Flow guide layer and preparation process and system thereof

Abstract

This invention discloses a flow guide layer and its preparation process and system. It includes the following steps: 1) opening, combing, and laying out a fiber web of both the usable and non-usable sides; 2) subjecting the non-usable side fiber web to two-stage drum hydroentangling reinforcement; 3) alkali treatment of the non-usable side fiber layer. Water droplet-shaped protrusions are prepared on the lower surface of the usable and / or non-usable side fiber webs, the diameter of which is 0.001-0.1 mm; the number of water droplet-shaped protrusions is 10-1000 per cm. 2 This invention utilizes ES fibers of different deniers, combined with low-melting-point PET / PA6 bicomponent orange-petal-shaped fibers and hygroscopic non-melting fibers. Through a special low-pressure hydroentangling and hot air consolidation process, an asymmetric structure with a pore size difference of more than 10 times is constructed, which greatly improves the permeation rate. Furthermore, the micropores on the fibers form capillary forces, and the inter-fiber pores form capillary forces, combined with the synergistic effect of the hydrophilic groups of the hydrophilic fibers, enhance the diffusion effect of the liquid in the bottom layer.

Description

Technical Field

[0001] This invention relates to a flow guide layer for hygiene products and its preparation process and system. Background Technology

[0002] Currently, hot air guiding layer materials suffer from significant differences in the number of bonding points and flatness between fibers on the usable side (the side in contact with the support mesh) and the non-usable side, resulting in lower pore structure strength. In actual sanitary napkin use, the guiding layer is bent into an arc shape. Due to fewer bonding points between fibers on the non-usable side, its resistance to deformation is weaker, making fibers more prone to slippage. Fiber slippage leads to deformation of the guiding layer's pore structure and reduces the number of contact points between fibers, thereby increasing the equivalent pore size on the non-usable side of the guiding layer, weakening capillary forces, and hindering rapid liquid infiltration and reducing backflow.

[0003] Because pure cotton surface layers have higher requirements for the permeation rate and backflow rate under the guide layer, a stronger capillary effect is needed to improve the performance of the guide layer.

[0004] For single-layer flow-guiding layer materials, a mixture of coarse and fine denier fibers can be used to form a two-layer structure with differences in porosity. Patent CN203436464U describes a flow-guiding layer with an upper, longitudinally combed fiber layer that disperses the liquid longitudinally, while the lower, transversely combed fiber layer rapidly absorbs the liquid and prevents backflow. However, the porosity difference in this method is not significant enough; typically, the ratio of pore size between the upper and lower layers is less than 10, offering limited improvement to the flow-guiding layer's performance.

[0005] By employing two fiber webs with different wettability and consolidating them with hot air to create a differential capillary effect, unidirectional water conduction of the material can be achieved, and the performance of the flow-guiding layer can be improved. For example, patent CN 117779347 A describes a directional moisture-guiding nonwoven fabric and its preparation method, as well as disposable hygiene products, which features low surface diffusion, effective shielding of menstrual blood, rapid liquid penetration, and low rewetting. However, the differential capillary effect created by the difference in wettability introduces some resistance during liquid wetting, reducing the absorption rate of the flow-guiding layer.

[0006] For multi-layer composite flow guide layers, the composite process easily damages the pore structure of the hot air cloth, and there are large gaps between the composites, making it impossible to fit tightly together. The performance is far inferior to that of integrally formed flow guide layer materials. Summary of the Invention

[0007] To overcome the above-mentioned defects, the purpose of this invention is to provide a novel flow guide layer and its preparation process.

[0008] To achieve the above objectives, the present invention provides a flow guiding layer, wherein the flow guiding layer is composed of a double-layer fiber web, wherein...

[0009] The basis weight of the diversion layer is 30-60 g / m2 The non-use fiber web has a basis weight of 18-36 g / m². 2 The basis weight of the fiber mesh used is 12-24 g / m². 2 ;

[0010] The thickness of the flow guiding layer is 0.8 to 1.6 mm, and the thickness ratio of the fiber mesh on the used surface to the fiber mesh on the non-used surface is 1:2 to 4.

[0011] The non-use surface fibers consist of bicomponent orange segment fibers and moisture-absorbing non-melting fibers.

[0012] Furthermore, the bicomponent orange-petal type fiber is made of PA6 and low-melting-point PET, with a denier of 3D to 6D, a length of 10-50mm, a petal number of 6 to 32, and a fineness of 0.05-1D after fiber opening.

