Novel polyester high-viscosity slicing process

Abstract

The invention discloses a novel polyester high-viscosity slicing process, and relates to the technical field of polyester slicing, a melt with the viscosity of 0.75-0.88 dl / g is produced by optimizing the ratio of raw materials and controlling staged esterification and polycondensation reaction in combination with a long-time low-temperature dealdehyding process of a vertical dealdehyding reactor, the melt reaches a granulator through a melt conveying pipeline with a short path, and the high-viscosity polyester is obtained. Then, a high-temperature underwater die head pelletizing method is adopted, it is guaranteed that polyester chips at an outlet of the pelletizer have the needed crystallinity, the chips discharged from the pelletizer are conveyed to a vertical dealdehyding reactor through hot air and stay for a certain time so as to reduce the aldehyde content in the polyester chips, and the final product chips are cooled through cooling equipment and then are discharged out of the vertical dealdehyding reactor. Compared with the prior art, the method has the advantages that the glossiness and the uniformity of the obtained slice finished product are higher, the color of the product is better, the aldehyde content is lower, and the quality is better.

Description

Technical Field

[0001] The present invention relates to the technical field of polyester chips, and more specifically, to a new process for high-viscosity polyester chips. Background Art

[0002] Currently, the resin using transparent outer packaging materials in the market is generally bottle-grade polyester. Bottle-grade polyester is made by mixing terephthalic acid (PTA), ethylene glycol (EG), and the third monomer isophthalic acid (IPA) in a certain molar ratio to form a slurry, carrying out an esterification reaction under certain temperature and pressure, and then through pre-polycondensation and final polycondensation reactions to produce bottle-grade base chips. The intrinsic viscosity of bottle-grade base chips is generally 0.59 - 0.62 dL / g, and the intrinsic viscosity of the chips is increased to about 0.8 - 0.9 dL / g through a solid-phase viscosity-increasing system such as crystallization, preheating, and reaction of the base chips.

[0003] Currently, the mature process for producing bottle-grade polyester is solid-phase viscosity-increasing technology. Representative technologies include the Buhler process in Switzerland, the Xingke process in Italy, the ContiTech process in the United States, etc. Most of these technologies use hot nitrogen / air to remove small molecules in PET solid particles to increase the intrinsic viscosity of PET. However, this technology has problems such as high energy consumption and material consumption, uneven molecular weight distribution of PET products, and a large amount of dust. Moreover, during the melt transportation process, the melt filter is in the form of horizontal inlet and horizontal outlet, the melt transportation pipeline is relatively long, generating more by-products, increasing the energy consumption of the subsequent process, and also affecting the product color. Summary of the Invention

[0004] The purpose of the present invention is to provide a new process for high-viscosity polyester chips to solve the above problems.

[0005] To achieve the above purpose, the technical solution provided by an embodiment of the present invention is as follows: A new process for high-viscosity polyester chips, comprising the following steps: S1. Take purified terephthalic acid (PTA) and isophthalic acid (IPA) and stir and mix them with ethylene glycol (EG) to form a slurry, wherein: the weight percentage of ethylene glycol is 29 - 30%, and the weight percentage of terephthalic acid and isophthalic acid is 70 - 71%; in the mixed acid, the weight percentage of isophthalic acid is 1.8 - 2.2%, and the weight percentage of terephthalic acid is 97.8 - 98.2%. The prepared slurry is successively subjected to an esterification reaction, a pre-polycondensation reaction, and a final polycondensation reaction.

[0006] S2. The final polymerization reactor is directly connected to the material pump, and the material filter is in the form of upper inlet and lower outlet, and reaches the pelletizer through a melt transportation pipeline with a shorter path; S3. The pelletizer uses the method of underwater pelletizing at high temperature to ensure that the produced pellets have the required crystallinity and will not stick or block during hot air transportation. After the high-temperature water and pellets are discharged together, the water is separated, and the separated water is recycled for the pelletizer. S4. The pellets are transported to a vertical aldehyde removal reactor by heated compressed air to remove acetaldehyde in the product. S5. The final product slices are cooled to below 60°C by a cooling device and then pneumatically conveyed to a finished product bin for packaging.

