Next Generation of TiO2 Pigments. Project RC-8828: Titanium Dioxide Grade with Superior+ Durability, High Hiding Power, Excellent Dispersibility and High Initial Gloss

Next Generation of TiO2 Pigments. Project RC-8828: Titanium Dioxide Grade with Superior+ Durability, High Hiding

Power, Excellent Dispersibility and High Initial Gloss.

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12th International Scientific-Technical Conference ACT'16, 8-10 November 2016, Sosnowiec, Poland -

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All titanium dioxide technologies in one place

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Next Generation of TiO2 Pigments. Project RC-8828: Titanium Dioxide Grade with Superior+

Durability, High Hiding Power, Excellent Dispersibility and High Initial Gloss.

Authors:

Andriy Gonchar, Co-Founder, Director of RD Titan Group, TOV

Viktor Troshchylo, Co-Founder, Technical Director of RD Titan Group, TOV

Abstract

The paper examines the antagonism between the key titanium dioxide pigments properties, such as

Durability, Hiding Power, Dispersibility, Initial Gloss. The paper contains a brief history overview of

TiO2 pigments, designed for applications where High and Superior Durability is needed. In the context

of Project RC-8828, developed by RD Titan Group, TOV company (approximately, the research on this

project will be finished in 2018-2019) the expected characteristics of the next generation Titanium

Dioxide Grade are presented; this grade combines antagonistic properties: Superior+ Durability, High

Hiding Power, Excellent Dispersibility and High Initial Gloss. Also the paper considers some problems

of industrial implementation of the new generation pigments, related both to the development of

appropriate technologies, and economic aspects of the commercialization of these technologies.

____________________

Titanium dioxide is an almost perfect white pigment among the materials known at the present time.

Actually, this is the only material that combines high pigment properties, wide occurrence of raw

materials for its production in nature and relative cheapness. The following parameters make titanium

dioxide unsurpassed material for pigmentation:

• The highest refraction index among known transparent materials;

• Whiteness is almost close to 100%;

• Low color tone;

• Wide occurrence of titanium raw materials in nature;

• Availability of well-proven and well-optimized titanium dioxide production technologies

(Sulfate and Chloride Processes), as well as the prospect of the new technology

commercialization (Hydrochloride-Organic Extraction Process);

• Relative cheapness.

Thus, alternatives to replace titanium dioxide as a white pigment are not expected in the next few

decades.

However, there is something that greatly limits the possibility of using titanium dioxide – it is its

photocatalytic activity. Titanium dioxide is a semiconductor and absorbs the UV portion of the

electromagnetic radiation.

The Mechanism of Photocatalytic Activity.

Of the two commercially used crystal modifications Rutile titanium dioxide as compared to Anatase

has higher scattering properties, which caused its wider use as a white pigment. The second reason is its

lower photocatalytic activity as compared to the Anatase modification. The point is that titanium dioxide

crystals of both Anatase and rutile modifications are semiconductors, which means that the introduction

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of certain energy forces titanium dioxide to conduct electric current. As it turns out, it is of the essence

for titanium dioxide pigment, since this energy can be introduced as a result of the absorption of photons

of electromagnetic radiation with a certain wavelength, which further leads to a series of consecutive

processes that significantly affect the durability of paint coatings or plastics.

Flow chart of photochemical reactions chain is shown in Picture 1.

Picture 1. Flow chart of photochemical reactions in TiO2 crystal (Anatase)1.

There are five steps of paint coating destruction cycle2.

Step 1. Absorption of a photon of electromagnetic

radiation with an energy that may lead to the excitation of

an electron in the valence band (VB) and its transition to

the conduction band (CB), in which electrons behave

similarly to electrons in metals, i.e. move freely, including

directionally under the influence. At the same time the

valence band still has a positively charged hole. A special

feature of this state is that the electron-hole pairs like

particles are able to move in the crystal. This excitation

state which is able to migrate in the crystal is called an

exciton and considered as a quasiparticle.

