How Disposable Diapers are made
There are three basic operational processes involved in the manufacture of baby diapers, they are…
- Ferberization of the fluff pulp, addition of superabsorbent polymer and absorbent pad formation
- Lamination with films, nonwoven materials and elastic elements
- Shaping, cutting, folding and packaging.
These 3 basic processes have remained constant over the years. With the introduction of new technologies and more sophisticated designs, major improvements have been made in increasing production line efficiency, product quality and reducing manufacturing waste.
Raw Materials
Wood pulp which would be transformed into the absorbent pad.
- Pulp would be mixed with polymer partials to make a fluffy absorbent pad. Polyacrylic acid is a polymer made from the monomer acrylic acid.
- The absorbent pad is made of SAP and wood pulp. The hydrocarbons that make up the SAP are both found naturally and made synthetically. When it is made synthetically, UV light and catalysts are added to the hydrocarbon to remove the salts.
- The absorbent pad is at the core of the diaper. It is held in place by nonwoven fabric sheets that form the body of the diaper. Nonwoven fabrics are different from traditional fabrics because of the way they are made. A dry laid process, such as the “melt-blown” method, is typically used to make nonwoven diaper fabrics.
- Polypropylene is typically the material used for the permeable top sheet, while polyethylene is the resin of choice for the non-permeable back sheet.
The most significant important property of a diaper is its ability to absorb and retain moisture.
Cotton material used in cloth diapers is reasonably absorbent, but synthetic polymers far exceed the capacity of natural fibres.
Latest innovations for disposable diaper will absorb 20 times its weight in water. This phenomenal absorption is due to the absorbent pad found in the core of the diaper. This pad is composed of two essential elements, a hydrophilic, polymer and a fibrous material such as wood pulp. The polymer is made of fine particles of an acrylic acid derivative, such as sodium acrylate, potassium acrylate, or an alkylate. These polymeric particles form a gel and act as tiny sponges that retain many times their weight in water.
When checked under a microscope these polymer molecules form long chains. Portions of these long chemical chains are designed to interact with water molecules. During cross-linking, process polymer has the ability to chemically link with different polymer molecules.
When a large number of these polymeric chains are cross-linked, they form a gel network that is not water soluble but that can absorb vast amounts of water. Polymers with this ability are referred to as hydrogels, superabsorbent, or hydrocolloids. The strength of gel can be adjusted by the process of controlling the degree of cross-linking. This is an important property because gel strength is related to the tendency of the polymer to deform or flow under stress.
If the strength is too high the polymer will not retain enough water. If it too low the polymer will deform too easily, and the outermost particles in the pad will absorb water too quickly, forming a gel that blocks water from reaching the inner pad particles. This problem, known as gel blocking, can be overcome by dispersing wood pulp fibres throughout the polymer matrix. These wood fibres act as thousands of tiny straws which suck up water faster and disperse it through the matrix more efficiently to avoid gel blocking. Manufacturers have optimized the combinations of polymer and fibrous material to yield the most efficient absorbency possible.
Other components
There are a variety of other ancillary components, such as elastic threads, hot melt adhesives, strips of tape or other closures, and inks used for printing decorations.