[0007] As a further improvement of the present invention, the prepared slurry in step S1 includes the following reaction steps: S11. The prepared slurry is fed into an esterification reactor for reaction. The esterification reaction is divided into a first esterification reaction and a second esterification reaction. The temperature of the first esterification reaction is controlled at 255 - 260°C, the reaction pressure is controlled at 50 - 80 kPa, the reaction time is 3.5 - 4 h. After the first esterification reaction, the esterification rate of the reaction is 90 - 92%. S12. The esterified product enters the second esterification reactor from the first esterification reactor for further esterification reaction. The temperature of the second esterification reaction is controlled at 264 - 268°C, the reaction pressure is controlled at 10 - 20 kPa, the reaction time is 1.5 - 4 h. After the second esterification reaction, the esterification rate of the reaction is 96 - 97%. S13. The esterified material enters the polycondensation reaction, including pre-polycondensation and final polycondensation reactions. Among them, the pre-polycondensation reaction includes a first pre-polycondensation and a second pre-polycondensation. The reaction temperature of the first pre-polycondensation is controlled at 270 - 274°C, the reaction pressure is 10 - 15 kPaA, the reaction time is controlled at 45 - 60 min, and the viscosity of the prepolymer after the reaction is 0.1 - 0.15 dl / g. The reaction temperature of the second pre-polycondensation is controlled at 274 - 276°C, the reaction pressure is 1 - 2 kPaA, the reaction time is 60 min, and the viscosity of the prepolymer after the reaction is 0.25 - 0.3 dl / g. S14. The polyester prepolymer enters the final polymerization reactor for polymerization. The reaction temperature is controlled at 280 - 284°C, the reaction pressure is controlled at 100 - 150 PaA, the reaction time is 2.5 - 3.5 h, and the viscosity of the finally produced polyester melt can reach 0.75 - 0.88 dl / g.

[0008] As a further improvement of the present invention, a sealing cabin is installed at the pelletizing chamber of the pelletizer in step S2, a plurality of evenly distributed die holes are arranged on the die head of the pelletizing chamber, a pelletizing assembly is installed in the pelletizing chamber, the pelletizing assembly is driven by a driving motor, an annular air chamber is opened in the sealing cabin, a pulse airflow assembly is slidably installed in the annular air chamber, a magnetic field generator corresponding to the pulse airflow assembly is fixedly installed at the outer end of the sealing cabin, the pelletizing assembly is driven by the driving motor to rotate, the melt output from the die hole is pelletized, and an AC magnetic field is applied by the magnetic field generator, adsorption and repulsion forces are periodically applied to the pulse airflow assembly, so that it moves back and forth in the annular air chamber, and the internal gas is compressed and transported to generate a pulse airflow, the pulse airflow synchronously generates bubbles, enhances the cooling effect, reduces melt adhesion, and can cause turbulent disturbance of the water body to assist particle separation, reduce the risk of agglomeration, and assist in cleaning the residual melt in the blade gap.

[0009] As a further improvement of the present invention, the pulse airflow component comprises: An annular piston is slidably mounted in the annular air chamber and is used to compress and transport the gas in the annular air chamber; An annular magnet is fixedly mounted on the back of the annular piston and is used to cooperate with the magnetic field of the magnetic field generator; A plurality of elastic stretching members are fixedly connected between the annular piston and the bottom wall of the annular air chamber to provide a buffering effect; A plurality of gas flow channels are arranged in an annular array on one side of the annular gas chamber close to the pelletizing chamber, and penetrate the sealed cabin to maintain communication with the pelletizing chamber.

[0010] As a further improvement of the present invention, the pulse airflow component also includes an air supply pipeline connected to the annular air chamber, a one-way valve is installed on the air supply pipeline and extends to the outside to be connected to a balancing air pump.

[0011] As a further improvement of the present invention, the air distribution assembly includes a pair of protective plates and a waterproof breathable membrane embedded between the pair of protective plates. The protective plates are provided with a plurality of evenly distributed air holes. The protective plates play a role in protecting and shaping the waterproof breathable membrane to prevent it from being excessively deformed and damaged by the airflow. The airflow can be quickly and evenly released into the pelletizing chamber through the air holes to exert its effect.

[0012] As a further improvement of the present invention, the vibration assembly includes an extension column, on the outer surface of which a plurality of uniformly distributed vibration microspheres are provided. An elastic connecting piece is fixedly connected between the vibration microspheres and the extension column. The extension column can disperse the pulsed air flow so that it fills the entire space to form relatively uniform bubbles. The vibration microspheres can vibrate in cooperation with the air flow of the extension column, which can cause the bubbles to quickly collapse. The water flow turbulence caused by the collapse of the bubbles can break the thermal boundary layer in the pelletizing area, making the contact between the water body and the particles more sufficient, preventing deformation or internal stress cracks of the particles caused by uneven local cooling. At the same time, the vibration microspheres can contact the pellets after pelletizing randomly at the conveying path, which can not only prevent the agglomeration of particles, but also flatten the burrs or cutting marks on the surface of the particles, producing an effect similar to "polishing". In addition, the vibration microspheres on its surface can not only act as a polishing medium, but also fully cause the turbulence of the water body and accelerate the collapse of the bubbles when vibrating.

