9 - Epoxies

Epoxide Polymers in Coatings

The University of Southern Mississippi

Hattiesburg, MS 39406

PSC 470/570, Fall Semester 2006

Outline for Epoxy PolymersI. Basic SynthesisII. Reactions of EpoxidesIII. Types of epoxy resins

A. BPA & BPF epoxidesB. Multifunctional epoxidesC. Miscellaneous epoxidesD. Cycloaliphatic epoxides

IV. Epoxide curing agentsA. AminesB. Aliphatic aminesC. Aliphatic amine adductsD. Aromatic aminesE. Acid anhydridesF. Carboxylated polymers

V. Modified epoxidesA. Acrylated epoxidesB. Coal Tar modified epoxidesC. Epoxide estersD. TGIC-PolyesterE. Amino epoxides

VI. DiluentsA. Epoxide based diluentsB. Acrylic monomersC. Non-reactive diluents

VII. Waterborne epoxides

Typical Epoxide Polymer

O CH2 CHOH

CH2 OH2C CH CH2 OO

CCH3

CH3

CCH3

CH3

O CH2 CH CH2

O

( )n

DGEBA Based

Typical Characteristics of Epoxide Polymers

Chemical and heat resistanceAdhesionLow shrinkageEase of fabricationToughnessFlexibilityAbrasion resistanceSuperior elevated temperature performance

Reactions of Epoxides

OCC + R CH

OR`

OR`R CH

OR`

O C C OR`

OCC + H3C C CH2 C

O O

OR C

C

C C

C

CH3

OH

OO

OCC + RCH2CN C C C CN

R

HOH

OCC + HC CR C C C CR

OH

OCC + RC

O

O CR

ORC

O

O C C O CR

O

OCC + RC Cl

O

Cl C C O CR

O

Acetals

Acetoacetates

Acetonitriles

Acetylenes

Acid Anhydrides

Acyl Halides

Handbook of Epoxy Resins, Lee and Neville, McGraw-Hill Book Company, New York, NY, 1967.

Reactions of EpoxidesO

CC + R OH RO C C OH

OCC + R C

O

HBF3 C

C

O

O

CR

H

OCC + RC NH2

ORC

O

NH

C C OH

RC

O

NH

C C OH

OCC + RC

O

N

C C OH

C C OH

OCC + RNH2 HO C C NHR

HO C C N

R

C C OH

Alcohols

Aldehydes

Amides

Amines - primary


Reactions of Epoxides (continued)O

CC + R2NH HO C C NR

R OCC + R3N

H2O HO C C N RR R

OH

OCC + NH3 HO C C NH2

HO C C N

H

C C OH

HO C C N C C OH

C

C

OH

Amines - secondary

Amines - tertiary

AmmoniaCarboxylic acids

OCC + C CORC

O

OHRC

O

OH


Reactions of Epoxides (cont.)

OCC + RC

O

RC

C

O

OC

R

R OCC + H3PO4 O P

O

O

O

C

C C

C OH

OH

C OHC

OCC CH2 CH2 O CH2 CH2 O CH2 CH2 O

n - 2

OCC + H2O HO C C OH C OHCOCCHO

Ketones Phosphoric acid

Self - polymerization

Water


Epoxide Polymers

Polymers in which the epoxide ring plays a part either in polymer synthesis or curing

Most of the epoxides are based on the condensation products of bisphenol-A and epichlorohydrin

This reaction, known as the “Taffy” process, is used to produce lower molecular weight epoxides

Protective Coatings, Clive H. Hare

Ambient-Cure Coatings Baking FinishesAir drying esters Baking systems

Industrial baking finishes

Maintenance & Marine Container coatings

Coatings

Electrodeposition coatings

High solids maintenance

and marine coatings Decorative powder coatings

UV cure coatings Powder coatings for pipe

UV cure coatings Electrical insulation

Decorative powder coatings

Epoxide Polymers in Coating Science

DriersAmino-plast resins

Aminoplast and phenoplast resins

Polyamides, amine adducts

Fattyacids

Ketoimineamidoamines

Cationic initiators

Free radicalinitiators

Acrylicacids

Isocyanates

Acid functionalpolyester and acrylic resins

Acid anhydride

Dicyandiamide

EpoxidePolymer

Epoxyesters

Acrylateesters

Synthesis of DGEBA

Chlorohydrin intermediate

Diglycidyl ether of bisphenol A (DGEBA)

