Diaper absorbent core

Functional adhesives provide the bonded product with a new or enhanced attribute. For example, adhesives now exist which promote the penetration of fluids into bonded non-woven products by virtue of their low contact angle with water [82]. These materials have been used successfully in both diapers and sanitary napkins for bonding the non-woven cover sheet to the absorbent core. Other examples are water absorbing adhesives that can act as wetness indicators by changing color [69] or can be bonded once moistened ]99]. Additional functionalities are currently underdevelopment. 

Many other high volume consumer products make use of one or more core layers with absorbent properties. Among the most quickly and highly developed applications are baby diapers, which use super absorbent fibers. Super absorbent polymer (SAP) molecules can trap and hold hundreds to thousands of times their own weight in fluid, ultimately forming a gel. The super absorbent core layer in a diaper is between a non-woven cover stock, a one or two layer non-woven fluff/pulp sheet that takes up, distributes, and draws liquid into the core, and a microporous back sheet. In addition, elastomeric materials and waterproof elements are incorporated. The super absorbent core not only stores liquid but actively pulls moisture out of the damp or even wet fluff/ pulp, thus leaving the contact areas soft and dry. 

Disposable diapers have an absorbent core with SAM. SAM is a revolutionary material that can absorb water up to 100 times its weight i.e., 1 gm of SAM can absorb up to 100 gm of water. SAM is added to the inner core of the diaper and it absorbs urine and converts it into a gel. It wicks away the urine and prevents the mixing of urine and feces, further contributing to better containment of feces within the diaper. Disposable diapers have been significantly more effective in prevention of leakage of urine and feces as compared to cloth nappies (with or without overlying plastic/vinyl pants). 

Coverstock n. A hghtweight non-woven material used to contain and conceal an underlying core material. Examples are the facing materials that cover the absorbent cores of diapers, sanitary napkins, and adult incontinence products. 

Disposable Infant Diapers. A basic disposable diaper consists of an absorbent core sandwiched between a liquid permeable top-sheet and an impermeable back-sheet (45). The top-sheet, next to the baby s skin, allows urine to flow through it into the core. The back-sheet, made of impermeable plastic, helps keep the bab s clothing dry. The core takes in the liquid, distributes it within the core and holds the liquid under compression from the baby. 

Thermal bonded air-laid nonwovens are widely used as an interior absorbent core material in feminine hygiene materials, incontinence, and baby diapers (Danweb, 2006). Thermal bonded technology uses PE/PP core/sheath bicomponent fibre (about 30—40% in air-laid) as bond fibre to stick pulp (Xuan, 2006). 

The ADL is very important to provide a sense of dryness to the skin, providing additional separation between the wet pad and the skin. ADLs should be used whenever the mix of SAP in the absorbent core exceeds about 15% by weight or when the liquid penetration time requires a boost in order to avoid diaper leakage due to liquid accumulation inside the diaper. ADLs are made either of through air bond nonwovens, curly fibres such as in P G s pampers and some Ontex diapers, or some kind of highloft nonwoven. An aperture film, made of perforated plastic film, has also been used successfully in some markets. Lower priced diapers sometimes use resin-bonded nonwovens, but they do not work as well. 

Tissue essentially serves as a carrier for the pad (the pad is the absorbent core of the diaper) and helps reduce the pinholes created during the compression process carried out by conAnuous drum forming systems. These tissues, typically at 16 g/m or more, protect the inner plasAc from the SAP. Instead of tissue, it is possible to use a low-gauge SMS nonwoven material as the carrier (for the pad) it can be placed right next to the back sheet or as a full wrap material around the core. In order for the SMS carrier to be cost compeAAve against tissue paper, it needs to be less than 12 g/m. ... 

SAPs and fluff cellulose pulp are usually mixed uniformly in diapers and incontinence products. This mixture of fluff and superabsorbents is formed in absorbent structures called absorbent cores. Unfortunately, physiological fluids are excreted and absorbed over only a small area of these absorbent cores. The superabsorbent performance of these absorbent cores is therefore not optimal. 

The usual disposable diaper consisted of (i) a top sheet through which water passes (ii) a water-absorbing core and (iii) a back panel that is impermeable. Until the beginning of the 1980s, approximately 70 g of pulp was used as the absorption core. Later, the core weight was reduced to 40 g by the introduction of a superabsorbent polymer. The use of the superabsorbent polymer provided such advantages as (i) no leakage (ii) no build up of heat (iii) the prevention of diaper rash and (iv) thin size. 

Dnring the development of diapers with improved performance, a separate layer of nonwoven fibers was added to improve urine distribution in the diaper. This distribution layer is placed between the composite absorbent core, consisting of cellulose fiber and SAPs, and the porous cover sheet. The distribution layer has a lower absorbency than either the standard cellulose fluff or SAP, thus allowing fast liquid distribution within the diaper. This layer is often made from nonabsorbent nonwoven materials such as polypropylene fibers, with snfficient porosity to allow liquid to pass through freely. 

An inherent limitation of fibrous absorbent cores is that the bulk of the fluid is weakly held in the capillary structure and can escape (leak) upon squeezing. Such flowback leaks are minimized by the inclusion of superabsorbent polymer in the absorbent matrix. In the modern disposable diaper, the absorption burden is shared almost equally between the superabsorbent polymer and the fibrous matrix. In addition to acting as a fluid repository, the fibrous matrix has the critical functions of accepting and transporting the absorbed urine throughout the absorbent core. Interactions between the components in an absorbent product and between the components and the absorbed fluid must be considered in product design. 

If you aren t set up to wash cloth diapers at home, conventional disposable diapers aren t a good option. One widely quoted study (published in Archives of Environmental Health and conducted by Anderson Laboratories back in 1999) found mice exposed to VOC chemicals emitted by conventional disposables had asthmalike reactions. They also contain chlorine and have high-tech chemical gel cores that activate when your baby pees to lock in moisture. The Children s Health Environmental Coalition says this absorbent material—sodium polyacrylate— could cause respiratory and skin irritations in occupational settings (where exposure is higher than with diaper use). We wonder how safe can that much chemical activity that close to a baby s genitals be twenty-four hours a day ... 

In a diaper, the poljmier is mixed with 0.5-10 times its mass of cellulose pulp fluff (processed wood fiber) to make up the core (46-48). Cores containing superabsorbents are thinner because a smaller volume of dry superabsorbent pol5mier can absorb the same volume of aqueous liquid as a larger volume of fluff. 

In addition to the specific absorbency of the superabsorbent polymer, the absorption rate of the diaper must be optimized to the urination rate of the baby. When the core absorbs too slowly relative to the urination rate, the liquid overflows... 

Most diapers currently available are bulk stmctures. A typical diaper is composed of three main components nonwoven layers (top sheet or facing sheet keep the surface dry to facilitate good skin care conditions, back sheet, and distribution layer that prevents leakage and give a cloth-like feel to the external surface), core layer (fluff pulp, tissue, and polymer transfer fluid from the surface, absorb, and hold excretes), and breathable film. Each has a different contribution to the thermal comfort property of the multilayered diaper, (llhan, ingik, im ek, 2015). 

Super absorbent polymers (SAP) have enjoyed rapid sales growth in disposable baby diapers because of their high absorptivity of water systems of low ionic strength. This application was selected for study because SAP s are now used in approximately 90% of the 19 billion disposable baby diapers produced annually ion the United States. However, the absorptivity of SAP s in pure form in laboratory tests is far greater than that observed when they are incorporated not the cellulose fluff pulp used in a diaper core. 

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