Heat-resistant polypropylene production process and production system

Abstract

The invention discloses a heat-resistant polypropylene production process and a production system, and relates to the technical field of heat-resistant polypropylene. The heat-resistant polypropylene is prepared from the following components in parts by weight: 100 parts of polypropylene resin, 0.2-0.8 part of a beta crystal form nucleating agent, 1.5-4 parts of an organic silicon acrylate composite cross-linking agent, 3-10 parts of surface modified nano boron nitride and 0.3-1 part of an antioxidant; the preparation method comprises the following steps: S1, carrying out ultrasonic dispersion on nano boron nitride and a silane coupling agent in ethanol according to a mass ratio of 1: 0.05 for 30 minutes, drying at 80 DEG C, premixing polypropylene resin and a beta crystal form nucleating agent, and stirring at 60 DEG C for 10 minutes; s2, the premix is added into a main feeding port of a double-screw extruder, and an organosilicone acrylate cross-linking agent is injected into the middle of the extruder 1 through a side feeding port. Through the synergistic effect of the beta crystal form nucleating agent and a cross-linking network, the heat deformation temperature is increased by 60% or above compared with pure PP, the cross-linking agent is injected through side feeding, the situation that a main feeding high-temperature area is decomposed in advance is avoided, and the mechanical property is improved; and it is ensured that the cross-linking reaction is completed in the melt homogenization section.

Description

Technical Field

[0001] The present invention relates to the technical field of heat-resistant polypropylene, and specifically to a production process and a production system for heat-resistant polypropylene. Background Art

[0002] Polypropylene is widely used due to its light weight, chemical corrosion resistance, and easy processing, etc. However, its heat resistance is poor and it is difficult to meet the requirements of high-temperature working conditions. The heat resistance of ordinary polypropylene is limited, which restricts its application in some high-temperature environments. At present, the methods to improve the heat resistance of polypropylene mainly include blending modification, copolymerization modification, and chemical modification, etc. But these methods have problems such as high cost, complex process, and great influence on product performance. Therefore, it is necessary to develop a simple, efficient, low-cost preparation method that can significantly improve the heat resistance of polypropylene. Summary of the Invention

[0003] The purpose of the present invention is to provide a production process and a production system for heat-resistant polypropylene to solve the deficiencies in the above-mentioned prior art.

[0004] To achieve the above purpose, the present invention provides the following technical solution: A production process and a production system for heat-resistant polypropylene, including heat-resistant polypropylene composed of the following weight components: 100 parts of polypropylene resin, 0.2 - 0.8 parts of β-crystalline nucleating agent, 1.5 - 4 parts of organosilicon acrylate composite cross-linking agent, 3 - 10 parts of surface-modified nano boron nitride, and 0.3 - 1 part of antioxidant;

[0005] It also includes the following steps:

[0006] S1, Ultrasonically disperse nano boron nitride and silane coupling agent (KH-570) in ethanol at a mass ratio of 1:0.05 for 30 minutes, dry at 80°C, pre-mix polypropylene resin and β-crystalline nucleating agent, and stir at 60°C for 10 minutes;

[0007] S2, Add the pre-mixed material to the main feeding port of the twin-screw extruder, inject the organosilicon acrylate cross-linking agent through the side feeding port in the middle of the extruder, control the extrusion temperature in zones at 170 - 215°C, and the screw speed at 300 - 400 rpm;

[0008] S3, Vertically extrude the strip, conduct preliminary cooling with a cooling device, then cool it in cooling water, pelletize after water cooling, and vacuum dry at 80°C for 6 hours to obtain the finished product.

[0009] Preferably, the organosilicon acrylate composite cross-linking agent is prepared by pre-polymerization reaction of vinyl-containing organosiloxane and acrylate monomer at a mass ratio of 1:0.5 - 1:2, and the molecular weight range of the cross-linking agent is 2000 - 8000 Da.

