Note: Descriptions are shown in the official language in which they were submitted.
21~3~91
`~ Mo4193
MD-93-136-lC
HIGH VISCOSITY, HIGH EQUIVALENT WEIGHT
POLYISOCYANATE MIXTURES CONTAINING
ALLOPHANATE AND ISOCYANURATE GROUPS
AND THEIR USE IN COATING COMPOSITIONS
5BACKGROUND OF THE INVENTION
Field of the Invention
The present invention is directed to high viscosity, high equivalent
weight polyisocyanate mixtures which contain allophanate groups and
10 isocyanurate groups, and to their use in one- and two-component coating
compositions.
Des~ iUtiGl I of the Prior Art
Presently, there are an increasing number of government
regulations which limit the amount of volatile solvents which may be
15 present in coating composilions. In order to reduce the viscosity of the
coating compositions, many attempts have been made to reduce the
viscosily of the individual components of the coating compositions,
particularly the isocyanate component. By reducing the viscosity of the
coating composition, less solvent will be necessary to attain the required
20 processing viscosity.
The viscosity of the polyisocyanate component has been reduced
by developing products which have lower equivalent weights and, thus,
lower viscosities, e.g., U.S. Patents 3,903,127; 4,801,663; and 5,124,427.
Because of their lower viscosilies, less solvent is needed to reduce the
25 viscosity of the resulting coating composition to the viscosity required for
subsequent processing.
Despite the efforts to develop high solids coating compositions by
reducing the viscosities of polyisocyanates, there is a need to further
reduce the amount of organic solvents present in coating compositions in
30 order to meet government regulations. The Applicants have discovered
that it is possible to reduce the amount of solvent that is necess~ry to
/vjt/121494
-2- 216359l
attain the required processing viscosity for two-componenl coating
compositions by the use of polyisocyanates containing isocyanurate
groups which have high viscosities and high equivalent weights. It is
totally unexpected in view of the literature available on coatings that it
would be possible to increase the solids content of a coating composition
by increasing the equivalent weight and, thus, the viscosity of the
polyisocyanate component.
One of the disadvantages of these isocyanurate group-containing
polyisocyanates is that to increase their viscosity requires a lengthy
reaction procedure which c~ ses the polyisocyanate component to yellow
and renders it unsuitable for many coating applicalions. ACCG~dj~YIY, it is
an object of the present invention to provide coating compositions which
retain the advantages of the coating compositions based on
isocyanurate-group containing polyisocyanates, but which may be used
to prepare coatings with improved yellowness properties.
This object may be achieved with the coating compositions of the
present invention in which the polyisocyanate component COII~;;IIS a
mixture of isocyanurate groups and allopllanale groups.
SUMMARY OF THE INVENTION
The present invention is directed to a polyisocyanate mixture
which
i) is prepared from a monomeric ~lal ling material containing
a) 30 to 100% by weight, based on the weight of a) and b), of
an aliphatic diisocyanate having 4 to 18 carbons in the
hydlocarL,on chain and
b) 0 to 70% by weight, based on the weight of a) and b), of a
diisocyanate other component a),
ii) has an equivalent weight that is at least 30% greater than the
average molecular weight of the monomeric starting material and a
Mo41 93
~3- 216 3591
viscosily of greater than 10,000 to 100,000 mPa.s when
determined at 25C on a sample having a solids content of 100%
and containing less than 2% by weight of unreacted diisocyanates
a) and b), and
iii) contains isocyanurate groups and allophanale groups in a molar
ratio of 10:1 to 1:10, wherein the allophanate groups are derived
from u,~ll,ane groups that are the reaction product of starting
material i) with 0.01 to 0.6 moles, per mole of starting material i),
of a monoalcohol having a molecular weight of up to 2500.
The present invention also relates to the use of these
polyisocyanate mixtures, optionally in blocked form, as an isocyanate
component in one- or two-component coating compositions.
