Polyethylene powder coating suitable for ship seawater pipeline and preparation process of polyethylene powder coating

Abstract

The invention relates to the field of coatings, and discloses a polyethylene powder coating suitable for ship seawater pipelines and a preparation process thereof, and the preparation process comprises the following steps: step (1): preparing the following components in percentage by mass: 32%-34% of low density polyethylene, 30%-34% of toughened polyethylene, 12%-16% of an environmental stress cracking resistant polymer, 13%-17% of an adhesive, 1%-3% of a curing agent and 1%-3% of a curing agent; the component A comprises the following components in percentage by weight: 0.5%-1.5% of epoxy resin, 4.5%-5.5% of pigment filler, 0.2%-0.4% of slipping agent, 1.0%-1.8% of anti-aging agent and 0.2%-0.4% (2) weighing and proportioning the components in the step (1), and fully mixing the proportioned components for 5-10 minutes to ensure that the components are uniformly dispersed; according to the marine pipeline environment, the marine pipeline has excellent corrosion resistance and environmental stress cracking resistance and can effectively resist chemical corrosion and mechanical stress under seawater and changeable climate conditions, and the service life of the pipeline is remarkably prolonged. In the formula, the toughened polyethylene and the environmental stress cracking resistant polymer are reasonably combined, so that the toughness and the cracking resistance of the coating are improved, and the coating is prevented from being damaged due to temperature change and mechanical vibration.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and in particular to a polyethylene powder coating suitable for ship seawater pipelines and a preparation process thereof. Background Art

[0002] In the shipbuilding industry, piping systems operate in high-humidity, high-salt corrosive environments for long periods of time, placing extremely high demands on their corrosion resistance. Currently, most shipbuilding steel pipes in my country still use hot-dip galvanizing as a corrosion protection method, but this process has problems such as heavy pollution and limited corrosion life, making it difficult to meet the needs of green manufacturing and long-term service. In contrast, countries such as Japan and South Korea have widely promoted polyethylene-coated steel pipes many years ago. Polyethylene thermoplastic materials are used to coat the inner and outer walls of steel pipes to form a dense anti-corrosion coating with excellent corrosion resistance and operational stability, making it the current international mainstream method for corrosion protection of ship piping systems.

[0003] my country currently faces a technological gap in this field. Early domestic polyethylene plastic-coated pipe production relied primarily on manual spraying or hot-dip methods. These crude processes resulted in inaccurate temperature control, poor powder flowability and adhesion, and difficulty in achieving a highly uniform and dense coating. To achieve technological advancement, it is imperative to master the preparation process and supporting equipment system for high-quality polyethylene plastic-coated powder materials.

[0004] In the production of polyethylene coated powder, the raw materials are melt-extruded at high temperatures to form granules. These granules then undergo crushing and screening to reduce them to a fine powder suitable for coating. Existing crushing and screening equipment generally suffers from poor adaptability to the material's state: when some extruded granules fail to cool sufficiently and remain softened, they tend to agglomerate during the crushing process, forming sticky clumps. These clumps can adhere to the crushing cutters or screen surfaces, causing equipment blockage, reduced screening efficiency, uneven powder size distribution, and even impacting the stable operation of the entire milling line.

[0005] Therefore, it is urgent to design a polyethylene powder crushing and screening device with a reasonable structure, stable operation, and the ability to process incompletely cooled particles. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a polyethylene powder coating suitable for ship seawater pipelines and a preparation process thereof, aiming to alleviate the above problems at least to a certain extent.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions:

[0008] The polyethylene powder coating preparation process includes the following steps:

[0009] Step (1): preparing the following components, calculated by mass percentage: low-density polyethylene 32%-34%, toughened polyethylene 30%-34%, environmental stress cracking resistant polymer 12%-16%, adhesive 13%-17%, pigment and filler 4.5%-5.5%, lubricant 0.2%-0.4%, anti-aging agent 1.0%-1.8%, and ultraviolet absorber 0.2%-0.4%;

[0010] Step (2): Weigh and mix the components in step (1), and mix them thoroughly for 5-10 minutes to ensure that the components are evenly dispersed;

[0011] Step (3): using a melt extrusion device for extrusion, controlling the extrusion temperature between 180-230° C. to obtain a uniform molten material, and cooling the extrudate;

[0012] Step (4): Use a crushing and screening device to crush and screen the powder to ensure that the powder particle size is uniform.

[0013] Preferably, in step (2), the mixing speed of the components after batching is 800 rpm and the mixing time is 6 minutes.

[0014] Preferably, the extrusion temperature is 150±10°C.

[0015] Preferably, the lubricant is oleamide.

[0016] Preferably, the ultraviolet absorber is a benzotriazole.

[0017] Preferably, the crushing and screening device in step (4) includes:

[0018] A crushing box body, wherein a hopper is provided in the crushing box body;

[0019] A crushing bin is provided at the bottom of the hopper, a crushing shaft is provided in the crushing bin, and a material dropping channel is formed between the crushing bin and the side wall of the crushing shaft;

[0020] a blade assembly disposed at the bottom of the crushing shaft, wherein a crushing cavity is formed between the bottom of the crushing shaft and the crushing chamber, and the blade assembly is disposed in the crushing cavity;

[0021] A filter cartridge is provided at the bottom of the crushing bin, and a plurality of filter screens are provided on the outside of the filter cartridge;

[0022] A filter bag provided at the bottom of the crushing box body is connected to the filter cartridge;

[0023] a crushing component provided between the crushing bin and the crushing shaft, for rotating the crushing shaft;

[0024] The hot air component is arranged between the pulverizing box and the hopper, and is used for conveying hot air into the hopper.

