CN119056838A

CN119056838A - Polyester waste recycling system and method

Info

Publication number: CN119056838A
Application number: CN202411302942.5A
Authority: CN
Inventors: 朱闻宇; 瞿新楼; 邓勇; 林耕宇; 李荣丽
Original assignee: Guangzhou Xiyin International Import and Export Co Ltd
Current assignee: Guangzhou Jingyi Green Spinning Technology Co.,Ltd.
Priority date: 2024-09-18
Filing date: 2024-09-18
Publication date: 2024-12-03

Abstract

本发明涉及涤纶回收技术领域，公开了一种涤纶废弃物回收系统及方法。一种涤纶废弃物回收系统，包括预处理单元、脱色单元、造粒单元和溶剂循环单元；所述预处理单元、脱色单元、造粒单元依次相连；所述脱色单元包括依次相连的1号脱色反应器、2号脱色反应器和3号脱色反应器；所述溶剂循环单元包括第一循环单元和第二循环单元；所述1号脱色反应器和2号脱色反应器分别连接第一循环单元；所述3号脱色反应器连接第二循环单元。本发明提供的涤纶废弃物回收系统，脱色单元能够有效脱除涤纶废弃物中的分散染料，保护纤维不受损伤，得到接近白色的、能够再次利用的涤纶废弃物；系统产生废液少，且利于环保和节约试剂成本。The present invention relates to the technical field of polyester recycling, and discloses a polyester waste recycling system and method. A polyester waste recycling system comprises a pretreatment unit, a decolorization unit, a granulation unit and a solvent circulation unit; the pretreatment unit, the decolorization unit and the granulation unit are connected in sequence; the decolorization unit comprises a decolorization reactor No. 1, a decolorization reactor No. 2 and a decolorization reactor No. 3 which are connected in sequence; the solvent circulation unit comprises a first circulation unit and a second circulation unit; the decolorization reactor No. 1 and the decolorization reactor No. 2 are respectively connected to the first circulation unit; the decolorization reactor No. 3 is connected to the second circulation unit. In the polyester waste recycling system provided by the present invention, the decolorization unit can effectively remove disperse dyes from polyester waste, protect fibers from damage, and obtain polyester waste that is close to white and can be reused; the system generates less waste liquid, is beneficial to environmental protection and saves reagent costs.

Description

Polyester waste recycling system and method

Technical Field

The invention relates to the technical field of terylene recycling, in particular to a terylene waste recycling system and a terylene waste recycling method.

Background

At present, the service cycle of the textile is shorter and shorter, and the number of the industrial textiles is gradually increased. The yield of terylene accounts for about 85% of the total textile fiber processing amount, but at the same time, the recovery amount of waste textiles is only about 4.4% of the yield, only 44% of waste clothes are directly discarded each year, and the recovery utilization rate of the waste textiles is extremely low, so that serious resource waste is caused.

Polyester is a hydrophobic fiber, has very low swelling degree in water and has compact molecular chain arrangement. In recent years, many studies have successfully achieved the reuse of colorless (white) waste polyester. However, for colored polyester fabrics, the application range of recycling is greatly limited due to the fact that the colored polyester fabrics contain more impurities, different dyes, pigments, additives and the like, and the problem of decolorization of colored polyester in the recycling process of the polyester fabrics is to be solved.

For the decolorization of polyester fabrics, hexadecylxylylenediamine hydrochloride is used initially, and the decolorization has been developed later on by using substances having strong oxidizing or reducing properties such as sodium dithionite, sodium hypochlorite, rongalite and potassium permanganate. The substances can achieve the decoloring effect by destroying dye molecules or changing the structure of the dye molecules, for example, sodium dithionite is a strong reducing agent, the decoloring of fibers can be achieved by reducing the dye molecules into colorless substances, sodium hypochlorite is a strong oxidizing agent, the dye molecules can lose color by oxidizing the dye molecules, and the purposes of decoloring are achieved by decomposing the dye molecules by utilizing the strong oxidizing property of the sodium dithionite and the potassium permanganate.

