Coatings Technology Handbook Episode 3 Part 1 doc

Driers

80

-3

coordination compounds such as ortho phenanthroline or, di-pyridyl seems to reduce or eliminate such
adsorption and prevent “loss of dry.” This may also be accomplished by using highly basic cobalt
compounds that slowly release cobalt into solution. By “basic,” we mean that the metal soap contains
more moles of metal than the equivalent moles of acid from which it is formed.
To accomplish complete drying of oil films, the cobalt drier is used with another that possesses the
property of initiating complete dry. Lead soaps are the most effective in this regard, but their use has
been limited because of toxicity.
Calcium and zirconium are the metals used to replace lead. They are considered auxiliary driers.
Calcium soaps at one time consisted of the napthenates, usually at 4% and 6% calcium concentration.
These were highly acidic and quite viscous. They have largely been replaced by calcium octoate, a highly
basic material, low in viscosity and odor and available in solvent solutions in various concentrations.
Zirconium 2-ethylhexanoate is also a basic soap, usually available in 12%, 18%, and 24% Zr concen-
trations. It seems to have a catalytic effect on cobalt and manganese driers, and is said to have a
coordination potential of namely 8, and a low redox potential. When electron-donating groups develop,
coordination polymerization occurs, assisting in the overall drying effect.
Barium 2-ethylhexanoate has also been used as a replacement for lead driers, but also has found limited
use because of its toxicity. Manganese is the other “active” drier that is widely used in oil paints and in
baking finishes. Although active as an oxidant, it seems to promote polymerization to a greater extent
than cobalt. Solutions of manganese 2-ethylhexanoate rapidly oxidize to a dark brown color on exposure
to air. The use of manganese in white paints presents discoloration problems that must be handled by
careful formulation. Manganese is often used alone in baking finishes.
A number of other metals have been used as auxiliary driers. Neodymium, lanthanum, and aluminum
are reported to be useful as “through” driers.

9

Vanadium is also effective but causes severe discoloration.
Bismuth soaps have been used as a replacement for lead soaps in drier systems.
Iron is a potent drier, similar to manganese in its effects. However, it is highly staining and is used in
systems where color is of no importance. Cerium may also be considered an oxidative drier, but it is of
low activity compared with cobalt or manganese.
Waterborne coatings present another problem for the formulator because the presence of large volumes
of water changes the chemistry of coating resins.

10

It was found that adequate drying required a larger
percent of cobalt drier rather than various cobalt combinations utilizing the cobalt concentrations
adequate for oil-based systems.
There is growing use of premixed blends of drier metal soaps according to the individual requirements
of the paint manufacturer. Formulation of such combinations requires careful study to achieve stable
blends, because the individual metal soaps may be normal, acid, or basic.
Antiskinning agents are antioxidants used to prevent formation of oxidized surface films on the paint
while stored in containers. The type of antioxidant and the concentration in the paint have to be carefully
considered. Phenolic compounds are most effective but will prolong the drying time of the film. The
oximes can be used over a wider range of concentrations without seriously affecting drying time. The
types most widely used are the oximes, such as acetone oxime, methyl ethylketoxime, butyraldoxime,
and cyclohexanone oxime. It is believed that these compounds function by forming weak complexes with
cobalt or manganese, thus inhibiting the oxidizing power of the metal. When the paint is exposed as a
thin film, the oxime volatilizes fairly rapidly, leaving the metal in its active state.
Var ious phenolic compounds are also used as antioxidants. These function by contributing protons
that interrupt the peroxide free radical oxidation chain and do not volatilize from the film. Compounds
such as hydroquinone, ortho isopropylphenol, eugenol, and guaiacol are used in paints formulated with

highly reactive vehicles such as tung oil, oiticica oil, and dehydrated castor oil.

References

1. S. Coffey,

J. Chem. Soc., 119

, 1408–1415 (1921).
2. J. S. Long, A. E. Rheineck, and G. L. Ball,

Ind. Eng. Chem., 25

, 1086–1091 (1933).

DK4036_C080.fm Page 3 Thursday, May 12, 2005 9:53 AM
© 2006 by Taylor & Francis Group, LLC

80

-4

Coatings Technology Handbook, Third Edition

3. A. C. Elm,

Ind. Eng. Chem., 26

, 386–388 (1934).
4. P. O. Powers,

Ind. Eng. Chem., 41

, 304–309 (1949).
5. P. S. Hess and G. A. O’Hare,

Ind. Eng. Chem., 44

, 2424–2428 (1952).
6. R. R. Myers and A. C. Zettlemoyer,

Ind. Eng. Chem., 46

, 2223–2225 (1954).
7. W. J. Steward,

Offic. Dig. Federation Paint & Varnish Prod. Clubs, 26

, 413 (1954).
8. M. Nowak and A. Fischer, U.S. Patent 2584041 (January 29, 1952).
9. R. W. Hein,

J. Coat. Technol., 71

, 898 (1999).
10. R. W. Hein,

J. Coat. Technol., 70

, 886 (1998).

