WO2025126965A1 - Material-recycled nylon 66 fiber - Google Patents

Abstract

This recycled nylon 66 fiber is characterized by including 5 wt% or more of recycled nylon 66 and having an overall fineness of 110-2100 dtex, a strength of 7.6-10.0 cN/dtex, and an elongation of 15.0-35.0%.　Provided is a material-recycled nylon 66 fiber having high strength and a good fluff quality.

Description

Material: Recycled nylon 66 fiber

The present invention relates to nylon 66 fiber made from recycled polyhexamethylene adipamide resin and a method for producing the same.

Nylon 6 and nylon 66 multifilaments have higher strength and elongation than general-purpose multifilaments such as polyester and polypropylene, and have excellent fluff quality, so they are used in a wide range of industrial applications, including airbags, tire cords, strings for sports rackets, ropes, fishing nets, and bag belts.

In addition, with the rise in environmental awareness in recent years, the value of environmentally friendly materials, such as products made from recycled materials, is increasing, and there is a demand for the development of fibers made from recycled materials.

Nylon 6 and polyester can be recycled relatively easily, and methods for producing recycled fibers with properties roughly equivalent to those of virgin fibers have been disclosed, such as in Patent Documents 1 and 2 below.

Patent Document 3 discloses a method in which nylon waste materials including nylon 66 all-gloss yarn, nylon 66 semi-gloss yarn, nylon 66 matte yarn, nylon 66 ultra-high strength yarn, nylon 66 high strength yarn, nylon 66 fine duny high strength yarn, nylon 66 fishing net waste wire, and nylon 66 waste cloth are crushed and washed to reduce the oil content to 0.22% by weight, dehydrated and melt granulated to produce material recycled nylon resin chips, and the material recycled nylon chips are melt spun to produce recycled nylon fibers. However, Patent Document 3 discloses that the stretching process included in the fiber manufacturing process has a stretching ratio set to 1.2 to 1.5 times, and it is stated that if the stretching ratio exceeds 1.5 times, the yarn becomes prone to breakage due to excessive stretching, so it is clear that the strength level required for industrial fibers cannot be achieved.

International Publication No. 2022/196407 JP 2003-13328 A Patent No. 6629943

However, compared to other polymers, nylon 66 is prone to thermal and oxidative degradation and gelation, making it difficult to recycle.

The object of the present invention is to solve the above problems by suppressing polymer degradation due to heat, oxidative degradation, etc., and to obtain material recycled nylon 66 fiber that has the same strength, elongation, and fluff quality as 100% virgin nylon 66 fiber.

The present invention has been made through extensive research in order to solve the above problems, and has the following configuration.
(1) Recycled nylon 66 fiber containing 5% by weight or more of recycled nylon 66 resin and having a total fineness of 110 to 2100 dtex, a strength of 7.6 to 10.0 cN/dtex, and an elongation of 15.0 to 35.0%.
(2) The recycled nylon 66 fiber according to (1) above, characterized in that the UVA value at a wavelength of 290 nm in a solution concentration of 5 mg/mL is 0.30 or less.
(3) The recycled nylon 66 fiber according to (1) or (2) above, characterized in that the number of fluffs is 0 to 3 pieces/10,000 m.
(4) The recycled nylon 66 fiber according to any one of (1) to (3) above, which is produced from repellentized chips using any one or more of the following as raw materials: waste from the fiber manufacturing process, waste edges of airbag base fabric, waste fabric from scouring processing, waste rejected airbag products, waste from cutting and sewing of airbags, and airbags collected from scrapped vehicles.
(5) A fabric for an airbag, characterized by using the recycled nylon 66 fiber described in (1) or (2) above.
(6) A tire cord using the recycled nylon 66 fiber described in (1) or (2) above.
(7) A racket string characterized by using the recycled nylon 66 fiber described in (1) or (2) above.
(8) A V-ribbed belt using the recycled nylon 66 fiber described in (1) or (2) above.
(9) A fabric for bags, characterized by using the recycled nylon 66 fiber described in (1) or (2) above.

