Preparation method of metallocene polyolefin wear-resistant scraper

Abstract

According to the scheme, the preparation method comprises the following steps: firstly, synthesizing hybrid nano microspheres containing double bonds and polysiloxane chain segments through a sol-gel method and a hydrosilylation reaction; then premixing the microspheres with metallocene polyolefin, an initiator and the like, and inducing an in-situ grafting reaction by utilizing a shearing field of a double-screw extruder to prepare composite modified granules; and finally forming, annealing and machining to obtain a finished product. The method is characterized in that a flexible lubricating chain segment is firmly locked in a matrix network by using a chemical anchoring technology, and the defect that a lubricant is easy to migrate and separate out due to traditional physical blending is overcome; on the basis that high strength of the scraper is ensured, durability and stability of lubrication and wear resistance under the long-term high-shear working condition are achieved, the service life of the scraper is remarkably prolonged, and the working efficiency of the scraper is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of polymer functional materials and polyolefin modification technology, specifically to a method for preparing metallocene polyolefin wear-resistant scrapers. Background Technology

[0002] With the continuous upgrading of industrial manufacturing, industries such as papermaking, printing, and industrial desiccant manufacturing are placing increasingly stringent performance requirements on doctor blade components. As a critical and vulnerable component that directly contacts materials on the production line, doctor blades need to maintain good dimensional stability and service life under high-speed friction and complex stress environments. Although traditional polyolefin doctor blades possess good chemical corrosion resistance and a certain degree of toughness, they exhibit the following technical challenges in actual working conditions: the wear resistance and self-lubricating properties of the materials are at a bottleneck; existing technologies typically employ physical blending to add small-molecule lubricants such as silicone oil, which can reduce the coefficient of friction initially, but due to the lack of chemical anchoring points between the lubricating components and the polyolefin matrix, under long-term shear forces... Under these conditions, small molecules are prone to surface precipitation and migration, leading to rapid failure of lubrication and even contamination of the processed product; it is difficult to balance rigidity enhancement and toughness maintenance; although the introduction of inorganic nanofillers can improve the hardness of the material, the poor interfacial compatibility between inorganic particles and organic polyolefin matrix makes it easy to generate stress concentration under impact, resulting in increased brittleness of the material and making it difficult to meet the requirements of use under high-load impact conditions; insufficient thermal stress control during processing; polyolefin materials generate significant molecular orientation stress during melt extrusion molding. If there is a lack of effective post-processing to eliminate residual stress, the scraper is prone to warping and deformation under high-temperature working conditions, affecting the flatness of the cutting edge and the accuracy of scraping.

[0003] Therefore, how to achieve chemical stabilization of lubricating components through microstructure design, thereby improving the wear resistance of materials while taking into account impact strength and dimensional stability, has become the core technical issue for improving the overall performance of metallocene polyolefin scrapers. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing metallocene polyolefin wear-resistant scrapers, which can solve the technical problems existing in the prior art. Specifically, the technical solution of this invention includes:

[0005] Functionalized wear-resistant modifiers were synthesized by combining sol-gel method with hydrosilylation reaction, resulting in hybrid nanospheres with reactive double bonds and polysiloxane segments.

[0006] Weigh out metallocene polyolefin resin, functionalized wear-resistant modifier, free radical initiator and antioxidant and mix them at high speed to prepare a premix;

[0007] The premixed material is added to a twin-screw extruder for reactive melt extrusion. Under the action of a shear field, the functionalized wear-resistant modifier and metallocene polyolefin resin undergo an in-situ grafting reaction. The resulting material is then extruded and granulated to obtain composite modified granules.

[0008] The composite modified granules are processed into scraper blanks through a molding process, and the scraper blanks are then annealed and machined to obtain the finished scrapers.

[0009] Preferably, the specific steps of synthesizing the functionalized wear-resistant modifier include:

[0010] The trifunctional vinylsilane was dissolved in a mixed solvent of ethanol and water, the pH was adjusted to 3-5, and the hydrolysis and condensation reaction was carried out under constant temperature water bath conditions. After the reaction was completed, the vinyl-functionalized nano-siloxane core was obtained by centrifugation.

[0011] The vinyl-functionalized nanosiloxane core was added to toluene solvent and ultrasonically dispersed to form a uniform suspension.

[0012] Hydrogen-containing polysiloxane and platinum catalyst were added dropwise to a suspension, and the molar ratio of silane-hydrogen bonds to vinyl groups was controlled to be 0.5~0.8. The reaction was carried out under nitrogen protection and refluxed with stirring. Polysiloxane segments were grafted onto the surface of nano-siloxane cores through hydrosilylation.

[0013] After the reaction is complete, the product is subjected to vacuum distillation to remove the solvent at a temperature not exceeding 60°C to obtain the functionalized wear-resistant modifier.

[0014] Preferably, the mass ratios of the metallocene polyolefin resin, the functionalized wear-resistant modifier, the free radical initiator, and the antioxidant are 100 parts, 2-8 parts, 0.05-0.2 parts, and 0.1-0.3 parts, respectively.

[0015] Preferably, the trifunctional vinylsilane is selected from vinyltrimethoxysilane or vinyltriethoxysilane;

[0016] The hydrogen-containing polysiloxane is selected from single-ended hydrogen-based polydimethylsiloxane or side-chain hydrogen-containing polydimethylsiloxane, with a molecular weight of 1000~10000.

