WO2024220053A1

WO2024220053A1 - A method for revaluation of acrylic fibre wastes in acrylic fibre production

Info

Publication number: WO2024220053A1
Application number: PCT/TR2023/051643
Authority: WO
Inventors: Gürcan KOMAN; Simge DİNÇER UZUNPINAR; Selçuk ERKOŞAN; Emrah EREN; Turgay Yilmaz
Original assignee: Aksa Akrilik Kimya Sanayii AS
Current assignee: Aksa Akrilik Kimya Sanayii AS
Priority date: 2023-12-22
Filing date: 2023-12-22
Publication date: 2024-10-24
Anticipated expiration: 2026-06-22

Abstract

The invention relates to the production method introduced to produce acrylic fibre with improved mechanical properties by recycling acrylic fibre waste without damaging their chemical structure, and to the recycled acrylic fibre obtained as a result of this method.

Description

A METHOD FOR REVALUATION OF ACRYLIC FIBRE WASTES IN ACRYLIC FIBRE PRODUCTION

TECHNICAL FIELD

The invention relates to the production of acrylic fibre by using/adding recycled waste materials.

STATE OF THE ART

Acrylic fibres, like other general-purpose synthetic fibres such as polyamide fibres and polyester fibres, are used in a wide variety of fields, such as clothing materials and interior product materials. On average, 15 billion pieces of clothing are thrown away unused annually worldwide. This type of thrown clothing has become a major problem in recent years and causes rapid depletion of natural resources. Although ready-made clothing and material manufacturers work to reuse and recycle these discarded clothes, the current situation causes delays in development due to the high labour cost required for separation work and the difficulty of high separation and collection technology, and prevents the recycling of waste products in sufficient quantities.

However, although a pre-consumer-derived recycling technology has been established for acrylic that uses waste in the production process, an end-consumer-derived recycling technology has not been established.

The disadvantage of previous uses is that since the products used for recycling are not acrylic fibres, the chemical structures of the products are deteriorated in the production of acrylic fibres and the resulting acrylic fibres are of poor quality.

The Russian document with publication number RU2722499C1 comprises basic information about the recycling of acrylic products. It is not possible to use the methods mentioned in this document for recycling without damaging the chemical structure of acrylic fibres.

Japanese document with publication number JP20221121 14A describes postconsumer recycled acrylic fibre and the production method thereof. The method involves grinding the textile products, separating, recovering and using the acrylic component. The proposed recycled acrylic fibre comprises the acrylic component obtained by milling a textile and recovered from a mixture of milled fibres with an aspect ratio (fibre length/fibre diameter) of 10 or less. The fibre product comprises a total of 5.0 to 99.0% by weight of the acrylic component. The method of recovering the acrylic component from the milled fibre mixture and then spinning it into yarn is described. The collected acrylic component is dissolved in a solvent to form an acrylic polymer solution (A), and this solution is turned into wet-yarn with a polymer mixture of 0.5% to 60.0% by weight, but the recovery rate is quite low compared to the energy spent. In addition, the strength and flexibility properties of the final product are low. A method that has better durability features and is better in terms of energy and manpower needs to be developed.

The Chinese document with publication number CN1 17164951 A describes the recovery method of waste acrylic fabrics in the technical field of environmental protection and recycling of waste acrylic fabrics. The method comprises the process steps of: Dissolving (completely dissolving the acrylic fibres by adding the waste acrylic fibre textile to a solvent, heating and mixing), Soaking (keeping the polyacrylonitrile solution at low temperature and turning it from yellow transparent liquid into polyacrylonitrile white gel), Shaping (placing the polyacrylonitrile white gel to cure in a heat environment), Extraction (soaking the polyacrylonitrile solid in an extractant and performing solvent extraction with continuous release) and Drying (obtaining polyacrylonitrile porous material by drying the polyacrylonitrile solid subjected to solvent extraction). The aim of this invention is not to obtain acrylic fibre, but to obtain material that can be used in making products made of polymer containing acrylonitrile monomer, which can be used in some technical fields. Acrylic fibres can be reused, but materials with sufficient durability cannot be created for acrylic fibre production. This invention is about converting wastes brought in solid and gel form into reusable materials. Technical work is required to work at more ergonomic and optimal temperatures and to obtain more durable products.