The present invention makes it possible to obtain recycled nylon 66 fiber that has the same strength and elongation as 100% virgin nylon 66 fiber and good fluff quality.

1 is a schematic diagram of a process for producing material recycled nylon 66 fiber according to the present invention.

The present invention is described in detail below.

The material recycled nylon 66 fiber according to an embodiment of the present invention is preferably nylon 66 blended with 5% or more by weight of material recycled polyhexamethylene adipamide resin. In other words, the recycled nylon 66 fiber of the present invention contains 5% or more by weight of material recycled polyhexamethylene adipamide resin. In view of the growing awareness of global environmental conservation in recent years, the higher the blending amount, the better, and nylon 66 fiber is preferably blended with 20% to 100% by weight of material recycled polyhexamethylene adipamide resin.

The polyhexamethylene adipamide resin may contain, for example, 10 mol% or less of other copolymerization components within a range that does not impair the effects of the present invention, but it is preferable to contain a large amount of hexamethylene adipamide units, as this increases the regularity of the molecular chains of the resulting fiber and makes it easier for oriented crystallization during the spinning process, resulting in a fiber with excellent mechanical properties. It is more preferable that the hexamethylene adipamide units are 95 mol% or more, and even more preferable that they are 98 mol% or more.

The recycled nylon 66 fiber of the present invention may contain components other than nylon, such as end-blocking agents such as monocarboxylic acids, matting agents such as titanium oxide, polymerization catalysts and heat resistance agents such as phosphorus compounds, and antioxidants and heat stabilizers such as copper compounds and alkali metal or alkaline earth metal halides, as necessary, but the nylon component is preferably 95% by weight or more, and more preferably 97% by weight or more. If the nylon component is less than 95% by weight, the heat resistance of the nylon decreases, which is not preferred.

The recycled nylon 66 fiber of the present invention has a total fineness of 110 to 2100 dtex. More preferably, it is in the range of 350 to 2100 dtex. If the fineness is less than 110 dtex, it is too thin to withstand the mechanical stretching at a high ratio required to achieve high strength, and there is a high possibility of fuzzing. If the fineness exceeds 2100 dtex, the cooling efficiency decreases, and the mechanical properties decrease, so this is not preferable. In addition, the single fiber fineness is preferably 2 to 35 dtex. If the single fiber fineness is 2 to 35 dtex, high-strength recycled 66 fiber can be stably obtained while maintaining the quality. There is no particular restriction on the number of single threads, and it is the single fiber fineness that is important.

The strength of the recycled nylon 66 fiber of the present invention is 7.6 to 10.0 cN/dtex. It is preferably 8.0 to 9.7 cN/dtex, and more preferably 8.5 to 9.7 cN/dtex. When the strength is in this range, the nylon fiber is suitable for industrial materials such as airbags and durable clothing fabrics. A strength of less than 7.6 cN/dtex is insufficient to improve the durability of fibers for industrial materials such as airbags. When attempting to obtain nylon fibers with a strength of more than 10.0 cN/dtex, mechanical stretching is performed at a high ratio, which deteriorates the fluff quality. Such recycled nylon 66 fibers are not suitable for industrial materials such as airbags, which require high quality, and are therefore undesirable.

The elongation is preferably 15.0% to 35.0%, and more preferably 17.0% to 30.0%. The higher the elongation, the better, but in order to obtain a certain strength with nylon, it is practically 35.0% or less. By keeping it in this range, the toughness and breaking work capacity of the material recycled nylon 66 fiber can be increased, and excellent durability can be maintained.

Although it depends on the total fineness and single fiber fineness, the strength and elongation product is preferably 38 cN/dtex x √% or more, and more preferably 40 cN/dtex x √% or more. A high strength and elongation product suppresses the generation of fuzz and thread breakage, resulting in a material recycled nylon 66 fiber that is extremely high quality even with high strength. Note that strength (cN/dtex) and elongation (%) are values measured under the constant-speed elongation conditions specified in JIS L1013 (1999) 8.5.1 standard time test, and the strength and elongation product is a value calculated by strength x √ (elongation).