[0025] Preferably, the hot air component includes a manifold connected to the inner wall of the pulverizing box, the pulverizing box is provided with a hot air blower, the air outlet of the hot air blower is connected to the manifold, the manifold is connected to a plurality of drying pipes, the drying pipes are inserted into the hopper and have a plurality of hot air outlets;

[0026] The blade assembly includes a connecting ring rotatably connected to the pulverizing chamber, a plurality of blades a are connected to the inner wall of the connecting ring, a plurality of connecting rods are connected to the connecting ring, the connecting rods are slidably connected to the bottom of the pulverizing shaft, and a spring is connected between the pulverizing shafts, and a plurality of blades b are connected to the bottom of the pulverizing shaft;

[0027] The outside of the crushing shaft is connected to an annular boss, and an annular groove is opened at the inner wall of the crushing bin corresponding to the annular boss. The gap between the annular boss and the annular groove, and the gap between the outer wall of the crushing shaft and the inside of the crushing bin form the material dropping channel.

[0028] Preferably, the crushing component can intermittently lift the position of the crushing shaft when driving the crushing shaft to rotate. When the crushing shaft is lifted to a preset position by the crushing component, it cooperates with the side wall of the crushing bin to close the discharge channel and simultaneously open the discharge path of the filter cartridge.

[0029] The crushing component includes a cover connected to the bottom of the crushing chamber, a motor is connected to the cover, a connecting shaft is connected to the driving shaft of the motor, the connecting shaft extends into the crushing chamber and is slidably connected to the crushing shaft;

[0030] The crushing component further includes a push rod slidably connected to the crushing bin, the push rod extending through the crushing bin to the inner wall thereof and contacting the annular boss, and the crushing bin is further rotatably connected to a lead screw, the push rod being threadedly engaged with the lead screw;

[0031] The shaft of the motor is connected to a gear a, which is an incomplete gear. The cover body is rotatably connected to a gear b that is adapted to the gear a. The bottom of the gear b is connected to a swing shaft, and the swing shaft is rotatably connected to a connecting rod. The other end of the connecting rod is rotatably connected to a driving rod that is slidably connected to the cover body. One end of the driving rod passes through the cover body and the crushing box and extends to one side of the lead screw. The lead screw is connected to a guide cylinder, and a spiral opening is opened on the outer wall of the guide cylinder. The top end of the driving rod is inserted into the spiral opening.

[0032] Preferably, when the material dropping channel is closed and the filter cartridge is opened, the hot air component can deliver hot air to the pulverizing chamber;

[0033] The bottom of the collecting pipe is connected to a shunt pipe, and the crushing chamber is connected to an air intake pipe, the air intake pipe is connected to the crushing chamber, a piston tube is slidably connected between the shunt pipe and the air intake pipe, the piston tube is fixedly connected to the driving rod, one end of the piston tube is inside the air intake pipe, and a plurality of air intake ports are opened on the outer wall of the piston tube;

[0034] A discharge port is provided at the bottom of the crushing chamber, the filter cartridge is slidably sleeved in the discharge port, a plurality of connection ports are provided on the outer wall of the filter cartridge, the filter screen is fixedly sleeved in the connection ports, a push rod is rotatably connected to the driving rod, and the other end of the push rod is rotatably connected to the filter cartridge.

[0035] Preferably, the inner wall of the filter cartridge is connected to a connecting boss, and the side wall of the cover body is fixed with a piston piece that slides with the connecting boss.

[0036] In summary, the present invention mainly has the following beneficial effects:

[0037] This application is aimed at the marine pipeline environment, and has excellent corrosion resistance and environmental stress cracking resistance. It can effectively resist chemical erosion and mechanical stress in seawater and changing climatic conditions, and significantly extend the service life of the pipeline. The rational combination of toughened polyethylene and environmental stress cracking resistant polymer in the formula improves the toughness and crack resistance of the coating, and prevents damage to the coating caused by temperature changes and mechanical vibrations. The adhesive enhances the bonding force between the components, improves the adhesion and mechanical strength of the coating, ensures that the coating is tightly bonded to the pipeline substrate, and avoids the coating from falling off. Pigments and anti-aging agents effectively improve the coating's resistance to ultraviolet rays and oxidation, and prevent aging and discoloration caused by long-term exposure to sunlight and marine environments. The addition of a lubricant ensures powder fluidity, ensures a uniform and defect-free coating, and improves construction efficiency and surface aesthetics.

[0038] Overall, the coating formula and process can significantly improve the protective performance and operational stability of ship pipelines, meeting the high-performance protection requirements under complex working conditions in the marine environment.

[0039] The crushing and screening device in this application, through the intermittent lifting design of the crushing shaft, realizes the periodic closure of the hopper and the crushing chamber blanking channel, temporarily stops the particle feeding, and cooperates with the hot air to efficiently dry and screen the powder in the crushing chamber. This design effectively avoids the continuous entry of softened particles leading to the accumulation of agglomerates in the crushing chamber (especially the toughened polyethylene and environmental stress cracking resistant polymers in the components of this application will have this problem), ensuring the stable progress of the drying and screening processes. Intermittent lifting can not only flexibly switch the opening and closing states of the feed channel, but also create a confined space for the hot air to circulate in the crushing chamber, thereby enhancing the hot air drying effect and promoting uniform drying of the powder and screening of uniform particle size.

[0040] In this application, when the material discharge channel is closed, the hot air component directs hot air into the pulverizing chamber, regulating the air pressure environment within the chamber, enhancing the power of powder to pass through the multi-layer filter screen and enter the filter bag, reducing powder flying and loss, and improving the cleanliness of equipment operation and powder recovery rate. The high-speed rotation of the pulverizing shaft and blade assembly generates a turbulent airflow, which, combined with the drying effect of the hot air, effectively destroys and disperses sticky agglomerates formed by insufficient drying of softened particles, reduces the cohesive strength of the agglomerates, promotes their crushing and refinement, and ensures the uniformity of powder particle size distribution and the continuous and stable screening.