2 + HO CCH3

CH3

OH

ClCH2CHOH

CH2 O CCH3

CH3

O CH2 CHCH2ClOH

+ NaOH2

H2C CH CH2

OO C

CH3

CH3

+ NaCl2 + H2O

ClCH2CH CH2

O

O CH2 CH CH2

O

NaOH

Epoxide Polymers

n value Molecular E.E.W. Meltingweight Point oC

0 -1 350-600 170-310 < 401-2 600-900 310-475 40-702-4 900-1600 475-900 70-1004-9 1400-2900 900-1750 100-1209-12 2900-3750 1750-3200 130-150

O CH2 CHOH

CH2 OH2C CH CH2 OO

CCH3

CH3

CCH3

CH3

O CH2 CH CH2

O( )

n

Epoxide Polymers (cont’d)

Pure DGEBA is not available commercially as it tends to crystallize easily

Low molecular weight epoxides are a polydisperse mix of epoxides with “n” values between 0 and 1 and have an average molecular weight of 350-600

The higher molecular weight epoxides are synthesized by the “fusion” or “advancement” process using benzyl trimethylammonium hydroxide as a catalyst

R.A. Pearson, A.F. Yee, “Toughening mechanisms in elastomer-modified epoxies,” Journal of Materials Science, 2571-2580, 1989.

“Fusion” aka “Advancement” Process

H2C CH CH2

OO C

CH3

CH3

O CH2 CH CH2

OHO C

CH3

CH3

OH+

O CH2 CHOH

CH2 OH2C CH CH2 OO

CCH3

CH3

CCH3

CH3

O CH2 CH CH2

O( )

n

CH2 N(CH3)3 OH+ -

“Fusion” Process (cont.)

Commercial bisphenol-A contains mono- and trifunctional byproducts which interfere with the linear structure of epoxide polymers

Hence, the “Fusion” process is preferred for preparing very high molecular weight epoxides due to the reduced likelihood of chain branching and unwanted increase in melting point and viscosity

Classes of Epoxide Resins

Low molecular weight

Medium molecular weight

High molecular weight

Very high molecular weight

Low Molecular Weight Liquid Epoxides

Liquid epoxides (n<1) are important in formulating zero and low VOC coatings for high performance applications

Two-pack systems with VOCs below 250 g/L (2.1 lb/gal) are commercially available

Cross-linkers with high equivalent weights such as amidoamines, polyamides, and polyglycol diamines are preferred to provide for flexibility

Medium molecular weight epoxides (n=2) are widely used as binders for two-pack amine and amide cured coatings

These polymers are normally available as 75% solutions in aromatic or ketone solvents with viscosities between 20-100 Poise

Amide cured epoxide coatings provide the best balance of properties with very good chemical resistance, hardness, flexibility, and adhesion

Medium Molecular Weight Epoxides

Pot lives varies from 1 hour to 24 hours depending on curing agents employed but dry-to-touch times are typically 4-8 hours.

Full cure may take up to 10 days for polyamide cured epoxide coatings

Applications include maintenance coatings for offshore oil rigs, bridges, aircraft primers, interior coatings for water and sewage treatment, concrete floor coatings, and swimming pool coatings

Medium Molecular Weight Epoxides (cont.)

High molecular weight epoxides (n=4) are used in the manufacture of epoxide esters

Epoxide esters are widely used in metal primers for appliances and automobiles and clear finishes for concrete floors

Linseed oil, DCO, and tall oil fatty acids are used in air-drying epoxide ester synthesis while coconut oil fatty acids are used for heat-curing epoxide esters

High Molecular Weight Epoxides

Epoxide esters are also classified according to their oil content as long, medium, and short oil epoxide esters like oil-modified polyesters

0.3-0.9 equivalents of acid per oxirane are used

This corresponds to 55-65% fatty acid modification for long oil esters and 30-45% fatty acid modification for short oil esters

High Molecular Weight Epoxides (cont.)

Epoxides with n = 4 are also used in dicyandiamide-cured powder coatings, cathodic electrodepositioncoatings, and in metal primers

Epoxides of n = 7 to 9 with high hydroxyl contents are used as co-reactants with:

Amino polymers Phenolic polymers in high temperature curing wire enamels, coil coatings, can coatings, and drum coatings Powder coating polymers for high build applications (>15 mils)

High Molecular Weight Epoxides (cont.)

