Amphoteric Starch

Posted on March 26, 2013 by admin

Amphoteric starch is a modified starch that contains positively and negatively charged substituent groups. It is used as wet-end additives, surface sizing agent and coating agent in the paper mill industries.

In the paper making process several materials are anionic such as wood fibers, titanium dioxide, clay, expanders, pigment dispersant, black liquor, bleach chemicals etc, whereas some materials are cationic such as alum, poly aluminium chloride (PAC), cationic resin, some retention aids etc. So it is very significant to maintain a clean and ionically balance environment to attain efficient result, which is done by amphoteric starch.

Amphoteric starch at the same time contains cationic group and anionic group. Usually cationic groups can be amino, ammonium, sulphonium or phosphonium group whereas anionic groups may be phosphate, phosphonate, sulfate, sulfonate or carboxyl groups. Among these cationic groups quaternary ammonium group is more preferred by the papermakers. On the other hand among the anionic groups phosphate group is best choice. The position of the anionic groups and cationic groups may be at same position or different position in the starch. The effective raw material for producing amphoteric starch is waxy maize due to highly content amylopectin.

Function of amphoteric starch
The benefits of amphoteric starch are following; especially when alum and PAC are used in paper making process.

  • enhances dry strength properties
  • improve drainage which lead to better sheet formation.
  • retention of fines and fillers
  • Better print quality

Specification of amphoteric starch:

  1. Physical appearance: odorless white to off white dry powder
  2. Moisture Content % w/w (at 105°C-110°C): 14max
  3. pH value: 10% aqueous solution, 5-8
  4. Viscosity 2% Solution at 50℃: 60-80 CPS
  5. Whiteness: 85%min.
  6. Fineness (100mesh): 99% min
  7. Nitrogen content: up to 0.3%
  8. Ash (dry solid basis): less than 3.0%
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Cationic starch

Posted on March 10, 2013 by admin

Cationic starch is a modified starch. The cationic starches mainly used as wet-end starch. Although native starch can be used as wet-end starch, but cationic starches are more preferable. As the cationic starches are positively charged, they are easily attracted by the negatively charged cellulose fiber and fillers. As a result fiber-to-fiber and fiber-to-filler bond are increased. Hence improved the retention of fines and filler and also increased paper sheet strength.

Commercially Available cationic starches are two types; quaternary ammonium type cationic starch and tertiary amino type cationic starch. Quaternary ammonium type starch is cationic in all pH range, whereas tertiary amino type starch is cationic only in the acidic range. It is the main problem of the application of tertiary amino type of cationic starch. Hence the applications of tertiary amino type of cationic starch are limited.
The quaternary ammonium containing group attached at the C6 position of the starch. Since the –OH group of this position is more active.

Benefit of Cationic Starch in Paper mill Industry:
Cationic starch enhances paper strength, water drainage, retention, improve paper quality; reduced dusting, linting and size addition; greater control of paper making process hence less paper web breaks and improve paper machine runnability as well as productivity. Cationic starch also allowed using more filler and more recycled fibers so reduce furnishes cost. As a surface size agent, cationic starch improves stiffness, opacity, printing quality and brightness.

Specification Of cationic starch

  1. Physical state: odorless powder
  2. Moisture Content % w/w (at 105°C-110°C): 14 max
  3. pH value: 10% solution, 5-8
  4. Viscosity 5% at 50℃: high (greater than 2200 cps)
  5. Whiteness: 88% min.
  6. Fineness (100 mesh): 99% min
  7. Nitrogen content: up to 0.3%
Posted in Dry strength additives | Tagged , , | 40 Comments

Maize starch

Posted on February 24, 2013 by admin

Maize starch is also known as corn starch. Maize starch is most popular among the native starch. It contains low ash and low protein. In paper mill industries maize starch or corn starch used as wet end additives, tub sizing or surface sizing agent, coating agent and binder. Maize Starch is changed into a smooth paste during cooking within a short time.

