POLYISOCYANATES PREPOLYMERS DISPERSIONS UV SYSTEMS

T O O L B O X F O R W A T E R B O R N E 2 K

P O LY U R E T H A N E C O A T I N G S Y S T E M S

CONTENTS

T H E C U T T I N G - E D G E TE C H NO LO GY

T h e g re e n Te c h n o l o g y M e g a Tre n d

Wa t e r- b a s e d 2 - C o m p o n e n t P U Sy s t e m s

4 – 7

T H E FO R M AT I O N O F A WATE R - B A S E D 2 K P U CO AT I N G 8 – 10

T H E TO O LB OX F RO M B AY E R M ATE R I A L S C I E N C E

S u p e r i o r C ro s s - L i n k i n g To o l s : D e s m o d u r ®, B a y h y d u r ®

T h e Wo r l d - c l a s s Po l yo l To o l Fo r Wa t e r- b a s e d 2 - C o m p o n e n t

P U A p p l i c a t i o n s – B a y h y d ro l ®

C o re - S h e l l Te c h n o l o g y

I n t e r n a l A c t i va t i o n

T h e A n t i - S c ra t c h To o l

O u t s t a n d i n g P ro d u c t i v i t y To o l s

B a y h y d ro l ® A

B a y h y d ro l ® U

1 1 – 2 5

S U M M A RY 2 6 – 2 7

3POLYISOCYANATES PREPOLYMERS DISPERSIONS UV SYSTEMS

Polyurethane is widely used as a binder in the

worldwide paint and coating industry. Bayer AG,

the originator and driving force behind poly-

urethane chemistry, has been a major contribu-

tor to this success story.

The world is changing. Green technology has

become an imperative of corporate responsibil-

ity and a milestone on the road to future sus-

tainability. An increasing number of our cus-

tomers share this view, and analysts, investors

and the general public expect to see assertive

action from the industry. Due to pressure from

B A Y E R M A T E R I A L S C I E N C E

PL ACE YOUR CONFIDENCE IN THE CUTTING-EDGE TECHNOLOGY OF THE WORLD MARKET LEADER

P U T T H E G R E E N TE C H NO LO GY M E G A T R E N D TO WO R K FO R YO U

the public and the media, green technology

has escalated very quickly into a mega trend

in the global marketplace. What began as an

“eco-trend” has entered the mainstream in re-

sponse to consumer demand. The market for

green products is ramping up rapidly and relent-

lessly. The Coatings, Adhesives and Specialties

(CAS) Business Unit at Bayer MaterialScience

recognized this trend very early on, and it has

positioned itself at the forefront of the new move-

ment. At the European Coatings Show 2009 in

Nuremberg we reinforced the message that for

technological and ecological reasons the future

belongs to water-based paint and adhesive sys-

tems. Demand for high-grade, eco-friendly prod-

ucts that can be produced and applied effi ciently

reinforces this trend, increasing the incentive for

us to develop and market appropriate solutions.

Fig. 1: Polyurethanes from Bayer MaterialScience provide a holistic technology platform for any application

or need, especially when it comes to creating value-add in the paint and varnish industry.

Fig. 2: The green product value-add chain from the perspective of the paint industry

– (very) high solids PU

– water-based PU

– water-based UV-curing PU

– green coating

materials

– green consumer

goods

– growing demand for

green products

P U S H P U L L

innovative (very)

high solids for

green products

raw material base for polyurethanes

used as binders in the paint industry

innovative water-

based materials

for green products

solventborne for traditional products

Our Desmophen®, Desmodur®, Bayhydrol®,

Bayhydur® and other binder systems have

earned a reputation bordering on the leg-

endary, making us the world market leader.

A large range of paints that are used to coat

cars, trucks, trains, aircrafts, furniture, parquet

and countless other products around the world

are based on this system. Users have been ex-

tremely enthusiastic about the features of these

products from day one. The coatings are tough

and durable, and in nearly all aspects of paint

engineering, their outstanding visual and tac-

tile properties have made them the yardstick

which other binder systems have to measure

up to. But why are we telling you this anyway?

After all, you use the product.

BAYER MATERIALSCIENCE

GREEN TECHNOLOGY

PLATFORM PAINT INDUSTRY APPLICATOR CONSUMER

5DISPERSIONS

Fig. 3: Proven 2-component cross-linking reaction for polyurethane

Our water-based PU coating systems are a clas-

sic example of a sophisticated green technol-

ogy platform. We have introduced the platform

using the high-impact slogan “Water is Green”

to develop a customer base which builds on

it to gain a signifi cant competitive advantage.

Our green technology PU platform is unique

and is one of the most advanced in the world.

As a supplement to established solventborne

PU systems, we offer our customers a range of

waterborne PU raw materials which are tech-

nically equivalent or even superior and which

offer the optimal solution for any painting and

coating application.

D R I V I N G G R E E N T E C H N O L O G I E S

In 2-component PU systems, a polyol (a poly-

mer with an active OH group) which is referred

to as the component A is cross-linked with a

polyisocyanate (PIC) referred to as the compo-

nent B (Fig. 3).

With conventional systems which have been the

industry standard in the past, the raw materials

are dissolved in a solvent for further process-

ing. The cross-linking reaction takes place in

a homogeneous phase (Fig. 4), which has the

disadvantage that volatile organic compounds

(VOC) evaporate during drying. Needless to say,

this effect is not acceptable for green products,

giving water-based paints a huge advantage.

