Polymer and pelletizing system and method, preparation system and preparation method
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CATHAY BIOTECH INC
- Filing Date
- 2023-04-19
- Publication Date
- 2026-06-16
Smart Images
Figure CN118809865B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a polymer and its pelletizing system and method, preparation system and preparation method. Background Technology
[0002] Most polymer pelletizing equipment is a strand-type pelletizer. The polymer melt is extruded from a perforated die, enters a water bath where it undergoes sufficient cooling to form a strip of material with a certain strength. This strip is then pulled out of the water bath by the pelletizer for pelletizing. By adjusting the traction speed of the pelletizer, the subsequent pelletizing process can be controlled to obtain the target polymer particle size. While strand pelletizers are inexpensive and easy to operate, they have significant drawbacks. Because the polymer strips must possess sufficient strength during the stranding process, polymers with lower molecular weights or lower melt strength cannot be used. Furthermore, the pelletizing volume cannot be too large. If one or more strips break during the rapid stretching through the water bath, it is extremely difficult to re-stretch them during the rapid pelletizing process, resulting in a large amount of waste. Therefore, the production line cannot be automatically controlled, and this method is not used in large-scale industrial pelletizing.
[0003] Compared to strip pelletizers, underwater pelletizers offer superior performance. Their main working principle involves extruding molten polymer onto a disc-shaped die placed underwater, where it is rapidly cut by a cutter attached to the die. Because the melt is not fully cooled upon initial contact with the water, the cut particles shrink further during cooling, forming spherical shapes with an aesthetically pleasing appearance. Underwater pelletizers are a new type of polymer semi-finished product processing machinery that achieves underwater pelletizing, and they are widely used in the processing of polyester, polyamide, and other plastics. They offer the following advantages: high cooling efficiency due to direct cooling in water after pelletizing; a smaller volume as the cutting chamber size allows the pelletizer blades to rotate freely over the die surface without restricting water flow; lower noise levels due to pelletizing in the molten state and the sound barrier effect of water; fewer blade replacements compared to cold-cutting systems; and a closed-loop operation, preventing dust and impurities from entering. Therefore, underwater pelletizers are widely used in large-scale industrial pelletizing.
[0004] Currently, the underwater pelletizing process still has the following shortcomings: (1) It is difficult to disassemble the cutter head and the mold, making it inconvenient to replace them; (2) During the underwater pelletizing process, pelletizing abnormalities often occur due to differences in polymer molecular weight and physical properties, which in turn leads to the production of unqualified pellets; (3) Underwater pelletizing also suffers from insufficient theoretical research, unclear mechanism, resulting in unreasonable structural design or improper setting of operating parameters, such as complex flow field and water flow state in the pelletizing chamber. In particular, when the underwater pelletizer is working normally, the internal water flow characteristics, particle motion trajectory and different forces on the cutter in the water chamber will affect the polymer pelletizing effect. In the conventional pelletizing water chamber, under the high-speed rotation of the cutter disc, the pelletizing water inside the water chamber will form a vortex-like turbulence and form a low-pressure zone in the central area of the cutter disc. Under the action of pressure gradient and turbulence, the pellets will gather in this area, which will greatly reduce the efficiency of the pellets flowing towards the outlet. At the same time, process problems such as polymer entanglement and polymer particle adhesion will also occur. Summary of the Invention
[0005] The technical problem this invention aims to solve is to overcome the shortcomings of existing systems or methods, such as their inability to be applied to pelletizing different polymers, low pelletizing efficiency, low product yield, and process problems caused by polymer entanglement and adhesion. This invention provides a polymer, its pelletizing system and method, and a preparation system and method. The system and method of this invention can meet the underwater pelletizing requirements of polymers of different types and viscosity characteristics; furthermore, the system of this invention improves pelletizing efficiency and product yield by disrupting the pressure gradient force within the system, reducing internal dead zones, and facilitating pellet discharge.
[0006] This invention provides a polymer pelletizing system, comprising: a feeding module, a cutting module, a pellet post-processing module, and a circulating water module; wherein,
[0007] The feeding module includes an extruder and a template. The template is provided on the discharge port end face of the extruder, and the template has a plurality of die holes along its thickness direction.
[0008] The cutting module includes a pelletizing chamber and a cutting disc. The pelletizing chamber has a vertically oriented partition plate dividing it into a front pelletizing chamber and a rear pelletizing chamber. The partition plate has several through holes, each with a guide pipe on one side of the rear pelletizing chamber, extending from the through hole towards the central axis of the partition plate. The template and the cutting disc are both located within the front pelletizing chamber. The cutting disc has a cutting blade on its side wall, positioned at the die outlet face of the template. The front pelletizing chamber has a water inlet, and the rear pelletizing chamber has a discharge outlet.
[0009] The particle post-processing module includes a solid-liquid separation device; the inlet of the solid-liquid separation device is connected to the outlet.
[0010] One end of the circulating water module is connected to the liquid phase outlet of the solid-liquid separation device, and the other end is connected to the water inlet.
[0011] In this invention, the feeding module may further include a melt pump, which is used to transfer polymer melt to the extruder.
[0012] In this invention, the extruder head and the template can be fixedly connected by bolts.
[0013] In this invention, preferably, the extruder is a twin-screw extruder.
[0014] In this invention, preferably, the template and the die hole satisfy one or more of the following conditions:
[0015] ① The cross-section of the template is disc-shaped;
[0016] ②The template is made of hard alloy or ferritic stainless steel;
[0017] ③ Several of the aforementioned mold holes are arranged in a ring on the template;
[0018] ④ The die hole is cylindrical, so that the melt forms a resin strip after passing through the die hole;
[0019] ⑤ The diameter of the die hole is 2.6-3.5 mm, for example 2.8 mm or 3.2 mm;
[0020] ⑥ The number of die holes can be determined according to the intrinsic viscosity and chemical composition of the polymer to be pelletized, preferably 10-100.
[0021] In this invention, according to the direction of water flow, the pelletizing chamber through which the water first flows is defined as the front pelletizing chamber, and the pelletizing chamber through which the water flows later is defined as the rear pelletizing chamber.
[0022] In this invention, preferably, the cutting disc satisfies one or more of the following conditions:
[0023] ① The cross-section of the cutting disc is circular;
[0024] ②The material of the cutting disc is stainless steel;
[0025] ③ The side wall of the cutting disc is provided with a plurality of mounting slots for mounting the cutting blade; preferably, the plurality of mounting slots are arranged in a ring matrix on the cutting disc;
[0026] ④ The cutter disc and the cutter can be fixedly connected by bolts;
[0027] ⑤ The cutting disc has several openings.
[0028] In this invention, preferably, the number of cutting blades is 4-10, more preferably 6-8.
[0029] In this invention, the gap between the cutter and the template can be determined according to the viscosity of the polymer, preferably 0.02-0.05 mm, and generally a smaller gap is used for low viscosity.
[0030] In this invention, the gap between the cutter and the template essentially refers to the distance between the cutter blade and the template.
[0031] In this invention, preferably, the cutter is inclinedly attached to the discharge end face of the die hole of the template; more preferably, the angle between the inclined portion of the cutter and the template is 10-60°, and even more preferably 30-60°. The inclined blade of the cutter can increase the cutting force with a shorter axial displacement, which can result in higher quality pellets and reduce the difficulty of adjusting the cutter.
[0032] In this invention, preferably, the cutter is braked by the rotation of the cutter disc via a transmission device. The transmission device includes a motor and a cutter shaft passing through the front pelletizing chamber and the rear pelletizing chamber. One end of the cutter shaft is connected to the motor, and the other end is connected to the cutter disc.
[0033] Preferably, the motor is a continuously variable frequency speed control motor.
[0034] In this invention, each of the through holes can be arranged along the thickness direction of the partition plate, that is, each of the through holes is perpendicularly inserted into the partition plate.
