Fiber suspension and dispersion method thereof

Abstract

The invention relates to the technical field of papermaking, and provides a fiber suspension and a dispersion method thereof. The dispersion method comprises the following steps: S100, carrying out pre-wetting treatment on a fiber raw material and a pre-wetting solution for 3-30 minutes to obtain pre-wetted fibers; s200, performing pulse vacuum infiltration treatment on the pre-wetted fibers, and adding dispersion liquid to obtain infiltration slurry; s300, carrying out primary loosening treatment on the infiltrated slurry to obtain primary unbundled slurry; s400, carrying out elongation flow unbundling treatment on the primary unbundling slurry to obtain dispersed slurry; and S500, carrying out stepped dilution on the dispersed slurry to obtain a stable fiber suspension. According to the method, air entrained in the fiber bundles is removed through pulse vacuum infiltration, dispersion liquid is promoted to enter the fiber bundles, the infiltrated fiber bundles are promoted to be opened step by step in the flowing direction through elongation flow unbundling, and reagglomeration caused by sudden concentration change is reduced through stepped dilution; therefore, the dispersion uniformity and suspension stability of the fiber suspension are improved.

Description

Technical Field

[0001] This invention relates to the field of papermaking technology, and more specifically, to a fiber suspension and its dispersion method. Background Technology

[0002] In papermaking and fiber material processing, it is often necessary to first disperse fiber raw materials in a liquid medium to prepare a uniform and stable fiber suspension, thereby meeting the requirements of subsequent forming, compounding, or functionalization. Current methods for preparing fiber suspensions typically involve directly adding the fiber raw materials to water or a dispersion, followed by dispersion through stirring, mechanical dispersing, or cyclic shearing. For some easily wetted and easily loosened fiber systems, these methods can meet the requirements to a certain extent.

[0003] However, for fiber raw materials existing in bundles, especially synthetic fibers, inorganic fibers, fibers with oil on the surface, or fibers with a high aspect ratio, after the addition of a liquid phase, the liquid often preferentially wets the outer layer of the fiber bundle, making it difficult to penetrate further into the fiber bundle. This results in air remaining inside the fiber bundle or it being in an insufficiently wetted state, creating a phenomenon of "outer layer wetted, inner layer unwetted." In this case, even if conventional stirring or mechanical dispersion is continued, it often only gradually loosens the outer layer of the fiber bundle, making it difficult to achieve overall fiber bundle opening. Ultimately, this leads to the presence of bundled fibers, agglomerates, or uneven dispersion in the suspension.

[0004] Therefore, there is an urgent need to provide a new method for dispersing fiber suspensions to improve the ability of liquid to penetrate into the fiber bundle, promote the overall opening of the fiber bundle, and improve the dispersion uniformity of the fiber suspension. Summary of the Invention

[0005] The problem solved by this invention is how to provide a method for dispersing fiber suspensions; The problem addressed by this invention is how to provide a fiber suspension.

[0006] To address the above problems, the present invention provides a method for dispersing a fiber suspension, the method comprising: S100. The fiber raw material is pre-wetted with the pre-wetting liquid for 3~30 min to obtain pre-wetted fiber; S200. The pre-wetted fiber is subjected to pulse vacuum impregnation treatment, and a dispersion is added to obtain an impregnation slurry. S300: The impregnating slurry is initially loosened to obtain a primary unbundling slurry; S400: The primary unbundled slurry is subjected to elongation flow unbundling treatment to obtain a dispersed slurry; S500: The dispersed slurry is diluted in stages to obtain a stable fiber suspension.

[0007] In the above technical solution, in S100, the fiber raw material includes at least one of wood pulp fiber, polyester fiber, aramid fiber, polyolefin fiber, basalt fiber, and glass fiber; and / or the pre-wetting liquid includes a wetting agent and deionized water.

[0008] In the above technical solution, the wetting aid includes at least one of nonionic surfactant and water-soluble polyol; and / or the total content of the wetting aid in the pre-wetting liquid is 0.01~5wt%.

[0009] The above technical solution specifically includes S200 as follows: S201. The pre-wetted fiber is vacuumed at a vacuum degree of -0.03~-0.095MPa for 20s~10min, and repeated 1~8 times to perform pulse vacuum impregnation treatment to obtain intermediate product; S202. After adding the dispersion to the intermediate product, apply a positive pressure of 0.02~0.3MPa and hold the pressure for 0.5~20min to obtain the impregnated slurry.

