Polyolefin graft modification method based on coating and photochemical reaction

Abstract

The invention discloses a polyolefin graft modification method based on coating and photochemical reaction, which comprises the following steps: step 1, raw material preparation: mixing 20-50 parts by weight of glycidyl methacrylate (GMA), 1-5 parts by weight of benzophenone (BP) and 1-2 parts by weight of triethylamine (TEA), and uniformly stirring to obtain a mixed solution; 2, coating: coating the surface of a polyolefin film with the mixed solution obtained in the step 1, wherein the coating weight is 1g / m < 2 >-3g / m < 2 >; the method has the beneficial effects that a peroxide initiator is not needed, the reaction is initiated by ultraviolet light, the reaction condition is mild, polyolefin degradation and side reaction are reduced, and the grafting rate is greater than 3.5%; ethyl acetate and other low-toxicity solvents are adopted, residual solvents can be removed through oven treatment, and the environment-friendly requirement is met; active groups such as an epoxy group are introduced into a grafted product, so that the compatibility with a polar material is remarkably improved, and the breaking strength is improved by more than 50% compared with that of common PP; the polyolefine can be used as an interface compatibilizer, a macromolecular coupling agent and the like, and the application of the polyolefine in the high-end field is expanded.

Description

Technical Field

[0001] This invention belongs to the field of synthetic resin and new material technology, specifically relating to a method for grafting modification of polyolefins based on coating and photochemical reaction. Background Technology

[0002] Synthetic resins, as the basic raw materials for industries such as plastics, synthetic fibers, coatings, and adhesives, are widely used not only in construction, agriculture, manufacturing, and packaging, but also in national defense, cutting-edge technology, and electronic information. They have become the fourth largest category of materials after metals, wood, and cement. my country's synthetic resin production has been growing at a double-digit rate annually, making it the world's second-largest consumer of synthetic resins after the United States. The variety, quality, production technology, equipment, and technological level of its products have greatly improved, placing it at the forefront of the world in some areas. Polypropylene (PP), one of the most widely used resins, possesses excellent chemical resistance and electrical insulation properties, and is lightweight, inexpensive, and easy to process. Its production technology and processing application levels have developed rapidly, achieving remarkable progress, just like other synthetic resins. Through different production equipment and methods, various products with different properties and uses are synthesized, and these products are widely used in industry, agriculture, machinery, aerospace, automobiles, electronics, electrical engineering, construction, medicine, and daily life, making them an indispensable material for national economic and defense construction. PP has become the fastest-growing variety of general-purpose resins, with its production volume second only to polyethylene and polyvinyl chloride.

[0003] Polypropylene (PP) possesses excellent heat resistance and mechanical properties. However, as a crystalline polymer, PP produces relatively large spherulites, which is the main reason for its susceptibility to cracking and low impact strength. Its non-polar and crystalline nature, when cooled from the molten state, easily forms large spherulites, resulting in low impact strength, low-temperature brittleness, and difficulty in dyeing, thus limiting its application areas to some extent. Refining the crystal structure of PP can improve its impact strength. Copolymerization and blending modification methods can improve PP's performance defects, but copolymerization is technically more difficult and cannot meet the needs of practical applications. Blending modification, due to its lower investment and faster results, has become one of the most active areas of research in polymer materials science both domestically and internationally. However, due to the poor compatibility of PP with other materials such as polar polymers, metals, or inorganic fillers, the mixed components in the blend system separate into two independent phases. The weak interphase adhesion and high surface tension prevent the achievement of good mechanical properties, thus greatly hindering the process of PP performance enhancement.

[0004] Currently, in the polymer synthesis industry, improving the flexibility of synthetic resins and plastics to enhance their impact resistance is mainly achieved through graft copolymerization. Graft modification technology is an important method for modifying polymer materials. The basic principle of graft modification is to utilize free radicals generated by initiators or irradiation to create active sites on the polymer backbone. Graft monomers are then introduced onto these active sites to form side chains containing functional groups. Through chemical reactions, functional chemical groups are grafted onto the polymer matrix molecules, modifying the polymer molecular chains at the microscopic level, thereby modifying and controlling the macroscopic properties of the material. Graft modification methods mainly include radiation grafting, solution grafting, melt grafting, solid-phase grafting, and suspension grafting.

