Production system and production method of copolyester white chips for PETG (Polyethylene Terephthalate Glycol) heat-shrinkable white film

Abstract

The invention discloses a production system of a copolyester white chip for a PETG heat shrinkage white film. The production system comprises a slurry preparation kettle, an esterification kettle I, an esterification kettle II, a titanium dioxide preparation system, a preshrinking kettle I, a preshrinking kettle II, a final shrinkage kettle and a granulator. The preparation method comprises the following steps: preparing a titanium dioxide EG solution in a titanium dioxide preparation system, putting the catalyst, the titanium dioxide EG solution, PTA, EG and CHDM into a slurry preparation kettle, mixing to obtain slurry, enabling the slurry to sequentially pass through an esterification kettle I, an esterification kettle II, a preshrinking kettle I, a preshrinking kettle II and a final shrinkage kettle to obtain PETG melt, and granulating and slicing the PETG melt through a granulator. And adding a titanium dioxide EG solution into the slurry preparation kettle, the esterification kettle I and the esterification kettle II, and finally directly producing white PETG slices, wherein the titanium dioxide concentration in the white PETG slices reaches 18wt%.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and in particular relates to a production system and a production method of copolyester white chips for PETG heat shrinkable white films. Background Art

[0002] PETG material is a transparent plastic, an amorphous copolyester, and its full name is polyethylene terephthalate-1,4-cyclohexanedimethanol. PETG in the prior art is a product of direct esterification and polycondensation of three monomers: terephthalic acid (PTA), ethylene glycol (EG) and 1,4-cyclohexanedimethanol (CHDM).

[0003] The existing PETG heat shrinkable white film production process is to feed PETG slices into the main feeding screw for extrusion and melting, and use another side feeding screw to feed titanium dioxide PETG white masterbatch for extrusion and melting. After that, it is mixed with the PETG melt of the main screw and sent to the film head for film drawing, thereby producing PETG white film.

[0004] Titanium dioxide PETG white masterbatch is made by grinding PETG slices into powder, mixing them with titanium dioxide powder and then melt blending. The intrinsic viscosity of the slices obtained by the blending method is as low as 0.45, and the titanium dioxide is mixed unevenly. In the subsequent white film production, the viscosity difference is too large after mixing with the PETG slice melt with a viscosity of about 0.75, resulting in uneven melt quality during subsequent film drawing and unstable production. Summary of the invention

[0005] The object of the present invention is to provide a production system and a production method of copolyester white chips for PETG heat shrinkable white film, wherein a titanium dioxide preparation tank is connected to an esterification kettle and a second esterification kettle, and a titanium dioxide EG solution is added during the esterification process to make the titanium dioxide concentration in the final finished product chips reach 18wt%.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] PETG heat shrinkable white film copolyester white chip production system, including

[0008] A slurry preparation kettle is used to mix the catalyst, titanium dioxide EG solution, CHDM, PTA and EG according to a proportion to form a slurry;

[0009] Esterification kettle, heating the slurry flowing out of the slurry preparation kettle to carry out esterification reaction to obtain the primary esterification product;

[0010] The second esterification kettle is used to heat the primary esterification product discharged from the first esterification kettle again for esterification to obtain the secondary esterification product;

[0011] A titanium dioxide preparation system, which prepares a titanium dioxide EG solution and flows the titanium dioxide EG solution into a slurry preparation kettle, an esterification kettle 1 and an esterification kettle 2;

[0012] Pre-shrinking the first kettle, and subjecting the secondary esterification product flowing out of the second esterification kettle to pre-polycondensation reaction to obtain the primary pre-shrinkage product;

[0013] The second pre-shrinking kettle is used to perform a pre-condensation reaction on the primary pre-shrinking product flowing out of the first pre-shrinking kettle to obtain a secondary pre-shrinking product;

[0014] The final shrinking kettle is used to polycondense the secondary pre-shrinkage product flowing out of the second pre-shrinking kettle to obtain PETG melt;

[0015] A pelletizer is used to pelletize the PETG melt to obtain copolyester white chips for PETG heat shrinkable white film;

[0016] The first esterification kettle and the second esterification kettle are respectively connected to the titanium dioxide finished product tank of the titanium dioxide EG solution. When the first esterification kettle and the second esterification kettle react, the titanium dioxide EG solution in the titanium dioxide finished product tank is pumped into the first esterification kettle and the second esterification kettle.

