Note: Descriptions are shown in the official language in which they were submitted.
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WO 97/30099 PCT/EP97/00579
10
C'oatina Composition
This invention relates to polyurethane coating compositions, their preparation
and use.
Coatings used for the original painting of motor vehicles and for their repair
are
required to have very good physical properties such as hardness and resistance
to water and
solvents. The coating compositions are also required to have good application
and
appearance properties so that they are easy to apply to a substrate using
spray application
and result in final films having a good Gloss.
One class of coating compositions commonly used for these applications
comprises
a hydroxyl functional polymer, such as a polyester or acrylic polymer, and a
polyisocyanate_
These two components react together after application to a substrate to form a
polyurethane coating.
Due to environmental considerations there is a general trend in the coatings
industry
towards coating compositions with reduced solvent content. One way to achieve
a lower
solvent content is to use so-called high solids compositions. High-solids
compositions are
solventborne compositions which contain a relatively high level of non-
volatile materials
such as film-forming polymer, pigments and fillers, and a relatively low level
of organic
solvent.
CA 02245730 1998-08-07
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2
A problem with formulating high solids coating compositions suitable for use
in
painting motor vehicles is that the compositions can have an unacceptably high
viscosity.
This is because the film forming polymers traditionally used in this field
have a high solution
viscosity in high solids solutions. The high viscosity gives rise to problems
in spray
application with poor paint atonuzation, and poor flow out and consequent low
gloss levels '
and poor appearance. In practice, these types of composition are formulated so
as to have a
predetermined viscosity to enable consistent spraying and this puts a limit on
the solids
content.
One way around the viscosity problem is to use lower molecular weight polymers
v,~ch generally have a lower solution viscosity. However this route has
limitations and
disadvantages. To produce low molecular weight acrylic polymers requires the
use of high
levels of initiators and chain transfer agents. These initiators and chain
transfer agents
become less efficient at high levels and lead to the presence of high levels
of recombination
products which cause toxicological and film performance problems. To produce
polyesters
of low molecular weight, conditions must be used under which a high level of
residual
polyol monomer remains which can cause film performance problems.
A better approach to very high solids compositions is to use a compound known
as
a reactive diluent as a partial or full replacement for the polyol. These
reactive diluents
reduce the viscosity of the polymer solution. Particularly useful reactive
diluents are
blocked or hindered amines such as aspartic esters, aldimines or ketimines.
Compositions
containing these types of viscosity modifier together with a hydroxyl
functional acrylic or
polyester polymer and a polyisocyanate are disclosed, for example, in EP-A-0
531 249.
Aldimines, ketimines and aspartic esters can be used to make compositions
having a
good balance of viscosity and solids content. However, partial replacement of
the polyol by
reactive diluent leads to compositions having a very short pot-life, probably
because the
diluent catalyses the reaction between the polyol and the polyisocyanate.
Replacement of all ,
of the polyol by diluent improves on the pot-life problem but the compositions
form brittle
films W th poor adhesion to a substrate, and are expensive due to the high
cost of the
4$ diluents.
CA 02245730 2004-10-27
~.Ye-have now discovered compositions which contain a polyisocyanate, an
aldimine
or a ketimine viscosity modifier and a particular hydrox-fl containing
component which
have both a good viscosity/solids balance and a good pot-life and which also
give films
having eood early properties such as hardness and drying.
According to the present invention there is provided a coating composition
comprising a solution in a volatile organic solvent of;
i) a polyisocyanate,
ii) a reactive diluent having blocked primary amine groups or hindered
secondary amine groups, and
I~
iii) a hydroxyl functional compound which is a polyester having secondary
hydroxyl goups.
The volatile of ~arLC SO1~'en_ can be any sol~: °::. which will
dissoh'e ti~:
~'', pOlVlpOVVanaLe, the ~'1W OSlty modiaer 2::~ Lh° h~'dr0\~'I
I'.'.':.:10:131 cOmpOUrt~. ;': Can be a.