[0010] In the above technical solution, in S300, the primary loosening treatment includes at least one of low-speed stirring, turning or circulating conveying; and / or the fiber concentration of the primary unbundling slurry is 1~10wt%.

[0011] In the above technical solution, in S400, the elongation flow unbundling process is achieved by at least one of a contraction-expansion channel, a venturi channel, a slit jet channel, or a coaxial jet mixing channel.

[0012] In the above technical solution, the pressure difference before and after the elongation flow unbundling treatment is 0.01~0.5MPa, and the number of cycles is 1~20.

[0013] In the above technical solution, in S500, the step dilution includes a first stage dilution and a second stage dilution; the amount of diluent added in the first stage dilution is 20-150% of the mass of the dispersed slurry; the amount of diluent added in the second stage dilution is 20-300% of the mass of the slurry after the first stage dilution.

[0014] In the above technical solution, the fiber concentration of the fiber suspension is 0.02~2wt%.

[0015] The present invention also provides a fiber suspension, which is prepared by any of the above dispersion methods.

[0016] Beneficial effects (1) This application combines pulsed vacuuming with differential pressure return to allow liquid to enter the fiber bundle, solving the problems of air entrainment and difficulty in internal wetting of the fiber bundle, and improving the overall wetting of the fiber bundle and subsequent unbundling conditions. (2) Unlike traditional stirring or pulping that relies on high shear, this application causes the fiber bundles to stretch and open along the flow direction by elongating the flow field, which can achieve more uniform dispersion at a lower level of fiber damage. (3) By controlling the concentration change path of the dispersion system through staged dilution, the re-agglomeration behavior during the concentration reduction process can be suppressed, which can enable the fibers to maintain the established dispersion state in the gradually diffused system and improve the stability and uniformity of the suspension. Detailed Implementation

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, a detailed description of specific embodiments of the present invention will be provided below.

[0018] Unless otherwise specified, all reagents and raw materials used in this invention are commercially available. Experimental methods in the following examples that do not specify particular conditions should be performed according to conventional methods and conditions, or as selected in the product instructions.

[0019] This invention aims to provide a fiber suspension and its dispersion method, addressing the problems in existing technologies where the fiber bundles are difficult to fully wet, resulting in uneven dispersion and difficulty in the overall opening of the fiber bundles. The dispersion method includes: S100. The fiber raw material is pre-wetted with the pre-wetting liquid for 3~30 min to obtain pre-wetted fiber; S200. The pre-wetted fiber is subjected to pulse vacuum impregnation treatment, and a dispersion is added to obtain an impregnation slurry. S300: The impregnating slurry is initially loosened to obtain a primary unbundling slurry; S400: The primary unbundled slurry is subjected to elongation flow unbundling treatment to obtain a dispersed slurry; S500: The dispersed slurry is diluted in stages to obtain a stable fiber suspension.

[0020] The dispersion method of this invention does not rely solely on increasing stirring intensity or dispersant dosage to achieve fiber dispersion. Instead, it first promotes liquid penetration into the fiber bundle, then gently opens the fiber bundle, and inhibits subsequent re-agglomeration. Specifically, pre-wetting reduces the wetting barrier on the fiber surface, allowing the liquid to spread more easily on the fiber surface. Next, pulsed vacuum impregnation removes air trapped inside the fiber bundle, and pressure difference drives the dispersion liquid to penetrate into the fiber bundle, transforming the fiber bundle from a state where the outer layer is wet and the inner layer is unimpregnated to a fully impregnated state. Subsequently, preliminary loosening and elongation flow unbundling gradually stretch and open the fully impregnated fiber bundle along the flow direction, reducing fiber cutting and surface damage caused by simple high shear. Finally, step dilution reduces re-flocculation and re-agglomeration caused by sudden changes in slurry concentration, thereby obtaining a fiber suspension with high dispersion uniformity and suspension stability. Therefore, this invention can improve fiber dispersion under conditions of low fiber damage, and is particularly suitable for the dispersion of difficult-to-wet and difficult-to-open fiber systems.

