EVOH high-barrier film for ensiling bag and preparation method of EVOH high-barrier film

Abstract

The invention provides an EVOH high-barrier film for an ensiling bag and a preparation method of the EVOH high-barrier film, and relates to the technical field of multilayer films for packaging. The EVOH high-barrier film comprises an inner layer, a bonding inner layer, a barrier layer, a bonding outer layer and an outer layer, the inner layer is prepared from acrylic acid grafted molybdenum disulfide, metallocene linear low-density polyethylene, low-density polyethylene, an antioxidant, a light stabilizer and a slip agent; the bonding inner layer is prepared from the following raw materials: an ethylene-acrylate copolymer, maleic anhydride grafted polyethylene and linear low-density polyethylene; the barrier layer is prepared from the following raw materials: an ethylene-vinyl alcohol copolymer, a NiCo-MBO LDHs nano composite material, an antioxidant, maleic anhydride grafted polyolefin and an ethylene-acrylate copolymer; the bonding outer layer is prepared from the following raw materials: an ethylene-acrylate copolymer, maleic anhydride grafted polyethylene and linear low-density polyethylene; the outer layer is prepared from the following raw materials: acrylic acid grafted molybdenum disulfide, high-density polyethylene, linear low-density polyethylene, an antioxidant, a light stabilizer and an anti-blocking agent. The barrier property and the stability are excellent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of multi-layer film for packaging, in particular to an EVOH high-barrier film for silage bag and a preparation method thereof. BACKGROUND

[0002] As a key way to store green feed in animal husbandry, silage can effectively retain the nutritional components of feed and alleviate seasonal feed shortages, playing an important role in large-scale breeding. The core of the silage process is to promote lactic acid bacteria fermentation by creating an anaerobic environment, reduce the pH value of the feed, and inhibit the reproduction of spoilage bacteria and mold, thereby achieving long-term preservation. Currently, ethylene-vinyl alcohol copolymer has strong barrier ability to oxygen and water vapor due to the hydroxyl group in its molecular structure, making it an ideal high-barrier base material. However, single ethylene-vinyl alcohol copolymer material still cannot meet the actual use requirements of silage bags, and needs to be combined with other polymer materials through multi-layer composite process to optimize the overall performance. The prior art with application number CN119858371A discloses a PA-EVOH multi-layer co-extrusion film, its preparation method and a composite film. By adopting a five-layer composite structure, the core layer is EVOH, and the other layers are mainly PA resin with the addition of functional masterbatch, solving the problems of poor barrier property of traditional polyolefin film and insufficient thermal stability of existing film. However, this technology still has limitations such as poor mechanical property adaptability and insufficient barrier performance. The prior art with application number CN118752872B discloses an ultra-high barrier EVOH aluminum-coated composite sheet and its preparation method. By designing the barrier layer as "modified EVOH film layer + aluminum layer", it solves the problems of strong hydrophilicity and poor water resistance of EVOH film, but still has defects such as large brittleness of the barrier layer, single mechanical property and poor stability.

[0003] In summary, although the existing technical solutions have improved some properties of EVOH barrier film to some extent, they still have the following technical problems: poor barrier performance, insufficient mechanical property and stability. SUMMARY

[0004] To solve the above-mentioned problems in the prior art, the present application provides an EVOH high-barrier film for silage bag and a preparation method thereof, and achieves the following invention purposes: preparing a silage packaging material with high barrier property, excellent mechanical property and stability.

[0005] To achieve the above-mentioned purposes, the technical solutions adopted are as follows: An EVOH high-barrier film for silage bag, which is composed of an inner layer, a bonding inner layer, a barrier layer, a bonding outer layer and an outer layer.

[0006] The inner layer raw material components include: 3-5 parts of acrylic acid grafted molybdenum disulfide, 45-55 parts of metallocene linear low density polyethylene, 25-35 parts of low density polyethylene, 0.2-0.5 parts of antioxidant, 0.1-0.3 parts of light stabilizer, 0.1-0.2 parts of slip agent.

[0007] The inner layer raw material components include: 3-5 parts of acrylic acid grafted molybdenum disulfide, 45-55 parts of metallocene linear low density polyethylene, 25-35 parts of low density polyethylene, 0.2-0.5 parts of antioxidant, 0.1-0.3 parts of light stabilizer, 0.1-0.2 parts of slip agent.

[0008] The barrier layer raw material components include: 60-70 parts of ethylene-vinyl alcohol copolymer, 5-8 parts of NiCo-MBO LDHs nanocomposite, 0.3-0.6 parts of antioxidant, 5-10 parts of maleic anhydride grafted polyolefin, 5-10 parts of ethylene-acrylic ester copolymer.

[0009] The inner layer raw material components include: 3-5 parts of acrylic acid grafted molybdenum disulfide, 45-55 parts of metallocene linear low density polyethylene, 25-35 parts of low density polyethylene, 0.2-0.5 parts of antioxidant, 0.1-0.3 parts of light stabilizer, 0.1-0.2 parts of slip agent.

[0010] The outer layer raw material components include: 5-8 parts of acrylic acid grafted molybdenum disulfide, 40-45 parts of high density polyethylene, 35-40 parts of linear low density polyethylene, 0.5-0.7 parts of antioxidant, 0.3-0.6 parts of light stabilizer, 0.1-0.3 parts of anti-blocking agent.

[0011] The above parts are all by weight.

[0012] The NiCo-MBO LDHs nanocomposite is prepared from Ni(NO3)2·6H2O, Co(NO3)2·6H2O and 2-mercaptobenzoxazole.

[0013] The acrylic acid grafted molybdenum disulfide is prepared from molybdenum disulfide, acrylic acid and potassium persulfate.

[0014] The metallocene linear low density polyethylene has a density of 0.914-0.922 g / cm 3 .

[0015] The low density polyethylene has a density of 0.917-0.925 g / cm 3 .

[0016] The linear low density polyethylene has a density of 0.918-0.922 g / cm 3 .

[0017] The high density polyethylene has a density of 0.941-0.955 g / cm 3 .

[0018] The ethylene-vinyl alcohol copolymer has an ethylene content of 40-44 mol%, and a density of 1.0-1.5 g / cm 3 .