[0035] In this invention, the guide tube and the through hole are generally connected by welding.
[0036] In this invention, preferably, the length of each of the guide tubes is 8-15 mm.
[0037] In this invention, preferably, the angle between the axial centerline of each of the guide tubes and the central axis of the partition plate is 20-60°.
[0038] In this invention, preferably, the water inlet is located at the bottom of the pre-granulation chamber.
[0039] In this invention, an inlet pipe is inclined at the water inlet, and the inclination angle of the inlet pipe is such that the water flow in the inlet pipe is tangent to the circumference of the cutter disc. When the water flows obliquely into the interior of the pre-granulation chamber from the water inlet and is tangent to the circle formed by the movement of the cutter on the cutter disc, it can prevent water from directly impacting the raw material, reduce the amount of powder formed, and thus improve the quality of granulation.
[0040] In this invention, preferably, the discharge port is located at the upper part of the post-granulation chamber.
[0041] In this invention, preferably, the volume ratio of the pre-granulation chamber to the post-granulation chamber is (1.1-1.4):1.
[0042] In this invention, preferably, viewing holes are provided on both sides of the pre-granulation chamber to facilitate observation of the granulation effect of the pre-granulation chamber.
[0043] In this invention, the cutting module may be equipped with a base, as is customary in the art, for fixing the motor of the transmission device.
[0044] In this invention, preferably, the discharge port is connected to the solid-liquid separation device via a pipeline, and the pipeline is equipped with a first particle water pump.
[0045] In this invention, preferably, the solid-liquid separation device includes a centrifugal dryer. The rotating airflow and centrifugal force generated by the rotor of the centrifugal dryer cause frictional dehydration between the polymer particles and the air.
[0046] In this invention, preferably, the solid phase outlet of the solid-liquid separation device is sequentially connected to a grading and screening machine and a silo. After dehydration, the polymer pellets are sorted by the grading and screening machine into standard-sized and non-standard-sized pellets, which are then sent to different silos.
[0047] In this invention, preferably, the circulating water module includes a pelletizing tank, a bag filter, a second pellet pump, and a cooler connected in sequence; the circulating water inlet of the pelletizing tank is connected to the liquid phase outlet of the solid-liquid separation device, and the cold fluid outlet of the cooler is connected to the water inlet. The cooler can cool the circulating water to the required temperature before it enters the pre-pelletizing chamber, thereby increasing the solidification efficiency of the pellets.
[0048] Preferably, the pelletizing water tank also includes a water exchange inlet and a water exchange outlet to facilitate the discharge and replenishment of the pelletizing water.
[0049] In this invention, the design of the front and rear pelletizing chambers, as well as the cutter disc openings, mitigates the vortices formed inside the water chambers due to the rapid rotation of the cutter. This reduces the pressure gradient force on the pellets towards the center of the pelletizing chamber, significantly minimizing the formation of low-pressure zones and facilitating efficient pellet discharge. Furthermore, the design of the partition plates in the pelletizing chambers maintains high turbulence intensity without affecting the transport process of pellets from the front to the rear chambers, which is beneficial for pellet dispersion and discharge. Additionally, optimizing the radial inlet of the pelletizing water and the cutter disc opening design further improves pellet discharge efficiency.
[0050] The present invention also provides a polymer pelletizing method, which employs the polymer pelletizing system described above and includes the following steps:
[0051] The polymer melt is fed into the cutting module through the feeding module. The water temperature in both the pre-particle cutting chamber and the post-particle cutting chamber is 15-80℃. After solid-liquid separation, polymer particles and cutting water are obtained. The ratio of the water flow rate at the inlet of the pre-particle cutting chamber to the output of the polymer particles is 0.8-2.5.
[0052] In this invention, preferably, in the feeding module, the die inlet pressure of the extruder is 60-120 bar, for example 73 bar or 80 bar.
[0053] In this invention, preferably, the temperature of the polymer melt is 230-315°C, more preferably 245-305°C.
[0054] In this invention, preferably, the water temperature of the pre-granulation chamber and the post-granulation chamber is 25-70°C.
[0055] In this invention, the water flow rate at the inlet of the pre-granulation chamber refers to the mass of water entering the pre-granulation chamber from the inlet per unit time; the polymer particle yield refers to the mass of polymer particles obtained by granulation per unit time.
[0056] In this invention, preferably, the rotational speed of the cutter is 600-2000 r / min, for example 650 r / min or 800 r / min.
[0057] In this invention, preferably, the length of the polymer particles is 2-3 mm.
[0058] In this invention, preferably, the polymer particles are elliptical or spherical.
[0059] In this invention, the polymer melt is immediately immersed in the water flow in the pre-granulation chamber after being pelletized, and is efficiently discharged from the pre-granulation chamber through the opening of the cutter disc along with the circulating pelletizing water flow. It then enters the post-granulation chamber through the opening of the partition plate and is restricted by the guide pipe, and is subsequently carried out of the post-granulation chamber by the water flow.
[0060] In this invention, preferably, in the particle post-processing module, the outlet pressure of the first particle water pump is 0.2-0.5 MPa, more preferably 0.3-0.45 MPa.
[0061] In this invention, preferably, the outlet pressure of the second particle pump in the circulating water module is 0.2-0.5 MPa, more preferably 0.3-0.45 MPa.
[0062] In this invention, preferably, the water flow rate at the inlet of the pre-granulation chamber is 250-1200 kg / h, more preferably 300-800 kg / h. In this invention, the yield of polymer particles refers to the mass of polymer particles finally produced by this method per unit time.
[0063] In this invention, preferably, the ratio of the water flow rate at the inlet of the pre-granulation chamber to the output of the polymer particles is 1-2.
[0064] In this invention, when the ratio of the water flow rate at the inlet of the pre-granulation chamber to the output of the polymer particles is greater than 2.5, it will increase energy consumption on the one hand and affect the flow state of the granulation water flow on the other hand; when the ratio of the water flow rate at the inlet of the pre-granulation chamber to the output of the polymer particles is less than 0.8, the polymer particles obtained by cutting will not be cooled, resulting in material agglomeration.
[0065] In this invention, the pelletizing water enters the pelletizing water tank after solid-liquid separation, and then enters the pelletizing water cooler after being filtered by a bag filter. After heat exchange, the pelletizing water returns to the pre-pelleting chamber for recycling.
[0066] The present invention also provides a polymer preparation system comprising a salt-forming reaction device, a concentration device, a prepolymerization reaction device, a flash evaporation device, a prepolymerization reaction device, and a postpolymerization reaction device connected in sequence, and a polymer pelletizing system as described above.
[0067] In this invention, the salt-forming reaction apparatus is a conventional salt-forming reaction vessel in the art, used to carry out a salt-forming reaction between diamines and dicarboxylic acids.
[0068] In this invention, the concentration device is a conventional concentration vessel in the art, used to concentrate and remove water from the product of the salt formation reaction to obtain a concentrated polyamide salt solution.
[0069] In this invention, the prepolymerization reaction device is a conventional prepolymerization reactor in the art, used to prepolymerize the concentrated polyamide salt solution.
[0070] In this invention, the flash evaporation device is a conventional flash evaporator in the art, used to flash evaporate the product of the prepolymerization reaction under reduced pressure.
[0071] In this invention, the pre-polymerization reaction device can be a conventional polymerization reactor in the art, used to perform gas-liquid separation and polymerization reaction on the product after flash evaporation and depressurization.
[0072] In this invention, the post-polymerization reaction apparatus can be a conventional polymerization reactor in the art, used to further polymerize the products of the polymerization reaction.
[0073] The present invention also provides the application of the polymer pelletizing system described above or the polymer preparation system described above in the preparation of polyamides.
