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Polyether Polyols
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Polyether polyols
can be used in coatings as modifier for high solids and
waterborne
industrial crosslinked coatings. Polyether polyols decrease VOC, improve flexibility and raise the application
solids. Polyether polyols can be used with melamine and with isocyanate crosslinked
coatings. Polyether polyols can also introduce potential problems
into coatings. Adhesion to metals surfaces and water resistance can
suffer. Additive levels of 5-10 % are for many applications
acceptable. Polyether polyols can be crosslinked with melamine
formaldehyde, with polyisocyanates, blocked isocyanate or with other
hydroxyl reactive crosslinker.
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Amine Polyols
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Amine polyols can function as neutralize
and emulsifier in a waterborne coating
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Polyether Polyols
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Addition reaction products of propylene oxide, ethylene oxide on
alcohols and phenols or THF polymer. Most polyether are soft and
give low Tg films. For increased hardness and improved water
resistance and corrosion resistance bisphenol A based polyether
polyols can be used.
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Applications
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PPG homo polymer MW 400-700
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Reactive diluent for high solids coatings and reactive co-solvent
replacement for waterborne crosslinked coatings. General industrial
single coat and primer crosslinked with HMMM melamine resin or with
polyisocyanate. Addition levels as high as 30 % are possible.
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PPG based triol, MW 400-1500
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Similar applications as above but increased crosslink density.
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THF polyol 400-1000
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More hydrophobic than polypropylene glycol, improved water
resistance and highly elastomeric properties. Higher cost than PPG
polyols.
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Bisphenol A EO or PO adduct
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Increased hardness and improved adhesion to metal surfaces. Modifier
for cationic epoxy resins.
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Features
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Low viscosity
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PPG diols and triols with a MW <1000, <500 cps at 25ºC
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Solubility
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Soluble in all polar solvents and in water
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Flexibility
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Glass transition temperature (Tg) of -80ºC
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Compatible
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Acrylic, polyester, alkyds,
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Hydrolytic stability
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Excellent stability at a pH of 3-14
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Function
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Flexibility
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5-10 % can increase flexibility, also low temperature flexibility
can be improved
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Hydrolytic stability
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Polyether resins have excellent hydrolytic stability under basic
conditions
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Reduction in cost
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Polyether polyols are lower in cost
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Higher solids
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Low viscosity permits an increase in application solids
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Reduction in VOC
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Can be used as reactive co solvent and diluent
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Disadvantage
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Softer films
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The low Tg of the polyol can reduce film hardness
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Exterior durability
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Polyether can reduce the exterior durability.
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Water sensitivity
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High levels of polyether can increase the water sensitivity. Use of
higher functional polyols can reduce water sensitivity.
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Adhesion
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Polyether have poorer adhesion to metal surfaces
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Gloss
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Higher levels of polyether can give pigment flocculation
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Amine Polyether
Polyols
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Amine polyether
polyols can be used in waterborne coatings to neutralize carboxyl
functional resins.
Amine Polyether Polyols improve flow and leveling and also aid
pigment dispersion. Amine polyether polyols are very effective
dispersants for carboxyl functional resins and pigments. It
is possible to disperse waterborne resins with only partial
neutralization of the resin.
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Applications
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High Solids
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Higher solids, improved flexibility
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Waterborne
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Higher solids, increased flexibility
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Wood coatings
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Flexibility
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General industrial
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Flexibility
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Features
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Nonvolatile
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Amine will co-react and be built into film
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Gloss
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Reduction in wrinkling for HMMM crosslinked coatings
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Solvent popping
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Increased film thickness without solvent popping.
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Catalyst
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Increase the rate of reaction of isocyanate crosslinked coatings.
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Disadvantage
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Cure inhibition
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The presence of amine can inhibit amino resin crosslinked coatings. High imino or
methylol functional melamine resins are less sensitive to cure
inhibition.
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Yellowing
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At very high cure temperature yellowing can be seen. Because the
amine is tertiary, yellowing is usually not a problem.
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Exterior durability
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Lower MW amine polyether have surprisingly good exterior durability.
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Waterborne coatings
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Polyether polyols to waterborne coatings do not necessarily have to
be water-soluble, water-insoluble polyether resins can be
solubilized in the presence of water-dispersible resins. Polyether
resins show inverted water solubility, therefore, accelerate testing
at higher temperatures can produce misleading results. Substantial
improvements in properties can be obtained with the use of either
bisphenol A EO or phenol formaldehyde EO or PO diols and polyols.
The presence of the aromatic moiety improves the adhesion and
corrosion resistance to metal surfaces, it increases hardness and
still give excellent flexibility. Exterior durability is
substantially impaired with these compounds. Short chain bisphenol A
EO and PO adducts can substantially improve the water resistance and
detergent resistance of coatings.
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Water soluble polyether
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PPG diol
polyether MW <700
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PPG triol
polyether MW <1000
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PPG
polyol functionality >3, MW <1000
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Bisphenol
A EO adducts 6-8 EO
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Water insoluble polyether
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PPG diol
with MW >700.
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THF diols
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Bisphenol
A adduct EO <6 EO
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Bisphenol
A adduct PO
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Water dispersible polyether
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PO-EO
block polymers
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Amine functional polyether
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Triethanolamine
PO adducts
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Ethylenediamine
PO/EO adducts
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High solids coatings
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Polyether polyols due their low Tg give exceptional low viscous
coatings. Modification of a polymer with a polyether is therefore
one of the lowest cost methods to reduce VOC of a coating and to
improve flexibility. The loss in hardness can be partially
compensated by using higher functional polyether
polyols.
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PPG diol
with MW >700.
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THF diols
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Bisphenol
A adduct EO <6 EO
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Bisphenol
A adduct PO
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