A method for improving the quality of spinning products

Abstract

The present invention belongs to the field of spinning technology, and relates to a method for improving the quality of spinning products. In the method, the melt flow rate of a metering pump during spinning is set to B; after the pump is stopped to clean the plate and the metering pump is turned on, if the temperature of the spinneret is lower than the temperature during spinning, the melt flow rate of the metering pump is adjusted to C to increase the temperature of the spinneret to the temperature during spinning; wherein C>B. The present invention can accelerate the recovery time of the spinneret temperature, and increase the spinneret temperature to the spinning temperature before spinning, thereby avoiding the quality of the bottom yarn being affected by the excessively low spinneret temperature at the beginning of spinning.

Description

Technical Field

[0001] The invention belongs to the technical field of spinning and relates to a method for improving the quality of spinning products. Background Art

[0002] In the production process of polyester filament, in order to ensure the spinnability and stable quality of the filament fiber, the spinning assembly will be cleaned (also called scraping) regularly. The main purpose is to remove the monomers produced by the high-temperature decomposition (degradation) of the polymer on the spinneret plate surface and the coke residue left after the silicone oil in the sprayed release agent evaporates at high temperature during cleaning.

[0003] After the spinning stops, the plate needs to be cleared. During this process, no silk will be produced and the temperature of the spinneret will drop rapidly because the spinneret at the bottom of the spinning assembly will be exposed to the air. When the plate clearing operation is completed, the pump will be turned on to repair the plate at a low speed, and the head will be grown after the plate repair is completed. During this process, the temperature of the spinneret rises relatively slowly. After the head is grown, the metering pump reaches the normal process setting speed, and the temperature of the spinneret will gradually return to normal. However, during the recovery of the spinneret temperature, due to the low surface temperature of the assembly spinneret, the temperature of the melt extruded from the spinneret is also low, which will cause the cross-section, tension, physical properties, and dyeing of the silk produced in this process to be significantly different from the silk produced continuously later (the spinneret temperature returns to a normal stable value) (that is, the fibers produced during the recovery of the spinneret temperature are abnormal fibers).

[0004] Therefore, it is of great significance to study a method to effectively solve the above problems in order to improve the quality of spinning products. Summary of the invention

[0005] The purpose of the present invention is to solve the problems existing in the prior art and provide a method for improving the quality of spinning products.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for improving the quality of spinning products, assuming that the melt flow rate (i.e., mass flow rate, in g / min) discharged by a metering pump during spinning is B; after the pump is stopped and the plate is cleared, the metering pump is turned on to detect the temperature of a spinneret; if the temperature of the spinneret is lower than the temperature during spinning, the melt flow rate discharged by the metering pump is adjusted to C to increase the temperature of the spinneret to the temperature during spinning; wherein, C>B, the greater the melt flow rate discharged by the metering pump, the faster the spinneret temperature recovery time is, and the melt passes through the spinneret, and when the melt heats the spinneret, the internal and external temperatures of the spinneret are consistent; the present invention increases the temperature of the spinneret to the spinning temperature before spinning, so as to avoid the spinneret temperature being too low at the beginning of spinning, thereby affecting the quality of the bottom yarn.

[0008] There are many methods for heating the spinneret disclosed in the prior art, for example, patent CN109295510A provides heating plates on the upper and lower sides of the spinneret to heat the spinneret, and patent CN113227470B provides a method for heating the spinneret by steam. However, these methods require complex modifications to the device, and both methods heat the spinneret from the outside to the inside, which will result in that even if the surface of the spinneret reaches the process temperature, it does not mean that the inside of the spinneret has also reached the process temperature. Therefore, when the melt passes through the inside of the spinneret, the melt temperature will still be disturbed, and it cannot be used to solve the above-mentioned problem of the present invention.

