Spinning method for reducing sheath-core structure of polyester industrial yarn

Abstract

The present invention relates to a spinning method for reducing a sheath-core structure of polyester industrial yarn. The method comprises: extruding a polyester melt by means of a spinneret, and then sequentially subjecting same to slow cooling with a heat retarder, cooling in an air-free zone, cooling in an air blowing zone, finishing, drawing, setting, interlacing and winding so as to prepare polyester industrial yarn, wherein the air blowing zone sequentially comprises a cold air zone a, a hot air zone and a cold air zone b from top to bottom; the cold air zone a has a height of 500-600 mm, the hot air zone has a height of 300-400 mm, and the cold air zone b has a height of 400-500 mm; and the cold air zone a has a temperature of 22-25°C, the hot air zone has a temperature of 120-130°C, and the cold air zone b has a temperature of 22-25°C. In the present invention, by additionally providing the hot air zone in the air blowing zone to heat tows, a reduction in a difference within a sheath-core structure is facilitated, and uniformly cooled fibers can be obtained; and the prepared polyester industrial yarn has a small breaking strength irregularity, a low breaking elongation irregularity, and uniform fiber chromaticity.

Description

A spinning method for reducing the core-skin structure of polyester industrial yarn Technical Field

[0001] The invention belongs to the technical field of polyester industrial yarns and relates to a spinning method for reducing the skin-core structure of polyester industrial yarns. Background Art

[0002] Polyester industrial yarn has excellent properties such as high breaking strength, high modulus, good light resistance, heat resistance and chemical corrosion resistance. It is widely used in special fields such as fire hoses, cables, climbing ropes, geotextiles, and advertising fabrics. With the rapid development of polyester industrial yarn and the expansion of its application fields, the development of polyester industrial yarn is required not only to meet basic mechanical properties, but also to meet the special requirements of certain application fields. For example, fire hoses and ropes require high wear resistance, stability, and dyeing uniformity, while advertising fabrics require good uniformity, no dark streaks, and no color difference. This requires polyester industrial yarn to have higher uniformity. The uniformity here is not limited to the linear density unevenness and strip unevenness we usually mention. It also requires improving the uniformity of crystallization between the filaments in the tow, the uniformity of color, the uniformity of strength (including wear resistance, dimensional stability, modulus), and the uniformity of dyeing.

[0003] The industrial yarn has a high linear density of 8-10 dtex. The melt is extruded from the spinneret during uniaxial tensile deformation. Due to the different temperatures of the cortex and the core layer, the melt viscosity of the cortex decreases under the action of cooling air, while the viscosity of the core layer decreases. Under the action of large tensile shear stress, the orientation and crystallization of the cortex are higher than those of the core layer, resulting in radial differences in the fiber structure and forming a skin-core structure.

[0004] The sheath-core structure is an important structural feature of high-speed spinning. The sheath-core structure is caused by the temperature difference between the sheath and the core layer. The temperature difference will cause a viscosity difference between the sheath and the core layer. The viscosity difference between the sheath and the core layer will lead to an increase in the difference in the orientation of the sheath and the core layer, which in turn affects the fiber strength and strength uniformity, dyeing uniformity, chromaticity uniformity, crystallization uniformity, etc.

[0005] To address this issue, prior art document 1 (Research on the Relationship between Circular Cross-Section Fiber Structure and Its Reflective Properties [D]. Jiangnan University, 2009) points out that the core-skin structure of a fiber affects the internal light reflected from the fiber, causing variations in the fiber's gloss, thus affecting gloss uniformity. European Patent EP0080906 discloses a polyester fiber and its production process, using hot air at 60-80°C to blow onto the filaments to delay cooling and reduce the difference in birefringence between the core and the skin. Increasing the air temperature or eliminating the air flow to extend the curing time can theoretically reduce this difference in the core-skin structure. However, these methods result in increased curing time and length, decreased coagulation speed, and significant sway, making the filaments susceptible to external interference. This results in poor filament uniformity, affecting gloss and dyeing uniformity.

[0006] U.S. Patent No. 4,867,925 discloses a process for producing polyester industrial yarns. The process uses composite spinning technology, with a high-viscosity melt as the core layer and a low-viscosity melt as the sheath layer. The residence time in the spinning manifold is adjusted to spin a sheath-core two-component composite yarn. The viscosity difference between the sheath and core is 0.003 to 0.04 dL / g, thereby reducing the difference in the sheath-core structure. This method uses a composite spinning manifold and components, has high technical costs, and is difficult to promote and implement.