[0010] Preferably, in the surface-modified nano boron nitride, the silane coupling agent is one of KH–550, KH–570 or KH–792, and the dosage of the modifier is 3–8% of the mass of the nano boron nitride.

[0011] Preferably, the antioxidant is a composite antioxidant, comprising a mixture of a hindered phenol main antioxidant and a phosphite auxiliary antioxidant, and the mass ratio is 2:1–1:1.

[0012] Preferably, the injection temperature of the side feeding port in S2 is 180–195 °C, and the vacuum degassing pressure of the extruder is ≤–0.06 MPa.

[0013] Preferably, the temperature zones of the extruder are set as follows: zone 1 at 170 °C, zone 2 at 190 °C, zone 3 at 210 °C, and zone 4 at 205 °C.

[0014] A heat-resistant polypropylene production system includes an extruder and a die head. A material pipe is provided at the discharge port of the extruder, and the die head is vertically installed on the material pipe. Polypropylene is discharged by the die head after being extruded by the extruder, and further includes:

[0015] A first cooling mechanism for shaping and cooling the polypropylene discharged from the die head;

[0016] A second cooling mechanism. The polypropylene cooled by the first cooling mechanism enters the second cooling mechanism for water cooling.

[0017] The coolant is circulated between the first cooling mechanism and the second cooling mechanism through a circulation component;

[0018] The first cooling mechanism includes a vertical shaping part, a first connection end, a second connection end, a connecting pipe, and a centering structure. The vertical shaping part is formed by splicing a plurality of cooling pipes. The first connection end and the second connection end are respectively connected to the upper and lower ends of the vertical shaping part. The connecting pipe is connected to the first connection end, and the other end of the connecting pipe is connected to the circulation component. The second connection end is connected to the second cooling mechanism. Polypropylene passes through the vertical shaping part. The centering structure includes a surrounding ring and a driving part. A flow cavity is formed in the cooling pipe. When the coolant flows along the flow cavity, the driving part is driven passively to displace the surrounding ring so that it fits on the outside of the polypropylene to achieve centering of the polypropylene.

[0019] Preferably, the circulation component includes a screw pump, a second conduit, and a first conduit. One end of the screw pump is connected to the second cooling mechanism through the second conduit, and the other end of the screw pump is connected to the first cooling mechanism through the first conduit.

[0020] Preferably, the centering structure includes a mounting groove, a retaining piece, a transmission shaft, an impeller, a fixing block, and a positioning rod. The mounting groove is formed in the cooling pipe. The retaining piece is installed in the mounting groove, and one end of the retaining piece extends into the flow cavity. The transmission shaft is rotatably connected in the cooling pipe. The impeller is installed on the transmission shaft and is located in the flow cavity. The retaining piece is positioned above the impeller. The fixing block is fixedly installed on the surrounding ring, and one end of the transmission shaft is threadedly connected to the fixing block. One end of the positioning rod is inserted into the fixing block, and the other end is fixed to the cooling pipe.

[0021] Preferably, it further includes a collecting assembly for collecting the sediment in the second cooling mechanism. The collecting assembly includes a track bar, a sliding groove, a displacement block, a scraping plate, a pressure chamber, a magnetic block, a flow channel, a water pipe, and a drain hole. The track bar is embedded in the lower sides of the second cooling mechanism. The sliding groove is formed in the track bar. The displacement block is slidably embedded in the sliding groove. The scraping plate is installed on the displacement block. The magnetic block is slidably connected in the pressure chamber. The flow channel connects the pressure chamber. The flow channel is connected to the first cooling mechanism through the water pipe. The coolant in the flow channel flows into the second cooling mechanism through the drain hole.

