Ethylene maleic anhydride copolymer and preparation and application methods thereof

Abstract

The invention provides an ethylene maleic anhydride copolymer and a preparation and application method thereof, and the preparation method comprises the following steps: dissolving a maleic anhydride monomer in an organic solvent to form a uniformly dispersed solution system, and transferring the solution system into a high-pressure reactor; ethylene gas in a supercritical state is introduced into the solution system of the high-pressure reactor to form a uniform ethylene-maleic anhydride solution system, wherein the pressure of the ethylene gas in the supercritical state is 5-30 Mpa; adding a free radical initiator into the ethylene-maleic anhydride solution system, raising the reaction temperature, and carrying out solution polymerization reaction to obtain a reaction system; a precipitant is added into a reaction system to separate out the ethylene-maleic anhydride copolymer, ethylene and maleic anhydride in the ethylene-maleic anhydride copolymer alternately exist in the form that the molar ratio of ethylene to maleic anhydride is 1: 1, high-performance bonding composite resin can also be formed by blending the ethylene-maleic anhydride copolymer and polyethylene, and the high-performance bonding composite resin is suitable for the fields of adhesives, coatings, composite materials and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials and composite materials, and particularly relates to an ethylene-maleic anhydride copolymer and a preparation and application method thereof. BACKGROUND

[0002] In the field of high polymer materials and composite materials, ethylene-maleic anhydride copolymer as an adhesive material has been widely used in wood-plastic adhesion, metal adhesion, and heterogeneous composite film adhesion. At present, the commercialized ethylene-maleic anhydride copolymer is mainly prepared by grafting maleic anhydride on polyethylene random copolymer, but it has the following significant defects: 1. Low grafting rate and uneven distribution: In the traditional grafting process, the grafting rate of maleic anhydride is usually less than 5%, and the insufficient content of polar groups limits the adhesion performance; at the same time, the maleic anhydride groups are randomly distributed on the polyethylene molecular chain, causing uneven polarity phase of the material, affecting the stability of the interface wetting effect and the bonding strength.

[0003] 2. Side reactions affect processing performance: In the process of polyolefin functionalization grafting reaction, unnecessary side reactions often occur, such as chain scission, chain crosslinking, etc., which leads to the deterioration of molecular chain structure and affects the melt processing performance (such as flowability, thermal stability) of the material, and even causes the performance fluctuation of the subsequent products.

[0004] 3. Insufficient outdoor durability: The chemical structure stability and mechanical property decay problem of the existing grafted copolymer under long-term sunlight irradiation, heat and humidity in outdoor environment has not been fully solved, which limits its application in harsh environments (such as agricultural mulch, outdoor packaging materials, etc.).

[0005] Although the existing technology attempts to improve the grafting process to improve the performance, but limited by the grafting reaction mechanism, it is difficult to achieve uniform distribution and high loading of maleic anhydride units, and the problem of side reactions always exists. Therefore, developing a synthesis method of ethylene-maleic anhydride copolymer with high polar group content, uniform distribution structure and excellent processing stability is still a technical problem to be solved in the field. SUMMARY

[0006] The purpose of the present application is to provide an ethylene-maleic anhydride copolymer and a preparation and application method thereof, which can prepare an ethylene-maleic anhydride copolymer with high molecular weight and excellent thermal stability. The ethylene-maleic anhydride copolymer can form a high-performance adhesive composite resin when blended with polyethylene, and is suitable for the fields of adhesives, coatings, composite materials, etc.

[0007] To achieve the above purpose, the technical scheme provides a preparation method of an ethylene-maleic anhydride copolymer, which comprises the following steps: S1: Dissolve maleic anhydride monomers in an organic solvent to form a uniformly dispersed solution system under inert gas protection, and transfer the solution system to a high-pressure reactor; S2: Under stirring conditions, supercritical state ethylene gas is introduced into the solution system in the high-pressure reactor to form a uniform ethylene-maleic anhydride solution system, wherein the pressure of the supercritical state ethylene gas is 5-30 Mpa; S3: Add a free radical initiator to the ethylene-maleic anhydride solution system and increase the reaction temperature to carry out solution polymerization to obtain a reaction system; S4: Add a precipitating agent to the reaction system to precipitate ethylene-maleic anhydride copolymer, wherein the ethylene-maleic anhydride copolymer has a 1:1 molar ratio of ethylene to maleic anhydride in the form of alternation.