[0007] Furthermore, patent CN102797057B provides a method for producing high-modulus, low-shrinkage polyester industrial yarn. This method utilizes a slow cooling device to reduce fiber pre-orientation and variations in the sheath-core structure. The slow cooling device maintains the melt temperature and slowly cools it in an air atmosphere at 260-300°C. Furthermore, a porous plate and a windless zone of a certain length are connected below the slow cooling device to further slow down the cooling of the yarn bundle, allowing heat from the core layer to be transferred out, thereby reducing variations in the sheath-core structure. The resulting polyester industrial yarn has a breaking strength unevenness of ≤2.5% and a breaking elongation unevenness of ≤7.0%. Patent CN113430658B discloses a low-pressure spinning method for polyester industrial yarn. Modified polytetrafluoroethylene is introduced into the polyester melt to improve fiber uniformity. The resulting polyester industrial yarn has a breaking strength unevenness of ≤2.0% and a breaking elongation unevenness of ≤5.0%. While the uniformity of polyester industrial yarn produced using existing technologies is gradually improving, there is still room for further improvement.

[0008] Therefore, it is of great practical significance to develop a spinning method for reducing the sheath-core structure of polyester industrial yarn in order to further reduce the sheath-core structure.

[0009] Summary of the Invention

[0010] The purpose of the present invention is to solve the problems existing in the prior art and provide a spinning method that reduces the sheath-core structure of polyester industrial yarn.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0012] A spinning method for reducing the core-skin structure of polyester industrial yarn, wherein the polyester melt is extruded through a spinneret and then subjected to slow cooling in a slow cooling device, cooling in a windless zone, cooling in a blowing zone, oiling, stretching, shaping, web-forming, and winding to produce the polyester industrial yarn, wherein the blowing zones are, from top to bottom, cold air zone a, hot air zone, and cold air zone b;

[0013] The height of the cold air zone a is 500-600mm, the height of the hot air zone is 300-400mm, and the height of the cold air zone b is 400-500mm;

[0014] The temperature of the cold air zone a is 22-25°C, the temperature of the hot air zone is 120-130°C, and the temperature of the cold air zone b is 22-25°C;

[0015] The length of the cold air zone a theoretically needs to be greater than or equal to the solidification length of the filament bundle, that is, the distance between the spinneret and the solidification point of the filament. Since the theoretical calculation is too complicated, the details can be found in Reference 2 (Principles of Polymer Material Processing [M]. Beijing: China Textile Press, 2002: 193); Reference 3 (Research on the Forming Mechanism and Structural Properties of Large Diameter Polymer Monofilaments [D]. Donghua University, 2011: 28) points out that the polymer solidification temperature is the glass transition temperature Tg or between the glass transition temperature Tg and the polymer melting point Tm, and the glass transition temperature of polyester is 67-81°C; the present invention directly measures the temperature of the filament bundle using an infrared thermometer to obtain the position of the solidification point; wherein, the solidification point temperature is selected to be higher than the glass transition temperature (75-90°C) to obtain the solidification length.

[0016] The length of the hot air zone is measured by an infrared thermometer. When the temperature of the filament bundle is maintained between 120 and 130°C, the position interval where the filament bundle is fully heated is measured. The distance between the end point of this position interval and the solidification point position measured previously is the length of the hot air zone.

[0017] The length of the cold air zone b is measured using an infrared thermometer to test the position where the temperature of the filament bundle is lower than the glass transition temperature. The distance between this position and the end point of the previous hot air zone is the length of the cold air zone b.

[0018] As the preferred technical solution:

[0019] In the spinning method for reducing the core-skin structure of polyester industrial yarn as described above, the wind speed in the cold air zone a is 0.5-0.7 m / s, the wind speed in the hot air zone is 0.5-0.8 m / s, and the wind speed in the cold air zone b is 0.5-0.7 m / s.

[0020] The spinning method for reducing the core-skin structure of polyester industrial yarn has a single yarn density of 2000-3000D, a breaking strength unevenness of ≤1.6%, a breaking elongation unevenness of ≤3.5%, and a chromaticity degradation rate of 10-15%.

[0021] A spinning method for reducing the core-skin structure of polyester industrial yarn as described in any one of the above items, wherein the cooling device used for cooling the blowing zone includes a porous plate, a hot air blower and a side-blowing blower;

[0022] The hot air bellows is a rectangular structure, the side blowing bellows is a trapezoidal structure, and the hot air bellows is fixed inside the side blowing bellows;

[0023] There are multiple holes evenly distributed on the upper and lower sides of the hot air blower, which correspond to the spinnerets one by one. Ring filter elements are installed in the holes.

