INK
INK
USING RAVEN® BLACKS IN INK APPLICATIONS
INK
Using Raven ® Blacks In Ink Applications
Introduction
Columbian Chemicals Company’s Raven® carbon blacks can be used in a wide
variety of ink applications. In this brochure, we will summarize these applications,
document the proper use of carbon black in the various types of ink systems, and
help you choose the appropriate Columbian carbon blacks for use in specific ink
applications. This brochure is intended to help you take full advantage of Raven®
blacks in ink applications.
T a b l e o f C o n t e n t s
3 Selection of Raven® Carbon Blacks For Ink Applications
3 Raven® Carbon Blacks Typically used in Ink Applications (Chart)
4 Fundamental Properties of Carbon Black
4 Ultra® Process Raven® Carbon Blacks
4 Ink Applications
Newsinks
4 Letterpress Newsinks
5 Web Offset Newsinks
5 Aqueous Newsinks
5 Oil Inks
5 Heatset (Web Offset) Inks
5 Sheetfed Inks
5 Ink Bases
5 Liquid Inks
5 Gravure Inks
6 Flexographic Inks
6 Pigmented Ink Jet
6 Making the Selection Decision
7 Dispersing Raven® Carbon Blacks
7 Dispersion Techniques Recommended for Carbon Blacks Used
in Ink Applications (Chart)
8 Dispersion Measurement
8 Comprehensive Dispersion Rating Method
Dispersion Requirements — Carbon Black Loading
8 Dispersion Quality and Stability
9 Carbon Black/Vehicle Solids Ratio
9 Problems and Limitations of High Loading
9 Millbase Viscosity
9 Resin Solids
9 Vehicle Chemistry
t a b l e o f c o n t e n t s c o n t .
9 Premixing
9 The Premixing Process
9 Choosing a Premixer
10 Premixing, Etc.
10 Dispersion
10 Three-Roll Mill Dispersion
11 High Plasticity Dispersion
11 Example — High Plasticity Dispersions for Liquid Inks
11 Dough Type (Stiff Paste) Dispersion
11 Ball Mill Dispersion
12 Limits of the Ball Mill
12 Formulating For Ideal Ball Mill Viscosity
12 Daniel’s Flow Point Method
12 Sample Flow Point Curve (Graph)
12 Determining The Flow Point
13 Example — Newsink Preparation in Steel Ball Mills
13 Finding The End Point
13 Example — Carbon Black Wax Ink Preparation in Ball Mills
13 Preparation of the Wax Melt For Milling
15 Cutback or Reduction of Milled Pastes
15 Colloidal Shock
15 Dilution of Aqueous Systems
16 Guidelines for Diluting Aqueous Systems
16 Beaded Blacks
16 North Bend Raven® Carbon Blacks (List)
16 Example — Bead Use in Liquid Inks - Presoaking
18 Customer Assistance
The statements, opinions and/or recommendations contained herein are based on information, data,
reports or tests believed to be reliable. HOWEVER, COLUMBIAN MAKES NO WARRANTY OR GUARANTEE
OF ACCURACY OR COMPLETENESS IN CONNECTION THEREWITH, NOR, WITH RESPECT TO ANY
COLUMBIAN PRODUCTS INVOLVED, ANY WARRANTY OR MERCHANTABILITY OR FITNESS FOR A PARTICU-
LAR PURPOSE OR USE. Statements concerning the possible use of Columbian products are not intended as
recommendations to use such products in the infringement of any patent.
3 Using Raven® Carbon Blacks In Ink Applications
SELECTION OF RAVEN® CARBON BLACKS FOR INK APPLICATIONS
Columbian’s Raven® carbon blacks have set a benchmark of quality and performance that others strive for. When it comes to Ink
Applications, Columbian produces 20 different carbon black products that meet or exceed the expectations of their users. We are
proud of the Raven® reputation for outstanding products and service.
There is a Raven® carbon black for every ink application. But if, at any time, you find that there is an ink application problem that
requires special properties we have not addressed, or you have a new technology with special needs, the people in our extensive
laboratory and research facilities will be there to find a solution for your situation.
In this section, we will provide you with the background and information needed to select the appropriate Raven® carbon black for
your ink application need. The table below is offered as a guide to help you select carbon blacks for specific applications. It is intend-
ed to serve only as an indicator of the blacks typically used and/or designed for the ink types shown.
— Raven® Carbon Blacks Typically used in Ink Applications —
Carbon Paper
Ribbon Inks
Publication
Silk Screen
Packaging
Letterpress
U.V. Inks
Newsink
Sheetfed
Heatset
Gravure
Flexo
Offset
Grade
Raven 1255
Raven 1200
Raven 1170
Raven 1100 Ultra
Raven 1060 Ultra
Raven 1040
Raven 1035
Raven 1020
Raven 1000
Raven 890
Raven 860 Ultra
Raven 850
Raven 820
Raven 760 Ultra
Raven 460
Raven 450
Raven 420
Raven 410
Raven H20
Raven 825 OB
Raven 680 OB
Using Raven® Carbon Blacks In Ink Applications 4
The following will provide you with a general understanding of ULTRA® PROCESS RAVEN® CARBON BLACKS
how carbon black properties, dispersion equipment, and the
vehicle system interact so you can better select the Raven® car-
Ultra® technology is a commercial development of the Columbian
bon black for your application needs.
Chemicals Company directed at manufacturing carbon black with
extremely high purity. Carbon black grades produced using this
FUNDAMENTAL PROPERTIES innovative technology typically have ash and 325 mesh residue
OF CARBON BLACKS levels one-tenth that of grades manufactured with conventional
technology. The inclusion of Ultra® in a Raven® name indicates
Several fundamental carbon black properties that influence the a product for inks that can be relied on to demonstrate improve-
final ink properties include: ments in ease of dispersion, gloss, stability, and consistency.
• Fineness, or Particle Size Distribution
• Structure, or Aggregate Size/Shape Distribution
• Porosity, or Pore Size Distribution, and There is a Raven® carbon black to fill
• Surface Chemistry, or Surface Activity Distribution any ink application need
All of these properties are distributional. A given grade of carbon
black, for example, cannot be produced at a single particle size Columbian makes more than 20 different Raven® carbon blacks
but is made up of a range of particle sizes. In general, we refer for ink applications. Newsinks, oil inks, aqueous inks, liquid inks,
to the mean particle size, but the breadth and shape of the dis- paste inks, and flexographic inks are among the application cat-
tribution are also important factors in the performance of the ink. egories for which Raven® products are available.