The recycled nylon 66 fiber of the present invention preferably has a fuzz count of 0 to 3 particles/10,000 m or less, more preferably 0 to 2 particles/10,000 m, and even more preferably 0 to 1 particle/10,000 m. The low fuzz count allows for use in applications that require excellent fuzz quality, such as airbags. The fuzz count is calculated by measuring the total number of fuzz particles over a filament length of 100,000 m or more while rewinding at a speed of 150 m/min, and converting it into the number of particles per 10,000 m.

The UVA value (absorbance) at a wavelength of 290 nm for the recycled nylon 66 fiber of the present invention at a solution concentration of 5 mg/mL is preferably 0.30 or less. More preferably, it is 0.27 or less, and even more preferably, it is 0.24 or less. It is known that as nylon deteriorates, it exhibits carbonyl group absorption around 290 nm, and by measuring this absorption, the degree of degradation of the polymer can be quantitatively evaluated. If the UVA value at a wavelength of 290 nm exceeds 0.30, the polymer has deteriorated, and the fiber with high strength and elongation as described above cannot be obtained.

Hereinafter, a method for producing material recycled polyhexamethylene adipamide resin chips (hereinafter referred to as nylon 66 chips) used for the material recycled nylon 66 fiber according to an embodiment of the present invention will be described.

The nylon 66 process waste used in the manufacture of nylon 66 chips in the embodiment of the present invention is generated in the fiber manufacturing process and the airbag base fabric manufacturing process. These include fiber waste (washed-away waste) generated between the attachment of the spinneret and the collection of the fiber product such as a drum package, fiber waste (broken thread waste) generated due to thread breakage problems in the spinning and drawing processes, waste obtained as the final form of the fiber product such as a drum package but rejected in product selection (product waste), and other fiber manufacturing process waste, as well as edge waste generated when weaving the airbag base fabric (airbag base fabric edge waste), waste generated during the refining process of the airbag base fabric (airbag refining base fabric waste), waste obtained as the final form of the airbag base fabric but rejected in product selection (rejected airbag waste), and waste generated when cutting and sewing the airbag from the airbag base fabric (airbag cutting and sewing waste), and any of these process wastes can be suitably used. In addition to process waste, airbags obtained by dismantling and sorting from scrapped cars (scrapped car collected airbags) can also be used.

The manufacturing process for nylon 66 chips in an embodiment of the present invention preferably comprises the steps of melting, filtering and discharging scraps, water-cooling and cutting the extruded resin, and immersing the chips in hot water. In addition, before melting the scraps, the scraps may be appropriately cut, immersed in hot water, and crushed. Furthermore, after water-cooling and cutting the extruded resin, the chips may be immersed in hot water. Each step is described below.

The moisture content of the nylon 66 process scrap used in the manufacture of nylon 66 chips in an embodiment of the present invention is preferably 30,000 ppm or less. As a result of extensive research, the inventors have discovered that when nylon 66 process scrap with a moisture content of 30,000 ppm or less is repellentized and chips are used for spinning, raw yarn having the UVA value specified in the present invention can be obtained, and material recycled nylon 66 fiber with excellent strength and elongation can be obtained.

In addition, one method for adjusting the moisture content of nylon 66 process scraps to the above range is, for example, placing it in a vacuum drying oven set at 100°C, but this is not limited to the methods described in the text.

The prepared scraps are then subjected to the melting, filtering and extrusion process. Melting methods include pressure melters and extruders, and nylon 66 chips can be manufactured using either melting method. The extruder can be either a single-screw or twin-screw type.

