Sizing Agents

Sizing agents are applied into the paper to impart certain desirable qualities. The main function of sizing agent is to increase the resistance to penetration of water or other liquids into the paper so that the paper is suitable for printing, writing and other purpose. It can be achieved either by using wet-end additives or by applying a suitable coating to the surface of the dried paper. Sometimes a combination of treatments is required. The wet-end Sizing agents also decrease dusting, control spreads of inks, improve dewatering, retention of filler and fibers, improve paper quality, smoothness, dimension stability, abrasion, decrease porosity and improve paper machine runnability.

Types of Sizing Agent
There are two types of sizing agents; internal sizing agents and surface sizing agents.

Internal Sizing Agents
Internal sizing agents are used in papermaking process at the wet end. The most important internal sizing chemicals are alkyl ketene dimer (AKD), rosin and alkyl succinic anhydride (ASA). The internal sizing agents should have some basic characteristics such as high hydrophobicity, good retention on fibers, uniform distribution throughout the fiber surfaces, and must strongly bonded with fibers.
The internal sizing agents can also be classified into acidic type sizing chemical and basic or neutral type sizing chemical. Rosin and its derivatives are acidic type sizing agent. On the other hand AKD and ASA are basic or neutral type sizing agent.

Surface Sizing Agents
Surface sizing agents have both hydrophilic and hydrophobic ends. It is forms a thin film on paper web, the hydrophilic tail of it joined with the fiber, whereas hydrophobic tail facing outwards. The thin film reduces paper dust; improve surface strength, printability and water resistance of the paper. There are different chemicals are used as surface sizing agent such as modified starches, Styrene Maleic Anhydride (SMA), Styrene Acrylic Emulsion (SAE), Styrene Acrylic Acid (SAA), Ethylene Acrylic Acid (EAA), gelatin and Polyurethane (PUR). It is normally applied in a paper mill though the size press at dry end section.

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27 Responses to Sizing Agents

  1. Baramki says:

    We are producer of carton board from recycle paper. It is used for shoe insole , we call it insole carton board , thickness about 1 to 1.5 mm. In our production we used a recycle paper : duplex ( the one side white and the other side grey ) , some times we add some SBR liquid , and sometimes no. We have a problem that this carton board we are producing is easy to broke , and also easy absorb water. So , what is your suggestion to can modify our formulation ?
    We wait your soon answers and technical data and uses.
    Rgds. Baramki

  2. amol patil says:

    how to reduce sizing (cobb vaulue) in recycle kraft paper mill our cpacity 30 ton/day in reainy season cobb value increased to 150 to 175 our acidity of water 400 approximate
    plz suggest

  3. By making the paper web more hydrophobic, the sizing agents influence dewatering and retention of fillers and fibers in the paper sheet.

  4. Elius says:

    How many have process in courting paper sizing increase

  5. tippy says:

    In recycled paper mill have a problem that split paper.I want to know its cause and how improvement it not have these problem ,thank you.

  6. Pagare says:

    How to achieve suitable IGT in board paper GSM 250 TO 400 by surface sizing.

  7. Pranav manjunath says:

    We are getting low burst strength factor and also worst sizing (cobb values) although we are using rosin with alum(al2so4).. I’m cordially requesting you to give your suggestions. Please help us.

  8. pradyuman patel says:

    we are manufacturing Water dispersible polyesters resine for paper wet end sizing to Water dispersible polyesters are used to treat and size paper by applying them at the wet-end of the paper process. The water dispersible polyesters can be used alone or with other chemicals typically used to treat or size paper in order to increase the paper’s dry strength, wet strength, stiffness, water repellency, water resistance, and sizing properties
    pl contact

  9. zenebe says:

    we are manufacture carton and white bond paper in acidic media buy using rosin internal sizing agent but know we need to replace rosin by other type of chemical and we need Sapporo if you maind

    • Hossein says:

      Hi Zenebe
      As you mentioned use rosin for sizing then are using Alum+Rosin for sizing and Alum is intermediate material.
      Before I was sizing like you but know I changed this internal sizing from acidic sizing to alkaline/nautral sizing with AKD and arrived to very good results; not only cobb but also strenght properties of paper.
      In this way first you should slowly slowly alkaline your system with CaCo3 and then use AKD.
      After you will get to good quality and most cost saving.don’t worry about strenght because AKD will improve all can use AKD 6-8 kg/MT of board.

  10. widi says:

    how do i know type or chemical agent of sizing in paper? what kind of method to do that?
    thank you

  11. Mohamed ahmed says:

    I am chemist at gypsum Board factory and we are using Weig paper grey and Ivory now we have a serious problem paper is expanded a lot of times making notable lines on the face of boards and we don’t no why and we have no solutions so kindly any suggestions

  12. siddharth says:

    We are doing printing on paper . To impart water resistance on printed paper we have tried different chemicals like SBR latex , Stryrene Acrylic Emulsion , Carnauba Wax emulsion etc . We are getting decent water resistance by using the above chemicals but we are facing problem of tack and the coated paper is become sticky due to these coatings . After winding the paper is getting blocked due to this. We are using gravure coating and the heating temp is around 80 deg celcius.

    Any help would be greatly appreciated .

  13. زهرا اوصالی says:

    we use recycle pulp . we have pr0blem in sizing . we use from AKD surface sizing and Alum in size press to control cobb of paper also in size press we add native starch to increase Burst factor but when add Alum we con not control Burst Factor . Burst factor decrease.

  14. زهرا اوصالی says:

    when we using native starch in producing fluting paper, did not have any problem in CMT factor but in semi k.l.b paper , the burst factor decrease.
    in semi Kraft paper we use from AKD surface sizing + Alum + native starch in size press
    pH in size press: 3.5-3.6
    have you any suggestions to increase the burst?

    • admin says:

      1. Why you use AKD surface sizing + Alum?; I have no much idea about this. But the sizing group is (alum+rosin) and (AKD+AKD fixing agent). The ketene group of AKD is very reactive that can be easily goes under chemical reaction with alum. Moreover, the function of AKD sizing agent depends on pH value of the fiber suspension.

      2. We use (alum+rosin) as internal sizing for Brown paper. I have no practical knowledge on Surface Sizing. Once we used ‍ AKD as a internal sizing but started using (alum+rosin) size again due to problems with the bust factor.

  15. bayat says:

    hi to all
    we have problem in burst factor parameter, in semi Kraft paper, in size press we add native starch + Alum+ AKD surface sizing agent, can the Alum decrease the burst factor? what is the relation between pH and burst factor? in fluting paper in size press we just add native starch and we have no problem. what is your suggestion?
    thanks a lot

  16. Fine way of describing, and good piece of writing to take data regarding my presentation focus, which
    i am going to present in college.


    How can we use WSR in HAND MADE PAPER MAKING in batch beating of 100%cellulose(cotton waste)

  18. B.K.Roy says:

    What do you suggest for sizing to manufacture kraft liner (100 to140 gsm) to maintain a standard cobb-60 value, at the same time to get higher bursting strength, by using starch at inclined size press. Raw materials are only indigenous & local box board / corrugated cuttings etc. And whether you can supply all the chemicals . The plant capacity is 120 TPD.

  19. hilia einy says:

    We produce paper for watercolor painting from recycled cotton fabrics. We use industrial or animal gelatin for sizing. Unfortunately, in some parts of the paper after drying, it is observed that the size is not fixed and it is not the same size as one point. to be Thank you for telling me the cause of this problem and the solution.

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