Calendering, Reeling and Finishing Sections PDF

We l e a d IWK 203/4 STOCK PREPARATION AND PAPERMAKING PENYEDIAAN STOK & PEMBUATAN KERTAS DR. KUSHAIRI MOHD SALLEH School of Industrial Technology Universiti Sains Malaysia 2024/2025  PAPERMAKING...

We l e a d IWK 203/4 STOCK PREPARATION AND PAPERMAKING PENYEDIAAN STOK & PEMBUATAN KERTAS DR. KUSHAIRI MOHD SALLEH School of Industrial Technology Universiti Sains Malaysia 2024/2025  PAPERMAKING We l e a d 2.1 INTRODUCTION OF PAPERMAKING 2.2 APPROACH FLOW SYSTEM 2.3 FORMING SECTION 2.4 PRESSING SECTION 2.5 DRYING SECTION 2.6 CALENDERING, REELING AND FINISHING SECTIONS  CALENDERING, REELING AND FINISHING SECTIONS We l e a d CALENDERING CALENDERING, REELING AND FINISHING SECTIONS DR. KUSHAIRI MOHD SALLEH SCHOOL OF INDUSTRIAL TECHNOLOGY UNIVERSITI SAINS MALAYSIA  CALENDERING, REELING AND FINISHING SECTIONS We l e a d Calendering After drying, most paper grades will go through arrangements of rolls in the calendering section. Calendering is a process where the paper will pass through nips, which are pressed between rolls at HIGH pressure. The calender stack is a series of solid rolls, usually steel or cast iron, mounted horizontally and stacked vertically. CALENDERING, REELING AND FINISHING SECTIONS We l e a d CALENDERING, REELING AND FINISHING SECTIONS We l e a d  CALENDERING, REELING AND FINISHING SECTIONS We l e a d The rolls may or may not be of equal hardness. The time taken for the pressing on the nip is very short. The main objectives for calendering are to a) reduce the thickness and b) to obtain a smooth surface of the paper. It is also used to control paper density and to smoothen the watermark on paper. CALENDERING, REELING AND FINISHING SECTIONS We l e a d  CALENDERING, REELING AND FINISHING SECTIONS We l e a d The upper stack rolls are intermediate rolls. These rolls consist of heated rolls and variable-crown rolls. Next, it is the queen rolls which are usually the driven rolls. The bottom rolls are the king rolls which also act as variable rolls.  CALENDERING, REELING AND FINISHING SECTIONS We l e a d The level of calendering depends on the finishing grade desired. Low-grade finishing needs the paper to pass through only one or two calendering nips. For high grade, the paper may pass through a series of calendering up to 3 sets of rolls (each set has 7-9 rolls).  CALENDERING, REELING AND FINISHING SECTIONS We l e a d Calendering operations are carried out on-machine or off-machine. For economic reasons and current technology expansions, on-machine calendering is used. Calendering at high temperatures makes the paper more pliable and can be calendered at low pressure. Usually, the first two rolls in the intermediate rolls stack are heated through an inlet of hot water into the rolls. CALENDERING, REELING AND FINISHING SECTIONS We l e a d  CALENDERING, REELING AND FINISHING SECTIONS We l e a d Type of Calenders The type of calenders depends on the rolls used. Calendered paper will be changed in terms of thickness, density and surface properties.  CALENDERING, REELING AND FINISHING SECTIONS We l e a d 1. Machine Calender Machine calender is the most commonly used type. It is an on-machine calendering and operates before the reeling process. Paper is pressed between a pair of hard metal rolls. This calendering is also known as a hard-nip machine calender, which produces paper with the same thickness. CALENDERING, REELING AND FINISHING SECTIONS We l e a d  CALENDERING, REELING AND FINISHING SECTIONS We l e a d Latest technology has developed the soft-nip machine calender to produce paper with uniform density. The soft roll layer is made of elastic material. It is an attempt to get some of the benefits of supercalendering without paying the high price.  CALENDERING, REELING AND FINISHING SECTIONS We l e a d Soft-nip machine calender could have many designs depending on the end product requirements If both web surface needs to be smoothed, then the design should be two nips in an inverted form. Four nip arrangement was used for finishing coated papers in some mills However, the addition of more nips contributes to cost. CALENDERING, REELING AND FINISHING SECTIONS We l e a d Inverted Inverted  CALENDERING, REELING AND FINISHING SECTIONS We l e a d The differences between both machine calendering. CALENDERING, REELING AND FINISHING SECTIONS We l e a d  CALENDERING, REELING AND FINISHING SECTIONS We l e a d The soft-nip calendering gives similar density. It gives better printing properties due to its uniform size distribution of pores So, there is no blackening effect (points with transparent condition) Blackening can cause problems in printing due to uneven absorption of ink.  CALENDERING, REELING AND FINISHING SECTIONS We l e a d 2. Supercalender Supercalender is an off-machine with low speed. Calendering is done after the reeling, winding or after the paper is coated. A supercalender is a multiroll calender composed of alternating hard and soft rolls. Paper is pressed between the hard and soft rolls. The soft rolls are layered with materials which almost the same hardness as paper, such as cotton, wool and a special kind of paper.  