Improvement Of Breathable Film For Diaper

1. Introduction of breathable film for diaper

Breathable film for diaper is an environmentally friendly, breathable (steam) and water-proof (liquid, bacteria, dust) functional material. The emergence of microporous breathable membrane has a history of more than 20 years, and it has developed rapidly in the past 10 years. China is at the initial stage in terms of technology, market and application. Breathable film is a functional inorganic product that is uniformly added to the polyolefin raw material, so that the product will have pores due to high stretching during the film forming process, so that it has the function of breathability and moisture conduction. The water absorption of a general breathable membrane has its limit. When the water absorption exceeds the limit that the breathable membrane can carry, the water-proof effect of the breathable membrane will lose its effect.

Based on the above situation, Zhang Shuigao proposed a technical solution that can improve the water absorption and water insulation effect of the breathable film for diaper: it includes a PE breathable film layer, the PE breathable film layer is provided with three layers, and the three layers of PE breathable film Each layer is provided with pores, and the pore diameters of the three-layer PE gas permeable membrane decrease sequentially from top to bottom.

2. Improvement of breathable film for diaper

After adopting this technical scheme of breathable film for diaper, the water barrier performance of the single-layer breathable film depends on the size of the air gap and the length of the passage, and the length-to-diameter ratio (L/D) of the formed tortuous passage is very large. According to the capillary principle, As long as the height of the liquid column is less than the length of the capillary, it can be guaranteed that the liquid will not leak out. But when the water pressure exceeds the withstand water pressure value, the water will leak out. Therefore, the water pressure resistance of a single-layer breathable membrane is limited. By setting three PE breathable film layers, the breathable film not only has a breathable effect, but also can play a part of the water absorption effect, reducing the water absorption pressure of the diaper. According to the capillary principle, the water pressure resistance of breathable film for diaper can be expressed by osmotic pressure ΔP. ΔP=2σcosα/d. 

Where ΔP—osmotic pressure (Pa), σ—surface tension (N/m), α—contact angle (degrees), d—capillary diameter. The diameters of the three layers of PE air-permeable film layers decrease sequentially, so that d decreases gradually, and ΔP increases gradually. A breathable film for diaper with a small diameter has a larger ΔP and has a higher resistance to water pressure. Because gas molecules can pass through the gas-permeable membrane, the permeability of the gas-permeable membrane will not be greatly affected. In addition, the diameters of the three layers of PE air-permeable membrane layers are successively reduced, so that the air-permeable membrane has multiple layers of insurance to prevent the air-permeable membrane from leaking. The pore diameter decreases, so that the water pressure resistance of the PE breathable film layer gradually increases. When water enters the bottom PE breathable film layer, because the water pressure resistance of the bottom breathable film for diaper is the largest, the user can have a longer buffer period to change diapers with less chance of water leakage.