[0013] Furthermore, teardrop-shaped protrusions are formed on the lower surface of the usable fiber web and / or the non-usable fiber web, the diameter of the teardrop-shaped protrusions being 0.001-0.1 mm; the number of the teardrop-shaped protrusions is 10-1000 per cm. 2 .

[0014] To achieve the above objectives, the present invention provides a process for preparing the flow guiding layer, the process comprising the following steps:

[0015] 1) Open, comb, and lay the fiber webs of the working and non-working surfaces; the non-working surface fiber webs are laid straight to ensure high longitudinal orientation of the fibers and denser fibers, which is conducive to longitudinal diffusion;

[0016] 2) The non-use surface fiber web is reinforced by two-stage rotary drum hydroentangling. The pressure of the first and second hydroentangling processes is 10-20 bar and 30-40 bar, respectively, and each hydroentangling process is equipped with 1-6 hydroentangling heads. The mesh count of the rotary drum screen 1 is 60-80 mesh, and the mesh count of the screen 2 is 10-30 mesh. After hydroentangling reinforcement, pressure rollers are installed to remove water trapped in the fiber web.

[0017] 3) Alkali treatment of non-use fiber layers.

[0018] 5. The process for preparing the flow guide layer, characterized in that it further includes the following steps:

[0019] Water droplet-shaped protrusions are prepared on the lower surface of the fiber web in the working and / or non-working areas. The diameter of the water droplet-shaped protrusions is 0.001-0.1 mm, and the number of water droplet-shaped protrusions is 10-1000 per cm. 2 .

[0020] Furthermore, it also includes the following steps: the step of preparing the teardrop-shaped protrusion includes:

[0021] Preparation of atomizing finishing solution; the atomizing finishing solution is composed of hydrophilic oil agent, binder and water.

[0022] Atomizing device is used to spray droplets of finishing liquid onto the surface of the fiber web;

[0023] At the same time, the suction device is used to adhere to the fiber surface to achieve a one-sided finishing effect;

[0024] Using the hot airflow to hold the liquid to change the viscosity of the atomized droplets facilitates the formation of water droplet structures;

[0025] Hot air is used to pre-reinforce the fibers while simultaneously solidifying the atomized droplets in the form of water droplets on the surface of the fiber web.

[0026] To achieve the above objectives, the guide layer preparation system of the present invention includes at least a non-use surface fiber web preparation system; the non-use surface fiber web preparation system includes: a carding machine; a web laying machine; a first drum screen; a first hydroentangling stage; a pressure roller; an alkali treatment device; a washing device; a second drum screen; a second hydroentangling stage; an atomizing device; a holding airflow jetting device; a suction device; and a hot air reinforcement drying oven; wherein...

[0027] 1) Non-use fiber webs are opened and carded using a carding machine;

[0028] The netting is laid by a netting machine;

[0029] After being laid, the fiber web undergoes its first hydroentangling process through a rotating drum screen.

[0030] After the first hydroentanglement process, the non-use fiber web is squeezed out of water by pressure rollers and then enters the alkali treatment equipment.

[0031] After the alkali treatment, the non-use fiber web is squeezed out of water by pressure rollers and then enters the washing equipment.

[0032] After washing, the non-use fiber web is squeezed out of water by pressure rollers and then passed through a rotating drum screen for a second hydroentanglement process.

[0033] 2) After the surface fiber web is opened and combed, there is no need to lay the web; it can be directly atomized and hot-air consolidated.

[0034] Surface atomization is achieved using a fiber mesh atomized by an atomizing device;

[0035] After being shaped by the holding air jet device and the suction device, it enters the hot air curing oven for further curing.

[0036] 3) Integrate the non-use surface fiber web processed in step 1) and the use surface fiber web processed in step 2).

[0037] The beneficial effects of this invention are as follows:

[0038] 1. Rapid penetration at the surface of the guiding layer and large diffusion area at the bottom layer. Using ES fibers of different deniers, combined with low-melting-point PET and PA6 bicomponent orange-petal-shaped fibers and hygroscopic non-melting fibers, an asymmetric structure with a pore size difference of more than 10 times is constructed through a special low-pressure hydroentangling and hot air consolidation process. This significantly improves the penetration rate. Furthermore, the synergistic effect between the capillary force formed by the micropores on the hydrophilic groups and fibers and the capillary force formed by the pores between fibers enhances the liquid diffusion effect at the bottom layer.

[0039] 2. By combining low-pressure hydroentangling and hot air processes, the fibers at the interface between the surface and bottom fiber webs become entangled to form a pore structure in a transitional state, creating a gradient structure that improves the phenomenon of weakened capillary force caused by a sudden change of 10 orders of magnitude in the pore structure.