[0005] Radiation grafting uses X-rays or high-energy electron beams instead of initiators to generate free radical active sites on the polyolefin molecular chain, thereby initiating a grafting reaction with the grafting monomer. Because radiation grafting of polyolefins often uses ultraviolet light, its penetration into materials is poor, and it is commonly used for grafting modification of polyolefin films. Solution grafting involves dissolving the polymer, monomer, and initiator in an organic solvent for the grafting reaction. The reaction conditions are relatively mild, and the reactants are heated uniformly. However, the organic solvents used in solution grafting generate significant costs and environmental problems during heating, recovery, and post-processing, limiting the development of solution grafting. Melt grafting involves pre-mixing the polyolefin, grafting monomer, and initiator thoroughly, then adding them to a screw extruder to melt at high temperatures to form a fluid for the grafting reaction. The grafting method has a small environmental impact, simple equipment, and low cost, but the temperature is high during melt grafting. The free radicals of polyolefin macromolecules are prone to side reactions such as fracture and cross-linking branching, which lead to material degradation and grafted monomer residues, affecting the grafting quality. Solid-phase grafting involves adding polyolefin, grafted monomer, initiator, and interface agent into a reaction vessel and heating the reaction in an inert gas environment. Solid-phase grafting has a low reaction temperature and fewer side reactions such as cross-linking and degradation. However, the grafting reaction generally occurs on the solid surface, in amorphous regions and lattice defects within the molecule, resulting in relatively poor grafting uniformity. Aqueous suspension grafting involves suspending polyolefin, initiator, and monomer in water to form a dispersed phase for grafting. Aqueous suspension grafting has a mild and easily controllable reaction, no organic solvents, is simple, and produces uniform grafting with a high grafting rate.

[0006] PP melt grafting has the advantages of simple operation and low cost, but the relationship between the components during the reaction is complex and there are many side reactions, which are generally mainly degradation, seriously affecting the performance of PP. Summary of the Invention

[0007] The purpose of this invention is to provide a method for grafting and modifying polyolefins based on coating and photochemical reaction. This method does not require a peroxide initiator and achieves covalent bonding between the coating and the substrate through coating and UV curing, thus solving the problems of poor compatibility between polyolefins and polar materials and numerous side reactions in existing grafting methods.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a method for graft modification of polyolefins based on coating and photochemical reaction, comprising the following steps:

[0009] Step 1: Raw material preparation: By weight, mix 20-50 parts glycidyl methacrylate (GMA), 1-5 parts benzophenone (BP), and 1-2 parts triethylamine (TEA) and stir until homogeneous to obtain a mixture.

[0010] Step 2 Coating: The mixture from Step 1 is coated onto the surface of the polyolefin film at a coating weight of 1 g / m². 2 -3g / m 2 ;

[0011] Step 3: Photochemical reaction: The coated polyolefin film is successively subjected to oven treatment and ultraviolet radiation to synthesize glycidyl methacrylate oligomer (PGMA-BPH) with half-pinacol dormant end groups on the polyolefin surface, thus obtaining a grafted resin film.

[0012] Step 4 Granulation: The grafted resin film obtained in Step 3 is melted, extruded, and granulated to obtain polyolefin grafted particles.

[0013] As a preferred embodiment of the present invention, the polyolefin includes polypropylene (PP) and polyethylene (PE), and the thickness of the polyolefin film is 15μm-40μm.

[0014] As a preferred technical solution of the present invention, the mixing conditions in step one are: stirring rate 200-300 r / min, stirring time 10-20 min, and ambient temperature 20-30℃.

[0015] As a preferred technical solution of the present invention, in step two, the coating is carried out using a gravure coating machine, and a diluent can be added to adjust the viscosity of the mixture. The diluent is one or a combination of at least two of ethanol, isopropanol, and ethyl acetate, and the volume ratio of the mixture to the diluent is 1:1-2:1.

[0016] As a preferred embodiment of the present invention, in step three, the oven treatment conditions are as follows: temperature 40-60℃, treatment time 3-5 min; ultraviolet radiation using an LED-UV light source with a wavelength of 365nm-405nm, radiation time 10-30s, and radiation intensity 1-10W / cm². 2 .