However, these substances which are decolorized by oxidation or reduction have various disadvantages in practical application, such as (1) many strong oxidizing and reducing chemical substances generate harmful byproducts or waste liquid in the decolorization process, such as sodium hypochlorite generates residual chlorides, sodium dithionite possibly generates sulfides after treatment, these chemical substances are discharged into the environment and pollute the water body and soil if not properly treated, (2) oxidation and reduction reactions often require strict control of reaction conditions, such as temperature, pH value, time and the like, and may cause poor decolorization effect, even damage to the physical properties of the fibers, such as potassium permanganate reactions need to be performed in specific acid-base environments, or the byproducts cannot be completely reduced or generated, and (3) the use of strong oxidizing agents and strong reducing agents also damages the molecular structure of polyester fibers, resulting in the reduction of mechanical properties, such as being used as a strong oxidizing agent possibly oxidizing ester bonds in the fibers, making the fibers become broken, and potassium permanganate also causes similar problems, resulting in the reduction of the toughness and strength of the fibers, and the like, and (4) the decolorization, high energy consumption, high water consumption, high consumption, and the like.

Disclosure of Invention

The present invention aims to solve at least one of the above technical problems in the prior art. Therefore, one of the objectives of the present invention is to provide a recycling system for polyester waste, and the other objective of the present invention is to provide a recycling method for polyester waste.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:

The first aspect of the invention provides a polyester waste recycling system, which comprises a pretreatment unit, a decoloring unit, a granulating unit and a solvent circulating unit;

the pretreatment unit, the decoloring unit and the granulating unit are connected in sequence;

The decoloring unit comprises a No.1 decoloring reactor, a No.2 decoloring reactor and a No. 3 decoloring reactor which are sequentially connected;

The solvent circulation unit comprises a first circulation unit and a second circulation unit;

the No. 1 decoloring reactor and the No. 2 decoloring reactor are respectively connected with a first circulating unit;

And the No. 3 decoloring reactor is connected with a second circulating unit.

Preferably, the pretreatment unit comprises a crushing device and a drying device which are connected in sequence.

Specifically, after entering a pretreatment unit, the terylene waste is crushed into fragments with uniform size by a crushing device so as to be convenient for the immersion of a decoloring solvent, and the crushed terylene waste is dried by a drying device to finish pretreatment.

Preferably, the number 1 and number 2 decolorizing reactors contain a first decolorizing solvent.

Preferably, the first decolorizing solvent comprises at least one of dimethyl sulfoxide, pyruvonitrile and dichloromethane, and further preferably, the first decolorizing solvent is Dichloromethane (DCM).

Specifically, the methylene dichloride can effectively dissolve disperse dye attached to the polyester fabric. These dyes are generally hydrophobic or weakly polar molecules, readily soluble in methylene chloride. Through permeation on the polyester fabric, the methylene dichloride can effectively dissolve and take away dye molecules from the fibers. As the fiber swells and the dye dissolves, dye molecules diffuse from the inside of the fiber into the methylene chloride solution. This process causes the dye in the fiber to be carried out continuously by continuous permeation and dynamic equilibrium of the solvent. The methylene dichloride is relatively chemically inert, so that the molecular structure of the polyester fiber is not damaged like a strong oxidant or a reducing agent, and the damage to the mechanical property of the fabric is reduced.

Preferably, the No.3 decolorizing reactor contains a second decolorizing solvent.

Preferably, the second decolorizing solvent comprises a cyclic carbonate, and more preferably, the second decolorizing solvent comprises at least one of ethylene carbonate and propylene carbonate.

In particular, cyclic carbonates are strongly polar solvents that are capable of forming very good interactions with polar and non-polar dye molecules. This polar effect helps to disrupt weak interactions between dye and fiber, such as van der waals forces and hydrogen bonding. Under high temperature conditions, the cyclic carbonate solvent can further swell the fibers, increasing the gaps between the molecular chains of the fibers. This action makes the dye molecules more susceptible to migration and detachment from the fiber. Cyclic carbonates (e.g., propylene carbonate having a boiling point of about 240 ℃) remain stable and less prone to decomposition at high temperatures and are suitable for high temperature short time decolorization.

Preferably, in the number 1 and number 2 decolorizing reactors, the mass ratio (bath ratio) of the terylene waste to the first decolorizing solvent is 1 (8-15), and further preferably, the mass ratio of the terylene waste to the first decolorizing solvent is 1 (9-11).

Preferably, in the number 1 and number 2 decoloring reactors, the decoloring reaction temperatures of the polyester waste are 40-55 ℃ respectively, and further preferably, the decoloring reaction temperatures of the polyester waste are 40-50 ℃ respectively.

Preferably, in the number 1 and number 2 decolorizing reactors, the decolorizing reaction time of the terylene waste is 30-70min respectively, and further preferably, the decolorizing reaction time of the terylene waste is 30-60min respectively.

Preferably, in the No. 3 decoloring reactor, the mass ratio of the terylene waste to the second decoloring solvent is 1 (8-15), and more preferably, the mass ratio of the terylene waste to the second decoloring solvent is 1 (9-11).

