Method for recycling and spinning ultra-high molecular weight polyethylene fibers

Abstract

The invention belongs to the technical field of ultra-high molecular weight material manufacturing, and particularly relates to an ultra-high molecular weight polyethylene fiber recycling spinning method which comprises the following five steps: S1, sorting; s2, dehydrating and degumming; s3, cutting is conducted; s4, dissolving; and S5, spinning. According to the method, the ultra-high molecular weight polyethylene fiber with the physical property equal to that of the protofilament can be recycled, the ultra-high molecular weight polyethylene fiber with the use performance higher than that of the protofilament can be obtained, and the application range of the recycled ultra-high molecular weight polyethylene fiber is effectively widened; the purposes of efficient and environment-friendly regeneration and high-quality recycling of the waste ultra-high molecular weight polyethylene fibers are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of ultra-high molecular weight material manufacturing, and in particular relates to a method for recycling and spinning ultra-high molecular weight polyethylene fibers. Background Art

[0002] Ultra-high molecular weight polyethylene fiber has been widely used in protective clothing, ropes, fishing nets, sporting goods and high-end industrial applications due to its excellent physical properties, such as high strength, wear resistance, chemical corrosion resistance and low density. With the continuous increase in the production and use of UHMWPE fibers, the treatment and recycling of discarded or waste UHMWPE fibers has become increasingly prominent. The traditional treatment methods are mainly landfill and incineration, which will cause serious pollution to the soil and the environment. For this reason, chemical treatment methods have been used to recycle UHMWPE fibers, but the treatment cost is high and it is very easy to cause secondary pollution to the environment.

[0003] In the prior art, there are studies on the problems of recycling UHMWPE fibers by chemical treatment methods, such as patent application CN105504440A - Preparation of ultra-high molecular weight polyethylene reinforced fiber, which uses continuous production processes such as crushing, mixing agglomeration, cooling, and extrusion to recycle ultra-high molecular weight polyethylene waste, solving the problems of high cost and environmental pollution in the current chemical treatment methods for recycling UHMWPE fibers. However, the existing methods for recycling ultra-high molecular weight polyethylene waste are difficult to ensure that the physical properties of the recycled fibers can reach the level of the original fibers, thereby limiting their scope of application. Therefore, a new technical solution is needed to solve the above technical problems. Summary of the invention

[0004] The purpose of the present invention is to provide a method for recycling and spinning ultra-high molecular weight polyethylene fibers, so as to solve the problem that the current method for recycling ultra-high molecular weight polyethylene waste proposed in the above-mentioned background technology is difficult to ensure that the physical properties of the recycled fibers can reach the level of the original fibers, thereby limiting their scope of application.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for recycling and spinning ultra-high molecular weight polyethylene fibers, comprising the following specific steps: S1. Classification and sorting: firstly, the waste of ultra-high molecular weight polyethylene fibers is classified and sorted according to product types; S2, dehydration and degumming: the sorted waste is dehydrated by a centrifuge or a press, and after dehydration, it is immersed in a degumming agent including 30% sodium bicarbonate, 25% citric acid, and 45% sodium silicate for 20 to 50 minutes at 85 to 105°C to obtain waste materials. After degumming, the waste materials need to be washed, bleached, dried, softened or antistatically treated to obtain recycled fibers with a moisture content of ≤0.2‰; S3. Cutting: Cut the recycled fiber into short fibers with a length of 1 to 10 mm, a diameter of 0.1 to 10 mm and a solid content of 8 to 30% by a band saw or a roller cutter; S4, dissolution: put 10-20 parts of staple fibers, 20-80 parts of white oil solvent, 3-5 parts of polyolefins and 2-3 parts of antioxidants in proportion according to mass fraction into a dissolution kettle at a solid content concentration of ≦10%, stir and mix at a rate of 10-100 rpm, and gradually heat to 165-180°C in four stages after stirring evenly. After the staple fibers are dissolved, a spinning solution is obtained, wherein the main raw material of the white oil solvent is petroleum, which is obtained through dewaxing, carbonization, neutralization and activated clay refining treatment. The antioxidant is one or more of tert-butylhydroquinone and dioctyl pyrophosphate. The four stages of heating are: the first stage is heated to 60-90°C, the second stage is heated to 90-120°C, the third stage is heated to 120-165°C, and the fourth stage is heated to 165-180°C; S4, spinning: the spinning solution is sequentially passed through a twin-screw extruder, a spinning metering pump, a spinneret, a coagulation bath, a dryer, a traction machine and a winder to be spun into ultra-high molecular weight polyethylene fiber filaments.