Bottom line: If green products and excellent busi-

ness performance are included in your strategic

roadmap, then the water-based 2-component PU

technology platform from Bayer MaterialScience

is the system of choice.

WATE R - B A S E D 2 - CO M P O N E N T P U S Y STE M S LO O K G O O D BY CO M PA R I S O N

polyisocyanate

(component B, PIC, cross-linker)

polyurethane polymer

reactive

hydroxyl group

reactive

isocyanate group

polyaddition

(curing, cross-linking)

chemical bonding

polyol

(component A)

Fig. 4: Solventborne PU paints (DD coatings) in homogeneous phase have been the industry standard up to

this point.

B PIC (cross-linker) in solvent

A polyol in solvent

homogeneous solution

(polyol + PIC + solvent)

curing (cross-

linking) begins

application

+ +

A discovery and its implications

As soon as people heard the term isocyanate, they associated the word water with hydrolysis

and the formation of polyurethane foam. For a long time, no one knew that water can be used

in place of organic solvents. A team at Bayer discovered that polyisocyanates form a thin pro-

tective polyurea membrane at the interface with water (Fig. 6). This acts as a barrier protecting

the polyisocyanate underneath it from continued hydrolysis and inactivation. From that point

on, it was clear that even in an aqueous environment reactive isocyanate groups were available

for the cross-linking reaction. With this groundbreaking discovery, Bayer MaterialScience laid

the foundation for its water-borne 2-component technology platform. The platform has been

continually improved and refi ned, and it is now one of the world’s leading technologies. Above

all, it has paved the way for successful green products. This has happened at just the right time,

as demand for green products continues to grow.

Fig. 6: Polyisocyanates remain stable in water after a protective membrane forms.

O

H

H

O

H

H

How does a waterborne 2K PU system work?

Actually, it is quite simple. During preparation

of the mix, the components are not dissolved in

a solvent. Instead, the polyol (A-side) is applied

as an aqueous dispersion (Fig. 5). A conventional

polyisocyanate (the B-side which is needed

for cross-linking) is hydrophobic and does not

mix spontaneously with the aqueous polyol

dispersion.

Fig. 5: Water-based 2-component PU systems use a 3-phase system.

B polyisocyanate

(PIC, cross-linker)

A polyol dispersion

application,

curing begins

3-phase sysem:

water (coherent phase)

polyol particles (disperse phase 1)

polyisocyanate droplets (disperse phase 2)

extremely thin protective

polyurea membrane

water

polyisocyanate droplets react on the

surface with water

7DISPERSIONS

Fig. 7: PIC-in-polyol emulsion containing fi ne droplets, formulated with a waterborne 2-component PU system

from Bayer MaterialScience

Fig. 8: PIC-in-polyol emulsion containing coarse, non-uniform droplets, formulated with a no-name waterborne

2-component PU system

perfectly formed PU layer

scattering clusters in the coating

high gloss

reduced gloss

good fi lm formation

fi lm formation defects

small particles, narrow

particle size distribution

insuffi cient PIC-in-polyol emulsion

coarse particles and broad particle size distribution

betternarrow

frequency

dp ~200 nm

particle size

frequency

dp ~1000 nm

particle size

To create a reactive polyol and PIC system which

is cross-linked in the wet fi lm of paint, the user

fi rst has to emulsify the hydrophobic PIC in the

polyol dispersion. The fi ner the emulsion drop-

lets, the better the coating (Fig. 7, 8). Simplifying

the emulsion process also makes things easier

for the user in practical application.

DIAGRAM SHOWING THE FORMATION OF A WATER-BASED 2K PU COATING

1: The water-based 2-component PU mix, the PIC-

in-polyol emulsion, is sprayed on.

2: The wet coating adheres to the substrate.

Drying and cross-linking begins.

3: Polyol particles and polyisocyanate droplets coa-

lesce and react. The fi lm begins to form. Interstitial

water evaporates.

spray nozzle

water-based 2-component PU mix

substrate

polyisocyanate droplets

polyol particles

interstitial water

substrate

9DISPERSIONS

5: Curing is complete. The result is a top-quality

paint coating.

4: A touch-dry fi lm forms. Physical drying is com-

plete, and chemical hardening is well underway.

polyisocyanate droplets

interstitial water

polyol particles

homogeneous PU fi lm forms

IT ’S WORTH MAKING THE SWITCH

If your formulations are based on waterborne

cross-link technology from Bayer MaterialScience,

you kill two birds with one stone. For one thing,

you only need small amounts of solvents or you

can do without them altogether (low or zero

VOC formulation). You can also offer coating

solutions for green products, which are excellent

in every respect and for which there is increas-

ing demand.

We would like to remind you once again that

polyurethane coatings made from waterborne

2-component systems disprove any precon-

ceived notion that the quality of green technol-

ogy is inferior to conventional solutions. The

opposite is actually the case, and your custom-

ers will enjoy the benefits of significantly higher

value-add.

It is definitely worth choosing the extensive green

technology platform from Bayer MaterialScience

as a source of raw materials for your paint. The

range of solutions with a proven track record

covers every imaginable substrate and applica-

tion space including automotive, wood, indus-

trial goods, construction and textiles.

How you benefit: The green technology platform

from Bayer MaterialScience opens the door to

ecologically credible and economically profit-

able green products for a whole variety of market

segments.