DK4036_C080.fm Page 4 Thursday, May 12, 2005 9:53 AM
© 2006 by Taylor & Francis Group, LLC

81

-1

81

Biocides for the

Coatings Industry

81.1 Introduction

81-

1
81.2 In-Can Preservatives

81-

1
81.3 Dry-Film Preservatives

81-

2
References

81-

3

81.1 Introduction

Microorganisms are ubiquitous in the environment. Many of them have simple requirements for growth
that can be met by most waterborne coatings. Adding an in-can preservative will protect these coatings
in the wet state during storage and transport. After a coating has been applied and dried, most waterborne
and solvent-borne coatings are susceptible to colonization by fungi or algae. The addition of a dry-film
preservative (fungicide or algaecide) will ensure long-term performance of the coating.

81.2 In-Can Preservatives

Industrial water-based formulations usually require protection against microbial spoilage. Examples of
such formulations include latexes, emulsions, paints, adhesives, caulks, and sealing mastics. Microbial
contaminants can be introduced by water (process water, wash water), raw materials (latex, fillers,
pigments, etc.), and poor plant hygiene. Bacteria are the most common spoilage organisms, but fungi
and yeasts are sometimes responsible for product deterioration. Among the most common contaminants
are

Aeromonas

sp.,

Bacillus

sp.,

Desulfovibrio

sp.,

Escherchia

sp.,

Enterobacter

sp., and

Pseudomonas

sp.
Microbial growth is usually manifested as a loss in functionality and may include gas formation, pH
changes, offensive odor, and changes in viscosity and color.

1

Spoilage of the water-based products, which
can go unnoticed until the product reaches the consumer, can result in significant economic loss to the
manufacturer. Good plant hygiene and manufacturing practices, when combined with the use of a
compatible broad spectrum biocide, will minimize the risk of microbial spoilage of the coating.

2


In selecting an in-can preservative, cost effectiveness, compatibility, stability, handling, and eco-toxicity
are important factors to take into account. Intrinsic properties of the coating, such as pH, viscosity, redox

potential, and the presence of certain ingredients may also affect the effectiveness of biocides. The best
way to determine the efficacy of a biocide in a specific formulation is by performing an in-can challenge
test. While there are several methodologies available to evaluate the efficacy of in-can preservatives,

3

they
all involve testing of preserved and unpreserved samples of the test coating when challenged with a battery
of microorganisms and then monitoring the samples for the presence of viable microorganisms and
changes in the coating properties. Typical use levels for in-can preservatives are in the range of 0.05 to
0.5 weight percent.

K. Winkowski

ISP Corp.

DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM
© 2006 by Taylor & Francis Group, LLC

82

-1

82

Clays

82.1 Kaolin

82-

1

82.2 Attapulgite

82-

3

82.3 Smectite

82-

5

Organoclays

References

82-

6
Clay is a general term used to describe minerals consisting mostly of hydrous aluminum silicates. Early
on, any particle that was submicron was considered clay. It was also thought that clay was a mixture of
amorphous materials with no definite composition. As described by Grim,

1

it was determined later on
that clay was properly defined by the clay mineral concept as being composed of extremely small

crystalline particles consisting mainly of hydrous aluminum silicates with substitution of aluminum by
magnesium, iron, alkalies, or alkaline earth elements.
Clays are used in many applications, such as in the manufacture of paper, ceramics, zeolites, catalysts,
plastics, rubber, absorbants, and paints. However, this discussion will pertain to the use of clays in paints
and inks. We will cover three main types of clays: kaolin, attapulgite, and smectite.

82.1 Kaolin

This type of clay consists mostly of hydrated alumino-silicate with a chemical formula Al

2

Si

2

O

5

(OH)

4

.
The particles have a platy structure and belong to the phylosilicate family. Under a microscope, it appears
as stacks of hexagonal platelets. It is crystalline in nature and occurs in nature as very fine particles. It is
formed by chemical modification of feldspar or mica. These minerals have some solubility in water, and
under certain geothermal conditions, they decompose to form kaolin with the removal of alkali and
alkaline earth and transition elements.

2


Kaolin can be broadly classified as primary or secondary. Primary kaolin deposits that are formed by
weathering consist of large amounts of impurities, mainly of quartz, feldspar, and mica. These deposits
are mainly found in Cornwall, England, and Saxony, Germany.
The percentage of kaolin present in these deposits is usually 15 to 20%. Secondary kaolin deposits
that have been transported by receding ocean water have relatively low amounts of impurities. These are
mainly found in the Southeastern United States and in the Amazon region of Brazil. Secondary kaolin
is usually less abrasive than primary kaolin.

