Preparation method of plateau fibrillated Lyocell fiber

Abstract

The invention discloses a preparation method of plateau fibrillated Lyocell fibers, and belongs to the technical field of cellulose fiber preparation. The preparation method comprises the following steps: step SS1: adding propyl gallate, a crystallization promoting agent and a delustering agent into a solvent NMMO with the mass concentration of 65 + / -5%, and stirring and dispersing to obtain a mixture A; step SS2, adding wood pulp into the mixture A, and stirring to obtain a mixture B; step SS3, heating the mixture B, and carrying out reduced pressure evaporation dehydration until the cellulose is completely dissolved, so as to obtain a spinning solution with the cellulose concentration of 7-11wt%; and step SS4, extruding the spinning solution from the spinneret plate, cooling in a coagulating bath, drafting and forming to obtain the plateau fibrillated Lyocell fiber. According to the preparation method of the plateau fibrillated Lyocell fiber, the technical problems that plateau fibrillated fabric is tedious in processing flow, long in processing time, serious in scratching and large in influence on fabric quality are effectively solved.

Description

Technical Field

[0001] The invention relates to a method for preparing high-altitude fibrillated Lyocell fibers, belonging to the technical field of cellulose fiber preparation. Background Art

[0002] Lyocell fiber is made from renewable resources such as wood and bamboo, and non-toxic organic solvent N-methylmorpholine-N-oxide (NMMO) is used as solvent through dry-jet wet spinning process. Lyocell fiber has the characteristics of high dry and wet strength, high modulus, low elongation, high hygroscopicity, good antistatic property, softness, easy biodegradability, etc., and is known as the green fiber of the 21st century.

[0003] Lyocell fiber has a characteristic that cannot be ignored, namely, the fibrillation phenomenon. Most fibers will undergo fibrillation, but some are serious, some are mild, some are easy to be seen in daily life and usage scenarios, and some are not easy to be seen. Because Lyocell fibers are highly oriented in the axial direction, and the transverse bonding effect of the fibrils is relatively poor, when the cellulose in the non-crystalline or amorphous region of the fiber absorbs a large amount of water and swells highly, some hydrogen bonds are destroyed, making its transverse bonding force weaker; coupled with the effect of continuous friction, the cortical fibers are very easy to fall off, and the fibrils are split into ultra-fine fibers of 1 to 4 μm in the longitudinal direction. Fibrillation was once considered by consumers to be a defect of the fiber, but with the in-depth research of researchers and textile industry-related companies on the fibrillation of Lyocell fibers, it is now gradually recognized as a major advantage in specific application fields. When the fibrils and the main fibers maintain a strong bond, end products with multiple functional effects such as high strength, low air resistance, and high water-absorbing particles can be produced.

[0004] The fibrillation of Lyocell fiber can be used to develop diversified products, expand the application field of Lyocell fiber, and increase the added value of Lyocell fiber products. By regulating the fibrillation during the manufacturing and processing of Lyocell fiber, many unexpected advantages can be brought, such as improving the surface effect of the fabric to prepare peach skin fabric, spunlace fabric with excellent filtration effect, battery separator and absorbent pad, etc.

[0005] At present, there are many studies on the anti-fibrosis of Lyocell fibers, but few studies on high-grade fibrosis Lyocell fibers. There is no patent published report on the preparation method of high-grade fibrosis Lyocell fibers.

[0006] Invention patent CN201210528630.7 discloses a processing method for ultra-soft home textile fabrics, which uses a special dyeing and finishing process to open the fibers multiple times, controls the fibrillation of Tencel to obtain a short-pile effect, and uses enzyme treatment to remove the fibrillation to obtain a short-pile effect, thereby obtaining an ultra-soft home textile fabric.

[0007] Invention patent CN202110655043.3 discloses a method for preparing lyocell peach skin fabric, which takes a woven fabric containing lyocell fiber as the grey cloth, and prepares the lyocell peach skin fabric through a process of singeing, desizing, bleaching, dyeing, stretching, alkali washing, enzyme washing and water washing.

