Production process for grafting modified polyolefin by solution method

Abstract

The invention discloses a production process for grafting modified polyolefin by a solution method, which comprises the following steps: dissolving a polyolefin raw material in an organic solvent, and adding a monomer and an initiator to carry out a solution method grafting reaction; and after the reaction is finished, conveying the obtained reaction liquid containing a large amount of volatile matters into screw devolatilization equipment for devolatilization treatment. The screw devolatilization treatment is carried out under reduced pressure and heating conditions, volatile matters are efficiently evaporated and separated from high-viscosity reaction liquid through multi-stage temperature control and adjustment of a screw structure and stroke, a pure grafting product in a molten state is directly obtained, and a final product is obtained through granulation. According to the method, the screw devolatilization technology is integrated into the solution method grafting process, so that the advantages of high grafting rate and uniform distribution of the solution method are maintained, the energy consumption and the solvent consumption are greatly reduced, the process flow is simplified, and continuous and large-scale production of the solution method grafted modified polyolefin is realized.

Description

Technical Field

[0001] This invention relates to the field of polymer material modification technology, specifically to a solution-based grafting modification process for polyolefins. Background Technology

[0002] Polyolefins (such as polyethylene and polypropylene) are widely used due to their excellent overall performance and low cost, but their non-polar surface properties limit their application in bonding, coating, and composite materials. Introducing polar groups into the polyolefin molecular chain through grafting modification is an effective way to improve their compatibility and adhesion.

[0003] Currently, the main methods for grafting modification of polyolefins include solution grafting, melt grafting, solid-phase grafting, radiation grafting, and plasma grafting. The latter three methods are primarily applied to surface grafting modification of polymers, representing localized modification, and are therefore less commonly used. Melt grafting is carried out in an extruder or internal mixer, offering a simple process and continuous production capability. However, it suffers from inherent drawbacks such as low grafting rate, poor grafting uniformity (microscopic heterogeneity), high risk of polyolefin cracking, and numerous byproducts, severely impacting the mechanical properties and long-term stability of the modified product. Solution grafting, on the other hand, involves the reaction in an organic solvent, allowing the polyolefin molecular chains to fully extend and resulting in a uniform distribution of monomers and initiators. Therefore, it offers significant advantages such as high grafting rate, uniform grafting distribution, fewer side reactions, and precise control of reaction conditions. However, its industrial application faces a major bottleneck: after the reaction, the product needs to be separated and purified from a large amount of solvent. The current post-processing of solution grafting involves slowly pouring the reaction solution into an excess (usually 10-20 times the product mass) of highly polar solutions such as acetone, methanol, or ethanol, causing the modified polyolefin to precipitate. Byproducts and residual monomers dissolve in the washing solution, followed by complex processes such as filtration, multiple washings, and drying (or distillation) to remove solvents, residual monomers, and oligomer byproducts. This process has the following serious drawbacks: (1) It consumes a large amount of precipitant and washing agent, resulting in extremely high energy consumption and costs for solvent recovery; (2) It generates a large amount of organic waste liquid, causing significant environmental pollution; (3) The process is cumbersome, with a long production cycle (usually 24-48 hours), making continuous production impossible and limiting it to high-value-added products or laboratory research. Therefore, developing a new process that retains the advantages of solution grafting while overcoming its post-processing defects is of great significance for promoting the large-scale application of high-performance grafted polyolefins. Summary of the Invention

[0004] To address the shortcomings of existing solutions-based grafted polyolefins, such as complex post-processing, high energy consumption, heavy pollution, and inability to achieve continuous production, this invention provides a production process for solutions-based grafted polyolefins. This process retains the advantages of high grafting rate and uniform grafting found in existing solutions-based grafting methods, while improving subsequent product processing. It employs a screw-type devolatilization device for rapid devolatilization, increasing efficiency, simplifying procedures, reducing energy consumption, and increasing production capacity, thus enabling continuous production using solutions-based grafting.

