*This article is about diaper polymer, SAP in diapers, sodium polyacrylate in diapers, the superabsorbent polymer in diapers, diaper absorbent polymer, and absorbent material that absorbs liquid.
Sodium polyacrylate
Sodium polyacrylate is an absorbent material that can absorb purified water up to hundreds of times of its own weight.
It is non-toxic, harmless, and nonpolluting
Sodium polyacrylate for hygiene products
Sodium polyacrylate is the important absorbent material in paper diapers, sodium polyacrylate, nursing mats, and other hygiene products.
Most of the SAPs used in sanitary products are polyacrylates, mainly sodium polyacrylates, followed by potassium polyacrylates, and a few are acrylic acid starch grafts and acrylic acid copolymers.
The baby diaper application dominates the sodium polyacrylate market in the world.
At present, the largest application is in personal hygiene products. In order of dosage, it is baby diapers, children's training pants, adult incontinence products and women's sanitary napkins. The largest amount of baby diapers accounts for more than 90% of the consumption of sanitary products SAP, and the growth rate of adult diapers demand has begun to exceed the growth rate of baby diapers in recent years. This segment held over 70% of the total market share in 2014. The huge market share of the baby diapers segment can be attributed to its ever growing demand in the developing nations. (from grandviewresearch)
Important indicators
| Indicators | Note |
| absorbent rate | It affects the urine-absorbent rate of diapers. |
| liquid permeability | It helps diapers absorb urine fast & evenly. |
| absorption in 0.9% NaCl | It affects the urine absorption ability of diapers. |
| absorption under pressure | It affects the urine absorption ability of diapers (under pressure ). |
| retention capacity after centrifugation | It affects the urine absorption ability of diapers (while were switched). |
SAP for Diapers
Baby diapers
Baby diapers consist of three basic designs: a porous top layer, an absorbent core layer, and a leak-proof bottom layer. The water-absorbing core layer contains superabsorbent resin.
Baby diapers have the following requirements for SAP:
- good water absorption，
- Absorbs the baby's ability to absorb urine after several urinations，
- Under the action of the shearing force generated by the movement of the baby's body, it remains free from spillage and has a continuous ability to absorb urine.
Adult diapers
Most of the users of adult incontinence materials are adults or the elderly who are paralyzed, incontinent, or incapacitated due to various injuries and diseases, and a small number are consumers who have to use it due to inconvenience in working for a long time, mainly in the form of diapers.
The structure of adult diapers is mainly divided into 4 layers, from the top layer to the bottom layer are the surface layer covering material, the liquid collecting diffusion transfer layer, the liquid absorbing core, and the back layer material, in addition to the leg guard, elastic material and hot melt adhesive, etc. member.
Among them, the absorbent core is the key functional layer of the adult incontinence material, which is mainly composed of fluff pulp and granular superabsorbent resin.
SAP for sanitary napkins
The liquid that sanitary napkins have to absorb is more complex, a more viscous mixture of water, salt, and cells.
Since the cells are very large, it is difficult for the superabsorbent polymer to absorb them into the network structure. Therefore, surfactants are often applied to the surface of the superabsorbent polymer particles to improve the dispersibility to blood.
Improve SAP in hygiene products
At present, the research on SAP mainly focuses on: reducing cost, improving gel strength after water absorption, improving
Polymer salt resistance.
improving gel strength after water absorption
To improve the strength of hydrogel after water absorption, surface cross-linking is mainly carried out post-treatment to reduce the content of water-soluble parts. Scientists Lind and Smith treated acrylic resins with a mixture of surfactants and olefin additives to reduce the residual monomer content to 50 mg/kg.
improving polymer salt resistance
In terms of improving the salt resistance of the polymer, the mixing method of SAP and ion exchange resin is adopted, and the ion exchange characteristics of the ion exchange resin are used to reduce the ion concentration of the aqueous solution, thereby improving the water absorption of SAP to the saline solution. The complex of SAP and the inorganic hydrogel is based on the good salt tolerance of inorganic hydrogel, and the combination of anionic SAP and inorganic hydrogel to form a gel complex is beneficial to improving the salt tolerance of SAP.