Flat round hole coated yarn and preparation method thereof

Abstract

The invention discloses a flat round hole coated yarn and a preparation method thereof. The preparation method comprises the following steps: spraying a PET (Polyethylene Terephthalate) melt through a spinneret plate to form a nascent fiber tow; spinneret holes in the spinneret plate are arranged in a multi-circle surrounding mode, the inner circle is round holes, and the outer circle is flat holes. The tows are cooled through the windless area and the two sections of annular blowing devices in sequence; the height of the windless area is 40-60 cm, and the first-section circular blowing device adopts low wind pressure and low wind temperature; the second-section annular blowing device adopts conventional air pressure and air temperature; the cooled tows are oiled and then subjected to stretching and heat setting through an eight-roller stretching and heat setting device, and the flat round hole coated yarn is obtained. Wherein two interlacers are arranged between the seventh roller and the eighth roller and are used for carrying out secondary cohesion on the tows. According to the invention, the structure of the spinneret plate is designed, the cooling mode is optimized, and the eight-roller stretching heat setting device is adopted, so that the flat round-hole coated yarn with excellent performance can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of spinning technology, in particular to a flat circular hole coated yarn and a preparation method thereof. Background Art

[0002] As people's living standards continue to improve, the performance requirements for textile products are constantly increasing. Among them, polyester FDY flat yarn, due to the special design of its cross-section, has high softness, moisture absorption, and wrinkle resistance. At the same time, it also has good gloss and breathability. According to its characteristics, it can also be subjected to a napping treatment in post-processing to obtain imitation plush products, which are deeply loved by consumers. In recent years, with the continuous expansion of market demand, flat yarn products have been continuously expanded in production, but flat products lack elasticity and wear resistance. Compared with the same round hole products, their elasticity is insufficient, the comfort is poor, and the service life is short. In order to enable polyester FDY flat products to have some special properties of round hole yarns and make the products more functional, a method is needed to prepare flat round hole coated yarns.

[0003] The production of flat, round-hole covered yarn requires technological innovation in the following three aspects due to the different cross-sections of the two yarns: ① Consideration must be given to how to achieve a flat exterior and round holes within the yarn, with the same single-filament linear density for both yarns, ensuring consistent overall density and stable product performance. ② The heat emitted from the spinneret differs between the two yarns, and selecting the optimal cooling conditions is a key step in controlling production stability and improving product quality. ③ Currently, most chemical fiber factories still use traditional equipment with four upper and lower hot boxes. For example, the composite differential shrinkage yarn production method disclosed in patent CN102560777A uses four hot rollers arranged in an upper and lower offset position. This equipment has only one stretching point, between the lower hot box (first hot roller, first separator roller) and the upper hot box (second hot roller, second separator roller). This makes it difficult to control the drawing stability of the flat and round-hole covered yarns, resulting in frequent breakage and fuzzy yarns, making mass production impossible. Therefore, special stretching and heat setting processes and equipment are required to achieve mass production of flat, round-hole covered yarns. Summary of the Invention

[0004] The present invention aims to overcome the above-mentioned problems existing in the production of flat round hole covered yarn, and provides a flat round hole covered yarn and a preparation method thereof. The spinneret structure is designed, the cooling method is optimized, and an 8-roller stretching and heat setting device is used to obtain a flat round hole covered yarn with excellent performance.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A method for preparing a flat circular hole coated wire, comprising the following steps: (1) PET melt is ejected through a spinneret to form a primary fiber bundle; the spinnerets on the spinneret are arranged in a multi-circle manner, with the inner circle being a circular hole and the outer circle being a flat hole, and the number of circular holes is 10-30% of the total number of spinnerets; (2) The tow is cooled in turn by a windless zone and two-stage annular blowing devices; the height of the windless zone is 40 to 60 cm, the length of the wind tube of the first stage annular blowing device is 23 to 27 cm, the wind temperature is 15 to 20°C, and the wind pressure is 10 to 25 Pa; the length of the wind tube of the second stage annular blowing device is 18 to 22 m, the wind temperature is 20 to 23°C, and the wind pressure is 25 to 40 Pa; (3) The cooled filament bundle is pre-networked and then stretched and heat-set using an 8-roller stretching and heat-setting device to obtain the flat round hole covered filament; wherein two network devices are provided between the seventh roller and the eighth roller to perform secondary bonding on the filament bundle.

[0006] The present invention designs the micropore arrangement of the spinneret, adopts an arrangement in which the inner circle is circular holes and the outer circle is flat holes, and limits the ratio of the number of circular holes and flat holes, so that the melt can be sprayed through the spinneret to form a primary fiber bundle with circular hole filaments in the inner layer and flat filaments in the outer layer.