Fig. 9: An impressive variety of waterborne polyurethane systems from Bayer MaterialScience already

have a proven track record and an established position in a wide range of applications.

11DISPERSIONS

PittsburghBarcelona

Dubai GuangzhouShanghai

Amagasaki

LeverkusenMoscow

Mumbai

Sao Paulo

Technical service & customer centers in all regions

F O R W A T E R - B A S E D 2 - C O M P O N E N T P O L Y U R E T H A N E F O R M U L A T I O N S

THE TOOLBOX FROM BAYER MATERIALSCIENCE

Bayer MaterialScience has developed an exten-

sive toolkit for waterborne 2-component formu-

lations to help you get faster and more consist-

ent results.

The toolbox contains the following:

• A wealth of inspiration: an outstanding prod-

uct portfolio of polyisocyanates, polyols and

state-of-the-art model formulations as a sug-

gested starting point for your own innovative

low and zero VOC products

• Precision instruments: sophisticated tools

which give you the flexibility to adjust formu-

lation parameters and manipulate the prop-

erties of the PU coating so that you get just

the result you want

• In-depth support: professional paint-engi-

neering support by our water-based paint

specialists at Bayer MaterialScience applica-

tion centers around the world or by special-

ists near you

• Impressive solutions: formulations with a

proven track record, which make it easy for

your customers to properly formulate the PU

systems you provide and achieve consistent

results

Our PU systems toolkit is part of our holistic,

user-centric strategy which is designed to help

our partners and customers.

• Rapid development and introduction of

waterborne 2-component PU systems

• The fast and dependable road to develop-

ment of green products to meet demand in

tomorrow’s markets

• Quick, painless transition from solventborne

to waterborne 2-component paint products

and targeted optimization of existing formu-

lations

Bottom line: The Bayer MaterialScience Toolbox

gives you a solid framework for designing and

quickly producing your innovative products. Visit

our website at www.bayercoatings.com or get

in touch with your engineering contact partner.

Bayer MaterialScience has application development centers for adhesive and paint raw ma-

terials around the world, and there is one near you.

When many groups contribute, success is a more likely outcome. Polyisocyanates from

Bayer MaterialScience are famous for their excellent functionality. The reason for this is that on aver-

age our polyisocyanate molecules have a high number (up to fi ve) of NCO groups available for cross-

linking. Our polyisocyanates have excellent cross-linking properties, and they are very economical.

S U P E R I O R C RO S S - LI N K I N G TO O L S : D E SM O D U R ®, B AY H Y D U R ®

Fig. 10: Low-viscosity Desmodur® polyisocyanates

have been specially developed. They are extremely

well suited for emulsifi cation in polyols. The

Desmodur®-in-polyol emulsion contains fi ne, uni-

form droplets (microscopic view).

3600 (Fig. 12), but also for the asymmetrical

Desmodur® N 3900 HDI trimer (Fig. 13) which was

created through a stroke of genius by the syn-

thesis research team at Bayer MaterialScience

(Fig. 13). The low-viscosity Desmodur® versions

substantially reduce the need to add solvents

during formulation of waterborne 2-component

polyurethane.

How you benefi t: Effi cient cross-linking, very

easy to work with to produce high-grade 2-

component PU coatings.

Fig. 11: Desmodur® polyisocyanates that were

designed to facilitate emulsifi cation. Compared to

standard HDI trimer polyisocyanates, they have

extremely low viscosity, making them ideal for

waterborne 2-component formulations.

Fig. 12: Diagram showing the idealised chemical

structure of HDI-based Desmodur® N 3600. This

workhorse for waterborne 2-component coatings is

highly functional and has low viscosity.

Fig. 13: Diagram showing the idealised chemical

structure of Desmodur® N 3900. The highly functional

asymmetrical trimer has extremely low viscosity,

and it sets the new market standard for green 2-

component PU coatings.

Desmodur® – a durability tool in a class of its

own

In general, polyisocyanates are easier to emul-

sify as the consistency gets thinner (Fig. 10).

With this in mind, our polymer designers have

lowered the viscosity of our familiar Desmodur®

products (Fig. 11). Our highly popular polyisocy-

anate cross-linkers fi t perfectly into our water-

borne 2-component PU systems, and their suit-

ability for emulsifi cation in polyol dispersions is

simply outstanding. This is true for HDI-based

polyisocyanates, for example Desmodur® N

symmetrical asymmetrical

Desmodur® polyisocyanate,

low viscosity

Desmodur®-in-polyol emulsion

better very good emulsifi cation

Desmodur® N 3900

Desmodur® N 3600

viscosity/mPas

standard HDI trimer PIC

730

1200

3000

13DISPERSIONS

Desmodur® reactive thinner – the

sophisticated easy-to-mix tool for the pros

Bayer MaterialScience offers another good

“green” alternative for controlling the viscos-

ity of polyisocyanates in waterborne 2-compo-

nent PU systems, namely Desmodur® reactive

thinners. These products perform two tasks.

They lower the viscosity of the polyisocyanate

curing agent to the point where they can easily

be worked into polyol dispersions, achieving a

very fi ne distribution (Fig. 14). The uretdione-

based polyisocyanates polymerize with reactive

NCO-groups into the network during fi lm forma-

tion. This makes organic solvents, which evap-

orate in the form of VOCs from the paint fi lm,

obsolete which is a big advantage. It eliminates

the need for wide-spread use of these solvents

to lower the viscosity of polyisocyanates. This is

good news for the environment, the customer

and the quality of the paint. Fig. 14: Desmodur® polyisocyanate reactive thinners from Bayer MaterialScience

provide a very effi cient method of lowering the viscosity of polyisocyanate cross-linkers.