The oxygen partial pressure in the molten atmosphere is preferably 1 to 1000 Pa, and more preferably in the range of 1 to 500 Pa. Nylon 66 is more susceptible to oxidative degradation and the associated gelation than other polymers, making it a polymer that is difficult to recycle. The inventors therefore conducted extensive research and discovered that by adjusting the oxygen partial pressure in the molten atmosphere to the above range and minimizing contact between the polymer and oxygen as much as possible, oxidative degradation during melting can be suppressed. To adjust the oxygen partial pressure in the molten atmosphere to the above range, it is preferable to replace (purge) it with an inert gas such as helium, argon, or nitrogen, or to evacuate it.

The melting temperature when melting fiber scraps is 240-360°C. If the melting temperature is 240°C or higher, there will be no unmelted material, and stable nylon 66 chips can be produced without problems such as increased filtration pressure in the melting system. If the melting temperature is 360°C or lower, and preferably 340°C or lower, thermal degradation of the nylon 66 chips can be suppressed.

It is extremely important to filter the fiber scraps when melting them. By filtering them at the same time as melting them, foreign matter can be removed from the nylon 66 chips. As a result, the increase in pressure inside the spinning pack during the production of nylon 66 fiber is suppressed, reducing spinning problems such as pack leaks and discharge abnormalities, making it possible to produce nylon 66 fiber with good operability.

As for the filtration filter, it is preferable to use a filter with a filtration accuracy of 5 to 50 μm. If the filtration accuracy is 5 μm or more, stable melting of fiber waste is possible without an increase in pressure due to filter clogging in the melting system. If the filtration accuracy is 50 μm or less, foreign matter can be removed from the nylon 66 chips. As for the filtration filter, any type of filter can be used as long as it can perform filtration normally, such as a wire mesh type, a metal nonwoven fabric type, or a metal short fiber type.

The melting and filtering time is preferably 5 min/kg or less. If it is 5 min/kg or less, the thermal degradation of the nylon 66 chips due to the thermal history of the melting and filtering can be suppressed, and yellowing of the resulting nylon 66 fibers can be suppressed.

The melted and filtered nylon 66 resin is extruded from a nozzle to form pellets. When extruding from the nozzle, it is preferable to extrude the pellets so that the diameter is 1 to 3 mm.

The nylon 66 resin discharged from the nozzle is subjected to a water cooling and cutting process. The nylon 66 resin may be water cooled to a degree that allows the nylon 66 resin to be easily cut. The nylon 66 resin may be cut by a known method, but it is preferable to cut it to a length of 1 to 4 mm.

FIG. 1 is a schematic diagram of a direct spinning and drawing apparatus preferably used in the present invention.

The manufacturing method for the material recycled nylon 66 fiber of the present invention will be explained below using Figure 1 as an example.

First, prepare raw nylon chips that will be the raw material for the material recycled nylon 66 fiber of the present invention. A publicly known polymerization method can be used for the polymerization of nylon.

The sulfuric acid relative viscosity (hereinafter referred to as viscosity) of the raw material chips for the recycled nylon 66 fiber of the present invention is preferably 2.8 to 3.9, and more preferably 3.0 to 3.9. When measuring and mixing the material recycled nylon 66 chips and virgin nylon 66 chips, the weighted average value according to the viscosity and ratio of each chip should be within the above range. If the viscosity of the chips exceeds 3.9, when the total fineness is within the range specified in this invention, minute foreign matter will be generated due to thickening due to long-term retention of the polymer, thermal deterioration, gelation, etc., and the fluff quality will deteriorate. If the viscosity of the chips is less than 2.8, it will be difficult to obtain recycled nylon 66 fiber with the strength specified in this invention. The sulfuric acid relative viscosity refers to the value measured at 25°C by dissolving a sample in 98% sulfuric acid and using an Ostwald viscometer.

