Preparation process of PET (Polyethylene Terephthalate) short fibers

Abstract

The invention provides a PET short fiber preparation process, and relates to the technical field of synthetic fiber production. The PET short fiber preparation technology comprises the steps that raw materials are prepared, proper PET slices are selected according to product performance requirements, a multi-stage impurity removal system is adopted, before recycled PET bottle materials enter a production process, large impurities are removed through physical screening, small impurities are removed through a chemical cleaning method, and characteristic parameters of the PET bottle materials need to meet production requirements. A multi-stage impurity removal system is adopted, before recycled PET bottle materials enter the production process, large impurities are removed through physical screening, small impurities are removed through a chemical cleaning method, a high-precision filtering device is installed, tiny impurities are further filtered out in the melt extrusion process, the purity of raw materials entering the spinning link is ensured, and the production efficiency is improved. The moisture content is strictly controlled, so that the influence of impurities on the performance of the finished fiber, the service life of a spinning assembly and other technical indexes of the finished fiber is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of synthetic fiber production, in particular to a PET short fiber preparation process. Background Art

[0002] Synthetic fiber is a chemical fiber made by spinning and post-processing a linear polymer with an appropriate molecular weight and solubility (or meltability). This type of polymer with fiber-forming properties is usually called a fiber-forming polymer. Compared with natural fibers and artificial fibers, the raw materials of synthetic fibers are made by artificial synthesis methods, and their production is not restricted by natural conditions. At present, there are many types of synthetic fibers, including PET staple fibers, which require the use of PET staple fiber preparation technology when they are prepared.

[0003] However, there are currently single-stage and two-stage processes in the production process of staple fibers, among which raw material processing is very critical. If the raw materials are not handled properly during the preparation of PET staple fibers, the quality will be seriously affected. The raw materials for PET staple fibers are usually recycled PET bottle flakes, etc. However, recycled PET bottle materials are widely available and are waste, and contain polystyrene, polyethylene, adhesives, sugars, paper, moisture and other impurities. The presence of these impurities mainly affects the performance of the finished fibers, the service life of the spinning components and other technical indicators of the finished fibers.

[0004] In addition, the poor dyeability of PET staple fibers has greatly affected its application range. This is mainly because there is no specific dyeing group on the polyester molecular chain, and the polarity is small, so it is difficult for dye molecules to enter the fiber, so dyeing is more difficult and the dyeability is poor, but the color fastness is good and it is not easy to fade. Due to the poor dyeability, PET fibers are limited in color selection and personalized customization in the textile field.

[0005] Therefore, in view of this, the existing preparation process is studied and improved to provide a dial remote control. Summary of the invention

[0006] 1. Technical issues to be solved

[0007] In view of the deficiencies in the prior art, the present invention provides a process for preparing PET staple fibers, which solves the problems raised by the background technology.

[0008] (II) Technical solution

[0009] To achieve the above objectives, the present invention is implemented through the following technical solutions: A PET staple fiber preparation process, comprising the following specific steps: S1. Raw material preparation, according to product performance requirements, select appropriate PET slices, adopt a multi-stage impurity removal system, before the recycled PET bottle material enters the production process, first remove larger impurities through physical screening, and use chemical cleaning methods to remove smaller impurities, its characteristic parameters must meet production requirements, and prepare additives;

[0010] S2. Slice drying, slicing the PET particles and drying them in a drying device to remove moisture therein, providing a stable, dry raw material for subsequent processing, and using a slicer to cut the PET particles into slices of appropriate size;

[0011] S3. melt extrusion, heating and melting the dried slices by electric heating, gas heating or oil heating, and extruding the melt into filaments through a screw extruder. Select an appropriate screw extruder, and install a high-precision filtering device during the melt extrusion process to further filter out tiny impurities and gel particles during the melt extrusion process;

[0012] S4. Spinning, spinning the melt into filaments through the spinneret holes of the spinning machine, selecting the appropriate spinneret hole size and number according to product specifications, and adjusting the spinning speed according to production efficiency and product quality requirements;

[0013] S5. Stretching and shaping: stretching the nascent fiber to increase its crystallinity and orientation. Determine the stretching multiple according to the fiber performance requirements and select the appropriate shaping temperature to ensure that the fiber maintains the required shape and performance during the cooling process. During the stretching and shaping process, the temperature needs to be precisely controlled;

