This page contains list of various types of pulp based on their pulping
process, raw material used or type of bleaching etc. All plant
material are basically consist of Cellulose Fiber, Hemicellulose and Lignin,
which bind cellulose fibers together. Pulping is nothing but breaking/removing
lignin to separate fibers. Lignin is physically and chemically weaker than
cellulose fiber. Hence when a physical force or chemical is applied to plant
(wood, grass, straw, rag etc.), lignin breaks down faster than cellulose. Heat
also weaken lignin faster than cellulose fiber.
So pulping processes varies from complete mechanical to complete chemical and
any combination in between.
Pulp made from abaca (manila hemp). Abaca pulp exhibits very high tensile and tear strengths, high viscosity and high porosity. These properties make it the preferred raw material for the production of dielectric, bank note, vacuum bag, tea bag and the full range of filtration papers, as well as various wet laid
non-wovens. It is also used in the production of various art, decorative and vellum papers.
Acetate Pulp
A highly purified (high alpha cellulose) pulp made especially to be
dissolved in acetic acid, acetic anhydride and sulfuric acid to make acetate
rayon and acetate fiber. For more info check at
http://www.azom.com/details.asp?ArticleID=1461
Acid Sulfite Dissolving Pulp
Dissolving grade pulp made using sulfite pulping process.
Agricultural Residue Pulp
Pulp made from agricultural residue such as straw, bagasse etc.
Alkaline Peroxide Mechanical Pulping (APMP)
Pulping sequence: Soaking of wood chips in alkaline solution, washing,
peroxide treatment and Refining.
Alkaline Pulping
Pulping by alkaline solutions of sodium hydroxide, with or without sodium
sulfide. Without sodium sulfide it is called soda process and with sodium
sulfide it is known as Kraft or sulfate process.
Alpha Pulp
A specially processed, high alpha cellulose content, chemical pulp. It is
also called dissolving pulp.
Aspen Hardwood Kraft Pulp
Aspen wood has a relatively low lignin content compared to other pulped
hardwoods which makes the pulp easier to bleach. Bleached ECF pulps are
available both at a standard brightness level(90%ISO) and sometimes higher
brightness levels can be obtained(91-92%ISO). Like birch kraft, Aspen kraft
pulps refine quickly producing a dense, smooth paper, but with less strength
compared to birch pulp.
Aspen kraft pulp can be used in a variety of printing grades and is
specifically useful where a higher brightness is required. Its high
smoothness characteristics are particularly suited for coated papers to be
gravure printed.
Typical properties of Aspen hardwood kraft pulp fiber.
Pulp made from bagasse. (Bagasse is sugarcane residue left after
extracting the juice)
Bamboo Pulp
Pulp made from bamboo, a grass native to Asia.
Birch Hardwood Kraft Pulp
Birch hardwood kraft pulps are thin walled and the pulped wood has a
relatively high hemicellulose content. These pulps refine quickly, producing
a pulp which tends to be lower in opacity and bulk compared to eucalyptus
hardwood kraft pulps, but higher in burst strength and tensile.
Occasional poor sheeting of birch pulps at the pulp mill can result in the
formation of hard fiber bundles. If such fiber bundles are present in the
paper furnish, they can cause transparent spots (sometimes called “windows”,
or “shiners” or “fisheyes”) when the paper is calendered. Such fiber bundles
can also cause uneven dyeing in colored papers.
Birch kraft pulps are often used interchangeably with other hardwood kraft
pulps such as eucalyptus krafts in mixed softwood/hardwood furnishes.
Typically birch pulps have been used in paper grades where extra
tensile/burst strength and a good formation is required. Birch pulps are
ideally suited for lightweight coated and uncoated “woodfree” printing
papers and for coated silicone release papers, where the birch fibre
provides a smooth surface with good hold out properties.
Typical properties of Birch hardwood kraft pulp fiber.
High yield Bleached CTMP. Non lignin destructive bleaching such as ozone
or per oxide bleaching is used to retain yield. Used in newsprint and other
printing paper. See CTMP.
Softwood BCTMP is produced at a similar yield (>85%) to Hardwood
BCTMP and the Softwood pulp is produced as a TCF pulp, since only peroxide
is used for bleaching to levels between 60-80% ISO Brightness. The key
characteristics of Softwood BCTMP are bulk, absorbency, internal bond and
stiffness. The pulp is usually co-refined with hardwood and softwood kraft
pulp, in varying percentages or sometimes mixed with Deinked (DIP) fiber.