[0019] The ethylene-acrylate copolymer has an AA content of 15-20%.

[0020] The maleic anhydride grafted polyethylene has a density of 0.92-0.94 g / cm 3 , and a grafting rate of 0.8-1.5%.

[0021] The maleic anhydride grafted polyolefin has a density of 0.86-0.88 g / cm 3 , and a grafting rate of 1.2-1.5%.

[0022] The light stabilizer is a hindered phenol light stabilizer, and the model is NOR356.

[0023] The antioxidant is a compound of antioxidant 1010 and antioxidant 168, and the mass ratio is 1:1.

[0024] The slip agent is erucic acid amide.

[0025] The anti-blocking agent is nano-silicon dioxide.

[0026] The application also provides a preparation method of the EVOH high-barrier film for silage bags. Step one, preparation of NiCo-MBOLDHs nanocomposite Ni(NO3)2·6H2O and Co(NO3)2·6H2O are dissolved in deionized water to prepare nickel nitrate solution and cobalt nitrate solution with a concentration of 0.2-0.3 mol / L; the nickel nitrate solution and the cobalt nitrate solution are uniformly mixed according to a volume ratio of (1-3):1 to obtain a nickel-cobalt mixed solution; 2-mercaptobenzoxazole is dissolved in methanol to prepare a 2-mercaptobenzoxazole solution with a concentration of 0.1-0.2 mol / L.

[0027] The 2-mercaptobenzoxazole solution is added dropwise into the nickel-cobalt mixed solution, stirring is started, the stirring rate is 700-800 rpm, the volume ratio of the 2-mercaptobenzoxazole solution to the nickel-cobalt mixed solution is (0.2-0.5):1; the pH value of the system is adjusted to 8.5-9.5 by adding the NaOH solution dropwise, and stirring is continued for 1-2 h to obtain a suspension. The suspension is transferred into a reaction kettle, the temperature is 120-160℃, and the reaction is carried out for 18-24 h; after the reaction is completed, natural cooling to room temperature is carried out, centrifugation is carried out at a speed of 8000-10000 rpm for 10-15 min; then the precipitate is washed alternately with deionized water and ethanol until the filtrate is neutral; after the washing is completed, drying is carried out at a temperature of 60-80℃ for 18-24 h to obtain the NiCo-MBO LDHs nanocomposite.

[0028] Step two, acrylic acid grafted molybdenum disulfide is prepared Molybdenum disulfide is added into DMF, the mass ratio of molybdenum disulfide to DMF is 1-1.2%, ultrasonic treatment is carried out, the ultrasonic power is 300-500 W, and the ultrasonic time is 4-6 h; then centrifugation is carried out at a speed of 7000-8000 rpm for 15-20 min, and the supernatant is taken after the centrifugation is completed to obtain a molybdenum disulfide dispersion.

[0029] Acrylic acid is added into the molybdenum disulfide dispersion, stirring is carried out uniformly, the mass ratio of acrylic acid to molybdenum disulfide is (1-2):1; nitrogen is introduced for 10-15 min, the nitrogen flow rate is 20-30 mL / min; then potassium persulfate is added, the mass ratio of potassium persulfate to acrylic acid is 5%-10%; under the protection of nitrogen, the reaction system is heated to 60-80℃, the stirring rate is 300-400 rpm, and stirring reaction is carried out for 6-8 h. After the reaction is completed, centrifugation is carried out at a speed of 9000-10000 rpm for 15-20 min; then the precipitate is washed repeatedly with deionized water and ethanol for 3-5 times, after the washing is completed, drying is carried out at a temperature of 60-70℃ for 12-14 h to obtain acrylic acid grafted molybdenum disulfide.

[0030] Step three, premixing of barrier layer raw materials The NiCo-MBO LDHs nanocomposite and ethylene-vinyl alcohol copolymer are added into a twin-screw extruder, the screw rotation speed is 200-300 rpm, the feeding section temperature of the extruder is 160-170℃, the melting section temperature is 190-210℃, the mixing section temperature is 200-220℃, the die head temperature is 180-190℃, the extruded material is air-cooled, the air ring cooling temperature is 20℃, the cooled material is added into a granulator for granulation, and after the granulation, the material is uniformly mixed with antioxidants, maleic anhydride grafted polyolefin, and ethylene-acrylic ester copolymer to obtain a barrier layer premix, which is ready for use.

[0031] Step four, co-extrusion The raw materials of the inner layer, the bonding inner layer, the bonding outer layer and the outer layer are mixed according to the formula to form the premix of each layer; the premixes of the inner layer, the bonding inner layer, the barrier layer, the bonding outer layer and the outer layer are added into a five-layer co-extrusion extruder, and the temperature of each section of the extruder is as follows: the feeding section is 145-170 DEG C, the compression section is 165-200 DEG C, the melting section is 180-210 DEG C, the homogenizing section is 185-210 DEG C, the connector is 180-210 DEG C, the transition section is 175-210 DEG C, the distributor is 175-205 DEG C, and the die outlet is 165-200 DEG C. After extrusion, film blowing, cooling, corona treatment and drying are performed to finally obtain an EVOH high-barrier film for silage bags. The film blowing parameters are as follows: the blow ratio is 3.0, and the pulling speed is 20 m / min; the cooling parameters are as follows: the air ring cooling temperature is 20 DEG C; the corona treatment parameters are as follows: the power is 10 kW, and the treatment speed is 15 m / min; and the drying parameters are as follows: the drying temperature is 60 DEG C. The thickness of the product obtained is 0.10 mm±5%, and the thickness ratio of the inner layer, the bonding inner layer, the barrier layer, the bonding outer layer and the outer layer is 3:1:3:1:2.

[0032] The beneficial effects of the present application are as follows: 1. The EVOH high-barrier film prepared by the present application has excellent barrier properties, and the oxygen transmission rate is 0.06-0.09 cm 3 / (m 2 ·d), and the water vapor transmission rate is 0.09-0.15 g / (m 2 ·d).

