A dual layer absorbent core

Abstract

The present application relates to the field of disposable sanitary products, in particular to a double-layer absorbent core, comprising a body, the body comprising a first non-woven fabric, a second non-woven fabric and a fluffy cotton clamped between the first non-woven fabric and the second non-woven fabric, an upper water-absorbing particle layer is arranged on the side of the fluffy cotton close to the first non-woven fabric, a lower water-absorbing particle layer is arranged on the side of the fluffy cotton close to the second non-woven fabric, the water-absorbing performance per unit area of the upper water-absorbing particle layer is defined as A1, the water-absorbing performance per unit area of the lower water-absorbing particle layer is defined as A2, A1:A2 is (7-9):10, and the uniformity of the body is 5% to 20%. The technical problem of distortion or low utilization caused by the unevenness of the absorption performance of the existing multi-layer absorbent is solved.

Description

Technical Field

[0001] This invention relates to the field of disposable hygiene products, and more particularly to a double-layer absorbent core. Background Technology

[0002] Currently, multi-layered absorbent cores are widely used in the field of disposable hygiene products. For example, Chinese patent application CN202320998452.8 discloses a non-woven absorbent core comprising a body, an upper fiber layer, a lower fiber layer, and an intermediate fiber layer sandwiched between the upper and lower fiber layers. The upper, lower, and intermediate fiber layers are bonded together to form an adhesive portion, the area of ​​which accounts for 5-100% of the body area. The fiber thickness of the upper and / or lower fiber layers is 4-12D, and the fiber thickness of the intermediate fiber layer is 0.6-2D. High-absorbency polymer particles are embedded within the upper and lower fiber layers. The average pore size of the upper and lower fiber layers is larger than the average diameter of the high-absorbency polymer particles, while the average pore size of the intermediate fiber layer is smaller than the average diameter of the high-absorbency polymer particles. Existing methods typically utilize fluffy cotton as the intermediate material layer, taking advantage of its numerous and large pores to create a stable space for the absorbent particles, thereby achieving two or more layers of absorbency.

[0003] However, due to the different water absorption properties of the multiple layers, the absorption performance of the absorbent is easily uneven, which can lead to problems such as distortion of the absorbent or low utilization rate. Summary of the Invention

[0004] Therefore, in view of the above problems, the present invention proposes a double-layer absorbent core, which solves the technical problems of distortion or low utilization rate caused by the uneven absorption performance of existing multi-layer absorbers.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a double-layer absorbent core, comprising a body, the body comprising a first nonwoven fabric, a second nonwoven fabric, and fluffy cotton sandwiched between the first and second nonwoven fabrics, wherein an upper absorbent particle layer is disposed on the side of the fluffy cotton closest to the first nonwoven fabric, and a lower absorbent particle layer is disposed on the side of the fluffy cotton closest to the second nonwoven fabric, wherein the fluffy cotton is provided with through or non-through slots, the area of ​​the slots being 10% to 15% of the area of ​​the body, and the size of the unit area is defined as 1 to 5 square centimeters. In the part of the body that does not contain slots, the water absorption performance per unit area of ​​the upper absorbent particle layer is defined as A1, and the water absorption performance per unit area of ​​the lower absorbent particle layer is defined as A2, wherein A1:A2 is (7 to 9):10.

[0006] Furthermore, the slot includes one or more strip-shaped holes arranged along the length direction of the body and two or more flow-limiting holes arranged at both ends along the length direction of the body.

[0007] Furthermore, the strip-shaped hole is a through slot, with one strip-shaped hole located in the middle of the body.

[0008] Furthermore, at least 90% of the water-absorbing particles in the upper absorbent particle layer are completely embedded in the fluffy cotton.

[0009] Furthermore, at least 70% by mass of the absorbent particles in the lower absorbent particle layer are completely embedded in the fluffy cotton.

[0010] Furthermore, the fluffy cotton includes a fluffy upper layer and a fluffy lower layer evenly arranged, with the upper absorbent particle layer located on the fluffy upper layer and the lower absorbent particle layer located on the fluffy lower layer.

[0011] Furthermore, during the water absorption performance test, 0.9% physiological saline was poured in, and after complete absorption, the mixture was left to stand for a certain period of time. Then, the fluffy upper layer and fluffy lower layer were separated, and three or more unit area samples of each were weighed and the average value was taken. The ratio between the average weight of the unit area of ​​the fluffy upper layer after water absorption and the average weight of the unit area of ​​the fluffy lower layer after water absorption is A1:A2.

[0012] Furthermore, the light transmittance of the body is 30% to 75%. The light transmittance is defined as follows: in a closed environment and when the body does not absorb water, after the slot is blocked, light is irradiated on one side of the body to allow light to pass through the body, and the intensity of the light is detected by detectors on both sides of the body. The ratio between the intensity of the light that passes through the body and the intensity of the light that does not pass through the body is the light transmittance.