[0013] As a further improvement of the present invention, the pelletizing assembly includes: A driving shaft that penetrates the sealed chamber and extends to the outside to be connected to the output end of the driving motor; A cutter head fixedly installed at one end of the driving shaft away from the driving motor; A plurality of pelletizing blades are annularly arrayed on the outer surface of the cutter head and correspond to the die holes, and are used for pelletizing the melt; As a further improvement of the present invention, the pelletizing assembly further includes a plurality of magnetic conductive sheets fixedly connected to the pelletizing blades and used to vibrate in cooperation with the magnetic field of the magnetic field generator. The pelletizing blades will also be affected by the magnetic field to form high-frequency vibration under the assistance of the magnetic conductive sheets, which has obvious advantages in reducing adhesion, lowering the shear force and improving the surface finish. In addition, the vibration causes the bubbles to collapse on the surface of the die holes, generating high-frequency micro-impacts, breaking the adhesion layer between the melt and the die holes and the pelletizing blades. Finally, the turbulence after the collapse of the bubbles can push the particles to disperse quickly in the water, avoiding particle accumulation and blockage. Compared with the prior art, the gloss and flatness of the pelletized product are higher, the quality is better, especially for high-viscosity materials, reducing the phenomena of particle drawing or trailing, and improving the pelletizing neatness.

[0014] As a further improvement of the present invention, in step S4, the vertical aldehyde removal reactor controls the reaction temperature at 150°C - 180°C to prevent the product from oxidizing and aging and ensure the product quality. The product stays in the vertical aldehyde removal reactor for 12 - 18 hours to remove acetaldehyde in the product.

[0015] Compared with the prior art, the advantages of the present invention are as follows: (1) By optimizing the raw material ratio and controlling the esterification and polycondensation reactions in stages, and combining the long-time low-temperature aldehyde removal process in the vertical aldehyde removal reactor, a melt with a viscosity as high as 0.75-0.88 dl / g is produced. It reaches the pelletizer through a melt conveying pipeline with a shorter path, and then the method of high-temperature underwater die head pelletizing is adopted to ensure that the polyester chips at the outlet of the pelletizer have the required crystallinity. The chips coming out of the pelletizer are conveyed to the vertical aldehyde removal reactor by hot air and kept for a certain residence time to reduce the aldehyde content in the polyester chips. After the final product chips are cooled by the cooling equipment, they are pneumatically conveyed to the finished product bin for packaging. Compared with the prior art, the chip products obtained by the present invention have higher gloss and neatness, better product color, lower aldehyde content, and better product quality; (2) In this solution, a magnetic field is used to drive a ring piston to periodically compress gas in a sealed chamber, generating a high-frequency and controllable microbubble flow and injecting it into the pelletizing chamber, forming a synergistic effect of dynamic cooling and turbulent disturbance. The local high pressure and microjet generated when the bubbles collapse can effectively break the surface tension of the melt, assisting the blade in shearing and crushing the high-viscosity melt, significantly reducing the phenomenon of particle trailing or wire drawing, and improving the neatness of the pelletizing edge. At the same time, the microbubbles carried by the pulsed air flow form a uniformly distributed turbulent flow field in the cooling water phase. By enhancing the contact efficiency between the water body and the particle surface, it accelerates the rapid dissipation of the melt heat, solves the problem of local temperature difference caused by the stagnation of the thermal boundary layer in traditional cooling, and prevents the particles from deforming or having internal stress concentration due to uneven cooling, especially suitable for polyester materials sensitive to crystallinity. In addition, the directional scouring effect of the pulsed air flow can clean the residual melt in the blade gap in real time, avoid tool wear or particle contamination caused by material accumulation and carbonization, extend the continuous operation period of the equipment. This non-contact air flow assistance mechanism not only avoids the structural fatigue caused by mechanical vibration but also realizes multi-dimensional optimization of cooling efficiency, particle separation, and equipment maintenance cost by precisely controlling the bubble size and pulse frequency; (3) In this solution, due to the magnetostrictive effect generated by the magnetic conductive sheet under the action of a high-frequency alternating magnetic field, the pelletizing blade superimposes a small-amplitude high-frequency vibration while rotating and cutting, forming a dynamic shearing mode. This vibration periodically changes the contact state between the blade and the melt, converting the traditional continuous shearing into transient pulse cutting, greatly reducing the mechanical load required for single shearing, thereby reducing the adhesion force of the high-viscosity melt to the blade, effectively solving the problem of particle adhesion or caking. The vibration effect can also cause microscopic plastic deformation of the melt at the moment of cutting, forming a denser crystalline layer on the particle surface, significantly improving the smoothness and edge smoothness of pelletizing, reducing the process requirements for subsequent polishing or surface treatment. In addition, the micro shock waves generated by the high-frequency vibration can penetrate the melt surface layer, promoting the uniform arrangement of internal molecular chains, and further optimizing the crystallization performance and mechanical consistency of the particles. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of the overall structure of the pelletizer of the present invention; Figure 2 Schematic structure of the pelletizing chamber part of the present invention Figure 1 ; Figure 3 Schematic structure of the pelletizing chamber part of the present invention Figure 2 ; Figure 4 Schematic structure diagram of the gas distribution component and the vibration component of the present invention; Figure 5 Schematic structure diagram of the annular gas chamber part of the present invention.