“Phenoxy”™ polymers have very high melting points, produce very high viscosity solutions, and do not require curing agents to form useful films

They are sold either as solids or as dilute solutions (35% solids) in MEK or cellosolve acetate

Thermoplastic coatings based on these polymers have good flexibility, impact and abrasion resistance, chemical resistance and excellent adhesion, but poor resistance to solvents from which they are cast

Very High Molecular Weight Epoxides

PhenoxyTM polymers can be crosslinked with amino polymers, phenolics or isocyanates to improve their hardness and resistance to heat and chemicals, but flexibility and impact resistance are adversely affected

Isocyanate cured systems have been used for jet fuel tank linings

Very High Molecular Weight Epoxides (cont.)

Other Epoxide Polymers

Bisphenol F based

Multifunctional

Cycloaliphatic

Miscellaneous

Bisphenol F Epoxide Polymers

H2C CH CH2

OO O CH2 CH CH2

OCH2

The isopropylidene linkage and presence of only para-para isomer confer rigidity to bisphenol-A polymers.

Bisphenol-F has ortho-ortho, ortho-para, and para-para isomers along with a methylene linkage which produces more flexible polymers.

The presence of isomers in bisphenol-F also reduces the crystallization tendency and produces polymers with a lower viscosity than bisphenol-A.

Bisphenol F Epoxide Polymers

Resole SynthesisAlkaline conditions:

The reactions possible are - a) Methylolation:OH

CH2O+OH-

OH

CH2OH

OH

CH2OH+

Di- and tri-methylol phenols are also producedOH

CH2HO CH2 OH

2,6 di-methylol phenol

OH

CH2 OH

CH2 OH

CH2HO

2,4,6 tri-methylol phenol

OH

CH2 OH

CH2 OH2,4 di-methylol phenol

The greater mobility of bisphenol-F facilitates a higher degree of crosslinking than bisphenol-A polymers of similar molecular weight leading to a higher Tg, and better solvent and chemical resistance

The lower viscosity facilitates formulating of low VOC coatings with a high degree of chemical resistance

Bisphenol-F epoxide coatings are replacing bisphenol-A epoxide coatings in many applications

Bisphenol F Epoxide Resins (cont’d)

Multi-functional Epoxides

Multi-functional epoxides are used in extreme service condition systems to produce a crosslinked polymers with outstanding chemical resistance.

Examples of such epoxides are:Epoxide novolacsTetraglycidyl-1,1,2,2-(para-hydroxyphenol) ethaneTriglycidyl para-amino phenolTriglycidyl isocyanurate

Tetraglycidyl-1,1,2,2-(para-hydroxyphenol) ethane

O CH2 CH CH2O

OCH2CHH2CO

O CH2 CH CH2

OOCH2CHH2C

O

CH CH

O CH2 CH CH2

O

NCH2 CH CH2

OCH2CHH2C

O

NN

N

O

OOCH2 CH CH2

OCH2CHH2C

O

CH2

HC

H2CO

Trigylcidyl para-aminophenol Triglycidyl isocyanurate

Multi-functional Epoxides

Cycloaliphatic Epoxides

Cycloaliphatic epoxides differ from conventional bisphenol-A based epoxides in several ways:

All aliphatic React readily with acids but not with amine/amide type conventional epoxide curing agentsViscosity of 350 cPsExcellent weatherability

Cycloaliphatic Epoxides

O

O

OO

OO

O

O

O O

3,4-Epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate

Bis-(3,4-epoxycyclohexyl) adipate

UVR-6105

UVR-6128

Miscellaneous Epoxides

Polyglycol epoxidesReplacing the bisphenol-A of conventional epoxides by polyoxyalkylene produces epoxides with all aliphatic structures, high flexibility and elongation, but also lower chemical, solvent and heat resistance properties

These epoxides are used as modifiers for conventional epoxides at levels up to 30 wt%

H2C CH CH2

OO CH2 CH

RO CH2CHCH2

OCH2 CH

RO

n

Cardanol based epoxidesCardanol (3-n-pentadecenyl phenol) is a major constituent of cashew nut shell liquid (CNSL)

Epoxidation is introduced via the phenolic hydroxyl or the unsaturation on the aliphatic chain

Miscellaneous Epoxides (cont.)

O CH2 CH CH2

O

(CH2)7 CH

CH3

(CH2)6

O CH2 CH CH2

O

Miscellaneous Epoxides (cont.)

