Synthetic sizing agents

Diketene also is widely employed as a natural and synthetic fiber cross-linking agent, wood preservative and paper-sizing agent. Both it and /3-propiolactone have wide application as chemical intermediates. The synthetic applications of diketene for the synthesis of aromatic, heterocyclic and aliphatic compounds is exceptionally extensive (74ACR265). 

Figure 6.26 Flow schematic of a three-stage feed-and-bleed ultrafiltration system used to recover poly(vinyl alcohol) (PVA) sizing agents used in the production of cotton/synthetic blend fabrics [28]...

CMC and water dispensible polyester based size materials are also used for sizing of synthetic fibre materials. They are insoluble in acidic form and soluble in the presence of dilute alkali and can be removed from the fabric at about 60 C. They are, however, precipitated in presence of metal ions in the washing bath and hence the addition of chelating agent is recommended to nullify its effect. Synthetic detergents of either anionic or non-ionic type may be used to remove the polyester size from the fabric. The CMC can be reclaimed, recycled and reapplied from other size material. 

Arkofil. [HoechstAG] Synthetic polymers sizing agents fa spun yams. 

Soromin . [BASF AG] Sizing agents, assistants fix synthetic fibers, primary spinning. 

AKD sizing has been available for almost 50 years and was the first commercially available Synthetic, reactive sizing agent. AKD is a wax normally derived from a mixture of stearic (CIS) and palmitic (C16) fatty acids with a melting range between 42 C and 55°C, dependent on the fatty acid blend. However, there are... 

Most sizing problems can be related to one main problem the lack of the sizing agent, be it rosin, AKD, ASA, polymeric, or any one of the other synthetic sizes available in the paper or board. 

Anionic trash, in synthetic sizing, has a similar effect on size retention as that for rosin size, except that in this case, it is the size that carries the cationic charge, not the alum. This will mean that it is the sizing agent that will be adsorbed onto the anionic trash. If the size is adsorbed onto the anionic trash, sizing will be subject to the retention of this anionic trash and will vary accordingly. This is why mnch more emphasis is placed on the correct retention system to improve anionic trash retention, or fmes/filler retention, as much of the size can also be adsorbed on this. 

The most commonly used sizing agents today are rosins, commonly used in acidic papermaking systems, and synthetic sizing agents such as alkyl ketene dimer (AKD) and alkenyl succinic anhydride (ASA), as shown in Figure 7.18. The latter two components are suitable for papermaking processes under neutral and alkaline conditions. 

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