[0017] The temperature of the hydrolysis-condensation reaction is controlled at 50℃~70℃, and the reaction time is 12~24 hours;

[0018] The temperature of the reflux stirring reaction is controlled at 70℃~90℃, and the reaction time is 3~6 hours.

[0019] Preferably, in the reactive melt extrusion, the temperature setting of the twin-screw extruder adopts gradient temperature control, specifically including:

[0020] The temperature of the feeding section is set to 150℃~170℃;

[0021] The temperature of the reaction section is set to 180℃~220℃;

[0022] The temperature of the die head section is set to 180℃~200℃;

[0023] The screw speed is set to 200~400 r / min, and the residence time of the material in the extruder is controlled to be 1~3 minutes.

[0024] Preferably, the annealing and machining processes specifically include:

[0025] The shaped scraper blank is placed in a constant temperature forced-air drying oven. ℃~ Keep at ℃ After 24 hours, the furnace is slowly cooled to room temperature to relieve internal stress.

[0026] The cooled scraper blank is precision-cut and sharpened, and the surface of the cutting edge is polished to make the surface roughness Ra less than 0.4μm.

[0027] Preferably, the metallocene polyolefin resin is selected from one or more of metallocene polyethylene, metallocene polypropylene, or metallocene ethylene-octene copolymer;

[0028] The free radical initiator is selected from dicumyl peroxide or 2,5-dimethyl-2,5-bis(tert-butyl peroxide)hexane.

[0029] Compared with the prior art, the present invention has the following improvements and advantages:

[0030] 1. This method constructs hybrid nanospheres with reactive double bonds through a sol-gel method and hydrosilylation reaction, and utilizes reactive melt extrusion technology to perform in-situ grafting of modifiers onto the polyolefin matrix. This in-situ grafting reaction firmly locks the polysiloxane segments into the matrix network, overcoming the defects of easy migration and precipitation of lubricants in traditional physical blending processes, and ensuring the long-term stability of the lubrication performance of the scraper under long-term high-shear conditions.

[0031] 2. This solution introduces hybrid nanospheres with vinyl-functionalized nanosiloxane cores and polysiloxane segments, forming a stable skeletal support at the microscopic level. The vinyl-functionalized nanosiloxane cores effectively resist abrasive cutting, improving hardness and wear resistance. Meanwhile, the polysiloxane segments on the surface enhance interfacial compatibility with the matrix, avoiding stress concentration. Test data shows that this technology significantly reduces wear while maintaining excellent notched impact strength, solving the problem of material brittleness caused by traditional inorganic fillers.

[0032] 3. This solution addresses the molecular orientation stress generated during the processing of polyolefins. This process effectively eliminates residual thermal stress inside the material through gradient temperature control and annealing after molding. This gives the finished doctor blade extremely high dimensional stability in high-temperature working environments, preventing warping and deformation of the cutting edge, thereby ensuring precise coating effects in applications such as high-speed printing or papermaking.

[0033] 4. This solution can flexibly adapt to metallocene polyethylene, metallocene polypropylene and various copolymer matrices by adjusting the types and molecular weights of trifunctional vinylsilanes and hydrogen-containing polysiloxanes, and optimizing the process parameters of reactive melt extrusion. This makes the resulting doctor blades not only suitable for papermaking doctor blades with low friction requirements, but also able to cope with industrial ink-scraping environments with high loads, high speeds or high heat generation, and has extremely strong engineering application value. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0035] Example 1:

[0036] A method for preparing a metallocene polyolefin wear-resistant scraper includes synthesizing a functionalized wear-resistant modifier by using a sol-gel method combined with hydrosilylation reaction to obtain hybrid nanospheres with reactive double bonds and polysiloxane segments.

[0037] This embodiment prepares a scraper product suitable for low-friction working conditions by precisely controlling the reaction conditions. The core of this method lies in using the reactive double bonds of hybrid nanospheres to achieve chemical bonding with the matrix.

[0038] The specific steps of synthesizing functionalized wear-resistant modifiers include dissolving trifunctional vinylsilane in a mixed solvent of ethanol and water, adjusting the pH value to 3-5, carrying out hydrolysis and polycondensation reaction under constant temperature water bath conditions, and separating by centrifugation after the reaction to obtain vinyl-functionalized nano-siloxane cores.

[0039] In this embodiment, the trifunctional vinylsilane is specifically vinyltrimethoxysilane, which is dissolved in a 3:1 mixture of ethanol and water. To control the hydrolysis rate and form a dense nanocore, the pH value is precisely adjusted to 3. The temperature of the hydrolysis-condensation reaction is controlled at 50°C, and the reaction time is 12 hours. This low-temperature, long-time reaction is beneficial for forming a siloxane framework with fewer defects. The specific process parameters for centrifugation are: rotation speed 8000 r / min, centrifugation time 15 minutes, to ensure complete sedimentation of the core particles.

[0040] Vinyl-functionalized nano-siloxane cores were added to toluene solvent and ultrasonically dispersed to form a uniform suspension. Hydrogen-containing polysiloxane and a platinum catalyst were then added dropwise to the suspension, with the molar ratio of silane-hydrogen bonds (Si-H) to vinyl groups (-CH=CH2) controlled at 0.5–0.8. The reaction was carried out under nitrogen protection with reflux stirring, grafting polysiloxane segments onto the surface of the nano-siloxane cores via hydrosilylation. After the reaction, the product was subjected to vacuum distillation at 55°C to remove the solvent, yielding a functionalized wear-resistant modifier.