211p1:a:l~;, or aromatic hydrocarbon suc;, as Solvesso 100 '-. toluene or
~c~,'iea~, an alcohe:
Such a5 butanol or isopropanol, an ester such as butyl a~c:tat° or
ethyl ac°:a.°, 2 4~etOr~
~; such as acetone, methyl isobutyl ketore or methyl ethy letoe. as ethe:,
2.~. etner-aICOCIC.
or a~ et:~er-ester or a t~i~:ure of an~~ e:i~.°se
Preferably the cernaositions coaain less than ~v~~ g 1 0~ volatile or=anic
solve-_
j~~ ba~~~ Oil the LOtal COmL~O~:;i.~,n, mCr2 ~r:r~rabl~' IzsS Il"~a~ .-'Si.,
Q~I ~i111 Li~.~Cr° ~'~:~ra5~~' le..
than 4?OQiI and most preferably less than 2~OQ'1.
Polyzsocyanates are well know ~1 in the coatings a::. Polvisocyanates ar a
compoune~
;~ having two or more isocyanate groups p:r :nolecule. The acvanate Groups
ca~~ be bloc~~::
but unblocked isocyanates are preferre~.
Suitable diisocyanates are aliphatic or aromatic diisocfanates. Exameles oL
suitabl°
-~p aliphatic diisocyanates are hexamethvlene diisocvanat~ and isophorone
diisocyanat:.
Examples of suitable aromatic diisocvanates ar: toluene diisecvanate a::;:
,~'-diphenylmethane diisocyanate.
Other suitable polyisocyanates iarclude the isocv'~LUrate trimers,
allophanates an;:
uretdiones of diisocyanates such as thus: described above as well as the
reaction product:
of these diisocyanates with polyols. Pefvols are compounds hsving three or
more hvdro»v
CA 02245730 1998-08-07
WO 97/30099 PCT/EP97/00579
4
groups. Suitable polyols include trimethylol propane, glycerol and
pentaerithritol. Many
such polyisocyanates are commercially available, for example under the
Desmodur trade
mark from Bayer or the Tolonate trade mark from Rhone Poulenc. .
Polyisocyanates are preferably used in an amount such that the ratio of
isocyanate
groups on the polyisocyanate to the total number of hydroxyl groups and
blocked or
unblocked amine groups in the composition is in the range 0.7:1 to 3:1, more
preferably
0.9:1 to 1.5:1.
Preferably the reactive diluent has blocked primary amine groups or hindered
1~ secondary amine groups. Examples of reactive diluents having blocked
primary amine
groups are aldimines and ketimines. Examples of reactive diluents having
hindered
secondary amine groups are aspartic esters.
~dimines or ketimines are compounds of formula (I)
R~ R'
\C -N R' N = C
R' ~ '
R
in which n_ is 0 to 4, R' and R'- are independently H, alkyl, cycloaliphatic
or substituted
alkyl, aryl or cycloaliphatic group, R' is aliphatic, cycloaliphatic, aromatic
or araliphatic
w~ch may also contain O, N, S, or Si.
Preferred ketimines and aldimines are obtained by reaction of a diamine and an
aldehyde or ketone. Preferred amines are diamines of the formula (II)
HzN R NH,
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WO 97/30099 PCT/EP97l00579
in which R is C2_,g aliphatic, cycloaliphatic or aryliphatic. Preferred
diamines are aliphatic an
aliphatic diamines. Examples of suitable aliphatic and cycloaliphatic
diaxnines are ethylene
diamine, propylene diamine and cycloaliphatic diamines of the formulas;
5
NH~ NHa NH=
NHz NHZ
NH"
TAN CH,- -NH, HyNCH:
CH,NH,
HrN - CHZ NHS NH= NHS
H,N CH, NH, H,NCH,
CH,NH,
HyN -~~ CHZ NHS H=N- CH= NHZ
NHS
j~' ~a
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6
AIdehydes and ketones suitable for use in making the aldimines and ketimines
are
those containing 1 to 8 carbon atoms such as propionaldehyde, butyraldehyde,
isobutyraldehyde, acetone, methyl ethyl ketone, methyl isobutyl ketone,
diisopropyl ketone,
cyclopentanone and cyclohexanone.
One particularly preferred aldimine is Desmophen TPLS 2142 (trade mark) from
Bayer.