[0005] The current process flow for solution grafting modification of polyolefins is as follows: (1) Raw material preparation Polyolefins, organic solvents, initiators, monomers; (2) Grafting reaction First, fully dissolve and swell the polyolefin in an organic solvent (temperature 80-150℃, solvent ratio 50-90%). Add initiator and monomer, and start the reaction under nitrogen gas, maintaining a certain temperature and time (usually 80-140℃, 2-10h). (3) Post-processing of products The reaction product is slowly added to an excess of washing solution (3-5 times the product mass of a highly polar liquid such as acetone / methanol / ethanol) under stirring. The grafted modified polyolefin will precipitate as a white or pale yellow solid, while the byproducts and residual monomers will dissolve in the washing solution. Separate the solids and wash repeatedly with excess cleaning solution 2-3 times (this will generate a large amount of waste liquid, and the subsequent waste liquid treatment also requires a lot of energy. Depending on the different polyolefin products, the amount of waste liquid is 10-20 times the mass of the modified polyolefin product). The separated solids are vacuum dried or granulated.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a solution-based graft-modified polyolefin production process. The main improvement lies in the post-processing of the product, which uses a screw devolatilization device to separate the solvent, oligomer byproducts, and residual monomers after the reaction. Specifically, the process includes the following steps: S1. Solution grafting reaction: Polyolefin is dissolved in an organic solvent, grafting monomer and initiator are added, and grafting reaction is carried out under an inert atmosphere to obtain a reaction solution containing volatiles, including organic solvent, unreacted monomer and by-products. S2, Screw devolatilization treatment: The reaction liquid (solvent content 50-90%) after the reaction in step S1 is directly added to the screw devolatilization equipment through the pipeline. Devolatilization treatment is carried out under heating and negative pressure conditions to vaporize and separate the volatiles in the reaction liquid to obtain molten grafted modified polyolefin. S3. Granulation: The molten grafted modified polyolefin obtained in step S2 is granulated by screw extrusion to obtain grafted modified polyolefin particles.

[0007] The core concept of this invention lies in creatively applying screw extrusion equipment, primarily used for polymer melt processing, to handle complex systems with "high volatile content and high viscosity" following solution grafting reactions. By systematically controlling temperature, vacuum, screw configuration, and material residence time, and utilizing the significant difference in volatility between polyolefin macromolecules (almost non-volatile) and small molecule volatiles (solvents, monomers, oligomer byproducts, etc.), the efficient and rapid vaporization and removal of small molecule volatiles are achieved during the screw's conveying, shearing, and mixing processes, resulting in a pure molten product in one step.

[0008] The devolatilization separation principle used in this invention is as follows: The factors affecting the volatilization of substances can be mainly divided into internal and external factors: Internal factors mainly include the cohesive forces (including hydrogen bonds and van der Waals forces) and molecular size of the substance itself, which can be specifically reflected in the boiling point. Modified polyolefins do not have a definite boiling point, but due to their high molecular weight, their melting point is usually between 100-180℃, while the boiling point of commonly used solvents is about 80-150℃. The molecular weights of monomers and oligomers are much lower than those of modified polyolefins. Therefore, it can be considered that the volatility of modified polyolefins is much lower than that of solvents (including water), monomers, and oligomer byproducts.

[0009] One of the external factors is temperature; the higher the temperature, the faster the substance evaporates. By utilizing the differences in volatility between modified polyolefins and solvents, residual monomers, and oligomer byproducts, and by setting an appropriate temperature, the modified polyolefins can be separated. The second external factor is surface area; the larger the surface area, the faster the evaporation. This invention uses a screw structure to increase the surface area of ​​the fluid, enabling rapid vaporization and separation of solvent, residual monomers, and oligomer byproducts. The third external factor is environmental pressure. When the ambient air pressure decreases, the molecules of substances are more likely to escape and volatilize. The screw devolatilization device in this invention has a negative pressure design, with a vacuum pump installed at the end of the exhaust pipe, which can reduce the internal pressure to below standard atmospheric pressure (usually 0.01 MPa to 0.03 MPa).

[0010] The fourth external factor is the speed of ambient air circulation. The volatilization of a substance is affected by its saturated vapor pressure. When the volatilization concentration reaches the saturation concentration of the environment, local volatilization and condensation reach equilibrium, and volatilization will stop. However, accelerating air circulation will cause volatilization to continue. Due to the negative pressure design, the vaporized solvent, residual monomers, and oligomer byproducts will be quickly transported out through the exhaust pipe, further accelerating their volatilization.

[0011] Furthermore, in step S2, the devolatilization treatment is carried out under reduced pressure conditions of 0.01-0.03 MPa.

