Recycling method of waste polyester packaging material

Abstract

The invention relates to the technical field of polyester recycling, in particular to a waste polyester packaging material recycling method which comprises the following steps: (1) crushing: crushing waste polyester into sheets; (2) alcoholysis: conveying the flaky waste polyester to an alcoholysis kettle, adding ethylene glycol with a first preset weight, heating the alcoholysis kettle to a first preset temperature, keeping a first preset pressure in the alcoholysis kettle, reacting for a first preset time, stirring, and performing alcoholysis on the flaky waste polyester into a liquid monomer A; (3) filtering for the first time: transferring the liquid monomer A to a dealcoholization kettle, arranging a first filter between the alcoholysis kettle and the dealcoholization kettle, and filtering the monomer A by the first filter before entering the dealcoholization kettle; (4) dealcoholization; (5) filtering for the second time; and (6) polymerization: adding a third preset weight of catalyst into the polymerization kettle, raising the temperature of the polymerization kettle to a second preset temperature, and vacuumizing to carry out polymerization reaction.

Description

Technical Field

[0001] The present invention relates to the technical field of polyester recycling, and in particular to a method for recycling waste polyester packaging. Background Art

[0002] Polyester mainly refers to polyethylene terephthalate (PET), which is a high molecular compound. Polyethylene terephthalate is produced by the condensation polymerization of terephthalic acid (PTA) and (ethylene glycol). It is a type of engineering plastic with excellent performance and wide application. It can also be made into polyester fibers and polyester films.

[0003] my country is a major consumer of polyester. The national polyester production capacity is expected to be 70.43 million tons in 2022 and 79.46 million tons in 2023, of which polyester packaging chips will be 11.52 million tons in 2022 and 16.61 million tons in 2023. With the rapid growth of polyester production capacity each year, more and more waste polyester is discharged into the nature. According to statistics, my country's waste polyester packaging is about 5.8 million tons per year. Although polyethylene terephthalate does not directly pollute the environment, it is difficult to be degraded by microorganisms or air due to its strong chemical inertness, and it will occupy a lot of space. Illegal landfill or incineration will cause great pressure on the environment. Therefore, the recycling of waste polyester has become one of the important issues of environmental protection.

[0004] At present, the mainstream method for processing waste polyester in my country is physical recycling. After turnover at the recycling station, the factory will screen, clean, crush, dry, and screw hot melt granulation. However, the physical recycling cost is high, and the product performance will deteriorate during the recycling process. Summary of the invention

[0005] In view of the deficiencies or problems existing in the prior art, the present invention provides a method for recycling waste polyester packaging materials, which has low cost and can realize the recycling of waste polyester packaging materials.

[0006] The technical solution adopted by the present disclosure to solve the above technical problems is: a method for recycling waste polyester packaging materials, comprising the following steps:

[0007] (1) Crushing: crushing the waste polyester into flakes;

[0008] (2) alcoholysis: conveying the waste polyester in flake form to an alcoholysis reactor, adding a first preset weight of ethylene glycol, raising the alcoholysis reactor to a first preset temperature, maintaining a first preset pressure in the alcoholysis reactor for a first preset time, and then stirring for a second preset time, so that the waste polyester in flake form is alcoholyzed into liquid A monomer;

[0009] (3) First filtration: The liquid A monomer is transferred to the dealcoholization kettle. A first filter is arranged between the alcoholysis kettle and the dealcoholization kettle. The A monomer is filtered by the first filter before entering the dealcoholization kettle.

[0010] (4) Dealcoholization: Then, dealcoholization is carried out in a dealcoholization kettle until the ethylene glycol is reduced from a first preset weight to a second preset weight to obtain liquid B monomer, and then a certain amount of sodium dimethyl isophthalate-5-sulfonate is added and stirred for a period of time to obtain liquid C monomer;

[0011] (5) Second filtration: The liquid C monomer is transferred to the polymerization kettle. A second filter is arranged between the dealcoholization kettle and the polymerization kettle. The C monomer is filtered through the second filter and converted into liquid D monomer.

[0012] (6) Polymerization: Add a third preset weight of catalyst into the polymerization kettle, raise the temperature of the polymerization kettle to the second preset temperature and evacuate the kettle to carry out polymerization reaction until the textile viscosity of the RCDP chips is 0.55-0.6 dl / g.