[0017] The titanium dioxide preparation system prepares the titanium dioxide EG solution, and the titanium dioxide EG solution is added to the first esterification kettle and the second esterification kettle, and finally white PETG slices are directly produced.

[0018] Furthermore, the first esterification kettle and the second esterification kettle are both connected to the same process tower, and the process tower is connected to the stripping tower.

[0019] The main function of the process tower is to remove the by-product water from the esterification kettle one and the esterification kettle two. The boiling point of EG is 197°, and the boiling point of water is 100°. The EG and water from the esterification kettle one and the esterification kettle two remove the water due to the difference in boiling points.

[0020] The main function of the stripping tower is to reduce the COD of the esterified water from 25000-30000mg / L to about 3500mg / L. The esterified water contains flammable and explosive low-boiling substances (mainly aldehydes and ethers). If it is not sent directly to wastewater treatment through the stripping tower, some organic matter will be directly discharged into the atmosphere during the aeration in the regulating tank. These organic matter directly discharged into the atmosphere through aeration will have a certain impact on the surrounding environment, and there will also be a strong odor on the downwind side of the wastewater treatment. After being treated by the stripping tower, the volatile organic matter is directly sent to the boiler and will not enter the atmosphere after the wastewater treatment. Reducing the burden of wastewater treatment and reducing the cost of wastewater treatment is both energy-saving and environmentally friendly.

[0021] Furthermore, the first pre-shrinking kettle, the second pre-shrinking kettle and the final shrinking kettle are respectively connected to their own scraper condensers, the scraper condensers are connected to vacuum jet pumps, the vacuum jet pumps are connected to the EG evaporator and the leaching tower, and a liquid ring vacuum pump is connected between the leaching tower and the vacuum jet pump.

[0022] The viscosity of the material is increased through gradual polycondensation reactions in three polycondensation reactors, and the vacuum degree in the reactor is gradually reduced to extract the small molecules produced by the reaction.

[0023] Polycondensation kettle 1, polycondensation kettle 2 and final polycondensation kettle are equipped with independent scraper condensers. The main function of the scraper condenser is to capture EG vapor, water vapor and other small molecules and oligomers entrained in the system by alternating hot and cold. Small molecule vapor is captured by EG spraying in the EG circulation system, and oligomers are captured by scrapers, hot well baskets, residue boxes and filters. The non-condensable gas in the polycondensation system is extracted by vacuum jet pumps and liquid ring vacuum pumps. The EG evaporator generates power steam for the vacuum system. The steam generates vacuum through three-stage injection and spraying to extract the small molecule gas in the reactor.

[0024] Furthermore, the titanium dioxide preparation system includes a preparation tank, a finished product tank, a finished product delivery pump, and a finished product filter. Titanium dioxide and EG solution are stirred in the preparation tank to form a titanium dioxide EG solution initial material. After the titanium dioxide EG solution initial material flows into the finished product tank, it passes through the finished product delivery pump and the finished product filter to obtain a titanium dioxide EG solution.

[0025] The production method using the copolyester white chip production system for PETG heat shrinkable white film comprises the following steps:

[0026] (1) Preparing titanium dioxide EG solution in the titanium dioxide preparation system;

[0027] (2) preparing the catalyst, placing the catalyst, titanium dioxide EG solution, PTA, EG and CHDM into a slurry preparation kettle and mixing them into a slurry;

[0028] (3) The slurry in the slurry preparation kettle enters the esterification kettle No. 1 for esterification reaction, and at the same time, the titanium dioxide EG solution in the titanium dioxide finished product tank is added to the esterification kettle No. 1 according to a set ratio to prepare a primary esterification product;

[0029] (4) The primary esterification product in the first esterification kettle enters the second esterification kettle for another esterification reaction, and at the same time, the titanium dioxide EG solution in the titanium dioxide finished product tank is added to the second esterification kettle according to a set ratio to prepare a secondary esterification product;

[0030] (5) the secondary esterification product in the second esterification kettle enters the first pre-condensation kettle for pre-condensation reaction to obtain the primary pre-condensation product;

[0031] (6) the primary pre-shrinked product in the first pre-shrinking kettle enters the second pre-shrinking kettle for another pre-shrinking polycondensation reaction to obtain a secondary pre-shrinked product;

[0032] (7) The secondary pre-shrinkage product in the second pre-shrinkage kettle enters the final shrinkage kettle for polycondensation reaction to obtain PETG melt;

[0033] (8) The PETG melt enters the pelletizer through a melt pump for pelletizing and slicing.

