Preparation method of easily degradable PE particles

Abstract

The invention discloses a preparation method of easily degradable PE particles. The preparation method comprises the following steps: S1, preparing raw materials, wherein the raw materials comprise the following components in parts by weight: 50 parts of CaCO3, 2 parts of a titanate coupling agent, 30 parts of a PE plastic carrier, 10 parts of magnesium stearate, 4 parts of cellulose and 3 parts of paraffin; s2, preparing a first mixture: mixing CaCO3, a titanate coupling agent, a PE plastic carrier and magnesium stearate in a high-temperature mixer, heating to melt, and stirring to obtain the first mixture; s3, preparing a second mixture: adding cellulose and paraffin into the first mixture, heating to melt, and stirring to obtain the second mixture; and S4, preparing PE particles: after the second mixture is cooled, preparing the PE particles through granulation equipment. Compared with the prior art, the proportion of biodegradable materials in the PE particles is reduced, the production cost is reduced, and the easily degradable performance is guaranteed by adding the calcium carbonate.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic preparation, and in particular, to a method for preparing degradable PE particles. Background Art

[0002] Polyethylene (PE), as a common plastic, especially its disposable products, is widely used. However, the problem of natural degradation caused by its structural stability has made "white pollution" a huge pressure on the ecological environment. Methods for treating such waste, such as deep burial, incineration, and recycling, all have limitations: the former may cause soil pollution, the middle one emits harmful gases, and the latter faces challenges of high cost and low efficiency.

[0003] Therefore, seeking a solution that can make polyethylene naturally degrade after being discarded has become an urgent need. This can not only effectively reduce the environmental burden, but also avoid new environmental problems brought by traditional treatment methods, while reducing treatment costs and improving resource utilization rates.

[0004] Existing degradation technologies are divided into three categories: biodegradation, photodegradation, and chemical degradation. Among them, biodegradation uses specific microorganisms or microbial communities to decompose plastics under specific environments and convert them into harmless substances such as carbon dioxide, water, and biomass; photodegradation adds photosensitizers to plastics or makes plastics photosensitive through chemical synthesis, and chemical reactions occur under light conditions, resulting in the destruction of the plastic structure, thereby achieving the purpose of degradation; chemical degradation breaks the plastic molecular chains through chemical methods (such as acidolysis, alkalinolysis, oxidation, etc.), thereby realizing the degradation of plastics.

[0005] However, materials that only use biodegradation often require the use of special bio-based raw materials or biocatalysts, and the costs of these raw materials are usually high; photodegradation and chemical degradation materials are unstable, for example, there is a possibility of rapid degradation due to the action of light or chemical substances. Therefore, there is an urgent need for a new method for preparing degradable PE particles to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for preparing degradable PE particles.

[0007] The purpose of the present invention is achieved by the following technical solutions: A method for preparing degradable PE particles, comprising the following steps: S1. Prepare raw materials: The raw materials include the following components by weight: 50 parts of CaCO3, 2 parts of titanate coupling agent, 30 parts of PE plastic carrier, 10 parts of magnesium stearate, 4 parts of cellulose, and 3 parts of paraffin; S2. Prepare the first mixture: Mix CaCO3, titanate coupling agent, PE plastic carrier, and magnesium stearate in a high-temperature mixer, heat up to melting, and then stir to obtain the first mixture; S3. Prepare the second mixture: Add cellulose and paraffin to the first mixture, heat up to melting, and then stir to obtain the second mixture; S4. Prepare PE particles: After the second mixture cools down, use granulation equipment to produce PE particles.

[0008] Preferably, the PE plastic carrier includes low-density polyethylene, linear low-density polyethylene, high-density polyethylene, ultra-high molecular weight polyethylene, medium-density polyethylene, or ultra-low density polyethylene.

[0009] Preferably, the temperature for heating and stirring in S2 is 120 °C, and the stirring time is 25 - 30 min.

[0010] Preferably, the temperature for heating and stirring in S3 is 190 - 220 °C, and the stirring time is 10 - 20 min.

[0011] Preferably, the granulation equipment includes an extruder, a cooling water tank, and a pelletizer connected in sequence.

[0012] Preferably, the pelletizer includes a housing, on which a feed inlet and a discharge outlet are oppositely arranged, and inside the housing, a traction component and a pelletizing component are sequentially arranged between the feed inlet and the discharge outlet, and a wiping member for wiping the material strip is arranged at the feed inlet.

[0013] Preferably, a screening mesh is arranged at the discharge outlet, the screening mesh is used to receive the plastic particles cut by the pelletizing component, and a vibration motor is arranged on the screening mesh.

