Breathable backsheet of baby diaper

Breathable backsheet of baby diaper

13 Jan, 2022

Breathable membrane is an essential material for diapers. The structure of diapers is divided into 3 layers: surface coating layer, absorbent core layer and bottom layer.

The surface layer of diapers is made of non-woven fabric, the absorbent core layer is water-absorbent beads and fluff fibers, and the bottom material is mainly made of PE film or PE film + non-woven fabric. The main purpose of PE breathable bottom film is to prevent leakage Pee.

Breathable membranes generally refer to PE functional materials with environmental protection, water and breathability, and are mainly used for the bottom film of women's sanitary napkins, the bottom film of pads, the bottom film of baby diapers, etc. It is compounded with non-woven fabrics and is also widely used in medical protective clothing , Medical mattresses in isolation suits, disposable beds, home textiles, etc. Whether the breathable base film is breathable, in addition to its own material function, the process is also very important.

The principle of    breathable membrane is very simple: inorganic matter + stretching = micropores, in fact, the operation is very particular, only micropores with proper size and uniform distribution are effective.

   When the water vapor concentration on one side of the membrane is greater than the environment on the other side of the membrane, a humidity gradient pressure difference is formed. This provides the basic conditions for gas (vapor) convection. Due to the formation of convection, the humidity environment on both sides of the film tends to be relatively balanced.

   Breathable membrane is used as a water-blocking membrane, which has a barrier effect on liquids. Because of the many passages in the film, the tortuous channel formed by it has a large "L/D" value, which can be understood as a capillary. Therefore, under the same liquid (such as water) and the same pressure, as long as the height of the liquid column of the capillary is less than the length of the capillary, it can be guaranteed that the liquid will not leak out.

   Therefore, the water barrier of the film depends directly on the pore size and the path length of the breathable membrane. This performance can usually be measured by the water pressure resistance (ΔP). When the water pressure exceeds the water pressure resistance value that the microporous membrane can withstand, water will leak out.

   1. Casting compound. This process relies on the viscous compound of the plastic itself after the plastic particles are hot melted. The disadvantage is that it is almost airtight. In 2014, there was no way around the world to use this process to produce true high-permeability, high-temperature, waterproof and breathable membranes.

   2. Spray glue or scrape glue compound (hot melt glue compound). This process was first applied to sanitary napkins, diapers, and protective clothing. At present, almost all domestic manufacturers use this process to produce highly breathable waterproof and breathable materials. The disadvantage is that the air permeability is relatively low, because the micropores of the middle breathable membrane are actually blocked by hot melt adhesive. In addition, the most fatal disadvantage is that the temperature resistance is very low, only able to withstand temperatures of 60 degrees. Because this glue is actually a pressure-sensitive adhesive (self-adhesive). A simple example is that in winter, the double-sided tape is almost non-sticky and will delaminate, but in summer, the adhesive on the surface of the double-sided tape will melt. The quality of waterproof and breathable membrane made by this process can be imagined. During construction, as long as there is a certain temperature, the non-woven fabric will be glued and layered. Which construction company can guarantee that the roof will be covered immediately after the waterproof and breathable membrane is laid? Therefore, this waterproof and breathable membrane can only be a fake and inferior product with a real waterproof and breathable membrane, and there is no market in the European and American countries at all.

   3. Hot pressing compound. At present, the domestic market is mixed with fish and dragons. There are actually few manufacturers that produce real waterproof and breathable membranes. Many factories or distributors say that their waterproof and breathable membranes are good. Almost most users have never thought that some manufacturers provide waterproof and breathable membranes that are not waterproof at all. . For example, our domestic counterparts tricked consumers into saying that they were an international company, using the technology and R&D achievements of a well-known international company. In fact, the hydrostatic pressure of the waterproof breathable membrane they produced was only about 750px, but the user did not know how to detect it. I only know that water is splashed on the waterproof and breathable membrane. This membrane does not leak. In fact, where do users know that water is under pressure and will permeate, the only way is to check each batch of waterproof and breathable membranes for inspection, so that fakes can not be fake Hide. In fact, the real waterproof breathable membrane should be high breathability, high temperature resistance, anti-aging, and the hydrostatic pressure reaches more than 2 meters. The production process should be pure thermal compound technology, without glue, so it can reach a temperature of 110 degrees or more, high strength and anti-aging. This is a product that can really reach the EU standard in China, and it is the latest domestic technology.

   determines the quality of the breathability mainly depends on the number of ventilation holes and production process of the breathable base film. It is important to note that colloids, including urine gel and structural glue.

Due to the small amount of structural glue used, many large companies tend to use cheaper products, which does not violate relevant national regulations, and there is no obvious information that it has a harmful effect on the human body, but it will smell a bit, sometimes Smell the smell of diapers, it may be the smell of breathable film. However, the taste of diapers is determined by many factors, not just the breathable membrane.

  Finally, it is best to choose large manufacturers of regular brands when choosing diapers. The material is guaranteed, and the breathable membrane will not be too hard, otherwise it will easily scratch the baby's butt.

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