U.S. patent application number 11/286717 was filed with the patent office on 2006-05-25 for polyisocyanate mixtures, a process for their preparation and their use in coating compositions.
This patent application is currently assigned to Bayer MaterialScience AG. Invention is credited to Martin Melchiors, Jorg Schmitz, Christian Wamprecht.
Application Number | 20060111539 11/286717 |
Document ID | / |
Family ID | 35986232 |
Filed Date | 2006-05-25 |
United States Patent
Application |
20060111539 |
Kind Code |
A1 |
Wamprecht; Christian ; et
al. |
May 25, 2006 |
Polyisocyanate mixtures, a process for their preparation and their
use in coating compositions
Abstract
The present invention relates to polyacrylate-modified
polyisocyanates which are i) prepared from aromatic, araliphatic,
cycloaliphatic and/or aliphatic polyisocyanates having an NCO
content of 5% to 25% by weight, an NCO functionality .gtoreq.2, a
viscosity measured as solvent free resin of 150 to 200,000 mPas at
23.degree. C., and ii) contain at least one structural unit of the
formula (I) ##STR1## wherein R is hydrogen or a methyl group,
R.sup.1 is an optionally heteroatom-containing hydrocarbon radical
and R.sup.2 is a hydrocarbon radical having at least one isocyanate
group and optionally urethane, allophanate, biuret, uretdione,
isocyanurate and/or iminooxadiazinedione groups and n ist a number
.gtoreq.1. The present invention also relates to a process for
preparing these polyisocyanates and to binder compositions
containing these polyisocyanates, which may be hydrophilically
modified, and a compound having NCO-reactive groups.
Inventors: |
Wamprecht; Christian;
(Neuss, DE) ; Melchiors; Martin; (Leichlingen,
DE) ; Schmitz; Jorg; (Koln, DE) |
Correspondence
Address: |
BAYER MATERIAL SCIENCE LLC
100 BAYER ROAD
PITTSBURGH
PA
15205
US
|
Assignee: |
Bayer MaterialScience AG
|
Family ID: |
35986232 |
Appl. No.: |
11/286717 |
Filed: |
November 23, 2005 |
Current U.S.
Class: |
528/44 |
Current CPC
Class: |
C08G 18/6254 20130101;
Y10T 428/31551 20150401; C08G 18/672 20130101; C08G 18/8116
20130101; C08G 18/6229 20130101 |
Class at
Publication: |
528/044 |
International
Class: |
C08G 18/00 20060101
C08G018/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 25, 2004 |
DE |
102004056849.9 |
Claims
1. A polyacrylate-modified polyisocyanate which is i) prepared from
an aromatic, araliphatic, cycloaliphatic and/or aliphatic
polyisocyanate having an NCO content of 5% to 25% by weight, an NCO
functionality.gtoreq.2 and a viscosity measured as solvent free
resin of 150 to 200,000 mPas at 23.degree. C., and ii) contains at
least one structural unit of the formula (I) ##STR3## where R is
hydrogen or a methyl group, R.sup.1 is an optionally
heteroatom-containing hydrocarbon radical and R.sup.2 is a
hydrocarbon radical having at least one isocyanate group and
optionally a urethane, allophanate, biuret, uretdione, isocyanurate
or iminooxadiazinedione group and n is a number .gtoreq.1.
2. The polyacrylate-modified polyisocyanate of claim 1 wherein
R.sup.2 contains at least one urethane, allophanate, biuret,
uretdione, isocyanurate and/or iminooxadiazinedione group.
3. A process for preparing the polyacrylate-modified polyisocyanate
of claim 1 which comprises reacting a portion of the isocyanate
groups of A) a starting polyisocyanate with B) a monoalcohol
containing acrylate and/or methacrylate groups, to form urethane
groups, and subsequently to or simultaneously with the
urethanization, reacting the unsaturated groups of the resulting
reaction product by free-radically initiated polymerization
optionally with C) other unsaturated monomers.
4. The process of claim 3 wherein starting polyisocyanate A)
comprises a polyisocyanate containing a urethane, uretdione,
allophanate, biuret, isocyanurate or iminooxadiazinedione group and
exclusively containing aliphatically and/or cycloaliphatically
bound NCO groups.
5. A polyurethane and/or polyurea prepared from the
polyacrylate-modified polyisocyanate of claim 1.
6. A coating, adhesive, or sealant composition comprising the
polyacrylate-modified polyisocyanate of claim 1.
7. A substrate coated with the coating composition of claim 6.
8. A binder composition comprising the polyacrylate-modified
polyisocyanate of claim 1, wherein optionally some or all of whose
NCO groups have been blocked, and a compound having NCO-reactive
groups.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to modified polyisocyanate
mixtures based on polyisocyanates and polyacrylate units, to a
process for preparing them and to their use as a curing component
in polyurethane coating compositions.
[0003] 2. Description of Related Art
[0004] With polyurethane coating compositions, particularly if they
are to be used in the vehicle, industrial or furniture sectors,
especially great value is generally placed on the resistance of
such coating compositions to different environmental influences.
The criteria are frequently hardness, chemical resistance and
solvent resistance, scratch resistance, including what is called
"reflow", light stability and weather resistance.
[0005] By "reflow" is meant the ability of a cured coating (film)
to compensate for minor film damage (in the Jim range), caused by
scratching or impact on the film, by cold flow of the coating
composition into the damaged site.
[0006] To improve the scratch resistance use is frequently made of
oligomeric polyisocyanates based on hexamethylene diisocyanate
(HDI) as the polyisocyanate component. The polyurethane coating
compositions prepared from such components are generally tough and
elastic with good reflow. Disadvantages of such coating
compositions include the somewhat slow drying at room temperature
and slightly elevated temperature, and also the merely moderate
acid resistance. Hard, fast-drying polyurethane coating
compositions with very good acid resistance are generally obtained
with polyisocyanate curatives based on isophorone diisocyanate
(IPDI). The scratch resistance and the reflow of such coating
compositions, however, are generally inadequate. Moreover,
IPDI-based polyisocyanates have a high viscosity and a relatively
low isocyanate content.
