Low-melting-point sheath-core fiber with high crimp shrinkage rate and good bulkiness and preparation method of low-melting-point sheath-core fiber

Abstract

The invention belongs to the technical field of chemical fibers, and particularly relates to a low-melting-point sheath-core fiber high in crimp shrinkage rate and good in bulkiness and a preparation method thereof.The low-melting-point sheath-core fiber high in crimp shrinkage rate and good in bulkiness is obtained by conducting puffing deformation on primary low-melting-point sheath-core fiber through hot air; the bulking deformation device is provided with a bulking nozzle; the primary low-melting-point sheath-core fibers are drafted and shaped before the bulking deformation. According to the low-melting-point skin-core fiber prepared by utilizing the bulking nozzle of the BCF drafting bulking equipment, particularly when the skin-core melting point difference is relatively large, the fiber crimp shrinkage rate is high, and the bulkiness is obviously superior to that of the existing low-melting-point skin-core fiber, and the low-melting-point skin-core fiber is applied to preparation of a fiber volatilization rod, a fiber pen point, a fiber filtering material, a fiber water diversion rod or a fiber water absorption rod; and the effect is obviously improved. Compared with DTY prepared by an elasticizer, the prepared low-melting-point sheath-core fiber has the advantages that the range of selectable materials of the sheath layer and the core layer is wider.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical fibers, and in particular relates to a low-melting-point sheath-core fiber with high curl shrinkage and good bulkiness, and a preparation method thereof. Background Art

[0002] There are two main materials for perfume sticks and aromatherapy sticks, one is natural plant rattan, and the other is fiber. At present, the specific material of the fiber is polyester stretch yarn, which absorbs and evaporates faster than rattan and is easy to store. At present, the method of using low-melting-point sheath-core fiber to make stretch yarn (DTY) is: first prepare low-melting-point sheath-core pre-oriented fiber (POY), then stretch and false-twist it through a texturing machine to obtain low-melting-point sheath-core curly fiber (DTY) filament, and then prepare multiple strands of low-melting-point sheath-core curly filament fibers by heating equipment, so that the low-melting-point material on the surface of part of the fiber is heated and melted, and bonded to each other to form cross-links, and at the same time, many micropores and capillary channels are generated inside the fiber. For example, a Chinese patent document (CN109501324A, 2019-03-22) discloses the use of elasticized sheath-core untwisted composite filaments as fiber materials, and the production of glue-free fibers by a method of thermoforming equipment.

[0003] However, there are some disadvantages in preparing DTY by the above method. The first is the difficulty of texturizing and the problem of limited materials. Low-melting-point core-skin fibers are usually composed of a core layer with a higher melting point and a skin layer with a lower melting point. Since all single fibers need to be heated as a whole to above the glass transition temperature of both the core and skin materials to obtain good tensile properties, but the upper hot box of the texturizing machine is relatively short, in order to make the fiber temperature reach above the glass transition temperature in the short time when the tow passes through the hot box, the hot box temperature must be set much higher than its glass transition temperature to successfully complete the stretching. While stretching, the filaments obtain the twist transmitted by the false twister. The higher the fiber temperature, the better the plasticization effect and the easier it is to twist and obtain fluffiness. Therefore, the higher the temperature of the first hot box, the better the fluffiness. However, if the hot box temperature is higher than the melting point of the skin material, it is likely to cause the skin to become sticky; at the same time, since POY is only a pre-oriented fiber with a low degree of orientation and no crystallization, the softening point temperature is low. Even if the hot box temperature is slightly lower than the fiber melting point, it will cause the fiber to become sticky and affect the elastic effect (for example, the hot box temperature for single-component 160°C melting point polyester fiber cannot exceed 120°C, and the hot box temperature for single-component 260°C melting point ordinary polyester fiber cannot exceed 220°C, otherwise it will cause the fiber to become sticky and affect the elastic effect and cause twisting). This requires that the melting point difference between the skin and core materials should not be too large, which limits the selection of low-melting point materials for the skin.

[0004] Secondly, for the stretching and false twisting of low-melting-point sheath-core POY fibers, due to the large difference in the materials of the sheath and core layers, and the long distance between the stretching gripping points of the texturing machine, if the stretching ratio is too low, there will be unstretched parts (stiff fibers) and the curling shrinkage rate is low and the bulkiness is poor. If the stretching ratio is too high, a large number of hairy fibers will appear in the fibers.