[0074] The present invention also provides a method for preparing a polymer, which employs the polymer preparation system described above and includes the following steps:
[0075] The reactants are sequentially subjected to salt formation reaction, concentration and dehydration, prepolymerization reaction, flash evaporation under reduced pressure, polymerization reaction and repolymerization reaction to obtain polymer melt. The pressure of the prepolymerization reaction is 1.7-2.5 MPa.
[0076] Then, polymer pellets are obtained using the polymer pelletizing method described above.
[0077] In this invention, the reactants undergo a salt-forming reaction in a conventional salt-forming apparatus in the art.
[0078] Preferably, the pressure of the salt formation reaction is 0.01-0.5 MPa.
[0079] Preferably, the temperature of the salt formation reaction is 75-95℃.
[0080] Preferably, the apparatus for the salt-forming reaction is a paddle-stirred salt-forming reactor; more preferably, the stirring speed of the paddle-stirred salt-forming reactor is 10-100 r / min; even more preferably, the stirring time of the paddle-stirred salt-forming reactor is 0.5-6 h.
[0081] Preferably, the atmosphere for the salt formation reaction can be conventional in the art, generally an inert atmosphere; more preferably, the inert atmosphere is a carbon dioxide atmosphere, a nitrogen atmosphere, or an argon atmosphere; even more preferably, the conditions of the inert atmosphere can be conventional in the art, for example, evacuating the apparatus for the salt formation reaction for 3-10 minutes, introducing an inert gas to atmospheric pressure, and cycling 5-10 times.
[0082] Preferably, the concentration of polyamide in the salt solution after the salt formation reaction is 40-60 wt%, more preferably 45-55 wt%.
[0083] The polyamide monomer comprises a diamine monomer and a diacid monomer; more preferably, the diamine monomer is selected from aliphatic diamines having 5 to 20 carbon atoms, and even more preferably from one or more of pentanediamine, hexanediamine, heptanediamine, octanediamine, nonanediamine, decanedanediamine, undecanediamine, and dodecanediamine; more preferably, the diacid monomer is selected from aromatic diacids and / or aliphatic diacids having 4 to 18 carbon atoms, and even more preferably from one or more of glutaric acid, adipic acid, octanoic acid, sebacic acid, terephthalic acid, isophthalic acid, undecanediic acid, dodecanediic acid, tridecanediic acid, tetradecanediic acid, pentadecanediic acid, and hexadecanediic acid.
[0084] The polyamide salt is generally formed by the reaction of a diacid with a diamine; preferably, the polyamide salt is one or more of caprolactam, 11-aminoundecanoic acid, dodecalactam, polyamide 56 salt, polyamide 5T salt, polyamide 66 salt, polyamide 6T salt, polyamide 10T salt, polyamide 12T salt, polyamide 610 salt, polyamide 612 salt, polyamide 1010 salt, polyamide 1012 salt, and polyamide 1212 salt.
[0085] In this invention, the solution after the salt formation reaction is concentrated and dehydrated using a conventional concentration device in the art.
[0086] Preferably, the temperature of the concentration vessel for water removal is 125-155℃.
[0087] After concentration and dehydration, the concentration of the polyamide salt solution is 65-75 wt%.
[0088] In this invention, the concentrated and dehydrated salt solution undergoes a prepolymerization reaction in a conventional prepolymerization reactor.
[0089] Preferably, the temperature of the prepolymerization reaction is 185-275℃.
[0090] Preferably, the pressure of the prepolymerization reaction is 1.9-2.3 MPa.
[0091] Preferably, the material residence time of the prepolymerization reaction is 1.5-4.5 h.
[0092] In this invention, the reaction products of the prepolymerization reaction are subjected to flash evaporation under reduced pressure in a conventional flash evaporation device in the art; during the flash evaporation under reduced pressure process, the moisture in the material is rapidly vaporized, and finally a gas-liquid mixed foam polymer is obtained.
[0093] In this invention, the reaction products after flash evaporation undergo polymerization in a conventional prepolymerization apparatus in the art.
[0094] The reaction products after flash evaporation can be transported to the prepolymerization reactor by a melt pump for gas-liquid separation and polymerization reaction; the gas generated during the polymerization reaction and the reaction vapor carried in from the flash evaporation device are discharged from the gas outlet of the polymerization device.
[0095] Preferably, the polymerization reaction is carried out at a temperature of 255-310°C.
[0096] Preferably, the material residence time of the polymerization reaction is 0.2-1.2 h.
[0097] In this invention, the reaction products of the polymerization reaction are subjected to a repolymerization reaction in a conventional post-polymerization reactor to obtain a polymer melt.
[0098] The product of the polymerization reaction can be transported to the post-polymerization reactor by a melt pump for repolymerization to obtain a polymer melt.
[0099] Preferably, the pressure of the repolymerization reaction is -0.06 MPa or below.
[0100] Preferably, the temperature of the repolymerization reaction is 280-335°C. The product after polymerization in the prepolymerization reactor undergoes a recondensation reaction in the postpolymerization reactor to form a polymer melt with a number average molecular weight of 22,000-38,000.
[0101] The present invention also provides a polymer prepared using the polymer preparation system or the polymer preparation method described above.
[0102] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.
[0103] The reagents and raw materials used in this invention are all commercially available.
[0104] The positive and progressive effects of this invention are as follows:
[0105] (1) This invention, through the design of front and rear pelletizing chambers, can smoothly transition the vortices formed inside the water chamber caused by the rapid rotation of the cutter, thereby reducing the pressure gradient force on the pellets towards the center of the pelletizing water chamber. This significantly reduces the formation of low-pressure zones and facilitates the efficient discharge of pellets from the front pelletizing water chamber. The design of the water chamber partition plate can reduce the vortices formed inside the pelletizing water chamber without affecting the transport of pellets from the front to the rear pelletizing chamber, without significantly reducing the turbulence intensity. It can still maintain a high turbulence intensity, which is beneficial for the dispersion and discharge of pellets. In addition, by setting a guide pipe on the water chamber partition plate, the pellets can flow with the water flow and the direction of the guide pipe, reducing the dead zone of pellets and further facilitating the discharge of pellets.
[0106] (2) By optimizing the existing underwater pelletizing and polymerization processes, the present invention obtains polyamide resin chips with a lower yellow index, better mechanical properties, and better product quality. Moreover, compared with the existing strip pelletizing, the underwater pelletizing of the present invention yields polyamide resin chips with higher bulk density and less dust.
[0107] (3) The system and method of the present invention can meet the requirements of underwater pelletizing of polymers of different types and different product viscosity. The polymers can be polyethylene terephthalate, polyamide, polyolefin and other types. Attached Figure Description
[0108] Figure 1 This is a schematic diagram of the polymer pelletizing system in Example 1;
[0109] Figure 2 This is a front view of the cutting disc of the cutting module in Example 1;
[0110] Figure 3 This is a schematic diagram of the partition plate in Example 1;
[0111] Explanation of reference numerals in the attached figures:
[0112] Polymerization Reaction System 1
[0113] Melt Pump 2
[0114] Extruder 3
[0115] Template 4
[0116] Cutting knife 5
[0117] Cutting disc 6
[0118] 601 opening
[0119] Divider 7
[0120] Through Hole 701
[0121] pelletizing chamber 8
[0122] Pre-granulation chamber 801
[0123] Post-granulation chamber 802
[0124] Cutting shaft 9
[0125] Motor 10
[0126] Cooler 11
[0127] First particle water pump 12
[0128] Second particle water pump 13
[0129] Centrifugal dryer 14
[0130] 15 pelletizing water tank
[0131] Water exchange inlet 16
[0132] Water exchange outlet 17
[0133] Bag filter 18
[0134] Grading and screening machine 19
[0135] 20 silos
[0136] Base 21
[0137] Mounting slot 22
[0138] Flow guide tube 23
[0139] Water inlet pipe 24. Detailed Implementation
[0140] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.
