Specialty Paper Machines

The category of specialty papers defines a very wide range of different paper grades with a wide variety of specialized end uses and thus different and particular quality demands. These require special production technologies and specific know-how. Some of the required properties are very common and similar to commodity papers, but they are usually more distinct or with a closer tolerance. Such characteristics include profile quality, formation, smoothness, strength, thickness, porosity, and absorption. Some are very particular characteristics, such as wet strength, electrical conductivity, pore size distribution, resistance to certain chemicals, chemical reactivity, fight proofness, heat resistance, and cleanliness. 

Not only are the quality requirements various but also the production of specialty papers covers a wide range of speed and basis weights. The basis weights extend from 12 g m for tea bag paper up to 300 g m for specific photo base 

The base sheet forming concept for specialty papers is the fourdrinier. It can be used for the whole basis weight range and up to a machine speed of about 1200 m mimf In order to achieve best results concerning formation and dimensional stability Dandy rolls or hybrid formers and effective vidre shaking units are frequently used. New machines however can exceed the speed limit of fourdri-niers, so gap former concepts are used in this case. 

The basic raw material for specialty papers is wood pulp. There are however grades like tea bag, plug wrap or filter paper where the required porosity, absorb- 

Another old fashioned well proven sheet forming technology which is found in specialty paper production only is the cylinder mould former (Fig. 6.87). This sheet forming technology is still used for the production of cotton based banknote paper. The paper production on a cylinder mould former enables the application of three key security features  

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The press sections in specialty paper machines need to be highly flexible. For paper grades where only one smooth side is required, multi-roll press concepts with two or three press nips and a closed sheet run can be used. For increased dryness and improved runnability these press concepts can be equipped with a... 

Anionic starches are obtained by reaction with phosphoric acid and alkali metal phosphates or by derivatization with carboxymethyl groups.30,31 This modification is primarily used to introduce amphoteric properties into cationic com starch for application on the wet end of the paper machine. Anionic starches with carboxymethyl substitution are used as thickeners in coating colors or as binders in coatings for specialty paper grades. Oxidized starches are inherently anionic but without thickening action. Potato starch already carries sufficient natural anionic charge to provide amphoteric properties after cationization.32... 

In specialty paper and tissue production, online measuring technique has often not been used in closed-loop control in the past because of many grade changes and complex process chemistry. Small production volumes and slow running machines were not supporting acceptable payback calculations for investments in measuring technology. 

Wet pulps are used in specialty paper applications such as speaker cones, filtration, and specialty papers. These pulps have been successfully processed on cylinder, rotoformer, and Fonrdrinier paper machines. As little as 15% of a highly fibrillated pulp can interlock other fibers or powders without the need for resin binders. 

Paper Machine Oils Specialty products may include ... 

Specialty papers can be divided into uncoated and coated grades. The uncoated grades are either machine finished, like cigarette papers or base papers for sub-... 

Uses Defoamer for paper machine and specialty coating applies. 

In addition to the common roving strands, raw material is available in many other forms, such as preimpregnated (prepreg) and wet systems, mats (paper and nonwovens), woven specialties with knit and braided reinforcement, multiple-ply broad goods, core materials as they apply to automation, fillers, extenders, and additives (films, coatings, plating, etc). The characteristics of the reinforcement must be familiar to the machine designer. 

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