Bayhydur® – the easy-to-mix tool in a class

of its own

Convenience sells, so we looked for a solution

which makes it as easy and foolproof as pos-

sible for users to mix waterborne 2-component

PU paint. The result of our efforts, easy-to-mix

Bayhydur® polyisocyanate, is very impressive.

What is the ideal behind this solution? Dur-

ing formulation of waterborne 2-component

PU paint, two components are mixed which do

not really go well together. To ensure that polyol

and PIC come together for cross-linking, the li-

pophile PIC has to be emulsifi ed in the aque-

ous polyol dispersion. An emulsifi er is needed

which acts as an intermediary between the two

immiscible phases.

How you benefi t: Green reactive thinners are

highly effective tools for controlling viscosity,

and they meet the needs of today’s market. They

are a VOC-free replacement for solvent thinners.

You could take the easy route and simply add

an external emulsifi er to the PIC and offer this

mixture as a ready-to-use single-pot cross-

linker. Emulsifi cation does take place, but the

risks are signifi cant and they can be very un-

pleasant for the user. The emulsifi er which is

added is not bonded to a PIC and therefore can-

not be anchored in the PU network of the paint

coating. Because it is still a foreign substance,

it can work itself free after a short time and form

clusters for instance (Fig. 15). The emulsifi er

can migrate to the paint/substrate boundary

or to the surface of the paint, where it impairs

key properties such as hardness, adhesion and

resistance to water. This is not something that

any user wants.

10 % additive: approx. –30 %

viscosity η/mPas@23°C

1200

900

640

10 20

viscosity of pure Desmodur® N 3600

weight % reactive thinner (Desmodur® XP 2730)

20 % additive: approx. –50 %

Bayhydur® eliminates problems associated

with stray emulsifi ers. The scientists who de-

veloped this unique water-based cross-linking

technology incorporated the emulsifying func-

tion directly into the PIC molecules. Covalent

bonds hold them fi rmly in place (Fig. 16). They

straighten up at the boundary, producing per-

fect, highly dependable emulsifi cation of the

hydrophobic PIC, in some cases spontaneously

without any stirring (Fig. 17).

In other words, Bayhydur® polyisocyanates with

emulsifi er functionality are directly involved in the

cross-linking process, and they polymerize com-

pletely into the PU network in the paint coating.

As a result, they are fi rmly anchored and homo-

geneously distributed (Fig. 18). Aqueous cross-

linking technology from Bayer MaterialScience

makes yet another essential contribution to the

quality of PU coatings.

How you benefi t: With Bayhydur®, your PU coat-

ings are exceptionally stable and durable. These

are features which users genuinely appreciate.

They know that they are always on the safe side

and do not have to contend with unpleasant sur-

prises.

Fig. 16: With Bayhydur® products, the emulsifying functions are attached to the polyisocyanate with covalent

bonds. They straighten up at the interface, facilitating the formation and stabilization of the emulsion.

Fig. 15: Emulsifi er clusters and fi lm defects can form in formulations which have free emulsifi ers.

substrate

lipophilic tail

hydrophilic head

unanchored emulsifi er

PU chains

unanchored emulsifi er

emulsifi er clusters

emulsifi er function anchored to the

Bayhydur® cross-linker molecule

protective polyurea membrane

Bayhydur® droplets in the emulsion

emulsifi er function straightens up at the

interface, stabilizing the emulsion

15DISPERSIONS

Fig. 17: When lightly stirred, Bayhydur® polyisocyanates emulsify spontaneously in the aqueous phase,

making it very easy to blend them into polyol dispersions without elaborate equipment i. e. using a wooden rod

at construction sites.

Fig. 18: The emulsifi er functions are fi rmly anchored

into the polymer network in paint coatings that are

produced using Bayhydur®. The result is perfect,

highly durable PU coatings.

substrate

PU chains

emulsifi er function

fi rmly anchored to

polymer chain

perfect PU coating

spontaneous emulsifi cation

gentle stirring

aqueous phase

Bayhydur®-in-water emulsion,

fi ne particles, durable

Bayhydur®

(organic phase)

Soft/hard tools for added fl exibility during

formulation

A fl exible response to the preferences of the

customer base and users is a key success factor

for any PU paint manufacturer, which is why

these companies need tools that give them add-

ed fl exibility. These application-oriented tools

enable paint manufacturers to achieve unique,

professional results with their 2-component PU

paint formulations.

With 2-component PU systems, the properties

of the polyisocyanates which are used in the

formulation can be manipulated to control a

number of paint parameters which affect me-

chanical and tactile properties, drying char-

acteristics and the durability of the coating.

HDI polyisocyanates are the archetypical so-

lution for highly durable, tenacious or fl exible

PU coatings. The “bulky” IPDI versions on the

other hand accentuate hardness in a PU paint

system (Fig. 19).

Our polymer designers have succeeded in

transferring the ability to vary the PU proper-

ties to waterborne systems by combining the

easy-to-mix tools mentioned above with the

hard-soft tools.

The results are very impressive. An extensive

range of HDI and IPDI based polyisocyanates is

now available, which can readily be emulsifi ed

in polyol dispersions. More importantly, they

help paint manufacturers defi ne and regulate

the properties of their products.