Preferably, the decolorizing reaction temperature of the terylene waste in the No. 3 decolorizing reactor is 100-130 ℃, and further preferably, the decolorizing reaction temperature of the terylene waste is 100-120 ℃.

Preferably, in the No. 3 decoloring reactor, the decoloring reaction time of the terylene waste is 10-20min, and further preferably, the decoloring reaction time of the terylene waste is 10-15min.

Preferably, after the decoloring rate of the terylene waste reaches 90% through the No.1 and No. 2 decoloring reactors, the terylene waste enters the No. 3 decoloring reactor.

The method comprises the steps of carrying out primary decolorization on polyester waste at normal temperature in a decolorizing unit by adopting a decolorizing reactor No. 1 and a decolorizing reactor No. 2, wherein a first decolorizing solvent is preferably methylene dichloride, and after the primary decolorizing rate reaches 90%, enabling the polyester waste to enter a decolorizing reactor No. 3 for carrying out high Wen Tuose, and a second decolorizing solvent is preferably cyclic carbonate. The methylene dichloride can efficiently dissolve hydrophobic or weak polar dye molecules attached to polyester waste, and ensures that most of dye is dissolved and separated at normal temperature through the strong dissolving capacity and mild treatment on fibers. The process not only effectively protects the mechanical properties of the polyester fibers, but also greatly improves the primary decoloring efficiency. The cyclic carbonate is used as a strong polar solvent, can form stronger interaction with dye molecules, swells polyester fibers at high temperature, and increases gaps among the fibers, thereby promoting the dye molecules to migrate and separate more easily. Through the mutual matching of the two solvents, the high-efficiency decolorization of the terylene waste is realized.

Preferably, the granulating unit comprises a screw feeding system, a granulating device, an air conveying device, a granulating device and a packaging device which are connected in sequence.

Preferably, a cleaning unit is arranged between the decoloring unit and the granulating unit.

Preferably, the cleaning temperature of the cleaning unit is 30-50 ℃.

Preferably, the washing unit is internally used for washing the decolored terylene waste with water to ensure that the decoloration solvent is completely removed.

Preferably, the first circulation unit and the second circulation unit respectively comprise a waste liquid collecting device, a distillation device, a condensing device, a condensate tank and a residue tank which are connected in sequence.

Preferably, in the first circulation unit, the waste liquid collecting device is respectively connected with a number 1 decolorizing reactor and a number 2 decolorizing reactor, and after the decolorizing reaction is finished, the waste liquid of the first decolorizing solvent enters the waste liquid collecting device.

Preferably, in the first circulation unit, the condensate tank is connected with a No. 1 decolorizing reactor and a No. 2 decolorizing reactor respectively, and the condensed first decolorizing solvent is returned to the No. 1 decolorizing reactor and the No. 2 decolorizing reactor and is continuously used for decolorizing polyester waste.

Preferably, in the second circulation unit, the waste liquid collecting device is connected with a No. 3 decolorizing reactor, and after the decolorizing reaction is finished, the waste liquid of the second decolorizing solvent enters the waste liquid collecting device.

Preferably, in the second circulation unit, the condensate tank is connected with a No. 3 decoloring reactor, and the condensed second decoloring solvent is returned to the No. 3 decoloring reactor to be continuously used for decoloring polyester waste.

Specifically, in the number 1, number 2 and number 3 decolorizing reactors, after the decolorizing reaction is finished, the waste liquid of the first decolorizing solvent and the waste liquid of the second decolorizing solvent both contain dyes and impurities, and the first decolorizing solvent and the second decolorizing solvent respectively enter different solvent circulation units for treatment due to different properties and actions. The waste liquid in the waste liquid collecting device enters a distillation device, the waste liquid is heated to a required temperature (usually under a lower boiling point, so as to save energy and avoid thermal decomposition) by an electric heating or steam heating mode, the pressure in the distillation device is reduced by a vacuum pump system so as to achieve the effect of reduced pressure distillation, thereby reducing the boiling point of a solvent, the contact area of gas and liquid is increased by using a filler or a tower plate in a distillation column, the separation efficiency is improved, the gas and liquid are condensed into a liquid state by cooling water or a refrigerant after the distillation is finished, the liquid state is collected into a condensate tank, the condensed first and second decolorizing solvents have high purity, and the first and second decolorizing solvents are respectively conveyed back to the No. 1 decolorizing reactors, the No. 2 decolorizing reactors and the No. 3 decolorizing of polyester waste, and the residual liquid or impurities with high boiling point remained in the distillation device are discharged to a residual liquid tank for further treatment.