[0007] U.S. Pat. No. 4,419,513 describes isocyanurate
polyisocyanates which are obtained by the mixed trimerization of
HDI and IPDI. It is disclosed that the mixed trimers have desirable
properties in terms of hardness and elasticity. A disadvantageous
consequence with these mixed trimers is that, due to the fraction
of IPDI, which is necessary for the requisite hardness and rapid
physical drying, the amount of isocyanate groups (relative to the
molecular weight) is lower than in the case of pure HDI trimers,
with attendant economic drawbacks.
[0008] EP-A 0 646 608 relates to polyisocyanates which are obtained
by the cyclic trimerization of at least one aliphatic or alicyclic
diisocyanate either after its reaction with a polyfunctional
alcohol or by trimerization in the presence of such an alcohol.
Although such polyisocyanates have high functionalities, the
fraction of polyfunctional alcohol in the polyisocyanate molecule
prepared lowers the weight fraction of isocyanate groups per
molecule and, as a consequence of the urethane groups that form,
there is a marked increase in viscosity. With regard to the use of
the polyisocyanate, this necessitates an economically undesirably
high amount of polyisocyanate curative and an increased volume of
solvent for adjusting the application viscosity of the coating
composition.
[0009] U.S. Pat. No. 4,454,317 describes polyisocyanate containing
isocyanurate groups which are obtainable by trimerizing HDI.
Described by way of example is an HDI trimer having an NCO content
of 20.8% by weight and a viscosity of 14 Pas at room temperature.
This patent does not disclose anything regarding the possibility of
using polyisocyanates of such high viscosity, in combination with
suitable polyols, to prepare polyurethane coating compositions
having improved chemical resistance.
[0010] The modified polyisocyanate mixtures disclosed in DE-A 100
13 187 are notable for a high isocyanate functionality, but this is
largely obtained at the expense of the isocyanate content of the
respective polyisocyanate. In the preparation of high functionality
or high molecular weight polyisocyanates by the oligomerization of
diisocyanates by known isocyanate reactions such as biuretization,
urethanization, trimerization and allophanatization, large numbers
of isocyanate groups are generally consumed for these molecular
weight-increasing and functionality-building isocyanate reactions.
In general the higher the molecular weight of the polyisocyanate
becomes, the more the isocyanate content of the end product falls.
This circumstance harbours economic drawbacks.
[0011] Therefore, it is an object of the present invention to
provide new polyisocyanate compositions, which function as a curing
component in polyurethane coating compositions and, in so doing,
are able to satisfy the broad spectrum of coating properties that
are required, and do not exhibit the stated disadvantages of prior
art polyisocyanates. These new polyisocyanate compositions should
be variable and should represent an optimum in terms of achievable
isocyanate content, molecular weight and functionality.
[0012] This object may be achieved with the polyacrylate-modified
polyisocyanate of the present invention, which exhibit the required
properties. These new polyisocyanates may be obtained by partial
reaction of known polyisocyanates with hydroxy-functional
unsaturated compounds to form urethane groups and subsequent
polymerization of the unsaturated groups and optionally
copolymerization with other unsaturated compounds. These new
polyisocyanate mixtures are capable of broad variation in terms of
their composition, their molecular weight and their functionality
and thus in terms of their overall profile of properties.
[0013] The modified polyisocyanate mixtures of the invention have
very good compatibility with a multitude of polyols and can be
formulated to polyurethane coating compositions having a broad
spectrum of properties. Particularly advantageous when compared to
the corresponding base polyisocyanates have proven to be the
markedly improved physical drying and significantly higher solvent
resistance and chemical resistance of corresponding polyurethane
coating compositions, particularly those based on HDI, without loss
of toughness and elasticity, the good reflow or the high scratch
resistance.
SUMMARY OF THE INVENTION
[0014] The present invention relates to polyacrylate-modified
polyisocyanates which are i) prepared from aromatic, araliphatic,
cycloaliphatic and/or aliphatic polyisocyanates having an NCO
content of 5% to 25% by weight, an NCO functionality .gtoreq.2, a
viscosity measured as solvent free resin of 150 to 200,000 mPas at
23.degree. C., and ii) contain at least one structural unit of the
formula (I) ##STR2##
[0015] R is hydrogen or a methyl group,
[0016] R.sup.1 is an optionally heteroatom-containing hydrocarbon
radical and
[0017] R.sup.2 is a hydrocarbon radical having at least one
isocyanate group and optionally urethane, allophanate, biuret,
uretdione, isocyanurate and/or iminooxadiazinedione groups and
[0018] n is a number .gtoreq.1.
[0019] The present invention also relates to a process for
preparing these polyisocyanates by reacting a portion of the
isocyanate groups of
[0020] A) a starting polyisocyanate with
[0021] B) a monoalcohol containing acrylate and/or methacrylate
groups, to form urethane groups, and subsequently to or
simultaneously with the urethanization, reacting the unsaturated
groups of the resulting reaction product by free-radically
initiated polymerization optionally with
[0022] C) other unsaturated monomers.
[0023] The present invention also relates to binder compositions
containing the polyacrylate-modified polyisocyanates of the
invention, optionally having blocked NCO groups, and a compound
having NCO-reactive groups.
[0024] The present invention also relates to water-dilutable or
aqueous binder compositions containing the polyacrylate-modified
polyisocyanates of the invention, wherein a portion of the NCO
groups have been hydrophilically modified with polyether units, and
a compound having NCO-reactive groups.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The hydrocarbon radical R.sup.2 is based preferably on
aromatic, cycloaliphatic, araliphatic and/or aliphatic di- and/or
polyisocyanates and preferably contains at least one of the
structural units referred to as optional.
[0026] Starting polyisocyanates A) include the di- and/or
polyisocyanates which are known in polyurethane chemistry. It is
immaterial whether these isocyanates are prepared with phosgene or
by phosgene-free processes. Preferred starting polyisocyanates are
lacquer polyisocyanates containing urethane, uretdione,
allophanate, biuret, isocyanurate and/or iminooxadiazinedione
groups and prepared from monomeric di- or triisocyanates.