[0013] Furthermore, the uniformity of the body is 5% to 20%. The uniformity is defined as follows: in a closed environment and when the body is fully absorbed by water, after the slot is blocked, light is irradiated on one side of the body to allow the light to penetrate the body, and the intensity of the light is detected on both sides of the body by detectors. The ratio between the intensity of the light that penetrates the body and the intensity of the light that does not penetrate the body is the uniformity.

[0014] Furthermore, a projection plate is set on one side of the main body. The total area of ​​the bright spots formed by the light passing through the main body on the projection plate is S1, and the projection area of ​​the main body on the projection plate is S2. The ratio of S1 to S2 is less than 1:20.

[0015] By adopting the aforementioned technical solution, the beneficial effects of the present invention are:

[0016] 1. In this design, the area of ​​the perforations is limited to 10% to 15% of the body area. Two absorbent layers are incorporated—an upper absorbent granule layer and a lower absorbent granule layer. Therefore, the perforation design has certain requirements. If the perforations penetrate the fluffy cotton, and the perforation area is large enough, liquid can easily pass through quickly without being absorbed by the upper and lower absorbent granule layers. If the perforations do not penetrate the fluffy cotton, liquid is easily absorbed quickly by the lower absorbent granule layer, resulting in less absorption by the upper absorbent granule layer, causing deformation of the absorbent body and discomfort. To achieve a more balanced effect, limiting the perforation area to 10% to 15% of the body area is optimal, and even better, it should be 12% to 13%.

[0017] After defining the slot size, the water absorption performance of the absorbent particles also needs to be controlled. In this scheme, the water absorption performance per unit area of ​​the upper absorbent particle layer is defined as A1, and the water absorption performance per unit area of ​​the lower absorbent particle layer is defined as A2, with A1:A2 being (7-9):10. This results in a certain enhancement in the water absorption performance of the lower absorbent particle layer compared to the upper absorbent particle layer. This enhancement is uniform and is limited to a specific unit area. It allows for rapid absorption and diffusion of the liquid in the lower absorbent particle layer during infiltration, while also ensuring that the upper absorbent particle layer also absorbs a certain amount. This results in better control of the deformation of the fluffy cotton after water absorption, preventing excessive twisting and ensuring a better distribution of water absorption, which is beneficial for maximizing the utilization rate of the body's water absorption performance.

[0018] 2. The function of the flow-limiting orifice is to restrict side leakage. It can limit the obstruction of liquid diffusion inside the fluffy cotton and improve the efficiency of liquid seepage. When liquid cannot be absorbed in time at the strip orifice, it may flow towards both ends along its length. The flow-limiting orifice effectively obstructs this flow and improves absorption performance. If the flow-limiting orifice is connected to the strip orifice to form a longer strip orifice, the effect is weaker. In addition, limiting the strip orifice to a through-hole, with one of the strip orifices located in the middle of the body, is beneficial for liquid diffusion.

[0019] 3. In the upper absorbent particle layer, at least 90% of the absorbent particles by mass are completely embedded within the fluffy cotton. This ensures the stability of the absorbent particle position. Since the absorbent particles are added by spreading, they are usually located on the surface of the fluffy cotton. A vibration device is then used to apply the absorbent particles, causing them to gradually penetrate into the fluffy cotton. However, due to the size of the pores, the size of the absorbent particles, and measures to prevent the absorbent particles from penetrating deeply into the fluffy cotton, some absorbent particles will still remain on the surface. Similarly, the lower absorbent particle layer is designed in the same way, except that at least 70% of the absorbent particles by mass are completely embedded within the fluffy cotton. The difference lies in the type of absorbent material. Since the upper absorbent particle layer is close to the body, the particles need to be embedded as much as possible within the fluffy cotton to ensure both comfort and absorbency. The lower absorbent particles, however, are further away from the body. As long as the particles not embedded in the fluffy cotton don't cause significant problems, that's sufficient. A small portion of these particles are located outside the fluffy cotton, specifically between the fluffy cotton and the second non-woven fabric. These particles are also secured with adhesive, reducing the deformation of the fluffy cotton after absorbing water and expanding. This, combined with the absorbency per unit area, minimizes the distortion and deformation of the material itself.

[0020] 4. When testing water absorption performance, pour in 0.9% physiological saline solution and wait for complete absorption. Let it stand for a certain period, then separate the fluffy upper layer from the fluffy lower layer. Take at least three unit area samples from each layer, weigh them separately, and take the average value. The three or more unit area samples should be of the same size and preferably from different locations, such as the ends and middle of the length. The standing time is usually 10-20 minutes. It is best to place them on a filter screen to reduce surface moisture, with the fluffy upper layer on top and the fluffy lower layer on the bottom.