[0041] In the process of synthesizing the functionalized wear-resistant modifier of this invention, by controlling the molar ratio of trifunctional vinylsilane to hydrogen-containing polysiloxane and controlling the reflux stirring reaction time, it is ensured that the vinyl groups on the surface of the nanosiloxane core are not completely consumed, thereby retaining reactive double bonds on the surface of the hybrid nanospheres; during the reactive melt extrusion process, the free radical initiator decomposes to generate primary free radicals, which induce the metallocene polyolefin molecular chains to generate macromolecular free radicals, and then undergo in-situ addition grafting reactions with the vinyl groups on the surface of the microspheres;

[0042] Grafting efficiency Defined as the percentage of the mass of the functionalized wear-resistant modifier grafted onto the metallocene polyolefin molecular chain, relative to the total amount of modifier added, calculated by weighing after removing ungrafted components using Soxhlet extraction; its grafting efficiency. The relationship with the interfacial bonding strength follows the free radical polymerization kinetics, which helps to form a stable three-dimensional lubrication network in the matrix;

[0043] In this step, the specific parameters for ultrasonic dispersion are set as follows: ultrasonic power 400W, processing time 30 minutes, to prevent nanoparticle aggregation; single-ended hydrogen-containing polydimethylsiloxane is selected, with a molecular weight of 1000, to introduce shorter flexible segments to reduce steric hindrance; the platinum catalyst is caster catalyst, with an amount of 20 ppm of the total mass of the reaction system; the temperature of the reflux stirring reaction is controlled at 70℃, and the reaction time is 3 hours to ensure that the grafting rate meets the design requirements;

[0044] Weigh out metallocene polyolefin resin, functionalized wear-resistant modifier, free radical initiator and antioxidant and mix them at high speed to prepare a premix;

[0045] In this embodiment, metallocene polyethylene is selected as the metallocene polyolefin resin; dicumyl peroxide (DCP) is selected as the free radical initiator; the mass ratio of each component is as follows: 100 parts of metallocene polyolefin resin, 2 parts of functionalized wear-resistant modifier, 0.05 parts of free radical initiator, and 0.1 parts of antioxidant; the high-speed mixing process parameters are set as follows: rotation speed 1500 r / min, mixing time 5 minutes, to ensure uniform dispersion of each component; the amount of free radical initiator is set to 0.05 parts, accounting for 0.05% of the resin mass, considering that metallocene polyethylene is sensitive to peroxides, and excessive dosage may easily lead to cross-linking side reactions in the matrix; 0.1 parts of antioxidant is sufficient to cope with the low processing temperature of 180°C in this embodiment, avoiding cost waste caused by excessive addition;

[0046] The premixed material is added to a twin-screw extruder for reactive melt extrusion. Under the action of a shear field, the functionalized wear-resistant modifier and metallocene polyolefin resin undergo an in-situ grafting reaction. The resulting material is then extruded and granulated to obtain composite modified granules.

[0047] The reactive melt extrusion employs gradient temperature control: the feeding section temperature is set at 150℃ to prevent premature decomposition of the initiator; the reaction section temperature is set at 180℃, utilizing shear heat and heating to initiate DCP decomposition and induce in-situ grafting reactions between vinyl groups on the surface of the functionalized wear-resistant modifier and metallocene polyolefin resin; the die section temperature is set at 180℃; the screw speed is set at 200 r / min, and the material residence time in the extruder is controlled to 1 minute;

[0048] The composite modified granules are prepared into scraper blanks through a molding process, and the scraper blanks are annealed and machined to obtain the finished scrapers.

[0049] The molding process adopts injection molding, with the injection pressure set at 80MPa and the mold temperature at 40℃. The annealing and machining are specifically performed as follows: the molded doctor blade blank is placed in a constant temperature forced-air drying oven and kept at 80℃ for 48 hours, and then slowly cooled to room temperature in the oven to eliminate internal stress; the cooled doctor blade blank is precision-cut and sharpened, and the surface of the cutting edge is polished so that the arithmetic mean deviation (Ra) of the surface roughness profile of the cutting edge is less than 0.4μm. The doctor blade prepared in this embodiment retains the toughness of metallocene polyethylene to the greatest extent and is suitable for papermaking doctor blade applications that require high impact strength but generate less frictional heat.

[0050] Example 2:

[0051] A method for preparing a metallocene polyolefin wear-resistant scraper includes synthesizing a functionalized wear-resistant modifier by using a sol-gel method combined with hydrosilylation reaction to obtain hybrid nanospheres with reactive double bonds and polysiloxane segments.

[0052] This embodiment optimizes the molecular structure and processing technology of the modifier to meet the needs of general-purpose industrial scrapers;

[0053] The specific steps of synthesizing functionalized wear-resistant modifiers include dissolving trifunctional vinylsilane in a mixed solvent of ethanol and water, adjusting the pH value to 3-5, carrying out hydrolysis and polycondensation reaction under constant temperature water bath conditions, and separating by centrifugation after the reaction to obtain vinyl-functionalized nano-siloxane cores.