Aspartic esters are secondary amine functional compounds made by nucleophilic
addition of a primary amine to an unsaturated carboxylic acid, ester or
anhydride. Examples
of suitable primary amines are aliphatic primary amines such as ethylamine,
propylamine
and butylamine. Preferred amines are diamines such as ethylene diamine,
hexane-1,6-diamine and 4,4'-methylenebis (2-methyl} cyclohexane amine.
Examples of
suitable unsaturated acids, esters and anhydrides are malefic and fumaric
acid, malefic
anhydride and malefic and fumaric acid esters such as dimethyl, diethyl and
dibutyl maleates
and fumarates.
Preferably the hydroxyl functional compound has a molecular weight of less
than
5000, more preferably less than 2500 and most preferably less than 2000.
Preferably the
secondary hydroxyl groups on the hydroxy functional compound are the product
of a
reaction between a carboxylic acid group and an epoxide group.
Preferably the hydroxyl functional compound is the reaction product of a
polyfunctional carboxylic acid and a monoepoxide, and so has secondary
hydroxyl groups
arising from the reaction of the acid groups on the polccarboxylic acid with
the epoxy
group on the monoepoxide.
preferred monoepoxides are glycidyl esters of C2-C20 alkanoic acids,
preferably
C8-C9 tertiary carboxylic acids such as versatic acid. One particularly
suitable
monoepoxide is Cardura EIO~'-".
The polyfunetional carboxylic acid can be a polyester with two or more
carboxylic
acid groups, preferably two to four carboxylic acid groups, more preferably
two or three
such groups. Polyesters are compounds containing more than one ester group.
Acid '
~nctional polyesters can be made by conventional methods from a mixture of
polyols,
diacids and anhydrides. One preferred acid functional polyester can be made by
reaction of
a polyol with a carboxylic acid anhydride. Poiyols are compounds with more
than one
a
CA 02245730 1998-08-07
WO 97/30099 PCTlEP97/00579
7
hydroxyl group. Preferably the polyol has from two to four hydroxyl groups per
molecule
and more preferably it is a diol or a triol, diols being particularly
preferred. Preferably the
polyol has a molecular weight of 66 to 150. Examples of suitable polyols are
ethylene
glycol, propylene glycol, neopentyl glycol, hexane-1,6-diol, glycerol,
trimethylol propane
and pentaerythritol. Preferred anhydrides are cyclic internal anhydrides of
dicarboxylic acids
such as malefic anhydride, succinic anhydride, phthalic anhydride and
hexahydroxyphthalic
a~ydride.
Preferably the reaction between the anhydride and the polyol is carried out
substantially stoichiometrically so that one anhydride molecule reacts with
each hydroxyl
group on the polyol. The resulting polyfunctional acid compound has
substantially the same
number of acid groups as the polyol had hydroxyl groups. Because the
hydroxyl/anhydride
reaction occurs at a Lower temperature than the carboxyl/hydroxyl or
transesterification
reactions, there are few side reactions and the molecular weight of the
product can be
controlled.
The reaction between the polyol and the anhydride can be carried out by
dissolving
the components in an organic solvent and then heating the solution preferably
to between
about 100 and 130°C for between about 1 and 3 hours so as to produce
the polyfunctional
carboxylic acid.
The reaction between the polyfunctional carboxylic acid and the monoepoxide
can
be carried out by adding the monoepoxide to a solution of the polycarbolylic
acid in a
suitable organic solvent in an amount so as to react each of the hydroxyl
groups on the
polyol with an epoxide group, and heating the mixture to between about 130 and
160°C for
between about 2 and 12 hours.
The compositions can also contain catalysts for the isocyanate-hydroxyl
reaction.
Suitable catalysts include tin catalysts such as dibutyl tin dilaurate and
amine catalysts such
as triethylamine. The compositions can also contain other conventional paint
additives
such as, pigments, fillers, UV absorbers and flow aids.
Preferably the non-volatile weight ratio of the reactive diluent to the
hydroxyl
functional polymer in the composition is 10:90 to 90:10, more preferably 60:40
to 40:60.
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WO 97/30099 PCT/EP97/00579
8
The compositions can be made by mixing the components, optionally dissolved in
organic solvent, in any order. Because of the limited pot-life of the
compositions, they are
preferably made by adding the polyisocyanate, to the reactive diluent and then
adding the
polyol.