The green technology platform includes ground-

breaking IPDI polyisocyanates, for example low-

viscosity Desmodur® XP 2565 and the emulsifi er-

modifi ed versions Bayhydur® 401-70 and XP 2759.

These products can be combined with the fa-

miliar HDI versions, providing an elegant path

to “green” formulations, simple handling, fast

drying and high application effi ciency.

How you benefi t: You have greater freedom in

your waterborne 2-component PU formulations.

You can vary the coating properties over a wide

range with greater precision than ever before,

so that you meet the needs of the particular

application.Fig. 20: Bayer MaterialScience offers a combination

of soft/hard and easy-to-mix tools to support optimal

formulation of waterborne 2-component PU coatings.

Product group HDI-based IPDI-based

Low viscosityDesmodur®

Bayhydur®

Fig. 19: Polyisocyanates from Bayer MaterialScience offer an exceptional amount of fl exibility to alter paint

properties in waterborne applications.

IPDI Types

– Hard and ductile coatings

– Very fast physical drying

– Higher early strength

– Slower cross-linking reaction

– Longer pot life

– High popping limit

– High weather resistance

– Excellent chemical resistances

(after curing at higher temperatures)

70 %

100 % HDI100 % IPDI

HDI Types

– For tough and elastic coatings

– Fast cross-linking reaction

– Cures at low temperatures possible

– High resistance to chemicals at low curing

temperatures

– Shorter potlife

– Excellent scratch resistance

– Lightfast

17DISPERSIONS

T H E WO R L D - C L A S S P O LYO L TO O L FO R WATE R - B A S E D 2 - CO M P O N E N T P U A P PLI C AT I O N S – B AY H Y D RO L ®

Thanks to our holistic approach to polymer

design, paint and coating manufacturers can

choose the best combination of raw materials

for their waterborne 2-component formula-

tions. It is hardly surprising therefore that in

addition to polyisocyanate chemistry, we are

also working intensively on the binders (poly-

ols). As a result of our efforts, we have produced

the Bayhydrol® series of waterborne disper-

sions (Fig. 21), which are perfectly tailored to

our polyisocyanate cross-linkers. Our binder

toolbox for waterborne 2-component PU paint

includes OH-functional Bayhydrol® A series

polyacrylate dispersions and Bayhydrol® U

series polyurethane dispersions. Both have been

specially optimized for aqueous cross-linking

applications. These Bayhydrol® polyols essen-

tially form the backbone of the paint binder, and

they are primarily responsible for the mechanical

and chemical properties of the paint fi lm.

The Bayhydrol® UH series of high-molecular

weight PU dispersions are the ideal mixing

partners. They can be used to control impor-

tant paint properties such as drying, adhesion

and the mechanical characteristics of the fi lm.

Bayhydrol® dispersions are supplied as white

or opaque liquids that can be thinned with

water. Isolated polyol droplets, which are fi nely

distributed and which “swim around” in the

aqueous phase, are present in the dispersions

(Fig. 22). Like charges on the surface of the

polyol droplets ensure that the droplets repel

each other and do not clump together to form

aggregates.

Fig. 21: Bayhydrol® stands for cutting-edge polyol

dispersion technology and the variety you need for

your fi nely tuned formulations.

combination with our polyisocyanates, particu-

larly regarding the key features of paint qual-

ity, namely the sheen and durability of the fi lm.

Polyols with a high molecular mass are the

solution of choice for quickly producing the

fi nal properties of the paint fi lm. We can easily

meet this requirement with our Bayhydrol® dis-

persions without a rapid increase in viscosity.

Despite the high molecular mass of the polymer

in the polyol droplets, our dispersions have low

viscosity (which is a very welcome effect) due

to their particle size distribution, and they are

easy to process.

How you benefi t: The Bayhydrol® brand stands

for one of the most advanced families of polyols

in the world, and they are tailored for water-

based 2-component PU formulations.

All of our fi ne polyol dispersions have a defi ned,

narrow particle size distribution. They remain

stable during storage and are not susceptible

to creaming or sedimentation. This is essential

to achieve perfect paint engineering results in

PUR/PAC hybrid

dispersions

high molecular PAC

dispersions

Polybutadien

Copolymer

dispersion

radiation-curing

PU dispersions

PES dispersions high molecular

PU dispersions

PU dispersions

PAC dispersions

waterborne 2K PU coatingsBayhydrol®

Fig. 22: Bayhydrol® dispersions and the schematic structure of a Bayhydrol® particle

CO R E - S H E LL TE C H NO LO GY – T H E P E R F E C T CO A LE S C E N C E A N D F I L M FO R M AT I O N TO O L

mers to create a core which is just right for the

particular application.

The same is true of the surrounding shell. The

functional design is tailored to ensure that the

shell offers a polyisocyanate droplet the opti-

mal opportunity to dock and initiate the cross-

linking process. The shell on Bayhydrol® polyols

also plays the role of a co-solvent. It promotes

fi lm formation and facilitates the homogeneous

reaction of the components during curing, guar-

anteeing outstanding painting results.

How you benefi t: Water-based 2-component

PU paint formulations containing Bayhydrol®

require only a minimum amount of co-solvent,

providing a very effective solution for reduc-

ing solvent emissions during application. This

makes them an important tool in the Green

Technology Platform, which opens the door to

green, VOC-reduced products.