[0054] In this embodiment, the trifunctional vinylsilane is vinyltriethoxysilane, which is dissolved in a mixed solvent of ethanol and water at a mass ratio of 4:1; the pH value is adjusted to 4; the temperature of the hydrolysis-condensation reaction is controlled at 60°C and the reaction time is 18 hours to obtain vinyl-functionalized nanosiloxane cores with more uniform particle size distribution; the centrifugation separation parameters are set as follows: rotation speed 10000 r / min, time 12 minutes, to separate cores with uniform particle size.

[0055] Vinyl-functionalized nano-siloxane cores were added to toluene solvent and ultrasonically dispersed to form a uniform suspension. Hydrogen-containing polysiloxane and a platinum catalyst were then added dropwise to the suspension, with the molar ratio of Si-H to -CH=CH2 controlled at 0.5~0.8. The reaction was carried out under nitrogen protection with reflux stirring, grafting polysiloxane segments onto the surface of the nano-siloxane cores via hydrosilylation. After the reaction, the product was subjected to vacuum distillation at 55℃ to remove the solvent, yielding a functionalized wear-resistant modifier. In this step, the specific parameters for ultrasonic dispersion were set as follows: ultrasonic power 400W, processing time 30 minutes, ensuring sufficient monodispersity of the cores in the solvent; the hydrogen-containing polysiloxane used was single-ended hydrogen-based polydimethylsiloxane with a specific molecular weight of 1000, a suitable molecular weight that ensured lubricity while avoiding excessive steric hindrance; the platinum catalyst was a caster catalyst, used at 20 ppm of the total mass of the reaction system; the reflux stirring reaction temperature was controlled at 80℃, and the reaction time was 4.5 hours.

[0056] Weigh out metallocene polyolefin resin, functionalized wear-resistant modifier, free radical initiator and antioxidant and mix them at high speed to prepare a premix;

[0057] In this embodiment, the metallocene polyolefin resin is metallocene polypropylene (m-PP); the free radical initiator is 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane; the mass ratio of each component is as follows: 100 parts of metallocene polyolefin resin, 5 parts of functionalized wear-resistant modifier, 0.12 parts of free radical initiator, and 0.2 parts of antioxidant; the high-speed mixing process parameters are set as follows: rotation speed 2000 r / min, mixing time 3 minutes; the choice of 0.12 parts (0.12%) of free radical initiator is to balance the grafting efficiency and degradation tendency of m-PP. Experiments show that the grafting rate is insufficient below 0.08 parts, while it will lead to serious degradation of PP matrix above 0.15 parts; the 0.2 parts of antioxidant is to cope with the risk of thermal oxidation under the processing environment of 200℃ and ensure the thermal stability of the material for long-term use;

[0058] The premixed material is added to a twin-screw extruder for reactive melt extrusion. Under the action of a shear field, the functionalized wear-resistant modifier and metallocene polyolefin resin undergo an in-situ grafting reaction. The resulting material is then extruded and granulated to obtain composite modified granules.

[0059] The reactive melt extrusion uses gradient temperature control: the feeding section temperature is set at 160℃; the reaction section temperature is set at 200℃, which matches the half-life of the initiator to ensure sufficient in-situ grafting reaction induced under strong shear field; the die section temperature is set at 190℃; the screw speed is set at 300 r / min; and the residence time of the material in the extruder is controlled at 2 minutes.

[0060] The composite modified granules are prepared into scraper blanks through a molding process, and the scraper blanks are annealed and machined to obtain the finished scrapers.

[0061] The molding process uses profile extrusion molding, with the die head pressure controlled at 15MPa. The annealing and machining are specifically performed as follows: the molded scraper blank is placed in a constant temperature forced-air drying oven and kept at 90℃ for 48 hours, then slowly cooled with the furnace; the cooled scraper blank is then precision-cut and polished to make the surface roughness Ra of the cutting edge less than 0.4μm. In this embodiment, the appropriate modifier content and molecular weight design enable the finished scraper to achieve a good balance between hardness, wear resistance and self-lubricating properties, and due to chemical bonding, no precipitation occurs during long-term use.

[0062] Example 3:

[0063] A method for preparing a metallocene polyolefin wear-resistant scraper includes synthesizing a functionalized wear-resistant modifier by using a sol-gel method combined with hydrosilylation reaction to obtain hybrid nanospheres with reactive double bonds and polysiloxane segments.

[0064] This embodiment aims to prepare a highly wear-resistant scraper suitable for high-load, high-speed operating conditions;

[0065] The specific steps for synthesizing functionalized wear-resistant modifiers include: dissolving trifunctional vinylsilane in a mixed solvent of ethanol and water, adjusting the pH to 3-5, and carrying out a hydrolysis-condensation reaction under constant temperature water bath conditions. After the reaction, the mixture is separated by centrifugation to obtain vinyl-functionalized nano-siloxane cores. In this embodiment, vinyltriethoxysilane is selected as the trifunctional vinylsilane and is dissolved in a mixed solvent of ethanol and water with a mass ratio of 2.5:1. The pH is adjusted to 5. The temperature of the hydrolysis-condensation reaction is controlled at 70°C, and the reaction time is 24 hours to promote the high cross-linking and growth of the siloxane cores. The centrifugation parameters are: rotation speed 12000 r / min, centrifugation time 20 minutes to effectively separate larger-sized nano-aggregates.

