtain the polyolefin composite film; the longitudinal stretching preheating temperature is 86-87°C, and the longitudinal stretching stretching temperature is 110-120°C; the transverse stretching preheating temperature is 98-100°C, the stretching temperature is 110-120°C, and the heat-setting temperature is 230-240°C.

[0029] Preferably, the compatibilizer is selected from one or more of styrene-maleic anhydride copolymer, polyethylene glycol methacrylate, polyethylene glycol monoether acrylate, maleic anhydride grafted polypropylene, and maleic anhydride grafted polyethylene.

[0030] Preferably, the nucleating agent is selected from one or more of talc, mica, aluminum benzoate, tert-butylphenyl aluminum formate, 2,2′-methylenebis(4,6-tert-butylphenol)phosphine aluminum salt, dibenzylidene sorbitol, di(p-monomethylbenzylidene) sorbitol, and di(p-chlorosubstituted benzylidene) sorbitol.

[0031] Preferably, the crosslinking agent is selected from one or more of dicumyl peroxide, dibenzoyl peroxide, di-tert-butyl peroxide, tert-butyl peroxyisopropyl carbonate, dicyclohexyl peroxydicarbonate, tert-butyl perbenzoate, tert-butyl peroxyvalerate and diisopropyl peroxydicarbonate.

[0032] Preferably, the antioxidant is selected from one or more of antioxidant 1010, antioxidant 1098 and antioxidant 626.

[0033] Preferably, the antistatic agent is selected from one or more of sorbitan monostearate, glyceryl monostearate or monotriglyceride.

[0034] Preferably, the toughening agent is selected from one or more of epoxidized polybutadiene, fatty alcohol glycidyl ether, hydroxyl-terminated polyether, amino-terminated polyether, hydroxyl-terminated polyester, hydroxyl-terminated polyester ether, and isophorone diamine.

[0035] The present application also claims protection for a polyolefin composite film prepared by the above method.

[0036] Working mechanism of the present invention:

[0037] The film of the present invention is a three-layer film structure, wherein the A layer structure is based on ternary polypropylene, and modified nano boron nitride is added as a nano filler 1; the B layer structure is based on modified polypropylene, and modified nano graphene is added as a nano filler 2; the C layer structure is based on low-density polyethylene, and modified mesoporous nano silica is added as a nano filler 3; the three nano fillers are modified and added to the substrate respectively to prepare the master batch of each layer, and then the master batch of each layer is melt co-extruded to obtain the composite film of the present invention, so that the composite film of the present invention has higher wear resistance, anti-aging and antistatic properties, as well as higher elongation at break, tear strength and tensile strength.

[0038] Due to the application of the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0039] 1. The polyolefin composite film prepared by the present invention is a composite film with a three-layer film structure. Since the A-layer structure masterbatch is added with nanofiller 1, the wear resistance, aging resistance and antistatic performance of the composite film are improved; the B-layer structure masterbatch is added with nanofiller 2 to cooperate with the A-layer structure to improve the anti-aging performance of the composite film;

[0040] 2. The polyolefin composite film prepared by the present invention has improved elongation at break, tear strength and tensile strength of the composite film due to the addition of nanofiller 3 to the C-layer structure masterbatch, and on this basis, the haze of the composite film is also reduced, thereby improving the clarity of the film;

[0041] 3. The preparation method of the present invention is simple, easy to implement and suitable for popularization and application. DETAILED DESCRIPTION

[0042] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, a specific implementation scheme is now described in detail.

[0043] The present invention is further described below in conjunction with the examples, but the present invention is not limited to the following examples. The implementation conditions used in the examples can be further adjusted according to the different requirements of specific use, and the implementation conditions not indicated are conventional conditions in the industry. The technical features involved in each embodiment of the present invention can be combined with each other as long as they do not conflict with each other.

[0044] Example 1

[0045] This embodiment provides a method for preparing a polyolefin composite film, wherein the polyolefin composite film comprises: an ABC three-layer structure stacked up and down, with a total thickness of 70 microns;

[0046] Among them: the A layer structure accounts for 30% of the total thickness;

[0047] The B layer structure accounts for 40% of the total thickness;

[0048] The C layer structure accounts for 30% of the total thickness;

[0049] The raw materials of the A layer structure are terpolymer, nano filler 1, hydroxypropyl methylcellulose, polyethylene glycol monoether acrylate, and di(p-methylbenzylidene) sorbitol;

[0050] The raw materials of the B layer structure are modified polypropylene, nano filler 2, polyethylene glycol monoether acrylate, dicyclohexyl peroxydicarbonate, and antioxidant 1010;

[0051] The raw materials of the C layer structure are low-density polyethylene, nanofiller 3, polyethylene glycol monoether acrylate, sorbitan monostearate, and epoxidized polybutadiene, and the density of the low-density polyethylene is 0.920;

[0052] The nano filler 1 is modified nano boron nitride, and the preparation method of the modified nano boron nitride is:

[0053] S1. The nano hexagonal boron nitride is subjected to high-temperature calcination treatment, cooled, mixed with deionized water, subjected to ultrasonic treatment, centrifugally dispersed, and then dried in a vacuum drying oven to obtain dispersed hydroxylated nano hexagonal boron nitride, wherein the average particle size of the nano hexagonal boron nitride is 400 nm, the temperature of the high-temperature calcination is controlled to be 1050° C., the heating rate is 8° C. / min, the ratio of the nano hexagonal boron nitride after high-temperature calcination to water is 7:500; the ultrasonic treatment time is 6 h; the ultrasonic power is 140 W; the centrifugal dispersion time is 70 min; the vacuum drying temperature is 75° C., and the drying time is 15 h;