[0008] The document "Preparation and Properties of High-Level Fibrillation Lyocell Fibers—(I) Effect of the Mass Fraction of NaOH Solution as Swelling Agent" uses NaOH solution as swelling agent to infiltrate conventional Lyocell fibers, and uses ultrasonic oscillation to prepare Lyocell fibers with different fibrillation degrees. The document "Preparation of High-Level Fibrillation Lyocell Fibers" uses sodium hypochlorite (NaClO) solution as oxidant, and uses steaming to prepare Lyocell fibers with different fibrillation degrees. Both of them are post-processed conventional Lyocell fibers to prepare high-level Fibrillation Lyocell fibers.

[0009] The above patented technology is to weave conventional Lyocell fibers into fabrics, and then achieve the high plateau fiberization effect of Lyocell fabrics through a series of finishing processes such as bleaching, alkali washing, and enzyme washing. However, there are problems such as long processing time, severe abrasions, and great impact on fabric quality. Summary of the invention

[0010] The object of the present invention is to overcome the technical defects existing in the prior art, effectively solve the problems of cumbersome processing flow, long processing time, serious abrasion, great impact on fabric quality, etc. of high-altitude fibrillation fabric, and propose a preparation method of high-altitude fibrillation Lyocell fiber, add a crystallization promoter in the spinning solution, accelerate the crystallization rate of microfibrils, make microfibrils grow rapidly into giant fibrils, and then make the crystal structure of fiber macromolecules rapidly perfect, and improve the crystallinity of Lyocell fiber. In addition, the crystallization promoter itself does not contain hydrogen bonds, which can effectively reduce the hydrogen bonding between adjacent cellulose macromolecules, making the lateral binding force of the fiber weaker. In addition, adding a nano-scale matting agent to the spinning solution plays a ball effect. During the rubbing and beating process, the ball sliding promotes the separation of microfibrils, which is more conducive to the high-altitude fibrillation of Lyocell fiber.

[0011] The present invention specifically adopts the following technical scheme: a method for preparing high-altitude fibrosis Lyocell fiber, comprising the following steps:

[0012] Step SS1: adding propyl gallate, a crystallizing agent and a matting agent into a solvent NMMO having a mass concentration of 65±5%, stirring and dispersing the mixture to obtain a mixture A;

[0013] Step SS2: adding wood pulp to mixture A and stirring to obtain mixture B;

[0014] Step SS3: Mixture B is heated and dehydrated by evaporation under reduced pressure until the cellulose is completely dissolved, thereby obtaining a spinning solution with a cellulose concentration of 7 to 11 wt %;

[0015] Step SS4: The spinning solution is extruded from the spinneret, cooled in a coagulation bath and stretched to obtain high-altitude fiberized Lyocell fibers.

[0016] As a preferred embodiment, the amount of the crystallization agent added in step SS1 is 0.1 to 3 wt % of the mass of the wood pulp.

[0017] As a preferred embodiment, the crystallization agent is at least one of polylactic acid, polycaprolactone, polypropylene carbonate, and polyethylene carbonate.

[0018] As a preferred embodiment, the amount of matting agent added in step SS1 is 0.1-2 wt % of the mass of wood pulp.

[0019] As a preferred embodiment, the matting agent is at least one of nano-sized white carbon black, barium sulfate, and titanium dioxide.

[0020] As a preferred embodiment, the mass ratio of wood pulp to NMMO solution in step SS2 is 1:10-15.

[0021] As a preferred embodiment, the premixing time in step SS2 is 40 to 60 minutes, and the premixing temperature is 70 to 100°C.

[0022] As a preferred embodiment, in step SS3, the dehydration temperature is 90-120° C., the dehydration pressure is -0.1 MPa, and the dehydration time is 90-180 minutes.

[0023] As a preferred embodiment, in the step SS4, the spinning speed of the spinning solution extruded from the spinneret is 20-60 m / min, and the spinning temperature is 90-110°C.

[0024] As a preferred embodiment, the NMMO concentration in the coagulation bath in step SS4 is 10-25%.

