CN115302654A - Granulation and spinning process of regenerated polyamide 6 - Google Patents

Abstract

The invention relates to a granulation and spinning process of regenerated polyamide 6, and belongs to the technical field of polymer copolymer preparation. In the granulation process of the regenerated polyamide 6, the waste blocks of polyamide 6 are crushed and deoiled, and then cut into pieces, and then dried and melted into a melt; It is extruded into strips, cooled and dried, cut into pellets, and dried again to obtain regenerated polyamide 6 masterbatches. The granulation process of the regenerated polyamide 6 can effectively reduce the moisture content of the regenerated polyamide 6 masterbatch through the steps of drying, degreasing and filtration for many times, reduce impurities, low elements and oil in the melt, and improve the The quality of recycled particles, so as to achieve 100% addition of recycled polyamide 6 to prepare polyamide 6 fibers.

Description

A kind of granulation and spinning process of recycled polyamide 6

technical field

The invention belongs to the technical field of polymer copolymer preparation, and relates to a granulation and spinning process of recycled polyamide 6.

Background technique

Nylon fiber is the first synthetic fiber to appear in the world. Its chemical name is polyamide (PA), commonly known as nylon. In terms of civil yarn, nylon filament is mostly used in knitting and woven industrial production, such as nylon elastic stockings, nylon scarves, mosquito nets, nylon lace, elastic nylon underwear, down jacket fabrics, sunscreen clothing, swimwear, etc. In the industry, nylon filaments are widely used to make cords, industrial fabrics, cables, conveyor belts, tents, fishing nets, etc. By 2021, the output of my country's nylon industry will be about 3.9 million tons. It is estimated that the output of the nylon industry may exceed 5 million tons in the next three years. The production capacity of the nylon industry will grow rapidly and the scale of application will continue to expand. The level of the reuse system needs to be improved urgently.

In recent years, with the demand for green development of the textile industry, major terminal retail brands are actively responding, and have formulated their own sustainable development strategies in terms of materials, aiming to use 100% recycled nylon in all nylon products in the next few years. Therefore, the market's attention and demand for recycled nylon have increased sharply in recent years.

Regeneration methods are divided into physical and chemical methods. The chemical recycling method is complex in process and high in cost. It is mainly used in the recycling of post-consumer products. Because it is difficult to decompose pure nylon in post-consumer clothing, it is mainly used to recycle fishing nets. At present, except for a few companies in Taiwan that have the technology of chemical regeneration, the rest of the country adopts the physical regeneration method. The physical regeneration method is not only simple in process, low in cost, but also has sufficient raw materials. The Chinese invention patent with the application publication number CN111876871A discloses a kind of recycled nylon air-covered yarn, which specifically discloses that after the waste nylon yarn is physically and chemically removed, it is melted at a high temperature to obtain a recycled polyamide melt, but the melt needs to be mixed with Conventional polyester is mixed and melted to obtain molded regenerated yarn. The maximum amount of regenerated polyamide melt added can only reach 68.5%, and it cannot be added 100% to make regenerated nylon.

Contents of the invention

In order to overcome the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide a granulation and spinning process of regenerated polyamide 6 with 100% regenerated nylon added.

In order to solve the above technical problems, the technical solution adopted in the present invention is: a granulation process of regenerated polyamide 6, comprising the following steps:

S1: Crushing the waste block of nylon 6, and shredding after degreasing;

S2: After the oil-free waste silk is dried, it is melted into a melt, and the melt is filtered for the first time and screw auxiliary machine in turn, and then filtered for the second time;

S3: Extrude the melt after the second filtration into strips, cool and dry, cut into pellets, and dry again to obtain regenerated polyamide 6 masterbatches.

The beneficial effect of the present invention is that: the granulation process of the regenerated polyamide 6 of the present invention can effectively reduce the moisture content of the regenerated polyamide 6 masterbatch and reduce the impurities in the melt through the steps of drying, degreasing and filtering for many times , low-element body and oil agent, prevent uneven feeding of raw materials, low melting efficiency, uneven heating and other phenomena during granulation, improve the quality of recycled particles, increase spinnability, and improve spinning efficiency; the prepared recycled polyamide 6 masterbatch does not need to be fused with conventional polyamide 6, but can be added 100%, to obtain recycled polyamide 6 fibers with high breaking strength, good dyeing uniformity, and low uniformity of fibers.