[0054] S2, dissolving 1,3-propylenediamine in deionized water, and stirring at room temperature after ultrasonic treatment to obtain solution 1 for standby use, placing the dispersed hydroxylated nano hexagonal boron nitride prepared in step S1 in solution 1 and continuing ultrasonic treatment, stirring the reaction, centrifuging and separating the precipitate, washing and drying to obtain the modified nano boron nitride, wherein the ratio of the dispersed hydroxylated nano hexagonal boron nitride to the solution 1 is 2:25; the ultrasonic power of the ultrasonic treatment is 110W, and the time is controlled to be 40min; the stirring rate is 600r / min, and the stirring time is controlled to be 4h; the centrifugal speed is 2600rpm, and the centrifugal time is 35min; the drying temperature is 75°C, and the drying time is 16h;

[0055] The nanofiller 2 is modified nanographene, the modified substance and preparation method of the modified nanographene are the same as those of the nanofiller 1 modified nanoboron nitride, and the average particle size of the nanographene is 250nm;

[0056] The nano filler 3 is modified mesoporous nano silica, and the preparation method of the modified mesoporous nano silica is:

[0057] The mesoporous nano-silica was dissolved in deionized water, and after ultrasonic treatment, the solution 2 was prepared by stirring at room temperature for standby use. Under the protection of nitrogen atmosphere, sodium hydroxide aqueous solution was added dropwise to the solution 2 to form a mixed solution 1. Isopropoxy tris (dioctyl pyrophosphate acyloxy) phthalate was added to the mixed solution 1 for co-condensation reaction to obtain modified mesoporous nano-silica; the average particle size of the mesoporous nano-silica was 180 nm, and the ratio of the solution 2 to the isopropoxy tris (dioctyl pyrophosphate acyloxy) phthalate was 5:11; the stirring rate at room temperature was 600 r / min, and the stirring time at room temperature was controlled to be 3 h; the co-condensation reaction conditions were At 5.5Kpa, the temperature was first raised to 100°C, the nitrogen purge flow rate was adjusted to 1.0L / min, and the polycondensation was carried out for 10 hours. The temperature was raised to 120°C again, the nitrogen purge flow rate was adjusted to 1.2L / min, and the polycondensation was carried out for 8 hours. The temperature was further raised to 150°C, the nitrogen purge flow rate was adjusted to 1.5L / min, and the polycondensation was carried out for 8 hours. The temperature was further raised to 180°C, the nitrogen purge flow rate was adjusted to 2.0L / min, and the polycondensation was carried out for 12 hours. The sodium hydroxide aqueous solution was 8wt% sodium hydroxide aqueous solution. The condition for adding the sodium hydroxide aqueous solution was: adding at room temperature for 20 minutes.

[0058] The preparation method of the polyolefin composite film:

[0059] (1) Preparation of A-layer structure masterbatch:

[0060] Hydroxypropyl methylcellulose is dissolved in deionized water and ultrasonically treated to obtain a hydroxypropyl methylcellulose solution, 92 parts of terpolymer, 10 parts of nanofiller 1, 4 parts of hydroxypropyl methylcellulose, 0.6 parts of polyethylene glycol monoether acrylate, and 2 parts of di(p-methylbenzylidene)sorbitol are placed in a twin-screw extruder for melt blending and extrusion granulation, wherein the main engine speed of the twin-screw extruder is 330 r / min, the main engine current is 21 A, the temperature of the twin-screw extruder head is controlled at 250° C., and the melt pressure is controlled at 2.1 MPa;

[0061] (2) Preparation of B-layer structure masterbatch:

[0062] 110 parts of modified polypropylene, 10 parts of nanofiller 2, 0.6 parts of polyethylene glycol monoether acrylate, 1 part of dicyclohexyl peroxydicarbonate, and 0.06 parts of antioxidant 1010 are placed in a twin-screw extruder for melt blending and extrusion granulation, wherein the modified polypropylene is a polypropylene-butadiene block copolymer; the main engine speed of the twin-screw extruder is 350 r / min, the main engine current is 21 A, the temperature of the twin-screw extruder head is controlled at 250° C., and the melt pressure is controlled at 2.0 MPa;

[0063] (3) Preparation of C-layer structure masterbatch:

[0064] 105 parts of low-density polyethylene, 5 parts of maleic anhydride and an initiator are placed in a twin-screw extruder, the temperature of the twin-screw extruder head is controlled to 180° C., the speed of the extruder host is controlled to 42 r / min, after melt blending, the temperature is increased to 250° C., 10 parts of nano filler 3, 1 part of polyethylene glycol monoether acrylate, 3 parts of sorbitan monostearate, and 3 parts of epoxidized polybutadiene are added thereto, the host speed of the extruder is adjusted to 350 r / min, the host current is 21 A, and the melt pressure is controlled to 2.0 MPa for melt blending and extrusion granulation;

[0065] (4) Preparation of polyolefin composite film:

[0066] The A layer structure masterbatch prepared in step (1), the B layer structure masterbatch prepared in step (2), and the C layer structure masterbatch prepared in step (3) are melted in layers, and the three layers of melt are co-extruded to form a sheet, and the sheet is cooled to form a cast sheet, and the cast sheet is longitudinally stretched, transversely stretched, heat-set, cooled, and rolled to obtain the polyolefin composite film; the longitudinal stretching preheating temperature is 86°C, and the longitudinal stretching stretching temperature is 115°C; the transverse stretching preheating temperature is 98°C, the stretching temperature is 115°C, and the heat-setting temperature is 240°C.