As a result, it has been understood that it is appropriate to make innovations in the relevant technical field along with alternative solutions to all the above-mentioned problems. THE AIM OF THE INVENTION

The main aim of the invention is to produce acrylic fibre from recyclable acrylic fibre waste.

The aim of the invention is to prevent environmental pollution caused by waste materials and to prevent the consumption of natural and/or artificial resources.

Another aim of the invention is to ensure the recovery of waste products.

The aim of the invention is to use it in the recycling process of waste in both solid and liquid form.

The invention was put forth to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

DETAILED DESCRIPTION OF THE INVENTION

In this detailed description, the invention is described with non-limiting examples only for better understanding of the subject.

The invention, described in detail below, was put forth to produce acrylic fibre by recycling acrylic fibre waste without damaging their chemical structure to achieve recovery in the range of 15% to 100%

In the acrylic fibre production process, polyacrylonitrile is dissolved with solvent and a mixture called dope is formed. PAN polymer can be homopolymer, co-polymer, modified polymer and sulphonated polymer. Dope fibre is produced by wet and dry spinning method. Polymers, dopes and fibres, which occur as a result of process stoppages due to malfunctions during polymer and fibre production, during installation periods and during transitional production to reach the target machine condition, become waste. Threads and fabrics produced from acrylic fibres also constitute waste. In the recovery process, dry and wet fibre waste is mixed with the appropriate solvent and the tanks are heated to melt the fibre waste. In addition, these are melted with a continuous mixing process to obtain a homogeneous solution.

The invention comprises the processes of feeding to the slurry tank from 3 points and the subsequent recycling process. One of said 3 feeding processes is the process of feeding the waste dope to the slurry tank. This process comprises the process steps of a.1 . collecting waste dope-containing materials in the storage tank, a.2. performing at least one filtration process with the help of a pump to ensure the separation of unusable materials, a.3. conveying the waste dope-containing mixture obtained after the filtration process to the waste feeding tank, a.4. feeding of waste materials with a waste content ranging from 15% to 26% solid matter and a feeding rate of 150 kg/s to 400 kg/s to the slurry tank from the feeding tank.

The process of feeding waste to the slurry tank ensures that the waste comes to appropriate conditions before being recycled and that the final product obtained after the recycling process can be created in the desired qualities.

In the preferred embodiment of the invention, the materials added to the storage tank in process step a.1 . are subjected to mixing to ensure a homogeneous mixture and are heated to a temperature in the range of 70-100°C to accelerate the process. The mixing process is continued by keeping the mixture at a temperature of 70-100°C for 4-10 hours. While a temperature below 70°C cannot achieve the desired effect on the mixture in the desired time, a temperature above 100°C causes burning, flashing and/or deformations in the mixture.

Another of said 3 feeding processes is the waste acrylic fibre feeding process with dilute dope addition to the slurry tank. This process comprises the process steps of b.1. adding dry waste containing waste acrylic fibre into the perforated tank and heating the tank to a temperature in the range of 70-110°C, b.2. cooling the acrylic fibre waste mixed with the dry waste separated from the perforated tank to a temperature between 50-90°C with the help of a pump and heat exchanger, and subjecting it to this process in a recirculating manner by re-entering it the perforated tank, b.3. mixing of waste acrylic fibre mixtures mixed with recirculating dry waste by transferring them from the perforated tank to the storage tank and heating to a temperature in the range of 70-110°C while mixing, b.4. applying filtration to the resulting mixture at least twice to ensure the separation of unusable products in the resulting mixture, b.5. feeding the mixture obtained after the filtration process to the heat exchanger and heating it, b.6. taking the mixture obtained after the filtration process into the slurry preparation tank, mixing it and heating it to a temperature between 70-110°C by adding solvent and stabilizer to the slurry preparation tank while the mixing process continues, and b.7. feeding the mixture obtained after the heating process in the reactor tank to the slurry tank with a solid matter content ranging from 15% to 20% and a feeding rate of 0 kg/s to 2500 kg/s.