The second aspect of the invention provides a method for recycling terylene waste, which comprises the steps of pretreating, decoloring, cleaning and granulating terylene waste by using the terylene waste recycling system of the first aspect of the invention, and recycling decolored terylene particles.

Compared with the prior art, the invention has the beneficial effects that:

(1) According to the polyester waste recycling system provided by the invention, the disperse dye in the polyester waste can be effectively removed by the decolorizing unit, and the fiber is protected from being damaged, so that nearly white polyester waste which can be reused is obtained; the system comprises a solvent circulation unit which is connected with the decoloring unit, can collect decoloring waste liquid and purify the waste liquid, so that the obtained high-purity decoloring solvent returns to the decoloring unit for continuous use, and the system has less waste liquid generation, is favorable for environmental protection and saves reagent cost;

(2) According to the method for recycling the polyester waste, the polyester waste recycling system is adopted to pretreat, decolor, clean and granulate the polyester waste, so that the polyester particles capable of being reused can be obtained, and the resource waste is reduced.

Drawings

FIG. 1 is a schematic diagram of a polyester waste recovery system;

FIG. 2 is a graph showing the comparison of the dyeing polyester waste (a) before and (b) after decolorization of the black ect dispersion in example 3;

FIG. 3 is a graph showing the comparison of (a) before and (b) after decoloring the dispersed black PUD-SDS-BS dyed polyester waste in example 4;

FIG. 4 is a graph showing the comparison of the disperse blue 56 dyed polyester waste before (a) and after (b) decolorization in example 5;

FIG. 5 is a graph showing the comparison of the dispersed violet PUD-SW dyed polyester waste before (a) and after (b) decolorization in example 6;

FIG. 6 is a graph showing the comparison of the disperse red 343 dyed polyester waste before (a) and after (b) bleaching in example 7;

FIG. 7 is a graph showing the comparative examples 1 to 4, wherein the disperse blue 56 dyeing polyester waste is decolorized before (a) and after 60 ℃ (b), 80 ℃ (C), 100 ℃ (d) and 110 ℃ (e) for 30min with sodium hypochlorite, respectively;

FIG. 8 is a graph showing the comparative examples 5 to 8, wherein the dyeing of the dispersed violet PUD-SW dyed polyester waste is performed before (a) and the dyeing of the dispersed violet PUD-SW dyed polyester waste with sodium hypochlorite is performed for 30min at 60 ℃ (b), 80 ℃ (C), 100 ℃ (d) and 110 ℃ (e), respectively;

FIG. 9 is a graph showing the comparative examples 9 to 12, wherein the disperse red 343 is used before the dyeing of the polyester waste (a) and the sodium hypochlorite is used after the dyeing of the polyester waste at 60 ℃, 80 ℃, 100 ℃ and 110 ℃ for 30min respectively;

FIG. 10 is a diagram showing the recovery of the decolorized polyester particles obtained in example 6.

Detailed Description

The present invention will be described in further detail with reference to specific examples. The starting materials, reagents or apparatus used in the examples and comparative examples were either commercially available from conventional sources or may be obtained by prior art methods unless specifically indicated. Unless otherwise indicated, assays or testing methods are routine in the art.

Fig. 1 is a schematic diagram of a polyester waste recycling system, and as can be seen from fig. 1, the polyester waste recycling system is composed of a pretreatment unit, a decoloring unit, a granulating unit, a cleaning unit and a solvent circulating unit, wherein the pretreatment unit, the decoloring unit, the cleaning unit and the granulating unit are sequentially connected. The pretreatment unit comprises a crushing device and a drying device, the decoloring unit comprises a No. 1 decoloring reactor, a No. 2 decoloring reactor and a No. 3 decoloring reactor which are sequentially connected, the granulating unit comprises a screw feeding system, a particle collecting device, an air conveying device, a particle cutting device and a packaging device which are sequentially connected, the solvent circulating unit comprises a first circulating unit and a second circulating unit, and the first circulating unit and the second circulating unit comprise a waste liquid collecting device, a distillation device, a condensing device, a condensate tank and a residual liquid tank.

The polyester waste recycling system and the recycling method of polyester waste in the embodiment will be described with reference to fig. 1.