DETAILED DESCRIPTION OF THE INVENTION
In a ,ureferled embodiment of the present invention the
15 polyisocyanate mixtures are prepared from
a) 30 to 100%, prer~rably 60 to 100%, more preferably 90 to 100%
and most prererably 100% by weight of one or more organic
diisocyanates represented by the formula
R'(NCO)2
wherein R' represents a divalent aliphatic hydrocarbon group
having 4 to 18 carbon atoms and
b) 0 to 70% by weight, prererably 0 to 40% by weight, more
prererably O to 10% by weight and most prererably 0% by weight
of one more orga,1ic diisocyanates represented by the formula
R''(NC0)2
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wherein R" represents a divalent cycloaliphatic hydrocarbon group
having 5 to 15 carbon atoms, a divalent araliphatic hydrocarbon
group having 7 to 15 carbon atoms and a divalent aromatic
hydrocarbon group having 6 to 15 carbon atoms.
Examples of suitable aliphatic diisocyanates a) include 1,4-
tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-
trimethyl-1,6-hexamethylene diisocyanate, 1,12-dodecamethylene
diisocyanate. Examples of suitable diisocyanates b) include
cyclohexane-1,3- and -1,4-diisocyanate, 1-isocyanato-2-isocyanatomethyl
cyclopentane, 1-isocyanato-3-isocyal1ato",ethyl-3,5,5-trimethylcyclo-
hexane (isophorone diisocyanate or IPDI), bis-(4-isocyanatocyclohexyl)-
methane, 2,4'-diisocyanato-dicyclohexyl methane, 1,3- and 1,4-bis-
(isocyanatomethyl)-cyclohexane, bis-(4-isocyanato-3-methyl-cyclohexyl)-
methane, xylylene diisocyanate, a,a,a',a'-tetramethyl-1,3- and/or -1,4-
xylylene diisocyanate, 1-isocyanato-1-methyl-4(3)-isocyanato-methyl
cyclohexane, and 2,4- and/or 2,6-hexahydrotoluylene diisocyanate, 1,3-
and/or 1,4-phenylene diisocyanate, 2,4- and/or 2,6-toluylene
diisocyanate, 2,4- and/or 4,4'-diphenylmethane diisocyanate, 1,5-
diisocyanato naphthalene and mixtures thereof.
The prerer,ed diisocyanate a) is 1,6-hexamethylene diisocyanate.
Preferred diisocyanates b) are isophorone diisocyanate, bis-(4-
isocyanatocyclohexyl)-methane, 2,4- and/or 2,6-toluylene diisocyanate
and 2,4- and/or 4,4'-diphenylmethane diisocyanate. Most prererably 1,6-
hexamethylene diisocyanate is used as the sole starting material.
It is also possible in accordance with the present invention to use
blends of the previously mentioned diisocyanates with monoisocyanates
or polyisocyanates having 3 or more isocyanate groups.
Suitable methods and catalysts for the preparation of
polyisocyanates containing isocyanurate groups and allophanate groups
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2163~91
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are known and described in U.S. Patents 5,124,427, 5,208,334 and
5,235,018, the disclosures of which are herein i,lco"uoraled by refere"ce.
The trimeri~alio,) of the starting diisocyanate mixture may be carried out
in the absence or in the presence of solvents which are inert to
5 isocyanate groups. Depending on the area of app' ~tion of the products
accordi"g to the invention, low to medium-boiling solvents or high-boiling
solvents can be used. Suitable solvents include esters such as ethyl
acetale or butyl acetate; ketones such as acetone or butanone; aromatic
compounds such as toluene or xylene; halogenated hydrocarbons such
10 as methylene chloride and l,icl1loroell,ylene; ethers such as
diisopropylether; and alkanes such as cyclohexane, petroleum ether or
ligroin.