[0021] 5. The limitation of light transmittance mainly restricts the distribution of absorbent particles. This is determined by comparing the intensity of light before and after transmission, thereby achieving a better distribution of absorbent particles. In this design, this also applies to the distribution of the upper and lower absorbent particle layers, ensuring uniformity and consistency. This results in better deformation stability and consistency of the body after liquid absorption, leading to a better wearing experience.

[0022] 6. The limitation on uniformity is related to the limitation on transmittance. The limitation on uniformity can effectively assist in improving transmittance, mainly by limiting the amount of water absorbed and the resulting blockage, thus achieving better water absorption performance. Of course, some areas may have special distribution of water-absorbing particles. For example, in certain areas, the distribution of water-absorbing particles may be relatively sparse, but these areas do not have slots. This will create light spots during measurement. The maximum allowable total area of ​​light spots is 1 / 20 of the body area. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the double-layer absorber forming device;

[0024] Figure 2 yes Figure 1 A structural diagram of the adsorption wheel has been added;

[0025] Figure 3 This is a schematic diagram of the structure of the present invention;

[0026] Figure 4 This is a cross-sectional structural diagram of the present invention.

[0027] Figure label:

[0028] 11. First forming die wheel; 12. First spreading device; 13. First glue spraying device; 21. Second forming die wheel; 22. Second spreading device; 23. Second glue spraying device; 3. Winding device; 4. Fluffy cotton input mechanism; 5. First nonwoven fabric input mechanism; 6. Second nonwoven fabric input mechanism; 7. Separation mechanism; 8. Adsorption wheel; 91. First nonwoven fabric; 92. Second nonwoven fabric; 93. Fluffy cotton; 931. Fluffy upper layer; 932. Fluffy lower layer; 94. Primary composite fabric; 951. Upper absorbent particle layer; 952. Lower absorbent particle layer; 96. Strip hole; 97. Flow limiting hole. Detailed Implementation

[0029] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0030] refer to Figure 3 , Figure 4 This embodiment provides a double-layer absorbent core, including a body. The body includes a first nonwoven fabric 91, a second nonwoven fabric 92, and a fluffy cotton 93 sandwiched between the first nonwoven fabric 91 and the second nonwoven fabric 92. An upper absorbent particle layer 951 is provided on the side of the fluffy cotton 93 near the first nonwoven fabric 91, and a lower absorbent particle layer 952 is provided on the side of the fluffy cotton 93 near the second nonwoven fabric 92. The fluffy cotton 93 is provided with through or non-through slots. The area of ​​the slots is 10% to 15% of the area of ​​the body, and the size of the unit area is defined as 1 to 5 square centimeters. Preferably, the size of the unit area is defined as 2 square centimeters. In the part of the body that does not contain slots, the water absorption performance per unit area of ​​the upper absorbent particle layer 951 is defined as A1, and the water absorption performance per unit area of ​​the lower absorbent particle layer 952 is defined as A2, where A1:A2 is (7~9):10, and preferably A1:A2 is 8:10.

[0031] The slot includes one or more strip-shaped holes 96 arranged along the length of the body and two or more flow-limiting holes 97 located at both ends of the length of the body. The strip-shaped holes 96 are through slots, with one strip-shaped hole 96 located in the middle of the body.

[0032] In the design and manufacturing of the absorber, the area ratio of the slots was carefully considered and limited. As a key part of the absorber structure, the size of the slots directly affects the liquid absorption efficiency and the overall performance of the absorber. To ensure that the liquid can be uniformly absorbed by the upper and lower absorbent particle layers and to avoid the liquid passing through too quickly or uneven absorption in certain areas, we limited the area of ​​the slots to 10% to 15% of the body area.

[0033] In practice, we first determine the shape and distribution of the slots to ensure their area proportion is within a set range. This step is crucial because the size of the slot area directly affects the liquid flow path and absorption rate. If the slot area is too large, the liquid will easily pass through the fluffy cotton layer quickly and cannot be fully absorbed by the upper and lower absorbent particle layers. Conversely, if the slot area is too small, it may restrict the liquid flow and affect absorption efficiency.

[0034] To achieve a more balanced absorption effect, we further optimized the area ratio of the slots. Through experimental verification, we found that when the area ratio of the slots is controlled between 12% and 13%, the absorbent achieves better performance. This setting ensures that the liquid can pass smoothly through the slots and be evenly absorbed by the upper and lower layers of absorbent particles, while avoiding problems such as uneven absorption or liquid leakage caused by slots that are too large or too small.

[0035] In addition, we paid special attention to the impact of whether the slots penetrate the fluffy cotton on the absorption effect. If the slots penetrate the fluffy cotton, the excessively large slot area will cause liquid to pass through quickly without being fully absorbed; while if the slots do not penetrate the fluffy cotton, the liquid may be absorbed too quickly by the lower absorbent granule layer, resulting in insufficient absorption by the upper absorbent granule layer, which in turn affects the overall shape of the absorbent and the wearing comfort.

