A reaction apparatus for a short-process bottle polyester and a method for preparing a bottle polyester using the same

Abstract

The application discloses a kind of short-process bottle polyester reaction equipment and its preparation bottle polyester method, the reaction equipment includes sequentially connected polycondensation reactor, filter, granulator, dryer and de-aldehyde tower;Wherein de-aldehyde tower is vertical tower type structure, and it is equipped with several fluidized bed perforated plate from top to bottom, and the bottom of each layer is equipped with airflow inlet air duct, and top is equipped with airflow outlet air duct;Airflow outlet air duct is sequentially connected with airflow drying purification system and airflow heating system, and airflow heating system is connected with airflow inlet air duct.The bottle polyester produced by the application is compared with SSP technology, and the process is shorter, and the product performance is more excellent, the screw rod temperature of post-processing can be reduced, the product quality is improved, and the breakthrough of green, low energy consumption, high-quality bottle polyester production process technology is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical production, in particular to a short-process bottle polyester reaction equipment and a method for preparing bottle polyester. BACKGROUND

[0002] Bottle polyester is prepared by mixing raw materials ethylene glycol (EG), terephthalic acid (PTA) and isophthalic acid (IPA) into slurry according to a certain molar ratio, completing esterification reaction of the slurry at a certain temperature and pressure to generate bis(2-hydroxyethyl) terephthalate (BHET) and bis(2-hydroxyethyl) isophthalate (BHEI), and then preparing isophthalic acid modified polyethylene terephthalate (PET) through pre-polycondensation and final polycondensation. The intrinsic viscosity of the base bottle polyester is generally 0.62 dL / g, and then the intrinsic viscosity of the PET is increased to more than 0.80 dL / g through solid-phase viscosity increase (SSP). At present, the production process of bottle polyester is mainly divided into solid-phase viscosity increase and liquid-phase viscosity increase. The solid-phase viscosity increase technology is relatively mature, and the representative enterprises include Switzerland Buhler, Italy Enimont, the United States Continental, China Yizheng Chemical Fiber, etc. The technology uses hot nitrogen / air to remove small molecules in the PET solid particles to increase the intrinsic viscosity of the PET, but the technology has problems such as high energy and material consumption, long process flow, uneven molecular weight distribution of the PET product, and much dust. The liquid-phase viscosity increase technology is to make the PET reach a high intrinsic viscosity (generally more than 0.80 dL / g) in the final polycondensation reactor, and then realize the preparation of bottle polyester through low-temperature de-aldehyde technology. The technology has advantages such as low energy and material consumption, uniform intrinsic viscosity inside and outside the particles, and less dust, but puts forward higher requirements for the structural design of the reactor. SUMMARY

[0003] The present application aims to provide a short-process bottle polyester reaction equipment which can reduce production energy consumption, improve product quality and processing performance, and a method for preparing green, low-energy, high-quality bottle polyester.

[0004] The short-process bottle polyester reaction equipment of the present application comprises a polycondensation reactor, a filter, a granulator, a dryer and a de-aldehyde tower which are connected in sequence. The de-aldehyde tower is a vertical tower structure, and a plurality of fluidized bed perforated plates are arranged in the de-aldehyde tower from top to bottom. A gas inlet air duct is arranged at the bottom of each layer, and a gas outlet air duct is arranged at the top of each layer. The gas outlet air duct is connected with a gas flow drying and purifying system and a gas flow heating system in sequence, and the gas flow heating system is connected with the gas inlet air duct.

[0005] Further, melt pumps are arranged between the polycondensation reactor and the filter, and between the filter and the granulator.

[0006] Furthermore, a material outlet is provided at the center of the fluidized bed perforated plate, and a baffle is provided between the airflow outlet duct and the fluidized bed perforated plate to prevent material from entering the duct.

[0007] Furthermore, the lower end of the formaldehyde removal tower is a conical material retention container, and the top of the material retention container is provided with an airflow outlet, and the bottom is provided with an airflow inlet.

[0008] On the other hand, the method for preparing bottle-grade polyester of the present invention includes the following steps:

[0009] (1) Using terephthalic acid, isophthalic acid, and ethylene glycol as raw materials, a polyester melt is obtained through continuous esterification and melt polymerization reactions; wherein terephthalic acid: (66.5~69.25)%, isophthalic acid: (0.25-3)%, ethylene glycol: 30.5%, and phosphoric acid: (0.001~0.002)%.