(Step 1) TiO2 + hv ↔ TiO2 (e- + p+)

Step 2. If the exciton is not annihilated and reaches the surface of the titanium dioxide particle on

which hydroxyl-ions are usually adsorbed, the hydroxyl-ion is oxidized to form a hydroxyl radical:

(Step 2) p+ + OH- ↔ •OH

The hydroxyl radicals are highly reactive and easily attack the polymer molecules (molecules of

binders in paint coatings or molecules of plastic). Typically, this initially leads to the separation of

hydrogen radicals from the polymer to form H2O and a polymer radical R•. The radical R• is further

reacted, e.g., with oxygen atoms to form peroxide radicals R-О-О•, or is decomposed forming other

radicals (R• → R1• + R2•).

Step 3. Because of the annihilation of the hole and the hydroxyl radical electron, an extra electron

still remains in the conduction band. When returning to the valence band it reduces Ti4+ to Ti3+.

(Step 3) Ti4+ + e- ↔ Ti3+

Step 4. At this stage the Ti3+ cation may be oxidized by the oxygen molecule, which is already

present on the surface or readsorbed to form a superoxide radical •O2-.

1 This figure is taken from Semiconductor/biomolecular composites for solar energy applications. Chuanhao Li, Feng Wang

and Jimmy C. Yu Energy Environ. Sci., 2011,4, 100-113 2 Jochen Winkler, Titanium Dioxide: Production, Properties and Effective Usage. Hanover: Vincentz Network, 2013, pp. 83-

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(Step 4) Ti3+ + O2 ↔ Ti4+ + •O2-

Step 5. This step is only possible in the presence of moisture, which is normal in most cases. At this

stage, a hydroperoxide radical is formed on reaction of •O2- with a water molecule, and also the presence

of OH-group extracted at Step 2 is restored.

(Step 5) Ti4+ + •O2- +H2O ↔ Ti4+ + OH- + •O2H

The resulting reaction of all five steps may be written in the following way:

TiO2+hv

H2O + O2 ----------→ •OH + •O2H

Actually, the two radicals •OH and •O2H are responsible for the destruction of paint coating binders

or molecules of plastics.

Ways to Eliminate Negative Effects of TiO2 Photocatalytic Activity.

There are several ways to eliminate negative effects of titanium dioxide photocatalytic activity:

• Coating the surface of titanium dioxide particles with dense dielectric layer to prevent the charge

transfer from TiO2 surface to the binder molecule. • SiO2

• Phosphates of some metals

• Coating the surface of titanium dioxide particles with materials, providing the capture of TiO2

photocatalytic activity products (•OH, •O2-, •O2H radicals) and their subsequent mutual

annihilation.

• Metal oxides / hydroxides, e.g., Zr

• Phosphates of some metals

• Doping of TiO2 lattice with atoms of other elements to create traps for excitons (migrating

electron-hole pairs within the crystal) with a view to reduce the number of excitons reaching the

surface of titanium dioxide particles.

• Introducing inhibitors to pigments to prevent the formation of Ti3+.

Antagonism of Pigment Properties.

Attempts to improve pigment weather resistance are not harmless to other key pigment properties:

using a variety of approaches to improve Durability has worsened to a greater or lesser degree some

other pigment properties, and vice versa, with the improvement of some important pigment properties

Durability deterioration is observed. Infogram 1 shows data dependencies.

As it follows from the infogram, some improved properties, such as Initial Gloss, can lead to

deterioration of other properties, e.g., Resistance to Photocatalytic Activity, but at the same time, for

example, improving UV Screening. UV Screening improvement affects the increase of Durability due to











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the screening effect, particularly in those systems that use resins with low or middle UV resistance.

However, photocatalytic activity increase, on the contrary, reduces Durability, particularly in the

systems that use resins with high UV resistance. As a result, pigment Durability can be different for

different systems depending on UV resistance of resins to be used: for systems using resins with low or

middle UV resistance one may well experience increased Durability, and for systems using resins with

high UV resistance - reduced Durability.

Infogram 1. Antagonism of Some Titanium Dioxide Pigment Properties.

Durable TiO2 Timeline.

Infogram 2 and Tables 1 and 2 show the system of rutile titanium dioxide grades classification

according to their types3.

Infogram 2. Classification of Rutile Titanium Dioxide Grades According to Their Types.

3Hereinafter is the classification of titanium dioxide grades by type as it is accepted in the RD Titan Group Innovative TiO2

publication “Comprehensive Dossier of the World's Titanium Dioxide Grades and TiO2 Manufacturers. Year 2016” -

http://innovativetio2.com/dossier/





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Table 1. Classification of Rutile Titanium Dioxide Grades According to Their Types:

Paint&Coatings Application.