[0007] In addition, the present invention optimizes the cooling method of the filament bundle. The single-hole flow rate of the round-hole filament and the flat filament are the same, and theoretically the total heat of the single-filament extrusion is the same, but because the cross-sectional shapes of the micropores of the two are different, they are affected differently by the wall shear rate and pressure drop, resulting in different heat ejected from the melt. In actual production, the shear distribution of the flat filament is wider and the pressure drop is greater, the heat ejected is higher than that of the round hole, and the specific surface area of the flat filament is larger than that of the round hole, making it easier to exchange heat with the cooling air. Therefore, its cooling process requires a shorter windless zone height and smaller wind pressure than that of the round-hole filament. Therefore, the cooling process of the two is different in the selection of windless zone and wind pressure, so conventional cooling process and equipment cannot meet the process requirements. In view of the above situation, the present invention improves the cooling method. According to the characteristics of the different cross-sections of the round hole and the flat filament, it is necessary to calculate the rheological properties of the melt separately in order to select the appropriate cooling process conditions.

[0008] Taking the production of 125dtex / 144f flat round hole covered yarn as an example, Round hole wire: shear rate Pressure drop

[0009] Flat wire: shear rate Pressure drop The dynamic viscosity η is 80 Pa.s.

[0010] According to the calculation, γ 圆 =7606S -1 , ΔP 圆 =87Kg.f / cm2 ; γ 扁 =17272S -1 , ΔP 扁 =296Kg.f / cm 2 .

[0011] Calculation results show that after the melt is ejected through the spinneret, the heat of the outer ring of flat filaments will be higher than that of the inner ring of circular holes. Therefore, the distance between the spinneret and the air duct needs to be shortened as much as possible in the design of the windless zone to allow the outer ring of filaments to cool rapidly. At the same time, the outer ring of flat filaments has a larger specific surface area, and the heat exchange between the filaments and the cooling air is faster than that of the inner ring of circular holes. Therefore, the wind pressure needs to be selected in conjunction with the windless zone and the length of the air duct. Therefore, the present invention adopts a two-stage design of the circular blowing device, which can be controlled separately, forming a three-stage cooling process to solve the above problem. The first stage is the selection of the height of the windless zone. The height of the windless zone is shortened, so that the outer ring of flat filaments quickly contacts the cooling air after being ejected and removes the heat. The second stage is the first stage of the circular blowing device, which uses low air pressure and low air temperature to exchange heat with the filaments, ensuring uniform cooling of the inner ring of circular holes. The third stage is the second stage of the circular blowing device, which uses conventional air pressure and air temperature to perform the final cooling of the inner and outer ring filaments. The cooling method of the present invention realizes the effect of uniform cooling inside and outside the filament bundle, and the obtained product has good uniformity in elongation, strength, and evenness, stable production, and high product quality.

[0012] At the same time, the present invention improves the stretching and heat setting device. Flat wire and round hole wire have different stretching and heating properties due to their different cross-sections. The single stretching point of the traditional upper and lower hot boxes cannot meet the stretching process of flat and round hole wires at the same time, which will lead to problems such as many broken ends and hairy wires in production. The present invention adopts an 8-roller stretching and heat setting device. Through multi-point stretching with slowly increasing speed and temperature between 8 rollers and a lower stretching ratio, the round hole wire and the flat wire are stretched and heat set under the same process conditions, and the product appearance is normal, the physical properties are uniform, and the production is stable. After the wire strips are stretched and heat set, they need to pass through the main network device for secondary bonding. Since the cross-sections of the inner and outer bundles of the product are different, their bonding properties are different. In order to enable the network degree of the product to meet the needs of the subsequent processing, the main network device has higher requirements. The traditional single network device can only be achieved by increasing the network pressure, but the higher network pressure will cause the silk strips to rub against the porcelain parts and produce hair. Therefore, the present invention has modified the device by installing two network devices between the seventh roller and the eighth roller, adding a silk stabilizer in the middle, and the network pressure is 3.0-4.0 bar, so that the product network density can reach 15-30 pieces / meter, and the appearance is normal.

[0013] Preferably, the intrinsic viscosity of the PET melt in step (1) is 0.620-0.630 dL / g, the terminal carboxyl content is 36-40 mol / t, and the temperature of the melt is 282-286°C.

[0014] Preferably, the number of holes of the spinneret in step (1) is 36 to 144 holes; the linear density of the spinneret holes is 75D to 120D.

[0015] Preferably, the spinneret holes in the spinneret of step (1) are divided into two sections along the thickness direction of the spinneret, the first section is the guide section, and the second section is the injection section, the cross-sectional area of the guide section is larger than the cross-sectional area of the injection section; the cross-sections of the guide section and the injection section of the circular hole are both circular, the cross-section of the guide section of the flat hole is circular, and the cross-section of the injection section is elliptical; during spinning, the single-hole flow rate and extrusion rate of each spinneret hole in the spinneret are the same.

[0016] As a preference, the shape of the injection section of the circular hole in the spinneret ensures that the shear rate of the ejected circular hole filament is 7000-12000s -1 , the pressure drops to 70~130Kg.f / cm 2 The shape of the flat hole injection section ensures that the shear rate of the ejected flat wire is 10000~40000S -1 , pressure drop to 150~600Kg.f / cm 2 .