[0012] Furthermore, in step S2, the screw devolatilization equipment has at least two devolatilization chambers connected in series. The material passes through each devolatilization chamber in sequence. The processing temperature of each devolatilization chamber is at least 10°C higher than the melting temperature of the grafted modified polyolefin and higher than the boiling point of the volatiles, while being lower than the degradation temperature of the grafted modified polyolefin. The set temperature of the subsequent devolatilization chamber is not higher than the set temperature of the previous devolatilization chamber.

[0013] Preferably, the set temperature of the first devolatilization chamber is within the range of the upper limit of the melt temperature of the grafted modified polyolefin + 10-30°C.

[0014] Preferably, the screw deswapping device has 3-5 deswapping sections, and the stroke of the subsequent deswapping section is not higher than the stroke of the previous deswapping section.

[0015] Furthermore, each devolatilization chamber has an exhaust port at its top, which connects to a negative pressure exhaust pipeline. A cooler is installed at the end of the negative pressure exhaust pipeline, and a collection tank is connected to the end of the pipeline. Gaseous volatiles enter the negative pressure exhaust pipeline through the exhaust port, are treated by the cooler, and are collected in the collection tank for recycling.

[0016] The screw devolatilization device in this invention blurs the original concepts of extruder conveying section, melting section, mixing section, venting section, and homogenization section. Each section is configured with different settings for multi-stage devolatilization to ensure that the volatile content in the product meets the final requirements. The volatiles are collected by condensation.

[0017] The following are detailed parameter examples for each compartment. These parameters can be adjusted according to different materials and solvents, and additional compartments can be added to meet the devolatilization requirements.

[0018] Products with high volatile content (50-90%) are transferred from the reactor to compartment 1 via pipelines. Compartment 1 typically has a long travel time (10-15 minutes). If a split-type screw compressor is used, a screw with a large surface area is preferred to accelerate volatilization. The temperature setting must be lower than the degradation temperature of the product, higher than the melting temperature of the product (usually about 10°C higher), and higher than the boiling point of the volatiles (under negative pressure). Taking POE and xylene as examples, the degradation temperature of POE is usually above 300°C, and the melting temperature of POE is approximately 60°C to 120°C. Xylene has a boiling point of 82°C to 85°C under negative pressure of 0.02 MPa. Theoretically, the temperature setting can be between 120°C and 300°C to balance processing difficulty and energy consumption requirements. Typically, the temperature is set between 130°C and 150°C. Taking polypropylene and ethylcyclohexane as examples, the degradation temperature of polypropylene is typically above 250℃, and its melting temperature is usually between 140℃ and 160℃. Ethylcyclohexane has a boiling point of 73℃ to 76℃ under a negative pressure of 0.02 MPa. Theoretically, the temperature can be set between 160℃ and 250℃. To balance processing difficulty and energy consumption, the temperature is usually set between 170℃ and 190℃. Therefore, the temperature setting is usually at least 10℃ higher than the product's melting temperature, while also considering the boiling point of the volatiles (under negative pressure) and the product's degradation temperature. At this stage, most of the volatiles have evaporated, and the product state changes from a low-viscosity fluid to a high-viscosity fluid. Measurements show that the volatile content can reach below 20%.

[0019] The product with reduced volatile content (less than 20%) is transferred to section 2. Section 2 typically has a longer stroke (8-15 minutes). Due to the increased viscosity, the screw angle can be appropriately reduced to increase shear capacity. Simultaneously, due to the decreased thermal uniformity, the set temperature can be appropriately lowered (it must be maintained at least 10°C above the product melting temperature) to prevent localized overheating and degradation of the product. At this stage, the product viscosity increases, but it remains a high-viscosity fluid; measurements show that the volatile content can reach below 10%.

[0020] The product with further reduced volatile content (less than 10%) is transferred to section 3. Section 3 is basically the same as section 2, but the stroke can be appropriately reduced. Simultaneously, as thermal uniformity further decreases, the set temperature is also appropriately lowered (it must be maintained at least 10°C above the product melting temperature). During this stage, the product viscosity continues to increase, and measurements show that the volatile content can reach below 3%.