Function of maize starch
In paper mill industries the primary function of corn starch or maize starch is increase dry strength and surface improvement of paper. As a wet end additives maize starch increase paper strength, increase paper stiffness and rattle of the paper. As a surface sizing agent it is improve appearance and erasibility, restrains ink penetration, form firm surface (which is suitable for better writing and printing) and also prepare the paper sheet for subsequent coating. As a Coating agent maize starch enhances printability and gives a glossy and a fine surface of the paper.
Since the pH value of maize starch paste is sustained in neutral range or below the neutral range so it is unnecessary to add any antifoaming agent into the maize starch systems because foaming is normally related with high pH. Moreover maize starch does not rupture during cooking whereas tapioca starches split up.

Specification of Maize starch

  1. Appearance: white or light yellow shadow
  2. Fineness (100 mesh): 99.5% min
  3. Moisture content % w/w (at 105°C-110°C): 14max
  4. pH value: 4.5-6.5
  5. Whiteness: 90.10 min
  6. Protein: 0.50% max.
  7. Ash content % w/w (at 550°C): 0.3 max.
  8. Cold water solubility: Nil
  9. Fat: max. 0.20%
  10. Adhesivity: good
  11. Shelf Life: 1-2years
  12. SO2: max 30mg/kg
Posted in Dry strength additives | Tagged , , , | 3 Comments

Tapioca starch

Posted on February 22, 2013 by admin

Tapioca starch is a native starch. The starches which are produce in Tropical countries-such as Brazil, Nigeria, Indonesia, West Africa and Thailand are called tapioca starches. The most common tapioca starch is Cassava starch. Other tapioca starches are arrowroot, sweet potato, taro, sago, and yam.
The properties of Cassava starch are highly desirable for paper-making. The benefits of cassava starch are following:-

  • Low price
  • Low dirt
  • Whiteness is high
  • Processes better water holding properties
  • High viscosity
  • Form clear paste and strong film

Application of cassava starch:
Cassava starch is widely used at wet end additives. Moreover it is also used as a tub size, surface size, beater size and surface coating in the paper mill industries.

Specifications of cassava starch

  1. Appearance: white
  2. Moisture content at 105°C-110°C %w/w: 14max.
  3. Adhesivity: Good
  4. pH value: 10% solution, 5-8
  5. Viscosity 5% at 50℃: high (greater than 2200cps)
  6. Nitrogen Content: 0.3% Min
  7. Solubility: rapidly and completely after batch or continuous cooking
  8. Toxicity: No health hazard during normal handling
  9. Shelf Life: more than 12 months (under normal storage and undamaged state).
Posted in Dry strength additives | Tagged , | 6 Comments

Starch

Posted on February 4, 2013 by admin

What is Starch
Starch is a natural carbohydrate polymer. The molecular formulae of starch is (C6H10O5)n. Mainly starch is used in paper mill to improve dry strength and surface. Its molecular weight is very high. Native starch has a very high viscosity. On the other hand modified starch has lower viscosity. The main sources of starches are regular corn, tapioca, waxy maize, wheat and potato. After cellulose fiber and mineral filler, starch is the third most widespread raw material in paper mill industries.

Molecular weight of starch is a factor for application of starch in paper mill industries. The maximum molecular weight (non-degraded) of starch is suitable for wet-end application. Because the non-degraded starches have huge dimensions, so the binding power is increased. On the other hand, reduced molecular weight (degraded) starches is suitable for surface application. This is the reason that degraded starches have lower viscosity.

Generally the starch is used in paper mill in three different stages for different function. The stages are wet end section for internal sizing, size press for surface sizing, and size press or off-machine application for coating. The most common wet-end starches are cationic starches or amphoteric starches or native starches while the surface starches are oxidized or hydroxyethylated.

Types of starches
Mainly starch is classified into two types. Native starch and modified starch.

Native starch: The most common native starches are corn starch, tapioca starch, waxy maize starch, potato starch, wheat starch and rice starch.

Modified starch: Cationic starch, amphoteric starch, oxidized starch etc.