[0041] This application makes full use of the synergistic effect of the intermittent lifting of the crushing shaft and hot air drying, overcomes the problems of traditional equipment that are difficult to handle softened particles and agglomeration, significantly improves the crushing efficiency, powder drying uniformity and equipment operation stability, and meets the strict requirements of high-quality polyethylene coated powder for particle size stability and drying quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the preparation process steps of the present invention;

[0043] Figure 2 It is a schematic structural diagram of the crushing and screening device of the present invention;

[0044] Figure 3 It is a cross-sectional schematic diagram of the structure of the crushing and screening device of the present invention;

[0045] Figure 4 is a schematic cross-sectional view of the crushing bin structure of the present invention;

[0046] Figure 5 This is a schematic structural diagram of the blade assembly of the present invention;

[0047] Figure 6 It is a schematic cross-sectional view of the crushing shaft structure of the present invention;

[0048] Figure 7 It is a schematic structural diagram of the crushing component of the present invention;

[0049] Figure 8Schematic diagram of the structure of gear a and gear b of the present invention;

[0050] Figure 9 is a schematic cross-sectional view of the piston tube structure of the present invention;

[0051] Figure 10 It is a schematic diagram of the top rod structure of the present invention;

[0052] Figure 11 It is a schematic diagram of the filter cartridge structure of the present invention;

[0053] Figure 12 It is a cross-sectional schematic diagram of the filter cartridge structure of the present invention.

[0054] Reference numerals:

[0055] 100. Crushing and screening device; 101. Crushing box; 102. Hopper; 103. Crushing chamber; 104. Crushing shaft; 105. Material drop channel; 106. Crushing chamber; 107. Filter cartridge; 108. Filter screen; 109. Filter bag;

[0056] 200, manifold; 201, hot air blower; 202, drying tube; 203, hot air outlet; 204, connecting ring; 205, blade a; 206, connecting rod; 207, spring; 208, blade b; 209, annular boss; 210, annular groove;

[0057] 300, housing; 301, motor; 302, connecting shaft; 303, ejector rod; 304, lead screw; 305, gear a; 306, gear b; 307, swing shaft; 308, connecting rod; 309, driving rod; 310, guide cylinder; 311, screw opening;

[0058] 400, diverter pipe; 401, air inlet pipe; 402, piston tube; 403, air inlet; 404, discharge port; 405, connection port; 406, push rod; 407, connecting boss; 408, piston plate. DETAILED DESCRIPTION

[0059] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0060] refer to Figures 1-12 , the polyethylene powder coating preparation process comprises the following steps

[0061] Step (1): prepare the following components, calculated by mass percentage: 32% low-density polyethylene, 32% toughened polyethylene, 14% environmental stress cracking resistant polymer, 15% adhesive, 5% pigment and filler, 0.3% lubricant, 1.4% anti-aging agent, and 0.3% ultraviolet absorber;

[0062] Among them, metallocene low-density polyethylene (MLLDPE) 32% is used as the base resin to give the coating good flexibility and processing performance, and the preferred density is about 0.91-0.93g / cm 3 , melting point is about 126℃, melt index (MI) range is 15g±1 / 10min;

[0063] Toughened polyethylene 32% to enhance the impact strength and toughness of the coating and improve impact resistance. High-density polyethylene (MHDPE) or linear low-density polyethylene (LLDPE) is preferred, with a density of 0.94-0.96 g / cm 3 , melt index 2±0.5g / 10min;

[0064] 14% of environmental stress cracking resistant polymer (ESCR polymer) improves the environmental stress cracking resistance of the coating, enhances the durability and aging resistance of the coating, and is preferably a stress cracking resistant ethylene-vinyl acetate copolymer (EVA), a modified resin with good environmental stress cracking resistance;

[0065] 15% adhesive, which promotes the bonding between different components and improves the adhesion and interlayer bonding strength of the coating, preferably maleic anhydride grafted polyethylene (PE-g-MA) or acrylic copolymer;

[0066] 5% pigments and fillers, which provide color and hiding power, and improve the mechanical strength and wear resistance of the coating. Preferably, inorganic fillers such as titanium dioxide (TiO2), calcium carbonate, and talc are used;

[0067] 0.3% lubricant, to improve powder fluidity, prevent powder agglomeration, and enhance coating quality. Oleamide, magnesium stearate, polyethylene glycol (PEG), polydimethylsiloxane, etc. are preferred;

[0068] 1.4% anti-aging agent, to extend the service life of the coating and prevent thermal oxidative degradation, preferably antioxidants such as butylated hydroxyanisole (BHT) and hindered amine light stabilizers (HALS);

[0069] 0.3% of ultraviolet absorber absorbs ultraviolet radiation and reduces the damage of ultraviolet radiation to the coating. Benzotriazole, benzophenone and other UV absorbers are preferred.

[0070] Step (2): weigh the components and mix them thoroughly for 5-10 minutes to ensure that the components are evenly dispersed;

[0071] Step (3): using a melt extrusion device for extrusion, controlling the extrusion temperature between 150±10°C to obtain a uniform molten material, and cooling the extrudate;

[0072] Step (4): crushing and screening the powder using the crushing and screening device 100 to ensure that the powder particle size is uniform;

[0073] Furthermore, in step (2), the mixing speed of the components after batching is 800 rpm, and the mixing time is 6 minutes.

[0074] Furthermore, the extrusion temperature is preferably 150±10°C.

[0075] The crushing and screening device 100 includes a crushing box 101, a hopper 102, a crushing bin 103, a crushing shaft 104, a blade assembly, a filter cartridge 107, a filter bag 109, a crushing component, and a hot air component.

[0076] The crushing box 101 is an integral supporting structure, and the hopper 102 is provided on the top of the crushing box 101 for receiving polyethylene extruded particles. The bottom of the hopper 102 is connected to the crushing bin 103, and the particles fall into the crushing bin 103 through the hopper 102.

[0077] A pulverizing shaft 104 is disposed in the pulverizing chamber 103. The pulverizing shaft 104 is arranged in a vertical direction, and a blade assembly is mounted at its bottom. The blade assembly is located in a pulverizing chamber 106 formed between the bottom of the pulverizing chamber 103 and the pulverizing shaft 104. A material drop channel 105 is formed between the side wall of the pulverizing shaft 104 and the pulverizing chamber 103 for material to fall into the pulverizing chamber 106.

[0078] The bottom of the crushing chamber 103 is provided with a filter cartridge 107, and the outside of the filter cartridge 107 is provided with multiple filter screens 108 for screening the crushed powder. The filter cartridge 107 is connected to a filter bag 109 provided at the bottom of the crushing box 101, and qualified powder passes through the screen into the filter bag 109 for collection.