[0066] Vinyl-functionalized nano-siloxane cores were added to toluene solvent and ultrasonically dispersed to form a uniform suspension. Hydrogen-containing polysiloxane and a platinum catalyst were then added dropwise to the suspension, with the molar ratio of Si-H to -CH=CH2 controlled at 0.5–0.8. The mixture was then refluxed and stirred under nitrogen protection, grafting polysiloxane segments onto the surface of the nano-siloxane cores via hydrosilylation. After the reaction, the product was subjected to vacuum distillation at 55°C to remove the solvent, yielding a functionalized wear-resistant modifier.

[0067] In this step, the ultrasonic dispersion power is set to 800W for 40 minutes to ensure the uniformity of the high-concentration system; the hydrogen-containing polysiloxane used is a side-chain hydrogen-containing polydimethylsiloxane with a specific molecular weight of 10,000, and the introduction of long chain segments aims to build a thicker surface lubricating layer; the amount of platinum catalyst is 25 ppm of the total mass of the reaction system; the temperature of the reflux stirring reaction is controlled at 90°C, and the reaction time is 6 hours.

[0068] Weigh out metallocene polyolefin resin, functionalized wear-resistant modifier, free radical initiator and antioxidant and mix them at high speed to prepare a premix;

[0069] In this embodiment, the metallocene polyolefin resin is metallocene ethylene-octene copolymer (POE); the free radical initiator is dicumyl peroxide (DCP); the mass ratio of each component is as follows: 100 parts of metallocene polyolefin resin, 8 parts of functionalized wear-resistant modifier, 0.2 parts of free radical initiator, and 0.3 parts of antioxidant; the high-speed mixing process parameters are set as follows: rotation speed 1800 r / min, mixing time 4 minutes; the free radical initiator of 0.2 parts (0.2%) is the upper limit set for the high viscosity characteristics of POE, in order to overcome the melt diffusion resistance and ensure sufficient grafting density; the high dosage of antioxidant of 0.3 parts is to resist the thermal history generated by high temperature of 220℃ and strong shear, to ensure the heat aging resistance of the material under high load conditions, and to prevent the oxidation induction period from being too short;

[0070] The premixed material is added to a twin-screw extruder for reactive melt extrusion. Under the action of a shear field, the functionalized wear-resistant modifier and metallocene polyolefin resin undergo an in-situ grafting reaction. The resulting material is then extruded and granulated to obtain composite modified granules.

[0071] The reactive melt extrusion uses gradient temperature control: the feeding section temperature is set at 170℃; the reaction section temperature is set at 220℃, as high temperature is beneficial for the plasticization and grafting reaction of high viscosity systems; the die section temperature is set at 200℃; the screw speed is set at 400 r / min; and the residence time of the material in the extruder is controlled at 3 minutes to ensure the dispersion and reaction of high molecular weight components.

[0072] The composite modified granules are prepared into scraper blanks through a molding process, and the scraper blanks are annealed and machined to obtain the finished scrapers.

[0073] The molding process adopts compression molding with a molding pressure of 12MPa. The annealing and machining are specifically performed as follows: the molded scraper blank is placed in a constant temperature forced-air drying oven and kept at 100℃ for 48 hours to eliminate the thermal history and internal stress caused by high-temperature extrusion; the cooled scraper blank is precision cut and polished to make the surface roughness Ra of the cutting edge less than 0.4μm. The scraper prepared in this embodiment has an extremely low coefficient of friction and excellent wear resistance. The long chain segments of the functionalized wear-resistant modifier are enriched on the surface to form a strong lubricating film.

[0074] Example 4:

[0075] A method for preparing a metallocene polyolefin wear-resistant scraper includes synthesizing a functionalized wear-resistant modifier by using a sol-gel method combined with hydrosilylation reaction to obtain hybrid nanospheres with reactive double bonds and polysiloxane segments.

[0076] This embodiment focuses on optimizing the material's processing fluidity and overall mechanical properties;

[0077] The specific steps of synthesizing functionalized wear-resistant modifiers include dissolving trifunctional vinylsilane in a mixed solvent of ethanol and water, adjusting the pH value to 3-5, carrying out hydrolysis and polycondensation reaction under constant temperature water bath conditions, and separating by centrifugation after the reaction to obtain vinyl-functionalized nano-siloxane cores.

[0078] In this embodiment, the trifunctional vinylsilane is vinyltrimethoxysilane; the pH value is adjusted to 3.5; the temperature of the hydrolysis-condensation reaction is controlled at 55°C and the reaction time is 15 hours;

[0079] Vinyl-functionalized nano-siloxane cores were added to toluene solvent and ultrasonically dispersed to form a uniform suspension. Hydrogen-containing polysiloxane and a platinum catalyst were then added dropwise to the suspension, with the molar ratio of Si-H to -CH=CH2 controlled at 0.5–0.8. The mixture was then refluxed and stirred under nitrogen protection, grafting polysiloxane segments onto the surface of the nano-siloxane cores via hydrosilylation. After the reaction, the product was subjected to vacuum distillation at 55°C to remove the solvent, yielding a functionalized wear-resistant modifier.

[0080] In this step, the hydrogen-containing polysiloxane selected is single-ended hydrogen-based polydimethylsiloxane with a specific molecular weight of 3000; the temperature of the reflux stirring reaction is controlled at 75°C, and the reaction time is 4 hours.

[0081] A premix was prepared by weighing and mixing metallocene polyolefin resin, functionalized wear-resistant modifier, free radical initiator, and antioxidant at high speed. In this embodiment, the metallocene polyolefin resin is a mixture of metallocene polyethylene and metallocene polypropylene; the free radical initiator is 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane; the mass ratio of each component is as follows: 100 parts of metallocene polyolefin resin, 3.5 parts of functionalized wear-resistant modifier, 0.08 parts of free radical initiator, and 0.15 parts of antioxidant.