TiO2

Grade

Type

Typical

TiO2Content

(%)

Inorganic

Surface

Treatment

Applications

P&C Type 1 94-96 Al Electrodeposition paints*, Automotive (Primers),

Can Coatings, Coil Coatings,

Water-borne and Solvent-borne Industrial and

Decorative Coatings, Wood Paints

P&C Type 2 92-94 Al, Si Water-borne and Solvent-borne Industrial and

Decorative Coatings

P&C Type 3 80-86 Al, Si Highly pigmented emulsion paints, Exterior and

interior trade sales paints, Paper filler and

coating applications, Wallpaper coatings, Flat

flexographic inks

P&C Type 4 94-96 Al Printing Inks, Can Coatings, Coil Coatings,

Wood Paints, Water-born or solvent-born

coatings with very high gloss

P&C Type 5 92-95 Al, Zr,

(sometimes

+Si)

Automotive finishes and Refinishes,

Coil Coatings, Powder coatings, Marine Coatings,

Water-born or solvent-born coatings

P&C Type 6

(Subtype A)

89-91 Al, Si Exterior Coatings, Automotive Finishes and

Refinishes, Coil Coatings, Powder Coatings,

Marine Coatings, Aerospace Coatings

P&C Type 6

(Subtype B)

92-93 Al, Si Exterior Coatings, Automotive Finishes and

Refinishes, Coil Coatings, Powder Coatings,

Marine Coatings, Aerospace Coatings











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Table 2. Classification of Rutile Titanium Dioxide Grades According to Their Types: Plastics and

Décor Paper Applications.

TiO2

Grade

Type

Typical

TiO2Content

(%)

Inorganic

Surface

Treatment

Applications

Plastic Type

1

97-98 Al

(+hydrophobic

surface

treatment)

Polyolefin Masterbatch, Flexible PVC (interior),

High Temperature Cast Films, Thin Films, PVC-

plastisols

Plastic Type

2

95-96 Al

(+hydrophobic

surface

treatment)

Polyolefin Masterbatch, Polyethylene,

Polypropylene, PVC (Interior), PVC (Exterior,

Chalking), PVC Pipe, ABS, Polycarbonate,

Polystyrene, Polyamide

Plastic Type

3

91-93 Al, Si or

sometimes Zr

(+hydrophobic

surface

treatment)

PVC and polyolefines (Exterior, Nonchalking),

Agricultural Films, Outdoor Furniture, PVC-

Windows sections

DP Type 1 87-90 Al, P

compounds

High and Low Pressure Laminate, Printing Inks

for Décor Paper, Melamine moulding powders

One of the first technologies to improve the durability of titanium dioxide in modern practice (since

the mid-1960s) was to coat titanium dioxide particles with dense dielectric layer, in particular, dense

SiO2 (P&C Type 6 [Subtype A]). The following benefits were achieved through that innovative

technology:

• Significant reduction of pigment photocatalytic activity;

• Superior durability when using binders having middle and high resistance to UV.

At the same time, compared to pigments with middle durability (for example, P & C Type 1), this

type has the following shortcomings:

• Deterioration of dispersibility;

• Initial gloss reduction;

• Low efficiency when using binders having low resistance to UV;

• Hiding power reduction;

• Tendency to yellow undertone (CBU).











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Due to the shortcomings of P&C Type 6 (Subtype A), in the 1980s some efforts were made to

develop the type of pigments that would have sufficiently high durability and no drawbacks of Type 6

(Subtype A). As a result of this work pigments surface-treated with a layer of zirconium oxides /

hydroxides and other treatment chemicals were developed (P&C Type 5).

The advantages of P&C Type 5:

• High durability when using binders having middle and high resistance to UV;

• High durability when using binders having low resistance to UV.

• High initial gloss;

• Neutral or blue undertone (CBU)

• High hiding power.

The drawbacks of P&C Type 5:

• Failure to reach the level of Superior Durability (in comparison to Type 6 [Subtype

A]).

Diagram 1. Properties of P&C Type 6 (Subtype A).