[0040] 3. The guide layer has numerous inter-fiber bonding points and high pore structure strength. Under simulated actual use curved surface conditions, the pore structure maintains good shape retention, capillary force changes little, and the guiding effect is better. The preceding hydroentangling process causes the fibers to bend and entangle, creating contact points, which in turn form more bonding points between the skin layers under the action of hot air flow.

[0041] 4. The guide layer has good flatness, with virtually no fuzz on the surface and bottom layers. Utilizing the reinforcing effect of water jet impact on the upper fiber web, combined with the supporting effect of the hot air mesh curtain on the lower fiber web, the surface and non-use surfaces have high flatness and minimal fuzz.

[0042] 5. The low-pressure hydroentangling and hot air consolidation process solves the problem of hydrophilic oil loss caused by high-pressure water jet impact on the surface of hot air fibers in the traditional hydroentangling process. It breaks through the bottleneck that the hot air consolidation process cannot use high-content non-thermal-melting fibers. Compared with the hydroentangling process, the required hydroentangling pressure is lower and no drying is required after hydroentangling. Compared with the hot air process, there is no significant difference in flatness between the usable surface and the non-usable surface. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the equipment for preparing the flow guide layer of the present invention.

[0044] Figure 2 This is a schematic diagram of the water jet plate.

[0045] Figure 3 for Figure 2 The main view.

[0046] Figure 4 These are the test results from the aperture measuring instrument.

[0047] Drawing number explanation:

[0048] 1-Non-use surface fiber web; 2-Cardging machine 1; 3-Web laying machine; 4-Drum screen 1; 5-Pre-process airflow reinforcement and water needle reinforcement; 6-1, 6-2, 6-3, 6-4 Pressure rollers; 7-1 Alkali treatment; 7-2 Water washing; 8-Use surface fiber web; 9-Cardging machine 2; 10-Drum screen 2; 11-Post-process hydroentangling; 13-1 Atomizing device; 13-2 Holding airflow jet device; 13-3 Holding hot airflow; 13-4 Suction device; 13-5 Atomized droplets; 14-Hot air reinforcement oven. Detailed Implementation

[0049] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0050] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0051] Example 1

[0052] This invention relates to a flow-guiding layer that optimizes the competition between liquid permeation and diffusion by constructing an integrated asymmetric structure with significant pore size differences, resulting in rapid permeation in the upper layer and rapid diffusion in the lower layer. Initially, after the liquid contacts the flow-guiding layer, permeation becomes the dominant process. Sufficient capillary pressure difference ΔP (as shown in Equation 1) is required for permeation to be dominant. In the equation, θ1 and θ2 are the contact angles of the non-use surface and the use surface, respectively; γ is the surface tension of the liquid in air; and D1 and D2 are the average equivalent diameters of the capillary channels on the non-use surface and the use surface, respectively. In this invention, by combining low-pressure hydroentangling with hot air consolidation, it is ensured that the contact angles of both the use surface and the non-use surface are hydrophilic (i.e., θ1, θ2 < 90°, cosθ > 0), and that D1 < D2, D2 / D1 ≥ 10, thereby significantly increasing the capillary pressure difference ΔP. Therefore, the liquid can be rapidly and directionally conducted from the macropore structure to the micropore structure under the capillary pressure difference.

[0053] When liquid penetrates to the lower layer, diffusion becomes the dominant effect, requiring a sufficiently large capillary force P at the bottom layer (as shown in Equation 2). Traditional hot air guiding layers mainly utilize the pore structure formed between fibers to create capillary action. This invention, by adding hygroscopic non-meltable fibers, utilizes the synergistic effect between the micropore capillary force P1 formed by their hydrophilic groups and micropores on the fibers and the capillary force P2 formed by the pores between fibers to further enhance liquid diffusion at the bottom layer, achieving rapid liquid diffusion on the lower fiber network.

[0054]

[0055] P = P1 + P2 (Equation 2)

[0056] This embodiment provides a method for preparing a 40 g / m² flow-guiding layer, comprising the following steps: the surface fiber web has a basis weight of 24 g / m². 2 The basis weight of the bottom fiber mesh is 16g / m². 2 The thickness ratio of the surface fiber web to the bottom fiber web is approximately 1:3.

[0057] (1) Prepare raw materials. The non-use surface fibers are orange-petal type bicomponent fibers and viscose fibers. The orange-petal type bicomponent fibers have a denier of 3D and 16 petals. The use surface fibers are mesh-core type bicomponent ES fibers with deniers of 6D and 12D, and a length of 50mm. The two types of fibers are uniformly mixed and carded on the non-use surface, with the ratio of orange-petal type bicomponent fibers to viscose fibers being 1:8. The two types of fibers are uniformly mixed and carded on the use surface, with the ratio of hydrophilic coarse denier ES fibers to hydrophilic medium denier ES fibers (by weight) being 1:8.

