A production process for cotton-type fibers made from low-melting-point PET

Abstract

This invention provides a process for producing cotton-type fibers from low-melting-point PET, comprising the following steps: (1) placing cotton-type fiber PET raw materials and low-melting-point PET chips into a rotary drum for drying to obtain a mixture, wherein the melting point of the cotton-type fiber PET raw materials is 250-260°C and the melting point of the low-melting-point PET chips is 180-220°C; (2) conveying the mixture to a screw extruder for melting; (3) filtering and extruding the molten melt; and (4) cooling and shaping; wherein the cooling and shaping includes ring blowing and winding oiling. This process for producing cotton-type fibers from low-melting-point PET avoids the problem of ring blockage during the screw feeding stage and prevents the chips from vaporizing at high temperatures to form bubble fibers that directly cause spinning breakage and fuzz.

Description

Technical Field

[0001] This invention relates to the field of textile technology, and in particular to a production process for cotton-type fibers made of low-melting-point PET. Background Technology

[0002] Chip spinning technology took root, sprouted, and grew in China in the 1990s. After more than 30 years of development, China has completed its chip spinning system, forming an industrialized chip spinning industry with upstream and downstream supply chains and enterprises. The chip spinning technology has also become increasingly mature and perfected. In the early days, chip spinning mainly used conventional polyester chips, and the quality requirements for the produced yarn were not high. However, with increasingly fierce market competition and the improvement of direct spinning technology, the cost and quality advantages of direct spinning have gradually become apparent. Chip spinning can no longer be satisfied with conventional polyester chip spinning and has fully shifted towards differentiation, refinement, and specialization. This has placed higher demands on the feeding of differentiated chips. However, the old chip spinning equipment or processes have problems such as feeding difficulties, blockage, oxidation, agglomeration, and long residence time. Especially with low melting point and amorphous chips, the chips are very easy to stick to the feed inlet or pipes, making it impossible to meet production requirements. Even if production is barely possible, there are insurmountable technical obstacles in terms of yarn quality stability and dyeing uniformity.

[0003] Cotton fiber is widely popular among consumers due to its excellent moisture absorption and soft feel. However, the production and price of cotton fiber fluctuate significantly, making the search for a substitute a major research focus. Polyester fiber has a large production volume and stable price, but its moisture absorption is poor, resulting in fabrics that are less comfortable to wear than cotton fabrics. However, it possesses high elasticity and strength, characteristics that cotton fabrics lack. To alleviate the large demand for cotton fiber, cotton-like polyester fiber has emerged, offering superior moisture absorption and breathability compared to cotton.

[0004] One existing method for manufacturing cotton-like polyester fibers involves adding modified monomers during the synthesis of polyester chips, followed by drying and melt spinning of the modified polyester chips. The resulting cotton-like polyester fibers are then drawn to obtain the final product. Currently, melt spinning is the main method for producing low-melting-point cotton fibers. Compared to ordinary fibers, its main characteristic is the lower melting point of the polymer, requiring corresponding adjustments to various process parameters during spinning and altering the requirements for spinning equipment. Before feeding, during the drying of the raw material chips, the low melting point of the polymer also lowers the softening point, making the chips prone to clumping. Furthermore, the moisture in the chips easily vaporizes at high temperatures, forming air bubbles that directly cause breakage and fuzzy fibers, hindering subsequent spinning. Chips with high moisture content are prone to ring blockage during the screw feeding stage, directly interrupting spinning. Therefore, some existing processes employ a low-temperature, long-time drying method, controlling the temperature between the glass transition temperature and the crystallization temperature during drying to allow sufficient time for the chips to expel surface and deep-seated moisture and to produce pre-crystallization. Then, after the slices crystallize, the temperature is rapidly increased to the highest temperature for drying the material to minimize the moisture content of the slices and reduce their adverse effects on spinning. However, this operation is difficult to implement and control in actual processes, and its effect is not ideal. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a production process for cotton-type fibers made from low-melting-point PET. On the one hand, this process is less likely to cause ring-shaped material blockage during the screw feeding stage. On the other hand, it avoids the problem of yarn breakage and fuzz caused by the vaporization of chips at high temperatures forming bubble fibers.