[0027] Monomeric isocyanates, which can be used alone or in
admixture include 1,6-di-isocyanatohexane,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane
(isophorone diisocyanate), 4,4'-diisocyanatodicyclohexylmethane,
4-isocyanatomethyl-1,8-octane diisocyanate,
1,4-diisocyanatocyclohexane, 1-methyl-2,4-diisocyanatocyclohexane
and mixtures thereof with up to 35% by weight, based on the total
mixture, of 1-methyl-2,6-diisocyanatocyclohexane, and
2,4-diisocyanatotoluene (TDI) and its mixtures with up to 35% by
weight, based on the total mixture, of 2,6-diisocyanatotoluene.
[0028] Preferably, lacquer polyisocyanates are used as component
A). They include lacquer polyisocyanates containing urethane
groups, which are prepared by reacting 2,4- and optionally
2,6-diisocyanatotoluene or 1-methyl-2,4- and optionally
1-methyl-2,6-diisocyanatocyclohexane with substoichiometric amounts
of trimethylolpropane or its mixtures with monomeric diols, such as
the isomeric propanediols or butanediols, for example. The
preparation of these lacquer polyisocyanates containing urethane
groups in virtually monomer-free form is described for example in
DE-A 109 01 96.
[0029] The lacquer polyisocyanates containing biuret groups include
in particular those based on 1,6-diisocyanatohexane and prepared as
described, for example, in EP-A 0 003505, DE-B 1 101 394, U.S. Pat.
No. 3,358,010 or U.S. Pat. No. 3,903,127.
[0030] The lacquer polyisocyanates containing isocyanurate groups
include the trimers or mixed trimers of the diisocyanates
exemplified above such as the isocyanurate-group-containing
polyisocyanates based on TDI as described in GB-A 1 060 430, GB-A 1
506 373 or GB-A 1 485 564; and the mixed trimers of TDI with
1,6-diisocyanatohexane, which are described, for example, in DE-A
164 480 9 or DE-A 314 467 2. Preferred lacquer polyisocyanates
containing isocyanurate groups are the aliphatic,
aliphatic/cycloaliphatic and/or cycloaliphatic trimers or mixed
trimers based on 1,6-diisocyanatohexane and/or isophorone
diisocyanate that are obtained, for example, as described in U.S.
Pat. No. 4,324,879, U.S. Pat. No. 4,288,586, DE-A310 026 2,DE-A310
026 3,DE-A303 386 0or DE-A314 467 2.
[0031] Other suitable lacquer polyisocyanates are those containing
iminooxadiazinedione groups, which may be prepared as described,
for example, in EP-A 798 299, EP-A 896 009, EP-A 962 454 and EP-A
962 455.
[0032] Especially preferred starting polyisocyanates are urethane,
uretdione, allophanate, biuret, isocyanurate and/or
iminooxadiazinedione group-containing polyisocyanates exclusively
containing aliphatically and/or cycloaliphatically bound NCO
groups.
[0033] Starting polyisocyanates A) preferably have an NCO group
content of 5% to 25% by weight, an average NCO functionality of 2.0
to 5.0, preferably 2.8 to 4.0, and a residual monomeric
diisocyanate content of below 1% by weight, preferably below 0.5%
by weight. The starting polyisocyanates have a viscosity of 150 to
200,000 mPas at 23.degree. C., measured using a rotational
viscometer in accordance with DIN 53019.
[0034] Preferred acrylate and/or methacrylate group-containing
monoalcohols B) include the hydroxy-functional esters of acrylic
and/or methacrylic acid. Suitable esters include hydroxyethyl
acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate (isomer
mixture formed in the addition reaction of propylene oxide with
acrylic acid), hydroxypropyl methacrylate (isomer mixture formed in
the addition reaction of propylene oxide with methacrylic acid) and
butanediol monoacrylate.
[0035] Also suitable are the reaction products of the preceding
hydroxy esters of acrylic or methacrylic acid with different
amounts of cyclic lactones or monoepoxides. A preferred cyclic
lactone is .epsilon.-caprolactone and preferred monoepoxides are
ethylene oxide, propylene oxide or mixtures thereof.
[0036] Also suitable as hydroxyl-functional compounds B) are the
reaction products of glycidyl acrylate or glycidyl methacrylate
with monocarboxylic acids, or the reaction products of acrylic or
methacrylic acid with monoepoxides.
[0037] Besides the (meth)acrylate-functional monoalcohols, other
suitable compounds B) include allyl alcohol or its alkoxylation
products, such as mono-, di- or polyethoxylated allyl alcohol.
Preference, however, is given to the exclusive use of the
previously described (meth)acrylate-functional alcohols as
compounds B).
[0038] In addition to the hydroxyl-functional unsaturated alcohols
in B), non-functional, olefinically unsaturated monomers, such as
for example styrene, methyl methylacrylate, ethyl acrylate, butyl
acrylate, 2-ethylhexyl acrylate and acrylonitrile etc., can also be
added. These monomers do not react with the starting isocyanates in
A) but can copolymerize later with the unsaturated groups of the
alcohols B).
[0039] The reaction of A) with B) can take place in the absence of
solvent or in the presence of solvents. Suitable solvents are those
which do not react with isocyanate groups or hydroxyl groups.
Examples include aliphatic, cycloaliphatic and/or aromatic
hydrocarbons such as alkylbenzenes, toluene and xylene; esters such
as ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl
acetate, n-hexyl acetate, 2-ethylhexyl acetate, ethyl propionate,
butyl propionate, pentyl propionate, ethylene glycol monoethyl
ether acetate and the corresponding methyl ether acetate; ethers
such as ethylene glycol acetate monomethyl, monoethyl and monobutyl
ether; ketones such as acetone, methyl ethyl ketone, methyl
isobutyl ketone and methyl n-amyl ketone; and mixtures of these
solvents.
[0040] In the urethanization reaction A) and B) are reacted with
one another in a ratio such that only some of the NCO groups of A)
are consumed. It is preferred to use a quantity of component B)
such that not more than 40 mole %, preferably not more than 30 mole
%, more preferably not more than 25 mole % and most preferably not
more than 20 mole %, based on the moles of isocyanate groups in
starting polyisocyanates A), are converted to urethane groups.