[0058] (2) Hydroentangling reinforcement. Hydroentangling reinforcement is performed using a rotary screen hydroentangling process. The upper fiber web, transported by screen 1 (a 60-mesh screen), is pre-wetted before hydroentangling reinforcement. After hydroentangling reinforcement, pressure rollers are installed to remove residual water from the fiber web. The first hydroentangling process uses two hydroentangling heads. The first hydroentangling head reinforces the front side with a pressure of 15 bar. The second hydroentangling head reinforces the back side with a pressure of 20 bar.

[0059] (3) Alkali treatment of non-use fiber layers. After the previous hydroentanglement reinforcement, the fiber web is placed in an alkaline solution for treatment, followed by washing with water. The alkaline solution concentration is 5 g / L, the bath ratio is 1:20, and the temperature is 80℃.

[0060] (4) Second hydroentangling reinforcement. The lower fiber web does not need to be pre-wetted. The upper and lower fiber webs are supported by the mesh curtain 2 and undergo a second hydroentangling reinforcement together. The mesh curtain 2 is a 10-mesh mesh curtain. The second hydroentangling process is equipped with two hydroentangling heads with pressures of 30 bar and 40 bar, and both are equipped with pressure rollers to remove water trapped in the fiber web.

[0061] (5) Hot air consolidation. The drying temperature is 130-150℃ and the drying speed is 40m / min.

[0062] Comparative Example 1: A hot air guiding layer material was prepared using a double-carded method, with a basis weight of 40 g / m². The non-functional surface fibers were selected from 3D core-sheath type bicomponent ES fibers, and the basis weight of the lower fiber web was 16 g / m². 2 The surface is made of 6D core-sheath type bicomponent ES fiber.

[0063] Comparative Example 2: The rest is the same as Example 1, except that the pressure of the first hydroentangling head is 80 bar and 85 bar; the pressure of the second hydroentangling head is 90 bar and 100 bar. The hydroentangling screen is made of plain weave screen, and the high-pressure water jets combined with the low mesh count make it easy to form a mesh structure on the guiding surface.

[0064] Comparative Example 3: The rest is the same as Example 1, except that the non-use surface fiber in Comparative Example 3 is a core-sheath bicomponent ES fiber.

[0065] The pore size and distribution of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were tested using a pore size meter (CFP-1100-AI) manufactured by PMI Corporation, USA. The size of the test sample was 3×3cm. 2 The ambient temperature and humidity were controlled at 20±2℃ and 65%±4%, respectively. The test results are as follows: Figure 4 As can be seen, the horizontal axis value in the legend represents a range of pore size, such as 10 micrometers representing the pore size range of 0-10 micrometers, and 20 micrometers representing the pore size range of 10-20 micrometers.

[0066] As seen from the pore size distribution curve of Example 1, the pore size of the flow guide layer in Example 1 is mainly distributed below 10 micrometers, 10-20 micrometers, and 140-150 micrometers. This invention relates to a flow guide layer with significant porosity differences. As seen from the pore size distribution curve of Comparative Example 1, the hot air flow guide layer has larger pores, mainly distributed above 70 micrometers, and there is no significant porosity difference. As seen from the pore size distribution curve of Comparative Example 2, high-pressure hydroentangling causes the fibers to become more tightly entangled, resulting in a higher proportion of small pores. As seen from the pore size distribution curve of Comparative Example 3, the proportion of pores below 10 micrometers and 10-20 micrometers is low, with pore sizes mainly distributed in the 40-70 micrometer and 140-150 micrometer ranges, and the porosity difference becomes smaller. Only by using non-thermally pleasing fibers and orange-petal-shaped bicomponent fibers on the non-use surface, combined with a low-pressure hydroentangling hot air process, can a porosity difference of more than ten times be achieved.

[0067] The absorption performance of the guide layer in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 was tested using the following method:

[0068] 1. Adjust the temperature of the pig's blood to 23±1℃;

[0069] 2. Test the thickness of each sample separately;

[0070] 3. Take one sample and place it on the arc-shaped sample holder of the absorbency meter, which meets the requirements of GB / T / 8939-2018 Sanitary Napkins and Panty Liners. The sample is backed with 15 layers of absorbent paper, and the basis weight of the absorbent paper is (145 ± 5) g / m³. 2 Liquid absorption is greater than 480% (determined according to GB / T24218.6). A standard test module is placed above the sample.