[0033] 2. The EVOH high-barrier film prepared by the present application has excellent mechanical properties, and the transverse tensile strength is 41.2-44.8 MPa, the longitudinal tensile strength is 43.7-47.5 MPa, the puncture strength is 52.4-60.7 N, and the right-angle tear strength is 145-152 N / mm.

[0034] 3. The EVOH high-barrier film prepared by the present application has excellent stability. After low-temperature treatment, the transverse tensile strength is maintained at 39.9-43.1 MPa, and the longitudinal tensile strength is maintained at 41.8-45.6 MPa; after high-temperature aging, the transverse tensile strength is maintained at 38.2-42.0 MPa, and the longitudinal tensile strength is maintained at 40.3-44.6 MPa; and after lactic acid immersion, the transverse tensile strength is maintained at 37.4-41.2 MPa, and the longitudinal tensile strength is maintained at 39.2-43.1 MPa.

[0035] 4. The silage bag prepared by the present application has excellent barrier properties, and the pH value of the pasture placed in the silage bag is stable at 3.8-4.2 during 1-3 months, the appearance color is basically unchanged, and the green color is maintained. BRIEF DESCRIPTION OF DRAWINGS

[0036] Attachment Figure 1 This is a transmission electron microscope image of the NiCo-MBO LDHs nanocomposite material in the step of "preparation of NiCo-MBO LDHs nanocomposite material" of the present invention. DETAILED DESCRIPTION

[0037] To make the purpose, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0038] Example 1: EVOH high barrier film for silage bags The invention discloses an EVOH high-barrier film for silage bags. The EVOH high-barrier film consists of an inner layer, an adhesive inner layer, a barrier layer, an adhesive outer layer, and an outer layer.

[0039] The raw material components of the inner layer include: 3 parts of acrylic acid grafted molybdenum disulfide, 45 parts of metallocene linear low-density polyethylene, 35 parts of low-density polyethylene, 0.2 parts of antioxidant, 0.3 parts of light stabilizer, and 0.1 parts of slip agent.

[0040] The raw material components of the bonding inner layer include: 30 parts of ethylene-acrylate copolymer, 55 parts of maleic anhydride grafted polyethylene, and 15 parts of linear low-density polyethylene.

[0041] The raw material components of the barrier layer include: 70 parts of ethylene-vinyl alcohol copolymer, 5 parts of NiCo-MBO LDHs nanocomposite material, 0.6 parts of antioxidant, 5 parts of maleic anhydride grafted polyolefin, and 10 parts of ethylene-acrylate copolymer.

[0042] The raw material components of the bonding outer layer include: 25 parts of ethylene-acrylate copolymer, 50 parts of maleic anhydride grafted polyethylene, and 20 parts of linear low-density polyethylene.

[0043] The outer layer raw material components include: 5 parts of acrylic acid grafted molybdenum disulfide, 45 parts of high-density polyethylene, 35 parts of linear low-density polyethylene, 0.7 parts of antioxidant, 0.3 parts of light stabilizer, and 0.3 parts of anti-blocking agent.

[0044] The above parts are all by weight.

[0045] The light stabilizer is a hindered phenol light stabilizer, model number NOR356.

[0046] The antioxidant is a compound of antioxidant 1010 and antioxidant 168, with a mass ratio of 1:1.

[0047] The slip agent is erucamide.

[0048] The anti-adhesion agent is nano-silica with a particle size of 15-25 nm.

[0049] A preparation method of an EVOH high-barrier film for silage bags, comprising the following steps: Step one, preparation of NiCo-MBOLDHs nanocomposite Ni(NO3)2·6H2O and Co(NO3)2·6H2O were dissolved in deionized water to prepare a nickel nitrate solution and a cobalt nitrate solution with a concentration of 0.2 mol / L; the nickel nitrate solution and the cobalt nitrate solution were mixed uniformly at a volume ratio of 1:1 to obtain a nickel-cobalt mixed solution; 2-mercaptobenzoxazole was dissolved in methanol to prepare a 2-mercaptobenzoxazole solution with a concentration of 0.2 mol / L.

[0050] The 2-mercaptobenzoxazole solution was added dropwise into the nickel-cobalt mixed solution, and stirring was started at a speed of 700 rpm; the volume ratio of the 2-mercaptobenzoxazole solution to the nickel-cobalt mixed solution was 0.2:1; NaOH solution was added dropwise to adjust the pH value of the system to 8.5, and stirring was continued for 1 h to obtain a suspension; the suspension was transferred into a reaction kettle, and the temperature was set to 120℃; the reaction was carried out for 24 h; after the reaction was completed, the system was naturally cooled to room temperature; centrifugation was carried out at a speed of 8000 rpm for 15 min; then the precipitate was washed alternately with deionized water and ethanol until the filtrate was neutral; after the washing was completed, drying was carried out at a temperature of 60℃ for 24 h to obtain the NiCo-MBOLDHs nanocomposite.

[0051] Step two, preparation of acrylic acid grafted molybdenum disulfide Molybdenum disulfide was added to DMF, and the molybdenum disulfide accounted for 1% of the mass of DMF; ultrasonic treatment was carried out at a power of 300 W for 6 h; then centrifugation was carried out at a speed of 7000 rpm for 20 min; the supernatant was taken after the centrifugation was completed to obtain a molybdenum disulfide dispersion.

[0052] Acrylic acid was added to the molybdenum disulfide dispersion and stirred uniformly; the mass ratio of acrylic acid to molybdenum disulfide was 1:1; nitrogen was introduced for 15 min at a flow rate of 20 mL / min; then potassium persulfate was added, and the amount of potassium persulfate was 5% of the mass of acrylic acid; under the protection of nitrogen, the reaction system was heated to 60℃, and stirring was carried out at a speed of 400 rpm for 8 h. After the reaction was completed, centrifugation was carried out at a speed of 9000 rpm for 20 min; then the precipitate was washed repeatedly with deionized water and ethanol for 3 times; after the washing was completed, drying was carried out at a temperature of 60℃ for 14 h to obtain acrylic acid grafted molybdenum disulfide.