[0036] Therefore, by precisely controlling the area ratio of the slots to between 10% and 15%, and further optimizing it to between 12% and 13%, we can achieve a more balanced absorption effect. This design not only improves the overall performance of the absorbent but also effectively avoids problems such as liquid leakage and uneven absorption, thus ensuring wearing comfort and effectiveness.

[0037] At least 90% by mass of the absorbent particles in the upper absorbent particle layer 951 are completely embedded within the fluffy cotton 93. At least 70% by mass of the absorbent particles in the lower absorbent particle layer 952 are completely embedded within the fluffy cotton 93.

[0038] The fluffy cotton 93 includes a fluffy upper layer 931 and a fluffy lower layer 932 evenly arranged, the upper absorbent particle layer 951 is located on the fluffy upper layer 931, and the lower absorbent particle layer 952 is located on the fluffy lower layer 932.

[0039] For water absorption performance testing, 0.9% physiological saline is poured in, and after complete absorption, it is allowed to stand for a certain period of time. Then, the fluffy upper layer 931 and fluffy lower layer 932 are separated, and at least three unit area samples of each are weighed and the average value is taken. The ratio between the average weight per unit area of ​​the fluffy upper layer 931 after water absorption and the average weight per unit area of ​​the fluffy lower layer 932 after water absorption is A1:A2. The indicator of complete absorption is that the absorption area of ​​the substrate no longer expands. The standing time is usually 10-20 minutes. The best method is to place it on a filter screen to reduce the surface moisture, with the fluffy upper layer on top and the fluffy lower layer on the bottom. Of course, other methods can also be used to determine complete absorption. The standing time and the standing method can also be adjusted according to actual needs.

[0040] In conducting water absorption performance tests, we employed a standardized method to ensure the accuracy and reliability of the results. First, we poured in 0.9% physiological saline solution to simulate the fluid environment within the human body, thus making the test results more practically meaningful. After pouring in the saline solution, we waited for the substrate to fully absorb it; this step is crucial as it ensures that we obtain the substrate's true water absorption capacity.

[0041] To determine if absorption is complete, we observe whether the absorption area of ​​the substrate continues to expand. Once absorption stops, it is considered saturated. At this point, we allow the substrate to stand for a period of time, typically 10-20 minutes, to allow the absorbed moisture to distribute more evenly within the substrate. For better test results, we recommend placing the substrate on a filter screen during this process. This effectively reduces surface moisture, leading to more accurate measurements. During this standing period, we ensure the upper fluffy layer 931 is on top and the lower fluffy layer 932 is on the bottom to maintain the substrate's natural state.

[0042] After settling, we proceed to the next step: separating the fluffy upper layer 931 from the fluffy lower layer 932. To ensure the representativeness of the results, we weighed at least three unit area samples from each layer and calculated their average value. In this way, we can obtain the average unit area weight of the water-absorbed fluffy upper layer 931 and fluffy lower layer 932, and thus determine their ratio A1:A2. This ratio is crucial for evaluating the water absorption performance of the substrate and the interlayer moisture distribution.

[0043] Furthermore, we emphasize that determining "complete absorption" is not limited to observing whether the absorption area has expanded. In practice, we can also use other indicators or methods to determine whether the substrate has reached absorption saturation. Similarly, while the settling time is usually set at 10-20 minutes, it can be flexibly adjusted according to actual needs. The settling method is also not fixed; the most suitable method can be chosen based on the specific circumstances.

[0044] Through these standardized operating procedures and flexible, adjustable settling times and methods, we can more comprehensively and accurately evaluate the water absorption performance of the product.

[0045] The transmittance of the substrate is between 30% and 75%. Transmittance is defined as measured in a strictly controlled, sealed environment. In this environment, the substrate is completely dry to ensure the accuracy of the measurement results. During the measurement process, all slots and holes are first blocked to avoid interference from external light. Next, a light source is shone on one side of the substrate, allowing light to attempt to penetrate it. To quantify the degree of light penetration, detectors are placed on both sides of the substrate to detect the light intensity before and after penetration. Finally, the transmittance is calculated by comparing the intensity of light passing through the substrate with the initial intensity of light not passing through it. This ratio, or transmittance, is a key indicator for measuring the light transmission performance of the substrate material.

[0046] First, a sealed environment minimizes the impact of external factors on the measurement results. Since external light, temperature, and humidity can all interfere with transmittance measurements, measurements taken in a sealed environment ensure accuracy and reliability. Second, the material's absence of water absorption is also crucial for accurate results. Water absorption can alter the material's optical properties, affecting transmittance measurements. Therefore, measurements taken in a dry state eliminate the influence of moisture on material properties, providing a more accurate reflection of the material's transmittance.