[0013] Wherein, in step (2), the waste polyester in flake form is transported to the alcoholysis reactor through an agitator;

[0014] The first preset weight is 0.5 to 2 times the weight of the waste polyester flakes, preferably 1.2 times;

[0015] The first preset temperature is 200-260° C., preferably, the first preset temperature is 230° C.;

[0016] The first preset pressure is 0.2-2 kg, preferably 0.5 kg;

[0017] The first preset time is 2 to 6 hours, preferably, the first preset time is 4 hours;

[0018] The second preset time is 15 to 60 minutes, and preferably, the second preset time is 30 minutes.

[0019] In step (3), the liquid A monomer is pressed from the alcoholysis reactor to the dealcoholization reactor by 2 kg of nitrogen;

[0020] The filter element of the first filter is a metal mesh, and the first filter is a coarse filter, mainly used to remove non-PET impurities and infusible materials.

[0021] In step (4), the dealcoholization temperature is 200-280°C, preferably 240°C;

[0022] The second preset weight is 0.6 times the first preset weight;

[0023] The mass of dimethyl 5-sodium sulfonate is 3% to 30% of the mass of the liquid B monomer.

[0024] After adding sodium dimethyl 5-sulfonate isophthalate, the mixture was stirred for 30 minutes.

[0025] In step (5), the liquid C monomer is pressed from the dealcoholization kettle to the polymerization kettle by 2 kg of nitrogen;

[0026] The filter element of the second filter is metal sintered felt. Preferably, the filter element of the second filter is 15U metal sintered felt.

[0027] In step (6), the third preset weight is 0.03% of the weight of the waste polyester flakes; and the catalyst is aluminum acetate.

[0028] The second preset temperature is 200-290°C, preferably 250°C.

[0029] The invention is respectively subjected to crushing, alcoholysis, first filtration, dealcoholization, second filtration and polymerization, and the final product obtained is RCDP chips, that is, regenerated cationic dye-dyable polyester chips.

[0030] Compared with the prior art, the method adopted by the present invention can obtain RCDP chips with a textile viscosity of 0.55 to 0.6 dl / g, which can be used for spinning, and is helpful to achieve high added value utilization of waste polyester, so that the waste polyester can be recycled; the use of inexpensive ethylene glycol as an organic solvent not only saves costs and is easy to recycle, but also, ethylene glycol is non-toxic, and the entire operation process is safer. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solution of the present disclosure, the present disclosure is described in detail, clearly and completely in conjunction with the embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are not used to limit the present disclosure.

[0032] Example 1

[0033] This embodiment provides a method for recycling waste polyester packaging materials, comprising the following steps:

[0034] (1) Crushing: crushing the waste polyester into pieces of uniform size;

[0035] (2) Alcoholysis: The waste polyester flakes are transported to an alcoholysis reactor through an agitator, ethylene glycol in an amount 0.5 times the weight of the waste polyester flakes is added, the alcoholysis reactor is heated to 230°C, and the pressure in the alcoholysis reactor is maintained at 0.4 kg for 3 hours, and then stirred for 15 minutes, and the waste polyester flakes are alcoholyzed into liquid A monomer;

[0036] (3) First filtration: The liquid A monomer is pressed from the alcoholysis kettle to the dealcoholization kettle by 2 kg of nitrogen. A first filter is arranged between the alcoholysis kettle and the dealcoholization kettle. The A monomer is filtered by the first filter before entering the dealcoholization kettle.

[0037] (4) Dealcoholization: The temperature of the dealcoholization kettle is then raised to 240° C. to carry out dealcoholization until the weight of ethylene glycol is reduced to 0.6 times of the original weight to obtain liquid B monomer, and then sodium dimethyl 5-sulfonate is added, wherein the weight of sodium dimethyl 5-sulfonate is 3% of the weight of the liquid B monomer, and then stirred for 30 minutes to obtain liquid C monomer;

[0038] (5) Second filtration: The liquid C monomer is pressed from the dealcoholization kettle to the polymerization kettle by 2 kg of nitrogen. A second filter is arranged between the dealcoholization kettle and the polymerization kettle. The C monomer is filtered by the second filter and converted into liquid D monomer;

[0039] (6) Polymerization: Aluminum acetate in an amount of 0.03% by weight of the polyester flakes was added to a polymerization kettle, the temperature of the polymerization kettle was raised to 290°C and the polymerization reaction was carried out under vacuum until the textile viscosity of the RCDP chips reached 0.55 dl / g.