[0009] As the preferred technical solution:

[0010] In the method for improving the quality of spinning products as described above, during the process of increasing the temperature of the spinneret to the temperature during spinning (i.e., the temperature required by the spinning process), the operator repairs the spinneret; repairing the spinneret refers to removing surface dirt from the plate holes during the discharge process.

[0011] As described above, a method for improving the quality of spinning products is provided, wherein the melt flow rate discharged by the metering pump during spinning is assumed to be A; after the temperature of the spinneret reaches the temperature during spinning, the melt flow rate discharged by the metering pump is adjusted to A to continue plate repair, and the spinneret is produced after the plate repair is completed. After the spinneret is produced, the melt flow rate discharged by the metering pump is adjusted to B for spinning; wherein, B>A; the reason for adjusting the melt flow rate discharged by the metering pump to A to continue plate repair, rather than continuing plate repair when the melt flow rate is C, is to reduce the output of waste silk.

[0012] As described above, a method for improving the quality of spinning products, the melt flow rate discharged by the metering pump is controlled by the speed of the metering pump. When the melt flow rate discharged by the metering pump is A, the speed of the metering pump is recorded as metering pump speed I, so that the output of waste silk during plate repair can be reduced. When the melt flow rate discharged by the metering pump is C, the speed of the metering pump is recorded as metering pump speed II. When the melt flow rate discharged by the metering pump is B, the speed of the metering pump is recorded as metering pump speed III, and low-speed spinning is started at this time; metering pump speed I < metering pump speed III < metering pump speed II.

[0013] Since the temperature of the melt itself is relatively high, as the speed of the metering pump increases, the flow rate of the melt will also increase, and the spinneret temperature recovery time will be faster. Therefore, the recovery speed of the spinneret temperature can also be accelerated as needed, and it is only necessary to meet the requirement of "metering pump speed I < metering pump speed III < metering pump speed II".

[0014] In the method for improving the quality of spinning products as described above, the temperature of the spinneret is detected by a temperature sensor; the temperature sensor is electrically connected to a controller, and the temperature sensor is used to send the detected temperature of the spinneret to the controller.

[0015] In a method for improving the quality of spinning products as described above, the controller is electrically connected to the winder and the metering pump respectively; when the metering pump is turned on, the controller controls the speed of the metering pump to be metering pump speed I, and when the temperature sensor detects that the temperature of the spinneret is lower than the temperature during spinning, the controller controls the speed of the metering pump to be metering pump speed II; when the temperature of the spinneret is increased to the temperature during spinning, the controller controls the speed of the metering pump to be metering pump speed I to continue plate repair, and the head is produced after the plate repair is completed; when the winder switches the fixed axis for spinning, the winder sends a spinning signal to the controller, and the controller controls the speed of the metering pump to be metering pump speed III.

[0016] In the method for improving the quality of spinning products as described above, the metering pump speed II is the maximum speed of the metering pump at rated power.

[0017] Beneficial effects:

[0018] The present invention controls the melt flow rate by controlling the rotation speed of the metering pump, which can accelerate the recovery time of the spinneret temperature, so that the temperature of the spinneret is quickly increased to the spinning temperature, avoiding the spinneret temperature being too low at the beginning of spinning and affecting the quality of the bottom yarn. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it 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 within the scope limited by the appended claims of the application equally.

[0020] The testing methods of the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0021] The yarns prepared 3 to 5 minutes after the start of spinning in each embodiment and each comparative example were taken as sample A to test the following properties:

[0022] Breaking strength and elongation at break: The breaking strength and elongation at break of sample A were measured with reference to GB / T 14344-2022 "Test method for tensile properties of chemical fiber filaments".

[0023] 10% force value: Sample A is stretched according to GB / T 14344-2022 "Test method for tensile properties of chemical fiber filaments". The 10% force value is the force required to stretch sample A to 110% of its original length.

[0024] Appearance grade: refer to 5.4 Appearance items and indicators in Q / 320584 NPA002-2024 "Polyester conventional, fine denier and ultra-fine denier drawn yarn" to measure sample A.