[0014] Preferably, a guiding channel is constructed at the top inside the housing and extends obliquely towards the wiping member side, the screening mesh is adapted to be able to rotate between a screening position and a pouring position, in the pouring position, the plastic particles on the screening mesh are poured into the guiding channel, and at least part of the wiping member is exposed in the guiding channel.

[0015] Preferably, the housing is configured with a blanking port at the bottom end of the guiding channel, a sealing plate is rotatably arranged at the blanking port, a notch is configured on the guiding channel, the wiping member includes a wiping roller and a water-absorbing layer arranged on the side wall of the wiping roller, the water-absorbing layer is engaged in the notch, a driving plate is rotatably arranged at the top end of the guiding channel of the housing, a transmission belt is drivingly connected between the rotating shaft of the driving plate and the rotating shaft of the sealing plate, and a torsion spring is arranged on at least one of the rotating shafts of the driving plate and the rotating shaft of the sealing plate; when the screening mesh rotates from the screening position to the blanking position, the screening mesh can push the sealing plate to drive the transmission belt to rotate, and then the sealing plate opens the blanking port; a one-way transmission mechanism is adapted between the transmission belt and the rotating shaft of the wiping roller, and the one-way transmission mechanism is adapted to drive the wiping roller to rotate only when the transmission belt rotates in one direction.

[0016] Preferably, the water-absorbing layer includes sponge or bristles.

[0017] The beneficial effects of the present invention are as follows: 1. When calcium carbonate is filled into PE plastic, during the degradation process of the plastic, calcium carbonate may react with CO2 and H2O to generate water-soluble Ca(HCO3)2 and leave the plastic film, thereby leaving micropores on the film. These micropores increase the contact area between the plastic and the surrounding air and microorganisms, facilitating the entry of microorganisms and the progress of the degradation process. Compared with the prior art, the present invention reduces the proportion of biodegradable materials in PE particles, not only reducing the production cost, but also ensuring the easy degradation performance by adding calcium carbonate.

[0018] 2. The online screening of plastic particles cut by the granulation component can be realized through the screening mesh, thereby ensuring the quality of the produced particles.

[0019] 3. By controlling the rotation of the screening mesh, unqualified plastic particles can be put into the guiding channel, and then a heat source can be provided for the wiping member exposed in the guiding channel. For example, it can have a drying effect on the wiping member to ensure the best water removal effect. Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of the embodiment (the screening mesh is shown in a dotted line at the blanking position); Figure 2 For Figure 1 Enlarged view of part A; Figure 3 It is a schematic structural diagram with the blanking port in the closed state; Figure 4 It is a schematic structural diagram of the one-way transmission mechanism; Figure 5It is a schematic structural view seen from the top-down projection direction at the material discharge port.

[0021] Reference numerals: 1, housing; 2, feed inlet; 3, discharge outlet; 4, traction member; 5, pelletizing member; 6, wiping member; 7, screening mesh; 8, guiding channel; 9, material discharge port; 10, sealing plate; 11, notch; 12, wiping roller; 14, driving plate; 15, transmission belt; 16, one-way transmission mechanism; 17, pushing claw; 18, transmission wheel; 19, transmission groove; 20, mounting cover. Detailed implementation manners

[0022] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present invention.

[0023] A method for preparing degradable PE particles includes the following steps: S1. Prepare raw materials: The raw materials include the following components in parts by weight: 50 parts of CaCO3, 2 parts of titanate coupling agent, 30 parts of PE plastic carrier, 10 parts of magnesium stearate, 4 parts of cellulose, and 3 parts of paraffin. S2. Prepare the first mixture: Mix CaCO3, titanate coupling agent, PE plastic carrier, and magnesium stearate in a high-temperature mixer, heat up to melting and then stir to obtain the first mixture. S3. Prepare the second mixture: Add cellulose and paraffin to the first mixture, heat up to melting and then stir to obtain the second mixture. S4. Prepare PE particles: After the second mixture is cooled, PE particles are prepared by a granulation device.

[0024] In some examples, the PE plastic carrier may include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, ultra-high molecular weight polyethylene, medium-density polyethylene, or ultra-low-density polyethylene. In S2, the temperature for heating and stirring is 120°C, and the stirring time is 25 - 30 min; in S3, the temperature for heating and stirring is 190 - 220°C, and the stirring time is 10 - 20 min.

[0025] In addition, the granulation device may preferably include an extruder, a cooling water tank, and a pelletizer connected in sequence. During granulation, the second mixture can be put into the extruder for melt extrusion, and the extruded strip can be finally sent into the pelletizer through the cooling of the cooling water tank to complete pelletizing.