[0040] Example 2

[0041] This embodiment provides a method for recycling waste polyester packaging materials, comprising the following steps:

[0042] (1) Crushing: crushing the waste polyester into pieces of uniform size;

[0043] (2) Alcoholysis: The waste polyester flakes are transported to an alcoholysis reactor through an agitator, ethylene glycol is added in an amount 1.2 times the weight of the waste polyester flakes, the alcoholysis reactor is heated to 200°C, and the pressure in the alcoholysis reactor is maintained at 0.2 kg for 6 hours, and then stirred for 30 minutes, and the waste polyester flakes are alcoholyzed into liquid A monomer;

[0044] (3) First filtration: The liquid A monomer is pressed from the alcoholysis kettle to the dealcoholization kettle by 2 kg of nitrogen. A first filter is arranged between the alcoholysis kettle and the dealcoholization kettle. The A monomer is filtered by the first filter before entering the dealcoholization kettle.

[0045] (4) Dealcoholization: The temperature of the dealcoholization kettle is then raised to 200° C. for dealcoholization until the weight of ethylene glycol is reduced to 0.6 times of the original weight to obtain liquid B monomer, and then dimethyl 5-sulfonate sodium isophthalate is added, wherein the weight of dimethyl 5-sulfonate sodium isophthalate is 10% of the weight of the liquid B monomer, followed by stirring for 30 minutes to obtain liquid C monomer;

[0046] (5) Second filtration: The liquid C monomer is pressed from the dealcoholization kettle to the polymerization kettle by 2 kg of nitrogen. A second filter is arranged between the dealcoholization kettle and the polymerization kettle. The C monomer is filtered by the second filter and converted into liquid D monomer;

[0047] (6) Polymerization: Aluminum acetate in an amount of 0.03% by weight of the polyester flakes was added to a polymerization kettle, the temperature of the polymerization kettle was raised to 200°C and the polymerization reaction was carried out in a vacuum until the textile viscosity of the RCDP chips was 0.58 dl / g.

[0048] Example 3

[0049] This embodiment provides a method for recycling waste polyester packaging materials, comprising the following steps:

[0050] (1) Crushing: crushing the waste polyester into pieces of uniform size;

[0051] (2) Alcoholysis: The waste polyester flakes are transported to an alcoholysis reactor through an agitator, ethylene glycol is added in an amount twice the weight of the waste polyester flakes, the alcoholysis reactor is heated to 260°C, and the pressure in the alcoholysis reactor is maintained at 1.5 kg for 3 hours, and then stirred for 60 minutes, and the waste polyester flakes are alcoholyzed into liquid A monomer;

[0052] (3) First filtration: The liquid A monomer is pressed from the alcoholysis kettle to the dealcoholization kettle by 2 kg of nitrogen. A first filter is arranged between the alcoholysis kettle and the dealcoholization kettle. The A monomer is filtered by the first filter before entering the dealcoholization kettle.

[0053] (4) Dealcoholization: Then, the temperature of the dealcoholization kettle is raised to 280° C. to carry out dealcoholization until the weight of ethylene glycol is reduced to 0.6 times of the original weight to obtain liquid B monomer, and then dimethyl isophthalate-5-sodium sulfonate is added, wherein the weight of dimethyl isophthalate-5-sodium sulfonate is 20% of the weight of the liquid B monomer, and then stirred for 30 minutes to obtain liquid C monomer;

[0054] (5) Second filtration: The liquid C monomer is pressed from the dealcoholization kettle to the polymerization kettle by 2 kg of nitrogen. A second filter is arranged between the dealcoholization kettle and the polymerization kettle. The C monomer is filtered by the second filter and converted into liquid D monomer;

[0055] (6) Polymerization: Aluminum acetate in an amount of 0.03% by weight of the polyester flakes was added to a polymerization kettle, the temperature of the polymerization kettle was raised to 220°C and the polymerization reaction was carried out under vacuum until the textile viscosity of the RCDP chips reached 0.6 dl / g.

[0056] Example 4

[0057] This embodiment provides a method for recycling waste polyester packaging materials, comprising the following steps:

[0058] (1) Crushing: crushing the waste polyester into pieces of uniform size;

[0059] (2) Alcoholysis: The waste polyester flakes are transported to an alcoholysis reactor through an agitator, ethylene glycol is added in an amount equal to one time the weight of the waste polyester flakes, the alcoholysis reactor is heated to 240°C, and the pressure in the alcoholysis reactor is maintained at 2 kg for 2 hours, and then stirred for 20 minutes, and the waste polyester flakes are alcoholyzed into liquid A monomer;

[0060] (3) First filtration: The liquid A monomer is pressed from the alcoholysis kettle to the dealcoholization kettle by 2 kg of nitrogen. A first filter is arranged between the alcoholysis kettle and the dealcoholization kettle. The A monomer is filtered by the first filter before entering the dealcoholization kettle.