[0082] The premixed material is added to a twin-screw extruder for reactive melt extrusion. Under the action of a shear field, the functionalized wear-resistant modifier and metallocene polyolefin resin undergo an in-situ grafting reaction. The resulting material is then extruded and granulated to obtain composite modified granules.

[0083] The reactive melt extrusion uses gradient temperature control: the feeding section temperature is set to 155℃; the reaction section temperature is set to 190℃; the die section temperature is set to 185℃; the screw speed is set to 250 r / min; and the material residence time in the extruder is controlled to 1.5 minutes.

[0084] The composite modified granules are prepared into scraper blanks through a molding process, and the scraper blanks are annealed and machined to obtain the finished scrapers.

[0085] The annealing and machining processes are performed as follows: the formed scraper blank is placed in a constant temperature drying oven and kept at 85°C for 48 hours; the cooled scraper blank is then precision-cut and polished to make the surface roughness Ra of the cutting edge less than 0.4μm; in this embodiment, through specific temperature and ratio control, the functionalized wear-resistant modifier is more evenly dispersed in the blended resin matrix, effectively improving the dimensional stability of the scraper.

[0086] Example 5:

[0087] A method for preparing a metallocene polyolefin wear-resistant scraper includes synthesizing a functionalized wear-resistant modifier by using a sol-gel method combined with hydrosilylation reaction to obtain hybrid nanospheres with reactive double bonds and polysiloxane segments.

[0088] This embodiment aims to balance wear resistance and creep resistance under high temperature environments;

[0089] The specific steps of synthesizing functionalized wear-resistant modifiers include dissolving trifunctional vinylsilane in a mixed solvent of ethanol and water, adjusting the pH value to 3-5, carrying out hydrolysis and polycondensation reaction under constant temperature water bath conditions, and separating by centrifugation after the reaction to obtain vinyl-functionalized nano-siloxane cores.

[0090] In this embodiment, the trifunctional vinylsilane is vinyltriethoxysilane; the pH value is adjusted to 4.5; the temperature of the hydrolysis-condensation reaction is controlled at 65°C and the reaction time is 20 hours;

[0091] Vinyl-functionalized nano-siloxane cores were added to toluene solvent and ultrasonically dispersed to form a uniform suspension. Hydrogen-containing polysiloxane and a platinum catalyst were then added dropwise to the suspension, with the molar ratio of Si-H to -CH=CH2 controlled at 0.5–0.8. The mixture was then refluxed and stirred under nitrogen protection, grafting polysiloxane segments onto the surface of the nano-siloxane cores via hydrosilylation. After the reaction, the product was subjected to vacuum distillation at 55°C to remove the solvent, yielding a functionalized wear-resistant modifier.

[0092] In this step, the hydrogen-containing polysiloxane selected is a side-chain hydrogen-containing polydimethylsiloxane with a specific molecular weight of 8000; the temperature of the reflux stirring reaction is controlled at 85°C and the reaction time is 5 hours.

[0093] Weigh out metallocene polyolefin resin, functionalized wear-resistant modifier, free radical initiator and antioxidant and mix them at high speed to prepare a premix;

[0094] In this embodiment, the metallocene polyolefin resin is metallocene polypropylene (m-PP); the free radical initiator is dicumyl peroxide (DCP); the mass ratio of each component is as follows: 100 parts of metallocene polyolefin resin, 6.5 parts of functionalized wear-resistant modifier, 0.16 parts of free radical initiator, and 0.25 parts of antioxidant.

[0095] The premixed material is added to a twin-screw extruder for reactive melt extrusion. Under the action of a shear field, the functionalized wear-resistant modifier and metallocene polyolefin resin undergo an in-situ grafting reaction. The resulting material is then extruded and granulated to obtain composite modified granules.

[0096] The reactive melt extrusion uses gradient temperature control: the feeding section temperature is set to 165℃; the reaction section temperature is set to 210℃; the die section temperature is set to 195℃; the screw speed is set to 350 r / min; and the material residence time in the extruder is controlled to 2.5 minutes.

[0097] The composite modified granules are prepared into scraper blanks through a molding process, and the scraper blanks are annealed and machined to obtain the finished scrapers.

[0098] The annealing and machining processes are performed as follows: the formed doctor blade blank is placed in a constant temperature drying oven and kept at 95°C for 48 hours; the cooled doctor blade blank is precision cut and polished so that the surface roughness Ra of the cutting edge is less than 0.4μm; the doctor blade prepared in this embodiment can still maintain good hardness and low friction characteristics under high temperature conditions, and is suitable for high-speed printing presses and other ink scraping scenarios with high heat generation.

[0099] Comparative Example 1:

[0100] This comparative example provides a method for preparing a metallocene polyolefin doctor blade as a basic control. Except for the absence of functionalized wear-resistant modifiers and free radical initiators, the remaining steps, including resin type, extrusion temperature, annealing treatment, etc., are consistent with those in Example 2. That is, 100 parts of metallocene polypropylene resin are directly mixed with 0.2 parts of antioxidant, extruded, and molded. This comparative example is used to verify the intrinsic properties of the matrix resin.