The mixture transferred to the slurry preparation tank as a result of the method step b.5. is dope. The resulting dope is in diluted form.

In the preferred embodiment of the invention, in the process step b.5., the environment is kept in the temperature range of 60-120°C to ensure the appropriate temperature by the heat exchanger.

In the preferred embodiment of the invention, the filtration process is applied at least once after the process step b.5. and before the process step b.6.. Filtration processes ensure that the impurity content of many different qualities is kept at the desired level and the contents that can damage the final product are removed.

In the preferred embodiment of the invention, said solvent in process step b.6. contains one of the groups or combinations of individuals comprises dimethylacetamide, dimethyl sulfoxide, dimethylformamide and N-methyl-2-pyrrolidone.

In the preferred embodiment of the invention, said polymer in process step b.6. is polyacrylonitrile (PAN). The polyacrylonitrile ratio in acrylic fibres determines whether the acrylic fibre is acrylic or modacrylic. Modacrylic fibres, which stand out with their flame retardant properties, contain polyacrylonitrile in the range of 35-85% by weight, while acrylic fibres contain more than 85% polyacrylonitrile by weight.

In the preferred embodiment of the invention, the PAN polymer is one of the individuals or combinations selected from the group consisting of homopolymer, co-polymer, modified polymer and sulponated polymer. In the preferred embodiment of the invention, PAN polymer is fed to the tank by measuring the feed amount with a scale using rotary valves. Rotary valve sets are adjusted and fed according to the recovery rate of polymer and waste polymer products.

In the preferred embodiment of the invention, there are nozzles in the tank where the polymer is fed. Solvent (solvent temperature 25-70°C), dilute dope prepared by melting dry fibre waste and heat stabilizer are given through these nozzles.

In the preferred embodiment of the invention, the mixture obtained after the process step b.6. comprises;

- PAN in a ratio range of 0.1 - 85 %,

- stabilizer in a ratio range of 0.5 - 1 .0 %,

- Dope with a dilution ratio of 5% to 20%, completing the mixture to 100% by weight.

Wastes in dry form are dissolved with solvent on the perforated surfaces in the tanks. Meanwhile, the tanks are put into circulation. During circulation, dope in dilute form is circulated through heating exchangers. Exchanger temperature is between 70-100°C. In the current process, it heats to 85°C. At the same time, heating is done in the tank shells and the tank internal temperature is kept between 70-100 °C. In the current process it is 80°C. Circulation in the tank continues for 4-10 hours depending on the amount and type of waste. In the current process, it is done for 6 hours. After the melting process is fully completed, the diluted dope is taken into the storage tank.

The last of said 3 feeding processes is the feeding process of waste acrylic fibre melted in a vacuum environment. This process proceeds in two directions when both solid and wet wastes are used. After the solid and wet wastes are processed separately, the processed wastes are combined, and the process continues. Vacuum tanks are used to melt waste in wet form. By creating a vacuum in the tanks and removing the water in the waste, homogeneous melting is achieved and coagulation and agglomeration that may occur in the water-borne solution is prevented. Gradual ejector and heat exchanger systems are used in these tanks and the tanks are vacuumed in this way. According to this information, the feeding process of waste acrylic fibre melted in a vacuum environment comprises the process steps of: c.1 . putting the mixture containing wet waste containing acrylic fibre waste into a vacuum tank to remove unwanted water and heating the tank to any temperature in the temperature range of 70-100°C, c.2. transferring the resulting mixture first to the heat exchanger and then to the ejector to separate the solid, liquid or gas particles in the mixture and clean the mixture. c.3. conveying the mixture separated from the ejector back to the vacuum tank after the completion of the separation process, c.4. applying a filtration process to ensure the separation of waste acrylic fibres in the mixture in the vacuum tank that may damage the mixture, c.5. adding dry waste to a different tank than the one mentioned in the process step c.1., mixing it with waste acrylic fibre and heating the tank to any temperature in the 70-100°C temperature range while the mixing process continues, c.6. applying a filtration process to separate and clean the mixture obtained in the process step c.5., c.7. mixing the mixture obtained after said filtration process in the process step c.4. with the mixture obtained after said filtration process in the process step c.6„ c.8. applying a filtration process to separate the waste acrylic fibres that are in the resulting mixture and cannot be used, c.9. transferring the separated mixture resulting from said filtration process in the process step c.8. to the storage tank and mixing it for 4-10 hours at a temperature range of 70-100°C, c.10. conveying the resulting mixture to a filter with the help of a pump and applying the filtration process, and c.1 1. feeding solid matter content ranging from 15% to 20% from the mixture obtained as a result of said filtration in the process step c.10. into the slurry tank with a feeding rate of 180kg/s to 2800kg/s.