[0034] Preferably, the catalyst in step (2) is a titanium catalyst with a concentration of 0.5 wt %. Common titanium catalysts include tetrabutyl titanate.

[0035] Preparation method: Add a certain amount of EG to the preparation tank, turn on the agitator, add a certain amount of titanium catalyst solution (5wt% concentration), stir for one hour, and obtain a titanium catalyst solution with a concentration of 0.5wt%. After qualified analysis, move the material to the finished product tank.

[0036] Preferably, the concentration of the titanium dioxide EG solution in step (2), step (3) and step (4) is 30 wt %, in step (3), the titanium dioxide EG solution is added at a concentration of 6.7 wt %, and in step (4), the titanium dioxide EG solution is added at a concentration of 6 wt %.

[0037] The mass concentration of the titanium dioxide EG solution in step (2), step (3) and step (4) is 55%. The titanium dioxide concentration of 55% is the solid content. The titanium dioxide with a concentration of 55% is adjusted to the required concentration by adding EG. The titanium dioxide solution weighs 1820 kg and has a concentration of 55%. All of it is put into the titanium dioxide preparation tank. After adding a certain amount of EG to dilute it, a titanium dioxide solution with a concentration of 30% is prepared. After the analysis is qualified, the titanium dioxide is moved to the titanium dioxide finished product tank.

[0038] Preferably, in step (2), the molar ratio of PTA, EG, CHDM and titanium dioxide is 120:10-20:10-20:10-20.

[0039] In step (1), the titanium content in the catalyst in the slice is 10-20PPM, and the amount of titanium dioxide EG solution added is calculated in the slurry tank according to the titanium dioxide concentration in the final slice reaching 8%, in esterification one according to the concentration in the final slice reaching 15%, and in esterification two according to the concentration in the final slice reaching 18%.

[0040] The unit consumption of PTA, EG, CHDM and titanium dioxide in the final product are 0.63, 0.19, 0.18 and 0.18 respectively.

[0041] Preferably, the reaction temperature in step (3) and step (4) is 250-265° C., the reaction pressure in step (3) is 50 Kpa-100 Kpa gauge pressure, the reaction pressure in step (4) is 8-14 Kpa gauge pressure, the reaction temperature in step (5) and step (6) is 269-285° C., the reaction pressure in step (5) is 10 Kpa absolute pressure, and the reaction pressure in step (6) is 1 Kpa absolute pressure.

[0042] Preferably, in step (1), sodium tripolyphosphate is added into the preparation tank, and the mass ratio of sodium tripolyphosphate to titanium dioxide is 1:400.

[0043] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0044] The titanium dioxide EG solution was added to the slurry preparation kettle, the first esterification kettle and the second esterification kettle using a titanium dioxide preparation system. The titanium dioxide EG solution was added during the esterification process, and finally white PETG slices were directly produced, and the titanium dioxide concentration in the slices reached 18wt%.

[0045] This method has high slice viscosity and uniform mixing of titanium dioxide. The side feeding screw is omitted during downstream film drawing processing, which saves electricity and equipment investment and improves product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention will be further described below with reference to the accompanying drawings.

[0047] Figure 1 This is a schematic diagram of the structure of the copolyester white chip production system for PETG heat shrinkable white film. DETAILED DESCRIPTION

[0048] like Figure 1 The copolyester white chip production system for PETG heat shrinkable white film shown includes slurry preparation kettles 1 connected in sequence, which mix the catalyst, titanium dioxide EG solution, CHDM, PTA and EG in the raw materials according to a proportion to form slurry;

[0049] The first esterification kettle 2 heats the slurry pumped into the slurry preparation kettle 1 to carry out esterification reaction to obtain a primary esterification product;

[0050] The second esterification kettle 3 heats the primary esterification product flowing out of the first esterification kettle 2 again for esterification to obtain a secondary esterification product;