Brominated epoxidesBrominated epoxides are used specifically in fire-retardant applicationsVarious levels of halogen substitution are feasible

O CH2 CHOH

CH2 O

Br

Br

H2C CH CH2 OO

CCH3

CH3

Br

Br

CCH3

CH3

Br

Br

O CH2 CH CH2

O

Br

Br

n

Epoxide Curing Agents

AminesKetimines

Amine adductsAromatic aminesAcid anhydridesAcrylics or PolyestersTGICAmino polymers

Amine Curing Agents

Primary and secondary amines are the most widely used curing agents for epoxides

Amine cured systems are employed as two-pack, ambient-cured coatings

The molecular weight of the amine, its nature, i.e., aliphatic/aromatic, primary/secondary/tertiary, controls the reaction rate and physical/chemical properties of the finished film


Amine Curing Agents (cont.)

CH CH2O

RNH2 CH CH2

OHNHR

CH CH2O

CH CH2

OHNR

CH2 CHOH

+



Unmodified alkylene amines such as diethylenetriamine (DETA), triethylene tetramine (TETA), and tetraethylene pentamine (TEPA) were among the first amines used as curing agents

These amines cure exothermically and generate highly crosslinked films with excellent resistance properties but low flexibility

These amines have high vapor pressures and are skin sensitizers and respiratory irritants


Handbook of Epoxy Resins by Lee H. and Neville K.

80

90

100

110

120

9 10 11 12 13

2

3

4

5

6

Def

lect

ion

tem

pera

ture

, oC

DETA

TETA

H2N CH2CH2 NH CH2CH2 NH2

H2N CH2CH2 NH CH2CH2 NH CH2CH2 NH2

phr of curing agent with DGEBA

Effect of Curing Agent Concentration on Epoxide Properties

Amine Curing Agents (Cont.)

Phenolic tertiary amines e.g. tris(dimethylaminomethyl) phenol, p-toluenesulfonicacid, salicylic acid and hydrogen bond donors such as phenol, alkyl phenols serve as catalysts for the epoxide-amine reaction

Hydrogen bond acceptors such as ethers, esters, and nitro groups act as retarders for this system

Ketones, especially acetone and MEK, form ketimineswith amines and hence act as retarders


Epoxide Reactivity DataReactivity of DGEBA vs. Basicity of Tertiary Amine

Amine Ionization constant Gel time (hours)

Benzyldimethylamine 8.5 x 10-6 5.3Benzyldiethylamine 3.6 x 10-5 >300Triethylamine 6.4 x 10-4 11.2Tripropylamine 5.5 x 10-4 29Pyridine 2.3 x 10-9 54

Substituent Effects on Tertiary Amine Reactivity with DGEBAAmine Gel time, hours

Benzyldimethylamine 5.3Benzyldiethylamine >300Dimethylethanolamine 4.3Diethylethanolamine 17.2Triethylamine 11.2Tripropylamine 29Tributylamine 33Pyridine 54


Epoxide Reactivity Data (cont.)

N CH3N

CH3

N CH3CH3

2-Picoline4-Picoline 2,6-Lutidine>50011258


Aliphatic Amine Adducts (cont.)

KetiminesKetimine blocking has become important in the formulation of two-pack, high solids systems where the maintenance of low application viscosities are critical

H2N R NH2C OR1

R2

CR1

R2

N R N CR2

R1+

H2O

H2O

-



Unmodified amines react rapidly with atmospheric carbon dioxide and moisture to form carbamates that produce “blushing” on the film surface, especially at low temperatures and high humidities

H2O CO2 H2CO3

H2CO3 RNH2 RNHCOOH

RNHCOOH RNH2

+

+

+ O CC

NH

R-

RNH3+

O


Amine induced blushing may be reduced by allowing an induction period after mixing the two components just before application



Amine Adducts

Epoxide-amineCyanoethylated aminePolyamidesAmido-aminesImidazolinesMannich basesPolyoxyalkyl amines

Aliphatic Amine Adducts

Epoxide amine adducts

H2C CH CH2

OO C

CH3

CH3

O CH2 CH CH2

OH2N R NH2+

CCH3

CH3

O CH2 CH CH2

OHNHRCH CH2 O

OHCH2RNH NH2H2N

2



Cycloaliphatic amines

Isophorone diamine, diamino cyclohexane, and 4,4-bis(p-amino cyclohexyl) methane are the commonly used cycloaliphatic amines with epoxides

