A method for preparing a polar olefin-based monomer-modified polyolefin resin, an anti-fog film and a method for preparing the same

Abstract

The application discloses a preparation method of a polar olefin monomer modified polyolefin resin, an antifog film and a preparation method thereof. The antifog film prepared from the resin has the advantages of reaching grade 1 in the antifog level, good antifog drop performance, long effective period and more than 20 months of continuous antifog effect. Due to the good compatibility in the processing process and the molecular structure design of the modified resin, the antifog film has excellent antifog performance, and further improves the tensile strength at break and the falling dart impact strength of the film, and the light transmittance of the film reaches more than 87%.

Description

Technical Field

[0001] This invention belongs to the field of polymers, specifically relating to a method for preparing a polar olefin resin-modified polyolefin resin, and an anti-fog film. Background Technology

[0002] In my country, the main type of plastic greenhouse film is polyethylene film, which is a hydrophobic resin. The surface tension of this film differs significantly from that of water. In early spring or late autumn, the temperature and humidity differences between the inside and outside of the greenhouse are substantial. When the surface temperature of the plastic film drops below the dew point, the water vapor in the air becomes saturated or supersaturated, causing condensation into numerous droplets on the inner wall of the film. The presence of these droplets leads to light scattering or reflection, reducing the light transmittance of the agricultural or horticultural greenhouse film and affecting crop photosynthesis. Furthermore, droplets falling on plants inside the greenhouse can cause the leaves, stems, and buds to wither or rot, directly reducing crop yield and quality. To prevent droplet formation on the film surface, the surface tension must be altered to be closer to that of water. This requires the presence of hydrophilic groups on the film surface, such as by adding surfactants. These surfactants increase the critical surface tension of polyethylene, causing the tiny water droplets condensed on the inner wall of the polyethylene film to spread into a transparent water film and flow downwards to the ground, achieving an anti-drip effect.

[0003] In existing technologies, there are two main methods to improve the wettability of plastic surfaces and impart non-drip properties: external coating with non-drip agents and internal addition of non-drip agents. The external coating method involves using a high-pressure spray gun to spray the surface inside the greenhouse. However, this method requires spraying equipment, is cumbersome to operate, and is costly. Furthermore, it poses the problem of solvent evaporation and environmental pollution. Therefore, the internal addition method is more commonly used in China. The internal addition method involves adding the non-drip agent to the raw resin during the production of the plastic greenhouse film, mixing and plasticizing them together, and then blow molding the film. Currently, the internal additive method is commonly used in my country, but it has several problems: (1) reduced transparency; (2) low thermal stability, with processing temperatures exceeding the temperature limit of the internal additives; (3) excessive anti-fogging additives will lead to a decrease in film strength; (4) due to the significant difference in polarity between the anti-fogging agent and the matrix resin, it is prone to migration and water erosion, resulting in a short drip-free life of polyethylene film, generally 3-6 months; (5) processing difficulties, as the anti-fogging agent is incompatible with polyethylene, making addition difficult and causing the blown film machine screw to slip. For these reasons, it is difficult to further improve the durability of anti-fogging films prepared by the internal additive method.

[0004] Polyolefin resins possess excellent overall performance and are inexpensive, making them the most produced and widely used polymeric materials among synthetic resins. However, the non-polar nature of their chain structure also limits their application in certain fields. Increasing the polarity of polyolefins can significantly improve their adhesion, surface properties, and miscibility, thus leading to their widespread use as dispersants, stabilizers, and plastic surface modifiers.

[0005] Weng W et al. (Copolymerization of Ethylene and Vinyl Fluoride by (Phosphine-Sulfonate)Pd(Me)(py)Catalysts[J]. Journal of the American Chemical Society, 2007, 129(50): 15450-1) reported that a phosphonobenzenesulfonic acid ligand and palladium catalyst can catalyze the copolymerization of ethylene and methyl acrylate to produce linear polymers. However, the catalyst is difficult to prepare and costly, and the copolymerization process has poor directional selectivity, resulting in linear polymers that lack structural applicability.

[0006] Patent CN112898464A discloses a method for preparing a polar polyolefin material, wherein the comonomer used in the polar polyolefin material includes ethylene monomer and comonomer containing polar functional groups. Although this method can solve problems such as the polarization of polyolefin materials, the method used is not economical.

