Converting Nonwovens For Improved Product Features

November 15, 2005

converters offer medical and hygiene producers new ways to meet product development challenges

Converting Nonwovens For Improved Product Features

converters offer medical and hygiene producers new ways to meet product development challenges

By Dan Aberly
vice president, manufacturing
Larsen Converting, Green Bay, WI

Converted products are frequently based on single-use disposable nonwovens. Applications ranging from medical drapes to dental bibs are the outcome of converting companies’ expertise in a whole range of processes.

The first step in creating medical disposables begins by breaking down mill rolls of nonwovens and other materials and slitting into smaller roll goods in preparation for further processing. Then, materials are combined, calendered, coated, laminated or subjected to other converting processes. Converting adds functional and sometimes aesthetic features targeted to medical and hygienic applications.

An overview of the processes and benefits of converting illustrates the many possibilities for nonwovens usage in medical and hygiene market segments. Some of the processes are sequential and some are carried out simultaneously. In many cases there are two or more converters involved in manufacturing end use products.

According to one disposable medical products supplier, “We have a lot of expertise in converting medical products within our facilities, but we also turn to valued suppliers for printing and other converting steps.” It’s a frequent way of doing business in medical converting where converters supplement each other’s skills, particularly in this converting corridor of Wisconsin.

Some examples show how this occurs:

•    A company skilled in slitting and rewinding breaks down mill rolls of nonwovens and other materials for another converter. An airlaid roll from Georgia-Pacific or another supplier may ship at more than 100 inches wide. Slitting brings it down to two or more rolls that fit the converter’s equipment.
•    In many cases the nonwovens need to be cut to the same roll size as another material such as a film for laminating.
•    A printer may print a logo or instructions on the nonwoven and ship the printed rolls to another converter for coating or laminating.
•    A medical drape may show a name, part number or have an arrow printed to identify a leading edge and then have a poly backing laminated at another facility or in another equipment “pass.”

Steps such as slitting, make it easier for the next conversion steps and for small converters. Converters also may combine processes (such as one or two pass capability to print, laminate and slit in-line).

By looking at converting processes in more detail, the value-added benefits become clearer.

Converting Categories Mill Roll Conversions

The first basic step is slitting and rewinding into manageable converting widths for wet and dry wipes production lines, dental bibs, drapes and other medical disposables. Mill “parent” rolls often arrive in “jumbo” sizes in terms of both width and diameter. Converting equipment often requires smaller rolls from specialized slitting and rewinding equipment.

Medical Laminates

Nonwovens are laminated to poly to achieve dual properties, such as an absorbent side backed by a barrier side, in products like medical drapes and dental bibs. Combining features of two or more substrates offers other benefits including soft side/rough side for cleansing and scrubbing.

Specialty micro-embossed poly offer better feel and drape, and are laminated to nonwovens. An adhesive laminate process is used, and extrusion laminating is another method. In addition, laminating can be done in-line with printing and slitting, which is more economical than moving materials to other facilities for additional processing.

Laminating offers product designers a complete range of possibilities including combining dissimilar substrates to create unique structures. Up to three-ply laminations are also possible. Some product design approaches made feasible by laminating include: Heat sealability; use of specialty adhesives for medical or other applications; and applications with full adhesive or patterned coverage.

Laminate structures containing nonwovens are often airlaid/poly or spunlace/poly. In some cases, finished product manufacturers can enter into new niche businesses more easily by buying pre-combined laminates for bedpads, incontinence and similar pad designs. Producers can receive rolls of pre-combined nonwovens and barrier backside poly. This complements the ability of airlaid manufacturers who can supply porous topsheets over airlaid, but generally cannot run the backside poly in-line.

Combining layers can facilitate adding fragrances or other additives, increase product thickness and allow for more designed features. Products that typically include combined features include:

• Infection control disposables, sterile fields, drapes
• Sanitary disposable products, absorbent haz-mats
• Medical packaging, kit wraps and CSR wraps
• Dental bibs, wipes for surface or skin cleansing

Printed Nonwovens

Automated converting processes allow for high quality and traceability

As medical disposables using nonwovens continue to grow and replace reusable products, the idea of adding printing is also growing. “Branding” in medical markets is increasingly done by everyone in the supply chain, from manufacturers, to distributors and marketers. Name recognition helps suppliers to build loyalty, make their business name or product name memorable, add graphic appeal, or have instructions right on the product.

On the printing production side, our job is to deliver high quality results on challenging nonwoven substrates with uneven surfaces, special printing ink, or registration requirements. Airlaid nonwovens can be uneven and highloft airlaids can also cause linting during processing; so we have special setups to minimize these issues. Other nonwovens with synthetic fibers may require inks that are smear-resistant or have other unique processing needs.

Coating & Additives

Coatings are another way of bringing additional benefits to nonwoven composites. In some cases, coatings can be an economical alternative to laminating. For example, some coatings provide enough barrier properties, and more expensive laminations are not required. In one such case, an added level of moisture resistance on one side could be provided by specialty coating. Suppliers may be able to coat in-line with other processes like slitting and printing to maximize production budgets.

Cohesive & adhesive coatings are frequently part of medical nonwovens combinations with peel-off backings or layered design.  

Substrate Calendaring

Nonwovens and other substrates are manufactured to specifications for thickness/caliper, density, loft and weight. In some cases, the original process does not quite meet all the downstream needs for these characteristics. For example, a lofty airlaid may need further calendering to provide a smoother surface for printing, laminating, or other converting processes. Special requirements may call for a higher level of consistent surface characteristics than calendering can achieve. In another case, some product designs call for a higher level of density.

Coating, laminating, printing and roll slitting are key converting processes for nonwovens medical disposables.

Other Converting Processes

With the increasing complexity of current medical and hygiene products, converting is constantly evolving. Many of us like to be “one-stop-shopping” sources for our customer partners. When we cannot do it all, we often suggest other nearby converters where we have collaborated with confidence and in a seamless step-by-step timeline. The full array of converting includes the processes already outlined and also involves multiple types of folding, sheeting, packaging, heat and sonic sealing and more.

Don’t hesitate to call on any of your converting partners. Ask how product features can be achieved in the converting process. Converters have wide ranging experience that can also lead to new ideas. Meeting to review possibilities up front can lead to delivery of “bonus” product benefits, economies and line extensions. Look to converting to conquer product development challenges.

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