Embossing

The mats are moved along the line to the press loader. When the loader is filled and the press opens to remove the load of freshly pressed boards, the loader pushes the new boards into the unloader and deposits the load of mats on the press platens. The press closes as quickly as possible to the desired panel thickness. More pressure, as much as 4.8—6.9 MPa (700—1000 psi) is required to press high density dry-process hardboard, because the dry fiber exhibits much more resistance to compression and densification than wet fiber. Press temperatures are also higher, in the range of 220—246°C. No screens are used in the dry-process, but the moisture in the mats requires a breathe cycle during pressing to avoid blowing the boards apart at the end of the cycle. Because no screens are used, the products are called smooth-two-sides (S-2-S), in contrast to the wet-process boards, which have a screen pattern embossed into the back side and are known as smooth-one-side (S-l-S). 

Several more recent variations of the film-to-fiber approach result in direct conversion of film to fabric. The film may be embossed in a controlled pattern and subsequently drawn uniaxiaHy or biaxiaHy to produce a variety of nonwoven products (47). Addition of chemical blowing agents to the film causes fibrillation upon extmsion. Nonwovens can be formed directly from blown film using a unique radial die and control of the biaxial draw ratio (48)... 

Sheet can be produced by melt extmsion, but in this case a three-roll stack of quenching roUs is generally used (Fig. 2). More than three roUs may be used where necessary. The roUs may be mounted vertically or horizontally. The web is extmded through a slot die in a thickness close to the desired final thickness. The die is in very close proximity to the first chill roU or chill-roll nip. The web may be cast horizontally directly onto the upper chill roU of the stack as shown (Fig. 2), or it may be extmded into the first nip directly. The roUs quench the sheet and provide the surface polish desired. In some applications, matte or embossed roUs maybe used to impart special surface characteristics for certain functions. Where the utmost in optical (glazing) quality is desired the trend has been to mount the roU stack horizontally. The hot melt is then extmded vertically down into the first nip. This avoids problems associated with sag of a horizontal hot melt no matter how short the distance between die and quench. 

There is no competitive situation for data storage disks with embossed iaformation (CD-ROM) and recordable/nonerasable disks (WORM) no counterpart to CD-ROM and WORM exists among magnetic memories. EOD drives are best compared to floppies and removable hard disk media given their possibiUty of easy and problem-free disk exchange and a capacity on the order of that of removable magnetic media (Tape, Bernoulli, SyQuest). 

Collation. Collation is the process by which the individual laminate pHes are assembled prior to curing in the press. The buildup of the laminate determines the final properties of the product. The topmost sheet in the buildup may be a texturing or embossing paper as well as being a release sheet to allow for separation of the laminate from the caul plate used to mold it. 

Miscellaneous Types. Various decorative effects have been developed which meet specific aesthetic requirements. These laminates may have special visual appeal, such as gloss finish, deeply embossed textures, and metallic surfaces. They are designed for specific installations and may not be suitable for all apphcations. For this reason, they are not included in these standards. Information concerning thein proper appHcation, properties, and care should be requested from the manufacturer. 

The apphcation of vegetable tanning materials has an additive effect on the leather. The more vegetable tannins appHed the more the leather becomes like vegetable-tanned leather. The color is changed, the fullness of feel increases, and the leather can be worked and embossed like vegetable leather. 

Specific terms have been designated according to the function and composition of various roUs. Steel roUs that impose pressure, transmit heat, and emboss a pattern onto the fabric are known as pattern roUs. Flexible surface roUs that transport the fabric and permit pressure transmission to the fabric are termed bowl roUs or bowls. Bowl roUs are usually larger in diameter than pattern roUs. The material used to make these types of roUs is chosen according to the depth of surface smoothness to be placed on the fabric being calendered, and must be compatible with the pattern roU. Cellulose pulp, cotton, wool, cotton—wool mixtures, com husk, and various polymer materials are used as fillers for the roU surface compound. 

Polyolefin—ceUulose composites also are used in nonasbestos flooring felts, waUpapers, filter media, labels, embossable papers, and other nonwoven fabrics that are made on paper machines. Use of synthetic fibers in paper has been reviewed (103,104). 

Asphalt-coated glass fiber venting base sheet with fine mineral surfacing on the top side and coarse granules on the bottom side perforated/embossed or not. The coarse granules provide an open, porous channel in the horizontal plane (5,11). 

At high (50—100 pph) saturation levels, with a near thermoplastic elastomer, a leather-like material results that can be embossed. The paper web used ia pressure-seasitive tape is prepared by latex saturatioa ia order to give it sufficieat internal strength to release without delamiaatioa. 

Zinc sheet and strip can be easily fabricated by drawing, spinning, bending, stamping, coining, embossing, blanking, and impact extmsion. 

K. Murata and S. Hattori, "Advantageous Features of Microporous Thin Embossed Waffle Shape Separator," 89th Battery Council International... 

---