Carbon properties influence performance. Various carbon
properties that can have an important influence on the way ink INK APPLICATIONS
applications perform include:
N E W S I N K S fall into three main classes: letterpress, web
Smaller Particle Size ( Higher Surface Area ) offset, and aqueous.
• Increases Blackness
• Increases Tint Letterpress Newsinks are printed on high-speed rotary presses.
• Increases UV Protection and Absorption The applied ink film is usually thick, requiring carbon black load-
• Increases Electrical Conductivity ings in the range of 10 to 15%. The ink does not dry but instead
• Increases Vehicle Demand and Viscosity is absorbed into the paper. The formulation is made up of three
• Lowers Dispersibility
major components with oil being the major component. Other
components of typical formulations are carbon black and a small
Higher Structure ( Increasing DBPA )
amount of wetting agent.
• Reduces Blackness and Tint
• Improves Dispersibility
Carbon black requirements for this type of ink include:
• Increases Vehicle Demand and Viscosity
• Ease of dispersion
• Increases Electrical Conductivity
• Blue undertone
• Minimum penetration into the substrate
Higher Porosity ( Larger differences between NSA and • Good rub resistance
STSA ) (Note: NSA and STSA measure total surface area and external • Long platelife
surface area respectively)
• Increases Vehicle Demand and Viscosity There are several Raven® carbon blacks that meet the require-
• Increases Electrical Conductivity
ments for this type of ink.
• Enables Reduced Loadings in Conductive Applications
Because of the ease of dispersion and blue tone requirements,
Higher Surface Activity ( Higher Volatile Content ) Raven® 825, a fine, high-structure black, is perfect for this appli-
• Improves Vehicle Wetting
cation. The large aggregates associated with high structure
• Reduces Viscosity of Liquid Systems
blacks like Raven® 825 tend not to penetrate the surface of the
• Lowers Electrical Conductivity
paper, thus maximizing jetness and print mileage.
Additional carbon black properties that may affect the perfor-
A lower structure black, like Raven® 680, is designed for appli-
mance of an ink include other constituents of the carbon black
cations where high rub resistance is desired.
such as sulfur, ash, residue, etc. and its Physical Form i.e. :
powder, beads or oil beads.
Both Raven® 825 and Raven® 680 are beaded with an oil
uniquely selected for its ability to act as a wetting agent for the
systems in which they are used.
5 Using Raven® Carbon Blacks In Ink Applications
Web Offset Newsinks must be fluid at high press speeds and Raven® 1000, Raven® 760, and Raven® 860 blacks have a fine
set on contact. Like letterpress newsinks, web offset inks “dry” particle size and lower structure and are standards for these inks.
by penetration into the paper on which they are printed. In this The low oil absorption of the black contributes to low viscosity,
process, hydrocarbon resins are sometimes added to reduce rub- long flow, and high gloss. The high tint strength provides print
off. The web process applies much thinner films to the paper mileage. The desired optical density is accomplished through rel-
and requires higher carbon loadings to achieve the necessary atively fine particle size combined with high carbon black con-
optical density. centrations.
Carbon black requirements for web offset newsinks include: Post-treated blacks such as Raven® 1255, Raven® 1035 and
• Ease of dispersion Raven® 1060 are recommended for inks requiring maximum
• High tint strength flow properties. The post-treatment enhances pigment wetting.
• High optical density
• Blue undertone
The widespread use of media milling for the preparation of oil
• Minimum penetration into the substrate
inks has increased due to advances in milling equipment, and
• Good rub resistance
• Low platewear the soft dry beads provided by Columbian are particularly well
suited for this dispersion technique. The powder version of these
Again, Raven® 825 is preferred for the standard inks. Raven® blacks is preferred where three-roll milling is used.
680 is the standard for situations where low rub-off and low vis-
cosity are desired. INK BASES
Ink bases may be defined as a concentrate of a pigment in a
Aqueous Newsinks are typically flexographic inks. The benefits vehicle system compatible with the final formulation in which it
of this ink type include: simplified presses, thinner paper, and will be used. Ink bases or paste inks can reach or exceed a car-
reduction of oil consumption. Raven® 820 is a carbon black that bon concentration of 50% or more. The high loadings provide
helps meet the unique challenges facing aqueous newsinks, high viscosity, which maximizes energy absorption during milling
including drying time, set-off on the second impression cylinder, and improves dispersion. Low structure and surface area con-
and halftone fill-in. tribute to the low viscosity needed to achieve high loadings in
these ink bases.
OIL INKS
Oil inks fall into two categories, heatset ( web offset ) and Raven® 760, Raven® 860, Raven® 1000, Raven® 1060, and
sheetfed. Raven 1255® blacks meet the carbon requirements for ink
bases, including:
Heatset ( Web Offset ) Inks must be capable of setting instan- • Low viscosity to maximize loading capability
taneously since they operate at very high press speeds on a web • One pass dispersibility
( roll ) fed press. This process requires a balance between fast- • High gloss
drying requirements and low viscosity to provide the desired • Blue undertone
transfer rates at high press speeds.
LIQUID INKS
Sheetfed Inks are formulated at directionally higher viscosities Liquid inks include Gravure and Flexographic types.
due to their lower printing speed requirements. The higher vis-
cosities enhance setting time, but the ultimate drying time tends Gravure Inks require low
to be slower than with a heatset ink. viscosity to accomplish Gravure Plate etched
the transfer to the paper Image Area serves
Oil inks, such as these, cure via a number of mechanisms: air oxi- of the ink from cells to hold ink
dation and penetration for the sheetfed types; and evaporation engraved into the plate’s
of a high boiling point solvent in heatset formulations. surface. The image area
of a gravure plate is
These inks are formulated for maximum color, strength, and below the surface of the
optical density. Carbon concentrations for these inks fall non-image area of the
between 15 and 22% to accommodate the very thin ink films plate. The excess ink is removed from the plate with a doctor
produced by these processes. blade, and the ink is transferred from the cells in the plate to the
paper by capillary action.
