LANXESS-Laux brochure english - BAYFERROX...4 The basic reaction in the Laux process, i.e. the reaction of ni-trobenzene with cast iron, is extremely exothermic. After vari-ous process

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Inorganic pigments

using the Laux process

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The LANXESS pigments business has been committed for many years to sustainable production processes as one of its core competencies. The Laux process in Krefeld-Uerdingen �� -duction method for iron oxide pigments.

The method is exemplary in that it fully exploits the heat pro-duced by the chemical reaction to generate steam and hot wa-��

The Laux process is the key to the special properties of LANXESS’s yellow, black and red shades. Particularly with the reds, a very broad range of hues can be produced, from reds with a yellow to reds with a blue undertone. The red shades with a blue undertone are quite unique compared with other iron oxide reds available on the market because they display only a slight color shift even under intense milling conditions.

�� -trobenzene with metallic iron to aniline and iron oxides, was implemented on an industrial scale as far back as 1911 at the Krefeld-Uerdingen site. While the aniline was needed to

manufacture dyestuffs, the iron oxide byprod-uct could not be put to �� 1914 to use the resulting iron oxide as a colorant, but the quality of the iron oxide was not adequate for pigment appli-cations. It took another eleven years before Dr. Laux, a chem-ist, succeeded in optimizing the process and obtaining iron � ��!��"�� #��1926, one year after its discovery, iron oxide production was launched in Krefeld.

Since then, iron oxide production at the Krefeld plant has un-dergone remarkable development. After starting out with a ca-pacity of roughly 1,000 metric tons in 1926, production has steadily increased. At present, 280,000 metric tons of iron oxide pigment are produced at the plant, two-thirds of that by the Laux process. In other words, LANXESS operates the world’s largest production plant for synthetic iron oxide pig-ments in Krefeld.

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Fig. 1: Basic patenton the Laux process

In the Laux process, nitrobenzene is reacted with cast iron borings. Depending on the reaction conditions and the control chemicals, a suspension of black or yellow iron oxide results, which subsequently is washed, concentrated and dried. Red

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pigments cannot be obtained directly by these means; they are produced by subsequent calcining of the black paste un-der oxidative conditions.

Nitrobenzene Cast iron

Reaction Aniline

Fe3O4

BlackFeO(OH)

Yellow

Reaction

Fe2O3

RedMixtureBrown

2 Fe + C6H5 - NO2 + 2 H2O

2 FeO(OH) + C6H5 - NH2

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9 Fe + 4 C6H5 - NO2 + 4 H2O

3 Fe3O4 + 4 C6H5 - NH2

��

2 Fe3O4 + 0,5 O2

3 Fe2O3

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Fig. 2: Diagram of the Laux process

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The basic reaction in the Laux process, i.e. the reaction of ni-trobenzene with cast iron, is extremely exothermic. After vari-ous process and plant optimizations, LANXESS has succeed-ed in exploiting virtually all the heat of reaction to produce hot water and steam for use in downstream processing steps. This

reduces primary energy demand by 28 % and cooling water output by as much as 56 %, making the Laux process one of the most ecologically compatible and resource-conserving processes for the production of iron oxide pigments.

One raw material in the Laux process is nitrobenzene, ob-tained by the nitration of benzene with nitric acid. The second raw material, cast iron borings, is a byproduct from the ma-chining of cast iron parts in various industries, such as auto-motive manufacturing.

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Pigment properties

��!��In the Laux process, all three basic iron oxide colors - red, yel-low and black - are available in a relatively broad color spec-trum. Due to the scattering power of iron oxides, the particle size has a direct influence on the shade.

RedWhen it comes to red, the smaller the particles, the more pro-nounced the yellow undertone, while larger particles produce more of a blue undertone. The difference in prevailing particle size spans a rather wide range, from 0.09 μm for Bayferrox® 105 M to 0.7 μm for Bayferrox® 180 M.

One unique advantage of the Laux process is its ability to produce red shades with a blue undertone. Significant differ-ences exist in this area between the Laux process and others, because the other manufacturing processes have difficulty ob-taining the required particle sizes.

BlackIn the case of black, the shade of the pigment likewise depends on the size of the primary particles, ranging from the bluish Bayferrox® 306 to the high-tinting-strength Bayferrox® 330. $�� &�� "�� size. The larger the primary particles, the bluer the undertone of the shade. However, this effect is obtained at the cost of tinting ��

Fig. 3: The Laux process produces red pigments with a bluish undertone that set it apart from other processes.

Bayferrox® 110 M Bayferrox® 140 M Bayferrox® 180 M

Bayferrox® 318 Bayferrox® 306

Particle size IncreasingTinting strength DecreasingShade Brownish Bluish

Fig. 4: Particle size affectsthe shade.

