Note: Descriptions are shown in the official language in which they were submitted.
38
TITLE
Acrylourethane Reaction Product
~ACKGRO~ND
The present invention concerns an
acrylourethane polymer useful in high solids
coating compositions.
Environmental and economic concerns
often make it desirable to minimize the quantity
of oryanic solvent released to the atmosphere in
the application of paints, such as to automobiles,
either in single color coats or in color coat/clear
coat or other applications. One way to do this
is to make a paint with higher solids content
which contains less solvent to evaporate.
Several properties must be balanced and reconciled
in developing such a paint.
It would be desirable to have polymers
which can be used to make paints with relatively
high solids content and low viscosity.
While acrylourethane coating compositions
are known including U.S. Patents 4,304,706 (1981);
4,208,494 (1980); 4,208,49S (1980); 3,975,457 (1976);
and 3,919,351 (1975) all to Chang et al, it is
difficult to find combinations and proportions of
acrylic, diol and diisocyanate that will not gel
on reaction. In U.S. Patent 4,208,495, Example 1
uses certain monoalcohols during the reaction to
avoid gelling, however, the low level of hydroxyl
; ethyl acrylate such as 9% or less does not permit
suitable curing at bake temperatures as low as
might be desired.
7302 35
~2~
SUMMARY OF THE INVENTION
The ungelled reaction product, by weight
based on total polymer solids, of (a) 50-70% of an
acrylic prepolymer having a number average molecular
weight of 2,000-10,000 and an average of 5-15,
hydroxyl groups per chain, said prepolymer comprising
the following monomers in percent by weight based on
the prepolymer: 40-60~ of one or more of butyl
methacrylate or butyl acrylate, 10-30% lauryl
methacrylate, 20-40% of one or more of hydroxyethyl
acrylate, hydroxyethyl methacrylate, hydroxypropyl
acrylate or hydroxypropyl methacrylate, and 0-30% o~
one or more of styrene, methyl methacrylate and
ethyl methacrylate, (b) 20-35~ of at least one of
a monomeric diol and an oligomeric diol having a
number average molecular weight of 200-2,000, (c)
5-15% of an aliphatic or aromatic diisocyanate, and
(d) 1.0-4.0~ of a monofunctional alcohol.
DETAILED DESCRIPTION
An acrylic prepolymer of number average
molecular weight of2,000-10,000 (preferably
3,000-5,000) having an average of 5-15 hydroxyl
groups per chain (preferably 6-12) is first pre-
pared at temperatures of 130-160C. The monomer
composition of he acrylic can he varied according
to end use. Typical monomers are styrene, butyl
acrylate, methyl methacrylate, n-butyl methacrylate,
lauryl methacrylate, ethyl methacrylate and such
hydroxy containing monomers as hydroxy ethyl
acrylate or hydroxy propyl methacrylate. This
acrylic prepolymer is prepared at Ç0-70% weight
solids and is then co-reacted with various diols
and diisocyanates in the presence of tin catalysts
~2~
and traces of monofunctional alcohols to provide
for hydroxy-functional acrylourethanes. The mole
ratio of diol to diisocyanate is about 1 to 1.
Monofunctional alcohol is present
during the polymerization reaction at level~ of
1.0-4.0~ on total polymer solids with a preferred
level of 2.5%. This alcohol is present to
prevent gellation since the mole ratio of diol to
diisocyanate inherently leads to a gelling network.
The amount of hydroxyl extension can be
varied from 5 to 50% of the existent acrylic
hydroxyl groups with a preferred limit of 10-30~.
The range of 20-40~ of hydroxy ethyl acrylate or
related monomers permits curing in the range of
lS 110~132C, preferably 121C, for about 30 min.
The diol portion can be cDmprised of
monomeric diols such as neopentyl glycol, ethylene
glycol, cyclohexanedimethanol, 1,6-hexane diol,
1,4-butane diol or any other suitable diol having
from 2-10 carbons. The diol portion can also be
of an oligomeric ester-diol type such as poly-
caprolactone diol or any polyester diols having
number average molecular weights in the xange of
200-2,000 wi h those of Mn 500-11500 heing
preferred.
The diisocyanate can be either aliphatic
or aromatic in nature such as isophorone diiso-
cyanate, bis-cyclohexylmethylene-4,4l-diisocyanate,
hexamethylene diisocyanate, trimethyl hexamethylene
diisocyanate and toluene diisocyanate.
The acid content of the acrylourethanes
can be controlled either by post reaction with
various anhydrides such as o-phthalic, succinic,
~x~
glutaric or trimellitic anhydrides to acid numbers
of 10 or greater (15-25 preferred) or by carrying
the chain extension out in the presence of such
extending diols as dimethylolproionic acid.
Acrylourethanes prepared by the methods
described in the examples can be formulated into
high solids flexible coating which provide for
coatings exhibiting excellent low temperature
flexibility, good mar resistance and toughness
under normal conditions.
EXAMPLES
In the following examples,parts,
percentages and proportions are by weight except
where indicated otherwise.
