Nasa Tech Briefs

This technology provides the ability to uniformly distribute and attach particulate matter onto fibrous composite sheet or web materials.

This technology provides a methodology and products that are formed from fibrous substrates or film-like surfaces by uniform impregnation with a particulate that is subsequently firmly attached. The extremely uniform distribution of the particulate is accomplished by 1) electrically charging a fibrous matrix with individual exposed surfaces to create a uniform distribution of charged sites; 2) applying particulates to this matrix so that particulates adhere at the charged sites; and 3) the particulates are attached to the individual fibers within the substrate by firm non-transient bonding.

Treatment of fibrous webs allows particulate distribution at Coulombic distances on exposed surfaces, giving improved coverage and performance.
Sheet and/or web materials are widely used in many types of products including personal care products such as absorbent structures, medical dressings or wound healing devices, filtration or adsorption devices, and medical fabrics.

Sheets or webs that incorporate other inexpensive raw materials in particulate form could have an even wider range of applications if these sheets or webs could be designed to have enhanced properties or attributes. Such is the nature of this invention, where internal particulate additives give rise to new and improved attributes and in new application fields.

Prior technologies have provided things such as internal additives for fibers to impart desired functional characteristics, or application of liquid coatings of fibers or webs to change properties. These coatings and internal additives have limits to the types of functional characteristics that can be economically imparted to sheets. On the other hand, particulate addition to sheets or webs has long been known to be desirable, but has suffered from low addition levels and especially poor distribution profiles.

Specifically, the first important breakthrough for uniformly distributing finely divided particulate matter onto individual exposed fibrous surfaces is to create electrically charged sites on these exposed surfaces. The electrical charge may be an electrostatic charge applied to a matrix of dielectric fibrous material by passing the matrix through a high-voltage field. Alternatively and/or additionally, the electrical charge may be an electric field applied directly to a matrix of non-dielectric fibrous material.

The second important step is to apply the particulates to the charged matrix of fibrous material by contact between the charged matrix and particulates suspended in a moving gas. For example, particulates may be applied to the charged matrix by passing a gaseous composition or fluidized bed of particulate matter through the charged matrix of fibers. Variations in this procedure may also be practiced, such as changing or removing particulate charges before contact with the web, recharging the matrix after application, or several layers of particulates may be attached to the matrix or excess particulate may be removed before subsequent steps.

The third important step is the adherence of the particulates to the fibrous material by substantially non-transient bonding, by using bonding techniques such as heat, adhesives, chemical reaction, and/or interfacial energy between the particulate surfaces and the surfaces of fibrous material. When heat bonding is utilized, heat may be supplied by means such as, but not limited to, infrared radiation, steam cans, hot ovens, microwaves, flame, hot gases, hot liquid, and radio frequency heating.

These manufacturing processes may be easily and cost effectively implemented in either batch or continuous processes. Processing options include, among others, the ability to control over a wide latitude the compositional parameters of the fibrous matter, the web or sheet properties, the permeability or porosity of the webs, the electrical properties of the webs, the compositional parameters of the particulate matter, the particle size of the particulate, the fluidizing media for deposition of the particulate, the ability to select patterned areas of the web for controlled deposition, and the manner of forming the strong non-transient bonds.

These and many other applications might benefit from improvements in fibrous webs containing uniformly distributed particulate matter that is firmly attached to the substrate, yet retain conventional properties of cloth-like webs to deliver unique product benefits.

This technology is offered by Kimberly-Clark Corp. For more information, view the TechPak at

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