[0006] To achieve the objective of this invention, a production process for cotton-type fibers made from low-melting-point PET is provided, comprising the following steps:

[0007] (1) Place cotton-type fiber PET raw material and low-melting-point PET chips into a rotating drum for drying to obtain a mixture. The melting point of the cotton-type fiber PET raw material is 250-260℃, and the melting point of the low-melting-point PET chips is 180-220℃.

[0008] (2) The mixture is fed to a screw extruder for melting; (3) The molten melt is filtered and extruded into fibers; (4) Cooling and forming; the cooling and forming includes ring blowing and winding oiling;

[0009] As described in step (1) above, the inner screen of the drum is first replaced, cotton-type fiber PET raw material is placed in, pre-extraction and cold extraction are started, and then switched to fine extraction. During fine extraction, all steam valves are opened for high-temperature drying. After the overall drying is completed, the steam is turned off, and then the exhaust is vented for cold extraction. After the temperature inside the drum drops to a certain level, low-melting-point chips are added, and then cold extraction is performed again. The moisture content is measured, and then the material is discharged. The temperature inside the drum dropping to a certain level can prevent the low-melting-point PET chips from clumping due to excessively high temperatures.

[0010] In the above steps, the inventors added a certain proportion of low-melting-point PET chips to the existing technology, which only uses a single cotton-type fiber PET raw material, and controlled the timing and conditions of adding the cotton-type fiber PET raw material and the low-melting-point PET chips, thereby solving the technical problems in the existing technology.

[0011] Preferably, in step (1), the pre-extraction and cold extraction time is 1.5 to 2.5 hours; during the fine extraction, the pressure is maintained at a negative pressure; the pressure is preferably -0.095 to -0.1 MPa.

[0012] Preferably, the high-temperature drying time is 5 to 6 hours, and the temperature inside the drum during the high-temperature drying is 150°C to 160°C.

[0013] Preferably, when the temperature inside the drum drops to 90-110°C, low-melting-point PET chips are added; after adding the low-melting-point PET chips, the cold drawing time is 50-80 minutes, and the material is discharged when the moisture content is ≤50PPM.

[0014] Preferably, in step (1), when the mixture is discharged, each batch of material is evenly distributed into the spinning hopper, and the discharge time is no more than 3 batches.

[0015] Preferably, before step (2), the spinneret assembly is installed and the assembly is insulated; the installation of the spinneret assembly includes filling sea sand and assembling the filter screen, cleaning the distribution and tightening assembly cylinder, and placing the distribution plate and the spinneret into the cylinder; when the assembly is insulated, the assembled assembly is placed in an insulation box and the temperature is set for more than 6 hours.

[0016] Preferably, the sea sand has a mesh size of 20-25, and the filter screen has a mesh size of 100-120.

[0017] Furthermore, in the screw extruder, the screw temperature is set as follows: Zone 1 250-260℃, Zone 2 260-270℃, Zone 3 275-285℃, Zone 4 280-290℃, Zone 5 280-290℃, Zone 6 275-285℃, Zone 7 270-280℃; the screw extrusion head temperature is 265-275℃.

[0018] Furthermore, in step (3), the filter temperature is set to 270–285°C, and the spinning box temperature is set to 260–270°C.

[0019] Furthermore, the process also includes step (5) post-processing, which includes stretching, cutting and packaging; in the stretching step, a low-melting-point special cationic oil is used for oiling; in the stretching step, cold roller stretching is used, the steam valve of the preheating roller in the heating box is closed, the oven is heated to 90-100℃ for drying and shaping, after the stretching is adjusted to normal, a normal sample is taken for inspection, and the stretching ratio is adjusted according to the rapid sample data.

[0020] Preferably, the mass ratio of the cotton-type fiber PET raw material to the low-melting-point PET chips is 7:1 to 10:1.

[0021] Because the drying of polyester chips requires high temperatures, prolonged exposure to high temperatures can easily lead to thermal decomposition, affecting the quality of the polyester chips. Conversely, excessively low temperatures can result in insufficient drying, leading to high moisture content in the melt formed during spinning, thus affecting the spinning quality and causing a defect in the quality of cotton-like polyester fibers. Considering these factors, this invention first improves the raw material of cotton-type fibers. Based on a single cotton-type PET raw material with a melting point of 250–260°C, low-melting-point PET chips with a melting point of 180–220°C are added. The drying process is divided into two stages: the cotton-type PET raw material first undergoes high-temperature drying, followed by a cold-drawing process with the addition of the low-melting-point chips. This process, optimized through extensive practical operation, ensures thorough drying without affecting the performance of the raw material and chips.