[0053] Step three, premixing of raw materials for the barrier layer The NiCo-MBO LDHs nanocomposite and ethylene-vinyl alcohol copolymer are added into a twin-screw extruder, the screw rotation speed is 200 rpm, the temperature of feeding section of the extruder is 160°C, the temperature of melting section is 190°C, the temperature of mixing section is 200°C, the temperature of die head is 180°C, the extruded material is air-cooled, the air ring cooling temperature is 20°C, the cooled material is added into a granulator for granulation, and the granulated material is uniformly mixed with antioxidant, maleic anhydride grafted polyolefin and ethylene-propyl acrylate copolymer to obtain a barrier layer premix, which is ready for use.

[0054] Step four, co-extrusion molding The raw materials of the inner layer, the bonding inner layer, the bonding outer layer and the outer layer are mixed according to the formula to form the premixes of the respective layers; the premixes of the inner layer, the bonding inner layer, the barrier layer, the bonding outer layer and the outer layer are added into a five-layer co-extrusion extruder, and the temperature process conditions of each zone in the extruder are shown in Table 1.

[0055] Table 1 Temperature process conditions of each zone in the extruder

[0056] After extrusion through the die head, film blowing, cooling, corona treatment and drying are performed to finally obtain an EVOH high-barrier film for silage bags. The film blowing parameters are: the blow-up ratio is 3.0, and the pulling speed is 20 m / min; the cooling parameters are: the air ring cooling temperature is 20°C; the corona treatment parameters are: the corona treatment power is 10 kW, and the treatment speed is 15 m / min; the drying parameters are: the drying temperature is 60°C. The thickness of the product obtained is 0.10 mm±5%, and the thickness ratio of the inner layer, the bonding inner layer, the barrier layer, the bonding outer layer and the outer layer is 3:1:3:1:2.

[0057] Example 2 An EVOH high-barrier film for silage bags An EVOH high-barrier film for silage bags, which comprises an inner layer, a bonding inner layer, a barrier layer, a bonding outer layer and an outer layer.

[0058] The raw material components of the inner layer include: 4 parts of acrylic acid grafted molybdenum disulfide, 50 parts of metallocene linear low density polyethylene, 30 parts of low density polyethylene, 0.4 parts of antioxidant, 0.2 parts of light stabilizer and 0.2 parts of slip agent.

[0059] The raw material components of the bonding inner layer include: 35 parts of ethylene-acrylate copolymer, 50 parts of maleic anhydride grafted polyethylene and 20 parts of linear low density polyethylene.

[0060] The raw material components of the barrier layer include: 65 parts of ethylene-vinyl alcohol copolymer, 8 parts of NiCo-MBO LDHs nanocomposite, 0.6 parts of antioxidant, 10 parts of maleic anhydride grafted polyolefin and 10 parts of ethylene-acrylate copolymer.

[0061] The outer layer raw material components include: ethylene-acrylic ester copolymer 30 parts, maleic anhydride grafted polyethylene 45 parts, linear low density polyethylene 25 parts.

[0062] The outer layer raw material components include: acrylic acid grafted molybdenum disulfide 6 parts, high density polyethylene 45 parts, linear low density polyethylene 40 parts, antioxidant 0.7 parts, light stabilizer 0.6 parts, anti-blocking agent 0.3 parts.

[0063] The above parts are all by weight.

[0064] The light stabilizer is a hindered phenolic light stabilizer, model NOR356.

[0065] The antioxidant is a compound of antioxidant 1010 and antioxidant 168, with a mass ratio of 1:1.

[0066] The slip agent is erucic acid amide.

[0067] The anti-blocking agent is nano-silicon dioxide with a particle size of 15-25 nm.

[0068] A preparation method of an EVOH high-barrier film for a silage bag, comprising the following steps: Step one, preparation of NiCo-MBO LDHs nanocomposite Ni(NO3)2·6H2O and Co(NO3)2·6H2O were dissolved in deionized water to prepare nickel nitrate solution and cobalt nitrate solution with a concentration of 0.3 mol / L; the nickel nitrate solution and the cobalt nitrate solution were mixed uniformly according to a volume ratio of 2:1 to obtain a nickel-cobalt mixed solution; 2-mercaptobenzoxazole was dissolved in methanol to prepare a 0.2 mol / L 2-mercaptobenzoxazole solution.

[0069] The 2-mercaptobenzoxazole solution was added dropwise into the nickel-cobalt mixed solution, and stirring was started at a stirring rate of 800 rpm, and the volume ratio of the 2-mercaptobenzoxazole solution to the nickel-cobalt mixed solution was 0.4:1; NaOH solution was added dropwise to adjust the pH value of the system to 9, and stirring was continued for 2 h to obtain a suspension. The suspension was transferred to a reaction kettle, the temperature was 140℃, and the reaction was carried out for 24 h; after the reaction was completed, the system was naturally cooled to room temperature, centrifugation was carried out at a speed of 10000 rpm for 10 min; then the precipitate was washed alternately with deionized water and ethanol until the filtrate was neutral; after the washing was completed, drying was carried out at a temperature of 70℃ for 24 h to obtain the NiCo-MBO LDHs nanocomposite.

[0070] Step two, preparation of acrylic acid grafted molybdenum disulfide The molybdenum disulfide was added to DMF, the mass fraction of molybdenum disulfide in DMF was 1.2%, and ultrasonic treatment was performed, the ultrasonic power was 400W, and the ultrasonic time was 6h; then centrifugation was performed, the speed was 8000rpm, and the time was 20min, and the supernatant was taken after centrifugation to obtain a molybdenum disulfide dispersion.

[0071] The acrylic acid was added to the molybdenum disulfide dispersion, and stirred uniformly, the mass ratio of acrylic acid to molybdenum disulfide was 2:1; nitrogen was introduced for 15min, the nitrogen flow rate was 30mL / min; then potassium persulfate was added, the mass fraction of potassium persulfate in acrylic acid was 10%; under the protection of nitrogen, the reaction system was heated to 70℃, the stirring speed was 400rpm, and the stirring reaction was performed for 8h. After the reaction was completed, centrifugation was performed, the speed was 10000rpm, and the centrifugation time was 20min; then deionized water and ethanol were repeatedly washed for 5 times, after the washing was completed, drying was performed, the temperature was 70℃, and the drying time was 14h, to obtain acrylic acid grafted molybdenum disulfide.