[0141] Example 1
[0142] This embodiment is a polymer pelletizing system. Figure 1 This is a schematic diagram of the polymer pelletizing system of this embodiment. The polymer pelletizing system includes: a feeding module, a cutting module, a pellet post-processing module, and a circulating water module; wherein, the feeding module includes a melt pump 2, an extruder 3, and a die 4. The melt pump 2 is used to transfer the polymer melt in the polymerization reaction system 1 to the extruder 3. The extruder 3 is a twin-screw extruder, and the die 4 is provided on the discharge port end face. The die head of the extruder 3 and the die 4 are fixedly connected by bolts.
[0143] The template 4, which has a disc-shaped cross-section, has a number of cylindrical holes with a diameter of 2.6-3.5 mm and a quantity of 10-100 holes along its thickness direction. These holes are arranged in a ring on the surface of the template so that the melt forms a resin strip after passing through the holes. The template 4 is made of hard alloy or ferritic stainless steel.
[0144] The cutting module includes a pelletizing chamber 8 and a cutting disc 6 with a circular cross-section, made of stainless steel, and having several openings 601. The pelletizing chamber 8 has a partition plate 7 in the vertical direction inside, which is used to divide the pelletizing chamber 8 into a front pelletizing chamber 801 and a rear pelletizing chamber 802. Figure 2 This is a front view of the cutting disc of the cutting module in this embodiment.
[0145] Figure 3 This is a schematic diagram of the partition plate in this embodiment. The partition plate 7 has several through holes 701, all arranged along the thickness direction of the partition plate 7. A guide tube 23 is welded to one side of each through hole 701 in the rear pelletizing chamber 802. Each guide tube 23 extends from the through hole 701 towards the central axis of the partition plate 7, with a length of 8-15 mm. The angle between the axial center line of each guide tube 23 and the central axis of the partition plate 7 is 20-60°. The template 4 and the cutter disc 6 are both located within the front pelletizing chamber 801. The cutter 5 is fixedly mounted on the side wall of the cutter disc 6 by bolts. On the mounting slot 22, several mounting slots 22 are arranged in a circular matrix on the cutter disc 6. The blade of the cutter 5 is inclined and attached to the discharge end face of the die hole of the template 4, with an included angle of 30-60°. The gap between the cutter 5 and the template 4 is 0.02-0.05mm, and the number is 6-8. The cutter 5 is braked by the rotation of the cutter disc 6 through the transmission device. The transmission device includes a motor 10 and a cutter shaft 9 passing through the front pelletizing chamber 801 and the rear pelletizing chamber 802. One end of the cutter shaft 9 is connected to the stepless frequency conversion speed regulating motor 10, and the other end is connected to the cutter disc 6. The bottom of the front pelletizing chamber 801 is provided with a water inlet; a water inlet pipe 24 is inclined at the water inlet, and the inclination angle of the water inlet pipe 24 is such that the water flow direction of the water inlet pipe 24 is tangent to the circumference of the cutter disc 6; the volume ratio of the front pelletizing chamber 801 to the rear pelletizing chamber 802 is (1.1-1.4):1; inspection holes are provided on both sides of the front pelletizing chamber 801; the cutting module is provided with a base 21 for fixing the motor 10 of the transmission device.
[0146] The upper part of the post-pelletizing chamber 802 is provided with a discharge port; the post-pelletizing module includes a solid-liquid separation device; the inlet of the solid-liquid separation device is connected to the discharge port; the discharge port is connected to the solid-liquid separation device through a pipeline, and the pipeline is equipped with a first pellet water pump 12; the solid-liquid separation device is a centrifugal dryer 14, and its solid phase outlet is connected in sequence to a grading and screening machine 19 and a silo 20; the circulating water module includes a pelletizing water tank 15, a bag filter 18, a second pellet water pump 13 and a cooler 11 connected in sequence; the circulating water inlet of the pelletizing water tank 15 is connected to the liquid phase outlet of the solid-liquid separation device, the cold fluid outlet of the cooler 11 is connected to the water inlet, and the pelletizing water tank 15 also includes a water exchange inlet 16 and a water exchange outlet 17.
[0147] One end of the circulating water module is connected to the liquid phase outlet of the solid-liquid separation device, and the other end is connected to the water inlet.
[0148] Example 2
[0149] This embodiment uses the polymer pelletizing system as described in Example 1. The die hole diameter of the template 4 is 2.8 mm, and the number of die holes is 30. The length of each guide tube 23 is 10 mm, and the angle between the axial centerline of each guide tube 23 and the central axis of the partition plate 7 is 30°. The blade of the cutter 5 is obliquely attached to the discharge end face of the die hole of the template 4 at an angle of 30°. The gap between the cutter 5 and the template 4 is 0.02 mm, and there are 6 cutters. The volume ratio of the front pelletizing chamber 801 to the rear pelletizing chamber 802 is 1.2:1.
[0150] The polymer pelletizing method in this embodiment includes the following steps:
[0151] The polyamide melt disclosed in Example 3 of the authorized patent CN108501247B is used, wherein the temperature of the polyamide melt is 272℃. The polyamide melt is fed into the cutting module from the feeding module through the melt pump 2. The die inlet pressure of the extruder 3 is 80 bar, the rotation speed of the cutter 5 is 650 r / min, and the water flow rate of the pre-pelletizing chamber 801 is 330 kg / h. The water temperature of the pre-pelletizing chamber 801 and the post-pelletizing chamber 802 is maintained at 55±3℃, and the outlet pressure of the first pelletizing water pump 12 is 0.35 MPa. After solid-liquid separation, polymer particles and pelletized water are obtained; the ratio of the water flow rate at the inlet of the pre-pelletizing chamber 801 to the polymer particle yield is 1.1. The pelletized water is returned to the pre-pelletizing chamber 801 through the second pelletizing water pump 13, and the outlet pressure of the second pelletizing water pump is 0.35 MPa.
[0152] The obtained polymer particles are spherical with a length of 2.5 mm. Their bulk density is 31% higher than that of underwater strip pelletizing (the above polymer melt is subjected to underwater strip pelletizing at a water temperature of 55±3℃), and the amount of dust is 17% lower than that of underwater strip pelletizing.
[0153] Example 3
[0154] This embodiment uses the polymer pelletizing system as described in Example 1. The template 4 has a die hole diameter of 3.2 mm and 35 die holes. Each guide tube 23 is 10 mm long, and the angle between the axial centerline of each guide tube 23 and the central axis of the partition plate 7 is 40°. The blade of the cutter 5 is obliquely attached to the discharge end face of the die hole of the template 4 at an angle of 35°. The gap between the cutter 5 and the template 4 is 0.03 mm, and there are 6 cutters. The volume ratio of the front pelletizing chamber 801 to the rear pelletizing chamber 802 is 1.1:1.
[0155] The polymer pelletizing method in this embodiment includes the following steps:
[0156] Using terephthalic acid and ethylene glycol or 1,4-butanediol as raw materials, the mixture passes through an esterification reactor and then into a pre-polymerization reactor, followed by a final polymerization reactor. A vacuum is maintained at a pressure below -0.03 MPa (gauge pressure) to obtain a PET melt with a melt temperature of 284°C. This PET melt is then fed into the cutting module via a melt pump 2 from the feeding module. The extruder 3 has a die inlet pressure of 73 bar, the cutter 5 rotates at 800 r / min, and the water flow rate in the pre-pelletizing chamber 801 is 480 kg / h. The water temperature in both the pre-pelletizing chamber 801 and the post-pelletizing chamber 802 is maintained at 58 ± 3°C, and the outlet pressure of the first particle pump 12 is 0.38 MPa. After solid-liquid separation, polymer particles and pelletized water are obtained. The ratio of the water flow rate at the inlet of the pre-pelletizing chamber to the polymer particle yield is 1.6. The pelletizing water is returned to the pre-pelleting chamber 801 via the second pellet pump 13, and the outlet pressure of the second pellet pump is 0.38 MPa.