[0014] S6. Winding and forming, winding the stretched and shaped fibers onto the bobbin for subsequent processing and use. According to product specifications and production requirements, select the appropriate bobbin material and size, use different winding methods and speeds to ensure that the fibers are wound tightly and neatly. At the same time, during the winding and forming process, the fiber tension needs to be controlled to ensure the neatness of the winding and the quality of the staple fiber products;

[0015] S7. Cutting: Use a cutter to cut. The number of blades and cutting speed of the cutter are selected according to production requirements. During the cutting process, it is necessary to ensure that the cut length of the fiber is uniform and the cut is neat. At the same time, the blade gap and cutting pressure of the cutter should be reasonably adjusted according to the characteristics of the fiber and the cut length.

[0016] S8. Post-treatment, i.e., heat setting, heat setting treatment of the cut PET staple fibers to eliminate the internal stress generated by the fibers during stretching, curling, etc., and oil treatment, oil treatment of the fibers, passing the fibers through an oil tank so that a layer of oil is evenly attached to the surface of the fibers;

[0017] S9. Quality inspection, including physical property inspection, chemical property inspection, and appearance quality inspection;

[0018] S10. Packaging and storage: Pack the PET staple fibers that have passed the quality inspection and store them in a dry, ventilated, and cool warehouse, avoiding direct sunlight and rain.

[0019] Preferably, in the storage stage of the raw material preparation, a drying method is used to dry the storage space to ensure that the relative humidity of the storage space is at a low level.

[0020] Preferably, the preparation of the additive includes developing new dyes and modifying existing dyes.

[0021] Preferably, the slice drying is divided into two stages: pre-crystallization and drying.

[0022] Preferably, during the melt extrusion of the PET staple fibers, the slices are dried and then heated and melted, and the melt is extruded into filaments by a screw extruder.

[0023] (III) Beneficial effects

[0024] The present invention provides a PET short fiber preparation process, which has the following beneficial effects:

[0025] 1. This PET staple fiber preparation process adopts a multi-stage impurity removal system. Before the recycled PET bottle material enters the production process, larger impurities are first removed by physical screening, and smaller impurities are removed by chemical cleaning. A high-precision filtering device is installed to further filter out tiny impurities during the melt extrusion process to ensure the purity of the raw materials entering the spinning stage, and strictly control the moisture content, thereby avoiding the presence of impurities affecting the performance of the finished fiber, the service life of the spinning component and other technical indicators of the finished fiber.

[0026] 2. This PET staple fiber preparation process develops new dyes, modifies existing dyes, and enhances the binding force between dyes and PET fibers by adding specific groups or changing molecular structures, thereby improving the dyeability of PET staple fibers, thereby reducing the limitations on color selection and personalized customization of PET fibers in the textile field. DETAILED DESCRIPTION

[0027] The following examples are used to illustrate the present invention, but they are not intended to limit the scope of the present invention.

[0028] In the description of the present invention, unless otherwise specified, “plurality” means two or more than two. In addition, the terms “first”, “second”, “third”, etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0029] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] Example:

[0031] The present invention provides a PET staple fiber preparation process, comprising the following specific steps:

[0032] S1. Raw material preparation. According to the product performance requirements, select appropriate PET slices and use a multi-stage impurity removal system. Before the recycled PET bottle material enters the production process, remove larger impurities such as paper pieces and adhesives through physical screening. Vibrating screens, wind sorting and other equipment can be used to separate different impurities according to their physical properties, and chemical cleaning methods can be used to remove smaller impurities. For smaller impurities such as sugar, polystyrene, polyethylene, etc., chemical cleaning methods can be used. Use specific cleaning agents to clean the bottle flakes at appropriate temperature and time to dissolve the impurities or separate them from PET. Its characteristic parameters must meet production requirements, and prepare additives;

[0033] S2. Slice drying: slice the PET pellets and dry them in a drying device to remove moisture from them, providing stable and dry raw materials for subsequent processing. Usually, airflow drying, vacuum drying or boiling drying equipment is used to ensure that the moisture content in the slices meets the requirements, and a slicer is used to cut the PET pellets into slices of appropriate sizes;