[0021] In S100, pre-wetting liquid contacts the fiber raw material, reducing the contact angle and interfacial tension of the fiber surface and improving the spreading ability of the liquid on the fiber surface. Additionally, it allows a continuous liquid film to form on the outer layer of the fiber bundle, mitigating the adverse effects of fiber surface hydrophobicity, surface oils, or air entrainment on subsequent impregnation, thus creating more favorable initial conditions for subsequent pulsed vacuum impregnation. Pre-wetting does not directly disperse the fiber bundle completely, but rather weakens the interfacial barrier preventing the liquid from entering the fiber bundle, transforming the outer layer of the fiber bundle from a dry or semi-wet state to a stable wet state. This reduces the difficulty of air migration and liquid replacement during subsequent vacuuming, thereby improving the efficiency and overall uniformity of pulsed vacuum impregnation.

[0022] Furthermore, the fiber raw materials include at least one of wood pulp fiber, polyester fiber, aramid fiber, polyolefin fiber, basalt fiber, and glass fiber; the above-mentioned fiber materials include wood pulp fiber, which is relatively easy to wet but easy to bundle, as well as polyester fiber and polyolefin fiber, which have low surface energy, strong hydrophobicity, or often have oil on their surface, and aramid fiber, basalt fiber, and glass fiber, which have high rigidity, special surface properties, and are not easy to disperse uniformly under conventional stirring. This indicates that the present invention is not only applicable to a certain type of single fiber, but can be widely applied to multiple types of difficult-to-disperse fiber systems.

[0023] Preferably, the pre-wetting liquid includes a wetting aid and deionized water. The wetting aid can further reduce the surface tension of the liquid and enhance the spreading and penetration ability of the liquid on the fiber surface. The wetting aid includes at least one of nonionic surfactants and water-soluble polyols; nonionic surfactants generally have good wetting properties and a wide range of applications, are not sensitive to changes in system pH and ionic strength, and are not prone to strong electrochemical interactions with ionic components on the fiber surface or in the subsequent system, thus being more conducive to forming a stable and uniform pre-wetting state; nonionic surfactants include at least one of fatty alcohol polyoxyethylene ethers, isomeric alcohol polyoxyethylene ethers, octylphenol polyoxyethylene ethers, nonylphenol polyoxyethylene ethers, polyoxyethylene sorbitan fatty acid esters, and alkyl glycosides. Polyols can improve the affinity of the liquid for the fiber surface, promote the retention and penetration of the liquid in the fiber gaps, and help slow down the rapid loss of liquid, thereby enhancing the continuity and uniformity of the pre-wetting process; water-soluble polyols include at least one of ethylene glycol, propylene glycol, glycerol, and polyethylene glycol.

[0024] Preferably, the total content of wetting agent is controlled within the range of 0.01 to 5 wt%. When the content of wetting agent is less than 0.01 wt%, its effect of reducing surface tension and improving spreading and penetration is limited, and it is difficult to significantly improve the pre-wetting of fibers. When the content of wetting agent is higher than 5 wt%, although the wetting ability may be further enhanced, it is easy to cause increased foaming of the system, excessive residual components, and may have an adverse effect on the subsequent dispersion process or the stability of the final fiber suspension.

[0025] It is understandable that fiber bundles typically contain numerous inter-fiber pores and entrained air, which hinders further liquid penetration. In the S200 process, pulsed vacuum treatment allows the air inside the fiber bundle to expand and escape. Introducing a dispersion and applying positive pressure then utilizes the pressure difference to drive the dispersion to replace the original air and enter the fiber bundle. Simultaneously, the liquid is also affected by capillary action within the fiber gaps. Under the combined effect of pressure difference and capillary penetration, the liquid gradually penetrates deep into the fiber bundle from the outside in, transforming the fiber bundle from a surface-wetted state to a fully impregnated state. This provides a uniform liquid phase basis for subsequent initial loosening and elongation flow unbundling. Compared to simply immersing or stirring the fibers in liquid, this method more effectively removes entrained air from the fiber bundle, mitigating the situation where the outer layer is wetted while the inner layer remains unimpregnated, and avoiding the problem of only the outer fibers loosening while the inner fibers remain tightly bound during subsequent dispersion.

[0026] In specific operations, S200 specifically includes: S201. The pre-wetted fiber is vacuumed at a vacuum degree of -0.03~-0.095MPa for 20s~10min, and repeated 1~8 times to perform pulse vacuum impregnation treatment to obtain intermediate product; S202. After adding the dispersion to the intermediate product, apply a positive pressure of 0.02~0.3MPa and hold the pressure for 0.5~20min to obtain the impregnated slurry.