[0025] The beneficial effects achieved by the present invention are as follows: First, the method of the present invention is to add a crystallization promoter to the spinning solution to accelerate the crystallization rate of microfibrils, so that the microfibrils can quickly grow into macrofibrils, and then the crystal structure of the fiber macromolecules can be quickly improved, thereby improving the crystallinity of the Lyocell fiber. In addition, the crystallization promoter itself does not contain hydrogen bonds, which can effectively reduce the hydrogen bonding between adjacent cellulose macromolecules, weaken the lateral bonding force of the fiber, and is beneficial to the fibrillation of the Lyocell fiber. Second, the nano-scale matting agent added to the spinning solution plays a ball effect. During the rubbing and beating process, the ball sliding promotes the separation of microfibrils, which is beneficial to the fibrillation of the Lyocell fiber. In addition, appropriately increasing the coagulation bath concentration and the spinning speed during the spinning process can improve the orientation of the amorphous region of the Lyocell fiber, which is also beneficial to obtaining high-fibrillation Lyocell. Third, the present invention relates to a method for preparing a highly fibrillated Lyocell fiber, comprising: firstly adding propyl gallate, a crystallizing agent, and a matting agent into a solvent NMMO and stirring and mixing, then adding wood pulp into the mixture for premixing, heating, and evaporating under reduced pressure to completely dissolve the cellulose, and obtaining a spinning solution. The spinning solution is subjected to a dry-jet wet spinning process to obtain Lyocell fibers, and an ultrasonic oscillation method is used to observe the fibrillation effect of the Lyocell fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the topology of the ultrasonic treatment device of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0028] Example 1

[0029] A mixture A was obtained by adding a crystallization agent (0.5% by weight of wood pulp) and a matting agent (0.3% by weight) to a solvent NMMO (60% by weight), and stirring and dispersing the mixture.

[0030] The wood pulp was mixed with the above mixture A at a ratio of 1:10 to obtain mixture B, with a premixing temperature of 70-80°C.

[0031] The spinning solution with a cellulose concentration of about 12% is obtained by negative pressure dehydration at 90-110°C. The spinning solution is extruded through a spinneret to form a spinning stream. The spinning stream enters a coagulation bath for cooling, and is washed, drawn, oiled, and dried to obtain a high-grade lyocell fiber. In this step, the spinning speed is 20 m / min, the coagulation bath concentration is 10%, and the coagulation bath temperature is 20°C.

[0032] Example 2

[0033] Based on Example 1, this example is different from Example 1 in that the amount of the crystallization agent added is 1 wt% of the mass of the wood pulp. Other process conditions and equipment used are the same as those in Example 1 and will not be described again.

[0034] Example 3

[0035] Based on Example 1, this example is different from Example 1 in that the amount of the crystallization agent added is 1.5 wt % of the mass of the wood pulp. Other process conditions and equipment used are the same as those in Example 1 and will not be described in detail here.

[0036] Comparative Example 1

[0037] On the basis of Example 1, this comparative example is compared with Example 1, except that no crystallization promoter and matting agent are added to the NMMO solution, and other process conditions and equipment used are consistent with Example 1, which will not be repeated here.

[0038] Comparative Example 2

[0039] On the basis of Example 2, this comparative example is compared with Example 2, except that the spinning speed is 40 m / min, and the other process conditions and equipment used are consistent with Example 1, which will not be repeated here.

[0040] Comparative Example 3

[0041] On the basis of Example 3, this comparative example is compared with Example 3, except that the spinning speed is 40 m / min, the coagulation bath concentration is 20%, and the other process conditions and equipment used are consistent with Example 1, which will not be repeated here.

[0042] There is no recognized standard method for measuring and characterizing fibrillation, but it is usually measured by the fibrillation index. The following is a common method for characterizing the fibrillation index. Figure 1 .

[0043] 1-2 mg of Lyocell fiber about 38 mm long was immersed in a glass vial filled with distilled water, and the ultrasonic probe was inserted into the center of the vial, with the end of the probe 10±1 mm away from the bottom of the vial. The vial was placed in an ice water bath and treated with a BILON-XCF500 ultrasonic disperser for 30 min at a power of 300 W. The ultrasonically treated fiber was placed under a microscope, and micrographs of representative areas of the sample were taken. The fibrillation index of the fiber can be calculated according to the micrographs as shown in Table 1.

[0044]

[0045] Where: F——fibrillation index;

[0046] L——Fiber segment length, in mm

[0047] li——length of the ith fibril, in mm.

[0048] Table 1

[0049]

[0050] The following conclusions can be drawn from the above results.