[0024] The hot air box is connected to a hot air duct, which is equipped with a hot air valve to adjust the size of the hot air.

[0025] The side-blowing bellows is provided with an air outlet, and the porous plate is a vertical plate, and the porous plate is arranged at the air outlet;

[0026] The porous plate is divided into an upper plate, a middle plate and a lower plate from top to bottom, corresponding to the cold air zone a, the hot air zone and the cold air zone b respectively, that is, the upper end of the upper plate is flush with the upper end of the cooling zone a, the lower end of the upper plate is flush with the lower end of the cooling zone a, the upper end of the middle plate is flush with the upper end of the hot air zone, the lower end of the middle plate is flush with the lower end of the hot air zone, the upper end of the lower plate is flush with the upper end of the cooling zone b, and the lower end of the lower plate is flush with the lower end of the cooling zone b; the upper plate and the lower plate have holes, but the middle plate has no holes;

[0027] The position of the hot air box corresponds to the position of the middle plate.

[0028] A spinning method for reducing the core-skin structure of polyester industrial yarn as described above, wherein the annular filter element is sealedly connected to the hot air blower to prevent air leakage from other places except the perforated mesh, thereby affecting the heating effect;

[0029] The hot air box is 1000-1100mm long, 280-300mm wide and 300-400mm high;

[0030] The diameter of the annular filter element is 200-210 mm, and the mesh number of the annular filter element is 80-100 mesh.

[0031] The spinning method for reducing the core-skin structure of polyester industrial yarn as described above has an upper plate aperture of 1.4 to 1.5 mm and an opening density of 400 to 450 per m 2 The aperture of the lower plate is 1.4-1.5 mm, and the opening density is 400-450 per m 2 .

[0032] Principle of the present invention:

[0033] In existing technology, after being extruded from the spinneret, polyester industrial yarn passes through a slow cooling zone and a windless zone before entering a cooling zone at a height of 1.3 to 1.6 meters. The air temperature in the blowing zone is 22 to 25°C, with a wind speed of 0.5 to 0.7 m / s. In the windless zone, the surface temperature of the yarn is 220 to 240°C, a significant difference from the cooling air temperature. After entering the blowing zone, the surface temperature of the yarn rapidly drops to around 100 to 110°C. Through intense convection heat transfer, the surface temperature of the yarn continues to decrease until it reaches the glass transition temperature, where the yarn surface solidifies. Polyester industrial yarn has a high linear density, and the cooling process is relatively intense. Although the sheath of the yarn has solidified, the core temperature remains high, making it very easy to form a skin-core structure. Although cooling continues, the fiber cortex has already solidified and bears the main spinning stress. The molecular chains are more likely to be oriented and crystallized along the fiber axis, which results in a dense structure in the fiber cortex (i.e., the free volume between the cortex solidified molecules becomes smaller, the polyester molecules are closely arranged, and the density of the cortex increases). This leads to the following problems:

[0034] First, the fiber cortex solidifies, the molecular chains are in a frozen state, the molecular chain movement is weakened, the energy transfer between the molecular chains is weakened, and the heat of the fiber core layer cannot be conducted out of the fiber cortex in time;

[0035] Second, the fiber produces a dense "skin" layer wrapped around the fiber surface, which plays a role in heat preservation and also limits the conduction of heat from the core layer.

[0036] The method of the present invention divides the cooling and blowing zone of the prior art into three zones from top to bottom: cold air zone a, hot air zone, and cold air zone b. While in cold air zone a, the surface heat of the filaments is rapidly removed by the cooling air. Upon exiting cooling zone a, the filaments reach their solidification point, their cortex solidifies, and they then enter the heating zone. The heating zone employs a circular blowing structure with a blowing temperature of 120-130°C and a wind speed of 0.5-0.8 m / s. This zone heats the fibers whose cortexes have solidified.

[0037] The main purpose of heating in the heating zone is twofold:

[0038] First, the hot air heats the fiber cortex, causing it to "melt" and degrade, and the viscosity difference between the fiber cortex and core layer decreases;

[0039] Second, the fiber "skin" layer "melts", which promotes the movement of molecular chains, facilitates the diffusion of heat from the fiber core layer, and reduces the temperature difference between the fiber skin and core layers; after passing through the heating zone, the viscosity and temperature difference between the fiber skin and core layers decrease.