[0027] In step S201, the pre-wetted fibers are subjected to pulsed vacuuming to remove residual air from the fiber bundle and interfiber spaces, creating space for the subsequent dispersion liquid to enter the fiber bundle. Compared to directly adding liquid without vacuum treatment, pulsed vacuum treatment can more effectively remove air barriers inside the fiber bundle. Since the fiber bundle is usually not a uniform open structure, the internal gas is often difficult to expel completely in one go. Using a pulsed method of multiple vacuuming and recovery allows the gas inside the bundle to expand, migrate, and release repeatedly, thereby improving the degassing effect. This reduces the chance of the liquid being blocked by residual air inside the bundle during subsequent liquid addition, improving the liquid introduction efficiency and wetting depth.

[0028] In S202, the internal gas content of the fiber bundle decreases after vacuum degassing, and the interfiber gaps' capacity to accommodate external liquids is enhanced. After adding the dispersion, applying positive pressure creates a further pressure gradient between the external environment and the fiber bundle interior, propelling the liquid through the surface and internal channel resistance of the fiber bundle. Simultaneously, once the dispersion enters the fiber bundle gaps, it can further expand into the micropores through fiber surface wetting and capillary action, thus achieving more thorough wetting within the bundle.

[0029] After pulsed vacuum impregnation, if the pressure is increased rapidly, although the liquid can enter some of the fiber gaps, it may also cause the outer layer of the fiber bundle to be compacted first, thus affecting the liquid's continued penetration into the fiber bundle.

[0030] In one alternative approach, after adding the dispersion, a first-stage positive pressure is applied and the mixture is allowed to stand; then, a second-stage positive pressure is applied and maintained to obtain the impregnated slurry.

[0031] Specifically, the first stage back pressure is 0.02~0.05 MPa, and the time is 10s~3min. Under the lower first-stage pressure, the liquid preferentially enters the less resistant surface channels and larger pores, and further diffuses along the fiber surface and interfiber spaces through capillary action during the settling process. At this time, the liquid distribution tends to be uniform, which helps to reduce localized excessively rapid liquid ingress and outer layer compaction. Subsequently, the second stage back pressure is 0.05~0.3 MPa, and the time is 0.5~10min. When a higher pressure is applied in the second stage, the liquid can further enter the more resistant internal fine gaps and deep regions based on the previously formed continuous liquid phase channels, thereby achieving gradual wetting from the outer layer to the inside. In other words, the lower positive pressure mainly provides a gentle external driving force, while the soaking and settling stage provides time for the liquid to migrate along the fiber surface and interfiber spaces under capillary action, thereby transforming the outer layer wetting into internal pre-penetration. After the first stage of treatment, some liquid pathways have been formed inside the fiber bundle. At this point, increasing the pressure can further overcome the liquid ingress obstacles in smaller pores and higher resistance areas on the basis of the existing continuous liquid phase, allowing the liquid to continue to advance inward along the existing channels and the newly opened channels, ultimately achieving more complete in-bundle wetting.

[0032] Preferably, the dispersant includes at least one of sodium polyacrylate, sodium salt of acrylic acid-maleic acid copolymer, sodium lignosulfonate, sodium salt of naphthalenesulfonic acid formaldehyde condensate, sodium hexametaphosphate, sodium pyrophosphate, polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol.

[0033] In S200, the dispersion liquid has entered the fiber bundle, and the original air interface between fibers is replaced by a liquid interface, changing the internal friction and interface states of the fiber bundle. Based on this, low-intensity mechanical disturbance causes relative displacement and initial separation of the outer layer and some internal fibers along the established liquid phase channels, gradually weakening the integrity of the bundle structure. In other words, S300 does not rely on force to completely disperse the fiber bundle, but rather utilizes the overall wetting conditions established in the previous step to gently induce the fiber bundle into an initial loose state that facilitates subsequent unbundling through gentle disturbance.

[0034] Preferably, the primary loosening treatment includes at least one of low-speed stirring, agitation, or circulating conveying, which allows the impregnated fiber bundles to be moderately disturbed and rearranged in the liquid phase, thereby promoting the gradual loosening of the fiber bundles. Low-speed stirring can generate a continuous and gentle flow of the slurry as a whole, promoting the separation of fiber bundles and reducing local accumulation; agitation can change the position and force direction of the fiber bundles in the container, allowing different surfaces of the fiber bundles to come into contact with the liquid and external disturbances, thereby improving uneven local impregnation; circulating conveying can utilize the repeated migration of the slurry in the flow path to gradually loosen the fiber bundles without subjecting them to severe impact.