[0067] Example 2

[0068] This embodiment provides a method for preparing a polyolefin composite film, wherein the polyolefin composite film comprises: an ABC three-layer structure stacked up and down, with a total thickness of 70 microns;

[0069] Among them: the A layer structure accounts for 30% of the total thickness;

[0070] The B layer structure accounts for 40% of the total thickness;

[0071] The C layer structure accounts for 30% of the total thickness;

[0072] The raw materials of the A layer structure are terpolymer, nano filler 1, hydroxypropyl methylcellulose, polyethylene glycol monoether acrylate, and di(p-methylbenzylidene) sorbitol;

[0073] The raw materials of the B layer structure are modified polypropylene, nano filler 2, polyethylene glycol monoether acrylate, dicyclohexyl peroxydicarbonate, and antioxidant 1010;

[0074] The raw materials of the C layer structure are low-density polyethylene, nanofiller 3, polyethylene glycol monoether acrylate, sorbitan monostearate, and epoxidized polybutadiene, and the density of the low-density polyethylene is 0.920;

[0075] The nano filler 1 is modified nano boron nitride, and the preparation method of the modified nano boron nitride is:

[0076] S1. The nano hexagonal boron nitride is subjected to high-temperature calcination treatment, cooled, mixed with deionized water, subjected to ultrasonic treatment, centrifugally dispersed, and then dried in a vacuum drying oven to obtain dispersed hydroxylated nano hexagonal boron nitride, wherein the average particle size of the nano hexagonal boron nitride is 400 nm, the temperature of the high-temperature calcination is controlled to be 1050° C., the heating rate is 8° C. / min, the ratio of the nano hexagonal boron nitride after high-temperature calcination to water is 7:500; the ultrasonic treatment time is 6 h; the ultrasonic power is 140 W; the centrifugal dispersion time is 70 min; the vacuum drying temperature is 75° C., and the drying time is 15 h;

[0077] S2, dissolving 1,3-propylenediamine in deionized water, and stirring at room temperature after ultrasonic treatment to obtain solution 1 for standby use, placing the dispersed hydroxylated nano hexagonal boron nitride prepared in step S1 in solution 1 and continuing ultrasonic treatment, stirring the reaction, centrifuging and separating the precipitate, washing and drying to obtain the modified nano boron nitride, wherein the ratio of the dispersed hydroxylated nano hexagonal boron nitride to the solution 1 is 3:25; the ultrasonic power of the ultrasonic treatment is 110W, and the time is controlled to be 40min; the stirring rate is 600r / min, and the stirring time is controlled to be 4h; the centrifugal speed is 2600rpm, and the centrifugal time is 35min; the drying temperature is 75°C, and the drying time is 16h;

[0078] The nanofiller 2 is modified nanographene, the modified substance and preparation method of the modified nanographene are the same as those of the nanofiller 1 modified nanoboron nitride, and the average particle size of the nanographene is 250nm;

[0079] The nano filler 3 is modified mesoporous nano silica, and the preparation method of the modified mesoporous nano silica is:

[0080] The mesoporous nano-silica was dissolved in deionized water, and after ultrasonic treatment, the solution 2 was prepared by stirring at room temperature for standby use. Under the protection of nitrogen atmosphere, sodium hydroxide aqueous solution was added dropwise to the solution 2 to form a mixed solution 1. Isopropoxy tris (dioctyl pyrophosphate acyloxy) phthalate was added to the mixed solution 1 for co-condensation reaction to obtain modified mesoporous nano-silica; the average particle size of the mesoporous nano-silica was 180 nm, and the ratio of the solution 2 to the isopropoxy tris (dioctyl pyrophosphate acyloxy) phthalate was 5:11; the stirring rate at room temperature was 600 r / min, and the stirring time at room temperature was controlled to be 3 h; the co-condensation reaction conditions were At 5.5Kpa, the temperature was first raised to 100°C, the nitrogen purge flow rate was adjusted to 1.0L / min, and the polycondensation was carried out for 10 hours. The temperature was raised to 120°C again, the nitrogen purge flow rate was adjusted to 1.2L / min, and the polycondensation was carried out for 8 hours. The temperature was further raised to 150°C, the nitrogen purge flow rate was adjusted to 1.5L / min, and the polycondensation was carried out for 8 hours. The temperature was further raised to 180°C, the nitrogen purge flow rate was adjusted to 2.0L / min, and the polycondensation was carried out for 12 hours. The sodium hydroxide aqueous solution was 8wt% sodium hydroxide aqueous solution. The condition for adding the sodium hydroxide aqueous solution was: adding at room temperature for 20 minutes.

[0081] The preparation method of the polyolefin composite film:

[0082] (1) Preparation of A-layer structure masterbatch:

[0083] Hydroxypropyl methylcellulose is dissolved in deionized water and ultrasonically treated to obtain a hydroxypropyl methylcellulose solution, 92 parts of terpolymer, 10 parts of nanofiller 1, 4 parts of hydroxypropyl methylcellulose, 0.6 parts of polyethylene glycol monoether acrylate, and 2 parts of di(p-methylbenzylidene)sorbitol are placed in a twin-screw extruder for melt blending and extrusion granulation, wherein the main engine speed of the twin-screw extruder is 330 r / min, the main engine current is 21 A, the temperature of the twin-screw extruder head is controlled at 250° C., and the melt pressure is controlled at 2.1 MPa;

[0084] (2) Preparation of B-layer structure masterbatch:

[0085] 110 parts of modified polypropylene, 10 parts of nanofiller 2, 0.6 parts of polyethylene glycol monoether acrylate, 1 part of dicyclohexyl peroxydicarbonate, and 0.06 parts of antioxidant 1010 are placed in a twin-screw extruder for melt blending and extrusion granulation, wherein the modified polypropylene is a polypropylene-butadiene block copolymer; the main engine speed of the twin-screw extruder is 350 r / min, the main engine current is 21 A, the temperature of the twin-screw extruder head is controlled at 250° C., and the melt pressure is controlled at 2.0 MPa;

[0086] (3) Preparation of C-layer structure masterbatch:

[0087] 105 parts of low-density polyethylene, 5 parts of maleic anhydride and an initiator are placed in a twin-screw extruder, the temperature of the twin-screw extruder head is controlled to 180° C., the speed of the extruder host is controlled to 42 r / min, after melt blending, the temperature is increased to 250° C., 10 parts of nano filler 3, 1 part of polyethylene glycol monoether acrylate, 3 parts of sorbitan monostearate, and 3 parts of epoxidized polybutadiene are added thereto, the host speed of the extruder is adjusted to 350 r / min, the host current is 21 A, and the melt pressure is controlled to 2.0 MPa for melt blending and extrusion granulation;

[0088] (4) Preparation of polyolefin composite film:

[0089] The A layer structure masterbatch prepared in step (1), the B layer structure masterbatch prepared in step (2), and the C layer structure masterbatch prepared in step (3) are melted in layers, and the three layers of melt are co-extruded to form a sheet, and the sheet is cooled to form a cast sheet, and the cast sheet is longitudinally stretched, transversely stretched, heat-set, cooled, and rolled to obtain the polyolefin composite film; the longitudinal stretching preheating temperature is 86°C, and the longitudinal stretching stretching temperature is 115°C; the transverse stretching preheating temperature is 98°C, the stretching temperature is 115°C, and the heat-setting temperature is 240°C.

[0090] Example 3

[0091] This embodiment provides a method for preparing a polyolefin composite film, wherein the polyolefin composite film comprises: an ABC three-layer structure stacked up and down, with a total thickness of 70 microns;

[0092] Among them: the A layer structure accounts for 30% of the total thickness;

[0093] The B layer structure accounts for 40% of the total thickness;

[0094] The C layer structure accounts for 30% of the total thickness;

[0095] The raw materials of the A layer structure are terpolymer, nano filler 1, hydroxypropyl methylcellulose, polyethylene glycol monoether acrylate, and di(p-methylbenzylidene) sorbitol;

[0096] The raw materials of the B layer structure are modified polypropylene, nano filler 2, polyethylene glycol monoether acrylate, dicyclohexyl peroxydicarbonate, and antioxidant 1010;

[0097] The raw materials of the C layer structure are low-density polyethylene, nanofiller 3, polyethylene glycol monoether acrylate, sorbitan monostearate, and epoxidized polybutadiene, and the density of the low-density polyethylene is 0.920;

[0098] The nano filler 1 is modified nano boron nitride, and the preparation method of the modified nano boron nitride is:

[0099] S1. The nano hexagonal boron nitride is subjected to high-temperature calcination treatment, cooled, mixed with deionized water, subjected to ultrasonic treatment, centrifugally dispersed, and then dried in a vacuum drying oven to obtain dispersed hydroxylated nano hexagonal boron nitride, wherein the average particle size of the nano hexagonal boron nitride is 400 nm, the temperature of the high-temperature calcination is controlled to be 1050° C., the heating rate is 8° C. / min, the ratio of the nano hexagonal boron nitride after high-temperature calcination to water is 7:500; the ultrasonic treatment time is 6 h; the ultrasonic power is 140 W; the centrifugal dispersion time is 70 min; the vacuum drying temperature is 75° C., and the drying time is 15 h;

[0100] S2, dissolving 1,3-propylenediamine in deionized water, and stirring at room temperature after ultrasonic treatment to obtain solution 1 for standby use, placing the dispersed hydroxylated nano hexagonal boron nitride prepared in step S1 in solution 1 and continuing ultrasonic treatment, stirring the reaction, centrifuging and separating the precipitate, washing and drying to obtain the modified nano boron nitride, wherein the ratio of the dispersed hydroxylated nano hexagonal boron nitride to the solution 1 is 4:25; the ultrasonic power of the ultrasonic treatment is 110W, and the time is controlled to be 40min; the stirring rate is 600r / min, and the stirring time is controlled to be 4h; the centrifugal speed is 2600rpm, and the centrifugal time is 35min; the drying temperature is 75°C, and the drying time is 16h;

[0101] The nanofiller 2 is modified nanographene, the modified substance and preparation method of the modified nanographene are the same as those of the nanofiller 1 modified nanoboron nitride, and the average particle size of the nanographene is 250nm;

[0102] The nano filler 3 is modified mesoporous nano silica, and the preparation method of the modified mesoporous nano silica is:

[0103] The mesoporous nano-silica was dissolved in deionized water, and after ultrasonic treatment, the solution 2 was prepared by stirring at room temperature for standby use. Under the protection of nitrogen atmosphere, sodium hydroxide aqueous solution was added dropwise to the solution 2 to form a mixed solution 1. Isopropoxy tris (dioctyl pyrophosphate acyloxy) phthalate was added to the mixed solution 1 for co-condensation reaction to obtain modified mesoporous nano-silica; the average particle size of the mesoporous nano-silica was 180 nm, and the ratio of the solution 2 to the isopropoxy tris (dioctyl pyrophosphate acyloxy) phthalate was 5:11; the stirring rate at room temperature was 600 r / min, and the stirring time at room temperature was controlled to be 3 h; the co-condensation reaction conditions were At 5.5Kpa, the temperature was first raised to 100°C, the nitrogen purge flow rate was adjusted to 1.0L / min, and the polycondensation was carried out for 10 hours. The temperature was raised to 120°C again, the nitrogen purge flow rate was adjusted to 1.2L / min, and the polycondensation was carried out for 8 hours. The temperature was further raised to 150°C, the nitrogen purge flow rate was adjusted to 1.5L / min, and the polycondensation was carried out for 8 hours. The temperature was further raised to 180°C, the nitrogen purge flow rate was adjusted to 2.0L / min, and the polycondensation was carried out for 12 hours. The sodium hydroxide aqueous solution was 8wt% sodium hydroxide aqueous solution. The condition for adding the sodium hydroxide aqueous solution was: adding at room temperature for 20 minutes.