[0079] The pulverizing assembly is used to rotate the pulverizing shaft 104 and has the function of lifting the pulverizing shaft 104 upward under specific operating conditions. When the pulverizing shaft 104 is lifted to a predetermined position, its upper structure cooperates with the side wall of the pulverizing chamber 103, closing the discharge channel 105 and simultaneously opening the discharge path of the filter cartridge 107.

[0080] The hot air component is disposed between the pulverizing box 101 and the hopper 102 and is used to deliver hot air to the hopper 102 or the pulverizing chamber 106. When the pulverizing shaft 104 is in an upward position, that is, when the discharge channel 105 is closed and the discharge path of the filter cartridge 107 is open, the hot air component can deliver hot air to the pulverizing chamber 106.

[0081] Through the above arrangement, in the process of preparing the polyethylene coated powder, the raw materials are extruded at high temperature to form particles, which are then dried and transported to the hopper 102 of the device through the transmission mechanism.

[0082] The hot air component can continuously heat the particles with hot air, further reducing the moisture content on the surface and inside the particles. This significantly improves the drying uniformity of the material and reduces the probability of particle agglomeration during subsequent transportation and crushing, fundamentally improving the continuity of crushing and the operational stability of the equipment.

[0083] After being blown by hot air and dried, the particles enter the crushing chamber 106 through the drop channel 105 with the help of gravity. The crushing shaft 104 is arranged in the vertical direction and is driven to rotate by the crushing component. The high-strength blade group installed at the bottom runs at high speed to shear and crush the polyethylene particles, effectively crushing them into fine powder that meets the particle size requirements.

[0084] During the crushing process, the crushing component has the function of intermittently lifting the crushing shaft 104. When the crushing shaft 104 is lifted to a preset height, its upper structure is sealed with the side wall of the crushing bin 103, closing the drop channel 105 between the hopper 102 and the crushing chamber 106. This closure not only effectively blocks new particles from entering the crushing chamber 106, preventing the continuous entry of softened particles and causing material accumulation, but more importantly, it prevents hot air from flowing back from the crushing chamber 106 to the hopper 102, ensuring that the hot air can act concentratedly on the inside of the crushing chamber 106, achieving efficient drying of the powder and airflow disturbance. Through this structural design, the efficiency of hot air drying is improved, the flying and loss of powder are avoided, and the cleanliness, stability and powder collection rate of the equipment and production environment are effectively protected.

[0085] When the discharge channel 105 is closed and the discharge path of the filter cartridge 107 is open, hot air can be delivered to the interior of the crushing chamber 106. Since the powder in the crushing chamber 106 passes through the multi-layer filter screen 108 and enters the filter bag 109, larger agglomerated particles cannot pass through the filter screen 108 smoothly. In this closed state, the hot air component directly delivers hot air to the interior of the crushing chamber 106. The flow of hot air not only regulates the air pressure environment in the chamber, but also enhances the momentum of the powder passing through the filter screen 108 and into the filter bag 109, thereby improving screening efficiency.

[0086] At the same time, the high-speed rotation of the pulverizing shaft 104 and the blade assembly generates disturbed airflow, which, combined with the drying effect of the hot air, effectively breaks up and disperses sticky agglomerates formed by insufficient drying of the softened particles. This synergistic effect of airflow disturbance and hot air drying not only prevents further growth and accumulation of agglomerates, but also weakens the binding force of their sticky structure, promoting the breakup and refinement of agglomerates, thereby ensuring uniform powder particle size distribution and stability of the screening process.

[0087] This device, through the dual mechanism of pulverizing shaft 104 lifting and closing material channel 105 and combined with hot air drying, overcomes the technical challenges of existing pulverizing and screening equipment, such as difficulty handling incompletely cooled and softened particles, clogging, and uneven powder particle size. This significantly improves pulverizing efficiency, screening uniformity, and powder dryness. This technical solution not only ensures the stability and compactness of the polyethylene plastic-coated powder particle size distribution, but also meets the stringent requirements for powder quality and equipment stability required for the production of high-quality marine plastic-coated pipe materials.

[0088] In this embodiment, the hot air component includes a manifold 200 mounted on the inner wall of the pulverizing box 101. The manifold 200 is connected to the air outlet of a hot air blower 201 located on the top of the pulverizing box 101 via a connecting pipe. The hot air blower 201 delivers heated air into the manifold 200.

[0089] The header 200 is equipped with multiple branching drying tubes 202, which are inserted into the interior of the hopper 102 and arranged rationally along the interior space of the hopper 102. Multiple hot air outlets 203 are evenly distributed on the outer wall of the drying tubes 202. After the hot air enters the drying tubes 202 from the header 200, it is evenly blown through these hot air outlets 203 to the polyethylene particles in the hopper 102.

[0090] With this setup, when polyethylene granules enter hopper 102, hot air blower 201 activates, evenly distributing the hot air to each drying tube 202 via manifold 200. The hot air is then blown into hopper 102 from hot air outlets 203 on the surfaces of the drying tubes 202, continuously applying hot air to the granules. This design ensures uniform heating and drying of the granules within hopper 102, further reducing the moisture content on and within the granules, and minimizing adhesion and agglomeration between granules, thereby significantly improving the efficiency of the subsequent pulverization process and the stable operation of the equipment.

[0091] In the present embodiment, the blade group comprises a connecting ring 204 rotatably connected in the crushing cavity 106, which is a circular ring structure and can rotate relative to the crushing cavity 106. The inner wall of the connecting ring 204 is provided with a plurality of blades a 205 arranged circumferentially. It is used for preliminary cutting and disturbance of particles. In order to enhance its flexible response and crushing adaptability, a plurality of connecting rods 206 are fixedly connected on the connecting ring 204, the connecting rods 206 are provided in and slidingly connected in the guide holes in the bottom of the crushing shaft 104, and a spring 207 is arranged between each connecting rod 206 and the crushing shaft 104.