[0051] 1. By comparing Examples 1, 2, and 3 with Comparative Example 1, it can be seen that after adding a crystallization promoter to the spinning solution, the dry breaking strength of the Lyocell fiber increases. This is because the crystallization promoter is beneficial to the growth of the longitudinal and transverse grain size of the Lyocell fiber, allowing the microfibrils to develop quickly and well, thereby improving the crystallinity of the fiber. As the crystallinity of the Lyocell fiber increases, the tensile strength of the fiber increases, but its lateral effect weakens. The added matting agent also reduces the effect of adjacent hydrogen bonds of the molecular chain to a certain extent, making its lateral effect weaker. The ball sliding effect under wet friction makes the fiber more prone to fibrillation, and the fibrillation index increases significantly.

[0052] 2. By comparing Example 2 and Comparative Example 2, it can be seen that: with the increase of spinning speed, the tensile strength of the fiber increases. This is because the resistance of the filament bundle in the coagulation bath increases, the tension on the filament bundle increases, and the cellulose macromolecules are further stretched and oriented, especially the molecular chains in the amorphous region are more regularly arranged along the axial direction, the entanglement between the molecular chains is reduced, and the hydrogen bonding effect of the molecular chains is weakened, so that the microfibrils are easier to be peeled out and the fibrillation is more obvious.

[0053] 3. By comparing Example 3 and Comparative Example 3, it can be seen that: when the NMMO concentration in the coagulation bath is 10%, the double diffusion rate of the fiber in the coagulation bath is faster, and the surface layer of the spinning solution stream solidifies and forms quickly, resulting in uneven coagulation of the inner and outer layers of the fiber and an imperfect crystalline structure. When the NMMO concentration in the coagulation bath is increased to 20%, the double diffusion rate of the fiber in the coagulation bath slows down, making the double diffusion more uniform, the lateral crystal size of the fiber increases, the degree of crystallinity increases, multiple crystal aggregates are formed, the bonding between molecular chains is weakened, and it is easy to slip and peel off microfibers under the action of wet external forces, thereby significantly increasing the degree of fibrillation.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing high-altitude fibrosis Lyocell fiber, characterized in that: The steps include: Step SS1: adding propyl gallate, a crystallizing agent and a matting agent into a solvent NMMO having a mass concentration of 65±5%, stirring and dispersing the mixture to obtain a mixture A; Step SS2: adding wood pulp to mixture A and stirring to obtain mixture B; Step SS3: Mixture B is heated and dehydrated by evaporation under reduced pressure until the cellulose is completely dissolved, thereby obtaining a spinning solution with a cellulose concentration of 7 to 11 wt %; Step SS4: The spinning solution is extruded from the spinneret, cooled in a coagulation bath and stretched to obtain high-altitude fiberized Lyocell fibers.

2. The method for preparing a high-density lyocell fiber according to claim 1, characterized in that: The amount of the crystallization agent added in step SS1 is 0.1 to 3 wt % of the mass of the wood pulp.

3. The method for preparing a high-density lyocell fiber according to claim 2, characterized in that: The crystallization promoting agent is at least one of polylactic acid, polycaprolactone, polypropylene carbonate and polyethylene carbonate.

4. The method for preparing a high-density lyocell fiber according to claim 1, characterized in that: The amount of matting agent added in step SS1 is 0.1-2 wt% of the mass of the wood pulp.

5. The method for preparing high-density lyocell fiber according to claim 4, characterized in that: The matting agent is at least one of nano-sized white carbon black, barium sulfate and titanium dioxide.

6. The method for preparing high-density lyocell fiber according to claim 1, characterized in that: The mass ratio of wood pulp to NMMO solution in step SS2 is 1:10-15.

7. The method for preparing high-density lyocell fiber according to claim 1, characterized in that: The premixing time in step SS3 is 40 to 60 minutes, and the premixing temperature is 70 to 100°C.

8. The method for preparing high-density lyocell fiber according to claim 1, characterized in that: In the step SS3, the dehydration temperature is 90-120° C., the dehydration pressure is -0.1 MPa, and the dehydration time is 90-180 minutes.

9. The method for preparing high-density lyocell fiber according to claim 1, characterized in that: In the step SS4, the spinning speed of the spinning solution extruded from the spinneret is 20-60 m / min, and the spinning temperature is 90-110°C.

10. The method for preparing high-density lyocell fiber according to claim 1, characterized in that: The NMMO concentration in the coagulation bath in step SS4 is 10-25%.

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