[0047] The uniformity of the body is 5% to 20%. The uniformity is defined as follows: in a sealed environment with the body fully absorbed water, after the slots are blocked, light is shone on one side of the body to allow light to penetrate it. Detectors on both sides of the body measure the light intensity. The ratio between the intensity of light that penetrates the body and the intensity of light that does not penetrate the body is the uniformity. A projection plate is placed on one side of the body. The total area of ​​the bright spots formed on the projection plate by the light passing through the body is S1, and the projected area of ​​the body on the projection plate is S2. The ratio of S1:S2 is less than 1:20.

[0048] The uniformity of the light distribution in the body is designed to be between 5% and 20%, a design that has been carefully calculated. The uniformity, a key parameter, is defined as follows: In a completely sealed environment, after the body has fully absorbed water, all the pores are blocked. Then, a light source is used to illuminate the body from one side, allowing light to penetrate. To accurately measure the light penetration, highly sensitive photodetectors are placed on both sides of the body to detect the light intensity.

[0049] The uniformity here refers to the ratio between the intensity of light passing through the bulk material and the original light intensity that does not pass through it. This ratio directly reflects the light transmittance of the bulk material, thus characterizing the uniformity of its internal structure and, consequently, the distribution of polymer particles. By precisely controlling this ratio between 5% and 20%, we can ensure that the bulk material maintains good water absorption while also possessing sufficient structural strength and stability.

[0050] To more intuitively observe and evaluate light penetration, a high-precision projection panel was placed on one side of the main body. When light passes through the main body, it forms a series of bright spots on the projection panel. The total area of ​​these bright spots is denoted as S1, and the complete projected area of ​​the main body on the projection panel is denoted as S2. By calculating the ratio of S1 to S2, we can further understand the distribution of light within the main body. In particular, when the ratio of S1 to S2 is less than 1:20, it means that the light distribution passing through the main body is relatively uniform, and no large bright spots appear, which also indirectly verifies the rationality of the uniform distribution design of the main body.

[0051] The beneficial effects of this invention are:

[0052] 1. In this design, the area of ​​the perforations is limited to 10% to 15% of the body area. Two absorbent layers are incorporated—an upper absorbent granule layer and a lower absorbent granule layer. Therefore, the perforation design has certain requirements. If the perforations penetrate the fluffy cotton, and the perforation area is large enough, liquid can easily pass through quickly without being absorbed by the upper and lower absorbent granule layers. If the perforations do not penetrate the fluffy cotton, liquid is easily absorbed quickly by the lower absorbent granule layer, resulting in less absorption by the upper absorbent granule layer, causing deformation of the absorbent body and discomfort. To achieve a more balanced effect, limiting the perforation area to 10% to 15% of the body area is optimal, and even better, it should be 12% to 13%.

[0053] After defining the slot size, the water absorption performance of the absorbent particles also needs to be controlled. In this scheme, the water absorption performance per unit area of ​​the upper absorbent particle layer is defined as A1, and the water absorption performance per unit area of ​​the lower absorbent particle layer is defined as A2, with A1:A2 being (7-9):10. This results in a certain enhancement in the water absorption performance of the lower absorbent particle layer compared to the upper absorbent particle layer. This enhancement is uniform and is limited to a specific unit area. It allows for rapid absorption and diffusion of the liquid in the lower absorbent particle layer during infiltration, while also ensuring that the upper absorbent particle layer also absorbs a certain amount. This results in better control of the deformation of the fluffy cotton after water absorption, preventing excessive twisting and ensuring a better distribution of water absorption, which is beneficial for maximizing the utilization rate of the body's water absorption performance.

[0054] 2. The function of the flow-limiting orifice is to restrict side leakage. It can limit the obstruction of liquid diffusion inside the fluffy cotton and improve the efficiency of liquid seepage. When liquid cannot be absorbed in time at the strip orifice, it may flow towards both ends along its length. The flow-limiting orifice effectively obstructs this flow and improves absorption performance. If the flow-limiting orifice is connected to the strip orifice to form a longer strip orifice, the effect is weaker. In addition, limiting the strip orifice to a through-hole, with one of the strip orifices located in the middle of the body, is beneficial for liquid diffusion.