[0072] Step three, premixing of barrier layer raw materials The NiCo-MBO LDHs nanocomposite and ethylene-vinyl alcohol copolymer were added into a twin-screw extruder, the screw rotation speed was 300rpm, the feeding section temperature of the extruder was 170℃, the melting section temperature was 200℃, the mixing section temperature was 210℃, and the die head temperature was 190℃, the extruded material was air-cooled, the air ring cooling temperature was 20℃, and the cooled material was added into a granulator for granulation, and then mixed uniformly with antioxidants, maleic anhydride grafted polyolefin, and ethylene-acrylic ester copolymer to obtain a barrier layer premix, which was ready for use.

[0073] Step four, co-extrusion molding The raw materials of the inner layer, the bonding inner layer, the bonding outer layer, and the outer layer were mixed according to the formula to form the premixes of the respective layers; the premixes of the inner layer, the bonding inner layer, the barrier layer, the bonding outer layer, and the outer layer were added into a five-layer co-extrusion machine, and the temperature process conditions of each zone in the extruder were shown in Table 2.

[0074] Table 2 Temperature process conditions of each zone in the extruder

[0075] After the die extrusion, film blowing, cooling, corona treatment, and drying were performed to finally obtain an EVOH high-barrier film for silage bags. The film blowing parameters were as follows: the blow-up ratio was 3.0, and the pulling speed was 20m / min; the cooling parameters were as follows: the air ring cooling temperature was 20℃; the corona treatment parameters were as follows: the corona treatment power was 10kW, and the treatment speed was 15m / min; and the drying parameters were as follows: the drying temperature was 60℃. The product prepared had a thickness of 0.10mm±5%, and the thickness ratio of the inner layer, the bonding inner layer, the barrier layer, the bonding outer layer, and the outer layer was 3:1:3:1:2.

[0076] Example 3: An EVOH high-barrier film for silage bag An EVOH high-barrier film for silage bag, which is composed of an inner layer, a bonding inner layer, a barrier layer, a bonding outer layer, and an outer layer.

[0077] The inner layer raw material components include: 5 parts of acrylic acid grafted molybdenum disulfide, 55 parts of metallocene linear low density polyethylene, 25 parts of low density polyethylene, 0.5 parts of antioxidant, 0.1 parts of light stabilizer, and 0.2 parts of slip agent.

[0078] The bonding inner layer raw material components include: 35 parts of ethylene-acrylic ester copolymer, 45 parts of maleic anhydride grafted polyethylene, and 20 parts of linear low density polyethylene.

[0079] The barrier layer raw material components include: 60 parts of ethylene-vinyl alcohol copolymer, 8 parts of NiCo-MBO LDHs nanocomposite, 0.3 parts of antioxidant, 10 parts of maleic anhydride grafted polyolefin, and 5 parts of ethylene-acrylic ester copolymer.

[0080] The bonding outer layer raw material components include: 35 parts of ethylene-acrylic ester copolymer, 45 parts of maleic anhydride grafted polyethylene, and 25 parts of linear low density polyethylene.

[0081] The outer layer raw material components include: 8 parts of acrylic acid grafted molybdenum disulfide, 40 parts of high density polyethylene, 40 parts of linear low density polyethylene, 0.5 parts of antioxidant, 0.6 parts of light stabilizer, and 0.1 parts of anti-blocking agent.

[0082] The above parts are all by weight.

[0083] The light stabilizer is a hindered phenolic light stabilizer, model NOR356.

[0084] The antioxidant is a compound of antioxidant 1010 and antioxidant 168 with a mass ratio of 1:1.

[0085] The slip agent is erucic acid amide.

[0086] The anti-blocking agent is nano-silicon dioxide with a particle size of 15-25 nm.

[0087] A preparation method of an EVOH high-barrier film for silage bag, the steps are as follows: Step one, preparation of NiCo-MBO LDHs nanocomposite Ni(NO3)2·6H2O and Co(NO3)2·6H2O were dissolved in deionized water to prepare a nickel nitrate solution and a cobalt nitrate solution with a concentration of 0.3 mol / L, respectively; the nickel nitrate solution and the cobalt nitrate solution were mixed uniformly at a volume ratio of 3:1 to obtain a nickel-cobalt mixed solution; 2-mercaptobenzoxazole was dissolved in methanol to prepare a 2-mercaptobenzoxazole solution with a concentration of 0.1 mol / L.

[0088] The 2-mercaptobenzoxazole solution was added dropwise into the nickel-cobalt mixed solution, and stirring was started at a stirring rate of 800 rpm; the volume ratio of the 2-mercaptobenzoxazole solution to the nickel-cobalt mixed solution was 0.5:1; NaOH solution was added dropwise to adjust the pH value of the system to 9.5, and stirring was continued for 2 h to obtain a suspension. The suspension was transferred into a reaction kettle, and the temperature was set to 160℃; the reaction was carried out for 18 h; after the reaction was completed, the system was naturally cooled to room temperature, centrifugation was carried out at a speed of 10,000 rpm for 10 min; then the precipitate was washed alternately with deionized water and ethanol until the filtrate was neutral; after the washing was completed, drying was carried out at a temperature of 80℃ for 18 h to obtain a NiCo-MBOLDHs nanocomposite.

[0089] Step two, acrylic acid grafted molybdenum disulfide was prepared Molybdenum disulfide was added to DMF, and the mass fraction of molybdenum disulfide in DMF was 1.2%; ultrasonic treatment was carried out at an ultrasonic power of 500 W for 4 h; then centrifugation was carried out at a speed of 8,000 rpm for 15 min, and the supernatant was taken after the centrifugation was completed to obtain a molybdenum disulfide dispersion.