H3C

H3C

NH2

H3C CH2NH2

CH2H2N NH2

NH2

NH2

Isophorone diamine Diaminocyclohexane

4,4-bis(p-amino cyclohexyl) methane



Cyanoethylated amines

These are less reactive than amines but have lower vapor pressure and higher equivalent weight which facilitates mixing in convenient volumesThese systems possess excellent chemical resistance and color, and cure satisfactorily under damp conditions to give blush-free films

H2C CH C NH2N R NH2

H2N R NH CH2 CH2 C N

+



PolyamidesLong chain fatty acid dimers derived from vegetable oils are reacted with slight excess of primary amines to synthesize polyamides

(CH2)7

C OOH

CHCHCH

CHCHCH

HCHC

(CH2)7 CO

OH

(CH2)5CH3 (CH2)5

CH3

H2N R NH2

(CH2)7

C O

CHCHCH

CHCHCH

HCHC

(CH2)7 CO

(CH2)5CH3 (CH2)5

CH3

R NH2NH

R NH2NH

+ 2


Polyamide-epoxide systems are the workhorse of high performance protective coatings Increased distance between crosslinking sites produces films that are more flexible and impact resistant than films cured with aminesResistance to chemicals and solvents are lowered though water resistance and corrosion protection are enhancedThe higher molecular weight of polyamides also facilitates mixing in convenient ratiosAn induction period is necessary after mixing and before application



Amido-aminesAmido-amines are condensation products of an amine and a monofunctional fatty acid

Viscosity of amido-amines ranges from 2-6 Ps while polyamides have viscosities above 16 PsLow viscosity and low VOC coatings can thus be formulated using amido-aminesResistance properties of epoxide-amido-amine systems are lower than epoxide-polyamide systemsApplications include concrete coatings, floor coatings, and coatings designed for damp substrates


CH3 (CH2)n COOH H2N R NH2 CH3 (CH2)n CO

NH R NH2+



ImidazolinesImidazolines are the condensation products of amines and monofunctional acids reacted at high temperatures

H2OH2O-

CH3 (CH2)n COOH

H2N (CH2)2 NH (CH2)2 NH2

+ CH3 (CH2)n CO

NH (CH2)2 NH (CH2)2 NH2

CH3 (CH2)n CN

N

CH2

CH2

(CH2)2 NH2

H2O H2O-


Imidazoline formation is accompanied by loss of the reactive amine functionality

Imidazolines are utilized in low VOC formulations due to their low viscosity, good compatibility with epoxides, and high equivalent weights

Like amido-amines, imidazolines have reduced reactivity, reduced cross link density and lower resistance properties

Imidazolines are also used to extend the pot life of aliphatic and cycloaliphatic amine catalyzed epoxide systems




Mannich basesAliphatic and cycloaliphatic amines are reacted with methylol phenols to yield Mannich bases

The functionality of the amine is reduced, but the phenolic hydroxyl acts as a catalystThese systems possess excellent adhesion and chemical resistance and can be applied and cured under damp and cold conditions (~0oC)

OH

CH2OH H2N R NH2+

OH

CH2NHRNH2


Unmodified cycloaliphatic amines require high temperatures for reaction with epoxides

Modification involves use of acid accelerators such as salicylic acid (dissolved in benzyl alcohol)

Use of cycloaliphatic amines improves color retention on exterior exposure

These systems cure well in cold and damp conditions and exhibit good adhesion to damp surfaces



Polyoxylalkylene amines

Polyoxyethylene and polyoxypropylene amines are primary amine derivatives of polyethylene and polypropylene glycol

These amines react slowly and contribute considerable flexibility to the crosslinked film

The oxyalkylene structures provide considerable water sensitivity leading to inferior water and corrosion resistance

These amines are mostly employed as flexibilizing agents in conjunction with other curing agents




H2N CH CH2

CH3

(OCH2CH)CH3

NH2n Polyoxypropylene diamine

H2N CH CH2

CH3

(OCH2CH)CH3

(OCH2CH2)CH3

NH2(OCH2CH)n m l

Diamine of mixed polyalkylene glycols

CH3 C CH2 (OCH2CH)CH3

NH23

Polyoxyalkylene triamine based on trimethylol propane


Aliphatic Amines

CH2NH2

CH2NH2

CH2NH2

CH2NH2

m-xylene diamine 1,3 - bis (aminomethyl) cyclohexane

Aromatic amines generate crosslinked films with higher rigidity and brittleness due to the increased aromatic content

Resistance properties are also enhanced relative to the aliphatic amine cured epoxides

All aromatic amines are dark colored, irritating, and toxic by nature

Applications include concrete sewer pipe linings, flooring applications and chemical resistant tank linings

Aromatic Amines

NH2

NH2

m-phenylene diamine

CH2H2N NH2

4,4’ - methylene dianiline

H2N SO

ONH2

Diamino diphenyl sulfone

H2N CH2 NH2

H2N

2,4 -bis (para-aminobenzoaniline)

Aromatic Amines (cont.)