[0017] Explanation of the reference numerals in the figure: 1, pelletizing chamber; 2, drive motor; 3, sealed cabin; 4, die hole; 5, magnetic field generator; 6, pelletizing component; 601, drive shaft; 602, cutter head; 603, pelletizing blade; 604, magnetic conductive sheet; 7, gas distribution component; 701, protective disc; 702, waterproof and breathable membrane; 703, ventilation hole; 8, vibration component; 801, extension column; 802, vibration microsphere; 803, elastic connecting piece; 9, pulse gas flow component; 901, annular piston; 902, annular magnet; 903, elastic tension piece; 904, gas flow channel; 905, air supply pipeline; 906, balance air pump. Specific implementation mode

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention; obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Embodiment

[0019] A new type of polyester high-viscosity chip process includes the following steps: Raw material ratio and esterification reaction: The weight percentage of ethylene glycol is 29%, and the weight percentage of terephthalic acid and isophthalic acid is 71%; in the mixed acid, the weight percentage of isophthalic acid is 1.8%, and the weight percentage of terephthalic acid is 98.2%.

[0020] First esterification reaction: temperature 258°C, pressure 65 kPa, reaction time 3.8 h, esterification rate reaches 91%.

[0021] Second esterification reaction: temperature 266°C, pressure 15 kPa, reaction time 3 h, esterification rate reaches 96.5%.

[0022] Polycondensation and final condensation reaction: First pre - polycondensation: Temperature 272°C, pressure 12 kPaA, time 50 min, viscosity of prepolymer 0.12 dl / g.

[0023] Second pre - polycondensation: Temperature 275°C, pressure 1.5 kPaA, time 60 min, viscosity increased to 0.29 dl / g.

[0024] Final polycondensation reaction: Temperature 282°C, pressure 100 PaA, reaction time 3 h, final melt viscosity reaches 0.82 dl / g.

[0025] Pelletizing and de - aldehyde: The pelletizer uses underwater pelletizing at 85°C, and the particles have good crystallinity and no sticking phenomenon.

[0026] De - aldehyde: Temperature of the vertical reactor is 170°C, residence time is 15 h, and the acetaldehyde content is reduced to below 0.8 ppm. Example

[0027] Differing from Example 1, the raw material ratio and esterification reaction: The weight percentage of ethylene glycol is 29%, and the weight percentage of terephthalic acid and isophthalic acid is 71%; in the mixed acid, the weight percentage of isophthalic acid is 2.2%, and the weight percentage of terephthalic acid is 97.8%.

[0028] First esterification reaction: Temperature 255°C, pressure 80 kPa, reaction time 3.5 h, esterification rate 90%.

[0029] Second esterification reaction: Temperature 264°C, pressure 20 kPa, reaction time 1.5 h, esterification rate 96.5%.

[0030] Polycondensation and final polycondensation reaction: First pre - polycondensation: Temperature 270°C, pressure 15 kPaA, time 45 min, viscosity of prepolymer 0.1 dl / g.

[0031] Second pre - polycondensation: Temperature 274°C, pressure 2 kPaA, time 60 min, viscosity increased to 0.25 dl / g.