[0017] As a preferred technical solution of the present invention, in step four, granulation is carried out using an environmentally friendly granulator, specifically including:

[0018] (a) Using grafted resin film as raw material, wherein the mass ratio of polyolefin substrate to PGMA-BPH is 100:4.6;

[0019] (b) The raw material is added to the hopper of the granulator and conveyed to the heating cylinder by the screw. The cylinder is heated in sections to melt the raw material into a viscous flow state.

[0020] (c) The molten material is extruded into strips through a porous membrane head, cooled by air, and then cut into cylindrical particles by a pelletizer.

[0021] As a preferred technical solution of the present invention, the raw material is added to the hopper of the pelletizer and conveyed to the heating cylinder by the screw. The cylinder is heated to 200-240°C in sections, so that the raw material melts into a viscous flow state. The melt is extruded into strips through a porous membrane head, cooled by air, and then cut into cylindrical particles by a pelletizer with a particle diameter of 2-3 mm and a length of 2-3 mm.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] No peroxide initiator is required; the reaction is initiated by ultraviolet light, resulting in mild reaction conditions, reduced polyolefin degradation and side reactions, and a grafting rate >3.5%.

[0024] It uses low-toxicity solvents such as ethyl acetate, and the oven treatment can remove residual solvents, which meets environmental protection requirements;

[0025] The grafted product introduces active groups such as epoxy groups, which significantly improves its compatibility with polar materials and increases the tensile strength by more than 50% compared with ordinary PP.

[0026] It can be used as an interface compatibilizer, macromolecular coupling agent, etc., to expand the application of polyolefins in high-end fields. Attached Figure Description

[0027] Figure 1 This is a flowchart of the method for polyolefin grafting modification according to the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] Please see Figure 1 This is the first embodiment of the present invention, which provides a method for grafting modification of polyolefins based on coating and photochemical reaction, comprising the following steps:

[0031] Raw material preparation: By weight, add 20 parts glycidyl methacrylate (GMA), 1 part benzophenone (BP), and 1 part triethylamine (TEA) into a stainless steel mixing tank and stir until homogeneous to obtain a mixture.

[0032] Coating and photochemical reaction: The mixture obtained above was coated onto a 15µm PP film using a gravure coater; then irradiated at a wavelength of 365nm for 10s with an intensity of 5W / cm². 2 LED-UV initiation was used to synthesize glycidyl methacrylate oligomers (PGMA-BPH) with dormant half-pinacol end groups on PP surfaces, with a coating weight of 1 g / m². 2 ;

[0033] The obtained PP film is melt-granulated using a twin-screw extruder to obtain the product: This film material is added to the hopper of the granulator and automatically conveyed to the heating cylinder by the screw. The cylinder is heated in sections to 200°C. The cylinder temperature is set to allow the film to gradually melt into a viscous flow state. The molten PP grafted material is extruded into strips through a porous die head. The extruded strips of PP grafted material are then conveyed to the pelletizer via a conveyor belt (air-cooled) and cut into cylindrical particles. These cylindrical particles are the PP grafted granule product.

[0034] Example 2

[0035] Please see Figure 1 This is a second embodiment of the present invention, which provides a method for grafting modification of polyolefins based on coating and photochemical reaction, comprising the following steps:

[0036] Raw material preparation: By weight, add 35 parts glycidyl methacrylate (GMA), 3 parts benzophenone (BP), and 1.5 parts triethylamine (TEA) into a stainless steel mixing tank and stir until homogeneous to obtain a mixture.

[0037] Coating and photochemical reaction: The mixture obtained above was coated onto a 25µm PP film using a gravure coating machine; after irradiation at a wavelength of 395nm for 20s, the irradiation intensity was 5W / cm². 2 LED-UV initiation was used to synthesize glycidyl methacrylate oligomers (PGMA-BPH) with dormant half-pinacol end groups on PP surfaces, with a coating weight of 2.6 g / m². 2 ;

[0038] The obtained PP film is melt-granulated using a twin-screw extruder to obtain the product: This film material is added to the hopper of the granulator and automatically conveyed to the heating cylinder by the screw. The cylinder is heated in sections to 220°C. The cylinder temperature is set to allow the film to gradually melt into a viscous flow state. The molten PP grafted material is extruded into strips through a porous die head. The extruded strips of PP grafted material are then conveyed to the pelletizer via a conveyor belt (air-cooled) and cut into cylindrical particles. These cylindrical particles are the PP grafted granule product.