[0157] The obtained polymer particles are spherical with a length of 3 mm. Their bulk density is 26% higher than that of underwater strip pelletizing (the above polymer melt is subjected to underwater strip pelletizing at a water temperature of 58±3℃), and the amount of dust is 20% lower than that of underwater strip pelletizing.
[0158] Example 4
[0159] This embodiment is a polymer preparation system, which includes a salt-forming reaction device, a concentration device, a prepolymerization reaction device, a flash evaporation device, a prepolymerization reaction device, and a postpolymerization reaction device connected in sequence, as well as a polymer pelletizing system as in Example 1. The salt-forming reaction device, concentration device, prepolymerization reaction device, flash evaporation device, prepolymerization reaction device, and postpolymerization reaction device are collectively referred to as polymerization reaction system 1.
[0160] Example 5
[0161] This embodiment describes a method for preparing polyamide PA56 resin, which uses the polymer preparation system as described in Example 4 and includes the following steps:
[0162] (1) Add 32976.2 kg (29.13 kmol) pentanediamine, 3224.1 kg (27.75 kmol) adipic acid, 43873 g sodium hypophosphite and 90% of the total mass of the materials to a paddle-stirred salt-forming reactor and stir for 55 min. Vacuum for 3 min and purge with inert gas to atmospheric pressure. Repeat this cycle 10 times. After the replacement is complete, heat the paddle-stirred salt-forming reactor to 75°C. Keep the pressure of the salt-forming reaction below 0.1 MPa and the stirring speed at 66 r / min for 3.5 h to form a salt solution with a concentration of 52.6% polyamide PA56.
[0163] (2) The polyamide PA56 salt solution formed in step (1) is fed into the concentration reactor through a salt solution transfer pump. The temperature of the concentration reactor is 133±2℃. After concentration, the salt solution is concentrated to 65.2wt%.
[0164] (3) The salt solution described in step (2) is passed sequentially through the polymerization reactor for prepolymerization. The reaction temperature is 255°C, the reactor pressure is 2.0 MPa, and after a residence time of 2.1 h, the reaction system is pumped into a flash evaporator for depressurization. During the depressurization process, the water in the reaction system rapidly vaporizes, resulting in a polymer with a water content of 10%.
[0165] (4) The reaction product obtained in step (3) is pumped to the prepolymerization reactor for gas-liquid separation and further polycondensation reaction. The reaction temperature of the prepolymerization reactor is 270°C and the residence time of the reactants is 0.8 h. Subsequently, the reaction product in the prepolymerization reactor is pumped into the postpolymerization reactor. The reaction pressure of the postpolymerization reactor is below -0.06 MPa and the reaction temperature of the postpolymerization reactor is 285°C. After further polycondensation reaction, polyamide melt is finally formed.
[0166] (5) The polyamide melt is pumped into an underwater pelletizing system, which is the same as in Example 2.
[0167] The extruder 3 has a die inlet pressure of 80 bar, a cutter speed of 650 r / min, a water flow rate of 330 kg / h in the pre-pelletizing chamber 801, and a water temperature of 55 ± 3℃ in both the pre-pelletizing chamber 801 and the post-pelletizing chamber 802. The outlet pressure of the first pellet water pump 12 is 0.35 MPa, and the outlet pressure of the second pellet water pump is also 0.35 MPa. After solid-liquid separation, polymer particles and pelletized water are obtained. The ratio of the water flow rate at the inlet of the pre-pelletizing chamber 801 to the polymer particle yield is 1.1.
[0168] Example 6
[0169] This embodiment describes a method for preparing polyamide PA5T / 56, which uses the polymer preparation system as described in Example 4 and includes the following steps:
[0170] (1) Add 2996.03 kg (29.32 kmol) pentanediamine, 1317.51 kg (7.93 kmol) terephthalic acid, 2921.98 kg (19.99 kmol) adipic acid, 2129 g sodium hypophosphite and 95% of the total mass of the materials to a paddle-stirred salt-forming reactor. Vacuum for 3 min, then pass inert gas to atmospheric pressure. Repeat this cycle 10 times. After the replacement is complete, heat the paddle-stirred salt-forming reactor to 86°C. Keep the pressure of the salt-forming reaction below 0.1 MPa, and maintain the stirring speed at 77 r / min for 3.2 h to form a 51.3% polyamide PA5T / 56 salt solution.
[0171] (2) The polyamide PA5T / 56 salt solution formed in step (1) is fed into the concentration reactor through a salt solution transfer pump. The temperature of the concentration reactor is 140°C. After concentration, the salt solution is concentrated to 68.4 wt%.
[0172] (3) The salt solution described in step (2) is passed sequentially through the polymerization reactor for prepolymerization. The reaction temperature is 263°C, the reactor pressure is 2.1 MPa, and after a residence time of 2.3 h, the reaction system is pumped into a flash evaporator for depressurization. During the depressurization process, the water in the reaction system rapidly vaporizes, resulting in a polymer with a water content of 11%.
[0173] (4) The reaction product obtained in step (3) is pumped to the prepolymerization reactor for gas-liquid separation and further polycondensation reaction. The reaction temperature of the prepolymerization reactor is 281°C, and the residence time of the reactants is 1.2 h. Subsequently, the reaction product in the prepolymerization reactor is pumped into the postpolymerization reactor. The reaction pressure of the postpolymerization reactor is below -0.06 MPa, and the reaction temperature of the postpolymerization reactor is 295°C. After further polycondensation reaction, polyamide melt is finally formed.
[0174] (5) The polyamide melt is pumped into an underwater pelletizing system by a melt pump. The underwater pelletizing system is the same as that in Example 2, except that the die hole diameter of the template 4 is 3.1 mm and the number of die holes is 46.
[0175] The extruder 3 has a die inlet pressure of 70 bar, a cutter speed of 400 r / min, a water flow rate of 390 kg / h in the pre-pelletizing chamber 801, and water temperatures of 62 ± 3℃ in both the pre-pelletizing chamber 801 and the post-pelletizing chamber 802. The outlet pressure of the first pellet pump 12 is 0.42 MPa, and the outlet pressure of the second pellet pump 12 is 0.42 MPa. After solid-liquid separation, polymer particles and pelletized water are obtained. The ratio of the water flow rate at the inlet of the pre-pelletizing chamber 801 to the polymer particle yield is 1.3.
[0176] Example 7
[0177] This embodiment describes a method for preparing polyamide PA10T / 1010, which uses the polymer preparation system as described in Example 4 and includes the following steps:
[0178] (1) 2874.07 kg (17.30 kmol) terephthalic acid, 2925.25 kg (16.78 kmol) 1,10-decanediamine, 105.17 kg (0.52 kmol) 1,10-decanediic acid, 63.50 kg (0.52 kmol) benzoic acid, 2984 g sodium hypophosphite and 90% of the total mass of the materials of water were added to a paddle-stirred salt-forming reactor. The reactor was evacuated for 3 min and then purged with inert gas to atmospheric pressure. This process was repeated 10 times. After the replacement was completed, the paddle-stirred salt-forming reactor was heated to 81 °C. The pressure of the salt-forming reaction was kept below 0.1 MPa and the stirring speed was 71 r / min for 3.2 h to form a polyamide PA10T / 1010 salt solution with a concentration of 52.6%.
[0179] (2) The polyamide PA10T / 1010 salt solution formed in step (1) is fed into the concentration reactor through a salt solution transfer pump. The temperature of the concentration reactor is 137°C. After concentration, the salt solution is concentrated to 70.5 wt%.
[0180] (3) The salt solution described in step (2) is passed sequentially through the polymerization reactor for prepolymerization. The reaction temperature is 285°C, the reactor pressure is 1.9 MPa, and after a residence time of 2.6 h, the reaction system is pumped into a flash evaporator for depressurization. During the depressurization process, the water in the reaction system rapidly vaporizes, resulting in a polymer with a water content of approximately 10%.