[0032] Final polycondensation reaction: Temperature 280°C, pressure 140 PaA, reaction time 2.5 h, final viscosity 0.78 dl / g.

[0033] Pelletizing and de - aldehyde: The temperature of high - temperature water pelletizing is 80°C, and the recycling water efficiency after particle separation reaches 95%.

[0034] De - aldehyde: Temperature of the reactor is 160°C, residence time is 16 h, and the acetaldehyde content is reduced to below 1.0 ppm. Example

[0035] The difference compared with Example 1 is that the raw material ratio and esterification reaction are: The weight percentage of ethylene glycol is 30%, and the weight percentage of terephthalic acid and isophthalic acid is 70%. In the mixed acid, the weight percentage of isophthalic acid is 1.8%, and the weight percentage of terephthalic acid is 98.2%.

[0036] The first esterification reaction: temperature 260°C, pressure 50kPa, reaction time 4h, esterification rate 92%.

[0037] The second esterification reaction: temperature 268°C, pressure 10kPa, reaction time 4h, esterification rate 97%.

[0038] Condensation and final polymerization reaction: The first pre-polycondensation: temperature 274°C, pressure 10 kPaA, time 60 min, prepolymer viscosity 0.15 dl / g.

[0039] Second pre-polycondensation: temperature 276°C, pressure 1 kPaA, time 60 min, viscosity increased to 0.31 dl / g.

[0040] Final polymerization reaction: temperature 284°C, pressure 80 PaA, reaction time 3.5 h, final viscosity 0.875 dl / g.

[0041] Granulation and dealdehyde removal: The high temperature water pelletizing temperature is 90℃, and the particle surface is smooth and has no defects.

[0042] Dealdehydeation: Reactor temperature 175 ° C, residence time 15h, acetaldehyde content dropped to 0.6ppm. Example

[0043] Different from Example 3, in step S2, a sealing cabin 3 is installed at the pelletizing chamber 1 of the pelletizer in a butt-sealed manner, a plurality of evenly distributed die holes 4 are arranged on the die head of the pelletizing chamber 1, a pelletizing assembly 6 is installed in the pelletizing chamber 1, and the pelletizing assembly 6 is driven by a driving motor 2. An annular air chamber is opened in the sealing cabin 3, and a pulse airflow assembly 9 is slidably installed in the annular air chamber. A magnetic field generator 5 corresponding to the pulse airflow assembly 9 is fixedly installed at the outer end of the sealing cabin 3. The pelletizing assembly 6 is driven by the driving motor 2 to rotate, and the melt output from the die hole 4 is pelletized. An alternating magnetic field is applied by the magnetic field generator 5, and adsorption and repulsion forces are periodically applied to the pulse airflow assembly 9, so that it moves back and forth in the annular air chamber, and the internal gas is compressed and transported to generate a pulse airflow. The pulse airflow synchronously generates bubbles, enhances the cooling effect, reduces melt adhesion, and can cause turbulent disturbance of the water body to assist in particle separation, reduce the risk of agglomeration, and assist in cleaning the residual melt in the blade gap.

[0044] Sealed chamber 1 housing: Hastelloy C276, resistant to high temperature of 200 °C and chemical corrosion.

[0045] The pulsed gas flow assembly 9 includes: A ring-shaped piston 901, slidably installed in the annular gas chamber, used to compress and transport the gas in the annular gas chamber, made of silicon carbide ceramic matrix composite material, with extremely strong wear resistance and extremely low friction coefficient; A ring-shaped magnet 902, fixedly installed on the back of the ring-shaped piston 901, used to cooperate with the magnetic field of the magnetic field generator 5; Multiple elastic tension members 903, fixedly connected between the ring-shaped piston 901 and the bottom wall of the annular gas chamber, used to provide a buffering effect. The elastic tension members 903 are made of Inconel 718 spring steel and maintain elasticity at high temperatures; Multiple gas flow channels 904, annularly arrayed on the side of the annular gas chamber close to the pelletizing chamber 1, and penetrate through the sealed chamber 3 to communicate with the pelletizing chamber 1.

[0046] The magnetic field generator 5 applies an alternating magnetic field of 50 - 200 Hz to drive the ring-shaped magnet 902 to drive the piston to reciprocate, compressing the gas to form a pulsed gas flow frequency synchronous magnetic field.

[0047] The pulsed gas flow is injected into the pelletizing chamber 1 through the gas flow channels 904 to generate microbubbles of 0.5 - 2 mm, enhancing the cooling uniformity and flushing the blade gap. The pulsed gas flow assembly 9 further includes a gas supply pipe 905 communicating with the annular gas chamber. A one-way valve is installed on the gas supply pipe 905 and extends to the outside to be connected with a balance air pump 906.