[0104] The preparation method of the polyolefin composite film:

[0105] (1) Preparation of A-layer structure masterbatch:

[0106] Hydroxypropyl methylcellulose is dissolved in deionized water and ultrasonically treated to obtain a hydroxypropyl methylcellulose solution, 92 parts of terpolymer, 10 parts of nanofiller 1, 4 parts of hydroxypropyl methylcellulose, 0.6 parts of polyethylene glycol monoether acrylate, and 2 parts of di(p-methylbenzylidene)sorbitol are placed in a twin-screw extruder for melt blending and extrusion granulation, wherein the main engine speed of the twin-screw extruder is 330 r / min, the main engine current is 21 A, the temperature of the twin-screw extruder head is controlled at 250° C., and the melt pressure is controlled at 2.1 MPa;

[0107] (2) Preparation of B-layer structure masterbatch:

[0108] 110 parts of modified polypropylene, 10 parts of nanofiller 2, 0.6 parts of polyethylene glycol monoether acrylate, 1 part of dicyclohexyl peroxydicarbonate, and 0.06 parts of antioxidant 1010 are placed in a twin-screw extruder for melt blending and extrusion granulation, wherein the modified polypropylene is a polypropylene-butadiene block copolymer; the main engine speed of the twin-screw extruder is 350 r / min, the main engine current is 21 A, the temperature of the twin-screw extruder head is controlled at 250° C., and the melt pressure is controlled at 2.0 MPa;

[0109] (3) Preparation of C-layer structure masterbatch:

[0110] 105 parts of low-density polyethylene, 5 parts of maleic anhydride and an initiator are placed in a twin-screw extruder, the temperature of the twin-screw extruder head is controlled to 180° C., the speed of the extruder host is controlled to 42 r / min, after melt blending, the temperature is increased to 250° C., 10 parts of nano filler 3, 1 part of polyethylene glycol monoether acrylate, 3 parts of sorbitan monostearate, and 3 parts of epoxidized polybutadiene are added thereto, the host speed of the extruder is adjusted to 350 r / min, the host current is 21 A, and the melt pressure is controlled to 2.0 MPa for melt blending and extrusion granulation;

[0111] (4) Preparation of polyolefin composite film:

[0112] The A layer structure masterbatch prepared in step (1), the B layer structure masterbatch prepared in step (2), and the C layer structure masterbatch prepared in step (3) are melted in layers, and the three layers of melt are co-extruded to form a sheet, and the sheet is cooled to form a cast sheet, and the cast sheet is longitudinally stretched, transversely stretched, heat-set, cooled, and rolled to obtain the polyolefin composite film; the longitudinal stretching preheating temperature is 86°C, and the longitudinal stretching stretching temperature is 115°C; the transverse stretching preheating temperature is 98°C, the stretching temperature is 115°C, and the heat-setting temperature is 240°C.

[0113] Example 4

[0114] This embodiment provides a method for preparing a polyolefin composite film, wherein the polyolefin composite film comprises: an ABC three-layer structure stacked up and down, with a total thickness of 70 microns;

[0115] Among them: the A layer structure accounts for 30% of the total thickness;

[0116] The B layer structure accounts for 40% of the total thickness;

[0117] The C layer structure accounts for 30% of the total thickness;

[0118] The raw materials of the A layer structure are terpolymer, nano filler 1, hydroxypropyl methylcellulose, polyethylene glycol monoether acrylate, and di(p-methylbenzylidene) sorbitol;

[0119] The raw materials of the B layer structure are modified polypropylene, nano filler 2, polyethylene glycol monoether acrylate, dicyclohexyl peroxydicarbonate, and antioxidant 1010;

[0120] The raw materials of the C layer structure are low-density polyethylene, nanofiller 3, polyethylene glycol monoether acrylate, sorbitan monostearate, and epoxidized polybutadiene, and the density of the low-density polyethylene is 0.920;

[0121] The nano filler 1 is modified nano boron nitride, and the preparation method of the modified nano boron nitride is:

[0122] S1. The nano hexagonal boron nitride is subjected to high-temperature calcination treatment, cooled, mixed with deionized water, subjected to ultrasonic treatment, centrifugally dispersed, and then dried in a vacuum drying oven to obtain dispersed hydroxylated nano hexagonal boron nitride, wherein the average particle size of the nano hexagonal boron nitride is 400 nm, the temperature of the high-temperature calcination is controlled to be 1050° C., the heating rate is 8° C. / min, the ratio of the nano hexagonal boron nitride after high-temperature calcination to water is 7:500; the ultrasonic treatment time is 6 h; the ultrasonic power is 140 W; the centrifugal dispersion time is 70 min; the vacuum drying temperature is 75° C., and the drying time is 15 h;

[0123] S2, dissolving 1,3-propylenediamine in deionized water, and stirring at room temperature after ultrasonic treatment to obtain solution 1 for standby use, placing the dispersed hydroxylated nano hexagonal boron nitride prepared in step S1 in solution 1 and continuing ultrasonic treatment, stirring the reaction, centrifuging and separating the precipitate, washing and drying to obtain the modified nano boron nitride, wherein the ratio of the dispersed hydroxylated nano hexagonal boron nitride to the solution 1 is 2:25; the ultrasonic power of the ultrasonic treatment is 110W, and the time is controlled to be 40min; the stirring rate is 600r / min, and the stirring time is controlled to be 4h; the centrifugal speed is 2600rpm, and the centrifugal time is 35min; the drying temperature is 75°C, and the drying time is 16h;

[0124] The nanofiller 2 is modified nanographene, the modified substance and preparation method of the modified nanographene are the same as those of the nanofiller 1 modified nanoboron nitride, and the average particle size of the nanographene is 250nm;

[0125] The nano filler 3 is modified mesoporous nano silica, and the preparation method of the modified mesoporous nano silica is:

[0126] The mesoporous nano-silica was dissolved in deionized water, and after ultrasonic treatment, the solution 2 was prepared by stirring at room temperature for standby use. Under the protection of nitrogen atmosphere, sodium hydroxide aqueous solution was added dropwise to the solution 2 to form a mixed solution 1. Isopropoxy tris (dioctyl pyrophosphate acyloxy) phthalate was added to the mixed solution 1 for co-condensation reaction to obtain modified mesoporous nano-silica; the average particle size of the mesoporous nano-silica was 180 nm, and the ratio of the solution 2 to the isopropoxy tris (dioctyl pyrophosphate acyloxy) phthalate was 5:12; the stirring rate at room temperature was 600 r / min, and the stirring time at room temperature was controlled to be 3 h; the co-condensation reaction conditions were: At 5.5Kpa, the temperature was first raised to 100°C, the nitrogen purge flow rate was adjusted to 1.0L / min, and the polycondensation was carried out for 10 hours. The temperature was raised to 120°C again, the nitrogen purge flow rate was adjusted to 1.2L / min, and the polycondensation was carried out for 8 hours. The temperature was further raised to 150°C, the nitrogen purge flow rate was adjusted to 1.5L / min, and the polycondensation was carried out for 8 hours. The temperature was further raised to 180°C, the nitrogen purge flow rate was adjusted to 2.0L / min, and the polycondensation was carried out for 12 hours. The sodium hydroxide aqueous solution was 8wt% sodium hydroxide aqueous solution. The condition for adding the sodium hydroxide aqueous solution was: adding at room temperature for 20 minutes.

[0127] The preparation method of the polyolefin composite film:

[0128] (1) Preparation of A-layer structure masterbatch:

[0129] Hydroxypropyl methylcellulose is dissolved in deionized water and ultrasonically treated to obtain a hydroxypropyl methylcellulose solution, 92 parts of terpolymer, 10 parts of nanofiller 1, 4 parts of hydroxypropyl methylcellulose, 0.6 parts of polyethylene glycol monoether acrylate, and 2 parts of di(p-methylbenzylidene)sorbitol are placed in a twin-screw extruder for melt blending and extrusion granulation, wherein the main engine speed of the twin-screw extruder is 330 r / min, the main engine current is 21 A, the temperature of the twin-screw extruder head is controlled at 250° C., and the melt pressure is controlled at 2.1 MPa;

[0130] (2) Preparation of B-layer structure masterbatch:

[0131] 110 parts of modified polypropylene, 10 parts of nanofiller 2, 0.6 parts of polyethylene glycol monoether acrylate, 1 part of dicyclohexyl peroxydicarbonate, and 0.06 parts of antioxidant 1010 are placed in a twin-screw extruder for melt blending and extrusion granulation, wherein the modified polypropylene is a polypropylene-butadiene block copolymer; the main engine speed of the twin-screw extruder is 350 r / min, the main engine current is 21 A, the temperature of the twin-screw extruder head is controlled at 250° C., and the melt pressure is controlled at 2.0 MPa;

[0132] (3) Preparation of C-layer structure masterbatch:

[0133] 105 parts of low-density polyethylene, 5 parts of maleic anhydride and an initiator are placed in a twin-screw extruder, the temperature of the twin-screw extruder head is controlled to 180° C., the speed of the extruder host is controlled to 42 r / min, after melt blending, the temperature is increased to 250° C., 10 parts of nano filler 3, 1 part of polyethylene glycol monoether acrylate, 3 parts of sorbitan monostearate, and 3 parts of epoxidized polybutadiene are added thereto, the host speed of the extruder is adjusted to 350 r / min, the host current is 21 A, and the melt pressure is controlled to 2.0 MPa for melt blending and extrusion granulation;

[0134] (4) Preparation of polyolefin composite film:

[0135] The A layer structure masterbatch prepared in step (1), the B layer structure masterbatch prepared in step (2), and the C layer structure masterbatch prepared in step (3) are melted in layers, and the three layers of melt are co-extruded to form a sheet, and the sheet is cooled to form a cast sheet, and the cast sheet is longitudinally stretched, transversely stretched, heat-set, cooled, and rolled to obtain the polyolefin composite film; the longitudinal stretching preheating temperature is 86°C, and the longitudinal stretching stretching temperature is 115°C; the transverse stretching preheating temperature is 98°C, the stretching temperature is 115°C, and the heat-setting temperature is 240°C.

[0136] Comparative Example 1

[0137] This comparative example is carried out on the basis of the above-mentioned embodiment 1, and the similarities with the above-mentioned embodiment are not repeated here.

[0138] In this comparative example, the ratio of dispersed hydroxylated nano hexagonal boron nitride to solution 1 is 5:25; the ratio of solution 2 to isopropoxy tris(dioctyl pyrophosphate)phthalate is 5:11.

[0139] Comparative Example 2

[0140] This comparative example is carried out on the basis of the above-mentioned embodiment 1, and the similarities with the above-mentioned embodiment are not repeated here.

[0141] In this comparative example, the ratio of dispersed hydroxylated nano hexagonal boron nitride to solution 1 is 1:25; the ratio of solution 2 to isopropoxy tris(dioctyl pyrophosphate)phthalate is 5:11.

[0142] Comparative Example 3

[0143] This comparative example is carried out on the basis of the above-mentioned embodiment 1, and the similarities with the above-mentioned embodiment are not repeated here.

[0144] In this comparative example, the ratio of dispersed hydroxylated nano hexagonal boron nitride to solution 1 is 0:25; the ratio of solution 2 to isopropoxy tris(dioctyl pyrophosphate)phthalate is 5:11.

[0145] Comparative Example 4

[0146] This comparative example is carried out on the basis of the above-mentioned embodiment 1, and the similarities with the above-mentioned embodiment are not repeated here.