[0008] This scheme uses supercritical state ethylene gas, which has low viscosity, high diffusivity and high liquid solubility, to fundamentally solve the problems of low grafting rate, uneven structure and multiple side reactions in traditional processes. It should be noted that supercritical ethylene (5-30 MPa) can significantly increase the solubility of ethylene in the solvent and promote the chain growth rate of ethylene monomer and maleic anhydride.

[0009] Regarding the improvement of grafting rate: This scheme uses supercritical state ethylene to control and free radical initiation system, which forces ethylene and maleic anhydride to strictly alternate copolymerization at a 1:1 molar ratio, forming an ethylene-maleic anhydride copolymer with a 50% molar insertion rate, including the following formula: .

[0010] Regarding the improvement of structure uniformity: The low viscosity (≈gas) and high diffusivity of supercritical state ethylene make it form nanoscale microbubbles during stirring, which uniformly mix with maleic anhydride molecules at the molecular level, avoiding local enrichment or depletion caused by insufficient stirring in traditional processes. Moreover, the dissociation efficiency of free radical initiators in supercritical state ethylene gas is high, and the primary free radicals produced can also uniformly initiate the addition of ethylene and maleic anhydride, forming a structurally uniform ethylene-maleic anhydride copolymer.

[0011] Regarding the reduction of side effects: Supercritical state ethylene can achieve efficient polymerization at a low temperature of 50-70℃, which is 80-100℃ lower than the traditional process, basically eliminating the risk of thermal degradation of the polyethylene main chain. Moreover, the high solubility of supercritical state ethylene can effectively disperse the reaction heat, avoiding local overheating caused by chain radical coupling termination or disproportionation termination. At the same time, the strong electron-withdrawing property of maleic anhydride improves the stability of chain radicals, and the monomer insertion reaction is preferentially carried out rather than side reactions.

[0012] The organic solvent for dissolving the maleic anhydride in step S1 is one or more of an alkane solvent, an aromatic hydrocarbon solvent, a halogenated alkane solvent, a halogenated aromatic hydrocarbon solvent, and an ester solvent.

[0013] In some embodiments, the organic solvent is one or more of pentane, n-hexane, petroleum ether, cyclohexane, benzene, toluene, xylene, chlorobenzene, decaline, ethyl acetate, butyl acetate, and isoamyl acetate.

[0014] Preferably, the organic solvent is toluene, n-hexane, ethyl acetate, or butyl acetate. Among them, toluene or n-hexane is selected because of its lower polarity which is conducive to promoting the dissolution of ethylene; ethyl acetate or butyl acetate is selected because of its excellent solubility for maleic anhydride and its ability to adjust the polarity of the reaction system under certain process conditions.

[0015] In some embodiments, the concentration of maleic anhydride in the solution system in step S1 is 0.1 mol / L to 5 mol / L.

[0016] In some embodiments, the high-pressure reactor is a semi-continuous batch reactor made of stainless steel or nickel-based alloy material that is resistant to high pressure and corrosion, ensuring the long-term stability of the reactor under high pressure and high temperature conditions.

[0017] In step S2, under stirring conditions, supercritical ethylene gas is introduced into the solution system in the high-pressure reactor to form a uniform ethylene-maleic anhydride solution system. At this time, a high-speed stirrer or vortex dispersion device is used in the high-pressure reactor to stir the ethylene-maleic anhydride solution system, promoting the micro-bubbling of supercritical ethylene gas and ensuring uniform contact between supercritical ethylene gas and maleic anhydride in the ethylene-maleic anhydride solution system.

[0018] It should be noted that under stirring conditions, supercritical ethylene gas is continuously introduced into the solution system in the high-pressure reactor to form a uniform ethylene-maleic anhydride solution system, but no solution system is added.

[0019] The pressure of the supercritical ethylene gas in the present scheme is controlled to be 5 to 30 MPa, and preferably, the pressure of the ethylene gas is 7 to 10 MPa, so that the ethylene gas is in a supercritical state, enhancing the diffusion and solvation properties of the ethylene monomer, promoting its alternating insertion with the maleic anhydride monomer, and reducing the chain termination side effects.