[0040] After passing through the cold air zone b, the fiber skin and core layer are further cooled. At this time, the filament temperature is 90-100°C, which is close to the glass transition temperature of polyester. The cooling pressure of the filament is reduced, the cooling process is smooth, and the formation of the skin-core structure is reduced. The subsequent hot roller stretching is beneficial to the improvement of fiber uniformity. Beneficial effects:

[0041] (1) A spinning method for reducing the skin-core structure of polyester industrial yarn of the present invention, by adding a hot air zone to the cooling blowing zone to heat the yarn bundle, is conducive to reducing the difference in the skin-core structure, and can obtain uniformly cooled fibers for preparing high-performance polyester industrial yarn;

[0042] (2) The spinning method of the present invention for reducing the core-skin structure of polyester industrial yarn has small unevenness in breaking strength, low unevenness in breaking elongation, and uniform fiber color. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG1 is a schematic diagram of the cooling process of the present invention;

[0044] FIG2 is a front view of a porous plate of the present invention;

[0045] FIG3 is a front sectional view of the hot air blower of the present invention;

[0046] FIG4 is a top view of the hot air blower of the present invention;

[0047] Among them, 1-upper plate, 2-middle plate, 3-lower plate, 4-hole, 5-hot air bellows, 6-annular filter element, 7-spinneret, 8-slow cooling zone, 9-windless zone, 10-cold air zone a, 11-hot air zone, 12-cold air zone b. DETAILED DESCRIPTION

[0048] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0049] The test methods involved in the embodiments of the present invention and the comparative examples are as follows:

[0050] Linear density: Tested in accordance with GB T 14343-2008 Test method for linear density of chemical fiber filaments and GB T 16604-2017 Test method for polyester industrial filaments;

[0051] Unevenness of breaking strength (CV value) and unevenness of breaking elongation (CV value): tested with reference to GB T 14337-2022 Test method for tensile properties of chemical staple fibers;

[0052] Chroma degradation rate: The yarn tow A to be tested and the standard yarn tow B are respectively wound on a yarn collecting device to form parallel yarn tow A strips and yarn tow B strips. The color difference between the yarn tow A strips and the yarn tow B strips is observed under a light source. The color difference grade of the yarn tow A strip is determined according to GB / T250-2008 "Grey Scale for Assessing Change in Color - Textiles - Tests for Color Fastness" (Grey Scale for Assessing Change in Color). The AA grade has a chroma grade of 4.0, and yarns with a chroma grade less than 4.0 are downgraded. The number of yarn cakes with degraded chroma and the number of yarn cakes sampled for chroma testing over a period of time are counted. The chroma degradation rate is the percentage of yarn cakes with degraded chroma to the number of yarn cakes sampled.

[0053] Example 1

[0054] A spinning method for reducing the core-skin structure of polyester industrial yarn, the specific process is as follows:

[0055] As shown in FIG1 , the polyester melt is extruded through the spinneret 7 and then subjected to slow cooling in the slow cooling device, cooling in the windless zone 9, cooling in the blowing zone, oiling, stretching, shaping, networking and winding to produce polyester industrial yarn;

[0056] The height of the slow cooling zone 8 where the slow cooler is located is 300 mm, and the temperature of the slow cooling zone 8 is 320°C; the height of the windless zone 9 is 300 mm;

[0057] The blowing zones are cold air zone a 10, hot air zone 11 and cold air zone b 12 from top to bottom;

[0058] The cooling device used in the blowing zone cooling includes a porous plate, a hot air blower 5 and a side blowing blower;

[0059] The hot air blower 5 is a rectangular structure, and the side blowing blower is a trapezoidal structure. The hot air blower 5 is 1100mm long, 300mm wide, and 400mm high. The hot air blower 5 is fixed in the side blowing blower.

[0060] As shown in Figures 3 and 4, a plurality of holes are evenly distributed on the upper and lower sides of the hot air blower 5, corresponding to the spinneret 7 one by one, and an annular filter element 6 is installed in the holes; the annular filter element 6 is sealed to the hot air blower 5; the diameter of the annular filter element 6 is 210 mm, and the mesh number of the annular filter element is 100 mesh;

[0061] The hot air box 5 is connected to a hot air duct, and a hot air valve is provided on the hot air duct;

[0062] The side-blowing bellows is provided with an air outlet, and the porous plate is a vertical plate, and the porous plate is arranged at the air outlet;

[0063] As shown in Figure 2, the porous plate is divided into upper plate 1, middle plate 2 and lower plate 3 from top to bottom, corresponding to cold air zone a 10, hot air zone 11 and cold air zone b 12 respectively; the upper plate 1 and lower plate 3 are perforated, while the middle plate 2 is not perforated; the aperture of the upper plate 1 (i.e., hole 4) is 1.5 mm, and the aperture density is 450 per m2 The aperture of the lower plate 3 is 1.5 mm and the opening density is 450 per m 2 ; The height of the upper plate 1 is 600mm, the height of the middle plate 2 is 400mm, and the height of the lower plate 3 is 500mm;