[0010] (2) The polyester melt is filtered, granulated underwater, and dried to obtain polyester particles;

[0011] (3) Polyester particles are transported to the formaldehyde removal tower by an inert gas flow. An inert gas flow is introduced into the formaldehyde removal tower, and the polyester particles pass through the multi-layer fluidized bed perforated plate in sequence and stay in the material residence container for a period of time. After formaldehyde removal, bottle-grade polyester is obtained.

[0012] Furthermore, in step (1), the intrinsic viscosity of the polyester melt is higher than 0.60 dL / g, the degree of polymerization is 100-135, and the acetaldehyde content is less than 60 μg / g.

[0013] Furthermore, in step (2), underwater granulation equipment is used to produce spherical basic particles with a weight of (1.5~1.8)g per 100 particles. The crystallinity of the particles at the outlet of the vibrating screen is 8~15%, and the temperature is below 90℃.

[0014] Furthermore, in step (3), the temperature of the inert gas flow is greater than 190°C and the gas flow velocity is greater than 0.15 SCFM.

[0015] Furthermore, in step (3), the formaldehyde removal temperature in the formaldehyde removal tower is 170-200℃, and the residence time is 20-40h.

[0016] Furthermore, in step (3), the polyester particles remain in the material residence container for 20 to 40 hours.

[0017] The process involves introducing polyester particles into a dealdehyde removal tower. These particles flow evenly into a fluidized bed perforated plate via an upper material distribution mechanism. A continuous airflow, at a velocity of at least 0.15 SCFM and a temperature of 190–220°C, is introduced from the airflow duct. This high-temperature, high-velocity airflow causes the material to boil and fluidize. The material overcomes gravity under the influence of the high-speed airflow and exits through the central outlet into the next bed layer. The bed height and residence time are adjusted according to different products. After passing through at least one fluidized bed, the residual acetaldehyde content in the material is rapidly reduced to below 10 μg / g. The material then enters a lower residence container, where it remains for 20–40 hours. During this residence, the airflow continuously removes residual acetaldehyde from the polyester polymer particles until the residual acetaldehyde content is below 1 μg / g.

[0018] Compared with conventional solid-phase thickening processes that require pre-crystallizers, crystallizers, and preheaters to improve particle crystallinity and temperature and prevent particle surface adhesion, this invention uses a multi-layer fluidized bed structure. Amorphous or low-crystallinity particles cannot stick together under the action of airflow after passing through the fluidized bed. At the same time, the airflow also provides an external heat source for the particles to heat up, enabling the particles to quickly reach the temperature required for formaldehyde removal.

[0019] The airflow temperature in the formaldehyde removal tower is controlled above 190℃. The formaldehyde removal temperature of the particles in the tower is controlled between 170 and 200℃, and the residence time is controlled between 20 and 40 hours to ensure that the acetaldehyde content in bottled PET products is below 1 μg / g. Under the formaldehyde removal temperature conditions, after fixing the formaldehyde removal temperature, as the residence time increases, small molecules such as acetaldehyde in the particles gradually diffuse and are removed, and the particle viscosity also gradually increases. However, experiments show that when the temperature is fixed, the increase in particle viscosity has a fixed value. After reaching a certain increase, it no longer increases with the extension of residence time. At this point, acetaldehyde continues to be removed until it is less than the national standard requirement of 1.0 μg / g. Based on this study, the correspondence between formaldehyde removal and polymer melt viscosity was determined. By adjusting the intrinsic melt viscosity, a fixed formaldehyde removal process can produce bottled polyester products with a viscosity of at least 0.80 dL / g. This technology is significantly different from SSP, which controls product viscosity by adjusting the solid phase residence time, and the process control is more stable.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0021] (1) The bottle-grade polyester produced by this invention has a crystallinity of less than 50%, a melting enthalpy of less than 55 J / g, a viscosity difference between the inside and outside of the particles of less than 0.01 dL / g, a dust content of less than 10 μg / g, an initial melt plasticizing temperature of less than 205℃, a narrow molecular weight distribution, and a non-acetaldehyde small molecule content of less than 0.5 μg / g in the finished product. The rheological properties of the particles at the screw processing injection molding temperature are significantly improved compared with SSP products, and the screw injection molding temperature can be lowered by more than 10℃. The acetaldehyde content of the injection-molded product is reduced by 15% compared with SSP products, the viscosity of the product is reduced by 24%, and the haze of the product is reduced by 50%.