Softwood BCTMP has been used in a variety of applications. The
pulp has been used to prepare fluff pulp (for diapers) up to 80% of the
furnish. It has been mixed with DIP furnishes in newsprint and tissue/towel
grades to improve bulk and absorbency of the latter. One of the principal
applications for Softwood BCTMP is mixed with Hardwood BCTMP in the
production of some multiply board grades as a chemical pulp substitute to
improve bulk and stiffness. It has also found limited uses in coated and
uncoated printing/writing grades and packaging grades but generally its use,
in both of these cases, has been superseded by Hardwood BCTMP.
Hardwoods BCTMP is higher (80-90%), compared to those
woods treated by the kraft or Sulfite process (circa 50%), because in the
former process most of the wood lignin is retained. Only TCF Hardwood BCTMP
is produced, since hydrogen peroxide is the sole bleaching agent. Pulps with
an ISO brightness of 88% can be produced, but some brightness reversion will
occur due to the presence of lignin. The Lignin levels are lower in
hardwoods than in softwoods so the degree of brightness reversion is less.
In the pulp mill, by varying the cooking/mechanical pulping conditions,
pulps with varying degrees of "Canadian Freeness" can be produced to enhance
bulk or pulp strength. In the paper mill hardwood BCTMP pulps are generally
used unrefined or with deflaker treatment only. Mill refining can increase
the pulp's brightness loss.
Lower brightness grades (circa 70% ISO) have been used as a part
hardwood kraft replacement in tissues and towel, especially for higher bulk
in towel. Brighter grades (circa 85% ISO) have been used as a part
replacement in a variety of paper grades, including printings and writings
(for higher opacity), in multiply boards (for higher bulk, stiffness and
improved creasing properties), coated grades (for bulk). In specialties
grades, such as decorative laminates, Aspen hardwood BCTMP pulps with the
highest brightness have been used to enhance bulk and surface smoothness. A
grade of Eucalyptus BCTMP has been used as a part hardwood kraft substitute,
to maximize bulk and opacity in grades such as book papers.
A mechanical pulp made from wood, which is steamed before grinding.
The color-bearing, non-cellulosic components of the wood remain with the
pulp. The pulp is generally used for wrapping and bag paper.
Mechanical pulp produced by treating wood chips with chemicals (usually
sodium sulfite) before mechanical defibration. Sequence of action:
Soaking wood chips in chemical - Refiner.
Same as CMP. Separate name to distinguish from CGP which is also chemi-Mechanical
Pulp. Sequence of action:
Soaking wood chips in chemical - Refiner.
Chemo-Thermo-Mechanical Pulp (CTMP)
Mechanical pulp produced by treating wood chips with chemicals (usually
sodium sulfite) and steam before mechanical defibration. Sequence of action:
Soaking wood chips in chemical- Steaming-Refiner.
Agricultural residue or straw pulp produced by soaking these material with
dilute caustic solution at atmospheric temperature and pressure. The cost in
plant and machinery is minimal. Pulp yield is high. Pulp is normally used
for making thick board.
Combined Deinking
Deinking process combining flotation and washing.
Continuous Pulping
Production of pulp in continuous digester as compared to a batch digester.
Cooking
Reacting fibrous raw material with chemical under pressure and temperature
to soften and or remove lignin to separate fibers.
Cotton Pulp
Pulp made from cotton linter/cotton waste. Cotton linter pulps are
available as ECF and TCF grades bleached to 88%+ ISO Brightness. Unrefined
these pulps have a very high bulk, air permeance and opacity. On refining
there is some development of Schopper Reigler wetness, but little
development of strength properties. The opacity increases as refining
proceeds due to the sheet closing up as the fibre shortens. The largest
change on refining is a loss of air permeance.
Cotton fiber has a very high alpha cellulose content, which makes this
pulp ideal for producing long life archival papers.
First cut cotton linters find uses in Artists Drawing papers, which must
have a resistance to fading, neutrality and stability. These are heavier
weight papers were the finish varies from a coarse surface for paint to a
smooth surface for graphic work. First cut linters also find uses in some
boards (eg. greetings cards) and Mill Run and First cut linters are used as
extenders to the much longer Staple Cotton fibers in currency papers.