[0041] The urethanization may take place at room temperature
(23.degree. C.), but can also be carried out above or below this
temperature. In order to accelerate the reaction it can be carried
out at up to 160.degree. C. Higher temperatures are not preferred,
since an uncontrolled polymerization of the acrylate or
methacrylate groups may occur.
[0042] Preferably, the unsaturated (meth)acrylate groups are not
reacted by free-radical (co)polymerization until after
urethanization has ended.
[0043] Suitable initiators for carrying out the (co)polymerization
of the unsaturated groups of unsaturated urethanized
polyisocyanates C) and if need further unsaturated groups of non
functional compounds are the known free-radical initiators based on
azo or peroxide compounds which within the temperature range
specified below possess a half-life whose duration is sufficient
for the polymerization, i.e. a half-life of about 5 seconds to
about 60 minutes. Suitable examples include azodiisobutyronitrile,
azobis-2-methylvaleronitrile, 2,2'-azobis-(2-methylpropanenitrile),
2,2'-azobis(2-methylbutanenitrile),
1,1'-azobis(cyclo-hexanecarbonitrile), symmetrical diacyl peroxides
(such as acetyl, propionyl or butyryl peroxide), benzoyl peroxides
(such as those substituted by bromine, nitro, methyl or methoxy
groups), lauryl peroxides, peroxydicarbonates (such as diethyl,
diisopropyl, dicyclohexyl and dibenzoyl peroxydicarbonate),
tert-butyl peroxyisopropyl carbonate, tert-butyl
peroxy-2-ethylhexanoate, tert-butyl
peroxy-3,5,5-trimethylhexanoate, tert-butyl perbenzoate, tert-butyl
peroxydiethylacetate, tert-butyl peroxyisobutyrate, hydroperoxides
(such as tert-butyl hydroperoxide, and cumene hydroperoxide),
dialkyl peroxides (such as dicumyl peroxide, tert-butyl cumyl
peroxide, di-tert-butyl peroxide and di-tert-amyl peroxide),
1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane and
1,1-di-tert-butylperoxycyclohexane.
[0044] Preferably the polymerization reaction takes place at a
temperature of 50 to 240.degree. C., more preferably 60 to
220.degree. C. and most preferably 70 to 200.degree. C. The
polymerization can be carried out under a pressure of up to 15
bar.
[0045] The initiators are used in amounts of 0.05% to 15%,
preferably 0.1% to 10% and more preferably 0.2% to 8% by weight,
based on the total amount of unsaturated compounds in B).
[0046] To carry out the polymerization reaction, urethane-modified
polyisocyanate mixture C) is heated to the desired polymerization
temperature. Then the free-radical initiator is metered into the
reaction mixture and the free-radical polymerization, which is
initiated by the decomposition of the free-radical initiator, is
carried out at the set polymerization temperature. This
polymerization temperature can also be altered as desired in order
to perform specific molecular weight adjustments. After the end of
the polymerization, the reaction mixture is cooled to room
temperature. The resulting polyacrylate-modified polyisocyanates of
the invention are generally pale-colored viscous liquids or
solutions if solvents were employed.
[0047] It is also possible to meter into the reaction mixture
during the performance of the polymerization other non-functional
unsaturated monomers which can then copolymerize with the
unsaturated polyisocyanates C).
[0048] It is also possible in the process of the invention to add
known additives such as PU catalysts, e.g.,
N,N-dimethylbenzylamine, N-methylmorpholine, zinc octoate, tin(II)
octoate or dibutyltin dilaurate.
[0049] The polyacrylate-modified polyisocyanates of the invention
constitute valuable raw materials for the preparation of binder
compositions for producing polyurethane-based coating, adhesive or
sealant compositions.
[0050] The reactive isocyanate groups of the polyacrylate-modified
polyisocyanates of the invention may be blocked with blocking
agents and then used as crosslinkers in 1K (one-component)
polyurethane (PU) coating compositions. Suitable blocking agents
include .epsilon.-caprolactam, butanone oxime, phenol and/or phenol
derivatives, secondary amines, 3,5-dimethylpyrazole, alkyl
malonates or monoalcohols.
[0051] Suitable compounds having NCO-reactive groups are the known
OH and/or NH-functional resins from coatings technology. Examples
include polyesters, polyacrylates, polyurethanes, polyureas,
polycarbonates or polyethers. Also suitable are hybrid resins or
mixtures of different hydroxy-functional resins.
[0052] Preferably the resins used are hydroxy-functional and/or
amino-functional and may contain carboxylic and/or sulphonic acid
groups or epoxid groups. It is also possible to use non-functional
resins, which dry physically or oxidatively, alone or in
combination with hydroxy-functional resins, as binder compounds and
reaction partners for the polyisocyanate mixtures of the
invention.
[0053] These resins have hydroxyl contents of 0.5% to 15.0%,
preferably 0.5% to 12.0%, more preferably 1.0% to 10.0% and most
preferably 1.0% to 8.0% by weight, based on resin solids. The acid
numbers of the solid resins are below 50 mg KOH/g, preferably below
30 mg KOH/g, more preferably below 20 mg KOH/g and most preferably
below 15 mg KOH/g.
[0054] The preceding resins based on addition polymer and/or
polyester, particularly on polyacrylate, are of particular interest
with regard to the level of requirements in the fields of
automotive OEM, automotive refinish and large-vehicle finishing,
general industrial coating, plastics coating, corrosion control,
and wood and furniture coating. In the construction sector or for
coating mineral substrates it is preferred to employ
polyether-based resins.
[0055] In the binder compositions of the invention the equivalent
ratio of free and blocked NCO groups to the NCO-reactive groups in
the binders is 5:1 to 1:2, preferably 2:1 to 1:2, more preferably
1.5:1 to 1:1.5 and most preferably 1.2:1 to 1:1.2.