[0022] In the above technical solution, for a heat-resistant polypropylene production process and production system provided by the present invention, the β-crystalline nucleating agent and the crosslinked network act synergistically, and the heat distortion temperature is increased by more than 60% compared with pure PP. A multi-temperature zone setting is adopted, and the crosslinking agent is injected through side feeding to avoid premature decomposition in the high-temperature zone of the main feed, ensuring that the crosslinking reaction is completed in the melt homogenization section. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0024] Figure 1 It is a schematic diagram of the overall structure of a heat-resistant polypropylene production process and production system of the present invention;

[0025] Figure 2 It is a schematic diagram of the circulation component of a heat-resistant polypropylene production process and production system of the present invention;

[0026] Figure 3 It is a schematic diagram of the vertical shaping part structure of a heat-resistant polypropylene production process and production system of the present invention;

[0027] Figure 4 It is a schematic diagram of the centering structure of a heat-resistant polypropylene production process and production system of the present invention when unfolded;

[0028] Figure 5 Schematic diagram of the centering structure of a heat-resistant polypropylene production process and production system of the present invention when it is closed;

[0029] Figure 6 Attachment of a heat-resistant polypropylene production process and production system of the present invention Figure 5 Enlarged schematic diagram of part A in the figure;

[0030] Figure 7 Schematic diagram of the structure of the collection component of a heat-resistant polypropylene production process and production system of the present invention;

[0031] Figure 8 Attachment of a heat-resistant polypropylene production process and production system of the present invention Figure 7 Enlarged schematic diagram of part B in the figure;

[0032] Figure 9 Schematic diagram of the structure of the collection component of a heat-resistant polypropylene production process and production system of the present invention when the displacement block is at the end section;

[0033] Figure 10 Attachment of a heat-resistant polypropylene production process and production system of the present invention Figure 9 Enlarged schematic diagram of part C in the figure;

[0034] Figure 11 Attachment of a heat-resistant polypropylene production process and production system of the present invention Figure 9 Enlarged schematic diagram of part D in the figure.

[0035] Explanation of reference numerals in the drawings: 1, extruder; 2, material pipe; 3, die head; 4, first cooling mechanism; 40, vertical shaping part; 41, cooling pipe; 411, flow cavity; 412, installation groove; 413, baffle; 414, transmission shaft; 415, impeller; 416, fixing block; 417, positioning rod; 418, surrounding ring; 42, first connection end; 43, second connection end; 44, connecting pipe; 5, second cooling mechanism; 6, guide roller; 7, circulation component; 71, screw pump; 72, second conduit; 73, first conduit; 8, collection component; 81, track bar; 82, chute; 83, displacement block; 84, scraper; 85, pressure cavity; 86, magnetic block; 87, flow channel; 88, water pipe; 89, drain hole. Detailed implementation manners

[0036] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further introduced in detail below in conjunction with the drawings.

[0037] Please refer to Figure 1–11, A heat-resistant polypropylene production process and production system provided by an embodiment of the present invention, comprising heat-resistant polypropylene composed of the following weight components: 100 parts of polypropylene resin, 0.2–0.8 parts of β-crystalline nucleating agent, 1.5–4 parts of organosilicon acrylate composite crosslinking agent, 3–10 parts of surface-modified nano boron nitride, 0.3–1 part of antioxidant;

[0038] It also includes the following steps:

[0039] S1, Ultrasonically disperse nano boron nitride and silane coupling agent (KH–570) in ethanol at a mass ratio of 1:0.05 for 30 minutes, dry at 80°C, premix polypropylene resin and β-crystalline nucleating agent, and stir at 60°C for 10 minutes;

[0040] S2, Add the premix to the main feeding port of twin-screw extruder 1, inject the organosilicon acrylate crosslinking agent through the side feeding port in the middle of the extruder 1, control the extrusion temperature zone to 170–215°C, and the screw speed to 300–400 rpm;

[0041] S3, Vertically extrude the material strip, perform preliminary cooling using a cooling device, then cool it in cooling water, pelletize after water cooling, and vacuum dry at 80°C for 6 hours to obtain the finished product.

[0042] Preferably, the organosilicon acrylate composite crosslinking agent is prepared by pre-polymerization reaction of vinyl-containing organosiloxane and acrylate monomer at a mass ratio of 1:0.5–1:2, and the molecular weight range of the crosslinking agent is 2000–8000 Da.