[0101] Comparative Example 2:

[0102] This comparative example provides a method for preparing a metallocene polyolefin scraper to verify the advantages of chemical grafting over physical blending. Based on Example 2, the functionalized wear-resistant modifier is replaced with an equal mass of ordinary dimethyl silicone oil, which is non-reactive and does not contain any free radical initiators. The remaining steps are consistent with Example 2. This comparative example is used to reveal the migration behavior of small molecule lubricants in the absence of reactive anchoring points.

[0103] Comparative Example 3:

[0104] This comparative example provides a method for preparing a metallocene polyolefin scraper to verify the advantages of organic-inorganic hybrid structures over traditional inorganic fillers. Based on Example 2, the functionalized wear-resistant modifier is replaced with an equal mass of nano-silica powder, without surface grafting treatment, and the remaining steps are consistent with Example 2. This comparative example is used to evaluate the effect of rigid fillers on the toughness and friction coefficient of materials.

[0105] Comparative Example 4:

[0106] This comparative example provides a method for preparing a metallocene polyolefin scraper to verify the effect of annealing on dimensional stability. The only difference from Example 2 is that the scraper blank after molding is not annealed and is directly cooled to room temperature before machining. This comparative example is used to confirm the necessity of the thermal history elimination process.

[0107] Verification test

[0108] The metallocene polyolefin wear-resistant scrapers prepared in Examples 1-5 and Comparative Examples 1-4 were subjected to corresponding performance tests, and the test results are shown below.

[0109] 1. Test Methods for Dynamic Friction Coefficient and Taber Wear: The dynamic friction coefficient is tested according to ASTM D1894 standard using a friction coefficient measuring instrument, and sliding friction is performed on the sample surface at room temperature. The Taber wear is tested according to ASTM D4060 standard using a CS-17 wear wheel, applying a 1kg load, and measuring the mass loss of the sample after 1000 revolutions. Each group of samples is tested 5 times, and the average value is taken.

[0110] 2. Test Methods for Surface Hardness and Notched Impact Strength: Surface hardness was measured using a Shore D hardness tester according to ASTM D2240 standard; notched impact strength was measured according to ASTM D256 standard using a cantilever beam impact tester to test specimens with standard notches and record the absorbed energy at fracture; 10 specimens were tested for each group of samples, and the highest and lowest values ​​were removed before taking the average value.

[0111] 3. Description of migration resistance and dimensional stability test methods: For migration resistance test, place the sample in an 80℃ constant temperature oven for 168 hours. After cooling, visually observe whether there is oily substance on the surface and wipe it with oil-absorbing paper to confirm. For dimensional stability assessment, place the standard sample in a 100℃ oven for 2 hours and measure its shrinkage rate and warping in the length direction. The qualitative evaluation is rated as excellent, good, or poor.

[0112] Table 1 Performance test data of Examples 1-5 and Comparative Examples 1-4

[0113] Test Project Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 coefficient of kinetic friction 0.18 0.12 0.10 0.15 0.11 0.35 0.13 0.32 0.12 Taber wear (mg) 18 12 8 15 10 45 30 25 14 Surface hardness (Shore D) 62 68 65 64 67 60 58 69 67 Notched impact strength (kJ / m²) 48 45 50 46 44 52 48 25 42 Migration resistance No precipitation No precipitation No precipitation No precipitation No precipitation none Obvious precipitation none No precipitation Dimensional stability excellent excellent excellent excellent excellent good good excellent Difference

[0114] As can be seen from the data analysis in Table 1, the metallocene polyolefin wear-resistant scrapers prepared in Examples 1-5 have significantly better comprehensive performance than the comparative examples, which verifies the effectiveness of the rigid inorganic core-flexible lubrication arm microstructure.

[0115] In terms of tribological properties, the dynamic friction coefficient of the Example Group (0.10-0.18) was significantly lower than that of Comparative Example 1 (0.35) and Comparative Example 3 (0.32); this indicates that the grafted polysiloxane segments in the functionalized wear-resistant modifier successfully constructed a low surface energy lubricating layer on the material surface; compared with Comparative Example 2, which physically added silicone oil, although the initial friction coefficients of the two were similar, the Example Group showed excellent characteristics of no precipitation in the migration resistance test, while Comparative Example 2 showed obvious oil precipitation;

[0116] This difference mechanistically confirms that the in-situ chemical anchoring technology achieved by reactive melt extrusion in this invention firmly anchors the lubricating component into the polyolefin matrix network using double bond reactions, effectively solving the industry problem of small molecule lubricants failing over time due to migration. Through this in-situ chemical anchoring technology, flexible polysiloxane segments easily accumulate and oriented towards the material surface under shear force, forming a low surface energy lubricating layer. The friction reduction effect of this lubricating layer can be expressed by the following formula:

[0117]

[0118] in, Let be the coefficient of kinetic friction of the system. The coefficient of friction of pure resin. It is a proportionality constant. The grafting density of the functionalized modifier; due to the presence of grafting points, It remains constant during high-speed friction, thus ensuring long-term lubrication effectiveness;

[0119] In terms of wear resistance and mechanical balance, the Taber wear of Examples 3 and 5 is extremely low, only about 20% of that of pure resin. This is attributed to the nano-siloxane core acting as a rigid framework at the microscopic level, effectively resisting abrasive cutting. In stark contrast, although Comparative Example 3 improved hardness by adding nano-silica, its notched impact strength dropped sharply to 25 kJ / m², indicating that the unmodified inorganic filler has weak interfacial bonding with the matrix, which easily leads to stress concentration. The Example group, while maintaining high wear resistance, still maintains an impact strength of 44-50 kJ / m², demonstrating the advantages of the organic-inorganic hybrid structure in energy dissipation and achieving a balance between rigidity and flexibility.