Ashok Khokhani

Engelhard Corporation

Note:

Mattex, Satintone, ASP, and Attagel are registered trademarks of Engelhard Corporation. Bentone is a
registered trademark of Elementis. Claytone is a registered trademark of Southern Clay products. Tixogel is a
registered trademark of Süd-Chemie.

DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM
© 2006 by Taylor & Francis Group, LLC
Manufacturing • Kaolin Categories • Benefits of Kaolin Use in
Dispersion • Application in Paints
Paints • Applications of Kaolin in Paints

83

-1

83

Fluorocarbon Resins for

Coatings and Inks

83.1 General

83-

1
83.2 Poly(Vinylidene Fluoride) (PVDF) Resins
for Coatings

83-

2
83.3 Fluorinated Ethylene Vinyl Ether (FEVE) Resins
for Coatings

83-

3
83.4 Fluorinated Acrylics

83-

4

83.5 Other Fluorinated Resins for Coatings and Inks

83-

4
Bibliography

83-

5

83.1 General

The commercially important fluorocarbon resins are based upon a handful of fluorinated monomers, as
produced, especially when copolymerization with other, nonfluorinated monomers is a possibility.
Besides polytetrafluoroethylene (PTFE) “coatings” — which are prepared by a high temperature
sintering process and which are not considered in this chapter — the most widely used fluorocarbon
coatings are based on poly(vinylidene fluoride) (PVDF) homopolymer. Typical PVDF coatings require
a high temperature bake and are applied on primed metal substrates by a coil coating or spray
technique. They are commonly used in high-end architectural applications such as skyscraper curtain
walls and other wall panel systems, window profiles, and commercial and residential metal roofing.
The first commercial grade of PVDF for coatings, KYNAR 500

®

, was introduced in 1965 by the Pennsalt
Company. This same resin grade continues to be sold today by Arkema, Inc., under a worldwide
licensing program.
Another commercially important class of fluorocarbon resins, fluorinated ethylene vinyl ether (FEVE)
polymers, was introduced in the early 1980s by Asahi Glass, under the Lumiflon

®

trademark. FEVE
products continue to enjoy their greatest success in the Far East, especially for site-applied (air-dry)
applications such as industrial maintenance topcoats. Both PVDF and FEVE coatings combine superior
weatherability with excellent protective and barrier properties. They are, therefore, able to simultaneously
function as decorative and functional finishes.
Among the other types of fluorocarbon resins used in coatings, fluorinated acrylics are also used in
significant volumes and have a long history. They are chiefly used as surface treatment agents, for
applications where low surface energy is sought, e.g., for water and oil repellency.

Kurt A. Wood

Arkema, Inc.

DK4036_C083.fm Page 1 Thursday, May 12, 2005 9:54 AM
© 2006 by Taylor & Francis Group, LLC
indicated in Table 83.1. From these basic building blocks, a wide variety of polymer products can be

84

-1

84

High Temperature

Pigments

84.1 Introduction

84-

1
84.2 The Technology

84-

2

84.3 Pigment Types

84-

4

84.4 Pigment Properties

84-

5
84.5 Typical Applications

84-

6

Plastics

Bibliography

84-

8

84.1 Introduction

High temperature pigments can be defined as chemical substances that impart color to a substrate or
binder and retain their color and finish at elevated temperatures.
There are many everyday applications where consumers require aesthetically pleasing finishes, in the
latest fashion colors, that last. There are many diverse, high performance applications that require careful
pigment selection to ensure that the coloration is long-lasting; rarely will a consumer be aware of the
technological considerations that apply when designing such products.
Chemically, high temperature pigments are inorganic compounds. Although many chemical classes
potentially fall into this category, an important family of pigments is termed complex inorganic color
pigments (CICPs), otherwise known as mixed metal oxides (MMOs) or complex inorganic pigments
(CIPs). These pigments are heat stable to temperatures exceeding 1832

°

F (1000

°

C), suitable for the
majority of applications. High performance pigments also include cadmium pigments, able to withstand
temperatures of up to 752

°

F (400

°

C), and bismuth vanadate pigments, with heat stability of up to 392

°

F
(200

°

C). These pigments exhibit excellent color properties but will not be covered in this review.
There are two distinct classes of CICPs, similar in chemistry but differentiated by end market and by
particle size; pigment-grade for plastics, surface coatings, building materials, and glass applications, and
ceramic-grade for ceramic applications.
It is interesting to note that some colors are more heat stable than others. For example, black is a
strong absorber of infrared (IR) radiation and therefore retains heat. Hence, black pigments and dark
colors require better heat stability than lighter colors or pastel shades.
Recent technology advances include pigments that provide color and functionality by building in the
ability to reflect IR rays away from the substrate or binder, and hence, lowering the heat buildup and
prolonging the lifetime of the product. These products are promoted by Energy Star for their benefit to
the environment in terms of energy-saving initiatives.