[0034] S3. Melt extrusion, heating and melting the dried slices by electric heating, gas heating or oil heating, and extruding the melt into filaments through a screw extruder. Select an appropriate screw extruder to ensure that the melt is fully mixed and plasticized during the extrusion process. In the melt extrusion process, in order to ensure the spinning quality, a high-precision filtering device is installed to further filter out tiny impurities and gel particles during the melt extrusion process to ensure the purity of the raw materials entering the spinning stage;

[0035] S4. Spinning, spinning the melt into filaments through the spinneret holes of the spinning machine, selecting the appropriate spinneret hole size and number according to product specifications, and adjusting the spinning speed according to production efficiency and product quality requirements;

[0036] S5. Stretching and shaping: stretching the nascent fiber to increase its crystallinity and orientation, improve the mechanical properties of the fiber, determine the stretching multiple according to the fiber performance requirements, and select the appropriate shaping temperature to ensure that the fiber maintains the required shape and performance during the cooling process. During the stretching and shaping process, the temperature needs to be precisely controlled;

[0037] S6. Winding and forming, winding the stretched and shaped fibers on the bobbin for subsequent processing and use. According to product specifications and production requirements, select the appropriate bobbin material and size, use different winding methods and speeds to ensure that the fibers are wound tightly and neatly, which is convenient for subsequent processing and use. At the same time, during the winding and forming process, the fiber tension needs to be controlled to ensure the neatness of the winding and the quality of the staple fiber products;

[0038] S7. Cutting: Use a cutter to cut. The number of blades and cutting speed of the cutter are selected according to production requirements. During the cutting process, ensure that the cut length of the fiber is uniform and the cut is neat to avoid problems such as uneven length or burrs. At the same time, the blade gap and cutting pressure of the cutter should be reasonably adjusted according to the characteristics of the fiber and the cut length.

[0039] S8. Post-treatment, i.e. heat setting, is to heat set the cut PET staple fibers to eliminate the internal stress generated by the fibers during stretching and curling, and improve the dimensional stability and heat resistance of the fibers. The heat setting temperature is generally between 120-200°C, and the time is determined according to the type and specification of the fibers, usually a few minutes to more than ten minutes. In addition, oil treatment is performed. In order to improve the surface properties of the fibers, reduce the friction and static electricity between the fibers, and improve the spinnability of the fibers, the fibers need to be treated with oil. The fibers are passed through an oil tank so that a layer of oil is evenly attached to their surface. The type and formula of the oil are selected according to the purpose and processing requirements of the fibers. Commonly used oil components include lubricants, antistatic agents, emulsifiers, etc.

[0040] S9. Quality inspection, including physical property inspection, chemical property inspection, and appearance quality inspection;

[0041] S10. Packaging and storage. The PET staple fibers that have passed the quality inspection shall be packaged. The packaging materials are usually plastic woven bags or cartons to prevent the fibers from moisture, contamination and damage. The packaging specifications and forms will vary according to different customer needs and transportation methods. The packaged PET staple fibers shall be stored in a dry, ventilated and cool warehouse to avoid direct sunlight and rain. The storage temperature is generally controlled between 5-35℃ and the relative humidity is controlled below 60%. At the same time, it should be noted that fibers of different specifications and varieties should be stored separately to avoid confusion.

[0042] Among them, the spinning methods mainly include melt spinning and solution spinning, among which melt spinning is more widely used. Melt spinning is to extrude the molten PET melt through the small holes on the spinneret to form a thin stream, and then cool and solidify it in the air to become a fiber. The number and diameter of the small holes on the spinneret are determined according to the product specifications and production requirements. For example, when producing fine denier fibers, the spinneret hole diameter is small, usually 0.1-0.3mm; when producing coarse denier fibers, the spinneret hole diameter is larger, up to 0.5-1mm.

[0043] Among them, spinning process parameters:

[0044] A Spinning temperature: affects the fluidity and viscosity of the melt, and thus affects the molding and quality of the fiber. Generally, the spinning temperature is slightly lower than the melting temperature, between 250-280°C. For example, for some products that require higher fiber fineness, it is necessary to spin at a lower spinning temperature to obtain better fiber fineness uniformity.

