The basic function of pull-ups is to keep them absorbent and dry. Therefore, the role of absorbent cores is particularly important. Prior to this, with the unremitting efforts of researchers at home and abroad, absorbent cores have been widely used in the market.
At present, the mixed material of SAP and fluff pulp is mainly used in the absorbent core layer of pull-up pants. the main function of SAP is to absorb and lock a large amount of water, while the function of fluff pulp is to speed up the absorption of liquid and make the liquid spread rapidly in the absorbent core, and the two complement each other. This absorbent core layer increases the amount of liquid absorption and retention, but the speed of liquid absorption is slow, and it is easy to back-bleed after absorbing liquid. Moreover, the thickness of such pull-ups is large, and the SAP is easy to form a doughy gel after absorbing liquid, which makes the absorbent core layer lumpy and broken and affects multiple absorption. In response to the above problems, relevant researchers began to explore and practice absorption core layer.
China's research on the absorption core layer started late, but has developed rapidly in recent years. In order to improve the absorption effect of pull-up pants, many domestic scholars mainly start from the structure of the absorbent core layer. Patent No. 201220676368.6 introduces an anti-backlash pull-up pants. The rear part of the product is placed with anti-backlash absorbent material. This new structure has good water absorption and water locking performance, and is not easy to occur back leakage. Patent No. 201910571030.0 discloses a grid absorbent core layer, dividing the absorbent core into several rectangular blocks and fixing them, with inflow grooves between two adjacent rectangular blocks, improving the efficiency of absorbing liquid, and SAP particles are not easy to slide in the core, improving the comfort of use. 201120564240.6 patent relates to an absorbent core composed of upper and lower cotton core layers. The SAP content of the upper cotton core in the absorbent body is smaller than that of the lower cotton core, while the vertical projection area of the upper cotton core is larger than that of the lower cotton core. Therefore, the SAP of the lower cotton core layer can quickly absorb liquid and firmly lock the liquid, so that the pull-up pants can ensure lasting dryness when worn. Patent No. 201920258566.2 relates to a composite absorbent core that can quickly absorb liquids. Its structural composition is covering surface, lint pulp layer, high absorbent resin wave fluffy cotton layer and covering bottom layer. Among them, the conical hole covering surface improves liquid permeability, avoids side leakage and improves its resistance to seepage. A new absorbent core layer disclosed in Patent No. 201910970439.X includes an upper spunbond, a lower hydroentangled fabric and an absorbent layer set between two layers of nonwoven fabric, wherein the absorbent layer consists of alternating columns of highly absorbent resin and columns of super absorbent fibers. On the spunbond, the corresponding highly absorbent resin is listed as the water-repellent treatment column and the corresponding superabsorbent fiber is listed as the hydrophilic treatment column, while the treatment on the spunlace fabric is reversed. This alternating structure ensures liquid infiltration and reduces hydrophilic area, thereby reducing back seepage and enabling uniform distribution of liquid in the absorbent core layer.
In today's era of advocating sustainable development, another development trend of absorbent core layer is: lint-free pulp. The main source of fluff pulp is natural coniferous wood. The extensive use of coniferous wood leads to a reduction in energy. At the same time, the noise and dust during the production process will increase, which is not conducive to environmental sustainability; moreover, as coniferous wood decreases, the price of fluff pulp will increase, which greatly limits the development of pull-on pants. Therefore, less use of fluff pulp has become an inevitable requirement. However, a lint-free core does not mean a 100% SAP core. It may refer to the use of green materials such as fast-growing broadleaf wood fibers or non-wood fibers to replace coniferous wood fibers, or the use of heterogeneous dry paper and a reduced amount of lint pulp. Patent No. 201220461754.3 describes a lint-free pulp absorbent core layer consisting of a nonwoven material wrapped in a polymeric absorbent body. Thus, it can inhibit the deformation after absorbing liquid and thus prevent leakage. The use of lint-free pulp not only protects the environment, but also reduces processing costs. Patent No. 201911032299.8 discloses a universal infusion absorbent core including an upper layer of hot air nonwoven, a first absorbent polymer layer, a fluffy nonwoven, a second absorbent polymer layer and a lower layer of hot air nonwoven, wherein the first absorbent polymer layer and the second absorbent polymer layer consist of SAP particles scattered on the surface of the fluffy nonwoven and do not contain lint-free pulp. The fluffy nonwoven is equipped with multiple guide flow grooves, which improves the diffusion of liquid on the core, resulting in a more uniform distribution of liquid on the pull-on pants and more absorption.