Adult diapers are used by more and more people because of their good convenience. In particular, the current aging trend in China is intensifying, and the use will further increase. Modern adult diaper is a liquid absorption control system established by multi-layer nonwoven materials, which is generally composed of surface coating, absorption core layer and bottom film. When wearing the product, it will form a closed skin, which is different from the external environment. When the human body urinates, the temperature and humidity in the microclimate will rise to a certain extent. In addition, the stimulation of urine may lead to corresponding symptoms, such as red ass, but this can be avoided when the air permeability is good. From the perspective of consumers' purchase, they believe that the thinner the more breathable, and manufacturers also tend to design soft and thin. Therefore, this article will comprehensively discuss the key factors affecting air permeability.
Test the air permeability of adult diapers according to Schopper method, seal the edge of the sample and prevent air side leakage. The measuring head of the instrument is a disc with an outer diameter of 6mm and an inner diameter of 3.57mm, and the test area is 10mm2. Balance adult diapers in an environment with a temperature of (23 ± 1) ℃ and a humidity of (50 ± 1)%. Make two rubber sheets which are the same as the measuring head, cut the sample and clamp the round sheet with a diameter of 10mm between the two rubber sheets neatly, and seal the two rubber sheets and the edge of the sample with a sealing film. Align the rubber sheet with the measuring head. Adjust the pressure difference to (1.00 ± 0.01) kPa and the test time is 120s. After removing the sample, carefully peel off the bottom film and clamp it between two rubber sheets to test the air permeability of the bottom film. Since the permeability and constant pressure difference are directly proportional to the test time and the test data are small, it is not necessary to calculate the permeability according to the standard formula. Just compare the air volume within 120s, that is, the air volume within 120s, that is, the air permeability. Test 10 data and take the average value.
It can be seen that the air permeability of adult diapers in the intact state is not much different from that of the bottom film, which indicates that the key part to determine the air permeability is the bottom film, and the influence of coating and absorption core on the air permeability is limited.
With the increase of normal saline absorption, the permeability of samples with different numbers decreased slightly. When the absorption is saturated, the permeability is close to zero. From the structural analysis, the core of adult diapers is mainly made of wood pulp and covered with polymer absorbent materials. When the fluff slurry and polymer absorb water completely, most of the air circulation channels of the whole core are blocked, resulting in almost air tightness. The higher the content of fluff pulp, the more water absorbent polymer can be fixed, that is, the thicker the core, the more water can be absorbed. When the product absorbs the same water, the core is unsaturated, so that the core maintains an air circulation channel and a certain air permeability.
The air permeability of adult diapers depends on the air permeability of the bottom film. The bottom film is mostly PE breathable bottom film, and the permeability of the bottom film depends on the number of holes in the bottom film. Since the bottom film and the absorption core layer are bonded with hot-melt adhesive, this process may lead to the blockage of the bottom film hole and further reduce the air permeability of the bottom film. In order to improve air permeability, manufacturers need to develop breathable bottom films with higher air permeability and no water leakage. The hot melt adhesive bonding process can be modified in the production process of adult diapers to maintain the air permeability of the bottom film to the greatest extent.