[0017] When spinning, the single hole flow calculation formula is:

[0018] Where: V1 is the machine speed, ρ is the melt density, and f is the number of holes. According to the formula, after the round hole yarn and flat yarn are formed into coated yarns, at the same machine speed, the single hole flow rate is the same. However, the melt ejected from the spinneret is also affected by the expansion effect and the stretching effect. In order to ensure the same single yarn linear density for both, it is necessary to control their single hole extrusion speed υ to be the same.

[0019] Single hole extrusion rate = Q / A, where A is the cross-sectional area of the micropore. In addition, according to the production experience in the industry, the shear rate of round hole wire is generally 7000~12000S -1 The production conditions and quality are better. For flat wire, the extrusion rate of the round hole needs to be combined with the extrusion rate of the round hole. Under the premise of ensuring the same extrusion rate of the two, the design with a lower shear rate is preferred to reduce the extrusion heat of the flat wire and better improve the cooling effect of the outer ring flat wire. Therefore, the design of the appropriate cross-sectional shape of the guide section can meet the production process requirements.

[0020] Preferably, in step (1), the PET melt is metered by a metering pump and first enters the sand cup of the component, and then enters the spinneret to be ejected; the sand cup includes two sleeved cylinders, the interior of the inner cylinder forms an inner cavity, and the outer cavity is formed between the outer cylinder and the inner cylinder; the inner cavity is connected to the circular hole portion of the inner ring of the spinneret; and the outer cavity is connected to the flat hole portion of the outer ring of the spinneret.

[0021] Preferably, in step (1), the PET melt is metered by two metering pumps according to the flow rates of the round holes and flat holes in the spinneret, and is transported to the inner cavity and outer cavity of the sand cup of the same component through respective melt distribution pipes.

[0022] Preferably, the network pressure during the pre-network treatment in step (3) is 0.15 to 0.25 bar.

[0023] Preferably, in the 8-roll stretching and heat setting device of step (3), the speed of the first roller, the second roller, and the third roller is 1000-3000 m / min, and the speed of the fourth roller, the fifth roller, the sixth roller, the seventh roller, and the eighth roller is 3000-5000 m / min; wherein, the first roller, the seventh roller, and the eighth roller are not heated, the temperature of the second roller and the third roller is 40-80°C, and the temperature of the fourth roller, the fifth roller, and the sixth roller is 80-130°C.

[0024] Preferably, the network pressure of the two network devices in step (3) is 3.0-4.0 bar.

[0025] Preferably, an oiling plate is provided between the sixth and seventh rollers of the 8-roller stretching and heat setting device in step (3) to oil the filament bundle, and the oil content of the filament bundle after oiling is 1.0-1.5%.

[0026] The present invention also provides a flat round hole coated wire prepared by the above preparation method.

[0027] Therefore, the present invention has the following beneficial effects: (1) There is no need to design and modify a more complex composite box. Only the sand cup cavity and spinneret need to be specially designed to achieve a cladding wire structure with round hole wire inside and flat wire outside. (2) The use of a two-stage ring blowing device achieves uniform cooling of the tow inside and outside, resulting in good uniformity in elongation, strength, and evenness of the product, stable production, and high product quality; (3) The 8-roller stretching and heat setting device is used. Through multi-point stretching and low stretching ratio processes, the flat yarn and round hole yarn are stretched and heat set at the same time under the same drafting process conditions. The obtained product has good uniformity in elongation, strength, and yarn dryness, with less broken ends, stable production, and conditions for mass production. (4) According to the different cross-sections of the inner and outer yarn bundles of the product, the network device is modified to adopt a double network form, and a silk stabilizer is added between the two network devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the spinning process of the present invention.

[0029] Figure 2 It is a schematic diagram of the connection structure of the sand cup and the spinneret of the present invention.

[0030] Figure 3 It is a top view of the spinneret of the present invention.

[0031] Figure 4 It is a structural schematic diagram of the silk road stabilizer of the present invention.

[0032] Figures 1 to 4 Middle: Spinning box 1, ring blowing device 2, wire guide hook frame 3, pre-network device 4, wire separator 5, scissors row 6, 8-roller stretching and heat setting device 7, one roller 7-1, two rollers 7-2, three rollers 7-3, four rollers 7-4, five rollers 7-5, six rollers 7-6, seven rollers 7-7, eight rollers 7-8, oiling tray 8, network device 9, silk path stabilizer 10, mounting base 10-1, stabilizing rod 10-2, screw adjustment hole 10-3, winding machine 11, sand cup 12, spinneret 13, outer cavity melt hole 14, inner cavity melt hole 15, annular sealing ring 16, flat hole 17, round hole 18.