Description of drawings

Fig. 1 shows the technological process schematic diagram of regenerated polyamide 6 masterbatch in the embodiment of the present invention 1;

Figure 2 is a schematic diagram of the process flow of the conventional regenerated polyamide 6 masterbatch in Comparative Example 1 of the present invention.

Detailed ways

In order to describe the technical content, achieved goals and effects of the present invention in detail, the following descriptions will be made in conjunction with the embodiments and accompanying drawings.

The most critical idea of the present invention is that through multiple steps of drying, degreasing and filtering, the moisture content of the regenerated polyamide 6 masterbatch can be effectively reduced, the impurities, low-element bodies and oil agents in the melt can be reduced, and the regenerated particles can be improved. 100% added recycled polyamide 6 to prepare polyamide 6 fiber.

Please refer to shown in Fig. 1, the granulation process of a kind of regenerated polyamide 6 of the present invention, comprises the following steps:

S1: Crushing the waste block of nylon 6, and shredding after degreasing;

S2: After the oil-free waste silk is dried, it is melted into a melt, and the melt is filtered for the first time and pressurized in turn, and then filtered for the second time;

S3: Extrude the melt after the second filtration into strips, cool and dry, cut into pellets, and dry again to obtain regenerated polyamide 6 masterbatches.

From the above description, it can be known that the beneficial effect of the present invention is: using conventional recycled masterbatches to prepare recycled polyamide 6 fibers, increasing the addition ratio of recycled masterbatches from 5% to 10%, the production of broken filaments will increase significantly, which does not meet the spinnability requirements.

The granulation process of the regenerated polyamide 6 of the present invention can effectively reduce the moisture content of the regenerated polyamide 6 masterbatch and reduce impurities, low-element bodies and oil agents in the melt through the steps of drying, degreasing and filtering for many times , prevent uneven feeding of raw materials, low melting efficiency, uneven heating and other phenomena during granulation, improve the quality of recycled particles, increase spinnability, and improve spinning efficiency; the prepared recycled polyamide 6 masterbatch does not need to be mixed with conventional polyamide Amide 6 is fused, and 80% of it can be added to prepare regenerated polyamide 6 fibers with high breaking strength, good dyeing uniformity and low evenness of the fibers.

The water content in the waste block of nylon 6 is relatively high, and severe hydrolysis reverse reaction occurs during the melting process, and the oligomer or monomer increases, which affects the melt strength and processability of polyamide. Therefore, the waste block of nylon 6 needs to be dried before processing to improve the quality of post-processing.

Further, the specific steps of deoiling are: sorting the crushed nylon 6 waste pieces into oil-free waste and oily waste, and the oily waste is washed and dried in sequence to obtain oil-free waste silk.

It can be seen from the above description that the oil agent contained in the waste block will affect the quality of the recycled polyamide 6 masterbatch.

Further, after crushing, the diameter of the waste block is less than 5mm. Preferably, the waste chunks are less than 4mm in diameter.

From the above description, it can be seen that the small diameter of the waste block is beneficial to improve the melting efficiency of the waste, the uniformity of heating, reduce the residence time of the melt in the screw, reduce the cracking of polyamide, and improve the spinning of recycled polyamide 6 masterbatch. Spinnability, filament dyeability and breaking strength.

Further, the moisture content of the recycled polyamide 6 masterbatch is less than 800ppm.

From the above description, it can be seen that the high moisture content of the recycled polyamide 6 masterbatch may lead to intense hydrolysis reaction of polyamide during spinning, and air bubbles are likely to be generated during spinning, which will cause the melt fine flow of the as-spun fiber to break during the drawing process, resulting in breakage. Silk.

Further, the first filtration is performed using a 600-mesh filter device, which is a hydraulic screen changer with a screen-changeable size of 47cm*30cm.

From the above description, it can be seen that the first filter is performed on the melt to reduce the impurities in the masterbatch.

Further, the second filtration is performed using a 1200-mesh filter device, which is a melt fine filter device with a specification of 40cm*35cm*70cm.