[0007] Patent CN114249853A discloses a method for preparing polar functionalized olefin homopolymers or copolymers from olefinically unsaturated polar monomers. The method involves obtaining homopolymers or copolymers of olefinically unsaturated polar monomers via a metal salt reverse micelle solution under certain conditions through supramolecular self-assembly. However, this method is complex, and the scale-up effect makes it difficult to revert small-scale products to changes in production parameters during supramolecular self-assembly. Consequently, the resulting polymers exhibit low comonomer insertion rates, limiting their potential for large-scale production.

[0008] Patent CN103755876B discloses a method for preparing amorphous polyalphaolefins modified with polar monomers, which is obtained by grafting amorphous polyalphaolefins with a peroxide initiator, a polar monomer, and a grafting agent under molten or melting conditions. Although this technology obtains polyolefin polymers containing polar monomers through grafting reactions, the conversion rate of polar monomers is low, the number of grafts is limited and uncontrollable, and low-molecular-weight polymers are easily generated due to side reactions such as chain scission in the high-temperature molten state. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing a polyolefin resin modified with a polar olefin monomer. The anti-fog film prepared using the resin obtained by this invention has an anti-fog level of 1, an anti-fog effect lasting for more than 20 months, a light transmittance of more than 87%, a tensile breaking strength of more than 20 MPa, and a drop weight impact strength of up to 680 g.

[0010] This invention is achieved through the following technical solution:

[0011] In a first aspect, the present invention provides a method for preparing a polar olefin monomer-modified polyolefin resin, comprising the following steps:

[0012] (1) Add solvent, RAFT reagent and initiator to high pressure reactor, add 1,3-butadiene, stir, heat up to initiate polymerization and reaction;

[0013] (2) Add titanium catalyst and triethylaluminum hexane solution to the product of step (1), and introduce ethylene to carry out polymerization reaction under certain temperature and pressure;

[0014] (3) Add polar olefin monomers to the product of step (2), add initiator, stir, heat, polymerize, and separate.

[0015] In step (1) of the present invention, the amount of solvent used is 1000-5000 parts by weight, preferably 2500-3000 parts by weight; the amount of RAFT reagent used is 10-50 parts by weight, preferably 25-30 parts by weight; the amount of initiator used is 1-5 parts by weight, preferably 3-4 parts by weight; and 1,3-butadiene is 300-500 parts by weight, preferably 350-400 parts by weight.

[0016] In step (1) of the present invention, the stirring time is 20-30 minutes.

[0017] In step (1) of the present invention, the temperature is raised to 60-90°C, preferably 70-80°C.

[0018] In step (1) of this invention, the reaction time is 30-50 minutes.

[0019] In step (2) of the present invention, the amount of titanium catalyst used is 0.01-0.02 parts by weight, preferably 0.015-0.018 parts by weight; the concentration of the triethylaluminum hexane solution is 0.8-1.2 mol / L, and the amount of the triethylaluminum hexane solution used is 1.7-2.3 parts by weight, preferably 1.9-2.1 parts by weight.

[0020] In step (2) of the present invention, the reaction temperature is 60-90℃, preferably 75-85℃, the reaction pressure is 1.0-2.0MPa, preferably 1.5-1.8MPa, and the reaction time is 1-2 hours.

[0021] In step (3) of the present invention, the amount of polar olefin monomer used is 600-1000 parts by weight, preferably 700-850 parts by weight; the amount of initiator used is 1-5 parts by weight, preferably 3-5 parts by weight.

[0022] In step (3) of this invention, the stirring time is 20-30 minutes.

[0023] In step (3) of the present invention, the temperature is raised to 60-90℃, preferably 70-80℃.

[0024] In step (3) of this invention, the polymerization reaction time is 1 hour to 2 hours.

[0025] As a preferred embodiment, in step (3), after separation, the obtained polymer is flash-evaporated to remove the solvent under a pressure of 1-10 kPa, preferably 2-5 kPa, to obtain a polyethylene resin material modified with polar olefin monomers.