[0020] In step S3, the free radical initiator is an azo compound and / or a peroxide compound.

[0021] In some embodiments, the azo compound includes any one or a combination of at least two of azobisisobutyronitrile, azobisisopentyl nitrile, azobisisoheptyl nitrile, azobiscyclohexyl cyanide, or dimethyl azobisbutyrate.

[0022] In some embodiments, the peroxide compound includes any one of dibenzoyl peroxide, dodecanoyl peroxide, dicumyl peroxide, or diisopropyl peroxydicarbonate, or a combination of at least two thereof.

[0023] Preferably, the free radical initiator is selected as azobisisobutyronitrile or azobisisoheptyl nitrile, which has the characteristics of low temperature and high activity, and can promote the initiation efficiency.

[0024] In some embodiments, the reaction temperature is raised to 50-150°C in step S3, and the reaction time of the solution polymerization is 2-10h.

[0025] Preferably, the reaction temperature is raised to 65°C in step S3 to balance the activity of the initiator and the amount of ethylene dissolved.

[0026] In step S4, the precipitant is water or a low-polarity solvent. After adding the precipitant to the reaction system to precipitate the precipitate, the precipitate is washed with an appropriate amount of organic solvent or distilled water. After washing, the precipitate is vacuum dried to obtain the purified ethylene maleic anhydride copolymer, wherein the ethylene and maleic anhydride in the ethylene maleic anhydride copolymer are in the form of 1:1 alternation.

[0027] In some embodiments, the precipitant is n-hexane.

[0028] In some embodiments, the ethylene maleic anhydride copolymer prepared in step S4 is in the form of powder, which is more convenient for post-processing and later processing than the blocky ethylene-maleic anhydride copolymer grafted by the traditional process.

[0029] It should be noted that the ethylene maleic anhydride copolymer synthesized by the present scheme has a strict 1:1 copolymerization structure. Since the 1:1 alternating structure is used, each maleic anhydride unit is directly connected to the ethylene segment, and no additional grafting step is needed, which simplifies the production process and makes the reaction activity and performance more consistent. That is, the maleic anhydride and ethylene units on the ethylene maleic anhydride copolymer obtained by the present scheme are uniformly distributed, and the functionalization degree of the molecular chain of the ethylene maleic anhydride copolymer is controllable. The ethylene maleic anhydride copolymer also improves the thermal stability of the material, and the molecular chain is not easily degraded during high-temperature processing, and problems such as chain scission and chain entanglement do not occur, and there is no free maleic anhydride monomer in the product, so it is more suitable for processing.

[0030] In addition, the ethylene-maleic anhydride copolymer of the present application is prepared by a direct solvent free radical copolymerization process, which has the advantages of high monomer reaction efficiency, less by-products, controllable process, and controllable product molecular weight, which is controlled by the concentration of maleic anhydride monomer, ethylene pressure, and free radical initiator concentration. Generally, the higher the concentration of maleic anhydride monomer, the greater the ethylene pressure, the higher the product molecular weight, and the higher the free radical initiator concentration, the lower the product molecular weight. Moreover, the present application utilizes the supercritical state of ethylene (critical point: Tc=9.2℃, Pc=5.04 MPa) to optimize the reaction pressure and catalyst system, to achieve low-temperature and high-efficiency polymerization, to break through the molecular weight bottleneck, and to reduce the equipment requirements.

[0031] In a second aspect, the present application provides a preparation method of the adhesive composite resin, which comprises the following steps: The polyethylene, the maleic anhydride grafted polyethylene, and the ethylene-maleic anhydride copolymer prepared in the first aspect are mixed after being sufficiently dried to obtain a solid premix; The solid premix is melt blended and extruded to obtain the adhesive composite resin.

[0032] In some embodiments, the ethylene-maleic anhydride copolymer has a regular structure formed by ethylene and maleic anhydride in a 1:1 ratio, and the number average molecular weight of the ethylene-maleic anhydride copolymer is greater than 100,000 g / mol. The high polarity density and uniform dispersion of the ethylene-maleic anhydride copolymer can significantly improve the adhesion between the ethylene-maleic anhydride copolymer and the polar / non-polar machine.