[0147] In this comparative example, the ratio of dispersed hydroxylated nano hexagonal boron nitride to solution 1 is 2:25; the ratio of solution 2 to isopropoxy tris(dioctyl pyrophosphate)phthalate is 5:13.

[0148] Comparative Example 5

[0149] This comparative example is carried out on the basis of the above-mentioned embodiment 1, and the similarities with the above-mentioned embodiment are not repeated here.

[0150] In this comparative example, the ratio of dispersed hydroxylated nano hexagonal boron nitride to solution 1 is 2:25; the ratio of solution 2 to isopropoxy tris(dioctyl pyrophosphate)phthalate is 5:9.

[0151] Comparative Example 6

[0152] This comparative example is carried out on the basis of the above-mentioned embodiment 1, and the similarities with the above-mentioned embodiment are not repeated here.

[0153] In this comparative example, filler 2 was not added.

[0154] The conditions of the above-mentioned embodiments and comparative examples and the test results of the prepared polyolefin composite films are listed in Table 1.

[0155] Table 1

[0156]

[0157] Table 2

[0158]

[0159] Table 3

[0160]

[0161] As can be seen from the above table, from Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that the ratio of dispersed hydroxylated nano hexagonal boron nitride to solution 1 will affect the performance of the film. When the amount of dispersed hydroxylated nano hexagonal boron nitride added is too much or too little, the antistatic performance will be significantly reduced, and the anti-aging performance will also be slightly reduced. From Example 3, it can be seen that when dispersed hydroxylated nano hexagonal boron nitride is not added, the antistatic performance will be significantly reduced and the anti-aging performance will also be significantly reduced. From Example 1, Comparative Example 4 and Comparative Example 5, it can be seen that the ratio of solution 2 to isopropoxy tris (dioctyl pyrophosphate acyloxy) phthalate will also affect the performance of the film. When isopropoxy tris (dioctyl pyrophosphate acyloxy) phthalate is added too much or too little, the tear strength and tensile strength will be significantly reduced. From Example 1 and Comparative Example 6, it can be seen that the anti-aging performance of the film without adding filler 2 will be significantly reduced, which also shows that the B-layer structure masterbatch adds nanofiller 2 to cooperate with the A-layer structure to improve the anti-aging performance of the composite film.

[0162] In summary, the polyolefin composite film prepared by the present invention improves the elongation at break, tear strength, and tensile strength of the film, improves the anti-aging performance and antistatic performance of the film, and reduces the haze of the film.

