OVERVIEWBYK ADDITIVES FOR
PAPER COATINGS

K-O 1

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BYK additives for paper coatings

Contents
03 Introduction
04 Range of BYK additives for paper coatings
05 Coating color preparation
07 Improved coating process
10 Paper surface improvements
12 Functional paper surfaces
15 Optimized solutions by BYK additives

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Introduction
Paper coatings can impart special properties to the surface of the paper todeliver a performance not exhibited by the uncoated base paper. In allcases, additives and functional materials are designed to deliver an
optimized paper surface and the required performance. BYK has a wide
range of products that can be incorporated into the formulation to:• assist in the preparation of a homogeneous coating color•	aid in the coating process to produce a high-quality finish to
the coating•	improve the paper performance when compared to uncoatedbase papers• provide specialized functional performance

Note
To ensure the best appearance
and full functionality, please
open in Adobe Acrobat.

For more information on
additives for paper coatingsplease visit us on byk.com
or contact your local sales
representative.

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BYK additives for paper coatings

Range of BYK additives for paper coatings
Coating color preparation

Improved coating process

Paper surface improvement

Functional paper surfaces

Wetting and dispersing
Defoamers and antifoams
Rheology control
Surface additives
Wax and polymer additives
Functional clay additives
T. 01

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BYK additives for paper coatings

Coating color preparation
Wetting and dispersing
One of the most important steps in the production ofpigmented paper coatings is the homogeneous distributionof solid pigments within the liquid binder solution. Paper
coatings contain a number of pigments which requiresufficient wetting to allow the dispersion to remain stableand prevent agglomeration.
Effective dispersion of all formulation components is criticalto ensure the best effects and performance is achieved on
the desired coated paper surface. Incomplete dispersion
leads to sub-optimal performance, coating defects, andpotential damage to the coating equipment itself.

Wetting and dispersing additives can be used to assist thisprocess and avoid lengthy, high energy dispersion processes.
Their addition to a formulation at the correct stage results ina homogeneous distribution of solid particles in liquid media
and ensures long-term stability.
Wetting agents are surface-active substances and improve
the wetting of solids. Dispersing agents prevent particles
flocculating by various mechanisms (electrostatic effects,
steric effects). Wetting and dispersing additives unite bothmechanisms of action in one product, i.e., they are bothwetting and stabilizing.

Wetting of pigments to form a stabilized dispersion
Agglomerated pigments

BYK and DISPERBYK products offer
a range of potential additives thatcan be matched to the materials to
be dispersed (such as anatase TiO2,
rutile TiO2, CaCO3 and kaolin).

A coating defect (blade streak) caused by poor dispersion

Ideal dispersion

G. 01

G. 02

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BYK additives for paper coatings / Coating color preparation

Rheology control

Defoamers and antifoams
The presence of entrained air in the coating color can leadto a number of issues during formulation. An increase in
the volume of the mix, difficulties in filling systems/
containers, interruptions to coating flow, and surface
defects during coating are all unwanted side effects
of foam. Not only do these cause logistical issues, butthey can result in an unattractive appearance and impact
the functional performance of the coating. As a result,removing or preventing foam is integral to a coating color.

Consequently, almost all formulations require a uniquesolution to foaming problems rather than a generalized
approach. Fortunately, the incorporation of defoamers andantifoams (or air release agents) can initially prevent air
bubbles from forming or destroy foam bubbles that havebeen formed. To enable a bespoke solution, BYK offer avariety of chemistries targeting both microfoam (< 100 µm)
and macrofoam (> 100 µm) formation to ensure that themost compatible solution can be achieved.

Virtually all the components in the coating formulation can
influence foaming behavior positively or negatively. The
method of mixing, the coating substrate and application
technique also have an impact on foaming behavior.

The BYK product range includes a number of silicone,
silicone-free, mineral oil and polymer defoamers to allow
maximum formulation windows.

Schematic of impact of defoamer on formulation parameters

During preparation of the coating color, it is essential that itremains a homogeneous system with a low enough viscosity
to easily incorporate the reagents, but with enough elasticity
to prevent settling of any pigment/filler particles.
OPTIGEL products are recommended for use in aqueous
sytems if anti-settling properties are required.

Anti-settling of TiO2 dispersion

defoaming

Without additive

With OPTIGEL additive

compatible

defects

incompatible

Optimumfoam

foam stabilization
G. 03

G. 04

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BYK additives for paper coatings

Improved coating process
Defoamers
Foam in the coating supply system can cause numerous
defects in the final coating from fish eyes and craters tocomplete miscoats as well as changes in the gloss and feelof the surface. By their nature, defoamers need to beincompatible with the system to disrupt the foam.
Therefore, a balance between compatibility andperformance needs to be met to ensure optimal defoaming
without impacting the final characteristics.
Selecting a suitable defoamer depends on the system andapplication. BYK therefore offers a wide range of defoamers
to cover all eventualities.