[0064] The temperature of the cold air zone a 10 is 25°C, the temperature of the hot air zone 11 is 130°C, and the temperature of the cold air zone b 12 is 25°C;

[0065] The wind speed in the cold air zone a 10 is 0.7 m / s, the wind speed in the hot air zone 11 is 0.8 m / s, and the wind speed in the cold air zone b 12 is 0.7 m / s;

[0066] The stretching ratio is 5.7 times, the setting temperature is 245°C, the network pressure is 0.4 MPa, and the winding speed is 3150 m / min.

[0067] The final polyester industrial yarn had a single yarn linear density of 2000D, a breaking strength unevenness rate of 0.9%, a breaking elongation unevenness rate of 1.9%, and a chromaticity degradation rate of 14%.

[0068] Comparative Example 1

[0069] A spinning method for polyester industrial yarn is basically the same as that of Example 1, except that the temperature in all areas of the blowing zone is 25°C. The final polyester industrial yarn has a single yarn linear density of 2000D, a breaking strength unevenness rate of 3.8%, a breaking elongation unevenness rate of 6.5%, and a chromaticity degradation rate of 22%.

[0070] By comparing Comparative Example 1 with Example 1, it can be seen that the unevenness of the breaking strength, unevenness of the breaking elongation, and color degradation rate of the fiber prepared in Comparative Example 1 are all large. This is because the low temperature of 25°C is adopted in all areas of the blowing zone, and the filament bundle is more likely to have a skin-core structure during the cooling process, resulting in uneven crystallization and orientation of the fiber skin and core layer, and inconsistent tension on the fiber cross section. Therefore, the unevenness of the fiber breaking strength and breaking elongation is significantly increased.

[0071] Example 2

[0072] A spinning method for reducing the core-skin structure of polyester industrial yarn, the specific process is as follows:

[0073] After the polyester melt is extruded through the spinneret, it is sequentially subjected to slow cooling in the slow cooling device, cooling in the windless zone, cooling in the blowing zone, oiling, stretching, shaping, networking and winding to produce polyester industrial yarn.

[0074] The height of the slow cooling zone where the slow cooler is located is 250mm, and the temperature of the slow cooling zone is 290℃; the height of the windless zone is 200mm;

[0075] The blowing areas are cold air area a, hot air area and cold air area b from top to bottom;

[0076] The cooling devices used in the blowing zone include porous plates, hot air blowers and side-blowing blowers;

[0077] The hot air bellows is a rectangular structure, and the side-blowing bellows is a trapezoidal structure. The hot air bellows is 1000mm long, 280mm wide, and 300mm high. The hot air bellows is fixed inside the side-blowing bellows.

[0078] The hot air blower is evenly distributed with multiple holes corresponding to the spinnerets on the upper and lower sides, and an annular filter element is installed in the holes; the annular filter element is sealed with the hot air blower; the annular filter element has a diameter of 200mm and a mesh size of 80;

[0079] The hot air box is connected to a hot air duct, and a hot air valve is provided on the hot air duct;

[0080] The side-blowing bellows is provided with an air outlet, and the porous plate is a vertical plate, and the porous plate is arranged at the air outlet;

[0081] The porous plate is divided into upper plate, middle plate and lower plate from top to bottom, corresponding to cold air zone a, hot air zone and cold air zone b respectively; the upper plate and lower plate have holes, while the middle plate has no holes; the hole diameter of the upper plate is 1.4mm, and the hole density is 400 / m 2 The hole diameter of the lower plate is 1.4 mm, and the hole density is 400 / m 2 ; The height of the upper plate is 500mm, the height of the middle plate is 300mm, and the height of the lower plate is 400mm;

[0082] The temperature of cold air zone a is 22°C, the temperature of hot air zone is 120°C, and the temperature of cold air zone b is 22°C;

[0083] The wind speed in the cold air zone a is 0.5 m / s, the wind speed in the hot air zone is 0.5 m / s, and the wind speed in the cold air zone b is 0.5 m / s;

[0084] The stretching ratio is 5.2 times, the setting temperature is 230°C, the network pressure is 0.3 MPa, and the winding speed is 2800 m / min.

[0085] The final polyester industrial yarn had a single yarn linear density of 2000D, a breaking strength unevenness rate of 1.0%, a breaking elongation unevenness rate of 2.6%, and a chromaticity degradation rate of 12%.