[0163] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a polyolefin composite film, characterized in that: The polyolefin composite film comprises: an ABC three-layer structure stacked up and down, with a total thickness of 50 to 80 microns; Among them: the A layer structure accounts for 25-35% of the total thickness; The B layer structure accounts for 35-45% of the total thickness; The C layer structure accounts for 25-35% of the total thickness; The raw materials of the A layer structure are terpolymer, nano filler 1, hydroxypropyl methylcellulose, a compatibilizer, and a nucleating agent; The raw materials of the B layer structure are modified polypropylene, nano filler 2, compatibilizer, crosslinking agent and antioxidant; The raw materials of the C layer structure are low-density polyethylene, nano filler 3, compatibilizer, antistatic agent, and toughening agent, and the density of the low-density polyethylene is 0.915-0.925; The nano filler 1 is modified nano boron nitride, and the preparation method of the modified nano boron nitride is: S1. The nano hexagonal boron nitride is subjected to high-temperature calcination treatment, cooled, mixed with deionized water, subjected to ultrasonic treatment, centrifugally dispersed, and then dried in a vacuum drying oven to obtain dispersed hydroxylated nano hexagonal boron nitride, wherein the average particle size of the nano hexagonal boron nitride is 300-500nm, the temperature of the high-temperature calcination is controlled to be 1000-1100°C, the heating rate is 7-9°C / min, the ratio of the nano hexagonal boron nitride after high-temperature calcination to water is 7-8:500-600; the ultrasonic treatment time is 5-6h; the ultrasonic power is 130-150W; the centrifugal dispersion time is 65-75min; the vacuum drying temperature is 70-80°C, and the drying time is 14-16h; S2, dissolving 1,3-propylenediamine in deionized water, and stirring at room temperature after ultrasonic treatment to obtain solution 1 for standby use, placing the dispersed hydroxylated nano hexagonal boron nitride prepared in step S1 in solution 1 and continuing ultrasonic treatment, stirring the reaction, centrifuging and separating the precipitate, washing and drying to obtain the modified nano boron nitride, the ratio of the dispersed hydroxylated nano hexagonal boron nitride to the solution 1 is 2-4:25; the ultrasonic power of the ultrasonic treatment is 100-110W, and the time is controlled to be 30-50min; the stirring rate is 550-650r / min, and the stirring time is controlled to be 3-4h; the centrifugal speed is 2500-2800rpm, and the centrifugal time is 32-35min; the drying temperature is 70-80℃, and the drying time is 14-16h; The nanofiller 2 is modified nanographene, the modified substance and preparation method of the modified nanographene are the same as those of the nanofiller 1 modified nanoboron nitride, and the average particle size of the nanographene is 200-300nm; The nano filler 3 is modified mesoporous nano silica, and the preparation method of the modified mesoporous nano silica is: The mesoporous nano-silica is dissolved in deionized water, and after ultrasonic treatment, the solution 2 is prepared by stirring at room temperature for standby use. Under the protection of nitrogen atmosphere, a sodium hydroxide aqueous solution is added dropwise to the solution 2 to form a mixed solution 1, and isopropoxy tris (dioctyl pyrophosphate acyloxy) phthalate is added to the mixed solution 1 for co-condensation reaction to obtain modified mesoporous nano-silica; the average particle size of the mesoporous nano-silica is 100-200nm, and the ratio of the solution 2 to the isopropoxy tris (dioctyl pyrophosphate acyloxy) phthalate is 5:10-12; the stirring rate at room temperature is 550-600r / min, and the stirring time at room temperature is controlled to be 2-3h; the co-condensation reaction conditions are 5.5-5.8Kpa , the temperature is first raised to 100-105°C, the nitrogen purge flow rate is adjusted to 1.0L / min, respectively, the polycondensation is 10-12h, the temperature is again raised to 120-125°C, the nitrogen purge flow rate is adjusted to 1.2L / min, respectively, the polycondensation is 8-10h, the temperature is further raised to 150-155°C, the nitrogen purge flow rate is adjusted to 1.5L / min, respectively, the polycondensation is 8-10h, the temperature is further raised to 180-190°C, the nitrogen purge flow rate is adjusted to 2.0L / min, respectively, the polycondensation is 12-14h; the sodium hydroxide aqueous solution is 8wt% sodium hydroxide aqueous solution; the condition of dripping the sodium hydroxide aqueous solution is: dripping at room temperature for 18-20min; The preparation method of the polyolefin composite film: (1) Preparation of A-layer structure masterbatch: Hydroxypropyl methylcellulose is dissolved in deionized water and subjected to ultrasonic treatment to obtain a hydroxypropyl methylcellulose solution; 90-95 parts of terpolymer, 8-10 parts of nanofiller 1, 4-5 parts of hydroxypropyl methylcellulose, 0.5-0.8 parts of a compatibilizer, and 2-3 parts of a nucleating agent are placed in a twin-screw extruder for melt blending and extrusion granulation; the main engine speed of the twin-screw extruder is 320-350 r / min, the main engine current is 21-22 A, the temperature of the twin-screw extruder head is controlled at 240-260° C., and the melt pressure is controlled at 2-2.2 MPa; (2) Preparation of B-layer structure masterbatch: 105-110 parts of modified polypropylene, 8-10 parts of nanofiller 2, 0.5-0.8 parts of compatibilizer, 1-2 parts of crosslinking agent, and 0.05-0.06 parts of antioxidant are placed in a twin-screw extruder for melt blending and extrusion granulation, wherein the modified polypropylene is a polypropylene-butadiene block copolymer; the main engine speed of the twin-screw extruder is 340-360r / min, the main engine current is 21-22A, the temperature of the twin-screw extruder head is controlled at 240-260°C, and the melt pressure is controlled at 1.9-2.1MPa; (3) Preparation of C-layer structure masterbatch: 100-105 parts of low-density polyethylene, 5-6 parts of maleic anhydride and an initiator are placed in a twin-screw extruder, the temperature of the twin-screw extruder head is controlled to be 178-180° C., the speed of the extruder host is controlled to be 40-45 r / min, after melt blending, the temperature is increased to 240-260° C., 8-10 parts of nano filler 3, 1-2 parts of compatibilizer, 3-4 parts of antistatic agent, 3-4 parts of toughening agent are added thereto, the main engine speed of the extruder is adjusted to 340-360 r / min, the main engine current is 21-22 A, and the melt pressure is controlled to be 1.9-2.1 MPa for melt blending and then extrusion granulation; (4) Preparation of polyolefin composite film: The A layer structure masterbatch prepared in step (1), the B layer structure masterbatch prepared in step (2), and the C layer structure masterbatch prepared in step (3) are melted in layers, and the three layers of melt are co-extruded to form a sheet, the sheet is cooled to form a cast sheet, and the cast sheet is longitudinally stretched, transversely stretched, heat-set, cooled, and rolled to obtain the polyolefin composite film; the longitudinal stretching preheating temperature is 86-87°C, and the longitudinal stretching stretching temperature is 110-120°C; the transverse stretching preheating temperature is 98-100°C, the stretching temperature is 110-120°C, and the heat-setting temperature is 230-240°C.

2. The method for preparing a polyolefin composite film according to claim 1, characterized in that: The compatibilizer is selected from one or more of styrene-maleic anhydride copolymer, polyethylene glycol methacrylate, polyethylene glycol monoether acrylate, maleic anhydride grafted polypropylene, and maleic anhydride grafted polyethylene.

3. The method for preparing a polyolefin composite film according to claim 1, characterized in that: The nucleating agent is selected from one or more of talc, mica, aluminum benzoate, tert-butylphenyl aluminum formate, 2,2'-methylenebis(4,6-tert-butylphenol)phosphine aluminum salt, dibenzylidene sorbitol, di(p-monomethylbenzylidene) sorbitol, and di(p-chlorosubstituted benzylidene) sorbitol.

4. The method for preparing a polyolefin composite film according to claim 1, characterized in that: The crosslinking agent is selected from one or more of dicumyl peroxide, dibenzoyl peroxide, di-tert-butyl peroxide, tert-butyl peroxyisopropyl carbonate, dicyclohexyl peroxydicarbonate, tert-butyl perbenzoate, tert-butyl peroxyvalerate and diisopropyl peroxydicarbonate.

5. The method for preparing a polyolefin composite film according to claim 1, characterized in that: The antioxidant is selected from one or more of antioxidant 1010, antioxidant 1098 and antioxidant 626.

6. The method for preparing a polyolefin composite film according to claim 1, characterized in that: The antistatic agent is selected from one or more of sorbitan monostearate, glyceryl monostearate or monotriglyceride.

7. The method for preparing a polyolefin composite film according to claim 1, characterized in that: The toughening agent is selected from one or more of epoxidized polybutadiene, fatty alcohol glycidyl ether, hydroxyl-terminated polyether, amino-terminated polyether, hydroxyl-terminated polyester, hydroxyl-terminated polyester ether, and isophorone diamine.

8. The polyolefin composite film prepared by the method for preparing a polyolefin composite film according to any one of claims 1 to 7.

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