Schematic of defoamer incorporation with coating properties

Optimum compatibility/good emulsification
Strong defoaming
Good substrate wetting/no cratering

Too compatible/over emulsification
Weak defoaming
Good substrate wetting/no cratering

Defoamer  Coating  

Substrate  

Shear/time  

Too incompatible/poor emulsification
Strong defoaming
Poor substrate wetting/cratering

G. 05

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BYK additives for paper coatings / Improved coating process

Rheology control
During the coating process, the coating color will be
subjected to a wide range of shear conditions. Throughout
these, the color must remain stable. Being able to withstandrapid changes in shear force enables a continuous flow ofmaterial to the coating head, resulting in an even coating
and maximizing machine runnability.

The RHEOBYK liquid rheology additives can be easily
incorporated into a wide range of systems. The productrange includes associative thickeners offering low shear,high shear and elongational stability.The use of rheology
modifiers can significantly improve the application propertiesof a wide variety of paper coating systems.

Rheology improvement for gravure coating

Without additive

With additive

G. 06

Viscosity η (Pa·s)

Schematic of typical rheology profiles
low shearmedium shear

high shear

100

storagetransportationlevelling

production

under stirring

settling

application

saging

0.01

0.001

0.01

0.1

1

10

100

1000

10000
Shear rate

(s-1)
G. 07

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BYK additives for paper coatings / Improved coating process

Surface additives
During the application of coatings onto the paper, different
surface defects can occur. A significant cause of such
defects is differing surface tensions between:• substrate and liquid coating• different coating layers• areas of the coating drying at different speeds

For some application methods (such as cast coating andgravure coating), surface additives can be used to improverelease from the coating rollers. This gives not only a better
quality coating but can also reduce machine downtime
when changing coating color due to faster roller clean
downs.

If, for example, the surface tension of the coating is higher
than that of the substrate, this manifests itself in poor
wetting (high contact angle) and, with that poor adhesion
and cratering.

Other application methods (such as curtain coating)require specific influence on the overall surface tension anddynamic surface tension behavior of the coating color.
Control of the coating surface tension in such applications
is needed to ensure new coating color surfaces are rapidly
stabilized. This in turn allows for maximised operational
speeds and production.

Surface wetting

45

mN/m

29

mN/m

30

mN/m

30

mN/m
G. 08

The BYK product range offers
silicone, silicone-free, siloxane
and polyacrylate surface
additives to positively influencea variety of systems.

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BYK additives for paper coatings

Paper surface improvements
Surface additives
After application and while the coating is drying, local surface
tension differences can cause unfavorable levelling andfloating of pigments. Defects such as craters, fat edges, rodlines and dewetting are unattractive but also result in lessthan optimum performance. Occurrence of such defects canalso result in costly QC failures and manufacturing remakes.
The evenness of a coating is related to the wetting of thepaper surface and penetration speed into the paper web.
Incorporating surface additives to reduce surface tensiondelivers a more uniform coating surface.

Printability is related to printing ink acceptance andadhesion which in turn is a function of the wettability
and uniformity of the paper surface. The correct balance
between polar and disperse components of the surface
tension is critical in delivering good printability. Failure toachieve this may lead to print mottle, missing dots anddot gain.
The BYK product range offers a variety of additives which
can improve or even prevent these surface defects.

Crater in paper coating

Levelling of rod lines with incorporation of a surface additive

Control

G. 09

With BYK additive

G. 10

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BYK additives for paper coatings / Paper surface improvements

Wax and polymer additives
Wax additives can be used to control the processability of
products or to improve the paper surface properties. Waxes
can be of a natural, semisynthetic or synthetic origin whichhave their own range of properties. The fundamental
properties are derived from the chemical basis, the melting
point and the polarity of a wax. Modifications and thesubsequent manufacturing methods also influence the end
properties.

Including waxes and polymers into the system can lead to:• improved rub and scratch resistance• reduction of penetration into the paper web improving
the effectiveness of the coating• reducing any tendency to mottling during printing
by creating a more uniform surface• adjustment in the friction between coated paper
sheets to increase and reduce slip

Improving printability and print density
Print without wax additive

With wax additive

G. 11

BYK sells its wax additives in arange of water-based emulsion,
dispersion and micronized solid
wax preparations, as part of the
AQUACER, CERAFLOUR and
HORDAMER product ranges.

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BYK additives for paper coatings

Functional paper surfaces
Wax and polymer additives
In addition to improving the properties of the coatedsurface, waxes and polymers can add functionality to thecoating. A common use is in the thermal transfer ofprinted images from paper to other substrates. Waxes
facilitate the transfer process due to their melting point,
which can be matched to the required temperature forthe application during formulation.
The melting point (or transition temperature) of waxes andpolymers is also critical for heat sealing. Combinations ofappropriate waxes and/or polymers will create a sufficient
seal for the application allowing paper and paperboard to
be used in a wide range of packaging from medical syringe
packets to coffee cups.
In addition to their other effects, waxes and polymers form
excellent barriers to certain gases and liquids. This isof particular importance in food and medical packaging
applications, offering alternatives to fluorochemical,
microplastic and single use plastic solutions.
The AQUACER and HORDAMER product ranges offer a
range of chemistries, delivery forms and melting points
providing excellent options for formulators.