In accordance with the present invention urethane groups and
sl lhse~ ~ently allophanate groups are incG, ,uorated into the polyiso-
15 cyanates by the use of ali~ l IdLiC, cycloaliphatic, araliphatic or aromaticmo,1oalcol,ols, i.e., alcohols in which the hydroxyl group is attached to
aliphatic, cycloali,uhalic, araliphatic or aromatic group. The monoalcohols
may be linear, bra"ched or cyclic, contain at least one carbon atom and
have a molecular weight of up to 2500. The monoalcohols may
20 optionally contain other hetero atoms in the form of, e.g., ether groups.
The molar ratio of monoalcohol to diisocyanate is about 0.01:1 to 0.60:1,
preferably about 0.02:1 to 0.50:1 and more prererdbly about 0.05:1 to
0.50:1. P,efe"~d monoalcohols are hydrocarbon monoalcohols.
The hyd~ocdrbon monoalcohols prererably contain 1 to 36, more
25 preferably 1 to 20 and most preferdbly 1 to 8 carbon atoms. Examples
of suitable mG"oalcol,ols include methanol, ethanol, n-propanol,
isopropa,1ol, n-butanol, isobutanol and tert. butanol, n-pentanol, 2-
hydroxy pentane, 3-hydroxy pentane, the isomeric methyl butyl alcohols,
the isomeric dimethyl propyl alcohols, neopentyl alcohol, n-hexanol, n-
Mo4193
2163~9l
heptanol, n-octanol, n-nonanol, 2-ethyl hexanol, trimethyl hexanol,
cyclohexanol, benzyl alcohol, phenol, the cresols, the xylenols, the
trimethyl,ul,enols, decanol, dodecanol, tetradecanol, hexadecanol,
oct.adec~nol, 2,6,8-trimethylno,1al1ol, 2-t-butyl-cyclohexanol, 4-cyclohexyl-
5 1-butanol, 2,4,6,-trimethyl benzyl alcohol, branched chain primary
alcohols and mixtures thereof (which are available from Henkel under to
Standamul trademark) and mixtures of linear primary alcohols (which are
available from Shell under the Neodol trademark).
~,ererled ether~ontaining monoalcohols include ethoxy methanol,
10 methoxy ethanol, ethoxy ethanol, the isomeric methoxy or ethoxy
propanols, the isomeric propoxy methanols and ethanols, the isomeric
methoxy butanols, the isomeric butoxy methanols, furfuralcohol and other
monoalcohols which have a molecular weight of up to 2500 and are
based on ethylene oxide, propylene oxide and/or butylene oxide.
It is also possible in accorda,1ce with the present invention to use
mixtures of the previously described monoalcohols.
When the polyisocyanates co"lai"ing isocyanurate groups and
allopha"aLe groups accorcli.,gly to the invention are prepared from
monoalcohols containing ethylene oxide units, the polyisocyanates may
be dispersed in water as described in U.S. Patent 5,200,489, the
disclosure of which is herein incorporated by reference.
The reaction temperature for isocyanurate and allophanate
formation in accordance with the present invention is about 40 to 180C,
prerera~ly about 80 to 150C and more preferably about 90 to 120C.
The process accordi, lg to the invention may take place either
batchwise or continuously, for example, as described below. The starting
diisocyanate is introduced with the exclusion of moisture and optionally
with an inert gas into a suitable stirred vessel or tube and optionally
mixed with a solvent which is inert to isocyanate groups such as toluene,
Mo4193
216~91.
--7-
butyl acetate, diisopropylether or cyclohexane. The previously described
monoalcohol may be introduced into the reaction vessel in accorda"ce
with several embodiments. The monoalcohol may be prereacted with the
starting diisocyanate to form urethane groups prior to introducing the
5 diisocyanates into the reaction vessel; the monoalcohol may be mixed
with the diisocyanates and introduced into the reaction vessel; the
monoalcohol may be separately added to the reaction vessel either
before or after, preferably after, the diisocyanates are added; or the
catalyst may be dissolved in the monoalcohol prior to introducing the
10 solution into the reaction vessel.