[0092] The bottom end of the crushing shaft 104 is further provided with a plurality of blades b 208, which are directly fixed to the bottom end of the crushing shaft 104 and are arranged in a staggered manner with the blades a 205, thereby forming a multi-level and multi-angle composite cutting structure.

[0093] Through the above arrangement, at the beginning of the crushing stage, the crushing shaft 104 is in a low position, and the material falling channel 105 is in an open state. The particles continuously fall into the crushing cavity 106 under the action of gravity, the blades a 205 and the blades b 208 form a double-layer cutting area superimposed on each other, and high-strength shearing is generated to rapidly crush the particles to the target particle size.

[0094] When the intermittent lifting action of the crushing part is performed, the crushing shaft 104 is lifted as a whole and closes the material falling channel 105. The connecting rods 206 slide upward in the guide holes and stretch the springs 207, so that the connecting ring 204 remains unchanged at the original height, the blades b 208 at the bottom end of the crushing shaft 104 are upwardly displaced relative to the blades a 205, and the lower part of the crushing cavity 106 instantaneously obtains an additional cavity volume. The "variable volume" design creates a low-density buffer zone for the crushing cavity 106 at the moment of closing the material, the bulk density of the powder is reduced, the hot air is more easily penetrated into the powder layer, the cavity volume is increased to cause a slight decrease in local air pressure, and the subsequent injection of hot air can form a more stable pressure difference in front of the filter screen 108, thereby improving the powder screen penetration speed and collection efficiency.

[0095] In the state that the material falling channel 105 is closed and the filter cartridge 107 is open, the hot air part rapidly injects high-temperature airflow into the increased crushing cavity 106. The hot air is uniformly diffused through the circumferential gap of the blades a 205, which on the one hand continues to evaporate the residual moisture of the powder, and on the other hand is coupled with the strong turbulent flow generated by the rotation of the blade group to form a "heat-flow-rotation" triple disturbance field. The heat carried by the turbulent flow first weakens the cohesion of the wet cohesive mass, and the shearing edge of the blades a 205 continuously sweeps across, which can further disintegrate the loose micro-aggregates into single particle powder, ensuring uniform particle size. Moreover, since the material falling channel 105 is completely closed, the hot air is locked in the crushing cavity 106-filter cartridge 107 loop for circulation, and cannot carry the powder back into the hopper 102, which not only ensures that there is no dust in the hopper 102 area, but also improves the heat energy utilization rate.

[0096] When the hot air drying and screening process is completed, the crushing component drives the crushing shaft 104 to return to the low position, the spring 207 resets the connecting ring 204 and the blade b 208 to restore the original spacing, and the material falling channel 105 is reopened, and a new round of feeding-crushing-lifting cycle begins. The periodic "lifting-drying-falling" strategy enables the device to maintain high efficiency and strong shear instantaneous crushing capacity, and to complete sufficient drying and uniform screening of the powder in each cycle, continuously outputting polyethylene powder with stable particle size, low moisture content and excellent flowability.

[0097] In this embodiment, the crushing shaft 104 is fixedly connected with an annular boss 209, which is located at the middle height position of the crushing shaft 104 and is arranged in a ring shape around the circumference of the crushing shaft 104. The inner wall of the crushing bin 103 is provided with an annular groove 210 at the position corresponding to the annular boss 209.

[0098] Through the above arrangement, when the crushing shaft 104 is lifted to the high position, the annular boss 209 can cooperate with the inner wall of the crushing bin 103 to achieve the sealing effect of the material falling channel 105. This sealing structure not only prevents the uncrushed particles in the upper hopper 102 from entering the crushing cavity 106, but also avoids material accumulation interfering with subsequent powder discharge.

[0099] In this embodiment, the crushing component includes a cover body 300 fixed to the bottom of the crushing bin 103, a motor 301 is fixedly installed in the cover body 300, and a connecting shaft 302 is coaxially connected to the drive shaft of the motor 301. The connecting shaft 302 penetrates the crushing bin 103 upward and extends into the crushing cavity 106, and is connected with the crushing shaft 104 in a sliding connection of spline and key groove. This kind of sliding connection can ensure the synchronous rotation of the two shafts while allowing the crushing shaft 104 to move up and down relative to the connecting shaft 302 in the axial direction, providing a structural basis for the intermittent lifting of the crushing shaft 104.

[0100] Through the above arrangement, after the motor 301 is started, the torque is reliably transmitted to the crushing shaft 104 through the connecting shaft 302, realizing the high-speed rotary cutting of the blade group. Since the connecting shaft 302 and the crushing shaft 104 are in a sliding fit structure, the connecting shaft 302 is connected with the crushing shaft 104 in a spline and key groove manner, and the rotary power transmission is always continuous when the crushing shaft 104 is lifted or falls.

[0101] In this embodiment, the crushing component is further provided with a slidable jack 303. The jack 303 is arranged along the side wall of the crushing bin 103, with its inner end extending into the crushing bin 103 and abutting against the annular boss 209 on the outer periphery of the crushing shaft 104. A lead screw 304 is rotatably installed outside the crushing bin 103, and the lead screw 304 and the jack 303 adopt a threaded fit structure.

[0102] Through this arrangement, when the lead screw 304 rotates, the threaded pair converts the rotational motion of the lead screw 304 into axial linear motion of the push rod 303, thereby precisely lifting the annular boss 209 and the crushing shaft 104. The lead screw 304 exhibits strong self-locking properties, high displacement accuracy, and a high load capacity. Once the crushing shaft 104 is lifted to a predetermined height by the push rod 303, it maintains a stable position, preventing impacts caused by the crushing shaft 104 accidentally sliding downward. This ensures that the blanking channel 105 closes at the correct time, leaving ample space for hot air drying.

[0103] In this embodiment, to achieve automated drive and precise control of the top rod 303, the crushing component further incorporates an intermittent mechanical transmission mechanism. Specifically, the drive shaft of the motor 301 is equipped with a gear a305. This gear a305 utilizes an incomplete gear structure, with only a portion of the ring gear having teeth, to achieve intermittent drive output. A gear b306, rotatably connected to the inside of the housing 300 and meshing with gear a305, is affixed to the lower swing shaft 307. This gear b306 transmits power to a drive rod 309, which slides within the housing 300, via a connecting rod 308.