[0071] 3. Use a pipette to put 5ml of pig blood into the standard test module and start timing the time required for the pig blood to be completely absorbed on the surface (i.e., absorption time s);

[0072] 4. After 5 minutes, cover the liquid addition point with a known weight of filter paper and place a 5kg arc-shaped pressure block on top (with the same curvature as the standard test module). After 2 minutes, weigh the filter paper W2 and calculate the increase in weight of the filter paper (i.e., the amount of backflow W).

[0073] 5. Repeat step 3 after 1 minute, repeating twice, for a total of 3 additions.

[0074] 6. Test the thickness of each sample after three additions of liquid.

[0075]

[0076] Compared with Comparative Example 1, Example 1 exhibits faster absorption speed and lower backflow rate on the arc surface. The minimal performance change after multiple liquid additions indicates that Example 1 maintains good shape retention of the pore structure on the arc surface, resulting in minimal change in capillary force. In contrast, Comparative Example 1 has lower pore structure strength, leading to fiber slippage and deformation of the pore structure of the guide layer after multiple liquid additions and pressurization. Furthermore, the number of contact points between fibers decreases, resulting in a larger equivalent pore size on the non-use surface of the guide layer and a weaker capillary force, which is detrimental to rapid liquid infiltration and reduced backflow.

[0077] Compared with Comparative Example 2, Example 1 showed a slower absorption rate and a higher amount of moisture return. Comparative Example 2 used high-pressure water jetting, which resulted in tight fiber entanglement, preventing the formation of a pore gradient. Furthermore, the high-pressure water jetting caused the loss of hydrophilic oils on the surface of the ES fibers.

[0078] Compared with Comparative Example 3, Example 1 showed a slower absorption rate, while Comparative Example 3 had a similar amount of moisture return. Comparative Example 3 did not use orange-petal-shaped bicomponent fibers or hygroscopic non-meltable fibers, resulting in a slightly slower absorption rate. The low-pressure hydroentangled flow guide layer exhibited high pore structure strength, good shape retention under simulated actual use curved surface conditions, minimal change in capillary force, and superior flow guiding effect.

[0079] Using Example 1, Comparative Example 1, and Comparative Example 3 as the absorbent layer materials for sanitary napkins, with a 100% cotton surface layer and a high-polymer wood pulp core, the performance of the sanitary napkins was tested according to the following methods:

[0080] 1. Adjust the temperature of the pig's blood to 23±1℃;

[0081] 2. Take one sample and place it on the arc-shaped sample holder of the absorption rate meter, which meets the requirements of GB / T / 8939-2018 Sanitary Napkins and Panty Liners. Place the standard test module on top of the sample;

[0082] 3. Use a pipette to put 5ml of pig blood into the standard test module and start timing the time required for the pig blood to be completely absorbed on the surface (i.e., absorption time s);

[0083] 4. After 5 minutes, cover the liquid addition point with a known weight of filter paper (110 mm in diameter) and place a 2.5 kg arc-shaped pressure block on top (with the same curvature as the standard test module). After 2 minutes, weigh the filter paper W2 and calculate the increase in weight of the filter paper (i.e., the amount of backflow W).

[0084] 5. Test the diffusion length between the surface layer and the core.

[0085]

[0086] Compared with Comparative Example 1, Example 1 exhibits faster absorption speed, less backflow, smaller surface diffusion area, and larger core diffusion area. The low-pressure water-jet hot air guiding layer maintains good shape retention of its pore structure on the curved surface and has significant pore differences, ensuring rapid infiltration of the surface liquid and diffusion and absorption in the core.

[0087] Compared with Comparative Example 3, Example 1 exhibits faster absorption speed, less backflow, smaller surface diffusion area, and larger core diffusion area. In Comparative Example 3, the diffusion effect was slightly worse because no ultrafine denier fibers were added to the guide layer. The low-pressure hydroentangled hot air guide layer can effectively regulate the competition between liquid penetration and diffusion within the guide layer, enabling rapid liquid penetration to the surface and rapid diffusion to the bottom layer.

[0088] Example 2

[0089] The flow-guiding layer material combining low-pressure hydroentanglement and hot air in this embodiment is prepared through a low-pressure hydroentanglement and hot air composite process, such as... Figure 1 As shown, the specific process is as follows:

[0090] (1) Non-use surface fiber web. The non-use surface fiber web is opened, combed and laid, and the non-use surface fibers are laid in a straight manner.

[0091] The non-use surface fiber web is laid straight to ensure high longitudinal fiber orientation and denser fibers, which is more conducive to longitudinal diffusion. The use surface fiber web is opened and combed, resulting in a sparse fiber arrangement.