In accorda"ce with another embodiment of the present invention
the polyisocyanates may be prepared by blending polyisocyanates
containing isocyanurate groups with polyisocyanates containing
allophanate groups.
At a temperature of about 40C and in the presence of the
required catalyst or catalyst solution the trimeri,alion begins and is
indicated by an exothermic reaction. As the reaction temperature
increases the conversion rate of urell~a~1e groups to allophanate groups
increases faster than the formation of isocyanurate groups. Accordingly,
20 at some temperature for a given degree of trime,i dlion, the urethane
groups are substantially converted to allopl,anale groups, while at some
lower temperature unreacted urethane groups remain. The progress of
the reaction is followed by determining the NC0 col,lenl by a suitable
method such as lil,dlion, ~er,~cli,/e index or IR analysis. Thus, the
25 reaction may be terminated at the desired degree of trimeri,dlion. The
trimerization reaction is generally terminated when 40 to 90%, preferably
45 to 65%, of the isocyanate groups have reacted. When using 1,6-
hexamethylene diisocyanate as the sole monomeric starting material,
Mo41 93
21 63591
-8-
these perce,1lages correspond to an NC0 cor,le"l for the reaction mixture
of 5 to 30%, preferably 18 to 28%.
By terminating the reaction at a lower NC0 content than is
conventionally done to prepare low viscosity polyisocyanates, higher
5 viscosity polyisocyanates are obtained due to the formation of
polyisocyanurates, polyallophanates and other higher molecular weight
polyisocyanates COI ,lai"ing both isocyanurate groups and allophanate
groups.
The termination of the trimeli~alion reaction can take place, for
10 example, by the addition of a catalyst poison of the type named by way
of example in the above-mentioned literature references. For example,
when using basic catalysts the reaction is terminated by the addition of a
quantity, which is at least equivalent to the catalyst quantity, of an acid
chloride such as benzoyl chloride. When using heat-labile catalysts, for
15 example, the previously described qualer"ary ammonium hydroxides, it is
possible, though not pr~ferled, to dispense with the addition of a catalyst
poison since these catalysts decompose during the course of the
reaction. When using such catalysts, the catalyst quantity and the
reaction temperature are preferably selected such that the catalyst, which
20 continuously decomposes, is totally decomposed when the desired
degree of trime, i~alion is reached. The quantity of catalyst or reaction
temperature which is necessary to achieve this decomposition can be
determined by a preliminary experiment. It is also possible initially to use
a lesser quantity of a heat sensitive catalyst than is necessary to achieve
25 the desired degree of trimerization and to subsequently catalyze the
reaction by a further incremental addition of catalyst, whereby the
quantity of catalyst added later is calculated such that when the desired
degree of trimeri~dlion is achieved, the total quantity of catalyst is spent.
The use of suspended catalysts is also possible. These catalysts are
Mo41 93
216359 1
g
removed after achieving the desired degree of trimeri~aliG" by filtering
the reaction mixture.
The working-up of the reaction mixture, optionally after previous
separalio" of insoluble catalyst constituents, may take place in various
5 ways depending upon how the reaction was conducted and the area of
application for the isocyanates. Any unreacted monomer present in the
polyisocyanate product and opliollally any solvent used during the
trimeli~alio,l reaction may be removed by distillation in known manner.
The product obtained after distillation generally contains a total of less
10 than 2% by weight, prerer;ably less than 1 % by weight, based on the
solids content of the polyisocyanate mixture, of free (unreacted)
monomeric diisocyanates. The products accorcli"g to the invention are
generally viscous liquids having a minimum viscosity of greater than
10,000, preferably gredler than 12,000 and more preferably greater than
15,000 and a maximum viscosity of 100,000, preferably 90,000 and more
preferably 70,000, when determined at 25C on a sample having a solids
content of 100% and containing less than 2% by weight of unreacted
diisocyanates a) and b).