The coating composition of the invention can be applied to the surface of a
substrate and then allowed or caused to dry and cure. According to the present
invention
there is provided a process for coating a substrate which comprises the steps
of applying a
layer of a coating composition according to the present invention to a surface
of the
substrate and thereafter causing or allowing the layer to cure.
The coating composition can be applied by conventional means such as by brush.
roller or spray, preferably spray. The substrate can be for example, metal,
plastic, wood or
glass. The compositions are particularly useful for refinishing motor
vehicles.
The applied layer can be allowed to cure at ambient temperature in the case
where
the hydroxyl polymer and crosslinker react together at ambient temperatures.
Alternatively
the layer can be baked at elevated temperatures, for example 50-120°C
to accelerate
curing. Drying and curing typically takes between 5 minutes and 24 hours
depending on the
ambient conditions and on the particular components used. Conveniently it
takes about 1 ~
minutes to about S hours.
According to the present invention there is also provided a coated article
obtainable
by the process.
The invention will now be illustrated by means of the following examples.
40
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WO 97/30099 PCT/EP97/00579
9
1. re aration of Polyesters 1 to 4 according to the invention.
1'1 Polyester 1 having secondary h d~ro_x~groups.
A mixture, of neopentyl glycol (56.5 parts) and hexahydroxy phthalic anhydride
(167.4 parts) were heated under nitrogen to about 95C so as to melt the
components. The
molten mixture was stirred and the temperature was slowly raised until an
exotherm
occurred at about 130C. At this point, heating was stopped and the temperature
went up to
I70C, then down to 150C whereupon heating was resumed and the mixture was held
at
16 150C for 1 hour. The mixture was then allowed to cool for lh. The mixture
was heated
back up to 150C, Cardura E 10~"f (glycidyl ester of a C8-9 carboxylic acid
from Shell, 276. I
parts) was added dropwise over a period of 3.5 hours and the mixture was
allowed to cool
to room temperature and left overnight. 'The mixture was heated to 150C for a
further 7
hours before being allowed to cool to room temperature. Butyl acetate (55
parts) was
added to give a theoretical non-volatile solids content of 90%. The final
measured acid
value was 0.5 mgKOH/g based on non-volatile content. The weight average
molecular
weight as measured by g.p.c was 719.
I-2 Polyester 2 having secondar~h~-drox~aroups
A mixture of trimethylol propane (49.3 parts) and hexahydroxy phthalic
anhydride
(170.1 parts) were treated under nitrogen to about 60C so as to melt the
components. The
molten mixture was stirred and the temperature was slowly raised until an
exotherm
occurred at about 150C. Heating was stopped and the temperature went up to
180C, and
back down to 150C. Heating was resumed and the mixture was held at 150C for 1
hour.
The mixture was allowed to cool for 1 hour. The mia-ture was heated back up to
i50C,
Cardura E10~"' (giycidyl ester of a C8-9 carboxylic acid from Shell, 280.6
parts) was added
dropwise over a period of 3 hours and the mixture was allowed to cool to room
temperature and left overnight. The mixture was heated to 150C for a further 7
hours
before being allowed to cool to room temperature. Butyl acetate {55 parts) was
added to
give a theoretical non-volatile solids content of 90%. The final measured acid
value was
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WO 97/30099 PCTIEP97/00579
l.6mgKOH/g based on non-volatile content. The weight average molecular weight
as
measured by g.p.c was 967.
5
1-33 P~lyester 3 having secondar~h d~ roxvl groups
A mixture of neopentyl glycol (57.3 parts) and phthalic anhydride (163.0
parts)
i 0 were heated to about 80C until the components melted. The molten mixture
was stirred and
the temperature was slowly raised until an exotherm occurred at about 110C.
The
temperature went up to 160C, and down to 150C. Cardura ElOT''~ (glycidyl ester
of a C8-9
carboxylic acid from Shell, 279.7 parts) was added dropivise over a period of
1.5 hours.
The mixture was allowed to cool for 1 hour and then heated back to 150C for a
further 2.5
hours before being allowed to cool to room temperature. Butyl acetate (55
parts) was
added to give a theoretical no-volatile solids content of 90%. The final
measured acid value
was l.lmgKOH/g based on non-volatile content. The weight average molecular
weight as
measured by g.p.c. was 791.