In the preferred embodiment of the invention, the internal pressure of the tank containing wet water mentioned in the process steps related to the feeding process of waste acrylic fibre melted in a vacuum environment is kept between 0.75 bar and full vacuum. After heating to 70-100°C depending on the amount of waste in the tank (85°C in the current process), the vacuum system is activated, and the vacuuming process is stopped when the temperature drops to 50-75°C (65°C in the current process).

Feeding is done to the slurry preparation tank according to the recovery rate from the storage tank mentioned in the process step c.9. Depending on the feed amount, recovery rates vary between 10% and 100%.

After said 3 feeding processes, the recycling method is applied starting from the slurry tank. This method comprises the process steps of: d.1. heating the slurry tank, d.2. separating the acrylic material that cannot be used in the resulting mixture by filtration process, d.3. heating the mixture resulting from the process step d.2. to 60-120°C using a slurry exchanger to ensure dope formation, d.4. cooling to 50-90 °C with the help of a heat exchanger to prevent the colour of the dope produced in the process step d.3. from changing, d.5. transferring it to the deaerator tank and heating it to remove air bubbles in the dope consisting of recycled materials obtained as a result of the filtration process. d.6. separating the material to be turned into fibre from impurities by applying at least one filtration process after the process in the deaerator tank, d.7. transferring the mixture obtained after the separation process to the feeding tank and heating it, d.8. transferring the material transferred to the feeding tank to the fibre spinning machine to produce acrylic fibre through the pump, and d.9. applying heat treatment to the fibres obtained after the fibre drawing process to improve the mechanical properties.

In the preferred embodiment of the invention, the slurry in the slurry tank is heated to 60-120°C using a heat exchanger and dope is prepared.

In the preferred embodiment of the invention, the filtration process is carried out by one of the individuals or combinations selected from the group consisting of filter presses, pot filter, basket filter and blunder filter. The above processes, which are applied after feeding the Slurry tank from 3 points, are sensitive processes and no step can be separated from the other.

The process steps that are desired to be covered by the protection of the invention are the 3 feedings to the slurry tank and the operations performed after the slurry tank. In other words, each of the 3 mentioned feeds is very important for the operation of the invention.

In order to ensure the realisation of the process, in the preferred embodiments of the invention, heating processes are carried out for 4-10 hours in order to obtain the desired mixture in all tanks.

In order to ensure process safety when reaching high temperatures in the process, in preferred embodiments of the invention, the tanks are kept under nitrogen cover. In this way, the process is carried out above the flash temperature of the solvent.

As a result of the fibre spinning process with dry and wet spinning methods, a recycled acrylic fibre product is obtained.

In an embodiment of the invention, after the process step d.8 and before the process step d.9, the mixture created with blue and violet pigments is given to the mixer and the mixture is injected into the dope in order to provide the whiteness parameter for colourless products in fibre production machines.

In alternative embodiments of the invention, different pigments can also be used for colouring. When coloured and/or colourless wastes are used, the dyeing process can be carried out.