[0033] In some embodiments, the grafting rate of the polyethylene of the maleic anhydride grafted polyethylene is 0.5-2.5 wt.%, which is used as a polar phase promoter to assist in improving the compatibility and forming a multi-polar interface network structure. Preferably, the grafting rate of the polyethylene of the maleic anhydride grafted polyethylene is 1.0-1.5 wt.%.

[0034] In some embodiments, the polyethylene is selected as any one of high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), or low-density polyethylene (LDPE), which can be adjusted according to the actual application to adjust the tensile property, flexibility, or heat sealing performance of the material.

[0035] In some embodiments, the polyethylene, the maleic anhydride grafted polyethylene, and the ethylene-maleic anhydride copolymer prepared in the first aspect are respectively placed in a vacuum drying oven or a dry air circulation system, and dried at 80-100℃ for 2-6 hours to remove the adsorbed water for sufficient drying, to prevent performance degradation caused by hydrolysis or degradation during subsequent melt processing.

[0036] In some embodiments, the mass ratio of the ethylene-maleic anhydride copolymer in the solid premix is 1-5%, the mass ratio of the maleic anhydride grafted polyethylene in the solid premix is 5-10%, the mass ratio of the polyethylene in the solid premix is 85-95%, and the total mass fraction of the polyethylene, the maleic anhydride grafted polyethylene and the ethylene-maleic anhydride copolymer is 100%. The scheme can reduce the addition amount of the maleic anhydride grafted polyethylene by introducing the ethylene-maleic anhydride copolymer.

[0037] In some preferred embodiments, the mass ratio of the polyethylene, the maleic anhydride grafted polyethylene and the ethylene-maleic anhydride copolymer prepared by the first aspect is 88:10:2 or 95:4:1.

[0038] In some embodiments, the solid premix is added to a twin-screw extruder, an internal mixer or an internal mixer, and melt blending is carried out under a set temperature and shear rate, wherein the time of melt blending is controlled to be 2-10 minutes. In some embodiments, the set temperature is 150-230°C, and the shear rate is 50-200 rpm.

[0039] Preferably, the time of melt blending is 5 minutes.

[0040] During the melt blending of the solid premix, the polar maleic anhydride units in the ethylene-maleic anhydride copolymer are uniformly distributed in the polyolefin phase, forming a synergistic polar network with the maleic anhydride grafted polyethylene, and significantly improving the wettability and interfacial bonding strength between the polar / non-polar interfaces.

[0041] In some embodiments, after melt blending, the product is extruded, and then cut into particles by water-cooled strand cutting or air-cooled hot cutting to obtain the adhesive composite resin in the form of particles, which has excellent dispersibility, flowability and processing stability, and can be directly used for the processing of cast film, co-extrusion film, injection molded products or hot melt adhesive products.

[0042] The scheme synergistically introduces a small proportion of ethylene-maleic anhydride copolymer and maleic anhydride grafted polyethylene into the polyethylene system, which not only realizes high-efficiency polar interfacial bonding performance, but also significantly reduces the use amount of the maleic anhydride grafted polyethylene, overcomes the problems of high cost and poor flowability, and reduces the addition amount of the maleic anhydride grafted polyethylene from 30% to 5-10% while maintaining or exceeding the bonding performance, which reflects the modification potential of high-efficiency polar functional materials in multi-component polyolefin systems.

[0043] Compared with the prior art, the technical scheme has the following characteristics and beneficial effects: The scheme realizes strict alternation copolymerization of ethylene and maleic anhydride at a 1:1 molar ratio to form regular segments by supercritical ethylene regulation and a free radical initiation system, breaks through the bottleneck of low grafting rate (usually <5%) in traditional grafting process, and the molar insertion rate reaches 50%, and the prepared ethylene maleic anhydride copolymer has excellent thermal stability and is not easy to degrade during high-temperature processing, and when blended with polyethylene, only 1-5% needs to be added to significantly reduce the amount of maleic anhydride grafted polyethylene, maintain or exceed the bonding performance, and has wide application prospects in the fields of adhesives, coatings, composites and the like. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is an NMR spectrum of the ethylene maleic anhydride copolymer. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the present application.