The recycled nylon 66 fiber of the present invention is preferably manufactured by a manufacturing process consisting of weighing out the material recycled nylon 66 chips or weighing and mixing the material recycled nylon 66 chips and virgin nylon 66 chips, and then drying to adjust to a predetermined moisture content, followed by so-called normal melt spinning, cooling, oiling, and drawing. The manufacturing device used in the embodiment of the present invention has a mixer capable of weighing out and mixing the material recycled nylon 66 chips and virgin nylon 66 chips, either in the melt spinning device or separately from the melt spinning device. The melt spinning device used in the embodiment of the present invention can be either an extruder type spinning machine or a pressure melter type spinning machine. When a colorant is added, the chips obtained by mixing the master chips to which the colorant has been added at a high concentration with the base chips may be fed into the spinning machine, or each chip may be weighed and fed directly above the spinning machine. The colorant may also be fed directly into the spinning machine in the form of a powder or liquid.

Next, the measured nylon chips are fed to an extruder-type spinning machine, and placed in a spinneret by a metering pump for melt spinning. At this time, in order to suppress thickening, thermal degradation, and gelation of the polymer, it is preferable that the pressure of the extruder supply section is in a vacuum state (pressure 0.0 kPa). In addition, the spinning temperature is set to a value 50°C higher than the melting point of the polymer. It is preferable that the nylon discharged from the spinneret 1 passes through a heating cylinder 2 that surrounds a range of 5 to 300 cm from directly below the spinneret. The temperature inside this heating cylinder is preferably -30 to +30°C with respect to the melting point of the polymer nylon, and more preferably -15 to +15°C. By gradually cooling the spun yarn through a high-temperature atmosphere surrounded by the heating cylinder rather than immediately cooling it, the orientation of the melt-spun nylon molecules is relaxed and the uniformity of the molecular orientation between the single fibers can be increased, making it possible to increase the strength of the material recycled nylon 66 fiber. On the other hand, if the undrawn yarn is cooled immediately without passing through a high-temperature atmosphere, the orientation of the undrawn yarn increases and the variation in the degree of orientation between single fibers increases. If such an undrawn yarn is hot-drawn, it may not be possible to obtain high-strength recycled nylon 66 fiber.

The undrawn yarn 5 that has passed through the high-temperature atmosphere is then cooled and solidified by blowing air at 10 to 80°C, preferably 10 to 50°C, onto it using a cross-flow cooling device 3. If the cooling air exceeds 80°C, the vibration of the single fibers during spinning will increase, causing collisions between the single fibers and resulting in poor spinnability.

Then, the cooled yarn obtained is oiled by a known oiling device 4, taken up by a take-up roller 6 (1FR), stretched, and then wound up. Any known oil can be used as the oil, but in order to prevent the single yarn from winding on the take-up roller 6, the amount of oil applied is preferably 0.3 to 1.5% by weight, and more preferably 0.5 to 1.0% by weight.

Furthermore, the spinning speed, defined by the rotation speed of the take-up roller 6, is preferably 500 to 1000 m/min, and more preferably 600 to 800 m/min. If the spinning speed is 500 m/min or more, the final production speed will be sufficient, and material recycled nylon 66 fiber can be produced efficiently and inexpensively. A spinning speed of 1000 m/min or less is preferable because it can prevent frequent thread breakage and fuzzing. Furthermore, the drawing speed, which is represented by the maximum speed of the drawing roll, is preferably 2800 m/min or more, and more preferably 3000 m/min or more.

The spun yarn obtained by the above-mentioned methods can be stretched, heat-treated to relax, and wound up using known methods. To give a specific example of two-stage stretching, the spun yarn taken up by the take-up roller 6 is wound around the yarn feed roller 7 (2FR), first stretch roller 8 (1DR), second stretch roller 9 (2DR), and relaxation roller 10 (RR) in that order, where it is heat-treated and stretched, and then wound up on the winder 11.

Pre-stretching is performed between 1FR and 2FR, the first stage of stretching is performed between 2FR and 1DR, and the second stage of stretching is performed between 1DR and 2DR. The temperature of 2FR is set to 30-50°C, the temperature of 1DR is set to 100-225°C, and it is preferable that pre-stretching and the first stage of stretching are hot stretched at around the glass transition temperature. The remaining stretching and heat setting temperatures are preferably performed at high temperatures, usually 180-240°C. More preferably, they are 200-220°C.