Helen Hatcher

Rockwood Pigments

DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM
© 2006 by Taylor & Francis Group, LLC
Color Mechanism • Chemical Structure • Production Methods
Rutile Pigments • Spinel Pigments • Zircon Stains
Surface Coatings • Ceramics • Building Materials • Glass •

High Temperature Pigments

84

-3

(1400

°

C). Intimate raw material mixtures are produced by wet milling techniques to ensure that all
components are finely divided. The surfaces of grain boundaries are often coated to achieve the best
reaction. Mineralizers can be used to aid the rate of reaction to ensure completion with minimum heat
work; these are frequently used when producing zircon pigments.
The calcination process can be a batch process, loading the pigment manually into refractory saggars
and firing in intermittent kilns, or it can be a continuous process using state-of-the-art rotary firing
techniques.
The pigments have developed their full color during firing but are refined by milling to the required
particle size, dependent on the application. Pigments for surface coatings, plastic, and glass applications
are usually designed with a fine particle size and a narrow particle size distribution, for maximum tinting
strength; conversely, pigments for ceramic applications tend to be coarser, with a wider size distribution,
for maximum masstone color strength.

TA BLE 84.1

Crystal Structure Types

Crystal
Structure
Typical
Formula
Typical
Pigment Type
Coloring
Metal Color

Rutile MO

2

(Ni,Sb,Ti)O

2

Ni Yellow
Spinel M

3

O

4

(Co,Zn)Al

2

O

4

Co Blue
Zircon M

2

O

4

(V,Zr)SiO

4

VTurquoise
Hematite M

2

O

3

(Fe,Cr)

2

O

3

Fe/Cr Black/Brown
Cassiterite M

2

O

3

(Co,Zn)SiO

3

Co Blue

FIGURE 84.2

Crystal structure types.

FIGURE 84.3

Saggar firing.
Rutile Spinel

DK4036_book.fm Page 3 Monday, April 25, 2005 12:18 PM
© 2006 by Taylor & Francis Group, LLC

85

-1

85

Polyurethane
Associative Thickeners

for Waterborne Coatings

85.1 Introduction

85-

1
85.2 Chemical Structure and Thickening Mechanism

85-

2

85.3 Flow Behavior and Related Properties Given by
PEUPU Thickeners

85-

3
85.4 Factors Affecting Thickener Efficiency

85-

4

85.5 Delivery Form and Incorporation

85-

6
85.6 Examples of Applications

85-

6
85.7

References

85-

7

85.1 Introduction

Rheological additives are widely used in the coatings industry to provide ideal flow behavior. They control
sag, leveling, penetration, and application properties along with many other fundamental coating char-

acteristics. A large range of different rheological additives like cellulose ether derivatives, natural gums,
alkali swellable emulsions, and clays is available. Newer polymeric materials — the polyether urea
polyurethane thickeners (PEUPUs) — are very important for modern high-quality finishes. These are
also known as urethane associative thickeners (UATs), polyether polyurethanes (PEPUs) or hydrophobi-
cally modified ethoxylated urethanes (HEURs).
PEUPUs are purely associative thickeners and behave totally differently from the more traditional
products. They are used in both industrial and decorative systems and can be applied with a wide variety
of techniques including spraying, rolling, and brushing. PEUPUs are used either alone or in combination
with other rheological additives depending on the precise flow and other coating characteristics required.
They are available as solids or suspensions of different concentrations. Although originally developed as
leveling agents, they have been modified significantly, and the flow they impart varies from strongly shear-
thinning to nearly Newtonian. These are the additives that give “solventborne” flow to “waterborne” paints.
The many benefits they bring to an application arise from their unique structuring mechanism. They
offer a good balance of flow and leveling, excellent gloss characteristics, ease of handling, good brush-
resistance and film-build and excellent roller-spatter resistance.

1,2,3,4

As they are nonionic polymers, their
function is also relatively pH independent.
However, the efficiency and performance of PEUPU thickeners is highly system dependent; also because
of the associative structuring mechanism. Several factors influence this: in particular, the cosolvents used,

Douglas N. Smith

Waterborne Coatings–Global
Elementis GmbH

Detlef van Peij

Solventborne Coatings–Europe
Elementis GmbH

DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM
© 2006 by Taylor & Francis Group, LLC
Structure • Thickening Mechanism
Influence of Cosolvents • Influence of Surfactants and Emulsion
Summary
85-7
Stabilizers • Influence of Latex Particle Size