1~4 Polvester 4 having secondar~vdroxYl_~roups
A mixture of cyclohexane dimethanol (75 parts) and hexahydroxy phthalic
a~Ydride (160.4 parts) were slowly heated under nitrogen with stirring. At
about 170C an
exotherrn occurred and the temperature went up to 180C, after which the
temperature was
reduced to 150C. Cardura E10~ (glycidyl ester of a C8-9 carboxylic acid from
Shell,
264.6 parts) was added dropwise over a period of 1.5 hours.The mixture ivas
allowed to
cool at room temperature for 1 hour and then heated back to 150C for a further
2.5 hours
before being allowed to cool to room temperature. Butyl acetate (55 parts) was
added to
give a theoretical non-volatile solids content of 90%. T= ~ final measured
acid value was 3.5
mgKOHJg based on non-volatile content. The weight average molecular weight as
measured by g.p.c, was 749.
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I1
1-55 Polyester 5 havinp~,secondary_ hvdroxyi rg_ ouns
A mixture of neopentyl glycol (3 I2 parts) and hexahydroxy phthalic anhydride
(924
parts) were added to Solvesso 100T'i (aliphatic hydrocarbon solvent from
Exxon, 660
parts) and the mixture was heated to 90C. An exotherm occurred, after which
the
temperature was raised to I20C. The mixture was stirred at 120C for 2 hours.
The
temperature of the reaction mixture was raised to 150C and Cardura ElO~f
(glycidyl ester
of a C8-9 carboxylic acid from Shell, 1416 parts) was added over a period of 3
hours and
the mixture was allowed to cool to room temperature and left overnight. The
mixture was
heated to i 50C and stirred for a further 7 hours before being allowed to cool
to room
temperature.
2. Prgparation o~olXmers not according to the invention
2-11 . Comparative Polyester 6 having primary H d~owl Groups.
A mixture of trimethylol propane {306.85 parts), hexahydroxy phthalic
anhydride
(320.75 parts) and neopentyl glycol (52.31 parts) were heated slowly under
nitrogen over
about 2.5 hours to about 210C with stirring in a vessel equipped with a Dean
and Stark
separator for rerrioving water. The mixture was held at between 200 and 210C
for 4.5
hours whilst the water produced in the reaction was removed, until the final
measured acid
value was 28.6mgKOH/g based on non-volatile content. About 130mi of water was
removed in this time. The mixture was allowed to cool to below 120C and 277.6
parts of
butyl acetate was added to give a final theoretical non-volatile solids
content of 70%. The
weight average molecular weight as measured by g.p.c. was 1738.
2-22 Acrylic Polymer 7
A mixture of 2-ethylhexyl acrylate (17.78 parts), butyl acrylate (16.16 paris)
styrene
(I3.13 parts) hydroxy isopropyl methacrylate {I9.3 parts),
azodiisobutyronitrile ('Tazo 67~'
from DuPont, 2.33 parts), primary octyl mercaptan (2.33 parts) and butyl
acetate (7.42
parts) were added slowly over 3 hours to a refluxing mixture of Solvesso 100~~
(10.57
parts) and butyl acetate (10.57 parts) with stirring under nitrogen. The mih-
ture was stirred
CA 02245730 1998-08-07
WO 97/30099 PCT/EP97/00579
12
for 15 minutes and a peroxy initiator (Trigonox 21s~'~'~'i from Akzo, 0.116
parts) was added.
The mixture was stirred for a further I hour and further Trigonox 21 s (0. I
I6 parts) was
added. The mixture was stirred for a further hour and then allowed to cool to
room
temperature. The weight average molecular weight was 6I00.
l0 3. Coating compositions 1 and 2
Two coating compositions were prepared comprising a hydroxyl functional resin,
an
aldimine (Desmophen TPLS 2142'-" from Bayer AG), a polyisocyanate (HDT LVT",
from
done-Poulenc) and butyl acetate. These were made so as to have a viscosity of
25s BSB4
cup.
Composition I comprised Polyester 1 from paragraph 1.1 above at a non-volatile
weight ratio of 1: I hydroxyl functional resin to aldimine. Comparative
composition 2 was
similar but contained a known, commerciaily available hydroxyl functional
reactive diluent
K-Flex 188T'f (from King Industries) instead of hydroxyl functional Polymer 1.