[0120] The data from Comparative Example 4 reveals the importance of the heat treatment process; although the unannealed doctor blades showed little difference in friction performance, they performed poorly in the dimensional stability test, indicating that if the orientation stress during the extrusion process is not eliminated, it will be released under high temperature conditions, leading to product warping and deformation; the example group ensured the dimensional accuracy of the doctor blades during long-term use through a strict annealing process.

[0121] The release of internal stress during annealing follows a thermal activation process, and residual stress... Over time The evolution conforms to the Arrhenius relation:

[0122]

[0123] in, Initial processing stress, For frequency factors, It is the activation energy for molecular chain segment motion. The molar gas constant, Absolute temperature Annealing time; by holding at 80℃~100℃ for 48 hours, it can be... The dimensional stability of the example group in Table 1 is reduced to an extremely low level, thereby ensuring excellent dimensional stability.

[0124] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a metallocene polyolefin wear-resistant scraper, characterized in that: include, Functionalized wear-resistant modifiers were synthesized by combining sol-gel method with hydrosilylation reaction, resulting in hybrid nanospheres with reactive double bonds and polysiloxane segments. Weigh out metallocene polyolefin resin, functionalized wear-resistant modifier, free radical initiator and antioxidant and mix them at high speed to prepare a premix; The premixed material is added to a twin-screw extruder for reactive melt extrusion. Under the action of a shear field, the functionalized wear-resistant modifier and metallocene polyolefin resin undergo an in-situ grafting reaction. The resulting material is then extruded and granulated to obtain composite modified granules. The composite modified granules are processed into scraper blanks through a molding process, and the scraper blanks are then annealed and machined to obtain the finished scrapers.

2. The method for preparing the metallocene polyolefin wear-resistant scraper as described in claim 1, characterized in that: The specific steps of synthesizing the functionalized wear-resistant modifier are as follows: include, The trifunctional vinylsilane was dissolved in a mixed solvent of ethanol and water, the pH was adjusted to 3-5, and the hydrolysis and condensation reaction was carried out under constant temperature water bath conditions. After the reaction was completed, the vinyl-functionalized nano-siloxane core was obtained by centrifugation. The vinyl-functionalized nanosiloxane core was added to toluene solvent and ultrasonically dispersed to form a uniform suspension. Hydrogen-containing polysiloxane and platinum catalyst were added dropwise to a suspension, and the molar ratio of silane-hydrogen bonds to vinyl groups was controlled to be 0.5~0.

8. The reaction was carried out under nitrogen protection and refluxed with stirring. Polysiloxane segments were grafted onto the surface of nano-siloxane cores through hydrosilylation. After the reaction is complete, the product is subjected to vacuum distillation to remove the solvent at a temperature not exceeding 60°C to obtain the functionalized wear-resistant modifier.

3. The method for preparing the metallocene polyolefin wear-resistant scraper as described in claim 1, characterized in that: The mass ratios of the metallocene polyolefin resin, functionalized wear-resistant modifier, free radical initiator, and antioxidant are 100 parts, 2-8 parts, 0.05-0.2 parts, and 0.1-0.3 parts, respectively.

4. The method for preparing the metallocene polyolefin wear-resistant scraper as described in claim 2, characterized in that: The trifunctional vinylsilane is selected from vinyltrimethoxysilane or vinyltriethoxysilane; The hydrogen-containing polysiloxane is selected from single-ended hydrogen-based polydimethylsiloxane or side-chain hydrogen-containing polydimethylsiloxane, with a molecular weight of 1000~10000. The temperature of the hydrolysis-condensation reaction is controlled at... ℃~ The temperature is ℃, and the reaction time is 12~24 hours; The temperature of the reflux stirring reaction is controlled at... ℃~ The reaction temperature is ℃, and the reaction time is 3-6 hours.

5. The method for preparing the metallocene polyolefin wear-resistant scraper as described in claim 1, characterized in that: The reactive melt extrusion, wherein the temperature setting of the twin-screw extruder adopts gradient temperature control, specifically including: The temperature of the feeding section is set to 150℃~170℃; The temperature of the reaction section is set to 180℃~220℃; The temperature of the die head section is set to 180℃~200℃; The screw speed is set to 200~400 r / min, and the residence time of the material in the extruder is controlled to be 1~3 minutes.

6. The method for preparing the metallocene polyolefin wear-resistant scraper as described in claim 1, characterized in that: The annealing and machining processes specifically include, The shaped scraper blank is placed in a constant temperature forced-air drying oven. ℃~ Keep at ℃ After 24 hours, the furnace is slowly cooled to room temperature to relieve internal stress. The cooled scraper blank is precision-cut and sharpened, and the surface of the cutting edge is polished to make the surface roughness Ra less than 0.4μm.

7. The method for preparing the metallocene polyolefin wear-resistant scraper as described in claim 1, characterized in that: The metallocene polyolefin resin is selected from one or more of metallocene polyethylene, metallocene polypropylene, or metallocene ethylene-octene copolymer; The free radical initiator is selected from dicumyl peroxide or 2,5-dimethyl-2,5-bis(tert-butyl peroxide)hexane.

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