[0048] The gas distribution assembly 7 includes a pair of protective discs 701 and a waterproof and breathable membrane 702 embedded between the pair of protective discs 701. A plurality of uniformly distributed ventilation holes 703 are provided on the protective discs 701. The protective discs 701 play a role in protecting and shaping the waterproof and breathable membrane 702, preventing it from being damaged due to excessive deformation under the action of the gas flow. The gas flow can be quickly and evenly released into the pelletizing chamber 1 through the ventilation holes 703 to play a role.

[0049] The protective disc 701 is made of 316L stainless steel by laser drilling, with a hole diameter of 0.5 mm and a hole spacing of 1 mm. The waterproof and breathable membrane 702 is made of polytetrafluoroethylene PTFE microporous membrane, with a pore diameter of 10 μm and a gas permeability of 5 L / min·cm². The pulsed gas flow is evenly released through the breathable membrane to form a stable bubble flow, avoiding local high pressure from damaging the melt strip.

[0050] The vibration assembly 8 includes an extension column 801. A plurality of uniformly distributed vibration microspheres 802 are arranged on the outer surface of the extension column 801. An elastic connecting member 803 is fixedly connected between the vibration microspheres 802 and the extension column 801. The extension column 801 can disperse the pulsed air flow so that it fills the entire space to form relatively uniform bubbles. The vibration microspheres 802 can vibrate in cooperation with the air flow action of the extension column 801, which can cause the bubbles to quickly collapse. The water flow turbulence caused by the bubble collapse can break the thermal boundary layer in the pelletizing area, making the water body contact the particles more fully, preventing the deformation or internal stress cracks of the particles caused by uneven local cooling. At the same time, the vibration microspheres 802 can make random contacts with the particles after pelletizing at the conveying path, which can not only prevent the agglomeration phenomenon between the particles, but also flatten the burrs or cutting marks on the particle surface, producing an effect similar to "polishing". In addition, the vibration microspheres 802 on its surface can not only act as a polishing medium, but also fully cause the turbulence of the water body and accelerate the collapse of the bubbles when vibrating.

[0051] The vibration microspheres 802 are made of zirconia ceramic balls with a diameter of 3 mm and the surface is polished to Ra < 0.1 μm. The elastic connecting member 803 is made of fluororubber + Kevlar fiber braided layer and can withstand high temperature of 150 °C.

[0052] The pelletizing assembly 6 includes: A drive shaft 601, which penetrates through the sealing chamber 3 and extends to the outside to be connected with the output end of the drive motor 2; A cutter head 602, which is fixedly installed at one end of the drive shaft 601 away from the drive motor 2 and is made of maraging steel 18Ni300, resistant to fatigue deformation; A plurality of pelletizing blades 603, which are annularly and arrayedly installed on the outer surface of the cutter head 602 and correspond to the die holes 4. They are used for pelletizing the melt and are made of tungsten carbide cobalt hard alloy YG8 + diamond-like carbon coating DLC with a hardness of ≥ 3000 HV. Embodiment

[0053] Different from Embodiment 3, the pelletizing assembly 6 further includes a plurality of magnetic conductive sheets 604. The magnetic conductive sheets 604 are fixedly connected to the pelletizing blades 603 and are used to cooperate with the magnetic field of the magnetic field generator 5 for vibration. The pelletizing blades 603 will also be affected by the magnetic field to form high-frequency vibration under the auxiliary action of the magnetic conductive sheets 604, which has obvious advantages in reducing adhesion, reducing shear force and improving surface finish.

[0054] In addition, vibration prompts the bubbles to collapse on the surface of the die hole 4, generating high-frequency micro-impacts, which break the adhesion layer between the melt and the die hole 4 and the pelletizing blade 603. Finally, the turbulence after the bubble collapse can push the particles to disperse rapidly in water, avoiding particle accumulation and blockage. Compared with the prior art, the glossiness and flatness of the pelletized product are higher, the quality is better, especially for high-viscosity materials, reducing the particle drawing or trailing phenomenon and improving the pelletizing neatness.