[0056] If the NCO groups of the polyacrylate-modified
polyisocyanates of the invention have not been blocked, the binder
compositions have only a limited processing life of approximately 3
to 24 hours and are processed either as they are (transparent
coating compositions), or preferably with the additional use of
known additives. These optional additives can be added either to
the mixture or to the individual components prior to their
mixing.
[0057] Suitable additives include solvents such as ethyl acetate,
n-propyl acetate, isopropyl acetate, n-butyl acetate, n-hexyl
acetate, n-heptyl acetate, 2-ethylhexyl acetate, methoxypropyl
acetate, methyl ethyl ketone, methyl isobutyl ketone, toluene,
xylene, higher aromatics mixtures, white spirit and mixtures
thereof.
[0058] Other additives include plasticizers such as tricresyl
phosphate, phthalic diesters and chlorinated paraffins; pigments
and fillers such as titanium dioxide, barium sulphate, chalk and
carbon black; catalysts such as N,N-dimethylbenzylamine,
N-methylmorpholine, zinc octoate, tin(II) octoate and dibutyltin
dilaurate; flow control agents; thickeners; stabilizers such as
substituted phenols; organo-functional silanes as adhesion
promoters; light stabilizers; and UV absorbers. Examples of light
stabilizers are sterically hindered amines, as described for
example in DE-A 2 417 353 and DE-A 2 456 864. Preferred light
stabilizers are bis(1,2,2,6,6-pentamethylpiperid-4-yl) sebacate,
bis(2,2,6,6-tetramethylpiperid-4-yl) sebacate, and
bis(1,2,2,6,6-pentamethylpiperid-4-yl)
n-butyl(3,5-di-tert-butyl-4-hydroxybenzyl) malonate.
[0059] The moisture present in the fillers and pigments can be
removed by drying beforehand or by the additional use of water
absorbers, such as molecular sieve zeolites.
[0060] The coatings obtained from the binder compositions of the
invention can be dried at room temperature with no need for any
increase in temperature to achieve the optimal properties mentioned
at the outset. When the binders are employed as refinish coating
compositions, however, a temperature increase to about 60 to
100.degree. C., preferably 60 to 80.degree. C., for a period of 20
to 60 minutes is often advisable in order to shorten the drying
time and cure time.
[0061] The resulting coating films are notable for high hardness,
good elasticity, excellent weathering stability and chemical
resistance, and high gloss. Particularly the cure times, both for
initial physical drying and for chemical crosslinking, are very
short, i.e., shorter than when using non-polyacrylate-modified
polyisocyanates, so that coated service articles are very rapidly
resistant to solvents and chemicals and can be taken into
service.
[0062] The coating compositions employed in accordance with the
invention are suitable in particular for the finishing of large
vehicles, such as aircraft, railway coaches and trams and lorry
bodies. Further preferred fields of use are automotive refinishing
and the coating of plastics. The coating compositions are
additionally suitable for corrosion control applications (such as
the coating of bridges and power masts), wood and furniture
coatings, general industrial coatings and automotive OEM
coatings.
[0063] These coating compositions are applied by customary methods,
such as spraying, casting, dipping, brushing, squirting or rolling.
The coating compositions of the invention are suitable both for
producing primer coats and for producing tie coats and are suitable
in particular for producing pigmented topcoats and also basecoats
and clearcoats on the substrates that are to be coated.
[0064] 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.
EXAMPLES
[0065] Abbreviations and ingredients used:
[0066] HEA: Hydroxyethyl acrylate
[0067] HEMA: Hydroxyethyl methacrylate
[0068] HPMA: Hydroxypropyl methacrylate
[0069] Desmodur.RTM. HL BA: Aromatic-aliphatic polyisocyanate based
on toluene diisocyanate/hexamethylene diisocyanate (HDI), 60% in
butyl acetate, NCO content 10.5%, available from Bayer
MaterialScience AG, Leverkusen DE.
[0070] Desmodur.RTM. IL BA: Aromatic polyisocyanate based on
toluene diisocyanate, 51% in butyl acetate, NCO content 8.0%,
available from Bayer MaterialScience AG, Leverkusen DE.
[0071] Desmoduro.RTM. 3200: Aliphatic, biuret group-containing
polyisocyanate based on HDI, solvent-free, NCO content 23.0%,
available from Bayer MaterialScience AG, Leverkusen DE.
[0072] Desmodur.RTM. N 3300: Isocyanurate group-containing
polyisocyanate based on HDI, solvent-free, NCO content 21.8%,
available from Bayer MaterialScience AG, Leverkusen DE.
[0073] Desmoduro.RTM. N 3600: Low viscosity, isocyanurate
group-containing polyisocyanate based on HDI, solvent-free, NCO
content 23.0%, available from Bayer MaterialScience AG, Leverkusen
DE.
[0074] Desmoduro.RTM. N 75 BA: Aliphatic, biuret group-containing
polyisocyanate based on HDI, 75% in butyl acetate, NCO content
16.5%, available from Bayer MaterialScience AG, Leverkusen DE.
[0075] Desmoduro.RTM. Z 4470 BA: Isocyanurate group-containing
polyisocyanate based on isophorone diisocyanate, 70% in butyl
acetate, NCO content 11.9%, available from Bayer MaterialScience
AG, Leverkusen DE.
[0076] Desmodur.RTM. XP 2410: Low-viscosity, iminooxadiazinedione
group-containing polyisocyanate based on hexamethylene
diisocyanate, solvent-free, NCO content 23.7%, available from Bayer
MateriaiScience AG, Leverkusen DE.
[0077] Peroxan.RTM. PO 49B: tert-Butyl peroxy-2-ethylhexanoate, 49%
in butyl acetate, available from Pergan GmbH, Bocholt DE.
[0078] The following properties were determined: solids content
(thick-film method: lid, 1 g sample, 1 h 125.degree. C., convection
oven, basis: DIN EN ISO 3251); viscosity (rotational viscometer VT
550 from Haake GmbH, Karlsruhe, DE, MV-DIN cup for viscosity
<10,000 mPas/23.degree. C., SV-DIN cup for viscosity >10,000
mPas/23.degree. C.); NCO content (solvent:acetone, dibutylamine
excess, urea formation, titration with 1 mol/1 HCl, basis: DIN EN
ISO 11909); and Hazen color number (Hazen color number: basis DIN
53995, Lico.RTM. 400 color number measuring instrument, Dr. Lange
GmbH, Berlin, DE).