[0104] One end of the drive rod 309 passes through the housing 300 and the crushing box 101 and extends to the vicinity of the screw 304 structure, and its top end is inserted into the spiral opening 311 on the guide cylinder 310 outside the screw 304. The guide cylinder 310 is fixed to the screw 304, allowing the screw 304 to rotate accordingly.

[0105] With this setup, when motor 301 begins rotating, gear a305 on its shaft begins to rotate accordingly. Because gear a305 is an incomplete gear structure, with only a portion of its outer ring having teeth, it only drives gear b306 when the toothed portion meshes with gear b306. When the toothless portion meshes with the gear, gear b306 stops rotating, creating a "stop-start-stop" intermittent output rhythm.

[0106] When gear b306 receives driving force, it drives the connecting rod 308 to swing via the swing shaft 307 connected to its bottom. The other end of the connecting rod 308 is connected to a drive rod 309 within the housing 300. Driven by the connecting rod 308, the drive rod 309 achieves a linear propulsion motion. The top end of the drive rod 309 is inserted into the spiral opening 311 of the guide cylinder 310 on the side of the crushing chamber 103. The guide cylinder 310 is fixedly connected to the lead screw 304, and the spiral opening 311 functions as a guide rail. Therefore, as the drive rod 309 moves linearly, its top end slides within the spiral groove, thereby driving the lead screw 304 to rotate.

[0107] When the lead screw 304 rotates, it drives the push rod 303, which is threaded with it, to produce axial linear displacement. The inner end of the push rod 303 contacts the annular boss 209 provided on the outside of the crushing shaft 104. When the push rod 303 is gradually pushed inward, it presses the annular boss 209, thereby lifting the crushing shaft 104 as a whole.

[0108] After the pulverizing shaft 104 is raised to a preset height, the annular boss 209 on its outer wall engages the annular groove 210 on the inner wall of the pulverizing chamber 103, sealing the material discharge channel 105. At this point, the pulverizing chamber 106 is separated from the hopper 102, preventing unprocessed material from falling in. Hot air can be directed into the pulverizing chamber 106 for effective drying. As the pulverizing shaft 104 is raised, the blade b 208 at its bottom moves upward, while the blade a 205 on the connecting ring 204 remains stationary. This expands the effective space in the pulverizing chamber 106, leaving more room for material to flow and tumble during the drying process, improving discharge flow and drying uniformity.

[0109] Subsequently, as the motor 301 continues to rotate, gear a305 enters the toothless section, gear b306 stops rotating, transmission stops, and the push rod 303 remains in the raised position, while the crushing shaft 104 remains raised, completing a cycle of crushing, discharging, and drying. When the next toothed section of gear a305 re-enters the meshing zone, the above process repeats, the drive rod 309 returns to its original position, the screw 304 rotates, and the push rod 303 is disengaged. The crushing shaft 104 moves downward, and the material discharge channel 105 reopens, entering the next round of feeding and crushing.

[0110] The swing link 308 is driven by the incomplete gear to achieve intermittent push on the drive rod 309, and then drive the screw 304 to rotate, so that the top rod 303 intermittently pushes the crushing shaft 104 to move upward, forming a stable automatic intermittent lifting mechanism. After closing the blanking channel 105, it can prevent hot air from flowing back into the hopper 102, ensuring that the heat energy is concentrated on the crushing chamber 106, pushing qualified powder through the filter screen 108 and into the filter bag 109 for collection, avoiding powder backflow or flying, and improving the collection rate and particle size distribution consistency.

[0111] In this embodiment, the bottom of the manifold 200 is connected to a diverter pipe 400, which serves as a hot air guide component for directing the hot air toward the crushing chamber 106. An air inlet pipe 401 is connected to the side wall of the crushing chamber 103 and communicates with the interior of the crushing chamber 106 for supplying hot air into the crushing chamber 106.

[0112] A piston tube 402 is slidably connected between the diverter tube 400 and the intake pipe 401. The piston tube 402 is hollow, with one end inserted into the intake pipe 401. The outer wall of the piston tube 402 is provided with a plurality of circumferentially spaced intake ports 403. The piston tube 402 is fixedly connected to the drive rod 309 and slides synchronously with the movement of the drive rod 309.

[0113] With the above arrangement, during the pulverizing operation, when the drive mechanism drives the drive rod 309 to intermittently move linearly, the piston tube 402 connected to the drive rod 309 also slides accordingly. This sliding action directly adjusts the relative position of the piston tube 402 and the air inlet pipe 401, thereby controlling the opening and closing state of the air inlet 403, and achieving rhythmic regulation of the hot air entering the pulverizing chamber 106.

[0114] When the driving rod 309 is in the initial non-moving state, the end of the piston tube 402 is still inside the air inlet pipe 401. At this time, the multiple air inlets 403 on the piston tube 402 are blocked by the inner wall of the air inlet pipe 401, forming a sealed state, resulting in the hot air transported by the collecting pipe 200 being unable to enter the crushing chamber 106, avoiding the hot air from entering the crushing chamber 106 in advance when the blanking channel 105 is opened, preventing the loss of hot air and reduced efficiency.

[0115] As the drive rod 309 moves axially, the piston tube 402 slides synchronously, gradually exposing the air inlet 403 on the piston tube 402 to the inner cavity of the air inlet pipe 401, thereby opening the hot air passage. At this time, the hot air in the manifold 200 enters the air inlet pipe 401 through the shunt pipe 400 and the air inlet 403 of the piston tube 402, and is finally transported to the inside of the crushing chamber 106. This design precisely controls the timing of the hot air entering the crushing chamber 106 by mechanically sliding the air inlet 403 to achieve synchronous coordination of hot air injection and the state of the crushing chamber 106 (such as the closure of the blanking channel 105), avoiding the waste of hot air at inappropriate times and effectively improving the hot air utilization rate and powder drying efficiency.

