Board calendering

An alternative method to apply starch to paper, especially to paperboard grades, is to use a water box at the calender. Water boxes are used for wet-finishing of paper-board prior to coating application. Use of starch in the water box will increase surface strength and lessen fiber reswelling after coating application. Dilute dispersions of oxidized starch are used, frequently in conjunction with a lubricant to prevent calender roll picking. 

These can be used as tubes for protection or for small powder drums of 100-200 g. They are made by spirally or convolutedly winding the various plies in turn around a mandrel (similar to kegs), bound together with suitable adhesives. The materials are basically grades of paper or light board but may contain PE, aluminium and fine calendered coated decorated paper as an outside layer. 

However, if they are cnred in the oven, the size will be able to spread and react. This is the so-called oven-cnred size value, which shows that the size is retained by the sheet. This cure effect is enhanced by calendering, rewinding and high temperatures in the reel. All of these exert temperature on the size particles, enabling them to react in the paper or board after production. 

There are four general types of synthetic coatings (1) cellulose esters and ethyl cellulose (2) vinyls and vinyl copolymers (3) rubber and synthetic rubber aud (4) oil in resins. These are applied by one of four methods (1) spreader or doctor knife (with cellulose nitrate) (2) calendering (with vinyls and rubbers) dipping (for oil in resin) and (4) rolling (for reversed coating and panel boards). Spraying is also used to a limited extent for special finishes. 

Filter paper Blotting paper Insulating, board Newsprint paper i tique book paper Lined straw board Super-calendered book paper... 

The Main Calendering Methods for Various Paper and Board Grades... 

Final cartonboard post-calendering is mainly done with soft-nip calenders. The Pope reeler can be used for reeling up to 3.5 m diameter, reelers with center torque are applied for diameters of up to 4 m. A state-of-the-art board machine (Fig. 6.83) with on-Hne coating and final calendering has a length of up to 350 m. 

Selected properties of some grades of paper and board Property LWC, Newsprint Wood-free Mechanical offset paper printing paper Bag paper SC-A, Boxboard Super-calendered mechanical uncoated magazine paper ... 

After the paper has been dried, it is often calendered to even the crossmachine profile. Calender stacks are made of two or more rolls whieh are set at close tolerances. The paper web pases between the rolls and is smoothed and levelled. On some paperboard maehines, ealender sizing is done. A light coating of starch or CMC is put onto the underside of the board for cure control. 

Uses Release agent for use in coating colors gloss aid during calendering food-pkg, adhesives, coatings, paper defoamer in food-contact coatings, paper/paper-board... 

Uses Lubricant for size press or calender stack applies. corrosion Inhibitor for steel rolls prevents sticking, picking, and blocking of surf, sizing formulations release agent for Yankee dryers reduces coeff. of friction (static and dynamic) on all paper and board component of paper/paperboard In contact with dry foods defoamer In food-contact paper/paperboard Features Forms stable emulsions compat. with all types of starch for use at neutral to alkaline pH at temps, below 165 F... 

Sheets of mineral-filled LCP materials have been used for thermoforming and electroplating for printed circuit boards. During the fabrication, calendering rolls have to be placed close to the die. The stiffness of the sheets requires a spool with a diameter about 200 times the thickness of the product. 

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