The polyisocyanate mixtures accordi, lg to the invention are almost
20 colorless, i.e., they have a yellowness index as measured on the APHA
color scale of 10 to 150, preferably 10 to 100 and more prererably 10 to
50. The polyisocyanate mixtures have an average functionality of at
least 2, preferably 2 to 7 and more preferably 2.5 to 5; and an equivalent
weight which is at least 30% greater, preferably 40% greater and more
25 preferably 50% greater, than the average molecular weight of the
monomeric starting material used to prepare the polyisocyanate mixture.
The products accordi, lg to the present invention are polyiso-
cyanates containing isocyanurate groups and allophanate groups. The
products may also conlai.) residual urethane groups which have not been
Mo4193
21fi3591
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converted to allopl ,a"ale groups depending upon the temperature
maintained during the reaction and the degree of isocyanate group
consumption. However, the content of urethane groups (c.~'cl~l~ted as
NHCOO, MW 59) should be less than 10% by weight, preferably less
5 than 5% by weight and more prererably less than 2%, based on the
solids co"le,ll of the polyisocyanate mixture. The ratio of isocyanurate
groups to al'o~.l ,anale groups in the polyisocyanates according to the
invention is about 10:1 to 1 :10, preferably about 5:1 to 1:7. These values
may be determined spectroscopically or by gel permeation
10 chromatography (GPC) using a standard.
The products according to the invention are valuable
starting materials for use in two-component coating compositions for the
production of polyisocyanate polyaddition products. Polyisocyanate
component A) is used in combination with compounds containing at least
15 two isocyanate-reactive groups, such as hydroxyl groups and/or amino
groups, preferably hydroxyl groups. The isocyanate-reactive component
preferat.ly has a viscosity (at 25C and a solids cGnle"l of 100%) which
is greater, I.rerelal,ly 20% greater and more preferably 50% greater than
the viscosity of polyisocyanate component A). The products according to
20 the invention may also be used as moisture-cure resins.
P,eferred reaction partners for the products according to the
invention, which may optionally be present in blocked form, are the
polyhydroxy polyesters, polyhydroxy polyethers, polyhydroxy poly-
acrylates, polyhydroxy polylactones, polyhydroxy polyurethanes,
25 polyhydroxy polyepoxides and optionally low molecular weight, polyhydric
alcohols known from polyurethane coatings technology. Polyamines,
particularly in blocked form, for example as polyketimines, oxazolidines or
polyaldimines are also suitable reaction partners for the products
accordi"g to the invention. Also suitable are polyaspartic acid derivatives
Mo41 93
11 2J 635~1
(aspa,lales) co"lai"ing secondary amino groups, which also function as
reactive diluents.
To prepare the coating compositions the amount of the polyiso-
cyanate component and the isocyanate reactive component are selected
5 to provide equivalent ratios of isocyanate groups (whether present in
blocked or unblocked form) to isocyanate-reactive groups of about 0.5 to
20, prererably 0.8 to 3 and more preferably about 0.9 to 1.5.
To accelerate hardening, the coating compositions may contain
known polyurethane catalysts, e.g., tertiary amines such as triethylamine,
10 pyridine, methyl pyridine, benzyl dimethylamine, N,N-dimethylamino
cyclohexane, N-methyl-piperidine, pentamethyl diethylene triamine, 1,4-
diazabicyclo[2,2,2]-octane and N,N'-dimethyl piperazine; or metal salts
such as iron(lll)-chloride, zinc chloride, zinc-2-ethyl caproate, tin(ll)-ethyl
caproale, dibutyltin(lV)-dilaurate and molybdenum glycolate.
The products according to the invention are also valuable starting
materials for two-component polyurethane stoving enamels in which the
isocyanate groups are used in a form blocked by known blocking agents.
The blocking reaction is carried out in known manner by reacting the
isocyanate groups with suitable blocking agents, ~JrereraL,ly at an
20 elevated temperature (e.g. about 40 to 160C), and optionally in the
presence of a suitable catalyst, for example, the previously desc,ibed
tertiary amines or metal salts.