[0116] The sliding shielding structure of piston tube 402 enables on-off rhythmic control of hot air injection without relying on complex electronic control components, ensuring that hot air is applied to the interior of crushing chamber 106 only under required operating conditions, improving energy efficiency. The use of mechanical linkage to achieve hot air control eliminates the need for additional control signals, resulting in direct response and accurate control rhythm, which helps improve the stability and maintenance of the entire machine. Because piston tube 402 is fixedly connected to drive rod 309, it can be synchronized with the lifting movement of crushing shaft 104. That is, when crushing shaft 104 is raised, discharge channel 105 is closed, and the discharge path of filter screen 108 is open, hot air is ensured to be smoothly injected, enhancing drying and screening efficiency.

[0117] In the embodiment, the bottom of the crushing cavity 106 is provided with a discharge port 404, and the filter cartridge 107 is sleeved in the discharge port 404 and used for screening the crushed polyethylene powder. The outer wall of the filter cartridge 107 is provided with a plurality of connecting ports 405, and the filter screen 108 is fixedly sleeved in the connecting port 405 and used for filtering the large agglomerates, and only allowing the fine powder meeting the requirements to pass through. The driving rod 309 is rotatably connected with a push rod 406, and the other end of the push rod 406 is rotatably connected with the filter cartridge 107. The reciprocating movement of the driving rod 309 drives the push rod 406 to move, and then the push and pull sliding control of the filter cartridge 107 is realized.

[0118] Through the above arrangement, the filter cartridge 107 and the push rod 406 are linked to realize the sliding movement of the filter cartridge 107, so that the crushing and screening process has good dynamic switching capability.

[0119] Specifically, when the crushing shaft 104 is lifted under the driving of the crushing part, the driving rod 309 synchronously drives the push rod 406 to move, so as to realize the sliding displacement of the filter cartridge 107. The filter cartridge 107 is originally in a closed state position in the discharge port 404, and is slid upward to displace the connecting port 405 to form an open state in the crushing cavity 106, so as to open the discharge channel at the bottom of the crushing cavity 106. In this process, the hot air conveyed by the hot air part can enter the inside of the crushing cavity 106, cooperate with the disturbance airflow to dry the powder, and promote the fine powder to pass through the filter screen 108 and enter the filter bag 109. The plurality of filter screens 108 connected to the outer wall of the filter cartridge 107 screen the entering powder, and the large agglomerates cannot pass through the filter screen 108 and are effectively blocked, so as to ensure that the collected powder has uniform particle size and is fully dried.

[0120] The sliding structure of the filter cartridge 107 not only optimizes the discharge path, but also has good operation flexibility. Through the mechanical linkage of the push rod 406 and the driving rod 309, the filter cartridge 107 can slide into the connecting port 405 after completing the screening task to close the discharge channel. When the filter cartridge 107 is lifted upward, the hot air acts on the inside of the crushing cavity 106, which not only improves the drying degree of the powder and reduces the moisture residue, but also further reduces the probability of the agglomeration phenomenon. When part of the particles that are not completely dried form agglomerates and adhere to the surface of the crushing shaft 104 or the blade group due to viscosity, the hot air and the rotating disturbance airflow cooperate to make the agglomerates gradually lose viscosity and be cut and dispersed by the blade group again, so as to ensure the particle size distribution and discharge continuity of the powder in the entire crushing and screening process. Through the lifting linkage of the crushing shaft 104 and the filter cartridge 107 discharge structure, not only the automatic switching of the powder screening path is realized, but also the powder quality is effectively improved in cooperation with the hot air drying process, and the stability and reliability of the equipment in the polyethylene coating powder preparation process are significantly enhanced.

[0121] In this embodiment, the inner wall of the filter cartridge 107 is further connected with an annular connecting boss 407 , and a piston piece 408 that slides with the connecting boss 407 is fixed at a corresponding position on the side wall of the cover body 300 . The piston piece 408 is arranged along the sliding direction of the filter cartridge 107 .

[0122] With this arrangement, during the initial operation, the filter cartridge 107 is in the closed position below the discharge port 404. The piston plate 408 is fully embedded within the connecting boss 407 on the inner wall of the filter cartridge 107, forming an annular sealing surface that securely seals and prevents leakage of powder or hot air. At this point, the pulverizing shaft 104 is in the lower position, the drop channel 105 is open, and the polyethylene particles continuously fall into the pulverizing chamber 106, completing high-speed shear pulverization.

[0123] As the pulverizing shaft 104 lifts and closes the discharge channel 105, the drive rod 309-push rod 406 mechanism pushes the filter cartridge 107 to slide upward. As the filter cartridge 107 rises, the connecting boss 407 slides smoothly along the outer wall of the piston plate 408 until the filter cartridge 107 reaches a predetermined height. The connecting port 405 on the outer wall of the filter cartridge 107 and its filter screen 108 are fully exposed to the interior of the pulverizing chamber 106. At this moment, the piston plate 408 disengages from the connecting boss 407, the discharge passage opens, and hot air is introduced into the pulverizing chamber 106. Under the rotational disturbance of the blade assembly, hot air forms a high-speed airflow, carrying the dried fine powder through the filter screen 108 and into the filter bag 109. Larger agglomerates are effectively blocked by the filter screen 108, ensuring that the discharged powder has a uniform particle size and is fully dried.

[0124] After discharge and drying are complete, the drive rod 309 reverses its motion, causing the filter cartridge 107 to descend along its original path. The connecting boss 407 rejoins and gradually engages the piston plate 408, sealing the discharge port 404 and creating a momentary compressed space between the interior of the filter cartridge 107 and the pulverizing chamber 106. The air pressure pulse generated by the downward extrusion of the filter cartridge 107 blows any remaining powder on the filter screen 108 back into the pulverizing chamber 106 by the reverse airflow, achieving self-cleaning of the filter screen 108. Finally, the filter cartridge 107 fully returns to its original position, and the piston plate 408 reengages the connecting boss 407, restoring the seal and preparing for the next cycle of continuous pulverization.