[0051] A titanium dioxide preparation system 4 is used to prepare a titanium dioxide EG solution and pump the titanium dioxide EG solution into a slurry preparation kettle 1, an esterification kettle 1 and an esterification kettle 2 and a second esterification kettle 3 through a titanium dioxide delivery pump;

[0052] The first pre-shrinking kettle 5 is used to perform a pre-polycondensation reaction on the secondary esterification product flowing out of the second esterification kettle 3 to obtain a primary pre-shrinking product;

[0053] The second pre-shrinking kettle 6 is used to perform a pre-polycondensation reaction on the primary pre-shrinking product flowing out of the first pre-shrinking kettle 5 to obtain a secondary pre-shrinking product;

[0054] The final shrinking kettle 7 carries out polycondensation reaction on the secondary pre-shrinking product flowing out of the second pre-shrinking kettle 6 to obtain a PETG melt;

[0055] The pelletizer 8 pelletizes the PETG melt to obtain copolyester white chips for PETG heat shrinkable white film.

[0056] The first esterification kettle 2 and the second esterification kettle 3 are both connected to the same process tower 17. The EG and water in the first esterification kettle 2 and the second esterification kettle 3 are separated by the process tower 17. The separated EG flows into the first esterification kettle 2 and the second esterification kettle 3 to continue the reaction, and the separated waste water flows into the stripping tower 18 for treatment.

[0057] The first pre-shrinking kettle 5 , the second pre-shrinking kettle 6 and the final shrinking kettle 7 are respectively connected to their own scraper condensers 9 , and the EG, water vapor and oligomers in the first pre-shrinking kettle 5 , the second pre-shrinking kettle 6 and the final shrinking kettle 7 flow into the scraper condensers 9 .

[0058] The three scraper condensers 9 are all connected to the same vacuum jet pump 10, and the non-condensable gas of the scraper condenser 9 flows into the vacuum jet pump 10. The vacuum jet pump 10 is connected to the EG evaporator 11 and the liquid ring vacuum pump 12, and the liquid ring vacuum pump 13 is connected to the leaching tower 13. The non-condensable gas in the polycondensation system is extracted by the vacuum jet pump 10 and the liquid ring vacuum pump 12, and the EG evaporator 11 generates the power steam of the vacuum system. The steam generates vacuum through three-stage injection and spraying to extract the small molecular gas in the pre-shrinking kettle 1 5, the pre-shrinking kettle 2 6 and the final shrinking kettle 7.

[0059] Among them, the titanium dioxide preparation system 4 includes a preparation tank, a finished product tank, a finished product delivery pump, and a finished product filter. Titanium dioxide and EG solution are stirred in the preparation tank to form a titanium dioxide EG solution initial material. After the titanium dioxide EG solution initial material flows into the finished product tank, it passes through the finished product delivery pump and the finished product filter to obtain a titanium dioxide EG solution.

[0060] Example 1

[0061] The production method using the copolyester white chip production system for PETG heat shrinkable white film comprises the following steps:

[0062] (1) A titanium dioxide EG solution is prepared in a titanium dioxide preparation system 4. Titanium dioxide, EG solution and sodium tripolyphosphate are stirred in a preparation tank to form a titanium dioxide EG solution initial material. The titanium dioxide EG solution initial material flows into a finished product tank and is then passed through a finished product filter by a finished product delivery pump to obtain a titanium dioxide EG solution with a concentration of 30 wt%. Sodium tripolyphosphate is added to the preparation tank at the same time as the titanium dioxide solution is prepared. The mass ratio of sodium tripolyphosphate added to titanium dioxide is 1:400.

[0063] (2) Put the catalyst tetrabutyl titanate, titanium dioxide EG solution, PTA, EG and CHDM into a slurry preparation kettle 1 and mix them into a slurry, wherein the mass unit consumption of the final product of PTA, EG, CHDM and titanium dioxide is 0.63, 0.19, 0.18 and 0.18 respectively, and the amount of tetrabutyl titanate added is based on the titanium content in the product of 10-20PPM.

[0064] (3) The slurry in the slurry preparation kettle 1 enters the esterification kettle 2 for esterification reaction. At the same time, the titanium dioxide EG solution in the titanium dioxide preparation product tank 15 is added into the esterification kettle 2 according to the titanium dioxide concentration of 6.7wt% to prepare the primary esterification product. The reaction temperature is 250°C and the reaction pressure is 50Kpa.