Carbon black requirements for these oil inks include:
• High levels of jetness
There are two types of gravure inks — publication gravure and
• Blue undertone
packaging gravure. Publication gravure inks are formulated to
• Low oil absorption
• High tint strength meet optical density and undertone requirements, and gloss
• Excellent flow would not be as important. However, packaging gravure inks
• Good dispersion properties that are printed on foil, Mylar, or similar non-absorbent sub-
Using Raven® Carbon Blacks In Ink Applications 6
strates will typically produce higher gloss. Abrasion resistance of F L E X O G R A P H I C I N K S differ from Gravure inks in
the finished print is a prerequisite for packaging inks and can be formulation but have similar viscosity requirements.
achieved by applying a clear overprint varnish.
The term “flexo” comes from the soft flexible plates used in the
One primary concern for gravure inks is meeting the fluid vis- process to transfer the ink to the paper. The image area of a
cosity needed for the printing process. Low structure blacks, flexo plate is raised above the non-image area.
such as Raven® 460 and Raven® 410, are excellent choices for
producing publication gravure inks. The low vehicle demand of Flexo plate cross section, raised areas
the low structure blacks contributes to the gloss that is deemed provide the Image
desirable for this application. The selection of coarse particle size
carbons provides blue undertone and ease of dispersion. The Blacks used in Flexo applications include Raven® 1200, Raven®
finer grades, such as Raven® 1000 and Raven® 1020, are rec- 1170, Raven® 1060, Raven® 1035, Raven® 1020, Raven®
ommended for packaging gravure. 1000, Raven® 890, Raven® 820, Raven® 760 Ultra, Raven
460, Raven® 450, and in limited cases Raven® H2O for its ease
Vehicles that are used in gravure inks consist of nitrocellulose, of dispersion in water based systems.
chlorinated rubber, vinyl, or other binders, which are solvated
with highly volatile solvents. The solvent is rapidly released when Much like the gravure inks, the preferred carbon black proper-
the ink is ideally formulated which results in tack-free prints ties for flexo inks include:
immediately when printed. • Low viscosity
• High tint strength
The desired carbon black properties for gravure inks are: • Blue undertone
• Low viscosity • Fast wetting
• High tint strength • Excellent dispersion
• Excellent gloss for packaging gravure • Dispersion stability
• Blue undertone
• Fast wetting Pigmented Ink Jet technology is a rapidly growing facet of the ink
• Excellent dispersion industry. This is due to the major growth in demand for personal
• Dispersion stability and commercial digital printing equipment and the very high cost
of the dyes associated with this application. Raven® 3500 pro-
vides the combination of particle size, optical density, and dis-
persibility that is needed for this application. Since jet inks are pri-
marily water-based, carbon blacks such as Raven® 3500 that are
subjected to surface oxidation are essential for this application.
MAKING THE SELECTION DECISION
Now that you have read all of this information, please refer to the chart at the beginning of this section. This chart provides an
easy and simple way to match your ink application to the Raven® carbon black perfect for your needs.
The following section describes recommended carbon black dispersing techniques and milling requirements. This information will
assist you in fully utilizing all the advantages of the full array of Raven® carbon blacks for your ink application needs.
7 Using Raven® Carbon Blacks In Ink Applications
Dispersing Raven® Carbon Blacks
This section describes the various methods and techniques used to properly disperse the Raven® carbon blacks for your ink appli-
cations. The previous section showed how to select the right Raven® carbon black for the needed application, while this section
details ways to optimize the use of Raven® carbon blacks.
The chart below provides a quick overview of the recommended dispersing techniques for Raven® carbon blacks used
in ink applications.
— Dispersion Techniques Recommended For Carbon Blacks Used In Ink Applications —
Dispersion Dispersion Premix Recommended Raven® Carbon
Equipment Classification Requirement Black Form
Powder preferred,
Media Mill Medium Shear Required Beads can be used with good premix
Three Roll Mill High Shear Required Powder
Two Roll Mill High Shear Desirable Beads
Ball Mill Medium Shear Not Needed Beads
Attritor Medium Shear Not Needed Beads
Rotor Stator Low Shear Not Needed Powder or Oil Beaded Blacks
High Speed Impeller Low Shear Used Primarily as a Premixer Powder
Using Raven® Carbon Blacks In Ink Applications 8
Raven® carbon blacks provide the “state of the art” blacks for channels are noted but are not included in the calculation of the
ink applications. But in order to take full advantage of the poten- % CDR.
tial of any carbon black, several steps must be taken, including:
• Incorporating the carbon black into the vehicle system The % CDR method is only a basic tool for describing the rela-
• Displacing the air entrained in the carbon black with the tive dispersion performance on an ink. Columbian uses gloss
vehicle (wetting out the pigment) measurements and light and electron microscopy combined with
• Reducing carbon black macroagglomerates to automated image analysis to complement the % CDR ratings
microagglomerates or aggregates through grinding and to evaluate dispersion.
Raven® carbon blacks will provide optimum performance in jet-
ness, undertone, tint, gloss, stability, and rheology when these
DISPERSION REQUIREMENTS —
steps are successfully taken.
CARBON BLACK LOADING
DISPERSION MEASUREMENT For efficient and economical ink production, the quantity of
black used in the dispersion process should be as high as possi-
ble, yet consistent with good mill performance and the type and
The ink industry uses a variety of tools, such as the Hegman and quality of product being produced.
NPIRI grind gages, to characterize the dispersion level achieved
in an ink. Different groups can interpret these tools in many Different inks require different levels of dispersion. In many
ways. cases, poor performance of a black ink can be directly attributed
to insufficient pigment dispersion. This exemplifies the impor-
Comprehensive Dispersion Rating Method tance of developing and maintaining good dispersion levels.