Suitable blocking agents include monophenols such as phenol, the
cresols, the trimethylphenols and the tert. butyl phenols; tertiary alcohols
25 such as tert. butanol, tert. amyl alcohol and dimethylphenyl carbinol;
compounds which easily form enols such as acetoacetic ester, acetyl
acetone and malonic acid derivatives, e.g. malonic acid diethylester;
secondary aromatic amines such as N-methyl aniline, the N-methyl
toluidine, N-phenyl toluidine and N-phenyl xylidine; imides such as
Mo41 93
2163591
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succinimide; lactams such as ~-caprolactam and ~-valerolactam; oximes
such as butanone oxime, methyl amyl ketoxime and cyclohexanone
oxime; mercaptans such as methyl mercaptal" ethyl mercaptan, butyl
mercapta,l, 2-merca~.tobe"~lhiazole, a-naphthyl mercaptan and dodecyl
5 mercapta"; and triazoles such as 1 H-1 ,2,4-triazole.
The coating compositions may also contain other additives such
as pigments, dyes, fillers, levelling agents and solvents. The coating
compositions may be applied to the substrate to be coated in solution or
from the melt by conventional methods such as painting, rolling, pouring
10 or spraying.
Due to their high equivalent weights, the products according to the
invention, when blended with a suitable isocyanate reactive component
will need less solvent to obtain a particular processing viscosity than a
similar coating composition prepared from a corresponding low viscosity,
15 low equivalent weight polyisocyanate and the same isocyanate reactive
component when both coating compositions are prepared at the same
equivalent ratio of isocyanate groups to isocyanate reactive groups.
The coating compositions containing the polyisocyanates
according to the invention provide coatings which have improved dry
20 times, adhere surprisingly well to a metallic base, and are particularly
light-fast, color-stable in the presence of heat and very resistant to
abrasion. Furthermore, they are characteli~ed by high hardness,
elasticity, very good resistance to chemicals, high gloss, good weather
resislal,ce, good environmental etch resistance and good pigmenting
25 qualities. The polyisocyanates according to the invention also possess
good compatibility with highly branched polyester resins.
The invention is further illustrated, but is not intended to be limited
by the following examples in which all parts and percentages are by
weight unless otherwise specified.
Mo41 93
-- -13- 21~35
EXAMPLES
Polyisocyanate 1 - According to the invention
To a reactor equipped with a gas bubbler, stirrer, thermometer and
dropping funnel were added 100 parts of hexamethylene diisocyanate
5 (HDI). The stirred HDI was heated to 90C while dry nitrogen was
bubbled through the HDI. To the stirred HDI were added 4.4 parts of n-
butanol containing 0.0068 parts of trimethylbenzyl ammonium hydroxide
at such a rate that the 90C temperature was maintained. After the
addition was complete the reaction mixture was held at 90C for an
10 additional 15 minutes followed by the addition of 0.0068 parts of di-(2-
ethylhexyl) phosphate to terminate the reaction. The reaction mixture
had an NCO w,lt~"l of 21.9%. The excess monomer was removed by
wiped thin film evaporation to provide a clear liquid having an APHA of
c50, a viscosity of 53,100 mPa.s (25C), an NC0 cGnLelll of 15.8%, and
15 a free monomer (HDI) c~nlellt of <0.1%.
Using the procedure described in Example 1, additional
polyisocyanates were prepared using the reactants and conditions set in
in Table 1.