Example 1

The best conditions for preliminary decolorization of the decolorizing reactors No.1 and No.2 are explored in this example, and the steps are as follows:

S1, conveying 100g of dyed polyester waste into a crushing and cleaning machine through a belt conveyor, and crushing into uniform fragments of 5cm multiplied by 5 cm;

S2, sequentially feeding the dried polyester waste fragments into a No. 1 decoloring reactor and a No. 2 decoloring reactor, wherein the reactors contain a first decoloring solvent, and the types, the bath ratio, the decoloring reaction temperature and the decoloring reaction time of the first decoloring solvent are changed to enable the polyester waste fragments to perform preliminary decoloring reaction;

S3, after the preliminary decolorization is finished, measuring the decolorization rate and the strong retention rate.

The method for calculating the decoloring rate and the strong retention rate comprises the following steps:

1) Decolorizing ratio by measuring K/S value before and after decolorizing with Datacolor color meter,

The decolorization ratio = [ (K/S decolorized-K/S as received)/K/S as received ] ×100%;

2) The strong retention rate is measured by using a HD026N+ electronic fabric strong instrument to obtain the bursting strength value F of the terylene waste before and after decolorization,

Strong retention = [ (F as such-F decolorized) F as such ] ×100%.

Example 1 the type, bath ratio, decolorizing reaction temperature and time of the first decolorizing solvent in the preliminary decolorizing reaction are shown in table 1, and the decolorizing rate and strong retention of the polyester waste in test groups 1 to 12 are shown in table 2:

TABLE 1 setting of the kind of the first decolorizing solvent, the bath ratio, the decolorizing reaction temperature and the time in the preliminary decolorizing reaction

Test group	Solvent(s)	Bath ratio	Temperature (° C)	Time (min)
					1	Dichloromethane (dichloromethane)	1:10	40	30
2	Dichloromethane (dichloromethane)	1:10	40	45
					3	Dichloromethane (dichloromethane)	1:10	50	60
4	Dichloromethane (dichloromethane)	1:15	40	30
					5	Dichloromethane (dichloromethane)	1:15	50	60
6	Dimethyl sulfoxide	1:10	40	30
					7	Dimethyl sulfoxide	1:10	40	45
8	Dimethyl sulfoxide	1:10	50	60
					9	Dimethyl sulfoxide	1:15	40	30
10	Pyruvonitrile (Acrylonitrile)	1:10	40	45
					11	Pyruvonitrile (Acrylonitrile)	1:10	50	60
12	Pyruvonitrile (Acrylonitrile)	1:15	50	60

TABLE 2 results of the decolorization and Strong Retention of polyester waste in test groups 1 to 12 of example 1

As shown in Table 2, the primary decolorization rate is 92% at a bath ratio of 1:10, a decolorization reaction temperature of 50 ℃ and a decolorization reaction time of 60min, and the retention rate can reach 90% under the conditions, so that the primary decolorization effect is the best. And the DCM is used for simple operation, the recovery rate is high, and the advantages are achieved.

The same decolorizing solvent is adopted in the decolorizing reactors No. 1 and No. 2, so that the decolorizing solvent is convenient to recycle and recycle, the operation steps and equipment configuration can be simplified, the process complexity is reduced, the operation controllability and consistency are improved, the cost is reduced, different bath ratios and temperatures have obvious influence on the decolorizing rate and the strong retention rate, the dissolving capacity of the solvent can be influenced by the bath ratios, the decolorizing efficiency is reduced, the solvent consumption is increased due to the excessively high bath ratio, the industrialization cost is improved, the same bath ratio, the same temperature and the same decolorizing reaction time are maintained in the decolorizing reactors No. 1 and No. 2, the use efficiency and the recovery rate of the solvent are optimized, and the unnecessary cost increase caused by the mixed use of various solvents is avoided.

The same bath ratio, temperature and decolorizing reaction time are adopted in the decolorizing reactors No. 1 and No. 2, and the decolorizing process can be ensured to be more uniform by two steps of decolorizing reaction at low temperature, and the stability in the continuous production process is low and the integral decolorizing effect is easily influenced when only one reactor is adopted although the primary decolorizing reaction can be completed by one reactor.

Example 2

The best conditions for decolorizing in the No. 3 decolorizing reactor are explored in this example, and the steps are as follows:

S1, taking the primarily decolorized polyester waste in the test group 3 of the embodiment 1 as a raw material, enabling the polyester waste to enter a No. 3 decolorizing reactor, wherein the reactor contains a second decolorizing solvent, and changing the type, the bath ratio, the decolorizing reaction temperature and the decolorizing reaction time of the second decolorizing solvent so as to enable the polyester waste fragments to be subjected to high Wen Tuose reaction;

S2, after the decoloring is finished, measuring the decoloring rate and the strong retention rate.