[0005] In addition, the POY-DTY process itself has other problems. For example, the fiber will have residual torque after false twisting, which will easily cause entanglement and affect the porosity; the POY needs to be oiled after false twisting, and too much residual oil will affect the performance of the final product; due to equipment limitations (and fiber heat transfer limitations), the fineness of a single spindle tow basically does not exceed 450 deniers, so the processing fineness of the texturing machine is relatively low, which also results in low production efficiency. Summary of the invention

[0006] The main purpose of the present invention is to solve the above-mentioned problems of difficulty in adding elasticity and material limitation. Therefore, the present invention provides the following technical solution: utilizing a composite spinning device capable of spinning low-melting-point sheath-core fibers, grafting a BCF (continuous bulked filament) stretching and bulking device (including a BCF stretching and shaping device and a BCF bulking device), and adopting a "one-step method" to produce low-melting-point sheath-core fibers with high curl shrinkage and good fluffiness.

[0007] The invention provides a low-melting-point core-skin fiber with high curl shrinkage and good bulkiness. The low-melting-point core-skin fiber with high curl shrinkage and good bulkiness is obtained by subjecting the primary low-melting-point core-skin fiber to expansion deformation using hot air in an expansion deformation device.

[0008] Furthermore, the puffing and deformation device (ie, the BCF puffing device) has a puffing nozzle; the primary low-melting-point sheath-core fiber is stretched and shaped before the puffing and deformation.

[0009] Furthermore, the puffing deformation is carried out in the puffing deformation device.

[0010] Furthermore, the puffing and deformation device is arranged in the BCF stretching and puffing equipment.

[0011] Furthermore, the BCF stretching and bulking equipment also includes a BCF stretching and shaping device.

[0012] Furthermore, the stretching and shaping are carried out in the BCF stretching and shaping device.

[0013] Furthermore, the primary low-melting-point core-skin fiber is composed of a core fiber and a skin fiber; the melting point of the core fiber is higher than the melting point of the skin fiber.

[0014] Furthermore, the difference between the melting point of the core layer fiber and the melting point of the sheath layer fiber is 25-120°C.

[0015] Furthermore, the difference between the melting point of the core layer fiber and the melting point of the sheath layer fiber is 50-100°C.

[0016] Furthermore, the material of the core layer fiber includes one or more of polyolefins, polyesters, polyamides, polylactic acid, polyurethanes, and polyphenylene sulfide; the material of the sheath fiber includes one or more of polyolefins, polyesters, polyamides, polylactic acid, polyurethanes, and polyphenylene sulfide; based on the mass of the primary low-melting-point sheath-core fiber as 100 parts, the mass ratio of the sheath fiber to the core layer fiber (sheath-core ratio) is 20-40:60-80.

[0017] Preferably, the polyolefin includes one or more of PE and PP; the polyester includes one or more of PET, PBT, PTT, HSPET, and ECDP; and the polyamide includes one or more of PA6, PA66, PA56, and PA510.

[0018] Furthermore, the curl shrinkage rate of the low-melting-point core-sheath fiber with high curl shrinkage rate and good bulkiness ranges from 8% to 28%.

[0019] Furthermore, the curl shrinkage rate of the low-melting-point core-sheath fiber with high curl shrinkage rate and good bulkiness ranges from 9% to 18%.

[0020] The present invention also provides a method for preparing the low-melting-point core-skin fiber with high curl shrinkage and good bulkiness, comprising the following steps:

[0021] S1, using a composite spinning manifold sheath-core composite component to prepare the primary low-melting-point sheath-core fiber;

[0022] S2, the nascent low-melting-point sheath-core fiber is stretched and shaped by multiple pairs of hot rollers to obtain stretched low-melting-point sheath-core fiber;

[0023] S3, the low-melting-point core-sheath fiber after stretching enters the puffing deformation device, and is puffed and deformed through the puffing nozzle to obtain the low-melting-point core-sheath fiber with high curling shrinkage and good fluffiness.

[0024] Furthermore, in step S2, the plurality of pairs of hot rollers are arranged in the stretching and shaping device of the BCF.