The
compositions are summarised below in Table 1.
Ta I 1
Composition
1 2
dimine 3 2 29.2
olyisocyanate 56 61.7
3 olyester i 3 5. 5 -
5
-Flex 188 - 29.2
utyl acetate 32.4 36
4. Te in
The compositions were applied to clean glass sample panels using a 150m block
spreader. One sample panel of each was allowed to stand at room temperature
(20C) and
the dust-free times of the films were measured by recording the time at which
dust would
CA 02245730 1998-08-07
WO 97130099 PCT/EP97/00579
13
no longer stick to the film surface when attempt was made to remove it with a
small paint
brush. A second sample panel of each composition was baked at 60C for 30
minutes and
the film hardness was measured using a Konig hardness tester after standing
for 1 hour.
The viscosities of the bulk compositions were measured in seconds using a BSB4
cup 3
hours after making them as a guide to their pot-life. The results are given in
Table 2 below.
Ta le 2
Composition
IS Invention Comparative
1 2
3h Viscosity Rise (s) 20 51
Dust free time (mins) 30-45 60-7~
20Hardness lh after bake (s) 31 I2
These results show that composition I according to the present invention shows
25 better pot-life, faster tack free times at ambient temperature and improved
hardness after
baking.
5. Coating Compositions 3 to 6
Four coating compositions were made comprising Polyesters 2 to 4 and Acrylic
P°lymer 7, a 50/50 by weight mixture of two polyisocyanates (HD 100~I
from Olin and
HI)T LV~''f), an aldimine (Desmophen TPLS 2142') and butyl acetate. The
compositions
were made so as to have a weight ratio of polymer to aldimine of 1:1. The
ratio of the
number of hydroxyl and imine groups to the number of isocyanate groups was 1:1
in each
case. The compositions were made to a theoretical solids content of ~0%. The
compositions are detailed in Table 3 below.
CA 02245730 1998-08-07
WO 97!30099 PCTlEP97/00579
14
Table 3
. Composition
Components 3 4 5 6
Polyester 2 35.3 - - _
Polyester 3 - 35.3 - -
Polyester 4 - - 35.5 -
10Acrylic Polymer 7 - - - 45.9
PoIyisocyanate 56.4 56.4 56 55.8
Aidimine 31.8 31.8 32 32.I
Butyl acetate 26.5 26.5 26.4 16.2
The
compositions
were
tested
for
initial
viscosity.
Additional
butyl
actetate
(3
parts)
was
added
to
Composition
6
in
order
to
bring
its
viscosity
down
to
s
BS
B4.
The
compositions
were
tested
for
viscosity-
rise
after
I
hour,
dust-free
time
and
hardness
after
20
low-bake
as
described
in
paragraph
4
above.
The
results
are
given
in
Table
4
below.
Ta
le
4
25 Composition
Test 3 4 5 6
Initial Viscosity (80%26 25 25 28
solids)
lh viscosity rise (s) 11 S 1 8 3
30Dust free time {min) 30-40 30-40 30-40 60-70
Hardness after low ~8 32 36 still tacky
bake (s)
The results show that the compositions according to the invention show better
dust
free times and very much better hardness after baking than the composition
containing
acrylic polymer 7.
6. Compositions 7 to 10 containing Polyesters 1 to 4 and Acrylic Polymer 7 ~
Four compositions were made comprising polyesters 1 to 4, together with
acrylic
polymer 7, a 50/50 blend of two polyzsocyanates, (HDT LVT" and HDi00T'f), an
aldimine
~rpLS 2I42~'T'') and butyl acetate solvent. The compositions were made so as
to have a
weight ratio of polymer to aldimine of 1:1. The ratio of the number of
hydroxyl and imine
CA 02245730 2004-10-27
l~
groups to the number of isocyanate groups was 1:1 in each case. The
compositions were
made to a theoretical solids content of 80%. The compositions are detailed in
Table ~
below.