[0046] Synthesis Example One of Ethylene Maleic Anhydride Copolymer Under the protection of high-purity nitrogen, 30 g of maleic anhydride monomer was dissolved in 300 ml of toluene to form a uniformly dispersed solution system, and the solution system was transferred to a high-pressure reactor; under stirring, 6.5 MPa of ethylene gas was introduced into the solution system in the high-pressure reactor to form a uniform ethylene-maleic anhydride solution system; 0.01 mol of AIBN was added to the ethylene-maleic anhydride solution system, and the reaction temperature was increased to 70°C, and the reaction system was obtained after 2 hours of reaction; n-hexane was added to the reaction system to precipitate the ethylene maleic anhydride copolymer.

[0047] The weight average molecular weight Mw of the ethylene maleic anhydride copolymer was measured to be 8.2*10 4 , the polydispersity index PDI was 2.34, and the yield was 17 g. The NMR spectrum of the ethylene maleic anhydride copolymer of synthesis example one is shown in Figure 1 , and the ethylene maleic anhydride copolymer has a strict 1:1 copolymerization structure.

[0048] Synthesis Example Two of Ethylene Maleic Anhydride Copolymer Under the protection of high-purity nitrogen, 30 g of maleic anhydride monomer was dissolved in 300 ml of toluene to form a uniformly dispersed solution system, and the solution system was transferred to a high-pressure reactor; under stirring, 6.5 MPa of ethylene gas was introduced into the solution system in the high-pressure reactor to form a uniform ethylene-maleic anhydride solution system; 0.01 mol of ABVN was added to the ethylene-maleic anhydride solution system, and the reaction temperature was raised to 55°C for 2 hours to obtain a reaction system; n-hexane was added to the reaction system to precipitate the ethylene-maleic anhydride copolymer.

[0049] The measured weight average molecular weight Mw of the ethylene-maleic anhydride copolymer was 8.9*10 4 , the polydispersity index PDI was 2.16, and the yield was 13 g.

[0050] Synthesis Example Three of Ethylene-Maleic Anhydride Copolymer Under the protection of high-purity nitrogen, 30 g of maleic anhydride monomer was dissolved in 300 ml of toluene to form a uniformly dispersed solution system, and the solution system was transferred to a high-pressure reactor; under stirring, 8.5 MPa of ethylene gas was introduced into the solution system in the high-pressure reactor to form a uniform ethylene-maleic anhydride solution system; 0.01 mol of AIBN was added to the ethylene-maleic anhydride solution system, and the reaction temperature was raised to 70°C for 2 hours to obtain a reaction system; n-hexane was added to the reaction system to precipitate the ethylene-maleic anhydride copolymer.

[0051] The measured weight average molecular weight Mw of the ethylene-maleic anhydride copolymer was 10.7*10 4 , the polydispersity index PDI was 2.32, and the yield was 19 g.

[0052] Synthesis Example Four of Ethylene-Maleic Anhydride Copolymer Under the protection of high-purity nitrogen, 30 g of maleic anhydride monomer was dissolved in 300 ml of toluene to form a uniformly dispersed solution system, and the solution system was transferred to a high-pressure reactor; under stirring, 8.5 MPa of ethylene gas was introduced into the solution system in the high-pressure reactor to form a uniform ethylene-maleic anhydride solution system; 0.01 mol of ABVN was added to the ethylene-maleic anhydride solution system, and the reaction temperature was raised to 70°C for 2 hours to obtain a reaction system; n-hexane was added to the reaction system to precipitate the ethylene-maleic anhydride copolymer.

[0053] The measured weight average molecular weight Mw of the ethylene-maleic anhydride copolymer was 12.3*10 4 , the polydispersity index PDI was 2.41, and the yield was 21 g.

[0054] Synthesis Example Five of Ethylene-Maleic Anhydride Copolymer Under the protection of high-purity nitrogen, 30 g of maleic anhydride monomer was dissolved in 300 ml of toluene to form a uniformly dispersed solution system, and the solution system was transferred to a high-pressure reactor; under stirring, 2.0 MPa of ethylene gas was introduced into the solution system in the high-pressure reactor to form a uniform ethylene-maleic anhydride solution system; 0.01 mol of AIBN was added to the ethylene-maleic anhydride solution system, and the reaction temperature was raised to 70°C for 2 hours to obtain a reaction system; n-hexane was added to the reaction system to precipitate the ethylene-maleic anhydride copolymer.