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YellowWith yellow, the range of shades achieved in pigments manu-factured by the Laux process is narrower. By selecting the right raw materials, the Laux process also can produce yel-low pigments that nearly rival precipitated pigments. Bayfer-rox® 3420 is the micronized version of Bayferrox® 420 and frequently selected as an alternative to precipitated yellow in paint and coating applications. The yellow grade, Bayferrox 415, is mainly used to color building materials on account of its darker, bluer shade.

��"��Iron oxide pigments are lightfast thanks to their chemical and physical properties. In practical pigment applications, however, the interface between pigment and binder is a critical factor, this being particularly evident in coloring laminates yellow. A distinct difference in color shift can be observed when using a yellow iron oxide pigment produced by the precipitation process (Bay-ferrox® 920), one by the Laux process (Bayferrox® 420) and a post-treated yellow pigment (Colortherm® Yellow 10).

UV radiation at the interface of the pigment/binder matrix pre-sumably leads to partial reduction of the resin, expressed by a green shift. This may be attributable to catalytic effects. In the

case of Colortherm® Yellow 10, the inorganic post-treatment �� -ening catalytic degradation and greatly reducing color shift.

Fig. 5: Differences in lightfastness

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Bayferrox® 920 Std‘03 Bayferrox® 420 Std‘99 Colortherm® Yellow 10

'E*ab

Lightfastness of Bayferrox® 920, 420 and Colortherm® 10(Blue Wool Scale, level 8)

Test conditions: Xenotest 150 S/ca. 160 h until wool sample 8 fades

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0

1

2

3

4

5

6

200 °C 220 °C 240 °C 260 °C 280 °C 300 °C 320 °C

#$

%��

Limit to DIN-EN 12877 Part 2

Colortherm® Red 110MPrecipitated Red

��&�� !�"��'�$(to DIN-EN 12877-2 Method B)

(��!��)�

Laminates increasingly are used in outdoor applications, a trend that tightens quality requirements on the lightfastness of the decorative papers.

(��!��In terms of temperature stability, Laux pigments again offer dis-tinct advantages over precipitated iron oxide pigments.

Although red as hematite (Fe2O

3) is heat-stable thanks to its

chemical structure, the various iron oxide reds nevertheless display remarkable differences attributable to the production process.

The red iron oxide pigments produced by the Laux process are heated to as high as 800 °C during calcining and therefore characterized by high temperature stability. Thermal stability is of particular importance in coloring plastics, because the elevat-��less color change versus red precipitated pigments.

Fig. 6: Thermal stability of various red pigments

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In contrast to Laux red pigments, precipitated red iron oxide pigments often have some water bound in the crystal lattice, which evaporates at high temperatures. This results in a de-crease in weight and a change in shade.

Similarly, Laux yellow pigments are more stable than precipitated products because of the manufacturing process. The post-treated Laux products Colortherm® Yellow 10 and Colortherm® Yellow 20 are particularly stable.

#$

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�� '�$(to DIN-EN 12877-2 Method B)

(��!��)�

0

4

8

12

16

2

6

10

14

18

200 220 240 260 280 300

Bayferrox® 420

Colortherm® Yellow 20

Bayferrox® 920

Max. level according to the European standard

Fig. 7: Moisture content and color change as a function of temperature

100 °C 500 °C

Calcined red: Decrease in weight: 0.11 % '<= = 0.1

Decrease in weight: 0.31 % '<= = 0.3

Calcined red, yellowish:



Precipitated red: Decrease in weight: 0.33 % '<= = 0.2


Precipitated red, yellowish:


Gewichtsverlust: 2.57 % '<= = 3.5

Fig. 8: Thermal stability of various yellow pigments

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The very strong shear forces prevailing in concrete applications bring out the advantages of Laux pigments. Even Bayferrox® 130 shows better color consistency in the application than a precipitated red iron oxide pigment. The darker the shade, the more pronounced the difference.

*��Because of the needle structure of yellow iron oxide pig-ments, their viscosity behavior is a very critical parameter. In general, the more pronounced the needle structure, the more problematic the viscosity behavior.

Dispersing time

#�%

Pigment comparison:+��"��-.��#�%�/!�� ;<(Olbrich shaker: Binder: Alkydal F48, PVC 10%)

0

2

4

6

8

10

1

3

5

7

9

10“ Dissolver 5“ Shaking 15“ Shaking 30“ Shaking 60“ Shaking

Calcined redPrecipitated red

�� to strong shear forces

+��"��Sintering occurs during the calcining step of the Laux process, with the primary particles forming larger agglomerates. These are hard and must be broken up by intensive milling to ensure good dispersibility in the end application.

As a result, Laux reds are much more stable than precipitated red pigments when exposed to any additional milling or other high shear forces in a customer application. For instance, the shade of Laux red pigments changes much less during bead milling than that of precipitated red pigments. The bluer the undertone of the red pigment, the more pronounced the differ-ence between these two production processes.