[0006] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention adopts a process for recycling waste ultra-high molecular weight polyethylene fibers, realizes effective conservation and recycling of resources, not only helps to alleviate the problem of resource shortage, but also conforms to the concept of sustainable development. By performing dehydration and degumming treatment before cutting, the waste of ultra-high molecular weight polyethylene fibers (including waste products, semi-finished products and defective products) can not only remove the colloid contained therein, but also effectively improve its performance in use, thereby ensuring the quality of the recycled ultra-high molecular weight polyethylene fibers. The method of gradually heating up and dissolving short fibers in four stages can not only make the dissolution process of the ultra-high molecular weight polyethylene fibers more stable, but also can retain the physical properties of the ultra-high molecular weight polyethylene fibers to the maximum extent, so that the recycled quality of the ultra-high molecular weight polyethylene fibers can reach the level of the original fibers, effectively improving the application scope of the recycled ultra-high molecular weight polyethylene fibers, and creating huge economic benefits. 2. The present invention adopts one of 30% sodium bicarbonate, 25% citric acid and 45% sodium silicate as a degumming agent, so that the colloid contained in the waste of ultra-high molecular weight polyethylene fiber can be effectively removed under the action of the degumming agent, and by washing, bleaching, drying and softening or antistatic treatment after degumming, the recycled fiber can not only remove the residual degumming agent and impurities, but also effectively improve the cleanliness and whiteness of the recycled fiber, and can also effectively improve its performance in use, thereby ensuring the quality of the recycled ultra-high molecular weight polyethylene fiber; 3. The present invention adopts a method of gradually increasing the temperature from low to high to dissolve, so that the short fibers can be completely dissolved while retaining the physical properties of the short fibers to the maximum extent, effectively improving the stability of dissolution, so that the quality of the recovered ultra-high molecular weight polyethylene fibers can reach the level of the original fibers, effectively improving the application scope of the recycled ultra-high molecular weight polyethylene fibers, and creating huge economic benefits; 4. The present invention adopts a recycling process of sorting-dehydration and degumming-cutting-dissolving-spinning, which can not only recycle ultra-high molecular weight polyethylene fibers with physical properties equivalent to those of the original fibers, but also obtain ultra-high molecular weight polyethylene fibers with performance higher than that of the original fibers, effectively improving the application scope of the recycled ultra-high molecular weight polyethylene fibers, achieving effective conservation and recycling of resources, helping to alleviate the problem of resource shortage, and ensuring the competitiveness and sustainable development capabilities of ultra-high molecular weight polyethylene fibers in the entire industrial chain. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a structural schematic diagram of the spinning process of the present invention.

[0008] Among them: 1. Twin-screw extruder; 2. Spinning metering pump; 3. Spinneret; 4. Coagulation bath; 5. Dryer; 6. Traction machine; 7. Winding machine. DETAILED DESCRIPTION

[0009] The following examples are used to further illustrate the content of the present invention, but do not limit the application of the present invention. Embodiment 1:

[0010] The present embodiment provides a method for recycling and spinning ultra-high molecular weight polyethylene fibers, comprising the following specific steps: first, classifying and sorting ultra-high molecular weight polyethylene fiber waste (including waste products, semi-finished products and defective products) according to product types; secondly, dehydrating the classified waste using a centrifuge or a press, and then naturally drying it in a well-ventilated place after dehydration to further remove residual moisture, and then immersing it in a degumming agent of 30% sodium bicarbonate at 85-105° C. for 20-50 minutes to obtain waste material, and after the degumming is completed, the waste material needs to be washed, bleached, dried, softened or antistatically treated to obtain recycled fibers with a moisture content of ≤0.2‰; and then, cutting the recycled fibers with a moisture content of ≤0.2‰ into fibers with a length of 1-10 mm, a diameter of 0.1-10 mm and a solid content of 8-30% of staple fibers; then, 12 parts of staple fibers, 25 parts of white oil solvent, 3.8 parts of polyolefins and 2.6 parts of dioctyl pyrophosphate are mixed in a dissolving kettle according to the mass fraction ratio at a solid content concentration of ≦10%, and stirred and mixed at a rate of 10-100 rpm. After being stirred evenly, the temperature is raised to 68°C in the first stage, and when the staple fibers are dissolved, the temperature is raised to 95°C in the second stage, and when a small part of the staple fibers are dissolved, the temperature is raised to 138°C in the third stage, and when most of the staple fibers are dissolved, the temperature is raised to 168°C in the fourth stage, until the staple fibers are completely dissolved to obtain a spinning solution; finally, the spinning solution is transported to a twin-screw extruder 1, and formed into filaments through a spinning metering pump 2 and a spinneret 3. The filaments are transported to a dryer 5 for drying after heat exchange in a coagulation bath 4, and then pulled to a winder 7 by a traction machine 6 to be curled into ultra-high molecular weight polyethylene fiber filaments (the spinning process can be seen Figure 1 As shown in the figure, the ultra-high molecular weight polyethylene fiber was tested according to the national standard GB / T29554-2013 "Ultra-high molecular weight polyethylene fiber", and its physical property retention rate was 96.7% and the recovery rate was 78.4%. Embodiment 2:

[0011] The method for recycling and spinning ultra-high molecular weight polyethylene fibers provided in this embodiment is consistent with that in embodiment 1, except that the amounts of degumming agent and dissolving agent used are different, that is, the dehydrated waste is immersed in a degumming agent of 25% citric acid and degummed at 85-105°C for 20-50 minutes to obtain waste material, and after the degumming, the waste material needs to be washed, bleached, dried, softened or treated with antistatic treatment to obtain recycled fibers with a moisture content of ≤0.2‰, and the recycled fibers with a moisture content of ≤0.2‰ are cut into staple fibers, and then 15.6 parts of staple fibers, 54 parts of white oil solvent, 4.3 parts of polyolefins and 2.8 parts of tert-butylhydroquinone are mixed according to the ratio For example, when the solid content concentration is ≤ 10%, the mixture is put into a dissolving kettle and stirred at a speed of 10 to 100 rpm. After being stirred evenly, the temperature is raised to 76°C in the first stage. When the staple fibers are dissolved, the temperature is raised to 105°C in the second stage. When a small part of the staple fibers are dissolved, the temperature is raised to 152°C in the third stage. When most of the staple fibers are dissolved, the temperature is raised to 173°C in the fourth stage until the staple fibers are completely dissolved to obtain a spinning solution. The spinning solution is sequentially spun into ultra-high molecular weight polyethylene fibers through a twin-screw extruder 1, a spinning metering pump 2, a spinneret 3, a coagulation bath 4, a dryer 5, a traction machine 6 and a winder 7 (the spinning process can be seen). Figure 1 As shown in the figure, the ultra-high molecular weight polyethylene fiber was tested according to the national standard GB / T 29554-2013 "Ultra-high molecular weight polyethylene fiber", and its physical property retention rate was 97.4% and the recovery rate was 88.6%. Embodiment 3:

[0012] The method for recycling and spinning ultra-high molecular weight polyethylene fibers provided in this embodiment is consistent with that in embodiment 1, except that the amounts of degumming agent and dissolving agent used are different, namely: the dehydrated waste is immersed in a degumming agent of 45% sodium silicate and degummed at 85-105°C for 20-50 minutes to obtain waste material, and after degumming, the waste material needs to be washed, bleached, dried, softened or treated with antistatic treatment to obtain recycled fibers with a moisture content of ≤0.2‰, and the recycled fibers with a moisture content of ≤0.2‰ are cut into staple fibers, and then 20 parts of staple fibers, 78 parts of white oil solvent, 5 parts of polyolefins and 3 parts of dioctyl pyrophosphate are added according to the ratio. When the solid content concentration is ≦10%, the mixture is put into a dissolving kettle and stirred at a speed of 10 to 100 rpm. After being stirred evenly, the temperature is raised to 88°C in the first stage. When the staple fibers are dissolved, the temperature is raised to 120°C in the second stage. When a small part of the staple fibers are dissolved, the temperature is raised to 163°C in the third stage. When most of the staple fibers are dissolved, the temperature is raised to 180°C in the fourth stage until the staple fibers are completely dissolved to obtain a spinning solution. The spinning solution is sequentially spun into ultra-high molecular weight polyethylene fibers through a twin-screw extruder 1, a spinning metering pump 2, a spinneret 3, a coagulation bath 4, a dryer 5, a traction machine 6 and a winder 7 (the spinning process can be seen). Figure 1As shown in the figure, the ultra-high molecular weight polyethylene fiber was tested according to the national standard GB / T 29554-2013 "Ultra-high molecular weight polyethylene fiber", and its physical property retention rate was 98.5% and the recovery rate was 90.1%.