[0079] Preparation of the Polyacrylate-Modified Polyisocyanates
[0080] A 1-liter three-necked flask with stirrer, reflux condenser
and dropping funnel was charged with the respective starting
polyisocyanate and, when appropriate, butyl acetate as solvent, and
this initial charge was heated to 130.degree. C. under a nitrogen
atmosphere. Then the unsaturated monoalcohol was metered in over a
period of 10 minutes and the mixture was subsequently stirred
further at 130.degree. C. for 1 hour before the desired
polymerization temperature (T) was set. When this temperature had
been reached the polymerization initiator, Peroxan.RTM. PO 49B, was
added in one portion, after which stirring took place at the set
polymerization temperature for 1 hour. The mixture was then cooled
to room temperature, giving the pale-colored, viscous
polyisocyanates (PICs).
[0081] Table 1 below sets forth the respective raw materials,
proportions and reaction conditions. Amounts are in g.
TABLE-US-00001 Butyl Desmodur Desmodur acetate N 3300 N 3600
Peroxan .RTM. PIC [g] [g] [g] HEA [g] HEMA [g] [g] T [.degree. C.]
1 75 412.25 -- 12.11 -- 0.64 130 2 75 412.25 -- 12.11 -- 0.64 100 3
-- 679.00 -- 19.95 -- 1.05 130 4 75 408.00 -- 16.15 -- 0.85 130 5
75 408.00 -- 16.15 -- 0.85 100 6 -- 672.00 -- 26.60 -- 1.40 130 7
-- 672.00 -- 26.60 -- 1.40 100 8 75 -- 412.25 12.11 -- 0.64 130 9
75 -- 412.25 12.11 -- 0.64 100 10 -- -- 679.00 19.95 -- 1.05 130 11
75 -- 408.00 16.15 -- 0.85 130 12 75 -- 408.00 16.15 -- 0.85 100 13
-- -- 672.00 26.60 -- 0.85 130 14 -- -- 672.00 26.60 -- 0.85 100 15
-- 676.62 -- -- 22.33 1.05 130 16 -- 668.78 -- -- 29.82 1.40 130 17
-- -- 676.62 -- 22.33 1.05 130 18 -- -- 668.78 -- 29.82 1.40
130
[0082] Table 2 below sets forth the properties of inventive
polyisocyanates PIC 1 to 18. TABLE-US-00002 TABLE 2 Viscosity Hazen
color Solids content at 23.degree. C. NCO content number PIC [% by
weight] [mPa s] [% by weight] {APHA} 1 84.7 593 16.8 0 2 85.2 726
16.8 0 3 99.9 13,012 20.0 0 4 85.0 948 16.3 0 5 84.6 1510 16.6 11 6
99.9 27,308 19.5 11 7 99.8 92,062 18.5 11 8 85.3 250 17.8 6 9 84.7
314 17.8 0 10 100.0 3703 21.1 11 11 85.1 440 17.4 9 12 85.4 664
17.4 0 13 99.9 8489 20.6 8 14 100 12,311 20.5 10 15 99.8 8958 20.8
2 16 99.9 12,511 20.4 11 17 99.9 3032 21.0 9 18 100 6706 20.5
11
[0083] Preparation of Modified Polyisocyanate PIC 19
[0084] Using the procedure described for Polyisocyanates 1-18,
604.8 g of Desmodur.RTM. XP 2410 in 35.0 g of butyl acetate were
reacted with 23.94 g of HEA and the product was subsequently
polymerized at 100.degree. C. by the addition of 0.62 g of
tert-butyl peroxy-2-ethylhexanoate in 35.64 g of butyl acetate. The
resulting colorless polyisocyanate mixture had a solids content of
90% by weight, a viscosity of 1181 mPas, an isocyanate content of
19.8% by weight and a color number of 16 APHA.
[0085] Preparation of Modified Polyisocyanate PIC 20
[0086] Using the procedure described for Polyisocyanates 1-18,
676.63 g of Desmodur.RTM. Z 4470 were reacted with 15.63 g of HPMA
in 7.00 g of solvent naphtha 100 and the product was subsequently
polymerized at 150.degree. C. by the addition of 0.74 g of
di-tert-butyl peroxide. The resulting pale-colored polyisocyanate
mixture had a solids content of 72.6% by weight, a viscosity of
2602 mPas, an isocyanate content of 10.6% by weight and a color
number of 54 APHA.
[0087] Preparation of Modified Polyisocyanate PIC 21
[0088] Using the procedure described for Polyisocyanates 1-18,
676.62 g of Desmodur.RTM. N 3200 were reacted with 22.33 g of
butanediol monoacrylate and the product was subsequently
polymerized at 160.degree. C. by the addition of 1.05 g of
di-tert-butyl peroxide. The resulting pale-colored polyisocyanate
mixture had a solids content of 98.8% by weight, a viscosity of
46,272 mPas, an isocyanate content of 21.7% by weight and a color
number of 50 APHA.
[0089] Preparation of Modified Polyisocyanate PIC 22
[0090] Using the procedure described for Polyisocyanates 1-18,
676.65 g of Desmodur.RTM. N 75 were reacted with 16.75 g of HPMA in
5.81 g of 1:1 methoxypropyl acetate (mPa)/xylene and the product
was subsequently polymerized at 145.degree. C. by the addition of
0.79 g of di-tert-butyl peroxide. The resulting pale-colored
polyisocyanate mixture had a solids content of 74.9% by weight, a
viscosity of 308 mPas, an isocyanate content of 15.6% by weight and
a color number of 16 APHA.