[0025] Dyeing grade: refer to GB / T 6508-2015 "Test method for dyeing uniformity of polyester filament" standard to evaluate the dyeing uniformity of sample A.

[0026] Relative radial profile: refer to FZ / T 50002-2013 "Test method for chemical fiber profile" 7.3 to measure the relative radial profile DR, DR = (1-r / R) * 100%, where R is the radius of the circumscribed circle of the fiber cross section, and r is the radius of the inscribed circle of the fiber cross section (with the same center as the circumscribed circle).

[0027] A method for improving the quality of spinning products, as follows:

[0028] The controller is electrically connected to the winding machine, the metering pump and the temperature sensor respectively; the temperature sensor is used to send the detected temperature of the spinneret to the controller;

[0029] After the scraping is completed, the metering pump is turned on first, and then the controller controls the speed of the metering pump to be metering pump speed I so that the melt flow rate spitted out by the metering pump is A. When the temperature sensor detects that the temperature of the spinneret is lower than the temperature during spinning, the data is sent to the controller, and the controller controls the speed of the metering pump to be metering pump speed II so that the melt flow rate spitted out by the metering pump is C, so as to increase the temperature of the spinneret to the temperature during spinning; wherein, the metering pump speed II is the maximum speed of the metering pump;

[0030] In the process of the temperature of the spinneret being raised to the spinning temperature, the spinneret is repaired (i.e., surface dirt is removed from the plate holes during the spinning process). After the temperature of the spinneret reaches the spinning temperature, the controller controls the speed of the metering pump to be metering pump speed I so that the melt flow rate discharged is A and the plate is repaired continuously. After the plate repair is completed, the head is produced;

[0031] When the spinning is completed, the winder switches the fixed axis and sends a spinning signal to the controller. The controller controls the speed of the metering pump to metering pump speed III so that the melt flow rate discharged by the metering pump is B before spinning; among them, C>B>A, metering pump speed I<metering pump speed III<metering pump speed II.

[0032] Example 1

[0033] A method for improving the quality of spinning products, the specific process is as follows:

[0034] The process flow for preparing semi-matt FDY is: polyester melt conveying → metering pump → spinning manifold → assembly → oiling → pre-network → first hot roller → second hot roller → main network → winding; wherein, the intrinsic viscosity of polyester is 0.680d / g, the terminal carboxyl content is 28.2mol / t, the L value is 86.3, the b value is 3.8, the TiO2 content is 0.28wt%, and the diethylene glycol content is 1.3wt%;

[0035] The process parameters for preparing semi-matte FDY are: spinning box temperature 295℃, metering pump speed 11.25rpm (metering pump specification 3.0cc / r), oil pump speed 24rpm, cooling air volume 50m 3 / h, pre-network pressure 0.06MPa, first hot roller speed 2130m / min, first hot roller temperature 87℃, second hot roller speed 4600m / min, second hot roller temperature 129℃, main network pressure 0.34MPa, winding speed 4500m / min.

[0036] When the scraping needs to be stopped during the above-mentioned process of preparing semi-matt FDY, the scraping time is 10 minutes, and the temperature of the spinneret surface will also drop from 295°C to 260°C during this stage; after the scraping is completed, the metering pump is turned on first, and then the controller controls the speed of the metering pump to be the metering pump speed I (7r / min) so that the melt flow rate spitted out by the metering pump is A (25.2g / min), and when the temperature sensor detects that the temperature of the spinneret (260°C) is lower than the temperature during spinning (295°C), the data is sent to the controller, and the controller controls the speed of the metering pump to gradually accelerate to the metering pump speed II (20r / min) so that the melt flow rate spitted out by the metering pump is C (72g / min), so as to increase the temperature of the spinneret to the temperature during spinning; wherein, the time required for the spinneret temperature to rise from 260°C to the temperature during spinning is 10 minutes;

[0037] During the process of the spinneret temperature rising to the spinning temperature, the spinneret is repaired (i.e., surface dirt is removed from the plate holes during the spinning process). After the spinneret temperature reaches the spinning temperature, the controller controls the metering pump speed to metering pump speed I (7r / min) so that the melt flow rate discharged is A (25.2g / min) and the plate is repaired continuously. After the plate repair is completed, the head is produced.