[0033] Figure 5 This is a cross-sectional view of the flat circular hole coated wire obtained in Example 2 of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0036] Overall embodiment: A method for preparing a flat circular hole coated wire, the process is as follows Figure 1 As shown in , the steps include: (1) The PET melt is metered by a metering pump in the spinning manifold 1 and then enters the sand cup of the component, and then enters the spinneret to be ejected to form a primary fiber bundle; Figure 3 As shown in , the spinnerets 13 are arranged in a multi-circle manner, with the inner circle being a circular hole 18 and the outer circle being a flat hole 17. The number of circular holes accounts for 10 to 30% of the total number of spinnerets; Figure 2 As shown in FIG, the sand cup 12 includes two sleeved cylinders. The interior of the inner cylinder forms an inner cavity, and an inner cavity melt hole 15 is provided at the top of the inner cavity. An outer cavity is formed between the outer cylinder and the inner cylinder, and an outer cavity melt hole 14 is provided at the top of the outer cavity. The inner cavity is connected to the circular hole portion of the inner ring of the spinneret; the outer cavity is connected to the flat hole portion of the outer ring of the spinneret; the sand cup and the spinneret are connected by an annular sealing ring 16. (2) The tow is cooled in turn by a windless zone and a two-stage annular blowing device 2; the height of the windless zone is 40 to 60 cm, the length of the wind tube of the first stage annular blowing device is 23 to 27 cm, the wind temperature is 15 to 20°C, and the wind pressure is 10 to 25 Pa; the length of the wind tube of the second stage annular blowing device is 18 to 22 m, the wind temperature is 20 to 23°C, and the wind pressure is 25 to 40 Pa; (3) The cooled filament bundle passes through the wire guide hook rack 3 and enters the pre-network device 4 for pre-networking; then passes through the wire separator 5 and the scissors row 6 in sequence and enters the 8-roller stretching and heat setting device 7 for stretching and heat setting to obtain the flat round hole coated wire; wherein the speed of the first roller 7-1, the second roller 7-2 and the third roller 7-3 is 1000-3000 m / min, and the speed of the fourth roller 7-5, the fifth roller 7-5, the sixth roller 7-6, the seventh roller 7-7 and the eighth roller 7-8 is 3000-5000 m / min; the first roller, the seventh roller and the eighth roller are not heated, the temperature of the second roller and the third roller is 40-80°C, and the temperature of the fourth roller, the fifth roller and the sixth roller is 80-130°C; an oiling pan 8 is provided between the sixth roller and the seventh roller to oil the filament bundle, two network devices 9 are provided between the seventh roller and the eighth roller to perform secondary bonding on the filament bundle, and a silk stabilizer 10 is provided between the two network devices; Figure 4 As shown in the figure, the silk path stabilizer includes a mounting base 10-1, on which a screw adjustment hole 10-3 and two stabilizing rods 10-2 are provided, and the screw adjustment hole is an arc-shaped hole; when in use, the silk path stabilizer is fixed to the back plate of the hot box through the screw adjustment hole, and the silk bundle passes between the two stabilizing rods. The silk path stabilizer can be rotated along the screw adjustment hole to adjust the angle between the stabilizing rod and the silk bundle.

[0037] As a specific embodiment, the intrinsic viscosity of the PET melt in step (1) is 0.620-0.630 dL / g, the terminal carboxyl content is 36-40 mol / t, and the temperature of the melt is 282-286°C.

[0038] As a specific implementation manner, the number of holes of the spinneret in step (1) is 36 to 144 holes; the linear density of the spinneret holes is 75D to 120D.

[0039] As a specific implementation method, the spinneret holes in the spinneret of step (1) are divided into two sections along the thickness direction of the spinneret, the first section is the guide section, and the second section is the injection section, the cross-sectional area of the guide section is larger than the cross-sectional area of the injection section; the cross-sections of the guide section and the injection section of the circular hole are both circular, the cross-section of the guide section of the flat hole is circular, and the cross-section of the injection section is elliptical; during spinning, the single-hole flow rate and extrusion rate of each spinneret hole in the spinneret are the same.

[0040] As a specific embodiment, the shape of the injection section of the circular hole in the spinneret ensures that the shear rate of the ejected circular hole filament is 7000-12000S -1 , the pressure drops to 70~130Kg.f / cm2 The shape of the flat hole injection section ensures that the shear rate of the ejected flat wire is 10000~40000S -1 , pressure drop to 150~600Kg.f / cm 2 .

[0041] As a specific implementation manner, the network pressure during the pre-network treatment in step (3) is 0.15 to 0.25 bar.

[0042] As a specific implementation method, the network pressure of the two network devices in step (3) is 3.0 to 4.0 bar.

[0043] As a specific embodiment, the oil content of the filament bundle after oiling on the oiling pan in step (3) is 1.0-1.5%.