[0055] 3. In the upper absorbent particle layer, at least 90% of the absorbent particles by mass are completely embedded within the fluffy cotton. This ensures the stability of the absorbent particle position. Since the absorbent particles are added by spreading, they are usually located on the surface of the fluffy cotton. A vibration device is then used to apply the absorbent particles, causing them to gradually penetrate into the fluffy cotton. However, due to the size of the pores, the size of the absorbent particles, and measures to prevent the absorbent particles from penetrating deeply into the fluffy cotton, some absorbent particles will still remain on the surface. Similarly, the lower absorbent particle layer is designed in the same way, except that at least 70% of the absorbent particles by mass are completely embedded within the fluffy cotton. The difference lies in the type of absorbent material. Since the upper absorbent particle layer is close to the body, the particles need to be embedded as much as possible within the fluffy cotton to ensure both comfort and absorbency. The lower absorbent particles, however, are further away from the body. As long as the particles not embedded in the fluffy cotton don't cause significant problems, that's sufficient. A small portion of these particles are located outside the fluffy cotton, specifically between the fluffy cotton and the second non-woven fabric. These particles are also secured with adhesive, reducing the deformation of the fluffy cotton after absorbing water and expanding. This, combined with the absorbency per unit area, minimizes the distortion and deformation of the material itself.

[0056] 4. When testing water absorption performance, pour in 0.9% physiological saline solution and wait for complete absorption. Let it stand for a certain period, then separate the fluffy upper layer from the fluffy lower layer. Take at least three unit area samples from each layer, weigh them separately, and take the average value. The three or more unit area samples should be of the same size and preferably from different locations, such as the ends and middle of the length. The standing time is usually 10-20 minutes. It is best to place them on a filter screen to reduce surface moisture, with the fluffy upper layer on top and the fluffy lower layer on the bottom.

[0057] 5. The limitation of light transmittance mainly restricts the distribution of absorbent particles. This is determined by comparing the intensity of light before and after transmission, thereby achieving a better distribution of absorbent particles. In this design, this also applies to the distribution of the upper and lower absorbent particle layers, ensuring uniformity and consistency. This results in better deformation stability and consistency of the body after liquid absorption, leading to a better wearing experience.

[0058] 6. The limitation on uniformity is related to the limitation on transmittance. The limitation on uniformity can effectively assist in improving transmittance, mainly by limiting the amount of water absorbed and the resulting blockage, thus achieving better water absorption performance. Of course, some areas may have special distribution of water-absorbing particles. For example, in certain areas, the distribution of water-absorbing particles may be relatively sparse, but these areas do not have slots. This will create light spots during measurement. The maximum allowable total area of ​​light spots is 1 / 20 of the body area.

[0059] To address the distribution of the upper and lower absorbent particles, a double-layer absorbent forming device was used for forming, as referenced. Figure 1 , Figure 2 A double-layer absorbent core forming device includes a first forming device, a second forming device and a winding device 3 for the double-layer absorbent body arranged in a production line. The first forming device is provided with a fluffy cotton input mechanism 4 for conveying fluffy cotton 93, a first non-woven fabric input mechanism 5 for conveying first non-woven fabric 91, and a second non-woven fabric input mechanism 6 for conveying second non-woven fabric 92 on one side.

[0060] The first molding device includes a first molding die wheel 11 and a first spreading device 12 for spreading polymers;

[0061] The second molding device includes a second molding die wheel 21 and a second spreading device 22 for spreading the second polymer;

[0062] The first nonwoven fabric input mechanism 5 is used to input the first nonwoven fabric 91 onto the surface of the first forming die wheel 11. The fluffy cotton input mechanism 4 is used to input fluffy cotton 93 onto the first forming die wheel 11 and cover the outer surface of the first nonwoven fabric. The second nonwoven fabric input mechanism 6 is used to input the second nonwoven fabric 92 onto the surface of the first forming die wheel 11 and cover the outer surface of the fluffy cotton 93. The first spreading device 12 is located above the first forming die wheel 11 and between the fluffy cotton 93 input end and the second nonwoven fabric 92 input end, and is used to spread polymer onto the outer surface of the fluffy cotton 93.

[0063] A separation mechanism 7 for separating the first nonwoven fabric 91 from the fluffy cotton 93 is provided between the first forming die wheel 11 and the second forming die wheel 21. The separation mechanism 7 separates the first nonwoven fabric 91 from the primary composite fabric 94.

[0064] The second forming die wheel 21 is used to receive the primary composite fabric 94 output by the first forming die wheel 11, and the second non-woven fabric 92 in the primary composite fabric 94 is attached to the outer surface of the second forming die wheel 21, and the fluffy cotton 93 is located on the outer surface of the second non-woven fabric 92.

[0065] The first nonwoven fabric separated by the separation mechanism 7 is wound around and then fed into the second forming die wheel 21, covering the outer surface of the primary composite fabric 94. The second spreading device 22 is located above the second forming die wheel 21 and between the input end of the primary composite fabric 94 and the input end of the separated first nonwoven fabric. The separation mechanism 7 can be a structure composed of multiple guide rollers for winding.