[0065] (4) The primary esterification product in the first esterification kettle 2 enters the second esterification kettle 3 for another esterification reaction. At the same time, the titanium dioxide EG solution in the titanium dioxide finished product tank 15 is added to the second esterification kettle 3 at a concentration of 6wt% to prepare a secondary esterification product. The reaction temperature is 265°C and the reaction pressure is 10Kpa.

[0066] (5) The secondary esterification product in the second esterification kettle 3 enters the first pre-condensation kettle 5 for pre-condensation reaction to obtain the primary pre-condensation product. The reaction temperature is 265°C and the reaction pressure is 10KPa.

[0067] (6) The primary pre-shrinked product in the first pre-shrinking kettle 5 enters the second pre-shrinking kettle 6 for another pre-shrinking polycondensation reaction to obtain a secondary pre-shrinked product. The reaction temperature is 275° C. and the reaction pressure is 1000 Pa.

[0068] (7) The secondary pre-shrinkage product in the second pre-shrinkage reactor 6 enters the final shrinkage reactor 7 for polycondensation reaction to obtain PETG melt, with a reaction temperature of 278°C and a reaction pressure of 250 Pa.

[0069] (8) The PETG melt enters the pelletizer 8 through a melt pump for pelletization and slicing.

[0070] The produced PETG white chips have a viscosity of 0.64 (dl / g) and a titanium dioxide content of 18 wt%.

[0071] Example 2

[0072] The production method using the copolyester white chip production system for PETG heat shrinkable white film comprises the following steps:

[0073] (1) A titanium dioxide EG solution is prepared in a titanium dioxide preparation system 4. Titanium dioxide, EG solution and sodium tripolyphosphate are stirred in a preparation tank to form a titanium dioxide EG solution initial material. The titanium dioxide EG solution initial material flows into a finished product tank and is then passed through a finished product filter by a finished product delivery pump to obtain a titanium dioxide EG solution with a concentration of 30 wt%, wherein the mass ratio of sodium tripolyphosphate to titanium dioxide is 1:400.

[0074] (2) Put the catalyst tetrabutyl titanate, titanium dioxide EG solution, PTA, EG and CHDM into the slurry preparation kettle 1 and mix them into slurry, wherein the mass unit consumption of the final product of PTA, EG, CHDM and titanium dioxide is 0.63, 0.19, 0.18 and 0.18. The amount of tetrabutyl titanate added is based on the titanium content of 10-20 PPM in the product.

[0075] (3) The slurry in the slurry preparation kettle 1 enters the esterification kettle 2 for esterification reaction. At the same time, the titanium dioxide EG solution in the titanium dioxide finished product tank 15 is added into the esterification kettle 2 at a concentration of 6.7wt% to prepare the primary esterification product. The reaction temperature is 260°C and the reaction pressure is 80Kpa.

[0076] (4) The primary esterification product in the first esterification kettle 2 enters the second esterification kettle 3 for another esterification reaction. At the same time, the titanium dioxide EG solution in the titanium dioxide finished product tank 15 is added to the second esterification kettle 3 at a concentration of 6wt% to prepare a secondary esterification product. The reaction temperature is 265°C and the reaction pressure is 14Kpa.

[0077] (5) The secondary esterification product in the second esterification kettle 3 enters the first pre-condensation kettle 5 for pre-condensation reaction to obtain the primary pre-condensation product. The reaction temperature is 272°C and the reaction pressure is 9KPa.

[0078] (6) The primary pre-shrinked product in the first pre-shrinking kettle 5 enters the second pre-shrinking kettle 6 for another pre-shrinking reaction to obtain a secondary pre-shrinked product. The reaction temperature is 280°C and the reaction pressure is 900 Pa.

[0079] (7) The secondary pre-shrinkage product in the second pre-shrinkage reactor 6 enters the final shrinkage reactor 7 for polycondensation reaction to obtain PETG melt, with a reaction temperature of 282°C and a reaction pressure of 200 Pa.

[0080] (8) The PETG melt enters the pelletizer 8 through a melt pump for pelletization and slicing.