A Comprehensive Dispersion Rating method (% CDR) was devel- Excellent dispersion is necessary for inks with stringent require-
ments for appearance and lay properties. For instance, ultimate
oped at Columbian Chemicals to combine the information
carbon black dispersion is usually not necessary for convention-
gained from the Hegman and NPIRI gages. al newsinks. However, better control over ink properties such as
mileage, tone, viscosity, rub-off, etc., can be accomplished by
Grind gages rely on a simple principle. When a dispersion sam- attaining a good grind level ( 20% ) to manufacture a carbon black dispersion. While • Removal of the bulk of entrained air.
high carbon black loading is desirable, limitations on the • Initiation of the dispersion process.
amount that can be used must be considered. The following • Earlier effective usage of additives such as dispersing and
describes these limitations: wetting agents, extra driers, etc.
• Sufficient time for partial equilibrium to take place between
Millbase Viscosity vehicle components and the Raven® carbon black surface.
• More uniform initial viscosities which provide for optimum
There are many types of milling equipment on the market which shearing.
vary in their effectiveness to provide adequate dispersion levels • Faster and more complete dispersion on the mill.
with carbon black. The single most important factor in this vari- • Less “puffiness” of mill paste due to entrained air and reduced
ation is the viscosity of the millbase. Dispersion equipment, such degradation of vehicles oversensitive to oxidation and
as a three-roll mill, is designed to accommodate high millbase polymerization.
viscosity. Media and ball / pebble mills require lower viscosity or
elevated temperature to handle concentrates.
The Premixing Process
Resin Solids Premixing should begin with small quantities of the vehicle in the
premixer while adding just enough Raven® carbon black to cre-
The amount of resin solids present in the grind will influence the ate a fairly stiff but mobile paste. More vehicle is then added and
final stability of the millbase. Reduction of resin solids tends to thoroughly blended, followed by the addition of more Raven®
reduce stability due to less resin available to establish a steric carbon black. This cycle is repeated until the charge in the mixer
“barrier” between carbon black agglomerates. Over time, mill- is completed. Mixing time should continue as long as possible
bases will exhibit increased thixotropic characteristics ( false for a more thorough premix.
body ), along with progressive stiffening, as vehicle solids are
reduced. “Fill-in” of halftones will occur due to overload of pig-
ment when finished inks are produced under these conditions. Choosing a Premixer
Today’s ink makers use a variety of premixes, ranging from
Vehicle Chemistry
Cowles-type high speed mixers to the Baker-Perkins dough mixer
styles. Ink makers can select from two types of premixers. They
Compatibility between the vehicle and the carbon black can dra-
can choose to produce their end products in one step or use a
matically affect dispersion time and the final stability of the ink.
Using Raven® Carbon Blacks In Ink Applications 10
base dispersion method where the pigment concentration in the DISPERSION
dispersion phase is well above that of the finished ink. The indi-
vidual producer will make this decision based on his equipment
Now that we have discussed premixing requirements, we can
capabilities and needs.
address the dispersion process.
Base inks typically have very high viscosity, which is cut back with
Three-Roll Mill Dispersion
the appropriate vehicles to a proper consistency after processing.
In this type of premixing process, a considerable amount of car-
To achieve the best dispersion of carbon black with open type
bon black dispersion may be accomplished. The extremely high
mills such as three-roll mills, several conditions are required. The
black concentrations in today’s base inks usually demand high
distance between shearing surfaces must be carefully adjusted
temperatures to maintain workable viscosities.
and maintained. Optimum clearance must take place to produce
high gloss, high order of dispersion, and good color. Careful
resetting of clearance between the shearing surfaces is essential
Premixing, Etc.
to produce uniformity of quality from batch to batch.
The following describes additional items that should be consid-
Three-roll mills are commonly used to “finish” a dispersion due
ered in the premixing process:
to the high shearing action imparted by this milling technique.
Use of this equipment generally requires a good premix stage so
1. Cutting back of heavy base inks should be carried out
that “hangback” of pigment is avoided.
with great care. The vehicle and thinners must be added slowly
in small increments with constant stirring to ensure homoge- Ink makers can use three-roll mills to handle high viscosity paste
neous mixtures. ink formulas at relatively low temperatures. This operation can
be used in the preparation of heavy offset - litho base inks. Up
2. Aging of the premixed base ink before mill dispersion is to 50% of Raven® 1255 type black can be dispersed in a
very helpful since it allows further pre-wetting. In this process, warmed litho varnish. The premixed batch, often hot when ran
however, heat losses must be considered. Upon aging, the sur- through the mill, produces a stiff, mirror-like base ink.
face of the carbon black can absorb the dispersing agents and
other ingredients from the vehicle, thus establishing an equi-
librium.
3. Sometimes it is desirable to use suitable metal soaps such
as calcium or iron naphthanates in the premixing cycle to allevi-
ate drier adsorption in the final product.
11 Using Raven® Carbon Blacks In Ink Applications
The superb dispersion of Raven® 1255 at a high loading is made In two-roll mill usage, high plasticity compounds are handled
possible, in part, by the chemisorbed oxygen on this post-treat- with resins, such as vinyls, nitrocellulose, cellulose acetate, and
ed black’s surface. This chemisorbed oxygen enhances the wet- alcohol soluble resins. All Raven® carbon blacks, from the finest
ting and reduces the viscosity. through the coarsest grades, can be employed.
If a roller mill paste is too thin, you can expect either less effi- In this process, the proportions of ingredients used and the tem-
ciency of dispersion or the requirement of considerably more perature of the mill should allow the batch to be soft enough to
time for milling. With very thin inks, tight roll clearances will be band around the two-roll mill at the beginning of the milling
required for good dispersion which can result in mill surface ero- process. As the temperature increases and the black disperses,
sion and excessive evaporation of thinners. the batch stiffens due to the surface area of the black becoming
available for vehicle adsorption. Temperature controls are
required to regulate the stiffness of the batch and to prevent
High Plasticity Dispersion excess loss of solvent and decomposition of the vehicle.
The use of two-roll mills involves the principle of high plasticity Depending on the product, the batch can be sheeted off the
milling. These mills consist of two closely spaced rollers that fre- two-roll mill, either as a flexible or brittle sheet, and cut back fur-
quently differ in surface speed. The distance between the rollers, ther with reducing vehicles and solvents in a suitable mixer. The
however, is not nearly as close as that employed on a three-roll mill. products that are sheeted off the two-roll mill can be broken up
into small pieces and stored for future use.
