Search

CN-122008433-A - Granulation process of high-toughness PTT resin with crystallinity regulated and controlled through multistage cooling

CN122008433ACN 122008433 ACN122008433 ACN 122008433ACN-122008433-A

Abstract

The invention relates to the technical field of high polymer material molding processing, and discloses a granulating process of high-toughness PTT resin with crystallinity regulated and controlled by multistage cooling, which sequentially completes granulation through PTT particle fusion conveying and pretreatment, quenching, gradient cooling treatment, granulating stretching and post-treatment to obtain the high-toughness PTT resin, and a gradient crystal structure is constructed in PTT particles through multistage cooling cooperative regulation and control to control the thickness and crystallinity of the surface layer of the particles, so that the resin particles form a gradient structure with low crystallinity and small grain size, sufficient toughness is provided, excellent impact resistance and mechanical strength are provided, process controllability is strong, raw material and equipment suitability is good, and industrial large-scale production of the high-toughness PTT resin can be realized.

Inventors

  • ZHOU QIANG
  • WU GANG
  • ZUO ZILONG
  • HUANG JIE
  • ZHANG ZEHUA

Assignees

  • 宁波巨化化工科技有限公司

Dates

Publication Date
20260512
Application Date
20260211

Claims (10)

  1. 1.A granulation process of high-toughness PTT resin with crystallinity regulated and controlled by multistage cooling is characterized by comprising the following steps: Melting PTT particles at 240-260 ℃ and conveying the PTT particles to a gear pump through a melt pipeline for pretreatment to obtain melt strips; Quenching, namely cooling 5% -8% ethanol aqueous solution containing 0.08% of antioxidant 168 to 8-12 ℃, and carrying out reverse jet cooling on the melt strip prepared in the step one through an annular jet tank, and carrying out quenching to obtain quenched melt strip; step three, gradient cooling, namely sequentially conveying the melt strip quenched in the step two into three-stage serial temperature control cooling tanks for cooling treatment to obtain a melt strip subjected to gradient cooling; Cutting the melt strip subjected to gradient cooling by adopting a high-speed cutter device, and conveying the cut particles into a double-roller stretcher to obtain stretched particles; And step five, post-treatment, namely carrying out gradient drying and cooling on the particles stretched in the step four through a warm water conveying tank to obtain the high-toughness PTT resin.
  2. 2. The granulation process of the high-toughness PTT resin with the crystallinity regulated and controlled by multistage cooling according to claim 1, wherein the gear pump pressure in the first step is 18-20 MPa, and the rotating speed is 40-50 r/min.
  3. 3. The granulation process of the high-toughness PTT resin with the crystallinity regulated and controlled by multistage cooling according to claim 1, wherein in the pretreatment process in the first step, the fluctuation of the viscosity of a melt is controlled to be less than or equal to 0.05dL/g, the melt is uniformly extruded by a heatable die head flow guiding device with the diameter of 2-3 mm and the length of 10mm, and the diameter deviation of a melt bar is controlled to be less than or equal to 0.1mm.
  4. 4. The granulation process of the high-toughness PTT resin with the crystallinity regulated and controlled by multistage cooling according to claim 1, wherein in the quenching treatment in the second step, the flow rate of the inner ring injection port of the annular injection groove is regulated to be 1.5-2.0 m/s, the cooling speed is 150-300 ℃ per second, the cooling time is 1200-1500 ms, the speed of the conveyor belt is 0.6m/s, the molten mass strip is discharged from the groove, the surface temperature of the molten mass strip is reduced to be 50-60 ℃, and the surface crystallinity is controlled to be 10% -15%.
  5. 5. The granulation process of the high-toughness PTT resin with the crystallinity regulated and controlled by multistage cooling according to claim 1, wherein the ethanol aqueous solution containing 0.08wt% of the antioxidant 168 at 8-12 ℃ in the second step is replaced by the 0.1wt% of the antioxidant 1010 aqueous solution at 8-12 ℃.
  6. 6. The granulation process of the high-toughness PTT resin with the crystallinity regulated and controlled through multistage cooling according to claim 1, wherein in the cooling treatment process in the third step, three stages of temperature-controlled cooling tanks are arranged in series, the volume of each stage is 50L, ultrasonic vibration is used in the cooling process, the frequency of the ultrasonic vibration is 20-30 kHz, the power is 500W, the ultrasonic vibration is arranged at the bottom of each stage of cooling unit, the temperature of the primary tank is 40-45 ℃, the residence time is 5s, the temperature of the secondary tank is 30-35 ℃, the residence time is 5s, the temperature of the tertiary tank is 20-25 ℃ and the residence time is 5s, the temperature difference in the control tank is less than or equal to 1 ℃, the temperature of a core layer is steadily reduced from 80-90 ℃ to 30-40 ℃, the crystallinity of the core layer is 25% -30%, and the crystal size is 2-3 mu m after the treatment is completed.
  7. 7. The granulation process of the high-toughness PTT resin with the crystallinity regulated and controlled by multistage cooling according to claim 6, wherein in the third step, ultrasonic vibration can be replaced by stirring, and blade stirring is adopted, wherein the diameter of a blade is 150mm, the temperature of a primary tank is 40-45 ℃, the stirring rotation speed is 80r/min, the residence time is 5s, the temperature of a secondary tank is 30-35 ℃, the stirring rotation speed is 60r/min, the residence time is 5s, the temperature of a tertiary tank is 20-25 ℃, the stirring rotation speed is 50r/min, the residence time is 5s, the temperature difference in a control tank is less than or equal to 1 ℃, the temperature of a core layer is steadily reduced from 80-90 ℃ to 30-40 ℃ after the treatment is completed, the crystallinity of the core layer is 25% -30%, and the crystal size is 2-3 μm.
  8. 8. The granulation process of the high-toughness PTT resin with the crystallinity regulated and controlled by multistage cooling according to claim 1, wherein in the cutting process in the fourth step, the rotating speed of a cutter is 2800-3200 r/min, and the length-diameter ratio of the particles is controlled to be 1 (0.9-1.1).
  9. 9. The granulation process of the high-toughness PTT resin with the crystallinity regulated and controlled by multistage cooling according to claim 1, wherein in the fourth step, in a double-roller stretcher, the roller surface temperature is set to be 55-65 ℃ and the stretching multiplying power is set to be 1.5-2.0 times, the degree of orientation of an induced molecular chain is 15% -20%, and particles with the size deviation of more than 0.5mm are screened and removed.
  10. 10. The granulation process of the high-toughness PTT resin with the crystallinity regulated and controlled by multistage cooling is characterized in that the preparation process of the high-toughness PTT resin in the fifth step is characterized in that the granules stretched in the fourth step are sent into a warm water conveying tank with the temperature of 45-50 ℃ and the water flow rate of 0.6-0.8 m/s, and are subjected to gradient drying after being conveyed for 8-10 min, the drying process is carried out at the temperature of 60 ℃, the wind speed of 1.0m/s and the heat preservation of 30min, the temperature of 70 ℃, the wind speed of 1.2m/s and the heat preservation of 30min, the water content of the granules is controlled to be less than or equal to 0.08% at the temperature of 80 ℃, and the temperature of the granules is reduced to the room temperature by a 25 ℃ cooling conveying belt, so that the high-toughness PTT resin is obtained.