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BYK additives for paper coatings / Functional paper surfaces

Functional clay additives
Modified clays can be used to deliver specialized functionalsurfaces for printing applications. Acid activation develops
a surface that has both excellent absorption properties andreactive sites to deliver an immediate, sharp and permanent
image. This has particular benefits in carbonless copy paper
enhanced by the consistent performance of the clay in allcolor former systems and microcapsule types.

The excellent absorption properties of activated clays can be
employed to deliver a bright, clear and sharp image in inkjet
printing. Controlled particle size distribution allows rapid
removal of the ink carrier to deliver fast drying, which is of
critical importance in high-speed printing applications.
The acid activated clays in the FULACOLOR range combine
controlled porosity with reactive surfaces to create products
suitable for various printing techniques.

Inkjet printing on uncoated paper (left) and
FULACOLOR coated paper (right)

Carbonless copy paperPen

Top sheet

Reactive clay layer

Microcapsulesof inkReactive clay layer

G. 12

G. 13

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BYK additives for paper coatings / Functional paper surfaces

LAPONITE is a synthetic high purity mineral which disperses
completely in water under moderate shear to individual
platelets to provide a clear dispersion. When the shear isremoved, the platelets quickly reassemble to form a “houseof cards” structure which can stabilize dispersions andprevent sedimentation. When the shear is reapplied, thestructure collapses providing a suitable liquid for coating.
Once coated onto paper, the LAPONITE platelets align toform a transparent film.

The high aspect ratio of the dispersed mineral and thecharge distribution of each platelet combine to produce
a conductive layer that can dissipate and prevent static
charge build up. This is particularly important in applications
where static can cause damage to components or increase
wear, such as in POS thermal printing, labels, thermaltransfer ribbons, and abrasive base papers for sanding belts.
The alignment of high aspect ratio platelets is also ideal for
creating a barrier to molecules by creating a “tortuouspath”. This can aid in providing a physical barrier coating todecrease permeation of gases and liquids.

Single LAPONITE platelet and the house of cards
structure that it forms

Tortuous path through high aspect ratio
clay platelets aligned in a film

Substrate

G. 14

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BYK additives for paper coatings

Optimized solutions by BYK additives
The variety of technologies available facilitate thedevelopment of optimized solutions for specialized paper
applications. This is supported by state-of-the-art analyticalcapability which allows characterization of the paper
surface. This understanding of the surface combined withan extensive knowledge of the requirements for applicationmeans that BYK additives can be easily selected to suitthe needs of each customer.

03/2022
K-O 1
BYK-Chemie GmbH
Abelstraße 4546483 Wesel
GermanyTel +49 281 670-0
Fax +49 281 65735

ADD-MAX®, ADD-VANCE®, ADJUST®, ADVITROL®, ANTI-TERRA®, AQUACER®, AQUAMAT®, AQUATIX®, BENTOLITE®, BYK®, BYK®-DYNWET®,
BYK®-MAX®, BYK®-SILCLEAN®, BYKANOL®, BYKETOL®, BYKJET®, BYKO2BLOCK®, BYKOPLAST®, BYKUMEN®, CARBOBYK®, CERACOL®, CERAFAK®,CERAFLOUR®, CERAMAT®, CERATIX®, CLAYTONE®, CLOISITE®, DISPERBYK®, DISPERPLAST®, FULACOLOR®, FULCAT®, GARAMITE®, GELWHITE®,
HORDAMER®, LACTIMON®, LAPONITE®, MINERAL COLLOID®, MINERPOL®, NANOBYK®, OPTIBENT®, OPTIFLO®, OPTIGEL®, POLYAD®, PRIEX®,
PURE THIX®, RECYCLOBLEND®, RECYCLOBYK®, RECYCLOSSORB®, RECYCLOSTAB®, RHEOBYK®, RHEOCIN®, RHEOTIX®, SCONA®, SILBYK®,TIXOGEL®, VISCOBYK® and Y 25® are registered trademarks of the BYK group.

info@byk.com
www.byk.com

The information herein is based on our present knowledge and experience. The information merely describes the properties of our products but noguarantee of properties in the legal sense shall be implied. We recommend testing our products as to their suitability for your envisaged purpose
prior to use. No warranties of any kind, either express or implied, including warranties of merchantability or fitness for a particular purpose, are maderegarding any products mentioned herein and data or information set forth, or that such products, data or information may be used without infringing
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This issue replaces all previous versions.