[0055] The measured weight average molecular weight Mw of the ethylene-maleic anhydride copolymer was 3.7*10 4 , the polydispersity index PDI was 2.73, and the yield was 11 g.

[0056] Synthesis Example Six of Ethylene-Maleic Anhydride Copolymer Under the protection of high-purity nitrogen, 20 g of maleic anhydride monomer was dissolved in 300 ml of toluene to form a uniformly dispersed solution system, and the solution system was transferred to a high-pressure reactor; under stirring, 3.0 MPa of ethylene gas was introduced into the solution system in the high-pressure reactor to form a uniform ethylene-maleic anhydride solution system; 0.01 mol of AIBN was added to the ethylene-maleic anhydride solution system, and the reaction temperature was raised to 70°C for 2 hours to obtain a reaction system; n-hexane was added to the reaction system to precipitate the ethylene-maleic anhydride copolymer.

[0057] The measured weight average molecular weight Mw of the ethylene-maleic anhydride copolymer was 6.1*10 4 , the polydispersity index PDI was 2.45, and the yield was 13 g.

[0058] Synthesis Example One of Adhesion Composite Resin: LLDPE (brand SP1520) and maleic anhydride grafted polyethylene PE-g-MA (grafting rate 1.0%) were dried at 80°C for 6 hours, and the dried raw materials were mixed in a ratio of PE:PE-g-MA = 90:10, and the solid premix was added to a twin-screw extruder for melt blending under the conditions of temperature 170°C and shear rate 70 rpm, to obtain an adhesion composite resin.

[0059] The adhesion composite resin was pressed into a 100 μm thin film on a flat plate vulcanizing instrument, which was used as a bonding layer of a nylon-polyethylene composite film, and the T-type peel strength of the thin film was tested according to GB / T2791-1995 using a universal tensile testing machine, and the peel strength reached 17.7 N / cm.

[0060] Synthesis Example Two of Adhesion Composite Resin: LLDPE (grade SP1520) and ethylene-maleic anhydride copolymer EMAH were dried at 80°C for 6 hours, and the dried raw materials were mixed in a ratio of PE:EMAH = 94:6. The solid premix was added to a twin-screw extruder for melt blending at a temperature of 170°C and a shear rate of 70 rpm to obtain the adhesive composite resin.

[0061] The adhesive composite resin was pressed into a 100 μm film on a flat vulcanizing instrument as a bonding layer of a nylon-polyethylene composite film. The T-type peel strength of the film was tested using a universal tensile testing machine according to GB / T2791-1995, and the peel strength reached 14.49 N / cm.

[0062] Synthesis Example Three of the Adhesive Composite Resin LLDPE (grade SP1520), maleic anhydride grafted polyethylene PE-g-MA (grafting rate 1.0%) and ethylene-maleic anhydride copolymer EMAH were dried at 80°C for 6 hours, and the dried raw materials were mixed in a ratio of PE:PE-g-MA:EMAH = 94:5:1. The solid premix was added to a twin-screw extruder for melt blending at a temperature of 170°C and a shear rate of 70 rpm to obtain the adhesive composite resin.

[0063] The adhesive composite resin was pressed into a 100 μm film on a flat vulcanizing instrument as a bonding layer of a nylon-polyethylene composite film. The T-type peel strength of the film was tested using a universal tensile testing machine according to GB / T2791-1995, and the peel strength reached 22.3 N / cm.

[0064] Synthesis Example Four of the Adhesive Composite Resin LLDPE (grade SP1520), maleic anhydride grafted polyethylene PE-g-MA (grafting rate 1.0%) and ethylene-maleic anhydride copolymer EMAH were dried at 80°C for 6 hours, and the dried raw materials were mixed in a ratio of PE:PE-g-MA:EMAH = 88:10:2. The solid premix was added to a twin-screw extruder for melt blending at a temperature of 170°C and a shear rate of 70 rpm to obtain the adhesive composite resin.

[0065] The adhesive composite resin was pressed into a 100 μm film on a flat vulcanizing instrument as a bonding layer of a nylon-polyethylene composite film. The T-type peel strength of the film was tested using a universal tensile testing machine according to GB / T2791-1995, and the peel strength reached 35.3 N / cm.