Two-roll mills are occasionally used to achieve ultimate disper-
sion when compounding carbon black in such products as nitro- Higher gloss will prevail in inks when the carbon black has been
cellulose lacquers for gravure inks. well dispersed in this manner. A superior degree of dispersion
also results in blacker masstone and bluer undertone.
High plasticity dispersion of carbon blacks has been used by ink
makers for many years and provides many advantages, such as:
• Better wetting Dough Type (stiff paste) Dispersion
• High degree of carbon black dispersion
• High gloss Stiff paste dispersion techniques are particularly useful since they
• High pigment loading in base ink allow the use of very high carbon black loadings. The dispersion
• Better development of color level achieved by this approach is generally poor such that a fin-
• Less aging of ink base required ishing dispersion step with other equipment, such as a three-roll
• Production results that would be difficult by other means mill, is required. The stiff paste end point can range from
• Improved effectiveness in the use of dispersing agents extremely stiff to moderately stiff using the heavy duty Baker-
Perkins dough type mixers. At any of these end points ( assum-
Many resins and vehicle solids can be used for high plasticity dis- ing precautions have been taken to ensure sufficient vehicle
persion ink products. Warning: Care must be taken to avoid a solids for the amount of pigment being dispersed, and that it has
fire or explosion when employing nitrocellulose. not been degraded by overheating ), the next important step is
the thinning or reduction of this plastic mass to a workable con-
The high plasticity process is a reliable dispersion method for sistency. Thinning down of the plastic mass to intermediate con-
inducing good color values, gloss, and other desirable require- sistencies should be handled with extreme care and should be
ments. However, as in all types of dispersion, requisites include done slowly.
the use of the proper dispersing agents, solvents, and ratios of
carbon black to vehicle solids combined with sufficient time to If the thinning vehicle is added too rapidly, lumps of the plastic
achieve the desired level of dispersion. mass will form and separate from the main batch. These lumps
will roll like ball bearings in oil and will be very difficult to break
Litho, offset, and other types of inks such as flexographic, down into a homogeneous mass. Many hours of work and loss
gravure, etc., can employ the end products of such high plastic- of production from recovery of an incomplete letdown can be
ity dispersion techniques. The use of the two-roll mill is not a avoided if sufficient time is invested in the appropriate cutback
requirement for this process; other equipment, such as a heavy techniques.
duty sand/shot mills, can be employed very satisfactorily.
Ball Mill Dispersion
EXAMPLE — High Plasticity Dispersions For Liquid Inks
The ball mill has attained important status among the ink
Several basic methods are available for making flexographic, maker’s production techniques. The beaded form of carbon
gravure and similar black inks. These dispersions can be carried black, pioneered by Columbian Chemicals Company, has made
out directly as a liquid in ball mills, attritors, or any variation of the ball mill popular for dispersing carbon blacks, not only for
shot mill or in a solid or plastic phase, followed by dilution with the ink maker.
large amounts of solvent.
Our studies of carbon black dispersion in a steel ball mill showed
that a careful balance of resin or vehicle solids, carbon black, and
Using Raven® Carbon Blacks In Ink Applications 12
solvent permits increased loadings of black with greater output This starting point, however, must be adjusted locally to a high-
of dispersed black. er or lower level depending on the many factors involved, i.e.,
type of vehicle, behavior under various temperature conditions,
The use of the beaded form of carbon black generally results in type of black in relation to vehicle, and many other considera-
better dispersion quality. This improved dispersion quality tions. Some pastes being dispersed may include vehicles that
appears to be due to the controlled wetting allowed by the bead have a heavy viscosity to start with and continue to hold this vis-
as compared to the high initial viscosity encountered when a cosity fairly well at somewhat elevated temperatures. Others,
powdered black is added to a liquid vehicle system. Such viscos- such as waxes, may attain a more water-like behavior at high
ity can actually hinder the tumbling action in the ball mill and temperatures.
thus hinder dispersion.
The ball mill is mainly used in the manufacture of the following Formulating For ideal Ball Mill Viscosity
types of inks:
News Daniel’s Flow Point Method — F.K. Daniel developed a method
Flexographic to optimize both pigment concentration and vehicle solids for
Gravure ball milling. For pigments such as TiO2, the method applies sim-
Publication ple stirring to incorporate the pigment into a vehicle using a
Carbon paper wax range of vehicle solids. The test calls for the slow addition of
Ribbon vehicle until flow is achieved.
The following illustration can be used to detect desirable flow
Limits of the Ball Mill properties:
The viscosity of the pigmented vehicle limits the effectiveness of The spatula is dipped into a pigment / vehicle mixture and is
the ball mill (or similar type of mill). In this type of mill, a very sat- withdrawn. The mixture will flow off the spatula and terminate
isfactory dispersion of carbon black can be obtained only when with an elastic snap back towards the spatula once an ideal flow
the proper viscosity is used in the millbase. is attained. When the viscosity is too high, the mixture will exhib-
it, at best, limited flow. If too much vehicle is added, the elastic
The beaded form of carbon black is available in practically all of snap will be lost.
the Columbian Raven® ink grades.
This effect can also be shown using a flow point curve ( sample
Some of the factors that must be considered in using a steel ball curve below ). The amount of vehicle per unit of pigment used
mill of this type are: is plotted against the vehicle solids.
• The best physical form of carbon black — beads
Vehicle Demand, g vehicle/10g CB
70
• The best type of carbon black for the ink
• The speed of mill and interior design 60
• The proper size ball and the quantity to be used 50
for best results 40
• The volume of ink or ink base to be dispersed
• The consistency or viscosity of the ink to be dispersed 30
• The temperature controls 20
• The cleanliness of the mill from one batch to another 10
• The timing of addition of formula components
0
10 15 20 25 30 35 40 45 50
% Vehicle Solids
Viscosity and yield values of the batch being dispersed are the
most important items to be considered in ball and pebble mill
operations. This is assuming the proper design of lining, baffles, The points on the plot are then connected to determine the min-
size of charge with the proper balls or pebbles selected, and con- imum point on the “flow point” curve. The minimum point on
trol of the temperature and speed are used. If the ink or ink base the curve indicates both the pigment concentration and the
is too thick, the media will not make proper contact, they will vehicle solids best suited for dispersion in a ball mill.
not cascade properly, and the carbon black beads or powder will
not be dispersed. Conversely, if the batch is too thin, the balls or
pebbles will grind against each other with minimum efficiency of Determining The Flow Point
dispersion. In addition, contamination from the media may
occur. The Daniel method requires modification for carbon black due to
the significant change in exposed surface area as the carbon
Laboratory work at Columbian Chemicals on steel ball mills has black is dispersed. When determining the “flow point” for car-
shown that, in a normal steel ball mill dispersion, a good start- bon blacks, the test should be carried out in a small, open top
ing point would be a viscosity between 1600 and 2400 cps at media mill, using a pint can, sand or shot, and a high speed
moderate shear (10-100 sec-1). mixer equipped with a 2” disk.