[0021] The product with further reduced volatile content (less than 3%) is transferred to section 4. The journey in section 4 takes approximately 6-10 minutes. Since the product at this stage is already a high-viscosity fluid close to a molten state, the screw angle can be appropriately reduced. Simultaneously, due to further reduced thermal uniformity, the temperature can be appropriately lowered (but must be maintained at least 10°C above the product's melting temperature). Through this stage, the product completely transforms into a molten fluid state free of volatiles.

[0022] If the volatiles cannot be completely removed after passing through section 4, you can adjust the travel settings or temperature settings, or increase the number of sections to meet the requirements.

[0023] The product is granulated to obtain the final particle product.

[0024] Furthermore, in step S1, the polyolefin is a thermoplastic polymer material formed by polymerization or copolymerization of olefin monomers, or a modified polyolefin material.

[0025] Specifically, the polyolefin raw material used in this invention refers to thermoplastic polymer materials formed by polymerization or copolymerization of olefin monomers such as ethylene and propylene, including polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer (POE / POP), ethylene-vinyl acetate copolymer (EVA), etc. Alternatively, it may be a modified polyolefin material that has been further modified due to functional requirements, such as chlorinated polypropylene (CPP), chlorinated polyethylene (CPE), maleic acid modified polypropylene (MAH-g-PP), glycidyl methacrylate modified ethylene-propylene copolymer (GMA-g-POE), etc.

[0026] The organic solvents used in this invention refer to aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, heptane, octane, and decane; alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane; halogenated hydrocarbons such as trichloroethylene, dichloroethylene, chlorobenzene, and chloroform; alcohol solvents such as methanol, ethanol, isopropanol, butanol, pentanol, hexanol, propylene glycol, and phenol; and acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, and isobutyl ketone. Ketone solvents such as phenone and acetophenone, cellosols such as methyl cellosol and ethyl cellosol, ester solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and butyl formate, and diol ether solvents such as ethylene glycol mono-n-butyl ether, ethylene glycol mono-isobutyl ether, ethylene glycol mono-tert-butyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-isobutyl ether, triethylene glycol mono-n-butyl ether, and tetraethylene glycol mono-n-butyl ether can be used individually or in combination.

[0027] The initiators used in this invention refer to peroxide initiators, including benzoyl peroxide (BPO), dicumyl peroxide (DCP), tert-butyl hydroperoxide (TBHP), di-tert-butyl peroxide (DTBP), methyl ethyl ketone peroxide (MEKP), tert-butyl peroxide (TBPB), lauroyl peroxide (LPO), tert-butyl peroxypentanoate (BPP), tert-butyl peroxide-2-ethylhexanoate (TBPEH), cyclohexanone peroxide (CHP), etc., and azo initiators, including azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (ABVN), azobiscyclohexanenitrile (ACCN), azobisisovalerate (AIVN), dimethyl azobisisobutyrate (AIBME), etc., which can be used alone or in combination.

[0028] Furthermore, in step S1, the monomer refers to a polymerizable monomer material containing unsaturated bonds.

[0029] Specifically, the monomers used in this invention refer to polymerizable monomer materials containing unsaturated bonds (usually vinyl groups), including but not limited to acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, fumaric acid, methyl methacrylate, butyl acrylate, ethyl acrylate, ethyl methacrylate, isooctyl acrylate, hydroxyethyl methacrylate, butyl methacrylate, lauryl acrylate, acrylonitrile, methacrylonitrile, cyanoethyl acrylate, glycidyl methacrylate, glycidyl acrylate, 3,4-epoxybutyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, acrylamide, styrene, butadiene, isoprene, etc., and can be used alone or in combination.

[0030] Furthermore, in step S2, after the screw devolatilization treatment, the residual volatile matter content in the obtained grafted modified polyolefin is less than 100 ppm.

[0031] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention completely eliminates the post-processing steps such as precipitation, washing and drying of a large amount of cleaning liquid that are relied upon by the traditional solution method. By innovatively introducing the screw devolatification step, the removal of volatiles, material concentration and melt granulation homogenization are integrated into one device and one continuous process, which greatly simplifies the process flow.