Second cut linters are valued for their bulk and purity. In addition to uses
in the above grades, Second cut linters are used in Fine and Security to add
bulk and prestige value. For Fine papers requiring a good formation, care
should be taken when selecting the linter grade to ensure that it is clear
of "Fiber Knots". The latter, if present in large numbers in the pulp, can
give rise to a poor formation or a "Fish Eye" problem.
Bleaching technique in which cooked and oxygen-delignified chemical pulp
is treated with enzymes prior to final bleaching. Allows pulp to be bleached
without chlorine chemicals.
Esparto Pulp
Pulp made from esparto grass, grown mainly
in Africa. Esparto fibers have thick walls and are short, normally less than 3 mm in length, with an average length of 1.5 mm. The fiber diameter varies from about 0.005 to 0.015 mm, with an average of about 0.012 mm, giving a length to diameter ratio of 125.
Esparto refines quite quickly yielding low strength properties, but
retains bulk, air permeance and excellent opacity. Its low fiber coarseness
provides the sheet with a good formation, smoothness and excellent opacity.
A particular property of this pulp is its ability to give the sheet a good
dimensional stability.
The formation, smoothness and optical characteristics of this pulp,
makes it suitable for all Fine paper grades. Its ability to create a
dimensionally stable sheet finds uses in wall paper base. The pulp also has
a low extract conductivity which finds application in some electrical
grades.
Generally these are high purity, high viscosity pulps that are swollen in sodium hydroxide initially, followed by reaction with organic epoxides or chlorides like ethylene oxide or methyl chloride to form an organic polymer called cellulose ethers (methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, etc.). Cellulose ethers are used for thickening of fluids such as toothpaste, ketchup, shampoos, diet drinks and hundreds of other applications.
Eucalyptus Pulp
Pulp made from eucalyptus. Eucalyptus is a fast growing hardwood, grown mainly
in Australia, India etc. Eucalyptus tree takes 5 -8 years for full growth.
Compared to most other hardwoods, eucalyptus pulps tend to give a higher
bulk, tear strength, opacity and formation (due to finer fibers). In all
grades of uncoated and coated printing and writings, eucalyptus is
used for opacity, formation and smoothness, up to 100% of the furnish in
some cases. It can also be used in towel and tissue grades without refining
to achieve bulk and air permeance.
Pulp made from flax. Flax fiber is soft, lustrous and flexible. It is stronger than cotton
fiber but less elastic. Flax pulp is used for the high quality paper such as
currency notes and cigarette tissue.
Flax Plant
Flotation Deinking
Using flotation method for removing ink from paper during the de-inking
process.
Fluff Pulp
A chemical, mechanical or combination of chemical/mechanical pulp, usually
bleached, used as an absorbent medium in disposable diapers, bed pads and
hygienic personal products. Also known as "fluffing" or "comminution"
pulp
A mechanically prepared (by grinding wood logs against a rough surfaced
roll rotating at very high speed) coarse wood pulp used in newsprint and
other low cost book grades where it contributes bulk, opacity, and
compressibility. Groundwood pulp is economical since all the wood is used;
however, it contains impurities that can cause discoloration and weakening
of the paper.
A pulp intentionally or un-intentionally cooked with less chemical or
shorter time or at lower temperature. The net result is less cooked but
higher yield pulp. Difficult to bleach.
Hard Wood (Beech) Sulfite Pulp
Pulps produced predominately from Beech Wood are characterized by being
very easily refined, but develop very little strength. Beech sulfite pulps
do however promote smoothness and opacity. This hardwood has a very low
lignin content and together with the aggressive nature of the pulping
process, pulps of this type are easy to bleach and can produce a high
brightness (>93% ISO) and cleanliness.
Beech sulfite pulps have been used in a variety of Fine papers and Cover
papers, usually of the higher grammage range to offset the low pulp
strength. Where high brightness and cleanliness pulps have been produced,
such grades find applications in photographic, drawing and ink jet papers.
Typical properties of Hard wood (beech) sulfite pulp fiber.
A pulp made from hemp. Hemp fibers are long and thin. Frequently used in the manufacture of cigarette papers but, due to their high opacity and tensile
strength, may be suitable for a wide variety of papers which require these specific characteristics.