An alternative embodiment of the invention also comprises the dyeing process after the process step d.9, and dope dyeing and/or gel dyeing method is used in this dyeing process.

The final product number resulting from the process step d.9. varies between 1.10 and 45 dtex. The strength of the product is 10-50 cN/T and the elongation is between 30- 60%. The process steps for which the invention is intended to be protected are the 3 feedings to the slurry tank, the post-slurry tank operations and the recycled acrylic fibre obtained as the final product.

The scope of protection of the invention is stated in the attached claims and cannot be limited to what is explained in this detailed description for exemplary purposes.

Because it is obvious that a person skilled in the art can produce similar structures in the light of those described above, without deviating from the main theme of the invention.

Claims

1. Acrylic fibre production method by recycling waste acrylic fibres to provide recovery in the range of 15%-100%, comprising the process steps of; a. as the process of feeding waste dope to slurry tank; a.1 . collecting waste dope-containing materials in the storage tank, a.2. Performing at least one filtration process with the help of a pump to ensure the separation of unusable materials, a.3. Conveying the waste dope-containing mixture obtained after the filtration process to the waste feeding tank, a.4. feeding of waste materials with a waste content ranging from 15% to 26% solid matter and a feeding rate of 150 kg/s to 400 kg/s to the slurry tank from the feeding tank, b. as the process of feeding waste acrylic fibre with dilute dope addition to the slurry tank; b.1. adding dry waste containing waste acrylic fibre into the perforated tank and heating the tank to a temperature in the range of 70-110°C, b.2. cooling the acrylic fibre waste mixed with the dry waste separated from the perforated tank to a temperature between 50-90°C with the help of a pump and heat exchanger, and subjecting it to this process in a recirculating manner by re-entering it the perforated tank, b.3. mixing of waste acrylic fibre mixtures mixed with recirculating dry waste by transferring them from the perforated tank to the storage tank and heating to a temperature in the range of 70-110°C while mixing, b.4. applying filtration to the resulting mixture at least twice to ensure the separation of unusable products in the resulting mixture, b.5. feeding the mixture obtained after the filtration process to the heat exchanger and heating it, b.6. taking the mixture obtained after the filtration process into the slurry preparation tank, mixing it and heating it to a temperature between 70- 110°C by adding solvent and stabilizer to the slurry preparation tank while the mixing process continues, and b.7. feeding the mixture obtained after the heating process in the reactor tank to the slurry tank with a solid matter content ranging from 15% to 20% and a feeding rate of 0 kg/s to 2500 kg/s, c. as the process of feeding waste acrylic fibre melted in vacuum environment; c.1 . putting the mixture containing wet waste containing acrylic fibre waste into a vacuum tank to remove unwanted water and heating the tank to any temperature in the temperature range of 70-100°C, c.2. transferring the resulting mixture first to the heat exchanger and then to the ejector to separate the solid, liquid or gas particles in the mixture and clean the mixture. c.3. conveying the mixture separated from the ejector back to the vacuum tank after the completion of the separation process, c.4. applying a filtration process to ensure the separation of waste acrylic fibres in the mixture in the vacuum tank that may damage the mixture, c.5. adding dry waste to a different tank than the one mentioned in the process step c.1 ., mixing it with waste acrylic fibre and heating the tank to any temperature in the 70-100°C temperature range while the mixing process continues, c.6. applying a filtration process to separate and clean the mixture obtained in the process step c.5., c.7. mixing the mixture obtained after said filtration process in the process step c.4. with the mixture obtained after said filtration process in the process step c.6., c.8. applying a filtration process to separate the waste acrylic fibres that are in the resulting mixture and cannot be used, c.9. transferring the separated mixture resulting from said filtration process in the process step c.8. to the storage tank and mixing it for 4-10 hours at a temperature range of 70-100°C, c.10. conveying the resulting mixture to a filter with the help of a pump and applying the filtration process, and c.1 1 . feeding solid matter content ranging from 15% to 20% from the mixture obtained as a result of said filtration in the process step c.10. into the slurry tank with a feeding rate of 180kg/s to 2800kg/s, d. as the method of recycling from slurry tank; d.1 . heating the slurry tank, d.2. separating the acrylic material that cannot be used in the resulting mixture by filtration process, d.3. heating the mixture resulting from the process step d.2. to 60-120°C using a slurry exchanger to ensure dope formation, d.4. cooling to 50-90 °C with the help of a heat exchanger to prevent the colour of the dope produced in the process step d.3. from changing, d.5. transferring it to the deaerator tank and heating it to remove air bubbles in the dope consisting of recycled materials obtained as a result of the filtration process. d.6. separating the material to be turned into fibre from impurities by applying at least one filtration process after the process in the deaerator tank, d.7. transferring the mixture obtained after the separation process to the feeding tank and heating it, d.8. transferring the material transferred to the feeding tank to the fibre spinning machine to produce acrylic fibre through the pump, and d.9. applying heat treatment to the fibres obtained after the fibre drawing process to improve the mechanical properties.