Aromatic Amines (cont.)

Some aryl diamines have amine groups removed from the ring by a methylene bridge

The methylene group enhances the reactivity of this class of amines providing rapid cure at ambient and sub-ambient temperatures

Hard, high gloss finishes are obtained with excellent chemical, water, and solvent resistance

These amines are also lighter in color and are less toxic than aromatic amines

Acid AnhydridesThe reaction of epoxides with anhydrides needs to be either acid or base catalyzed to facilitate the opening of the anhydride

In presence of acid catalysts, etherification reaction between epoxide molecules predominates and anhydride levels required drop to 55% of the stoichoiometric level

In presence of base catalysts, esterification reaction between the epoxide and anhydride ensues completely and stoichiometric levels of anhydrides are required for full cure

Curing temperatures are high, 1-2 hours at 200oC, as most anhydrides are solids and need to be melted

Anhydride cured systems have lower chemical resistance than the amine cured systems, but are less toxic, cure with lower exotherm, and have longer pot lives

These systems are used in casting and laminating applications, and in powder coatings

Acid Anhydrides (cont.)

Acid Anhydrides (cont.)

CC

O

O

O

Phthalicanhydride

CC

O

O

O

HOOC CC

O

O

O

CC

O

O

O

Trimelliticanhydride

Pyromelliticanhydride

CC

O

O

O

Hexahydrophthalic anhydride

Carboxylated Polymers

Epoxides will react with polymers containing carboxyl groups, such as acrylics and polyesters under base catalyzed conditions

Epoxides will also react with the hydroxyl groups in these polymers under acid catalyzed conditions

Curing temperatures are high, i.e. 175-200oC

TGIC-Polyester SystemsEpoxide (TGIC)-polyester systems are used extensively in powder coatings

NN

N

O

OOCH2

CH2

CH2

CH

CHCH CH2

CH2

O

O

H2CO

COOH

NN

N

O

OOCH2

CH2

CH2

CH

CHCH CH2

CH2

OH OH

OH

O

O

CH2O

C

CCO O

O+

Polyester

Amino Polymers

Epoxide polymers crosslink with amino polymers mainly through their secondary hydroxyl groups

Epoxide-amino polymer systems are widely used in coil coating primers and in beverage can coatings

Urea formaldehyde based systems cure faster or at a lower temperature than melamine formaldehyde based systems

Modified Epoxides

Acrylated epoxides

Coal tar modified epoxides

Epoxide esters

Diluents used with epoxides

Waterborne epoxides

Acrylated Epoxides

Acrylated epoxides are synthesized by reacting acrylic acid with low molecular weight bisphenol-A epoxides

These polymers are used to improve the chemical resistance, hardness and gloss of conventional acrylics

Applications include radiation cured coatings, inks, adhesives, and laminates

H2C CH CH2

OO C

CH3

CH3

O CH2 CH CH2

O

H2C CH COOH

O CH2 CH CH2

OHCCH3

CH3

O CO

CH CH2CH CH2 OOH

CH2OCO

CHH2C

Acrylated Epoxides (cont.)

Difunctional acrylated epoxide

2

Acrylated Epoxides (cont.)

H2C CH CH2

OO C

CH3

CH3

O CH2 CH CH2

OCH CH C

OOHC

ORO

O CH2 CH CH2

OHCCH3

CH3

O CO

CH CH CO

ORCH CH2 OOH

CH2OCO

CHCHCO

RO

CH CO

H2C Cl

O CH2 CH CH2

OCO CH CH2

CCH3

CH3

O CO

CH CH CO

ORCH CH2 OCH2OCO

CHCHCO

ROOCO CH CH2

+

Tetrafunctional acrylated epoxide

Coal Tar Modified Epoxides

Refined coal tar pitch is blended with epoxide-amine systems at levels of 1.5-3 times coal tar to epoxide-amine solids

While the exact mechanism occurring in the reaction is not clear, it has been proposed that the phenolic components of coal tar pitch react with the epoxides and also catalyze the epoxide-amine reaction

Medium hard grade coal tar pitches are preferred for use with epoxide systems for best chemical resistance

At higher levels of coal tar, resistance to water, corrosion and dilute acids improves

At lower levels of coal tar, hardness and resistance to solvent and alkalis improves

Coal Tar Modified Epoxides (cont.)