[0025] Furthermore, in step S2, the drawing temperature is higher than the glass transition temperature of the core fiber; and in step S3, the expansion deformation temperature is within a range of 75 to 200°C.

[0026] Furthermore, in step S3, the temperature of the expansion deformation is within a range of 95 to 180°C.

[0027] Furthermore, in step S2, the difference between the drawing temperature and the glass transition temperature of the core fiber is 5-50°C.

[0028] Furthermore, in step S2, the difference between the drawing temperature and the glass transition temperature of the core fiber is within a range of 10 to 26°C.

[0029] Furthermore, in step S3, the expansion deformation temperature is higher than the glass transition temperature of the core fiber.

[0030] Furthermore, under the condition of ensuring no adhesion, the higher the shaping temperature in step S2, the lower the boiling water shrinkage of the low-melting-point core-sheath fiber with high curl shrinkage and good bulkiness.

[0031] Furthermore, after the primary low-melting-point core-sheath fiber is stretched and shaped, the softening point temperatures of the core fiber and the sheath fiber are both increased.

[0032] Furthermore, in the primary low-melting-point sheath-core fiber, the material of the sheath fiber is polyolefin, and the material of the core fiber is polyolefin.

[0033] Furthermore, when the material of the skin fiber is polyolefin and the material of the core fiber is polyolefin, the expansion deformation temperature in step S3 is not higher than or slightly higher than the softening point temperature of the skin fiber.

[0034] Furthermore, in the primary low-melting-point sheath-core fiber, the material of the sheath fiber is polyester or polyamide, and the material of the core fiber is polyester or polyamide.

[0035] Furthermore, when the material of the skin layer fiber is polyester or polyamide and the material of the core layer fiber is polyester or polyamide, the temperature of the expansion deformation in step S3 is higher than the glass transition temperature of the core layer fiber.

[0036] Furthermore, in step S3, the speed of the puffing deformation is 1800-2800 m / min.

[0037] The present invention also provides an application of the low-melting-point core-skin fiber with high curling shrinkage and good bulkiness, which is used to prepare one or more of a fiber volatile rod, a fiber pen tip, a fiber filter material, a fiber water guide rod, and a fiber water absorption rod.

[0038] Furthermore, the fiber volatilization stick includes a perfume stick or an aromatherapy stick, and the fiber filter material includes a filter disc, a filter element or a filter tube.

[0039] The present invention utilizes a composite spinning box for spinning low-melting-point sheath-core fibers grafted with a BCF stretching and bulking device to prepare sheath-core fibers, and its advantages are: in the BCF stretching and bulking device of the present invention (including a BCF stretching and shaping device and a BCF bulking device), not only the heat released during the orientation crystallization of the stretched low-melting-point sheath-core fibers and the waste heat of the stretching and shaping rollers can maintain a relatively high temperature of the fibers entering the bulking device, but also the high-temperature and high-pressure compressed air is used to spray the hot-stretched filament bundle into the deformation blade chamber at high speed through the bulking nozzle, and each single filament in the filament bundle is in full contact with the high-temperature compressed air, and the heat transfer efficiency is high. Therefore, the present invention does not need to significantly increase the temperature of the first hot box like the texturing machine in the POY-DTY process to ensure that the sheath and core materials are above the glass transition temperature, and good expansion deformation conditions can be obtained. At the same time, it is not necessary to significantly increase the deformation temperature like the texturing machine, and the low-melting-point sheath material of the low-melting-point sheath-core structure is also protected.

[0040] A further advantage is that under the condition that the melting points of the skin material and the core material are greatly different, the skin material and the core material can be of the same type, or different types of materials can be selected according to actual needs, such as polyolefins (such as PE, PP), polyesters (such as PET, PBT, PTT, HSPET, ECDP, etc.), polyamides (such as PA6, PA66, PA56, PA510, etc.), and any combination of similar or different types of materials such as polylactic acid, polyurethane, and polyphenylene sulfide.

[0041] The present invention utilizes a composite spinning box for spinning low-melting-point sheath-core fibers grafted with a BCF stretching and puffing device to prepare sheath-core fibers, and has the advantages of utilizing the puffing nozzle of the BCF stretching and puffing device to heat and prepare air-deformed fibers, without the need to set the temperature of the stretching hot roller, and the puffing and deformation temperature being much higher than the glass transition temperature of the core layer material to ensure the puffing and curling of the fibers, and to avoid the adhesion of the filament bundles, thereby ensuring the fluffiness of the product; the fluffiness of the product can even be ensured when the melting points of the sheath and core layer materials are quite different.