[0066] A first adhesive spraying device 13 is provided between the second nonwoven fabric input mechanism 6 and the first forming die wheel 11 for spraying adhesive onto the input second nonwoven fabric 92. A second adhesive spraying device 23 is provided between the input end of the separation mechanism 7 and the second forming die wheel 21 for spraying adhesive onto the separated first nonwoven fabric 91. Both the first adhesive spraying device 13 and the second adhesive spraying device 23 are conventional adhesive spraying equipment in the art and can be purchased from the market.

[0067] The aforementioned cotton input mechanism 4, first nonwoven fabric input mechanism 5, second nonwoven fabric input mechanism 6, and winding device 3 each include one or more of the following: unwinding mechanism, correction mechanism, buffer mechanism, tensioning mechanism, conveying mechanism, and guiding mechanism. The aforementioned unwinding mechanism, correction mechanism, buffer mechanism, tensioning mechanism, conveying mechanism, and guiding mechanism are all conventional technical means in this field and can be derived from the applicant's relevant patents. For example, the unwinding mechanism can refer to an off-line unwinding device disclosed in Chinese Patent Application No. CN201510264615.X; the correction structure can refer to a paper web correction mechanism disclosed in Chinese Patent Application No. CN201621469755.7; the buffer and tensioning mechanisms can refer to a material tension control device disclosed in Chinese Patent Application No. CN201420387213.X; and the conveying and guiding mechanisms can refer to a material unwinding control method disclosed in Chinese Patent Application No. CN202011605786.1. The above mechanisms can be added, removed, or combined as needed, and other conventional devices can also be added. Similarly, the separation mechanism 7 can also be a combination of one or more of the following: unwinding mechanism, correction mechanism, buffer mechanism, tensioning mechanism, conveying mechanism, and guiding mechanism.

[0068] Both the first forming mold wheel 11 and the second forming mold wheel 21 are mold wheels with negative pressure adsorption.

[0069] The aforementioned fluffy cotton 93, also known as fluffy nonwoven fabric, can be made of other materials, as long as they can support the spreading of polymers on both sides. The aforementioned winding device 3 is a conventional technical means in this field, and reference can also be made to the applicant's relevant patents, such as the coreless winding device disclosed in Chinese Patent Application No. CN202222975300.4.

[0070] See again Figure 2 , and Figure 1 The difference lies in the fact that an adsorption wheel 8 is provided between the first forming mold wheel 11 and the second forming mold wheel 21 to remove dust generated by the first forming mold wheel 11 and the second forming mold wheel 21. In fact, the adsorption wheel 8 can also be replaced with other structural forms, such as an adsorption conveyor belt. Furthermore, it can be replaced with other functional components, such as a vibration mechanism.

[0071] In practical applications, a first oscillation mechanism and a second oscillation mechanism can be set to oscillate the composite fabric and the complete composite body, which can achieve a more stable and uniform distribution of polymers within the fluffy cotton. During oscillation, there are two options: one is to achieve polymer aggregation in the center of the fluffy cotton. This method stabilizes the position of the polymers within the fluffy cotton, prevents polymer clumping, and results in better uniformity of water absorption. The other is to achieve uniform distribution of polymers on the surface of the fluffy cotton. This utilizes the pores of the fluffy cotton to position the polymer particles, resulting in better uniformity of particle arrangement. Furthermore, during water absorption, both the upper and lower surfaces of the fluffy cotton can absorb water, while the center of the fluffy cotton acts as a water passage channel, thus achieving rapid water absorption. The first and second oscillation mechanisms are conventional techniques in this field and can be obtained commercially; therefore, they will not be described in detail here, nor are they indicated in the figures. That is, by using the first oscillation mechanism and the second oscillation mechanism, at least 90% of the mass of the absorbent particles in the upper absorbent particle layer 951 can be completely embedded in the fluffy cotton 93. At least 70% of the mass of the absorbent particles in the lower absorbent particle layer 952 can be completely embedded in the fluffy cotton 93.

[0072] A method for forming a double-layer absorbent core includes the following steps:

[0073] First, the first nonwoven fabric 91 is fed into the first forming die wheel 11 using the first nonwoven fabric input mechanism 5, and the fluffy cotton 93 is fed into the first forming die wheel 11 using the fluffy cotton input mechanism 4, and the fluffy cotton 93 covers the outer surface of the first nonwoven fabric 91. Then, the polymer is spread onto the outer surface of the fluffy cotton 93 using the first spreading device 12.

[0074] The second step involves using the second nonwoven fabric input mechanism 6 to input the second nonwoven fabric 92 into the first forming die wheel 11, and the second nonwoven fabric 92 covers the outer surface of the fluffy cotton 93 to achieve coverage of the fluffy cotton 93 after the polymer is spread.

[0075] The third step is to output the preliminary composite of the first nonwoven fabric 91, fluffy cotton 93, and second nonwoven fabric 92. After output by the separation mechanism 7, the first nonwoven fabric 91 in the preliminary composite is separated to form a primary composite fabric 94.