A disadvantage of these systems are their poor color and poor resistance to UV light

Being highly cohesive in nature, these systems require blast cleaned surfaces with a high surface profile for good adhesion

Coal tar epoxide systems have been used very effectively in buried, immersed, hidden, and similar difficult-to-access areas providing long-term service without much maintenance

Coal Tar Modified Epoxides (cont.)

Epoxide EstersOil Types Epoxide Ester Properties

Linseed Oil FA Fast air drying systems with poor color retention

DCO FA Fast air drying or heat cured systems with good flexibility and chemical resistance

Soybean FA Air drying systems with good color and soft flexible films

Coconut FA Non air drying systems with very good color, chemical resistance, and flexibility

With increasing fatty acid content:

Chemical resistance FlowFilm hardness Solubility in aliphaticDrying time hydrocarbon solventsAdhesion Water resistanceGloss retention FlexibilityCost Pigment wettingViscosity Exterior durability

Color retention

Epoxide Esters (cont.)

H2C CHO

CO

OH CO

O CH2 CHOH

+

CO

OH CHOH

CHO C

O

H2O+ +

Esterification

During these first two steps, viscosity rise is small corresponding to a large decrease in acid number


Etherification

CHOH

H2C CHO

CHO CH2 CH

OH

+

In order to produce commercially desirable low viscosity, low acid number esters, it is necessary to suppress the etherification while encouraging the esterification steps


They are similar to polyester polymers, yet they offer some superior film properties:

AdhesionFlexibilityChemical resistance

Overall properties are inferior to two-pack epoxide polymer films, but their advantages are:

Lower costBetter pigmentation propertiesLong shelf life


Applications of Epoxide Esters

Automotive primersAppliance primersFlexible tube coatingsDrum liningsMarine finishesFloor sealers and top coatsMetal decorating lacquersEnamels for hardware and metal furnitureIndustrial maintenance primers and topcoats

Epoxide-based Diluents

Mono- and di-functional epoxide diluents are employed to reduce the VOC of epoxide based formulations

Incorporation of such diluents lowers the hardness, chemical resistance, and heat resistance of coatings while flexibility may be improved due to a lower crosslink density

Epoxide-based Diluents (cont’d)

H9C4 O CH2 CH CH2

O

Butyl glycidyl ether Diglycidyl ether of neopentyl glycol

O CH2 CH CH2

OOCH2CHH2C

OCH2 C

CH3

CH3

CH2

CH3

O CH2 CH CH2

O

Cresyl glycidyl ether

O CH2 CH CH2

O

O CH2 CH CH2

O

Diglycidyl ether of resorcinol

CH2 CH CH2

OOC

OCR1

R2

R3

Glycidylneodecanoate

Acrylic Monomers

Acrylic monomers react readily with amines (by Michael addition) and hence when they are incorporated into an epoxide-amine system, they lower the crosslink density of the coating by reducing the amount of amine available for reaction with the epoxides

Acrylic monomers are lower in viscosity than low molecular weight epoxides which helps reduce the viscosity of epoxide coatings

Hexanediol diacrylate

(CH2)6 OO CO

CH CH2CO

CHH2C

CH3 CH2 CCH2

CH2

CH2

CH2CHOCO

CH2CHOCO

O CO

CH CH2

Trimethylolpropanetriacrylate

Acrylic Monomers (cont’d)

Non-reactive Diluents

Being non-reactive with the epoxides or its cross-linkers, these diluents serve to improve the flexibility of coatings, but solvent resistance, hardness, and heat resistance is lowered

Some common examples are:Coumarone indene copolymersPlasticizers such as butyl benzyl phthalate

CC

O

O

OC4H9

OCH2C6H5

Butyl benzyl phthalate

Non-reactive Diluents (cont’d)

2K Epoxy

Hardener is typically a polyamine or polyamide

O CH2 CHOH

CH2 OH2C CH CH2 OO

CCH3

CH3

CCH3

CH3

O CH2 CH CH2

O

Resin CO

NH RResin NH2 or

Epoxy Resin

+

ResinH2NEpoxy Resin CH2 CH CH2

O

Epoxy Resin CH2 CH CH2

OHNH Resin

+

Part A

Part B

2K Epoxy Properties

Toughness

Excellent adhesion

Commonly used as primers in the general metal industry

Waterborne Epoxides

Performance properties are lower than solventborne epoxides

Amine is used as surfactant

Epoxide is dispersed with surfactant in waterHigh concentration of surfactant

With all waterborne epoxide systems, viscosity increases are not a very reliable indicator of potlife as the crosslinking reaction takes place within a micelle