[0035] Furthermore, the fiber concentration of the primary unbundling slurry is 1-10 wt%. Maintaining an appropriate fiber-to-fiber contact probability and system flowability during the primary loosening stage ensures effective unbundling of fiber bundles under disturbance without compromising the primary unbundling effect due to excessively thin or thick systems. If the fiber concentration is too low, the system becomes too thin, weakening the interaction between fiber bundles and between fiber bundles and fluid disturbances. While flow resistance is low, insufficient opportunities for collisions, tumbling, and relative displacement during the primary loosening process may lead to a decrease in initial loosening efficiency. Conversely, if the fiber concentration is too high, the slurry viscosity increases significantly, making fiber bundles more prone to entanglement, accumulation, or the formation of new bridging structures. This hinders liquid redistribution between bundles, reduces the gentle unbundling effect of low-speed stirring, agitation, or circulation, and may even create localized high-resistance zones, affecting the uniformity of subsequent elongation flow unbundling.

[0036] Compared to relying solely on high-speed stirring, strong shearing, or mechanical pulping to disperse fiber bundles, S400 employs an elongation flow disintegration method. Because the fiber bundles are sufficiently wetted by the liquid, the fiber bonding state changes from a dry, tightly packed state to a wet, slippery state, and the overall fiber bundle transforms from a dense bundle to a relatively loose, semi-disintegrated state. Based on this, when the slurry passes through a geometrically abrupt flow channel or a controlled jet region, the fluid velocity changes significantly along the flow direction, creating an elongation flow field dominated by stretching and unfolding. Within this elongation flow field, the fiber bundle is subjected to a velocity gradient along the flow direction; the different velocities at the beginning and end of the bundle cause a directional separation tendency among the fibers, gradually pulling and disintegrating the fiber bundle along its original bundle direction.

[0037] Preferably, the elongation flow unbundling treatment is achieved through at least one of a contraction-expansion channel, a venturi channel, a slit jet channel, or a coaxial jet mixing channel. This is because the aforementioned channels or mixing structures can create significant velocity variation zones and directional stretching zones during slurry flow, thereby generating an elongation flow field favorable to the fiber bundles. Processes such as contraction, expansion, jetting, throat acceleration, or dual-velocity mixing all cause velocity differences at different locations in the slurry, resulting in different fluid drag forces on the fiber bundle's front and rear ends, and on the outer and inner layers. For fiber bundles that are already wetted and in a semi-unbundled state, this directional velocity difference can cause relative displacement and separation of the fibers within the bundle along the bundle direction, thereby gradually opening the bundle structure.

[0038] Furthermore, the pressure difference before and after the elongation flow unbundling treatment is 0.01~0.5MPa. This pressure difference is the direct driving force for the slurry to flow through the channel and create velocity changes. An appropriate pressure difference allows the slurry to generate sufficient acceleration in the contraction, throat, or jetting regions, and subsequent flow field reorganization in the expansion or mixing regions, thus producing an elongation effect beneficial to the fiber bundles. When the pressure difference is within a suitable range, the front and rear parts of the fiber bundle can withstand a relatively balanced and continuous directional stretching effect, causing the fibers within the bundle to gradually separate rather than being subjected to excessive instantaneous damage. The number of cycles is 1~20. For different types, densities, and aspect ratios of fiber bundles, the degree of unbundling obtained from a single pass through the elongation flow dispersion unit may vary. By setting a certain number of cycles, the fiber bundles can be gradually opened under multiple controlled flow field actions, without having to use excessively high pressure differences or excessively strong mechanical action at once. This is more conducive to achieving gentle, gradual unbundling. If the number of cycles is too few, some of the denser fiber bundles may not be fully opened; if the number of cycles is too many, it will increase processing time, energy consumption, and the risk of cumulative damage to the fibers due to repeated stress.

[0039] In S500, although the fiber bundles are significantly opened, the fibers in the system still maintain a certain contact frequency and local interaction. If a large amount of diluent is added at this time, it can easily cause sudden changes in the local flow field, concentration field, and liquid phase environment around the fibers. This can lead to some of the opened fibers re-aggregating, tangling, or flocculating, affecting the uniformity and stability of the final suspension. By using a stepwise dilution method to gradually reduce the system concentration, the risk of re-aggregation caused by sudden concentration changes can be reduced. This allows the fibers to maintain a better dispersion state in the gradually expanding liquid phase space, thereby improving the uniformity, stability, and subsequent suitability of the final fiber suspension.