[0026] The solvent described in this invention is one or more of n-hexane, cyclohexane, n-pentane, cyclopentane, and toluene, preferably n-hexane and / or toluene.

[0027] The RAFT reagent described in this invention is a trithioester, preferably S-1-dodecyl-S′-(α,α′-dimethyl-α"-acetic acid) trithiocarbonate.

[0028] The initiator described in this invention is a peroxide initiator, such as one or more of dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, tert-butyl cumyl peroxide, di-tert-butyl peroxide, tert-butyl benzoate, tert-butyl hydroperoxide, and tert-amyl hydroperoxide, preferably one or two of tert-butyl hydroperoxide and tert-amyl hydroperoxide.

[0029] The titanium-based catalyst described in this invention is a Ziegler-Natta catalyst, selected from the manufacturer XY-S, a solar catalyst manufacturer.

[0030] The polar olefin monomers described in this invention are one or more selected from vinyl acetate, methacrylic acid, methacrylate, methacrolein, and derivatives of methacrylamide. Preferably, vinyl acetate and methacrylic acid are selected from one or both.

[0031] This invention utilizes RAFT polymerization to prepare RAFT-terminated 1,3-butadiene polymers in a solvent using a peroxide initiator. Since 1,3-butadiene contains two double bonds, when one double bond participates in polymerization, the steric hindrance of the macromolecular chain makes it difficult for the unpolymerized double bond to contact the active sites of the catalyst, thus preserving the double bond. The degree of polymerization is controlled between 30-300 by adjusting the monomer to RAFT reagent ratio. Too low a degree of polymerization fails to form a well-defined branched cross-linked core structure after polymerization with ethylene, thus affecting the mechanical properties of the final product. Conversely, a degree of polymerization exceeding 300 results in a higher degree of cross-linking due to the presence of more double bonds, leading to the formation of high-molecular-weight polymers with a high degree of cross-linking in the subsequent copolymerization with ethylene. This hinders the incorporation of polar monomers and can cause crystal point problems in downstream applications.

[0032] Ethylene is then introduced, and under the action of Ziegler-Natta catalyst, the double bonds on the side chains of the 1,3-butadiene polymerization unit in the above polymer continue to react and polymerize with ethylene to obtain RAFT reagent-terminated polyolefin resin. By limiting the reaction temperature, pressure, time, and amount of catalyst added in this step, the molecular weight of the obtained polyolefin resin is between 80,000 and 120,000.

[0033] The reaction continues with the addition of polar olefin monomers. Based on the RAFT radical capture mechanism, the subsequently added polar olefin monomers grow by intercalating between the RAFT reagent and the 1,3-butadiene polymer backbone. Therefore, as the reaction proceeds, a polar olefin monomer-modified polyolefin resin with a controllable molecular weight outer polar hydrophilic layer and a polyolefin core is obtained. The degree of polymerization of the polar olefin monomer blocks is controlled between 60-400 by adjusting the ratio of the added polar olefin monomer to the previously added RAFT reagent. Too low a degree of polymerization makes it difficult to form the hydrophilic layer structure encapsulating the polyolefin resin, reducing the anti-fogging effect in product applications. Conversely, too high a degree of polymerization in these blocks will affect the mechanical properties of the modified polyolefin resin.

[0034] An anti-fog film comprising the following components:

[0035]

[0036] The present invention also provides a method for preparing an anti-fog film, comprising the following steps:

[0037] 1) The polar olefin monomer modified polyolefin resin, LDPE polyethylene granule resin, antioxidant and light stabilizer are mixed evenly and added to a twin-screw extruder. After extrusion and granulation, anti-fog transparent polyethylene composite material masterbatch is obtained.

[0038] 2) The above-mentioned anti-fog transparent polyethylene composite material masterbatch is placed into a biaxially oriented film stretching machine for film forming to obtain an anti-fog transparent polyethylene film.

[0039] In step 1) of the present invention, the mixing temperature is 90-100℃ and the mixing time is 5-10min.