The type, bath ratio, decolorizing reaction temperature and time of the second decolorizing solvent in the high temperature decolorizing reaction are shown in Table 3, and the decolorizing rate and strong retention of the polyester waste in test groups 1-8 are shown in Table 4:

TABLE 3 example 2 setting of the type of the second decolorizing solvent, the bath ratio, the decolorizing temperature and the time in the high temperature decolorizing reaction

Test group	Solvent(s)	Bath ratio	Temperature (° C)	Time (min)
					1	Ethylene carbonate	1:10	100	10
2	Ethylene carbonate	1:10	100	15
					3	Ethylene carbonate	1:10	120	10
4	Ethylene carbonate	1:10	120	15
					5	Propylene carbonate	1:10	100	10
6	Propylene carbonate	1:10	100	15
					7	Propylene carbonate	1:10	120	10
8	Propylene carbonate	1:10	120	15

Table 4 results of the decolorizing Rate and Strong Retention Rate of polyester waste in test groups 1-8 of example 2

Test group	High temperature decoloration Rate (%)	Strong retention (%)
			1	94	92
2	95	90
			3	96	88
4	98	85
			5	94	90
6	95	88
			7	97	87
8	99	85

As is clear from Table 4, propylene carbonate was used as the second decoloring solvent, and the highest Wen Tuose rate was 99% under the conditions of a bath ratio of 1:10, a decoloring reaction temperature of 120℃and a decoloring reaction time of 15min, and the retention rate was 85% under the conditions, so that the fiber damage was small, and the high Wen Tuose effect under the conditions was the best.

Example 3

In the embodiment, the dyeing polyester waste is treated and recycled by adopting the polyester waste recycling system, and the steps are as follows:

s1, feeding polyester waste dyed by disperse black ect (o.w.f=1%) into a crushing and cleaning machine through a belt conveyor, and crushing into uniform fragments of 5cm multiplied by 5 cm;

S2, enabling the dried polyester waste fragments to enter a No. 1 decoloring reactor, wherein dichloromethane is contained in the polyester waste fragments (the bath ratio is 1:10), decoloring for 60min at 50 ℃, then entering a No. 2 decoloring reactor, wherein dichloromethane is contained in the polyester waste fragments (the bath ratio is 1:10), continuously decoloring for 60min at 50 ℃, and completing preliminary decoloring;

S3, enabling the decolored fragments to enter a cleaning tank, washing with clear water at 40 ℃, and completely removing a decoloring solvent;

S4, conveying the cleaned chips into a granulating unit through a belt conveyor, and sequentially passing through a screw feeding system, a granulating device, an air conveying device, a granulating device and a packaging device to recover and obtain decolorized polyester granules.

In the recovery process, methylene dichloride waste liquid in the No. 1 decolorizing reactor and methylene dichloride waste liquid in the No. 2 decolorizing reactor are both fed into a waste liquid collecting device of a first circulating unit, fed into a distilling device through a feeding pump, fed into a condensing device after distillation is finished, condensed to obtain high-purity methylene dichloride, fed into a condensing liquid tank, respectively fed back into the No. 1 decolorizing reactor and the No. 2 decolorizing reactor and continuously used for decolorizing polyester waste, and propylene carbonate waste liquid in the No. 3 decolorizing reactor is fed into a waste liquid collecting device of a second circulating unit, fed into the distilling device through a feeding pump, fed into the condensing device after distillation is finished, condensed to obtain high-purity propylene carbonate, fed into the condensing liquid tank and fed back into the No. 3 decolorizing reactor and continuously used for decolorizing the polyester waste.

Example 4

s1, feeding the dispersed black PUD-SDS-BS dyed polyester waste (o.w.f=1%) into a crushing and cleaning machine through a belt conveyor, and crushing the polyester waste into uniform fragments of 5cm multiplied by 5 cm;

Example 5

s1, feeding polyester waste dyed with disperse blue 56 (o.w.f=1%) into a crushing and cleaning machine through a belt conveyor, and crushing the polyester waste into uniform fragments of 5cm multiplied by 5 cm;

Example 6

S1, feeding the polyester waste dyed by the disperse violet PUD-SW (o.w.f=1%) into a crushing and cleaning machine through a belt conveyor, and crushing the polyester waste into uniform fragments of 5cm multiplied by 5 cm;

Example 7

S1, feeding the polyester waste dyed by disperse red 343 (o.w.f=1%) into a crushing and cleaning machine through a belt conveyor, and crushing the polyester waste into uniform fragments of 5cm multiplied by 5 cm;

Comparative example 1

In the comparative example, sodium hypochlorite is used as a decoloring agent to decolor dyed polyester waste, and the steps are as follows:

Disperse blue 56 dyed polyester waste (o.w.f=1%) is immersed in sodium hypochlorite for decolorization (bath ratio 1:10) at 60 ℃ for 30min.