5
Table ~
Composition
10 Components 7 8 9 10
Polyester 1 17.8 - - -
Polvester 2 - 17.7 - I -
Polvester ~ - - 17.7 -
15 Polyester -'.'. - - - 17.8
acrylic Pol~~er 7 2'?.8 22.8 I 22.8 I 22.9
Polvisocvanate mixture ~6 ~6.? ~6.? ~ ~6
~
Aldimine I 3? I 31.9 31.9 , 32
20 Butyl acetate I ? 1.~ ? 1.1 ( 26.~ ~ ? 1.:~
The compositions were thinned to '_'~s BS B4 and tested for viscoaiy rise
after 1
hour. dust-free time and hardness a&er low-bake as described in paragraeh ~
above. The
~~ results are Qiven in Table 6 below-.
Table 6
Composition
'0Test 7 8 9 ~ 10
added Solvent to '_'~s 0 ? 2 ~ 1
BS B=1
1 h viscosiy rise (s) 7 7 18 I 7
35Dust free time (min) 30-=10 30-=10 ?0-30 30-40
I
Hardness lh afrer bake 29 36 ~3 ~ 32
(s)
40 7. Compositions l 1 and 12 co~r tainin~ Polyester 1. Comparative Polyester
6 and
ketimines.
Two compositions were made comprising Polyester 1 and Comparati~~e Polyester
6, a
4> j0/~0 blend of t<vo polvisocyanates, HDT LVr" and HDIOOr"', a ketimine
(Desmophen
VPLS 296~T" from Bayer ~G) and buyl acetate solvent. The compositions were
made so
CA 02245730 2004-10-27
16
as to have a weight ratio of polymer to aldimine of l:l. The ratio of the
number of
hydroxyl and imine groups to the number of isocyanate groups was 1:1 in each
case. The
compositions were made to a theoretical solids content of 80%. The
compositions are
5
detailed in Table 7 below.
10
Composition
Components 11 1?
Polyester 1 ( 37.7 ( -
1 Polyester 6 ( - ~ -10
~
Polvisocvanate mixture ( 6?.? i 6s
hetimine ~ 3 3 . 9 ~ ~ s
But~i acetate ~ 26.? ( 18
20
The comoositiuns «-zre tested for vi:cosit-~ rise afrer 1 hour, dust-free time
and hardness
afrer low--bake as described in paragraph -1 above. The results are given in
Table 8 below.
Table 3
Composition
Test ( 11 12 (
lh viscosity rise (s} 7 73
Dust free time (min) 90-120 30-=1~
Hardness 1 h after bake36 109
(s)
35
The results clearly show that Composition l1 has an acceptable pot-life while
Composition 1? has an unacceptably short pot-life.
40
3. Primer Com~Qsition
s. l Fillers Heucophos ZP ~T" (762.1 ) and Byk 110'x'' (36g), iVlistron
Vlonomi:c~'' (329.=18g) and Vlicrodol E:ctrar'' (668.96g), were added slowly
in the order given to a mixture of Polyester 3 from 1.3 above (160.370
and a solvent mixture (60g) comprising equal quantities of xylene, butyl
Ta !e 7
CA 02245730 1998-08-07
WO 97130099 PCT/EP97/00579
17
acetate and propylene glycol monomethyl ether in a Dispermat HSD '~'M high
speed disperser. A pigment mixture of Bentone SD2~'t {12.6g) and titanium
dioxide ( 128.64g) was added slowly and the mzxture was dispersed for a
further 45 minutes. Further solvent mixture (544g) was added to form a
pigmented primer base.
8.2 Ketimine (Desmophen VPLS 2965~'f from Bayer AG; 8.65 parts)
and a polyisocyanate (HDT 90~"f, from Rhone-Poulenc, 14.35 parts) were
added to the composition (77 parts) and the composition was thinned to 25
seconds BSB4 with butyl acetate.
8.3 The composition was applied to clean glass sample panel using a
150m block spreader, the panel was allowed to stand at room temperature
(20°C) and the dust-free time of the film was measured to be 25 minutes
by
recording the time at which dust would no longer stick to the film surface
when attempt was made to remove it with a small paint brush. The viscosity
of the bulk composition was measured using a BSB4 cup 0.5 hours after
m~ng it as a guide to its pot-life to be 43s.
35
45
~z ?" ~ t : ~ ~ .. ~-.. , ~ __ R,c~~, T. ; "~
r . t. .