[0022] (2) The bottle polyester produced by this invention has a shorter process and better product performance compared with SSP technology. It can reduce the temperature of the screw in the post-processing stage, improve product quality, and achieve a breakthrough in green, low-energy consumption and high-quality bottle polyester production process technology. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0025] Bottle-grade polyester chips typically contain 0.25-3% isophthalic acid by weight.

[0026] Example 1

[0027] like Figure 1 As shown, the reaction equipment for short-process bottle polyester of the present invention includes a polycondensation reactor 1, a filter 2, a granulator 3, a dryer 4, and a formaldehyde removal tower 5 connected in sequence; wherein the formaldehyde removal tower 5 is a vertical tower structure, and it is provided with a plurality of fluidized bed porous plates 502 from top to bottom, and each layer is provided with an air inlet duct 503 at the bottom and an air outlet duct 501 at the top; the air outlet duct 501 is connected in sequence to an air drying and purification system 6 and an air heating system 7, and the air heating system 7 is connected to the air inlet duct 503, wherein melt pumps are respectively provided between the polycondensation reactor 1 and the filter 2, and between the filter 2 and the granulator 3.

[0028] The specific formaldehyde removal tower 5 is a tower structure, including a fluidized bed perforated plate 502, a discharge port 505, a material inlet 504, an airflow inlet duct 503, a lower residence container 506, and an airflow inlet duct 503. Several fluidized bed perforated plates 502 are spaced apart on the tower wall. The bottom of each fluidized bed perforated plate 502 has an airflow inlet duct 503 for the inflow of inert gas. An additional airflow inlet duct 503 is located on the upper tower wall above the fluidized bed perforated plates 502 for the outflow of inert gas. The airflow inlet ducts 503 and 504 share a single centrifugal fan.

[0029] The material inlet 504 is located at the top center of the equipment, and the outlet 505 is located at the center of the fluidized bed perforated plate 502. The material inlet 504 and outlet 505 are on the same vertical line. The bottom of the material inlet 504 is partially open, with a central obstruction allowing material to flow out from both sides. The outlet 505 has an opening at its upper end opposite the obstruction at the bottom, while the outlet 505 has no opening at its upper end opposite the material flowing out of the material inlet 504. This design allows material to enter through the material inlet 504 and flow out from both sides, rather than flowing directly out of the outlet 505, instead draining to both sides of the outlet. A material distribution structure is provided at the upper material inlet of the material inlet 504 to ensure uniform material distribution.

[0030] The discharge port 505 includes an inner cylinder and an outer cylinder. The outer cylinder is located outside the inner cylinder and its height is adjustable. When the material needs to remain on the fluidized bed perforated plate 502 for a period of time, the outer cylinder rises, with the height exceeding the height of the highest point of the material, thus preventing the material from flowing into the next layer. When the material needs to flow into the next layer, the height of the outer cylinder decreases, becoming flush with the fluidized bed perforated plate 502, and the material flows into the next layer from the discharge port 505. The lower end of the discharge port 505 is equipped with a barrier identical to the lower end of the material inlet 504, allowing the material to flow out from both sides of the discharge port 505. The lower retention container 506 shares a tower wall with the fluidized bed perforated plate 502. The lower retention container 506 is conical, and the top diameter of the lower retention container 506 is the same as the diameter of the fluidized bed perforated plate 502. There is at least one layer of fluidized bed perforated plates 502, each layer being at least 2 meters high, and the bed layer uses perforated plates with a diameter of at least 1.5 mm. The lower end of the container 506 has an airflow inlet duct 503 and an airflow inlet duct 503 respectively located at diagonal positions on both sides.