[0032] (2) In traditional processes, the heating, evaporation, and condensation recovery of large amounts of precipitants (such as acetone and methanol) consumes a great deal of energy. This invention directly avoids the use of precipitants and their energy-intensive recovery process. The screw devolatilization under reduced pressure lowers the boiling point of the volatiles, relatively reducing the heat input required for removal. Furthermore, the volatile vapors can be efficiently and directly recovered after condensation. The dual reduction in material and energy consumption, coupled with the sharp decrease in the cost of waste treatment, significantly reduces the overall production cost of the product.

[0033] (3) The reactor and the screw devolatilization equipment can be directly connected, making the entire solution grafting process possible for continuous and large-scale production for the first time, and significantly improving production efficiency. The production mode has changed from "batch" to "continuous", bringing about a qualitative leap in production efficiency. The production cycle has been shortened from tens of hours to several hours, laying the equipment and process foundation for the large-scale industrial application of solution grafting products.

[0034] (4) Experimental verification shows that the grafting rate and grafting uniformity of the grafted product obtained by the method of this invention are basically consistent with those of the product obtained by the traditional solvent washing and precipitation method (deviation <1%). This indicates that the innovative post-processing process of this invention successfully retains the inherent advantages of the solution method of "high grafting rate, uniform distribution, and few side reactions". At the same time, through negative pressure design, precise temperature control and shear design, the main chain degradation problem common in the melt method is effectively avoided, achieving an excellent balance between "efficiency" and "quality". Moreover, the final product of this invention has extremely low volatile content (<100ppm) and high purity. This high purity characteristic allows the product to be directly used in high-end application fields with strict requirements for odor, VOC release or product purity, such as automotive interiors, food contact materials, and high-performance composite materials, thus broadening the market application scope of the product. Attached Figure Description

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0036] Figure 1 This is a schematic diagram of the screw devouring device used in the embodiments of the present invention; The specific reference numerals in the attached figures are as follows: 1. Feed pipeline; 2. Main body of screw degassing equipment; 3. Negative pressure exhaust pipeline; 4. Cooler; 5. Collection tank; 6. Molten material outlet. Detailed Implementation

[0037] 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.

[0038] The structure of the screw devouring device used in each embodiment of the present invention is as follows: Figure 1 As shown, the main body 2 of the screw devouring equipment consists of multiple temperature control compartments connected in series. After the reaction in the reactor, the solution is transferred to the first compartment through the feed pipe 1, and the outlet end of the last compartment is the molten material outlet 6.

[0039] Each devolatilization chamber has an exhaust port at the top, which is connected to a negative pressure exhaust pipe 3. A cooler 4 is installed at the end of the negative pressure exhaust pipe 3, and a collection tank 5 is connected to the end of the cooler 4. Gaseous volatiles enter the negative pressure exhaust pipe 3 through the exhaust port, are processed by the cooler 4 and collected in the collection tank 5, and can be recycled.

[0040] Example 1 A method for preparing maleic acid-modified propylene-ethylene copolymer: 100 kg of propylene-ethylene copolymer 3980FL (Mobil) and 900 kg of xylene were added to the reactor and dissolved completely at 110°C.

[0041] Add 6 kg of maleic anhydride and dissolve it thoroughly. Under nitrogen gas, add 1.5 kg of benzoyl peroxide initiator, heat to 120°C, and stir for 10 h.

[0042] The reaction products in the reactor are then transferred to the screw devolatilization equipment through the feed pipeline, and then granulated by screw devolatilization to obtain the product (the product was tested to have 88 ppm of volatile residue and a maleic acid grafting rate of 1.74%).

[0043] After washing the product with acetone, the maleic acid grafting rate was retested and found to be 1.74%. This method can reduce the amount of cleaning solution used by 5-10 tons compared to the original solution process, and the production cycle, which originally took 24-36 hours, is now shortened by half.

[0044] The parameter settings for the screw devouring device in this embodiment are shown in Table 1.

[0045] Table 1 Equipment parameters temperature air pressure Process time Degree of devolatilization (solid content of the product) Section 1 150℃ 0.02Mpa 10min 83.60% Section 2 145℃ 0.02Mpa 8min 92.50% Section 3 140℃ 0.02Mpa 6min 98.90% Section 4 135℃ 0.02Mpa 6min 100.00% Example 2 A method for preparing maleic acid-modified propylene-ethylene copolymer: Based on the experimental data of Example 1, the amount of maleic anhydride added was changed to 8 kg, and the amount of initiator benzoyl peroxide added was changed to 2 kg, resulting in a product (60 ppm of volatile residue and 2.44% maleic acid grafting rate).