Regarding the total draw ratio (hereinafter simply referred to as the draw ratio), i.e. the ratio between the take-up roller 6 and the second draw roller 9, it is preferable to adopt a high draw ratio in order to obtain high-strength recycled nylon 66 fiber, and within the fineness range described in this invention, drawing at 3.8 to 5.0 times is sufficient. Note that the winding speed is usually preferably 2000 to 5000 m/min, and more preferably 2500 to 4500 m/min. Also, it is preferable to wind the material into a cheese strip using a winding device under conditions of a winding tension of 20 to 250 gf.

By using the above method, it is possible to produce the high-strength, high-fuzz recycled nylon 66 fiber described in this invention.

The present invention will be described in detail below with reference to examples. The definitions and measurement methods of each characteristic in the present invention are as follows.

(1) Sulfuric acid relative viscosity (ηr): 0.25 g of a polymer chip or fiber sample was dissolved in 25 ml of 98% sulfuric acid, and the viscosity was measured at 25° C. using an Ostwald viscometer. The viscosity was calculated from the average value of five samples.
ηr=number of seconds for sample solution to flow down/number of seconds for sulfuric acid alone to flow down.

(2) UVA value (absorbance): Using a polymer chip or fiber as a sample, 1 g or 0.1 g of the sample was dissolved in 20 ml of special-grade formic acid, and the absorbance at 290 nm was read from the spectrum measured at a temperature of 25°C and a wavelength range of 250 to 340 nm using a Hitachi U-3900H self-recording spectrophotometer.

(3) Total fineness: Measured according to JIS L1090 (1999).

(4) Number of single fibers: Calculated using the method specified in JIS L1013 (1999) 8.4.

(5) Single fiber fineness: Calculated by dividing the total fineness by the number of single fibers.

(6) Tenacity, strength and elongation: Measured under the constant speed elongation conditions specified in JIS L1013 (1999) 8.5.1 Standard Time Test. The sample was a Tensilon UCT-100 manufactured by Orientec Co., Ltd., with a gripping distance of 25 cm and a pulling speed of 30 cm/min. Tenacity was determined from the maximum strength in the S-S curve, elongation from the elongation at the point showing the maximum strength in the S-S curve, and strength was calculated by dividing the strength by the total fineness.

(7) Number of fuzz in yarn: The obtained fiber package was rewound at a speed of 150 m/min. A laser-type fuzz detector "Flytech V" manufactured by Heberlein was placed 2 m away from the yarn being rewound, and the total number of fuzz detected was evaluated. The evaluation was carried out for more than 100,000 m, and the number of fuzz was converted and displayed as the number per 10,000 m.

Example 1
<Production of virgin nylon 66 chips>
A 5% by weight aqueous solution of copper acetate was added as an antioxidant to the nylon 66 chips obtained by the liquid phase polymerization, and mixed to add and adsorb 68 ppm of copper relative to the polymer weight. Next, a 50% by weight aqueous solution of potassium iodide and a 20% by weight aqueous solution of potassium bromide were added and adsorbed in an amount of 0.1 part by weight per 100 parts by weight of the polymer chips, and solid-phase polymerization was carried out using a batch-type solid-phase polymerization apparatus to obtain nylon 66 chips with a relative viscosity in sulfuric acid of 3.75.

<Production of recycled nylon 66 chips>
The rejected airbag scraps were melted at 340°C in a pressure melter with an oxygen partial pressure of 50 Pa by _N2 purging and vacuuming, and the molten polymer was introduced into a single-screw type extruder. The melting temperature in the extruder was 290°C, and the melt was melted while maintaining a tip pressure of 8 MPa, and filtered through a nonwoven fabric filter with a filtration accuracy of 37 μm. At this time, the discharge amount was adjusted so that the total melt filtration time was 5 minutes/kg. The filtered molten polymer was discharged from a nozzle, cooled with water, and cut to obtain material recycled nylon 66 chips with a diameter of 1.2 mm and a length of 2.0 mm.