[0043] Preferably, in the surface-modified nano boron nitride, the silane coupling agent is one of KH–550, KH–570 or KH–792, and the dosage of the modifier is 3–8% of the mass of nano boron nitride.

[0044] The antioxidant is a composite antioxidant, comprising a mixture of a hindered phenol main antioxidant and a phosphite auxiliary antioxidant, with a mass ratio of 2:1–1:1.

[0045] The injection temperature of the side feeding port in S2 is 180–195°C, and the vacuum degassing pressure of extruder 1 ≤ –0.06 MPa.

[0046] The temperature zone of extruder 1 is set as: zone 1 at 170°C, zone 2 at 190°C, zone 3 at 210°C, zone 4 at 205°C.

[0047] In Example 1 of the present invention: 100 parts of polypropylene, 0.5 part of β-crystalline nucleating agent, 3 parts of organosilicon acrylate composite crosslinking agent, 6 parts of surface-modified nano boron nitride, 0.6 part of composite antioxidant;

[0048] Add nano boron nitride and KH–570 to an ethanol solution at a mass ratio of 1:0.05, and ultrasonically disperse for 30 minutes (power 300W, frequency 40kHz). Then dry in a vacuum drying oven at 80°C for 6 hours to obtain surface-modified nano boron nitride; add the pretreated PP mixture and surface-modified nano boron nitride to the main feeding port of a twin-screw extruder (feeding rate 10kg / h);

[0049] The organosilicon acrylate crosslinking agent is injected through the side feeding port in the 4th zone of the extruder (temperature 190°C) at an injection rate of 0.8kg / h;

[0050] The temperature zoning settings of the extruder are: zone 1 at 170°C, zone 2 at 190°C, zone 3 at 210°C, zone 4 at 205°C, and the die head at 300°C;

[0051] The screw rotation speed is 350rpm, the length-diameter ratio is 44:1, and the vacuum degassing pressure is –0.08MPa;

[0052] The heat-resistant polypropylene prepared above has the following parameters: heat distortion temperature (1.82MPa): 162°C, tensile strength: 35MPa, impact strength: 8.2kJ / m 2 。

[0053] Example 2:

[0054] Formulation adjustment: Dosage of organosilicon acrylate composite crosslinking agent: 4 parts (the rest is the same as in Example 1). Process adjustment: The injection rate of the crosslinking agent at the side feeding port is increased to 1.0kg / h

[0055] Test results: The heat distortion temperature is increased to 168°C, but the impact strength is reduced to 6.8kJ / m 2 。

[0056] Conclusion: Excessive crosslinking agent leads to too high crosslinking degree of the material and decreased fluidity.

[0057] Example 3:

[0058] Surface-modified nano boron nitride: KH–550 replaces KH–570, and the dosage of the modifier is 8%

[0059] Test results: Heat distortion temperature: 158°C, impact strength: 7.5kJ / m 2

[0060] The following conclusion is drawn after SEM interface analysis: The nano boron nitride modified by KH–550 is evenly dispersed in the PP matrix, but the interfacial bonding force is slightly lower than that of the KH–570 system.

[0061] Comparative Example 1:

[0062] Directly use unmodified nano boron nitride (the others are the same as in Example 1);

[0063] Test results: Heat distortion temperature: 145 °C, Impact strength: 5.1 kJ / m 2 ;

[0064] SEM observation: Severe agglomeration of nano boron nitride, obvious pores appear in the matrix.

[0065] Comparative example 2:

[0066] Without adding TMB–5 nucleating agent (others are the same as in Example 1);

[0067] Test results: Heat distortion temperature: 132 °C;

[0068] DSC analysis: The crystallinity of the material decreased from 52% in Example 1 to 38%, and the proportion of β crystal form decreased from 65% to less than 10%.