[0086] Example 3

[0087] A spinning method for reducing the core-skin structure of polyester industrial yarn, the specific process is as follows:

[0088] After the polyester melt is extruded through the spinneret, it is sequentially subjected to slow cooling in the slow cooling device, cooling in the windless zone, cooling in the blowing zone, oiling, stretching, shaping, networking and winding to produce polyester industrial yarn.

[0089] The height of the slow cooling zone where the slow cooler is located is 300mm, and the temperature of the slow cooling zone is 300℃; the height of the windless zone is 300mm;

[0090] The blowing areas are cold air area a, hot air area and cold air area b from top to bottom;

[0091] The cooling devices used in the blowing zone include porous plates, hot air blowers and side-blowing blowers;

[0092] The hot air bellows is a rectangular structure, and the side-blowing bellows is a trapezoidal structure. The hot air bellows is 1040mm long, 290mm wide, and 340mm high. The hot air bellows is fixed inside the side-blowing bellows.

[0093] The hot air blower is evenly distributed with multiple holes corresponding to the spinnerets on the upper and lower sides, and an annular filter element is installed in the holes; the annular filter element is sealed with the hot air blower; the annular filter element has a diameter of 204mm and a mesh size of 90;

[0094] The hot air box is connected to a hot air duct, and a hot air valve is provided on the hot air duct;

[0095] The side-blowing bellows is provided with an air outlet, and the porous plate is a vertical plate, and the porous plate is arranged at the air outlet;

[0096] The porous plate is divided into upper plate, middle plate and lower plate from top to bottom, corresponding to cold air zone a, hot air zone and cold air zone b respectively; the upper plate and lower plate have holes, while the middle plate has no holes; the hole diameter of the upper plate is 1.44mm, and the hole density is 420 / m 2 The aperture of the lower plate is 1.44 mm, and the opening density is 420 per m 2 The height of the upper plate is 540mm, the height of the middle plate is 340mm, and the height of the lower plate is 440mm.

[0097] The temperature of cold air zone a is 23°C, the temperature of hot air zone is 124°C, and the temperature of cold air zone b is 23°C;

[0098] The wind speed in the cold air zone a is 0.6 m / s, the wind speed in the hot air zone is 0.6 m / s, and the wind speed in the cold air zone b is 0.6 m / s;

[0099] The stretching ratio is 5.5 times, the setting temperature is 240°C, the network pressure is 0.34 MPa, and the winding speed is 2900 m / min.

[0100] The final polyester industrial yarn had a single yarn linear density of 3000D, a breaking strength unevenness rate of 1.1%, a breaking elongation unevenness rate of 3.2%, and a chromaticity degradation rate of 13.6%.

[0101] Example 4

[0102] A spinning method for reducing the core-skin structure of polyester industrial yarn, the specific process is as follows:

[0103] After the polyester melt is extruded through the spinneret, it is sequentially subjected to slow cooling in the slow cooling device, cooling in the windless zone, cooling in the blowing zone, oiling, stretching, shaping, networking and winding to produce polyester industrial yarn.

[0104] The height of the slow cooling zone where the slow cooler is located is 250mm, and the temperature of the slow cooling zone is 295℃; the height of the windless zone is 250mm;

[0105] The blowing areas are cold air area a, hot air area and cold air area b from top to bottom;

[0106] The cooling devices used in the blowing zone include porous plates, hot air blowers and side-blowing blowers;

[0107] The hot air bellows is a rectangular structure, and the side-blowing bellows is a trapezoidal structure. The hot air bellows is 1020mm long, 285mm wide, and 320mm high. The hot air bellows is fixed inside the side-blowing bellows.

[0108] The hot air blower is evenly distributed with multiple holes corresponding to the spinnerets on the upper and lower sides, and an annular filter element is installed in the holes; the annular filter element is sealed with the hot air blower; the annular filter element has a diameter of 202mm and a mesh size of 85;

[0109] The hot air box is connected to a hot air duct, and a hot air valve is provided on the hot air duct;

[0110] The side-blowing bellows is provided with an air outlet, and the porous plate is a vertical plate, and the porous plate is arranged at the air outlet;

[0111] The porous plate is divided into upper plate, middle plate and lower plate from top to bottom, corresponding to cold air zone a, hot air zone and cold air zone b respectively; the upper plate and lower plate have holes, while the middle plate has no holes; the hole diameter of the upper plate is 1.42mm, and the hole density is 410 / m 2 The aperture of the lower plate is 1.42 mm, and the opening density is 410 per m 2 The height of the upper plate is 520mm, the height of the middle plate is 320mm, and the height of the lower plate is 420mm.