<Production of recycled nylon 66 fiber>
The obtained virgin nylon 66 chips and material recycled nylon 66 chips were weighed and mixed in the ratios shown in Table 1, and then fed to an extruder with a diameter of 110 mm and melted at a melting temperature of 300 ° C. under vacuum. The molten polymer was adjusted in discharge amount by a metering pump so that a multifilament having a total fineness of 470 dtex was obtained, and placed in a spinning pack. After that, it was filtered with a metal nonwoven fabric filter having a roughness of 15 μm in the spinning pack, and then spun through a nozzle with circular holes and 72 holes. A heating cylinder with a heating cylinder length of 15 cm was installed 3 cm below the nozzle surface, and heated so that the atmospheric temperature inside the cylinder was 250 ° C. Here, the atmospheric temperature inside the cylinder is the air temperature at the center of the heating cylinder length and 1 cm away from the inner wall. A uniflow chimney for blowing air from one direction was attached directly below the heating cylinder, and cold air at 20° C. was blown onto the yarn at a speed of 35 m/min to cool and solidify it, after which an oil agent was applied to the yarn.

The undrawn yarn treated with oil was wound around the 1FR rotating at a surface speed of 818 m/min, and then drawn at a total draw ratio of 4.5 times. The drawn yarn was continuously stretched by 5% between the take-up roller and the 2FR without being wound up, and then the first stage of drawing was performed at a rotation speed ratio of 2.80 times, followed by a second stage of drawing at a rotation speed ratio of 1.46 times, and then wound up at a speed of 3358 m/min. The roller surfaces of 1FR and 2FR were mirror-finished, while 1DR, 2DR, and RR were matte-finished. The roller temperatures were as follows: 1FR was unheated, 2FR was 40°C, 1DR was 150°C, 2DR was 225°C, and RR was 150°C. Material recycled nylon 66 fiber was obtained by such melt spinning and drawing. The entanglement process was carried out by spraying high-pressure air perpendicular to the running yarn in the entanglement device. Guides were provided before and after the entanglement device to regulate the running yarn, and the pressure of the sprayed air was kept constant at 0.4 MPa.

Example 2
Material Recycle The same procedure as in Example 1 was repeated except that the raw material for the nylon 66 chips was changed to waste from the fiber manufacturing process, the total stretch ratio was changed to 4.8 times, and the ratio of recycled chips was changed to 100%.

Example 3
The same procedure as in Example 1 was repeated, except that the raw material for the material recycled nylon 66 chips was changed to airbag base fabric edge scraps, the total stretch ratio was changed to 4.6 times, the ratio of recycled chips was changed to 50%, and the total fineness of the material recycled nylon 66 fiber was changed to 110 dtex.

Example 4
The same procedure as in Example 1 was repeated except that the raw material for the material recycled nylon 66 chips was airbag cutting and sewing waste, the total draw ratio was 5.8 times, the draw speed was 2645 m/min, the ratio of recycled chips was 5%, and the total fineness of the material recycled nylon 66 fiber was 1400 dtex.

(Example 5)
The same procedure as in Example 1 was repeated except that the raw material of the material recycled nylon 66 chips was airbags recovered from scrapped automobiles, the total draw ratio was 5.7 times, the draw speed was 2050 m/min, and the total fineness of the material recycled nylon 66 fibers was 2100 dtex.

Example 6
The same procedure as in Example 1 was repeated except that the raw material for the material recycled nylon 66 chips was base fabric scraps from the scouring process, the melting atmosphere during the production of the material recycled nylon 66 chips was a vacuum, and the total fineness of the material recycled nylon 66 fibers was 350 dtex.

(Comparative Example 1)
The same procedure as in Example 1 was carried out except that the ratio of raw material chips used was changed to 100% virgin chips and the total stretch ratio was changed to 4.4 times.

(Comparative Example 2)
Material Recycled Nylon 66 chips were produced in the same manner as in Example 1, except that the molten atmosphere was changed to normal air.

