Absorbent articles, such as disposable diapers, training pants, and adult incontinence undergarments, absorb and contain body exudates. Many absorbent articles, like diapers, contain superabsorbent polymer material. Superabsorbent polymers are typically present in the core of the absorbent articles in the form of particles. Superabsorbent polymer particles are able to absorb liquid and swell when entering into contact with liquid exudates. However, it has been shown in the past that not all categories of superabsorbent polymer particles are equally suitable for use in an absorbent article.
It is known that in order to have absorbent articles comprising superabsorbent polymer particles which exhibit good absorbing and containing functions, specific technical requirements need to be fulfilled by the superabsorbent polymer particles.
The superabsorbent polymer particles need first to be able to absorb the liquid exudates fast. The absorption speed of superabsorbent polymer particles has generally been characterized in the prior art by measuring the Free Swell Rate (FSR) of the particles.
In addition to having a high absorption speed, the superabsorbent polymer particles present in the core need to be also highly permeable to liquid. A poor permeability of the superabsorbent polymer particles may induce leakage of the absorbent article due to gel blocking. Gel blocking can occur in the absorbent core when swelling superabsorbent polymer particles block the void spaces between the particles. In such a case, the liquid exudates can not or only slowly reach underneath layers of superabsorbent polymer particles disposed in the core. The liquid exudates remain on the surface of the absorbent core and may therefore leak from the diaper.
The permeability of the superabsorbent polymer particles has typically been characterized in the prior art by measuring the SFC (Saline Flow Conductivity) of the particles. This parameter is measured at equilibrium, i.e. the measure is performed on a fully preswollen gel bed of superabsorbent polymer particles.
However, the inventors have now surprisingly found that absorbent cores comprising superabsorbent polymer particles having high FSR and high SFC values do not automatically conduct to fast acquisition times of liquid exudates into the absorbent article, especially at the first gush, i.e. when the absorbent cores first come into contact with liquid.
The present invention therefore provides an absorbent article having improved absorption properties and therefore reduced leakage, especially at the first gush, i.e. when the article starts to be wetted.
USPTO Backgrounds
USPTO Backgrounds