[0038] After the spinning is completed, the winder switches the fixed axis and sends a spinning signal to the controller. The controller controls the speed of the metering pump to metering pump speed III (11.25r / min) so that the melt flow rate discharged by the metering pump is B (40.5g / min) before spinning.

[0039] The semi-dull FDY produced within 3 to 5 minutes after the start of spinning has a specification of 90dtex / 72f, a linear density of 90.2dtex, a breaking strength of 4.31cN / dtex, an elongation at break of 33.05%, a 10% force of 283.1cN, an appearance grade of AA, a dyeing grade of 4.5, and no abnormality in the appearance dyeing.

[0040] Comparative Example 1

[0041] A spinning method is basically the same as Example 1, except that: the metering pump is turned on after the scraping is completed, and before the spinning is completed, the controller always controls the speed of the metering pump to be the metering pump speed I (7r / min) so that the melt flow rate discharged by the metering pump is A (25.2g / min).

[0042] The temperature of the spinneret was raised from 260°C to 275°C from the time of plate repair to the end of spinning, and the time required for this stage was 16 minutes; the time required for the spinneret temperature to rise from 275°C to the temperature during spinning was 20 minutes;

[0043] The time from the end of shoveling to the start of spinning is the same as that in Example 1. The breaking strength of the semi-dull FDY obtained within 3 to 5 minutes after the start of spinning (at this time, the temperature of the spinneret at the 5th minute is 281.7°C) is 4.10 cN / dtex, the breaking elongation is 28.15%, the 10% force value is 295.3 cN, the appearance grade is A, the dyeing grade is 4.0, and the appearance has problems of hairy and uneven dyeing. The semi-dull FDY obtained 20 minutes after spinning (at this time, the temperature of the spinneret at the 20th minute is 295°C) has a specification of 90 dtex / 72f, a linear density of 90.2 dtex, a breaking strength of 4.30 cN / dtex, a breaking elongation of 33.11%, a 10% force value of 283.3 cN, an appearance grade of AA, a dyeing grade of 4.5, and no abnormal appearance dyeing.

[0044] By comparing Comparative Example 1 with Example 1, it can be seen that the temperature of the spinneret in Comparative Example 1 has a slow heating rate, and during the high-speed spinning stage, the temperature of the spinneret has not reached the temperature required for spinning. When the melt temperature is low, it will lead to insufficient fluidity of the molecular chains inside the fiber, reduced orientation crystallinity of the polyester, and reduced breaking strength and elongation of the fiber. During the stretching process, problems such as single filament breakage, reduced appearance grade, and poor dyeability occur. The spinneret temperature reached the process temperature 20 minutes after the start of spinning, and all aspects of the fiber performance are basically consistent with those in Example 1.

[0045] Example 2

[0046] A method for improving the quality of spinning products, the specific process is as follows:

[0047] The process flow of preparing full matt FDY is: slice drying and crystallization → screw → metering pump → spinning manifold → assembly → oiling → pre-network → first hot roller → second hot roller → main network → winding;

[0048] Drying and crystallization of polyester chips: Full matte polyester chips (FD-PET, manufactured by Jiangsu Hengke New Materials Co., Ltd., brand CD-300, TiO2 content of 2.15wt%) were crystallized in a crystallization bed at a temperature of 176°C for 3 minutes, then transported to a drying tower and introduced with dry air (temperature of 170°C, air flow rate of 240m 3 / h, dew point -99℃) to reduce the moisture content to 40ppm;