[0040] In step 1) of the method described in this invention, the mixing is completed in a high-speed mixer with a mixing speed of 800-1500 r / min. The temperature setting range of the extruder is 150℃-190℃. As a preferred example: the temperatures of zones one, two, and three of the extruder are set to 160℃-165℃, zone four to 165℃-170℃, zone five to 170℃-180℃, zones six and seven to 175℃-180℃, zones eight and nine to 180℃-190℃, and the die head to 170℃-175℃. The main extruder is set to 80-100 r / min, and the feed rate is set to 6-8 r / min.

[0041] In step 2) of the method of the present invention, the longitudinal stretching temperature of the biaxial stretching film machine is set to 96-106℃ with a stretching ratio of 4-4.5, and the transverse stretching temperature is set to 148-156℃ with a stretching ratio of 7-9.

[0042] The LDPE polyethylene granule resin used in this invention is preferably low-density polyethylene LD150 produced by Yanshan Petrochemical, with a density of 0.920 g / cm³. 3 The melt flow rate is 0.8 g / 10 min.

[0043] The antioxidant described in this invention is preferably a compound formed by combining phenolic antioxidant 1010 from Shandong Sanfeng and phosphite antioxidant (tris[2,4-di-tert-butylphenyl]phosphite) in a mass ratio of 1:1.

[0044] The light stabilizer described in this invention is preferably BASF's light stabilizer 770.

[0045] The polar olefin monomer-modified polyolefin resin described in this invention, due to the abundance of polar hydrophilic groups in its outer macromolecular segments, exhibits excellent anti-fogging properties when prepared as an anti-fogging masterbatch for film fabrication. Unlike smaller molecules that migrate out and become ineffective, it provides superior anti-fogging performance with a long service life. As a polyolefin resin, it exhibits good compatibility with LDPE film during processing, promoting uniform dispersion of the anti-fogging polyolefin resin within the film and enhancing its anti-fogging performance. Simultaneously, the resin's high branching degree reduces crystallinity, increasing film transmittance. The cross-linked structure further enhances film strength, improving tensile strength at break and drop impact strength, thus increasing film durability.

[0046] The beneficial effects of this invention are as follows: the resin prepared by this invention has both excellent hydrophilic surface activity and the excellent mechanical properties of polyolefin resins. The anti-fogging film prepared by it has an anti-fogging level of 1, an anti-fogging effect lasting for more than 20 months, a light transmittance of more than 87%, a tensile breaking strength of 20 MPa, and a drop weight impact strength of 680 g. Detailed Implementation

[0047] To better understand the technical solution of the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0048] Information on the main raw materials in the embodiments and comparative examples of this invention:

[0049] n-Hexane: Beijing Innocare, AR grade.

[0050] RAFT reagents: Sigma-Aldrich trithioester RAFT reagents.

[0051] Peroxide initiators: tert-butyl hydroperoxide and tert-amyl hydroperoxide, purchased from Sigma-Aldrich.

[0052] 1,3-Butadiene: Purchased from Mingju Gas Company, 99% purity or sampled from the equipment.

[0053] Ethylene: Purchased from liquid air ethylene, 99.999% purity.

[0054] Titanium-based catalysts: XY-S, a manufacturer of solar catalysts.

[0055] The polar olefin monomers were vinyl acetate, methacrylic acid, methacrylate, methacrolein, and methacrylamide, all of which were purchased from Beijing Innocare Reagent Co., Ltd.

[0056] Low-density polyethylene resin: Low-density polyethylene LD150 produced by Yanshan Petrochemical, with a density of 0.920 g / cm³. 3 The melt flow rate is 0.8 g / 10 min.

[0057] Antioxidant: A compound agent formed by combining Shandong Sanfeng's phenolic antioxidant 1010 and phosphite antioxidant (tris[2,4-di-tert-butylphenyl]phosphite) in a mass ratio of 1:1.

[0058] Stabilizer: BASF's light stabilizer 770.

[0059] Unless otherwise specified, all raw materials used in the examples and comparative examples were obtained from commercial sources.

[0060] Example 1

[0061] 1) Add 3000 parts by weight of n-hexane, 30 parts by weight of RAFT reagent S-1-dodecyl-S′-(α,α′-dimethyl-α"-acetic acid) trithiocarbonate, and 3 parts by weight of initiator tert-amyl hydrogen peroxide to a high-pressure reactor. Purge with nitrogen for 30 minutes, evacuate three times, add 325 parts by weight of 1,3-butadiene using a metering pump, stir for 25 minutes, and then heat to 80°C to initiate polymerization. React for 30 minutes. The degree of polymerization is controlled at 60 by the ratio of 1,3-butadiene monomer to RAFT reagent.

