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SAP Distribution Nozzle

IP.com Disclosure Number: IPCOM000008183D
Publication Date: 2002-May-23
Document File: 6 page(s) / 63K

Publishing Venue

The IP.com Prior Art Database

Abstract

Discusses a method and apparatus to achieve a desired distribution of superabsorbent polymer (SAP) or any other particulate material in an absorbent pad of disposable absorbent articles. Specifically it strikes a compromise between the desire for homogeneous distributions for product performance, and layered distributions for minimizing SAP losses in the converting process. The particulate distribution achieved can generally be described as a statistical bell curve (normal distribution) in the thickness (or Z-direction) dimension. The result is well mixed SAP with significantly diminished particulate concentrations on the top and bottom of the pad.

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This publication discusses a method and apparatus to achieve a desired distribution of superabsorbent polymer (SAP) or any other particulate material in an absorbent pad of disposable absorbent articles.  Specifically it strikes a compromise between the desire for homogeneous distributions for product performance, and layered distributions for minimizing SAP losses in the converting process.  The particulate distribution achieved can generally be described as a statistical bell curve (normal distribution) in the thickness (or Z-direction) dimension.  The result is well mixed SAP with significantly diminished particulate concentrations on the top and bottom of the pad.

The reduced top and bottom SAP concentration significantly reduces the problems associated with particulates which escape from the pad and deposit onto the equipment and floor.  Studies have shown this distribution may reduce in-process fall-out.  The economic advantages of not losing SAP out of the product and not having the expense of collecting and disposing of the fallout are obvious.

This “normal distribution” may be obtained by pneumatically conveying particulate (SAP) out of a round tubular nozzle upward at an angle towards the discharge of the fiberizer.  The SAP and fluff combine by virtue of colliding momentum and turbulence, to form a well-mixed distribution and are deposited onto a forming drum or wire section below.

Two versions of the improved SAP nozzle are presented here and are applicable dependent on the direction of rotation of the forming drum (see Figures 1 & 2).  While the specific nozzle geometries may appear different, they are actually both delivering the SAP into the entry side of the forming chamber, and directing the SAP up into and against the forming chamber airflow and the discharge of the fiberizer.

A nozzle geometry which may provide improved results is one having an upward angle which is capable of projecting the SAP up and away from the forming drum.  The upward geometry may provides a significantly longer projectile path for the SAP to travel compared with more traditional nozzles, thus providing more time for dispersion and mixing with the fluff fibers.  Further, the upward geometry creates an impact between the SAP and the airflow and inertia of the forming chamber.  The collision created by the counter acting airflow further enhances mixing and the distribution of SAP within the pad.

The velocity of the SAP as it exits the nozzle affects the inertia and hence distribution of the SAP within the absorbent. The velocity may be controlled, for instance, by adjusting mass flow rate, transport air flow, diameter of the delivery tube, and diameter and shape of the nozzle openings. Velocities of from 1,000 to 10,000 ft/min may be used. A transport velocity of 3,500 to 7,000 ft/min has been found to yield effective results.  If the velocity is too low, the SAP add-on may become excessively variable and layered.  If the velocity to too large, the SAP could ricoc...