[0044] Example 1: A method for preparing 125dtex / 144f flat round hole covered yarn, comprising the following steps: (1) Preparation of PET melt: PET melt was prepared from terephthalic acid, ethylene glycol, and antimony glycol through slurry preparation, esterification I, esterification II, pre-polycondensation, and final polycondensation. The intrinsic viscosity of the PET melt was 0.625 dL / g, the end carboxyl content was 37 mol / t, the melt temperature was 283°C, the L value was 86.8, the b value was 4.7, and the TiO2 mass fraction was 0.20%. (2) Metering by metering pumps: The obtained PET melt passes through a booster pump, a cooler, and is transported to a metering pump at the spinning position; one spinning position has two metering pumps, which meter the melt according to the flow rate of the round hole yarn and the flat yarn respectively; after the melt is metered by the metering pumps, it is transported to the inner cavity and outer cavity of the sand cup of the same component through their respective melt distribution pipes; (3) Spinning out of the spinneret: The PET melt is ejected from the sand cup into the spinneret to form a primary fiber bundle with round hole filaments in the inner layer and flat filaments in the outer layer; the spinneret diameter is selected as Φ=104, and the total number of spinneret holes is 144; the spinneret holes are arranged in 5 circles with the center of the spinneret as the circle: the first and second circles from the inside to the outside are the inner circle of round holes, with 14 holes and 22 holes respectively; the third, fourth and fifth circles from the inside to the outside are the outer circle of flat holes, with 30 holes, 36 holes and 42 holes respectively; the total number of round holes accounts for 25%, and the total number of flat holes accounts for 75%; The circular holes and flat holes are divided into two sections along the thickness direction of the spinneret: the first section is the flow guide section and the second section is the injection section. The cross-sections of the flow guide section and injection section of the circular hole are both circular, while the cross-section of the flow guide section of the flat hole is circular and the injection section is elliptical. The diameter of the flow guide section of the circular hole is 2 mm, the diameter of the injection section is 0.18 mm, and the hole length is 0.63 mm. The diameter of the flow guide section of the flat hole is 2 mm, the hole width w of the injection section is 0.42 mm, the hole height h is 0.06 mm, and the hole length L is 0.63 mm. Single hole flow Extrusion rate The melt density ρ is 1.18 g / cm 3 , the speed V is 3550m / min, A is the cross-sectional area, and according to the formula, the extrusion rate of the circular hole and the flat hole is 10m / min, so the selection is appropriate; (4) Circular cooling: The height of the windless zone is selected to be 45m; the length of the duct of the first section of the circular blowing device is 25cm, the wind temperature is 18℃, and the circular blowing pressure is 18Pa; the length of the duct of the second section of the circular blowing device is 20cm, the wind temperature is 21℃, and the circular blowing pressure is 30Pa; (5) Pre-network treatment: The tow after circular cooling is subjected to pre-network treatment, and the network pressure is 0.20bar; (6) Stretching and heat setting: the speed of the first roller is 2000 m / min, the speed of the second roller is 2350 m / min, the speed of the third roller is 2650 m / min, the speed of the fourth roller is 3430 m / min, the speed of the fifth roller is 3520 m / min, the speed of the sixth roller is 3540 m / min, the speed of the seventh roller is 3555 m / min, and the speed of the eighth roller is 3545 m / min. Among them, the first, seventh and eighth rollers are not heated, the temperature of the second roller is 55°C, the temperature of the third roller is 75°C, the temperature of the fourth roller is 93°C, the temperature of the fifth roller is 102°C, and the temperature of the sixth roller is 118°C; (7) Oiling: The tow is oiled by the oiling plate between the sixth and seventh rollers. The oil content of the tow after oiling is 1.2%; (8) Secondary bonding: The first network pressure between the seventh and eighth rollers is 3.0 bar, the second network pressure is 3.7 bar, and the product network density is 20 pieces / meter; after the secondary bonding, the winding machine is used for package forming at a speed of 3550m / min to obtain the flat round hole coated wire.