[0062] 2) Add 0.018 parts by weight of titanium catalyst and 2 parts by weight of 1 mol / L triethylaluminum hexane solution to the reactor containing the above-mentioned polymer containing double bonds. Introduce ethylene and heat to 80°C to carry out the polymerization reaction. After the reactor pressure reaches 1.8 MPa, control the pressure to keep constant and continue to add ethylene. Maintain the reaction temperature and continue the reaction for 1 hour.

[0063] 3) After depressurizing the above reactor, add 775 parts by weight of the polar olefin monomer methacrylic acid. The degree of block polymerization is controlled at 100 by the ratio of monomer to initial RAFT reagent. Add 3 parts by weight of initiator tert-amyl hydrogen peroxide. After stirring for 20 minutes, raise the temperature to 70°C. Stop the reaction after 2 hours of polymerization. The separated polymer is flash-evaporated to remove the solvent under a pressure of 2 kPa to obtain the polyethylene resin material modified with the polar olefin monomer.

[0064] 4) Take 10 parts of polar olefin monomer-modified polyethylene resin, 85 parts of LDPE polyethylene granule resin, 3 parts of antioxidant and 2 parts of light stabilizer, mix them evenly in a high-speed mixer with a speed of 1200 r / min, a mixing temperature of 95℃ and a mixing time of 10 min to obtain a mixture; add it to a twin-screw extruder, the temperature settings of the extruder are 165℃ for zones 1, 170℃ for zone 4, 175℃ for zone 5, 178℃ for zones 6 and 7, 185℃ for zones 8 and 9, 175℃ for the die head, 90 r / min for the main extruder and 7 r / min for the feed. After extrusion and granulation, anti-fog transparent polyethylene composite material is obtained.

[0065] 5) The above-mentioned anti-fog transparent polyethylene composite masterbatch is placed into a biaxial stretching film machine for film making. The longitudinal stretching temperature is set to 100℃ and the stretching ratio is 4, the transverse stretching temperature is set to 152℃ and the stretching ratio is 9, and an anti-fog transparent polyethylene film is obtained.

[0066] Example 2

[0067] 1) Add 2750 parts by weight of toluene, 25 parts by weight of RAFT reagent S-1-dodecyl-S′-(α,α′-dimethyl-α"-acetic acid) trithiocarbonate, and 2.5 parts by weight each of initiators tert-butyl hydroperoxide and tert-amyl hydroperoxide to a high-pressure reactor. Purge with nitrogen for 30 minutes and evacuate three times. Add 400 parts by weight of 1,3-butadiene using a metering pump. Stir for 25 minutes and then heat to 75°C to initiate polymerization. React for 40 minutes. The degree of polymerization is controlled at 165 by the ratio of 1,3-butadiene monomer to RAFT reagent.

[0068] 2) Add 0.015 parts by weight of titanium catalyst and 2.3 parts by weight of 1 mol / L triethylaluminum hexane solution to the reactor containing the above-mentioned polymer containing double bonds. Introduce ethylene and heat to 75°C to carry out the polymerization reaction. After the reactor pressure reaches 1.5 MPa, control the pressure to keep constant and continue to add ethylene. Maintain the reaction temperature and continue the reaction for 1 hour.

[0069] 3) After depressurizing the above reactor, add 500 parts by weight each of the polar olefin monomers vinyl acetate and methacrylic acid. The degree of block polymerization is controlled at 230 by the ratio of monomers to the initial RAFT reagent. Add 1 part by weight of the initiator tert-butyl hydrogen peroxide. After stirring for 20 minutes, raise the temperature to 75°C. Stop the reaction after 1.5 hours of polymerization. The obtained polymer is flash-evaporated to remove the solvent under a pressure of 3.5 kPa to obtain the polyethylene resin material modified with polar olefin monomers.

[0070] 4) The subsequent granulation, film-making formulation and parameter settings are the same as in Example 1, and the anti-fog transparent polyethylene composite material is obtained.