[0045] B Spinning speed: determines the stretching degree and crystallinity of the fiber, and has an important influence on the mechanical and physical properties of the fiber. The spinning speed is usually between 500-3000m / min. For example, when producing high-strength fibers, the spinning speed can be appropriately increased to increase the stretching multiple of the fiber, thereby improving the strength of the fiber.

[0046] C Cooling conditions: The cooling method and cooling speed have a significant impact on the structure and performance of the fiber. Common cooling methods include air cooling and water cooling. Air cooling uses air flow to cool the fiber, and the cooling speed is relatively slow. It is suitable for the production of some products that do not require high fiber crystallinity. Water cooling uses water to cool the fiber, and the cooling speed is fast, which can make the fiber solidify quickly, which is conducive to improving the crystallinity and orientation of the fiber. It is suitable for the production of high-strength and high-modulus fibers. The cooling temperature is generally between 10-40℃, and the cooling wind speed or water flow speed is adjusted according to the specific production equipment and process requirements.

[0047] The purpose of stretching is to stretch the primary fibers so that the molecular chains in the fibers are oriented along the fiber axis, thereby increasing the crystallinity and orientation of the fibers, thereby significantly improving the mechanical properties (such as strength, modulus) and dimensional stability of the fibers.

[0048] Among them, the stretching methods mainly include primary stretching and multi-stage stretching. Primary stretching is to complete the stretching of the fiber in one stretching stage, while multi-stage stretching is to divide the stretching process into multiple stages and gradually increase the stretching multiple. For example, for some high-performance PET staple fibers, two-stage or three-stage stretching may be used. Different stretching temperatures, stretching multiples and stretching speeds are set in different stretching stages to obtain better stretching effects. The stretching temperature is generally between 60-150°C, and the stretching multiple is determined according to product requirements, usually between 3-6 times.

[0049] When the antibacterial PET staple fibers are spun, 10% by mass of antibacterial masterbatch is added, the amount of sand added to the components is reduced, the initial pressure of the components is reduced to 6.0-7.0 MPa, the spinning temperature is controlled at 288-292°C, the annular air temperature is 24-26°C, the wind speed is 1.05 m / s, and the post-processing speed and stretching temperature are reduced, so that the production can be stabilized and the antibacterial rate of the antibacterial PET staple fibers obtained can reach more than 99%.

[0050] Among them, the tensile shaping of PET staple fibers needs to be strictly controlled. The standard prepared samples are stretched to break on an electronic universal testing machine to measure their mechanical properties such as breaking strength, elongation at break and modulus, so as to evaluate their material quality and performance. The reference standard "GB / T 14337-2022 Test method for tensile properties of chemical fiber staple fibers" is used. The test temperature is generally around room temperature 25°C, the load sensor is 50N, the sample name is PET staple fiber specimen, and the test speed is 100mm / min.

[0051] Among them, safety issues need to be paid attention to during the winding and molding process of PET staple fibers. When producing polyester staple fibers, they are bundled, stretched, shaped, curled, cut, and then packaged. The winding speed of the winding machine is very high. If you are not careful during operation, it is easy to bring in hooks, causing flying hooks to hurt people. Therefore, it is necessary to educate operators to concentrate on the operation and stand in a favorable and safe position to avoid flying hooks.

[0052] During the storage process of raw material preparation, a drying method is used to dry the storage space, including but not limited to desiccants or installing dehumidification equipment to maintain a dry environment, prevent the raw materials from absorbing moisture in the air, and ensure that the relative humidity of the storage space is at a low level.

[0053] Among them, the preparation of additives includes the development of new dyes, modification of existing dyes, and enhancing the binding force between dyes and PET fibers by adding specific groups or changing the molecular structure, thereby improving the dyeability of PET staple fibers and reducing the limitations on color selection and personalized customization of PET fibers in the textile field.

[0054] Among them, the slice drying is divided into two stages: pre-crystallization and drying. In the crystallization stage, heating is carried out in a crystallization tower to arrange the molecules of the PET slices neatly, increase the glass transition temperature of the slices, and avoid adhesion during subsequent drying and hopper processes. The crystallization time is generally 30-90 minutes, and the temperature is lower than 149°C. In the drying stage, because water will hydrolyze PET at high temperatures, resulting in a decrease in inherent adhesion, especially as the molecular weight decreases, the physical properties will be affected, so the PET slices must be dried to a moisture content of less than 0.005%. For this purpose, a drying and dehumidifying dryer is used, and hot air with a dew point below -40°C is used for closed-loop continuous drying. Because PET material is hygroscopic, water penetrates into the surface of the slice to form molecular bonds. Water deep inside the slice is difficult to dry, and ordinary hot air cannot be used.