The gloss of waterborne epoxide systems begins to decrease with time once the crosslinking has proceeded beyond an unacceptable level in the can

This can lead to visibly distinct patches of different glosses especially on large architectural areas

Waterborne Epoxides

Advantages DisadvantagesNo organic solvents Short pot lifeEasy equipment cleaning Gloss stabilityExcellent adhesion Water evaporates slowlyExcellent interlayer adhesion Lower chemical resistCoating of plastics possible Wastewater treatment

Flash rust

Waterborne Epoxides (cont.)

Waterborne Epoxides: Type I

Epoxy resinLow molecular weightEquivalent weight ~190

Amine curing agentPolyaminesSalt is formed by reacting with acid

• Increased ability to form micelles

Amine curing agent

R NH3+

O CO

R"

Liquid epoxy resin

Amine hardener emulsifies epoxy resin

Part A Part B

Mixing justprior to use -


With liquid epoxides (EEW ~ 190):The curing agents - polyamines or polyamides are neutralized to form quarternary ammonium salts which can emulsify epoxide polymers when the two components are mixed together

Cosolvents, non-ionic surfactants, defoamers/anti-foaming agents constitute the rest of the formulation

Waterborne epoxides based on liquid epoxides are generally used as concrete and floor coatings because of their ability to cure on damp concrete

Ref: Van de Mark M., et al, APCJ, Jan 15, 1997

Waterborne Epoxides: Type II

Epoxy resinPre-emulsified using surfactants, shear and/or hydrophilic modification of the epoxyEquivalent weight is >1000

Amine hardenerMixed with the epoxy to form an emulsionMay be salted or used as straight amine

Michael Van De Mark and Kurt A. Kirby, Amer. Paint & Coat. Jour., 81 (15), 20-21, 1997.

Emulsified epoxy resin Aqueous phase amine


Epoxides of medium molecular weight (n ~ 2) have been rendered water soluble by reacting with hydrated maleinized fatty acids

H3C COOH

OO OCC

CHHC

H3C COOHHC CH

C CO

OO+

JOCCA, Novakov P. et al, 1993 (3) pp 111-115

H3C COOHHC CH

C CO

OO

H3C COOHHC CH

COOHHOOC

H2O

H2C CHO

CH2CHO

H2C CHOH

O CO

CH2CHOH

O CO H3C COOH

HC CH COOHH3C

HC CH COOH

COOH

+



The modified epoxide is then dissolved in water along with a neutralizing agent such as triethylamine

Cosolvents are also added to provide better film coalescence

These modified epoxides have been found to be suitable for electro deposition and dipping applications



Waterborne Epoxides

2K - do not require solvents for stabilityEpoxy is low MW; low equivalent weightUsed as concrete and floor coatingsDefoamers are important

Type I1K- need solvents for freeze-thaw stabilityEpoxy is higher MW; higher equivalent weightUsed for masonry coatings, metal primers, and architectural coatingsLonger pot life

Type II

Michael Van De Mark and Kurt A. Kirby, Amer. Paint & Coat. Jour., 81 (15), 20-21, 1997.

Development and Use of Waterborne Coatings for Rail Vehicles in Germany

J. Kruger, Journal of Protective Coatings and Liners, p. 30-38, September, 2000.

Maintenance coatings for passenger cars, rail cars, and locomotives is being done exclusively with waterborne coatings:

Primer: two-pack waterborne epoxy

Topcoat: two-pack waterborne polyurethane(Hydroxy polyester/acrylic hardened with polyisocyanate)

Development and Use of Waterborne Coatings for Rail Vehicles in Germany

J. Kruger, Journal of Protective Coatings and Liners,p. 30-38, September, 2000.

New locomotives, rail cars, and passenger cars are currently coated with solventborne coatings.

Next year waterborne coatings will be used for all new rail vehicles.

Primer: two-pack WB epoxy or PUIntermediate: two-pack WB epoxy or PUTopcoat: two-pack WB aliphatic PUAnti-graffiti: solventborne clearcoat

9 - Epoxies

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