[0071] Example 3

[0072] 1) Add 2500 parts by weight of n-pentane, 27.5 parts by weight of RAFT reagent S-1-dodecyl-S′-(α,α′-dimethyl-α"-acetic acid) trithiocarbonate, and 1 part by weight of initiator tert-butyl hydroperoxide to a high-pressure reactor. Purge with nitrogen for 30 minutes and evacuate three times. Add 250 parts by weight of 1,3-butadiene using a metering pump. Stir for 25 minutes and then heat to 90°C to initiate polymerization. React for 40 minutes. The degree of polymerization is controlled at 60 by the ratio of 1,3-butadiene monomer to RAFT reagent.

[0073] 2) Add 0.010 parts by weight of titanium catalyst and 1.7 parts by weight of 1 mol / L triethylaluminum hexane solution to the reactor containing the above-mentioned polymer containing double bonds. Introduce ethylene and heat to 60°C to carry out the polymerization reaction. After the reactor pressure reaches 1 MPa, control the pressure to keep constant and continue to add ethylene. Maintain the reaction temperature and continue the reaction for 1.5 hours.

[0074] 3) After depressurizing the above reactor, add 700 parts by weight of the polar olefin monomer methacrylamide. The degree of block polymerization is controlled at 150 by the ratio of monomer to initial RAFT reagent. Add 1 part by weight of initiator tert-butyl hydrogen peroxide. After stirring for 25 minutes, raise the temperature to 80°C. Stop the reaction after 1 hour of polymerization. The separated polymer is flash-evaporated to remove the solvent under a pressure of 5 kPa to obtain the polyethylene resin material modified with polar olefin monomer.

[0075] 4) The subsequent granulation, film-making formulation and parameter settings are the same as in Example 1, and the anti-fog transparent polyethylene composite material is obtained.

[0076] Example 4

[0077] 1) Add 1000 parts by weight of cyclohexane, 50 parts by weight of RAFT reagent S-1-dodecyl-S′-(α,α′-dimethyl-α"-acetic acid) trithiocarbonate, and 4 parts by weight of initiator dicumyl peroxide to a high-pressure reactor. Purge with nitrogen for 30 minutes, evacuate three times, add 300 parts by weight of 1,3-butadiene using a metering pump, stir for 20 minutes, and then heat to 60°C to initiate polymerization. React for 40 minutes. The degree of polymerization is controlled at 30 by the ratio of 1,3-butadiene monomer to RAFT reagent.

[0078] 2) Add 0.0165 parts by weight of titanium catalyst and 1.9 parts by weight of 1 mol / L triethylaluminum hexane solution to the reactor containing the above-mentioned polymer containing double bonds. Introduce ethylene and heat to 85°C to carry out the polymerization reaction. After the reactor pressure reaches 1.65 MPa, control the pressure to keep constant and continue to add ethylene. Maintain the reaction temperature and continue the reaction for 1.5 hours.

[0079] 3) After depressurizing the above reactor, add 600 parts by weight of polar olefin monomer methacrylate. The degree of block polymerization is controlled at 60 by the ratio of monomer to initial RAFT reagent. Add 4 parts by weight of initiator dicumyl peroxide. After stirring for 25 minutes, raise the temperature to 60°C. Stop the reaction after 1.5 hours of polymerization. The separated polymer is flash-evaporated to remove the solvent under 10 kPa pressure to obtain a polyethylene resin material modified with polar olefin monomer.

[0080] 4) The subsequent granulation, film-making formulation and parameter settings are the same as in Example 1, and the anti-fog transparent polyethylene composite material is obtained.

[0081] Example 5

[0082] 1) Add 2500 parts by weight each of n-hexane and toluene, 10 parts by weight of RAFT reagent S-1-dodecyl-S′-(α,α′-dimethyl-α"-acetic acid) trithiocarbonate, and 3.5 parts by weight of initiator tert-butyl hydroperoxide to a high-pressure reactor. Purge with nitrogen for 30 minutes, evacuate three times, add 500 parts by weight of 1,3-butadiene using a metering pump, stir for 30 minutes, and then heat to 70°C to initiate polymerization. React for 50 minutes. The degree of polymerization is controlled at 300 by the ratio of 1,3-butadiene monomer to RAFT reagent.