CALENDERING, REELING AND FINISHING SECTIONS We l e a d UNWIND WINDER SOFT HARD SUPERCALENDER  2.6 CALENDERING, REELING AND FINISHING SECTIONS We l e a d The soft rolls allow good smoothness without severe blackening of the paper. Its drawback is to change the rolls quite often. It also has speed limitations. Its speed sometimes cannot exceed 500 m/min.  CALENDERING, REELING AND FINISHING SECTIONS We l e a d Reeling REELING After drying and calendering, the paper needs to be collected at the end of the machine by wrapping it in a metal cylinder called a reel spool crossing the paper machine. This process is called reeling. Reeling is a way of collecting paper which is gained from the paper machine. It will produce a big paper loop (full reel).  CALENDERING, REELING AND FINISHING SECTIONS We l e a d For on-machine calendering, reeling is done after the calendering process. For off-machine calendering, reeling is done before the calendering process. The main components in the reeling process are driving drum or reel drum, reel spool, primary arm and secondary arm. Driving drum is the most important component because it controls the reeling speed. CALENDERING, REELING AND FINISHING SECTIONS We l e a d CALENDERING, REELING AND FINISHING SECTIONS We l e a d  CALENDERING, REELING AND FINISHING SECTIONS We l e a d Usually, the diameter of the reel spool is between 20 – 100 cm. The choice of the reel depends on the full reel or paper loop (1.5 - 3.0 m). The reeling process starts by transferring the reel spool (located at the primary arm) to the secondary arms. Pressure from the secondary arms makes the paper on the driving drum being wrapped on the reel spool. Reeling keeps operating until it reaches a desired diameter (full reel). CALENDERING, REELING AND FINISHING SECTIONS We l e a d  CALENDERING, REELING AND FINISHING SECTIONS We l e a d Then the secondary arms release their pressure (slow down the process) and at the proper moment, the backtender breaks the paper at the full reel. The full reel is rolled to the end of the rail. At the same time, the empty reel spool start to be wrapped. The primary arms are lowered to the rail. Then, the secondary arms engage the reel spool to maintain the driving pressure against the drum reel. The full reel (paper loop) is ready to be transferred and retreated off-machine. The common treatment used in paper mill is off-machine calendering or winding process.  CALENDERING, REELING AND FINISHING SECTIONS We l e a d The typical reeling defect is wrinkles and subsequent breaks due to the air pocket development. Especially on dense and low porosity paper grades.  CALENDERING, REELING AND FINISHING SECTIONS We l e a d Winding WINDING After reeling, the paper needs to go through the final process called winding. The purpose of winding is to cut and wind the full paper reel into suitable size rolls. When the full reel is placed in its position, the end of the paper is placed into the lead-in roll to start the winding operation. CALENDERING, REELING AND FINISHING SECTIONS We l e a d  CALENDERING, REELING AND FINISHING SECTIONS We l e a d During the winding process, both edges of the paper are trimmed off at the slitter section. The broke is conveyed back to the stock preparation section to be recycled. Meanwhile, the middle part of the paper is cut depending on the width desired by customers. CALENDERING, REELING AND FINISHING SECTIONS We l e a d  CALENDERING, REELING AND FINISHING SECTIONS We l e a d The paper with certain width is rolled on core made from paper or plastic on the winding drum. Usually, cores are 76 mm in diameter with a wall thickness about 10 mm. Finally, the paper rolls are wrapped with plastic and labeled. Important details which are often written on the labels include the grammage, thickness, type, length and width of the paper.  CALENDERING, REELING AND FINISHING SECTIONS We l e a d Then, the paper rolls will be sent to customers for treatment or processing into various types of other paper products.  CALENDERING, REELING AND FINISHING SECTIONS We l e a d Finishing (Surface Sizing/Coatings) To improve the surface paper properties. It fills the cavities and covers the base paper surface increasing smoothness. Uncoated Paper 3 Layer Coated Paper  CALENDERING, REELING AND FINISHING SECTIONS We l e a d It will decrease ink absorption. Gloss increases, with the objective often being the increase of print gloss. Opacity increases, and hopefully also brightness. Mechanical strength of paper decreases when coated and uncoated papers are compared at the same basis weight.  CALENDERING, REELING AND FINISHING SECTIONS We l e a d Surface Sizing Size press puts surface coatings of a sizing agent on paper. Usually starch. Decreases water and air permeability and increases paper strength.  CALENDERING, REELING AND FINISHING SECTIONS We l e a d To Dryer Pigment Coatings Knife or Air Fine filler particles Paper mixed with binders put on surface of paper. Coatings Improves sheet surface for printing.  CALENDERING, REELING AND FINISHING SECTIONS We l e a d Conventionally, paper finishing is done after paper machine section (off machine). Finishing  CALENDERING, REELING AND FINISHING SECTIONS We l e a d In modern paper machine, it is done on machine.  CALENDERING, REELING AND FINISHING SECTIONS We l e a d Main paper coating principles Blade Coating Size Press Curtain Coating Spray Coating Film Coating CALENDERING, REELING AND FINISHING SECTIONS We l e a d Thank you