In the 1990s, a number of Western companies developed technologies of uniform coating with dense

SiO2, due to which they managed to reduce the amount of silica used for surface treatment (3-3,5% vs

4,5-7% ) in comparison to P&C Type 6 (Subtype A) and to increase the TiO2 content (92,5-93% vs 88-

91%), as well as to improve dispersibility and initial gloss. As a result, a new type of pigments came

into the market (P&C Type 6 [Subtype B]).











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Diagram 2. Properties of P&C Type 5.

The advantages of the new type of pigments:

• Superior durability when using binders having middle and high resistance to UV;

• High efficiency when using binders having low resistance to UV.

• High initial gloss;

• Neutral or blue undertone (CBU)

• High hiding power.

The drawbacks of P&C Type 6 (Subtype B):

• Slightly inferior to the level of durability in comparison to pigments of Type 6

[Subtype A] with 6-7% level of SiO2 treatment

• Slightly inferior to the hiding power in comparison to pigments of P&C Type 1.

Diagram 3. Properties of P&C Type 6 (Subtype B).











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Achievements of RD Titan Group Innovative TiO2 in the Development of Durable TiO2 Grades.

We, RD Titan Group Innovative TiO24, spent a lot of years to develop High Durable and Super

Durable TiO2 pigment grades. We have developed P&C Type 55 and P&C Type 6 (Subtype B)6 grades

production technologies and offer them on the market at the present time. We also work with two

separate areas:

• Plastics: the technology for Super Durable Plastic Type 37 production;

• Décor Paper: the technology for Lightfastness DP Type 18.

Thus, the RD Titan Group Innovative TiO2 portfolio has all state-of-the-art technologies for the

production of Durable TiO2 grades for different applications.

Next Generation of TiO2 Pigments. Project RC-8828.

Last few years we focused on research to develop a new generation of TiO2 pigments with improved

pigment properties and new level of Durability. One of such projects is the development of the pigment

grade production technology under the conventional name RC-8828. This pigment is a continuation of

Super Durable pigments line. The minimum task is to eliminate the shortcomings of P&C Type 5, P&C

Type 6 (Subtypes A, B) pigments. The maximum task is to obtain the pigment with improved

properties, which the pigments of P&C Type 5, P&C Type 6 (Subtypes A, B) do not possess. Infogram

3 shows the diagram of primary efforts for the development of RC-8828 grade production technology.

4 RD Titan Group Innovative TiO2 is the subsidiary startup of the registered company RD Titan Group, TOV. 5 «Technology package for manufacturing of special high durable TiO2 grade with high initial gloss RC-54 for Paint &

Coatings application» by RD Titan Group Innovative TiO2. 6«Technology package for manufacturing of special super durable TiO2 grade with high initial gloss RC-74 for Paint &

Coatings application» by RD Titan Group Innovative TiO2. 7 «Technology package for manufacturing of special super durable TiO2 grade RP-72 for Plastic application» by RD Titan

Group Innovative TiO2. 8 «Technology package for manufacturing of special lightfastness TiO2 grade RL-96 for Décor Paper application» by RD

Titan Group Innovative TiO2.











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Infogram 3. Primary Efforts for the Development of Project RC-8828.

The objective of this project is to provide the pigment of a new type, which will overcome the

antagonism of some key pigment properties. For example, the pigment will combine super high

resistance to photocatalytic activity and high UV screening, which will provide Superior+ Durability

(higher than that of P&C Type 5, P&C Type 6 (Subtypes A, B) pigments, irrespective of UV-resistance

of resins to be used). Thus, pigmentary properties such as Hiding Power and Initial Gloss will be similar

to or even higher than the levels of P&C Type 1 pigments. Diagram 4 shows the properties of RC-8828

grade as compared to some other titanium dioxide types: P&C Type 1, P&C Type 5, P&C Type 6

(Subtypes A, B).

By now our researchers have made significant progress towards the improvement of Durability in

Project RC-8828:

• Reduction of TiO2 lattice photocatalytic activity as a result of a special doping technology;

• Improved Resistance to Photocatalitic Activity as a result of super dense surface treatment with

impermeable SiO2 layer.

Picture 2 shows the results of uncoated TiO2 Calciner Discharge exposure to UV in the so-called

‘lead test’, based on the reduction of metal lead from oxides, hydroxides or salts in the process of

photocatalysis. The more photochemically active the sample, the greater amount of metallic lead is

formed, the greyer the sample becomes. Sample 1 is an experimental sample of Project RC-8828

Calciner Discharge. According to the measurement results photocatalytic activity of Sample 1 is reduced

by 5-6 times compared to other samples.