It can be seen from the above description that the second filtration can further reduce impurities and improve particle purity, which is beneficial to the stability of the spinning assembly pressure during spinning and improves the spinnability of spinning.

Further, in S2, a twin-screw extruder is used for melting, the main screw temperature of the twin-screw extruder is 240°C-273°C, the die head temperature is 250°C, the sub-screw temperature is 250°C-253°C, and the auxiliary mold ( Screw auxiliary machine die head) temperature is 250 ℃ ~ 255 ℃.

It can be seen from the above description that the screw temperature of the present invention is relatively low, and the screw temperature is lowered on the basis of ensuring that the polyamide is completely melted and fluid, so as to avoid thermal decomposition reactions under the joint action of thermal cracking, high-temperature oxidation, and high-temperature hydrolysis.

Another technical solution of the present invention is: a spinning process for regenerated polyamide 6, which uses a regenerated polyamide 6 masterbatch for spinning, comprising the following steps:

S1: Melt spinning recycled polyamide 6 masterbatch, and pre-oriented molding process to obtain recycled polyamide 6 pre-oriented yarn;

S2: The regenerated polyamide 6 pre-oriented yarn is stretched and deformed to obtain the regenerated polyamide 6 stretched textured yarn.

From the above description we can see that:

(可逆反应)Polyamide 6 polycondensation reaction formula is:

(Reversible reaction)

The polymerization process of polyamide 6 is a reversible equilibrium reaction, so the polymer in the spinning screw extruder and the melt pipe is prone to depolymerization reaction, so that the proportion of monomers and oligomers increases, and with the melt Increased temperature or residence time increases (the rate will slow down when approaching the equilibrium point). In the spinning process, the higher the content of monomers and oligomers in the polymer, the wider the relative molecular weight distribution, the poorer melt viscoelasticity, and the higher the number of spinning breaks. The regenerated polyamide 6 masterbatch of the present invention reduces the content of impurities, monomers and oligomers through multi-step drying and filtration, and reduces the phenomenon of spinning ends.

During the melting process, the slice stays in the melt pipe of the screw machine at a high temperature for a certain period of time. Under the joint action of thermal cracking, high temperature oxidation and high temperature hydrolysis, a thermal decomposition reaction occurs. The thermal decomposition reaction may cause the melt to change color, In severe cases, melt gel will be produced, which will affect the stability of the spinning process. The regenerated polyamide 6 masterbatch of the present invention has less water content, can reduce the above synergy, and obtain a stable spinning process.

Further, S1 is specifically: mixing recycled polyamide 6 masterbatches with masterbatches containing an epoxy chain extender, melt spinning, and performing a pre-orientation molding process to obtain regenerated polyamide 6 pre-oriented filaments.

Further, the epoxy equivalent of the masterbatch containing the epoxy chain extender is 450, and the weight average molecular weight is 6000.

Further, the molecular structure of the epoxy chain extender is shown in Formula 1:

From the above description, it can be known that the impurities in the recycled nylon 6 masterbatch are easily degraded during the spinning process to form terminal amino and carboxyl groups (-NH ₂ , -COOH), and these functional groups can in turn accelerate the degradation of polyamide. Therefore, the masterbatch containing epoxy chain extender is mixed and melted with the recycled nylon 6 masterbatch. The masterbatch containing epoxy chain extender has the effect of polyamide chain extension and thermal stability, and the molecule of the epoxy chain extender contains ring Oxygen functional groups can react with both amino groups and carboxyl groups to play the role of chain extension, branching and crosslinking. Thereby stabilizing the molecular weight of the polyamide 6 melt during the spinning process, reducing oligomers, thereby improving the spinning efficiency and the breaking strength of the product.

The use of masterbatches containing epoxy chain extenders to assist spinning can improve spinnability and meet the requirements of 100% recycled spinning.

Further, the weight of the regenerated polyamide 6 masterbatch accounts for 10% to 100% of the total weight of the regenerated polyamide 6 fiber.

It can be known from the above description that the regenerated polyamide 6 masterbatch of the present invention does not need to be fused with conventional polyamide 6, and can be prepared by adding 100% to obtain a regenerated polyamide with high breaking strength, good dyeing uniformity, and low evenness of the fiber. Amide 6 fibers for improved spinning efficiency and recycling of polyamide 6 waste.