[0061] (4) Dealcoholization: The temperature of the dealcoholization kettle is then raised to 260° C. to carry out dealcoholization until the weight of ethylene glycol is reduced to 0.6 times of the original weight to obtain liquid B monomer, and then sodium dimethyl 5-sulfonate is added, wherein the weight of sodium dimethyl 5-sulfonate is 30% of the weight of the liquid B monomer, and then stirred for 30 minutes to obtain liquid C monomer;

[0062] (5) Second filtration: The liquid C monomer is pressed from the dealcoholization kettle to the polymerization kettle by 2 kg of nitrogen. A second filter is arranged between the dealcoholization kettle and the polymerization kettle. The C monomer is filtered by the second filter and converted into liquid D monomer;

[0063] (6) Polymerization: Aluminum acetate in an amount of 0.03% by weight of the polyester flakes was added to a polymerization kettle, the temperature of the polymerization kettle was raised to 260°C and the polymerization reaction was carried out under vacuum until the textile viscosity of the RCDP chips reached 0.56 dl / g.

[0064] Example 5

[0065] This embodiment provides a method for recycling waste polyester packaging materials, comprising the following steps:

[0066] (1) Crushing: crushing the waste polyester into pieces of uniform size;

[0067] (2) Alcoholysis: The waste polyester flakes are transported to an alcoholysis reactor through an agitator, ethylene glycol is added in an amount 1.5 times the weight of the waste polyester flakes, the alcoholysis reactor is heated to 250°C, and the pressure in the alcoholysis reactor is maintained at 0.6 kg for 5 hours, and then stirred for 50 minutes, and the waste polyester flakes are alcoholyzed into liquid A monomer;

[0068] (3) First filtration: The liquid A monomer is pressed from the alcoholysis kettle to the dealcoholization kettle by 2 kg of nitrogen. A first filter is arranged between the alcoholysis kettle and the dealcoholization kettle. The A monomer is filtered by the first filter before entering the dealcoholization kettle.

[0069] (4) Dealcoholization: The temperature of the dealcoholization kettle is then raised to 270° C. to carry out dealcoholization until the weight of ethylene glycol is reduced to 0.6 times of the original weight to obtain liquid B monomer, and then dimethyl 5-sulfonate sodium isophthalate is added, wherein the weight of dimethyl 5-sulfonate sodium isophthalate is 15% of the weight of the liquid B monomer, and then stirred for 30 minutes to obtain liquid C monomer;

[0070] (5) Second filtration: The liquid C monomer is pressed from the dealcoholization kettle to the polymerization kettle by 2 kg of nitrogen. A second filter is arranged between the dealcoholization kettle and the polymerization kettle. The C monomer is filtered by the second filter and converted into liquid D monomer;

[0071] (6) Polymerization: Aluminum acetate in an amount of 0.03% by weight of the polyester flakes was added to a polymerization kettle, the temperature of the polymerization kettle was raised to 280°C and vacuum was applied to carry out polymerization reaction until the textile viscosity of the RCDP chips was 0.57 dl / g.

[0072] Example 6

[0073] This embodiment provides a method for recycling waste polyester packaging materials, comprising the following steps:

[0074] (1) Crushing: crushing the waste polyester into pieces of uniform size;

[0075] (2) Alcoholysis: The waste polyester flakes are transported to an alcoholysis reactor through an agitator, ethylene glycol is added in an amount 1.2 times the weight of the waste polyester flakes, the alcoholysis reactor is heated to 230°C, and the pressure in the alcoholysis reactor is maintained at 0.5 kg for 4 hours, and then stirred for 35 minutes, and the waste polyester flakes are alcoholyzed into liquid A monomer;

[0076] (3) First filtration: The liquid A monomer is pressed from the alcoholysis kettle to the dealcoholization kettle by 2 kg of nitrogen. A first filter is arranged between the alcoholysis kettle and the dealcoholization kettle. The A monomer is filtered by the first filter before entering the dealcoholization kettle.