[0092] (2) Hydroentangling reinforcement of non-use surface fibers. Hydroentangling reinforcement adopts a rotary drum spunling process. The non-use surface fiber web is pre-wetted and then subjected to the first hydroentangling reinforcement while being transported by the mesh curtain. The first hydroentangling process has two spunling heads. The first spunling head is for front reinforcement with a pressure of 15 bar; the second spunling head is for back reinforcement with a pressure of 20 bar.

[0093] The first hydroentangling process uses a hydroentangling head consisting of a main body, a hydroneedle plate, and a bottom cover, as shown in the figure. The bottom cover has a hollow structure, and its lower surface has protruding conical injection holes, which are connected to the hollow bottom cover. In this embodiment, low-pressure hydroentangling is used, which places lower demands on the strength of the cover plate, and the hollow structure of the cover plate can still meet the hydroentangling requirements. The conical injection holes are linearly distributed on the lower surface of the bottom cover. The hydroneedle plate is located at the center of the bottom cover, and its holes are linearly distributed, arranged parallel to the conical injection holes, and alternately spaced. The diameter of the conical injection holes is approximately 1-5 times that of the hydroneedle plate, and they are closer to the mesh curtain. While the hydroneedles are reinforcing the fiber, a high-pressure airflow is generated by an air source and enters the conical injection holes from the hollow bottom cover, forming a reinforcing airflow that impacts the fiber surface. The air pressure in the conical injection holes is 10 bar to 40 bar. The second hydroentangling process does not require airflow-assisted reinforcement.

[0094] Airflow kinetic energy has a short duration of hold and is easily dispersed. Although its reinforcement effect is relatively average, and the reinforced material is loose with many fuzzy surfaces, the easy dispersion of airflow allows fine denier viscose fibers to shift significantly at large angles, altering fiber orientation. Water jet kinetic energy has a long duration of hold and is concentrated, having less impact on fiber orientation and resulting in tighter fiber entanglement, which is more conducive to forming a dense porous structure. Using alternating distributions of airflow and water jets to reinforce the fiber web creates alternating loose and tightly entangled regions along the material's width. The loosely entangled regions at the bottom layer have a loose, fuzzy structure. During lamination, these fuzzy areas extend into the fiber web on the usable surface and entangle with it, mitigating the abrupt change in pore diameter from the usable to non-usable surface, thus forming more transitional porous structures and improving the slow absorption rate. Simultaneously, the fiber orientation along the material's width becomes an alternating structure of random and longitudinal distribution. Longitudinal fiber distribution promotes good longitudinal diffusion of liquids, but the fewer entanglements in longitudinally distributed fibers lead to faster capillary attenuation. Randomly distributed fibers have more entanglements and stronger capillary effects, but diffusion lacks directionality. Alternating structures of random and longitudinal distributions not only improve longitudinal diffusion but also increase the number of entanglements, significantly enhancing the diffusion performance of the underlying layer.

[0095] Retained water in the fiber web creates resistance, affecting the reinforcement effect of hydroentanglement. However, this effect is minimal for high-pressure hydroentanglement (above 100 bar). Low-pressure hydroentanglement, with its lower kinetic energy, is also affected by the resistance from retained water, impacting its reinforcement effect. For low-pressure hydroentanglement, removing retained water using a pressure roller device can improve the consolidation effect.

[0096] In hydroentanglement, the mesh curtain acts as a support for the fiber web, while the energy reflected by the water jets further strengthens the web, forming a denser mesh structure. The non-use surface of the fiber web adopts a high-mesh-count mesh curtain structure, allowing the fiber web to absorb more positive water jet energy and fully utilize the reflected water jet energy, resulting in tighter fiber entanglement.

[0097] Through the energy of the water injection, the orange-petal-shaped bicomponent fiber achieves initial fiber opening. A certain gap will be generated between the different components in the fiber, which is more conducive to the subsequent entry of alkaline solution into the fiber interior and improves the subsequent fiber opening effect.

[0098] (3) Alkali treatment of the non-use fiber layer. After the first hydroentanglement reinforcement, the fiber web is immersed in an alkaline solution for treatment, followed by washing with water. The concentration of the alkaline solution is 4-6 g / L, the bath ratio is 1:20-1:30, and the temperature is 40-80℃. The alkaline treatment has two main effects: 1. It weakens the interfacial strength between the orange-segment type bicomponents, improving the subsequent fiber opening effect. The ester bonds undergo hydrolysis when they encounter the alkaline solution, which erodes the interface of the composite fiber, thereby weakening the interfacial bonding strength; 2. It reduces the crystallinity of cellulose in the hygroscopic non-meltable fiber, increases the amorphous region in the fiber, improves the liquid absorption capacity of the fiber, and increases the fineness of the non-use surface fibers.