Hemp Fiber
Hot Groundwood Pulp or Thermo Groundwood
Mechanical pulp produced by grinding logs that have been pre-treated with
steam.
Hydrogen Peroxide Bleaching
A method in which pulp is bleached in an alkaline environment with
hydrogen peroxide (H2O2), sometimes using oxygen reinforcement. The method
considerably reduces the need for chlorine-containing chemicals in the final
bleaching of chemical pulps.
A pulp made from jute. Jute is a long, soft, shiny fiber that can be spun into coarse, strong threads. It is one of the cheapest natural fibers, and is second only to cotton in amount produced and variety of uses. Jute fibers are composed primarily of the plant materials cellulose, lignin, and pectin. Both the fiber and the plant from which it comes are commonly called jute.
The fibers are off-white to brown and 3 to 15 feet (0.9 to 4.5 meters) long. Due to its
porosity, this pulp can be used for applications like tea bag and high porosity cigarette papers.
A complex constituent of the wood that cement the cellulose fibers
together. Lignin is brown in color. Lignin is largely responsible for the
strength and rigidity of plants, but its presence in paper is believed to
contribute to chemical degradation. To a large extent, lignin can be removed
during manufacturing.
Pulp which is made to be used elsewhere for the production of paper.
Usually dried to reduce freight costs but may be "wet lap" ( 50%
water).
Mechanical Pulp
Pulp produced by mechanically grinding logs or wood chips. It is used
mainly for newsprint and as an ingredient of base stock for lower grade
printing papers.
Micro Crystalline Cellulose Pulp
Like Ethers Pulps, these pulps are used in thickening and pharmaceutical applications, particularly in construction of tablets and other non-capsular pills.
High purity pulps that are reacted with nitric acid to form a class of chemical derivatives called cellulose nitrates. Cellulose nitrates are used in applications ranging from solvents to smokeless (gunpowder) propellants.
The pulps produced from "Whole Tree Waste" are generally easy to refine,
have good opacity and smoothness, but are not particularly strong. The
refinability and properties of the pulps produced in a controlled blend, are
generally dependent on the dominant species in that blend. For example pulps
containing a higher proportion of maple fibre, tend to refine quickly giving
a high opacity, smoothness, good formation and watermarking quality, but low
strength.
Pulps from "Whole Tree Waste" have been used as extenders to birch or
eucalyptus pulps up to a limited 20% of the furnish. These pulps, and the
blended types containing a higher proportion of birch or aspen, have been
used in some lightweight papers such as bible paper or directory stock.
Where maple fiber is the dominant species (sometimes almost 100% maple),
such pulps have been used in coated papers, plastic base surface papers,
photographic papers and deep dyed bulky papers.
Typical properties of Southern Mixed Hard Wood Kraft pulp fiber.
A chemical wood pulping process in which neutral sodium sulfite and sodium
carbonate solution is used for cooking. The cooking is carried in slightly
alkaline conditions. It is semi-chemical pulping process.
Non Wood Pulp
Chemical or semi-chemical pulp made from Non-wood plant material such
as straw, grasses, rag etc.
The properties of Radiata Pine pulps is considered to be part way between
the characteristics of Northern Softwood and Southern Pine pulp, but
generally closer to Northern softwoods.
Typical properties of Radiata Pine Soft wood pulp fiber.
The term “rag” is often used interchangeably with “cotton fiber
content” and harkens to a period of time when paper was actually made
using cotton rags which were cleaned and then broken down into fibers which
were then used to manufacture paper. In a sense it could be stated that the
fine paper business has been engaged in recycling materials for production
since its very beginning. Today paper is no longer made from rags and the
term “rag” is falling in disfavor by the industry in lieu of the phrase
“cotton fiber content”.
Rag Pulp
Papermaking pulp made from textile waste, cotton, hemp or flax..
The pulpwood is largely Scots pine containing 20-25% summerwood
(latewood), depending on the north to south wood location. Bleached pulps
from this area have a good burst and tear strength, but are the least bulky
of the softwood kraft pulps.
These pulps can be used interchangeably in most printing and writing grades.
Pulps produced from wood grown mainly in the north of Scaninavia tend to
have a higher, thinner walled, springwood content. Such pulps are useful for
lighter wight papers. Pulps produced from wood grown mainly in the south of
the region, tend to be more absorbent and bulky (due to a higher, thicker
walled, summerwood content) and these pulps find uses in grades such as
coffee filters.
