Paper properties, control

The major tobacco polycarboxylic acids— malic, citric, and fumaric plus the sodium salts of citric and lactic acids (3486). In the late 1950s, a mixture of sodium and potassium citrates was used as an additive on cigarette paper to control its combustion properties. ... 

Inter-puff SSS, the major contributor to total SSS, is primarily controlled by cigarette tobacco blend and weight and to a lesser degree by paper properties and additives. 

In order to successfully control both the desired paper properties and the production process, papermakers introduce functional additives and process chemicals into the fibrous suspension. Flowever, these chemicals have to interact with the fibres if positive results are to be obtained. 

The need for higher drying rates and controlled paper properties has revived the Papridryer, i.e., combined impingement and through-air drying, idea in the last decade. Recent experimental studies [53,54] reaffirmed the drying benefits, but still there is no commercial application. 

It is known that the physical properties of a polymer depend not only on the type of monomer(s) comprising it, but also on the secondary and tertiary structures, i.e., the stereochemistry of the linkage, the chain length and its distribution, its ability to crystallize or remain amorphous under various conditions, and the shape or distribution of the shapes of the chain in the crystalline and amorphous states. Through advances in polymer chemistry, in most cases polymers can be designed with specific properties. Control of the microstructure, e.g., the tacticity and molecular weight distribution of vinyl polymers, has been the focus of a number of papers in the last two decades. 

Torgnysdotter A, Kulachenko A, Gradin P et al (2007) The link between the fiber contact zone and the physical properties of paper a way to control paper properties. J Compos Mater 41 1619-1633... 

Many paper properties can be controlled in small control zones across the machine, to ensure uniform quahty in CD. Such actuators are located e. g. in the headbox to control basis weight, in the press and in the dryer section to control moisture content, and in the calender section to control cahper across the paper width. 

It can be easily found that the chance of forced collision is very high for very low pulp concentration (e.g., below 0.1%]. This makes it difficult to maintain pulp as homogeneous and stable fibrous suspension. As a result, flocculation is responsible for the local variations of the pulp concentration and further variations in paper properties. On the other hand, this effect—if properly controlled—supports paper web forming process. Flocculation must be carefully controlled particularly in the headbox of the paper machine. Different chemical agents are usually used for this purpose. 

Uses Dispersant, emulsifier in cleaners, contaminant control for pulp and paper Properties Liq. disp. in water sol. in most polar and aromatic soivs. dens. 1.01 pour pt. <0C flash pt. > 100 C HLB 6,8 sapon, no, 115-125 pH (5% in water) 5-7 100% cone. 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly(vinyl acetate)—poly(vinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system. Poly(vinyl alcohol) is typically formed by hydrolysis of the poly(vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as weU as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a coUoid protection system. The protective coUoids are similar to those used paint (qv) to stabilize latex. For poly(vinyl acetate), the protective coUoids are isolated from natural gums and ceUulosic resins (carboxymethylceUulose or hydroxyethjdceUulose). The hydroHzed polymer may also be used. The physical properties of the poly(vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended appHcation. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly(vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. AppHcations are found mosdy in the area of adhesion to paper and wood (see Vinyl polymers). 

Additives. Because of their versatility, imparted via chemical modification, the appHcations of ethyleneimine encompass the entire additive sector. The addition of PEI to PVC plastisols increases the adhesion of the coatings by selective adsorption at the substrate surface (410). PEI derivatives are also used as adhesion promoters in paper coating (411). The adducts formed from fatty alcohol epoxides and PEI are used as dispersants and emulsifiers (412). They are able to control the viscosity of dispersions, and thus faciHtate transport in pipe systems (413). Eatty acid derivatives of PEI are even able to control the viscosity of pigment dispersions (414). The high nitrogen content of PEIs has a flame-retardant effect. This property is used, in combination with phosphoms compounds, for providing wood panels (415), ceUulose (416), or polymer blends (417,418) with a flame-retardant finish. 

Caro s acid is effective ia delignifying wood pulp (qv) made by chlorine-free bleaching sequences. When conditions are carefully controlled, the mechanical properties of the final paper (qv) are not impaired. These processes were developed ia the 1980s and commercialized ia the 1990s (68). 

Dicyandiamide reduces the viscosity of certain coUoidal solutions. This property is of commercial significance ia the manufacture of glues and adhesives, ia the coating and sizing of paper and textiles, and ia the conditioning of phosphate drilling muds (see Petroleum). This action may prove useful ia other appHcations where control of viscosity is important (54). 

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