[0031] The steps for preparing bottle-grade polyester using the above-described reaction equipment are as follows:

[0032] (1) PET bottle-grade polyester is made from terephthalic acid, isophthalic acid, ethylene glycol, and phosphoric acid. Terephthalic acid accounts for 69.25% of the melt mass, isophthalic acid accounts for 0.25% of the melt mass, ethylene glycol accounts for 30.5% of the melt mass, and phosphoric acid accounts for 0.001% of the melt mass. After pulping, esterification, pre-condensation, and final condensation, the intrinsic viscosity of the final condensation melt is controlled at 0.60 dL / g, and the acetaldehyde content of the melt is 60 μg / g.

[0033] (2) Use underwater granulation equipment to produce spherical basic particles with a weight of 1.5g per 100 particles. The surface temperature of the particles after leaving the water is 90℃ and the crystallinity is 15%.

[0034] The particles are fed into the acetaldehyde removal equipment by nitrogen gas. The fluidized bed of the acetaldehyde removal tower has 5 layers. The air temperature of the acetaldehyde removal tower is 220℃, the fluidized particle temperature is 200℃, the residence time is controlled at 20h, and the acetaldehyde content of the outlet particles is 0.8μg / g.

[0035] (3) The particles leaving the formaldehyde removal tower are cooled by cold air and the residual dust and irregular pieces are removed by a vibrating screen. The final product of bottle polyester has an intrinsic viscosity of 0.80 dL / g, a crystallinity of 50%, a melting enthalpy of 55 J / g, a viscosity difference of 0.01 dL / g between the inside and outside of the particles, an initial melting and plasticizing temperature of 205℃, and a molecular weight distribution index of 2.10.

[0036] Example 2

[0037] The steps for preparing the bottle-grade polyester of the present invention are as follows:

[0038] (1) PET bottle-grade polyester is made from terephthalic acid, isophthalic acid, ethylene glycol, and phosphoric acid. Terephthalic acid accounts for 66.5% of the melt mass, isophthalic acid accounts for 3.0% of the melt mass, ethylene glycol accounts for 30.5% of the melt mass, and phosphoric acid accounts for 0.0015% of the melt mass. After pulping, esterification, pre-condensation, and final condensation, the intrinsic viscosity of the final condensation melt is controlled at 0.65 dL / g, and the acetaldehyde content of the melt is 58 μg / g.

[0039] (2) Use underwater granulation equipment to produce spherical basic particles with a weight of 1.6g per 100 particles. The surface temperature of the particles after leaving the water is 80℃ and the crystallinity is 12%.

[0040] The particles are fed into the acetaldehyde removal tower by nitrogen gas. The acetaldehyde removal tower has 5 fluidized bed layers, the nitrogen temperature in the acetaldehyde removal tower is 200℃, the fluidized particle temperature is 180℃, the residence time is controlled at 35h, and the acetaldehyde content of the outlet particles is 0.9μg / g.

[0041] (3) The particles leaving the formaldehyde removal tower are cooled by cold air and the residual dust and irregular pieces are removed by a vibrating screen. The final product of bottle polyester has an intrinsic viscosity of 0.80 dL / g, a crystallinity of 48%, a melting enthalpy of 52 J / g, a viscosity difference of 0.008 dL / g between the inside and outside of the particles, an initial melting and plasticizing temperature of 204℃, and a molecular weight distribution index of 2.05.

[0042] Example 3

[0043] The steps for preparing the bottle-grade polyester of the present invention are as follows:

[0044] (1) PET bottle-grade polyester is made from terephthalic acid, isophthalic acid, ethylene glycol and phosphoric acid. After pulping, esterification, pre-condensation and final condensation, the intrinsic viscosity of the final condensation melt is controlled at 0.70 dL / g and the acetaldehyde content of the melt is 55 μg / g.

[0045] (2) Use underwater granulation equipment to produce spherical basic particles with a weight of 1.7g per 100 particles. The surface temperature of the particles after leaving the water is 60℃ and the crystallinity is 8%.

[0046] The particles are fed into the acetaldehyde removal equipment by nitrogen gas. The fluidized bed of the acetaldehyde removal tower has 6 layers. The gas flow temperature of the acetaldehyde removal tower is 190℃, the fluidized particle temperature is 175℃, the residence time is controlled at 40h, and the acetaldehyde content of the outlet particles is 0.7μg / g.