[0040] Furthermore, the stepped dilution includes a first-stage dilution and a second-stage dilution. The first-stage dilution involves adding 20-150% of the mass of the dispersed slurry, used to achieve a smooth reduction in concentration from the unbundled slurry to the transition slurry. The second-stage dilution involves adding 20-300% of the mass of the slurry after the first-stage dilution, used to further reduce the concentration of the transition slurry to its final usable state. This step-by-step concentration reduction method effectively reduces the risk of fiber re-flocculation and improves the dispersion uniformity and suspension stability of the fiber suspension.

[0041] The present invention also provides a fiber suspension, which is prepared by any of the above dispersion methods. The fiber concentration of the fiber suspension of the present invention is 0.02~2wt%. When the fiber concentration is less than 0.02wt%, the system is too thin. Although the risk of re-agglomeration between fibers is low, the fiber content per unit volume is too low, which is not conducive to actual production and use, and will also increase the cost of transportation and storage. When the fiber concentration is higher than 2wt%, the probability of contact and entanglement between fibers increases significantly, which can easily induce re-flocculation, uneven sedimentation or local agglomeration, which is not conducive to maintaining a stable suspension state.

[0042] This application has undergone multiple experiments, and some of the test results are presented here for reference to further describe the invention in detail. The following is a detailed description in conjunction with specific embodiments. Example 1

[0043] This embodiment provides a fiber suspension and its dispersion method, the dispersion method including the following steps: S100. Add 0.45g AEO-9 and 9.00g propylene glycol to 990.55g deionized water to prepare a pre-wetting solution; pre-wet 60g bleached sulfate wood pulp fiber and 40g polyester staple fiber with the pre-wetting solution for 10min until the fiber surface is uniformly wetted and there are no obvious floating dry fibers to obtain pre-wetted fiber. S201. Transfer the pre-wetted fiber into a vacuum impregnation tank, evacuate at -0.08MPa for 3 minutes, and restore to normal pressure for 30 seconds; repeat this pulse vacuum impregnation process 3 times to obtain the intermediate product. S202 is a dispersion prepared from 0.15wt% sodium polyacrylate, 0.05wt% sodium lignosulfonate, 0.05wt% PVP K30, and the balance deionized water. The dispersion is added to the intermediate product, and the first stage of positive pressure impregnation is carried out at 0.03MPa for 1 min. Then, the second stage of positive pressure is carried out at 0.15MPa for 5 min until no continuous bubbles escape. The fiber bundles are randomly disassembled, and the core of the bundle has no obvious dry white core, thus obtaining the impregnated slurry. S300: Place the impregnated slurry in a paddle mixer and stir at a low speed of 250 rpm for 8 minutes; then circulate it twice through a circulating pump to obtain a primary unbundling slurry with a fiber concentration of 2 wt%. S400. The primary unbundled slurry is introduced into a Venturi flow channel device for processing; the Venturi throat diameter is 2mm, the pressure difference before and after is controlled at 0.12MPa, and the slurry is circulated 5 times to obtain a dispersed slurry. S500. First stage dilution of the dispersion slurry: add deionized water at 120% of the mass of the dispersion slurry and stir at low speed of 150 rpm for 5 min; then perform second stage dilution: add deionized water at 120% of the mass of the slurry after the first stage dilution and stir at low speed of 100 rpm for 10 min to obtain a fiber suspension with a concentration of 0.41 wt%. Example 2

