Web formation

Four basic methods are used to form a web, and non-wovens are usually referred to by one of these methods dry-laid, spun-laid, wet-laid and other techniques. Carding, garnetting and air-laying are examples of the dry-laid processes. The dry-laid processes provide maximum product versatility, since most textile fibers and bonding systems can be utilized and conventional textile fiber processing equipment can be readily adapted with minimum additional investment. 

The wet-laid process is similar to paper making, where a dilute slurry of water and fibers are deposited on a moving wire screen and drained to form a web. A wide range of natural, mineral, and synthetic fibers of varying length can be used. 

Other techniques include a group of specialized technologies in which the fiber production, web structure and bonding usually occur at the same time and in the same place, as melt-blown and flash spun web formation methods. 

Detailed description of these technologies can be found elsewhere [1,4]. As seen in Fig. 10-6, spun-laid and dry-laid are two preferred processes both in North America and Europe. The spun-laid process showed the strongest growth during a last decade [1, 7]. Products produced by the spun-laid technique account for 20-25 % of the market in Japan and China [5, 6]. 

---

Weber numbers Weber s law Web formation Web knitting Web offset inks Webster hardness gauge Weed killers... 

Nonwoven technologies that employ machinery and processing principles traditionally used to manufacture textile, paper, or extmded materials, when viewed collectively, form what may be termed the primary or basic nonwoven fabric manufacturing systems. These systems are or can be continuous processes. Common to each of these systems are four sequential phases fiber selection and preparation, web formation, bonding, and finishing. 

From a practical standpoint, the fiber or polymer must interact or process freely with the dynamics of web formation, and the resulting fiber network must be in register with the interlocking arrangement or media, in order for the fabric stmcture to transmit the maximum potential inherent in the properties of individual fibers. Ultimately, if a nonwoven fabric is to be totally effective and its properties fuUy utilized, it must be appropriately configured to meet its end use apptication or appropriately placed in the end use item in such a way that the performance of the product reflects the position and characteristics of individual fibers. 

Textile fibers can be air-formed ditectiy into end use configuration by including a shaped condensing surface or, as in the production of pillows, an air-permeable collection package. Aerodynamic web formation is a suitable means for processing brittie fibers such as glasses and ceramics, and stiff fibers such as metaUics and wood. 

Nonwoven bonding processes iatedock webs or layers of fibers, filaments, or yams by mechanical, chemical, or thermal means. The extent of bonding is a significant factor ia determining fabric strength, dexibiUty, porosity, density, loft, and thickness. Bonding is normally a sequential operation performed ia tandem with web formation, but it is also carried out as a separate and distinct operation. 

The fabric may also be given one or more of a number of other finishing treatments, either ia tandem with web formation and bonding or off-line as a separate operation, as a means of enhancing fabric performance or aesthetic properties. Performance properties iaclude functional characteristics such as moisture transport, absorbency, or repeUency flame retardancy electrical conductivity or static propensity abrasion resistance and frictional behavior. Aesthetic properties iaclude appearance, surface texture, and smell. 

Iowa Drug Information Service. A bibliographical database with access to full text, IDIS [98] provides access to the therapeutic and clinical pharmaceutic English language journal literature from 17 countries. FDA Summary Basis of Approval documents are indexed and available in full text. Updated monthly, the database contains over 450,000 records from 1966 forward with bibliographic citation, keyword indexes, and, for over 60% of citations, the author s abstract. IDIS is commercially available in microfiche, compact disc, and web formats and via DataStar, DIALOG. 

Aero-derivative systems, 10 142 Aerodynamic diameter, of a particle, 26 694 Aerodynamic web formation, 17 502-504 Aerogels, 1 748-769 23 56... 

Spinning systems, wet ring, 11 615-616 Spinning/web formation, for spunbonded non woven fabrics, 17 469-474 Spinodal curves, 20 320-321 Spinodal decomposition, in polymer blends, 20 321, 322... 

Web formation/spinning, for spunbonded nonwoven fabrics, 27 469-474 Web knitting, 27 507 Web layering... 

Simpson A, Economikos L, Jamin FF, Ticknor A. Fixed abrasive technology for STI CMP on a web format tool. Mater Res Soc Symp Proc 2001 671 M4.1.1-M4.1.9. 

Non-woven The AQUATHANES inherently have excellent water and oil resistance in technical wet and dry laid application. They show further process aid in their release properties from surface contact in web formation and drying. 

The Dandy roll on the upper surface does not dewater. It is included to improve web formation by introducing shear to the mix where it is around 2-3% consistency, when the web is very compressible. 

Kibblewhite RP (1984) Web formation, consolidation and water removal and their relationships with fibre and wet web properties and behaviour. Fundamentals of paper performance. Technical Association of Australian and New Zealand Pulp and Paper Industry, Vol. 3 1-12... 

World Generic Markets. England Espicom Business Intelligence. Monthly newsletter covering manufacturers, products, litigation, pricing, etc. Available in print, email, and Web format. 

Fields Way, Chichester, West Sussex, PO20 2FS, U.K. Phone +44-1243-533322, Fax +44-1243-533418. North American contact 116 Village Boulevard, Princeton Forrestal Village, Princeton, NJ 08540, U.S.A. Phone +1 609-951-2227. Fax +1 609-734-7428. URL http //www.espicom.com. Pharmaceutical Agreement News (PAN) is an alliance news source that covers new, updated, and discontinued alliances and agreements in the industry. The newsletter is produced bimonthly and is available in print, e-mail, and Web formats. 

Nonwoven geotextiles. Nonwoven fabrics are defined as a sheet, web, or batt of directionally or randomly oriented fibres/filaments, bonded either by friction, and/or cohesion, and/or adhesion. In general, nonwoven fabric formation can be considered as a two-step process web formation (aligning the fibres with certain orientation characteristics) and bonding these fibres by mechanical, thermal, or chemical means. This two-step process has formed the classification of nonwoven structures, i.e. carded, airlaid, spunlaid, meltblown, needlepunched, hydroentangled, adhesive bonded, thermal bonded, stitch bonded, etc. Some of the important processes that are used for the manufacture of nonwoven geotextiles are discussed below. 

Disposable absorbent articles generally contain absorbent fibrous webs, such as airlaid or bonded carded webs. Such webs are often stabilized with binder fibers during web formation. 

Table 9.3 General requirements to be met by reclaimed fibre quality depending on the web formation process...

As can be seen in Table 9.3, both the aerodynamic and mechanical processes of web formation raise different questions with regard to the quality of reclaimed fibres. When producing the fibres, quality parameters can be set to some degree. 

Our laboratory equipment allows the making of reclaimed fibres into yams. We have both rotor spinning and yam-covering spinning units available. In addition, there are several plants to make nonwovens. Both mechanical and aerodynamic web formation are possible. We use mechanical as well as thermochemical processes to fix the webs (needle-punching, hydroentangling, meshing to a variety of processes, thermofixation, thermofusion). 

One effective way to lower the cost of making nonwovens of high mass per unit areas is seen in the elimination of some of the process steps and the combination of others for the production of reclaimed fibres and for web formation. This combination of processes makes use of a special breaking-down machine. It is designed to make a novel mat-like structure based on textile waste, eliminating some of the cost-intensive working steps. 

---