[0026] Such as Figures 1 to 5As shown, in some embodiments, the pelletizer may include a housing 1. For example, a feed inlet 2 and a discharge outlet 3 may be relatively configured on the housing 1. Between the feed inlet 2 and the discharge outlet 3, a traction member 4 and a pelletizing member 5 are sequentially arranged. The traction member 4 is used to traction the strip cooled by the cooling water tank and feed it into the pelletizing member 5 for pelletizing. For example, the traction member 4 may include upper and lower opposed traction rollers, and the pelletizing member 5 may include a rotatably arranged pelletizing moving knife. A pelletizing stationary knife may be oppositely arranged in the housing 1 relative to the pelletizing moving knife.

[0027] In the specific pelletizing process, the traction member 4 feeds the strip between the pelletizing moving knife and the pelletizing stationary knife. Subsequently, the pelletizing moving knife rotates driven by a rotational drive source such as a motor, etc., thereby completing the pelletizing cutting of the strip.

[0028] During actual production, the inventor found that since the strip was not dried in time after being cooled by water, the water content of the pellets was relatively large, which in turn affected the subsequent processing of the plastic pellets. To address the above technical problem, in this disclosure, a wiping member 6 for wiping the strip is provided at the feed inlet 2 on the housing 1, and the wiping member 6 wipes the moisture of the strip before it enters the pelletizer.

[0029] In addition, the plastic particles cut out may have uneven particle sizes due to problems such as the dulling of the cutting edge of the pelletizing moving knife or the sway caused by the assembly gap. Uneven particle sizes of the plastic particles will result in inconsistent material densities, which in turn will affect the physical and mechanical properties of plastic products such as strength, toughness, ductility, hardness, etc., reducing the service life and safety factor of the products.

[0030] To address the above technical problem, in this disclosure, a screening mesh 7 is provided at the discharge outlet 3 inside the housing 1, and a vibration motor is provided on the screening mesh 7. It can be understood that the screening mesh 7 can receive the plastic particles cut out by the pelletizing member 5, and under the vibration of the vibration motor, the plastic particles meeting the particle size can be normally exported from the discharge outlet 3 through the screening mesh 7.

[0031] In some embodiments, a guiding channel 8 extending obliquely towards the wiping member 6 is formed at the top inside the housing 1. For example, the guiding channel 8 may be defined by a guiding plate obliquely arranged inside the housing 1, and at least part of the wiping member 6 is exposed in the guiding channel 8. In addition, the screening mesh 7 is also adapted to be rotatably arranged inside the housing 1. For example, the screening mesh 7 can rotate between a screening position and a discharging position.

[0032] At the screening position, the screening mesh 7 can be located at the lowest end and is used to receive the plastic particles cut from the granulating component 5; at the discharging position, the screening mesh 7 can be located at the topmost end and pour the plastic particles intercepted thereon into the guiding channel 8. Under the action of gravity, the plastic particles will roll to the bottom end of the guiding channel 8. For example, the plastic particles can cover the wiping member 6. Since the plastic particles are not completely cooled under water cooling, that is, the plastic particles still have a certain amount of heat, especially the heat perception will be more obvious after a period of time when the plastic strip is separated from the cooling water tank. Thus, this part of the heat can be provided to the wiping member 6, and then it can play a drying role on the wiping member 6, enabling the wiping member 6 to achieve the best wiping effect.

[0033] In a possible example, when the granulating equipment is used to manufacture plastic particles with strong hydrophilicity, unqualified plastic particles with strong hydrophilicity can be reserved in the guiding channel 8. Thus, this part of the plastic particles can also play a water absorption effect on the wiping member 6, and the best wiping effect of the wiping member 6 is ensured. For example, the plastic particles with strong hydrophilicity can include nylon, polyamides or polyvinyl alcohol. Of course, it can also be plastic particles with water absorption affected by additives. For example, acrylic itself is not easy to absorb water because there are no hydrogen bonds in its molecular structure, but if additives are added, its water resistance will be reduced. Similarly, in this large category of plastics called polymers, including ABS, PVC, PMMA, etc., their water absorption performance will also be significantly improved when additives are added.

[0034] It can be understood that by wiping and drying the plastic strip before it enters the granulator, especially the damage of moisture to the traction component 4 and the granulating component 5 can be prevented. For example, the possibility of rusting can be prevented.