Please refer to shown in Fig. 1, embodiment 1 of the present invention is:

A granulation process of recycled polyamide 6, comprising the following steps:

S1: Crushing the waste block of nylon 6, the diameter after crushing is less than 5mm;

Sorting the crushed nylon 6 waste blocks into oil-free waste and oily waste, the oil-free waste is shredded, and the oily waste is shredded after successive washing and drying steps to obtain oil-free waste silk ;

S2: After drying oil-free waste silk at 120°C for 12 hours, use a twin-screw extruder to melt into a melt, and the melt is filtered through a 600-mesh filter device for the first time, and then pressurized by a screw auxiliary machine, and then use a 1200-mesh filter device Perform a second filter;

S3: The melt after the second filtration is extruded into strips through the casting head, and then passed through the cooling water tank, drying fan, pelletizer, cyclone separator and KF drying equipment to obtain recycled polyamide 6 with a moisture content of 700ppm Masterbatch.

The 600-mesh filter device is a hydraulic screen changer that can change the screen, and the specification is 47cm*30cm;

The 1200-mesh filter device is melt fine filter equipment with a specification of 40cm*35cm*70cm.

The temperature parameters of the twin-screw extruder are shown in Table 1.

Table 1

temperature control zone set temperature main screw area 240°C Main screw area two 250°C Three zones of the main screw 270°C Main screw zone 4 270°C Main screw zone five 273°C Die one area 250°C Die zone 2 250°C Secondary screw inlet 250°C Auxiliary screw area 253°C Secondary screw area 253°C Auxiliary mold area 253°C Auxiliary mold area two 253°C

A kind of spinning process of regenerated polyamide 6 (6 FDY 40den/34f full extinction product), uses regenerated polyamide 6 masterbatch to carry out spinning, comprises the following steps:

S1: Mix recycled polyamide 6 masterbatches accounting for 10% of the total mass of recycled polyamide 6 with 90% polyamide 6 chips, melt-spin, and obtain recycled polyamide 6 pre-oriented filaments through a pre-orientation molding process;

S2: The regenerated polyamide 6 pre-oriented yarn is stretched and deformed to obtain the regenerated polyamide 6 stretched textured yarn.

Among them, the process parameters of the spinning process are shown in Table 2.

Table 2

project unit Process parameters spinning Kg/cm2 120 Melt temperature ℃ 259 Component pressure Kg/cm2 150 Cooling speed m/sec 0.45 Cooling temperature and humidity °C/% 16.5/95 Nozzle height cm 72 draft ratio % 1.23 Hot roller temperature ℃ 160 Winding speed m/min 4600

Embodiment 2 of the present invention is:

The difference between Example 2 and Example 1 is that in the spinning process, the regenerated polyamide 6 masterbatch accounts for 30% of the total mass of the regenerated polyamide 6, and the polyamide 6 chips account for 70% of the total mass of the regenerated polyamide 6.

Embodiment 3 of the present invention is:

The difference between Example 3 and Example 1 is that in the spinning process, the regenerated polyamide 6 masterbatch accounts for 50% of the total mass of the regenerated polyamide 6, and the polyamide 6 chips account for 50% of the total mass of the regenerated polyamide 6.

Embodiment 4 of the present invention is:

The difference between Example 4 and Example 1 is that in the spinning process, the regenerated polyamide 6 masterbatch accounts for 80% of the total mass of the regenerated polyamide 6, and the polyamide 6 chips account for 20% of the total mass of the regenerated polyamide 6.

Embodiment 5 of the present invention is:

The difference between Example 5 and Example 1 is that: in the spinning process, the regenerated polyamide 6 masterbatch accounts for 100% of the total mass of the regenerated polyamide 6.