[0055] Among them, in the melt extrusion process of PET staple fibers, PET staple fibers are processed from polyester (PET) chips through melt spinning and other processes. The chips are dried and then heated and melted. The chips can be heated and melted by electric heating, gas heating or oil heating, and the melt is extruded into filaments through a screw extruder. In addition to melting the polyester resin chips, heating the resin to a certain temperature and making the resin melt have a certain fluidity, the extruder is also responsible for controlling the extrusion amount.

[0056] The embodiments of the present invention are given for the purpose of illustration and description, and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

Claims

1. A process for preparing PET staple fibers, characterized in that: The specific steps include: S1. Raw material preparation: Select appropriate PET slices according to product performance requirements, use a multi-stage impurity removal system, and remove larger impurities through physical screening before the recycled PET bottle enters the production process. Use chemical cleaning to remove smaller impurities. Its characteristic parameters must meet production requirements, and prepare additives; S2. Slice drying: slice the PET pellets and dry them in a drying device to remove moisture, provide stable and dry raw materials for subsequent processing, and use a slicer to cut the PET pellets into slices of appropriate size; S3. Melt extrusion, using electric heating, gas heating or oil heating to heat and melt the dried slices, and extrude the melt into filaments through a screw extruder. Select an appropriate screw extruder and install a high-precision filtering device during the melt extrusion process to further filter out tiny impurities and gel particles during the melt extrusion process; S4. Spinning, spinning the melt into filaments through the spinneret holes of the spinning machine, selecting the appropriate spinneret hole size and number according to product specifications, and adjusting the spinning speed according to production efficiency and product quality requirements; S5. Stretching and shaping: stretching the nascent fiber to increase its crystallinity and orientation. Determine the stretching multiple according to the fiber performance requirements and select the appropriate shaping temperature to ensure that the fiber maintains the required shape and performance during the cooling process. During the stretching and shaping process, the temperature needs to be precisely controlled; S6. Winding and forming, winding the stretched and shaped fibers onto the bobbin for subsequent processing and use. According to product specifications and production requirements, select the appropriate bobbin material and size, use different winding methods and speeds to ensure that the fibers are wound tightly and neatly. At the same time, during the winding and forming process, the fiber tension needs to be controlled to ensure the neatness of the winding and the quality of the staple fiber products; S7. Cutting: Use a cutting machine to cut. The number of blades and cutting speed of the cutting machine are selected according to production requirements. During the cutting process, it is necessary to ensure that the cutting length of the fiber is uniform and the incision is neat. At the same time, the blade gap and cutting pressure of the cutting machine should be reasonably adjusted according to the characteristics of the fiber and the cutting length. S8. Post-treatment, i.e., heat setting, heat setting treatment is performed on the cut PET staple fibers to eliminate the internal stress generated by the fibers during stretching, curling, etc., and oil treatment is performed on the fibers to pass through an oil tank so that a layer of oil is evenly attached to the surface of the fibers; S9. Quality inspection, including physical property inspection, chemical property inspection, and appearance quality inspection; S10. Packaging and storage: Pack the PET staple fibers that have passed the quality inspection and store them in a dry, ventilated and cool warehouse, avoiding direct sunlight and rain.

2. A PET staple fiber preparation process according to claim 1, characterized in that: In the storage stage of the raw material preparation, a drying method is used to dry the storage space to ensure that the relative humidity of the storage space is at a low level.

3. A PET staple fiber preparation process according to claim 1, characterized in that: The preparation of the additives includes developing new dyes and modifying existing dyes.

4. A PET staple fiber preparation process according to claim 1, characterized in that: The slice drying is divided into two stages: pre-crystallization and drying.

5. A process for preparing PET staple fibers according to claim 1, characterized in that: During the melt extrusion of the PET staple fibers, the chips are dried and then heated and melted, and the melt is extruded into filaments through a screw extruder.