[0042] It is worth mentioning that the nascent low-melting-point core-skin fiber of the present invention is first stretched and shaped before BCF expansion. During the stretching process, the macromolecules of the low-order region (i.e., the amorphous region for crystalline polymers) of the low-melting-point core-skin fiber change along the fiber axis, such as the degree of orientation and crystallinity, and the like, along with the increase in the softening point temperature. Therefore, the nascent low-melting-point core-skin fiber after stretching and shaping has a high degree of orientation crystallinity and can withstand a high expansion temperature to obtain good fiber fluffiness. Moreover, the hot roller stretching of the BCF stretching and expanding equipment of the present invention avoids the problem of too low stretching multiples, resulting in unstretched parts, and low curl shrinkage due to the long distance between the stretching gripping points of the texturizing machine. Therefore, the low-melting-point core-skin fiber with high curl shrinkage and good fluffiness obtained by stretching and shaping before BCF expansion deformation has a high fiber curl shrinkage, good curl stability, and low boiling water shrinkage.

[0043] For a series of fiber-forming polymers, effective stretching can be performed as long as the fiber temperature is higher than the glass transition temperature. However, for olefin fiber-forming polymers (such as PE and PP), since there are only C and H in the molecular chain, the distance between molecules is relatively close, the force between molecular chains is relatively large, and the molecular chains are relatively regular, causing entanglement with each other. Therefore, the stretching of olefin fibers needs to be much higher than its glass transition temperature to fully activate its molecular chains for stretching. However, the stretching process of all fibers should try to avoid staying at a temperature higher than its softening point for too long to avoid adhesion between fibers. In the present invention, the hot roller only plays a stretching role. The contact time of the filaments on the hot roller is increased by winding around it, so the temperature of the hot roller only needs to be higher than the glass transition temperature. However, when the filaments are falsely twisted by the texturing machine, since the first hot box is shorter, the temperature of the hot box needs to be set relatively high to make the temperature of the filaments higher than the glass transition temperature of the fiber, so as to successfully complete the stretching. While stretching, the filaments obtain the twist transmitted by the false twister. The higher the fiber temperature, the better the plasticization effect and the easier it is to twist and obtain fluffiness. Therefore, in order to obtain better fluffiness, the temperature of the first hot box is usually set much higher than the glass transition temperature of the core fiber, and the higher the temperature of the first hot box, the better the fluffiness. The present invention does not need to significantly increase the stretching temperature like the texturing machine, and also protects the low-melting-point skin material of the low-melting-point skin-core structure.

[0044] In summary, by using the method of the present invention to prepare low-melting-point sheath-core fibers with high curl shrinkage and good bulkiness, the difference in melting points between the sheath material and the core material can be greater.

[0045] In addition, the fiber required for the subsequent process of preparing the fiber is untwisted filament, and in the two-step POY-DTY process, the DTY after false twisting by the texturing machine through the twist transmitted by the false twister has residual torque, so only by S twisting and Z twisting two fibers in opposite directions can the residual torque be eliminated, which also causes waste of POY and reduced production efficiency, and it is also easy to produce waste products caused by only one fiber still being wound after one of them is broken during false twisting; and the storage environment and time of the low-melting-point core-skin fiber POY will affect the indicators of the final product in the subsequent process. The present invention can obtain a stable untwisted product through the one-step production of spinning-stretching-setting-bulking-winding by BCF production equipment, without residual torque, and easy to process; the one-step method can also effectively avoid the disadvantages of the two-step POY-DTY process, and well reduce and control the oil content of the product.

[0046] Regarding the low-melting-point core-sheath fiber with high curling shrinkage and good bulkiness of the present invention, there is no residual torque: the expansion is carried out by means of a high-speed jet airflow at the upper part of the nozzle wire guide tube. At the same time, due to the sharp drop in the flow velocity inside and outside the lower tube of the nozzle wire guide tube, the overflow of the hot fluid causes a rapid stall, causing the filaments to relax sharply; and then due to the combined effects of turbulence and vortex caused by the jet airflow, the filaments are curled in three dimensions; at the same time, due to the overflow force of the jet flow, the filaments are pressed against the tube wall to form a wire plug, and after sufficient cooling, the curled fibers are shaped, thereby making high-bulky expanded deformed filaments. It can be seen that the low-melting-point core-sheath fiber with high curling shrinkage and good bulkiness of the present invention does not have twist.