[0044] This embodiment provides a fiber suspension and its dispersion method. The dispersion method is the same as in Embodiment 1, except that: In S100, 0.60g of alkyl glycoside APG0810 and 12.00g of glycerol were added to 1187.40g of deionized water to prepare a pre-wetting solution; 70g of aramid staple fiber and 30g of bleached wood pulp fiber were pre-wetted with the pre-wetting solution for 3min to obtain pre-wetted fiber. In S201, a vacuum of -0.09 MPa was applied for 4 minutes, followed by restoration to normal pressure for 30 seconds; this pulsed vacuum immersion treatment was repeated 4 times. In S202, a dispersion was prepared by mixing 0.10 wt% sodium polyacrylate, 0.08 wt% sodium hexametaphosphate, 0.05 wt% polyethylene glycol PEG-400, and the balance deionized water. The dispersion was subjected to a first stage of positive pressure impregnation at 0.04 MPa for 2 min, followed by a second stage of positive pressure impregnation at 0.20 MPa for 8 min to obtain the impregnated slurry. In S300, the impregnating slurry is stirred at a low speed of 200 rpm for 10 min; then it is circulated 3 times by a circulating pump to obtain a primary unbundling slurry with a fiber concentration of 3 wt%. In the S400, the primary unbundled slurry is introduced into a shrink-expansion channel device for processing; the pressure difference before and after is controlled at 0.18 MPa, and the slurry is circulated 8 times to obtain a dispersed slurry. S500. First stage dilution of the dispersion slurry: add deionized water at 60% of the mass of the dispersion slurry; then perform second stage dilution: add deionized water at 180% of the mass of the slurry after the first stage dilution, to obtain a fiber suspension with a concentration of 0.67wt%. Example 3

[0045] This embodiment provides a fiber suspension and its dispersion method. The dispersion method is the same as in Embodiment 1, except that: In S100, 0.30g Tween 80 and 7.00g polyethylene glycol 400 were added to 992.70g deionized water to prepare a prewetting solution; 30g basalt fiber, 20g glass fiber and 50g bleached wood pulp fiber were prewetting with the prewetting solution for 30min to obtain prewetting fiber; In S201, a vacuum of -0.07 MPa is applied for 2 minutes, followed by restoration to normal pressure for 30 seconds; this pulsed vacuum immersion treatment is repeated 5 times. In S202, a dispersion was prepared by mixing 0.15 wt% sodium lignosulfonate, 0.10 wt% sodium hexametaphosphate, 0.05 wt% polyethylene glycol PEG-400, and the balance deionized water. The dispersion was subjected to a first stage of positive pressure impregnation at 0.02 MPa for 2 min, followed by a second stage of positive pressure impregnation at 0.10 MPa for 6 min to obtain the impregnated slurry. In S300, the impregnating slurry is stirred at a low speed of 150 rpm for 10 min; then agitated for 2 min to obtain a primary unbundling slurry with a fiber concentration of 5 wt%. In the S400, the primary unbundled slurry is introduced into a coaxial jet mixing channel device for processing; the pressure difference before and after is controlled at 0.08 MPa, and the mixture is circulated 3 times to obtain a dispersed slurry. S500. First stage dilution of the dispersion slurry: add deionized water at 100% of the mass of the dispersion slurry; then perform second stage dilution: add deionized water at 150% of the mass of the slurry after the first stage dilution, to obtain a fiber suspension with a concentration of 1.0 wt%. Example 4

[0046] This embodiment provides a fiber suspension and its dispersion method. The dispersion method is the same as in Embodiment 1, except that in S202, segmented back pressure impregnation is not performed. That is, after adding the dispersion to the intermediate product, a positive pressure of 0.15 MPa is applied for 6 minutes to obtain the impregnated slurry.

[0047] Comparative Example 1 This comparative example provides a fiber suspension and its dispersion method. The dispersion method is the same as in Example 1, except that there is no S100, that is, no pre-wetting step.

[0048] Comparative Example 2 This comparative example provides a fiber suspension and its dispersion method. The dispersion method is the same as in Example 1, except that there is no S200, that is, no pulsed vacuum impregnation step.

[0049] Comparative Example 3 This comparative example provides a fiber suspension and its dispersion method. The dispersion method is the same as in Example 1, except that in S400, high-speed stirring is used instead of S400 elongation flow unbundling, that is, the Venturi channel treatment is not used. The primary unbundled slurry is placed in a high-speed disperser and stirred at 3000 rpm for 8 minutes.

[0050] Comparative Example 4 This comparative example provides a fiber suspension and its dispersion method. The dispersion method is the same as in Example 1, except that in S500, the same total mass of diluent as in Example 1 is added to the dispersion slurry at one time, and the mixture is stirred at low speed for 15 minutes to adjust the final fiber concentration to 0.41 wt%.