Fig. 23: Core-shell technology: schematic drawing

showing the structure and surface of a Bayhydrol®

particle

functional shell

polymer core

docking point for polyisocyanates

hydrophilic surface-active group

on the surface

docking point for

polyisocyanate

droplets

polymer corefunctional

shell

hydrophilic tenside molecule

Our Bayhydrol® series polyols are no ordinary

dispersions. They are complex binders which

have been specially optimized for the water-

borne 2-component PU world (Fig. 23). During

production of the dispersion, our polymer de-

signers fi rst synthesize a (normally harder) core

and then cover it with a functional shell (core-

shell technology).

The core is the “nerve” of the polymer micro-

structure in the fi nished PU coating, and it

largely determines the durability of the paint-

work. We match the composition of the mono-

19DISPERSIONS

Internal activation is an extremely important

additional function of selected polyols made

by Bayer MaterialScience. This function ad-

dresses a specifi c problem. You may be aware

of the fact that it takes time for the OH groups

in the polyol to react with the NCO groups in the

polyisocyanate cross-linker. Sometimes it takes

too much time, and that can be a real handi-

cap for users who need short drying times to

achieve high productivity during paint applica-

tion. The standard solution is to add dibutyl tin

dilaurate (DBTL) or other external catalysts to

speed up cross-linking/drying, but this has a

major disadvantage. It signifi cantly reduces pot

life, and users often do not have enough time to

properly prepare and apply their 2-component

PU mix. The paint fi lm can show signs of streak-

ing, reduced gloss or other defects. There are

also concerns about the environmental impact

of organic tin compounds.

This is not the case with internally activated

Bayhydrol® polyols from Bayer MaterialScience.

Eco-friendly activation centers are virtually built

right into the Bayhydrol® A particles (Fig. 24).

This activation system is a classic example of

green technology, and compared to conventional

catalysts it has the advantage that the pot life

is not affected despite that fact that the paint

dries faster. With these Bayhydrol® products,

customers can mix their 2-component PU paints

in large batches and use them over a long period

of time as usual (Fig. 25).

How you benefi t: Outstanding green technology

ensures quick drying and long pot life based on

the internal activation of selected Bayhydrol®

polyols.

I N TE R N A L AC T I VAT I O N – T H E G R E E N TO O L TO AC H I E V E Q U I C K D RY I N G A N D LO N G P OT LI F E

Fig. 24: Internal activation from Bayer MaterialScience, eco-friendly design and a milestone in fast drying

waterborne 2-component PU paint

Fig. 25: In contrast to standard catalysis, special

Bayhydrol® polyols with internal activation ensure

long pot life.

polyisocynate

droplet

internal activation seeds

polyurethane

fast

coalescenceBayhydrol® A

particle

better

pot life

50 %

100 %

without catalysis

with normal catalysis

with internal

Bayhydrol®

activation

self-healing beginscoating fully restored

substrate

intact PU coating

scratch

T H E A N T I - S C R ATC H TO O L FO R S E L F - H E A LI N G PA I N T CO AT I N G S

Bayer MaterialScience has established another

“green” benchmark by developing waterborne

2-component polyurethane systems with vir-

tually unparalleled self-healing capabilities

which are able to repair scratches in coatings

caused by mechanical damage. Urethane-modi-

fi ed Bayhydrol® U series polyester polyols have

a very high number of hydrogen bonds which

are cleaved when the coating is scratched. How-

Fig. 26: Molecular-level view of damage and self-repair in polyurethane coatings (schematic). Hydrogen bonds (A)

in the PU coating are cleaved as a result of mechanical damage (B). The process is reversible. The bonds reform,

repairing the coating (C).

Fig. 27: Schematic diagram showing self-healing of

polyurethane coatings.

moderate

warming

ever, the damage is reversible. There is suffi cient

mobility in our polyurethane coatings and due

to partially charged –Hδ+/–Oδ− groups the hydro-

gen bonds reform and the scratches repair them-

selves (Fig. 26, 27).

How you benefi t: You can prepare formulations

for self-healing anti-scratch coatings using

waterborne 2-component polyurethanes made

by Bayer MaterialScience.

partial charges

(δ+ and δ-) attract

each other

PU coating repairs

itself completely

reversible formation

of H bridges

polyurethane, linked

with H bridges

H bridges mechanically

severed

A B C

21DISPERSIONS

O U TSTA N D I N G P RO D U C T I V I T Y TO O L S

We take a very close look at the productivity

and application reliability aspects for the en-

tire applications spectrum of our waterborne

2-component PU systems. Forced drying at high

temperature is a major issue, because it can

lead to surface defects such as pinholes and

cratering.

Fig. 28: Forced drying and fi nish quality

(A) Suboptimal formulation leads to surface defects caused by a diffusion barrier

(B) Waterborne cross-linking technology from Bayer MaterialScience produces excellent fi nish quality

poor deaeration of

wet coating

no diffusion

barrier

signifi cant crater-

ing and pinholes

forced drying

(40–60 °C)

wet PU coating

perfect fi nish with mini-

mum surface defects

excellent deaeration

of the wet coating

surface defects

skin (diffusion

barrier)

PU coating PU coating

A

B

Our application centers understand the com-

plex relationship between the composition of

the formulation and elimination of coating de-

fects when the coating is force-dried. We do

not just understand the theory. Our expertise

is also based on practical experience. We can

provide specifi c advice to our customers and us-

ers on how to formulate paint using Bayhydrol®

polyols to achieve exactly the coating results

that they are looking for.