[0047] The present invention realizes one-step production, adopts a puffing device that introduces hot air to puff the fibers, has high efficiency, and can realize the production of a bundle of fibers with a specification of up to more than 3,000 deniers. Compared with the single-spindle fiber bundle fineness not exceeding 450 deniers in the POY-DTY process, the production efficiency of the present invention is significantly improved.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1) There is no technology that combines low-melting-point sheath-core fiber with "composite spinning-BCF stretching and bulking" to produce low-melting-point sheath-core fiber with high curl shrinkage and good bulkiness. The present invention fills this technical gap.

[0050] 2) The present invention utilizes the puffing nozzle and heated air of the BCF stretching puffing equipment to prepare deformed low-melting-point sheath-core fibers. When the melting points of the sheath layer and the core layer differ greatly, the curling shrinkage rate and the fluffiness of the low-melting-point sheath-core fibers with high curling shrinkage rate and good fluffiness are still guaranteed. Therefore, compared with the POY-DTY process for preparing DTY with a texturizing machine, the range of materials that can be selected for the sheath and core layers of the nascent low-melting-point sheath-core fibers used in the present invention is wider.

[0051] 3) The primary low-melting-point core-skin fiber of the present invention is first subjected to heat stretching and shaping before BCF expansion; and compared with the preparation of DTY with a texturing machine (problems with the stretching gripping point may cause part of the fiber to not be stretched), the low-melting-point core-skin fiber with high curl shrinkage and good bulkiness of the present invention has better oriented crystallinity and can withstand high temperature expansion deformation, so that the final fiber has high curl shrinkage and good bulkiness.

[0052] 4) The fiber used as the front-end raw material of the rod needs to be twist-free. The traditional technology adopts the stretching false twist route of the texturing machine to prepare DTY, which requires two fibers to be S-twisted and Z-twisted and then plied, which will cause low production efficiency, waste of raw fibers, and storage affecting product quality. The preparation method of the low-melting-point core-skin fiber with high curl shrinkage and good fluffiness of the present invention adopts a one-step method, which is more stable than the product using the two-step POY-DTY process, while improving product quality and production efficiency and saving costs.

[0053] 5) At the same time, compared with the preparation of DTY by a texturing machine, the preparation method of the present invention uses a BCF stretching and bulking device to significantly improve the production fineness, thereby greatly improving the production efficiency.

[0054] 6) The low-melting-point sheath-core fiber obtained by the present invention has a high curling shrinkage rate, good fluffiness and uniformity, and can conveniently allow customers to obtain terminal rod products with controllable fiber gaps by adjusting different hot-melt processing temperatures. The water absorption and volatility are more stable, and the performance is more stable. It can be used to prepare fiber volatile rods, fiber pen tips, fiber filter materials, fiber water-drawing rods or fiber water-absorbing rods, and its effect is significantly improved. DETAILED DESCRIPTION

[0055] To make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments. Unless otherwise specified, the materials used in the following examples are all commercially available products.

[0056] The BCF production equipment used in the following Examples 1, 3, 4, and 6 is a composite spinning beam grafted BCF stretching and bulking equipment (including a BCF stretching and shaping device and a BCF bulking device), manufactured by Truetzschler, model MO40-04HP-C. Other commercially available BCF production equipment is also applicable.

[0057] Example 1

[0058] The dried PP and PE slices are heated and melted by their respective screws and then enter the composite spinning box. After being accurately metered by the melt metering pump (the skin-core ratio is 30:70), they enter the skin-core composite assembly, are ejected from the spinneret, cooled by side blowing, and then stretched and shaped by multiple pairs of hot rollers. They enter the BCF puffing device and use the high-temperature compressed air and the full contact heat transfer of the filament bundle. By adjusting the process, low-melting-point skin-core fibers with high curling shrinkage and good fluffiness can be obtained. Among them, the melting point of the skin layer PE is 120℃, the melting point of the core layer PP is 170℃, the puffing temperature is 98~110℃, and the puffing production speed can reach 2400m / min.