13 Using Raven® Carbon Blacks In Ink Applications
The media and pigment should be gently mixed together. The The time involved for dispersion depends on mill efficiency, vehi-
vehicles should then be slowly added with sufficient disk speed cles, etc. Typically, eight hours or less is required for ball milling
to create a vortex in the mini sand mill. When a flowing condi- a newsink.
tion is achieved, the mixing should be allowed to proceed to
ensure that the black’s surface area has been exposed to the
vehicle. Small additions of the vehicle will be required as the Finding The End Point
black disperses to compensate for the additional surface area
being wetted. The flow properties of the mixture should be The end point of the dispersion cycle is indicated by the black
determined after dispersion has been achieved. being dispersed to a “grind” fineness demanded by the cus-
tomer’s requirements. For those new at this type of operation,
The modified Daniel’s method can be used to quickly develop a samples should be taken from the ball mill at various intervals,
mill base formulation with sufficient vehicle for good mill flow. starting after four hours of grinding. Additional dispersion
However, this flow point formulation does not provide good col- checks should be made periodically until the desired dispersion
loidal stability. It is therefore recommended that the vehicle com- quality has been attained, guaranteeing a reasonable uniformity
ponent be increased by 5% to 10% at the end of the dispersion of product. The “grind” can be determined with the use of grind
cycle to provide colloidal stability and to reduce the potential for gages and/or filtration to determine if a specific residue level has
flocculation during storage or letdown. been achieved.
Temperature control is another important consideration in find- The stability of dispersion and viscosity of the concentrated base
ing the proper formulation. If the formulation requires reduction should be examined after it has cooled to typical storage tem-
in viscosity by heat, which is true in many important cases, then peratures and/or it has cooled to the lower temperatures possi-
the temperature controls must be adequate. If the temperature bly encountered in a cold storage room, or those found if it is
is not kept uniformly high, a batch may thicken up which would shipped to a distant blending point. The stability should also be
cause dispersion to be minimized. examined at intervals of days, weeks, or months, depending on
how soon the concentrated base will be used before dilution or
Despite all these factors and precautions, ball and pebble mill cutback.
dispersions are relatively easy to attain with normal care. This
method is also an efficient and clean operation requiring mini-
mum attention once the various controls are set. EXAMPLE — Carbon Black Wax Ink Preparation in Ball Mills
Dispersion of carbon black in wax inks requires elevated temper-
EXAMPLE — Newsink Preparation in Steel Ball Mills atures to provide a fluid condition. When introducing raw mate-
rials into the process, emphasis is placed on close temperature
Newsink can be made in a steel ball without undue precautions. controls. Such heat is necessary to melt carnauba and other
However, there are a few simple everyday rules that should be blending waxes.
followed.
Temperatures up to 90°C or more can be employed unless heat-
A superb dispersion is not required in this situation, since high sensitive organic toners are used. Warm or hot vehicles wet the
gloss is not a factor in newsinks. Between the paper used, the carbon black better and accelerate dispersion.
newsprint, and its relatively poor surface, truly fine printing is
not demanded. In order to maintain low production costs, the Since high mill temperatures can be used, it is possible to further
minimum time should be employed to disperse the bead black. increase the loading of the black. The high milling temperatures
also create a greater fluidity of the vehicle and result in efficient
Oil beaded carbon blacks such as Raven® 680 OB and Raven® milling and discharge of the batch. With the combination of ele-
825 OB for newsinks are recommended for the following reasons: vated temperatures and resultant better wetting and dispersion,
• Freedom from dust somewhat higher viscosities can be employed.
• Ease of handling
• Fast incorporation of the black by the vehicle The temperature limits in this process must be high enough to
• Less air involved keep the waxes in a highly fluid condition and low enough to
• Built-in wetting agent prevent decomposition of the soluble organic toners and other
• Controlled surface area development in the early stages heat-sensitive pigments. Caution, however, should be taken to
of milling resulting in faster dispersion of the black. prevent overheating the waxes.
In producing newsinks, a petroleum residue pitch should be
blended with a mineral oil to benefit from the advantages of the Preparation of the Wax Melt For Milling
dispersing effect, as well as lowered viscosity and increased flow
which are so important in this operation. This is the same proce- In preparing the wax melt for milling, several process choices are
dure that the early ink makers employed to make the “long var- available.
nish” — mineral oil plus a pitch — which was blended by heat-
ing the two together. This method can be used for the ball The first choice is to premelt the waxes; to add the oils, Raven®
milling operation, and can be prepared in advance for introduc- carbon black, fillers, and other components of the formula; then
tion into the mill. to stir carefully until thorough wetting and blending take place.
Using Raven® Carbon Blacks In Ink Applications 14
When preparing wax inks which will contain methyl violet-oleic Still another method is to charge a heated ball mill with the solid
acid toner or other organic toners, temperatures in excess of waxes and oils, melt the waxes, and then add the carbon black.
