Preservatives

There are two main types of solutions found in wet wipes: aqueous or emulsion based. Both require preservatives in order to protect them from bacterial or even fungal contamination and most importantly protect the consumer. Preservatives do this by stopping micro-organisms from multiplying in a product.   

Wet wipe products that contain high alcohol content (say above 15%) can be self preserving and may not require additional preservatives. In the institutional healthcare markets is not uncommon to find products with an alcohol content of up to 70% for high level disinfection.

For cosmetic and personal care markets (i.e. for use on skin) it is a very different story: alcohol is not well accepted and consumers are looking for products to contain no controversial preservative ingredients. Choose of right preservative is a success key factor for this category.

Fragrance

Fragrance is made from aroma compounds added to the formulation. These compounds are made of volatile chemicals that, at standard temperature, create an odour which can be sensed by the olfactory receptors in the nose.

A fragrance can consist of multiple different oils, extracts and other compounds. They are grouped into families based on smell. A selection of top notes, middle notes and base notes are fused together to create an accord (a balance of 3-4 notes) which you are able to smell. 

Surfactants

Role of surfactant is to lower the surface tension of water making it easier to remove material, for example, soil from surface or skin. They also provide a cleaning effect by being able to dissolve dirt. 

Surfactants do this by forming spherical or tubular structures called micelles in water. Micelles are critical to cleaning and mildness. They help keep solid particles from separating out of a liquid.

Other roles surfactants can play are as emulsifiers enabling oil and water to mix or as a boosting foam. 

Emollients           

Emollients are another ingredient that can be found in Wet Wipes. Their role is to help avoiding drying the skin, not by putting moisture into the skin, but by reducing water loss through a protective film on the skin.

They are typically used to treat dry skin conditions such as eczema and are particularly important in both to reduce itching and protecting against environmental irritants.

The everyday use of soaps, shampoos and shower gels can remove your skin’s surface layer of natural oils. This can make your skin dry and can further aggravate long-term skin conditions such as eczema. 

Other Ingredients

pH adjusters - The formulation often contains a pH adjuster such as Citric Acid or Sodium Citrate. This is common in skin care wet wipe products, where you will often see ‘pH balanced’ on the packaging. The pH is set around 4.5 -5.0 which is close to that of healthy skin.

Anti-oxidants - In a formulation potentially some oils could turn rancid due to oxidation and give off an unpleasant odour. If those oils are present anti-oxidants are included like Vitamin E acetate in order to prevent oxidation from occurring.

Moisturisers - Moisturisers such as D-Panthenol can be added to a formulation to help increase the water content of the skin and keep if soft. These are typically found in skin care products such as make-up removal wipes, face wipes and hand wipes.

 

Such improvements can mostly be classified to primarily fall within either of two categories: primarily relating to "core technology", i.e. "absorbency" in the broad sense of the word, or primarily relating to "chassis technology", i.e. fit.

The first addresses how to pick up and retain the body waste (generally in some state of fluidity) in an "absorbent (or core) structure", whereby the waste material is acquired by the article (picked up), then conducted away from the location of acquisition (distribution), and then stored (retained).

The second category deals - generally - with the so called "chassis elements" to contain the body waste within the confinement of the article. This can be done by separating the absorbent (core) structure and the outside, e.g. wearers garments or skin, by using an impermeable backsheet. Moreover the chassis should prevent bodily exudates from escaping through the space between the absorbent article and the body of the wearer, which can be achieved by elasticized gatherings at leg and waist openings. Other chassis aspects are enabling application of the article to the wearer - e.g. by providing closure means such as tapes – that are strongly correlated to the “fit”.

Often the terminology "comfort" for the wearer was predominantly addressed by improving chassis elements, such as by adopting the chassis elements of the diaper to provide good "fit" of the article and to be soft and cushioning. It is also well established that reducing the thickness of the article by reducing the primary thickness cause, i.e. the absorbent (core) structure,  helps to improve comfort. This however was always a question of balance between liquid handling performance and thickness. Also a substantial amount of cushioning was considered necessary for comfortable diapers.

The development of absorbent (core) structures of particular thinness has also other beneficial aspects making such a development the subject of substantial commercial interest. For example, thinner diapers are not just less bulky to wear and fit better under clothing they are also more compact in the package, making the diapers easier for the consumer to carry and store. Compactness in packaging also results in reduced distribution costs for the manufacturer and distributor, including less shelf space required in the store per diaper unit.

Our recommendation is to design an HB core.

Good products have core with a tridimensional shape. It means that a core with uncompressed fluff show a tipical increased thickness (it means more absorbent material) in the crotch area and especially in the front side. See simplified core design on the right. You can see there is a first layer along the whole core and a second one positioned in the center/front area. These two layers can be two distinct cores but generally it is a single core with a 3D profile (usually it is obtained through a profiled mould filled by absorbent material).

You can identify 3 different zones

        * shallow zone:    it is the lightest area mainly teh back of the core

        * deep zone:    it is the heaviest area and it is located where you need more absorbency

        * transition zone:    it is the area between shallow and deep

Typical basis weights vary from 100 to 200 for shallow zone and fro 400 to 700 for deep zone. As you can easily understand depending on what deep zone shape and basis weights you choose for your core you will have a specific distribution of absorbent capacity from front to back. Pic shows a graph of capacity profile for a specific product obtained through a xls software developed by iResolve named PocketShape

Since we choosed to design an HB core it means SAP will follow fluff distribution (if our equipment is able to do it!!). More SAP we add more absorbent capacity you have distributed along the core with same “capacity diagram” that fluff defined.

A simple spreadsheet like PocketShape will help you to obtain the proper “capacity diagram” and modify your core geometry accordingly.