Embodiment 6 of the present invention is:

The difference between embodiment 6 and embodiment 1 is: a spinning process of regenerated polyamide 6 (6FDY 40den/34f full extinction product), using regenerated polyamide 6 masterbatch for spinning, comprising the following steps:

S1: Mix 10% recycled polyamide 6 masterbatch, 2% masterbatch containing epoxy chain extender and 88% polyamide 6 chips, which account for 10% of the total mass of recycled polyamide 6, melt spinning, and pre-orientation Forming process to obtain regenerated polyamide 6 pre-oriented yarn;

The epoxy equivalent of the masterbatch containing the epoxy chain extender is 450, and the weight average molecular weight is 6000; the molecular structure of the epoxy chain extender is shown in formula 1:

Embodiment 7 of the present invention is:

The difference between Example 7 and Example 6 is that in the spinning process, the regenerated polyamide 6 masterbatch accounts for 30% of the total mass of regenerated polyamide 6, and the masterbatch containing epoxy chain extender accounts for 30% of the total mass of regenerated polyamide 6. 2%, polyamide 6 chips accounted for 68% of the total mass of recycled polyamide 6.

Embodiment 8 of the present invention is:

The difference between Example 8 and Example 6 is that in the spinning process, the regenerated polyamide 6 masterbatch accounts for 50% of the total mass of regenerated polyamide 6, and the masterbatch containing epoxy chain extender accounts for 50% of the total mass of regenerated polyamide 6. 2%, polyamide 6 chips accounted for 48% of the total mass of recycled polyamide 6.

Embodiment 9 of the present invention is:

The difference between Example 9 and Example 6 is that in the spinning process, the regenerated polyamide 6 masterbatch accounts for 80% of the total mass of regenerated polyamide 6, and the masterbatch containing epoxy chain extender accounts for 80% of the total mass of regenerated polyamide 6. 2%, polyamide 6 chips accounted for 18% of the total mass of recycled polyamide 6.

Embodiment 10 of the present invention is:

The difference between Example 9 and Example 6 is that in the spinning process, the regenerated polyamide 6 masterbatch accounts for 98% of the total mass of regenerated polyamide 6, and the masterbatch containing epoxy chain extender accounts for 98% of the total mass of regenerated polyamide 6. 2%.

Please refer to shown in Figure 2, comparative example 1 of the present invention is:

The difference between comparative example 1 and embodiment 1 is:

A kind of granulation process of conventional regenerated polyamide 6 comprises the following steps:

S1: Crushing and shredding the waste blocks of nylon 6 in sequence;

S2: Use a twin-screw extruder to melt into a melt, and the melt passes through a screw auxiliary machine;

S3: The melt after the second filtration is extruded into strips through a casting head, and then passed through a cooling water tank and a pelletizer in turn to obtain conventional recycled polyamide 6 masterbatches.

A spinning process of regenerated polyamide 6 (6 FDY 40den/34f full extinction product), using conventional regenerated polyamide 6 masterbatch for spinning, comprising the following steps:

S1: Mix conventional regenerated polyamide 6 masterbatches accounting for 5% of the total mass of regenerated polyamide 6 with 95% polyamide 6 chips, melt-spin, and undergo a pre-orientation molding process to obtain conventional regenerated polyamide 6 pre-orientation Silk;

S2: The conventional regenerated polyamide 6 pre-oriented yarn is stretched and deformed to obtain the conventional regenerated polyamide 6 stretched textured yarn.

Comparative example 2 of the present invention is:

The difference between Comparative Example 2 and Comparative Example 1 is that in the spinning process, conventional regenerated polyamide 6 masterbatch accounts for 10% of the total mass of regenerated polyamide 6, and polyamide 6 chips account for 90% of the total mass of regenerated polyamide 6.

The relative viscosity, moisture content, amino-terminated content, carboxyl-terminated content and extractables content of the regenerated polyamide 6 masterbatch in Example 1 and the conventional regenerated polyamide 6 masterbatch in Comparative Example 1 were tested. The test results are shown in Table 3.

table 3

project unit Example 1 Comparative example 1 relative viscosity - 2.57 2.59 moisture content ppm 6300 660 terminal amino group mmol/kg 37 40 Carboxyl terminal mmol/kg 59 63 extractables % 2.23 1.65

It can be seen from Table 3 that the content of amino-terminated, carboxyl-terminated and extractables of the regenerated polyamide 6 masterbatch prepared by the present invention is less than that of the conventional regenerated polyamide 6 masterbatch, and the moisture content is much lower than that of the conventional regenerated polyamide 6 masterbatch , the quality of recycled particles is higher, and the spinnability and spinning efficiency are higher.