[0022] Although the drying process of this invention involves multiple steps, it is easy to control and simple to operate.

[0023] This invention not only cleverly controls the drying process, but also makes many improvements in subsequent processes such as mixing, extrusion spinning, and post-processing. These improvements include the selection of sea sand and filter screens, and the control of process parameters for the screw extruder and spinning box. These improvements, combined with the clever operation of the drying process, ensure the optimization and improvement of the entire process flow, avoiding problems such as feed adhesion, blockage, oxidation, agglomeration, and long residence time. On the one hand, it is less likely to cause ring blockage during the screw feeding stage, and on the other hand, it avoids the problem of chip vaporization at high temperature forming bubble filaments that directly cause spinning breakage and fuzzy filaments. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the following embodiments are provided to further illustrate this invention in detail. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0025] The specific operation and effects of the technical solution of the present invention will be illustrated below through several specific embodiments.

[0026] Example 1

[0027] The low-melting-point PET cotton-type fiber product prepared in this embodiment has a specification of 2.5D*38mm. The specific preparation steps are as follows:

[0028] (1) Prepare cotton-type fiber PET raw materials and low-melting-point PET chips. The melting point of the cotton-type fiber PET raw materials is 255℃, and the melting point of the low-melting-point PET chips is 200℃. Replace the inner screen of the drum, put in the cotton-type fiber PET raw materials, turn on the pre-extraction and cold extraction and then switch to fine extraction. During fine extraction, all steam valves are opened for high-temperature drying. The pre-extraction and cold extraction time is 2 hours. During fine extraction, the pressure is maintained at negative pressure -0.1pa. After the overall high-temperature drying is completed, turn off the steam. The high-temperature drying time is 5.5 hours. The temperature inside the drum during high-temperature drying is 150℃. Then exhaust the air and perform cold extraction. When the temperature inside the drum drops to 100℃, add the low-melting-point PET chips and perform cold extraction for another 60 minutes. When the moisture content is ≤50PPM, discharge the material. The mass ratio of the cotton-type fiber PET raw materials to the low-melting-point PET chips is 9:1.

[0029] In step (1), when the mixture is discharged, each batch is evenly distributed into the return hopper, with 3 drums discharged each time.

[0030] (2) First, the spinneret assembly is installed and insulated. The spinneret assembly installation includes filling with sea sand and assembling the filter screen. The distribution and tightening cylinder is cleaned, and the distribution plate and spinneret are placed inside the cylinder. When insulating the assembly, the assembled assembly is placed in an insulation box, and the temperature is set for 7 hours. The sea sand has a mesh size of 20, and the filter screen has a mesh size of 100. After the above work is completed, the mixture is conveyed to the screw extruder for melting. In the screw extruder, the screw temperature is set as follows: Zone 1 250-260℃, Zone 2 260-270℃, Zone 3 275-285℃, Zone 4 280-290℃, Zone 5 280-290℃, Zone 6 275-285℃, Zone 7 270-280℃; the screw extrusion head temperature is 265-275℃.

[0031] (3) The molten melt is filtered and extruded into fibers. The filter temperature is set to 280℃, the spinning box temperature is set to 265℃, the air temperature is 18~20℃, and the air pressure is 240Pa.

[0032] (4) Cooling and forming; the cooling and forming includes ring blowing and winding oiling;

[0033] (5) Drawing, cutting, and packaging; In the drawing step, a low-melting-point cationic oil agent is used for oiling; In the drawing step, cold roller drawing is used, the steam valve of the preheating roller in the heating box is closed, the oven is heated to 95°C for drying and shaping, and after the drawing is adjusted to normal, normal samples are taken for testing, and the drawing ratio is adjusted according to the rapid sample data.

[0034] Example 2

[0035] The low-melting-point PET cotton-type fiber product prepared in this embodiment has a specification of 2.5D*51mm.