Fig. 10: Prismatic particle structures are characterized by low viscosity

Bayferrox® 420 Bayferrox® 415

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Compared to the distinct needle shape of Bayferrox® 420, the primary particles in Bayferrox® 415 are more prismatic. Pigment preparations of Bayferrox® 415 therefore have a sig-nificantly lower viscosity than those of Bayferrox® 420, a prop-erty that becomes most evident in pigment suspensions for the building industry. Bayferrox® 415 permits a significantly higher solids content.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Shear rate [1/s]

Vis

cosi

ty [

P a*

s]

Viscosity in universal paste after production

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Bayferrox® 420 Std. 99

Bayferrox® 415 Std. 83

Fig. 11: Viscosity in universal paste after production

For concrete manufacturers, it is important to minimize the influence of a color pigment on the consistency of the concrete as much as possible, because more water other-wise may have to be added to achieve the same workability. More water, however, translates into lower concrete strength. Yellow Laux pigments therefore have less of an influence on concrete consistency than yellow pigments produced by other methods.

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Bayferrox®

105 M A red shade with a yellow undertone for the paint and coatings industry110 (M)

The shade exhibits an increasingly blue undertone as the number increases

120 N(M)120 (M)130 (M)130 B(M)140 (M)160 (M)180 N(M)180 (M) A red shade with a blue undertone for the paint and coatings industry

?�� !�"��$��@A

Bayferrox®

415 Low-viscosity yellow pigment primarily for the building materials industry420 Standard yellow pigment 3420 Micronized variant of Bayferrox 420

?�� !�"��E�F

Bayferrox®

306 Black shade with a blue undertone 316318318 M Iron oxide black for the paint and coatings industry320 Black pigment for the building materials industry330 Very high-tinting-strength black pigment for the building materials industry340 Black pigment for the building materials industry

��G��H� �� !�"��

Colortherm®

Yellow 10 Heat-stabilized yellow pigment for the paint and coatings industryYellow 20 ?��"��!��@��JBlack 318 Heat-stabilized black pigment with high tinting strength for all common plastics applications

Health and Safety Information: Appropriate literature has

been assembled which provides information concerning

the health and safety precautions that must be observed

when handling the LANXESS products mentioned in

this publication. For materials mentioned which are not

LANXESS products, appropriate industrial hygiene and

other safety precautions recommended by their manu-

facturers should be followed. Before working with any of

these products, you must read and become familiar with

the available information on their hazards, proper use

and handling. This cannot be overemphasized. Informa-

tion is available in several forms, e.g., material safety data

sheets, product informa-tion and product labels. Consult

your LANXESS representative in Germany or contact

the Regulatory Affairs and Product Safety Department of

LANXESS Germany or – for business in the USA – the

LANXESS Product Safety and Regulatory Affairs Depart-

ment in Pittsburgh, Pennsylvania.

Regulatory Compliance Information: Some of the end

uses of the products described in this publication must

comply with applicable regulations, such as the FDA,

BfR, NSF, USDA, and CPSC. If you have any questions

on the regulatory status of these products, please con-

sult your LANXESS representative in Germany or contact

the Regulatory Affairs and Product Safety Department of

LANXESS Germany or – for business in the USA – your

LANXESS Corporation representative, the LANXESS

Regulatory Affairs Manager in Pittsburgh, Pennsylvania.

The manner in which you use and the purpose to which

you put and utilize our products, technical assistance and

information (whether verbal, written or by way of produc-

tion evaluations), including any suggested formulations

and recommendations are beyond our control. There-

fore, it is imperative that you test our products, technical

assistance and information to determine to your own

satisfaction whether they are suitable for your intended

��

must at least include testing to determine suitability from

a technical as well as health, safety, and environmental

standpoint. Such testing has not necessarily been done

by us. Unless we otherwise agree in writing, all products

are sold strictly pursuant to the terms of our General Con-

ditions of Sale and Delivery. All information and technical

assis-tance is given without guarantee and is subject to

change without notice. It is expressly understood and

agreed that you assume and hereby expressly release us

from all liability, in tort, contract or otherwise, incurred in

connection with the use of our products, technical assis-

tance, and information.

Any statement or recommendation not contained in this

brochure is unauthorized and shall not bind us. Nothing

herein shall be construed as a recommendation to use

��&��

as patents covering any material or its use. No license is

implied or in fact granted under the claims of industrial

property rights such as patents. Edition 11/2011

LANXESS Deutschland GmbHBusiness UnitInorganic Pigments47812 KrefeldGERMANYTel.: +49 2151 88-8814Fax: +49 2151 88-8090

www.lanxess.comwww.bayferrox.comwww.colortherm.com

Bayferrox® is a registered trademark of Bayer AG, Leverkusen, Germany.

Colortherm® is a registered trademark of the LANXESS Group, Leverkusen, Germany.

Documents

LANXESS-Laux brochure english - BAYFERROX...4 The basic reaction in the Laux process, i.e. the reaction of ni-trobenzene with cast iron, is extremely exothermic. After vari-ous process