[0047] (3) The particles leaving the formaldehyde removal tower are cooled by cold air and the residual dust and irregular pieces are removed by a vibrating screen. The final product of bottle polyester has an intrinsic viscosity of 0.80 dL / g, a crystallinity of 45%, a melting enthalpy of 49 J / g, a viscosity difference between the inside and outside of the particles of 0.006 dL / g, an initial melting and plasticizing temperature of 202℃, and a molecular weight distribution index of 2.00.

[0048] Example 4

[0049] The steps for preparing the bottle-grade polyester of the present invention are as follows:

[0050] (1) PET bottle-grade polyester is made from terephthalic acid, isophthalic acid, ethylene glycol, and phosphoric acid. Terephthalic acid accounts for 67.7% of the melt mass, isophthalic acid accounts for 1.8% of the melt mass, ethylene glycol accounts for 30.5% of the melt mass, and phosphoric acid accounts for 0.002% of the melt mass. After pulping, esterification, pre-condensation, and final condensation, the intrinsic viscosity of the final condensation melt is controlled at 0.75 dL / g, and the acetaldehyde content of the melt is 50 μg / g.

[0051] (2) Use underwater granulation equipment to produce spherical basic particles with a weight of 1.8g per 100 particles. The surface temperature of the particles after leaving the water is 50℃ and the crystallinity is 7%.

[0052] The particles are fed into the acetaldehyde removal equipment by nitrogen gas. The fluidized bed of the acetaldehyde removal tower has 8 layers. The gas flow temperature of the acetaldehyde removal tower is 190℃, the fluidized particle temperature is 170℃, the residence time is controlled at 35h, and the acetaldehyde content of the outlet particles is 0.9μg / g.

[0053] (3) The particles leaving the dealdehyde tower are cooled by cold air and the residual dust and irregular pieces are removed by a vibrating screen. The final product of bottle polyester has an intrinsic viscosity of 0.80 dL / g, a crystallinity of 46%, a melting enthalpy of 50 J / g, a viscosity difference of 0.007 dL / g between the inside and outside of the particles, an initial melting and plasticizing temperature of 201℃, and a molecular weight distribution index of 2.08.

[0054] Example 5

[0055] The steps for preparing the bottle-grade polyester of the present invention are as follows:

[0056] (1) PET bottle-grade polyester is made from terephthalic acid, isophthalic acid, ethylene glycol, and phosphoric acid. Terephthalic acid accounts for 67.7% of the melt mass, isophthalic acid accounts for 1.8% of the melt mass, ethylene glycol accounts for 30.5% of the melt mass, and phosphoric acid accounts for 0.0015% of the melt mass. After pulping, esterification, pre-condensation, and final condensation, the intrinsic viscosity of the final condensation melt is controlled at 0.78 dL / g, and the acetaldehyde content of the melt is 49 μg / g.

[0057] (2) Use underwater granulation equipment to produce spherical basic particles with a weight of 1.7g per 100 particles. The surface temperature of the particles after leaving the water is 50℃ and the crystallinity is 8%.

[0058] The particles are fed into the acetaldehyde removal equipment by nitrogen gas. The fluidized bed of the acetaldehyde removal tower has 8 layers. The gas flow temperature of the acetaldehyde removal tower is 195℃, the fluidized particle temperature is 180℃, the residence time is controlled at 35h, and the acetaldehyde content of the outlet particles is 0.6μg / g.

[0059] (3) The particles leaving the formaldehyde removal tower are cooled by cold air and the residual dust and irregular pieces are removed by a vibrating screen. The final bottle polyester produced has an intrinsic viscosity of 0.85 dL / g, a crystallinity of 49%, a melting enthalpy of 52 J / g, a viscosity difference between the inside and outside of the particles of 0.009 dL / g, an initial melting and plasticizing temperature of 204℃, and a molecular weight distribution index of 2.02.

[0060] Example 6

[0061] The steps for preparing the bottle-grade polyester of the present invention are as follows:

[0062] (1) PET bottle-grade polyester is made from terephthalic acid, isophthalic acid, ethylene glycol, and phosphoric acid. Terephthalic acid accounts for 67.7% of the melt mass, isophthalic acid accounts for 1.8% of the melt mass, ethylene glycol accounts for 30.5% of the melt mass, and phosphoric acid accounts for 0.0015% of the melt mass. After pulping, esterification, pre-condensation, and final condensation, the intrinsic viscosity of the final condensation melt is controlled at 0.80 dL / g, and the acetaldehyde content of the melt is 49 μg / g.