[0051] Performance testing The fiber suspensions obtained in Examples 1-4 and Comparative Examples 1-4 were tested as follows, and the results are shown in Tables 1 and 2. Number of residual clusters: Take 100 mL of each of Examples 1-4 and Comparative Examples 1-4, place them in transparent petri dishes, and observe them under the same light conditions. Count the number of clusters with a length greater than 1 mm and greater than 3 mm. Average particle size of flocs: The samples of Examples 1-4 and Comparative Examples 1-4 were diluted to 0.05 wt%, and the average particle size D50 of the flocs was determined by image analysis or laser particle size distribution. 24h sedimentation rate: Take 250mL of fiber suspension from each of Examples 1-4 and Comparative Examples 1-4 and place it in a graduated cylinder. Let it stand for 24 hours, record the height or volume of the bottom sediment layer, and calculate the sedimentation rate based on the initial liquid column height or volume. Concentration difference between upper and lower layers: After the samples of Examples 1-4 and Comparative Examples 1-4 were allowed to stand for 30 minutes, the upper and lower layer samples were taken respectively, the solid content was measured, and the concentration difference between upper and lower layers was calculated to characterize the suspension uniformity. Table 1 Table 2 As shown in Tables 1 and 2, the fiber suspensions obtained in Examples 1-4 are significantly better than those in Comparative Examples 1-4 in terms of the number of residual clusters, average particle size of flocs, 24-hour sedimentation rate, and concentration difference between upper and lower layers. This indicates that the present application, through a combination of pre-wetting, pulsed vacuum impregnation, preliminary loosening, elongation flow unbundling, and step dilution, can effectively improve the wetting ability of liquid into the fiber bundle, promote the overall opening of the fiber bundle, and reduce re-agglomeration during the subsequent concentration reduction process, thereby significantly improving the dispersion uniformity and suspension stability of the fiber suspension.

[0052] Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method of dispersing a fiber suspension, characterized by, The dispersion method includes: S100. The fiber raw material is pre-wetted with the pre-wetting liquid for 3~30 min to obtain pre-wetted fiber; S200. The pre-wetted fiber is subjected to pulse vacuum impregnation treatment, and a dispersion is added to obtain an impregnation slurry; S300. The impregnating slurry is subjected to preliminary loosening treatment to obtain a primary unbundling slurry. S400. The primary unbundling slurry is subjected to elongation flow unbundling treatment to obtain a dispersed slurry; S500: The dispersed slurry is diluted in stages to obtain a stable fiber suspension.

2. The dispersion method according to claim 1, characterized by, In S100, The fiber raw material includes at least one of wood pulp fiber, polyester fiber, aramid fiber, polyolefin fiber, basalt fiber, and glass fiber; and / or The pre-wetting solution includes a wetting aid and deionized water.

3. The dispersion method according to claim 2, characterized in that, The wetting aid includes at least one of a nonionic surfactant and a water-soluble polyol; and / or The total content of the wetting aid in the pre-wetting liquid is 0.01~5wt%.

4. The dispersion method according to claim 1, characterized in that, Specifically, S200 includes: S201. The pre-wetted fiber is evacuated at a vacuum degree of -0.03 to -0.095 MPa for 20s to 10min, and repeated 1 to 8 times to perform pulse vacuum impregnation treatment to obtain an intermediate product. S202. After adding the dispersion to the intermediate product, apply a positive pressure of 0.02~0.3MPa and hold the pressure for 0.5~20min to obtain the impregnating slurry.

5. The dispersion method according to claim 1, characterized in that, In S300, The primary loosening process includes at least one of low-speed stirring, agitation, or circulating conveying; and / or The fiber concentration of the primary unbundling slurry is 1~10wt%.

6. The dispersion method according to claim 1, characterized in that, In S400, the elongation flow unbundling process is achieved by at least one of a contraction-expansion channel, a venturi channel, a slit jet channel, or a coaxial jet mixing channel.

7. The dispersion method according to claim 6, characterized in that, The pressure difference before and after the elongation flow unbundling treatment is 0.01~0.5MPa, and the number of cycles is 1~20.

8. The dispersion method according to claim 1, characterized in that, In S500, the step dilution includes a first-stage dilution and a second-stage dilution; The amount of diluent added in the first stage of dilution is 20-150% of the mass of the dispersion slurry; The amount of diluent added in the second stage of dilution is 20-300% of the mass of the slurry after the first stage of dilution.

9. The dispersion method according to any one of claims 1-8, characterized in that, The fiber concentration of the fiber suspension is 0.02~2wt%.

10. A fiber suspension, characterized in that, It is prepared by the dispersion method according to any one of claims 1-9.

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