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Diagram 4. RC-8828 Properties.

• New level of Durability: +10÷15%; • Increased Hiding Power: +5÷10%; • Superior Initial Gloss: similar to P&C Type 1; • Strong blue undertone (CBU): similar to P&C Type 1 or even P&C Type 4; • Equilibrium of properties; • Greater versatility.

Table 3 shows the results of the ‘acid test’ - the procedure of titanium dioxide dissolution in the

concentrated sulfuric acid at a temperature of 175°C to evaluate the completeness of titanium dioxide

coating with a SiO2 layer (silica is not dissolved in hot sulfuric acid, as opposed to titanium dioxide).

The more uniform and dense the SiO2 layer coating titanium dioxide particles, the less is the degree of

pigment dissolution during the test.

At the moment, we have achieved more than twice the better effect for Project RC-8828 in

comparison with one of the best P&C Type 6 (Subtype B) representatives – Grade ‘E’.

Research on Project RC-8828 is continuing. Project RC-8828 research completion date is

approximately 2018-2019 yrs.











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Picture 2. Behavior of Different TiO2 Calciner Discharge Samples in the ‘Lead Test’

1 – Calciner Discharge with reduced photocatalytic activity, Project RC-8828. 2 -

Calciner Discharge No.1, a European manufacturer ‘А’. 3 - Calciner Discharge No.2, a

European manufacturer ‘А’. 4 - Calciner Discharge, a Chinese manufacturer ‘B’,

belonging to Top-15 Chinese TiO2 Manufacturers. 5 - Calciner Discharge, a Chinese

manufacturer ‘С’, belonging to Top-5 Chinese TiO2 Manufacturers. 6 - Calciner

Discharge, a European manufacturer ‘D’.

Table 3. Results of ‘Acid Test’ for Different TiO2 Grades

# Grade Acid solubility, % TiO2 Type Notes

1 E 11

Super Durable

Grade, P&C Type

6 (Subtype B)

Grade produced by

Manufacturer ‘E’ belonging

to Top-5 global TiO2

producers

2 RC-74 11

Super Durable

Grade, P&C Type

6 (Subtype B)

Produced according to RD

Titan Group Innovative TiO2

proprietary technology

3 F 17

Super Durable

Grade, P&C Type

6 (Subtype B)

Grade produced by

Manufacturer ‘F’ belonging


producers

After the UV exposure

Not exposed to UV-irradiation

Not exposed to UV-irradiation

After the UV exposure











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# Grade Acid solubility, % TiO2 Type Notes

4 G 26

Medium-High

Durable Grade,

P&C Type 2

Grade produced by

Manufacturer ‘G’ belonging


producers

5 H 54

Medium Durable

Grade, P&C Type

2

Grade produced by

Manufacturer ‘H’ belonging


producers

6 Uncoated

rutile J 59

Low-medium

Durable Uncoated

Rutile

Sample provided by a

European manufacturer ‘J’

7

Prototype

from Project

RC-8828

5

Super+ Durable

Grade of the Next

Generation TiO2

Pilot sample produced

according to RD Titan

Group Innovative TiO2

proprietary technology for

Project RC-8828

Commercialization of Technology and Economic Aspects.

There are some optimistic expectations concerning the successful commercialization of Project RC-

8828.

Negative factors affecting the RC-8828 grade cost supplement are as follows:

• Expenditures for R&D;

• Costs for additional production equipment;

• Additional costs for energy and auxiliary materials;

• Increase in the production process stages.

Positive factors affecting the increase in the RC-8828 grade customer value are as follows:

• Improvement of quality characteristics of materials that use Next Generation TiO2

Types;

• Reducing the amount of titanium dioxide used in formulations;

• Versatility of titanium dioxide, expansion of areas where the same grade can be used

for different applications, which previously required different types of grades;

• Development of new directions in which titanium dioxide use has previously been

limited due to its insufficient Durability.

As we expect, we will be able to minimize the impact of negative factors, and maximize the customer

value of the pigment manufactured according to RC-8828 technology, so that this product can be

successfully commercialized after our research is finished.