[0045] Example 2: A method for preparing 90dtex / 40f flat round hole covered yarn, comprising the following steps: (1) Preparation of PET melt: PET melt was prepared from terephthalic acid, ethylene glycol, and antimony glycol through slurry preparation, esterification I, esterification II, pre-polycondensation, and final polycondensation. The intrinsic viscosity of the PET melt was 0.623 dL / g, the end carboxyl content was 38 mol / t, the melt temperature was 285°C, the L value was 86.8, the b value was 4.7, and the TiO2 mass fraction was 0.20%. (2) Metering by metering pumps: The obtained PET melt passes through a booster pump, a cooler, and is transported to a metering pump at the spinning position; one spinning position has two metering pumps, which meter the melt according to the flow rate of the round hole yarn and the flat yarn respectively; after the melt is metered by the metering pumps, it is transported to the inner cavity and outer cavity of the sand cup of the same component through their respective melt distribution pipes; (3) Spinning out of the spinneret: The PET melt is ejected from the sand cup into the spinneret to form a primary fiber bundle with round hole filaments in the inner layer and flat filaments in the outer layer; the spinneret diameter is selected as Φ=104, and the total number of spinneret holes is 40; the spinneret holes are arranged in three circles with the center of the spinneret as the circle: the first circle from the inside to the outside is the inner circle of round holes, with 8 round holes; the second and third circles from the inside to the outside are the outer circle of flat holes, with 14 and 18 flat holes respectively; the total number of round holes accounts for 20%, and the total number of flat holes accounts for 80%; The circular holes and flat holes are divided into two sections along the thickness direction of the spinneret: the first section is the flow guide section and the second section is the injection section. The cross-sections of the flow guide section and injection section of the circular hole are both circular, while the cross-section of the flow guide section of the flat hole is circular and the injection section is elliptical. The diameter of the flow guide section of the circular hole is 2 mm, the diameter of the injection section is 0.23 mm, and the hole length is 0.65 mm. The diameter of the flow guide section of the flat hole is 2 mm, the hole width w of the injection section is 0.7 mm, the hole height h is 0.06 mm, and the hole length L is 0.65 mm. Single hole flow Extrusion rate The melt density ρ is 1.18 g / cm 3 , the speed V is 4000m / min, A is the cross-sectional area, and according to the formula, the extrusion rate of the round hole and the flat hole is 18m / min, so the selection is appropriate; (4) Circular cooling: The height of the windless zone is selected to be 60m; the length of the duct of the first section of the circular blowing device is 25cm, the wind temperature is 20℃, and the circular blowing pressure is 25Pa; the length of the duct of the second section of the circular blowing device is 20cm, the wind temperature is 21℃, and the circular blowing pressure is 30Pa; (5) Pre-network treatment: The tow after circular cooling is subjected to pre-network treatment, and the network pressure is 0.23bar; (6) Stretching and heat setting: the speed of the first roller is 2500 m / min, the speed of the second roller is 2420 m / min, the speed of the third roller is 2760 m / min, the speed of the fourth roller is 3510 m / min, the speed of the fifth roller is 3590 m / min, the speed of the sixth roller is 3860 m / min, the speed of the seventh roller is 4010 m / min, and the speed of the eighth roller is 3950 m / min. Among them, the first, seventh and eighth rollers are not heated, the temperature of the second roller is 59°C, the temperature of the third roller is 68°C, the temperature of the fourth roller is 90°C, the temperature of the fifth roller is 100°C, and the temperature of the sixth roller is 113°C; (7) Oiling: The tow is oiled by the oiling plate between the sixth and seventh rollers. The oil content of the tow after oiling is 1.2%; (8) Secondary bonding: The first network pressure between the seventh and eighth rollers is 3.0 bar, the second network pressure is 3.3 bar, and the product network density is 22 per meter; after the secondary bonding, the winding machine is used for package forming at a speed of 4000 m / min to obtain the flat round hole covered wire, the cross-sectional view of which is shown in FIG. Figure 5 As shown in .

[0046] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the stretching and heat setting step in step (6) is completed by a 4-roller device with upper and lower hot boxes, and the specific parameters are as follows: one roller is a heating roller, two rollers are wire-separating rollers, and both are in the lower hot box; three rollers are heating rollers, four rollers are wire-separating rollers, and both are in the upper hot box; the speed of the first roller is 2500 m / min, the temperature is 90°C, and the speed of the second roller is automatically synchronized with the speed of the first roller; the speed of the third roller is 4010 m / min, the temperature is 113°C, and the speed of the fourth roller is automatically synchronized with the speed of the third roller; The remaining steps are the same as in Example 1.

[0047] The properties of the products obtained in Example 1 and Comparative Example 1 were tested, and the results are shown in Table 1.

[0048] Table 1: Performance test results of the products obtained in Example 1 and Comparative Example 1. project Example 1 Comparative Example 1 Full roll rate (%) 97.0％-97.8％ 94.2-95.3％ Wool(pieces / bit) 0-1 5-12 Staining M rate (%) 99.8％ 95.0％ Breaking strength (CN / dtex) 4.1 3.5 Elongation at break (%) 31 27 Strip unevenness (cv) 0.67 1.53 Boiling water shrinkage (%) 7.2 7.3 Network speed (unit / meter) 20 20

[0049] As can be seen from the data comparison in Table 1, flat round-hole covered yarn, because its tow is composed of a composite of flat monofilaments and round-hole monofilaments, is well known. Due to the different cross-sections, the stretching and heating properties of flat products are different from those of round-hole products. Traditional four-roller equipment only uses one stretching point to complete the stretching process and two rollers to complete the heating and shaping process. It is unable to simultaneously take into account the performance of flat and round-hole monofilaments. As a result, the monofilaments in the final product tow are understretched or overstretched, and there are deviations in heating and shaping. This leads to low full-wind rate, low dyeing rate, low elongation and strength, poor yarn uniformity, and a high amount of fuzz in the product.

[0050] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that only one section of circular blowing device is used in the circular blowing cooling step of step (4), and the height of the windless zone is 60m; the wind tube length of the circular blowing device is 45cm, the wind temperature is 20℃, and the circular blowing pressure is 30Pa; the remaining steps are the same as in Example 2.

[0051] The properties of the products obtained in Example 2 and Comparative Example 2 were tested, and the results are shown in Table 2.

[0052] Table 2: Performance test results of the products obtained in Example 2 and Comparative Example 2.