90°C may cause decomposition of the toner. This caution applies
to important formulations where the methyl violet-oleic acid Ball mill temperatures should be monitored closely so that for-
toner or its equivalent acts as an excellent dispersing agent. This mation of steam in the batch is prevented. Temperatures should
formulation gives lower viscosities and better flow in the mill also be reduced after waxes are melted. Finally, preheating the
during the dispersion cycle. pigments in the melt for a while before milling will allow the
vaporization of the moisture, since the waxes will preferentially
Next, the mix can be poured into the heated ball mill or pumped wet the surface of the black and displace the adsorbed moisture.
to a heated media mill. Up to 20 or more parts of the beaded
blacks can be incorporated, depending upon type of black, the Another adverse effect of excessive temperature is foaming. If
formula, the grade of carbon, and the paper to be coated. the mill temperatures are too high, the small amounts of mois-
ture carried in by pigments or other materials may cause serious
If an oil or wax soluble dye is to be dissolved in the carnauba wax problems when the discharge cover is removed from the ball mill
early in the milling cycle, the temperature must be kept low from in order to drain the mill. The hot molten wax foam will pour out
the beginning. under pressure, creating safety and housekeeping problems.
These problems can be minimized by shutting off the heat at
For ball milling, another method of charging the mill is to pour least one hour before discharge.
in both the molten waxes and the oils first and then to pour in
the Raven® carbon black. After the temperature has been A constant temperature control can avoid problems
reduced to a safe level, the oleic acid solution of the organic dyes before they happen.
is added. This procedure will prevent decomposition.
15 Using Raven® Carbon Blacks In Ink Applications
CUTBACK OR REDUCTION OF MILLED PASTES 7. In some ink systems where solvents and diluents are used,
a combination that does not hold the resin or varnish solids in
Since so much time has been spent explaining how to obtain the solution should not be used; otherwise, a “throw-out” or floc-
maximum in blackness, hiding power, and gloss from a Raven® culation of the vehicle solids can occur, carrying the pigment
carbon black paste, we would be remiss if we did not discuss the along with it. While not noticed in production, the “throw-out”
method of cutback from paste to the final ink. Each of the areas may develop while standing in the customer’s warehouse or
previously discussed contributes to the end result, i.e., the best factory.
ink film. Still, it must be recalled that we are working with col-
loidal dispersions of carbon black. During warm weather, it might not be noticed at either the pro-
ducer’s or user’s factory, but in cold weather, the flocculation will
Even if, in the processing up to this point, the best techniques occur during shipment or at the customer’s cold warehouse.
have been employed, it is quite possible to completely ruin all of This situation should be monitored in gravure, flexographic, and
the good work by a poorly-handled cutback of the base to the similar solvent types of inks. Such “throw-out” of the pigment
final ink. The following describes ways to avoid this trouble: can also be caused by excess solvent.
1. If the base paste is viscous, the cutback should be made
slowly, adding the reducing vehicle in small increments. COLLOIDAL SHOCK
Otherwise, formation of large lumps or very small gel-like specks
of paste that are difficult to break down might be encountered. The loss of stability during dilution or cutback of the paste is due
The latter results in a rough surface, dirty inks, “fill-in”, and to colloidal shock.
other press troubles.
The addition of the clear vehicle, particularly if the introduction
2. Whether using a thin paste or a heavy paste the reduc- is too rapid, can cause an upset in the equilibrium of the two
ing vehicle should never be added too rapidly. Colloidal shock main paste components — black and vehicle solids. It takes time
can occur and result in either flocculation of the pigment, loss of for the paste phase to blend with the new liquid phase and
color, brownness of shade, or a combination of the three. reach equilibrium or maximum stability of the final ink. In this
interval of reorientation, a drop in color and a change of shade
3. The normal paste should be stirred or milled continuous- can occur due to a temporary flocculation of pigment alone, or
ly to keep it soft, while at the same time, slowly adding the pigment and paste solids. As indicated before, the colloidal
shock can be temporary, but can have great effect if excessive
reducing vehicle.
volatile phase is used. The dilution effect alone can be destructive.
4. Attention should be given to the temperature of the paste
These variables should be watched with special regard to match-
or the reducing varnish. A cold-reducing varnish should not be
ing standards of blackness, working properties, control of black
added to a hot or warm paste. Flocculation, loss of color, etc., purchased, and deliveries of finished inks to the all-important
due to colloidal shock will occur. This situation is particularly true customers. A factory batch may be passed by the laboratory on
in cold weather, when the operator brings in the reducing var- a freshly-made ink but may not pass if it is tested after aging
nish from the warehouse or outside storage at a temperature overnight.
potentially much lower than the batch to be reduced.
Stability can be enhanced by a thorough, long blending time
5. Heavily-pigmented pastes should not be stored for too under the proper conditions.
long an interval, since, in some cases, the vehicle used is not a
good colloidal stabilizer due to performance requirements. Protective agents ( those that help give greater stability of dis-
Setting up or gelling of the paste can occur, plus flocculation or persion, i.e., dispersing agents, synthetic or natural ) can help to
agglomeration of the black. In these cases, it is safer to cut back keep borderline stability in check. However, it is a dangerous
habit to depend on.
as soon as possible after milling. The same is true for a good dis-
persing vehicle if over-pigmented. It is good practice to use some of the protective agents in the
diluting vehicle. These agents will act as colloidal stabilizers both
6. The choice of reducing resin or vehicle should be made
in organic and aqueous systems.
carefully, keeping the specification requirements of the final
product in mind. The best vehicle to do the job should be
employed, and should be clean and free of fine gel particles,
DILUTION OF AQUEOUS SYSTEMS
overcooked resin or any other contamination.
In aqueous systems, care should be taken to use sufficient dis-
Such contamination can sometimes induce “seeding”, “dirti- persing and wetting agents in the base ink to withstand the later
dilution with the reducing vehicle, the water alone, or water
ness”, “grit”, etc., which, upon aging, will give specky, dirty
containing vehicle solids.
impressions caused by “fill-in”. With black gloss inks of all types,
this surface roughness is much more noticeable than with
other colors.
Using Raven® Carbon Blacks In Ink Applications 16
Guidelines for Diluting Aqueous Systems
North Bend Raven® Carbon Blacks
In aqueous systems, the same general rules apply, i.e., stirring in
the reducing vehicle slowly. The incorporation of a portion of the Raven® 1255
colloidal stabilizers in the reducing vehicle is also recommended. Raven® 1200
The pH behavior must be controlled throughout the dispersing Raven® 1170
and “cutback” cycle. If optimum stability of the water base Raven® 1100 Ultra®
requires a pH close to 7, as in some flexographic inks, then the Raven® 1060 Ultra®
pH should not be allowed to decrease in the freshly-made ink or Raven® 1040
on aging in the customer’s plant. Raven® 1035
Raven® 1020
With certain systems if the pH is allowed to go too high, reduc- Raven® 1000
tion in the viscosity can occur. This, in turn, may result in settling Raven® 860 Ultra®
of the pigment. However, other ink systems may maintain their Raven® 850
stability at higher pH levels. This could be due to the particular Raven® 760 Ultra®
ingredients used in the formulation, such as a suspending agent Raven® 450
in the form of a thickener.