[0066] In addition, the adhesion of the adhesive composite resins prepared in different examples was compared, and the adhesion of the adhesive composite resins with different ratios is shown in Table 1. .

[0067] As shown in Table 1, the adhesion of the adhesion composite resin prepared by mixing polyethylene PE, maleic anhydride grafted polyethylene PE-g-MA and ethylene maleic anhydride copolymer EMAH is the best.

[0068] Those skilled in the art should understand that each technical feature of the above embodiments can be combined arbitrarily, and for the sake of brevity, each technical feature in the above embodiments is not described in all possible combinations, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0069] The above embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the present application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of variations and improvements can be made, which are all within the scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A method for preparing an ethylene-maleic anhydride copolymer, characterized in that, Includes the following steps: S1: Under inert gas protection, maleic anhydride monomer is dissolved in an organic solvent to form a uniformly dispersed solution system, and the solution system is transferred to a high-pressure reactor; S2: Under stirring conditions, supercritical ethylene gas is introduced into the solution system of a high-pressure reactor to form a homogeneous ethylene-maleic anhydride solution system, wherein the pressure of the supercritical ethylene gas is 5~30 MPa. S3: Add a free radical initiator to the ethylene-maleic anhydride solution system and increase the reaction temperature to carry out solution polymerization to obtain the reaction system; S4: Add a precipitant to the reaction system to precipitate the ethylene-maleic anhydride copolymer, wherein the ethylene and maleic anhydride in the ethylene-maleic anhydride copolymer exist alternately in a 1:1 molar ratio.

2. The preparation method according to claim 1, characterized in that, The maleic anhydride monomers are selected from one or more of maleic anhydride, maleamide, N-alkylmaleamide, fumaric anhydride or phthalic anhydride.

3. According to the preparation method of claim 1, the organic solvent for dissolving maleic anhydride is one or more of alkane solvents, aromatic solvents, haloalkane solvents, and haloaromatic solvents.

4. The preparation method according to claim 1, characterized in that, The concentration of the maleic anhydride monomer in the solution system is 0.1 mol / L to 5 mol / L.

5. The method for preparing the ethylene-maleic anhydride copolymer according to claim 1, characterized in that, The high-pressure reactor is a semi-continuous batch reactor.

6. The method for preparing the ethylene-maleic anhydride copolymer according to claim 1, characterized in that, Under stirring conditions, supercritical ethylene gas is continuously introduced into the solution system of the high-pressure reactor to form a homogeneous ethylene-maleic anhydride solution system. The reaction temperature is increased to 50~150℃, and the reaction time of the solution polymerization reaction is 2~10h.

7. The method for preparing the ethylene-maleic anhydride copolymer according to claim 1, characterized in that, The free radical initiator is an azo compound and / or a peroxide compound.

8. A method for preparing an adhesive composite resin, characterized in that, Includes the following steps: After thorough drying, polyethylene, maleic anhydride-grafted polyethylene, and the α-olefin-maleic anhydride alternating copolymer prepared according to any one of claims 1 to 8 are mixed to obtain a solid premix. The solid premix is ​​blended in a molten state and then extruded and granulated to obtain an adhesive composite resin.

9. The method for preparing the adhesive composite resin according to claim 8, characterized in that, The grafting rate of maleic anhydride-grafted polyethylene is 0.5–2.5 wt.%, and the polyethylene is selected as any one of high-density polyethylene, linear low-density polyethylene, or low-density polyethylene. The ethylene-maleic anhydride copolymer has a regular structure formed by alternating ethylene and maleic anhydride in a 1:1 ratio, and the number average molecular weight of the ethylene-maleic anhydride copolymer is greater than 100,000 g / mol.

10. The method for preparing the adhesive composite resin according to claim 8, characterized in that, The alternating copolymer has a mass ratio of 1-5% in the solid premix, the maleic anhydride-grafted polyethylene has a mass ratio of 5-10% in the solid premix, the polyethylene has a mass ratio of 85%-95% in the solid premix, and the total mass fraction of polyethylene, maleic anhydride-grafted polyethylene and alternating copolymer is 100%.

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