We also provide useful tips to customers, for

example which defoamers and co-solvents to

use and how to balance the ratio of lipophilic

and hydrophobic polyisocyanates to ensure a

perfect visual appearance with low popping

limits and minimal cratering when drying takes

place at room temperature or if the coating is

force-dried. Bayer MaterialScience offers paint

manufacturers and their customers the benefi ts

of high-productivity and outstanding coating

results, which is good news for everyone in-

volved.

B AY H Y D RO L ® A – T H E B E ST TO O L TO P RO D U C E D U R A B LE , FA ST- D RY I N G CO AT I N G S

Bayhydrol® A series polyacrylate dispersions

(PAC) are available in two versions. The sec-

ondary dispersions are highly compatible with

the Desmodur® and Bayhydur® polyisocyanate

cross-linkers from Bayer MaterialScience. The

paint system version offers virtually unbeatable

handling features and durability. This includes

both the primary dispersions and the high mo-

lecular weight Bayhydrol® A versions, which are

suitable for accelerated physical drying.

Bayhydrol® A polyacrylates in combination with

polyisocyanate cross-linkers play a vital role.

The specifi c strengths of Bayhydrol® A come

into play, as a “durability network” forms in

the cross-linked coating (Fig. 29). Due to the

chemical properties of its unsaponifi able C-C

chain, for example, it has excellent resistance

to everything which comes into contact with the

coating during its lifecycle. The network formed

by Bayhydrol® A polyacrylates and our polyiso-

cyanate hardeners is highly resistant to acids,

alkaline solutions, solvents, food and cleaning

agents (Fig. 30). It comes as no surprise that our

raw materials are now included in many formu-

lations that are designed specifi cally for extra

durability. Examples include anti-graffi ti paint

used as coatings in public transportation sys-

tems such as trains and busses. These coatings

are so durable that even the most stubborn graf-

fi ti can be removed without trace, much to the

annoyance of illegal spray artists. Raw materi-

als from Bayer MaterialScience are usually in-

volved when coatings for the transportation and

logistics markets pass certifi cation testing car-

ried out by large mobility and rail companies.

How you benefi t: Bayhydrol® A, the world-

class polyol, forms a “durability network” in

polyurethane coatings made from waterborne

2-component systems.

Fig. 29: Diagram showing cross-linking of Bayhydrol® A with a polyisocyanate.

Fig. 30: Cross-linked polyurethanes made of Bayhydrol® A and polyisocyanate are extremely resistant to

any type of attack.

polyisocyanate

(B-side, PIC, curing agent)

polyurethane polymer

polyurethane polymershoe polish

cleaning agent

mustard,

ketchup,

mayonnaise

base

acid

reactive OH groupreactive isocyanate

group

stable C-C chain

polyaddition

(curing)

polyacrylate backbone

with C-C chain

durability network

polyacrylate cross-linked with polyisocyanate

Bayhydrol® A

(polyol, A-side)

+ +

✗

✗

✗

✗

✗

23DISPERSIONS

B AY H Y D RO L ® U – T H E I D E A L TO O L FO R C R E AT I N G H A R M O NY I N YO U R FO R M U L AT I O N S

The Bayhydrol® U versions are other highly

useful members of the polyol family. These

polyol binders have a sophisticated structure.

Our polymer designers combine polyesters or

polycarbonates with special polyisocyanates to

produce urethane-modifi ed polyesters or poly-

carbonates. These products offer a number of

advantages during formulation. They still have

suffi cient OH groups for subsequent cross-link-

ing and they contain no reactive NCO groups.

They are easy to work with and they give the

paint top-class mechanical and visual proper-

ties. What more could you want? The special

polyesters in Bayhydrol® U are designed for

high compatibility, and they harmonize ex-

tremely well with other paint constituents such

as inorganic and organic pigments, fi llers, etc.

The forces that they generate with these sub-

stances are either polar (H bridge) or disperse

(van der Waals), and they are very balanced.

With Bayhydrol® U binders, the pigments and

other solids in the formulation are very effec-

tively wetted, encapsulated and permanently

integrated into the polymer network (Fig. 31).

Consequently, the good pigment wetting of

Bayhydrol® U is evident in the extremely high

durability and excellent gloss of the coating.

How you benefi t: Bayhydrol® U act as highly ver-

satile mediators in complex paint formulations.

Fig. 31: Bayhydrol® U guarantees outstanding

wetting of pigments in waterborne 2-component

PU systems.

substrate

substrate

inorganic pigments i. e.

titanium dioxide

organic pigments

excellent adhesion proper-

ties of Bayhdrol® U on any

substrate

superb wetting of

pigments

B AY H Y D RO L ® U – T H E U N B E ATA B LE F LE X I B I LI T Y FO R M U L AT I O N TO O L

The reaction of Bayhydrol® U with the polyiso-

cyanates in waterborne 2-component systems

produces something which is particularly ap-

preciated in the world of paint, namely a poly-

urethane fi lm with special properties. Depend-

ing on the formulation, the solution can cover

a huge range of mechanical, tactile and visual

properties on the surface of a substrate.