[0181] (4) The reaction product obtained in step (3) is pumped to the prepolymerization reactor for gas-liquid separation and further polycondensation reaction. The reaction temperature of the prepolymerization reactor is 315°C and the residence time of the reactants is 0.8h. Subsequently, the reaction product in the prepolymerization reactor is pumped into the postpolymerization reactor. The reaction pressure of the postpolymerization reactor is below -0.06MPa and the reaction temperature is 333°C. After further polycondensation reaction, polyamide melt is finally formed.
[0182] (5) The polyamide melt is pumped into an underwater pelletizing system by a melt pump. The underwater pelletizing system is the same as that in Example 2, except that the die hole diameter of the template 4 is 3.2 mm and the number of die holes is 42.
[0183] The extruder 3 has a die inlet pressure of 78 bar, a cutter speed of 510 r / min, a water flow rate of 540 kg / h in the pre-pelletizing chamber 801, and a water temperature of 51 ± 3℃ in both the pre-pelletizing chamber 801 and the post-pelletizing chamber 802. The outlet pressure of the first pellet pump 12 is 0.38 MPa, and the outlet pressure of the second pellet pump 12 is 0.35 MPa. After solid-liquid separation, polymer particles and pelletized water are obtained. The ratio of the water flow rate at the inlet of the pre-pelletizing chamber 801 to the polymer particle yield is 1.8.
[0184] Example 8
[0185] This embodiment describes a method for preparing polyamide PA6T / 66, which uses the polymer preparation system as described in Example 4 and includes the following steps:
[0186] (1) Add 4761.03 kg (40.97 kmol) hexamethylenediamine, 2278.45 kg (15.59 kmol) adipic acid, 3159.49 kg (19.02 kmol) terephthalic acid, 3059 g sodium hypophosphite, 4588 g antioxidant H10 and 90% of the total mass of the materials of water to a paddle-stirred salt-forming reactor. Vacuum for 3 min, and then pass inert gas to atmospheric pressure. Repeat this cycle 10 times. After the replacement is completed, heat the paddle-stirred salt-forming reactor to 85°C. Keep the pressure of the salt-forming reaction below 0.1 MPa, and keep the stirring speed at 66 r / min for 4.7 h to form a polyamide PA6T / 66 salt solution with a concentration of 52.6%.
[0187] (2) The polyamide PA6T / 66 salt solution formed in step (1) is fed into the concentration reactor through a salt solution transfer pump. The temperature of the concentration reactor is 145°C. After concentration, the salt solution is concentrated to 73.6 wt%.
[0188] (3) The salt solution described in step (2) is passed sequentially through the polymerization reactor for prepolymerization. The reaction temperature is 291°C, the reactor pressure is 2.3 MPa, and after a residence time of 3.6 h, the reaction system is pumped into a flash evaporator for depressurization. During the depressurization process, the water in the reaction system rapidly vaporizes, resulting in a polymer with a water content of approximately 10%.
[0189] (4) The reaction product obtained in step (3) is pumped to the prepolymerization reactor for gas-liquid separation and further polycondensation reaction. The reaction temperature of the prepolymerization reactor is 321°C and the residence time of the reactants is 0.9 h. Subsequently, the reaction product in the prepolymerization reactor is pumped into the postpolymerization reactor. The reaction pressure of the postpolymerization reactor is below -0.06 MPa and the reaction temperature is 335°C. After further polycondensation reaction, polyamide melt is finally formed.
[0190] (5) The polyamide melt is pumped into an underwater pelletizing system by a melt pump. The underwater pelletizing system is the same as that in Example 2, except that the die hole diameter of the template 4 is 3.4 mm and the number of die holes is 38.
[0191] The die head inlet pressure is 94 bar, the cutter speed is 550 r / min, the water flow rate in the front pelletizing chamber is 690 kg / h, the water temperature in the front pelletizing chamber 801 and the rear pelletizing chamber 802 is maintained at 57±3℃, the outlet pressure of the first pellet water pump is 0.41 MPa, the outlet pressure of the second pellet water pump is 0.41 MPa, and after solid-liquid separation, polymer particles and pelletizing water are obtained; the ratio of the water flow rate at the inlet of the front pelletizing chamber to the output of the polymer particles is 2.3.
[0192] Example 9
[0193] In this example, steps (1)-(5) are the same as in Example 6. The only difference is that the inlet of the pre-granulation chamber in the polymer pelletizing system used in (5) is designed with a radial inlet, that is, the water flows vertically upward into the pre-granulation chamber.
[0194] Comparative Example 1
[0195] In this comparative example, steps (1)-(5) are the same as in Example 5, except that the reactor pressure in (3) is 1.5 MPa, the water temperature in the pre-pelletizing chamber 801 and the post-pelletizing chamber 802 in (5) is 85±3℃, and the inlet flow rate of the pre-pelletizing chamber 801 is 900 kg / h.
[0196] Comparative Example 2-1
[0197] In this example, steps (1)-(5) are the same as in Example 6, except that the cutting module of the polymer pelletizing system used in (5) does not have a partition plate and has only one pelletizing chamber.
[0198] Comparative Example 2-2
[0199] In this comparative example, steps (1)-(5) are the same as in Example 6, except that the reactor pressure in (3) is 1.5 MPa and the water temperature in the pre-pellet chamber 801 and post-pellet chamber 802 in (5) is 85 ± 3 °C.
[0200] Comparative Example 3
[0201] In this example, steps (1)-(5) are the same as in Example 7, except that the reactor pressure in (3) is 1.6 MPa, the water temperature in the pelletizing chamber in (5) is 85±3℃, and the inlet flow rate of the pre-pelletizing chamber 801 is 150 kg / h.
[0202] Comparative Example 4
[0203] In this example, steps (1)-(5) are the same as in Example 8, except that the reactor pressure in (3) is 1.9 MPa, the water temperature in the pre-pelletizing chamber 801 and the post-pelletizing chamber 802 in (5) is 85±3℃, and the inlet flow rate of the pre-pelletizing chamber 801 is 180 kg / h.
[0204] Example 1
[0205] (1) Method for detecting relative viscosity ηr
[0206] Testing instrument: Ubbelohde viscometer AVS600, purchased from Shanghai Luwen Scientific Instruments Co., Ltd.
[0207] Test method: Ubbelohde viscometer concentrated sulfuric acid method. Accurately weigh 0.5±0.0002g of dried polyamide resin material sample, add 50mL of concentrated sulfuric acid (96%) to dissolve it, and measure and record the flow time t0 of concentrated sulfuric acid and the flow time t of polyamide resin material solution in a 25℃ constant temperature water bath. Relative viscosity calculation formula: Relative viscosity ηr=t / t0; where: t: solution flow time; t0: solvent flow time.
[0208] (2) Melting point test
[0209] Test instrument: Differential scanning calorimeter DSC Q20, purchased from TA Instruments, USA.
[0210] Test method: Weigh 5-8 mg of sample into an aluminum crucible, with an empty crucible as a control. Under nitrogen protection (gas flow rate of 50 mL / min), heat to 300 °C at 20 °C / min, hold for 3 min to eliminate thermal history, then cool to 30 °C at 20 °C / min, and then heat to 300 °C at 20 °C / min. Record the thermo-analytic change during the temperature scan.
[0211] (3) Yellowness Index Test
[0212] Testing instrument: Yellowness index meter
[0213] Test method: The test method refers to HG / T3862-2006.
[0214] (4) Molecular weight test
[0215] Testing instrument: Gel permeation chromatography
[0216] Test method: The test was performed by gel permeation chromatography (GPC). The standard substance was PMMA, and the solvent was trifluoroethanol + 0.05% potassium trifluoroacetate. After complete dissolution, the solution was filtered through a PTFE membrane and injected at 40°C for analysis to obtain the molecular weight and distribution relative to PMMA.