[0069] From the above examples and comparative examples, it can be seen that: the heat resistance of the present invention is significantly improved: the β crystal form nucleating agent and the crosslinked network act synergistically, and the heat distortion temperature is increased by more than 60% compared with pure PP; the interface modification of nano boron nitride effectively balances rigidity (heat resistance) and toughness; wide process adaptability: by adjusting the injection position and temperature of the crosslinking agent, different types of extrusion equipment can be adapted.

[0070] Based on the above preparation process, traditional polypropylene is directly cooled by water after discharging. The cooling is fast and efficient, but the rapid cooling will cause a large temperature difference between the inside and outside of the material, the outer layer is quickly solidified while the inner layer continues to shrink, forming uneven internal stress. This residual stress may cause warping, cracking or dimensional instability of the product, and polypropylene is a semi-crystalline polymer. Too fast cooling will hinder the orderly arrangement of molecular chains, and will weaken the hardness, stiffness and heat resistance of the material. Therefore, we propose a heat-resistant polypropylene production system to solve the above problems.

[0071] A heat-resistant polypropylene production system, including an extruder 1 and a die head 3. A material pipe 2 is arranged at the discharge port of the extruder 1, and the die head 3 is vertically installed on the material pipe 2. Polypropylene is extruded by the extruder 1 and discharged by the die head 3. It also includes:

[0072] The first cooling mechanism 4, which is used to shape and cool down the polypropylene discharged from the die head 3;

[0073] The second cooling mechanism 5, and the polypropylene cooled by the first cooling mechanism 4 enters the second cooling mechanism 5 for water cooling;

[0074] The coolant circulation between the first cooling mechanism 4 and the second cooling mechanism 5 is realized through a circulation component 7;

[0075] The first cooling mechanism 4 includes a vertical shaping part 40, a first connection end 42, a second connection end 43, a connecting pipe 44, and a centering structure. The vertical shaping part 40 is formed by splicing a plurality of cooling pipes 41. The first connection end 42 and the second connection end 43 are respectively connected to the upper and lower ends of the vertical shaping part 40. The connecting pipe 44 is connected to the first connection end 42, and the other end of the connecting pipe 44 is connected to a circulation assembly 7. The second connection end 43 is connected to a second cooling mechanism 5. Polypropylene passes through the vertical shaping part 40. The centering structure includes a surrounding ring 418 and a driving part. A flow cavity 411 is formed in the cooling pipe 41. When the coolant flows along the flow cavity 411, the driving part passively drives the surrounding ring 418 to displace so as to fit against the outside of the polypropylene, thereby achieving centering of the polypropylene.

[0076] In an embodiment of the present invention, polypropylene is extruded by an extruder 1 into an inner die head 3 of a die head 3. The die head 3 shapes the polypropylene. The polypropylene is discharged vertically into the first cooling mechanism 4. The first cooling mechanism 4 continuously injects coolant through a circulation assembly 7 for cooling, so that the polypropylene passing through the first cooling mechanism 4 can be cooled down. When cooling down, the vertical shaping part 40 does not contact the polypropylene. At the initial stage of polypropylene feeding, the polypropylene is in a state of slow cooling, avoiding the instability of the polypropylene size and the decline of performance caused by the fast cooling rate of the polypropylene. A centering structure is arranged in the vertical shaping part 40. Since the vertical shaping part 40 is relatively long in the vertical direction, in order to ensure that the polypropylene moves down along the center of the vertical shaping part 40, it is necessary to use the surrounding ring 418 to center the polypropylene to make its downward movement more stable. And the surrounding ring 418 can be passively closed. When the polypropylene just starts to be discharged, the surrounding ring 418 is in an unfolded state to ensure that the polypropylene can pass through smoothly. After the polypropylene production is stable, by starting the circulation assembly 7, the circulation of the coolant is realized through the circulation assembly 7. The coolant can drive the movement of the driving part, so that the driving part passively drives the surrounding ring 418 to close, and thus the surrounding ring 418 centers the polypropylene.