[0035] In some embodiments, a notch 11 is formed on the guiding channel 8, and the wiping member 6 includes a wiping roller 12 and a water absorption layer provided on the side wall of the wiping roller 12. For example, the water absorption layer can be a sponge or bristles, and the water absorption layer is engaged in the notch 11. Specifically, a discharging port 9 is further formed on the housing 1 at the bottom end of the guiding channel 8. The plastic particles entering the guiding channel 8 will roll towards the discharging port 9 under the action of gravity. A blocking plate 10 is rotatably provided at the discharging port 9. When the blocking plate 10 is in a closed state with respect to the discharging port 9, the plastic particles will be blocked in the guiding channel 8, especially they can be accumulated on the water absorption layer to achieve the above-mentioned drying effect. For example, a drive plate 14 is rotatably provided at the top of the guiding channel 8 inside the housing 1, and a transmission belt 15 is drivingly connected between the rotating shafts of the drive plate 14 and the plugging plate 10. In addition, a torsion spring (not shown in the figure) is provided on at least one of the rotating shafts of the drive plate 14 and the plugging plate 10. Preferably, a one-way transmission mechanism 16 is further adapted between the transmission belt 15 and the rotating shaft of the wiping roller 12, and the one-way transmission mechanism 16 is adapted to drive the wiping roller 12 to rotate only when the transmission belt 15 rotates in one direction.

[0036] Based on this, the present disclosure may have the following operating process: 100. The strip cooled by the cooling water tank is wiped by the wiping member 6 and then enters the housing 1 through the feeding port 2, and is granulated under the cutting of the granulating member 5. Among them, the cut plastic particles can fall into the screening mesh 7 at the screening position for on-line screening, and the plastic particles with unqualified particle sizes will be retained on the screening.

[0037] 201. Control the screening mesh 7 to rotate from the screening position to the dumping position to pour the retained plastic particles into the guiding channel 8. At the same time, the screening mesh 7 can push the drive plate 14 to rotate and drive the transmission belt 15 to rotate. As a result, the plugging plate 10 will also rotate and open the dumping port 9. At this time, the plastic particles originally accumulated on the guiding channel 8 can be discharged through the dumping port 9, and the newly poured plastic particles roll from the top to the bottom side. Subsequently, the screening mesh 7 returns to the screening position for screening. Under the action of the torsion spring, the plugging plate 10 closes the dumping port 9 again, so as to ensure that the newly poured plastic particles are not easily discharged.

[0038] 202. While the transmission belt 15 rotates, the one-way transmission mechanism 16 will drive the wiping roller 12 to rotate, so that the water absorption layer in different areas can be replaced to contact the strip to achieve a better wiping effect; when the torsion spring drives the transmission belt 15 to rotate in the reverse direction, the one-way transmission mechanism 16 is in a disengaged state, so that it is not easy to drive the wiping roller 12 to rotate back.

[0039] In some embodiments, a motor for driving the screening mesh 7 to rotate between the screening position and the dumping position may be provided on the housing 1. In addition, the one-way transmission mechanism 16 may include a push claw 17 rotatably provided on the transmission belt 15, a transmission wheel 18 is provided on the rotating shaft of the wiping roller 12, and a plurality of transmission grooves 19 are formed in the circumferential direction on the transmission wheel 18. Among them, the two sides of the push claw 17 have inclined surfaces with different slopes. For example, the slope of the inclined surface facing the dumping port 9 is greater than the slope of the inclined surface facing the drive plate 14.

[0040] Therefore, when the screening mesh 7 pushes the driving plate 14 to drive the transmission belt 15 to rotate, the pushing claw 17 will snap into the transmission groove 19, thereby driving the transmission wheel 18 and the wiping roller 12 to rotate; when the torsion spring drives the transmission belt 15 to rotate in the reverse direction, the pushing claw 17 disengages from the transmission groove 19 and is not likely to drive the rotation of the wiping roller 12.

[0041] As another solution, the one-way transmission mechanism 16 can also be a ratchet and pawl structure adapted between the transmission belt 15 and the rotating shaft of the wiping roller 12, or other one-way transmission solutions achieved, for example, through the clutch engagement control. Preferably, an installation cover 20 is further provided in the guiding channel 8, and the above-mentioned transmission belt 15 and one-way transmission mechanism 16 are both located inside the installation cover 20, so as to avoid the influence of plastic particles on their transmission performance. In addition, the specific installation form of the transmission belt 15 and whether guide wheels are needed for steering or changing the transmission angle, etc. are all prior arts, and those skilled in the art can select according to the actual situation, so no further description will be given here.