The spinnability, breaking strength, uniformity of evenness, and rate of excellent dyed products of the regenerated polyamide 6 fibers prepared in Examples 1-10 and Comparative Examples 1-2 were tested. The test results are shown in Table 4.

Table 4

It can be seen from Table 4 that if the conventional recycled masterbatch is used for spinning, the addition ratio increases from 5% to 10%, and the number of broken filaments in the production increases significantly, which does not meet the spinnability requirements. Using the regenerated masterbatch of the present invention for spinning, the addition ratio increases from 10% to 100%, and when the addition ratio reaches 30%, the production of floating yarn increases slightly, and when the addition ratio reaches 80%, the production efficiency basically does not meet the spinnability requirements. During this process, as the proportion of recycled particles increases, the spinning efficiency decreases, the fiber breaking strength and dyeing uniformity decrease, and the evenness of the fiber increases. The use of masterbatches containing epoxy chain extenders to assist spinning can improve spinnability and meet the requirements of 100% recycled masterbatch spinning.

In summary, the granulation process of recycled polyamide 6 provided by the present invention controls the moisture content, impurities, and fineness of raw materials, reduces the melting temperature as much as possible on the basis of ensuring smooth melt, and reduces the polyamide granulation process. The degree of degradation, reduce the generation of oligomers, improve the spinnability and breaking strength of fibers.

The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent transformations made by using the description of the present invention and the contents of the accompanying drawings, or directly or indirectly used in related technical fields, are all included in the same principle. Within the scope of patent protection of the present invention.

Claims (10)

1. a granulation process of regenerated polyamide 6, is characterized in that, comprises the following steps: S1: Crushing the waste block of nylon 6, and shredding after degreasing to obtain oil-free waste silk; S2: After the oil-free waste silk is dried, it is melted into a melt, and the melt is filtered for the first time and screw auxiliary machine in turn, and then filtered for the second time; S3: Extrude the melt after the second filtration into strips, cool and dry, cut into pellets, and dry again to obtain regenerated polyamide 6 masterbatches. 2. The granulation process of regenerated polyamide 6 according to claim 1, characterized in that, after the crushing process, the diameter of the waste block is less than 5mm. 3. The granulation process of regenerated polyamide 6 according to claim 1, characterized in that, the moisture content of the regenerated polyamide 6 masterbatch is less than 800ppm. 4. The granulation process of regenerated polyamide 6 according to claim 1, characterized in that, the first filtration uses a 600 mesh filter to filter. 5. The granulation process of regenerated polyamide 6 according to claim 1, characterized in that, the second filtration uses a 1200 mesh filter device to filter. 6. The granulation process of regenerated polyamide 6 according to claim 1, characterized in that a twin-screw extruder is used for melting in the S2, and the main screw temperature of the twin-screw extruder is 240° C. to 273°C, the temperature of the die head is 250°C, the temperature of the sub-screw is 250°C-253°C, and the temperature of the auxiliary mold is 250°C-255°C. 7. a spinning process of regenerated polyamide 6, uses the regenerated polyamide 6 masterbatch in claim 1 to carry out spinning, is characterized in that, comprises the following steps: S1: Melt spinning recycled polyamide 6 masterbatch, and pre-oriented molding process to obtain recycled polyamide 6 pre-oriented yarn; S2: The regenerated polyamide 6 pre-oriented yarn is stretched and deformed to obtain the regenerated polyamide 6 stretched textured yarn. 8. The spinning process of regenerated polyamide 6 according to claim 7, characterized in that, said S1 is specifically: mixing regenerated polyamide 6 masterbatches with masterbatches containing epoxy chain extenders, and melt spinning , and obtained regenerated polyamide 6 pre-oriented yarn through pre-orientation molding process. 9. The spinning process of regenerated polyamide 6 according to claim 8, characterized in that, the epoxy equivalent of the masterbatch containing epoxy chain extender is 450, and the weight average molecular weight is 6000. 10. A regenerated polyamide 6 fiber, characterized in that the weight of the regenerated polyamide 6 masterbatch in claim 1 accounts for 10% to 100% of the total weight of the regenerated polyamide 6 fiber.

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