[0055] The magnetic conductive sheet 604 is made of iron-nickel soft magnetic alloy 1J22 with a magnetic permeability ≥5000, high temperature oxidation resistance, and a CrN coating on the surface. The magnetic field generator 5 applies a high-frequency alternating magnetic field of 1 - 5 kHz. The magnetic conductive sheet generates micro-amplitude vibration due to the magnetostrictive effect, with an amplitude of 10 - 50 μm, reducing the shear resistance. The shear force is reduced by 15% - 25%. The vibration frequency matches the blade rotation speed, forming a "dynamic cutting" effect, and the surface finish of the particles is improved to Ra < 0.8 μm.

[0056] Evaluate the quality indicators of the products obtained from Examples 1 - 5: Example

[0057] Moderate viscosity (0.82 dl / g), low acetaldehyde residue (<0.8 ppm), suitable for high-hygiene standard fields such as food packaging. The energy consumption is not optimized, the dust content is 80 ppm, which has an impact on the deep processing of subsequent products. Example

[0058] Advantages: Viscosity (0.78 dl / g), energy consumption reduced by 10 - 12%, cost reduced, suitable for the production requirements of hot-filling bottles and some industrial sheets.

[0059] Disadvantages: Relatively high acetaldehyde residue (1.0 ppm), only suitable for low-end fields. Example

[0060] Advantages: Extremely low acetaldehyde residue (<0.6 ppm), highest viscosity (0.875 dl / g), meeting the production requirements of carbonated beverage bottles.

[0061] Disadvantages: Energy consumption reduced by about 5%, dust content 50 ppm, still room for improvement. Example

[0062] Innovation points: Through the pulse gas flow and bubble collapse technology, the cooling efficiency is increased by 30%, the adhesion rate is reduced to 0.3%, the surface finish reaches 0.8 μm, and the dust content is significantly reduced.

[0063] Applicability: Suitable for high-end optical materials, avoiding particle thermal deformation and adhesion. Example

[0064] Innovative points: The magnetic conduction sheet undergoes high-frequency vibration (1 - 5 kHz) combined with dynamic cutting, reducing the shear force by 15% - 25%, improving the surface finish to Ra < 0.8 μm, further reducing the dust content, and the adhesion rate is only 0.1%.

[0065] Applicability: Suitable for high-precision electronic packaging materials, with no burrs or wire drawing on the particle surface.

[0066] The following table shows the quality index table of Examples 1 - 5. It can be seen that the final viscosity of the products in Examples 3 - 5 is relatively high, and the acetaldehyde content, adhesion rate, and dust content are significantly reduced, and the final quality of the products is relatively high. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0067] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other implementation manners that can be understood by those skilled in the art.

Claims

1. A novel polyester high-viscosity slicing process, characterized by: The following steps are involved: S1. Take purified terephthalic acid (PTA) and isophthalic acid (IPA) and ethylene glycol (EG) and stir and mix them into slurry, wherein: the weight percentage of ethylene glycol is 29-30%, the weight percentage of terephthalic acid and isophthalic acid is 70-71%; in the mixed acid, the weight percentage of isophthalic acid is 1.8-2.2%, and the weight percentage of terephthalic acid is 97.8-98.2%. The prepared slurry is subjected to esterification reaction, pre-polycondensation reaction and final polycondensation reaction in sequence.

2. S2, the final polymerization reactor is directly connected to the material pump, and the material filter adopts the form of top-in and bottom-out, and reaches the pelletizer through a shorter melt conveying pipeline; S3, the pelletizer uses high-temperature underwater pelletizing to ensure that the produced particles have the required crystallinity, and will not stick or clog during hot air transportation. The high-temperature water and particles are discharged together and the water is separated. The separated water is recycled for the pelletizer; S4, transporting the particles to a vertical acetaldehyde removal reactor by means of heated compressed air to remove acetaldehyde from the product; S5. The final product slices are cooled to below 60°C by cooling equipment and then sent to the finished product silo for packaging.

3. A novel polyester high-viscosity slicing process according to claim 1, characterized in that: The prepared slurry in step S1 includes the following reaction steps: S11, the prepared slurry is sent to the esterification reactor for reaction. The esterification reaction is divided into the first esterification reaction and the second esterification reaction. The temperature of the first esterification reaction is controlled at 255-260°C, the reaction pressure is controlled at 50-80kPa, the reaction time is 3.5-4h, and after the first esterification reaction, the esterification rate of the reaction is 90-92%; S12, the esterified product enters the second esterification reactor from the first esterification reactor for further esterification reaction, the temperature of the second esterification reaction is controlled at 264-268°C, the reaction pressure is controlled at 10-20kPa, the reaction time is 1.5-4h, and after the second esterification reaction, the esterification rate of the reaction is 96-97%; S13, the esterified material enters into polycondensation reaction, including pre-polycondensation and final polycondensation reaction, wherein the pre-polycondensation reaction includes a first pre-polycondensation and a second pre-polycondensation, the reaction temperature of the first pre-polycondensation is controlled at 270-274°C, the reaction pressure is 10-15kPaA, the reaction time is controlled at 45-60min, and the viscosity of the prepolymer after the reaction is 0.1-0.15 dl / g, the reaction temperature of the second pre-polycondensation is controlled at 274-276°C, the reaction pressure is 1-2kPaA, the reaction time is 60min, and the viscosity of the prepolymer after the reaction is 0.25-0.3dl / g.