[0053] By comparing the data of Example 2 and Comparative Example 2, it can be found that although the first cooling stage of Comparative Example 2 and Example 2 both use a windless zone height of 60 cm, Example 2 uses a two-stage circular blowing cooling device: the first stage circular blowing device uses low wind pressure and low wind temperature to perform heat exchange on the filament bundle, ensuring uniform cooling of the inner ring round hole filament; the second stage circular blowing device uses conventional wind pressure and wind temperature to perform final cooling on the inner and outer ring filament bundles. In Comparative Example 2, although the length of the circular blowing device is the same as the total length of the circular blowing device in Example 2, its single wind temperature and wind pressure are obviously insufficient to cool the flat round hole coated filaments, and cannot effectively achieve uniform cooling of flat monofilaments and round hole monofilaments with different cross-sections and different extrusion heat. Therefore, when the method of Comparative Example 2 is used for production, the product has a low full roll rate, a lot of hairy yarns, poor dyeing performance, and a large strip of product.

[0054] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that only one network device is set between the seventh roller and the eighth roller, and the network pressure is 3.7 bar; the remaining steps are the same as in Example 2.

[0055] The properties of the products obtained in Example 2 and Comparative Example 3 were tested, and the results are shown in Table 3.

[0056] Table 3: Performance test results of the products obtained in Example 2 and Comparative Example 3. project Example 2 Comparative Example 3 First network pressure (bar) 3.0 3.7 Second network pressure (bar) 3.3 none Full roll rate (%) 97.2％-98.0％ 97.2％-98.0％ Wool(pieces / bit) 0-1 3-7 Staining M rate (%) 99.6％ 99.6％ Breaking strength (CN / dtex) 4.0 3.7 Elongation at break (%) 30.2 29.0 Strip unevenness (cv) 0.61 0.85 Boiling water shrinkage (%) 7.4 7.4 Network speed (unit / meter) 22 17

[0057] By comparing the data of Example 2 and Comparative Example 3, it can be found that in Comparative Example 3, a single main network device is used. By increasing the network device pressure to 3.7 bar, the network degree of the product can reach 17 / meter, which is still not as good as the network degree of the two network devices in Example 2. Moreover, after increasing the network device pressure, the vibration of the silk strips is aggravated, the collision between the monofilaments is aggravated, the friction between the silk strips and the porcelain parts is increased, and the hair of the product is increased. Therefore, continuing to increase the network degree by increasing the network pressure cannot meet the product requirements. At the same time, as the friction of the silk strips increases, the strength and elongation of the product will decrease, thereby affecting other properties of the product.

[0058] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that the diameter of the guide section of the circular hole in the spinneret is 2 mm, the diameter D of the injection section is 0.18 mm, and the hole length L is 0.63 mm; the micropores in the outer ring b have a diameter of 2 mm in the guide section, a width w of 0.50 mm in the injection section, a hole height h of 0.05 mm, and a hole length L of 0.63 mm; Single hole flow Extrusion rate The melt density ρ is 1.18 g / cm 3 , the speed V is 3550m / min, A is the cross-sectional area, and according to the formula, the extrusion rate of the circular hole and the flat hole is 10m / min, so the selection is appropriate; The height of the windless zone during ring blowing cooling is 45m; the wind tube length of the first section of the ring blowing device is 25cm, the wind temperature is 18°C, and the ring blowing pressure is 25Pa; the wind tube length of the second section of the ring blowing device is 20cm, the wind temperature is 21°C, and the ring blowing pressure is 35Pa; the rest are the same as in Example 1.

[0059] The spinneret hole size, shear rate and pressure drop calculation results in Example 1 and Comparative Example 4 are shown in Table 4.

[0060] Table 4: Spinneret selection results in Example 1 and Comparative Example 4.

[0061] Calculation results show that the extrusion rates for the flat and round holes in Comparative Example 4 are identical, both at 10 m / min, as in Example 1. However, calculations of shear rate and pressure drop reveal that the flat filaments in Comparative Example 4 have higher shear rates and pressure drops, resulting in significantly greater extrusion heat than in Example 1. To meet production requirements, the filaments were cooled under different cooling conditions and the product performance was compared. The results are shown in Table 5.

[0062] Condition 1: The height of the windless zone is 45m; the length of the wind tube of the first section of the circular blowing device is 25cm, the wind temperature is 18℃, and the circular blowing pressure is 25Pa; the length of the wind tube of the second section of the circular blowing device is 20cm, the wind temperature is 21℃, and the circular blowing pressure is 35Pa.

[0063] Condition 2: The wind-free zone is 45 meters high. The first section of the circular air blowing device has a 25-cm air duct length, an air temperature of 18°C, and an air pressure of 30 Pa. The second section of the circular air blowing device has a 20-cm air duct length, an air temperature of 21°C, and an air pressure of 38 Pa. The air pressure and air volume are further increased to enhance the cooling effect of the tow.

[0064] Table 5: Performance test results of the products obtained in Example 1 and Comparative Example 4. project Example 1 Comparative Example 4 (Condition 1) Comparative Example 4 (Condition 2) Full roll rate (%) 97.0％-97.8％ 95.2-95.5％ 95.2-96.0％ Wool(pieces / bit) 0-1 0-1 1-4 Staining M rate (%) 99.8％ 99.7％ 99.8％ Breaking strength (CN / dtex) 4.1 4.0 4.0 Elongation at break (%) 31 31 31 Strip unevenness (cv) 0.67 0.73 0.86 Boiling water shrinkage (%) 7.2 7.3 7.3 Network speed (unit / meter) 20 20 20

[0065] A comparison of Condition 1 in Example 1 and Comparative Example 4 shows that the full roll rate in Condition 1 decreases significantly, and the yarn unevenness increases, validating the aforementioned spinneret selection calculation results. Furthermore, in Comparative Example 4, due to the reduced height h and increased width w of the flat yarn, its cross-sectional profile becomes more elongated, increasing the difficulty of flat yarn production.