[0046] After washing the product with acetone, the maleic acid grafting rate was retested and found to be 2.43%. This method can reduce the amount of cleaning solution used by 5-10 tons compared to the original solution process, and the production cycle, which originally took 24-36 hours, is now shortened by half.

[0047] The parameter settings for the screw devouring device in this embodiment are shown in Table 2.

[0048] Table 2 Equipment parameters temperature air pressure Process time Degree of devolatilization (solid content of the product) Section 1 150℃ 0.02Mpa 10min 82.50% Section 2 145℃ 0.02Mpa 8min 92.30% Section 3 142℃ 0.02Mpa 6min 99.00% Section 4 140℃ 0.02Mpa 6min 100.00% Example 3 A method for preparing maleic acid-modified propylene-butene copolymer: 200 kg of propylene-butene copolymer XM-7080S (Mitsui) and 800 kg of methylcyclohexane were added to the reactor and dissolved completely at 90°C.

[0049] Add 10 kg of maleic anhydride and dissolve thoroughly. Under nitrogen purging, add 3 kg of benzoyl peroxide initiator, maintain 90°C, and stir for 3 hours.

[0050] The reaction products in the reactor are then transferred to the screw devolatilization equipment through the feed pipeline, and then granulated by screw devolatilization to obtain the product (68 ppm of volatile residue and 2.11% maleic acid grafting rate).

[0051] After washing the product with acetone, the maleic acid grafting rate was retested and found to be 2.11%. This method can reduce the amount of cleaning solution used by 5-10 tons compared to the original solution process, and the production time that originally took 18-24 hours can now be reduced to only 4-5 hours.

[0052] The parameter settings for the screw devouring device in this embodiment are shown in Table 3.

[0053] Table 3 Equipment parameters temperature air pressure Process time Degree of devolatilization (solid content of the product) Section 1 135℃ 0.02Mpa 10min 86.60% Section 2 135℃ 0.02Mpa 8min 94.50% Section 3 132℃ 0.02Mpa 6min 99.20% Section 4 130℃ 0.02Mpa 6min 100.00% Example 4 A method for preparing a propylene-butene copolymer modified with glycidyl methacrylate (GMA): 200 kg of propylene-butene copolymer XM-7080S (Mitsui) and 800 kg of xylene were added to the reactor and dissolved completely at 120°C.

[0054] Add 20 kg of glycidyl methacrylate (GMA) and dissolve it thoroughly. Under nitrogen purging, add 3 kg of benzoyl peroxide initiator, heat to 140°C, and stir for 3 hours.

[0055] The reaction products in the reactor are then transferred to a screw devolatilization unit through a feed pipeline. The product is then obtained by screw devolatilization and granulation (47 ppm volatile residue, 2.95% GMA branching rate).

[0056] After washing the product with acetone, the GMA grafting rate was retested and found to be 2.94%. This method can reduce the amount of cleaning solution used by 5-10 tons compared to the original solution process, and the production time that originally took 18-24 hours can now be reduced to only 4-5 hours.

[0057] The parameter settings for the screw devouring device in this embodiment are shown in Table 4.

[0058] Table 4 Equipment parameters temperature air pressure Process time Degree of devolatilization (solid content of the product) Section 1 150℃ 0.02Mpa 10min 81.60% Section 2 145℃ 0.02Mpa 8min 92.40% Section 3 142℃ 0.02Mpa 6min 98.80% Section 4 140℃ 0.02Mpa 6min 100.00% Example 5 A method for preparing maleic acid-modified propylene-ethylene copolymer: 200 kg of propylene-ethylene copolymer GA-1875 (Dow) and 800 kg of toluene were added to the reactor and dissolved completely at 90°C.

[0059] Add 15 kg of maleic anhydride and dissolve it thoroughly. Under nitrogen purging, add 3 kg of benzoyl peroxide initiator dropwise, maintain 90°C, and stir for 10 h.

[0060] The reaction product was then granulated by screw devolatilization to obtain the final product (volatile residue 45 ppm, maleic acid grafting rate 2.20%). After washing the product with acetone, the maleic acid grafting rate was retested and found to be 2.20%.