[0112] The temperature of cold air zone a is 22.5°C, the temperature of hot air zone is 122°C, and the temperature of cold air zone b is 22.5°C;

[0113] The wind speed in the cold air zone a is 0.55 m / s, the wind speed in the hot air zone is 0.55 m / s, and the wind speed in the cold air zone b is 0.55 m / s;

[0114] The stretching ratio is 5.4 times, the setting temperature is 235°C, the network pressure is 0.32 MPa, and the winding speed is 2850 m / min.

[0115] The final polyester industrial yarn had a single yarn linear density of 2500D, a breaking strength unevenness rate of 1.5%, a breaking elongation unevenness rate of 3.0%, and a chromaticity degradation rate of 13%.

[0116] Example 5

[0117] A spinning method for reducing the core-skin structure of polyester industrial yarn, the specific process is as follows:

[0118] After the polyester melt is extruded through the spinneret, it is sequentially subjected to slow cooling in the slow cooling device, cooling in the windless zone, cooling in the blowing zone, oiling, stretching, shaping, networking and winding to produce polyester industrial yarn.

[0119] The height of the slow cooling zone where the slow cooler is located is 300mm, and the temperature of the slow cooling zone is 310℃; the height of the windless zone is 200mm;

[0120] The blowing areas are cold air area a, hot air area and cold air area b from top to bottom;

[0121] The cooling devices used in the blowing zone include porous plates, hot air blowers and side-blowing blowers;

[0122] The hot air bellows is a rectangular structure, and the side-blowing bellows is a trapezoidal structure. The hot air bellows is 1080mm long, 300mm wide, and 380mm high. The hot air bellows is fixed inside the side-blowing bellows.

[0123] The hot air blower is evenly distributed with multiple holes corresponding to the spinnerets on the upper and lower sides, and an annular filter element is installed in the holes; the annular filter element is sealed with the hot air blower; the annular filter element has a diameter of 208mm and a mesh size of 98;

[0124] The hot air box is connected to a hot air duct, and a hot air valve is provided on the hot air duct;

[0125] The side-blowing bellows is provided with an air outlet, and the porous plate is a vertical plate, and the porous plate is arranged at the air outlet;

[0126] The porous plate is divided into upper plate, middle plate and lower plate from top to bottom, corresponding to cold air zone a, hot air zone and cold air zone b respectively; the upper and lower plates have holes, while the middle plate has no holes; the hole diameter of the upper plate is 1.48mm, and the hole density is 440 / m 2 The aperture of the lower plate is 1.48 mm, and the opening density is 440 per m 2The height of the upper plate is 580mm, the height of the middle plate is 380mm, and the height of the lower plate is 480mm.

[0127] The temperature of cold air zone a is 24°C, the temperature of hot air zone is 128°C, and the temperature of cold air zone b is 24°C;

[0128] The wind speed in the cold air zone a is 0.7 m / s, the wind speed in the hot air zone is 0.7 m / s, and the wind speed in the cold air zone b is 0.7 m / s;

[0129] The stretching ratio is 6 times, the setting temperature is 250°C, the network pressure is 0.38 MPa, and the winding speed is 3200 m / min.

[0130] The final polyester industrial yarn had a single yarn linear density of 3000D, a breaking strength unevenness of 1.4%, a breaking elongation unevenness of 2.0%, and a chromaticity degradation rate of 14.5%.

[0131] Example 6

[0132] A spinning method for reducing the core-skin structure of polyester industrial yarn, the specific process is as follows:

[0133] After the polyester melt is extruded through the spinneret, it is sequentially subjected to slow cooling in the slow cooling device, cooling in the windless zone, cooling in the blowing zone, oiling, stretching, shaping, networking and winding to produce polyester industrial yarn.

[0134] The height of the slow cooling zone where the slow cooler is located is 250mm, and the temperature of the slow cooling zone is 305℃; the height of the windless zone is 250mm;

[0135] The blowing areas are cold air area a, hot air area and cold air area b from top to bottom;

[0136] The cooling devices used in the blowing zone include porous plates, hot air blowers and side-blowing blowers;

[0137] The hot air bellows is a rectangular structure, and the side-blowing bellows is a trapezoidal structure. The hot air bellows is 1060mm long, 295mm wide, and 360mm high. The hot air bellows is fixed inside the side-blowing bellows.