Mo41 93
FlNAL PRODUCT2
DExample #Alcohol Parts Parts Crude % % NCOEquiv. wt. % Visc. @ APHA
Alcohol perCatalyst' NCO Increase in 25C Color
100 parts Equiv. wt.3 mPas
HDI
2 1-BuOH 4.4 0.0050 25.1 17.3 243 44.5 18,000 ~ 25
3 1-BuOH 4.4 0.0052 24.1 16.7 251 49.7 24,600 < 25
4 1-BuOH 4.4 0.0064 23.3 16.4 256 52.4 41,200
1-BuOH 6.0 0.0040 23.0 15.8 266 58.2 20,100 ~ 25
6 1-BuOH 6.0 0.0045 20.1 14.9 282 67.8 83,400 c 25
7 1-BuOH 10.0 0.0040 20.6 13.6 309 83.8 51,800 < 25
8 Isocetyl 14.4 0.0075 18.6 13.7 307 82.5 50,600
9 Cyclohexanol 5.9 0.0050 25.7 17.1 246 46.2 20,000
Cyclohexanol 5.9 0.0060 24.2 16.5 255 51.5 49,400
11 Cyclohexanol 5.9 0.0090 21.9 16.0 263 56.3 99,000
12(Comp) 1-BuOH 0.12 0.0060 26.5 18.4 228 35.7 54,800 75
1 - the same amount of di(2-ethylhexyl)phosphd~e was added. C~
2 - the final product contained <0.1% free HDI Monomer.
3 - % increase in equivalent weight coll,par~d to monomeric starting material.
2163S91
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In the preparation of the polyisocyanate of Comparison Example
12, a minor amount of alcohol was used to dissolve the catalyst.
However, this amount was outside the scope of the present invention.
The resulting product, which did not contain the amount of allophanate
groups required by the present invention, had an APHA color of 75, while
the polyisocyanates accordi~y to the invention, which did contain
allophanate groups, had an APHA color of less than 25. It is apparent
from the yellowness values that the presence of allophanate groups
su".risi"gly improves the color of the high equivalent weight, high
viscosity polyisocyanates.
To demonstrate that high solids coating compositions can be
pre~ared with the high viscosil~ polyisocyanates accordi"g to the
invention, coating compositions were prepared from the-following
ingredients. One coating composition contained Polyisocyanate 4 as the
polyisocyanate component, while the other contained a commercially
available isocyanurate group-contai"ing polyisocyanate prepared from
1,6-hexamethylene diisocyanate (HDI) and having an isocyanate conle"l
of 21.6%, a conlenl of monomeric diisocyanate of ~0.2% and a viscosity
at 20C of 3000 mPa.s (available from Miles Inc. as Desmodur N 3300).
In both compositions the NCO/OH equivalent ratio was 1.1:1.0, the
solids content was 38.4% by weight and the VOC content was 5.0
Ibs/gal. The coating compositions contained the following ingredients:
Mo4193
2163~91
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Composition accordi"g Compariso"
to the invention Composition
Component 1
Polyol A4 37.19 39.61
Additives 0.24 0.24
Catalyst A6 0.12 0.12
Butyl acetale 21.29 20.03
Total Solvent 39.89 39.84
Component 2
Polyisocyanate from Example 4 6.16
Commercial Polyisocyanate - 5.0
4 - an acrylic polyol having a solids colltellt of 50% (available from Miles
as Desmophen A-450).
5 - an acrylate copolymer (available as Byk 358 from Byk Chemie).
6 - a 10% solution in butyl acetate of dibutyltin dilaurate (available as
Metacure T-12 from Air Products and Chemicals).
The initial viscosity of the compositions was determined at 25C
using a Brookfield LV Viscometer with a #2 spindle at 60 rpm.
Viscosity for composition according to the invention 125 mPa.s
Viscosity for comparisol, composition 130 mPa.s
The results demollslrale that even though the compositions
accordi"g to the invention were prepared from a polyisocyanate having a
viscosity of 41,200 mPa.s, they resulted in a lower viscosil~, than the
comparison compositions, which were prepared from a polyisocyanate
having a viscosity of 3000 mPa.s.
Mo4193
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Although the invention has been described in detail in the
foregoing for the purpose of illustration, it is to be understood that such
detail is solely for that purpose and that varialior,s can be made therein
by those skilled in the art without departing from the spirit and scope of
5 the invention except as it may be limited by the claims.
Mo41 93