Of corse you can design a more stylish cores, rounded and narrow at crotch area  but the basic rules we have described here above are the same.

Just their application requires more sophisticated tools to predict core performances.

These SAPs are superior to fluff in their ability to absorb large volumes of aqueous body fluids, such as urine (i.e., at least about 15 g/g), thus making smaller, thinner absorbent structures feasible. In addition SAP particles typically pack closer than fibrous structures, thus achieving even thinner cores at elevated concentrations.

These SAPs are often made by initially polymerizing unsaturated carboxylic acids or derivatives thereof, such as acrylic acid, alkali metal (e.g., sodium and/or potassium) or ammonium salts of acrylic acid, alkyl acrylates, and the like. These polymers are rendered water-insoluble, yet water-swellable, by slightly cross-linking the carboxyl group-containing polymer chains with conventional di- or poly-functional monomer materials, such as N, N'-methylene-bisacryl-amide, trimethylol-propane-triacrylate or triallyl-amine. These slightly cross-linked absorbent polymers still comprise a multiplicity of anionic (charged) carboxyl groups attached to the polymer backbone. It is these charged carboxyl groups that enable the polymer to absorb body fluids as the result of osmotic forces, thus forming hydrogels.

The degree of cross-linking determines not only the water-insolubility of these SAPs, but is also an important factor in establishing two other characteristics of these polymers: their absorbent capacity and gel strength.

Absorbent capacity or "gel volume" is a measure of the amount of water or body fluid that a given amount of SAPs will absorb. Gel strength relates to the tendency of the SAPs to deform or "flow" under an applied stress. SAPs useful as absorbents in absorbent structures and articles such as disposable diapers need to have adequately high gel volume, as well as adequately high gel strength. Gel volume needs to be sufficiently high to enable the SAP to absorb significant amounts of the aqueous body fluids encountered during use of the absorbent article. Gel strength needs to be such that the SAP formed does not deform and fill to an unacceptable degree the capillary void spaces in the absorbent structure or article, thereby inhibiting the absorbent capacity of the structure/article, as well as the fluid distribution throughout the structure/article.

Prior absorbent structures have generally comprised relatively low amounts (e.g., less than about 50 % by weight) of these SAPs. There are several reasons for this. The SAPs employed in prior absorbent structures have generally not had an absorption rate that would allow them to quickly absorb body fluids, especially in "gush" situations. This has necessitated the inclusion of fibers, typically wood pulp fibers, to serve as temporary reservoirs to hold the discharged fluids until absorbed by the SAP.

More importantly, many of the known SAPs exhibited gel blocking.

"Gel blocking" occurs when particles of the SAP are wetted and the particles swell so as to inhibit fluid transmission to other regions of the absorbent structure. Wetting of these other regions of the absorbent member therefore takes place via a very slow diffusion process. In practical terms, this means acquisition of fluids by the absorbent structure is much slower than the rate at which fluids are discharged, especially in gush situations. Leakage from the absorbent article can take place well before the particles of SAP in the absorbent member are even close to being fully saturated or before the fluid can diffuse or wick past the "blocking" particles into the rest of the absorbent member. Gel blocking can be a particularly acute problem if the particles of SAP do not have adequate gel strength and deform or spread under stress once the particles swell with absorbed fluid.

This gel blocking phenomena has typically necessitated the use of a fibrous matrix in which are dispersed the particles of SAP. This fibrous matrix keeps the particles of SAP separated from one another. This fibrous matrix also provides a capillary structure that allows fluid to reach the SAP located in regions remote from the initial fluid discharge point. However, dispersing the SAP in a fibrous matrix at relatively low concentrations in order to minimize or avoid gel blocking can lower the overall fluid storage capacity of thinner absorbent structures. Usage of lower concentrations of these SAPs limits somewhat the real advantage of these materials, namely their ability to absorb and retain large quantities of body fluids per given volume.

Another reason why extremely high concentrations of SAP were not possible resides in the physical integrity disadvantage of structures made of particulate material. Creating a fibrous matrix therefore also had the advantage of providing a fiber re-enforced structure, similar to those used in many other technical situations where structural re-enforcement is provided by fibrous elements, such as in fiberglass. 

Besides increasing gel strength, other physical and chemical characteristics of these SAPs have been manipulated to improve their performance especially to decrease gel blocking.

 

A transdermal patch uses a special membrane to control the rate at which the liquid drug contained in the reservoir within the patch can pass through the skin and into the bloodstream. The basic components of any transdermal delivery system include the drug(s) dissolved or dispersed in a reservoir or inert polymer matrix; an outer backing film of paper, plastic, or foil; and a pressure-sensitive adhesive that anchors the patch to the skin. The adhesive is covered by a release liner, which needs to be peeled off before applying the patch to the skin.

Drugs administered via skin patches include scopolamine, nicotine, estrogen, nitroglycerin, and lidocaine. Basically the molecules of the medication must be small enough to pass through the skin

This is a non invasive way to treat many diseases and disorders. In addition to the aspects of each patch - there are four types of transdermal patches. These four types are: Single layer drug in adhesive, multi layer drug in adhesive, reservoir and matrix.

Wetting of the interior subsequently takes place via a very slow diffusion process. In practical terms this means that the absorption is much slower than discharge of fluid to be absorbed, and failure of a diaper or sanitary napkin or other absorbent structure may take place well before the hydrogel material in the absorbent structure is fully wet.

 Rif E. Carus, "First International Absorbent Products Conference Proceedings", November, t98Q, Section V-I; and J. H. Field, "Pulp Parameters Affecting Product Performance", TAPPI, 65(7) 1982, pp. 93-97.