Function of starches:

  • Starch enhances the stiffness and bonding of paper sheet.
  • Improve formation
  • improve internal bond,
  • Improve surface strength and wax-pick
  • Increase tensile strength
  • Improve fiber fines, filler and chemical retention.
  • Improve drainage.
  • increase dry strength properties
  • better writing and printing surface
  • reduce linting and dusting
  • Reduce cost, because it is allowed to use more filler and more recycled fibers.
  • Increase runnability and productivity. As breaks are lower.
  • Energy consumption lower due to high binding power.
Posted in Dry strength additives | Tagged | 33 Comments

Sizing Agents

Posted on January 30, 2013 by admin

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.

Posted in Sizing Agents | Tagged | 28 Comments

Talc

Posted on January 17, 2013 by admin

What is Talc
Talc is well-known as talcum powder. It is a natural hydrated magnesium silicate – H2Mg3(SiO3)4. Talc is a soft, low abrasive, flat-like particle, chemically inert and organophilic material. These are reason why many paper mill use this filler. commercially talcum powder is a wide range of mineral mixtures. Hence pure talc is difficult to find. Following parameters are important for choice of talcum powder brightness, loss on ignation, fineness, moisture, pH value etc.

Advantages of Talc

  • The uses of talc as a paper filler is suitable for rotogravure printing process. Two things are very important for rotogravure paper; paper smoothness and good spool formation. As talc is a flat-like particle, it helps improve the paper smoothness. The low coefficient of friction of talc helps to produce a large spool with constant tension.
  • Talc is an organophilic, so absorbs impurities from the process, such as pitch, resin particles. Hence talc is used as a cleaner of the wet-end system of the paper machine. Talc also prevents agglomeration. Therefore improve paper machine runnability.
  • Low cost hence it is economical.
  • Good retention
  • Less wire abrasion hence extends life time of the wire cloth in paper machine compare with the GCC and PCC.
  • Improve dewatering.
  • Lower effect on the paper strength compare with other fillers.
  • As talc is organophilic it is helps to reduce dye consumption and two-sidedness in colored paper.

Disadvantages of Talc

  • Higher dusting tendency during printing and in dryer section during paper production.
  • Talc is a hydrophobic, hence it is difficult to preparation water-based dispersion.
  • As talc is an organophilic, hence it is not suitable for offset printing. Because in offset printing process image transfer by using a hydrophilic/hydrophobic action.
Posted in paper filler | Tagged , , | 7 Comments

Calcium Carbonate

Posted on January 1, 2013 by admin

Calcium carbonate is used in paper mill as a filler material in the alkaline papermaking process. Now a days Calcium carbonate dominant over other papermaking filler materials; though at the first stage of papermaking kaolin was 1st choice. The main reason behind the preference of calcium carbonate is the demand for brighter and bulkier paper.

There are significant benefits to the use of calcium carbonate in the al¬kaline papermaking process. But Calcium Carbonate filler is unsuitable in acid papermaking and wood-containing paper.

Usually Calcium carbonate occurs in three natural forms such as limestone, chalk and marble. Naturally it is forms between the reactions of calcium salt and carbon dioxide. This process is still going on in the Oceans.
There are two types of calcium carbonate used in paper mill – ground calcium carbonate (GCC) and precipitated calcium carbonate (PCC).

Ground calcium carbonate (GCC)
Ground calcium carbonate is manufactured by grinding limestone or marble because of their high brightness and purity. Generally the particle shape of ground calcium carbonate is rhombohedral. This filler material is used in alkaline wood free papermaking process. The brightness of GCC is 86-95%.

Advantages of Ground calcium carbonate (GCC)
GCC is cheaper and it has high brightness.
GCC creates a porous surface on the paper sheet due to its rhombohedral particle shape.
GCC is hydrophobic as a result it is liberate water more rapidly.
Improve printability
Lower binder demand

Disadvantages of Ground calcium carbonate (GCC)
The rough particle shape of GCC creates a problem; it is more abrasive and shortens the life of paper machine clothes.

Precipitated calcium carbonate (PCC)
Precipitated calcium carbonate is the form of CaCO3 which is manufactured by chemical reactions and the process is known as carbonation process. PCC improve the drawback of GCC, it is provide better gloss and opacity properties for the paper. Because of the structure of PCC is different from the structure of GCC. The crystal structure of PCC are needle-shaped, rhombohedral(cubic), scalenohedral (triangular) and prismatic. The brightness of PCC is 90-97%.