[0125] Through the coordinated action of the guide seal and air pressure backblowing between the piston plate 408 and the connecting boss 407, the opening and closing process of the filter cartridge 107 is smooth and precise, and the automatic cleaning efficiency of the filter screen 108 is high, which not only avoids the leakage of powder and hot air, but also keeps the screening channel unobstructed, thereby continuously outputting high-quality polyethylene coated powder with consistent particle size and low moisture content, significantly improving the operating reliability, sealing safety and product quality consistency of the equipment.

[0126] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A process for preparing polyethylene powder coating, characterized in that: The following steps are involved: Step (1): preparing the following components, calculated by mass percentage: low-density polyethylene 32%-34%, toughened polyethylene 30%-34%, environmental stress cracking resistant polymer 12%-16%, adhesive 13%-17%, pigment and filler 4.5%-5.5%, lubricant 0.2%-0.4%, anti-aging agent 1.0%-1.8%, and ultraviolet absorber 0.2%-0.4%; Step (2): Weigh and mix the components in step (1), and mix them thoroughly for 5-10 minutes to ensure that the components are evenly dispersed; Step (3): using a melt extrusion device for extrusion, controlling the extrusion temperature between 150±10°C to obtain a uniform molten material, and cooling the extrudate; Step (4): Use a crushing and screening device to crush and screen the powder to ensure that the powder particle size is uniform.

2. The process for preparing polyethylene powder coating according to claim 1, characterized in that: In step (2), the mixing speed of the components after batching is 800 rpm and the mixing time is 6 minutes.

3. The process for preparing polyethylene powder coating according to claim 1, wherein: The extrusion temperature is 200°C.

4. The process for preparing polyethylene powder coating according to claim 1, wherein: The lubricant is oleamide.

5. The process for preparing polyethylene powder coating according to claim 1, characterized in that: The ultraviolet absorber is a benzotriazole.

6. The process for preparing polyethylene powder coating according to claim 1, characterized in that: The crushing and screening device described in step (4) includes: A crushing box body, wherein a hopper is provided in the crushing box body; A crushing bin is provided at the bottom of the hopper, a crushing shaft is provided in the crushing bin, and a material dropping channel is formed between the crushing bin and the side wall of the crushing shaft; a blade assembly disposed at the bottom of the crushing shaft, wherein a crushing cavity is formed between the bottom of the crushing shaft and the crushing chamber, and the blade assembly is disposed in the crushing cavity; A filter cartridge is provided at the bottom of the crushing bin, and a plurality of filter screens are provided on the outside of the filter cartridge; A filter bag provided at the bottom of the crushing box body is connected to the filter cartridge; a crushing component provided between the crushing bin and the crushing shaft, for rotating the crushing shaft; The hot air component is arranged between the pulverizing box and the hopper, and is used for conveying hot air into the hopper.

7. The process for preparing polyethylene powder coating according to claim 6, characterized in that: The hot air component includes a header connected to the inner wall of the pulverizing box, a hot air blower is provided on the pulverizing box, the air outlet of the hot air blower is connected to the header, and the header is connected to a plurality of drying pipes, which are inserted into the hopper and have a plurality of hot air outlets; The blade assembly includes a connecting ring rotatably connected to the pulverizing chamber, a plurality of blades a are connected to the inner wall of the connecting ring, a plurality of connecting rods are connected to the connecting ring, the connecting rods are slidably connected to the bottom of the pulverizing shaft, and a spring is connected between the pulverizing shafts, and a plurality of blades b are connected to the bottom of the pulverizing shaft; The outside of the crushing shaft is connected to an annular boss, and an annular groove is opened at the inner wall of the crushing bin corresponding to the annular boss. The gap between the annular boss and the annular groove, and the gap between the outer wall of the crushing shaft and the inside of the crushing bin form the material dropping channel.

8. The process for preparing polyethylene powder coating according to claim 7, characterized in that: The crushing component can also intermittently lift the position of the crushing shaft when driving the crushing shaft to rotate. When the crushing component lifts the crushing shaft to a preset position, the crushing shaft cooperates with the side wall of the crushing bin to close the discharge channel and simultaneously open the discharge path of the filter cartridge; The crushing component includes a cover connected to the bottom of the crushing chamber, a motor is connected to the cover, a connecting shaft is connected to the driving shaft of the motor, the connecting shaft extends into the crushing chamber and is slidably connected to the crushing shaft; The crushing component further includes a push rod slidably connected to the crushing bin, the push rod extending through the crushing bin to the inner wall thereof and contacting the annular boss, and the crushing bin is further rotatably connected to a lead screw, the push rod being threadedly engaged with the lead screw; The shaft of the motor is connected to a gear a, which is an incomplete gear. The cover body is rotatably connected to a gear b that is adapted to the gear a. The bottom of the gear b is connected to a swing shaft, and the swing shaft is rotatably connected to a connecting rod. The other end of the connecting rod is rotatably connected to a driving rod that is slidably connected to the cover body. One end of the driving rod passes through the cover body and the crushing box and extends to one side of the lead screw. The lead screw is connected to a guide cylinder, and a spiral opening is opened on the outer wall of the guide cylinder. The top end of the driving rod is inserted into the spiral opening.

9. The process for preparing polyethylene powder coating according to claim 8, characterized in that: When the material dropping channel is closed and the filter cartridge is opened, the hot air component can deliver hot air to the crushing chamber; The bottom of the collecting pipe is connected to a shunt pipe, and the crushing chamber is connected to an air intake pipe, the air intake pipe is connected to the crushing chamber, a piston tube is slidably connected between the shunt pipe and the air intake pipe, the piston tube is fixedly connected to the driving rod, one end of the piston tube is inside the air intake pipe, and a plurality of air intake ports are opened on the outer wall of the piston tube; A discharge port is provided at the bottom of the crushing chamber, the filter cartridge is slidably sleeved in the discharge port, a plurality of connection ports are provided on the outer wall of the filter cartridge, the filter screen is fixedly sleeved in the connection ports, a push rod is rotatably connected to the driving rod, and the other end of the push rod is rotatably connected to the filter cartridge.

10. A polyethylene powder coating, characterized in that: The invention is prepared by the preparation process according to any one of claims 1 to 9.

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