[0083] 2) Add 0.02 parts by weight of titanium catalyst and 2.1 parts by weight of 1 mol / L triethylaluminum hexane solution to the reactor containing the above-mentioned polymer containing double bonds. Introduce ethylene and heat to 90°C to carry out the polymerization reaction. After the reactor pressure reaches 2 MPa, control the pressure to keep constant and continue to add ethylene. Maintain the reaction temperature and continue the reaction for 2 hours.

[0084] 3) After depressurizing the above reactor, add 1000 parts by weight of the polar olefin monomer vinyl acetate. The degree of block polymerization is controlled at 400 by the ratio of monomer to initial RAFT reagent. Add 3.5 parts by weight of the initiator tert-butyl hydrogen peroxide. After stirring for 30 minutes, raise the temperature to 90°C. Stop the reaction after 1 hour of polymerization. The separated polymer is flash-evaporated to remove the solvent under 1 kPa pressure to obtain the polyethylene resin material modified with the polar olefin monomer.

[0085] 4) The subsequent granulation, film-making formulation and parameter settings are the same as in Example 1, and the anti-fog transparent polyethylene composite material is obtained.

[0086] Comparative Example 1

[0087] Except that in step 1), the amount of 1,3-butadiene is changed to 60 parts by weight, and the degree of polymerization is controlled at 10. The rest is the same as in Example 1.

[0088] Comparative Example 2

[0089] Except for step 1), where the amount of RAFT reagent S-1-dodecyl-S′-(α,α′-dimethyl-α"-acetic acid) trithiocarbonate is changed to 4 parts by weight and the degree of polymerization is controlled at 550, the rest is the same as in Example 2.

[0090] Comparative Example 3

[0091] Except for step 2), where the amount of titanium catalyst is changed to 0.005 parts by weight, the rest is the same as in Example 3.

[0092] Comparative Example 4

[0093] Except for step 2), where the amount of 1 mol / L triethylaluminum hexane solution is changed to 0.5 parts by weight; the rest is the same as in Example 4.

[0094] Comparative Example 5

[0095] Except for step 2), where ethylene is continuously added at a constant pressure after the pressure in the reactor reaches 0.5 MPa; the rest is the same as in Example 5.

[0096] Comparative Example 6

[0097] Except for step 3), the amount of polar olefin monomer methacrylic acid is changed to 200 parts by weight, and the degree of block polymerization is controlled at 25 by the ratio of monomer to initial RAFT reagent; the rest is the same as in Example 1.

[0098] Five samples of anti-fog transparent polyethylene film obtained from Examples 1 to 5 of this invention and six samples of polyethylene film obtained from Comparative Examples 1 to 6 were subjected to anti-fog performance tests. The mechanical properties of the anti-fog transparent polyethylene films before and after being placed in a thermo-oxidative aging chamber (140℃, 200h) were tested according to the ISO 527-1 test standard, including tensile strength, elongation at break, and drop impact strength. The main testing equipment is as follows:

[0099] Experimental line for co-rotating parallel twin-screw compounding extrusion water-drawing granulation, Nanjing Juli Chemical Machinery Co., Ltd.

[0100] Small biaxially oriented film stretching machine, Guangzhou Putong Instrument Equipment Co., Ltd.;

[0101] Transmittance and haze meter, Shanghai Precision Scientific Instruments Co., Ltd.

[0102] Dart impact testing machine, Jinan Langguang Electromechanical Technology Co., Ltd.

[0103] Intelligent tensile testing machine, Jinan Langguang Electromechanical Technology Co., Ltd.;

[0104] Membrane air permeability tester, Jinan Langguang Electromechanical Technology Co., Ltd.;

[0105] Anti-fogging performance includes anti-fogging performance testing and film contact angle. The film anti-fogging performance is determined according to GB / T31726-2015 "Test Method for Anti-fogging Properties of Plastic Films". The main methods for testing film anti-fogging properties are the water bath hot fog method and the rapid hot fog method. The contact angle is determined according to the method specified in ASTM D 5725-1999 (R2008).