[0036] The operation steps of Example 2 are the same as those of Example 1, and the operation parameters in steps (1)-(5) are as follows:

[0037] In step (1), the melting point of the cotton-type fiber PET raw material is 260℃, the melting point of the low-melting-point PET chips is 180℃, the pre-extraction and cold-extraction time is 1.5 hours, and the pressure is maintained at negative pressure -0.1pa during fine extraction; the high-temperature drying time is 6 hours, and the temperature inside the drum during high-temperature drying is 160℃; when the temperature inside the drum drops to 90℃, the low-melting-point PET chips are added, and then cold-extraction is performed for another 80 minutes. The material is discharged when the moisture content is ≤50PPM; the mass ratio of the cotton-type fiber PET raw material to the low-melting-point PET chips is 7:1.

[0038] When the mixture is discharged, the material is evenly distributed into the spinning hopper from each drum, with 3 drums discharging each time.

[0039] In step (2), the temperature is set and kept warm for 8 hours; the sea sand has a mesh size of 25 and the filter screen has a mesh size of 120.

[0040] In step (3), the filter temperature is set to 285°C and the spinning box temperature is set to 270°C.

[0041] In step (5), the oven is heated to 90°C to dry and set the shape.

[0042] The remaining parameters for steps (1)-(5) are the same as in Example 1.

[0043] Example 3

[0044] The low-melting-point PET cotton-type fiber product prepared in this embodiment has a specification of 2.5D*38mm.

[0045] The operation steps of Example 3 are the same as those of Example 1, and the operation parameters in steps (1)-(5) are as follows:

[0046] In step (1), the melting point of the cotton-type fiber PET raw material is 250℃, the melting point of the low-melting-point PET chips is 200℃, the pre-extraction and cold extraction time is 2 hours, and the pressure is maintained at negative pressure -0.1pa during fine extraction; the high-temperature drying time is 5 hours, and the temperature inside the drum during high-temperature drying is 155℃; when the temperature inside the drum drops to 110℃, the low-melting-point PET chips are added, and then cold-extracted for 70 minutes. The material is discharged when the moisture content is ≤50PPM; the mass ratio of the cotton-type fiber PET raw material to the low-melting-point PET chips is 8:1.

[0047] When the mixture is discharged, the material is evenly distributed into the spinning hopper from each drum, with 3 drums discharging each time.

[0048] In step (2), the components are placed in an insulated box and the temperature is set for 7 hours; the sea sand has a mesh size of 25 and the filter screen has a mesh size of 100.

[0049] In step (3), the filter temperature is set to 270°C and the spinning box temperature is set to 260°C.

[0050] In step (5), the oven is heated to 100°C to dry and set the shape.

[0051] The remaining parameters for steps (1)-(5) are the same as in Example 1.

[0052] Example 4

[0053] The low-melting-point PET cotton-type fiber product prepared in this embodiment has a specification of 1.5D*38mm.

[0054] The operation steps of Example 3 are the same as those of Example 1, and the operation parameters in steps (1)-(5) are as follows:

[0055] In step (1), the melting point of the cotton-type fiber PET raw material is 255℃, the melting point of the low-melting-point PET chips is 220℃, the pre-extraction and cold-extraction time is 2.5 hours, and the pressure is maintained at negative pressure -0.1pa during fine extraction; the high-temperature drying time is 5.5 hours, and the temperature inside the drum during high-temperature drying is 150℃; when the temperature inside the drum drops to 100℃, the low-melting-point PET chips are added, and then cold-extraction is performed for another 50 minutes. The material is discharged when the moisture content is ≤50PPM; the mass ratio of the cotton-type fiber PET raw material to the low-melting-point PET chips is 10:1.

[0056] When the mixture is discharged, the material is evenly distributed into the spinning hopper from each drum, with 3 drums discharging each time.

[0057] In step (2), the components are placed in an insulated box and the temperature is set for 6 hours; the sea sand has a mesh size of 20 and the filter screen has a mesh size of 120.

[0058] In step (3), the filter temperature is set to 280°C and the spinning box temperature is set to 270°C.

[0059] In step (5), the oven is heated to 95°C to dry and set the shape.