[0063] (2) Use underwater granulation equipment to produce spherical basic particles with a weight of 1.7g per 100 particles. The surface temperature of the particles after leaving the water is 50℃ and the crystallinity is 8%.

[0064] The particles are fed into the acetaldehyde removal equipment by nitrogen gas. The fluidized bed of the acetaldehyde removal tower has 8 layers. The gas flow temperature of the acetaldehyde removal tower is 190℃, the fluidized particle temperature is 175℃, the residence time is controlled at 30h, and the acetaldehyde content of the outlet particles is 0.9μg / g.

[0065] (3) The particles leaving the formaldehyde removal tower are cooled by cold air and the residual dust and irregular pieces are removed by a vibrating screen. The final product of bottle polyester has an intrinsic viscosity of 0.87 dL / g, a crystallinity of 48%, a melting enthalpy of 53 J / g, a viscosity difference between the inside and outside of the particles of 0.008 dL / g, an initial melting and plasticizing temperature of 203℃, and a molecular weight distribution index of 2.04.

[0066] Example 7

[0067] The steps for preparing the bottle-grade polyester of the present invention are as follows:

[0068] (1) PET bottle-grade polyester is made from terephthalic acid, isophthalic acid, ethylene glycol, and phosphoric acid. Terephthalic acid accounts for 67.7% of the melt mass, isophthalic acid accounts for 1.8% of the melt mass, ethylene glycol accounts for 30.5% of the melt mass, and phosphoric acid accounts for 0.0015% of the melt mass. After pulping, esterification, pre-condensation, and final condensation, the intrinsic viscosity of the final condensation melt is controlled at 0.72 dL / g, and the acetaldehyde content of the melt is 58 μg / g.

[0069] (2) Use underwater granulation equipment to produce spherical basic particles with a weight of 1.7g per 100 particles. The surface temperature of the particles after leaving the water is 40℃ and the crystallinity is 7%.

[0070] The particles are fed into the acetaldehyde removal equipment by nitrogen gas. The fluidized bed of the acetaldehyde removal tower has 6 layers. The gas flow temperature of the acetaldehyde removal tower is 195℃, the fluidized particle temperature is 180℃, the residence time is controlled at 32h, and the acetaldehyde content of the outlet particles is 0.8μg / g.

[0071] (3) The particles leaving the dealdehyde tower are cooled by cold air and the residual dust and irregular pieces are removed by a vibrating screen. The final product of bottle polyester has an intrinsic viscosity of 0.80 dL / g, a crystallinity of 47%, a melting enthalpy of 51 J / g, a viscosity difference between the inside and outside of the particles of 0.005 dL / g, an initial melting plasticizing temperature of 200℃, and a molecular weight distribution index of 2.01.

[0072] Comparative Example 1

[0073] PET bottle-grade polyester is made from terephthalic acid, isophthalic acid, ethylene glycol, and phosphoric acid. Terephthalic acid accounts for 67.7% of the melt mass, isophthalic acid for 1.8%, ethylene glycol for 30.5%, and phosphoric acid for 0.0015%. After pulping, esterification, pre-polymerization, and final polymerization, the intrinsic viscosity of the final polymerized melt is controlled at 0.60 dL / g, and the acetaldehyde content is 80 μg / g.

[0074] Columnar basic particles with a weight of 1.7g per 100 particles were produced using a strip granulation equipment. After being cooled to 50°C, the particles passed through a pre-crystallizer, crystallizer, and preheater in the solid-phase thickening process to reach 210°C before being conveyed to the solid-phase thickening reactor. The particles accumulated in a bed inside the reactor, with nitrogen gas introduced at the bottom and escaping from the top. The nitrogen gas temperature at the bottom was 60°C, and the particle temperature inside the reactor was 220°C. The reaction residence time was 18 hours, and the acetaldehyde content of the outlet particles was 0.80μg / g.

[0075] The final product has an intrinsic viscosity of 0.80 dL / g, a crystallinity of 55%, a melting enthalpy of 60 J / g, a viscosity difference between the inside and outside of the particles of 0.015 dL / g, a dust content of 20 μg / g per ton of product, an initial melt plasticizing temperature of 225℃, an acetaldehyde content of 6.5 μg / g in the injection molded product, and a product viscosity of 0.74 dL / g.