Comparative example 2

disperse blue 56 dyed polyester waste (o.w.f=1%) is immersed in sodium hypochlorite for decolorization (bath ratio 1:10) at 80 ℃ for 30min.

Comparative example 3

Disperse blue 56 dyed polyester waste (o.w.f=1%) is immersed in sodium hypochlorite for decolorization (bath ratio 1:10) at 100 ℃ for 30min.

Comparative example 4

Disperse violet PUD-SW dyed polyester waste (o.w.f=1%) is immersed in sodium hypochlorite for decolorization (bath ratio 1:10) at 110 ℃ for 30min.

Comparative example 5

The disperse violet PUD-SW dyed polyester waste (o.w.f=1%) is immersed in sodium hypochlorite for decolorization (bath ratio 1:10) at 60 ℃ for 30min.

Comparative example 6

the disperse violet PUD-SW dyed polyester waste (o.w.f=1%) is immersed in sodium hypochlorite for decolorization (bath ratio 1:10) at 80 ℃ for 30min.

Comparative example 7

disperse violet PUD-SW dyed polyester waste (o.w.f=1%) is immersed in sodium hypochlorite for decolorization (bath ratio 1:10) at 100 ℃ for 30min.

Comparative example 8

Comparative example 9

Disperse red 343 dyed polyester waste (o.w.f=1%) was decolorized by immersing in sodium hypochlorite (bath ratio 1:10) for 30min at 60 ℃.

Comparative example 10

Disperse red 343 dyed polyester waste (o.w.f=1%) was decolorized by immersing in sodium hypochlorite (bath ratio 1:10) for 30min at 80 ℃.

Comparative example 11

disperse red 343 dyed polyester waste (o.w.f=1%) was decolorized by immersing in sodium hypochlorite (bath ratio 1:10) for 30min at 100 ℃.

Comparative example 12

Disperse red 343 dyed polyester waste (o.w.f=1%) was decolorized by immersing in sodium hypochlorite (bath ratio 1:10) for 30min at 110 ℃.

The decoloring rates of the dyed polyester waste after the decoloring reaction in examples 3 to 7 and comparative examples 1 to 12 were measured and calculated as shown in table 5:

TABLE 5 bleaching rate of dyed polyester waste after the end of bleaching in examples 3 to 7 and comparative examples 1 to 12

Group of	Decoloring Rate (%)	Group of	Decoloring Rate (%)	Group of	Decoloring Rate (%)
						Example 3	99.1	Comparative example 1	20.07	Comparative example 7	78.30
Example 4	99.4	Comparative example 2	69.66	Comparative example 8	89.05
						Example 5	99.5	Comparative example 3	87.42	Comparative example 9	50.32
Example 6	99.6	Comparative example 4	89.42	Comparative example 10	79.87
						Example 7	99.7	Comparative example 5	23.88	Comparative example 11	80.09
/	/	Comparative example 6	59.57	Comparative example 12	90.05

Table 5 shows the decoloring rates of the dyed polyester waste after the decoloring reaction in examples 3 to 7 and comparative examples 1 to 12, and as can be seen from Table 5, the decoloring rates of the dyed polyester waste dyed by the disperse black, disperse blue, disperse violet and disperse red different disperse dyes in the decoloring unit are all over 99% by using methylene dichloride as a first decoloring solvent, performing preliminary decoloring on the dyed polyester waste under the conditions of a bath ratio of 1:10, a decoloring reaction temperature of 50 ℃ and a decoloring reaction time of 60min, using propylene carbonate as a second decoloring solvent in the decoloring reactor No. 3, and performing high Wen Tuose on the dyed polyester waste under the conditions of a bath ratio of 1:10, a decoloring reaction temperature of 120 ℃ and a decoloring reaction time of 15 min. In comparative examples 1 to 12, the dyeing polyester waste was subjected to the decoloring treatment with the conventional decoloring agent sodium hypochlorite, and the decoloring rate was gradually increased with the increase of the temperature, but was lower than 90%, and the sodium hypochlorite as a strong oxidizing agent may oxidize ester bonds in the fibers, so that the fibers become brittle, easily broken, and unfavorable for recycling of the polyester waste.