[0106] The test results of the polyethylene films prepared in the examples and comparative examples are shown in Tables 1 and 2:

[0107] Table 1. Anti-fog performance test results

[0108]

[0109]

[0110] Table 2 Mechanical property test results

[0111]

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a polar olefin monomer-modified polyolefin resin, comprising the following steps: (1) Add solvent, RAFT reagent and initiator to high pressure reactor, add 1,3-butadiene, stir, heat to initiate polymerization and reaction; (2) Add titanium catalyst and triethylaluminum hexane solution to the product of step (1), and introduce ethylene to carry out polymerization reaction under certain temperature and pressure; (3) Add polar olefin monomers to the product of step (2), add initiator, stir, heat, polymerize, and separate; In step (1), the amount of RAFT reagent is 10-50 parts by weight; the amount of initiator is 1-5 parts by weight; 300-500 parts by weight of 1,3-butadiene; and the degree of polymerization of the RAFT-terminated 1,3-butadiene polymer obtained in step (1) is 30-300. The reaction pressure in step (2) is 1.0-2.0 MPa; the amount of titanium catalyst used in step (2) is 0.01-0.02 parts by weight; the concentration of the triethylaluminum hexane solution is 0.8-1.2 mol / L; and the amount of the triethylaluminum hexane solution used is 1.7-2.3 parts by weight. The degree of polymerization of the polar olefin monomer block obtained in step (3) is 60-400.

2. The method according to claim 1, characterized in that, In step (1), the amount of RAFT reagent is 25-30 parts by weight; the amount of initiator is 3-4 parts by weight; and the amount of 1,3-butadiene is 350-400 parts by weight.

3. The method according to claim 1, characterized in that, In step (2), the amount of titanium catalyst used is 0.015-0.018 parts by weight.

4. The method according to claim 3, characterized in that, The amount of the triethylaluminum hexane solution used is 1.9-2.1 parts by weight.

5. The method according to claim 1, characterized in that, In step (3), the amount of polar olefin monomer used is 600-1000 parts by weight; the amount of initiator used is 1-5 parts by weight.

6. The method according to claim 1, characterized in that, In step (3), the amount of polar olefin monomer used is 700-850 parts by weight; the amount of initiator used is 3-5 parts by weight.

7. The method according to claim 1, characterized in that, The RAFT reagent is S-1-dodecyl-S′-(α,α′-dimethyl-α"-acetic acid) trithiocarbonate.

8. The method according to claim 1, characterized in that, The polar olefin monomer is one or more of vinyl acetate, methacrylic acid, methacrylate, methacrolein, and methacrylamide.

9. An anti-fog film comprising the following components: 70-95 parts by weight of polar olefin monomer-modified polyolefin resin prepared by the method according to any one of claims 1-8; LDPE polyethylene granules resin 5-25 parts by weight; Antioxidant 1-4 parts by weight; 1-2 parts by weight of light stabilizer.

10. A method for preparing the antifog film according to claim 9, comprising the following steps: 1) The polar olefin monomer modified polyolefin resin, LDPE polyethylene granule resin, antioxidant and light stabilizer are mixed evenly and added to a twin-screw extruder. After extrusion and granulation, anti-fog transparent polyethylene composite material masterbatch is obtained. 2) The above-mentioned anti-fog transparent polyethylene composite material masterbatch is placed into a biaxially oriented film forming machine to form a film, thereby obtaining an anti-fog transparent polyethylene film.

11. The method according to claim 10, characterized in that, In step 1), the temperature setting range of the extruder is 150℃-190℃.

12. The method according to claim 11, characterized in that, In step 1), the temperature of the extruder is set as follows: the temperature of zone 1, zone 2 and zone 3 of the extruder is set to 160℃-165℃, the temperature of zone 4 is 165℃-170℃, the temperature of zone 5 is 170℃-180℃, the temperature of zone 6 and zone 7 is 175℃-180℃, the temperature of zone 8 and zone 9 is 180℃-190℃, and the temperature of the die head is 170℃-175℃.

13. According to the method of claim 10, in step 2), the longitudinal stretching temperature of the biaxial stretching film machine is set to 96-106℃, the stretching ratio is 4-4.5, and the transverse stretching temperature is set to 148-156℃, the stretching ratio is 7-9.

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