[0217] The resin materials prepared in Examples 5-9 and Comparative Examples 1-4 were tested, and the test results are shown in Table 1. Table 1 shows the performance test results of the polymer pellets prepared in Examples 5-9 and Comparative Examples 1-4.
[0218] Table 1
[0219] sample Relative viscosity ηr Melting point Tm (°C) Yellow Index YI Product molecular weight Example 5 2.73 254.5 0.58 23500 Example 6 2.62 271.3 1.36 26800 Example 7 2.21 298.7 2.11 24900 Example 8 2.28 302.1 2.89 29100 Example 9 2.59 269.6 1.44 26100 Comparative Example 1 2.55 252.4 4.59 22300 Comparative Example 2-1 2.57 268.7 1.58 25900 Comparative Example 2-2 2.46 268.5 6.74 24300 Comparative Example 3 1.87 296.4 5.25 21000 Comparative Example 4 2.16 300.2 3.66 27500
[0220] As shown in Table 1, by changing the prepolymerization reaction pressure in the polymerization process and the water temperature and inlet flow rate in the pelletizing chamber of the polymer pelletizing system, the final resin product exhibits significantly different properties. Increasing the prepolymerization reaction pressure raises the boiling point of the diamine in the reaction system, preventing the volatilization of the diamine component and resulting in a higher molecular weight of the final product. Appropriate water temperature and inlet flow rate in the pelletizing chamber also affect the crystallization rate of the product to a certain extent, ultimately manifesting in differences in product color.
[0221] Comparing Examples 5 and 1, 6 and 9 with Comparative Examples 2-1 and 2-2, 7 and 3, and 8 and 4, it is evident that changing the prepolymerization reaction pressure, pelletizing chamber water temperature, and inlet water flow rate all decrease the relative viscosity, melting point, and molecular weight of the resulting polymer pellets, while simultaneously increasing the yellow index. Furthermore, Comparative Example 2-1 exhibits unfavorable process phenomena such as "blade entanglement" and "particle adhesion." Therefore, a suitable polymerization process combined with underwater pelletizing yields a product of superior quality.
[0222] Example 2
[0223] Resin mechanical property testing
[0224] Testing instruments: UTM4304 electronic universal testing machine and PTM1000 impact strength tester, both purchased from Shenzhen Sansi Zongheng Technology Co., Ltd.
[0225] Test methods: Polyamide resin chips were dried to a moisture content below 1000 ppm and then injection molded using an injection molding machine (any conventional equipment in this field is acceptable). The tensile strength (MPa) and elongation at break (%) of the resin were determined according to GB / T14344-2008 (tensile test specimen specifications: 170*20*4mm, dumbbell shape); the flexural strength (MPa) of the resin was determined according to ISO527-2 (flexural test specimen specifications: 80*10*4mm); and the notched impact strength of the resin cantilever beam (kJ·m) was measured. -2 The test method refers to ISO 197 / leA (impact test specimen specifications: 80*10*4mm, with a notch on one side).
[0226] The resin materials prepared in Examples 5-9 and Comparative Examples 1-4 were tested, and the test results are shown in Table 2. Table 2 shows the performance test results of the polymer pellets prepared in Examples 5-9 and Comparative Examples 1-4.
[0227] Table 2
[0228]
[0229] Table 2 shows that the polyamide resin materials in Examples 1-4 have better mechanical properties, while the resin properties produced after changing the pressure of the prepolymer reactor, the water cooling temperature of the pelletizing chamber, and the inlet water flow rate are reduced.
[0230] The above embodiments are merely explanations of the technical solutions and do not constitute a limitation on the technology of this invention.
[0231] Unless otherwise specified, the terms used in this invention have the meanings commonly understood by those skilled in the art.
[0232] The embodiments described in this invention are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Those skilled in the art can make various other substitutions, changes and improvements within the scope of this invention. Therefore, this invention is not limited to the above embodiments, but is only defined by the claims.
Claims
1. A polymer pelletizing system, characterized in that, It includes: The system comprises a feeding module, a cutting module, a pellet post-processing module, and a circulating water module; among which, The feeding module includes an extruder and a template. The template is provided on the discharge port end face of the extruder, and the template has a plurality of die holes along its thickness direction. The cutting module includes a pelletizing chamber and a cutting disc. The pelletizing chamber has a vertically oriented partition plate dividing it into a front pelletizing chamber and a rear pelletizing chamber. The partition plate has several through holes, each with a guide pipe on one side of the rear pelletizing chamber, extending from the through hole towards the central axis of the partition plate. The template and the cutting disc are both located within the front pelletizing chamber. The cutting disc has a cutting blade on its side wall, positioned at the die outlet face of the template. The front pelletizing chamber has a water inlet, and the rear pelletizing chamber has a discharge outlet. The particle post-processing module includes a solid-liquid separation device; the inlet of the solid-liquid separation device is connected to the outlet. One end of the circulating water module is connected to the liquid phase outlet of the solid-liquid separation device, and the other end is connected to the water inlet.
2. The polymer pelletizing system as described in claim 1, characterized in that, The feeding module also includes a melt pump, which is used to transfer polymer melt to the extruder; And / or, the extruder head and the template are fixedly connected by bolts; And / or, the extruder is a twin-screw extruder; And / or, the template and the die hole satisfy one or more of the following conditions: ① The cross-section of the template is disc-shaped; ②The template is made of hard alloy or ferritic stainless steel; ③ Several of the aforementioned mold holes are arranged in a ring on the surface of the template; ④ The die hole is cylindrical, so that the melt forms a resin strip after passing through the die hole; ⑤ The diameter of the die hole is 2.6-3.5 mm; ⑥ The number of the die holes is 10-100; And / or, the cutter disc satisfies one or more of the following conditions: ① The cross-section of the cutting disc is circular; ②The material of the cutting disc is stainless steel; ③ The side wall of the cutter disc is provided with several mounting grooves for mounting the cutter; ④ The cutter disc and the cutter are fixedly connected by bolts; ⑤ The cutting disc has several openings; And / or, the number of the cutters is 4-10; And / or, the gap between the cutter and the template is 0.02-0.05 mm; And / or, the cutter is inclined at the die outlet end face of the template; And / or, the cutter is braked by the rotation of the cutter disc via a transmission device, the transmission device including a motor and a cutter shaft passing through the front pelletizing chamber and the rear pelletizing chamber, one end of the cutter shaft being connected to the motor and the other end being connected to the cutter disc; And / or, each of the through holes is provided along the thickness direction of the partition plate; And / or, the guide tube is connected to the through hole by welding; And / or, the length of each of the aforementioned guide tubes is 8-15 mm; And / or, the angle between the axial centerline of each of the guide tubes and the central axis of the partition plate is 20-60°; And / or, the water inlet is located at the bottom of the pre-granulation chamber; And / or, an inlet pipe is inclined at the inlet, and the inclination angle of the inlet pipe is such that the water flow in the inlet pipe is tangent to the circumference of the cutter disc; And / or, the discharge port is located at the upper part of the post-granulation chamber; And / or, the volume ratio of the pre-granulation chamber to the post-granulation chamber is (1.1-1.4):1; And / or, viewing holes are provided on both sides of the pre-granulation chamber; And / or, the cutting module is provided with a base for fixing the motor of the transmission device; And / or, the discharge port is connected to the solid-liquid separation device via a pipeline, and the pipeline is equipped with a first particle water pump; And / or, the solid-liquid separation device includes a centrifugal dryer; And / or, the solid phase outlet of the solid-liquid separation device is connected in sequence to a grading and screening machine and a silo; And / or, the circulating water module includes a pelletizing tank, a bag filter, a second pellet pump, and a cooler connected in sequence; the circulating water inlet of the pelletizing tank is connected to the liquid phase outlet of the solid-liquid separation device, and the cold fluid outlet of the cooler is connected to the water inlet.