[0090] Acrylic acid was added to the molybdenum disulfide dispersion, and stirring was carried out until the acrylic acid and the molybdenum disulfide were uniformly mixed; the mass ratio of the acrylic acid to the molybdenum disulfide was 2:1; nitrogen was introduced for 10 min at a flow rate of 30 mL / min; then potassium persulfate was added, and the mass fraction of the potassium persulfate in the acrylic acid was 10%; under the protection of nitrogen, the reaction system was heated to 80℃, and stirring was carried out at a speed of 300 rpm for 6 h. After the reaction was completed, centrifugation was carried out at a speed of 10,000 rpm for 15 min; then the precipitate was washed repeatedly with deionized water and ethanol for 5 times; after the washing was completed, drying was carried out at a temperature of 70℃ for 12 h to obtain acrylic acid grafted molybdenum disulfide.

[0091] Step three, premixing of raw materials for the barrier layer The NiCo-MBOLDHs nanocomposite and ethylene-vinyl alcohol copolymer are added into a twin-screw extruder, the screw rotation speed is 300 rpm, the feeding section temperature of the extruder is 170°C, the melting section temperature is 210°C, the mixing section temperature is 220°C, the die head temperature is 190°C, the extruded material is air-cooled, the air ring cooling temperature is 20°C, the cooled material is added into a granulator for granulation, and the granulated material is uniformly mixed with antioxidant, maleic anhydride grafted polyolefin and ethylene-propyl acrylate copolymer to obtain a barrier layer premix, which is ready for use.

[0092] Step four, co-extrusion molding The raw materials of the inner layer, the bonding inner layer, the bonding outer layer and the outer layer are mixed according to the formula to form a layer premix; the inner layer, the bonding inner layer, the barrier layer, the bonding outer layer and the outer layer premix are added into a five-layer co-extrusion extruder, and the temperature process conditions of each zone in the extruder are shown in Table 3.

[0093] Table 3 Temperature process conditions of each zone in the extruder

[0094] After the die extrusion, film blowing, cooling, corona and drying are performed to finally obtain an EVOH high-barrier film for silage bags. The film blowing parameters are: the blow ratio is 3.0, and the pulling speed is 20 m / min; the cooling parameters are: the air ring cooling temperature is 20°C; the corona parameters are: the corona treatment power is 10 kW, and the treatment speed is 15 m / min; the drying parameters are: the drying temperature is 60°C. The product prepared has a thickness of 0.10 mm±5%, and the thickness ratio of the inner layer, the bonding inner layer, the barrier layer, the bonding outer layer and the outer layer is 3:1:3:1:2.

[0095] Comparative Example 1 An EVOH high-barrier film, which is composed of an inner layer, a bonding inner layer, a barrier layer, a bonding outer layer and an outer layer.

[0096] The inner layer raw material components include: 4 parts of acrylic acid grafted molybdenum disulfide, 50 parts of metallocene linear low density polyethylene, 30 parts of low density polyethylene, 0.4 parts of antioxidant, 0.2 parts of light stabilizer and 0.2 parts of slip agent.

[0097] The bonding inner layer raw material components include: 35 parts of ethylene-acrylate copolymer, 50 parts of maleic anhydride grafted polyethylene and 20 parts of linear low density polyethylene.

[0098] The barrier layer raw material components include: 65 parts of ethylene-vinyl alcohol copolymer, 0.6 parts of antioxidant, 10 parts of maleic anhydride grafted polyolefin and 10 parts of ethylene-acrylate copolymer.

[0099] The outer layer raw material components include: ethylene-acrylate copolymer 30 parts, maleic anhydride grafted polyethylene 45 parts, linear low density polyethylene 25 parts.

[0100] The outer layer raw material components include: acrylic acid grafted molybdenum disulfide 6 parts, high density polyethylene 45 parts, linear low density polyethylene 40 parts, antioxidant 0.7 parts, light stabilizer 0.6 parts, anti-blocking agent 0.3 parts.

[0101] The above parts are all by weight.

[0102] The light stabilizer is a hindered phenolic light stabilizer, model NOR356.

[0103] The antioxidant is a compound of antioxidant 1010 and antioxidant 168, with a mass ratio of 1:1.

[0104] The slip agent is erucic acid amide.

[0105] The anti-blocking agent is nano-silicon dioxide with a particle size of 15-25 nm.

[0106] A preparation method of an EVOH high barrier film, the steps are as follows: Step one, acrylic acid grafted molybdenum disulfide is prepared This step is the same as the "preparation of acrylic acid grafted molybdenum disulfide" step in Example 2.

[0107] Step two, premixing of barrier layer raw materials This step is the same as the "premixing of barrier layer raw materials" step in Example 2.

[0108] Step three, co-extrusion molding This step is the same as the "co-extrusion molding" step in Example 2.

[0109] Comparative Example 2 An EVOH high barrier film, the EVOH high barrier film is composed of an inner layer, a bonding inner layer, a barrier layer, a bonding outer layer, and an outer layer.

[0110] The inner layer raw material components include: metallocene linear low density polyethylene 50 parts, low density polyethylene 30 parts, antioxidant 0.4 parts, light stabilizer 0.2 parts, slip agent 0.2 parts.

[0111] The bonding inner layer raw material components include: ethylene-acrylate copolymer 35 parts, maleic anhydride grafted polyethylene 50 parts, linear low density polyethylene 20 parts.

[0112] The barrier layer raw material components include: ethylene-vinyl alcohol copolymer 65 parts, NiCo-MBO LDHs nanocomposite 8 parts, antioxidant 0.6 parts, maleic anhydride grafted polyolefin 10 parts, ethylene-acrylate copolymer 10 parts.

[0113] The outer layer raw material components include: ethylene-acrylate copolymer 30 parts, maleic anhydride grafted polyethylene 45 parts, linear low density polyethylene 25 parts.

[0114] The outer layer raw material components include: high density polyethylene 45 parts, linear low density polyethylene 40 parts, antioxidant 0.7 parts, light stabilizer 0.6 parts, anti-blocking agent 0.3 parts.

[0115] The above parts are all by weight.

[0116] The light stabilizer is a hindered phenolic light stabilizer, model NOR356.

[0117] The antioxidant is a compound of antioxidant 1010 and antioxidant 168, with a mass ratio of 1:1.

[0118] The slip agent is erucic acid amide.

[0119] The anti-blocking agent is nano-silicon dioxide with a particle size of 15-25 nm.

