Today's baby diapers have a surface, absorbent core and coating. The skin directly contacts the surface layer. Whether it is wet or dry, the touch must be soft and will not stimulate the skin. The main function of the surface layer is to separate and filter. When the liquid is discharged, the liquid can pass through the fabric smoothly. Therefore, this kind of nonwovens must have certain hydrophilic properties, do not absorb water, so as to keep the surface dry, and have enough holes to allow liquid to pass through. Therefore, it is particularly important to improve the structural properties and quality of surface materials.
Medical and sanitary nonwovens such as baby diapers have the following quality requirements as surface nonwovens:
(1) It has certain strength and small vertical and horizontal strength ratio;
(2) Good water permeability, rapid penetration of liquid;
(3) Low moisture return, keep skin dry and comfortable;
(4) No peculiar smell, beautiful, uniform, white and hygienic;
(5) Good softness and breathability, feel comfortable.
(6) The surface is smooth and plump, and the fiber fineness is small;
(7) It is not allergic to human skin, rash and itch, and has no toxicity.
The permeability of surface material refers to the ability of water molecules to penetrate from one side to the other, which is related to the tightness of nonwoven structure. The utility model is only used for the sanitary napkin with good water absorption performance on the surface layer; As the baby diaper layer needs to be kept dry, hydrophobic fiber or hydrophobic treatment fiber is generally selected. The capillary and water pressure between the fiber and the fiber are the main water permeable form of the baby diaper layer through the fabric gap.
In the past 20 years, acrylic nonwovens have the highest utilization rate of baby diaper surface materials. This is mainly due to the hydrophobicity of polypropylene fiber. Through hydrophilic treatment, polypropylene nonwovens make urine quickly penetrate the baby's diaper layer into the guide layer. At present, ES hot air nonwovens are mainly used as surface materials, which is more common. The surface of sanitary napkin is mostly made of cotton, which can quickly absorb liquid.
At present, most of the surface materials in China are hot air nonwovens, with good spatial structure, tortuous passage of liquid through porous holes and relatively small penetration time. Es bicomponent fiber is the most commonly used fiber for hot air bonding. Its outer layer is low melting point polyethylene (PE) and its core layer is polypropylene (PP) or polyester (PET), which can make the nonwovens feel particularly soft and greatly improve the tear strength. PP / PE and PET / PE fibers are collectively referred to as ES fibers.
Because the surface layer of baby diapers is the part that contacts the skin, improper selection will not only make the wearer feel uncomfortable, but also cause a series of adverse reactions such as allergic diaper rash, which will endanger the reputation of consumers.