[0059] Example 2

[0060] Take the PE / PP sheath-core POY (sheath-core ratio is 30:70) that has not been stretched and fixed after the composite box is produced, and use the texturing machine to stretch and false twist. When passing through the first hot box, the PE is already sticky and cannot be false twisted. Among them, the melting point of the skin PE is 120℃, the temperature of the first hot box of the texturing machine is 110℃, the length of the first hot box is generally not more than 3m, and the texturing production speed is 200m / min. When the hot box temperature is reduced to 90℃, the fiber is basically not sticky, but the fluffiness of the processed fiber is extremely poor.

[0061] Example 3

[0062] The dried low-melting-point polyester modified for the skin layer (melting point 130℃) and the ordinary PTT polyester selected for the core layer (melting point 228℃) are heated and melted by their respective screws and then enter the composite spinning box. After being accurately metered by the melt metering pump (the skin-core ratio is 40:60), they enter the skin-core composite assembly, are ejected from the spinneret, cooled and oiled by side blowing, and then stretched and shaped by multiple pairs of hot rollers. They enter the BCF puffing device and are puffed by the full contact heat transfer between the high-temperature compressed air and the filament bundle. By adjusting the process, low-melting-point skin-core fibers with high curling shrinkage and good bulkiness can be obtained. Among them, the puffing temperature is 95-110℃, and the puffing production speed can reach 2000m / min.

[0063] The parameters of the preparation methods of Examples 1 to 3 are shown in Table 1.

[0064] The sheath-core fibers obtained in Examples 1 to 3 were tested for crimp shrinkage according to the test standard in the test method for crimp performance of synthetic fiber textured yarn GB / T6506-2017, and the test results are shown in Table 1. In Table 1, the softening point temperature is indicated for PE and PP, and the glass transition temperature is indicated for polyester according to the general marking method.

[0065] Table 1

[0066]

[0067] As can be seen from Table 1, different deformation processes are used in Example 1 and Example 2 for preparing PE / PP low melting point sheath-core fibers, and Example 3 for preparing 130°C low melting point sheath-core fibers, and the effects are significantly different. Example 1 and Example 3 can obtain low melting point sheath-core fibers with good fluffiness by using the preparation method of the present invention; Example 2 cannot complete false twist deformation by using a texturing machine, and the analysis is as follows:

[0068] 1) For the PE / PP low melting point sheath-core fiber of Example 2, even if the production speed of the texturing machine is reduced to 200 m / min, the time for the tow to pass through the hot box is only about 1.5 seconds. Therefore, the temperature of the first hot box needs to be not less than 140°C to make the core layer PP fiber reach the condition for stretching and false twisting. However, since the melting point of the sheath PE is about 120°C, and the fiber is not stretched and shaped, the softening point temperature is lower and it is easier to be sticky; in Example 2, the conventional texturing machine uses a hot box temperature control temperature of low-temperature biphenyl set to 110°C. At this time, when the tow passes through the first hot box, the sheath PE is already sticky (the melting point of the sheath PE is about 120°C), and the temperature of the core material of the tow at this temperature cannot reach effective stretching and false twisting. Even if the first hot box is subsequently modified to reduce the hot box temperature to ensure that the fiber is not sticky, the fiber is basically not fluffy.

[0069] Therefore, the PE / PP low-melting-point core-skin fiber of Example 2 cannot be effectively false-twisted on the texturing machine, while Example 1 of the same material using the preparation method of the present invention does not affect the deformation effect even if the expansion deformation temperature reaches 110°C. Example 1 can obtain a low-melting-point core-skin fiber with good fluffiness.

[0070] 2) The 130°C low melting point sheath-core fiber of Example 3 can be expanded and deformed according to the method of the present invention, but if it is according to the method of Example 2, it cannot be effectively false-twisted on the texturing machine.

[0071] Based on the above analysis, compared with the preparation method using a texturing machine (Example 2), the melting point difference between the sheath and the core layer of the primary low-melting-point sheath-core fiber in the method of the present invention (Examples 1 and 3) can be larger; at the same time, the primary low-melting-point sheath-core fiber in the method of the present invention (Examples 1 and 3) is first subjected to heat stretching and shaping before expansion deformation, so that it has better oriented crystallinity and can withstand expansion deformation at higher temperatures, so that the final fiber has a high curling shrinkage rate and good fluffiness.