[0091] Preparation of Modified Polyisocyanate PIC 23
[0092] Using the procedure described for Polyisocyanates 1-18,
676.59 g of Desmodur HL.RTM. were reacted with 13.40 g of
HPMA.sup.3) in 9.38 g of butyl acetate and the product was
subsequently polymerized at 130.degree. C. by the addition of 0.63
g of tert-butyl peroxy-2-ethylhexanoate, 50% in butyl acetate. The
resulting pale-colored polyisocyanate mixture had a solids content
of 62.3% by weight, a viscosity of 2182 mPas, an isocyanate content
of 10.3% by weight and a color number of 39 APHA.
[0093] Preparation of Modified Polyisocyanate PIC 24
[0094] Using the procedure described for Polyisocyanates 1-18,
676.60 g of Desmodur IL.RTM. were reacted with 13.39 g of HPMA in
11.48 g of butyl acetate and the product was subsequently
polymerized at 130.degree. C. by the addition of 0.54 g of
tert-butyl peroxy-2-ethylhexanoate, 50% in butyl acetate. The
resulting pale-colored polyisocyanate mixture had a solids content
of 52.1% by weight, a viscosity of 2522 mPas, an isocyanate content
of 7.35% by weight and a color number of 94 APHA.
[0095] Preparation of Modified Polyisocyanate PIC 25
[0096] Using the procedure described for Polyisocyanates 1-18,
601.9 g of Desmodur.RTM. N 3600 in solution in 35.0 g of butyl
acetate were reacted with 13.42 g of HEMA. Thereafter 13.42 g of
styrene were added and the mixture was subsequently polymerized at
100.degree. C. by the addition of 0.62 g of tert-butyl
peroxy-2-ethylhexanoate in 35.64 g of butyl acetate. The resulting
colorless polyisocyanate mixture had a solids content of 89.7% by
weight, a viscosity of 1531 mPas, an isocyanate content of 18.7% by
weight and a color number of 9 APHA.
[0097] Preparation of Modified Polyisocyanate PIC 26
[0098] Using the procedure described for Polyisocyanates 1-18,
601.9 g of Desmodur.RTM. N 3600 in 35.0 g of butyl acetate were
reacted with 13.42 g of HEMA. Thereafter 13.42 g of methyl
methacrylate were added and the mixture was subsequently
polymerized at 100.degree. C. by the addition of 0.62 g of
tert-butyl peroxy-2-ethylhexanoate in 35.64 g of butyl acetate. The
resulting colorless polyisocyanate mixture had a solids content of
89.9% by weight, a viscosity of 2662 mPas, an isocyanate content of
18.9% by weight and a color number of 15 APHA.
[0099] Preparation of Modified Polyisocyanate PIC 27
[0100] Using the procedure described for Polyisocyanates 1-18,
601.9 g of Desmodur.RTM. N 3600 in 35.0 g of butyl acetate were
reacted with 13.42 g of HEMA. Thereafter 13.42 g of styrene were
added and the mixture was subsequently polymerized at 100.degree.
C. by the addition of 0.62 g of tert-butyl peroxy-2-ethylhexanoate
in 35.64 g of butyl acetate. The resulting colorless polyisocyanate
mixture had a solids content of 89.7% by weight, a viscosity of
1531 mPas, an isocyanate content of 18.7% by weight and a color
number of 9 APHA.
[0101] Preparation of Modified Polyisocyanate PIC 28
[0102] Using the procedure described for Polyisocyanates 1-18,
601.9 g of Desmodur.RTM. XP 2410 in 35.0 g of butyl acetate were
reacted with 13.42 g of HEMA. Thereafter 13.42 g of styrene were
added and the mixture was subsequently polymerized at 100.degree.
C. by the addition of 0.62 g of tert-butyl peroxy-2-ethylhexanoate
in 35.64 g of butyl acetate. The resulting colorless polyisocyanate
mixture had a solids content of 89.8% by weight, a viscosity of
1010 mPas, an isocyanate content of 18.65% by weight and a color
number of 16 APHA.
[0103] Preparation of Modified Polyisocyanate PIC 29
[0104] Using the procedure described for Polyisocyanates 1-18,
601.9 g of Desmodur.RTM. XP 2410 in 35.0 g of butyl acetate were
reacted with 13.42 g of HEMA. Thereafter 13.42 g of methyl
methacrylate were added and the mixture was subsequently
polymerized at 100.degree. C. by the addition of 0.62 g of
tert-butyl peroxy-2-ethylhexanoate in 35.64 g of butyl acetate. The
resulting polyisocyanate mixture had a solids content of 90.0% by
weight, a viscosity of 919 mPas, an isocyanate content of 19.2% by
weight and a color number of 11 APHA.
USE EXAMPLES
[0105] These examples describe the preparation of ready-to-use
coating compositions based on the polyisocyanates PIC in comparison
with the corresponding non-polyacrylate-modified starting
polyisocyanates, the application of these coating compositions, and
the testing of the resulting coating films.
[0106] The general coating properties were assessed by preparing
transparent varnishes. For that purpose the polyisocyanates were
each combined with a polyol at an NCO/OH equivalent ratio of 1:1.
The polyol used was Desmophen.RTM. A 870, a polyacrylate polyol
available from Bayer MaterialScience AG, Leverkusen, DE, which has
a solids content of 70% by weight in butyl acetate, a viscosity of
3500 mPas at 23.degree. C., an acid number of 7.5 mg KOH/g (based
on as-supplied form) and an OH content of 2.95% by weight (based on
as-supplied form). Based on resin solids (sum of the solid
fractions of polyol and polyisocyanate) the following amounts of
additives were used. TABLE-US-00003 % by weight, Constituents
solids on solids Dabco 33 LV (PU catalyst from Air Products, 10%
0.3 in butyl acetate) BYK 331 (Flow control agent from BYK-Chemie
0.3 Wesel, DE, 50% in butyl acetate) BYK 141 (Silicone defoamer
from BYK-Chemie 0.03 Wesel, DE, 3% in 11:2 alkylbenzene/
isobutanol) Tinuvin 292 (Light stabilizer from Ciba Geigy Basel,
1.0 CH, 50% in xylene)
[0107] A mixture of solvent naphtha 100, methoxypropyl acetate,
xylene and n-butyl acetate (1:1:1:1) was added which resulted in a
binder content of 56% by weight and an additives content of 2% by
weight. The flow time (DIN 53 211, 4-mm nozzle) of the resulting
varnishes was 25 s. The varnishes are in a ready-to-spray
formulation and have a VOC (volatile organic compounds) content of
3.5 lbs/gal.