[0060] The remaining parameters for steps (1)-(5) are the same as in Example 1.

[0061] Table 1 Performance Tests of Examples

[0062]

[0063] As can be seen from the quality test report in the table above, all parameters in Examples 1-3 meet the technical specifications and standards. Furthermore, during the production process, there are no issues such as ring knots hindering the material, spinning breakage, or fuzzy fibers. The entire process is smooth and easy for technicians to operate.

[0064] In summary, although the present invention has been disclosed above with reference to preferred embodiments, the above preferred embodiments are not intended to limit the present invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope defined in the claims.

Claims

1. A process for producing cotton type fibers made of low melting point PET, characterized in that, The process comprises the following steps: (1) drying cotton type fiber PET raw material and low melting point PET chips in a rotating drum to obtain a mixture, the melting point of the cotton type fiber PET raw material is 250-260 DEG C, and the melting point of the low melting point PET chips is 180-220 DEG C; (2) conveying the mixture to a screw extruder to melt the mixture; (3) filtering and extruding the melt after melting; (4) cooling and forming; the cooling and forming comprises ring blowing and oiling; in step (1), first replace the vacuum filter screen in the rotating drum, put in the cotton type fiber PET raw material, open the pre-extraction and cold extraction, and then switch to fine extraction, during fine extraction, open all steam valves for high temperature drying, after overall drying, close the steam, then exhaust for cold extraction, when the temperature in the rotating drum decreases to a certain temperature, add the low melting point PET chips, then cold extraction, measure the water content, and then discharge; the high temperature drying time is 5-6 hours, the temperature in the rotating drum during high temperature drying is 150-160 DEG C; when the temperature in the rotating drum decreases to 90-110 DEG C, add the low melting point PET chips; after adding the low melting point PET chips, the cold extraction time is 50-80 min, and the water content is ≤50 PPM when discharging; the mass ratio of the cotton type fiber PET raw material to the low melting point PET chips is 7:1-10:

1.

2. The process for producing low melting point PET-made cotton-type fibers according to claim 1, characterized in that: In step (1), the pre-extraction and cold extraction time is 1.5-2.5 hours.

3. Process for the production of low-melting PET-made cotton-type fibres according to claim 1 or 2, characterised in that: In step (1), when discharging the mixture, evenly divide each drum into the spinning material bin, and each discharge is not more than 3 drums.

4. The process for producing low melt PET made cotton type fiber as claimed in claim 1 wherein: Before step (2), first install the spinneret assembly and assemble the assembly; the spinneret assembly installation comprises filling sea sand and assembling a filter screen, cleaning the distribution top tight assembly sleeve, and placing the distribution plate and the spinneret in the sleeve; when assembling the assembly, place the assembled assembly in a heat preservation furnace, the temperature of the heat preservation furnace is 280-290 DEG C, and the temperature is set to be preserved for more than 6 hours.

5. The process for producing low melt PET made cotton type fiber as claimed in claim 4 wherein: The mesh number of the sea sand is 20-25 meshes, and the mesh number of the filter screen is 100-120 meshes.

6. The process for producing low melt PET made cotton type fiber as claimed in claim 1 wherein: In the screw extruder, the screw temperature is set as follows: zone 1 250-260 DEG C, zone 2 260-270 DEG C, zone 3 275-285 DEG C, zone 4 280-290 DEG C, zone 5 280-290 DEG C, zone 6 275-285 DEG C, and zone 7 270-280 DEG C; the screw extrusion head temperature is 265-275 DEG C.

7. The process for producing low melting point PET-made cotton-type fibers according to claim 1 or 6, characterized in that: In step (3), the filter temperature is set to 270-285 DEG C, and the spinning box temperature is set to 260-270 DEG C.

8. The process for producing low melt PET made cotton type fiber as claimed in claim 1 wherein: The process further comprises step (5) post-treatment, the post-treatment comprises drafting, cutting and packaging; in the drafting step, low melting point special cationic oil is used for oiling; in the drafting step, cold roller drafting is used, the heating box preheating roller steam valve is closed, the oven is heated to 90-100 DEG C for drying and setting, after normal drafting adjustment, normal samples are taken for inspection, and the drafting ratio is adjusted according to the rapid sample data.

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