[0049] The process parameters for preparing full-dull FDY are as follows: the temperature of the conveying section of the screw is 276°C, the temperature of the melting section is 295°C, the temperature of the mixing section is 290°C, and the temperature of the extrusion section is 288°C; the temperature of the spinning box is 287°C, the speed of the metering pump is 16.42rpm, the speed of the oil pump is 28rpm, and the cooling air is 65m 3 / h, pre-network pressure 0.06MPa, first hot roller speed 1450m / min, first hot roller temperature 89℃, second hot roller speed 3800m / min, second hot roller temperature 127℃, main network pressure 0.32MPa, winding speed 3800m / min;

[0050] If it is necessary to stop the scraping during the above-mentioned preparation of full-dull FDY, since the scraping time is 10 minutes, the temperature of the spinneret surface will also drop from 287°C to 260°C during this stage; after the scraping is completed, the metering pump (the specification of the metering pump is 1.6cc / r) is turned on first, and then the controller controls the speed of the metering pump to be the metering pump speed I (9.5r / min) so that the melt flow rate spitted out by the metering pump is A (18.24g / min), and when the temperature sensor detects that the temperature of the spinneret (260°C) is lower than the temperature during spinning (i.e., 287°C), the data is sent to the controller, and the controller controls the speed of the metering pump to gradually accelerate to the metering pump speed II (30r / min) so that the melt flow rate spitted out by the metering pump is C (57.6g / min), so as to increase the temperature of the spinneret to the temperature during spinning; wherein, the time required for the spinneret temperature to rise from 260°C to the temperature during spinning is 12 minutes;

[0051] When the temperature of the spinneret is raised to the spinning temperature, the controller controls the speed of the metering pump to metering pump speed I (9.5r / min) so that the melt flow rate discharged by the metering pump is A (18.24g / min), and the plate is repaired. After the plate repair is completed, the head is assembled; when the winder switches the fixed axis for spinning, the winder sends a spinning signal to the controller, and the controller controls the speed of the metering pump to metering pump speed III (16.42r / min) so that the melt flow rate discharged by the metering pump is B (31.54g / min).

[0052] The specifications of the fully matte wavy flat yarn produced within 3-5 minutes after the start of spinning are 83dtex / 72f, the linear density is 83.2dtex, the breaking strength is 3.91cN / dtex, the breaking elongation is 34.91%, the 10% force value is 236.1cN, the relative radial profile is 52.60%, the appearance grade is AA, the dyeing grade is 4.5, and the appearance dyeing is normal. The profile of the fully matte wavy flat yarn prepared from the start of spinning remains unchanged.

[0053] Comparative Example 2

[0054] A spinning method is basically the same as Example 2, except that: the metering pump is turned on after the scraping is completed, and before the spinning is completed, the controller always controls the speed of the metering pump to be the metering pump speed I (9.5r / min) so that the melt flow rate discharged by the metering pump is A (18.24g / min).

[0055] The temperature of the spinneret was raised from 260°C to 275°C from the time of plate repair to the end of spinning, and the time required for this stage was 16 minutes; the time required for the spinneret temperature to rise from 275°C to the temperature during spinning was 20 minutes;

[0056] The time from the end of shoveling to the start of spinning is the same as that in Example 2. The breaking strength of the fully matte FDY obtained within 3 to 5 minutes after the start of spinning (at this time, the temperature of the spinneret at the 5th minute is 283°C) is 3.76 cN / dtex, the elongation at break is 31.24%, the 10% force value is 250.8 cN, the relative radial profile is 55.36%, the appearance grade is A, the dyeing grade is 4.0, and the appearance has problems of hairiness and uneven dyeing; 20 minutes after the start of spinning (at this time, the temperature of the spinneret is 287°C), the specification of the fully matte wavy flat yarn obtained is 83 dtex / 72f, the linear density is 83.2 dtex, the breaking strength is 3.90 cN / dtex, the elongation at break is 34.89%, the 10% force value is 236.4 cN, the relative radial profile is 52.65%, the appearance grade is AA, the dyeing grade is 4.5, and there is no abnormality in the appearance dyeing.