[0120] A preparation method of an EVOH high barrier film, the steps are as follows: Step one, preparation of NiCo-MBO LDHs nanocomposite This step is the same as the "preparation of NiCo-MBO LDHs nanocomposite" step in Example 2.

[0121] Step two, premixing of barrier layer raw materials This step is the same as the "premixing of barrier layer raw materials" step in Example 2.

[0122] Step three, co-extrusion molding This step is the same as the "co-extrusion molding" step in Example 2.

[0123] Example 4 Performance test (1) Barrier performance test The EVOH high barrier films prepared in Examples 1-3 and Comparative Examples 1-2 were tested for oxygen transmission rate according to the test method provided in GB / T 19789-2005, and for water vapor transmission rate according to the test method provided in GB / T 26253-2010. The specific test results are shown in Table 4.

[0124] Table 4

[0125] As can be seen from the test results in Table 4, the oxygen transmission rate of the EVOH high barrier films prepared in Examples 1-3 is 0.06-0.09 cm 3 / (m 2• d), water vapor transmission rate is 0.09-0.15 g / (m 2 • d), compared with the comparative example, there is a significant reduction. It is proved that the EVOH high barrier film prepared by the present application has excellent barrier properties.

[0126] (II) Mechanical property test The EVOH high barrier films prepared in Examples 1-3 and Comparative Examples 1-2 were tested for transverse tensile strength and longitudinal tensile strength according to the test method provided in GB / T 1040-2006, for puncture strength according to the test method provided in GB / T 10004-2008, and for right angle tear strength according to the test method provided in GB / T 16578.2-2009. The specific test results are shown in Table 5.

[0127] Table 5

[0128] As can be seen from the test results in Table 5, the transverse tensile strength of the EVOH high barrier films prepared in Examples 1-3 is 41.2-44.8 MPa, the longitudinal tensile strength is 43.7-47.5 MPa, the puncture strength is 52.4-60.7 N, and the right angle tear strength is 145-152 N / mm. It is proved that the EVOH high barrier film prepared by the present application has excellent mechanical properties.

[0129] (III) Stability test The EVOH high barrier films prepared in Examples 1-3 and Comparative Examples 1-2 were tested for low temperature resistance, high temperature aging resistance and corrosion resistance. The EVOH high barrier film was placed at -20℃ for 12h, and the tensile strength was tested immediately after taking out; the EVOH high barrier film was heat aged at 80℃ for 168h, and the tensile strength after aging was tested; the EVOH high barrier film was immersed in a 3% lactic acid solution at 30℃ for 72h, and the tensile strength was tested after drying. The specific test results are shown in Table 6.

[0130] Table 6

[0131] From the test results of Table 6, it can be seen that the EVOH high-barrier film prepared in Examples 1-3 has a transverse tensile strength of 39.9-43.1 MPa and a longitudinal tensile strength of 41.8-45.6 MPa after low-temperature treatment; the transverse tensile strength is 38.2-42.0 MPa and the longitudinal tensile strength is 40.3-44.6 MPa after high-temperature aging; the transverse tensile strength is 37.4-41.2 MPa and the longitudinal tensile strength is 39.2-43.1 MPa after lactic acid immersion. It is proved that the EVOH high-barrier film prepared in the application has excellent stability.

[0132] (Four) The EVOH high-barrier films prepared in Examples 1-3 and Comparative Examples 1-2 are made into silage bags. The prepared EVOH high-barrier films are cut into a width of 800-1200 mm; then three-edge heat sealing is performed to make bags, and the heat sealing parameters are as follows: temperature 180-220 ℃, pressure 0.3-0.5 MPa, time 0.5-1.5 s, and sealing edge width 8-12 mm; a one-way exhaust valve is installed on the top or side of the bag body. The pasture is added to the silage bag and vacuumized, and the pH value of the pasture is detected and the color change is observed regularly (1 week, 1 month, 3 months). The specific test results are shown in Table 7.

[0133] Table 7

[0134] From the test results of Table 7, it can be seen that the pH value of the pasture is stable at 3.8-4.2 and the appearance color basically does not change and remains green during 1 month to 3 months of storage in the silage bag. It is proved that the silage bag prepared in the application has excellent barrier performance.

[0135] The specific parameters of the raw materials used in the application are as follows: The density of the metallocene linear low-density polyethylene is 0.914-0.922 g / cm 3 .

[0136] The density of the low-density polyethylene is 0.917-0.925 g / cm 3 .

[0137] The density of the linear low-density polyethylene is 0.918-0.922 g / cm 3 .

[0138] The density of the high-density polyethylene is 0.941-0.955 g / cm 3 .

[0139] The ethylene content of the ethylene-vinyl alcohol copolymer is 40-44 mol%, and the density is 1.0-1.5 g / cm 3 .

[0140] The ethylene-acrylate copolymer has an AA content of 15-20%.

[0141] The maleic anhydride grafted polyethylene has a density of 0.92-0.94 g / cm 3 , the grafting rate is 0.8-1.5%.

[0142] The maleic anhydride grafted polyolefin has a density of 0.86-0.88 g / cm 3 , the grafting rate is 1.2-1.5%.

[0143] Obviously, there are many specific implementation methods that can be changed under the concept of the present invention. Here, it should be stated that any changes made under the inventive concept of the present invention will fall within the scope of protection of the present invention.

Claims

1. An EVOH high-barrier film for silage bags, characterized by: The EVOH high barrier film consists of an inner layer, an adhesive inner layer, a barrier layer, an adhesive outer layer, and an outer layer; The inner layer materials include: acrylic acid grafted molybdenum disulfide, metallocene linear low-density polyethylene, low-density polyethylene, antioxidant, light stabilizer, and slip agent; the slip agent is erucamide; The materials of the bonding inner layer include: ethylene-acrylate copolymer, maleic anhydride grafted polyethylene, and linear low-density polyethylene; The barrier layer materials include: ethylene-vinyl alcohol copolymer, NiCo-MBO LDHs nanocomposite, antioxidant, maleic anhydride grafted polyolefin, and ethylene-acrylate copolymer; The bonding outer layer materials include: ethylene-acrylate copolymer, maleic anhydride grafted polyethylene, linear low-density polyethylene; The outer layer raw materials include: acrylic acid grafted molybdenum disulfide, high-density polyethylene, linear low-density polyethylene, antioxidant, light stabilizer, anti-adhesion agent; the anti-adhesion agent is nano-silicon dioxide; The NiCo-MBO LDHs nanocomposite material is prepared from Ni(NO3)2·6H2O, Co(NO3)2·6H2O, and 2-mercaptobenzoxazole; The acrylic acid grafted molybdenum disulfide is prepared from molybdenum disulfide, acrylic acid and potassium persulfate.