[0081] The produced PETG white chips have a viscosity of 0.64 (dl / g) and a titanium dioxide content of 18 wt%.

[0082] Example 3

[0083] The production method using the copolyester white chip production system for PETG heat shrinkable white film comprises the following steps:

[0084] (1) A titanium dioxide EG solution is prepared in a titanium dioxide preparation system 4. Titanium dioxide, EG solution and sodium tripolyphosphate are stirred in a preparation tank to form a titanium dioxide EG solution initial material. The titanium dioxide EG solution initial material flows into a finished product tank and is then passed through a finished product filter by a finished product delivery pump to obtain a titanium dioxide EG solution with a concentration of 30 wt%, wherein the mass ratio of sodium tripolyphosphate to titanium dioxide is 1:400.

[0085] (2) Put the catalyst tetrabutyl titanate, titanium dioxide EG solution, PTA, EG and CHDM into the slurry preparation kettle 1 and mix them into slurry, wherein the mass unit consumption of the final product of PTA, EG, CHDM and titanium dioxide is 0.63, 0.19, 0.18 and 0.18. The amount of tetrabutyl titanate added is based on the titanium content of 10-20 PPM in the product.

[0086] (3) The slurry in the slurry preparation kettle 1 enters the esterification kettle 2 for esterification reaction. At the same time, the titanium dioxide EG solution in the titanium dioxide preparation kettle is added into the esterification kettle 2 at a concentration of 6.7wt% to prepare the primary esterification product. The reaction temperature is 265°C and the reaction pressure is 100Kpa.

[0087] (4) The primary esterification product in the first esterification kettle 2 enters the second esterification kettle 3 for another esterification reaction. At the same time, the titanium dioxide EG solution in the titanium dioxide finished product tank 15 is added to the second esterification kettle 3 at a concentration of 6wt% to prepare a secondary esterification product. The reaction temperature is 268°C and the reaction pressure is 20Kpa.

[0088] (5) The secondary esterification product in the second esterification kettle 3 enters the first pre-condensation kettle 5 for pre-condensation reaction to obtain the primary pre-condensation product. The reaction temperature is 275°C and the reaction pressure is 8KPa.

[0089] (6) The primary pre-shrinked product in the first pre-shrinking kettle 5 enters the second pre-shrinking kettle 6 for another pre-shrinking polycondensation reaction to obtain a secondary pre-shrinked product. The reaction temperature is 278° C. and the reaction pressure is 800 Pa.

[0090] (7) The secondary pre-shrinkage product in the second pre-shrinkage reactor 6 enters the final shrinkage reactor 7 for polycondensation to obtain PETG melt, with a reaction temperature of 282° C. and a reaction pressure of 160 Pa.

[0091] (8) The PETG melt enters the pelletizer 8 through a melt pump for pelletization and slicing.

[0092] The produced PETG white chips have a viscosity of 0.64 (dl / g) and a titanium dioxide content of 18 wt%.

[0093] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.

Claims

1. PETG heat shrinkable white film copolyester white chip production system, characterized by: include A slurry preparation kettle is used to mix the catalyst, titanium dioxide EG solution, CHDM, PTA and EG according to a proportion to form a slurry; In the first esterification kettle, the slurry pumped into the slurry preparation kettle is heated to carry out esterification reaction to obtain the primary esterification product; The second esterification kettle is used to heat the primary esterification product discharged from the first esterification kettle again for esterification to obtain the secondary esterification product; A titanium dioxide preparation system is used to prepare a titanium dioxide EG solution and flow the titanium dioxide EG solution into the slurry preparation kettle, the first esterification kettle and the second esterification kettle; Pre-shrinking one kettle, subjecting the secondary esterification product flowing out of the second esterification kettle to pre-polycondensation reaction to obtain the primary pre-shrinkage product; pre-shrinking two kettles, subjecting the primary pre-shrinkage product flowing out of the first pre-shrinkage kettle to pre-polycondensation reaction again to obtain the secondary pre-shrinkage product; The final shrinking kettle is used to polycondense the secondary pre-shrinking product flowing out of the second pre-shrinking kettle to obtain PETG melt; The pelletizer granulates the PETG melt to obtain copolyester white chips for PETG heat shrinkable white film.