[0077] (4) Dealcoholization: The temperature of the dealcoholization kettle is then raised to 240° C. to carry out dealcoholization until the weight of ethylene glycol is reduced to 0.6 times of the original weight to obtain liquid B monomer, and then sodium dimethyl 5-sulfonate is added, wherein the weight of sodium dimethyl 5-sulfonate is 25% of the weight of the liquid B monomer, and then stirred for 30 minutes to obtain liquid C monomer;

[0078] (5) Second filtration: The liquid C monomer is pressed from the dealcoholization kettle to the polymerization kettle by 2 kg of nitrogen. A second filter is arranged between the dealcoholization kettle and the polymerization kettle. The C monomer is filtered by the second filter and converted into liquid D monomer;

[0079] (6) Polymerization: Aluminum acetate in an amount of 0.03% by weight of the polyester flakes was added to a polymerization kettle, the temperature of the polymerization kettle was raised to 250°C and the polymerization reaction was carried out under vacuum until the textile viscosity of the RCDP chips reached 0.6 dl / g.

[0080] The present application is described in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the present application and its core ideas. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A method for recycling waste polyester packaging, characterized in that: The steps include: (1) Crushing: crushing the waste polyester into flakes; (2) alcoholysis: conveying the waste polyester in flake form to an alcoholysis reactor, adding a first preset weight of ethylene glycol, raising the alcoholysis reactor to a first preset temperature, maintaining a first preset pressure in the alcoholysis reactor for a first preset time, and then stirring for a second preset time, so that the waste polyester in flake form is alcoholyzed into liquid A monomer; (3) First filtration: The liquid A monomer is transferred to the dealcoholization kettle. A first filter is arranged between the alcoholysis kettle and the dealcoholization kettle. The A monomer is filtered by the first filter before entering the dealcoholization kettle. (4) Dealcoholization: Then, dealcoholization is carried out in a dealcoholization kettle until the ethylene glycol is reduced from a first preset weight to a second preset weight to obtain liquid B monomer, and then a certain amount of sodium dimethyl isophthalate-5-sulfonate is added and stirred for a period of time to obtain liquid C monomer; (5) Second filtration: The liquid C monomer is transferred to the polymerization kettle. A second filter is arranged between the dealcoholization kettle and the polymerization kettle. The C monomer is filtered through the second filter and converted into liquid D monomer. (6) Polymerization: Add a third preset weight of catalyst into the polymerization kettle, raise the temperature of the polymerization kettle to the second preset temperature and evacuate the kettle to carry out polymerization reaction until the textile viscosity of the RCDP chips is 0.55-0.6 dl / g.

2. The method for recycling waste polyester packaging according to claim 1, characterized in that: In step (2), the waste polyester flakes are transported to the alcoholysis reactor through an agitator; the first preset weight is 0.5 to 2 times the weight of the waste polyester flakes.

3. The method for recycling waste polyester packaging according to claim 1, characterized in that: The first preset temperature is 200-260° C.; the first preset pressure is 0.2-2 kg.

4. The method for recycling waste polyester packaging according to claim 1, characterized in that: The first preset time is 2 to 6 hours; the second preset time is 15 to 60 minutes.

5. The method for recycling waste polyester packaging according to claim 1, characterized in that: In step (3), the liquid A monomer is pressed from the alcoholysis reactor to the dealcoholization reactor by 2 kg of nitrogen.

6. The method for recycling waste polyester packaging according to claim 1, characterized in that: The filter element of the first filter is a metal mesh, and the first filter is a coarse filter.

7. The method for recycling waste polyester packaging according to claim 1, characterized in that: In step (4), the dealcoholization temperature is 200-280° C.; and the second preset weight is 0.6 times the first preset weight.

8. The method for recycling waste polyester packaging according to claim 1, characterized in that: The mass of the added sodium dimethyl 5-sulfonate is 3% to 30% of the mass of the liquid B monomer; after adding the sodium dimethyl 5-sulfonate, stirring is carried out for 30 minutes.

9. The method for recycling waste polyester packaging according to claim 1, characterized in that: In step (5), the liquid C monomer is pressed from the dealcoholization kettle to the polymerization kettle by 2 kg of nitrogen; the filter element of the second filter is metal sintered felt.

10. The method for recycling waste polyester packaging according to claim 1, characterized in that: In step (6), the third preset weight is 0.03% of the weight of the waste polyester flakes; the catalyst is aluminum acetate; and the second preset temperature is 200-290°C.