[0076] Table 1. Impact of process parameter variations on product performance and finished product performance.

[0077]

Claims

1. A reaction apparatus for polyester in short-flow bottles, characterized in that, The equipment includes a polycondensation reactor (1), a filter (2), a granulator (3), a dryer (4), and a formaldehyde removal tower (5) connected in sequence. The formaldehyde removal tower (5) is a vertical tower structure with several fluidized bed perforated plates (502) from top to bottom. Each layer has an air inlet duct (503) at the bottom and an air outlet duct (501) at the top. The air outlet duct (501) is connected to the air drying and purification system (6) and the air heating system (7) in sequence. The air heating system (7) is connected to the air inlet duct (503). The formaldehyde removal tower includes a fluidized bed perforated plate, a discharge port, a material inlet, a material residence container, and an air inlet duct. The material inlet is located at the top center of the equipment, and the discharge port is located at the center of the fluidized bed perforated plate. The material inlet and the discharge port are located at the same position. On the vertical axis, the bottom of the material inlet is partially open, with a blockage in the middle to allow material to flow out from both sides of the inlet. The upper part of the outlet, opposite the blockage at the bottom of the inlet, has an opening, while the upper part of the outlet, opposite the material flowing out of the inlet, has no opening. The outlet includes an inner cylinder and an outer cylinder, with the outer cylinder located outside the inner cylinder and its height adjustable. When material needs to remain on the fluidized bed perforated plate for a period, the outer cylinder is raised, exceeding the height of the highest point of the material, thus preventing the material from flowing into the next layer. When material needs to flow into the next layer, the outer cylinder is lowered to be flush with the fluidized bed perforated plate, allowing the material to flow into the next layer from the outlet. The lower end of the outlet has the same blockage as the lower end of the material inlet, allowing material to flow out from both sides of the outlet.

2. The reaction apparatus for short-process bottle-type polyester according to claim 1, characterized in that, Melt pumps are installed between the polycondensation reactor (1) and the filter (2), and between the filter (2) and the granulator (3).

3. The reaction apparatus for short-process bottled polyester according to claim 1, characterized in that, The fluidized bed perforated plate (502) has a material outlet in the center, and a baffle is set between the air outlet duct (501) and the fluidized bed perforated plate (502) to block the material from entering the duct.

4. The reaction apparatus for short-process bottle-type polyester according to claim 1, characterized in that, The lower end of the formaldehyde removal tower (5) is a conical material retention container, and the top of the material retention container is provided with an airflow outlet and the bottom is provided with an airflow inlet.

5. A method for preparing bottle-grade polyester using the short-process bottle-grade polyester reaction equipment according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Using terephthalic acid, isophthalic acid and ethylene glycol as raw materials, polyester melt is obtained through continuous esterification and melt polymerization reaction; the intrinsic viscosity of polyester melt is higher than 0.60 dL / g, the degree of polymerization is 100~135, and the acetaldehyde content is less than 60 μg / g; (2) The polyester melt is filtered, granulated underwater, and dried to obtain polyester particles; (3) Polyester particles are transported to the formaldehyde removal tower by an inert gas flow. An inert gas flow is introduced into the formaldehyde removal tower, and the polyester particles pass through the multi-layer fluidized bed perforated plate in sequence and stay in the material residence container for a period of time. After formaldehyde removal, bottle-grade polyester is obtained.

6. The method for preparing bottle-grade polyester according to claim 5, characterized in that, In step (2), the surface temperature of the particles after underwater granulation is less than 90°C after leaving the water, and the crystallinity is 8~15%.

7. The method for preparing bottle-grade polyester according to claim 5, characterized in that, In step (3), the temperature of the inert gas flow is greater than 190°C and the gas flow velocity is greater than 0.15 SCFM.

8. The method for preparing bottle-grade polyester according to claim 5, characterized in that, In step (3), the formaldehyde removal temperature in the formaldehyde removal tower is 170~200℃ and the residence time is 20~40h.

9. The method for preparing bottle-grade polyester according to claim 5, characterized in that, In step (3), the polyester particles stay in the material residence container for 20~40 hours.

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