2. The copolyester white chip production system for PETG heat shrinkable white film according to claim 1, characterized in that: The first esterification kettle and the second esterification kettle are both connected to the same process tower, and the process tower is connected to a stripping tower.

3. The copolyester white chip production system for PETG heat shrinkable white film according to claim 1, characterized in that: The first pre-contraction kettle, the second pre-contraction kettle and the final contraction kettle are respectively connected to their own scraper condensers, and the three scraper condensers are all connected to the same vacuum jet pump, and the vacuum jet pump is connected to the EG evaporator and the tail gas condensation tank, and a liquid ring vacuum pump is connected between the tail gas condensation tank and the vacuum jet pump.

4. The system for producing copolyester white chips for PETG heat shrinkable white film according to claim 1, characterized in that: The titanium dioxide preparation system comprises a preparation tank, a finished product tank, a finished product delivery pump, and a finished product filter. Titanium dioxide and EG solution are stirred in the preparation tank to form a titanium dioxide EG solution initial material. The initial titanium dioxide EG solution flows into the finished product tank and then passes through the finished product filter via the finished product delivery pump to obtain the titanium dioxide EG solution.

5. A production method using the copolyester white chip production system for PETG heat shrinkable white film according to any one of claims 1 to 4, characterized in that: The steps include: (1) Preparing titanium dioxide EG solution in the titanium dioxide preparation system; (2) preparing the catalyst, placing the catalyst, titanium dioxide EG solution, PTA, EG and CHDM into a slurry preparation kettle and mixing them into a slurry; (3) The slurry in the slurry preparation kettle enters the esterification kettle No. 1 for esterification reaction, and at the same time, the titanium dioxide EG solution in the titanium dioxide finished product tank is added to the esterification kettle No. 1 according to a set ratio to prepare a primary esterification product; (4) The primary esterification product in the first esterification kettle enters the second esterification kettle for another esterification reaction, and at the same time, the titanium dioxide EG solution in the titanium dioxide finished product tank is added to the second esterification kettle according to a set ratio to prepare a secondary esterification product; (5) the secondary esterification product in the second esterification kettle enters the first pre-condensation kettle for pre-condensation reaction to obtain the primary pre-condensation product; (6) the primary pre-shrinked product in the first pre-shrinking kettle enters the second pre-shrinking kettle for another pre-shrinking polycondensation reaction to obtain a secondary pre-shrinked product; (7) The secondary pre-shrinkage product in the second pre-shrinkage kettle enters the final shrinkage kettle for polycondensation reaction to obtain PETG melt; (8) The PETG melt enters the pelletizer through a melt pump for pelletizing and slicing.

6. The production method of the copolyester white chip production system for PETG heat shrinkable white film according to claim 5, characterized in that: The catalyst in step (2) is a titanium-based catalyst with a concentration of 0.5 wt%.

7. The production method of the copolyester white chip production system for PETG heat shrinkable white film according to claim 5, characterized in that: The concentration of the titanium dioxide EG solution in step (2), step (3) and step (4) is 30wt%. In step (3), the titanium dioxide EG solution is added at a concentration of 6.7wt%, and in step (4), the titanium dioxide EG solution is added at a concentration of 6wt%.

8. The production method using the copolyester white chip production system for PETG heat shrinkable white film according to claim 5, characterized in that: In step (2), the molar ratio of PTA, EG, CHDM and titanium dioxide is 120:10-20:10-20:10-20, and the amount of titanium catalyst added is 10-20 PPM of the titanium content in the product.

9. The production method using the copolyester white chip production system for PETG heat shrinkable white film according to claim 5, characterized in that: The reaction temperature in step (3) and step (4) is 250-265° C., the reaction pressure in step (3) is 50 Kpa-100 Kpa gauge pressure, the reaction pressure in step (4) is 8-14 Kpa gauge pressure, the reaction temperature in step (5) and step (6) is 269-285° C., the reaction pressure in step (5) is 10 Kpa absolute pressure, and the reaction pressure in step (6) is 1 Kpa absolute pressure.

10. The production method using the copolyester white chip production system for PETG heat shrinkable white film according to claim 5, characterized in that: In step (1), sodium tripolyphosphate is added into a titanium dioxide preparation tank, and the mass ratio of sodium tripolyphosphate to titanium dioxide is 1:400.

Images