. Chemical feed systems for the global process industry.

Home	Corporate	Services		Ask Us	Catalog	Register	Login		Support

Internal sizing of paper with ASA and polymer or starch

Alkenyl Succinic Anhydride Sizing and Related Process Equipment
Your ASA sizing needs are easily filled at Chem-Flow. We supply a complete range of ASA Emulsifiers and dosing equipment. Our solution is designed as a suite of equipment that when used together provide a complete solution for making up and dosing ASA sizing.

General Information about ASA sizing equipment:
Alkenylsuccinic anhydride is used to internally size paper products. Sizing creates characteristics in the paper for resisting water without making the surface slippery or appear coated. To achieve a solution of ASA sizing ready to add to the process, the ASA must be emulsified with a emulsifier (cationic starch or acrylimide polymer). This is typically done by metering ASA and the emulsifier into water and passing the chemicals through an homogenizer or turbine at a high pressure. The solution usually around 8-12% is then diluted further with water.

The emulsifier used can take several forms. Many sites take a stream of cooked starch from an on site starch cooker and use the starch as the carrier. Ready made starches are also available that do not require any preparation prior to introduction to the system. Polymers are also used as a cationic emulsifier and are available from many specialty chemical companies.

ASA systems are either batch or continuous systems. a batch system will prepare a dilute ASA solution into a tank for dosing by some type of metering system. A continuous system is typically used with cooked starches and are used where the process sees significant performance increases from freshly delivered ASA emulsion.

For recycle mills and gypsum board liner, most users achieve the desired results at the best price with a batch system. Continuous ASA emulsifiers require significant automation and redundant equipment so that loss of sizing will not be a problem. Batch systems provided with two emulsifier units and a dosing system with tank can be purchased for less than the price of a single continuous system.

The critical factors to any emulsifier are its ability to apply enough energy to create uniform ASA droplets of 0.8-1.0 micrometer and to not produce a solution unless adequate dilution is provided to the turbine/homogenizer. If either factor is not met there will be poor performance of the size, high potential for deposits to form in the paper, and potential equipment damage and loss of production.

The adjoining photo is of a 40 GPM ASA emulsifier for batch preparation of ASA. Typically two of these feeders are used to feed ASA to a feed tank where it is then dosed to the process. Two feeders can be set up so as to automatically start the second feeder if the first feeder can not keep up with production or has failed to start. Any ASA system should have a water alarm to stop the system from making up without dilution. This is a very messy situation and can result in deposits on the paper machine and damage to the turbine. When starting up an ASA emulsifier with starch or polymer it is good to check particle size to assure that you are producing 0.8-1.0 particles.

More Information on ASA Sizing
Below is a link to an article by Dr. Martin Hubbe of North Carolina State University. He is one of the leading experts in the field of wet end chemistry and was a guest writer for our newsletter on the subject of ASA sizing and the importance of particle size.

Article on ASA particle size

Additional articles and links relating to ASA sizing

Chem-Flow Industry Information Home Page
Chem-Flow Industry Selections