Advantages Precipitated calcium carbonate (PCC)
Increase machine speed and productivity.
Improve water drainage
Improve machine runnability
Improve print quality
Cost-effective papermaking process
Increased opacity and brightness
PCC is less abrasive than GCC
Reduce fiber consumption compared with GCC or talc
More retention compare than other paper fillers

Disadvantages Precipitated calcium carbonate (PCC)
PCC containing paper sheets are poorer formation than GCC containing paper sheets.

Posted in paper filler | Tagged | 15 Comments

Slimicides

Posted on December 24, 2012 by admin

Slimicide or antislime agent is a substance which is used as antimicrobial agents to kill slime-producing microorganisms in the papermaking process such as bacteria, slime, fungi and algae. It helps reducing production costs due to occasional breaks and shuts which save energy and time. Since paper can be manufactured under acidic or alkaline conditions, a slimicide should ideally be able to function over a wide pH range and compatible with common papermaking additives. Some slimicides are effective only for alkaline system and some are equally effective for Acidic and Alkaline media.
Slimicides or antislime agent has anti action on slime. Slimicides can be liquid or powder. The chemical types of anti-slime agents are organic sulfur, bromium and quaternary ammonium compounds, as well as aldehydes.

Why slime is developing
In a paper mill industry water is used mostly in re-circulation process. Moreover different water-based chemicals and materials are added in this papermaking process to increase productivity and improve the quality of the finished paper. The environmental condition (temperature, pH etc) of this recirculating water is ideal for growth of many undesirable microorganisms such as bacteria, slime, fungi, algae, yeast and mold. Sometimes spots of aluminum hydroxide gel or other inorganic matter are mistakenly judged as slime spots.

Effects of slime on paper/paper machine
The growth of microorganisms in the papermaking process creates a number of process and paper quality problems. For example –

  • Slime lumps create holes, spots and breaks in paper web. Hence decreases paper machine runnability. To improve paper machine runnability need to be system cleaning. As a result increase downtime and energy loss.
  • Clogged piping
  • spray nozzle blockages
  • Reduction of drainage, thermal transfer efficiency and flow.
  • Sticking of valves and fittings causing operational troubles.
  • corrosion of equipment
  • Offensive odors
  • Quality deviation out of discoloration of finished paper sheet.
  • Above all reduce paper quality and increase cost of production.

Benefits of slimicides/anti slime agent

  • Check of bacteria, slime, fungi, algae, yeast and mold growth and fibre degradation.
  • Decrease paper web breaks and improve paper machine runnability.
  • Prevents clogged piping, blockages, corrosion of equipment.
  • Improves drainage, thermal transfer efficiency and flow.
  • Slimicides can be act as a biocide and strong oxidizer and remove unwanted smell.
  • Improve paper quality and increase productivity.

Application:
Slimicide ought to be added to a paper making process where mixing is uniform such as broke chest, beaters, drop chest, head box, and especially in wire pit. For a good result from a slimicide correct dosage is also very important. A continuous addition is necessary with very dilute solution in the chest.

Posted in Slimicides | Tagged | 4 Comments

Specification of antislime agent

Posted on December 22, 2012 by admin

Antislime agents or slimicides are used as a cost savings materials in paper mill. Antislime agents are available as powders and in liquid emulsion form. Every paper mill used Antislime agent depends on some criteria. Here I mention a specification of a paper mill.

Specification

  1. Appearance: Pale yellowish to green liquid.
  2. ingredient: Amphoteric poly-acrylamide derivatives
  3. pH (at 25°C): 11.0±1.0
  4. Specific gravity: 1.o8±0.05 g/cm3
  5. Miscibility in H2O: Fully miscible
  6. Shelf life: 5 month.

Guarantee: For any reason if the chemicals/packing found defective or not conforming to the specification governing the supple. The sellers held responsible for all loss and consequences. In case of quality expiry chemicals defective container the materials must be replaced the supplier.

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