[0077] The polypropylene passing through the first cooling mechanism 4 will be sent to the second cooling mechanism 5. The second cooling mechanism 5 contains coolant. The coolant contacts the polypropylene to fully cool the polypropylene. Through the cooperation of the first cooling mechanism 4 and the second cooling mechanism 5, gradient cooling of the polypropylene is realized, greatly improving the quality of the polypropylene.

[0078] Moreover, at the initial cooling stage, the air flow amplitude around the polypropylene is small, and the number of dust particles in the air contacting the polypropylene is small, reducing the dust prevention requirements for the production workshop.

[0079] After preliminary cooling and shaping, the polypropylene is put into water, reducing the loss of polypropylene material.

[0080] The polypropylene discharges vertically, and its size is better controlled, reducing the problem of uneven local thickness caused by gravity. It can cool the material surface more evenly and reduce the crystallinity difference caused by directional cooling.

[0081] In an embodiment of the present invention, please refer to Figure 2 , the circulation component 7 includes a screw pump 71, a second conduit 72, a first conduit 73. One end of the screw pump 71 is connected to the second cooling mechanism 5 through the second conduit 72, and the other end of the screw pump 71 is connected to the first cooling mechanism 4 through the first conduit 73. The screw pump 71 can extract the coolant in the second cooling mechanism 5. A filter screen is provided in the first conduit 73 and the second conduit 72 to filter impurities in the coolant. The screw pump 71 can realize the forward and reverse transportation of the coolant. When the screw pump 71 rotates forward, the coolant in the second conduit 72 can be transported to the first conduit 73, and when it rotates in reverse, the coolant in the first conduit 73 is transported into the second conduit 72.

[0082] In an embodiment of the present invention, please refer to Figure 3 –6, the centering structure includes a mounting groove 412, a retaining piece 413, a transmission shaft 414, an impeller 415, a fixing block 416 and a positioning rod 417. The mounting groove 412 is opened in the cooling pipe 41. The retaining piece 413 is installed in the mounting groove 412. One end of the retaining piece 413 extends into the flow cavity 411. The transmission shaft 414 is rotatably connected in the cooling pipe 41. The impeller 415 is installed on the transmission shaft 414. The impeller 415 is located in the flow cavity 411. The retaining piece 413 is above the impeller 415. The fixing block 416 is fixedly installed on the circumferential ring 418. One end of the transmission shaft 414 is threadedly connected to the fixing block 416. One end of the positioning rod 417 is inserted into the fixing block 416 and the other end is fixed to the cooling pipe 41.

[0083] A part of the mounting groove 412 coincides with the flow cavity 411. Therefore, after the retaining piece 413 is installed, a part of the flow cavity 411 will be blocked, and a part of the impeller 415 is blocked by the retaining piece 413. When the coolant moves from top to bottom along the flow cavity 411, the impeller 415 will rotate under the push of the coolant. When the impeller 415 rotates, it will drive the transmission shaft 414 to rotate. When the transmission shaft 414 rotates, since there is a threaded connection between the fixing block 416 and the transmission shaft 414, the fixing block 416 will move, and the fixing block 416 will move away from the direction where the impeller 415 is located. While the fixing block 416 moves, it drives the circumferential ring 418 to close to achieve centering of the polypropylene;

[0084] By reversing the screw pump 71, the coolant can be transported from bottom to top. Similarly, the surrounding ring 418 will be expanded. By expanding the surrounding ring 418, in the initial discharge state of the die head 3, the polypropylene can smoothly pass through the centering structure.

[0085] In the embodiments of the present invention, please refer to Figure 1 , Figure 7 – Figure 11 , also includes a collecting component 8, which is used to collect the sediment in the second cooling mechanism 5, the collecting component 8 includes a track bar 81, a slide groove 82, a displacement block 83, a scraper 84, a pressure chamber 85, a magnetic block 86, a flow channel 87, a water pipe 88, and a drainage hole 89. The track bar 81 is embedded on both sides of the lower part of the second cooling mechanism 5, the slide groove 82 is opened in the track bar 81, the displacement block 83 is slidably embedded in the slide groove 82, the scraper 84 is installed on the displacement block 83, the magnetic block 86 is slidably connected to the pressure chamber 85, the flow channel 87 is connected to the pressure chamber 85, the flow channel 87 is connected to the first cooling mechanism 4 through the water pipe 88, and the coolant in the flow channel 87 flows into the second cooling mechanism 5 through the drainage hole 89.