[0061] This method can reduce the amount of cleaning fluid used by 5T-10T compared to the original solution process, and the production time that originally took 36-48 hours can now be reduced to only 12-15 hours.

[0062] Table 5 Equipment parameters temperature air pressure Process time Degree of devolatilization (solid content of the product) Section 1 130℃ 0.02Mpa 10min 88.70% Section 2 128℃ 0.02Mpa 8min 96.50% Section 3 125℃ 0.02Mpa 6min 99.40% Section 4 120℃ 0.02Mpa 6min 100.00% The method of the present invention (Examples 1-5) was compared with the traditional solution post-treatment process and melt grafting method. The results are shown in Table 6: Table 6 Comparison Projects Existing solution process mainstream melt process The improved solution process of this invention Grafting uniformity Macroscopic homogeneity, microscopic homogeneity Macroscopic homogeneous, microscopic heterogeneous Macroscopic homogeneity, microscopic homogeneity Grafting rate high Low high reaction temperature higher High (above melting point) higher Side reactions few many few Solvent and cleaning agent dosage 10-20 times the amount of resin none Recycling and recycling, with minimal net consumption. Process time 24-48h 1-2h 4-12h Production methods intermittent Continuous Continuous or intermittent is acceptable As can be seen from the table above, the method of the present invention combines the advantages of solution method and melting method, while overcoming the main disadvantages of both, and is an advanced processing method with great industrial application prospects.

[0063] Although embodiments of the invention have been shown and described, 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 solution-based grafting process for producing modified polyolefins, characterized in that, Includes the following steps: S1. Solution grafting reaction: Polyolefin is dissolved in an organic solvent, grafting monomer and initiator are added, and grafting reaction is carried out under an inert atmosphere to obtain a reaction solution containing volatiles, including organic solvent, unreacted monomer and by-products. S2, Screw devolatilization treatment: The reaction liquid obtained in step S1 is directly added to the screw devolatilization equipment and devolatilization is carried out under heating and negative pressure conditions to vaporize and separate the volatiles in the reaction liquid to obtain molten grafted modified polyolefin. S3. Granulation: The molten grafted modified polyolefin obtained in step S2 is granulated by screw extrusion to obtain grafted modified polyolefin particles.

2. The production process of solution-grafted modified polyolefins according to claim 1, characterized in that, In step S2, the devolatilization treatment is carried out under reduced pressure conditions of 0.01-0.03 MPa.

3. The production process of solution-grafted modified polyolefins according to claim 2, characterized in that, In step S2, the screw devolatilization equipment has at least two devolatilization chambers connected in series. The material passes through each devolatilization chamber in sequence. The processing temperature of each devolatilization chamber is at least 10°C higher than the melting temperature of the grafted modified polyolefin and higher than the boiling point of the volatiles, while being lower than the degradation temperature of the grafted modified polyolefin. The set temperature of the next devolatilization chamber is not higher than the set temperature of the previous devolatilization chamber.

4. The production process of solution-grafted modified polyolefins according to claim 3, characterized in that, The set temperature of the first devolatilization chamber is within the range of the upper limit of the melt temperature of the grafted modified polyolefin + 10-30℃.

5. The production process of solution-grafted modified polyolefins according to claim 3 or 4, characterized in that, The screw descrambling device has 3-5 descrambling sections, and the stroke of the subsequent descrambling section is no greater than the stroke of the previous descrambling section.

6. The production process of solution-grafted modified polyolefins according to claim 5, characterized in that, Each devouring chamber section has an exhaust port at the top, which is connected to a negative pressure exhaust pipe. A cooler is installed at the end of the negative pressure exhaust pipe, and a collection tank is connected at the end.

7. The production process of solution-grafted modified polyolefins according to claim 1, characterized in that, In step S1, the polyolefin is a thermoplastic polymer material formed by polymerization or copolymerization of olefin monomers, or a modified polyolefin material.

8. The production process of solution-grafted modified polyolefins according to claim 1, characterized in that, In step S1, the monomer refers to a polymerizable monomer material containing unsaturated bonds.

9. The production process of solution-grafted modified polyolefins according to claim 1, characterized in that, In step S2, after the screw devolatilization treatment, the residual volatiles in the grafted modified polyolefin are less than 100 ppm.

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