[0099] (4) Second hydroentangling reinforcement. The non-use-side fiber web, after alkali treatment and washing, and the use-side fiber web undergo a second hydroentangling reinforcement process together under the support of a screen. The non-use-side fiber web does not require pre-wetting. The upper and lower fiber webs undergo a second hydroentangling reinforcement process together under the support of screen 2, which is a 10-mesh screen. The second hydroentangling process is equipped with two hydroentangling heads with pressures of 30 bar and 40 bar, both equipped with pressure rollers to remove water trapped in the fiber web. This process is used for opening the orange-petal-shaped bicomponent fibers on the non-use side and for the composite of the two-layer fiber web.

[0100] The interfacial forces of the orange-segment fiber composite are weakened after the first hydroentangling and alkali treatment. Further hydroentangling causes 20%–40% of the orange-segment fibers to split into ultra-fine denier fibers, resulting in numerous pores of 10–20 micrometers or less between the fiber webs. The remaining unbroken orange-segment fibers contain a certain amount of low-melting-point PET, which, during subsequent hot air reinforcement, thermally bonds with each other, further enhancing the strength of the pore structure.

[0101] The fiber mesh used was not pre-wetted and contained a certain amount of air. The air hindered the energy of the water jet. At the same time, the fiber mesh was relatively coarse and had high bending stiffness. Even after subsequent hydroentangling reinforcement, it could still maintain a loose and porous structure.

[0102] In the subsequent hydroentangling process, a low-mesh-count mesh curtain 2 is used, which allows the water jets to penetrate the fiber mesh better and is less prone to reflection, ensuring that the double-layer fiber mesh can be composited and that the surface fibers remain fluffy.

[0103] (5) After the surface fiber web is opened and combed, there is no need to lay the web, and it can be directly atomized and hot air consolidated.

[0104] The atomized finishing liquid is composed of hydrophilic oil agents, binders, and water. Atomized finishing primarily utilizes a high-speed airflow through an atomizing device to break the finishing liquid into very small droplets. These droplets adhere to the lower surface of the fibers, achieving a one-sided finishing effect. The diameter of the finishing droplets is 0.001-0.1 mm; the number is 10-1000 droplets / cm². 2 In this embodiment, a holding hot airflow is provided between the atomizing device and the suction device. The holding hot airflow mainly serves two purposes: improving the atomization finishing efficiency and increasing the viscosity of the finishing liquid. The holding airflow ensures that the atomized droplets are evenly distributed on the surface of the fiber mesh used for finishing. During the process of finishing droplets adhering to the fiber mesh, the holding airflow can gradually evaporate the water in the finishing droplets, increasing the viscosity of the finishing droplets. When finishing droplets with high surface tension and high viscosity adhere to the fiber mesh, most of the finishing liquid will adhere to the entanglement of the fibers, and due to the high viscosity, the droplets will change from a spherical shape to a teardrop shape under the action of the suction device. When the seeping liquid comes into contact with the solidified teardrop-shaped adhesive droplets, the Laplace pressure gradient difference caused by the change in curvature can accelerate the seepage of the liquid.

[0105] The atomizing liquid uses a hydrophilic oil agent whose main component is a hydroxyl-modified organosilicon hydrophilic oil agent, and a binder made of modified polyvinyl alcohol. The mass fractions of the hydrophilic oil agent and the binder are 5% and 2%, respectively. The temperature of the holding airflow is set to 95–105°C, and the holding airflow pressure is 1–10 bar.

[0106] After entering the atomization finishing stage, the fabric undergoes hot air consolidation in a hot air drying oven. During hot air consolidation, the airflow penetrates from the fiber web on the usable side to the fiber web on the non-usable side, and the non-usable side fiber web adheres to the roller or mesh curtain. After hot air consolidation, the fabric is rolled and slit to obtain the sanitary napkin's guide layer. The drying temperature is 130–150℃, and the drying speed is 40 m / min. For traditional hot air fabrics, the hot airflow causes fiber displacement and fuzz when it acts on the fiber web. Due to the support of the roller or mesh curtain, the side closest to the roller or mesh curtain has less fuzz and more consolidation points. By first undergoing hydroentangling followed by hot air treatment, the non-usable side is directly exposed to the water jets, while the usable side is supported by the mesh, preventing fuzz formation on either side. Furthermore, hydroentangling creates more contact points between fibers, forming more adhesion points during subsequent hot air consolidation, thereby increasing pore strength.