[0042] In some embodiments, a discharge track is further provided on the housing 1 below the discharge opening 9, and the plastic particles discharged through the discharge opening 9 can be deposited in the discharge track. Preferably, the discharge track can be arranged obliquely. For example, the end of the discharge track can be joined to the storage box, whereby the unqualified plastic particles can be introduced into the storage box for storage, so as to facilitate subsequent recycling.

[0043] The above are only the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be changed within the scope of the concepts described herein through the above teachings or the technology or knowledge in related fields. And the changes and alterations made by those skilled in the art without departing from the spirit and scope of the present invention shall all be within the protection scope of the appended claims of the present invention.

Claims

1. A preparation method of degradable PE particles, characterized in that: The steps include: S1. Prepare raw materials: the raw materials include the following components by weight: 50 parts of CaCO3, 2 parts of titanate coupling agent, 30 parts of PE plastic carrier, 10 parts of magnesium stearate, 4 parts of cellulose, and 3 parts of paraffin; S2, preparing a first mixed material: mixing CaCO3, a titanate coupling agent, a PE plastic carrier and magnesium stearate in a high-temperature mixer, heating them until they are melted and stirring them to obtain a first mixed material; S3, preparing a second mixed material: adding cellulose and paraffin into the first mixed material, heating them until they are melted, and stirring them to obtain a second mixed material; S4, preparing PE particles: after the second mixed material is cooled, PE particles are prepared by granulation equipment.

2. The preparation method of the degradable PE particles according to claim 1, characterized in that: The PE plastic carrier includes low-density polyethylene, linear low-density polyethylene, high-density polyethylene, ultra-high molecular weight polyethylene, medium-density polyethylene or ultra-low-density polyethylene.

3. The preparation method of the easily degradable PE particles according to claim 1, characterized in that: The temperature of the heating and stirring in S2 is 120° C., and the stirring time is 25-30 min.

4. The preparation method of the easily degradable PE particles according to claim 1, characterized in that: The temperature of the heating and stirring in S3 is 190-220° C., and the stirring time is 10-20 min.

5. The preparation method of the degradable PE particles according to any one of claims 1-4, characterized in that: The granulation equipment comprises an extruder, a cooling water tank and a granulator which are connected in sequence.

6. The preparation method of the degradable PE particles according to claim 5, characterized in that: The pelletizer comprises a shell (1), on which a feed port (2) and a discharge port (3) are arranged opposite to each other, and a traction component (4) and a pelletizing component (5) are arranged in sequence between the feed port (2) and the discharge port (3) in the shell (1), and a wiping member (6) for wiping a material strip is arranged at the feed port (2).

7. The preparation method of the easily degradable PE particles according to claim 6, characterized in that: A screening net (7) is provided at the discharge port (3), the screening net (7) is used to receive the plastic particles cut by the pelletizing component (5), and a vibration motor is provided on the screening net (7).

8. The preparation method of the degradable PE particles according to claim 7, characterized in that: The top of the shell (1) is configured with a guide channel (8) extending obliquely toward one side of the wiper (6); the screening net (7) is adapted to be rotatable between a screening position and a pouring position; in the pouring position, the plastic particles on the screening net (7) are poured into the guide channel (8), and the wiper (6) is at least partially exposed in the guide channel (8).

9. The preparation method of the degradable PE particles according to claim 8, characterized in that: The shell (1) is located at the bottom end of the guide channel (8) and is provided with a discharge port (9), a sealing plate (10) is rotatably provided at the discharge port (9), a notch (11) is provided on the guide channel (8), the wiping member (6) comprises a wiping roller (12) and a water-absorbing layer provided on the side wall of the wiping roller (12), the water-absorbing layer is engaged in the notch (11), the shell (1) is located at the top end of the guide channel (8) and is provided with a driving plate (14) rotatably provided, a transmission belt (15) is connected between the rotating shaft of the driving plate (14) and the rotating shaft of the sealing plate (10), and a torsion spring is provided on at least one of the rotating shaft of the driving plate (14) and the rotating shaft of the sealing plate (10); When the screening mesh (7) rotates from the screening position to the dumping position, the screening mesh (7) can push the plugging plate (10) to drive the conveyor belt (15) to rotate, and then the plugging plate (10) opens the dumping port (9). A one-way transmission mechanism (16) is adapted between the conveyor belt (15) and the rotating shaft of the wiping roller (12), and the one-way transmission mechanism (16) is adapted such that the conveyor belt (15) drives the wiping roller (12) to rotate only when rotating in one direction.

10. The method for preparing degradable PE particles according to claim 8, characterized in that: The water absorption layer includes sponge or bristles.

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