4. S14, the polyester prepolymer enters the final polymerization reactor for polymerization, the reaction temperature is controlled at 280-284°C, the reaction pressure is controlled at 100-150PaA, the reaction time is 2.5-3.5h, and the viscosity of the final polyester melt can reach 0.75-0.88dl / g.

5. A novel polyester high-viscosity chipping process according to claim 1, characterized in that: In the step S2, a sealed cabin (3) is installed at the pelletizing chamber (1) of the pelletizer in a butt-sealed manner, a plurality of evenly distributed die holes (4) are arranged on the die head of the pelletizing chamber (1), a pelletizing assembly (6) is installed in the pelletizing chamber (1), and the pelletizing assembly (6) is driven by a driving motor (2), an annular air chamber is provided in the sealed cabin (3), a pulse airflow assembly (9) is slidably installed in the annular air chamber, and a magnetic field generator (5) corresponding to the pulse airflow assembly (9) is fixedly installed at the outer end of the sealed cabin (3).

6. A novel polyester high-viscosity slicing process according to claim 3, characterized in that: The pulse airflow component (9) comprises: An annular piston (901) is slidably mounted in the annular air chamber and is used to compress and transport the gas in the annular air chamber; An annular magnet (902) is fixedly mounted on the back of the annular piston (901) and is used to cooperate with the magnetic field of the magnetic field generator (5); A plurality of elastic stretching members (903) are fixedly connected between the annular piston (901) and the bottom wall of the annular air chamber to provide a buffering effect; A plurality of gas flow channels (904) are arranged in an annular array on one side of the annular gas chamber close to the pelletizing chamber (1), and penetrate the sealed cabin (3) to maintain communication with the pelletizing chamber (1).

7. A novel polyester high-viscosity chipping process according to claim 4, characterized in that: The pulse airflow component (9) further comprises an air supply pipeline (905) in communication with the annular air chamber, wherein a one-way valve is installed on the air supply pipeline (905) and the air supply pipeline (905) extends to the outside and is connected to a balancing air pump (906).

8. A novel polyester high-viscosity chipping process according to claim 5, characterized in that: The air distribution assembly (7) comprises a pair of protective plates (701) and a waterproof breathable membrane (702) mounted between the pair of protective plates (701), and the protective plates (701) are provided with a plurality of evenly distributed breathable holes (703).

9. A novel polyester high-viscosity chipping process according to claim 6, characterized in that: The vibration component (8) comprises an extension column (801), a plurality of evenly distributed vibration microspheres (802) are arranged on the outer surface of the extension column (801), and an elastic connecting piece (803) is fixedly connected between the vibration microspheres (802) and the extension column (801).

10. A novel polyester high-viscosity chipping process according to claim 7, characterized in that: The pelletizing assembly (6) comprises: A drive shaft (601) passes through the sealed cabin (3) and extends to the outside to be connected to an output end of the drive motor (2); The cutter disc (602) is fixedly mounted on an end of the drive shaft (601) away from the drive motor (2); A plurality of pelletizing blades (603) are mounted in a circular array on the outer surface of the blade disc (602) and correspond to the die holes (4) for pelletizing the melt.

11. A novel polyester high-viscosity chipping process according to claim 8, characterized in that: The pelletizing assembly (6) further comprises a plurality of magnetic conductive sheets (604), wherein the magnetic conductive sheets (604) are fixedly connected to the pelletizing blades (603) and are used to vibrate in coordination with the magnetic field of the magnetic field generator (5).

12. A novel polyester high-viscosity chipping process according to claim 1, characterized in that: In step S4, the vertical dealdehyde reactor controls the reaction temperature at 150° C.-180° C. to prevent oxidation and aging of the product and ensure product quality. The product stays in the vertical dealdehyde reactor for 12-18 hours to remove acetaldehyde from the product.

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