[0072] Example 4

[0073] The dried 160℃ low-melting polyester modified for the skin layer and the ordinary PET slices (melting point 260℃) selected for the core layer are heated and melted by their respective screws and then enter the composite spinning box. After being accurately metered by the melt metering pump (the skin-core ratio is 35:65), they enter the skin-core composite assembly, are ejected from the spinneret, cooled and oiled by side blowing, and then stretched and shaped by multiple pairs of hot rollers. They enter the BCF puffing device and are puffed by the full contact heat transfer between the high-temperature compressed air and the filament bundle. By adjusting the process, low-melting-point skin-core fibers with high curling shrinkage and good bulkiness can be obtained. Among them, the puffing temperature is 135-145℃ and the production speed is 2400m / min.

[0074] Example 5

[0075] Take the unstretched 160℃ low-melting point polyester fiber sheath-core POY (skin-core ratio is 35:65) produced by the composite box, the core layer is also made of ordinary PET (melting point 260℃), the sheath modified low-melting point polyester has a melting point of 160℃, and is stretched and false-twisted using a texturing machine. When the temperature of the first hot box is higher than 125℃, stickiness occurs. At this temperature, the core material temperature of the filament bundle cannot completely reach above the glass transition temperature, and the processed fiber has basically no fluffiness.

[0076] Example 6

[0077] The dried skin modified 220℃ low melting point polyester and the ordinary PET slices (melting point 260℃) selected for the core layer are heated and melted by their respective screws and enter the composite spinning box. After being accurately metered by the melt metering pump (the skin-core ratio is 35:65), they enter the skin-core composite assembly, are ejected from the spinneret, cooled and oiled by side blowing, and then stretched and shaped by multiple pairs of hot rollers. They enter the BCF expansion device and expand by using the high-temperature compressed air and the full contact heat transfer of the filament bundle. By adjusting the process, low-melting point skin-core fibers with high curling shrinkage and good fluffiness can be obtained. Among them, the expansion temperature is 165-180℃, and the production speed can reach 2600m / min.

[0078] Example 7

[0079] The unstretched low-melting-point polyester fiber sheath-core POY (sheath-core ratio is 25:75) that has passed through the composite box is taken. The core layer is made of ordinary PET (melting point 260℃), and the sheath is modified low-melting-point polyester with a melting point of 220℃. The product is stretched and false-twisted using a texturing machine to ensure that the product has normal fluffiness under non-sticky process conditions.

[0080] The parameters of the preparation methods of Examples 4 to 7 are shown in Table 2.

[0081] The sheath-core fibers obtained in Examples 4 to 7 were tested for curl shrinkage (refer to the test standard GB / T6506-2017 for the test method for curling performance of synthetic fiber textured yarns). The test results are shown in Table 2 below.

[0082] Table 2

[0083]

[0084]

[0085] It can be seen that the preparation examples 4, 5, 6 and 7 of the low melting point sheath-core fiber use different deformation processes on the basis of using ordinary PET as the POY core material, and the effects are significantly different. The analysis is as follows:

[0086] In Example 5, the sheath has a low melting point (160°C) because the elastic false twisting method is adopted, and because the POY has not been stretched, the fiber orientation crystallinity is low, and thus the softening point temperature is still low, which limits the increase in the temperature of the first hot box, and a fluffy low-melting sheath-core fiber cannot be obtained by stretching and false twisting. In Example 7, although the melting point of the sheath PET is relatively high (220°C), the POY has not been stretched and shaped, and the fiber orientation and crystallinity are low, so the softening point temperature is still low, making it impossible to increase the temperature of the first hot box to the optimal stretching and false twisting temperature of the core layer material when the filament bundle passes through the hot box, resulting in the product DTY not being very ideal in terms of bulkiness.

[0087] Compared with Example 7, Example 6 uses the same material but can obtain fibers with higher curl shrinkage and better bulkiness. It can be seen that the method of the present invention can prepare low-melting-point core-skin fibers with high curl shrinkage and good bulkiness. From the analysis of the difference in melting points of the cortex and core layers, Example 4 and Example 5 use the same material, and the difference in melting points of the cortex and core also reaches 100°C, but the method of Example 4 can obtain low-melting-point core-skin fibers with high curl shrinkage and good bulkiness, indicating that compared with the existing preparation method, the method of the present invention can use cortex and core materials with a larger difference in melting points to prepare low-melting-point core-skin fibers with high curl shrinkage and good bulkiness.