[0057] Comparing Comparative Example 2 with Example 2, it can be seen that the temperature of the spinneret in Comparative Example 2 has not reached the required spinning temperature during the high-speed spinning stage due to the slow heating rate. When the temperature of the polyester melt is low, the molecular chain fluidity inside the fiber is insufficient, the orientation crystallinity of the polyester is reduced, the breaking strength and elongation of the fiber are reduced, and the single filament breaks, the appearance grade is reduced, and the dyeability is poor during the stretching process; and the plate surface temperature of Comparative Example 2 is low within 3 to 5 minutes after the start of spinning, and the melt fluidity is poor, which also leads to a higher degree of profile of the full matte FDY prepared in Comparative Example 2, which can only remain relatively stable and close to the degree of profile of Example 2 after 20 minutes of spinning. Due to the difference in elongation and profile between the bottom yarn of the profiled yarn and the yarn produced by the normal process, the full matte FDY prepared when the spinneret temperature does not reach the required spinning temperature is more likely to have uneven dyeing during dyeing.

Claims

1. A method for improving the quality of spinning products, characterized in that: Assume that the melt flow rate discharged by the metering pump during spinning is A, and the melt flow rate discharged by the metering pump during spinning is B; after stopping the pump to clean the plate and restarting the metering pump, the temperature of the spinneret is detected. If the temperature of the spinneret is lower than the temperature during spinning, adjust the melt flow rate discharged by the metering pump to C to increase the temperature of the spinneret to the temperature during spinning; wherein, C>B; In the process of increasing the temperature of the spinneret to the temperature during spinning, the spinneret is repaired; repairing the spinneret means removing surface dirt from the plate holes during the discharge process; After the temperature of the spinneret reaches the spinning temperature, the melt flow rate discharged by the metering pump is adjusted to A to continue plate repairing. After the plate repairing is completed, the head is grown. After the head is grown, the melt flow rate discharged by the metering pump is adjusted to B for spinning; wherein, B>A.

2. A method for improving the quality of spinning products according to claim 1, characterized in that: The melt flow rate discharged by the metering pump is controlled by the speed of the metering pump. When the melt flow rate discharged by the metering pump is A, the speed of the metering pump is recorded as metering pump speed I, when the melt flow rate discharged by the metering pump is C, the speed of the metering pump is recorded as metering pump speed II, when the melt flow rate discharged by the metering pump is B, the speed of the metering pump is recorded as metering pump speed III; metering pump speed I < metering pump speed III < metering pump speed II.

3. A method for improving the quality of spinning products according to claim 2, characterized in that: The temperature of the spinneret is detected by a temperature sensor; the temperature sensor is electrically connected to a controller, and the temperature sensor is used to send the detected temperature of the spinneret to the controller.

4. A method for improving the quality of spinning products according to claim 3, characterized in that: The controller is electrically connected to the winder and the metering pump respectively; when the metering pump is turned on, the controller controls the speed of the metering pump to be metering pump speed I; when the temperature sensor detects that the temperature of the spinneret is lower than the temperature during spinning, the controller controls the speed of the metering pump to be metering pump speed II; when the temperature of the spinneret is increased to the temperature during spinning, the controller controls the speed of the metering pump to be metering pump speed I to continue repairing the spinneret, and the head is grown after the repairing is completed; when the winder switches the fixed axis for spinning, the winder sends a spinning signal to the controller, and the controller controls the speed of the metering pump to be metering pump speed III.

5. A method for improving the quality of spinning products according to claim 4, characterized in that: Metering pump speed II is the maximum speed of the metering pump at rated power.