3. The polymer pelletizing system as described in claim 2, characterized in that, Several of the mounting slots are arranged in a ring matrix on the cutting disc.
4. The polymer pelletizing system as described in claim 2, characterized in that, The number of cutting blades is 6-8.
5. The polymer pelletizing system as described in claim 2, characterized in that, The angle between the inclined part of the cutter and the template is 10-60°.
6. The polymer pelletizing system as described in claim 5, characterized in that, The angle between the inclined part of the cutter and the template is 30-60°.
7. The polymer pelletizing system as described in claim 2, characterized in that, The motor is a stepless variable frequency speed control motor.
8. The polymer pelletizing system as described in claim 2, characterized in that, The pelletizing tank also includes a water exchange inlet and a water exchange outlet.
9. A method for pelletizing a polymer, characterized in that, It employs the polymer pelletizing system as described in any one of claims 1-8 and includes the following steps: The polymer melt is fed into the cutting module through the feeding module. The water temperature in both the pre-particle cutting chamber and the post-particle cutting chamber is 15-80℃. After solid-liquid separation, polymer particles and cutting water are obtained. The ratio of the water flow rate at the inlet of the pre-particle cutting chamber to the output of the polymer particles is 0.8-2.
5.
10. The polymer pelletizing method as described in claim 9, characterized in that, In the feeding module, the die inlet pressure of the extruder is 60-120 bar; And / or, the temperature of the polymer melt is 230-315°C; And / or, the water temperature in both the pre-pelleting chamber and the post-pelleting chamber is 25-70℃; And / or, the rotational speed of the cutter is 600-2000 r / min; And / or, the length of the polymer particles is 2-3 mm; And / or, the polymer particles are elliptical or spherical; And / or, in the particle post-treatment module, the outlet pressure of the first particle water pump is 0.2-0.5 MPa; And / or, in the circulating water module, the outlet pressure of the second particulate water pump is 0.2-0.5 MPa; And / or, the water flow rate at the inlet of the pre-granulation chamber is 250-1200 kg / h; And / or, the ratio of the water flow rate at the inlet of the pre-granulation chamber to the yield of the polymer particles is 1-2.
11. The polymer pelletizing method as described in claim 10, characterized in that, The temperature of the polymer melt is 245-305℃.
12. The polymer pelletizing method as described in claim 10, characterized in that, The outlet pressure of the first particulate water pump is 0.3-0.45 MPa.
13. The polymer pelletizing method as described in claim 10, characterized in that, The outlet pressure of the second particulate water pump is 0.3-0.45 MPa.
14. A polymer preparation system, characterized in that, It includes a salt-forming reaction device, a concentration device, a prepolymerization reaction device, a flash evaporation device, a prepolymerization reaction device, and a postpolymerization reaction device connected in sequence, and a polymer pelletizing system as described in any one of claims 1-8.
15. The polymer preparation system according to claim 14, characterized in that, The salt-forming reaction apparatus is used to carry out a salt-forming reaction between diamines and dicarboxylic acids; The concentration device is used to concentrate and remove water from the product of the salt formation reaction to obtain a concentrated polyamide salt solution. The prepolymerization reaction device is used to perform a prepolymerization reaction on the concentrated polyamide salt solution; The flash evaporation device is used to flash-evaporate the product of the prepolymerization reaction under reduced pressure. The prepolymerization reactor is used to perform gas-liquid separation and polymerization reaction on the product after flash evaporation and depressurization. The post-polymerization reaction apparatus is used to further polymerize the products of the polymerization reaction.
16. The use of a polymer pelletizing system as described in any one of claims 1-8 or a polymer preparation system as described in claim 14 or 15 in the preparation of polyamides.
17. A method for preparing a polymer, characterized in that, It employs the polymer preparation system as described in claim 14 or 15, and includes the following steps: The reactants are sequentially subjected to a salt formation reaction, concentration and dehydration, prepolymerization reaction, flash evaporation under reduced pressure, polymerization reaction, and repolymerization reaction to obtain a polymer melt; the reactants include polyamide monomers and / or polyamide salts, and the pressure of the prepolymerization reaction is 1.7-2.5 MPa; Then, polymer pellets are obtained by using the polymer pelletizing method as described in any one of claims 9-13.
18. The method for preparing the polymer according to claim 17, characterized in that, The pressure of the salt formation reaction is 0.01-0.5 MPa; And / or, the temperature of the salt formation reaction is 75-95°C; And / or, the apparatus for the salt-forming reaction is a paddle-type stirred salt-forming reactor; And / or, the atmosphere for the salt formation reaction is an inert atmosphere; And / or, the concentration of polyamide in the salt solution after the salt-forming reaction is 40-60 wt%; And / or, the polyamide monomer includes a diamine monomer and a diacid monomer; And / or, the polyamide salt is formed by reacting a diacid with a diamine; And / or, the temperature of the concentration vessel for concentrating and removing water is 125-155°C; And / or, after the concentration and dehydration, the concentration of the polyamide salt solution is 65-75 wt%; And / or, the temperature of the prepolymerization reaction is 185-275°C; And / or, the material residence time of the prepolymerization reaction is 1.5-4.5 h; And / or, the polymerization reaction is carried out at a temperature of 255-310°C; And / or, the pressure of the prepolymerization reaction is 1.9-2.3 MPa; And / or, the material residence time of the polymerization reaction is 0.2-1.2 h; And / or, the pressure of the repolymerization reaction is -0.06 MPa or below; And / or, the temperature of the repolymerization reaction is 280-335°C.
19. The method for preparing the polymer according to claim 18, characterized in that, The stirring speed of the paddle-type stirred salt-forming reactor is 10-100 r / min.
20. The method for preparing the polymer according to claim 18, characterized in that, The stirring time of the paddle-type stirred salt-forming reactor is 0.5-6 h.
21. The method for preparing the polymer according to claim 18, characterized in that, The inert atmosphere is a carbon dioxide atmosphere, a nitrogen atmosphere, or an argon atmosphere.
22. The method for preparing the polymer according to claim 21, characterized in that, The conditions for the inert atmosphere are as follows: evacuate the apparatus for the salt formation reaction for 3-10 minutes, introduce inert gas to atmospheric pressure, and cycle 5-10 times.
23. The method for preparing the polymer according to claim 18, characterized in that, The concentration of polyamide in the salt solution after the salt formation reaction is 45-55 wt%.
24. The method for preparing the polymer according to claim 18, characterized in that, The diamine monomer is selected from aliphatic diamines with 5 to 20 carbon atoms.
25. The method for preparing the polymer according to claim 24, characterized in that, The diamine monomer is one or more selected from pentamethylenediamine, hexamethylenediamine, heptaethylenediamine, octanediamine, nonanediamine, decanediamine, undecanediamine, and dodecanediamine.
26. The method for preparing the polymer according to claim 18, characterized in that, The dicarboxylic acid monomer is selected from aromatic dicarboxylic acids and / or aliphatic dicarboxylic acids with 4 to 18 carbon atoms.
27. The method for preparing the polymer according to claim 26, characterized in that, The diacid monomer is one or more of the following: glutaric acid, adipic acid, octanoic acid, sebacic acid, terephthalic acid, isophthalic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, and hexadecanoic acid.
28. The method for preparing the polymer according to claim 18, characterized in that, The polyamide salt is one or more of the following: caprolactam, 11-aminoundecanoic acid, dodecalactam, polyamide 56 salt, polyamide 5T salt, polyamide 66 salt, polyamide 6T salt, polyamide 10T salt, polyamide 12T salt, polyamide 610 salt, polyamide 612 salt, polyamide 1010 salt, polyamide 1012 salt, and polyamide 1212 salt.
29. A polymer, characterized in that, It is prepared using the polymer preparation system as described in claim 14 or 15 or the polymer preparation method as described in any one of claims 17-28.