It is quite obvious that the “cutback” step, or dilution, is just as Oil beading is used with selected blacks to enhance the dis-
important as any preceding processing step. A good job of dis- persibility. Oils uniquely selected for their ability to act as a wet-
persion can be deteriorated or made commercially unacceptable ting agent for the systems in which they are used are incorpo-
by not exercising care when making the letdown. Production rated into the black during the beading process. Raven® 680
rate versus quality should always be kept in mind. and Raven® 825 are both oil beaded carbon blacks.
Dispersion techniques properly applied result in the optimum In some special cases, the customer may choose to pulverize the
quality attainable with a given pigment/vehicle combination. carbon black beads prior to incorporation into the vehicle sys-
tem. Proper air handling / ventilation eqiupment is required for
dust containment if pulverization is to be pracitcal.
BEADED BLACKS
Example — Bead Use In Liquid Inks - presoaking
Powder blacks are very popular in ink production due to the ease
If solvents are used in the ink, soaking the beads in the solvent
in which they can be dispersed. However, bulk handling, eco-
will soften them and make them more readily dispersible. The
nomics, freight, cleanliness or a particular required property may
following experiment, which is carried out on a glass plate, will
mandate the use of a beaded black.
prove this statement.
When using beaded blacks, wetting / premix times should be
Take a small amount of beads and add just enough solvent to
extended as much as possible to ensure that the beads have
soak them. Work the beads with a spatula until a creamy mass
been broken down. The ink maker can anticipate dispersion to
is obtained. Blend the mass into a heavy varnish vehicle and note
require more work when using a beaded black. However, this
the ease of incorporation. Contrast this with the use of the dry,
additional work can be offset by faster incorporation of the
unsoaked bead. This method is only practicable with inks where
beaded black into the vehicle and significant improvements in
solvent in a sufficient quantity can be used. The addition of dis-
handling and housekeeping.
persing agents in this solvent soaking/wetting cycle is very helpful.
Batches made with beaded blacks should be treated in the same
manner used to make extremely heavy offset base inks. High
shearing forces and high energy input are required for success-
ful batches.
Columbian’s North Bend plant is outfitted with specialized
equipment to produce beaded blacks which are particularly easy
to disperse. The ink grade carbons listed below are produced at
the North Bend plant.
INTERNATIONAL
U.S. SALES OFFICES SALES OFFICES
GEORGIA CANADA JAPAN
1800 West Oak Commons Court Columbian Chemicals Canada, Ltd. Columbian Carbon Japan, Ltd.
Marietta, Georgia 30062 P. O. Box 3398, Station C No. 8-12 Horidomecho 1-Chome
(770) 792-9400 755 Parkdale Avenue North Nihonbaski, Chuo-Ko
(800) 438-6968 Hamilton, Ontario L8H 7M2, Canada Tokyo 103, Japan
Fax: (770) 792-9625 Hamilton (905) 544-3343 (81) 3-3663-2881
Toronto (905) 922-3363 Fax: (81) 3-3667-1569
ILLINOIS Fax: (905) 544-8641
500 Park Boulevard PHILIPPINES
Suite 810 ENGLAND Columbian Carbon Philippines, Inc.
Itasca, IL 60143 COLUMBIAN CHEMICALS, UK MCC P. O. Box 1969
(630) 773-6650 Sevalco, Ltd. 1259 Makati, Metro Manila
(800) 325-9701 Severn Road Philippines
Fax: (630) 773-4622 Chittening (63) 2-810-0386
Bristol, BS11 OYU England Fax: (63) 2 818-7337
NEW JERSEY (44) 117-9235532
7 Centre Drive Admin. Fax: (44) 117-9235444 SPAIN
Suite 2 Sales Fax: (44) 117-9235333 Columbian Carbon Spain, SA
Jamesburg, NJ 08831 Complejo de Santander
(609) 395-8181 FRANCE Gajano (Cantabria)
(800) 257-5076 Columbian Carbon International Apartado 23
Fax: (609) 395-8196 2 rue de la Couture E-39710 Solares, Spain
SILIC 229 (34) 42-503030
OHIO 94528 Rungis Cedex, France Fax: (34) 42-502165
3200 West Market Street (33) 146879241
Suite 200 Fax: (33) 146879062
Akron, OH 44333 WORLDWIDE
(330) 867-5800 GERMANY
(800) 336-2068 Columbian Chemicals HEADQUARTERS
Fax: (330) 867-0648 Deutschland GmbH
Kreisstr. 20 COLUMBIAN CHEMICALS COMPANY
D-30629 Hannover, Misburg Germany 1800 West Oak Commons Court
(49) 511-95935-0 Marietta, Georgia 30062
Fax: (49) 511-95935-59 (770) 792-9400
(800) 235-4003
HUNGARY Fax: (770) 792-9623
Columbian Tiszai Carbon Ltd.
H-3581 Tiszaújváros
P. O. Box 61, Hungary
(36) 49-321-724
Fax: (36) 49-322-003
ITALY
Columbian Carbon Europa SRL
Via S. Cassiano, 140
P. O. Box 184
I-28069 San Martino Di Trecate
Italy
(39) 321-7981
Fax: (39) 321-798250
Customer Assistance
At Columbian Chemicals Company, we are proud to provide you with the informa-
tion and assistance to help you use our Raven® carbon blacks. We are committed
to providing our customers with the finest in service, information, and support,
while manufacturing the finest carbon blacks available anywhere.
We understand that you may have questions or need assistance with the processes
and products mentioned in this brochure. Please feel free to call us and let us know
how we can help you.
COLUMBIAN CHEMICALS COMPANY
World Headquarters Marietta, Georgia USA
European Headquarters Hannover, Germany
A subsidiary of