Typical properties of Scandinavian Soft Wood Kraft pulp fiber.
An alkaline pulping process that uses a simple, sulphur- free sodium
hydroxide as cooking liquor.
Sisal Pulp
The main characteristic of sisal pulp is its high porosity, making it an excellent raw material for papers such as dielectric, plug wrap, laminating substrate, vacuum bag, tea bag, filtration papers and wet laid
non-wovens
Soft Cooked Pulp
A pulp intentionally or un-intentionally cooked with more chemical or
longer time or at higher temperature. The net result is over cooked but
lower yield pulp. Easy to bleach.
Soft Wood Sulfite Pulp
Softwood Sulfite pulps requires less refining to reach a given freeness (°
SR). They are characterized by having a high initial wet strength at low
refining values, but have a low bulk, tear, opacity and absorbency at the
same tensile level compared with Softwood kraft pulps. Softwood Sulfite
pulps can provide a good surface and formation. Pulps produced in Western
Canada tend to be stronger than those produced in Scandinavia/Europe.
Softwood Sulfite pulps are used in printing and writing papers, both
uncoated and coated and in high grade card stock. In colored papers the use
of Softwood sulfite fibers at a high level of the furnish promotes even
dyeing. These pulps have a particular application in tissue grades, since
the pulp can develop adequate tensile strength very quickly, has a low
adhesion to MG dryers and can provide softness to the tissue grade. When
heavily refined, sulfite pulps produce a very dense paper and this property
finds uses in such products as greaseproof and tracing papers. The easy
bleaching nature of sulfite pulps can enable the pulp supplier, in a few
cases, to produce a grade with a very high brightness (circa 93/94% ISO) for
use in photographic grades or papers suitable for Artists use.
Typical properties of Soft wood sulfite pulp fiber.
Southern mixed hardwoods refine at a similar rate to bleached eucalyptus
globulus pulps. These pulps tend to retain a higher tear strength, bulk,
stiffness and porosity, but are generally weak in tensile and have a lower
opacity. Their high coarseness value detracts from the paper's formation and
if the pulp should contain a high percentage of white oak fiber, this can
give rise to vessel picking problems.
Southern mixed hardwoods are generally used at up to 50% of a
papermaking furnish with single species softwoods. Southern mixed hardwoods
has been used in high volume paper qualities, including printings and
writings, packaging grades and uncoated art papers (for stiffness and bulk).
The pulp also finds use in towel grades were it contributes to bulk and
absorbency.
Typical properties of Southern Mixed Hard Wood Kraft pulp fiber.
Southern Pine pulps have thick fiber walls, due to a high summer wood
content. These pulps are characterized by having a high tear strength, bulk
and absorbency, but require much more refining to develop a useful tensile
strength, compared to Scandinavian softwood krafts. The opacity of Southern
Pine pulps is less than other softwoods and their high coarseness can lead
to formation difficulties.
Pulps produced from single species in the more northern part of the
Southern Pine region or those produced from juvenile wood, can be part
interchanged with Northern softwoods in a range of both coated and uncoated,
Fine Printing and Writing grades.
The high absorbency of Southern Pine pulps find applications in tissue,
towel and filter (EG Coffee Filters) grades. These pulps are also used in
packaging grades and circuit boards. Their resistance to refining and high
tear, due to the long fiber and thick fiber wall, finds some application in
Tracing Paper.
Typical properties of Southern Pine Soft Wood Kraft pulp fiber.
Totally chlorine free applies to virgin fiber papers that are unbleached
or processed with a sequence that includes no chlorine or chlorine
derivatives. (Also see ECF)
Semi-chemical or Chemical pulp before washing. A stage in pulping process
where pulp is cooked and transfer to storage tank but spent and residual
cooking liquor is not separated from fibers.
Fiber that has never been used before in the manufacture of paper or other
products.
Viscose Pulp or Rayon Grade Pulp
Viscose pulps are high purity pulps that are mixed with sodium hydroxide to form a material called alkali cellulose and then reacted in a mixture of sodium hydroxide and carbon disulfide. This resulting substance, called cellulose xanthate is further reacted with a mineral acid to regenerate pure cellulose. The regenerated cellulose can be a fiber, like rayon, or other forms, like the film cellophane.