[0076] In the fourth step, the composite fabric 94 is fed into the second forming die wheel 21, so that the second nonwoven fabric 92 is attached to the outer surface of the second forming die wheel 21, and the fluffy cotton 93 is covered on the outer surface of the second nonwoven fabric 92. Then, the polymer is spread onto the outer surface of the fluffy cotton 92 using the second spreading device 22.

[0077] Fifth step: Cover the outer surface of the fluffy cotton 93 on the second forming die wheel 21 with the separated first nonwoven fabric 91;

[0078] The sixth step is to output the complete composite of the first nonwoven fabric 91, fluffy cotton 93, and the second nonwoven fabric 92, and then wind it up using the winding device 3.

[0079] In the second step, the second adhesive spraying device 23 is used to spray adhesive onto the second nonwoven fabric 92 to achieve bonding with the fluffy cotton 93.

[0080] In the fifth step, the first adhesive spraying device 13 is used to spray adhesive onto the first nonwoven fabric 91 to achieve bonding with the fluffy cotton 93.

[0081] In the third step, the dust generated by the first forming mold wheel 11 and the second forming mold wheel 21 is removed by using the adsorption wheel 8 set between the first forming mold wheel 11 and the second forming mold wheel 21.

[0082] In the third step, an oscillation mechanism set between the first forming mold wheel 11 and the second forming mold wheel 21 is used to oscillate the primary composite fabric 94 to achieve a reasonable distribution of polymer on the fluffy cotton 93.

[0083] In the sixth step, the second oscillation mechanism, located outside the second molding die 21, is used to oscillate the complete composite material to achieve a reasonable distribution of polymer on the fluffy cotton 93.

[0084] The outer surface of the fluffy cotton in the first step and the outer surface of the fluffy cotton in the fourth step are actually two opposite sides. The fluffy cotton achieves surface flipping after passing through the first and second forming mold wheels, thus realizing the spreading of polymer on different sides of the fluffy cotton. This process can achieve high work efficiency.

[0085] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A double-layer absorbent core, comprising a body, the body comprising a first nonwoven fabric, a second nonwoven fabric, and a fluffy cotton sandwiched between the first and second nonwoven fabrics, wherein an upper absorbent particle layer is disposed on the side of the fluffy cotton closest to the first nonwoven fabric, and a lower absorbent particle layer is disposed on the side of the fluffy cotton closest to the second nonwoven fabric, characterized in that: The fluffy cotton includes a fluffy upper layer and a fluffy lower layer that are evenly arranged, with the upper absorbent particle layer located on the fluffy upper layer and the lower absorbent particle layer located on the fluffy lower layer; The fluffy cotton is provided with through or non-through slots, and the size of the unit area is defined as 1 to 5 square centimeters. In the part of the body that does not contain slots, the water absorption performance per unit area of ​​the upper absorbent particle layer is defined as A1, and the water absorption performance per unit area of ​​the lower absorbent particle layer is defined as A2. When measuring the water absorption performance, 0.9% physiological saline is poured in, and after complete absorption, it is left to stand for a certain period of time. Then, the fluffy upper layer and fluffy lower layer are separated, and three or more unit area samples of each are taken, weighed, and the average value is taken. The ratio between the average weight of the unit area of ​​the fluffy upper layer after water absorption and the average weight of the unit area of ​​the fluffy lower layer after water absorption is A1:A2, where A1:A2 is (7 to 9):

10. The uniformity of the body is 5% to 20%. The uniformity is defined as follows: in a closed environment and when the body is fully absorbed by water, after the slot is blocked, light is irradiated on one side of the body to allow the light to penetrate the body, and the intensity of the light is detected on both sides of the body by detectors. The ratio between the intensity of the light that penetrates the body and the intensity of the light that does not penetrate the body is the uniformity.

2. The double-layer absorber core according to claim 1, characterized in that: The area of ​​the slot is 10% to 15% of the body area, and the slot includes one or more strip holes arranged along the length direction of the body and two or more flow-limiting holes arranged at both ends of the length direction of the body.

3. The double-layer absorbent core according to claim 2, characterized in that: The strip-shaped hole is a through slot, with one of the strip-shaped holes located in the middle of the body.

4. The double-layer absorber core according to claim 1, characterized in that: At least 90% of the water-absorbing particles in the upper absorbent particle layer are completely embedded in the fluffy cotton.

5. A double-layer absorber core according to claim 1, characterized in that: At least 70% by mass of the absorbent particles in the lower absorbent particle layer are completely embedded in the fluffy cotton.

6. A double-layer absorber core according to claim 1, characterized in that: A projection plate is set on one side of the main body. The total area of ​​the bright spots formed by the light passing through the main body on the projection plate is S1, and the projection area of ​​the main body on the projection plate is S2. The ratio of S1:S2 is less than 1:20.

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