[0138] The hot air blower is evenly distributed with multiple holes corresponding to the spinnerets on the upper and lower sides, and an annular filter element is installed in the holes; the annular filter element is sealed with the hot air blower; the annular filter element has a diameter of 206mm and a mesh size of 95;

[0139] The hot air box is connected to a hot air duct, and a hot air valve is provided on the hot air duct;

[0140] The side-blowing bellows is provided with an air outlet, and the porous plate is a vertical plate, and the porous plate is arranged at the air outlet;

[0141] The porous plate is divided into upper plate, middle plate and lower plate from top to bottom, corresponding to cold air zone a, hot air zone and cold air zone b respectively; the upper plate and lower plate have holes, while the middle plate has no holes; the hole diameter of the upper plate is 1.46mm, and the hole density is 430 / m 2 The hole diameter of the lower plate is 1.46mm, and the hole density is 430 / m 2 The height of the upper plate is 560mm, the height of the middle plate is 360mm, and the height of the lower plate is 460mm.

[0142] The temperature of cold air zone a is 23.4°C, the temperature of hot air zone is 126°C, and the temperature of cold air zone b is 23.4°C;

[0143] The wind speed in the cold air zone a is 0.65 m / s, the wind speed in the hot air zone is 0.65 m / s, and the wind speed in the cold air zone b is 0.65 m / s;

[0144] The stretching ratio is 5.8 times, the setting temperature is 242°C, the network pressure is 0.35 MPa, and the winding speed is 3000 m / min.

[0145] The final polyester industrial yarn had a single yarn linear density of 2500D, a breaking strength unevenness rate of 0.8%, a breaking elongation unevenness rate of 2.3%, and a chromaticity degradation rate of 14.3%.

Claims

1. A spinning method for reducing the skin-core structure of polyester industrial yarns. After the polyester melt is extruded through a spinneret, it is successively cooled by a slow cooler, cooled in a windless area, cooled in a blowing area, oiled, stretched, shaped, textured, and wound to obtain polyester industrial yarns, characterized in that: The blowing area from top to bottom is successively the cold air area a, the hot air area, and the cold air area b; The height of the cold air area a is 500 - 600 mm, the height of the hot air area is 300 - 400 mm, and the height of the cold air area b is 400 - 500 mm; The position of the filament solidification point is within the range of the cooling area a, so that when the filament exits the cooling area a, it reaches the solidification point and the filament skin is solidified; The filament solidification point is the polyester glass transition temperature; The temperature of the cold air area a is 22 - 25 °C, the temperature of the hot air area is 120 - 130 °C, and the temperature of the cold air area b is 22 - 25 °C; The single filament linear density of the polyester industrial yarn is 2000 - 3000 D, the unevenness rate of breaking strength ≤ 1.6%, the unevenness rate of breaking elongation ≤ 3.5%, and the chromaticity degradation rate is 10 - 15%.

2. The spinning method for reducing the skin-core structure of polyester industrial yarn according to claim 1, characterized in that, The wind speed of the cold air area a is 0.5 - 0.7 m / s, the wind speed of the hot air area is 0.5 - 0.8 m / s, and the wind speed of the cold air area b is 0.5 - 0.7 m / s.

3. The spinning method for reducing the skin-core structure of polyester industrial yarn according to claim 1 or 2, characterized in that The cooling device used for cooling in the blowing area includes a perforated plate, a hot air box, and a side blowing box; the hot air box is fixed inside the side blowing box; A plurality of holes corresponding to the spinneret plate one by one are evenly distributed on the upper and lower surfaces of the hot air box, and annular filter elements are installed in the holes; A hot air pipe is connected to the hot air box, and a hot air valve is provided on the hot air pipe; An air outlet is provided on the side blowing box, the perforated plate is a vertical plate, and the perforated plate is arranged at the air outlet; The perforated plate is successively divided into an upper plate, a middle plate, and a lower plate from top to bottom, corresponding to the cold air area a, the hot air area, and the cold air area b respectively; holes are opened on the upper plate and the lower plate, and no holes are opened on the middle plate; The position of the hot air box corresponds to the position of the middle plate.

4. A spinning method for reducing the skin-core structure of polyester industrial yarn according to claim 3, characterized in that, The annular filter element is hermetically connected to the hot air box; The hot air box is 1000 - 1100 mm long, 280 - 300 mm wide, and 300 - 400 mm high; The diameter of the annular filter element is 200 - 210 mm, and the mesh number of the annular filter element is 80 - 100 meshes.

5. A spinning method for reducing the skin-core structure of polyester industrial yarn according to claim 3, characterized in that, The aperture of the upper plate is 1.4 - 1.5 mm, and the hole density is 400 - 450 holes per meter 2 ; The aperture of the lower plate is 1.4 - 1.5 mm, and the hole density is 400 - 450 holes per meter 2 .

Images