[0086] When the screw pump 71 rotates forward, the coolant flows into the flow channel 87 through the water pipe 88. As the pressure in the flow channel 87 increases, a part of the coolant will be discharged from the drainage hole 89 into the second cooling mechanism 5. Since the drainage hole 89 is small in size and the drainage is not timely, the water pressure in the flow channel 87 continues to increase, which increases the pressure of the pressure chamber 85 connected to it, so that the pressure on both sides of the magnetic block 86 is inconsistent. Therefore, the magnetic block 86 will move along the pressure chamber 85, and the displacement block 83 can be moved by the magnetic block. Attraction, when the magnetic block 86 is displaced, the displacement block 83 will be displaced synchronously. The displacement of the displacement block 83 drives the scraper 84 to concentrate the attachments at the bottom of the second cooling mechanism 5 to the far end, so as to ensure the cleanliness of the polypropylene water inlet area. Similarly, after the production is completed, the screw pump 71 is reversed to generate negative pressure in the flow channel 87. Similarly, if the drainage hole 89 does not enter the water in time, negative pressure will be generated in the pressure chamber 85 to displace the adsorption treatment block 86 in the direction of the flow channel 87 to achieve the resetting of the scraper 84.

[0087] The device further comprises guide rollers 6 for conveying the cooled polypropylene so as to move along the second cooling mechanism 5 .

[0088] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A heat-resistant polypropylene production process and production system, characterized in that: The heat-resistant polypropylene consists of the following weight components: 100 parts of polypropylene resin, 0.2 - 0.8 parts of β-crystal nucleating agent, 1.5 - 4 parts of organosilicon acrylate composite cross-linking agent, 3 - 10 parts of surface-modified nano boron nitride, and 0.3 - 1 part of antioxidant; It also includes the following steps: S1. Ultrasonically disperse nano boron nitride and silane coupling agent in ethanol at a mass ratio of 1:0.05 for 30 minutes, dry at 80 °C, premix polypropylene resin and β-crystal nucleating agent, and stir at 60 °C for 10 minutes; S2. Add the premixed material to the main feeding port of the twin-screw extruder (1), inject the organosilicon acrylate cross-linking agent through the side feeding port in the middle of the extruder (1), control the extrusion temperature zone at 170 - 215 °C, and the screw speed at 300 - 400 rpm; S3. Vertically extrude the material strip, conduct preliminary cooling with a cooling device, then cool it in cooling water, pelletize after water cooling, and vacuum dry at 80 °C for 6 hours to obtain the finished product.

2. The heat-resistant polypropylene production process and production system according to claim 1, characterized in that, The organosilicon acrylate composite cross-linking agent is prepared by prepolymerization reaction of vinyl-containing organosiloxane and acrylate monomer at a mass ratio of 1:0.5 - 1:2, and the molecular weight range of the cross-linking agent is 2000 - 8000 Da.

3. A heat-resistant polypropylene production process and production system according to claim 1, characterized in that, In the surface-modified nano boron nitride, the silane coupling agent is one of KH-550, KH-570 or KH-792, and the dosage of the modifier is 3 - 8% of the mass of nano boron nitride.

4. A heat-resistant polypropylene production process and production system according to claim 1, characterized in that, The antioxidant is a composite antioxidant, which is a mixture of a hindered phenol main antioxidant and a phosphite auxiliary antioxidant, and the mass ratio is 2:1 - 1:

1.

5. A heat-resistant polypropylene production process and production system according to claim 1, characterized in that, In S2, the injection temperature of the side feeding port is 180 - 195 °C, and the vacuum degassing pressure of the extruder (1) ≤ -0.06 MPa.