[0039] Example 3

[0040] Please see Figure 1 This is the third embodiment of the present invention, which provides a method for graft modification of polyolefins based on coating and photochemical reaction, comprising the following steps:

[0041] Raw material preparation: By weight, add 50 parts glycidyl methacrylate (GMA), 5 parts benzophenone (BP), and 2 parts triethylamine (TEA) into a stainless steel mixing tank and stir until homogeneous to obtain a mixture.

[0042] Coating and photochemical reaction: The mixture obtained above was coated onto a 40µm PP film using a gravure coating machine; it was then irradiated at a wavelength of 405nm for 30s with an intensity of 5W / cm². 2 LED-UV initiation was used to synthesize glycidyl methacrylate oligomers (PGMA-BPH) with dormant half-pinacol end groups on PP surfaces, with a coating amount of 3 g / m². 2 ;

[0043] The obtained PP film is melt-granulated using a twin-screw extruder to obtain the product: This film material is added to the hopper of the granulator and automatically conveyed to the heating cylinder by the screw. The cylinder is heated in sections to 240°C. The cylinder temperature is set to allow the film to gradually melt into a viscous flow state. The molten PP grafted material is extruded into strips through a porous die head. The extruded strips of PP grafted material are then conveyed to the pelletizer via a conveyor belt (air-cooled) and cut into cylindrical particles. These cylindrical particles are the PP grafted granule product.

[0044] The advantages of the formulation and method of this invention are:

[0045] The polymerization mechanism is clear:

[0046] Benzophenone (BP) is a highly efficient hydrogen-abstracting photoinitiator. When exposed to UV light, it is first excited to the singlet state (s), and then rapidly jumps to the more stable triplet state (T). The polymerization reaction begins with the reduction of BP in the triplet state by the hydrogen donor triethylamine (TEA). BP is converted into a stable halfpinacol radical, and TEA is converted into a very active amine alkyl radical.

[0047]

[0048] The latter has strong addition activity to vinyl monomers and is the main active component for initiating polymerization; while the halfpinacol radical mainly acts as a chain terminator and couples with the free radical of the PGMA growing chain, ultimately introducing the halfpinacol group BPH at the end of the polymer PGMA molecular chain.

[0049]

[0050] During the melt grafting reaction, when PP is heated above a certain temperature, the covalent bonds connecting the dormant halfpinacol group on PGMA-BPH to the PGMA molecular chain break, forming GMA oligomer free radicals R1 and halfpinacol free radicals. Under the repeated shearing and extrusion of the processing equipment at high temperatures, the polypropylene macromolecules undergo thermal degradation, leading to chain breakage and generating macromolecular free radicals R11. The transfer of oligomer free radicals R1 to the polypropylene macromolecular chain can also form polypropylene macromolecular chain free radicals RIII. RIII is prone to β-fracture to form free radical RIV. Polypropylene macromolecular free radicals R11, RIII, and RIV can all couple with oligomer free radical R1 to form the polypropylene-GMA oligomer graft PP-g-PGMA. Meanwhile, halfpinacol free radicals can couple with polypropylene macromolecular free radical R11 to terminate the coupling, forming a polypropylene macromolecular chain with dormant halfpinacol groups at the end. This polymer can undergo reversible fracture upon heating to form free radicals again, ultimately causing the reaction to continue cyclically.

[0051]

[0052] Compared with traditional grafting methods initiated by peroxide initiators, this invention has the advantages of simple reaction system, simple product composition, mild reaction process and environmentally friendly reaction, opening up a new way for the functional modification of polypropylene.

[0053] Glycidyl methacrylate with benzophenone (BP) and triethylamine (TEA) as photoinitiators was coated onto a polypropylene film. After photochemical reaction, glycidyl methacrylate oligomers (PGMA-BPH) with dormant halfpinacol end groups were conveniently synthesized on the film.