2. The EVOH high-barrier film for silage bags according to claim 1, characterized in that: The weight ratio of the raw material components of the inner layer is: 3-5 parts of acrylic acid grafted molybdenum disulfide, 45-55 parts of metallocene linear low-density polyethylene, 25-35 parts of low-density polyethylene, 0.2-0.5 parts of antioxidant, 0.1-0.3 parts of light stabilizer, and 0.1-0.2 parts of slip agent; The weight ratio of the raw material components of the bonding inner layer is: 30-35 parts of ethylene-acrylate copolymer, 45-55 parts of maleic anhydride grafted polyethylene, and 15-20 parts of linear low-density polyethylene; The weight ratio of the raw material components of the barrier layer is: 60-70 parts of ethylene-vinyl alcohol copolymer, 5-8 parts of NiCo-MBO LDHs nanocomposite material, 0.3-0.6 parts of antioxidant, 5-10 parts of maleic anhydride grafted polyolefin, and 5-10 parts of ethylene-acrylate copolymer; The weight ratio of the raw material components of the bonding outer layer is: 25-35 parts of ethylene-acrylate copolymer, 45-50 parts of maleic anhydride grafted polyethylene, and 20-25 parts of linear low-density polyethylene; The weight ratio of the outer layer raw material components is: 5-8 parts of acrylic acid grafted molybdenum disulfide, 40-45 parts of high-density polyethylene, 35-40 parts of linear low-density polyethylene, 0.5-0.7 parts of antioxidant, 0.3-0.6 parts of light stabilizer, and 0.1-0.3 parts of anti-blocking agent.

3. The method for preparing an EVOH high-barrier film for silage bags according to any one of claims 1-2, characterized in that: The method includes the steps of preparing NiCo-MBO LDHs nanocomposite material, preparing acrylic acid grafted molybdenum disulfide, premixing barrier layer raw materials, and co-extrusion molding; The NiCo-MBO LDHs nanocomposite material is prepared by dissolving Ni(NO3)2·6H2O and Co(NO3)2·6H2O in deionized water to prepare a nickel nitrate solution and a cobalt nitrate solution; the nickel nitrate solution and the cobalt nitrate solution are uniformly mixed in a volume ratio of (1-3):1 to obtain a nickel-cobalt mixed solution; and 2-mercaptobenzoxazole is dissolved in methanol to prepare a 2-mercaptobenzoxazole solution. The 2-mercaptobenzoxazole solution is added dropwise to the nickel-cobalt mixed solution, the pH value of the system is adjusted, and stirring is continued for 1-2 hours to obtain a suspension; the suspension is transferred to a reactor, the temperature is 120-160°C, and the reaction is carried out for 18-24 hours; after the reaction is completed, the suspension is naturally cooled to room temperature, and the NiCo-MBO LDHs nanocomposite material is obtained after centrifugation, washing, and drying.

4. The method for preparing an EVOH high-barrier film for silage bags according to claim 3, characterized in that: The volume ratio of the 2-mercaptobenzoxazole solution to the nickel-cobalt mixed solution is (0.2-0.5):

1.

5. The method for preparing an EVOH high-barrier film for silage bags according to claim 3, characterized in that: The pH value of the system is adjusted by adding NaOH solution dropwise to adjust the pH value of the system to 8.5-9.

5.

6. The method for preparing an EVOH high-barrier film for silage bags according to claim 3, characterized in that: The method for preparing acrylic acid-grafted molybdenum disulfide comprises adding molybdenum disulfide to DMF, wherein the molybdenum disulfide accounts for 1-1.2% of the mass of the DMF, performing ultrasonic treatment for 4-6 hours, and then centrifuging to obtain a molybdenum disulfide dispersion. Acrylic acid is added to the molybdenum disulfide dispersion and stirred evenly; nitrogen is introduced, potassium persulfate is added, and under nitrogen protection, the reaction system is heated to 60-80°C and stirred for 6-8 hours; after the reaction is completed, the molybdenum disulfide grafted with acrylic acid is obtained after centrifugation, washing, and drying.

7. The method for preparing an EVOH high-barrier film for silage bags according to claim 6, characterized in that: The mass ratio of the acrylic acid to molybdenum disulfide is (1-2):

1.

8. The method for preparing an EVOH high-barrier film for silage bags according to claim 6, characterized in that: The potassium persulfate is 5%-10% of the mass of acrylic acid.

9. The method for preparing an EVOH high-barrier film for silage bags according to claim 3, characterized in that: The barrier layer raw material premixing comprises the following steps: adding the NiCo-MBO LDHs nanocomposite material and the ethylene-vinyl alcohol copolymer into a twin-screw extruder; setting the extruder feeding section temperature at 160-170° C., the melting section temperature at 190-210° C., the mixing section temperature at 200-220° C., and the die head temperature at 180-190° C.; cooling and granulating the extruded material; and then uniformly mixing the material with an antioxidant, maleic anhydride grafted polyolefin, and ethylene-acrylate copolymer to obtain a barrier layer premix.

10. The method for preparing an EVOH high-barrier film for silage bags according to claim 3, characterized in that: The co-extrusion molding comprises the following steps: pre-mixing the raw materials of each layer and then adding them into a five-layer co-extruder; the temperature of each section of the extruder is as follows: the feeding section is 145-170°C, the compression section is 165-200°C, the melting section is 180-210°C, the homogenizing section is 185-210°C, the connector is 180-210°C, the transition section is 175-210°C, the distributor is 175-205°C, and the die outlet is 165-200°C; and after extrusion from the die, film blowing, cooling, corona treatment, and drying are performed to finally obtain an EVOH high-barrier film for silage bags.

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