[0108] The pot life was tested by measuring the increase in
viscosity of the varnishes over a period of 7 hours.
[0109] The varnishes were applied to glass plates at 23.degree. C.
and 50% relative humidity, dried both at room temperature and at
60.degree. C. for 30 minutes, during which the drying rate (DIN 53
150) was determined, and then stored at room temperature for 7
days. The dry film thickness was 55 to 60 .mu.m. Thereafter the
Konig hardness (DIN 53 157), the Gardner gloss at an angle of
20.degree., the Haze (DIN 67 530), and the water and solvent
resistance using water, super-grade petrol, methoxypropyl acetate
and xylene [instantaneous, and after 1, 4 and 7 days after curing
at 60.degree. C. for 30 minutes] were tested.
[0110] Table 3 below set forth the test results of the tested
varnishes of the invention and of the comparison varnishes.
TABLE-US-00004 TABLE 3 Test results of transparent 2K PU varnishes
(B1 = .RTM. Desmodur N 3300, B2 = .RTM. Desmodur N 3600) Varnish
based on polyisocyanate PIC 1 PIC 2 PIC 4 PIC 5 PIC 8 PIC 9 PIC 11
PIC 12 B1 B2 Viscosity (s) instantaneous 24 24 25 25 25 25 24 25 25
25 after 1 h 24 26 25 25 25 25 25 25 25 25 2 h 25 26 25 26 25 25 25
25 25 26 3 h 26 26 26 26 26 25 25 25 26 27 4 h 26 26 27 26 26 26 26
26 27 27 5 h 27 27 28 28 27 27 27 28 27 27 6 h 28 29 28 28 28 27 28
28 29 28 Gloss (.angle. 20.degree.) 91 91 90 91 90 90 91 92 92 92
Haze <10 <10 14 10 14 12 <10 <10 <10 <10 Drying
(h) T1 1.5 1.5 1.5 1.0 2.0 2.0 2.0 2.0 2.0 2.5 T2 5.0 4.5 4.0 4.0
5.5 5.5 5.5 5.5 5.5 8.0 T3 5.5 5.5 5.0 5.0 6.5 6.5 7.0 6.0 8.0
>8 T4 7.5 7.0 7.5 7.5 8.0 8.0 8.0 8.0 >8 >8 Pendulum
damping instantaneous 37 39 38 36 58 51 34 31 32 21 (s) +1 d RT 131
141 127 130 137 134 124 112 124 98 after 30 min at 4 d RT 167 177
167 166 157 157 151 148 164 141 60.degree. C. 7 d RT 171 181 173
170 161 163 162 152 164 145 Water resistance.sup.1)2) instantaneous
2 2 2 2 2 2 2 2 3 4 after 30 min at +1 d RT 0 0 0 0 0 0 0 0 0 0
60.degree. C. 4 d RT 0 0 0 0 0 0 0 0 0 0 7 d RT 0 0 0 0 0 0 0 0 0 0
16 h 50.degree. C. 0 0 0 0 0 0 0 0 0 0 .sup.1)Exposure time: 60
minutes .sup.2)= best worth (without any damage), 5 = poorest worth
(film dissolved) Super-grade petrol instantaneous 4 4 4 4 4 4 4 4
4-5 4-5 resistance.sup.1)2) +1 d RT 2 1-2 1-2 2 2 2 1-2 2 2-3 2-3
after 30 min at 4 d RT 0 0 0 0 0-1 0-1 0 0 0 0-1 60.degree. C. 7 d
RT 0 0 0 0 0 0 0 0 0 0 16 h 50.degree. C. 0 0 0 0 0 0 0 0 0 0 MPA
resistance.sup.1)2) instantaneous 4 4 4 4 4 4 4 4 5 5 after 30 min
at +1 d RT 2 3 2 2 3 2 3 3 3 4 60.degree. C. 4 d RT 1 1 0 1 1 1 1 1
1 1 7 d RT 1 0-1 0 1 1 1 1 1 1 1 16 h 50.degree. C. 1 0-1 0 1 1 1 1
1 1 1 Xylene instantaneous 4 4 4 4 4 4 4 4 5 5 resistance.sup.1)2
+1 d RT 3 3 2 2 3 2 3 3 3 4 after 30 min at 4 d RT 1 1 0-1 1 1 1 1
0 1 1 60.degree. C. 7 d RT 1 0-1 0-1 0 1 1 0-1 0 1 0 16 h
50.degree. C. 0-1 0-1 0-1 0 0 0 0 0 0-1 0 Sulphuric acid, 2% 7 d RT
0 0 0 0 0 0 0 0 0 0 strength.sup.1)2) Sodium hydroxide 7 d RT 0 0 0
0 0 0 0 0 0 0 solution, 2% strength.sup.1)2 .sup.1)Exposure time: 5
minutes .sup.2)= best worth (without any damage), 5 = poorest worth
(film dissolved)
[0111] Both the inventive varnishes based on the
polyacrylate-modified polyisocyanates and the comparison varnishes
based on polyisocyanates B) had a long processing life without a
marked rise in viscosity and yielded high gloss varnish films
having very low Haze values. The tests also demonstrated that the
inventive coatings based on PICs 1, 2, 4 and 5, in contrast to the
comparison varnish based on unmodified polyisocyanate B1, exhibited
more rapid drying, a higher hardness and a slightly better solvent
resistance. The same results were also obtained by the inventive
varnishes based on PIC 8, PIC 9, PIC 11 and PIC 12 when compared to
the comparison varnish based on unmodified polyisocyanate B2. The
test results demonstrated the clear advantages of the varnishes of
the invention, particularly with respect to the important
properties of drying rate, hardness and early water and solvent
resistance, which play a significant part, particularly in
automotive refinishing.
[0112] 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 variations can
be made therein by those skilled in the art without departing from
the spirit and scope of the invention except as it may be limited
by the claims.
* * * * *