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Superabsorbent polymer insertion technology: a simple solution.

Superabsorbent Polymer Insertion Technology: A Simple Solution

there are a variety of methods for inserting superabsorbents into personal care products; the author takes a look at one that may fit depending on the producers' situation Almost overnight, the absorbent products market has demanded various levels of "ultra" absorbency. It is no wonder that the solutions for adding the polymer to the product have covered the full scale from stone-age methods to space age technology.

Now that the situation is calming, what is the best way to apply the polymer? As you may guess, there is no single best solution, so let's explore some of the possibilities.

Blending of SAP in the hammermill: This method of polymer insertion is very basic and gives uniform distribution throughout the fluff pad. Installation is simple and economical. Since there is some size reduction of SAP particles, forming screen "blinding" may be a problem. Excessive amounts of polymer may pass through the screen to the filter system.

Scatter applicators outside of forming: Scatter applicators can offer spot or patch placement by using a "stepping" drive motor for intermittent operation. However, placement of polymer at varying pad depths may be difficult or impossible. More current applicators claim to offer intermittent operation with air insertion.

Precision metering screws: A simple, economical method of inserting SAP in varying widths and depths of the product fluff pad. This low maintenance system may be a solution where intermittent operation is not required.

Pulse spray applicators: This popular method combines high technology with application flexibility for products requiring intermittent placement of polymer. Precise volume and placement of SAP are the major features. Initial purchase price is usually greater than other insertion devices. High tech electronics may require more qualified plant technicians.

Laminate polymer sheets: Laminate sheets are not widely used but may offer added stability and a quick method of entering the ultra products market. Price and supply should be a factor in selecting this method.

SAP flock/fiber and other fibers: There are currently several companies working on superabsorbent fibers as well as non-polymer fibers that can enhance the stability and wicking characteristics of conventional fluff pads.

Precision Metering Screw Insertion Method

The remainder of this article will cover the precision metering screw insertion method. The use of this method certainly depends on the manufacturing situation. There are several companies manufacturing precision metering screw units that are compatible with desired dosing of various polymers. Most of these units have a rugged yet simple screw or auger used to move and measure the polymer (Figure 1).

Both the speed (rpm) of the screw and the pitch determine the volume of material to be metered. The pitch of the screw is the distance between flights or spirals; this distance can vary as well as the depth of the cut on these flights. A specific screw design is required to fit production speed (pieces/minute), polymer per piece (grams) and density of polymer. The rotation of this screw is accomplished by a D.C. drive responding to a tach generator signal from the production machine.

Metering of the polymer is only half of the project. Application of the SAP onto/into the product is the final requirement. This can be accomplished by placing the screw discharge in the forming chamber or transferring the SAP to an air stream for conveying and inserting by means of a low volume pneumatic system. The pneumatic method is most desirable since it allows remote positioning of the polymer metering unit and more precise adjustment of polymer placement position. This can be accomplished without the use of compressed air (Figure 2).

By inserting a 60 mm oval nozzle into the forming chamber, the polymer can be located in a controlled strip down the center of the product. The distance from the forming screen and attitude of the oval nozzle will determine the width of the polymer strip. The nozzle can be aimed in a fashion to position the polymer in the bottom, center or top of the fluff pad (Figure 3). This method does not allow for intermittent application. However, many users are not using this intermittent feature application.

If the SAP insertion nozzle is placed between the hammermill and forming section, a homogeneous mixture of fluff and polymer can be accomplished. This will allow a uniform disbursement of polymer through the entire fluff pad (Figure 4).

A Viable Option

The precision screw with pneumatic insertion system may be a viable consideration since it offers:

1. Low initial cost--most systems will be in the $12,000 to $20,000 range.

2. System flexibility--includes various pad depth and width placements plus uniform placements throughout the pad. Various types of polymer can be run with minor adjustments.

3. Bulk bag unloading capability--direct to screw or by means of transfer tube and auger. Jumbo-tainers and/or supersacks are acceptable.

4. Simple components--allows plant installation and start-up usually without factory technicians. Change out of parts requires minimum time due to tie-rod construction. There are several reliable manufacturers of all components.

4. Ability to control position(s) of polymer--allows various products to be produced with same dosing unit.

5. Accurate measure over a wide range--allows running different grams per product without changing internal metering screw.

Regardless of the final selection, manufacturers should carefully weigh all factors in this fast-changing market. A good decision today may not be be a good decision tomorrow if the selected equipment does not have a wide degree of flexibility. [Figures 1-4 Omitted]

JOHN CORK President Osprey Corporation Atlanta, GA
COPYRIGHT 1989 Rodman Publications, Inc.
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Copyright 1989 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Special Report: Markets for Nonwovens; use in personal care products
Author:Cork, John
Publication:Nonwovens Industry
Date:Aug 1, 1989
Previous Article:Superabsorbent review: an absorbing year.
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