[0066] A comparison of the data under Condition 2 in Example 1 and Comparative Example 4 shows that the full roll rate of the product does not improve significantly with increasing air pressure and air volume. Furthermore, excessive annular air pressure exacerbates the shaking of the tow within the duct, leading to collision and friction between the tows, resulting in fuzzy fibers, an increase in the number of fuzzy fibers, and an increase in the dryness of the product.

[0067] Therefore, the spinneret selection parameters in Comparative Example 4 are not the optimal process conditions. Combined with Example 1, the spinneret selection still needs to reduce the shear rate and pressure drop of the flat filaments to achieve the best cooling effect.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a flat circular hole coated wire, characterized in that the steps include: (1) PET melt is ejected through the spinneret to form a primary fiber bundle; the spinneret holes on the spinneret are arranged in a multi-circle manner, with the inner circle being a circular hole and the outer circle being a flat hole. The number of circular holes accounts for 10-30% of the total number of spinneret holes; (2) The tow is cooled in turn by a windless zone and two-stage annular blowing devices; the height of the windless zone is 40~60cm, the length of the wind tube of the first stage annular blowing device is 23~27cm, the wind temperature is 15~20℃, and the wind pressure is 10~25Pa; the length of the wind tube of the second stage annular blowing device is 18~22m, the wind temperature is 20~23℃, and the wind pressure is 25~40Pa; (3) The cooled filament bundle is subjected to pre-network treatment and then stretched and heat-set using an 8-roller stretching and heat-setting device to obtain the flat round hole covered filament; There are two network devices between the seventh and eighth rollers to perform secondary bonding on the tow.

2. The method for preparing the flat round hole covered wire according to claim 1, wherein: The intrinsic viscosity of the PET melt in step (1) is 0.620-0.630 dL / g, the end carboxyl content is 36-40 mol / t, and the temperature of the melt is 282-286°C.

3. The method for preparing the flat round hole covered wire according to claim 1, wherein: The number of holes of the spinneret in step (1) is 36 to 144 holes; the linear density of the spinneret holes is 75D to 120D.

4. The method for preparing the flat circular hole covered wire according to claim 1 or 3, wherein: The spinneret holes in step (1) are divided into two sections along the thickness direction of the spinneret, the first section is the flow guide section, and the second section is the injection section, the cross-sectional area of the flow guide section is larger than the cross-sectional area of the injection section; the cross-sections of the flow guide section and the injection section of the circular hole are both circular, the cross-sectional area of the flow guide section of the flat hole is circular, and the cross-sectional area of the injection section is elliptical; during spinning, the single hole flow rate and extrusion rate of each spinneret hole in the spinneret are the same.

5. The method for preparing the flat round hole covered wire according to claim 1, wherein: In step (1), the PET melt is metered by a metering pump and first enters the sand cup of the component, and then enters the spinneret for ejection; the sand cup includes two sleeved cylinders, the interior of the inner cylinder forms an inner cavity, and the outer cavity is formed between the outer cylinder and the inner cylinder; the inner cavity is connected to the circular hole portion of the inner ring of the spinneret; and the outer cavity is connected to the flat hole portion of the outer ring of the spinneret.

6. The method for preparing the flat round hole covered wire according to claim 5, wherein: In step (1), the PET melt is metered by two metering pumps according to the flow rates of the circular holes and the flat holes in the spinneret, and is transported to the inner cavity and the outer cavity of the sand cup of the same component through their respective melt distribution pipes.

7. The method for preparing a flat circular hole covered wire according to claim 1, wherein: The network pressure during the pre-network treatment in step (3) is 0.15~0.25bar; the network pressure of the two network devices is 3.0~4.0bar.

8. The method for preparing a flat circular hole covered wire according to claim 1, wherein: In the 8-roll stretching and heat-setting device of step (3), the speed of the first roller, the second roller, and the third roller is 1000~3000 m / min, and the speed of the fourth roller, the fifth roller, the sixth roller, the seventh roller, and the eighth roller is 3000~5000 m / min; wherein, the first roller, the seventh roller, and the eighth roller are not heated, the temperature of the second roller and the third roller is 40~80℃, and the temperature of the fourth roller, the fifth roller, and the sixth roller is 80~130℃.

9. The method for preparing the flat round hole covered wire according to claim 1 or 8, wherein: In step (3), an oiling plate is provided between the sixth and seventh rollers of the 8-roller stretching and heat setting device to oil the filament bundle, and the oil content of the filament bundle after oiling is 1.0-1.5%.

10. A flat round hole covered wire, characterized in that: It is prepared using the preparation method according to any one of claims 1 to 9.

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