[0054] By utilizing the re-initiation characteristics of the dormant group of halfpinacol under thermal action, PGMA-BPH was melt-grafted onto polypropylene film in the absence of any other initiators, thereby introducing reactive epoxy groups onto the PP macromolecular chain and realizing the functional modification of polypropylene.

[0055] Because no initiator is used in the melt grafting stage, the degradation and cross-linking reaction of PP are reduced, and the grafting rate is greater than 3.5%.

[0056] Photochemical grafting allows the material to grow a new grafted polymer layer with special properties, thereby achieving the purpose of material modification, while the intrinsic properties of the matrix material remain unaffected, making it convenient and safe to use.

[0057] Experiments verify the beneficial effects of this application, as detailed below:

[0058] Table 1: Performance Test Table of Plastics Prepared Using Coated and Photochemically Reacted PP as a Solubilizer

[0059]

[0060] Table 2: Performance Test Table of Ordinary PP and Coated PP and Photochemical Reaction PP Particles

[0061]

[0062] Note: Samples were tested according to standards such as GB / T 3682, GB / T 1040, GB / T 3682, and GB / T 2412.

[0063] Although embodiments of the invention have been shown and described in detail above, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for graft modification of polyolefins based on coating and photochemical reaction, characterized in that: Includes the following steps: Step 1: Raw material preparation: By weight, mix 20-50 parts glycidyl methacrylate (GMA), 1-5 parts benzophenone (BP), and 1-2 parts triethylamine (TEA) and stir until homogeneous to obtain a mixture. Step 2 Coating: The mixture from Step 1 is coated onto the surface of the polyolefin film at a coating weight of 1 g / m². 2 -3g / m 2 ; Step 3: Photochemical reaction: The coated polyolefin film is successively subjected to oven treatment and ultraviolet radiation to synthesize glycidyl methacrylate oligomer (PGMA-BPH) with half-pinacol dormant end groups on the polyolefin surface, thus obtaining a grafted resin film. Step 4 Granulation: The grafted resin film obtained in Step 3 is melted, extruded, and granulated to obtain polyolefin grafted particles.

2. The method for graft modification of polyolefins based on coating and photochemical reaction according to claim 1, characterized in that: The polyolefin includes polypropylene (PP) and polyethylene (PE), and the thickness of the polyolefin film is 15μm-40μm.

3. The method for graft modification of polyolefins based on coating and photochemical reaction according to claim 1, characterized in that: The mixing conditions in step one are: stirring rate 200-300 r / min, stirring time 10-20 min, and ambient temperature 20-30℃.

4. The method for graft modification of polyolefins based on coating and photochemical reaction according to claim 1, characterized in that: In step two, the coating is performed using a gravure coating machine. A diluent can be added to adjust the viscosity of the mixture. The diluent is one or a combination of at least two of ethanol, isopropanol, and ethyl acetate. The volume ratio of the mixture to the diluent is 1:1 to 2:

1.

5. The method for graft modification of polyolefins based on coating and photochemical reaction according to claim 1, characterized in that: In step three, the oven treatment conditions are as follows: temperature 40-60℃, treatment time 3-5 min; ultraviolet radiation using an LED-UV light source, wavelength 365nm-405nm, radiation time 10-30s, radiation intensity 1-10W / cm². 2 .

6. The method for graft modification of polyolefins based on coating and photochemical reaction according to claim 1, characterized in that: In step four, granulation is performed using an environmentally friendly granulator, specifically including: (a) Using grafted resin film as raw material, wherein the mass ratio of polyolefin substrate to PGMA-BPH is 100:4.6; (b) The raw material is added to the hopper of the granulator and conveyed to the heating cylinder by the screw. The cylinder is heated in sections to melt the raw material into a viscous flow state. (c) The molten material is extruded into strips through a porous membrane head, cooled by air, and then cut into cylindrical particles by a pelletizer.

7. The method for graft modification of polyolefins based on coating and photochemical reaction according to claim 6, characterized in that: Raw materials are added to the hopper of the pelletizer and conveyed to the heating cylinder by the screw. The cylinder is heated in sections to 200-240℃, causing the raw materials to melt into a viscous flow state. The melt is extruded into strips through a porous membrane head, cooled by air, and then cut into cylindrical particles by a pelletizer with a diameter of 2-3 mm and a length of 2-3 mm.

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