2. Method according to Claim 1 , wherein in the process step a.1., the materials added to the storage tank are mixed by keeping the temperature between 70- 100°C for 4-10 hours.

3. Method according to Claim 1 , wherein In the process step b.5., the environment is kept in the temperature range of 60-120°C by the exchanger to ensure the temperature suitable for melting.

4. Method according to Claim 1 , wherein after the process step b.5., and before the process step b.6., filtration process is applied at least once to reduce the damages that may occur due to impurities and to ensure the separation of unusable acrylic fibre waste.

5. Method according to Claim 1 , wherein the mixture obtained after the process step b.6. comprises: - PAN in a ratio range of 0.1 - 85 %,

- stabilizer in a ratio range of 0.5 - 1 .0 %,

6. Method according to Claims 1 or 5, wherein in process step b.6., one of the groups or combinations of individuals comprising dimethylacetamide, dimethyl sulphoxide, dimethylformamide and N-methyl-2-pyrrolidone is used as the solvent.

7. Method according to Claims 1 , 5 or 6, wherein in process step b.6., polyacrylonitrile (PAN) is used as the polymer.

8. Method according to Claim 7, wherein the PAN used in process step b.6. is used as one of an individual or combination selected from the group consisting of homopolymer, co-polymer, modified polymer and sulphonated polymer.

9. Method according to Claims 1 , 7 or 8, wherein in process step b.6., the feed amount of PAN polymer is measured with a scale and transferred to the slurry preparation tank in order to control dope formation,

10. Method according to Claims 1 or 9, wherein in process step b.6., PAN polymer is transferred to the slurry preparation tank with rotary valves to ensure that the recovery rate of the polymer and waste polymer products can be adjusted.

11. Method according to Claim 1 , wherein in the process step e.6., the solvent is transferred to the slurry preparation tank where the polymer is fed through nozzles with a temperature range of 25-70°C.

12. Method according to Claim 1 , wherein, to prevent a humid environment from delaying or stopping the melting process, the tank internal pressure is kept between 0.75 bar and full vacuum by ensuring that the vacuum system is activated after heating up to 70-100°C and that the vacuuming process is stopped when it drops to 50-75°C depending on the waste amount of the vacuum tank mentioned in the process step c.

13. Method according to Claim 1 , wherein, the filtration process is carried out by one of the individuals or combinations selected from the group consisting of filter presses, pot filter, basket filter and blunder filter.

14. Method according to Claim 1 , wherein, when the recovery rate is reduced according to the recovery rate to provide recovery in the range of 10%-100%, the filtered mixture is fed to the slurry preparation tank in the process step c.10., increasing the feeding rate from the storage tank mentioned in the process step c.9.

15. Method according to Claim 1 , wherein, after the process step d.8. and before the process step d.9., coloured pigments are injected into the dope obtained in the process step d in order to provide the whiteness parameter for colourless products in fibre production machines.

16. Acrylic fiber prepared by the method according to any of the claims 1 -15 to provide 10-50 cN/T strength and 30-60% elongation properties in the 1 .10 - 5.60 dtex number range.