Example la - Acrylic Prepol~mer
50~ butyl methacrylate
20~ lauryl methacrylate
30~ hydroxy ethylacrylate
To a 5-liter flask equipped with electric
heating mantle, mechanical stirrer, batch and vapor
thermometers, water cooled condenser, nitrogen
purge and addition funnels are added 100 grams of
xylene and 900 grams of aromatic hydrocarbon (bp.
160-170-C). The solvent is heated to reflux at
batch temperature of 150-160C.
A mixture of 1200 g n-butyl methacxylate,
400 g lauryl methacrvlate and 720 g hydroxyethyl
acrylate is added to the flask over a 4-hour
period. A solution of 38 grams of a 70% solution
of t-butyl peracetate and 3D grams of xylene is
added concomitantly with the monomer mix over 4
hours and twenty minutes. The batch is kept at
reflux duxing the additions and for twenty minutes
beyond the initiator feed at 150-160C. The
resultant acrylic resin has the following
characteristics:
Theoretical Acid No; 1-5 mg ~OH at 100
weight solids
Theoretical Hydroxyl No.: 140-lS0 mg KOH .
at 100% weight solids
Glass transition temperatures (Tg) -36C as
measured by differential scanning
calorimetry (DSC~
Wt. Solids: 67-69~ (determined with
heating at 110C for 1 hr)
Gar~ner-Holdt viscosity = T-V Q 25C
GPC (gel permeation chromatography) molecular
weight distribution:
number average Mn - 3570
; weight average Mw = 7520
Z average Mz = 13200
polydispersity d = 2.10
Example lb - AcrYlourethane Resin
To a 12-liter flask equipped with electric
heating mantle, mechanical stirrer, batch and vapor
thermometers, nitrogen purge, water cooled con-
~: denser and addition funnel are added 6710.60 q ~f
acrylic prepolymer from Example la, 1~32.2 g
CAPA-210 polycaprolactone diol, 175.4 g n~butyl
: alcohol, 0.4 g of dibutyl tin dilaurate, and
1066.3 g of methyl ethyl ketone.
The mixture is heated to reflux at
temperatures of 105-115C and then ~80 g of
Desmodur-W* diisocyanate and added over 30 minutes.
The mixture is then heated ~t reflux for 3 hours
at 105-115~C at which point thc isocyanate is
completely consumed as monitored by infrared. The
: 35 resultant resin has the following characteristics:
* denotes txade mark
1~8~ B
at 105~115C at which point the isocyanate is
completely consumed as monitored by infrared. The
resultant resin has the following characteristics:
Acid NoO: 1-5 mg KOH
Hydroxyl No.: 110-120 mg KOH
~ Wt. Solids = 67-69% (110C for 1 hr)
Gardner-Holdt viscosity: O-Q at 25C
Tg for the two polymer components: -48C
and -4C (DSC)
GPC Mol Wt.
Mn = 3720
Mw = 21700
Mz = 84100
d = 5.83
Example 2 - Acid Modified Acrylourethane
The acrylourethane from Example lb can
be post reacted with trimellitic anhydride in the
following manner.
Upon completion of the chain extension
reaction, the batch is allowed to cool to 80C
or less to provide for safe solids addition. A
total of 218.15 g of trimellitic anhydride is
added and the mixture is then heated a reflux at
105-115C for 30 minutes or until the acid number
is 15-22 mg KOH. The characteristics of the resin
are:
Acid No~: lS 20 mg XOH
Hydroxyl No.: 100-110 mg KOH
% Wt. Solids: 69-71 (110~C ~or 1 hr)
~ardner-Holdt viscosity: S-U at 25C
Tg: -45C and -4C as measured by DSC
GPC Mol Wt,
same as Example lb
:
~Z8Z~
E:cample 3 - Coatings from Acrylourethanes
Polymers of the present invention have
been formulated into various high solids flexible
enamels. A typical coating composition for an
unpigmented clear flexible ~namel is as follows:
60 parts solid acrylourethane resin of
Example lb
40 parts Resimene*755 melamine-formaldehyde
crosslinking resin made by Monsanto
2 parts on binder of Tinuvin*328 ultraviolet
absorber made by Ciba Geigy
1 part on binder of Tinuvin 079 hindered
amine light stabilizer made by
Ciba Geigy
1.2 parts on binder dodecyl benzene sulfonic
acid.
: The clear coating is diluted to 60% weight
solids with a 1/1 blend of xylene and methyl amyl
ketone to a viscosi~y of 35-40 seconds #2 ~isher cup.
The clear coating is then spray applied to primed RIM
sub trate to give a dry film build of 50 ~m + 2.5 ~m
of (2.0 mils - 0.1 mils) at a bake of 250F for 30
minu~es.
~: ~his clear coating exhibits excellent low
temperature flexibility as tested by ~ bend test
over a 1.27 cm 11/2 inch) cylindrical mandrel at
: -20F. The hardness is measured at 2.0-3.0 Knoops
by Tukon hardness, and the clear co2ting has
excellent humidity resistance and adhesion after
~ 30 exposure to 96 hours at lOO~F and 100% relative
: humidity.
* denotes trade mark