[0107] Comparing the absorption performance of the guide layer and the performance of the sanitary napkin in Examples 1 and 2, the reinforcement of the fiber web by alternating distribution of airflow and water needles can improve the abrupt change in the pore diameter from the used surface to the non-used surface, thereby forming more transitional pore structures. Combined with the water droplet structure design, it can significantly improve the absorption speed of the guide layer and reduce the amount of backflow.

[0108]

[0109]

[0110] Note: The maximum width of the core is 75.

[0111] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0112] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0113] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A flow guide layer, characterized in that, The flow guiding layer is composed of a double-layer fiber web, wherein, The flow guide layer has a basis weight of 30-60 g / m 2 The non-use surface fiber web has a basis weight of 18-36 g / m 2 The use surface fiber web has a basis weight of 12-24 g / m 2 The flow guide layer satisfies D2 / D1≥10, wherein D1 and D2 are the average equivalent diameters of the capillary channels in the non-use surface and the use surface, respectively. The thickness of the flow guiding layer is 0.8 to 1.6 mm, and the thickness ratio of the fiber mesh on the used surface to the fiber mesh on the non-used surface is 1:2 to 4. The non-use surface fiber web is composed of bicomponent orange-petal-shaped fibers and hygroscopic non-melting fibers.

2. The flow guide layer of claim 1, wherein, The bicomponent orange-petal type fiber is made of PA6 and low-melting-point PET, with a denier of 3D to 6D, a length of 10-50mm, a petal number of 6 to 32, and a fineness of 0.05-1D after fiber opening.

3. The flow guide layer of claim 1, wherein, In the use of the surface fiber net, the lower surface of the fiber net is formed with water drop type protrusions, the diameter of the water drop type protrusions is 0.001-0.1mm; the number of the water drop type protrusions is 10-1000 per cm 2 .

4. A process for preparing a flow-guiding layer as described in claim 1, characterized in that, The process includes the following steps: 1) Non-use fiber webs are opened and carded using a carding machine; The netting is laid by a netting machine; After being laid, the fiber web undergoes its first hydroentangling process through a rotating drum screen. After the first hydroentanglement process, the non-use fiber web is squeezed out of water by pressure rollers and then enters the alkali treatment equipment. After the alkali treatment, the non-use fiber web is squeezed out of water by pressure rollers and then enters the washing equipment. After washing, the non-use fiber web is squeezed dry by pressure rollers; 2) After the fiber mesh is opened and combed, there is no need to lay the mesh; it can be directly atomized and hot-air consolidated. Surface atomization is achieved using a fiber mesh atomized by an atomizing device; After being shaped by the holding air jet device and the suction device, it enters the hot air curing oven for further curing. 3) Integrate the non-use surface fiber web processed in step 1) and the use surface fiber web processed in step 2), and perform a second hydroentanglement reinforcement through the rotary drum screen.

5. The process for preparing the flow guiding layer as described in claim 4, characterized in that, It also includes the following steps: The water-drop type protrusions are prepared on the lower surface of the surface fiber web, the diameter of the water-drop type protrusions is 0.001-0.1mm, and the number of the water-drop type protrusions is 10-1000 / cm 2 .

6. The process for preparing the flow guide layer as described in claim 5, characterized in that, The steps for preparing the teardrop-shaped protrusion include: Preparation of atomizing finishing solution; the atomizing finishing solution is composed of hydrophilic oil agent, binder and water; The atomizing device is used to spray droplets of the finishing liquid onto the surface of the fiber mesh used in the application. The droplets adhere to the fiber surface under the action of the suction device to achieve a one-sided finishing effect; By utilizing the holding of hot airflow to change the viscosity of atomized droplets, a droplet-shaped structure can be formed. Hot air is used to pre-reinforce the fibers while simultaneously solidifying the atomized droplets in the form of water droplets on the surface of the fiber web.

7. A flow guide layer preparation system for implementing the flow guide layer preparation process as described in claim 4, characterized in that, The system includes at least a non-use surface fiber web preparation system; the non-use surface fiber web preparation system includes a carding machine, a web laying machine, a rotary drum screen, a first hydroentangling stage, a pressure roller, an alkali treatment device, and a washing device arranged in sequence; the system also includes a carding machine for preparing the use surface fiber web, an atomizing device, a holding air jet device, a suction device, and a hot air strengthening oven; and a second rotary drum screen and a second hydroentangling stage for integrating the non-use surface fiber web and the use surface fiber web.

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