[0013] Comparative Example: In this comparative example, the waste of ultra-high molecular weight polyethylene fibers is only cut or crushed, and the temperature is directly raised to 165-180° C. during the dissolution process. The remaining ultra-high molecular weight polyethylene fiber recovery and spinning processes are consistent with those in Example 1. The ultra-high molecular weight polyethylene fiber yarn is tested according to the national standard GB / T 29554-2013 "Ultra-high Molecular Weight Polyethylene Fiber", and its physical property retention rate is 56.8%, and the recovery rate is 64.2%.

[0014] The following is a comparison table of relevant data of Examples 1 to 3 and Comparative Examples: ; It can be seen from the above table that the recycling process of sorting - dehydration and degumming - cutting - dissolving - spinning can not only recycle ultra-high molecular weight polyethylene fibers with physical properties equivalent to those of the original fibers, but also obtain ultra-high molecular weight polyethylene fibers with higher performance than the original fibers, which effectively expands the application scope of recycled ultra-high molecular weight polyethylene fibers and achieves the purpose of efficient, environmentally friendly regeneration and high-quality recycling and reuse of waste ultra-high molecular weight polyethylene fibers.

Claims

1. A method for recycling and spinning ultra-high molecular weight polyethylene fibers, characterized in that: The specific steps are as follows: S1. Classification and sorting: firstly, the waste of ultra-high molecular weight polyethylene fibers is classified and sorted according to product types; S2, dehydration and degumming: the sorted waste is dehydrated by a centrifuge or a press, and then immersed in a degumming agent for degumming to obtain waste material, and the waste material is further post-processed to obtain recycled fiber with a moisture content of ≤0.2‰; S3, cutting: cutting the recycled fiber into short fibers by a band saw or a roller cutter; S4, dissolution: put the staple fibers, white oil solvent, polyolefin and antioxidant into a dissolution kettle according to the proportion, stir and mix when the solid content concentration is ≤10%, and after stirring evenly, gradually heat up to 165-180°C in four stages, and obtain the spinning solution after the staple fibers are dissolved; S5. Spinning: The spinning solution is sequentially passed through a twin-screw extruder, a spinning metering pump, a spinneret, a coagulation bath, a dryer, a traction machine and a winder to be spun into ultra-high molecular weight polyethylene fiber filaments.

2. The method for recycling and spinning ultra-high molecular weight polyethylene fibers according to claim 1, characterized in that: In S2, the degumming agent is one of 30% sodium bicarbonate, 25% citric acid, and 45% sodium silicate.

3. The method for recycling and spinning ultra-high molecular weight polyethylene fibers according to claim 1, characterized in that: In S2, the temperature during degumming is controlled at 85 to 105° C., and the degumming time is 20 to 50 minutes.

4. The method for recycling and spinning ultra-high molecular weight polyethylene fibers according to claim 1, characterized in that: In S2, the waste post-treatment is washing, bleaching, drying and softening or antistatic treatment after degumming to obtain recycled fibers.

5. The method for recycling and spinning ultra-high molecular weight polyethylene fibers according to claim 1, characterized in that: In S3, the length of the staple fibers is 1 to 10 mm, the diameter of the staple fibers is 0.1 to 10 mm and the solid content thereof is 8 to 30%.

6. The method for recycling and spinning ultra-high molecular weight polyethylene fibers according to claim 1, characterized in that: In S4, according to the mass fraction, there are: 10 to 20 parts of staple fibers, 20 to 80 parts of white oil solvent, 3 to 5 parts of polyolefin and 2 to 3 parts of antioxidant.

7. The method for recycling and spinning ultra-high molecular weight polyethylene fibers according to claim 1 or 6, characterized in that: In S4, the main raw material of white oil solvent is petroleum, which is refined through dewaxing, carbonization, neutralization and activated white clay.

8. The method for recycling and spinning ultra-high molecular weight polyethylene fibers according to claim 1 or 6, characterized in that: In S4, the antioxidant is one or more of tert-butylhydroquinone and dioctyl pyrophosphate.

9. The method for recycling and spinning ultra-high molecular weight polyethylene fibers according to claim 1, characterized in that: In S4, the stirring rate is 10 to 100 rpm.

10. The method for recycling and spinning ultra-high molecular weight polyethylene fibers according to claim 1, characterized in that: In S4, the temperature is increased in four stages: the first stage is increased to 60-90°C, the second stage is increased to 90-120°C, the third stage is increased to 120-165°C, and the fourth stage is increased to 165-180°C.

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