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Hydrophilic PP non-wovens

Polypropylene spunbond nonwovens are hydrophobic and non wettable by water.

Hydrophilic finishes are the answer to the problem of making PP wettable or rewettable and useful as a construct in hygiene articles such as baby diapers, where controlled liquid management is essential.

To meet differing requirements, finishes with variable performance profiles are on the market. Today's state of the art durable hydrophilic finishes are based on modified silicones, which make PP nonwovens rewettable for a few insults. New silicone free durable hydrophilic finishes add value to the disposable absorbents market by improved cost benefit ratio.

Untreated polypropylene itself is desirably cheap compared to other polymers, but shows the distinct hydrophobicity which is inherent in polyolefins/hydrocarbons.

Its specific surface energy of approximately 30 cN/m does not allow wetting by water or aqueous liquids and would prevent the universal use of PP nonwovens in hygiene articles where control of liquid strike through, acquisition, distribution and absorption is essential for the total performance.

Hydrophilic finishes are the answer to the problem of making PP nonwovens wettable or rewettable. A thin layer of surface active hydrophilic finish applied onto the surface of PP will hide the hydrophobicity of this polymer and provide the ability of being wettable or even rewettable depending on the performance profile of the finish.

Hydrophilic finishes like Silastol GF16, Silastol PST or Silastol GF 602 which are designed to make PP nonwovens just wettable, can easily be washed off and the fabric will loose the wettability after the first insult. If a fabric is required which can withstand multiple insults a durable hydrophilic finish like Silastol PHP26 or Silastol PHP90 needs to be applied to the nonwoven which cannot easily be washed off.

The conformation of molecules like this, favours a strong adsorption on the surface of PP by hydrophobic interactions and an orientation of the hydrophilic functionality, at the same time resulting in a molecular layer which bridges the opposing properties of polyolefin and water[1].

In addition to support of this mechanism, easy handling and application is the main purpose of additional ingredients in existing formulations.

Because of the outstanding performance and versatility of silicone based finishes the high price of this type of chemistry compared to organic types of finishes has been tolerated over recent years. Since the penetration of the US and the EU markets by disposable absorbent hygiene products, market saturation has been reached and the cost structure of all raw materials in the supply chain of hygiene articles is now as crucial for the success of a product idea or even more for any R&D efforts of a supplier to the highly competitive hygiene market. Under this pressure, a better cost benefit ratio of finishes is desirable.

While finish contribute only a very small part to the total cost of the final nonwoven, Schill & Seilacher has created new silicone free durable hydrophilic finishes with performance profiles which are comparable to silicone-based finishes in respect of strike through, rewet and even surface tension.

The new silicone-free finishes already show remarkable versatility in tests on various nonwoven substrates by many well respected PP nonwoven producers.

The new finish chemistry is considered to be more friendly to baby's skin than any other established finish. All components comply with FDA regulations.

The specific finish cost will be significantly reduced by use of these new durable non-silicone finishes which add value to nonwovens by improved cost effectiveness.