Fig. 2 is a comparative graph of (a) before and (b) after the dyeing of the polyester waste of disperse black ect in example 3, fig. 3 is a comparative graph of (a) before and (b) after the dyeing of the polyester waste of disperse black PUD-SDS-BS in example 4, fig. 4 is a comparative graph of (a) before and (b) after the dyeing of the polyester waste of disperse blue 56 in example 5, fig. 5 is a comparative graph of (a) before and (b) after the dyeing of the polyester waste of disperse violet PUD-SW in example 6, fig. 6 is a comparative graph of (a) before and (b) after the dyeing of the polyester waste of disperse red 343 in example 7, and fig. 10 is a physical graph of the obtained decolorized polyester particles recovered in example 6. As can be seen from fig. 2 to 6 and fig. 10, the method for recycling the dyed polyester waste by using the polyester waste recycling system provided by the invention has the advantages of high decoloring rate, nearly pure white recycled polyester particles and reutilization.

Fig. 7 is a comparative graph of comparative examples 1 to 4, in which the dyeing polyester waste before (a) and sodium hypochlorite were decolorized at 60C (b), 80C (d), 100C (d), and 110C (e) for 30min, respectively, fig. 8 is a comparative graph of comparative examples 5 to 8, in which the dyeing polyester waste before (a) and sodium hypochlorite were decolorized at 60C (b), 80C (C), 100C (d), and 110C (e) for 30min, respectively, and fig. 9 is a comparative graph of comparative examples 9 to 12, in which the dyeing polyester waste before (a) and sodium hypochlorite were decolorized at 60C (b), 80C (d), 100C (e), and 30min, respectively. As can be seen from fig. 7 to 9, the dyeing polyester waste can be decolorized by using sodium hypochlorite as a decolorizing agent, but the decolorizing effect is inferior to that of examples 5 to 7, and the fibrous tissue is easily damaged by oxidation of sodium hypochlorite, which is not beneficial to reuse.

The polyester waste recycling system provided by the invention has the advantages that the decoloring rate of the decoloring unit is high, the used decoloring solvent does not damage fiber tissues, the recycling of polyester waste is facilitated, the solvent circulating unit is arranged in the system, the decoloring solvent can be recycled, the waste liquid is less, and the environment protection is facilitated. According to the method for recycling the polyester waste, disclosed by the invention, the polyester waste is subjected to pretreatment, decolorization, cleaning and granulation treatment to obtain nearly colorless (white) waste polyester particles, so that the waste polyester particles can be reused, and the resource waste is reduced.

Claims

1. The terylene waste recycling system is characterized by comprising a pretreatment unit, a decoloring unit, a granulating unit and a solvent circulating unit;

And the No. 3 decoloring reactor is connected with a second circulating unit.

2. The polyester waste recycling system according to claim 1, wherein the pretreatment unit comprises a crushing device and a drying device connected in sequence.

3. The polyester waste recycling system according to claim 1, wherein the No.1 and No. 2 decoloring reactors contain a first decoloring solvent;

preferably, the first decolorizing solvent includes at least one of dimethyl sulfoxide, pyruvonitrile, and methylene chloride.

4. The polyester waste recycling system according to claim 1, wherein the No. 3 decoloring reactor contains a second decoloring solvent;

Preferably, the second decolorizing solvent comprises a cyclic carbonate.

5. The polyester waste recycling system according to claim 3, wherein in the number 1 and number 2 decolorizing reactors, the mass ratio of the polyester waste to the first decolorizing solvent is 1 (8-15);

And/or the decoloring reaction temperature of the terylene waste is respectively 40-55 ℃;

and/or the decoloring reaction time of the terylene waste is respectively 30-70min.

6. The polyester waste recycling system according to claim 4, wherein the mass ratio of the polyester waste to the second decolorizing solvent in the No. 3 decolorizing reactor is 1 (8-15);

And/or the decoloring reaction temperature of the terylene waste is 100-130 ℃;

and/or the decoloring reaction time of the terylene waste is 10-20min.

7. The polyester waste recycling system according to claim 1, wherein the granulating unit comprises a screw feeding system, a granulating device, an air-feeding device, a granulating device and a packing device which are sequentially connected.

8. The polyester waste recycling system according to claim 1, wherein a cleaning unit is provided between the decoloring unit and the granulating unit;

and/or the cleaning temperature of the cleaning unit is 30-50 ℃.

9. The polyester waste recycling system according to claim 1, wherein the first circulation unit and the second circulation unit respectively comprise a waste liquid collecting device, a distillation device, a condensing device, a condensate tank and a residue tank which are sequentially connected.

10. A method for recycling polyester waste, characterized by comprising the steps of pretreating, decoloring, cleaning and granulating the polyester waste by using the polyester waste recycling system according to any one of claims 1 to 9, and recycling decolored polyester particles.