Anything is possible, from hard as bone to soft,

from smooth and fi rm to super-soft touch, from

matte to high gloss with a wet look and a fas-

cinating depth which refl ects objects back

(Fig. 32). Bayhydrol® U is a genuine universal

and fl exible tool. One of the factors behind this

unique versatility is the access which our poly-

mer designers have to the world’s largest range

of isocyanate products. Almost at will, they can

modify and optimize basic polymers such as

polyesters and polycarbonates by adding

urethane functions to deliver exactly the paint

features which users want.

How you benefi t: Bayhydrol® U opens the door

to an enormous variety of options for designing

in paint features on waterborne PU systems.

With urethane-modifi ed polyesters, the issue of

chemical and especially hydrolytic resistance

naturally arises. There is no doubt that ester

groups, including those that form in polymer

chains, tend to hydrolyze and saponify quite

readily when they are attacked by acids or bases

(Fig. 33). This applies both to the polyester

dispersion as supplied in the aqueous form and

to the paint coating when it is exposed to acid

rain or other hydrolytic attack.

Bayhydrol® U is an intelligent and effective

answer to this.

Fig. 32: Bayhydrol® U – a new world of freedom to formulate specifi c paint features

Fig.33: Normal polyesters have a weakness which makes them vulnerable

to attack by water in the presence of acids or alkalis.

soft

super soft-touch

polyester chain

clearage of esters

(saponifi cation)

hydrolysis

high gloss, wet-look

hard

smooth

matte

MECHANICAL PROPERTIES

HAPTIC PROPERTIES

VISUAL PROPERTIES

OH–OH–

H+

25DISPERSIONS

B AY H Y D RO L ® U – T H E TO O L TO P ROTE C T AG A I N ST H Y D RO LY S I S

The basic problem with polyester dispersions is

the polar emulsifying functions that are need-

ed to stabilize the dispersion. Because of their

polarity, they attract water as if by magic and

help the water molecules reach the groups in

the polyester chain that are susceptible to at-

tack by water, hydrolyzing the ester.

Bayhydrol® U uses the core-shell technology

as described above for the effective protection

of the polyester groups that are susceptible to

hydrolytic attack. The polar emulsifi er functions

in the shell stand up like bristles in the direc-

tion of the water phase. Underneath, stable

urethane chains prevent further water ingres-

sion into the core. This double hydrolysis bar-

rier ensures optimal stabilization of the polyes-

ter polyurethane polyols in the dispersion and

provides effective protection again hydrolytic

attack. This is a somewhat complex solution,

but it is very effective (Fig. 34, 35).

The developers at Bayer MaterialScience have

taken a similar approach in adding a protective

barrier for the polyester chains in Bayhydrol®

A series polyester-polyacrylate hybrid-disper-

sions. In this instance, hydrolytically stable

polyacrylate chains in the shell of the disper-

sion particles protect the polyester chains in

the interior, keeping them intact until the time

comes.

How you benefi t: Sophisticated protectors en-

sure polyester stabilization in the formulation

and in the fi nal coating.

Fig. 34: Urethane groups in the Bayhydrol® U series

of urethane-modifi ed polyesters protect the vulner-

able ester bond from hydrolytic attack.

Fig. 35: Bayhydrol® U is the world’s fi rst urethane-

modifi ed polyester polyol which withstands hydrolytic

attack.

functional shell

protective urethane layer

polyester core

H2O

H2O

✗

✗water cannot

penetrate

Abbreviations:

CAS: Coatings Adhesives Specialties; DIS: Dispersions; 2K : 2-Component; PU, PUR: Polyurethane;

PIC: Polyisocyanate; VOC: Volatile Organic Compounds

Desmodur®, Desmophen®, Bayhydur®, Bayhydrol® are registered trademarks of Bayer AG

urethane protecting

ester function

H+

✗

OH–

✗OH–

✗

D R I V I N G G R E E N T E C H N O L O G I E S

We develop products which are more than green:

• eco-friendly

• superior quality & performance

• highly effi cient coating processes

OUR GREEN TECHNOLOGY PLATFORM STANDS FOR THE TECHNICAL AND COMMERCIAL SUCCESS OF OUR CUSTOMERS!

• General industry

• Transportation and ACE

• Automotive and industrial plastics

• Wood

• Paper and printing

• Flooring

WATERBORNE 2K PU TECHNOLOGY:VOC COMPLIANT, SUPERIOR, SUSTAINABLE

Waterborne 2K PU raw materials from Bayer MaterialScience are technically equivalent to

solventborne systems – and in many cases even better. The new generation of Bayhydrol®,

Desmodur® and Bayhydur® products are effi cient and fast in application and curing and enable

the formulation of low VOC coatings with excellent mechanical and chemical resistance in areas

such as:

27DISPERSIONS

2 K P U WATE R B O R N E – M A I N M A R K E TS & A P PLI C AT I O N S

Plastic Industrial + Automotive

General Industrial

Wood

Paper & Print

Flooring

Automotive

TransportationACE

Bayer MaterialScience AG51368 LeverkusenGermany

www. bayercoatings.comCAS@bayermaterialscience.com

This information and our technical advice – whether verbal, in writing or by way of trials – is given in good faith but

without a warranty, and this also applies where proprietary rights of third parties are involved. It does not release

you from the obligation to test the products supplied by us as to their suitability for the intended processes and

uses. The application, use and processing of the products are beyond our control and, therefore, entirely your own

responsibility. We will only sell our products on the basis of our General Conditions of Sale and Delivery. Edition:

2010-12 · Order-No.: MS00048001 · Printed in Germany · E