(Comparative Example 3)
Material Recycle The same procedure as in Example 1 was carried out except that the raw material moisture content of the nylon 66 chips was 49,000 ppm and the ratio of recycled chips was 100%.

(Comparative Example 4)
Material Recycle The same procedure as in Example 1 was carried out except that the raw material moisture content of the nylon 66 chips was 150,000 ppm and the ratio of recycled chips was 100%.

The physical properties of the virgin nylon 66 fiber obtained in Comparative Example 1 and the material recycled nylon 66 fibers obtained in Examples 1 to 6 and Comparative Examples 2 to 4 were evaluated and are shown in Table 1.

As is clear from Table 1, the recycled nylon 66 fiber of the present invention has the same strength and elongation as virgin nylon 66 fiber, but has good fluff quality.

In Examples 1 to 5, the type of recycled raw material, the proportion of material recycled nylon 66, and the total fiber size were changed in various ways to produce the material recycled nylon 66 fiber of the present invention, but in all cases, the raw yarn properties were comparable to those of virgin nylon 66 fiber.

In addition, when the pre-melting atmosphere during the production of material recycled nylon 66 chips is changed to a vacuum as in Example 6, the moisture contained in the recycled raw material is removed, and the chip viscosity increases, but there is no deterioration in the UVA value, and the recycled fiber still has the same raw yarn properties as virgin fiber. On the other hand, when the pre-melting atmosphere during the production of material recycled nylon 66 chips is changed to air as in Comparative Example 2, the UVA value deteriorates, and it can be seen that the strength, elongation, and fluff quality of the raw yarn are worse than those of virgin fiber.

Also, as in Comparative Examples 3 and 4, when the moisture content of the process waste that is the raw material for the recycled nylon 66 chips exceeds 30,000 ppm, the UVA value of the chips deteriorates, and as a result, it can be seen that the strength and elongation of the raw yarn deteriorates compared to virgin fibers.

These results suggest that reducing the oxygen partial pressure in the pre-melting atmosphere during the production of recycled nylon 66 chips, and keeping the moisture content of the process waste that is the raw material for recycled nylon 66 chips within a specified range, are important for producing recycled nylon 66 fibers with high strength and good fluff quality that are suitable for industrial material applications.

The recycled nylon 66 fiber of the present invention has high strength and good fluff quality, making it ideal for making sustainable industrial materials, mainly for airbags, tire cords, etc.

1: spinneret 2: heating cylinder 3: cross-flow cooling device 4: oil supply device 5: yarn 6: take-up roller (1FR)
7: Yarn feeding roller (2FR)
8: First drawing roller (1DR)
9: Second drawing roller (2DR)
10: Relaxation roller (RR)
11. Winder

Claims (9)

Recycled nylon 66 fiber containing 5% or more by weight of recycled nylon 66, with a total fineness of 110-2100 dtex, strength of 7.6-10.0 cN/dtex, and elongation of 15.0-35.0%. The recycled nylon 66 fiber according to claim 1, characterized in that the UVA value (absorbance) at a wavelength of 290 nm at a solution concentration of 5 mg/mL is 0.30 or less. Recycled nylon 66 fiber according to claim 1 or 2, characterized in that the number of fuzz particles is 0 to 3 per 10,000 m. The recycled nylon 66 fiber according to any one of claims 1 to 3 is produced from repellentized chips using any one or more of the following raw materials: waste from the textile manufacturing process, waste airbag base fabric edges, waste base fabric from scouring processing, waste airbag rejected products, waste airbag cutting and sewing, and airbags collected from scrapped automobiles. A fabric for airbags, characterized by using the recycled nylon 66 fiber described in claim 1 or 2. A tire cord characterized by using the recycled nylon 66 fiber described in claim 1 or 2. Racket strings made from the recycled nylon 66 fiber described in claim 1 or 2. A V-ribbed belt characterized by using the recycled nylon 66 fiber described in claim 1 or 2. A woven fabric for bags, comprising the recycled nylon 66 fiber according to claim 1 or 2.

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