[0088] In summary, compared with the preparation method using a texturing machine (Examples 5 and 7), the melting point difference between the sheath and the core layer of the primary low-melting-point sheath-core fiber in the method of the present invention (Examples 4 and 6) can be larger; at the same time, the primary low-melting-point sheath-core fiber in the method of the present invention (Examples 4 and 6) is first subjected to heat stretching and shaping before expansion deformation, so that it has better oriented crystallinity and can withstand expansion deformation at higher temperatures, so that the final fiber has a high curling shrinkage rate and good fluffiness.

[0089] The above disclosure is only the preferred embodiment of the present invention, which cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A low melting point core-skin fiber with high crimp shrinkage and good bulkiness, characterized in that: The low-melting-point core-skin fiber with high curl shrinkage and good bulkiness is obtained by subjecting the primary low-melting-point core-skin fiber to expansion deformation using hot air in an expansion deformation device.

2. The low melting point core-skin fiber with high crimp shrinkage and good bulkiness according to claim 1, characterized in that: The device for bulking and deforming has a bulking nozzle; the primary low-melting-point sheath-core fiber is stretched and shaped before the bulking and deformation.

3. The low melting point core-skin fiber with high crimp shrinkage and good bulkiness according to claim 1, characterized in that: The primary low-melting-point core-skin fiber consists of a core fiber and a skin fiber; the melting point of the core fiber is higher than the melting point of the skin fiber.

4. The low melting point core-skin fiber with high crimp shrinkage and good bulkiness according to claim 3, characterized in that: The difference between the melting point of the core layer fiber and the melting point of the sheath layer fiber is 25-120°C.

5. The low melting point core-skin fiber with high crimp shrinkage and good bulkiness according to claim 3, characterized in that: The material of the core layer fiber includes one or more of polyolefins, polyesters, polyamides, polylactic acid, polyurethanes, and polyphenylene sulfide; the material of the sheath fiber includes one or more of polyolefins, polyesters, polyamides, polylactic acid, polyurethanes, and polyphenylene sulfide; based on 100 parts of the mass of the primary low-melting-point sheath-core fiber, the mass ratio of the sheath fiber to the core layer fiber is 20-40:60-80.

6. The low melting point core-skin fiber with high crimp shrinkage and good bulkiness according to claim 5, characterized in that: The polyolefin includes one or more of PE and PP; the polyester includes one or more of PET, PBT, PTT, HSPET, and ECDP; and the polyamide includes one or more of PA6, PA66, PA56, and PA510.

7. The low melting point core-skin fiber with high crimp shrinkage and good bulkiness according to claim 1, characterized in that: The curl shrinkage rate of the low-melting-point core-sheath fiber with high curl shrinkage rate and good bulkiness ranges from 8% to 28%.

8. A method for preparing a low melting point core-skin fiber with high curl shrinkage and good bulkiness as claimed in claim 3, characterized in that: The steps include: S1, using a composite spinning manifold sheath-core composite component to prepare the primary low-melting-point sheath-core fiber; S2, the nascent low-melting-point sheath-core fiber is stretched and shaped by multiple pairs of hot rollers to obtain stretched low-melting-point sheath-core fiber; S3, the low-melting-point core-sheath fiber after stretching enters the puffing deformation device, and is puffed and deformed through the puffing nozzle to obtain the low-melting-point core-sheath fiber with high curling shrinkage and good fluffiness.

9. The method for preparing the low melting point core-skin fiber with high crimp shrinkage and good bulkiness according to claim 8, characterized in that: In step S2, the drawing temperature is higher than the glass transition temperature of the core fiber; in step S3, the expansion deformation temperature is within a range of 75 to 200°C.

10. An application of the low melting point core-skin fiber with high crimp shrinkage and good bulkiness according to any one of claims 1 to 7, characterized in that: It is used to prepare one or more of fiber volatilization sticks, fiber pen tips, fiber filtering materials, fiber water-drawing sticks, and fiber water-absorbing sticks.

Images