Description

Granulation process of high-toughness PTT resin with crystallinity regulated and controlled through multistage cooling Technical Field The invention relates to the technical field of high polymer material molding processing, in particular to a granulation process of high-toughness PTT resin with crystallinity regulated and controlled by multistage cooling. Background PTT (polytrimethylene terephthalate) is used as crystalline polymer resin with excellent performance, has good chemical stability, processability and biocompatibility, and has wide application prospect in the fields of textile fibers, automobile parts, flexible packages, engineering plastics and the like. The mechanical property of the PTT resin is closely related to the crystallization behavior, the crystallization property is influenced by the thermodynamic parameter of the PTT resin, when the crystallinity is more than 40%, the brittleness of the PTT resin is rapidly increased, the elongation at break is reduced to below 100%, the flexibility of textile fiber products is insufficient, the PTT resin is easy to break, the requirement of the textile fiber products on high toughness cannot be met, and when the crystallinity is less than 20%, the toughness of the PTT resin can be improved to a certain extent, but the tensile strength is greatly reduced, the impact resistance is insufficient, and the PTT resin is difficult to adapt in the scene with higher requirements on brittle fracture resistance. Meanwhile, the crystal size and the distribution uniformity of the PTT resin are critical to the performance stability, if the crystallization process is controlled improperly, the structural difference of amorphous surface layer and coarse core layer crystal easily occurs, so that the PTT product is cracked and deformed due to uneven internal stress in the processing process, and the product qualification rate is seriously affected. In the PTT resin production process, cooling control in the granulation process is a key link, and the cooling system directly influences the crystallinity, crystal size and distribution of PTT by regulating and controlling the temperature reduction rate of the melt, so as to determine the mechanical properties of the final product. In the existing PTT granulation process, a single quenching process is one of the most widely applied mainstream technologies, takes single medium water, liquid nitrogen and the like as cores for rapid cooling, solidifies PTT melt into particles from a molten state, and has the advantages of simple equipment structure, high cooling efficiency and small capacity (less than or equal to 5 tons/day) in adaptation. However, when the technology is used for PTT resin, obvious defects exist, cold water is cooled down excessively fast to cause the instantaneous solidification of PTT particle surface melt, so that a low crystallinity surface layer of 15% -20% is formed, the heat of a core layer cannot be released timely, PTT molecular chains are stacked in sufficient time on the core layer to form coarse crystals with the size of 5-10 mu m, the bonding interface of the amorphous layer of the surface layer and the coarse crystals of the core layer is easy to crack due to internal stress, the toughness and the strength of PTT particles cannot be considered cooperatively, and the product is easy to brittle failure when being stressed. The single gradient cooling process can refine the PTT crystal size to 5-8 mu m through slow cooling, but the overall crystallinity is as high as 35-42%, which is far superior to the requirement of PTT high-toughness application scene, and the requirement of textile fiber and the like on flexibility cannot be met. The gas-cooling and heat-transferring die surface technology is far lower than water in gas heat transfer efficiency, so that the difference of cooling rates between the surfaces and the interiors of PTT particles is overlarge, a reverse gradient structure with high crystallization on the surfaces and low crystallization in the interiors is formed, and the surfaces of PTT products are first brittle when the PTT products are stressed, so that the application range of the PTT products is further limited. In addition, the design of the existing cooling device cannot be accurately matched with the thermodynamic characteristics (Tg is approximately 45 DEG and C, tc is approximately 160 ℃) of PTT, so that the control precision of the PTT crystal grain size is low, and the structure regulation efficiency in industrial production is poor. Meanwhile, the process does not consider the synergy of parameters of cooling, granulating and stretching, such as mismatching of the rotating speed of a cutter and the cooling rate of the PTT melt, so that the deviation of the length-diameter ratio of PTT particles is larger, the uneven crystallization is further aggravated, and the performance qualification rate of the PTT particles produced by the prior process is only about 80%. Theref