6. The heat-resistant polypropylene production process and production system according to claim 1, characterized in that, The temperature zone of the extruder (1) is set as: zone 1 at 170 °C, zone 2 at 190 °C, zone 3 at 210 °C, and zone 4 at 205 °C.

7. A heat-resistant polypropylene production system, which is implemented based on the heat-resistant polypropylene production process described in any one of claims 1-6, characterized in that, It includes an extruder (1) and a die head (3). A material pipe (2) is arranged at the discharge port of the extruder (1), and the die head (3) is vertically installed on the material pipe (2). Polypropylene is extruded by the extruder (1) and discharged by the die head (3). It also includes: A first cooling mechanism (4), which is used for shaping and cooling the polypropylene discharged from the die head (3); A second cooling mechanism (5), and the polypropylene cooled by the first cooling mechanism (4) enters the second cooling mechanism (5) for water cooling; The first cooling mechanism (4) and the second cooling mechanism (5) realize the coolant circulation through a circulation component (7); The first cooling mechanism (4) includes a vertical shaping part (40), a first connection end (42), a second connection end (43), a connecting pipe (44), and a centering structure. The vertical shaping part (40) is formed by splicing a plurality of cooling pipes (41). The first connection end (42) and the second connection end (43) are respectively connected to the upper and lower ends of the vertical shaping part (40). The connecting pipe (44) is connected to the first connection end (42), and the other end of the connecting pipe (44) is connected to a circulation component (7). The second connection end (43) is connected to a second cooling mechanism (5). Polypropylene penetrates through the vertical shaping part (40). The centering structure includes a surrounding ring (418) and a driving part. A flow cavity (411) is formed in the cooling pipe (41). When the coolant flows along the flow cavity (411), the driving part drives the surrounding ring (418) to displace passively so as to fit against the outside of the polypropylene, thereby realizing centering of the polypropylene.

8. A heat-resistant polypropylene production system according to claim 7, characterized in that, The circulation component (7) includes a screw pump (71), a second conduit (72), and a first conduit (73). One end of the screw pump (71) is connected to the second cooling mechanism (5) through the second conduit (72), and the other end of the screw pump (71) is connected to the first cooling mechanism (4) through the first conduit (73).

9. The heat-resistant polypropylene production system according to claim 8, characterized in that, The centering structure includes a mounting groove (412), a retaining piece (413), a transmission shaft (414), an impeller (415), a fixing block (416), and a positioning rod (417). The mounting groove (412) is formed in the cooling pipe (41). The retaining piece (413) is installed in the mounting groove (412), and one end of the retaining piece (413) extends into the flow cavity (411). The transmission shaft (414) is rotatably connected in the cooling pipe (41). The impeller (415) is installed on the transmission shaft (414), and the impeller (415) is located in the flow cavity (411). The retaining piece (413) is above the impeller (415). The fixing block (416) is fixedly installed on the surrounding ring (418). One end of the transmission shaft (414) is threadedly connected to the fixing block (416), and one end of the positioning rod (417) is inserted into the fixing block (416) and the other end is fixed to the cooling pipe (41).

10. A heat-resistant polypropylene production system according to claim 7, characterized in that, It further includes a collecting component (8) for collecting the sediment in the second cooling mechanism (5). The collecting component (8) includes a track bar (81), a sliding groove (82), a displacement block (83), a scraping plate (84), a pressure chamber (85), a magnetic block (86), a flow channel (87), a water pipe (88), and a drain hole (89). The track bar (81) is embedded on both sides of the lower part of the second cooling mechanism (5). The sliding groove (82) is opened in the track bar (81). The displacement block (83) is slidably embedded in the sliding groove (82). The scraping plate (84) is installed on the displacement block (83). The magnetic block (86) is slidably connected in the pressure chamber (85). The flow channel (87) is connected to the pressure chamber (85). The flow channel (87) is connected to the first cooling mechanism (4) through the water pipe (88). The coolant in the flow channel (87) flows into the second cooling mechanism (5) through the drain hole (89).

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